181 research outputs found
Questions on pure luminosity evolution for ellipticals
The explanation for the existence of an excess population of faint blue
galaxies (FBGs) has been a mystery for nearly two decades, and remains one of
the grand astronomical issues to date. Existing models cannot explain all of
the observational data such as galaxy number counts in the optical and infrared
passbands and the redshift distributions of galaxies. Here, by modelling the
morphological number counts derived from the Hubble Space Telescope, as well as
the number counts in optical and infrared passbands, and the redshift and color
distributions of galaxies obtained from ground-based observations, we show that
the `FBG problem' cannot be resolved if elliptical galaxies are assumed to have
formed in an instantaneous burst of star formation at high redshift with no
subsequent star formation events, which is just the conventional scenario for
formation and evolution of ellipticals. There exist great discrepancies between
the observed color distribution and the predicted distribution for
ellipticals by such a pure luminosity evolution (PLE) model in the context of
the conventional scenario. Neither can the mild evolution (i.e., the star
formation events have lasted for a longer time than those of the instantaneous
burst and passive evolution since the formation of galaxies) for ellipticals be
accepted in the context of PLE assumption. The introduction of dust extinction
also cannot save the PLE models. This conclusion holds for each of the three
cosmological models under consideration: flat, open and -dominated.
Hence, our investigation suggests that PLE assumption for elliptical galaxies
is questionable, and number evolution may be essential for ellipticals.Comment: 20pages (AASTeX), 10 eps figures, 4 tables, to appear in ApJ, 1999,
Vol. 51
A Longitudinal 6-Year Study of the Molecular Epidemiology of Clinical Campylobacter Isolates in Oxfordshire, United Kingdom
Temporal and seasonal trends in Campylobacter genotypes causing human gastroenteritis were investigated in a 6-year study of 3,300 recent isolates from Oxfordshire, United Kingdom. Genotypes (sequence types [ST]) were defined using multilocus sequence typing and assigned to a clonal complex (a cluster of related strains that share four or more identical alleles with a previously defined central genotype). A previously undescribed clonal complex (ST-464) was identified which, together with ST-42, ST-45, and ST-52 complexes, showed increasing incidence. Concurrently, the incidence of ST-574, ST-607, and ST-658 complexes declined. The relative frequencies of three clonal complexes (ST-45, ST-283, and ST-42) peaked during summer and those of two (ST-353 and ST-403) peaked during winter. Nine clonal complexes (ST-22, ST-45, ST-48, ST-61, ST-257, ST-283, ST-403, ST-658, and ST-677) were significantly associated with ciprofloxacin sensitivity (P < 0.05). Seven clonal complexes (ST-49, ST-206, ST-354, ST-446, ST-460, ST-464, and ST-607) were associated with ciprofloxacin resistance (P < 0.05). Clonal complexes exhibited changing incidence and differences in seasonality and antibiotic resistance phenotype. These data also demonstrated that detailed surveillance at a single site captures information which reflects that observed nationally
Cosmic Physics: The High Energy Frontier
Cosmic rays have been observed up to energies times larger than those
of the best particle accelerators. Studies of astrophysical particles (hadrons,
neutrinos and photons) at their highest observed energies have implications for
fundamental physics as well as astrophysics. Thus, the cosmic high energy
frontier is the nexus to new particle physics. This overview discusses recent
advances being made in the physics and astrophysics of cosmic rays and cosmic
gamma-rays at the highest observed energies as well as the related physics and
astrophysics of very high energy cosmic neutrinos. These topics touch on
questions of grand unification, violation of Lorentz invariance, as well as
Planck scale physics and quantum gravity.Comment: Topical Review Paper to be published in the Journal of Physics G, 50
page
Evolution of an Agriculture-Associated Disease Causing Campylobacter coli Clade: Evidence from National Surveillance Data in Scotland
The common zoonotic pathogen Campylobacter coli is an important cause of bacterial gastroenteritis worldwide but its evolution is incompletely understood. Using multilocus sequence type (MLST) data of 7 housekeeping genes from a national survey of Campylobacter in Scotland (2005/6), and a combined population genetic-phylogenetics approach, we investigated the evolutionary history of C. coli. Genealogical reconstruction of isolates from clinical infection, farm animals and the environment, revealed a three-clade genetic structure. The majority of farm animal, and all disease causing genotypes belonged to a single clade (clade 1) which had comparatively low synonymous sequence diversity, little deep branching genetic structure, and a higher number of shared alleles providing evidence of recent clonal decent. Calibration of the rate of molecular evolution, based on within-species genetic variation, estimated a more rapid rate of evolution than in traditional estimates. This placed the divergence of the clades at less than 2500 years ago, consistent with the introduction of an agricultural niche having had an effect upon the evolution of the C. coli clades. Attribution of clinical isolate genotypes to source, using an asymmetric island model, confirmed that strains from chicken and ruminants, and not pigs or turkeys, are the principal source of human C. coli infection. Taken together these analyses are consistent with an evolutionary scenario describing the emergence of agriculture-associated C. coli lineage that is an important human pathogen
A Novel Campylobacter jejuni Sequence Type from a Culture-Negative Patient in The Gambia
The introduction of molecular diagnostic methods is crucial for improved understanding of the aetiology and epidemiology of bacterial infections in communities in resource poor settings. A blood sample from a 7 month old patient diagnosed with malaria in 2001 in a Gambian outpatient clinic was reported as culture negative after it was subjected to traditional bacterial culture protocols. We re-addressed the analysis of the blood sample from this case more recently (after 6.5 years in archival storage) in pilot work establishing 16S rRNA PCR in our molecular laboratory. Initial 16S rRNA PCR results confirmed the presence of bacterial DNA in the sample. 16S rRNA sequence analysis identified the organism as Campylobacter spp. In light of the molecular evidence we successfully grew the organism using appropriate culture conditions and subsequently biochemically confirmed that the isolate was Campylobacter jejuni. PCR and DNA sequencing of a set of seven C. jejuni housekeeping genes and in silico Multilocus Sequence Typing (MLST) analysis revealed that the isolate exhibits a novel sequence type (ST) of C. jejuni (ST 2928) and belongs to ST-443 clonal complex. This study demonstrates the potential for molecular tools to enhance the diagnosis of bacterial infections, which remain a major killer globally, not least in children in the developing world. Improvements in diagnostics are needed, and will be important not only for sick individuals but also for populations, where better measures of disease burden will contribute significantly to the improvement of public health policy
Laparoscopic adjustable banded roux-en-y gastric bypass as a primary procedure for the super-super-obese (body mass index > 60 kg/m2)
<p>Abstract</p> <p>Background</p> <p>Currently, there is no consensus opinion regarding the optimal procedure of choice in super-super-morbid obesity (Body mass index, BMI > 60 kg/m2). Roux-en-Y gastric bypass (RYGB) is associated with failure to achieve or maintain 50% excess weight loss (EWL) or BMI < 35 in approximately 15% of patients. Also, percent EWL is significantly less after 1-year in the super-super-obese group as compared with the less obese group and many patients are still technically considered to be obese (lowest post-surgical BMI > 35) following RYGB surgery in this group. The addition of adjustable gastric band (AGB) to RYGB has been reported as a revisional procedure but this combined bariatric procedure has not been explored as a primary operation.</p> <p>Methods</p> <p>In a primary laparoscopic RYGB, an AGB is drawn around the gastric pouch through a small opening between the blood vessels on the lesser curve and the gastric pouch. The band is then fixed by suturing the gastric remnant to the gastric pouch both above and below the band to prevent slippage.</p> <p>Results</p> <p>Between November 2009 and March 2010, 6 consecutive super-super-obese patients underwent a primary laparoscopic adjustable banded Roux-en-Y gastric bypass procedure at our institution. One male patient (21 years, BMI 70 kg/mÂČ) developed a pneumonia postoperatively. No other postoperative complications were observed.</p> <p>Conclusion</p> <p>To the best of our knowledge, this is the first series of patients that underwent a laparoscopic adjustable banded RYGB as a primary operation for the super-super obese in the indexed literature. With the combined procedure, a sequential action mechanism for weight loss is to be expected. The restrictive, malabsorptive and hormonal working mechanism of the RYGB will induce weight loss from the start reaching a stabilised plateau of weight after 12 - 18 months. At that time, filling of the band can be started resulting in further gastric pouch restriction and increased weight loss. Moreover, besides improving the results of total weight loss, a gradual filling of the band can as well prevent the RYGB patient from weight regain if restriction would fade away with time.</p
Recording behaviour of indoor-housed farm animals automatically using machine vision technology: a systematic review
Large-scale phenotyping of animal behaviour traits is time consuming and has led to increased demand for technologies that can automate these procedures. Automated tracking of animals has been successful in controlled laboratory settings, but recording from animals in large groups in highly variable farm settings presents challenges. The aim of this review is to provide a systematic overview of the advances that have occurred in automated, high throughput image detection of farm animal behavioural traits with welfare and production implications. Peer-reviewed publications written in English were reviewed systematically following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. After identification, screening, and assessment for eligibility, 108 publications met these specifications and were included for qualitative synthesis. Data collected from the papers included camera specifications, housing conditions, group size, algorithm details, procedures, and results. Most studies utilized standard digital colour video cameras for data collection, with increasing use of 3D cameras in papers published after 2013. Papers including pigs (across production stages) were the most common (n = 63). The most common behaviours recorded included activity level, area occupancy, aggression, gait scores, resource use, and posture. Our review revealed many overlaps in methods applied to analysing behaviour, and most studies started from scratch instead of building upon previous work. Training and validation sample sizes were generally small (mean±s.d. groups = 3.8±5.8) and in data collection and testing took place in relatively controlled environments. To advance our ability to automatically phenotype behaviour, future research should build upon existing knowledge and validate technology under commercial settings and publications should explicitly describe recording conditions in detail to allow studies to be reproduced
Distribution and Genetic Profiles of Campylobacter in Commercial Broiler Production from Breeder to Slaughter in Thailand
Poultry and poultry products are commonly considered as the major vehicle of Campylobacter infection in humans worldwide. To reduce the number of human cases, the epidemiology of Campylobacter in poultry must be better understood. Therefore, the objective of the present study was to determine the distribution and genetic relatedness of Campylobacter in the Thai chicken production industry. During June to October 2012, entire broiler production processes (i.e., breeder flock, hatchery, broiler farm and slaughterhouse) of five broiler production chains were investigated chronologically. Representative isolates of C. jejuni from each production stage were characterized by flaA SVR sequencing and multilocus sequence typing (MLST). Amongst 311 selected isolates, 29 flaA SVR alleles and 17 sequence types (STs) were identified. The common clonal complexes (CCs) found in this study were CC-45, CC-353, CC-354 and CC-574. C. jejuni isolated from breeders were distantly related to those isolated from broilers and chicken carcasses, while C. jejuni isolates from the slaughterhouse environment and meat products were similar to those isolated from broiler flocks. Genotypic identification of C. jejuni in slaughterhouses indicated that broilers were the main source of Campylobacter contamination of chicken meat during processing. To effectively reduce Campylobacter in poultry meat products, control and prevention strategies should be aimed at both farm and slaughterhouse levels
Response of a Specialist Bat to the Loss of a Critical Resource
Human activities have negatively impacted many species, particularly those with unique traits that restrict their use of resources and conditions to specific habitats. Unfortunately, few studies have been able to isolate the individual and combined effects of different threats on population persistence in a natural setting, since not all organisms can be associated with discrete habitat features occurring over limited spatial scales. We present the results of a field study that examines the short-term effects of roost loss in a specialist bat using a conspicuous, easily modified resource. We mimicked roost loss in the natural habitat and monitored individuals before and after the perturbation to determine patterns of resource use, spatial movements, and group stability. Our study focused on the disc-winged bat Thyroptera tricolor, a species highly morphologically specialized for roosting in the developing furled leaves of members of the order Zingiberales. We found that the number of species used for roosting increased, that home range size increased (before: mean 0.14±SD 0.08 ha; after: 0.73±0.68 ha), and that mean association indices decreased (before: 0.95±0.10; after: 0.77±0.18) once the roosting habitat was removed. These results demonstrate that the removal of roosting resources is associated with a decrease in roost-site preferences or selectivity, an increase in mobility of individuals, and a decrease in social cohesion. These responses may reduce fitness by potentially increasing energetic expenditure, predator exposure, and a decrease in cooperative interactions. Despite these potential risks, individuals never used roost-sites other than developing furled leaves, suggesting an extreme specialization that could ultimately jeopardize the long-term persistence of this species' local populations
The Efficacy of Energy-Restricted Diets in Achieving Preoperative Weight Loss for bariatric Pateints: A Systematic Review
The final publication is available at Springer via https://doi.org/10.1007/s11695-018-3451-1In bariatric practice, a preoperative weight loss of at least 5% is recommended. However, the hypocaloric diets prescribed vary
and no consensus exists. This study examined the efficacy of preoperative diets in achieving 5% weight loss. From a systematic
literature search, eight randomised controlled trials (n = 862) were identified. Half of the trials used a Bvery-low-calorie diet^
whilst the rest employed a Blow-calorie diet^. Only five diets achieved â„ 5% weight loss over varying durations and energy
intakes. By inference, compliance with a 700â1050 kcal (2929â4393 kJ) diet, consisting of moderate carbohydrate, high protein
and low/moderate fat, for 3 weeks is likely to achieve 5% weight loss. A low-carbohydrate diet (< 20 g/day) may achieve this
target within a shorter duration. Additional research is required to validate these conclusions
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