934 resultados para system structure
Resumo:
The recombinant heat shock protein (18 kDa-hsp) from Mycobacterium leprae was studied as a T-epitope model for vaccine development. We present a structural analysis of the stability of recombinant 18 kDa-hsp during different processing steps. Circular dichroism and ELISA were used to monitor protein structure after thermal stress, lyophilization and chemical modification. We observed that the 18 kDa-hsp is extremely resistant to a wide range of temperatures (60% of activity is retained at 80ºC for 20 min). N-Acylation increased its ordered structure by 4% and decreased its ß-T1 structure by 2%. ELISA demonstrated that the native conformation of the 18 kDa-hsp was preserved after hydrophobic modification by acylation. The recombinant 18 kDa-hsp resists to a wide range of temperatures and chemical modifications without loss of its main characteristic, which is to be a source of T epitopes. This resistance is probably directly related to its lack of organization at the level of tertiary and secondary structures.
Resumo:
Ionotropic glutamate receptors are major excitatory receptors in the central nervous system and also have a far reaching influence in other areas of the body. Their modular nature has allowed for the isolation of the ligand-binding domain and for subsequent structural studies using a variety of spectroscopic techniques. This review will discuss the role of specific ligand:protein interactions in mediating activation in the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid subtype of glutamate receptors as established by various spectroscopic investigations of the GluR2 and GluR4 subunits of this receptor. Specifically, this review will provide an introduction to the insight gained from X-ray crystallography and nuclear magnetic resonance investigations and then go on to focus on studies utilizing vibrational spectroscopy and fluorescence resonance energy transfer to study the behavior of the isolated ligand-binding domain in solution and discuss the importance of specific ligand:protein interactions in the mechanism of receptor activation.
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To explore whether an environment of weightlessness will cause damage to the reproductive system of animals, we used the tail-suspension model to simulate microgravity, and investigated the effect of microgravity on the tissue structure and function of the testis in sexually mature male rats. Forty-eight male Wistar rats weighing 200-250 g were randomly assigned to three groups (N = 16 each): control, tail traction, and tail suspension. After the rats were suspended for 7 or 14 days, morphological changes of testis were evaluated by histological and electron microscopic methods. The expression of HSP70, bax/bcl-2 and AR (androgen receptor) in testis was measured by immunohistochemistry. Obvious pathological lesions were present in the testis after the rats were suspended for 7 or 14 days. We detected overexpression of HSP70 and an increase of apoptotic cells, which may have contributed to the injury to the testis. The expression of AR, as an effector molecule in the testis, was significantly decreased in the suspended groups compared to control (P < 0.01). We also observed that, with a longer time of suspension, the aforementioned pathological damage became more serious and some pathological injury to the testis was irreversible. The results demonstrated that a short- or medium-term microgravity environment could lead to severe irreversible damage to the structure of rat testis.
Resumo:
In this thesis the basic structure and operational principals of single- and multi-junction solar cells are considered and discussed. Main properties and characteristics of solar cells are briefly described. Modified equipment for measuring the quantum efficiency for multi-junction solar cell is presented. Results of experimental research single- and multi-junction solar cells are described.
Resumo:
Modern food systems face complex global challenges such as climate change, resource scarcities, population growth, concentration and globalization. It is not possible to forecast how all these challenges will affect food systems, but futures research methods provide possibilities to enable better understanding of possible futures and that way increases futures awareness. In this thesis, the two-round online Delphi method was utilized to research experts’ opinions about the present and the future resilience of the Finnish food system up to 2050. The first round questionnaire was constructed based on the resilience indicators developed for agroecosystems. Sub-systems in the study were primary production (main focus), food industry, retail and consumption. Based on the results from the first round, the future images were constructed for primary production and food industry sub-sections. The second round asked experts’ opinion about the future images’ probability and desirability. In addition, panarchy scenarios were constructed by using the adaptive cycle and panarchy frameworks. Furthermore, a new approach to general resilience indicators was developed combining “categories” of the social ecological systems (structure, behaviors and governance) and general resilience parameters (tightness of feedbacks, modularity, diversity, the amount of change a system can withstand, capacity of learning and self- organizing behavior). The results indicate that there are strengths in the Finnish food system for building resilience. According to experts organic farms and larger farms are perceived as socially self-organized, which can promote innovations and new experimentations for adaptation to changing circumstances. In addition, organic farms are currently seen as the most ecologically self-regulated farms. There are also weaknesses in the Finnish food system restricting resilience building. It is important to reach optimal redundancy, in which efficiency and resilience are in balance. In the whole food system, retail sector will probably face the most dramatic changes in the future, especially, when panarchy scenarios and the future images are reflected. The profitability of farms is and will be a critical cornerstone of the overall resilience in primary production. All in all, the food system experts have very positive views concerning the resilience development of the Finnish food system in the future. Sometimes small and local is beautiful, sometimes large and international is more resilient. However, when probabilities and desirability of the future images were questioned, there were significant deviations. It appears that experts do not always believe desirable futures to materialize.
Resumo:
Modern food systems face complex global challenges such as climate change, resource scarcities, population growth, concentration and globalization. It is not possible to forecast how all these challenges will affect food systems, but futures research methods provide possibilities to enable better understanding of possible futures and that way increases futures awareness. In this thesis, the two-round online Delphi method was utilized to research experts’ opinions about the present and the future resilience of the Finnish food system up to 2050. The first round questionnaire was constructed based on the resilience indicators developed for agroecosystems. Sub-systems in the study were primary production (main focus), food industry, retail and consumption. Based on the results from the first round, the future images were constructed for primary production and food industry sub-sections. The second round asked experts’ opinion about the future images’ probability and desirability. In addition, panarchy scenarios were constructed by using the adaptive cycle and panarchy frameworks. Furthermore, a new approach to general resilience indicators was developed combining “categories” of the social ecological systems (structure, behaviors and governance) and general resilience parameters (tightness of feedbacks, modularity, diversity, the amount of change a system can withstand, capacity of learning and self- organizing behavior). The results indicate that there are strengths in the Finnish food system for building resilience. According to experts organic farms and larger farms are perceived as socially self-organized, which can promote innovations and new experimentations for adaptation to changing circumstances. In addition, organic farms are currently seen as the most ecologically self-regulated farms. There are also weaknesses in the Finnish food system restricting resilience building. It is important to reach optimal redundancy, in which efficiency and resilience are in balance. In the whole food system, retail sector will probably face the most dramatic changes in the future, especially, when panarchy scenarios and the future images are reflected. The profitability of farms is and will be a critical cornerstone of the overall resilience in primary production. All in all, the food system experts have very positive views concerning the resilience development of the Finnish food system in the future. Sometimes small and local is beautiful, sometimes large and international is more resilient. However, when probabilities and desirability of the future images were questioned, there were significant deviations. It appears that experts do not always believe desirable futures to materialize.
Resumo:
ABSTRACTThe international financial system has undergone deep changes since the 1970s and its stability cannot be reached in spite of actor's interests or the existence of countless coordination fora. Analyzing the system's incentive structure, one can note that its stability depends on the control of imbalances, which are not always harmful for States, creating, thus, a disturbing component in the quest for international financial management. Furthermore, non-state actors have acquired a disproportional share of power following financial globalization, escaping the control of States and of the international community.
Resumo:
Tutkimus sai innoituksensa, kun tutkija huomasi tarpeen liiketaloudelliselle, ajantasaiselle ja realistiselle tutkimukselle Pohjois-Korean markkinoista, joka kuvailisi markkinoiden olemassaolevia ja puuttuvia rakenteita sekä tutkisi mahdollisuuksia ylittää puuttuvat rakenteet. Institutionaalinen teoria valittiin sopivaksi viitekehykseksi kuvailla ja tutkia markkinarakennetta. Tutkimuskysymys muotoiltiin seuraavasti: “Miten ulkomaiset yritykset voivat reagoida puuttuviin markkinarakenteisiin Pohjois-Koreassa?”. Tutkimuskysymys jaettiin kolmeen osakysymykseen: (1) Millainen on Pohjois-Korean markkinoiden institutionaalinen ympäristö? (2) Mitkä ovat merkittävimmät puuttuvat markkinarakenteet Pohjois-Koreassa? (3) Mitä mahdollisuuksia ulkomaisilla yrityksillä voisi olla reagoida puuttuviin markkinarakenteisiin? Tutkimus toteutettiin kvalitatiivisena, koska tutkimuskysymys on deskriptiivinen. Aineisto kerättiin asiantuntijahaastattelun ja kvalitatiivisen sisällönanalyysin keinoin. Primääriaineiston muodostavat 2 asiantuntijahaastattelua ja sekundääriaineiston muodostavat 95 artikkelia, jotka kerättiin 40 lähteestä. Aineisto analysoitiin kvalitatiivisen sisällönanalyysin keinoin. Aineisto koodattiin, luokiteltiin ja esitettiin kokonaisuuksina luokittelurungon avulla, joka laadittiin tutkimusta varten muodostetun teoreettisen viitekehyksen mukaan. Tulokset ja johtopäätökset voidaan tiivistää seuraavasti. (1) Pohjois-Korean markkinan instituutioihin vaikuttaa kaksoisrakenne, jossa muodollinen, sosialistinen rakenne ja epämuodollinen, markkinalähtöinen rakenne toimivat päällekkäin. (2) Puuttuvia rakenteita on sekä markkinan kontekstissa että markkinatasolla. Puutteet ovat osittain seurausta vanhojen rakenteiden korvaantumisesta uusilla, jotka eivät ole institutionalisoituneet. (3) Yritykset voivat käyttää samoja mahdollisuuuksia reagoida puuttuviin markkinarakenteisiin Pohjois-Koreassa, joita kehittyvien markkinoiden yhteydessä on esitetty. Sen tulkittiin vähentävän käsitystä, jonka mukaan Pohjois-Korean markkina on liian erikoinen yritystoiminnalle. (4) Kasvava keskiluokka sekä yrittäjyyden ja naisten yhä merkittävämpi rooli liike-elämässä aiheuttavat alhaalta ylöspäin suuntautuvaa kehitystä markkinoilla. Nämä ovat merkkejä viimeaikaisesta kehityksestä, jotka eivät ole saaneet laajaa huomiota länsimaisessa mediassa. Se korostaa tarvetta liiketaloudelliselle, ajantasaiselle jatkotutkimukselle Pohjois-Korean markkinoista.
Resumo:
The research was sparked by an exchange in South Korea, as the author identified a gap in research that provides economic, up to date and realistic information about the North Korean market in English language. A need for a research was identified that would describe the market’s existing and missing market structures and explore possibilities to overcome the missing market structures. Institutional theory was chosen as a suitable framework to describe and explore the market. The research question was formulated as follows: “How can foreign companies overcome institutional voids in the North Korean market?”. To answer the research question, it was divided into three sub-questions as follows: (1) What is the institutional environment in North Korea like? (2) What are the major institutional voids in the North Korean market? (3) What possibilities do foreign companies have to overcome institutional voids? The research is qualitative by nature due to the descriptive and exploratory nature of the research question. Data collection consisted of expert interview and content analysis, resulting in primary data of two interviews and secondary data of 95 articles from 40 different sources. The data was analyzed with the systematical technique of content analysis. The data was coded, classified and presented as concepts with the help of a classification system that was build following the theoretical framework adapted for this study. The findings can be summarized as follows. (1) The market institutions are characterized by an overlapping dual system of formal, socialist structures and informal, market-oriented structures. (2) Institutional voids prevail on both the market’s contextual and on the market level. They are partly result of old institutions being replaced by new institutions that lack institutionalization. (3) Identified possibilities to overcome institutional voids correspond with possibilities drawn from previous research. This decreases the image of North Korea as an impossibly unique market to operate in. (4) Emerging middle class, rapidly growing entrepreneurial activities and women’s increasing role in business drive a down-to-up change in the market. This signals the recent development of the market, yet has been overlooked in the Western media. Thus there is a need for further economic, up to date research concerning North Korea.
Resumo:
The successful performance of company in the market relates to the quality management of human capital aiming to improve the company's internal performance and external implementation of the core business strategy. Companies with matrix structure focusing on realization and development of innovation and technologies for the uncertain market need to select thoroughly the approach to HR management system. Human resource management has a significant impact on the organization and use a variety of instruments such as corporate information systems to fulfill their functions and objectives. There are three approaches to strategic control management depending on major impact on the major interference in employee decision-making, development of skills and his integration into the business strategy. The mainstream research has focus only on the framework of strategic planning of HR and general productivity of firm, but not on features of organizational structure and corporate software capabilities for human capital. This study tackles the before mentioned challenges, typical for matrix organization, by using the HR control management tools and corporate information system. The detailed analysis of industry producing and selling electromotor and heating equipment in this master thesis provides the opportunity to improve system for HR control and displays its application in the ERP software. The results emphasize the sustainable role of matrix HR input control for creating of independent project teams for matrix structure who are able to respond to various uncertainties of the market and use their skills for improving performance. Corporate information systems can be integrated into input control system by means of output monitoring to regulate and evaluate the processes of teams, using key performance indicators and reporting systems.
Resumo:
To study emerging diseases, I employed a model pathogen-host system involving infections of insect larvae with the opportunistic fungus Aspergillus flavus, providing insight into three mechanisms ofpathogen evolution namely de novo mutation, genome decay, and virulence factoracquisition In Chapter 2 as a foundational experiment, A. flavus was serially propagated through insects to study the evolution of an opportunistic pathogen during repeated exposure to a single host. While A. flavus displayed de novo phenotypic alterations, namely decreased saprobic capacity, analysis of genotypic variation in Chapter 3 signified a host-imposed bottleneck on the pathogen population, emphasizing the host's role in shaping pathogen population structure. Described in Chapter 4, the serial passage scheme enabled the isolation of an A. flavus cysteine/methionine auxotroph with characteristics reminiscent of an obligate insect pathogen, suggesting that lost biosynthetic capacity may restrict host range based on nutrient availability and provide selection pressure for further evolution. As outlined in Chapter 6, cysteine/methionine auxotrophy had the pleiotrophic effect of increasing virulence factor production, affording the slow-growing auxotroph with a modified pathogenic strategy such that virulence was not reduced. Moreover in Chapter 7, transformation with a virulence factor from a facultative insect pathogen failed to increase virulence, demonstrating the necessity of an appropriate genetic background for virulence factor acquisition to instigate pathogen evolution.
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This case study examines the impact of a computer information system as it was being implemented in one Ontario hospital. The attitudes of a cross section of the hospital staff acted as a barometer to measure their perceptions of the implementation process. With The Mississauga Hospital in the early stages of an extensive computer implementation project, the opportunity existed to identify staff attitudes about the computer system, overall knowledge and compare the findings with the literature. The goal of the study was to develop a greater base about the affective domain in the relationship between people and the computer system. Eight exploratory questions shaped the focus of the investigation. Data were collected from three sources: a survey questionnaire, focused interviews, and internal hospital documents. Both quantitative and qualitative data were analyzed. Instrumentation in the study consisted of a survey distributed at two points in time to randomly selected hospital employees who represented all staff levels.Other sources of data included hospital documents, and twenty-five focused interviews with staff who replied to both surveys. Leavitt's socio-technical system, with its four subsystems: task, structure, technology, and people was used to classify staff responses to the research questions. The study findings revealed that the majority of respondents felt positive about using the computer as part of their jobs. No apparent correlations were found between sex, age, or staff group and feelings about using the computer. Differences in attitudes, and attitude changes were found in potential relationship to the element of time. Another difference was found in staff group and perception of being involved in the decision making process. These findings and other evidence about the role of change agents in this change process help to emphasize that planning change is one thing, managing the transition is another.
Resumo:
Linear alkylbenzenes, LAB, formed by the Alel3 or HF catalyzed alkylation of benzene are common raw materials for surfactant manufacture. Normally they are sulphonated using S03 or oleum to give the corresponding linear alkylbenzene sulphonates In >95 % yield. As concern has grown about the environmental impact of surfactants,' questions have been raised about the trace levels of unreacted raw materials, linear alkylbenzenes and minor impurities present in them. With the advent of modem analytical instruments and techniques, namely GCIMS, the opportunity has arisen to identify the exact nature of these impurities and to determine the actual levels of them present in the commercial linear ,alkylbenzenes. The object of the proposed study was to separate, identify and quantify major and minor components (1-10%) in commercial linear alkylbenzenes. The focus of this study was on the structure elucidation and determination of impurities and on the qualitative determination of them in all analyzed linear alkylbenzene samples. A gas chromatography/mass spectrometry, (GCIMS) study was performed o~ five samples from the same manufacturer (different production dates) and then it was followed by the analyses of ten commercial linear alkylbenzenes from four different suppliers. All the major components, namely linear alkylbenzene isomers, followed the same elution pattern with the 2-phenyl isomer eluting last. The individual isomers were identified by interpretation of their electron impact and chemical ionization mass spectra. The percent isomer distribution was found to be different from sample to sample. Average molecular weights were calculated using two methods, GC and GCIMS, and compared with the results reported on the Certificate of Analyses (C.O.A.) provided by the manufacturers of commercial linear alkylbenzenes. The GC results in most cases agreed with the reported values, whereas GC/MS results were significantly lower, between 0.41 and 3.29 amu. The minor components, impurities such as branched alkylbenzenes and dialkyltetralins eluted according to their molecular weights. Their fragmentation patterns were studied using electron impact ionization mode and their molecular weight ions confirmed by a 'soft ionization technique', chemical ionization. The level of impurities present i~ the analyzed commercial linear alkylbenzenes was expressed as the percent of the total sample weight, as well as, in mg/g. The percent of impurities was observed to vary between 4.5 % and 16.8 % with the highest being in sample "I". Quantitation (mg/g) of impurities such as branched alkylbenzenes and dialkyltetralins was done using cis/trans-l,4,6,7-tetramethyltetralin as an internal standard. Samples were analyzed using .GC/MS system operating under full scan and single ion monitoring data acquisition modes. The latter data acquisition mode, which offers higher sensitivity, was used to analyze all samples under investigation for presence of linear dialkyltetralins. Dialkyltetralins were reported quantitatively, whereas branched alkylbenzenes were reported semi-qualitatively. The GC/MS method that was developed during the course of this study allowed identification of some other trace impurities present in commercial LABs. Compounds such as non-linear dialkyltetralins, dialkylindanes, diphenylalkanes and alkylnaphthalenes were identified but their detailed structure elucidation and the quantitation was beyond the scope of this study. However, further investigation of these compounds will be the subject of a future study.
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Gramicidin is an antibiotic peptide that can be incorporated into the monolayers of cell membranes. Dimerization through hydrogen bonding between gramicidin monomers in opposing leaflets of the membrane results in the formation of an iontophoretic channel. Surrounding phospholipids, with various associated mechanical properties, have been shown to influence the gating properties of this channel. Conversely, gramicidin incorporation has been shown to affect the structure of spontaneously formed lipid assemblies. Using small-angle x-ray diffraction and model systems composed of phospholipids and gramicidin, the physical effects incurred by gramicidin incorporation were measured. The reverse hexagonal (H^) phase composed of dioleoylphosphatidylethanolamine (DOPE) monolayers decreased in lattice dimension with increasing incorporation of gramicidin. This indicated that gramicidin was adding negative curvature to the monolayers. In this system, gramicidin was measured to have an apparent intrinsic radius of curvature (Rop*™") of -7. 1 A. The addition of up to 4 mol% gramicidin in mixtures with DOPE did not result in the monolayers becoming stiffer, as indicated by unaltered bending moduli for each composition. Dioleoylphosphatidylcholine (DOPC) alone forms the lamellar (LJ phase when hydrated, but undergoes a transition into the H^ phase when mixed with gramicidin. The lattice repeat dimension decreases systematically with increased gramicidin content. Again, this indicated that gramicidin was adding negative curvature to the monolayers. At 12 mol% gramicidin in mixtures with DOPC, the apparent radius of intrinsic curvature of gramicidin (Rop*"^) was measured to be -7.4 A. This mixture formed monolayers that were very resistant to bending under osmotic pressure, with a measured bending modulus of 1 15 kT. The measurements made in this study demonstrate that peptides are able to modulate the spontaneous curvature and other mechanical properties of phospholipid assemblies.
Resumo:
The cell wall composition of Choanephora cucur - bitarum and the host-parasite interface, after infection with Piptocephalis virginiana , were examined in detail. The cell walls of C_. cucurbitarum were determined to be composed of chitin (17%), chitosan (28.4%), neutral sugars (7.2%),uronic acid (2.4%), proteins (8.2%) and lipids (13.8%). The structure of hyphal walls investigated by electron microscopy of shadowed replicas before and after alkali-acid hydrolysis, showed two distinct regions: microfibrillar and amorphous. The microfibrils which were composed of mainly chitin, were organized into two distinct layers: an outer, thicker layer of randomly orientated microfibrils and an inner, thin layer of parallel microfibrils.Electronmicrographs of the host-parasite interface of C_. cucurbitarum and the mycoparasite , P_. virginiana , 30 h following inoculation, showed that the sheath zone has a similar electron density to that of the host cell wall. The sheath was not present around the young (18 h old) haustorium. High-resolution autoradiographs of infected host hyphae showed that radioactive N-acetyl-D-glucosamine , a precursor of chitin, was incorporated preferentially in the host cell wall and sheath zone. Cell fractionation of label fed hyphae showed that 84% of the label was present in the cell wall and specifically in the chitin portion of the wall. The antifungal antibiotic, Polyoxin D, a specific inhibitor of the enzyme, chitin synthetase, suppressed the incorporation of the label in the cell wall and sheath zone and resulted in a decrease in electron density of the developing sheath. The significance of these results is discussed in the light of host resistance.