4,254 research outputs found
A three-dimensional simulation of transition and early turbulence in a time-developing mixing layer
The physics of the transition and early turbulence regimes in the time developing mixing layer was investigated. The sensitivity of the mixing layer to the disturbance field of the initial condition is considered. The growth of the momentum thickness, the mean velocity profile, the turbulence kinetic energy, the Reynolds stresses, the anisotropy tensor, and particle track pictures of computations are all examined in an effort to better understand the physics of these regimes. The amplitude, spectrum shape, and random phases of the initial disturbance field were varied. A scheme of generating discrete orthogonal function expansions on some nonuniform grids was developed. All cases address the early or near field of the mixing layer. The most significant result shows that the secondary instability of the mixing layer is produced by spanwise variations in the straining field of the primary vortex structures
Exploring a cardio-thoracic hospital ward soundscape in relation to restoration
Hospitals can provide stressful experiences for both patients and medical staff. A well-designed hospital soundscape should avoid adding to negative emotional states (e.g. stress), limit any detrimental cognitive effects (e.g. attentional fatigue), and enable restoration. Experiences of the cardio-thoracic ward soundscape, in a UK public University hospital, were explored via semi-structured interviews with 11 patients and 16 nurses. Thematic coding analysis resulted in 11 key themes including notions of restoration and emotional responses. The themes were used to develop a conceptual model to describe the processes involved in the perception and evaluation of the soundscape. The language used by patients and nurses indicated the emotional response to the soundscape was at times stressful and at others potentially restorative. Coping methods of accepting and habituating to individual sounds were noted. The impact of the patients' and nurses' ability to maintain these coping strategies are discussed in relation to restoration and the temporal variation of the soundscape. A period of 'quiet time' was in operation at the hospital and the importance of this was noted through various responses relating to emotion and restoration. The results suggest the soundscape has potentially, a beneficial role in facilitating restoration thus helping patients' recovery and medical staff's ability to remain productive. This research supports the need to study hospital soundscapes further so that design implications can be considered for the production of a more restorative environment, possibly through the masking/removal of unwanted sounds and optimising positive sounds
Proton transport and torque generation in rotary biomotors
We analyze the dynamics of rotary biomotors within a simple
nano-electromechanical model, consisting of a stator part and a ring-shaped
rotor having twelve proton-binding sites. This model is closely related to the
membrane-embedded F motor of adenosine triphosphate (ATP) synthase, which
converts the energy of the transmembrane electrochemical gradient of protons
into mechanical motion of the rotor. It is shown that the Coulomb coupling
between the negative charge of the empty rotor site and the positive stator
charge, located near the periplasmic proton-conducting channel (proton source),
plays a dominant role in the torque-generating process. When approaching the
source outlet, the rotor site has a proton energy level higher than the energy
level of the site, located near the cytoplasmic channel (proton drain). In the
first stage of this torque-generating process, the energy of the
electrochemical potential is converted into potential energy of the
proton-binding sites on the rotor. Afterwards, the tangential component of the
Coulomb force produces a mechanical torque. We demonstrate that, at low
temperatures, the loaded motor works in the shuttling regime where the energy
of the electrochemical potential is consumed without producing any
unidirectional rotation. The motor switches to the torque-generating regime at
high temperatures, when the Brownian ratchet mechanism turns on. In the
presence of a significant external torque, created by ATP hydrolysis, the
system operates as a proton pump, which translocates protons against the
transmembrane potential gradient. Here we focus on the F motor, even though
our analysis is applicable to the bacterial flagellar motor.Comment: 24 pages, 5 figure
Proposing a conceptual framework to develop the hospital soundscape through visual communication
Sound level measurement is used to assess sound within any environment, never more so than in hospitals. This is due to the negative effects that high sound level can have on patients and staff. However, other ways of exploring sound and the soundscape within the hospital context have been used: sound art has conveyed the experiences of heart transplant patients. Art may act as juxtaposition to objective sound level measurement but the two fundamentally attempt to depict attributes of the soundscape. Using theory from design and concepts from art a framework is presented for designing a positive soundscape experience. This is not through the addition of sound per se but through creatively communicating the information contained within a soundscape to enable the everyday listener to interpret a cacophony of hospital sounds more positively. In representing visual communication of sound as a design object, a new way to explore sound may exist
Interpersonal functioning in obsessive-compulsive personality disorder
The core symptoms of obsessive-compulsive personality disorder (OCPD) often lead to interpersonal difficulties. However, little research has explored interpersonal functioning in OCPD. This study examined interpersonal problems, interpersonal sensitivities, empathy, and systemizing, the drive to analyze and derive underlying rules for systems, in a sample of 25 OCPD individuals, 25 individuals with comorbid OCPD and obsessive-compulsive disorder (OCD), and 25 healthy controls. We found that OCPD individuals reported hostile-dominant interpersonal problems and sensitivities with warm-dominant behavior by others, whereas OCPD+OCD individuals reported submissive interpersonal problems and sensitivities with warm-submissive behavior by others. Individuals with OCPD, with and without OCD, reported less empathic perspective taking relative to healthy controls. Finally, we found that OCPD males reported a higher drive to analyze and derive rules for systems than OCPD females. Overall, results suggest that there are interpersonal deficits associated with OCPD and the clinical implications of these deficits are discussed
Fluctuating Hall resistance defeats the quantized Hall insulator
Using the Chalker-Coddington network model as a drastically simplified, but
universal model of integer quantum Hall physics, we investigate the
plateau-to-insulator transition at strong magnetic field by means of a
real-space renormalization approach. Our results suggest that for a fully
quantum coherent situation, the quantized Hall insulator with R_H approx. h/e^2
is observed up to R_L ~25 h/e^2 when studying the most probable value of the
distribution function P(R_H). Upon further increasing R_L ->\infty the Hall
insulator with diverging Hall resistance R_H \propto R_L^kappa is seen. The
crossover between these two regimes depends on the precise nature of the
averaging procedure.Comment: major revision, discussion of averaging improved; 8 pages, 7 figures;
accepted for publication in EP
Quantitative Nanofriction Characterization of Corrugated Surfaces by Atomic Force Microscopy
Atomic Force Microscopy (AFM) is a suitable tool to perform tribological
characterization of materials down to the nanometer scale. An important aspect
in nanofriction measurements of corrugated samples is the local tilt of the
surface, which affects the lateral force maps acquired with the AFM. This is
one of the most important problems of state-of-the-art nanotribology, making
difficult a reliable and quantitative characterization of real corrugated
surfaces. A correction of topographic spurious contributions to lateral force
maps is thus needed for corrugated samples. In this paper we present a general
approach to the topographic correction of AFM lateral force maps and we apply
it in the case of multi-asperity adhesive contact. We describe a complete
protocol for the quantitative characterization of the frictional properties of
corrugated systems in the presence of surface adhesion using the AFM.Comment: 33 pages, 9 figures, RevTex 4, submitted to Journal of Applied
Physic
Measuring the Stellar Masses of z~7 Galaxies with Spitzer Ultrafaint Survey Program (SURFS UP)
We present Spitzer/IRAC observations of nine -band dropouts highly
magnified (2<mu<12) by the Bullet Cluster. We combine archival imaging with our
Exploratory program (SURFS UP), which results in a total integration time of
~30 hr per IRAC band. We detect (>3sigma) in both IRAC bands the brightest of
these high-redshift galaxies, with [3.6]=23.80+-0.28 mag, [4.5]=23.78+-0.25
mag, and (H-[3.6])=1.17+-0.32 mag. The remaining eight galaxies are undetected
to [3.6]~26.4 mag and [4.5]~26.0 mag with stellar masses of ~5x10^7 M_sol. The
detected galaxy has an estimated magnification of mu=12+-4, which implies this
galaxy has an ultraviolet luminosity of L_1500~0.3 L*_{z=7} --- the lowest
luminosity individual source detected in IRAC at z>7. By modeling the broadband
photometry, we estimate the galaxy has an intrinsic star-formation rate of
SFR~1.3 M_sol/yr and stellar mass of M~2x10^9 M_sol, which gives a specific
star-formation rate of sSFR~0.7 Gyr^-1. If this galaxy had sustained this
star-formation rate since z~20, it could have formed the observed stellar mass
(to within a factor of ~2), we also discuss alternate star-formation histories
and argue the exponentially-increasing model is unlikely. Finally, based on the
intrinsic star-formation rate, we estimate this galaxy has a likely [C II] flux
of = 10^{-17} erg/s/cm2.Comment: Accepted to ApJL. 6 pages, 3 figures, 2 table
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