1,205 research outputs found
A personal computer-based, multitasking data acquisition system
A multitasking, data acquisition system was written to simultaneously collect meteorological radar and telemetry data from two sources. This system is based on the personal computer architecture. Data is collected via two asynchronous serial ports and is deposited to disk. The system is written in both the C programming language and assembler. It consists of three parts: a multitasking kernel for data collection, a shell with pull down windows as user interface, and a graphics processor for editing data and creating coded messages. An explanation of both system principles and program structure is presented
MAPPER: A personal computer map projection tool
MAPPER is a set of software tools designed to let users create and manipulate map projections on a personal computer (PC). The capability exists to generate five popular map projections. These include azimuthal, cylindrical, mercator, lambert, and sinusoidal projections. Data for projections are contained in five coordinate databases at various resolutions. MAPPER is managed by a system of pull-down windows. This interface allows the user to intuitively create, view and export maps to other platforms
Calibration of a photomultiplier array spectrometer
A systematic approach to the calibration of a photomultiplier array spectrometer is presented. Through this approach, incident light radiance derivation is made by recognizing and tracing gain characteristics for each photomultiplier tube
Climate change at the ecosystem scale: a 50-year record in New Hampshire
Observing the full range of climate change impacts at the local scale is difficult. Predicted rates of change are often small relative to interannual variability, and few locations have sufficiently comprehensive long-term records of environmental variables to enable researchers to observe the fine-scale patterns that may be important to understanding the influence of climate change on biological systems at the taxon, community, and ecosystem levels. We examined a 50-year meteorological and hydrological record from the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, an intensively monitored Long-Term Ecological Research site. Of the examined climate metrics, trends in temperature were the most significant (ranging from 0.7 to 1.3 °C increase over 40–50 year records at 4 temperature stations), while analysis of precipitation and hydrologic data yielded mixed results. Regional records show generally similar trends over the same time period, though longer-term (70–102 year) trends are less dramatic. Taken together, the results from HBEF and the regional records indicate that the climate has warmed detectably over 50 years, with important consequences for hydrological processes. Understanding effects on ecosystems will require a diversity of metrics and concurrent ecological observations at a range of sites, as well as a recognition that ecosystems have existed in a directionally changing climate for decades, and are not necessarily in equilibrium with the current climate
How Lyman Alpha Emission Depends On Galaxy Stellar Mass
In this work, we show how the stellar mass (M) of galaxies affects the
3<z<4.6 Ly-alpha equivalent width (EW) distribution. To this end, we design a
sample of 629 galaxies in the M range 7.6 < logM/Msun < 10.6 from the
3D-HST/CANDELS survey. We perform spectroscopic observations of this sample
using the Michigan/Magellan Fiber System, allowing us to measure Ly-alpha
fluxes and use 3D-HST/CANDELS ancillary data. In order to study the Ly-alpha EW
distribution dependence on M, we split the whole sample in three stellar mass
bins. We find that, in all bins, the distribution is best represented by an
exponential profile of the form dN(M)/dEW= A(M)exp(-EW/W0(M))/W0(M). Through a
Bayesian analysis, we confirm that lower M galaxies have higher Ly-alpha EWs.
We also find that the fraction A of galaxies featuring emission and the
e-folding scale W0 of the distribution anti- correlate with M, recovering
expressions of the forms A(M)= -0.26(.13) logM/Msun+3.01(1.2) and W0(M)=
-15.6(3.5) logM/Msun +166(34). These results are crucial for proper
interpretation of Ly-alpha emission trends reported in the literature that may
be affected by strong M selection biases.Comment: 4 pages, 5 figure
B_s->D_s/B->D Semileptonic Form-Factor Ratios and Their Application to BR(B^0_s->\mu^+\mu^-)
We calculate form-factor ratios between the semileptonic decays
\bar{B}->D^+\ell^-\bar{\nu} and \bar{B}_s->D_s^+\ell^-\bar{\nu} with lattice
QCD. These ratios are a key theoretical input in a new strategy to determine
the fragmentation fractions of the neutral B decays, which are needed for
measurements of BR(B^0_s-> \mu^+\mu^-). We use the MILC ensembles of gauge
configurations with 2+1 flavors of sea quarks at two lattice spacings of
approximately 0.12 fm and 0.09 fm. We use the model-independent
z-parametrization to extrapolate our simulation results at small recoil toward
maximum recoil. Our results for the form-factor ratios are
and
. In
contrast to a QCD sum-rule calculation, no significant departure from U-spin
(ds) symmetry is observed.Comment: 30 pages, 11 figures. Fig. 1 updated. Table II added. Conforms with
version published in Physical Review D, except typos fixed, as in the PRD
Erratum, in Table V (previously Table IV in arXiv v1). Results unchange
Form factors for semi-leptonic B decays
We report on form factors for the B->K l^+ l^- semi-leptonic decay process.
We use several lattice spacings from a=0.12 fm down to 0.06 fm and a variety of
dynamical quark masses with 2+1 flavors of asqtad quarks provided by the MILC
Collaboration. These ensembles allow good control of the chiral and continuum
extrapolations. The b-quark is treated as a clover quark with the Fermilab
interpretation. We update our results for f_\parallel and f_\perp, or,
equivalently, f_+ and f_0. In addition, we present new results for the tensor
form factor f_T. Model independent results are obtained based upon the
z-expansion.Comment: 7 pages, 4 figures, presented at The XXXth International Symposium on
Lattice Field Theory - Lattice 2012, June 24-29, 2012 Cairns, Australia, to
appear as PoS(Lattice 2012)12
D semileptonic form factors and |V_cs(d)| from 2+1 flavor lattice QCD
The measured partial widths of the semileptonic decays D to K l nu and D to
pi l nu can be combined with the form factors calculated on the lattice to
extract the CKM matrix elements |V_cs| and |V_cd|. The lattice calculations can
be checked by comparing the form factor shapes from the lattice and experiment.
We have generated a sizable data set by using heavy clover quarks with the
Fermilab interpretation for charm and asqtad staggered light quarks on 2+1
flavor MILC ensembles with lattice spacings of approximately 0.12, 0.09, 0.06,
and 0.045 fm. Preliminary fits to staggered chiral perturbation theory suggest
that we can reduce the uncertainties in the form factors at zero invariant mass
to below 5%.Comment: 7 pages, 4 figures, proceedings of the XXIX International Symposium
on Lattice Field Theory - Lattice 2011, July 10-16, 2011, Squaw Valley, Lake
Tahoe, Californi
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