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Because of its high energy density and low cost, the room-temperature sodium-sulfur (RT Na-S) battery is a promising candidate to power the next-generation large-scale energy storage system. However, its practical utilization is hampered by the short life span owing to the severe shuttle effect, which originates from the "solid-liquid-solid" reaction mechanism of the sulfur cathode. In this work, fluoroethylene carbonate is proposed as an additive, and tetraethylene glycol dimethyl ether is used as the base solvent. For the sulfurized polyacrylonitrile cathode, a robust F-containing cathode-electrolyte interphase (CEI) forms on the cathode surface during the initial discharging. The CEI prohibits the dissolution and diffusion of the soluble intermediate products, realizing a "solid-solid" reaction process. The RT Na-S cell exhibits a stable cycling performance: a capacity of 587 mA h g

The water-in-salt strategy successfully expands the electrochemical window of the aqueous electrolyte from 1.23 to ∼3.0 V, which can lead to a breakthrough in the energy output of the aqueous battery system while maintaining the advantage of high safety. The expanded electrochemical window of the water-in-salt electrolytes can be ascribed to the decreased water activity and the solid electrolyte interphase formed on the anode. The solid electrolyte interphase in the aqueous system is not fully understood, and the basic composition, the structure, and the formation mechanism are still cloaked in mystery. This perspective summarizes the published research with emphasis on the most possible formation mechanism and composition of the interphase layer in the aqueous system. Further understanding of the interphase as well as rounded assessment of the water-in-salt electrolyte in practical operating conditions is encouraged. The full understanding of the interface will guide the design of aqueous electrolytes and help to build novel aqueous batteries with high safety and high energy density.

"Water-in-salt" electrolytes have significantly expanded the electrochemical stability window of the aqueous electrolytes from 1.23 to 3 V, making highly safe 3.0 V aqueous Li-ion batteries possible. However, the awkward cathodic limit located at 1.9 V (versus Li

Fiber-based linear actuators (FLAs) are a key module in microrobots and biomimetic devices. It has been a great challenge to develop linear actuators that can balance output stress and output strain and hence provide high working density. Herein, we report the preparation and performance of a FLA system made from commercially available materials and allowed mass production at relatively low cost. The FLAs can lift up or lay down objects more than 1000 times of its own weight during active contraction and expansion under environmental stimuli. The contraction ratio and output stress can reach 30% and 0.24 MPa, respectively, and the sustainable work density is about 80 J/kg, which is 10 times the typical value of human skeletal muscles. Especially, the FLAs show stable catch-state (lock-up state) with no creeping and no further energy consumption.

In this work, a polyelectrolyte complex (PEC) fiber of alginate (ALG) and poly(diallyldimethylammonium chloride) (PDDA) is prepared by restricting polyelectrolyte complexation with salt to fit wet-...

Lithium sulfur (Li–S) battery is considered as one of the most viable candidates for next-generation rechargeable batteries. However, the development of Li–S battery is severely hindered by the stubborn “shuttle” issue that arises from the dissolution of the intermediate polysulfides. Herein, a new kind of organosulfur polymer composite is designed as cathode material for Li–S batteries. Via a facile two-step heating method, the ring opening S is copolymerized with triallyl isocyanurate. The resulting S-triallyl isocyanurate organosulfur polymer composite (STI) demonstrates a unique two-phase structure: ultrafine monoclinic S particles embedded in the organosulfur polymer matrix, which enables a S content as high as 90 ​wt%. The STI cathode delivers a high initial reversible capacity of 904 ​mA ​h ​g−1 at 0.5 ​C, and an ultraslow capacity decay rate of 0.017% over 350 cycles at 1 ​C. The work offers new insights into the design of S-rich copolymer composite cathode for highly-stable Li–S batteries.

Sodium (Na) metal batteries have attracted much attention due to their rich resources, low cost, and high energy density. As a promising solid electrolyte, Na

Room-temperature sodium-sulfur (RT-Na/S) batteries hold great promise to meet the requirements of large-scale energy storage due to their high theoretical energy density, low material cost, resource abundance, and environmental benignity. However, the poor cycle performance and low utilization of active sulfur greatly hinder their practical application. As the essential part directly related to the battery performance, the S-based cathode has attracted tremendous research interests in recent years. This review highlights recent progress in cathode materials for RT-Na/S batteries. Particularly, basic insights into the Na/S reaction mechanism are presented and representative works on S-based cathode materials are systematically summarized. The remaining challenges and developing trends of RT-Na/S batteries are also discussed. We hope this review can shed light on the field of next-generation metal-sulfur batteries.

Here, we report the preparation of hydrogen-bonded complex fibers of graphene oxide (GO) and polyethylene oxide (PEO) and their reduction to conductive fiber. The complexation behaviors of PEO and GO at different pH values are investigated. When pH is below 2.0, PEO and GO will form the complex which precipitates out from the solution quickly. When pH is higher than 5.0, GO and PEO mixed solution will be homogenous. At pH 6.0 the GO/PEO solution shows good fluidity and pre-orientation of GO sheets. The solution is extruded into 1.0 M HCl solution where hydrogen bonding between PEO and GO is constructed and hence the fiber forms. After reduction, the fibers show good mechanical and electrical properties, and the mechanical strength is close to 500 MPa while the conductivity is more than 200 S/cm. The reduced fibers can be assembled into flexible supercapacitor, exhibiting potential for wearable electronics.

Lipid peroxidation plays a crucial role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and cystine/glutamate antiporter system Xc- has been proved to be associated with glutathione (GSH) synthesis, which protects cells against oxidative damage. Antioxidant effect of system Xc- is mediated by Beclin 1 (BECN1). Therefore, this study aimed to determine whether administration of BECN1 small interfering RNA (siRNA) could attenuate EBI after SAH experiment, specifically through suppressing lipid peroxidation and increasing system Xc- activity. Endovascular perforation was performed to induce SAH in a rat model and BECN1 siRNA was administered through intracerebroventricular injection. Neurological score, brain edema, lipid peroxidation (malondialdehyde, MDA), and antioxidation system, containing GSH, glutathione peroxidase (GSH-Px), glutathione reductase (GR), and anti-reactive oxygen species (anti-ROS), were examined. The expression of BECN1 and light chain of system Xc- (xCT) was detected by western blot, immunoprecipitation, and immunofluorescence staining. This study confirmed that SAH induced neurological deficits and brain edema, which was accompanied by the increase of BECN1 expression and lipid peroxidation, and the decrease of xCT expression and antioxidative capacity. However, downregulation of BECN1 by siRNA could decrease the formation of the BECN1-xCT complex and lipid peroxidation, enhance antioxidative capacity, and ameliorate neurological deficits and brain edema in SAH rats. The results suggested that inhibition of BECN1 suppresses accumulation of lipid peroxidation by increasing system Xc- activity in EBI after SAH, and BECN1 may be a new effective target for EBI treatment after SAH.

Exploring efficient luminophores in the electrochemiluminescence (ECL) system is highly desired to pursue a sensitive ECL sensing platform. Herein, the black phosphorus nanosheets (BP NSs) with excellent ECL properties are investigated and serve as the luminophore with the coreactant of peroxydisulfate (S2O82-) solution. Moreover, owing to the overlapping of emission and absorbance spectra, effective resonance energy transfer (RET) is realized between the BP NSs and the introduced Au nanoparticles. In order to achieve the portable and miniaturized developing trends for the paper-based ECL sensing platform, a paper-based perovskite solar cell (PSC) device is designed to act as the power source to replace the commonly utilized expensive and cumbersome electrochemical workstation. Benefiting from that, a PSC driven paper-based constant potential ECL-RET sensing platform is constructed, thereby realizing sensitive microRNAs (miRNAs) detection. What's more, to attain the preferable analytical performance, the duplex-specific nuclease (DSN) is also introduced to assist the target recycling signal amplification strategy. Based on this, highly sensitive detection of miRNA-107 with a range from 0.1 pM to 15 nM is achieved by this designed sensing platform. Most importantly, this work not only pioneers a precedent for developing a high-sensitivity PSC triggered ECL sensing platform but also explores the application prospect of BP nanomaterial in the field of bioanalysis.

The lithium-sulfur (Li-S) battery is considered as one of the most promising options because the redox couple has almost the highest theoretical specific energy (2600 Wh kg

Introduction The objective of the study was to identify trends in incidence of adult diffuse gliomas in the United States and evaluate the contribution of age, period, and cohort effects to the trends. Methods Using the Surveillance, Epidemiology, and End Results 9 database, primary diffuse glioma patients (≥20 years old) diagnosed from 1973 to 2014 were identified. Incidence trends were analyzed using joinpoint regression and age‐period‐cohort modeling. Results Overall, the incidence for adult glioma decreased slowly from 1985 to 2014 (annual percent change [APC] = 0.5%, 95% confidence intervals [CI], 0.3%‐0.6%). In histology subtype‐stratified analysis, glioblastoma and nonglioblastoma exhibited opposite trends. The incidence for glioblastoma increased from 1978 to 2014 (APC for year 1978‐1992 = 2.7%, 95% CI, 1.8%‐3.6%; APC for 1992‐2014 = 0.3%, 95% CI, 0%‐0.6%), while the incidence for nonglioblastoma decreased significantly from 1982 to 2014 (APC = 2.2%, 95% CI, 2.0%‐2.5%). Age‐period‐cohort modeling revealed significant period and cohort effects, with the patterns for glioblastoma and nonglioblastoma distinctive from each other. Compared with adults born 1890s, those born 1920s had approximately 4‐fold the risk of glioblastoma after adjustment of age and period effects, while the risk of nonglioblastoma was reduced by half in individuals in the 1939 cohort as compared with those in the 1909 cohort. Conclusions The results support the hypothesis of etiological heterogeneity of diffuse gliomas by histology subtypes. The established risk factors cannot fully explain the distinct patterns by histology subtypes, which necessitate further epidemiological studies.

Poly(acrylic acid) (PAA) was partially grafted with dopamine (PAA-dopa), and then layer-by-layer assembled with poly(vinylpyrrolidone) (PVPON) to prepare hydrogen-bonded (PVPON/PAA-dopa)n film. Polydopamine (PDA) was deposited on (PVPON/PAA-dopa)n film in the presence of oxidant, and hence the whole (PVPON/PAA-dopa)nPDA film was cross-linked. (PVPON/PAA-dopa)nPDA could be utilized as a platform to produce the free-standing Janus film because of the easy detaching process and various chemical reactivity of PDA layer. Ag nanoparticles were formed on (PVPON/PAA-dopa)nPDA film by electroless metallization. 1H,1H,2H,2H-Perfluorodecanethiol (PFDT) was used to further modify the film through Michael addition. After detaching from the substrate, (PVPON/PAA-dopa)20PDA/Ag/PFDT exhibits reversible swelling–shrinking behavior as the pH value changes. This free-standing film shows Janus character, one side is hydrophobic, whereas the other side is hydrophilic. In addition, the hydrophobic surface exhibits a surface-en...

Anode-free Li metal batteries are considered the ultimate configuration for next-generation high energy-density Li-based batteries due to the elimination of excess Li metal. However, the limited Li source aggravates issues such as dendrite growth and “dead” Li formation. Any Li loss caused by the SEI formation and dead Li has a great influence on the performance of the full cell. Here, we introduce LiI with shuttle effect to suppress the Li dendrites and reactivate the dead Li in the anode-free LiFePO4 (LFP) ∣Cu full cells. During cycling, the iodine transforms between I− and I3 −, and a chemical reactions occur spontaneously between I3 − and Li dendrites or dead Li. The generated Li+ in the electrolyte remains active in the following cycling. The anode-free LFP∣Cu cells deliver an initial discharge capacity of 139 mAh g−1 and maintain capacities of 100 mAh g−1 with a capacity retention of 72% after 100 cycles. Both the anode-free LFP∣Cu coin cells and pouch cells with LiI additive show much-improved performances. This work provides a new strategy for high-performance anode-free Li metal batteries.

This work presents the design of hollow fiber T-type zeolite membrane modules with different geometric configurations. The module performances were evaluated by pervaporation dehydration of ethanol/water mixtures. Strong concentration polarization was found for the modules with big membrane bundles. The concentration polarization was enhanced at high temperature due to the higher water permeation flux. The increase of feed flow could improve water permeation flux for the membrane modules with small membrane bundle. Computational fluid dynamics was used to visualize the flow field distribution inside of the modules with different configurations. The membrane module with seven bundles exhibited highest separation efficiency due to the uniform distribution of flow rate. The packing density could be 10 times higher than that of the tubular membrane module. The hollow fiber membrane module exhibited good stability for ethanol dehydration.

The polymer complex fibers of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) were produced by inhibiting the complexation to obtain spinnable fluid and initiating the complexation in coagulation bath to make fiber formation. With sulfonic acid as coagulation solution, PVA/PAA fiber can be cross-linked at mild temperature while with hydrochloric acid as coagulation solution is not. The mechanical properties of PVA/PAA fibers strongly depend on environment humidity. As the humidity increases, the fibers show a transition from a glassy state to a rubbery state. Furthermore, dynamic mechanical analysis (DMA) with humidity scans detects not only glass-rubber transition of the cross-linked PVA/PAA fiber but also the secondary relaxation, which reflects molecular motions at the difference scales in the fiber.

Lipid peroxidation plays a crucial role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and cystine/glutamate antiporter system X

CHA zeolite membranes were hydrothermally synthesized by secondary growth method. Original and ball-milled seeds were compared for induction of CHA zeolite membranes. The synthetic parameters were investigated extensively in terms of seed size, precursor composition and crystallization temperature. Impurity MER phase was readily generated in membrane layers when using original CHA seeds (average particle size ∼ 3.80 μm) in an individual K + -containing synthetic medium. Comparatively, pure phase CHA zeolite membranes could be obtained by induction of ball-milled seeds in a broad SiO 2 /Al 2 O 3 ratio and at a low K + concentration. The as-synthesized membranes showed better separation performance than those induced with original seeds. Typically, the CHA zeolite membrane synthesized at 433 K for 20 h in a synthesis gel of 11 SiO 2 :1 Al 2 O 3 :1 K 2 O:1 Na 2 O:550 H 2 O showed a water permeation flux of 2.5 kg m −2 h −1 and separation factor of 2980 for pervaporation dehydration of 90 wt.% ethanol solution at 348 K. The CHA zeolite membrane synthesized with ball-milled seeds was stable for dehydration of acidic ethanol solution (pH ∼3) at 348 K while the membrane induced with original seeds showed a declined separation behavior.

The aim of the present study was to assess the association between the efficacy and adverse events (AEs) of transcatheter arterial chemoembolization (TACE) combined with sorafenib in patients with unresectable hepatocellular carcinoma (HCC). Between July 2008 and May 2011, 50 patients with unresectable HCC were enrolled and assigned to receive TACE combined with sorafenib in the present study. The primary outcomes were considered as time to disease progression (TTP) and sorafenib-related AEs. In the present study, 34 of 50 patients had disease progression with a median TTP (mTTP) of 210 days. The most common AEs included hand-foot skin reaction (HFSR), fatigue, diarrhea and hypertension. The mTTP of patients with HFSR extended 140 days compared to that of the patients without HFSR. Kaplan-Meier analysis was used for mTTP between the two groups of patients. This difference was statistically significant when analyzed by the univariate COX proportional hazards regression model. In conclusion, TACE in combination with sorafenib had an acceptable safety profile in the treatment of unresectable HCC. Additionally, it also revealed that HFSR served as a good prognostic predictor in using combination therapy. Therefore, discontinuation of sorafenib treatment should be prevented to avoid disease progression.

NaA zeolite membranes were prepared on an external surface of novel four-channel α-Al2O3 hollow fiber (4CF) supports for pervaporation dehydration of ethanol. The 4CF supports were first seeded with ball-milled NaA zeolite seeds by a dip-coating approach and followed by hydrothermal crystallization at 100 °C for 4 h. Influences of the seeding condition and microstructure of the 4CF supports were extensively investigated. The separation performances of the as-synthesized membranes were evaluated by pervaporation dehydration of 90 wt% ethanol/water mixtures at 75 °C. A notably high water permeation flux of 12.8 kg m−2 h−1 and a separation factor of >10 000 was obtained in the membrane supported on 4CF which had a porosity of 55% as well as a high mechanical strength of 18 N. In comparison with single-channel α-Al2O3 hollow fiber supported NaA zeolite membranes, the 4CF supported membranes were considerably superior in permeation flux, mechanical strength and convenience of seeding operation. Allowing for high reproducibility as well as high performance, there would be great potential in industrial applications for 4CF-supported NaA zeolite membranes.

Some observational studies have shown that elevated serum selenium levels are associated with reduced prostate cancer risk; however, not all published studies support these results. A literature search of PubMed, Embase, Medline, and the Cochrane Library up until September 2016 identified 17 studies suitable for further investigation. A meta-analysis was conducted on these studies to investigate the association between serum selenium levels and subsequent prostate cancer risk. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the overall OR of prostate cancer for the highest versus the lowest levels of serum selenium. We found a pooled OR (95% CI) of 0.76 (0.64, 0.91; P

A number of epidemiological studies have suggested that obesity is associated, albeit inconsistently, with the incidence of prostate cancer (PCa). In order to provide a quantitative assessment of this association, the present study examined the correlation between obesity and the incidence and associated mortalities of PCa in an updated meta-analysis of cohort studies. The cohort studies were identified by searching the EMBASE and MEDLINE databases on January 1, 2014. The summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated using random-effects models. In total, 17 studies, which included 3,569,926 individuals overall, were selected according to predefined inclusion criteria. Based upon the results of the random-effects models, obesity was not significantly correlated with the incidence of PCa (RR, 1.00; 95% CI, 0.95–1.06). However, further analysis revealed that obesity was significantly correlated with an increased risk of aggressive PCa (RR, 1.14; 95% CI, 1.04–1.25). Furthermore, an increased risk of PCa-associated mortality was significantly associated with obesity (RR, 1.24; 95% CI, 1.15–2.33), without any heterogeneity between the studies (I2=0.0%; P=0.847). The present study provides preliminary evidence to demonstrate that obesity is a significant risk factor for aggressive PCa and PCa-specific mortality. The low survival rates observed among obese males with PCa may be a likely explanation for this association.

The applicability of model predictive accuracy and the selection of suitable model parameters for the membrane flux prediction and prediction of the filtration characteristics of dead-end filtration systems were assessed. In determining the model predictive accuracy using model parameters, the selection of suitable model parameters is of great significance. A series of experiments were conducted. The relative deviations, average deviations, and root mean square between the experimental and predicted values were calculated to evaluate predictive accuracy. The results showed that the model parameter has changed nonlinearly with operating conditions. Particularly, in the membrane flux prediction model, the time-dependent character of the model parameter can result in a considerable error. However, model prediction accuracy can be improved indisputably and the model will get higher predictive accuracy than that of other predictive models if the constant membrane fouling index in the flux prediction model is e...

A new type of the surface acoustic wave (SAW) sensor system was delivered. Urease from several kinds of plant seeds was extracted with different extracting solvents. The urease activity, Michaelis constant and other kinetic parameters were estimated for the first time by means of the new device–-SAW sensor system. Some factors such as pH, temperature, activators and inhibitors are also discussed. The method can be applied to the determination of urea content in human urine and the experimental results consist with those reported.

The LED industry is extremely price sensitive to manufacturing cost. The challenge is to produce modules (or the light engines) without compromising reliability. The present approach is to work within the standard assembly flow structure and focus on improving the manufacturing yield through efficient process control. These yield enhancements are usually achieved in small increments. Therefore, it is necessary to revolutionize the packaging and interconnect technology and implement new assembly methodology concepts.

An adjustable parameter k was introduced in an original model based on Darcy’s Law to increase its accuracy, and a new semi-empirical model predicting permeate flux for dead-end microfiltration (MF) systems was proposed. The adjustable parameter k was validated in laboratory experiments by using two different suspensions (kaolin and yeast). The membranes adopted in this research included flat PES and PVDF with 0.2μ and 0.1μ average pore size respectively. The experiments showed that this adjustable parameter was almost independent of operating conditions pressure, concentration and temperature), but depended on the character of the cake formed on the membrane surface and on the type of membrane. The average values of k for yeast and kaolin are 4.15 and 1.10 respectively. The results showed good agreement between model prediction and experimental observations.

Historically, it was taken for granted that public services would be delivered by a staff of career civil service employees, working within the structure of centralised public agencies budgeted with appropriated funds. Today, none of these are true‐public programmes are more than likely performed by alternative organisations or mechanisms rather than by public agencies (International City Management Association, 1989); and when public agencies are used, they are more likely to be staffed by contingent workers hired through flexible employment mechanisms rather than permanent employees protected by civil service regulations and collective bargaining agreements (Kilbom, 1995).

Poly(vinylidene fluoride) (PVDF), polymethyl methacrylate (PMMA) and cellulose acetate (CA) in the presence of N-methyl pyrrolidone were blended in various combinations by using dimethylformamide (DMF) and glacial acetic acid (CH3COOH) as solvent and used to prepare flat-sheet membranes by the phase-inversion process. A square-crossing table with four factors and three levels for the PVDF-PMMA-CA system was designed to study the influences of the casting solution composition and gelation conditions on membrane pore size; preparation conditions for the system were optimized. The results showed that the effect of the casting solution composition was stronger than that of the solid content and the content of the coagulation medium on characteristics of the prepared membrane. The suitable composition for the PVDF-PMMA-CA system was found to be a solid content of 18%, an additive content of 4%, DMF/CH3COOH = 4:1 and a Na2CO3 solution with aa concentration of 2% as the coagulation medium. In addition, it was found that carbon dioxide gas produced by the reaction of glacial acetic acid in the cast solution with sodium carbonate in a coagulation bath can be used to control the even distribution of the membrane pore size during the process of coagulation.

An intelligent micro-manipulator based on 3-PRS in-parallel mechanism was developed for the purpose of assembling micro-machines, operating biological cells, and performing micro-surgery. The micro-manipulator consists of a left finger and a right finger driven separately by three driving units. With such construction it can mimic the motion of Chinese chopsticks to manipulate a micro-object with a relatively large workspace and high precision. Presented here are the structure design method and the approach for kinematic analysis. The experimental setup for micro-manipulation is also discussed.

A thiol-substituted carotenoid, 7‘-apo-7‘-(4-mercaptomethylphenyl)-β-carotene, (AMC) was allowed to self-assemble on polycrystalline gold surfaces. The stability, packing density, optical absorption, and hydrophobicity of the resulting monolayers were investigated with X-ray photoelectron spectroscopy (XPS), Fourier transform infrared reflection−absorption spectroscopy (FTIR-RAS), UV-Vis spectroscopy, spectroscopic ellipsometry, and contact angle measurements. XPS and spectroscopic ellipsometry measurements reveal the saturation coverage is ∼4 × 1014 AMC molecules/cm2 and the film thickness is ∼20 A, respectively. FTIR-RAS and contact angle measurements suggest that the polyene chains are packed well enough to create a hydrophobic interface.

2-Diformylmethylene-1,3-diselenole was prepared and condensed with dithiolium phoshonium bromides and dithiolium phosphonates in the presence of base to give dendralene-type vinylogs of TTF bearing a 1,3-diselenole moiety. The electrochemistry of these dendrimers was studied. SEEPR measurements were also carried out. Calculations were carried out on the radical cations and correlated with the EPR values.

Self-assembled monolayers (SAMs) formed by adsorption of thiols onto gold provide a flexible method to study the electrochemical reactivity of 7,7‘-diapo-(7E,7‘Z)-diphenylcarotene (DDC) on such bar...

Carotenoids are widely distributed among plants, certain bacteria and animals, serving for light harvesting and photoprotection in photosynthesis and as antioxidants. Electrochemical data (such as oxidation potentials, reaction rate constants, kinetic equilibrium constants) for 12 naturally occurring carotenoids are summarized in this paper. Electrochemical parameters were estimated by simulating experimental cyclic voltammograms (CVs). Conventional electrochemical techniques (cyclic voltammetry and Osteryoung square-wave voltammetry) were used in these studies. CVs of some natural carotenoids are presented and discussed. The dependence of redox potentials and other kinetic parameters on the structures of carotenoids is summarized. The oxidation potential of neutral carotenoid ( E ° 1 ), which corresponds to the formation of cation radicals, varies from 0.50 to 0.72 V versus SCE. The oxidation potential of carotenoid cation radical ( E ° 2 ), which corresponds to the formation of a dication, usually lies in the region of 0.52–0.95 V versus SCE. The electrochemical data presented in this article should be helpful in the study of reaction processes in model systems or actual photosynthesis reaction centers.

The initial stages of the anodic oxidation of Au(111) were investigated by means of cyclic voltammetry as well as in situ scanning tunneling microscopy (STM). The results suggest that the place exchange process, which initiates the oxide formation, starts at step edges. The oxide phase was imaged in situ by scanning tunneling and atomic force microscopy (AFM). The topographic information acquired by the two techniques is compared. Keywords: gold, gold oxide, corrosion, scanning tunneling microscopy (STM), atomic force microscopy (AFM).

A simple and sensitive extraction-gravimetric method for the determination of dipyridamole is presented. The method is based on the extraction of free dipyridamole with chloroform, after neutralization with a basic agent, followed by measurement of the frequency shift response of the specially designed surface acoustic wave resonator sensor after evaporation of the extractant from the surface of the resonator. The frequency shift response was proportional to the amount of dipyridamole in the range 0.065-1.12 micrograms. Experimental parameters and the effect of interfering substances on the assay of dipyridamole were also examined in this study. The method was applied to the determination of dipyridamole in tablets.

Theory and characteristics of the surface acoustic wave (SAW)/impedance sensor system in electrolyte solution are reported. This kind of sensor was constructed by a 62-MHz SAW resonator and a pair of conductive electrodes in series. By using the circuit network analysis theory, two oscillation equations were derived and used to explain the frequency-shift response to solution conductance. Results showed that the sensor possesses high sensitivity to the solution conductivity and can be applied to conductivity measurements in solution. Its sensitivity and accuracy could be improved in the presence of a large amount of unreacting foreign electrolytes. The sensor was successfully applied to four types of titration (acid-base, precipitation, oxidation-reduction and compleximetric titration) by monitoring the frequency-shift response. Factors influencing the frequencimetric titration curve were also investigated. Analytes at levels down to 1 × 10 −5 M could be determined by the proposed titration technique. The total acidity in several food samples was determined and the results were consistent with those obtained by conventional methods.