Composition, distribution and abundance of ichthyoplankton in the Sundays River Estuary

The species composition, distribution and seasonal abundance of ichthyoplankton in the Sundays River estuary was investigated at five stations from March 1986 to March 1987. Two estuarine taxa, the clupeid Gilchristella aestuaria and gobies Caffrogobius spp., accounted for 86% of the ichthyoplankton community, while the marine Mugilidae and sparid Rhabdosargus holubi together comprised 12% of the total catch. Ichthyoplankton densities were highest in the middle and upper reaches of the estuary where zooplankton stocks were greatest. Juvenile G. aestuaria predominated in the bottom waters throughout the system but the larvae were more evenly distributed (vertically) within the water column. In contrast, the mugilids were concentrated in surface waters throughout the estuary. Larvae were most abundant during spring and summer months, coinciding with the documented spawning period of most species and the peak in zooplankton biomass

Diffusion with rearranging traps

A model for diffusion on a cubic lattice with a random distribution of traps is developed. The traps are redistributed at certain time intervals. Such models are useful for describing systems showing dynamic disorder, such as ion-conducting polymers. In the present model the traps are infinite, unlike an earlier version with finite traps, this model has a percolation threshold. For the infinite trap version a simple analytical calculation is possible and the results agree qualitatively with simulation.Comment: Latex, five figure

High Temperature Electron Localization in dense He Gas

We report new accurate mesasurements of the mobility of excess electrons in high density Helium gas in extended ranges of temperature $[(26\leq T\leq 77) K ]$ and density $[ (0.05\leq N\leq 12.0) {atoms} \cdot {nm}^{-3}]$ to ascertain the effect of temperature on the formation and dynamics of localized electron states. The main result of the experiment is that the formation of localized states essentially depends on the relative balance of fluid dilation energy, repulsive electron-atom interaction energy, and thermal energy. As a consequence, the onset of localization depends on the medium disorder through gas temperature and density. It appears that the transition from delocalized to localized states shifts to larger densities as the temperature is increased. This behavior can be understood in terms of a simple model of electron self-trapping in a spherically symmetric square well.Comment: 23 pages, 13 figure

Nature of Sonoluminescence: Noble Gas Radiation Excited by Hot Electrons in "Cold" Water

We show that strong electric fields occurring in water near the surface of collapsing gas bubbles because of the flexoelectric effect can provoke dynamic electric breakdown in a micron-size region near the bubble and consider the scenario of the SBSL. The scenario is: (i) at the last stage of incomplete collapse of the bubble the gradient of pressure in water near the bubble surface has such a value and sign that the electric field arising from the flexoelectric effect exceeds the threshold field of the dynamic electrical breakdown of water and is directed to the bubble center; (ii) mobile electrons are generated because of thermal ionization of water molecules near the bubble surface; (iii) these electrons are accelerated in ''cold'' water by the strong electric fields; (iv) these hot electrons transfer noble gas atoms dissolved in water to high-energy excited states and optical transitions between these states produce SBSL UV flashes in the trasparency window of water; (v) the breakdown can be repeated several times and the power and duration of the UV flash are determined by the multiplicity of the breakdowns. The SBSL spectrum is found to resemble a black-body spectrum where temperature is given by the effective temperature of the hot electrons. The pulse energy and some other characteristics of the SBSL are found to be in agreement with the experimental data when realistic estimations are made.Comment: 11 pages (RevTex), 1 figure (.ps

About Bianchi I with VSL

In this paper we study how to attack, through different techniques, a perfect fluid Bianchi I model with variable G,c and Lambda, but taking into account the effects of a $c$-variable into the curvature tensor. We study the model under the assumption,div(T)=0. These tactics are: Lie groups method (LM), imposing a particular symmetry, self-similarity (SS), matter collineations (MC) and kinematical self-similarity (KSS). We compare both tactics since they are quite similar (symmetry principles). We arrive to the conclusion that the LM is too restrictive and brings us to get only the flat FRW solution. The SS, MC and KSS approaches bring us to obtain all the quantities depending on \int c(t)dt. Therefore, in order to study their behavior we impose some physical restrictions like for example the condition q<0 (accelerating universe). In this way we find that $c$ is a growing time function and Lambda is a decreasing time function whose sing depends on the equation of state, w, while the exponents of the scale factor must satisfy the conditions $\sum_{i=1}^{3}\alpha_{i}=1$ and $\sum_{i=1}^{3}\alpha_{i}^{2}<1,$ $\forall\omega$, i.e. for all equation of state$,$ relaxing in this way the Kasner conditions. The behavior of $G$ depends on two parameters, the equation of state $\omega$ and $\epsilon,$ a parameter that controls the behavior of $c(t),$ therefore $G$ may be growing or decreasing.We also show that through the Lie method, there is no difference between to study the field equations under the assumption of a $c-$var affecting to the curvature tensor which the other one where it is not considered such effects.Nevertheless, it is essential to consider such effects in the cases studied under the SS, MC, and KSS hypotheses.Comment: 29 pages, Revtex4, Accepted for publication in Astrophysics & Space Scienc

Genetic and genomic analysis of acute lymphoblastic leukaemia in older adults reveals a distinct profile of abnormalities: analysis of 210 patients from the UKALL14 and UKALL60+ clinical trials

Despite being predominantly a childhood disease, the incidence of ALL has a second peak in adults aged 60 years and over. These older adults fare extremely poorly with existing treatment strategies and very few studies have undertaken a comprehensive genetic and genomic characterisation to improve prognosis in this age group. We performed cytogenetic, single nucleotide polymorphism (SNP) array and next generation sequencing (NGS) analyses on samples from 210 patients aged ≥60 years from the UKALL14 and UKALL60+ clinical trials. BCR-ABL1 positive disease was present in 26% (55/210) of patients, followed by low hypodiploidy/near triploidy in 13% (28/210). Cytogenetically cryptic rearrangements in CRLF2, ZNF384 and MEF2D were detected in 5%, 1% and 1% of patients respectively. Copy number abnormalities were common and deletions in ALL driver genes were seen in 77% of cases. IKZF1 deletion was present in 51% (40/78) of samples tested and the IKZF1plus profile identified in over a third (28/77) of BCP-ALL cases. The genetic good risk abnormalities high hyperdiploidy (n=2), ETV6-RUNX1 (no cases) and ERG deletion (no cases) were exceptionally rare in this cohort. RAS pathway mutations were seen in 17% (4/23) of screened samples. KDM6A abnormalities, including biallelic deletions, were discovered in 5% (4/78) of SNP array and 9% (2/23) of NGS samples, and represent a novel, potentially therapeutically actionable lesions using EZH2 inhibitors. Outcome remained poor with five-year event-free (EFS) and overall survival (OS) rates of 17% and 24% respectively across the cohort indicating a need for novel therapeutic strategies

Metal-insulator and magnetic transition of NiO at high pressures

Published versio

Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths

We review observations of several classes of neutron-star-powered outflows: pulsar-wind nebulae (PWNe) inside shell supernova remnants (SNRs), PWNe interacting directly with interstellar medium (ISM), and magnetar-powered outflows. We describe radio, X-ray, and gamma-ray observations of PWNe, focusing first on integrated spectral-energy distributions (SEDs) and global spectral properties. High-resolution X-ray imaging of PWNe shows a bewildering array of morphologies, with jets, trails, and other structures. Several of the 23 so far identified magnetars show evidence for continuous or sporadic emission of material, sometimes associated with giant flares, and a few possible "magnetar-wind nebulae" have been recently identified.Comment: 61 pages, 44 figures (reduced in quality for size reasons). Published in Space Science Reviews, "Jets and Winds in Pulsar Wind Nebulae, Gamma-ray Bursts and Blazars: Physics of Extreme Energy Release

A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants

Tourism culture(s): The Hospitality Dimension

The focus of the paper is on tourism culture as it operates where commercial hospitality is on offer, especially at hotels and resorts in developing countries. It is suggested that three quite distinct perspectives can assist in helping us understand this aspect of tourism culture, which emerges where worker and tourist roles inevitably converge and interact. In themselves, such perspectives are not new, but they rarely seem to have been applied in the context of hotels and resorts. The first perspective, derived from the work of Homi Bhabha, conceives of tourism culture as hybrid in nature, operating in a ‘third space’ between tourist and ‘host,’ and directs attention to the uncertain and negotiated aspects of tourism culture. In the second, that of the socio-technical system, tourism culture is seen as an interface between, on the one hand, the formal operational rules and procedures designed to deliver an organisation’s mission and, on the other hand, the on-going and lived-in cultures brought into the ‘system’ by tourists and the hospitality providers. The third perspective, that of the total institution, derived from Goffman, focuses to the social and physical boundaries that separate the hotel or resort from the outside world and on the cultural practices that serve to further differentiate it and its population from the outside. It is suggested that use of these perspectives can further our understanding of the nature of tourism at different destinations and the ways hotels and similar institutions impact on both staff members and holidaymakers. As a consequence, they are theoretically, empirically relevant and politically important