334 research outputs found
Towards precise predictions for Higgs-boson production in the MSSM
We study the production of scalar and pseudoscalar Higgs bosons via gluon
fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD
calculation implemented in the public code SusHi, we provide precise
predictions for the Higgs-production cross section in six benchmark scenarios
compatible with the LHC searches. We also provide a detailed discussion of the
sources of theoretical uncertainty in our calculation. We examine the
dependence of the cross section on the renormalization and factorization
scales, on the precise definition of the Higgs-bottom coupling and on the
choice of PDFs, as well as the uncertainties associated to our incomplete
knowledge of the SUSY contributions through NNLO. In particular, a potentially
large uncertainty originates from uncomputed higher-order QCD corrections to
the bottom-quark contributions to gluon fusion.Comment: 62 pages, 24 pdf figures; v2: minor clarifications, improved plot
quality, matches published versio
The ZAX Herbivory Trainer—Free software for training researchers to visually estimate leaf damage
Plants lose a remarkable amount of energy to herbivorous animals, and this damage has substantial impacts on plant fitness and species' distributions. There are many ways ecologists can measure leaf damage, with some methods being more time-consuming than others. Due to a high variance in herbivory, accurate quantification of damage at the population level requires sampling of many leaves. A simple yet effective solution to this problem is to estimate leaf damage visually. Visually estimating leaf damage may be less accurate than scanning methods, but visual estimates of leaf damage are much faster than digital measurements. Using simulations, we show that gathering larger quantities of data at a slightly higher level of inaccuracy gives a more accurate estimate of a population's overall leaf damage than fewer, exact measurements. We then introduce the ZAX Herbivory Trainer, a free online application that teaches researchers to accurately visually estimate leaf damage. On average, users took ~9Â min and 48 images to complete our trainer which significantly decreased their estimate inaccuracy from 13.2% to 6%. This low level of inaccuracy can be retained up to 3Â months post-training so researchers can use the ZAX Herbivory Trainer once prior to short fieldwork or every 3Â months for extensive fieldwork. We also recommend a cut-off point, whereby if a person has not completed the app in 17.5Â min or 85 images (90th percentile), they may not be suitable to estimate herbivory for research purposes. The ZAX Herbivory Trainer will allow researchers of any experience level to assess herbivory quickly and accurately in a globally standardised way. International collaborators, students and citizen scientists can all find use in this app, no matter the scale of their projects. From this we can gather better data to address big picture questions in ecology such as patterns in herbivory relating to latitude or climate change
Southern hemisphere plants show more delays than advances in flowering phenology
Shifts in flowering phenology have been studied in detail in the northern hemisphere and are a key plant response to climate change. However, there are relatively fewer data on species' phenological shifts in the southern hemisphere. We combined historic field data, data from herbarium specimens dating back to 1842 and modern field data for 37 Australian species to determine whether species were flowering earlier in the year than they had in the past. We also combined our results with data compiled in the southern and northern hemispheres, respectively, to determine whether southern hemisphere species are showing fewer advances in flowering phenology through time. Across our study species, we found that 12 species had undergone significant shifts in flowering time, with four species advancing their flowering and eight species delaying their flowering. The remaining 25 species showed no significant shifts in their flowering phenology. These findings are important because delays or lack of shifts in flowering phenology can lead to mismatches in trophic interactions between plants and pollinators or seed dispersers, which can have substantial impacts on ecosystem functioning and primary productivity. Combining our field results with data compiled from the literature showed that only 58.5% of southern hemisphere species were advancing their flowering time, compared with 81.6% of species that were advancing their flowering time in the northern hemisphere. Our study provides further evidence that it is not adequate for ecologists to assume that southern hemisphere ecosystems will respond to future climate change in the same way as ecosystems north of the Equator. Synthesis. Field data and data from the literature indicate that southern hemisphere species are showing fewer advances in their flowering phenology through time, especially in comparison to northern hemisphere species
More than a feeling: A unified view of stress measurement for population science.
Stress can influence health throughout the lifespan, yet there is little agreement about what types and aspects of stress matter most for human health and disease. This is in part because "stress" is not a monolithic concept but rather, an emergent process that involves interactions between individual and environmental factors, historical and current events, allostatic states, and psychological and physiological reactivity. Many of these processes alone have been labeled as "stress." Stress science would be further advanced if researchers adopted a common conceptual model that incorporates epidemiological, affective, and psychophysiological perspectives, with more precise language for describing stress measures. We articulate an integrative working model, highlighting how stressor exposures across the life course influence habitual responding and stress reactivity, and how health behaviors interact with stress. We offer a Stress Typology articulating timescales for stress measurement - acute, event-based, daily, and chronic - and more precise language for dimensions of stress measurement
Extreme dietary specialisation in adult male southern elephant seals: determining variation between individual trophic diets
Although dietary studies have provided important insights into the causes and ramifications of diet variation for the southern elephant seal (SES) (Mirounga leonina), adult males are comparatively underrepresented within that literature. Individual males can vary morphologically as well as behaviourally, leading to differences in their life history trajectories and outcomes. Therefore, to improve our understanding of the male diet, we sought to determine the degree of dietary variation between as well as within individuals from the West Antarctic Peninsula. Secondly, we investigated whether individual morphological traits, seasonality, and year influenced their dietary variation. Whiskers were sampled from 31 adult male seals and used to measure the bulk stable isotope nitrogen (δ15N). We sequentially segmented each whisker to create a time series of datapoints for each individual, allowing us to compare δ15N variation within each seal as well as assess variation between the seals. We then investigated the relationships between male dietary variation and body length, girth, season, and year. We found that adult male SESs maintained an extremely specialised diet. Variation between individuals was strongly correlated with their body size, with larger seals feeding higher up the trophic web. Interestingly, seasonality and year both influenced variation within the seals’ diets, but only year was seen to influence the variability between seals. We discuss the possible causes and ramifications of dietary specialisation for the SES and highlight the need for combined tracking and stable isotope investigations to improve our understanding of the ontogeny of the seals’ dietary specialisation
Southern hemisphere plants show more delays than advances in flowering phenology
Shifts in flowering phenology have been studied in detail in the northern hemisphere and are a key plant response to climate change. However, there are relatively fewer data on species' phenological shifts in the southern hemisphere.
We combined historic field data, data from herbarium specimens dating back to 1842 and modern field data for 37 Australian species to determine whether species were flowering earlier in the year than they had in the past. We also combined our results with data compiled in the southern and northern hemispheres, respectively, to determine whether southern hemisphere species are showing fewer advances in flowering phenology through time.
Across our study species, we found that 12 species had undergone significant shifts in flowering time, with four species advancing their flowering and eight species delaying their flowering. The remaining 25 species showed no significant shifts in their flowering phenology. These findings are important because delays or lack of shifts in flowering phenology can lead to mismatches in trophic interactions between plants and pollinators or seed dispersers, which can have substantial impacts on ecosystem functioning and primary productivity. Combining our field results with data compiled from the literature showed that only 58.5% of southern hemisphere species were advancing their flowering time, compared with 81.6% of species that were advancing their flowering time in the northern hemisphere. Our study provides further evidence that it is not adequate for ecologists to assume that southern hemisphere ecosystems will respond to future climate change in the same way as ecosystems north of the Equator.
Synthesis. Field data and data from the literature indicate that southern hemisphere species are showing fewer advances in their flowering phenology through time, especially in comparison to northern hemisphere species
Baryogenesis with Superheavy Squarks
We consider a setup where R-parity is violated in the framework of split
supersymmetry. The out-of-equilibrium decays of heavy squarks successfully lead
to the generation of a baryon asymmetry. We restrict the R-parity violating
couplings to the baryon number violating subset to keep the neutralino
sufficiently stable to provide the dark matter. The observed baryon asymmetry
can be generated for squark masses larger than 10^11 GeV, while neutralino dark
matter induces a stronger bound of 10^13 GeV. Some mass splitting between left-
and right-handed squarks may be needed to satisfy also constraints from gluino
cosmology.Comment: 18 pages, LaTeX, 4 figure
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Stress Measurement in Primary Care: Conceptual Issues, Barriers, Resources, and Recommendations for Study
Objective: Exposure to stressors in daily life and dysregulated stress responses are associated with increased risk for a variety of chronic mental and physical health problems, including anxiety disorders, depression, asthma, heart disease, certain cancers, and autoimmune and neurodegenerative disorders. Despite this fact, stress exposure and responses are rarely assessed in the primary care setting and infrequently targeted for disease prevention or treatment. Method: In this narrative review, we describe the primary reasons for this striking disjoint between the centrality of stress for promoting disease and how rarely it is assessed by summarizing the main conceptual, measurement, practical, and reimbursement issues that have made stress difficult to routinely measure in primary care. The following issues will be reviewed: (1) assessment of stress in primary care; (2) biobehavioral pathways linking stress and illness; (3) the value of stress measurements for improving outcomes in primary care; (4) barriers to measuring and managing stress; and (5) key research questions relevant to stress assessment and intervention in primary care. Results: Based on our synthesis, we suggest several approaches that can be pursued to advance this work, including feasibility and acceptability studies, cost-benefit studies, and clinical improvement studies. Conclusions: Although stress is recognized as a key contributor to chronic disease risk and mortality, additional research is needed to determine how and when instruments for assessing life stress might be useful in the primary care setting, and how stress-related data could be integrated into disease prevention and treatment strategies to reduce chronic disease burden and improve human health and wellbeing
Direct probes of R-parity-violating supersymmetric couplings via single-top-squark production
We study the s-channel production of a single top squark in hadron collisions
through an R-parity-violating mechanism, examining in detail the case in which
the squark decays through an R-parity-conserving process into a bottom quark, a
lepton, and missing energy. We show that the top squark can be discovered if
its mass is less than 400 GeV, or that the current bound on the size of the
R-parity-violating couplings can be reduced by up to one order of magnitude
with existing data and by two orders of magnitude at the forthcoming run II of
the Fermilab Tevatron.Comment: To appear in Phys. Rev. D; 32 pgs., 17 ps figs., uses RevTeX; 1 new
fig., slight textual clarification
Psychosocial and clinical characteristics of a patient with Takotsubo syndrome and her healthy monozygotic twin: a case report
Background: Takotsubo syndrome (TTS) is an acute heart failure syndrome characterized by transient left ventricular dysfunction, increased myocardial biomarkers, and electrocardiographic changes. Symptoms of TTS are similar to those of acute coronary syndromes, but there is often no significant coronary stenosis. Although emotional and physical stressors are often reported as having triggered TTS, the pathogenesis is largely unknown. To address this issue, we comprehensively characterized a monozygous pair of twin sisters, one of whom experienced TTS.
Case summary: The 60-year-old Caucasian monozygotic female twins with and without TTS were examined at the University Hospital Zurich in Switzerland. The twins completed questionnaires and clinical interviews assessing several sociopsychological factors. The twin sister with TTS exhibited higher levels of anxiety, vital exhaustion, social inhibition, and alexithymia, and lower levels of quality of and meaning in life. She was given the diagnoses of social phobia, adjustment disorder, specific anxiety disorder, obsessive-compulsive personality disorder, and an accentuated anxiety-avoidant personality disorder. Additionally, the twin with TTS experienced more-and also more severe-stressors involving life-threatening and dangerous situations over the life course.
Discussion: These monozygous female twins with and without TTS differed in several notable aspects of their psychological functioning, psychiatric status, personality, and lifetime stressor exposure. The results thus highlight several factors, besides genetic components, that may play an important role in the pathogenesis of TTS. Looking forward, larger studies using experimental and longitudinal designs are needed to elucidate the role that psychosocial factors play in TTS.
Keywords: Case report; Monozygotic twins; Psychology; Stress-induced cardiomyopathy; Takotsubo syndrom
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