2,036 research outputs found
Conditions for extreme sensitivity of protein diffusion in membranes to cell environments
We study protein diffusion in multicomponent lipid membranes close to a rigid
substrate separated by a layer of viscous fluid. The large-distance, long-time
asymptotics for Brownian motion are calculated using a nonlinear stochastic
Navier-Stokes equation including the effect of friction with the substrate. The
advective nonlinearity, neglected in previous treatments, gives only a small
correction to the renormalized viscosity and diffusion coefficient at room
temperature. We find, however, that in realistic multicomponent lipid mixtures,
close to a critical point for phase separation, protein diffusion acquires a
strong power-law dependence on temperature and the distance to the substrate
, making it much more sensitive to cell environment, unlike the logarithmic
dependence on and very small thermal correction away from the critical
point.Comment: 19 pages, 4 figure
Capture and Decay of Electroweak WIMPonium
The spectrum of Weakly-Interacting-Massive-Particle (WIMP) dark matter
generically possesses bound states when the WIMP mass becomes sufficiently
large relative to the mass of the electroweak gauge bosons. The presence of
these bound states enhances the annihilation rate via resonances in the
Sommerfeld enhancement, but they can also be produced directly with the
emission of a low-energy photon. In this work we compute the rate for SU(2)
triplet dark matter (the wino) to bind into WIMPonium -- which is possible via
single-photon emission for wino masses above 5 TeV for relative velocity v <
O(10^{-2}) -- and study the subsequent decays of these bound states. We present
results with applications beyond the wino case, e.g. for dark matter inhabiting
a nonabelian dark sector; these include analytic capture and transition rates
for general dark sectors in the limit of vanishing force carrier mass,
efficient numerical routines for calculating positive and negative-energy
eigenstates of a Hamiltonian containing interactions with both massive and
massless force carriers, and a study of the scaling of bound state formation in
the short-range Hulthen potential. In the specific case of the wino, we find
that the rate for bound state formation is suppressed relative to direct
annihilation, and so provides only a small correction to the overall
annihilation rate. The soft photons radiated by the capture process and by
bound state transitions could permit measurement of the dark matter's quantum
numbers; for wino-like dark matter, such photons are rare, but might be
observable by a future ground-based gamma-ray telescope combining large
effective area and a low energy threshold.Comment: 3rd version. An interference sign fixed and changes propagated
through the paper. Topline qualitative conclusions unchange
Strain measurement at the knee ligament insertion sites
We describe the modification of an existing method of ligament strain measurement at the knee joint in detail. At ten fresh joint specimens we used that technique where strain gauges are attached to the ligamentous insertions and origins. We both improved the preparation of the attachment site and the application of the strain gauges. In a special apparatus the specimens were moved from 0degrees extension to 100degrees flexion while simulating muscle strength and axial force. Testing was performed at the posterior cruciate ligament with both intact and transsected anterior cruciate ligament. In contrast to other existing techniques it does not affect the motion of the joint or the integrity and the function of the ligaments. Unlike the original description of that method we could register a loading behaviour of the posterior cruciate ligament that is similar to those reported in the literature
Zugkraftmessungen beim knöchernen Segmenttransport – in vivo Untersuchungen am Menschen
Bone transport applying the principle of distraction osteogenesis makes it possible to reconstruct long bone defects caused by trauma or resection of bone tumors. The method employing a central cable, developed in Munich, is especially suitable for such applications. The main bone fragments are stabilized by an external fixateur, and bone transport is effected with a single central cable fixed to the tip of the segment, and driven by an external, programmable motor. In 15 patients the tractive forces during the entire bone transport were measured with a strain gauge incorporated within the cable. On the basis of the force profiles characteristics normal bone transport (forces between 150 - 250 N) can be distinguished from a critical transport (forces > 250 N) with the risk of premature consolidation. There is some evidence that at a very high level of force, just before premature consolidation a very effective form of bone transport with good bone neoformation can be achieved. Transport systems employing a central cable allow this special form of distraction osteogenesis, since there is continuous force monitoring, and there is the option of employing the traction force as a control factor in a loop
Resummed Photon Spectra for WIMP Annihilation
We construct an effective field theory (EFT) description of the hard photon
spectrum for heavy WIMP annihilation. This facilitates precision predictions
relevant for line searches, and allows the incorporation of non-trivial energy
resolution effects. Our framework combines techniques from non-relativistic
EFTs and soft-collinear effective theory (SCET), as well as its multi-scale
extensions that have been recently introduced for studying jet substructure. We
find a number of interesting features, including the simultaneous presence of
SCET and SCET modes, as well as collinear-soft modes
at the electroweak scale. We derive a factorization formula that enables both
the resummation of the leading large Sudakov double logarithms that appear in
the perturbative spectrum, and the inclusion of Sommerfeld enhancement effects.
Consistency of this factorization is demonstrated to leading logarithmic order
through explicit calculation. Our final result contains both the exclusive and
the inclusive limits, thereby providing a unifying description of these two
previously-considered approximations. We estimate the impact on experimental
sensitivity, focusing for concreteness on an SU(2) triplet fermion dark
matter - the pure wino - where the strongest constraints are due to a search
for gamma-ray lines from the Galactic Center. We find numerically significant
corrections compared to previous results, thereby highlighting the importance
of accounting for the photon spectrum when interpreting data from current and
future indirect detection experiments.Comment: 55+25 pages, 11+2 figures; v3, updated an expression in the appendix
to make it applicable at higher order - no impact on the results in this wor
Zentrale Zugseilsysteme – vollautomatische, kontinuierliche Kallusdistraktion zur Behandlung langstreckiger Knochendefekte
Distraction osteogenesis involving bone transport enables the reconstruction of large bone defects. The main bone fragments are usually stablilised externally, an intermediate bone segment is separated and moved through the defect at a rate of about 1 mm/day. New high-quality bone is built up in the constantly enlarging osteotomy gap. A major problem associated with the method is the fact that the fixation pins are also moved over the same distance, and cut through the soft tissue, often resulting in painful pin tract infections and ugly scars. An automatic motorized bone transport system employing a single central cable now eliminates this problem. The system can be combined with any external fixateur, since the relevant implanted parts for bone transport are independent of the external stabilizer. The surgical procedure, which is easy on the patient, consists of bone segment separation, central cable fixation, and stabilisation of the main fragments, and requires the use of numerous special tools. The distraction itself results in significantly less soft tissue irritation and pain. Pin tract infections are rare, so that changeover to internal fixation after completion of bone transport carries little risk of infection. This article details the technical features of the stabilizing system and the transport and the control systems, and describes the clinical application in a patient
Systematic Improvement of Parton Showers with Effective Theory
We carry out a systematic classification and computation of next-to-leading
order kinematic power corrections to the fully differential cross section in
the parton shower. To do this we devise a map between ingredients in a parton
shower and operators in a traditional effective field theory framework using a
chain of soft-collinear effective theories. Our approach overcomes several
difficulties including avoiding double counting and distinguishing
approximations that are coordinate choices from true power corrections.
Branching corrections can be classified as hard-scattering, that occur near the
top of the shower, and jet-structure, that can occur at any point inside it.
Hard-scattering corrections include matrix elements with additional hard
partons, as well as power suppressed contributions to the branching for the
leading jet. Jet-structure corrections require simultaneous consideration of
potential 1 -> 2 and 1 -> 3 branchings. The interference structure induced by
collinear terms with subleading powers remains localized in the shower.Comment: 54 pages, 24 figures, plus a few appendices. v2: included a parameter
"eta" to account for energy loss, title improved, journal versio
Banddehnungsmessung am Kniegelenk - Der Dehnungsmeßstreifen und seine Alternativen
Those techniques for measuring ligament tension at the knee joint that are most commonly cited and easiest to carry out are discussed, These include four techniques based on the use of strain gauges. Apart from the Omega transducer and the buckle transducer, there is also the tendon force transducer, and the application of strain gauges to the bony ligament insertion sites, Other indirect measuring methods considered are the mercury strain transducer and the Hall effect transducer. The parameter measured with all of these methods is fluctuating current or voltage, which is then correlated with ligament tension. Three direct measurements are also discussed: the separation distances of marked fibres of the ligaments, replacement of fibres by threads, and a load cell/bone plug construction. The measured value is equated with the effective change in ligament length
A sensitive non-radioactive in situ hybridization method for the detection of chicken IgG γ-chain mRNA: a technique suitable for detecting of variety of mRNAs in tissue sections
We established a sensitive non-radioactive in situ hybridization (ISH) method for the detection of chicken IgG γ-chain mRNA in paraffin sections. RNA probes were transcribed in vitro from cloned chicken IgG CH1 nucleotide sequences with SP6/T7 RNA polymerases in the presence of DIG-UTP. These probes were used for hybridization and were immunodetected using anti-DIG antibodies conjugated to horseradish peroxidase. The immunoreactive products were visualized with DAB-H(2)O(2). IgG γ-chain mRNA-expressing cells were localized in both the spleen and oviductal tissues. This method demonstrated an excellent sensitivity since the ISH signal was clear and the background was negligible. We found that in the spleen IgG γ-chain mRNA-expressing cells were present mainly in the red pulp, whereas in the oviduct they appeared mainly in the mucosal stroma and not in the mucosal epithelium
Broadband Dielectric Spectroscopic Detection of Aliphatic Alcohol Vapors With Surface-Mounted HKUST-1 MOFs as Sensing Media
We leveraged chemical-induced changes to microwave signal propagation characteristics (i.e., S-parameters) to characterize the detection of aliphatic alcohol (methanol, ethanol, and 2-propanol) vapors using TCNQ-doped HKUST-1 metal-organic-framework films as the sensing material, at temperatures under 100 °C. We show that the sensitivity of aliphatic alcohol detection depends on the oxidation potential of the analyte, and the impedance of the detection setup depends on the analyte-loading of the sensing medium. The microwaves-based detection technique can also afford new mechanistic insights into VOC detection, with surface-anchored metal-organic frameworks (SURMOFs), which is inaccessible with the traditional coulometric (i.e., resistance-based) measurements
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