Male behaviour drives assortative reproduction during the initial stage of secondary contact.

Phenotypic divergence in allopatry can facilitate speciation by reducing the likelihood that individuals of different lineages hybridize during secondary contact. However, few studies have established the causes of reproductive isolation in the crucial early stages of secondary contact. Here, we establish behavioural causes of assortative reproduction between two phenotypically divergent lineages of the European wall lizard (Podarcis muralis), which have recently come into secondary contact. Parentage was highly assortative in experimental contact zones. However, despite pronounced divergence in male phenotypes, including chemical and visual sexual signals, there was no evidence that females discriminated between males of the two lineages in staged interactions or under naturalistic free-ranging conditions. Instead, assortative reproduction was driven by male mate preferences and, to a lesser extent, male-male competition. The effects were more pronounced when the habitat structure promoted high lizard densities. These results emphasize that assortative reproduction can occur in the absence of female choice and that male behaviour may play an important role in limiting hybridization during the initial stages of secondary contact.

Magnetically guided fast electrons in cylindrically compressed matter.

Fast electrons produced by a 10 ps, 160 J laser pulse through laser-compressed plastic cylinders are studied experimentally and numerically in the context of fast ignition. K(α)-emission images reveal a collimated or scattered electron beam depending on the initial density and the compression timing. A numerical transport model shows that implosion-driven electrical resistivity gradients induce strong magnetic fields able to guide the electrons. The good agreement with measured beam sizes provides the first experimental evidence for fast-electron magnetic collimation in laser-compressed matter.

Ultrafast melting of carbon induced by intense proton beams.

Laser-produced proton beams have been used to achieve ultrafast volumetric heating of carbon samples at solid density. The isochoric melting of carbon was probed by a scattering of x rays from a secondary laser-produced plasma. From the scattering signal, we have deduced the fraction of the material that was melted by the inhomogeneous heating. The results are compared to different theoretical approaches for the equation of state which suggests modifications from standard models.

Electron bunch length measurements from laser-accelerated electrons using single-shot THz time-domain interferometry.

Laser-plasma wakefield-based electron accelerators are expected to deliver ultrashort electron bunches with unprecedented peak currents. However, their actual pulse duration has never been directly measured in a single-shot experiment. We present measurements of the ultrashort duration of such electron bunches by means of THz time-domain interferometry. With data obtained using a 0.5 J, 45 fs, 800 nm laser and a ZnTe-based electro-optical setup, we demonstrate the duration of laser-accelerated, quasimonoenergetic electron bunches [best fit of 32 fs (FWHM) with a 90% upper confidence level of 38 fs] to be shorter than the drive laser pulse, but similar to the plasma period.

Trachoma.

Trachoma is a keratoconjunctivitis caused by ocular infection with Chlamydia trachomatis. Repeated or persistent episodes lead to increasingly severe inflammation that can progress to scarring of the upper tarsal conjunctiva. Trichiasis develops when scarring distorts the upper eyelid sufficiently to cause one or more lashes to abrade the cornea, scarring it in turn and causing blindness. Active trachoma affects an estimated 84 million people; another 7.6 million have end-stage disease, of which about 1.3 million are blind. Trachoma should stand on the brink of extinction thanks to a 1998 initiative launched by WHO--the Global Elimination of Trachoma by 2020. This programme advocates control of trachoma at the community level with four inter-related population-health initiatives that form the SAFE strategy: surgery for trichiasis, antibiotics for active trachoma, facial cleanliness, and environmental improvement. Evidence supports the effectiveness of this approach, and if current world efforts continue, blinding trachoma will indeed be eliminated by 2020.

Heart rate in spiders: influence of body size and foraging energetics.

Resting heart rates in 18 species of spiders as determined by a cool laser transillumination technique range from 9 to 125 beats per minute. Cardiac frequencies obtained in this fashion may readily serve as a measure of standard rates of metabolism. A spider's resting heart rate is a function of body size and of foraging energetics.

Trachoma, cataracts and uncorrected refractive error are still important contributors to visual morbidity in two remote indigenous communities of the Northern Territory, Australia.

PURPOSE: To assess the contribution of trachoma, cataract and refractive error to visual morbidity among Indigenous adults living in two remote communities of the Northern Territory. DESIGN, SETTING AND PARTICIPANTS: Cross-sectional survey of all adults aged 40 and over within a desert and coastal community. MAIN OUTCOME MEASURES: Visual acuity, clinical signs of trachoma using the simplified WHO grading system and assessment of cataract through a non-dilated pupil. RESULTS: Two hundred and sixty individuals over the age of 40 years participated in the study. The prevalence of visual impairment (<6/12) was 17%. The prevalence of blindness (<3/60) was 2%, 40-fold higher than seen in an urban Australian population when adjusted for age. In total, 78% of adults who grew up in a desert community had trachomatous scarring compared with 26% of those who grew up in a coastal community (P < or = 0.001). In the desert community the prevalence of trachomatous trichiasis was 10% and corneal opacity was 6%. No trachomatous trichiasis or corneal opacity was seen in the coastal community. CONCLUSIONS: Trachoma, cataract and uncorrected refractive error remain significant contributors to visual morbidity in at least two remote indigenous communities. A wider survey is required to determine if these findings represent a more widespread pattern and existing eye care services may need to be re-assessed to determine the cause of this unmet need.

Supersonic plasma turbulence in the laboratory.

The properties of supersonic, compressible plasma turbulence determine the behavior of many terrestrial and astrophysical systems. In the interstellar medium and molecular clouds, compressible turbulence plays a vital role in star formation and the evolution of our galaxy. Observations of the density and velocity power spectra in the Orion B and Perseus molecular clouds show large deviations from those predicted for incompressible turbulence. Hydrodynamic simulations attribute this to the high Mach number in the interstellar medium (ISM), although the exact details of this dependence are not well understood. Here we investigate experimentally the statistical behavior of boundary-free supersonic turbulence created by the collision of two laser-driven high-velocity turbulent plasma jets. The Mach number dependence of the slopes of the density and velocity power spectra agree with astrophysical observations, and supports the notion that the turbulence transitions from being Kolmogorov-like at low Mach number to being more Burgers-like at higher Mach numbers.

Optimization of the blood culture pathway: a template for improved sepsis management and diagnostic antimicrobial stewardship.

Laboratory processing of blood cultures has remained static over the past 30 years, despite increasing antibiotic resistance and advances in analyser design. At the study hospital, siting the blood culture analyser in the blood sciences laboratory and optimizing the pre-analytical and analytic phases of blood culture management resulted in a reduction in the time taken to detect most blood culture isolates to <12h. Fifty percent of positive blood cultures containing Escherichia coli were definitively reported with antibiotic susceptibilities in <24h. More than 85% of blood cultures positive for E. coli had antibiotic susceptibilities reported within 36h of collection, compared with 66h at a comparator hospital.

Trachoma and poverty: unnecessary blindness further disadvantages the poorest people in the poorest countries.

Trachoma is the leading cause of infectious blindness worldwide. Many populations living in poverty are affected by trachoma. The infectious organism is provided with an ideal milieu for transmission, where markers of poverty are present. These include overcrowding, lack of adequate water resources, limited use of water for personal hygiene, inadequate waste disposal and other conditions that encourage the proliferation of flies. This review summarises treatment strategies that have been effectively instituted in many countries to reduce the prevalence of trachoma. The review promotes partnerships working towards achieving the Millennium Development Goals developed by the United Nations to address issues associated with poverty. These goals are in keeping with many of the strategies to reduce the burden of potentially blinding trachoma that afflicts some of the world's poorest citizens.

An ultra-high gain and efficient amplifier based on Raman amplification in plasma.

Raman amplification arising from the excitation of a density echelon in plasma could lead to amplifiers that significantly exceed current power limits of conventional laser media. Here we show that 1-100 J pump pulses can amplify picojoule seed pulses to nearly joule level. The extremely high gain also leads to significant amplification of backscattered radiation from "noise", arising from stochastic plasma fluctuations that competes with externally injected seed pulses, which are amplified to similar levels at the highest pump energies. The pump energy is scattered into the seed at an oblique angle with 14 J sr-1, and net gains of more than eight orders of magnitude. The maximum gain coefficient, of 180 cm-1, exceeds high-power solid-state amplifying media by orders of magnitude. The observation of a minimum of 640 J sr-1 directly backscattered from noise, corresponding to ≈10% of the pump energy in the observation solid angle, implies potential overall efficiencies greater than 10%.

Experimental measurements of the collisional absorption of XUV radiation in warm dense aluminium.

The collisional (or free-free) absorption of soft x rays in warm dense aluminium remains an unsolved problem. Competing descriptions of the process exist, two of which we compare to our experimental data here. One of these is based on a weak scattering model, another uses a corrected classical approach. These two models show distinctly different behaviors with temperature. Here we describe experimental evidence for the absorption of 26-eV photons in solid density warm aluminium (T_{e}≈1 eV). Radiative x-ray heating from palladium-coated CH foils was used to create the warm dense aluminium samples and a laser-driven high-harmonic beam from an argon gas jet provided the probe. The results indicate little or no change in absorption upon heating. This behavior is in agreement with the prediction of the corrected classical approach, although there is not agreement in absolute absorption value. Verifying the correct absorption mechanism is decisive in providing a better understanding of the complex behavior of the warm dense state.

Clinical examination and laboratory tests for estimation of trachoma prevalence in a remote setting: what are they really telling us?

Worldwide, an estimated 84 million people have active trachoma and 7.6 million people have trachomatous trichiasis. WHO's SAFE strategy is an effective tool in the worldwide effort to eliminate blinding trachoma, but its institution and monitoring requires a simple, reliable, and cost-effective method to detect disease. To date, clinical examination has provided the main method of diagnosis. Detection of Chlamydia trachomatis with nucleic acid amplification tests does not always correlate well with clinical findings, which has prompted the suggestion that these methods should replace clinical examination. However, a review of the research carried out in animals and human beings suggests the relation between laboratory tests and clinical examination is due to the kinetics of trachoma and not to an inherent problem in either detection system. Given the increased difficulties of using laboratory tests in parts of the world where trachoma is endemic, we should not abandon clinical grading as a tool to assess the need for, and the effectiveness of, trachoma intervention programmes.

Service innovation in glaucoma management: using a Web-based electronic patient record to facilitate virtual specialist supervision of a shared care glaucoma programme.

AIM: To assess the importance of specialist supervision in a new model of glaucoma service delivery. METHODS: An optometrist supported by three technicians managed each glaucoma clinic. Patients underwent testing and clinical examination before the optometrist triaged them into one of five groups: 'normal', 'stable', 'low risk', 'unstable' and 'high risk'. Patient data were uploaded to an electronic medical record to facilitate virtual review by a glaucoma specialist. RESULTS: 24 257 glaucoma reviews at three glaucoma clinics during a 31-month period were analysed. The clinic optometrists and glaucoma specialists had substantial agreement (κ 0.69). 13 patients were identified to be high risk by the glaucoma specialist that had not been identified as such by the optometrist. Glaucoma specialists amended 13% of the optometrists' interim decisions resulting in an overall reduction in review appointments by 2.4%. CONCLUSIONS: Employing technicians and optometrists to triage glaucoma patients into groups defined by risk of blindness allows higher risk patients to be directed to a glaucoma specialist. Virtual review allows the glaucoma specialist to remain in overall control while reducing the risk that patients are treated or followed-up unnecessarily. Demand for glaucoma appointments can be reduced allowing scarce medical resources to be directed to patients most in need.

Spatial and temporal shifts in the regulation of neurogenesis in a peripheral ganglion.

In the cardiac ganglion of the frog Xenopus laevis, the number of cholinergic neurons increases over several months. During this time, each neuron must insert itself into the control circuit of the functioning heart. Like all neurons, increases in cell number depend on the timing of both proliferation and differentiation of neuronal precursors. The characteristics of the cardiac ganglion provided an opportunity to test how proliferation and differentiation regulate the production of a specific population of neurons. The prolonged accumulation of cardiac neurons suggested that their site of origin shifted from the neural crest migratory pathway to the heart at later stages of development. 3H-thymidine labeling of neurons in organ culture confirmed that neuronal precursors in the heart divide over a period of at least 3 weeks of development. Quantitative analysis of individual cardiac neurons subjected to different labeling and sampling protocols provided an estimate of their cell cycle length. It also showed that the rate of neuron proliferation during normal development matched the rate of neuron accumulation. Labeling DNA and blocking its synthesis indicated that the time of cardiac neuron differentiation was variable, but the range did not change as the site of cardiac neurogenesis shifted. On the other hand, the regular proliferation of cardiac neuron precursors during the first few days of development slowed or stopped at later times. This change in regulation of neuronal precursor proliferation occurred during their change in location.

Physiological development of a monosynaptic connection involved in an adult insect behavior.

Locust flight is an exclusively adult behavior whose neural basis has been extensively studied. The coordinated neural pattern underlying this behavior appears rapidly at the end of postembryonic development. This paper examines the ontogeny of elements of the nervous system involved in the behavior. Alternative extreme hypotheses are: 1) the neurons and synapses involved develop concomitant with the behavior, or 2) they are constructed early in development, and are activated at the appropriate time by, for example, the release of inhibition. These hypotheses were evaluated by selecting a synapse that is important in adult flight, and monitoring its physiological features during postembryonic development. The synapse between the forewing Stretch Receptor (SR) and the First Basalar (BA) motor neuron, two uniquely identified neurons, mediates a monosynaptic reflex which operates only in flight. The EPSP, initiated by SR in BA, was recorded intracellularly during the last four of six postembryonic instars. As early as third instar, the monosynaptic EPSP is present and appears to be as effective as in the adult. It also decrements and summates similarly in younger animals and adults. Therefore, some flight system synapses are present and effective throughout most of postembryonic development, and thus do not develop concomitant with the behavior.

Differentiation of an identified sensory neuron (SR) and associated structures (CTO) in grasshopper embryos.

The differentiation of an identified sensory neuron, the grasshopper wing hinge Stretch Receptor (SR), is examined throughout embryogenesis. The morphological features of the SR axon, as it finds its path from the peripheral cell body to the CNS, and the timing of this peripheral growth were determined by intracellular injection of Lucifer yellow. The course of growth of the SR axon within the CNS and the sequence of formation of the identified branches in its characteristic central arborization were investigated by silver intensification of cobalt-stained axons. In addition, intracellular recording from the cell body of SR was used to determine the onset of electrical excitability and the characteristics of the somal action potential. A brief account of the differentiation of the closely associated wing hinge Chordotonal Organ is also given. During differentiation, the cell bodies of SR and the first wing hinge Chordotonal Organ neuron (CTN1) extended processes and migrate posteriorly along a peripheral epithelial ridge. The cell bodies migrate up to 150 micrometers with a group of undifferentiated cells to a specific site at the posterior edge of the segment. As the SR and CTN1 cell bodies migrate, their trailing axons stretch across the epithelial ridge. These axons from the medial body wall nerve (1D2) that the axons of subsequent sensory neurons follow.

A nonrandom interneuronal pattern in the developing frog spinal cord.

In the developing spinal cord of the frog, Xenopus laevis, a population of interneurons assumes a pattern that represents a previously undescribed level of organization. Glyoxylic acid treatment and immunocytochemistry show that the neurons contain catecholamines and their synthetic enzyme, tyrosine hydroxylase. Cells are located within the ependymal layer of the floor plate region of the larval spinal cord. The cells have several processes including a long one that projects toward the brain without fasciculating with other labeled processes. In addition, the cytoplasm of the catecholaminergic cells extends into the central canal, showing that they are a population of cerebrospinal fluid-contacting neurons. The spatial domain of catecholaminergic neurons starts abruptly at the boundary between the hindbrain and spinal cord and continues to the tip of the tail. The neurons occupy two longitudinal columns within the sheet of floor plate cells, which includes cells that do not exhibit the catecholaminergic phenotype. Unlabeled cells are intercalated between catecholaminergic cells in each column, giving the labeled cells the appearance of being spaced along the length of the spinal cord. This general arrangement is evident at the time of hatching. Spatial analysis showed that the position of cells along a column is not random. The nonrandom behavior is due to cells being excluded from the area immediately surrounding other catecholaminergic cells. Further analysis showed that the cellular pattern lacks segmental or other periodic repeats. Ultimately, the location of a cell within a column depends upon the position of its closest catecholaminergic neighbor.

Morphogenesis of catecholaminergic interneurons in the frog spinal cord.

During embryonic and larval development of the frog Xenopus laevis, a bilateral population of cerebrospinal fluid-contacting neurons matures in the ventral spinal cord. These cells are catecholaminergic and form a dispersed or nonrandom pattern of spacing within each of their spinal cord columns. In order to test the mechanisms underlying pattern formation of these neurons, it is first necessary to understand their normal morphogenesis. Morphogenetic changes were examined by using immunocytochemistry for tyrosine hydroxylase as a cell marker. Immunoreactivity in spinal cord cells was detected as early as 1.4 days (stage 28) of embryonic development. Subsequently, these cells underwent changes in shape, and rapid, regressive changes in cell size. The population emerges gradually during development, but the major characteristic of nonrandom spacing, their dispersion from other catecholaminergic cells, is apparent at early stages of differentiation. Increases in cell density occur over an extended period of time and can be divided into an initial phase of large, rapid changes and a subsequent plateau phase of gradual changes. The two longitudinal columns of catecholaminergic cells that are characteristic of older animals become apparent just before hatching, when density increases until cells on both sides of the midline are present in the same region. Although the dispersed pattern exists within each column, cross-correlation analysis shows that there is a random relationship between cells in opposite columns. During larval development, the catecholaminergic cell domain expands in both a rostral and caudal direction. The morphogenetic changes of the catecholaminergic cell population begin to show how the cells become partitioned within the floor plate region of the spinal cord.

Morphogenesis of adrenergic cells in a frog parasympathetic ganglion.

The development of the parasympathetic cardiac ganglion of the frog Xenopus laevis was marked by the differentiation of a population of adrenergic small intensely fluorescent (SIF) cells. The neural crest contributes precursors for both SIF cells and the well-studied cholinergic cardiac ganglion neurons; this situation provided an opportunity to determine whether morphogenesis of the two cell types was correlated. Accordingly, we examined the initial differentiation, developmental regulation, and territorial domain of cardiac SIF cells for comparison with their cholinergic neuron neighbors. Adrenergic SIF cells were present during the time when the first cholinergic precursors were becoming postmitotic. Although SIF cells were present first, cholinergic neurons differentiated almost 16 times faster during the first week of embryonic and larval development and outnumbered SIF cells at all subsequent stages. Nonetheless, the accumulation of both cell types were correlated, since the ratio of cholinergic neurons to SIF cells remained at approximately 10 to 1 up to adult life. Early in development, SIF cells and cholinergic neurons were clustered in the sinus venosus portion of the atrium. The asymmetric distribution of cholinergic neurons within the atrium was lost but that of the SIF cells was maintained throughout life. These results identify relationships between the morphogenesis of two cell types in an autonomic ganglion and place constraints upon the cellular mechanisms that could produce the cells from their neural crest precursors.