623 research outputs found
The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor
We investigated the nature of the magnetic phase transition in the
Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the
range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization
measurements performed in the magnetic field up to 90 kOe and temperature range
2-200 K showed that the magnetic ordering at temperatures below T = 50 K
exhibits features characteristic for both spin-glass and ferromagnetic phases.
The modified Sherrington - Southern model was applied to explain the observed
transition temperatures. The calculations showed that the spin-glass state is
preferred in the range of the experimental carrier concentrations and Mn
content. The value of the Mn hole exchange integral was estimated to be J/pd/ =
0.45+/-0.05 eV. The experimental magnetization vs temperature curves were
reproduced satisfactory using the non-interacting spin-wave theory with the
exchange constant J/pd/ values consistent with those calculated using modified
Sherrington - Southern model. The magnetization vs magnetic field curves showed
nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of
strong magnetic frustration in the system. The experimental results were
reproduced theoretically with good accuracy using the molecular field
approximation-based model of a disordered ferromagnet with long-range RKKY
interaction.Comment: 9 pages, 6 figure
”Friskere liv med forebygging”. Forebyggende hjemmebesøk til friske eldre
Kommunale helse- og omsorgstjenester står foran betydelige utfordringer knyttet blant annet til en sterkt voksende eldre befolkning (Helse og omsorgsdepartementet, 2006). De tre Utviklingssentrene i Agder; Grimstad, Kristiansand og Songdalen søkte og fikk midler fra Helsedirektoratet til et 3 – årig prosjekt med helsefremmende arbeid rettet mot eldre, med fokus på ”Forebyggende hjemmebesøk”. Prosjektet ”Friskere liv med forebygging” er ett av 5 som har fått midler fra Helsedirektoratet til Forebyggende hjemmebesøk og har hatt årlige samlinger med de andre
A rare case of arterial avulsion presenting with occult blood loss following total hip arthroplasty: a case report
INTRODUCTION: Iatrogenic arterial damage during total hip replacement is a rare but potentially life- or limb-threatening complication. To the best of our knowledge, this is the first reported case of an avulsion injury to a posterior branch of the profunda femoral artery during primary hip arthroplasty. CASE PRESENTATION: We describe the case of a 55-year-old Caucasian man who underwent a total hip replacement. The patient's hemoglobin levels dropped postoperatively, but there was no obvious bleeding, hemodynamic instability, pulsatile mass, or limb ischemia. The patient's hemoglobin levels continued to drop despite nine units of transfused blood. Three days after surgery, the patient underwent an angiography that showed an avulsion injury to a posterior branch of the profunda femoral artery. The avulsion was ligated and the hematoma was evacuated. CONCLUSION: Vascular damage may present in many ways including obvious bleeding, haemodynamic instability, a pulsatile mass, limb ischemia, and occult blood loss. Any of these signs in isolation or in combination could represent a vascular injury and an urgent angiogram should be considered
Synchronisation in networks of delay-coupled type-I excitable systems
We use a generic model for type-I excitability (known as the SNIPER or SNIC
model) to describe the local dynamics of nodes within a network in the presence
of non-zero coupling delays. Utilising the method of the Master Stability
Function, we investigate the stability of the zero-lag synchronised dynamics of
the network nodes and its dependence on the two coupling parameters, namely the
coupling strength and delay time. Unlike in the FitzHugh-Nagumo model (a model
for type-II excitability), there are parameter ranges where the stability of
synchronisation depends on the coupling strength and delay time. One important
implication of these results is that there exist complex networks for which the
adding of inhibitory links in a small-world fashion may not only lead to a loss
of stable synchronisation, but may also restabilise synchronisation or
introduce multiple transitions between synchronisation and desynchronisation.
To underline the scope of our results, we show using the Stuart-Landau model
that such multiple transitions do not only occur in excitable systems, but also
in oscillatory ones.Comment: 10 pages, 9 figure
Upregulation of p16INK4A and Bax in p53 wild/p53-overexpressing crypts in ulcerative colitis-associated tumours
In ulcerative colitis (UC)-associated tumours, p53 gene mutations and p53 protein overexpression are frequently found in early stages, but the two types of alteration do not always coincide. To clarify this discrepancy, p53 mutations and expression of p53-associated molecules were analysed in UC-associated dysplasias by a combination of microdissection, polymerase chain reaction-direct sequencing and immunohistochemistry at the single crypt level. Mismatch of p53 protein overexpression (+)/mutation (−) or p53 overexpression (−)/gene mutation (+) was found in nine crypts in regenerative mucosa (19 crypts), in 27 in low-grade dysplasia (41), in one in high-grade dysplasia (5) and in 12 in invasive carcinomas (17). Regarding these mismatched crypts of the first type, significant increase in p16INK4A and Bax expression was found. The Ki-67 labelling index was depressed in such p53-diffusely positive lesions with the wild-type p53 gene, compared to their p53-diffusely positive and mutant type counterparts. p16INK4A was upregulated indirectly as part of the negative feedback, and increase in Bax, directly controlled by wild-type p53, indicates upregulation of apoptosis. No significant relation with p53-related gene products was detected with the p53 protein overexpression (−)/p53 mutation (+) mismatch. Therefore, a tumorigenesis pathway independent of p53 dysfunction appears to exist in association with ulcerative colitis
Ultrahard carbon film from epitaxial two-layer graphene
Atomically thin graphene exhibits fascinating mechanical properties, although
its hardness and transverse stiffness are inferior to those of diamond. To
date, there hasn't been any practical demonstration of the transformation of
multi-layer graphene into diamond-like ultra-hard structures. Here we show that
at room temperature and after nano-indentation, two-layer graphene on SiC(0001)
exhibits a transverse stiffness and hardness comparable to diamond, resisting
to perforation with a diamond indenter, and showing a reversible drop in
electrical conductivity upon indentation. Density functional theory
calculations suggest that upon compression, the two-layer graphene film
transforms into a diamond-like film, producing both elastic deformations and
sp2-to-sp3 chemical changes. Experiments and calculations show that this
reversible phase change is not observed for a single buffer layer on SiC or
graphene films thicker than 3 to 5 layers. Indeed, calculations show that
whereas in two-layer graphene layer-stacking configuration controls the
conformation of the diamond-like film, in a multilayer film it hinders the
phase transformation.Comment: Published online on Nature Nanotechnology on December 18, 201
MicroRNA-135b promotes cancer progression by acting as a downstream effector of oncogenic pathways in colon cancer
MicroRNA deregulation is frequent in human colorectal cancers (CRCs), but little is known as to whether it represents a bystander event or actually drives tumor progression in vivo. We show that miR-135b overexpression is triggered in mice and humans by APC loss, PTEN/PI3K pathway deregulation, and SRC overexpression and promotes tumor transformation and progression. We show that miR-135b upregulation is common in sporadic and inflammatory bowel disease-associated human CRCs and correlates with tumor stage and poor clinical outcome. Inhibition of miR-135b in CRC mouse models reduces tumor growth by controlling genes involved in proliferation, invasion, and apoptosis. We identify miR-135b as a key downsteam effector of oncogenic pathways and a potential target for CRC treatment
Multi-Particle Collision Dynamics -- a Particle-Based Mesoscale Simulation Approach to the Hydrodynamics of Complex Fluids
In this review, we describe and analyze a mesoscale simulation method for
fluid flow, which was introduced by Malevanets and Kapral in 1999, and is now
called multi-particle collision dynamics (MPC) or stochastic rotation dynamics
(SRD). The method consists of alternating streaming and collision steps in an
ensemble of point particles. The multi-particle collisions are performed by
grouping particles in collision cells, and mass, momentum, and energy are
locally conserved. This simulation technique captures both full hydrodynamic
interactions and thermal fluctuations. The first part of the review begins with
a description of several widely used MPC algorithms and then discusses
important features of the original SRD algorithm and frequently used
variations. Two complementary approaches for deriving the hydrodynamic
equations and evaluating the transport coefficients are reviewed. It is then
shown how MPC algorithms can be generalized to model non-ideal fluids, and
binary mixtures with a consolute point. The importance of angular-momentum
conservation for systems like phase-separated liquids with different
viscosities is discussed. The second part of the review describes a number of
recent applications of MPC algorithms to study colloid and polymer dynamics,
the behavior of vesicles and cells in hydrodynamic flows, and the dynamics of
viscoelastic fluids
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