2,979 research outputs found
Austin's high-tech industry: played out or just beginning?
Recessions ; High technology industries
Pulmonary artery catheters in acute heart failure: end of an era?
Whereas the pulmonary artery catheter (PAC) is still widely used in guiding assessment and treatment of heart failure, controversy surrounding its safety and efficacy has prompted development of newer, less invasive techniques. For these purposes, the transpulmonary thermodilution technique allows assessment of preload, cardiac output, filling volumes, and metrics of contractility without the need to pass a catheter through the right heart. In a previous issue of Critical Care, Ritter and colleagues compare metrics of transpulmonary thermodilution with the PAC in patients with acute heart failure and severe sepsis. The results add to a growing body of evidence that the PAC adds little to information attainable by less invasive methods in many conditions, including acute heart failure. Whether newer devices improve outcome needs to be tested in well-controlled prospective trials
SUPPLY AND DEMAND RISKS IN LABORATORY FORWARD AND SPOT MARKETS: IMPLICATIONS FOR AGRICULTURE
Laboratory experimental methods are used to investigate the impacts of supply and/or demand risks on prices, quantities traded, and earnings within forward and spot market institutions. Random demand and/or supply shifts can be as much as 25 percent of the expected equilibrium outcome. Nevertheless, results suggest that the spot or forward trading institution itself has a greater influence on market outcomes than the presence of risk within the trading institutions. Sellers tend to have relatively higher earnings in a spot market than buyers, regardless of the risk. Total surplus, however, generally is greater in a forward market.laboratory markets, forward market, spot market, supply and/or demand risks, Demand and Price Analysis, Marketing,
SUPPLY AND DEMAND RISKS IN FORWARD AND SPOT MARKETS: IMPLICATIONS FOR AGRICULTURE
Laboratory methods are used to investigate the impacts of supply and/or demand risks on prices, quantities traded, and earnings within forward and spot market institutions. Results suggest that the spot or forward trading institution itself has a greater influence on market outcomes than supply/demand risks within the institution.Marketing,
Ultrabroadband Nonlinear Optics in Nanophotonic Periodically Poled Lithium Niobate Waveguides
Quasi-phasematched interactions in waveguides with quadratic nonlinearities enable highly efficient nonlinear frequency conversion. In this article, we demonstrate the first generation of devices that combine the dispersion-engineering available in nanophotonic waveguides with quasi-phasematched nonlinear interactions available in periodically poled lithium niobate (PPLN). This combination enables quasi-static interactions of femtosecond pulses, reducing the pulse energy requirements by several orders of magnitude, from picojoules to femtojoules. We experimentally demonstrate two effects associated with second harmonic generation. First, we observe efficient quasi-phasematched second harmonic generation with <100 fJ of pulse energy. Second, in the limit of strong phase-mismatch, we observe spectral broadening of both harmonics with as little as 2-pJ of pulse energy. These results lay a foundation for a new class of nonlinear devices, in which co-engineering of dispersion with quasi-phasematching enables efficient nonlinear optics at the femtojoule level
High-sensitivity dual-comb and cross-comb spectroscopy across the infrared using a widely-tunable and free-running optical parametric oscillator
Coherent dual-comb spectroscopy (DCS) is a form of Fourier transform
spectroscopy that enables high-resolution measurements at high speeds without
the trade-off between resolution and update rate inherent to mechanical delay
scanning. However, high complexity of the optical system and limited
sensitivity of the measurements remain major challenges for deploying broadband
DCS in the short-wave infrared (SWIR, 1.4-3 um) and mid-infrared (mid-IR, >3
um) regions where many molecules have strong absorption bands. We address these
challenges via a wavelength-tunable dual-comb optical parametric oscillator
(OPO) combined with a new detection method. Both OPO pump beams are generated
in a single spatially-multiplexed laser cavity, while both signal and idler
beams are generated in a single spatially-multiplexed OPO cavity. The
near-common-path of the beams in each cavity ensures that even in free-running
operation the noise sources of the two combs are highly correlated,
facilitating comb-line-resolved and aliasing-free measurements with 250-MHz
spectral resolution. At an instantaneous bandwidth below 1 THz, high power per
comb line of up to 70 uW (signal) and 150 uW (idler) is achieved. The
accessible spectrum spans 1290 nm to 1670 nm (signal) and 2700 nm to 5160 nm
(idler). In a SWIR DCS measurement, we achieve a signal-to-noise ratio (SNR) of
33 dB Hz^1/2. For mid-IR measurements, we introduce a novel cross-comb
spectroscopy implementation to overcome limitations posed by traditional mid-IR
detection, obtaining a record-high SNR of 41 dB Hz^1/2. Our results are a
promising route towards dual-comb spectroscopy with high sensitivity and high
resolution over a wide spectral range
Evolution of the Near-Infrared Tully-Fisher Relation: Constraints on the Relationship Between the Stellar and Total Masses of Disk Galaxies since z=1
Using a combination of Keck spectroscopy and near-infrared imaging, we
investigate the K-band and stellar mass Tully-Fisher relation for 101 disk
galaxies at 0.2 < z < 1.2, with the goal of placing the first observational
constraints on the assembly history of halo and stellar mass. Our main result
is a lack of evolution in either the K-band or stellar mass Tully-Fisher
relation from z = 0 - 1.2. Furthermore, although our sample is not
statistically complete, we consider it suitable for an initial investigation of
how the fraction of total mass that has condensed into stars is distributed
with both redshift and total halo mass. We calculate stellar masses from
optical and near-infrared photometry and total masses from maximum rotational
velocities and disk scale lengths, utilizing a range of model relationships
derived analytically and from simulations. We find that the stellar/total mass
distribution and stellar-mass Tully-Fisher relation for z > 0.7 disks is
similar to that at lower redshift, suggesting that baryonic mass is accreted by
disks along with dark matter at z < 1, and that disk galaxy formation at z < 1
is hierarchical in nature. We briefly discuss the evolutionary trends expected
in conventional structure formation models and the implications of extending
such a study to much larger samples.Comment: ApJ, in press, 9 page
Markarian 421's Unusual Satellite Galaxy
We present Hubble Space Telescope (HST) imagery and photometry of the active
galaxy Markarian 421 and its companion galaxy 14 arcsec to the ENE. The HST
images indicate that the companion is a morphological spiral rather than
elliptical as previous ground--based imaging has concluded. The companion has a
bright, compact nucleus, appearing unresolved in the HST images. This is
suggestive of Seyfert activity, or possibly a highly luminous compact star
cluster. We also report the results of high dynamic range long-slit
spectroscopy with the slit placed to extend across both galaxies and nuclei. We
detect no emission lines in the companion nucleus, though there is evidence for
recent star formation. Velocities derived from a number of absorption lines
visible in both galaxies indicate that the two systems are probably tidally
bound and thus in close physical proximity. Using the measured relative
velocities, we derive a lower limit on the MKN 421 mass within the companion
orbit (R \sim 10 kpc) of 5.9 \times 10^{11} solar masses, and a mass-to-light
ratio of >= 17. Our spectroscopy also shows for the first time the presence of
H\alpha and [NII] emission lines from the nucleus of MKN 421, providing another
example of the appearance of new emission features in the previously
featureless spectrum of a classical BL Lac object. We see both broad and narrow
line emission, with a velocity dispersion of several thousand km s^{-1} evident
in the broad lines.Comment: LaTeX (aaspp4 style), 28 pages, 8 figures, to appear in AJ. Revised
text from ref. comments; new & modified figures; new photometry included;
minor corrections of typos. Color version of Fig. 1 to appear in Feb. 2000
Sky & Telescop
Selective Effects of D- and L-Govadine in Preclinical Tests of Positive, Negative, and Cognitive Symptoms of Schizophrenia
There is a critical need to develop novel pharmacotherapeutics capable of addressing the positive, negative, and cognitive symptoms of schizophrenia. Building on recent studies with a racemic mixture of the synthetic tetrahydroprotoberberine, D,L-Govadine, we isolated the D- and L-stereoisomers and employed a battery of behavioral, neurochemical, and electrophysiological procedures to assess their individual therapeutic potential. Rodent models predictive of antipsychotic efficacy and those that model positive symptoms were employed and we found that L-Govadine, but not D-Govadine, improved these measures. Pretreatment with either stereoisomer during CS pre-exposure prevented the disruption of latent inhibition by amphetamine. Moreover, pretreatment with either stereoisomer also improved deficits in social interaction in the neonatal ventral hippocampal lesioned rat. Improved cognitive performance in two different prefrontal cortex-dependent tasks was observed with D-, but not L-Govadine, which strongly suggests that the D-steroisomer may be an effective cognitive enhancer. Alterations in dopamine efflux were also assessed and L-Govadine increased dopamine efflux in both the prefrontal cortex and nucleus accumbens. However, D-Govadine only increased dopamine efflux in the prefrontal cortex and not in the nucleus accumbens. Electrophysiological studies confirmed that L-Govadine is a DA-D2 antagonist, whereas D-Govadine shows no appreciable physiological effects at this receptor. Collectively these data show that L-Govadine performs well on measures predictive of antipsychotic efficacy and rodent models of positive symptoms through antagonism of DA-D2 receptors, whereas D-Govadine improves impairments in compromised memory function in delayed response tasks possibly through selective increases in DA efflux in the frontal cortex
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