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Zn4Sb3 has received interest for thermoelectric (TE) applications due to its low cost and low environmental impact. In this study, the Zn4Sb3 TE material was diffusion-bonded with multiple electrode materials of Ni, Ag, Cu, Pd and Ti for evaluation of the manufacturing of TE modules. Intermetallic compounds formed at the interfaces of the Zn4Sb3 diffusion couples, with Ni, Ag, Cu, and Pd exhibiting the selective reaction effect with zinc due to its high chemical affinity and low formation energies. Optimized bonding strengths of 6.6 to 8.2 MPa were achieved in Zn4Sb3 bonded with Ni, Ag and Cu materials at 350 °C. The Pd material could only bond at a temperature above 300 °C, and cracks presented after longer bonding times. As for the titanium, Zn4Sb3/Ti was successfully joined only at temperatures between 400 °C and 500 °C. It was observed that a rather thin TiSb2 intermetallic compound formed during the interfacial reactions between Zn4Sb3 and Ti, which grew significantly more slowly than those formed at the interfaces of Zn4Sb3 diffusion-coupled with Ni, Ag, Cu, and Pd metallic materials. Our results provide a reference for evaluating these common materials as suitable electrode and barrier layer candidates for utilizing the Zn4Sb3 TE material.

A Bi0.5Sb1.5Te3 thermoelectric (TE) element was directly soldered to a Cu electrode using Sn-3Ag-0.5 Cu alloy. The interface was sound and the bonding strength was satisfactory (8.6 MPa). However, the solder layer was exhausted quickly during high-temperature storage (HTS) tests at 150°C for 300 h and 600 h, and the bonding strength drastically decreased to 1.5 MPa. The consumption of the solder was prevented by electroplating a Ni barrier layer on the TE element, though a low bonding strength of 1.9 MPa resulted. Adding a Sn-rich thin film and a Ni barrier layer onto the Bi0.5Sb1.5Te3 element led to a high bonding strength of 12.1 MPa, which decreased only slightly after HTS reliability tests at 150°C for 1000 h. The sound interfaces of the Bi0.5Sb1.5Te3/Cu joints maintained their stability even after HTS at 175°C for 1000 h.

Folate-mediated one-carbon (1C) metabolism is a major target of many therapies in human diseases. Studies have focused on the metabolism of serine 3-carbon as it serves as a major source for 1C units. The serine 3-carbon enters the mitochondria transferred by folate cofactors and eventually converted to formate and serves as a major building block for cytosolic 1C metabolism. Abnormal glycine metabolism has been reported in many human pathological conditions. The mitochondrial glycine cleavage system (GCS) catalyzes glycine degradation to CO2 and ammonium, while tetrahydrofolate (THF) is converted into 5,10-methylene-THF. GCS accounts for a substantial proportion of whole-body glycine flux in humans, yet the particular metabolic route of glycine 2-carbon recycled from GCS during mitochondria glycine decarboxylation in hepatic or bone marrow 1C metabolism is not fully investigated, due to the limited accessibility of human tissues. Labeled glycine at 2-carbon was given to humans and primary cells in previous studies for investigating its incorporations into purines, its interconversion with serine, or the CO2 production in the mitochondria. Less is known on the metabolic fate of the glycine 2-carbon recycled from the GCS, hence, a model system tracing its metabolic fate would help in this regard. We took the direct approach of isotopic labeling to further explore the in vitro and in vivo metabolic fate of the 2-carbon from [2-13C]glycine and [2-13C]serine. As the 2-carbon of glycine and serine is decarboxylated and catabolized via the GCS, the original 13C-labeled 2-carbon is transferred to THF and yield methyleneTHF in the mitochondria. In human hepatoma cell-lines, 2-carbon from glycine was found to be incorporated into deoxythymidine (dTMP, dT + 1), M + 3 species of purines (deoxyadenine, dA and deoxyguanine, dG), and methionine (Met + 1). In healthy mice, incorporation of GCS-derived formate from glycine 2-carbon was found in serine (Ser + 2 via cytosolic serine hydroxy methyl transferase), methionine, dTMP, and methylcytosine (mC + 1) in bone marrow DNA. In these experiments, labeled glycine 2-carbon directly incorporates into Ser + 1, A + 2, and G + 2 (at C2 and C8 of purine) in the cytosol. It is noteworthy that since the serine 3-carbon is unlabeled in these experiments, the isotopic enrichments in dT + 1, Ser + 2, dA + 3, dG + 3, and Met + 1 solely come from the 2-carbon of glycine/serine recycled from GCS, re-enters the cytosolic 1C metabolism as formate, and then being used for cytosolic syntheses of serine, dTMP, purine (M + 3) and methionine. Taken together, we established model systems and successfully traced the metabolic fate of mitochondrial GCS-derived formate from glycine 2-carbon in vitro and in vivo. Nutritional supply significantly alters formate generation from GCS. More GCS-derived formate was used in hepatic serine and methionine syntheses, whereas more GCS-derived formate was used in dTMP synthesis in the bone marrow, indicating that the utilization and partitioning of GCS-derived 1C unit are tissue-specific. These approaches enable better understanding concerning the utilization of 1C moiety generated from mitochondrial GCS that can help to further elucidate the role of GCS in human disease development and progression in future applications. More studies on GCS using these approaches are underway.

Cheap, environmentally-friendly zinc antimonide is considered more favorable than conventional tellurite-based and skutterudite thermoelectric (TE) materials. Although the highly mobile zinc atoms located in the interstitial sites of the Zn4Sb3 crystalline structure greatly increase the figure of merit (ZT) of TE materials, the high chemical activity of zinc also makes it difficult to find suitable barrier layer and electrode materials. This paper introduces a method of joining titanium with Zn4Sb3 by means of diffusion bonding, in which the critical mutual-interdiffusion phenomenon is prevented. Optimal process parameters for manufacturing TE modules are suggested in this work. The intermetallic compounds (IMCs) that formed at the interface of Zn4Sb3/Ti diffusion couples were proved to be stable at the temperature with the highest conversion efficiency of Zn4Sb3. The growth kinetics of IMCs were also investigated, and the joint strength could be enhanced to 13.9 MPa after long-term reliability tests of 1000 h without deterioration. The results indicated that titanium is feasible barrier layer and electrode material for Zn4Sb3 TE modules.

We perform molecular dynamics simulations to investigate the effect of a glass preparation on its yielding transition under oscillatory shear. We use swap Monte Carlo to investigate a broad range of glass stabilities from poorly annealed to highly stable systems. We observe a qualitative change in the nature of yielding, which evolves from ductile to brittle as glass stability increases. Our results disentangle the relative role of mechanical and thermal annealing on the mechanical properties of amorphous solids, which is relevant for various experimental situations from the rheology of soft materials to fatigue failure in metallic glasses., See http://www.r.phys.nagoya-u.ac.jp/yeh-sm.pdf or https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.225502 for the Supplemental Material

The current co-hydrolysis used for the preparation of Nb-doped TiO2 starts from expensive and unstable niobium-based precursors, which is not suitable for mass production. In this paper, a scalable synthesis of Nb-doped TiO2 nanoparticles (NPs) made by mixing TiO2 paste with functionalized Nb2O5 sol gel is developed for the photoanodes in dye-sensitized solar cells (DSSCs). By doping Nb into TiO2, the positive shift of conduction band minimum (CBM) enhances the electron injection and the improved electron conductivity facilitates the electron transport, leading to an improved Jsc. In addition, the Nb-doping suppresses the surface recombination at TiO2-electrolyte interface, resulting in the increase of Voc. Therefore, the DSSCs based on 2.0 mol% Nb-doped TiO2 photoanodes improve both Jsc and Voc to achieve 18.9% improvement of photoconversion efficiency as compared with the standard DSSCs. The DSSCs with Nb-doped TiO2 photoanode is also shown an improved long-term stability.

A (Pb, Sn)Te thermoelectric (TE) material coated with a Ni barrier layer and a Ag reaction layer was bonded with a Ag-coated Cu electrode at low temperatures in the range of 175–250 °C with an In thin film. The In film reacted initially with the Ag layer to form a double layer of Ag3In and Ag2In intermetallic compounds, which then completely reacted with the Ag layer to form a Ag3In intermetallics layer having a melting point of 690 °C. The resulting module can thus be applied at the optimized operation temperature of (Pb, Sn)Te material (400 °C). The bonding strengths ranged from 6.3 to 7.8 MPa for various bonding temperatures at 30 min, and shear tests revealed that the specimens fractured along the interface between the (Pb, Sn)Te thermoelectric element and the Ni barrier layer. The adhesion of the TE/Ni interface was improved through pre-electroplating a 1 μm Sn film on the surface of the thermoelectric element and heating at 250 °C for 3 min. In this case, the bonding strengths increased to values between 10.9 MPa and 13.2 MPa for a bonding time of 30 min at temperatures ranging from 175 to 250 °C, and in shear tested TE modules, fracture occured in the interior of the TE elements. After high-temperature storage at 400 °C for 200 h, the shear strengths of TE/Cu joints bonded at various temperatures for 30 min decreased to values of 10.5–10.8 MPa, and the fracture occurred in the Ni3Sn4 intermetallics at the (Pb, Sn)Te/Ni interfaces.

In this work, a series of porous epoxy composites containing microscale, hollow epoxy spheres were synthesized and characterized. First, microscale epoxy spheres were produced using amino-modified silica (AMS) particles with diameters of ∼1 μm through a base-catalyzed sol–gel route. The as-synthesized AMS particles were then characterized through Fourier-transform infrared, 13C nuclear magnetic resonance (NMR), and 29Si-NMR spectroscopy. The prepared core–shell particles were immersed into a 1 wt.% of HF solution for 24 h to remove the inner part of the silica core, leading to the formation of hollow spheres of epoxy with a wall thickness of ∼100 nm. These hollow epoxy spheres (HES) were characterized by scanning electron microscopy (SEM), Transmission electron microscopy, and thermogravimetric analysis (TGA). Finally, a series of hybrid materials was synthesized by performing thermal ring-opening polymerization reactions of epoxy resin in the presence of as-synthesized HES. Based on SEM observations on the morphology, the HES showed good dispersion capability in the polymer matrices, which led to a significantly reduced thermal conductivity and slightly decreased dielectric constant based on the transient plane source and LCR measurements, respectively. For example, the thermal conductivity and dielectric constant decreased by 49.3% and 12.6%, respectively, in the porous epoxy material synthesized with a final HES loading of about 10%. One possible reason was the large amount of air present in the material. Other physical characteristics such as the thermal and mechanical properties based on the results of TGA, differential scanning calorimetry, and dynamic mechanical analysis were investigated.

It was found that the introduction of graphene oxide (GO) in metal-insulator-semiconductor (MIS) tunneling diodes can improve the rectifying characteristic and responsivity when acting as a photodetector. In this paper, we tuned the coverage ratio of GO using different degrees of hydrophilic treatments. GO samples with different coverage ratios were compared to identify the role of GO in MIS tunneling diodes. We prove that the improvement is due to the negative fixed charge in the GO layer. It is interesting that the partial coverage of GO results in the best performance.

In this study, the coloration mechanism of isotactic poly(1-butene) (iPB) in o-xylene and o-xylene/ethyl alcohol mixture gels were carried out. iPB gel becomes yellow because of transmitted light or blue because of reflected light. Changing the temperature, solvent composition, or even the thickness of samples of this gel continuously changes its color to blue, violet, purple, red, and yellow. Structural characterization, electron microscopy, and transmittance measurements were carried out for iPB dissolved in o-xylene to form a three-dimensional sponge-like network with different mesh sizes under various conditions. Subsequently, the relative refractive index between the solvent and gel network produces incoherent Tyndall blue scattering. Finally, color change due to variations in solvent composition or temperature contributes to the interplay between the refractive index of network structure nnetwork and solvent ns. For a Tyndall medium with ns/nnetwork >1, normal reflection creates a blue gel; when ns/nnetwork ≒1, strong transmittance of light passing through the medium leads to a yellowish gel. This is the first report on the concept of structural color for polymeric physical gel systems.

A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue is assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description for tissue dynamics at long-wavelength, long-time limit is developed, and the analysis reveals important insight for the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface could enhance small perturbations. This destabilizing mechanism is general for continuous self-renewal multi-layered tissues, it could be related to the origin of certain tissue morphology and developing pattern., Comment: 33pages, 8 figures

In this article, a comparative study of the preparation and physical properties of as-prepared PMMA-silica nano-hybrid (PSN) and sub-micro-hybrid (PSM) latexes is successfully presented. Vinyl-modified silica spheres were prepared using the Stob er pro- cess with/without a chelating agent to control parti- cle size. The as-prepared vinyl-modified silica spheres with different particle sizes were subse- quently characterized by SEM, 13 C-solid-state NMR, and 29 Si-solid-state NMR spectroscopy. A certain feeding amount of silica spheres was reacted with MMA monomers by emulsion polymerization to yield a series of PSN and corresponding PSM. Both as-prepared nano/sub-micronscale hybrid materials were further characterized by FTIR, SEM-EDX map- ping, and TEM studies. The comparative study on the physical properties of both as-prepared nano/sub- micron-scale hybrid materials was done systemati- cally based on a series of instrumentation evalua- tions performed using a dynamic mechanical ana- lyzer, electrochemical corrosion measurements, salt spray test, and gas permeability analysis. Results indicated that PSN has more effectively enhanced mechanical properties, corrosion protection proper- ties, as well as gas barrier compared to PSM. POLYM. COMPOS., 32:1607-1616, 2011. a 2011 Society of Plastics

To increase electrical conductivity and reduce number of processes, this paper aims to fabricate in situ photocurable conductive adhesives with Ag nano-particles in the absence of polymeric protector. The mixture of epoxy–acrylic resin and reactive monomer, as well as AgNO3 in ethylene glycol, is irradiated by UV light to form silver nano-particles without capping agent and was followed by adding photoinitiator to produce photocurable adhesive with silver nano-particles. In particular, as measured by transmission electron microscopy, the diameter of Ag nano-particle is 30–50 nm for 1 M and 80–90 nm for 2 and 3 M of AgNO3, in ethylene glycol. Furthermore, taking 1:1 weight ratio of photosensitive mixture to 3 M of AgNO3 in ethylene glycol as an example, the surface electrical resistivity of photocurable conductive adhesive may be reduced to 8.803×106 (Ω/□) after exposing to 900 mJ/cm2.

In this paper, high electrocatalytic and wettable nitrogen-doped microwave-exfoliated graphene (N-MEG) nanosheets are used as Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). A low cost solution-based process is developed by using cyanamide (NH2 CN) at room temperature and normal pressure. The pyrrolic and pyridinic N atoms are doped into the carbon conjugated lattice to enhance electrocatalytic activity. N-MEG film having N-doping active sites and large porosity provides a wettable surface to facilitate electrolyte diffusion so that improves fill factor. Moreover, the control of the air exposure time after completing N-MEG film is found to be crucial to obtain a reliable N-MEG CE. A high DSSC efficiency up to 7.18% can be achieved based on N-MEG CE, which is nearly comparable to conventional Pt CE.

Traditionally, encoders or resolvers are used to get the position feedback in permanent magnet synchronous motor (PMSM) drives. However, due to the drawbacks associated with these sensors, significant research has been conducted in the area of sensorless control. Most of the sensorless control methods such as neural network, particle swarm optimization, sliding-mode observer, or their combinations, require sophisticated algorithms to achieve the estimation of rotor position. In this paper, a simple approach is proposed to obtain its primitive value by adopting necessary current sensors and the 120-degree difference relationship between the two phase current signals. The estimated rotor angle is given by proportionally tuning the position error for considering the factors of speed command and speed sampling period. As a result, the complexity and computing ability of the processor used in the drive will be reduced and cheaper at the product stage. Furthermore, the conventional proportional-plusintegral (PI) control is adopted for the controlled system. With the aid of Bode diagram, an extension of the frequency zone-based method can decouple the multiple tuning gains so that the PI gain constants may be adjusted individually. Finally, the experimental results of the proposed method implemented in a DSP-based motor drive system with a 2-kg disc load are presented to show the effectiveness.

In this paper, we propose a parallel design of Viterbi decoder for Software-Defined Radio (SDR). Our method implements a divide-and-conquer approach by tiling decoding sequences, performing independent speculated Viterbi decoding, and merging partial candidate paths into the final path. For each independent Viterbi decoding, the best path is selected by calculating Hamming distances trellis-by-trellis in parallel. Our method shows up to 14.6x speedup on an NVIDIA 8800 GTX over a sequential C implementation on a 2.4GHz Intel Core 2 CPU. Also, compared with the existing GPU-based implementation, our method outperforms up to 2.5x.

In this study, we have inserted the graphene oxide (GO) in the metal/insulator/semiconductor tunneling diodes. The graphene oxide devices reveal the better stability as compared with the control devices. At a small positive bias, different control devices have different magnitude of photocurrents, while photocurrents of GO devices have close magnitude. At 2 V, the photocurrent density of the GO device have a minimum value of 2.7×10-3 A/cm2, while the control device can only reach a maximum value of 1.4×10-3 A/cm2. The simple GO process can obviously improve the characteristics of metal/insulator/semiconductor tunneling diodes

In recent years, graphene studies have increased rapidly. Graphene oxide, which is an intermediate product to form graphene, is insulating, and it should be thermally reduced to be electrically conductive. We herein describe an attempt to make use of the insulating properties of graphene oxide. The graphene oxide layers are deposited onto Si substrates, and a metal-insulator-semiconductor tunneling structure is formed and its optoelectronic properties are studied. The accumulation dark current and inversion photocurrent of the graphene oxide device are superior to the control device. The introduction of graphene oxide improves the rectifying characteristic of the diode and enhances its responsivity as a photodetector. At 2 V, the photo-to-dark current ratio of the graphene oxide device is 24, larger than the value of 15 measured in the control device.