7,570 research outputs found
Diffusional Kurtosis and Diffusion Tensor Imaging Reveal Different Time-Sensitive Stroke-Induced Microstructural Changes
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MRI-based Surgical Planning for Lumbar Spinal Stenosis
The most common reason for spinal surgery in elderly patients is lumbar
spinal stenosis(LSS). For LSS, treatment decisions based on clinical and
radiological information as well as personal experience of the surgeon shows
large variance. Thus a standardized support system is of high value for a more
objective and reproducible decision. In this work, we develop an automated
algorithm to localize the stenosis causing the symptoms of the patient in
magnetic resonance imaging (MRI). With 22 MRI features of each of five spinal
levels of 321 patients, we show it is possible to predict the location of
lesion triggering the symptoms. To support this hypothesis, we conduct an
automated analysis of labeled and unlabeled MRI scans extracted from 788
patients. We confirm quantitatively the importance of radiological information
and provide an algorithmic pipeline for working with raw MRI scans
Dynamics of the chiral phase transition from AdS/CFT duality
We use Lorentzian signature AdS/CFT duality to study a first order phase
transition in strongly coupled gauge theories which is akin to the chiral phase
transition in QCD. We discuss the relation between the latent heat and the
energy (suitably defined) of the component of a D-brane which lies behind the
horizon at the critical temperature. A numerical simulation of a dynamical
phase transition in an expanding, cooling Quark-Gluon plasma produced in a
relativistic collision is carried out.Comment: 30 pages, 5 figure
Ballistic nanofriction
Sliding parts in nanosystems such as Nano ElectroMechanical Systems (NEMS)
and nanomotors, increasingly involve large speeds, and rotations as well as
translations of the moving surfaces; yet, the physics of high speed nanoscale
friction is so far unexplored. Here, by simulating the motion of drifting and
of kicked Au clusters on graphite - a workhorse system of experimental
relevance -- we demonstrate and characterize a novel "ballistic" friction
regime at high speed, separate from drift at low speed. The temperature
dependence of the cluster slip distance and time, measuring friction, is
opposite in these two regimes, consistent with theory. Crucial to both regimes
is the interplay of rotations and translations, shown to be correlated in slow
drift but anticorrelated in fast sliding. Despite these differences, we find
the velocity dependence of ballistic friction to be, like drift, viscous
Computer simulation of simultaneous evolution of individual texture components During recrystallization of an IF steel
Computer simulation of simultaneous evolution of individual texture components during recrystallization of an IF steel is carried out. A new methodology has been developed that takes as its starting point experimental data of each texture component evolving during recrystallization. In particular, Magnusson et al. data on IF steel was analyzed in a previous work with the help of the exact analytical tools developed by Rios and Villa for simultaneous transformations. From this analysis parameters such as number of nuclei of each texture component per unit of volume could be obtained and were employed as input for the present computer simulation. From this input 3-d microstructures could then be generated. The methodology proposed here combines experimental data, exact analytical methods and computer simulation and may be employed to extract the maximum information from the experimental data
Do MRI findings identify patients with chronic low back pain and Modic changes who respond best to rest or exercise: A subgroup analysis of a randomised controlled trial
Background: No previous clinical trials have investigated MRI findings as effect modifiers for conservative treatment of low back pain. This hypothesis-setting study investigated if MRI findings modified response to rest compared with exercise in patients with chronic low back pain and Modic changes. Methods: This study is a secondary analysis of a randomised controlled trial comparing rest with exercise. Patients were recruited from a specialised outpatient spine clinic and included in a clinical trial if they had chronic low back pain and an MRI showing Modic changes. All patients received conservative treatment while participating in the trial. Five baseline MRI findings were investigated as effect modifiers: Modic changes Type 1 (any size), large Modic changes (any type), large Modic changes Type 1, severe disc degeneration and large disc herniation. The outcome measure was change in low back pain intensity measured on a 0-10 point numerical rating scale at 14-month follow-up (n = 96). An interaction = 1.0 point (0-10 scale) between treatment group and MRI findings in linear regression was considered clinically important. Results: The interactions for Modic Type 1, with large Modic changes or with large Modic changes Type 1 were all potentially important in size (-0.99 (95% CI -3.28 to 1.29), -1.49 (-3.73 to 0.75), -1.49 (-3.57 to 0.58), respectively) but the direction of the effect was the opposite to what we had hypothesized-that people with these findings would benefit more from rest than from exercise. The interactions for severe disc degeneration (0.74 (-1.40 to 2.88)) and large disc herniation (-0.92 (3.15 to 1.31)) were less than the 1.0-point threshold for clinical importance. As expected, because of the lack of statistical power, no interaction term for any of the MRI findings was statistically significant. Conclusions: Three of the five MRI predictors showed potentially important effect modification, although the direction of the effect was surprising and confidence intervals were wide so very cautious interpretation is required. Further studies with adequate power are warranted to study these and additional MRI findings as potential effect modifiers for common interventions
Collective Excitations of Holographic Quantum Liquids in a Magnetic Field
We use holography to study N=4 supersymmetric SU(Nc) Yang-Mills theory in the
large-Nc and large-coupling limits coupled to a number Nf << Nc of
(n+1)-dimensional massless supersymmetric hypermultiplets in the Nc
representation of SU(Nc), with n=2,3. We introduce a temperature T, a baryon
number chemical potential mu, and a baryon number magnetic field B, and work in
a regime with mu >> T,\sqrt{B}. We study the collective excitations of these
holographic quantum liquids by computing the poles in the retarded Green's
function of the baryon number charge density operator and the associated peaks
in the spectral function. We focus on the evolution of the collective
excitations as we increase the frequency relative to T, i.e. the
hydrodynamic/collisionless crossover. We find that for all B, at low
frequencies the tallest peak in the spectral function is associated with
hydrodynamic charge diffusion. At high frequencies the tallest peak is
associated with a sound mode similar to the zero sound mode in the
collisionless regime of a Landau Fermi liquid. The sound mode has a gap
proportional to B, and as a result for intermediate frequencies and for B
sufficiently large compared to T the spectral function is strongly suppressed.
We find that the hydrodynamic/collisionless crossover occurs at a frequency
that is approximately B-independent.Comment: 45 pages, 8 png and 47 pdf images in 22 figure
Impact of germline DNA repair gene variants on prognosis and treatment of men with advanced prostate cancer.
The clinical importance of germline variants in DNA repair genes (DRGs) is becoming increasingly recognized, but their impact on advanced prostate cancer prognosis remains unclear. A cohort of 221 newly diagnosed metastatic castration-resistant prostate cancer (mCRPC) patients were screened for pathogenic germline variants in 114 DRGs. The primary endpoint was progression-free survival (PFS) on first-line androgen signaling inhibitor (ARSI) treatment for mCRPC. Secondary endpoints were time to mCRPC progression on initial androgen deprivation therapy (ADT) and overall survival (OS). Twenty-seven patients (12.2%) carried a germline DRG variant. DRG carrier status was independently associated with shorter PFS on first-line ARSI [HR 1.72 (1.06-2.81), Pâ=â0.029]. At initiation of ADT, DRG carrier status was independently associated with shorter progression time to mCRPC [HR 1.56, (1.02-2.39), Pâ=â0.04] and shorter OS [HR 1.99, (1.12-3.52), Pâ=â0.02]. Investigating the contributions of individual germline DRG variants on PFS and OS revealed CHEK2 variants to have little effect. Furthermore, prior taxane treatment was associated with worse PFS on first-line ARSI for DRG carriers excluding CHEK2 (Pâ=â0.0001), but not for noncarriers. In conclusion, germline DRG carrier status holds independent prognostic value for predicting advanced prostate cancer patient outcomes and may potentially inform on optimal treatment sequencing already at the hormone-sensitive stage
A 'resource allocator' for transcription based on a highly fragmented T7 RNA polymerase
Synthetic genetic systems share resources with the host, including machinery for transcription and translation. Phage RNA polymerases (RNAPs) decouple transcription from the host and generate high expression. However, they can exhibit toxicity and lack accessory proteins (Ï factors and activators) that enable switching between different promoters and modulation of activity. Here, we show that T7 RNAP (883 amino acids) can be divided into four fragments that have to be coâexpressed to function. The DNAâbinding loop is encoded in a Câterminal 285âaa âÏ fragmentâ, and fragments with different specificity can direct the remaining 601âaa âcore fragmentâ to different promoters. Using these parts, we have built a resource allocator that sets the core fragment concentration, which is then shared by multiple Ï fragments. Adjusting the concentration of the core fragment sets the maximum transcriptional capacity available to a synthetic system. Further, positive and negative regulation is implemented using a 67âaa Nâterminal âα fragmentâ and a null (inactivated) Ï fragment, respectively. The α fragment can be fused to recombinant proteins to make promoters responsive to their levels. These parts provide a toolbox to allocate transcriptional resources via different schemes, which we demonstrate by building a system which adjusts promoter activity to compensate for the difference in copy number of two plasmids.United States. Office of Naval Research (N00014â13â1â0074)National Institutes of Health (U.S.) (5R01GM095765)National Science Foundation (U.S.) (Synthetic Biology Engineering Research Center (SA5284â11210))United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship (NDSEG) Program))Hertz Foundation (Fellowship
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