The origin and evolution of terrestrial and Martian rock labyrinths

The morphological characteristics and evolutionary development of rock labyrinths on Earth (in sandstone, volcanics, and carbonates) are compared with those on Mars. On Earth rock labyrinths originate as parallel, an echelon, or intersecting narrow grabens, or develop where fault and joint networks are selectively eroded. Labyrinths frequently contain both downfaulted and erosional elements. Closed labyrinths contain depressions; open labyrinths do not, they are simple part of a fluvial network generally of low order. As closed labyrinths made up of intersecting grabens or made up of connected erosional depressions are extremely common on Mars, the research focussed on an understanding of these labyrinth types. Field investigations were carried out in Canyonlands National Park, Utah, and in the Chirachahua Mountains of Arizona. Martian labyrinths were investigated using Viking orbiter images. In addition, research was undertaken on apparent thermokarst features in Lunae Planum and Chryse Planitia where closed depressions are numerous and resemble atlas topography

Detecting Low-Velocity Impact Damage in Composite Plates via a Minimization of Measured and Simulated Origin Approach

In this paper, a new method for identifying impact locations applying a comparative simulated approach of minimization of measurement error against simulated data in a composite carbon plate-like structure using acoustic Lamb wave is proposed and reviewed. The purposed model detects impact locations by using an error minimizing algorithm based on the measured Lamb waves from an actual real impact and demonstrates a high-level of flexibility. Furthermore, the proposed model can be straightforwardly calibrated for different velocities and other parameters inherent in carbon-based structures, reducing the effects of the structure’s anisotropic properties. In particular, the time of arrival of an impact signal is calculated by applying wavelet transform and threshold crossing methods. Experiment results illustrate the effectiveness of the proposed method by presenting a very accurate detection rate of real low-velocity impacts on a carbon-based plate-like structure. This promising technique enables inspection and on-line monitoring of impacts on composite structures. Further developments of the suggested model are discussed, and are mainly focused on producing a velocity independent extension mode

MaGICC baryon cycle: The enrichment history of simulated disc galaxies

Using cosmological galaxy formation simulations from the MaGICC (Making Galaxies in a Cosmological Context) project, spanning stellar mass from ∼107 to 3 × 1010 M⊙, we trace the baryonic cycle of infalling gas from the virial radius through to its eventual participation in the star formation process. An emphasis is placed upon the temporal history of chemical enrichment during its passage through the corona and circumgalactic medium. We derive the distributions of time between gas crossing the virial radius and being accreted to the star-forming region (which allows for mixing within the corona), as well as the time between gas being accreted to the star-forming region and then ultimately forming stars (which allows for mixing within the disc). Significant numbers of stars are formed from gas that cycles back through the hot halo after first accreting to the star-forming region. Gas entering high-mass galaxies is pre-enriched in low-mass proto-galaxies prior to entering the virial radius of the central progenitor, with only small amounts of primordial gas accreted, even at high redshift (z ∼ 5). After entering the virial radius, significant further enrichment occurs prior to the accretion of the gas to the star-forming region, with gas that is feeding the star-forming region surpassing 0.1 Z⊙ by z = 0. Mixing with halo gas, itself enriched via galactic fountains, is thus crucial in determining the metallicity at which gas is accreted to the disc. The lowest mass simulated galaxy (Mvir ∼ 2 × 1010 M⊙, with M⋆ ∼ 107 M⊙), by contrast, accretes primordial gas through the virial radius and on to the disc, throughout its history. Much like the case for classical analytical solutions to the so-called ‘G-dwarf problem’, overproduction of low-metallicity stars is ameliorated by the interplay between the time of accretion on to the disc and the subsequent involvement in star formation – i.e. due to the inefficiency of star formation. Finally, gas outflow/metal removal rates from star-forming regions as a function of galactic mass are presented

The role of beta-lactamase-producing-bacteria in mixed infections

Beta-lactamase-producing bacteria (BLPB) can play an important role in polymicrobial infections. They can have a direct pathogenic impact in causing the infection as well as an indirect effect through their ability to produce the enzyme beta-lactamase. BLPB may not only survive penicillin therapy but can also, as was demonstrated in in vitro and in vivo studies, protect other penicillin-susceptible bacteria from penicillin by releasing the free enzyme into their environment. This phenomenon occurs in upper respiratory tract, skin, soft tissue, surgical and other infections. The clinical, in vitro, and in vivo evidence supporting the role of these organisms in the increased failure rate of penicillin in eradication of these infections and the implication of that increased rate on the management of infections is discussed

Trends in HIV testing and recording of HIV status in the UK primary care setting: a retrospective cohort study 1995-2005

Objectives: To provide nationally representative data on trends in HIV testing in primary care and to estimate the proportion of diagnosed HIV positive individuals known to general practitioners (GPs). Methods: We undertook a retrospective cohort study between 1995 and 2005 of all general practices contributing data to the UK General Practice Research Database (GPRD), and data on persons accessing HIV care (Survey of Prevalent HIV Infections Diagnosed). We identified all practice-registered patients where an HIV test or HIV positive status is recorded in their general practice records. HIV testing in primary care and prevalence of recorded HIV positive status in primary care were estimated. Results: Despite 11-fold increases in male testing and 19-fold increases in non-pregnant female testing between 1995 and 2005, HIV testing rates remained low in 2005 at 71.3 and 61.2 tests per 100 000 person years for males and females, respectively, peaking at 162.5 and 173.8 per 100 000 person years at 25–34 years of age. Inclusion of antenatal tests yielded a 129-fold increase in women over the 10-year period. In 2005, 50.7% of HIV positive individuals had their diagnosis recorded with a lower proportion in London (41.8%) than outside the capital (60.1%). Conclusion: HIV testing rates in primary care remain low. Normalisation of HIV testing and recording in primary care in antenatal testing has not been accompanied by a step change in wider HIV testing practice. Recording of HIV positive status by GPs remains low and GPs may be unaware of HIV-related morbidity or potential drug interactions

Primary care consultations and costs among HIV-positive individulas in UK primary care 1995-2005: a cohort study

Objectives: To investigate the role of primary care in the management of HIV and estimate primary care-associated costs at a time of rising prevalence. Methods: Retrospective cohort study between 1995 and 2005, using data from general practices contributing data to the UK General Practice Research Database. Patterns of consultation and morbidity and associated consultation costs were analysed among all practice-registered patients for whom HIV-positive status was recorded in the general practice record. Results: 348 practices yielded 5504 person-years (py) of follow-up for known HIV-positive patients, who consult in general practice frequently (4.2 consultations/py by men, 5.2 consultations/py by women, in 2005) for a range of conditions. Consultation rates declined in the late 1990s from 5.0 and 7.3 consultations/py in 1995 in men and women, respectively, converging to rates similar to the wider population. Costs of consultation (general practitioner and nurse, combined) reflect these changes, at £100.27 for male patients and £117.08 for female patients in 2005. Approximately one in six medications prescribed in primary care for HIV-positive individuals has the potential for major interaction with antiretroviral medications. Conclusion: HIV-positive individuals known in general practice now consult on a similar scale to the wider population. Further research should be undertaken to explore how primary care can best contribute to improving the health outcomes of this group with chronic illness. Their substantial use of primary care suggests there may be potential to develop effective integrated care pathways

The role of feedback in shaping the structure of the interstellar medium

We present an analysis of the role of feedback in shaping the neutral hydrogen (H I) content of simulated disc galaxies. For our analysis, we have used two realizations of two separate Milky Way-like (similar to L star) discs - one employing a conservative feedback scheme (McMaster Unbiased Galaxy Survey), the other significantly more energetic [Making Galaxies In a Cosmological Context (MaGICC)]. To quantify the impact of these schemes, we generate zeroth moment (surface density) maps of the inferred H I distribution; construct power spectra associated with the underlying structure of the simulated cold interstellar medium, in addition to their radial surface density and velocity dispersion profiles. Our results are compared with a parallel, self-consistent, analysis of empirical data from The H I Nearby Galaxy Survey (THINGS). Single power-law fits (P proportional to k(gamma)) to the power spectra of the stronger feedback (MaGICC) runs (over spatial scales corresponding to similar to 0.5 to similar to 20 kpc) result in slopes consistent with those seen in the THINGS sample (gamma similar to -2.5). The weaker feedback (MUGS) runs exhibit shallower power-law slopes (gamma similar to -1.2). The power spectra of the MaGICC simulations are more consistent though with a two-component fit, with a flatter distribution of power on larger scales (i.e. gamma similar to -1.4 for scales in excess of similar to 2 kpc) and a steeper slope on scales below similar to 1 kpc (gamma similar to -5), qualitatively consistent with empirical claims, as well as our earlier work on dwarf discs. The radial H I surface density profiles of the MaGICC discs show a clear exponential behaviour, while those of the MUGS suite are essentially flat; both behaviours are encountered in nature, although the THINGS sample is more consistent with our stronger (MaGICC) feedback runs