A batch processed titanium-vanadium oxide nanocomposite based solid-state electrochemical sensor for zeptomolar nucleic acid detection

Approaching a nucleic acid amplification test (NAAT) based diagnosis of a pathogen from an electrochemistry pathway is a relatively economical, decentralized, and yet highly sensitive route. This work aimed to construct an electrochemical biosensor with a 2-electrode geometry using a transition metal oxide (TMO) based sensing layer. A series of batch-processed TiO₂-V₂O₅ (TVO) nanocomposite-based electrodes were fabricated to probe their electrochemical performance and attain a highly sensitive dual-electrode electrochemical sensor (DEES) compared to pristine V₂O₅. The XRD analysis of the electrodes confirmed the formation of a nanocomposite, while the XPS analysis correlated the formation of oxygen vacancies with improved electrical conduction measured via EIS and I-V characterization. Furthermore, the work demonstrated the application of the optimized electrode in electrochemical detection of end-point loop-mediated isothermal amplification (LAMP) readout for 10¹-10⁴ copies (0.1 zeptomoles to 0.1 attomoles) of SARS-CoV-2 RNA dependent RNA polymerase (RdRp) plasmid DNA and in vitro transcribed RNA in an aqueous solution. The device achieved a limit of detection as low as 2.5 and 0.25 copies per μL for plasmid DNA and in vitro transcribed RNA, respectively. The DEES was able to successfully detect in situ LAMP performed on magneto-extracted SARS-CoV-2 plasmid and RNA from (a) an aqueous solution, (b) a sample spiked with excess human genomic DNA, and (c) a serum-spiked sample. The DEES results were then compared with those of real-time fluorescence and commercially available screen-printed electrodes (SPEs).

Stereometric analysis of Ti1- x Alx N thin films deposited by direct current/radio frequency magnetron sputtering

A study of image analysis of Ti_1-x Al_x N films deposited on corning glass substrates by a direct current (DC)/radio frequency (RF) magnetron sputtering system was performed. Atomic force microscopy (AFM) data were studied to understand how the impact of the concentration of Al content influences the 3D surface morphology as well as the surface texture parameters. The results showed that the superficial morphology was modified by the increase of Al content in the Ti_1-x Al_x N films, as well as the surface microtexture. It has also been observed that the Ti_1-x Al_x N film surface with the highest aluminum (Al) doping concentration presented a similar surface morphology to pristine titanium nitride (TiN) thin films. The Abbott-Firestone curves for all films exhibited an S-like shape suggesting topographic uniformity and Gaussian distribution of heights. An increase in surface uniformity is observed with Al concentration. The characterization of the surface morphology of Ti_1-x Al_x N films by the evaluation of surface statistical parameters suggests that the surface topography can be adjusted by suitable doping of aluminum and offers a deeper understanding of the applicability of these films.

Elevated performance of binder-free Co3O4 electrode for the supercapacitor applications

In the present work, we have designed a symmetric supercapacitor (SS) device by synthesizing a pseudocapacitive binder-free cobalt oxide (Co3O4) thin film based electrode using reactive DC magnetron sputtering technique. The thin film electrodes were characterized by x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy to reveal the crystallographic details, stoichiometry, and electronic configuration, respectively. Furthermore, Co3O4 thin film electrode is used for pseudocapacitor and electrochemically tested in 1M aqueous KOH electrolyte solution, in addition, a symmetric supercapacitor (SS) device was fabricated. It was found that the SS device exhibits tremendous electrochemical stability in terms of high capacitance and good cycling stability. The value of specific capacitance for Co3O4 thin film electrodes and the SS device was calculated to be 392 Fg−1 and 95 Fg−1, respectively, at a scan rate of 2 mAcm−2. The SS device exhibits high specific energy (29 W-hkg−1) along with comparable good specific power (4745 Wkg−1). In this work, the fabricated SS device demonstrates 91.40% cyclic and capacitance retention at 8 mAcm−2 beyond 10 000 cycles. The excellent electrochemical stability and capacitive performance of the SS device suggest that it would be an ideal and potential candidate for energy storage applications in the future.

Electron energy loss spectroscopy analysis of the interaction of Cr and V with MWCNTs

The presented scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) results show the strong reaction of Cr and V with the graphitic walls of MWCNTs. For Vanadium, an interfacial VC layer could be observed at the interface between VN and MWCNTs, when the samples were heated in situ to 750°C. Knowledge about this interfacial VC layer is important for the formation of VN-MWCNT hybrid materials, used in supercapacitor electrodes, often synthesized at high temperatures. Chromium reacts at 500°C with the MWCNTs to form Cr3C2 and in some cases, dissolved the MWCNT completely. Together with the previously published results about the interaction of MWCNTs with Cu (no interaction) and Ni (a slight rehybridisation trend for the outermost MWCNT-wall observed with EELS) (Ilari et al., 2015) the influence of the valence d-orbital occupancy of 3d transition metals on the interaction strength with CNTs is shown experimentally. For a transition metal to form chemical bonds towards CNT-walls, unoccupied states in its valence d-orbitals are needed. While Ni (2 unoccupied states) interacts only slightly, Cr (5 unoccupied states) and V (7 unoccupied states) react much stronger and can dissolve the MWCNTs, at least partially.

Morphology and crystallinity control of ultrathin TiO2 layers deposited on carbon nanotubes by temperature-step atomic layer deposition

Carbon nanotubes (CNTs) coated with titanium oxide (TiO2) have generated considerable interest over the last decade and become a promising nanomaterial for a wide range of energy applications. The efficient use of the outstanding electrical properties of this nanostructure relies heavily on the quality of the interface and the thickness and morphology of the TiO2 layer. However, complete surface coverage of the chemically inert CNTs and appropriate control of the morphology of the TiO2 layer have not been achieved so far. Here, we report a new strategy to obtain ultrathin TiO2 coatings deposited by "Temperature-step" Atomic Layer Deposition (TS-ALD) with complete surface coverage of non-functionalized multiwall carbon nanotubes (MWCNTs) and controlled morphology and crystallinity of the TiO2 film. This strategy consists of adjusting the temperature during the ALD deposition to obtain the desired morphology. Complete coverage of long non-functionalized MWCNTs with conformal anatase layers was obtained by using a low temperature of 60 °C during the nucleation stage followed by an increase to 220 °C during the growth stage. This resulted in a continuous and amorphous TiO2 layer, covered with a conformal anatase coating. Starting with the deposition at 220 °C and reducing to 60 °C resulted in sporadic crystal grains at the CNT/TiO2 interface covered with an amorphous TiO2 layer. The results were accomplished through an extensive study of nucleation and growth of titanium oxide films on MWCNTs, of which a detailed characterization is presented in this work.

Use of radiofrequency power to enable glow discharge optical emission spectroscopy ultrafast elemental mapping of combinatorial libraries with nonconductive components: nitrogen-based materials

Combinatorial chemistry and high-throughput techniques are an efficient way of exploring optimal values of elemental composition. Optimal composition can result in high performance in a sequence of material synthesis and characterization. Materials combinatorial libraries are typically encountered in the form of a thin film composition gradient which is produced by simultaneous material deposition on a substrate from two or more sources that are spatially separated and chemically different. Fast spatially resolved techniques are needed to characterize structure, composition, and relevant properties of these combinatorial screening samples. In this work, the capability of a glow discharge optical emission spectroscopy (GD-OES) elemental mapping system is extended to nitrogen-based combinatorial libraries with nonconductive components through the use of pulsed radiofrequency power. The effects of operating parameters of the glow discharge and detection system on the achievable spatial resolution were investigated as it is the first time that an rf source is coupled to a setup featuring a push-broom hyperspectral imaging system and a restrictive anode tube GD source. Spatial-resolution optimized conditions were then used to characterize an aluminum nitride/chromium nitride thin-film composition spread. Qualitative elemental maps could be obtained within 16.8 s, orders of magnitude faster than typical techniques. The use of certified reference materials allowed quantitative elemental analysis maps to be extracted from the emission intensity images. Moreover, the quantitative procedure allowed correcting for the inherent emission intensity inhomogeneity in GD-OES. The results are compared to quantitative depth profiles obtained with a commercial GD-OES instrument.

Modeling and optimization of atomic layer deposition processes on vertically aligned carbon nanotubes

Many energy conversion and storage devices exploit structured ceramics with large interfacial surface areas. Vertically aligned carbon nanotube (VACNT) arrays have emerged as possible scaffolds to support large surface area ceramic layers. However, obtaining conformal and uniform coatings of ceramics on structures with high aspect ratio morphologies is non-trivial, even with atomic layer deposition (ALD). Here we implement a diffusion model to investigate the effect of the ALD parameters on coating kinetics and use it to develop a guideline for achieving conformal and uniform thickness coatings throughout the depth of ultra-high aspect ratio structures. We validate the model predictions with experimental data from ALD coatings of VACNT arrays. However, the approach can be applied to predict film conformality as a function of depth for any porous topology, including nanopores and nanowire arrays.

Interfacial coherency stress distribution in TiN/AlN bilayer and multilayer films studied by FEM analysis

The development of interfacial coherency stresses in TiN/AlN bilayer and multilayer films was investigated by finite element method (ABAQUS) using the four-node bilinear quadrilateral axisymmetric element CAX4R. The TiN and AlN layers are always in compression and tension at the interface, respectively, as may be expected from the fact TiN has larger lattice parameter than AlN. Both, the bi-layer and the multilayer stacks bend due to the coherency stresses. For the TiN/AlN bilayer system, the curvature of the bending is largest for the TiN/AlN thickness ratios ∼0.5 and ∼2 (at which one of the two layers is fully in compression or tension), while it is smaller for the layers with the same thickness (at which both layers posses regions with compressive as well as tensile stresses). This stress distribution over the bi-layer thickness is shown to be strongly influenced by the presence and the properties of a substrate. Furthermore, the coherency stress profile and specimen curvature of a TiN/AlN multilayer system was studied as a function of the top-most layer thickness. The curvature is maximum for equal number of TiN and AlN layers, and decreases with increasing the number of TiN/AlN periods. Within the growth of an additional TiN/AlN bilayer, the curvature first decreases to zero for a vertically symmetrical geometry over the layers when the TiN layer growth is finished (e.g. for (n + 1) layers of TiN and n layers of AlN). At this stage, the coherency stresses in TiN and AlN are same in each layer type (independent on the layer position). The growth of the second half of the TiN/AlN bi-layer (i.e. the AlN) to finish the period, again bends the specimen, and generates a non-uniform stress distribution. This suggests that the top layer as well as the overall specimen geometry plays a critical role on the actual coherency stress profile.

The Effect of Transdermal Nitroglycerine on Intrathecal Fentanyl with Bupivacaine for Postoperative Analgesia following Gynaecological Surgery

Fentanyl is a short-acting synthetic opioid with spinal analgesic properties and dose-dependent side-effects. The analgesic effect of opioids is mediated in part through activation of inhibitory descending pain pathways involving nitric oxide (as a central neurotransmitter) through the NO-cGMP system. This NO-cGMP pathway plays an important role in spinal nociception. The aim of the study was to evaluate the effect of transdermal nitroglycerine on the analgesic action of intrathecal fentanyl in patients undergoing abdominal hysterectomy. Patients (n=120) were randomised into one of four groups. All received 3 ml bupivacaine 0.5% plus 0.5 ml of an intrathecal test drug. Twenty minutes after lumbar puncture, a transdermal patch of either nitroglycerine or placebo was applied. Group B received spinal bupivacaine plus saline 0.5 ml and a placebo patch. Group B-N received bupivacaine plus saline 0.5 ml and a nitroglycerine patch. Group F received bupivacaine plus fentanyl 25 μg and a placebo patch. Group F-N received bupivacaine plus fentanyl 25 μg and a nitroglycerine patch. The duration of effective analgesia was longer in group FN (363.53±34.09 min) compared from the other groups (P <0.001). The times to two-segment regression in group F-N and group F were 132.87±31.2 min and 126.40±26.81 min respectively. The visual analog scale pain score at the time of the first rescue analgesic was similar in all groups. We conclude that nitroglycerine does not result in postoperative analgesia but enhances the analgesic effect of intrathecal fentanyl.

Clinical profile of group A meningococcal outbreak in Delhi

We present a retrospective analysis of clinical profile of 100 children admitted to a Government hospital at Delhi between April 2005 and December 2006 with group A meningococcal infection. Maximum children presented in late winter and spring. Younger children were less affected (5% children < 1 year). Fever (86%), vomiting (64%) and rash (63%) were the most common presenting symptoms. All children presented within 5 days of onset of symptoms and 52% within 24 hours. 67 % children had meningococcal meningitis; 20% had meningococcemia; and 13% had both. Overall mortality was 17%. Altered sensorium and shock at presentation significantly increased the mortality. All culture positive cases had group A Neisseria meningitides. All meningococcal isolates were sensitive to penicillin/ampicillin, ciprofloxacin, ceftriaxone, chloramphenicol and erythromycin except, one each resistant to ampicillin and erythromycin.

Epidemic of leptospirosis: an ICU experience

AIMS

To study the clinical profile and outcome of critically ill patients suffering from leptospirosis with organ dysfunction and correlate mortality with individual risk factors.

METHODS

A study of critically ill patients suffering from leptospirosis was carried out in the Medical Intensive Care Unit of a tertiary centre of a metropolitan city between 1st June 2002 and 31st May 2003. All the patients in whom diagnosis was confirmed by ELISA IgM antibody testing underwent thorough clinical examination and necessary biochemical investigations. They received standard antimicrobial therapy and extensive supportive therapy as required. Mortality was correlated with individual risk factors.

RESULTS

Out of 834 total admissions in this period, 60 (7.2%) patients suffered from leptospirosis. There were 48 males and 12 females with age ranging from 12 to 60 years, mean age being 40 years. The clinical manifestations varied from fever (58 patients), jaundice (38), subconjunctival haemorrhages (24), to altered sensorium (22). All the patients had evidence of severe sepsis. Forty six patients had multiple organ dysfunction syndrome (MODS) and 26 required ventilatory support. The total mortality in leptospirosis patients was 52% which was much higher compared to the total MICU mortality (31.4%) in the same period.

CONCLUSION

Leptospirosis is an important infection associated with high mortality when associated with organ dysfunction. The poor prognostic factors are preponderance of male sex, alcohol dependence, age group > 50 years, MODS, acute respiratory distress syndrome (ARDS), presence of acidosis and need for mechanical ventilation. However, timelyintervention and intensive therapy can save many young lives.

Genetic analysis of Karnal bunt (Neovossia indica) resistance in wheat

Embryos excised from seeds of six generations (P1, P2, F1, BC1, BC2 and F2) of a cross WH 283 WH 533 were cultured on modified MS medium already inoculated with secondary sporidia of Neovossia indica. Significant variations for callusing response (CR) (54 55-75 55%) were observed among generations but the presence or absence of N. indicia did not affect callusing response. A clear inhibition zone (IZ) was formed around each embryo showing callusing. The diameter of IZ varied significantly among generations and was maximum in the resistant genotype, WH 283 (3 60 cm). Fresh weight and dry weight of calli, initiated from embryo cultured and inoculated with N. indica, varied significantly among generations. Coefficient of infection as well as percentage of infection reflected the overdominance of susceptibility. Generation mean analysis showed that the three parameter model was adequate for diameter of IZ only. Six-parameter model showed that additive (in presence of N. indica), additive and additive dominance (in absence of N. indica) effects were also significant. Complementary type of epistasis for fresh weight of calli and dominance, and dominance dominance effects for dry weight of calli were observed in the presence of N. indica. Magnitude of additive effects was higher for diameter of IZ in three parameter model. Therefore, selection might assist in improving this trait and thus indirectly help in attaining the resistance towards N. indica.

Characterization of polyvinylalcohol microspheres of diclofenac sodium: application of statistical design

Microspheres of polyvinylalcohol (PVA) containing diclofenac sodium were prepared by an emulsion-chemical cross-linking method. A statistical design was used to study the variables that affect the preparation of microspheres and to study the release profile of diclofenac from the microspheres. To account for the drug content, a mass balance study of the process was performed. A high concentration of polyvinylalcohol, a high stirring speed, and a low level of glutaraldehyde were found to be important to obtain spherical and discrete microspheres. The concentration of polyvinylalcohol and the amount of heavy liquid paraffin were found to be critical factors in influencing the t50 value. Almost 98% of the total diclofenac sodium added was accounted for in mass balance studies.

Infants of diabetic mothers: a prospective study of neonatal complications in Harare, Zimbabwe

Complications in 42 newborn infants of diabetic mothers (IDM), both insulin- and non-insulin-dependent, were studied prospectively over a period of 16 months at Harare Maternity Hospital. Hypoglycaemia, the most common complication observed, was present in 23 (55%): only seven of these were symptomatic. In 21 of these 23 cases, blood glucose was stabilized during the first 24 hours of life. Jaundice and transient tachypnoea were each seen in 12 cases (29%). There were no cases of respiratory distress syndrome. One infant had polycythaemia requiring partial exchange transfusion. No life-threatening congenital malformations were seen. All infants were given special care initially and in the majority of cases this could be discontinued after 24 hours. With simple interventions, the morbidity of IDM born was found to be comparable to levels reported from developed countries.

Congenital syphilis in the newborn

We studied 53 newborn babies with congenital syphilis. The common clinical features seen were low birth weight, hepatosplenomegaly, anaemia, jaundice, and symmetrical superficial desquamation of the skin affecting palms and soles. The presence of these clinical signs is highly suggestive of early congenital syphilis. Hydrops fetalis without rhesus or ABO isoimmunisation should always arouse the suspicion of congenital syphilis.

Tuberculous manifestations in children

An analysis of 110 cases of primary tuberculosis in Zambian children revealed that 47% of them had protein energy malnutrition. Of all pulmonary manifestations, simple primary tuberculosis was predominant followed by segmental lesions. A high incidence of extra pulmonary involvement mainly tuberculous lymphadenitis was observed. Previous BCG inoculation was not protective in 37 (33.6%) children.