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This paper delves into the impact of electromagnetic fields on isotropic spherical charged gravastar (CGS) systems within the framework of f (R , Σ , T) gravity. The investigation focuses on singularity-free exact systems of relativistic spheres with a specific equation of state (EoS), employing a suitable choice of the effective field for different regions of the gravastar. The exterior region considers the Reissner–Nordström spacetime, while the interior charged manifold is matched at the junction interface. By utilizing graphical representations, the study examines various physical characteristics of the spherical gravastar system in the presence of an electromagnetic field. The findings reveal that the electric charge plays a significant role in shaping the optimal length, energy content, entropy, EoS parameter of the stellar system, and the energy conditions of our system. Additionally, the stability of the system is also investigated. Here are some of the results obtained. It is determined that both the matter density and pressure remain constant within the interior region of the CGS. The EoS is always negative. Also, the energy conditions are violated in our cosmological system. [ABSTRACT FROM AUTHOR]

We investigate how the Re content affects the coefficient of thermal expansion (CTE) of the non-stoichiometric W-based σ and χ phases, forming upon neutron irradiation of W, to explore and quantify its mismatch between precipitates (W-Re) and matrix (W). To this end, we have conducted first-principles calculations using two approaches: the Debye-Grüneisen (DG) model and the quasi-harmonic approximation (QHA). The two approaches yield different results: the QHA, which is deemed to be the most accurate of the two, predicts substantial changes with Re content, while the acoustic-modes based DG model does not. The CTE of the σ and χ at stable Re contents is compared to experimental values for bcc-W and bcc-W-Re containing 25 at.% Re. Taking bcc-W as a reference, we find a significant mismatch in CTE of up to 37% and 62% for σ and χ, respectively, which may contribute to thermal stress buildup in the material at elevated temperatures. The mismatch is shown to increase with the temperature and Re content for both phases. The produced data are used to fit a temperature and Re concentration-dependent analytical function of the CTE for both phases, which can be employed as input for continuum mechanical modeling.

In this article, we define generalized $(\varphi,\sigma,\gamma)$-rational contraction, generalized $(\alpha\beta,\varphi\theta,F)$-rational contraction and establish some new fixed point results in $(\phi,\psi)$-metric space. We also present instances to support our main results. We will use the results we obtained to investigate the existence and uniqueness of solutions to first-order differential equations.

In this paper, the energy, and wavefunctions of the low-lying bound and resonance states of Λ 6 1 Ca and Λ Λ 6 2 Ca are studied. For Λ 6 1 Ca we adopted Λ + 6 0 Ca two-body cluster model while for Λ Λ 6 2 Ca we adopted Λ + Λ + 6 0 Ca three-body cluster model. Two models of potentials, namely SH: Hulthén type and WS: Woods–Saxon type potentials, each having a spin-orbit coupling term is chosen for the Λ -nucleus pair while three-range Gaussian (TRG) Nijmegen hardcore and softcore potential models are chosen for Λ Λ pair. The resulting few-body (two- and three-body) Schrödinger equations are solved numerically to get the bound state energies and wavefunctions. For the three-body calculation, we used hyperspherical coordinates. The formalism of supersymmetric quantum mechanics is applied to construct a one-parameter family of isospectral potential to investigate the resonance states of the Λ + 6 0 Ca ( = Λ 6 1 Ca) core- Λ two-body system. To study the effect of replacement of the outer core valence nucleon(s) of 6 2 Ca by Λ hyperon(s), two- and three-body cluster model calculations for the bound states of 6 1 Ca and 6 2 Ca are also carried out using the same set of two-body potentials, as used for Λ 6 1 Ca and Λ Λ 6 2 Ca respectively. And a clear enhancement in the one- and two- Λ separation energies and a shrinking of the overall size of the nucleus is indicated. The computed results are compared with some of those found in the literature. [ABSTRACT FROM AUTHOR]

In this paper, we design a framework to obtain efficient algorithms for several problems with a global constraint (acyclicity or connectivity) such as Connected Dominating Set, Node Weighted Steiner Tree, Maximum Induced Tree, Longest Induced Path, and Feedback Vertex Set. We design a meta-algorithm that solves all these problems and whose running time is upper bounded by $2^{O(k)}\cdot n^{O(1)}$, $2^{O(k \log(k))}\cdot n^{O(1)}$, $2^{O(k^2)}\cdot n^{O(1)}$, and $n^{O(k)}$ where $k$ is respectively the clique-width, $\mathbb{Q}$-rank-width, rank-width, and maximum induced matching width of a given decomposition. Our approach simplifies and unifies the known algorithms for each of the parameters and its running time matches asymptotically also the running times of the best known algorithms for basic \sf NP-hard problems such as Vertex Cover and Dominating Set. Our framework is based on the $d$-neighbor equivalence defined in [B. Bui-Xuan, J. A. Telle, and M. Vatshelle, Theoret. Comput. Sci., (2013), pp. 66--76] and the rank-based approach introduced in [H. L. Bodlaender, M. Cygan, S. Kratsch, and J. Nederlof, Inform. and Comput., 243 (2015), pp. 86--111]. The results we obtain highlight the importance of the $d$-neighbor equivalence relation on the algorithmic applications of width measures. We also prove that our framework could be useful for ${\sf W}[1]$-hard problems parameterized by clique-width such as Max Cut and Maximum Minimal Cut. For these latter problems, we obtain $n^{O(k)}$, $n^{O(k)}$, and $n^{2^{O(k)}}$ time algorithms where $k$ is respectively the clique-width, the $\mathbb{Q}$-rank-width, and the rank-width of the input graph. [ABSTRACT FROM AUTHOR]

Bayesian networks are now widespread for modelling uncertain knowledge. They graph probabilistic relationships, which are quantified using conditional probability tables (CPTs). When empirical data are unavailable, experts may specify CPTs. Here we propose novel methodology for quantifying CPTs: a Bayesian statistical approach to both elicitation and encoding of expert-specified probabilities, in a way that acknowledges their uncertainty. We illustrate this new approach using a case study describing habitat most at risk from feral pigs. For complicated CPTs, it is difficult to elicit all scenarios (CPT entries). Like the CPT Calculator software program, we ask about a few scenarios (e.g. under a one-factor-at-a-time design) to reduce the experts' workload. Unlike CPT Calculator, we adopt a global rather than local regression to 'fill out' CPT entries. Unlike other methods for scenario-based elicitation for regression, we capture uncertainty about each probability in a sequence that explicitly controls biases and enhances interpretation. Furthermore, to utilize all elicited information, we introduce Bayesian rather than Classical generalised linear modelling (GLM). For large CPTs (e.g. >3 levels per parent) we show Bayesian GLM supports richer inference, particularly on interactions, even with few scenarios, providing more information regarding accuracy of encoding. [ABSTRACT FROM AUTHOR]

In this paper we report synthesis and analysis of low cost screen printed coating of TiO _2 in the form of thick film fabricated on glass substrate followed by annealing at 350 °C. The film has been characterized by x-ray diffraction (XRD), Scanning electron microscope (SEM) with energy dispersive x-ray (EDX), UV-visible and Fourier-transform infrared(FTIR) spectroscopy and current-voltage (I-V) measurement via two probe. The XRD analysis showed that the prepared thick film has crystal structure of anatase phase with preferred orientation of (1 0 1)plane. The SEM image identified porous nature of film while EDX spectra revealed the presence of titanium and oxygen atoms in the film. The FTIR spectrum displayed the strong presence of TiO _2 . DC electrical conductivity measurements revealed that electrical conductivity increases on increasing temperature which confirms semiconducting behaviour.

Let S be a unital ring, S[t;σ,δ] a skew polynomial ring where σ is an injective endomorphism and δ a left σ-derivation, and suppose f ∊ S[t;σ,δ] has degree m and an invertible leading coefficient. Using right division by f to define the multiplication, we obtain unital nonassociative algebras Sf on the set of skew polynomials in S[t;σ,δ] of degree less than m. We study the structure of these algebras. When S is a Galois ring and f base irreducible, these algebras yield families of finite unital nonassociative rings A, whose set of (left or right) zero divisors has the form pA for some prime p. For reducible f, the Sf can be employed both to design linear (f,σ,δ)-codes over unital rings and to study their behaviour. [ABSTRACT FROM AUTHOR]

The sulfur oxidization (Sox) system is the central sulfur oxidization pathway of phototrophic and chemotrophic sulfur-oxidizing bacteria. Regulation and function of the Sox system in the chemotrophic Paracoccus pantotrophus has been elucidated; however, to date, no information is available on the regulation of this system in the chemolithotrophic Acidithiobacillus caldus, which is widely utilized in bioleaching. We described the novel tspSR- sox-like clusters in A. caldus and other chemolithotrophic sulfur-oxidizing bacteria containing Sox systems. The highly homologous σ-dependent two-component signaling system (TspS/R), upstream of the sox operons in these novel clusters, was identified by phylogenetic analyses. A typical σ-dependent promoter, P, was identified upstream of soxX-I in the sox-I cluster of A. caldus MTH-04. The transcriptional start site (G) and the −12/−24 regions (GC/GG) of P were determined by rapid amplification of cDNA ends (5′RACE), and the upstream activator sequences (UASs; TGTCCCAAATGGG ACA) were confirmed by electrophoretic mobility shift assays (EMSAs) in vitro and by UAS-probe-plasmids assays in vivo. Sequence analysis of promoter regions in tspSR- sox-like clusters revealed that there were similar σ-dependent promoters upstream of the soxX genes. Based on our results, we proposed a TspSR-mediated signal transduction and transcriptional regulation pathway for the Sox system in A. caldus. The regulation of σ-dependent two-component systems (TCSs) for Sox pathways were explained for the first time in A. caldus, A. thiooxidans, T. tepidarius, and T. denitrificans, indicating the significance of modulating the sulfur oxidization in these chemolithotrophic sulfur oxidizers. [ABSTRACT FROM AUTHOR]

The synthesis, reactivity, and potential of well-defined dinuclear gold complexes as precursors for dual gold catalysis are explored. Using the preorganizing abilities of the ditopic PNHPiPr ( LH) ligand, dinuclear AuI-AuI complex 1 and mixed-valent AuI-AuIII complex 2 provide access to structurally characterized chlorido-bridged cationic species 3 and 4 upon halide abstraction. For 2, this transformation involves unprecedented two-electron oxidation of the redox-active ligand, generating a highly rigidified environment for the Au2 core. Facile reaction with phenylacetylene affords the σ,π-activated phenylacetylide complex 5. When applied in the dual gold heterocycloaddition of a urea-functionalized alkyne, well-defined precatalyst 3 provides high regioselectivities for the anti-Markovnikov product, even at low catalyst loadings, and outperforms common mononuclear AuI systems. This proof-of-concept demonstrates the benefit of preorganization of two gold centers to enforce selective non-classical σ,π-activation with bifunctional substrates. [ABSTRACT FROM AUTHOR]

The food-borne pathogenic bacteria Listeria monocytogenes can form biofilms on various surfaces including food-processing equipment. Biofilms offer survival benefits to the organisms entrapped against environmental insults. Moreover, the σ transcription factor of L. monocytogenes plays an important role in its survival under various stress conditions. In this study, we evaluated whether σ contributes to biofilm formation when L. monocytogenes is grown under various temperatures and media. When the wild-type strain was grown under static biofilm culture below ambient temperature (15°C) for 72 h, the difference in viable cell number (in both planktonic and biofilm cells) between the wild-type and Δ sigB mutant increased by adding NaCl to BHI broth (9% salt BHI > 6% salt BHI > BHI, w/v), and the specific activity of β-galactosidase was highly induced in the wild-type strain grown in 6% salt containing BHI broth. Furthermore, we measured surface-adhered biofilm forming ability using the crystal violet staining method. The wild-type strain formed a four times larger biofilm than that of the Δ sigB mutant in 6% salt-BHI medium at 15°C over a 72 h incubation and also showed the highest level of β-galactosidase specific activity. However, both the wild-type and Δ sigB mutant L. monocytogenes were defective for forming a biofilm in 9% salt-BHI medium at 15°C. Our results suggest that σ plays an enhanced role in surface-adhered biofilm formation when L. monocytogenes encounters dual stress conditions, such as 6% NaCl and low temperature. [ABSTRACT FROM AUTHOR]

σ is an extracytoplasmic function (ECF) σ factor in the bacterium Streptomyces avermitilis that plays a differential regulatory role in avermectin and oligomycin biosynthesis. Gene deletion, complementation, and overexpression experiments showed that σ inhibited avermectin production but promoted oligomycin production. σ indirectly inhibited avermectin production by affecting the transcription of the pathway-specific activator gene aveR, whereas it directly activated oligomycin production by initiating transcription of the pathway-specific activator gene olmRI. The divergently transcribed genes smrAB are located upstream of sig25 and encode a putative two-component system (TCS). σ was found to initiate its own transcription, and its expression was directly activated by SmrA. The precise SmrA-binding sites in the region upstream of sig25 were determined by DNase I footprinting assays and identified two direct repeat sequences CTGTGA-n- CTGTGA, suggesting that SmrA regulates sig25 transcription by binding to these direct repeats. The deletion of smrAB had the similar effect on avermectin and oligomycin A production to the deletion of sig25, indicating that σ and SmrAB function similarly in the regulation of antibiotic production. These findings helpfully clarify the regulation of antibiotic biosynthesis by an ECF σ factor-TCS signal transduction system in S. avermitilis. [ABSTRACT FROM AUTHOR]

We study the global properties of ${\mathcal{D}}_n$, the Turing degrees of the n-r.e. sets. In Theorem 1.5, we show that the first order of ${\mathcal{D}}_n$ is not decidable. In Theorem 1.6, we show that for any two n and m with n < m, ${\mathcal{D}}_n$ is not a Σ1-substructure of ${\mathcal{D}}_m$. [ABSTRACT FROM AUTHOR]

Abstract: The level structure of 183W has been studied using gamma–gamma coincidences from thermal neutron capture in 182W accompanied with the reaction . From these data and those of previous studies a total of 76 levels and about 490 connecting γ-transitions have been established for energies below 2.4 MeV. An analysis based on the standard distorted-wave Born approximation (DWBA) provides the lj-angular momentum transfers and spectroscopic factors for 36 levels up to 2.2 MeV excitation energy. A large number of particle transitions indicate an influence of strong mixing between particle and probably hole states. The extra exchange of phonons across the Fermi surface leads to a fine structure in the fragmentation of most single particle strengths and at the same time has the effect of breakdown of the individual properties of Nilsson states. The extracted and 2 (d, p) sum below 2 MeV has about the same magnitude as in 185,187W. It comprises a rather small fraction of the expected strengths. The observed states below 2 MeV are compared with predictions of the quasiparticle–phonon model. Of particular interest is the identification of “quasi-bands” with inverse spin sequence based on the state at 622.8 keV; this indicates some transition aspects from rigid rotors of light W to γ-soft nuclei in the Os-Pt region. [Copyright &y& Elsevier]

In recent years, small RNAs (sRNAs) have been identified as important regulators of gene expression in bacteria. Most sRNAs are encoded from intergenic regions and are only expressed under highly specific growth conditions. In Staphylococcus aureus, the alternative sigma factor, σ, is known to contribute to the overall stress response, antibiotic resistance, and virulence. The σ regulon in S. aureus is well described and comprises approximately 200 annotated genes, including several genes encoding virulence factors. In the present study, we have identified three novel σ-dependent transcripts encoded from genomic regions previously annotated as intergenic. All three transcripts, named SbrA, SbrB, and SbrC, are highly conserved in S. aureus, and we confirmed their presence in four different isolates (SH1000, Newman, COL, and UAMS-1). Curiously, two of these genes ( sbrA and sbrB) were found to contain open reading frames encoding small, highly basic peptides that are conserved among Staphylococci. The third transcript (SbrC) did not contain any likely open reading frame and thus constitute a genuine non-coding sRNA. The functions of these genes are currently unknown but are likely to be important for the σ-mediated response of S. aureus to adverse conditions. [ABSTRACT FROM AUTHOR]

Abstract: In our experiment we studied three body momentum correlations of 6He breakup products emitted in the quasifree knockout reaction 4He(6He, 2α) at 6He beam energy . For the first time a detailed study of nuclear structure was done in the reaction of quasifree scattering with an unbound system as a spectator. In the experiment we used a detection system of large angular acceptance allowing us to investigate the process in a wide range of kinematical parameters. It was shown that the data obtained in the experiment are well consistent with the predictions obtained with the use of the Plane Wave Impulse Approximation allowing for the final state interaction between the two spectator neutrons. [Copyright &y& Elsevier]

Abstract: For a non-degenerate convex subset Y of the n-dimensional Euclidean space , let be the family of all fuzzy sets of , which are upper-semicontinuous, fuzzy convex and normal with compact supports contained in Y. We show that the space with the topology of endograph metric is homeomorphic to the Hilbert cube iff Y is compact; and the space is homeomorphic to iff Y is non-compact and locally compact. [Copyright &y& Elsevier]

Abstract: Fusion, breakup and scattering for the 9Be+ 144Sm system at near barrier energies are investigated by different approaches. We show that at energies above the barrier there is a small complete fusion suppression when compared with predictions from a double folding potential and with a similar tightly bound system. At sub-barrier energies there is no significant deviation from the predictions using coupled channel calculations that do not include the breakup channel. The energy dependence of the optical potential does not show the usual threshold anomaly found in tightly bound systems. From a simultaneous analysis of fusion and scattering data we estimate the distance where breakup starts to occur. [Copyright &y& Elsevier]

Two independent σ- and π- substituent effect descriptors, sEDA and pEDA, were constructed using the Natural Population Analysis (NPA) approach. The descriptors are based on parameters of 32 monosubstituted benzene molecules calculated at the B3LYP/6-31G** level which is easily applicable to large molecular systems. The sEDA and pEDA descriptors have a clear physical meaning—they show to what extent the σ and π electrons are donated or withdrawn by the substituent from the substituted system. The descriptors were successfully tested to be independent of either of the applicable theoretical methods (DFT or MP2), basis set (6-31G** or cc-pVTZ), and solvent presence. We also demonstrated that the sEDA descriptor described equally well methane derivatives, whereas the pEDA descriptor explained behavior of ethene derivatives. Moreover, the two descriptors work out well for as different molecular systems as triazoles. A comparison of the sEDA and pEDA descriptors with the selected well-known substituent effect scales shows that the sEDA descriptor correlates well (R = 0.961) with the Boyd & Boyd/Boyd– Edgecombe χ descriptor and that so does also the pEDA descriptor (R = 0.943) with the Taft–Topsom σR- resonance constant. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The double differential cross-sections (DDX) for the emission of alpha particles from 27Al()24Na and Ni() reactions induced by 14.77 MeV neutrons were estimated from the alpha particle spectra recorded at 30°, 50°, 90°, 110° angles for aluminium, and at 20°, 45°, 90°, 110° for natural nickel. The results indicate that the alpha particles below and around the most probable energies (∼6.3 MeV from aluminium and ∼8 MeV from natural nickel) are emitted predominantly through the compound nucleus formation process, and the higher energy alpha particles are emitted through the pre-equilibrium or the direct reaction. In general, the measured double-differential cross-sections are in agreement with the theoretical cross-sections estimated using Talys-1.0 and Preco2007 computer programs. The present value of the level density parameter for 24Na is close to the literature value and, therefore, these results reveal consistency in the alpha particle spectra recorded with a single silicon surface barrier detector at different scattering angles. [Copyright &y& Elsevier]

Abstract: Although premature ejaculation (PE) represents the most common male sexual dysfunction, brain mechanisms controlling ejaculatory process remain poorly understood. Recently a group of neurons, identified in the lumbar spinal cord, has been proposed to constitute a spinal ejaculation generator. This key site in ejaculation control, relaying sensory inputs to the brain, is under supraspinal excitatory (medial preoptic area, paraventricular nucleus of the hypothalamus) and inhibitory (nucleus paragigantocellularis) controls. Activation of brain excitatory areas by dopamine (DA) or DA agonists being demonstrated to facilitate ejaculation, it seems particularly interesting to further understand the implication of central DA in the complex process leading to ejaculation. Moreover, the fact that dopaminergic pathways are involved in sexual behavior and that DA release in some brain regions is an important facilitator of male sexual behavior reinforces the crucial implication of DA. Clearly, a better understanding of DA incerto-hypothalamic pathways and targeting brain DA receptor subtypes mediating ejaculation (especially D3 receptors) will benefit the development of new pharmacological strategies to treat ejaculatory dysfunction including PE. [Copyright &y& Elsevier]

Abstract: For a finite and positive measure space and any weakly compact convex subset of a fixed point theorem for a class of nonexpansive self-mappings is proved. An analogous result is obtained for the space . Also, for a bounded domain with boundary , we construct a family of Banach spaces , , which are continuously embedded in and possess the fixed point property. [Copyright &y& Elsevier]

We give a generalized Lagrangian density of 1 + 1 Dimensional O(3) nonlinear σ model with subsidiary constraints, different Lagrange multiplier fields and topological term, find a lost intrinsic constraint condition, convert the subsidiary constraints into inner constraints in the nonlinear σ model, give the example of not introducing the lost constraint $$\dot N$$ = 0, by comparing the example with the case of introducing the lost constraint, we obtain that when not introducing the lost constraint, one has to obtain a lot of various non-intrinsic constraints. We further deduce the gauge generator, give general BRST transformation of the model under the general conditions. It is discovered that there exists a gauge parameter β originating from the freedom degree of BRST transformation in a general O(3) nonlinear sigma model, and we gain the general commutation relations of ghost field. [ABSTRACT FROM AUTHOR]

The leukocyte common antigen-related (LAR) subfamily of receptor protein tyrosine phosphatases (RPTPs), LAR, RPTP-σ, and RPTP-δ, regulate neuroendocrine development, axonal regeneration, and hippocampal long-term potentiation in mammals. In Drosophila, RPTPs are required for appropriate axon targeting during embryonic development. In contrast, deletion of any one of the three LAR-RPTP family members in mammals does not result in gross axon targeting defects. Both RPTP-σand RPTP-δ are highly expressed in the developing mammalian nervous system, suggesting they might be functionally redundant. To test this hypothesis, we generated RPTP-σ and RPTP-δ (RPTP-σ/δ) double-mutant mice. Although embryonic day 18.5 RPTP-σ and RPTP-δ single-mutant embryos were viable, RPTP-σ/δ double mutants were paralyzed, were never observed to draw a breath, and died shortly after cesarean section. RPTP-σ/δ double mutants exhibit severe muscle dysgenesis and severe loss of motoneurons in the spinal cord. Detailed analysis of the projections of phrenic nerves in RPTP-σ/δdouble mutants indicated that these motoneuron axons emerge normally from the cervical spinal cord, but stall on reaching the diaphragm. Our results demonstrate that RPTP-σ and RPTP-δ complement each other functionally during mammalian development, and reveal an essential contribution of RPTP-σ and RPTP-δ to appropriate motoneuron axon targeting during mammalian axonogenesis. [ABSTRACT FROM AUTHOR]

We give an algorithm for deciding whether an embedding of a finite partial order ${\mathcal P}$ into the enumeration degrees of the ${\Sigma_2^0}$-sets can always be extended to an embedding of a finite partial order ${\mathcal Q} \supset {\mathcal P}$. [ABSTRACT FROM AUTHOR]

Expression of the rpoS gene encoding the σS subunit of E. coli RNA polymerase was studied on transition to the stationary phase and under conditions of starvation. Polyamines, in particular putrescine, are involved in regulation of the rpoS expression by concentration-dependent stimulation at the levels of translation and stability of the protein σS. The stimulatory effect of exogenous putrescine inversely depended on its content in the cell and was the most pronounced in the beginning of the exponential growth. Possible mechanisms of the polyamine effect on the rpoS expression on post-transcriptional and post-translational levels are discussed. [ABSTRACT FROM AUTHOR]

The influence of solidification microstructure on σ-phase precipitation in two refractory stainless steels (26Cr–3Ni) with different microstructures is analyzed. Depending upon cooling rates the existence of Cr7C3 strongly increases the σ-phase precipitation rate, whereas σ precipitation is delayed when this carbide is not present in the alloy. [Copyright &y& Elsevier]

Expression of genes encoding type II restriction/modification (R/M) systems, which are widely spread in eubacteria, must be tightly regulated to ensure that host DNA is protected from restriction endonucleases at all times. Examples of coordinated expression of R/M genes that rely on the action of regulatory factors or the ability of methyl transferases to repress their own synthesis by interacting with the promoter DNA have been described. Here, we characterize the molecular mechanism of factor-independent regulation in the CfrBI R/M system. Regulation of the cfrBIM gene transcription occurs through CfrBIM-catalyzed methylation of a cytosine residue in the cfrBIM promoter. The covalent modification inhibits cfrB1M promoter complex formation by interfering with the RNA polymerase σ70 subunit region 4.2 recognition of the −35 promoter element. The decrease in the cfrBIM promoter complex formation leads to increase in the activity of overlapping cfrBIR promoters. This elegant factor-independent regulatory system ensures coordinated expression of the cfrBI genes. [Copyright &y& Elsevier]

We have performed molecular modeling studies on several σ1 specific ligands, including PD144418, spipethiane, haloperidol, pentazocine, and others to develop a pharmacophore for σ1 receptor–ligand binding, under the assumption that all the compounds interact at the same receptor binding site. The modeling studies have investigated the conformational and electrostatic properties of the ligands. Superposition of active molecules gave the coordinates of the hypothetical 5-point σ1 pharmacophore, as follows: R1 (0.85, 7.26, 0.30); R2 (5.47, 2.40, −1.51); R3 (−2.57, 4.82, −7.10); N (−0.71, 3.29, −6.40); carbon centroid (3.16, 4.83, −0.60), where R1, R2 were constructed onto the aromatic ring of each compound to represent hydrophobic interactions with the receptor; and R3 represents a hydrogen bond between the nitrogen atom and the receptor. Additional analyses were used to describe secondary binding sites to electronegative groups such as oxygen or sulfur atom. Those coordinates are (2.34, 5.08, −4.18). The model was verified by fitting other σ1 receptor ligands. This model may be used to search conformational databases for other possibly active ligands. In conjunction with rational drug design techniques the model may be useful in design and synthesis of novel σ1 ligands of high selectivity and potency. Calculations were performed using Sybyl 6.5. [Copyright &y& Elsevier]

Compounds having two p-phenoxyl radicals bridged by a 1,2-diphenylenedisilanylene unit in m,p- and p,p- fashions were synthesized and the intramolecular spin–spin interaction was examined by Curie plots of ESR signal intensities due to the ΔMS=±2 transition at low temperature. It was found that bridging two phenoxyl radicals at meta and para positions of the bridge led to triplet ground state or degeneracy of triplet/singlet states. In contrast, two phenoxyl radicals put at both para positions interacted in an antiferromagnetic fashion through the diphenylenedisilanylene bridge, to realize singlet ground state. [Copyright &y& Elsevier]

In this study, using the new sigma1/2 (σ1/2) compound MR200, its parent drug haloperidol and the σ ligand 1,3-di-o-tolylguanidine (DTG), we have investigated the role of striatal σ receptors in the control of basal dopamine (DA) outflow, by coupling in vitro binding experiments and in vivo microdialysis in the striatum of halothane-anesthetized rats. MR200 with respect to haloperidol, exhibits high affinity for σ1 (1.5 nM) and σ2 (21.9 nM) receptors, but only negligible affinity for DA receptors. Compared to DTG, MR200 has similar selectivity across neurotransmitter systems, and 46 times higher affinity for σ1 receptors. Intrastriatal application of MR200 at 10, but not 0.1 or 1 μM, elicited a pronounced decrease in striatal DA release (−45% of control values). This inhibitory effect was preceded by a transient increase in DA release (+50% over baseline) after 100 μM MR200 administration. DTG at 100, but not 10 μM, significantly reduced DA release (−40%). Haloperidol, whilst increasing DA release at 1 μM, induced a delayed decrease in DA release after 10 μM application. Finally, haloperidol (10 μM) did not modify the inhibitory effect of 10 μM MR200. These results show that striatal σ receptors control striatal DA release in resting conditions. [Copyright &y& Elsevier]

We cloned and characterized sigH encoding a stress-response sigma factor, σH, of Streptomyces griseus. Nucleotide sequencing of the sigH gene cluster revealed an identical gene organization as in the orthologous region of Streptomyces coelicolor A3(2). Transcriptional analysis by S1 nuclease mapping showed the presence of three tandem promoters (P1–P3) that direct transcription of sigH. The activity of P1 was markedly reduced in a sigH-depleted mutant, suggesting its dependence on σH. P1 was induced by addition of 0.7 M NaCl, and P2 was induced by heat shock at 45 °C or addition of 4% ethanol. The sigH mutant of S. griseus showed conditional defect in aerial mycelium formation and streptomycin production depending on high concentration of glucose (>2%). Meanwhile, the wild-type strain of S. griseus introduced with rshA encoding a probable anti-sigma factor for σH on a high-copy-number plasmid was unable to perform development on media containing 1% glucose while it showed wild-type phenotype on media containing 1% maltose. RshA inhibited the σH-dependent in vitro run-off transcription at P1, which confirmed its role as a negative regulator for σH. Analysis of RshA–σ interaction by an Escherichia coli two-hybrid system showed specific interaction of RshA with σH and two related sigma factors, σL and σF. We speculate that the high copy number of rshA represses morphological and physiological development of S. griseus through simultaneous inactivation of σH and related stress-response sigma factors, which play an essential role in the onset of cellular differentiation and antibiotic production on glucose media. [Copyright &y& Elsevier]

Sterically congested cis-2-(t-butyl)-3-(organosilyl)cyclohexanones were irradiated with UV light to give a mixture of Norrish type I and II products, as well as the corresponding trans-2-(t-butyl)-3-(organosilyl)cyclohexanones. In comparison with the trans isomers, the quantum yields and rate constants of the photolytic reactions were greater for the cis isomers. [Copyright &y& Elsevier]

Dendritic polysilanes consist of silicon chains that emanate from a silicon core and branch one or more times. First- and second-generation dendrimers have been prepared that possess longest chains up to 13 silicon atoms. Ultraviolet absorption occurs at a wavelength similar to that of straight polysilane chains of similar length. The intensity of electronic absorption, however, is enhanced on a molar basis compared with linear structures. The dendrimers are robust and often crystalline. Numerous crystal structures have been solved, providing unique information about polysilane conformations. [Copyright &y& Elsevier]

Synthesis, structures, and electronic properties of silicon polymers and oligomers having hypervalent silicon moieties, polar substituents, or transition metal moieties are reported. UV spectra of pentacoordinate silicon oligomers reveal that the introduction of pentacoordinate silicon moieties into oligosilanes leads to a drastic change of the σSiSi→σ*SiSi excitation energies. 29Si-NMR spectra have proved that the conformation of pentacoordinate oligosilanes is tightly locked, indicating that free rotation about the Si&z.sbnd;Si single bonds is nearly completely inhibited by electrostatic interaction. UV–vis spectra of polysilanes substituted with (alkoxycarbonyl)methyl groups exhibit unusual spectral properties such as long-wavelength absorption above 400 nm, and temperature- or solvent-dependent change of the UV spectra. Effective electron delocalization in Si&z.sbnd;Ru&z.sbnd;Ru&z.sbnd;Si&z.sbnd;C6H4 polymers was demonstrated by the absorption spectra. Solvent-sensitive skeletal rearrangement of the Si&z.sbnd;Ru&z.sbnd;Ru&z.sbnd;Si moieties gives rise to a remarkable change of the optical properties of the polymers. [Copyright &y& Elsevier]

Recent experimental and theoretical aspects of the conformation dependence of UV absorption of short chain peralkylated oligosilanes are surveyed. In the current interpretation of the conformational effect on tetrasilane electronic transitions it is not the excitation energy but the intensity of the lowest valence transitions that changes significantly as the SiSiSiSi dihedral angle varies. The latest synthetic advances have enabled us to constrain the conformation of silicon backbone in oligosilanes to some extent to provide strong experimental evidence for the theoretical proposals. A similar conformational effect has been found for a series of hexasilane conformers. [Copyright &y& Elsevier]

The binding profile of [3H]BHDP ([3H]N-benzyl-N′-(2-hydroxy-3,4-dimethoxybenzyl)-piperazine) was evaluated. [3H]BHDP labelled a single class of binding sites with high affinity (Kd=2–3 nM) in rat liver mitochondria and synaptic membranes. The pharmacological characterization of these sites using σ reference compounds revealed that these sites are σ receptors and, more particularly, σ1 receptors. Indeed, BHDP inhibited [3H]pentazocine binding, a marker for σ1 receptors, with high affinity in a competitive manner. BHDP is selective for σ1 receptors since it did not show any relevant affinity for most of the other receptors, ion channels or transporters tested. Moreover, in an in vitro model of cellular hypoxia, BHDP prevented the fall in adenosine triphosphate (ATP) levels caused by 24 h hypoxia in cultured astrocytes. Taken together, these results demonstrate that [3H]BHDP is a potent and selective ligand for σ1 receptors showing cytoprotective effects in astrocytes. [Copyright &y& Elsevier]

Subphthalocyanine and subnaphthalocyanine dyes and their mixture were investigated by means of the spectroscopic and photoelectric methods. Absorption, fluorescence, steady-state and time-resolved photothermal measurements for the dyes and their mixture were done in order to get information about the radiative and non-radiative deactivation processes as competetive processes to charge separation. It was shown that energy transfer between the dyes improved the photocurrent generation in photoelectrochemical cells (PEC) based on In2O3 and SnO2 as an electrode. The possible participation of the dye triplet states in non-radiative processes was discussed. [Copyright &y& Elsevier]

Reaction of Li[Cp(CO)2Re(COPh)] (1) with CF3SO3Me afforded, besides the expected carbene complex [Cp(CO)2Re&z.dbnd6;C(OMe)(Ph)] (2) and the alkyl–acyl derivative [Cp(CO)2Re(Me)(COPh)] (3), a third structural isomer [Cp(CO)2Re{OC(Me)Ph}] (4), which contains an acetophenone molecule coordinated to the metal center. The X-ray analysis showed that in solid acetophenone is bound to ‘CpRe(CO)2’ exclusively through an oxygen σ-donor interaction, while in solution an equilibrium between σ-bound (η1) and π-bound (η2) forms occurs, as judged by IR data and 1H and 13C variable temperature NMR spectra (π/σ ratio 2.87 at 183 K and 1.16 at 263 K in CD2Cl2, ΔH°=−4.5 kJ mol−1 for the σ&iff;π reaction, Ea 58(1) kJ mol−1). In solvents different from Et2O (n-hexane, THF, acetone) and with alkylating agent different from CF3SO3Me (MeI, Me3OBF4) the formation of 4 was negligible. It has been demonstrated that 4 does not originate by acetophenone reductive elimination from 3. No evidence of the involvement of radicals has been obtained. [Copyright &y& Elsevier]

When complexed with Escherichia coli RNA polymerase core enzyme, purified RpoI protein of Rhizobium leguminosarum initiated transcription in vitro from promoters of the vbsADL and vbsGSO operons, which are needed to synthesise the siderophore vicibactin. There is a single transcription initiation site for rpoI, regardless of whether the cells are grown in Fe-replete or Fe-depleted media, but levels of rpoI mRNA were reduced, though not abolished, in the presence of Fe. Unlike PvdS, a similar Pseudomonas σ factor needed to transcribe genes involved in pyoverdine synthesis, RpoI transcribes vbsADL and vbsGSO in the absence of the cognate siderophore. The RpoI σ factor is not required for transcription of rpoI. [Copyright &y& Elsevier]

Non-functional mutants of σ38(σS) were studied in vitro to identify the nature of their defects. Mutations in four amino acids led to severe defects in DNA binding and enzyme isomerization with promoter fork junction probes containing single-stranded non-template DNA. The same properties were previously seen with DNA mutations at the fork junction, implying that sigma:DNA interactions at the fork junction are used both for DNA binding and enzyme isomerization. An overlapping set of four mutants had defects that appear to be associated with DNA melting to create the fork junction. When mapped onto the σ70 structure, these groups of mutants suggest motifs used by σ factors to melt DNA and isomerize RNA polymerase to form functional open promoter complexes. [Copyright &y& Elsevier]

Allylic nucleophilic substitution of trifluoromethyl-group substituted cinnamyl carbonate with diethyl malonate anion in the presence of palladium complex catalyst gave regio- and stereoselectively the SN2′ product. The regiochemistry caused by the polar effect of trifluoromethyl group was opposite to the methylated cinnamyl substrate in a similar steric environment. The sterically more hindered mesityl and tert-butyl substrates than phenyl derivative also gave the products reacted at the more hindered sites. Although o-substituted substrates expecting intramolecular coordination to affect regiochemistry were examined, no alternative regioisomers were detected. [Copyright &y& Elsevier]

Previous work has shown that the base sequence of the DNA segment immediately upstream of the −10 hexamer at bacterial promoters (the extended −10 element) can make a significant contribution to promoter strength. Guided by recently published structural information, we used alanine scanning and suppression mutagenesis of Region 2.4 and Region 3.0 of the Escherichia coli RNA polymerase σ70 subunit to identify amino acid sidechains that play a role in recognition of this element. Our study shows that changes in these regions of the σ70 subunit can affect the recognition of different extended −10 element sequences. [Copyright &y& Elsevier]

Fourier-transform IR frequencies ν(C&z.dbnd6;O) and integrated intensities A(C&z.dbnd6;O) of the carbonyl groups of a series of benzaldehydes (53 compounds) have been measured in dimethyl sulphoxide. Excellent and satisfactory correlations have been found between ν(C&z.dbnd6;O) and σ+ substituent constants of the m- and p-substituted compounds. Diortho-substituted compounds deviate strongly from the correlation lines because of the steric ortho-effects mainly. σ+ constants of ionic substituents (10 examples) have proved satisfactorily valid in the series studied. [Copyright &y& Elsevier]