Magnetic Ground State of Pr0.89_{0.89}LaCe0.11_{0.11}CuO4+α−δ_{4+\alpha-\delta} with Varied Oxygen Depletion Probed by Muon Spin Relaxation

The magnetic ground state of an electron-doped cuprate superconductor Pr$_{1-x}$LaCe$_x$CuO$_{4+\alpha-\delta}$ ($x=0.11, \alpha\simeq0.04$) has been studied by means of muon spin rotation/relaxation (\msr) over a wide variety of oxygen depletion, $0.03\le\delta\le0.12$. Appearance of weak random magnetism over entire crystal volume has been revealed by a slow exponential relaxation. The absence of $\delta$-dependence for the random magnetism and the multiplet pattern of muon Knight shift at higher fields strongly suggest that the random moments are associated with excited Pr$^{3+}$ ions under crystal electric field.Comment: 6 pages, 4 figures, submitted to J. Phys. Soc. Jp

Weak localization in InSb thin films heavily doped with lead

The paper reports on the investigations of the weak localization (WL) effects in 3D polycrystalline thin films of InSb. The films are closely compensated showing the electron concentration n>10^{16} cm^{-3} at the total concentration of the donor and acceptor type structural defects >10^{18} cm^{-3}. Unless Pb-doped, the InSb films do not show any measurable or show very small WL effect at 4.2 K. The Pb-doping to the concentration of the order of 10^{18} cm^{-3} leads to pronounced WL effects below 7 K. In particular, a clearly manifested SO scattering is observed. From the comparison of the experimental data on temperature dependence of the magnetoresistivity and sample resistance with the WL theory, the temperature dependence of the phase destroying time is determined. The determination is performed by fitting theoretical terms obtained from Kawabata's theory to experimental data on magnetoresistance. It is concluded that the dephasing process is connected to three separate interaction processes. The first is due to the SO scatterings and is characterized by temperature-independent relaxation time. The second is associated with the electron-phonon interaction. The third dephasing process is characterized by independent on temperature relaxation time tau_c. This relaxation time is tentatively ascribed to inelastic scattering at extended structural defects, like grain boundaries. The resulting time dephasing time shows saturation in its temperature dependence. The temperature dependence of the resistance of the InSb films can be explained by the electron-electron interaction for T2 K.Comment: 15 pages with 5 figure

Low-lying continuum structures in B8 and Li8 in a microscopic model

We search for low-lying resonances in the B8 and Li8 nuclei using a microscopic cluster model and a variational scattering method, which is analytically continued to complex energies. After fine-tuning the nucleon-nucleon interaction to get the known 1+ state of B8 at the right energy, we reproduce the known spectra of the studied nuclei. In addition, our model predicts a 1+ state at 1.3 MeV in B8, relative to the Be7+p threshold, whose corresponding pair is situated right at the Li7+n threshold in Li8. Lacking any experimental evidence for the existence of such states, it is presently uncertain whether these structures really exist or they are spurious resonances in our model. We demonstrate that the predicted state in B8, if it exists, would have important consequences for the understanding of the astrophysically important Be7(p,gamma)B8 reaction.Comment: 6 pages with 1 figure. The postscript file and more information are available at http://nova.elte.hu/~csot

Quantum Point Contacts and Coherent Electron Focusing

I. Introduction II. Electrons at the Fermi level III. Conductance quantization of a quantum point contact IV. Optical analogue of the conductance quantization V. Classical electron focusing VI. Electron focusing as a transmission problem VII. Coherent electron focusing (Experiment, Skipping orbits and magnetic edge states, Mode-interference and coherent electron focusing) VIII. Other mode-interference phenomenaComment: #3 of a series of 4 legacy reviews on QPC'

Non Linear Current Response of a Many-Level Tunneling System: Higher Harmonics Generation

The fully nonlinear response of a many-level tunneling system to a strong alternating field of high frequency $\omega$ is studied in terms of the Schwinger-Keldysh nonequilibrium Green functions. The nonlinear time dependent tunneling current $I(t)$ is calculated exactly and its resonance structure is elucidated. In particular, it is shown that under certain reasonable conditions on the physical parameters, the Fourier component $I_{n}$ is sharply peaked at $n=\frac {\Delta E} {\hbar \omega}$, where $\Delta E$ is the spacing between two levels. This frequency multiplication results from the highly nonlinear process of $n$ photon absorption (or emission) by the tunneling system. It is also conjectured that this effect (which so far is studied mainly in the context of nonlinear optics) might be experimentally feasible.Comment: 28 pages, LaTex, 7 figures are available upon request from [email protected], submitted to Phys.Rev.

Complete Genomic Structure of the Cultivated Rice Endophyte Azospirillum sp. B510

We determined the nucleotide sequence of the entire genome of a diazotrophic endophyte, Azospirillum sp. B510. Strain B510 is an endophytic bacterium isolated from stems of rice plants (Oryza sativa cv. Nipponbare). The genome of B510 consisted of a single chromosome (3 311 395 bp) and six plasmids, designated as pAB510a (1 455 109 bp), pAB510b (723 779 bp), pAB510c (681 723 bp), pAB510d (628 837 bp), pAB510e (537 299 bp), and pAB510f (261 596 bp). The chromosome bears 2893 potential protein-encoding genes, two sets of rRNA gene clusters (rrns), and 45 tRNA genes representing 37 tRNA species. The genomes of the six plasmids contained a total of 3416 protein-encoding genes, seven sets of rrns, and 34 tRNAs representing 19 tRNA species. Eight genes for plasmid-specific tRNA species are located on either pAB510a or pAB510d. Two out of eight genomic islands are inserted in the plasmids, pAB510b and pAB510e, and one of the islands is inserted into trnfM-CAU in the rrn located on pAB510e. Genes other than the nif gene cluster that are involved in N2 fixation and are homologues of Bradyrhizobium japonicum USDA110 include fixABCX, fixNOQP, fixHIS, fixG, and fixLJK. Three putative plant hormone-related genes encoding tryptophan 2-monooxytenase (iaaM) and indole-3-acetaldehyde hydrolase (iaaH), which are involved in IAA biosynthesis, and ACC deaminase (acdS), which reduces ethylene levels, were identified. Multiple gene-clusters for tripartite ATP-independent periplasmic-transport systems and a diverse set of malic enzymes were identified, suggesting that B510 utilizes C4-dicarboxylate during its symbiotic relationship with the host plant

Self-structuring of lamellar bridged silsesquioxanes with long side spacers

Diurea cross-linked bridged silsesquioxanes (BSs) C(10)C(11)C(10) derived from organosilane precursors, including decylene chains as side spacers and alkylene chains with variable length as central spacers (EtO)(3)Si- (CH(2))(10)-Y(CH(2))(n)-Y-(CH(2))(10)-Si(OEt)(3) (n = 7, 9-12; Y = urea group and Et = ethyl), have been synthesized through the combination of self-directed assembly and an acid-catalyzed sol gel route involving the addition of dimethylsulfoxide (DMSO) and a large excess of water. This new family of hybrids has enabled us to conclude that the length of the side spacers plays a unique role in the structuring of alkylene-based BSs, although their morphology remains unaffected. All the samples adopt a lamellar structure. While the alkylene chains are totally disordered in the case of the C(10)C(7)C(10) sample, a variable proportion of all-trans and gauche conformers exists in the materials with longer central spacers. The highest degree of structuring occurs for n = 9. The inclusion of decylene instead of propylene chains as side spacers leads to the formation of a stronger hydrogen-bonded urea-urea array as evidenced by two dimensional correlation Fourier transform infrared spectroscopic analysis. The emission spectra and emission quantum yields of the C(10)C(n)C(10) Cm materials are similar to those reported for diurea cross-linked alkylene-based BSs incorporating propylene chains as side spacers and prepared under different experimental conditions. The emission of the C(10)C(n)C(10) hybrids is ascribed to the overlap of two distinct components that occur within the urea cross-linkages and within the siliceous nanodomains. Time-resolved photoluminescence spectroscopy has provided evidence that the average distance between the siliceous domains and the urea cross-links is similar in the C(10)C(n)C(10) BSs and in oxyethylene-based hybrid analogues incorporating propylene chains as side spacers (diureasils), an indication that the longer side chains in the former materials adopt gauche conformations. It has also allowed us to demonstrate for the first time that the emission features of the urea-related component of the emission of alkylene-based BSs depend critically on the length of the side spacers

Salivary Gland Transcriptomes and Proteomes of Phlebotomus tobbi and Phlebotomus sergenti, Vectors of Leishmaniasis

Phlebotomine female sand flies require a blood meal for egg development, and it is during the blood feeding that pathogens can be transmitted to a host. Leishmania parasites are among these pathogens and can cause disfiguring cutaneous or even possibly fatal visceral disease. The Leishmania parasites are deposited into the bite wound along with the sand fly saliva. The components of the saliva have many pharmacologic and immune functions important in blood feeding and disease establishment. In this article, the authors identify and investigate the protein components of saliva of two important vectors of leishmaniasis, Phlebotomus tobbi and P. sergenti, by sequencing the transcriptomes of the salivary glands. We then compared the predicted protein sequences of these salivary proteins to those of other bloodsucking insects to elucidate the similarity in composition, structure, and enzymatic activity. Finally, this descriptive analysis of P. tobbi and P. sergenti transcriptomes can aid future research in identifying molecules for epidemiologic assays and in investigating sand fly-host interactions

The Complete Genome of Propionibacterium freudenreichii CIRM-BIA1T, a Hardy Actinobacterium with Food and Probiotic Applications

Background: Propionibacterium freudenreichii is essential as a ripening culture in Swiss-type cheeses and is also considered for its probiotic use [1]. This species exhibits slow growth, low nutritional requirements, and hardiness in many habitats. It belongs to the taxonomic group of dairy propionibacteria, in contrast to the cutaneous species P. acnes. The genome of the type strain, P. freudenreichii subsp. shermanii CIRM-BIA1 (CIP 103027T), was sequenced with an 11-fold coverage. Methodology/Principal Findings: The circular chromosome of 2.7 Mb of the CIRM-BIA1 strain has a GC-content of 67% and contains 22 different insertion sequences (3.5% of the genome in base pairs). Using a proteomic approach, 490 of the 2439 predicted proteins were confirmed. The annotation revealed the genetic basis for the hardiness of P. freudenreichii, as the bacterium possesses a complete enzymatic arsenal for de novo biosynthesis of aminoacids and vitamins (except panthotenate and biotin) as well as sequences involved in metabolism of various carbon sources, immunity against phages, duplicated chaperone genes and, interestingly, genes involved in the management of polyphosphate, glycogen and trehalose storage. The complete biosynthesis pathway for a bifidogenic compound is described, as well as a high number of surface proteins involved in interactions with the host and present in other probiotic bacteria. By comparative genomics, no pathogenicity factors found in P. acnes or in other pathogenic microbial species were identified in P. freudenreichii, which is consistent with the Generally Recognized As Safe and Qualified Presumption of Safety status of P. freudenreichii. Various pathways for formation of cheese flavor compounds were identified: the Wood-Werkman cycle for propionic acid formation, amino acid degradation pathways resulting in the formation of volatile branched chain fatty acids, and esterases involved in the formation of free fatty acids and esters. Conclusions/Significance: With the exception of its ability to degrade lactose, P. freudenreichii seems poorly adapted to dairy niches. This genome annotation opens up new prospects for the understanding of the P. freudenreichii probiotic activity