首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Bilateral ablation of dorsolateral frontal cortex in the newborn animal failed to produce the frontal lobe syndrome typical of the adolescent and adult stages. The crucial tests (delayed response, string tests, and discrimination learning) were performed 3 to 4 months postoperatively. At this time, no significant differences between normal animals and animals with prefrontal lesions were found.  相似文献   

2.
运用大体解剖的方法对驯鹿头骨进行了形态学观察,并将其与双峰驼牛、马的头骨进行了比较。结果表明:驯鹿的梨骨特别发达。泪骨,额骨和鼻骨之间围成一个狭长的筛鼻甲窦(部)。下凳骨比牛、马、驼窄而长,下颌角钝圆。泪骨的形态较特殊,颜而形成纵形深窝,泪孔有两个,位于眶缘上,并有尖状的泪突分开,眶缘与颧骨交界处有一个深切迹,无泪囊窝。  相似文献   

3.
Recognition of a specific visual target among equally familiar distracters requires neural mechanisms for tracking items in working memory. Event-related functional magnetic resonance imaging revealed evidence for two such mechanisms: (i) Enhanced neural responses, primarily in the frontal cortex, were associated with the target and were maintained across repetitions of the target. (ii) Reduced responses, primarily in the extrastriate visual cortex, were associated with stimulus repetition, regardless of whether the stimulus was a target or a distracter. These complementary neural mechanisms track the status of familiar items in working memory, allowing for the efficient recognition of a currently relevant object and rejection of irrelevant distracters.  相似文献   

4.
本文解剖了15例北京鸭的眶部,左右两侧共30面。观察了眶部的骨骼、肌肉、血管、神经以及眼球的附属构造。北京鸭的眶部由额骨、筛骨、泪骨、蝶骨及鳞颞骨共同组成骨骼支架。眶底部有眶中隔。泪骨与颧突间由下颌长韧带相连,形成完整的眶缘。眶部的肌肉有眼睑肌和眼球肌。第三睑即瞬膜由瞬膜方肌和瞬膜锥状肌牵引。眶部的神经除动眼神经,滑车神经和外展神经分布至眼球肌外,尚有由上颌神经的分支——额后神经,下睑神经和颧神经分布至眼睑及周围的皮肤。由眼神经分出的睫状长神经入眼球,额前神经分布至眼前角的皮肤。眶部的血管有眶上动脉、筛动脉、眼颞动脉及眼内动脉的分支分布。它们间互相吻合。  相似文献   

5.
非粮生物质原料体系研发进展及方向   总被引:6,自引:14,他引:6  
非粮生物质原料供应是生物质能产业发展的最主要限制因素。本文系统分析了适合中国国情的非粮生物质和宜能非粮地概念,阐述粮食安全和生物质能源发展的关系,认为发展可持续非粮生物质能源是实现粮食、能源、生态、农村经济多赢的战略举措。进而,重点综述了当前中国非粮生物质原料及其供应体系研究进展,分析了当前迫切需要研发的重点任务,内容包括废弃物生物质资源及其可获得性,非粮能源植物种类筛选、育种和生产技术,原料生产、收获、收集和物流及其机械化,宜能非粮地的面积、分布和生产潜力,原料生产与供应的可持续性和标准化,供应产业模式及能源农业发展,发展规划和政策。  相似文献   

6.
Emotion is normally regulated in the human brain by a complex circuit consisting of the orbital frontal cortex, amygdala, anterior cingulate cortex, and several other interconnected regions. There are both genetic and environmental contributions to the structure and function of this circuitry. We posit that impulsive aggression and violence arise as a consequence of faulty emotion regulation. Indeed, the prefrontal cortex receives a major serotonergic projection, which is dysfunctional in individuals who show impulsive violence. Individuals vulnerable to faulty regulation of negative emotion are at risk for violence and aggression. Research on the neural circuitry of emotion regulation suggests new avenues of intervention for such at-risk populations.  相似文献   

7.
茶叶加工技术的创新发展   总被引:2,自引:0,他引:2  
李荣林  周建涛  彭英 《江西农业学报》2011,(10):128-130,132
茶作为世界上三大无酒精饮料之一,在我国有着悠久的历史。本文从茶叶加工的视角对茶的非食品用途、提高茶叶的品质、各种制茶工艺的交叉应用、生物技术的应用、低碳节能和清洁化生产等方面的先进技术的运用进行了探讨。  相似文献   

8.
Down's syndrome in adults: brain metabolism   总被引:4,自引:0,他引:4  
The cerebral metabolic rate for glucose, as measured with positron emission tomography and fluorine-18-labeled 2-deoxy-D-glucose, was significantly higher in four healthy young subjects with trisomy 21 syndrome (Down's syndrome) than the mean rate in healthy young controls. The rate of cerebral glucose utilization in the frontal lobe of a 51-year-old subject with Down's syndrome was significantly lower than the rate in the young subjects with this syndrome, but approximated the rate in middle-aged controls. Thus glucose utilization by the brain appears to be excessive in young adults with Down's syndrome but may decline with age in some brain regions.  相似文献   

9.
Ice-edge eddies in the fram strait marginal ice zone   总被引:1,自引:0,他引:1  
Five prominent ice-edge eddies in Fram Strait on the scale of 30 to 40 kilometers were observed over deep water within 77 degrees N to 79 degrees N and 5 degrees W to 3 degrees E. The use of remote sensing, a satellite-tracked buoy, and in situ oceanographic measurements showed the presence of eddies with orbital speeds of 30 to 40 centimeters per second and lifetimes of at least 20 days. Ice ablation measurements made within one of these ice-ocean eddies indicated that melting, which proceeded at rates of 20 to 40 centimeters per day, is an important process in determining the ice-edge position. These studies give new insight on the formation, propagation, and dissipation of ice-edge eddies.  相似文献   

10.
Modification of plant lipid synthesis   总被引:1,自引:0,他引:1  
Genetic engineering of new storage oils and fats has produced oil crop plants with fatty acid compositions unattainable by plant breeding alone. The combination of classical breeding methods with molecular techniques provides new ways for designing oils for food and nonfood uses. Alterations in the position and number of double bonds, variation in fatty acid chain length, and the introduction of desired functional groups have already been achieved in model systems. Short-term prospects include crops such as rapeseed or soybean engineered to have greater than 70 to 80 percent medium-chain fatty acids by content, greater than 90 percent oleic acid, and high erucic acid content, and engineered to form ricinoleic acid in seed storage tissues.  相似文献   

11.
武汉市城郊耕地流失特征与对策研究   总被引:1,自引:0,他引:1  
柏振忠 《安徽农业科学》2011,39(31):19555-19557
阐述了武汉市城郊耕地呈现出总量和人均占有量呈双下降、质量下降和土壤环境恶化相互制约、现有资源浪费和后备资源缺乏同时并存、功能"非粮化"趋向明显等特征,运用产权制度经济学和委托—代理理论深入剖析了武汉市城郊耕地快速流失的深层原因,并提出相应的建议。  相似文献   

12.
以豫麦49-198为供试材料,研究了不同施氮水平对籽粒淀粉粒度分布及大、小淀粉粒糊化特性的影响。结果表明,大、小淀粉粒的糊化参数明显不同,大淀粉粒的糊化时间和糊化温度明显低于小淀粉粒,而峰值黏度、低谷黏度和最终黏度则明显高于小淀粉粒。随着施氮水平的增加,大、小淀粉粒及总淀粉峰值黏度、低谷黏度、最终黏度总体呈增加趋势,以N3或N4处理的数值最高,表明增施氮肥有利于改善小麦淀粉糊化特性。随着施氮水平增加,2.0μm和9.8μm淀粉粒数目、体积和表面积百分比呈下降趋势,而9.8μm的淀粉粒数目和表面积百分比呈升高趋势。表明增施氮肥,降低了小淀粉粒数目、体积和表面积百分比,而增加了大淀粉粒的数目和表面积百分比。  相似文献   

13.
Bilateral ablation of the superior cervical ganglia appears to deprive the pineal body of sympathetic innervation. Although this procedure presumably interrupts the neural circuit for transmission of optic information to the pineal, oviposition rates of ganglionectomized females exposed to stimulatory (15-hour) or to nonstimulatory (4-hour) daily photoperiods do not differ from those of the controls.  相似文献   

14.
The questions of how planets form and how common Earth-like planets are can be addressed by measuring the distribution of exoplanet masses and orbital periods. We report the occurrence rate of close-in planets (with orbital periods less than 50 days), based on precise Doppler measurements of 166 Sun-like stars. We measured increasing planet occurrence with decreasing planet mass (M). Extrapolation of a power-law mass distribution fitted to our measurements, df/dlogM = 0.39 M(-0.48), predicts that 23% of stars harbor a close-in Earth-mass planet (ranging from 0.5 to 2.0 Earth masses). Theoretical models of planet formation predict a deficit of planets in the domain from 5 to 30 Earth masses and with orbital periods less than 50 days. This region of parameter space is in fact well populated, implying that such models need substantial revision.  相似文献   

15.
运用大体解剖学方法,研究了双峰驼的6个头骨,并将其与单峰驼、马、牛、猪的头骨进行了比较,结果表明:双峰驼的枕骨结构复杂,位于头骨后下部;额骨上的眶孔与圆孔合成一较大的眶圆孔;筛骨迷路分为上、中、下三部分;上颌骨无面嵴,面结节也不明显;鼻甲骨分为上、中、下三部分,下鼻甲骨又分为总鼻甲板和两个支三部分;下颌骨上有下颌骨髁下切迹,下颌骨髁上的关节面呈阶梯形。  相似文献   

16.
In primates, certain areas of the frontal cortex play a role in guiding movements toward visual or auditory objects in space. The projections from auditory centers to the frontal cortex of the bat Pteronotus parnellii were examined because echolocating bats utilize auditory cues to guide their movements in space. An area in the frontal cortex receives a direct projection from a division of the auditory thalamus, the suprageniculate nucleus, which in turn receives input from the anterolateral peri-olivary nucleus, an auditory center in the medulla. This pathway to the frontal cortex bypasses the main auditory centers in the midbrain and cortex and could involve as few as four neurons between the cochlea and the frontal cortex. The auditory cortex is also a major source of input to the frontal cortex. This area of the frontal cortex may link the auditory and motor systems by its projections to the superior colliculus.  相似文献   

17.
Somatostatin receptor concentrations were measured in patients with Alzheimer's disease and controls. In the frontal cortex (Brodmann areas 6, 9, and 10) and temporal cortex (Brodmann area 21), the concentrations of somatostatin in receptors in the patients were reduced to approximately 50 percent of control values. A 40 percent reduction was seen in the hippocampus, while no significant changes were found in the cingulate cortex, postcentral gyrus, temporal pole, and superior temporal gyrus. Scatchard analysis showed a reduction in receptor number rather than a change in affinity. Somatostatin-like immunoreactivity was significantly reduced in both the frontal and temporal cortex. Somatostatin-like immunoreactivity was linearly related to somatostatin-receptor binding in the cortices of Alzheimer's patients. These findings may reflect degeneration of postsynaptic neurons or cortical afferents in the patients' cerebral cortices. Alternatively, decreased somatostatin-like immunoreactivity in Alzheimer's disease might indicate increased release of somatostatin and down regulation of postsynaptic receptors.  相似文献   

18.
Landsat images of the Selima sand sheet in southwestern Egypt display alternating light and dark chevron-shaped patterns that occur downwind from low scarps and major dune fields. Images acquired between 1972 and 1988 indicate that these features move as discrete bedforms at a rate of up to 500 meters per year. Extremely long-wavelength (130 to 1200 meters), low-amplitude (10 to 30 centimeters) bedforms were measured in the field; the light chevrons seen in the orbital data may be thin accumulations of active sand sheet deposits in the lee of these bedforms. Dark chevrons contain an admixture of coarse-granule lag deposits that are continually winnowed by aeolian erosion on the windward sides of the large bedforms. Sediment transport budgets derived from orbital and field analyses suggest net movement of up to 83,000 cubic meters per year for a single light chevron; such measurements can be used as a check on similar calculations from dunes and other smaller scale features to determine sand transport budgets for large areas of the eastern Sahara.  相似文献   

19.
The virtual endocast of MH1 (Australopithecus sediba), obtained from high-quality synchrotron scanning, reveals generally australopith-like convolutional patterns on the frontal lobes but also some foreshadowing of features of the human frontal lobes, such as posterior repositioning of the olfactory bulbs. Principal component analysis of orbitofrontal dimensions on australopith endocasts (MH1, Sts 5, and Sts 60) indicates that among these, MH1 orbitofrontal shape and organization align most closely with human endocasts. These results are consistent with gradual neural reorganization of the orbitofrontal region in the transition from Australopithecus to Homo, but given the small volume of the MH1 endocast, they are not consistent with gradual brain enlargement before the transition.  相似文献   

20.
Heat and steam from the crater fumaroles have melted over 5700 feet (1737 meters) of cave passage in the ice-filled east crater of Mount Rainier. The caves are in approximate balance with the present geothermal heat release. Future changes in the thermal activity of the summit cone will cause corresponding changes in cave passage dimensions, location, and ceiling and wall ablation features.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号