1,106 research outputs found
Parametric Model Order Reduction of Port-Hamiltonian Systems by Matrix Interpolation
In this paper, parametric model order reduction of linear time-invariant systems by matrix interpolation is adapted to large-scale systems in port-Hamiltonian form. A new weighted matrix interpolation of locally reduced models is introduced in order to preserve the port-Hamiltonian structure, which guarantees the passivity and stability of the interpolated system. The performance of the new method is demonstrated by technical example
Nkx2-5 and Sarcospan genetically interact in the development of the muscular ventricular septum of the heart
The muscular ventricular septum separates the flow of oxygenated and de-oxygenated blood in air-breathing vertebrates. Defects within it, termed muscular ventricular septal defects (VSDs), are common, yet less is known about how they arise than rarer heart defects. Mutations of the cardiac transcription factor NKX2-5 cause cardiac malformations, including muscular VSDs. We describe here a genetic interaction between Nkx2-5 and Sarcospan (Sspn) that affects the risk of muscular VSD in mice. Sspn encodes a protein in the dystrophin-glycoprotein complex. Sspn knockout (Sspn(KO)) mice do not have heart defects, but Nkx2-5(+/â)/Sspn(KO) mutants have a higher incidence of muscular VSD than Nkx2-5(+/â) mice. Myofibers in the ventricular septum follow a stereotypical pattern that is disrupted around a muscular VSD. Subendocardial myofibers normally run in parallel along the left ventricular outflow tract, but in the Nkx2-5(+/â)/Sspn(KO) mutant they commonly deviate into the septum even in the absence of a muscular VSD. Thus, Nkx2-5 and Sspn act in a pathway that affects the alignment of myofibers during the development of the ventricular septum. The malalignment may be a consequence of a defect in the coalescence of trabeculae into the developing ventricular septum, which has been hypothesized to be the mechanistic basis of muscular VSDs
Thermal conductivity and photoluminescence of light-emitting silicon nitride films
Silicon-rich and rare-earth-doped nitride materials are promising candidates for silicon-compatible photonic sources. This work investigates the thermal conductivity and photoluminescence (PL) of light emitting samples fabricated with a range of excess silicon concentrations and annealing temperatures using time-domain picosecond thermoreflectance and time-resolved photoluminescence. A direct correlation between the thermal conductivity and photoluminescence dynamics is demonstrated, as well as a significant reduction of thermal conductivity upon incorporation of erbium ions. These findings highlight the role of annealing and stoichiometry control in the optimization of light emitting microstructures suitable for the demonstration of efficient Si-compatible light sources based on the silicon nitride platform. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3682508
Porcine Head Response to Blast
Recent studies have shown an increase in the frequency of traumatic brain injuries related to blast exposure. However, the mechanisms that cause blast neurotrauma are unknown. Blast neurotrauma research using computational models has been one method to elucidate that response of the brain in blast, and to identify possible mechanical correlates of injury. However, model validation against experimental data is required to ensure that the model output is representative of in vivo biomechanical response. This study exposes porcine subjects to primary blast overpressures generated using a compressed-gas shock tube. Shock tube blasts were directed to the unprotected head of each animal while the lungs and thorax were protected using ballistic protective vests similar to those employed in theater. The test conditions ranged from 110 to 740âkPa peak incident overpressure with scaled durations from 1.3 to 6.9âms and correspond approximately with a 50% injury risk for brain bleeding and apnea in a ferret model scaled to porcine exposure. Instrumentation was placed on the porcine head to measure bulk acceleration, pressure at the surface of the head, and pressure inside the cranial cavity. Immediately after the blast, 5 of the 20 animals tested were apneic. Three subjects recovered without intervention within 30âs and the remaining two recovered within 8âmin following respiratory assistance and administration of the respiratory stimulant doxapram. Gross examination of the brain revealed no indication of bleeding. Intracranial pressures ranged from 80 to 390âkPa as a result of the blast and were notably lower than the shock tube reflected pressures of 300â2830âkPa, indicating pressure attenuation by the skull up to a factor of 8.4. Peak head accelerations were measured from 385 to 3845 Gâs and were well correlated with peak incident overpressure (R2â=â0.90). One SD corridors for the surface pressure, intracranial pressure (ICP), and head acceleration are presented to provide experimental data for computer model validation
Long-term culture of human pancreatic slices as a model to study real-time islet regeneration.
The culture of live pancreatic tissue slices is a powerful tool for the interrogation of physiology and pathology in an in vitro setting that retains near-intact cytoarchitecture. However, current culture conditions for human pancreatic slices (HPSs) have only been tested for short-term applications, which are not permissive for the long-term, longitudinal study of pancreatic endocrine regeneration. Using a culture system designed to mimic the physiological oxygenation of the pancreas, we demonstrate high viability and preserved endocrine and exocrine function in HPS for at least 10 days after sectioning. This extended lifespan allowed us to dynamically lineage trace and quantify the formation of insulin-producing cells in HPS from both non-diabetic and type 2 diabetic donors. This technology is expected to be of great impact for the conduct of real-time regeneration/developmental studies in the human pancreas.post-print3.907 K
Isometric exercise in cardiac magnetic resonance imaging: an initial experience using fast imaging
Introduction:
Isometric exercise is a powerful stimulator of the cardiovascular
system. Therefore, exercise can be used to
unmask subtle cardiovascular changes that are not
evident at rest. MRI is a proven method for comprehensive
cardiovascular assessment in the resting state.
Unfortunately, lack of fast imaging sequences and an
appropriate exercise test has prohibited the use of
isometric exercise in MRI.
Purpose:
We aimed to devise an isometric exercise test for use in
MRI in order to comprehensively assess the hemodynamic
response to exercise using fast-imaging MRI
Factors Associated with Previable Delivery following Second Trimester Rupture of Membranes
Objective To identify factors associated with previable delivery in second trimester preterm rupture of membranes (PROM). Study Design We conducted a single-center retrospective cohort study of women with pregnancies complicated by second trimester PROM (14.0-21.9 weeks' gestation) from 2000 to 2015 who elected expectant pregnancy management and achieved at least 24 hours latency. Maternal characteristics and clinical factors were compared among pregnancies that reached viability (â„ 23.0 weeks) and pregnancies delivered before viability ( 1cm, Group B streptococcus carrier status, bacterial vaginosis, and chlamydial infection during pregnancy were similar between groups. Median time to delivery was significantly shorter in women who delivered < 23 weeks compared with those who reached â„ 23 weeks (6 vs. 46 days, p < 0.01). Conclusion Previable delivery occurred in the majority of women with second trimester PROM. No maternal or clinical factors were associated with delivery prior to viability. Counseling women with second trimester PROM should include the inability to determine which pregnancies will reach viability
Determination of the branching ratios and
Improved branching ratios were measured for the decay in a
neutral beam at the CERN SPS with the NA31 detector: and .
From the first number an upper limit for and transitions in neutral kaon decay is derived. Using older results for the
Ke3/K3 fraction, the 3 branching ratio is found to be , about a factor three more
precise than from previous experiments
Detection of minimal residual disease identifies differences in treatment response between T-ALL and precursor B-ALL
We performed sensitive polymerase chain reaction-based minimal residual
disease (MRD) analyses on bone marrow samples at 9 follow-up time points
in 71 children with T-lineage acute lymphoblastic leukemia (T-ALL) and
compared the results with the precursor B-lineage ALL (B-ALL) results (n =
210) of our previous study. At the first 5 follow-up time points, the
frequency of MRD-positive patients and the MRD levels were higher in T-ALL
than in precursor-B-ALL, reflecting the more frequent occurrence of
resistant disease in T-ALL. Subsequently, patients were classified
according to their MRD level at time point 1 (TP1), taken at the end of
induction treatment (5 weeks), and at TP2 just before the start of
consolidation treatment (3 months). Patients were considered at low risk
if TP1 and TP2 were MRD negative and at high risk if MRD levels at TP1 and
TP2 were 10(-3) or higher; remaining patients were considered at
intermediate risk. The relative distribution of patients with T-ALL (n =
43) over the MRD-based risk groups differed significantly from that of
precursor B-ALL (n = 109). Twenty-three percent of patients with T-ALL and
46% of patients with precursor B-ALL were classified in the low-risk group
(P =.01) and had a 5-year relapse-free survival (RFS) rate of 98% or
greater. In contrast, 28% of patients with T-ALL were classified in the
MRD-based high-risk group compared to only 11% of patients with precursor
B-ALL (P =.02), and the RFS rates were 0% and 25%, respectively (P =.03).
Not only was the distribution of patients with T-ALL different over the
MRD-based risk groups, the prognostic value of MRD levels at TP1 and TP2
was higher in T-ALL (larger RFS gradient), and consistently higher RFS
rates were found for MRD-negative T-ALL patients at the first 5 follow-up
time points
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