Electrophilic quinodimethanes

Two new electrophilic monomers, 7,8-di(alkoxycarbonyl)-7,8-dicyanoquinodimethanes, were prepared. These quinodimethanes exhibit moderate electron-acceptor abilities and are highly reactive toward spontaneous homopolymerization in solution as well as in the solid state. Quinodimethane homopolymers were also obtained from heterogeneous spontaneous solution polymerization in the presence of styrene, p-methoxystyrene and isobutyl vinyl ether.     

基于网络学堂辅助高等数学教学的应用性研究简

本文针对网络学堂如何辅助高等数学课堂教学进行了研究,介绍了建设高等数学网络学堂的必要性,提出了建设高等数学网络学堂的途径,最后探讨了如何利用网络学堂提高高等数学教学质量。     

The development of a sound viewer for an open hypermedia system

Abstract

While rich support for a wide variety of media such as text, video and image is common among contemporary hypermedia systems, so too is the inadequate support for audio. The primary reason that audio has not attracted as much attention as other media can be attributed to its obvious lack of visual identity. The main focus of this work was to identify a generic and meaningful visual representation of audio within a hypermedia context, and significantly promote hypermedia support for audio through the provision of a sound viewer.

This paper describes the inherent difficulties in providing a consistent interface to audio, and discusses in some depth the issues raised during the development process. The sound viewer is then introduced and the associated concepts described. The creation and traversal of links to and from audio are facilitated by the sound viewer across formats including WAV (proprietary digital sound file format from Microsoft), CD (Compact Disc) Audio and MIDI (Musical Instrument Digital Interface). The resultant viewer provides a unified and extensible framework for interacting with audio from within an open hypermedia environment. The open hypermedia system Microcosm was used as the development platform for this work. Microcosm can be augmented to supply a hypermedia link service to additional media with minimal overhead.     

Autobiographical Accounts of Students' Experiences Learning Mathematics: A Review

ABSTRACT

In this article, we review published literature that draws on autobiographical accounts of students' experiences learning mathematics. We summarize the main findings of the target literature and present recommendations for further research that will extend this field. Our review indicates that autobiographical and narrative methodological approaches have the potential to occasion important advances in our knowledge of students' experiences learning mathematics. However, relative to accounts of preservice teacher learning, there is a paucity of published research that documents the mathematics learning experiences of kindergarten to Grade 12 students.     

Comparison of satellite-derived and in-situ observations of ice and snow surface temperatures over Greenland

The most practical way to get spatially broad and continuous measurements of the surface temperature in the data-sparse cryosphere is by satellite remote sensing. The uncertainties in satellite-derived LSTs must be understood to develop internally-consistent decade-scale land surface temperature (LST) records needed for climate studies. In this work we assess satellite-derived “clear-sky” LST products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and LSTs derived from the Enhanced Thematic Mapper Plus (ETM+) over snow and ice on Greenland. When possible, we compare satellite-derived LSTs with in-situ air temperature observations from Greenland Climate Network (GC-Net) automatic weather stations (AWS). We find that MODIS, ASTER and ETM+ provide reliable and consistent LSTs under clear-sky conditions and relatively-flat terrain over snow and ice targets over a range of temperatures from ? 40 to 0 °C. The satellite-derived LSTs agree within a relative RMS uncertainty of ~ 0.5 °C. The good agreement among the LSTs derived from the various satellite instruments is especially notable since different spectral channels and different retrieval algorithms are used to calculate LST from the raw satellite data. The AWS record in-situ data at a “point” while the satellite instruments record data over an area varying in size from: 57 × 57 m (ETM+), 90 × 90 m (ASTER), or to 1 × 1 km (MODIS). Surface topography and other factors contribute to variability of LST within a pixel, thus the AWS measurements may not be representative of the LST of the pixel. Without more information on the local spatial patterns of LST, the AWS LST cannot be considered valid ground truth for the satellite measurements, with RMS uncertainty ~ 2 °C. Despite the relatively large AWS-derived uncertainty, we find LST data are characterized by high accuracy but have uncertain absolute precision.     

Does oral experience terminate ingestion?

Using data from studies of ingestive behavior in developing rat pups we demonstrate how oral experience can contribute to the termination of ingestion. In rat pups, repeated oral stimulation with sweet solutions causes a decline in oral responsiveness. The diminished responsiveness is specific to the flavor of the stimulus experienced orally and can persist for several hours. We suggest that this experience-based decrement in responsiveness is best considered "oral habituation" and that oral habituation largely accounts for the onset of satiety. Post-ingestive feedback signals may have their influence through the oral habituation process or act in the context of oral habituation. Oral habituation is also shown to depend on the pattern of stimulus presentation, a phenomenon that adds considerable complexity to assessing the contributions of oral experience to satiety. The concept of oral habituation may be useful in understanding the immediate control of ingestion and the moment-to-moment expression of ingestive behavior in adult animals.     

Semantic constraints on word learning: proper names and adjectives

4 experiments examined 3- and 4-year-olds' interpretations of novel words applied to familial objects in the sentence frame, "This Y is X," where X is a novel word, and Y is a familiar basic-level count noun (e.g., "dog," "cup"). These novel words are ambiguous and could be interpreted either as proper names (e.g., "Fred") or as adjectives/mass nouns (e.g., "red"/"lead"). The experiments addressed 2 questions. First, do children appreciate that the words can be construed either as proper names referring to individuals or as adjectives/mass nouns referring to salient properties/material kinds? The results showed that children could easily make either interpretation. Second, what factors affect children's tendency to make either a proper name or an adjective/mass noun interpretation? In the experiments, children learned the novel words for a range of animals and artifacts. Most children who learned the words for typical pets (e.g., a bird) made proper name interpretations, as did the majority of those who learned the words for certain non-pet animals (e.g., a caterpillar) described as possessed by someone, but only about half of those who learned the words for such non-pet animals not so described. Very few children who learned the words for either simple (e.g., a shoe) or complex (e.g., a boat) artifacts made proper name interpretations. The results provide clear evidence of the role of semantic information in constraining children's interpretation of a novel word, and they help to refine an understanding of what counts as a nameable individual for preschoolers.     

An investigation of 2'-deoxyribonucleoside cyanoboranes in mice for therapeutic safety

A standard acute toxicity study was undertaken to assess 2'-deoxyribonucleoside cyanoboranes for therapeutic safety. 2'-Deoxyribonucleoside cyanoboranes and related derivatives were nontoxic at doses required for anti-neoplastic and hypolipidemic activities. At higher doses (50 and 100 mg/kg/day IP for 7 days), all treated animals survived with slight reductions in total body weight and small decrements in daily food consumption. No clinical chemistry value was elevated to a magnitude suggesting onset of organ specific toxicity. However, agents appeared to modulate subpopulations of white blood cells, i.e., more lymphocytes than PMNs were present in blood from treated animals as determined by differential cell counts. This modulation is correlated with increases in granulomatous foci in the spleen and mesentery of treated animals after 7 days. The kidney was damaged only by Compound 5 at 50 and 100 mg/kg/day; Compound 5 had the most potent anti-neoplastic activity. The compounds demonstrated no in vitro toxicity against human HCT-8 ileum cells. LD(50) values were greater than 1000 mg/kg, IP, for all compounds.     

Prosthetic valve endocarditis: superiority of surgical valve replacement versus medical therapy only

The objective of our study was to assess the long-term outcome of patients with prosthetic valve endocarditis. We used a multicenter, prospective, observational study design. Six university teaching hospitals with high volume cardiothoracic surgery participated. Seventy-four patients with prosthetic valve endocarditis as defined by explicit, objective criteria were selected for participation. All patients were followed up prospectively for 1 year. Thirty-one percent and 69% had development of endocarditis within 60 days of valve insertion ("early") and after 60 days ("late"), respectively. The most common causes were Staphylococcus epidermidis (40%), Staphylococcus aureus (20%), streptococcal species (18%), and aerobic gram-negative bacilli (11%). Physical signs of endocarditis (new or changing murmur, stigmata, emboli) were seen in 58%. At 6 months and 12 months, mortality was 46% and 47%, respectively. Surgical replacement of the infected valve led to significantly lower mortality (23%) as compared with medical therapy alone (56%), as assessed by both univariate and multivariate analyses (p < 0.05). Improved outcome was seen for the surgical group even when controlling for severity of illness at time of diagnosis. From these findings we conclude that accurate assessment of outcome in prosthetic valve endocarditis requires long-term follow-up of at least 6 months following diagnosis. Surgical therapy warrants greater scrutiny; evaluation in controlled clinical trials is appropriate.