一类不可逆奥托循环性能的优化分析

应用有限时间热力学方法,导出一类不可逆奥托循环的输出功和效率与不可逆绝热因子、压缩比、高低温比之间的关系,分析绝热过程的不可逆性对奥托循环性能参数的影响.所得结果可为实际热机的优化设计和性能改善提供一些新的理论依据.     

Decomposition and nutrient release pattern of agro-processing by-products biodegraded by fly larvae in Acrisols

ABSTRACT

Fly larvae are increasingly being promoted as animal feed and their production on agro-processing by-products generates a high amount of residues. Understanding the decomposition and nutrients release pattern in the soil of these residues is of importance to evaluate their quality as soil amendment. A litter bag experiment was carried out over 75 days in southern Benin with corn bran, a mixture of soybean bran and corn bran and a mixture of soybean bran and corn hull, all biodegraded in advance by larvae of Musca domestica and Hermetia illucens. Bags with 200 g dry matter of each residue were buried in the soil. The first order equation of mono-component model Y_t = Y₀×e^?kt was suitable and described well the decomposition and mineralization pattern of the residues. The residues decomposed quickly and released nutrients readily into the soil. The mass remaining at the end of the decomposition process ranged between 38% and 42% of the initial weight. The half-life of the organic carbon in the residues ranged between 50 and 58 days. Organic nitrogen mineralized fast, with rates ranging between 0.007 and 0.011 day^?1. These organic residues can be used as soil amendments to improve crop productivity in an Acrisol.     

PCB partitioning during sediment remobilization—a 1D column experiment

Purpose

Remobilization of polychlorobiphenyl (PCB)-contaminated sediments by anthropogenic activities (e.g. dredging) or natural flow conditions could lead to the release of PCBs into the water column and consequently increase the availability of PCBs to benthic organisms. The fate of the released PCBs following such events is not well understood and such knowledge is necessary for the management of contaminated sediments. The objective of this study was to understand the processes that control the fate of PCBs following remobilization of field-aged contaminated sediments.

Materials and methods

Sediments contaminated with PCBs collected from Lake Bourget (Savoie, France) were resuspended in a column experiment. The relationships between physical–chemical parameters—i.e. suspended particulate matter, pH, inorganic and organic carbon content, redox-sensitive species and the concentrations of dissolved PCBs both in the water column and in the interstitial water of the sediment—were investigated so as to determine the key processes controlling PCB fate.

Results and discussion

Following the simulated resuspension event (SRE), dissolved PCBs were found in much higher concentrations in the water column than under stationary conditions. Desorption of PCBs from the sediment depended on the degree of the hydrophobicity of the PCBs and the initial PCB content in the sediment. Principal component analysis showed that the variations in the concentrations of released PCBs over time and space closely followed those of suspended particulate matter (SPM) and not those of redox conditions. The partitioning behaviour of PCBs on SPM showed that equilibrium state was not attained within 40 days following the SRE. A particle size fractionation study, before and after remobilization of the sediment, showed the presence of PCBs in every fraction of the sediment, but with higher amounts in large particles with high organic matter content and in the finest fractions. Remobilization of contaminated sediment did not affect this distribution profoundly but a significant enrichment in PCBs of the clay-sized fraction was observed in the re-settled sediment.

Conclusions

Sediment resuspension induced non-equilibrium conditions in the water column for more than 5 weeks and led to the enrichment with PCBs of the newly formed surface bed sediment. This enrichment was due to the preferential re-sorption of PCBs on clay-sized particles during the SRE and to the physical segregation and accumulation of the less dense particles at the surface of the sediment column; such particles thought to be the principal carriers of contaminants. These changes concerned <0.05 % of the total PCB content.     

How does summer environmental degradation influence native mussels in Corbicula invaded rivers?

1. Droughts and heat waves are becoming more frequent, persistent, and intense in a global warming context. Although previous studies reported Corbicula mass mortality events associated with the occurrence of extreme summer conditions, knowledge of their effects lags behind ecosystem functioning.
2. The goal of this study was to determine whether summer environmental degradation (droughts, extreme temperatures, and spikes in ammonium concentration) influences the survival and behaviour of native mussels in rivers invaded by Corbicula and, in consequence, their functioning in ecosystems.
3. Unio delphinus mussels were exposed to increasing summer environmental degradation. Water column and pore water samples were collected at six sampling time-points for nutrient analysis. Environmental conditions, survival and behaviour were monitored at 12-hour intervals.
4. Mortality risk was greatest under no-flow conditions, reaching 100% of mortality after 84 ± 22 hours of exposure to anoxic (<2 mg O₂ L⁻¹) conditions. At the sub-lethal level, quiescent conditions impaired filtration activity. In addition, when facing rising temperatures, native mussels buried deeply and vertical movements were depleted.
5. There were significant differences between the water column and the pore water in physicochemical characteristics. Oxygen and nitrate concentration were generally higher in the water column. In contrast, ammonium and phosphate maximum concentrations were measured in the pore water.
6. The results suggest that environmental degradation affects the role of mussels in ecosystem functioning. For instance, prolonged valve closure under poor water quality conditions may have impacts on particle removal from the water column. Furthermore, impairment of vertical movements may reduce nutrient release from sediments.
7. The present study has key implications for water management and for the conservation of mussel populations. For instance, a responsible approach for maintaining ecosystem integrity should include the water needs of freshwater mussels in environmental flow recommendations and the conservation of riparian vegetation corridors to mitigate the effects of increased water temperature in rivers.

     

Effect of organic and mineral nitrogen fertilization on yield and nutritive value of butterhead lettuce

A plot trial was conducted in order to compare the influence of mineral or organic nitrogen fertilizers, such as ammonium nitrate, chilean nitrate of soda and cake derived from castor-oil seeds on the yield and the nutritive value of head lettuce. Fertilizations were applied on a N-equivalent basis, i.e. 120 and 200kg/ha. Equivalent yields were obtained regardless of the kind of fertilizer or the nitrogen supply. Dry matter, mineral and protein contents were not drastically influenced, while the nitrate contents of organically grown lettuces were significantly lower. Results are discussed referring to the influence of agricultural practices on the quality of vegetable foods for humans, especially concerning nitrates.     

Transport versus on-farm slaughter of bison: Physiological stress,animal welfare,and avoidable trim losses

Ranched bison are typically less acclimated to handling than are domesticated livestock, suggesting that they might be more vulnerable to handling and transportation stressors. Grain-finished bison were slaughtered on-farm (n = 11), or held for 48 h, transported to a research abattoir, held in lairage for 18 h, and then slaughtered (n = 11). An additional group (n = 10) was sampled at a conventional fixed location abattoir. Measures included serum cortisol and corticosterone concentrations during on-farm handling and exsanguination, serum glucose, creatinine phosphokinase (CPK), aspartate aminotransferase (AST), and trim losses. Transport was associated with an increase in trim loss. On-farm, glucose was elevated, CPK was positively associated with handling order over 12 h, and corticosterone concentration, although lower than cortisol concentration, showed a greater response to prolonged disturbance. With appropriate on-farm handling facilities, the use of on-farm slaughter and mobile abattoir could avoid muscle damage and trim losses, and mitigate injuries sustained during handling and transport of bison.     

Eradication of feline dermatophytosis in a shelter: a field study

Enzootic dermatophytosis in a shelter with approximately 140 cats was treated according to a protocol combining identification, isolation and treatment of subclinical carrier and affected animals in accordance with a three‐area system: healthy animals (no lesions and negative cultures), subclinical carrier animals (no lesions but with positive cultures) and clinically affected animals (lesions and positive cultures). The cats were examined and inspected under a Wood’s lamp and had samples taken for fungal culture every 2 weeks. Thirty‐three per cent of the cats had a positive fungal culture at the start of the study. Clinically affected animals and carriers were treated with a 0.2% enilconazole lotion (Imaverol^®) twice a week and given itraconazole (Itrafungol^®) 5 mg/kg SID orally every other week. The environment was treated once a day with a 1% bleach solution and once a week with a 0.6% enilconazole (Clinafarm^®) solution. Treated animals were considered cured after two consecutive negative fungal cultures. All cats were cured within 56 days. Prophylactic measures against dermatophytosis were implemented for new arrivals consisting of individual quarantine and the systematic taking of fungal cultures. No relapses were observed based on the fungal cultures taken from the animals and the environment over the first 10 months.     

The major genetic determinants of HIV-1 control affect HLA class I peptide presentation

Infectious and inflammatory diseases have repeatedly shown strong genetic associations within the major histocompatibility complex (MHC); however, the basis for these associations remains elusive. To define host genetic effects on the outcome of a chronic viral infection, we performed genome-wide association analysis in a multiethnic cohort of HIV-1 controllers and progressors, and we analyzed the effects of individual amino acids within the classical human leukocyte antigen (HLA) proteins. We identified >300 genome-wide significant single-nucleotide polymorphisms (SNPs) within the MHC and none elsewhere. Specific amino acids in the HLA-B peptide binding groove, as well as an independent HLA-C effect, explain the SNP associations and reconcile both protective and risk HLA alleles. These results implicate the nature of the HLA-viral peptide interaction as the major factor modulating durable control of HIV infection.     

生态立区 产业发展 努力实现林业“双增”目标——关于广西林业发展情况的调研报告

近10年来,特别是＂十一五＂时期是广西林业发展又好又快的时期,森林资源和林地等实现稳步增长。广西林业的发展之路,为全国实现胡锦涛总书记提出的林业发展＂双增＂目标积累了许多成功的经验。当然,实现＂双增＂目标还面临一些实际困难。因此,建议采取分解任务,将林业发展＂双增＂目标落实到地方政府;坚持营造林基础地位不动摇;开展分类经营试点示范等对策。