443 research outputs found
Scaling determination of the nonlinear I-V characteristics for 2D superconducting networks
It is shown from computer simulations that the current-voltage (-)
characteristics for the two-dimensional XY model with resistively-shunted
Josephson junction dynamics and Monte Carlo dynamics obeys a finite-size
scaling form from which the nonlinear - exponent can be determined to
good precision. This determination supports the conclusion , where
is the dynamic critical exponent. The results are discussed in the light of the
contrary conclusion reached by Tang and Chen [Phys. Rev. B {\bf 67}, 024508
(2003)] and the possibility of a breakdown of scaling suggested by Bormann
[Phys. Rev. Lett. {\bf 78}, 4324 (1997)].Comment: 6 pages, to appear in PR
Substrate Type Affects the Drying Speed and Desiccation Tolerance of Fern Gametophytes
Although most ferns require abundant water to thrive, some ferns can survive in habitats with limited water. Previous studies have examined the adaptations that allow xeric ferns to thrive in mediterranean-type ecosystems such as southern California. However, the large fern sporophyte only represents one stage of the fern life cycle; the independent gametophyte phase must also survive water stress, including the six-month summer drought periods of the Santa Monica Mountains. Some fern gametophytes have been reported to be desiccation tolerant (capable of recovery from near-complete drying), and this trait is believed to be dependent on the plant’s drying speed. In order to test whether substrate type affects fern gametophyte dry out speed and level of recovery, we dried out gametophytes on five different substrates ranging from slow to fast drying speed: filter paper, agar, non-acclimated and acclimated soil plugs, and soil plates. Dark-adapted chlorophyll fluorescence (Fv/Fm) was measured to assess how long it took the gametophytes to desiccate completely and recover following rehydration. This study found that the substrate type affected both the gametophytes’ drying speed and their ability to recover. Specifically, gametophytes that were acclimated to and tested on soil plates experienced the slowest drying and the greatest recovery in Fv/Fm. The adaptations of fern gametophytes remain elusive despite their critical position in the fern life cycle. With increasing global temperatures and longer drought periods, a better understanding of gametophyte ecology will illuminate fern species’ susceptibility to climate change
Langevin Simulations of Two Dimensional Vortex Fluctuations: Anomalous Dynamics and a New -exponent
The dynamics of two dimensional (2D) vortex fluctuations are investigated
through simulations of the 2D Coulomb gas model in which vortices are
represented by soft disks with logarithmic interactions. The simulations
trongly support a recent suggestion that 2D vortex fluctuations obey an
intrinsic anomalous dynamics manifested in a long range 1/t-tail in the vortex
correlations. A new non-linear IV-exponent a, which is different from the
commonly used AHNS exponent, a_AHNS and is given by a = 2a_AHNS - 3, is
confirmed by the simulations. The results are discussed in the context of
earlier simulations, experiments and a phenomenological description.Comment: Submitted to PRB, RevTeX format, 28 pages and 13 figures, figures in
postscript format are available at http://www.tp.umu.se/~holmlund/papers.htm
Current-voltage characteristics of the two-dimensional XY model with Monte Carlo dynamics
Current-voltage characteristics and the linear resistance of the
two-dimensional XY model with and without external uniform current driving are
studied by Monte Carlo simulations. We apply the standard finite-size scaling
analysis to get the dynamic critical exponent at various temperatures. From
the comparison with the resistively-shunted junction dynamics, it is concluded
that is universal in the sense that it does not depend on details of
dynamics. This comparison also leads to the quantification of the time in the
Monte Carlo dynamic simulation.Comment: 5 pages in two columns including 5 figures, to appear in PR
Vortex dynamics for two-dimensional XY models
Two-dimensional XY models with resistively shunted junction (RSJ) dynamics
and time dependent Ginzburg-Landau (TDGL) dynamics are simulated and it is
verified that the vortex response is well described by the Minnhagen
phenomenology for both types of dynamics. Evidence is presented supporting that
the dynamical critical exponent in the low-temperature phase is given by
the scaling prediction (expressed in terms of the Coulomb gas temperature
and the vortex renormalization given by the dielectric constant
) both for RSJ and TDGL
and that the nonlinear IV exponent a is given by a=z+1 in the low-temperature
phase. The results are discussed and compared with the results of other recent
papers and the importance of the boundary conditions is emphasized.Comment: 21 pages including 15 figures, final versio
Magnetic-field dependence of dynamical vortex response in two-dimensional Josephson junction arrays and superconducting films
The dynamical vortex response of a two-dimensional array of the resistively
shunted Josephson junctions in a perpendicular magnetic field is inferred from
simulations. It is found that, as the magnetic field is increased at a fixed
temperature, the response crosses over from normal to anomalous, and that this
crossover can be characterized by a single dimensionless parameter. It is
described how this crossover should be reflected in measurements of the complex
impedance for Josephson junction arrays and superconducting films.Comment: 4 pages including 5 figures in two columns, final versio
The outcome of arthroscopic treatment of temporomandibular joint arthoropathy
The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.Ninety patients underwent arthroscopic temporomandibular joint surgery to 124 joints for arthropathy which had failed to respond to at least six months of non-surgical treatment. They were surveyed at between 6 months and 5 years (mean 2.5 years) after surgery and 63 per cent responded to the survey. They reported an 82 per cent improvement for pain (50 to 100 per cent better), 80 per cent for clicking and 82 per cent for locking. There was no morbidity following the treatment. Arthroscopic surgery sould be considered for advanced temporomandibular joint arthropathy which is refractory to non-surgical treatment.I. Rosenburg and A. N. Gos
Charge Transport in the Dense Two-Dimensional Coulomb Gas
The dynamics of a globally neutral system of diffusing Coulomb charges in two
dimensions, driven by an applied electric field, is studied in a wide
temperature range around the Berezinskii-Kosterlitz-Thouless transition. I
argue that the commonly accepted ``free particle drift'' mechanism of charge
transport in this system is limited to relatively low particle densities. For
higher densities, I propose a modified picture involving collective ``partner
transfer'' between bound pairs. The new picture provides a natural explanation
for recent experimental and numerical findings which deviate from standard
theory. It also clarifies the origin of dynamical scaling in this context.Comment: 4 pages, RevTeX, 2 eps figures included; some typos corrected, final
version to be published in Phys. Rev. Let
Predicting self-injurious thoughts in daily life using ambulatory assessment of state cognition
Self-injurious thoughts (SITs) fluctuate considerably from moment to moment. As such, “static” and temporally stable predictors (e.g., demographic variables, prior history) are suboptimal in predicting imminent SITs. This concern is particularly true for “online” cognitive abilities, which are important for understanding SITs, but are typically measured using tests selected for temporal stability. Advances in ambulatory assessments (i.e., real-time assessment in a naturalistic environment) allow for measuring cognition with improved temporal resolution. The present study measured relationships between “state” cognitive performance, measured using an ambulatory-based Trail Making Test, and SITs. Self-reported state hope and social connectedness was also measured. Data were collected using a specially designed mobile application (administered 4x/week up to 28 days) in substance use inpatients (N = 99). Consistent with prior literature, state hope and social connectedness was significantly associated with state SITs. Importantly, poorer state cognitive performance also significantly predicted state SITs, independent of hallmark static and state self-report risk variables. These findings highlight the potential importance of “online” cognition to predict SITs. Ambulatory recording reflects an efficient, sensitive, and ecological valid methodology for evaluating subjective and objectives predictors of imminent SITs
Maternal vitamin D status, gestational diabetes and infant birth size
Background: Maternal vitamin D status has been associated with both gestational diabetes mellitus (GDM) and fetal growth restriction, however, the evidence is inconsistent. In Finland, maternal vitamin D status has improved considerably due to national health policies. Our objective was to compare maternal 25-hydroxy vitamin D concentrations [25(OH)D] between mothers with and without GDM, and to investigate if an association existed between maternal vitamin D concentration and infant birth size. Methods: This cross-sectional study included 723 mother-child pairs. Mothers were of Caucasian origin, and infants were born at term with normal birth weight. GDM diagnosis and birth size were obtained from medical records. Maternal 25(OH)D was determined on average at 11 weeks of gestation in pregnancy and in umbilical cord blood (UCB) at birth. Results: GDM was observed in 81 of the 723 women (11%). Of the study population, 97% were vitamin D sufficient [25(OH)D >= 50 nmol/L]. There was no difference in pregnancy 25(OH)D concentration between GDM and non-GDM mothers (82 vs 82 nmol/L, P = 0.99). Regression analysis confirmed no association between oral glucose tolerance test results and maternal 25(OH)D (P > 0.53). Regarding the birth size, mothers with optimal pregnancy 25(OH)D (>= 80 nmol/L) had heavier newborns than those with suboptimal pregnancy 25(OH)D (P = 0.010). However, mothers with optimal UCB 25(OH) D had newborns with smaller head circumference than those with suboptimal 25(OH)D (P = 0.003), which was further confirmed as a linear association (P = 0.024). Conclusions: Maternal vitamin D concentration was similar in mothers with and without GDM in a mostly vitamin D sufficient population. Associations between maternal vitamin D status and birth size were inconsistent. A sufficient maternal vitamin D status, specified as 25(OH)D above 50 nmol/L, may be a threshold above which the physiological requirements of pregnancy are achieved.Peer reviewe
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