897 research outputs found
Gravitational lensing in fourth order gravity
Gravitational lensing is investigated in the weak field limit of fourth order
gravity in which the Lagrangian of the gravitational field is modified by
replacing the Ricci scalar curvature R with an analytical expression .
Considering the case of a pointlike lens, we study the behaviour of the
deflection angle in the case of power law Lagrangians, i.e. with f(R) = f_0
R^n. In order to investigate possible detectable signatures, the position of
the Einstein ring and the solutions of the lens equation are evaluated
considering the change with respect to the standard case. Effects on the
amplification of the images and the Paczynski curve in microlensing experiments
are also estimated.Comment: 10 pages, 3 figures, accepted for publication on Physical Review
Health and Occupational Injury Experienced by Latinx Child Farmworkers in North Carolina, USA
Children as young as 10 years old are hired to work on farms in the United States (U.S.).
These children are largely Latinx. Using interview data collected from 202 North Carolina Latinx child
farmworkers in 2017, this analysis documents the heath characteristics and occupational injuries of
Latinx child farmworkers and delineates characteristics associated with their health and occupational
injuries. Latinx child farmworkers include girls (37.6%) and boys (62.4%), aged 10 to 17 years, with
17.8% being migrant farmworkers. Three-quarters reported receiving medical and dental care in
the past year. Respiratory (15.8%) and vision (20.3%) problems were prevalent. Girls more than
boys, and younger more than older children had greater health service utilization. Occupational
injuries were common, with 26.2% reporting a traumatic injury, 44.1% a dermatological injury, 42.6%
a musculoskeletal injury, and 45.5% heat-related illness in the past year. Age increased the odds
of reporting work injuries and heat-related illness, and being a non-migrant reduced the odds
of reporting work injuries. These results emphasize the need for greater documentation of child
farmworker occupational health and safety. They underscore the need to change occupational safety
policy to ensure that children working in agriculture have the same protections as those working in
all other U.S. industries
Workplace, Household, and Personal Predictors of Pesticide Exposure for Farmworkers
In this article we identify factors potentially associated with pesticide exposure among farmworkers, grade the evidence in the peer-reviewed literature for such associations, and propose a minimum set of measures necessary to understand farmworker risk for pesticide exposure. Data sources we reviewed included Medline, Science Citation Index, Social Science Citation Index, PsycINFO, and AGRI-COLA databases. Data extraction was restricted to those articles that reported primary data collection and analysis published in 1990 or later. We read and summarized evidence for pesticide exposure associations. For data synthesis, articles were graded by type of evidence for association of risk factor with pesticide exposure as follows: 1 = association demonstrated in farmworkers; 2 = association demonstrated in nonfarmworker sample; 3 = plausible association proposed for farmworkers; or 4 = association plausible but not published for farmworkers. Of more than 80 studies we identified, only a third used environmental or biomarker evidence to document farmworker exposure to pesticides. Summaries of articles were compiled by level of evidence and presented in tabular form. A minimum list of data to be collected in farmworker pesticide studies was derived from these evidence tables. Despite ongoing concern about pesticide exposure of farmworkers and their families, relatively few studies have tried to test directly the association of behavioral and environmental factors with pesticide exposure in this population. Future studies should attempt to use similar behavioral, environmental, and psychosocial measures to build a body of evidence with which to better understand the risk factors for pesticide exposure among farmworkers
Non-Invasive Study on the Sinope Gospels
The 6th century Codex Sinopensis or Sinope Gospels (Paris, Biblioth\ue8que nationale de France) is one of the most precious purple codices that survive from the Late Antique period. Together with the Vienna Genesis (Wien,
6sterreichische Nationalbibliothek) and the Rossano Gospels (Rossano Calabro, Museo Diocesano), it has an unusually rich decorative apparatus with scenes representing biblical episodes. It can be, therefore, considered one of the most important preserved artistic productions of the early medieval era. The manuscript has been subjected to a non-invasive diagnostic campaign to evaluate the quality of the colourants used in its decoration, to understand how the parchment was coloured, and to carry out a comparison with the Vienna Genesis and the Rossano Gospels. The techniques used were UV-visible diffuse reflectance spectrophotometry with optical fibres (FORS), X-ray fluorescence spectrometry (XRF), spectrofluorimetry, and optical microscopy. Analyses highlighted the presence of ultramarine blue, which, besides the use of pure gold for the ink and paint, certifies the high value of the manuscript. In addition, this must be seen as one of the earliest examples of its use in paintings. The purple colour of the parchment was identified as orchil, a dye extracted from lichens, similar to the results of analytical investigations carried out on other purple codices, and not the expected Tyrian purple dye
Evaluating the suitability of several AR devices and tools for industrial applications
In recent years, there has been an increasing interest in Industrial Augmented Reality (IAR) due to its prominent role in the ongoing revolution known as Industry 4.0. For companies and industries it is essential to evaluate carefully which of the developed AR-based technologies to adopt, and when, for tasks such as training, maintenance, assistance, and collaborative design. There is also a wide array of hardware and software alternatives on the market, characterized by a significant heterogeneity in terms of functionalities, performance and cost. With this work, our objective is to study and compare some widely available devices and Software Development Kits (SDKs) for AR by leveraging a set of evaluation criteria derived from the actual literature which have been deemed capable to qualify the above assets as suitable for industrial applications. Such criteria include the operative range, robustness, accuracy and stability. Both marker-based and marker-less solutions have been considered, in order to investigate a wide range of possible use cases
Comparison of structural transformations and superconductivity in compressed Sulfur and Selenium
Density-functional calculations are presented for high-pressure structural
phases of S and Se. The structural phase diagrams, phonon spectra,
electron-phonon coupling, and superconducting properties of the isovalent
elements are compared. We find that with increasing pressure, Se adopts a
sequence of ever more closely packed structures (beta-Po, bcc, fcc), while S
favors more open structures (beta-Po, simple cubic, bcc). These differences are
shown to be attributable to differences in the S and Se core states. All the
compressed phases of S and Se considered are calculated to have weak to
moderate electron-phonon coupling strengths consistent with superconducting
transition temperatures in the range of 1 to 20 K. Our results compare well
with experimental data on the beta-Po --> bcc transition pressure in Se and on
the superconducting transition temperature in beta-Po S. Further experiments
are suggested to search for the other structural phases predicted at higher
pressures and to test theoretical results on the electron-phonon interaction
and superconducting properties
Equal-time two-point correlation functions in Coulomb gauge Yang-Mills theory
We apply a functional perturbative approach to the calculation of the
equal-time two-point correlation functions and the potential between static
color charges to one-loop order in Coulomb gauge Yang-Mills theory. The
functional approach proceeds through a solution of the Schroedinger equation
for the vacuum wave functional to order g^2 and derives the equal-time
correlation functions from a functional integral representation via new
diagrammatic rules. We show that the results coincide with those obtained from
the usual Lagrangian functional integral approach, extract the beta function,
and determine the anomalous dimensions of the equal-time gluon and ghost
two-point functions and the static potential under the assumption of
multiplicative renormalizability to all orders.Comment: 33 pages, 7 figures with Feyman diagrams generated with pstricks;
revised version with additional references and comments on possible
applications added in the conclusions; accepted for publication in Nucl.
Phys.
Culture as a mediator of climate change adaptation: Neither static nor unidirectional
Though there is increasing recognition of the cultural dimensions that shape climate change adaptation, our experience from working with actors engaged in adaptation policy and practice suggests that the role of culture still tends to be conceived in overly narrow and fixed terms. This is exemplified in portrayals of conservative cultural norms as stifling positive change. A growing body of research across the world indicates that the reality is seldom as simple as this – culture works in complex and variable ways, and, most importantly, is inherently dynamic. Drawing especially from research work on vulnerability and adaptation conducted in semi-arid regions, we illustrate this argument by briefly exploring three themes - multiple knowledge systems for farming in Botswana, the dynamics of pastoralist values and livelihoods in Kenya, and the interplay of caste and livelihood choices in India. Understanding how different facets of culture such as these operate in context helps move away from viewing culture statically as a barrier or enabler, and toward a more plural and dynamic appreciation of the role of culture in adaptation. This includes recognising the potential for factors that may be construed as barriers to become enablers. Critical, balanced engagement with cultural dimensions in both research and practice, understanding and working with these dynamic social structures, is essential if adaptation is to create meaningful and lasting change for those who need it most
Nonconstant electronic density of states tunneling inversion for A15 superconductors: Nb3Sn
We re-examine the tunneling data on A15 superconductors by performing a
generalized McMillan-Rowell tunneling inversion that incorporates a nonconstant
electronic density of states obtained from band-structure calculations. For
Nb3Sn, we find that the fit to the experimental data can be slightly improved
by taking into account the sharp structure in the density of states, but it is
likely that such an analysis alone is not enough to completely explain the
superconducting tunneling characteristics of this material. Nevertheless, the
extracted Eliashberg function displays a number of features expected to be
present for the highest quality Nb3Sn samples.Comment: 11 pages, 11 figure
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