973 research outputs found
Percutaneous aortic valve replacement: valvuloplasty studies in vitro
Objective: Valvuloplasty of the aortic valve is currently used in selected patients for severe calcified aortic valve disease, but clinical effectiveness is low and complication rate remains high. In this study, the total particle load after valvuloplasty and the embolization risk of calcific debris into the coronary arteries was analyzed in an in vitro model. Methods: Three highly calcified human aortic leaflets have been sutured into a porcine annulus (N=9). Both coronary arteries were separated and each was anastomized to a silicon line, which was drained off into a measuring beaker. Then valvuloplasty was performed (Thyshak II, 20mm, 1.5atm). After removal of the balloon, 100ml of sodium chloride solution irrigated the ascending aorta. After passing through the separated coronary arteries, the solution was filtered (filter size 0.45μm), dried, and the total amount of particles was analyzed microscopically. Results: Nine experiments were analyzed. After valvuloplasty, all hearts showed a median of 18 particles larger than 1mm in the coronary arteries (range 0-307). The amount of particles smaller than 1mm was 6574 (median, range 2207-14200). In five cases, coronary arteries were completely occluded by bulky particles. Conclusion: This study demonstrated a large amount of calcific particles after valvuloplasty with a consequently high risk for coronary embolic events in case of highly calcified aortic valves. In times of valvuloplasty rediscovering as part of transcatheter valve implantation, the risk of embolization should be taken into consideration and filtering techniques have to be develope
Spherical Colloids: Effect of Discrete Macroion Charge Distribution and Counterion Valence
We report the coupled effects of macroion charge discretization and
counterion valence in the primitive model for spherical colloids. Instead of
considering a uniformly charged surface, as it is traditionally done, we
consider a more realistic situation where \textit{discrete monovalent
microscopic charges} are randomly distributed over the sphere. Monovalent or
multivalent counterions ensure global electroneutrality. We use molecular
dynamics simulations to study these effects at the ground state and for finite
temperature. The ground state analysis concerns the counterion structure and
\textit{charge inversion}. Results are discussed in terms of simple analytical
models. For finite temperature, strong and weak Coulomb couplings are treated.
In this situation of finite temperature, we considered and discussed the
phenomena of ionic pairing (pinning) and unpairing (unpinning).Comment: 24 pages, 12 (main) figures (28 EPS files). To appear in Physica
Using a reinforcement learning approach in a discrete event manufacturing system
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Cerebral lesions on magnetic resonance imaging correlate with preoperative neurological status in neonates undergoing cardiopulmonary bypass surgery
OBJECTIVES To determine the prevalence, spectrum and course of cerebral lesions in neonates with congenital heart disease (CHD) undergoing full flow cardiopulmonary bypass (CPB) surgery using magnetic resonance imaging (MRI) and to examine the correlation between cerebral lesions and clinical neurological abnormalities. METHODS Prospective cohort study of neonates with d-transposition of the great arteries (n = 22), univentricular heart malformation with hypoplastic aortic arch (n = 6) and aortic arch obstructions (n = 2) undergoing CPB. Neonates underwent cerebral MRI and blinded standardized neurological examination before (median day 6) and after surgery (day 13). The MRI findings were compared with those of 20 healthy controls. RESULTS Preoperative cerebral lesions were present in 7 of 30 patients (23%) with isolated mild or moderate white matter injury (WMI) (n = 4), isolated small cerebral stroke (n = 1) and combined WMI and stroke (n = 2). None of the healthy controls had cerebral lesions on MRI. CHD neonates with preoperative cerebral lesions had more neurological abnormalities (P = 0.01) than neonates without cerebral lesions. Low arterial oxygen saturation (P = 0.03) was a risk factor for preoperative cerebral lesions, while balloon atrioseptostomy (P = 0.19) was not. After surgery, preoperative cerebral lesions persisted in 5 of 7 neonates, and 2 neonates (7%) showed signs of additional WMI in their postoperative MRI. CONCLUSIONS In neonates with severe CHD, WMI was the predominant preoperative finding, while cerebral strokes were less frequent. New postoperative lesions were rare. Preoperative neurological abnormalities correlated with the presence of cerebral lesions on MR
Архитектура программного комплекса "профиль студента"
Software system architecture represented as shown in the diagram components, described in a unified modeling language UML. This architecture allows you to receive and process information, both internal and external systems. And it allows build and receive analytical reports in accordance with the requirements of Russian legislation
Region Specific and Worldwide Distribution of Collagen-Binding M Proteins with PARF Motifs among Human Pathogenic Streptococcal Isolates
Some of the variety of Streptococcus pyogenes and Streptococcus dysgalactiae ssp. equisimilis (SDSE) M proteins act as collagen-binding adhesins that facilitate acute infection. Moreover, their potential to trigger collagen autoimmunity has been implicated in the pathogenesis of acute rheumatic fever and attributed to a collagen-binding motif called PARF (peptide associated with rheumatic fever). For the first time we determine the rate of clinical isolates with collagen-binding M proteins that use a PARF motif (A/T/E)XYLXX(L/F)N in a defined geographic region, Vellore in South India. In this region both, incidence of streptococcal infections and prevalence of acute rheumatic fever are high. M proteins with PARF motif conferred collagen-binding activity to 3.9% of 153 S. pyogenes and 10.6% of 255 SDSE clinical isolates from Vellore. The PARF motif occurred in three S. pyogenes and 22 SDSE M protein types. In one of the S. pyogenes and five of the SDSE M proteins that contained the motif, collagen-binding was impaired, due to influences of other parts of the M protein molecule. The accumulated data on the collagen binding activity of certain M protein types allowed a reanalysis of published worldwide emm-typing data with the aim to estimate the rates of isolates that bind collagen via PARF. The results indicate that M proteins, which bind collagen via a PARF motif, are epidemiologically relevant in human infections, not only in Vellore. It is imperative to include the most relevant collagen-binding M types in vaccines. But when designing M protein based vaccines it should be considered that collagen binding motifs within the vaccine antigen remain potential risk factors
Indices from flow-volume curves in relation to cephalometric, ENT- and sleep-O2 saturation variables in snorers with and without obstructive sleep-apnoea
In a group of 37 heavy snorers with obstructive sleep apnoea (OSA, Group
1) and a group of 23 heavy snorers without OSA (Group 2) cephalometric
indices, ENT indices related to upper airway collapsibility, and nocturnal
O2 desaturation indices were related to variables from maximal expiratory
and inspiratory flow-volume (MEFV and MIFV) curves. The cephalometric
indices used were the length and diameter of the soft palate (spl and
spd), the shortest distance between the mandibular plane and the hyoid
bone (mph) and the posterior airway space (pas). Collapsibility of the
upper airways was observed at the level of the tongue base and soft palate
by fibroscopy during a Muller manoeuvre (mtb and msp) and ranked on a five
point scale. Sleep indices measured were the mean number of oxygen
desaturations of more than 3% per hour preceded by an apnoea or hypopnoea
of more than 10 s (desaturation index), maximal sleep oxygen desaturation,
baseline arterial oxygen saturation (Sa,O2) and, in the OSA group,
percentage of sleep time with Sa,O2 < 90%. The variables obtained from the
flow-volume curves were the forced vital capacity (FVC), forced expiratory
and inspiratory volume in 1 s (FEV1 and FIV1), peak expiratory and peak
inspiratory flows (PEF and PIF), and maximal flow after expiring 50% of
the FVC (MEF50). The mean of the flow-volume variables, influenced by
upper airway aperture (PEF, FIV1) was significantly greater than
predicted.(ABSTRACT TRUNCATED AT 250 WORDS
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