Increasing the linear density uniformity of yarn spun from an aggressive solution

Conclusions It has been found experimentally that to increase the uniformity of linear density of yarn spun from an aggressive spinning solution of 40–50 Pa·sec viscosity, it is necessary to use metering pumps of high output and to maintain a positive pressure difference of up to 1 MPa between the spinning solution pressure at intake and that at discharge from the pump.A new candle filter construction has been proposed for maintaining a positive difference between the spinning solution pressure at intake and at discharge.Translated from Khimicheskie Volokna, No. 1, pp. 40–41, January–February, 1986.     

Using biochemically purified water at coke plants

The use of biochemically purified water in place of industrial-grade water for the exhaust-gas scrubbers in the drying department of the coal-enrichment shop and for irrigation of the cyclone washers in the coke shops at OAO ZSMK is considered. It is found that biochemically purified water may be used for 100% of the water needs in coke production. Using biochemically purified water in the dust-trapping equipment, the coaland coke-dust content of the atmospheric emissions may be reduced by 24.5%. Additional purification of wastewater by adsorption on coke and coal dust is possible.     

High-temperature luminescence in an n-GaSb/n-InGaAsSb/p-AlGaAsSb light-emitting heterostructure with a high potential barrier

The electroluminescent properties of an n-GaSb/n-InGaAsSb/p-AlGaAsSb heterostructure with a high potential barrier in the conduction band (large conduction-band offset) at the n-GaSb/n-InGaAsSb type-II heterointerface (ΔE _c = 0.79 eV) are studied. Two bands with peaks at 0.28 and 0.64 eV at 300 K, associated with radiative recombination in n-InGaAsSb and n-GaSb, respectively, are observed in the electroluminescence (EL) spectrum. In the entire temperature range under study, T = 290–480 K, additional electron-hole pairs are formed in the n-InGaAsSb active region by impact ionization with hot electrons heated as a result of the conduction-band offset. These pairs contribute to radiative recombination, which leads to a nonlinear increase in the EL intensity and output optical power with increasing pump current. A superlinear increase in the emission power of the long-wavelength band is observed upon heating in the temperature range T = 290–345 K, and a linear increase is observed at T > 345 K. This work for the first time reports an increase in the emission power of a light-emitting diode structure with increasing temperature. It is shown that this rise is caused by a decrease in the threshold energy of the impact ionization due to narrowing of the band gap of the active region.     

Customizing MRI-Compatible Multifunctional Neural Interfaces through Fiber Drawing

Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical, and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low-loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here, two fabrication approaches are introduced: 1) an iterative thermal drawing with a soft, low melting temperature (T_m) metal indium, and 2) a metal convergence drawing with traditionally non-drawable high T_m metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low-impedance metallic electrodes and low-loss waveguides, capable of recording optically-evoked and spontaneous neural activity in mice over several weeks. These fibers are coupled with a light-weight mechanical microdrive (1 g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, the compatibility of these fibers with magnetic resonance imaging is demonstrated and they are applied to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber-based neural probes in neuroscience and neuroengineering.     

Temperature profile effects in accelerated thermal cycling of SnPb and Pb-free solder joints

Accelerated thermal cycling (ATC) has been widely used in the microelectronics industry for reliability assessment. ATC testing decreases life cycle test time by one or more of the following means: increasing the heating and cooling rate, decreasing the hold time, or increasing the range of the applied temperature. The relative effect of each of these cycle parameters and the failure mechanisms they induce has been the subject of many studies; however uncertainty remains, particularly regarding the role of the heating and cooling rate. In this research, three conditions with two ramp rates (14 °C/min and 95 °C/min) and two temperature ranges (ΔT = 0–100 °C and −40 to 125 °C) were applied to resistor 2512 and PBGA 256 test vehicles assembled with SnPb and Pb-free solders. The test results showed that the higher ramp rate reduced the testing time while retaining the same failure modes, and that the damage per cycle increased with the temperature difference. For the resistors, the Pb-free solder joints lasted longer than the SnPb joints at the smaller ΔT, but were inferior at the larger ΔT. In contrast, the Pb-free solder joints in the PBGA test vehicles lasted longer than the SnPb solder under both conditions.     

Schottky barriers on n-GaN grown on SiC

Characteristics of Schottky barriers fabricated on n-type GaN were investigated. The barriers were formed by vacuum thermal evaporation of Cr, Au, and Ni. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the barriers were measured in a wide temperature and current density range. Fundamental parameters (barrier height and built-in potential) of the Schottky barriers were determined. The dependence of the barrier ideality factor on doping concentration in GaN was measured. Correlation between the barrier height and metal work function was observed. The electron affinity for GaN was determined using both C-V and I-V characteristics. The current flow mechanism through the barriers is discussed.     

Polymer Fiber Probes Enable Optical Control of Spinal Cord and Muscle Function In Vivo

Restoration of motor and sensory functions in paralyzed patients requires the development of tools for simultaneous recording and stimulation of neural activity in the spinal cord. In addition to its complex neurophysiology, the spinal cord presents technical challenges stemming from its flexible fibrous structure and repeated elastic deformation during normal motion. To address these engineering constraints, we developed highly flexible fiber probes, consisting entirely of polymers, for combined optical stimulation and recording of neural activity. The fabricated fiber probes exhibit low‐loss light transmission even under repeated extreme bending deformations. Using our fiber probes, we demonstrate simultaneous recording and optogenetic stimulation of neural activity in the spinal cord of transgenic mice expressing the light sensitive protein channelrhodopsin 2 (ChR2). Furthermore, optical stimulation of the spinal cord with the polymer fiber probes induces on‐demand limb movements that correlate with electromyographical (EMG) activity.     

Irradiation with Argon Ions of Cr/4H-SiC Photodetectors

Semiconductors - The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range...