Topological quantum materials are a class of compounds featuring electronic band structures, which are topologically distinct from common metals and insulators. These materials have emerged as exceptionally fertile ground for materials science research. The topologically nontrivial electronic structures of these materials support many interesting properties, ranging from the topologically protected states, manifesting as high mobility and spin-momentum locking, to various quantum Hall effects, axionic physics, and Majorana modes. In this article, we describe different topological matters, including topological insulators, Weyl semimetals, twisted graphene, and related two-dimensional Chern magnetic insulators, as well as their heterostructures. We focus on recent materials discoveries and experimental advancements of topological materials, and their heterostructures. Finally, we conclude with prospects for the discovery of additional topological materials for studying quantum processes, quasiparticles and their composites, as well as exploiting potential applications of these materials.

Harnessing the nonvolatility of magnetism and the power of electric control, magnetoelectric devices that control magnetism electrically promise to deliver next-generation electronics systems that can store and compute large amounts of information with minimal power consumption and ultrafast processing speed. We highlight progress in magnetoelectric memory and logic prototypes using the voltage-controlled magnetic anisotropy (VCMA) effect. First, important performance metrics of VCMA-based magnetoelectric random access memory (MeRAM) are benchmarked against embedded complementary metal oxide semiconductor and other emerging embedded nonvolatile memories. We then discuss scaling of MeRAM from the physics and materials perspectives of the VCMA effect, as well as the use of magnetoelectric logic devices and circuits to realize new computing paradigms with VCMA. Finally, challenges to realize the full potential of VCMA-based memory and logic are presented: VCMA coefficient of 1000 fJ/V-m for energy-efficient write with low errors and tunneling magnetoresistance of 1000% for high density and low noise margin readout. New approaches for deterministic switching based on VCMA are needed. We share perspectives to address these challenges using new materials and device operation schemes.

The objective of this study was to investigate the effects of maternal protein or energy restriction on hormonal and metabolic status of pregnant goats during late gestation and their postnatal male kids. Forty-five pregnant goats were fed a control (CON), 40% protein-restricted (PR) or 40% energy-restricted (ER) diet from 90 days of gestation until parturition. Plasma of mothers (90, 125 and 145 days of gestation) and kids (6 weeks of age) were sampled to determine metabolites and hormones. Glucose concentration for pregnant goats subjected to PR or ER was less (P<0.001) than that of CON goats at 125 and 145 days of gestation. However, plasma nonesterified fatty acids concentration was greater (P<0.01) at 125 and 145 days for PR and ER than CON. Protein restriction increased (P<0.01) maternal cortisol concentration by 145 days of gestation, and ER decreased (P<0.01) maternal insulin concentration at 125 days of gestation. Moreover, maternal amino acid (AA) concentrations were affected by nutritional restriction, with greater (P<0.05) total AA (TAA) and nonessential AA (NEAA) for PR goats but less (P<0.05) TAA and NEAA for ER goats at 125 days of gestation. After 6 weeks of nutritional recovery, plasma concentrations of most metabolic and hormonal parameters in restricted kids were similar to CON kids, except for reduced (P<0.05) insulin concentration in ER, and reduced (P<0.05) Asp concentration in PR and ER kids. These results provide information on potential metabolic mechanisms responsible for fetal programming.

Batch cultures of mixed rumen micro-organisms were used to evaluate varying enzyme products with high xylanase activity (EPX), four of which were recombinant single xylanase activity developmental enzyme products (EPX1–EPX4, products of xylanase genes derived from Trichoderma harzianum, Trichoderma reesei, Orpinomyces and Aspergillus oryzae, respectively), for their potential to improve in vitro ruminal fermentation of three forages [maize (Zea mays) stover (MS), rice (Oryza sativa) straw (RS) and Guimu No. 1 grass (Pennisetum americanum×Pennisetum purpureum, GM)]. The enzyme product EPX5, derived from Trichoderma longibrachiatum, was used as a positive control that could improve in vitro fermentation of forages. Enzymes were supplied at dose rates of 0 (control), 20 (low), 50 (medium) and 80 (high) enzymic units of xylanase/g of dry matter (DM). There were no interactions between EPX and dose for the fermentation characteristics evaluated. Increasing EPX dose linearly increased gas production (GP) kinetic characters [i.e. asymptotic GP (VF), half time when GP is half of the theoretical maximum GP (t0·5), and initial fractional rate of degradation (FRD0)] and methane (CH4) production from RS and GM at 24 h, and increased degradability of DM at 24 h for MS and RS. A linear increase in degradability of neutral detergent fibre (NDF) of the three forages at 24 h was observed with increasing dose of EPX, but at 48 h only NDF degradability of RS was increased. There were differences in the effects of EPX on degradability of DM and NDF from RS at 24 h, with EPX4 having the highest and EPX1 having the lowest. In addition, increasing EPX dose linearly increased acetate proportion at 24 h and total volatile fatty acids (TVFA) at 48 h in MS. Increasing EPX dose linearly increased TVFA at 24 h, and ammonia-nitrogen (NH3-N) concentration at 48 h in RS. For GM, linear or quadratic effects of dose on acetate and butyrate concentration were observed at 24 and 48 h. The present study indicates that applying EPX to low-quality forages has the potential to improve rumen degradability and utilization. Furthermore, EPX from different sources differed in their effects when applied at the same dose rate, with the responses being forage-specific. For RS, the EPX derived from A. oryzae showed the greatest positive effects on forage degradation; whereas for MS and GM, the source of micro-organism where EPX gene was derived did not affect the degradation, with little difference among the EPX evaluated.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

This study attempts to examine convection caused by the combined effects of temperature and concentration gradients in an annular enclosure with steps. An experimental study of thermosolutal convection of a CuSO4+ H2SO4+ H2O solution in a horizontal annular enclosure with steps is conducted using an electrochemical system that enables either opposing or cooperating in temperature and concentration gradients to be imposed. The shadowgraph recording technique is utilized to visualize and analyze the flow field phenomenon. The large difference between the thermal and solutal diffusion rates causes the flow to exhibit double-diffusive characteristics. In both cooperating and opposing cases, some finger-type flow can be visualized in the layered flow structure. Furthermore, Sh (mass transfer rate) increased with increasing Grt for fixed Grm and S*. Sh is larger in the cooperating case than in the opposing case for given Grt and Grm values.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

We analyze spin wave-based logic circuits as a possible route to building reconfigurable magnetic circuits compatible with conventional electron-based devices. A distinctive feature of the spin wave logic circuits is that a bit of information is encoded into the phase of the spin wave. It makes possible to transmit information as a magnetization signal through magnetic waveguides without the use of an electric current. By exploiting sin wave superposition, a set of logic gates such as AND, OR, and Majority gate can be realized in one circuit. We present experimental data illustrating the performance of a three-terminal micrometer scale spin wave-based logic device fabricated on a silicon platform. The device operates in the GHz frequency range and at room temperature. The output power modulation is achieved via the control of the relative phases of two input spin wave signals. The obtained data shows the possibility of using spin waves for achieving logic functionality. The scalability of the spin wave-based logic devices is defined by the wavelength of the spin wave, which depends on the magnetic material and waveguide geometry. Potentially, a multifunctional spin wave logic gate can be scaled down to 0.1μm2. Another potential advantage of the spin wave-based logic circuitry is the ability to implement logic gates with fewer elements as compared to CMOS-based circuits in achieving same functionality. The shortcomings and disadvantages of the spin wave-based devices are also discussed.

The objectives of this study were to determine true phosphorus (P) digestibility, degradability of phytate-P complex and the endogenous P outputs associated with brown rice feeding in weanling pigs by using the simple linear regression analysis technique. Six barrows with an average initial body weight of 12.5 kg were fitted with a T-cannula and fed six diets according to a 6 × 6 Latin-square design. Six maize starch-based diets, containing six levels of P at 0.80, 1.36, 1.93, 2.49, 3.04, and 3.61 g/kg per kg dry-matter (DM) intake (DMI), were formulated with brown rice. Each experimental period lasted 10 days. After a 7-day adaptation, all faecal samples were collected on days 8 and 9. Ileal digesta samples were collected for a total of 24 h on day 10. The apparent ileal and faecal P digestibility values of brown rice were affected ( P < 0.01) by the P contents in the assay diets. The apparent ileal and faecal P digestibility values increased from − 48.0 to 36.7% and from − 35.6 to 40.0%, respectively, as P content increased from 0.80 to 3.61 g/kg DMI. Linear relationships ( P < 0.05), expressed as g/kg DMI, between the apparent ileal and faecal digestible P and dietary levels of P, suggested that true P digestibility and the endogenous P outputs associated with brown rice feeding could be determined by using the simple regression analysis technique. There were no differences ( P>0.05) in true P digestibility values (57.7 ± 5.4 v. 58.2 ± 5.9%), phytate P degradability (76.4 ± 6.7 v. 79.0 ± 4.4%) and the endogenous P outputs (0.812 ± 0..096 v. 0.725 ± 0.083 g/kg DMI) between the ileal and the faecal levels. The endogenous faecal P output represented 14 and 25% of the National Research Council (1998) recommended daily total and available P requirements in the weanling pig, respectively. About 58% of the total P in brown rice could be digested and absorbed by the weanling pig. Our results suggest that the large intestine of the weanling pigs does not play a significant role in the digestion of P in brown rice. Diet formulation on the basis of total or apparent P digestibility with brown rice may lead to P overfeeding and excessive P excretion in pigs.

The development of new etching and contact metallurgies for the ZnO/ZnMgO/ZnCdO materials system and various approaches for realizing ZnO LEDs are reviewed. ZnO nanorod MOSFETs and pH sensors have been demonstrated. In addition, selective detection of hydrogen with Pt-coated single ZnO nanorods is discussed discussed. The Pt-coated single nanorods show a current response approximately a factor of three larger at room temperature upon exposure to 500ppm H2 in N2 than thin films of ZnO. The power consumption of these sensors can be very small (in the nW range) when using discontinuous coatings of Pt. Once the Pt coating becomes continuous, the current required to operate the sensors increases to the μW range. The ZnO nanorods are insensitive to oxygen in the measurement ambient.

Quantum dot infrared photodetectors (QDIPs) have been studied widely for normal-incidence infrared detection. The 3D confinement provided by quantum dots allows for the elimination of gratings that are typically required for normal-incidence detection in quantum well infrared photodetectors (QWIPs). Furthermore, the growth of Ge dots on Si substrates offers the potential for integration with existing CMOS platforms. To date, however, Ge QDIPs have typically been grown epitaxially by Stranski-Krastonov growth – producing pancake-like dots with base dimensions of 50-100 nm, heights of 7-10 nm, and an aerial dot density of 109–1010 cm−2. Such dots have poor lateral confinement, causing them to have non-ideal normal-incidence absorption characteristics, similar to quantum wells. In this work, we demonstrate infrared absorption in Ge dots with base dimensions of approximately 15 nm. These dots are epitaxially grown on pre-patterned Si substrates, with an aerial dot density of approximately 1011 cm−2. The substrates are prepared by using diblock copolymers to create a nano-pattern on the substrate surface which is transferred to the substrate by dry etching. The size of this pattern determines the base dimensions of the Ge dots. After growth, these dots are then tested for their infrared absorption properties using Fourier Transform Infrared (FTIR) Spectroscopy. The normal-incidence absorption of the dots can be studied with FTIR by varying the polarization angle of the infrared light. We present FTIR absorption spectra for samples grown with various conditions (e.g., different dot doping levels, numbers of layers, and dot base dimensions) and investigate the effects of different growth conditions on infrared absorption properties. We also report on the normal-incidence absorption characteristics of these dots by presenting absorption spectra for various polarization angles of infrared light.

An experimental study of thermosolutal convection in an inclined rectangular enclosure with a partition is presented in this article. Aspect ratio, partition ratio, and inclination angle were kept constant at Ar =0.5, Ap = 0.25 and φ = 30°, respectively. The convective flow is generated by both inclined temperature and concentration gradients under limiting current condition. Both the thermal and solutal buoyancies, which either cooperated or opposed one another, were induced from the copper plates. The temperature gradient was maintained and controlled using two separate constant temperature baths that circulated heated or cooled water through a heat exchanger. We used copper sulphate-sulfuric acid solution as both the working fluid and the electrolyte. An electrochemical method based on a diffusion-controlled electrode reaction was employed to create the concentration gradient. We used the shadowgraph recording technique to visualize and analyze the flow field phenomenon. Thermal Grashof numbers ranging from 8.16 × 105 to 16.32 × 105 and a solutal Grashof number Grm = 4.36 × 106 were investigated. It is demonstrated that the mass transfer rate increases with the increasing thermal Grashof numbers within our experimental ranges. Multilayer structures are found in the cooperating case or the opposing case.

A study on the ecological distribution of alveolar Echinococcus was carried out in the Hulunbeier Pasture of Inner Mongolia, China during 1998 and 1999. Animals examined included wolves (Canis lupus), red foxes (Vulpes vulpes), sand foxes (Vulpes corsac), domestic dogs (Canis familiaris), Microtus brandti, Meriones unguiculatus, Citellus dauricus, Allactaga sibirica, Phodopus sungorus and Ochotona daurica. Three wolves were found to be infected with E. granulosus. Two sand foxes were infected with E. multilocularis. The majority of infections of alveolar echinococcus was found in M. brandti. Based on the structure of metacestodes found in the livers of naturally infected M. brandti, 3 main variants were observed. Type I had small alveolar cysts with thin cyst walls. Type II had a larger cyst with a thick cyst wall. Infection of laboratory mice with the gravid segments isolated from the naturally infected sand foxes led to the formation of mature Type I alveolar metacestodes in the lungs and Type II metacestodes in the livers of infected animals, respectively.

FePtCu nanoparticles with varying composition were synthesized by chemical solution-phase reduction of platinum and copper reagents and thermal decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine stabilizers. As prepared the particles had fcc structure with an average diameter of 3.5 nm and were superparamagnetic. The particles were well dispersed in hydrocarbon solvents and could be self-assembled into two or three dimensions particles arrays with a variety of close-packing arrangements. Heat-treatment of the self-assembled films at temperatures above 550°C transformed the particles from the fcc to the L10 phase, giving in-plane coercivities as high as 9000 Oe. X-ray diffraction revealed that the Cu remained in the annealed FePtCu films and the presence of an extra peak, indicated a second phase was present. Consistent with one or more phases, the magnetic hysteresis curves could be decomposed into a hard component (Hc > 5,000 Oe) and a soft component (Hc < 2,000 Oe). Unlike our earlier results for Ag in FePt, adding Cu to FePt did not lower the temperature required for phase transformation from the fcc to the fct L10 phase.

Temperature and power dependent photoluminescence measurements were carried out on the multi-layer structure of GeSi dots grown on Si(001) substrate by gas-source molecular beam epitaxy. The transfer of photon-induced carriers from wetting layers into the dots and the region near the dots was evidenced. Different power dependent behaviors of the photoluminescence peak position were observed for the dots and the wetting layer. Accordingly, type-II and type-I band alignments were proposed for the dots and the wetting layers, respectively. After annealing, the photoluminescence peaks from the dots and the wetting layers showed blueshift due to the atomic intermixing. For the samples annealed at temperature above 850°C for 5min, the band alignment of the dots changes from type-II to type-I.

In this paper, a set of methods is developed to measure the Seebeck coefficient, electrical conductivity, and thermal conductivity in the cross-plane direction of thin films. The method employs microfabricated heaters, voltage and temperature sensors, and phase-lock amplifiers to determine the temperature and Seebeck voltage oscillation in the cross-plane direction of the samples, from which the thermal conductivity and Seebeck coefficient of thin films are determined simultaneously. The cross-plane electrical conductivity is also measured by a modified transmission line model. These methods are applied to Si/Ge superlattices grown by molecular beam epitaxy.