Cloning and functional characterization of the SUR2/SYR2 gene encoding sphinganine hydroxylase in Pichia ciferrii

Saccharomyces cerevisiae sphinganine C4-hydroxylase encoded by the SUR2 gene catalyses the conversion of sphinganine to phytosphingosine. We isolated the SUR2 gene from Pichia ciferrii using nucleotide sequence homology to S. cerevisiae SUR2 to study hydroxylation of sphinganine in the sphingoid base overproducing yeast P. ciferrii. A positive clone was confirmed by nucleotide sequencing. A syringomycin-E resistance phenotype of a S. cerevisiae sur2-null mutant was complemented by expression of the cloned P. ciferrii SUR2 gene. Restoration of phytosphingosine production in the complemented strain was also confirmed, indicating that the cloned gene is a functional homologue of S. cerevisiae SUR2. .     

Arrays of silicon micro/nanostructures formed in suspended configurations for deterministic assembly using flat and roller-type stamps

The ability to create and manipulate large arrays of inorganic semiconductor micro/nanostructures for integration on unconventional substrates provides new possibilities in device engineering. Here, simple methods are described for the preparation of structures of single crystalline silicon in suspended and tethered configurations that facilitate their deterministic assembly using transfer-printing techniques. Diverse shapes (e.g., straight or curved edges), thicknesses (between 55 nm and 3 μm), and sizes (areas of 4000 μm(2) to 117 mm(2) ) of structures in varied layouts (regular or irregular arrays, with dense or sparse coverages) can be achieved, using either flat or cylindrical roller-type stamps. To demonstrate the technique, printing with 100% yield onto curved, rigid supports of glass and ceramics and onto thin sheets of plastic is shown. The fabrication of a printed array of silicon p(+) -i-n(+) junction photodiodes on plastic is representative of device-printing capabilities.     

Direct amination on 3-dimensional pyrolyzed carbon micropattern surface for DNA detection

Three-dimensional pyrolyzed carbon micropatterns were fabricated by using photolithography and pyrolysis process. Direct amination was achieved by functionalizing its surface with ultraviolet (UV) irradiation under ammonia gas. Quantified amino groups on the carbon surface were estimated by X-ray photoelectron spectroscopy. Hybridization intensity and intensity profile were investigated by epifluorescence microscopy.     

Observation of notch effect in Al6061-T6 specimens under tensile loading using digital image correlation and finite element method

The fracture of ductile materials such as Al6061-T6 usually starts from void nucleation. In this study, we investigated strengthening effect and stress triaxiality behavior in notched Al alloy specimens. Various specimens, one un-notched and two with different U-types of notch, one with large diameter (L-notched) and another with small diameter (S-notched), having the same width were selected. The distribution of strain in the full-field was examined using the digital image correlation (DIC) method. Under the tensile test, S-notched specimens showed a more pronounced strengthening effect than the L-notched specimens. The results of DIC confirmed that the notch tip of the S-notched specimen experienced high strain, while the L-notched specimen experienced high strain at the center. The maximum stress triaxiality moved rapidly from the notch tip to the center with the increase in notch radius over 10 mm. The results of the stress triaxiality analysis by finite element method were in good agreement with the above DIC measurement results and predicted the void generation and fracture sites in L-notched and S-notched specimens.     

Effect of Surface Roughness on Droplet Bouncing in Droplet-Based Manufacturing Processes

In droplet-based manufacturing processes, such as drop-wise rapid prototyping, solder bumping and spray forming, the bouncing phenomenon adversely affects the quality of the deposit. This study investigates the effect of surface roughness on bouncing of liquid metal droplets from the substrate. An analytical model was developed to correlate the surface roughness with a non-dimensional droplet bouncing potential. In addition, an experimental study was conducted to image the deposition behavior of Pb-37wt% Sn solder droplets, 280 μm in diameter, on Au-plated substrates with a wide range of surface roughness. The high-speed image data correlate well with the model prediction that droplet bouncing increases as the surface roughness increases.     

Waveguide attachment influences on acoustic emission evaluation for marginal disintegration of dental composite restorations

Influence of the waveguide attenuation was investigated on acoustic emission (AE) estimation for the marginal disintegration states of dental composite restorations. For the AE measurement, a human molar tooth substrate with an artificial class 1 cavity was made. A bonding agent was applied and a composite resin was tightly packed in the hole of the substrate. Under the light exposure to the composite resin the polymerization shrinkage occurred and the marginal failure generated AE waves. It was ascertained that the waveguide attachment brought about a great decrease in AE hits and amplitudes. Compensation for the attenuation loss of the AE parameters could offer some equivalency to the AE measurements by the direct attachment of the sensor on the substrate.     

Contamination of silicon surface due to contact with solid polymers

The present research investigates material transfer associated with the contact between polymers and silicon surfaces. Material transfer from a variety of solid polymers (UHMWPE, Teflon, KEL-F, PMMA, Nylon 66, and PEEK) was studied and characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, and by computer image analysis. Experimental results suggest that material transfer is affected by the Hertz contact area. The number of particles and the total particle area increase with an increase in load and a decrease in the Young's modulus. Also, material transfer increases when the contacting surfaces are rougher. Friction appears to be a weak parameter in the material transfer phenomenon. Additionally, hardness is significant only when normal loading is great enough to initiate plastic deformation in the polymer     

High-energy X-ray computed tomography of the progression of the solidification front in pure aluminum

An X-ray computed tomography (CT) system was developed for monitoring the solidification front in metal casting. The X-ray source was a 6 MeV linear accelerator (linac) emitting photons in 5 μs pulses at a rate of 180 Hz. The source intensity was 300 R/min at 1 m. The X-ray beam was collimated in a 30 deg fan shape with a 10-mm height. A detector array comprising 128 elements was located 845 mm from the source. Pure aluminum in a clay-graphite crucible (178-mm o.d., 146-mm i.d.) was melted in a resistance heater furnace, and a cooling tube at the center of the crucible solidified the molten aluminum to simulate the casting process. A solidification front formed around the tube and progressed outward over an hour until the aluminum was completely solidified. X-ray attenuation measurements were taken every minute during this time. Density images were later reconstructed from these measurements using CT. From these images, the progression of the solidification front was determined with a planar resolution of 1.3 mm and a sensitivity of 3.7 pct. The density maps agree with expected values and correlate well with temperature measurements obtained independently by thermocouples.     

Switchable Xe/Kr Selectivity in a Hofmann-Type Metal–Organic Framework via Temperature-Responsive Rotational Dynamics

The development of adsorbents for Kr and Xe separation is essential to meet industrial demands and for energy conservation. Although a number of previous studies have focused on Xe-selective adsorbents, stimuli-responsive Xe/Kr-selective adsorbents still remain underdeveloped. Herein, a Hofmann-type framework Co(DABCO)[Ni(CN)₄] (referred to as CoNi-DAB ; DABCO = 1,4-diazabicyclo[2,2,2]octane) that provides a temperature-dependent switchable Xe/Kr separation performance is reported. CoNi-DAB showed high Kr/Xe (0.8/0.2) selectivity with significant Kr adsorption at 195 K as well as high Xe/Kr (0.2/0.8) selectivity with superior Xe adsorption at 298 K. Such adsorption features are associated with the temperature-dependent rotational configuration of the DABCO ligand, which affects the kinetic gate-opening temperature of Xe and Kr. The packing densities of Xe (2.886 g cm⁻³ at 298 K) and Kr (2.399 g  cm⁻³ at 195 K) inside the framework are remarkable and comparable with those of liquid Xe (3.057 g cm⁻³) and liquid Kr (2.413 g cm⁻³), respectively. Breakthrough experiments confirm the temperature-dependent reverse separation performance of CoNi-DAB at 298 K under dry and wet (88% relative humidity) conditions and at 195 K under dry conditions. The unique adsorption behavior is also verified through van der Waals (vdW)-corrected density functional theory (DFT) calculations and nudged elastic band (NEB) simulations.     

A banked-promotion translation lookaside buffer system

We present a simple but high performance translation lookaside buffer (TLB) system with low power consumption for use in embedded systems. Our TLB structure supports two page sizes dynamically and selectively to achieve high performance with low hardware cost. To minimize power consumption, a banked-TLB is constructed by dividing one fully associative (FA) TLB space into two separate FA TLBs. These two structures are integrated to form a banked-promotion (BP) TLB. Promotion overcomes the unbalanced utilization of a banked-TLB by moving adjacent entries out of the primary banks into a separate super-page TLB. Simulation results show that the Energy*Delay product can be reduced by about 99.8%, 19.2%, 24.2%, and 24.4% compared with a FA TLB, a micro-TLB, a banked-TLB, and a victim-TLB respectively. Therefore, the BP TLB offers high performance with low power consumption and low hardware cost.