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Many Previous Studies (many + previous_studies)
Selected AbstractsA Reexamination of the Tradeoff between the Future Benefit and Riskiness of R&D IncreasesJOURNAL OF ACCOUNTING RESEARCH, Issue 1 2008ALLAN EBERHART ABSTRACT Many previous studies document a positive relation between research and development (R&D) and equity value. Though R&D can increase equity value by increasing firm value, it can also increase equity value at the expense of bondholder wealth through an increase in firm risk because equity is analogous to a call option on the underlying firm value. Shi [2003] tests this hypothesis by examining the relation between a firm's R&D intensity and its bond ratings and risk premiums at issuance. His results show that the net effect of R&D is negative for bondholders. We reexamine Shi's [2003] findings and in so doing make three contributions to the literature. First, we find that Shi's [2003] results are sensitive to the method of measuring R&D intensity. When we use what we argue is a better measure of R&D intensity, we find that the net effect of R&D is positive for bondholders. Second, when we use tests that Shi [2003] recognizes are even better than the ones that he uses, we find even stronger evidence of the positive effect of R&D on bondholders. Third, we examine cross-sectional differences in the effect of R&D on debtholders. Consistent with our main finding, we document a negative relation between R&D increases and default risk. The default risk reduction is also more pronounced for firms with higher initial default scores (where the debtholders have more to gain from an R&D increase) and for firms with more bank debt (where the debtholders have greater covenant protection from the possible detriments associated with R&D increases). [source] Socio-economic position, household composition, health status and indicators of the well-being of mothers of children with and without intellectual disabilitiesJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 12 2006E. Emerson Abstract Background Many previous studies have reported that mothers of children with intellectual disabilities (IDs) are more likely to show signs of psychological distress and have lower well-being than mothers of ,typically developing' children. Our aim was to estimate the extent to which these differences may be accounted for by between-group differences in socio-economic position. Methods This study involved secondary analysis of happiness, self-esteem and self-efficacy variables in a nationally representative sample of 6954 British mothers with dependent children under the age of 17 years, 514 of whom were supporting a child with an ID. Results Mothers of children with IDs reported lower levels of happiness, self-esteem and self-efficacy than mothers of children without IDs. Statistically controlling for differences in socio-economic position, household composition and maternal characteristics fully accounted for the between-group differences in maternal happiness, and accounted for over 50% of the elevated risk for poorer self-esteem and self-efficacy. Conclusions A socially and statistically significant proportion of the increased risk of poorer well-being among mothers of children with IDs may be attributed to their increased risk of socio-economic disadvantage. [source] Evolution of the southern Mu US desert in north China over the past 50 years: an analysis using proxies of human activity and climate parametersLAND DEGRADATION AND DEVELOPMENT, Issue 4 2005X. Wang Abstract Many previous studies have attributed the degradation in the Mu Us Desert in China to many centuries of human activity. The present study includes analysis of proxies of human activity such as arable land area, population and livestock number, and variations of precipitation, evaporation, temperature, sand-driving wind and dust events, covering the period since 1950. It is demonstrated that desertification and vegetation rehabilitation during this period were principally related to the climatic variation, especially correlated to sand-driving winds. It also suggests that the desert evolution in the past 2000 years was controlled by climate change rather than human activity. Although human activity was significant in the desert evolution processes over the past 50 years, the impacts seems to be overestimated in previous studies. Desertification and desert evolution in the Mu Us Desert are mainly in response to climatic trends and fluctuations. Copyright © 2005 John Wiley & Sons, Ltd. [source] Price Premium and Foreclosure RiskREAL ESTATE ECONOMICS, Issue 2 2006Seow Eng Ong Many previous studies identify loan, property, borrower and environmental factors that impact the probability of foreclosure. Implicit in these studies is the assumption that the property was purchased at fair value. We question this assumption based on several empirical findings regarding property value uncertainty. In contrast to previous research, we explicitly quantify the price premium from a hedonic pricing model. Using a comprehensive database of real estate transactions in Singapore during 1989,2000, we document a price premium associated with properties that are subsequently foreclosed based on actual sales transactions. In addition, we find that the premium paid at purchase significantly increases the probability of foreclosure. These results are robust and continue to hold after controlling for other property-specific factors, time-varying macroeconomic conditions, alternative model specifications and definitions of price premium. [source] Diagnostic study of generalized moist potential vorticity in a non-uniformly saturated atmosphere with heavy precipitationTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 650 2010Zhaoming Liang Abstract A Meiyu front accompanied by a band of heavy precipitation in East Asia is typically characterized by a much larger moisture gradient than temperature gradient. Many previous studies have suggested use of equivalent potential temperature as a thermodynamic variable under this circumstance. However, dynamic variables coupled with such a thermodynamic variable, e.g. a derived moist potential vorticity (MPV) based on equivalent potential temperature, does not provide useful dynamic insight into these systems. In this study, generalized moist potential vorticity (GMPV) is derived based on a generalized form of potential temperature. Diagnoses of numerical simulations for three typical Meiyu rainfall events show that GMPV provides remarkably accurate tracking of rainfall location, suggesting its potential use as a dynamic tracer for heavy rainfall events such as Meiyu rain bands. Copyright © 2010 Royal Meteorological Society [source] Surgery for temporal lobe epilepsy associated with mesial temporal sclerosis in the older patient: A long-term follow-upEPILEPSIA, Issue 6 2010Michael Murphy Summary Purpose:, To assess the outcomes from temporal lobectomy for hippocampal sclerosis in patients 50 years or older. Controversy exists as to the suitability of older patients for epilepsy surgery, with most of the previous studies demonstrating a correlation between increasing age and poor outcome. However, the inclusion of temporal lobe epilepsy of multiple etiologies has confounded many previous studies of this age group. Methods:, Twenty-one patients aged 50 years or older (mean 54.9 years) at the time of surgery were included in the study group. All patients had a pathologic diagnosis of hippocampal sclerosis. A retrospective analysis was performed comparing seizure outcomes following a standardized anterior temporal lobectomy with those from 103 patients younger than 50 (mean age 34.7 years) operated upon over the same time period. The mean follow-up period for the study was 9.57 years. Results:, Twenty of the 21 patients in the older group (95.2%) had a satisfactory seizure outcome (Engel classes I and II) compared with 90.3% of the younger patients. There was no statistically significant difference in the outcomes between the two groups (p = 0.719). Across both groups of patients combined, there was no significant difference between the mean age in the patients with a satisfactory seizure outcome compared to those with an unsatisfactory outcome (38.3 vs. 34.7 years, p = 0.213). Discussion:, Patients 50 years or older with intractable seizures from hippocampal sclerosis have seizure outcomes following temporal lobectomy that are comparable to young patients over the long term. Older patients should not be denied treatment on the basis of age. [source] Hydrologic prediction for urban watersheds with the Distributed Hydrology,Soil,Vegetation ModelHYDROLOGICAL PROCESSES, Issue 21 2008Lan Cuo Abstract Some relatively straightforward modifications to the Distributed Hydrology,Soil,Vegetation Model (DHSVM) are described that allow it to represent urban hydrological processes. In the modified model, precipitation that falls on impervious surfaces becomes surface runoff, and a spatially varying (depending on land cover) fraction of surface runoff is connected directly to the stream channel, with the remainder stored and slowly released to represent the effects of stormwater detention. The model was evaluated through application to Springbrook Creek watershed in a partially urbanized area of King County, Washington. With calibration, the modified DHSVM simulates hourly streamflow from these urbanized catchments quite well. It is also shown how the revised model can be used to study the effects of continuing urbanization in the much larger Puget Sound basin. Model simulations confirm many previous studies in showing that urbanization increases peak flows and their frequency, and decreases peak flow lag times. The results show that the urbanization parameterizations for DHSVM facilitate use of the model for prediction and/or reconstruction of a range of historic and future changes in land cover that will accompany urbanization as well as other forms of vegetation change. Copyright © 2008 John Wiley & Sons, Ltd. [source] The recent Sahel drought is realINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2004Aiguo Dai Abstract Using station rainfall data extracted from two comprehensive data sets, we show that large decreasing rainfall trends were widespread in the Sahel (10,20°N and 18°W,20°E) from the late 1950s to the late 1980s. Thereafter, Sahel rainfall has recovered somewhat through 2003, although the drought conditions have not ended in the region. These results confirm the findings of many previous studies. We also found that large multi-year oscillations appear to be more frequent and extreme after the late 1980s than previously. Analyses of Sahel regional rainfall time series derived from a fixed subset of stations and from all available stations show that the decreasing trend in Sahel rainfall is not an artifact of changing station networks. The rainfall model used by Chappell and Agnew (2004 International Journal of Climatology24: 547,554) is incorrect and their modelled rainfall time series is totally unrepresentative of Sahel average rainfall. Their conclusion about the Sahel rainfall trends being an artifact of changing station locations is emphatically wrong and their speculative statements about the implications of their results for other studies and other regions of the world are completely unfounded. Copyright © 2004 Royal Meteorological Society [source] "No Thanks, We're Full": Individual Characteristics, National Context, and Changing Attitudes Toward Immigration1INTERNATIONAL MIGRATION REVIEW, Issue 2 2008Rima Wilkes In this paper we examine how individual-level characteristics and national context affect attitudes toward immigration. Although many previous studies have compared attitudes toward immigration across countries, little attention has been paid to how attitudes may be affected by changes within a country over time. We take advantage of seventeen national Canadian Gallup surveys to consider how differences in national economic conditions and changing immigration flows affect attitudes and changes in attitudes between 1975 and 2000. While the state of the national economy affects attitudes this is not the case for the rate of immigration. Rather than affecting some groups more than others the state of the economy has a relatively uniform effect across groups. Our results also show that far from being a continuum, being anti-immigration and being pro-immigration are qualitatively different. Interest, ideology, and the national economy affect anti-immigration sentiments, but only ideology affects pro-immigration sentiments. [source] Advances in mechanisms of postsurgical gastroparesis syndrome and its diagnosis and treatmentJOURNAL OF DIGESTIVE DISEASES, Issue 2 2006Ke DONG Postsurgical gastroparesis syndrome (PGS) is a complex disorder characterized by post-prandial nausea and vomiting, and gastric atony in the absence of mechanical gastric outlet obstruction, and is often caused by operation at the upper abdomen, especially by gastric or pancreatic resection, and sometimes also by operation at the lower abdomen, such as gynecological or obstetrical procedures. PGS occurs easily with oral intake of food or change in the form of food after operation. These symptoms can be disabling and often fail to be alleviated by drug therapy, and gastric reoperations usually prove unsuccessful. The cause of PGS has not been identified, nor has its mechanism quite been clarified. PGS after gastrectomy has been reported in many previous studies, with an incidence of approximately 0.4,5.0%. PGS is also a frequent complication of pylorus-preserving pancreatoduodenectomy (PPPD), and the complication occurs in the early postoperative period in 20,50% of patients. PGS caused by pancreatic cancer cryoablation (PCC) has been reported about in 50,70% of patients. Therefore, PGS has a complex etiology and might be caused by multiple factors and mechanisms. The frequency of this complication varies directly with the type and number of gastric operations performed. The loss of gastric parasympathetic control resulting from vagotomy contributes to PGS via several mechanisms. It has been reported that the interstitial cells of Cajal (ICC) may play a role in the pathogenesis of PGS. Recent studies in animal models of diabetes suggest specific molecular changes in the enteric nervous system may result in delayed gastric emptying. The absence of the duodenum, and hence gastric phase III, may be a cause of gastric stasis. It was thought that PGS after PPPD might be attributable, at least in part, to delayed recovery of gastric phase III, due to lowered concentrations of plasma motilin after resection of the duodenum. The damage to ICC might play a role in the pathogenesis of PGS after PCC, for which multiple factors are possibly responsible, including ischemic and neural injury to the antropyloric muscle and the duodenum after freezing of the pancreatoduodenal regions or reduction of circulating levels of motilin. As the treatment of gastroparesis is far from ideal, non-conventional approaches and non-standard medications might be of use. Multiple treatments are better than single treatment. This article reviews almost all the papers related to PGS from various journals published in English and Chinese in recent years in order to facilitate a better understanding of PGS. [source] Interracial and Intraracial Patterns of Mate Selection Among America's Diverse Black PopulationsJOURNAL OF MARRIAGE AND FAMILY, Issue 3 2006Christie D. Batson Despite recent immigration from Africa and the Caribbean, Blacks in America are still viewed as a monolith in many previous studies. In this paper, we use newly released 2000 census data to estimate log-linear models that highlight patterns of interracial and intraracial marriage and cohabitation among African Americans, West Indians, Africans, and Puerto Rican non-Whites, and their interracial marriage and cohabitation with Whites. Based on data from several metropolitan areas, our results show that, despite lower socioeconomic status, native-born African Americans are more likely than other Blacks to marry Whites; they also are more likely to marry other Black ethnics. West Indians, Africans, and Puerto Rican non-Whites are more likely to marry African Americans than to marry Whites. Interracial relationships represent a greater share of cohabiting unions than marital unions. The majority of interracial unions, including native and immigrant Blacks, consist of a Black man and White woman. The implications for marital assimilation are discussed. [source] On the Cost of Adverse Selection in Individual Annuity Markets: Evidence From SingaporeJOURNAL OF RISK AND INSURANCE, Issue 2 2002Wai Mun Fong New evidence is presented on the cost of adverse selection in individual annuity markets using Singapore data. The Singapore annuity market is an interesting setting to examine the cost of adverse selection for three reasons. First, unlike many Western countries, the Singapore government provides very limited public financial assistance for retirees. Second, while social security contributions mandated under the Central Provident Fund (CPF) result in a high forced savings rate, a large proportion of CPF savings, are used up for housing. Third, to ensure that retirees have sufficient funds to meet basic needs, individuals who reach age 55 are required to set aside a minimum amount of their CPF savings, which can be withdrawn at age 62. The CPF Board allows various options for investing the minimum sum, but the most attractive option is to purchase an annuity. The institutional setting in Singapore in effect provides insurers with a large captive market for annuities. It is conjectured that this should be reflected in a significantly lower cost of adverse selection for annuities sold in Singapore as compared with other countries. The results herein, using data for CPF-approved insurers, are strongly consistent with this conjecture. On average, money's worth of annuities is higher than annuities sold to a similar age-gender mix in the United States, United Kingdom, and Australia. Adverse selection accounts for less than 13 percent of the cost of longevity insurance compared to 30,50 per- cent documented in many previous studies. These results suggest that one way to resolve the adverse selection problem is to adopt a universal individual defined contribution pension scheme that mandates or provides strong incentives for retirees to purchase annuities. [source] Functional variation in a disease resistance gene in populations of Arabidopsis thalianaMOLECULAR ECOLOGY, Issue 22 2008T. H. JORGENSEN Abstract Analyses of functional genetic diversity in natural populations may provide important new insights into gene function and are necessary to understand the evolutionary processes maintaining diversity itself. The importance of including diversity within and between local populations in such studies is often ignored although many of the processes affecting genetic diversity act on this scale. Here we examine the molecular diversity in RPW8 (Recognition of Powdery Mildew), a gene conferring broad-spectrum resistance to powdery mildews in Arabidopsis thaliana stock-center accessions. Our eight UK study populations of the weedy A. thaliana were from locations judged to be subject to a minimum of anthropogenic disturbance and potentially long established. The majority of populations comprised considerable variation both in disease phenotype and RPW8 genotype. Although resistant individuals shared a major RPW8 genotype, no single allele was uniquely associated with resistance. It is concluded that RPW8 is an essential component of resistance to powdery mildews in A. thaliana, but not the only genetic factor involved in this process. No signature of selection was detected at RPW8 with a microsatellite multilocus test using an empirical null model. Unlike many previous studies of this model plant species, we found high levels of genetic diversity and relatively low differentiation (FST = 0.31) between populations at 14 microsatellite markers. This is judged to be due to our sampling being aimed at potentially long established populations and highlights the importance of population choice for studies of genetic diversity within this species. [source] Evaluation of a High Exposure Solar UV Dosimeter for Underwater UsePHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Peter W. Schouten ABSTRACT Solar ultraviolet radiation (UV) is known to have a significant effect upon the marine ecosystem. This has been documented by many previous studies using a variety of measurement methods in aquatic environments such as oceans, streams and lakes. Evidence gathered from these investigations has shown that UVB radiation (280,320 nm) can negatively affect numerous aquatic life forms, while UVA radiation (320,400 nm) can both damage and possibly even repair certain types of underwater life. Chemical dosimeters such as polysulphone have been tested to record underwater UV exposures and in turn quantify the relationship between water column depth and dissolved organic carbon levels to the distribution of biologically damaging UV underwater. However, these studies have only been able to intercept UV exposures over relatively short time intervals. This paper reports on the evaluation of a high exposure UV dosimeter for underwater use. The UV dosimeter was fabricated from poly 2,6-dimethyl-1,4-phenylene oxide (PPO) film. This paper presents the dose response, cosine response, exposure additivity and watermarking effect relating to the PPO dosimeter as measured in a controlled underwater environment and will also detail the overnight dark reaction and UVA and visible radiation response of the PPO dosimeter, which can be used for error correction to improve the reliability of the UV data measured by the PPO dosimeters. These results show that this dosimeter has the potential for long-term underwater UV exposure measurements. [source] Occupational Trajectories of Legal US Immigrants: Downgrading and RecoveryPOPULATION AND DEVELOPMENT REVIEW, Issue 3 2008Ilana Redstone Akresh Data from the New Immigrant Survey 2003 are examined to analyze trajectories in occupational prestige between the last job abroad and the first US job and from the first US job to the current US job for a select sample of men and women. Incorporating the first job in the United States overcomes an important limitation faced by many previous studies that were generally restricted to a comparison of the last job abroad and the US job as measured at the time of the survey. Distinctions are made between class-of-admission groups, since the trajectories toward labor market success vary systematically along that dimension. Consistent with a model of immigrant occupational assimilation, all preference groups show a U-shaped adjustment pattern with, on average, initial downgrading followed by subsequent ascension. However, although all groups exhibit a similar pattern, the trough of the U is deepest for refugees, who also experience the steepest subsequent upward climb. [source] Prevalence of dementia in the older Japanese-Brazilian populationPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 1 2002Tatsuo Yamada MD Abstract The prevalence of dementing disorders in Campo Grande of a community of Japanese-Brazilians who immigrated from Okinawa was studied. Previous reports showed that the dietary pattern in Japanese immigrants in Brazil, which characterized by a low fish and large meat intake, is possibly responsible for increased risk of cardiovascular diseases compared with Japanese in Okinawa. A total of 157 persons over 70-year-old were examined, and 19 cases were diagnosed as having dementia. The prevalence (cases/100 aged 70-year-older) was 12.1 for all types of dementia, 5.7 for Alzheimer's disease (AD), 0.6 for vascular dementia (VD), 4.5 for mixed dementia (AD/VD) and 1.3 for other types of dementia. There was no case of dementia with Lewy bodies or frontotemporal lobar degeneration. These results are similar to many previous studies in Western countries and some recent surveys in Japan, and clearly show that more AD than VD appears even in the Japanese-Brazilian population. The higher prevalence rate of dementia in Japanese-Brazilians compared with several studies in Japan may indicate the importance of dietary factors rather than genetic factors. [source] Technical Inefficiency and Production Risk in Rice Farming: Evidence from Central Luzon Philippines,ASIAN ECONOMIC JOURNAL, Issue 1 2006Renato Villano Q12; C13 There have been many previous studies of technical inefficiency in rice production in the Philippines, but none has focused simultaneously on production risk and technical inefficiency at the farm level. Rice production is inherently risky because of the heterogeneous production environment. In this study, we analyze technical inefficiency in a rainfed lowland rice environment in Central Luzon using a stochastic frontier production function with a heteroskedastic error structure. An 8-year panel dataset collected from 46 rainfed rice farmers was used to estimate flexible functional specifications. Over the whole period, the average technical efficiency was found to be 79 percent. Results indicate that there is a high degree of variability in technical efficiency estimates, which can be attributed to the instability of farming conditions in the rainfed lowland environment. Mean output was signifificantly influenced by area planted to rice, labor and the amount of fertilizer used. Consequently, these inputs were found to be risk-increasing, whereas herbicide was found to be a risk-reducing input. [source] | ||||||||||||||||||||||