bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Different Root Canal Obturating Materials on Push‐Out Bond Strength of a Fiber Dowel
Authors: Aggarwal Vivek , Singla Mamta , Miglani Sanjay , Kohli Sarita
Published: April 2012

Purpose: During dowel space preparation, the instrumentation forms a thick smear layer along with sealer‐occluded dentinal tubules. The purpose of this study was to evaluate the effect of different obturating materials on push‐out bond strength of a fiber dowel.

Materials and Methods: Fifty human uniradicular teeth were decoronated and prepared using the step‐back technique. The specimens were divided into five groups on the basis of obturating materials: group I received no obturation; group II (ZOE) gutta‐percha and zinc oxide eugenol sealer; group III (ZOAH) gutta‐percha and AH plus sealer; group IV (GF) GuttaFlow; and group V (RE) with Resilon Epiphany system. Dowel spaces were made with manufacturer's provided drills, and a fiber dowel was luted. Horizontal slices were obtained from the middle third, and push‐out bond strength (S) was evaluated. Statistical analysis was carried out using one‐way ANOVA and post hoc Tukey's test.

Results: The push‐out bond strength values in the control group, ZOE, ZOAH, GF, and RE were 9.303 ± 0.565 MPa, 8.859 ± 0.539 MPa, 8.356 ± 0.618 MPa, 9.635 ± 0.435 MPa, and 8.572 ± 0.256 MPa, respectively. There was no statistically significant difference between the S values of all the groups (p > 0.05).

Conclusion: There was no effect of different tested obturating materials on the push‐out bond strength of fiber dowels; however, further studies should be conducted.
Why Firms Use Currency Derivatives
Authors: GÉCZY CHRISTOPHER , MINTON BERNADETTE A. , SCHRAND CATHERINE
Published: April 2012

We examine the use of currency derivatives in order to differentiate among existing theories of hedging behavior. Firms with greater growth opportunities and tighter financial constraints are more likely to use currency derivatives. This result suggests that firms might use derivatives to reduce cash flow variation that might otherwise preclude firms from investing in valuable growth opportunities. Firms with extensive foreign exchange‐rate exposure and economies of scale in hedging activities are also more likely to use currency derivatives. Finally, the source of foreign exchange‐rate exposure is an important factor in the choice among types of currency derivatives.
On The Robustness of Size and Book‐to‐Market in Cross‐Sectional Regressions
Authors: KNEZ PETER J. , READY MARK J.
Published: April 2012

We use a robust regression estimator to analyze the risk premia on size and book‐to‐market. We find that the risk premium on size that was estimated by Fama and French (1992) completely disappears when the 1 percent most extreme observations are trimmed each month. We also show that the negative average of the monthly size coefficients reported by Fama and French can be entirely explained by the 16 months with the most extreme coefficients. We argue that further investigation of these results could lead to an understanding of the economic forces underlying the size effect, and may also yield important insights into how firms grow.
Approximating the Asset Pricing Kernel
Authors: CHAPMAN DAVID A.
Published: April 2012

This article tests a simple consumption‐based asset pricing model by approximating the true asset pricing kernel using low‐order orthonormal polynomials based on the model's state variables. Approximated kernels based solely on next period's consumption growth are not rejected by overall measures of model fit, but they produce statistically and economically large pricing errors. Approximated kernels based on two quarters of future consumption growth and technology shocks have substantially improved overall fit. In particular, the best of these kernels are capable of eliminating the small firm effect.
Defensive Mechanisms and Managerial Discretion
Authors: GIAMMARINO RONALD , HEINKEL ROBERT , HOLLIFIELD BURTON
Published: April 2012

We study a model where firms may possess free cash flow and takeovers may be disruptive. We show that the possibility of a takeover, combined with defensive mechanisms and the ability to pay greenmail, can solve the free cash flow problem in an efficient way. The payment of greenmail reveals information that generates a stock price decline that exceeds the value of the greenmail payment, even though the payment of greenmail is value maximizing. Optimal defensive measures limit takeover attempts if the target stock price is too low. We also provide cross‐sectional implications of the analysis.
CEO Contracting and Antitakeover Amendments
Authors: BOROKHOVICH KENNETH A. , BRUNARSKI KELLY R. , PARRINO ROBERT
Published: April 2012

This article examines incentives for adopting antitakeover charter amendments (ATAs) that are associated with compensation contracts. The evidence is consistent with the hypothesis that antitakeover measures such as ATAs help managers protect above‐market levels of compensation. Chief executive officers (CEOs) of firms that adopt ATAs receive higher salaries and more valuable option grants than CEOs at similar firms that do not adopt them. Furthermore, the magnitude of this difference increases following ATA adoption. The evidence is inconsistent with the hypothesis that ATAs facilitate the writing of efficient compensation contracts.
Institutions and Individuals at the Turn‐of‐the‐Year
Authors: SIAS RICHARD W. , STARKS LAURA T.
Published: April 2012

This article evaluates the tax‐loss‐selling hypothesis against the window‐dressing hypothesis as explanations for turn‐of‐the‐year anomalies. We examine differences between securities dominated by individual investors versus those dominated by institutional investors and find that the effect is more pervasive in the former. Controlling for capitalization, we find that in early January (late December), stocks with greater individual investor interest outperform (underperform) stocks with greater institutional investor interest. These results hold for both stocks that previously appreciated in value and stocks that previously depreciated in value. The results are most consistent with the tax‐loss‐selling hypothesis as an explanation for the turn‐of‐the‐year effect.
Informed Traders, Intervention, and Price Leadership: A Deeper View of the Microstructure of the Foreign Exchange Market
Authors: PEIERS BETTINA
Published: April 2012

This article identifies price leadership patterns in foreign exchange trading, with a focus on central bank intervention as an informational trigger for leadership positioning. Granger causality tests applied to DM/US$ spot rate quotes reveal Deutsche Bank as a price leader up to 60 minutes prior to Bundesbank interventionary reports. By the minus 25‐minute mark, interbank quote adjustments become two‐way Granger‐causal. These results suggest that central bank activity is revealed in stages: first to the price leader, then to competitors, and lastly to the general public.
Public Offerings of State‐Owned And Privately‐Owned Enterprises: An International Comparison
Authors: DEWENTER KATHRYN L. , MALATESTA PAUL H.
Published: April 2012

We compare initial offer prices in privatizations to initial prices in public offerings of private companies. The evidence indicates that government officials in the United Kingdom underprice IPOs significantly more than their private company counterparts. In Canada and Malaysia, however, the opposite is true. There does not appear to be a general tendency for privatizations to be underpriced to a greater degree than private company IPOs. We provide additional evidence on the determinants of privatization initial returns. Our findings indicate that initial returns are significantly higher in relatively primitive capital markets and for privatized companies in regulated industries.
The Relation Between Default‐Free Interest Rates and Expected Economic Growth Is Stronger Than You Think
Authors: KAMARA AVRAHAM
Published: April 2012

The relation between default‐free interest rates and expected economic growth is substantially stronger than suggested by extant literature. Futures‐implied Treasury bill yield spreads are more highly correlated with future real consumption, investment, and GNP growth than spot spreads. This stronger relation arises because using futures removes a component of the spot term structure that covaries negatively with real economic growth. Treasury forward rates from spot bills contain a premium for the risk that short‐sellers will default. This risk premium is negatively related to expected economic growth.
Do Changes in Dividends Signal the Future or the Past?
Authors: BENARTZI SHLOMO , MICHAELY RONI , THALER RICHARD
Published: April 2012

Many dividend theories imply that changes in dividends have information content about the future earnings of the firm. We investigate this implication and find only limited support for it. Firms that increase dividends in year 0 have experienced significant earnings increases in years −1 and 0, but show no subsequent unexpected earnings growth. Also, the size of the dividend increase does not predict future earnings. Firms that cut dividends in year 0 have experienced a reduction in earnings in year 0 and in year −1, but these firms go on to show significant increases in earnings in year 1. However, consistent with Lintner's model on dividend policy, firms that increase dividends are less likely than nonchanging firms to experience a drop in future earnings. Thus, their increase in concurrent earnings can be said to be somewhat “permanent.” In spite of the lack of future earnings growth, firms that increase dividends have significant (though modest) positive excess returns for the following three years.
Stock Market Efficiency and Economic Efficiency: Is There a Connection?
Authors: DOW JAMES , GORTON GARY
Published: April 2012

In a capitalist economy, prices serve to equilibrate supply and demand for goods and services, continually changing to reallocate resources to their most efficient uses. However, secondary stock market prices, often viewed as the most “informationally efficient” prices in the economy, have no direct role in the allocation of equity capital since managers have discretion in determining the level of investment. What is the link between stock price informational efficiency and economic efficiency? We present a model of the stock market in which: (i) managers have discretion in making investments and must be given the right incentives; and (ii) stock market traders may have important information that managers do not have about the value of prospective investment opportunities. In equilibrium, information in stock prices will guide investment decisions because managers will be compensated based on informative stock prices in the future. The stock market indirectly guides investment by transferring two kinds of information: information about investment opportunities and information about managers' past decisions. However, because this role is only indirect, the link between price efficiency and economic efficiency is tenuous. We show that stock price efficiency is not sufficient for economic efficiency by showing that the model may have another equilibrium in which prices are strong‐form efficient, but investment decisions are suboptimal. We also suggest that stock market efficiency is not necessary for investment efficiency by considering a banking system that can serve as an alternative institution for the efficient allocation of investment resources.
Legal Determinants of External Finance
Authors: LA PORTA RAFAEL , LOPEZ‐DE‐SILANES FLORENCIO , SHLEIFER ANDREI , VISHNY ROBERT W.
Published: April 2012

Using a sample of 49 countries, we show that countries with poorer investor protections, measured by both the character of legal rules and the quality of law enforcement, have smaller and narrower capital markets. These findings apply to both equity and debt markets. In particular, French civil law countries have both the weakest investor protections and the least developed capital markets, especially as compared to common law countries.
Do Long‐Term Shareholders Benefit From Corporate Acquisitions?
Authors: LOUGHRAN TIM , VIJH ANAND M.
Published: April 2012

Using 947 acquisitions during 1970–1989, this article finds a relationship between the postacquisition returns and the mode of acquisition and form of payment. During a five‐year period following the acquisition, on average, firms that complete stock mergers earn significantly negative excess returns of −25.0 percent whereas firms that complete cash tender offers earn significantly positive excess returns of 61.7 percent. Over the combined preacquisition and postacquisition period, target shareholders who hold on to the acquirer stock received as payment in stock mergers do not earn significantly positive excess returns. In the top quartile of target to acquirer size ratio, they earn negative excess returns.
The Operating Performance of Firms Conducting Seasoned Equity Offerings
Authors: LOUGHRAN TIM , RITTER JAY R.
Published: April 2012

Recent studies have documented that firms conducting seasoned equity offerings have inordinately low stock returns during the five years after the offering, following a sharp run‐up in the year prior to the offering. This article documents that the operating performance of issuing firms shows substantial improvement prior to the offering, but then deteriorates. The multiples at the time of the offering, however, do not reflect an expectation of deteriorating performance. Issuing firms are disproportionately high‐growth firms, but issuers have much lower subsequent stock returns than nonissuers with the same growth rate.
International Portfolio Investment Flows
Authors: BRENNAN MICHAEL J. , CAO H. HENRY
Published: April 2012

This article develops a model of international equity portfolio investment flows based on differences in informational endowments between foreign and domestic investors. It is shown that when domestic investors possess a cumulative information advantage over foreign investors about their domestic market, investors tend to purchase foreign assets in periods when the return on foreign assets is high and to sell when the return is low. The implications of the model are tested using data on United States (U.S.) equity portfolio flows.
International Asset Pricing and Portfolio Diversification with Time‐Varying Risk
Authors: DE SANTIS GIORGIO , GERARD BRUNO
Published: April 2012

We test the conditional capital asset pricing model (CAPM) for the world's eight largest equity markets using a parsimonious generalized autoregressive conditional heteroskedasticity (GARCH) parameterization. Our methodology can be applied simultaneously to many assets and, at the same time, accommodate general dynamics of the conditional moments. The evidence supports most of the pricing restrictions of the model, but some of the variation in risk‐adjusted excess returns remains predictable during periods of high interest rates. Our estimates indicate that, although severe market declines are contagious, the expected gains from international diversification for a U.S. investor average 2.11 percent per year and have not significantly declined over the last two decades.
Risk Premia and Variance Bounds
Authors: BALDUZZI PIERLUIGI , KALLAL HÉDI
Published: April 2012

If a pricing kernel assigns a premium to a risk variable that differs from the one assigned by the minimum‐variance admissible kernel, then the pricing kernel must exhibit more variability than the minimum‐variance kernel. Based on this intuition, we derive a variance bound that is more stringent than that of Hansen and Jagannathan (1991). When we apply our bound to the kernel of a representative consumer with power utility, we find that the consumption risk premium increases the severity of the “equity‐premium puzzle” of Mehra and Prescott (1985).
Stock Return Predictability and The Role of Monetary Policy
Authors: PATELIS ALEX D.
Published: April 2012

This article examines whether shifts in the stance of monetary policy can account for the observed predictability in excess stock returns. Using long‐horizon regressions and short‐horizon vector autoregressions, the article concludes that monetary policy variables are significant predictors of future returns, although they cannot fully account for observed stock return predictability. I undertake variance decompositions to investigate how monetary policy affects the individual components of excess returns (risk‐free discount rates, risk premia, or cash flows).
Cost of Transacting and Expected Returns in the Nasdaq Market
Authors: ELESWARAPU VENKAT R.
Published: April 2012

This article empirically examines the liquidity premium predicted by the Amihud and Mendelson (1986) model using Nasdaq data over the 1973–1990 period. The results support the model and are much stronger than for the New York Stock Exchange (NYSE), as reported by Chen and Kan (1989) and Eleswarapu and Reinganum (1993). I conjecture that the stronger evidence on the Nasdaq is due to the dealers' inside spreads on the Nasdaq being a better proxy for the actual cost of transacting than the quoted spreads on the NYSE, since the Nasdaq dealers do not face competition from limit orders or floor traders.
An Examination of Uncovered Interest Rate Parity in Segmented International Commodity Markets
Authors: HOLLIFIELD BURTON , UPPAL RAMAN
Published: April 2012

We examine the effect of segmented commodity markets on the relation between forward and future spot exchange rates in a dynamic economy. We calculate the slope coefficient in our theoretical economy from regressing exchange rate changes on forward premia. With reasonable parameter values, the slope coefficient is less than unity. However, even for extreme parameters the slope is not less than zero, as found in the data. A negative slope coefficient in a nominal version of the model requires the covariance between monetary shocks and relative output shocks to be significantly negative, in contrast to the covariance in the data.
Evidence on the Characteristics of Cross Sectional Variation in Stock Returns
Authors: DANIEL KENT , TITMAN SHERIDAN
Published: April 2012

Firm sizes and book‐to‐market ratios are both highly correlated with the average returns of common stocks. Fama and French (1993) argue that the association between these characteristics and returns arise because the characteristics are proxies for nondiversifiable factor risk. In contrast, the evidence in this article indicates that the return premia on small capitalization and high book‐to‐market stocks does not arise because of the comovements of these stocks with pervasive factors. It is the characteristics rather than the covariance structure of returns that appear to explain the cross‐sectional variation in stock returns.
Transactions Costs and Holding Periods for Common Stocks
Authors: ATKINS ALLEN B. , DYL EDWARD A.
Published: April 2012

Amihud and Mendelson (1986) and Constantinides (1986) provide a theoretical basis for the proposition that assets with higher transactions costs are held by investors for longer holding periods, and vice versa. We examine average holding periods and bid‐ask spreads for Nasdaq stocks from 1983 through 1991 and for New York Stock Exchange (NYSE) stocks from 1975 through 1989 and find strong evidence that, as predicted, the length of investors' holding periods is related to bid‐ask spreads. We also find that the relation between holding periods and bid‐ask spreads is much stronger on Nasdaq, where spreads are larger, than on the NYSE, where spreads are smaller.
The Delisting Bias in CRSP Data
Authors: SHUMWAY TYLER
Published: April 2012

I document a delisting bias in the stock return data base maintained by the Center for Research in Security Prices (CRSP). I find that delists for bankruptcy and other negative reasons are generally surprises and that correct delisting returns are not available for most of the stocks that have been delisted for negative reasons since 1962. Using over‐the‐counter price data, I show that the omitted delisting returns are large. Implications of the bias are discussed.
Dividends, Taxes, and Signaling: Evidence from Germany
Authors: AMIHUD YAKOV , MURGIA MAURIZIO
Published: April 2012

The higher taxation of dividends in the United States gave rise to theories that explain why companies pay dividends. Tax‐based signaling models propose that the higher tax on dividends is a necessary condition to make them informative about companies' values. In Germany, where dividends are not tax‐disadvantaged and in fact are taxed lower for most investor classes, these models predict that dividends are not informative. However, we find that the stock price reaction to dividend news in Germany is similar to that found in the United States. This suggests other reasons, beyond taxation, that make dividends informative.
Analyst Following of Initial Public Offerings
Authors: RAJAN RAGHURAM , SERVAES HENRI
Published: April 2012

We examine data on analyst following for a sample of initial public offerings completed between 1975 and 1987 to see how they relate to three well‐documented IPO anomalies. We find that higher underpricing leads to increased analyst following. Analysts are overoptimistic about the earnings potential and long term growth prospects of recent IPOs. More firms complete IPOs when analysts are particularly optimistic about the growth prospects of recent IPOs. In the long run, IPOs have better stock performance when analysts ascribe low growth potential rather than high growth potential. These results suggest that the anomalies may be partially driven by overoptimism.
Are There Tax Effects in the Relative Pricing of U.S. Government Bonds?
Authors: GREEN RICHARD C. , ØDEGAARD BERNT A.
Published: April 2012

We investigate the impact of the Tax Reform Act of 1986 on the relative pricing of U.S. Treasury bonds. We obtain positive statistically and economically significant estimates for the implicit tax rates of a “representative” investor in the late 1970s and early 1980s. After the 1986 Tax Reform, the point estimates for the tax rate are close to zero. Tests for a regime shift associated with the 1986 Tax Reform support the hypothesis that this event largely eliminated tax effects from the term structure. We discuss both institutional and statutory explanations for this change.
Tick Size, Share Prices, and Stock Splits
Authors: ANGEL JAMES J.
Published: April 2012

Minimum price variation rules help explain why stock prices vary substantially across countries, and other curiosities of share prices. Companies tend to split their stock so that the institutionally mandated minimum tick size is optimal relative to the stock price. A large relative tick size provides an incentive for dealers to make markets and for investors to provide liquidity by placing limit orders, despite its placing a high floor on the quoted bid‐ask spread. A simple model suggests that idiosyncratic risk, firm size, and visibility of the firm affect the optimal relative tick size and thus the share price.
Firm Size, Book‐to‐Market Ratio, and Security Returns: A Holdout Sample of Financial Firms
Authors: BARBER BEAD M. , LYON JOHN D.
Published: April 2012

Fama and French (1992) document a significant relation between firm size, book‐to‐market ratios, and security returns for nonfinancial firms. Because of their initial interest in leverage as an explanatory variable for security returns, Fama and French exclude from their analysis financial firms, thus creating a natural holdout sample on which to test the robustness of their results. We document that the relation between firm size, book‐to‐market ratios, and security returns is similar for financial and nonfinancial firms. In addition, we present evidence that survivorship bias does not significantly affect the estimated size or book‐to‐market premiums in returns. Our results indicate data‐snooping and selection biases do not explain the size and book‐to‐market patterns in returns.
Price Limit Performance: Evidence from the Tokyo Stock Exchange
Authors: KIM KENNETH A. , RHEE S. GHON
Published: April 2012

Price limit advocates claim that price limits decrease stock price volatility, counter overreaction, and do not interfere with trading activity. Conversely, price limit critics claim that price limits cause higher volatility levels on subsequent days (volatility spillover hypothesis), prevent prices from efficiently reaching their equilibrium level (delayed price discovery hypothesis), and interfere with trading due to limitations imposed by price limits (trading interference hypothesis). Empirical research does not provide conclusive support for either positions. We examine the Tokyo Stock Exchange price limit system to test these hypotheses. Our evidence supports all three hypotheses suggesting that price limits may be ineffective.
Phase Equilibria in the Mn–V–O System Near MnO–V2O3 Isopleth
Authors: Kim Min‐Su , Kang Youn‐Bae , Cha Woo‐Yeol , Lee Hae‐Geon
Published: April 2012

Phase equilibria in the Mn–V–O system near MnO–V2O3 isopleth has been investigated in the temperature range from 1200°C to 1600°C and in the range of oxygen partial pressure from ∼10−6 to ∼10−13 atm. High‐temperature equilibration, quenching and electron probe microanalysis were employed to obtain equilibrium compositions of liquid and several solid solutions. XRD analysis was also employed to confirm the stable phases. The phases which have been observed are; liquid oxide, (MnO)s.s., (V2O3)s.s., and (MnV2O4)s.s.. The (MnV2O4)s.s. phase was confirmed to be the only intermediate phase near the MnO–V2O3 isopleth under the conditions in the present study. It was found that sub‐solidus phase equilibria are considerably affected by the oxygen partial pressure. From the effect of oxygen partial pressure on the sub–solidus phase equilibria, the structures (Mn2+, V2+)T(Mn2+, Mn3+, Mn4+, V3+, Va)O4, (V3+, Mn3+, V4+)2O3+y and (Mn2+, Mn3+, V2+)1−zO are proposed for MnV2O4, V2O3, and MnO solid solutions, respectively.
Psychopathological View of Posttraumatic Stress Reactions is in the Eye of the Beholder. A Commentary on Schok et al.
Authors: BRAMSEN INGE
Published: April 2012

Schok et al. (2011)concluded that military veterans with “suspicious minds” are at risk for posttraumatic stress disorder. The authors recommended that negative appraisals of peacekeeping missions are prevented or changed to positive appraisals. In developing their argument, they misrepresented previous Dutch research as adopting a “psychopathological perspective.” This commentary criticizes the medicalization of posttraumatic stress responses that tends to ignore contextual factors and moral issues at stake. Also, the implicit assumptions of a “positive psychology” of posttraumatic stress in military veterans are discussed. Results on the process of attributing meaning are presented and related to the differences in theoretical perspective. A contextualized psychology that appreciates human diversity without prejudice and that stimulates moral and cultural sensitivity is advocated.
Preventing Contagion With Avian Influenza: Disease Salience, Attitudes Toward Foreigners, and Avoidance Beliefs1
Authors: KRINGS FRANCISKA , GREEN EVA T. , BANGERTER ADRIAN , STAERKLÉ CHRISTIAN , CLÉMENCE ALAIN , WAGNER‐EGGER PASCAL , BORNAND THIERRY
Published: April 2012

Building on an evolutionary approach to out‐group avoidance, this study showed relations between perceived disease salience and beliefs in the efficacy of avoiding foreigners as protective measures in the context of a real‐life pandemic risk; i.e., avian influenza. People for whom avian influenza was salient and who held unfavorable attitudes toward foreigners were more likely to believe that avoiding contact with foreigners protects against infection. This finding suggests that individual differences in social attitudes moderate evolved mechanisms relating threat of disease to out‐group avoidance.
Sintering and Dielectric Properties of Li2O–B2O3–Al2O3–SiO2 Glass‐Added (Ca0.7Sr0.3O)1.03(Ti0.1Zr0.9)O2 for Copper Electrode
Authors: Shin Hyunho , Lee Sang‐Wook , Jung Hyun Suk
Published: April 2012

When 1.5 wt% of Li2O–B2O3–SiO2 and 1.5 wt% of Li2O–B2O3–Al2O3 glass‐added (Ca0.7Sr0.3O)1.03(Ti0.1Zr0.9)O2 batch was ball milled for 10~30 h followed by sintering at 950°C in flowing N2‐10%H2 atmosphere, an apparent density of approximately 4.5 g/cm3, a dielectric constant of approximately 26, and a quality factor of roughly about 3300 GHz were demonstrated. A prolonged ball mill time thereafter significantly decreased both of the dielectric properties because of the enhanced reduction of the specimens during sintering. The apparent evidence of a material reaction between the dielectric material and the copper electrode was not observed.
Wake-Up or Unclear-Onset Strokes: Are they Waking up to the World of Thrombolysis Therapy?
Authors: Kang Dong-Wha , Kwon Joo Y. , Kwon Sun U. , Kim Jong S.
Published: April 2012

Wake-up or unclear-onset strokes occur in up to one-fourth of patients with ischemic stroke. Although stroke severity and clinical outcomes appear to be poorer in wake-up strokes than nonwake-up strokes, many patients with wake-up strokes do not receive thrombolytic therapy because stroke onset time cannot be determined. Recent studies have suggested, however, that the actual onset time of wake-up stroke is close to the wake-up time. Furthermore, advanced imaging technologies may enable us to identify patients with favorable risk-benefit profiles for thrombolysis. Indeed, empirical thrombolytic treatments have suggested safety and feasibility of such therapy in these patients. Based on these promising results and the development of multimodal imaging methods, prospective thrombolysis trials using predefined imaging criteria are currently under way to test the safety and efficacy of thrombolysis in patients with wake-up or unclear-onset strokes. The establishment of optimal acute treatment strategies in this important yet so far neglected group of patients is eagerly awaited.
FINDING THE POSSIBLE IN THE IMPOSSIBLE: THE CLINICAL AND THEORETICAL WORK OF NINA FARHI
Authors: White Jean
Published: April 2012

abstract

In a psychoanalytic career spanning three decades, Nina Farhi (1943–2009) worked primarily with people who had survived near impossible emotional and psychological circumstances. In a series of clinical papers, she theorized the ways in which her patients had managed to preserve embryonic self‐states against all odds and the arduous, imaginative and resourceful psychoanalytic work required to transform these vestiges of survival into creative living. This paper traces the evolution of Farhi's clinical thought, from her surprising and fresh uses of particular concepts of Winnicott's to her original re‐working of some of Marion Milner's foundational insights. It explores the ways in which Farhi's clinical practice was original and the clinical and theoretical legacy she leaves.
RETAIL THERAPY: THE ENJOYMENT OF THE CONSUMER
Authors: Plastow Michael
Published: April 2012

abstract

The discourse of economics and consumerism has not only penetrated into the clinical setting; it has had a pervasive effect upon each of us and upon the society in which we live. This state of affairs is taken up by reference to the now commonly used phrase ‘retail therapy’, in order to examine the implications of the promotion of this concept. These ideas are further elaborated through an examination of the consumerist bent our societies have taken, promoting as they do an unfettered enjoyment of consumer goods. But for society to function and for desire to take root in the subject, it is proposed that there is a necessary loss of enjoyment which from psychoanalysis we can designate as castration. The contemporary difficulty to undergo such a loss is tied here to a prolongation of the state Freud described as polymorphously perverse. It is here that the psychoanalyst has an ethical responsibility to unveil whatever discourses function to alienate the subject from his or her desire.
Framework and Tool for Rapid Assessment of Stream Susceptibility to Hydromodification1
Authors: Bledsoe Brian P. , Stein Eric D. , Hawley Robert J. , Booth Derek
Published: April 2012

Bledsoe, Brian P., Eric D. Stein, Robert J. Hawley, and Derek Booth, 2012. Framework and Tool for Rapid Assessment of Stream Susceptibility to Hydromodification. Journal of the American Water Resources Association (JAWRA) 48(4): 788‐808. DOI: 10.1111/j.1752‐1688.2012.00653.x

Abstract:  Changes in streamflow and sediment loading associated with urban development have the potential to exacerbate channel erosion, and result in impacts to wetland, riparian, and stream habitats, as well as infrastructure and property losses. The typical “one‐size‐fits‐all” management prescription of flow control with retention or detention basins has not been wholly effective, pointing to a need for improved management strategies and tools for mitigating the impacts of “hydromodification.” We present an approach for developing screening‐level tools for assessing channel susceptibility to hydromodification, and describe a novel tool for rapid, field‐based assessments of the relative susceptibility of stream segments. The tool is based on the results of extensive field surveys, which indicate that susceptibility is the driver of channel response, not the magnitude of urbanization. A combination of relatively simple, but quantitative, field indicators are used as input parameters for a set of decision trees that follow a logical progression in assigning categorical susceptibility ratings to the channel segment being assessed. The susceptibility rating informs the level of data collection, modeling, and ultimate mitigation efforts that can be expected for a particular stream segment type. The screening approach represents a critical first step toward tailoring hydromodification management strategies and mitigation measures to different stream types and geomorphic settings.
A Question of Boundaries: The Importance of “Revenuesheds” for Watershed Protection1
Authors: Patterson Lauren A. , Hughes Jeffrey , Barnes Glenn , Berahzer Stacey I.
Published: April 2012

Patterson, Lauren A., Jeffrey Hughes, Glenn Barnes, and Stacey I. Berahzer, 2012. A Question of Boundaries: The Importance of “Revenuesheds” for Watershed Protection. Journal of the American Water Resources Association (JAWRA) 48(4): 838‐848. DOI: 10.1111/j.1752‐1688.2012.00655.x

Abstract:  Watersheds transcend jurisdictional boundaries; raising important questions of who should pay for watershed protection, and how can watershed governance be funded? The responsibility and cost for watershed protection has progressively devolved to local governments, resulting in additional negative externalities and financing challenges. Watershed governance structures have formed at the scale of the watershed, but they often lack the financing mechanisms needed to achieve policy goals. Financing mechanisms via local governments provide a reliable source of revenue and the flexibility to address watershed specific issues. We develop a “revenueshed” approach to access the initial challenges local governments face when seeking to finance trans‐jurisdictional watershed governance. The revenueshed approach engages local governments into discussion and implementation of financial strategies for collaborative watershed governance. Legislation places water quality regulations primarily on local governments inside the watershed. The revenueshed approach extends the financial and stewardship discussion to include local governments outside the watershed that benefit from the watershed. We applied the revenueshed approach to the Mills River and Upper Neuse watersheds in North Carolina. Mills River had a partnership governance seeking revenue for specific projects, whereas the Upper Neuse sought long‐term financial stability to meet new water quality legislation.
Implant removal by means of an expansion of the alveolar bony crest: report of a clinical technique
Authors: Beolchini M. , Lilliu S. , Faria P. , Botticelli D.
Published: April 2012

Aim:  To describe the adaptation of the Edentulous Ridge Expansion (E.R.E.) technique for implant removal.

Material and Methods:  The E.R.E. technique for the removal of failed implants is described in detail. A clinical case is also reported. In a patient carrying a full arch removable prosthesis in the upper jaw, sustained by two bars, two out of five implants were found to be fractured. Bucco‐lingual partial‐thickness flaps were used to access the fractured implants. The implants were subsequently removed applying the E.R.E. technique. Two recipient sites were prepared in the same position, using bone expanders, and two new implants were installed.

Results:  After 4 months of healing, the implants were integrated and a new bar was fabricated, and the old prosthesis readapted.

Conclusion:  The ERE technique may be successfully applied for the removal of failed implants, and the immediate or delayed reinstallation of new implants.
Modulation of Bladder Afferent Activity by Propiverine and its Active Metabolites (M‐1 and M‐2) in Rats
Authors: MATSUMOTO Yoshihiro , TORIMOTO Kazumasa , HAYASHI Yukio , NANRI Masato , KINIWA Mamoru , HIRAO Yoshihiko , YOSHIMURA Naoki
Published: April 2012

Objectives: To evaluate the effects of propiverine and its active metabolites (M‐1 and M‐2) on bladder function through modulation of afferent activity in rats.

Methods: Cystometry was performed in urethane anesthetized female rats. We examined the effects of intravesical administration of propiverine, M‐1 and M‐2 on bladder overactivity induced by oxotremorine‐M (Oxo‐M; non‐selective mAChR agonist).

Results: Intravesical administration of Oxo‐M (200 µM) elicited bladder overactivity as evidenced by decreased intercontraction interval (ICI) and pressure threshold (PT) without changing maximum voiding pressure or baseline pressure. These effects were blocked by intravesical administration of propiverine (30 µM) or M‐2 (300 µM). Intravesical administration of M‐1 (30 µM) alone increased ICI and PT, but did not prevent Oxo‐M‐induced decreases in ICI and PT.

Conclusion: These results suggest that propiverine and M‐2 have anticholinergic effects on bladder afferent activity and that M‐1 has an inhibitory effect through the mechanism other than muscarinic receptor modulation. Thus, clinical benefits of propiverine in patients with overactive bladder could be mediated by multiple actions of propiverine and its active metabolites.
A thoracic surgeon's perspective on the elastofibroma dorsi: A benign tumor of the deep infrascapular region
Authors: Findikcioglu Alper , Kilic Dalokay , Karadayi Şule , Canpolat Tuba , Reyhan Mehmet , Hatipoglu Ahmet
Published: April 2012

Background:  An elastofibroma is a benign, soft‐tissue tumor and is important in the differential diagnosis of thoracic wall masses. Here, patients with elastofibromas who underwent thoracic surgery were retrospectively reviewed to elucidate elastofibroma formation and to facilitate the differential diagnosis.

Methods:  This is a retrospective and descriptive study of a series of 30 patients with elastofibroma dorsi. The data was obtained by review of the hospital records.

Results:  There were 27 female and three male patients (mean age, 55.13 ± 8.7 years) with a total of 42 elastofibroma dorsi tumors (12 bilateral cases, 18 unilateral cases) diagnosed between January 2004 and October 2011. Twenty patients (67%) underwent surgery as a result of subscapular swelling and pain. In 10 (33%) asymptomatic patients, elastofibromas were found incidentally during a thoracotomy. Imaging methods in symptomatic patients included computerized tomography (15 cases), magnetic resonance (three), and ultrasonography (two). For five patients, fluorodeoxyglucose uptake values were available and revealed mild metabolic activity in the elastofibromas. Elastofibromas were significantly larger in symptomatic patients (8.15 ± 1.9 vs. 6.2 ± 2.3; P= 0.02). Exposure to long‐term repetitive micro‐trauma was a precipitating factor in 23 (77%) patients. Seroma formation, the most common surgical complication, was observed in 40% of patients.

Conclusion:  The differential diagnosis of elastofibroma dorsi is straightforward, and preoperative histology is unnecessary when the clinical, radiological, and metabolic characteristics are known. Repetitive micro‐trauma may predispose to hyperproliferation of fibroelastic tissue, and genetics may also play a role. Surgical treatment can be reserved for cases with severe symptoms.
Fabrication and characterization of cesium-based photocathodes for free electron lasers
Authors: Khan Saara A. , Montgomery Eric J. , Riddick Blake C. , O’Shea Patrick
Published: April 2012

To meet future demands of free electron lasers, reliable and long lasting photocathodes are needed. With current photocathodes lacking a sufficient combination of both lifetime and high quantum efficiency, research continues to explore ways to formulate improved photocathodes. In this work, we investigate the photoemissive and thermal stability properties of CsAu on a porous tungsten substrate. Quantum efficiency (QE) and robustness characterization of evaporatively deposited metal cathodes, such as gold, opens possibilities for future long-lived high QE dispenser photocathodes on both conductive and insulating diffusion barriers.
Beam characteristics in two different proton uniform scanning systems: A side‐by‐side comparison
Authors: Nichiporov Dmitri , Hsi Wen , Farr Jonathan
Published: April 2012

Purpose:

To compare clinically relevant dosimetric characteristics of proton therapy fields produced by two uniform scanning systems that have a number of similar hardware components but employ different techniques of beam spreading.

Methods:

This work compares two technologically distinct systems implementing a method of uniform scanning and layer stacking that has been developed independently at Indiana University (IU) and by Ion Beam Applications, S. A. (IBA). Clinically relevant dosimetric characteristics of fields produced by these systems are studied, such as beam range control, peak‐to‐entrance ratio (PER), lateral penumbra, field flatness, effective source position, precision of dose delivery at different gantry angles, etc.

Results:

Under comparable conditions, both systems controlled beam range with an accuracy of 0.5 mm and a precision of 0.1 mm. Compared to IBA, the IU system produced pristine peaks with a slightly higher PER (3.23 and 3.45, respectively) and smaller, symmetrical, lateral in‐air penumbra of 1 mm compared to about 1.9/2.4 mm in the inplane/crossplane (IP/CP) directions for IBA. Large field flatness results in the IP/CP directions were similar: 3.0/2.4% for IU and 2.9/2.4% for IBA. The IU system featured a longer virtual source‐to‐isocenter position, which was the same for the IP and CP directions (237 cm), as opposed to 212/192 cm (IP/CP) for IBA. Dose delivery precision at different gantry angles was higher in the IBA system (0.5%) than in the IU system (1%).

Conclusions:

Each of the two uniform scanning systems considered in this work shows some attractive performance characteristics while having other features that can be further improved. Overall, radiation field characteristics of both systems meet their clinical specifications and show comparable results. Most of the differences observed between the two systems are clinically insignificant.
Increasing the oscillation frequency of strong magnetic fields above 101 kHz significantly raises peripheral nerve excitation thresholds
Authors: Weinberg Irving N. , Stepanov Pavel Y. , Fricke Stanley T. , Probst Roland , Urdaneta Mario , Warnow Daniel , Sanders Howard , Glidden Steven C. , McMillan Alan , Starewicz Piotr M. , Reilly J. Patrick
Published: April 2012

Purpose:

A time‐varying magnetic field can cause unpleasant peripheral nerve stimulation (PNS) when the maximum excursion of the magnetic field (ΔB) is above a frequency‐dependent threshold level [P. Mansfield and P. R. Harvey, Magn. Reson. Med. 29, 746–758 (1993)]. Clinical and research magnetic resonance imaging (MRI) gradient systems have been designed to avoid such bioeffects by adhering to regulations and guidelines established on the basis of clinical trials. Those trials, generally employing sinusoidal waveforms, tested human responses to magnetic fields at frequencies between 0.5 and 10 kHz [W. Irnich and F. Schmitt, Magn. Reson. Med. 33, 619–623 (1995), T. F. Budinger et al., J. Comput. Assist. Tomogr. 15, 909–914 (1991), and D. J. Schaefer et al., J. Magn. Reson. Imaging 12, 20–29 (2000)]. PNS thresholds for frequencies higher than 10 kHz had been extrapolated, using physiological models [J. P. Reilly et al., IEEE Trans. Biomed. Eng. BME‐32(12), 1001–1011 (1985)]. The present study provides experimental data on human PNS thresholds to oscillating magnetic field stimulation from 2 to 183 kHz. Sinusoidal waveforms were employed for several reasons: (1) to facilitate comparison with earlier reports that used sine waves, (2) because prior designers of fast gradient hardware for generalized waveforms (e.g., including trapezoidal pulses) have employed quarter‐sine‐wave resonant circuits to reduce the rise‐ and fall‐times of pulse waveforms, and (3) because sinusoids are often used in fast pulse sequences (e.g., spiral scans) [S. Nowak, U.S. patent 5,245,287 (14 September 1993) and K. F. King and D. J. Schaefer, J. Magn. Reson. Imaging 12, 164–170 (2000)].

Methods:

An IRB‐approved prospective clinical trial was performed, involving 26 adults, in which one wrist was exposed to decaying sinusoidal magnetic field pulses at frequencies from 2 to 183 kHz and amplitudes up to 0.4 T. Sham exposures (i.e., with no magnetic fields) were applied to all subjects.

Results:

For 0.4 T pulses at 2, 25, 59, 101, and 183 kHz, stimulation was reported by 22 (84.6%), 24 (92.3%), 15 (57.7%), 2 (7.7%), and 1 (3.8%) subjects, respectively.

Conclusions:

The probability of PNS due to brief biphasic time‐varying sinusoidal magnetic fields with magnetic excursions up to 0.4 T is shown to decrease significantly at and above 101 kHz. This phenomenon may have particular uses in dynamic scenarios (e.g., cardiac imaging) and in studying processes with short decay times (e.g., electron paramagnetic resonance imaging, bone and solids imaging). The study suggests the possibility of new designs for human and preclinical MRI systems that may be useful in clinical practice and scientific research.
Beam properties and stability of a flattening‐filter free 7 MV beam—An overview
Authors: Dzierma Yvonne , Licht Norbert , Nuesken Frank , Ruebe Christian
Published: April 2012

Purpose:

Several works have recently focused on flattening‐filter‐free (FFF) beams of linear accelerators of various companies (in particular, Varian and Elekta), but no overview as yet exists for the flattening‐filter free 7XU beam (Siemens Artiste).

Methods:

Dosimetric properties of the 7XU beam were measured in May and September 2011. We present depth dose curves and beam profiles, output factors, and MLC transmission and assess the stability of the measurements. The 7XU beam was commissioned in the Pinnacle³ treatment planning system (TPS), and modeling results including the spectrum are presented.

Results:

The percent depth dose curve of the 7XU beam is similar to the flat 6X beam line, with a slightly smaller surface dose. The beam profiles show the characteristic shape of flattening‐filter free beams, with deviations between measurements of generally less than 1%. The output factors of the 7XU beam decrease more slowly than for the 6X beam. The MLC transmission is comparable but slightly less for the 7XU beam. The 7XU beam can be adequately modeled by the Pinnacle³ TPS, with successful dosimetric verification. The spectrum of the 7XU beam has lower photon fluence up to approximately 2.5 MeV and higher fluence beyond, with a slightly higher mean energy.

Conclusions:

The 7XU beam has been commissioned for clinical use after successful modeling, stability checks, and dosimetric verification.