A review on chitosan/metal oxide nanocomposites for applications in environmental remediation

A cleaner and safer environment is one of the most important requirements in the future. It has become increasingly urgent and important to fabricate novel environmentally-friendly materials to remove various hazardous pollutants. Compared with traditional materials, chitosan is a more environmentally friendly material due to its abundance, biocompatibility, biodegradability, film-forming ability and hydrophilicity. As an abundant of -NH2 and -OH groups on chitosan molecular chain could chelate with all kinds of metal ions efficiently, chitosan-based materials hold great potential as a versatile supporting matrix for metal oxide nanomaterials (MONMs) (TiO2, ZnO, SnO2, Fe3O4, etc.). Recently, many chitosan/metal oxide nanomaterials (CS/MONMs) have been reported as adsorbents, photocatalysts, heterogeneous Fenton-like agents, and sensors for potential and practical applications in environmental remediation and monitoring. This review analyzed and summarized the recent advances in CS/MONMs composites, which will provide plentiful and meaningful information on the preparation and application of CS/MONMs composites for wastewater treatment and help researchers to better understand the potential of CS/MONMs composites for environmental remediation and monitoring. In addition, the challenges of CS/MONM have been proposed.

Development of a Strategy for L-Lactic Acid Production by Rhizopus oryzae Using Zizania latifolia Waste and Cane Molasses as Carbon Sources

As a biodegradable and renewable material, polylactic acid is considered a major environmentally friendly alternative to petrochemical plastics. Microbial fermentation is the traditional method for lactic acid production, but it is still too expensive to compete with the petrochemical industry. Agro-industrial wastes are generated from the food and agricultural industries and agricultural practices. The utilization of agro-industrial wastes is an important way to reduce costs, save energy and achieve sustainable development. The present study aimed to develop a method for the valorization of Zizania latifolia waste and cane molasses as carbon sources for L-lactic acid fermentation using Rhizopus oryzae LA-UN-1. The results showed that xylose derived from the acid hydrolysis of Z. latifolia waste was beneficial for cell growth, while glucose from the acid hydrolysis of Z. latifolia waste and mixed sugars (glucose and fructose) from the acid hydrolysis of cane molasses were suitable for the accumulation of lactic acid. Thus, a three-stage carbon source utilization strategy was developed, which markedly improved lactic acid production and productivity, respectively reaching 129.47 g/L and 1.51 g/L·h after 86 h of fermentation. This work demonstrates that inexpensive Z. latifolia waste and cane molasses can be suitable carbon sources for lactic acid production, offering an efficient utilization strategy for agro-industrial wastes.

Adsorptive removal of anionic azo dye by Al3+-modified magnetic biochar obtained from low pyrolysis temperatures of chitosan

Magnetic γ-Fe₂O₃/Al³⁺@chitosan-derived biochar (m-Fe₂O₃/Al³⁺@CB) was prepared by introducing magnetic maghemite (γ-Fe₂O₃) nanoparticles and aluminum sulfate [Al₂(SO₄)₃] into chitosan-derived biochar (CB) obtained at low pyrolysis temperatures. m-Fe₂O₃/Al³⁺@CB was used to remove typical anionic azo dye (Congo red, CR). Effects of initial CR concentration, contact time, initial pH value, background electrolytes, and temperature on CR adsorption by m-Fe₂O₃/Al³⁺@CB were studied. Compared with magnetic chitosan-derived biochar (m-Fe₂O₃@CB), m-Fe₂O₃/Al³⁺@CB exhibited excellent performance for a wider range of pH values (pH 1-7) and in the presence of background electrolyte. The introduction of Al³⁺ is an effective method for improving the properties of magnetic chitosan-derived biochar. High CR adsorption capacity (636.94 mg g^-1) of m-Fe₂O₃/Al³⁺@CB could result from collaborative effect of flocculation/coagulation and electrostatic attraction. These results demonstrated that m-Fe₂O₃/Al³⁺@CB is a potential adsorbent for effective removal of organic dyes from aqueous solution due to its high adsorption capacity and convenient magnetic recovery and stronger anti-interference ability against coexisting anions in wastewater.

Magnetic Fe3O4 embedded chitosan-crosslinked-polyacrylamide composites with enhanced removal of food dye: Characterization, adsorption and mechanism

The water solubility in acid solution, relative low adsorption capacities and unsatisfactory separation performance limit application of traditional chitosan-based adsorbents in wastewater treatment. To break the limitation, a hydrophilic magnetic Fe₃O₄ embedded chitosan-crosslinked-polyacrylamide composites (abbreviated as m-CS-c-PAM) were prepared by a two-step method. The m-CS-c-PAM composites were systematically characterized using SEM, XRD, FTIR, VSM, TGA and BET. Sunset yellow (SY) was selected as model food dye to investigate adsorption kinetics and thermodynamic parameters of food dye adsorption onto m-CS-c-PAM. Compared with magnetic Fe₃O₄/chitosan, m-CS-c-PAM can adapt to a wider range of pH (2-10) and resist the presence of inorganic salts. m-CS-c-PAM was proved to have high adsorption capacity (359.71 mg g^-1) for SY dye at 298 K, much higher than magnetic Fe₃O₄/chitosan and many reported adsorbents. Moreover, m-CS-c-PAM could be rapidly and efficiently separated from treated solution within 15 s by an external magnet and regenerated by NaOH solution. With its excellent adsorption capacity, pH-independent adsorption capability for food dye, easy and convenient separation ability, satisfactory reusability, m-CS-c-PAM can be a promising material for food wastewater treatment.

Efficient Co-production of Docosahexaenoic Acid Oil and Carotenoids in Aurantiochytrium sp. Using a Light Intensity Gradient Strategy

Aurantiochytrium is a promising source of docosahexaenoic acid (DHA) and carotenoids, but their synthesis is influenced by environmental stress factors. In this study, the effect of different light intensities on the fermentation of DHA oil and carotenoids using Aurantiochytrium sp. TZ209 was investigated. The results showed that dark culture and low light intensity conditions did not affect the normal growth of cells, but were not conducive to the accumulation of carotenoids. High light intensity promoted the synthesis of DHA and carotenoids, but caused cell damage, resulting in a decrease of oil yield. To solve this issue, a light intensity gradient strategy was developed, which markedly improved the DHA and carotenoid content without reducing the oil yield. This strategy produced 30.16 g/L of microalgal oil with 15.11 g/L DHA, 221 µg/g astaxanthin, and 386 µg/g β-carotene. This work demonstrates that strain TZ209 is a promising DHA producer and provides an efficient strategy for the co-production of DHA oil together with carotenoids.

[Progress in research of economic evaluation of non-pharmaceutical interventions for COVID-19 prevention and control]

Objective: To understand the research progresses of economic evaluation of non-pharmaceutical interventions (NPIs) both at home and abroad, and provide reference for economic evaluation of NPIs using real-world data in China. Methods: The literature retrieval was conducted by searching Chinese and English databases to indude papers about economic evaluation of NPIs and integrated NPIs published from January, 2020 to December, 2021, and the results were analyzed comprehensively. Results: A total of 30 Chinese and English literatures about economic evaluation of NPIs for COVID-19 prevention and control were included; including 7 papers about nucleic acid and testing and screening, 6 papers about individual prevention and protection measures, 12 papers about integrated implementation of individual prevention and protection, social distancing, nucleic acid or antigen testing, community screening and symptom screening, as well as close contact tracing and isolation/quarantine, and 5 papers about contain strategies, such as lockdown. This study found that personal protection, social distancing, and testing-tracing-isolation measures were cost-effective; however, different combinations of NPIs might lead to different results. Moreover, the cost of lockdown was high, which might cause huge economic burden. Conclusions: Most NPIs are cost-effective except lockdown, while the cost-effectiveness of the integrations of NPIs at different levels and in different scenarios needs to be further evaluated. It is necessary to carry out economic evaluation of integrated NPIs and the combination of NPIs with other interventions, such as vaccination and medication, based on real-world settings in China.

[Clinical and microbiological characteristics of hypervirulent Klebsiella pneumoniae lung abscess]

Objective: To study the clinical and microbiological characteristics of hypervirulent Klebsiella pneumoniae (hvKP) lung abscess, and to compare with the classic Klebsiella pneumoniae (cKP) lung abscess. Methods: A total of 18 patients with Klebsiella pneumoniae lung abscesses admitted to the First Affiliated Hospital of Zhejiang University School of Medicine from January 2017 to September 2020 enrolled. The strains with positive result of string test were defined as hvKP, and the negative strains were defined as cKP. The patients' basic diseases, symptoms, laboratory data and other clinical characteristics were collected. The microbiological characteristics of the strains included as following: VITEK method to determine the in vitro susceptibility of the strains to antibiotics; PCR to detect the capsular serotypes and virulence genes. The differences in clinical characteristics and microbiological characteristics of strains between hvKP group and cKP group were compared. Results: Among the 18 patients with Klebsiella pneumoniae lung abscess, 12 were hvKP infection, mainly male (10 cases), with a median age of 59.0 years; 8 cases in the hvKP group had an onset time of ≤2 weeks, and the median onset time was 10.5 days. There were significantly more diabetes (12 cases) and extrapulmonary abscesses (11 cases) in hvKP group than those in cKP group (both P<0.001). The extrapulmonary abscesses in the hvKP group were mainly liver abscesses (10 cases), and 4 cases were multi-site (≥3) abscesses. The number of indwelling catheters and invasive procedures before infection were higher in cKP group than those in hvKP group (both P=0.025). The imaging of Klebsiella pneumoniae lung abscess was mainly subpleural with the size of less than 10 cm. There were more multiple abscesses cases in hvKP group (9 cases) than cKP group (P=0.009). The median interval time between the detection of a pulmonary abscess and an extrapulmonary abscess was 1.0 day. The resistance rate of common antibiotics was significantly lower in hvKP than cKP. Conclusions: hvKP lung abscesses are more common in patients with diabetes, and the clinical manifestations are nonspecific. The lung imaging manifestations are multiple subpleural abscesses, indicating hematogenous dissemination. Liver abscesses were present in most cases, suggesting the source of infection. The main virulent gene of hypervirulent Klebsiella pneumoniae is aero. For patients with hvKP lung abscess, attention should be paid to finding hidden lesions.

[Progress in research of economic evaluation of COVID-19 vaccination strategies]

Objective: To understand the research progresses of economic evaluation of COVID-19 vaccination strategies both at home and abroad, and provide reference for the economic evaluation of COVID-19 vaccination strategies using real word data in China. Methods: Literature retrieval was conducted for related papers published from January, 2020 to December, 2021 in Chinese and English databases, including the economic evaluation of COVID-19 vaccination, and the results of the related literatures were narratively integrated. Results: A total of 16 English literatures (including 3 reviews) were included, and it was found that the COVID-19 vaccination was cost-effective or cost-saving regardless of the vaccine types, while the cost-effectiveness in different population and under different vaccination dose strategies varied due to vaccine efficacy, vaccine price, duration of natural immunity, duration of vaccination campaign, vaccine supply, and vaccination pace. Conclusions: China lacks suitable evidences of economic evaluation of COVID-19 vaccination strategies based on real-world data in the context of long-term epidemic. Therefore, further researches of suitable strategies of booster COVID-19 vaccination are needed.

Integrated sensing layer of bacterial cellulose and polyethyleneimine to achieve high sensitivity of ST-cut quartz surface acoustic wave formaldehyde gas sensor

Surface acoustic wave (SAW)-based formaldehyde gas sensor using bi-layer nanofilms of bacterial cellulose (BC) and polyethyleneimine (PEI) was developed on an ST-cut quartz substrate using sol-gel and spin coating processes. BC nanofilms significantly improve the sensitivity of PEI films to formaldehyde gas, and reduces response and recovery times. The BC films have superfine filamentary and fibrous network structures, which provide a large number of attachment sites for the PEI particles. Measurement results obtained using in situ diffuse reflectance Fourier transform infrared spectroscopy showed that the primary amino groups of PEI strongly adsorb formaldehyde molecules through nucleophilic reactions, thus resulting in a negative frequency shift of the SAW sensor due to the mass loading effect. In addition, experimental results showed that the frequency shifts of the SAW devices are determined by thickness of PEI film, concentration of formaldehyde and relative humidity. The PEI/BC sensor coated with three layers of PEI as the sensing layer showed the optimal sensing performance, which had a frequency shift of 35.6 kHz for 10 ppm formaldehyde gas, measured at room temperature and 30 % RH. The sensor also showed good selectivity and stability, with a low limit of detection down to 100 ppb.

[Clinical feature analysis of 30 cases with pulmonary actinomycosis]

Objective: To summarize the clinical characteristics of pulmonary actinomycosis and analyze its diagnostic methods. Methods: The clinical symptoms, underlying diseases, imaging characteristics, preliminary diagnosis, diagnostic methods, treatment and prognosis of 30 patients with pulmonary actinomycetes admitted into the First Affiliated Hospital of Zhejiang University School of Medicine during the 10 years (January 2007 to November 2017) were retrospectively analyzed. Results: The 30 patients with pulmonary actinomycetes included were from 47 to 81 years old, with an average age of (59.5±7.8) years, with a course of disease from 5 days to 48 months, and a median course of disease of 1.5 months; 18 patients (60.0%) were complicated with underlying diseases, 10 patients (33.3%) had a history of smoking, 10 patients (33.3%) had a history of alcohol abuse. The main clinical manifestations were cough in 29 cases (96.7%), followed by sputum in 22 cases (73.3%), hemoptysis in 20 cases (66.7%), fever in 12 cases (40.0%), chest pain in 5 cases (16.7%) and shortness of breath in 3 cases (10.0%). Mass, nodules, consolidation, atelectasis can be seen by imaging, there can be a low-density lesion necrosis, formation of voids or vacuoles. Among the 25 patients (83.3%) who underwent bronchoscopy, 14 cases were abnormal, 5 cases showed endotracheal polypoid neoplasms, 9 cases showed endotracheal mucosal inflammatory changes, 2 cases of them showed bronchial foreign body, and 1 case showed broncholithiasis. All cases were diagnosed by pathology. Nine cases (30.0%) were confirmed by bronchoscopic biopsy. Two cases (6.7%) underwent CT-guided percutaneous lung biopsy, 18 cases (60.0%) underwent surgical resection of pathology, and 1 case (3.3%) was diagnosed by puncture of chest wall mass. Sufficient dose and course of penicillin were effective. Surgical excision of the lesion with antibiotics for 2-4 weeks was effective. Conclusion: The clinical manifestation of pulmonary actinomycosis is lack of specificity, obtaining positive pathological specimens is the key to the diagnosis of this disease, the first choice is bronchoscopy and percutaneous lung biopsy.

KrasG12D-LOH promotes malignant biological behavior and energy metabolism of pancreatic ductal adenocarcinoma cells through the mTOR signaling pathway

Oncogenic Kras with loss of heterozygosity (LOH) is frequently detected in various tumours. However, the exact function and mechanism by which KrasG12D-LOH operates remain unclear. Therefore, the current study investigated the effect of KrasG12D-LOH on the malignant phenotype of pancreatic ductal adenocarcinoma (PDAC) cells. Our investigation revealed that KrasG12D-LOH is associated with increased proliferation, invasion and reduced apoptosis in PDAC cells. The results also exhibited enhanced glycolytic phenotype of KrasG12D-LOH PDAC cells. Hyperactive mTOR plays a significant role in the initiation and maintenance of tumors. To investigate the correlation between KrasG12D-LOH and mTOR, the mTOR signaling pathway was detected by western blot analysis. We found that KrasG12D-LOH up-regulated Akt, AMPK, REDD1 and mTOR in PDAC cells. In summary, our results demonstrated that KrasG12D-LOH promotes oncogenic Kras-induced PDAC by regulating energy metabolism and mTOR signaling pathway. These data may provide novel therapeutic perspectives for PDAC.

[Patients of Escherichia coli bloodstream infection: analysis of antibiotic resistance and predictors of mortality]

Objective: To analyze the drug resistance of Escherichia coli (E.coli) from bloodstream infection (BSI) and the predictors of mortality in E. coli bloodstream infection (BSI). Methods: The clinical data of 139 E. coli BSI cases diagnosed from January 2012 to December 2015 in The Second Affiliated Hospital of Zhejiang University School of Medicine, Lanxi Branch (Lanxi People's Hospital), Zhejiang Province, were retrospectively analyzed. The antimicrobial susceptibility testing was performed using Vitek 2 system. Extended-spectrum beta-lactamases (ESBLs) were detected by disk diffusion confirmatory testing. The factors associated with ESBLs-producing strains were identified by univariate analysis. Multivariate analysis was used to identify independent predictors of infection mortality by applying Logistic regression. Results: 42.4% of E. coli isolates were ESBLs-producing. The resistant rate of imipenem was 0.7%. The percent of ESBLs in hospital-acquired infection was higher than that in community-acquired infection but without statistical significance (48.7% versus 40.0%, P=0.350). Univariate analysis suggested that the percent of ESBLs-producing strains in BSI happened on ≥15 d after admission and in BSI of biliary tract infection source was 76.9% and 68.0%, which were much higher than those in BSI happened on <15 d after admission and in BSI of non-biliary tract infection source (34.6% and 36.8%, P=0.013 and 0.004). The overall mortality of E. coli BSI was 13.7%. Multivariate Logistic regression analysis indicated that Sequential Organ Failure Assessment (SOFA ) score (OR=1.393, P<0.001), ceftazidime non-susceptibility (OR=4.444, P=0.018) and liver cirrhosis (OR=13.513, P=0.001) were independent risk factors of mortality. Conclusions: The frequency of ESBLs-producing E. coli was high in primary hospital of Zhejiang Province. SOFA score, ceftazidime non-susceptibility and cirrhosis were predictors of poor outcome in E. coli BSI.

Bimorph material/structure designs for high sensitivity flexible surface acoustic wave temperature sensors

A fundamental challenge for surface acoustic wave (SAW) temperature sensors is the detection of small temperature changes on non-planar, often curved, surfaces. In this work, we present a new design methodology for SAW devices based on flexible substrate and bimorph material/structures, which can maximize the temperature coefficient of frequency (TCF). We performed finite element analysis simulations and obtained theoretical TCF values for SAW sensors made of ZnO thin films (~5 μm thick) coated aluminum (Al) foil and Al plate substrates with thicknesses varied from 1 to 1600 μm. Based on the simulation results, SAW devices with selected Al foil or plate thicknesses were fabricated. The experimentally measured TCF values were in excellent agreements with the simulation results. A normalized wavelength parameter (e.g., the ratio between wavelength and sample thickness, λ/h) was applied to successfully describe changes in the TCF values, and the TCF readings of the ZnO/Al SAW devices showed dramatic increases when the normalized wavelength λ/h was larger than 1. Using this design approach, we obtained the highest reported TCF value of −760 ppm/K for a SAW device made of ZnO thin film coated on Al foils (50 μm thick), thereby enabling low cost temperature sensor applications to be realized on flexible substrates.

[Application of improved regional citrate anticoagulation in continuous hemofiltration in children]

Objective: To investigate the application of regional citrate anticoagulation with calcium hemofiltration basic solution in continuous hemofiltration in children. Method: The clinical data of 18 patients with citrate anticoagulation in continuous hemofiltration in children, excluding the hepatic failure and septic shock cases, were analyzed retrospectively, from September 2015 to August 2016 in Intensive Care Unit of the Children's Hospital of Chongqing Medical University.The commercial calcium hemofiltration basic solution was used as displacement liquid . The blood gas analysis, electrolyte, four coagulation tests during the treatment and the corresponding relations of quantity of blood flow(QB), quantity of citrate flow(QCi), quantity of sodium bicarbonate flow(QSB), quantity of calcium flow(QCa), quantity of filtered solution flow (Qf) were monitored. Meanwhile, the blood gas analysis, electrolyte, four coagulation tests, useful life of filter, bleeding and clotting events internal and external before, during and after the treatments were monitored, too. And the common complications of citrate anticoagulation, such as hypocalcaemia, metabolic alkalosis, citrate accumulation and hypernatremia were observed. Result: Continuous hemofiltration was applied in 18 patients for 734.5 hours, and the average useful life of filter was (25±11)h.There was no obvious clotting event. There were 168 groups of datum of the blood gas analysis, electrolyte, four coagulation tests during the treatment and the relationships of QB, QCi, QSB, QCa, Qf had been collected. The relationships of the initial parameter settings of QB, QCi, QSB, QCa and Qf were concluded as QCi=1.8×QB, QCa=0.12×QB, QSB=0.01×Qf . There were 150 times(89.3%)of extracorporeal ionized calcium(iCa(E)(2+)) and 162 times(96.4%) of intracorporal ionized calcium(iCa(I)(2+)) reached the anticoagulation target. Although all the comparisons of Na(+) ((136.2±4.1)vs.(138.2±2.4)vs.(138.5±3.9)mmol/L), iCa(2+) ((1.07±0.11)vs.(1.21±0.12)vs.(1.17±0.09)mmol/L), HCO(3)(-) ((22±4)vs.(28±5)vs. (26±4)mmol/L) among before, during and after treatment had significant difference(F=6.414, 18.950, 19.151; P=0.002, 0.000, 0.000). Each mean parameter was within the nearly normal range, except that the HCO(3)(-) increased slightly. High HCO(3)(-) was the most common complications, which happened 87 times (51.8%) during the treatment and 11 cases(37.9%) after the treatment. There was none with refractory hypocalcemia and total ionized calcium(TCa(2+) )/iCa(2+) above 2.5, which hints the accumulation of citrate. Conclusion: The commercialized displacement liquid containing calcium can be used in RCA-CHF in children safely and simply.

High-efficiency l-lactic acid production by Rhizopus oryzae using a novel modified one-step fermentation strategy

In this study, lactic acid fermentation by Rhizopus oryzae was investigated using the two different fermentation strategies of one-step fermentation (OSF) and conventional fermentation (CF). Compared to CF, OSF reduced the demurrage of the production process and increased the production of lactic acid. However, the qp was significantly lower than during CF. Based on analysis of μ, qs and qp, a novel modified OSF strategy was proposed. This strategy aimed to achieve a high final concentration of lactic acid, and a high qp by R. oryzae. In this strategy, the maximum lactic acid concentration and productivity of the lactic acid production stage reached 158g/l and 5.45g/(lh), which were 177% and 366% higher, respectively, than the best results from CF. Importantly, the qp and yield did not decrease. This strategy is a convenient and economical method for l-lactic acid fermentation by R. oryzae.

High sensitivity flexible Lamb-wave humidity sensors with a graphene oxide sensing layer

This paper reports high performance flexible Lamb wave humidity sensors with a graphene oxide sensing layer. The devices were fabricated on piezoelectric ZnO thin films deposited on flexible polyimide substrates. Two resonant peaks, namely the zero order antisymmetric (A0) and symmetric (S0) mode Lamb waves, were observed and fitted well with the theoretical analysis and modelling. With graphene oxide microflakes as the sensing layer, the sensing performance of both wave modes was investigated. The humidity sensitivity of the A0 mode is 145.83 ppm per %RH (at humidity 85%RH), higher than that of S0 mode of 89.35 ppm per %RH. For the first time, we have demonstrated that the flexible humidity sensors work as usual without noticeable deterioration in performance even under severe bending conditions up to 1500 με. Also the sensors showed an excellent stability upon repeated bending for thousand times. All the results demonstrated that the Lamb wave flexible humidity sensors have a great potential for application in flexible electronics.

Sputtered ZnO film on aluminium foils for flexible ultrasonic transducers

Nanocrystalline ZnO films with both C-axis vertical grown and inclined angled grown were sputter-deposited onto aluminium foils (50 μm thick) and characterised for using as flexible ultrasonic transducers. As-deposited C-axis grown ZnO films were annealed at different temperatures up to 600 °C to enhance film crystallinity and reduce film stress. The C-axis grown ZnO film on the Al foil were bonded onto steel plates, and the pulse-echo tests verified a good performance (with dominant longitudinal waves) of the ultrasonic transducers made from both as-deposited and post-annealed films. Inclined angled ZnO films on the Al foil glued onto steel plates generated mixed shear and longitudinal waves in the pulse-echo test.

Comparison of tetragonal and cubic tin as anode for Mg ion batteries

Using first-principles calculation based on density functional theory, diffusion of Mg atom into α- and β-Sn was investigated. The diffusion barriers are 0.395 and 0.435 eV for an isolated Mg atom in the α- and β-Sn, respectively. However, the diffusion barriers of the Mg atom decrease in the α-Sn, whereas they increase in the β-Sn, when an additional Mg atom was inserted near the original diffusing Mg atom, which is mainly due to strong binding of Mg-Mg atoms in the β-Sn. Therefore, it is better to use the α-Sn, rather than the β-Sn, as an anode material for Mg ion batteries.

Annealing effect on the generation of dual mode acoustic waves in inclined ZnO films

ZnO films with different inclined angles on steel substrates were sputter-deposited by changing the substrate tilt angle during deposition and then used to fabricate ZnO film ultrasonic transducers. The ultrasonic performance of those devices was characterized using a standard pulse-echo method. A dual mode wave with both longitudinal and shear wave components was detected from the ZnO device at 0° inclined angle. At a columnar inclined angle of 31°, longitudinal wave excitation was suppressed with a nearly pure shear wave detected. Post annealing of the ZnO film improved the crystallinity and decreased the film stress. The dispersion of the received echoes was observed when the grain sizes of ZnO films were increased after annealing. The frequency components of the waveforms were analyzed and identified using a short time Fourier transform. Post-annealing of the ZnO films changed the primary frequency and enhanced the propagation of the relative high-frequency acoustic wave.

Novel ZnO nanorod films by chemical solution deposition for planar device applications

Smooth and continuous ZnO films consisting of densely packed ZnO nanorods (NRs), which can be used for electronic device fabrication, were synthesized using a hydro-thermo-chemical solution deposition method. Such devices would have the novelty of high performance, benefiting from the inherited unique properties of the nanomaterials, and can be fabricated on these smooth films using a conventional, low cost planar process. Photoluminescence measurements showed that the NR films have much stronger shallow donor to valence band emissions than those from discrete ZnO NRs, and hence have the potential for the development of ZnO light emission diodes and lasers, etc. The NR films have been used to fabricate large area surface acoustic wave devices by conventional photolithography. These demonstrated two well-defined resonant peaks and their potential for large area device applications. The chemical solution deposition method is simple, reproducible, scalable and economic. These NR films are suitable for large scale production on cost-effective substrates and are promising for various fields such as sensing systems, renewable energy and optoelectronic applications.

Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets

We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1-30 μl) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F{NA}=Fλ/(σ/R_{d})≥0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, λ is the SAW wavelength, σ is the surface tension, and R{d} is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ≤1 μW (F{NA}<0.002). Furthermore, we demonstrate that the increase of F{NA} above 0.45 induces not only internal streaming, but also the deformation of droplets.

Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets

We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1-30 μl) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F{NA}=Fλ/(σ/R_{d})≥0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, λ is the SAW wavelength, σ is the surface tension, and R{d} is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ≤1 μW (F{NA}<0.002). Furthermore, we demonstrate that the increase of F{NA} above 0.45 induces not only internal streaming, but also the deformation of droplets.

Microfluidics based on ZnO/nanocrystalline diamond surface acoustic wave devices

Surface acoustic wave (SAW) devices with 64 μm wavelength were fabricated on a zinc oxide (ZnO) film deposited on top of an ultra-smooth nanocrystalline diamond (UNCD) layer. The smooth surface of the UNCD film allowed the growth of the ZnO film with excellent c-axis orientation and low surface roughness, suitable for SAW fabrication, and could restrain the wave from significantly dissipating into the substrate. The frequency response of the fabricated devices was characterized and a Rayleigh mode was observed at ∼65.4 MHz. This mode was utilised to demonstrate that the ZnO/UNCD SAW device can be successfully used for microfluidic applications. Streaming, pumping, and jetting using microdroplets of 0.5 and 20 μl were achieved and characterized under different powers applied to the SAW device, focusing more on the jetting behaviors induced by the ZnO SAW.

Integrated microfluidics system using surface acoustic wave and electrowetting on dielectrics technology

This paper presents integrated microfluidic lab-on-a-chip technology combining surface acoustic wave (SAW) and electro-wetting on dielectric (EWOD). This combination has been designed to provide enhanced microfluidic functionality and the integrated devices have been fabricated using a single mask lithographic process. The integrated technology uses EWOD to guide and precisely position microdroplets which can then be actuated by SAW devices for particle concentration, acoustic streaming, mixing and ejection, as well as for sensing using a shear-horizontal wave SAW device. A SAW induced force has also been employed to enhance the EWOD droplet splitting function.

Fabrication of micro DOE using micro tools shaped with focused ion beam

A novel method is proposed to fabricate micro Diffractive Optical Elements (DOE) using micro cutting tools shaped with focused ion beam (FIB) milling. Micro tools with nanometric cutting edges and complicated shapes are fabricated by controlling the tool facet's orientation relative to the FIB. The tool edge radius of less than 30 nm is achieved for the nano removal of the work materials. Semi-circular micro tools and DOE-shaped micro tools are developed to fabricate micro-DOE and sinusoidal modulation templates. Experiments show that the proposed method can be a high efficient way in fabricating micro-DOE with nanoscale surface finishes.

Characterization of spark plasma sintered Ag nanopowders

The low temperature sintering behaviour of nanocrystalline Ag powder (with an average size of 70 nm) was characterized. Using spark plasma sintering (SPS), the Ag nanopowders can be successfully sintered at low pressure for only 5 min without external heating, and the sintering density increases and porosity decreases significantly with increase in the sintering temperature. Nanoindentation has been used to characterize the SPS sintered Ag samples. The mechanisms of the low sintering temperature behaviour of the nano-Ag powder and the nanoscale mechanical performance have been discussed. Compression tests were also used to characterize the mechanical properties of the sintered Ag sample with a maximum strain up to 15%.

High precision high voltage divider and its application to electron beam ion traps

A high precision high voltage divider has been developed for the electron beam ion trap in Shanghai. The uncertainty caused by the temperature coefficient of resistance (TCR) and the voltage coefficient of resistance has been studied in detail and was minimized to the level of ppm (10(-6)) range. Once the TCR was matched between the resistors, the precision of the dividing ratio finally reached the ppm range also. We measured the delay of the divider caused by the capacitor introduced to minimize voltage ripple to be 2.35 ms. Finally we applied the divider to an experiment to measure resonant energies for some dielectronic recombination processes for highly charged xenon ions. The final energies include corrections for both space charge and fringe field effects are mostly under 0.03%.

Stress and crystallization of plasma enhanced chemical vapour deposition nanocrystalline silicon films

Nanocrystalline Si films were prepared with a RF-PECVD system using different SiH4/H2 ratios, plasma powers, substrate temperatures and annealing conditions. The film's intrinsic stress was characterized in relation to the crystallization fraction. Results show that an increasing H2 gas ratio, plasma power or substrate temperature can shift the growth mechanism across a transition point, past which nanocrystalline Si is dominant in the film structure. The film's intrinsic stress normally peaks during this transition region. Different mechanisms of stress formation and relaxation during film growth were discussed, including ion bombardment effects, hydrogen induced bond-reconstruction and nanocomposite effects (nanocrystals embedded in an amorphous Si matrix). A three-parameter schematic plot has been proposed which is based on the results obtained. The film structure and stress are presented in relation to SiH4 gas ratio, plasma power and temperature.

In-situ observation of transition between surface relief and wrinkling in thin film shape memory alloys

Significant surface morphology evolution between relief and wrinkling was observed on a 3.5 microm thick TiNiCu film sputter-deposited on a silicon substrate. At room temperature, variation in surface relief morphology (from separated martensite crystals embedded in amorphous matrix to fully interweaved martensite plates) was observed with slight change in film composition. The phenomenon was attributed to variations in crystallization temperatures of as-deposited amorphous films during annealing because of the compositional difference. During thermal cycling between room temperature and 100 degrees C, reversible surface morphology changes can be observed between surface relief and wrinkling patterns. The formation of the surface wrinkling is attributed to the large compressive stress in the film during high temperature post-annealing and crystallization, whereas surface relief is caused by the martensitic transformation to relieve the large tensile stress in the film. Compositional effect on this surface morphology evolution is discussed. Results also indicate that there is a critical dimension for the wrinkling to occur, and a small circular island can only relax by in-plane expansion.

Depth Profiling of Charging Effect of Si Nanocrystals Embedded in SiO2: A Study of Charge Diffusion among Si Nanocrystals

Si nanocrystal (nc-Si) embedded in SiO2 thin film is synthesized with low-energy Si ion implantation. Depth profiling of the charging effect of the nc-Si is determined from X-ray photoemission measurement. It is observed that there is a strong correlation between the depth profile of the charging effect and the nc-Si depth distribution. The charging effect is found to decrease with the increase of nc-Si concentration and to vanish when a densely stacked nanocrystal layer is formed. The phenomenon is attributed to the charge diffusion among the nanocrystals. The charge diffusion in the nanocrystal layer may have an important implication for nanocrystal flash memory. When such a layer is used as the charge-storage layer in the memory cells, the stored charges could be lost due to the rapid charge diffusion among the nc-Si if a single defect exists in the tunneling oxide, causing a reliability problem in data retention.

Analyses of cis -acting elements that affect the transposition of Mos1 mariner transposons in vivo

The left (5') inverted terminal repeat (ITR) of the Mos1 mariner transposable element was altered by site-directed mutagenesis so that it exactly matched the nucleotide sequence of the right (3') ITR. The effects on the transposition frequency resulting from the use of two 3' ITRs, as well as those caused by the deletion of internal portions of the Mos1 element, were evaluated using plasmid-based transposition assays in Escherichia coli and Aedes aegypti. Donor constructs that utilized two 3' ITRs transposed with greater frequency in E. coli than did donor constructs with the wild-type ITR configuration. The lack of all but 10 bp of the internal sequence of Mos1 did not significantly affect the transposition frequency of a wild-type ITR donor. However, the lack of these internal sequences in a donor construct that utilized two 3' ITRs resulted in a further increase in transposition frequency. Conversely, the use of a donor construct with two 3' ITRs did not result in a significant increase in transposition in Ae. aegypti. Furthermore, deletion of a large portion of the internal Mos1 sequence resulted in the loss of transposition activity in the mosquito. The results of this study indicate the possible presence of a negative regulator of transposition located within the internal sequence, and suggest that the putative negative regulatory element may act to inhibit binding of the transposase to the left ITR. The results also indicate that host factors which are absent in E. coli, influence Mos1 transposition in Ae. aegypti.

Hybrid microdiffractive-microrefractive lens with a continuous relief fabricated by use of focused-ion-beam milling for single-mode fiber coupling

The design, microfabrication, and testing of a hybrid microdiffractive-microrefractive lens with a continuous relief that is used with a laser diode for monomode fiber coupling is discussed. The hybrid microlens with a diameter as small as 65 mum and a numerical aperture of 0.25 is fabricated directly onto a spherical surface by use of focused-ion-beam milling technology. A focused Ga(+) ion beam is used to mill the continuous relief microstructure at an acceleration voltage of 50 kV. From the test results a coupling efficiency of 71% (-1.49 dB) was achieved at room temperature. A diffraction efficiency of the main diffractive order, -1, was measured to as high as 90.5% at a wavelength of 635 nm. This indicates that the hybrid microlens was suitably designed within the application requirements and satisfactorily manufactured with focused-ion-beam milling.