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排序方式: 共有268条查询结果,搜索用时 15 毫秒
141.
RA Seymour J Frame TW Negus JE Hawkesford J Marsden IR Matthew 《Canadian Metallurgical Quarterly》1998,36(5):375-379
BACKGROUND AND OBJECTIVES: Congenital lens subluxation may be a difficult therapeutic problem. Surgical treatment options include iris manipulation or lens decision, aspiration, intracapsular or extracapsular extraction, and lensectomy through the pars plana. It is not established which kind of aphakic correction is the most appropriate in these cases. PATIENTS AND METHODS: A father and his two sons with Marfan's syndrome were operatively treated for lens dislocation in both eyes. Pars plana vitrectomy was done in all eyes. Dislocated lenses were removed by lensectomy in three eyes and with an intracapsular method in three eyes. The outside-in scleral fixation technique was used for primary posterior chamber intraocular lens (PC IOL) implantation in all cases. RESULTS: All eyes achieved good visual acuity (20/20-20/25). Time of observation ranged between 8 and 20 months. There were no intraoperative or post-operative complications. CONCLUSION: Pars plana vitrectomy and primary scleral-fixated IOL implantation is a safe procedure and gives good visual rehabilitation in adult patients with Marfan's syndrome. 相似文献
142.
A physics teaching survey was constructed and sent to the 83 radiation oncologist training programs. The survey requested program information regarding size, staffing, curriculum, lab/rotation programs, organization, requirements, instructor makeup, teaching materials, and board certification examination results. The surveys were sent to the physicist responsible for the physics program. Forty-nine (59%) institutions returned completed surveys, of which 43 (88%) were university-associated programs, and 27 (55%) were 4-year programs. On average, there were two residents/year. Most programs (39) taught physics exclusively during the first year (PG2). Some programs taught different subjects (or levels) to different year residents. Radiation dosimetry, treatment planning, and brachytherapy constituted nearly half of the teaching hours. On average the total classroom time expended by physicists was 61.4 h/year with a range of 24-118 h. The mean for laboratory/demonstration time was 27 h/year with 18 programs providing none. Physics orientation/rotations ranged from 1 to 480 h with a mean of 170 h for a physics rotation taking place in year 2 (PG3). Mandatory attendance was 80% for first-year residents and decreased in later years. Homework was assigned in 76% of the programs, and 65% of the programs were graded. The primary instructors averaged 18.2 years of experience, and the majority were ABR/ABMP certified. Khan's textbook was the most prevalent resource for most subjects. No correlation could be made between teaching hours and ABR physics percentile scoring. The survey results reveal enormous differences in national teaching efforts. 相似文献
143.
144.
The clinical and electrophysiological characteristics of eight patients with propriospinal myoclonus are described. Myoclonus developed within days or weeks of cervical trauma in half the patients. Seven cases had axial flexion jerks, and one axial extension jerks. Myoclonic EMG activity consisted of repetitive bursts with a frequency of 1-7 Hz. The jerks in three of the cases were comprised of alternating and rhythmic bursts of EMG activity in rectus abdominis and the paraspinal muscles. From these new observations, it is proposed that cervical trauma can lead to the partial release of a spinal pattern generator. The latter is capable of recruiting muscles through long propriospinal pathways into complex rhythmic activity. 相似文献
145.
J Vaughan A Durr J Tassin B Bereznai T Gasser V Bonifati G De Michele E Fabrizio G Volpe O Bandmann WG Johnson LI Golbe M Breteler G Meco Y Agid A Brice CD Marsden NW Wood 《Canadian Metallurgical Quarterly》1998,44(2):270-273
Deoxyguanosine kinase (dGK) is an enzyme responsible for the phosphorylation of purine deoxynucleosides in mitochondria of mammalian cells. Its role in activation of pharmacologically used nucleoside analogs is not well understood, because of the low levels of dGK found in tissue extracts and its inactivation during purification. The cDNA for dGK was recently cloned and expressed in Escherichia coli. Here we present an improved procedure for expression and purification of a highly active form of human recombinant dGK. The enzyme showed a broad substrate specificity toward natural purine and pyrimidine deoxynucleosides as well as toward important nucleoside analogs. The Km and Vmax values for deoxyguanosine, deoxyinosine, deoxyadenosine, and deoxycytidine were 4, 13, 460, 330 microM and 43, 330, 430 and 60 nmol/min/mg of protein, respectively. Antileukemic purine analogs such as arabinosyl guanine, 2-chloro-2'-deoxyadenosine, 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine, and 2-fluoro-arabinosyl-adenine were phosphorylated as efficiently by dGK as the natural nucleoside substrates. This is the first report in which 2-fluoro-arabinosyl-adenine and 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine were shown to be good substrates for dGK. The antiviral analogs dideoxyinosine and arabinosyl adenine also showed significant activity with dGK, as did several pyrimidine analogs (e.g., the cytostatic drugs 5-fluoro-2'-deoxycytidine and difluorodeoxycytidine). The broad specificity of dGK described here may change our understanding of the mechanisms responsible for the efficacy and mitochondrial toxicity of several nucleoside analogs. 相似文献
146.
Mature (3-4 months) and aged (18-19 months) Sprague-Dawley (SD) rats were treated with 5-HT receptor agonists and drug-induced behaviours monitored. The 5-HT2/1C agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), induced wet dog shakes and back muscle contractions which were significantly increased in aged, compared to mature, rats, suggesting an age-related enhancement of 5-HT2 receptor function. In contrast, the selective 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) induced forepaw treading, flat body posture, hypothermia and hyperactivity which were not significantly different in aged compared to mature rats. Levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the hippocampus and frontal cortex were measured using high performance liquid chromatography with electrochemical detection. There were no age-related changes in hippocampal 5-HT or 5-HIAA. However both 5-HT and 5-HIAA were increased in the frontal cortex of aged SD rats. 8-OH-DPAT reduced 5-HIAA in both regions examined in mature rats, an effect which was attenuated in the aged rats, suggesting an age-related reduction in presynaptic 5-HT1A receptor function. DOI did not induce any changes in 5-HT or 5-HIAA in either of the regions examined. Radioligand binding studies with [3H] ketanserin showed there to be no significant age-related changes in cortical 5-HT2 receptor density or affinity.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
147.
148.
A comparison of outlet boundary treatments for prevention of backflow divergence with relevance to blood flow simulations 总被引:1,自引:1,他引:0
Mahdi?Esmaily Moghadam Yuri?Bazilevs Tain-Yen?Hsia Irene?E.?Vignon-Clementel Alison?L.?Marsden Modeling of Congenital Hearts Alliance 《Computational Mechanics》2011,48(3):277-291
Simulation divergence due to backflow is a common, but not fully addressed, problem in three-dimensional simulations of blood
flow in the large vessels. Because backflow is a naturally occurring physiologic phenomenon, careful treatment is necessary
to realistically model backflow without artificially altering the local flow dynamics. In this study, we quantitatively compare
three available methods for treatment of outlets to prevent backflow divergence in finite element Navier–Stokes solvers. The
methods examined are (1) adding a stabilization term to the boundary nodes formulation, (2) constraining the velocity to be
normal to the outlet, and (3) using Lagrange multipliers to constrain the velocity profile at all or some of the outlets.
A modification to the stabilization method is also discussed. Three model problems, a short and long cylinder with an expansion,
a right-angle bend, and a patient-specific aorta model, are used to evaluate and quantitatively compare these methods. Detailed
comparisons are made to evaluate robustness, stability characteristics, impact on local and global flow physics, computational
cost, implementation effort, and ease-of-use. The results show that the stabilization method offers a promising alternative
to previous methods, with reduced effect on both local and global hemodynamics, improved stability, little-to-no increase
in computational cost, and elimination of the need for tunable parameters. 相似文献
149.
This study was conducted to determine how well Clostridium perfringens spores germinate and grow in restructured roast beef treated with different commercial organic salts during an alternative chilling procedure. The meat was prepared according to an industrial recipe (10% water, 1.5% sodium chloride, and 0.5% sodium triphosphate). The base meat was treated with sodium citrate at 2 or 4.8% (wt/wt), buffered to a pH of 5.6, 5.0, or 4.4 (six treatments); a 60% (wt/wt) solution of sodium lactate at 2 or 4.8% (wt/wt); sodium acetate at 0.25% (wt/wt); or sodium diacetate at 0.25% (wt/wt). Untreated meat was used as a control. Meat samples were inoculated with a three-strain cocktail of C. perfringens spores (strains ATCC 10388, NCTC 8238, and NCTC 8239). Meat was vacuum packaged in bags and cooked in a stirred water bath to an internal temperature of 75 degrees C for 20 min, and then the bags were cooled from 54.4 to 4.4 degrees C within 18 h. Samples were taken after inoculation, after cooking, and after chilling. Spore and vegetative cell counts were obtained after incubation at 37 degrees C for 8 to 10 h in Fung's Double Tubes containing tryptose sulfite agar without egg yolk enrichment. Cooking was not sufficient to eliminate C. perfringens spores. Over the 18-h cooling period, sodium citrate, sodium lactate, and sodium diacetate reduced the growth of C. perfringens to < 1 log unit, a growth level that meets U.S. Department of Agriculture performance standards. The use of sodium citrate or sodium lactate at a concentration of > or = 2% (wt/wt) inhibited C. perfringens growth over the 18-h cooling period. 相似文献
150.
J. Ellen Marsden Carrie L. Kozel Brian D. Chipman 《Journal of Great Lakes research》2018,44(1):166-173
Lake trout were extirpated from Lake Champlain by 1900, and are currently the focus of intensive efforts to restore a self-sustaining population. Stocking of yearling lake trout since 1972 has re-established adult populations, spawning occurs at multiple sites lake-wide, and fry production at several sites is very high. However, little to no recruitment past age-0 has occurred, as evidenced by the absence of adults without hatchery fin clips in fall assessments; no regular sampling for juveniles is conducted. We began focused sampling for juvenile lake trout in fall, 2015, in the Main Lake using bottom trawling, and expanded sampling to sites in the north and south of the lake in 2016. In 2015 we collected 303 lake trout < 350 mm total length, of which 23.8% were unclipped. Based on non-overlapping length modes, these wild fish comprised at least three age classes (young-of-year, age-1, and age-2). In 2016, we collected 1215 lake trout < 350 mm, including a fourth wild year class (2016 young-of-year). Forty-nine percent of juvenile lake trout from the Main Lake were unclipped; however, only 20% from the north lake and 9% from the south lake were unclipped. The absence of older unclipped fish indicates that recruitment of wild fish began recently. We discuss several hypotheses to explain this sudden, substantial recruitment success, and factors that may be affecting lake trout restoration in Lake Champlain and the Great Lakes. 相似文献