Current State-of-the-Art in the Interface/Surface Modification of Thermoelectric Materials

Thermoelectric (TE) materials are prominent candidates for energy converting applications due to their excellent performance and reliability. Extensive efforts for improving their efficiency in single-/multi-phase composites comprising nano/micro-scale second phases are being made. The artificial decoration of second phases into the thermoelectric matrix in multi-phase composites, which is distinguished from the second-phase precipitation occurring during the thermally equilibrated synthesis of TE materials, can effectively enhance their performance. Theoretically, the interfacial manipulation of phase boundaries can be extended to a wide range of materials. High interface densities decrease thermal conductivity when nano/micro-scale grain boundaries are obtained and certain electronic structure modifications may increase the power factor of TE materials. Based on the distribution of second phases on the interface boundaries, the strategies can be divided into discontinuous and continuous interfacial modifications. The discontinuous interfacial modifications section in this review discusses five parts chosen according to their dispersion forms, including metals, oxides, semiconductors, carbonic compounds, and MXenes. Alternatively, gas- and solution-phase process techniques are adopted for realizing continuous surface changes, like the core–shell structure. This review offers a detailed analysis of the current state-of-the-art in the field, while identifying possibilities and obstacles for improving the performance of TE materials

Water-Free SbOx ALD Process for Coating Bi2Te3 Particle

We developed a water-free atomic layer deposition (ALD) process to homogeneously deposit SbOx using SbCl5 and Sb-Ethoxide as precursors, and report it here for the first time. The coating is applied on Bi2Te3 particles synthesized via the solvothermal route to enhance the thermoelectric properties (i.e., Seebeck coefficient, thermal and electrical conductivity) via interface engineering. The amorphous character of the coating was shown by the missing reflexes on the X-ray diffractograms (XRD). A shift from the oxidation state +III to +V of the Sb species was observed using X-ray photoelectron spectroscopy (XPS), indicating increased thickness of the SbOx coating layer. Additionally, a peak shift of the Sb 3d5/2 + O 1s peak indicated increased n-type doping of the material. Electrical measurements of spark plasma-sintered bulk samples confirmed the doping effect on the basis of decreased specific resistivity with increasing SbOx layer thickness. The Seebeck coefficient was improved for the coated sample with 500 cycles of SbOx, while the total thermal conductivity was reduced, resulting in enhancement of the zT. The results distinctly show that surface engineering via powder ALD is an effective tool for improving key properties of thermoelectric materials like electrical conductivity and the Seebeck coefficient

Influencing the conductance in biphenyl-like molecular junctions with THz radiation

We investigate the torsional vibrations in biphenyl-like molecular junctions and transport properties in the presence of an external THz field. Ab-initio calculations including external electric fields show that the torsional angle {\phi} of a thiolated biphenyl junction exhibits virtually no response. However, if functional groups are added to the molecule, creating a dipole moment in each of the rings, an external field becomes more effective for changing {\phi}. A model based on the cos2{\phi} dependence of the current is proposed for the biphenyl-like molecular junctions in presence of an external THz field including 2,2'-bipyridine, 3,3'-bipyridine and 2,2',4,4'- tetramethyl-3,3'-bipyridine. The current through these molecules is shown to change if the THz frequency gets in resonance to the torsional vibration mode.Comment: 9 pages, 10 figures, submitted to PSS

Influence of momentum-dependent interactions on balance energy and mass dependence

We aim to study the role of momentum-dependent interactions in transverse flow as well as in its disappearance. For the present study, central collisions involving mass between 24 and 394 are considered. We find that momentum-dependent interactions have different impact in lighter colliding nuclei compared to heavier colliding nuclei. In lighter nuclei, the contribution of mean field towards the flow is smaller compared to heavier nuclei where binary nucleon-nucleon collisions dominate the scene. The inclusion of momentum-dependent interactions also explains the energy of vanishing flow in $^{12}C+^{12}C$ reaction which was not possible with the static equation of state. An excellent agreement of our theoretical attempt is found for balance energy with experimental data throughout the periodic table

Disappearance of Transverse Flow in Central Collisions for Heavier Nuclei

For the first time, mass dependence of balance energy only for heavier systems has been studied. Our results are in excellent agreement with the data which allow us to predict the balance energy of U+U, for the first time, around 37-39 MeV/nucleon. Also our results indicate a hard equation of state along with nucleon-nucleon cross-section around 40 mb.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

1-(1-Arylethylpiperidin-4-yl)thymine analogs as antimycobacterial TMPK inhibitors

A series of Mycobacterium tuberculosis TMPK (MtbTMPK) inhibitors based on a reported compound 3 were synthesized and evaluated for their capacity to inhibit MtbTMPK catalytic activity and the growth of a virulent M. tuberculosis strain (H37Rv). Modifications of the scaffold of 3 failed to afford substantial improvements in MtbTMPK inhibitory activity and antimycobacterial activity. Optimization of the substitution pattern of the D ring of 3 resulted in compound 21j with improved MtbTMPK inhibitory potency (three-fold) and H37Rv growth inhibitory activity (two-fold). Moving the 3-chloro substituent of 21j to the para-position afforded isomer 21h, which, despite a 10-fold increase in IC50-value, displayed promising whole cell activity (minimum inhibitory concentration (MIC) = 12.5 μM)

Conservationists’ perspectives on poverty: an empirical study

1. Biodiversity conservation interventions have long confronted challenges of human poverty. The ethical foundations of international conservation, including conservation’s relationship with poverty, are currently being interrogated in animated debates about the future of conservation. However, while some commentary exists, empirical analysis of conservation practitioner perspectives on poverty, and their ethical justification, has been lacking thus far. 2. We used Q methodology complemented by more detailed qualitative analysis to examine empirically perspectives on poverty and conservation within the conservation movement, and compare these empirical discourses to positions within the literature. We sampled conservation practitioners in western headquartered organisations, and in Bolivia, China, Nepal and Uganda, thereby giving indications of these perspectives in Latin America, Asia and Africa. 3. While there are some elements of consensus, for instance the principle that the poor should not shoulder the costs of conserving a global public good, the three discourses elicited diverge in a number of ways. Anthropocentrism and ecocentrism differentiate the perspectives, but beyond this, there are two distinct framings of poverty which conservation practitioners variously adhere to. 4. The first prioritises welfare, needs and sufficientarianism, and is more strongly associated with the China, Nepal and Uganda case studies. The second framing of poverty focuses much more on the need for ‘do no harm’ principles and safeguards, and follows an internationalised human rights-oriented discourse. 5. There are also important distinctions between discourses about whether poverty is characterised as a driver of degradation, or more emphasis is placed on overconsumption and affluence in perpetuating conservation threats. This dimension particularly illuminates shifts in thinking in the 30 or so years since the Brundtland report, and reflecting new global realities. 6. This analysis serves to update, parse and clarify differing perspectives on poverty within the conservation, and broader environmental movement, in order to illuminate consensual aspects between perspectives, and reveal where critical differences remain

Design, Synthesis, and Characterization of Brequinar Conjugates as Probes to Study DHODH Inhibition

Brequinar, a potent dihydroorotate dehydrogenase (DHODH) inhibitor, has been evaluated in multiple clinical trials as a potential treatment for cancer. To further understand brequinar‐based DHODH inhibition and DHODH′s therapeutic relevance in cancer, we have developed novel brequinar‐based probes. We disclose a 16‐step convergent synthesis of the first brequinar‐PROTAC and a four‐step approach towards the first mitochondrial‐directed brequinar probe. A PROTAC and mitochondria‐directed probe of brequinar both possess cytotoxicity that is superior to brequinar in a colony formation assay.Brequin′ news: A novel convergent synthesis of brequinar‐based probes to induce protein degradation (16 steps) and improve mitochondria accumulation (four steps) is disclosed.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138895/1/chem201702999_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138895/2/chem201702999-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138895/3/chem201702999.pd

Epigenetic regulation of microRNA expression in colorectal cancer

In the last years, microRNAs (miRNA) have emerged as new molecular players involved in carcinogenesis. Deregulation of miRNAs expression has been shown in different human cancer but the molecular mechanism underlying the alteration of miRNA expression is unknown. To identify tumor-supressor miRNAs silenced through aberrant epigenetic events in colorectal cancer (CRC), we used a sequential approach. We first identified 5 miRNAs down-regulated in colorectal cancer patient samples and located around/on a CpG island. Treatment with a DNA methyltransferase inhibitor and a HDAC inhibitor restored expression of 3 of the 5 microRNAs (hsa-miR-9, hsa-miR-129 and hsa-miR-137) in 3 CRC cell lines. Expression of hsa-miR-9 was inversely correlated with methylation of their promoter regions as measure by MSP and bisulphate sequencing. Further, methylation of the hsa-miR-9-1, hsa-miR-129-2 and hsa-miR- 137 CpG islands were frequently observed in CRC cell lines and in primary CRC tumors, but not in normal colonic mucosa. Finally, methylation of hsa-miR-9-1 was associated with the presence of lymph node metastasis. In summary, our results aid in the understanding of miRNA gene regulation showing that aberrant DNA methylation and histone modifications work together to induce silencing of miRNAs in CRC