16,926 research outputs found
The structure of latherin, a surfactant allergen protein from horse sweat and saliva
Latherin is a highly surface-active allergen protein found in the sweat and saliva of horses and other equids. Its surfactant activity is intrinsic to the protein in its native form, and is manifest without associated lipids or glycosylation. Latherin probably functions as a wetting agent in evaporative cooling in horses, but it may also assist in mastication of fibrous food as well as inhibition of microbial biofilms. It is a member of the PLUNC family of proteins abundant in the oral cavity and saliva of mammals, one of which has also been shown to be a surfactant and capable of disrupting microbial biofilms. How these proteins work as surfactants while remaining soluble and cell membrane-compatible is not known. Nor have their structures previously been reported. We have used protein nuclear magnetic resonance spectroscopy to determine the conformation and dynamics of latherin in aqueous solution. The protein is a monomer in solution with a slightly curved cylindrical structure exhibiting a ‘super-roll’ motif comprising a four-stranded anti-parallel β-sheet and two opposing α-helices which twist along the long axis of the cylinder. One end of the molecule has prominent, flexible loops that contain a number of apolar amino acid side chains. This, together with previous biophysical observations, leads us to a plausible mechanism for surfactant activity in which the molecule is first localized to the non-polar interface via these loops, and then unfolds and flattens to expose its hydrophobic interior to the air or non-polar surface. Intrinsically surface-active proteins are relatively rare in nature, and this is the first structure of such a protein from mammals to be reported. Both its conformation and proposed method of action are different from other, non-mammalian surfactant proteins investigated so far
First observation of Li ground state
The ground state of neutron-rich unbound Li was observed for the first
time in a one-proton removal reaction from Be at a beam energy of 53.6
MeV/u. The Li ground state was reconstructed from Li and two
neutrons giving a resonance energy of 120 keV. All events
involving single and double neutron interactions in the Modular Neutron Array
(MoNA) were analyzed, simulated, and fitted self-consistently. The three-body
(Li+) correlations within Jacobi coordinates showed strong
dineutron characteristics. The decay energy spectrum of the intermediate
Li system (Li+) was described with an s-wave scattering length
of greater than -4 fm, which is a smaller absolute value than reported in a
previous measurement.Comment: Accepted for publication in Phys. Rev. C as a Rapid Communicatio
Quantum Phases of Vortices in Rotating Bose-Einstein Condensates
We investigate the groundstates of weakly interacting bosons in a rotating
trap as a function of the number of bosons, , and the average number of
vortices, . We identify the filling fraction as the
parameter controlling the nature of these states. We present results indicating
that, as a function of , there is a zero temperature {\it phase
transition} between a triangular vortex lattice phase, and strongly-correlated
vortex liquid phases. The vortex liquid phases appear to be the Read-Rezayi
parafermion states
Spin-echo small-angle neutron scattering (SESANS) studies of diblock copolymer nanoparticles
Poly(glycerol monomethacrylate)–poly(benzyl methacrylate) (PGMA–PBzMA) diblock copolymer nanoparticles were synthesized via polymerization-induced self-assembly (PISA) using reversible addition–fragmentation chain-transfer (RAFT) aqueous emulsion polymerization in D2O. Such PISA syntheses produce sterically-stabilized nanoparticles in situ and can be performed at relatively high copolymer concentrations (up to 50 wt%). This PGMA–PBzMA formulation is known to form only spherical nanoparticles in water using aqueous emulsion polymerization (Macromolecules, 2014, 47, 5613–5623), which makes it an ideal model system for exploring new characterization methods. The polymer micelles were characterized using small-angle X-ray scattering (SAXS) and a recently developed form of neutron scattering, spin-echo small-angle neutron scattering (SESANS). As far as we are aware, this is the first report of a study of polymer micelles by SESANS, and the data agree well with reciprocal-space scattering. Using this technique enables characterization of the concentrated, as synthesized dispersions directly without dilution, and this will provide a method to study self-assembled polymer systems that have concentration dependent morphologies, while still maintaining the advantages of scattering techniques
AEGIS: Enhancement of Dust-enshrouded Star Formation in Close Galaxy Pairs and Merging Galaxies up to z ~ 1
Using data from the DEEP2 Galaxy Redshift Survey and HST/ACS imaging in the
Extended Groth Strip, we select nearly 100 interacting galaxy systems including
kinematic close pairs and morphologically identified merging galaxies. Spitzer
MIPS 24 micron fluxes of these systems reflect the current dusty star formation
activity, and at a fixed stellar mass (M_{*}) the median infrared luminosity
(L_{IR}) among merging galaxies and close pairs of blue galaxies is twice (1.9
+/- 0.4) that of control pairs drawn from isolated blue galaxies. Enhancement
declines with galaxy separation, being strongest in close pairs and mergers and
weaker in wide pairs compared to the control sample. At z ~ 0.9, 7.1% +/- 4.3%
of massive interacting galaxies (M_{*} > 2*10^{10} M_{solar}) are found to be
ULIRGs, compared to 2.6% +/- 0.7% in the control sample. The large spread of IR
luminosity to stellar mass ratio among interacting galaxies suggests that this
enhancement may depend on the merger stage as well as other as yet unidentified
factors (e.g., galaxy structure, mass ratio, orbital characteristics, presence
of AGN or bar). The contribution of interacting systems to the total IR
luminosity density is moderate (<= 36 %).Comment: 12 pages, 2 figures, 1 table, minor changes to match the proof
version, accepted for publication in the ApJL AEGIS Special Issu
What makes you not a Buddhist? : a preliminary mapping of values
This study sets out to establish which Buddhist values contrasted with or were shared by adolescents from a non-Buddhist population. A survey of attitude toward a variety of Buddhist values was fielded in a sample of 352 non-Buddhist schoolchildren aged between 13 and 15 in London. Buddhist values where attitudes were least positive concerned the worth of being a monk/nun or meditating, offering candles & incense on the Buddhist shrine, friendship on Sangha Day, avoiding drinking alcohol, seeing the world as empty or impermanent and Nirvana as the ultimate peace. Buddhist values most closely shared by non-Buddhists concerned the Law of Karma, calming the mind, respecting those deserving of respect, subjectivity of happiness, welfare work, looking after parents in old age and compassion to cuddly animals. Further significant differences of attitude toward Buddhism were found in partial correlations with the independent variables of sex, age and religious affiliation. Correlation patterns paralleled those previously described in theistic religions. Findings are applied to spiritual, moral, social and cultural development and for the teaching of religious to pupils of no faith adherence. The study recommends that quantitative psychometrics employed to conceptualize Buddhist values by discriminant validity in this study could be extended usefully to other aspects of the study of Buddhism, particularly in quest of validity in the conceptualization of Buddhist identity within specifically Buddhist populations
Quantum Melting and Absence of Bose-Einstein Condensation in Two-Dimensional Vortex Matter
We demonstrate that quantum fluctuations suppress Bose-Einstein condensation
of quasi-two-dimensional bosons in a rapidly-rotating trap. Our conclusions
rest in part on an effective-Lagrangian description of the triangular vortex
lattice, and in part on microscopic Bogoliubov equations in the rapid-rotation
limit. We obtain analytic expressions for the collective-excitation dispersion,
which, in a rotating system, is quadratic rather than linear. Our estimates for
the boson filling factor at which the vortex lattice melts at zero temperature
due to quantum fluctuations are consistent with recent exact-diagonalization
calculations.Comment: 4 pages, 1 figures, version to appear in Phys. Rev. Let
The electric dipole response of Se above 4 MeV
The dipole response of Se in the energy range 4 to 9 MeV has been
analyzed using a polarized photon scattering
technique, performed at the High Intensity -Ray Source facility, to
complement previous work performed using unpolarized photons. The results of
this work offer both an enhanced sensitivity scan of the dipole response and an
unambiguous determination of the parities of the observed J=1 states. The
dipole response is found to be dominated by excitations, and can
reasonably be attributed to a pygmy dipole resonance. Evidence is presented to
suggest that a significant amount of directly unobserved excitation strength is
present in the region, due to unobserved branching transitions in the decays of
resonantly excited states. The dipole response of the region is underestimated
when considering only ground state decay branches. We investigate the electric
dipole response theoretically, performing calculations in a 3D cartesian-basis
time-dependent Skyrme-Hartree-Fock framework.Comment: 20 pages, 18 figures, to be submitted to PR
One step forward and two steps back? The ‘20 Principles’ for questioning vulnerable witnesses and the lack of an evidence-based approach
It is a widely held belief that questioning vulnerable witnesses is a specialist skill. In England and Wales vulnerable witness advocacy training built around ‘20 Principles’ has been developed and is being delivered. The 20 Principles do not cite a tested theoretical framework(s) or empirical evidence in support. This paper considers whether the 20 Principles are underpinned by research evidence. It is submitted that advocacy training and the approach to questioning witnesses in the courtroom should take into account the already available research evidence. The authors make recommendations for revision of the training and for a wider review of the approach taken to the handling of witness evidence
Lower Limb Muscle Strength and Muscle Mass Are Associated With Incident Symptomatic Knee Osteoarthritis: A Longitudinal Cohort Study
Recent literature suggests that sarcopenia, often represented by low lower limbs muscle mass and strength, can be considered a potential risk factor for knee osteoarthritis (OA), but the available literature is still limited. We therefore aimed to investigate whether sarcopenia is associated with a higher risk of radiographic (ROA) and symptomatic knee OA (SxOA) in a large cohort of North American people in the context of the OA initiative. Sarcopenia at baseline was diagnosed in case of low skeletal muscle mass (i.e., lower skeletal mass index) and poor performance in the chair stands test. The outcomes of interest for this study included ROA (radiographical osteoarthritis) if a knee developed a Kellgren and Lawrence (KL) grade ≥2 at follow-up, and SxOA (symptomatic osteoarthritis) defined as new onset of a combination of painful knee OA. Altogether, 2,492 older participants (mean age: 68.4 years, 61.4% females) were included. At baseline, sarcopenia was present in 6.1% of the population. No significant difference in ROA prevalence was observed between those with and without sarcopenia (p=0.76), whilst people with sarcopenia reported a significant higher prevalence of SxOA (p<0.0001). Using a logistic regression analysis, adjusting for potential confounders at baseline and the diagnosis of sarcopenia during follow-up, sarcopenia was associated with a higher incidence of knee SxOA (odds ratio, OR=2.29; 95%CI [confidence interval]: 1.42-3.71; p=0.001), but not knee ROA (OR=1.48; 95%CI: 0.53-4.10; p=0.45). In conclusion, sarcopenia could be associated with a higher risk of negative knee OA outcomes, in particular symptomatic forms
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