Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers With Linear Polarization Maintenance

We propose a geometrical model based on the concept of dynamic eigenstates of polarization to describe the behavior of nonlinear polarization rotation (NPR) arising in semiconductor optical amplifiers (SOAs). The rotation axis with respect to either the bias current or the optical power variation is demonstrated on the Poincare sphere (PS), meanwhile a procedure to find the rotation axis is presented. Thus, the SOA-based NPR with linear polarization maintenance (zero polarization ellipticity angle) can be achieved experimentally. The rotation of polarization azimuth on the PS with respect to the bias current, the probe signal power, and the pump signal power variation is measured experimentally. The 180deg phase difference between the transverse electric and the transverse magnetic modes can be all achieved with linear polarization maintenance.     

Spoofing detection on hand images using quality assessment

Multimedia Tools and Applications - Recent research on biometrics focuses on achieving a high success rate of authentication and addressing the concern of various spoofing attacks. Although hand...     

Study of TiAlSiN coatings post-treated with N and C + N ion implantations. Part 2: The tribological analysis

Ion implantation has found to be an effective approach to modify surface properties of materials. The present research investigates the effect of (1) nitrogen (N), and (2) carbon subsequently with nitrogen (C + N) implantations on the mechanical and tribological properties of the titanium–aluminium–silicon–nitride (Ti–Al–Si–N) coatings. Superhard TiAlSiN coatings produced by magnetron sputtering, of approximately 2.5 μm thickness, were post-treated by implantations of N or C + N at an energy level of 50 keV. The dose range was between 5 × 10¹⁶ and 1 × 10¹⁸ ions cm^?2. After implantation, the tribological performance of the coatings was investigated by a ball-on-disk tribometer against WC–6 wt.%Co ball under dry condition in ambient air. The wear performance of the samples was examined by a variety of characterization techniques, such as secondary electron microscopy (SEM), 3D profilometry, atomic force microscopy (AFM), and micro-Raman. The results showed that the wear performance of the samples depended strongly on the implanted elements and doses. There was slight improvement on the samples implanted with N whereas significant improvement was found on the C + N implantations. Particularly, the friction coefficient of the sample with 5 × 10¹⁷ C⁺ cm^?2 and 5 × 10¹⁷ N⁺ cm^?2 could reach 0.1. In addition, the specific wear rate of the sample was extremely low (0.85 × 10^?7 mm³/Nm), which was nearly two orders of magnitude below that of the un-implanted coating. The speculation of the mechanical and tribological analyses of the samples indicates that the improvement of the N implanted and C + N implanted TiAlSiN samples could be due to a combined effect of improved hardness, plus enhanced adhesive and cohesive strength. In addition, the improved performance of the C + N implanted samples could be explained by the formation of lubricating implanted-layer, which existed mostly in sp² C–C and C–N forms. The formation of such implanted layer could lead to a change of wear mode from strong abrasive wear to mostly adhesive wear, and result in a drop of friction coefficient and wear rate.     

On‐Demand Droplet Collection for Capturing Single Cells

Droplet‐based microfluidic techniques are extensively used in efficient manipulation and genome‐wide analysis of individual cells, probing the heterogeneity among populations of individuals. However, the extraction and isolation of single cells from individual droplets remains difficult due to the inevitable sample loss during processing. Herein, an automated system for accurate collection of defined numbers of droplets containing single cells is presented. Based on alternate sorting and dispensing in three branch channels, the droplet number can be precisely controlled down to single‐droplet resolution. While encapsulating single cells and reserving one branch as a waste channel, sorting can be seamlessly integrated to enable on‐demand collection of single cells. Combined with a lossless recovery strategy, this technique achieves capture and culture of individual cells with a harvest rate of over 95%. The on‐demand droplet collection technique has great potential to realize quantitative processing and analysis of single cells for elucidating the role of cell‐to‐cell variations.     

Development and validation of an LC/MS/MS procedure for the quantification of endogenous myo-inositol concentrations in rat brain tissue homogenates

myo-Inositol is being investigated as a biomarker to monitor disease states involving the central nervous system. We have developed and validated a quantitative method to study endogenous myo-inositol metabolism in rat brain tissue. Tissue samples were homogenized, and their myo-inositol content was determined using spiked calibration curves and mass spectrometry. The assay was validated on an LC/MS/MS platform, and specificity was evaluated using accurate mass measurements. A novel chiral LC/MS/MS method was also developed to resolve myo-inositol from other endogenous inositol epimers and confirm the selectivity of the quantitative procedure. The validated method is selective, convenient, precise (<15% RSD), accurate (<15% RE), and sensitive over a linear range of 0.100-100 microg/mL. This method could potentially be used as an instrument for monitoring pathological conditions related to psychotherapeutics, as well as a tool for screening curative pharmaceuticals for efficacy.     

Generation of High‐Order All‐Aqueous Emulsion Drops by Osmosis‐Driven Phase Separation

Droplets containing ternary mixtures can spontaneously phase‐separate into high‐order structures upon a change in composition, which provides an alternative strategy to form multiphase droplets. However, existing strategies always involve nonaqueous solvents that limit the potential applications of the resulting multiple droplets, such as encapsulation of biomolecules. Here, a robust approach to achieve high‐order emulsion drops with an all‐aqueous nature from two aqueous phases by osmosis‐induced phase separation on a microfluidic platform is presented. This technique is enabled by the existence of an interface of the two aqueous phases and phase separation caused by an osmolality difference between the two phases. The complexity of emulsion drops induced by phase separation could be controlled by varying the initial concentration of solutes and is systematically illustrated in a state diagram. In particular, this technique is utilized to successfully achieve high‐order all‐aqueous droplets in a different aqueous two‐phase system. The proposed method is simple since it only requires two initial aqueous solutions for generating multilayered, organic‐solvent‐free all‐aqueous emulsion drops, and thus these multiphase emulsion drops can be further tailored to serve as highly biocompatible material templates.     

New approach to determine the effects of polarization mode dispersion and chromatic dispersion on pulse and RF signals

We present a novel analytical expression relating the output state of polarization (SOP) and the polarization mode dispersion (PMD) vector, including polarization-dependent chromatic dispersion (PCD), in terms of the angle of precession of the output SOP around the PMD vector. We derive a number of new expressions incorporating for the first time this angle of precession. First, a general relation to study the effect of differential group delay, PCD, and chromatic dispersion on pulses of arbitrary shapes is given. From this general relation, we derive expressions for pulse broadening and power penalty for Gaussian pulses. Moreover, a new expression for PMD-induced power fading for single-sideband modulated radio frequency signals is also derived. Measured experimental results are presented to support the derived expressions.     

Tunable microwave generation based on a dual-wavelength single-longitudinal-mode fiber laser using a phase-shifted grating on a triangular cantilever

Frequency tunable microwave signal generation, based on a dual-wavelength single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser, incorporating a phase-shifted fiber Bragg grating (PS-FBG) with two π-phase shifts, is demonstrated. In the proposed configuration, the PS-FBG with two ultranarrow transmission bands is embedded in a triangular cantilever to serve as a wavelength spacing tunable filter with a fixed center wavelength by applying various strains on the cantilever. A section of unpumped EDF is employed as a saturable absorber to ensure SLM operation in each of the two lasing lines. By beating the two wavelengths at a photodiode, a tunable microwave signal ranging from 8.835 to 24.360 GHz is successfully achieved.     

Structured review of neonatal deaths in a managed care organisation

We sought to quantify neonatal mortality (< 28 days) in a 10-hospital system, determine what proportion was associated with suboptimal neonatal care and make recommendations on how neonatal mortality rates (NMRs) could be used in quality improvement efforts. Deaths were identified using electronic linkage to the State of California Death Certificate Tapes. Individual fatalities were reviewed by a minimum of two physicians who did not care for the infant. Deaths were classified as either being associated with suboptimal care or not. For deaths where suboptimal care was an issue, emphasis was on delineating the process involved in the death. Subjects were all neonatal deaths among 64,469 babies born in 1990-91 in the 10 birth facilities of the Kaiser Permanente Medical Care Program, Northern California Region. A total of 241 neonatal deaths were identified. Adjusting for prematurity by increasing the follow-up period in preterm babies (included as neonatal deaths if they died up to 40 weeks corrected gestational age + 27.9 days) increased overall mortality rates by 5%. Birthweight-specific NMRs in Kaiser Permanente are similar to those of other published reports. Among the 198 deaths in babies weighing > or = 500 g at birth, only 14 (7%) were possibly associated with suboptimal care. In populations with access to health insurance, reporting only aggregate NMRs is of limited use. The number of deaths that could be ascribed to suboptimal neonatal care is very small and measuring variations in rates of such deaths is difficult. Future measurements of quality of care will require more sophisticated measures, database systems, review strategies and dissemination methods.