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864.
To understand neural circuits completely, it is necessary to know not only how they work, but also why they work that way. Answers to the latter question have been almost teleological in their assumption of optimal design. However, close examination of certain systems has revealed features that apparently lack adaptive value. Their existence can be understood only if the evolution of these circuits is considered and, in particular, how nonadaptive determinants have guided that evoluton. 相似文献
865.
Robertson JA 《Science (New York, N.Y.)》1978,199(4329):657-664
CANDU power reactors are characterized by the combination of heavy water as moderator and pressure tubes to contain the fuel and coolant. Their excellent neutron economy provides the simplicity and low costs of once-through natural-uranium fueling. Future benefits include the prospect of a near-breeder thorium fuel cycle to provide security of fuel supply without the need to develop a new reactor such as the fast breeder. These and other features make the CANDU system an appropriate technology for countries, like Canada, of intermediate economic and industrial capacity. 相似文献
866.
Rebekka R.E. Artz Stephen J. Chapman A.H. Jean Robertson Jacqueline M. Potts Fatima Laggoun-Défarge Sébastien Gogo Laure Comont Jean-Robert Disnar Andre-Jean Francez 《Soil biology & biochemistry》2008,40(2):515-527
Vegetational changes during the restoration of cutover peatlands leave a legacy in terms of the organic matter quality of the newly formed peat. Current efforts to restore peatlands at a large scale therefore require low cost and high throughput techniques to monitor the evolution of organic matter. In this study, we assessed the merits of using Fourier transform infrared (FTIR) spectra to predict the organic matter composition in peat samples at various stages of peatland regeneration from five European countries. Using predictive partial least squares (PLS) analyses, we were able to reconstruct peat C:N ratio and carbohydrate signatures with reasonable accuracy, but not the micromorphological composition of vegetation remains. Despite utilising different size fractions, both carbohydrate (<200 μm fraction) and FTIR (bulk soil) analyses report on the composition of plant cell wall constituents in the peat and therefore essentially reveal the composition of the parent vegetational material. The accuracy of the FTIR-based PLS models for C:N ratios and carbohydrate signatures was adequate to allow for their use as initial screening tools in the evaluation of the present and future organic matter composition of peat during monitoring of restoration efforts. 相似文献
867.
Kirk A. Muñoz Sheilah A. Robertson Deborah V. Wilson 《Veterinary anaesthesia and analgesia》2017,44(4):766-774
Objective
To determine the intubation dose and select physiologic effects of alfaxalone alone or in combination with midazolam or ketamine in dogs.Study design
Prospective, clinical study.Animals
Fifty-three healthy client-owned dogs [mean ± standard deviation (SD)] 5.1 ± 1.8 years, 27 ± 15.4 kg, scheduled for elective orthopedic surgery.Methods
After premedication with acepromazine (0.02 mg kg–1) and hydromorphone (0.1 mg kg–1) intramuscularly, alfaxalone (0.25 mg kg–1) was administered intravenously over 15 seconds followed immediately by 0.9% saline (AS), midazolam (0.3 mg kg–1; AM), ketamine (1 mg kg–1; AK1), or ketamine (2 mg kg–1; AK2). Additional alfaxalone (0.25 mg kg–1 increments) was administered as required to permit endotracheal intubation. The incidence of apnea and the time from intubation until spontaneous movement were recorded. Heart rate (HR) and blood pressure were recorded 15 minutes after premedication, after intubation and 2, 5, 10 and 15 minutes thereafter. Blood was collected for measurement of serum glucose and insulin concentrations before induction, after intubation and at 2, 5, 10 and 50 minutes. Data were analyzed by split-plot anova with Bonferroni adjustment for the number of group comparisons.Results
Mean ± SD alfaxalone mg kg–1 doses required for endotracheal intubation were AS (1.0 ± 0.4), AM (0.4 ± 0.2), AK1 (0.5 ± 0.3) and AK2 (0.5 ± 0.4) (p = 0.0005). Differences in cardiopulmonary variables among groups were minor; HR decreased in AS, while in other groups, HR increased transiently postintubation. Incidence of apnea in AS was 54% with no significant difference among groups. Midazolam significantly prolonged time from intubation until spontaneous movement (p < 0.002).Conclusions and clinical relevance
Midazolam and ketamine reduced the alfaxalone dose required for endotracheal intubation. Serum glucose and insulin concentrations were not influenced by administration of alfaxalone alone or when administered with midazolam or ketamine. 相似文献868.
Irfan Nunkoo Mark J Weston Cecile C Reed Carl D van der Lingen Sven Kerwath 《African Zoology》2017,52(4):237-241
Parasites are an important but neglected component of ecosystems that can be used as indicators of host biology and ecology. In the present study, the metazoan parasite assemblage of Ruvettus pretiosus, an understudied but widely distributed predatory gempylid, caught off South Africa was surveyed. A total of seven parasite taxa, including four new infection records (Bolbosoma capitatum, Rhadinorhynchus sp., Hepatoxylon trichiuri and Anisakis sp.), two new locality records (B. capitatum and Rhipidocotyle sp.) as well as the ectoparasitic copepod Sagum foliaceus and the cestode Tentacularia coryphaenae were recovered from the eight specimens examined. 相似文献
869.
The mechanical development of wheat flour and water creates micro and macro structures in dough or batter that critically influence the ability to separate starch from protein by fluid displacement. This study sought to identify specific structural and rheological features and to relate these to separation as indexed by the separation factor. Structural features, especially protein and starch distributions, were examined using visible light microscopy applied to dough samples that had been exposed to a protein dye. Flour and water samples were developed in a Brabender microfarinograph at conditions (water content and time of development) generally suitable for use of the USDA Western Regional Research Center, cold‐ethanol fluid‐displacement method. No truly homogenous structures were observed. However, distinct segregation of protein and starch were apparent at all conditions. Structural features correlated qualitatively with the success of separation indexed by the overall separation factor (αp/s) for the separation process. Highly segregated states characterized by large protein bands, clustered starch, and large open spaces were obtained with intermediate development (25 ± 5 min) and were most readily separated (αp/s = 118 ± 7). Segregated states with relatively thin protein bands (≤10 μm dia) in complex networks entrapping starch were obtained after additional development (≥45 min) and were less completely separable (αp/s = 32 ± 2). Segregated states with irregularly organized protein in the form of clumps and bands were obtained with minimal development and were partially separable (αp/s = 65 ± 4). Consistency indicated on the microfarinograph increases monotonically throughout and beyond the period of maximum separability. However, elasticity changes and a high rate of increase in consistency evident in the microfarinogram may reflect changes in the structure that also reduce separability. The study demonstrated the use of the ethanol method to isolate development from displacement phenomena forindependent study. 相似文献