Improved thermoelectric generator performance using high temperature thermoelectric materials

Thermoelectric generator (TEG) has received more and more attention in its application in the harvesting of waste thermal energy in automotive engines. Even though the commercial Bismuth Telluride thermoelectric material only have 5% efficiency and 250°C hot side temperature limit, it is possible to generate peak 1kW electrical energy from a heavy-duty engine. If being equipped with 500W TEG, a passenger car has potential to save more than 2% fuel consumption and hence CO2 emission reduction. TEG has advantages of compact and motionless parts over other thermal harvest technologies such as Organic Rankine Cycle (ORC) and Turbo-Compound (TC). Intense research works are being carried on improving the thermal efficiency of the thermoelectric materials and increasing the hot side temperature limit. Future thermoelectric modules are expected to have 10% to 20% efficiency and over 500°C hot side temperature limit. This paper presents the experimental synthesis procedure of both p-type and n-type skutterudite thermoelectric materials and the fabrication procedure of the thermoelectric modules using this material. These skutterudite materials were manufactured in the chemical lab in the University of Reading and then was fabricated into modules in the lab in Cardiff University. These thermoelectric materials can work up to as high as 500°C temperature and the corresponding modules can work at maximum 400°C hot side temperature. The performance loss from materials to modules has been investigated and discussed in this paper. By using a validated TEG model, the performance improvement using these modules has been estimated compared to commercial Bisemous Telluride module

Synthesis and gelation property of amino acids-based dendronised oligomers

<div><p>The first- and second-generation dendrons constructed from alanine and aspartic acids were synthesised and further modified with a polymerisable acrylamide group at the focal point (MG1 and MG2). The corresponding dendronised oligomers were obtained by polymerisation, and then hydrolysed to afford them with multi-carboxyl groups on the periphery of branched side chains (PG1-COOH and PG2-COOH). The structures of the oligomers were characterised by ¹H NMR, Fourier transform infrared and gel permeation chromatograph, and their gelation behaviour was examined. It was found that PG1-COOH and PG2-COOH could form two-component gels, especially, PG1-COOH showed better gelation property. For example, it could gel with aliphatic primary or secondary amines in dimethylformamide and with melamine in acidic aqueous solution. Transmission electron microscopy and atomic force microscopy images showed that the gelators self-assembled into the fibrous networks.</p></div

Management Modalities for Traumatic Macular Hole: A Systematic Review and Single-Arm Meta-Analysis

<p><i>Purposes</i>: The purposes of this study were to (i) determine macular hole (MH) closure rates and visual outcomes by comparing two methods of managing traumatic MH (TMH)—an event resulting in severe loss of visual acuity (VA); (ii) characterize patients who undergo spontaneous TMH closure; (iii) determine which TMH patients should be observed before resorting to surgical repair; and (iv) elucidate factors that influence postoperative visual outcomes.</p> <p><i>Methods</i>: Studies (n=10) of patients who were managed by surgery or observation for TMH were meta-analyzed retrospectively. Management modalities included <i>surgical repair</i> (surgery group) and <i>observation</i> for spontaneous hole closure (observation group). In addition, a 12-case series of articles (1990–2014) on spontaneous hole closure was statistically summarized. SAS and Comprehensive Meta-Analysis (CMA) (version 3.0) were used for analysis.</p> <p><i>Results</i>: For surgery group patients, the fixed-model pooled event rate for hole closure was 0.919 (range, 0.861–0.954) and for observation group patients, 0.368 (range, 0.236–0.448). The random-model pooled event rate for improvement of visual acuity (VA) for surgery group patients was 0.748 (range, 0.610–0.849) and for observation group patients, 0.505 (range, 0.397–0.613). For patients in both groups, the mean age of spontaneous closure was 18.71±10.64 years; mean size of TMHs, 0.18±0.06 decimal degrees (DD); and mean time for hole closure, 3.38±3.08 months. The pooled event rate for visual improvement was 0.748 (0.610–0.849).</p> <p><i>Conclusions</i>: Hole closure and VA improvement rates of surgery group patients were significantly higher than those for observation group patients. Patients of ≤ 24 years of age with MH sizes of ≤ 0.2DD were more likely to achieve spontaneous hole closure. The interval of time from injury to surgery was statistically significantly associated with the level of visual improvement.</p

Highly Enantioselective Hydrogenation of <i>ο</i>‑Alkoxy Tetrasubstituted Enamides Catalyzed by a Rh/(<i>R</i>,<i>S</i>)‑JosiPhos Catalyst

Rh/(<i>R,S</i>)-JosiPhos complex-catalyzed asymmetric hydrogenation of <i>o</i>-alkoxy tetrasubstituted enamides has been achieved, and it furnished a set of β-amino alcohol analogues in high yields and excellent enantiomeric excesses (>99% conversion, up to 99% ee).This method provides valuable chiral building blocks in chiral pharmaceuticals and useful motifs for catalysts

Application of Automated Reaction Path Search Methods to a Systematic Search of Single-Bond Activation Pathways Catalyzed by Small Metal Clusters: A Case Study on H–H Activation by Gold

A new theoretical approach to find metal-cluster-catalyzed single bond activation pathways is introduced. The proposed approach combines two automated reaction path search techniques: the anharmonic downward distortion following (ADDF) and the artificial force induced reaction (AFIR) methods, developed in our previous works [Maeda, S.; Ohno, K.; Morokuma, K. <i>Phys. Chem. Chem. Phys.</i> <b>2013</b>, <i>15</i>, 3683–3701]. A simple model reaction of the H–H bond activation catalyzed by Au_<i>n</i> (<i>n</i> = 7, 8) clusters is considered as an example. We have automatically found 33 and 20 transition-state (TS) structures for H₂ dissociation on Au₇ and Au₈ clusters, respectively, and successfully identified the best dissociation pathways with the lowest barrier. Systematic analysis of the structure-dependent reactivity of small gold clusters is performed. It is demonstrated that the most stable structures of the gold clusters are not always highly reactive and several isomeric structures must be taken into account for adequate description of the reaction rates at finite temperatures. The proposed approach can serve as a promising tool for investigation of the chemical reactions catalyzed by small metal clusters

Near-Infrared Fluorescent Probe for Imaging Mitochondrial Hydrogen Polysulfides in Living Cells and in Vivo

Hydrogen polysulfides (H₂S_<i>n</i>, <i>n</i> > 1), derived from hydrogen sulfide (H₂S), have attracted increasing attention in biochemical research, which may perform as the actual signaling molecules during cell signaling processes. Because of the closed biological and chemical relationship between H₂S and H₂S_<i>n</i>, it is of great value to develop sensitive and specific techniques to distinguish the intracellular level of H₂S_<i>n</i>. To improve the understanding of the physiological and pathological roles played by H₂S_<i>n</i>, we now develop a specific fluorescent probe Mito-ss for capturing H₂S_<i>n</i> in cells and in vivo. When triggered by H₂S_<i>n</i>, Mito-ss replies a turn-on fluorescence signal and exhibits a higher selectivity toward H₂S_<i>n</i> than other abundant competing biothiols, such as glutathione, cysteine and H₂S. The probe Mito-ss can also be applied to visual H₂S_<i>n</i> in living cells, as well as in vivo, providing a potentially powerful approach for probing H₂S_<i>n</i> in biological systems

Delaying Frost Formation by Controlling Surface Chemistry of Carbon Nanotube-Coated Steel Surfaces

Superhydrophobic surfaces are appealing as anti-icing surfaces, given their excellent water repellent performance. However, when water condenses on the surface due to high humidity, the water becomes pinned, and superhydrophobic surfaces fail to perform. Here we studied how the stability of the superhydrophobicity affected water condensation and frost formation. We created rough surfaces with the same surface structure, but with a variety of surface chemistries, and compared their antifrost properties as a function of intrinsic contact angle. Frost initiation was significantly delayed on surfaces with higher intrinsic contact angles. We coupled these macromeasurements with environmental scanning electron microscopy of water droplet initiation under high humidity conditions. These provide experimental evidence toward previous hypotheses that for a lower intrinsic-angle rough surface, Wenzel state is thermodynamically favorable, whereas the higher intrinsic-angle surface maintains a Cassie–Baxter state. Surfaces with a thermodynamically stable Cassie–Baxter state can then act both as antisteam and antifrost surfaces. This research could answer the persistent question of why superhydrophobic surfaces sometimes are not icephobic; anti-icing performance depends on the surface chemistry, which plays a critical role in the stability of the superhydrophobic surfaces

Photoresponsive Dendronized Copolymers of Styrene and Maleic Anhydride Pendant with Poly(amidoamine) Dendrons as Side Groups

A series of photoresponsive dendronized polymers <b>PG<i>n</i>-NB</b> (<i>n</i> = 1, 2, 3) were synthesized by attaching <i>o</i>-nitrobenzyl alcohol-terminated amidoamine dendrons (<b>G1</b>–<b>G3</b>) to the alternating styrene and maleic anhydride copolymer (PSt-<i>alt</i>-PMAh). The structures and the molecular weights of the obtained polymers were characterized by ¹H NMR and FTIR measurements. It is found that the coverage degrees of the dendrons are 74%, 42%, and 26%, respectively, indicating that the numbers of the appended dendrons decrease in the order of <b>G1</b> > <b>G2</b> > <b>G3</b> due to the steric hindrance of higher generation dendrons with more branches. The photocleavable behavior of <b>G1</b>–<b>G3</b> was detected by UV–vis and ¹H NMR measurements. As a result, <b>G2</b> showed a faster cleavage rate compared to <b>G1</b> and <b>G3</b>. The critical aggregation concentration (CAC) of <b>PG<i>n</i>-NB</b> (<i>n</i> = 1, 2, 3), measured by using pyrene as a fluorescence probe, were 0.05 mg/mL (<b>PG1-NB</b>), 0.01 mg/mL (<b>PG2-NB</b>), and 0.03 mg/mL (<b>PG3-NB</b>), which displayed that the structure of <b>PG2-NB</b> was in favor of forming aggregates at lower concentrations. Light scattering study indicated that both the apparent molecular weight and the chain density of the aggregates formed by <b>PG2-NB</b> decreased with the irradiation time. Atomic force microscope (AFM) measurements also showed that the size of the aggregates increased dramatically from 15 to 70 nm before and after UV irradiation, evidencing that the UV light induced structure change. Nile Reds, as the guest molecules, were loaded in the aggregates from <b>PG2-NB</b>, and the release profiles upon UV stimulus were monitored by the fluorescence spectroscopy

Photomodulated Self-Assembly of Hydrophobic Thiol Monolayer-Protected Gold Nanorods and Their Alignment in Thermotropic Liquid Crystal

Three terminal thiols possessing azobenzene and perylene diimide (PDI) segments covalently linked by alkylene spacers of different lengths (P_<i>n</i>SH, <i>n</i> = 4, 6, and 8) were synthesized to stabilize and functionalize gold nanorods (GNRs) via strong covalent Au–S bonds onto the gold surface. The resulting hydrophobic thiol monolayer-protected GNRs (P<i>_n</i>GNRs) were stable in both organic solvent and the solid state and exhibited fascinating photoresponsive self-assembly behavior. The PDI moieties provided π–π interactions to promote GNR self-assemblies while the photoresponsive azobenzene moieties offered a way to phototune the assemblies in a reversible manner. Interestingly, when P_<i>n</i>GNRs were mixed with a structurally similar room-temperature thermotropic liquid-crystal perylene diimide (LCP), the UV-irradiated P<i>_n</i>GNRs showed more compatibility with the LCP host than their corresponding unirradiated ones. Furthermore, the P<i>_n</i>GNRs with varied alkylene chain lengths showed different dispersion abilities in LCP. The UV-irradiated P₄GNRs did not disperse well in LCP, whereas the UV-irradiated P₆GNRs and P₈GNRs dispersed well in LCP and were further aligned upon mechanical shearing. In addition, preliminary molecular simulation was performed to explain this interesting photomodulated self-assembly of the GNRs

Detection rates and false alarm rates for Dataset20-100k with k = 0.25.

<p>Detection rates and false alarm rates for Dataset20-100k with k = 0.25.</p