423 research outputs found
Modelling the advection of vertically migrating shrimp larvae
The role of larval advection in determining the complex, large-scale patterns of immigration of penaeid postlarvae in the Gulf of Carpentaria is investigated by modelling the interaction between diurnal vertical migration of larvae with wind-forced and tidal currents. Eight vertical migration schemes are modelled in which both the timing of the migration and the position of the larvae in the water column are varied. These schemes are then coupled with both two-dimensional and three-dimensional models of the currents of the Gulf, to examine horizontal advection of larvae. When the larvae migrate vertically with a diurnal period, their horizontal advection is enhanced. The largest horizontal advection distances occur when the larvae move diurnally from the water column into the bottom boundary layer. Advection distances of up to 165 km are possible during the two to three week planktonic larval period. This distance corresponds to, and may determine, the offshore extent of the adult distribution. The onshore advection pattern of larvae varies in both space and time (on a seasonal scale) and is consistent with the observed spatial and temporal recruitment patterns seen by sampling postlarval immigation into nursery areas. During the period of highest reproductive activity (March) in the southeastern corner of the Gulf, the area of the largest fishery, the advection of larvae is offshore and little recruitment of postlarvae to the nursery grounds is accomplished. Six months later, during the next period of reproductive activity (October), when the number of spawning female shrimp is much lower, the phase of the tidal currents, relative to the day-night cycle, has progressed 180° and the larvae are moved onshore allowing postlarvae access to their estuarine nursery grounds several months prior to the main fishing season (March)
Approaches to canine health surveillance
Effective canine health surveillance systems can be used to monitor disease in the general population, prioritise disorders for strategic control and focus clinical research, and to evaluate the success of these measures. The key attributes for optimal data collection systems that support canine disease surveillance are representativeness of the general population, validity of disorder data and sustainability. Limitations in these areas present as selection bias, misclassification bias and discontinuation of the system respectively. Canine health data sources are reviewed to identify their strengths and weaknesses for supporting effective canine health surveillance. Insurance data benefit from large and well-defined denominator populations but are limited by selection bias relating to the clinical events claimed and animals covered. Veterinary referral clinical data offer good reliability for diagnoses but are limited by referral bias for the disorders and animals included. Primary-care practice data have the advantage of excellent representation of the general dog population and recording at the point of care by veterinary professionals but may encounter misclassification problems and technical difficulties related to management and analysis of large datasets. Questionnaire surveys offer speed and low cost but may suffer from low response rates, poor data validation, recall bias and ill-defined denominator population information. Canine health scheme data benefit from well-characterised disorder and animal data but reflect selection bias during the voluntary submissions process. Formal UK passive surveillance systems are limited by chronic under-reporting and selection bias. It is concluded that active collection systems using secondary health data provide the optimal resource for canine health surveillance
An epidemiological study of diabetes mellitus in dogs attending first opinion practice in the UK
Objectives: To estimate the prevalence of canine diabetes mellitus (DM) in primarycare clinics in England, to identify risk factors associated with DM and to describe the survival of affected dogs.
Methods: Cases of DM were identified within the electronic patient records of 89 small-animal practices. A nested case-control study identified risk factors for the diagnosis of DM using logistic regression models. Cox proportional hazards models were used to analyse variables associated with survival.
Results: Four-hundred and thirty-nine canine DM cases were identified, giving an apparent prevalence of 0.34% (95% confidence interval 0.31 - 0.37%). Neutered males were at an increased risk of diabetes compared to entire males, whereas neutering was not associated with DM in females. Compared with crossbred dogs, Yorkshire terriers had increased odds, whereas German shepherd dogs and golden retrievers had lower odds of DM. Being classified as overweight and having a diagnosis of pancreatitis, hyperadrenocorticism or a urinary tract infection were positively associated with DM. Older dogs and those diagnosed with pancreatitis had a higher hazard of death, whereas insured and neutered dogs had a lower hazard.
Clinical significance: This study provides an objective assessment of canine DM using primary-care veterinary practice data and is a valuable benchmark against which future epidemiological trends in DM can be assessed and improvements in the management of DM in primary-care practice can be judged
Prevalence of disorders recorded in Cavalier King Charles Spaniels attending primary-care veterinary practices in England
Background: Concerns have been raised over breed-related health issues in purebred dogs, but reliable prevalence estimates for disorders within specific breeds are sparse. Electronically stored patient health records from primary-care practice are emerging as a useful source of epidemiological data in companion animals. This study used large volumes of health data from UK primary-care practices participating in the VetCompass animal health surveillance project to evaluate in detail the disorders diagnosed in a random selection of over 50% of dogs recorded as Cavalier King Charles Spaniels (CKCSs). Confirmation of breed using available microchip and Kennel Club (KC) registration data was attempted. Results: In total, 3624 dogs were recorded as CKCSs within the VetCompass database of which 143 (3.9%) were confirmed as KC-registered via microchip identification linkage of VetCompass to the KC database. 1875 dogs (75 KC registered and 1800 of unknown KC status, 52% of both groups) were randomly sampled for detailed clinical review. Clinical data associated with veterinary care were recorded in 1749 (93.3%) of these dogs. The most common specific disorders recorded during the study period were heart murmur (541 dogs, representing 30.9% of study group), diarrhoea of unspecified cause (193 dogs, 11.0%), dental disease (166 dogs, 9.5%), otitis externa (161, 9.2%), conjunctivitis (131, 7.4%) and anal sac infection (129, 7.4%). The five most common disorder categories were cardiac (affecting 31.7% of dogs), dermatological (22.2%), ocular (20.6%), gastrointestinal (19.3%) and dental/periodontal disorders (15.2%). Discussion and conclusions: Study findings suggest that many of the disorders commonly affecting CKCSs are largely similar to those affecting the general dog population presented for primary veterinary care in the UK. However, cardiac disease (and MVD in particular) continues to be of particular concern in this breed
Epidemiological associations between brachycephaly and upper respiratory tract disorders in dogs attending veterinary practices in England
Background: Brachycephalic dog breeds are increasingly common. Canine brachycephaly has been associated with upper respiratory tract (URT) disorders but reliable prevalence data remain lacking. Using primary-care veterinary clinical data, this study aimed to report the prevalence and breed-type risk factors for URT disorders in dogs. Results: The sampling frame included 170,812 dogs attending 96 primary-care veterinary clinics participating within the VetCompass Programme. Two hundred dogs were randomly selected from each of three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) and three common small-to medium sized breed types (moderate brachycephalic: Yorkshire Terrier and non-brachycephalic: Border Terrier and West Highland White Terrier). Information on all URT disorders recorded was extracted from individual patient records. Disorder prevalence was compared between groups using the chi-squared test or Fisher’s test, as appropriate. Risk factor analysis used multivariable logistic regression modelling. During the study, 83 (6.9 %) study dogs died. Extreme brachycephalic dogs (median longevity: 8.6 years, IQR: 2.4-10.8) were significantly younger at death than the moderate and non-brachycephalic group of dogs (median 12.7 years, IQR 11.1-15.0) (P \u3c 0.001). A higher proportion of deaths in extreme brachycephalic breed types were associated with URT disorders (4/24 deaths, 16.7 %) compared with the moderate and non-brachycephalic group (0/59 deaths, 0.0 %) (P = 0.001). The prevalence of having at least one URT disorder in the extreme brachycephalic group was higher (22.0 %, 95 % confidence interval (CI): 18.0-26.0) than in the moderate and non-brachycephalic group (9.7 %, 95 % CI: 7.1-12.3, P \u3c 0.001). The prevalence of URT disorders varied significantly by breed type: Bulldogs 19.5 %, French Bulldogs 20.0 %, Pugs 26.5 %, Border Terriers 9.0 %, West Highland White Terriers 7.0 % and Yorkshire Terriers 13.0 % (P \u3c 0.001). After accounting for the effects of age, bodyweight, sex, neutering and insurance, extreme brachycephalic dogs had 3.5 times (95 % CI: 2.4-5.0, P \u3c 0.001) the odds of at least one URT disorder compared with the moderate and non-brachycephalic group. Conclusions: In summary, this study reports that URT disorders are commonly diagnosed in Bulldog, French Bulldog, Pug, Border Terrier, WHWT and Yorkshire Terrier dogs attending primary-care veterinary practices in England. The three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) were relatively short-lived and predisposed to URT disorders compared with three other small-to-medium size breed types that are commonly owned (moderate brachycephalic Yorkshire Terrier and non-brachycephalic: Border Terrier and WHWT). Conclusions: In summary, this study reports that URT disorders are commonly diagnosed in Bulldog, French Bulldog, Pug, Border Terrier, WHWT and Yorkshire Terrier dogs attending primary-care veterinary practices in England. The three extreme brachycephalic breed types (Bulldog, French Bulldog and Pug) were relatively short-lived and predisposed to URT disorders compared with three other small-to-medium size breed types that are commonly owned (moderate brachycephalic Yorkshire Terrier and non-brachycephalic: Border Terrier and WHWT)
Discovery of a ~1 Hz quasi-periodic oscillation in the low-mass X-ray binary 4U 1746-37
We have discovered a ~1 Hz quasi-periodic oscillation (QPO) in the persistent
X-ray emission and during type I X-ray bursts of the globular cluster source,
dipper and low-mass X-ray binary (LMXB) 4U 1746-37. The QPO properties resemble
those of QPOs found recently in the LMXB dippers 4U 1323-62, and EXO 0748-676,
which makes 4U 1746-37 the third source known to exhibit this type of QPOs. We
present evidence for X-ray spectral changes in this source similar to those
observed in LMXBs referred to as atoll sources. We detect two states, a low
intensity and spectrally hard state, and a higher intensity and spectrally soft
state. This may explain the different spectral characteristics reported for 4U
1746-37 earlier. The high intensity state resembles the banana branch state of
atoll sources. The QPOs are only seen in the low intensity state, and are
absent when the source is in the banana branch. This strongly suggests that
either the accretion disk or an extended central source change shape between
the low intensity state and the banana branch. Twelve bursts were detected, of
which 5 took place while the source was on the banana branch and 7 when the
source was in the low intensity state. The bursts occurring on the banana
branch had an e-folding time ~3 times longer than those which occurred in the
low intensity state. Whereas previously detected dips showed only a decrease in
count rate of ~15%, we found in one observation a dip in which the count rate
dropped from ~200 counts per second to ~20 counts per second. This dip lasted
only ~250 seconds, during which clear spectral hardening occured. This is the
first time strong evidence for spectral changes during a dip are reported for
this source.Comment: 17 pages, accepted for publication in Ap
Rationale for and protocol of a multi-national population-based bacteremia surveillance collaborative
<p>Abstract</p> <p>Background</p> <p>Bloodstream infections are frequent causes of human illness and cause major morbidity and death. In order to best define the epidemiology of these infections and to track changes in occurrence, adverse outcome, and resistance rates over time, population based methodologies are optimal. However, few population-based surveillance systems exist worldwide, and because of differences in methodology inter-regional comparisons are limited. In this report we describe the rationale and propose first practical steps for developing an international collaborative approach to the epidemiologic study and surveillance for bacteremia.</p> <p>Findings</p> <p>The founding collaborative participants represent six regions in four countries in three continents with a combined annual surveillance population of more than 8 million residents.</p> <p>Conclusion</p> <p>Future studies from this collaborative should lead to a better understanding of the epidemiology of bloodstream infections.</p
Multiwavelength study of Cygnus A II. X-ray inverse-Compton emission from a relic counterjet and implications for jet duty-cycles
The duty-cycle of powerful radio galaxies and quasars such as the prototype
Cygnus A is poorly understood. X-ray observations of inverse-Compton scattered
Cosmic Microwave Background (ICCMB) photons probe lower Lorentz-factor
particles than radio observations of synchrotron emission. Comparative studies
of the nearer and further lobes, separated by many 10s of kpc and thus 10s of
thousands of years in light-travel time, yield additional temporal resolution
in studies of the lifecycles. We have co-added all archival Chandra ACIS-I data
and present a deep 200 ks image of Cygnus A. This deep image reveals the
presence of X-ray emission from a counterjet i.e. a jet receding from Earth and
related to a previous episode of jet activity. The non-thermal X-ray emission,
we interpret as ICCMB radiation. There is an absence of any discernible X-ray
emission associated with a jet flowing towards Earth. We conclude that: (1) The
emission from a relic jet, indicates a previous episode of jet activity, that
took place earlier than the current jet activity appearing as synchrotron radio
emission. (2) The presence of X-ray emission from a relic counterjet of Cygnus
A and the absence of X-ray emission associated with any relic approaching jet
constrains the timescale between successive episodes of jet activity to ~10^6
years. (3) Transverse expansion of the jet causes expansion losses which shifts
the energy distribution to lower energies. (4) Assuming the electrons cooled
due to adiabatic expansion, the required magnetic field strength is
substantially smaller than the equipartition magnetic field strength. (5) A
high minimum Lorentz factor for the distribution of relativistic particles in
the current jet, of a few 10^3, is ejected from the central nucleus of this
active galaxy. Abridged.Comment: Accepted for publication by MNRAS, 8 pages Dates in Table 1 correcte
Controls on Dissolved Cobalt in Surface Waters of the Sargasso Sea: Comparisons with Iron and Aluminum
Dissolved cobalt (dCo), iron (dFe) and aluminum (dAl) were determined in water column samples along a meridional transect (∼31°N to 24°N) south of Bermuda in June 2008. A general north-to-south increase in surface concentrations of dFe (0.3-1.6 nM) and dAl (14-42 nM) was observed, suggesting that aerosol deposition is a significant source of dFe and dAl, whereas no clear trend was observed. for near-surface dCo concentrations. Shipboard aerosol samples indicate fractional solubility values of 8-100% for aerosol Co, which are significantly higher than corresponding estimates of the solubility of aerosol Fe (0.44-45%). Hydrographic observations and analysis of time series rain samples from Bermuda indicate that wet deposition accounts for most (\u3e80%) of the total aeolian flux of Co, and hence a significant proportion of the atmospheric input of dCo to our study region. Our aerosol data imply that the atmospheric input of dCo to the Sargasso Sea is modest, although this flux may be more significant in late summer. The water column dCo profiles reveal a vertical distribution that predominantly reflects nutrient-type behavior, vs. scavenged-type behavior for dAl, and a hybrid of nutrient- and scavenged-type behavior for dFe. Mesoscale eddies also appear to impact on the vertical distribution of dCo. The effects of biological removal of dCo from the upper water column were apparent as pronounced sub-surface min. (21 ± 4 pM dCo), coincident with maxima in Prochlorococcus abundance. These observations imply that Prochlorococcus plays a major role in removing dCo from the euphotic zone, and that the availability of dCo may regulate Prochlorococcus growth in the Sargasso Sea
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