891 resultados para Units of measurement.
Resumo:
Amorphous samples of polyether ketone with cardo(PEK-C) have been studied in the solution state by C-13, H-1 high-resolution NMR, The H-1 and C-13 1D NMR spectra were assigned using two dimensional chemical shift correlated spectroscopy, 2D homonuclear correlated(COSY) and heteronuclear correlated (HETCOR) spectroscopy present important information. In this work, the structural units of PEK-C was determined by NMR. For some peaks, these assignments are confirmed by two dimensional long-range heteronuclear correlation experiments, A little modification is made on the original C-13 peak assignments for the main chain, The symmetry and the isotacticity of the chain structure for PEK-C are obvious on NMR data.
Resumo:
Three kinds of high-performance polyimides 1 (poly(ketone-imide) PKI), 2 (poly(ether-imide) PEI) and 3 (poly(oxy-imide) POI) were studied using nuclear magnetic resonance (NMR). The NMR spectra of the polyimides were assigned according to the comprehensive consideration of the substitution effect of different substituting groups, viz. distortionless enhancement by polarization transfer (DEPT), no nuclear Overhauser effect (NNE), analysis of relaxation time, and two-dimensional correlated spectroscopy (COSY) techniques. The structural units of these three polyimides were determined. Carbon-13 and proton relaxation times for PEI and PKI were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (JS model) and anisotropic group rotation such as phenyl group rotation and methyl group rotation. Correlation times for the main-chain motion are in the tens of picosecond range which indicates the high flexibility of polyimide chains. Correlation times for phenyl group and methyl group rotations are more than 1 order of magnitude lower and approximately 1 order of magnitude higher than that of the main chain, respectively.
Resumo:
Through random sequencing, we found a total of 884000 base-pairs (bp) of random genomic sequences in the genome of Chinese shrimp (Fenneropenaeus chinensis). Using bio-soft Tandem Repeat Finder (TRF) software, 2159 tandem repeats were found, in which there were 1714 microsatellites and 445 minisatellites, accounting for 79.4% and 20.6% of repeat sequences, respectively. The cumulative length of repeat sequences was found to be 116685 bp, accounting for 13.2% of the total DNA sequence; the cumulative length of microsatellites occupied 9.78% of the total DNA sequence, and that of minisatellites occupied 3.42%. In decreasing order, the 20 most abundant repeat sequence classes were as follows: AT (557), AC (471), AG (274), AAT (92), A (56), AAG (28), ATC (27), ATAG (27), AGG (18), ACT (15), C (11), AAC (11), ACAT (11), CAGA (10), AGAA (9), AGGG (7), CAAA (7), CGCA (6), ATAA (6), AGAGAA (6). Dinucleotide repeats, not only in the aspect of the number, but also in cumulative length, were the preponderant repeat type. There were few classes and low copy numbers of repeat units of the pentanucleotide repeat type, which included only three classes: AGAGA, GAGGC and AAAGA. The classes and copy numbers of heptanucleotide, eleven-nucleotide and thirteen-nucleotide primer-number-composed repeats were distinctly less than that of repeat types beside them.
Resumo:
A genomic fragment encoding alpha(APC) and beta(APC) (i.e., alpha and beta units of the allophycocyanin, APC) from Anacystis nidulans UTEX 625 was cloned and sequenced. This fragment, containing a non-coding sequence of 56 nucleotides in between, was then subcloned into the expression vector pMal-c2 downstream from and in frame with the malE gene of E. coli encoding MBP ( maltose binding protein). The fusion protein was purified by amylose affinity chromatography and cleaved by coagulation factor Xa. alpha(APC) and beta(APC) were then separated from MBP and MBP fusion proteins, respectively, and concentrated by membrane centrifugation. The study provides a method to produce recombinant allophycocyanin subunits for biomedical and biotechnological applications.
Resumo:
Zenisu deep-sea channel originated from a volcanic arc region, Izu-Ogasawara Island Arc, and vanished in the Shikoku Basin of the Philippine Sea. According to the swath bathymetry, the deep-sea channel can be divided into three,segments. They are Zenisu canyon, E-W fan channel and trough-axis channel. A lot of volcanic detritus were deposited in the Zenisu Trough via the deep-sea channel because it originated from volcanic arc settings. On the basis of the swath bathymetry, submersible and seismic reflection data, the deposits are characterized by turbidite and debrite deposits as those in the other major deep-sea channels. Erosion or few sediments were observed in the Zenisu canyon, whereas a lot of turbidites and debrites occurred in the E-W channel and trough axis channel. Cold seep communities, active fault and fluid flow were discovered along the lower slope of the Zenisu Ridge. Vertical sedimentary sequences in the Zenisu Trough consist of the four post-rift sequence units of the Shikoku Basin, among which Units A and B are two turbidite units. The development of Zenisu canyon is controlled by the N-S shear fault, the E-W fan channel is related to the E-W shear fault, and the trough-axis channel is related to the subsidence of central basin.
Resumo:
琼胶是一种从石花菜等红藻中提取的,目前生产工艺和结构等方面研究比较成熟的海藻多糖,广泛应用于医药、仪器等行业。但是,海藻多糖因为具有分子量大,粘度大,溶解度较小的等特点,而使其应用范围受到限制。利用降解的手段对其进行修饰,降低分子量和粘度,改善溶解性,可以拓展其应用范围。并且根据文献报道,琼 胶寡糖具有一些特殊的生物活性,如抗氧化性,抗炎症等。因此,对琼胶降解的研究具有生要意义。本研究中,为了选择一种合适的降解方法,进行了几种水解方法的尝试,其中包括在不同湿度和酸度下盐酸水解,过氧化氢和醋酸催化水解,Fenton体系羟基自由基降解。对于酸水解和Fenton体系氧化还原降解方法,通过粘度法对反应的速度进行了比较,表明氧化还原降解反应中琼胶的粘度降低比较快,并且具有代表性和新意,确定为本实验的降解琼胶的方法并对氧化还原降解所得的产物进行了活性实验。通过模仿自然界普遍存在的氧化还原降解反应,利用Vc诱导的Fenton体系产生的羟基自由基氧化还原降解琼胶得到低分子量的琼胶。降解产物经过高速离心、60%乙醇沉淀,除去分子量比较大的降解产物和磷酸盐,得到可溶于60%乙醇的分子量估计小于3000的降争产物,其产率为85%。利用经Sephadex-G25凝胶色谱分离所香的不同分子量的级分进行分子量和α-葡萄糖苷酶抑制活性关系的实验。降解产物对α-葡萄糖苷酶的抑制率和各级分的浓度呈线性正相关,并且各级分的IC_(50)则随着分子量的降低而降低。另外,对所得的降解产物混合物进行了红外吸收光谱、质子去偶核磁共震碳谱和负离子基质辅助激光诱导-飞行时间质谱结构分析。结果表明,氧化还原降解反应的专一性差,在得到寡糖的同时,在光谱图中出现一些比较复杂的副产物的结构信息。最后,根据MTT法的原理,以有体皮肤成纤维细胞为材料,通过紫外线辐射产生自由基造成氧化损伤,研究降解产物对成纤维细胞的保护作用。当无紫外线辐射时,降解产物对成纤维细胞具有显著的促进生长增殖作用:当经UVa、UBb辐射时则可以显著地表现出对损伤的保护作用,并且这种促进生长和保护作用呈显著的量效关系,表明降解产物具有清除基自由基的作用。但是,因为氧化还原降解以应的机理尚不十分明的以及琼羟胶的特殊结构,使得反应的副产物很难预测,也就使得分离工作难以进行,所以,根据目前所得的信息,尚不能确定是降解产物的什么级分产生的以上两种生物活性。
Resumo:
The classical method for preparation of covalently boned cellulose derivative chiral stationary phases (CSP) with diisocyanate as spacer was improved. Diisocyanate was firstly allowed to react with 3-aminopropyltriethoxysilane, and the resulting product was then applied as the spacer reagent to immobilize cellulose derivatives onto silica gel. Influences of the amount and the length of the spacer on the optical resolution ability of the CSP were investigated. Comparing improved procedure to classical diisocyanate method, the cross-linking between the glucose units of the cellulose derivatives was avoided to the most extent. With the improved procedure, regio-nonselective ways could be adopted to prepare covalently bonded CSP, which showed an advantage for the rapid preparation.
Resumo:
There are a variety of guidelines and methods available to measure and assess survey quality. Most of these are based on qualitative descriptions. In practice, they are not easy to implement and it is very difficult to make comparisons between surveys. Hence there is a theoretical and pragmatic demand to develop a mainly quantitative based survey assessment tool. This research aimed to meet this need and make contributions to the evaluation and improvement of survey quality. Acknowledging the critical importance of measurement issues in survey research, this thesis starts with a comprehensive introduction to measurement theory and identifies the types of measurement errors associated with measurement procedures through three experiments. Then it moves on to describe concepts, guidelines and methods available for measuring and assessing survey quality. Combining these with measurement principles leads to the development of a quantitative based statistical holistic tool to measure and assess survey quality. The criteria, weights and subweights for the assessment tool are determined using Multi-Criteria Decision-Making (MCDM) and a survey questionnaire based on the Delphi method. Finally the model is applied to a database of surveys which was constructed to develop methods of classification, assessment and improvement of survey quality. The model developed in this thesis enables survey researchers and/or commissioners to make a holistic assessment of the value of the particular survey(s). This model is an Excel based audit which takes a holistic approach, following all stages of the survey from inception, to design, construction, execution, analysis and dissemination. At each stage a set of criteria are applied to assess quality. Scores attained against these assessments are weighted by the importance of the criteria and summed to give an overall assessment of the stage. The total score for a survey can be obtained by a combination of the scores for every stage weighted again by the importance of each stage. The advantage of this is to construct a means of survey assessment which can be used in a diagnostic manner to assess and improve survey quality.
Resumo:
Background: ‘Birth Satisfaction’ is a term that encompasses a woman’s evaluation of her birth experience. The term includes factors such as her appraisal of the quality of care she received, a personal assessment of how she coped, and her reconstructions of what happened on that particular day. Her accounts may be accurate or skewed, yet correspond with her reality of how events unfolded. Objective: To evaluate properties of an instrument designed to measure birth satisfaction in a Greek population of postnatal women. Study design: We assessed factor structure, internal consistency, divergent validity and known-groups discriminant validity of the 30-item Greek Birth Satisfaction Scale – Long Form (30-item G-BSS-LF) and its revised version the 10-item Greek-BSS-Revised (10-item-G-BSS-R), using survey data collected in Athens. Participants: A convenience sample of healthy Greek postnatal women (n = 162) aged 22–46 years who had delivered between 34 and 42 weeks’ gestation. Results: The 30-item-G-BSS-LF performed poorly in terms of factor structure. The short-form 10-item-G-BSS-R performed well in terms of measurement replication of the English equivalent version as a multidimensional instrument. The short-form 10-item-G-BSS-R comprises three subscales which measure distinct but correlated domains of: (1) quality of care provision (4 items), (2) women’s personal attributes (2 items), and (3) stress experienced during labour (4 items). Key conclusions: The 10-item-G-BSS-R is a valid and reliable multidimensional psychometric instrument for measuring birth satisfaction in Greek postnatal women.
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The human urge to represent the three-dimensional world using two-dimensional pictorial representations dates back at least to Paleolithic times. Artists from ancient to modern times have struggled to understand how a few contours or color patches on a flat surface can induce mental representations of a three-dimensional scene. This article summarizes some of the recent breakthroughs in scientifically understanding how the brain sees that shed light on these struggles. These breakthroughs illustrate how various artists have intuitively understand paradoxical properties about how the brain sees, and have used that understanding to create great art. These paradoxical properties arise from how the brain forms the units of conscious visual perception; namely, representations of three-dimensional boundaries and surfaces. Boundaries and surfaces are computed in parallel cortical processing streams that obey computationally complementary properties. These streams interact at multiple levels to overcome their complementary weaknesses and to transform their complementary properties into consistent percepts. The article describes how properties of complementary consistency have guided the creation of many great works of art.
Resumo:
Background: Most cardiovascular disease (CVD) occurs in the presence of traditional risk factors, including hypertension and dyslipidemia, and these in turn are influenced by behavioural factors such as diet and lifestyle. Previous research has identified a group at low risk of CVD based on a cluster of inter-related factors: body mass index (BMI) < 25 Kg/m2, moderate exercise, alcohol intake, non-smoking and a favourable dietary pattern. The objective of this study was to determine whether these factors are associated with a reduced prevalence of hypertension and dyslipidemia in an Irish adult population. Methods: The study was a cross-sectional survey of 1018 men and women sampled from 17 general practices. Participants completed health, lifestyle and food frequency questionnaires and provided fasting blood samples for analysis of glucose and insulin. We defined a low risk group based on the following protective factors: BMI <25 kg/m2; waist-hip ratio (WHR) <0.85 for women and <0.90 for men; never smoking status; participants with medium to high levels of physical activity; light alcohol consumption (3.5–7 units of alcohol/week) and a "prudent" diet. Dietary patterns were assessed by cluster analysis. Results: We found strong significant inverse associations between the number of protective factors and systolic blood pressure, diastolic blood pressure and dyslipidemia. The prevalence odds ratio of hypertension in persons with 1, 2, 3, ≥ 4 protective factors relative to those with none, were 1.0, 0.76, 0.68 and 0.34 (trend p < 0.01). The prevalence odds ratio of dyslipidemia in persons with 1, 2, 3, ≥ 4 protective factors relative to those with none were 0.83, 0.98, 0.49 and 0.24 (trend p = 0.001). Conclusion: Our findings of a strong inverse association between low risk behaviours and two of the traditional risk factors for CVD highlight the importance of 'the causes of the causes' and the potential for behaviour modification in CVD prevention at a population level.
Resumo:
As a prominent form of land use across much of upland Europe, extensive livestock grazing may hold the key to the sustainable management of these landscapes. Recent agricultural policy reform, however, has resulted in a decline in upland sheep numbers, prompting concern for the biodiversity value of these areas. This study quantifies the effects of varying levels of grazing management on plant, ground beetle and breeding bird diversity and assemblage in the uplands and lowlands of hill sheep farms in County Kerry, Ireland. Farms represent a continuum of light to heavy grazing, measured using a series of field indicators across several habitats, such as the internationally important blanket bog, home to the ground beetle, Carabus clatratus. Linear mixed effects modelling and non-metric multidimensional scaling are employed to disentangle the most influential management and environmental factors. Grazing state may be determined by the presence of Molinia caerulea or Nardus stricta, and variables such as % traditional ewes, % vegetation litter and % scrub prove valuable indicators of diversity. Measures of ecosystem functioning, e.g. plant biomass (nutrient cycling) and % vegetation cover (erosion rates) are influenced by plant diversity, which is influenced by grazing management. Levels of the ecosystem service, soil organic carbon, vary with ground beetle abundance and diversity, potentially influencing carbon sequestration and thereby climate change. The majority of species from all three taxa are found in the lowlands, with the exception of birds such as meadow pipit and skylark. The scale of measurement should be determined by the size and mobility of the species in question. The challenge is to manage these high nature value landscapes using agri-environment schemes which enhance biodiversity by maintaining structural heterogeneity across a range of scales, altitudes and habitats whilst integrating the decisions of people living and working in these marginal areas.
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Most studies that apply qualitative comparative analysis (QCA) rely on macro-level data, but an increasing number of studies focus on units of analysis at the micro or meso level (i.e., households, firms, protected areas, communities, or local governments). For such studies, qualitative interview data are often the primary source of information. Yet, so far no procedure is available describing how to calibrate qualitative data as fuzzy sets. The authors propose a technique to do so and illustrate it using examples from a study of Guatemalan local governments. By spelling out the details of this important analytic step, the authors aim at contributing to the growing literature on best practice in QCA. © The Author(s) 2012.
Resumo:
Over the last few decades, global warming has accelerated both the rate and magnitude of changes observed in many functional units of the Earth System. In this context, plankton are sentinel organisms because they are sensitive to subtle levels of changes in temperature and might help in identifying the current effects of climate change on pelagic ecosystems. In this paper, we performed a comparative approach in two regions of the North Atlantic (i.e. the Northeast Atlantic and the North Sea) to explore the relationships between changes in marine plankton, the regional physico-chemical environment and large-scale hydro-climatic forcing using four key indices: the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), the East Atlantic (EA) pattern and Northern Hemisphere Temperature (NHT) anomalies. Our analyses suggest that long-term changes in the states of the two ecosystems were synchronous and correlated to the same large-scale hydro-climatic variables: NHT anomalies, the AMO and to a lesser extent the EA pattern. No significant correlation was found between long-term ecosystem modifications and the state of the NAO. Our results suggest that the effect of climate on these ecosystems has mainly occurred in both regions through the modulation of the thermal regime.
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The paper presents the description of one new order (Asplenietalia septentrionalo-cuneifolii) and two new alliances (Arenarion bertolonii and Physoplexido comosae- Saxifragion petraeae). In addition, the syntaxon Asplenietalia lanceolato-obovati is here formally raised to the order level and the name Hypno-Polypodietalia vulgaris is validated.