SU(3) techniques for angular momentum projected matrix elements in multi‐cluster problems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87456/2/518_1.pd

Surface flashover breakdown mechanisms on liquid immersed dielectrics

Flashover formation and expansion mechanisms on the surfaces of different dielectrics immersed in transformer oil have been numerically analyzed. Streamers emanating from a needle electrode tend to transform to surface flashovers if the immersed dielectric permittivity is higher than the liquid permittivity and/or the dielectric interfacial surface cuts the path of the streamer. Perpendicular interface of the immersed dielectric impedes the breakdown by deflecting the streamer and slowing down the surface flashover. The parallel dielectric interface, however, assists the breakdown by regulating the surface flashover velocity to an approximately constant value (∼10 km/s).IEEE Dielectrics and Electrical Insulation Societ

Effects of Impulse Voltage Polarity, Peak Amplitude, and Rise Time on Streamers Initiated From a Needle Electrode in Transformer Oil

An electrothermal hydrodynamic model is presented to evaluate effects of the applied lightning impulse voltage parameters such as polarity, magnitude, and rise time on the initiation and propagation of the streamers formed in an IEC defined needle-sphere electrode geometry filled with transformer oil. Instantaneous velocity, column diameter, head curvature, maximum electric field, and the volume charge density have been investigated as the main characteristics of the streamer. Modeling results indicate that greater applied voltage peak amplitudes form streamers with higher velocity, greater head curvatures, and thicker columns. The bushy negative streamers usually initiate at almost twice the applied voltage magnitude and propagate slower than filamentary positive streamers. Results also show that in transformer oil at the same impulse voltage peak amplitude, shorter rise times create thicker positive and negative streamers.ABB Corporate Research Center (Vasteras, Sweden

Concordance of attachment representations in preschool siblings assessed by the attachment story completion task

Several studies have indicated only a modest concordance of attachment security in siblings in infancy. Until now, very little was known about the concordance of siblings’ attachment security beyond infancy, as assessed by the attachment story completion task. This cross-sectional study aims to examine the concordance of attachment representations of 38 first-born (4–7 years) and 38 second-born (3–5 years) siblings living in middle-class two-parent families. Personality factors and the level of parenting stress of the biological mothers (30–43 years) were analysed in relation to children’s attachment security. The results indicate a 43 % secure-insecure concordance rate between siblings’ attachment representations. Sibling’s gender correspondence, age differences and differences in parenting stress were not related to attachment concordance whereas gender of the first-born child was related to attachment concordance. The results also indicate that older children more frequently had secure attachment representations compared to younger children and that attachment insecurity was associated with greater negative impacts of life events, lower maternal life satisfaction and higher parenting stress. Our study indicates that siblings’ attachment representations may lack concordance even when siblings are assessed by the same method at the same time. If maternal and environmental factors are able to explain a substantial amount of variance in the attachment security of individual children, non-shared environmental factors might be underestimated when studying siblings’ attachment representations. The significant effect of age on children’s attachment representations found in this study suggests the need for future research on the stability of attachment representations during the preschool years

An SU(3) approach to nuclear multi-cluster problems

By combining SU(3) recoupling techniques with the use of the Bargmann-Segal integral transform closed expressions are derived for the interaction kernels of the nuclear cluster model. In a cluster model basis in which the relative motion and internal oscillator wave functions (with arbitrary and different oscillator frequencies) are expanded in SU(3) coupled form, SU(3) reduced matrix elements are evaluated by integral transform methods. Matrix elements in a basis of good angular momentum can be constructed for multi-cluster systems by combining these SU(3) reduced matrix elements with readily available SU(3) Wigner coefficients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23585/1/0000547.pd

The Bargmann-Segal transform, SU(3) symmetry, and nuclear cluster norms

By combining the use of the Bargmann-Segal integral transform with SU(3) recoupling techniques a new method is developed for the calculation of matrix elements in a basis of cluster model wave functions. An analytic expression is derived for the norm of an [alpha] + heavy fragment "cluster" function. Norms in p and sd shell nuclei can be calculated by a simple formula involving a few tabulated coefficients and readily available SU(3) Racah coefficients. Specific tabulations are given for nuclei with 12 [less, double equals] A [less, double equals] 24.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23668/1/0000636.pd

Impulse breakdown delay in liquid dielectrics

Theoretical images of streamers, revealing the mechanisms behind impulse breakdown in liquid dielectrics, are presented. Streamers lead to electrical breakdown by forming paths, capable of carrying large current amplitudes between electrodes. Breakdown delays and terminal currents are calculated for various electrode geometries (40 μm needle and 6.35 mm sphere) and gap distances (up to 10 mm). Modeling results indicate that the breakdown in needle-needle electrodes requires higher impulse voltage amplitudes than in needle-sphere electrodes for the same gap distances. Streamers in needle-sphere geometries are about 50% thicker than streamers propagating in needle-needle geometries under similar impulse voltage amplitudes.ABB Corporate Research Center (Vasteras, Sweden)IEEE Dielectrics and Electrical Insulation Society (Fellowship

Correction of severe valgus osteoarthritis by total knee arthroplasty is associated with increased postoperative ankle symptoms

Purpose: The aim of this study was to assess the mid-term clinical outcome of the ankle joint after total knee arthroplasty (TKA) in high-grade valgus osteoarthritis. Methods: In this case–control study, n=36 patients with a preoperative mechanical tibiofemoral angle (mTFA)≥15° who underwent TKA between December 2002 and December 2012 were included. The control group (mTFA<15°) of n=60 patients was created using case matching. Radiological [mechanical tibiofemoral angle (mTFA) and ankle joint orientation to the ground (G-AJLO)] and clinical parameters [Foot Function Index (FFI), Knee Society Score, Forgotten Joint Score, and Range of Motion (ROM)] were analysed. The mean follow-up time was 59 months (IQR [56, 62]). Results: The degree of correcting the mTFA by TKA signifcantly correlated with the postoperative FFI (R=0.95, p<0.05), although the knee and ankle joint lines were corrected to neutral orientations. A cut-of value of 16.5° [AUC 0.912 (0.85–0.975 95% CI), sensitivity=0.8, specifcity=0.895] was calculated, above which the odds ratio (OR) for developing ankle symptoms increased vastly [OR 34.0 (9.10–127.02 95% CI)]. ROM restrictions of the subtalar joint displayed a strong sig nifcant correlation with the FFI (R=0.74, p<0.05), demonstrating that decreased ROM of the subtalar joint was associated with aggravated outcomes of the ankle joint. Conclusions: In this study, higher degrees of leg axis correction in TKA were associated with increased postoperative ankle symptoms. When TKA is performed in excessive valgus knee osteoarthritis, surgeons should be aware that this might trigger the onset or progression of ankle symptoms, particularly in cases of a stif subtalar joint. Level of evidence III

Body fat distribution and risk of incident ischemic stroke in men and women aged 50 to 74 years from the general population: the KORA Augsburg cohort study

It remains controversial whether measures of general or abdominal adiposity are better risk predictors for ischemic stroke. Furthermore, so far it is unclear whether body fat mass index (BFMI) and fat free mass index (FFMI) are risk predictors for ischemic stroke. This study examined the sex-specific relevance of body mass index (BMI), BROCA Index, waist circumference (WC), waist-height ratio (WHtR), BFMI and FFMI for the development of ischemic stroke in a Caucasian population.The prospective population-based cohort study was based on 1917 men and 1832 women (aged 50 to 74 years) who participated in the third (1994/95) or fourth (1999/2001) MONICA/KORA Augsburg survey. Subjects were free of stroke at baseline. Standardized anthropometric and bioelectric impedance measurements were obtained at baseline. Hazard ratios (HR) were estimated from Cox proportional hazard models.During a median follow-up of 9.3 years 128 ischemic strokes occurred in men and 81 in women, respectively. Coded as quartiles WC and WHtR were significantly associated with incident stroke in multivariable analyses in women (comparing the 4th vs. the bottom quartile), but none of the adiposity measures was significantly associated with incident stroke in multivariable adjusted analyses in men. When anthropometric measures were used as continuous variables, these findings were confirmed. After multivariable adjustment the associations between obesity measures and incident ischemic stroke were statistically significant only for WC (HR 1.39, 95%CI 1.12-1.72) and WHtR in women (HR 1.39, 95%CI 1.12-1.73) per increase of 1 standard deviation. In both sexes the measures BFMI and FFMI were no independent predictors for incident ischemic stroke.Abdominal obesity measures are independent predictors of incident ischemic stroke in women but not in men from the general adult population. Thus, it may be of particular importance for women to prevent central obesity in order to reduce their risk of ischemic stroke