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61.
Antonio Torralba Rob Fergus William T Freeman 《IEEE transactions on pattern analysis and machine intelligence》2008,30(11):1958-1970
With the advent of the Internet, billions of images are now freely available online and constitute a dense sampling of the visual world. Using a variety of non-parametric methods, we explore this world with the aid of a large dataset of 79,302,017 images collected from the Internet. Motivated by psychophysical results showing the remarkable tolerance of the human visual system to degradations in image resolution, the images in the dataset are stored as 32 x 32 color images. Each image is loosely labeled with one of the 75,062 non-abstract nouns in English, as listed in the Wordnet lexical database. Hence the image database gives a comprehensive coverage of all object categories and scenes. The semantic information from Wordnet can be used in conjunction with nearest-neighbor methods to perform object classification over a range of semantic levels minimizing the effects of labeling noise. For certain classes that are particularly prevalent in the dataset, such as people, we are able to demonstrate a recognition performance comparable to class-specific Viola-Jones style detectors. 相似文献
62.
63.
Cyclic GMP (cGMP) is a crucial intracellular messenger in neuronal, muscle, and endocrine cells. The intracellular concentration of cGMP is regulated by various neurotransmitters, including acetylcholine (ACh) and nitric oxide (NO). While much is known about the biochemical steps leading to cGMP synthesis, little is known about cGMP kinetics in intact cells. Here, we use "patch-cramming," in which an excised, inside-out membrane patch containing cyclic nucleotide-gated ion channels is used as a biosensor, to obtain the first real-time measurements of cGMP in intact cells. Patch-cramming experiments on neuroblastoma cells show that both muscarinic agonists and NO rapidly elevate cGMP. NO elicits cGMP responses repeatedly without decrement, whereas responses to muscarinic agonists exhibit a profound and prolonged desensitization. Remarkably, muscarinic agonists also cause long-term (>30 min) suppression (LTS) of cGMP responses elicited by NO. Biochemical measurements reveal that rat sympathetic neurons also exhibit LTS of cGMP, suggesting that LTS is a widespread mechanism that may contribute to synaptic plasticity. 相似文献
64.
Y Wu EC Unger TP McCreery RH Sweitzer D Shen G Wu MD Vielhauer 《Canadian Metallurgical Quarterly》1998,33(12):880-885
RATIONALE AND OBJECTIVES: A thrombus-specific ultrasound contrast agent, MRX-408, has been developed recently. This agent consists of phospholipid-coated microbubbles with a ligand capable of targeting the GPIIb/IIIa receptor, thereby allowing the microbubbles to bind with thrombi rich in activated platelets. In vitro and in vivo animal experiments have been conducted to examine imaging enhancement and sonothrombolysis using this agent compared with a nontargeted agent. METHODS: For clot binding, blood-smeared slides were incubated with microbubbles and examined under a light microscope. Change in backscatter signals from the blood clots after binding was examined by both an ultrasound scanner and two single-element transducers arranged in a transmitter-receiver pair. For clot lysis, either 1-MHz or 20-KHz ultrasound was used to enhance the lysing effects of MRX-408 with or without urokinase. RESULTS: Evidence of binding was demonstrated under a microscope. In vitro experiments showed that the "acoustic signature", or properties, of blood clots changed after binding. Clots became more echogenic and nonlinear. In vivo fundamental ultrasound imaging confirmed that as a result of binding, blood clots were more visible, the area of detection was improved, and shadowing behind clots was more noticeable. Under 1-MHz ultrasound and 30 minutes of treatment, lysis efficiency reached 34% with MRX-408, whereas there was no visible clot lysis with saline. CONCLUSION: The results of these preliminary studies show that as a contrast agent, MRX-408 enhanced clots under ultrasound imaging and facilitated sonothrombolysis with or without thrombolytic drugs. 相似文献
65.
EL Wallace DM Surgenor HS Hao J An RH Chapman WH Churchill 《Canadian Metallurgical Quarterly》1993,33(2):139-144
A poor response to L-DOPA in addition to parkinsonian, cerebellar, and autonomic signs is commonly regarded as indicative of clinical multiple system atrophy (MSA). We compared the motor response to a single oral administration of 250 mg L-DOPA/25 mg carbidopa in eight MSA patients and eight Parkinson's disease (PD) patients with the "on-off" phenomenon, evaluating L-DOPA peripheral pharmacokinetics. Motor response was consistently good in all PD patients, but only four MSA patients had a (moderate) response. Pharmacokinetic parameters did not differ between the groups. The varying extent of putaminal damage could be responsible for the differing motor response to L-DOPA in MSA patients. 相似文献
66.
Gene transfer with vectors derived from murine retroviruses is restricted to cells which are proliferating and synthesizing DNA at the time of infection. This suggests that retroviral-mediated gene transfer might permit targeting of gene integration into malignant cells in organs composed mainly of quiescent nonproliferating cells, such as in the brain. Accordingly, selective introduction of genes encoding for susceptibility to otherwise nontoxic drugs ("suicide" genes) into proliferating brain tumors may be used to treat this cancer. We investigated the efficacy and dynamics of in vivo transduction of growing brain tumors with the herpes simplex-thymidine kinase gene followed by administration of the antiviral drug ganciclovir. Ganciclovir is phosphorylated by thymidine kinase to toxic triphosphates that interfere with DNA synthesis, resulting in the preferential death of the transduced tumor cells. Rats inoculated with 4 x 10(4) 9L gliosarcoma cells into the frontal lobe were treated 7 days later with an intratumoral stereotaxic injection of murine fibroblasts (NIH 3T3 cells) that were producing a retroviral vector containing the herpes simplex-thymidine kinase gene. Controls received vector producer and nonproducer NIH 3T3 cell lines containing the Escherichia coli lacZ (beta-galactosidase) gene as well as nonproducer NIH 3T3 cells containing the thymidine kinase gene. The animals were rested for 7 days to allow time for in situ transduction of the proliferating tumor cells with the herpes-thymidine kinase retroviral vector. The animals were then treated with ganciclovir, 15 mg/kg i.p. twice a day for 14 days. Gliomas receiving an injection of 3-5 x 10(6) thymidine kinase producer cells regressed completely in 23 of 30 rats given ganciclovir therapy, while 25 of 26 control rats developed large tumors. Intratumoral injection of a lower concentration of thymidine kinase vector producer cells (1.8 x 10(6)) resulted in a lower frequency of tumor regression (5 of 13 rats). To estimate the efficiency of in vivo gene transfer, 9L brain tumors were given injections of 5 x 10(6) beta-galactosidase vector producer cells. 5-Bromo-4-chloro-3-indolyl-beta-D-galactopyranaside staining revealed maximal staining of beta-galactosidase within the tumor 7-14 days after injection of the vector producer cells. In vivo transduction rates in harvested tumors ranged from 10 to 70%. There was no evidence of transduction of the surrounding normal neural tissue. Occasional blood vessel endothelial cells within or adjacent to the tumor were observed to be 5-bromo-4- chloro-3-indolyl-beta-D-galactopyranaside positive.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
67.
We have previously demonstrated that mouse brain membrane fractions have a specific, saturable receptor for diadenylated nucleotides. Binding is specific for two adenosines, and the length of the phosphate bridge is critical, with four phosphates being optimal [Hilderman et al. (1991) J. Biol. Chem. 266, 6915-6918]. In this report, we demonstrate that adenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) binding to its receptor is dependent upon an activation step that requires divalent cations and a serine protease. Monoclonal antibodies (Mabs) are identified that inhibit Ap4A binding to its membrane receptor. These antibodies recognize a 212-kDa membrane protein. However, SDS-PAGE analysis of Ap4A cross-linked to membrane fractions reveals that Ap4A is not attached to the 212-kDa peptide but to a 30-kDa polypeptide. Appearance of the 30-kDa polypeptide is dependent on the activation step, and one of the inhibitory antibodies blocks its appearance. We suggest that the protease-dependent processing step involves cleavage of the 212-kDa component with the appearance of an active 30-kDa receptor. 相似文献
68.
An experiment is reported which tests the hypothesis, put forward by Poulton (1976a, b) that the detrimental effects of noise are due to the masking of auditory feedback. The results of the experiment showed that noise impaired the performance of a tracking task both in the presence and absence of task-related auditory feedback. These findings are contrary to Poulton's predictions. 相似文献
69.
This study examined the question, ‘What is the impact of a digital math intervention on secondary ELL students’ mathematical capabilities and perceptions of their future possibilities?’ The hypothesis was that through its direct effect on increasing students’ math ability and its indirect effect on increasing students’ perceived math self-efficacy, the digital intervention affects students’ perceptions of their functionings and future possibilities. A path analysis, with qualitative data nested into the design, was used to analyze the conceptualized relationships. The study was conducted with 50 ninth-and-10th-grade Hispanic students in a Colorado high school, over 6 months. The primary finding was that through its direct effect on increasing students’ math ability and its indirect effect on increasing students’ perceived math self-efficacy, the digital intervention improved students’ perceptions of their functionings and future possibilities. What this study specifically underscores is the importance of taking a coherent and purposeful approach toward the design of digital student-directed educational technology, especially for ELL students who may have specific learning needs. 相似文献
70.
We have followed the growth of stature, sitting height, skinfolds, muscle widths measured radiologically, and skeletal maturity in growth hormone-deficient patients in whom hGH was given and withheld in alternating three-month periods throughout puberty (referred to as "off-hGH" and "on-hGH" periods). Six boys and four girls had true isolated GH deficiency and developed puberty spontaneously. Two boys had gonadotrophin deficiency plus GH deficiency, and five boys had multiple deficiencies; in these boys the signs of puberty were induced by hormone treatment. Boys with true isolated deficiency grew about two-thirds as much in height in the off-hGH periods as in the on-hGH periods; their total gain in height during the adolescent spurt would have been about 20 cm, instead of 30 cm, if hGH had been discontinued at the beginning of puberty. The effect of hGH was entirely on growth in leg-length, however, which virtually ceased during the off-hGH periods. Growth in sitting height altered little when hGH was withdrawn. Growth in limb muscles, however, was GH dependent throughout puberty; during the majority of periods when hGH was withheld, muscle was actually lost; this occurred in the boys who were receiving large doses of testosterone as well as in those producing their own normal amounts. Subcutaneous fat diminished when hGH was given and increased when it was withdrawn; this occurred independently of administration of testosterone. There was little evidence that growth of pubic and axillary hair progressed faster during on-hGH periods, except perhaps in patients with multiple deficiencies. There was some evidence, however, that bone age progressed less rapidly during on-hGH periods than during off-hGH periods in the patients with isolated deficiency. The results in the girls agreed with those in boys so far as stature was concerned, but the relationship with sitting height and leg length appeared to be different; the reasons for this are discussed. We conclude that all children with GH deficiency should continue on treatment with hGH throughout puberty, ideally until growth ceases. 相似文献