bluuebunny/crossref_metadata_2025 huggingface dataset:
Associations Between Early-Adolescent Substance Use and Subsequent Young-Adult Substance Use Disorders and Psychiatric Disorders Among a Multiethnic Male Sample in South Florida
Authors: Gil Andres G. , Wagner Eric F. , Tubman Jonathan G.
Published: December 2008

Objectives. We examined the associations among early-adolescent substance use, subsequent young-adult substance use disorders, and psychiatric disorders among a community sample of males.

Methods. Early-adolescent data were collected in classroom surveys (1990–1993), and young-adult data were collected in face-to-face interviews (1998–2000).

Results. We found strong associations between early-adolescent substance use and young-adult substance use disorders and psychiatric disorders. The magnitudes of these associations varied by racial/ethnic group and were strongest among African Americans and foreign-born Hispanics, who reported the lowest early-adolescent substance use.

Conclusions. Early-adolescent substance use is most strongly associated with a later pattern of dysfunction among the racial/ethnic groups that reported the lowest levels of early use. The implications of our findings in the context of primary and secondary prevention are discussed.
Hepatitis A Virus Immunity and Seroconversion Among Contacts of Acute Hepatitis A Patients in Amsterdam, 1996–2000: An Evaluation of Current Prevention Policy
Authors: Sonder Gerard J. B. , van Steenbergen Jim E. , Bovee Lian P. M. J. , Peerbooms Paul G. H. , Coutinho Roel A. , van den Hoek Anneke
Published: December 2008

Objectives. We evaluated the hepatitis A virus (HAV) control policy (hygienic precautions and passive immunization with immune globulin) for “household contacts” (defined as all people who lived in the same house and who shared the same toilet with the patient, people who took care of an HAV-infected child, and sexual partners of the patient) of acute hepatitis A patients between 1996 and 2000.

Methods. We examined the characteristics and the serological outcomes of household contacts. All susceptible contacts were invited for retesting 6 weeks after they received immune globulin.

Results. Of 1242 contacts of 569 HAV patients, more than 50% (n = 672) were found to be HAV immune. Among the remaining contacts, 161 (28.2%) had a concurrent infection, and 86 of these individuals were symptomatic. The remaining 409 susceptible contacts received immune globulin, with 186 (45%) returning for retesting 6 weeks later (64 [34%] were infected, but only 12 had symptoms).

Conclusions. Immune globulin does not protect all household contacts from HAV infection; however, it attenuates symptoms and effectively reduces further HAV transmission.
Agricultural Production Clubs: Viability and Welfare Implications
Authors: Langinier Corinne , Babcock Bruce A.
Published: December 2008

Consumers are, in general, less informed than producers about the quality of agricultural goods. To reduce the information gap, consumers can rely on certification that ensures the quality and origin of the goods. Certification can be voluntarily adopted by a group of producers, as is the case for geographical indications. We model such a group as a club, and analyze the certification decision of the club and its welfare implication. We find that for intermediate values of certification costs, the industry and a club of a given size have divergent incentives, and there may be overprovision of certification. If club members can erect barriers to entry, an optimal size of the club exists. There may be a conflict between the efficient outcome (that maximizes the aggregate profit of the firms) and the equilibrium, which may be socially undesirable. In the absence of a barrier to entry, it is less likely that a club will emerge.
The Role of Fault Quotient in Determination of the Distance to a Transmission Line Fault
Authors: Survilo J.
Published: December 2008

The Role of Fault Quotient in Determination of the Distance to a Transmission Line Fault

The notion of fault quotient refers to single-phase-earth and phase-to-phase faults in one-terminal and two-terminal (double fed), single or parallel power lines at determination of the distance to a fault place using the apparent impedance method. The fault quotient is determined as the ratio of the current through a fault place (fault current) to the current in a faulty phase at single-phase-earth faults and to the difference of currents in faulty phases at phase-to-phase faults. For one-terminal lines at single-phase-earth faults, neglecting capacitive and load currents, this ratio is 1, and for phase-to-phase faults it equals 1/2. For other cases it is a complex quantity, with the absolute value > 1 for single-phase-earth faults. Its significance grows with the fault resistance Rf. At Rf = 0 this ratio loses its significance for determination of the distance to a fault place. The tangent of the fault quotient angle with a real axis enters into the ultimate expressions for the reactance to fault place and for the fault resistance. The use of such a quotient facilitates reiterative calculations of the distance to a fault place.
Electronic Nose for Identification of Lung Diseases
Authors: Ogorodnik V. , Kleperis J. , Taivans I. , Jurka N. , Bukovskis M.
Published: December 2008

Electronic Nose for Identification of Lung Diseases

In the paper, the authors analyze the preliminary results of testing a classical gas sensing instrument - the electronic nose (a metal oxide transistor sensor of chemical substances) in a hospital where patients with different lung diseases are treated. To reveal the correlation between the amplitudes of the sensor's responses and the patients' diagnoses, different statistical analysis methods have been used. It is shown that the lung cancer can easily be discriminated from other lung diseases if short breath sampling and analysis time (less than 1 min) is used in the test. Volatiles obtained from a breath sample of a patient with lung cancer give the major contribution to the responses of different e-nose sensors, so in these cases highly precise identification could be achieved.
Use of Smart Card Data to Define Public Transit Use in Seoul, South Korea
Authors: Park Jin Young , Kim Dong-Jun , Lim Yongtaek
Published: December 2008

In South Korea, use of the smart card to pay public transit fares has grown since its introduction in 1996. The proportion of smart card use in Seoul, South Korea, is more than 90% for buses and 75% for Metro. In 2004, the Seoul metropolitan government introduced a new smart card system that has a distance-based fare system, which requires the input of detailed user data, such as boarding time and Global Positioning System–based vehicle location. To investigate the reliability of smart card data, the number of users of every Metro station in Seoul, gathered from smart card data, was directly compared with data obtained from the Seoul Metro Company. By using two simple manipulations to include daily variations and the number of cash users, smart card data appear to be statistically similar to the surveyed data obtained from the Seoul Metro Company. By analyzing the line-specific proportions of smart card use rather than the average smart card use, the accuracy of the results is improved. From the results, it can be seen that smart card data show potential as a basis for describing the characteristics of public transit users, such as the number of transfers, boarding time, hourly trip distribution of the number of trips for different transit modes, and travel time distribution for all transit modes and user types.
ADAMS
Authors: Cevallos Fabian , Wang Xiaobo
Published: December 2008

Business intelligence strategies, like data mining and analysis, can be used in public transportation to efficiently address various transit planning, scheduling, and operational issues. With the use of data mining and analysis technology, the ADAMS (APTS Data Archiving and Mining System) software was developed and implemented as part of the Research for Advanced Public Transit Systems (RAPTS) program. ADAMS contributes valuable knowledge for any transportation agency implementing advanced system technologies. ADAMS also is an effective tool for improving on-time performance, predicting possible results based on histogram data sets, and enhancing the amount and quality of data available for planning and operational analysis. A technology overview is given for data use in data mining and reporting for three primary APTS technologies: automatic passenger counters, automatic vehicle location, and electronic fare collection systems. Also described are the methodologies used to set up data management, data mining, reporting services, and performance measures. New software technology, which is able to process large amounts of data, is applied to implement the system. Results from this research promise to help improve operational efficiencies and quality of service.
Identifying Feasible Locations for Rail Transit Stations
Authors: Samanta Sutapa , Jha Manoj K.
Published: December 2008

A public transportation system is a viable alternative to reducing traffic congestion and environmental pollution in urban areas. A metro, subway, or light rail system may be a viable commuting alternative connected with a coordinated service of feeder buses in urban and suburban neighborhoods. The decision to build a rail transit system is largely driven by available land and feasible sites for tracks and stations. Factors like ridership and public perception are considered in identifying suitable rail corridor and station locations. A two-stage analytical model is developed for identifying feasible rail transit station sites based on the real geographical and demographic data. The model uses a genetic algorithm (GA) for optimally locating the stations and works in parallel with a geographical information system (GIS). The model is applied in an example by using real GIS data, road network, and demographic information. The potential station sites are identified in the first stage, and the optimization using the GA is performed in the second stage by minimizing the total cost of locating the stations.
Object-Oriented Analysis of Carsharing System
Authors: Morency Catherine , Trépanier Martin , Martin Basile
Published: December 2008

Carsharing systems are gaining new members every month. However, few studies formally define the system and illustrate the systematic processing of administrative data sets to estimate indicators regarding both demand and supply objects. The first outcome of this research is the definition of the object model for a carsharing system. Rich transaction data sets, generally used for the production of monthly bills, are used to estimate indicators describing how the carsharing system is used in the Montreal area of Quebec, Canada. Indicators describing the main objects of the system—members, trip chains (transactions), cars, and stations—are estimated by using continuous data. The demand object analysis focuses on the study of members and their trip chains using the shared cars. The analysis shows that carsharing members are younger than the overall population, with an overrepresentation of 25- to 39-year-olds. The persistency of active members within the carsharing system is estimated at around 60% after 4 months and 50% after 12 months. The supply–objects analysis focuses on the study of cars and stations. Spatial dispersion of members with respect to stations used and typical use of cars is illustrated over long periods. With the increase in the number of members, transactions, cars, and stations, carsharing organizations need to find new ways to manage growth and optimize their networks. A clearer understanding of how their systems are used will help them develop enhanced planning and modeling abilities.
Understanding Links between Transit Ridership and Gasoline Prices
Authors: Currie Graham , Phung Justin
Published: December 2008

Gasoline price increases have been cited as a major recent motivator for transit ridership growth. Research in 2007 established that for every 10% increase in gas prices, U.S. transit demand has increased by 1.2%, a cross-elasticity of demand to gas prices (e) of 0.12. Results also showed much higher effects on U.S. light rail systems (e 0.27 to 0.38) for heavy rail (e = 0.17) but low sensitivity for bus (e = 0.04). In Australia, the impact of gas prices on ridership has been larger (e = 0.22) because of higher gas prices (20% to 30% higher than U.S. prices). Recent research demonstrates a significant impact on low-income travelers and links among increased gas prices, rising home-loan interest rates, and ridership growth. Australian research is summarized to establish the impact of both gasoline prices and home-loan interest rates on transit demand. The research disaggregates effects by individual transit mode (rail, bus rapid transit, and bus), service group, and time period to explore causal factors. The research relates Australian findings to the U.S. trends. Findings show that housing affordability is a critical influence on interest rate effects that may be relevant to the United States. Low values for e in U.S. bus systems may be explained by noncommute and low-income ridership features of U.S. bus systems. High values of e were found for high-quality transit, including Australian rail and bus rapid transit, which correlates with high values for U.S. rail. Longer-distance travel was also associated with ridership effects of higher gas prices.
Land Use–Based Transit Planning
Authors: Milam Ronald T. , Luo Tao (Anna)
Published: December 2008

Bus rapid transit (BRT) is gaining greater interest by transportation planners and decision makers in the United States because of concerns about growing traffic congestion and a desire for improved environmental quality and sustainable land use development patterns. To help planners and decision makers, FTA developed the BRT implementation guidelines based on the 26 case studies located in North America, Australia, Europe, and South America. The FTA guidelines serve as a valuable source for the basic BRT concepts including the main system components and their types, general planning principles, and general design guidelines. However, the detailed implementation process, such as BRT station selection and route alignment determination, as one of the primary and practical concerns by transportation planners and decision makers, has not been studied in detail. A conceptual planning approach used to quickly evaluate potential BRT stations and alignments based on a case study in Placer County, California, is presented. The approach relies on land use development criteria and an analogous station-matching process to determine an initial range of potential ridership for future stations based on existing stations with similar land use development patterns. This information is combined to help gauge station feasibility and alignment options. The criteria used in this planning process were developed from a comprehensive literature review of the relationship between land use development and transit station ridership, as well as a unique database of transit ridership and land use development intensity for more than 80 existing transit stations in the San Francisco Bay Area and the Sacramento, California, region.
Transit Use at Transit-Oriented Developments in Portland, Oregon, Area
Authors: Dill Jennifer
Published: December 2008

Many regions throughout the United States are turning to various smart growth concepts, including transit-oriented development (TOD), to address a variety of concerns. Public agencies in the Portland, Oregon, region were early adopters of policies to promote TOD. More than 300 residents of TODs near four rail stations in the Portland area were surveyed about their travel behavior. The neighborhoods were selected to represent a range of styles of TODs while controlling for income. All the TODs surveyed were market-price units, most of them for sale, generally marketed to higher-income households. None of the neighborhoods completely satisfies agreed-on standards for good TODs: higher density, good land use mix, pedestrian friendly, and close to transit. The research found that households in the neighborhoods tend to be smaller than in the surrounding cities and often are without children. The residents of the surveyed TODs are not transit dependent, although they did commute by transit at a significantly higher rate than residents city-wide. The physical features and locations of the TODs did not appear to affect levels of transit commuting but did influence access mode to the station and transit use for noncommute travel. Distance to a rail station and parking pricing were important factors in commute mode choice. Respondents also reported using transit more than they had at their previous residences.
Geographic and Demographic Profiles of Morning Peak-Hour Commuters on Highways in North Metropolitan Atlanta, Georgia
Authors: Nelson Jennifer Indech , Guensler Randall , Li Hainan
Published: December 2008

During the summer of 2006, license plate data on morning peak-hour commuters were collected to assist with the creation of a potential participant pool for the congestion pricing phase of the Commute Atlanta (Atlanta, Georgia) instrumented-vehicle study. The Commute Atlanta study needed to identify census block groups with the highest probability of yielding study participants eligible for recruitment. Approximately 17,000 unique vehicle registration addresses in a six-county area were obtained from the license plates of vehicles observed traveling on several metropolitan Atlanta highways. The data collection enabled further geographic and demographic analyses of peak-hour commuters at the census block group level, providing new insight on limited-access highway commutersheds and demographic characteristics, such as the census block group income distribution, the travel modes, and the travel times of the highway-based commuters who contributed substantially to the region's traffic congestion and worsening air quality. Observation sites were located near the intersections of radial highways and a perimeter highway encircling Atlanta at a 10- to 12-mi radius from the downtown central business district. On average, commuters registered their vehicles (and presumably lived) 13 mi from the observation sites. The registration addresses were located a mean straight-line distance of 4.2 mi from the centerlines of the highways on which they were spotted. Demographically, highway commuter households had incomes 14.4% higher than the average household income, although this percentage varied by observation site. They were less likely to carpool or use nonautomobile forms of transportation on their journey to work, but they were more likely to work at home. Highway commuters were also more likely to report longer travel times to work than their neighbors in the census survey. These findings have implications for congestion pricing and related equity concerns.
Market Segmentation Analysis using Attitudes toward Transportation
Authors: Beirão Gabriela , Cabral José Sarsfield
Published: December 2008

Traveler attitudes and preferences as well as demographic variables are important components of travel behavior. By using travel attitudes, factor and cluster analyses were conducted to segment the sample. Six distinct groups were extracted: transit enthusiasts, anxious status seekers, carless riders, green cruisers, frugal travelers, and obstinate drivers. The segments showed unique combinations of attitudes with distinct travel behaviors and various degrees of intention to use public transportation. Gender differences were then investigated, and the results suggest that women and men exhibit differences in attitudes, preferences, and behaviors. The design of strategies to promote alternatives to car use should target the market segments that are most motivated to change, focusing on the attitudes that can induce a change, such as pro transit or sensibility to the environment.
Economic Impact of Traffic Incidents on Businesses
Authors: Khattak Asad J. , Fan Yingling , Teague Corey
Published: December 2008

Incidents and the resulting congestion on Interstate highways add uncertainty to travel times, imposing significant costs on business operations and regional economic development. This paper describes the results of an effort to quantify the economic impact of traffic incidents on North Carolina's Interstate facilities. The businesses to be interviewed were carefully chosen on the basis of their substantial shipping needs. Analyses of 29 selected businesses, including carriers, were conducted and showed an average hourly cost of unexpected delay of $145 to the businesses surveyed (2005 dollars). A more focused analysis by sector and region showed that various types of businesses and regions differ in their sensitivities to unexpected congestion. Of the industrial sectors sampled, transportation and warehousing had the highest hourly costs, followed by the retail trade and manufacturing sectors. Case studies further showed that although a majority used information technology to track shipments, few businesses sought preshipment traffic information or were aware of the traffic information services available. The businesses surveyed generally expressed a desire for better communication and information services from the state department of transportation. It is clear from this study that businesses incur costs because of unexpected delays on the Interstate system, adding to the cost of production. The implications of the results are discussed.
Modeling Driver Behavior within a Signalized Intersection Approach Decision–Dilemma Zone
Authors: Rakha Hesham , Amer Ahmed , El-Shawarby Ihab
Published: December 2008

This study uses data gathered in a field test on 60 test participants to develop models that characterize driver brake perception–reaction times (PRTs), brake times, and stop–go decisions at the onset of a yellow indication at a high-speed signalized intersection approach. The study demonstrates that driver PRTs are influenced only by the driver's time to intersection (TTI) at the onset of the yellow indication. The driver PRT is found to increase linearly with TTI and is not affected by the vehicle speed (in the range of 54 to 88 km/h), driver gender, or driver age. In the case of stop–go behavior, the older driver (≥65 years of age) dilemma zone is wider, ranging from a TTI of 4.81 to 1.66 s versus 4.90 to 2.87 s for the younger age group. Female drivers are more likely to stop than male drivers and tend to have a dilemma zone that is closer to the intersection. Finally, the study demonstrates that dilemma zone control systems should consider a dilemma zone from 5.0 to 1.5 s instead of the current state of practice of 5.5 to 2.5 s to capture all potential driver age and gender groups.
Driver Performance at Two-Way Stop-Controlled Intersections on Divided Highways
Authors: Bao Shan , Boyle Linda Ng
Published: December 2008

The goal of this study is to examine differences in driving performance at rural expressway intersections with respect to age (younger, middle-aged, and older) and intersection (high- and low-crash area). Such intersections occur where a median-divided highway meets a two-lane, stop-controlled minor road. One intersection was identified as a high-crash area with horizontal curves; the other one was a low-crash area with no curves. All participants were asked to perform three driving maneuvers (i.e., going straight across, making a left and a right turn) from the two-lane minor roads. Age and intersection differences immediately before entering and within these intersections were examined. Sixty drivers participated in the study and were divided evenly between the younger (18 to 25), middle-aged (35 to 55), and older (65 to 80) groups. Data for each participant were collected from an on-road study in an instrumented vehicle. Results showed that both older and younger drivers were likely to run stop signs and less likely to yield at medians when compared with middle-aged drivers. The effect of age difference on driving performance before intersection entry was consistent with previous studies. Middle-aged drivers approached the high-crash intersection with significantly less brake pedal differential time and were less likely to run stop signs compared with actions by drivers in other age groups. Higher traffic volume and more complicated road geometry at the high-crash intersection may be factors contributing to the differences observed.
Impact of Drug Plan Management Policies in Canada: A Systematic Review
Authors: Morrison Alena , MacKinnon Neil J. , Hartnell Nicole R. , McCaffrey Karen J.
Published: December 2008

Background/objective:

In Canada, pharmaceutical expenditures require an increasing proportion of total health care dollars. Drug plan managers use various policies to manage medication use and control costs, but these policies can have unintended consequences. The objective of this systematic review is to evaluate the impact of drug policies on economic, clinical and humanistic (quality of life or satisfaction) outcomes.

Methods:

Articles in which the primary objective was to evaluate the impact of a drug policy tool or technique in Canada and that measured one or more economic, clinical or humanistic outcomes were considered for inclusion. Studies were excluded if they were based in institutions or not published in peer-reviewed journals. The search process included searching 9 electronic databases, searching the reference lists of identified articles and working papers and contacting drug policy researchers. Studies were assessed for quality and suitability for meta-analysis. We performed a qualitative synthesis of the study design, study sample and outcomes.

Results:

Thirty-five articles satisfied the inclusion criteria. Most ( n= 25, 71%) determined that drug policies reduced the costs, utilization or both of the studied drug therapy. Only 13 studies (37%) measured the impact of the drug policy on the cost or utilization of medical care, and the impact of the policy was favourable in only 4 of these cases. Six studies (17%) evaluated the impact of the policy on clinical outcomes; none reported a favourable impact. No studies evaluated the impact of the drug policy on humanistic outcomes.

Discussion:

Although the drug policies in most of the studies included in this systematic review did achieve the desired goal of reducing drug costs, utilization or both, the impact on other outcomes was seldom examined. In the 6 studies in which clinical outcomes were included in the evaluation framework, the impact was inconclusive. Humanistic outcomes have been completely excluded from evaluations to date.
Génesis de Nódulos de Cuarzo en el Paleozoico de la Ibérica (Rama Aragonesa)
Authors: Navas A. , Tena J.
Published: December 2008

En formaciones samíticas y pelíticas del Paleozoico inferior de la Rama Aragonesa de la Cordillera Ibérica se generan nódulos de sílice que son apreciables a escala microscópica y mesoscópica. Con formas subesféricas y/o elipsoidales, tienen origen diagenético y están constituídos por asociaciones en mosaico de cristales de cuarzo de muy distinto tamaño y hábito cristalino. Se ha observado una relación bastante estrecha entre características tectónicas y alineaciones y orientación de los nódulos, y se han comprobado distintas etapas en su desarrollo, desde la formación de un mosaico microcristalino hasta la inferida reorientación y anastomosamiento de cristales preformados que dan lugar a un monocristal.
Implicaciones de la zona Ossa-Morena y dominios equivalentes en el modelo geodinámico de la Cadena Hercinica europea
Authors: Castro A.
Published: December 2008

La zona Ossa-Morena (ZOM) del hercínico peninsular posee unas características peculiares que la diferencian netamente de los otros dominios internos de la Cadena. Se trata de un dominio cortical (microcontinente ?) adosado a la corteza de la Zona Centro-Ibérica (ZCI) desde el Paleozoico Inferior. Durante la colisión continental hercínica (Palezoico Superior) la ZOM responde de diferente forma que las zonas adyacentes (ZCI) debido a su diferente constitución (menor espesor) y peculiar evolución prehercínica (rifting ordovícico). Esta zona y sus equivalentes en otros dominios del hercínico peninsular y europeo, tienen fuertes implicaciones en el desarrollo del orógeno hercínico. Parte de la corteza continental de la ZOM fue, junto con la corteza oceánica desarrollada localmente en su interior durante el rifting ordovícido, obducida sobre los dominios internos (ZCI) en zonas de colisión frontal (e.g. NW peninsular y Macizo Céntral Francés) y fuertemente estirada en zonas de colisión oblicua (e.g. ZOM del SW peninsular y dominios norarmoricanos).
Las ignimbritas del complejo volcánico Coranzuli (Puna Argentina-Andes Centrales)
Authors: Seggiaro R. , Gorustovich S. A. , Martí J.
Published: December 2008

El Coranzuli es uno de los grandes complejos volcánicos que representan el remate final de las Cadenas Volcánicas Transversales de la Puna Argentina, en los Andes Centrales. Se trata de un complejo volcánico del Mioceno superior situado a los 66º 15' W 23º S en el NW de Argentina en la provincia de Jujuy, en la intersección entre dos fallas regionales de dirección NE-SW y NW-SE, respectivamente. La actividad eruptiva se caracterizó por la existencia de, al menos, cuatro erupciones ignimbríticas que produjeron cuatro diferentes mantos ignimbríticos. Se trata de ignimbritas bien soldadas, muy ricas en cristales, pobre en fragmentos líticos y que presentan un contenido en fragmentos pumíticos de moderado a alto. El volumen total que representan estas ignimbritas supera los 650 km3. Los datos preliminares indican que el magma juvenil deriva de una cámara magmática homogénea no zonada. Las características de emplazamiento de estas ignimbritas, así como la falta de depósitos plinianos de caída en la base o intercalados entre las ignimbritas sugieren que las erupeiones se desarrollaron rápidamente en unas proporciones masivas.
Estratigrafía y sedimentología del Muschelkalk inferior del dominio Monrserrat-Llobregat (Catalanides)
Authors: Ramon X. , Calvet F.
Published: December 2008

La evolución sedimentaria del Muschelkalk inferior de las cadenas costero catalanas se caracteriza por una primera secuencia de profundización, seguida por una segunda secuencia de somerización, constituída por pequeños ciclos somerizantes. Las dos secuencias están separadas por una discontinuidad estratigráfica de carácter regional.
El tramo superior de la primera secuencia está dolomitizado por procesos de dolomitización secundaria él partir de la discontinuidad estratigráfica regional; en otros dominios de los Catalánides. la dolomitización puede afectar a casi toda la secuencia. La segunda secuencia está constituída por dolomías de tipo primario. El Muschelkalk inferior del dominio Montseny-Llobregat se diferencia del resto de los Catalánides, principalmente por la existencia, en la secuencia de profundización, de cuatro rupturas sedimentarias interpretadas como superficies karstificadas intra-Muschelkalk. Todo el Muschelkalk inferior se desarrolla en facies mareales en un contexto de rampa carbonatada tipo homoclinal ramp. El estudio palinológico confirma una edad Anisiense medio-superior.
Kinetic and morphological differentiation of Ettringites in plain and blended Portland cements using Metakaolin and the ASTM C 452-68 test. Part I: kinetic differentiation
Authors: Talero R.
Published: December 2008

In this first part of the study, the results obtained in prior research with XRD and SEM, as well as the Le Chatelier-Ansttet test were confirmed with the ASTM C 452-68 test. To this end, 20%, 30% and 40% metakaolin (MK) was added to ten Portland cements, six OPCs and four SRPCs. Both the ten plain PCs and the 30 metakaolin (MK) blends were tested for two years under ASTM C 452-68 specifications, determining not only the percentage increase in length, ΔL(%), of the specimens, but also the sulphate content in the curing water. Other parameters studied included: chemical analysis of the cementitious materials used and specific properties of some of the cements tested.The experimental results, ΔL(%) versus time, re-confirmed that the formation rate of ettringite from the reactive alumina, Al2O3r-, present in the pozzolan must be substantially higher than the formation rate of ettringite from the C3A present in the PC. This was verified by the variation of the sulphate content in the specimen curing water throughout the test. In light of those findings, in this article these two types of ettringite are denominated rapid forming ettringite or ett-rf, and slow forming ettringite or ett-lf.
Effect of paint on vapour resistivity in plaster
Authors: De Villanueva L.
Published: December 2008

The vapour resistivity of plaster coatings such as paint and their effectiveness as water repellents were studied in several types of plaster. To this end, painted, unpainted and pigmented specimens were tested. Experimental values were collected on diffusion and vapour permeability, or its inverse, water vapour resistivity.The data obtained were very useful for evaluating moisture exchange between plaster and the surrounding air, both during initial drying and throughout the life of the material. They likewise served as a basis for ensuring the proper evacuation of water vapour in walls, and use of the capacity of the porous network in plaster products to regulate moisture content or serve as a water vapour barrier to avoid condensation.Briefly, the research showed that pigments, water-based paints and silicon-based water repellents scantly raised vapour resistance. Plastic paints, enamels and lacquers, however, respectively induced five-, ten- and twenty-fold increases in vapour resistivity, on average.
Development of cross‐linked starch microcellular foam by solvent exchange and reactive supercritical fluid extrusion
Authors: Patel Sameerkumar , Venditti Richard A. , Pawlak Joel J. , Ayoub Ali , Rizvi Syed S. H.
Published: December 2008

Starch microcellular foams (SMCFs) are prepared by pore preserving drying or formation processes and contain pores in the micron size range. SMCFs have high specific surface area and are useful for applications such as opacifying pigments or as adsorbent materials. The objective of this research was to determine how the processing conditions and use of a crosslinking agent would affect the foam structure and properties. SMCFs (crosslinked and uncrosslinked) were prepared from molded aquagels and carbon dioxide extrusion processes separately and then solvent exchanged. Extruded samples showed macroscopic pores whereas samples from aquagels showed a much finer micropore structure. Aquagel‐based SMCF samples had lower density and higher brightness than did extruded samples. The starch foams with micropore structure had low density and high brightness. The solvent exchange process was the most important variable in generating a microcellular structure. Micropores and not macropores contributed to increased brightness of these materials. The brightness and density of the foams were found to be linearly related. Crosslinking with epichlorohydrin imparted significant water resistance to the extruded samples as evidenced in lower water swelling and higher contact angles. Equilibrium moisture content was correlated with the microporous structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis of poly(styrene‐co‐4‐vinylpyridine) microspheres via dispersion polymerization: Effect of the concentration of 4‐vinylpyridine
Authors: Han Hyekyung , Hong Chang Kook , Hong Jinho , Park Dong Wha , Shim Sang Eun
Published: December 2008

Amphiphilic copolymer microspheres of poly(styrene‐co‐4‐vinylpyridine) were prepared by dispersion polymerization in an alcohol/water medium. The synthesis of poly(styrene‐co‐4‐vinylpyridine) microparticles was successfully carried out, and the latexes had a spherical morphology with good monodispersity. The degree of conversion in the early stage of polymerization decreased with increasing 4‐vinylpyridine (4VP) monomer content, but the final conversions were similar (>95%). The copolymerization rate decreased with increasing 4VP content, and a broad particle size distribution was observed with 20 wt % 4VP because of the prolonged nucleation time. With the 4VP concentration increasing, the molecular weight of the copolymer microspheres decreased, and the glass‐transition temperature of the copolymers increased; this indicated that all the copolymers were random and homogeneous. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Time Dependent Differential Yield as a Scale‐up Parameter in Enzyme and Fermentation Reactors
Authors: Crooke P. S. , Tanner R. D. , Park D.‐H.
Published: December 2008

The yield function, for an enzyme‐substrate kinetic model of the system, is investigated. Considering Y to be a function of the substrate concentration S, its value as S → O+ is investigated.

In the “pseudo‐steady‐state domain,” this differential yield function is shown to be bounded above and below by yield functions that are obtained by using the Michaelis‐Menten and Briggs‐Haldane functions to relate the enzyme‐substrate concentration C to S. It is also shown that the yield constant, which is commonly used for enzyme and fermentation systems, is an integral average of the differential yield function. The average yield constant can be used to show consistency of data by relating the area above and below the average yield line when the yield function is plotted against the substrate concentration. The role of the dimensionless parameter, ε = km/E*, on the asymptotic yield, is also investigated. The mathematical results are demonstrated on experimental data for a horseradish‐peroxidase enzyme system and a gluconic acid fermentation process.
Oxygen Transfer in Membrane‐Ceramic Composite Materials For Immobilized‐Cell Monolithic Reactors
Authors: Kornfield Julia , Stephanopoulos Gregory , Voecks G. E.
Published: December 2008

A novel bioreactor concept is described for facilitated gas‐liquid mass transfer, specifically oxygen supply, at low shear rates and low power input. The cross flow monolithic reactor is a single piece of ceramic consisting of continuous flow passages manifolded in a cross flow arrangement. Liquid medium circulates through the passages in one direction and gas circulates through the passages in an orthogonal direction; thus, the two streams are contacted across a large area of a porous ceramic, gas permeable membrane composite.

A test cell was designed and used to measure the rate of oxygen transfer across such a composite. High oxygen transfer rates (6.62g O2 × l−1 × hr−1), with minimal power requirements (estimated below 5 × 10−3 watts/l reactor volume), were found. This corresponds to a transfer efficiency of greater than 1000 kg O2/kW · hr, orders of magnitude greater than the values reported by Serieys, et al.14 due to the low flow rates and low pressure drops required in a cross flow monolith. This contacting configuration could be employed with highly aerobic, immobilized‐cell fermentations to enhance oxygen transfer rates with a parallel decrease of process power requirements.
Dual‐Functional Affinity Protein Purification
Authors: Ruaan R.‐C. , Blair J. B. , Shaeiwitz J. A.
Published: December 2008

A rapid, single stage purification scheme for the enzyme pyruvate kinase (PK), overproduced by a genetically altered strain of Saccharomyces cerevisiae, is presented. A single affinity adsorption, washing and elution stage using a novel dual‐functional polyacrylamide affinity gel produces 60% recovery of PK and purification to near homogeneity within a few hours. A second elution step increases the recovery to 77%, but does not enhance purification. The novel dual‐functional polyacrylamide affinity gel is a crosslinked matrix containing both Cibacron Blue F3G‐A and carboxylic acid groups, resulting in a higher fraction of accessible Cibacron Blue F3G‐A groups than Blue Sepharose CL‐6B. The significant purification achieved in a single stage is due in part to the large initial PK concentration in the recombinant yeast. However, the unique dual‐functional interaction between PK and the support surface greatly facilitates the one‐step purification. PK interacts with the pseudoaffinity ligand, Cibacron Blue F3G‐A, as well as the carboxylic acid groups on the gel support. This dual functional binding increases the strength of the PK‐gel binding and the selectivity for PK when binding is carried out below the pI of PK. Elution is accomplished under mild conditions, by raising the pH above the isoelectric pH of PK, making the interaction between PK and the carboxylic acid groups repulsive. The general applicability to other enzymes is demonstrated in the purification of 3‐phosphoglycerate kinase, initially present as 3–5% of the total intracellular protein, which is purified 13‐fold in a similar single stage operation.
Electrochromatography
Authors: Rudge S. R. , Ladisch M. R.
Published: December 2008

A review of some of the theoretical and practical aspects of chromatography and electrophoresis.

Models are generally considered either as stochastic or continuum in nature.
Detection of pathogenic E. coli O157:H7 by a hybrid microfluidic SPR and molecular imaging cytometry device
Authors: Zordan Michael D. , Grafton Meggie M. G. , Acharya Ghanashyam , Reece Lisa M. , Cooper Christy L. , Aronson Arthur I. , Park Kinam , Leary James F.
Published: December 2008

Current methods to screen for bacterial contamination involve using costly reagents such as antibodies or PCR reagents or time‐costly growth in cultures. There is need for portable, real‐time, multiplex pathogen detection technology that can predict the safety of food. Surface plasmon resonance (SPR) imaging is a sensitive, label‐free method that can detect the binding of an analyte to a surface by the changes in refractive index that occur upon binding. We have designed a hybrid microfluidic biochip to perform multiplexed detection of single‐celled pathogens using a combination of SPR and fluorescence imaging. The device consists of an array of gold spots, each functionalized with a capture biomolecule targeting a specific pathogen. This biosensor array is enclosed by a polydimethylsiloxane microfluidic flow chamber that delivers a magnetically concentrated sample to be tested. The sample is imaged by SPR on the bottom of the biochip and epi‐fluorescence on the top. The prototype instrument was successfully able to image antibody‐captured E. coli O157:H7 bacteria by SPR and fluorescence imaging. The efficiency of capture of these bacteria by the magnetic particles was determined using spectrophotometric ferric oxide absorbance measurements. The binding of the E. coli to each spot was quantified by measuring the percent of the gold spot area upon which the bacteria was bound and analyzed using NIH ImageJ software. This hybrid imaging approach of pathogenic E. coli detection coupled with an estimate of relative infectivity is shown to be a working example of a testing device for potential foodborne pathogens. © 2008 International Society for Advancement of Cytometry
Expanding the Size of Organometallic Nanostructures: A Hexanuclear (Cymene)Ru Cylinder with a Length of More Than 3 nm
Authors: Olivier Céline , Scopelliti Rosario , Severin Kay
Published: December 2008

Coordination cages based on organometallic half‐sandwich complexes are of interest, because they can display unique structures and host properties. This communication describes the synthesis and structure of a cylindrical nanostructure containing six (p‐cymene)RuII fragments. The complex was obtained by reaction of [(p‐cymene)RuCl2]2 with a novel C3‐symmetrical ligand containing a triarylamine core and three dihydroxypyridine groups in its periphery. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
[4+2]/HyBRedOx Approach to C‐Naphthyl Glycosides: Failure in the Projuglone Series and Reinvestigation of the HyBRedOx Sequence
Authors: Maingot Lucie , Vu Nguyen Quang , Collet Sylvain , Guingant André , Martel Arnaud , Dujardin Gilles
Published: December 2008

C‐Naphthyl glycosides displaying a 1,5‐difunctionality on the naphthalene ring that can undergo oxidation to bromonaphthoquinone are key intermediates in the synthesis of natural C‐aryl glycoside analogues. In this area, sugar‐modified derivatives are of specific interest, but their synthesis is challenging. The de novo access to such compounds has been investigated through a [4+2] heterocycloaddition route, previously validated in a model series. For this purpose, two new dienophiles, conveniently protected at the phenolic positions, were synthesized. From an extensive study of their reactivity towards a range of 4‐hetero‐substituted (“prosugar”) heterodienes, the expected heteroadducts were stereoselectively obtained in acceptable yields. Application of the hydroboration/reduction/oxidation sequence did not afford the target C‐glycosides from the reduced adducts. The negative effect of the conformational bias of the substrate on this tandem reaction is discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Binding and uptake of Aβ1‐42 by primary human astrocytes in vitro
Authors: Nielsen Henrietta M. , Veerhuis Robert , Holmqvist Bo , Janciauskiene Sabina
Published: December 2008

Clearance of the amyloid‐β peptide (Aβ) as a remedy for Alzheimer's disease (AD) is a major target in on‐going clinical trials. In vitro studies confirmed that Aβ is taken up by rodent astrocytes, but knowledge on human astrocyte‐mediated Aβ clearance is sparse. Therefore, by means of flow cytometry and confocal laser scanning microscopy (CLSM), we evaluated the binding and internalization of Aβ1‐42 by primary human fetal astrocytes and adult astrocytes, isolated from nondemented subjects (n = 8) and AD subjects (n = 6). Furthermore, we analyzed whether α1‐antichymotrypsin (ACT), which is found in amyloid plaques and can influence Aβ fibrillogenesis, affects the Aβ uptake by human astrocytes. Upon over night exposure of astrocytes to FAM‐labeled Aβ1‐42 (10 μM) preparations, (80.7 ± 17.7)% fetal and (52.9 ± 20.9)% adult Aβ‐positive astrocytes (P = 0.018) were observed. No significant difference was found in Aβ1‐42 uptake between AD and non‐AD astrocytes, and no influence of ApoE genotype on Aβ1‐42 uptake was observed in any group. There was no difference in the percentage of Aβ‐positive cells upon exposure to Aβ1‐42 (10 μM) combined with ACT (1,000:1, 100:1, and 10:1 molar ratio), versus Aβ1‐42 alone. CLSM revealed binding of Aβ1‐42 to the cellular surfaces and cellular internalization of smaller Aβ1‐42 fragments. Under these conditions, there was no increase in cellular release of the proinflammatory chemokine monocyte‐chemoattractant protein 1, as compared with nontreated control astrocytes. Thus, primary human astrocytes derived from different sources can bind and internalize Aβ1‐42, and fetal astrocytes were more efficient in Aβ1‐42 uptake than adult astrocytes. © 2008 Wiley‐Liss, Inc.
Oligodendrocyte positioning in cerebral cortex is independent of projection neuron layering
Authors: Tan Seong‐Seng , Kalloniatis Michael , Truong Hue‐Trung , Binder Michele D. , Cate Holly S. , Kilpatrick Trevor J. , Hammond Vicki E.
Published: December 2008

The factors affecting normal oligodendrocyte positioning in the cerebral cortex are unknown. Apart from the white matter, the highest numbers of oligodendrocytes in the rodent cortex are found in Layers V/VI, where the infragranular neurons normally reside. Few, if any, oligodendrocytes are normally found in the superficial cortical layers. To test whether or not this asymmetric positioning of oligodendrocytes is linked to the lamina positions of Layer V/VI projection neurons, mutant mice that cause neuronal layer inversion were examined. In three lines of mutant mice (Reeler, disabled‐1, and p35) examined, representing two different genetic signaling pathways, the oligodendrocyte distribution was altered from an asymmetric to a symmetric distribution pattern. Unlike cortical neurons that are inverted in these mutant mice, the lack of oligodendrocyte inversion suggests a decoupling of the genetic mechanisms governing neuronal versus oligodendrocyte patterning. We conclude that oligodendrocyte positioning is not linked to the layer positions of V/VI projection neurons. © 2008 Wiley‐Liss, Inc.