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)     

Signal Transduction of Barnacle Egg-Hatching Pheromone: Pharmacological Assays Indicate a Comparatively Simple Mechanism of Eicosanoid Action

Eicosanoids are generally regarded as autocoids that act via G-protein-linked receptors. There are exceptions to this model, however, both in terms of function and mechanism of action. The present paper concerns one such example, an hydroxy fatty acid that acts as a pheromone, not an autocoid, in inducing barnacle egg hatching. Preliminary findings of pharmacological assays on the mechanism of action of this eicosanoid pheromone do not support the involvement of G proteins, Ca²⁺, or protein kinase C in signal transduction. Instead it is concluded, tentatively, that barnacle egg hatching pheromone acts via a comparatively simple pathway involving the second messenger, cyclic AMP.     

Signals and Noise in Evoked Brain Potentials

Event-related brain potentials measured with scalp electrodes are always corrupted by unrelated electrical discharges occurring in the brain. These unrelated electrical discharges, generally referred to as noise, have temporal and spectral characteristics similar to evoked potential waveforms, and they greatly increase the difficulty of detecting and estimating the parameters of the evoked potential waveforms themselves. This problem has been analyzed by computing the probability distributions for measured amplitudes and latencies of ERP components measured in the presence of the ongoing EEG. The analytical results have been verified over a wide range of signal-to-noise ratios by computer simulation. Comparisons of theoretical results to measured data indicate that the latency variations found experimentally greatly exceed what would be expected if they were due only to additive noise. It may be concluded, therefore, that the single ERP is not a signal whose components are deterministically related to the stimulus, but is made up of components that shift significantly in both amplitude and latency from one stimulus application to the next. Using the expressions developed in the paper, it is possible to separate the contributions to the variance due to interference from the ongoing EEG and that inherent in the ERP.     

TERRA COTTA KILN SLAB INVESTIGATION1

Following several discussions as to the constitution of a good kiln slab for terra cotta manufacture, a coöperative test was made in which slabs of various compositions were manufactured by a producer of refractories, tested under actual service conditions, and physical measurements were determined by the Ceramic Department, Rutgers University. Series included the use of tight-firing medium refractory clays, open-firing refractory clays with grog, both vitreous and porous. Grogs were sized (definite proportions of size ranges constituting the different members). Conclusions were drawn as to effect of all these variables.     

创意自然

<正>当今,人类与自然不和谐、不符合自然规律的关系普遍存在。从农业砍伐森林、筑坝发电,到工业污染物充斥的空气,这些互动往往意味着破坏。即使破坏性的干预措施被更富有创意的措施取代,这种不和谐仍然存在。     

A Theoretical Analysis of the Harmonic Content of PWM Waveforms for Multiple-Frequency Modulators

This paper theoretically identifies the harmonic components of a carrier-based pulsewidth-modulated (PWM) voltage-source converter (VSC) output voltage when the modulating wave includes fundamental and baseband harmonic components. This occurs, for example, when a VSC is used as an active power filter. The general analytical solution provided can be applied with a minimum additional mathematical effort to any harmonic combination in the modulation signal. The analysis undertaken in this paper determines how the fundamental and low-order harmonics (in the modulation signal) interact with the carrier to produce the low (and high) order frequencies in the PWM VSC output voltage. The analysis is based on a double Fourier series expansion in two variables. This approach to harmonic identification is evaluated by a comparison with a fast Fourier transform analysis of simulated PWM waveforms.      

《新奥尔良电车》

<正>相机介绍现今八十多岁的弗兰克也记不得这张照片当年用的是哪款莱卡相机拍摄的了,不过,他对莱卡ⅢC却一直情有独钟。20世纪20至50年代,德国一直雄踞世界照相机王国的宝座。莱卡相机也是当时世界各国竞相仿制生产的名牌相机,在世界上享有极高的声誉。在二十世纪五十年代到六十年代期间,莱卡相机已经相继研制出了2型、3型相机。与此同时开始转换研制G系列的1G、2G、3G相机。到目前为止,莱卡M系列仍在出新产品。在第二次世界大战中,莱卡相机成了当时随军记者的重要工具。照片背后《美国人》在法国首次出版于1958年,然后是1959年在美国。弗兰克的惊世名著《美国人》刚出版时,此书遭到了他人的质疑。直到十多年后,这本书才引起了人们的关注,不仅是在美国,全世界的摄影家都在从中汲取养分,从而开     

Concentration and distribution of heavy metals in urban airborne particulate matter in Frankfurt am Main, Germany

Heavy metal concentrations were measured in airborne dust collected at three sites with different traffic densities from August 2001 to July 2002 in the Frankfurt am Main area. Bulk samples of particulate matter (PM) with an aerodynamic equivalent diameter of <22 microm were collected on cellulose nitrate filters using air filtration devices. Fractionated samples of PM with an aerodynamic equivalent diameter of <10 microm were collected using an eight-stage Andersen impactor. Pb, Cd, Mn, Ni, Zn, V, As, Sb, Cu, Cr, Co, and Ce were determined by inductively coupled plasma sector field mass spectrometry, Pt and Rh were determined by adsorptive voltammetry, and Pd was determined by total reflection X-ray fluorescence analysis. The results show that the highest airborne heavy metal concentrations occurred at the main street with a large volume of traffic. With the exception of Co, V, Ce, and Mn, the heavy metals had an elevated enrichment factor compared to their concentrations in the continental crust. The main street site was especially contaminated with Sb, Zn, Cu, V, and Ni. Motor vehicles are the likely source of emissions. With the exception of Cr, Cu, and Zn, most of the airborne heavy metal concentrations determined for impactor samples deviate slightly from the results for total airborne dust. Heavy metal particle size distributions can be divided into three groups. For metals such as As, Cd, Pb, and V, the main fraction can be found in fine particles with a diameter of <2.1 microm, whereas Ce, Cr, Co, and Ni occur mainly in coarse particles with a diameter of >2.1 microm. Cu, Mn, Sb, Zn, Pt, Pd, and Rh occur in high concentrations in the medium range of the impactor stages (particle diameters of 1.1-4.7 microm). Metal concentrations in fine dust particles are needed to assess the human health risks of their inhalation.