422 research outputs found
Geologic framework of the Massabesic Anticlinorium and the Merrimack Trough, southeastern New Hampshire
Geology of the coastal lowlands, Boston to Kennebunk, Maine: The 76th annual meeting New England Intercollegiate Geological Conference, Danvers, Massachusetts, October 12-14, 1984: Trip B-
Mid-Paleozoic calc-alkaline igneous rocks of the Nashoba Block and Merrimack Trough
Guidebook for field trips in southwestern Maine: New England Intercollegiate Geological Conference, 78th annual meeting, Bates College, Lewiston, Maine, October 17, 18, and 19, 1986: Trip A-3. Irregular pagination
Lattice Dynamics and the High Pressure Equation of State of Au
Elastic constants and zone-boundary phonon frequencies of gold are calculated
by total energy electronic structure methods to twofold compression. A
generalized force constant model is used to interpolate throughout the
Brillouin zone and evaluate moments of the phonon distribution. The moments are
used to calculate the volume dependence of the Gruneisen parameter in the fcc
solid. Using these results with ultrasonic and shock data, we formulate the
complete free energy for solid Au. This free energy is given as a set of closed
form expressions, which are valid to compressions of at least V/V_0 = 0.65 and
temperatures up to melting. Beyond this density, the Hugoniot enters the
solid-liquid mixed phase region. Effects of shock melting on the Hugoniot are
discussed within an approximate model. We compare with proposed standards for
the equation of state to pressures of ~200 GPa. Our result for the room
temperature isotherm is in very good agreement with an earlier standard of
Heinz and Jeanloz.Comment: 13 pages, 8 figures. Accepted by Phys. Rev.
Dying mRNA Tells a Story of Its Life
In this issue of Cell, Pelechano et al. report that sequencing of mRNA decay intermediates shows surprisingly tight coupling of a major decay pathway to the movement of the last translating ribosome, revealing stress- and starvation-dependent modulation of translation elongation
Single Spin Measurement using Single Electron Transistors to Probe Two Electron Systems
We present a method for measuring single spins embedded in a solid by probing
two electron systems with a single electron transistor (SET). Restrictions
imposed by the Pauli Principle on allowed two electron states mean that the
spin state of such systems has a profound impact on the orbital states
(positions) of the electrons, a parameter which SET's are extremely well suited
to measure. We focus on a particular system capable of being fabricated with
current technology: a Te double donor in Si adjacent to a Si/SiO2 interface and
lying directly beneath the SET island electrode, and we outline a measurement
strategy capable of resolving single electron and nuclear spins in this system.
We discuss the limitations of the measurement imposed by spin scattering
arising from fluctuations emanating from the SET and from lattice phonons. We
conclude that measurement of single spins, a necessary requirement for several
proposed quantum computer architectures, is feasible in Si using this strategy.Comment: 22 Pages, 8 Figures; revised version contains updated references and
small textual changes. Submitted to Phys. Rev.
Study of the production of and hadrons in collisions and first measurement of the branching fraction
The product of the () differential production
cross-section and the branching fraction of the decay () is
measured as a function of the beauty hadron transverse momentum, ,
and rapidity, . The kinematic region of the measurements is and . The measurements use a data sample
corresponding to an integrated luminosity of collected by the
LHCb detector in collisions at centre-of-mass energies in 2011 and in 2012. Based on previous LHCb
results of the fragmentation fraction ratio, , the
branching fraction of the decay is
measured to be \begin{equation*} \mathcal{B}(\Lambda_b^0\rightarrow J/\psi
pK^-)= (3.17\pm0.04\pm0.07\pm0.34^{+0.45}_{-0.28})\times10^{-4},
\end{equation*} where the first uncertainty is statistical, the second is
systematic, the third is due to the uncertainty on the branching fraction of
the decay , and the
fourth is due to the knowledge of . The sum of the
asymmetries in the production and decay between and
is also measured as a function of and .
The previously published branching fraction of , relative to that of , is updated.
The branching fractions of are determined.Comment: 29 pages, 19figures. All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-032.htm
Can ceftazidime-avibactam and aztreonam overcome β-lactam resistance conferred by metallo-β-lactamases in Enterobacteriaceae?
Based upon knowledge of the hydrolytic profile of major β-lactamases found in Gram-negative bacteria, we tested the efficacy of the combination of ceftazidime-avibactam (CAZ-AVI) with aztreonam (ATM) against carbapenem-resistant enteric bacteria possessing metallo-β-lactamases (MBLs). Disk diffusion and agarbased antimicrobial susceptibility testing were initially performed to determine the in vitro efficacy of a unique combination of CAZ-AVI and ATM against 21 representative Enterobacteriaceae isolates with a complex molecular background that included blaIMP, blaNDM, blaOXA-48, blaCTX-M, blaAmpC, and combinations thereof. Time-kill assays were conducted, and the in vivo efficacy of this combination was assessed in a murine neutropenic thigh infection model. By disk diffusion assay, all 21 isolates were resistant to CAZ-AVI alone, and 19/21 were resistant to ATM. The in vitro activity of CAZ-AVI in combination with ATM against diverse Enterobacteriaceae possessing MBLs was demonstrated in 17/21 isolates, where the zone of inhibition was ≥21 mm. All isolates demonstrated a reduction in CAZ-AVI agar dilution MICs with the addition of ATM. At 2 h, time-kill assays demonstrated a ≥4-log10-CFU decrease for all groups that had CAZ-AVI with ATM (8 μg/ml) added, compared to the group treated with CAZ-AVI alone. In the murine neutropenic thigh infection model, an almost 4-log10-CFU reduction was noted at 24 h for CAZ-AVI (32 mg/kg every 8 h [q8h]) plus ATM (32 mg/kg q8h) versus CAZ-AVI (32 mg/kg q8h) alone. The data presented herein require us to carefully consider this new therapeutic combination to treat infections caused by MBL-producing Enterobacteriaceae
High-time Resolution Astrophysics and Pulsars
The discovery of pulsars in 1968 heralded an era where the temporal
characteristics of detectors had to be reassessed. Up to this point detector
integration times would normally be measured in minutes rather seconds and
definitely not on sub-second time scales. At the start of the 21st century
pulsar observations are still pushing the limits of detector telescope
capabilities. Flux variations on times scales less than 1 nsec have been
observed during giant radio pulses. Pulsar studies over the next 10 to 20 years
will require instruments with time resolutions down to microseconds and below,
high-quantum quantum efficiency, reasonable energy resolution and sensitive to
circular and linear polarisation of stochastic signals. This chapter is review
of temporally resolved optical observations of pulsars. It concludes with
estimates of the observability of pulsars with both existing telescopes and
into the ELT era.Comment: Review; 21 pages, 5 figures, 86 references. Book chapter to appear
in: D.Phelan, O.Ryan & A.Shearer, eds.: High Time Resolution Astrophysics
(Astrophysics and Space Science Library, Springer, 2007). The original
publication will be available at http://www.springerlink.co
Impact of Chlamydia trachomatis in the reproductive setting: British Fertility Society Guidelines for practice
Chlamydia trachomatis infection of the genital tract is the most common sexually transmitted infection and has a world-wide distribution. The consequences of infection have an adverse effect on the reproductive health of women and are a common cause of infertility. Recent evidence also suggests an adverse effect on male reproduction. There is a need to standardise the approach in managing the impact of C. trachomatis infection on reproductive health. We have surveyed current UK practice towards screening and management of Chlamydia infections in the fertility setting. We found that at least 90% of clinicians surveyed offered screening. The literature on this topic was examined and revealed a paucity of solid evidence for estimating the risks of long-term reproductive sequelae following lower genital tract infection with C. trachomatis. The mechanism for the damage that occurs after Chlamydial infections is uncertain. However, instrumentation of the uterus in women with C. trachomatis infection is associated with a high risk of pelvic inflammatory disease, which can be prevented by appropriate antibiotic treatment and may prevent infected women from being at increased risk of the adverse sequelae, such as ectopic pregnancy and tubal factor infertility. Recommendations for practice have been proposed and the need for further studies is identified
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