Recoil effect of photoelectrons in the Fermi edge of simple metals

High energy resolution photoelectron spectroscopy of conduction electrons in the vicinity of the Fermi edge in Al and Au at excitation energies of 880 and 7940 eV was carried out using synchrotron radiation. For the excitation energy of 7940 eV, the observed Fermi energy of Al shows a remarkable shift to higher binding energy as compared with that of Au, with accompanying broadening. This is due to the recoil effect of the emitted photoelectrons. The observed spectra are well reproduced by a simple model of Bloch electrons based on the isotropic Debye model.

Programmatic implementation of rapid DST for Mycobacterium tuberculosis in Peru

BACKGROUND

Performance characteristics of novel rapid drug susceptibility tests (DST) for Mycobacterium tuberculosis may change when moving from research to implementation in actual public health practice. We describe the performance characteristics of a direct, rapid DST when implemented in Lima, Peru.

METHODS

A district laboratory validated conventional proportions and nitrate reductase methods. We collected data on samples submitted for DST from January 2005 to June 2007 and calculated frequency of testing and results, and median time to test results.

RESULTS

A total of 4102 DSTs were performed by conventional DST and 895 by nitrate reductase. Results were obtained from 72.8% of samples by conventional DST and from 70.2% of those processed by Griess; respectively 26.4% and 31.5% were multidrug-resistant tuberculosis. The median time from sample collection to test result was 31 days for Griess vs. 99 days for conventional DST.

CONCLUSIONS

Preliminary experience with the Griess method demonstrates favorable performance under program conditions.

Revisiting the valence-band and core-level photoemission spectra of NiO

We have reexamined the valence-band (VB) and core-level electronic structure of NiO by means of hard and soft x-ray photoemission spectroscopies. The spectral weight of the lowest energy state was found to be enhanced in the bulk sensitive Ni 2p core-level spectrum. A configuration-interaction model including a bound state screening has shown agreement with the core-level spectrum and off- and on-resonance VB spectra. These results identify the lowest energy states in the core-level and VB spectra as the Zhang-Rice (ZR) doublet bound states, consistent with the spin-fermion model and recent ab initio calculations within dynamical mean-field theory. The results indicate that the ZR character first ionization (the lowest hole-addition) states are responsible for transport properties in NiO and doped NiO.

Temperature-dependent localized excitations of doped carriers in superconducting diamond

Laser-excited photoemission spectroscopy is used to show that the doped carriers in metallic or superconducting diamond couple strongly to the lattice via high-energy (approximately 150 meV) optical phonons, with direct observations of localized Franck-Condon multiphonon sidebands appearing as Fermi-edge replicas. It exhibits a temperature-dependent spectral weight transfer from higher to lower energy sidebands and zero-phonon Fermi-edge states. The quantified coupling strength shows a systematic increase on lowering temperature, implicating its relation to the normal state transport and superconductivity.

A versatile system for ultrahigh resolution, low temperature, and polarization dependent laser-angle-resolved photoemission spectroscopy

We have developed a low temperature ultrahigh resolution system for polarization dependent angle-resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet (vuv) laser (hnu=6.994 eV) as a photon source. With the aim of addressing low energy physics, we show the system performance with angle-integrated PES at the highest energy resolution of 360 mueV and the lowest temperature of 2.9 K. We describe the importance of a multiple-thermal-shield design for achieving the low temperature, which allows a clear measurement of the superconducting gap of tantalum metal with a T(c)=4.5 K. The unique specifications and quality of the laser source (narrow linewidth of 260 mueV, high photon flux), combined with a half-wave plate, facilitates ultrahigh energy and momentum resolution polarization dependent ARPES. We demonstrate the use of s- and p-polarized laser-ARPESs in studying the superconducting gap on bilayer-split bands of a high T(c) cuprate. The unique features of the quasi-continuous-wave vuv laser and low temperature enables ultrahigh-energy and -momentum resolution studies of the spectral function of a solid with large escape depth. We hope the present work helps in defining polarization dependent laser excited angle-resolved photoemission spectroscopy as a frontier tool for the study of electronic structure and properties of materials at the sub-meV energy scale.

Bulk electronic structure of the antiferromagnetic superconducting phase in ErNi2B2C

We have performed temperature- (T-)dependent laser-photoemission spectroscopy of the antiferromagnetic (AF) superconductor ErNi2B2C to study the electronic-structure evolution reflecting the interplay between antiferromagnetism and superconductivity. The spectra at the superconducting (SC) phase show a very broad spectral shape. A T-dependent SC gap shows a sudden deviation from the BCS prediction just below TN. This observation can be explained well by the theoretical model and thus represents the characteristic bulk electronic structure of the AF SC phase for the first time.

179 MODULATION OF RHOPHILIN-2 MAY REGULATE THE PROGRESSION OF CELL DIVISION IN FERTILIZED MOUSE EGGS

It has been reported that activity of Rho, one of the GTPases, is essential for division of nuclei and cytoplasm of fertilized mouse eggs. Since it has been reported that alteration of activities of GTPases modifies their ability to attach to each of their effector proteins in somatic cells, effector proteins seem to be able to control not only progression but also repression of cell division by changing their cellular localizations through activities of GTPases. For this reason, Rhophilin-2, one of the effector proteins of Rho, seems to be involved in the decision of progression of division of fertilized mouse eggs. To examine whether this involvement works in fertilized mouse eggs, cellular localization of Rho and Rhophilin-2 in fertilized mouse eggs that were treated with Rho inhibitor were analyzed. Moreover, cellular localization of GABA A receptor association protein (GABARAP), which was identified in our previous study (Matsuoka et al. 2006 Reprod. Fertil. Dev. 18, 176–177) as a protein that interacts with Rhophilin-2, was also analyzed. Fertilized mouse eggs were obtained from in vitro fertilization technique. One group of fertilized eggs was obtained at 24 h after insemination as experimental control. To obtain the mouse eggs in which Rho activities were inhibited, Clostridium botulinum C3 exoenzyme (C3-CB), an inhibitor of Rho activity, was injected into the other group of fertilized mouse eggs at 12 h after insemination, and were collected after 12 h of subsequent culture. Cellular localization of Rho (n = 100), Rhophilin-2 (n = 10). and GABARAP (n = 10) in the collected oocytes was analyzed by using immunofluorescence. Our results showed that Rho and Rhophilin-2 were co-localized at the midbody microtubule, which is an important device for cytoplasmic division in control eggs. However, the inhibition of Rho activity did not modify the co-localization of Rho and Rhophilin-2. On the other hand, localization of GABARAP was modified by the inhibition of Rho activity, and GABARAP was detected around the nuclei of fertilized eggs in which Rho activity was inhibited. In the next experiment, we examined whether interaction of Rhophilin-2 and GABARAP was modified by the inhibition of Rho activity by using a co-immunoprecipitation assay (co-IP) (n = 100). The interaction of Rhophilin-2 and GABARAP was found to disappear after inhibition of Rho activity. These results suggest that activity of Rho seems to regulate cytoplasmic division through Rhophilin-2 modification. Moreover, Rho seem to modulate the nuclear division of fertilized mouse eggs by regulating the interaction between Rhophilin-2 and GABARAP. This study was supported by a Grant-in-Aid for the 21st Century COE Program of the Japan Mext and by a grant for the Wakayama Prefecture Collaboration of Regional Entities for the Advancement of Technology Excellence of the JST.

The analysis of milk components and pathogenic bacteria isolated from bovine raw milk in Korea

Bovine mastitis can be diagnosed by abnormalities in milk components and somatic cell count (SCC), as well as by clinical signs. We examined raw milk in Korea by analyzing SCC, milk urea nitrogen (MUN), and the percentages of milk components (milk fat, protein, and lactose). The associations between SCC or MUN and other milk components were investigated, as well as the relationships between the bacterial species isolated from milk. Somatic cell counts, MUN, and the percentages of milk fat, protein, and lactose were analyzed in 30,019 raw milk samples collected from 2003 to 2006. The regression coefficients of natural logarithmic-transformed SCC (SCCt) on milk fat (-0.0149), lactose (-0.8910), and MUN (-0.0096), and those of MUN on milk fat (-0.3125), protein (-0.8012), and SCCt (-0.0671) were negative, whereas the regression coefficient of SCCt on protein was positive (0.3023). When the data were categorized by the presence or absence of bacterial infection in raw milk, SCCt was negatively associated with milk fat (-0.0172), protein (-0.2693), and lactose (-0.4108). The SCCt values were significantly affected by bacterial species. In particular, 104 milk samples infected with Staphylococcus aureus had the highest SCCt (1.67) compared with milk containing other mastitis-causing bacteria: coagulase-negative staphylococci (n = 755, 1.50), coagulase-positive staphylococci (except Staphylococcus aureus; n = 77, 1.59), Streptococcus spp. (Streptococcus dysgalactiae, n = 37; Streptococcus uberis, n = 12, 0.83), Enterococcus spp. (n = 46, 1.04), Escherichia coli (n = 705, 1.56), Pseudomonas spp. (n = 456, 1.59), and yeast (n = 189, 1.52). These results show that high SCC and MUN negatively affect milk components and that a statistical approach associating SCC, MUN, and milk components by bacterial infection can explain the patterns among them. Bacterial species present in raw milk are an important influence on SCC in Korea.