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The article highlights the potential threat of the Peters's Rock Agama, a non-native species from sub-Saharan Africa, to reptile diversity in the Lesser Antilles. The introduction of non-native species is causing a loss of biodiversity in the region, which is known for its unique and endemic species. The Peters's Rock Agama has already been sighted in Florida, the Bahamas, and Tortola, and if it establishes a population in the Lesser Antilles, it could negatively impact native species through predation and competition. The article urges local stakeholders to be vigilant and report any sightings to relevant authorities. Additionally, the text emphasizes the importance of state authorities, transport providers, and shipping providers in preventing the spread of invasive species and calls for collaboration between Florida-based conservationists and alien species experts to address this threat. [Extracted from the article]

Various Cs-137 source distributions were imaged with the UCL (University College London) Germanium Compton camera. A reduced camera setup was used consisting of 16 pixels of 4 x 4 x 4 [mm.sup.3] size each in the front detector and 4 pixels of 4 x 4 x 10 [mm.sup.3] size each in the back detector. The preamplifier signal was digitised by GRT4 VME readout cards. The deposited energy was extracted online using the moving window deconvolution technique implemented in the FPGAs of the GRT4 cards. A pulse height determination algorithm leading to worse energy resolution was applied offline for comparative studies. For the image reconstruction ITEM (Imaginary Time Expectation Maximization) was used, an iterative algorithm based on quantum mechanics energy minimization. ITEM is very flexible and can easily be applied to every possible Compton camera geometry. An improved backprojection taking into account the changing camera sensitivity in the image space has been used and its limitations investigated. ITEM is shown to work very fast. An image with 10000 pixels can be reconstructed from 40000 events in about 20 s using one 3 GHz Pentium CPU. Data was taken with point, line and circular sources in a plane 2 cm from the front detector. Through analysis of point and line spread functions the angular resolution of the camera was estimated to be around 10 deg. Index Terms--Compton imaging, gamma-ray, Germanium, ITEM, medical imaging, nuclear medicine, reconstruction.

Purpose: To provide an x-ray phase contrast imaging (XPCI) method working with conventional sources that could be readily translated into clinical practice. XPCI shows potential in synchrotron studies but attempts at translating it for use with conventional sources are subject to limitations in terms of field of view, stability, exposure time, and possibly most importantly, delivered dose. Methods: Following the adaptation of our 'edge-illumination' XPCI technique for use with conventional x-ray sources through the use of x-ray masks, the authors have further modified the design of such masks to allow further reducing the dose delivered to the sample without affecting the phase sensitivity of the method. Results: The authors have built a prototype based on the new mask design and used it to image ex vivo breast tissue samples containing malignant lesions. The authors compared images acquired with this prototype to those obtained with a conventional system. The authors demonstrate and quantify image improvements, especially in terms of microcalcification detection. On calcifications detected also by the conventional system, the authors measure contrast increases from five to nine fold; calcifications and other features were also detected which are completely invisible in the conventional image. Dose measurements confirmed that the above enhancements were achieved while delivering doses compatible with clinical practice. Conclusions: The authors obtained phase-related image enhancements in mammography by means of a system built with components available off-the-shelf that operates under exposure time and dose conditions compatible with clinical practice. This opens the way to a straightforward translation of phase enhanced imaging methods into clinical practice. [ABSTRACT FROM AUTHOR]

Methods for dealing with tied event times in the Cox proportional hazards model are well developed. Also, the partial likelihood provides a natural way to handle covariates that change over time. However, ties between event times and the times that discrete time-varying covariates change have not been systematically studied in the literature. In this article, we discuss the default behavior of current software and propose some simple methods for dealing with such ties. A simulation study shows that the default behavior of current software can lead to biased estimates of the coefficient of a binary time-varying covariate and that two proposed methods (Random Jitter and Equally Weighted) reduce estimation bias. The proposed methods can be easily implemented with existing software. The methods are illustrated on the well-known Stanford heart transplant data and data from a study on intimate partner violence and smoking. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose: This study investigates the image quality of tomosynthesis slices obtained from several acquisition sets with synchrotron radiation using a breast phantom incorporating details that mimic various breast lesions, in a heterogeneous background. Methods: A complex Breast phantom (MAMMAX) with a heterogeneous background and thickness that corresponds to 4.5 cm compressed breast with an average composition of 50% adipose and 50% glandular tissue was assembled using two commercial phantoms. Projection images using acquisition arcs of 24°, 32°, 40°, 48°, and 56° at incident energy of 17 keV were obtained from the phantom with the synchrotron radiation for medical physics beamline at ELETTRA Synchrotron Light Laboratory. The total mean glandular dose was set equal to 2.5 mGy. Tomograms were reconstructed with simple multiple projection algorithm (MPA) and filtered MPA. In the latter case, a median filter, a sinc filter, and a combination of those two filters were applied on the experimental data prior to MPA reconstruction. Visual inspection, contrast to noise ratio, contrast, and artifact spread function were the figures of merit used in the evaluation of the visualisation and detection of low- and high-contrast breast features, as a function of the reconstruction algorithm and acquisition arc. To study the benefits of using monochromatic beams, single projection images at incident energies ranging from 14 to 27 keV were acquired with the same phantom and weighted to synthesize polychromatic images at a typical incident x-ray spectrum with W target. Results: Filters were optimised to reconstruct features with different attenuation characteristics and dimensions. In the case of 6 mm low-contrast details, improved visual appearance as well as higher contrast to noise ratio and contrast values were observed for the two filtered MPA algorithms that exploit the sinc filter. These features are better visualized at extended arc length, as the acquisition arc of 56° with 15 projection images demonstrates the highest image reconstruction quality. For microcalcifications, filtered MPA implemented with a combination of median and sinc filters indicates better feature appearance due to efficient suppression of background tissue. The image quality of these features is less sensitive to the acquisition arc. Calcifications with size ranging from 170 to 500 μm, like the ones presently studied, are well identified and visualized for all arcs used. The comparison of single projection images obtained under different beam conditions showed that the use of monochromatic beam can produce an image with higher contrast and contrast to noise ratio compared to an image corresponding to a polychromatic beam even when the latter is acquired with double incident exposure. Conclusions: Filter optimization in respect to the type of feature characteristics is important before the reconstruction. The MPA combined with median and sinc filters results in improved reconstruction of microcalcifications and low-contrast features. The latter are better visualized at extended arc length, while microcalcifications are less sensitive to this acquisition parameter. Use of monochromatic beams may result in tomographic images with higher contrast acquired at lower incident exposures. [ABSTRACT FROM AUTHOR]

This study represents a survey performed among staff who, according to the Ionising Radiation (Medical Exposures) Regulations of 2000 (IRMER), are responsible for justifying radiological examinations in the UK. The aim of the survey is to map the current situation regarding knowledge of risks from X-ray exposures and the criteria used for their justification. An anonymous electronic questionnaire was emailed to 219 radiologists and radiographers of five National Health Service hospitals. The questions were designed to investigate the way the sample group defines/assesses risk and benefit when justifying medical exposures, and to test their knowledge on radiation doses, risk communication, and on relevant national legislation. The majority of the respondents are aware of the relevant legislation/guidelines. Patient's medical condition, age and sex, and alternative techniques using less or no ionising radiation are the main criteria used for justification. However, when estimating the effective dose of various examinations in chest radiograph equivalents, the majority of the responses were incorrect. Although there is good knowledge of legislation around justification of medical exposures, there seems to be a lack of knowledge on radiation doses and risks among IRMER practitioners. [ABSTRACT FROM PUBLISHER]

Nest predation is an important practical challenge for the conservation of egg-laying reptiles, with the potential to reduce hatchling recruitment and slow the recovery of threatened populations. Accurately forecasting where and when predation will occur has the potential to optimize predation management. Survival analysis, a set of statistical techniques recently popularized in studies of avian nest success, provides a unique approach for modelling variation in egg mortality risk throughout development. We used Cox proportional hazards regression to model the survival of sea turtle eggs from predation by the small Asian mongoose Herpestes javanicus, a widely introduced and destructive sea turtle nest predator in the Caribbean. We evaluated the ability of models to predict egg survival using 7 years of nest predation data for critically endangered hawksbill sea turtles Eretmochelys imbracata in Barbados. Daily predation risk was the highest for freshly laid nests, decreasing rapidly with nest age but increasing again near the end of development. Predation risk was the highest in and near patches of beach vegetation, increased over the nesting season and increased with nest density on the open beach but not in vegetation. Survival models calibrated using data from 2004 to 2005 showed excellent discrimination and ≥84% accuracy when predicting the fate of nests from previous years. Our study provides the first quantification of the daily variation in predation risk for incubating turtle eggs, revealing a narrow time window early in development during which the application of predation reduction measures is likely to have the greatest impact on nest survival. More generally, we demonstrate the utility of survival analysis for generating fine-scale predictions of spatiotemporal variation in turtle egg mortality, providing a flexible tool for the conservation of sea turtles and other egg-laying reptiles. [ABSTRACT FROM AUTHOR]

The article examines the origin and characteristics of hares in Barbados. Based on a study by C. H. W. Feilden, it is reported that European hares, Lepus europaeus, were shipped to Barbados in 1842 in which they were bred in captivity and escaped after a heavy rain destroyed their enclosure. It notes that by the 1940s, hares became common in the country and that they were abundant in open and grassy areas. Surveys on the hares of Barbados also reveal that part of their diet was a sugar cane trash and stalks left in the fields or cart roads by sugar cane workers. It also mentions that apart from sugar cane trash, hares also eat crops, slips of plants, and the bark of young trees.

Purpose: In this article, the image quality of reconstructed volumes by four algorithms for digital tomosynthesis, applied in the case of breast, is investigated using synchrotron radiation. Methods: An angular data set of 21 images of a complex phantom with heterogeneous tissue-mimicking background was obtained using the SYRMEP beamline at ELETTRA Synchrotron Light Laboratory, Trieste, Italy. The irradiated part was reconstructed using the multiple projection algorithm (MPA) and the filtered backprojection with ramp followed by hamming windows (FBR-RH) and filtered backprojection with ramp (FBP-R). Additionally, an algorithm for reducing the noise in reconstructed planes based on noise mask subtraction from the planes of the originally reconstructed volume using MPA (MPA-NM) has been further developed. The reconstruction techniques were evaluated in terms of calculations and comparison of the contrast-to-noise ratio (CNR) and artifact spread function. Results: It was found that the MPA-NM resulted in higher CNR, comparable with the CNR of FBP-RH for high contrast details. Low contrast objects are well visualized and characterized by high CNR using the simple MPA and the MPA-NM. In addition, the image quality of the reconstructed features in terms of CNR and visual appearance as a function of the initial number of projection images and the reconstruction arc was carried out. Slices reconstructed with more input projection images result in less reconstruction artifacts and higher detail CNR, while those reconstructed from projection images acquired in reduced angular range causes pronounced streak artifacts. Conclusions: Of the reconstruction algorithms implemented, the MPA-NM and MPA are a good choice for detecting low contrast objects, while the FBP-RH, FBP-R, and MPA-NM provide high CNR and well outlined edges in case of microcalcifications. [ABSTRACT FROM AUTHOR]

Title. Creating case scenarios or vignettes using factorial study design methods.Aim. This paper is a report of a study conducted to develop clinical case vignettes using an adaptation of an incomplete factorial study design methodology.Background. In health care, vignettes or cases scenarios are core to problem-based learning, common in practice guideline development processes, and increasingly being used in patient or care-giver studies of chronic or life-threatening illnesses. A large number of behavioural, psycho-social and clinical factors can be relevant in such decision problems. Unbiased methods for choosing what factors to include are needed, when it is not possible to include all relevant combinations of factors in the vignettes.Method. The factors to be considered, number of levels or categories for each factor, and desired number of scenarios were decided in advance. An algorithm was used first to create the full factorial data set, and then a random subset of combinations was generated, according to predefined criteria, based on maximizing determinants. The subset of combinations was incorporated into written vignettes. The study was conducted in 2004-2005.Findings. Application of the method yielded diverse and balanced scenarios that covered the full range of factors to be considered for a project to elicit health providers' processes in diet counselling for dyslipidemia.Conclusion. The approach is flexible, decreases possible researcher bias in the creation of vignettes, and can improve statistical power in survey research. This novel application of study design methodology merits consideration when vignettes are being developed to elicit opinions or decisions in studies of complex health issues. [ABSTRACT FROM AUTHOR]

The marine turtle fishery of Grenada was assessed using interviews with marine turtle fishermen and by examination of turtle catch data from a major landing site. An estimated 782 turtles, mainly Endangered green turtles Chelonia mydas and Critically Endangered hawksbill turtles Eretmochelys imbricata, were caught around Grenada and its sister island Carriacou each year between 1996 and 2001 during an annual 8-month open season, with only a small percentage being officially recorded at a landing site. Turtles were primarily caught with nets and spearguns, with more green turtles caught by net fishermen and more hawks-bill turtles by spear fishermen. Catch per unit effort data suggested that relative abundance had declined since the previous estimate was made in 1969. Few adult green or loggerhead turtles Caretta caretta were caught, indicating the relative scarcity of this size class of these two species around Grenada. Adult-sized hawksbill turtles were caught regularly, with larger adults being caught in the non-breeding months of the open season than in the breeding months. A higher percentage of adult hawksbill turtles present during the breeding season are likely to be animals that nest in Grenada, and their smaller size may result from historically heavy fishing pressure. The larger sized adults caught during the non-breeding season are likely to be animals that forage around Grenada but breed elsewhere in the Caribbean where they are protected. [ABSTRACT FROM AUTHOR]

Patient radiation doses during interventional radiology procedures may reach the thresholds for radiation-induced skin and eye lens injuries. This study investigates the irradiated areas and doses received by patients undergoing cerebral embolisation, which is regarded as a high dose interventional radiology procedure. For each procedure the fluoroscopic and digital dose-area product (DAP), the fluoroscopic time, the total number of acquired images and entrance-skin dose (ESD) calculated by the angiographic unit were recorded. The ESD was measured by means of thermoluminescent dosimeters. In this study, the skin, eye and thyroid gland doses and the irradiated area for 30 patients were recorded. The average ESD was found to be 0.77 Gy for the posteroanterior plane and 0.78 Gy for the lateral plane. The average DAP was 48 Gy cm(2) for the posteroanterior plane and 58 Gy cm(2) for the lateral plane. The patient's average right eye dose was 60 mGy and the dose to the thyroid gland was 24 mGy. Seven patients received a dose above 1 Gy, one patient exceeded the threshold for transient erythema and one exceeded the threshold for temporary epilation. A good correlation between the DAP and the ESD for both planes has been found. The doctor's eye dose has also been measured for 17 procedures and the average dose per procedure was 0.13 mGy. [ABSTRACT FROM AUTHOR]