Defect Engineering in Ambipolar Layered Materials for Mode-Regulable Nociceptor

Defect engineering represents a significant approach for atomically thick 2D semiconductor material development to explore the unique material properties and functions. Doping-induced conversion of conductive polarity is particularly beneficial for optimizing the integration of layered electronics. Here, controllable doping behavior in palladium diselenide (PdSe₂) transistor is demonstrated by manipulating its adatom-vacancy groups. The underlying mechanisms, which originate from reversible adsorption/desorption of oxygen clusters near selenide vacancy defects, are investigated systematically via their dynamic charge transfer characteristics and scanning tunneling microscope analysis. The modulated doping effect allows the PdSe₂ transistor to emulate the essential characteristics of photo nociceptor on a device level, including firing signal threshold and sensitization. Interestingly, electrostatic gating, acting as a neuromodulator, can regulate the adaptive modes in nociceptor to improve its adaptability and perceptibility to handle different danger levels. An integrated artificial nociceptor array is also designed to execute unique image processing functions, which suggests a new perspective for extension of the promise of defect engineered 2D electronics in simplified sensory systems toward use in advanced humanoid robots and artificial visual sensors.     

Flow microcalorimetry on dilute polymer solutions

A flow microcalorimeter designed to measure the heat of mixing of dilute polymer solutions is described. The instrument is sensitive to steady state heating rates of ～10 μJ/sec. Measurements of heats of mixing of solutions of differing concentrations of n-hexane and cyclohexane are reported and are compared with recommended data of McGlashan and Stoeckli. Values of:

$\text{K}{}_1\text{=}\text{lim}\text{V}{}_2\text{→ 0}$

$\text{(}\text{H}\text{?}{}_1\text{?}\text{H}\text{?}{}^0{}_1\text{RTv}{}^2{}_2$ are obtained for four polymer—solvent systems: polyisobutylene—benzene, 0.22; polystyrene (PS)—cyclohexane, 0.33; PS—n-butyl acetate, ?0.06 all at 25°C; and PS—toluene, ?0.05 at 40°C. Various theoretical calculations of second virial coefficients A₂ made with use of the calorimetric data are compared with previously measured A₂ for the first two mixtures.     

Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays

In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300?nm and lengths up to 20?μm were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10?Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells' traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.     

Lattice-Distortion-Enhanced Yield Strength in a Refractory High-Entropy Alloy

Severe distortion is one of the four core effects in single-phase high-entropy alloys (HEAs) and contributes significantly to the yield strength. However, the connection between the atomic-scale lattice distortion and macro-scale mechanical properties through experimental verification has yet to be fully achieved, owing to two critical challenges: 1) the difficulty in the development of homogeneous single-phase solid-solution HEAs and 2) the ambiguity in describing the lattice distortion and related measurements and calculations. A single-phase body-centered-cubic (BCC) refractory HEA, NbTaTiVZr, using thermodynamic modeling coupled with experimental verifications, is developed. Compared to the previously developed single-phase NbTaTiV HEA, the NbTaTiVZr HEA shows a higher yield strength and comparable plasticity. The increase in yield strength is systematically and quantitatively studied in terms of lattice distortion using a theoretical model, first-principles calculations, synchrotron X-ray/neutron diffraction, atom-probe tomography, and scanning transmission electron microscopy techniques. These results demonstrate that severe lattice distortion is a core factor for developing high strengths in refractory HEAs.     

The influence of the instruction of visual design principles on improving pre-service teachers’ visual literacy

This study investigated whether the instruction of visual design principles had an influence on pre-service teachers’ perception and analysis (interpretation) of visual materials. In addition, the relationships between pre-service teachers’ visual intelligence and their perception and analysis (interpretation) of visual materials were also explored. Participants were 86 pre-service teachers who took a one-credit required educational technology course at a mid-western university in the United States. Some participants were absent in the weeks when data were collected, resulting in a total of 59 responses included in data analysis. Findings implied that the instruction of visual design principles could possibly improve pre-service teachers’ visual literacy. Suggestions for future research were discussed.     

Regeneration of spent-NaBH4 back to NaBH4 by using high-energy ball milling

High-energy ball milling was employed to regenerate spent-sodium borohydride, i.e., mainly the sodium metaborate (NaBO₂), back to sodium borohydride (NaBH₄) by a reaction with magnesium hydride (MgH₂). The samples were characterized using scanning electron microscopy (SEM), Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy. In general, as the ball-milling duration increases, the yield of NaBH₄ increases accordingly and leads to an extreme value of 76%, when MgH₂ in stoichiometric excess by 40% was initially present in ball mills.     

Mesoporous silica supported cobalt catalysts for hydrogen generation in hydrolysis of ammonia borane

Mesoporous silica supported cobalt boride (Co–B) catalysts are rationally designed for hydrogen generation in ammonia–borane hydrolysis reactions under ambient conditions. Cobalt boride catalysts are supported on three different mesoporous silica, including beta-zeolite seeded MCM-41 (Co@M41S) and traditional MCM-41 (Co@M41T) via chemical adsorption onto functionalized surface with 3-trihydroxysilylpropylmethylphosphonate (THPMP), and one-step co-precipitation into mesoporous silica framework (Co@M41C). Our preparation strategies provide two insights to the reactions: first, cobalt oxide species are intrinsically deposited as ultra-small nanoparticles (<2 nm) on mesoporous silica supports; subsequently the nanoparticles are converted to active Co–B catalysts by reduction with sodium borohydride (SB). Three catalysts exhibit significant differences in catalytic reactivities with hydrogen production rates ranked in an order of Co@M41S > Co@M41T > Co@M41C. Detailed analysis of the coordination environments from in situ X-ray absorption spectroscopy (XAS) results confirm reducibility in SB. Amorphous nature of Co–B catalysts are responsible for efficient catalytic activity in Co@M41S and Co@M41T. Ammonia temperature programmed desorption (NH₃-TPD) demonstrates support acidity that correlates to the degree of high dispersity and effective reducibility to Co–B. Effects from catalyst sizes, reducibility in SB treatment and surface acidity are studied in detail to compare catalytic reactivities among three types of supports.     

Synthesis of solid-state NaBH4/Co-based catalyst composite for hydrogen storage through a high-energy ball-milling process

Solid-state composites of NaBH₄ and Co-based catalyst have been fabricated for hydrogen generation via a novel mechanochemical technique, i.e. the high-energy ball milling, in which the gravimetric storage capacity of hydrogen has reached 6.7 wt%, meeting the 2010 target of at least 0.06 kg H₂/kg set by the U.S. Department of Energy (DOE). The active catalysts used in the hydrolysis reaction of sodium borohydride for hydrogen generation are mainly cobalt oxides. Controlled addition of water, namely water used as a limiting agent, to the solid composites of NaBH₄ and Co-based catalyst greatly improves the H₂ storage capacity and resolved the issues of low gravimetric H₂ storage in conventional aqueous system of sodium borohydride. Factors influencing the performance of hydrogen production such as amounts of H₂O added, catalyst loadings and durations of ball-milling processes are investigated. Moreover the hydrolyzed products of NaBH₄ and spent catalysts are analyzed as well.     

Effect of Yam (Dioscorea alata Compared to Dioscorea japonica) on Gastrointestinal Function and Antioxidant Activity in Mice

ABSTRACT:  Effects of Chinese yam ( Dioscorea alata) and Japanese yam ( Dioscorea japonica ) on gastrointestinal functions including intestinal microflora and intestinal enzymes' activities, as well as antioxidant protection against lipopolysaccharide (LPS)-induced oxidative damage, in Balb/cA mice were examined. In part I, mice were fed yam-supplemented diet for 4 or 8 wk, and killed with carbon dioxide. In part II, mice were fed yam-supplemented diet for 4 wk, and followed by intraperitoneal LPS treatment (i.p. 4 mg/kg bodyweight). The intake of Chinese yam and Japanese yam significantly changed intestinal microflora, in which the colony numbers of Bifidobacterium and Lactobacillus were increased and the colony numbers of Clostridium perfringens were decreased ( P < 0.05). The intake of both Chinese and Japanese yams also significantly elevated the activity of leucine aminopeptidase and lipase ( P < 0.05), and the activities of sucrase and maltase were increased only in 20% yam-treated groups ( P < 0.05). The preintake of yam significantly alleviated subsequent LPS-induced oxidative injury by decreasing lipid oxidation level and fibronectin production and elevating superoxide dismutase activity ( P < 0.05). Both Chinese and Japanese yams contained dietary fibers, polyphenols, and flavonoids, which may contribute to the observed gastrointestinal function and antioxidant protection. These results suggest that both Chinese yam and Japanese yam were beneficial for intestinal health and oxidation prevention.