73 research outputs found
N-Alkylpyridinium sulfonates for retention time indexing in reversed-phase-liquid chromatography-mass spectrometry–based metabolomics.
No full textChromatographic retention time information is valuable, orthogonal information to MS and MS/MS data that can be used in metabolite identification. However, while comparison of MS data between different instruments is possible to a certain degree, retention times (RTs) can vary extensively, even when nominally the same phase system is used. Different factors such as column dead volumes, system extra column volume, and gradient dwell volume can influence absolute retention times. Retention time indexing (RTI), routinely employed in gas chromatography (e.g., Kovats index), allows compensation for deviations in experimental conditions. Different systems have been reported for RTI in liquid chromatography, but none of them have been applied to metabolomics to the same extent as they have with GC. Recently, a more universal RTI system has been reported based on a homologous series of N-alkylpyridinium sulfonates (NAPS). These reference standards ionize in both positive and negative ionization modes and are UV-active. We demonstrate the NAPS can be used for retention time indexing in reversed-phase-liquid chromatography-mass spectrometry (RP-LC–MS)–based metabolomics. Having measured >500 metabolite standards and varying flow rate and column dimension, we show that conversion of RT to retention indices (RI) substantially improves comparability of retention information and enables to use of RI for metabolite annotation and identification. [Figure not available: see fulltext.]
Retention time indexing as an approach to standardize reporting of retention data in metabolomics.
No full textUma aplicação das tecnicas de preferencia declarada ao setor hoteleiro de Florianopolis
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina. Centro TecnologicoAs técnicas de preferência declarada têm sido utilizadas em diversas áreas como forma de avaliar as preferências dos indivíduos por produtos e serviços. Constituem-se em técnicas atuais empregadas para estudos de marketing e transporte. Conhecendo as preferências dos clientes, um hotel tem condições de elaborar estratégias de atração mais adequadas às aspirações do segmento atendido, investindo em atributos que mais agregam valor para o consumidor. A viabilidade da abordagem proposta é demonstrada através de um estudo dos hotéis quatro e cinco estrelas de Florianópolis. A pesquisa foi realizada durante os meses de setembro e outubro de 1995 e identificou os cinco principais fatores que influenciam a escolha de um hotel pelos turistas. Após o ajuste do modelo foram dadas sugestões sobre os fatores e seus efeitos nos hotéis
Benefits of travel time savings for freight transportation : beyond the costs
No full textThe purpose of this presentation is to investigate whether current practices in Cost Benefit Analysis do not underestimate the actual benefits accruing to the economy when transport investment reduces transport time. In a first section we define the different time related attributes of transport. We differentiate the various time dimensions of freight transportation services (time, reliability, frequency, responsiveness, etc). We decide to focus our analysis on Travel Time savings. We also investigate the meaning of the expression value of time in the specific context of freight transportation. We also recognise the variability of time perception among freight operators and between circumstances. In a second section we investigate the current practices in various European countries. We find that the overwhelming majority of countries estimate the benefits of improved network through the reduction in transport costs. However there is a strong case that the total benefits may exceed this mere cost reduction. In a third section, we show that shippers exhibit a significant willingness to pay for faster deliveries. This may have different causes like potential reorganisation of the production and distribution process, trading time consuming production technique against transport time, or increasing the time dimension of goods and services. This question should be carefully distinguished from the recurrent question about indirect effects. If direct effects are those that are captured by the supplier and consumer surplus of the market under study, then the potential extra benefit that are scrutinised in the study are part of the direct and not indirect effects. We also demonstrate that a benefit analysis based on traditional definitions of surplus should take into account these additional effects. We try to identify methods to measure these extra benefits. We review results obtained by previous attempts to measure this willingness to pay, based on RP data and SP exercises. We present the benefits and drawbacks of different measurement methods. Eventually, we show the impact of taking into account these extra benefits on projects' evaluation. and test the sensibility of Cost Benefit Ratio on a set of typical road investment projects in the U.K.
Análise Epidemiológica dos óbitos ocorridos no trânsito no ano de 1997.
No full textTrabalho de Conclusão de Curso - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Departamento de Clínica Médica, Curso de Medicina, Florianópolis, 199
Improvements in medical care and technology and reductions in traffic-related fatalities in Great Britain
No full textTraffic-related fatalities in the UK have fallen dramatically over the last 30 years by about 50%. This decline has been observed in many other developed countries with similar rates of reduction. Many factors have been associated with this decline, including safer vehicle design, increased seat-belt use, changing demographics, and improved infrastructure. One factor not normally considered is the role that improved medical technology may have in reducing total traffic-related fatalities. This study analyzed cross-sectional time-series data in the UK to examine this relationship. Various proxies for medical technology improvement were included in a fixed effects negative binomial model to assess whether they are associated with reductions in traffic-related fatalities. Various demographic variables, such as age cohorts, GDP and changes in per-capita income are also included. The statistical methods employed control for heterogeneity in the data and therefore other factors that may affect the dependent variable for which data are not available do not need to be considered. Results suggest a strong relationship between improved medical technology and reductions in traffic-related fatalities as well as expected relationships with demographic factors. These results could imply that continued reductions in UK fatalities may be more difficult to achieve if medical technology improvements are diminishing, however, demographic changes will likely contribute to a further downward trend.
A Geo-Statistical Analysis of Road Mortality in the Enlarged EU
No full textThis paper aims at showing and understanding the spatial regional disparities hidden behind average national statistics on road fatalities in Europe; special attention is given on the EU last enlargement. The work is not limited on differences descriptions, but unveils what is hidden behind the observed infra-national heterogeneity in terms of road risk. It is indeed common practice to compare countries in terms of road safety performance and to rank them in terms of a risk indicator such as the mortality rate, which is often expressed by the number of fatalities due to road accidents per 100,000 inhabitants. Some countries are known for their very bad risk records and are often pointed out by national or international authorities, without any understanding of the regional differences hidden behind a national mean value. The data analysis shows that changes in the level of spatial aggregation of the data produce significant differences in the variables describing the level of road safety, and hence in operational recommendation and conclusions. Beside the differences in national conditions and polices, the regional differences in road environment characteristics, traffic performance, road user mix, travel speeds, seat-belt use, and availability of emergency care have been major contributors to these variations. Road safety professionals and decision makers should be aware of the differences existing when trying to reduce road toll of the country in sustainable and cost-effective way.
Comparing pedestal structure in JET-ILW H-mode plasmas with a model for stiff ETG turbulent heat transport
No full textA predictive model for the electron temperature profile of the H-mode pedestal is described, and its results are compared with the pedestal structure of JET-ILW plasmas. The model is based on a scaling for the gyro-Bohm normalized, turbulent electron heat flux qe/qe,gB resulting from electron temperature gradient (ETG) turbulence, derived from results of nonlinear gyrokinetic (GK) calculations for the steep gradient region. By using the local temperature gradient scale length L-Te in the normalization, the dependence of q(e)/q(e,g)B on the normalized gradients R/L-Te and R/(Lne) can be represented by a unified scaling with the parameter eta(e) = L-ne/L-Te, to which the linear stability of ETG turbulence is sensitive when the density gradient is sufficiently steep. For a prescribed density profile, the value of R/L-Te determined from this scaling, required to maintain a constant electron heat flux qe across the pedestal, is used to calculate the temperature profile. Reasonable agreement with measurements is found for different cases, the model providing an explanation of the relative widths and shifts of the T-e and n(e) profiles, as well as highlighting the importance of the separatrix boundary conditions. Other cases showing disagreement indicate conditions where other branches of turbulence might dominate.This article is part of a discussion meeting issue "H-mode transition and pedestal studies in fusion plasmas'
Analyzing the determinants of freight shipper's behavior: own account versus purchased transport
No full textPrevious work in the demand for freight transportation has focused in the rail-truck substitution problem, leaving aside the prior own-account versus third-party trade-off, often found in transportation decision-making. The purpose of this paper is to analyze shippers’ behavior relative to this question, paying particular attention to whether the decision to use a private form of transport is taken on a short term or on a medium term horizon. In order to provide a quantitative evaluation, as an illustrative case, the models developed are tested on data gathered by means of a sample survey conducted to Andalusian enterprises belonging to the food industry. JEL classification: R410: Transportation: Supply, Demand and Congestion. C350: Econometric Methods: Multiple/Simultaneous Equation Models: Truncated and Censored Models.
Market power and the need for regulation in the German airport market
No full textWith the increasing profit orientation of German airport operators the question as to weather they possess market power is gaining more importance. Whereas there have been some studies about the degree of market power of individual airports in countries as Australia and Great Britain, the German airport market has not yet been studied in detail. This paper is a part of a research project that tries to assess market power in this market. It indicates which of the 35 examined German airports possess market power and therefore need special regulatory attendence. We calculate a substitution coefficient for inter-airport competition that quantifies the quality of the best substitute for a certain airport. It is defined as the proportion of inhabitants within the relevant regional market of an airport that consider another airport, which has been identified as meeting the demands of the airlines, to be a good substitute from their perspective as well. The analysis is complemented by an assessment of intermodal substitution and countervailing power of airlines. The study gives strong indication that 23 out of the 35 German airports do not possess relevant market power. In contrast to this, four airports (HAM, FRA, MUC, STR) and Berlin Airport System (THF, TXL, SXF) have strong, five (BRE, DRS, LEJ, NUE, HAJ) have modest market power. The results provide a basis for the construction of an efficient regulatory framework for the German airport market.airport competition, counterveiling power, market power, substitution
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