1,185 research outputs found
Period tripling causes rotating spirals in agitated wet granular layers
Pattern formation of a thin layer of vertically agitated wet granular matter
is investigated experimentally. Rotating spirals with three arms, which
correspond to the kinks between regions with different colliding phases, are
the dominating pattern. This preferred number of arms corresponds to period
tripling of the agitated granular layer, unlike predominantly subharmonic
Faraday crispations in dry granular matter. The chirality of the spatiotemporal
pattern corresponds to the rotation direction of the spirals.Comment: 4 pages, 6 figures, to appear in Physical Review Letter
Mass intentions: Memorials, money and the meaning of the Eucharist
Thesis advisor: John BaldovinThesis advisor: James ConnThesis (STL) — Boston College, 2011.Submitted to: Boston College. School of Theology and Ministry.Discipline: Sacred Theology
Antagonism of neuromuscular blockade but not muscle relaxation affects depth of anaesthesia
Background. Conflicting effects of neuromuscular blocking drugs and anticholinesterases on depth of anaesthesia have been reported. Therefore we evaluated the effect of atracurium and neostigmine on bispectral index (BIS) and middle-latency auditory evoked potentials (AAI). Methods. We studied 40 patients (ASA I-II) aged 18-69 yr. General anaesthesia consisted of propofol and remifentanil by target-controlled infusion and neuromuscular function was monitored by electromyography. When BIS reached stable values, patients were randomly assigned to one of two groups. Group 1 received atracurium 0.4 mg kg−1 and, 5 min later, the same volume of NaCl 0.9%; group 2 received saline first and then atracurium. When the first twitch of a train of four reached 10% of control intensity, patients were again randomized: one group (N) received neostigmine 0.04 mg kg−1 and glycopyrrolate 0.01 mg kg−1, and the control group (G) received only glycopyrrolate. Results. Injection of atracurium or NaCl 0.9% had no effect on BIS or AAI. After neostigmine-glycopyrrolate, BIS and AAI increased significantly (mean maximal change of BIS 7.1 [sd 7.5], P<0.001; mean maximal change of AAI 9.7 [10.5], P<0.001). When glycopyrrolate was injected alone BIS and AAI also increased (mean maximal change of BIS 2.2 [3.4], P=0.008; mean maximal change of AAI 3.5 [5.7], P=0.012), but this increase was significantly less than in group N (P=0.012 for BIS; P=0.027 for AAI). Conclusion. These data suggest that neostigmine alters the state of propofol-remifentanil anaesthesia and may enhance recover
Amyloid-beta Leads to Impaired Cellular Respiration, Energy Production and Mitochondrial Electron Chain Complex Activities in Human Neuroblastoma Cells
Evidence suggests that amyloid-beta (Aβ) protein is a key factor in the pathogenesis of Alzheimer's disease (AD) and it has been recently proposed that mitochondria are involved in the biochemical pathway by which Aβ can lead to neuronal dysfunction. Here we investigated the specific effects of Aβ on mitochondrial function under physiological conditions. Mitochondrial respiratory functions and energy metabolism were analyzed in control and in human wild-type amyloid precursor protein (APP) stably transfected human neuroblastoma cells (SH-SY5Y). Mitochondrial respiratory capacity of mitochondrial electron transport chain (ETC) in vital cells was measured with a high-resolution respirometry system (Oxygraph-2k). In addition, we determined the individual activities of mitochondrial complexes I-IV that compose ETC and ATP cellular levels. While the activities of complexes I and II did not change between cell types, complex IV activity was significantly reduced in APP cells. In contrast, activity of complex III was significantly enhanced in APP cells, as compensatory response in order to balance the defect of complex IV. However, this compensatory mechanism could not prevent the strong impairment of total respiration in vital APP cells. As a result, the respiratory control ratio (state3/state4) together with ATP production decreased in the APP cells in comparison with the control cells. Chronic exposure to soluble Aβ protein may result in an impairment of energy homeostasis due to a decreased respiratory capacity of mitochondrial electron transport chain which, in turn, may accelerate neurons demis
Chains of Viscoelastic Spheres
Given a chain of viscoelastic spheres with fixed masses of the first and last
particles. We raise the question: How to chose the masses of the other
particles of the chain to assure maximal energy transfer? The results are
compared with a chain of particles for which a constant coefficient of
restitution is assumed. Our simple example shows that the assumption of
viscoelastic particle properties has not only important consequences for very
large systems (see [1]) but leads also to qualitative changes in small systems
as compared with particles interacting via a constant restitution coefficient.Comment: 11 pages, 6 figure
A model of ballistic aggregation and fragmentation
A simple model of ballistic aggregation and fragmentation is proposed. The
model is characterized by two energy thresholds, Eagg and Efrag, which
demarcate different types of impacts: If the kinetic energy of the relative
motion of a colliding pair is smaller than Eagg or larger than Efrag, particles
respectively merge or break; otherwise they rebound. We assume that particles
are formed from monomers which cannot split any further and that in a
collision-induced fragmentation the larger particle splits into two fragments.
We start from the Boltzmann equation for the mass-velocity distribution
function and derive Smoluchowski-like equations for concentrations of particles
of different mass. We analyze these equations analytically, solve them
numerically and perform Monte Carlo simulations. When aggregation and
fragmentation energy thresholds do not depend on the masses of the colliding
particles, the model becomes analytically tractable. In this case we show the
emergence of the two types of behavior: the regime of unlimited cluster growth
arises when fragmentation is (relatively) weak and the relaxation towards a
steady state occurs when fragmentation prevails. In a model with mass-dependent
Eagg and Efrag the evolution with a cross-over from one of the regimes to
another has been detected
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