Sampling Time Frame Research Articles

Determining the sampling time frame for In-Vehicle Data Recorder measurement in assessing drivers

The present paper describes a method for choosing a sampling time frame for an In-Vehicle Data Recorder (IVDR) as an assessment tool in analyzing driving patterns and changes in the behavior of drivers over time. The study was a short-term follow-up to assess the driving patterns of 64 cab drivers. IVDRs installed in the vehicle of each participant recorded detailed information about undesirable events that occurred during the trip regarding the position of the vehicle, its speed, vertical and horizontal acceleration, and maneuvers. A statistical analysis was carried out on the IVDR data to identify the time at which the rate of driving events stabilizes in order to find a reasonable sampling time frame. The analysis indicates that collecting a sample of ≈300h per driver should result in a relatively stable and reliable measure for assessing the driver’s average event rate, and that sampling less than 100 driving hours per driver does not result in a reliable measure. Sampling between 100–300h may also result in a stable measure but it is less recommended. The advantage of IVDR monitoring technology is that it makes it possible to evaluate changes over time and use the results to create custom-tailored interventions that can be implemented on different driving populations such as professional drivers, drivers with ADHD, new drivers, and others.

STATISTIK SPASIAL KEPADATAN PENDUDUK TERHADAP KEJADIAN MALARIA DI KABUPATEN PURWOREJO DENGAN MENGGUNAKAN GIS

Background: Malaria was a problem in tropical countries including Indonesia. Purworejo regency lay on Central Java Province is a low malaria endemic area but in the end of year 2010 outbreak occurred. Malaria influenced by behavior, social economic condition include the population density. Objective: To determine the relationship between malaria incidence and population density using GIS tool (spatial statistic). Methods: This type of study is analytic research with GIS as tool analysis. Sample time frame is Nov 2010-March 2011 and the unit research for population density is village. Results: Majority Village in Purworejo categorized in low population density. Malaria incidence at Nov 2010-March 2011 lay on the village with low population density. Result of Spatial statistic (using Geoda) spatially weighted regression shows that no relationship between malaria incidence and population density, z value = -0,800; p= 0,432 (p > 0, 05) Conclusion: There was no relationship between malaria incidence and population density (spatial statistic using Geoda). Key words: malaria, GIS, population density

Does specific psychopathology predict development of psychosis in ultra high-risk (UHR) patients?

Studies have attempted to identify additional risk factors within the group identified as 'ultra high risk' (UHR) for developing psychotic disorders in order to characterise those at highest risk. However, these studies have often neglected clinical symptom types as additional risk factors. We aimed to investigate the relationship between baseline clinical psychotic or psychotic-like symptoms and the subsequent transition to a psychotic disorder in a UHR sample. A retrospective 'case-control' methodology was used. We identified all individuals from a UHR clinic who had subsequently developed a psychotic disorder (cases) and compared these to a random sample of individuals from the clinic who did not become psychotic within the sampling time frame (controls). The sample consisted of 120 patients (60 cases, 60 controls). An audit tool was used to identify clinical symptoms reported at entry to the clinic (baseline) using the clinical file. Diagnosis at transition was assessed using the Operational Criteria for Psychotic Illness (OPCRIT) computer program. The relationship between transition to a psychotic disorder and baseline symptoms was explored using survival analysis. Presence of thought disorder, any delusions and elevated mood significantly predicted transition to a psychotic disorder. When other symptoms were adjusted for, only the presence of elevated mood significantly predicted subsequent transition (hazard ratio 2.69, p = 0.002). Thought disorder was a predictor of transition to a schizophrenia-like psychotic disorder (hazard ratio 3.69, p = 0.008). Few individual clinical symptoms appear to be predictive of transition to a psychotic disorder in the UHR group. Clinicians should be cautious about the use of clinical profile alone in such individuals when determining who is at highest risk.

Reply to Frerichs et al.: Chasing the genetic diversity, not source attribution

Frerichs et al. (1) view the prevalence of Vibrio cholerae non-O1/O139 skeptically in the early weeks of the Haitian epidemic (2). Unexpected findings spawn skeptics. Setting aside differences in sampling time frames, differences in recoveries might readily be traced to comprehensive sampling and methodologies. Using a combination of thiosulphate-citrate-bile salt-sucrose and taurocholate tellurite gelatin agar medium to substantiate detection of both sucrose fermenting and nonfermenting V. cholerae reported in this region (3), we picked multiple single-colony isolates (average of 4, depending on availability of well-separated colonies and colony morphologies) on each original plate, which were screened systematically, using a battery of specific biochemical, serological, and molecular methods. Sensitive and discriminating, but more expensive and labor- and time-intensive, our approach is seldom used in settings like Haiti National Public Health Laboratory. Our approach uncovered non-O1/O139 in the numbers reported, which less fastidious conventional screening would underestimate. We advocate for such an approach to become standard.

Evaluation of land use regression models for NO2 in El Paso, Texas, USA

Developing suitable exposure estimates for air pollution health studies is problematic due to spatial and temporal variation in concentrations and often limited monitoring data. Though land use regression models (LURs) are often used for this purpose, their applicability to later periods of time, larger geographic areas, and seasonal variation is largely untested. We evaluate a series of mixed model LURs to describe the spatial-temporal gradients of NO2 across El Paso County, Texas based on measurements collected during cool and warm seasons in 2006–2007 (2006–7). We also evaluated performance of a general additive model (GAM) developed for central El Paso in 1999 to assess spatial gradients across the County in 2006–7. Five LURs were developed iteratively from the study data and their predictions were averaged to provide robust nitrogen dioxide (NO2) concentration gradients across the county. Despite differences in sampling time frame, model covariates and model estimation methods, predicted NO2 concentration gradients were similar in the current study as compared to the 1999 study. Through a comprehensive LUR modeling campaign, it was shown that the nature of the most influential predictive variables remained the same for El Paso between 1999 and 2006–7. The similar LUR results obtained here demonstrate that, at least for El Paso, LURs developed from prior years may still be applicable to assess exposure conditions in subsequent years and in different seasons when seasonal variation is taken into consideration.

Remifentanil versus fentanyl for intravenous patient-controlled labour analgesia: an observational study

We undertook a retrospective study to compare the analgesic efficacy and effects on neonatal outcome of administering either remifentanil or fentanyl intravenous patient-controlled analgesia (IVPCA) during labour. A five-year retrospective cohort study was undertaken of women with more than 24weeks of gestation who had received either IVPCA remifentanil or fentanyl for labour analgesia at Mount Sinai Hospital. The sampling timeframe was from November 2005 to March 2010. The standard IVPCA regimen for the remifentanil group consisted of a PCA bolus 0.25μg·kg(-1) with a lockout interval of two minutes, a four-hour limit of 3mg, and a background infusion of 0.025-0.05 μg·kg(-1)·min(-1), whereas the standard IVPCA regimen for the fentanyl group consisted of a PCA bolus 25-50 μg with a lockout interval of three to six minutes and a four-hour limit of 1-1.5mg. The following data were compared: maternal hourly pain scores (verbal pain score scale 0-10), sedation scores (scale 0-3), adverse effects, and neonatal outcomes. Mixed linear modelling was used to analyze longitudinal data on pain scores over time. The exact Wilcoxon test and the Fisher's exact test were used for other comparisons. Ninety-eight women were studied. There was no significant difference in the model-adjusted pain scores between the two groups (P=0.86). There was a moderate decrease in pain scores in both groups compared with the baseline values. There was no difference in maternal side effects between the two groups, although transient oxygen desaturation was observed more frequently in the remifentanil group than in the fentanyl group (13% vs 2%, respectively; odds ratio, 7.32; 95% confidence interval [CI], 0.85 to 63.3). A larger number of neonates in the fentanyl group required resuscitation compared with neonates in the remifentanil group (59% vs 25%, respectively; odds ratio, 4.33; 95% CI, 1.75 to 10.76); adjusted (44% vs 8%, respectively; odds ratio, 8.56; 95% CI, 2.17 to 33.77). Intravenous patient-controlled analgesia with either remifentanil or fentanyl provides a moderate degree of labour analgesia, whereas transient maternal oxygen desaturation is observed more commonly with remifentanil. Fentanyl is associated with a higher need for neonatal resuscitation.

The Effect of Earned Income Tax Credit Expansions on the Smoking Behavior of Women

We investigate the impact of Earned Income Tax Credit (EITC) expansions on the smoking behavior of women. The differential increases in federal EITC benefits by family size as part of the 1993 OBRA expansion allow for a comparison of smoking status changes between women with and without children and between mothers with one and more than one child. We exploit these changes in a difference-in-differences framework using data from the 1993-2001 waves of the Behavioral Risk Factor Surveillance System (BRFSS) to show that the increase in EITC benefits yielded a significant decline in the likelihood of smoking among unmarried women with less than a college degree. These results are also robust to an alternative measure of EITC expansion, specifically the maximum state-level EITC benefit (in dollars), which varies across states and over the full course of the sample time frame.

Electroconvulsive Therapy Training and Confidence in Administration

: As the lack of on-site electroconvulsive therapy (ECT) facilities in many psychiatric hospitals in Ireland may impact negatively on ECT training, we conducted a national survey of trainees with the aims of establishing the current standard of ECT training and to assess trainees' confidence in their abilities in ECT administration. : A national postal survey of 415 trainees was conducted in September 2008 using a self-designed 15-item questionnaire for the purpose of the study, containing no identification data and incorporating relevant questionnaire items from similar published trainee survey. Reminders were distributed to the entire study sample 4 weeks afterward within a sampling time frame of 3 months. Trainee responses were coded and converted to anonymized data, which the lead author held. : The overall response rate was 61%. Ninety-one percent of trainees had worked in ECT centers, of which 36% had given ECT on an occasion without direct consultant supervision. Overall, 12% of trainees had never administered or observed ECT, which includes 2 trainees on the national senior registrar scheme, and 19% of trainees had nil or minimal confidence in their ability to administer ECT. : Our findings indicate deficiencies in training and supervision, which is reflected in the proportion of trainees reporting nil or minimal confidence in their ability to administer ECT. Greater collaboration between training scheme coordinators, clinical tutors, and the College of Psychiatry of Ireland is essential to ensure ongoing monitoring and implementation of standards.

Errors in particle tracking velocimetry with high-speed cameras

Velocity errors in particle tracking velocimetry (PTV) are studied. When using high-speed video cameras, the velocity error may increase at a high camera frame rate. This increase in velocity error is due to particle-position uncertainty, which is one of the two sources of velocity errors studied here. The other source of error is particle acceleration, which has the opposite trend of diminishing at higher frame rates. Both kinds of errors can propagate into quantities calculated from velocity, such as the kinetic temperature of particles or correlation functions. As demonstrated in a dusty plasma experiment, the kinetic temperature of particles has no unique value when measured using PTV, but depends on the sampling time interval or frame rate. It is also shown that an artifact appears in an autocorrelation function computed from particle positions and velocities, and it becomes more severe when a small sampling-time interval is used. Schemes to reduce these errors are demonstrated.

Economic growth and multi-tasking by state-owned enterprises: An analytic framework and empirical study based on Chinese provincial data

By preventing large-scale unemployment during China's economic transition, state-owned enterprises (SOEs) helped maintain social stability, which supported the development of non-state sectors through a positive externality. Yet this burden reduced the productive efficiency of SOEs. Using a simple framework with two sectors, our paper decomposes the conflicting contributions of SOEs (lower efficiency but enhanced stability) to regional economic growth during 1992–2007. We find that productive efficiency in the state sector was lower than in other sectors and identify a significant positive externality that supported non-state sectors. Since these two effects offset each other, the contribution of SOEs to economic growth in China during our sample time frame was not significantly different from that of non-state enterprises.

The influence of the underwriting syndicate on the valuation of Spanish initial public offerings

The aim of this paper is to analyze the role of the underwriting syndicate in relation to firms that went public on the Madrid Stock Exchange between 1985 and 2004. The sample time frame chosen, which covers a period of twenty years, allows us to analyze the evolution of the role of the underwriting syndicate in valuation and information production throughout the process of going public in the case of the Spanish stock market. The results obtained provide evidence that the forming of larger underwriting syndicates leads to a better valuation of the offered titles. Likewise, in light of the results obtained, less underpricing is observed for those IPOs whose final offering price has been upwardly revised from the registration statement.

Epstein-Barr Virus (EBV) Prevalence and the Risk of Reactivation in Patients with Inflammatory Arthritis Using Anti-TNF Agents and in those who are Biologic Naive

Objective:Anti-TNF agents (etanercept, infliximab and adalimumab) are widely used in inflammatory conditions, such as rheumatoid arthritis; however, they are not without side effects, potentially including lymphoma. We compared Epstein-Barr virus (EBV) levels in patients with inflammatory arthritis taking biologic agents and controls matched for disease, age, gender and disease duration who were biologic naïve. Secondly, we determined the risk of reactivation of EBV in patients taking biologics.Methods:One hundred and twenty-two patients were recruited and blood samples were collected. Immunoglobulin G (IgG) antibody to EBV was analysed using enzyme-linked immunosorbent assay. EBV DNA was analysed using polymerase chain reaction (PCR) on all positive IgG samples. Quantitative measures of viral DNA were made and expressed as copies/reaction volume. Reactivation was defined as the presence of viral DNA in the plasma and PCR activity was evaluated between 6 and 18 months after anti-TNF therapy.Results:IgG for EBV was detected in 98% of controls and 90% of cases. Viral reactivation related to EBV was not observed in this study. There was one patient who tested positive for EBV using PCR, but upon confirmatory testing, this sample was actually negative. No samples were positive on PCR at the follow-up time points.Conclusion:There was a high rate of EBV IgG in the cases and controls in this study. Given the small sample size and timeframe for this study, treatment with anti-TNF agents does not seem to lead to EBV reactivation, and thus, this is likely not a mechanism for the development of lymphoma in patients taking biologics.

Effects of restrained eating behaviour on insulin sensitivity in normal-weight individuals

Restrained eating behaviour has been linked to abnormalities in metabolic and endocrine functions. However, the impact of restraint on fasting insulin and glucose plasma levels and insulin sensitivity remains controversial. Moreover, the few postprandial studies to date are limited by an inappropriate sampling time frame and a low “net” energy and carbohydrate load. The aims of this study are to assess the role of dietary restraint on fasting and postprandial plasma levels of insulin, glucose, triacylglycerol (TAG) and non esterified fatty acids (NEFA) in healthy volunteers with a normal and stable body weight and to determine whether the effect of restraint on the plasma levels of the previous hormones/metabolites is load dependent. Normal-weight participants (21 women and 12 men) were classified as restrained/unrestrained based on the restraint scale of the Three Factor Eating Questionnaire-18R and Dutch Eating Behaviour Questionnaire. The impact of restraint on the plasma levels of different hormones/metabolites was measured, in response to a 500 kcal and 1000 kcal breakfast, using a randomised crossover design. Restraint was associated with lower fasting insulin plasma levels ( P < 0.05) and a lower insulin ( P < 0.015) and glucose ( P < 0.05) plasma levels in the postprandial state, but did not impact on TAG or NEFA. Moreover, restrained eaters showed a better fasting ( P < 0.05) and postprandial insulin sensitivity ( P < 0.01). Restrained eating behaviour has, therefore, a significant impact on both fasting and postprandial glucose metabolism, being associated with increased insulin sensitivity. These findings suggest the need for adjusting for restraint level in studies where glucose metabolism is a major outcome.

Perpetration of Violence, Violent Victimization, and Severe Mental Illness: Balancing Public Health Concerns

This review examined U.S. empirical studies published since 1990 of the perpetration of violence and of violent victimization among persons with severe mental illness and their relative importance as public health concerns. MEDLINE, PsycINFO, and Web of Science were searched for published empirical investigations of recent prevalence or incidence of perpetration or victimization among persons with severe mental illness. Studies of special populations were included if separate rates were reported for persons with and without severe mental illness. The search yielded 31 studies of violence perpetration and ten studies of violent victimization. Few examined perpetration and victimization in the same sample. Prevalence rates varied by sample type and time frame (recall period). Half of the studies of perpetration examined inpatients; of these, about half sampled only committed inpatients, whose rates of perpetration (17%-50%) were higher than those of other samples. Among outpatients, 2% to 13% had perpetrated violence in the past six months to three years, compared with 20% to 34% who had been violently victimized. Studies combining outpatients and inpatients reported that 12% to 22% had perpetrated violence in the past six to 18 months, compared with 35% who had been a victim in the past year. Perpetration of violence and violent victimization are more common among persons with severe mental illness than in the general population. Victimization is a greater public health concern than perpetration. Ironically, the discipline's focus on perpetration among inpatients may contribute to negative stereotypes.

Successful diversification strategies of electricity companies: An explorative empirical study on the success of different diversification strategies of German electricity companies in the wake of the European market liberalization

Based on the EC directive 96/92, the liberalization of electricity markets is forcing electricity companies, to rethink their product and market strategy. However, neither the level of the initiated diversification efforts of former monopolies, nor their direction or their success are known or have been analyzed before. Therefore, Müller [2006. Diversifikationsstrategien von Stromversorgungsunternehmen: Handlungsempfehlungen für schweizerische Stromversorgungsunternehmen auf der Basis einer empirischen Analyse des liberalisierten deutschen Strommarktes. IIMT University Press, Fribourg] has quantitatively determined the extent and direction of the diversification efforts in the electricity sector. Additionally, based on an exploratory case study research, successful diversification strategies have been identified and incorporated into 73 observations which form the basis of a set of normative recommendations for diversifying electricity companies. Since the analyses are based on the German electricity market, which fully liberalized earlier than most of its continental European counterparts, the results may especially guide other European electricity companies in their strategic diversification decisions. This paper publishes both the quantitative analysis on the degree and extents of diversification (sample time frame 1995–2000) as well as the qualitative analysis on the success of diversification strategies (sample time frame 1995–2003). Additionally, based on the obtained explorative observations, the diversification strategy of an idealized-electricity company is firstly presented for practitioners as normative recommendation, and secondly for academics, as starting point for future quantitative analysis framework.

Exploring the sources of privatization‐induced performance changes

PurposeThe purpose of this paper is to study the variance of post‐privatization performance outcomes by three institutional arrangements taken place in the process of ownership transfer in Taiwan.Design/methodology/approachThe logistic regression models were used for the study to link the likelihood of performance improvements after privatization with a set of explanatory variables.FindingsThe findings from the research suggest an indispensable role of supportive policy measures, including market openness, post‐privatization involvement of government and corporate reforms prior to privatization, in the performance effects of privatization.Research limitations/implicationsBoth the sample size and time frame available for a quantitative analysis are constrained by the progress of Taiwan's privatization. A questionnaire survey, as part of a more integrated model, is suggested to follow this study and probe into organizational or strategic changes after privatization.Practical implicationsThe study shows that performance improvement of privatized firms cannot be taken for granted merely by ownership change; instead, the performance gains of privatization could be realized only in concert with other institutional arrangements, including market openness, the modest and short‐term bureaucratic control after privatization, and corporate health prior to privatization.Originality/valueThe study aims to add to the body of literature by identifying sources of performance changes in privatized firms, based on Taiwan's experience in privatization. Taiwan represents an interesting example of a country in the process of catching up in terms of economic development, as well as one whose institutional environment stands between western and transition countries. As such, the use of Taiwan's data may lead to an assessment of the generalizability of conclusions drawn from prior research conducted in both kinds of countries.

The early employment influences of sales representatives on the development of organizational commitment

PurposeThis paper aims to assess the status of the organizational commitment construct and introduce a new way of looking at organizational commitment – especially in early stages of employment, wherein the target company seems to be having problems.Design/methodology/approachChange in organizational commitment is measured at two points in the early employment of new salespersons in order to isolate the effects of early employment exposure of the medical representatives, a period of 18‐month when attrition of new employees is high.FindingsTraining satisfaction and perceived reward equity were the only antecedent factors that showed significant positive relationship with organizational commitment. Manager commitment showed positive contribution, the relationship was not significant. All the three antecedents significantly contributed to organizational commitment. The strongest contributor was manager commitment.Research limitations/implicationsThe sample time frame is limited to two data points. Additional research is needed to determine whether these variables have similar influence in other organizations or whether other antecedent variables can be identified.Practical implicationsCompany management must pay more attention to early employment experiences. New salespersons need the training to feel competent and able to meet company mandated and/or personal objectives. Salespeople have primary contact to the organization via their immediate sales manager and need to feel like they are fairly rewarded for their efforts. Commitment to the organization partly due to a commitment to the area manager. It is important to build strong relations at the area manager level.Originality/valueThis effort is a by‐product of a research activity on the effectiveness a pharmaceutical company's training program for newly hired sales representatives.

Detecting declines in catch rates of diverse trawl bycatch species, and implications for monitoring

Trawl fisheries around the world are being pressured to demonstrate that their impacts on both the target and bycatch species are sustainable in the long-term. However, the effectiveness of sampling catches to assess the viability of populations of non-targeted species is rarely examined. We estimated the levels of fishery-dependent sampling effort required to detect declines in catch rates of prawn trawl bycatch from 95 commercial trawls in two regions of Australia's Northern Prawn Fishery. We explore a range of possible monitoring options including combining different sampling intensities, time-frames and levels of statistical power. Poisson and negative binomial models were used to determine the number of trawls required to detect a range of declines. We found that between 15,536 and 24,933 trawls, depending on the region, would be required to detect a 20% decline in catch rates of the rarest taxa (<0.1 individuals h −1), assuming a power of 90% and a level of significance of 5%. Assuming a lower detection power (70%), trawl numbers would drop to 9126 and 14,646, respectively. Using a model of a constant decline in relative abundance (over 5 years), data accumulated from modest-sized annual surveys (52 and 43 trawls in two regions) would provide increasing power to detect changes in catch rates. After 3 years, surveys of this size (and power of 70%), could detect declines of 99.9% in 72–81% of taxa, declines of 50% in 34–43% of taxa, and declines of 20% in 20–34% of taxa, depending on the region. After 5 years, the power to detect declines of 50% had increased to cover 43–72% of taxa, and declines of 20% in 34–43% of taxa. Our results indicate that the power to detect even quite large declines in catch rates of rarely caught species would only be possible after some years of modest-sized annual surveys.

BUILDING PHENOLOGICAL MODELS FROM PRESENCE/ABSENCE DATA FOR A BUTTERFLY FAUNA

Species phenology is increasingly being used to explore the effects of climate change and other environmental stressors. Long-term monitoring data sets are essential for understanding both patterns manifest by individual species and more complex patterns evident at the community level. This study used records of 78 butterfly species observed on 626 days across 27 years at a site in northern California, USA, to build quadratic logistic regression models of the observation probability of each species for each day of the year. Daily species probabilities were summed to develop a potential aggregate species richness (PASR) model, indicating expected daily species richness. Daily positive and negative contributions to PASR were calculated, which can be used to target optimum sampling time frames. Residuals to PASR indicate a rate of decline of 0.12 species per year over the course of the study. When PASR was calculated for wet and dry years, wet years were found to delay group phenology by up to 17 days and reduce the maximum annual expected species from 32.36 to 30. Three tests to determine how well the PASR model reflected the butterfly fauna dynamics were all positive: We correlated probabilities developed with species presence/absence data to observed abundance by species, tested species' predicted phenological patterns against known biological characteristics, and compared the PASR curve to a spline-fitted curve calculated from the original species richness observations. Modeling individual species' flight windows was possible from presence/absence data, an approach that could be used on other similar records for butterfly communities with seasonal phenologies, and for common species with far fewer dates than used here. It also provided a method to assess sample frequency guidelines for other butterfly monitoring programs.

Biomonitoring of exposure in farmworker studies.

Although biomonitoring has been used in many occupational and environmental health and exposure studies, we are only beginning to understand the complexities and uncertainties involved with the biomonitoring process—from study design, to sample collection, to chemical analysis—and with interpreting the resulting data. We present an overview of concepts that should be considered when using biomonitoring or biomonitoring data, assess the current status of biomonitoring, and detail potential advancements in the field that may improve our ability to both collect and interpret biomonitoring data. We discuss issues such as the appropriateness of biomonitoring for a given study, the sampling time frame, temporal variability in biological measurements to nonpersistent chemicals, and the complex issues surrounding data interpretation. In addition, we provide recommendations to improve the utility of biomonitoring in farmworker studies.