1,224 research outputs found
Simple Current Actions of Cyclic Groups
Permutation actions of simple currents on the primaries of a Rational
Conformal Field Theory are considered in the framework of admissible weighted
permutation actions. The solution of admissibility conditions is presented for
cyclic quadratic groups: an irreducible WPA corresponds to each subgroup of the
quadratic group. As a consequence, the primaries of a RCFT with an order n
integral or half-integral spin simple current may be arranged into multiplets
of length k^2 (where k is a divisor of n) or 3k^2 if the spin of the simple
current is half-integral and k is odd.Comment: Added reference, minor change
Fifteen years of clinical liver transplantation
Liver transplantation in humans was first attempted more than 15 yr ago. The 1-yr survival has slowly improved until it has now reached about 50%. In our experience, 46 patients have lived for at least 1 yr, with the longest survival being 9 yr. The high acute mortality in early trials was due in many cases to technical and management errors and to the use of damaged organs. With elimination of such factors, survival increased. Further improvements will depend upon better immunosuppression. Orthotopic liver transplantation (liver replacement) is the preferred operation in most cases, but placement of an extra liver (auxiliary transplantation) may have a role under special circumstances. © 1979
Dune Dynamics Drive Discontinuous Barrier Retreat
Barrier islands and spits tend to migrate landward in response to sea-level rise through the storm-driven process of overwash, but overwash flux depends on the height of the frontal dunes. Here, we explore this fundamental linkage between dune dynamics and barrier migration using the new model Barrier3D. Our experiments demonstrate that discontinuous barrier retreat is a prevalent behavior that can arise directly from the bistability of foredune height, occurring most likely when the storm return period and characteristic time scale of dune growth are of similar magnitudes. Under conditions of greater storm intensity, discontinuous retreat becomes the dominant behavior of barriers that were previously stable. Alternatively, higher rates of sea-level rise decrease the overall likelihood of discontinuous retreat in favor of continuous transgression. We find that internal dune dynamics, while previously neglected in exploratory barrier modeling, are an essential component of barrier evolution on time scales relevant to coastal management
The UK risk assessment scheme for all non-native species
1. A pest risk assessment scheme, adapted from the EPPO (European and Mediterranean Plant Protection Organisation) scheme, was developed to assess the risks posed to UK species, habitats and ecosystems by non-native taxa.
2. The scheme provides a structured framework for evaluating the potential for non-native organisms, whether intentional or unintentional introductions, to enter, establish, spread and cause significant impacts in all or part of the UK. Specialist modules permit the relative importance of entry pathways, the vulnerability of receptors and the consequences of policies to be assessed and appropriate risk management options to be selected. Spreadsheets for summarising the level of risk and uncertainty, invasive attributes and economic impact were created. In addition, new methods for quantifying economic impact and summarising risk and uncertainty were explored.
3. Although designed for the UK, the scheme can readily be applied elsewhere
Alkali Metal Trihalides: MX Ì Ion Pair or MX-X Complex?
The alkali metal trihalides MX3 (M = Li, Na, K, Rb, and Cs; X = Cl, Br, and I) are systematically studied using coupled-cluster methods. Benchmarks using CCSD(T) against diatomic experimental results suggest satisfactory performance for the weighted core-valence basis sets (new basis sets for K, Rb, and Cs) selected for predicting reliable structures and harmonic vibrational frequencies. An isomer search using the B3LYP functional yields a planar, yet asymmetric T-shaped Cs structure as the global minimum for all MX3 species. Much higher level CCSD(T) computations show a moderate to strong distortion of the X3Ë anion by the M+ cation in the respective equilibrium geometries. Most obviously, for LiCl3 the two Cl-Cl distances are separated by 0.786 Ă
. Even for CsI3, the structure least distorted from the M+X3Ë model, the two I-I distances differ by 0.243 Ă
. It does not take much energy to distort the parent anions along an asymmetric stretch, so this is no surprise. The normal modes of vibration of the MX3 molecules are in better agreement with matrix isolation experiments than previous calculations. And these normal modes are revealing -- instead of the well-established antisymmetric and symmetric stretches of the âfreeâ X3Ë anions, relatively localized and mutually-perturbed X-X and M-X stretches are calculated. The suggestion emerges that the MX3 system may be alternatively described as an MX-X2 complex, rather than the M+X3Ë ion pair. This perspective is supported by bonding analyses showing low electron densities at the bond critical points and natural bond orders between the MX and X2 moieties. The thermochemistry of fragmentations of MX3 to MX + X2 vs. M+ + X3Ë also supports the alternative viewpoint of the bonding in this class of molecules
Exposure to secondhand smoke, exclusive breastfeeding and infant adiposity at age 5 months in the Healthy Start study
Background: Infant adiposity may be influenced by several environmental risk factors, but few studies have explored these interactions. Objective: To examine the interaction between exposure to secondhand smoke and breastfeeding exclusivity on adiposity at age 5 months. Methods: We studied 813 mother-offspring pairs from the longitudinal Healthy Start study. Fat mass and fat-free mass were measured by air displacement plethysmography. Linear regression analyses were used to estimate the association between household smokers (none, any) with fat mass, fat-free mass, percent fat mass, weight-for-age z-score, weight-for-length z-score and BMI-for-age z-score as separate outcomes. Interaction terms between household smokers and breastfeeding exclusivity (<5 months, â„5 months) were added to separate models. Results: The combination of exposure to secondhand smoke and a lack of exclusive breastfeeding was associated with increased adiposity at age 5 months. For example, within the not exclusively breastfed strata, exposure to secondhand smoke was associated with increased fat mass (0.1 kg; 95% CI: 0.0â0.2; P = 0.05). Conversely, within the exclusively breastfed strata, there was virtually no difference in fat mass between exposed and non-exposed infants (coefficient: â0.1; 95% CI: â0.3â0.1; P = 0.25). Conclusions: Our findings may inform new public health strategies with potential relevance for both smoking cessation and obesity prevention
Parent Skills Training: Expanding School-Based Services for Adolescent Mothers
This article reports the results of a collaborative intervention effort between a teen-parent program and a school of social work Social work faculty and students participated in a program aimed at strengthening parental skills and the utilization of social support among adolescent mothers who were enrolled in a special high school program. The results of this evaluation study point to additional factors, such as empathy training and stress management, which need to be included in a comprehensive service-delivery program for school-age mothers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68359/2/10.1177_104973159200200203.pd
Longitudinal Associations of Neighborhood Crime and Perceived Safety with Blood Pressure: The Multi-Ethnic Study of Atherosclerosis (MESA)
Background: High neighborhood crime and low perceptions of safety may influence blood pressure (BP) through chronic stress. Few studies have examined these associations using longitudinal data. Methods: We used longitudinal data from 528 participants of the Multi-Ethnic Study of Atherosclerosis (aged 45-84, nonhypertensive at baseline) who lived in Chicago, Illinois. We examined associations of changes in individual-level perceived safety, aggregated neighborhood-level perceived safety, and past-year rates of police-recorded crime in a 1, =, or = mile buffer per 1,000 population with changes in systolic and diastolic BPs using fixed-effects linear regression. BP was measured five times between 2000 and 2012 and was adjusted for antihypertensive medication use (+10 mm Hg added to systolic and +5 mm Hg added to diastolic BP for participants on medication). Models were adjusted for time-varying sociodemographic and healthrelated characteristics and neighborhood socioeconomic status. We assessed differences by sex. Results: A standard deviation increase in individual-level perceived safety was associated with a 1.54 mm Hg reduction in systolic BP overall (95% confidence interval [CI]: 0.25, 2.83), and with a 1.24 mm Hg reduction in diastolic BP among women only (95% CI: 0.37, 2.12) in adjusted models. Increased neighborhood-level safety was not associated with BP change. An increase in police-recorded crime was associated with a reduction in systolic and diastolic BPs among women only, but results were sensitive to neighborhood buffer size. Conclusions: Results suggest individual perception of neighborhood safety may be particularly salient for systolic BP reduction relative to more objective neighborhood exposures
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