Growth, structural, optical, thermal and dielectric properties of a novel semi-organic nonline ar optical crystal: Dichloro-diglycine zinc II

Dichloro-diglycine zinc II(DCDGZ II),a semi-organic nonlinear optical material has been synthesized and single crystals were grown from the aqueous solution up to dimensions 20×10×3 mm3.The title compound,DCDGZ II(C4H10Cl2N2O4Zn H2O) crystallizes into monoclinic structure with the space group of C2/c.The unit-cell parameters were found to be a=14.4191(7),b=6.9180(2),c=12.9452(6) and Z=4.In the crystal structure,DCDGZ II layer is building up alternatingly with layers of water in which the zinc ions lie on a twofold axis.Theoretical calculations for polarizability,which are useful for device fabrication were made using Clausius–Mosotti equation and Penn analysis and the results were compared.Fourier transform infrared(FTIR) spectroscopic studies were performed for the identification of the different functional groups presented in the compound.The UV–vis–NIR absorption spectrum reveals that the lower UV cut-off wavelength is 240 nm.The optical band gap of the crystal was estimated as 2.2 eV.The surface morphology,thermal behaviour,dielectric properties have been studied using SEM,TG/DTA and LCR HITESTER analyzer.The nonlinear optical property of the crystal was also confirmed using Kurtz powder technique.     

Preserving cell shape under environmental stress

Maintaining cell shape and tone is crucial for the function and survival of cells and tissues. Mechanotransduction relies on the transformation of minuscule mechanical forces into high-fidelity electrical responses. When mechanoreceptors are stimulated, mechanically sensitive cation channels open and produce an inward transduction current that depolarizes the cell. For this process to operate effectively, the transduction machinery has to retain integrity and remain unfailingly independent of environmental changes. This is particularly challenging for poikilothermic organisms, where changes in temperature in the environment may impact the function of mechanoreceptor neurons. Thus, we wondered how insects whose habitat might quickly vary over several tens of degrees of temperature manage to maintain highly effective mechanical senses. We screened for Drosophila mutants with defective mechanical responses at elevated ambient temperatures, and identified a gene, spam, whose role is to protect the mechanosensory organ from massive cellular deformation caused by heat-induced osmotic imbalance. Here we show that Spam protein forms an extracellular shield that guards mechanosensory neurons from environmental insult. Remarkably, heterologously expressed Spam protein also endowed other cells with superb defence against physically and chemically induced deformation. We studied the mechanical impact of Spam coating and show that spam-coated cells are up to ten times stiffer than uncoated controls. Together, these results help explain how poikilothermic organisms preserve the architecture of critical cells during environmental stress, and illustrate an elegant and simple solution to such challenge.     

The northward extension of reptiles in the Palearctic,with the Jordan Valley (Israel) as a model: snakes outrace lizards (Reptilia: Squamata)

The geographical distribution of reptiles is known to be climate dependent. Our analysis of literature data from the Palearctic confirmed that snakes, as a group (186 species), tend to extend further to the north, into cooler climate, than lizards (460 species). This has also been reported for the Nearctic. On a smaller scale, as a model, we investigated the expansion of reptiles from the warm southern desert of Israel northwards along the Jordan valley into cooler climate, based on 587 locality records of 17 species. It transpired that the snakes significantly extend further to the north than the lizards, paralleling and exemplifying the global scale. The ability of snakes to inhabit relatively cooler climates appears to accord with three physiological traits of snakes: lower optimal body temperatures, absence of temperature-dependent sex determination, and ability to thrive on infrequent meals.     

Catching the WAVE: The Weight-Adjusting Account of Values and Evidence

It is commonly argued that values “fill the logical gap” of underdetermination of theory by evidence, namely, values affect our choice between two or more theories that fit the same evidence. The underdetermination model, however, does not exhaust the roles values play in evidential reasoning. I introduce WAVE – a novel account of the logical relations between values and evidence. WAVE states that values influence evidential reasoning by adjusting evidential weights. I argue that the weight-adjusting role of values is distinct from their underdetermination gap-filling role. Values adjust weights in three ways. First, values affect our trust in the testimony of others. Second, values influence the evidential thresholds required for justified epistemic judgments. Third, values influence the relative weight of a certain type of evidence within a body of multimodal discordant evidence. WAVE explains, from an epistemic perspective, rather than psychological, how smokers, for example, can find the same evidence about the dangers of smoking less persuasive than non-smokers. WAVE allows for a wider effect of values on our accepted scientific theories and beliefs than the effect for which the underdetermination model allows alone; therefore, science studies scholars must consider WAVE in their research and analysis of evidential case studies.     

Scientific Consensus and Expert Testimony in Courts: Lessons from the Bendectin Litigation

A consensus in a scientific community is often used as a resource for making informed public-policy decisions and deciding between rival expert testimonies in legal trials. This paper contains a social-epistemic analysis of the high-profile Bendectin drug controversy, which was decided in the courtroom inter alia by deference to a scientific consensus about the safety of Bendectin. Drawing on my previously developed account of knowledge-based consensus, I argue that the consensus in this case was not knowledge based, hence courts’ deference to it was not epistemically justified. I draw sceptical lessons from this analysis regarding the value of scientific consensus as a desirable and reliable means of resolving scientific controversies in public life.     

The role of Drosophila Piezo in mechanical nociception

Transduction of mechanical stimuli by receptor cells is essential for senses such as hearing, touch and pain. Ion channels have a role in neuronal mechanotransduction in invertebrates; however, functional conservation of these ion channels in mammalian mechanotransduction is not observed. For example, no mechanoreceptor potential C (NOMPC), a member of transient receptor potential (TRP) ion channel family, acts as a mechanotransducer in Drosophila melanogaster and Caenorhabditis elegans; however, it has no orthologues in mammals. Degenerin/epithelial sodium channel (DEG/ENaC) family members are mechanotransducers in C. elegans and potentially in D. melanogaster; however, a direct role of its mammalian homologues in sensing mechanical force has not been shown. Recently, Piezo1 (also known as Fam38a) and Piezo2 (also known as Fam38b) were identified as components of mechanically activated channels in mammals. The Piezo family are evolutionarily conserved transmembrane proteins. It is unknown whether they function in mechanical sensing in vivo and, if they do, which mechanosensory modalities they mediate. Here we study the physiological role of the single Piezo member in D. melanogaster (Dmpiezo; also known as CG8486). Dmpiezo expression in human cells induces mechanically activated currents, similar to its mammalian counterparts. Behavioural responses to noxious mechanical stimuli were severely reduced in Dmpiezo knockout larvae, whereas responses to another noxious stimulus or touch were not affected. Knocking down Dmpiezo in sensory neurons that mediate nociception and express the DEG/ENaC ion channel pickpocket (ppk) was sufficient to impair responses to noxious mechanical stimuli. Furthermore, expression of Dmpiezo in these same neurons rescued the phenotype of the constitutive Dmpiezo knockout larvae. Accordingly, electrophysiological recordings from ppk-positive neurons revealed a Dmpiezo-dependent, mechanically activated current. Finally, we found that Dmpiezo and ppk function in parallel pathways in ppk-positive cells, and that mechanical nociception is abolished in the absence of both channels. These data demonstrate the physiological relevance of the Piezo family in mechanotransduction in vivo, supporting a role of Piezo proteins in mechanosensory nociception.