bluuebunny/crossref_metadata_2025 huggingface dataset:
The Political Determinants of International Trade: The Major Powers, 1907–1990
Authors: Morrow James D. , Siverson Randolph M. , Tabares Tressa E.
Published: May 2006

We test three arguments about the effect of international politics on trade flows. The first argument states that trade flows are greater between states with similar interests than those with dissimilar interests, the second that trade flows are greater in democratic dyads than nondemocratic dyads, and the third that trade flows are greater between allies. We examine trade flows between the major powers from 1907 to 1990. This period provides variation on all three independent variables of interest and allows us to separate the three arguments empirically. We estimate a gravity model of trade with the above political variables added. Our results demonstrate that joint democracy and common interests increase trade in a dyad, but alliances generally do not, even when controlling for polarity of the system.
The Effect of Economic Priorities on the Measurement of Value Change: New Experimental Evidence
Authors: Clarke Harold D. , Kornberg Allan , McIntyre Chris , Bauer-Kaase Petra , Kaase Max
Published: May 2006

The Euro-Barometer values battery has provided much of the empirical evidence for the thesis that a shift from materialist to postmaterialist values has occurred in advanced industrial societies over the past two decades. It has been argued, however, that this widely used instrument is seriously flawed because of its sensitivity to current economic conditions. We present data from experiments in Canada and Germany that tested the performance of the values battery in an era of joblessness. Analyses reveal that (1) substituting an unemployment statement for the standard inflation statement in the battery has major consequences for the classification of respondents as materialist or postmaterialist and (2) answers to the battery are conditioned by the interaction between its content and respondents' economic issue concerns. These findings support the argument that much of the shift from materialist to postmaterialist values recorded by the Euro-Barometer since the early 1980s is a measurement artifact.
The Illusion of Power and the Disruption of Moral Norms: Thucydides' Critique of Periclean Policy
Authors: Monoson S. Sara , Loriaux Michael
Published: May 2006

Scholars in both international relations and political theory have been turning their attention to Thucydides with increasing frequency but with dissimilar questions. We draw on both traditions of inquiry to reexamine Thucydides' view of Pericles. We argue that antithetical reasoning is present in the treatment of Pericles and is manifested in the opposition between the statesman's brilliance and the infelicitous consequences of his statecraft, as become evident in the work as a whole. This antithesis undermines the claim advanced by certain figures in the History, as well as by contemporary realists, that states (statesmen) should not be held to the same moral standards as individuals because to do so subverts their capacity to conduct prudent policy. We propose that Thucydides' work suggests, instead, that it is precisely when the norms of moral conduct are disrupted that states and individuals find it next to impossible to chart a prudent course of action.
The Public's Conditional Response to Supreme Court Decisions
Authors: Johnson Timothy R. , Martin Andrew D.
Published: May 2006

To investigate the effect of the Supreme Court on public opinion, we offer the conditional response hypothesis based on a theory of Supreme Court legitimacy and a microlevel social-psychological theory of attitude formation. Together these theories predict that the Court may affect public opinion when it initially rules on a salient issue, but that subsequent decisions on the same issue will have little influence on opinion. To test our predictions, we analyze public opinion data before and after the Supreme Court ruled in a highly visible abortion case (Webster v. Reproductive Health Services [1989]) and before and after three key capital punishment rulings (Furman v. Georgia [1972], Gregg v. Georgia [1976], and McCleskey v. Kemp [1987]). The results suggest that our theory is not issue bound but is generally applicable to how the Supreme Court affects public opinion when it rules in highly salient cases.
Prospecting for Participants: Rational Expectations and the Recruitment of Political Activists
Authors: Brady Henry E. , Schlozman Kay Lehman , Verba Sidney
Published: May 2006

A survey of the American public is used to model citizen political recruitment as a two-stage process. First, those who recruit others to become active in politics seek likely activists through “rational prospecting.” Second, they seek acquiescence to their requests. We model each part of the process, delineating the characteristics of individuals that make them attractive prospects and that make them likely to say “yes.” Recruiters who have information about, and leverage over, their targets are more likely to be successful. In seeking out people who would be likely not only to participate but also to participate effectively, rational prospectors select people with characteristics that are already overrepresented among participants. The net result of the recruitment process for political activity in general—and for financial contributions, in particular—is to exacerbate participatory stratification.
Cabinet Terminations and Critical Events
Authors: Diermeier Daniel , Stevenson Randolph T.
Published: May 2006

We present an empirical assessment of Lupia and Strøm's noncooperative bargaining model of cabinet terminations. We construct a stochastic version of the model and derive several testable implications. As the next mandatory election approaches: (1) the probability of an early election increases; (2) a cabinet's risks of being replaced without an intermediate election may be flat or even decrease; and (3) the overall chance that a cabinet falls (for whatever reason) increases. Using nonparametric duration analysis on a 15-country data set, we find qualified support for the Lupia and Strøm model. We conclude that the strategic approach is more promising than the nonstrategic alternative, but a more fully dynamic strategic model will be required to account for the dynamics of cabinet stability.
City Size and Civic Involvement in Metropolitan America
Authors: Oliver J. Eric
Published: May 2006

Given the coincidence between America's recent migration to smaller, suburban cities and declines in civic participation, Dahl's speculations on the ideal-sized democratic polity have gained more pertinence. I explore the effects of city size on participation in four local civic activities using 1990 data. Controlling for both individual- and city-level characteristics, I find people in larger cities are much less likely to contact officials, attend community or organizational meetings, or vote in local elections. Lower civic participation is attributable partly to differences in social relations and psychological orientation between residents of larger and smaller places. People in big cities are less likely to be recruited for political activity by neighbors and are less interested in local affairs. These differences occur irrespective of the size of the surrounding metropolitan area and demonstrate the importance of municipal institutions for fostering civil society. The implications for studies of participation, suburbanization, and democratic political theory are discussed.
Jury Verdicts and Preference Diversity
Authors: Gerardi Dino
Published: May 2006

I develop a model of decision making in juries when there is uncertainty about jurors' preferences. I provide a characterization of the equilibrium strategy under any voting rule and show that nonunanimous rules are asymptotically efficient. Specifically, large juries make the correct decision with probability close to one. My analysis also demonstrates that under the unanimous rule, large juries almost never convict the defendant. The last result contrasts markedly with the literature and suggests that the unanimity rule can protect the innocent only at the price of acquitting the guilty.
An Experimental Study of Jury Decision Rules
Authors: Guarnaschelli Serena , McKelvey Richard D. , Palfrey Thomas R.
Published: May 2006

We present experimental results on groups facing a decision problem analogous to that faced by a jury. We consider three treatment variables: group size (three or six), number of votes needed for conviction (majority or unanimity), and pre-vote deliberation. We find evidence of strategic voting under the unanimity rule: A large fraction of our subjects vote for a decision analogous to conviction even when their private information indicates a state analogous to innocence. This is roughly consistent with the game theoretic predictions of Feddersen and Pesendorfer. Although individual behavior is explained well by the game theoretic model, there are discrepancies at the level of the group decision. Contrary to Feddersen and Pesendorfer, in our experiments there are fewer outcomes analogous to incorrect convictions under unanimity rule than under majority rule. In the case of no deliberation, we simultaneously account for the individual and group data using quantal response equilibrium.
International Peacebuilding: A Theoretical and Quantitative Analysis
Authors: Doyle Michael W. , Sambanis Nicholas
Published: May 2006

International peacebuilding can improve the prospects that a civil war will be resolved. Although peacebuilding strategies must be designed to address particular conflicts, broad parameters that fit most conflicts can be identified. Strategies should address the local roots of hostility, the local capacities for change, and the (net) specific degree of international commitment available to assist sustainable peace. One can conceive of these as the three dimensions of a triangle whose area is the “political space”—or effective capacity—for building peace. We test these propositions with an extensive data set of 124 post–World War II civil wars and find that multilateral, United Nations peace operations make a positive difference. UN peacekeeping is positively correlated with democratization processes after civil war, and multilateral enforcement operations are usually successful in ending the violence. Our study provides broad guidelines for designing the appropriate peacebuilding strategy, given the mix of hostility, local capacities, and international capacities.
Recovering the Political Aristotle: A Critical Response to Smith
Authors: Terchek Ronald J. , Moore David K.
Published: May 2006

Thomas Smith presents an Aristotelian view of the common good that resembles much contemporary political theory in that it focuses on ethics rather than politics. Smith contends that Aristotle is a potent remedy to a society in crisis due to its unconcern about the common good. Against Smith's apolitical reading of Aristotle, we examine how Aristotle's views of common advantage, the multiple needs of citizens, and political friendship support neither harmonizing conceptions of the good nor a personal “radical conversion” that makes the common good our primary political concern. In engaging the political Aristotle, we find instead that he is concerned with the necessary conflict that resists attempts to arrive at the common advantage, with the material basis of good citizenship, and with the institutions and practices that foster a good deliberative politics.
The Political Relevance of Political Trust
Authors: Hetherington Marc J.
Published: May 2006

Scholars have debated the importance of declining political trust to the American political system. By primarily treating trust as a dependent variable, however, scholars have systematically underestimated its relevance. This study establishes the importance of trust by demonstrating that it is simultaneously related to measures of both specific and diffuse support. In fact, trust's effect on feelings about the incumbent president, a measure of specific support, is even stronger than the reverse. This provides a fundamentally different understanding of the importance of declining political trust in recent years. Rather than simply a reflection of dissatisfaction with political leaders, declining trust is a powerful cause of this dissatisfaction. Low trust helps create a political environment in which it is more difficult for leaders to succeed.
An Information Rationale for the Power of Special Interests
Authors: Lohmann Susanne
Published: May 2006

Political decisions are often biased in favor of special interests at the expense of the general public, and they are frequently inefficient in the sense that the losses incurred by the majority exceed the gains enjoyed by the minority. This article explains the bias in terms of information asymmetries and the free-rider problem. First, incumbents increase their reelection prospects by biasing policy toward groups that are better able to monitor their activities. Second, because smaller groups are better able to overcome the free-rider problem of costly monitoring, policy will be biased in their favor. Third, the effect of asymmetric monitoring on voter welfare is ambiguous. The inefficiencies created by thepolicy biasare offset by a positively valuedselection bias:Incumbents of above-average quality are more likely to survive voter scrutiny than are low-quality types.
Improving Quantitative Studies of International Conflict: A Conjecture
Authors: Beck Nathaniel , King Gary , Zeng Langche
Published: May 2006

We address a well-known but infrequently discussed problem in the quantitative study of international conflict: Despite immense data collections, prestigious journals, and sophisticated analyses, empirical findings in the literature on international conflict are often unsatisfying. Many statistical results change from article to article and specification to specification. Accurate forecasts are nonexistent. In this article we offer a conjecture about one source of this problem: The causes of conflict, theorized to be important but often found to be small or ephemeral, are indeed tiny for the vast majority of dyads, but they are large, stable, and replicable wherever the ex ante probability of conflict is large. This simple idea has an unexpectedly rich array of observable implications, all consistent with the literature. We directly test our conjecture by formulating a statistical model that includes its critical features. Our approach, a version of a “neural network” model, uncovers some interesting structural features of international conflict and, as one evaluative measure, forecasts substantially better than any previous effort. Moreover, this improvement comes at little cost, and it is easy to evaluate whether the model is a statistical improvement over the simpler models commonly used.
Senate Representation and Coalition Building in Distributive Politics
Authors: Lee Frances E.
Published: May 2006

The Senate's equal representation of states shapes coalition building in distributive politics. The great variation in state population means that some states have far greater need for federal funds than others, but all senators have equal voting weight. As a result, even though all senators' votes are of equal value to the coalition builder, they are not of equal “price.” Coalition builders can include benefits for small states at considerably less expense to program budgets than comparable benefits for more populous states. Building on formal models of coalition building, two hypotheses are developed and tested. First, coalition builders will seek out less costly members to build supportive coalitions efficiently. Second, the final outcomes of distributive policy will more closely reflect the preferences of small-state senators than large-state senators. The hypotheses are tested by examining the 1991 and 1997–98 reauthorizations of federal surface transportation programs. The findings support both hypotheses.
Highly Efficient Approach to 4‐Ethoxy‐5,6‐dihydro‐6,6‐disubstituted Pyran‐2‐ones using a Combinational Lewis Acid‐Base System
Authors: Liu Jie , Li Xing , Wang Jun , Feng Xiaoming
Published: May 2006

The first efficient approach to 5,6‐dihydro‐6,6‐disubstituted pyran‐2‐ones was successfully achieved from the reaction between commercially available ethyl 3‐ethoxybut‐2‐enoate and ketones in the presence of BF3⋅Et2O, InBr3 and LDA. BF3⋅Et2O and InBr3 were employed as the Lewis acid to activate the ketone and LDA was employed as the Lewis base to activate ethyl 3‐ethoxybut‐2‐enoate. Aromatic, aliphatic, and heterocyclic ketones were converted to the corresponding δ‐lactones containing quaternary carbon atom centers in excellent yields (up to 99%) under mild conditions.
Candida antarctica Lipase B: An Ideal Biocatalyst for the Preparation of Nitrogenated Organic Compounds
Authors: Gotor‐Fernández Vicente , Busto Eduardo , Gotor Vicente
Published: May 2006

Candida antarctica lipase B (CAL‐B) is a very effective catalyst for the production of amines and amides using different enzymatic procedures. Simplicity of use, low cost, commercial availability and recycling possibility make this lipase an ideal tool for the synthesis and resolution of a wide range of nitrogenated compounds that can be used for the production of pharmaceuticals and interesting manufactures in the industrial sector.
Gilt die Minersche Regel für Sand?
Authors: Wichtmann Torsten , Niemunis Andrzej , Triantafyllidis Theodor
Published: May 2006

Belastungen mit variierender Amplitude werden in Berechnungen mit einem expliziten (hochzyklischen) Akkumulationsmodell vereinfacht durch Zyklenpakete mit jeweils konstanter Amplitude ersetzt. Diese Paketierung nach dem Kriterium der Amplitude setzt voraus, daß die Reihenfolge hinsichtlich des Endwertes der bleibenden Verformung von untergeordneter Bedeutung ist, d. h., daß die sog. Miner sche Regel gilt. Leider liegen für Sand nur wenige experimentelle Studien mit einer geringen Zyklenanzahl vor. Dieser Beitrag präsentiert die Ergebnisse von Triaxialversuchen mit Zyklenpaketen, in denen die Gültigkeit der Miner schen Regel für Sand bei größeren Zyklenanzahlen (N ≥ 105) überprüft wurde. Es zeigt sich, daß der Einfluß der Reihenfolge der Pakete (zumindest bei Zyklen mit konstanter Polarisation) vernachlässigt werden kann, d. h., daß die Vorgehensweise expliziter Modelle legitim ist. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust methods for multivariate data analysis
Authors: Møller S. Frosch , von Frese J. , Bro R.
Published: May 2006

Outliers may hamper proper classical multivariate analysis, and lead to incorrect conclusions. To remedy the problem of outliers, robust methods are developed in statistics and chemometrics. Robust methods reduce or remove the effect of outlying data points and allow the ‘good’ data to primarily determine the result. This article reviews the most commonly used robust multivariate regression and exploratory methods that have appeared since 1996 in the field of chemometrics. Special emphasis is put on the robust versions of chemometric standard tools like PCA and PLS and the corresponding robust estimates of regression, location and scatter on which they are based. Copyright © 2006 John Wiley & Sons, Ltd.
Monitorization of consumer and naïf panels in the sensory evaluation of two types of potato chips by predictive biplots applied to generalized procrustes and three‐way Tucker‐1 analysis
Authors: Alves M. Rui , Oliveira M. Beatriz
Published: May 2006

Potato chips of industrial and domestic types, produced in batch and continuous plants, with oils of different qualities, were analyzed by a naïf panel with five assessors following an insipient quantitative descriptive analysis (QDA), and by a panel of 15 consumers following a simplified free‐choice profiling (FCP) technique. The naïf panel results were analyzed by a three‐way Tucker‐1 common loadings model with predictive biplots, which proved to be a very good way to evaluate each assessor's perceptions and scoring patterns and to monitor the evolution of the overall panel's performance during training, including the validation of the list of attributes. The consumer panel results were also analyzed by predictive biplots applied to individual dimensions in generalized procrustes analysis (GPA), following data compression through principal components analysis. This technique, which can be extended to a detailed analysis of scoring patterns, enabled the checking of the main consumer's perceptions and beliefs, and simultaneously the evaluation of the interplay of constructs in the build up of consumers' main dimensions. Both panels were able to distinguish the main types of potato chips, as well as the different status of oil quality, producing similar overall solutions to the problem. However, it is observed that when working with consumer panels, due to the great variability involved, at least a reasonably trained sensory panel will help to validate the results obtained. Copyright © 2006 John Wiley & Sons, Ltd.
Method for monitoring of mitochondrial cytochrome c release during cell death: Immunodetection of cytochrome c by flow cytometry after selective permeabilization of the plasma membrane
Authors: Campos Claudia B. L. , Paim Bruno A. , Cosso Ricardo G. , Castilho Roger F. , Rottenberg Hagai , Vercesi Anibal E.
Published: May 2006

Background:

Cytochrome c release from mitochondria to cytosol is a hallmark of apoptosis and is used to characterize the mitochondria‐dependent pathway of this type of cell death. Techniques currently used to measure cytochrome c release, Western blot and fluorescence microscopy of immunolabeled cells, are time‐consuming and inaccurate, and the latter is still limited by sample size.

Methods:

We developed a rapid and reliable technique to detect cytochrome c release during drug‐induced apoptosis, using flow cytometry. Plasma membrane of apoptotic HL‐60 cells and thymocytes, treated with staurosporine and dexamethasone, respectively, were selectively permeabilized by digitonin at a low concentration. The released cytochrome c was quickly washed out from cells and that which remained in the mitochondria was immunolabeled after fixing the cells.

Results:

The fraction of cells that retained their mitochondrial cytochrome c, or the highly fluorescent cells, gradually decreased so that after 4–8 h of drug treatment almost all the cells lost their cytochrome c and emerged as a population of low fluorescent cells. This was confirmed by parallel fluorescence microscopy of cells immunolabeled for cytochrome c.

Conclusions:

This technique allows the analysis of cytochrome c release from mitochondria of a large number of apoptotic cells in a short period of time and is proposed as an alternative to the methods currently used for this same purpose. © 2006 International Society for Analytical Cytology
Spectral imaging perspective on cytomics
Authors: Levenson Richard M.
Published: May 2006

Background:

Cytomics involves the analysis of cellular morphology and molecular phenotypes, with reference to tissue architecture and to additional metadata. To this end, a variety of imaging and nonimaging technologies need to be integrated. Spectral imaging is proposed as a tool that can simplify and enrich the extraction of morphological and molecular information. Simple‐to‐use instrumentation is available that mounts on standard microscopes and can generate spectral image datasets with excellent spatial and spectral resolution; these can be exploited by sophisticated analysis tools.

Methods:

This report focuses on brightfield microscopy‐based approaches. Cytological and histological samples were stained using nonspecific standard stains (Giemsa; hematoxylin and eosin (H&E)) or immunohistochemical (IHC) techniques employing three chromogens plus a hematoxylin counterstain. The samples were imaged using the Nuance™ system, a commercially available, liquid‐crystal tunable‐filter‐based multispectral imaging platform. The resulting data sets were analyzed using spectral unmixing algorithms and/or learn‐by‐example classification tools.

Results:

Spectral unmixing of Giemsa‐stained guinea‐pig blood films readily classified the major blood elements. Machine‐learning classifiers were also successful at the same task, as well in distinguishing normal from malignant regions in a colon‐cancer example, and in delineating regions of inflammation in an H&E‐stained kidney sample. In an example of a multiplexed ICH sample, brown, red, and blue chromogens were isolated into separate images without crosstalk or interference from the (also blue) hematoxylin counterstain.

Conclusion:

Cytomics requires both accurate architectural segmentation as well as multiplexed molecular imaging to associate molecular phenotypes with relevant cellular and tissue compartments. Multispectral imaging can assist in both these tasks, and conveys new utility to brightfield‐based microscopy approaches. © 2006 International Society for Analytical Cytology
Biocompatibility of subsieve‐size capsules versus conventional‐size microcapsules
Authors: Sakai Shinji , Mu Changjun , Kawabata Kenji , Hashimoto Ichiro , Kawakami Koei
Published: May 2006

Biocompatibility of cell‐enclosing capsules, defined as suppression of pericapsular cellular reactions, is one of the factors governing the success of enclosed cell transplantation in in vivo cell therapy. Agarose capsules of subsieve size, less than 100 μm in diameter, and conventional size, ∼300–1000 μm in diameter, were implanted into the peritoneal cavity and epididymal fat pads of mice and rats, respectively, to determine the effect of a reduction in diameter to subsieve size. The degree of cellular reaction to the subsieve‐size capsules was much lower than that of the conventional‐size microcapsules, independent of implantation site. The frequency of overgrown subsieve‐size capsules retrieved from the peritoneal cavities was less than 5% in contrast to ∼20% for capsules 387 μm in diameter. In addition, no increase in floating cells, which are generated through capsule stimulation, was observed in the peritoneal cavity only with subsieve‐size capsules. From these results, we concluded that subsieve‐size capsules are more biocompatible than microcapsules of conventional size. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Contact stress assessment of conventional and highly crosslinked ultra high molecular weight polyethylene acetabular liners with finite element analysis and pressure sensitive film
Authors: Plank Gordon R. , Estok Daniel M. , Muratoglu Orhun K. , O'Connor Daniel O. , Burroughs Brian R. , Harris William H.
Published: May 2006

Stress magnitude and distribution of both conventional polyethylene versus a crosslinked polyethylene in the liner of a total hip replacement (THR) were examined using finite element analysis and pressure sensitive film. Both types of polyethylene were assessed against head sizes of 22 and 28 mm with 5‐mm thick polyethylene liners and head sizes of 28, 38, and 46 mm with 3‐mm thick polyethylene liners. Liners with 5‐mm conventional polyethylene represented successful combinations with long track records. Our hypothesis was that although the combination of the large head and the lower modulus of the highly crosslinked polyethylene would lead to lower stresses, the stresses would be excessive if the liner was extremely thin at 3 mm. Von Mises stresses at the articulating surface of the highly crosslinked liners were lower, when compared to conventional polyethylene, in every THR size examined. Specifically, however, the 38‐ and 46‐mm inner diameter (ID) highly crosslinked polyethylene even at the extreme of only 3‐mm thick had lower stresses than the 22‐mm ID conventional liner of 5‐mm thickness. These data indicate that the use of a large head against highly crosslinked material even at 3‐mm thickness results in lower stresses than in an existing conventional 22‐mm head and 5‐mm thick combination. Obviously, other considerations will influence the minimum thickness to be recommended. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Hydrothermal crystallization of carbonate‐containing hydroxyapatite coatings prepared by radiofrequency‐magnetron sputtering method
Authors: Nakamura Satoshi , Hamagami Jun‐Ichi , Yamashita Kimihiro
Published: May 2006

Carbonate‐containing hydroxyapatite (HA) films were prepared by low‐temperature hydrothermal annealing from carbonate‐containing calcium phosphate amorphous coatings on titanium substrates. The biocompatibility of the carbonate‐containing HA layers was estimated by in vitro tests using simulated body fluid (SBF). Precursory amorphous coatings were deposited with rf‐magnetron sputtering apparatus, using calcium phosphate glass target in Ar/CO2 atmosphere. The carbonate‐containing HA coatings were successfully formed by the annealing at above 130°C for 20 h. On the basis of SEM observation, about 2‐μm thickness films coated rigidly were durable enough for the hydrothermal treatment. The coating layer was revealed to consist of single phase of PO4− and OH− partially carbonated HA by XRD and IR analyses. Overgrowing of bone‐like apatite layers on the carbonate‐containing HA surfaces in the SBF implied that the obtained films acquired a sufficient osteoconductivity, while it was still unclear that activity was enhanced, compared to pure HA coatings. The low‐temperature hydrothermal annealing method was effective for preparation of rigid HA coatings on titanium as well as modification of their chemical compositions. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Use of 3‐acetoxymethoxycarbonyl‐2,2,5,5‐tetramethyl‐1‐pyrrolidinyloxyl as an EPR oximetry probe: Potential for in vivo measurement of tissue oxygenation in mouse brain
Authors: Shen Jiangang , Liu Shimin , Miyake Minoru , Liu Wenlan , Pritchard Aaron , Kao Joseph P.Y. , Rosen Gerald M. , Tong Yao , Liu Ke Jian
Published: May 2006

Measurement of oxygen concentration and distribution in the brain is essential for understanding the pathophysiology of stroke. Low‐frequency electron paramagnetic resonance (EPR) spectroscopy with a paramagnetic probe is an attractive imaging modality that potentially can be used to map O2 concentration in the brain. We examined two nitroxides, 3‐methoxycarbonyl‐2,2,5,5‐tetramethyl‐1‐pyrrolidinyloxyl [2] and 3‐acetoxymethoxycarbonyl‐2,2,5,5‐tetramethyl‐1‐pyrrolidinyloxyl [3], as pro‐imaging agents to deliver 3‐carboxy‐2,2,5,5‐tetramethyl‐1‐pyrrolidinyloxyl [1] across the blood–brain barrier (BBB). In primary cultured neurons, nitroxide [3] but not [2] was hydrolyzed by intracellular esterases to [1], which, being anionic at physiologic pH, was well retained intracellularly. In contrast, [2] was not well retained by neurons. In vivo pharmacokinetic and pharmacodynamic studies in mice suggested that esterase‐labile nitroxide [3] crossed the BBB, and was converted to [1] and retained. Retention occurred in brain tissue and not in the extensive vasculature, as evidenced by the fact that removal of blood by whole‐body saline perfusion did not eliminate the nitroxide EPR signal from the brain. The EPR linewidths of [1] and [3] were more O2‐sensitive than that of the commonly‐used oximetry probe 4‐oxo‐2,2,6,6‐tetramethylpiperidine‐d16‐1‐15N‐oxyl [4]. Moreover, we used [3] in vivo to estimate O2 concentration in mouse brains. These results indicate that nitroxide [3] could be useful for mapping O2 distribution in the brain following stroke. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Consideration of magnetically‐induced and conservative electric fields within a loaded gradient coil
Authors: Mao Weihua , Chronik Blaine A. , Feldman Rebecca E. , Smith Michael B. , Collins Christopher M.
Published: May 2006

We present a method to calculate the electric (E)‐fields within and surrounding a human body in a gradient coil, including E‐fields induced by the changing magnetic fields and “conservative” E‐fields originating with the scalar electrical potential in the coil windings. In agreement with previous numerical calculations, it is shown that magnetically‐induced E‐fields within the human body show no real concentration near the surface of the body, where nerve stimulation most often occurs. Both the magnetically‐induced and conservative E‐fields are shown to be considerably stronger just outside the human body than inside it, and under some circumstances the conservative E‐fields just outside the body can be much larger than the magnetically‐induced E‐fields there. The order of gradient winding and the presence of conductive RF shield can greatly affect the conservative E‐field distribution in these cases. Though the E‐fields against the outer surface of the body are not commonly considered, understanding gradient E‐fields may be important for reasons other than peripheral nerve stimulation (PNS), such as potential interaction with electrical equipment. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Detecting microcirculatory changes in blood oxygen state with steady‐state free precession imaging
Authors: Dharmakumar Rohan , Qi Xiuling , Hong Juimiin , Wright Graham A.
Published: May 2006

Recently, it has been demonstrated that oxygen‐weighted images of whole blood can be obtained with steady‐state methods. In this article, based on computational and experimental models, we investigate the potential for employing this technique to monitor oxygen changes in microcirculation. Results show that oxygen‐sensitive images of rabbit kidney and muscle may be obtained at high signal‐to‐noise ratio within a few seconds. The results also show that in steady‐state free precession imaging, in addition to the exchange mechanism that generates oxygen contrast in blood, there are additional mechanisms that provide oxygen‐sensitive contrast in microcirculation. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Asymmetric vegetation responses to mid-Holocene aridity at the prairie–forest ecotone in south-central Minnesota
Authors: Umbanhowar Charles E. , Camill Philip , Geiss Christoph E. , Teed Rebecca
Published: May 2006

The mid-Holocene (ca. 8000–4000 cal yr BP) was a time of marked aridity throughout much of Minnesota, and the changes due to mid-Holocene aridity are seen as an analog for future responses to global warming. In this study, we compare the transition into (ca. 9000–7000 yr ago) and out of (ca. 5000–2500 yr ago) the mid-Holocene (MH) period at Kimble Pond and Sharkey Lake, located along the prairie forest ecotone in south-central Minnesota, using high resolution (∼ 5–36 yr) sampling of pollen, charcoal, sediment magnetic and loss-on-ignition properties. Changes in vegetation were asymmetrical with increasing aridity being marked by a pronounced shift from woodland/forest-dominated landscape to a more open mix of grassland and woodland/savanna. In contrast, at the end of the MH, grassland remained an important component of the landscape despite increasing effective moisture, and high charcoal influxes (median 2.7–4.0 vs. 0.6–1.7 mm2cm− 2yr− 1at start of MH) suggest the role of fire in limiting woodland expansion. Asymmetric vegetation responses, variation among and within proxies, and the near-absence of fire today suggest caution in using changes associated with mid-Holocene aridity at the prairie forest boundary as an analog for future responses to global warming.
Water waves in a deep square basin
Authors: Bryant Peter J. , Stiassnie Michael
Published: May 2006

The form and evolution of three-dimensional standing waves in deep water are calculated analytically from Zakharov's equation and computationally from the full nonlinear bounddary value problem. The water is contained in a basin with a square cross-cection, when three-dimensional properties to pairs of sides are the same. It is found that non-periodic standing waves commonly follow forms of cyclic recurrence over times. The two-dimensional Stokes type of periodic standing waves (dominated by the fundamental harmonic) are shown to be unstable to three dimensional disturbances, but over long times the waves return cyclically close to their initial state. In contrast, the three-dimensional Stokes type of periodic standing waves are found to be stabel to small disturbances. New two-dimensional periodic standing waves with amplitude maxima at other than the fundamental harmonic have been investigated recently (Bryant & Stiassnie 1994). The equivalent three-dimensional standing waves are described here. The new two-dimensional periodic standing waves, like the two-dimensional Stokes standing waves, are found to be unstable to three-dimensional disturbances, and to exhibit cyclic recurrence over long times. Only some of the new three-dimensional periodic standing waves are found to be stable to small disturbances.
Direct numerical simulation of turbulent flow over a modeled riblet covered surface
Authors: Goldstein D. , Handler R. , Sirovich L.
Published: May 2006

An immersed boundary technique is used to model a riblet covered surface on one wall of a channel bounding fully developed turbulent flow. The conjecture that the beneficial drag reduction effect of riblets is a result of the damping of cross-flow velocity fluctuations is then examined. This possibility has been discussed by others but is unverified. The damping effect is explicitly modelled by applying a cross-flow damping force field in elongated streamwise zones with a height and spacing corresponding to the riblet crests. The same trends are observed in the turbulence profiles above both riblet and damped surfaces, thus supporting cross-flow damping as a beneficial mechanism. It is found in the examples presented that the effect of the riblets on the mean flow field quantities (mean velocity profile, velocity fluctuations, Reynolds shear stress, and low–speed sreak spacing) is small. The riblests cause a relatively small drag reduction of about 4%, a figure that is in rough agreement with experiments and other computations. The simulations also suggest a mechanism for the observed displacement of the turbulence quantities away from the wall.

The immersed boundary technique used to model the riblets consists of creating an externally imposed spatially localized body force which opposes the flow velocity and creates a riblet-like surface. For unstead viscous flow the calculation of the force is done with a feedback scheme in which the velocity is used to iteratively determine the desired value. In particular, the surface body force is determined by the relationf(xs,t) = α ∫t0U(xs,t′)dt′ + βU(xs,t) for surface pointsxs, velocityUtimetand negative constants α and β. All simulations are done with a spectral code in a single computational domain without any mapping of the mesh. The combination of the immersed boundary and spectral techniques can potentially be used to solve other problems having complex geometry and flow physics.
Beschäftigtenfluktuation bei Pflegenden: Ein Vergleich der Bedeutung von arbeitsbedingtem Stress, organisationalen und individuellen Faktoren für die Absicht zum Berufswechsel und zum innerberuflichen Arbeitsplatzwechsel
Authors: Nolting Hans-Dieter , Grabbe Yvonne , Genz Hartmut O. , Kordt Martin
Published: May 2006

Die vorliegende Studie vergleicht anhand von Daten einer schriftlich befragten Stichprobe von 454 Pflegenden die Prädiktoren für die Berufsaufgabe einerseits und den innerberuflichen Arbeitsplatzwechsel andererseits. Als mögliche Prädiktoren der beiden Fluktuationsarten werden arbeitsbedingter psychischer Stress, die Belastung durch den Zustand und das Verhalten der Patienten, körperliche und allgemeine Beschwerden, organisationale, strukturelle sowie soziodemografische Variablen einbezogen. Die relevanten Prädiktoren werden mittels zweier multipler, linearer Regressionsanalysen identifiziert. Für die Berufsaufgabe erweisen sich körperliche und allgemeine Beschwerden, fehlender Handlungsspielraum, psychische Arbeitsintensität, niedriges Arbeitsplatzalter, Belastung durch nörgelnde und aggressive Patienten, die Art der Zusammenarbeit mit den Ärztinnen und Ärzten, geringe Unterstützung durch die/den Vorgesetzte/n sowie die berufliche Stellung prädiktiv (R2 = 30%). Für die Absicht zum innerberuflichen Arbeitsplatzwechsel sind als Prädiktoren eine geringe soziale Unterstützung durch die Kolleginnen und Kollegen, eine geringe Unterstützung der/des direkten Vorgesetzten, körperliche und allgemeine Beschwerden, niedriges Alter, niedriges Arbeitsplatzalter sowie die Anzahl der Betten auf der Station bedeutsam (R2 = 44%). Aus den Ergebnissen lässt sich schließen, dass hinsichtlich der Verhinderung des Berufsausstiegs eine individuelle Frühprävention sinnvoll ist, wohingegen erste Ansatzpunkte für eine Verminderung der Anzahl der Arbeitsplatzwechsler das Stationsklima bzw. die Kommunikationskultur und Kooperation zwischen den Kolleginnen und Kollegen sein sollten.
Sex Differences in the Full and Reduced Versions of the Aggression Questionnaire
Authors: Condon Lorena , Morales-Vives Fabia , Ferrando Pere Joan , Vigil-Colet Andreu
Published: May 2006

Sex differences in aggression have been widely analyzed using the Buss and Perry (1992) aggression questionnaire (AQ). The sex effects obtained when this questionnaire has been shortened and refined indicate some difficulties in replicating the results obtained with the full questionnaire. The present paper attempts to analyze whether these difficulties indicate sex bias in the AQ. To this end we administered the AQ to a sample of 416 subjects and analyzed the possible sex bias of the AQ by using confirmatory factor analysis models. Results show that the AQ is free of sex bias and that sex differences in the AQ and in the two revised versions seem to be the result of true sex differences and are specific to the physical aggression scale.
Field evidence of pressure gradient induced incipient motion
Authors: Foster D. L. , Bowen A. J. , Holman R. A. , Natoo P.
Published: May 2006

Recently, models for the onshore migration of nearshore sandbars were improved by including an empirical acceleration term in the sediment transport formulation (Hoefel and Elgar, 2003). Here, field observations of the fluid‐sediment interface suggest that the success of this empirical parameter may result from unsteady forcing of sediment beds by nearshore waves. The velocity and sediment observations show that, under large pressure gradients present during the strengthening of onshore‐directed flow, several centimeters of previously still sediment can be mobilized and transported onshore. The onshore‐directed mobile‐bed layer rapidly settles as the wave velocity weakens. These observations are inconsistent with traditional sediment transport theories (Shields, 1936; Bagnold, 1966) that assume incipient motion is solely based on the force applied by bed stress but are consistent with theories that include an additional force induced by the horizontal pressure gradient (Madsen, 1974; Sleath, 1999). In this paper, we provide the first field evidence of incipient motion that is significantly influenced by the unsteady forcing introduced by the horizontal pressure gradient due to surface gravity waves.
Progress toward fabrication of graded doped beryllium and CH capsules for the National Ignition Facility
Authors: Nikroo A. , Chen K. C. , Hoppe M. L. , Huang H. , Wall J. R. , Xu H. , McElfresh M. W. , Alford C. S. , Cook R. C. , Cooley J. C. , Fields R. , Hackenberg R. , Doerner R. P. , Baldwin M.
Published: May 2006

Current ignition designs require graded doped beryllium or CH capsules. This paper reports on the progress toward fabricating both beryllium and CH capsules that meet the current design criteria for achieving ignition on the National Ignition Facility (NIF) [S. Hann et al., Phys. Plasmas 12, 056316 (2005)]. NIF scale graded copper doped beryllium capsules have been made by sputter coating, while graded germanium doped CH capsules have been made by plasma polymer deposition. The sputtering process used for fabricating graded beryllium shells was produced with a void fraction of ∼5%. Varying the deposition parameters can lead to several different beryllium microstructures, which have been tuned to reduce the void size and fraction to within specifications. In addition, polishing of beryllium-coated shells reduces the outer surface roughness of shells to ignition specifications. Transmission electron microscopy has been used to characterize void fraction and grain structure of beryllium coatings. The plasma polymer deposition process has produced dense, void-free graded doped CH shells that nearly meet the ignition surface finish requirements. Layer thickness and dopant concentrations have been measured by quantitative contact radiography.
A molecular dynamics study of free energy of micelle formation for sodium dodecyl sulfate in water and its size distribution
Authors: Yoshii Noriyuki , Iwahashi Kensuke , Okazaki Susumu
Published: May 2006

Free energy of micelle formation has been evaluated for spherical sodium dodecyl sulfate (SDS) in water by a thermodynamic integration method combined with a series of large-scale molecular dynamics calculations following the chemical species model. In particular, free energy change Δμn+10 with respect to the addition of one surfactant molecule to the spherical micelle of size n was obtained as a function of n. The free energy profile showed a minimum followed by a maximum, which corresponds to a peak in the size distribution. The calculated peak size n=57 near its critical micelle concentration is in good agreement with the experimental averaged aggregation number n=55–75 of the SDS micelle. The distribution showed a rather sharp peak, indicating that the size is almost a monodisperse one. The size is likely to be insensitive to the total concentration of the surfactant.
Late-time radiography of beryllium ignition-target ablators in long-pulse gas-filled hohlraums
Authors: Cobble J. A. , Tierney T. E. , Hoffman N. M. , DeVolder B. G. , Swift D. C.
Published: May 2006

A multiple-laboratory campaign is underway to qualify beryllium as a fusion capsule ablator for the National Ignition Facility [Moses and Wuest, Fusion Sci. Technol. 43, 420 (2003)]. Although beryllium has many advantages over other ablator materials, individual crystals of beryllium have anisotropic properties, e.g., sound speed, elastic constants, and thermal expansion coefficients, which may seed hydrodynamic instabilities during the implosion phase of ignition experiments. Experiments based on modeling have begun at the OMEGA laser [Boehly, McCrory, Verdon et al., Fusion Eng. Design 44, 35 (1999)] to create a test bed for measuring instability growth rates with face-on radiography of perturbed beryllium samples with the goal of establishing a specification for microstructure in beryllium used as an ablator. The specification would include the size and distribution of sizes of grains and voids and the impurity content. The experimental platform is a 4kJ laser-heated (for ∼6ns) hohlraum that is well modeled for radiation temperature and for shock pressure and breakout timing through the driven beryllium sample. A 1atm methane gas fill has been used to maintain a clear line of sight through the hohlraum for radiography with acceptable plasma backscatter losses. The peak radiation temperature is 145eV; the pressure early in the laser pulse is 1Mbar for over 1ns. Radiographs of sinusoidally perturbed copper-doped (0.9% by atom) beryllium samples have been obtained more than 10ns after drive initiation. With the current laser drive, a growth factor approaching ten has been measured for initial 2.5μm perturbations with on-axis radiography.
On quantum extensions to classical spherical harmonics expansion/Fokker-Planck models
Authors: Bourgade J.-P. , Degond P. , Méhats F. , Ringhofer C.
Published: May 2006

By following a strategy introduced in previous works, quantum extensions of the classical electron-phonon scattering operator are deduced from first principles. These quantum collision operators satisfy a quantum H-theorem and relax towards quantum equilibria. Then, under an assumption of dominant elastic interactions, a hierarchy of quantum spherical harmonic expansion (SHE) models is derived by a diffusive approximation of collisional Wigner equations. These models are proven entropic and their expansions into powers of the reduced Planck constant ℏ are calculated, leading to ℏ2 corrections for the classical SHE model.