4,547 research outputs found
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
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
A recent rebuilding of most spirals ?
Re-examination of the properties of distant galaxies leads to the evidence
that most present-day spirals have built up half of their stellar masses during
the last 8 Gyr, mostly during several intense phases of star formation during
which they took the appearance of luminous infrared galaxies (LIRGs). Distant
galaxy morphologies encompass all of the expected stages of galaxy merging,
central core formation and disk growth, while their cores are much bluer than
those of present-day bulges. We have tested a spiral rebuilding scenario, for
which 75+/-25% of spirals have experienced their last major merger event less
than 8 Gyr ago. It accounts for the simultaneous decreases, during that period,
of the cosmic star formation density, of the merger rate, of the number
densities of LIRGs and of compact galaxies, while the densities of ellipticals
and large spirals are essentially unaffected.Comment: (1) GEPI, Obs. Meudon, France ;(2)Max-Planck Institut fuer
Astronomie, Germany (3) National Astronomical Observatories, CAS, China. Five
pages, 1 figure. To be published in "Starbursts: From 30 Doradus to Lyman
Break Galaxies", held in Cambridge, ed. R. de Grijs & R. M. Gonzalez Delgado
(Dordrecht: Kluwer
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
The main sequence of star-forming galaxies across cosmic times
By compiling a comprehensive census of literature studies, we investigate the evolution of the main sequence (MS) of star-forming galaxies (SFGs) in the widest range of redshift (0 < z < 6) and stellar mass (108.5–1011.5 M☉) ever probed. We convert all observations to a common calibration and find a remarkable consensus on the variation of the MS shape and normalization across cosmic time. The relation exhibits a curvature towards the high stellar masses at all redshifts. The best functional form is governed by two parameters: the evolution of the normalization and the turnover mass (M0(t)), which both evolve as a power law of the Universe age. The turn-over mass determines the MS shape. It marginally evolves with time, making the MS slightly steeper towards z ∼ 4–6. At stellar masses below M0(t), SFGs have a constant specific SFR (sSFR), while above M0(t) the sSFR is suppressed. We find that the MS is dominated by central galaxies. This allows to turn M0(t) into the corresponding host halo mass. This evolves as the halo mass threshold between cold and hot accretion regimes, as predicted by the theory of accretion, where the central galaxy is fed or starved of cold gas supply, respectively. We, thus, argue that the progressive MS bending as a function of the Universe age is caused by the lower availability of cold gas in haloes entering the hot accretion phase, in addition to black hole feedback. We also find qualitatively the same trend in the largest sample of star-forming galaxies provided by the IllustrisTNG simulation. Nevertheless, we still note large quantitative discrepancies with respect to observations, in particular at the high-mass end. These can not be easily ascribed to biases or systematics in the observed SFRs and the derived MS
Pharmacokinetic and safety profile of raltegravir and ribavirin, when dosed separately and together, in healthy volunteers
Results: No statistically significant differences in PK parameters were observed for raltegravir between phases 2 and 3. A statistically significant decrease in maximum plasma concentration (Cmax) and an increase in time to maximum plasma concentration (Tmax) were observed for ribavirin in phase 3 compared with phase 1 [GMR (95% confidence interval) 0.79 (0.62 –1.00) and 1.39 (1.08 –1.78), respectively], whereas no significant differences in other ribavirin PK parameters were observed between study phases. No clinically significant safety concerns were reported. Conclusions: The PK profile of ribavirin is altered when administered with raltegravir (reduced Cmax and increased Tmax), with no safety concerns identified. This is unlikely to be of clinical significance or have an impact on the antiviral effects of ribavirin in HIV-1- and HCV-co-infected subjects
Childhood solid tumours in relation to population mixing around the time of birth
In a retrospective cohort study of 673 787 live births in the Northern Region of England, 1975 - 1994, we investigated whether a higher level of population mixing around birth was a risk factor for solid tumours, by diagnostic group (Hodgkin's disease, brain and spinal tumours, neuroblastoma, other solid tumours), diagnosed during 1975-2001 under age 15 years. Logistic regression was used to relate risk to population mixing, based on (i) all movers and (ii) incomers from outside the region. Both ward and county district level analyses were performed. There was a decreased risk of brain and spinal tumours with increasing population mixing based on incomers from outside the region (OR for trend across three categories = 0.79, 95% CI: 0.66-0.95, P = 0.01 in the ward level analysis). Although this may be because of chance, it is consistent with a role of exposure to infection and immunological response in the aetiology of these tumours. For other tumour groups, there was no consistent evidence of an association between risk and population mixing
The evolution of galaxy star formation activity in massive halos
There is now a large consensus that the current epoch of the Cosmic Star
Formation History (CSFH) is dominated by low mass galaxies while the most
active phase at 1<z<2 is dominated by more massive galaxies, which undergo a
faster evolution. Massive galaxies tend to inhabit very massive halos such as
galaxy groups and clusters. We aim to understand whether the observed "galaxy
downsizing" could be interpreted as a "halo downsizing", whereas the most
massive halos, and their galaxy populations, evolve more rapidly than the halos
of lower mass. Thus, we study the contribution to the CSFH of galaxies
inhabiting group-sized halos. This is done through the study of the evolution
of the Infra-Red (IR) luminosity function of group galaxies from redshift 0 to
~1.6. We use a sample of 39 X-ray selected groups in the Extended Chandra Deep
Field South (ECDFS), the Chandra Deep Field North (CDFN), and the COSMOS field,
where the deepest available mid- and far-IR surveys have been conducted with
Spitzer MIPS and Hersche PACS. Groups at low redshift lack the brightest,
rarest, and most star forming IR-emitting galaxies observed in the field. Their
IR-emitting galaxies contribute <10% of the comoving volume density of the
whole IR galaxy population in the local Universe. At redshift >~1, the most
IR-luminous galaxies (LIRGs and ULIRGs) are preferentially located in groups,
and this is consistent with a reversal of the star-formation rate vs .density
anti-correlation observed in the nearby Universe. At these redshifts, group
galaxies contribute 60-80% of the CSFH, i.e. much more than at lower redshifts.
Below z~1, the comoving number and SFR densities of IR-emitting galaxies in
groups decline significantly faster than those of all IR-emitting galaxies. Our
results are consistent with a "halo downsizing" scenario and highlight the
significant role of "environment" quenching in shaping the CSFH.Comment: 14 pages, 10 figures, accepted for publication by A&
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
The role of massive halos in the Star Formation History of the Universe
The most striking feature of the Cosmic Star Formation History (CSFH) of the
Universe is a dramatic drop of the star formation (SF) activity, since z~1. In
this work we investigate if the very same process of assembly and growth of
structures is one of the major drivers of the observed decline. We study the
contribution to the CSFH of galaxies in halos of different masses. This is done
by studying the total SFR-halo mass-redshift plane from redshift 0 to redshift
z~1.6 in a sample of 57 groups and clusters by using the deepest available mid-
and far-infrared surveys conducted with Spitzer MIPS and Herschel PACS and
SPIRE. Our results show that low mass groups provide a 60-80% contribution to
the CSFH at z~1. Such contribution declines faster than the CSFH in the last 8
billion years to less than 10% at z<0.3, where the overall SF activity is
sustained by lower mass halos. More massive systems provide only a marginal
contribution (<10%) at any epoch. A simplified abundance matching method shows
that the large contribution of low mass groups at z~1 is due to a large
fraction (>50%) of very massive, highly star forming Main Sequence galaxies.
Below z~1 a quenching process must take place in massive halos to cause the
observed faster suppression of their SF activity. Such process must be a slow
one though, as most of the models implementing a rapid quenching of the SF
activity in accreting satellites significantly underpredicts the observed SF
level in massive halos at any redshift. Starvation or the transition from cold
to hot accretion would provide a quenching timescale of 1 Gyrs more consistent
with the observations. Our results suggest a scenario in which, due to the
structure formation process, more and more galaxies experience the group
environment and, thus, the associated quenching process. This leads to the
progressive suppression of their SF activity shaping the CSFH below z~1.Comment: 18 pages, 21 figures, accepted for publication by A&
- …