4,903 research outputs found
Forces generated during stretch in the heart of the lobster Homarus americanus are anisotropic and are altered by neuromodulators
Mechanical and neurophysiological anisotropies mediate three-dimensional responses of the heart of Homarus americanus. Although hearts in vivo are loaded multi-axially by pressure, studies of invertebrate cardiac function typically use uniaxial tests. To generate whole-heart length-tension curves, stretch pyramids at constant lengthening and shortening rates were imposed uniaxially and biaxially along longitudinal and transverse axes of the beating whole heart. To determine whether neuropeptides that are known to modulate cardiac activity in H. americanus affect the active or passive components of these length-tension curves, we also performed these tests in the presence of SGRNFLRFamide (SGRN) and GYSNRNYLRFamide (GYS). In uniaxial and biaxial tests, both passive and active forces increased with stretch along both measurement axes. The increase in passive forces was anisotropic, with greater increases along the longitudinal axis. Passive forces showed hysteresis and active forces were higher during lengthening than shortening phases of the stretch pyramid. Active forces at a given length were increased by both neuropeptides. To exert these effects, neuropeptides might have acted indirectly on the muscle via their effects on the cardiac ganglion, directly on the neuromuscular junction, or directly on the muscles. Because increases in response to stretch were also seen in stimulated motor nerve-muscle preparations, at least some of the effects of the peptides are likely peripheral. Taken together, these findings suggest that flexibility in rhythmic cardiac contractions results from the amplified effects of neuropeptides interacting with the length-tension characteristics of the heart
Large-scale wind-tunnel tests of descent performance of an airplane model with a tilt wing and differential propeller thrust
Wind tunnel tests of wing stall, performance, and longitudinal stability & control of large model v/stol tilt wing transport aircraf
On almost randomizing channels with a short Kraus decomposition
For large d, we study quantum channels on C^d obtained by selecting randomly
N independent Kraus operators according to a probability measure mu on the
unitary group U(d). When mu is the Haar measure, we show that for
N>d/epsilon^2. For d=2^k (k qubits), this includes Kraus operators
obtained by tensoring k random Pauli matrices. The proof uses recent results on
empirical processes in Banach spaces.Comment: We added some background on geometry of Banach space
Aerodynamic characteristics of a large-scale V/STOL transport model with tandem lift fans mounted at mid-semispan of the wing
Aerodynamic characteristics of V/STOL transport model with tandem lift fans mounted at mid-semispan of win
The Evolution of the Optical and Near-Infrared Galaxy Luminosity Functions and Luminosity Densities to z~2
Using Hubble Space Telescope and ground-based U through K- band photometry
from the Great Observatories Origins Deep Survey (GOODS), we measure the
evolution of the luminosity function and luminosity density in the rest-frame
optical (UBR) to z ~ 2, bridging the poorly explored ``redshift desert''
between z~1 and z~2. We also use deep near-infrared observations to measure the
evolution in the rest-frame J-band to z~1. Compared to local measurements from
the SDSS, we find a brightening of the characteristic magnitude, (M*), by ~2.1,
\~0.8 and ~0.7 mag between z=0.1 and z=1.9, in U, B, and R bands, respectively.
The evolution of M* in the J-band is in the opposite sense, showing a dimming
between redshifts z=0.4 and z=0.9. This is consistent with a scenario in which
the mean star formation rate in galaxies was higher in the past, while the mean
stellar mass was lower, in qualitative agreement with hierarchical galaxy
formation models. We find that the shape of the luminosity function is strongly
dependent on spectral type and that there is strong evolution with redshift in
the relative contribution from the different spectral types to the luminosity
density.
We find good agreement in the luminosity function derived from an R-selected
and a K-selected sample at z~1, suggesting that optically selected surveys of
similar depth (R < 24) are not missing a significant fraction of objects at
this redshift relative to a near-infrared-selected sample. We compare the
rest-frame B-band luminosity functions from z~0--2 with the predictions of a
semi-analytic hierarchical model of galaxy formation, and find qualitatively
good agreement. In particular, the model predicts at least as many optically
luminous galaxies at z~1--2 as are implied by our observations.Comment: 43 pages; 15 Figures; 5 Tables, Accepted for publication in Ap.
The role of fractional exhaled nitric oxide in the assessment of athletes reporting exertional dyspnoea
Background: Exercise-induced bronchoconstriction (EIB) is a common cause of breathing difficulty in athletes. Fractional exhaled nitric oxide (FeNO) is an indirect marker of airway inflammation, recommended for the assessment and management of asthma; however, the role of FeNO in detecting and monitoring EIB has yet to be fully established. The aim of this study was therefore to evaluate the predictive value of FeNO to confirm or refute EIB in athletes presenting with exertional dyspnoea.
Method: Seventy athletes (male: n = 45) (age: 35 ± 11 years) reporting respiratory symptoms (i.e. wheeze, cough and dyspnoea) during exercise attended the laboratory on a single occasion. All athletes performed resting FeNO and spirometry pre-and-post a eucapnic voluntary hyperpnoea challenge (EVH) in accordance with international guidelines. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for established FeNO thresholds: (intermediate [≥25ppb] and high [>50ppb]) and evaluated against objective evidence of EIB: (EVH diagnostic cut-off [-10% ΔFEV1 at two consecutive time-points] and [-15% ΔFEV1 at one time-point]). The diagnostic accuracy of FeNO was calculated using receiver operating characteristics area under the curve (ROC-AUC).
Results: All had normal resting lung function (>80% FEV1 pred). The prevalence of EIB was 33% (-10% ΔFEV1) and 23% (-15% ΔFEV1) (median (IQR) ΔFEV1 = -7% (10.02)). FeNO values ≥25ppb and >50ppb were observed in 49% and 23% of the cohort, respectively. ROC-AUC for FeNO was 75% (-10% ΔFEV1) and 86% (-15% ΔFEV1). Sensitivity, specificity, PPV and NPV are presented in Table 1.
Conclusion: Our findings indicate that FeNO >50ppb provides good specificity for a positive EVH test; however, should not replace indirect bronchoprovocation for diagnostic purposes. The high proportion of athletes reporting breathing difficulty in the absence of EIB highlights the requirement to consider alternative causes of exertional dyspnoea during clinical work-up
Aerodynamic characteristics of a large scale lift fan transport model with podded fans forward and lift cruise fans mounted above the wing
The aerodynamic characteristics of a large scale V/STOL transport model powered by tip-turbine driven lift fans were investigated. The model had four fans; the forward fans were mounted in pods forward of the wing at midsemispan. The aft fans were placed in cruise nacelles behind and above the wing. A cascade of variable camber exit louvers was placed behind each of the lift-cruise fans to turn the fan flow in the lift direction for hover and transition to wing supported flight. The wing of the model was mounted above the fuselage, had an aspect ratio of 5.8, sweepback of 35 deg at the quarter chord line and a taper ratio of 0.3. Various configurations of the model were tested to explore the transition speed range. Fan performance, turning effectiveness of the variable camber exit louvers, longitudinal and lateral-directional characteristics with fan operation in crossflow are presented
Calculation of the Density of States Using Discrete Variable Representation and Toeplitz Matrices
A direct and exact method for calculating the density of states for systems
with localized potentials is presented. The method is based on explicit
inversion of the operator . The operator is written in the discrete
variable representation of the Hamiltonian, and the Toeplitz property of the
asymptotic part of the obtained {\it infinite} matrix is used. Thus, the
problem is reduced to the inversion of a {\it finite} matrix
Functional capacity and self-esteem of people with cerebral palsy
OBJECTIVE: We assessed whether functional capacity predicts self-esteem in people with cerebral palsy (CP).
METHOD: We conducted a cross-sectional observational study of 108 people with CP, ages 16-65 yr, who were residents of Spain. Self-esteem was captured using the Rosenberg Self-Esteem Scale (RSES), and functional capacity using the Barthel Index (BI). Sociodemographic characteristics were recorded. The relationship between the RSES score and the BI score was analyzed using linear regression.
RESULTS: RSES scores increased significantly as BI scores increased (regression coefficient = 0.047, 95% confidence interval [0.017, 0.078], p = .003). People with a higher level of education, active employment, and independent living arrangements tended to have better functional capacity and higher self-esteem.
CONCLUSION: Greater functional capacity predicted higher self-esteem; this effect is probably partly mediated by education, employment, and living arrangements
C-Band All-Sky Survey: A First Look at the Galaxy
We present an analysis of the diffuse emission at 5 GHz in the first quadrant
of the Galactic plane using two months of preliminary intensity data taken with
the C-Band All Sky Survey (C-BASS) northern instrument at the Owens Valley
Radio Observatory, California. Combining C-BASS maps with ancillary data to
make temperature-temperature plots we find synchrotron spectral indices of
between 0.408 GHz and 5 GHz and between 1.420 GHz and 5 GHz for ,
. Through the subtraction of a radio recombination
line (RRL) free-free template we determine the synchrotron spectral index in
the Galactic plane () to be between
0.408 GHz and 5 GHz, with a contribution of per cent from free-free
emission at 5\,GHz. These results are consistent with previous low frequency
measurements in the Galactic plane. By including C-BASS data in spectral fits
we demonstrate the presence of anomalous microwave emission (AME) associated
with the HII complexes W43, W44 and W47 near 30 GHz, at 4.4 sigma, 3.1 sigma
and 2.5 sigma respectively. The CORNISH VLA 5 GHz source catalogue rules out
the possibility that the excess emission detected around 30\;GHz may be due to
ultra-compact HII regions. Diffuse AME was also identified at a 4 sigma level
within , between 5
GHz and 22.8 GHz.Comment: 16 pages, 9 figures, submitted to MNRAS, referee's corrections made,
awaiting for final approval for publicatio
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