数字化回传技术

对于有线电视运营商来说，为满足当今快速增长的语音和高速数据业务的需要．双向通信系统中的“上行”回传就显得尤为重要。最初的“广播”网中，回传通道只局限于对覆盖用户的状态监控和基本的机顶盒控制，随着时间的推进，情况逐步发生变化：先是受限机顶盒交互的QPSK调制，然后是DOCSIS 1．x的16QAM调制,再到DOCSIS2．0和DOCSIS3．0的64QAM调制。     

Vocal learning in the grey parrot (Psittacus erithacus): Effects of species identity and number of trainers.

Grey parrots (Psittacus erithacus) learn referential English labels when they view and interact with 2 humans who model vocal labeling and who demonstrate referentiality and functionality of a label (I. M. Pepperberg, 1990a). To test if both trainers are necessary, the authors contrasted 2-trainer modeling with training by 1 human who presented targeted labels to a bird in concert with appropriate items, who asked questions, and who would reward attempts at the label with the item. The bird was also tutored by either 1 or 2 interactive humans in conjunction with a conspecific who already used referential labels. Referential labels were learned from multiple live tutors but not a single trainer. Presence of a conspecific enhanced learning compared with single-trainer sessions but did not affect acquisition in 2-human sessions. Specific aspects of paired tutoring seem critical for acquiring referential vocal labels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anionic functional initiators. 1: 3-dimethylaminopropyllithium as an initiator for the synthesis of Bi- and difunctional polybutadienes

Methods are described whereby a series of novel bi- and difunctional (telechelic) high 1,4-microstructure polybutadienes are prepared by use of an anionic functional initiator. This initiator, 3-dimethylaminopropyllithium, has been extensively investigated and methods for its preparation and use in non-polar solvents are described. When utilised in such non-polar solvents the polybutadienes produced are uniquely functionalised, possessing a high 1,4-structure and a low glass transition temperature. Evidence is presented to demonstrate that these reactions are true ‘living’ polymerisations and that quantitative functional termination reactions may be used to yield a wide range of multi-, bi- or difunctional polymers.     

Segregation in Yttrium Aluminum Garnet: II, Theoretical Calculations

Calculations based on ionic space-charge models of doped yttrium aluminum garnet (YAG) have been compared to experimental measurements of surface segregation in crystals of various compositions. The comparison allows limits for vacancy-formation energies to be set. The range for anion:cation formation-energy ratios has been established to be 0.20-0.23, based on the reasonable assumptions that the formation energy of the yttrium ion is 75% of that of the aluminum ion and the Schottky defect formation energy is 4.2 eV. The model explains the experimental observation of calcium at the surface regardless of net acceptor excess or net donor excess. The relationship between vacancy-formation energy and dopant excess has been used to construct segregation maps for YAG, which are useful in materials design strategies.     

A longitudinal study of the relationships between haemostatic, lipid, and oestradiol changes during normal human pregnancy

BACKGROUND: Chronic leukemia is a disease characterized by the malignant proliferation of immunologically incompetent lymphocytes. The knowledge of open heart surgery in patients with this disorder is limited. METHODS: Twelve patients with chronic lymphocytic leukemia underwent open heart surgery (nine coronary artery bypass grafting (CABG), two aortic valve replacement (AVR), one CABG and AVR) from September 1991 to September 1996. There were nine males and three females with a mean age of 68 years (41-81 years). Staging was assigned according to the Rai Classification. There were seven Stage 0, two Stage I, zero Stage II, one Stage III and two Stage IV patients. Cardiopulmonary bypass (CPB) was performed using standard techniques of cannulation, moderate hypothermia and antegrade/retrograde cardioplegia. RESULTS: Hospital mortality occurred in two (17%) patients. Both patients died of sepsis. Hospital morbidity occurred in seven (58%) patients. The most common complications were infections. Five patients were found to have other malignancies (basal cell, laryngeal, prostate, bladder and breast cancers). Transfusion of blood products was required in eight (67%) patients. The average length of stay was 15 days (7-50 days). Follow-up was complete. Late mortality occurred in four patients at a mean of 7 months (1-18 months). All deaths were non-cardiac related (ruptured AAA, kidney failure, respiratory failure and sepsis). Six patients remain alive at a mean of 25 months (1-48 months). CONCLUSION: Hospital mortality and morbidity in patients with chronic lymphocytic leukemia undergoing open heart surgery are high. Infection is the leading cause of hospital death, as well as the most common complication. The majority of patients receive blood products during the course of their hospitalization. Late mortality is high and non-cardiac related. Based on these findings, a re-definition of the aims, goals and expectations of open heart surgery in patients with chronic leukemia is necessary. Suggestions in management are presented.     

Regulatory focus as a mediator of the influence of initiating structure and servant leadership on employee behavior.

In this research, the authors test a model in which the regulatory focus of employees at work mediates the influence of leadership on employee behavior. In a nationally representative sample of 250 workers who responded over 2 time periods, prevention focus mediated the relationship of initiating structure to in-role performance and deviant behavior, whereas promotion focus mediated the relationship of servant leadership to helping and creative behavior. The results indicate that even though initiating structure and servant leadership share some variance in explaining other variables, each leadership style incrementally predicts disparate outcomes after controlling for the other style and dispositional tendencies. A new regulatory focus scale, the Work Regulatory Focus (WRF) Scale, also was developed and initially validated for this study. Implications for the results and the WRF Scale are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroanatomical localization of the motor hand area with magnetic resonance imaging: The left hemisphere is larger in great apes.

Magnetic resonance images of the brain were obtained from 2 gorillas (Gorilla gorilla gorilla), 4 orangutans (Pongo pygmaeus), 14 chimpanzees (Pan troglodytes), and 4 bonobos (Pan paniscus), The region on the motor cortex of humans identified as responsible for motor skill of the hand (the "knob") was identified in this sample on consecutive 1-mm axial scans. The shape of the knob area was traced on each scan from both hemispheres, and the area from all scans was summed to calculate the knob volume. The width of the knob was also measured and correlated highly with knob volume. A significant population-level leftward asymmetry in the volume and width of the knob was revealed (p?     

Detection of Optically Excited States in Wide-Band-Gap Semiconductors with Tunneling Spectroscopy

Tunneling spectroscopy has been used to detect the photoexcitation of charge carriers in the wide-band-gap semiconductors, ZnO and cubic SiC. Photoexcitation, which increases the charge carrier population and thus reduces the width of the depletion layer at the semiconductor surface, is detected as an enhancement in the tunnel current. Because the process is energy sensitive, valence-to-conduction band or defect charge transfer transitions may be selectively excited and detected by tunneling spectroscopy. Two types of transitions were detected which change the tunneling response; for cubic SiC valence-to-conduction band transitions were excited, while for Co²⁺ - and Mn²⁺ -doped ZnO electron charge transfer transitions from the dopants to the conduction bands occur. The enhancement of the current was greater in air than under vacuum and more easily detected at small sample-tip separations.     

Analysis of attribution data: Theory testing and effects estimation.

Statistical models are presented for the analysis of attribution data (H. H. Kelley, 1967, 1973; L. A. McArthur, 1972) that are more appropriate than previously used methods and that enable researchers to address a broader range of theoretical issues. These new models allow researchers to determine the separate and joint influence of consensus, distinctiveness, and consistency information on attributions to the person, stimulus, and circumstance. The techniques are illustrated on several data sets (M. Hewstone and J. M. Jaspars [see PA, Vol 75:4348]; D. J. Hilton and J. M. Jaspars [see PA, Vol 75:35411]; J. M. Jaspars [1983]; and L. A. McArthur [1972]), and an appendix is included describing how researchers can fit these models using a computing package such as SPSS-X (M. J. Norusis, 1985). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Local Phenomena in Oxides by Advanced Scanning Probe Microscopy

In the last two decades, scanning probe microscopies (SPMs) have become the primary tool for addressing structure and electronic, mechanical, optical, and transport phenomena on the nanometer and atomic scales. Here, we summarize basic principles of SPM as applied for oxide materials characterization and present recent advances in high-resolution imaging and local property measurements. The use of advanced SPM techniques for solutions of material related problems is illustrated on the examples of grain boundary transport in polycrystalline oxides and ferroelectric domain imaging and manipulation. Future prospects for SPM applications in materials science are discussed.