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Time Limits (time + limit)
Selected AbstractsEffects of Differentially Time-Consuming Tests on Computer-Adaptive Test ScoresJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 2 2004Brent Bridgeman Time limits on some computer-adaptive tests (CATs) are such that many examinees have difficulty finishing, and some examinees may be administered tests with more time-consuming items than others. Results from over 100,000 examinees suggested that about half of the examinees must guess on the final six questions of the analytical section of the Graduate Record Examination if they were to finish before time expires. At the higher-ability levels, even more guessing was required because the questions administered to higher-ability examinees were typically more time consuming. Because the scoring model is not designed to cope with extended strings of guesses, substantial errors in ability estimates can be introduced when CATs have strict time limits. Furthermore, examinees who are administered tests with a disproportionate number of time-consuming items appear to get lower scores than examinees of comparable ability who are administered tests containing items that can be answered more quickly, though the issue is very complex because of the relationship of time and difficulty, and the multidimensionality of the test. [source] Effective radial Liapunov exponent for the radial diffusion of test electronsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2003A. Maluckov Abstract The radial diffusion of test electrons in the bounded magnetic field region with irregularities is a realization of the magnetic (deterministic) and collisional (statistical) stochasticities. To clarify the development of stochasticities the effective radial Liapunov exponent Ler, the number of the electron trajectories (magnetic field lines) with positive radial Liapunov exponent Np, the distribution of the radial Liapunov exponent, Kolmogorov entropy and 3D Liapunov exponent are calculated numerically. In the absence of collisions the overlapping among magnetic islands (generation of the global stochasticity) is indicated by the qualitative change from negative to positive Ler in the long time limit. The fact that Np < N, where N is the number of test electrons, is the sign of sticking to the magnetic field structures. From the viewpoint of the radial Liapunov exponents both stochasticities manifest similarly. It is shown that the distribution of the radial Liapunov exponents is not the elementary one, except in the region of the extremely frequent collisions and partially destroyed magnetic field. Transition of the radial diffusion from the strange to the standard diffusion [1] is related with neglecting sticking of the electrons to the magnetic field structures by enough frequent collisions. [source] Electronic Medical Record Review as a Surrogate to Telephone Follow-up to Establish Outcome for Diagnostic Research Studies in the Emergency DepartmentACADEMIC EMERGENCY MEDICINE, Issue 11 2005Jeffrey A. Kline MD Abstract Background: Follow-up for diagnostic research studies might be facilitated if medical record review (MRR) could be used instead of telephone calls. Objectives: The authors hypothesized that MRR would yield similar accuracy to telephone follow-up. Methods: This was a secondary analysis of 2,178 initially disease-free patients who were followed after enrollment in a diagnostic study of either acute coronary syndrome (45 days) or pulmonary embolism (90 days) conducted in an urban teaching emergency department (ED). Disease status (positive or negative) was defined explicitly. Using structured data forms, trained researchers performed MRR using a comprehensive electronic database, and formulated an opinion about disease status. Trained researchers, blinded to the MRR, then dialed telephone numbers, asked questions from a script, and categorized disease status. The criterion standard was adjudication by consensus of two of three physicians who independently determined disease status based on explicit criteria and access to all follow-up data. Results: Adjudicators found that 13 of 2,178 patients developed disease during follow-up; all 13 true positives occurred among the 2,054 (94.3%) of patients who acknowledged intent to return to the study hospital. Telephone follow-up was successful in 81% of patients, and found all 13 true positives (sensitivity 100%) but with three additional false-positive cases. MRR disclosed 12 of 13 cases of disease (sensitivity 92%) with no false-positive cases. Further review of the one false-negative case from MRR revealed that it occurred after the prescribed time limit for follow-up. Conclusions: Under limited circumstances, accurate clinical follow-up for diagnostic studies conducted in the ED can be obtained by medical record review. [source] Short-term harvest planning including scheduling of harvest crewsINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2003J. Karlsson Abstract The problem we consider is short-term harvesting planning for a total planning period of 4,6 weeks where we want to decide the harvest sequences or schedules for harvest crews. A schedule is an order or sequence of harvest areas assigned to each crew. The harvesting of areas is planned in order to meet industrial demand. The total cost includes harvesting, transportation, and storage. One considerable cost is due to the quality reduction of logs stored at harvest areas. There are a number of restrictions to be considered. Areas are of varying size and the composition of assortments in each area is different. Each harvest team has different skills, a different home base, and different production capacity. Another aspect is the road network. There is a cost related to road opening (restoring, snow removal). In this paper, we develop a mixed integer programming (MIP) model for the problem. The schedules are represented by 0/1 variables. With a limited number of schedules, the problem can be solved by a commercial MIP solver. We have also developed a heuristic solution approach that provides high-quality integer solutions within a distinct time limit to be used when more schedules are used. Computational results from a major Swedish forest company are presented. [source] Detecting Differential Speededness in Multistage TestingJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 2 2007Wim J. Van Der Linden A potential undesirable effect of multistage testing is differential speededness, which happens if some of the test takers run out of time because they receive subtests with items that are more time intensive than others. This article shows how a probabilistic response-time model can be used for estimating differences in time intensities and speed between subtests and test takers and detecting differential speededness. An empirical data set for a multistage test in the computerized CPA Exam was used to demonstrate the procedures. Although the more difficult subtests appeared to have items that were more time intensive than the easier subtests, an analysis of the residual response times did not reveal any significant differential speededness because the time limit appeared to be appropriate. In a separate analysis, within each of the subtests, we found minor but consistent patterns of residual times that are believed to be due to a warm-up effect, that is, use of more time on the initial items than they actually need. [source] Y-STR Profiling in Extended Interval (,3 days) Postcoital Cervicovaginal Samples,JOURNAL OF FORENSIC SCIENCES, Issue 2 2008Kathleen A. Mayntz-Press M.S. Abstract:, Depending upon specific situations, some victims of sexual assault provide vaginal samples more than 36,48 h after the incident. We have tested the ability of commercial and in-house Y-STR systems to provide DNA profiles from extended interval (,3 days) postcoital samples. The commercial Y-STR systems tested included the AmpF,STR® YfilerÔ (Applied Biosystems), PowerPlex® Y (Promega) and Y-PLEXÔ 12 (Reliagene) products whereas the in-house systems comprised Multiplex I (MPI) and Multiplex B (MPB). Three donor couples were recruited for the study. Postcoital cervicovaginal swabs (x2) were recovered by each of the three females at specified intervals after sexual intercourse (3,7 days). Each time point sample was collected after a separate act of sexual intercourse and was preceded by a 7-day abstention period. As a negative control, a precoital swab was also recovered prior to coitus for each sampling and only data from postcoital samples that demonstrated a lack of male DNA in the associated precoital sample was used. A number of DNA profile enhancement strategies were employed including sampling by cervical brushing, nondifferential DNA extraction methodology, and post-PCR purification. Full Y-STR profiles from cervicovaginal samples recovered 3,4 days after intercourse were routinely obtained. Profiles were also obtainable 5,6 days postcoitus although by this stage partial profiles rather than full profiles were a more likely outcome. The DNA profiles from the sperm fraction of a differential lysis were superior to that obtained when a nondifferential method was employed in that the allelic signal intensities were generally higher and more balanced and exhibited less baseline noise. The incorporation of a simple post-PCR purification process significantly increased the ability to obtain Y-STR profiles, particularly from 5- to 6-day postcoital samples. Remarkably an 8 locus Y-STR profile was obtained from a 7-day postcoital sample, which is approaching the reported time limit for sperm detection in the cervix. [source] Automated stir plate (bar) sorptive extraction coupled to high-performance liquid chromatography for the determination of polycyclic aromatic hydrocarbonsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2010Chunhe Yu Abstract Automated methods of PDMS/,-CD/divinylbenzene-coated stir plate sorptive extraction (SPSE) coupled to HPLC-fluorescence detector were reported for the first time. Three automation modes, static SPSE, circular flow SPSE and continuous flow SPSE, were evaluated and critically compared with stir bar sorptive extraction by using six polycyclic aromatic hydrocarbons as model analytes. It was found that the operable sample volume for circular flow SPSE and continuous flow SPSE was larger than that for static SPSE. Under the same extraction conditions, continuous flow SPSE exhibited the highest extraction efficiencies in all automated modes and manual stir bar sorptive extraction for the target compounds. Compared with the manual operation (approximately 5,10,min), automated SPSE required a relatively short time (117,180,s) to finish sampling, washing and sample loading. Besides being labor-saving and time-saving, automated SPSE has other advantages, such as no time limit and non-attended operation. The proposed continuous flow PDMS/,-CD/divinylbenzene-coated SPSE-HPLC-fluorescence detector was successfully applied to environmental water analysis. [source] Mechanisms of force failure during repetitive maximal efforts in a human upper airway muscleMUSCLE AND NERVE, Issue 1 2002Christiana DelloRusso BS Abstract The upper airway respiratory muscles play an important role in the regulation of airway resistance, but surprisingly little is known about their contractile properties and endurance performance. We developed a technique that allows measurement of force and the electromyogram (EMG) of human nasal dilator muscles (NDMs). Endurance performance was quantified by measuring NDM "flaring" force and EMG activity as healthy human subjects performed 10 s maximal voluntary contractions (MVCs), separated by 10 s rest, until the area under the force curve fell to 50% MVC (the time limit of the fatigue task, Tlim), which was reached in 34.2 ± 3.1 contractions (685.0 ± 62.3 s). EMG activity was unchanged except at Tlim, where it averaged 78.7 ± 3.6% of pretest activity (P < 0.01). M-wave amplitude did not change, suggesting that neuromuscular propagation was not impaired. MVC force increased to 80% of the pretest level within 10 min of recovery but twitch force failed to recover, suggesting low-frequency fatigue. The data suggest that a failure of the nervous system to excite muscle could explain at most only a small fraction of the NDM force loss during an intermittent fatigue task, and then only at Tlim. Thus, the majority of the force failure during this task is due to impairment of mechanisms that reside within the muscle fibers. © 2002 Wiley Periodicals, Inc. Muscle Nerve 26: 94,100, 2002 [source] RUN/EDIT information processing mode and phasic cardiac accelerationPSYCHOPHYSIOLOGY, Issue 6 2008Tytus Sosnowski Abstract Our previous research showed that tasks demanding running of ready-to-use programs (RUN tasks) caused a greater tonic heart rate increase than did tasks that require problem solving (EDIT tasks). We found also a similar though not so consistent effect in the analysis of phasic cardiac acceleration. The aim of the present study was to replicate the last finding using new experimental tasks. Fifty-four male secondary school pupils were divided randomly into three experimental groups. Each group performed a different version of a nonsignaled reaction time (RT) task: simple RT, sensory choice RT, and semantic choice RT. Participants had to respond within an established time limit, but this limit was continuously modified in such a way that each participant was given positive feedback in approximately 50% of trials. According to expectations, the simple RT task evoked greater phasic cardiac acceleration than did the choice RT tasks. [source] Probing of Thin Slipping Films by Persistent External DisturbancesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2007N. Alleborn Abstract This paper investigates the propagation of thickness disturbances on the free surface of a thin viscous liquid film on a solid substrate. On the free surface of the film the disturbances are induced by moving local external pressure perturbations acting on the surface. The analysis is performed by the Fourier-Laplace transform applied to the linearized perturbation equations for small amplitudes. The amplitude of the interface deflection caused by the disturbance, is reconstructed by the inverse Fourier-Laplace transform and numerically evaluated in the long time limit in long wave approximation. The proposed technique appears promising for probing the slip length of a thin film by recording its free surface response to a moving perturbation. On étudie dans cet article la propagation des perturbations d'épaisseur à la surface libre d'un film liquide visqueux sur un substrat solide. Sur la surface libre du film, les perturbations sont provoquées en déplaçant des perturbations de pression externes locales agissant sur la surface. L'analyse est effectuée par l'application de la transformée de Fourier-Laplace aux équations de perturbation linéarisées pour des petites amplitudes. L'amplitude de la déviation de surface causée par la perturbation est reconstruite par la transformée de Fourier-Laplace inverse et évaluée numériquement pour un temps très long par l'approximation des ondes longues. La technique proposée apparaît prometteuse pour sonder la longueur de glissement d'un film mince en enregistrant la réponse de sa surface libre à une perturbation mobile. [source] Acute Stroke Care at Rural Hospitals in Idaho: Challenges in Expediting Stroke CareTHE JOURNAL OF RURAL HEALTH, Issue 1 2006James G. Gebhardt MD ABSTRACT:,Context: Thrombolytics are currently the most effective treatment for stroke. However, the National Institute for Neurological Disorders and Stroke criteria for initiation of thrombolytic therapy, most notably the 3-hour time limit from symptom onset, have proven challenging for many rural hospitals to achieve. Purpose: To provide a snapshot of stroke care at rural hospitals in Idaho and to investigate the experiences of these hospitals in expediting stroke care. Methods: Using a standard questionnaire, a telephone survey of hospital staff at 21 rural hospitals in Idaho was performed. The survey focused on acute stroke care practices and strategies to expedite stroke care. Findings: The median number of stroke patients treated per year was 23.3. Patient delays were reported by 77.8% of hospitals, transport delays by 66.7%, in-hospital delays by 61.1%, equipment delays by 22.2%, and ancillary services delays by 61.1%. Approximately 67% of hospitals had implemented a clinical pathway for stroke and 80.0% had provided staff with stroke-specific training. No hospitals surveyed had a designated stroke team, and only 33.3% reported engaging in quality improvement efforts to expedite stroke care. Thrombolytics (tPA) were available and indicated for stroke at 55.6% of the hospitals surveyed. Conclusions: Rural hospitals in Idaho face many difficult challenges as they endeavor to meet the 3-hour deadline for thrombolytic therapy, including limited resources and experience in acute stroke care, and many different types of prehospital and in-hospital delays. [source] Horizontal resolution impact on short- and long-range forecast errorTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 649 2010Roberto Buizza Abstract The impact of horizontal resolution increases from spectral truncation T95 to T799 on the error growth of ECMWF forecasts is analysed. Attention is focused on instantaneous, synoptic-scale features represented by the 500 and 1000 hPa geopotential height and the 850 hPa temperature. Error growth is investigated by applying a three-parameter model, and improvements in forecast skill are assessed by computing the time limits when fractions of the forecast-error asymptotic value are reached. Forecasts are assessed both in a realistic framework against T799 analyses, and in a perfect-model framework against T799 forecasts. A strong sensitivity to model resolution of the skill of instantaneous forecasts has been found in the short forecast range (say up to about forecast day 3). But sensitivity has shown to become weaker in the medium range (say around forecast day 7) and undetectable in the long forecast range. Considering the predictability of ECMWF operational, high-resolution T799 forecasts of the 500 hPa geopotential height verified in the realistic framework over the Northern Hemisphere (NH), the long-range time limit ,(95%) is 15.2 days, a value that is one day shorter than the limit computed in the perfect-model framework. Considering the 850 hPa temperature verified in the realistic framework, the time limit ,(95%) is 16.6 days for forecasts verified in the realistic framework over the NH (cold season), 14.1 days over the SH (warm season) and 20.6 days over the Tropics. Although past resolution increases have been providing continuously better forecasts especially in the short forecast range, this investigation suggests that in the future, although further increases in resolution are expected to improve the forecast skill in the short and medium forecast range, simple resolution increases without model improvements would bring only very limited improvements in the long forecast range. Copyright © 2010 Royal Meteorological Society [source] Intermethod Reliability of Real-time Versus Delayed Videotaped Evaluation of a High-fidelity Medical Simulation Septic Shock ScenarioACADEMIC EMERGENCY MEDICINE, Issue 9 2009Justin B. Williams MD Abstract Objectives:, High-fidelity medical simulation (HFMS) is increasingly utilized in resident education and evaluation. No criterion standard of assessing performance currently exists. This study compared the intermethod reliability of real-time versus videotaped evaluation of HFMS participant performance. Methods:, Twenty-five emergency medicine residents and one transitional resident participated in a septic shock HFMS scenario. Four evaluators assessed the performance of participants on technical (26-item yes/no completion) and nontechnical (seven item, five-point Likert scale assessment) scorecards. Two evaluators provided assessment in real time, and two provided delayed videotape review. After 13 scenarios, evaluators crossed over and completed the scenarios in the opposite method. Real-time evaluations were completed immediately at the end of the simulation; videotape reviewers were allowed to review the scenarios with no time limit. Agreement between raters was tested using the intraclass correlation coefficient (ICC), with Cronbach's alpha used to measure consistency among items on the scores on the checklists. Results:, Bland-Altman plot analysis of both conditions revealed substantial agreement between the real-time and videotaped review scores by reviewers. The mean difference between the reviewers was 0.0 (95% confidence interval [CI] = ,3.7 to 3.6) on the technical evaluation and ,1.6 (95% CI = ,11.4 to 8.2) on the nontechnical scorecard assessment. Comparison of evaluations for the videotape technical scorecard demonstrated a Cronbach's alpha of 0.914, with an ICC of 0.842 (95% CI = 0.679 to 0.926), and the real-time technical scorecard demonstrated a Cronbach's alpha of 0.899, with an ICC of 0.817 (95% CI = 0.633 to 0.914), demonstrating excellent intermethod reliability. Comparison of evaluations for the videotape nontechnical scorecard demonstrated a Cronbach's alpha of 0.888, with an ICC of 0.798 (95% CI = 0.600 to 0.904), and the real-time nontechnical scorecard demonstrated a Cronbach's alpha of 0.833, with an ICC of 0.714 (95% CI = 0.457 to 0.861), demonstrating substantial interrater reliability. The raters were consistent in agreement on performance within each level of training, as the analysis of variance demonstrated no significant differences between the technical scorecard (p = 0.176) and nontechnical scorecard (p = 0.367). Conclusions:, Real-time and videotaped-based evaluations of resident performance of both technical and nontechnical skills during an HFMS septic shock scenario provided equally reliable methods of assessment. [source] BRIEF PSYCHOANALYTIC PSYCHOTHERAPY: THE IMPACT OF ITS FUNDAMENTALS ON THE THERAPEUTIC PROCESSBRITISH JOURNAL OF PSYCHOTHERAPY, Issue 2 2001Ilana Laor ABSTRACT By identifying the three fundamentals of brief psychoanalytic psychotherapy , (1) time limit, (2) therapeutic focus, (3) therapist's activity , this type of therapy is established as a distinct therapeutic modality with distinct ,active containing'. The way this ,custom-tailored structure' may be adapted to the patient and used to reflect and intensify dynamic aspects of the treatment's focus is demonstrated through clinical material. [source] The yield of expanding the therapeutic time window for tPAACTA NEUROLOGICA SCANDINAVICA, Issue 5 2006J. F. Owe Objectives,,, Intravenous thrombolysis with recombinant tissue plasminogen activator (tPA) for acute ischemic stroke has been proved to be effective when given within 3 h of onset of stroke symptoms. Partly due to this time limit, less than 10% of stroke patients are treated with tPA. This study assessed the potential for increased tPA utilization with a theoretical time limit of 6 h. Materials and methods,,, A total of 117 patients admitted with a diagnosis of acute cerebrovascular disease were prospectively registered over a 3-month period, with emphasis on timing and criteria for tPA treatment. Results,,, Eighty-eight of 117 patients (75%) had an acute ischemic stroke. Of these, 23% arrived within 3 h, 8% within 3,6 h, and 69% later than 6 h after symptom onset. Of the seven patients in the 3,6 h group, only one had time delay as the only contraindication to tPA. Conclusions,,, This study suggests that reducing patient delay, rather than increasing the time limit for thrombolytic treatment, may increase the frequency of tPA utilization. Changing time limits for thrombolysis may reduce time delay from stroke onset to arrival in hospital due to more rapid handling of patients by the emergency medical services. [source] Social functioning as an outcome measure in schizophrenia studiesACTA PSYCHIATRICA SCANDINAVICA, Issue 6 2007T. Burns Objective:, Deficits in social functioning are a core feature of schizophrenia. Method:, A literature search of English language articles published between January 1990 and December 2006 was undertaken to identify: i) scales used most frequently to assess social functioning in schizophrenia; and ii) the most frequently used social functioning scales in randomized, controlled trials of antipsychotics. A further search (without time limits) examined their psychometric properties. Results:, A total of 301 articles employed social functioning scales in the assessment of schizophrenia. These contained 87 potentially relevant measures. Only 14 randomized, controlled studies of antipsychotic agents were identified that examined social functioning. Scales varied greatly in terms of measurement approach, number and types of domains covered and scoring systems. A striking lack of data on psychometric properties was observed. Conclusion:, Limited consensus on the definition and measurement of social functioning exists. The Personal and Social Performance Scale is proposed as a useful tool in future research. [source] Memory of Social Partners in Hermit Crab DominanceETHOLOGY, Issue 3 2005Francesca Gherardi We investigated the possibility that invertebrates recognize conspecific individuals by studying dominance relationships in the long-clawed hermit crab, Pagurus longicarpus. We conducted three sets of laboratory experiments to define the time limits for acquiring and maintaining memory of an individual opponent. The results reveal two characteristics that make individual recognition in this species different from standard associative learning tasks. Firstly, crabs do not require training over many repeated trials; rather, they show evidence of recognition after a single 30-min exposure to a stimulus animal. Secondly, memory lasts for up to 4 d of isolation without reinforcement. A third interesting feature of individual recognition in this species is that familiar opponents are recognized even before the formation of a stable hierarchical rank. That is, recognition seems to be relatively independent of repeated wins (rewards) or losses (punishments) in a dominance hierarchy. The experimental protocol allowed us to show that this species is able to classify conspecifics into two ,heterogeneous subgroups', i.e. familiar vs. unfamiliar individuals, but not to discriminate one individual of a group from every other conspecific from ,a unique set of cues defining that individual'. In other words, we demonstrated a ,binary', and not a ,true', individual recognition. However, 1 d of interactions with different crabs did not erase the memory of a former rival, suggesting that P. longicarpus uses a system of social partner discrimination more refined than previously shown. [source] Integrated psychodynamic therapy for bulimia nervosa and binge eating disorder: theory, practice and preliminary findingsEUROPEAN EATING DISORDERS REVIEW, Issue 6 2005Susan Murphy Abstract While there is a substantial evidence base for the use of more recently developed therapeutic approaches, there is very little evidence that psychodynamically based treatments are effective in treating bulimia nervosa or binge-eating disorder. Clinicians have suggested that such an approach should be supplemented with behavioural foci and that it should be time-limited. This paper outlines an integrative approach to the outpatient treatment of these eating disorders, where psychodynamic principles and practice are used in tandem with behavioural strategies, and presents preliminary data on behavioural changes among patients who undertake this programme. A case series design was used, employing this approach with a selected group of 21 female patients. Data are presented on failure to complete the programme, as well as changes in body mass index and frequency of bingeing and vomiting. All of the 21 patients completed the programme, though 5 were lost to the study by the last follow-up point. Those who completed the programme had a stable body mass index, but showed clinically and statistically significant reductions in bulimic symptoms. These preliminary findings indicate that the bulimic disorders can be treated effectively using a psychodynamic approach that is integrated with behavioural techniques and that has time limits. While further research is needed to support this conclusion, it appears to be important to use a more integrative psychodynamic approach than is commonly used. Copyright © 2005 John Wiley & Sons, Ltd and Eating Disorders Association. [source] Procrastination as self-regulation failure of performance: effects of cognitive load, self-awareness, and time limits on ,working best under pressure'EUROPEAN JOURNAL OF PERSONALITY, Issue 5 2001Joseph R. Ferrari Effects of cognitive load, objective self-awareness and time limits on the self-regulation of performance speed and accuracy were investigated between procrastinators and non-procrastinators. In experiment 1 chronic procrastinators completed fewer items (slow speed) and made more errors (less accuracy) than non-procrastinators under high but not low cognitive load conditions when the time span was limited and brief. In experiment 2 chronic procrastinators performed slower than non-procrastinators under a 2 second, but not under no limit, 1 second, or 4 second time limit conditions. Chronic procrastinators compared to non-procrastinators also performed more slowly and made more performance errors under objective self-awareness conditions regardless of the length of time. These experiments indicate that chronic procrastinators regulate ineffectively their performance speed and accuracy when they ,work under pressure' (defined by high cognitive load, objective self-awareness, and imposed time limitations). Copyright © 2001 John Wiley & Sons, Ltd. [source] Interpretation of Spring Recession CurvesGROUND WATER, Issue 5 2002H. Amit Recession curves contain information on storage properties and different types of media such as porous, fractured, cracked lithologies and karst. Recession curve analysis provides a function that quantitatively describes the temporal discharge decay and expresses the drained volume between specific time limits (Hall 1968). This analysis also allows estimating the hydrological significance of the discharge function parameters and the hydrological properties of the aquifer. In this study, we analyze data from perennial springs in the Judean Mountains and from others in the Galilee Mountains, northern Israel. All the springs drain perched carbonate aquifers. Eight of the studied springs discharge from a karst dolomite sequence, whereas one flows out from a fractured, slumped block of chalk. We show that all the recession curves can be well fitted by a function that consists of two exponential terms with exponential coefficients ,1 and ,2. These coefficients are approximately constant for each spring, reflecting the hydraulic conductivity of different media through which the ground water flows to the spring. The highest coefficient represents the fast flow, probably through cracks, or quickflow, whereas the lower one reflects the slow flow through the porous medium, or baseflow. The comparison of recession curves from different springs and different years leads to the conclusion that the main factors that affect the recession curve exponential coefficients are the aquifer lithology and the geometry of the water conduits therein. In normal years of rainy winter and dry summer, ,1 is constant in time. However, when the dry period is longer than usual because of a dry winter, ,1 slightly decreases with time. [source] TIME-INCONSISTENCY AND WELFARE PROGRAM PARTICIPATION: EVIDENCE FROM THE NLSY,INTERNATIONAL ECONOMIC REVIEW, Issue 4 2009Hanming Fang We empirically implement a dynamic structural model of labor supply and welfare program participation for agents with potentially time-inconsistent preferences. Using panel data on the choices of single women with children from the National Longitudinal Surveys (NLSY) 1979, we provide estimates of the degree of time-inconsistency, and of its influence on the welfare take-up decision. With these estimates, we conduct counterfactual experiments to quantify a measure of the utility loss stemming from the inability to commit to future decisions, and the potential gains from commitment mechanisms such as welfare time limits and work requirements. [source] Dental hygienists' work environment: motivating, facilitating, but also tryingINTERNATIONAL JOURNAL OF DENTAL HYGIENE, Issue 3 2010A Candell To cite this article: Int J Dent Hygiene,8, 2010; 204,212 DOI: 10.1111/j.1601-5037.2009.00420.x Candell A, Engström M. Dental hygienists' work environment: motivating, facilitating, but also trying Abstract:, The aim of the present study was to describe dental hygienists' experiences of their physical and psychosocial work environment. The study was descriptive in design and used a qualitative approach. Eleven dental hygienists participated in the study and data were collected during spring 2008 using semi-structured interviews. The material was analysed using qualitative content analysis. The results showed that the dental hygienists experienced their work environment as motivating and facilitating, but at the same time as trying. The three categories revealed a theme: Being controlled in a modern environment characterized by good relationships. Motivating factors were the good relationship with co-workers, managers and patients, seeing the results of your work, having your own responsibility and making your own decisions. The new, pleasant and modern clinics, good cooperation between co-workers and varying duties were described as facilitating factors. The trying factors, as described by the dental hygienists, were above all being controlled by time limits or by some elements of the work, such as teamwork. The dental hygienists also felt stress because appointments were too-short. To conclude, the participants described their work environment as trying in several ways, despite the modern clinics and good relationships. [source] Effects of Differentially Time-Consuming Tests on Computer-Adaptive Test ScoresJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 2 2004Brent Bridgeman Time limits on some computer-adaptive tests (CATs) are such that many examinees have difficulty finishing, and some examinees may be administered tests with more time-consuming items than others. Results from over 100,000 examinees suggested that about half of the examinees must guess on the final six questions of the analytical section of the Graduate Record Examination if they were to finish before time expires. At the higher-ability levels, even more guessing was required because the questions administered to higher-ability examinees were typically more time consuming. Because the scoring model is not designed to cope with extended strings of guesses, substantial errors in ability estimates can be introduced when CATs have strict time limits. Furthermore, examinees who are administered tests with a disproportionate number of time-consuming items appear to get lower scores than examinees of comparable ability who are administered tests containing items that can be answered more quickly, though the issue is very complex because of the relationship of time and difficulty, and the multidimensionality of the test. [source] How welfare reform affects young children: Experimental findings from Connecticut,A research noteJOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 4 2003Susanna Loeb As welfare-to-work reforms increase women's labor market attachment, the lives of their young children are likely to change. This note draws on a random-assignment experiment in Connecticut to ask whether mothers' rising employment levels and program participation are associated with changes in young children's early learning and cognitive growth. Children of mothers who entered Connecticut's Jobs First program, an initiative with strict 21-month time limits and work incentives, displayed moderate advantages in their early learning, compared with those in a control group. A number of potential mechanisms for this effect are explored, including maternal employment and income, home environment, and child care. Mothers in the new welfare program are more likely to be employed, have higher income, are less likely to be married, have more children's books in their home, and take their children to libraries and museums more frequently. However, these effects explain little of the observed gain in child outcomes. Other parenting practices and the home's social environment do explain early learning, but these remained unaffected by welfare reform. © 2003 by the Association for Public Policy Analysis and Management [source] From Welfare to Work: Has Welfare Reform Worked?JOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 4 2001Neeraj Kaushal This paper discusses estimates of the effect of welfare reform,as measured by the imposition of time limits and family cap provisions, on the employment and fertility of less educated unmarried women. This analysis shows that welfare reform has induced less educated unmarried women to move from welfare to work in significant numbers. The imposition of time limits and other administrative reforms correlated with it have increased the employment of unmarried women with 12 or fewer years of education by an estimated 363,171, approximately 28 percent of the decline in welfare caseloads for this group since 1994. Furthermore, evidence shows that women who have left welfare for employment worked approximately 29 hours per week, which even at low wages may significantly improve their financial status relative to public assistance. However, little evidence can be found to show that the imposition of time limits and family caps affect the fertility of less educated unmarried women. © 2001 by the Association for Public Policy Analysis and Management. [source] APPROXIMATING GARCH-JUMP MODELS, JUMP-DIFFUSION PROCESSES, AND OPTION PRICINGMATHEMATICAL FINANCE, Issue 1 2006Jin-Chuan Duan This paper considers the pricing of options when there are jumps in the pricing kernel and correlated jumps in asset prices and volatilities. We extend theory developed by Nelson (1990) and Duan (1997) by considering the limiting models for our approximating GARCH Jump process. Limiting cases of our processes consist of models where both asset price and local volatility follow jump diffusion processes with correlated jump sizes. Convergence of a few GARCH models to their continuous time limits is evaluated and the benefits of the models explored. [source] Scaling up CBOs for second-order devolution in welfare reformNONPROFIT MANAGEMENT & LEADERSHIP, Issue 4 2003Dennis L. Poole The Personal Responsibility and Work Opportunity Act of 1996 created a paradigm shift in the financing, organization, and delivery of welfare programs in the United States. The act shifted revenue and authority to states, giving them great discretion to determine the specifics of their programs. First-order devolution, combined with time limits and work requirements, set in motion a chain of events that moved Temporary Assistance to Needy Families (TANF) recipients into the labor force and off state welfare rolls. Second-order devolution shifted revenue and authority to community-based organizations (CBOs) to help former recipients remain employed, advance to higher paying jobs, and move their families toward economic self-sufficiency. Early findings from project innovations in Texas and other states raise doubts about the capacity of these organizations to achieve these goals. State funders will need to provide ongoing technical assistance and support to "scale up" the capacity of CBOs to plan, implement, and manage local innovations in welfare reform. [source] TIME MATTERS IN TEAM PERFORMANCE: EFFECTS OF MEMBER FAMILIARITY, ENTRAINMENT, AND TASK DISCONTINUITY ON SPEED AND QUALITYPERSONNEL PSYCHOLOGY, Issue 3 2003DAVID A. HARRISON We compared the speed and quality of performance for familiar, initially unfamiliar but continuing, and one-shot (single session) teams. We also proposed and observed entrainment effects for task time limits. Over the course of weekly sessions with changing tasks, continuing teams reached speed levels of the initially familiar teams, but the one-shot teams were consistently slower. Continuing teams also tended to have higher-quality output than the one-shot teams. There were no differences in how quickly each type of group entrained to time limits on the tasks. Entrainment was not robust to task discontinuity (Task A, then B). However, entrainment on repeated trials of a task persisted even when a different type of task "interrupted" those repeated trials (Task A, then B, then A again). Results compel a richer incorporation of time as a medium for complex task sequences, and time-based constructs as a feature of team membership in the study of group effectiveness. [source] Influence of successive bouts of fatiguing exercise on perceptual and physiological markers during an incremental exercise testPSYCHOPHYSIOLOGY, Issue 1 2009Jeremy B.J. Coquart Abstract The purpose of this study was to examine the effects of a succession of fatiguing stages, on ratings of perceived exertion (RPE) and estimated time limits (ETL) during an incremental exercise test. Twenty-seven cyclists performed a continuous incremental test and a discontinuous test with randomized workloads. A linear mixed model was used to compare the RPE, ETL, respiratory gas, heart rate, and blood data obtained during the two exercise tests. RPE and ETL were not significantly different between the tests. Ventilation, breathing frequency, heart rate, and blood lactate concentration were significantly higher during the last incremental test workloads. In conclusion, although the incremental exercise test generated higher cardiorespiratory and muscular workloads than observed during the randomized exercise test, most likely due to a greater fatiguing process, these higher workloads did not influence the perceptual response. [source] Managing complex development projects: arenas, knowledge processes and timeR & D MANAGEMENT, Issue 5 2002Jonas Söderlund The literature on project management has been dominated by techniques and methods for separating activities and making thought out plans. Closely related to this research stream is the research on product development, which seems to advocate somewhat of a different strategy where managing projects is a matter of enabling the crossing of functions and knowledge bases. This paper attempts to integrate these two lines of research. The paper is based on two in,depth case studies of project management in product development contexts. The projects under study were highly complex and consisted of multiple interrelated parts, which called for ,tightly coupled' organizational solutions. From our point of view, much effort by the project management teams was put into establishing a project that was responsive and where participating local units were oriented toward various ,global' measures. In our conception, the overall deadline seemed to have played an important role for promoting communal and interactive problem solving. Furthermore, the deadline emphasized the need for global arenas where the interactive problem solving could take place. It is argued that time,based controls set a global time for the project. The paper also demonstrates the importance of various global arenas, such as testing activities and project management forums, in order to keep track of time limits and to trigger global knowledge processes. Furthermore, based on the notion of ,separation' and ,coupling' of sub,systems and project phases, the paper suggests a model identifying four types of project organizations. The paper contributes to the knowledge on project management in complex product development. [source] | ||||||||||||||||||||||