Tunneling magnetoresistance in diluted magnetic semiconductor tunnel junctions

Using the spin-polarized tunneling model and taking into account the basic physics of ferromagnetic semiconductors, we study the temperature dependence of the tunneling magnetoresistance (TMR) in the diluted magnetic semiconductor (DMS) trilayer heterostructure system (Ga,Mn)As/AlAs/(Ga,Mn)As. The experimentally observed TMR ratio is in reasonable agreement with our result based on the typical material parameters. It is also shown that the TMR ratio has a strong dependence on both the itinerant-carrier density and the magnetic ion density in the DMS electrodes. This can provide a potential way to achieve larger TMR ratio by optimally adjusting the material parameters.Comment: 5 pages (RevTex), 3 figures (eps), submitted to PR

Effect of nonnutritive sucking and oral stimulation on feeding performance in preterm infants: a randomized controlled trial.

OBJECTIVES: To evaluate the effectiveness of nonnutritive sucking (NNS) and oral stimulation (OS), either applied alone or in combination, to reduce the transition time from tube feeding to independent oral feeding. DESIGN: Randomized controlled trial. SETTING: A 40-bed neonatal ICU in a university hospital in the People's Republic of China. PATIENTS: A total of 120 preterm infants were admitted to the neonatal ICU from December 2012 to July 2013. INTERVENTIONS: Oral motor interventions. MEASUREMENTS AND MAIN RESULTS: One hundred twelve preterm infants were assigned to three intervention groups (NNS, OS, and combined NNS + OS) and one control group. Primary outcome was the number of days needed from introduction of oral feeding to autonomous oral feeding (transition time). Secondary outcome measures were the rate of milk transfer (mL/min), proficiency (intake first 5 min/volume ordered), volume transfer (volume transferred during entire feeding/volume prescribed), weight, and hospital length of stay. Transition time was reduced in the three intervention groups compared with the control group (p < 0.001). The milk transfer rate in the three intervention groups was greater than in the control group (F3,363 = 15.37; p < 0.001). Proficiency in the NNS and OS groups did not exceed that in the control group while the proficiency in the NNS + OS group was greater than that in the control group at the stage when the infants initiated the oral feeding (p = 0.035). Among all groups, no significant difference was found on weight gain and length of stay. CONCLUSIONS: The combined NNS + OS intervention reduced the transition time from introduction to independent oral feeding and enhanced the milk transfer rate. The combined intervention seems to have a beneficial effect on oral feeding proficiency in preterm infants

Phase transitions and magnetic domain coexistence in Nd0.5Sr0.5MnO3 thin films

We present a study of the physical properties of perovskite oxide Nd0.5Sr0.5MnO3 (NSMO) thin films grown on (110)-oriented SrTiO3 substrates. In bulk form, NSMO displays coupled magnetic and electronic transitions from paramagnetic/insulator to ferromagnetic (FM)/metal and then to antiferromagnetic (AFM)/charge-ordered insulator with decreasing temperature. In thin films, the AFM ordering only occurs when the films exist in an anisotropic strain state such as those obtained on (110)-oriented cubic substrates. In this work, resonant X-ray reflectivity, soft X-ray photoemission electron microscopy (X-PEEM), and magnetometry measurements showed that the NSMO film displays both vertical and lateral magnetic phase separation. Specifically, the film consists of three layers with different density and magnetic properties. The FM and AFM properties of the main NSMO layer were probed as a function of temperature using soft X-ray magnetic spectroscopy, and the coexistence of lateral FM and AFM domains was demonstrated at 110 K using X-PEEM

Unexpected intercalation-dominated potassium storage in WS₂ as a potassium-ion battery anode

Unexpected intercalation-dominated process is observed during K^{+} insertion in WS_{2} in a voltage range of 0.01–3.0 V. This is different from the previously reported two-dimensional (2D) transition metal dichalcogenides that undergo a conversion reaction in a low voltage range when used as anodes in potassium-ion batteries. Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate the different ion storage mechanisms. The Na^{+} storage proceeds through intercalation and conversion reactions while the K^{+} storage is governed by an intercalation reaction. Owing to the reversible K+ intercalation in the van der Waals gaps, the WS_{2} anode exhibits a low decay rate of 0.07% per cycle, delivering a capacity of 103 mAh·g^{-1} after 100 cycles at 100 mA·g^{-1}. It maintains 57% capacity at 800 mA·g^{-1} and shows stable cyclability up to 400 cycles at 500 mA·g-1. Kinetics study proves the facilitation of K^{+} transport is derived from the intercalation-dominated mechanism. Furthermore, the mechanism is verified by the density functional theory (DFT) calculations, showing that the progressive expansion of the interlayer space can account for the observed results

Aquatic macrophytes in morphological and physiological responses to the nanobubble technology application for water restoration

Nanobubble technology, as an emerging and sustainable approach, has been used for remediation of eutrophication. However, the influence of nanobubbles on the restoration of aquatic vegetation and the mechanisms are unclear. In this study, the effect of nanobubbles at different concentrations on the growth of Iris pseudacorus (Iris) and Echinodorus amazonicus (Echinodorus) was investigated. The results demonstrated that nanobubbles can enhance the delivery of oxygen to plants, while appropriate nanobubble levels will promote plant growth, excess nanobubbles could inhibit plant growth and photosynthesis. The nanobubble concentration thresholds for this switch from growth promotion to growth inhibition were 3.45 × 107 and 1.23 × 107 particles/mL for Iris and Echinodorus, respectively. Below the threshold, an increase in nanobubble concentration enhanced plant aerobic respiration and ROS generations in plants, resulting in superior plant growth. However, above the threshold, high nanobubble concentrations induced hyperoxia stress, particularly in submergent plants, which result in collapse of the antioxidant system and the inhibition of plant physiological activity. The expression of genes involved in modulating redox potential and the oxidative stress response, as well as the generation of relevant hormones, were also altered. Overall, this study provides an evidence-based strategy to guide the future application of nanobubble technology for sustainable management of natural waters

Two lathyrane diterpenoid stereoisomers containing an unusual trans-gem-dimethylcyclopropane from the seeds of Euphorbia lathyris

Two novel lathyrane-type diterpenoids, the Euphorbia factors L(2a) (1) and L(2b) (2), and their stereoisomer Euphorbia factor L(2) (3) were obtained from seeds of Euphorbia lathyris. Both Euphorbia factors L(2a) and L(2b) possess an unprecedented trans-gem-dimethylcyclopropane as structural feature. Also, the Euphorbia factor L(2a) is the first example of a lathyrane diterpenoid with an endocyclic 12(Z)-double bond. The structures of the molecules and their absolute configurations were elucidated by comprehensive spectroscopic analyses, Cu-Kα radiation X-ray diffraction, and comparison with calculated electronic circular dichroism (ECD) data. The Euphorbia factor L(2b) exhibited an inhibitory effect against U937 cell line with an IC(50) value of 0.87 μM

Seasonal dynamics of Arctic soils: Capturing year-round processes in measurements and soil biogeochemical models

The Arctic is undergoing rapid changes in climate, altering the status and functioning of high-latitude soils and permafrost. The vast majority of studies on Arctic soils and permafrost are conducted during the summer period due to ease of accessibility, sampling, instrument operation, and making measurements, in comparison to during winter and transition seasons. However, there is increasing evidence that microbial activity continues in Arctic soils outside of the summer period. Moreover, it is becoming clear that understanding the seasonal dynamics of Arctic soils is of critical importance, especially considering that the under-studied winter is the period that is most sensitive to climate warming. Soil biogeochemical models have advanced our understanding of the functioning and fate of soils in the Arctic, however it is vital that seasonality in biotic and abiotic processes is accurately captured in these models. Here we synthesize recent investigations and observations of the year-round functioning of Arctic soils, review soil biogeochemical modelling frameworks, and highlight certain processes and behaviors that are shaped by seasonality and thus warrant particular consideration within these models. More attention to seasonal processes will be critical to improving datasets and soil biogeochemical models that can be used to understand the year-round functioning of soils and the fate of the soil carbon reservoir in the Arctic

Orientation direction dependency of cavitation in pre-oriented isotactic polypropylene at large strains

YesOrientation direction dependency of whitening activated at large strains was studied using four pre-oriented isotactic polypropylene (iPP) samples with different molecular weights stretched along different directions with respect to the pre-orientation (0°, 45°, and 90°) by means of in situ wide-, small-, and ultra-small-angle X-ray scattering techniques. A macroscopic fracture of iPP materials was also observed following the stress whitening at large strains. These two associated processes in pre-oriented iPP samples at elevated temperatures were found to be governed by not only the molecular weight of iPP but also the pre-orientation direction. For a certain pre-orientation direction of iPP, both the critical stress of cavitation induced-whitening and failure stress increased with increasing molecular weight. For one given molecular weight, the pre-oriented iPP showed the smallest critical stress for whitening and failure stress along the pre-orientation direction (0°) while the samples displayed larger values for the same behaviors when stretched at 45° or 90° with respect to the pre-orientation direction. Such behavior suggested that oriented amorphous networks, with different mechanical strengths, can be generated during the second deformation processes in these pre-oriented iPP samples. The evolution of inter-fibrillar tie chains in highly oriented amorphous networks was considered as the main factor controlling the response of the inner network to the external stress since the cavitation-induced whitening activated at large strains was caused by the failure of load bearing inter-fibrillar tie chains in the oriented amorphous network

Die geometry induced heterogeneous morphology of polypropylene inside the die during die-drawing process

YesThe morphology distribution of isotactic-polypropylene (iPP) shaped through a die during hot stretching process was investigated via wide-angle X-ray diffraction technique. The evolution of micro-structures in the outer layer (layer closer to the die wall) and the inner layer (layer in the center of die) of die-drawn iPP were both recorded. It turned out that the difference of morphology distribution between outer and inner layers changes with the distance from the die entrance to exit. In general, a larger difference between outer and inner layers could be found at the intermediate deformation region inside the die while such difference disappeared at both of the entrance and exit regions of die. These behaviors could be interpreted as a result of the existence of a heterogeneous distribution of force field inside the die, which was caused by the die geometry and inclination of the drawing force. This work showed that the heterogeneous force field inside the die could be revealed through analyzing the morphology of a die-drawn sample