523 research outputs found
Comment on ``Evidence for Narrow Baryon Resonances in Inelastic pp Scattering''
Compton scattering data are sensitive to the existence of low-mass resonances
reported by Tatischeff et al. We show that such states, with their reported
properties, are excluded by previous Compton scattering experiments.Comment: One page, submitted to PR
Adjusting foraging strategies : a comparison of rural and urban common mynas (Acridotheres tristis)
The research was funded by a FP7-PEOPLE-2013-IRSES research staff exchange grant to TB, SH, OG and ASG. OG was additionally supported by Gu227/16-1 and IF by an FWF grant (Y366-B17) to TB.Establishment in urbanized environments is associated with changes in physiology, behaviour, and problem-solving. We compared the speed of learning in urban and rural female common mynas, Acridotheres tristis, using a standard visual discrimination task followed by a reversal learning phase. We also examined how quickly each bird progressed through different stages of learning, including sampling and acquisition within both initial and reversal learning, and persistence following reversal. Based on their reliance on very different food resources, we expected urban mynas to learn and reversal learn more quickly but to sample new contingencies for proportionately longer before learning them. When quantified from first presentation to criterion achievement, urban mynas took more 20-trial blocks to learn the initial discrimination, as well as the reversed contingency, than rural mynas. More detailed analyses at the level of stage revealed that this was because urban mynas explored the novel cue-outcome contingencies for longer, and despite transitioning faster through subsequent acquisition, remained overall slower than rural females. Our findings draw attention to fine adjustments in learning strategies in response to urbanization and caution against interpreting the speed to learn a task as a reflection of cognitive ability.PostprintPeer reviewe
A Brief Introduction to Chiral Perturbation Theory
A brief introduction to the subject of chiral perturbation theory (pt)
is presented, including a discussion of effective field theory and applications
of pt in the arena of purely mesonic interactions as well as in the sector.Comment: 15 pages, talk given at TAPS detector workshop, Rez, Czech Republic,
Sept. 1999, to be published in Czech. J. Phy
Duration of acute kidney injury in critically ill patients
BACKGROUND:Duration of acute kidney injury (AKI) has been recognized a risk factor for adverse outcomes following AKI. We sought to examine the relationship of AKI duration and recurrent AKI with short-term outcomes in critically ill patients who were mechanically ventilated and met criteria for the acute respiratory distress syndrome. METHODS:Participants in the NHLBI ARDS Network SAILS multicenter trial who developed AKI were included in this analysis and divided into groups based on AKI duration. Differences in outcomes were evaluated using t test and Chi-square test. Competing risks regression and Cox regression were used to evaluate factors associated with resolving AKI and recurrent AKI. RESULTS:In total, 238 patients were included in the study. Seventy-seven patients had short duration AKI (1-2 days), 47 medium duration AKI (3-7 days), 87 persistent AKI (> 7 days) and 38 died during their AKI episode. Persistent AKI was associated with worse outcomes including increased ICU length of stay, time on the ventilator and days with cardiovascular failure. We found no clinical differences between patients with short and medium duration AKI, even when accounting for AKI severity and recurrent AKI. Patients with resolving AKI were less likely to have oliguria or moderate/severe ARDS on the day AKI criteria were met. Recurrent AKI was associated with poorer clinical outcomes. No baseline clinical factors were found to predict development of recurrent AKI. CONCLUSIONS:In critically ill patients with sepsis-associated ARDS and AKI, the impact of short and medium duration AKI on clinical outcomes was modest. Persistent and recurrent AKI were both associated with worse clinical outcomes, emphasizing the importance of identifying these patients, who may benefit from novel interventions
Mass Determination of Groups of Galaxies: Effects of the Cosmological Constant
The spherical infall model first developed by Lema\^{i}tre and Tolman was
modified in order to include the effects of a dark energy term. The resulting
velocity-distance relation was evaluated numerically. This equation, when
fitted to actual data, permits the simultaneous evaluation of the central mass
and of the Hubble parameter. Application of this relation to the Local Group,
when the dark energy is modeled by a cosmological constant, yields a total mass
for the M31-Milky Way pair of (2.5 +/- 0.7) x 10^12 M\_sun, a Hubble parameter
H\_0 = 74 +/- 4 km s^-1 Mpc^-1 and a 1-D velocity dispersion for the flow of
about 39 km s^-1. The zero-velocity and the marginally bound surfaces of the
Local Group are at about 1.0 and 2.3 Mpc respectively from the center of mass.
A similar analysis for the Virgo cluster yields a mass of (1.10 +/- 0.12) x
10^15 M\_sun and H\_0 = 65 +/- 9 km s^-1 Mpc^-1. The zero-velocity is located
at a distance of 8.6 +/- 0.8 Mpc from the center of the cluster. The predicted
peculiar velocity of the Local Group towards Virgo is about 190 kms^-1, in
agreement with other estimates. Slightly lower masses are derived if the dark
energy is represented by a fluid with an equation of state P = w\epsilon with w
= -2/3.Comment: 13 pages, 3 figures. Version to appear in New Astronomy. Typing
errors corrected in relation (1) and in percentage value in page
Coordinated Control of HVAC Systems
This paper describes the development of new control logic for starting and stopping energy-intensive
equipment in buildings such as staged air-conditioning units. The concept is to use pulse-width
modulation (PWM) instead of level-crossing logic. A finite state machine is used to handle the case where
a single unit has multiple stages of operation. An optimized coordinator determines the phase of the PWM
signals of each unit so that peak demand for power is minimized over each PWM period. Control logic
for the PWM function was developed so that the phase could be manipulated by the coordinator.
Computer simulations were used to assess the performance of the new strategy and to compare it to levelcrossing
logic. The following five metrics were used to assess the performance: 1) magnitude of the
control error, 2) start/stop frequency, 3) average power consumption, 4) standard deviation of the power
consumption, 5) peak power consumption. The computer simulations showed that the new strategy could
reduce peak power consumption by 20% relative to level-crossing logic. The computer simulations also
showed that the new strategy increased the magnitude of the space temperature control error by 11% and
increased the number of start/stop operations by 27% relative to level-crossing logic
Cepheid Calibration of the Peak Brightness of SNe Ia -- IX. SN 1989B in NGC 3627
(Abridged) Repeated imaging observations have been made of NGC 3627 with the
HST in 1997/98, over an interval of 58 days. Images were obtained on 12 epochs
in the F555W band and on five epochs in the F814W band. The galaxy hosted the
prototypical, `Branch normal', type Ia supernova SN 1989B. A total of 83
variables have been found, of which 68 are definite Cepheid variables with
periods ranging from 75 days to 3.85 days. The de-reddened distance modulus is
determined to be (m-M)_0= 30.22+/-0.12 (internal uncertainty) using a subset of
the Cepheid data whose reddening and error parameters are secure.
The photometric data of Wells et al. (1994), combined with the Cepheid data
for NGC 3627 give M_B(max)= -19.36+/-0.18 and M_V(max)= -19.34+/-0.16 for SN
1989B. Combined with the previous six calibrations in this program, plus two
additional calibrations determined by others gives the mean absolute magnitudes
at maximum of = -19.48+/-0.07 and = -19.48 +/-0.07 for `Branch
normal' SNe Ia at this interim stage in the calibration program.
The second parameter correlations of M(max) of blue SNe Ia with decay rate,
color at maximum, and Hubble type are re-investigated. The dependence of
on decay rate is non-linear, showing a minimum for decay rates between
1.0< Delta m_15 <1.6. Magnitudes corrected for decay rate show no dependence on
Hubble type, but a dependence on color remains. Correcting both the fiducial
sample of 34 SNe Ia with decay-rate data and the current 8 calibrating SNe Ia
for the correlation with decay rate as well as color gives H_0= 60+/-2
(internal) km/s/Mpc, in both B and V. The same value to within 4% is obtained
if only the SNe Ia in spirals (without second parameter corrections) are
considered.Comment: 32 pages (with 7 tables and 14 figures) LaTeX, uses emulateapj.sty; a
full-resolution version with complete figs. 4 and 5 is available at
http://www.astro.unibas.ch/cosmology/papers.html ; accepted for publication
in Ap
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