One-parameter Darboux-transformed quantum actions in Thermodynamics

We use nonrelativistic supersymmetry, mainly Darboux transformations of the general (one-parameter) type, for the quantum oscillator thermodynamic actions. Interesting Darboux generalizations of the fundamental Planck and pure vacuum cases are discussed in some detail with relevant plots. It is shown that the one-parameter Darboux-transformed Thermodynamics refers to superpositions of boson and fermion excitations of positive and negative absolute temperature, respectively. Recent results of Arnaud, Chusseau, and Philippe physics/0105048 regarding a single mode oscillator Carnot cycle are extended in the same Darboux perspective. We also conjecture a Darboux generalization of the fluctuation-dissipation theoremComment: 14 pages, 13 figures, correction of the formula in the text after Eq. 7, accepted at Physica Script

Serial analysis of gene expression reveals differential expression between endometriosis and normal endometrium. Possible roles for AXL and SHC1 in the pathogenesis of endometriosis

<p>Abstract</p> <p>Background</p> <p>Endometriosis is a clinical condition that affects up to 10% of the women of reproductive age. Endometriosis is characterized by the presence of endometrial tissues outside the uterine cavity and can lead to chronic pelvic pain, infertility and, in some cases, to ovarian cancer.</p> <p>Methods</p> <p>In order to better understand the pathogenesis of endometriosis, we have used Serial Analysis of Gene Expression (SAGE) to identify genes differentially in this disease by studying three endometriotic tissues and a normal endometrium sample. Promising candidates (AXL, SHC1, ACTN4, PI3KCA, p-AKT, p-mTOR, and p-ERK) were independently validated by immunohistochemistry in additional normal and endometriotic tissues.</p> <p>Results</p> <p>We identified several genes differentially expressed between endometriosis and normal endometrium. IGF2, ACTN4, AXL, and SHC1 were among the most upregulated genes. Comparison of the endometriosis gene expression profiles with the gene expression patterns observed in normal human tissues allowed the identification of endometriosis-specific genes, which included several members of the MMP family (MMP1,2,3,10,11,14). Immunohistochemical analysis of several candidates confirmed the SAGE findings, and suggested the involvement of the PI3K-Akt and MAPK signaling pathways in endometriosis.</p> <p>Conclusion</p> <p>In human endometriosis, the PI3K-Akt and MAPK signaling pathways may be activated via overexpression of AXL and SHC1, respectively. These genes, as well as others identified as differentially expressed in this study, may be useful for the development of novel strategies for the detection and/or therapy of endometriosis.</p

Partial Substitution of Cu Sites by Mg for the Improvement of CuWO4 Photoanodes Performance

The photoelectrochemical properties of CuWO4 (Mg x%) thin-films obtained by solution-based methods are investigated as a function of the material composition. The thin-films are prepared by spin-coating a single precursor solution onto FTO-coated glass substrates, followed by an annealing process at 550 °C. XRD, Raman, XPS, and electrochemical data studies indicate the formation of single-phase CuWO4 (Mg x%), with Mg2+ partially substituting Cu2+ sites. Photoelectrochemical studies under monochromatic illumination show an 88.2% increase in photocurrent responses and a 2-fold increase in charge carriers bulk separation efficiency at 1.0 V vs RHE, upon replacing 2.5% of Cu by Mg. DFT calculations reveal that Mg incorporation rearranges electron density, shifting the position of magnesium toward an axial oxygen atom, increasing the covalent nature of the bond and decreasing the Cu–O bond length. It is proposed that a change in the localization of the electron density away from the sphere of influence of the oxygen atom, and toward the shared space of the covalent bond, leads to better carrier mobility and the generation of higher photocurrents

Down-regulation of cell surface CXCR4 by HIV-1

<p>Abstract</p> <p>Background</p> <p>CXC chemokine receptor 4 (CXCR4), a member of the G-protein-coupled chemokine receptor family, can serve as a co-receptor along with CD4 for entry into the cell of T-cell tropic X4 human immunodeficiency virus type 1 (HIV-1) strains. Productive infection of T-lymphoblastoid cells by X4 HIV-1 markedly reduces cell-surface expression of CD4, but whether or not the co-receptor CXCR4 is down-regulated has not been conclusively determined.</p> <p>Results</p> <p>Infection of human T-lymphoblastoid cell line RH9 with HIV-1 resulted in down-regulation of cell surface CXCR4 expression. Down-regulation of surface CXCR4 correlated temporally with the increase in HIV-1 protein expression. CXCR4 was concentrated in intracellular compartments in H9 cells after HIV-1 infection. Immunofluorescence microscopy studies showed that CXCR4 and HIV-1 glycoproteins were co-localized in HIV infected cells. Inducible expression of HIV-1 envelope glycoproteins also resulted in down-regulation of CXCR4 from the cell surface.</p> <p>Conclusion</p> <p>These results indicated that cell surface CXCR4 was reduced in HIV-1 infected cells, whereas expression of another membrane antigen, CD3, was unaffected. CXCR4 down-regulation may be due to intracellular sequestering of HIV glycoprotein/CXCR4 complexes.</p

A generalised model for dynamic photocurrent responses at dye-sensitised liquid|liquid interfaces

The heterogeneous photoinduced electron transfer involving dyes adsorbed at the interface between two immiscible electrolyte solutions and redox molecules located in the adjacent phase manifests itself as photocurrent responses under potentiostatic conditions. Photocurrent transients as functions of the light intensity and bias potential allow the extraction of insightful information on the kinetics of the various processes associated with the photoinduced reaction. Previous analyses of this type of responses were based on phenomenological models that did not consider mass transport. In the present paper, we develop a generalised model for photocurrent transients taking into account the diffusion of reacting species to the interface. Comparison with the experimental data confirms that the responses can be described adequately by applying stationary conditions to the surface concentration of the photoactive species. Mechanistic aspects associated with the nature of the photocurrent relaxation on the microsecond time scale are examined. In particular, the dependence of the transient response on the light intensity indicates that charge recombination proceeds mainly as a first order reaction from an interfacial geminate ion pair. Coupled ion transfer reactions involving the photoproducts can also contribute to the photocurrent, depending on the formal ion transfer potential of the corresponding species

Tellurium-doped lanthanum manganite as catalysts for the oxygen reduction reaction

The effect of tellurium (Te) doping on the electrocatalytic activity of La1−xTexMnO3 toward the oxygen reduction reaction is investigated for the first time. La1−xTexMnO3 with x-values up 23% were synthesized from a single ionic liquid-based precursor, yielding nanoparticles with mean diameter in the range of 40–68 nm and rhombohedral unit cell. Electrochemical studies were performed on carbon-supported particles in alkaline environment. The composition dependence activity is discussed in terms of surface density of Mn sites and changes in the effective Mn oxidation state

Adsorption and photoreactivity of CdSe nanoparticles at liquid|liquid interfaces

The voltage induced assembly and photoreactivity of cadmium selenide (CdSe) nanoparticles protected by mercaptosuccinic acid are studied at the polarisable interface between water and 1,2-dichloroethane electrolyte solutions. Cyclic voltammograms and admittance measurements show an increase of the interface excess charge associated with the adsorption of CdSe nanoparticles as the Galvani potential difference is tuned to negative values with respect to the potential in the organic phase. Within the potential range where the nanoparticles are adsorbed, band-gap illumination leads to heterogeneous electron transfer from CdSe nanoparticles to electron acceptors located in the organic phase. The interfacial Galvani potential difference plays an important role in these phenomena, as it affects the interfacial density of the nanoparticles, as well as the driving force for the electron transfer. The photocurrent efficiency also strongly depends on the formal redox potential of the electron acceptor, indicating that the heterogeneous photoreaction is kinetically controlled. The interfacial electron transfer occurs via depopulation of the deep trap states in the band gap. Analysis of the photocurrent transient responses reveals that the magnitude of the instantaneous photocurrent upon illumination is determined by the kinetics of heterogeneous electron transfer, while photogenerated holes are swiftly captured by species present in the aqueous phase. The photocurrent decay upon constant illumination is associated with the diffusion of the acceptor to the interfacial region. From the phenomenological point of view, the photoelectrochemical behaviour of CdSe nanoparticles can be compared to a self-assembled ultrathin p-type semiconductor photoelectrode

Characterization of Electronic Transport through Amorphous TiO_2 Produced by Atomic-Layer Deposition

Electrical transport in amorphous titanium dioxide (a-TiO_2) thin films, deposited by atomic layer deposition (ALD), and across heterojunctions of p+-Si|a-TiO_2|metal substrates that had various top metal contacts has been characterized by ac conductivity, temperature-dependent dc conductivity, space-charge-limited current spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, X-ray photoelectron spectroscopy, and current density versus voltage (J–V) characteristics. Amorphous TiO_2 films were fabricated using either tetrakis(dimethylamido)-titanium with a substrate temperature of 150 °C or TiCl_4 with a substrate temperature of 50, 100, or 150 °C. EPR spectroscopy of the films showed that the Ti^(3+) concentration varied with the deposition conditions and increases in the concentration of Ti^(3+) in the films correlated with increases in film conductivity. Valence band spectra for the a-TiO_2 films exhibited a defect-state peak below the conduction band minimum (CBM) and increases in the intensity of this peak correlated with increases in the Ti^(3+) concentration measured by EPR as well as with increases in film conductivity. The temperature-dependent conduction data showed Arrhenius behavior at room temperature with an activation energy that decreased with decreasing temperature, suggesting that conduction did not occur primarily through either the valence or conduction bands. The data from all of the measurements are consistent with a Ti^(3+) defect-mediated transport mode involving a hopping mechanism with a defect density of 10^(19) cm^(–3), a 0.83 wide defect band centered 1.47 eV below the CBM, and a free-electron concentration of 10^(16) cm^(–3). The data are consistent with substantial room-temperature anodic conductivity resulting from the introduction of defect states during the ALD fabrication process as opposed to charge transport intrinsically associated with the conduction band of TiO_2

Ion flow in a zeolitic imidazolate framework results in ionic diode phenomena

Ionic transport (for applications in nanofluidics or membranes) and “ionic diode” phenomena in a zeolitic imidazolate framework (ZIF-8) are investigated by directly growing the framework from aqueous Zn2+ and 2-methylimidazole as an “asymmetric plug” into a 20 ?m diameter pore in a ca. 6 ?m thin poly-ethylene-terephthalate (PET) film