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1.
Excess adiposity and high‐carbohydrate diets have been associated with an atherogenic lipoprotein phenotype (ALP) characterized by increased concentrations of small, dense low‐density lipoprotein (LDL) particles (pattern B). We tested whether weight loss and normalization of adiposity could reverse ALP in overweight men with pattern B. After consuming a moderate‐carbohydrate, high‐fat diet for 3 weeks, pattern B and nonpattern B (pattern A) men were randomized to a weight loss (n = 60 and n = 36, respectively) or control weight‐stable arm (n = 20 and n = 17, respectively). Men in the weight loss arm consumed ~1,000 fewer calories per day over 9 weeks to induce an average ~9 kg weight loss. In the control group, weight stability was maintained for 4 weeks after randomization. Weight loss led to the conversion of pattern B to pattern A in 58% of baseline pattern B men. Among men who achieved BMIs of <25 kg/m2 (62% of pattern B men vs. 83% of pattern A men), 81% of pattern B men converted to pattern A. Weight loss was associated with a significantly greater decrease in small, dense LDL subclass 3b in pattern B relative to pattern A men. The lipoprotein profiles of pattern A men who converted from pattern B were comparable to those of men with pattern A at baseline. Conversion of LDL subclass pattern B to pattern A and reversal of ALP can be achieved in a high proportion of overweight men by normalization of adiposity.  相似文献   

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Transducers employing a spatial electrode pattern in the form of a Fresnel zone plate (FZP) are useful in acoustic imaging systems for focusing an ultrasonic beam. A technique has been developed to predict the spatial acoustic output of such a transducer from a knowledge of the spatial electrode pattern. It has been shown that, due to mechanical aberration, sharp edges in the electrode pattern are not reproduced in the output pattern. The mechanism producing the aberration can be modeled as a low-pass spatial filter. A desired acoustic spatial pattern may be generated by a synthesized electrode pattern obtained through inverse filtering. The approach is to assume that the desired acoustic pattern is the output of a linear spatial system and then to synthesize the electrode pattern that would produce it by multiplying it with the inverse of the aberrating low-pass filter. The synthesized electrode pattern will then generate an acoustic pattern which replicates the desired acoustic pattern very closely.  相似文献   

4.
栽培模式对冬小麦光能利用和产量的影响   总被引:1,自引:1,他引:0  
以‘泰农18’小麦为材料,于2012—2013年进行大田试验,设置当地农民习惯栽培模式(FP)、超高产栽培模式(SH)和高产高效栽培模式(HH)3个处理,研究了不同栽培模式对小麦光能截获量、光能利用效率、干物质积累量、收获指数、籽粒产量和肥料偏生产力的影响.结果表明: SH模式小麦全生育期的光能截获量、光能利用效率、干物质积累量和籽粒产量显著高于FP模式.相对于FP模式,虽然HH模式的小麦全生育期光能截获量较低,但其光能利用效率、干物质积累量及收获指数均显著提高,从而使其籽粒产量显著提高.相对于SH模式,虽然HH模式的籽粒产量在高、低肥力水平下分别降低3.8%和2.8%,而氮、磷、钾肥的偏生产力在两肥力水平下分别提高26.4%、68.5%、92.6%.在本试验条件下,综合考虑籽粒产量和养分利用效率,以“降肥、增密、延播”为技术特点的高产高效栽培模式为推荐的优化栽培模式.  相似文献   

5.
干旱半干旱区坡面覆被格局的水土流失效应研究进展   总被引:17,自引:0,他引:17  
植被恢复与建设是控制水土流失的重要措施.在干旱半干旱地区,植被在空间上的分布呈现离散特征,在坡面上形成的裸地-植被镶嵌和植被条带分布等覆被格局对水土流失过程具有重要影响.覆被格局与水土流失关系研究是景观生态学格局与过程研究的重要内容.从植被斑块、坡面覆被格局对水土流失的影响与耦合覆被格局与水土流失的手段和方法三个方面对国内外相关研究进行总结分析.从中发现,植被类型、层次结构和形态特征是植被斑块尺度上影响径流泥沙的关键因素;不同覆被类型的产流产沙特征与覆被格局的准确描述是研究覆被格局水土流失效应的重要基础;坡面覆被格局对水土流失的影响关键在于其改变了径流泥沙运移和汇集的连续性,应重点关注径流泥沙源汇区的连通性和空间分布在水土流失中的作用;以坡面的精确覆被制图为基础,建立基于水土流失过程的覆被格局指数和耦合格局信息的径流与侵蚀模型是定量研究覆被格局影响的有效手段.今后应加强以下研究:以动态系统的观点研究覆被格局的变化对水土流失的影响,系统理解覆被格局与水土流失之间的相互联系与反馈机制,探讨两者间动态关系随尺度变化的规律性并发展尺度上推方法;构建过程意义明确且简单实用的格局指数,将覆被格局与水土流失过程有机联系起来;发展覆被格局的动态信息与产流产沙过程相结合的水文模型,加强对格局与径流泥沙反馈系统的耦合,建立真正意义上的覆被格局-水土流失过程耦合模型.  相似文献   

6.
Some interesting properties on pattern separation have been shown through researches by neural models of cerebellar cortex. It seems to us that those results are a part of the properties of pattern separation. A two layer random nerve net with inhibitory connections is given as a model of the cerebellar cortex. The model is composed of threshold elements there. A more general theory of pattern separation than those studied earlier is given, and the pattern separability of the model is considered. It is revealed that the standard deviation of threshold values of threshold elements has a great effect on the pattern separability and the control of the firing rate. The present study is also intended to investigate the pattern separability in such a case that the firing rate of input patterns are not equal, and a pattern includes the other pattern. It is assumed there that the standard deviation is small. Some properties of the degree of pattern separation are cleaned up.  相似文献   

7.
The relationship between the nuclear DNA histogram pattern of tumor cells obtained by bronchoscopic brushing and the response to combination chemotherapy (Cytoxan + Adriamycin + Vincristine) was studied in 28 patients with small-cell carcinoma of the lung. Microspectrophotometric analysis of the tumor cells showed a near-diploid nuclear DNA pattern in 18 patients and a hyperdiploid pattern in 10 patients. Eight of the ten patients with the hyperdiploid pattern showed a good response (complete or partial response) to the chemotherapy. However, of the 18 patients with the near-diploid DNA pattern, only 2 displayed a good response; the remaining 16 patients exhibited no response. The hyperdiploid DNA pattern of tumor cells was thus associated with a better response to chemotherapy than was the near-diploid pattern. These results indicate that the nuclear DNA histogram pattern may be an indicator for predicting the degree of response to chemotherapy in small-cell carcinoma of the lung.  相似文献   

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Owing to recent findings of certain unusual sex steroid binding in liver disease--particularly an allosteric biphasic pattern (pattern A) unique to the serum of patients with hepatocellular carcinoma--the serum binding characteristics for 5 alpha-dihydrotestosterone were examined in serum samples from six patients with primary biliary cirrhosis who had developed hepatocellular carcinoma. In all serum samples taken after the development of tumour pattern A binding only was obtained, and in four cases in which earlier samples were also examined there was a transformation from the normal, non-specific binding pattern, or an allosteric plateau pattern seen in non-malignant liver disease (designated D and C respectively), to pattern A coincident with the rise in serum alpha fetoprotein. In one patient chemotherapy leading to a fall in alpha fetoprotein abolished pattern A binding, showing further its close association with tumour growth. The value of pattern A binding as a tumour marker in hepatocellular carcinoma warrants further study.  相似文献   

10.
Sexes' roles in post‐copulatory processes have important effects on individual fitness and are promising to study in species showing complex mating behaviours. In the spider Schizocosa malitiosa, males perform two different copulatory patterns, pattern 1 includes 80% of total pedipalp insertions and pattern 2 includes 20%. Both patterns produce similar number of offspring, but pattern 1 induces higher female reluctance to remating than pattern 2. We hypothesised that the complex copulatory patterns are linked to post‐copulatory sexual selection, affecting males' sperm transfer and the resulting sperm storage by females. First, we examined amounts of sperm in males and live females from uninterrupted (pattern 1 + 2) and interrupted matings (pattern 1, pattern 2). Second, in order to disentangle male and female actions, we induced males to mate with dead females and examined amounts of sperm. Males transfer in total 71% of the sperm available in their pedipalps, being higher but not significant in pattern 1 than in pattern 2. Females drastically reduced the amount of sperm stored in their spermathecae and such control is stronger in pattern 1 compared to pattern 2 matings. We propose that cryptic female control is a main factor driving males to strengthen sperm transfer. Active female reduction in ejaculate most probably diminished her reluctance to remate.  相似文献   

11.
Randomly amplified polymorphic DNA (RAPD) was used to examine possible origin of Varroa jacobsoni Oudemans in the Americas. Among 64 primers screened, 2 primers provided variation which was informative for this study. All V. jacobsoni collected from the United States had the same banding pattern to that of mites collected from Russia, Morocco, Germany, Italy, Spain, and Portugal (Russian pattern). This banding pattern was different from the pattern found for mites collected from Japan, Brazil, and Puerto Rico (Japanese pattern). The Japanese pattern lacked a 766-bp band found in the Russian pattern (OPE-07). With primer OPP-03, the Russian pattern had a distinct band at 442 bp not found in the Japanese pattern. Two bands located at 675 and 412 bp were specific to the Japanese pattern. These results suggest that the V. jacobsoni of the United States is probably predominantly Russian in origin (via Europe), while the V. jacobsoni of Brazil and Puerto Rico are probably predominantly Japanese in origin.  相似文献   

12.
The modes of pattern regulation found in the ciliates Dileptus and Paraurostyla are compared. These forms are systematically distant but both possess very extensive regenerative capacities. They are characterized by 2 types of ciliary patterns: the ciliature of Dileptus has largely a simple pattern composed of single kinetosomes while that of Paraurostyla has a complex pattern composed of aggregates of kinetosomes interconnected by amorphic matter. In both ciliates a change in cell size evokes pattern regulation which differs substantially in the extent of pattern replacement, timing, and localization of morphogenetic activities. It is concluded that these differences result from the pattern constituents.  相似文献   

13.
不同种植方式下转Bt基因水稻对稻田节肢动物群落的影响   总被引:6,自引:2,他引:6  
如何设置庇护所使其在转基因作物靶标害虫抗性治理中达到更高的效率,就此,本文 研究了Bt水稻与非Bt水稻不同种植方式对Bt稻田节肢动物群落的影响。结果表明,整体上,块块种植和列列混栽方式对Bt稻田节肢动物群落多样性、均匀度和优势集中性无显著影响;但混栽方式下的Bt稻田节肢动物群落个体密度和物种丰富度显著偏低。在水稻发育中期,混栽方式下Bt稻田节肢动物群落季节动态与块块种植方式下的明显不同,其多样性、均匀度、优势集中性指数均类似于同种植方式下非Bt稻上各参数的季节动态。混栽方式下的庇护所效应更明显。  相似文献   

14.
Bacteroides fragilis is an important anaerobic pathogen accounting for up to 10% of bacteremias in adult patients. Enterotoxin producing B. fragilis (ETBF) strains have been identified as enteric pathogens of children and adults. In order to further characterize the B. fragilis pathogenicity island (BfPAI) and using PCR assays for bft- and mpII-metalloprotease genes, we determined the frequency of B. fragilis strains with pattern I (containing the BfPAI and its flanking region), pattern II (lacking both the BfPAI and the flanking region), and pattern III (lacking the BfPAI but containing the flanking region) in 63 blood culture isolates. The results were compared to 197 B. fragilis isolates from different clinical sources. We found 19% of blood culture isolates were pattern I (ETBF), 43% were pattern II (NTBF) and 38% were pattern III (NTBF). Comparatively, B. fragilis isolates from other clinical sources were 10% pattern I, 47% pattern II and 43% pattern III. This suggests that the pathogenicity island and the flanking elements may be general virulence factors of B. fragilis.  相似文献   

15.
群落二维格局分析的两种方法   总被引:4,自引:0,他引:4  
张金屯 《西北植物学报》2004,24(8):1448-1451
群落二维空间格局研究能够更好地揭示群落的特征,但在分析方法上有较大的困难。用垂直相交的两条样带在两个方向上同时取样的二维取样法,获得数据,用DCA排序与格局分析相结合的方法,得到群落不同格局规模斑块的长、宽及面积,实现二维格局研究。在亚高山草甸群落格局研究中应用表明,两个方法均是有效的。  相似文献   

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Experiments with crucians (Carassius carassius L.) and goldfish (Carassius auratus L.) have shown that a consolidated memory trace of a simple visual pattern became disturbed by later seeing series of similar patterns (unrewarded), that is to say by latent learning. In a test in which the experimental group (es) had to choose between the originally learnt and the similar pattern, it did not prefer the former, whereas the control group (cs), which had only seen white walls of the aquarium, still preferred the originally learnt pattern. The same happened when es learnt a similar pattern by reward after the memory of the original pattern had been consolidated. In another set of experiments the negative influence of post-exposure could be demonstrated in facilitation of later learning the postexposed pattern as positive versus the originally learnt pattern, now negative. When es had seen a dissimilar wall-paper pattern then the memory of the primarily learnt pattern was not disturbed. A tentative explanation is based on the notion that two similar engrams have part of the neuronal network in common.  相似文献   

18.
Chromatin was prepared from the citric acid nuclei of normal rat liver and Novikoff hepatoma ascites cells. After sulfuric acid extraction, the dehistonized chromatin was solubilized by digestion with deoxyribonuclease I. The proteins of normal liver and of Novikoff hepatoma chromatin fractions were analyzed by two-dimensional polyacrylamide gel electrophoresis. The liver pattern contained 69 components and the hepatoma pattern contained 84 components. Comparison of the two patterns revealed two dense protein spots migrating in the B region in the liver pattern that were absent from the tumor pattern and two dense protein spots migrating in the C region in the tumor pattern that were absent from the liver pattern.  相似文献   

19.
黑龙江西部生态脆弱带景观格局研究   总被引:1,自引:0,他引:1  
贾利  周光达  张艳秋 《植物研究》2003,23(3):353-355
运用景观生态学格局的分析方法,对黑龙江西部生态脆弱带典型的土地景观进行了分析,并对各种分析方法进行了对比,探讨了各种景观类型的关系,并对人类活动的影响与景观之间的关系进行了分析。  相似文献   

20.
BACKGROUND: It is known that the visibility of patterns presented through stationary multiple slits is significantly improved by pattern movements. This study investigated whether this spatiotemporal pattern interpolation is supported by motion mechanisms, as opposed to the general belief that the human visual cortex initially analyses spatial patterns independent of their movements. RESULTS: Psychophysical experiments showed that multislit viewing could not be ascribed to such motion-irrelevant factors as retinal painting by tracking eye movements or an increase in the number of views by pattern movements. Pattern perception was more strongly impaired by the masking noise moving in the same direction than by the noise moving in the opposite direction, which indicates the direction selectivity of the pattern interpolation mechanism. A direction-selective impairment of pattern perception by motion adaptation also indicates the direction selectivity of the interpolation mechanism. Finally, the map of effective spatial frequencies, estimated by a reverse-correlation technique, indicates observers' perception of higher spatial frequencies, the recovery of which is theoretically impossible without the aid of motion information. CONCLUSIONS: These results provide clear evidence against the notion of separate analysis of pattern and motion. The visual system uses motion mechanisms to integrate spatial pattern information along the trajectory of pattern movement in order to obtain clear perception of moving patterns. The pattern integration mechanism is likely to be direction-selective filtering by V1 simple cells, but the integration of the local pattern information into a global figure should be guided by a higher-order motion mechanism such as MT pattern cells.  相似文献   

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