Modeling rural landowners' hunter access policies in East Texas,USA

Private landowners in East Texas, USA, were aggregated into one of four policy categories according to the degree of access allowed to their lands for hunting. Based on these categories, a logistic regression model of possible determinants of access policy was developed and probabilities of policy adoption were calculated. Overwhelmingly, attitudes toward hunting as a sport, incentives, and control over the actions of hunters were most predictive of landowners' policies. Additionally, the availability of deer was found to be negatively correlated with access, thereby suggesting management efforts to increase deer populations may be counter to increasing access. Further, probabilities derived from the model indicated that there was almost a 7 in 10 chance (0.66) that landowners would adopt policies commensurate with allowing family and personal acquaintances to hunt on their property. However, the probability of increasing access beyond this level, where access was provided for the general public, dropped off drastically to less than 5% (0.04).     

Wilderness politics: Public participation and values

This article deals with wilderness politics in relationship to values and public participation; these terms are defined for the purpose of the study. It is argued that the survival, quantity, and quality of wilderness everywhere will basically be determined by the political and governmental processes through values. Yet there is a strong tendency in these processes to avoid value exposure and emphasis.Much of governmental approach toward wilderness affairs hinges upon economic development, technoscientific facts, and short-term considerations, in contrast to the intangible noneconomic and long-term values of wilderness. By not articulating nd involving wilderness values more in public participation and the political processes, the public often misses opportunities for influencing far-reaching wilderness decisions. In short, wilderness values need to be more explicitly and implicitly stated and implemented politically.More study and emphasis need to be given to wilderness values per se. It is necessary to develop more innovative ways of educating the public on wilderness values in terms of their lives and of ensuring that their value inputs are effectively incorporated into public participation and political processes. The last section of this article is devoted to efforts by the author and others to identify and describe wilderness tropical forest values.     

Urban visual air quality judgments: Reliability and validity

A procedure based on judgments of human observers for measuring visual air quality in urban areas is described, and its reliability and validity are examined using the results of several studies conducted in a metropolitan area. It is concluded that the procedure provides a measure that is sufficiently reliable and valid to warrant its use in studies of the causes and consequences of changes in visual air quality. Substantial agreement was found among individuals with regard to judgments of visual air quality, but the possibility of differences between experienced and inexperienced observers requires further investigation. The paper provides an example of methods that can be used, and issues that should be addressed, in the development of perceived environmental quality indices.     

Influence of CO<Subscript>2</Subscript> on the micro-structural properties of spider dragline silk: X-ray microdiffraction results

The mechanical properties of spider dragline fibres are altered by CO₂ exposure under anaesthetizing conditions during the spinning process. In order to relate these macroscopic changes to a microscopic model, the extrusion of dragline silk was studied by synchrotron radiation microdiffraction. A brief exposure of a female Nephila senigalensis spider to CO₂ results after an incubation time of less than 7 min in the extrusion of a thread (two fibres) swollen with water. The data are interpreted for a model of crystalline -sheet domains containing nanofibrils, which reinforce a network of protein chains. The protein network absorbs water, leaving the nanofibrils unaffected. A continuous flow of CO₂ results in a co-extrusion of a dragline thread and an isotropic silk fraction, which probably has a glycine-rich sequence. Long CO₂ exposure reduces the axial alignment of nanofibrils, presumably due to a partial destruction of the amorphous network.     

First-trimester prenatal diagnosis of osteogenesis imperfecta type II by DNA analysis and sonography

Osteogenesis imperfecta type II was diagnosed prenatally by analysis of DNA obtained from chorionic villus sampling (CVS) performed at 12 weeks of gestation in a woman who previously had had an affected child. The father had been shown to be mosaic for a mutation in the gene (COL1A2) which encodes the α2(I) chain of type I collagen. An affected fetus was predicted by detection of the mutation in amplified chorionic villus genomic DNA. Ultrasound examination at 13 weeks 4 days demonstrated femoral deformity and virtual absence of calvarial mineralization. In pregnancies at risk for osteogenesis imperfecta type II, sonographic evidence of skeletal abnormalities may be evident by 13 weeks' gestation.     

Prenatal diagnosis of lissencephaly

We report two cases of prenatal detection of lissencephaly by high-resolution ultrasound. The first case studied was referred for high-risk obstetrical management and serial antenatal ultrasounds because of a family history of lissencephaly in an unresolved chromosomal abnormality. Diagnosis of a smooth gyral pattern consistent with lissencephaly was made at 32 weeks' gestation. The second case was referred for prenatal ultrasound because of a size versus dates discrepancy. The ultrasound examination showed a smooth gyral pattern at 31.5 weeks. In light of this ultrasound finding, a fetal blood sample was obtained and a chromosomal abnormality reported, confirming the diagnosis. To our knowledge, these cases represent the first report of the sonographic prenatal diagnosis of cerebral agyria or lissencephaly.     

废弃电子设备的资源化研究发展现状

分析了废弃电子设备的主要特点、资源化回收与利用的不同方法及其优缺点，并详细介绍了废弃电子设备机械处理的研究及工业应用现状。     

Alternative reproductive tactics in the spider Meta segmentata

Summary In the spider Meta segmentata web site quality and competitive ability determine female distributions, and ultimately male mating strategy. Large, fecund females position their webs in aggregations in high quality habitats, whereas small females live alone in lower quality sites. Competition for web sites is intense. Large females have a fighting advantage, but web ownership can offset size disadvantages of about 10%. Males compete for access to female webs. The smallest males are excluded from aggregations of females but have a very high probability of mating monogamously with females in poor habitats. The largest males move about within aggregations and by mating with many females achieve the highest reproductive gains. Moderately sized males only have a low probability of mating in an aggregation, but for those that do succeed the reproductive gains are higher than for those that mate monogamously in low quality areas. On average, moderately sized males obtain reproductive gains from the high risk, high gain strategy of defending webs in aggregations that are equal to those from definding solitary females in poor areas. That 18 of 21 moderately sized males defend females in aggregations suggests that M. segmentata behaves in a riskprone fashion.     

Unexpected consequences of vertebrate pest control: predictions from a four-species community model.

Although indirect effects are important structuring forces in ecological communities, they are seldom considered in the design of pest control operations. However, such effects may cause unpredicted and deleterious changes in other populations that could reduce or even negate the benefit to endangered species for which control is undertaken. Furthermore, the complexity and nonlinearities inherent in interacting ecological communities may cause thresholds in the strength of pest control, on either side of which indirect effects could vary greatly in their magnitude and desirability. We constructed a four-species simulation model for a common pest community in New Zealand beech (Nothofagus spp.) forests: house mice, ship rats, stoats, and brushtail possums. When the model was perturbed to simulate common control techniques, marked increases in the abundance of nontarget pest species were observed at the next forest mast. Higher mouse numbers were observed following both toxin (1080) application and rat kill-trapping, and higher rat numbers were observed following stoat kill-trapping, due to a release from predation in all cases. In comparison, a marked decrease in stoat abundance at the next forest mast was observed following simultaneous control of rats and mice, due to the effects of decreased prey abundance on the stoat population. For rat control, the size of the indirect effect on mouse numbers increased monotonically with control strength. Because the curvature of the relationship is slight, the relationship between the direct benefits of control and the indirect costs incurred would remain relatively unchanged regardless of the strength of control employed. For simultaneous mouse and rat control, however, high levels of control (as initially simulated) were predicted to cause decreased peak stoat abundance at the next mast event, whereas intermediate and low levels of control were predicted to cause increased stoat abundance. Hence, this study demonstrates two points of concern for pest managers. First, indirect effects of control operations do have the potential to reduce the planned-for benefit. Second, thresholds in the strength of control employed can potentially occur, across which indirect effects switch from being of conservation benefit to being of conservation concern.