Isotope forensics of polycyclic aromatic compounds (PACs) in a contaminated shallow aquifer

Diesel was accidently released into the shallow subsurface at an industrial site in the province of Québec, Canada, in the late 1980s. Subsequent remediation efforts removed much of the contamination; however, traces of petroleum hydrocarbons continue to impact the local aquifer. In addition to the historical diesel spill, more recent yet unconfirmed accidental releases from ongoing on-site and neighbouring industrial activities may have potentially contributed to elevated levels of polycyclic aromatic compounds (PACs) in groundwater. To identify the main source(s) of contamination, compound-specific stable carbon isotope ratios (δ13C) of PACs in groundwater monitoring wells were compared to those in asphalt produced from a nearby plant and in fuel oil #6 oil being used by local industry. The δ13C values of five individual compounds (biphenyl, C2-naphthalene, C1-fluorene, dibenzothiophene and phenanthrene) and two groups of combined C1-phenanthrenes/anthracenes in all groundwater samples were within analytical uncertainty (±0.5‰). Moreover, the δ13CPAC values in groundwater samples were distinct from those in asphalt and fuel oil #6, indicating negligible contributions from these sources. The similarity in δ13CPAC values across monitoring wells, including one situated in the former source zone containing a floating hydrocarbon phase, pointed to a common source of subsurface contamination that was attributed to the historical diesel spill. These results thus demonstrate that δ13CPAC values can be used for source apportionment in shallow aquifers decades after the original spill event.

Case Report: Fetoscopic Laparoschisis (FETO-LAP)-A New Therapeutic Route to Explore for Fetuses with Severe Diaphragmatic Hernias

BACKGROUND

The purpose of this report is to describe the seminal case of a near-term human fetus with a life-threatening left diaphragmatic hernia that underwent fetoscopic tracheal occlusion (FETO) combined with fetoscopic partial removal of herniated bowel from the fetal chest by fetoscopic laparoschisis (FETO-LAP).

CASE SUMMARY

A life-threatening left diaphragmatic hernia (liver-up; o/e LHR of ≤25%; MRI lung volume ≤ 20%) was observed in a human fetus at 34 weeks of gestation. After counselling the mother about the high risks of postnatal demise if left untreated, the expected limitations of fetoscopic tracheal occlusion (FETO), and the previously untested option of combining FETO with fetoscopic laparoschisis, i.e., partial removal of the herniated bowel from the fetal chest (FETO-LAP), she consented to the latter novel treatment approach. FETO-LAP was performed at 36 + 5 weeks of gestation under general maternofetal anesthesia. Mother and fetus tolerated the procedure well. The neonate was delivered and the balloon removed on placental support at 37 + 2 weeks of gestation. On ECMO, a rapid increase in tidal volume was seen over the next eight days. Unfortunately, after this period, blood clots obstructed the ECMO circuit and the neonate passed away.

DISCUSSION

This seminal case shows that in a fetus with severe left diaphragmatic hernia, partial removal of the herniated organs from the fetal chest is not only possible by minimally invasive fetoscopic techniques but also well tolerated. As the effect of FETO alone is limited in saving severely affected fetuses, combining FETO with fetoscopic laparoschisis (FETO-LAP) offers a new therapeutic route with multiple, potentially life-saving implications.

A balancing act: sex selection after pre-implantation genetic testing for aneuploidy for first versus second baby

STUDY QUESTION

How often do patients undergoing frozen embryo transfer (FET) after preimplantation genetic testing for aneuploidy (PGT-A) choose to select for sex and do sex selection rates differ before and after successful delivery of a first baby?

SUMMARY ANSWER

When a choice was available between male and female embryos, patients selected the sex more frequently when trying to conceive the second child (62%) as compared to the first child (32.4%) and most commonly selected for the opposite sex of the first child.

WHAT IS KNOWN ALREADY

Sex selection is widely available in US fertility clinics. However, the rate of sex selection for patients undergoing FET after PGT-A is unknown.

STUDY DESIGN, SIZE, DURATION

This is a retrospective cohort study of 585 patients that took place between January 2013 and February 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study took place at a single, urban academic fertility center in the USA. Patients were included if they had a live birth after single euploid FET and returned for at least one subsequent euploid FET. The primary outcomes were the rates of sex selection for first versus second baby. Secondary outcomes were rate of selection for same versus opposite sex as first live birth and overall rate of selection for males versus females.

MAIN RESULTS AND THE ROLE OF CHANCE

Five hundred and eighty-five patients underwent a total of 1560 single euploid FETs resulting in either one or two live births. A choice between male and female euploid embryos was available for 919 FETs (first child: 67.5% (519/769) versus second child: 50.6% (400/791), P < 0.01). When a choice was available, patients selected the sex more frequently when trying to conceive the second child (first child: 32.4% (168/519) versus second child: 62.0% (248/400), P < 0.01). When sex was selected after first live birth, the opposite sex of the first child was selected 81.8% (203/248 FETs) of the time. Of transfers that involved sex selection, rates of male and female selection were similar for the first child, but selection for females was greater for the second child (first child: 51.2% (86/168) male versus 48.9% (82/168) female, second child: 41.1% (102/248) male versus 58.9% (146/248) female, P < 0.04).

LIMITATIONS, REASONS FOR CAUTION

The study was performed at one urban academic medical center in the Northeastern US, which may limit generalizability to other settings where PGT-A may be performed less frequently, or sex selection may be limited or not permitted. In addition, we could not reliably account for whether patients or their partners had prior children and if so, of what sex.

WIDER IMPLICATIONS OF THE FINDINGS

Patients undergoing PGT-A with both male and female euploid embryos were more likely to select for sex when attempting a second child and usually selected for the opposite sex of their first child. These findings highlight the potential for family balancing for patients who undergo PGT-A in settings where sex selection is permitted.

STUDY FUNDING/COMPETING INTEREST(S)

This study received no funding. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Evaluation of scale-up effect on cold-active enzyme production and biodegradation tests using pilot-scale bioreactors and a 3D soil tank

Despite recent attention being paid to the biodegradation of petroleum hydrocarbons in cold environments, scale-up studies of biodegradation are lacking. Herein, the effect of scale-up on the enzymatic biodegradation of highly contaminated soil at low temperatures was studied. A novel cold-adapted bacteria (Arthrobacter sp. S2TR-06) was isolated that could produce cold-active degradative enzymes (xylene monooxygenase (XMO) and catechol 2,3-dioxygenase (C2,3D)). Enzyme production was investigated on 4 different scales (lab to pilot scale). The results showed a shorter fermentation time, and the highest production of enzymes and biomass (107 g/L for biomass, 109 U/mL, and 203 U/mL for XMO and C2,3D after 24 h) was achieved in the 150-L bioreactor due to enhanced oxygenation. Multi-pulse injection of p-xylene into the production medium was needed every 6 h. The stability of membrane-bound enzymes can be increased up to 3-fold by adding FeSO₄ at 0.1% (w/v) before extraction. Soil tests also showed that biodegradation is scale-dependent. The maximum biodegradation rate decreased from 100% at lab-scale to 36% in the 300-L sand tank tests due to limited access of enzymes to trapped p-xylene in soil pores, low dissolved oxygen in the water-saturated zone, soil heterogeneity, and the presence of the free phase of p-xylene. The result demonstrated that formulation of enzyme mixture with FeSO₄ and direct injection of enzyme mixture (third scenario) can increase the efficiency of bioremediation in heterogeneous soil. In this study, it was demonstrated that cold-active degradative enzyme production can be scaled up to an industrial scale and enzymatic treatment can be used to effectively bioremediate p-xylene contaminated sites. This study could provide key scale-up guidance for the enzymatic bioremediation of mono-aromatic pollutants in water-saturated soil under cold conditions.

Formulation of synthetic bacteria consortia for enzymatic biodegradation of polyaromatic hydrocarbons contaminated soil: soil column study

As an efficient method to remove contaminants from highly polluted sites, enzyme biodegradation addresses unresolved issues such as bioremediation inefficiency. In this study, the key enzymes involved in PAH degradation were brought together from different arctic strains for the biodegradation of highly contaminated soil. These enzymes were produced via a multi-culture of psychrophilic Pseudomonas and Rhodococcus strains. As a result of biosurfactant production, the removal of pyrene was sufficiently prompted by Alcanivorax borkumensis. The key enzymes (e.g., naphthalene dioxygenase, pyrene dioxygenase, catechol-2,3 dioxygenase, 1-hydroxy-2-naphthoate hydroxylase, protocatechuic acid 3,4-dioxygenase) obtained via multi-culture were characterized by tandem LC-MS/MS and kinetic studies. To simulate in situ application of produced enzyme solutions, pyrene- and dilbit-contaminated soil was bioremediated in soil columns and flask tests by injecting enzyme cocktails from the most promising consortia. The enzyme cocktail contained about 35.2 U/mg protein pyrene dioxygenase, 61.4 U/mg protein naphthalene dioxygenase, 56.5 U/mg protein catechol-2,3-dioxygenase, 6.1 U/mg protein 1-hydroxy-2-naphthoate hydroxylase, and 33.5 U/mg protein protocatechuic acid (P3,4D) 3,4-dioxygenase enzymes. It was found that after 6 weeks, the average pyrene removal values showed that the enzyme solution could be effective in the soil column system (80-85% degradation of pyrene).

Isotopic and microbial evidence for biodegradation of diluted bitumen in the unsaturated zone

The oil sands region in Western Canada is one of the world's largest proven oil reserves. To facilitate pipeline transport, highly viscous oil sands bitumen is blended with lighter hydrocarbon fractions to produce diluted bitumen (dilbit). Anticipated increases in dilbit production and transport raise the risk of inland spills. To understand the behaviour of dilbit in the unsaturated or vadose zone following a surface spill, we ran parallel dilbit and conventional heavy crude exposures, along with an untreated control, using large soil-filled columns over 104 days. Phospholipid fatty acids (PLFAs), biomarkers for the active microbial population, were extracted from column soil cores. Stable carbon isotope contents (δ¹³C) of individual PLFAs and radiocarbon contents (Δ¹⁴C) of bulk PLFAs were characterized over the course of the experiment. The Δ¹⁴C_PLFA values in soils impacted by dilbit (-221.1 to -54.7‰) and conventional heavy crude (-259.4 to -97.9‰) indicated similar levels of microbial uptake of fossil carbon. In contrast, Δ¹⁴C_PLFA values in the control column (-46.1 to +53.7‰) reflected assimilation of more recently fixed organic carbon. Sequencing of 16S ribosomal RNA genes extracted from soil cores revealed a significant increase in the relative abundance of Polaromonas, a known hydrocarbon-degrader, following exposure to both types of oil. This study demonstrates that in the first several months following a surface spill, dilbit has a similar potential for biodegradation by a native shallow subsurface microbial community as conventional heavy crude oil.

Duplex Phenotype Detection and Targeting of Breast Cancer Cells Using Nanotube Nanoprobes and Raman Imaging

We designed, synthesized, and characterized a Raman nanoprobe made of dye-sensitized single-walled carbon nanotubes (SWCNTs) that can selectively target biomarkers of breast cancer cells. The nanoprobe is composed of Raman-active dyes encapsulated inside a SWCNT, whose surface is covalently grafted with poly(ethylene glycol) (PEG) at a density of ∼0.7% per carbon. Using α-sexithiophene- and β-carotene-derived nanoprobes covalently bound to an antibody, either anti-E-cadherin (E-cad) or anti-keratin-19 (KRT19), we prepared two distinct nanoprobes that specifically recognize biomarkers on breast cancer cells. Immunogold experiments and transmission electron microscopy (TEM) images are first used to guide the synthesis protocol for higher PEG-antibody attachment and biomolecule loading capacity. The duplex of nanoprobes was then applied to target E-cad and KRT19 biomarkers in T47D and MDA-MB-231 breast cancer cell lines. Hyperspectral imaging of specific Raman bands allows for simultaneous detection of this nanoprobe duplex on target cells without the need for additional filters or subsequent incubation steps. Our results confirm the high reproducibility of the nanoprobe design for duplex detection and highlight the potential of Raman imaging for advanced biomedical applications in oncology.

Fluorescence anisotropy using highly polarized emitting dyes confined inside BNNTs

Polarized fluorescence emission of nanoscale emitters has been extensively studied for applications such as bioimaging, displays, and optical communication. Extending the polarization properties in large assemblies of compact emitters is, however, challenging because of self-aggregation processes, which can induce depolarization effects, quenching, and cancellations of molecular dipoles. Here we use α-sexithiophene (6T) molecules confined inside boron nitride nanotubes (6T@BNNTs) to induce fluorescence anisotropy in a transparent host. The experiments first indicate that individual 6T@BNNTs exhibit a high polarization extinction ratio, up to 700, at room temperature. Using aberration-corrected HRTEM, we show that the fluorescence anisotropy is consistent with a general alignment of encapsulated 6T molecules along the nanotube axis. The molecular alignment is weakly influenced by the nanotube diameter, a phenomenon ascribed to stronger molecule-to-sidewall interactions compared to intermolecular interactions. By stretching a flexible thin film made of transparent polymers mixed with 6T@BNNTs, we induce a macroscopic fluorescence anisotropy within the film. This work demonstrates that the dyes@BNNT system can be used as an easy-to-handle platform to induce fluorescence anisotropy in photonic materials.

Simulation of novel jellyfish type of process for bioremediation application

A bioinspired device was fabricated as a sustainable remedial method and its performance as a membrane-enzyme reactor with cyclic ultrafiltration was investigated. The body of the jellyfish-like device was composed of two parts: 1) Jellyfish arms: Mono and co-axial electrospinning have been utilized to synthesize the flexible parts (e.g., multilayer membrane PS-PVDF/PAN/PS-PVDF) used for immobilization of aliphatic degrading enzymes, and 2) Jellyfish tentacles: Hollow fiber membranes were selected for physical immobilization of polycyclic aromatic hydrocarbon (PAH) degrading enzymes. To study the behavior of the membrane/enzyme reactor, the hollow fiber enzyme reactor with pulsation was operated by recycling an enzyme solution to assess ultrafiltration efficiency. A mathematical model was suggested to describe the experimental data obtained in this study to predict the effectiveness of the reactor for PAH removal. When testing the performance of the jellyfish-like device, those equipped with nanofibers with an oil sorption capacity of (10. ±0.7gdilbit/gfiber) were more effective at removing oil particles before they touched the hollow fiber membrane surface. Moreover, the reaction rate measured in a free soluble enzyme and a recirculating immobilized enzyme solution exhibited a slight difference in the kinetic parameter, K_m (0.03 and 0.021 mM) due to the internal diffusional resistance. Based on biodegradation studies, a synergistic effect between membrane adsorption, enzymatic degradation, and ultrafiltration was proposed for the removal of anthracene from the column of water.

Foam injection for enhanced recovery of diesel fuel in soils: Sand column tests monitored by CT scan imagery

The use of surfactant foam for the remediation of diesel fuel, a Light Non-Aqueous Phase Liquid (LNAPL), was investigated in sand column experiments using X-ray Computed Tomography (CT). A preliminary series of tests were carried out on six surfactant candidates in order to measure their physical properties, including critical micelle concentrations and interfacial tensions (IFT) with the LNAPL. Batch tests for foam stability were carried out with and without added LNAPL, in order to measure the half-life of foam columns produced with each surfactant candidate. Foam flow-rate co-injection tests were carried out for each surfactant candidate in 405 cm³ sand columns contaminated with LNAPL at residual saturation. These tests revealed that a 1:1 mixture of sodium dodecyl sulfate and cocamidopropyl betaine, injected at a total volumetric flow-rate (Q_foam) of 45 mL/min, resulted in successful generation and propagation of foam within the contaminated porous medium. Finally, two sand column tests, carried out respectively under high- and low-pressure conditions, were imaged with a CT-scanner in order to compare and contrast foam morphology evolution as well as the LNAPL desaturation dynamics involved in both scenarios. The saturation profiles extracted from CT images provided valuable new insights.

Visible Out-of-plane Polarized Luminescence and Electronic Resonance in Black Phosphorus

Black phosphorus (BP) is unique among layered materials because of its homonuclear lattice and strong structural anisotropy. While recent investigations on few-layer BP have extensively explored the in-plane (a, c) anisotropy, much less attention has been given to the out-of-plane direction (b). Here, the optical response from bulk BP is probed using polarization-resolved photoluminescence (PL), photoluminescence excitation (PLE), and resonant Raman scattering along the zigzag, out-of-plane, and armchair directions. An unexpected b-polarized luminescence emission is detected in the visible, far above the fundamental gap. PLE indicates that this emission is generated through b-polarized excitation at 2.3 eV. The same electronic resonance is observed in resonant Raman with the enhancement of the A_g phonon modes scattering efficiency. These experimental results are fully consistent with DFT calculations of the permittivity tensor elements and demonstrate the remarkable extent to which the anisotropy influences the optical properties and carrier dynamics in black phosphorus.

Dynamic Gate Control of Aryldiazonium Chemistry on Graphene Field-Effect Transistors

As graphene field-effect transistors (GFETs) are becoming increasingly valued for sensor applications, efficiency and control of their surface functionalization become critical. Here, we introduce an innovative method using a gate electrode to precisely modulate aryldiazonium functionalization directly on graphene devices. Although this covalent chemistry is well-known, we show that its spontaneous reaction on GFETs is highly heterogeneous with a low overall yield. By dynamically tuning the gate voltage in the presence of the reactant, we can quickly enable or suppress the reaction, resulting in a high degree of homogeneity between devices. We are also able to monitor and control functionalization kinetics in real time. The mechanism for our approach is based on electron transfer availability, analogous to chemical, substrate-based, or electrochemical doping, but has the practical advantage of being fully implementable on devices or chips. This work illustrates how powerful the FET platforms are to study surface reactions on nanomaterials in real time.

Biodegradation of p-xylene-a comparison of three psychrophilic Pseudomonas strains through the lens of gene expression

p-Xylene is considered a recalcitrant compound despite showing a similar aromatic structure to other BTEXs (benzene, toluene, ethylbenzene, xylene isomers). This study evaluated the p-xylene biodegradation potential of three psychrophilic Pseudomonas strains (Pseudomonas putida S2TR-01, Pseudomonas synxantha S2TR-20, and Pseudomonas azotoformans S2TR-09). The p-xylene metabolism-related catabolic genes (xylM, xylA, and xylE) and the corresponding regulatory genes (xylR and xylS) of the selected strains were investigated. The biodegradation results showed that the P. azotoformans S2TR-09 strain was the only strain that was able to degrade 200 mg/L p-xylene after 60 h at 15 °C. The gene expression study indicated that the xylE (encoding catechol 2,3-dioxygenase) gene represents the bottleneck in p-xylene biodegradation. A lack of xylE expression leads to the accumulation of intermediates and the inhibition of biomass production and complete carbon recovery. The activity of xylene monooxygenase and catechol 2,3-dioxygenase was significantly increased in P. azotoformans S2TR-09 (0.5 and 0.08 U/mg, respectively) in the presence of p-xylene. The expression of the ring cleavage enzyme and its encoding gene (xylE) and activator (xylS) explained the differences in the p-xylene metabolism of the isolated bacteria and can be used as a novel biomarker of efficient p-xylene biodegradation at contaminated sites.

Enzymatic biodegradation of highly p-xylene contaminated soil using cold-active enzymes: A soil column study

Enzymatic bioremediation is a sustainable and environment-friendly method for the clean-up of contaminated soil and water. In the present study, enzymatic bioremediation was designed using cold-active enzymes (psychrozymes) which catalyze oxidation steps of p-xylene biodegradation in highly contaminated soil (initial concentration of 13,000 mg/kg). The enzymes were obtained via co-culture of two psychrophilic Pseudomonas strains and characterized by kinetic studies and tandem LC-MS/MS. To mimic in situ application of enzyme mixture, bioremediation of p-xylene contaminated soil was carried out in soil column (140 mL) tests with the injection (3 pore volume) of different concentrations of enzyme cocktails (X, X/5, and X/10). Enzyme cocktail in X concentration contained about 10 U/mL of xylene monooxygenase (XMO) and 20 U/mL of catechol 2, 3 dioxygenases (C2,3D). X/5 and X/10 correspond to 5x and 10x dilution of enzyme cocktail respectively. The results showed that around 92-94% p-xylene removal was achieved in the treated soil column with enzyme concentration X, X/5 after second enzyme injection. While the p-xylene removal rate obtained by X/10 concentration of enzyme was less than 30% and near to untreated soil column (22.2%). The analysis of microbial diversity and biotoxicity assay (root elongation and seed germination) confirmed the advantage of using enzymes as a green and environmentally friendly approach for decontamination of pollutants with minimal or even positive effects on microbial community and also enrichment of soil after treatment.

Column tests for evaluation of the enzymatic biodegradation capacity of hydrocarbons (C10-C50) contaminated soil

Though many studies pertaining to soil bioremediation have been performed to study the microbial kinetics in shake flasks, the process efficiency in column tests is seldom. In the present study, soil columns tests were carried out to study the biodegradation of soil contaminated with a high concentration of diesel (≈19.5 g/kg) petroleum hydrocarbons expressed as C₁₀-C₅₀. Experiments were done with crude enzymatic cocktail produced by the hydrocarbonoclastic bacterium, Alcanivorax borkumensis. A. borkumensis was grown on a media with 3% (v/v) motor oil as the sole carbon and energy source. The effects of the enzyme concentration, treatment time and oxidant on the bioremediation efficiency of C₁₀-C₅₀ were investigated. A batch test was also carried out in parallel to investigate the stability of the enzymes and the effect of the biosurfactants on the desorption and the bioconversion of C₁₀-C₅₀. Batch tests indicated that the biosurfactants significantly affected the desorption and alkane hydroxylase and lipase enzymes, maintained their catalytic activity during the 20-day test, with a half-life of 7.44 days and 8.84 days, respectively. The crude enzyme cocktail, with 40 U/mL of lipase and 10 U/mL of alkane hydroxylase, showed the highest conversion of 57.36% after 12 weeks of treatment with a degradation rate of 0.0218 day^-1. The results show that the soil column tests can be used to optimize operating conditions for hydrocarbon degradation and to assess the performance of the overall bioremediation process.

Sustainable production and co-immobilization of cold-active enzymes from Pseudomonas sp. for BTEX biodegradation

Toluene/o-Xylene Monooxygenase (ToMO) is equipped with a broad spectrum of aromatic substrate specificity (such as BTEX; benzene, toluene, ethylbenzene, and isomers of xylenes). TOMO has can hydroxylate more than a single position of aromatic rings in two consecutive monooxygenation reactions. Catechol 1,2-dioxygenase (C1,2D) is an iron-containing enzyme able to cleave the ring of catechol (the converted product from ToMO) for complete detoxification of BTEX. In this study, cold-active ToMO and C1,2D were produced using newly isolated psychrophilic Pseudomonas S2TR-14 in the minimal salt medium supplemented with crustacean waste and different concentrations of used motor oil (0.2-2% (v/v)). Crude ToMO and C1,2D were immobilized into micro/nano biochar-chitosan matrices and used for BTEX biodegradation. The results showed that the highest enzyme production (12 U/mg for ToMO and 22 U/mg for C1,2D) was achieved at the presence of 0.5% v/v used motor oil compared to the control group without motor oil (0.07 and 0.06 U/mg). High immobilization yield was achieved due to covalent bonding of ToMO (92.26% for micro matrix and 77.20% for nano matrix) and C1,2D (87.57% for micro matrix and 74.79% for nano matrix) with matrices. FTIR spectra confirmed the immobilization of enzymes on the surface of microbiochar and nanobiochar-chitosan matrices as proper support. The immobilization increased the storage stability of the enzymes with more than 50% residual activity after 30 days at 4 ± 1 °C, while the free form of enzymes had less than 10% of its activity. Immobilized enzymes degraded more than 80% of BTEX (~200 mg/L in groundwater and ~10,000 mg/kg in soil) at 10 ± 1 °C in groundwater and soil. Therefore, integrated use of microbiochar and nanobiochar with chitosan for co-immobilization of ToMO and C1,2D can be a potential way to remove petroleum hydrocarbons with higher efficiency from contaminated groundwater and soil.

Incorporation-limiting mechanisms during nitrogenation of monolayer graphene films in nitrogen flowing afterglows

Monolayer graphene films are exposed to the flowing afterglow of a low-pressure microwave nitrogen plasma, characterized by the absence of ion irradiation and significant populations of N atoms and N₂(A) metastables. Hyperspectral Raman imaging of graphene domains reveals damage generation with a progressive rise of the D/G and D/2D band ratios following subsequent plasma treatments. Plasma-induced damage is mostly zero-dimensional and the graphene state remains in the pre-amorphous regime. Over the range of experimental conditions investigated, damage formation increases with the fluence of energy provided by heterogenous surface recombination of N atoms and deexcitation of N₂(A) metastable species. In such conditions, X-ray photoelectron spectroscopy reveals that the nitrogen incorporation (either as pyridine, pyrrole, or quaternary moieties) does not simply increase with the fluence of plasma-generated N atoms but is also linked to the damage generation. Based on these findings, a surface reaction model for monolayer graphene nitrogenation is proposed. It is shown that the nitrogen incorporation is first limited by the plasma-induced formation of defect sites at low damage and then by the adsorption of nitrogen atoms at high damage.

Psychrozymes as novel tools to biodegrade p-xylene and potential use for contaminated groundwater in the cold climate

Sites contaminated by petroleum hydrocarbons in cold-climate regions have recently received significant attention due to their sensitive ecosystem and human health impacts. Two cold-adapted pseudomonas strains were isolated from contaminated groundwater and soil. As xylene monooxygenase from Pseudomonas synxantha S2TR-26 and catechol 2,3-dioxygenase from Pseudomonas mandelii S2TR-08, have a matching end product, they acted in symphony to degrade p-xylene. Their unique thermodynamic and kinetic behavior permits them to achieve rapid degradation of p-xylene at low temperatures (<15 °C). The results showed that the sequential action led to the conversion of 200 mg/l of p-xylene within 72 h and complete degradation after 120 h. The cocktail of these enzymes with a ratio of 1:1.5 (xylene monooxygenase: catechol 2, 3-dioxygenase) confirmed the complete degradation of p-xylene within 48 h at 15 °C. This approach will allow efficient biodegradation of p-xylene to minimize the bioremediation duration in cold-climate regions.

Preferential self-healing at grain boundaries in plasma-treated graphene

Engineering of defects located in grains or at grain boundaries is central to the development of functional materials. Although there is a surge of interest in the formation, migration and annihilation of defects during ion and plasma irradiation of bulk materials, these processes are rarely assessed in low-dimensional materials and remain mostly unexplored spectroscopically at the micrometre scale due to experimental limitations. Here, we use a hyperspectral Raman imaging scheme providing high selectivity and diffraction-limited spatial resolution to examine plasma-induced damage in a polycrystalline graphene film. Measurements conducted before and after very low-energy (11-13 eV) ion bombardment show defect generation in graphene grains following a zero-dimensional defect curve, whereas domain boundaries tend to develop as one-dimensional defects. Damage generation is slower at grain boundaries than within the grains, a behaviour ascribed to preferential self-healing. This evidence of local defect migration and structural recovery in graphene sheds light on the complexity of chemical and physical processes at the grain boundaries of two-dimensional materials.

Case report: Infant with a Fast-growing Soft Tissue Tumor on the Thumb, Revealing a PLAG1-positive Connatal Lipoblastoma

At the age of 4 months, an infant was presented to us with a nodular subcutaneous tumor on the right thumb measuring 2cm, already seen prenatally via ultrasound. An MRI in sedation performed at the age of 4.5 months had no diagnostic specificity. By a biopsy at the age of 5 months malignancy could be excluded. Finally at the age of 16 months the tumor which had meanwhile grown to a monstrous size (5 cm of diameter) could be entirely removed by microsurgical technique maintaining the integrity of all intrinsic structures. The diagnosis of myxoid lipoblastoma was confirmed. According to literature, Lipoblastomas often present as connatal rapid growing soft tissue tumors and are benign. Total removal is essential for avoiding a local recurrence.

RDX degradation by chemical oxidation using calcium peroxide in bench scale sludge systems

The ability of calcium peroxide (CaO₂) to degrade hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in contaminated soil slurries using CaO₂-based modified Fenton oxidation was investigated. Results showed that increasing the CaO₂ dose increased degradation rates of RDX and pH. RDX concentrations decreased to below detection after 18 h with 2 M and 2.5 M CaO₂, after 30 h with 1.5 M CaO₂, after 54 h with 1 M CaO₂, but 0.1 M CaO₂ achieved no significant RDX removal. Increasing the soil organic matter content decreased the rate and extent of RDX degradation. RDX degradation products 4-nitro-2,4-diazabutanal (NDAB) and methylenedinitramine (MEDINA) were quantified, and the greater accumulation of NDAB than MEDINA suggests denitration of RDX was the most likely initial degradation step. Isotopic ratios for nitrogen and oxygen associated with RDX oxidation are also consistent with either nitrification of NH₄⁺ from soil or precipitation. Existing technologies merely only extract energetics from soils for treatment ex situ, whereas the approach introduced herein destroys RDX in situ with a one-step application.

Confinement of Dyes inside Boron Nitride Nanotubes: Photostable and Shifted Fluorescence down to the Near Infrared

Fluorescence is ubiquitous in life science and used in many fields of research ranging from ecology to medicine. Among the most common fluorogenic compounds, dyes are being exploited in bioimaging for their outstanding optical properties from UV down to the near IR (NIR). However, dye molecules are often toxic to living organisms and photodegradable, which limits the time window for in vivo experiments. Here, it is demonstrated that organic dye molecules are passivated and photostable when they are encapsulated inside a boron nitride nanotube (dyes@BNNT). The results show that the BNNTs drive an aggregation of the encapsulated dyes, which induces a redshifted fluorescence from visible to NIR-II. The fluorescence remains strong and stable, exempt of bleaching and blinking, over a time scale longer than that of free dyes by more than 10⁴ . This passivation also reduces the toxicity of the dyes and induces exceptional chemical robustness, even in harsh conditions. These properties are highlighted in bioimaging where the dyes@BNNT nanohybrids are used as fluorescent nanoprobes for in vivo monitoring of Daphnia Pulex microorganisms and for diffusion tracking on human hepatoblastoma cells with two-photon imaging.

Probing plasma-treated graphene using hyperspectral Raman

Raman spectroscopy provides rich optical signals that can be used, after data analysis, to assess if a graphene layer is pristine, doped, damaged, functionalized, or stressed. The area being probed by a conventional Raman spectrometer is, however, limited to the size of the laser beam (∼1 µm); hence, detailed mapping of inhomogeneities in a graphene sample requires slow and sequential acquisition of a Raman spectrum at each pixel. Studies of physical and chemical processes on polycrystalline and heterogeneous graphene films require more advanced hyperspectral Raman capable of fast imaging at a high spatial resolution over hundreds of microns. Here, we compare the capacity of two different Raman imaging schemes (scanning and global) to probe graphene films modified by a low-pressure plasma treatment and present an analysis method providing assessments of the surface properties at local defects, grain boundaries, and other heterogeneities. By comparing statistically initial and plasma-treated regions of graphene, we highlight the presence of inhomogeneities after plasma treatment linked to the initial state of the graphene surface. These results provided statistical results on the correlation between the graphene initial state and the corresponding graphene-plasma interaction. This work further demonstrates the potential use of global hyperspectral Raman imaging with advanced Raman spectra analysis to study graphene physics and chemistry on a scale of hundreds of microns.

Bioremediation of Unconventional Oil Contaminated Ecosystems under Natural and Assisted Conditions: A Review

It is a general understanding that unconventional oil is petroleum-extracted and processed into petroleum products using unconventional means. The recent growth in the United States shale oil production and the lack of refineries in Canada built for heavy crude processes have resulted in a significant increase in U.S imports of unconventional oil since 2018. This has increased the risk of incidents and catastrophic emergencies during the transportation of unconventional oils using transmission pipelines and train rails. A great deal of effort has been made to address the remediation of contaminated soil/sediment following the traditional oil spills. However, spill response and cleanup techniques (e.g., oil recuperation, soil-sediment-water treatments) showed slow and inefficient performance when it came to unconventional oil, bringing larger associated environmental impacts in need of investigation. To the best of our knowledge, there is no coherent review available on the biodegradability of unconventional oil, including Dilbit and Bakken oil. Hence, in view of the insufficient information and contrasting results obtained on the remediation of petroleum, this review is an attempt to fill the gap by presenting the collective understanding and critical analysis of the literature on bioremediation of products from the oil sand and shale (e.g., Dilbit and Bakken oil). This can help evaluate the different aspects of hydrocarbon biodegradation and identify the knowledge gaps in the literature.

Reaching out to reduce health inequities for Māori youth

AIM

This paper describes an initiative facilitating comprehensive assessment and delivery of brief interventions for Māori youth in Northland, New Zealand.

BACKGROUND

The population in Northland is predominantly Māori and is one of New Zealand's most deprived populations. Māori youth have the highest youth suicide rate in the developed world and elevated numbers of youth displaying mental health issues and/or risk behaviours are of grave national concern. Like Indigenous peoples worldwide, inequities persist for Māori youth accessing and engaging with healthcare services.

DESCRIPTION

Taking services out to Māori youth in remote and isolated areas, Northland's youth specialist nurses are reducing some barriers to accessing health care. The youth version of the Case-finding and Help Assessment Tool is a New Zealand-developed, e-screening tool for youth psychosocial issues, facilitating comprehensive assessment and brief intervention delivery.

DISCUSSION

Early detection of, and timely intervention for, mental health and risk behaviours can significantly improve health outcomes in youth. However, for this to happen barriers preventing youth from accessing appropriate care need to be overcome.

CONCLUSION

Youth specialist nurses could improve access to care for youth from ethnic minorities, rural and isolated regions, and areas of high deprivation without overwhelming the medical profession.

IMPLICATIONS FOR NURSING POLICY

Specialist nurses are trained and empowered to practice at the top of their scope. With general practitioner oversight and standing order sign off specialist nurses can work autonomously to improve access to health services, without increasing the workload of doctors.

IMPLICATIONS FOR NURSING PRACTICE

Encouraging continuous self-reflection of the nurse's effectiveness in meeting patient needs, holistically and culturally, facilitates the provision of accessible care that is patient-centred and culturally safe.

Etched glass micromodel for laboratory simulation of NAPL recovery mechanisms by surfactant solutions in fractured rock

Fractured porous media receive less attention than classic porous media in terms of remediation processes and sui` techniques that can be applied efficiently. An etched glass micromodel was built in order to simulate a fractured bedrock. The purpose of this paper was to evaluate the feasibility of surfactant-alcohol injection to recover NAPL with this fractured glass micromodel. The influence of several parameters influencing NAPL recovery via surfactant injection were tested in the micromodel: the ratio of alcohol to surfactant, the total concentration of active matter (alcohol + surfactant), the number of pore volume injected, the direction of the injection, and the continuous or pulsed injection mode. These tests made it possible to identify the key parameters for a better recovery of NAPL in a fractured environment, which are: continuous upward injection, six pore volume of surfactant solution and a n-AmOH/n-BuOH ratio of 2.5. Micromodel experiments were compared to previous reported experiments using the same surfactant solutions injected in classical porous media. The lower capillary number being required for NAPL recovery in porous media is probably related to the better sweep and the increase in surface area available for NAPL dissolution. NAPL recovery may be improved by increasing the capillary number by increasing the injected surfactant solution viscosity with polymer or by injecting foam.

Momentum-Resolved Dielectric Response of Free-Standing Mono-, Bi-, and Trilayer Black Phosphorus

Black phosphorus (BP), a 2D semiconducting material of interest in electronics and photonics, exhibits physical properties characterized by strong anisotropy and band gap energy that scales with reducing layer number. However, the investigation of its intrinsic properties is challenging because thin-layer BP is photo-oxidized under ambient conditions and the energy of its electronic states shifts in different dielectric environments. We prepared free-standing samples of few-layer BP under glovebox conditions and probed the dielectric response in a vacuum using scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS). Thresholds of the excitation energy are measured at 1.9, 1.4, and 1.1 eV for the mono-, bi-, and trilayer BP, respectively, and these values are used to estimate the corresponding optical band gaps. A comparison of our results with electronic structure calculations indicates that the variation of the quasi-particle gap is larger than that of the exciton binding energy. The dispersion of the plasmons versus momentum for one- to three-layer BP and bulk BP highlights a deviation from parabolic to linear dispersion and strong anisotropic fingerprints.

Resonant, Plasmonic Raman Enhancement of α-6T Molecules Encapsulated in Carbon Nanotubes

Surface-enhanced Raman scattering (SERS) and resonant Raman scattering are widely used techniques to enhance the Raman intensity of molecules and nanomaterials by several orders of magnitude. In SERS, typically, molecules are investigated and their intrinsic resonance is often ignored while discussing the plasmonic enhancement. Here, we study α-sexithiophenes encapsulated in carbon nanotubes placed in the center of a nanodimer. By dielectrophoretic deposition, we place the nanotubes precisely in the center of a plasmonic gold nanodimer and observe SERS enhancement from individual tube bundles. The encapsulated molecules are not subjected to chemical enhancement because of the protective character of the nanotube. Polarization-dependent Raman measurements confirm the alignment of the molecules within the carbon nanotubes (CNTs) and reveal the influence of the plasmonic near field on the molecule's Raman intensity. We investigate the encapsulated molecules in small CNT bundles with and without plasmonic enhancement and determine the molecular and plasmonic resonance by tuning the excitation wavelength. We observe a strong red shift of the maximum Raman intensity under plasmonic enhancement toward the plasmon resonance.

Alignment of semiconducting graphene nanoribbons on vicinal Ge(001)

Chemical vapor deposition of CH4 on Ge(001) can enable anisotropic growth of narrow, semiconducting graphene nanoribbons with predominately smooth armchair edges and high-performance charge transport properties. However, such nanoribbons are not aligned in one direction but instead grow perpendicularly, which is not optimal for integration into high-performance electronics. Here, it is demonstrated that vicinal Ge(001) substrates can be used to synthesize armchair nanoribbons, of which ∼90% are aligned within ±1.5° perpendicular to the miscut. When the growth rate is slow, graphene crystals evolve as nanoribbons. However, as the growth rate increases, the uphill and downhill crystal edges evolve asymmetrically. This asymmetry is consistent with stronger binding between the downhill edge and the Ge surface, for example due to different edge termination as shown by density functional theory calculations. By tailoring growth rate and time, nanoribbons with sub-10 nm widths that exhibit excellent charge transport characteristics, including simultaneous high on-state conductance of 8.0 μS and a high on/off conductance ratio of 570 in field-effect transistors, are achieved. Large-area alignment of semiconducting ribbons with promising charge transport properties is an important step towards understanding the anisotropic nanoribbon growth and integrating these materials into scalable, future semiconductor technologies.

Assessment of vulnerability and control measures to protect the Salbarua ecosystem from hypothetical spill sites

Population pressure, urbanization, and industrial developments, among other factors, have resulted in severe degradation of environmental resources such as wetlands. Thus, a groundwater model (MODFLOW) was integrated with a particle tracking MODPATH model to simulate the hydrodynamic flow head field and to analyze the vulnerability of the Salburua ecosystem and propose control measures to protect the riparian area. The simulations show that pathways of particle tracking originating at potential contaminant sources will tend to migrate downwards towards the sensitive ecosystem, which suggests that the quality of the hydrological ecosystem is likely to deteriorate in the future. Variation in exit points of particles indicates that the time-related capture areas are affected by changes of the hydraulic gradients. Two control measures of potential sources of pollutants in the vicinity of the Salbarua ecosystem were analyzed. The study results suggest that the travel time-related capture zone with a funnel-and-gate system is much smaller than without the control alternative, which indicates that the gate configuration has an effect on capture zone size and shape and on the residence time with a better attenuation performance. It is also shown that a leakage-proof barrier is less effective for point-source containment, assuming that hydraulic control performance and cost-efficiency are the criteria for pollution control effectiveness. Instead, a program of monitoring wells would effectively characterize water quality in the aquifer and provide a decision support system. This approach may be used in helping water managers to develop more physically based and quantitative protection strategies.

Comparative Study of Various Types of Metal-Free N and S Co-Doped Porous Graphene for High Performance Oxygen Reduction Reaction in Alkaline Solution

Heteroatom doping into carbon structures is an effective approach to enhance the electrochemical performance of carbon materials. In the work presented here, the electrocatalysts including: nitrogen and co-doped nitrogen and sulfur on porous graphene (PG) were synthesized by different precursors. The physico-chemical properties of the prepared samples were determined using X-ray Diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), N2 sorption-desorption, Transmission electron microscopy (TEM), Field Emission Scanning Electron Microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The prepared samples were further applied for oxygen reduction reaction (ORR) and the effects of pyrolysis temperature, precursor type and dose, on the prepared samples structure and their electrochemical performances were investigated. The results revealed that synergistic effect of nitrogen and sulfur co-doped on the graphene structure leads to improvement in catalytic activity and current. Furthermore, S and N co-doped graphene prepared using sulfur trioxide pyridine complex exhibited excellent methanol tolerance and long-term stability.

Second-Order Raman Scattering in Exfoliated Black Phosphorus

Second-order Raman scattering has been extensively studied in carbon-based nanomaterials, for example, nanotube and graphene, because it activates normally forbidden Raman modes that are sensitive to crystal disorder, such as defects, dopants, strain, and so forth. The sp²-hybridized carbon systems are, however, the exception among nanomaterials, where first-order Raman processes usually dominate. Here we report the identification of four second-order Raman modes, named D₁, D₁^', D₂ and D₂^', in exfoliated black phosphorus (P(black)), an elemental direct-gap semiconductor exhibiting strong mechanical and electronic anisotropies. Located in close proximity to the A_g¹ and A_g² modes, these new modes dominate at an excitation wavelength of 633 nm. Their evolutions as a function of sample thickness, excitation wavelength, and defect density indicate that they are defect-activated and involve high-momentum phonons in a doubly resonant Raman process. Ab initio simulations of a monolayer reveal that the D' and D modes occur through intravalley scatterings with split contributions in the armchair and zigzag directions, respectively. The high sensitivity of these D modes to disorder helps explaining several discrepancies found in the literature.

Cellular imaging by targeted assembly of hot-spot SERS and photoacoustic nanoprobes using split-fluorescent protein scaffolds

The in cellulo assembly of plasmonic nanomaterials into photo-responsive probes is of great interest for many bioimaging and nanophotonic applications but remains challenging with traditional nucleic acid scaffolds-based bottom-up methods. Here, we address this quandary using split-fluorescent protein (FP) fragments as molecular glue and switchable Raman reporters to assemble gold or silver plasmonic nanoparticles (NPs) into photonic clusters directly in live cells. When targeted to diffusing surface biomarkers in cancer cells, the NPs self-assemble into surface-enhanced Raman-scattering (SERS) nanoclusters having hot spots homogenously seeded by the reconstruction of full-length FPs. Within plasmonic hot spots, autocatalytic activation of the FP chromophore and near-field amplification of its Raman fingerprints enable selective and sensitive SERS imaging of targeted cells. This FP-driven assembly of metal colloids also yields enhanced photoacoustic signals, allowing the hybrid FP/NP nanoclusters to serve as contrast agents for multimodal SERS and photoacoustic microscopy with single-cell sensitivity.

Traditional methods for the assembly of plasmonic nanoparticles into photo-responsive probes suffer from multiple problems. Here the authors use split fluorescent protein fragments as molecular glue to form stable nanoclusters for surface enhanced Raman scattering and photoacoustic imaging in live cells.

Electrostatic Deposition of Large-Surface Graphene

This work describes a method for electrostatic deposition of graphene over a large area using controlled electrostatic exfoliation from a Highly Ordered Pyrolytic Graphite (HOPG) block. Deposition over 130 × 130 µm² with 96% coverage is achieved, which contrasts with sporadic micro-scale depositions of graphene with little control from previous works on electrostatic deposition. The deposition results are studied by Raman micro-spectroscopy and hyperspectral analysis using large fields of view to allow for the characterization of the whole deposition area. Results confirm that laser pre-patterning of the HOPG block prior to cleaving generates anchor points favoring a more homogeneous and defect-free HOPG surface, yielding larger and more uniform graphene depositions. We also demonstrate that a second patterning of the HOPG block just before exfoliation can yield features with precisely controlled geometries.

A Conceptual Model of Fate and Transport Processes for RDX Deposited to Surface Soils of North American Active Demolition Sites

The use of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) as an energetic material (EM) in ammunition constituents such as detonators, primers, mines, and rocket boosters and in plastic explosives has led to an international warning on possible soil, surface water, and groundwater contamination on military training sites. In Canada, the demolition sites of range training areas are known to be the second most contaminated sites by EM residues in terms of their concentrations in soil after anti-tank ranges. This research proposes a conceptual model of the presence of RDX at the field scale at demolition sites according to previous soil and water characterization studies. This model illustrates the origin of RDX contamination, the main RDX transport pathways and processes, and the main threatened receptors. This conceptual model is of importance to visualize and understand RDX's environmental fate and behavior and to ultimately enable the production of a detailed quantitative model that can help to manage those RDX-contaminated sites.

Impact of heterogeneous properties of soil and LNAPL on surfactant-enhanced capillary desaturation

This paper investigates low-concentration (<1wt%) surfactant flushing when used as a follow-up technology for multiphase vacuum extraction on heterogeneous sites. Challenges posed by soil permeability, pore-size distribution, mineralogy, light non-aqueous phase liquid (LNAPL) weathering and groundwater hardness were quantified through batch and soil column tests. Compatibility issues between the mixed mineralogy soils, hard groundwater, mixed LNAPL and usual anionic surfactants were observed. The selected solution was a Winsor type I system promoting an interfacial tension of 0.06mN/m between the site LNAPL and the amphoteric surfactant CAS in aqueous solution at pH12. Surfactant loses to adsorption and pore media plugging were observed in the fine soil fraction. The capillary desaturation curves (CDC) obtained with the column tests suggested mixed-wettability behavior. The soil permeability strongly influenced LNAPL recovery, as expressed by the relationship obtained between capillary numbers (N_Ca) and hydraulic gradients. In this case, the critical N_Ca, marking the onset of capillary desaturation, could only be obtained with realistic hydraulic gradients in the coarse soil fraction. At those gradients, potential LNAPL recovery was 30% at the most. Unlike previously published CDCs, the relationship between N_Ca (log-scale) and LNAPL recovery was not linear but dependant on residual LNAPL saturation.

Synthesis of Antimonene on Germanium

The lack of large-area synthesis processes on substrates compatible with industry requirements has been one of the major hurdles facing the integration of 2D materials in mainstream technologies. This is particularly the case for the recently discovered monoelemental group V 2D materials which can only be produced by exfoliation or growth on exotic substrates. Herein, to overcome this limitation, we demonstrate a scalable method to synthesize antimonene on germanium substrates using solid-source molecular beam epitaxy. This emerging 2D material has been attracting a great deal of attention due to its high environmental stability and its outstanding optical and electronic properties. In situ low energy electron microscopy allowed the real time investigation and optimization of the 2D growth. Theoretical calculations combined with atomic-scale microscopic and spectroscopic measurements demonstrated that the grown antimonene sheets are of high crystalline quality, interact weakly with germanium, exhibit semimetallic characteristics, and remain stable under ambient conditions. This achievement paves the way for the integration of antimonene in innovative nanoscale and quantum technologies compatible with the current semiconductor manufacturing.

A field-deployed surface plasmon resonance (SPR) sensor for RDX quantification in environmental waters

A field-deployable surface plasmon resonance (SPR) sensor is reported for the detection RDX at ppb concentration in environmental samples.

Plasmonic enhancement of SERS measured on molecules in carbon nanotubes

We isolated the plasmonic contribution to surface-enhanced Raman scattering (SERS) and found it to be much stronger than expected. Organic dyes encapsulated in single-walled carbon nanotubes are ideal probes for quantifying plasmonic enhancement in a Raman experiment. The molecules are chemically protected through the nanotube wall and spatially isolated from the metal, which prevents enhancement by chemical means and through surface roughness. The tubes carry molecules into SERS hotspots, thereby defining molecular position and making it accessible for structural characterization with atomic-force and electron microscopy. We measured a SERS enhancement factor of 10⁶ on α-sexithiophene (6T) molecules in the gap of a plasmonic nanodimer. This is two orders of magnitude stronger than predicted by the electromagnetic enhancement theory (10⁴). We discuss various phenomena that may explain the discrepancy (including hybridization, static and dynamic charge transfer, surface roughness, uncertainties in molecular position and orientation), but found all of them lacking in enhancement for our probe system. We suggest that plasmonic enhancement in SERS is, in fact, much stronger than currently anticipated. We discuss novel approaches for treating SERS quantum mechanically that appear promising for predicting correct enhancement factors. Our findings have important consequences on the understanding of SERS as well as for designing and optimizing plasmonic substrates.

Polarization-Resolved Raman Study of Bulk-like and Davydov-Induced Vibrational Modes of Exfoliated Black Phosphorus

Owing to its crystallographic structure, black phosphorus is one of the few 2D materials expressing strongly anisotropic optical, transport, and mechanical properties. We report on the anisotropy of electron-phonon interactions through a polarization-resolved Raman study of the four vibrational modes of atomically thin black phosphorus (2D phosphane): the three bulk-like modes A_g¹, B_2g, and A_g² and the Davydov-induced mode labeled A_g(B_2u). The complex Raman tensor elements reveal that the relative variation in permittivity of all A_g modes is irrespective of the atomic motion involved lowest along the zigzag direction, the basal anisotropy of these variations is most pronounced for A_g² and A_g(B_2u), and interlayer interactions in multilayer samples lead to reduced anisotropy. The bulk-forbidden A_g(B_2u) mode appears for n ≥ 2 and quickly subsides in thicker layers. It is assigned to a Davydov-induced IR to Raman conversion of the bulk IR mode B_2u and exhibits characteristics similar to A_g². Although this mode is expected to be weak, an electronic resonance significantly enhances its Raman efficiency such that it becomes a dominant mode in the spectrum of bilayer 2D phosphane.

Aggregation Control of α-Sexithiophene via Isothermal Encapsulation Inside Single-Walled Carbon Nanotubes

Liquid-phase encapsulation of α-sexithiophene (6T) molecules inside individualized single-walled carbon nanotubes (SWCNTs) is investigated using Raman imaging and spectroscopy. By taking advantage of the strong Raman response of this system, we probe the encapsulation isotherms at 30 and 115 °C using a statistical ensemble of SWCNTs deposited on a oxidized silicon substrate. Two distinct and sequential stages of encapsulation are observed: Stage 1 is a one-dimensional (1D) aggregation of 6T aligned head-to-tail inside the nanotube, and stage 2 proceeds with the assembly of a second row, giving pairs of aligned 6Ts stacked together side-by-side. The experimental data are fitted using both Langmuir (type VI) and Ising models, in which the single-aggregate (stage 1) forms spontaneously, whereas the pair-aggregate (stage 2) is endothermic in toluene with formation enthalpy of ΔH_pair = (260 ± 20) meV. Tunable Raman spectroscopy for each stage reveals a bathochromic shift of the molecular resonance of the pair-aggregate, which is consistent with strong intermolecular coupling and suggestive of J-type aggregation. This quantitative Raman approach is sensitive to roughly 10 molecules per nanotube and provides direct evidence of molecular entry from the nanotube ends. These insights into the encapsulation process guide the preparation of well-defined 1D molecular crystals having tailored optical properties.

Assessing Groundwater Depletion and Dynamics Using GRACE and InSAR: Potential and Limitations

In the last decade, remote sensing of the temporal variation of ground level and gravity has improved our understanding of groundwater dynamics and storage. Mass changes are measured by GRACE (Gravity Recovery and Climate Experiment) satellites, whereas ground deformation is measured by processing synthetic aperture radar satellites data using the InSAR (Interferometry of Synthetic Aperture Radar) techniques. Both methods are complementary and offer different sensitivities to aquifer system processes. GRACE is sensitive to mass changes over large spatial scales (more than 100,000 km² ). As such, it fails in providing groundwater storage change estimates at local or regional scales relevant to most aquifer systems, and at which most groundwater management schemes are applied. However, InSAR measures ground displacement due to aquifer response to fluid-pressure changes. InSAR applications to groundwater depletion assessments are limited to aquifer systems susceptible to measurable deformation. Furthermore, the inversion of InSAR-derived displacement maps into volume of depleted groundwater storage (both reversible and largely irreversible) is confounded by vertical and horizontal variability of sediment compressibility. During the last decade, both techniques have shown increasing interest in the scientific community to complement available in situ observations where they are insufficient. In this review, we present the theoretical and conceptual bases of each method, and present idealized scenarios to highlight the potential benefits and challenges of combining these techniques to remotely assess groundwater storage changes and other aspects of the dynamics of aquifer systems.

2D sandbox experiments of surfactant foams for mobility control and enhanced LNAPL recovery in layered soils

The ability of surfactant foam to enhance mobility control and LNAPL recovery in a heterogeneous porous media was investigated through sandbox experiments with p-xylene used as LNAPL. A layered heterogeneous porous media was represented in a 2D sandbox filled with two layers of coarse and medium silica sand. Based on previous tests, the surfactant solution used was Ammonyx Lo at a concentration of 0.1% (w/w). The sandbox experimental program included tracer tests done under both uncontaminated and contaminated conditions, foam injection under uncontaminated conditions and surfactant solution and foam injection under contaminated conditions. Tracer tests indicated that the permeability contrast between sand layers was increased by LNAPL contamination. Foam injection under uncontaminated conditions presented a S-shaped front that indicated a better mobility control than the piston-shaped front obtained during tracer tests. During foam injection, complete sweep of the sandbox was achieved with 1.8pore volume (PV) compared to 2.8PV during tracer injection, thus indicating better mobility control with foam. Pre-flush of the contaminated sandbox with surfactant solution initiated p-xylene mobilization but no free phase was recovered at the effluent. A negligible p-xylene residual saturation was reached following foam injection in the contaminated sandbox. However, mass balance indicated a total recovery of only 48% of the initial p-xylene, thus indicating an underestimation of the recovery by volatilization. Recovery by volatilization was corrected, which gave the following proportions of LNAPL recovery mechanisms: 19% by mobilization, 16% by dissolution and 65% by volatilization. Results show the potential efficiency of foam remediation of LNAPL source zones in heterogeneous porous media. Still, further developments are needed prior to field scale application, which could benefit from in situ foam production that would simplify on-site operations.

Effect of energetic materials wettability on their outdoor effective elution rate

Energetic materials (EM) contained in military ammunitions have been found in the surface soil and water of training areas and may potentially represent a threat to human health and the environment. EM wettability is an essential physical parameter to characterize because it controls EM dissolution rate. This paper was conducted to determine the wettability of conventional and new EM formulations used in military ammunition. Wettability was estimated in the laboratory via contact angle measurements of water droplets on different EM surfaces. Results show that 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazinane (RDX), Octol and energetic thermoplastic elastomer (ETPE) 1000 are hydrophilic while Composition B, XRT, GIM, CX-85, ETPE 2000, and C4 are hydrophobic whereas HELOVA gun propellant has a mixed wettability oscillating between hydrophilic and hydrophobic. The present study demonstrates that wettability of EM formulation is generally controlled by their matrix constituents. Results indicate that hydrophobic formulations have a much slower outdoor environmental effective elution rate than hydrophilic ones, with the exception of the hydrophobic C4 formulation whose elution rate is extremely high. The addition of hydrophobic components into EM formulations is recommended to diminish the environmental impact on water, as it has already been done with XRT, GIM and CX-85 formulations.

Dynamics and Mechanisms of Exfoliated Black Phosphorus Sublimation

We report on real time observations of the sublimation of exfoliated black phosphorus layers throughout annealing using in situ low energy electron microscopy. We found that sublimation manifests itself above 375 ± 20 °C through the nucleation and expansion of asymmetric, faceted holes with the long axis aligned along the [100] direction and sharp tips defined by edges consisting of alternating (10) and (11) steps. This thermally activated process repeats itself via successive sublimation of individual layers. Calculations and simulations using density functional theory and kinetic Monte Carlo allowed to determine the involved atomic pathways. Sublimation is found to occur via detachments of phosphorus dimers rather than single atoms. This behavior and the role of defects is described using an analytical model that captures all essential features. This work establishes an atomistic-level understanding of the thermal stability of exfoliated black phosphorus and defines the temperature window available for material and device processing.

Distance to faults as a proxy for radon gas concentration in dwellings

This research was done to demonstrate the usefulness of the local structural geology characteristics to predict indoor radon concentrations. The presence of geologic faults near dwellings increases the vulnerability of the dwellings to elevated indoor radon by providing favorable pathways from the source uranium-rich bedrock units to the surface. Kruskal-Wallis one-way analyses of variance by ranks were used to determine the distance where faults have statistically significant influence on indoor radon concentrations. The great-circle distance between the 640 spatially referenced basement radon concentration measurements and the nearest fault was calculated using the Haversine formula and the spherical law of cosines. It was shown that dwellings located less than 150 m from a major fault had a higher radon potential. The 150 m threshold was determined using Kruskal-Wallis ANOVA on: (1) all the basement radon measurements dataset and; (2) the basement radon measurements located on uranium-rich bedrock units only. The results indicated that 22.8% of the dwellings located less than 150 m from a fault exceeded the Canadian radon guideline of 200 Bq/m(3) when using all the basement radon measurements dataset. This percentage fell to 15.2% for the dwellings located between 150 m and 700 m from a fault. When using only the basement radon measurements located on uranium-rich bedrock units, these percentages were 30.7% (0-150 m) and 17.5% (150 m-700 m). The assessment and management of risk can be improved where structural geology characteristics base maps are available by using this proxy indicator.

Direct oriented growth of armchair graphene nanoribbons on germanium

Graphene can be transformed from a semimetal into a semiconductor if it is confined into nanoribbons narrower than 10 nm with controlled crystallographic orientation and well-defined armchair edges. However, the scalable synthesis of nanoribbons with this precision directly on insulating or semiconducting substrates has not been possible. Here we demonstrate the synthesis of graphene nanoribbons on Ge(001) via chemical vapour deposition. The nanoribbons are self-aligning 3° from the Ge〈110〉 directions, are self-defining with predominantly smooth armchair edges, and have tunable width to <10 nm and aspect ratio to >70. In order to realize highly anisotropic ribbons, it is critical to operate in a regime in which the growth rate in the width direction is especially slow, <5 nm h⁻¹. This directional and anisotropic growth enables nanoribbon fabrication directly on conventional semiconductor wafer platforms and, therefore, promises to allow the integration of nanoribbons into future hybrid integrated circuits.

Semiconducting armchair graphene nanoribbons with sub-10 nm width are of great technological importance but yet to realize. Here, the authors report growth of such nanoribbons on germanium and controlled crystallographic orientation and well-defined armchair edges are obtained.