Optical pumping via incoherent Raman transitions

A new optical pumping scheme is presented that uses incoherent Raman transitions to prepare a trapped Cesium atom in a specific Zeeman state within the 6S_{1/2}, F=3 hyperfine manifold. An important advantage of this scheme over existing optical pumping schemes is that the atom can be prepared in any of the F=3 Zeeman states. We demonstrate the scheme in the context of cavity quantum electrodynamics, but the technique is equally applicable to a wide variety of atomic systems with hyperfine ground-state structure.Comment: 8 pages, 4 figure

Validation of a New PCR-Based Screening Method for Prevention of Serratia marcescens Outbreaks in the Neonatal Intensive Care Unit

Background: Serratia marcescens may cause severe nosocomial infections, mostly in very low birth weight infants. Since S. marcescens exhibits by far the highest adjusted incidence rate for horizontal transmission, it can cause complex outbreak situations in neonatal intensive care units. Objective: The aim of this study was to establish a fast and highly sensitive colonization screening for prompt cohorting and barrier nursing strategies. Methods: A probe-based duplex PCR assay targeting the 16S rRNA gene of S. marcescens was developed and validated by using 36 reference strains, 14 S. marcescens outbreak- and nonoutbreak isolates, defined by epidemiological linkage and molecular typing, and applied in 1,347 clinical specimens from 505 patients. Results and Conclusions: The novel PCR assay proved to be highly specific and had an in vitro sensitivity of 100 gene copies per reaction (∼15 bacteria). It showed a similar (in laryngeal/tracheal specimens) or even higher (in rectal/stoma swabs) in vivo sensitivity in comparison to routine microbial culture and was much quicker (<24 h vs. 2 days). By combining different oligonucleotide primers, there was robust detection of genetic variants of S. marcescens strains. PCR inhibition was low (1.6%) and observed with rectal swabs only. Cohort analysis illustrated applicability of the PCR assay as a quick tool to prevent outbreak scenarios by allowing rapid decisions on cohorting and barrier nursing. In summary, this novel molecular screening for colonization by S. marcescens is specific, highly sensitive, and substantially accelerates detection

Li/MgO with spin sensors as catalyst for the oxidative coupling of methane

Co-doping of Li/MgO, a well-known catalyst for the oxidative coupling of methane, was investigated. It is demonstrated that Gd3+ and Fe3+ can be used as spin sensors in these solids to investigate the structure via EPR spectroscopy. These aliovalent ions occupy Mg2+ sites in the lattice; the expected coupling with charge-compensating neighboring Li+ was detected. A strong increase of the activity was observed. However, all samples suffered from deactivation. The solubility of Gd3+ in MgO turned out to be inhibited. No such restriction was observed for Fe3+

Transition-Metal-Doping of CaO as Catalyst for the OCM Reaction, a Reality Check

In this study, first-row transition metal-doped calcium oxide materials (Mn, Ni, Cr, Co., and Zn) were synthesized, characterized, and tested for the OCM reaction. Doped carbonate precursors were prepared by a co-precipitation method. The synthesis parameters were optimized to yield materials with a pure calcite phase, which was verified by XRD. EPR measurements on the doped CaO materials indicate a successful substitution of Ca2+ with transition metal ions in the CaO lattice. The materials were tested for their performance in the OCM reaction, where a beneficial effect towards selectivity and activity effect could be observed for Mn, Ni, and Zn-doped samples, where the selectivity of Co- and Cr-doped CaO was strongly reduced. The optimum doping concentration could be identified in the range of 0.04-0.10 atom%, showing the strongest decrease in the apparent activation energy, as well as the maximum increase in selectivity

The nature of iron-oxygen vacancy defect centers in PbTiO3

The iron(III) center in ferroelectric PbTiO3 together with an oxygen vacancy forms a charged defect associate, oriented along the crystallographic c-axis. Its microscopic structure has been analyzed in detail comparing results from a semi-empirical Newman superposition model analysis based on finestructure data and from calculations using density functional theory. Both methods give evidence for a substitution of Fe3+ for Ti4+ as an acceptor center. The position of the iron ion in the ferroelectric phase is found to be similar to the B-site in the paraelectric phase. Partial charge compensation is locally provided by a directly coordinated oxygen vacancy. Using high-resolution synchrotron powder diffraction, it was verified that lead titanate remains tetragonal down to 12 K, exhibiting a c/a-ratio of 1.0721.Comment: 11 pages, 5 figures, accepted in Phys. Rev.

The radical cation of bacteriochlorophyll b. A liquid-phase endor and triple resonance study

The previous termradical cationnext term of bacterioehlorophyll b (BChl b) is investigated by ENDOR and TRIPLE resonance in liquid solution. The experimental hyperfine coupling constants, ten proton and three nitrogen couplings, are compared with the predictions from advanced molecular-orbital calculations (RHF INDO/SP). The detailed picture obtained of the spin density distribution is a prerequisite for the investigation of the primary electron donor previous termradical cationnext term in BChl b containing photosynthetic bacteria

Early-life Farm Exposure and Ovarian Reserve in a US Cohort of Women

Background: In a previous exploratory study, we reported lower concentrations of the ovarian reserve biomarker anti-Müllerian hormone (AMH) in adulthood with prenatal farm exposure. We now examine this association as well as childhood farm exposure using enrollment data from the Sister Study, a large US cohort of women. Methods: We collected prenatal and childhood farm exposure data by questionnaire and telephone interview. However, serum AMH data were available only for a nested subset: premenopausal women ages 35-54 subsequently diagnosed with breast cancer (n = 418 cases) and their matched controls (n = 866). To avoid potential bias from restricting analyses to only premenopausal controls, we leveraged the available cohort data. We used data from both premenopausal cases and controls as well as postmenopausal women ages 35-54 (n = 3,526) (all presumed to have undetectable AMH concentrations) and applied weights to produce a sample representative of the cohort ages 35-54 (n = 17,799). The high proportion of undetectable AMH concentrations (41%) was addressed using reverse-scale Cox regression. An adjusted hazard ratio (HR) <1.0 indicates that exposed individuals had lower AMH concentrations than unexposed individuals. Results: Prenatal exposure to maternal residence or work on a farm was associated with lower AMH concentrations (HR 0.66; 95% confidence intervals [CI] = 0.48 to 0.90). Associations between childhood farm residence exposures and AMH were null or weak, except childhood contact with pesticide-treated livestock or buildings (HR 0.69; 95% CI = 0.40 to 1.2). Conclusions: Replication of the prenatal farm exposure and lower adult AMH association raises concern that aspects of prenatal farm exposure may result in reduced adult ovarian reserve

Differential Effects of Aging on Fore– and Hindpaw Maps of Rat Somatosensory Cortex

Getting older is associated with a decline of cognitive and sensorimotor abilities, but it remains elusive whether age-related changes are due to accumulating degenerational processes, rendering them largely irreversible, or whether they reflect plastic, adaptational and presumably compensatory changes. Using aged rats as a model we studied how aging affects neural processing in somatosensory cortex. By multi-unit recordings in the fore- and hindpaw cortical maps we compared the effects of aging on receptive field size and response latencies. While in aged animals response latencies of neurons of both cortical representations were lengthened by approximately the same amount, only RFs of hindpaw neurons showed severe expansion with only little changes of forepaw RFs. To obtain insight into parallel changes of walking behavior, we recorded footprints in young and old animals which revealed a general age-related impairment of walking. In addition we found evidence for a limb-specific deterioration of the hindlimbs that was not observed in the forelimbs. Our results show that age-related changes of somatosensory cortical neurons display a complex pattern of regional specificity and parameter-dependence indicating that aging acts rather selectively on cortical processing of sensory information. The fact that RFs of the fore- and hindpaws do not co-vary in aged animals argues against degenerational processes on a global scale. We therefore conclude that age-related alterations are composed of plastic-adaptive alterations in response to modified use and degenerational changes developing with age. As a consequence, age-related changes need not be irreversible but can be subject to amelioration through training and stimulation