bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling Time Series of Ground Water Head Fluctuations Subjected to Multiple Stresses
Authors: Von Asmuth Jos R. , Maas Kees , Bakker Mark , Petersen Jörg 
Published: November 2007

AbstractThe methods behind the predefined impulse response function in continuous time (PIRFICT) time series model are extended to cover more complex situations where multiple stresses influence ground water head fluctuations simultaneously. In comparison to autoregressive moving average (ARMA) time series models, the PIRFICT model is optimized for use on hydrologic problems. The objective of the paper is twofold. First, an approach is presented for handling multiple stresses in the model. Each stress has a specific parametric impulse response function. Appropriate impulse response functions for other stresses than precipitation are derived from analytical solutions of elementary hydrogeological problems. Furthermore, different stresses do not need to be connected in parallel in the model, as is the standard procedure in ARMA models. Second, general procedures are presented for modeling and interpretation of the results. The multiple‐input PIRFICT model is applied to two real cases. In the first one, it is shown that this model can effectively decompose series of ground water head fluctuations into partial series, each representing the influence of an individual stress. The second application handles multiple observation wells. It is shown that elementary physical knowledge and the spatial coherence in the results of multiple wells in an area may be used to interpret and check the plausibility of the results. The methods presented can be used regardless of the hydrogeological setting. They are implemented in a computer package named Menyanthes (www.menyanthes.nl).
A New Method for the Interpretation of Pumping Tests in Leaky Aquifers
Authors: Trinchero Paolo , Sanchez‐Vila Xavier , Copty Nadim , Findikakis Angelos 
Published: November 2007

AbstractA novel methodology for the interpretation of pumping tests in leaky aquifer systems, referred to as the double inflection point (DIP) method, is presented. The method is based on the analysis of the first and second derivatives of the drawdown with respect to log time for the estimation of the flow parameters. Like commonly used analysis procedures, such as the type‐curve approach developed by Walton (1962) and the inflection point method developed by Hantush (1956), the mathematical development of the DIP method is based on the assumption of homogeneity of the leaky aquifer layers. However, contrary to the two methods developed by Hantush and Walton, the new method does not need any fitting process. In homogeneous media, the two classic methods and the one proposed here provide exact results for transmissivity, storativity, and leakage factor when aquifer storage is neglected and the recharging aquifer is unperturbed. The real advantage of the DIP method comes when applying all methods independently to a test in a heterogeneous aquifer, where each method yields parameter values that are weighted differently, and thus each method provides different information about the heterogeneity distribution. Therefore, the methods are complementary and not competitive. In particular, the combination of the DIP method and Hantush method is shown to lead to the identification of contrasts between the local transmissivity in the vicinity of the well and the equivalent transmissivity of the perturbed aquifer volume.
Redox Processes and Water Quality of Selected Principal Aquifer Systems
Authors: McMahon P.B. , Chapelle F.H. 
Published: November 2007

AbstractReduction/oxidation (redox) conditions in 15 principal aquifer (PA) systems of the United States, and their impact on several water quality issues, were assessed from a large data base collected by the National Water‐Quality Assessment Program of the USGS. The logic of these assessments was based on the observed ecological succession of electron acceptors such as dissolved oxygen, nitrate, and sulfate and threshold concentrations of these substrates needed to support active microbial metabolism. Similarly, the utilization of solid‐phase electron acceptors such as Mn(IV) and Fe(III) is indicated by the production of dissolved manganese and iron. An internally consistent set of threshold concentration criteria was developed and applied to a large data set of 1692 water samples from the PAs to assess ambient redox conditions. The indicated redox conditions then were related to the occurrence of selected natural (arsenic) and anthropogenic (nitrate and volatile organic compounds) contaminants in ground water. For the natural and anthropogenic contaminants assessed in this study, considering redox conditions as defined by this framework of redox indicator species and threshold concentrations explained many water quality trends observed at a regional scale. An important finding of this study was that samples indicating mixed redox processes provide information on redox heterogeneity that is useful for assessing common water quality issues. Given the interpretive power of the redox framework and given that it is relatively inexpensive and easy to measure the chemical parameters included in the framework, those parameters should be included in routine water quality monitoring programs whenever possible.
THE CYCLICALITY OF MONETARY AND FISCAL POLICY IN SOUTH AFRICA SINCE 1994
Authors: Du Plessis Stan , Smit Ben , Sturzenegger Federico 
Published: November 2007

AbstractThis paper uses a structural vector‐autoregression approach to discuss the cyclicality of fiscal and monetary policy in South Africa since 1994. There is substantial South African literature on this topic, but much disagreement remains. Though not undisputed, there is growing consensus that monetary policy has contributed to the remarkable stabilisation of the South African economy over this period. The evaluation of the role of fiscal policy in stabilisation has been less favourable and there is little evidence that a countercyclical fiscal stance was a priority over this period. This paper considers these issues in an empirical framework that addresses some of the shortcomings in the literature. Specifically, it constructs a structural model in contrast with the reduced form models typically used in the South African literature, incorporates the dynamic interaction between monetary and fiscal shocks on the demand side and supply shocks on the other, and avoids controversy over “neutral” base years and the size of fiscal elasticities. The model confirms the consensus on monetary policy, finding it to have been largely countercyclical since 1994. On fiscal policy, this paper finds evidence of pro‐cyclicality, especially in the more recent period, though the policy simulations suggest that the pro‐cyclicality of fiscal policy has had little destabilising impact on real output.
THE REVENUE‐EXPENDITURE NEXUS: HISTORICAL EVIDENCE FOR SOUTH AFRICA
Authors: Lusinyan Lusine , Thornton John 
Published: November 2007

AbstractResults from unit root and cointegration tests suggest that, allowing for structural breaks, government revenue and expenditure in South Africa during 1895‐2005 were I(1) series and cointegrated. Results from Granger‐type causality tests suggest that a bidirectional Granger‐causal relation existed between revenue and expenditure for the full sample period and for sub‐periods up to the 1960s, consistent with the so‐called “fiscal synchronisation hypothesis”. However, in the 1960s the causal relation appears to have shifted to run from expenditure to taxation, consistent with Peacock and Wiseman's “displacement effect”. In the context of the recent fiscal consolidation literature, the South African fiscal experience would appear to be generally consistent with either revenue‐ or expenditure‐led fiscal consolidation efforts, but with the more recent evidence favoring expenditure‐led consolidations.
A COMPARISON OF SOUTH AFRICAN HEDGE FUND RISK MEASURES
Authors: Botha Marius 
Published: November 2007

AbstractAlthough hedge funds have enjoyed unrivalled dominance after years of stellar returns, a combination of low interest rates, sustained economic growth and diminished arbitrage opportunities now threaten them. Distinguishing between funds – an onerous task with notoriously opaque investment strategies – has become paramount in the search for optimal returns. Simple risk and return performance measures cannot cope with the demands of an increasingly complex financial milieu. Interest has thus focused on more effective discriminatory performance measures. The innovative Omega ratio is calculated for South African hedge funds and compared with both Sharpe and Sortino ratios. Omega emerges as the superior measure.
EXPORT AND ECONOMIC GROWTH IN NAMIBIA: A GRANGER CAUSALITY ANALYSIS
Authors: Jordaan Andre C , Eita Joel Hinaunye 
Published: November 2007

AbstractThe purpose of this paper is to analyse the causality between exports and GDP of Namibia and to evaluate the relationship of these variables for the period 1970 to 2005. Time‐series econometric techniques (Granger causality and cointegration) are applied to test the hypothesis of a growth strategy led by exports. It tests whether export Granger causes GDP, or whether the causality runs from GDP to exports, or if there is bi‐directional causality between exports and GDP. The results revealed that exports Granger cause GDP and GDP per capita. This suggests that the export‐led growth strategy through various incentives has a positive influence on growth.
DEMAND FOR MONEY AND EXPENDITURE COMPONENTS IN SOUTH AFRICA: ASSESSMENT FROM UNRESTRICTED ERROR‐CORRECTION MODELS
Authors: Ziramba Emmanuel 
Published: November 2007

AbstractThe main aim of this study is to examine empirically the long‐run relationship of money demand and its determinants in South Africa. In contrast with existing studies on the subject, the present study considers various components of real income as determinants. The disaggregated components are final consumption expenditure, expenditure on investment goods and exports. The other determinants are domestic interest rate, yield on government bonds and the exchange rate. The results confirm that the different components of real income have different impacts on the demand for money in South Africa. The presence of long‐run equilibrium relationships between the demand for real M1, M2 and M3 and their determinants is confirmed based on the results of bounds testing.
CYCLICAL UNEMPLOYMENT AND CYCLICAL OUTPUT: AN ESTIMATION OF OKUN'S COEFFICIENT FOR SOUTH AFRICA
Authors: Marinkov Marina , Geldenhuys Jean‐pierre 
Published: November 2007

AbstractPersistently high unemployment in South Africa, especially in the face of improved economic conditions since 1994, begs the question: Does unemployment in South Africa respond to changes in output? Okun's law refers to the inverse relationship that exists between cyclical output and cyclical unemployment. This paper estimates Okun's coefficient for the South African economy, using annual data from 1970‐2005. Output and unemployment are decomposed into their trend and cyclical components, using a variety of detrending methods. The presence of structural breaks in Okun's relationship is also investigated, while cointegration analysis was also considered. Evidence of a statistically significant relationship between cyclical output and cyclical unemployment are found in both symmetric (estimates range from −0.77 to −0.16) and asymmetric (estimates range from −0.77 to −0.18) specifications of Okun's law, irrespective of the detrending technique. However, cyclical unemployment constitutes only a relatively small fraction of total (observed) unemployment, which implies that a more expansionary macroeconomic policy stance might only have a limited impact on total unemployment in South Africa.
TAX REFORM AND THE PROGRESSIVITY OF PERSONAL INCOME TAX IN SOUTH AFRICA
Authors: Nyamongo Morekwa E. , Schoeman Nicolaas J. 
Published: November 2007

AbstractThis paper investigates the progressivity of personal income tax in South Africa over the period 1989 to 2003. We use the effective, redistributive and disproportionality measures of progressivity and find that progressivity of the tax system increased over the period 1990 to 1994. However, during the first phase of the reform programmes the results are inconclusive with the Kakwani index (disproportionality measure) showing increased progressivity. The redistributive effect measure, on the other hand, indicates a marginal decline in progressivity. During the second phase of the reform programmes, both techniques suggest a worsening in progressivity. One explanation for the decline in progressivity during the latter period in the analysis is the fact that many more “new” taxpayers entered the tax net (higher income groups in our database) which made the distribution of pre‐tax income more unequal thus impacting on progressivity. On the other hand, the disproportionality measure shows a continuous, albeit volatile increase in progressivity over the latter period under investigation.
DETERMINANTS OF SOUTH AFRICA‐US INTRA‐INDUSTRY TRADE IN SERVICES: A WILD BOOTSTRAP DYNAMIC PANEL DATA ANALYSIS1
Authors: Sichei Moses Muse , Harmse Chris , Kanfer Frans 
Published: November 2007

AbstractThe study attempts to empirically identify factors that determine South Africa–US intra‐industry trade (IIT) in selected services during the period 1994‐2002. The study utilises Liu‐Davidson‐Flachaire wild bootstrap, which is robust to heteroscedasticity and provides estimates of the degree of parameter bias. The empirical results, in principle, show that South Africa–US IIT in the selected services is determined by factors similar to goods‐based “North‐South” IIT studies. Specifically, differences in per capita income and differences in market size negatively affect IIT. The study also indicates that US foreign direct investment in South Africa positively contributes to the unaffiliated IIT in services.
CONVERGENCE OF A KIND: EDUCATIONAL ATTAINMENT AND INTERGENERATIONAL SOCIAL MOBILITY IN SOUTH AFRICA
Authors: Louw Megan , Van Der Berg Servaas , Yu Derek 
Published: November 2007

AbstractTo a large degree, the notoriously high levels of income inequality in South Africa have their roots in differential access to wage‐earning opportunities in the labour market, which in turn are influenced by family background. This paper therefore investigates the role that parents' education plays in children's human capital accumulation. The study analyses patterns of educational attainment in South Africa during the period 1970‐2001, asking whether intergenerational social mobility has improved. It tackles the issue in two ways, combining extensive descriptive analysis of progress in educational attainment with a more formal evaluation of intergenerational social mobility using indices constructed by Dahan and Gaviria, and Behrmanet al. Both types of analysis indicate that intergenerational social mobility within race groups improved over the period, with the indices suggesting that South African children are currently better able to take advantage of educational opportunities than the bulk of their peers in comparable countries, at least up to lower secondary school level. However, the greater distance to go in achieving educational convergence between race groups at higher education levels reflect a major deficit: Educationalqualitydifferentials are still large and reflected in big differences in matriculation rates and tertiary qualifications by race.
DETERMINANTS OF SCHOOL ENROLMENT AND EDUCATION ATTAINMENT: EMPIRICAL EVIDENCE FROM KENYA1
Authors: Kabubo‐mariara Jane , Mwabu Domisiano K. 
Published: November 2007

AbstractThis paper investigates the determinants of demand for schooling in Kenya. Probit and ordered probit methods are used to model enrolment and attainment respectively. The results show that child characteristics, parental education and other household characteristics, quality and cost of schooling are important determinants of demand for education services in Kenya. The results further show that girls would be more affected by policy changes than boys. The findings call for targeting in efforts to boost and sustain demand for schooling in Kenya. The study recommends immediate policy interventions focusing on improving quality of education and poverty alleviation.
Effect of Strength Matching and Strain Hardening Capacity on Fracture
Performance of X80 Line Pipe Girth Welded Joint Subjected to Uniaxial Tensile
Loading
Authors: Motohashi Hiroyuki , Hagiwara Naoto 
Published: November 2007

Abstract
By conducting curved wide plate tensile tests for girth welded joints of X80 line pipe containing a surface notch in the weld metal, the effects of strength matching on fracture performance were evaluated. Parametric studies were also conducted using a finite element method simulating the experiments to clarify the effects of strain hardening capacity of the base metal, softening in the heat affected zone, and groove configuration on fracture performance. A strain at failure significantly decreased with the decreasing strength matching. This was expected to be due to a difference in local straining behavior at the notch tip caused by the shielding effect. The analytical studies revealed that the strain hardening capacity of the base metal, the softening in the heat affected zone, and the groove configuration affected the allowable strain for a given toughness level in the case of overmatching. However, these factors hardly affected the allowable strain in the case of undermatching.
Scattering of Surface and Internal Waves by Rectangular
Dikes
Authors: Kumar P. Suresh , Bhattacharjee J. , Sahoo T. 
Published: November 2007

Abstract
The scattering of surface and internal waves by a single dike or a pair of identical dikes in a two-layer fluid is analyzed in two dimensions within the context of linearized theory of water waves. The dikes are approximated as cylinders of rectangular geometry and are placed in a two-layer fluid of finite depth. In the study, both the cases of surface-piercing and bottom-standing dikes are considered. The solution of the associated boundary value problem is derived by a matched eigenfunction expansion method. Because of the flow discontinuity at the interface, the eigenfunctions involved have an integrable singularity at the interface and the orthonormal relation used in the present analysis is a generalization of the classical one corresponding to a single-layer fluid. The reflection coefficients and force amplitudes are computed and analyzed in various cases. The computed results in a two-layer fluid are compared with those existing in the literature for a single-layer fluid. The results obtained by the matched eigenfunction expansion method are compared with that of wide-spacing approximation method, and it is observed that the results from both the methods are in good agreement when the dikes are widely spaced. The general behavior of reflection coefficients for interface-piercing and non-interface-piercing obstacles is found to be different in both cases of surface-piercing and bottom-standing dikes. Moreover, for surface-piercing dikes, the results show the possibility of very large resonant motions between the dikes but with a very narrow bandwidth for the frequency of interest.
Determination of Cytokine Protein Levels in Cervical Mucus Samples from Young Women by a Multiplex Immunoassay Method and Assessment of Correlates
Authors: Lieberman Jay A. , Moscicki Anna-Barbara , Sumerel Jan L. , Ma Yifei , Scott Mark E. 
Published: November 2007

ABSTRACT

Cytokines in cervical mucus are likely to play important roles in controlling pathogens. The cervical mucosal environment is complex, however, with many endogenous and exogenous factors that may affect cytokine levels. We used a multiplex, suspension-array-based immunoassay method to measure 10 proinflammatory (interleukin-1β [IL-1β], IL-6, and IL-8) and immunoregulatory (gamma interferon [IFN-γ], IL-2, IL-4, IL-5, IL-10, IL-12, and IL-13) cytokines in cervical mucus specimens collected via ophthalmic sponge from 72 healthy, nonpregnant women and correlate their levels with biologic and behavioral covariates in a cross-sectional design. Proinflammatory and immunoregulatory cytokines were readily detected, although proinflammatory cytokines were present at markedly higher levels than were immunoregulatory cytokines. Among the covariates examined, the most striking finding was the significant (
P
≤ 0.05) association between depressed levels of the cytokines IFN-γ, IL-1β, IL-6, and IL-10 and cigarette smoking. Also, nonsignificant trends toward lower cytokine levels were found in the settings of incident and persistent human papillomavirus infection. The ready detection of proinflammatory cytokines may be reflective of the female genital tract as an anatomic site that is constantly exposed to immunogenic stimulation. Cigarette smoking appears to downregulate cytokine responses in the cervical mucosa, which may help explain the implicated role of tobacco use as a cofactor for cervical cancer development.
Human Skin Endothelial Cells Can Express All 10TLRGenes and Respond to Respective Ligands
Authors: Fitzner Nicole , Clauberg Sigrid , Essmann Frank , Liebmann Joerg , Kolb-Bachofen Victoria 
Published: November 2007

ABSTRACTBreakdown of the skin barrier requires the recognition of and rapid responses to invading pathogens. Since wounding usually also affects endothelial intactness, the expression of receptors of the Toll-like family involved in pathogen recognition in human skin vessel endothelia was examined. We found that human skin-derived microvascular endothelial cells can express all 10 Toll-like receptors (TLRs) currently known and will respond to respective ligands. Using immortalized skin-derived (HMEC-1) and primary dermal endothelial cells (HDMEC), we screened for TLR expression by real-time PCR. Endothelial cells express 7 (for HDMEC) and 8 (for HMEC-1) of the 10 known human TLRs under resting conditions but can express all 10 receptors in proinflammatory conditions. To provide evidence of TLR functionality, endothelial cells were challenged with TLR ligands, and after the TLR downstream signaling, MyD88 recruitment as well as early (interleukin-8 [IL-8] release) and late immune markers (inducible nitric oxide synthase mRNA expression) were monitored. Surprisingly, the responses observed were not uniform but were highly specific depending on the respective TLR ligand. For instance, lipopolysaccharides highly increased IL-8 release, but CpG DNA induced significant suppression. Additionally, TLR-specific responses were found to differ between resting and activated endothelial cells. These results show that human skin-derived endothelial cells can function as an important part of the innate immune response, can actively sense pathogen-associated molecular patterns, and can mount an increased or reduced inflammatory signal upon exposure to any of the currently known TLR ligands. Moreover, we also show here that proinflammatory conditions may affect TLR expression in a specific and nonuniform pattern.