7,613 research outputs found
Noncontact atomic force microscopy simulator with phase-locked-loop controlled frequency detection and excitation
A simulation of an atomic force microscope operating in the constant
amplitude dynamic mode is described. The implementation mimics the electronics
of a real setup including a digital phase-locked loop (PLL). The PLL is not
only used as a very sensitive frequency detector, but also to generate the
time-dependent phase shifted signal driving the cantilever. The optimum
adjustments of individual functional blocks and their joint performance in
typical experiments are determined in detail. Prior to testing the complete
setup, the performances of the numerical PLL and of the amplitude controller
were ascertained to be satisfactory compared to those of the real components.
Attention is also focused on the issue of apparent dissipation, that is, of
spurious variations in the driving amplitude caused by the nonlinear
interaction occurring between the tip and the surface and by the finite
response times of the various controllers. To do so, an estimate of the minimum
dissipated energy that is detectable by the instrument upon operating
conditions is given. This allows us to discuss the relevance of apparent
dissipation that can be conditionally generated with the simulator in
comparison to values reported experimentally. The analysis emphasizes that
apparent dissipation can contribute to the measured dissipation up to 15% of
the intrinsic dissipated energy of the cantilever interacting with the surface,
but can be made negligible when properly adjusting the controllers, the PLL
gains and the scan speed. It is inferred that the experimental values of
dissipation usually reported in the literature cannot only originate in
apparent dissipation, which favors the hypothesis of "physical" channels of
dissipation
Pharmacogenetic Analysis of Voriconazole Treatment in Children
Voriconazole is among the first-line antifungal drugs to treat invasive fungal infections in children and known for its pronounced inter- and intraindividual pharmacokinetic variability. Polymorphisms in genes involved in the metabolism and transport of voriconazole are thought to influence serum concentrations and eventually the therapeutic outcome. To investigate the impact of these genetic variants and other covariates on voriconazole trough concentrations, we performed a retrospective data analysis, where we used medication data from 36 children suffering from invasive fungal infections treated with voriconazole. Data were extracted from clinical information systems with the new infrastructure SwissPKcdw, and linear mixed effects modelling was performed using R. Samples from 23 children were available for DNA extraction, from which 12 selected polymorphism were genotyped by real-time PCR. 192 (49.1%) of 391 trough serum concentrations measured were outside the recommended range. Voriconazole trough concentrations were influenced by polymorphisms within the metabolizing enzymes CYP2C19 and CYP3A4, and within the drug transporters ABCC2 and ABCG2, as well as by the co-medications ciprofloxacin, levetiracetam, and propranolol. In order to prescribe an optimal drug dosage, pre-emptive pharmacogenetic testing and careful consideration of co-medications in addition to therapeutic drug monitoring might improve voriconazole treatment outcome of children with invasive fungal infections.
Keywords: ABCC2; ABCG2; CYP2C19; CYP3A4; children; non-linear mixed effects modelling; pediatric pharmacology; pharmacogenetics; therapeutic drug monitoring; voriconazol
Recycled water causes no salinity or toxicity issues in Napa vineyards
In response to Napa Sanitation District's interest in expanding its delivery of recycled
water to vineyards for irrigation, we conducted a feasibility study to assess the
suitability of the water for this use. We adopted two approaches: comparing the water
quality characteristics of the recycled water with those of other local sources of
irrigation water, and evaluating soil samples from a vineyard that was irrigated for
8 years with the recycled water. Results indicate that the quality of the recycled
water is suitable for irrigation, and also that long-term accumulation of salts and
toxic ions have not occurred in the vineyards studied and are unlikely to occur. Nutrients
in the recycled water may be beneficial to vineyards, though the levels of nitrogen
may need to be reduced by planting cover crops in some vineyards
Radiofrequency multipole traps: Tools for spectroscopy and dynamics of cold molecular ions
Multipole radiofrequency ion traps are a highly versatile tool to study
molecular ions and their interactions in a well-controllable environment. In
particular the cryogenic 22-pole ion trap configuration is used to study
ion-molecule reactions and complex molecular spectroscopy at temperatures
between few Kelvin and room temperatures. This article presents a tutorial on
radiofrequency ion trapping in multipole electrode configurations. Stable
trapping conditions and buffer gas cooling, as well as important heating
mechanisms, are discussed. In addition, selected experimental studies on cation
and anion-molecule reactions and on spectroscopy of trapped ions are reviewed.
Starting from these studies an outlook on the future of multipole ion trap
research is given
Radioactive 26Al and massive stars in the Galaxy
Gamma-rays from radioactive 26Al (half life ~7.2 10^5 yr) provide a
'snapshot' view of ongoing nucleosynthesis in the Galaxy. The Galaxy is
relatively transparent to such gamma-rays, and emission has been found
concentrated along the plane of the Galaxy. This led to the conclusion1 that
massive stars throughout the Galaxy dominate the production of 26Al. On the
other hand, meteoritic data show locally-produced 26Al, perhaps from spallation
reactions in the protosolar disk. Furthermore, prominent gamma-ray emission
from the Cygnus region suggests that a substantial fraction of Galactic 26Al
could originate in localized star-forming regions. Here we report high spectral
resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that
the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide
origin. We determine a present-day equilibrium mass of 2.8 (+/-0.8) M_sol of
26Al. We use this to estimate that the frequency of core collapse (i.e. type
Ib/c and type II) supernovae to be 1.9(+/- 1.1) events per century.Comment: accepted for publication in Nature, 24 pages including Online
Supplements, 11 figures, 1 tabl
Conformally Flat Smoothed Particle Hydrodynamics: Application to Neutron Star Mergers
We present a new 3D SPH code which solves the general relativistic field +
hydrodynamics equations in the conformally flat approximation. Several test
cases are considered to test different aspects of the code. We finally apply
then the code to the coalescence of a neutron star binary system. The neutron
stars are modeled by a polytropic equation of state (EoS) with adiabatic
indices , and . We calculate the
gravitational wave signals, luminosities and frequency spectra by employing the
quadrupole approximation for emission and back reaction in the slow motion
limit. In addition, we consider the amount of ejected mass.Comment: 23 pages, 12 figures. Accepted for publication in Phys. Rev. D. v3:
Final Versio
High Diversity of the Saliva Microbiome in Batwa Pygmies
We describe the saliva microbiome diversity in Batwa Pygmies, a former hunter-gatherer group from Uganda, using next-generation sequencing of partial 16S rRNA sequences. Microbial community diversity in the Batwa is significantly higher than in agricultural groups from Sierra Leone and the Democratic Republic of Congo. We found 40 microbial genera in the Batwa, which have previously not been described in the human oral cavity. The distinctive composition of the salvia microbiome of the Batwa may have been influenced by their recent different lifestyle and diet
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
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