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Previous meta-analyses have produced conflicting conclusions about suicidality risk among psoriasis patients. We aimed to update the evidence on the risk for the whole continuum of incident suicidality in psoriasis patients. We performed an update systematic review and meta-analysis and searched CENTRAL, PubMed, and Embase from January 1, 2017 to August 14, 2021 for relevant new cohort studies and incorporated new studies into our previous systematic review. Random-effects model meta-analysis was used to obtain pooled hazard ratio (HR) with 95% confidence interval (CI). Subgroup analysis was conducted according to age and disease severity. A total of 12 studies were included in this meta-analysis. We detected no significant differences in the risk for incident completed suicide (HR 1.33, 95% CI 0.91-1.95), suicide attempt (HR 1.22, 95% CI 0.96-1.56), suicidal behavior (HR 1.08, 95% CI 0.98-1.19), and suicide ideation (HR 1.74, 95% CI 0.99-3.06) between psoriasis patients and non-psoriatic controls. In the subgroup analysis based on age, an increased risk for incident suicide ideation was observed in pediatric subgroup (HR 1.50, 95% CI 1.12-2.03). The updated evidence suggests no increased risk for whole continuum of incident suicidality spectrum in psoriasis patients but an increased risk for incident suicide ideation among pediatric psoriasis patients. Involving mental health professionals may be crucial in psoriasis management especially in young patients.

Many mortality models, such as the Lee–Carter model, have unsatisfactory estimation in the case of small populations. Increasing population size is a natural choice to stabilize the estimation, if ...

Ageing is a major demographic issue for the world of the 21st century and is caused by substantial declines in fertility and mortality rates. Without international migration, most developed countries would not be able to balance the resulting losses of population and work force. The proportion of elderly (aged 65 and over) in Taiwan reached the threshold of 7%, indicating an ageing society, in 1993, and has been increasing dramatically since then. The county-level populations in Taiwan are also ageing rapidly, but the local changes vary widely because domestic migration rates of each county are different. Urbanization is becoming more obvious, with people tending to move to large cities and counties with better social welfare programs. As a result, domestic migration plays an important role in population ageing at the county level, and the people in counties with larger numbers of domestic immigrants are expected to have a longer life expectancy. However, the life expectancies of people in these counties do not bear out this trend. In the present study, based on domestic migration records from the Department of the Interior of Taiwan, we applied graduation methods and small-area estimation skills to construct county-level life tables, and evaluate whether domestic immigrants have lower mortality rates than those who do not migrate. We found that the domestic immigrants of Kinmen County have significantly lower mortality rates, but those of Hsinchu County do not.

The purpose of the study is to identify emerging themes influencing U.S. Gen Z consumers’ motivations toward secondhand shopping and their willingness to purchase secondhand clothing. A qualitative method approach was used to conduct 18 in-depth interviews as a data collection method. The interviews were semi-structured with the deliverance of open-ended/semistructured questions carried out in a conversational style. For understanding Gen Z consumer’s buying behavior, theory planned behavior (TPB) is applied to explore their motivation for buying secondhand clothing. TPB includes three variables: attitude,subjective norm, and perceived behavioral control. Those three variables have an impact on behavioral intention, which consequently will influence the actual purchase behavior of consumers. The participants were motivated to shop secondhand clothing for the following values perceived: (1) financial benefit, (2) social value, (3) emotional value,(4) convenience value, (5) sustainability value, and (6) perceived behavior control.

A low defect-density AlN template film using V/III ratio modulation and nano-patterned sapphire substrate (NPSS) was achieved by metalorganic chemical vapor deposition. In contrast to conventional high-quality AlN/NPSS obtained with high coalescence thickness (>6 μm) using high growth temperatures (≥1250 oC), this study reveals the high crystallinity of AlN with the lower thickness of 2.55 μm grown under a lower temperature of 1130 °C. It could effectively increase the heater lifetime and reduce the epi-wafer warpage. The growth of AlN/NPSS dominated by epitaxial lateral overgrowth achieves a dramatic reduction of full width at half maximum values along ( 10 1 ¯ 2 ) plane from 1640 to 714 arcsec, and lowest dislocation density of approximately 1 × 108 cm−2, as well as a ultra-low etching pit density of 2.3 × 105 cm−2. The crack-free AlN/NPSS with a compressive stress owing to the tensile stress was relaxed by the existence of some key-shaped holes upon the patterned region. Details of the surface evolution, mechanism and dislocation behavior of AlN/NPSS will be discussed and these results demonstrate this low-defect template technique of high potential for AlGaN-based device applications.

SiO2-MgF2/TiO2 double-layer films with antireflective, self-cleaning and adherent properties were prepared by spin-coating SiO2-MgF2 and TiO2 sol on glass substrate successively and subsequently being calcined at 250°C. The optical and structural properties of films have been investigated by visible spectrophotometer and field emission scanning electron microscope, respectively. At the same time, self-cleaning property generated from superhydrophilicity and photocatalysis was obtained. The results indicated that the as-prepared SiO2-MgF2/TiO2 double-layer films show a maximum increase in transmittance near 520 nm wavelength of 2.8% and photocatalytic property with the R value of 4.7(JIS R 1703–2).It has been demonstrated that high transmittance, self-cleaning and adherent composite has been obtained by a simple sol–gel route presenting good potential to be applied on photovoltaics systems.

F-FDG PET/CT is a valuable diagnostic tool in the evaluation of cardiac sarcoidosis. Appropriate patient preparation is important because the diagnostic accuracy of this procedure depends on adequate suppression of physiologic glucose uptake. This systematic review and meta-analysis aims to assess the effect of different patient preparations on the diagnostic accuracy of F-FDG PET/CT in cardiac sarcoidosis.We searched the PubMed/MEDLINE, Embase, and Cinicaltrials.gov databases. Sixteen studies (n = 559) were identified to be suitable for this systemic review. Studies were stratified according to fasting duration and means of physiologic suppression of F-FDG by cardiac tissue, which involves the use of heparin infusion or high-fat, low-carbohydrate diet before imaging. Study quality was assessed using the QUADAS-2 tool. Forest plots of sensitivity and specificity were calculated in Review Manager 5.3, and a random-effects hierarchical summary receiver operating characteristic model was created using MetaDiSc. Meta-regression was performed to investigate sources of heterogeneity.PET/CT had an overall Specificity of 0.75 (95% confidence interval [CI], 0.69-0.80) and specificity of 0.81 (95% CI, 0.76-0.85) for the diagnosis of cardiac sarcoidosis. This modest diagnostic accuracy was attributed to the inclusion of large single study in which a short fasting duration before scanning likely influenced its sensitivity. Its exclusion resulted in an overall sensitivity of 0.81 (95% CI, 0.76-0.86) and specificity of 0.82 (95% CI, 0.77-0.86). Meta-regression showed that the diagnostic odds ratio was significantly affected by fasting time and heparin administration before scanning (P = 0.01, 0.02) but not with high-fat, low-carbohydrate diet (P = 0.17).F-FDG PET/CT plays an integral role in the diagnosis of cardiac sarcoidosis. Diagnostic accuracy is affected by fasting duration and means of cardiomyocyte glucose uptake suppression before scanning.

A novel structure was built by alternating high and low V/III ratios to improve the quality of the AlN layer at a lower temperature (1100 °C) as compared with conventional growth temperatures (≥1300 °C). This novel structure was applied to fabricate the stacking structure and superlattice layers. We designed four different AlN epitaxial structures to verify the effect of these new structures on the crystallinity. The dislocation density decreased by about one order of magnitude from 7.8 × 109 cm−2 to 7.4 × 108 cm−2 after inserting the superlattice in the middle AlN layer. The full width at half maximum values of AlN (0002) and (10−12) also were improved. Interestingly, we found that the growth mechanism and dislocation behavior were greatly dependent on the inserting sites of the superlattice by transmission electron microscopy. As the superlattice was grown first, the growth of the AlN layer was dominated by an island mode forming a column-like structure with twist boundaries. Most of the threading dislocations were decreased by bending and combining with each other along the grain boundary in the columnar structure. We believed that this novel structure could help achieve the growth of an AlN epilayer with optimal quality at a low temperature under the consideration of prolonging the lifetime of the heating system.

The effect of growth pressure on defect formation in InAlN epilayers grown on GaN/sapphire templates by metal–organic chemical vapor deposition was systematically investigated in this study. From X-ray diffraction measurements, it was found that a serious phase separation occurred in the InAlN epilayers grown at 1 × 104 Pa (100 mbar). The inhomogeneity of the In composition was observed at the beginning of the InAlN growth as examined by transmission electron microscopy. The initial In composition inhomogeneity close to the InAlN/GaN interface was confirmed to play an important role in the formation of V-shaped defects and the phase separation. When the growth pressure increased from 1 × 104 Pa (100 mbar) to 5 × 104 Pa (500 mbar), the phase separation diminished over 3 × 104 Pa (300 mbar), and the In content continuously increased from 6.0 to 25%. However, in spite of the fact that there was no phase separation in the InAlN layer grown at 3 × 104 Pa (300 mbar), the inhomogeneity of the In composition still existed near the surface instead of the InAlN/GaN interface. This was caused by the fact that the In adatoms preferred to accumulate at the V-shaped defects which were induced by the low surface mobility and parasitic reaction of Al adatoms. Two distinct formation mechanisms of the V-shaped defects at the low and high growth pressures were confirmed. To explore the effect of thickness on the epilayer quality, a series of InAlN samples (In = ~20%) with various thicknesses ranging from 5 to 125 nm were investigated. The InAlN epilayer with a thickness of 10 nm showed the optimum crystallinity and minimum surface roughness. A higher growth pressure (≥3 × 104 Pa (300 mbar)) and a thinner thickness (≤10 nm) favored the In composition homogeneity and suppressed the formation of V-shaped defects. Both key growth parameters were demonstrated in detail to achieve a high-quality InAlN epilayer for device applications.

In this study, high internal-quantum-efficiency (IQE) AlGaN multiple quantum wells (MQWs) were successfully demonstrated on low-defect-density AlN templates with nano-patterned sapphire substrates. These templates consisted of AlN structures with 0∼30 periods superlattices (SLs) by alternating high (100) and low (25) V/III ratios under a low growth temperature (1130 °C). Compared to conventional high crystal-quality AlN epilayers achieved at temperatures ≥1300 °C, lower thermal budget can reduce the production cost and wafer warpage. Via optimization of the SL period, the AlN crystallinity was systematically improved. Strong dependence of SL period number on the X-ray full-width-at-half-maximum (FWHM) of the AlN epilayer was observed. The AlN template with 20-period SLs exhibited the lowest FWHM values for (0002) and (10ī2), namely 331 and 652 arcsec, respectively, as well as an ultra-low etching pit density of 1 × 105 cm−2. The relative IQE of 280 nm AlGaN MQWs exhibited a dramatically increase from 22.8% to 85% when the inserted SL increased from 0 to 20 periods. It has hardly ever been reported for the AlGaN MQW sample. The results indicate that the engineered AlN templates have high potential applications in deep ultraviolet light emitters.

In this study, low-temperature (LT) and high-temperature (HT) AlN insertion layers (ILs) grown at 680 and 970 °C were integrated with 3.7-μm GaN-based heterostructure grown on 150-mm Si (111) substrates by metalorganic chemical vapor deposition. Under a V/III flow ratio of 1960, the GaN epilayer with a continuous interface resulting from the LT AlN IL was subject to a compressive stress of −0.109 GPa. However, the GaN epilayer with discontinuous interfaces resulting from the HT AlN IL growth under the same flow ratio was subject to a tensile stress of 0.174 GPa. To realize continuous interfaces between the GaN epilayer and HT AlN IL, a higher V/III ratio of 5960 was utilized to suppress the decomposition of GaN. It results in changing the stress state of the GaN-based heterostructure from tensile to compressive. This strategic finding indicates that a stress-controllable GaN on Si can be achieved via the incorporation of HT AlN ILs. A minimum curvature at 5 km−1 is demonstrated for the 3.7-μm GaN-based heterostructure on a 150-mm Si (111) substrate, which has high potential for power switching device applications.

In this paper, the thickness effect of an undoped Al 0.23 Ga 0.77 N inserted in the Mg-doped Al 0.23 Ga 0.77 N electron-blocking layer (EBL) on the characteristics of the ultraviolet light-emitting diodes (UV-LEDs) was analyzed. The results of secondary-ion-mass spectrometry clearly show that the concentration of Mg back-diffusion from the p-GaN and the Mg-doped EBL decreases with the thickness of an undoped EBL. The radiative recombination rate in the multiple quantum wells (MQWs) can be obviously enhanced after inserting an undoped EBL from the simulated results, and the sample with a 6-nm-thick undoped EBL has the highest radiative recombination rate. It is worth noticing that the hole carrier concentration in the MQWs increases with increasing the thickness of an undoped EBL. The UV-LED possesses 400% enhancement in the output power (at 20 mA) by inserting a 6-nm-thick undoped EBL. The significant enhancement is ascribed to the decrease of nonradiative recombination defects formed by Mg atoms and the increase of hole concentration in the MQWs.

In this study, 1.61-µm-thick GaN/graded AlGaN/AlN epilayers were prepared on Si substrates by using metalorganic chemical vapor deposition. To determine whether the insertion of a Si x N y interlayer enhances the epitaxial quality of the GaN layer, various numbers of Si x N y interlayers were inserted at different locations, and the effects were investigated. In addition to analyzing crystal quality, epilayer stress was investigated in detail by performing Raman, photoluminescence, and curvature measurements. Inserting Si x N y into the AlGaN layer resulted in a deterioration in epitaxial quality and the appearance of serious surface cracks because of the concentration of Al atoms near pits, which enabled new and bigger centers of defects to form. A crack-free surface and relatively high crystal quality were achieved by inserting a Si x N y interlayer into a GaN epilayer; the resultant improvement in crystal quality was attributed to the bending and annihilation of dislocations. For a sample in which Si x N y was not inserted, Raman and photoluminescence measurements revealed that the stresses were 0.535 and 0.741 GPa, respectively. The addition of a single Si x N y interlayer into the GaN epilayer significantly reduced these stresses to 0.279 and 0.556 GPa, respectively.

The GaN epilayers were grown on Si(111) substrates via combining the techniques of AlN buffer, the graded AlGaN structure and the SixNy interlayer by metalorganic chemical vapor deposition. The SixNy interlayers with various growth times of 0–60 s were introduced into the growth of GaN epilayers. To thoroughly realize the growth evolution of SixNy, measurements of atomic force microscopy, field emission scanning electron microscopy and nano-Auger electron spectroscopy were performed. From the measurement by transmission electron microscopy, it can be proven that nanocrystalline SixNy is preferentially located at the dislocation cores and pits during the growth process. For the fabrication of GaN/graded AlGaN/AlN/Si, the full width at half maximum of the X-ray diffraction rocking curve at the GaN(102) plane was reduced effectively from 965 to 771 arcsec by inserting SixNy into the GaN epilayer, which resulted from the bending and annihilation of dislocations.

Single-crystalline β-Ga2O3 epilayer on (0001) sapphire was grown at low temperature and low pressure by MOCVD. The as-grown β-Ga2O3 epilayer was annealed at 800 ºC in atmosphere. Crystal structure and quality of the epilayer remained the same after annealing. Influence of surface states and point defects of β-Ga2O3 epilayers before and after annealing are studied using room-temperature Photoluminescence (PL) and I-V characteristics. The significant difference in PL property of β-Ga2O3 and big difference (~5 orders in magnitude) in dark current before and after annealing is attributed to the healing of the surface states and point defects. Gallium oxide is known for its high density of oxygen vacancies. Annealing single-crystalline β-Ga2O3 epilayer at high temperature makes the healing possible, probably due to oxygen adsorption. A significant healing of surface states and point defects in single-crystalline β-Ga2O3 indicates its high potential in fabrication of optoelectronic devices.

In this letter, the ultraviolet light emitting diode (UV-LED) with an undoped Al0.23Ga0.77N electron-blocking layer (EBL) between the p-type doped Al0.23Ga0.77N EBL and last barrier was proposed. After inserting the undoped EBL, both the photoluminescence and electroluminescence (EL) characteristics of UV-LED were significantly improved. As the undoped EBL was inserted, the 365-nm UV-LED possessed 400% improvement in output power (at 19 A/cm2). However, the enhancement in output power was significantly reduced to 20% when the insertion of undoped EBL was applied for 375-nm UV-LED. In addition, the long-term reliability was enhanced efficiently with the addition of undoped EBL. After the aging test for 1032 h, it presented the 365-nm UV-LED inserted with an undoped EBL had the obvious improvements both in the characteristics of EL intensity and leakage current density.

Donnan equilibrium between a salt-free colloidal dispersion and an electrolyte solution has been investigated by Monte Carlo simulations. The Donnan potential is directly calculated by considering two compartments separated by a semipermeable membrane. In order to understand the role played by colloid–ion interactions, the influences of colloidal characteristics, including particle size R, intrinsic particle charge Z, counterion valency z c , and concentration c p , on Donnan potential Ψ D and effective charge Z eff are examined. Our simulations show that the electroneutrality condition is not followed in both compartments and the Donnan potential arises due to the net charge density. The Donnan potential grows by increasing c p and Z eff and by decreasing dielectric constant e r , i.e., Ψ D ∼ Z eff c p / e r approximately. Note that the effective charge varies with R , Z , c p , e r and z c as well. When the salt concentration is increased, the net charge density is lowered and thus the Donnan potential decays accordingly. The validity of the classical theory based on the Nernst equation and the electroneutrality assumption is also examined. In general, the simulation results at high-salt condition can be well represented by such mean-field theory.

The objective of this paper is to present the utilization of information produced during plasma etching for the prediction of etch bias. A plasma etching process typically relies on the concentration of electrically activated chemical species in a reaction chambers over time, depending on chamber pressure, gas flow rate, power level, and other chamber and wafer properties. Plasma properties, as well as equipment factors, are complex and vary over time. In this paper, we will use various statistical techniques to address challenges due to the nature of plasma data: high dimensionality, colinearity, parameter interactions and nonlinearities, variation of data structure due to equipment condition changing over time, etc. The emphasis will be data integrity, variable selection, accommodation for process dynamics, and model-building methods. Different techniques will be evaluated with an industrial dataset.

This study investigated characteristics of a chitosan membrane from the carapace of the soldier crab Mictyris brevidactylus intended to construct an amperometric biosensor. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used in this study to characterize these chitosan membranes intended for constructing enzymatic biosensors. Chitosan membranes suffering various durations (10 min) of deacetylation had small charge-transfer resistances (7.88 kohms) but large double-layer capacitances (0.55 microF). They were found in EIS where both the solution resistance and Warburg impedance upon electrode interface were almost independent of the durations and degree of deacetylation. The degree of deacetylation and the thickness of chitosan membranes were also determined. Membrane thickness was slightly dependent with the duration but degree of deacetylation was slightly dependent on the duration. Chitosan membranes with various thicknesses suffered various durations of deacetylation, but this did not influence their electrochemical characteristics. The chitinous membrane was covalently immobilized with glucose oxidase (EC 1.3.4.3) and then attached onto the platinum electrode of a homemade amperometric flow cell. Sensor signal was linearly related to glucose concentration (r=0.999 for glucose up to 1.0 mM). The system was sensitive (S/N5 for 10 microM glucose) and reproducible (CV1.3% for 50 microM glucose, n=5).

Feasibility of single-wafer rapid-thermal process as an alternative to the conventional batch-type furnace process is evaluated on a 0.15-/spl mu/m 128-Mb mask read only memory (MROM) product. Excellent gate oxide integrity and device characteristics are achieved with a single-wafer rapid-thermal process. Superior yield and product reliability by using single-wafer process tool have also been achieved. Shortened process cycle time and better thermal process uniformity by using single-wafer rapid-thermal processing are demonstrated.

MOCVD-grown single-crystal β-Ga2O3 epilayers on (0001) sapphire substrates were developed at low temperature and low pressure. As-grown β-Ga2O3 epilayers were post-annealed at different temperatures in the atmosphere. Crystalline structure and quality of epilayers, tracked by X-ray diffraction (XRD), remained almost unchanged after post-annealing. Effect of surface states and point defects of β-Ga2O3 epilayers before and after annealing are studied using room temperature Photoluminescence (PL) and I-V characteristics (dark current). The significant difference in PL property and dark current before and after annealing is attributed to healing of the surface states and point defects, as β-Ga2O3 is known for its high density of oxygen vacancies. Post-annealing single-crystal β-Ga2O3 epilayers at high temperature makes the healing possible, probably due to oxygen diffusion and surface band bending. A significant healing of surface states and point defects in single-crystal β-Ga2O3 indicates its high potential in fabrication of optoelectronic devices.

We created a material with a composition gradient within each grain. Due to the graded composition the ceramic does not show a sharp change in dielectric constant near the relaxation frequency. Instead, we observe gradual decrease in dielectric constant with frequency, with the loss tangent remaining practically unchanged (below 0.02 everywhere within the frequency range 0.0003–3 GHz). The tunability of the ceramic decreases with increasing frequency but remains in the order of 10% at 3 GHz. Thus we conclude that the dielectric relaxation in high purity (Ba,Sr)TiO3 occurs predominantly by Ti 4+ ion hopping relaxation. We also expect that the concept of intragrain concentration gradient ceramics may become a useful material for a wide range of electronic devices. PACS: 77.22.Gm, 77.22.Ch, 77.84.Dy # 2002 Elsevier Science Ltd. All rights reserved.

The miniaturization of electronic devices has led to a need for tunable dielectric materials. These materials must exhibit high tunability and low loss in the microwave region. We observed high tunability and low loss throughout the microwave region, from .3 MHz to 3 GHz, in (Ba,Sr)TiO3 ceramics with intragrain concentration gradients. The tunability varied slightly with frequency and was measured to be ∼10% at 3 GHz under 10kV/cm bias and the loss tangent remained virtually unchanged, below .02 in this region. Our data is consistent with the theory of ion hopping clusters[1]. The graded composition results in suppression of ferroelectric resonance and thus dispersion of peak dielectric loss. The concept of intragrain concentration gradient materials can lead to a variety of applications in the microwave communications field.

High indium composition InGaN films were co-deposited on u-GaN templates using low temperature (300°C) pulsed laser deposition (PLD). The du-composition target consisted of a 3-inch indium sheet drilled with periodic rectangular holes mounted on a normal GaN wafer. By changing the ratio of the holes areas to total sheet area, the indium concentration in two InGaN films was set to 33% and 60%. The structural and optical characteristics of these films are investigated through isochronal and isothermal annealing. X-ray diffraction (XRD) and cathodeluminescence results for the 33% sample exhibited no significant differences in line-shape and peak position even after annealing at 800°C for 100 minutes. In contrast, the XRD peak of 60% sample became broadened under the same annealing condition. This slight inhomogeneity in composition also resulted in two visible peaks in the photoluminescence spectrum. Although the optical properties of the 60% sample can be considered merely acceptable, the advantages of applying PLD to the growth of high thermal stability and high indium composition InGaN have been made clear. The PLD technique shows promise for developing long wavelength devices.

The β-Ga2O3 films were grown on (0001) sapphire at 500 °C by metal organic chemical vapor deposition. In the analysis of crystal structure, we found that the (-201) oriented single crystal β-Ga2O3 epilayer can be obtained under low chamber pressure of 15 torr. Moreover, a metal-semiconductor-metal solar-blind deep ultraviolet photodetector was fabricated with the β-Ga2O3 epilayer. As the bias voltage is 5 V, the photodetector exhibits a relatively low dark current about 0.2 pA, which induced by the highly resistive nature of the β-Ga2O3 thin films. From the responsivity result, it can be observed that photodetector shows a maximum responsivity at 260 nm, revealing the β-Ga2O3 photodetector was really solar-blind. The responsivity of the photodetector was as high as 20.1 A/W with an applied bias of 5 V and an incident light wavelength of 260 nm. The improved performance is attributed to the high quality of β-Ga2O3 epilayer.

Air motors have often been utilized in industrial servo systems in the automation industry due to their advantages such as small volume, low cost, light weight, convenience of operation, and no overheating problems. Recently, the development of control technology has improved, making the requirements for control precision higher than ever before. Accurate control performance in pneumatic systems is facilitated by the implementation of nonlinear control techniques. The purpose of this study is to analyze the behavior of a biaxial pneumatic table motion system with a vane-type air motor, and to design a backstepping sliding mode controller for this system. A proportional integral derivative controller compared with this new backstepping design. The tracking circle error and tracking error of the two axes are noted. The experimental results show that accurate tracking circle trajectory performance can be achieved with the proposed controller.

The sedimentation profile of a dilute colloidal solution follows the barometric distribution owing to the balance between gravitational force and thermal fluctuation. However, the electrostatic interactions may lead to significant deviation even in the low volume fraction limit (e.g., 10(-5)). On the basis of Monte Carlo simulations for a dilute, salt-free colloidal dispersion, five regimes can be identified through the resulting colloidal sedimentation profile and the counterion distribution. The electrostatic interactions depends on the Coulomb strength E(c) defined as the ratio of the Bjerrum length to the colloid size. At weak colloid-ion attractions (small E(c)), counterions tend to distribute uniformly in the container. However, both barometric and inflated profiles of colloids can be observed. On the contrary, at strong colloid-ion attraction (large E(c)), counterions accumulate in the vicinity of the colloids. Significant counterion condensation effectively decreases the strength of colloid-colloid repulsion and barometric profile of colloids can be obtained as well. As a result, the sedimentation profile and counterion distribution are indicative of the strength of effective colloid-colloid and colloid-ion interactions. It is also found that local electroneutrality condition is generally not satisfied and charge separation (or internal electric field) is neither a sufficient nor necessary condition for nonbarometric distributions.

The effective charge Z* is often invoked to account for the accumulation of counterions near the colloid with intrinsic charge Z. Although the ion concentrations ci are not uniform in the solution due to the presence of the charged particle, their chemical potentials are uniform everywhere. Thus, on the basis of ion chemical potential, effective ion concentrations ci*, which can be experimentally measured by potentiometry, are defined with the pure salt solution as the reference state. The effective charge associated with the charged particle can then be determined by the global electroneutrality condition. In terms of the charge ratio α = Z*/Z, the effects of added salt concentration, counterion valency, and particle charge are examined. The effective charge declines with increasing salt concentration and the multivalent salt is much more efficient in reducing the effective charge of the colloidal solution. Moreover, the extent of effective charge reduction is decreased with increasing intrinsic charge f...

Micellization of a diblock copolymer in dilute solution is studied by dissipative particle dynamics. The influence of the compatibility between blocks A and B and the interaction between the insoluble block and solvent on aggregation number P and micellar core radius Rc are examined. The micelle size distribution is obtained, and it is quite polydisperse. Different from the scaling theory for starlike micelles, the mean aggregation number based on weight averagePw decreases with increasing soluble-block length NA and the power law relation can be obtained,Pw approximately NA(-alpha). Similarly, the micellar core radius declines with NA, following Rc approximately NA(-beta) with beta=alpha/3. However, the exponent depends on the mutual compatibility between soluble and insoluble blocks. For the same composition, the incompatible diblocks form a smaller micelle and its aggregation number declines with a smaller exponent alpha. When NA approximately NB, the micelles deviate significantly from the spherical shape and solvophilic blocks are observed to be entrapped in the solvophobic core for compatible diblocks.

Counterion condensation and release in micellar solutions are investigated by direct measurement of counterion concentration with ion-selective electrode. Monte Carlo simulations based on the cell model are also performed to analyze the experimental results. The degree of counterion condensation is indicated by the concentration ratio of counterions in the bulk to the total ionic surfactant added, alphaor =1. The ionic surfactant is completely dissociated below the critical micelle concentration (cmc). However, as cmc is exceeded, the free counterion ratio alpha declines with increasing the surfactant concentration and approaches an asymptotic value owing to counterion condensation to the surface of the highly charged micelles. Micelle formation leads to much stronger electrostatic attraction between the counterion and the highly charged sphere in comparison to the attraction of single surfactant ion with its counterion. A simple model is developed to obtain the true degree of ionization, which agrees with our Monte Carlo results. Upon addition of neutral polymer or monovalent salts, some of the surfactant counterions are released to the bulk. The former is due to the decrease of the intrinsic charge (smaller aggregation number) and the degree of ionization is increased. The latter is attributed to competitive counterion condensation, which follows the Hefmeister series. This consequence indicates that the specific ion effect plays an important role next to the electrostatic attraction.

At strong electrostatic coupling, counterions are accumulated in the vicinity of the surface of the charged particle with intrinsic charge Z. In order to explain the behavior of highly charged particles, effective charge Z(*) is therefore invoked in the models based on Debye-Huckel approximation, such as the Derjaguin-Landau-Verwey-Overbeek potential. For a salt-free colloidal suspension, we perform Monte Carlo simulations to obtain various thermodynamic properties omega in a spherical Wigner-Seitz cell. The effect of dielectric discontinuity is examined. We show that at the same particle volume fraction, counterions around a highly charged sphere with Z may display the same value of omega as those around a weakly charged sphere with Z(*), i.e., omega(Z)=omega(Z(*)). There exists a maximally attainable value of omega at which Z=Z(*). Defining Z(*) as the effective charge, we find that the effective charge passes through a maximum and declines again due to ion-ion correlation as the number of counterions is increased. The effective charge is even smaller if one adopts the Debye-Huckel expression omega(DH). Our results suggest that charge renormalization can be performed by chemical potential, which may be observed in osmotic pressure measurements.

Summary form only given. Optical communication links between 100 meters and 10 kilometers will require new cost effective transceiver solutions. We have demonstrated single mode and high-speed modulation in long wavelength VCSELs with low threshold current. Research is ongoing to improve high temperature characteristics and high-speed performance optimization. Coupled with component and packaging development, we plan to release Honeywell's first commercially available long wavelength VCSELs by 2003.

In this paper we describe both the 1310 and 1550 nm VCSEL development work at Honeywell using both InP and GaAs substrates, and using both MOCVD and MBE. We describe the material systems, the designs, the growth techniques, and the promising results obtained and compare them to the needs of the communications industry. InGaAsN quantum well based VCSELs have been demonstrated to 1338 nm lasing at temperatures up to 90 C. Continuous wave InP based 1550 nm VCSELs have also been demonstrated.

Glucose oxidase (EC 1.3.4.3) was immobilized on chitosan membrane (0.1 mm in thickness) prepared from the carapace of the soldier crab Mictyris brevidactylus. A glucose electrode was constructed by covering a platinum electrode (2.0 mm in diameter) with the enzyme membrane. The enzyme electrode sensed glucose amperometrically (1.0 micro A/mM, with linear range up to 0.5 mM, r = 0.999) when positively imposed with 0.6 V against an Ag/AgCl reference electrode. The glucose biosensor was sensitive (0.1 micro M, S/N3), reproducible (CV for 55 micro M glucose3%, n = 5), reagentless, and durable for months.

InGaN films with 33% and 60% indium contents were deposited by pulsed laser deposition (PLD) at a low growth temperature of 300 °C. The films were then annealed at 500-800 °C in the non-vacuum furnace for 15 min with an addition of N(2) atmosphere. X-ray diffraction results indicate that the indium contents in these two films were raised to 41% and 63%, respectively, after annealing in furnace. In(2)O(3) phase was formed on InGaN surface during the annealing process, which can be clearly observed by the measurements of auger electron spectroscopy, transmission electron microscopy and x-ray photoelectron spectroscopy. Due to the obstruction of indium out-diffusion by forming In(2)O(3) on surface, it leads to the efficient increment in indium content of InGaN layer. In addition, the surface roughness was greatly improved by removing In(2)O(3) with the etching treatment in HCl solution. Micro-photoluminescence measurement was performed to analyze the emission property of InGaN layer. For the as-grown InGaN with 33% indium content, the emission wavelength was gradually shifted from 552 to 618 nm with increasing the annealing temperature to 800 °C. It reveals the InGaN films have high potential in optoelectronic applications.

Thermal stability on the structural and optical properties of high indium content InGaN films grown using pulsed laser deposition (PLD) was investigated through long-duration and high-temperature annealing. X-ray diffraction and cathode- luminescence measurements of the 33% indium InGaN revealed no differences in the line-shape and peak position even after annealing at 800°C for 95 min; similar structural stability was found for the 60% samples after annealing for 75 min. The higher thermal stability is attributed to nanoscale InN domains with different orientations create mixed-polarity InGaN/InN interfaces, resulting in higher activation energies at interfaces and increasing the thermal stability of the material. Furthermore, the InGaN films were subjected to metalorganic chemical vapor deposition treatment to regrow a GaN layer; results are promising for the development of high thermal stability InGaN films using the PLD technique.

High indium compositions InGaN films were grown on sapphires using low temperature pulse laser deposition (PLD) with a dual-compositing target. This target was used to overcome the obstacle in the InGaN growth by PLD due to the difficulty of target preparation, and provided a co-deposition reaction, where InGaN grains generated from the indium and GaN vapors deposit on sapphire surface and then act as nucleation seeds to promote further InGaN growth. The effects of co-deposition on growth mechanisms, surface morphology, and electrical properties of films were thoroughly investigated and the results clearly show promise for the development of high indium InGaN films using PLD technique with dual-compositing targets.

The effects of macromolecular architecture on the osmotic pressure pi and virial coefficients (B(2) and B(3)) of star and comb polymers in good solvents are studied by dissipative particle dynamics simulations for both dilute and semiconcentrated regimes. The dependence of the osmotic pressure on polymer concentration is directly calculated by considering two reservoirs separated by a semipermeable, fictitious membrane. Our simulation results show that the ratios A(n+1) identical with B(n+1)/R(g)(3n) are essentially constant and A(2) and A(3) are arm number (f) dependent, where R(g) is zero-density radius of gyration. The value of dimensionless virial ratio g = A(3)/A(2)(2) increases with arm number of stars whereas it is essentially arm number independent for comb polymers. In semiconcentrated regime the scaling relation between osmotic pressure and volume fraction, pi proportional to phi(lambda), still holds for both star and comb polymers. For comb polymers, the exponent lambda is close to lambda(*) (approximately = 2.73 for linear chains) and is independent of the arm number. However, for star polymers, the exponent lambda deviates from lambda(*) and actually grows with increasing the arm number. This may be attributed to the significant ternary interactions near the star core in the many-arm systems.