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MA Nasr  CJ Nicol  JC Murrell 《PloS one》2012,7(8):e42420
The European ban on battery cages has forced a change towards the use of non-cage or furnished cage systems, but unexpectedly this has been associated with an increased prevalence of keel bone fractures in laying hens. Bone fractures are acutely painful in mammals, but the effect of fractures on bird welfare is unclear. We recently reported that keel bone fractures have an effect on bird mobility. One possible explanation for this is that flying becomes mechanically impaired. However it is also possible that if birds have a capacity to feel pain, then ongoing pain resulting from the fracture could contribute to decreased mobility. The aim was to provide proof of concept that administration of appropriate analgesic drugs improves mobility in birds with keel fracture; thereby contributing to the debate about the capacity of birds to experience pain and whether fractures are associated with pain in laying hens. In hens with keel fractures, butorphanol decreased the latency to land from perches compared with latencies recorded for these hens following saline (mean (SEM) landing time (seconds) birds with keel fractures treated with butorphanol and saline from the 50, 100 and 150 cm perch heights respectively 1.7 (0.3), 2.2 (0.3), p = 0.05, 50 cm; 12.5 (6.6), 16.9 (6.7), p = 0.03, 100 cm; 20.6 (7.4), 26.3 (7.6), p = 0.02 150 cm). Mobility indices were largely unchanged in birds without keel fractures following butorphanol. Critically, butorphanol can be considered analgesic in our study because it improved the ability of birds to perform a complex behaviour that requires both motivation and higher cognitive processing. This is the first study to provide a solid evidential base that birds with keel fractures experience pain, a finding that has significant implications for the welfare of laying hens that are housed in non-cage or furnished caged systems.  相似文献   

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Tracking Wetland Restoration: Do Mitigation Sites Follow Desired Trajectories?   总被引:12,自引:0,他引:12  
Hypothetical models in the scientific literature suggest that ecosystem restoration and creation sites follow a smooth path of development (called a trajectory), rapidly matching natural reference sites (the target). Multi-million-dollar mitigation agreements have been based on the expectation that damages to habitat will be compensated within 5–10 years, and monitoring periods have been set accordingly. Our San Diego Bay study site, the Sweetwater Marsh National Wildlife Refuge, has one of the longest and most detailed records of habitat development at a mitigation site: data on soil organic matter, soil nitrogen, plant growth, and plant canopies for up to 10 years from a 12-year-old site. High interannual variation and lack of directional changes indicate little chance that targets will be reached in the near future. Other papers perpetuate the trajectory model, despite data that corroborate our findings. After reviewing “trajectory models” and presenting our comprehensive data for the first time, we suggest alternative management and mitigation policies.  相似文献   

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We conducted a preliminary study to examine whether Chinese readers’ spontaneous word segmentation processing is consistent with the national standard rules of word segmentation based on the Contemporary Chinese language word segmentation specification for information processing (CCLWSSIP). Participants were asked to segment Chinese sentences into individual words according to their prior knowledge of words. The results showed that Chinese readers did not follow the segmentation rules of the CCLWSSIP, and their word segmentation processing was influenced by the syntactic categories of consecutive words. In many cases, the participants did not consider the auxiliary words, adverbs, adjectives, nouns, verbs, numerals and quantifiers as single word units. Generally, Chinese readers tended to combine function words with content words to form single word units, indicating they were inclined to chunk single words into large information units during word segmentation. Additionally, the “overextension of monosyllable words” hypothesis was tested and it might need to be corrected to some degree, implying that word length have an implicit influence on Chinese readers’ segmentation processing. Implications of these results for models of word recognition and eye movement control are discussed.  相似文献   

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The ultimate destiny of a cell to undergo division, differentiation, survival, and death results from an intricate balance between multiple regulators including oncogenes, tumor suppressor genes, and cell cycle associated proteins. Deregulation of the cell cycle machinery switches the phenotype from a normal cell to a cancerous cell. Fundamental alterations of tumor suppressor genes may result in an unregulated cell cycle with the accumulation of mutations and eventual neoplastic transformation. As such, one may define cancer as a genetic disease of the cell cycle. In this review, we will emphasize our current understanding of how the cell cycle machinery maintains cellular homeostasis by studying the consequences of its deregulation.  相似文献   

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Replacing Sources with Sinks: When Do Populations Go Down the Drain?   总被引:1,自引:0,他引:1  
We investigate the scenario in which some amount of higher quality habitat is destroyed and is then replaced by some undetermined amount of lower quality habitat. We examined how much low‐quality habitat would need to be created to maintain the equilibrium population abundance in the entire geographic area. Using a source–sink model, we find that (1) the number of hectares of created habitat per hectare of destroyed habitat must equal the ratio of the high‐quality habitat's productivity to the low‐quality habitat's productivity, however, (2) if the created habitat is a sink, then there is a threshold fraction of destroyed high‐quality habitat below which the initial population abundance cannot be maintained through the creation of habitat. We illustrate these results using data on Red‐winged Blackbirds (Agelaius phoeniceus) in two different regions where high‐quality habitat is being replaced by or converted into lower quality habitat.  相似文献   

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Background

The theory has been put forward that if a null hypothesis is true, P-values should follow a Uniform distribution. This can be used to check the validity of randomisation.

Method

The theory was tested by simulation for two sample t tests for data from a Normal distribution and a Lognormal distribution, for two sample t tests which are not independent, and for chi-squared and Fisher’s exact test using small and using large samples.

Results

For the two sample t test with Normal data the distribution of P-values was very close to the Uniform. When using Lognormal data this was no longer true, and the distribution had a pronounced mode. For correlated tests, even using data from a Normal distribution, the distribution of P-values varied from simulation run to simulation run, but did not look close to Uniform in any realisation. For binary data in a small sample, only a few probabilities were possible and distribution was very uneven. With a sample of two groups of 1,000 observations, there was great unevenness in the histogram and a poor fit to the Uniform.

Conclusions

The notion that P-values for comparisons of groups using baseline data in randomised clinical trials should follow a Uniform distribution if the randomisation is valid has been found to be true only in the context of independent variables which follow a Normal distribution, not for Lognormal data, correlated variables, or binary data using either chi-squared or Fisher’s exact tests. This should not be used as a check for valid randomisation.  相似文献   

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We hypothesize that black women experience accelerated biological aging in response to repeated or prolonged adaptation to subjective and objective stressors. Drawing on stress physiology and ethnographic, social science, and public health literature, we lay out the rationale for this hypothesis. We also perform a first population-based test of its plausibility, focusing on telomere length, a biomeasure of aging that may be shortened by stressors. Analyzing data from the Study of Women’s Health Across the Nation (SWAN), we estimate that at ages 49–55, black women are 7.5 years biologically “older” than white women. Indicators of perceived stress and poverty account for 27% of this difference. Data limitations preclude assessing objective stressors and also result in imprecise estimates, limiting our ability to draw firm inferences. Further investigation of black-white differences in telomere length using large-population-based samples of broad age range and with detailed measures of environmental stressors is merited.  相似文献   

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This qualitative research examines the influence of animosity on physicians during clinical encounters and its ethical implications. Semi‐structured interviews were conducted with ten Israeli‐Jewish physicians: four treated Syrians and six treated Palestinian terrorists/Hezbollah militants or Palestinian civilians. An interpretive phenomenological analysis was used to uncover main themes in these interviews. Whereas the majority of physicians stated they are obligated to treat any patient, physicians who treated Syrians exhibited stronger emotional expression and implicit empathy, while less referring to the presence of the Israeli‐Arab conflict. In contrast, physicians who treated enemy combatants or Palestinian civilians showed the exact opposite. Linking these results to the “Implicit Bias” theory, the role of empathy and the beneficence principle in medical ethics, we argue that: (a) the unconscious decreased emotional involvement among the latter group of physicians is a deficiency that needs to be recognized; and (b) this deficiency undermines the principle of beneficence, thereby possibly influencing the fulfillment of the commitment to treat patients. Acknowledging and addressing the potential emotional and ethical deficiencies entailed in encounters with the so‐called enemy‐patients are of importance to the global medical community, since such encounters are increasingly an integral part of the current political realities faced by both the developed and developing worlds.  相似文献   

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Men may find women with small feet relative to body size more attractive because foot size reliably indexes nubility—i.e., age and parity. I collected judgments of attractiveness in response to drawings of women with varying foot sizes from a sample of 159 Karo Batak respondents from North Sumatra, Indonesia, as part of a collaborative project on foot size and attractiveness. The data revealed a contrarian preference among the Karo Batak for women with big feet. The judgments were compared with the results of an existing cross-cultural study that found a preference for women with small feet in aggregate, but a mix of small- and large-foot preferences in the societies taken individually. Using contingency table analysis, I found that ecology and less exposure to Western media were associated with a preference for women with big feet; patriarchal values were not. The findings suggest that human mating preferences may arise in response to local ecological conditions, and may persist and spread via cultural transmission. This has implications for the concept of universality espoused in some versions of evolutionary psychology.  相似文献   

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Entomologists from the late 19th century onwards recognized the evolutionary interest of the association of black forms of the peppered moth with industrialization. They developed a qualitative explanation of the phenomenon involving a change in relative crypsis of the phenotypes due to the blackening of the moth's resting background by air pollution. More recently, ecological geneticists have obtained some estimates of predation by birds and of population parameters such as migration rate. Models incorporating these estimates have explored the ways in which natural selection influences spatial variation and the maintenance of polymorphism. Studies on the peppered moth and some of the many other insects exhibiting industrial melanism have concentrated on the variability and dynamics of adult populations. Recent work which has begun to examine the ecology and behaviour of individuals, complete life cycles, and gene-phenotype relationships, is refining our understanding of this adaptation and also of present-day declines in melanic frequencies in response to falling air pollution.  相似文献   

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Age‐related patterns of survival and reproduction have been explained by accumulated experience (‘experience hypothesis’), increased effort (‘effort hypothesis’), and intrinsic differences in phenotypes (‘selection hypothesis’). We examined the experience and effort hypotheses using a 40‐year data set in a population of Leach's storm‐petrels Oceanodroma leucorhoa, long‐lived seabirds for which the effect of phenotypic variation has been previously demonstrated. Age was quantified by time since recruitment (‘breeding age’). The best model of adult survival included a positive effect of breeding age (1, 2, 3+ years), sex (male > female), and year. Among‐individuals variation (fixed heterogeneity) accounted for 31.6% of the variance in annual reproductive success. We further examined within‐individual patterns in reproductive success (dynamic heterogeneity) in the subset of individuals with at least five breeding attempts. Three distinct phases characterized reproductive success – early increase, long asymptotic peak, late decline. No effect of early reproductive output on longevity was found, however, early success was positively correlated with lifetime reproductive success. Reproductive success was lower earlier than later in life. Among the few natally philopatric individuals in the population, age of first breeding had no effect on longevity, lifetime reproductive success, or early reproductive success. No support for the effort hypothesis was found in this population. Instead, age‐specific patterns of survival and reproduction in these birds are best explained by the experience hypothesis over and above the effect of intrinsic differences among individuals.  相似文献   

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