dataService

您的位置: 首页 > 数据服务 > 数据列表页

筛选

共检索到18358条 ,权限内显示50条;

Data from: Setup in a clinical workflow and impact on radiotherapy routine of an in vivo dosimetry procedure with an electronic portal imaging device
负责人:
关键词:
Imaging equipment;Cancer treatment;in vivo dosimetry;oncology;Thorax;Radiation therapy;pelvis;Abdomen;Computed axial tomography
摘要:
High conformal techniques such as intensity-modulated radiation therapy and volumetric-modulated arc therapy are widely used in overloaded radiotherapy departments. In vivo dosimetric screening is essential in this environment to avoid important dosimetric errors. This work examines the feasibility of introducing in vivo dosimetry (IVD) checks in a radiotherapy routine. The causes of dosimetric disagreements between delivered and planned treatments were identified and corrected during the course of treatment. The efficiency of the corrections performed and the added workload needed for the entire procedure were evaluated. The IVD procedure was based on an electronic portal imaging device. A total of 3682 IVD tests were performed for 147 patients who underwent head and neck, abdomen, pelvis, breast, and thorax radiotherapy treatments. Two types of indices were evaluated and used to determine if the IVD tests were within tolerance levels: the ratio R between the reconstructed and planned isocentre doses and a transit dosimetry based on the ?-analysis of the electronic portal images. The causes of test outside tolerance level was investigated and corrected and IVD test was repeated during subsequent fraction. The time needed for each step of the IVD procedure was registered. Pelvis, abdomen, and head and neck treatments had 10% of tests out of tolerance whereas breast and thorax treatments accounted for up to 25%. The patient setup was the main cause of 90% of the IVD tests out of tolerance and the remaining 10% was due to patient morphological changes. An average time of 42 min per day was sufficient to monitor a daily workload of 60 patients in treatment. This work shows that IVD performed with an electronic portal imaging device is feasible in an overloaded department and enables the timely realignment of the treatment quality indices in order to achieve a patient’s final treatment compliant with the one prescribed.
Data from: Consequences of a nectar yeast for pollinator preference and performance
负责人:
关键词:
Bombus impatiens;nectar yeasts;pollinator reproduction;Metschnikowia reukaufii;pollinator preference
摘要:
Pollinators utilize floral resources that vary in colour, scent and reward quality. Variation in such traits, including nectar rewards, in addition to cues associated with their quality, can influence pollinator foraging decisions with consequences for pollinator reproductive success. Nectar is commonly subject to colonization by micro-organisms capable of affecting a suite of traits important for pollinator attraction and fitness; yet, links between microbial presence and changes in pollinator preference and performance remain few. Here, we evaluated the effects of a nectar-inhabiting micro-organism on pollinator foraging behaviour and reproduction using the common eastern bumblebee Bombus impatiens and the cosmopolitan nectar yeast Metschnikowia reukaufii. Using a combination of choice and no-choice behavioural and feeding assays, we manipulated the presence and viability of M. reukaufii in nectar and assessed bumblebee foraging and reproductive responses. Bombus impatiens workers responded positively to the presence of yeasts. Foragers trained to associate yeast presence with flower colour visited a significantly greater proportion of flowers inoculated with yeast when subject to a colour discrimination test. Moreover, foragers na?ve to nectar yeasts incorporated more yeast-inoculated flowers into initial foraging bouts when presented with a novel floral array. In addition, bees spent significantly longer foraging on yeast-inoculated flowers compared to yeast-free flowers. However, when we manipulated yeast presence and viability in microcolonies of queenless workers, we found no effect of yeast on components of bumblebee reproduction, such as initiation of egg laying and number of eggs laid. This lack of an effect of yeast persisted even under conditions of pollen limitation. Taken together, these results suggest that nectar yeasts can enhance floral signalling and alter pollinator foraging behaviour at individual flowers, though they may not directly affect pollinator performance. Thus, nectar yeasts may play a significant role in mediating pollinator foraging behaviour, with consequences for plant fitness and evolution of floral traits.
Data from: Plant population and maize grain yield: a global systematic review of rainfed trials
负责人:
关键词:
Conservation agriculture;Row spacing;Soil tillage;Zea mays;Plant population;no time limitation;Agronomic management
摘要:
Maize (Zea mays L.) productivity has increased globally as a result of improved genetics and agronomic practices. Plant population and row spacing are two key agronomic factors known to have a strong influence on maize grain yield. A systematic review was conducted to investigate the effects of plant population on maize grain yield, differentiating between rainfall regions, N input, and soil tillage system (conventional tillage [CT] and no-tillage [NT]). Data were extracted from 64 peer-reviewed articles reporting on rainfed field trials, representing 13 countries and 127 trial locations. In arid environments, maize grain yield was low (mean maize grain yield = 2448 kg ha?1) across all plant populations with no clear response to plant population. Variation in maize grain yield was high in semiarid environments where the polynomial regression (p < 0.001, n = 951) had a maximum point at ?140,000 plants ha?1, which reflected a maize grain yield of 9000 kg ha?1. In subhumid environments, maize grain yield had a positive response to plant population (p < 0.001). Maize grain yield increased for both CT and NT systems as plant population increased. In high-N-input (r2 = 0.19, p < 0.001, n = 2 018) production systems, the response of plant population to applied N was weaker than in medium-N-input (r2 = 0.49, p < 0.001, n = 680) systems. There exists a need for more metadata to be analyzed to provide improved recommendations for optimizing plant populations across different climatic conditions and rainfed maize production systems. Overall, the importance of optimizing plant population to local environmental conditions and farming systems is illustrated.
Data from: Hybrid asexuality as a primary postzygotic barrier between nascent species: on the interconnection between asexuality, hybridization and speciation
负责人:
关键词:
Evolution of Asexuality;phylogeography;hybridization;Coalescence;Balance Hypothesis;speciation
摘要:
Although sexual reproduction is ubiquitous throughout nature, the molecular machinery behind it has been repeatedly disrupted during evolution, leading to the emergence of asexual lineages in all eukaryotic phyla. Despite intensive research, little is known about what causes the switch from sexual reproduction to asexuality. Interspecific hybridization is one of the candidate explanations but the reasons for the apparent association between hybridization and asexuality remain unclear. In this study we combined cross-breeding experiments with population genetic and phylogenomic approaches to reveal the history of speciation and asexuality evolution in European spined loaches (Cobitis). Contemporary species readily hybridize in hybrid zones, but produce infertile males and fertile but clonally reproducing females that cannot mediate introgressions. However, our analysis of exome data indicates that intensive gene flow between species has occurred in the past. Crossings among species with various genetic distances showed that, while distantly related species produced asexual females and sterile males, closely related species produce sexually reproducing hybrids of both sexes. Our results suggest that hybridization leads to sexual hybrids at the initial stages of speciation, but as the species diverge further, the gradual accumulation of reproductive incompatibilities between species could distort their gametogenesis towards asexuality. Interestingly, comparative analysis of published data revealed that hybrid asexuality generally evolves at lower genetic divergences than hybrid sterility or inviability. Given that hybrid asexuality effectively restricts gene flow, it may establish a primary reproductive barrier earlier during diversification than other ‘classical’ forms of postzygotic incompatibilities. Hybrid asexuality may thus indirectly contribute to the speciation process.
Data from: Balance between inbreeding and outcrossing in a nannandrous species, the moss Homalothecium lutescens
负责人:
关键词:
sporophytes;post-fertilization selection;sexual reproduction;dwarf males;Homalothecium lutescens;phyllodioicy;polyandry;Inbreeding;nannandry;bryophytes
摘要:
Epiphytic dwarf males on the females present a possible solution to the problem of short fertilization distances in mosses. However, leptokurtic spore dispersal makes dwarf males likely to be closely related to their host shoot, with an accompanying risk of inbreeding. The capacity of a female to harbour a high number of different dwarf males suggests that there may be mechanisms in place that counteract inbreeding, such as polyandry and post-fertilization selection. We have genotyped sporophytes, female host shoots and dwarf males in four populations of the moss Homalothecium lutescens. We found no evidence of selective sporophyte abortion based on level of heterozygosity. The occurrence of entirely homozygous sporophytes together with significantly positive inbreeding coefficients in three of the populations (mean FIS between 0.48 and 0.64) suggest frequent mother–son mating events. However, 23% of all sampled sporophytes had a higher level of heterozygosity compared with the mean expected heterozygosity at the population level. Polyandry was frequent, on average 59% of the sporophytes on a female shoot were sired by distinct fathers. In conclusion, sporadic fertilizations by dwarf males originating from nonhost female shoots appear to counteract strong inbreeding.
Data from: Genetic monitoring reveals temporal stability over 30 years in a small, lake resident brown trout population
负责人:
关键词:
Salmo trutta
摘要:
Knowledge of the degree of temporal stability of population genetic structure and composition is important for understanding microevolutionary processes and for addressing issues on human impact on natural populations. We know little about how representative single samples in time are to reflect population genetic constitution. We explore the temporal genetic variability patterns over a 30-year period of annual sampling of a lake resident brown trout (Salmo trutta) population, covering 37 consecutive cohorts and five generations. Levels of variation remain largely stable over this period with no indication of substructuring within the lake. We detect genetic drift, however, and the genetically effective population size (Ne) was assessed from allele frequency shifts between consecutive cohorts using an unbiased estimator that accounts for the effect of overlapping generation. The overall mean Ne is estimated as 74. We find indications that Ne varies over time, but th ere is no obvious temporal trend. We also estimated Ne using a one-sample approach based on linkage disequilibrium (LD) not accounting for the effect of overlapping generations. Combining one-sample estimates for all years gives an Ne estimate of 76. This similarity between estimates may be coincidental or reflecting a general robustness of the LD approach to violations of the discrete generations assumption. In contrast to the observed genetic stability, body size and catch per effort have increased over the study period. Estimates of annual effective number of breeders (Nb) correlated with catch per effort suggesting that genetic monitoring can be used for detecting fluctuations in abundance.
Data from: Experimental brood enlargement differentially influences the magnitude of the corticosterone stress response in closely related, co?occurring songbirds
负责人:
关键词:
brood size;Growth;Glucocorticoids;corticosterone;violet-green swallow;Tachycineta;Tree swallow
摘要:
1. Rearing environments can shape offspring phenotype across taxa, yet little is known about how brood size influences hypothalamic-pituitary axis functioning, whether its expression trades off with growth, and the degree to which these relationships vary between species. 2. We evaluated how brood size influenced nestling physiological (glucocorticoids) and somatic traits (growth), and the extent to which these relationships differed between two closely related, sympatric songbirds when experiencing identical rearing environments. Specifically, we used a cross-fostering approach to alter brood size and create an experimental gradient of nestmate competition, and then tested whether experimentally manipulated brood sizes resulted in nestlings with altered concentrations of corticosterone and if corticosterone responses traded off with growth. 3. Nestlings of both species experienced elevated concentrations of baseline and stressor-induced corticosterone when raised in enlarged broods, relative to control and reduced broods, but neither measurement was found to trade off with growth or be linked to survival to fledging. 4. In contrast, we found divergence in the magnitude of the corticosterone stress response between species across all brood treatments, with greater stressor-induced corticosterone concentrations found in the Violet-green Swallow (Tachycineta thalassina) relative to the closely related Tree Swallow (T. bicolor). 5. Our study demonstrated that brood size can lead to changes in offspring corticosterone concentrations in swallows, and that nestlings of sympatric species, even those that are closely related and ecologically similar, can diverge in their corticosterone stress response when experiencing identical rearing conditions. 6. We conclude that corticosterone appears to play a key role for balancing energetic demands that arise in the face of nestmate competition in Tachycineta swallows, and that elevated concentrations of corticosterone may enhance offspring survival during challenging environmental conditions, such as when brood competition is strong.
Data from: Characteristics of pneumonia deaths after earthquake and tsunami: an ecological study of 5.7 million subjects in 131 municipalities, Japan
负责人:
关键词:
Infectious Diseases;Epidemiology;Public health
摘要:
Objective: On 11 March 2011, the Great East Japan Earthquake struck off Japan. Although some studies showed that the earthquake increased the risk of pneumonia death, no study reported whether and how much tsunami increased the risk. We examined the risk for pneumonia death after the earthquake/tsunami. Design: This is an ecological study. Setting: Data on population and pneumonia deaths obtained from the Vital Statistics 2010 and 2012, National Census 2010 and Basic Resident Register 2010 and 2012 in Japan. Participants: About 5.7 million subjects residing in Miyagi, Iwate and Fukushima Prefectures during 1 year after the disaster were targeted. All municipalities (n=131) were categorized into inland (n=93), that is, the earthquake-impacted area, and coastal types (n=38), that is, the earthquake- and tsunami-impacted area. Outcome measures: The number of pneumonia deaths per week was totaled from 12 March 2010 to 9 March 2012. The number of observed pneumonia deaths (O) and the sum of the sex- and age-classes in the observed population multiplied by the sex- and age-classes of expected pneumonia mortality (E) were calculated. Expected pneumonia mortality was the pneumonia mortality during the year before. Standardized mortality ratios (SMRs) were calculated for pneumonia deaths (O/E), adjusting for sex and age using the indirect method. SMRs were then calculated by coastal and inland municipalities. Results: Six thousand six hundred three subjects died of pneumonia during 1 year after the earthquake. SMRs significantly increased during the 1st to 12th week. In the 2nd week, SMRs in coastal and inland municipalities were 2.49 (95% CI 2.02 to 7.64) and 1.48 (95% CI 1.24 to 2.61), respectively. SMRs of coastal municipalities were higher than those of inland municipalities. Conclusions: Earthquake increased the risk of pneumonia death and tsunamis additionally increased the risk.
Data from: Pivotal effect of early-winter temperatures and snowfall on population growth of alpine Parnassius smintheus butterflies
负责人:
关键词:
Rocky Mountains;butterfly;snow;alpine;Prediction;weather extremes;Winter;regression trees;Parnassius smintheus;randomForests;population dynamics;climate change
摘要:
Geographic range shifts in species’ distributions, due to climate change, imply altered dynamics at both their northern and southern range limits, or at upper and lower elevational limits. There is therefore a need to identify specific weather or climate variable(s), and life stages or cohorts on which they act, and how these affect population growth. Identifying such variables permits prediction of population increase or decline under a changing climate, and shifts in a species’ geographic range. For relatively well studied groups, such as butterflies, geographic range shifts are well documented, but weather variables and mechanisms causing those shifts are not well known. The Holarctic butterfly genus Parnassius (Papilionidae) inhabits northern and alpine environments subject to variable and extreme weather. As such, Parnassius species are vulnerable not only to long-term changes in average conditions but especially to short-term extreme weather events. We use population growth estimates for the alpine butterfly, Parnassius smintheus, from 21 populations in the Rocky Mountains of Canada, over a 20-year interval, combined with techniques of machine learning (randomForests) and parametric modeling to identify the important weather variables determining population growth. We do this to determine the seasons and life-stages of P. smintheus most affected by climate change. Extreme minimum and maximum temperatures in November, in combination with November snowfall, affect annual population growth most, more so than do mean temperatures in November, and more so than weather at any other time of year. Populations decline both in years with low extreme minimum temperatures in November, and especially in years with high extreme maximum temperatures in November, indicating that overwintering eggs are particularly vulnerable to early-winter weather. Snowfall ameliorates the negative effects of extreme temperatures, particularly for extreme warm events. Results provide insight into biological mechanisms by which over-wintering eggs might be affected by early winter weather. Short-term extreme weather in November, acting on a single pivotal life-stage (egg) is a far better predictor of population change of alpine Parnassius smintheus butterflies than is the general index of climate, the Pacific Decadal Oscillation (PDO).

首页上一页12345下一页尾页

意 见 箱

匿名:登录

个人用户登录

找回密码

第三方账号登录

忘记密码

个人用户注册

必须为有效邮箱
6~16位数字与字母组合
6~16位数字与字母组合
请输入正确的手机号码

信息补充