High Bath Research Articles

Orientation effect of asymmetric diatomic molecules in transport diffusion

Non-equilibrium transport is an important research area in statistical physics. The influences of the structures of polyatomic molecules on their transport have attracted the attention of researchers. Up to now, most of researchers deemed that temperature gradient is the main factor for molecular orientation and neglected the effect of the chemical potential gradient on the molecular orientation. To make up the deficiency in the study of chemical potential gradients, we build a non-equilibrium system with both chemical potential gradient and temperature gradient, and study the transport diffusion behavior of asymmetric diatomic molecules by using molecular dynamics and Monte Carlo methods. It is found that the diatomic molecules implement the orientation effect during non-equilibrium transport. Under the chemical potential gradient, the molecular orientation effect leads to the fact that the large atom tends to be in the direction of low concentration particle bath, while the small atom tends to be in the direction of high concentration particle bath. The molecular orientation is opposite to the direction of the flow. Under the temperature gradient, the molecular orientation effect leads to the fact that the large atom tends to be in the direction of high temperature particle bath, while the small atom tends to be in the direction of low temperature particle bath. The molecular orientation is the same as the direction of the flow. The orientation direction caused by concentration gradients is opposite to that caused by temperature gradients and it appears as a competitive relationship. At the same time, the influence of the asymmetry of the molecule itself on the molecular orientation is also studied. The larger the asymmetry of the molecule itself (σB/σA), the more obvious the molecular orientation effect is. When σB/σA>1.6, the influence of the asymmetry of the molecule itself on the orientation effect is gradually saturated. When σB/σA=1, which is also for a symmetric molecule, even if neither the temperature gradient nor the chemical potential gradient is zero, no molecular orientation occurs. We explain the physical mechanism of orientation through the principle of minimum entropy production. This work is of theoretical significance for in depth understanding the relationship between mass transport and molecular structure under non-equilibrium conditions.

High-current-density electrodeposition using pulsed and constant currents to produce thick CoPt magnetic films on silicon substrates

This paper investigates methods for electroplating thick (>20 μm), high-coercivity CoPt films using high current densities (up to 1 A/cm2) and elevated bath temperatures (70 °C). Correlations are made tying current-density and temperature process parameters with plating rate, elemental ratio and magnetic properties of the deposited CoPt films. It also investigates how pulsed currents can increase the plating rate and film to substrate adhesion. Using 500 mA/cm2 and constant current, high-quality, dense CoPt films were successfully electroplated up to 20 μm thick in 1 hr on silicon substrates (0.35 μm/min plating rate). After standard thermal treatment (675°C, 30 min) to achieve the ordered L10 crystalline phase, strong magnetic properties were measured: coercivities up 850 kA/m, remanences >0.5 T, and maximum energy products up to 46 kJ/m3.

Controlled and Selective Growth of 1D and 3D CdTe Nanostructures through a Structurally Engineered Porous Alumina Template for Enhanced Optical Applications

Current manuscript describes porous alumina (PA) template assisted electrodeposition of high aspect ratio nanowires and dense hierarchical structures of CdTe. We demonstrate here for the first time that simple structural engineering of a PA template can lead to electrochemical growth of diverse shapes of CdTe nanostructures. Facile and cost-effective modifications have been implemented for the fabrication of self-organized through-hole PA membrane and its transfer onto any rough substrate. These modifications have facilitated extended duration (30 minute to 1 hour) electrodeposition of CdTe nanostructures at high bath temperature of 60°C without delaminating the PA membrane. High aspect ratio nanowires of 60 nm diameter and 2.8 μm length were growth through the self-ordered PA membrane without any underlying metal coating i.e. without altering its optical properties. An average of 56% optical absorption (within 350 nm – 1400 nm wavelength) and a moderate photoluminescence was observed for the CdTe nanowires. Minor variation in the anodization process resulted into a non-uniform/branched PA template that enabled the formation of dense 3D hierarchical structures of CdTe using similar electrodeposition conditions as that used for CdTe nanowires. The hierarchical CdTe nanostructures exhibited very high total optical absorption of ∼90% within 350 nm – 1400 nm wavelength and a strong photoluminescence was also demonstrated that was almost 10 fold more intense than the CdTe nanowires.

Prevalence and risk factors of low bone mineral density in spondyloarthritis and prevalence of vertebral fractures

BackgroundInvestigate the prevalence and risk factors of low bone mineral density (BMD) in patients with axial spondyloarthritis as well as investigating the prevalence of vertebral fractures.MethodsPatients underwent BMD measurements with dual-energy X-ray absorptiometry (DXA) in the anterior-posterior lumbar spine, lateral spine and hip. We screened for vertebral fractures using vertebral fracture assessment, and then checked for syndesmophytes on the VFA images. Sociodemographic and clinical variables were collected.ResultsA total of 89 patients (41,6% female) took part in the study with a mean age of 44 ± 14 years and disease duration 10.2 ± 10.6 years. According to World Health Organization (WHO) criteria, 48,3% of patients displayed osteopenia and 6,7% osteoporosis. In the subgroup of women who underwent measurement at all sites including the lateral spine, the prevalence of osteopenia was 39.3% in the anterior-posterior spine, 32.1% in the lateral spine, and 64.3% with all sites together. VFA led to the diagnosis of at least one vertebral fracture in 6.2% of patients. On VFA, syndesmophytes were found in 24.3% of patients. The variables associated in multivariate analyses with low BMD in different measurement sites were low body mass index (BMI), a high physician’s global assessment score, a high Bath Ankylosing Spondylitis Functional Index (BASFI) score and female gender.ConclusionOur study found a high prevalence (around 50%) of low BMD in SpA. Conversely, the prevalence of osteoporosis (6.7% according to WHO criteria) and vertebral fractures (6.2%) was lower than generally reported in the literature. While lateral spine BMD measurement did little to improve the detection of osteopenia in women, the sample size was not large enough to enable us to draw definite conclusions.

ELECTROLESS QUATERNARY NI-CU-CO-P ALLOY DEPOSITION MECHANISM IN ACIDIC BATH USING CYCLIC VOLTAMMETRY MEASUREMENT

Quaternary nickel alloy of Ni-Co-Cu-P has been successfully deposit on Fe substrate for corrosion resistant material. However, the reaction mechanism of quaternary nickel alloy deposition is less known and requires investigation. In this study, using similar bath component is used to produce electroless Ni-Cu-Co-P alloy. Cyclic voltammetry (CV) study is done in various plating bath component at bath pH 4.50, 4.75 and 5.00. A coating of Ni-Cu-Co-P alloy was deposited on a Fe substrate to evaluate surface morphology and composition. From CV results, higher bath pH, increases the [H2PO2-] oxidation peak and shifted the oxidation potential towards less noble potential. The reduction potential of the Ni alloy moved to noble potential, hence, elevate deposition rate from 3.95 to 5.95 mm/hr. The Ni-Cu-Co-P alloy composition on Fe substrate in descending manner is Ni (68.55 – 82.09 wt%), Cu (14.11 – 27.80 wt%) and Co (1.32 - 1.52wt%). The P content remained lower than 3.00 wt%. Hence, Co act as reaction inhibitor, while Cu act as both reaction accelerator and stabilizer.

A New Route for Direct Electroless Ni-P Plating on Magnesium Alloys

This report describes a new route for direct electroless Ni-P plating on magnesium alloys using nickel sulfate as the main salt component. The surface morphology, chemical composition and corrosion resistance of coatings were determined using SEM, EDX and electrochemical polarization techniques. Ni-P coatings with good corrosion resistance and high adhesion were obtained using this route and improved pretreatments. A mixture of H3PO4 and HNO3 was used as a pickling solution for Mg substrate pretreatment. A coarse surface was produced via the developed pickling procedure. A mechanical occlusive force is believed to exist between the coatings and the substrates. Twice activations, K4P2O7 and NH4HF2 as activation components, respectively, were applied for the pretreatment of magnesium alloy plating. An optimal F/O ratio on the Mg substrate surface was obtained by this pretreatment method. The activation film has insoluble partial fluorides which can depress the active points on substrate surface against the reaction of Mg with Ni2+ and H+ in the plating bath. A highly stable bath with pH 5 buffer was identified. The advantages of the developed process include chromium-free, low fluoride, and high bath stability. It is applicable for the production of motorcycle part plating.

Printability study of hydrogel solution extrusion in nanoclay yield-stress bath during printing-then-gelation biofabrication

Yield-stress support bath-enabled extrusion printing is emerging as a promising filament-based direct-write strategy for different applications in tissue engineering and regenerative medicine. Central to the printing quality of complex three-dimensional structures fabricated by the support bath-enabled fabrication approach is the formation of a continuous filament with well-defined geometry. The objective of this research is to study the printability of hydrogel precursor solutions in a Laponite nanoclay yield-stress bath during extrusion printing where the printed hydrogel precursor solutions remain liquid. The printability herein is mainly evaluated based on the morphology and dimensions of printed liquid filaments. Seven filament types are observed during extrusion in the nanoclay bath: three types of well-defined filaments (swelling, equivalent diameter, and stretched) and four types of irregular filaments (rough surface, over-deposited, compressed, and discontinuous). When the alginate concentration increases, the diameter of filaments made of alginate-gelatin blends decreases. The nanoclay concentration significantly affects the morphology of deposited filaments: low concentration Laponite bath (such as 0.5% (w/v)) may lead to the formation of irregular filaments such as rough surface and over-deposited filaments while high concentration bath (such as 8.0% (w/v)) may result in the formation of compressed filaments. Operating conditions affect the filament diameter and morphology similar to those as observed during conventional extrusion printing. The printability knowledge enables the successful fabrication of cellular vascular constructs in the Laponite nanoclay bath.

Eight-Year Retention Rate of First-Line Tumor Necrosis Factor Inhibitors in Spondyloarthritis: A Multicenter Retrospective Analysis.

To evaluate the 8-year survival of the first tumor necrosis factor inhibitor (TNFi) in patients with axial spondyloarthritis (SpA) or psoriatic arthritis (PsA), identify the predictive factors for withdrawal, and compare the discontinuation rates for infliximab, etanercept, and adalimumab. We evaluated PsA and axial SpA patients treated with a first-line TNFi between 2005 and 2015 at 4 Italian tertiary centers. Eight-year drug survival was calculated by the Kaplan-Meier method, and risk for discontinuation among treatment groups compared by stratified log-rank test. Univariate and multivariate Cox proportional hazard models were developed to examine predictors of withdrawal. Of 614 patients (316 axial with SpA, 298 with PsA), 203 received adalimumab, 131 etanercept, and 280 infliximab, with similar frequencies in axial SpA and PsA subgroups. The cumulative 8-year retention rate in the whole population was 55.1% (57.2% and 51.9% for axial SpA and PsA, respectively; P = not significant). No significant differences were observed in drug persistence among individual TNFi in either group. Male sex (hazard ratio [HR] 0.595 [95% confidence interval (95% CI) 0.405-0.875]; P = 0.008) and concomitant methotrexate use (HR 0.648 [95% CI 0.426-0.985]; P = 0.042) were associated with a lower risk of withdrawal in PsA. High baseline Bath Ankylosing Spondylitis Disease Activity Index (HR 0.9842 [95% CI 0.9708-0.9980]; P = 0.028) was associated with a lower risk of withdrawal in axial SpA. No difference was found in the comparative analysis of reasons for discontinuation between PsA and axial SpA. We reported that the real-life 8-year retention rate of the first TNFi in axial SpA and PsA is greater than 50%, with no significant differences between axial SpA and PsA, irrespective of the individual TNFi.

Quantum Zeno and anti-Zeno effects in quantum dissipative systems

We investigate the quantum Zeno and anti-Zeno effects in quantum dissipative systems by employing a hierarchical equations of motion approach which is beyond the usual Markovian approximation, the rotating wave approximation, and the perturbative approximation. The quantum Zeno and anti-Zeno dynamics of a biased qubit-boson model and a biased qutrit-boson model are provided as illustrative examples. It is found that (i) there exists multiple Zeno-anti-Zeno crossover phenomena, (ii) the non-Markovian characteristic of the bath may be favorable for the accessibility of the Zeno dynamics, and (iii) high bath temperature may add the difficulty in observing the quantum Zeno effect in quantum dissipative systems.

The Properties of Epoxy/Graphene Conductive Materials Using High Speed Mechanical Stirrer and Bath Sonicator

In this work, two instruments were used to disperse graphene nanofillers into epoxy matrices, high speed mechanical stirrer and bath sonicator. Two stages experiment were conducted in order to achieve better dispersion of graphene fillers. Flexural test, fracture toughness test and density test were conducted on neat epoxy, 0.2 vol%, 0.4 vol%, 0.6 vol%, 0.8 vol% and 1 vol% graphene incorporated epoxy nanocomposites to observe the loading effect of graphene on the mechanical properties. Flexural results shown improvement in flexural strength graphene incorporated epoxy nanocomposites over neat epoxy. However, these enhancement were observed only up to 0.2 vol% filler loading after which the properties were seen to reduce. Reagglomeration of graphene nanofillers might be the factor that explained this phenomenon. Flexural modulus increased continuously as long as filler concentration increased. Fracture toughness results revealed the fracture toughness of nanocomposites fabricated using bath sonication has shown increasing trend with increasing filler concentration up to 1.0 vol% which not reach to optimum value yet. Nanocomposites fabricated using high speed mechanical stirrer has reached to optimum fracture toughness value at 0.6 vol% loadings. Further addition of graphene nanofillers promoted poor filler dispersion that resulting in decreased fracture toughness of nanocomposites. In addition, density of nanocomposites increased when greater amount of graphene nanofillers added regardless the processing techniques used. These results indicates that both processing techniques were suitable to disperse fillers at low loading only. However, bath sonication method was able to fabricate epoxy/graphene nanocomposites with more homogeneous filler dispersion compared to high speed mechanical mixing.

Monitoring of zincate pre-treatment of aluminium prior to electroless nickel plating

Zincating is used as a pre-treatment for aluminium prior to electroless nickel deposition during preparation of magnetic computer memory discs. Four immersion zincating solutions were evaluated at 22°C using single step or double zincating followed by electroless nickel deposition from a high phosphorus hypophosphite bath at 90°C. The coating process was monitored by potential vs. time curves obtained under open-circuit conditions during zincating then electroless nickel plating. The surface morphology of the aluminium, at various stages, was imaged by scanning electron microscopy and atomic force microscopy. Zero resistance ammetry was used to record galvanic currents between the aluminium and an inert platinum counter electrode during zincating. This, together with potential-time measurements, provided simple and valuable methods for following the zincating process and subsequent electroless Ni plating. Double zincating enabled a shorter induction time for electroless Ni deposition and resulted in a more complete coverage of the surface by Zn.

Design of Spinning and Subsequent Drawing Parameters to Improve the Mechanical Properties of PVA Fibers

In this study, efforts were made to enhance the mechanical properties of the poly(vinyl alcohol) (PVA) fibers of medium molecular weight(number-average degree of polymerization=1735) varying the ratio in DMSO/H2O mixed solvent and spinning/drawing conditions. The gel fibers prepared from pure DMSO were opaquely frozen in the coagulating bath of -20℃. However, transparent gel fibers were formed without freezing for the mixture to contain water less than 80wt%. As the amount of water in the mixture increased the residual solvent in the coagulated gel fibers decreased ranging from 85 to 42wt%. The complex viscosity increased with increasing PVA concentration in 80/20 DMSO/H2O exhibiting remarkable shear thinning at 18wt%. In the Cole-Cole plot, the 18wt% PVA solutions gave a deviated curve from 12 and 15wt% ones. Thus the optimum PVA concentration for the spinning processing of medium MW PVA solutions in 80/20 DMSO/H2O was determined to 18wt% with rheological concept. Low degree of drawing during hot drawing process in the dry state was available for high bath draft in the coagulation bath. The most improved mechanical properties were observed by applying the highest possible draw ratio attained by reducing bath draft over multi-step drawing process. In the given bath draft, linear relationship was observed between both tensile strength and modulus and draw ratio showing the inflection points at the draw ratio of 19.5 and 18.0 for tensile strength and modulus, respectively.

Effect of Zn(NO3)2 concentration in hydrothermal–electrochemical deposition on morphology and photoelectrochemical properties of ZnO nanorods

Zn(NO3)2 concentration had been reported to be significantly influential on electrodeposition of ZnO structures. In this work, this issue is revisited using hydrothermal–electrochemical deposition (HED). Seedless, cathodic electrochemical deposition of ZnO films is carried out on ITO electrode at 130°C in a closed glass reactor with varying Zn(NO3)2 concentration. Regardless of the concentration of Zn2+ precursor (0.001–0.1M) in the deposition solution, vertically aligned 1-D ZnO nanorods are obtained as opposed to electrodepositions at lower temperatures (70–80°C). We also report the effects of high bath temperature and pressure on the photoelectrochemical properties of the ZnO films. Manipulation of precursor concentration in the deposition solution allows adjustment of the aspect ratio of the nanorods and the degree of texturation along the c-axis; hence photoinduced current density. HED is shown to provide a single step synthesis route to prepare ZnO rods with desired aspect ratio specific for the desired application just by controlling the precursor concentration.

Effect of Metal Doped Zinc Oxide Nanorods on Photoelectrical Characteristics of ZnO/Polyaniline Heterojunction

The n-type vertically aligned metal doped ZnO nanorods (NRs) and p-type proton acid doped polyaniline (PANI) inorganic/organic heterojunction diodes have been fabricated. Aluminium (Al) and iron (Fe) doped ZnO NRs were grown on seed ZnO layer on fluorine doped tin oxide coated glass substrates by high temperature chemical bath deposition method. The elemental analysis using EDAX confirm doping of Al and Fe in ZnO. The morphology of doped ZnO nanorods and ZnO/PANI heterojunction exhibit well defined uniform nanorod arrays and interface between nanorods and polyaniline matrix respectively. The dark current–voltage curves confirmed the rectifying diode like behaviors of the heterojunctions, whereas under illumination, the junction revealed good sensitivity to UV and visible range with increased current densities. The highest ideality factor and lowest barrier height was found for FeZnO/PANI heterojunction under dark and under light compared to that of ZnO/PANI, AlZnO/PANI. This research is innovative with respect to low cost synthesis of efficient and sensitive hybrid p–n junction diodes and possibly serves as the building blocks for future optoelectronic applications.

Properties of PAN Fibers Solution Spun into a Chilled Coagulation Bath at High Solvent Compositions

In this work, multifilament, continuous polyacrylonitrile (PAN) fiber tow was solution spun mimicking industrial processing at the small pilot scale (0.5 k tow), while carefully altering the composition of the coagulation bath, in order to determine the effect on the resulting fiber shape, density, orientation, and tensile properties at varying points in the spinning process. Novel here are the abnormally high coagulation bath solvent compositions investigated, which surpass those often reported in the literature. In addition, the coagulation bath was maintained at a slightly chilled temperature, contrary to reported methods to produce round fibers. Further, by altering the composition of the bath in a step-wise fashion during a single spinning run, variations in all other process parameters were minimized. We found that with increasing solvent composition in the coagulation bath, the fibers not only became round in cross section, but also became smaller in diameter, which persisted down the spin line. With this decrease in diameter, all else equal, came an accompanying increase in apparent fiber density via a reduction in microvoid content. In addition, molecular orientation and tensile properties also increased. Therefore, it was found that inadequate understanding of the coagulation bath effects, and spinning at low coagulation bath solvent compositions, can hinder the ability of the fiber to reach optimum properties.

Effect of Processing on Microstructure and Corrosion Mitigating Properties of Hydrotalcite Coatings on AA 6061 Alloy

Pitting corrosion of the aluminium cladding of spent nuclear fuels stored in light water pools has been observed. To prevent this, coating of the Al cladding with hydrotalcite (HTC) was proposed. This paper presents the effect of chemical bath and processing parameters on microstructure and corrosion behavior of HTC coatings on alloy AA 6061 specimens. The HTC coating from the high temperature nitrate bath was homogeneous, thicker and consisted of well-defined intersecting platelets than that formed from the room temperature carbonate bath. Electrochemical polarization tests carried out with HTC coated AA 6061 specimens in 0.01 M NaCl revealed that specimens coated with HTC from the nitrate bath and further treated in a cerium salt solution were the most resistant to corrosion. Field tests in which un-coated and coated AA 6061 alloy coupons as well as full-size plates were exposed to the IEA-R1 reactor's spent fuel basin for duration of up to 14 months further corroborated the high corrosion resistance imparted by the high temperature HTC + Ce coating. The mechanism by which the HTC coating and cerium protect the Al alloy is discussed.

Accelerometer Quantification of Physical Activity and Activity Patterns in Patients with Ankylosing Spondylitis and Population Controls.

To compare the total amount of physical activity (TPA) and time spent in various activity intensities of patients with ankylosing spondylitis (AS) and population controls, and to explore factors related to physical activity (PA). Subjects were asked to wear a triaxial accelerometer for 7 days and to complete a series of questionnaires. Multivariable regressions were used to assess generic determinants of TPA in patients and controls, and in patients to explore demographic and disease-specific determinants of various PA intensities. One hundred and thirty-five patients [51 ± 13 yrs, 60% men, body mass index (BMI) 26.0 ± 4.3 kg/m(2)] and 99 controls (45 ± 12 yrs, 67% men, BMI 25.1 ± 4.3 kg/m(2)) were included. Patients did not differ from controls regarding TPA (589 vs 608 vector count/min, p = 0.98), minutes/day spent in sedentary (524 vs 541, p = 0.17), and light PA (290 vs 290 p = 0.95), but spent fewer minutes/day in moderate to vigorous PA (MVPA; 23 vs 30 min/day, p = 0.006). Perceived functional ability (physical component summary of the Medical Outcomes Study Short Form-36) and BMI were associated with TPA independent of having AS (p interaction = 0.21 and 0.94, respectively). Additional analyses in patients showed that time spent in MVPA was negatively influenced by BMI, physical function (Bath AS Functional Index), and disease duration. In patients ≥ 52 years old, a higher Bath AS Disease Activity Index was associated with less time spent in sedentary and more time spent in light activities. Compared with controls, patients with AS had similar TPA, but may avoid engagement in higher intensities of PA. Lower levels of functional ability and higher BMI were associated with lower TPA in both patients and controls.

EFFECT OF BATH pH ON ELECTROLESSNi–PCOATING DEPOSITED ON OPEN-CELL ALUMINUM FOAMS

Different electroless Ni – P coatings were deposited on open-cell aluminum foams at various bath pH. The effect of bath pH on the morphology, structure, components, phases and corrosion resistance of the Ni – P coating was studied by scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), immersion test and electrochemical polarization measurement, respectively. The experimental results show that the bath pH not only changed the reactivity of the bath, but also had a influence on the microstructure and anticorrosive property of electroless Ni – P coating. The high pH bath raises the thickness of Ni – P coating but decreases the content of phosphorus element in the Ni – P coating. The corrosion resistance of the coated aluminum foams increases when the bath pH rises.

A residual compensation method for the calibration equation of negative temperature coefficient thermistors

We propose a calibration equation for negative temperature coefficient thermistors. This equation is modified from the basic thermistor equation by a residual compensation method. The residual compensated equation includes a 2nd order error correction term. This equation is convenient for converting temperature to resistance and vice versa. Calibrations of various thermistors were performed in a high precision temperature bath to test the resistance–temperature relation. The thermistors were calibrated in glass tubes using a reference thermometer. Most calibrations are performed in a temperature span (15–35°C). From the resistance–temperature curves, the fitting function of the basic thermistor equation and the residual compensated equation were evaluated and their fitting errors were compared. Standard fitting errors (1σ) in temperature of the basic equation and the residual compensated basic equation were 8.131mK and 0.151mK respectively. The residual compensated equation showed about 1/54 smaller fitting errors than the basic thermistor equation.

Empirical model to predict mass gain of cobalt electroless deposition on ceramic particles using response surface methodology

This investigation was undertaken to predict the mass gain (MG) of cobalt electroless deposition (ED) on ceramic SiC particles. Response surface methodology (RSM) based on a full factorial design with three ED parameters and 30 runs was used to conduct the experiments and to establish a mathematical model by means of Design-Expert software. Three ED parameters considered were pH, bath temperature and ceramic particle morphology. Analysis of variance was applied to validate the predicted model. The results of confirmation analysis by scanning electron microscopy (SEM) show that the developed models are reasonably accurate. The pH is the most effective parameter for the MG. Also, the highest mass gain is obtained for the lowest pH, highest bath temperatures and heat-treated SiC particles. In addition, the developed model shows that the optimal parameters to get a maximum value of mass gain are pH, bath temperature and ceramic particle state of 8, 70 °C and heat treatment, respectively.