Polarization due to emergent polarity in elemental semiconductor thinfilms under bending.

Polarization via strain engineering provides a facial way to functionalize materials. We investigate the origin of electronic polarization in the bent elemental semiconductor thinfilms by combining analytical modeling with quantum mechanical simulation. A bond orbital model reveals a polarity of covalent bonds induced by strain gradient such that polarization along the strain gradient dimension can be induced, giving rise to the flexoelectric effect. At strain gradient1/R=0.01 nm-1, the net charge differences between the two sides are5×10-4e,2.5×10-3eand7.2×10-3efor C, Si and Ge films respectively. On the other hand, due to the emergent bond polarity, the polarization can be effectively tuned by normal strain applied to the bent film, mimicking the piezoelectric effect. Simulations using the generalized Bloch theorem strongly support this revelation. Findings have important implications for delineating the formation of polarization and related phenomena in semiconductors.

Decreased anti-regenerative effects after spinal cord injury in spry4-/- mice.

Previously, we have demonstrated a role for fibroblast growth factor (Fgf) in spinal cord regeneration in both zebrafish and mouse. We have shown that exogenous Fgf2 treatment attenuates astrocytic gliosis and induces glia cells to become progenitors that undergo neurogenesis as well as differentiating into bipolar astrocytes that support axonal regeneration (Goldshmit et al., 2012, 2014). One of the downstream signaling target genes of Fgf is spry4, which acts as a feedback inhibitor for Fgf signaling. In this study we examined the effects of increased endogenous Fgf signaling, in spry4-/- mice, on the early events that occur after spinal cord injury (SCI). We demonstrate that in spry4-/- mice inflammatory responses, such as tumor necrosis factor α (TNFα) secretion and macrophage/neutrophil invasion into the lesion site are reduced. In addition, astrocytic gliosis is attenuated and neuronal survival is increased. These results further support a pro-regenerative role of Fgf after SCI, and suggest that increased endogenous Fgf signaling after SCI may contribute to functional recovery and therefore presents this pathway as a target for new therapy development.

Crystal structures and magnetic properties of new cyano-bridged two-dimensional grid-like bimetallic assemblies [Ni(tn)2]2[Cr(CN)5((NO)]OH*H2O and [NI(tn)2]2[Co(CN)6]NO3*2H2O (tn=1,3-propanediamine).

Two bimetallic assemblies, [Ni(tn)(2)](2)[Cr(CN)(5)(NO)]OH.H(2)O (1) and [Ni(tn)(2)](2)[Co(CN)(6)]NO(3).2H(2)O (2) (tn = 1,3-diaminopropane), have been prepared and structurally and magnetically characterized. Crystal data for 1 (2): space group P1 (P1), a = 8.698(3) (8.937(2)) A, b = 10.001(2) (9.863(1)) A, c = 10.158(2) (10.064(1)) A, alpha = 87.40(2) (86.064(10)) degrees, beta = 65.10(2) (65.489(10)) degrees, gamma = 81.63(2) (81.572(12)) degrees and Z = 1 (1). Both structures consist of two-dimensional grid-like polycations containing Ni-N triple bond C-M linkages (M = Cr or Co) and counteranions (OH, NO(3)). Magnetic studies of 1 showed that the complex displays a metamagnetic behavior originating from intralayer ferromagnetic and interlayer antiferromagnetic interactions. Long-range antiferromagnetic ordering was observed at T(N) = 3.3 K. Complex 2 exhibits intramolecular ferromagnetic interactions through the diamagnetic N triple bond C-Co-N triple bond C bridges, owing to superexchange involving the empty d(sigma) orbital of the diamagnetic Co(III) ion.

Oxamato-bridged trinuclear Ni(II)Cu(II)Ni(II) complexes with irregular spin state structures and a binuclear Ni(II)Cu(II) complex with an unusual supramolecular structure: crystal structure and magnetic properties.

Four oxamato-bridged heterotrinuclear Ni(II)Cu(II)Ni(II) complexes of formula ([Ni(bispictn)](2)Cu(pba))(ClO(4))(2).2.5H(2)O (1), ([Ni(bispictn)](2)Cu(pbaOH))(ClO(4))(2).H(2)O (2), ([Ni(cth)](2)Cu(pba))(ClO(4))(2) (3), and ([Ni(cth)](2)Cu(opba))(ClO(4))(2).H(2)O (4) and a binuclear Ni(II)Cu(II) complex of formula [Cu(opba)Ni(cth)].CH(3)OH (5) have been synthesized and characterized by means of elemental analysis, IR, ESR, and electronic spectra, where pba = 1,3-propylenebis(oxamato), pbaOH = 2-hydroxyl-1,3-propylenebis(oxamato), opba = o-phenylenebis(oxamato), bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, and cth = rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane. The crystal structures of 1, 3, and 5 have been determined. The structures of complexes 1 and 3 consist of trinuclear cations and perchlorate anions, and that of 5 consists of neutral binuclear molecules which are connected by hydrogen bonds and pi-pi interactions to produce a unique supramolecular "double" sheet. In the three complexes, the copper atom in a square-planar or axially elongated octahedral environment and the nickel atom in a distorted octahedral environment are bridged by the oxamato groups, with Cu.Ni separations between 5.29 and 5.33 A. The magnetic properties of all five complexes have been investigated. The chi(M)T versus T plots for 1-4 exhibit the minimum characteristic of antiferromagnetically coupled NiCuNi species with an irregular spin state structure and a spin-quartet ground state. The chi(M)T versus T plot for 5 is typical of an antiferromagnetically coupled NiCu pair with a spin-doublet ground state. The Ni(II)-Cu(II) isotropic interaction parameters for the five complexes were evaluated and are between 102 and 108 cm(-)(1) (H = -JS(Cu).S(Ni)).

Infection of hamsters with epidemiologically important strains of Clostridium difficile.

Five different toxigenic strains of Clostridium difficile of known human epidemiologic importance were tested for virulence in hamsters. Three strains-types B1, J9, and K14-have caused hospital outbreaks. Type Y2 is associated with a high rate of asymptomatic colonization in patients. The fifth strain, type CF2, is a toxin A-negative, toxin B-positive strain implicated in multiple human cases of C. difficile-associated diarrhea. Groups of 10 hamsters per strain were given 1 dose of clindamycin, followed 5 days later with gastric inoculation of 100 cfu of C. difficile. Hamsters given types B1, J9, K14, or Y2 showed 90%-100% colonization (albeit at a slower rate with type Y2) and 100% mortality of colonized animals. Hamsters challenged with type CF2 showed 60% (P= .01) colonization and 30% mortality (P= .0003). The hamster model demonstrated pathogenicity differences between a toxin variant strain and standard toxigenic strains but no significant differences among the standard strains.

A novel series of non-quaternary oxadiazoles acting as full agonists at muscarinic receptors.

1 A novel series of non-quaternary oxadiazole-based muscarinic agonists demonstrated high affinity for muscarinic receptors. 2. These agonists possessed high efficacy in the nanomolar range at muscarinic receptors in the superior cervical ganglion, atrium and ileum but did not show selectivity across the tissue preparations. 3. Two amino oxadiazoles, one from a quinuclidine series (L-660,863) and one from a 1-azanorbornane series (L-670,207) possessed a high ratio of potency for displacing the binding of [3H]-N-methyl-scopolamine ([3H]-NMS) to potency for displacing the agonist [3H]-oxotremorine-M cortex. 4. The two azanorbornane derivatives L-670,548 and L-670,207 stimulated the turnover of phosphatidylinositol in the cortex with a potency higher than that obtained with any other known muscarinic agonist (ED50 0.26 and 0.18 microM respectively). 5. The maximum response obtained with L-670,207 was greater than that observed for carbachol but was comparable to that of the natural ligand acetylcholine. 6. These oxadiazole muscarinic agonists are among the most potent and efficacious non-quaternary muscarinic agonists ever described.