Energy and exergy efficiencies of different configurations of the ejector-based CO2 refrigeration systems

Carbon dioxide (CO2) is an appropriate replacement for conventional refrigerants due to its low global warming effects. However, its application within a traditional refrigeration compression cycle leads to low thermodynamic performance due to the large expansion losses in a throttling process. The application of ejectors allows reducing these losses. Many scenarios of ejector-based cycles have been proposed. Among them four different configurations may be distinguished: an expansion work recovery cycle (EERC), a liquid recirculation cycle (LRC), an increasing compressor discharge pressure cycle (CDPC) and a vapor jet refrigeration cycle (VJRC). This study deals with the comparative analysis of these cycles. In order to study the performance of the cycles, the numerical simulations are developed using EES software. Two performance criteria, energy efficiency (COP) and exergy efficiency are evaluated for each cycle. The highest values of these criteria point to the most thermodynamically efficient cycle. The results show that the EERC has the highest COP and exergy efficiency compared to other cycles. For example, the COP of the EERC is 3.618 and the exergy efficiency is 9.68%. The COP (resp. exergy efficiency) is approximately 23.3% (resp. 23.3%), 24.9% (resp. 25.5%) and 5.6 times (resp. 56.2%) higher than the corresponding energy and exergy efficiencies of LRC, CDPC and VJRC. Moreover, in comparison with a basic throttling valve cycle, the COP and exergy efficiency in EERC are higher up to 23% and 24% correspondingly. The detailed exergy analysis of EERC cycle has pinpointed the equipment where the major exergy losses take place. The largest losses occur in the evaporator (about 33% of the total exergy destruction of the cycle) followed by the compressor (25.5%) and the ejector (24.4%).This project is a part of the Collaborative Research and Development (CRD) Grants Program at ‘Université de Sherbrooke’. The authors acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, Hydro-Québec, Rio Tinto, Alcan and Canmet ENERGY Research Center of Natural Resources Canada

Folkbotanical classification: morphological, ecological and utilitarian characterization of plants in the Napf region, Switzerland

Background: Discussions surrounding ethnobiological classification have been broad and diverse. One of the recurring questions is whether classification is mainly based on the “inherent structure of biological reality” or on cultural, especially utilitarian needs. So far, studies about ethnobotanical classification have mainly been done in indigenous societies. Comparable data from industrialized countries are scarce. In this paper, folkbotanical classification data from the Napf region in central Switzerland is analysed and cross-culturally compared. Methods: Structured and semi-structured interviews were conducted with 60 adults and children chosen by random sampling. Descriptive statistics, t-tests and cultural domain analysis were used to analyze the data. Results: Close to 500 folk taxa have been documented during field work. As life-form taxa appeared tree, bush, grass, herb, flower, and mushroom. Intermediate taxa mentioned regularly were sub-categories of the life form tree and bush, i.e. conifer, deciduous tree, fruit tree, stone fruits, pomaceous fruits, and berry bush. The rank of the folk generic was by far the largest with 316 taxa (85.4% monotypical). The specific rank contained 145 taxa, the varietal 14 taxa. The 475 generic, specific and varietal folk taxa could be assigned to 298 wild growing plant species, which make up 28.13% of the local flora, and to 213 cultivated plant species, subspecies and cultivars. Morphology, mainly life-form, fruits, leaves, and flowers, was the most important criterion for classifying plants. Other important criteria were their use (mainly edibility) and habitat (mainly meadow, forest and garden). The three criteria emerged spontaneously out of open questioning. Conclusion: The classification system of the Napf region is comparable to classification systems of indigenous societies, both in its shallow hierarchical structure and in the amount of recognized taxa. The classification of plants was mainly guided by morphology, habitat and use. The three aspects seem to be mutually linked for certain plant groups, which results in always the same groups, independent from the different sorting criteria. Sensory perception allows for a broader explanation of the known coincidence of morphology and use groups.(VLID)90705

A Fragmented China

This paper studies the degree of integration of China's domestic market and investigates the determinants of inter-provincial trade barriers under the rubric endogenous trade policy theory. I rely on industry-level trade flows extracted from provincial input-output tables to develop a model that analyzes the magnitude and evolution of Chinese provinces' engagement in domestic trade by computing all-inclusive indicators of trade barriers. Results underline that over the 1990s, not only was China's domestic market fragmentation along provincial borders great, but it also has become more severe at least between 1992 and 1997. The investigation of province-level and industry-level trade barriers confirms the relevance of applying the framework of endogenous protection to explain the level of impediments to trade between Chinese provinces. Findings emphasize that provinces' domestic trade protection pursues a dual objective of socioeconomic stability preservation and fiscal revenues maximization

A comparison of in situ and in vitro methods to estimate in vivo fermentable organic matter of forages in ruminants

Farmers in five districts of north-eastern Uganda were interviewed to generate information on sweet potato production and constraints, with emphasis on damage by millipedes. Participatory rural appraisal methodology was used to interview 148 farmers. The peak period of planting sweet potato was from the end of May till the beginning of July in order to produce dried form food (amukeke) for storage in the dry season, which sets in around November. Vine cuttings were usually planted on mounds and weeding was mostly done only once. Osukut, Araka Red and Araka White were the most popular varieties. Many respondents obtained planting material from volunteer plants. Separation of plots over time and in space was often not practised. Sweet potato crop rotations were diverse. Millet, groundnut and maize were commonly grown after sweet potato. Cassava, sweet potato, groundnut and maize are host crops for millipedes and were often grown in succession. Millipede incidences were not statistically different for the three agro-ecological zones of north-eastern Uganda, but depended on the frequency of millipede hosts (including sweet potato) in the crop rotations. Groundnut planted after sweet potato had high levels of millipede attack. Millipede incidence was often associated with the incidence of weevils. The results of this inventory show that most farmers consider millipedes as a pest of sweet potato and other major food and cash crops, but that many farmers lack the knowledge to control them

Thermal Performance of the LHC Connection Cryostat

The 16 connection cryostats for the Large Hadron Collider (LHC) being built at CERN are designed to fill the gap existing between the dispersion suppressor zones and the standard arcs of the accelerator. The first connection cryostat was cold tested down to superfluid helium temperature in August 2005, and the measured thermal performance was as expected. This paper presents the test results and a new thermal modeling of the connection cryostat based on the measurement of the thermal resistances of the braids used for thermalisation, allowing the precise determination of cool down times and equilibrium temperatures of the shielding under various conditions such as lead heating

CcpA represses the expression of the divergent cit operons of Enterococcus faecalis through multiple cre sites

<p>Abstract</p> <p>Background</p> <p>In <it>Enterococcus faecalis </it>the genes encoding the enzymes involved in citrate metabolism are organized in two divergent operons, <it>citHO </it>and <it>oadHDB-citCDEFX-oadA-citMG </it>(<it>citCL </it>locus). Expression of both operons is specifically activated by adding citrate to the medium. This activation is mediated by binding of the GntR-like transcriptional regulator (CitO) to the <it>cis</it>-acting sequences located in the <it>cit </it>intergenic region. Early studies indicated that citrate and glucose could not be co-metabolized suggesting some form of catabolite repression, however the molecular mechanism remained unknown.</p> <p>Results</p> <p>In this study, we observed that the <it>citHO </it>promoter is repressed in the presence of sugars transported by the Phosphoenolpyruvate:carbohydrate Phosphotranserase System (PTS sugars). This result strongly suggested that Carbon Catabolic Repression (CCR) impedes the expression of the activator CitO and the subsequent induction of the <it>cit </it>pathway. In fact, we demonstrate that CCR is acting on both promoters. It is partially relieved in a <it>ccpA</it>-deficient <it>E. faecalis </it>strain indicating that a CcpA-independent mechanism is also involved in regulation of the two operons. Furthermore, sequence analysis of the <it>citH</it>/<it>oadH </it>intergenic region revealed the presence of three putative catabolite responsive elements (<it>cre</it>). We found that they are all active and able to bind the CcpA/P-Ser-HPr complex, which downregulates the expression of the <it>cit </it>operons. Systematic mutation of the CcpA/P-Ser-HPr binding sites revealed that <it>cre1 </it>and <it>cre2 </it>contribute to <it>citHO </it>repression, while <it>cre3 </it>is involved in CCR of <it>citCL</it></p> <p>Conclusion</p> <p>In conclusion, our study establishes that expression of the <it>cit </it>operons in <it>E. faecalis </it>is controlled by CCR via CcpA-dependent and -independent mechanisms.</p

Factors Influencing the Filing of Complaints, Their Investigation, and Subsequent Legal Judgment in Cases of Sexual Assault.

In Geneva, examination of victims of sexual assault is performed by a gynecologist and a medical examiner. 48% of the victims file a complaint and we wanted to investigate the factors leading to file a complaint, those leading the Prosecutor to go to trial, and those influencing a conviction. Between 2006 and 2012, 676 victims of sexual assault were investigated (averaged age 26 year, mean 22). Information on injuries, perpetrators, and circumstances of the assault was collected and analyzed. The attacker being the ex-spouse or a friend and the presence of semen were factors leading to file a complaint. The assailant being a family member or ex-spouse and the presence of genital/anal lesions were factors influencing the Prosecutor. The presence of nongenital lesions, the assailant being known by the victim, influenced conviction. This study shows that the medical examiner plays a vital role in the investigation of cases of sexual assault