Glasslike vs. crystalline thermal conductivity in carrier-tuned Ba8Ga16X30 clathrates (X = Ge, Sn)

The present controversy over the origin of glasslike thermal conductivity observed in certain crystalline materials is addressed by studies on single-crystal x-ray diffraction, thermal conductivity k(T) and specific heat Cp(T) of carrier-tuned Ba8Ga16X30 (X = Ge, Sn) clathrates. These crystals show radically different low-temperature k(T) behaviors depending on whether their charge carriers are electrons or holes, displaying the usual crystalline peak in the former case and an anomalous glasslike plateau in the latter. In contrast, Cp(T) above 4 K and the general structural properties are essentially insensitive to carrier tuning. We analyze these combined results within the framework of a Tunneling/Resonant/Rayleigh scatterings model, and conclude that the evolution from crystalline to glasslike k(T) is accompanied by an increase both in the effective density of tunnelling states and in the resonant scattering level, while neither one of these contributions can solely account for the observed changes in the full temperature range. This suggests that the most relevant factor which determines crystalline or glasslike behavior is the coupling strength between the guest vibrational modes and the frameworks with different charge carriers.Comment: 8 pages, 4 figures, 4 tables, submitted to Phys. Rev.

Cage-size control of guest vibration and thermal conductivity in Sr8Ga16Si30-xGex

We present a systematic study of thermal conductivity, specific heat, electrical resistivity, thermopower and x-ray diffraction measurements performed on single-crystalline samples of the pseudoquaternary type-I clathrate system Sr8Ga16Si30-xGex, in the full range of 0 < x < 30. All the samples show metallic behavior with n-type majority carriers. However, the thermal conductivity and specific heat strongly depend on x. Upon increasing x from 0 to 30, the lattice parameter increases by 3%, from 10.446 to 10.726 A, and the localized vibrational energies of the Sr guest ions in the tetrakaidekahedron (dodecahedron) cages decrease from 59 (120) K to 35 (90) K. Furthermore, the lattice thermal conductivity at low temperatures is largely suppressed. In fact, a crystalline peak found at 15 K for x = 0 gradually decreases and disappears for x > 20, evolving into the anomalous glass-like behavior observed for x = 30. It is found that the increase of the free space for the Sr guest motion directly correlates with a continuous transition from on-center harmonic vibration to off-center anharmonic vibration, with consequent increase in the coupling strength between the guest's low-energy modes and the cage's acoustic phonon modes.Comment: 7 pages, 7 figures, submitted to PR

Uma sonda de calor transiente controlada por computador para medir fluxo de fluido em meios porosos.

Uma sonda de calor transiente controlada por computador foi desenvolvida para medir fluxo em meios porosos. O sistema e operado automaticamente com o auxilio de uma placa de computador e basicamente composto de um sensor do tipo sonda-termistor, uma fonte de corrente eletrica constante de dois niveis, um conversor de sinal analogicos para digital, um transistor de efeito de campo e um conjunto de amplificadores operacionais. A sonda e alternadamente comutada entre dois modulos de operacao, alta e baixa potencia. Um programa foi desenvolvido para solicitar ao usuario os tempos para controlar o termistor e permitir os registros de identificacao do local, data, horario e dados para posicoes especificas da memoria. Os principios, a concepcao, a montagem e o funcionamento de toda a instrumentacao sao descritos. O sistema foi testado e avaliado em dois diferentes meios porosos. Resultados indicaram que o termistor aquecido e capaz de detectar o fluxo de fluido uma vez que sua resposta termica transiente foi afetada pela taxa de fluxo local

Regression of murine lung tumors by the let-7 microRNA.

MicroRNAs (miRNAs) have recently emerged as an important new class of cellular regulators that control various cellular processes and are implicated in human diseases, including cancer. Here, we show that loss of let-7 function enhances lung tumor formation in vivo, strongly supporting the hypothesis that let-7 is a tumor suppressor. Moreover, we report that exogenous delivery of let-7 to established tumors in mouse models of non-small-cell lung cancer (NSCLC) significantly reduces the tumor burden. These results demonstrate the therapeutic potential of let-7 in NSCLC and point to miRNA replacement therapy as a promising approach in cancer treatment

Surface expression and limited proteolysis of ADAM10 are increased by a dominant negative inhibitor of dynamin

<p>Abstract</p> <p>Background</p> <p>The amyloid precursor protein (APP) is cleaved by β- and γ-secretases to generate toxic amyloid β (Aβ) peptides. Alternatively, <it>α</it>-secretases cleave APP within the Aβ domain, precluding Aβ formation and releasing the soluble ectodomain, sAPPα. We previously showed that inhibition of the GTPase dynamin reduced APP internalization and increased release of sAPPα, apparently by prolonging the interaction between APP and α-secretases at the plasma membrane. This was accompanied by a reduction in Aβ generation. In the present study, we investigated whether surface expression of the α-secretase ADAM (a disintegrin and metalloprotease)10 is also regulated by dynamin-dependent endocytosis.</p> <p>Results</p> <p>Transfection of human embryonic kidney (HEK) cells stably expressing M3 muscarinic receptors with a dominant negative dynamin I mutant (dyn I K44A), increased surface expression of both immature, and mature, catalytically active forms of co-expressed ADAM10. Surface levels of ADAM10 were unaffected by activation of protein kinase C (PKC) or M3 receptors, indicating that receptor-coupled shedding of the ADAM substrate APP is unlikely to be mediated by inhibition of ADAM10 endocytosis in this cell line. Dyn I K44A strongly increased the formation of a C-terminal fragment of ADAM10, consistent with earlier reports that the ADAM10 ectodomain is itself a target for sheddases. The abundance of this fragment was increased in the presence of a γ-secretase inhibitor, but was not affected by M3 receptor activation. The dynamin mutant did not affect the distribution of ADAM10 and its C-terminal fragment between raft and non-raft membrane compartments.</p> <p>Conclusions</p> <p>Surface expression and limited proteolysis of ADAM10 are regulated by dynamin-dependent endocytosis, but are unaffected by activation of signaling pathways that upregulate shedding of ADAM substrates such as APP. Modulation of ADAM10 internalization could affect cellular behavior in two ways: by altering the putative signaling activity of the ADAM10 C-terminal fragment, and by regulating the biological function of ADAM10 substrates such as APP and N-cadherin.</p

Thermoelectric transport of perfectly conducting channels in two- and three-dimensional topological insulators

Topological insulators have gapless edge/surface states with novel transport properties. Among these, there are two classes of perfectly conducting channels which are free from backscattering: the edge states of two-dimensional topological insulators and the one-dimensional states localized on dislocations of certain three-dimensional topological insulators. We show how these novel states affect thermoelectric properties of the systems and discuss possibilities to improve the thermoelectric figure of merit using these materials with perfectly conducting channels.Comment: 10 pages, 6 figures, proceedings for The 19th International Conference on the Application of High Magnetic Fields in Semiconductor Physics and Nanotechnology (HMF-19

Cerclage outcome by the type of suture material (COTS): study protocol for a pilot and feasibility randomised controlled trial

BACKGROUND: Cervical incompetence is one of the causes of preterm birth and mid-trimester pregnancy loss. Cervical cerclage is a surgical procedure to treat cervical incompetence. Cervical cerclage reduces the incidence of preterm birth in women at risk of recurrent preterm birth, without a statistically significant reduction in perinatal mortality or neonatal morbidity. Multifilament/braided sutures such as Mersilene tape have been traditionally used for cervical cerclage. Braided sutures, particularly mesh-like non-absorbable sutures, have been associated with an increased risk of infection and, hence, some obstetricians prefer to use monofilament/non-braided sutures. However, these claims are not substantiated by any scientific or clinical evidence. We propose a pilot/feasibility study which will provide the necessary information for planning a definitive trial investigating the clinical effectiveness of monofilament non-braided suture materials in reducing pregnancy loss rate following cervical cerclage compared to the traditional multifilament braided sutures. METHODS/DESIGN: Women eligible for elective or ultrasound-indicated cerclage at 12 to 21 + 6 weeks of gestation will be randomised to having the procedure using either a monofilament non-braided suture (Ethilon) or a Multifilament braided suture (Mersilene tape) inserted using a McDonald technique. Consent for participation in the Cerclage outcome by the type of suture (COTS) study will be obtained from each eligible participant. CLINICAL TRIALS REGISTRATION: COTS is registered with the International Standard Research for Clinical Trials (ISRCTN17866773). Registered on 27 March 2013

A Variant in a MicroRNA complementary site in the 3' UTR of the KIT oncogene increases risk of acral melanoma.

MicroRNAs (miRNAs) are small ∼22nt single stranded RNAs that negatively regulate protein expression by binding to partially complementary sequences in the 3' untranslated region (3' UTRs) of target gene messenger RNAs (mRNA). Recently, mutations have been identified in both miRNAs and target genes that disrupt regulatory relationships, contribute to oncogenesis and serve as biomarkers for cancer risk. KIT, an established oncogene with a multifaceted role in melanogenesis and melanoma pathogenesis, has recently been shown to be upregulated in some melanomas, and is also a target of the miRNA miR-221. Here, we describe a genetic variant in the 3' UTR of the KIT oncogene that correlates with a greater than fourfold increased risk of acral melanoma. This KIT variant results in a mismatch in the seed region of a miR-221 complementary site and reporter data suggests that this mismatch can result in increased expression of the KIT oncogene. Consistent with the hypothesis that this is a functional variant, KIT mRNA and protein levels are both increased in the majority of samples harboring the KIT variant. This work identifies a novel genetic marker for increased heritable risk of melanoma

Paedophiles in the community: inter-agency conflict, news leaks and the local press

This article explores the leaking of confidential information about secret Home Office plans to house convicted paedophiles within a local community (albeit inside a prison). It argues that a politics of paedophilia has emerged in which inter-agency consensus on the issue of ‘what to do’ with high-profile sex offenders has broken down. Accordingly, the article situates newspaper ‘outing’ of paedophiles in the community in relation to vigilante journalism and leaked information from official agencies. The article then presents research findings from a case study of news events set in train following a whistle-blowing reaction by Prison Officers’ Association officials to Home Office plans. Drawing from a corpus of 10 interviews with journalists and key protagonists in the story, the article discusses both the dynamics of whistle blowing about paedophiles and also what happens after the whistle has blown