A contribution to the understanding of crystallization

Thermodynamic and kinetic studies of the vapor/liquid phase transition of a Lennard-Jones model fluid are presented which challenge the conventional interpretation of the mechanism of the condensation process. We have lifted the usual approximations (incompressible phases, constant surface tension, and non-depleting vapor phase) applied in classical nucleation theory to investigate the nature of the barrier to condensation. Based on the 1[superscript]st Yvon-Born-Green integro-differential equation we have developed a thermodynamically consistent molecular theory which accurately predicts the radially dependent surface tension and the location of the surface of tension of microscopically small droplets. The droplet size dependence of the inter-facial free energy is sufficiently strong that the free energy barrier to the nucleation is absent;Computer simulations of ionic and neutral fluids have been performed to study the dynamical behavior of the fluid during the phase separation. We find that phase transitions in the metastable region for both systems are characterized by the instantaneous formation of concentration fluctuations. In the vapor phase of the Lennard-Jones fluid nearly spherical, disjoint, high density regions are formed, whereas in the ionic vapor a network of charged chains is observed. The connectivity between the clusters and their linearity diminishes with charge asymmetry. The short induction time where small clusters are spontaneously formed is followed by two rate determining regimes. First, the clusters absorb surrounding atoms and smaller clusters. During this regime, the evolution of the number of atoms in the cluster is linear in time and can be described by a modified Lifshitz-Slyozov theory. Second, the clusters undergo Brownian motion and further growth is mainly driven by coalescence. The Brownian character of this motion is due to unsymmetric internal motion near the surface. This is in contrast to the usual interpretation of the origin of Brownian motion as environmental noise;These results support our earlier conclusions that the free energy of formation of a spherical droplet is irrelevant to a description of vapor condensation, but require an alternative mechanism for the persistence of metastability. We have constructed a new model for the vapor/liquid phase transition, which regards the phase separation as a cascade of Brownian walkers whose mass grows linearly in time. The nucleation rate is then simply determined by the sum over the first passage times required for the binary coalescence event. These intervals scale like time to the 11/6 and supersaturation to the -2/3 providing an explanation of the sensitivity of nucleation rate to supersaturation

Optimism and the Experience of Pain:A Systematic Review

A growing body of literature provides evidence of the health-promoting effects of optimism, including its protective role in acute and chronic pain. Optimists are characterized by positive expectations concerning the future. These positive outcome expectancies lead to more and longer goal-directed efforts and the use of approach coping strategies. No systematic review on the effects of optimism on the experience of pain has so far been conducted. A search in the databases PubMed, Web of Science and PsycInfo, and the scanning of reference lists identified 69 eligible studies. These were categorized according to sample size, participants’ age and sex, design, optimism-pain relation as primary vs. secondary study objective, and level of study/publication quality. Overall percentages of positive, zero, and negative associations between optimism and pain as well as relative frequencies of these associations in the different categories were analyzed. About 70% of the studies showed a positive, i.e., beneficial association between optimism and at least one pain outcome. A larger percentage of beneficial associations was found in studies with experimental designs, in studies with the optimism-pain relation as primary objective, in high-quality studies/publications, and in studies including participants with a higher average age. The review suggests that optimism is associated with less acute and chronic pain, especially since a higher percentage of beneficial associations was found with high study/publication quality and with the primary focus on this relationship. For the moderating role of age, different explanations are proposed. Further research on causal relationships and on optimism-fostering clinical interventions is needed

Hair coloration by gene regulation: fact or fiction?

The unravelling of hair pigmentation genetics and robust delivery systems to the hair follicle (HF) will allow the development of a new class of colouring products. The challenge will be changing hair colour from inside out by safely regulating the activity of target genes through the specific delivery of synthetic/natural compounds, proteins, genes, or small RNAs.T.M. acknowledge sher post doctoral fellowship SFRH/BPD/102153/2014.The authors thank the FCT Strategic Project of UID/BIO/04469/2013 and UID/BIA/04050/2013, the project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462), and the Project ‘BioHealth – Biotechnology and Bioengineering Approaches to Improve Health Quality’, Ref. NORTE-07-0124-FEDER-000027,cofunded by the Programa Operacional Regional do Norte (ON.2 – O Novo Norte), QREN, FEDER

Adiabatic Evolution of Mass-losing Stars

We have calculated the equilibrium properties of a star in a circular, equatorial orbit about a Super-Massive Black Hole (SMBH), when the star fills and overflows its Roche lobe. The mass transfer time scale is anticipated to be long compared with the dynamical time and short compared with the thermal time of the star, so that the entropy as a function of the interior mass is conserved. We have studied how the stellar entropy, pressure, radius, mean density, and orbital angular momentum vary when the star is evolved adiabatically, for a representative set of stars. We have shown that the stellar orbits change with the stellar mean density. Therefore, sun-like stars, upper main sequence stars and red giants will spiral inward and then outward with respect to the hole in this stable mass transfer process, while lower main sequence stars, brown dwarfs and white dwarfs will always spiral outward.Comment: 8 pages, 19 figures, submitted to MNRA

Volatile organic compound speciation above and within a Douglas Fir forest

Mixing ratios and fluxes of volatile organic compounds (VOCs) were measured by PTR-MS (and GC-MS) and virtual disjunct eddy covariance during a three-week field campaign in summer 2009 within and above a Douglas fir (Pseudotsuga menziesii) forest in Speulderbos, the Netherlands. Measurements included the first non-terpenoid species fluxes and mixing ratios for Douglas fir canopy. Above-canopy emissions of monoterpenes were comparable to previous studies of P. menziesii, with standard emission factors for the first and second halves of the campaign of 0.8 ± 0.4 and 0.8 ± 0.3 µg gdw-1 h-1, and temperature coefficients of 0.19 ± 0.06 and 0.08 ± 0.05 °C-1, respectively. Isoprene standard emission factors for the two halves of the campaign were 0.09 ± 0.12 and 0.16 ± 0.18 µg gdw-1 h-1. Fluxes of several non-terpenoid VOCs were significant, with maximum fluxes greater than has been measured for other coniferous species. α-Pinene was the dominant monoterpene within and above the canopy. Within canopy mixing ratios of individual species were generally greatest in early evening consistent with reduced vertical mixing and continued temperature-dependent emissions. Acetaldehyde, acetone and monoterpenes had elevated mixing ratios toward the bottom of the canopy (5-10 m) with assumed contribution from the large quantities of forest-floor leaf litter. MBO (2-methyl-3-buten-2-ol) and estragole had peak mixing ratios at the top of the canopy and are known to have coniferous sources. MVK + MACR (methyl vinyl ketone and methacrolein) also had highest mixing ratios at the top of the canopy consistent with formation from in-canopy oxidation of isoprene. The work highlights the importance of quantifying a wider variety of VOCs from biogenic sources than isoprene and monoterpenes

Rapid Change in Articulatory Lip Movement Induced by Preceding Auditory Feedback during Production of Bilabial Plosives

BACKGROUND: There has been plentiful evidence of kinesthetically induced rapid compensation for unanticipated perturbation in speech articulatory movements. However, the role of auditory information in stabilizing articulation has been little studied except for the control of voice fundamental frequency, voice amplitude and vowel formant frequencies. Although the influence of auditory information on the articulatory control process is evident in unintended speech errors caused by delayed auditory feedback, the direct and immediate effect of auditory alteration on the movements of articulators has not been clarified. METHODOLOGY/PRINCIPAL FINDINGS: This work examined whether temporal changes in the auditory feedback of bilabial plosives immediately affects the subsequent lip movement. We conducted experiments with an auditory feedback alteration system that enabled us to replace or block speech sounds in real time. Participants were asked to produce the syllable /pa/ repeatedly at a constant rate. During the repetition, normal auditory feedback was interrupted, and one of three pre-recorded syllables /pa/, /Φa/, or /pi/, spoken by the same participant, was presented once at a different timing from the anticipated production onset, while no feedback was presented for subsequent repetitions. Comparisons of the labial distance trajectories under altered and normal feedback conditions indicated that the movement quickened during the short period immediately after the alteration onset, when /pa/ was presented 50 ms before the expected timing. Such change was not significant under other feedback conditions we tested. CONCLUSIONS/SIGNIFICANCE: The earlier articulation rapidly induced by the progressive auditory input suggests that a compensatory mechanism helps to maintain a constant speech rate by detecting errors between the internally predicted and actually provided auditory information associated with self movement. The timing- and context-dependent effects of feedback alteration suggest that the sensory error detection works in a temporally asymmetric window where acoustic features of the syllable to be produced may be coded

Identification and characterisation of isoprene-degrading bacteria in an estuarine environment

Approximately one-third of volatile organic compounds (VOCs) emitted to the atmosphere consists of isoprene, originating from the terrestrial and marine biosphere, with a profound effect on atmospheric chemistry. However, isoprene provides an abundant and largely unexplored source of carbon and energy for microbes. The potential for isoprene degradation in marine and estuarine samples from the Colne Estuary, UK, was investigated using DNA-Stable Isotope Probing (DNA-SIP). Analysis at two timepoints showed the development of communities dominated by Actinobacteria including members of the genera Mycobacterium, Rhodococcus, Microbacterium and Gordonia. Representative isolates, capable of growth on isoprene as sole carbon and energy source, were obtained from marine and estuarine locations, and isoprene-degrading strains of Gordonia and Mycobacterium were characterised physiologically and their genomes were sequenced. Genes predicted to be required for isoprene metabolism, including four-component isoprene monooxygenases (IsoMO), were identified and compared with previously characterised examples. Transcriptional and activity assays of strains growing on isoprene or alternative carbon sources showed that growth on isoprene is an inducible trait requiring a specific IsoMO. This study is the first to identify active isoprene degraders in estuarine and marine environments using DNA-SIP and to characterise marine isoprene-degrading bacteria at the physiological and molecular level

Identification and characterisation of isoprene-degrading bacteria in an estuarine environment

Approximately one-third of volatile organic compounds (VOCs) emitted to the atmosphere consists of isoprene, originating from the terrestrial and marine biosphere, with a profound effect on atmospheric chemistry. However, isoprene provides an abundant and largely unexplored source of carbon and energy for microbes. The potential for isoprene degradation in marine and estuarine samples from the Colne Estuary, UK, was investigated using DNA-Stable Isotope Probing (DNA-SIP). Analysis at two timepoints showed the development of communities dominated by Actinobacteria including members of the genera Mycobacterium, Rhodococcus, Microbacterium and Gordonia. Representative isolates, capable of growth on isoprene as sole carbon and energy source, were obtained from marine and estuarine locations, and isoprene-degrading strains of Gordonia and Mycobacterium were characterised physiologically and their genomes were sequenced. Genes predicted to be required for isoprene metabolism, including four-component isoprene monooxygenases (IsoMO), were identified and compared with previously characterised examples. Transcriptional and activity assays of strains growing on isoprene or alternative carbon sources showed that growth on isoprene is an inducible trait requiring a specific IsoMO. This study is the first to identify active isoprene degraders in estuarine and marine environments using DNA-SIP and to characterise marine isoprene-degrading bacteria at the physiological and molecular level

Analysis of LIGO data for gravitational waves from binary neutron stars

We report on a search for gravitational waves from coalescing compact binary systems in the Milky Way and the Magellanic Clouds. The analysis uses data taken by two of the three LIGO interferometers during the first LIGO science run and illustrates a method of setting upper limits on inspiral event rates using interferometer data. The analysis pipeline is described with particular attention to data selection and coincidence between the two interferometers. We establish an observational upper limit of $\mathcal{R}<$1.7 \times 10^{2}$per year per Milky Way Equivalent Galaxy (MWEG), with 90coalescence rate of binary systems in which each component has a mass in the range 1--3$M_\odot$.Comment: 17 pages, 9 figure

Search for Kaluza-Klein Graviton Emission in ppˉp\bar{p} Collisions at s=1.8\sqrt{s}=1.8 TeV using the Missing Energy Signature

We report on a search for direct Kaluza-Klein graviton production in a data sample of 84 ${pb}^{-1}$ of \ppb collisions at $\sqrt{s}$ = 1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a $3+1+n$-dimensional Kaluza-Klein scenario in which gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for $n$=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71 TeV, respectively.Comment: Submitted to PRL, 7 pages 4 figures/Revision includes 5 figure