bluuebunny/crossref_metadata_2025 huggingface dataset:
SAMS: Stochastic Analysis With Minimal Sampling—A Fast Algorithm for Analysis and Design Under Uncertainty
Authors: Mawardi A. , Pitchumani R.
Published: June 2005

Design of processes and devices under uncertainty calls for stochastic analysis of the effects of uncertain input parameters on the system performance and process outcomes. The stochastic analysis is often carried out based on sampling from the uncertain input parameters space, and using a physical model of the system to generate distributions of the outcomes. In many engineering applications, a large number of samples—on the order of thousands or more—is needed for an accurate convergence of the output distributions, which renders a stochastic analysis computationally intensive. Toward addressing the computational challenge, this article presents a methodology of S̱tochastic A̱nalysis with M̱inimal S̱ampling (SAMS). The SAMS approach is based on approximating an output distribution by an analytical function, whose parameters are estimated using a few samples, constituting an orthogonal Taguchi array, from the input distributions. The analytical output distributions are, in turn, used to extract the reliability and robustness measures of the system. The methodology is applied to stochastic analysis of a composite materials manufacturing process under uncertainty, and the results are shown to compare closely to those from a Latin hypercube sampling method. The SAMS technique is also demonstrated to yield computational savings of up to 90% relative to the sampling-based method.
Decomposition-Based Assembly Synthesis of Multiple Structures for Minimum Manufacturing Cost
Authors: Cetin Onur L. , Saitou Kazuhiro
Published: June 2005

An extension of decomposition-based assembly synthesis for structural modularity is presented where the early identification of shareable components within multiple structures is posed as an outcome of the minimization of estimated manufacturing costs. The manufacturing costs of components are estimated under given production volumes considering the economies of scale. Multiple structures are simultaneously decomposed, and the types of welded joints at component interfaces are selected from a given library, in order to minimize the overall manufacturing cost and the reduction of structural strength due to the introduction of joints. A multiobjective genetic algorithm is used to allow effective examination of trade-offs between manufacturing cost and structural strength. A new joint-oriented representation of structures combined with a “direct” crossover is introduced to enhance the efficiency of the search. A preliminary case study with two simplified aluminum space frame automotive bodies is presented to demonstrate that not all types of component sharing are economically justifiable under a certain production scenario.
Smart Actuator Positioning and Displacement Transmissibility in Serial and Parallel Robot Manipulators for Performance Enhancement
Authors: Rastegar J. , Yuan L. , Zhang J.
Published: June 2005

A method is presented for the evaluation of the transmissibility of displacement from smart (active) actuators integrated in the structure of robot manipulators to the manipulator joint and end-effector displacements. The method is based on studying the characteristics of the Jacobian of the mapping function between the two displacements for a given position of the robot manipulator. The developed method provides a tool for the determination of the positioning of smart actuators to provide maximum effectiveness in eliminating high harmonics of the joint or the end-effector motion. In robots with serial and parallel kinematics chains containing nonprismatic joints, due to the associated kinematics nonlinearity, if the joint motions were synthesized with low harmonic trajectories, the end-effector trajectory would still contain high harmonics of the joint motions. Alternatively, if the end-effector motion were synthesized with low harmonic components, due to the inverse kinematics nonlinearity, the actuated joint trajectories would contain a significant high harmonic component. As a result, the operating speed and tracking precision are degraded. By integrating smart materials based actuators in the structure of robot manipulators to provide small amplitude and high frequency motions, the high harmonic component of the actuated joint and/or the end-effector motions can be significantly reduced, thereby making it possible to achieve higher operating speed and tracking precision.
On the Design of a Passive Orthosis to Gravity Balance Human Legs
Authors: Fattah Abbas , Agrawal Sunil K.
Published: June 2005

This paper presents the design of a passive two leg orthosis to gravity balance human legs for use by subjects with both leg impairment. This design combines the use of auxiliary parallelograms to locate the center of mass along with springs to achieve balancing of each leg. The gravity balancing for all motions of the leg and pelvis is achieved by assuming the center of mass of the pelvis to be located on the line joining the two hip joints. A method for deriving the effectiveness of the gravity balancing due to practical limitations is also outlined. We illustrate the gravity balancing feature of the orthosis and examine the assumptions through computer simulations.
Perturbations Methods in Structural Dynamics and Applications to Cyclic Symmetric Domains
Authors: Lalanne Bernard
Published: June 2005

The design of components must take into account the irregularities inherent to the manufacturing process. When the structures have close eigenvalues, small mass and stiffness variations or the damping generate strong variations of the eigenmodes: these structures are then not robust. Here, their dynamics has been analyzed by perturbation method, in the dissipative cases and with coupling within a light fluid. A new perturbation method allows first order developments whatever the spectral density may be. Applications to many different vibration problems are presented: aeroelasticity, mode veering problem, maximum amplitude of forced response in cyclic symmetric domains, with detuning and/or mistuning, i.e., the most important reliability problem in turbomachinery. The results of this study provide a new estimation of the amplification factor and damping due to mistuning and aerodynamic coupling.
GRAVITOMAGNETISM IN BRANS-DICKE THEORY OF GRAVITY
Authors: BARROS A. , ROMERO C.
Published: June 2005

We discuss the gravitomagnetism in the context of Brans-Dicke theory of gravity. We obtain the equation of motion of a particle in terms of gravitoelectric and gravitomagnetic fields. Comparing the result obtained with that predicted by general relativity we show that the difference between the two theories lies in the gravitomagnetic force.
GREEN FUNCTIONS FOR TOPOLOGY CHANGE
Authors: PINTO-NETO NELSON , MARTIN JÉRÔME , SOARES ÍVANO DAMIÃO
Published: June 2005

We explicitly calculate the Green functions describing quantum changes of topology in Friedmann-Lemaître-Robertson-Walker Universes whose spacelike sections are compact but endowed with distinct topologies. The calculations are performed using the long wavelength approximation at second order in the gradient expansion. We argue that complex metrics are necessary in order to obtain a non-vanishing Green functions and interpret this fact as demonstrating that a quantum topology change can be viewed as a quantum tunneling effect. The result shows that the quantum topology changes in the direction of negatively curved hypersurfaces are strongly enhanced as time goes on, while transitions in the opposite direction are suppressed.
PROBLEM OF COSMOLOGICAL SINGULARITY AND ITS POSSIBLE RESOLUTION
Authors: MINKEVICH A. V.
Published: June 2005

The possible resolution of the problem of cosmological singularity in the framework of gauge theories of gravitation is discussed. Generalized cosmological Friedmann equations for homogeneous isotropic models filled by scalar fields and usual gravitating matter and its solutions are investigated. Regular bouncing character of cosmological models is analyzed.
POWER OF THE V-RECONSTRUCTION METHOD — A DIRECT AND INVERSE PROBLEM IN THE QUINTESSENTIAL COSMOLOGY
Authors: SZYDŁOWSKI MAREK
Published: June 2005

We demonstrate that the FRW model filled with dark energy fluid, satisfying the general form of the equation of state, p = w(z)ρ, can be reduced to the one-dimensional Hamiltonian flow. On the other hand we show that potential of this system can be reconstructed from the supernovae type Ia (SNIa) data. We show that the V-reconstruction method can be used to differentiate between dark energy models.
AN OPEN INFLATIONARY MODEL FOR DIMENSIONAL REDUCTION AND ITS EFFECTS ON THE OBSERVABLE PARAMETERS OF THE UNIVERSE
Authors: KARACA KORAY , BAYIN SELÇUK
Published: June 2005

Assuming that higher dimensions existed in the early stages of the universe where the evolution was inflationary, we construct an open, singularity-free, spatially homogeneous and isotropic cosmological model to study the effects of dimensional reduction that may have taken place during the early stages of the universe. We consider dimensional reduction to take place in a stepwise manner and interpret each step as a phase transition. By imposing suitable boundary conditions we trace their effects on the present day parameters of the universe.
COHOMOLOGICAL GAUGE THEORIES IN D > 4 WITH SPECIAL HOLONOMY Spin(7) AND G2
Authors: GEYER BODO
Published: June 2005

From Minkowskian 10D super Yang-Mills theory, by dimensional reduction and continuous Weyl-rotation, the 8D Euclidean, cohomological Spin(7)-invariant action [Formula: see text] is derived, by reduction to 7D the cohomological G2-invariant action [Formula: see text] with global SU(2) symmetry obtains. Compatibility of chirality with generalized self-duality and octonionic algebra is shown. Using the chiral primary operator and the 8D analogue of the Pontryagin invariant a cohomological extension of [Formula: see text] has been constructed.
HIDDEN SYMMMETRIES OF SOME BIANCHI A METRICS
Authors: VALENT GALLIANO
Published: June 2005

We show that most of the Bianchi A metrics with self-dual connection (hence self-dual Riemann curvature) have an integrable geodesic flow.
WEYL GEOMETRY QUANTIZATION IN SOLAR SYSTEM
Authors: MOYASSARI P. , JALALZADEH S.
Published: June 2005

In the present work we show that planetary mean distances can be calculated through considering the Weyl geometry. We interpret the Weyl gauge field as a vector field associated with the hypercharge of the particles and apply the gauge concept of the Weyl geometry. The results obtained are shown to agree with the observed orbits of all the planets and of the asteroid belt in the solar system, with some empty states.
METABOLIC ADAPTATION IN INDIGENOUS SIBERIAN POPULATIONS
Authors: Leonard William R. , Snodgrass J. Josh , Sorensen Mark V.
Published: June 2005

Previous research has suggested that arctic populations have elevated metabolic rates in response to their cold, marginal climate. Recent studies of indigenous Siberian groups have confirmed these earlier findings and have shed light on the mechanisms through which northern populations adapt to their environments. Indigenous Siberians show significant elevations in basal metabolic rate compared with reference values. Total energy expenditure is variable across Siberian groups and is correlated with levels of acculturation. Siberian populations appear to have adapted to cold stress through both short-term acclimatization and genetic adaptations, with thyroid hormones playing an important role in shaping metabolic responses. Elevated metabolic rates also have important consequences for health and may contribute to the low serum lipid levels observed in Siberian groups. Further research is needed to elucidate the underlying mechanisms of metabolic adaptation and their implications for ongoing health changes among indigenous Siberians.
RNA SILENCING SYSTEMS AND THEIR RELEVANCE TO PLANT DEVELOPMENT
Authors: Meins Frederick , Si-Ammour Azeddine , Blevins Todd
Published: June 2005

RNA silencing refers to a broad range of phenomena sharing the common feature that large, double-stranded RNAs or stem-loop precursors are processed to ca. 21–26 nucleotide small RNAs, which then guide the cleavage of cognate RNAs, block productive translation of these RNAs, or induce methylation of specific target DNAs. Although the core mechanisms are evolutionarily conserved, epigenetic maintenance of silencing by amplification of small RNAs and the elaboration of mobile, RNA-based silencing signals occur predominantly in plants. Plant RNA silencing systems are organized into a network with shared components and overlapping functions. MicroRNAs, and probably trans-acting small RNAs, help regulate development at the posttranscriptional level. Small interfering RNAs associated with transgene- and virus-induced silencing function primarily in defending against foreign nucleic acids. Another system, which is concerned with RNA-directed methylation of DNA repeats, seems to have roles in epigenetic silencing of certain transposable elements and genes under their control.
CENTROSOMES IN CELLULAR REGULATION
Authors: Doxsey Stephen , McCollum Dannel , Theurkauf William
Published: June 2005

Centrosomes, spindle pole bodies, and related structures in other organisms are a morphologically diverse group of organelles that share a common ability to nucleate and organize microtubules and are thus referred to as microtubule organizing centers or MTOCs. Features associated with MTOCs include organization of mitotic spindles, formation of primary cilia, progression through cytokinesis, and self-duplication once per cell cycle. Centrosomes bind more than 100 regulatory proteins, whose identities suggest roles in a multitude of cellular functions. In fact, recent work has shown that MTOCs are required for several regulatory functions including cell cycle transitions, cellular responses to stress, and organization of signal transduction pathways. These new liaisons between MTOCs and cellular regulation are the focus of this review. Elucidation of these and other previously unappreciated centrosome functions promises to yield exciting scientific discovery for some time to come.
OPPORTUNITIES FOR GENETIC INVESTIGATION AFFORDED BYACINETOBACTER BAYLYI, A NUTRITIONALLY VERSATILE BACTERIAL SPECIES THAT IS HIGHLY COMPETENT FOR NATURAL TRANSFORMATION
Authors: Young David M. , Parke Donna , Ornston L. Nicholas
Published: June 2005

The genetic and physiological properties of Acinetobacter baylyi strain ADP1 make it an inviting subject for investigation of the properties underlying its nutritional versatility. The organism possesses a relatively small genome in which genes for most catabolic functions are clustered in several genetic islands that, unlike pathogenicity islands, give little evidence of horizontal transfer. Coupling mutagenic polymerase chain reaction to natural transformation provides insight into how structure influences function in transporters, transcriptional regulators, and enzymes. With appropriate selection, mutants in which such molecules have acquired novel function may be obtained. The extraordinary competence of A. baylyi for natural transformation and the ease with which it expresses heterologous genes make it a promising platform for construction of novel metabolic systems. Steps toward this goal should take into account the complexity of existing pathways in which transmembrane trafficking plays a significant role.
Functional Characterization of Des-IGF-1 Action at Excitatory Synapses in the CA1 Region of Rat Hippocampus
Authors: Ramsey Melinda M. , Adams Michelle M. , Ariwodola Olusegun J. , Sonntag William E. , Weiner Jeff L.
Published: June 2005

Insulin-like growth factor-1 (IGF-1) and growth hormone play a major role in the growth and development of tissues throughout the mammalian body. Plasma IGF-1 concentrations peak during puberty and decline with age. We have determined that chronic treatments to restore plasma IGF-1 concentrations to adult levels attenuate spatial learning deficits in aged rats, but little is known of the acute actions of IGF-1 in the brain. To this end, we utilized hippocampal slices from young Sprague-Dawley rats to characterize the acute effects of des-IGF-1 on excitatory synaptic transmission in the CA1 region. We observed a 40% increase in field excitatory postsynaptic potential (fEPSP) slope with application of des-IGF-1 (40 ng/ml) and used whole cell patch-clamp recordings to determine that this enhancement was due to a postsynaptic mechanism involving α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) but not N-methyl-d-aspartate receptors. Furthermore, the enhancement was completely blocked by the broad-spectrum tyrosine kinase inhibitor, genistein (220 μM), and significantly reduced by the PI3K blockers wortmannin (1 μM) and 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (10 μM), suggesting that the effect was predominantly dependent on PI3K activation. This characterization of the acute actions of des-IGF-1 at hippocampal excitatory synapses may provide insight into the mechanism by which long-term increases in plasma IGF-1 impart cognitive benefits in aged rats. Increases in AMPA receptor-mediated synaptic transmission may contribute directly to cognitive improvement or initiate long-term changes in synthesis of proteins such as brain-derived neurotrophic factor that are important to learning and memory.
Blood Pressure in Adulthood and Life Expectancy With Cardiovascular Disease in Men and Women
Authors: Franco Oscar H. , Peeters Anna , Bonneux Luc , de Laet Chris
Published: June 2005

Limited information exists about the consequences of hypertension during adulthood on residual life expectancy with cardiovascular disease. We aimed to analyze the life course of people with high blood pressure levels at age 50 in terms of total life expectancy and life expectancy with and without cardiovascular disease compared with normotensives. We constructed multistate life tables for cardiovascular disease, myocardial infarction, and stroke using data from 3128 participants of the Framingham Heart Study who had their 50th birthday while enrolled in the study. For the life table calculations, we used hazard ratios for 3 transitions (healthy to death, healthy to disease, and disease to death) by categories of blood pressure level and adjusted by age, sex, and confounders. Irrespective of sex, 50-year-old hypertensives compared with normotensives had a shorter life expectancy, a shorter life expectancy free of cardiovascular disease, myocardial infarction, and stroke, and a longer life expectancy lived with these diseases. Normotensive men (22% of men) survived 7.2 years (95% confidence interval, 5.6 to 9.0) longer without cardiovascular disease compared with hypertensives and spent 2.1 (0.9 to 3.4) fewer years of life with cardiovascular disease. Similar differences were observed in women. Compared with hypertensives, total life expectancy was 5.1 and 4.9 years longer for normotensive men and women, respectively. Increased blood pressure in adulthood is associated with large reductions in life expectancy and more years lived with cardiovascular disease. This effect is larger than estimated previously and affects both sexes similarly. Our findings underline the tremendous importance of preventing high blood pressure and its consequences in the population.
Periodontal Disease and Coronary Heart Disease
Authors: Beck James D. , Eke Paul , Heiss Gerardo , Madianos Phoebus , Couper David , Lin Dongming , Moss Kevin , Elter John , Offenbacher Steven
Published: June 2005

Background—

Results from studies relating periodontal disease to cardiovascular disease have been mixed. Residual confounding by smoking and use of clinical measures of periodontal disease rather than measures of infection have been 2 major criticisms. The aims of this study were to investigate relationships between prevalent coronary heart disease (CHD) and 2 exposures, (1) clinical periodontal disease and (2) IgG antibodies to 17 oral organisms, and to evaluate the role of smoking in these relationships.

Methods and Results—

Our study is based on a subset of participants in the Atherosclerosis Risk in Communities (ARIC) Study, who received a complete periodontal examination during visit 4 (1996–1998). The exposures were periodontal status and serum IgG antibody levels against 17 periodontal organisms, and the outcome was prevalent CHD at visit 4. Multivariable analyses indicate that periodontal status is not significantly associated with CHD in either ever smokers or never smokers. Similar analyses evaluating antibodies indicate that high antibodies (above the median) to
Treponema denticola
(odds ratio [OR]=1.7; 95% CI, 1.2 to 2.3),
Prevotella intermedia
(OR=1.5; 95% CI, 1.1 to 2.0),
Capnocytophaga ochracea
(OR=1.5; 95% CI, 1.1 to 2.1), and
Veillonella parvula
(OR=1.7; 95% CI, 1.2 to 2.3) are significantly associated with CHD among ever smokers, whereas
Prevotella nigrescens
(OR=1.7; 95% CI, 1.1 to 2.6),
Actinobacillus actinomycetemcomitans
(OR=1.7; 95% CI, 1.2 to 2.7), and
Capnocytophaga ochracea
(OR=2.0; 95% CI, 1.3 to 3.0) were associated with CHD among never smokers.

Conclusions—

Clinical signs of periodontal disease were not associated with CHD, whereas systemic antibody response was associated with CHD in ever smokers and never smokers. These findings indicate that the quality and quantity of the host response to oral bacteria may be an exposure more relevant to systemic atherothrombotic coronary events than clinical measures.
Prediction of Myocardial Infarction by N-Terminal-Pro-B-Type Natriuretic Peptide, C-Reactive Protein, and Renin in Subjects With Cerebrovascular Disease
Authors: Campbell Duncan J. , Woodward Mark , Chalmers John P. , Colman Samuel A. , Jenkins Alicia J. , Kemp Bruce E. , Neal Bruce C. , Patel Anushka , MacMahon Stephen W.
Published: June 2005

Background—

B-type natriuretic peptide (BNP), C-reactive protein (CRP), and renin are elevated in persons at risk for cardiovascular disease. However, data that directly compare these markers in the prediction of myocardial infarction (MI) are limited.

Methods and Results—

N-terminal-proBNP (NT-proBNP), CRP, and renin were measured in baseline blood samples from a nested case-control study of the 6105 participants of the Perindopril Protection Against Recurrent Stroke Study (PROGRESS), a placebo-controlled study of a perindopril-based blood pressure-lowering regimen among individuals with previous stroke or transient ischemic attack. Each of 206 subjects who experienced MI, either fatal or nonfatal, during a mean follow-up of 3.9 years was matched to 1 to 3 control subjects. Most MI cases (67%) occurred in subjects without a history of coronary heart disease. NT-proBNP, CRP, and renin each predicted MI; the odds ratio for subjects in the highest compared with the lowest quarter was 2.2 (95% CI, 1.3 to 3.6) for NT-proBNP, 2.2 (95% CI, 1.3 to 3.6) for CRP, and 1.7 (95% CI, 1.1 to 2.8) for renin. NT-proBNP and renin, but not CRP, remained predictors of MI after adjustment for all other predictors, including LDL and HDL cholesterol levels. Individuals with both NT-proBNP and renin in their highest quarters had 4.5 times the risk of MI compared with subjects with both biological markers in their lowest quarters.

Conclusions—

NT-proBNP and renin, but not CRP, are independent predictors of MI risk after stroke or transient ischemic attack, providing information additional to that provided by classic risk factors, and may enable more effective targeting of MI prevention strategies.
Representation of Water Table Dynamics in a Land Surface Scheme. Part I: Model Development
Authors: Yeh Pat J-F. , Eltahir Elfatih A. B.
Published: June 2005

Most of the current land surface parameterization schemes lack any representation of regional groundwater aquifers. Such a simplified representation of subsurface hydrological processes would result in significant errors in the predicted land surface states and fluxes especially for the shallow water table areas in humid regions. This study attempts to address this deficiency. To incorporate the water table dynamics into a land surface scheme, a lumped unconfined aquifer model is developed to represent the regional unconfined aquifer as a nonlinear reservoir, in which the aquifer simultaneously receives the recharge from the overlying soils and discharges runoff into streams. The aquifer model is linked to the soil model in the land surface scheme [Land Surface Transfer Scheme (LSX)] through the soil drainage flux. The total thickness of the unsaturated zone varies in response to the water table fluctuations, thereby interactively coupling the aquifer model with the soil model. The coupled model (called LSXGW) has been tested in Illinois for an 11-yr period from 1984 to 1994. The results show reasonable agreements with the observations. However, there are still secondary biases in the LSXGW simulation partially resulting from not accounting for the spatial variability of water table depth. The issue of subgrid variability of water table depth will be addressed in a companion paper.
Representation of Water Table Dynamics in a Land Surface Scheme. Part II: Subgrid Variability
Authors: Yeh Pat J-F. , Eltahir Elfatih A. B.
Published: June 2005

A lumped unconfined aquifer model has been developed and interactively coupled to a land surface scheme in a companion paper. Here, the issue of the representation of subgrid variability of water table depths (WTDs) is addressed. A statistical–dynamical (SD) approach is used to account for the effects of the unresolved subgrid variability of WTD in the grid-scale groundwater runoff. The dynamic probability distribution function (PDF) of WTD is specified as a two-parameter gamma distribution based on observations. The grid-scale groundwater rating curve (i.e., aquifer storage–discharge relationship) is derived statistically by integrating a point groundwater runoff model with respect to the PDF of WTD. Next, a mosaic approach is utilized to account for the effects of subgrid variability of WTD in the grid-scale groundwater recharge. A grid cell is categorized into different subgrids based on the PDF of WTD. The grid-scale hydrologic fluxes are computed by averaging all of the subgrid fluxes weighted by their fractions. This new methodology combines the strengths of the SD approach and the mosaic approach. The results of model testing in Illinois from 1984 to 1994 indicate that the simulated hydrologic variables (soil saturation and WTD) and fluxes (evaporation, runoff, and groundwater recharge) agree well with the observations. Because of the paucity of the large-scale observations on WTD, the development of a practical parameter estimation procedure is indispensable before the global implementation of the developed scheme of water table dynamics in climate models.
Diagnosing Natural Variability of North Atlantic Water Masses in HadCM3
Authors: Haines Keith , Old Chris
Published: June 2005

A study of thermally driven water mass transformations over 100 yr in the ocean component of the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) is presented. The processes of surface-forced transformations, subduction and mixing, both above and below the winter mixed layer base, are quantified. Subtropical Mode Waters are formed by surface heat fluxes and subducted at more or less the same rate. However, Labrador Seawater and Nordic Seawater classes (the other main subduction classes) are primarily formed by mixing within the mixed layer with very little formation directly from surface heat fluxes. The Subpolar Mode Water classes are dominated by net obduction of water back into the mixed layer from below.

Subtropical Mode Water (18°C) variability shows a cycle of formation by surface fluxes, subduction ∼2 yr later, followed by mixing with warmer waters below the winter mixed layer base during the next 3 yr, and finally obduction back into the mixed layer at 21°C, ∼5 yr after the original formation. Surface transformation of Subpolar Mode Waters, ∼12°C, are led by surface transformations of warmer waters by up to 5 yr as water is transferred from the subtropical gyre. They are also led by obduction variability from below the mixed layer, by ∼2 yr. The variability of obduction in Subpolar Mode Waters also appears to be preceded, by 3–5 yr, by variability in subduction of Labrador Sea Waters at ∼6°C. This supports a mechanism in which southward-propagating Labrador seawater anomalies below the subpolar gyre can influence the upper water circulation and obduction into the mixed layer.
A Comparison of SNOTEL and GHCN/CRU Surface Temperatures with Free-Air Temperatures at High Elevations in the Western United States: Data Compatibility and Trends
Authors: Pepin N. C. , Losleben M. , Hartman M. , Chowanski K.
Published: June 2005

This paper compares high-elevation surface temperatures based on the Global Historical Climate Network/Climatic Research Unit (GHCN/CRU) and snow telemetry (SNOTEL) datasets, with simultaneous free-air equivalent temperatures, interpolated from NCEP–NCAR reanalysis. Mean monthly temperature anomalies from 1982 to 1999 are examined for 60 SNOTEL and 296 GHCN/CRU sites at elevations over 500 m with relatively homogenous records. The surface/free-air temperature difference ΔT (Ts − Ta) is calculated for both the SNOTEL and GHCN/CRU datasets. Topography influences the correlation between surface and free-air temperature anomalies. Physically realistic diurnal and seasonal changes in ΔT\E are illustrated. Systematic secular trends in surface temperatures, free-air temperatures, and ΔT are revealed, but the sign and magnitude of change depends on location, meaning that regional signals are weak. The Ts trends are positive for most GHCN and CRU sites, and for SNOTEL sites at night. Daytime cooling in the SNOTEL network reduces the mean daily warming trend. The Ta trends are consistently positive for both networks and are often larger than Ts. Thus mean ΔT trends are negative for both datasets. The smaller sample size in the SNOTEL dataset means that error estimates for regional signals are much wider than for the GHCN/CRU dataset. Trend difference maps identify potentially anomalous SNOTEL records. Trends show no correlation with elevation and topography. Surface trends show higher variability and account for most of the uncertainty in ΔT trends. Sensitivity of trends to time period is also discussed. Such changes in the free-air/surface temperature difference may indicate change in the energy balance of mountain areas.
Role of the Drake Passage in Controlling the Stability of the Ocean’s Thermohaline Circulation
Authors: Sijp Willem P. , England Matthew H.
Published: June 2005

The role of a Southern Ocean gateway in permitting multiple equilibria of the global ocean thermohaline circulation is examined. In particular, necessary conditions for the existence of multiple equilibria are studied with a coupled climate model, wherein stable solutions are obtained for a range of bathymetries with varying Drake Passage (DP) depths. No transitions to a Northern Hemisphere (NH) overturning state are found when the Drake Passage sill is shallower than a critical depth (1100 m in the model described herein). This preference for Southern Hemisphere sinking is a result of the particularly cold conditions of the Antarctic Bottom Water (AABW) formation regions compared to the NH deep-water formation zones. In a shallow or closed DP configuration, this forces an exclusive production of deep/bottom water in the Southern Hemisphere. Increasing the depth of the Drake Passage sill causes a gradual vertical decoupling in Atlantic circulation, removing the influence of AABW from the upper 2000 m of the Atlantic Ocean. When the DP is sufficiently deep, this shifts the interaction between a North Atlantic Deep Water (NADW) cell and an AABW cell to an interaction between an (shallower) Antarctic Intermediate Water cell and an NADW cell. This latter situation allows transitions to a Northern Hemisphere overturning state.
Tropical Atlantic Moisture Flux, Convection over Northeastern Brazil, and Pertinence of the PIRATA Network*
Authors: Durand Bruno , Servain Jacques , Laurent Henri , Machado Luiz A. T.
Published: June 2005

This study aims to examine the relationship between the tropical Atlantic latent heat flux and convective cloud coverage over northeast Brazil (NEB) during the four months of the main rainy season (February–May). The correlation with anomalies of these data is investigated, both without lag and with a 1-month lag (the heat flux in advance). In both cases, a significant positive correlation appears in the northwestern tropical Atlantic, and a significant negative correlation is obtained for a limited area off eastern NEB. These two correlation patterns are linked to anomalies in the trade wind intensity and in the meridional position of the intertropical convergence zone (ITCZ), which relate to the latent heat flux anomalies and NEB convective coverage anomalies, respectively. The positive correlation pattern is spread over a large part of the northern tropical Atlantic, whereas the negative correlation pattern is confined off NEB. This indicates the existence of different regional mechanisms in the tropical Atlantic basin. The impact of the Atlantic heat fluxes on NEB convection is somewhat different from the classical meridional dipole related to the SST variability. The analysis of the horizontal moisture flux shows that during flood years an additional meridional inflow balances the eastward loss, and the upward velocity reinforced over NEB contributes to intensify NEB convection. The positive correlation pattern indicates that the location of the northern branch of the Pilot Research moored Array in the Tropical Atlantic (PIRATA) moorings is pertinent to monitor the ocean–atmosphere interface parameters. The negative correlation pattern off NEB provides new support for the possible extension of the PIRATA array toward the Brazilian coast. Complementary results at 1-month lag and the real-time availability of the PIRATA data confirm the potential of NEB forecasting.
WSR-88D Radar, Tornado Warnings, and Tornado Casualties
Authors: Simmons Kevin M. , Sutter Daniel
Published: June 2005

The impact of the installation of Weather Surveillance Radar-1988 Doppler (WSR-88D) radars in the 1990s on the quality of tornado warnings and occurrence of tornado casualties is examined. This analysis employs a dataset of tornadoes in the contiguous United States between 1986 and 1999. The date of WSR-88D radar installation in each National Weather Service Weather Forecast Office is used to divide the sample. Tornado warnings improved after the installation of Doppler radar; the percentage of tornadoes warned for increased from 35% before WSR-88D installation to 60% after installation while the mean lead time on warnings increased from 5.3 to 9.5 min and the false alarm ratio fell slightly. A regression analysis of tornado casualties, which controls for the characteristics of a tornado and its path, reveals that expected fatalities and expected injuries were 45% and 40% lower for tornadoes occurring after WSR-88D radar was installed in the NWS Weather Forecast Office. This analysis also finds that expected casualties are significantly lower for tornadoes occurring during the day or evening than late at night throughout the sample, which provides indirect evidence of the life-saving effects of tornado warnings.
Diamonds, Blood, and Taxes
Authors: Snyder Richard , Bhavnani Ravi
Published: June 2005

This article addresses an important gap in research on the causes of civil war: the lack of a theory that explains why lootable resources like alluvial diamonds are linked to civil war in some cases and peace in others. To help fill this gap, we propose a revenue-centered theoretical framework that shifts the focus from rebels to rulers and states, situates rulers in the context of the institutional and economic constraints on their ability to earn revenue, and combines this focus on revenue with a focus on state spending. In countries rich in lootable resources, the ability of rulers to achieve political order depends on (1) the availability of nonlootable resources; (2) the mode of extraction of lootable resources, especially whether they are extracted by hard-to-tax artisans or, alternatively, by large, taxable industrial firms; and (3) patterns of state spending. This framework supplements widely used models of civil war that emphasize the state’s capacity to defeat an insurgency yet do not answer the important prior question of why state capacity varies so widely across resource-rich countries.
Scaling Up HIV Voluntary Counseling and Testing in Africa
Authors: Glick Peter
Published: June 2005

Although there is a widespread belief that scaling up HIV voluntary counseling and testing (VCT) programs in Africa will have large prevention benefits through reductions in risk behaviors, these claims are difficult to establish from existing evaluations of VCT. Considerations from behavioral models and the available data suggest that as VCT coverage expands, marginal program effects are likely to decline owing to changes in the degree of client selectivity, and that potential uptake among those at highest risk is uncertain. The article also assesses two other common perceptions about VCT in Africa: that a policy of promoting couples-oriented VCT would be more successful than one emphasizing individual testing and that VCT demand and prevention impacts will be enhanced where scaling up is accompanied by the provision of antiretroviral drugs.
Multiple sequence alignments of partially coding nucleic acid sequences
Authors: Stocsits Roman R , Hofacker Ivo L , Fried Claudia , Stadler Peter F
Published: June 2005

Background

High quality sequence alignments of RNA and DNA sequences are an important prerequisite for the comparative analysis of genomic sequence data. Nucleic acid sequences, however, exhibit a much larger sequence heterogeneity compared to their encoded protein sequences due to the redundancy of the genetic code. It is desirable, therefore, to make use of the amino acid sequence when aligning coding nucleic acid sequences. In many cases, however, only a part of the sequence of interest is translated. On the other hand, overlapping reading frames may encode multiple alternative proteins, possibly with intermittent non-coding parts. Examples are, in particular, RNA virus genomes.

Results

The standard scoring scheme for nucleic acid alignments can be extended to incorporate simultaneously information on translation products in one or more reading frames. Here we present a multiple alignment tool, codaln, that implements a combined nucleic acid plus amino acid scoring model for pairwise and progressive multiple alignments that allows arbitrary weighting for almost all scoring parameters. Resource requirements of codaln are comparable with those of standard tools such as ClustalW.

Conclusion

We demonstrate the applicability of codaln to various biologically relevant types of sequences (bacteriophage Levivirus and Vertebrate Hox clusters) and show that the combination of nucleic acid and amino acid sequence information leads to improved alignments. These, in turn, increase the performance of analysis tools that depend strictly on good input alignments such as methods for detecting conserved RNA secondary structure elements.
The polymorphic nature of the human dopamine D4 receptor gene: A comparative analysis of known variants and a novel 27 bp deletion in the promoter region
Authors: Szantai E , Szmola R , Sasvari-Szekely M , Guttman A , Ronai Z
Published: June 2005

Background

The human dopamine D4 receptor (DRD4) is a candidate gene of great interest in molecular studies of human personality and psychiatric disorders. This gene is unique in having an exceptionally high amount of polymorphic sites both in the coding and in the promoter region.

Results

We report the identification of a new 27 bp deletion starting 524 bp upstream of the initiation codon (27 bp del) of the dopamine D4 receptor (DRD4) gene, in the close vicinity of the -521C>T SNP. The presence of the 27 bp deletion leads to the misgenotyping of the -616C>G SNP by the Sau 96 I RFLP method, thus the genotype determination of the mutation is of additional importance. The frequency of this novel sequence variation is considerably low (allele frequency is = 0.16%), as no homozygotes, and only 3 heterozygote carriers were found in a healthy, unrelated Caucasian sample (N = 955).

Conclusion

Remarkably, the deleted region contains consensus sequences of binding sites for several known transcription factors, suggesting that the different alleles may affect the transcriptional regulation of the gene. A comparison of methods and results for the allelic variations of the DRD4 gene in various ethnic groups is also discussed, which has a high impact in psychiatric genetic studies.
A cluster randomized trial to assess the impact of opinion leader endorsed evidence summaries on improving quality of prescribing for patients with chronic cardiovascular disease: rationale and design [ISRCTN26365328]
Authors: Majumdar Sumit R , McAlister Finlay A , Tsuyuki Ross T
Published: June 2005

Background

Although much has been written about the influence of local opinion leaders on clinical practice, there have been few controlled studies of their effect, and almost none have attempted to change prescribing in the community for chronic conditions such as heart failure (HF) or ischemic heart disease (IHD). These two conditions are common and there is very good evidence about how to best prevent morbidity and mortality – and good evidence that quality of care is, in general, suboptimal. Practice audits have demonstrated that about one-half of eligible HF patients are prescribed ACE inhibitors (with fewer still reaching appropriate target doses) and less than one-third of patients with established IHD are prescribed statins (with many fewer reaching recommended cholesterol targets). It is apparent that interventions to improve quality of prescribing are urgently needed. We hypothesized that an intervention that consisted of patient-specific one-page evidence summaries, generated and then endorsed by local opinion leaders, would be able to change prescribing practices of community-based primary care physicians.

Methods (study design)

A pragmatic single-centre cluster randomized controlled trial comparing an opinion leader-based intervention to usual care for patients with HF or IHD. Randomization will be clustered at the level of the primary care physician; as the design effect is anticipated to be negligible, the unit of analysis will be the patient. Patients with HF or IHD (not receiving ACE inhibitors or statins, respectively) will be recruited from community pharmacies and allocated to intervention or usual care based on the randomization status of their primary care physician. The primary outcome is improvement in prescription of proven efficacious therapies for HF (ACE inhibitors) or IHD (statins) within 6 months of the intervention.

Conclusion

If the methods used in this intervention are found to improve prescribing practices, similar interventions could be designed for other chronic conditions dealt with in the outpatient setting.
Retinopathy of prematurity and risk factors: a prospective cohort study
Authors: Karna Padmani , Muttineni Jyotsna , Angell Linda , Karmaus Wilfried
Published: June 2005

Background

Increased survival of extremely low birth infants due to advances in antenatal and neonatal care has resulted in a population of infants at high risk of developing retinopathy of prematurity (ROP). Therapeutic interventions include the use of antenatal and postnatal steroids however, their effects on the severity of ROP is in dispute. In addition, it has not been investigated whether severe ROP is due to therapeutic interventions or due to the severity of illness. The aim of the present study was to assess the association between the incidence of severe retinopathy of prematurity (greater than stage 2 – International classification of ROP) and mechanical ventilation, oxygen therapy, gestational age, antenatal and postnatal steroids in extremely low birth weight infants.

Methods

Neonates admitted to the neonatal intensive care unit in Lansing, Michigan, during 1993–2000 were followed to determine factors influencing the development of severe retinopathy of prematurity. Ophthalmologic examinations were started at 6 weeks and followed until resolution. We used logistic regression to estimate the relative risk (odds ratio) associated with risk factors of ROP.

Results

Of the neonates with ≤ 1500 g birth weight, admitted to the neonatal intensive care unit, 85% (616/725) survived. Severe retinopathy of prematurity was detected in 7.8% of 576 neonates who had eye examinations. Neonates of lower gestational age (≤ 25 weeks and 26–28 weeks) had an increased odds ratio of 8.49 and 3.19 for the development of severe retinopathy of prematurity, respectively, compared to those 29 weeks and older. Late postnatal steroid treatment starting after 3 weeks of life showed 2.9-fold increased odds ratio, in particular administration for two weeks and more (OR: 4.09, 95% CI: 1.52–11.03). With increasing antenatal steroids courses the risk of severe retinopathy of prematurity decreased, however, it was not significant. Lower gestational age, dependence on ventilation, and use of postnatal steroids were intertwined. Simultaneous presence of these factors seems to indicate severe disease status.

Conclusion

Prolonged and late postnatal steroids treatment in very low birth weight infants may pose an increased risk for the development of severe retinopathy of prematurity; however, use of postnatal steroids may also be a marker for severity of illness. Further studies need to focus on biologic markers in the pathogenesis of retinopathy of prematurity and to better understand the influence of therapies.
Top 10 health care ethics challenges facing the public: views of Toronto bioethicists
Authors: Breslin Jonathan M , MacRae Susan K , Bell Jennifer , Singer Peter A ,   the University of Toronto Joint Centre for Bioethics Clinical Ethics Group
Published: June 2005

Background

There are numerous ethical challenges that can impact patients and families in the health care setting. This paper reports on the results of a study conducted with a panel of clinical bioethicists in Toronto, Ontario, Canada, the purpose of which was to identify the top ethical challenges facing patients and their families in health care. A modified Delphi study was conducted with twelve clinical bioethicist members of the Clinical Ethics Group of the University of Toronto Joint Centre for Bioethics. The panel was asked the question, what do you think are the top ten ethical challenges that Canadians may face in health care? The panel was asked to rank the top ten ethical challenges throughout the Delphi process and consensus was reached after three rounds.

Discussion

The top challenge ranked by the group was disagreement between patients/families and health care professionals about treatment decisions. The second highest ranked challenge was waiting lists. The third ranked challenge was access to needed resources for the aged, chronically ill, and mentally ill.

Although many of the challenges listed by the panel have received significant public attention, there has been very little attention paid to the top ranked challenge. We propose several steps that can be taken to help address this key challenge.