358 research outputs found
Detection of confinement and jumps in single molecule membrane trajectories
We propose a novel variant of the algorithm by Simson et al. [R. Simson, E.D.
Sheets, K. Jacobson, Biophys. J. 69, 989 (1995)]. Their algorithm was developed
to detect transient confinement zones in experimental single particle tracking
trajectories of diffusing membrane proteins or lipids. We show that our
algorithm is able to detect confinement in a wider class of confining potential
shapes than Simson et al.'s one. Furthermore it enables to detect not only
temporary confinement but also jumps between confinement zones. Jumps are
predicted by membrane skeleton fence and picket models. In the case of
experimental trajectories of -opioid receptors, which belong to the family
of G-protein-coupled receptors involved in a signal transduction pathway, this
algorithm confirms that confinement cannot be explained solely by rigid fences.Comment: 4 pages, 3 figure
Stacking order dynamic in the quasi-two-dimensional dichalcogenide 1T-TaS probed with MeV ultrafast electron diffraction
Transitions between different charge density wave (CDW) states in
quasi-two-dimensional materials may be accompanied also by changes in the
inter-layer stacking of the CDW. Using MeV ultrafast electron diffraction, the
out-of-plane stacking order dynamics in the quasi-two-dimensional
dichalcogenide 1T-TaS is investigated for the first time. From the
intensity of the CDW satellites aligned around the commensurate = 1/6
characteristic stacking order, it is found out that this phase disappears with
a 0.5 ps time constant. Simultaneously, in the same experiment, the emergence
of the incommensurate phase, with a slightly slower 2.0 ps time constant, is
determined from the intensity of the CDW satellites aligned around the
incommensurate = 1/3 characteristic stacking order. These results might be
of relevance in understanding the metallic character of the laser-induced
metastable "hidden" state recently discovered in this compound
Norwalk Virus–specific Binding to Oyster Digestive Tissues
Specific binding of virus to oysters can selectively concentrate a human pathogen
Assessment of human enteric viruses in cultured and wild bivalve molluscs
Standard and real-time reverse transcription-PCR (rRT-PCR) procedures were used to monitor cultured and wild bivalve molluscs from the RĂa de Vigo (NW Spain) for the main human enteric RNA viruses, specifically, norovirus (NoV), hepatitis Avirus (HAV), astrovirus (AsV), rotavirus (RT), enterovirus (EV), and Aichi virus (AiV). The results showed the presence of at least one enteric virus in 63.4% of the 41 samples analyzed. NoV GII was the most prevalent virus, detected in 53.7% of the samples, while NoV GI, AsV, EV, and RV were found at lower percentages (7.3, 12.2, 12.2, and 4.9%, respectively). In general, samples obtained in the wild were more frequently contaminated than those from cultured (70.6 vs. 58.3%) molluscs and were more readily contaminated with more than one virus. However, NoV GI was detected in similar amounts in cultured and wild samples (6.4 Ă— 102 to 3.3 Ă— 103 RNA copies per gram of digestive tissue) while the concentrations of NoV GII were higher in cultured (from 5.6 Ă— 101 to 1.5 Ă— 104 RNA copies per gram of digestive tissue) than in wild (from 1.3 Ă— 102 to 3.4 Ă— 104 RNA copies per gram of digestive tissue) samples. [Int Microbiol 2009; 12(3):145-151
Spin configurations in Co2FeAl0.4Si0.6 Heusler alloy thin film elements
We determine experimentally the spin structure of half-metallic
Co2FeAl0.4Si0.6 Heusler alloy elements using magnetic microscopy. Following
magnetic saturation, the dominant magnetic states consist of quasi-uniform
configurations, where a strong influence from the magnetocrystalline anisotropy
is visible. Heating experiments show the stability of the spin configuration of
domain walls in confined geometries up to 800 K. The switching temperature for
the transition from transverse to vortex walls in ring elements is found to
increase with ring width, an effect attributed to structural changes and
consequent changes in magnetic anisotropy, which start to occur in the narrower
elements at lower temperatures.Comment: 4 pages, 4 figure
Multiorgan failure after sickle cell vaso occlusive attack: integrated clinical and biological emergency
We describe the case of a 30-year-old patient, suffering from composite S/beta + sickle cell disease. He was hospitalized following a vaso-occlusive attack with acute bone pains. Despite an analgesic treatment and transfusion of three units of red blood cells, a non-regenerative anemia appeared within 24 hours. One day later an acute chest syndrome with atelectasis of the left lung and desaturation and multi-organ failure occurred and necessitated the patient\u27s intubation and required him to be placed in an artificial coma. A bronchoalveolar lavage was performed, which eliminated pneumonia but proved, after staining with oil red O, many neutral fatty acid microvacuoles in more than 80% of macrophages, suggesting a pulmonary fat embolism. The hypothesis of a bone marrow necrosis causing a pulmonary fat embolism was discussed and confirmed the next day by the characteristic appearance of the bone marrow. A therapeutic protocol associating iteratively bleeding and red blood cells transfusion was administered on the second day with the objective of maintaining haemoglobin S at less than 20% rate. Successive haemoglobin S assay was applied using a high performance liquid chromatography (HPLC) technique with a quick response within one hour after transfusion or bleeding. This protocol resulted in an improvement in the patient\u27s condition, with a gradual normalization of vital signs and extubation twelve days later and discharge without sequelae twenty-five days later. The succession of rare but serious sickle cell complications anaemia which occurred in this patient could be controlled by adapting the laboratory for the clinical emergency
Element resolved ultrafast demagnetization rates in ferrimagnetic CoDy
Femtosecond laser induced ultrafast magnetization dynamics have been studied
in multisublattice CoxDy1-x alloys. By performing element and time-resolved
X-ray spectroscopy, we distinguish the ultrafast quenching of Co3d and Dy4f
magnetic order when the initial temperatures are below (T=150K) or above
(T=270K) the temperature of magnetic compensation (Tcomp). In accordance with
former element-resolved investigations and theoretical calculations, we observe
different dynamics for Co3d and Dy4f spins. In addition we observe that, for a
given laser fluence, the demagnetization amplitudes and demagnetization times
are not affected by the existence of a temperature of magnetic compensation.
However, our experiment reveals a twofold increase of the ultrafast
demagnetization rates for the Dy sublattice at low temperature. In parallel, we
measure a constant demagnetization rate of the Co3d sublattice above and below
Tcomp. This intriguing difference between the Dy4f and Co3d sublattices calls
for further theoretical and experimental investigations.Comment: 6 Figure, 2 Table
Magnetic switching in granular FePt layers promoted by near-field laser enhancement
Light-matter interaction at the nanoscale in magnetic materials is a topic of
intense research in view of potential applications in next-generation
high-density magnetic recording. Laser-assisted switching provides a pathway
for overcoming the material constraints of high-anisotropy and high-packing
density media, though much about the dynamics of the switching process remains
unexplored. We use ultrafast small-angle x-ray scattering at an x-ray
free-electron laser to probe the magnetic switching dynamics of FePt
nanoparticles embedded in a carbon matrix following excitation by an optical
femtosecond laser pulse. We observe that the combination of laser excitation
and applied static magnetic field, one order of magnitude smaller than the
coercive field, can overcome the magnetic anisotropy barrier between "up" and
"down" magnetization, enabling magnetization switching. This magnetic switching
is found to be inhomogeneous throughout the material, with some individual FePt
nanoparticles neither switching nor demagnetizing. The origin of this behavior
is identified as the near-field modification of the incident laser radiation
around FePt nanoparticles. The fraction of not-switching nanoparticles is
influenced by the heat flow between FePt and a heat-sink layer
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