1,096 research outputs found
A periodic elastic medium in which periodicity is relevant
We analyze, in both (1+1)- and (2+1)- dimensions, a periodic elastic medium
in which the periodicity is such that at long distances the behavior is always
in the random-substrate universality class. This contrasts with the models with
an additive periodic potential in which, according to the field theoretic
analysis of Bouchaud and Georges and more recently of Emig and Nattermann, the
random manifold class dominates at long distances in (1+1)- and
(2+1)-dimensions. The models we use are random-bond Ising interfaces in
hypercubic lattices. The exchange constants are random in a slab of size
and these coupling constants are periodically repeated
along either {10} or {11} (in (1+1)-dimensions) and {100} or {111} (in
(2+1)-dimensions). Exact ground-state calculations confirm scaling arguments
which predict that the surface roughness behaves as: and , with in
-dimensions and; and , with in -dimensions.Comment: Submitted to Phys. Rev.
On the thermodynamics of first-order phase transition smeared by frozen disorder
The simplified model of first-order transition in a media with frozen
long-range transition-temperature disorder is considered. It exhibits the
smearing of the transition due to appearance of the intermediate inhomogeneous
phase with thermodynamics described by the ground state of the short-range
random-field Ising model. Thus the model correctly reproduce the persistence of
first-order transition only in dimensions d > 2, which is found in more
realistic models. It also allows to estimate the behavior of thermodynamic
parameters near the boundaries of the inhomogeneous phase.Comment: 4 page
Sonic Hedgehog Signaling and Development of the Dentition
Sonic hedgehog (Shh) is an essential signaling peptide required for normal embryonic development. It represents a highly-conserved marker of odontogenesis amongst the toothed vertebrates. Signal transduction is involved in early specification of the tooth-forming epithelium in the oral cavity, and, ultimately, in defining tooth number within the established dentition. Shh also promotes the morphogenetic movement of epithelial cells in the early tooth bud, and influences cell cycle regulation, morphogenesis, and differentiation in the tooth germ. More recently, Shh has been identified as a stem cell regulator in the continuously erupting incisors of mice. Here, we review contemporary data relating to the role of Shh in odontogenesis, focusing on tooth development in mammals and cartilaginous fishes. We also describe the multiple actions of this signaling protein at the cellular level
Aeolian sans ripples: experimental study of saturated states
We report an experimental investigation of aeolian sand ripples, performed
both in a wind tunnel and on stoss slopes of dunes. Starting from a flat bed,
we can identify three regimes: appearance of an initial wavelength, coarsening
of the pattern and finally saturation of the ripples. We show that both initial
and final wavelengths, as well as the propagative speed of the ripples, are
linear functions of the wind velocity. Investigating the evolution of an
initially corrugated bed, we exhibit non-linear stable solutions for a finite
range of wavelengths, which demonstrates the existence of a saturation in
amplitude. These results contradict most of the models.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett. Title changed,
figures corrected and simplified, more field data included, text clarifie
The neural correlates of social connection
Cultivating social connection has long been a goal of psychology, philosophy, religion, and public policy. Yet the psychological and neural responses that accompany a feeling of connection to others remain unclear. In the present study, we used functional neuroimaging to shed light on the neural correlates of self- and other-focused processes during the successful self-generation of feelings of social connection. To do this, we used a trait judgment task to localize functional activation related to self-focused thought. We then examined brain responses during guided exercises designed both to encourage feeling love and connection from others (i.e., self-focused) and to generate feelings of love and connection toward others (i.e., other-focused). Our results indicated that generating feelings of social connection recruited a portion of the medial prefrontal cortex (MPFC) implicated in thinking about both the self and others. Within this larger area, we observed distinct profiles of activation within different subregions. Although rostral anterior cingulate cortex was more strongly activated by other-focused components of the task, a more dorsal portion of MPFC was comparatively more active during primarily self-focused components of the task. Somewhat surprisingly, stronger feelings of social connection were not associated with greater activation in the anterior cingulate, but rather with less activation in the dorsal region of the MPFC related to self-focused thought. These results are consistent with the possibility that reducing certain kinds of self-focused thought might yield a greater sense of social connection to and care for others
Magnetic nanocomposites at microwave frequencies
Most conventional magnetic materials used in the electronic devices are
ferrites, which are composed of micrometer-size grains. But ferrites have small
saturation magnetization, therefore the performance at GHz frequencies is
rather poor. That is why functionalized nanocomposites comprising magnetic
nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm,
and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have
a significant potential for the electronics industry. When the size of the
nanoparticles is smaller than the critical size for multidomain formation,
these nanocomposites can be regarded as an ensemble of particles in
single-domain states and the losses (due for example to eddy currents) are
expected to be relatively small. Here we review the theory of magnetism in such
materials, and we present a novel measurement method used for the
characterization of the electromagnetic properties of composites with
nanomagnetic insertions. We also present a few experimental results obtained on
composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table
The prognostic value of extramural venous invasion in preoperative MRI of rectal cancer patients
Aim This study aimed to examine the prognostic value of extramural venous invasion observed in preoperative MRI on survival and recurrences. Method In total, 778 rectal cancer patients were evaluated in multidisciplinary meetings in Helsinki University Hospital during the years 2016-2018. 635 patients met the inclusion criteria of stage I-III disease and were intended for curative treatment at the time of diagnosis. 128 had extramural venous invasion in preoperative MRI. Results The median follow-up time was 2.5 years. In a univariate analysis extramural venous invasion was associated with poorer disease-specific survival (hazard ratio [HR] 2.174, 95% CI 1.118-4.224, P = 0.022), whereas circumferential margin = T3c or nodal positivity were not. Disease recurrence occurred in 17.3% of the patients: 13.4% had metastatic recurrence only, 1.7% mere local recurrence and 2.2% both metastatic and local recurrence. In multivariate analysis, extramural venous invasion (HR 1.734, 95% CI 1.127-2.667, P = 0.012) and nodal positivity (HR 1.627, 95% CI 1.071-2.472, P = 0.023) were risk factors for poorer disease-free survival (DFS). Circumferential marginPeer reviewe
Loving-kindness meditation: a tool to improve healthcare provider compassion, resilience, and patient care
Background:
Stress is a critical problem facing many healthcare institutions. The consequences of stress include increased provider burnout and decreased quality of care for patients. Ironically, a key factor that may help buffer the impact of stress on provider well-being and patient health outcomes—compassion—is low in healthcare settings and declines under stress. This gives rise to an urgent question: what practical steps can be taken to increase compassion, thereby benefitting both provider well-being and patient care?
Methods:
We investigated the relative effectiveness of a short, 10-minute session of loving-kindness meditation (LKM) to increase compassion and positive affect. We compared LKM to a non-compassion positive affect induction (PAI) and a neutral visualization (NEU) condition. Self- and other-focused affect, self-reported measures of social connection, and semi-implicit measures of self-focus were measured pre- and post- meditation using repeated measures ANOVAs and via paired sample t-tests for follow-up comparisons.
Results:
Findings show that LKM improves well-being and feelings of connection over and above other positive-affect inductions, at both explicit and implicit levels, while decreasing self-focus in under 10 minutes and in novice meditators.
Conclusions:
These findings suggest that LKM may be a viable, practical, and time-effective solution for preventing burnout and promoting resilience in healthcare providers and for improving quality of care in patients
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