WorldWideScience

Sample records for variance unplanned downtime

  1. Hardwood sawmill downtime costs

    Science.gov (United States)

    Jan Wiedenbeck; Kyle Blackwell

    2003-01-01

    How time flies when you don't pay attention to it. With hardwood sawmill operating costs ranging from $4 to $25 per operating minute ($95/MBF to $335/MBF) and gross profit margins ranging from $0.10/BF to $0.35/BF, five extra minutes of downtime per day will cost a sawmill that produces an average of 20,000 BF per day (5 MMBF annually) between $21 and $73 per day...

  2. Hoist motor replacements. Help slash downtime, unplanned outages

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, J.

    2004-11-01

    The article describes the design and retrofitting of a 'Dynamic Field Control' system to a P & H 4100 shovel. Designed by Drives and Controls Services Inc., this is a control system operated with a programmable logic control that enhances the performance of the hoist motor on the shovel. Flanders Electric Motor Service fitted prototype M22 motors with these control to P & H 4100 shovels in February 2001. Since then they have been retrofitted successfully to other shovels, in operation in India and Australia. 4 figs.

  3. Unplanned Hospital Visits - National

    Data.gov (United States)

    U.S. Department of Health & Human Services — Unplanned Hospital Visits – national data. This data set includes national-level data for the hospital return days (or excess days in acute care) measures, the...

  4. Leading unplanned change.

    Science.gov (United States)

    Erickson, Jeanette Ives

    2014-03-01

    The article presents reflections on how Magnet® principles help nurse leaders through unplanned change using the 1-year anniversary of the Boston Marathon bombings and the response at Massachusetts General Hospital as an exemplar.

  5. 3. Unplanned pregnancy

    African Journals Online (AJOL)

    Sitwala

    Design: Using a cross-sectional study design the disclosure .... violence, upsetting family members, and accusation. 16,17,18,19 .... pregnancies and other studies have also shown violence as an ..... issue: domestic violence and unplanned.

  6. Downtime after Critical Incidents in Emergency Medical Technicians/Paramedics

    Directory of Open Access Journals (Sweden)

    Janice Halpern

    2014-01-01

    Full Text Available Effective workplace-based interventions after critical incidents (CIs are needed for emergency medical technicians (EMT/paramedics. The evidence for a period out of service post-CI (downtime is sparse; however it may prevent posttraumatic stress disorder (PTSD and burnout symptoms. We examined the hypothesis that downtime post-CI is associated with fewer symptoms of four long-term emotional sequelae in EMT/paramedics: depression, PTSD, burnout, and stress-related emotional symptoms (accepted cut-offs defined high scores. Two hundred and one paramedics completed questionnaires concerning an index CI including downtime experience, acute distress, and current emotional symptoms. Nearly 75% received downtime; 59% found it helpful; 84% spent it with peers. Downtime was associated only with lower depression symptoms, not with other outcomes. The optimal period for downtime was between 1 day being less effective. Planned testing of mediation of the association between downtime and depression by either calming acute post-CI distress or feeling helped by others was not performed because post-CI distress was not associated with downtime and perceived helpfulness was not associated with depression. These results suggest that outcomes of CIs follow different pathways and may require different interventions. A brief downtime is a relatively simple and effective strategy in preventing later depression symptoms.

  7. Measurement of Sedentary Behaviors or "Downtime" in Rett Syndrome

    DEFF Research Database (Denmark)

    Stahlhut, Michelle; Hill, Kylie; Bisgaard, Anne-Marie

    2017-01-01

    measured duration of sedentary time with a mean difference (limit of agreement) of -1.0 (6.3) minutes. The duration of Bouchard activity record downtime accounted for 73% of the variance of sedentary time measured by the activPAL (coefficient 0.762, 95% CI 0.413 to 1.111). These data provide clinicians......This study aimed to validate measures of sedentary time in individuals with Rett syndrome. Twenty-six individuals (median [IQR] age 16.0 (9.4-20.6) years) wore an activPAL accelerometer during video-taped activities and agreement was determined between sedentary time determined by the activ......PAL and observation. For 11 individuals (median [IQR] age 14.5 (11.5-25.6) years), linear regression was used to determine the relationship between sedentary time recorded on the modified Bouchard activity record diary card and measured using the activPAL. In comparison to observation, the activPAL accurately...

  8. World-class materiel flexibility: one plant's victory over materiel-related downtime.

    Science.gov (United States)

    Samelson, Q B

    1997-05-01

    It is not uncommon for the materiel managers in a manufacturing company to be blamed for downtime and the consequent failure to meet production targets. To avoid downtime, materiel managers need to look at their role in solving materiel-related downtime and to address the problems that cause downtime in the same way they would address other process quality problems.

  9. Maintenance strategies to reduce downtime due to machine positional errors

    OpenAIRE

    Shagluf, Abubaker; Longstaff, A.P.; Fletcher, S.

    2014-01-01

    Proceedings of Maintenance Performance Measurement and Management (MPMM) Conference 2014 Manufacturing strives to reduce waste and increase Overall Equipment Effectiveness (OEE). When managing machine tool maintenance a manufacturer must apply an appropriate decision technique in order to reveal hidden costs associated with production losses, reduce equipment downtime competentely and similiarly identify the machines performance. Total productive maintenance (TPM) is a maintenance progr...

  10. Availability, reliability and downtime of systems with repairable components

    DEFF Research Database (Denmark)

    Kiureghian, Armen Der; Ditlevsen, Ove Dalager; Song, J.

    2007-01-01

    Closed-form expressions are derived for the steady-state availability, mean rate of failure, mean duration of downtime and lower bound reliability of a general system with randomly and independently failing repairable components. Component failures are assumed to be homogeneous Poisson events in ...

  11. Algorithm of probabilistic assessment of fully-mechanized longwall downtime

    Science.gov (United States)

    Domrachev, A. N.; Rib, S. V.; Govorukhin, Yu M.; Krivopalov, V. G.

    2017-09-01

    The problem of increasing the load on a long fully-mechanized longwall has several aspects, one of which is the improvement of efficiency in using available stoping equipment due to the increase in coefficient of the machine operating time of a shearer and other mining machines that form an integral part of the longwall set of equipment. The task of predicting the reliability indicators of stoping equipment is solved by the statistical evaluation of parameters of downtime exponential distribution and failure recovery. It is more difficult to solve the problems of downtime accounting in case of accidents in the face workings and, despite the statistical data on accidents in mine workings, no solution has been found to date. The authors have proposed a variant of probability assessment of workings caving using Poisson distribution and the duration of their restoration using normal distribution. The above results confirm the possibility of implementing the approach proposed by the authors.

  12. Unplanned readmission following transoral robotic surgery.

    Science.gov (United States)

    Topf, Michael C; Vo, Amanda; Tassone, Patrick; Shumrick, Christopher; Luginbuhl, Adam; Cognetti, David M; Curry, Joseph M

    2017-12-01

    To determine the rate of unplanned readmission after transoral robotic surgery (TORS), and to determine which patient or surgical factors increase the likelihood of readmission. Retrospective chart review of all patients who underwent TORS for squamous cell carcinoma at our institution from March 2010 through July 2016. Primary outcome was unplanned readmission to the hospital within 30 days of discharge. Univariable and multivariable logistic regression were performed to identify risk factors for unplanned readmission. 297 patients met eligibility criteria. 23 patients (7.7%) had unplanned readmissions within 30 days. Most common reasons for readmission were oropharyngeal bleed (n = 13) and pain/dehydration (n = 10). Average time to unplanned readmission was 6.52 days (range 0-25 days). Discharge on clopidogrel was the only variable independently associated with an increased risk of 30-day unplanned readmission on multivariable analysis with an OR = 6.85 (95% CI 1.59-26.36). Unplanned return to the operating room during initial hospitalization (OR = 7.55, 95% CI 1.26-38.50) and discharge on clopidogrel (OR = 10.45, 95% CI 1.06-82.69) were associated with increased risk of postoperative bleeding. Bilateral neck dissection (OR = 5.17, 95% CI 1.15-23.08) was associated with significantly increased odds of unplanned readmission secondary to pain and dehydration. Unplanned readmission following TORS occurs in a small but significant number of patients. Oropharyngeal bleeding and dehydration were the most common reasons for unplanned readmission following TORS. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Noninvasive positive pressure ventilation in unplanned extubation

    Energy Technology Data Exchange (ETDEWEB)

    Eryuksel, Emel; Sait, Karakurt; Celikel, Turgay [Dept. of Pulmonary and Critical Care, Marmara Univ. Hospital, (Turkey)

    2009-07-01

    Unplanned extubation is quite common in intensive care unit (ICU) patients receiving mechanical ventilatory support. The present study aimed to investigate the effectiveness of noninvasive positive pressure ventilation (NPPV) in patients with unplanned extubation. A total of 15 patients (12 male, age: 57 + - 24 years, APACHE II score: 19 + - 7) monitored at the medical ICU during the year 2004 who developed unplanned extubation were included in the study. NPPV was tried in all of them following unplanned extubation. Indications for admission to the ICU were as follows: nine patients with pneumonia, three with status epilepticus, one with gastrointestinal bleeding, one with cardiogenic pulmonary edema and one with diffuse alveolar bleeding. Eleven of the patients (74%) were at the weaning period at the time of unplanned extubation. Among these 11 patients, NPPV was successful in 10 (91%) and only one (9%) was reintubated due to the failure of NPPV. The remaining four patients (26%) had pneumonia and none of them were at the weaning period at the time of extubation, but their requirement for mechanical ventilation was gradually decreasing. Unfortunately, an NPPV attempt for 6-8 h failed and these patients were reintubated. Patients with unplanned extubation before the weaning criteria are met should be intubated immediately. On the other hand, when extubation develops during the weaning period, NPPV may be an alternative. The present study was conducted with a small number of patients, and larger studies on the effectiveness of NPPV in unplanned extubation are warranted for firm conclusions. (author)

  14. Noninvasive positive pressure ventilation in unplanned extubation

    International Nuclear Information System (INIS)

    Eryuksel, Emel; Karakurt Sait; Celikel, Turgay

    2009-01-01

    Unplanned extubation is quite common in intensive care unit (ICU) patients receiving mechanical ventilatory support. The present study aimed to investigate the effectiveness of noninvasive positive pressure ventilation (NPPV) in patients with unplanned extubation. A total of 15 patients (12 male, age: 57 + - 24 years, APACHE II score: 19 + - 7) monitored at the medical ICU during the year 2004 who developed unplanned extubation were included in the study. NPPV was tried in all of them following unplanned extubation. Indications for admission to the ICU were as follows: nine patients with pneumonia, three with status epilepticus, one with gastrointestinal bleeding, one with cardiogenic pulmonary edema and one with diffuse alveolar bleeding. Eleven of the patients (74%) were at the weaning period at the time of unplanned extubation. Among these 11 patients, NPPV was successful in 10 (91%) and only one (9%) was reintubated due to the failure of NPPV. The remaining four patients (26%) had pneumonia and none of them were at the weaning period at the time of extubation, but their requirement for mechanical ventilation was gradually decreasing. Unfortunately, an NPPV attempt for 6-8 h failed and these patients were reintubated. Patients with unplanned extubation before the weaning criteria are met should be intubated immediately. On the other hand, when extubation develops during the weaning period, NPPV may be an alternative. The present study was conducted with a small number of patients, and larger studies on the effectiveness of NPPV in unplanned extubation are warranted for firm conclusions. (author)

  15. Improvements in longwall downtime analysis and fault identification

    Energy Technology Data Exchange (ETDEWEB)

    Daniel Bongers [CRCMining (Australia)

    2006-12-15

    In this project we have developed a computer program for recording detailed information relating to face equipment downtime in longwall mining operations. This software is intended to replace the current manual recording of delay information, which has been proven to be inaccurate. The software developed is intended to be operated from the maingate computer. Users are provided with a simple user interface requesting that nature of each delay in production, which is time-stamped in alignment with the SCADA system, removing the need for operators to estimate the start time and duration of each delay. Each instance of non-production is recorded to a database, which may be accessed by surface computers, removing the need for transcribing of the deputy's report into the delay database. An additional suggestive element has been developed, based on sophisticated fault detection technology, which reduces the data input required by operators, and provides a basis for the implementation of real-time fault detection. Both the basic recording software and the suggestive element offer improvements in efficiency and accuracy to longwall operations. More accurate data allows improved maintenance planning and improved measures of operational KPIs. The suggestive element offers the potential for rapid fault diagnosis, and potentially delay forecasting, which may be used to reduce lost time associated with machine downtime.

  16. Beam reliability and equipment downtime tracking how Lansce closes the loop

    International Nuclear Information System (INIS)

    Callaway, N.T.; Ryder, R.D.

    2003-01-01

    LANSCE uses a semi-automated accounting system to track how well we meet our stated beam delivery goals. When an equipment failure prevents delivery of the desired beam to our customers, the first order cause is identified and an accurate measurement of the downtime is recorded. For equipment downtimes of significant duration, we investigate the causes and make recommendations that will hopefully eliminate or mitigate the impact of similar downtimes in the future. (authors)

  17. Downtime procedures for the 21st century: using a fully integrated health record for uninterrupted electronic reporting of laboratory results during laboratory information system downtimes.

    Science.gov (United States)

    Oral, Bulent; Cullen, Regina M; Diaz, Danny L; Hod, Eldad A; Kratz, Alexander

    2015-01-01

    Downtimes of the laboratory information system (LIS) or its interface to the electronic medical record (EMR) disrupt the reporting of laboratory results. Traditionally, laboratories have relied on paper-based or phone-based reporting methods during these events. We developed a novel downtime procedure that combines advance placement of orders by clinicians for planned downtimes, the printing of laboratory results from instruments, and scanning of the instrument printouts into our EMR. The new procedure allows the analysis of samples from planned phlebotomies with no delays, even during LIS downtimes. It also enables the electronic reporting of all clinically urgent results during downtimes, including intensive care and emergency department samples, thereby largely avoiding paper- and phone-based communication of laboratory results. With the capabilities of EMRs and LISs rapidly evolving, information technology (IT) teams, laboratories, and clinicians need to collaborate closely, review their systems' capabilities, and design innovative ways to apply all available IT functions to optimize patient care during downtimes. Copyright© by the American Society for Clinical Pathology.

  18. 40 CFR 60.4385 - How are excess emissions and monitoring downtime defined for SO2?

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false How are excess emissions and monitoring downtime defined for SO2? 60.4385 Section 60.4385 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... downtime defined for SO2? If you choose the option to monitor the sulfur content of the fuel, excess...

  19. Planned and Unplanned Childbearing among Unmarried Women.

    Science.gov (United States)

    Musick, Kelly

    2002-01-01

    Uses data from the 1995 National Survey of Family Growth to examine social, demographic, and economic correlates of planned and unplanned childbearing among unmarried women. Finds that low education increases the likelihood such childbearing outside of marriage for all race and ethnic groups. Results suggest ways in which the meaning of…

  20. Changed planning for planned and unplanned change

    NARCIS (Netherlands)

    Woerkum, van C.; Aarts, N.; Herzele, Van A.

    2011-01-01

    Change, planned and unplanned, can be the product of events (change by chance), new language (change from societal interaction), and practices (track-bound change), and can involve many different societal actors. To position planning as an activity within this broader context, we present a model

  1. Safety aspects of unplanned shutdowns and trips

    International Nuclear Information System (INIS)

    1986-05-01

    The issue of unplanned shutdowns and trips is receiving increased attention worldwide in view of its importance to plant safety and availability. There exists significant variation in the number of forced shutdowns for nuclear power plants of the same type operating worldwide. The reduction of the frequency of these events will have safety benefits in terms of reducing the frequency of plant transients and the challenges to the safety systems, and the risks of possible incidents. This report provides an insight into the causes of unplanned shutdowns experienced in operating nuclear power plants worldwide, the good practices that have been found effective in minimizing their occurrence, and the measures that have been taken to reduce these events. Specific information on the experiences, approaches and practices of some countries in dealing with this issue is presented in Appendix A

  2. Unplanned pregnancies in the United States.

    Science.gov (United States)

    Grimes, D A

    1986-03-01

    Unplanned pregnancies constitute an epidemic in the United States. Over 3 million unplanned pregnancies occur, and over 1.5 million induced abortions are performed each year. Women of minority races and those with less than 12 years of education are at high risk of having unwanted children. Fear of complications (not the complications themselves) is the most powerful deterrent to women's use of contraception. Much of this fear is due to bad press. Recent good news about contraception, such as protection against ovarian and endometrial cancer, protection against ectopic pregnancy, and absence of teratogenic effects, has not received appropriate media coverage. For healthy women younger than 35 years, failure to use fertility control is more dangerous than use of any method.

  3. [Maternal and neonatal outcomes of unplanned deliveries].

    Science.gov (United States)

    Nguyen, M-L; Lefèvre, P; Dreyfus, M

    2016-01-01

    Know the impact of the unplanned deliveries in a town of medium size, the characteristics of these women and maternal and neonatal risks. This was a retrospective study conducted between January 2002 and December 2009. Unexpected delivery was defined as any delivery taking place outside of a non-elective way maternity. Each unexpected delivery was matched at nearest delivery of equivalent term, at the CHU maternity, with an onset of spontaneous labour. Ninety-four women gave birth unexpectedly for a total of 48,721 births (incidence of 0.19%). There was a significant difference between cases and controls for parity (1.8 versus 0.9), the lack of follow-up of pregnancy (21.3% versus 1.1%), tobacco (57.4% versus 25.5%), the socio-economic level, the type of feeding (artificial: 61.7% versus 30.6%), the home-hospital distance and obstetric follow-up. We found a significant increase in perinatal mortality (6.4% versus 1%) and stay in Neonatal ICU (19.1% versus 9.2%). The main neonatal morbidity was hypothermia. It is difficult to target a population at risk because the type of these women is non-specific. Prevention of unplanned deliveries and their morbidities through information of patients on the grounds of urgent consultation and support of the newborn to limit hypothermia. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  4. Unplanned complex suicide: Two case reports

    Directory of Open Access Journals (Sweden)

    Nikolić Slobodan

    2010-01-01

    Full Text Available Introduction The term complex suicide refers to suicides in which multiple suicidal methods are utilized, as opposed to simple suicide successfully done after one attempt. In planned complex suicides two or more methods are employed simultaneously in order to make sure that death will occur after failure of previous attempt. In unplanned complex suicides, several other methods of suicide tried after the first chosen method either failed or was too painful. Outline of Cases We report two cases of unplanned complex suicides. The first case was a female who first tried to commit suicide by cutting the wrists, and then hanged herself. In the other case, a male first tried to commit suicide by stubbing his chest with a knife, and then jumped into a well and drowned himself. In both reported cases the second, successful suicidal method was of higher lethality score. Conclusion From the forensic point of view, the presence of several injuries of different origin strongly suggests infliction by other person. The event could be reconstructed, based on autopsy findings and traces found at the scene. .

  5. Formalisation of Unplanned Settlements and Its Implications on ...

    African Journals Online (AJOL)

    Formalisation of Unplanned Settlements and Its Implications on Poverty Reduction: The Case of Dar es Salaam City. ... Properties found in these areas are sound or improvable. ... Key words: regularisation, formalisation, land tenure, property rights, unplanned/informal settlements, poverty reduction, Dar es Salaam ...

  6. Tobacco and alcohol use in adolescents with unplanned pregnancies

    African Journals Online (AJOL)

    Results: In adolescents with unplanned pregnancies, the prevalence of active smoking was 21.2% and of alcohol consumption, 41.5%. The percentage of smoking at home was 57.4% and alcohol consumption, 77.5%. Approximately, 80.3% of adolescents with unplanned pregnancies had friends who smoked and 90.6% ...

  7. No fixed place of birth: unplanned BBAs in Victoria, Australia.

    Science.gov (United States)

    McLelland, Gayle; McKenna, Lisa; Archer, Frank

    2013-02-01

    the primary objective-to present data on the incidence of unplanned births before arrival (BBAs) in Victoria between 1991 and 2008. The secondary objective-to provide an extensive literature review highlighting the issues surrounding an unplanned BBA. the incidence of BBAs in Victoria published in the relevant government reports. data were extracted from published government reports pertaining to perinatal statistics in Victoria-The Australian Institute of Health and Wellbeing and the Perinatal Data Collection Unit of Victoria. Data on place of birth for each year from both sources was identified and tabulated. Comparisons between the data sources were undertaken to provide a picture of the scope of out of hospital birth. the incidence and absolute numbers of unplanned birth before arrival (BBA) to hospital in Victoria, are low compared to the total births. However, this number is comparable to unplanned BBAs in other developed countries with similar health systems. The incidence of unplanned BBAs has slowly but steadily doubled since 1991-2008. The two data sources almost mirror each other except for 1999 when there was an unexplained difference in the reported incidence in unplanned BBAs. Maternal and neonatal outcomes are disproportionally much poorer after unplanned BBAs than either planned home births or in hospital births. Various maternal factors can increase the risk of an unplanned BBA. multiple approaches should be adopted to manage unplanned BBAs. Antenatal screening should be undertaken to identify the women most at risk. Strategies can be developed that will reduce poor neonatal and maternal outcomes, including education for women and their partners on immediate management of the newborn; ensuring paramedics have current knowledge on care during childbirth; and maternity and ambulance services should develop management plans for care of women having unplanned BBAs. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Exploring unplanned ICU admissions: a systematic review.

    Science.gov (United States)

    Vlayen, Annemie; Verelst, Sandra; Bekkering, Geertruida E; Schrooten, Ward; Hellings, Johan; Claes, Nerée

    Adverse events are unintended patient injuries or complications that arise from healthcare management resulting in death, disability or prolonged hospital stay. Adverse events that require critical care are a considerable financial burden to the healthcare system. Medical record review seems to be a reliable method for detecting adverse events. To synthesize the best available evidence regarding the estimates of the incidence and preventability of adverse events that necessitate intensive care admission; to determine the type and consequences (patient harm, mortality, length of ICU stay and direct medical costs) of these adverse events. MEDLINE (from 1966 to present), EMBASE (from 1974 to present) and CENTRAL (version 1-2010) were searched for studies reporting on unplanned admissions to intensive care units (ICUs). Databases of reports, conference proceedings, grey literature, ongoing research, relevant patient safety organizations and two journals were searched for additional studies. Reference lists of retrieved papers were searched and authors were contacted in an attempt to find any further published or unpublished work. Only quantitative studies that used chart review for the detection of adverse events requiring intensive care admission were considered for eligibility. Studies that were published in the English, Dutch, German, French or Spanish language were included. Two reviewers independently extracted data and assessed the methodological quality of the included studies. 28 studies in the English language and one study in French were included. Of these, two were considered duplicate publications and therefore 27 studies were reviewed. Meta-analysis of the data was not appropriate due to statistical heterogeneity between studies; therefore, results are presented in a descriptive way. Studies were categorized according to the population and the providers of care. 1) The majority of the included studies investigated unplanned intensive care admissions after

  9. Causes of unplanned interruption of radiotherapy

    International Nuclear Information System (INIS)

    Diegues, Sylvia Suelotto; Ciconelli, Rozana Mesquita; Segreto, Roberto Araujo

    2008-01-01

    Objective: To evaluate the occurrence and causes of unplanned interruption of radiotherapy. Materials and methods: Retrospective study developed in the Division of Radiotherapy of Hospital Alemao Oswaldo Cruz in Sao Paulo, SP, Brazil, with data collected from 560 dossiers of patients submitted to radiotherapy in the period between January 1, 2005 and December 31, 2005. Chi-squared and Student t tests were utilized in the data analysis, and p < 0.05 was considered as statistically significant. Results: Interruption of treatment was identified in 350 cases, corresponding to 62.5% of the patients. The reasons for treatment interruption were the following: preventive device maintenance (55%), patient's own private reasons (13%), adverse reactions to the treatment or to combined radiotherapy/chemotherapy (6%), clinical worsening (3%), two or more combined reasons (23%). The interruption time interval ranged between 1 and 24 days (mean 1.4 day). One-day interruption was mostly due to preventive device maintenance (84.4%); two-five-day interruption was due to combined reasons (48.28%). Conclusion: The most frequent cause of interruption was preventive device maintenance, with maximum two-day time interval. (author)

  10. Dialysis access, infections, and hospitalisations in unplanned dialysis start patients

    DEFF Research Database (Denmark)

    Machowska, Anna; Alscher, Mark Dominik; Vanga, Satyanarayana Reddy

    2017-01-01

    Introduction: Unplanned dialysis start (UPS) associates with worse clinical outcomes, higher utilisation of healthcare resources, lower chances to select dialysis modality and UPS patients typically commenced in-centre haemodialysis (HD) with central venous catheter (CVC). We evaluated patient ou...

  11. Downside Variance Risk Premium

    OpenAIRE

    Feunou, Bruno; Jahan-Parvar, Mohammad; Okou, Cedric

    2015-01-01

    We propose a new decomposition of the variance risk premium in terms of upside and downside variance risk premia. The difference between upside and downside variance risk premia is a measure of skewness risk premium. We establish that the downside variance risk premium is the main component of the variance risk premium, and that the skewness risk premium is a priced factor with significant prediction power for aggregate excess returns. Our empirical investigation highlights the positive and s...

  12. The use of fault tree analysis to minimize research reactor downtime

    International Nuclear Information System (INIS)

    Dodd, B.; Wang, C.H.; Anderson, T.V.

    1984-01-01

    For many reasons it is often highly desirable to maintain a research reactor in a continuously operable state and in the event of any failures to minimize the length of the reactor downtime. In order to keep the length of future downtimes to less than ten days for the sixteen year old OSU TRIGA reactor, a fault tree analysis was performed for all of the systems required to maintain the reactor operational. As a result of this analysis, it was possible to determine the critical parts and key components. By examining the availability and delivery times for each of these items, it was then possible to make reasoned decisions relating to the advance purchase of spare parts. This paper outlines the above process, along with examples of fault trees developed, and a recent history of the efficacy of this technique. (author)

  13. Maintenance Strategies to Reduce Downtime Due to\\ud Machine Positional Errors

    OpenAIRE

    Shagluf, Abubaker; Longstaff, Andrew P.; Fletcher, Simon

    2014-01-01

    Manufacturing strives to reduce waste and increase\\ud Overall Equipment Effectiveness (OEE). When managing machine tool maintenance a manufacturer must apply an appropriate decision technique in order to reveal hidden costs associated with production losses, reduce equipment downtime\\ud competently and similarly identify the machines’ performance.\\ud Total productive maintenance (TPM) is a maintenance program that involves concepts for maintaining plant and equipment effectively. OEE is a pow...

  14. MCNP variance reduction overview

    International Nuclear Information System (INIS)

    Hendricks, J.S.; Booth, T.E.

    1985-01-01

    The MCNP code is rich in variance reduction features. Standard variance reduction methods found in most Monte Carlo codes are available as well as a number of methods unique to MCNP. We discuss the variance reduction features presently in MCNP as well as new ones under study for possible inclusion in future versions of the code

  15. Estimation of measurement variances

    International Nuclear Information System (INIS)

    Anon.

    1981-01-01

    In the previous two sessions, it was assumed that the measurement error variances were known quantities when the variances of the safeguards indices were calculated. These known quantities are actually estimates based on historical data and on data generated by the measurement program. Session 34 discusses how measurement error parameters are estimated for different situations. The various error types are considered. The purpose of the session is to enable participants to: (1) estimate systematic error variances from standard data; (2) estimate random error variances from data as replicate measurement data; (3) perform a simple analysis of variances to characterize the measurement error structure when biases vary over time

  16. Characteristics of planned and unplanned home births in 19 States.

    Science.gov (United States)

    Declercq, Eugene; Macdorman, Marian F; Menacker, Fay; Stotland, Naomi

    2010-07-01

    To estimate the differences in the characteristics of mothers having planned and unplanned home births that occurred at home in a 19-state reporting area in the United States in 2006. Data are from the 2006 U.S. vital statistics natality file. Information on whether a home birth was planned or unplanned was available from 19 states, representing 49% of all home births nationally. Data were examined by maternal age, race or ethnicity, education, marital status, live birth order, birthplace of mother, gestational age, prenatal care, smoking status, state, population of county of residence, and birth attendant. We could not identify planned home births that resulted in a transfer to the hospital. Of the 11,787 home births with planning status recorded in the 19 states studied here, 9,810 (83.2%) were identified as planned home births. The proportion of all births that occurred at home that were planned varied from 54% to 98% across states. Unplanned home births are more likely to involve mothers who are non-white, younger, unmarried, foreign-born, smokers, not college-educated, and with no prenatal care. Unplanned home births are also more likely to be preterm and to be attended by someone who is neither a doctor nor a midwife and is listed as either "other" or "unknown." Planned and unplanned home births differ substantially in characteristics, and distinctions need to be drawn between the two in subsequent analyses. III.

  17. Lower chest compression fraction associated with ROSC in OHCA patients with longer downtimes.

    Science.gov (United States)

    Talikowska, Milena; Tohira, Hideo; Inoue, Madoka; Bailey, Paul; Brink, Deon; Finn, Judith

    2017-07-01

    To investigate the relationship between chest compression fraction (CCF) and survival outcomes in OHCA, including whether the relationship varied based upon downtime from onset of arrest to provision of cardiopulmonary resuscitation (CPR) by emergency medical services (EMS). Data from resuscitations performed by St John Ambulance Western Australia (SJA-WA) paramedics between July 2014 and June 2016 was captured using the Q-CPR feedback device. Logistic regression analysis was used to study the relationship between CCF and return of spontaneous circulation (ROSC). Various lengths of Q-CPR data were used ranging from the first 3min to all available episode data. Cases were subsequently divided into groups based upon downtime; ≤15min, >15min and unknown. Univariate and multivariable logistic regression analyses were performed in each group. There were 341 cases eligible for inclusion. CCF >80% was significantly associated with decreased odds of ROSC compared to CCF≤80% (aOR: 0.49, 95%CI: 0.28-0.87). This relationship remained significant whether the first 3min of data was used, the first 5min or all available episode data. Among the group with a downtime >15min, CCF was significantly lower for those who achieved ROSC compared to those who did not (mean (SD): 73.01 (12.99)% vs. 83.05 (9.38)% p=0.002). The adjusted odds ratio for achieving ROSC in this group was significantly less with CCF>80% compared to CCF≤80% (aOR: 0.06, 95%CI: 0.01-0.38). We demonstrated an inverse relationship between CCF and ROSC that varied depending upon the time from arrest to provision of EMS-CPR. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Unplanned Complex Suicide-A Consideration of Multiple Methods.

    Science.gov (United States)

    Ateriya, Navneet; Kanchan, Tanuj; Shekhawat, Raghvendra Singh; Setia, Puneet; Saraf, Ashish

    2018-05-01

    Detailed death investigations are mandatory to find out the exact cause and manner in non-natural deaths. In this reference, use of multiple methods in suicide poses a challenge for the investigators especially when the choice of methods to cause death is unplanned. There is an increased likelihood that doubts of homicide are raised in cases of unplanned complex suicides. A case of complex suicide is reported where the victim resorted to multiple methods to end his life, and what appeared to be an unplanned variant based on the death scene investigations. A meticulous crime scene examination, interviews of the victim's relatives and other witnesses, and a thorough autopsy are warranted to conclude on the cause and manner of death in all such cases. © 2017 American Academy of Forensic Sciences.

  19. Unplanned Pregnancy and Contraceptive Use in Hull and East Yorkshire

    Science.gov (United States)

    Bexhell, Helen; Guthrie, Kate; Cleland, Kelly; Trussell, James

    2015-01-01

    Objective This study has two aims. The first is to assess the proportion of unplanned pregnancies among women attending antenatal clinics and those undergoing induced abortion (IA). The second is to assess both their previous contraceptive use and contraceptive intention, with particular focus on the use or consideration of any long acting reversible contraceptives in Hull and East Riding in order to inform service redesign. Study Design Consecutive women attending their first antenatal clinic (ANC) appointment and women attending a gynaecology clinic undergoing induced abortion (IA) were asked to complete a 2-page questionnaire that contained a validated pregnancy intendedness questionnaire (the London Measure of Unplanned Pregnancy (LMUP)) and questions to establish contraceptive use and access prior to this index pregnancy. Results The overall response rate was 69%. We received 648 evaluable questionnaires for women undergoing IA. Of these pregnancies, 75.8% (95% CI 72.3%-79.0%) were unplanned (LMUP score 0-3). We received 1001 evaluable questionnaires from women booking at antenatal clinics. Of these pregnancies, 5.5% (95% CI 4.2%-7.0%) were unplanned. Among those with unplanned pregnancies who were not using contraception 31% reported that they were unable to obtain the method they wanted. Among those using a method immediately prior to the index unplanned pregnancy, 33% stated it was not the method they wanted; of these 75% would have preferred sterilization, the implant, injectable, or intrauterine contraceptive. Conclusion Unplanned pregnancies in this population are common among women undergoing IA but are uncommon among women attending an ANC. About a third of women not using contraception reported that they were unable to obtain the method they wanted, and about a third of women using contraception stated that they were not using the method they would have preferred. Implications Opportunities to prevent unplanned pregnancies are missed when staff in

  20. Estimation of measurement variances

    International Nuclear Information System (INIS)

    Jaech, J.L.

    1984-01-01

    The estimation of measurement error parameters in safeguards systems is discussed. Both systematic and random errors are considered. A simple analysis of variances to characterize the measurement error structure with biases varying over time is presented

  1. A COSMIC VARIANCE COOKBOOK

    International Nuclear Information System (INIS)

    Moster, Benjamin P.; Rix, Hans-Walter; Somerville, Rachel S.; Newman, Jeffrey A.

    2011-01-01

    Deep pencil beam surveys ( 2 ) are of fundamental importance for studying the high-redshift universe. However, inferences about galaxy population properties (e.g., the abundance of objects) are in practice limited by 'cosmic variance'. This is the uncertainty in observational estimates of the number density of galaxies arising from the underlying large-scale density fluctuations. This source of uncertainty can be significant, especially for surveys which cover only small areas and for massive high-redshift galaxies. Cosmic variance for a given galaxy population can be determined using predictions from cold dark matter theory and the galaxy bias. In this paper, we provide tools for experiment design and interpretation. For a given survey geometry, we present the cosmic variance of dark matter as a function of mean redshift z-bar and redshift bin size Δz. Using a halo occupation model to predict galaxy clustering, we derive the galaxy bias as a function of mean redshift for galaxy samples of a given stellar mass range. In the linear regime, the cosmic variance of these galaxy samples is the product of the galaxy bias and the dark matter cosmic variance. We present a simple recipe using a fitting function to compute cosmic variance as a function of the angular dimensions of the field, z-bar , Δz, and stellar mass m * . We also provide tabulated values and a software tool. The accuracy of the resulting cosmic variance estimates (δσ v /σ v ) is shown to be better than 20%. We find that for GOODS at z-bar =2 and with Δz = 0.5, the relative cosmic variance of galaxies with m * >10 11 M sun is ∼38%, while it is ∼27% for GEMS and ∼12% for COSMOS. For galaxies of m * ∼ 10 10 M sun , the relative cosmic variance is ∼19% for GOODS, ∼13% for GEMS, and ∼6% for COSMOS. This implies that cosmic variance is a significant source of uncertainty at z-bar =2 for small fields and massive galaxies, while for larger fields and intermediate mass galaxies, cosmic

  2. Reliability analysis of repairable safety systems of a reprocessing plant allowing for tolerable system downtimes

    International Nuclear Information System (INIS)

    Schaefer, H.

    1987-01-01

    GRS has been engaged in safety analysises of the German Reprocessing Plant for several years. The development and verification of appropriate reliability analysis methods, the generation of data as well as the search for an adequate structural presentation of the results to form a basis of recommendations for technical or administrative measures or contributions to risk oriented evaluations have been or are in the process of being established. In contrast to NPP-studies, the reliability assessment of safety systems of a reprocessing plant is applied to repairable and often relatively small systems allowing for tolerable system downtimes. A sketch of the diverse cooling systems of a vessel containing a selfheating solution is given. The interruption of the cooling function for about one day might be tolerable before boiling will be reached. This interval is suitable for transfer of the solution to a spare vessel or for repairing the failed components, thus restoring the cooling function

  3. Performance issues, downtime recovery and tuning in the Next Linear Collider (NLC)

    International Nuclear Information System (INIS)

    Zimmermann, F.; Adolphsen, C.; Assmann, R.

    1997-05-01

    The Next Linear Collider (NLC) consists of several large subsystems, each of which must be operational and tuned in order to deliver luminosity. Considering specific examples, we study how the different subsystems respond to various perturbations such as ground motion, temperature changes, drifts of beam-position monitors etc., and we estimate the overall time requirements for tuning and downtime recovery of each subsystem. The succession of subsystem failures and recoveries as well as other performance degradations can be modeled as a Markov process, where each subsystem is characterized, e.g., by its failure rate and recovery time. Such a model allows the prediction of the overall NLC availability. Our mathematical description of a linear collider is benchmarked against the known performance of the Stanford Linear Collider (SLC)

  4. SU-E-T-173: Clinical Comparison of Treatment Plans and Fallback Plans for Machine Downtime

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, W [University of Texas Health Science Center at San Antonio, San Antonio, TX (United States); Cancer Therapy and Research Center, San Antonio, TX (United States); Papanikolaou, P [University of Texas Health Science Center at San Antonio, San Antonio, TX (United States); Mavroidis, P [University of North Carolina, Chapel Hill, NC (United States); Stathakis, S [Cancer Therapy and Research Center, San Antonio, TX (United States)

    2015-06-15

    Purpose: The purpose of this study was to determine the clinical effectiveness and dosimetric quality of fallback planning in relation to machine downtime. Methods: Plans for a Varian Novalis TX were mimicked, and fallback plans using an Elekta VersaHD machine were generated using a dual arc template. Plans for thirty (n=30) patients of various treatment sites optimized and calculated using RayStation treatment planning system. For each plan, a fall back plan was created and compared to the original plan. A dosimetric evaluation was conducted using the homogeneity index, conformity index, as well as DVH analysis to determine the quality of the fallback plan on a different treatment machine. Fallback plans were optimized for 60 iterations using the imported dose constraints from the original plan DVH to give fallback plans enough opportunity to achieve the dose objectives. Results: The average conformity index and homogeneity index for the NovalisTX plans were 0.76 and 10.3, respectively, while fallback plan values were 0.73 and 11.4. (Homogeneity =1 and conformity=0 for ideal plan) The values to various organs at risk were lower in the fallback plans as compared to the imported plans across most organs at risk. Isodose difference comparisons between plans were also compared and the average dose difference across all plans was 0.12%. Conclusion: The clinical impact of fallback planning is an important aspect to effective treatment of patients. With the complexity of LINACS increasing every year, an option to continue treating during machine downtime remains an essential tool in streamlined treatment execution. Fallback planning allows the clinic to continue to run efficiently should a treatment machine become offline due to maintenance or repair without degrading the quality of the plan all while reducing strain on members of the radiation oncology team.

  5. REDUCING AMMONIA CONCENTRATIONS IN ATMOSPHERE AFTER ITS UNPLANNED RELEASE

    Directory of Open Access Journals (Sweden)

    L. V. Amelina

    2017-08-01

    Full Text Available Purpose. The aim of this work is development of numerical model, which allows to calculate the efficiency of neutralizer supply for reduction of air pollution in case of unplanned ammonia emission at the territory of ammonia pump station. The numerical model should allow fast calculating, taking into account the meteorological parameters and buildings situated near the source of toxic chemical emission and equipment for neutralizer supply. Methodology. The developed model is based on the equation for potential flow and equation of pollutant dispersion. To simulate the chemical interaction between ammonia and neutralizer the stoichiometry equation is used. Equation of potential flow is used to compute flow pattern among buildings. To solve the equation for potential flow the Samarskii implicit difference scheme is used. The implicit change-triangle difference scheme is used to solve equation of mass transfer. While for the numerical integration the authors use the rectangular difference grid. Method of porosity technique («markers method» is applied to create the form of comprehensive computational region. Emission of ammonia is modeled using Delta function for point source. Findings. Developed numerical model belongs to the class of «diagnostic models». This model takes into account the main physical factors affecting the process of dispersion of ammonia and neutralizer in the atmosphere, as well as the influence of buildings on admixture dispersion. On the basis of the developed numerical models the authors carried out a computational experiment to estimate the efficiency of neutralizer supply for reduction of air pollution in case of unplanned ammonia release at ammonia pump station. Originality. Developed numerical model allows calculating the flow pattern among buildings and estimating the efficiency of neutralizer supply for reduction of air pollution in the case unplanned ammonia release. Practical value. Model allows performing fast

  6. Unplanned readmission after hospital discharge in burn patients in Iran.

    Science.gov (United States)

    Jafaryparvar, Zakiyeh; Adib, Masoomeh; Ghanbari, Atefeh; Leyli, Ehsan Kazemnezhad

    2018-02-21

    Burns are considered as one of the most serious health problems throughout the world. They may lead to adverse consequences and outcomes. One of these outcomes is unplanned readmission. Unplanned readmission has been commonly used as a quality indicator by hospitals and governments. This study aimed to determine the predictors of unplanned readmission in patients with burns hospitalized in a burn center in the North of Iran (Guilan province, Rasht). This retrospective analytic study has been done on the medical records of hospitalized patients with burns in Velayat Sub-Specialty Burn and Plastic Surgery Center, Rasht, Iran during 2008-2013. In general, 703 medical records have been reviewed but statistical analysis was performed on 626 medical records. All data were entered in SPSS (version 16) and analyzed by descriptive and inferential statistics. Among 626 patients with burns, the overall readmission rate was 5.1%. Predictors of readmission included total body surface area (OR 1.030, CI 1.011-1.049), hypertension (OR 2.923, CI 1.089-7.845) and skin graft (OR 7.045, CI 2.718-18.258). Considering the outcome, predictors following burn have a crucial role in the allocation of treatment cost for patients with burns and they can be used as one of the quality indicators for health care providers and governments.

  7. Restricted Variance Interaction Effects

    DEFF Research Database (Denmark)

    Cortina, Jose M.; Köhler, Tine; Keeler, Kathleen R.

    2018-01-01

    Although interaction hypotheses are increasingly common in our field, many recent articles point out that authors often have difficulty justifying them. The purpose of this article is to describe a particular type of interaction: the restricted variance (RV) interaction. The essence of the RV int...

  8. On the effect of downtime costs and budget constraint on preventive and replacement policies

    International Nuclear Information System (INIS)

    Pascual, R.; Meruane, V.; Rey, P.A.

    2008-01-01

    This work proposes a general approach to study and improve the effectiveness of the system with respect to its expected life-cycle cost rate. The model we propose considers a production system which is protected against demand fluctuations and failure occurrences with elements like stock piles, line and equipment redundancy, and the use of alternative production methods. These design policies allow to keep or minimize the effect on the nominal throughput, while corrective measures are taken. The system is also subject to an aging process which depends on the frequency and quality of preventive actions. Making decisions is difficult because of discontinuities in intervention and downtime costs and the limited budget. We present a non-linear mixed integer formulation that minimizes the expected overall cost rate with respect to repair, overhaul and replacement times and the overhaul improvement factor proposed in the literature. The model is deterministic and considers minimal repairs and imperfect overhauls. We illustrate its application with a case based on a known benchmark example

  9. Local variances in biomonitoring

    International Nuclear Information System (INIS)

    Wolterbeek, H.Th; Verburg, T.G.

    2001-01-01

    The present study was undertaken to explore possibilities to judge survey quality on basis of a limited and restricted number of a-priori observations. Here, quality is defined as the ratio between survey and local variance (signal-to-noise ratio). The results indicate that the presented surveys do not permit such judgement; the discussion also suggests that the 5-fold local sampling strategies do not merit any sound judgement. As it stands, uncertainties in local determinations may largely obscure possibilities to judge survey quality. The results further imply that surveys will benefit from procedures, controls and approaches in sampling and sample handling, to assess both average, variance and the nature of the distribution of elemental concentrations in local sites. This reasoning is compatible with the idea of the site as a basic homogeneous survey unit, which is implicitly and conceptually underlying any survey performed. (author)

  10. Local variances in biomonitoring

    International Nuclear Information System (INIS)

    Wolterbeek, H.T.

    1999-01-01

    The present study deals with the (larger-scaled) biomonitoring survey and specifically focuses on the sampling site. In most surveys, the sampling site is simply selected or defined as a spot of (geographical) dimensions which is small relative to the dimensions of the total survey area. Implicitly it is assumed that the sampling site is essentially homogeneous with respect to the investigated variation in survey parameters. As such, the sampling site is mostly regarded as 'the basic unit' of the survey. As a logical consequence, the local (sampling site) variance should also be seen as a basic and important characteristic of the survey. During the study, work is carried out to gain more knowledge of the local variance. Multiple sampling is carried out at a specific site (tree bark, mosses, soils), multi-elemental analyses are carried out by NAA, and local variances are investigated by conventional statistics, factor analytical techniques, and bootstrapping. Consequences of the outcomes are discussed in the context of sampling, sample handling and survey quality. (author)

  11. Factors Affecting Unplanned Pregnancy in Semnan Province, Iran

    Directory of Open Access Journals (Sweden)

    Hajieh Razeghi

    2018-04-01

    Full Text Available Background & aim: Despite the success of family planning programs in Iran in the recent decades, considerable proportions of pregnancies are still unintended and can be a cause of poor mental and physical health of the mother and child. The aim of this study was to investigate some important factors affecting uplanned pregnancies among married women in Semnan province, one of the developed provinces of Iran with below replacement fertility level. Methods: The data for this study were drawn from a cross-sectional survey conducted in Semnan province in 2014. A total of 363 married women within the age range of 15-49 years who were pregnant or had the history of at least one delivery were considered. The study sample was selected using multi-stage stratified sampling method. The data were collected using a self-structured questionnaire with 90 items and Cronbach's alpha coefficient of 0.88. Data analysis was performed in SPSS (version 20 using Crammer’s V coefficients and Chi-square tests. Logistic regression analysis was also applied to model the risk of unintended pregnancies based on selected covariates. Results: According to the results, around 18.2% of the pregnancies were unplanned, 7.7% and 10.5% of which were mistimed and unwanted, respectively. Based on the logistic regression analysis, birth cohort, number of children ever born, and contraceptive methods had significant effects on the risk of unintended pregnancies. Furthermore, about 48% of the women experiencing unintended pregnancy were using a traditional contraceptive method before or at the time of the conception.   Conclusion: As the findings indicated, the women who used contraceptive method, as well as those with higher number of children and younger birth cohorts had higher risk of unplanned pregnancies. It should be noted that the majority of unplanned pregnancies among the women in younger birth cohort were mistimed pregnancies. So it is recommended to continue offering

  12. Effect of Guided Imagery on Maternal Fetal Attachment in Nulliparous Women with Unplanned Pregnancy

    OpenAIRE

    Masoumeh Kordi; Maryam Fasanghari; Negar Asgharipour; Habibollah Esmaily

    2016-01-01

    Introduction and Objectives: Nulliparous women with unplanned pregnancy experience high levels of anxiety, which may adversely affect maternal-fetal attachment. Therefore, in this study, we aimed to determine the effect of guided imagery on maternal-fetal attachment in nulliparous women with unplanned pregnancy. Materials and Methods: In this clinical trial, 67 nulliparous women with unplanned pregnancy were randomly divided into two groups of intervention (n=35) and control (n=32) in 2015. D...

  13. Spectral Ambiguity of Allan Variance

    Science.gov (United States)

    Greenhall, C. A.

    1996-01-01

    We study the extent to which knowledge of Allan variance and other finite-difference variances determines the spectrum of a random process. The variance of first differences is known to determine the spectrum. We show that, in general, the Allan variance does not. A complete description of the ambiguity is given.

  14. Sociocultural Factors Affecting Unplanned Deliveries at Home: A Community-Based Case Control Study.

    Science.gov (United States)

    Catak, Binali; Oner, Can

    2015-01-01

    Unplanned home deliveries can vary with social and cultural factors. The aim of this study was to define the risk factors of unplanned home births. This case control study was conducted in Istanbul, Turkey. The study group was composed of 229 women who had unplanned home delivery. Six factors (presence of health insurance, duration of living in Istanbul, educational status of the woman, the number of individuals living in the household, the age of the woman at the time of current delivery, and the status of having received care prior to delivery) were determined as independent risk factors for unplanned deliveries at home.

  15. Assessing slope stability in unplanned settlements in developing countries.

    Science.gov (United States)

    Anderson, Malcolm G; Holcombe, Liz; Renaud, Jean-Philippe

    2007-10-01

    Unplanned housing in developing countries is often located on steep slopes. Frequently no building code is enforced for such housing and mains water is provided with no drainage provision. Both of these factors can be particularly significant in terms of landslide risk if, as is so often the case, such slopes lack any planned drainage provision. There is thus a need to develop a model that facilitates the assessment of slope stability in an holistic context, incorporating a wide range of factors (including surface cover, soil water topographic convergence, slope loading and point source water leakage) in order that appropriate advice can be given as to the general controls on slope stability in such circumstances. This paper outlines a model configured for this specific purpose and describes an application to a site in St. Lucia, West Indies, where there is active slope movement in an unplanned housing development on relatively steep topography. The model findings are in accord with the nature of the current failure at the site, provide guidance as to the significance of slope drainage and correspond to inferences drawn from an application of resistance envelope methods to the site. In being able to scenario test a uniquely wide range of combinations of factors, the model structure is shown to be highly valuable in assessing dominant slope stability process controls in such complex environments.

  16. US pediatric trauma patient unplanned 30-day readmissions.

    Science.gov (United States)

    Wheeler, Krista K; Shi, Junxin; Xiang, Henry; Thakkar, Rajan K; Groner, Jonathan I

    2018-04-01

    We sought to determine readmission rates and risk factors for acutely injured pediatric trauma patients. We produced 30-day unplanned readmission rates for pediatric trauma patients using the 2013 National Readmission Database (NRD). In US pediatric trauma patients, 1.7% had unplanned readmissions within 30days. The readmission rate for patients with index operating room procedures was no higher at 1.8%. Higher readmission rates were seen in patients with injury severity scores (ISS)=16-24 (3.4%) and ISS ≥25 (4.9%). Higher rates were also seen in patients with LOS beyond a week, severe abdominal and pelvic region injuries (3.0%), crushing (2.8%) and firearm injuries (4.5%), and in patients with fluid and electrolyte disorders (3.9%). The most common readmission principal diagnoses were injury, musculoskeletal/integumentary diagnoses and infection. Nearly 39% of readmitted patients required readmission operative procedures. Most common were operations on the musculoskeletal system (23.9% of all readmitted patients), the integumentary system (8.6%), the nervous system (6.6%), and digestive system (2.5%). Overall, the readmission rate for pediatric trauma patients was low. Measures of injury severity, specifically length of stay, were most useful in identifying those who would benefit from targeted care coordination resources. This is a Level III retrospective comparative study. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Unplanned readmission within 90 days after pediatric neurosurgery.

    Science.gov (United States)

    Chotai, Silky; Guidry, Bradley S; Chan, Emily W; Sborov, Katherine D; Gannon, Stephen; Shannon, Chevis; Bonfield, Christopher M; Wellons, John C; Naftel, Robert P

    2017-12-01

    OBJECTIVE Readmission and return to operating room after surgery are increasingly being used as a proxy for quality of care. Nearly 60% of these readmissions are unplanned, which translates into billions of dollars in health care costs. The authors set out to analyze the incidence of readmission at their center, to define causes of unplanned readmission, and to determine the preoperative and surgical variables associated with readmissions following pediatric neurosurgery. METHODS A total of 536 children who underwent operations for neurosurgical diagnoses between 2012 and 2015 and who were later readmitted were included in the final analysis. Unplanned readmissions were defined to have occurred as a result of complications within 90 days after index surgery. Patient records were retrospectively reviewed to determine the primary diagnosis, surgery indication, and cause of readmission and return to operating room. The cost for index hospitalization, readmission episode, and total cost were derived based on the charges obtained from administrative data. Bivariate and multivariable analyses were conducted. RESULTS Of 536 patients readmitted in total, 17.9% (n = 96) were readmitted within 90 days. Of the overall readmissions, 11.9% (n = 64) were readmitted within 30 days, and 5.97% (n = 32) were readmitted between 31 and 90 days. The median duration between discharge and readmission was 20 days (first quartile [Q1]: 9 days, third quartile [Q3]: 36 days). The most common reason for readmission was shunt related (8.2%, n = 44), followed by wound infection (4.7%, n = 25). In the risk-adjusted multivariable logistic regression model for total 90-day readmission, patients with the following characteristics: younger age (p = 0.001, OR 0.886, 95% CI 0.824-0.952); "other" (nonwhite, nonblack) race (p = 0.024, OR 5.49, 95% CI 1.246-24.2); and those born preterm (p = 0.032, OR 2.1, 95% CI 1.1-4.12) had higher odds of being readmitted within 90 days after discharge. The total

  18. Model for Estimating Power and Downtime Effects on Teletherapy Units in Low-Resource Settings

    Directory of Open Access Journals (Sweden)

    Rachel McCarroll

    2017-10-01

    Full Text Available Purpose: More than 6,500 megavoltage teletherapy units are needed worldwide, many in low-resource settings. Cobalt-60 units or linear accelerators (linacs can fill this need. We have evaluated machine performance on the basis of patient throughput to provide insight into machine viability under various conditions in such a way that conclusions can be generalized to a vast array of clinical scenarios. Materials and Methods: Data from patient treatment plans, peer-reviewed studies, and international organizations were combined to assess the relative patient throughput of linacs and cobalt-60 units that deliver radiotherapy with standard techniques under various power and maintenance support conditions. Data concerning the frequency and duration of power outages and downtime characteristics of the machines were used to model teletherapy operation in low-resource settings. Results: Modeled average daily throughput was decreased for linacs because of lack of power infrastructure and for cobalt-60 units because of limited and decaying source strength. For conformal radiotherapy delivered with multileaf collimators, average daily patient throughput over 8 years of operation was equal for cobalt-60 units and linacs when an average of 1.83 hours of power outage occurred per 10-hour working day. Relative to conformal treatments delivered with multileaf collimators on the respective machines, the use of advanced techniques on linacs decreased throughput between 20% and 32% and, for cobalt machines, the need to manually place blocks reduced throughput up to 37%. Conclusion: Our patient throughput data indicate that cobalt-60 units are generally best suited for implementation when machine operation might be 70% or less of total operable time because of power outages or mechanical repair. However, each implementation scenario is unique and requires consideration of all variables affecting implementation.

  19. Incidence and etiology of unplanned cast changes for fractures in the pediatric population.

    Science.gov (United States)

    DiPaola, Matthew J; Abzug, Joshua M; Pizzutillo, Peter D; Herman, Martin J

    2014-09-01

    The majority of pediatric fractures are treated in casts due to the child's ability to heal rapidly and remodel. Unplanned cast changes are a time and economic burden with potentially adverse effects on fracture management. The purpose of this study is to document the incidence, etiology, and complications related to unplanned cast changes. A prospective study was conducted over a 6-month period to determine the incidence of unplanned cast changes. All casts applied were nonwaterproof. Data collected include the reason for cast placement, type of cast placed, duration of wear before the unplanned change, reason for the unplanned change, experience level of the original cast applicator, and cast-related complications. A total of 1135 casts were placed with 58% placed by a resident, 38% by a cast technician, 2% by a physician's assistant, and 2% by an attending physician. Sixty casts (5.3%) required an unplanned change including 19 short-arm casts, 18 short-leg casts, 17 long-arm casts, 4 thumb spica casts, and 2 long-leg casts. The average duration from cast application until the unplanned change was 13 days. Twenty-eight (47%) were changed for wetness, 20 (33%) for wear/breakage, 2 (3%) for skin irritation, and 10 (17%) for other reasons including objects in the cast and patient self-removal. Two patients had superficial skin infections requiring oral antibiotics. No fracture reductions were lost secondary to an unplanned cast change. The need for an unplanned cast change did not correlate with the level of experience of the applicator. Most unplanned cast changes were the result of patient nonadherence to instructions and not related to cast application technique. Improved patient and family education regarding cast care may reduce the frequency of unplanned cast changes, thus reducing an economic and time burden on the health care system. Level II--prognostic study.

  20. Introduction to variance estimation

    CERN Document Server

    Wolter, Kirk M

    2007-01-01

    We live in the information age. Statistical surveys are used every day to determine or evaluate public policy and to make important business decisions. Correct methods for computing the precision of the survey data and for making inferences to the target population are absolutely essential to sound decision making. Now in its second edition, Introduction to Variance Estimation has for more than twenty years provided the definitive account of the theory and methods for correct precision calculations and inference, including examples of modern, complex surveys in which the methods have been used successfully. The book provides instruction on the methods that are vital to data-driven decision making in business, government, and academe. It will appeal to survey statisticians and other scientists engaged in the planning and conduct of survey research, and to those analyzing survey data and charged with extracting compelling information from such data. It will appeal to graduate students and university faculty who...

  1. Preventing Unplanned Pregnancy and Completing College: An Evaluation of Online Lessons. 2nd Edition

    Science.gov (United States)

    Antonishak, Jill; Connolly, Chelsey

    2014-01-01

    The National Campaign to Prevent Teen and Unplanned Pregnancy published free online lessons that help students take action to prevent unplanned pregnancy and complete their education. From the fall of 2012 to the spring of 2014, approximately 2,800 students took the online lessons and participated in pre- and post-lesson evaluation surveys at four…

  2. Clinical Correlates of Planned and Unplanned Suicide Attempts.

    Science.gov (United States)

    Chaudhury, Sadia R; Singh, Tanya; Burke, Ainsley; Stanley, Barbara; Mann, J John; Grunebaum, Michael; Sublette, M Elizabeth; Oquendo, Maria A

    2016-11-01

    Suicide attempters differ in the degree of planning for their suicide attempts. The purpose of this study was to identify differences between individuals who make planned (≥3 hours of planning) and unplanned (suicide attempts. Depressed suicide attempters (n = 110) were compared based on degree of planning of their most recent suicide attempt on demographic and clinical variables. Participants who made planned suicide attempts were more likely to have family history of completed suicide, more severe and frequent suicidal ideation, greater trait impulsivity, and greater suicidal intent and more severe medical consequences for both their most recent and most serious suicide attempts. These results suggest clear clinical differences based on the degree of suicide attempt planning. Severe suicidal ideation, high suicide intent, family history of suicide completion, and high levels of motor impulsivity contribute to a phenotype that is at greater risk of planned, highly lethal suicide attempts.

  3. Analysis of 275 planned and 10 unplanned home births.

    Science.gov (United States)

    Schneider, G; Soderstrom, B

    1987-05-01

    The purpose of this study is to describe the outcome in one family practice of planned home births attended by a physician and an experienced birth assistant in a self-selected, but subsequently screened, population over an 11-year period. All but 26 primigravidas were screened out, as were multiple pregnancies and malpresentations. Study parameters included characteristics of the population and maternal and neonatal outcomes. Of 275 intended home confinements, nine were screened out for medical reasons before labour, five in very early labour, and three for failure to progress. Of the 273 who delivered at home, including 10 unplanned births, two were transferred to hospital for postpartum hemorrhage. One neonate was hospitalized for complications. The results of this study, as well as a review of the relevant literature, illustrate that, for a selected population, home birth is a reasonable alternative to hospital.

  4. Causes and Timing of Unplanned Early Readmission After Neurosurgery.

    Science.gov (United States)

    Taylor, Blake E S; Youngerman, Brett E; Goldstein, Hannah; Kabat, Daniel H; Appelboom, Geoffrey; Gold, William E; Connolly, Edward Sander

    2016-09-01

    Reducing the rate of 30-day hospital readmission has become a priority in healthcare quality improvement policy, with a focus on better characterizing the reasons for unplanned readmission. In neurosurgery, however, peer-reviewed analyses describing the patterns of readmission have been limited in their number and generalizability. To determine the incidence, timing, and causes of 30-day readmission after neurosurgical procedures. We conducted a retrospective longitudinal study from 2009 to 2012 using the Statewide Planning And Research Cooperative System, which collects patient-level details for all admissions and discharges within New York. We identified patients readmitted within 30 days of initial discharge. The rate of, reasons for, and time to readmission were determined overall and within 4 subgroups: craniotomies, cranial surgery without craniotomy, spine, and neuroendovascular procedures. There were 163 743 index admissions, of whom 14 791 (9.03%) were readmitted. The most common reasons for unplanned readmission were infection (29.52%) and medical complications (19.22%). Median time to readmission was 11 days, with hemorrhagic strokes and seizures occurring earlier, and medical complications and infections occurring later. Readmission rates were highest among patients undergoing cerebrospinal fluid shunt revision and malignant tumor resection (15.57%-22.60%). Spinal decompressions, however, accounted for the largest volume of readmissions (33.13%). Many readmissions may be preventable and occur at predictable time intervals. The causes and timing of readmission vary significantly across neurosurgical subgroups. Future studies should focus on detecting specific complications in select cohorts at predefined time points, which may allow for interventions to lower costs and reduce patient morbidity. CSF, cerebrospinal fluidIQR, interquartile rangeSPARCS, Statewide Planning And Research Cooperative System.

  5. Polypharmacy and Unplanned Hospitalizations in Patients with Rheumatoid Arthritis.

    Science.gov (United States)

    Filkova, Maria; Carvalho, João; Norton, Sam; Scott, David; Mant, Tim; Molokhia, Mariam; Cope, Andrew; Galloway, James

    2017-12-01

    Polypharmacy (PP), the prescribing of multiple drugs for an individual, is rising in prevalence. PP associates with an increased risk of adverse drug reactions (ADR) and hospital admissions. We investigated the relationship between PP, characteristics of rheumatoid arthritis (RA), and the risk of unplanned hospital admissions. Patients from a hospital RA cohort were retrospectively analyzed. Information was collected from electronic medical records. Cox proportional hazards were used to compare hospitalization risk according to levels of PP. Admissions were adjudicated to determine whether an ADR was implicated. The study included 1101 patients; the mean number of all medications was 5. PP correlated with increasing age, disease duration, disease activity, and disability. At least 1 unplanned admission occurred for 16% of patients. Patients taking ≥ 10 medications had an adjusted HR for hospitalization of 3.1 (95% CI 2.1-4.5), compared to those taking 0-5 medications. Corticosteroid use associated with a doubling in adjusted risk of admission of 1.7 (95% CI 1.2-2.4). The most common reason for hospitalization was infection (28%). While in half of all admissions an ADR was a possible contributing factor, only 2% of admissions were found to directly result from an ADR. PP is common in RA and is a prognostic marker associated with increased risk of acute hospitalizations. Our data suggest that PP may be an indicator of comorbidity burden rather than a contributing cause of a drug-related toxicity. PP should be monitored to minimize inappropriate combination of prescribed medications. PP may be a useful predictor of clinical outcomes in epidemiologic studies.

  6. Analysis of Unplanned Intensive Care Unit Admissions in Postoperative Pediatric Patients.

    Science.gov (United States)

    Landry, Elizabeth K; Gabriel, Rodney A; Beutler, Sascha; Dutton, Richard P; Urman, Richard D

    2017-03-01

    Currently, there are only a few retrospective, single-institution studies that have addressed the prevalence and risk factors associated with unplanned admissions to the pediatric intensive care unit (ICU) after surgery. Based on the limited amount of studies, it appears that airway and respiratory complications put a child at increased risk for unplanned ICU admission. A more extensive and diverse analysis of unplanned postoperative admissions to the ICU is needed to address risk factors that have yet to be revealed by the current literature. To establish a rate of unplanned postoperative ICU admissions in pediatric patients using a large, multi-institution data set and to further characterize the associated risk factors. Data from the National Anesthesia Clinical Outcomes Registry were analyzed. We recorded the overall risk of unplanned postoperative ICU admission in patients younger than 18 years and performed univariate and multivariate logistic regression analysis to identify the associated patient, surgical, and anesthetic-related characteristics. Of the 324 818 cases analyzed, 211 reported an unexpected ICU admission. There was an increased likelihood of unplanned postoperative ICU in infants (age anesthesia were also associated with unplanned ICU admissions. This study establishes a rate of unplanned ICU admission following surgery in the heterogeneous pediatric population. This is the first study to utilize such a large data set encompassing a wide range of practice environments to identify risk factors leading to unplanned postoperative ICU admissions. Our study revealed that patient, surgical, and anesthetic complexity each contributed to an increased number of unplanned ICU admissions in the pediatric population.

  7. Drivers and Risk Factors of Unplanned 30-Day Readmission Following Spinal Cord Stimulator Implantation.

    Science.gov (United States)

    Elsamadicy, Aladine A; Sergesketter, Amanda; Ren, Xinru; Mohammed Qasim Hussaini, Syed; Laarakker, Avra; Rahimpour, Shervin; Ejikeme, Tiffany; Yang, Siyun; Pagadala, Promila; Parente, Beth; Xie, Jichun; Lad, Shivanand P

    2018-01-01

    Unplanned 30-day readmission rates contribute significantly to growing national healthcare expenditures. Drivers of unplanned 30-day readmission after spinal cord stimulator (SCS) implantation are relatively unknown. The aim of this study was to determine drivers of 30-day unplanned readmission following SCS implantation. The National Readmission Database was queried to identify all patients who underwent SCS implantation for the 2013 calendar year. Patients were grouped by readmission status, "No Readmission" and "Unplanned 30-day Readmission." Patient demographics and comorbidities were collected for each patient. The primary outcome of interest was the rate of unplanned 30-day readmissions and associated driving factors. A multivariate analysis was used to determine independent predictors of unplanned 30-day readmission after SCS implantation. We identified 1521 patients who underwent SCS implantation, with 113 (7.4%) experiencing an unplanned readmission within 30 days. Baseline patient demographics, comorbidities, and hospital characteristics were similar between both cohorts. The three main drivers for 30-day readmission after SCS implantation include: 1) infection (not related to SCS device), 2) infection due to device (limited to only hardware infection), and 3) mechanical complication of SCS device. Furthermore, obesity was found to be an independent predictor of 30-day readmission (OR: 1.86, p = 0.008). Our study suggests that infectious and mechanical complications are the primary drivers of unplanned 30-day readmission after SCS implantation, with obesity as an independent predictor of unplanned readmission. Given the technological advancements in SCS, repeated studies are necessary to identify factors associated with unplanned 30-day readmission rates after SCS implantation to improve patient outcomes and reduce associated costs. © 2017 International Neuromodulation Society.

  8. Plan to Have No Unplanned: A Collaborative, Hospital-Based Quality-Improvement Project to Reduce the Rate of Unplanned Extubations in the Pediatric ICU.

    Science.gov (United States)

    Tripathi, Sandeep; Nunez, Denise J; Katyal, Chaavi; Ushay, H Michael

    2015-08-01

    Although under-reported and understudied, unplanned extubations carry a significant risk of patient harm and even death. They are an important yardstick of quality control of care of intubated patients in the ICU. A unit-based risk assessment and multidisciplinary approach is required to decrease the incidence of unplanned extubations. As part of a quality-improvement initiative of Children's Hospital at Montefiore, all planned and unplanned extubations in a multidisciplinary 20-bed pediatric ICU were evaluated over a 12-month period (January to December 2010). At the end of 6 months, an interim analysis was performed, and high-risk patient groups and patient care factors were identified. These factors were targeted in the second phase of the project. Over this period, there were a total of 267 extubations, of which 231 (87%) were planned extubations and 36 (13%) were unplanned. A patient care policy targeting the risk factors was instituted, along with extensive nursing and other personnel education in the second phase. As a result of this intervention, the unplanned extubation rate in the pediatric ICU decreased from 3.55 to 2.59/100 intubation days. All subjects who had an unplanned extubation during nursing procedures or transport required re-intubation, whereas none of the unplanned extubations during ventilator weaning required re-intubation. A targeted approach based on unit-specific risk factors is most effective in quality-improvement projects. A specific policy for sedation and weaning can be very helpful in managing intubated patients and preventing unintended harm. Copyright © 2015 by Daedalus Enterprises.

  9. Neurologic outcome in comatose patients resuscitated from out-of-hospital cardiac arrest with prolonged downtime and treated with therapeutic hypothermia

    Science.gov (United States)

    Kim, Won Young; Giberson, Tyler A.; Uber, Amy; Berg, Katherine; Cocchi, Michael N.; Donnino, Michael W.

    2014-01-01

    Background Previous reports have shown that prolonged duration of resuscitation efforts in out-of-hospital cardiac arrest (OHCA) is associated with poor neurologic outcome. This concept has recently been questioned with advancements in post-cardiac arrest care including the use of therapeutic hypothermia (TH). The aim of this study was to determine the rate of good neurologic outcome based on the duration of resuscitation efforts in OHCA patients treated with TH. Methods This prospective, observational, study was conducted between January 2008 and September 2012. Inclusion criteria consisted of adult non-traumatic OHCA patients who were comatose after return of spontaneous circulation (ROSC) and received TH. The primary endpoint was good neurologic outcome defined as a cerebral performance category score of 1 or 2. Downtime was calculated as the length of time between the patient being recognized as pulseless and ROSC. Results 105 patients were treated with TH and 19 were excluded due to unknown downtime, leaving 86 patients for analysis. The median downtime was 18.5 (10.0–32.3) minutes and 33 patients (38.0%) had a good neurologic outcome. When downtime was divided into four groups (≤10 min, 11-20 min, 21-30 min, > 30 min), good neurologic outcomes were 62.5%, 37%, 25%, and 21.7%, respectively (p=0.02). However, even with downtime >20 minutes, 22.9% had a good neurologic outcome, and this percentage increased to 37.5% in patients with an initial shockable rhythm. Conclusions Although longer downtime is associated with worse outcome in OHCA patients, we found that comatose patients who have been successfully resuscitated and treated with TH have neurologically intact survival rates of 23% even with downtime > 20 minutes. PMID:24746783

  10. Neurologic outcome in comatose patients resuscitated from out-of-hospital cardiac arrest with prolonged downtime and treated with therapeutic hypothermia.

    Science.gov (United States)

    Kim, Won Young; Giberson, Tyler A; Uber, Amy; Berg, Katherine; Cocchi, Michael N; Donnino, Michael W

    2014-08-01

    Previous reports have shown that prolonged duration of resuscitation efforts in out-of-hospital cardiac arrest (OHCA) is associated with poor neurologic outcome. This concept has recently been questioned with advancements in post-cardiac arrest care including the use of therapeutic hypothermia (TH). The aim of this study was to determine the rate of good neurologic outcome based on the duration of resuscitation efforts in OHCA patients treated with TH. This prospective, observational, study was conducted between January 2008 and September 2012. Inclusion criteria consisted of adult non-traumatic OHCA patients who were comatose after return of spontaneous circulation (ROSC) and received TH. The primary endpoint was good neurologic outcome defined as a cerebral performance category score of 1 or 2. Downtime was calculated as the length of time between the patient being recognized as pulseless and ROSC. 105 patients were treated with TH and 19 were excluded due to unknown downtime, leaving 86 patients for analysis. The median downtime was 18.5 (10.0-32.3)min and 33 patients (38.0%) had a good neurologic outcome. When downtime was divided into four groups (≤10min, 11-20min, 21-30min, >30min), good neurologic outcomes were 62.5%, 37%, 25%, and 21.7%, respectively (p=0.02). However, even with downtime >20min, 22.9% had a good neurologic outcome, and this percentage increased to 37.5% in patients with an initial shockable rhythm. Although longer downtime is associated with worse outcome in OHCA patients, we found that comatose patients who have been successfully resuscitated and treated with TH have neurologically intact survival rates of 23% even with downtime >20min. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  11. Unplanned versus planned extubation in respiratory intensive care unit, predictors of outcome

    Directory of Open Access Journals (Sweden)

    Mohammed F. Ismaeil

    2014-01-01

    Conclusions: An increase in severity of illness on ICU admission, agitation, less use of sedation with lower Ramsay score during MV intensify the risk of unplanned extubation, which usually occurs during the night shift, even with the use of physical restraints. Unplanned extubation is associated with an increased incidence of failed extubation (especially with accidental extubation and mortality. Factors affecting airway competence; magnitude of cough on command and abundant amount of E/T secretions are significant predictors of extubation failure in planned and unplanned extubation. Prolonged minute ventilation recovery time, failed DSA test and lower swallowing score are associated with an increased risk of failed planned extubation.

  12. Outcomes and risk factors for unplanned delivery at home and before arrival to the hospital.

    Science.gov (United States)

    Lazić, Zlatko; Takač, Iztok

    2011-01-01

    The aim of this study was to analyze the outcomes and risk factors for unplanned delivery at home and before arrival to the hospital in Maribor region, Slovenia. We used data from medical records of all deliveries in Maribor region from the year 1997 to the year 2005. We analysed a total of 17,846 births from annual reports of the Maribor University Hospital. Among the total of 17,846 births, there were 58 (3.2‰) unplanned births at home and on the way to the hospital. The study based on the data from medical records on safety of unplanned home birth reveals that hospital delivery is approximately 7 times safer than unplanned home delivery. This conclusion is reached by comparing perinatal mortality, which was 68‰ for unplanned deliveries at home versus 8.8‰ for deliveries at hospital. The prematurity was more common in unplanned home deliveries: 13 (22%) versus 1399 (8%) for hospital deliveries. Unplanned deliveries at home and on the way to the hospital were more common in multiparous women (ratio 4:1 compared to 1:1 for hospital births). When for all hospital deliveries the pregnancies were followed, for one third of unplanned deliveries at home or on the way to the hospital the pregnancies were not monitored. Mothers who gave birth at home or on the way to the hospital were without higher education (i.e. 55.2%) and mothers who gave birth in hospital were with higher education (i.e. 87.4%). There was higher rate of perinatal morbidity for unplanned home deliveries compared to hospital deliveries. Factors that make unplanned home deliveries more common are high parity, absence or inadequacy of antenatal care, marital status and lower education. Some conditions in newborn, such as hypothermia, were clearly the result of unplanned birth at home. Additional effort to improve antenatal care and also identifying social vulnerabilities would possibly decrease the number of unplanned deliveries and improve the perinatal outcomes.

  13. Approximation errors during variance propagation

    International Nuclear Information System (INIS)

    Dinsmore, Stephen

    1986-01-01

    Risk and reliability analyses are often performed by constructing and quantifying large fault trees. The inputs to these models are component failure events whose probability of occuring are best represented as random variables. This paper examines the errors inherent in two approximation techniques used to calculate the top event's variance from the inputs' variance. Two sample fault trees are evaluated and several three dimensional plots illustrating the magnitude of the error over a wide range of input means and variances are given

  14. Risk factors for 30-day unplanned readmission following infrainguinal endovascular interventions

    NARCIS (Netherlands)

    Bodewes, Thomas C F; Soden, Peter A.; Ultee, Klaas H J; Zettervall, Sara L.; Pothof, Alexander B.; Deery, Sarah E.; Moll, Frans L.; Schermerhorn, Marc L.

    2017-01-01

    Objective Unplanned hospital readmissions following surgical interventions are associated with adverse events and contribute to increasing health care costs. Despite numerous studies defining risk factors following lower extremity bypass surgery, evidence regarding readmission after endovascular

  15. Factors Associated with Unplanned Dialysis Starts in Patients followed by Nephrologists: A Retropective Cohort Study.

    Directory of Open Access Journals (Sweden)

    Pierre Antoine Brown

    Full Text Available The number of patients starting dialysis is increasing world wide. Unplanned dialysis starts (patients urgently starting dialysis in hospital is associated with increased costs and high morbidity and mortality. Risk factors for starting dialysis urgently in hospital have not been well studied. The primary objective of this study was to identify risk factors for unplanned dialysis starts in patients followed in a multidisciplinary chronic kidney disease (CKD clinic. We performed a retrospective cohort study of 649 advanced CKD patients followed in a multidisciplinary CKD clinic at a tertiary care hospital from January 01, 2010 to April 30, 2013. Patients were classified as unplanned start (in hospital or elective start. Multivariable logistic regression was used to identify variables associated with unplanned dialysis initiation. 184 patients (28.4% initiated dialysis, of which 76 patients (41.3% initiated dialysis in an unplanned fashion and 108 (58.7% starting electively. Unplanned start patients were more likely to have diabetes (68.4% versus 51.9%; p = 0.04, CAD (42.1% versus 24.1%; p = 0.02, congestive heart failure (36.8% versus 17.6%; p = 0.01, and were less likely to receive modality education (64.5% vs 89.8%; p < 0.01 or be assessed by a surgeon for access creation (40.8% vesrus 78.7% p < 0.01. On multivariable analysis, higher body mass index (OR 1.07, 95% CI 1.02, 1.13, and a history of congestive heart failure (OR 2.41, 95% CI 1.09, 5.41 were independently associated with an unplanned start. Unplanned dialysis initiation is common among advanced CKD patients, even if they are followed in a multidisciplinary chronic kidney disease clinic. Timely education and access creation in patients at risk may lead to lower costs and less morbidity and mortality.

  16. Estimation of Downtime and of Missed Energy Associated with a Wave Energy Converter by the Equivalent Power Storm Model

    Directory of Open Access Journals (Sweden)

    Felice Arena

    2015-10-01

    Full Text Available The design of any wave energy converter involves the determination of relevant statistical data on the wave energy resource oriented to the evaluation of the structural reliability and energy performance of the device. Currently, limited discussions concern the estimation of parameters connected to the energy performance of a device. Thus, this paper proposes a methodology for determining average downtime and average missed energy, which is the energy that is not harvested because of device deactivations during severe sea storms. These quantities are fundamental for evaluating the expected inactivity of a device during a year or during its lifetime and are relevant for assessing the effectiveness of a device working at a certain site. For this purpose, the equivalent power storm method is used for their derivation, starting from concepts pertaining to long-term statistical analysis. The paper shows that the proposed solutions provide reliable estimations via comparison with results obtained by processing long wave data.

  17. A programme to reduce down-time and site radiation dose through improvements in control rod design

    International Nuclear Information System (INIS)

    Izatt, J.A.; Scobie, J.

    1985-01-01

    On the UTR-300 reactor at SURRC, it has been found necessary to carry out preventive or remedial maintenance at least once per year on the in-core elements of the control rod assemblies. This has led to reduced availability of the reactor and to significant overall radiation doses to the few long-serving staff members who carry out this work. In an attempt to reduce down-time and radiation dose to staff a radical re-design of the control assemblies was undertaken in-house, and a conversion programme has been underway over the last four years. Details of the design improvements are presented together with a discussion of the operating experience to date. (author)

  18. Means and Variances without Calculus

    Science.gov (United States)

    Kinney, John J.

    2005-01-01

    This article gives a method of finding discrete approximations to continuous probability density functions and shows examples of its use, allowing students without calculus access to the calculation of means and variances.

  19. Family Caregiver Knowledge, Patient Illness Characteristics, and Unplanned Hospital Admissions in Older Adults With Cancer.

    Science.gov (United States)

    Geddie, Patricia I; Wochna Loerzel, Victoria; Norris, Anne E

    2016-07-01

    To explore factors related to unplanned hospital admissions and determine if one or more factors are predictive of unplanned hospital admissions for older adults with cancer.
. A prospective longitudinal design and a retrospective chart review.
. Adult oncology outpatient infusion centers and inpatient units at Orlando Regional Medical Center in Florida.
. A convenience sample of 129 dyads of older adults with cancer and their family caregivers. 
. Family caregiver demographic and side effect knowledge data were collected prospectively during interviews with family caregivers using a newly developed tool, the Nurse Assessment of Family Caregiver Knowledge and Action Tool. Patient demographic and clinical data were obtained through a retrospective chart review. Descriptive statistics and logistic regression analyses were used to evaluate data and examine relationships among variables.
. Patient illness characteristics; impaired function; side effects, such as infection, fever, vomiting, and diarrhea; family caregiver knowledge; and unplanned hospital admissions.
. Unplanned hospital admissions were more likely to occur when older adults had impaired function and side effects, such as infection, fever, vomiting, and diarrhea. Impaired function and family caregiver knowledge did not moderate the effects of these side effects on unplanned hospital admissions. 
. Findings suggest that the presence of impaired function and side effects, such as infection, fever, vomiting, and diarrhea, predict unplanned hospital admissions in older adults with cancer during the active treatment phase. Side effects may or may not be related to chemotherapy and may be related to preexisting comorbidities. 
. Nurses can conduct targeted assessments to identify older adults and their family caregivers who will need additional follow-up and support during the cancer treatment trajectory. Information gained from these assessments will assist nurses to provide practical and

  20. Why babies die in unplanned out?of?institution births: an enquiry into perinatal deaths in Norway 1999?2013

    OpenAIRE

    Gunnarsson, Bj?rn; Fasting, Sigurd; Skogvoll, Eirik; Sm?rason, Alexander K.; Salvesen, Kjell ?.

    2017-01-01

    Introduction The aims were to describe causes of death associated with unplanned out-of-institution births, and to study whether they could be prevented. Material and methods Retrospective population-based observational study based on data from the Medical Birth Registry of Norway and medical records. Between 1 January 1999 and 31 December 2013, 69 perinatal deaths among 6027 unplanned out-of-institution births, whether unplanned at home, during transportation, or unspecified, were...

  1. Planned and unplanned home births and hospital births in Calgary, Alberta, 1984-87.

    Science.gov (United States)

    Abernathy, T J; Lentjes, D M

    1989-01-01

    Information collected on all home births in Calgary (Canada) between the years 1984 and 1987, was examined and analyzed according to whether the home birth environment had been planned or unplanned. The two groups were compared to each other and to all hospital births according to demographic characteristics of mothers, indicators of prenatal care, and birth outcome. Mothers who had planned their home birth were more likely to be primiparous, attend prenatal classes, obtain regular prenatal care from a physician, and have babies with a higher birth weight than either the unplanned or hospital group. Of particular concern, however, were the subset of unplanned home births who were primiparous. These mothers attended prenatal classes less frequently than any other group, reported the lowest number of physician visits, were youngest, and least likely to be married. In addition their babies averaged the shortest gestational age and the lowest birth weight. Findings in general show that planned and unplanned home births must be considered as heterogeneous groups in any comparison of risk factors and of birth outcome between home and hospital births. Further, within the unplanned group, multiparous women differ from primiparous women. Given the limitations inherent in this and similar studies, the apparent better outcome in the planned home birth group, as measured by birth weight, must be viewed with caution.

  2. Unplanned 30-Day Readmissions in a General Internal Medicine Hospitalist Service at a Comprehensive Cancer Center.

    Science.gov (United States)

    Manzano, Joanna-Grace M; Gadiraju, Sahitya; Hiremath, Adarsh; Lin, Heather Yan; Farroni, Jeff; Halm, Josiah

    2015-09-01

    Hospital readmissions are considered by the Centers for Medicare and Medicaid as a metric for quality of health care delivery. Robust data on the readmission profile of patients with cancer are currently insufficient to determine whether this measure is applicable to cancer hospitals as well. To address this knowledge gap, we estimated the unplanned readmission rate and identified factors influencing unplanned readmissions in a hospitalist service at a comprehensive cancer center. We retrospectively analyzed unplanned 30-day readmission of patients discharged from the General Internal Medicine Hospitalist Service at a comprehensive cancer center between April 1, 2012, and September 30, 2012. Multiple independent variables were studied using univariable and multivariable logistic regression models, with generalized estimating equations to identify risk factors associated with readmissions. We observed a readmission rate of 22.6% in our cohort. The median time to unplanned readmission was 10 days. Unplanned readmission was more likely in patients with metastatic cancer and those with three or more comorbidities. Patients discharged to hospice were less likely to be readmitted (all P values quality measures in cancer hospitals. Copyright © 2015 by American Society of Clinical Oncology.

  3. Impact of Inpatient Versus Outpatient Total Joint Arthroplasty on 30-Day Hospital Readmission Rates and Unplanned Episodes of Care.

    Science.gov (United States)

    Springer, Bryan D; Odum, Susan M; Vegari, David N; Mokris, Jeffrey G; Beaver, Walter B

    2017-01-01

    This article describes a study comparing 30-day readmission rates between patients undergoing outpatient versus inpatient total hip (THA) and knee (TKA) arthroplasty. A retrospective review of 137 patients undergoing outpatient total joint arthroplasty (TJA) and 106 patients undergoing inpatient (minimum 2-day hospital stay) TJA was conducted. Unplanned hospital readmissions and unplanned episodes of care were recorded. All patients completed a telephone survey. Seven inpatients and 16 outpatients required hospital readmission or an unplanned episode of care following hospital discharge. Readmission rates were higher for TKA than THA. The authors found no statistical differences in 30-day readmission or unplanned care episodes. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Revision: Variance Inflation in Regression

    Directory of Open Access Journals (Sweden)

    D. R. Jensen

    2013-01-01

    the intercept; and (iv variance deflation may occur, where ill-conditioned data yield smaller variances than their orthogonal surrogates. Conventional VIFs have all regressors linked, or none, often untenable in practice. Beyond these, our models enable the unlinking of regressors that can be unlinked, while preserving dependence among those intrinsically linked. Moreover, known collinearity indices are extended to encompass angles between subspaces of regressors. To reaccess ill-conditioned data, we consider case studies ranging from elementary examples to data from the literature.

  5. Unplanned cigarette purchases and tobacco point of sale advertising: a potential barrier to smoking cessation.

    Science.gov (United States)

    Clattenburg, Eben J; Elf, Jessica L; Apelberg, Benjamin J

    2013-11-01

    In the USA, tobacco marketing expenditure is increasingly concentrated at the point of sale (POS). Previous studies have demonstrated an association between exposure to tobacco POS advertising and increased smoking initiation, but limited evidence is available on adult smokers' decisions and behaviours. An immediate post-cigarette purchase survey was administered to 301 cigarette purchasers outside of two grocery stores in Vermont to assess the prevalence of unplanned purchases and opinions about POS tobacco advertising and displays. In total, 11.3% of purchases were reported as unplanned. Certain groups were more likely to make unplanned purchases including: 18-24-year-olds (OR: 2.1, 95% CI 1.0 to 4.4), less than daily smokers (OR: 5.6, 95% CI 1.9 to 16.9), smokers who made 3+ quit attempts in the previous year (OR: 2.4, 95% CI 0.9 to 6.0), those who plan to quit in the next month (OR: 3.7, 95% CI 1.6 to 9.0), and those who agreed that tobacco POS advertising makes quitting smoking harder (OR: 2.3, 95% CI 1.1 to 4.8). Overall, 31.2% of participants agreed that tobacco POS advertising makes quitting smoking harder. Individuals who intended to quit within the next month, made 3+ quit attempts in the last year, or made an unplanned cigarette purchase were the most likely to agree. Young adults and individuals making multiple quit attempts or planning to quit in the next month are more likely to make unplanned cigarette purchases. Reducing unplanned purchases prompted by tobacco POS advertising could improve the likelihood of successful cessation among smokers.

  6. Binge drinking, reflection impulsivity, and unplanned sexual behavior: impaired decision-making in young social drinkers.

    Science.gov (United States)

    Townshend, Julia M; Kambouropoulos, Nicolas; Griffin, Alison; Hunt, Frances J; Milani, Raffaella M

    2014-04-01

    The repeated pattern of heavy intoxication followed by withdrawal from alcohol (i.e., "binge drinking") has been found to have substantial adverse effects on prefrontal neural systems associated with decision-making and impulse control. Repeated binge drinking has been linked to risky and unplanned sexual behavior; however few studies have examined the role of impulsivity and related cognitive processes in understanding this association. The aim of this study was to examine the relationship between binge drinking, "reflection impulsivity" (deficits in gathering and evaluating information during decision-making), alcohol-related expectancies, and unplanned sexual behavior in a sample of young social drinkers. Ninety-two university students completed the alcohol use questionnaire (AUQ) to measure alcohol intake and binge drinking. Two groups (low-binge and high-binge) were generated from the AUQ data. The Information Sampling Task (IST) was used to measure reflection impulsivity; the Alcohol Expectancy Questionnaire (AEQ) for alcohol outcome expectancies; and an unplanned sexual behavior questionnaire, which asked about the number of unplanned sexual events. When compared to the low-binge drinking group, the high-binge drinkers had significantly more unplanned sexual encounters and were impaired on the IST, reflection-impulsivity task. They scored higher on the alcohol expectancy factors of sociability, risk and aggression, negative self-perception, and in particular liquid courage. In a regression analysis, number of unplanned sexual encounters, binge drinking score, and liquid courage were all significantly related. These results support the role of binge drinking in reduced impulse control and decision-making deficits. The findings indicate that high-binge drinkers demonstrate impairments on an impulse control task similar to that observed in dependent samples and this may be a factor in understanding the negative behavioral consequences associated with excessive

  7. Reproductive counseling, contraception, and unplanned pregnancy in fertile women treated by gynecologic oncologists

    Directory of Open Access Journals (Sweden)

    Sarah M Crafton

    2017-02-01

    Members of the Society of Gynecologic Oncology (SGO were surveyed electronically regarding consistency of counseling patterns of contraception and fertility concerns, most and least common contraceptive methods utilized, referral patterns, and incidence of unplanned pregnancy. Of the 1424 SGO members identified, 261 participated in the questionnaire, yielding a response rate of 18%. Eighty-two percent of respondents agreed unplanned pregnancy is a potential problem, but only 57% believed their patients understood unplanned pregnancy is possible during treatment. Half of respondents report “always” in terms of frequency that contraception is addressed among their high-risk patients. After adjustment for gender, we found that the odds of reporting providing fertility counseling were nearly three times higher among attendings as compared to fellows [AOR = 2.72; 95% CI = (1.44, 5.12, three times higher in women as compared to men [AOR = 2.80; 95% CI = (1.46, 5.38], as well as in individuals 50+ years as compared to those <40 years old [AOR = 4.91; 95% CI = (2.05, 11.74]. Ninety-six percent reported <5 unplanned pregnancies, to their knowledge, in the previous five years of clinical practice. Most providers acknowledge that unplanned pregnancy is a potential risk in fertile gynecologic oncology patients, but only half believe their patients understand an unplanned pregnancy is possible. An opportunity exists to provide more directed counseling regarding fertility during and after cancer therapy, and to educate patients and providers regarding more reliable, long acting contraceptive methods.

  8. Modelling volatility by variance decomposition

    DEFF Research Database (Denmark)

    Amado, Cristina; Teräsvirta, Timo

    In this paper, we propose two parametric alternatives to the standard GARCH model. They allow the variance of the model to have a smooth time-varying structure of either additive or multiplicative type. The suggested parameterisations describe both nonlinearity and structural change in the condit...

  9. Gini estimation under infinite variance

    NARCIS (Netherlands)

    A. Fontanari (Andrea); N.N. Taleb (Nassim Nicholas); P. Cirillo (Pasquale)

    2018-01-01

    textabstractWe study the problems related to the estimation of the Gini index in presence of a fat-tailed data generating process, i.e. one in the stable distribution class with finite mean but infinite variance (i.e. with tail index α∈(1,2)). We show that, in such a case, the Gini coefficient

  10. Gravidez não planejada no extremo Sul do Brasil: prevalência e fatores associados Unplanned pregnancy in Southern Brazil: prevalence and associated factors

    Directory of Open Access Journals (Sweden)

    Silvio Omar Macedo Prietsch

    2011-10-01

    Full Text Available Este estudo teve por objetivo identificar fatores associados à ocorrência de gravidez não planejada em Rio Grande, Rio Grande do Sul, Brasil. Em 2007, aplicou-se questionário padronizado a todas as parturientes residentes neste município, investigando sobre características demográficas e reprodutivas maternas, nível socioeconômico da família e assistência recebida na gestação e parto. A análise ajustada foi realizada utilizando-se regressão de Poisson com ajuste robusto da variância. Dentre as 2.557 gestantes incluídas no estudo, 65% não planejaram a gravidez. Após ajuste para confundimento, as seguintes variáveis mostraram-se significativamente associadas à gravidez não planejada: cor da pele parda/preta, idade inferior a 20 anos, sem companheiro, baixa renda familiar, aglomeração familiar, tabagismo e mais de um parto. Abortamento prévio mostrou-se protetor para a gravidez não planejada. A elevada ocorrência de gravidez não planejada, sobretudo entre aquelas com maiores riscos de complicações durante a gestação e o parto, indica a necessidade de se estabelecerem programas de saúde à atenção desta população.The purpose of this study was to investigate factors associated with unplanned pregnancies in Rio Grande, Rio Grande do Sul State, Brazil. A standardized questionnaire was applied in 2007 to all pregnant women in the city, including demographic characteristics, childbearing history, socioeconomic status, and prenatal and childbirth care. The study used Poisson multivariate regression analysis with robust adjustment of variance. Among the 2,557 women included in the study, 65% had not planned the current pregnancy. After adjusting for confounders, the following variables were significantly associated with unplanned pregnancy: black or mixed race, age < 20 years, single marital status, low family income, household crowding, smoking, and multiparity. Previous abortion was a protective factor against

  11. HAVmS: Highly Available Virtual Machine Computer System Fault Tolerant with Automatic Failback and Close to Zero Downtime

    Directory of Open Access Journals (Sweden)

    Memmo Federici

    2014-12-01

    Full Text Available In scientic computing, systems often manage computations that require continuous acquisition of of satellite data and the management of large databases, as well as the execution of analysis software and simulation models (e.g. Monte Carlo or molecular dynamics cell simulations which may require several weeks of continuous run. These systems, consequently, should ensure the continuity of operation even in case of serious faults. HAVmS (High Availability Virtual machine System is a highly available, "fault tolerant" system with zero downtime in case of fault. It is based on the use of Virtual Machines and implemented by two servers with similar characteristics. HAVmS, thanks to the developed software solutions, is unique in its kind since it automatically failbacks once faults have been fixed. The system has been designed to be used both with professional or inexpensive hardware and supports the simultaneous execution of multiple services such as: web, mail, computing and administrative services, uninterrupted computing, data base management. Finally the system is cost effective adopting exclusively open source solutions, is easily manageable and for general use.

  12. A programme to reduce down-time and site radiation dose through improvements in control rod design

    International Nuclear Information System (INIS)

    Izatt, J.A.; Scobie, J.

    1983-01-01

    In many nuclear facilities a high proportion of the total radiation dose to staff may be ascribed to very few routine operations. Often this critical operation will require significant shut-down time, both to perform the function itself and to allow sufficient decay time to reduce radiation levels to acceptable values. This situation arises on the UTR-300 reactor at S.U.R.R.C., where over the twenty years of operation it has been found necessary to carry out preventive, and on some occasions remedial, maintenance at least once per year on the in-core elements of the control rod assemblies. This had led inevitably to reduced availability of the reactor and to significant overall radiation doses to the few long-serving staff members who carry out this work. The source of the problem seems to lie in the basic design of the assemblies, which may have been adequate for the original 10 KW versions of this reactor, but has proven to be deficient in several respects at the present 300 KW operating level. In an attempt to reduce down-time and radiation dose to staff a radical re-design of the control assemblies was undertaken in-house, and a conversion programme has been underway over the last two years. Details of the design improvements are presented with a discussion of the operating experience to date. (author)

  13. Planned and unplanned terminations of foster care placements in the Netherlands: Relationships with characteristics of foster children and foster placements

    NARCIS (Netherlands)

    van Rooij, F.; Maaskant, A.; Weijers, I.; Weijers, D.; Hermanns, J.

    2015-01-01

    This study examined the role of placement and child characteristics in the unplanned termination of foster placements. Data were used from 169 foster children aged 0 to 20. Results showed that 35% of all foster placement terminations were unplanned. Outcomes of logistic regression analyses

  14. Do Older Rural and Urban Veterans Experience Different Rates of Unplanned Readmission to VA and Non-VA Hospitals?

    Science.gov (United States)

    Weeks, William B.; Lee, Richard E.; Wallace, Amy E.; West, Alan N.; Bagian, James P.

    2009-01-01

    Context: Unplanned readmission within 30 days of discharge is an indicator of hospital quality. Purpose: We wanted to determine whether older rural veterans who were enrolled in the VA had different rates of unplanned readmission to VA or non-VA hospitals than their urban counterparts. Methods: We used the combined VA/Medicare dataset to examine…

  15. Variance based OFDM frame synchronization

    Directory of Open Access Journals (Sweden)

    Z. Fedra

    2012-04-01

    Full Text Available The paper deals with a new frame synchronization scheme for OFDM systems and calculates the complexity of this scheme. The scheme is based on the computing of the detection window variance. The variance is computed in two delayed times, so a modified Early-Late loop is used for the frame position detection. The proposed algorithm deals with different variants of OFDM parameters including guard interval, cyclic prefix, and has good properties regarding the choice of the algorithm's parameters since the parameters may be chosen within a wide range without having a high influence on system performance. The verification of the proposed algorithm functionality has been performed on a development environment using universal software radio peripheral (USRP hardware.

  16. Variance decomposition in stochastic simulators.

    Science.gov (United States)

    Le Maître, O P; Knio, O M; Moraes, A

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  17. Variance decomposition in stochastic simulators

    Science.gov (United States)

    Le Maître, O. P.; Knio, O. M.; Moraes, A.

    2015-06-01

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  18. Variance decomposition in stochastic simulators

    Energy Technology Data Exchange (ETDEWEB)

    Le Maître, O. P., E-mail: olm@limsi.fr [LIMSI-CNRS, UPR 3251, Orsay (France); Knio, O. M., E-mail: knio@duke.edu [Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708 (United States); Moraes, A., E-mail: alvaro.moraesgutierrez@kaust.edu.sa [King Abdullah University of Science and Technology, Thuwal (Saudi Arabia)

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  19. Variance decomposition in stochastic simulators

    KAUST Repository

    Le Maî tre, O. P.; Knio, O. M.; Moraes, Alvaro

    2015-01-01

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  20. On Mean-Variance Analysis

    OpenAIRE

    Li, Yang; Pirvu, Traian A

    2011-01-01

    This paper considers the mean variance portfolio management problem. We examine portfolios which contain both primary and derivative securities. The challenge in this context is due to portfolio's nonlinearities. The delta-gamma approximation is employed to overcome it. Thus, the optimization problem is reduced to a well posed quadratic program. The methodology developed in this paper can be also applied to pricing and hedging in incomplete markets.

  1. Factors that Adolescent Males Take into Account in Decisions about an Unplanned Pregnancy

    Science.gov (United States)

    Corkindale, Carolyn J.; Condon, John T.; Russell, Alan; Quinlivan, Julie A.

    2009-01-01

    Little is known about what factors adolescent males consider important when making decisions concerning the resolution of an unplanned pregnancy with a teenage partner. Young men's influence on pregnancy outcome decisions can play an important part in the subsequent psychological adjustment of the female. The present report draws on data from a…

  2. Does an Unplanned Pregnancy Have Long-Term Implications for Mother-Child Relationships?

    Science.gov (United States)

    Nelson, Jackie A.; O'Brien, Marion

    2012-01-01

    The effect of pregnancy planning on the quality of mother-adolescent relationships 15 years later was examined among 373 first-time parents and 472 experienced parents using a mediated moderation model. Among first-time mothers only, the experience of an unplanned pregnancy was related to higher maternal depressive symptoms when mothers also…

  3. Rates and risk factors of unplanned 30-day readmission following general and thoracic pediatric surgical procedures.

    Science.gov (United States)

    Polites, Stephanie F; Potter, Donald D; Glasgow, Amy E; Klinkner, Denise B; Moir, Christopher R; Ishitani, Michael B; Habermann, Elizabeth B

    2017-08-01

    Postoperative unplanned readmissions are costly and decrease patient satisfaction; however, little is known about this complication in pediatric surgery. The purpose of this study was to determine rates and predictors of unplanned readmission in a multi-institutional cohort of pediatric surgical patients. Unplanned 30-day readmissions following general and thoracic surgical procedures in children readmission per 30 person-days were determined to account for varied postoperative length of stay (pLOS). Patients were randomly divided into 70% derivation and 30% validation cohorts which were used for creation and validation of a risk model for readmission. Readmission occurred in 1948 (3.6%) of 54,870 children for a rate of 4.3% per 30 person-days. Adjusted predictors of readmission included hepatobiliary procedures, increased wound class, operative duration, complications, and pLOS. The predictive model discriminated well in the derivation and validation cohorts (AUROC 0.710 and 0.701) with good calibration between observed and expected readmission events in both cohorts (p>.05). Unplanned readmission occurs less frequently in pediatric surgery than what is described in adults, calling into question its use as a quality indicator in this population. Factors that predict readmission including type of procedure, complications, and pLOS can be used to identify at-risk children and develop prevention strategies. III. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Knowledge sharing behaviour within organisations; A diary-based study of unplanned meetings between researchers

    NARCIS (Netherlands)

    Appel-Meulenbroek, Rianne; Weggeman, Mathieu; Torkkeli, Marko

    2018-01-01

    This paper analyses Knowledge Sharing (KS) behaviour of employees during unplanned, work-related face-to-face meetings with colleagues. Hypotheses were formulated from theory on how this behaviour relates to three categories of known KS antecedents (knowledge components, organisational distance, and

  5. Planned versus Unplanned Risks: Neurocognitive Predictors of Subtypes of Adolescents' Risk Behavior

    Science.gov (United States)

    Maslowsky, Julie; Keating, Daniel P.; Monk, Christopher S.; Schulenberg, John

    2011-01-01

    Risk behavior contributes to substantial morbidity and mortality during adolescence. This study examined neurocognitive predictors of proposed subtypes of adolescent risk behavior: planned (premeditated) versus unplanned (spontaneous). Adolescents (N = 69, 49% male, M = 15.1 [1.0] years) completed neurocognitive tasks (Iowa Gambling Task [IGT],…

  6. Risk factors for unplanned pregnancy in women with mental illness living in a developing country.

    Science.gov (United States)

    du Toit, Elsa; Jordaan, Esme; Niehaus, Dana; Koen, Liezl; Leppanen, Jukka

    2018-06-01

    Pregnant women in general are at an increased risk of experiencing symptoms of mental illness, and those living in a developing country are even more vulnerable. Research points towards a causal relationship between unplanned pregnancy and perinatal mental illness and suggests that pregnancy planning can aid in reducing the negative impact of mental illness on a woman, her unborn baby, and the rest of the family. In this quantitative, descriptive study, we investigated both socio-demographic factors and variables relating to mental illness itself that may place women at an increased risk of experiencing unplanned pregnancy. Data was gathered at two maternal mental health clinics in Cape Town by means of semi-structured interviews. Univariate analyses of the data revealed five independent key risk factors for unplanned pregnancy: lower levels of education, unmarried status, belonging to the Colored ethnic population, substance use, and having a history of two or more suicide attempts. Some of these factors overlap with findings of similar studies, but others are unique to the specific population (women with mental illness within a developing country). Screening of women based on these risk predictors may pave the way for early interventions and reduce the incidence of unplanned pregnancy and the negative consequences thereof in the South African population.

  7. The development of a risk score for unplanned removal of peripherally inserted central catheter in newborns

    Directory of Open Access Journals (Sweden)

    Priscila Costa

    2015-06-01

    Full Text Available OBJECTIVE: to develop a risk score for unplanned removal of peripherally inserted central catheter in newborns.METHOD: prospective cohort study conducted in a neonatal intensive care unit with newborn babies who underwent 524 catheter insertions. The clinical characteristics of the newborn, catheter insertion and intravenous therapy were tested as risk factors for the unplanned removal of catheters using bivariate analysis. The risk score was developed using logistic regression. Accuracy was internally validated based on the area under the Receiver Operating Characteristic curve.RESULTS: the risk score was made up of the following risk factors: transient metabolic disorders; previous insertion of catheter; use of a polyurethane double-lumen catheter; infusion of multiple intravenous solutions through a single-lumen catheter; and tip in a noncentral position. Newborns were classified into three categories of risk of unplanned removal: low (0 to 3 points, moderate (4 to 8 points, and high (≥ 9 points. Accuracy was 0.76.CONCLUSION: the adoption of evidence-based preventative strategies based on the classification and risk factors faced by the newborn is recommended to minimize the occurrence of unplanned removals.

  8. Knee mechanics during planned and unplanned sidestepping: a systematic review and meta-analysis.

    Science.gov (United States)

    Brown, Scott R; Brughelli, Matt; Hume, Patria A

    2014-11-01

    Knee joint mechanics during sidestepping are associated with anterior cruciate ligament injury. Unplanned sidestepping more closely emulates game scenarios when compared with planned sidestepping by limiting decision time, increasing knee loading and challenging the integrity of soft-tissue structures in the knee. It is important to quantify the loads that may challenge the integrity of the knee during planned and unplanned sidestepping. Our objective was to review literature on knee mechanics during planned and unplanned phases of sidestepping. PubMed, CINAHL, MEDLINE (EBSCO), SPORTDiscus and Web of Science were searched using the terms knee mechanics OR knee kine*, AND plan*, unplan*, anticipat*, unanticipat*, side*, cut* or chang*. A systematic approach was used to evaluate 4,629 records. Records were excluded when not available in English, only available in abstract of conference proceedings, not involving a change-of-direction sidestep, not comparing planned and unplanned or maintaining a running velocity greater than 2 m s(−1). Included studies were evaluated independently by two authors using a custom-designed methodological quality assessment derived from the Physiotherapy Evidence Database (PEDro) scale and then confirmed by a third author. Only six studies met the inclusion criteria and were retained for meta-analysis. Magnitude-based inferences were used to assess the standardised effect of the differences between planned and unplanned sidestepping. Knee angles and knee moments were extracted and reported for flexion/extension, abduction/adduction and internal/external rotation for initial contact, weight acceptance, peak push-off and final push-off phases of sidestepping. For kinematic variables, unplanned sidestepping produced a wide range of small to large increases in knee extension angles, small and moderate increases in knee abduction angles and a small increase in internal rotation angle relative to planned sidestepping during the sidestepping

  9. A preliminary inquiry on the problem of unplanned (extra-quota) second births.

    Science.gov (United States)

    Zhao, L; Zhu, C

    1984-01-01

    The resurgence of child births in China in 1981 was marked by a decline in the multiparity birth rates and a drastic rise in the rate of unplanned 2nd births, resulting in unplanned 2nd births outnumbering multiparity births. The aim of this investigation was to find the objective and subjective causes for the unplanned 2nd births and explore ways to bring them under strict control. In the countryside there are loud voices that give insufficient labor as their reason for wanting 2nd births. An analysis of 923 cases of unplanned 2nd births in connection with the economic conditions of the families, the sex of the 1st births, intervals between the births, and the parents' cultural level shows that 61.87% of the total number of families suffered a decline in their income. The effect of the sex of the 1st birth over the 2nd birth varies with different localities. Among those having unplanned births, illiterates accounted for more than 35% in Nanzheng and Yanchuan counties and over 20% in Mianxian and Wubao counties. The current rise in 2nd births is due mainly not to economic reasons but to social and psychological reasons. To effectively hold down 2nd births under the current conditions, the following suggestions are offered: 1) step up propaganda and education work to gradually raise people's consciousness for practicing family planning, 2) family planning measures of economic restriction and reward must be implemented, 3) on the basis of enforcing the new marriage law, late marriage should be promoted, 4) a population tax should be imposed, and 5) social insurance for the elderly should be enlarged.

  10. Unplanned extubations in an intensive care unit: Findings from a critical incident technique.

    Science.gov (United States)

    Danielis, Matteo; Chiaruttini, Simona; Palese, Alvisa

    2018-05-15

    Patients on mechanical ventilation are at risk of experiencing a potentially life-threatening unplanned extubation in the intensive care unit, which can lead to arrhythmias, bronchial aspiration, difficulty in reintubation or even sudden cardiac arrest. Although incidence and outcomes of the phenomenon have been documented in several quantitative studies, no studies have investigated the antecedents as experienced by critical care nurses. To gain a greater understanding of the antecedents of unplanned extubations. A qualitative study design involving the critical-incident technique. A total of 10 registered nurses who reported one or more episodes of unplanned extubations were involved in an in-depth interview. According to the nurses' experience, episodes of unplanned extubations are determined by predisposing, precipitating and mediating factors. The predisposing factors have been recognised in the (a) weaning programme (expected/unexpected decreased sedation) and in the (b) patient factors (increased needs due to discomfort, restlessness and desire to communicate). The precipitating factors have been divided into (a) organisational (failures in multi-professional communication), (b) environmental (excessive environmental chaos and barriers preventing direct surveillance) and (c) nursing care factors (ensuring privacy by creating barriers, avoiding disturbing other patients and poor nurse-to-patient ratio). Among the mediating factors, which are affected by the precipitating factors, decreased surveillance and mechanical restraints' use have been identified. Identifying risk factors of unplanned extubation, specifically those that are modifiable, such as increasing interprofessional communication, reducing excessive environment chaos, implementing strategies aimed at overcoming barriers threatening direct surveillance and ensuring appropriate nurse-to-patient ratio, can prevent the occurrence of these events. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Unplanned quitting in a triethnic sample of U.S. smokers.

    Science.gov (United States)

    Resnicow, Ken; Zhou, Yan; Scheuermann, Taneisha S; Nollen, Nicole L; Ahluwalia, Jasjit S

    2014-06-01

    Smokers who report quitting without prior planning have been shown to report longer abstinence compared with those who planned. Little is known about unplanned quitting (UQ) among U.S. smokers, minorities, or nondaily and light smokers. Using an online panel, we recruited equal numbers of Black, White, and Latino nondaily, light daily, and moderate/heavy daily smokers. Of the 1,127 who reported a past-year quit attempt, we queried whether it was planned and the maximum number of days abstinent. Overall, 38% reported that their last quit attempt was unplanned. The impact of planned versus unplanned quitting interacted with smoking level and race. Among White moderate/heavy smokers, mean days abstinent was 99 for those who reported an unplanned quit attempt compared with 60 days for those who reported a planned attempt (p = .02). Among Black moderate/heavy smokers, the mean days abstinent was higher among those whose last attempt was planned, 92 days, compared with 56 days among those whose last attempt was unplanned (p = .09). The pattern among Latinos resembled Whites but was not significant. Results remained after adjusting for confounds such as age, gender, education, income, time to first cigarette, and menthol use. There were no significant differences in abstinence by quit type for light or nondaily smokers. Future studies are needed to elucidate why UQ appears to have differential effectiveness across racial/ethnic groups and different levels of cigarette use. Research examining the impact of UQ on long-term quitting, which is not addressed here, is needed.

  12. Task types and error types involved in the human-related unplanned reactor trip events

    International Nuclear Information System (INIS)

    Kim, Jae Whan; Park, Jin Kyun

    2008-01-01

    In this paper, the contribution of task types and error types involved in the human-related unplanned reactor trip events that have occurred between 1986 and 2006 in Korean nuclear power plants are analysed in order to establish a strategy for reducing the human-related unplanned reactor trips. Classification systems for the task types, error modes, and cognitive functions are developed or adopted from the currently available taxonomies, and the relevant information is extracted from the event reports or judged on the basis of an event description. According to the analyses from this study, the contributions of the task types are as follows: corrective maintenance (25.7%), planned maintenance (22.8%), planned operation (19.8%), periodic preventive maintenance (14.9%), response to a transient (9.9%), and design/manufacturing/installation (6.9%). According to the analysis of the error modes, error modes such as control failure (22.2%), wrong object (18.5%), omission (14.8%), wrong action (11.1%), and inadequate (8.3%) take up about 75% of the total unplanned trip events. The analysis of the cognitive functions involved in the events indicated that the planning function had the highest contribution (46.7%) to the human actions leading to unplanned reactor trips. This analysis concludes that in order to significantly reduce human-induced or human-related unplanned reactor trips, an aide system (in support of maintenance personnel) for evaluating possible (negative) impacts of planned actions or erroneous actions as well as an appropriate human error prediction technique, should be developed

  13. Task types and error types involved in the human-related unplanned reactor trip events

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Whan; Park, Jin Kyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-12-15

    In this paper, the contribution of task types and error types involved in the human-related unplanned reactor trip events that have occurred between 1986 and 2006 in Korean nuclear power plants are analysed in order to establish a strategy for reducing the human-related unplanned reactor trips. Classification systems for the task types, error modes, and cognitive functions are developed or adopted from the currently available taxonomies, and the relevant information is extracted from the event reports or judged on the basis of an event description. According to the analyses from this study, the contributions of the task types are as follows: corrective maintenance (25.7%), planned maintenance (22.8%), planned operation (19.8%), periodic preventive maintenance (14.9%), response to a transient (9.9%), and design/manufacturing/installation (6.9%). According to the analysis of the error modes, error modes such as control failure (22.2%), wrong object (18.5%), omission (14.8%), wrong action (11.1%), and inadequate (8.3%) take up about 75% of the total unplanned trip events. The analysis of the cognitive functions involved in the events indicated that the planning function had the highest contribution (46.7%) to the human actions leading to unplanned reactor trips. This analysis concludes that in order to significantly reduce human-induced or human-related unplanned reactor trips, an aide system (in support of maintenance personnel) for evaluating possible (negative) impacts of planned actions or erroneous actions as well as an appropriate human error prediction technique, should be developed.

  14. Confidence Interval Approximation For Treatment Variance In ...

    African Journals Online (AJOL)

    In a random effects model with a single factor, variation is partitioned into two as residual error variance and treatment variance. While a confidence interval can be imposed on the residual error variance, it is not possible to construct an exact confidence interval for the treatment variance. This is because the treatment ...

  15. Fermilab may face downtime

    CERN Multimedia

    Salles, Andre

    2007-01-01

    "A freeze on federal funding may result in a monthlong closure at Fermi National Accelerator Laboratory and could hamper the lab's efforts to secure a major new particle collisions device." (1/2 page)

  16. Risk Factors for 30-day Unplanned Readmission following Infrainguinal Endovascular Interventions

    Science.gov (United States)

    Bodewes, Thomas C.F.; Soden, Peter A.; Ultee, Klaas H.J.; Zettervall, Sara L.; Pothof, Alexander B.; Deery, Sarah E.; Moll, Frans L.; Schermerhorn, Marc L.

    2016-01-01

    Objective Unplanned hospital readmissions following surgical interventions are associated with adverse events and contribute to increasing healthcare costs. Despite numerous studies defining risk factors following lower extremity bypass surgery, evidence regarding readmission after endovascular interventions is limited. This study aims to identify predictors of 30-day unplanned readmission following infrainguinal endovascular interventions. Methods We identified all patients undergoing an infrainguinal endovascular intervention in the Targeted Vascular module of the American College of Surgeons National Surgical Quality Improvement Program between 2012 and 2014. Perioperative outcomes were stratified by symptom status (chronic limb-threatening ischemia [CLI] vs. claudication). Patients who died during index admission, and those who remained in the hospital after 30 days, were excluded. Indications for unplanned readmission related to the index procedure were evaluated. Multivariable logistic regression was used to identify preoperative and in-hospital (during index admission) risk factors of 30-day unplanned readmission. Results 4449 patients underwent infrainguinal endovascular intervention, of which 2802 (63%) had CLI (66% tissue loss) and 1647 (37%) had claudication. The unplanned readmission rates for CLI and claudication patients were 16% (N=447) and 6.5% (N=107), respectively. Mortality after index admission was higher for readmitted patients compared to those not readmitted (CLI: 3.4% vs. 0.7%, P readmissions were related to the index procedure. Among CLI patients, the most common indication for readmission related to the index procedure was wound- or infection-related (42%), while patients with claudication were mainly readmitted for recurrent symptoms of peripheral vascular disease (28%). In patients with CLI, predictors of unplanned readmission included diabetes (OR: 1.3, 95% CI: 1.01–1.6), congestive heart failure (1.6, 1.1–2.5), renal insufficiency

  17. Exploring the preventable causes of unplanned readmissions using root cause analysis

    DEFF Research Database (Denmark)

    Fluitman, K. S.; van Galen, L. S.; Merten, H

    2016-01-01

    Importance: Unplanned readmissions within 30 days are a common phenomenon in everyday practice and lead to increasing costs. Although many studies aiming to analyze the probable causes leading to unplanned readmissions have been performed, an in depth-study analyzing the human (healthcare worker...... and unpreventable readmissions. Results: Most root causes for readmission were disease-related (46%), followed by human (healthcare worker)-(33%) and patient-(15%) related root causes. Half of the readmissions studied were considered to be potentially preventable. Preventable readmissions predominantly had human......-related (coordination) failures. Conclusion and relevance: Our study suggests that improving human-related (coordinating) factors contributing to a readmission can potentially decrease the number of preventable readmissions. (C) 2015 European Federation of Internal Medicine. Published by Elsevier B.V. All rights...

  18. The New Rich and Their Unplanned Births: Stratified Reproduction under China's Birth-planning Policy.

    Science.gov (United States)

    Shi, Lihong

    2017-12-01

    This article explores the creation and ramifications of a stratified reproductive system under China's state control of reproduction. Within this system, an emerging group of "new rich" are able to circumvent birth regulations and have unplanned births because of their financial capabilities and social networks. While China's birth-planning policy is meant to be enforced equally for all couples, the unequal access to wealth and bureaucratic power as a result of China's widening social polarization has created disparate reproductive rights and experiences. This article identifies three ways in which reproductive privileges are created. It further explores how a stratified reproductive system under state population control reinforces social polarization. While many socially marginalized couples are unable to register their unplanned children for citizenship status and social benefits, the new rich are able to legitimate their births and transfer their privilege and status to their children, thus reproducing a new generation of elites. © 2016 by the American Anthropological Association.

  19. Physical activity and unplanned illness-related work absenteeism: Data from an employee wellness program.

    Science.gov (United States)

    Losina, Elena; Yang, Heidi Y; Deshpande, Bhushan R; Katz, Jeffrey N; Collins, Jamie E

    2017-01-01

    Illness-related absenteeism is a major threat to work productivity. Our objective was to assess the relationship between physical activity and unplanned illness-related absenteeism from work. We implemented physical activity program for sedentary non-clinician employees of a tertiary medical center. Financial rewards were available for reaching accelerometer-measured ambulatory physical activity goals over a 24-week period. We categorized participants into three groups based on mean levels of physical activity: low (0-74 min/week), medium (75-149 min/week) and meeting CDC guidelines (≥150 min/week). We built a multivariable Poisson regression model to evaluate the relationship between physical activity and rates of unplanned illness-related absenteeism. The sample consisted of 292 employees who participated in the program. Their mean age was 38 years (SD 11), 83% were female, and 38% were obese. Over the 24 intervention weeks, participants engaged in a mean of 90 min/week (SD 74) of physical activity and missed a mean of 14 hours of work (SD 38) due to illness. Unplanned absenteeism due to illness was associated with physical activity. As compared to the group meeting CDC guidelines, in multivariable analyses those in the medium physical activity group had a 2.4 (95% CI 1.3-4.5) fold higher rate of illness-related absenteeism and those in the lowest physical activity group had a 3.5 (95% CI 1.7-7.2) fold higher rate of illness-related absenteeism. Less physical activity was associated with more illness-related absenteeism. Workforce-based interventions to increase physical activity may thus be a promising vehicle to reduce unplanned illness-related absenteeism.

  20. Physical activity and unplanned illness-related work absenteeism: Data from an employee wellness program.

    Directory of Open Access Journals (Sweden)

    Elena Losina

    Full Text Available Illness-related absenteeism is a major threat to work productivity. Our objective was to assess the relationship between physical activity and unplanned illness-related absenteeism from work.We implemented physical activity program for sedentary non-clinician employees of a tertiary medical center. Financial rewards were available for reaching accelerometer-measured ambulatory physical activity goals over a 24-week period. We categorized participants into three groups based on mean levels of physical activity: low (0-74 min/week, medium (75-149 min/week and meeting CDC guidelines (≥150 min/week. We built a multivariable Poisson regression model to evaluate the relationship between physical activity and rates of unplanned illness-related absenteeism.The sample consisted of 292 employees who participated in the program. Their mean age was 38 years (SD 11, 83% were female, and 38% were obese. Over the 24 intervention weeks, participants engaged in a mean of 90 min/week (SD 74 of physical activity and missed a mean of 14 hours of work (SD 38 due to illness. Unplanned absenteeism due to illness was associated with physical activity. As compared to the group meeting CDC guidelines, in multivariable analyses those in the medium physical activity group had a 2.4 (95% CI 1.3-4.5 fold higher rate of illness-related absenteeism and those in the lowest physical activity group had a 3.5 (95% CI 1.7-7.2 fold higher rate of illness-related absenteeism.Less physical activity was associated with more illness-related absenteeism. Workforce-based interventions to increase physical activity may thus be a promising vehicle to reduce unplanned illness-related absenteeism.

  1. Physical activity and unplanned illness-related work absenteeism: Data from an employee wellness program

    Science.gov (United States)

    Yang, Heidi Y.; Katz, Jeffrey N.; Collins, Jamie E.

    2017-01-01

    Background Illness-related absenteeism is a major threat to work productivity. Our objective was to assess the relationship between physical activity and unplanned illness-related absenteeism from work. Methods We implemented physical activity program for sedentary non-clinician employees of a tertiary medical center. Financial rewards were available for reaching accelerometer-measured ambulatory physical activity goals over a 24-week period. We categorized participants into three groups based on mean levels of physical activity: low (0–74 min/week), medium (75–149 min/week) and meeting CDC guidelines (≥150 min/week). We built a multivariable Poisson regression model to evaluate the relationship between physical activity and rates of unplanned illness-related absenteeism. Results The sample consisted of 292 employees who participated in the program. Their mean age was 38 years (SD 11), 83% were female, and 38% were obese. Over the 24 intervention weeks, participants engaged in a mean of 90 min/week (SD 74) of physical activity and missed a mean of 14 hours of work (SD 38) due to illness. Unplanned absenteeism due to illness was associated with physical activity. As compared to the group meeting CDC guidelines, in multivariable analyses those in the medium physical activity group had a 2.4 (95% CI 1.3–4.5) fold higher rate of illness-related absenteeism and those in the lowest physical activity group had a 3.5 (95% CI 1.7–7.2) fold higher rate of illness-related absenteeism. Discussion Less physical activity was associated with more illness-related absenteeism. Workforce-based interventions to increase physical activity may thus be a promising vehicle to reduce unplanned illness-related absenteeism. PMID:28472084

  2. Basic Characteristics of Human Erroneous Actions during Test and Maintenance Activities Leading to Unplanned Reactor Trips

    International Nuclear Information System (INIS)

    Kim, Jae Whan; Park, Jin Kyun

    2010-01-01

    Test and maintenance (T and M) activities of nuclear power plants are essential for sustaining the safety of a power plant and maintaining the reliability of plant systems and components. However, the potential of human errors during T and M activities has also the potential to induce unplanned reactor trips or power derate or making safety-related systems unavailable. According to the major incident/accident reports of nuclear power plants in Korea, contribution of human errors takes up about 20% of the total events. The previous study presents that most of human-related unplanned reactor trip events during normal power operation are associated with T and M activities (63%), which are comprised of plant maintenance activities such as a 'periodic preventive maintenance (PPM)', a 'planned maintenance (PM)' and a 'corrective maintenance (CM)'. This means that T and M activities should be a major subject for reducing the frequency of human-related unplanned reactor trips. This paper aims to introduce basic characteristics of human erroneous actions involved in the test and maintenance-induced unplanned reactor trip events that have occurred between 1986 and 2006 in Korean nuclear power plants. The basic characteristics are described by dividing human erroneous actions into planning-based errors and execution-based errors. For the events associated with planning failures, they are, firstly, classified according to existence of the work procedure and then described for what aspects of the procedure or work plan have deficiency or problem. On the other hand, for the events associated with execution failures, they are described from the aspect of external error modes

  3. Planned and unplanned home births and hospital births in Calgary, Alberta, 1984-87.

    OpenAIRE

    Abernathy, T J; Lentjes, D M

    1989-01-01

    Information collected on all home births in Calgary (Canada) between the years 1984 and 1987, was examined and analyzed according to whether the home birth environment had been planned or unplanned. The two groups were compared to each other and to all hospital births according to demographic characteristics of mothers, indicators of prenatal care, and birth outcome. Mothers who had planned their home birth were more likely to be primiparous, attend prenatal classes, obtain regular prenatal c...

  4. Planned and unplanned deliveries at home: implications of a changing ratio.

    OpenAIRE

    Murphy, J F; Dauncey, M; Gray, O P; Chalmers, I

    1984-01-01

    The observation that perinatal mortality among babies delivered at home has tended to increase beyond that among babies delivered in consultant obstetric units has caused alarm and prompted recommendations that delivery at home should be further phased out. With data derived from the Cardiff Births Survey the possibility was investigated that this trend might reflect a changing ratio of planned to unplanned domiciliary births. At the beginning of the 1970s deliveries at home that were planned...

  5. Effect of Guided Imagery on Maternal Fetal Attachment in Nulliparous Women with Unplanned Pregnancy

    Directory of Open Access Journals (Sweden)

    Masoumeh Kordi

    2016-10-01

    Full Text Available Introduction and Objectives: Nulliparous women with unplanned pregnancy experience high levels of anxiety, which may adversely affect maternal-fetal attachment. Therefore, in this study, we aimed to determine the effect of guided imagery on maternal-fetal attachment in nulliparous women with unplanned pregnancy. Materials and Methods: In this clinical trial, 67 nulliparous women with unplanned pregnancy were randomly divided into two groups of intervention (n=35 and control (n=32 in 2015. Data collection tools included a demographic form and London, DASS 21, and Cranley's maternal-fetal attachment questionnaires. In the intervention group, one session of guided imagery on maternal role was performed in 34th week of pregnancy in groups of four to seven. Afterwards, guided imagery CDs were given to mothers to be performed at home twice a week for two weeks; the control group only received the routine care. Maternal-fetal attachment was assessed before and two weeks after the intervention. To analyze the data, independent t-test, paired t-test, Chi-squared, Fisher’s exact test, and Mann-Whitney U tests were run using SPSS version 21. Results: Maternal mean age was 24.1±4.3 years, and most mothers (49.3% had high school education. Mean score of maternal-fetal attachment was significantly different between the intervention (94.26±6.7 and control (90.22 ± 9.5 groups after the intervention (P=0.04. Also, there was a significant difference between mean score of maternal-fetal attachment at the beginning and end of the intervention in the intervention and control groups (5.86±7.2 vs. 1.72±3.2; P=0.004. Conclusion: Guided imagery promoted maternal-fetal attachment in women with unplanned pregnancy; thus, it is recommended to use this method in prenatal care for these women.

  6. Contraceptive failure after hysteroscopic sterilization: Analysis of clinical and demographic data from 103 unplanned pregnancies

    Science.gov (United States)

    Li, Xiang; Jones, Christopher A.; Wood, Samuel H.

    2015-01-01

    Objective This investigation examined data on unplanned pregnancies following hysteroscopic sterilization (HS). Methods A confidential questionnaire was used to collect data from women with medically confirmed pregnancy (n=103) registered after undergoing HS. Results Mean (±SD) patient age and body mass index (BMI) were 29.5±4.6 years and 27.7±6.1 kg/m2, respectively. Peak pregnancy incidence was reported at 10 months after HS, although <3% of unplanned pregnancies occurred within the first three months following HS. Mean (±SD) interval between HS and pregnancy was 19.6±14.9 (range, 2 to 84) months. Patients age ≥30 years and BMI <25 reported conception after HS somewhat sooner than younger patients, although the differences in time to pregnancy were not significant (P=0.24 and 0.09, respectively). The recommended post-HS hysterosalpingogram (to confirm proper placement and bilateral tubal occlusion) was obtained by 66% (68/103) of respondents. Conclusion This report is the first to provide patient-derived data on contraceptive failures after HS. While adherence to backup contraception 3 months after HS can be poor, many unintended pregnancies with HS occur long after the interval when alternate contraceptive is required. Many patients who obtain HS appear to ignore the manufacturer's guidance regarding the post-procedure hysterosalpingogram to confirm proper device placement, although limited insurance coverage likely contributes to this problem. The greatest number of unplanned pregnancies occurred 10 months after HS, but some unplanned pregnancies were reported up to 7 years later. Age, BMI, or surgical history are unlikely to predict contraceptive failure with HS. Further follow-up studies are planned to capture additional data on this issue. PMID:26623413

  7. Unplanned intensive care unit admission after general anaesthesia in children: A single centre retrospective analysis.

    Science.gov (United States)

    Mitchell, John; Clément de Clety, Stephan; Collard, Edith; De Kock, Marc; Detaille, Thierry; Houtekie, Laurent; Jadin, Laurence; Bairy, Laurent; Veyckemans, Francis

    2016-06-01

    To determine the main causes for unplanned admission of children to the paediatric intensive care unit (PICU) following anaesthesia in our centre. To compare the results with previous publications and propose a data sheet for the prospective collection of such information. Inclusion criteria were any patient under 16 years who had an unplanned post-anaesthetic admission to the PICU from 1999 to 2010 in our university hospital. Age, ASA score, type of procedure, origin and causes of the incident(s) that prompted admission and time of the admission decision were recorded. Out of a total of 44,559 paediatric interventions performed under anaesthesia during the study period, 85 were followed with an unplanned admission to the PICU: 67% of patients were younger than 5 years old. Their ASA status distribution from I to IV was 13, 47, 39 and 1%, respectively. The cause of admission was anaesthetic, surgical or mixed in 50, 37 and 13% of cases, respectively. The main causes of anaesthesia-related admission were respiratory or airway management problems (44%) and cardiac catheterisation complications (29%). In 62%, the admission decision was taken in the operating room. Unplanned admission to the PICU after general anaesthesia is a rare event. In our series, most cases were less than 5 years old and were associated with at least one comorbidity. The main cause of admission was respiratory distress and the main type of procedure associated with admission was cardiac catheterisation. Copyright © 2016 Société française d'anesthésie et de réanimation (Sfar). Published by Elsevier Masson SAS. All rights reserved.

  8. Planned and unplanned deliveries at home: implications of a changing ratio.

    Science.gov (United States)

    Murphy, J F; Dauncey, M; Gray, O P; Chalmers, I

    1984-05-12

    The observation that perinatal mortality among babies delivered at home has tended to increase beyond that among babies delivered in consultant obstetric units has caused alarm and prompted recommendations that delivery at home should be further phased out. With data derived from the Cardiff Births Survey the possibility was investigated that this trend might reflect a changing ratio of planned to unplanned domiciliary births. At the beginning of the 1970s deliveries at home that were planned to be so outnumbered those that were not by nearly five to one. By 1979 unplanned deliveries at home outnumbered planned deliveries. The characteristics of the mothers, the health care they received, and the outcome of delivery differed strikingly between planned and unplanned deliveries at home. It is concluded, firstly, that every year the maternity services must try to meet the various needs of about 2000 women in England and Wales who give birth at home without planning to do so; and, secondly, that the heterogeneity of births at home and in hospital will continue to obstruct the search for unbiased estimates of the risks attributable to delivery in specialist obstetric units, general practitioner units, and at home.

  9. Perinatal outcomes of unplanned out-of-hospital deliveries: a case-control study.

    Science.gov (United States)

    Pasternak, Yael; Wintner, Eliana Muskin; Shechter-Maor, Gil; Pasternak, Yehonatan; Miller, Netanella; Biron-Shental, Tal

    2018-04-01

    To compare the pregnancy and perinatal outcomes of unplanned home or car births vs. in-hospital deliveries. A retrospective, case-control study of women who underwent unplanned out-of-hospital deliveries vs. in-hospital deliveries from 2004 through 2014. Matching was based on gestational age and parity in a ratio of 2:1. There were no significant differences between the groups regarding demographic criteria, prenatal care and delivery complications. Women who delivered out of hospital (n = 90) had significantly fewer cesarean deliveries (1.1 vs. 10.6%; p = 0.05) and operative deliveries (2.2 vs. 13.3%; p = 0.004) in their obstetrical history than did the control group (n = 180). Significantly more newborns delivered out of the hospital had polycythemia (25.6 vs. 1.7%; p unplanned out-of-hospital deliveries tend to have fewer complications in their previous deliveries. Higher rates of polycythemia and hypothermia require attention for neonates born out of the hospital.

  10. Characteristics of 64 sarcoma patients referred to a sarcoma center after unplanned excision.

    Science.gov (United States)

    Dyrop, Heidi Buvarp; Safwat, Akmal; Vedsted, Peter; Maretty-Kongstad, Katja; Hansen, Bjarne Hauge; Jørgensen, Peter Holmberg; Baad-Hansen, Thomas; Keller, Johnny

    2016-02-01

    Unplanned excision of sarcoma before referral to specialist centers can affect prognosis and surgical outcome. The diagnostic pathway of these patients is uncertain and needs to be reviewed. We aimed to describe patient and tumor characteristics, initial symptoms, initial and final diagnosis, and explore reasons for unplanned excision in this patient group. From a previous study on 258 sarcoma patients, we identified 64 patients referred after surgery. Medical records were reviewed. The majority were soft tissue sarcomas, most often with thoracic location. Leiomyosarcoma was the most frequent final diagnosis, lipoma, and fibroma/dermatofibroma the most frequent initial diagnoses. Fifty percent were superficial small tumors, and 60.9% had not received diagnostic imaging before surgery. Fifty percent were referred from public surgical departments, and 1/3 from private specialists. Twenty-three patients had initial presence of alarm symptoms registered before surgery, the remaining 2/3 fell outside referral criteria or alarm symptoms were not discovered. Patients referred after unplanned excision often have small superficial tumors and the majority fall outside of defined referral criteria. Referral criteria are not a guarantee for detection of all sarcomas and surgeons should always be aware of the possibility of malignancy when removing a tumor. © 2016 Wiley Periodicals, Inc.

  11. The spatial study of unplanned settlements on the coastal of Belawan Medan fishermen village

    Science.gov (United States)

    Marpaung, B. O. Y.; Winny Silaban, Nadia

    2018-03-01

    One of the determining factors that formed informal settlements is the high demand for homes that are not comparable with the homes that were provided by the government. The settlement of Fisherman Village in Belawan Medan was built without a plan by settlers and was not involve government interference so that the spatial pattern formed uncontrollable. The shape of space that stretches represents the distribution of unplanned space. The purpose of this study is to find the structure of settlement and the relationship between the space structures with the spatial pattern in Belawan Medan Fishermen Village. In the process of collecting data, the researcher makes the maps of the observation area, the structure of the space, and the relationship between one space function with the other space functions. Also, the researchers identify the spacing pattern and the effect of one spatial element against the other. This study found a similar spatial pattern between one unplanned settlement and another unplanned settlement and there are also some tendencies of Belawan Medan Fishermen Village settlers when building the built environment in the relationship between building masses and the road network.

  12. Unplanned pregnancy-risks and use of emergency contraception: a survey of two Nigerian Universities.

    Science.gov (United States)

    Ajayi, Anthony Idowu; Nwokocha, Ezebunwa Ethelbert; Adeniyi, Oladele Vincent; Ter Goon, Daniel; Akpan, Wilson

    2017-06-02

    The vulnerabilities of young women of low socio-economic status and those with little or no formal education tend to dominate the discourse on unplanned pregnancy, unsafe abortion and emergency contraception (EC) in sub-Saharan Africa. This article draws on a survey conducted among female undergraduate students to shed light on sexual behaviour and the dynamics of emergency contraceptive use among this cohort. The survey involved 420 female undergraduate students drawn using a multistage sampling technique, while a self-administered questionnaire was used for data collection. Univariate and bivariate analyses were applied to examine the factors associated with the use of emergency contraception. Of the 176 female students who reported being sexually active in the year preceding the survey, only 38.6% reported the use of condom during the entire year. Of those who reported unplanned pregnancy anxiety n = 94, about 30.1% used EC, 20.4% used non-EC pills as EC, while others reported having used no EC. A few respondents (n = 3) had terminated a pregnancy under unsafe conditions. Awareness of EC (p contraceptive methods. Poor knowledge of EC methods and timing of use, as well as wrong perception about EC side effects, are barriers to the utilisation of EC for the prevention of unplanned pregnancy among the study participants.

  13. Speed Variance and Its Influence on Accidents.

    Science.gov (United States)

    Garber, Nicholas J.; Gadirau, Ravi

    A study was conducted to investigate the traffic engineering factors that influence speed variance and to determine to what extent speed variance affects accident rates. Detailed analyses were carried out to relate speed variance with posted speed limit, design speeds, and other traffic variables. The major factor identified was the difference…

  14. Microbial composition in a deep saline aquifer in the North German Basin -microbiologically induced corrosion and mineral precipitation affecting geothermal plant operation and the effects of plant downtime

    Science.gov (United States)

    Lerm, Stephanie; Westphal, Anke; Miethling-Graff, Rona; Alawi, Mashal; Seibt, Andrea; Wolfgramm, Markus; Würdemann, Hilke

    2013-04-01

    The microbial composition in fluids of a deep saline geothermal used aquifer in the North German Basin was characterized over a period of five years. The genetic fingerprinting techniques PCR-SSCP and PCR-DGGE revealed distinct microbial communities in fluids produced from the cold and warm side of the aquifer. Direct cell counting and quantification of 16S rRNA genes and dissimilatory sulfite reductase (dsrA) genes by real-time PCR proved different population sizes in fluids, showing higher abundance of Bacteria and sulfate reducing bacteria (SRB) in cold fluids compared to warm fluids. Predominating SRB in the cold well probably accounted for corrosion damage to the submersible well pump, and iron sulfide precipitates in the near wellbore area and topside facility filters. This corresponded to a lower sulfate content in fluids produced from the cold well as well as higher content of hydrogen gas that was probably released from corrosion, and maybe favoured growth of hydrogenotrophic SRB. Plant downtime significantly influenced the microbial biocenosis in fluids. Samples taken after plant restart gave indications about the processes occurring downhole during those phases. High DNA concentrations in fluids at the beginning of the restart process with a decreasing trend over time indicated a higher abundance of microbes during plant downtime compared to regular plant operation. It is likely that a gradual drop in temperature as well as stagnant conditions favoured the growth of microbes and maturation of biofilms at the casing and in pores of the reservoir rock in the near wellbore area. Furthermore, it became obvious that the microorganisms were more associated to particles then free-living. This study reflects the high influence of microbial populations for geothermal plant operation, because microbiologically induced precipitative and corrosive processes adversely affect plant reliability. Those processes may favourably occur during plant downtime due to enhanced

  15. Variance function estimation for immunoassays

    International Nuclear Information System (INIS)

    Raab, G.M.; Thompson, R.; McKenzie, I.

    1980-01-01

    A computer program is described which implements a recently described, modified likelihood method of determining an appropriate weighting function to use when fitting immunoassay dose-response curves. The relationship between the variance of the response and its mean value is assumed to have an exponential form, and the best fit to this model is determined from the within-set variability of many small sets of repeated measurements. The program estimates the parameter of the exponential function with its estimated standard error, and tests the fit of the experimental data to the proposed model. Output options include a list of the actual and fitted standard deviation of the set of responses, a plot of actual and fitted standard deviation against the mean response, and an ordered list of the 10 sets of data with the largest ratios of actual to fitted standard deviation. The program has been designed for a laboratory user without computing or statistical expertise. The test-of-fit has proved valuable for identifying outlying responses, which may be excluded from further analysis by being set to negative values in the input file. (Auth.)

  16. Hours Lost to Planned and Unplanned Dental Visits Among US Adults.

    Science.gov (United States)

    Kelekar, Uma; Naavaal, Shillpa

    2018-01-11

    Poor oral health is associated with lost hours at work or school, which may affect a person's productivity. The objective of our study was to estimate work or school hours lost to dental visits among adults aged 18 and older by the types of visits (emergency or unplanned; routine, planned, or orthodontic; or cosmetic) and to determine the factors associated with hours lost. We used the most recent Oral Health Supplement data, from the 2008 National Health Interview Survey (NHIS), to estimate the total hours lost at work or school for dental visits among adults in the United States. The associations of the hours lost in unplanned and planned dental visits with socioeconomic characteristics, oral health status, and affordability were calculated. We used χ 2 tests and logistic regression to determine associations at P work or school hours were lost annually for dental care in the United States, of which 92.4 million hours were for emergency (unplanned) care (0.99 h/adult), 159.8 million for routine (planned) care or orthodontic care (1.71 h/adult), and 68.6 million for cosmetic care (0.73 h/adult). Adults with poor oral health were more likely to lose one or more hours in unplanned dental visits (OR = 5.60; 95% confidence interval [CI], 3.25-9.63) than those who reported very good oral health. Not being able to afford dental care was positively associated with more work hours lost in unplanned care (odds ratio [OR] = 2.56; 95% CI, 1.76-3.73). Compared with Hispanic adults, non-Hispanic white adults (OR = 2.09; 95% CI, 1.40-3.11) and non-Hispanic Asian adults and adults of other races/ethnicities (OR =1.91; 95% CI, 1.06-3.47) were more likely to lose any hours for planned care. Consistently, those with more than a high school education were more likely to lose any hours in planned care (OR = 1.39; 95% CI, 1.06-1.83) than those with a high school education or less. Dental problems result in hours lost from work and may adversely affect a person's productivity. There is

  17. Unplanned Start on Peritoneal Dialysis Right after PD Catheter Implantation for Older People with End-Stage Renal Disease.

    Science.gov (United States)

    Povlsen, Johan V; Sørensen, Anette Bagger; Ivarsen, Per

    2015-11-01

    Unplanned start on dialysis remains a major problem for the dialysis community worldwide. Late-referred patients with end-stage renal disease (ESRD) and urgent need for dialysis are overrepresented among older people. These patients are particularly likely to be started on in-center hemodialysis (HD), with a temporary vascular access known to be associated with excess mortality and increased risks of potentially lethal complications such as bacteremia and central venous thrombosis or stenosis.The present paper describes in detail our program for unplanned start on automated peritoneal dialysis (APD) right after PD catheter implantation and summarizes our experiences with the program so far. Compared with planned start on PD after at least 2 weeks of break-in between PD catheter implantation and initiation of dialysis, unplanned start may be associated with a slight increased risk of mechanical complications but apparently no detrimental effect on mortality, peritonitis-free survival, or PD technique survival.In our opinion and experience, the risk of serious complications associated with the implantation and immediate use of a PD catheter is less than the risk of complications associated with unplanned start on HD with a temporary central venous catheter (CVC). Unplanned start on APD is a gentle, safe, and feasible alternative to unplanned start on HD with a temporary CVC that is also valid for the late-referred older patient with ESRD and urgent need for dialysis. Copyright © 2015 International Society for Peritoneal Dialysis.

  18. Evolution of Genetic Variance during Adaptive Radiation.

    Science.gov (United States)

    Walter, Greg M; Aguirre, J David; Blows, Mark W; Ortiz-Barrientos, Daniel

    2018-04-01

    Genetic correlations between traits can concentrate genetic variance into fewer phenotypic dimensions that can bias evolutionary trajectories along the axis of greatest genetic variance and away from optimal phenotypes, constraining the rate of evolution. If genetic correlations limit adaptation, rapid adaptive divergence between multiple contrasting environments may be difficult. However, if natural selection increases the frequency of rare alleles after colonization of new environments, an increase in genetic variance in the direction of selection can accelerate adaptive divergence. Here, we explored adaptive divergence of an Australian native wildflower by examining the alignment between divergence in phenotype mean and divergence in genetic variance among four contrasting ecotypes. We found divergence in mean multivariate phenotype along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with much of the divergence in phenotype among ecotypes associated with changes in trait combinations containing substantial levels of genetic variance. Overall, our results suggest that natural selection can alter the distribution of genetic variance underlying phenotypic traits, increasing the amount of genetic variance in the direction of natural selection and potentially facilitating rapid adaptive divergence during an adaptive radiation.

  19. Influence of Family Structure on Variance Decomposition

    DEFF Research Database (Denmark)

    Edwards, Stefan McKinnon; Sarup, Pernille Merete; Sørensen, Peter

    Partitioning genetic variance by sets of randomly sampled genes for complex traits in D. melanogaster and B. taurus, has revealed that population structure can affect variance decomposition. In fruit flies, we found that a high likelihood ratio is correlated with a high proportion of explained ge...... capturing pure noise. Therefore it is necessary to use both criteria, high likelihood ratio in favor of a more complex genetic model and proportion of genetic variance explained, to identify biologically important gene groups...

  20. Efficient Cardinality/Mean-Variance Portfolios

    OpenAIRE

    Brito, R. Pedro; Vicente, Luís Nunes

    2014-01-01

    International audience; We propose a novel approach to handle cardinality in portfolio selection, by means of a biobjective cardinality/mean-variance problem, allowing the investor to analyze the efficient tradeoff between return-risk and number of active positions. Recent progress in multiobjective optimization without derivatives allow us to robustly compute (in-sample) the whole cardinality/mean-variance efficient frontier, for a variety of data sets and mean-variance models. Our results s...

  1. Women's experiences with unplanned pregnancy and abortion in Kenya: A qualitative study.

    Directory of Open Access Journals (Sweden)

    Ruvani T Jayaweera

    Full Text Available Safe and legal abortions are rarely practiced in the public health sector in Kenya, and rates of maternal mortality and morbidity from unsafe abortion is high. Little is known about women's experiences seeking and accessing abortion in informal settlements in Nairobi, Kenya.Seven focus group discussions were conducted with a total of 71 women and girls recruited from an informal settlement in Nairobi. The interview guide explored participants' perceptions of unplanned pregnancy, abortion, and access to sexual and reproductive health information in their community. Thematic analysis of the focus group transcripts was conducted using MAX QDA Release 12.Participants described a variety of factors that influence women's experiences with abortion in their communities. According to participants, limited knowledge of sexual and reproductive health information and lack of access to contraception led to unplanned pregnancy among women in their community. Participants cited stigma and loss of opportunities that women with unplanned pregnancies face as the primary reasons why women seek abortions. Participants articulated stigma as the predominant barrier women in their communities face to safe abortion. Other barriers, which were often interrelated to stigma, included lack of education about safe methods of abortion, perceived illegality of abortion, as well as limited access to services, fear of mistreatment, and mistrust of health providers and facilities.Women in informal settlements in Nairobi, Kenya face substantial barriers to regulating their fertility and lack access to safe abortion. Policy makers and reproductive health advocates should support programs that employ harm reduction strategies and increase women's knowledge of and access to medication abortion outside the formal healthcare system.

  2. Causes, costs, and risk factors for unplanned return visits after adenotonsillectomy in children.

    Science.gov (United States)

    Duval, Melanie; Wilkes, Jacob; Korgenski, Kent; Srivastava, Rajendu; Meier, Jeremy

    2015-10-01

    To review the causes, costs, and risk factors for unplanned return visits and readmissions after pediatric adenotonsillectomy (T&A). Review of administrative database of outpatient adenotonsillectomy performed at any facility within a vertically integrated health care system in the Intermountain West on children age 1-18 years old between 1998 and 2012. Data reviewed included demographic variables, diagnosis associated with return visit and costs associated with return visits. Data from 39,906 children aged 1-18 years old were reviewed. A total of 2499 (6.3%) children had unplanned return visits. The most common reasons for return visits were bleeding (2.3%), dehydration, (2.3%) and throat pain (1.2%). After multivariate analysis, the main risk factors for any type of return visits were Medicaid insurance (OR=1.64 95% CI 1.47-1.84), Hispanic race (OR=1.36 95% CI 1.13-1.64), and increased severity of illness (SOI) (OR=11.29 95% CI 2.69-47.4 for SOI=3). The only factor associated with increased odds of requiring an inpatient admission on return visit was length of time spent in PACU (prelationship was also observed between the child's age and the risk of post-tonsillectomy hemorrhage. Children with increased severity of illness, those insured with Medicaid, and children of Hispanic ethnicity should be targeted with increased education and interventions in order to reduce unplanned visits after T&A. Further studies on post-tonsillectomy complications should include evaluating the effect of surgical technique and post-operative pain management on all complications and not solely post-tonsillectomy hemorrhage. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  3. Women's experiences with unplanned pregnancy and abortion in Kenya: A qualitative study.

    Science.gov (United States)

    Jayaweera, Ruvani T; Ngui, Felistah Mbithe; Hall, Kelli Stidham; Gerdts, Caitlin

    2018-01-01

    Safe and legal abortions are rarely practiced in the public health sector in Kenya, and rates of maternal mortality and morbidity from unsafe abortion is high. Little is known about women's experiences seeking and accessing abortion in informal settlements in Nairobi, Kenya. Seven focus group discussions were conducted with a total of 71 women and girls recruited from an informal settlement in Nairobi. The interview guide explored participants' perceptions of unplanned pregnancy, abortion, and access to sexual and reproductive health information in their community. Thematic analysis of the focus group transcripts was conducted using MAX QDA Release 12. Participants described a variety of factors that influence women's experiences with abortion in their communities. According to participants, limited knowledge of sexual and reproductive health information and lack of access to contraception led to unplanned pregnancy among women in their community. Participants cited stigma and loss of opportunities that women with unplanned pregnancies face as the primary reasons why women seek abortions. Participants articulated stigma as the predominant barrier women in their communities face to safe abortion. Other barriers, which were often interrelated to stigma, included lack of education about safe methods of abortion, perceived illegality of abortion, as well as limited access to services, fear of mistreatment, and mistrust of health providers and facilities. Women in informal settlements in Nairobi, Kenya face substantial barriers to regulating their fertility and lack access to safe abortion. Policy makers and reproductive health advocates should support programs that employ harm reduction strategies and increase women's knowledge of and access to medication abortion outside the formal healthcare system.

  4. Variables associated with emergency department and/or unplanned hospital utilization for children with epilepsy.

    Science.gov (United States)

    Patel, Anup D

    2014-02-01

    In the United States, approximately one million people are evaluated annually in an emergency department (ED) for the diagnosis of a seizure or epilepsy. The highest percentages of these patients are less than five years of age. No studies have been performed on assessing potential variables associated with recurrent ED visits and/or unplanned hospitalizations for children with epilepsy. Institutional review board approval from Nationwide Children's Hospital was obtained prior to study initiation. An accountable care organization (ACO), Partner for Kids (PFK), database was searched for patients with the highest and the lowest number of ED visits and/or unplanned hospitalizations from 2007 through 2011 using ICD-9 codes of 345.xx and 780.39. The patients were stratified into a high and a low utilizer group. The total number of visits and their associated health care costs were noted for each patient. In total, 120 patients were included for review. Information on the total number of no-shows to outpatient neurology clinic visits and telephone calls to neurology triage nursing was noted. A chart review was performed by a pediatric epileptologist to determine if each individual patient was an appropriate candidate for an emergency seizure treatment. The dose of emergency seizure medication was cross-checked to the patient's actual dose during the time of ED or hospital presentation to determine if the dose given was high, low, or accurate based on dosing recommendations. Multivariable logistic regression was used to test the effects of factors. When controlling for other factors, patients who were given an incorrect or no emergency seizure dosing had a high probability of having multiple ED visits/unplanned hospitalizations compared with patients who were given correct dosing (odds ratio=11.28, 95% CI of odds ratio=(2.42, 52.63), p valuechildren with epilepsy. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. The phenotypic variance gradient - a novel concept.

    Science.gov (United States)

    Pertoldi, Cino; Bundgaard, Jørgen; Loeschcke, Volker; Barker, James Stuart Flinton

    2014-11-01

    Evolutionary ecologists commonly use reaction norms, which show the range of phenotypes produced by a set of genotypes exposed to different environments, to quantify the degree of phenotypic variance and the magnitude of plasticity of morphometric and life-history traits. Significant differences among the values of the slopes of the reaction norms are interpreted as significant differences in phenotypic plasticity, whereas significant differences among phenotypic variances (variance or coefficient of variation) are interpreted as differences in the degree of developmental instability or canalization. We highlight some potential problems with this approach to quantifying phenotypic variance and suggest a novel and more informative way to plot reaction norms: namely "a plot of log (variance) on the y-axis versus log (mean) on the x-axis, with a reference line added". This approach gives an immediate impression of how the degree of phenotypic variance varies across an environmental gradient, taking into account the consequences of the scaling effect of the variance with the mean. The evolutionary implications of the variation in the degree of phenotypic variance, which we call a "phenotypic variance gradient", are discussed together with its potential interactions with variation in the degree of phenotypic plasticity and canalization.

  6. Conducting an Unplanned Participant Observation: The Case of a Non-Birder in Bird Watchers' Land

    Directory of Open Access Journals (Sweden)

    Roni Berger

    2016-12-01

    Full Text Available This article describes two participant observations of birdwatchers, which occurred by serendipity. Characteristics of personal and interpersonal behavior patterns are identified and illustrated. Specifically, four themes including total immersion and dedication to details of birders as well the collaborative-competitive nature of their interactions and sub-culture are discussed in the context of available knowledge about subcultures in other types of sports and leisure activities. Methodological and ethical aspects of unplanned participant observation are also addressed. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs170187

  7. High rate of unplanned pregnancy in the context of integrated family planning and HIV care services in South Africa.

    Science.gov (United States)

    Adeniyi, Oladele Vincent; Ajayi, Anthony Idowu; Moyaki, Mayowa Gabriel; Goon, Daniel Ter; Avramovic, Gordana; Lambert, John

    2018-02-27

    Integration of family planning services into HIV care was implemented in South Africa as a core strategy aimed at reducing unintended pregnancies among childbearing women living with HIV. However, it is unclear whether this strategy has made any significant impact at the population level. This paper describes the prevalence and correlates of self-reported unplanned pregnancy among HIV-infected parturient women attending three large maternity centres in the Eastern Cape, South Africa. We also compare unplanned pregnancy rates between HIV-infected parturient women already in care (who have benefitted from services' integration) and newly diagnosed parturient women (who have not benefitted from services' integration). Drawing from the baseline data of the East London Prospective Cohort Study (ELPCS), data of 594 parturient women living with HIV in the Eastern Cape were included. Chi-square statistics and binary logistics regression were employed to determine the correlates of unplanned pregnancy among the cohort. The prevalence of unplanned pregnancy was 71% (n = 422) with a higher rate among parturient women newly diagnosed during the index pregnancy (87%). Unplanned pregnancy was significantly associated with younger age, single status, HIV diagnosis at booking, high parity and previous abortion. Women who reported unplanned pregnancy were more likely to book late and have lower CD4 counts. After adjusting for confounding variables, having one child and five to seven children (AOR = 2.2; CI = 1.3-3.1), age less than 21 years (AOR = 3.3; CI = 1.1-9.8), late booking after 27 weeks (AOR = 2.7; CI = 1.5-5.0), not married (AOR = 4.3; CI = 2.7-6.8) and HIV diagnosis at booking (AOR = 3.0; CI = 1.6-5.8) were the significant correlates of unplanned pregnancy in the cohort. Unplanned pregnancy remains high overall among parturient women living with HIV in the region, however, with significant reduction among those who were

  8. Least-squares variance component estimation

    NARCIS (Netherlands)

    Teunissen, P.J.G.; Amiri-Simkooei, A.R.

    2007-01-01

    Least-squares variance component estimation (LS-VCE) is a simple, flexible and attractive method for the estimation of unknown variance and covariance components. LS-VCE is simple because it is based on the well-known principle of LS; it is flexible because it works with a user-defined weight

  9. Expected Stock Returns and Variance Risk Premia

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Zhou, Hao

    risk premium with the P/E ratio results in an R2 for the quarterly returns of more than twenty-five percent. The results depend crucially on the use of "model-free", as opposed to standard Black-Scholes, implied variances, and realized variances constructed from high-frequency intraday, as opposed...

  10. Nonlinear Epigenetic Variance: Review and Simulations

    Science.gov (United States)

    Kan, Kees-Jan; Ploeger, Annemie; Raijmakers, Maartje E. J.; Dolan, Conor V.; van Der Maas, Han L. J.

    2010-01-01

    We present a review of empirical evidence that suggests that a substantial portion of phenotypic variance is due to nonlinear (epigenetic) processes during ontogenesis. The role of such processes as a source of phenotypic variance in human behaviour genetic studies is not fully appreciated. In addition to our review, we present simulation studies…

  11. Variance estimation for generalized Cavalieri estimators

    OpenAIRE

    Johanna Ziegel; Eva B. Vedel Jensen; Karl-Anton Dorph-Petersen

    2011-01-01

    The precision of stereological estimators based on systematic sampling is of great practical importance. This paper presents methods of data-based variance estimation for generalized Cavalieri estimators where errors in sampling positions may occur. Variance estimators are derived under perturbed systematic sampling, systematic sampling with cumulative errors and systematic sampling with random dropouts. Copyright 2011, Oxford University Press.

  12. Validation of consistency of Mendelian sampling variance.

    Science.gov (United States)

    Tyrisevä, A-M; Fikse, W F; Mäntysaari, E A; Jakobsen, J; Aamand, G P; Dürr, J; Lidauer, M H

    2018-03-01

    Experiences from international sire evaluation indicate that the multiple-trait across-country evaluation method is sensitive to changes in genetic variance over time. Top bulls from birth year classes with inflated genetic variance will benefit, hampering reliable ranking of bulls. However, none of the methods available today enable countries to validate their national evaluation models for heterogeneity of genetic variance. We describe a new validation method to fill this gap comprising the following steps: estimating within-year genetic variances using Mendelian sampling and its prediction error variance, fitting a weighted linear regression between the estimates and the years under study, identifying possible outliers, and defining a 95% empirical confidence interval for a possible trend in the estimates. We tested the specificity and sensitivity of the proposed validation method with simulated data using a real data structure. Moderate (M) and small (S) size populations were simulated under 3 scenarios: a control with homogeneous variance and 2 scenarios with yearly increases in phenotypic variance of 2 and 10%, respectively. Results showed that the new method was able to estimate genetic variance accurately enough to detect bias in genetic variance. Under the control scenario, the trend in genetic variance was practically zero in setting M. Testing cows with an average birth year class size of more than 43,000 in setting M showed that tolerance values are needed for both the trend and the outlier tests to detect only cases with a practical effect in larger data sets. Regardless of the magnitude (yearly increases in phenotypic variance of 2 or 10%) of the generated trend, it deviated statistically significantly from zero in all data replicates for both cows and bulls in setting M. In setting S with a mean of 27 bulls in a year class, the sampling error and thus the probability of a false-positive result clearly increased. Still, overall estimated genetic

  13. Model of unplanned smoking initiation of children and adolescents: an integrated stage model of smoking behavior.

    Science.gov (United States)

    Kremers, S P J; Mudde, A N; De Vries, H

    2004-05-01

    Two lines of psychological research have attempted to spell out the stages of adolescent smoking initiation. The first has focused on behavioral stages of smoking initiation, while the second line emphasized motivational stages. A large international sample of European adolescents (N = 10,170, mean age = 13.3 years) was followed longitudinally. Self-reported motivational and behavioral stages of smoking initiation were integrated, leading to the development of the Model of Unplanned Smoking Initiation of Children and Adolescents (MUSICA). The MUSICA postulates that youngsters experiment with smoking while they are in an unmotivated state as regards their plans for smoking regularly in the future. More than 95% of the total population resided in one of the seven stages distinguished by MUSICA. The probability of starting to smoke regularly during the 12 months follow-up period increased with advanced stage assignment at baseline. Unique social cognitive predictors of stage progression from the various stages were identified, but effect sizes of predictors of transitions were small. The integration of motivational and behavioral dimensions improves our understanding of the process of smoking initiation. In contrast to current theories of smoking initiation, adolescent uptake of smoking behavior was found to be an unplanned action.

  14. NUMERICAL SIMULATION OF AIR POLLUTION IN CASE OF UNPLANNED AMMONIA RELEASE

    Directory of Open Access Journals (Sweden)

    L. V. Amelina

    2017-06-01

    Full Text Available Purpose. Development fast calculating model which takes into account the meteorological parameters and buildings which are situated near the source of toxic chemical emission. Methodology. The developed model is based on the equation for potential flow and equation of pollutant dispersion. Equation of potential flow is used to compute wind pattern among buildings. To solve equation for potential flow Samarskii implicit difference scheme is used. The implicit change – triangle difference scheme is used to solve equation of mass transfer. Numerical integration is carried out using the rectangular difference grid. Method of porosity technique («markers method» is used to create the form of comprehensive computational region. Emission of ammonia is modeled using Delta function for point source. Findings. Developed 2D numerical model belongs to the class of «diagnostic models». This model takes into account the main physical factors affecting the process of dispersion of pollutants in the atmosphere. The model takes into account the influence of buildings on pollutant dispersion. On the basis of the developed numerical models a computational experiment was carried out to estimate the level of toxic chemical pollution in the case of unplanned ammonia release at ammonia pump station. Originality. Developed numerical model allows to calculate the 2D wind pattern among buildings and pollutant dispersion in the case unplanned ammonia release. Model allows to perform fast calculations of the atmosphere pollution. Practical value. The model can be used when developing the PLAS (Emergency Response Plan.

  15. Is Generalized Maternal Optimism or Pessimism During Pregnancy Associated with Unplanned Cesarean Section Deliveries in China?

    Directory of Open Access Journals (Sweden)

    Cheryl A. Moyer

    2010-01-01

    Full Text Available This research examines whether maternal optimism/pessimism is associated with unplanned Cesarean section deliveries in China. If so, does the association remain after controlling for clinical factors associated with C-sections? A sample of 227 mostly primiparous women in the third trimester of pregnancy was surveyed in a large tertiary care hospital in Beijing, China. Post-delivery data were collected from medical records. In bivariate analysis, both optimism and pessimism were related to unplanned c-section. However, when optimism and pessimism were entered into a regression model together, optimism was no longer statistically significant. Pessimism remained significant, even when adjusting for clinical factors such as previous abortion, previous miscarriage, pregnancy complications, infant gestational age, infant birthweight, labor duration, birth complications, and self-rated difficulty of the pregnancy. This research suggests that maternal mindset during pregnancy has a role in mode of delivery. However, more research is needed to elucidate potential causal pathways and test potential interventions.

  16. Planning the Unplanned Experiment: Assessing the Efficacy of Standards for Safety Critical Software

    Science.gov (United States)

    Graydon, Patrick J.; Holloway, C. Michael

    2015-01-01

    We need well-founded means of determining whether software is t for use in safety-critical applications. While software in industries such as aviation has an excellent safety record, the fact that software aws have contributed to deaths illustrates the need for justi ably high con dence in software. It is often argued that software is t for safety-critical use because it conforms to a standard for software in safety-critical systems. But little is known about whether such standards `work.' Reliance upon a standard without knowing whether it works is an experiment; without collecting data to assess the standard, this experiment is unplanned. This paper reports on a workshop intended to explore how standards could practicably be assessed. Planning the Unplanned Experiment: Assessing the Ecacy of Standards for Safety Critical Software (AESSCS) was held on 13 May 2014 in conjunction with the European Dependable Computing Conference (EDCC). We summarize and elaborate on the workshop's discussion of the topic, including both the presented positions and the dialogue that ensued.

  17. Exploring utilitarian and hedonic antecedents for adopting information from a recommendation agent and unplanned purchase behaviour

    Science.gov (United States)

    Huang, Li-Ting

    2016-01-01

    Research indicated that in order for properly utilizing recommendation agents (RAs), customers must rationally evaluate capability and suggestions of RAs during the interaction process. However, enjoying interactive processes and interface is also important. Methods for increasing user enjoyment of RAs are yet unknown. This study investigated the influences of utilitarian and hedonic factors on intention to adopt RAs suggestions and their antecedents. Involvement influences relative importance of utilitarian and hedonic factors. Contrary to common assumptions, customers may make unplanned purchases, rather than rational purchase. A field experiment with 2 × 2 × 2 factorial design reveals main findings. First, information diagnosticity and enjoyment enhance adoption intention simultaneously. Information diagnosticity is more important than enjoyment. Diagnosticity was determined by outcome similarity, and enjoyment was determined by both outcome similarity and atmospherics. The context of interacting with RAs is important. Outcome similarity even directly affects adoption intention. Second, highly involved users considered enjoyment and diagnosticity when forming adoption intentions, while users with low involvement only considered enjoyment. Third, information cascades altered the relationship between adoption intention and unplanned purchases. Most customers change selection after seeing ratings from other customers, even if they originally strongly want to adoption suggestion from RAs. Theoretical and managerial implications are proposed.

  18. Early discharge and home care after unplanned cesarean birth: nursing care time.

    Science.gov (United States)

    Brooten, D; Knapp, H; Borucki, L; Jacobsen, B; Finkler, S; Arnold, L; Mennuti, M

    1996-09-01

    This study examined the mean nursing time spent providing discharge planning and home care to women who delivered by unplanned cesarean birth and examined differences in nursing time required by women with and without morbidity. A secondary analysis of nursing time from a randomized trial of transitional care (discharge planning and home follow-up) provided to women after cesarean delivery. An urban tertiary-care hospital. The sample (N = 61) of black and white women who had unplanned cesarean births and their full-term newborn was selected randomly. Forty-four percent of the women had experienced pregnancy complications. Advanced practice nurses provided discharge planning and 8-week home follow-up consisting of home visits, telephone outreach, and daily telephone availability. Nursing time required was dictated by patient need and provider judgment rather than by reimbursement plan. More than half of the women required more than two home visits; mean home visit time was 1 hour. For women who experienced morbidity mean discharge planning time was 20 minutes more and mean home visit time 40 minutes more. Current health care services that provide one or two 1-hour home visits to childbearing women at high risk may not be meeting the education and resource needs of this group.

  19. Portfolio optimization with mean-variance model

    Science.gov (United States)

    Hoe, Lam Weng; Siew, Lam Weng

    2016-06-01

    Investors wish to achieve the target rate of return at the minimum level of risk in their investment. Portfolio optimization is an investment strategy that can be used to minimize the portfolio risk and can achieve the target rate of return. The mean-variance model has been proposed in portfolio optimization. The mean-variance model is an optimization model that aims to minimize the portfolio risk which is the portfolio variance. The objective of this study is to construct the optimal portfolio using the mean-variance model. The data of this study consists of weekly returns of 20 component stocks of FTSE Bursa Malaysia Kuala Lumpur Composite Index (FBMKLCI). The results of this study show that the portfolio composition of the stocks is different. Moreover, investors can get the return at minimum level of risk with the constructed optimal mean-variance portfolio.

  20. Unplanned Readmission in Outpatient Hand Surgery: An Analysis of 23,613 Patients in the NSQIP Data Set.

    Science.gov (United States)

    Donato, Daniel P; Kwok, Alvin C; Bishop, Michael O; Presson, Angela P; Agarwal, Jayant P

    2017-01-01

    Objective: In an era of controlling cost and improving care, 30-day readmission rates have become an important quality measure. The purpose of this study was to identify the rates of 30-day unplanned readmission and the associated risk factors in patients undergoing outpatient hand surgery. Methods: The 2011-2014 National Surgical Quality Improvement Project data were queried for patients who met 368 hand-specific Current Procedural Terminology codes. Univariable and multivariable analyses were performed to identify patient- and surgery-specific risk factors associated with unplanned readmission within 30 days. Results: Of the 368 Current Procedural Terminology codes queried, 208 were represented in the data, for a total of 23,613 patients. The overall unplanned readmission rate was 0.88% (207/23,613). On both univariable and multivariable analyses, operative year (2012), increasing age, obesity, smoking status, chronic obstructive pulmonary disease, preoperative steroid use, preoperative anemia, increasing American Society of Anesthesiologists classification, increasing operative time, and a procedure performed by a surgeon other than a plastic or orthopedic surgeon were associated with increased readmission rates. Diabetes, hypertension, low albumin levels, elevated international normalized ratio, and dirty/infected wound classification were only significant in univariable analysis. Current Procedural Terminology codes associated with the highest readmission rates were related to amputations. The most common readmission diagnoses were wound complications, followed by uncontrolled postoperative pain. Conclusions: The incidence of unplanned readmission is low in patients undergoing outpatient hand surgery. Specific patient comorbidities are associated with increased unplanned readmission rates. This information may be useful in identifying patients at higher risk for unplanned readmission and in counseling of high-risk patients preparing for surgery.

  1. Portfolio optimization using median-variance approach

    Science.gov (United States)

    Wan Mohd, Wan Rosanisah; Mohamad, Daud; Mohamed, Zulkifli

    2013-04-01

    Optimization models have been applied in many decision-making problems particularly in portfolio selection. Since the introduction of Markowitz's theory of portfolio selection, various approaches based on mathematical programming have been introduced such as mean-variance, mean-absolute deviation, mean-variance-skewness and conditional value-at-risk (CVaR) mainly to maximize return and minimize risk. However most of the approaches assume that the distribution of data is normal and this is not generally true. As an alternative, in this paper, we employ the median-variance approach to improve the portfolio optimization. This approach has successfully catered both types of normal and non-normal distribution of data. With this actual representation, we analyze and compare the rate of return and risk between the mean-variance and the median-variance based portfolio which consist of 30 stocks from Bursa Malaysia. The results in this study show that the median-variance approach is capable to produce a lower risk for each return earning as compared to the mean-variance approach.

  2. Grammatical and lexical variance in English

    CERN Document Server

    Quirk, Randolph

    2014-01-01

    Written by one of Britain's most distinguished linguists, this book is concerned with the phenomenon of variance in English grammar and vocabulary across regional, social, stylistic and temporal space.

  3. A Mean variance analysis of arbitrage portfolios

    Science.gov (United States)

    Fang, Shuhong

    2007-03-01

    Based on the careful analysis of the definition of arbitrage portfolio and its return, the author presents a mean-variance analysis of the return of arbitrage portfolios, which implies that Korkie and Turtle's results ( B. Korkie, H.J. Turtle, A mean-variance analysis of self-financing portfolios, Manage. Sci. 48 (2002) 427-443) are misleading. A practical example is given to show the difference between the arbitrage portfolio frontier and the usual portfolio frontier.

  4. Dynamic Mean-Variance Asset Allocation

    OpenAIRE

    Basak, Suleyman; Chabakauri, Georgy

    2009-01-01

    Mean-variance criteria remain prevalent in multi-period problems, and yet not much is known about their dynamically optimal policies. We provide a fully analytical characterization of the optimal dynamic mean-variance portfolios within a general incomplete-market economy, and recover a simple structure that also inherits several conventional properties of static models. We also identify a probability measure that incorporates intertemporal hedging demands and facilitates much tractability in ...

  5. Genetic variants influencing phenotypic variance heterogeneity.

    Science.gov (United States)

    Ek, Weronica E; Rask-Andersen, Mathias; Karlsson, Torgny; Enroth, Stefan; Gyllensten, Ulf; Johansson, Åsa

    2018-03-01

    Most genetic studies identify genetic variants associated with disease risk or with the mean value of a quantitative trait. More rarely, genetic variants associated with variance heterogeneity are considered. In this study, we have identified such variance single-nucleotide polymorphisms (vSNPs) and examined if these represent biological gene × gene or gene × environment interactions or statistical artifacts caused by multiple linked genetic variants influencing the same phenotype. We have performed a genome-wide study, to identify vSNPs associated with variance heterogeneity in DNA methylation levels. Genotype data from over 10 million single-nucleotide polymorphisms (SNPs), and DNA methylation levels at over 430 000 CpG sites, were analyzed in 729 individuals. We identified vSNPs for 7195 CpG sites (P mean DNA methylation levels. We further showed that variance heterogeneity between genotypes mainly represents additional, often rare, SNPs in linkage disequilibrium (LD) with the respective vSNP and for some vSNPs, multiple low frequency variants co-segregating with one of the vSNP alleles. Therefore, our results suggest that variance heterogeneity of DNA methylation mainly represents phenotypic effects by multiple SNPs, rather than biological interactions. Such effects may also be important for interpreting variance heterogeneity of more complex clinical phenotypes.

  6. The Variance Composition of Firm Growth Rates

    Directory of Open Access Journals (Sweden)

    Luiz Artur Ledur Brito

    2009-04-01

    Full Text Available Firms exhibit a wide variability in growth rates. This can be seen as another manifestation of the fact that firms are different from one another in several respects. This study investigated this variability using the variance components technique previously used to decompose the variance of financial performance. The main source of variation in growth rates, responsible for more than 40% of total variance, corresponds to individual, idiosyncratic firm aspects and not to industry, country, or macroeconomic conditions prevailing in specific years. Firm growth, similar to financial performance, is mostly unique to specific firms and not an industry or country related phenomenon. This finding also justifies using growth as an alternative outcome of superior firm resources and as a complementary dimension of competitive advantage. This also links this research with the resource-based view of strategy. Country was the second source of variation with around 10% of total variance. The analysis was done using the Compustat Global database with 80,320 observations, comprising 13,221 companies in 47 countries, covering the years of 1994 to 2002. It also compared the variance structure of growth to the variance structure of financial performance in the same sample.

  7. Delayed Recognition of Deterioration of Patients in General Wards Is Mostly Caused by Human Related Monitoring Failures: A Root Cause Analysis of Unplanned ICU Admissions

    NARCIS (Netherlands)

    van Galen, Louise S.; Struik, Patricia W.; Driesen, Babiche E. J. M.; Merten, Hanneke; Ludikhuize, Jeroen; van der Spoel, Johannes I.; Kramer, Mark H. H.; Nanayakkara, Prabath W. B.

    2016-01-01

    An unplanned ICU admission of an inpatient is a serious adverse event (SAE). So far, no in depth-study has been performed to systematically analyse the root causes of unplanned ICU-admissions. The primary aim of this study was to identify the healthcare worker-, organisational-, technical,- disease-

  8. Where do youth in foster care receive information about preventing unplanned pregnancy and sexually transmitted infections?

    Science.gov (United States)

    Hudson, Angela L

    2012-10-01

    Adolescents in foster care are at risk for unplanned pregnancy and sexually transmitted infections, including HIV infection. A study using a qualitative method was conducted to describe how and where foster youth receive reproductive health and risk reduction information to prevent pregnancy and sexually transmitted infections. Participants also were asked to describe their relationship with their primary health care provider while they were in foster care. Nineteen young adults, recently emancipated from foster care, participated in individual interviews. Using grounded theory as the method of analysis, three thematic categories were generated: discomfort visiting and disclosing, receiving and not receiving the bare essentials, and learning prevention from community others. Recommendations include primary health care providers providing a confidential space for foster youth to disclose sexual activity and more opportunities for foster youth to receive reproductive and risk prevention information in the school setting. Copyright © 2012 Elsevier Inc. All rights reserved.

  9. Effect on Perceived Stimulation dan Perceived Crowding on the Decision of the Unplanned Purchase (Impulse Buying

    Directory of Open Access Journals (Sweden)

    Enggal Sriwardiningsih

    2011-11-01

    Full Text Available Purchase decisions aren’t made necessarily planned, because impulsive buying is such a result of environmental stimuli shopping. Things affecting unplanned purchasing decisions are perceived by stimulation and crowding. The purpose of this study is to determine whether there are influences between perceived crowding and stimulation of impulse buying simultaneously or partial. The object used is one of the largest retailers in Cilegon. This research design is quantitative analysis of the consumer unit. The collecting data technique includes using questionnaires, interviews, and literature from previous research. Data processed using the SPSS 16.0 program through the validity and reliability, normality test, and regression analysis. The study states that there is significant influence between perceived crowding and perceived stimulation both simultaneous and partial response to impulse buying. 

  10. Determinants of emergency contraception non-use among women in unplanned or ambivalent pregnancies

    Directory of Open Access Journals (Sweden)

    Osmara Alves dos Santos

    2014-08-01

    Full Text Available Objective To analyze the determinants of emergency contraception non-use among women in unplanned and ambivalent pregnancies. Method Cross-sectional study with a probabilistic sample of 366 pregnant women from 12 primary health care units in the city of São Paulo, Brazil. A multinomial logistic regression was performed, comparing three groups: women who used emergency contraception to prevent ongoing pregnancies (reference; women who made no use of emergency contraception, but used other contraceptive methods; and women who made no use of any contraceptive methods at all. Results Cohabitation with a partner was the common determinant of emergency contraception non-use. No pregnancy risk awareness, ambivalent pregnancies and no previous use of emergency contraception also contributed to emergency contraception non-use. Conclusion Apart from what is pointed out in the literature, knowledge of emergency contraception and the fertile period were not associated to its use.

  11. Evaluation of the psychometric properties of the London Measure of Unplanned Pregnancy in Brazilian Portuguese.

    Science.gov (United States)

    Borges, Ana Luiza Vilela; Barrett, Geraldine; Dos Santos, Osmara Alves; Nascimento, Natalia de Castro; Cavalhieri, Fernanda Bigio; Fujimori, Elizabeth

    2016-08-24

    Estimates of unplanned pregnancy worldwide are of concern, especially in low and middle-income countries, including Brazil. Although the contraceptive prevalence rate is high in Brazil, almost half of all pregnancies are reported as unintended. The only source of nationally representative data about pregnancy intention is the Demographic and Health Survey, as with many other countries. In more recent years, however, it has been realized that concept of unintended pregnancy is potentially more complex and requires more sophisticated measurement strategies, such as the London Measure of Unplanned Pregnancy (LMUP). The LMUP has been translated and validated in other languages, but not Portuguese yet. In this study, we evaluate the psychometric properties of the LMUP in the Portuguese language, Brazilian version. A Brazilian Portuguese version of the LMUP was produced via translation and back-translation. After piloting, the mode of administration was changed from self-completion to interviewer-administration. The measure was field tested with pregnant, postpartum, and postabortion women recruited at maternity and primary health care services in Sao Paulo city. Reliability (internal consistency) was assessed using Cronbach's alpha and item-total correlations. Construct validity was assessed using principal components analysis and hypothesis testing. Scaling was assessed with Mokken analysis. 759 women aged 15-44 completed the Brazilian Portuguese LMUP. There were no missing data. The measure was acceptable and well targeted. Reliability testing demonstrated good internal consistency (alpha = 0.81, all item-rest correlations >0.2). Validity testing confirmed that the measure was unidimensional and that all hypotheses were met: there were lower LMUP median scores among women in the extreme age groups (p Portuguese LMUP is a valid and reliable measure of pregnancy planning/intention that is now available for use in Brazil. It represents a useful addition to the

  12. Adult birth mothers who made open infant adoption placements after adolescent unplanned pregnancy.

    Science.gov (United States)

    Clutter, Lynn B

    2014-01-01

    To summarize birth mothers' descriptions of how their adolescent or young adult unplanned pregnancies and decision for open infant adoption placement influenced their lives. Naturalistic inquiry using unstructured interviews. One to 2-hour telephone interviews with participants in their home settings were recorded and transcribed. Deidentified transcripts were analyzed for qualitative content themes. Fifteen women who had experienced unplanned adolescent or young adult pregnancy and relinquished their infants through open adoption were interviewed. Birth mothers who had been members of an agency support group were identified by an agency representative as having been typical of open adoption and were purposively recruited for study participation. Participants described the open adoption decision as "one of the most difficult but best" choices of their lives. Themes were summarized using the acronym AFRESH: A--adoption accomplishments, F--fresh start, R--relationship changes, E--emotions, S--support, H--healing. Findings indicated that benefits of open adoption outweighed challenges of pregnancy, birth, and emotional transitions. Birth children were perceived as thriving with adoptive families who were cherished like extended family. Birth mothers perceived themselves as being better people with better lives than before the unintended pregnancy. Growth with improved life direction was seen as a result of personal maturation from the experience. Open adoption is reinforced as a positive resolution of adolescent unintended pregnancy. Birth mothers believed teens who feel "stuck" with a pregnancy should consider open adoption; nurses should provide support and uphold the process. © 2014 AWHONN, the Association of Women's Health, Obstetric and Neonatal Nurses.

  13. Unplanned unavailability of the French nuclear plants. Evolution. Outstanding facts applications

    International Nuclear Information System (INIS)

    Coppe, P.

    2001-01-01

    The presentation gives a description of the unplanned unavailability of the whole French nuclear units on the aspect performance. The French fleet comprises 58 nuclear units including 34 from the series 900 MW, 20 from the stage 1300 MW and 4 units from the new series N4 of 1450 MW recently commissioned. Because of this width, even if the unavailability of the park remains on a low level on average, the experience feedback on this parameter gives very a rich lesson. The general evolution of unavailability over the last years is the subject of the first part of the talk. Several modes of analysis are examined: by year on the whole of the units, for the various series, by order of age of the various units. The different modes of gathering are examined and others are evoked, in order to reveal those which allow an optimal use of the experience feedback. The outstanding facts are then presented: the principal causes of unavailability are raised and examined. Certain equipment stand out particularly: the reasons of these singularities are exposed as well as the lesson and the modifications brought, the committed actions. Finally the applications resulting from the studies of the unplanned unavailability of the nuclear units are developed. Of course they relate in the forefront to the field of maintenance with the use of these studies within the framework of optimized and adapted programs of maintenance. The contributions are examined. The aging evolution of the plants is also analyzed starting from these studies. The stress is put however on a less obvious application: this one of the future units in design. (author)

  14. From point-of-purchase to path-to-purchase : How pre-shopping factors drive unplanned buying

    NARCIS (Netherlands)

    Bell, D.R.; Corsten, D.; Knox, G.A.H.

    2011-01-01

    Many retailers believe that a majority of purchases are unplanned, so they spend heavily on in-store marketing to stimulate these types of purchases. At the same time, the effects of “preshopping” factors—the shoppers' overall trip goals, store-specific shopping objectives, and prior marketing

  15. Ethnic variations in unplanned readmissions and excess length of hospital stay: a nationwide record-linked cohort study

    NARCIS (Netherlands)

    de Bruijne, M.C.; van Rosse, F.; Uiters, E.; Droomers, M.; Suurmond, J.; Stronks, K.; Essink-Bot, M.L.

    2013-01-01

    Background: Studies in the USA have shown ethnic inequalities in quality of hospital care, but in Europe, this has never been analysed. We explored variations in indicators of quality of hospital care by ethnicity in the Netherlands. Methods: We analysed unplanned readmissions and excess length of

  16. Ethnic variations in unplanned readmissions and excess length of hospital stay: a nationwide record-linked cohort study

    NARCIS (Netherlands)

    de Bruijne, Martine C.; van Rosse, Floor; Uiters, Ellen; Droomers, Mariël; Suurmond, Jeanine; Stronks, Karien; Essink-Bot, Marie-Louise

    2013-01-01

    Studies in the USA have shown ethnic inequalities in quality of hospital care, but in Europe, this has never been analysed. We explored variations in indicators of quality of hospital care by ethnicity in the Netherlands. We analysed unplanned readmissions and excess length of stay (LOS) across

  17. The Stability and Workload Index for Transfer score predicts unplanned intensive care unit patient readmission: initial development and validation

    NARCIS (Netherlands)

    Gajic, Ognjen; Malinchoc, Michael; Comfere, Thomas B.; Harris, Marcelline R.; Achouiti, Ahmed; Yilmaz, Murat; Schultz, Marcus J.; Hubmayr, Rolf D.; Afessa, Bekele; Farmer, J. Christopher

    2008-01-01

    OBJECTIVE: Unplanned readmission of hospitalized patients to an intensive care unit (ICU) is associated with a worse outcome, but our ability to identify who is likely to deteriorate after ICU dismissal is limited. The objective of this study is to develop and validate a numerical index, named the

  18. Predicting 7-day, 30-day and 60-day all-cause unplanned readmission: a case study of a Sydney hospital.

    Science.gov (United States)

    Maali, Yashar; Perez-Concha, Oscar; Coiera, Enrico; Roffe, David; Day, Richard O; Gallego, Blanca

    2018-01-04

    The identification of patients at high risk of unplanned readmission is an important component of discharge planning strategies aimed at preventing unwanted returns to hospital. The aim of this study was to investigate the factors associated with unplanned readmission in a Sydney hospital. We developed and compared validated readmission risk scores using routinely collected hospital data to predict 7-day, 30-day and 60-day all-cause unplanned readmission. A combination of gradient boosted tree algorithms for variable selection and logistic regression models was used to build and validate readmission risk scores using medical records from 62,235 live discharges from a metropolitan hospital in Sydney, Australia. The scores had good calibration and fair discriminative performance with c-statistic of 0.71 for 7-day and for 30-day readmission, and 0.74 for 60-day. Previous history of healthcare utilization, urgency of the index admission, old age, comorbidities related to cancer, psychosis, and drug-abuse, abnormal pathology results at discharge, and being unmarried and a public patient were found to be important predictors in all models. Unplanned readmissions beyond 7 days were more strongly associated with longer hospital stays and older patients with higher number of comorbidities and higher use of acute care in the past year. This study demonstrates similar predictors and performance to previous risk scores of 30-day unplanned readmission. Shorter-term readmissions may have different causal pathways than 30-day readmission, and may, therefore, require different screening tools and interventions. This study also re-iterates the need to include more informative data elements to ensure the appropriateness of these risk scores in clinical practice.

  19. Women undergoing aortic surgery are at higher risk for unplanned readmissions compared with men especially when discharged home.

    Science.gov (United States)

    Flink, Benjamin J; Long, Chandler A; Duwayri, Yazan; Brewster, Luke P; Veeraswamy, Ravi; Gallagher, Katherine; Arya, Shipra

    2016-06-01

    Women undergoing vascular surgery have higher morbidity and mortality. Our study explores gender-based differences in patient-centered outcomes such as readmission, length of stay (LOS), and discharge destination (home vs nonhome facility) in aortic aneurysm surgery. Patients were identified from the American College of Surgeons National Surgical Quality Improvement Project database (2011-2013) undergoing abdominal, thoracic, and thoracoabdominal aortic aneurysms (N = 17,763), who were discharged and survived their index hospitalization. The primary outcome was unplanned readmission, and secondary outcomes were discharge to a nonhome facility, LOS, and reasons for unplanned readmission. Univariate, multivariate, and stratified analyses based on gender and discharge destination were used. Overall, 1541 patients (8.7%) experienced an unplanned readmission, with a significantly higher risk in women vs men (10.8% vs 8%; P women compared with men persisted in multivariate analysis after controlling for covariates (odds ratio [OR], 1.21; 95% confidence interval [CI], 1.05-1.4). Similarly, the rate of discharge to a nonhome facility was nearly double in women compared with men (20.6% vs 10.7%; P women compared with men occurred in patients who were discharged home (OR, 1.2; 95% CI, 1.02-1.4) but not in those who were discharged to a nonhome facility (OR, 1.06; 95% CI, 0.8-1.4). Significant differences in LOS were seen in patients who were discharged home. No gender differences were found in reasons for readmission with the three most common reasons being thromboembolic events, wound infections, and pneumonia. Gender disparity exists in the risk of unplanned readmission among aortic aneurysm surgery patients. Women who were discharged home have a higher likelihood of unplanned readmission despite longer LOS than men. These data suggest that further study into the discharge planning processes, social factors, and use of rehabilitation services is needed for women

  20. Simulation study on heterogeneous variance adjustment for observations with different measurement error variance

    DEFF Research Database (Denmark)

    Pitkänen, Timo; Mäntysaari, Esa A; Nielsen, Ulrik Sander

    2013-01-01

    of variance correction is developed for the same observations. As automated milking systems are becoming more popular the current evaluation model needs to be enhanced to account for the different measurement error variances of observations from automated milking systems. In this simulation study different...... models and different approaches to account for heterogeneous variance when observations have different measurement error variances were investigated. Based on the results we propose to upgrade the currently applied models and to calibrate the heterogeneous variance adjustment method to yield same genetic......The Nordic Holstein yield evaluation model describes all available milk, protein and fat test-day yields from Denmark, Finland and Sweden. In its current form all variance components are estimated from observations recorded under conventional milking systems. Also the model for heterogeneity...

  1. Integrating Variances into an Analytical Database

    Science.gov (United States)

    Sanchez, Carlos

    2010-01-01

    For this project, I enrolled in numerous SATERN courses that taught the basics of database programming. These include: Basic Access 2007 Forms, Introduction to Database Systems, Overview of Database Design, and others. My main job was to create an analytical database that can handle many stored forms and make it easy to interpret and organize. Additionally, I helped improve an existing database and populate it with information. These databases were designed to be used with data from Safety Variances and DCR forms. The research consisted of analyzing the database and comparing the data to find out which entries were repeated the most. If an entry happened to be repeated several times in the database, that would mean that the rule or requirement targeted by that variance has been bypassed many times already and so the requirement may not really be needed, but rather should be changed to allow the variance's conditions permanently. This project did not only restrict itself to the design and development of the database system, but also worked on exporting the data from the database to a different format (e.g. Excel or Word) so it could be analyzed in a simpler fashion. Thanks to the change in format, the data was organized in a spreadsheet that made it possible to sort the data by categories or types and helped speed up searches. Once my work with the database was done, the records of variances could be arranged so that they were displayed in numerical order, or one could search for a specific document targeted by the variances and restrict the search to only include variances that modified a specific requirement. A great part that contributed to my learning was SATERN, NASA's resource for education. Thanks to the SATERN online courses I took over the summer, I was able to learn many new things about computers and databases and also go more in depth into topics I already knew about.

  2. Decomposition of Variance for Spatial Cox Processes.

    Science.gov (United States)

    Jalilian, Abdollah; Guan, Yongtao; Waagepetersen, Rasmus

    2013-03-01

    Spatial Cox point processes is a natural framework for quantifying the various sources of variation governing the spatial distribution of rain forest trees. We introduce a general criterion for variance decomposition for spatial Cox processes and apply it to specific Cox process models with additive or log linear random intensity functions. We moreover consider a new and flexible class of pair correlation function models given in terms of normal variance mixture covariance functions. The proposed methodology is applied to point pattern data sets of locations of tropical rain forest trees.

  3. Variance in binary stellar population synthesis

    Science.gov (United States)

    Breivik, Katelyn; Larson, Shane L.

    2016-03-01

    In the years preceding LISA, Milky Way compact binary population simulations can be used to inform the science capabilities of the mission. Galactic population simulation efforts generally focus on high fidelity models that require extensive computational power to produce a single simulated population for each model. Each simulated population represents an incomplete sample of the functions governing compact binary evolution, thus introducing variance from one simulation to another. We present a rapid Monte Carlo population simulation technique that can simulate thousands of populations in less than a week, thus allowing a full exploration of the variance associated with a binary stellar evolution model.

  4. Estimating quadratic variation using realized variance

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Shephard, N.

    2002-01-01

    with a rather general SV model - which is a special case of the semimartingale model. Then QV is integrated variance and we can derive the asymptotic distribution of the RV and its rate of convergence. These results do not require us to specify a model for either the drift or volatility functions, although we...... have to impose some weak regularity assumptions. We illustrate the use of the limit theory on some exchange rate data and some stock data. We show that even with large values of M the RV is sometimes a quite noisy estimator of integrated variance. Copyright © 2002 John Wiley & Sons, Ltd....

  5. Characteristics and outcome of unplanned out-of-institution births in Norway from 1999 to 2013: a cross-sectional study.

    Science.gov (United States)

    Gunnarsson, Björn; Smárason, Alexander K; Skogvoll, Eirik; Fasting, Sigurd

    2014-10-01

    To study the incidence, maternal characteristics and outcome of unplanned out-of-institution births (= unplanned births) in Norway. Register-based cross-sectional study. All births in Norway (n = 892 137) from 1999 to 2013 with gestational age ≥22 weeks. Analysis of data from the Medical Birth Registry of Norway from 1999 to 2013. Unplanned births (n = 6062) were compared with all other births (reference group). The annual incidence rate of unplanned births was 6.8/1000 births and remained stable during the period of study. Young multiparous women residing in remote municipalities were at the highest risk of experiencing unplanned births. The unplanned birth group had higher perinatal mortality rate for the period, 11.4/1000 compared with 4.9/1000 for the reference group (incidence rate ratio 2.31, 95% confidence interval 1.82-2.93, p life, compared with reference births in the same birthweight category. Unplanned births are associated with adverse outcome. Excessive mortality is possibly caused by reduced availability of necessary medical interventions for vulnerable newborns out-of-hospital. © 2014 The Authors. Acta Obstetricia et Gynecologica Scandinavica published by John Wiley & Sons Ltd on behalf of Nordic Federation of Societies of Obstetrics and Gynecology (NFOG).

  6. Geriatric Assessment of Older Adults With Cancer During Unplanned Hospitalizations: An Opportunity in Disguise.

    Science.gov (United States)

    Mariano, Caroline; Williams, Grant; Deal, Allison; Alston, Shani; Bryant, Ashley Leak; Jolly, Trevor; Muss, Hyman B

    2015-07-01

    Geriatric assessment (GA) is an important tool for management of older cancer patients; however, GA research has been performed primarily in the outpatient setting. The primary objective of this study was to determine feasibility of GA during an unplanned hospital stay. Secondary objectives were to describe deficits found with GA, to assess whether clinicians recognized and addressed deficits, and to determine 30-day readmission rates. The study was designed as an extension of an existing registry, "Carolina Senior: Registry for Older Patients." Inclusion criteria were age 70 and older and biopsy-proven solid tumor, myeloma, or lymphoma. Patients had to complete the GA within 7 days of nonelective admission to University of North Carolina Hospital. A total of 142 patients were approached, and 90 (63%) consented to participation. All sections of GA had at least an 83% completion rate. Overall, 53% of patients reported problems with physical function, 63% had deficits in instrumental activities of daily living, 34% reported falls, 12% reported depression, 31% had ≥10% weight loss, and 12% had abnormalities in cognition. Physician documentation of each deficit ranged from 20% to 46%. Rates of referrals to allied health professionals were not significantly different between patients with and without deficits. The 30-day readmission rate was 29%. GA was feasible in this population. Hospitalized older cancer patients have high levels of functional and psychosocial deficits; however, clinician recognition and management of deficits were poor. The use of GA instruments to guide referrals to appropriate services is a way to potentially improve outcomes in this vulnerable population. Geriatric assessment (GA) is an important tool in the management of older cancer patients; however, its primary clinical use has been in the outpatient setting. During an unplanned hospitalization, patients are extremely frail and are most likely to benefit from GA. This study demonstrates

  7. 29 CFR 1920.2 - Variances.

    Science.gov (United States)

    2010-07-01

    ...) PROCEDURE FOR VARIATIONS FROM SAFETY AND HEALTH REGULATIONS UNDER THE LONGSHOREMEN'S AND HARBOR WORKERS...) or 6(d) of the Williams-Steiger Occupational Safety and Health Act of 1970 (29 U.S.C. 655). The... under the Williams-Steiger Occupational Safety and Health Act of 1970, and any variance from §§ 1910.13...

  8. 78 FR 14122 - Revocation of Permanent Variances

    Science.gov (United States)

    2013-03-04

    ... Douglas Fir planking had to have at least a 1,900 fiber stress and 1,900,000 modulus of elasticity, while the Yellow Pine planking had to have at least 2,500 fiber stress and 2,000,000 modulus of elasticity... the permanent variances, and affected employees, to submit written data, views, and arguments...

  9. Variance Risk Premia on Stocks and Bonds

    DEFF Research Database (Denmark)

    Mueller, Philippe; Sabtchevsky, Petar; Vedolin, Andrea

    Investors in fixed income markets are willing to pay a very large premium to be hedged against shocks in expected volatility and the size of this premium can be studied through variance swaps. Using thirty years of option and high-frequency data, we document the following novel stylized facts...

  10. Biological Variance in Agricultural Products. Theoretical Considerations

    NARCIS (Netherlands)

    Tijskens, L.M.M.; Konopacki, P.

    2003-01-01

    The food that we eat is uniform neither in shape or appearance nor in internal composition or content. Since technology became increasingly important, the presence of biological variance in our food became more and more of a nuisance. Techniques and procedures (statistical, technical) were

  11. Decomposition of variance for spatial Cox processes

    DEFF Research Database (Denmark)

    Jalilian, Abdollah; Guan, Yongtao; Waagepetersen, Rasmus

    Spatial Cox point processes is a natural framework for quantifying the various sources of variation governing the spatial distribution of rain forest trees. We introduce a general criterion for variance decomposition for spatial Cox processes and apply it to specific Cox process models...

  12. Decomposition of variance for spatial Cox processes

    DEFF Research Database (Denmark)

    Jalilian, Abdollah; Guan, Yongtao; Waagepetersen, Rasmus

    2013-01-01

    Spatial Cox point processes is a natural framework for quantifying the various sources of variation governing the spatial distribution of rain forest trees. We introduce a general criterion for variance decomposition for spatial Cox processes and apply it to specific Cox process models...

  13. Decomposition of variance for spatial Cox processes

    DEFF Research Database (Denmark)

    Jalilian, Abdollah; Guan, Yongtao; Waagepetersen, Rasmus

    Spatial Cox point processes is a natural framework for quantifying the various sources of variation governing the spatial distribution of rain forest trees. We introducea general criterion for variance decomposition for spatial Cox processes and apply it to specific Cox process models with additive...

  14. Variance Swap Replication: Discrete or Continuous?

    Directory of Open Access Journals (Sweden)

    Fabien Le Floc’h

    2018-02-01

    Full Text Available The popular replication formula to price variance swaps assumes continuity of traded option strikes. In practice, however, there is only a discrete set of option strikes traded on the market. We present here different discrete replication strategies and explain why the continuous replication price is more relevant.

  15. Zero-intelligence realized variance estimation

    NARCIS (Netherlands)

    Gatheral, J.; Oomen, R.C.A.

    2010-01-01

    Given a time series of intra-day tick-by-tick price data, how can realized variance be estimated? The obvious estimator—the sum of squared returns between trades—is biased by microstructure effects such as bid-ask bounce and so in the past, practitioners were advised to drop most of the data and

  16. Variance Reduction Techniques in Monte Carlo Methods

    NARCIS (Netherlands)

    Kleijnen, Jack P.C.; Ridder, A.A.N.; Rubinstein, R.Y.

    2010-01-01

    Monte Carlo methods are simulation algorithms to estimate a numerical quantity in a statistical model of a real system. These algorithms are executed by computer programs. Variance reduction techniques (VRT) are needed, even though computer speed has been increasing dramatically, ever since the

  17. Reexamining financial and economic predictability with new estimators of realized variance and variance risk premium

    DEFF Research Database (Denmark)

    Casas, Isabel; Mao, Xiuping; Veiga, Helena

    This study explores the predictive power of new estimators of the equity variance risk premium and conditional variance for future excess stock market returns, economic activity, and financial instability, both during and after the last global financial crisis. These estimators are obtained from...... time-varying coefficient models are the ones showing considerably higher predictive power for stock market returns and financial instability during the financial crisis, suggesting that an extreme volatility period requires models that can adapt quickly to turmoil........ Moreover, a comparison of the overall results reveals that the conditional variance gains predictive power during the global financial crisis period. Furthermore, both the variance risk premium and conditional variance are determined to be predictors of future financial instability, whereas conditional...

  18. Completion of Gamma Knife radiosurgery for AVM treatment after unplanned interruption-technical note.

    Science.gov (United States)

    Raman, Hari S; Santanam, Lakshmi; Vellimana, Ananth K; Drzymala, Robert E; Tsien, Christina I; Zipfel, Gregory J

    2018-02-17

    Gamma Knife radiosurgery is an established technique for non-urgent treatment of various intracranial pathologies. Intra-procedural dislodgement of the stereotactic frame is an uncommon occurrence that could lead to abortion of ongoing treatment and necessitate more invasive treatment strategies. In this case report, we describe a novel method for resumption of Gamma Knife treatment after an unplanned intra-procedural interruption. The case example involves a radiosurgical treatment of a Spetzler-Martin grade I arteriovenous malformation. Our technique involves integration of scans and coordinate systems from two imaging sessions using the composite isodose line to resolve translational differences, thereby limiting delivery of remaining shots to the untreated region of the lesion. MRI follow-up at 13 months showed a reduction in the nidus size with no evidence of any radiation injury to the surrounding brain parenchyma. We believe this technique will allow care teams to effectively salvage interrupted Gamma Knife procedures and reduce progression to more invasive treatment options.

  19. Pre-planned versus unplanned decision making in the case of environmental decontamination

    International Nuclear Information System (INIS)

    Paschoa, A.S.; Tranjan Filho, A.

    2000-01-01

    Until a few years ago it was not usual to pre-plan realistic countermeasures directly related to a radiological emergency or a nuclear accident (RENA), mostly because the probability of occurrence of such events was considered to be too low for real concern. The Three Mile Island, Chernobyl and Goiania accidents, however, changed long accepted views of the decision making community throughout the world. Today, meetings are being held just to discuss how one can go about making decisions to face the problems that may occur in a number of RENAs. The present work will examine several well established scientifically based radiological criteria to be used in decision making processes concerning either radioactive decontamination following a severe RENA, or decommissioning procedures. Such criteria can certainly be used to select pre-planned countermeasures, but can also be helpful as guidance to decision makers when facing a choice of untested and unplanned options. Selected advantages and disadvantages of each criterion based option will be presented and briefly discussed, as, for example, the amount of radioactive waste produced vis-B-vis the risk (concentration or projected dose) level adopted in the decontamination procedures. In addition, non-scientific aspects will be brought into the discussion, because their social, economical, and political implications cannot be ignored by responsible decision makers. Uncertainties associated with both non-scientific aspects and scientifically based environmental and dosimetric models will also be examined for specific cases. (author)

  20. Planning the Unplanned Experiment: Towards Assessing the Efficacy of Standards for Safety-Critical Software

    Science.gov (United States)

    Graydon, Patrick J.; Holloway, C. M.

    2015-01-01

    Safe use of software in safety-critical applications requires well-founded means of determining whether software is fit for such use. While software in industries such as aviation has a good safety record, little is known about whether standards for software in safety-critical applications 'work' (or even what that means). It is often (implicitly) argued that software is fit for safety-critical use because it conforms to an appropriate standard. Without knowing whether a standard works, such reliance is an experiment; without carefully collecting assessment data, that experiment is unplanned. To help plan the experiment, we organized a workshop to develop practical ideas for assessing software safety standards. In this paper, we relate and elaborate on the workshop discussion, which revealed subtle but important study design considerations and practical barriers to collecting appropriate historical data and recruiting appropriate experimental subjects. We discuss assessing standards as written and as applied, several candidate definitions for what it means for a standard to 'work,' and key assessment strategies and study techniques and the pros and cons of each. Finally, we conclude with thoughts about the kinds of research that will be required and how academia, industry, and regulators might collaborate to overcome the noted barriers.

  1. Opportunities and Challenges of Unplanned Follow-up Interviews: Experiences with Polish Migrants in London

    Directory of Open Access Journals (Sweden)

    Louise Ryan

    2016-05-01

    Full Text Available Although there is growing interest in qualitative longitudinal research as a way of taking time seriously (ADAM, 2000, this approach still holds many challenges for the social researcher. In this article we use a reflexive approach, drawing on a Goffmanian analysis of self-presentation, to consider our separate but related experience of re-interviewing Polish migrants over intervals of several years. In each case, the repeat interviews were not part of the original research design and were undertaken years later for a range of different reasons. After briefly presenting case studies from our individual interviews, we critically reflect upon some opportunities and challenges of researching change through time. We first consider the ways in which repeat interviews may challenge earlier analyses and findings. We then explore some of the ethical considerations involved in unplanned repeat interviews. Next, we reflect upon dilemmas about self-revelation, particularly in contexts of social media and on-line technologies. Finally, we discuss what we have learned from our different experiences and what implications there are for this kind of ad hoc longitudinal research in migration studies. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs1602266

  2. R package MVR for Joint Adaptive Mean-Variance Regularization and Variance Stabilization.

    Science.gov (United States)

    Dazard, Jean-Eudes; Xu, Hua; Rao, J Sunil

    2011-01-01

    We present an implementation in the R language for statistical computing of our recent non-parametric joint adaptive mean-variance regularization and variance stabilization procedure. The method is specifically suited for handling difficult problems posed by high-dimensional multivariate datasets ( p ≫ n paradigm), such as in 'omics'-type data, among which are that the variance is often a function of the mean, variable-specific estimators of variances are not reliable, and tests statistics have low powers due to a lack of degrees of freedom. The implementation offers a complete set of features including: (i) normalization and/or variance stabilization function, (ii) computation of mean-variance-regularized t and F statistics, (iii) generation of diverse diagnostic plots, (iv) synthetic and real 'omics' test datasets, (v) computationally efficient implementation, using C interfacing, and an option for parallel computing, (vi) manual and documentation on how to setup a cluster. To make each feature as user-friendly as possible, only one subroutine per functionality is to be handled by the end-user. It is available as an R package, called MVR ('Mean-Variance Regularization'), downloadable from the CRAN.

  3. The effect of maternal role training program on role attainment and maternal role satisfaction in nulliparous women with unplanned pregnancy

    OpenAIRE

    Kordi, Masoumeh; Fasanghari, Maryam; Asgharipour, Negar; Esmaily, Habibollah

    2017-01-01

    INTRODUCTION: The maternal role is one of the most basic and important roles played by women during their lifetime. The process of the maternal role starts during pregnancy and to continue and develop after postpartum with the growth of suckling. However, unplanned pregnancy may jeopardize achieving the maternal role and reduce maternal role satisfaction. Therefore, the researcher conducted the present study to determine the impact of maternal role training program on attainment of role and r...

  4. Collaborative survey of perinatal loss in planned and unplanned home births. Northern Region Perinatal Mortality Survey Coordinating Group.

    OpenAIRE

    1996-01-01

    OBJECTIVE: To document the outcome of planned and unplanned births outside hospital. DESIGN: Confidential review of every pregnancy ending in stillbirth or neonatal death in which plans had been made for home delivery, irrespective of where delivery eventually occurred. The review was part of a sustained collaborative survey of all perinatal deaths. SETTING: Northern Regional Health Authority area. SUBJECTS: All 558,691 registered births to women normally resident in the former Northern Regio...

  5. Why babies die in unplanned out-of-institution births: an enquiry into perinatal deaths in Norway 1999-2013.

    Science.gov (United States)

    Gunnarsson, Björn; Fasting, Sigurd; Skogvoll, Eirik; Smárason, Alexander K; Salvesen, Kjell Å

    2017-03-01

    The aims were to describe causes of death associated with unplanned out-of-institution births, and to study whether they could be prevented. Retrospective population-based observational study based on data from the Medical Birth Registry of Norway and medical records. Between 1 January 1999 and 31 December 2013, 69 perinatal deaths among 6027 unplanned out-of-institution births, whether unplanned at home, during transportation, or unspecified, were selected for enquiry. Hospital records were investigated and cases classified according to Causes of Death and Associated Conditions. 63 cases were reviewed. There were 25 (40%) antepartum deaths, 10 (16%) intrapartum deaths, and 24 neonatal (38%) deaths. Four cases were in the unknown death category (6%). Both gestational age and birthweight followed a bimodal distribution with modes at 24 and 38 weeks and 750 and 3400 g, respectively. The most common main cause of death was infection (n = 14, 22%), neonatal (n = 14, 22%, nine due to extreme prematurity) and placental (n = 12, 19%, seven placental abruptions). There were 86 associated conditions, most commonly perinatal (n = 32), placental (n = 15) and maternal (n = 14). Further classification revealed that the largest subgroup was associated perinatal conditions/sub-optimal care, involving 25 cases (40%), most commonly due to sub-optimal maternal use of available care (n = 14, 22%). Infections, neonatal, and placental causes accounted for almost two-thirds of perinatal mortality associated with unplanned out-of-institution births in Norway. Sub-optimal maternal use of available care was found in more than one-fifth of cases. © 2016 The Authors. Acta Obstetricia et Gynecologica Scandinavica published by John Wiley & Sons Ltd on behalf of Nordic Federation of Societies of Obstetrics and Gynecology (NFOG).

  6. Realized Variance and Market Microstructure Noise

    DEFF Research Database (Denmark)

    Hansen, Peter R.; Lunde, Asger

    2006-01-01

    We study market microstructure noise in high-frequency data and analyze its implications for the realized variance (RV) under a general specification for the noise. We show that kernel-based estimators can unearth important characteristics of market microstructure noise and that a simple kernel......-based estimator dominates the RV for the estimation of integrated variance (IV). An empirical analysis of the Dow Jones Industrial Average stocks reveals that market microstructure noise its time-dependent and correlated with increments in the efficient price. This has important implications for volatility...... estimation based on high-frequency data. Finally, we apply cointegration techniques to decompose transaction prices and bid-ask quotes into an estimate of the efficient price and noise. This framework enables us to study the dynamic effects on transaction prices and quotes caused by changes in the efficient...

  7. The Theory of Variances in Equilibrium Reconstruction

    International Nuclear Information System (INIS)

    Zakharov, Leonid E.; Lewandowski, Jerome; Foley, Elizabeth L.; Levinton, Fred M.; Yuh, Howard Y.; Drozdov, Vladimir; McDonald, Darren

    2008-01-01

    The theory of variances of equilibrium reconstruction is presented. It complements existing practices with information regarding what kind of plasma profiles can be reconstructed, how accurately, and what remains beyond the abilities of diagnostic systems. The σ-curves, introduced by the present theory, give a quantitative assessment of quality of effectiveness of diagnostic systems in constraining equilibrium reconstructions. The theory also suggests a method for aligning the accuracy of measurements of different physical nature

  8. Fundamentals of exploratory analysis of variance

    CERN Document Server

    Hoaglin, David C; Tukey, John W

    2009-01-01

    The analysis of variance is presented as an exploratory component of data analysis, while retaining the customary least squares fitting methods. Balanced data layouts are used to reveal key ideas and techniques for exploration. The approach emphasizes both the individual observations and the separate parts that the analysis produces. Most chapters include exercises and the appendices give selected percentage points of the Gaussian, t, F chi-squared and studentized range distributions.

  9. Variance analysis refines overhead cost control.

    Science.gov (United States)

    Cooper, J C; Suver, J D

    1992-02-01

    Many healthcare organizations may not fully realize the benefits of standard cost accounting techniques because they fail to routinely report volume variances in their internal reports. If overhead allocation is routinely reported on internal reports, managers can determine whether billing remains current or lost charges occur. Healthcare organizations' use of standard costing techniques can lead to more realistic performance measurements and information system improvements that alert management to losses from unrecovered overhead in time for corrective action.

  10. Some folded issues related to over-shielded and unplanned rooms for medical linear accelerators - A case study

    Science.gov (United States)

    Muhammad, Wazir; Ullah, Asad; Hussain, Amjad; Ali, Nawab; Alam, Khan; Khan, Gulzar; Matiullah; Maeng, Seongjin; Lee, Sang Hoon

    2015-08-01

    A medical linear accelerator (LINAC) room must be properly shielded to limit the outside radiation exposure to an acceptable safe level defined by individual state and international regulations. However, along with this prime objective, some additional issues are also important. The current case-study was designed to unfold the issues related to over-shielded and unplanned treatment rooms for LINACs. In this connection, an apparently unplanned and over-shielded treatment room of 610 × 610 cm2 in size was compared with a properly designed treatment room of 762 × 762 cm2 in size ( i.e., by following the procedures and recommendations of the IAEA Safety Reports Series No. 47 and NCRP 151). Evaluation of the unplanned room indicated that it was over-shielded and that its size was not suitable for total body irradiation (TBI), although the license for such a treatment facility had been acquired for the installed machine. An overall 14.96% reduction in the total shielding volume ( i.e., concrete) for an optimally planned room as compared to a non-planned room was estimated. Furthermore, the inner room's dimensions were increased by 25%, in order to accommodate TBI patients. These results show that planning and design of the treatment rooms are imperative to avoid extra financial burden to the hospitals and to provide enough space for easy and safe handling of the patients. A spacious room is ideal for storing treatment accessories and facilitates TBI treatment.

  11. Alcohol consumption and its related harms in The Netherlands since 1960: relationships with planned and unplanned factors.

    Science.gov (United States)

    Knibbe, Ronald A; Derickx, Mieke; Allamani, Allaman; Massini, Giulia

    2014-10-01

    to establish which unplanned (social developments) and planned (alcohol policy measures) factors are related to per capita consumption and alcohol-related harms in the Netherlands. linear regression was used to establish which of the planned and unplanned factors were most strongly connected with alcohol consumption and harms. Artificial Neural Analysis (ANN) was used to inspect the interconnections between all variables. mothers age at birth was most strongly associated with increase in consumption. The ban on selling alcoholic beverages at petrol station was associated with a decrease in consumption. The linear regression of harms did not show any relation between alcohol policy measures and harms. The ANN-analyses indicate a very high interconnectedness between all variables allowing no causal inferences. Exceptions are the relation between price of beer and wine and the consumption of these beverages and the relation between a decrease in transport mortality and the increased use of breathalyzers tests and a restriction of paracommercial selling. unplanned factors are most strongly associated with per capita consumption and harms. ANN-analysis indicates that price of alcoholic beverages, breath testing, and restriction of sales may have had some influence. The study's limitations are noted.

  12. Increasing Short-Stay Unplanned Hospital Admissions among Children in England; Time Trends Analysis ’97–‘06

    Science.gov (United States)

    Saxena, Sonia; Bottle, Alex; Gilbert, Ruth; Sharland, Mike

    2009-01-01

    Background Timely care by general practitioners in the community keeps children out of hospital and provides better continuity of care. Yet in the UK, access to primary care has diminished since 2004 when changes in general practitioners' contracts enabled them to ‘opt out’ of providing out-of-hours care and since then unplanned pediatric hospital admission rates have escalated, particularly through emergency departments. We hypothesised that any increase in isolated short stay admissions for childhood illness might reflect failure to manage these cases in the community over a 10 year period spanning these changes. Methods and Findings We conducted a population based time trends study of major causes of hospital admission in children 2 days. By 2006, 67.3% of all unplanned admissions were isolated short stays <2 days. The increases in admission rates were greater for common non-infectious than infectious causes of admissions. Conclusions Short stay unplanned hospital admission rates in young children in England have increased substantially in recent years and are not accounted for by reductions in length of in-hospital stay. The majority are isolated short stay admissions for minor illness episodes that could be better managed by primary care in the community and may be evidence of a failure of primary care services. PMID:19829695

  13. The Genealogical Consequences of Fecundity Variance Polymorphism

    Science.gov (United States)

    Taylor, Jesse E.

    2009-01-01

    The genealogical consequences of within-generation fecundity variance polymorphism are studied using coalescent processes structured by genetic backgrounds. I show that these processes have three distinctive features. The first is that the coalescent rates within backgrounds are not jointly proportional to the infinitesimal variance, but instead depend only on the frequencies and traits of genotypes containing each allele. Second, the coalescent processes at unlinked loci are correlated with the genealogy at the selected locus; i.e., fecundity variance polymorphism has a genomewide impact on genealogies. Third, in diploid models, there are infinitely many combinations of fecundity distributions that have the same diffusion approximation but distinct coalescent processes; i.e., in this class of models, ancestral processes and allele frequency dynamics are not in one-to-one correspondence. Similar properties are expected to hold in models that allow for heritable variation in other traits that affect the coalescent effective population size, such as sex ratio or fecundity and survival schedules. PMID:19433628

  14. Discussion on variance reduction technique for shielding

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Fujio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    As the task of the engineering design activity of the international thermonuclear fusion experimental reactor (ITER), on 316 type stainless steel (SS316) and the compound system of SS316 and water, the shielding experiment using the D-T neutron source of FNS in Japan Atomic Energy Research Institute has been carried out. However, in these analyses, enormous working time and computing time were required for determining the Weight Window parameter. Limitation or complication was felt when the variance reduction by Weight Window method of MCNP code was carried out. For the purpose of avoiding this difficulty, investigation was performed on the effectiveness of the variance reduction by cell importance method. The conditions of calculation in all cases are shown. As the results, the distribution of fractional standard deviation (FSD) related to neutrons and gamma-ray flux in the direction of shield depth is reported. There is the optimal importance change, and when importance was increased at the same rate as that of the attenuation of neutron or gamma-ray flux, the optimal variance reduction can be done. (K.I.)

  15. Minimum variance and variance of outgoing quality limit MDS-1(c1, c2) plans

    Science.gov (United States)

    Raju, C.; Vidya, R.

    2016-06-01

    In this article, the outgoing quality (OQ) and total inspection (TI) of multiple deferred state sampling plans MDS-1(c1,c2) are studied. It is assumed that the inspection is rejection rectification. Procedures for designing MDS-1(c1,c2) sampling plans with minimum variance of OQ and TI are developed. A procedure for obtaining a plan for a designated upper limit for the variance of the OQ (VOQL) is outlined.

  16. Race and Sex Differences in Post-Myocardial Infarction Angina Frequency and Risk of 1-Year Unplanned Rehospitalization.

    Science.gov (United States)

    Hess, Connie N; Kaltenbach, Lisa A; Doll, Jacob A; Cohen, David J; Peterson, Eric D; Wang, Tracy Y

    2017-02-07

    Race and sex disparities in in-hospital treatment and outcomes of patients with acute myocardial infarction (MI) have been described, but little is known about race and sex differences in post-MI angina and long-term risk of unplanned rehospitalization. We examined race and sex differences in post-MI angina frequency and 1-year unplanned rehospitalization to identify factors associated with unplanned rehospitalization, testing for whether race and sex modify these relationships. Using TRANSLATE-ACS (Treatment With Adenosine Diphosphate Receptor Inhibitors: Longitudinal Assessment of Treatment Patterns and Events after Acute Coronary Syndrome) data, we examined 6-week and 1-year angina frequency and 1-year unplanned rehospitalization stratified by race and sex among MI patients treated with percutaneous coronary intervention. We used multivariable logistic regression to assess factors associated with unplanned rehospitalization and tested for interactions among angina frequency, race, and sex. A total of 11 595 MI patients survived to 1 year postdischarge; there were 66.6% white male patients, 24.3% white female patients, 5.3% black male patients, and 3.8% black female patients. Overall, 29.7% had angina at 6 weeks, and 20.6% had angina at 1 year postdischarge. Relative to white patients, black patients were more likely to have angina at 6 weeks (female: 44.2% versus 31.8%; male: 33.5% versus 27.1%; both Prace or sex (adjusted 3-way P interaction =0.41). One-fifth of MI patients treated with percutaneous coronary intervention report 1-year postdischarge angina, with black and female patients more likely to have angina and to be rehospitalized. Better treatment of post-MI angina may improve patient quality of life and quality of care and help to lower rates of rehospitalization overall and particularly among black and female patients, given their high prevalence of post-MI angina. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01088503. © 2017 American

  17. Operative variables are better predictors of postdischarge infections and unplanned readmissions in vascular surgery patients than patient characteristics.

    Science.gov (United States)

    Hicks, Caitlin W; Bronsert, Michael; Hammermeister, Karl E; Henderson, William G; Gibula, Douglas R; Black, James H; Glebova, Natalia O

    2017-04-01

    Although postoperative readmissions are frequent in vascular surgery patients, the reasons for these readmissions are not well characterized, and effective approaches to their reduction are unknown. Our aim was to analyze the reasons for vascular surgery readmissions and to report potential areas for focused efforts aimed at readmission reduction. The 2012 to 2013 American College of Surgeons National Quality Improvement Program (ACS NSQIP) data set was queried for vascular surgery patients. Multivariable models were developed to analyze risk factors for postdischarge infections, the major drivers of unplanned 30-day readmissions. We identified 86,403 vascular surgery patients for analysis. Thirty-day readmission occurred in 8827 (10%), of which 8054 (91%) were unplanned. Of the unplanned readmissions, 61% (n = 4951) were related to the index vascular surgery procedure. Infectious complications were the most common reason for a surgery-related readmission (1940 [39%]), with surgical site infection being the most common type of infection related to unplanned readmission. Multivariable analysis showed the top five preoperative risk factors for postdischarge infections were the presence of a preoperative open wound, inpatient operation, obesity, work relative value unit, and insulin-dependent diabetes (but not diabetes managed with oral medications). Cigarette smoking was a weak predictor and came in tenth in the mode (overall C index, 0.657). When operative and postoperative factors were included in the model, total operative time was the strongest predictor of postdischarge infectious complications (odds ratio [OR] 1.2 for each 1-hour increase in operative time), followed by presence of a preoperative open wound (OR, 1.5), inpatient operation (OR, 2), obesity (OR, 1.8), and discharge to rehabilitation facility (OR, 1.7; P model was fair (C statistic, 0.686). Infectious complications dominate the reasons for unplanned 30-day readmissions in vascular surgery

  18. Using unplanned fires to help suppressing future large fires in Mediterranean forests.

    Directory of Open Access Journals (Sweden)

    Adrián Regos

    Full Text Available Despite the huge resources invested in fire suppression, the impact of wildfires has considerably increased across the Mediterranean region since the second half of the 20th century. Modulating fire suppression efforts in mild weather conditions is an appealing but hotly-debated strategy to use unplanned fires and associated fuel reduction to create opportunities for suppression of large fires in future adverse weather conditions. Using a spatially-explicit fire-succession model developed for Catalonia (Spain, we assessed this opportunistic policy by using two fire suppression strategies that reproduce how firefighters in extreme weather conditions exploit previous fire scars as firefighting opportunities. We designed scenarios by combining different levels of fire suppression efficiency and climatic severity for a 50-year period (2000-2050. An opportunistic fire suppression policy induced large-scale changes in fire regimes and decreased the area burnt under extreme climate conditions, but only accounted for up to 18-22% of the area to be burnt in reference scenarios. The area suppressed in adverse years tended to increase in scenarios with increasing amounts of area burnt during years dominated by mild weather. Climate change had counterintuitive effects on opportunistic fire suppression strategies. Climate warming increased the incidence of large fires under uncontrolled conditions but also indirectly increased opportunities for enhanced fire suppression. Therefore, to shift fire suppression opportunities from adverse to mild years, we would require a disproportionately large amount of area burnt in mild years. We conclude that the strategic planning of fire suppression resources has the potential to become an important cost-effective fuel-reduction strategy at large spatial scale. We do however suggest that this strategy should probably be accompanied by other fuel-reduction treatments applied at broad scales if large-scale changes in fire

  19. Development of a preliminary risk index to identify trauma patients at risk for an unplanned intubation.

    Science.gov (United States)

    Kim, Dennis; Kobayashi, Leslie; Chang, David; Fortlage, Dale; Coimbra, Raul

    2014-01-01

    The development of respiratory failure requiring an emergent unplanned intubation (UI) is a potentially preventable complication associated with increased morbidity and mortality. The objective of this study was to develop a clinical risk index for UI based on readily available clinical data to assist in the identification of trauma patients at risk for this complication. We also sought to determine the impact of UI on patient outcomes. This is a 3-year retrospective analysis of our Level 1 trauma center registry to identify all patients requiring a UI. Patients who required a UI were compared with patients who were never intubated. An additive risk index consisting of 10 clinical variables was created using the final significant variables from a stepwise logistic regression model. The sensitivity and specificity of every possible index score were calculated and added together to calculate the "gain in certainty" values. During the 3-year period, 7,552 patients were admitted, of whom 967 (12.8%) required intubation. Of these, 55 (5.7%) underwent a UI. The final risk index consisted of 10 variables as follows: age 55 years to 64 years, age 65 years or older, male sex, Glasgow Coma Scale (GCS) score of 9 to 13, seizures, chronic obstructive pulmonary disease, traumatic brain injury, four or more rib fractures, spine fractures, and long-bone fractures. Gain in certainty was maximized at an index score of 4, with the highest combined sensitivity and specificity of 86.0% and 74.9%, respectively. The probability of UI increased from 0.9% at a score of 1 to 2.9% at 4 and 43% at 9. UI was associated with increased overall complications, length of stay, and mortality (p the development of an additive risk index. Prospective validation of the risk index is potentially warranted. Diagnostic study, level III.

  20. Impulsive traits and unplanned suicide attempts predict exaggerated prefrontal response to angry faces in the elderly.

    Science.gov (United States)

    Vanyukov, Polina M; Szanto, Katalin; Siegle, Greg J; Hallquist, Michael N; Reynolds, Charles F; Aizenstein, Howard J; Dombrovski, Alexandre Y

    2015-08-01

    Abnormal responses to social stimuli are seen in people vulnerable to suicidal behavior, indicating possible disruptions in the neural circuitry mediating the interpretation of socioemotional cues. These disruptions have not been empirically related to psychological and cognitive pathways to suicide. In the present study of older suicide attempters, we examined neural responses to emotional faces and their relationship to impulsivity, one of the components of the suicidal diathesis. Using functional magnetic resonance imaging, we recorded neurohemodynamic responses to angry faces in a carefully characterized sample of 18 depressed elderly with history of suicide attempts, 13 depressed nonsuicidal patients, and 18 healthy individuals, all aged 60+. Impulsivity was assessed with the Social Problem Solving Inventory Impulsivity/Carelessness Style subscale and Barratt Impulsiveness Scale. The Suicide Intent Scale planning subscale was used to describe the degree of planning associated with the most lethal attempt. Depression and history of attempted suicide were not associated with neural responses to angry faces, failing to replicate earlier studies. Higher impulsivity, however, predicted exaggerated responses to angry faces in fronto-opercular and dorsomedial prefrontal cortex (pcorr suicide attempts also predicted increased fronto-opercular responses. Results were robust to effects of medication exposure, comorbid anxiety and addiction, severity of depression, burden of physical illness, and possible brain injury from suicide attempts. Impulsive traits and history of unplanned suicide attempts partly explain the heterogeneity in neural responses to angry faces in depressed elderly. Displays of social emotion command excessive cortical processing in impulsive suicide attempters. Copyright © 2015 American Association for Geriatric Psychiatry. Published by Elsevier Inc. All rights reserved.

  1. An unaddressed issue: domestic violence and unplanned pregnancies among pregnant women in Turkey.

    Science.gov (United States)

    Sahin, H A; Sahin, H G

    2003-06-01

    The aim of this study was to estimate the prevalence and type of domestic violence during pregnancy in Turkey and to compare socioeconomic background factors. A survey was carried out among a representative sample of 475 pregnant women. Data were collected on the incidence and the nature of domestic violence perpetrated by the woman's spouse or other family members during her current pregnancy and before. Sociodemographic characteristics such as age, duration of marriage, number of children, monthly income, education, occupation of the husband, domestic violence towards children, contribution to family decisions, smoking habits, sexual relations and whether the pregnancy was planned or not, were also recorded. Of the 475 women screened for domestic violence during pregnancy, 158 (33.3%) reported physical or sexual abuse since they had become pregnant. The source of the domestic violence was mainly the husband in 105 (66.5%) women. Types of abuse were psychological in 71 (44.9%) and physical in 87 (55.1%) women. The rate of women's satisfaction with their sexual life among abused women was 43.67% compared to 61.2% among non-abused women. Abused pregnant women were less educated, had lower income, had more children, had a longer duration of marriage, were applying violence towards their children, were not contributing to family decisions, were less satisfied with their sexual life and were more likely to have unplanned pregnancies when compared to non-abused women. Antenatal care protocols should be modified to address domestic violence and contributing factors during pregnancy so that identified women can be counseled appropriately and attempts can be made to intervene to prevent further episodes of domestic violence in primary care settings.

  2. Using unplanned fires to help suppressing future large fires in Mediterranean forests.

    Science.gov (United States)

    Regos, Adrián; Aquilué, Núria; Retana, Javier; De Cáceres, Miquel; Brotons, Lluís

    2014-01-01

    Despite the huge resources invested in fire suppression, the impact of wildfires has considerably increased across the Mediterranean region since the second half of the 20th century. Modulating fire suppression efforts in mild weather conditions is an appealing but hotly-debated strategy to use unplanned fires and associated fuel reduction to create opportunities for suppression of large fires in future adverse weather conditions. Using a spatially-explicit fire-succession model developed for Catalonia (Spain), we assessed this opportunistic policy by using two fire suppression strategies that reproduce how firefighters in extreme weather conditions exploit previous fire scars as firefighting opportunities. We designed scenarios by combining different levels of fire suppression efficiency and climatic severity for a 50-year period (2000-2050). An opportunistic fire suppression policy induced large-scale changes in fire regimes and decreased the area burnt under extreme climate conditions, but only accounted for up to 18-22% of the area to be burnt in reference scenarios. The area suppressed in adverse years tended to increase in scenarios with increasing amounts of area burnt during years dominated by mild weather. Climate change had counterintuitive effects on opportunistic fire suppression strategies. Climate warming increased the incidence of large fires under uncontrolled conditions but also indirectly increased opportunities for enhanced fire suppression. Therefore, to shift fire suppression opportunities from adverse to mild years, we would require a disproportionately large amount of area burnt in mild years. We conclude that the strategic planning of fire suppression resources has the potential to become an important cost-effective fuel-reduction strategy at large spatial scale. We do however suggest that this strategy should probably be accompanied by other fuel-reduction treatments applied at broad scales if large-scale changes in fire regimes are to be

  3. [Health risk induced by estrogens during unplanned indirect potable reuse of reclaimed water from domestic wastewater].

    Science.gov (United States)

    Wu, Qian-Yuan; Shao, Yi-Ru; Wang, Chao; Sun, Yan; Hu, Hong-Ying

    2014-03-01

    The estrogenic endocrine disruptors in reclaimed water from domestic wastewater may induce health risks to human being, when reclaimed water is used for augmentation of drinking water unplannedly and indirectly. This study investigated changes in concentrations of estrone, estradiol, 17alpha-ethinyl estradiol, bisphenol A, nonylphenol and octylphenol in reclaimed water during the reuse of reclaimed water for augmentation to water source such as lakes and reservoir via river. Thereafter, health risk induced by estrogens during the resue of reclaimed water was evaluated. The concentration of estrogen in secondary effluent ranged 0.1-100 ng x L(-1). The highest concentrations of bisphenol A and nonylphenol reached up to 1-10 microg x L(-1). During the indirect reuse of reclaimed water as potable water, the dilution and degradation in river and lake, and the removal by drinking water treatment process could change the concentrations of estrogen. The non-carcinogenic risks of estrone, estradiol, bisphenol A, nonylphenol and octylphenol were lower than 1. When the hydraulic retention time of 17alpha-ethinyl estradiol (EE2) in lakes and reservoir was higher than 30 days, the non-carcinogenic risk of EE2 was lower than 1 in most cases. When the hydraulic retention time of EE2 in lakes and reservoir was less than 30 days and the percentages of reclaimed water in drinking water were higher than 50%, the non-carcinogenic risk induced by EE2 was higher than 1 in 20%-50% samples. This indicated that the risks of EE2 should be concerned.

  4. Optimizing Prevention of HIV and Unplanned Pregnancy in Discordant African Couples.

    Science.gov (United States)

    Wall, Kristin M; Kilembe, William; Vwalika, Bellington; Haddad, Lisa B; Khu, Naw Htee; Brill, Ilene; Onwubiko, Udodirim; Chomba, Elwyn; Tichacek, Amanda; Allen, Susan

    2017-08-01

    Dual method use, which combines condoms with a more effective modern contraceptive to optimize prevention of HIV and unplanned pregnancy, is underutilized in high-risk heterosexual couples. Heterosexual HIV-discordant Zambian couples were enrolled from couples' voluntary HIV counseling and testing services into an open cohort with 3-monthly follow-up (1994-2012). Relative to dual method use, defined as consistent condom use plus modern contraception, we examine predictors of (1) condom-only use (suboptimal pregnancy prevention) or (2) modern contraceptive use with inconsistent condom use (effective pregnancy prevention and suboptimal HIV prevention). Among 3,049 couples, dual method use occurred in 28% of intervals in M+F- and 23% in M-F+, p HIV+ (adjusted hazard ratio, aHR = 1.15); baseline oral contraceptive pill (aHR = 0.76), injectable (aHR = 0.48), or implant (aHR = 0.60) use; woman's age (aHR = 1.04 per 5 years) and lifetime number of sex partners (aHR = 1.01); postpartum periods (aHR = 1.25); and HIV stage of the index partner III/IV versus I (aHR = 1.10). Predictors (p HIV+ male circumcision (aHR = 1.51), while time-varying implant use was associated with more consistent condom use (aHR = 0.80). Three-quarters of follow-up intervals did not include dual method use. This highlights the need for counseling to reduce unintended pregnancy and HIV transmission and enable safer conception.

  5. Risk factors and direct medical cost of early versus late unplanned readmissions among diabetes patients at a tertiary hospital in Singapore.

    Science.gov (United States)

    Png, May Ee; Yoong, Joanne; Chen, Cynthia; Tan, Chuen Seng; Tai, E Shyong; Khoo, Eric Y H; Wee, Hwee Lin

    2018-02-20

    To examine the risk factors and direct medical costs associated with early (≤30 days) versus late (31-180 days) unplanned readmissions among patients with type 2 diabetes in Singapore. Risk factors and associated costs among diabetes patients were investigated using electronic medical records from a local tertiary care hospital from 2010 to 2012. Multivariable logistic regression was used to identify risk factors associated with early and late unplanned readmissions while a generalized linear model was used to estimate the direct medical cost. Sensitivity analysis was also performed. A total of 1729 diabetes patients had unplanned readmissions within 180 days of an index discharge. Length of index stay (a marker of acute illness burden) was one of the risk factors associated with early unplanned readmission while patient behavior-related factors, like diabetes-related medication adherence, were associated with late unplanned readmission. Adjusted mean cost of index admission was higher among patients with unplanned readmission. Sensitivity analysis yielded similar results. Existing routinely captured data can be used to develop prediction models that flag high risk patients during their index admission, potentially helping to support clinical decisions and prevent such readmissions.

  6. Visual SLAM Using Variance Grid Maps

    Science.gov (United States)

    Howard, Andrew B.; Marks, Tim K.

    2011-01-01

    An algorithm denoted Gamma-SLAM performs further processing, in real time, of preprocessed digitized images acquired by a stereoscopic pair of electronic cameras aboard an off-road robotic ground vehicle to build accurate maps of the terrain and determine the location of the vehicle with respect to the maps. Part of the name of the algorithm reflects the fact that the process of building the maps and determining the location with respect to them is denoted simultaneous localization and mapping (SLAM). Most prior real-time SLAM algorithms have been limited in applicability to (1) systems equipped with scanning laser range finders as the primary sensors in (2) indoor environments (or relatively simply structured outdoor environments). The few prior vision-based SLAM algorithms have been feature-based and not suitable for real-time applications and, hence, not suitable for autonomous navigation on irregularly structured terrain. The Gamma-SLAM algorithm incorporates two key innovations: Visual odometry (in contradistinction to wheel odometry) is used to estimate the motion of the vehicle. An elevation variance map (in contradistinction to an occupancy or an elevation map) is used to represent the terrain. The Gamma-SLAM algorithm makes use of a Rao-Blackwellized particle filter (RBPF) from Bayesian estimation theory for maintaining a distribution over poses and maps. The core idea of the RBPF approach is that the SLAM problem can be factored into two parts: (1) finding the distribution over robot trajectories, and (2) finding the map conditioned on any given trajectory. The factorization involves the use of a particle filter in which each particle encodes both a possible trajectory and a map conditioned on that trajectory. The base estimate of the trajectory is derived from visual odometry, and the map conditioned on that trajectory is a Cartesian grid of elevation variances. In comparison with traditional occupancy or elevation grid maps, the grid elevation variance

  7. Markov bridges, bisection and variance reduction

    DEFF Research Database (Denmark)

    Asmussen, Søren; Hobolth, Asger

    . In this paper we firstly consider the problem of generating sample paths from a continuous-time Markov chain conditioned on the endpoints using a new algorithm based on the idea of bisection. Secondly we study the potential of the bisection algorithm for variance reduction. In particular, examples are presented......Time-continuous Markov jump processes is a popular modelling tool in disciplines ranging from computational finance and operations research to human genetics and genomics. The data is often sampled at discrete points in time, and it can be useful to simulate sample paths between the datapoints...

  8. The value of travel time variance

    OpenAIRE

    Fosgerau, Mogens; Engelson, Leonid

    2010-01-01

    This paper considers the value of travel time variability under scheduling preferences that are de�fined in terms of linearly time-varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can free...

  9. Variance-based Salt Body Reconstruction

    KAUST Repository

    Ovcharenko, Oleg

    2017-05-26

    Seismic inversions of salt bodies are challenging when updating velocity models based on Born approximation- inspired gradient methods. We propose a variance-based method for velocity model reconstruction in regions complicated by massive salt bodies. The novel idea lies in retrieving useful information from simultaneous updates corresponding to different single frequencies. Instead of the commonly used averaging of single-iteration monofrequency gradients, our algorithm iteratively reconstructs salt bodies in an outer loop based on updates from a set of multiple frequencies after a few iterations of full-waveform inversion. The variance among these updates is used to identify areas where considerable cycle-skipping occurs. In such areas, we update velocities by interpolating maximum velocities within a certain region. The result of several recursive interpolations is later used as a new starting model to improve results of conventional full-waveform inversion. An application on part of the BP 2004 model highlights the evolution of the proposed approach and demonstrates its effectiveness.

  10. A zero-variance-based scheme for variance reduction in Monte Carlo criticality

    Energy Technology Data Exchange (ETDEWEB)

    Christoforou, S.; Hoogenboom, J. E. [Delft Univ. of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

    2006-07-01

    A zero-variance scheme is derived and proven theoretically for criticality cases, and a simplified transport model is used for numerical demonstration. It is shown in practice that by appropriate biasing of the transition and collision kernels, a significant reduction in variance can be achieved. This is done using the adjoint forms of the emission and collision densities, obtained from a deterministic calculation, according to the zero-variance scheme. By using an appropriate algorithm, the figure of merit of the simulation increases by up to a factor of 50, with the possibility of an even larger improvement. In addition, it is shown that the biasing speeds up the convergence of the initial source distribution. (authors)

  11. A zero-variance-based scheme for variance reduction in Monte Carlo criticality

    International Nuclear Information System (INIS)

    Christoforou, S.; Hoogenboom, J. E.

    2006-01-01

    A zero-variance scheme is derived and proven theoretically for criticality cases, and a simplified transport model is used for numerical demonstration. It is shown in practice that by appropriate biasing of the transition and collision kernels, a significant reduction in variance can be achieved. This is done using the adjoint forms of the emission and collision densities, obtained from a deterministic calculation, according to the zero-variance scheme. By using an appropriate algorithm, the figure of merit of the simulation increases by up to a factor of 50, with the possibility of an even larger improvement. In addition, it is shown that the biasing speeds up the convergence of the initial source distribution. (authors)

  12. Knowledge and attitudes of Latin American gynecologists regarding unplanned pregnancy and use of combined oral contraceptives

    Directory of Open Access Journals (Sweden)

    Bahamondes L

    2015-05-01

    Full Text Available Luis Bahamondes,1 Josefina Lira-Plasencia,2 Ricardo Martin,3 Victor Marin,4 Maria Y Makuch1 1Department of Obstetrics and Gynecology, School of Medical Sciences, University of Campinas (UNICAMP, Campinas, Brazil; 2Instituto Nacional de Perinatología, México, DF, México; 3Hospital Universitario, Fundación Santa Fe de Bogotá, Bogotá, Colombia; 4Hospital Central, Petróleos Mexicanos, México, DF, México Background: Unintended pregnancy is a public health problem and unmet medical need worldwide. It is estimated that in the year 2012, almost 213 million pregnancies occurred, and the global pregnancy rate decreased only slightly from 2008 to 2012. It was also estimated that 85 million pregnancies (40% of all pregnancies were unintended and that 38% ended in an unintended birth. Objectives: To assess knowledge and attitudes of Latin American (LA obstetricians and gynecologists (OBGYNs regarding unintended pregnancies and aspects of combined oral contraceptive (COC use. Methods: A survey was conducted during a scientific meeting about contraception in 2014, in which OBGYNs from 12 LA countries who provide attention in contraception were invited to respond to a multiple-choice questionnaire to assess their knowledge and attitudes regarding unplanned pregnancy and some aspects regarding COC use. Results: A total of 210 OBGYNs participated in the study. Their knowledge regarding COC failure was low. The participants reported they believed that their patients habitually forgot to take a pill and that their patients did not know what to do in these situations. They were aware of the benefits of COC use; however, they were less prone to prescribe COCs for the purpose of protecting against ovarian and endometrial cancer, and one-quarter of them had doubts about the association between COC use and cancer risk. Conclusion: The interviewed LA OBGYNs showed some flaws in terms of knowledge of COC failure rates and the non-contraceptive benefits and risks

  13. Predictors associated with unplanned hospital readmission of medical and surgical intensive care unit survivors within 30 days of discharge.

    Science.gov (United States)

    Ohnuma, Tetsu; Shinjo, Daisuke; Brookhart, Alan M; Fushimi, Kiyohide

    2018-01-01

    Reducing the 30-day unplanned hospital readmission rate is a goal for physicians and policymakers in order to improve quality of care. However, data on the readmission rate of critically ill patients in Japan and knowledge of the predictors associated with readmission are lacking. We investigated predictors associated with 30-day rehospitalization for medical and surgical adult patients separately. Patient data from 502 acute care hospitals with intensive care unit (ICU) facilities in Japan were retrospectively extracted from the Japanese Diagnosis Procedure Combination (DPC) database between April 2012 and February 2014. Factors associated with unplanned hospital readmission within 30 days of hospital discharge among medical and surgical ICU survivors were identified using multivariable logistic regression analysis. Of 486,651 ICU survivors, we identified 5583 unplanned hospital readmissions within 30 days of discharge following 147,423 medical hospitalizations (3.8% readmitted) and 11,142 unplanned readmissions after 339,228 surgical hospitalizations (3.3% readmitted). The majority of unplanned hospital readmissions, 60.9% of medical and 63.1% of surgical case readmissions, occurred within 15 days of discharge. For both medical and surgical patients, the Charlson comorbidity index score; category of primary diagnosis during the index admission (respiratory, gastrointestinal, and metabolic and renal); hospital length of stay; discharge to skilled nursing facilities; and having received a packed red blood cell transfusion, low-dose steroids, or renal replacement therapy were significantly associated with higher unplanned hospital readmission rates. From patient data extracted from a large Japanese national database, the 30-day unplanned hospital readmission rate after ICU stay was 3.4%. Further studies are required to improve readmission prediction models and to develop targeted interventions for high-risk patients.

  14. Ethnic variations in unplanned readmissions and excess length of hospital stay: a nationwide record-linked cohort study.

    Science.gov (United States)

    de Bruijne, Martine C; van Rosse, Floor; Uiters, Ellen; Droomers, Mariël; Suurmond, Jeanine; Stronks, Karien; Essink-Bot, Marie-Louise

    2013-12-01

    Studies in the USA have shown ethnic inequalities in quality of hospital care, but in Europe, this has never been analysed. We explored variations in indicators of quality of hospital care by ethnicity in the Netherlands. We analysed unplanned readmissions and excess length of stay (LOS) across ethnic groups in a large population of hospitalized patients over an 11-year period by linking information from the national hospital discharge register, the Dutch population register and socio-economic data. Data were analysed with stepwise logistic regression. Ethnic differences were most pronounced in older patients: all non-Western ethnic groups > 45 years had an increased risk for excess LOS compared with ethnic Dutch patients, with odds ratios (ORs) (adjusted for case mix) varying from 1.05 [95% confidence intervals (95% CI) 1.02-1.08] for other non-Western patients to 1.14 (95% CI 1.07-1.22) for Moroccan patients. The risk for unplanned readmission in patients >45 years was increased for Turkish (OR 1.24, 95% CI 1.18-1.30) and Surinamese patients (OR 1.11, 95% CI 1.07-1.16). These differences were explained partially, although not substantially, by differences in socio-economic status. We found significant ethnic variations in unplanned readmissions and excess LOS. These differences may be interpretable as shortcomings in the quality of hospital care delivered to ethnic minority patients, but exclusion of alternative explanations (such as differences in patient- and community-level factors, which are outside hospitals' control) requires further research. To quantify potential ethnic inequities in hospital care in Europe, we need empirical prospective cohort studies with solid quality outcomes such as adverse event rates.

  15. Risk factors for unplanned readmissions in older adult trauma patients in Washington State: a competing risk analysis.

    Science.gov (United States)

    Fawcett, Vanessa J; Flynn-O'Brien, Katherine T; Shorter, Zeynep; Davidson, Giana H; Bulger, Eileen; Rivara, Frederick P; Arbabi, Saman

    2015-03-01

    Hospital readmission is a significant contributor to increasing health care use related to caring for older trauma patients. This study was undertaken with the following aims: determine the proportion of older adult trauma patients who experience unplanned readmission, as well as risk factors for these readmissions and identify the most common readmission diagnoses among these patients. We conducted a retrospective cohort study of trauma patients age 55 years and older who survived their hospitalization at a statewide trauma center between 2009 and 2010. Linking 3 statewide databases, nonelective readmission rates were calculated for 30 days, 6 months, and 1 year after index discharge. Competing risk regression was used to determine risk factors for readmission and account for the competing risk of dying without first being readmitted. Subhazard ratios (SHR) are reported, indicating the relative risk of readmission by 30 days, 6 months, and 1 year. The cumulative readmission rates for the 14,536 participants were 7.9%, 18.9%, and 25.2% at 30 days, 6 months, and 1 year, respectively. In multivariable models, the strongest risk factors for readmission at 1 year (based on magnitude of SHR) were severe head injury (adjusted SHR = 1.47; 95% CI, 1.24-1.73) and disposition to a skilled nursing facility (SHR = 1.54; 95% CI, 1.39-1.71). The diagnoses most commonly associated with readmission were atrial fibrillation, anemia, and congestive heart failure. In this statewide study, unplanned readmissions after older adult trauma occurred frequently up to 1 year after discharge, particularly for patients who sustained severe head trauma and who could not be discharged home independently. Examining common readmission diagnoses might inform the development of interventions to prevent unplanned readmissions. Copyright © 2015 American College of Surgeons. All rights reserved.

  16. Power Estimation in Multivariate Analysis of Variance

    Directory of Open Access Journals (Sweden)

    Jean François Allaire

    2007-09-01

    Full Text Available Power is often overlooked in designing multivariate studies for the simple reason that it is believed to be too complicated. In this paper, it is shown that power estimation in multivariate analysis of variance (MANOVA can be approximated using a F distribution for the three popular statistics (Hotelling-Lawley trace, Pillai-Bartlett trace, Wilk`s likelihood ratio. Consequently, the same procedure, as in any statistical test, can be used: computation of the critical F value, computation of the noncentral parameter (as a function of the effect size and finally estimation of power using a noncentral F distribution. Various numerical examples are provided which help to understand and to apply the method. Problems related to post hoc power estimation are discussed.

  17. Analysis of Variance in Statistical Image Processing

    Science.gov (United States)

    Kurz, Ludwik; Hafed Benteftifa, M.

    1997-04-01

    A key problem in practical image processing is the detection of specific features in a noisy image. Analysis of variance (ANOVA) techniques can be very effective in such situations, and this book gives a detailed account of the use of ANOVA in statistical image processing. The book begins by describing the statistical representation of images in the various ANOVA models. The authors present a number of computationally efficient algorithms and techniques to deal with such problems as line, edge, and object detection, as well as image restoration and enhancement. By describing the basic principles of these techniques, and showing their use in specific situations, the book will facilitate the design of new algorithms for particular applications. It will be of great interest to graduate students and engineers in the field of image processing and pattern recognition.

  18. Variance Risk Premia on Stocks and Bonds

    DEFF Research Database (Denmark)

    Mueller, Philippe; Sabtchevsky, Petar; Vedolin, Andrea

    We study equity (EVRP) and Treasury variance risk premia (TVRP) jointly and document a number of findings: First, relative to their volatility, TVRP are comparable in magnitude to EVRP. Second, while there is mild positive co-movement between EVRP and TVRP unconditionally, time series estimates...... equity returns for horizons up to 6-months, long maturity TVRP contain robust information for long run equity returns. Finally, exploiting the dynamics of real and nominal Treasuries we document that short maturity break-even rates are a power determinant of the joint dynamics of EVRP, TVRP and their co-movement...... of correlation display distinct spikes in both directions and have been notably volatile since the financial crisis. Third $(i)$ short maturity TVRP predict excess returns on short maturity bonds; $(ii)$ long maturity TVRP and EVRP predict excess returns on long maturity bonds; and $(iii)$ while EVRP predict...

  19. The value of travel time variance

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Engelson, Leonid

    2011-01-01

    This paper considers the value of travel time variability under scheduling preferences that are defined in terms of linearly time varying utility rates associated with being at the origin and at the destination. The main result is a simple expression for the value of travel time variability...... that does not depend on the shape of the travel time distribution. The related measure of travel time variability is the variance of travel time. These conclusions apply equally to travellers who can freely choose departure time and to travellers who use a scheduled service with fixed headway. Depending...... on parameters, travellers may be risk averse or risk seeking and the value of travel time may increase or decrease in the mean travel time....

  20. Hybrid biasing approaches for global variance reduction

    International Nuclear Information System (INIS)

    Wu, Zeyun; Abdel-Khalik, Hany S.

    2013-01-01

    A new variant of Monte Carlo—deterministic (DT) hybrid variance reduction approach based on Gaussian process theory is presented for accelerating convergence of Monte Carlo simulation and compared with Forward-Weighted Consistent Adjoint Driven Importance Sampling (FW-CADIS) approach implemented in the SCALE package from Oak Ridge National Laboratory. The new approach, denoted the Gaussian process approach, treats the responses of interest as normally distributed random processes. The Gaussian process approach improves the selection of the weight windows of simulated particles by identifying a subspace that captures the dominant sources of statistical response variations. Like the FW-CADIS approach, the Gaussian process approach utilizes particle importance maps obtained from deterministic adjoint models to derive weight window biasing. In contrast to the FW-CADIS approach, the Gaussian process approach identifies the response correlations (via a covariance matrix) and employs them to reduce the computational overhead required for global variance reduction (GVR) purpose. The effective rank of the covariance matrix identifies the minimum number of uncorrelated pseudo responses, which are employed to bias simulated particles. Numerical experiments, serving as a proof of principle, are presented to compare the Gaussian process and FW-CADIS approaches in terms of the global reduction in standard deviation of the estimated responses. - Highlights: ► Hybrid Monte Carlo Deterministic Method based on Gaussian Process Model is introduced. ► Method employs deterministic model to calculate responses correlations. ► Method employs correlations to bias Monte Carlo transport. ► Method compared to FW-CADIS methodology in SCALE code. ► An order of magnitude speed up is achieved for a PWR core model.

  1. Predicting Unprotected Sex and Unplanned Pregnancy among Urban African-American Adolescent Girls Using the Theory of Gender and Power.

    Science.gov (United States)

    Rosenbaum, Janet E; Zenilman, Jonathan; Rose, Eve; Wingood, Gina; DiClemente, Ralph

    2016-06-01

    Reproductive coercion has been hypothesized as a cause of unprotected sex and unplanned pregnancies, but research has focused on a narrow set of potential sources of reproductive coercion. We identified and evaluated eight potential sources of reproductive coercion from the Theory of Gender and Power including economic inequality between adolescent girls and their boyfriends, cohabitation, and age differences. The sample comprised sexually active African-American female adolescents, ages 15-21. At baseline (n = 715), 6 months (n = 607), and 12 months (n = 605), participants completed a 40-min interview and were tested for semen Y-chromosome with polymerase chain reaction from a self-administered vaginal swab. We predicted unprotected sex and pregnancy using multivariate regression controlling for demographics, economic factors, relationship attributes, and intervention status using a Poisson working model. Factors associated with unprotected sex included cohabitation (incidence risk ratio (IRR) 1.48, 95 % confidence interval (1.22, 1.81)), physical abuse (IRR 1.55 (1.21, 2.00)), emotional abuse (IRR 1.31 (1.06, 1.63)), and having a boyfriend as a primary source of spending money (IRR 1.18 (1.00, 1.39)). Factors associated with unplanned pregnancy 6 months later included being at least 4 years younger than the boyfriend (IRR 1.68 (1.14, 2.49)) and cohabitation (2.19 (1.35, 3.56)). Among minors, cohabitation predicted even larger risks of unprotected sex (IRR 1.93 (1.23, 3.03)) and unplanned pregnancy (3.84 (1.47, 10.0)). Adolescent cohabitation is a marker for unprotected sex and unplanned pregnancy, especially among minors. Cohabitation may have stemmed from greater commitment, but the shortage of affordable housing in urban areas could induce women to stay in relationships for housing. Pregnancy prevention interventions should attempt to delay cohabitation until adulthood and help cohabiting adolescents to find affordable housing.

  2. Predicting risk of unplanned hospital readmission in survivors of critical illness: a population-level cohort study.

    Science.gov (United States)

    Lone, Nazir I; Lee, Robert; Salisbury, Lisa; Donaghy, Eddie; Ramsay, Pamela; Rattray, Janice; Walsh, Timothy S

    2018-04-05

    Intensive care unit (ICU) survivors experience high levels of morbidity after hospital discharge and are at high risk of unplanned hospital readmission. Identifying those at highest risk before hospital discharge may allow targeting of novel risk reduction strategies. We aimed to identify risk factors for unplanned 90-day readmission, develop a risk prediction model and assess its performance to screen for ICU survivors at highest readmission risk. Population cohort study linking registry data for patients discharged from general ICUs in Scotland (2005-2013). Independent risk factors for 90-day readmission and discriminant ability (c-index) of groups of variables were identified using multivariable logistic regression. Derivation and validation risk prediction models were constructed using a time-based split. Of 55 975 ICU survivors, 24.1% (95%CI 23.7% to 24.4%) had unplanned 90-day readmission. Pre-existing health factors were fair discriminators of readmission (c-index 0.63, 95% CI 0.63 to 0.64) but better than acute illness factors (0.60) or demographics (0.54). In a subgroup of those with no comorbidity, acute illness factors (0.62) were better discriminators than pre-existing health factors (0.56). Overall model performance and calibration in the validation cohort was fair (0.65, 95% CI 0.64 to 0.66) but did not perform sufficiently well as a screening tool, demonstrating high false-positive/false-negative rates at clinically relevant thresholds. Unplanned 90-day hospital readmission is common. Pre-existing illness indices are better predictors of readmission than acute illness factors. Identifying additional patient-centred drivers of readmission may improve risk prediction models. Improved understanding of risk factors that are amenable to intervention could improve the clinical and cost-effectiveness of post-ICU care and rehabilitation. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights

  3. Increased risk of peripartum perinatal mortality in unplanned births outside an institution: a retrospective population-based study.

    Science.gov (United States)

    Engjom, Hilde M; Morken, Nils-Halvdan; Høydahl, Even; Norheim, Ole F; Klungsøyr, Kari

    2017-08-01

    Births in midwife-led institutions may reduce the frequency of medical interventions and provide cost-effective care, while larger institutions offer medically and technically advanced obstetric care. Unplanned births outside an institution and intrapartum stillbirths have frequently been excluded in previous studies on adverse outcomes by place of birth. The objective of the study was to assess peripartum mortality by place of birth and travel time to obstetric institutions, with the hypothesis that centralization reduces institution availability but improves mortality. This was a national population-based retrospective cohort study of all births in Norway from 1999 to 2009 (n = 648,555) using data from the Medical Birth Registry of Norway and Statistics Norway and including births from 22 gestational weeks or birthweight ≥500 g. Main exposures were travel time to the nearest obstetric institution and place of birth. The main clinical outcome was peripartum mortality, defined as death during birth or within 24 hours. Intrauterine fetal deaths prior to start of labor were excluded from the primary outcome. A total of 1586 peripartum deaths were identified (2.5 per 1000 births). Unplanned birth outside an institution had a 3 times higher mortality (8.4 per 1000) than institutional births (2.4 per 1000), relative risk, 3.5 (95% confidence interval, 2.5-4.9) and contributed 2% (95% confidence interval, 1.2-3.0%) of the peripartum mortality at the population level. The risk of unplanned birth outside an institution increased from 0.5% to 3.3% and 4.5% with travel time 2 hours, respectively. In obstetric institutions the mortality rate at term ranged from 0.7 per 1000 to 0.9 per 1000. Comparable mortality rates in different obstetric institutions indicated well-functioning routines for referral. Unplanned birth outside an institution was associated with increased peripartum mortality and with long travel time to obstetric institutions. Structural determinants have

  4. Sigsearch: a new term for post hoc unplanned search for statistically significant relationships with the intent to create publishable findings.

    Science.gov (United States)

    Hashim, Muhammad Jawad

    2010-09-01

    Post-hoc secondary data analysis with no prespecified hypotheses has been discouraged by textbook authors and journal editors alike. Unfortunately no single term describes this phenomenon succinctly. I would like to coin the term "sigsearch" to define this practice and bring it within the teaching lexicon of statistics courses. Sigsearch would include any unplanned, post-hoc search for statistical significance using multiple comparisons of subgroups. It would also include data analysis with outcomes other than the prespecified primary outcome measure of a study as well as secondary data analyses of earlier research.

  5. Joint Adaptive Mean-Variance Regularization and Variance Stabilization of High Dimensional Data.

    Science.gov (United States)

    Dazard, Jean-Eudes; Rao, J Sunil

    2012-07-01

    The paper addresses a common problem in the analysis of high-dimensional high-throughput "omics" data, which is parameter estimation across multiple variables in a set of data where the number of variables is much larger than the sample size. Among the problems posed by this type of data are that variable-specific estimators of variances are not reliable and variable-wise tests statistics have low power, both due to a lack of degrees of freedom. In addition, it has been observed in this type of data that the variance increases as a function of the mean. We introduce a non-parametric adaptive regularization procedure that is innovative in that : (i) it employs a novel "similarity statistic"-based clustering technique to generate local-pooled or regularized shrinkage estimators of population parameters, (ii) the regularization is done jointly on population moments, benefiting from C. Stein's result on inadmissibility, which implies that usual sample variance estimator is improved by a shrinkage estimator using information contained in the sample mean. From these joint regularized shrinkage estimators, we derived regularized t-like statistics and show in simulation studies that they offer more statistical power in hypothesis testing than their standard sample counterparts, or regular common value-shrinkage estimators, or when the information contained in the sample mean is simply ignored. Finally, we show that these estimators feature interesting properties of variance stabilization and normalization that can be used for preprocessing high-dimensional multivariate data. The method is available as an R package, called 'MVR' ('Mean-Variance Regularization'), downloadable from the CRAN website.

  6. 76 FR 78698 - Proposed Revocation of Permanent Variances

    Science.gov (United States)

    2011-12-19

    ... Administration (``OSHA'' or ``the Agency'') granted permanent variances to 24 companies engaged in the... DEPARTMENT OF LABOR Occupational Safety and Health Administration [Docket No. OSHA-2011-0054] Proposed Revocation of Permanent Variances AGENCY: Occupational Safety and Health Administration (OSHA...

  7. variance components and genetic parameters for live weight

    African Journals Online (AJOL)

    admin

    Against this background the present study estimated the (co)variance .... Starting values for the (co)variance components of two-trait models were ..... Estimates of genetic parameters for weaning weight of beef accounting for direct-maternal.

  8. The Distribution of the Sample Minimum-Variance Frontier

    OpenAIRE

    Raymond Kan; Daniel R. Smith

    2008-01-01

    In this paper, we present a finite sample analysis of the sample minimum-variance frontier under the assumption that the returns are independent and multivariate normally distributed. We show that the sample minimum-variance frontier is a highly biased estimator of the population frontier, and we propose an improved estimator of the population frontier. In addition, we provide the exact distribution of the out-of-sample mean and variance of sample minimum-variance portfolios. This allows us t...

  9. Dynamics of Variance Risk Premia, Investors' Sentiment and Return Predictability

    DEFF Research Database (Denmark)

    Rombouts, Jerome V.K.; Stentoft, Lars; Violante, Francesco

    We develop a joint framework linking the physical variance and its risk neutral expectation implying variance risk premia that are persistent, appropriately reacting to changes in level and variability of the variance and naturally satisfying the sign constraint. Using option market data and real...... events and only marginally by the premium associated with normal price fluctuations....

  10. Analytical basis for evaluating the effect of unplanned interventions on the effectiveness of a human-robot system

    International Nuclear Information System (INIS)

    Shah, Julie A.; Saleh, Joseph H.; Hoffman, Jeffrey A.

    2008-01-01

    Increasing prevalence of human-robot systems in a variety of applications raises the question of how to design these systems to best leverage the capabilities of humans and robots. In this paper, we address the relationships between reliability, productivity, and risk to humans from human-robot systems operating in a hostile environment. Objectives for maximizing the effectiveness of a human-robot system are presented, which capture these coupled relationships, and reliability parameters are proposed to characterize unplanned interventions between a human and robot. The reliability metrics defined here take on an expanded meaning in which the underlying concept of failure in traditional reliability analysis is replaced by the notion of intervention. In the context of human-robotic systems, an intervention is not only driven by component failures, but includes many other factors that can make a robotic agent to request or a human agent to provide intervention, as we argue in this paper. The effect of unplanned interventions on the effectiveness of human-robot systems is then investigated analytically using traditional reliability analysis. Finally, we discuss the implications of these analytical trends on the design and evaluation of human-robot systems

  11. Collaborative survey of perinatal loss in planned and unplanned home births. Northern Region Perinatal Mortality Survey Coordinating Group.

    Science.gov (United States)

    1996-11-23

    To document the outcome of planned and unplanned births outside hospital. Confidential review of every pregnancy ending in stillbirth or neonatal death in which plans had been made for home delivery, irrespective of where delivery eventually occurred. The review was part of a sustained collaborative survey of all perinatal deaths. Northern Regional Health Authority area. All 558,691 registered births to women normally resident in the former Northern Regional Health Authority area during 1981-94. Perinatal death. The estimated perinatal mortality during 1981-94 among women booked for a home birth was 14 deaths in 2888 births. This was less than half that among all women in the region. Only three of the 14 women delivered outside hospital. Independent review suggested that two of the 14 deaths might have been averted by different management. Both births occurred in hospital, and in only one was management before admission of the mother judged inappropriate. Perinatal loss to the 64 women who booked for hospital delivery but delivered outside and to the 67 women who delivered outside hospital without ever making arrangements to receive professional care during labour accounted for the high perinatal mortality (134 deaths in 3466 deliveries) among all births outside hospital. The perinatal hazard associated with planned home birth in the few women who exercised this option (unplanned delivery outside hospital.

  12. Delayed Recognition of Deterioration of Patients in General Wards Is Mostly Caused by Human Related Monitoring Failures: A Root Cause Analysis of Unplanned ICU Admissions.

    Directory of Open Access Journals (Sweden)

    Louise S van Galen

    Full Text Available An unplanned ICU admission of an inpatient is a serious adverse event (SAE. So far, no in depth-study has been performed to systematically analyse the root causes of unplanned ICU-admissions. The primary aim of this study was to identify the healthcare worker-, organisational-, technical,- disease- and patient- related causes that contribute to acute unplanned ICU admissions from general wards using a Root-Cause Analysis Tool called PRISMA-medical. Although a Track and Trigger System (MEWS was introduced in our hospital a few years ago, it was implemented without a clear protocol. Therefore, the secondary aim was to assess the adherence to a Track and Trigger system to identify deterioration on general hospital wards in patients eventually transferred to the ICU.Retrospective observational study in 49 consecutive adult patients acutely admitted to the Intensive Care Unit from a general nursing ward. 1. PRISMA-analysis on root causes of unplanned ICU admissions 2. Assessment of protocol adherence to the early warning score system.Out of 49 cases, 156 root causes were identified. The most frequent root causes were healthcare worker related (46%, which were mainly failures in monitoring the patient. They were followed by disease-related (45%, patient-related causes (7, 5%, and organisational root causes (3%. In only 40% of the patients vital parameters were monitored as was instructed by the doctor. 477 vital parameter sets were found in the 48 hours before ICU admission, in only 1% a correct MEWS was explicitly documented in the record.This in-depth analysis demonstrates that almost half of the unplanned ICU admissions from the general ward had healthcare worker related root causes, mostly due to monitoring failures in clinically deteriorating patients. In order to reduce unplanned ICU admissions, improving the monitoring of patients is therefore warranted.

  13. Ten-Year Trends and Independent Risk Factors for Unplanned Readmission Following Elective Total Joint Arthroplasty at a Large Urban Academic Hospital.

    Science.gov (United States)

    Varacallo, Matthew A; Herzog, Leah; Toossi, Nader; Johanson, Norman A

    2017-06-01

    Total joint arthroplasty procedures continue to provide consistent, long-term success and high patient satisfaction scores. However, early unplanned readmission to the hospital imparts significant financial risks to individual institutions as we shift away from the traditional fee-for-service payment model. Using a combination of our hospital's administrative database and retrospective chart reviews, we report the 30-day and 90-day readmission rates and all causes of readmission following all unilateral, primary elective total hip and knee arthroplasty procedures at a large, urban, academic hospital from 2004 to 2013. In total, 1165 primary total hip (511) and knee (654) arthroplasty procedures were identified, and the 30-day and 90-day unplanned readmission rates were 4.6% and 7.3%, respectively. A multivariate regression model controlled for a variety of potential clinical and surgical confounders. Increasing body mass index levels, an American Society of Anesthesiologists score of ≥3, and discharge to an inpatient rehab facility each independently correlated with risk of both 30-day and 90-day unplanned readmission to our institution. Additionally, use of general anesthesia during the procedure independently correlated with risk of readmission at 30 days only, while congestive heart failure independently correlated with risk of 90-day unplanned readmission. Readmissions related directly to the surgical site accounted for 47% of the cases, and collectively totaled more than any single medical or clinical complication leading to unplanned readmission within the 90-day period. Increasing body mass index values, general anesthesia, an American Society of Anesthesiologists score of ≥3, and discharge to an inpatient rehab facility each were independent risk factors for early unplanned readmission. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Gene set analysis using variance component tests.

    Science.gov (United States)

    Huang, Yen-Tsung; Lin, Xihong

    2013-06-28

    Gene set analyses have become increasingly important in genomic research, as many complex diseases are contributed jointly by alterations of numerous genes. Genes often coordinate together as a functional repertoire, e.g., a biological pathway/network and are highly correlated. However, most of the existing gene set analysis methods do not fully account for the correlation among the genes. Here we propose to tackle this important feature of a gene set to improve statistical power in gene set analyses. We propose to model the effects of an independent variable, e.g., exposure/biological status (yes/no), on multiple gene expression values in a gene set using a multivariate linear regression model, where the correlation among the genes is explicitly modeled using a working covariance matrix. We develop TEGS (Test for the Effect of a Gene Set), a variance component test for the gene set effects by assuming a common distribution for regression coefficients in multivariate linear regression models, and calculate the p-values using permutation and a scaled chi-square approximation. We show using simulations that type I error is protected under different choices of working covariance matrices and power is improved as the working covariance approaches the true covariance. The global test is a special case of TEGS when correlation among genes in a gene set is ignored. Using both simulation data and a published diabetes dataset, we show that our test outperforms the commonly used approaches, the global test and gene set enrichment analysis (GSEA). We develop a gene set analyses method (TEGS) under the multivariate regression framework, which directly models the interdependence of the expression values in a gene set using a working covariance. TEGS outperforms two widely used methods, GSEA and global test in both simulation and a diabetes microarray data.

  15. What weekday? How acute? An analysis of reported planned and unplanned GP visits by older multi-morbid patients in the Patient Journey Record System database.

    Science.gov (United States)

    Surate Solaligue, David Emanuel; Hederman, Lucy; Martin, Carmel Mary

    2014-08-01

    Timely access to general practitioner (GP) care is a recognized strategy to address avoidable hospitalization. Little is known about patients seeking planned (decided ahead) and unplanned (decided on day) GP visits. The Patient Journey Record System (PaJR) provides a biopsychosocial real-time monitoring and support service to chronically ill and older people over 65 who may be at risk of an avoidable hospital admission. This study aims to describe reported profiles associated with planned and unplanned GP visits during the week in the PaJR database of regular outbound phone calls made by Care Guides to multi-morbid older patients. One hundred fifty consecutive patients with one or more chronic condition (including chronic obstructive pulmonary disease, heart/vascular disease, heart failure and/or diabetes), one or more hospital admission in previous year, and consecutively recruited from hospital discharge, out-of-hour care and GP practices comprised the study sample. Using a semistructured script, Care Guides telephoned the patients approximately every 3 week days, and entered call data into the PaJR database in 2011. The PaJR project identified and prompted unplanned visits according to its algorithms. Logistic regression modelling and descriptive statistics identified significant predictors of planned and unplanned visits and patterns of GP visits on weekdays reported in calls. In 5096 telephone calls, unplanned versus planned GP visits were predicted by change in health state, significant symptom concerns, poor self-rated health, bodily pain and concerns about caregiver or intimates. Calls not reporting visits had significantly fewer of these features. Planned visits were associated with general and medication concerns, reduced social participation and feeling down. Planned visits were highest on Monday and trended downwards to Fridays. Unplanned visits were reported at the same rate each weekday and more frequently when the interval between calls was ≥3 days

  16. Prevalence and determinants of unplanned pregnancy in HIV-positive and HIV-negative pregnant women in Cape Town, South Africa: a cross-sectional study.

    Science.gov (United States)

    Iyun, Victoria; Brittain, Kirsty; Phillips, Tamsin K; le Roux, Stanzi; McIntyre, James A; Zerbe, Allison; Petro, Greg; Abrams, Elaine J; Myer, Landon

    2018-04-03

    Prevention of unplanned pregnancy is a crucial aspect of preventing mother-to-child HIV transmission. There are few data investigating how HIV status and use of antiretroviral therapy (ART) may influence pregnancy planning in high HIV burden settings. Our objective was to examine the prevalence and determinants of unplanned pregnancy among HIV-positive and HIV-negative women in Cape Town, South Africa. Cross-sectional analysis. Single primary-level antenatal care clinic in Cape Town, South Africa. HIV-positive and HIV-negative pregnant women, booking for antenatal care from March 2013 to August 2015, were included. Unplanned pregnancy was measured at the first antenatal care visit using the London Measure of Unplanned Pregnancy (LMUP). Analyses examined LMUP scores across four groups of participants defined by their HIV status, awareness of their HIV status prior to the current pregnancy and/or whether they were using antiretroviral therapy (ART) prior to the current pregnancy. Among 2105 pregnant women (1512 HIV positive; 593 HIV negative), median age was 28 years, 43% were married/cohabiting and 20% were nulliparous. Levels of unplanned pregnancy were significantly higher in HIV-positive versus HIV-negative women (50% vs 33%, p<0.001); and highest in women who were known HIV positive but not on ART (53%). After adjusting for age, parity and marital status, unplanned pregnancy was most common among women newly diagnosed and women who were known HIV positive but not on ART (compared with HIV-negative women, adjusted OR (aOR): 1.43; 95% CI 1.05 to 1.94 and aOR: 1.57; 95% CI 1.13 to 2.15, respectively). Increased parity and younger age (<24 years) were also associated with unplanned pregnancy (aOR: 1.42; 95% CI 1.25 to 1.60 and aOR: 1.83; 95% CI 1.23 to 2.74, respectively). We observed high levels of unplanned pregnancy among HIV-positive women, particularly among those not on ART, suggesting ongoing missed opportunities for improved family planning and

  17. Regional sensitivity analysis using revised mean and variance ratio functions

    International Nuclear Information System (INIS)

    Wei, Pengfei; Lu, Zhenzhou; Ruan, Wenbin; Song, Jingwen

    2014-01-01

    The variance ratio function, derived from the contribution to sample variance (CSV) plot, is a regional sensitivity index for studying how much the output deviates from the original mean of model output when the distribution range of one input is reduced and to measure the contribution of different distribution ranges of each input to the variance of model output. In this paper, the revised mean and variance ratio functions are developed for quantifying the actual change of the model output mean and variance, respectively, when one reduces the range of one input. The connection between the revised variance ratio function and the original one is derived and discussed. It is shown that compared with the classical variance ratio function, the revised one is more suitable to the evaluation of model output variance due to reduced ranges of model inputs. A Monte Carlo procedure, which needs only a set of samples for implementing it, is developed for efficiently computing the revised mean and variance ratio functions. The revised mean and variance ratio functions are compared with the classical ones by using the Ishigami function. At last, they are applied to a planar 10-bar structure

  18. Factors influencing access to education, decision making, and receipt of preferred dialysis modality in unplanned dialysis start patients

    DEFF Research Database (Denmark)

    Machowska, Anna; Alscher, Mark Dominik; Vanga, Satyanarayana Reddy

    2016-01-01

    for patients receiving education, making a decision, and receiving their preferred modality choice in UPS patients following a UPS educational program (UPS-EP). Methods: The Offering Patients Therapy Options in Unplanned Start (OPTiONS) study examined the impact of the implementation of a specific UPS......-EP, including decision support tools and pathway improvement on dialysis modality choice. Linear regression models were used to examine the factors predicting three key steps: referral and receipt of UPS-EP, modality decision making, and actual delivery of preferred modality choice. A simple economic assessment...... was performed to examine the potential benefit of implementing UPS-EP in terms of dialysis costs. Results: The majority of UPS patients could receive UPS-EP (214/270 patients) and were able to make a decision (177/214), although not all patients received their preferred choice (159/177). Regression analysis...

  19. Estimating the encounter rate variance in distance sampling

    Science.gov (United States)

    Fewster, R.M.; Buckland, S.T.; Burnham, K.P.; Borchers, D.L.; Jupp, P.E.; Laake, J.L.; Thomas, L.

    2009-01-01

    The dominant source of variance in line transect sampling is usually the encounter rate variance. Systematic survey designs are often used to reduce the true variability among different realizations of the design, but estimating the variance is difficult and estimators typically approximate the variance by treating the design as a simple random sample of lines. We explore the properties of different encounter rate variance estimators under random and systematic designs. We show that a design-based variance estimator improves upon the model-based estimator of Buckland et al. (2001, Introduction to Distance Sampling. Oxford: Oxford University Press, p. 79) when transects are positioned at random. However, if populations exhibit strong spatial trends, both estimators can have substantial positive bias under systematic designs. We show that poststratification is effective in reducing this bias. ?? 2008, The International Biometric Society.

  20. MRI findings associated with microscopic residual tumor following unplanned excision of soft tissue sarcomas in the extremities

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lee; Chelala, Lydia; Jose, Jean; Subhawong, Ty K. [University of Miami Miller School of Medicine/Jackson Memorial Hospital, Department of Radiology, Miami, FL (United States); Pretell-Mazzini, Juan [University of Miami Miller School of Medicine, Department of Orthopaedic Surgery, Division of Musculoskeletal Oncology, Miami, FL (United States); Kerr, Darcy A. [University of Miami Miller School of Medicine, Department of Pathology, Miami, FL (United States); Yang, Xuan [University of Miami Miller School of Medicine, Department of Public Health Sciences, Miami, FL (United States)

    2018-02-15

    MRI is often used to determine the presence of residual disease following unplanned excisions (UPE) of soft tissue sarcomas (STS). We sought to identify MRI features associated with histologic evidence of residual disease after TBE. This was an IRB-approved retrospective review of 27 patients with R1-type UPE of STS over a 32-month period, with subsequent MRI and TBE. MRI studies were retrospectively evaluated to determine depth of tissue involvement, presence of nodular enhancement, and maximum length of soft tissue edema normalized to extremity size. MRI findings were correlated with histology from unplanned excision and TBE. Among the 21 subjects, there were 13 males and 8 females, mean age 58. Eighteen of 21 STS were grade 2 or 3. Deep compartments were involved in 5/21 cases. Original margins were positive in 17/21 UPE, with inadequate margin assessment in the remaining 4 cases. Residual tumor was present at TBE in 11/21 cases; it was found in 4/6 cases with nodular enhancement and 7/15 cases without nodular enhancement (sensitivity = 0.36; specificity = 0.80; PPV = 0.67; NPV = 0.53). Increased extent of soft tissue edema increased the likelihood of residual tumor at TBE (OR = 35.0; 95% CI = 1.6 to 752.7; p = 0.023). Nodular enhancement is neither sensitive nor specific in predicting residual microscopic tumor in TBE following UPE. Extensive soft tissue edema on MRI after UPE increases the likelihood of finding a residual microscopic tumor, justifying ample margins at TBE and consideration of adjuvant therapy. (orig.)

  1. Variance swap payoffs, risk premia and extreme market conditions

    DEFF Research Database (Denmark)

    Rombouts, Jeroen V.K.; Stentoft, Lars; Violante, Francesco

    This paper estimates the Variance Risk Premium (VRP) directly from synthetic variance swap payoffs. Since variance swap payoffs are highly volatile, we extract the VRP by using signal extraction techniques based on a state-space representation of our model in combination with a simple economic....... The latter variables and the VRP generate different return predictability on the major US indices. A factor model is proposed to extract a market VRP which turns out to be priced when considering Fama and French portfolios....

  2. Towards a mathematical foundation of minimum-variance theory

    Energy Technology Data Exchange (ETDEWEB)

    Feng Jianfeng [COGS, Sussex University, Brighton (United Kingdom); Zhang Kewei [SMS, Sussex University, Brighton (United Kingdom); Wei Gang [Mathematical Department, Baptist University, Hong Kong (China)

    2002-08-30

    The minimum-variance theory which accounts for arm and eye movements with noise signal inputs was proposed by Harris and Wolpert (1998 Nature 394 780-4). Here we present a detailed theoretical analysis of the theory and analytical solutions of the theory are obtained. Furthermore, we propose a new version of the minimum-variance theory, which is more realistic for a biological system. For the new version we show numerically that the variance is considerably reduced. (author)

  3. RR-Interval variance of electrocardiogram for atrial fibrillation detection

    Science.gov (United States)

    Nuryani, N.; Solikhah, M.; Nugoho, A. S.; Afdala, A.; Anzihory, E.

    2016-11-01

    Atrial fibrillation is a serious heart problem originated from the upper chamber of the heart. The common indication of atrial fibrillation is irregularity of R peak-to-R-peak time interval, which is shortly called RR interval. The irregularity could be represented using variance or spread of RR interval. This article presents a system to detect atrial fibrillation using variances. Using clinical data of patients with atrial fibrillation attack, it is shown that the variance of electrocardiographic RR interval are higher during atrial fibrillation, compared to the normal one. Utilizing a simple detection technique and variances of RR intervals, we find a good performance of atrial fibrillation detection.

  4. Multiperiod Mean-Variance Portfolio Optimization via Market Cloning

    Energy Technology Data Exchange (ETDEWEB)

    Ankirchner, Stefan, E-mail: ankirchner@hcm.uni-bonn.de [Rheinische Friedrich-Wilhelms-Universitaet Bonn, Institut fuer Angewandte Mathematik, Hausdorff Center for Mathematics (Germany); Dermoune, Azzouz, E-mail: Azzouz.Dermoune@math.univ-lille1.fr [Universite des Sciences et Technologies de Lille, Laboratoire Paul Painleve UMR CNRS 8524 (France)

    2011-08-15

    The problem of finding the mean variance optimal portfolio in a multiperiod model can not be solved directly by means of dynamic programming. In order to find a solution we therefore first introduce independent market clones having the same distributional properties as the original market, and we replace the portfolio mean and variance by their empirical counterparts. We then use dynamic programming to derive portfolios maximizing a weighted sum of the empirical mean and variance. By letting the number of market clones converge to infinity we are able to solve the original mean variance problem.

  5. Network Structure and Biased Variance Estimation in Respondent Driven Sampling.

    Science.gov (United States)

    Verdery, Ashton M; Mouw, Ted; Bauldry, Shawn; Mucha, Peter J

    2015-01-01

    This paper explores bias in the estimation of sampling variance in Respondent Driven Sampling (RDS). Prior methodological work on RDS has focused on its problematic assumptions and the biases and inefficiencies of its estimators of the population mean. Nonetheless, researchers have given only slight attention to the topic of estimating sampling variance in RDS, despite the importance of variance estimation for the construction of confidence intervals and hypothesis tests. In this paper, we show that the estimators of RDS sampling variance rely on a critical assumption that the network is First Order Markov (FOM) with respect to the dependent variable of interest. We demonstrate, through intuitive examples, mathematical generalizations, and computational experiments that current RDS variance estimators will always underestimate the population sampling variance of RDS in empirical networks that do not conform to the FOM assumption. Analysis of 215 observed university and school networks from Facebook and Add Health indicates that the FOM assumption is violated in every empirical network we analyze, and that these violations lead to substantially biased RDS estimators of sampling variance. We propose and test two alternative variance estimators that show some promise for reducing biases, but which also illustrate the limits of estimating sampling variance with only partial information on the underlying population social network.

  6. Multiperiod Mean-Variance Portfolio Optimization via Market Cloning

    International Nuclear Information System (INIS)

    Ankirchner, Stefan; Dermoune, Azzouz

    2011-01-01

    The problem of finding the mean variance optimal portfolio in a multiperiod model can not be solved directly by means of dynamic programming. In order to find a solution we therefore first introduce independent market clones having the same distributional properties as the original market, and we replace the portfolio mean and variance by their empirical counterparts. We then use dynamic programming to derive portfolios maximizing a weighted sum of the empirical mean and variance. By letting the number of market clones converge to infinity we are able to solve the original mean variance problem.

  7. Discrete and continuous time dynamic mean-variance analysis

    OpenAIRE

    Reiss, Ariane

    1999-01-01

    Contrary to static mean-variance analysis, very few papers have dealt with dynamic mean-variance analysis. Here, the mean-variance efficient self-financing portfolio strategy is derived for n risky assets in discrete and continuous time. In the discrete setting, the resulting portfolio is mean-variance efficient in a dynamic sense. It is shown that the optimal strategy for n risky assets may be dominated if the expected terminal wealth is constrained to exactly attain a certain goal instead o...

  8. Discrete time and continuous time dynamic mean-variance analysis

    OpenAIRE

    Reiss, Ariane

    1999-01-01

    Contrary to static mean-variance analysis, very few papers have dealt with dynamic mean-variance analysis. Here, the mean-variance efficient self-financing portfolio strategy is derived for n risky assets in discrete and continuous time. In the discrete setting, the resulting portfolio is mean-variance efficient in a dynamic sense. It is shown that the optimal strategy for n risky assets may be dominated if the expected terminal wealth is constrained to exactly attain a certain goal instead o...

  9. Unplanned Sexual Activity as a Consequence of Alcohol Use: A Prospective Study of Risk Perceptions and Alcohol Use among College Freshmen

    Science.gov (United States)

    Klein, William; Geaghan, Thomas; MacDonald, Tara

    2007-01-01

    Objective: The authors' goal was to show how risk perceptions regarding unplanned sexual activity following alcohol use are prospectively related to subsequent alcohol consumption. Participants: Undergraduate students (N = 380) completed questionnaires at 2 time points during their freshman year. Methods: In the middle of the academic year (T1),…

  10. Alaska Native and Rural Youths' Views of Sexual Health: A Focus Group Project on Sexually Transmitted Diseases, HIV/AIDS, and Unplanned Pregnancy

    Science.gov (United States)

    Leston, Jessica D.; Jessen, Cornelia M.; Simons, Brenna C.

    2012-01-01

    Background: The disparity in rates of sexually transmitted diseases (STDs), HIV/AIDS, and unplanned pregnancy between Alaska Native (AN) and non-AN populations, particularly among young adults and females, is significant and concerning. Focus groups were conducted to better understand the knowledge, attitudes, and beliefs of rural Alaska youth…

  11. Association between age at first sexual intercourse and knowledge, attitudes and practices regarding reproductive health and unplanned pregnancy: a cross-sectional study.

    Science.gov (United States)

    Shu, C; Fu, A; Lu, J; Yin, M; Chen, Y; Qin, T; Shang, X; Wang, X; Zhang, M; Xiong, C; Yin, P

    2016-06-01

    Age at first sexual intercourse (AFSI) is decreasing among adolescents in developed nations. An early sexual debut has been associated, to some extent, with multiple sexual partners, infrequent use of condoms, unplanned pregnancy, unsafe abortion, and sexually transmitted disease and human immunodeficiency virus infection. Unplanned pregnancy among adolescents has both physical and social adverse effects. In total, 78,400 self-administered anonymous questionnaires were distributed to college students in seven cities in China to determine the age at which Chinese college students first engage in sexual activity, and the association between AFSI and knowledge, attitudes and practices (KAP) regarding reproductive health and unplanned pregnancy. Approximately 10,164 students reported that they were sexually active, and most reported that they had engaged in sexual intercourse for the first time during college. The average AFSI was 20.14 [standard deviation (SD) 2.98] years, and the average AFSI by gender was 19.97 (SD 2.97) years for males and 20.41 (SD 2.97) years for females. The unplanned pregnancy rate among the participants was 34.03%. Participants lacked knowledge about contraception and reproductive health, although most believed that it is necessary to have this knowledge. Participants' attitudes towards premarital sex were varied. Factors that were found to be associated with unplanned pregnancy were AFSI, contraceptive methods used for first sexual act, and whether contraceptive methods were used for every sexual act. The college period is a key time for Chinese students in terms of becoming sexually active. As such, comprehensive and informative reproductive health education should be provided before and during the college period. Furthermore, reproductive health education should include appropriate sexual morality education and comprehensive sex education. Gender traits and needs should be considered in sex education. Copyright © 2016 The Royal Society

  12. ANALISIS PORTOFOLIO RESAMPLED EFFICIENT FRONTIER BERDASARKAN OPTIMASI MEAN-VARIANCE

    OpenAIRE

    Abdurakhman, Abdurakhman

    2008-01-01

    Keputusan alokasi asset yang tepat pada investasi portofolio dapat memaksimalkan keuntungan dan atau meminimalkan risiko. Metode yang sering dipakai dalam optimasi portofolio adalah metode Mean-Variance Markowitz. Dalam prakteknya, metode ini mempunyai kelemahan tidak terlalu stabil. Sedikit perubahan dalam estimasi parameter input menyebabkan perubahan besar pada komposisi portofolio. Untuk itu dikembangkan metode optimasi portofolio yang dapat mengatasi ketidakstabilan metode Mean-Variance ...

  13. Capturing option anomalies with a variance-dependent pricing kernel

    NARCIS (Netherlands)

    Christoffersen, P.; Heston, S.; Jacobs, K.

    2013-01-01

    We develop a GARCH option model with a variance premium by combining the Heston-Nandi (2000) dynamic with a new pricing kernel that nests Rubinstein (1976) and Brennan (1979). While the pricing kernel is monotonic in the stock return and in variance, its projection onto the stock return is

  14. Realized range-based estimation of integrated variance

    DEFF Research Database (Denmark)

    Christensen, Kim; Podolskij, Mark

    2007-01-01

    We provide a set of probabilistic laws for estimating the quadratic variation of continuous semimartingales with the realized range-based variance-a statistic that replaces every squared return of the realized variance with a normalized squared range. If the entire sample path of the process is a...

  15. Diagnostic checking in linear processes with infinit variance

    OpenAIRE

    Krämer, Walter; Runde, Ralf

    1998-01-01

    We consider empirical autocorrelations of residuals from infinite variance autoregressive processes. Unlike the finite-variance case, it emerges that the limiting distribution, after suitable normalization, is not always more concentrated around zero when residuals rather than true innovations are employed.

  16. Evaluation of Mean and Variance Integrals without Integration

    Science.gov (United States)

    Joarder, A. H.; Omar, M. H.

    2007-01-01

    The mean and variance of some continuous distributions, in particular the exponentially decreasing probability distribution and the normal distribution, are considered. Since they involve integration by parts, many students do not feel comfortable. In this note, a technique is demonstrated for deriving mean and variance through differential…

  17. Adjustment of heterogenous variances and a calving year effect in ...

    African Journals Online (AJOL)

    Data at the beginning and at the end of lactation period, have higher variances than tests in the middle of the lactation. Furthermore, first lactations have lower mean and variances compared to second and third lactations. This is a deviation from the basic assumptions required for the application of repeatability models.

  18. Direct encoding of orientation variance in the visual system.

    Science.gov (United States)

    Norman, Liam J; Heywood, Charles A; Kentridge, Robert W

    2015-01-01

    Our perception of regional irregularity, an example of which is orientation variance, seems effortless when we view two patches of texture that differ in this attribute. Little is understood, however, of how the visual system encodes a regional statistic like orientation variance, but there is some evidence to suggest that it is directly encoded by populations of neurons tuned broadly to high or low levels. The present study shows that selective adaptation to low or high levels of variance results in a perceptual aftereffect that shifts the perceived level of variance of a subsequently viewed texture in the direction away from that of the adapting stimulus (Experiments 1 and 2). Importantly, the effect is durable across changes in mean orientation, suggesting that the encoding of orientation variance is independent of global first moment orientation statistics (i.e., mean orientation). In Experiment 3 it was shown that the variance-specific aftereffect did not show signs of being encoded in a spatiotopic reference frame, similar to the equivalent aftereffect of adaptation to the first moment orientation statistic (the tilt aftereffect), which is represented in the primary visual cortex and exists only in retinotopic coordinates. Experiment 4 shows that a neuropsychological patient with damage to ventral areas of the cortex but spared intact early areas retains sensitivity to orientation variance. Together these results suggest that orientation variance is encoded directly by the visual system and possibly at an early cortical stage.

  19. Beyond the Mean: Sensitivities of the Variance of Population Growth.

    Science.gov (United States)

    Trotter, Meredith V; Krishna-Kumar, Siddharth; Tuljapurkar, Shripad

    2013-03-01

    Populations in variable environments are described by both a mean growth rate and a variance of stochastic population growth. Increasing variance will increase the width of confidence bounds around estimates of population size, growth, probability of and time to quasi-extinction. However, traditional sensitivity analyses of stochastic matrix models only consider the sensitivity of the mean growth rate. We derive an exact method for calculating the sensitivity of the variance in population growth to changes in demographic parameters. Sensitivities of the variance also allow a new sensitivity calculation for the cumulative probability of quasi-extinction. We apply this new analysis tool to an empirical dataset on at-risk polar bears to demonstrate its utility in conservation biology We find that in many cases a change in life history parameters will increase both the mean and variance of population growth of polar bears. This counterintuitive behaviour of the variance complicates predictions about overall population impacts of management interventions. Sensitivity calculations for cumulative extinction risk factor in changes to both mean and variance, providing a highly useful quantitative tool for conservation management. The mean stochastic growth rate and its sensitivities do not fully describe the dynamics of population growth. The use of variance sensitivities gives a more complete understanding of population dynamics and facilitates the calculation of new sensitivities for extinction processes.

  20. Genotypic-specific variance in Caenorhabditis elegans lifetime fecundity.

    Science.gov (United States)

    Diaz, S Anaid; Viney, Mark

    2014-06-01

    Organisms live in heterogeneous environments, so strategies that maximze fitness in such environments will evolve. Variation in traits is important because it is the raw material on which natural selection acts during evolution. Phenotypic variation is usually thought to be due to genetic variation and/or environmentally induced effects. Therefore, genetically identical individuals in a constant environment should have invariant traits. Clearly, genetically identical individuals do differ phenotypically, usually thought to be due to stochastic processes. It is now becoming clear, especially from studies of unicellular species, that phenotypic variance among genetically identical individuals in a constant environment can be genetically controlled and that therefore, in principle, this can be subject to selection. However, there has been little investigation of these phenomena in multicellular species. Here, we have studied the mean lifetime fecundity (thus a trait likely to be relevant to reproductive success), and variance in lifetime fecundity, in recently-wild isolates of the model nematode Caenorhabditis elegans. We found that these genotypes differed in their variance in lifetime fecundity: some had high variance in fecundity, others very low variance. We find that this variance in lifetime fecundity was negatively related to the mean lifetime fecundity of the lines, and that the variance of the lines was positively correlated between environments. We suggest that the variance in lifetime fecundity may be a bet-hedging strategy used by this species.

  1. On the Endogeneity of the Mean-Variance Efficient Frontier.

    Science.gov (United States)

    Somerville, R. A.; O'Connell, Paul G. J.

    2002-01-01

    Explains that the endogeneity of the efficient frontier in the mean-variance model of portfolio selection is commonly obscured in portfolio selection literature and in widely used textbooks. Demonstrates endogeneity and discusses the impact of parameter changes on the mean-variance efficient frontier and on the beta coefficients of individual…

  2. 42 CFR 456.522 - Content of request for variance.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 4 2010-10-01 2010-10-01 false Content of request for variance. 456.522 Section 456.522 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN... perform UR within the time requirements for which the variance is requested and its good faith efforts to...

  3. 29 CFR 1905.5 - Effect of variances.

    Science.gov (United States)

    2010-07-01

    ...-STEIGER OCCUPATIONAL SAFETY AND HEALTH ACT OF 1970 General § 1905.5 Effect of variances. All variances... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... concerning a proposed penalty or period of abatement is pending before the Occupational Safety and Health...

  4. 29 CFR 1904.38 - Variances from the recordkeeping rule.

    Science.gov (United States)

    2010-07-01

    ..., DEPARTMENT OF LABOR RECORDING AND REPORTING OCCUPATIONAL INJURIES AND ILLNESSES Other OSHA Injury and Illness... he or she finds appropriate. (iv) If the Assistant Secretary grants your variance petition, OSHA will... Secretary is reviewing your variance petition. (4) If I have already been cited by OSHA for not following...

  5. Gender Variance and Educational Psychology: Implications for Practice

    Science.gov (United States)

    Yavuz, Carrie

    2016-01-01

    The area of gender variance appears to be more visible in both the media and everyday life. Within educational psychology literature gender variance remains underrepresented. The positioning of educational psychologists working across the three levels of child and family, school or establishment and education authority/council, means that they are…

  6. Minimum Variance Portfolios in the Brazilian Equity Market

    Directory of Open Access Journals (Sweden)

    Alexandre Rubesam

    2013-03-01

    Full Text Available We investigate minimum variance portfolios in the Brazilian equity market using different methods to estimate the covariance matrix, from the simple model of using the sample covariance to multivariate GARCH models. We compare the performance of the minimum variance portfolios to those of the following benchmarks: (i the IBOVESPA equity index, (ii an equally-weighted portfolio, (iii the maximum Sharpe ratio portfolio and (iv the maximum growth portfolio. Our results show that the minimum variance portfolio has higher returns with lower risk compared to the benchmarks. We also consider long-short 130/30 minimum variance portfolios and obtain similar results. The minimum variance portfolio invests in relatively few stocks with low βs measured with respect to the IBOVESPA index, being easily replicable by individual and institutional investors alike.

  7. Unplanned pregnancy and subsequent psychological distress in partnered women: a cross-sectional study of the role of relationship quality and wider social support.

    Science.gov (United States)

    Barton, Katherine; Redshaw, Maggie; Quigley, Maria A; Carson, Claire

    2017-01-26

    Research into the impact of unintended pregnancy on the wellbeing of women tends to focus on pregnancies ending in either termination or lone motherhood. Unintended pregnancy is common in partnered women, but little is known about the association between unintended pregnancy and postpartum affective disorders, such as depression and anxiety in this group. Poor relationship quality and lack of social support are considered risk factors for psychological distress (PD). We examined the association between unplanned motherhood and subsequent PD in partnered women, for whom evidence is sparse, accounting for the role of relationship quality and social support. Data for 12,462 partnered mothers were drawn from the first survey of Millennium Cohort Study, completed at 9 months postpartum. Women reported whether their baby was planned, and how they felt when they discovered that they were pregnant. Pregnancy intention is categorised as "planned", "unplanned/happy", "unplanned/ambivalent" and "unplanned/unhappy". PD was assessed using the modified 9-item Rutter Malaise Inventory. Social support was measured by a composite score for perceived support, and a measure of actual support from friends and family. Relationship quality was assessed using a modified Golombok-Rust Inventory of Marital State. The effect of pregnancy intention on the odds of PD at 9 months was estimated, adjusting for potential confounding factors. All analyses were weighted for response and design effects. In total 32.8%(weighted) (4343/12462) of mothers reported an unplanned pregnancy: 23.3 wt% (3087) of mothers felt happy, 3.5 wt% (475) ambivalent, and 6.0 wt% (781) unhappy upon discovery. Unplanned pregnancy was associated with a significantly increased odds of PD compared to planned (OR 1.73 (95%CI: 1.53, 1.95)). This was more pronounced among women who reported negative or ambivalent feelings in early pregnancy (OR 2.72 (95%CI:2.17, 3.41) and 2.56 (95%CI:1.95, 3.34), respectively), than those

  8. Risk factors for unplanned and unwanted teenage pregnancies occurring over two years of follow-up among a cohort of young South African women.

    Science.gov (United States)

    Christofides, Nicola J; Jewkes, Rachel K; Dunkle, Kristin L; McCarty, Frances; Jama Shai, Nwabisa; Nduna, Mzikazi; Sterk, Claire

    2014-01-01

    Although teenage pregnancies in South Africa have declined, the short and longer term health and social consequences are a potential public health concern. This longitudinal study aimed to describe the range of risk and protective factors for incident unwanted and unplanned pregnancies occurring over 2 years of follow-up among a cohort of adolescent women in the Eastern Cape, South Africa. It also investigated the relationship between gender inequality and gender-based violence and subsequent unplanned and unwanted pregnancies among the cohort. Teenage girls, aged 15-18 years (n=19), who were volunteer participants in a cluster randomized controlled trial and who had data from at least one follow-up were included in this analysis. To assess risk and protective factors for incident unwanted or unplanned pregnancies, we constructed multivariate polytomous regression models adjusting for sampling clusters as latent variables. Covariates included age, having a pregnancy prior to baseline, education, time between interviews, study intervention arm, contraceptive use, experience of intimate partner violence, belief that the teenage girl and her boyfriend are mutual main partners, and socioeconomic status. Overall, 174 pregnancies occurred over the 2-year follow-up period. Beliefs about relationship control were not associated with unwanted and unplanned pregnancies, nor were experiences of forced first sex or coerced sex under the age of 15. Hormonal contraception was protective against unplanned pregnancies (OR 0.40; 95% CI 0.21-0.79); however, using condoms was not protective. Physical abuse (OR 1.69; 95% CI 1.05-2.72) was a risk factor for, and having a pregnancy prior to baseline was protective against an unwanted pregnancy (OR 0.25; 95% CI 0.07-0.80). Higher socioeconomic status was protective for both unplanned and unwanted pregnancies (OR 0.69; 95% CI 0.58-0.83 and OR 0.78; 95% CI 0.64-0.96). Believing that the teenage girl and her boyfriend were mutual main

  9. Risk factors for unplanned and unwanted teenage pregnancies occurring over two years of follow-up among a cohort of young South African women

    Directory of Open Access Journals (Sweden)

    Nicola J. Christofides

    2014-08-01

    Full Text Available Background: Although teenage pregnancies in South Africa have declined, the short and longer term health and social consequences are a potential public health concern. This longitudinal study aimed to describe the range of risk and protective factors for incident unwanted and unplanned pregnancies occurring over 2 years of follow-up among a cohort of adolescent women in the Eastern Cape, South Africa. It also investigated the relationship between gender inequality and gender-based violence and subsequent unplanned and unwanted pregnancies among the cohort. Objective: Teenage girls, aged 15–18 years (n=19, who were volunteer participants in a cluster randomized controlled trial and who had data from at least one follow-up were included in this analysis. To assess risk and protective factors for incident unwanted or unplanned pregnancies, we constructed multivariate polytomous regression models adjusting for sampling clusters as latent variables. Covariates included age, having a pregnancy prior to baseline, education, time between interviews, study intervention arm, contraceptive use, experience of intimate partner violence, belief that the teenage girl and her boyfriend are mutual main partners, and socioeconomic status. Results: Overall, 174 pregnancies occurred over the 2-year follow-up period. Beliefs about relationship control were not associated with unwanted and unplanned pregnancies, nor were experiences of forced first sex or coerced sex under the age of 15. Hormonal contraception was protective against unplanned pregnancies (OR 0.40; 95% CI 0.21–0.79; however, using condoms was not protective. Physical abuse (OR 1.69; 95% CI 1.05–2.72 was a risk factor for, and having a pregnancy prior to baseline was protective against an unwanted pregnancy (OR 0.25; 95% CI 0.07–0.80. Higher socioeconomic status was protective for both unplanned and unwanted pregnancies (OR 0.69; 95% CI 0.58–0.83 and OR 0.78; 95% CI 0.64–0.96. Believing

  10. Integrating mean and variance heterogeneities to identify differentially expressed genes.

    Science.gov (United States)

    Ouyang, Weiwei; An, Qiang; Zhao, Jinying; Qin, Huaizhen

    2016-12-06

    In functional genomics studies, tests on mean heterogeneity have been widely employed to identify differentially expressed genes with distinct mean expression levels under different experimental conditions. Variance heterogeneity (aka, the difference between condition-specific variances) of gene expression levels is simply neglected or calibrated for as an impediment. The mean heterogeneity in the expression level of a gene reflects one aspect of its distribution alteration; and variance heterogeneity induced by condition change may reflect another aspect. Change in condition may alter both mean and some higher-order characteristics of the distributions of expression levels of susceptible genes. In this report, we put forth a conception of mean-variance differentially expressed (MVDE) genes, whose expression means and variances are sensitive to the change in experimental condition. We mathematically proved the null independence of existent mean heterogeneity tests and variance heterogeneity tests. Based on the independence, we proposed an integrative mean-variance test (IMVT) to combine gene-wise mean heterogeneity and variance heterogeneity induced by condition change. The IMVT outperformed its competitors under comprehensive simulations of normality and Laplace settings. For moderate samples, the IMVT well controlled type I error rates, and so did existent mean heterogeneity test (i.e., the Welch t test (WT), the moderated Welch t test (MWT)) and the procedure of separate tests on mean and variance heterogeneities (SMVT), but the likelihood ratio test (LRT) severely inflated type I error rates. In presence of variance heterogeneity, the IMVT appeared noticeably more powerful than all the valid mean heterogeneity tests. Application to the gene profiles of peripheral circulating B raised solid evidence of informative variance heterogeneity. After adjusting for background data structure, the IMVT replicated previous discoveries and identified novel experiment

  11. Factors influencing access to education, decision making, and receipt of preferred dialysis modality in unplanned dialysis start patients.

    Science.gov (United States)

    Machowska, Anna; Alscher, Mark Dominik; Reddy Vanga, Satyanarayana; Koch, Michael; Aarup, Michael; Qureshi, Abdul Rashid; Lindholm, Bengt; Rutherford, Peter A

    2016-01-01

    Unplanned dialysis start (UPS) leads to worse clinical outcomes than planned start, and only a minority of patients ever receive education on this topic and are able to make a modality choice, particularly for home dialysis. This study aimed to determine the predictive factors for patients receiving education, making a decision, and receiving their preferred modality choice in UPS patients following a UPS educational program (UPS-EP). The Offering Patients Therapy Options in Unplanned Start (OPTiONS) study examined the impact of the implementation of a specific UPS-EP, including decision support tools and pathway improvement on dialysis modality choice. Linear regression models were used to examine the factors predicting three key steps: referral and receipt of UPS-EP, modality decision making, and actual delivery of preferred modality choice. A simple economic assessment was performed to examine the potential benefit of implementing UPS-EP in terms of dialysis costs. The majority of UPS patients could receive UPS-EP (214/270 patients) and were able to make a decision (177/214), although not all patients received their preferred choice (159/177). Regression analysis demonstrated that the initial dialysis modality was a predictive factor for referral and receipt of UPS-EP and modality decision making. In contrast, age was a predictor for referral and receipt of UPS-EP only, and comorbidity was not a predictor for any step, except for myocardial infarction, which was a weak predictor for lower likelihood of receiving preferred modality. Country practices predicted UPS-EP receipt and decision making. Economic analysis demonstrated the potential benefit of UPS-EP implementation because dialysis modality costs were associated with modality distribution driven by patient preference. Education and decision support can allow UPS patients to understand their options and choose dialysis modality, and attention needs to be focused on ensuring equity of access to educational

  12. High incidence of unplanned pregnancy after antiretroviral therapy initiation: findings from a prospective cohort study in South Africa.

    Directory of Open Access Journals (Sweden)

    Sheree R Schwartz

    Full Text Available Increased fertility rates in HIV-infected women receiving antiretroviral therapy (ART have been attributed to improved immunological function; it is unknown to what extent the rise in pregnancy rates is due to unintended pregnancies.Non-pregnant women ages 18-35 from four public-sector ART clinics in Johannesburg, South Africa, were enrolled into a prospective cohort and followed from August 2009-March 2011. Fertility intentions, contraception and pregnancy status were measured longitudinally at participants' routine ART clinic visits.Of the 850 women enrolled, 822 (97% had at least one follow-up visit and contributed 745.2 person-years (PY at-risk for incident pregnancy. Overall, 170 pregnancies were detected in 161 women (incidence rate [IR]: 21.6/100 PY [95% confidence interval (CI: 18.5-25.2]. Of the 170 pregnancies, 105 (62% were unplanned. Unmet need for contraception was 50% higher in women initiating ART in the past year as compared to women on ART>1 year (prevalence ratio 1.5 [95% CI: 1.1-2.0]; by two years post-ART initiation, nearly one quarter of women had at least one unplanned pregnancy. Cumulative incidence of pregnancy was equally high among recent ART initiators and ART experienced participants: 23.9% [95% CI: 16.4-34.1], 15.9% [12.0-20.8], and 21.0% [16.8-26.1] for women on ART 0-1 yr, >1 yr-2 yrs, and >2 yrs respectively (log-rank, p = 0.54. Eight hormonal contraceptive failures were detected [IR: 4.4 [95% CI: 2.2-8.9], 7/8 among women using injectable methods. Overall 47% (80/170 of pregnancies were not carried to term.Rates of unintended pregnancies among women on ART are high, including women recently initiating ART with lower CD4 counts and higher viral loads. A substantial burden of pregnancy loss was observed. Integration of contraceptive services and counselling into ART care is necessary to reduce maternal and child health risks related to mistimed and unwanted pregnancies. Further research into injectable

  13. Comparing estimates of genetic variance across different relationship models.

    Science.gov (United States)

    Legarra, Andres

    2016-02-01

    Use of relationships between individuals to estimate genetic variances and heritabilities via mixed models is standard practice in human, plant and livestock genetics. Different models or information for relationships may give different estimates of genetic variances. However, comparing these estimates across different relationship models is not straightforward as the implied base populations differ between relationship models. In this work, I present a method to compare estimates of variance components across different relationship models. I suggest referring genetic variances obtained using different relationship models to the same reference population, usually a set of individuals in the population. Expected genetic variance of this population is the estimated variance component from the mixed model times a statistic, Dk, which is the average self-relationship minus the average (self- and across-) relationship. For most typical models of relationships, Dk is close to 1. However, this is not true for very deep pedigrees, for identity-by-state relationships, or for non-parametric kernels, which tend to overestimate the genetic variance and the heritability. Using mice data, I show that heritabilities from identity-by-state and kernel-based relationships are overestimated. Weighting these estimates by Dk scales them to a base comparable to genomic or pedigree relationships, avoiding wrong comparisons, for instance, "missing heritabilities". Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Risk factors for unplanned readmission within 30 days after pediatric neurosurgery: a nationwide analysis of 9799 procedures from the American College of Surgeons National Surgical Quality Improvement Program

    Science.gov (United States)

    Sherrod, Brandon A.; Johnston, James M.; Rocque, Brandon G.

    2017-01-01

    Objective Readmission rate is increasingly used as a quality outcome measure after surgery. The purpose of this study was to establish, using a national database, the baseline readmission rates and risk factors for readmission after pediatric neurosurgical procedures. Methods The American College of Surgeons National Surgical Quality Improvement Program–Pediatric database was queried for pediatric patients treated by a neurosurgeon from 2012 to 2013. Procedures were categorized by current procedural terminology code. Patient demographics, comorbidities, preoperative laboratory values, operative variables, and postoperative complications were analyzed via univariate and multivariate techniques to find associations with unplanned readmission within 30 days of the primary procedure. Results A total of 9799 cases met the inclusion criteria, 1098 (11.2%) of which had an unplanned readmission within 30 days. Readmission occurred 14.0 ± 7.7 days postoperatively (mean ± standard deviation). The 4 procedures with the highest unplanned readmission rates were CSF shunt revision (17.3%), repair of myelomeningocele > 5 cm in diameter (15.4%), CSF shunt creation (14.1%), and craniectomy for infratentorial tumor excision (13.9%). Spine (6.5%), craniotomy for craniosynostosis (2.1%), and skin lesion (1.0%) procedures had the lowest unplanned readmission rates. On multivariate regression analysis, the odds of readmission were greatest in patients experiencing postoperative surgical site infection (SSI; deep, organ/space, superficial SSI and wound disruption: OR > 12 and p readmission risk. Independent patient risk factors for unplanned readmission included Native American race (OR 2.363, p = 0.019), steroid use > 10 days (OR 1.411, p = 0.010), oxygen supplementation (OR 1.645, p = 0.010), nutritional support (OR 1.403, p = 0.009), seizure disorder (OR 1.250, p = 0.021), and longer operative time (per hour increase, OR 1.059, p = 0.014). Conclusions This study may aid in

  15. Variance computations for functional of absolute risk estimates.

    Science.gov (United States)

    Pfeiffer, R M; Petracci, E

    2011-07-01

    We present a simple influence function based approach to compute the variances of estimates of absolute risk and functions of absolute risk. We apply this approach to criteria that assess the impact of changes in the risk factor distribution on absolute risk for an individual and at the population level. As an illustration we use an absolute risk prediction model for breast cancer that includes modifiable risk factors in addition to standard breast cancer risk factors. Influence function based variance estimates for absolute risk and the criteria are compared to bootstrap variance estimates.

  16. Estimating High-Frequency Based (Co-) Variances: A Unified Approach

    DEFF Research Database (Denmark)

    Voev, Valeri; Nolte, Ingmar

    We propose a unified framework for estimating integrated variances and covariances based on simple OLS regressions, allowing for a general market microstructure noise specification. We show that our estimators can outperform, in terms of the root mean squared error criterion, the most recent...... and commonly applied estimators, such as the realized kernels of Barndorff-Nielsen, Hansen, Lunde & Shephard (2006), the two-scales realized variance of Zhang, Mykland & Aït-Sahalia (2005), the Hayashi & Yoshida (2005) covariance estimator, and the realized variance and covariance with the optimal sampling...

  17. Meta-analysis of SNPs involved in variance heterogeneity using Levene's test for equal variances

    Science.gov (United States)

    Deng, Wei Q; Asma, Senay; Paré, Guillaume

    2014-01-01

    Meta-analysis is a commonly used approach to increase the sample size for genome-wide association searches when individual studies are otherwise underpowered. Here, we present a meta-analysis procedure to estimate the heterogeneity of the quantitative trait variance attributable to genetic variants using Levene's test without needing to exchange individual-level data. The meta-analysis of Levene's test offers the opportunity to combine the considerable sample size of a genome-wide meta-analysis to identify the genetic basis of phenotypic variability and to prioritize single-nucleotide polymorphisms (SNPs) for gene–gene and gene–environment interactions. The use of Levene's test has several advantages, including robustness to departure from the normality assumption, freedom from the influence of the main effects of SNPs, and no assumption of an additive genetic model. We conducted a meta-analysis of the log-transformed body mass index of 5892 individuals and identified a variant with a highly suggestive Levene's test P-value of 4.28E-06 near the NEGR1 locus known to be associated with extreme obesity. PMID:23921533

  18. Impact of Unplanned Care Interruption on CD4 Response Early After ART Initiation in a Nigerian Cohort.

    Science.gov (United States)

    Ahonkhai, Aimalohi A; Adeola, Juliet; Banigbe, Bolanle; Onwuatuelo, Ifeyinwa; Adegoke, Abdulkabir B; Bassett, Ingrid V; Losina, Elena; Freedberg, Kenneth A; Okonkwo, Prosper; Regan, Susan

    The authors conducted a retrospective cohort study of unplanned care interruption (UCI) among adults initiating antiretroviral therapy (ART) from 2009 to 2011 in a Nigerian clinic. The authors used repeated measures regression to model the impact of UCI on CD4 count upon return to care and rate of CD4 change on ART. Among 2496 patients, 83% had 0, 15% had 1, and 2% had ≥2 UCIs. Mean baseline CD4 for those with 0, 1, or ≥2 UCIs was 228/cells/mm 3 , 355/cells/mm 3 , and 392/cells/mm 3 ( P ART, patients with 0 UCI gained 10 cells/µL/mo (95% CI: 7-4). Those with 1 and ≥2 UCIs lost 2 and 5 cells/µL/mo (95% CI: -18 to 13 and -26 to 16). Patients with UCI did not recover from early CD4 losses associated with UCI. Preventing UCI is critical to maximize benefits of ART.

  19. Psychometric properties of the Dutch version of the London Measure of Unplanned Pregnancy in women with pregnancies ending in birth.

    Science.gov (United States)

    Goossens, Joline; Verhaeghe, Sofie; Van Hecke, Ann; Barrett, Geraldine; Delbaere, Ilse; Beeckman, Dimitri

    2018-01-01

    To evaluate the psychometric properties of the Dutch version of the London Measure of Unplanned Pregnancy in women with pregnancies ending in birth. A two-phase psychometric evaluation design was set-up. Phase I comprised the translation from English into Dutch and pretesting with 6 women using cognitive interviews. In phase II, the reliability and validity of the Dutch version of the LMUP was assessed in 517 women giving birth recently. Reliability (internal consistency) was assessed using Cronbach's alpha, inter-item correlations, and corrected item-total correlations. Construct validity was assessed using principal components analysis and hypothesis testing. Exploratory Mokken scale analysis was carried out. 517 women aged 15-45 completed the Dutch version of the LMUP. Reliability testing showed acceptable internal consistency (alpha = 0.74, positive inter-item correlations between all items, all corrected item-total correlations >0.20). Validity testing confirmed the unidimensional structure of the scale and all hypotheses were confirmed. The overall Loevinger's H coefficient was 0.57, representing a 'strong' scale. The Dutch version of the LMUP is a reliable and valid measure that can be used in the Dutch-speaking population in Belgium to assess pregnancy planning. Future research is necessary to assess the stability of the Dutch version of the LMUP, and to evaluate its psychometric properties in women with abortions.

  20. Big Data-Based Approach to Detect, Locate, and Enhance the Stability of an Unplanned Microgrid Islanding

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Huaiguang; Li, Yan; Zhang, Yingchen; Zhang, Jun Jason; Gao, David Wenzhong; Muljadi, Eduard; Gu, Yi

    2017-10-01

    In this paper, a big data-based approach is proposed for the security improvement of an unplanned microgrid islanding (UMI). The proposed approach contains two major steps: the first step is big data analysis of wide-area monitoring to detect a UMI and locate it; the second step is particle swarm optimization (PSO)-based stability enhancement for the UMI. First, an optimal synchrophasor measurement device selection (OSMDS) and matching pursuit decomposition (MPD)-based spatial-temporal analysis approach is proposed to significantly reduce the volume of data while keeping appropriate information from the synchrophasor measurements. Second, a random forest-based ensemble learning approach is trained to detect the UMI. When combined with grid topology, the UMI can be located. Then the stability problem of the UMI is formulated as an optimization problem and the PSO is used to find the optimal operational parameters of the UMI. An eigenvalue-based multiobjective function is proposed, which aims to improve the damping and dynamic characteristics of the UMI. Finally, the simulation results demonstrate the effectiveness and robustness of the proposed approach.

  1. Comparison of variance estimators for metaanalysis of instrumental variable estimates

    NARCIS (Netherlands)

    Schmidt, A. F.; Hingorani, A. D.; Jefferis, B. J.; White, J.; Groenwold, R. H H; Dudbridge, F.; Ben-Shlomo, Y.; Chaturvedi, N.; Engmann, J.; Hughes, A.; Humphries, S.; Hypponen, E.; Kivimaki, M.; Kuh, D.; Kumari, M.; Menon, U.; Morris, R.; Power, C.; Price, J.; Wannamethee, G.; Whincup, P.

    2016-01-01

    Background: Mendelian randomization studies perform instrumental variable (IV) analysis using genetic IVs. Results of individual Mendelian randomization studies can be pooled through meta-analysis. We explored how different variance estimators influence the meta-analysed IV estimate. Methods: Two

  2. Capturing Option Anomalies with a Variance-Dependent Pricing Kernel

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Heston, Steven; Jacobs, Kris

    2013-01-01

    We develop a GARCH option model with a new pricing kernel allowing for a variance premium. While the pricing kernel is monotonic in the stock return and in variance, its projection onto the stock return is nonmonotonic. A negative variance premium makes it U shaped. We present new semiparametric...... evidence to confirm this U-shaped relationship between the risk-neutral and physical probability densities. The new pricing kernel substantially improves our ability to reconcile the time-series properties of stock returns with the cross-section of option prices. It provides a unified explanation...... for the implied volatility puzzle, the overreaction of long-term options to changes in short-term variance, and the fat tails of the risk-neutral return distribution relative to the physical distribution....

  3. Phenotypic variance explained by local ancestry in admixed African Americans.

    Science.gov (United States)

    Shriner, Daniel; Bentley, Amy R; Doumatey, Ayo P; Chen, Guanjie; Zhou, Jie; Adeyemo, Adebowale; Rotimi, Charles N

    2015-01-01

    We surveyed 26 quantitative traits and disease outcomes to understand the proportion of phenotypic variance explained by local ancestry in admixed African Americans. After inferring local ancestry as the number of African-ancestry chromosomes at hundreds of thousands of genotyped loci across all autosomes, we used a linear mixed effects model to estimate the variance explained by local ancestry in two large independent samples of unrelated African Americans. We found that local ancestry at major and polygenic effect genes can explain up to 20 and 8% of phenotypic variance, respectively. These findings provide evidence that most but not all additive genetic variance is explained by genetic markers undifferentiated by ancestry. These results also inform the proportion of health disparities due to genetic risk factors and the magnitude of error in association studies not controlling for local ancestry.

  4. Allowable variance set on left ventricular function parameter

    International Nuclear Information System (INIS)

    Zhou Li'na; Qi Zhongzhi; Zeng Yu; Ou Xiaohong; Li Lin

    2010-01-01

    Purpose: To evaluate the influence of allowable Variance settings on left ventricular function parameter of the arrhythmia patients during gated myocardial perfusion imaging. Method: 42 patients with evident arrhythmia underwent myocardial perfusion SPECT, 3 different allowable variance with 20%, 60%, 100% would be set before acquisition for every patients,and they will be acquired simultaneously. After reconstruction by Astonish, end-diastole volume(EDV) and end-systolic volume (ESV) and left ventricular ejection fraction (LVEF) would be computed with Quantitative Gated SPECT(QGS). Using SPSS software EDV, ESV, EF values of analysis of variance. Result: there is no statistical difference between three groups. Conclusion: arrhythmia patients undergo Gated myocardial perfusion imaging, Allowable Variance settings on EDV, ESV, EF value does not have a statistical meaning. (authors)

  5. Host nutrition alters the variance in parasite transmission potential.

    Science.gov (United States)

    Vale, Pedro F; Choisy, Marc; Little, Tom J

    2013-04-23

    The environmental conditions experienced by hosts are known to affect their mean parasite transmission potential. How different conditions may affect the variance of transmission potential has received less attention, but is an important question for disease management, especially if specific ecological contexts are more likely to foster a few extremely infectious hosts. Using the obligate-killing bacterium Pasteuria ramosa and its crustacean host Daphnia magna, we analysed how host nutrition affected the variance of individual parasite loads, and, therefore, transmission potential. Under low food, individual parasite loads showed similar mean and variance, following a Poisson distribution. By contrast, among well-nourished hosts, parasite loads were right-skewed and overdispersed, following a negative binomial distribution. Abundant food may, therefore, yield individuals causing potentially more transmission than the population average. Measuring both the mean and variance of individual parasite loads in controlled experimental infections may offer a useful way of revealing risk factors for potential highly infectious hosts.

  6. Minimum variance Monte Carlo importance sampling with parametric dependence

    International Nuclear Information System (INIS)

    Ragheb, M.M.H.; Halton, J.; Maynard, C.W.

    1981-01-01

    An approach for Monte Carlo Importance Sampling with parametric dependence is proposed. It depends upon obtaining by proper weighting over a single stage the overall functional dependence of the variance on the importance function parameter over a broad range of its values. Results corresponding to minimum variance are adapted and other results rejected. Numerical calculation for the estimation of intergrals are compared to Crude Monte Carlo. Results explain the occurrences of the effective biases (even though the theoretical bias is zero) and infinite variances which arise in calculations involving severe biasing and a moderate number of historis. Extension to particle transport applications is briefly discussed. The approach constitutes an extension of a theory on the application of Monte Carlo for the calculation of functional dependences introduced by Frolov and Chentsov to biasing, or importance sample calculations; and is a generalization which avoids nonconvergence to the optimal values in some cases of a multistage method for variance reduction introduced by Spanier. (orig.) [de

  7. Advanced methods of analysis variance on scenarios of nuclear prospective

    International Nuclear Information System (INIS)

    Blazquez, J.; Montalvo, C.; Balbas, M.; Garcia-Berrocal, A.

    2011-01-01

    Traditional techniques of propagation of variance are not very reliable, because there are uncertainties of 100% relative value, for this so use less conventional methods, such as Beta distribution, Fuzzy Logic and the Monte Carlo Method.

  8. Some variance reduction methods for numerical stochastic homogenization.

    Science.gov (United States)

    Blanc, X; Le Bris, C; Legoll, F

    2016-04-28

    We give an overview of a series of recent studies devoted to variance reduction techniques for numerical stochastic homogenization. Numerical homogenization requires that a set of problems is solved at the microscale, the so-called corrector problems. In a random environment, these problems are stochastic and therefore need to be repeatedly solved, for several configurations of the medium considered. An empirical average over all configurations is then performed using the Monte Carlo approach, so as to approximate the effective coefficients necessary to determine the macroscopic behaviour. Variance severely affects the accuracy and the cost of such computations. Variance reduction approaches, borrowed from other contexts in the engineering sciences, can be useful. Some of these variance reduction techniques are presented, studied and tested here. © 2016 The Author(s).

  9. Heritability, variance components and genetic advance of some ...

    African Journals Online (AJOL)

    Heritability, variance components and genetic advance of some yield and yield related traits in Ethiopian ... African Journal of Biotechnology ... randomized complete block design at Adet Agricultural Research Station in 2008 cropping season.

  10. Variance Function Partially Linear Single-Index Models1.

    Science.gov (United States)

    Lian, Heng; Liang, Hua; Carroll, Raymond J

    2015-01-01

    We consider heteroscedastic regression models where the mean function is a partially linear single index model and the variance function depends upon a generalized partially linear single index model. We do not insist that the variance function depend only upon the mean function, as happens in the classical generalized partially linear single index model. We develop efficient and practical estimation methods for the variance function and for the mean function. Asymptotic theory for the parametric and nonparametric parts of the model is developed. Simulations illustrate the results. An empirical example involving ozone levels is used to further illustrate the results, and is shown to be a case where the variance function does not depend upon the mean function.

  11. Variance estimation in the analysis of microarray data

    KAUST Repository

    Wang, Yuedong; Ma, Yanyuan; Carroll, Raymond J.

    2009-01-01

    Microarrays are one of the most widely used high throughput technologies. One of the main problems in the area is that conventional estimates of the variances that are required in the t-statistic and other statistics are unreliable owing

  12. Volatility and variance swaps : A comparison of quantitative models to calculate the fair volatility and variance strike

    OpenAIRE

    Röring, Johan

    2017-01-01

    Volatility is a common risk measure in the field of finance that describes the magnitude of an asset’s up and down movement. From only being a risk measure, volatility has become an asset class of its own and volatility derivatives enable traders to get an isolated exposure to an asset’s volatility. Two kinds of volatility derivatives are volatility swaps and variance swaps. The problem with volatility swaps and variance swaps is that they require estimations of the future variance and volati...

  13. ASYMMETRY OF MARKET RETURNS AND THE MEAN VARIANCE FRONTIER

    OpenAIRE

    SENGUPTA, Jati K.; PARK, Hyung S.

    1994-01-01

    The hypothesis that the skewness and asymmetry have no significant impact on the mean variance frontier is found to be strongly violated by monthly U.S. data over the period January 1965 through December 1974. This result raises serious doubts whether the common market portifolios such as SP 500, value weighted and equal weighted returns can serve as suitable proxies for meanvariance efficient portfolios in the CAPM framework. A new test for assessing the impact of skewness on the variance fr...

  14. Towards the ultimate variance-conserving convection scheme

    International Nuclear Information System (INIS)

    Os, J.J.A.M. van; Uittenbogaard, R.E.

    2004-01-01

    In the past various arguments have been used for applying kinetic energy-conserving advection schemes in numerical simulations of incompressible fluid flows. One argument is obeying the programmed dissipation by viscous stresses or by sub-grid stresses in Direct Numerical Simulation and Large Eddy Simulation, see e.g. [Phys. Fluids A 3 (7) (1991) 1766]. Another argument is that, according to e.g. [J. Comput. Phys. 6 (1970) 392; 1 (1966) 119], energy-conserving convection schemes are more stable i.e. by prohibiting a spurious blow-up of volume-integrated energy in a closed volume without external energy sources. In the above-mentioned references it is stated that nonlinear instability is due to spatial truncation rather than to time truncation and therefore these papers are mainly concerned with the spatial integration. In this paper we demonstrate that discretized temporal integration of a spatially variance-conserving convection scheme can induce non-energy conserving solutions. In this paper the conservation of the variance of a scalar property is taken as a simple model for the conservation of kinetic energy. In addition, the derivation and testing of a variance-conserving scheme allows for a clear definition of kinetic energy-conserving advection schemes for solving the Navier-Stokes equations. Consequently, we first derive and test a strictly variance-conserving space-time discretization for the convection term in the convection-diffusion equation. Our starting point is the variance-conserving spatial discretization of the convection operator presented by Piacsek and Williams [J. Comput. Phys. 6 (1970) 392]. In terms of its conservation properties, our variance-conserving scheme is compared to other spatially variance-conserving schemes as well as with the non-variance-conserving schemes applied in our shallow-water solver, see e.g. [Direct and Large-eddy Simulation Workshop IV, ERCOFTAC Series, Kluwer Academic Publishers, 2001, pp. 409-287

  15. Problems of variance reduction in the simulation of random variables

    International Nuclear Information System (INIS)

    Lessi, O.

    1987-01-01

    The definition of the uniform linear generator is given and some of the mostly used tests to evaluate the uniformity and the independence of the obtained determinations are listed. The problem of calculating, through simulation, some moment W of a random variable function is taken into account. The Monte Carlo method enables the moment W to be estimated and the estimator variance to be obtained. Some techniques for the construction of other estimators of W with a reduced variance are introduced

  16. Cumulative prospect theory and mean variance analysis. A rigorous comparison

    OpenAIRE

    Hens, Thorsten; Mayer, Janos

    2012-01-01

    We compare asset allocations derived for cumulative prospect theory(CPT) based on two different methods: Maximizing CPT along the mean–variance efficient frontier and maximizing it without that restriction. We find that with normally distributed returns the difference is negligible. However, using standard asset allocation data of pension funds the difference is considerable. Moreover, with derivatives like call options the restriction to the mean-variance efficient frontier results in a siza...

  17. Global Variance Risk Premium and Forex Return Predictability

    OpenAIRE

    Aloosh, Arash

    2014-01-01

    In a long-run risk model with stochastic volatility and frictionless markets, I express expected forex returns as a function of consumption growth variances and stock variance risk premiums (VRPs)—the difference between the risk-neutral and statistical expectations of market return variation. This provides a motivation for using the forward-looking information available in stock market volatility indices to predict forex returns. Empirically, I find that stock VRPs predict forex returns at a ...

  18. Global Gravity Wave Variances from Aura MLS: Characteristics and Interpretation

    Science.gov (United States)

    2008-12-01

    slight longitudinal variations, with secondary high- latitude peaks occurring over Greenland and Europe . As the QBO changes to the westerly phase, the...equatorial GW temperature variances from suborbital data (e.g., Eck- ermann et al. 1995). The extratropical wave variances are generally larger in the...emanating from tropopause altitudes, presumably radiated from tropospheric jet stream in- stabilities associated with baroclinic storm systems that

  19. Temperature variance study in Monte-Carlo photon transport theory

    International Nuclear Information System (INIS)

    Giorla, J.

    1985-10-01

    We study different Monte-Carlo methods for solving radiative transfer problems, and particularly Fleck's Monte-Carlo method. We first give the different time-discretization schemes and the corresponding stability criteria. Then we write the temperature variance as a function of the variances of temperature and absorbed energy at the previous time step. Finally we obtain some stability criteria for the Monte-Carlo method in the stationary case [fr

  20. Mean-Variance Optimization in Markov Decision Processes

    OpenAIRE

    Mannor, Shie; Tsitsiklis, John N.

    2011-01-01

    We consider finite horizon Markov decision processes under performance measures that involve both the mean and the variance of the cumulative reward. We show that either randomized or history-based policies can improve performance. We prove that the complexity of computing a policy that maximizes the mean reward under a variance constraint is NP-hard for some cases, and strongly NP-hard for others. We finally offer pseudo-polynomial exact and approximation algorithms.

  1. The asymptotic variance of departures in critically loaded queues

    NARCIS (Netherlands)

    Al Hanbali, Ahmad; Mandjes, M.R.H.; Nazarathy, Y.; Whitt, W.

    2011-01-01

    We consider the asymptotic variance of the departure counting process D(t) of the GI/G/1 queue; D(t) denotes the number of departures up to time t. We focus on the case where the system load ϱ equals 1, and prove that the asymptotic variance rate satisfies limt→∞varD(t) / t = λ(1 - 2 / π)(ca2 +

  2. Variance and covariance calculations for nuclear materials accounting using ''MAVARIC''

    International Nuclear Information System (INIS)

    Nasseri, K.K.

    1987-07-01

    Determination of the detection sensitivity of a materials accounting system to the loss of special nuclear material (SNM) requires (1) obtaining a relation for the variance of the materials balance by propagation of the instrument errors for the measured quantities that appear in the materials balance equation and (2) substituting measured values and their error standard deviations into this relation and calculating the variance of the materials balance. MAVARIC (Materials Accounting VARIance Calculations) is a custom spreadsheet, designed using the second release of Lotus 1-2-3, that significantly reduces the effort required to make the necessary variance (and covariance) calculations needed to determine the detection sensitivity of a materials accounting system. Predefined macros within the spreadsheet allow the user to carry out long, tedious procedures with only a few keystrokes. MAVARIC requires that the user enter the following data into one of four data tables, depending on the type of the term in the materials balance equation; the SNM concentration, the bulk mass (or solution volume), the measurement error standard deviations, and the number of measurements made during an accounting period. The user can also specify if there are correlations between transfer terms. Based on these data entries, MAVARIC can calculate the variance of the materials balance and the square root of this variance, from which the detection sensitivity of the accounting system can be determined

  3. Variance estimation in the analysis of microarray data

    KAUST Repository

    Wang, Yuedong

    2009-04-01

    Microarrays are one of the most widely used high throughput technologies. One of the main problems in the area is that conventional estimates of the variances that are required in the t-statistic and other statistics are unreliable owing to the small number of replications. Various methods have been proposed in the literature to overcome this lack of degrees of freedom problem. In this context, it is commonly observed that the variance increases proportionally with the intensity level, which has led many researchers to assume that the variance is a function of the mean. Here we concentrate on estimation of the variance as a function of an unknown mean in two models: the constant coefficient of variation model and the quadratic variance-mean model. Because the means are unknown and estimated with few degrees of freedom, naive methods that use the sample mean in place of the true mean are generally biased because of the errors-in-variables phenomenon. We propose three methods for overcoming this bias. The first two are variations on the theme of the so-called heteroscedastic simulation-extrapolation estimator, modified to estimate the variance function consistently. The third class of estimators is entirely different, being based on semiparametric information calculations. Simulations show the power of our methods and their lack of bias compared with the naive method that ignores the measurement error. The methodology is illustrated by using microarray data from leukaemia patients.

  4. Why risk is not variance: an expository note.

    Science.gov (United States)

    Cox, Louis Anthony Tony

    2008-08-01

    Variance (or standard deviation) of return is widely used as a measure of risk in financial investment risk analysis applications, where mean-variance analysis is applied to calculate efficient frontiers and undominated portfolios. Why, then, do health, safety, and environmental (HS&E) and reliability engineering risk analysts insist on defining risk more flexibly, as being determined by probabilities and consequences, rather than simply by variances? This note suggests an answer by providing a simple proof that mean-variance decision making violates the principle that a rational decisionmaker should prefer higher to lower probabilities of receiving a fixed gain, all else being equal. Indeed, simply hypothesizing a continuous increasing indifference curve for mean-variance combinations at the origin is enough to imply that a decisionmaker must find unacceptable some prospects that offer a positive probability of gain and zero probability of loss. Unlike some previous analyses of limitations of variance as a risk metric, this expository note uses only simple mathematics and does not require the additional framework of von Neumann Morgenstern utility theory.

  5. Approximate zero-variance Monte Carlo estimation of Markovian unreliability

    International Nuclear Information System (INIS)

    Delcoux, J.L.; Labeau, P.E.; Devooght, J.

    1997-01-01

    Monte Carlo simulation has become an important tool for the estimation of reliability characteristics, since conventional numerical methods are no more efficient when the size of the system to solve increases. However, evaluating by a simulation the probability of occurrence of very rare events means playing a very large number of histories of the system, which leads to unacceptable computation times. Acceleration and variance reduction techniques have to be worked out. We show in this paper how to write the equations of Markovian reliability as a transport problem, and how the well known zero-variance scheme can be adapted to this application. But such a method is always specific to the estimation of one quality, while a Monte Carlo simulation allows to perform simultaneously estimations of diverse quantities. Therefore, the estimation of one of them could be made more accurate while degrading at the same time the variance of other estimations. We propound here a method to reduce simultaneously the variance for several quantities, by using probability laws that would lead to zero-variance in the estimation of a mean of these quantities. Just like the zero-variance one, the method we propound is impossible to perform exactly. However, we show that simple approximations of it may be very efficient. (author)

  6. A versatile omnibus test for detecting mean and variance heterogeneity.

    Science.gov (United States)

    Cao, Ying; Wei, Peng; Bailey, Matthew; Kauwe, John S K; Maxwell, Taylor J

    2014-01-01

    Recent research has revealed loci that display variance heterogeneity through various means such as biological disruption, linkage disequilibrium (LD), gene-by-gene (G × G), or gene-by-environment interaction. We propose a versatile likelihood ratio test that allows joint testing for mean and variance heterogeneity (LRT(MV)) or either effect alone (LRT(M) or LRT(V)) in the presence of covariates. Using extensive simulations for our method and others, we found that all parametric tests were sensitive to nonnormality regardless of any trait transformations. Coupling our test with the parametric bootstrap solves this issue. Using simulations and empirical data from a known mean-only functional variant, we demonstrate how LD can produce variance-heterogeneity loci (vQTL) in a predictable fashion based on differential allele frequencies, high D', and relatively low r² values. We propose that a joint test for mean and variance heterogeneity is more powerful than a variance-only test for detecting vQTL. This takes advantage of loci that also have mean effects without sacrificing much power to detect variance only effects. We discuss using vQTL as an approach to detect G × G interactions and also how vQTL are related to relationship loci, and how both can create prior hypothesis for each other and reveal the relationships between traits and possibly between components of a composite trait.

  7. Variance-based sensitivity indices for models with dependent inputs

    International Nuclear Information System (INIS)

    Mara, Thierry A.; Tarantola, Stefano

    2012-01-01

    Computational models are intensively used in engineering for risk analysis or prediction of future outcomes. Uncertainty and sensitivity analyses are of great help in these purposes. Although several methods exist to perform variance-based sensitivity analysis of model output with independent inputs only a few are proposed in the literature in the case of dependent inputs. This is explained by the fact that the theoretical framework for the independent case is set and a univocal set of variance-based sensitivity indices is defined. In the present work, we propose a set of variance-based sensitivity indices to perform sensitivity analysis of models with dependent inputs. These measures allow us to distinguish between the mutual dependent contribution and the independent contribution of an input to the model response variance. Their definition relies on a specific orthogonalisation of the inputs and ANOVA-representations of the model output. In the applications, we show the interest of the new sensitivity indices for model simplification setting. - Highlights: ► Uncertainty and sensitivity analyses are of great help in engineering. ► Several methods exist to perform variance-based sensitivity analysis of model output with independent inputs. ► We define a set of variance-based sensitivity indices for models with dependent inputs. ► Inputs mutual contributions are distinguished from their independent contributions. ► Analytical and computational tests are performed and discussed.

  8. Variance and covariance calculations for nuclear materials accounting using 'MAVARIC'

    International Nuclear Information System (INIS)

    Nasseri, K.K.

    1987-01-01

    Determination of the detection sensitivity of a materials accounting system to the loss of special nuclear material (SNM) requires (1) obtaining a relation for the variance of the materials balance by propagation of the instrument errors for the measured quantities that appear in the materials balance equation and (2) substituting measured values and their error standard deviations into this relation and calculating the variance of the materials balance. MAVARIC (Materials Accounting VARIance Calculations) is a custom spreadsheet, designed using the second release of Lotus 1-2-3, that significantly reduces the effort required to make the necessary variance (and covariance) calculations needed to determine the detection sensitivity of a materials accounting system. Predefined macros within the spreadsheet allow the user to carry out long, tedious procedures with only a few keystrokes. MAVARIC requires that the user enter the following data into one of four data tables, depending on the type of the term in the materials balance equation; the SNM concentration, the bulk mass (or solution volume), the measurement error standard deviations, and the number of measurements made during an accounting period. The user can also specify if there are correlations between transfer terms. Based on these data entries, MAVARIC can calculate the variance of the materials balance and the square root of this variance, from which the detection sensitivity of the accounting system can be determined

  9. Analysis of Task Types and Error Types of the Human Actions Involved in the Human-related Unplanned Reactor Trip Events

    International Nuclear Information System (INIS)

    Kim, Jae Whan; Park, Jin Kyun; Jung, Won Dea

    2008-02-01

    This report provides the task types and error types involved in the unplanned reactor trip events that have occurred during 1986 - 2006. The events that were caused by the secondary system of the nuclear power plants amount to 67 %, and the remaining 33 % was by the primary system. The contribution of the activities of the plant personnel was identified as the following order: corrective maintenance (25.7 %), planned maintenance (22.8 %), planned operation (19.8 %), periodic preventive maintenance (14.9 %), response to a transient (9.9 %), and design/manufacturing/installation (9.9%). According to the analysis of error modes, the error modes such as control failure (22.2 %), wrong object (18.5 %), omission (14.8 %), wrong action (11.1 %), and inadequate (8.3 %) take up about 75 % of all the unplanned trip events. The analysis of the cognitive functions involved showed that the planning function makes the highest contribution to the human actions leading to unplanned reactor trips, and it is followed by the observation function (23.4%), the execution function (17.8 %), and the interpretation function (10.3 %). The results of this report are to be used as important bases for development of the error reduction measures or development of the error mode prediction system for the test and maintenance tasks in nuclear power plants

  10. Analysis of Task Types and Error Types of the Human Actions Involved in the Human-related Unplanned Reactor Trip Events

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae Whan; Park, Jin Kyun; Jung, Won Dea

    2008-02-15

    This report provides the task types and error types involved in the unplanned reactor trip events that have occurred during 1986 - 2006. The events that were caused by the secondary system of the nuclear power plants amount to 67 %, and the remaining 33 % was by the primary system. The contribution of the activities of the plant personnel was identified as the following order: corrective maintenance (25.7 %), planned maintenance (22.8 %), planned operation (19.8 %), periodic preventive maintenance (14.9 %), response to a transient (9.9 %), and design/manufacturing/installation (9.9%). According to the analysis of error modes, the error modes such as control failure (22.2 %), wrong object (18.5 %), omission (14.8 %), wrong action (11.1 %), and inadequate (8.3 %) take up about 75 % of all the unplanned trip events. The analysis of the cognitive functions involved showed that the planning function makes the highest contribution to the human actions leading to unplanned reactor trips, and it is followed by the observation function (23.4%), the execution function (17.8 %), and the interpretation function (10.3 %). The results of this report are to be used as important bases for development of the error reduction measures or development of the error mode prediction system for the test and maintenance tasks in nuclear power plants.

  11. CMB-S4 and the hemispherical variance anomaly

    Science.gov (United States)

    O'Dwyer, Márcio; Copi, Craig J.; Knox, Lloyd; Starkman, Glenn D.

    2017-09-01

    Cosmic microwave background (CMB) full-sky temperature data show a hemispherical asymmetry in power nearly aligned with the Ecliptic. In real space, this anomaly can be quantified by the temperature variance in the Northern and Southern Ecliptic hemispheres, with the Northern hemisphere displaying an anomalously low variance while the Southern hemisphere appears unremarkable [consistent with expectations from the best-fitting theory, Lambda Cold Dark Matter (ΛCDM)]. While this is a well-established result in temperature, the low signal-to-noise ratio in current polarization data prevents a similar comparison. This will change with a proposed ground-based CMB experiment, CMB-S4. With that in mind, we generate realizations of polarization maps constrained by the temperature data and predict the distribution of the hemispherical variance in polarization considering two different sky coverage scenarios possible in CMB-S4: full Ecliptic north coverage and just the portion of the North that can be observed from a ground-based telescope at the high Chilean Atacama plateau. We find that even in the set of realizations constrained by the temperature data, the low Northern hemisphere variance observed in temperature is not expected in polarization. Therefore, observing an anomalously low variance in polarization would make the hypothesis that the temperature anomaly is simply a statistical fluke more unlikely and thus increase the motivation for physical explanations. We show, within ΛCDM, how variance measurements in both sky coverage scenarios are related. We find that the variance makes for a good statistic in cases where the sky coverage is limited, however, full northern coverage is still preferable.

  12. Online Work Force Analyzes Social Media to Identify Consequences of an Unplanned School Closure – Using Technology to Prepare for the Next Pandemic

    Science.gov (United States)

    Rainey, Jeanette J.; Kenney, Jasmine; Wilburn, Ben; Putman, Ami; Zheteyeva, Yenlik; O’Sullivan, Megan

    2016-01-01

    Background During an influenza pandemic, the United States Centers for Disease Control and Prevention (CDC) may recommend school closures. These closures could have unintended consequences for students and their families. Publicly available social media could be analyzed to identify the consequences of an unplanned school closure. Methods As a proxy for an unplanned, pandemic-related school closure, we used the district-wide school closure due to the September 10–18, 2012 teachers’ strike in Chicago, Illinois. We captured social media posts about the school closure using the Radian6 social media-monitoring platform. An online workforce from Amazon Mechanical Turk categorized each post into one of two groups. The first group included relevant posts that described the impact of the closure on students and their families. The second group included irrelevant posts that described the political aspects of the strike or topics unrelated to the school closure. All relevant posts were further categorized as expressing a positive, negative, or neutral sentiment. We analyzed patterns of relevant posts and sentiment over time and compared our findings to household surveys conducted after other unplanned school closures. Results We captured 4,546 social media posts about the district-wide school closure using our search criteria. Of these, 930 (20%) were categorized as relevant by the online workforce. Of the relevant posts, 619 (67%) expressed a negative sentiment, 51 (5%) expressed a positive sentiment, and 260 (28%) were neutral. The number of relevant posts, and especially those with a negative sentiment, peaked on day 1 of the strike. Negative sentiment expressed concerns about childcare, missed school lunches, and the lack of class time for students. This was consistent with findings from previously conducted household surveys. Conclusion Social media are publicly available and can readily provide information on the impact of an unplanned school closure on students

  13. Risk factors for unplanned readmission within 30 days after pediatric neurosurgery: a nationwide analysis of 9799 procedures from the American College of Surgeons National Surgical Quality Improvement Program.

    Science.gov (United States)

    Sherrod, Brandon A; Johnston, James M; Rocque, Brandon G

    2016-09-01

    OBJECTIVE Hospital readmission rate is increasingly used as a quality outcome measure after surgery. The purpose of this study was to establish, using a national database, the baseline readmission rates and risk factors for patient readmission after pediatric neurosurgical procedures. METHODS The American College of Surgeons National Surgical Quality Improvement Program-Pediatric database was queried for pediatric patients treated by a neurosurgeon between 2012 and 2013. Procedures were categorized by current procedural terminology (CPT) code. Patient demographics, comorbidities, preoperative laboratory values, operative variables, and postoperative complications were analyzed via univariate and multivariate techniques to find associations with unplanned readmissions within 30 days of the primary procedure. RESULTS A total of 9799 cases met the inclusion criteria, 1098 (11.2%) of which had an unplanned readmission within 30 days. Readmission occurred 14.0 ± 7.7 days postoperatively (mean ± standard deviation). The 4 procedures with the highest unplanned readmission rates were CSF shunt revision (17.3%; CPT codes 62225 and 62230), repair of myelomeningocele > 5 cm in diameter (15.4%), CSF shunt creation (14.1%), and craniectomy for infratentorial tumor excision (13.9%). The lowest unplanned readmission rates were for spine (6.5%), craniotomy for craniosynostosis (2.1%), and skin lesion (1.0%) procedures. On multivariate regression analysis, the odds of readmission were greatest in patients experiencing postoperative surgical site infection (SSI; deep, organ/space, superficial SSI, and wound disruption: OR > 12 and p 10 days (OR 1.411, p = 0.010), oxygen supplementation (OR 1.645, p = 0.010), nutritional support (OR 1.403, p = 0.009), seizure disorder (OR 1.250, p = 0.021), and longer operative time (per hour increase, OR 1.059, p = 0.029). CONCLUSIONS This study may aid in identifying patients at risk for unplanned readmission following pediatric neurosurgery

  14. Online Work Force Analyzes Social Media to Identify Consequences of an Unplanned School Closure - Using Technology to Prepare for the Next Pandemic.

    Science.gov (United States)

    Rainey, Jeanette J; Kenney, Jasmine; Wilburn, Ben; Putman, Ami; Zheteyeva, Yenlik; O'Sullivan, Megan

    During an influenza pandemic, the United States Centers for Disease Control and Prevention (CDC) may recommend school closures. These closures could have unintended consequences for students and their families. Publicly available social media could be analyzed to identify the consequences of an unplanned school closure. As a proxy for an unplanned, pandemic-related school closure, we used the district-wide school closure due to the September 10-18, 2012 teachers' strike in Chicago, Illinois. We captured social media posts about the school closure using the Radian6 social media-monitoring platform. An online workforce from Amazon Mechanical Turk categorized each post into one of two groups. The first group included relevant posts that described the impact of the closure on students and their families. The second group included irrelevant posts that described the political aspects of the strike or topics unrelated to the school closure. All relevant posts were further categorized as expressing a positive, negative, or neutral sentiment. We analyzed patterns of relevant posts and sentiment over time and compared our findings to household surveys conducted after other unplanned school closures. We captured 4,546 social media posts about the district-wide school closure using our search criteria. Of these, 930 (20%) were categorized as relevant by the online workforce. Of the relevant posts, 619 (67%) expressed a negative sentiment, 51 (5%) expressed a positive sentiment, and 260 (28%) were neutral. The number of relevant posts, and especially those with a negative sentiment, peaked on day 1 of the strike. Negative sentiment expressed concerns about childcare, missed school lunches, and the lack of class time for students. This was consistent with findings from previously conducted household surveys. Social media are publicly available and can readily provide information on the impact of an unplanned school closure on students and their families. Using social media to

  15. Perspectives of veterans with mild traumatic brain injury on community reintegration: Making sense of unplanned separation from service.

    Science.gov (United States)

    Libin, Alexander V; Schladen, Manon Maitland; Danford, Ellen; Cichon, Samantha; Bruner, Dwan; Scholten, Joel; Llorente, Maria; Zapata, Slavomir; Dromerick, Alexander W; Blackman, Marc R; Magruder, Kathryn M

    2017-01-01

    For veterans separated from the military as a result of acquired mild traumatic brain injury (mTBI), the transition from a military identity to a civilian one is complicated by health, cognitive, and psychosocial factors. We conducted in-depth interviews with 8 veterans with mTBI to understand how they perceived the experience of departure from the military, rehabilitation services provided at a Department of Veterans Affairs (VA) Polytrauma Network Site, and reentry into civilian life. Two distinct patterns of thinking about community reintegration emerged. The first pattern was characterized by the perception of a need to fade one's military identity. The second pattern, conversely, advanced the perception of a need to maintain the integrity of one's military identity though living in a civilian world. These perceptions may be linked to individuals' roles while in the military and whether violent acts were committed in carrying out the mission of service, acts not consonant with positive self-appraisal in the civilian world. The crisis of unplanned, involuntary separation from the military was universally perceived as a crisis equal to that of the precipitating injury itself. The perception that civilians lacked understanding of veterans' military past and their current transition set up expectations for interactions with health care providers, as well as greatly impacting relationships with friend and family. Our veterans' shared perceptions support existing mandates for greater dissemination of military culture training to health care providers serving veterans both at VA and military facilities as well as in the civilian community at large. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  16. Multidisciplinary interventions and continuous quality improvement to reduce unplanned extubation in adult intensive care units: A 15-year experience.

    Science.gov (United States)

    Chao, Chien-Ming; Lai, Chih-Cheng; Chan, Khee-Siang; Cheng, Kuo-Chen; Ho, Chung-Han; Chen, Chin-Ming; Chou, Willy

    2017-07-01

    We conduct a retrospective study of patients with unplanned extubation (UE) in adult intensive care units (ICU) at a medical center. In 2001, a multidisciplinary team of intensivists, senior residents, nurses, and respiratory therapists was established at Chi Mei Medical Center. The improvement interventions, implemented between 2001 and 2015, were organized around 8 key areas: standardizing procedures, improving communication skills, revising sedation and weaning protocols, changing strategies for restraints, establishing a task force for identifying and managing high-risk patients, using new quality-improvement models as breakthrough series and team resource management, using the strategy of accountability without assigning blame, and changing a new method to secure endotracheal tube. We measured the outcome as the annual event and the rate of UE. During this 15-year period, there were 1404 episodes of UE, with 44,015 episodes of mechanical ventilation (MV) (319,158 ventilator-days). The overall rate of UE was 3.19/100 ventilated patients (4.40/1000 ventilator-days). In 2001, there were 188 episodes of UE and the rate of UE was 6.82/100 ventilated patients or 9.0/1000 ventilator-days. After this continue quality improvement project had been implemented, the annual number of episodes of UE declined to 27, and the rate fell to 0.95/100 ventilated patients or 1.36/1000 ventilator-days in 2015. Overall, the trend analysis showed the change was significant with P continuously and effectively reduced using multidisciplinary and sequential quality improvement interventions.

  17. Study of transient heat transfer in a fuel rod 3D, in a situation of unplanned shutdown of a PWR

    Energy Technology Data Exchange (ETDEWEB)

    Affonso, Renato Raoni Werneck; Martins, Rodolfo Ienny; Sampaio, Paulo Augusto Berquo de; Moreira, Maria de Lourdes, E-mail: raoniwa@yahoo.com.br, E-mail: rodolfoienny@gmail.com, E-mail: sampaio@ien.gov.br, E-mail: malu@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    The study, in situations involving accidents, of heat transfer in fuel rods is of known importance, since it can be used to predict the temperature limits in designing a nuclear reactor, to assist in making more efficient fuel rods, and to increase the knowledge about the behavior of the reactor's components, a crucial aspect for safety analysis. This study was conducted using as parameter the fuel rod that has the highest average power in a typical PWR reactor. For this, we developed a program (Fuel{sub R}od{sub 3}D) in Fortran language using the Finite Elements Method (FEM) for the discretization of a fuel rod and coolant channel, in order to study the temperature distribution in both the fuel rod and the coolant channel. Transient parameters were coupled to the heat transfer equations in order to obtain details of the behavior of the rod and the channel, which allows the analysis of the temperature distribution and its change over time. This work aims to present a study case of an accident where there is a lack of energy in the reactor's coolant pumps and in the diesel engines, resulting in an unplanned shutdown of the reactor. In order to achieve the intended goal, the present work was divided as follows: a short introduction about heat transfer, including the equations concerning the fuel rod and the energy equation in the channel, an explanation about how the verification of the Fuel{sub R}od{sub 3}D program was made, and the analysis of the results. (author)

  18. Genetic Variance in Homophobia: Evidence from Self- and Peer Reports.

    Science.gov (United States)

    Zapko-Willmes, Alexandra; Kandler, Christian

    2018-01-01

    The present twin study combined self- and peer assessments of twins' general homophobia targeting gay men in order to replicate previous behavior genetic findings across different rater perspectives and to disentangle self-rater-specific variance from common variance in self- and peer-reported homophobia (i.e., rater-consistent variance). We hypothesized rater-consistent variance in homophobia to be attributable to genetic and nonshared environmental effects, and self-rater-specific variance to be partially accounted for by genetic influences. A sample of 869 twins and 1329 peer raters completed a seven item scale containing cognitive, affective, and discriminatory homophobic tendencies. After correction for age and sex differences, we found most of the genetic contributions (62%) and significant nonshared environmental contributions (16%) to individual differences in self-reports on homophobia to be also reflected in peer-reported homophobia. A significant genetic component, however, was self-report-specific (38%), suggesting that self-assessments alone produce inflated heritability estimates to some degree. Different explanations are discussed.

  19. How does variance in fertility change over the demographic transition?

    Science.gov (United States)

    Hruschka, Daniel J; Burger, Oskar

    2016-04-19

    Most work on the human fertility transition has focused on declines in mean fertility. However, understanding changes in the variance of reproductive outcomes can be equally important for evolutionary questions about the heritability of fertility, individual determinants of fertility and changing patterns of reproductive skew. Here, we document how variance in completed fertility among women (45-49 years) differs across 200 surveys in 72 low- to middle-income countries where fertility transitions are currently in progress at various stages. Nearly all (91%) of samples exhibit variance consistent with a Poisson process of fertility, which places systematic, and often severe, theoretical upper bounds on the proportion of variance that can be attributed to individual differences. In contrast to the pattern of total variance, these upper bounds increase from high- to mid-fertility samples, then decline again as samples move from mid to low fertility. Notably, the lowest fertility samples often deviate from a Poisson process. This suggests that as populations move to low fertility their reproduction shifts from a rate-based process to a focus on an ideal number of children. We discuss the implications of these findings for predicting completed fertility from individual-level variables. © 2016 The Author(s).

  20. Impact of Damping Uncertainty on SEA Model Response Variance

    Science.gov (United States)

    Schiller, Noah; Cabell, Randolph; Grosveld, Ferdinand

    2010-01-01

    Statistical Energy Analysis (SEA) is commonly used to predict high-frequency vibroacoustic levels. This statistical approach provides the mean response over an ensemble of random subsystems that share the same gross system properties such as density, size, and damping. Recently, techniques have been developed to predict the ensemble variance as well as the mean response. However these techniques do not account for uncertainties in the system properties. In the present paper uncertainty in the damping loss factor is propagated through SEA to obtain more realistic prediction bounds that account for both ensemble and damping variance. The analysis is performed on a floor-equipped cylindrical test article that resembles an aircraft fuselage. Realistic bounds on the damping loss factor are determined from measurements acquired on the sidewall of the test article. The analysis demonstrates that uncertainties in damping have the potential to significantly impact the mean and variance of the predicted response.

  1. Genetic and environmental variance in content dimensions of the MMPI.

    Science.gov (United States)

    Rose, R J

    1988-08-01

    To evaluate genetic and environmental variance in the Minnesota Multiphasic Personality Inventory (MMPI), I studied nine factor scales identified in the first item factor analysis of normal adult MMPIs in a sample of 820 adolescent and young adult co-twins. Conventional twin comparisons documented heritable variance in six of the nine MMPI factors (Neuroticism, Psychoticism, Extraversion, Somatic Complaints, Inadequacy, and Cynicism), whereas significant influence from shared environmental experience was found for four factors (Masculinity versus Femininity, Extraversion, Religious Orthodoxy, and Intellectual Interests). Genetic variance in the nine factors was more evident in results from twin sisters than those of twin brothers, and a developmental-genetic analysis, using hierarchical multiple regressions of double-entry matrixes of the twins' raw data, revealed that in four MMPI factor scales, genetic effects were significantly modulated by age or gender or their interaction during the developmental period from early adolescence to early adulthood.

  2. A new variance stabilizing transformation for gene expression data analysis.

    Science.gov (United States)

    Kelmansky, Diana M; Martínez, Elena J; Leiva, Víctor

    2013-12-01

    In this paper, we introduce a new family of power transformations, which has the generalized logarithm as one of its members, in the same manner as the usual logarithm belongs to the family of Box-Cox power transformations. Although the new family has been developed for analyzing gene expression data, it allows a wider scope of mean-variance related data to be reached. We study the analytical properties of the new family of transformations, as well as the mean-variance relationships that are stabilized by using its members. We propose a methodology based on this new family, which includes a simple strategy for selecting the family member adequate for a data set. We evaluate the finite sample behavior of different classical and robust estimators based on this strategy by Monte Carlo simulations. We analyze real genomic data by using the proposed transformation to empirically show how the new methodology allows the variance of these data to be stabilized.

  3. Pricing perpetual American options under multiscale stochastic elasticity of variance

    International Nuclear Information System (INIS)

    Yoon, Ji-Hun

    2015-01-01

    Highlights: • We study the effects of the stochastic elasticity of variance on perpetual American option. • Our SEV model consists of a fast mean-reverting factor and a slow mean-revering factor. • A slow scale factor has a very significant impact on the option price. • We analyze option price structures through the market prices of elasticity risk. - Abstract: This paper studies pricing the perpetual American options under a constant elasticity of variance type of underlying asset price model where the constant elasticity is replaced by a fast mean-reverting Ornstein–Ulenbeck process and a slowly varying diffusion process. By using a multiscale asymptotic analysis, we find the impact of the stochastic elasticity of variance on the option prices and the optimal exercise prices with respect to model parameters. Our results enhance the existing option price structures in view of flexibility and applicability through the market prices of elasticity risk

  4. Monte Carlo variance reduction approaches for non-Boltzmann tallies

    International Nuclear Information System (INIS)

    Booth, T.E.

    1992-12-01

    Quantities that depend on the collective effects of groups of particles cannot be obtained from the standard Boltzmann transport equation. Monte Carlo estimates of these quantities are called non-Boltzmann tallies and have become increasingly important recently. Standard Monte Carlo variance reduction techniques were designed for tallies based on individual particles rather than groups of particles. Experience with non-Boltzmann tallies and analog Monte Carlo has demonstrated the severe limitations of analog Monte Carlo for many non-Boltzmann tallies. In fact, many calculations absolutely require variance reduction methods to achieve practical computation times. Three different approaches to variance reduction for non-Boltzmann tallies are described and shown to be unbiased. The advantages and disadvantages of each of the approaches are discussed

  5. The mean and variance of phylogenetic diversity under rarefaction.

    Science.gov (United States)

    Nipperess, David A; Matsen, Frederick A

    2013-06-01

    Phylogenetic diversity (PD) depends on sampling depth, which complicates the comparison of PD between samples of different depth. One approach to dealing with differing sample depth for a given diversity statistic is to rarefy, which means to take a random subset of a given size of the original sample. Exact analytical formulae for the mean and variance of species richness under rarefaction have existed for some time but no such solution exists for PD.We have derived exact formulae for the mean and variance of PD under rarefaction. We confirm that these formulae are correct by comparing exact solution mean and variance to that calculated by repeated random (Monte Carlo) subsampling of a dataset of stem counts of woody shrubs of Toohey Forest, Queensland, Australia. We also demonstrate the application of the method using two examples: identifying hotspots of mammalian diversity in Australasian ecoregions, and characterising the human vaginal microbiome.There is a very high degree of correspondence between the analytical and random subsampling methods for calculating mean and variance of PD under rarefaction, although the Monte Carlo method requires a large number of random draws to converge on the exact solution for the variance.Rarefaction of mammalian PD of ecoregions in Australasia to a common standard of 25 species reveals very different rank orderings of ecoregions, indicating quite different hotspots of diversity than those obtained for unrarefied PD. The application of these methods to the vaginal microbiome shows that a classical score used to quantify bacterial vaginosis is correlated with the shape of the rarefaction curve.The analytical formulae for the mean and variance of PD under rarefaction are both exact and more efficient than repeated subsampling. Rarefaction of PD allows for many applications where comparisons of samples of different depth is required.

  6. Variance estimation for sensitivity analysis of poverty and inequality measures

    Directory of Open Access Journals (Sweden)

    Christian Dudel

    2017-04-01

    Full Text Available Estimates of poverty and inequality are often based on application of a single equivalence scale, despite the fact that a large number of different equivalence scales can be found in the literature. This paper describes a framework for sensitivity analysis which can be used to account for the variability of equivalence scales and allows to derive variance estimates of results of sensitivity analysis. Simulations show that this method yields reliable estimates. An empirical application reveals that accounting for both variability of equivalence scales and sampling variance leads to confidence intervals which are wide.

  7. Studying Variance in the Galactic Ultra-compact Binary Population

    Science.gov (United States)

    Larson, Shane; Breivik, Katelyn

    2017-01-01

    In the years preceding LISA, Milky Way compact binary population simulations can be used to inform the science capabilities of the mission. Galactic population simulation efforts generally focus on high fidelity models that require extensive computational power to produce a single simulated population for each model. Each simulated population represents an incomplete sample of the functions governing compact binary evolution, thus introducing variance from one simulation to another. We present a rapid Monte Carlo population simulation technique that can simulate thousands of populations on week-long timescales, thus allowing a full exploration of the variance associated with a binary stellar evolution model.

  8. Variance of a product with application to uranium estimation

    International Nuclear Information System (INIS)

    Lowe, V.W.; Waterman, M.S.

    1976-01-01

    The U in a container can either be determined directly by NDA or by estimating the weight of material in the container and the concentration of U in this material. It is important to examine the statistical properties of estimating the amount of U by multiplying the estimates of weight and concentration. The variance of the product determines the accuracy of the estimate of the amount of uranium. This paper examines the properties of estimates of the variance of the product of two random variables

  9. Variance components for body weight in Japanese quails (Coturnix japonica

    Directory of Open Access Journals (Sweden)

    RO Resende

    2005-03-01

    Full Text Available The objective of this study was to estimate the variance components for body weight in Japanese quails by Bayesian procedures. The body weight at hatch (BWH and at 7 (BW07, 14 (BW14, 21 (BW21 and 28 days of age (BW28 of 3,520 quails was recorded from August 2001 to June 2002. A multiple-trait animal model with additive genetic, maternal environment and residual effects was implemented by Gibbs sampling methodology. A single Gibbs sampling with 80,000 rounds was generated by the program MTGSAM (Multiple Trait Gibbs Sampling in Animal Model. Normal and inverted Wishart distributions were used as prior distributions for the random effects and the variance components, respectively. Variance components were estimated based on the 500 samples that were left after elimination of 30,000 rounds in the burn-in period and 100 rounds of each thinning interval. The posterior means of additive genetic variance components were 0.15; 4.18; 14.62; 27.18 and 32.68; the posterior means of maternal environment variance components were 0.23; 1.29; 2.76; 4.12 and 5.16; and the posterior means of residual variance components were 0.084; 6.43; 22.66; 31.21 and 30.85, at hatch, 7, 14, 21 and 28 days old, respectively. The posterior means of heritability were 0.33; 0.35; 0.36; 0.43 and 0.47 at hatch, 7, 14, 21 and 28 days old, respectively. These results indicate that heritability increased with age. On the other hand, after hatch there was a marked reduction in the maternal environment variance proportion of the phenotypic variance, whose estimates were 0.50; 0.11; 0.07; 0.07 and 0.08 for BWH, BW07, BW14, BW21 and BW28, respectively. The genetic correlation between weights at different ages was high, except for those estimates between BWH and weight at other ages. Changes in body weight of quails can be efficiently achieved by selection.

  10. Levine's guide to SPSS for analysis of variance

    CERN Document Server

    Braver, Sanford L; Page, Melanie

    2003-01-01

    A greatly expanded and heavily revised second edition, this popular guide provides instructions and clear examples for running analyses of variance (ANOVA) and several other related statistical tests of significance with SPSS. No other guide offers the program statements required for the more advanced tests in analysis of variance. All of the programs in the book can be run using any version of SPSS, including versions 11 and 11.5. A table at the end of the preface indicates where each type of analysis (e.g., simple comparisons) can be found for each type of design (e.g., mixed two-factor desi

  11. Variance squeezing and entanglement of the XX central spin model

    International Nuclear Information System (INIS)

    El-Orany, Faisal A A; Abdalla, M Sebawe

    2011-01-01

    In this paper, we study the quantum properties for a system that consists of a central atom interacting with surrounding spins through the Heisenberg XX couplings of equal strength. Employing the Heisenberg equations of motion we manage to derive an exact solution for the dynamical operators. We consider that the central atom and its surroundings are initially prepared in the excited state and in the coherent spin state, respectively. For this system, we investigate the evolution of variance squeezing and entanglement. The nonclassical effects have been remarked in the behavior of all components of the system. The atomic variance can exhibit revival-collapse phenomenon based on the value of the detuning parameter.

  12. Asymptotic variance of grey-scale surface area estimators

    DEFF Research Database (Denmark)

    Svane, Anne Marie

    Grey-scale local algorithms have been suggested as a fast way of estimating surface area from grey-scale digital images. Their asymptotic mean has already been described. In this paper, the asymptotic behaviour of the variance is studied in isotropic and sufficiently smooth settings, resulting...... in a general asymptotic bound. For compact convex sets with nowhere vanishing Gaussian curvature, the asymptotics can be described more explicitly. As in the case of volume estimators, the variance is decomposed into a lattice sum and an oscillating term of at most the same magnitude....

  13. Variance squeezing and entanglement of the XX central spin model

    Energy Technology Data Exchange (ETDEWEB)

    El-Orany, Faisal A A [Department of Mathematics and Computer Science, Faculty of Science, Suez Canal University, Ismailia (Egypt); Abdalla, M Sebawe, E-mail: m.sebaweh@physics.org [Mathematics Department, College of Science, King Saud University PO Box 2455, Riyadh 11451 (Saudi Arabia)

    2011-01-21

    In this paper, we study the quantum properties for a system that consists of a central atom interacting with surrounding spins through the Heisenberg XX couplings of equal strength. Employing the Heisenberg equations of motion we manage to derive an exact solution for the dynamical operators. We consider that the central atom and its surroundings are initially prepared in the excited state and in the coherent spin state, respectively. For this system, we investigate the evolution of variance squeezing and entanglement. The nonclassical effects have been remarked in the behavior of all components of the system. The atomic variance can exhibit revival-collapse phenomenon based on the value of the detuning parameter.

  14. Planning the unplanned

    DEFF Research Database (Denmark)

    Halloran, Afton Marian Szasz; Magid, Jakob

    2013-01-01

    Despite significant contributions to human health, livelihoods and food security, urban agriculture in Dar es Salaam has received relatively little political support from central and local government due to its informal state. As a result, many urban farmers' experience insecurity of land access ...

  15. Unplanned ecological engineering

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Gislason, Henrik

    2017-01-01

    unexpectedly large catches by removing predators from the ecosystem. Such ecosystem engineering stands in stark contrast to reigning management paradigms that do not allow fishing down predators to increase the productivity of their prey. The theoretical support for such a feat of ecosystem engineering is well...

  16. Demonstration of a zero-variance based scheme for variance reduction to a mini-core Monte Carlo calculation

    Energy Technology Data Exchange (ETDEWEB)

    Christoforou, Stavros, E-mail: stavros.christoforou@gmail.com [Kirinthou 17, 34100, Chalkida (Greece); Hoogenboom, J. Eduard, E-mail: j.e.hoogenboom@tudelft.nl [Department of Applied Sciences, Delft University of Technology (Netherlands)

    2011-07-01

    A zero-variance based scheme is implemented and tested in the MCNP5 Monte Carlo code. The scheme is applied to a mini-core reactor using the adjoint function obtained from a deterministic calculation for biasing the transport kernels. It is demonstrated that the variance of the k{sub eff} estimate is halved compared to a standard criticality calculation. In addition, the biasing does not affect source distribution convergence of the system. However, since the code lacked optimisations for speed, we were not able to demonstrate an appropriate increase in the efficiency of the calculation, because of the higher CPU time cost. (author)

  17. Demonstration of a zero-variance based scheme for variance reduction to a mini-core Monte Carlo calculation

    International Nuclear Information System (INIS)

    Christoforou, Stavros; Hoogenboom, J. Eduard

    2011-01-01

    A zero-variance based scheme is implemented and tested in the MCNP5 Monte Carlo code. The scheme is applied to a mini-core reactor using the adjoint function obtained from a deterministic calculation for biasing the transport kernels. It is demonstrated that the variance of the k_e_f_f estimate is halved compared to a standard criticality calculation. In addition, the biasing does not affect source distribution convergence of the system. However, since the code lacked optimisations for speed, we were not able to demonstrate an appropriate increase in the efficiency of the calculation, because of the higher CPU time cost. (author)

  18. Multivariate Variance Targeting in the BEKK-GARCH Model

    DEFF Research Database (Denmark)

    Pedersen, Rasmus Søndergaard; Rahbek, Anders

    This paper considers asymptotic inference in the multivariate BEKK model based on (co-)variance targeting (VT). By de…nition the VT estimator is a two-step estimator and the theory presented is based on expansions of the modi…ed like- lihood function, or estimating function, corresponding...

  19. Multivariate Variance Targeting in the BEKK-GARCH Model

    DEFF Research Database (Denmark)

    Pedersen, Rasmus Søndergaard; Rahbek, Anders

    2014-01-01

    This paper considers asymptotic inference in the multivariate BEKK model based on (co-)variance targeting (VT). By definition the VT estimator is a two-step estimator and the theory presented is based on expansions of the modified likelihood function, or estimating function, corresponding...

  20. Multivariate Variance Targeting in the BEKK-GARCH Model

    DEFF Research Database (Denmark)

    Pedersen, Rasmus Søndergaard; Rahbek, Anders

    This paper considers asymptotic inference in the multivariate BEKK model based on (co-)variance targeting (VT). By de…nition the VT estimator is a two-step estimator and the theory presented is based on expansions of the modi…ed likelihood function, or estimating function, corresponding...

  1. Analysis of Variance: What Is Your Statistical Software Actually Doing?

    Science.gov (United States)

    Li, Jian; Lomax, Richard G.

    2011-01-01

    Users assume statistical software packages produce accurate results. In this article, the authors systematically examined Statistical Package for the Social Sciences (SPSS) and Statistical Analysis System (SAS) for 3 analysis of variance (ANOVA) designs, mixed-effects ANOVA, fixed-effects analysis of covariance (ANCOVA), and nested ANOVA. For each…

  2. Genetic variance components for residual feed intake and feed ...

    African Journals Online (AJOL)

    Feeding costs of animals is a major determinant of profitability in livestock production enterprises. Genetic selection to improve feed efficiency aims to reduce feeding cost in beef cattle and thereby improve profitability. This study estimated genetic (co)variances between weaning weight and other production, reproduction ...

  3. Cumulative Prospect Theory, Option Returns, and the Variance Premium

    NARCIS (Netherlands)

    Baele, Lieven; Driessen, Joost; Ebert, Sebastian; Londono Yarce, J.M.; Spalt, Oliver

    The variance premium and the pricing of out-of-the-money (OTM) equity index options are major challenges to standard asset pricing models. We develop a tractable equilibrium model with Cumulative Prospect Theory (CPT) preferences that can overcome both challenges. The key insight is that the

  4. Hydrograph variances over different timescales in hydropower production networks

    Science.gov (United States)

    Zmijewski, Nicholas; Wörman, Anders

    2016-08-01

    The operation of water reservoirs involves a spectrum of timescales based on the distribution of stream flow travel times between reservoirs, as well as the technical, environmental, and social constraints imposed on the operation. In this research, a hydrodynamically based description of the flow between hydropower stations was implemented to study the relative importance of wave diffusion on the spectrum of hydrograph variance in a regulated watershed. Using spectral decomposition of the effluence hydrograph of a watershed, an exact expression of the variance in the outflow response was derived, as a function of the trends of hydraulic and geomorphologic dispersion and management of production and reservoirs. We show that the power spectra of involved time-series follow nearly fractal patterns, which facilitates examination of the relative importance of wave diffusion and possible changes in production demand on the outflow spectrum. The exact spectral solution can also identify statistical bounds of future demand patterns due to limitations in storage capacity. The impact of the hydraulic description of the stream flow on the reservoir discharge was examined for a given power demand in River Dalälven, Sweden, as function of a stream flow Peclet number. The regulation of hydropower production on the River Dalälven generally increased the short-term variance in the effluence hydrograph, whereas wave diffusion decreased the short-term variance over periods of white noise) as a result of current production objectives.

  5. Gravity interpretation of dipping faults using the variance analysis method

    International Nuclear Information System (INIS)

    Essa, Khalid S

    2013-01-01

    A new algorithm is developed to estimate simultaneously the depth and the dip angle of a buried fault from the normalized gravity gradient data. This algorithm utilizes numerical first horizontal derivatives computed from the observed gravity anomaly, using filters of successive window lengths to estimate the depth and the dip angle of a buried dipping fault structure. For a fixed window length, the depth is estimated using a least-squares sense for each dip angle. The method is based on computing the variance of the depths determined from all horizontal gradient anomaly profiles using the least-squares method for each dip angle. The minimum variance is used as a criterion for determining the correct dip angle and depth of the buried structure. When the correct dip angle is used, the variance of the depths is always less than the variances computed using wrong dip angles. The technique can be applied not only to the true residuals, but also to the measured Bouguer gravity data. The method is applied to synthetic data with and without random errors and two field examples from Egypt and Scotland. In all cases examined, the estimated depths and other model parameters are found to be in good agreement with the actual values. (paper)

  6. Bounds for Tail Probabilities of the Sample Variance

    Directory of Open Access Journals (Sweden)

    Van Zuijlen M

    2009-01-01

    Full Text Available We provide bounds for tail probabilities of the sample variance. The bounds are expressed in terms of Hoeffding functions and are the sharpest known. They are designed having in mind applications in auditing as well as in processing data related to environment.

  7. Robust estimation of the noise variance from background MR data

    NARCIS (Netherlands)

    Sijbers, J.; Den Dekker, A.J.; Poot, D.; Bos, R.; Verhoye, M.; Van Camp, N.; Van der Linden, A.

    2006-01-01

    In the literature, many methods are available for estimation of the variance of the noise in magnetic resonance (MR) images. A commonly used method, based on the maximum of the background mode of the histogram, is revisited and a new, robust, and easy to use method is presented based on maximum

  8. Stable limits for sums of dependent infinite variance random variables

    DEFF Research Database (Denmark)

    Bartkiewicz, Katarzyna; Jakubowski, Adam; Mikosch, Thomas

    2011-01-01

    The aim of this paper is to provide conditions which ensure that the affinely transformed partial sums of a strictly stationary process converge in distribution to an infinite variance stable distribution. Conditions for this convergence to hold are known in the literature. However, most of these...

  9. Computing the Expected Value and Variance of Geometric Measures

    DEFF Research Database (Denmark)

    Staals, Frank; Tsirogiannis, Constantinos

    2017-01-01

    distance (MPD), the squared Euclidean distance from the centroid, and the diameter of the minimum enclosing disk. We also describe an efficient (1-e)-approximation algorithm for computing the mean and variance of the mean pairwise distance. We implemented three of our algorithms and we show that our...

  10. Estimation of the additive and dominance variances in South African ...

    African Journals Online (AJOL)

    The objective of this study was to estimate dominance variance for number born alive (NBA), 21- day litter weight (LWT21) and interval between parities (FI) in South African Landrace pigs. A total of 26223 NBA, 21335 LWT21 and 16370 FI records were analysed. Bayesian analysis via Gibbs sampling was used to estimate ...

  11. A note on minimum-variance theory and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Feng Jianfeng [Department of Informatics, Sussex University, Brighton, BN1 9QH (United Kingdom); Tartaglia, Giangaetano [Physics Department, Rome University ' La Sapienza' , Rome 00185 (Italy); Tirozzi, Brunello [Physics Department, Rome University ' La Sapienza' , Rome 00185 (Italy)

    2004-04-30

    We revisit the minimum-variance theory proposed by Harris and Wolpert (1998 Nature 394 780-4), discuss the implications of the theory on modelling the firing patterns of single neurons and analytically find the optimal control signals, trajectories and velocities. Under the rate coding assumption, input control signals employed in the minimum-variance theory should be Fitts processes rather than Poisson processes. Only if information is coded by interspike intervals, Poisson processes are in agreement with the inputs employed in the minimum-variance theory. For the integrate-and-fire model with Fitts process inputs, interspike intervals of efferent spike trains are very irregular. We introduce diffusion approximations to approximate neural models with renewal process inputs and present theoretical results on calculating moments of interspike intervals of the integrate-and-fire model. Results in Feng, et al (2002 J. Phys. A: Math. Gen. 35 7287-304) are generalized. In conclusion, we present a complete picture on the minimum-variance theory ranging from input control signals, to model outputs, and to its implications on modelling firing patterns of single neurons.

  12. A Visual Model for the Variance and Standard Deviation

    Science.gov (United States)

    Orris, J. B.

    2011-01-01

    This paper shows how the variance and standard deviation can be represented graphically by looking at each squared deviation as a graphical object--in particular, as a square. A series of displays show how the standard deviation is the size of the average square.

  13. Multidimensional adaptive testing with a minimum error-variance criterion

    NARCIS (Netherlands)

    van der Linden, Willem J.

    1997-01-01

    The case of adaptive testing under a multidimensional logistic response model is addressed. An adaptive algorithm is proposed that minimizes the (asymptotic) variance of the maximum-likelihood (ML) estimator of a linear combination of abilities of interest. The item selection criterion is a simple

  14. Asymptotics of variance of the lattice point count

    Czech Academy of Sciences Publication Activity Database

    Janáček, Jiří

    2008-01-01

    Roč. 58, č. 3 (2008), s. 751-758 ISSN 0011-4642 R&D Projects: GA AV ČR(CZ) IAA100110502 Institutional research plan: CEZ:AV0Z50110509 Keywords : point lattice * variance Subject RIV: BA - General Mathematics Impact factor: 0.210, year: 2008

  15. Vertical velocity variances and Reynold stresses at Brookhaven

    DEFF Research Database (Denmark)

    Busch, Niels E.; Brown, R.M.; Frizzola, J.A.

    1970-01-01

    Results of wind tunnel tests of the Brookhaven annular bivane are presented. The energy transfer functions describing the instrument response and the numerical filter employed in the data reduction process have been used to obtain corrected values of the normalized variance of the vertical wind v...

  16. Estimates of variance components for postweaning feed intake and ...

    African Journals Online (AJOL)

    Mike

    2013-03-09

    Mar 9, 2013 ... transformation of RFIp and RDGp to z-scores (mean = 0.0, variance = 1.0) and then ... generation pedigree (n = 9 653) used for this analysis. ..... Nkrumah, J.D., Basarab, J.A., Wang, Z., Li, C., Price, M.A., Okine, E.K., Crews Jr., ...

  17. An observation on the variance of a predicted response in ...

    African Journals Online (AJOL)

    ... these properties and computational simplicity. To avoid over fitting, along with the obvious advantage of having a simpler equation, it is shown that the addition of a variable to a regression equation does not reduce the variance of a predicted response. Key words: Linear regression; Partitioned matrix; Predicted response ...

  18. An entropy approach to size and variance heterogeneity

    NARCIS (Netherlands)

    Balasubramanyan, L.; Stefanou, S.E.; Stokes, J.R.

    2012-01-01

    In this paper, we investigate the effect of bank size differences on cost efficiency heterogeneity using a heteroskedastic stochastic frontier model. This model is implemented by using an information theoretic maximum entropy approach. We explicitly model both bank size and variance heterogeneity

  19. The Threat of Common Method Variance Bias to Theory Building

    Science.gov (United States)

    Reio, Thomas G., Jr.

    2010-01-01

    The need for more theory building scholarship remains one of the pressing issues in the field of HRD. Researchers can employ quantitative, qualitative, and/or mixed methods to support vital theory-building efforts, understanding however that each approach has its limitations. The purpose of this article is to explore common method variance bias as…

  20. Variance in parametric images: direct estimation from parametric projections

    International Nuclear Information System (INIS)

    Maguire, R.P.; Leenders, K.L.; Spyrou, N.M.

    2000-01-01

    Recent work has shown that it is possible to apply linear kinetic models to dynamic projection data in PET in order to calculate parameter projections. These can subsequently be back-projected to form parametric images - maps of parameters of physiological interest. Critical to the application of these maps, to test for significant changes between normal and pathophysiology, is an assessment of the statistical uncertainty. In this context, parametric images also include simple integral images from, e.g., [O-15]-water used to calculate statistical parametric maps (SPMs). This paper revisits the concept of parameter projections and presents a more general formulation of the parameter projection derivation as well as a method to estimate parameter variance in projection space, showing which analysis methods (models) can be used. Using simulated pharmacokinetic image data we show that a method based on an analysis in projection space inherently calculates the mathematically rigorous pixel variance. This results in an estimation which is as accurate as either estimating variance in image space during model fitting, or estimation by comparison across sets of parametric images - as might be done between individuals in a group pharmacokinetic PET study. The method based on projections has, however, a higher computational efficiency, and is also shown to be more precise, as reflected in smooth variance distribution images when compared to the other methods. (author)

  1. 40 CFR 268.44 - Variance from a treatment standard.

    Science.gov (United States)

    2010-07-01

    ... complete petition may be requested as needed to send to affected states and Regional Offices. (e) The... provide an opportunity for public comment. The final decision on a variance from a treatment standard will... than) the concentrations necessary to minimize short- and long-term threats to human health and the...

  2. Application of effective variance method for contamination monitor calibration

    International Nuclear Information System (INIS)

    Goncalez, O.L.; Freitas, I.S.M. de.

    1990-01-01

    In this report, the calibration of a thin window Geiger-Muller type monitor for alpha superficial contamination is presented. The calibration curve is obtained by the method of the least-squares fitting with effective variance. The method and the approach for the calculation are briefly discussed. (author)

  3. The VIX, the Variance Premium, and Expected Returns

    DEFF Research Database (Denmark)

    Osterrieder, Daniela Maria; Ventosa-Santaulària, Daniel; Vera-Valdés, Eduardo

    2018-01-01

    . These problems are eliminated if risk is captured by the variance premium (VP) instead; it is unobservable, however. We propose a 2SLS estimator that produces consistent estimates without observing the VP. Using this method, we find a positive risk–return trade-off and long-run return predictability. Our...

  4. Some asymptotic theory for variance function smoothing | Kibua ...

    African Journals Online (AJOL)

    Simple selection of the smoothing parameter is suggested. Both homoscedastic and heteroscedastic regression models are considered. Keywords: Asymptotic, Smoothing, Kernel, Bandwidth, Bias, Variance, Mean squared error, Homoscedastic, Heteroscedastic. > East African Journal of Statistics Vol. 1 (1) 2005: pp. 9-22 ...

  5. Variance-optimal hedging for processes with stationary independent increments

    DEFF Research Database (Denmark)

    Hubalek, Friedrich; Kallsen, J.; Krawczyk, L.

    We determine the variance-optimal hedge when the logarithm of the underlying price follows a process with stationary independent increments in discrete or continuous time. Although the general solution to this problem is known as backward recursion or backward stochastic differential equation, we...

  6. Adaptive Nonparametric Variance Estimation for a Ratio Estimator ...

    African Journals Online (AJOL)

    Kernel estimators for smooth curves require modifications when estimating near end points of the support, both for practical and asymptotic reasons. The construction of such boundary kernels as solutions of variational problem is a difficult exercise. For estimating the error variance of a ratio estimator, we suggest an ...

  7. A note on minimum-variance theory and beyond

    International Nuclear Information System (INIS)

    Feng Jianfeng; Tartaglia, Giangaetano; Tirozzi, Brunello

    2004-01-01

    We revisit the minimum-variance theory proposed by Harris and Wolpert (1998 Nature 394 780-4), discuss the implications of the theory on modelling the firing patterns of single neurons and analytically find the optimal control signals, trajectories and velocities. Under the rate coding assumption, input control signals employed in the minimum-variance theory should be Fitts processes rather than Poisson processes. Only if information is coded by interspike intervals, Poisson processes are in agreement with the inputs employed in the minimum-variance theory. For the integrate-and-fire model with Fitts process inputs, interspike intervals of efferent spike trains are very irregular. We introduce diffusion approximations to approximate neural models with renewal process inputs and present theoretical results on calculating moments of interspike intervals of the integrate-and-fire model. Results in Feng, et al (2002 J. Phys. A: Math. Gen. 35 7287-304) are generalized. In conclusion, we present a complete picture on the minimum-variance theory ranging from input control signals, to model outputs, and to its implications on modelling firing patterns of single neurons

  8. Handling nonnormality and variance heterogeneity for quantitative sublethal toxicity tests.

    Science.gov (United States)

    Ritz, Christian; Van der Vliet, Leana

    2009-09-01

    The advantages of using regression-based techniques to derive endpoints from environmental toxicity data are clear, and slowly, this superior analytical technique is gaining acceptance. As use of regression-based analysis becomes more widespread, some of the associated nuances and potential problems come into sharper focus. Looking at data sets that cover a broad spectrum of standard test species, we noticed that some model fits to data failed to meet two key assumptions-variance homogeneity and normality-that are necessary for correct statistical analysis via regression-based techniques. Failure to meet these assumptions often is caused by reduced variance at the concentrations showing severe adverse effects. Although commonly used with linear regression analysis, transformation of the response variable only is not appropriate when fitting data using nonlinear regression techniques. Through analysis of sample data sets, including Lemna minor, Eisenia andrei (terrestrial earthworm), and algae, we show that both the so-called Box-Cox transformation and use of the Poisson distribution can help to correct variance heterogeneity and nonnormality and so allow nonlinear regression analysis to be implemented. Both the Box-Cox transformation and the Poisson distribution can be readily implemented into existing protocols for statistical analysis. By correcting for nonnormality and variance heterogeneity, these two statistical tools can be used to encourage the transition to regression-based analysis and the depreciation of less-desirable and less-flexible analytical techniques, such as linear interpolation.

  9. Molecular variance of the Tunisian almond germplasm assessed by ...

    African Journals Online (AJOL)

    The genetic variance analysis of 82 almond (Prunus dulcis Mill.) genotypes was performed using ten genomic simple sequence repeats (SSRs). A total of 50 genotypes from Tunisia including local landraces identified while prospecting the different sites of Bizerte and Sidi Bouzid (Northern and central parts) which are the ...

  10. Starting design for use in variance exchange algorithms | Iwundu ...

    African Journals Online (AJOL)

    A new method of constructing the initial design for use in variance exchange algorithms is presented. The method chooses support points to go into the design as measures of distances of the support points from the centre of the geometric region and of permutation-invariant sets. The initial design is as close as possible to ...

  11. Decomposition of variance in terms of conditional means

    Directory of Open Access Journals (Sweden)

    Alessandro Figà Talamanca

    2013-05-01

    Full Text Available Two different sets of data are used to test an apparently new approach to the analysis of the variance of a numerical variable which depends on qualitative variables. We suggest that this approach be used to complement other existing techniques to study the interdependence of the variables involved. According to our method, the variance is expressed as a sum of orthogonal components, obtained as differences of conditional means, with respect to the qualitative characters. The resulting expression for the variance depends on the ordering in which the characters are considered. We suggest an algorithm which leads to an ordering which is deemed natural. The first set of data concerns the score achieved by a population of students on an entrance examination based on a multiple choice test with 30 questions. In this case the qualitative characters are dyadic and correspond to correct or incorrect answer to each question. The second set of data concerns the delay to obtain the degree for a population of graduates of Italian universities. The variance in this case is analyzed with respect to a set of seven specific qualitative characters of the population studied (gender, previous education, working condition, parent's educational level, field of study, etc..

  12. A Hold-out method to correct PCA variance inflation

    DEFF Research Database (Denmark)

    Garcia-Moreno, Pablo; Artes-Rodriguez, Antonio; Hansen, Lars Kai

    2012-01-01

    In this paper we analyze the problem of variance inflation experienced by the PCA algorithm when working in an ill-posed scenario where the dimensionality of the training set is larger than its sample size. In an earlier article a correction method based on a Leave-One-Out (LOO) procedure...

  13. Heterogeneity of variance and its implications on dairy cattle breeding

    African Journals Online (AJOL)

    Milk yield data (n = 12307) from 116 Holstein-Friesian herds were grouped into three production environments based on mean and standard deviation of herd 305-day milk yield and evaluated for within herd variation using univariate animal model procedures. Variance components were estimated by derivative free REML ...

  14. Effects of Diversification of Assets on Mean and Variance | Jayeola ...

    African Journals Online (AJOL)

    Diversification is a means of minimizing risk and maximizing returns by investing in a variety of assets of the portfolio. This paper is written to determine the effects of diversification of three types of Assets; uncorrelated, perfectly correlated and perfectly negatively correlated assets on mean and variance. To go about this, ...

  15. Perspective projection for variance pose face recognition from camera calibration

    Science.gov (United States)

    Fakhir, M. M.; Woo, W. L.; Chambers, J. A.; Dlay, S. S.

    2016-04-01

    Variance pose is an important research topic in face recognition. The alteration of distance parameters across variance pose face features is a challenging. We provide a solution for this problem using perspective projection for variance pose face recognition. Our method infers intrinsic camera parameters of the image which enable the projection of the image plane into 3D. After this, face box tracking and centre of eyes detection can be identified using our novel technique to verify the virtual face feature measurements. The coordinate system of the perspective projection for face tracking allows the holistic dimensions for the face to be fixed in different orientations. The training of frontal images and the rest of the poses on FERET database determine the distance from the centre of eyes to the corner of box face. The recognition system compares the gallery of images against different poses. The system initially utilises information on position of both eyes then focuses principally on closest eye in order to gather data with greater reliability. Differentiation between the distances and position of the right and left eyes is a unique feature of our work with our algorithm outperforming other state of the art algorithms thus enabling stable measurement in variance pose for each individual.

  16. On zero variance Monte Carlo path-stretching schemes

    International Nuclear Information System (INIS)

    Lux, I.

    1983-01-01

    A zero variance path-stretching biasing scheme proposed for a special case by Dwivedi is derived in full generality. The procedure turns out to be the generalization of the exponential transform. It is shown that the biased game can be interpreted as an analog simulation procedure, thus saving some computational effort in comparison with the corresponding nonanalog game

  17. A mean-variance frontier in discrete and continuous time

    NARCIS (Netherlands)

    Bekker, Paul A.

    2004-01-01

    The paper presents a mean-variance frontier based on dynamic frictionless investment strategies in continuous time. The result applies to a finite number of risky assets whose price process is given by multivariate geometric Brownian motion with deterministically varying coefficients. The derivation

  18. Hedging with stock index futures: downside risk versus the variance

    NARCIS (Netherlands)

    Brouwer, F.; Nat, van der M.

    1995-01-01

    In this paper we investigate hedging a stock portfolio with stock index futures.Instead of defining the hedge ratio as the minimum variance hedge ratio, we considerseveral measures of downside risk: the semivariance according to Markowitz [ 19591 andthe various lower partial moments according to

  19. The variance quadtree algorithm: use for spatial sampling design

    NARCIS (Netherlands)

    Minasny, B.; McBratney, A.B.; Walvoort, D.J.J.

    2007-01-01

    Spatial sampling schemes are mainly developed to determine sampling locations that can cover the variation of environmental properties in the area of interest. Here we proposed the variance quadtree algorithm for sampling in an area with prior information represented as ancillary or secondary

  20. Properties of realized variance under alternative sampling schemes

    NARCIS (Netherlands)

    Oomen, R.C.A.

    2006-01-01

    This paper investigates the statistical properties of the realized variance estimator in the presence of market microstructure noise. Different from the existing literature, the analysis relies on a pure jump process for high frequency security prices and explicitly distinguishes among alternative

  1. Variance component and heritability estimates of early growth traits ...

    African Journals Online (AJOL)

    as selection criteria for meat production in sheep (Anon, 1970; Olson et ai., 1976;. Lasslo et ai., 1985; Badenhorst et ai., 1991). If these traits are to be included in a breeding programme, accurate estimates of breeding values will be needed to optimize selection programmes. This requires a knowledge of variance and co-.

  2. Variances in consumers prices of selected food Items among ...

    African Journals Online (AJOL)

    The study focused on the determination of variances among consumer prices of rice (local white), beans (white) and garri (yellow) in Watts, Okurikang and 8 Miles markets in southern zone of Cross River State. Completely randomized design was used to test the research hypothesis. Comparing the consumer prices of rice, ...

  3. Age Differences in the Variance of Personality Characteristics

    Czech Academy of Sciences Publication Activity Database

    Mottus, R.; Allik, J.; Hřebíčková, Martina; Kööts-Ausmees, L.; Realo, A.

    2016-01-01

    Roč. 30, č. 1 (2016), s. 4-11 ISSN 0890-2070 R&D Projects: GA ČR GA13-25656S Institutional support: RVO:68081740 Keywords : variance * individual differences * personality * five-factor model Subject RIV: AN - Psychology Impact factor: 3.707, year: 2016

  4. Risk factors affecting unplanned reoperation after laparoscopic gastrectomy for gastric cancer: experience from a high-volume center.

    Science.gov (United States)

    Li, Ping; Huang, Chang-Ming; Tu, Ru-Hong; Lin, Jian-Xian; Lu, Jun; Zheng, Chao-Hui; Xie, Jian-Wei; Wang, Jia-Bin; Chen, Qi-Yue; Cao, Long-Long; Lin, Mi

    2017-10-01

    To evaluate the risk factors affecting unplanned reoperation (URO) after laparoscopic gastrectomy (LAG) for gastric cancer (GC) and establish a model to predict URO preoperatively. Between May 2007 and December 2014, we prospectively collected and retrospectively analyzed the data of 2608 GC patients who underwent LAG. Among them, 2580 patients not requiring an URO were defined as the Non-URO group, and 28 patients requiring an URO were defined as the URO group. Univariate, multivariate, and bootstrap analyses were performed to determine the independent predictors for URO, and a nomogram was constructed to preoperatively predict the rate of URO after LAG. Of the 2608 patients, the URO rate was 1.1% (28/2608) within the 30-day hospitalization. The mean URO time interval to first operation was 5.6 ± 5.5 (0.10-18.5) days. The main causes requiring URO were intraabdominal bleeding (57.1%), anastomotic bleeding (17.9%), anastomotic leakage (7.1%), and intraabdominal infection (7.1%). Compared to the Non-URO group, the URO group had a significantly longer hospital stay (p 70 years (odds ratio (OR) = 2.232, 95% confidence interval (CI) = 1.023-4.491, p = 0.028), male gender (OR = 32.983, 95% CI 1.405-25.343 × 10 6 , p = 0.027), and body mass index (BMI) > 25 kg/m 2 (OR = 2.550, 95% CI 1.017-5.398, p = 0.012) were independent risk factors for URO. A multivariable nomogram model for predicting URO exhibited a strong optimism-adjusted discrimination (concordance index, 0.687). No significant correlation was noted between the URO rate and operative period by Spearman analysis (r = 0.012, p = 0.548). Age > 70 years, Male, and BMI > 25 kg/m 2 were independent risk factors for URO. Based on the three risk factors, we developed a simple and practical nomogram to predict URO preoperatively, which might aid surgeons in reducing the URO rate when planning to perform LAG for GC.

  5. Variance in exposed perturbations impairs retention of visuomotor adaptation.

    Science.gov (United States)

    Canaveral, Cesar Augusto; Danion, Frédéric; Berrigan, Félix; Bernier, Pierre-Michel

    2017-11-01

    Sensorimotor control requires an accurate estimate of the state of the body. The brain optimizes state estimation by combining sensory signals with predictions of the sensory consequences of motor commands using a forward model. Given that both sensory signals and predictions are uncertain (i.e., noisy), the brain optimally weights the relative reliance on each source of information during adaptation. In support, it is known that uncertainty in the sensory predictions influences the rate and generalization of visuomotor adaptation. We investigated whether uncertainty in the sensory predictions affects the retention of a new visuomotor relationship. This was done by exposing three separate groups to a visuomotor rotation whose mean was common at 15° counterclockwise but whose variance around the mean differed (i.e., SD of 0°, 3.2°, or 4.5°). Retention was assessed by measuring the persistence of the adapted behavior in a no-vision phase. Results revealed that mean reach direction late in adaptation was similar across groups, suggesting it depended mainly on the mean of exposed rotations and was robust to differences in variance. However, retention differed across groups, with higher levels of variance being associated with a more rapid reversion toward nonadapted behavior. A control experiment ruled out the possibility that differences in retention were accounted for by differences in success rates. Exposure to variable rotations may have increased the uncertainty in sensory predictions, making the adapted forward model more labile and susceptible to change or decay. NEW & NOTEWORTHY The brain predicts the sensory consequences of motor commands through a forward model. These predictions are subject to uncertainty. We use visuomotor adaptation and modulate uncertainty in the sensory predictions by manipulating the variance in exposed rotations. Results reveal that variance does not influence the final extent of adaptation but selectively impairs the retention of

  6. Variance risk premia in CO_2 markets: A political perspective

    International Nuclear Information System (INIS)

    Reckling, Dennis

    2016-01-01

    The European Commission discusses the change of free allocation plans to guarantee a stable market equilibrium. Selling over-allocated contracts effectively depreciates prices and negates the effect intended by the regulator to establish a stable price mechanism for CO_2 assets. Our paper investigates mispricing and allocation issues by quantitatively analyzing variance risk premia of CO_2 markets over the course of changing regimes (Phase I-III) for three different assets (European Union Allowances, Certified Emissions Reductions and European Reduction Units). The research paper gives recommendations to regulatory bodies in order to most effectively cap the overall carbon dioxide emissions. The analysis of an enriched dataset, comprising not only of additional CO_2 assets, but also containing data from the European Energy Exchange, shows that variance risk premia are equal to a sample average of 0.69 for European Union Allowances (EUA), 0.17 for Certified Emissions Reductions (CER) and 0.81 for European Reduction Units (ERU). We identify the existence of a common risk factor across different assets that justifies the presence of risk premia. Various policy implications with regards to gaining investors’ confidence in the market are being reviewed. Consequently, we recommend the implementation of a price collar approach to support stable prices for emission allowances. - Highlights: •Enriched dataset covering all three political phases of the CO_2 markets. •Clear policy implications for regulators to most effectively cap the overall CO_2 emissions pool. •Applying a cross-asset benchmark index for variance beta estimation. •CER contracts have been analyzed with respect to variance risk premia for the first time. •Increased forecasting accuracy for CO_2 asset returns by using variance risk premia.

  7. Evaluation of Performance Status and Hematopoietic Cell Transplantation Specific Comorbidity Index on Unplanned Admission Rates in Patients with Multiple Myeloma Undergoing Outpatient Autologous Stem Cell Transplantation.

    Science.gov (United States)

    Obiozor, Cynthia; Subramaniam, Dipti P; Divine, Clint; Shune, Leyla; Singh, Anurag K; Lin, Tara L; Abhyankar, Sunil; Chen, G John; McGuirk, Joseph; Ganguly, Siddhartha

    2017-10-01

    Although outpatient autologous stem cell transplantation (ASCT) is safe and feasible in most instances, some patients undergoing planned outpatient transplantation for multiple myeloma (MM) will need inpatient admission for transplantation-related complications. We aim to evaluate the difference, if any, between outpatient and inpatient ASCT cohorts of MM patients in terms of admission rate, transplantation outcome, and overall survival. We also plan to assess whether the Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) and Karnofsky Performance Status (KPS) can predict unplanned admissions after adjusting for confounding factors. Patients with MM (n = 448) who underwent transplantation at our institution between 2009 and 2014 were included in this retrospective analysis. Patients were grouped into 3 cohorts: cohort A, planned inpatient ASCT (n = 216); cohort B, unplanned inpatient admissions (n = 57); and cohort C, planned outpatient SCT (n = 175). The statistical approach included descriptive, bivariate, and survival analyses. There were no differences among the 3 cohorts in terms of type of myeloma, stage at diagnosis, time from diagnosis to transplantation, CD34 cell dose, engraftment kinetics, and 100-day response rates. Serum creatinine was higher and patients were relatively older in both the planned inpatient (median age, 62 years; range, 33 to 80 years) and unplanned (median age, 59 years; range, 44 to 69 years) admission cohorts compared with the outpatient-only cohort (median age, 57 years; range, 40 to 70 years) (P Performance status (cohort A: median, 90%; range, 60% to 100%; cohort B: 80%, 50% to 100%; cohort C: 80%, 60% to 100%) was lower (P performance status (KPS 2 also appeared to be associated with worse outcomes compared with HCT-CI 0 to 1, the the difference did not reach statistical significance (hazard ratio, 1.41l 95% confidence interval, 0.72 to 2.76). Only 1 patient out of 448 died from a transplantation

  8. Impact of high- versus low-dose neuromuscular blocking agent administration on unplanned 30-day readmission rates in retroperitoneal laparoscopic surgery.

    Directory of Open Access Journals (Sweden)

    Martijn Boon

    Full Text Available Recent data shows that a neuromuscular block (NMB induced by administration of high doses of rocuronium improves surgical conditions in certain procedures. However, there are limited data on the effect such practices on postoperative outcomes. We performed a retrospective analysis to compare unplanned 30-day readmissions in patients that received high-dose versus low-dose rocuronium administration during general anesthesia for laparoscopic retroperitoneal surgery. This retrospective cohort study was performed in the Netherlands in an academic hospital where routine high-dose rocuronium NMB has been practiced since July 2015. Charts of patients receiving anesthesia between January 2014 and December 2016 were searched for surgical cases receiving high-dose rocuronium and matched with respect to procedure, age, sex and ASA classification to patients receiving low-dose rocuronium. The primary post-operative outcome was unplanned 30-day readmission rate. There were 130 patients in each cohort. Patients in the high- and low-dose rocuronium cohorts received 217 ± 49 versus 37 ± 5 mg rocuronium, respectively. In the high-dose rocuronium group neuromuscular activity was consistently monitored; matched patients were unreliably monitored. All patients receiving high-dose rocuronium were reversed with sugammadex, while just 33% of matched patients were reversed with sugammadex and 20% with neostigmine; the remaining patients were not reversed. Unplanned 30-day readmission rate was significantly lower in the high-dose compared to the low-dose rocuronium cohort (3.8% vs. 12.7%; p = 0.03; odds ratio = 0.33, 95% C.I. 0.12-0.95. This small retrospective study demonstrates a lower incidence of unplanned readmissions within 30-days following laparoscopic retroperitoneal surgery with high-dose relaxant anesthesia and sugammadex reversal in comparison to low-dose relaxant anesthesia. Further prospective studies are needed in larger samples to corroborate our

  9. Impact of high- versus low-dose neuromuscular blocking agent administration on unplanned 30-day readmission rates in retroperitoneal laparoscopic surgery.

    Science.gov (United States)

    Boon, Martijn; Martini, Chris; Yang, H Keri; Sen, Shuvayu S; Bevers, Rob; Warlé, Michiel; Aarts, Leon; Niesters, Marieke; Dahan, Albert

    2018-01-01

    Recent data shows that a neuromuscular block (NMB) induced by administration of high doses of rocuronium improves surgical conditions in certain procedures. However, there are limited data on the effect such practices on postoperative outcomes. We performed a retrospective analysis to compare unplanned 30-day readmissions in patients that received high-dose versus low-dose rocuronium administration during general anesthesia for laparoscopic retroperitoneal surgery. This retrospective cohort study was performed in the Netherlands in an academic hospital where routine high-dose rocuronium NMB has been practiced since July 2015. Charts of patients receiving anesthesia between January 2014 and December 2016 were searched for surgical cases receiving high-dose rocuronium and matched with respect to procedure, age, sex and ASA classification to patients receiving low-dose rocuronium. The primary post-operative outcome was unplanned 30-day readmission rate. There were 130 patients in each cohort. Patients in the high- and low-dose rocuronium cohorts received 217 ± 49 versus 37 ± 5 mg rocuronium, respectively. In the high-dose rocuronium group neuromuscular activity was consistently monitored; matched patients were unreliably monitored. All patients receiving high-dose rocuronium were reversed with sugammadex, while just 33% of matched patients were reversed with sugammadex and 20% with neostigmine; the remaining patients were not reversed. Unplanned 30-day readmission rate was significantly lower in the high-dose compared to the low-dose rocuronium cohort (3.8% vs. 12.7%; p = 0.03; odds ratio = 0.33, 95% C.I. 0.12-0.95). This small retrospective study demonstrates a lower incidence of unplanned readmissions within 30-days following laparoscopic retroperitoneal surgery with high-dose relaxant anesthesia and sugammadex reversal in comparison to low-dose relaxant anesthesia. Further prospective studies are needed in larger samples to corroborate our findings and

  10. Adaptation to Variance of Stimuli in Drosophila Larva Navigation

    Science.gov (United States)

    Wolk, Jason; Gepner, Ruben; Gershow, Marc

    In order to respond to stimuli that vary over orders of magnitude while also being capable of sensing very small changes, neural systems must be capable of rapidly adapting to the variance of stimuli. We study this adaptation in Drosophila larvae responding to varying visual signals and optogenetically induced fictitious odors using an infrared illuminated arena and custom computer vision software. Larval navigational decisions (when to turn) are modeled as the output a linear-nonlinear Poisson process. The development of the nonlinear turn rate in response to changes in variance is tracked using an adaptive point process filter determining the rate of adaptation to different stimulus profiles. Supported by NIH Grant 1DP2EB022359 and NSF Grant PHY-1455015.

  11. PORTFOLIO COMPOSITION WITH MINIMUM VARIANCE: COMPARISON WITH MARKET BENCHMARKS

    Directory of Open Access Journals (Sweden)

    Daniel Menezes Cavalcante

    2016-07-01

    Full Text Available Portfolio optimization strategies are advocated as being able to allow the composition of stocks portfolios that provide returns above market benchmarks. This study aims to determine whether, in fact, portfolios based on the minimum variance strategy, optimized by the Modern Portfolio Theory, are able to achieve earnings above market benchmarks in Brazil. Time series of 36 securities traded on the BM&FBOVESPA have been analyzed in a long period of time (1999-2012, with sample windows of 12, 36, 60 and 120 monthly observations. The results indicated that the minimum variance portfolio performance is superior to market benchmarks (CDI and IBOVESPA in terms of return and risk-adjusted return, especially in medium and long-term investment horizons.

  12. Compounding approach for univariate time series with nonstationary variances

    Science.gov (United States)

    Schäfer, Rudi; Barkhofen, Sonja; Guhr, Thomas; Stöckmann, Hans-Jürgen; Kuhl, Ulrich

    2015-12-01

    A defining feature of nonstationary systems is the time dependence of their statistical parameters. Measured time series may exhibit Gaussian statistics on short time horizons, due to the central limit theorem. The sample statistics for long time horizons, however, averages over the time-dependent variances. To model the long-term statistical behavior, we compound the local distribution with the distribution of its parameters. Here, we consider two concrete, but diverse, examples of such nonstationary systems: the turbulent air flow of a fan and a time series of foreign exchange rates. Our main focus is to empirically determine the appropriate parameter distribution for the compounding approach. To this end, we extract the relevant time scales by decomposing the time signals into windows and determine the distribution function of the thus obtained local variances.

  13. Variance inflation in high dimensional Support Vector Machines

    DEFF Research Database (Denmark)

    Abrahamsen, Trine Julie; Hansen, Lars Kai

    2013-01-01

    Many important machine learning models, supervised and unsupervised, are based on simple Euclidean distance or orthogonal projection in a high dimensional feature space. When estimating such models from small training sets we face the problem that the span of the training data set input vectors...... the case of Support Vector Machines (SVMS) and we propose a non-parametric scheme to restore proper generalizability. We illustrate the algorithm and its ability to restore performance on a wide range of benchmark data sets....... follow a different probability law with less variance. While the problem and basic means to reconstruct and deflate are well understood in unsupervised learning, the case of supervised learning is less well understood. We here investigate the effect of variance inflation in supervised learning including...

  14. Robust LOD scores for variance component-based linkage analysis.

    Science.gov (United States)

    Blangero, J; Williams, J T; Almasy, L

    2000-01-01

    The variance component method is now widely used for linkage analysis of quantitative traits. Although this approach offers many advantages, the importance of the underlying assumption of multivariate normality of the trait distribution within pedigrees has not been studied extensively. Simulation studies have shown that traits with leptokurtic distributions yield linkage test statistics that exhibit excessive Type I error when analyzed naively. We derive analytical formulae relating the deviation from the expected asymptotic distribution of the lod score to the kurtosis and total heritability of the quantitative trait. A simple correction constant yields a robust lod score for any deviation from normality and for any pedigree structure, and effectively eliminates the problem of inflated Type I error due to misspecification of the underlying probability model in variance component-based linkage analysis.

  15. Response variance in functional maps: neural darwinism revisited.

    Directory of Open Access Journals (Sweden)

    Hirokazu Takahashi

    Full Text Available The mechanisms by which functional maps and map plasticity contribute to cortical computation remain controversial. Recent studies have revisited the theory of neural Darwinism to interpret the learning-induced map plasticity and neuronal heterogeneity observed in the cortex. Here, we hypothesize that the Darwinian principle provides a substrate to explain the relationship between neuron heterogeneity and cortical functional maps. We demonstrate in the rat auditory cortex that the degree of response variance is closely correlated with the size of its representational area. Further, we show that the response variance within a given population is altered through training. These results suggest that larger representational areas may help to accommodate heterogeneous populations of neurons. Thus, functional maps and map plasticity are likely to play essential roles in Darwinian computation, serving as effective, but not absolutely necessary, structures to generate diverse response properties within a neural population.

  16. Response variance in functional maps: neural darwinism revisited.

    Science.gov (United States)

    Takahashi, Hirokazu; Yokota, Ryo; Kanzaki, Ryohei

    2013-01-01

    The mechanisms by which functional maps and map plasticity contribute to cortical computation remain controversial. Recent studies have revisited the theory of neural Darwinism to interpret the learning-induced map plasticity and neuronal heterogeneity observed in the cortex. Here, we hypothesize that the Darwinian principle provides a substrate to explain the relationship between neuron heterogeneity and cortical functional maps. We demonstrate in the rat auditory cortex that the degree of response variance is closely correlated with the size of its representational area. Further, we show that the response variance within a given population is altered through training. These results suggest that larger representational areas may help to accommodate heterogeneous populations of neurons. Thus, functional maps and map plasticity are likely to play essential roles in Darwinian computation, serving as effective, but not absolutely necessary, structures to generate diverse response properties within a neural population.

  17. Replica approach to mean-variance portfolio optimization

    Science.gov (United States)

    Varga-Haszonits, Istvan; Caccioli, Fabio; Kondor, Imre

    2016-12-01

    We consider the problem of mean-variance portfolio optimization for a generic covariance matrix subject to the budget constraint and the constraint for the expected return, with the application of the replica method borrowed from the statistical physics of disordered systems. We find that the replica symmetry of the solution does not need to be assumed, but emerges as the unique solution of the optimization problem. We also check the stability of this solution and find that the eigenvalues of the Hessian are positive for r  =  N/T  optimal in-sample variance is found to vanish at the critical point inversely proportional to the divergent estimation error.

  18. Variance reduction methods applied to deep-penetration problems

    International Nuclear Information System (INIS)

    Cramer, S.N.

    1984-01-01

    All deep-penetration Monte Carlo calculations require variance reduction methods. Before beginning with a detailed approach to these methods, several general comments concerning deep-penetration calculations by Monte Carlo, the associated variance reduction, and the similarities and differences of these with regard to non-deep-penetration problems will be addressed. The experienced practitioner of Monte Carlo methods will easily find exceptions to any of these generalities, but it is felt that these comments will aid the novice in understanding some of the basic ideas and nomenclature. Also, from a practical point of view, the discussions and developments presented are oriented toward use of the computer codes which are presented in segments of this Monte Carlo course

  19. Spatial analysis based on variance of moving window averages

    OpenAIRE

    Wu, B M; Subbarao, K V; Ferrandino, F J; Hao, J J

    2006-01-01

    A new method for analysing spatial patterns was designed based on the variance of moving window averages (VMWA), which can be directly calculated in geographical information systems or a spreadsheet program (e.g. MS Excel). Different types of artificial data were generated to test the method. Regardless of data types, the VMWA method correctly determined the mean cluster sizes. This method was also employed to assess spatial patterns in historical plant disease survey data encompassing both a...

  20. A mean-variance frontier in discrete and continuous time

    OpenAIRE

    Bekker, Paul A.

    2004-01-01

    The paper presents a mean-variance frontier based on dynamic frictionless investment strategies in continuous time. The result applies to a finite number of risky assets whose price process is given by multivariate geometric Brownian motion with deterministically varying coefficients. The derivation is based on the solution for the frontier in discrete time. Using the same multiperiod framework as Li and Ng (2000), I provide an alternative derivation and an alternative formulation of the solu...

  1. Efficient Scores, Variance Decompositions and Monte Carlo Swindles.

    Science.gov (United States)

    1984-08-28

    to ;r Then a version .of Pythagoras ’ theorem gives the variance decomposition (6.1) varT var S var o(T-S) P P0 0 0 One way to see this is to note...complete sufficient statistics for (B, a) , and that the standard- ized residuals a(y - XB) 6 are ancillary. Basu’s sufficiency- ancillarity theorem

  2. Variance-based sensitivity analysis for wastewater treatment plant modelling.

    Science.gov (United States)

    Cosenza, Alida; Mannina, Giorgio; Vanrolleghem, Peter A; Neumann, Marc B

    2014-02-01

    Global sensitivity analysis (GSA) is a valuable tool to support the use of mathematical models that characterise technical or natural systems. In the field of wastewater modelling, most of the recent applications of GSA use either regression-based methods, which require close to linear relationships between the model outputs and model factors, or screening methods, which only yield qualitative results. However, due to the characteristics of membrane bioreactors (MBR) (non-linear kinetics, complexity, etc.) there is an interest to adequately quantify the effects of non-linearity and interactions. This can be achieved with variance-based sensitivity analysis methods. In this paper, the Extended Fourier Amplitude Sensitivity Testing (Extended-FAST) method is applied to an integrated activated sludge model (ASM2d) for an MBR system including microbial product formation and physical separation processes. Twenty-one model outputs located throughout the different sections of the bioreactor and 79 model factors are considered. Significant interactions among the model factors are found. Contrary to previous GSA studies for ASM models, we find the relationship between variables and factors to be non-linear and non-additive. By analysing the pattern of the variance decomposition along the plant, the model factors having the highest variance contributions were identified. This study demonstrates the usefulness of variance-based methods in membrane bioreactor modelling where, due to the presence of membranes and different operating conditions than those typically found in conventional activated sludge systems, several highly non-linear effects are present. Further, the obtained results highlight the relevant role played by the modelling approach for MBR taking into account simultaneously biological and physical processes. © 2013.

  3. The mean and variance of phylogenetic diversity under rarefaction

    OpenAIRE

    Nipperess, David A.; Matsen, Frederick A.

    2013-01-01

    Phylogenetic diversity (PD) depends on sampling intensity, which complicates the comparison of PD between samples of different depth. One approach to dealing with differing sample depth for a given diversity statistic is to rarefy, which means to take a random subset of a given size of the original sample. Exact analytical formulae for the mean and variance of species richness under rarefaction have existed for some time but no such solution exists for PD. We have derived exact formulae for t...

  4. On mean reward variance in semi-Markov processes

    Czech Academy of Sciences Publication Activity Database

    Sladký, Karel

    2005-01-01

    Roč. 62, č. 3 (2005), s. 387-397 ISSN 1432-2994 R&D Projects: GA ČR(CZ) GA402/05/0115; GA ČR(CZ) GA402/04/1294 Institutional research plan: CEZ:AV0Z10750506 Keywords : Markov and semi-Markov processes with rewards * variance of cumulative reward * asymptotic behaviour Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.259, year: 2005

  5. Mean-Variance Analysis in a Multiperiod Setting

    OpenAIRE

    Frauendorfer, Karl; Siede, Heiko

    1997-01-01

    Similar to the classical Markowitz approach it is possible to apply a mean-variance criterion to a multiperiod setting to obtain efficient portfolios. To represent the stochastic dynamic characteristics necessary for modelling returns a process of asset returns is discretized with respect to time and space and summarized in a scenario tree. The resulting optimization problem is solved by means of stochastic multistage programming. The optimal solutions show equivalent structural properties as...

  6. Analytic solution to variance optimization with no short positions

    Science.gov (United States)

    Kondor, Imre; Papp, Gábor; Caccioli, Fabio

    2017-12-01

    We consider the variance portfolio optimization problem with a ban on short selling. We provide an analytical solution by means of the replica method for the case of a portfolio of independent, but not identically distributed, assets. We study the behavior of the solution as a function of the ratio r between the number N of assets and the length T of the time series of returns used to estimate risk. The no-short-selling constraint acts as an asymmetric \

  7. Estimating Predictive Variance for Statistical Gas Distribution Modelling

    International Nuclear Information System (INIS)

    Lilienthal, Achim J.; Asadi, Sahar; Reggente, Matteo

    2009-01-01

    Recent publications in statistical gas distribution modelling have proposed algorithms that model mean and variance of a distribution. This paper argues that estimating the predictive concentration variance entails not only a gradual improvement but is rather a significant step to advance the field. This is, first, since the models much better fit the particular structure of gas distributions, which exhibit strong fluctuations with considerable spatial variations as a result of the intermittent character of gas dispersal. Second, because estimating the predictive variance allows to evaluate the model quality in terms of the data likelihood. This offers a solution to the problem of ground truth evaluation, which has always been a critical issue for gas distribution modelling. It also enables solid comparisons of different modelling approaches, and provides the means to learn meta parameters of the model, to determine when the model should be updated or re-initialised, or to suggest new measurement locations based on the current model. We also point out directions of related ongoing or potential future research work.

  8. Improved estimation of the variance in Monte Carlo criticality calculations

    International Nuclear Information System (INIS)

    Hoogenboom, J. Eduard

    2008-01-01

    Results for the effective multiplication factor in a Monte Carlo criticality calculations are often obtained from averages over a number of cycles or batches after convergence of the fission source distribution to the fundamental mode. Then the standard deviation of the effective multiplication factor is also obtained from the k eff results over these cycles. As the number of cycles will be rather small, the estimate of the variance or standard deviation in k eff will not be very reliable, certainly not for the first few cycles after source convergence. In this paper the statistics for k eff are based on the generation of new fission neutron weights during each history in a cycle. It is shown that this gives much more reliable results for the standard deviation even after a small number of cycles. Also attention is paid to the variance of the variance (VoV) and the standard deviation of the standard deviation. A derivation is given how to obtain an unbiased estimate for the VoV, even for a small number of samples. (authors)

  9. Improved estimation of the variance in Monte Carlo criticality calculations

    Energy Technology Data Exchange (ETDEWEB)

    Hoogenboom, J. Eduard [Delft University of Technology, Delft (Netherlands)

    2008-07-01

    Results for the effective multiplication factor in a Monte Carlo criticality calculations are often obtained from averages over a number of cycles or batches after convergence of the fission source distribution to the fundamental mode. Then the standard deviation of the effective multiplication factor is also obtained from the k{sub eff} results over these cycles. As the number of cycles will be rather small, the estimate of the variance or standard deviation in k{sub eff} will not be very reliable, certainly not for the first few cycles after source convergence. In this paper the statistics for k{sub eff} are based on the generation of new fission neutron weights during each history in a cycle. It is shown that this gives much more reliable results for the standard deviation even after a small number of cycles. Also attention is paid to the variance of the variance (VoV) and the standard deviation of the standard deviation. A derivation is given how to obtain an unbiased estimate for the VoV, even for a small number of samples. (authors)

  10. A general transform for variance reduction in Monte Carlo simulations

    International Nuclear Information System (INIS)

    Becker, T.L.; Larsen, E.W.

    2011-01-01

    This paper describes a general transform to reduce the variance of the Monte Carlo estimate of some desired solution, such as flux or biological dose. This transform implicitly includes many standard variance reduction techniques, including source biasing, collision biasing, the exponential transform for path-length stretching, and weight windows. Rather than optimizing each of these techniques separately or choosing semi-empirical biasing parameters based on the experience of a seasoned Monte Carlo practitioner, this General Transform unites all these variance techniques to achieve one objective: a distribution of Monte Carlo particles that attempts to optimize the desired solution. Specifically, this transform allows Monte Carlo particles to be distributed according to the user's specification by using information obtained from a computationally inexpensive deterministic simulation of the problem. For this reason, we consider the General Transform to be a hybrid Monte Carlo/Deterministic method. The numerical results con rm that the General Transform distributes particles according to the user-specified distribution and generally provide reasonable results for shielding applications. (author)

  11. Modality-Driven Classification and Visualization of Ensemble Variance

    Energy Technology Data Exchange (ETDEWEB)

    Bensema, Kevin; Gosink, Luke; Obermaier, Harald; Joy, Kenneth I.

    2016-10-01

    Advances in computational power now enable domain scientists to address conceptual and parametric uncertainty by running simulations multiple times in order to sufficiently sample the uncertain input space. While this approach helps address conceptual and parametric uncertainties, the ensemble datasets produced by this technique present a special challenge to visualization researchers as the ensemble dataset records a distribution of possible values for each location in the domain. Contemporary visualization approaches that rely solely on summary statistics (e.g., mean and variance) cannot convey the detailed information encoded in ensemble distributions that are paramount to ensemble analysis; summary statistics provide no information about modality classification and modality persistence. To address this problem, we propose a novel technique that classifies high-variance locations based on the modality of the distribution of ensemble predictions. Additionally, we develop a set of confidence metrics to inform the end-user of the quality of fit between the distribution at a given location and its assigned class. We apply a similar method to time-varying ensembles to illustrate the relationship between peak variance and bimodal or multimodal behavior. These classification schemes enable a deeper understanding of the behavior of the ensemble members by distinguishing between distributions that can be described by a single tendency and distributions which reflect divergent trends in the ensemble.

  12. IT and communication technologies dominate adolescent downtime

    OpenAIRE

    Bohmann, Sandra; Schupp, Jürgen

    2016-01-01

    Today's teenagers spend their free time very differently than they did 15 years ago: engagement with IT and communications technologies is now their most significant leisure activity. Representative statistics based on data from the Socio-Economic Panel (SOEP) longitudinal study indicate that Internet and computer-based recreation plays a major role for more than 95 percent of all 17-year-olds in Germany, regardless of gender. Even though access to the Internet and computer-based technologies...

  13. Magnet powering with zero downtime - a dream?

    CERN Document Server

    Zerlauth, Markus

    2012-01-01

    Despite a number of improvements already applied in the course of the year, the magnet powering system of the LHC still accounts for around 50% of the premature beam dumps. This number might even further increase when moving to higher beam energies in the next years. With mitigations of radiation effects and the prospects for beam induced magnet quenches being discussed elsewhere, we aim at identifying possible mid- and long-term improvements within the various equipment systems to further reduce the number of equipment failures leading to a loss of the particle beams. Amongst others, this includes the sensitivity of equipment to external causes such as electromagnetic perturbations or perturbations on the electrical network. To conclude, the gain of the identified mitigations will have to be balanced against the potential impact on schedule and cost.

  14. A proxy for variance in dense matching over homogeneous terrain

    Science.gov (United States)

    Altena, Bas; Cockx, Liesbet; Goedemé, Toon

    2014-05-01

    Automation in photogrammetry and avionics have brought highly autonomous UAV mapping solutions on the market. These systems have great potential for geophysical research, due to their mobility and simplicity of work. Flight planning can be done on site and orientation parameters are estimated automatically. However, one major drawback is still present: if contrast is lacking, stereoscopy fails. Consequently, topographic information cannot be obtained precisely through photogrammetry for areas with low contrast. Even though more robustness is added in the estimation through multi-view geometry, a precise product is still lacking. For the greater part, interpolation is applied over these regions, where the estimation is constrained by uniqueness, its epipolar line and smoothness. Consequently, digital surface models are generated with an estimate of the topography, without holes but also without an indication of its variance. Every dense matching algorithm is based on a similarity measure. Our methodology uses this property to support the idea that if only noise is present, no correspondence can be detected. Therefore, the noise level is estimated in respect to the intensity signal of the topography (SNR) and this ratio serves as a quality indicator for the automatically generated product. To demonstrate this variance indicator, two different case studies were elaborated. The first study is situated at an open sand mine near the village of Kiezegem, Belgium. Two different UAV systems flew over the site. One system had automatic intensity regulation, and resulted in low contrast over the sandy interior of the mine. That dataset was used to identify the weak estimations of the topography and was compared with the data from the other UAV flight. In the second study a flight campaign with the X100 system was conducted along the coast near Wenduine, Belgium. The obtained images were processed through structure-from-motion software. Although the beach had a very low

  15. Estimation of noise-free variance to measure heterogeneity.

    Directory of Open Access Journals (Sweden)

    Tilo Winkler

    Full Text Available Variance is a statistical parameter used to characterize heterogeneity or variability in data sets. However, measurements commonly include noise, as random errors superimposed to the actual value, which may substantially increase the variance compared to a noise-free data set. Our aim was to develop and validate a method to estimate noise-free spatial heterogeneity of pulmonary perfusion using dynamic positron emission tomography (PET scans. On theoretical grounds, we demonstrate a linear relationship between the total variance of a data set derived from averages of n multiple measurements, and the reciprocal of n. Using multiple measurements with varying n yields estimates of the linear relationship including the noise-free variance as the constant parameter. In PET images, n is proportional to the number of registered decay events, and the variance of the image is typically normalized by the square of its mean value yielding a coefficient of variation squared (CV(2. The method was evaluated with a Jaszczak phantom as reference spatial heterogeneity (CV(r(2 for comparison with our estimate of noise-free or 'true' heterogeneity (CV(t(2. We found that CV(t(2 was only 5.4% higher than CV(r2. Additional evaluations were conducted on 38 PET scans of pulmonary perfusion using (13NN-saline injection. The mean CV(t(2 was 0.10 (range: 0.03-0.30, while the mean CV(2 including noise was 0.24 (range: 0.10-0.59. CV(t(2 was in average 41.5% of the CV(2 measured including noise (range: 17.8-71.2%. The reproducibility of CV(t(2 was evaluated using three repeated PET scans from five subjects. Individual CV(t(2 were within 16% of each subject's mean and paired t-tests revealed no difference among the results from the three consecutive PET scans. In conclusion, our method provides reliable noise-free estimates of CV(t(2 in PET scans, and may be useful for similar statistical problems in experimental data.

  16. On the noise variance of a digital mammography system

    International Nuclear Information System (INIS)

    Burgess, Arthur

    2004-01-01

    A recent paper by Cooper et al. [Med. Phys. 30, 2614-2621 (2003)] contains some apparently anomalous results concerning the relationship between pixel variance and x-ray exposure for a digital mammography system. They found an unexpected peak in a display domain pixel variance plot as a function of 1/mAs (their Fig. 5) with a decrease in the range corresponding to high display data values, corresponding to low x-ray exposures. As they pointed out, if the detector response is linear in exposure and the transformation from raw to display data scales is logarithmic, then pixel variance should be a monotonically increasing function in the figure. They concluded that the total system transfer curve, between input exposure and display image data values, is not logarithmic over the full exposure range. They separated data analysis into two regions and plotted the logarithm of display image pixel variance as a function of the logarithm of the mAs used to produce the phantom images. They found a slope of minus one for high mAs values and concluded that the transfer function is logarithmic in this region. They found a slope of 0.6 for the low mAs region and concluded that the transfer curve was neither linear nor logarithmic for low exposure values. It is known that the digital mammography system investigated by Cooper et al. has a linear relationship between exposure and raw data values [Vedantham et al., Med. Phys. 27, 558-567 (2000)]. The purpose of this paper is to show that the variance effect found by Cooper et al. (their Fig. 5) arises because the transformation from the raw data scale (14 bits) to the display scale (12 bits), for the digital mammography system they investigated, is not logarithmic for raw data values less than about 300 (display data values greater than about 3300). At low raw data values the transformation is linear and prevents over-ranging of the display data scale. Parametric models for the two transformations will be presented. Results of pixel

  17. Fringe biasing: A variance reduction technique for optically thick meshes

    Energy Technology Data Exchange (ETDEWEB)

    Smedley-Stevenson, R. P. [AWE PLC, Aldermaston Reading, Berkshire, RG7 4PR (United Kingdom)

    2013-07-01

    Fringe biasing is a stratified sampling scheme applicable to Monte Carlo thermal radiation transport codes. The thermal emission source in optically thick cells is partitioned into separate contributions from the cell interiors (where the likelihood of the particles escaping the cells is virtually zero) and the 'fringe' regions close to the cell boundaries. Thermal emission in the cell interiors can now be modelled with fewer particles, the remaining particles being concentrated in the fringes so that they are more likely to contribute to the energy exchange between cells. Unlike other techniques for improving the efficiency in optically thick regions (such as random walk and discrete diffusion treatments), fringe biasing has the benefit of simplicity, as the associated changes are restricted to the sourcing routines with the particle tracking routines being unaffected. This paper presents an analysis of the potential for variance reduction achieved from employing the fringe biasing technique. The aim of this analysis is to guide the implementation of this technique in Monte Carlo thermal radiation codes, specifically in order to aid the choice of the fringe width and the proportion of particles allocated to the fringe (which are interrelated) in multi-dimensional simulations, and to confirm that the significant levels of variance reduction achieved in simulations can be understood by studying the behaviour for simple test cases. The variance reduction properties are studied for a single cell in a slab geometry purely absorbing medium, investigating the accuracy of the scalar flux and current tallies on one of the interfaces with the surrounding medium. (authors)

  18. Fringe biasing: A variance reduction technique for optically thick meshes

    International Nuclear Information System (INIS)

    Smedley-Stevenson, R. P.

    2013-01-01

    Fringe biasing is a stratified sampling scheme applicable to Monte Carlo thermal radiation transport codes. The thermal emission source in optically thick cells is partitioned into separate contributions from the cell interiors (where the likelihood of the particles escaping the cells is virtually zero) and the 'fringe' regions close to the cell boundaries. Thermal emission in the cell interiors can now be modelled with fewer particles, the remaining particles being concentrated in the fringes so that they are more likely to contribute to the energy exchange between cells. Unlike other techniques for improving the efficiency in optically thick regions (such as random walk and discrete diffusion treatments), fringe biasing has the benefit of simplicity, as the associated changes are restricted to the sourcing routines with the particle tracking routines being unaffected. This paper presents an analysis of the potential for variance reduction achieved from employing the fringe biasing technique. The aim of this analysis is to guide the implementation of this technique in Monte Carlo thermal radiation codes, specifically in order to aid the choice of the fringe width and the proportion of particles allocated to the fringe (which are interrelated) in multi-dimensional simulations, and to confirm that the significant levels of variance reduction achieved in simulations can be understood by studying the behaviour for simple test cases. The variance reduction properties are studied for a single cell in a slab geometry purely absorbing medium, investigating the accuracy of the scalar flux and current tallies on one of the interfaces with the surrounding medium. (authors)

  19. An Empirical Temperature Variance Source Model in Heated Jets

    Science.gov (United States)

    Khavaran, Abbas; Bridges, James

    2012-01-01

    An acoustic analogy approach is implemented that models the sources of jet noise in heated jets. The equivalent sources of turbulent mixing noise are recognized as the differences between the fluctuating and Favre-averaged Reynolds stresses and enthalpy fluxes. While in a conventional acoustic analogy only Reynolds stress components are scrutinized for their noise generation properties, it is now accepted that a comprehensive source model should include the additional entropy source term. Following Goldstein s generalized acoustic analogy, the set of Euler equations are divided into two sets of equations that govern a non-radiating base flow plus its residual components. When the base flow is considered as a locally parallel mean flow, the residual equations may be rearranged to form an inhomogeneous third-order wave equation. A general solution is written subsequently using a Green s function method while all non-linear terms are treated as the equivalent sources of aerodynamic sound and are modeled accordingly. In a previous study, a specialized Reynolds-averaged Navier-Stokes (RANS) solver was implemented to compute the variance of thermal fluctuations that determine the enthalpy flux source strength. The main objective here is to present an empirical model capable of providing a reasonable estimate of the stagnation temperature variance in a jet. Such a model is parameterized as a function of the mean stagnation temperature gradient in the jet, and is evaluated using commonly available RANS solvers. The ensuing thermal source distribution is compared with measurements as well as computational result from a dedicated RANS solver that employs an enthalpy variance and dissipation rate model. Turbulent mixing noise predictions are presented for a wide range of jet temperature ratios from 1.0 to 3.20.

  20. Double Minimum Variance Beamforming Method to Enhance Photoacoustic Imaging

    OpenAIRE

    Paridar, Roya; Mozaffarzadeh, Moein; Nasiriavanaki, Mohammadreza; Orooji, Mahdi

    2018-01-01

    One of the common algorithms used to reconstruct photoacoustic (PA) images is the non-adaptive Delay-and-Sum (DAS) beamformer. However, the quality of the reconstructed PA images obtained by DAS is not satisfying due to its high level of sidelobes and wide mainlobe. In contrast, adaptive beamformers, such as minimum variance (MV), result in an improved image compared to DAS. In this paper, a novel beamforming method, called Double MV (D-MV) is proposed to enhance the image quality compared to...

  1. A Note on the Kinks at the Mean Variance Frontier

    OpenAIRE

    Vörös, J.; Kriens, J.; Strijbosch, L.W.G.

    1997-01-01

    In this paper the standard portfolio case with short sales restrictions is analyzed.Dybvig pointed out that if there is a kink at a risky portfolio on the efficient frontier, then the securities in this portfolio have equal expected return and the converse of this statement is false.For the existence of kinks at the efficient frontier the sufficient condition is given here and a new procedure is used to derive the efficient frontier, i.e. the characteristics of the mean variance frontier.

  2. Variance reduction techniques in the simulation of Markov processes

    International Nuclear Information System (INIS)

    Lessi, O.

    1987-01-01

    We study a functional r of the stationary distribution of a homogeneous Markov chain. It is often difficult or impossible to perform the analytical calculation of r and so it is reasonable to estimate r by a simulation process. A consistent estimator r(n) of r is obtained with respect to a chain with a countable state space. Suitably modifying the estimator r(n) of r one obtains a new consistent estimator which has a smaller variance than r(n). The same is obtained in the case of finite state space

  3. A guide to SPSS for analysis of variance

    CERN Document Server

    Levine, Gustav

    2013-01-01

    This book offers examples of programs designed for analysis of variance and related statistical tests of significance that can be run with SPSS. The reader may copy these programs directly, changing only the names or numbers of levels of factors according to individual needs. Ways of altering command specifications to fit situations with larger numbers of factors are discussed and illustrated, as are ways of combining program statements to request a variety of analyses in the same program. The first two chapters provide an introduction to the use of SPSS, Versions 3 and 4. General rules conce

  4. Diffusion-Based Trajectory Observers with Variance Constraints

    DEFF Research Database (Denmark)

    Alcocer, Alex; Jouffroy, Jerome; Oliveira, Paulo

    Diffusion-based trajectory observers have been recently proposed as a simple and efficient framework to solve diverse smoothing problems in underwater navigation. For instance, to obtain estimates of the trajectories of an underwater vehicle given position fixes from an acoustic positioning system...... of smoothing and is determined by resorting to trial and error. This paper presents a methodology to choose the observer gain by taking into account a priori information on the variance of the position measurement errors. Experimental results with data from an acoustic positioning system are presented...

  5. A Fay-Herriot Model with Different Random Effect Variances

    Czech Academy of Sciences Publication Activity Database

    Hobza, Tomáš; Morales, D.; Herrador, M.; Esteban, M.D.

    2011-01-01

    Roč. 40, č. 5 (2011), s. 785-797 ISSN 0361-0926 R&D Projects: GA MŠk 1M0572 Institutional research plan: CEZ:AV0Z10750506 Keywords : small area estimation * Fay-Herriot model * Linear mixed model * Labor Force Survey Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.274, year: 2011 http://library.utia.cas.cz/separaty/2011/SI/hobza-a%20fay-herriot%20model%20with%20different%20random%20effect%20variances.pdf

  6. Variational Variance Reduction for Monte Carlo Criticality Calculations

    International Nuclear Information System (INIS)

    Densmore, Jeffery D.; Larsen, Edward W.

    2001-01-01

    A new variational variance reduction (VVR) method for Monte Carlo criticality calculations was developed. This method employs (a) a variational functional that is more accurate than the standard direct functional, (b) a representation of the deterministically obtained adjoint flux that is especially accurate for optically thick problems with high scattering ratios, and (c) estimates of the forward flux obtained by Monte Carlo. The VVR method requires no nonanalog Monte Carlo biasing, but it may be used in conjunction with Monte Carlo biasing schemes. Some results are presented from a class of criticality calculations involving alternating arrays of fuel and moderator regions

  7. Parameter uncertainty effects on variance-based sensitivity analysis

    International Nuclear Information System (INIS)

    Yu, W.; Harris, T.J.

    2009-01-01

    In the past several years there has been considerable commercial and academic interest in methods for variance-based sensitivity analysis. The industrial focus is motivated by the importance of attributing variance contributions to input factors. A more complete understanding of these relationships enables companies to achieve goals related to quality, safety and asset utilization. In a number of applications, it is possible to distinguish between two types of input variables-regressive variables and model parameters. Regressive variables are those that can be influenced by process design or by a control strategy. With model parameters, there are typically no opportunities to directly influence their variability. In this paper, we propose a new method to perform sensitivity analysis through a partitioning of the input variables into these two groupings: regressive variables and model parameters. A sequential analysis is proposed, where first an sensitivity analysis is performed with respect to the regressive variables. In the second step, the uncertainty effects arising from the model parameters are included. This strategy can be quite useful in understanding process variability and in developing strategies to reduce overall variability. When this method is used for nonlinear models which are linear in the parameters, analytical solutions can be utilized. In the more general case of models that are nonlinear in both the regressive variables and the parameters, either first order approximations can be used, or numerically intensive methods must be used

  8. Variance of indoor radon concentration: Major influencing factors

    Energy Technology Data Exchange (ETDEWEB)

    Yarmoshenko, I., E-mail: ivy@ecko.uran.ru [Institute of Industrial Ecology UB RAS, Sophy Kovalevskoy, 20, Ekaterinburg (Russian Federation); Vasilyev, A.; Malinovsky, G. [Institute of Industrial Ecology UB RAS, Sophy Kovalevskoy, 20, Ekaterinburg (Russian Federation); Bossew, P. [German Federal Office for Radiation Protection (BfS), Berlin (Germany); Žunić, Z.S. [Institute of Nuclear Sciences “Vinca”, University of Belgrade (Serbia); Onischenko, A.; Zhukovsky, M. [Institute of Industrial Ecology UB RAS, Sophy Kovalevskoy, 20, Ekaterinburg (Russian Federation)

    2016-01-15

    Variance of radon concentration in dwelling atmosphere is analysed with regard to geogenic and anthropogenic influencing factors. Analysis includes review of 81 national and regional indoor radon surveys with varying sampling pattern, sample size and duration of measurements and detailed consideration of two regional surveys (Sverdlovsk oblast, Russia and Niška Banja, Serbia). The analysis of the geometric standard deviation revealed that main factors influencing the dispersion of indoor radon concentration over the territory are as follows: area of territory, sample size, characteristics of measurements technique, the radon geogenic potential, building construction characteristics and living habits. As shown for Sverdlovsk oblast and Niška Banja town the dispersion as quantified by GSD is reduced by restricting to certain levels of control factors. Application of the developed approach to characterization of the world population radon exposure is discussed. - Highlights: • Influence of lithosphere and anthroposphere on variance of indoor radon is found. • Level-by-level analysis reduces GSD by a factor of 1.9. • Worldwide GSD is underestimated.

  9. Variance Component Selection With Applications to Microbiome Taxonomic Data

    Directory of Open Access Journals (Sweden)

    Jing Zhai

    2018-03-01

    Full Text Available High-throughput sequencing technology has enabled population-based studies of the role of the human microbiome in disease etiology and exposure response. Microbiome data are summarized as counts or composition of the bacterial taxa at different taxonomic levels. An important problem is to identify the bacterial taxa that are associated with a response. One method is to test the association of specific taxon with phenotypes in a linear mixed effect model, which incorporates phylogenetic information among bacterial communities. Another type of approaches consider all taxa in a joint model and achieves selection via penalization method, which ignores phylogenetic information. In this paper, we consider regression analysis by treating bacterial taxa at different level as multiple random effects. For each taxon, a kernel matrix is calculated based on distance measures in the phylogenetic tree and acts as one variance component in the joint model. Then taxonomic selection is achieved by the lasso (least absolute shrinkage and selection operator penalty on variance components. Our method integrates biological information into the variable selection problem and greatly improves selection accuracies. Simulation studies demonstrate the superiority of our methods versus existing methods, for example, group-lasso. Finally, we apply our method to a longitudinal microbiome study of Human Immunodeficiency Virus (HIV infected patients. We implement our method using the high performance computing language Julia. Software and detailed documentation are freely available at https://github.com/JingZhai63/VCselection.

  10. Worldwide variance in the potential utilization of Gamma Knife radiosurgery.

    Science.gov (United States)

    Hamilton, Travis; Dade Lunsford, L

    2016-12-01

    OBJECTIVE The role of Gamma Knife radiosurgery (GKRS) has expanded worldwide during the past 3 decades. The authors sought to evaluate whether experienced users vary in their estimate of its potential use. METHODS Sixty-six current Gamma Knife users from 24 countries responded to an electronic survey. They estimated the potential role of GKRS for benign and malignant tumors, vascular malformations, and functional disorders. These estimates were compared with published disease epidemiological statistics and the 2014 use reports provided by the Leksell Gamma Knife Society (16,750 cases). RESULTS Respondents reported no significant variation in the estimated use in many conditions for which GKRS is performed: meningiomas, vestibular schwannomas, and arteriovenous malformations. Significant variance in the estimated use of GKRS was noted for pituitary tumors, craniopharyngiomas, and cavernous malformations. For many current indications, the authors found significant variance in GKRS users based in the Americas, Europe, and Asia. Experts estimated that GKRS was used in only 8.5% of the 196,000 eligible cases in 2014. CONCLUSIONS Although there was a general worldwide consensus regarding many major indications for GKRS, significant variability was noted for several more controversial roles. This expert opinion survey also suggested that GKRS is significantly underutilized for many current diagnoses, especially in the Americas. Future studies should be conducted to investigate health care barriers to GKRS for many patients.

  11. Hidden temporal order unveiled in stock market volatility variance

    Directory of Open Access Journals (Sweden)

    Y. Shapira

    2011-06-01

    Full Text Available When analyzed by standard statistical methods, the time series of the daily return of financial indices appear to behave as Markov random series with no apparent temporal order or memory. This empirical result seems to be counter intuitive since investor are influenced by both short and long term past market behaviors. Consequently much effort has been devoted to unveil hidden temporal order in the market dynamics. Here we show that temporal order is hidden in the series of the variance of the stocks volatility. First we show that the correlation between the variances of the daily returns and means of segments of these time series is very large and thus cannot be the output of random series, unless it has some temporal order in it. Next we show that while the temporal order does not show in the series of the daily return, rather in the variation of the corresponding volatility series. More specifically, we found that the behavior of the shuffled time series is equivalent to that of a random time series, while that of the original time series have large deviations from the expected random behavior, which is the result of temporal structure. We found the same generic behavior in 10 different stock markets from 7 different countries. We also present analysis of specially constructed sequences in order to better understand the origin of the observed temporal order in the market sequences. Each sequence was constructed from segments with equal number of elements taken from algebraic distributions of three different slopes.

  12. Waste Isolation Pilot Plant no-migration variance petition

    International Nuclear Information System (INIS)

    1990-01-01

    Section 3004 of RCRA allows EPA to grant a variance from the land disposal restrictions when a demonstration can be made that, to a reasonable degree of certainty, there will be no migration of hazardous constituents from the disposal unit for as long as the waste remains hazardous. Specific requirements for making this demonstration are found in 40 CFR 268.6, and EPA has published a draft guidance document to assist petitioners in preparing a variance request. Throughout the course of preparing this petition, technical staff from DOE, EPA, and their contractors have met frequently to discuss and attempt to resolve issues specific to radioactive mixed waste and the WIPP facility. The DOE believes it meets or exceeds all requirements set forth for making a successful ''no-migration'' demonstration. The petition presents information under five general headings: (1) waste information; (2) site characterization; (3) facility information; (4) assessment of environmental impacts, including the results of waste mobility modeling; and (5) analysis of uncertainties. Additional background and supporting documentation is contained in the 15 appendices to the petition, as well as in an extensive addendum published in October 1989

  13. Deterministic mean-variance-optimal consumption and investment

    DEFF Research Database (Denmark)

    Christiansen, Marcus; Steffensen, Mogens

    2013-01-01

    In dynamic optimal consumption–investment problems one typically aims to find an optimal control from the set of adapted processes. This is also the natural starting point in case of a mean-variance objective. In contrast, we solve the optimization problem with the special feature that the consum......In dynamic optimal consumption–investment problems one typically aims to find an optimal control from the set of adapted processes. This is also the natural starting point in case of a mean-variance objective. In contrast, we solve the optimization problem with the special feature...... that the consumption rate and the investment proportion are constrained to be deterministic processes. As a result we get rid of a series of unwanted features of the stochastic solution including diffusive consumption, satisfaction points and consistency problems. Deterministic strategies typically appear in unit......-linked life insurance contracts, where the life-cycle investment strategy is age dependent but wealth independent. We explain how optimal deterministic strategies can be found numerically and present an example from life insurance where we compare the optimal solution with suboptimal deterministic strategies...

  14. MENENTUKAN PORTOFOLIO OPTIMAL MENGGUNAKAN MODEL CONDITIONAL MEAN VARIANCE

    Directory of Open Access Journals (Sweden)

    I GEDE ERY NISCAHYANA

    2016-08-01

    Full Text Available When the returns of stock prices show the existence of autocorrelation and heteroscedasticity, then conditional mean variance models are suitable method to model the behavior of the stocks. In this thesis, the implementation of the conditional mean variance model to the autocorrelated and heteroscedastic return was discussed. The aim of this thesis was to assess the effect of the autocorrelated and heteroscedastic returns to the optimal solution of a portfolio. The margin of four stocks, Fortune Mate Indonesia Tbk (FMII.JK, Bank Permata Tbk (BNLI.JK, Suryamas Dutamakmur Tbk (SMDM.JK dan Semen Gresik Indonesia Tbk (SMGR.JK were estimated by GARCH(1,1 model with standard innovations following the standard normal distribution and the t-distribution.  The estimations were used to construct a portfolio. The portfolio optimal was found when the standard innovation used was t-distribution with the standard deviation of 1.4532 and the mean of 0.8023 consisting of 0.9429 (94% of FMII stock, 0.0473 (5% of  BNLI stock, 0% of SMDM stock, 1% of  SMGR stock.

  15. Variance decomposition-based sensitivity analysis via neural networks

    International Nuclear Information System (INIS)

    Marseguerra, Marzio; Masini, Riccardo; Zio, Enrico; Cojazzi, Giacomo

    2003-01-01

    This paper illustrates a method for efficiently performing multiparametric sensitivity analyses of the reliability model of a given system. These analyses are of great importance for the identification of critical components in highly hazardous plants, such as the nuclear or chemical ones, thus providing significant insights for their risk-based design and management. The technique used to quantify the importance of a component parameter with respect to the system model is based on a classical decomposition of the variance. When the model of the system is realistically complicated (e.g. by aging, stand-by, maintenance, etc.), its analytical evaluation soon becomes impractical and one is better off resorting to Monte Carlo simulation techniques which, however, could be computationally burdensome. Therefore, since the variance decomposition method requires a large number of system evaluations, each one to be performed by Monte Carlo, the need arises for possibly substituting the Monte Carlo simulation model with a fast, approximated, algorithm. Here we investigate an approach which makes use of neural networks appropriately trained on the results of a Monte Carlo system reliability/availability evaluation to quickly provide with reasonable approximation, the values of the quantities of interest for the sensitivity analyses. The work was a joint effort between the Department of Nuclear Engineering of the Polytechnic of Milan, Italy, and the Institute for Systems, Informatics and Safety, Nuclear Safety Unit of the Joint Research Centre in Ispra, Italy which sponsored the project

  16. Concentration variance decay during magma mixing: a volcanic chronometer.

    Science.gov (United States)

    Perugini, Diego; De Campos, Cristina P; Petrelli, Maurizio; Dingwell, Donald B

    2015-09-21

    The mixing of magmas is a common phenomenon in explosive eruptions. Concentration variance is a useful metric of this process and its decay (CVD) with time is an inevitable consequence during the progress of magma mixing. In order to calibrate this petrological/volcanological clock we have performed a time-series of high temperature experiments of magma mixing. The results of these experiments demonstrate that compositional variance decays exponentially with time. With this calibration the CVD rate (CVD-R) becomes a new geochronometer for the time lapse from initiation of mixing to eruption. The resultant novel technique is fully independent of the typically unknown advective history of mixing - a notorious uncertainty which plagues the application of many diffusional analyses of magmatic history. Using the calibrated CVD-R technique we have obtained mingling-to-eruption times for three explosive volcanic eruptions from Campi Flegrei (Italy) in the range of tens of minutes. These in turn imply ascent velocities of 5-8 meters per second. We anticipate the routine application of the CVD-R geochronometer to the eruptive products of active volcanoes in future in order to constrain typical "mixing to eruption" time lapses such that monitoring activities can be targeted at relevant timescales and signals during volcanic unrest.

  17. Mean-Variance-Validation Technique for Sequential Kriging Metamodels

    International Nuclear Information System (INIS)

    Lee, Tae Hee; Kim, Ho Sung

    2010-01-01

    The rigorous validation of the accuracy of metamodels is an important topic in research on metamodel techniques. Although a leave-k-out cross-validation technique involves a considerably high computational cost, it cannot be used to measure the fidelity of metamodels. Recently, the mean 0 validation technique has been proposed to quantitatively determine the accuracy of metamodels. However, the use of mean 0 validation criterion may lead to premature termination of a sampling process even if the kriging model is inaccurate. In this study, we propose a new validation technique based on the mean and variance of the response evaluated when sequential sampling method, such as maximum entropy sampling, is used. The proposed validation technique is more efficient and accurate than the leave-k-out cross-validation technique, because instead of performing numerical integration, the kriging model is explicitly integrated to accurately evaluate the mean and variance of the response evaluated. The error in the proposed validation technique resembles a root mean squared error, thus it can be used to determine a stop criterion for sequential sampling of metamodels

  18. PET image reconstruction: mean, variance, and optimal minimax criterion

    International Nuclear Information System (INIS)

    Liu, Huafeng; Guo, Min; Gao, Fei; Shi, Pengcheng; Xue, Liying; Nie, Jing

    2015-01-01

    Given the noise nature of positron emission tomography (PET) measurements, it is critical to know the image quality and reliability as well as expected radioactivity map (mean image) for both qualitative interpretation and quantitative analysis. While existing efforts have often been devoted to providing only the reconstructed mean image, we present a unified framework for joint estimation of the mean and corresponding variance of the radioactivity map based on an efficient optimal min–max criterion. The proposed framework formulates the PET image reconstruction problem to be a transformation from system uncertainties to estimation errors, where the minimax criterion is adopted to minimize the estimation errors with possibly maximized system uncertainties. The estimation errors, in the form of a covariance matrix, express the measurement uncertainties in a complete way. The framework is then optimized by ∞-norm optimization and solved with the corresponding H ∞ filter. Unlike conventional statistical reconstruction algorithms, that rely on the statistical modeling methods of the measurement data or noise, the proposed joint estimation stands from the point of view of signal energies and can handle from imperfect statistical assumptions to even no a priori statistical assumptions. The performance and accuracy of reconstructed mean and variance images are validated using Monte Carlo simulations. Experiments on phantom scans with a small animal PET scanner and real patient scans are also conducted for assessment of clinical potential. (paper)

  19. Argentine Population Genetic Structure: Large Variance in Amerindian Contribution

    Science.gov (United States)

    Seldin, Michael F.; Tian, Chao; Shigeta, Russell; Scherbarth, Hugo R.; Silva, Gabriel; Belmont, John W.; Kittles, Rick; Gamron, Susana; Allevi, Alberto; Palatnik, Simon A.; Alvarellos, Alejandro; Paira, Sergio; Caprarulo, Cesar; Guillerón, Carolina; Catoggio, Luis J.; Prigione, Cristina; Berbotto, Guillermo A.; García, Mercedes A.; Perandones, Carlos E.; Pons-Estel, Bernardo A.; Alarcon-Riquelme, Marta E.

    2011-01-01

    Argentine population genetic structure was examined using a set of 78 ancestry informative markers (AIMs) to assess the contributions of European, Amerindian, and African ancestry in 94 individuals members of this population. Using the Bayesian clustering algorithm STRUCTURE, the mean European contribution was 78%, the Amerindian contribution was 19.4%, and the African contribution was 2.5%. Similar results were found using weighted least mean square method: European, 80.2%; Amerindian, 18.1%; and African, 1.7%. Consistent with previous studies the current results showed very few individuals (four of 94) with greater than 10% African admixture. Notably, when individual admixture was examined, the Amerindian and European admixture showed a very large variance and individual Amerindian contribution ranged from 1.5 to 84.5% in the 94 individual Argentine subjects. These results indicate that admixture must be considered when clinical epidemiology or case control genetic analyses are studied in this population. Moreover, the current study provides a set of informative SNPs that can be used to ascertain or control for this potentially hidden stratification. In addition, the large variance in admixture proportions in individual Argentine subjects shown by this study suggests that this population is appropriate for future admixture mapping studies. PMID:17177183

  20. Spatially tuned normalization explains attention modulation variance within neurons.

    Science.gov (United States)

    Ni, Amy M; Maunsell, John H R

    2017-09-01

    Spatial attention improves perception of attended parts of a scene, a behavioral enhancement accompanied by modulations of neuronal firing rates. These modulations vary in size across neurons in the same brain area. Models of normalization explain much of this variance in attention modulation with differences in tuned normalization across neurons (Lee J, Maunsell JHR. PLoS One 4: e4651, 2009; Ni AM, Ray S, Maunsell JHR. Neuron 73: 803-813, 2012). However, recent studies suggest that normalization tuning varies with spatial location both across and within neurons (Ruff DA, Alberts JJ, Cohen MR. J Neurophysiol 116: 1375-1386, 2016; Verhoef BE, Maunsell JHR. eLife 5: e17256, 2016). Here we show directly that attention modulation and normalization tuning do in fact covary within individual neurons, in addition to across neurons as previously demonstrated. We recorded the activity of isolated neurons in the middle temporal area of two rhesus monkeys as they performed a change-detection task that controlled the focus of spatial attention. Using the same two drifting Gabor stimuli and the same two receptive field locations for each neuron, we found that switching which stimulus was presented at which location affected both attention modulation and normalization in a correlated way within neurons. We present an equal-maximum-suppression spatially tuned normalization model that explains this covariance both across and within neurons: each stimulus generates equally strong suppression of its own excitatory drive, but its suppression of distant stimuli is typically less. This new model specifies how the tuned normalization associated with each stimulus location varies across space both within and across neurons, changing our understanding of the normalization mechanism and how attention modulations depend on this mechanism. NEW & NOTEWORTHY Tuned normalization studies have demonstrated that the variance in attention modulation size seen across neurons from the same cortical

  1. Kriging with Unknown Variance Components for Regional Ionospheric Reconstruction

    Directory of Open Access Journals (Sweden)

    Ling Huang

    2017-02-01

    Full Text Available Ionospheric delay effect is a critical issue that limits the accuracy of precise Global Navigation Satellite System (GNSS positioning and navigation for single-frequency users, especially in mid- and low-latitude regions where variations in the ionosphere are larger. Kriging spatial interpolation techniques have been recently introduced to model the spatial correlation and variability of ionosphere, which intrinsically assume that the ionosphere field is stochastically stationary but does not take the random observational errors into account. In this paper, by treating the spatial statistical information on ionosphere as prior knowledge and based on Total Electron Content (TEC semivariogram analysis, we use Kriging techniques to spatially interpolate TEC values. By assuming that the stochastic models of both the ionospheric signals and measurement errors are only known up to some unknown factors, we propose a new Kriging spatial interpolation method with unknown variance components for both the signals of ionosphere and TEC measurements. Variance component estimation has been integrated with Kriging to reconstruct regional ionospheric delays. The method has been applied to data from the Crustal Movement Observation Network of China (CMONOC and compared with the ordinary Kriging and polynomial interpolations with spherical cap harmonic functions, polynomial functions and low-degree spherical harmonic functions. The statistics of results indicate that the daily ionospheric variations during the experimental period characterized by the proposed approach have good agreement with the other methods, ranging from 10 to 80 TEC Unit (TECU, 1 TECU = 1 × 1016 electrons/m2 with an overall mean of 28.2 TECU. The proposed method can produce more appropriate estimations whose general TEC level is as smooth as the ordinary Kriging but with a smaller standard deviation around 3 TECU than others. The residual results show that the interpolation precision of the

  2. Regional Versus General Anesthesia and the Incidence of Unplanned Health Care Resource Utilization for Postoperative Pain After Wrist Fracture Surgery: Results From a Retrospective Quality Improvement Project.

    Science.gov (United States)

    Sunderland, Sarah; Yarnold, Cynthia H; Head, Stephen J; Osborn, Jill A; Purssell, Andrew; Peel, John K; Schwarz, Stephan K W

    2016-01-01

    The establishment at our center of a dedicated regional anesthesia service in 2008-2009 has resulted in a marked increase in single-shot brachial plexus blocks (sBPBs) for ambulatory wrist fracture surgery. Despite the documented benefits of regional over general anesthesia (GA), there has been a perceived increase among sBPB patients in postoperative return rates for pain at our institution. We conducted a retrospective quality improvement project to examine this. After exemption from human ethics board review, we sought to identify and contact all wrist fracture surgery patients treated at our center between 2003 and 2012. Our primary outcome was the incidence of unplanned physician visits (office/clinic or emergency department) for pain in the first 48 hours after surgery. Other main outcomes included the incidence of seeking any form of medical attention for pain and self-reporting of severe pain in the first 48 hours. Of 1008 identified patients, 419 could be contacted; 195 qualified for analysis. The incidence of unplanned physician visits in the first 48 hours was 12% (13 of 118) among sBPB patients versus 4% (3 of 77) in GA patients (odds ratio [OR], 3.1; 95% confidence interval [95% CI], 0.8-11.1; P = 0.11). More sBPB versus GA patients sought any form of medical attention for pain (20% vs 5%; OR, 4.7; 95% CI, 1.4-10.9; P = 0.003). Similarly, more sBPB patients reported severe postoperative pain (41% vs 10%; OR, 5.9; 95% CI, 2.6-13.4; P resource utilization caused by pain after hospital discharge than those undergoing GA. These findings warrant confirmation in a prospective trial and emphasize the need for a defined postdischarge analgesic pathway as well as the potential merits of perineural home catheters.

  3. Estimation of measurement variance in the context of environment statistics

    Science.gov (United States)

    Maiti, Pulakesh

    2015-02-01

    The object of environment statistics is for providing information on the environment, on its most important changes over time, across locations and identifying the main factors that influence them. Ultimately environment statistics would be required to produce higher quality statistical information. For this timely, reliable and comparable data are needed. Lack of proper and uniform definitions, unambiguous classifications pose serious problems to procure qualitative data. These cause measurement errors. We consider the problem of estimating measurement variance so that some measures may be adopted to improve upon the quality of data on environmental goods and services and on value statement in economic terms. The measurement technique considered here is that of employing personal interviewers and the sampling considered here is that of two-stage sampling.

  4. Risk Management - Variance Minimization or Lower Tail Outcome Elimination

    DEFF Research Database (Denmark)

    Aabo, Tom

    2002-01-01

    on future cash flows (the budget), while risk managers concerned about costly lower tail outcomes will hedge (considerably) less depending on the level of uncertainty. A risk management strategy of lower tail outcome elimination is in line with theoretical recommendations in a corporate value......This paper illustrates the profound difference between a risk management strategy of variance minimization and a risk management strategy of lower tail outcome elimination. Risk managers concerned about the variability of cash flows will tend to center their hedge decisions on their best guess......-adding perspective. A cross-case study of blue-chip industrial companies partly supports the empirical use of a risk management strategy of lower tail outcome elimination but does not exclude other factors from (co-)driving the observations....

  5. Draft no-migration variance petition. Volume 1

    International Nuclear Information System (INIS)

    1995-01-01

    The Department of Energy is responsible for the disposition of transuranic (TRU) waste generated by national defense-related activities. Approximately 2,6 million cubic feet of these waste have been generated and are stored at various facilities across the country. The Waste Isolation Pilot Plant (WIPP), was sited and constructed to meet stringent disposal requirements. In order to permanently dispose of TRU waste, the DOE has elected to petition the US EPA for a variance from the Land Disposal Restrictions of RCRA. This document fulfills the reporting requirements for the petition. This report is Volume 1 which discusses the regulatory frame work, site characterization, facility description, waste description, environmental impact analysis, monitoring, quality assurance, long-term compliance analysis, and regulatory compliance assessment

  6. Static models, recursive estimators and the zero-variance approach

    KAUST Repository

    Rubino, Gerardo

    2016-01-07

    When evaluating dependability aspects of complex systems, most models belong to the static world, where time is not an explicit variable. These models suffer from the same problems than dynamic ones (stochastic processes), such as the frequent combinatorial explosion of the state spaces. In the Monte Carlo domain, on of the most significant difficulties is the rare event situation. In this talk, we describe this context and a recent technique that appears to be at the top performance level in the area, where we combined ideas that lead to very fast estimation procedures with another approach called zero-variance approximation. Both ideas produced a very efficient method that has the right theoretical property concerning robustness, the Bounded Relative Error one. Some examples illustrate the results.

  7. Batch variation between branchial cell cultures: An analysis of variance

    DEFF Research Database (Denmark)

    Hansen, Heinz Johs. Max; Grosell, M.; Kristensen, L.

    2003-01-01

    We present in detail how a statistical analysis of variance (ANOVA) is used to sort out the effect of an unexpected batch-to-batch variation between cell cultures. Two separate cultures of rainbow trout branchial cells were grown on permeable filtersupports ("inserts"). They were supposed...... and introducing the observed difference between batches as one of the factors in an expanded three-dimensional ANOVA, we were able to overcome an otherwisecrucial lack of sufficiently reproducible duplicate values. We could thereby show that the effect of changing the apical medium was much more marked when...... the radioactive lipid precursors were added on the apical, rather than on the basolateral, side. Theinsert cell cultures were obviously polarized. We argue that it is not reasonable to reject troublesome experimental results, when we do not know a priori that something went wrong. The ANOVA is a very useful...

  8. Interdependence of NAFTA capital markets: A minimum variance portfolio approach

    Directory of Open Access Journals (Sweden)

    López-Herrera Francisco

    2014-01-01

    Full Text Available We estimate the long-run relationships among NAFTA capital market returns and then calculate the weights of a “time-varying minimum variance portfolio” that includes the Canadian, Mexican, and USA capital markets between March 2007 and March 2009, a period of intense turbulence in international markets. Our results suggest that the behavior of NAFTA market investors is not consistent with that of a theoretical “risk-averse” agent during periods of high uncertainty and may be either considered as irrational or attributed to a possible “home country bias”. This finding represents valuable information for portfolio managers and contributes to a better understanding of the nature of the markets in which they invest. It also has practical implications in the design of international portfolio investment policies.

  9. Ant Colony Optimization for Markowitz Mean-Variance Portfolio Model

    Science.gov (United States)

    Deng, Guang-Feng; Lin, Woo-Tsong

    This work presents Ant Colony Optimization (ACO), which was initially developed to be a meta-heuristic for combinatorial optimization, for solving the cardinality constraints Markowitz mean-variance portfolio model (nonlinear mixed quadratic programming problem). To our knowledge, an efficient algorithmic solution for this problem has not been proposed until now. Using heuristic algorithms in this case is imperative. Numerical solutions are obtained for five analyses of weekly price data for the following indices for the period March, 1992 to September, 1997: Hang Seng 31 in Hong Kong, DAX 100 in Germany, FTSE 100 in UK, S&P 100 in USA and Nikkei 225 in Japan. The test results indicate that the ACO is much more robust and effective than Particle swarm optimization (PSO), especially for low-risk investment portfolios.

  10. Minimum variance linear unbiased estimators of loss and inventory

    International Nuclear Information System (INIS)

    Stewart, K.B.

    1977-01-01

    The article illustrates a number of approaches for estimating the material balance inventory and a constant loss amount from the accountability data from a sequence of accountability periods. The approaches all lead to linear estimates that have minimum variance. Techniques are shown whereby ordinary least squares, weighted least squares and generalized least squares computer programs can be used. Two approaches are recursive in nature and lend themselves to small specialized computer programs. Another approach is developed that is easy to program; could be used with a desk calculator and can be used in a recursive way from accountability period to accountability period. Some previous results are also reviewed that are very similar in approach to the present ones and vary only in the way net throughput measurements are statistically modeled. 5 refs

  11. Cosmic variance in inflation with two light scalars

    Energy Technology Data Exchange (ETDEWEB)

    Bonga, Béatrice; Brahma, Suddhasattwa; Deutsch, Anne-Sylvie; Shandera, Sarah, E-mail: bpb165@psu.edu, E-mail: suddhasattwa.brahma@gmail.com, E-mail: asdeutsch@psu.edu, E-mail: shandera@gravity.psu.edu [Institute for Gravitation and the Cosmos and Physics Department, The Pennsylvania State University, University Park, PA, 16802 (United States)

    2016-05-01

    We examine the squeezed limit of the bispectrum when a light scalar with arbitrary non-derivative self-interactions is coupled to the inflaton. We find that when the hidden sector scalar is sufficiently light ( m ∼< 0.1 H ), the coupling between long and short wavelength modes from the series of higher order correlation functions (from arbitrary order contact diagrams) causes the statistics of the fluctuations to vary in sub-volumes. This means that observations of primordial non-Gaussianity cannot be used to uniquely reconstruct the potential of the hidden field. However, the local bispectrum induced by mode-coupling from these diagrams always has the same squeezed limit, so the field's locally determined mass is not affected by this cosmic variance.

  12. Deviation of the Variances of Classical Estimators and Negative Integer Moment Estimator from Minimum Variance Bound with Reference to Maxwell Distribution

    Directory of Open Access Journals (Sweden)

    G. R. Pasha

    2006-07-01

    Full Text Available In this paper, we present that how much the variances of the classical estimators, namely, maximum likelihood estimator and moment estimator deviate from the minimum variance bound while estimating for the Maxwell distribution. We also sketch this difference for the negative integer moment estimator. We note the poor performance of the negative integer moment estimator in the said consideration while maximum likelihood estimator attains minimum variance bound and becomes an attractive choice.

  13. What Is the Economic Cost of Unplanned Pregnancy Following Hysteroscopic Sterilization in the US? A New National Estimate Based on Essure® Procedure Prevalence, Failure Rates and Workforce Productivity.

    Science.gov (United States)

    Sills, E Scott; Fernandez, Luca P; Jones, Christopher A

    Although hysteroscopic sterilization (HS) (Essure ®) has been available in the US since 2002, there is disagreement regarding its efficacy, and there has been no study of the economic impact of HS failure. Our investigation examined the economic consequences of contraceptive failure with Essure in the US. Contraceptive failure rates (CFR) of 5.7%, 7.7% and 9.6% were applied to the US cohort of HS patients (n = 600,000). Direct economic impact of productivity losses resulting from unplanned conceptions after HS was calculated by factoring Essure failure rate, the exposed population, US female labour force participation, unemployment rate, time away from work owing to vaginal delivery or pregnancy termination and weekly wages. For the 9.6% CFR scenario, US workforce productivity loss from unplanned pregnancy and delivery was estimated at 771,065 days (2,112 years). Productivity loss secondary to conception and subsequent termination of pregnancy after Essure was approximately 23,725 days (65 years). Assuming CFR at 5.7%, livebirth delivery with total time missed from work at 65 days, this was associated with an aggregate economic impact of $49.2M in lost annual wages. Direct economic impact of unplanned pregnancy after Essure irrespective of outcome (terminations and deliveries) was estimated to result in US productivity losses valued at ~$130M. Although not all unplanned pregnancy costs are attributable to failed HS, estimates derived from earlier surveys have not considered this contraceptive method, and the economic consequences of unplanned pregnancy after Essure are not trivial. Quantifying the economic consequences of HS failure would be improved with specific ICD-10 coding for Essure-associated symptoms.

  14. Continuous-Time Mean-Variance Portfolio Selection under the CEV Process

    OpenAIRE

    Ma, Hui-qiang

    2014-01-01

    We consider a continuous-time mean-variance portfolio selection model when stock price follows the constant elasticity of variance (CEV) process. The aim of this paper is to derive an optimal portfolio strategy and the efficient frontier. The mean-variance portfolio selection problem is formulated as a linearly constrained convex program problem. By employing the Lagrange multiplier method and stochastic optimal control theory, we obtain the optimal portfolio strategy and mean-variance effici...

  15. The pricing of long and short run variance and correlation risk in stock returns

    NARCIS (Netherlands)

    Cosemans, M.

    2011-01-01

    This paper studies the pricing of long and short run variance and correlation risk. The predictive power of the market variance risk premium for returns is driven by the correlation risk premium and the systematic part of individual variance premia. Furthermore, I find that aggregate volatility risk

  16. Spot Variance Path Estimation and its Application to High Frequency Jump Testing

    NARCIS (Netherlands)

    Bos, C.S.; Janus, P.; Koopman, S.J.

    2012-01-01

    This paper considers spot variance path estimation from datasets of intraday high-frequency asset prices in the presence of diurnal variance patterns, jumps, leverage effects, and microstructure noise. We rely on parametric and nonparametric methods. The estimated spot variance path can be used to

  17. Variance bias analysis for the Gelbard's batch method

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Jae Uk; Shim, Hyung Jin [Seoul National Univ., Seoul (Korea, Republic of)

    2014-05-15

    In this paper, variances and the bias will be derived analytically when the Gelbard's batch method is applied. And then, the real variance estimated from this bias will be compared with the real variance calculated from replicas. Variance and the bias were derived analytically when the batch method was applied. If the batch method was applied to calculate the sample variance, covariance terms between tallies which exist in the batch were eliminated from the bias. With the 2 by 2 fission matrix problem, we could calculate real variance regardless of whether or not the batch method was applied. However as batch size got larger, standard deviation of real variance was increased. When we perform a Monte Carlo estimation, we could get a sample variance as the statistical uncertainty of it. However, this value is smaller than the real variance of it because a sample variance is biased. To reduce this bias, Gelbard devised the method which is called the Gelbard's batch method. It has been certificated that a sample variance get closer to the real variance when the batch method is applied. In other words, the bias get reduced. This fact is well known to everyone in the MC field. However, so far, no one has given the analytical interpretation on it.

  18. Waste Isolation Pilot Plant No-Migration Variance Petition

    International Nuclear Information System (INIS)

    1990-03-01

    The purpose of the WIPP No-Migration Variance Petition is to demonstrate, according to the requirements of RCRA section 3004(d) and 40 CFR section 268.6, that to a reasonable degree of certainty, there will be no migration of hazardous constituents from the facility for as long as the wastes remain hazardous. The DOE submitted the petition to the EPA in March 1989. Upon completion of its initial review, the EPA provided to DOE a Notice of Deficiencies (NOD). DOE responded to the EPA's NOD and met with the EPA's reviewers of the petition several times during 1989. In August 1989, EPA requested that DOE submit significant additional information addressing a variety of topics including: waste characterization, ground water hydrology, geology and dissolution features, monitoring programs, the gas generation test program, and other aspects of the project. This additional information was provided to EPA in January 1990 when DOE submitted Revision 1 of the Addendum to the petition. For clarity and ease of review, this document includes all of these submittals, and the information has been updated where appropriate. This document is divided into the following sections: Introduction, 1.0: Facility Description, 2.0: Waste Description, 3.0; Site Characterization, 4.0; Environmental Impact Analysis, 5.0; Prediction and Assessment of Infrequent Events, 6.0; and References, 7.0

  19. Mean-Variance Portfolio Selection with Margin Requirements

    Directory of Open Access Journals (Sweden)

    Yuan Zhou

    2013-01-01

    Full Text Available We study the continuous-time mean-variance portfolio selection problem in the situation when investors must pay margin for short selling. The problem is essentially a nonlinear stochastic optimal control problem because the coefficients of positive and negative parts of control variables are different. We can not apply the results of stochastic linearquadratic (LQ problem. Also the solution of corresponding Hamilton-Jacobi-Bellman (HJB equation is not smooth. Li et al. (2002 studied the case when short selling is prohibited; therefore they only need to consider the positive part of control variables, whereas we need to handle both the positive part and the negative part of control variables. The main difficulty is that the positive part and the negative part are not independent. The previous results are not directly applicable. By decomposing the problem into several subproblems we figure out the solutions of HJB equation in two disjoint regions and then prove it is the viscosity solution of HJB equation. Finally we formulate solution of optimal portfolio and the efficient frontier. We also present two examples showing how different margin rates affect the optimal solutions and the efficient frontier.

  20. Beyond the GUM: variance-based sensitivity analysis in metrology

    International Nuclear Information System (INIS)

    Lira, I

    2016-01-01

    Variance-based sensitivity analysis is a well established tool for evaluating the contribution of the uncertainties in the inputs to the uncertainty in the output of a general mathematical model. While the literature on this subject is quite extensive, it has not found widespread use in metrological applications. In this article we present a succinct review of the fundamentals of sensitivity analysis, in a form that should be useful to most people familiarized with the Guide to the Expression of Uncertainty in Measurement (GUM). Through two examples, it is shown that in linear measurement models, no new knowledge is gained by using sensitivity analysis that is not already available after the terms in the so-called ‘law of propagation of uncertainties’ have been computed. However, if the model behaves non-linearly in the neighbourhood of the best estimates of the input quantities—and if these quantities are assumed to be statistically independent—sensitivity analysis is definitely advantageous for gaining insight into how they can be ranked according to their importance in establishing the uncertainty of the measurand. (paper)

  1. Scale dependence in species turnover reflects variance in species occupancy.

    Science.gov (United States)

    McGlinn, Daniel J; Hurlbert, Allen H

    2012-02-01

    Patterns of species turnover may reflect the processes driving community dynamics across scales. While the majority of studies on species turnover have examined pairwise comparison metrics (e.g., the average Jaccard dissimilarity), it has been proposed that the species-area relationship (SAR) also offers insight into patterns of species turnover because these two patterns may be analytically linked. However, these previous links only apply in a special case where turnover is scale invariant, and we demonstrate across three different plant communities that over 90% of the pairwise turnover values are larger than expected based on scale-invariant predictions from the SAR. Furthermore, the degree of scale dependence in turnover was negatively related to the degree of variance in the occupancy frequency distribution (OFD). These findings suggest that species turnover diverges from scale invariance, and as such pairwise turnover and the slope of the SAR are not redundant. Furthermore, models developed to explain the OFD should be linked with those developed to explain species turnover to achieve a more unified understanding of community structure.

  2. Improving computational efficiency of Monte Carlo simulations with variance reduction

    International Nuclear Information System (INIS)

    Turner, A.; Davis, A.

    2013-01-01

    CCFE perform Monte-Carlo transport simulations on large and complex tokamak models such as ITER. Such simulations are challenging since streaming and deep penetration effects are equally important. In order to make such simulations tractable, both variance reduction (VR) techniques and parallel computing are used. It has been found that the application of VR techniques in such models significantly reduces the efficiency of parallel computation due to 'long histories'. VR in MCNP can be accomplished using energy-dependent weight windows. The weight window represents an 'average behaviour' of particles, and large deviations in the arriving weight of a particle give rise to extreme amounts of splitting being performed and a long history. When running on parallel clusters, a long history can have a detrimental effect on the parallel efficiency - if one process is computing the long history, the other CPUs complete their batch of histories and wait idle. Furthermore some long histories have been found to be effectively intractable. To combat this effect, CCFE has developed an adaptation of MCNP which dynamically adjusts the WW where a large weight deviation is encountered. The method effectively 'de-optimises' the WW, reducing the VR performance but this is offset by a significant increase in parallel efficiency. Testing with a simple geometry has shown the method does not bias the result. This 'long history method' has enabled CCFE to significantly improve the performance of MCNP calculations for ITER on parallel clusters, and will be beneficial for any geometry combining streaming and deep penetration effects. (authors)

  3. Advanced Variance Reduction Strategies for Optimizing Mesh Tallies in MAVRIC

    International Nuclear Information System (INIS)

    Peplow, Douglas E.; Blakeman, Edward D; Wagner, John C

    2007-01-01

    More often than in the past, Monte Carlo methods are being used to compute fluxes or doses over large areas using mesh tallies (a set of region tallies defined on a mesh that overlays the geometry). For problems that demand that the uncertainty in each mesh cell be less than some set maximum, computation time is controlled by the cell with the largest uncertainty. This issue becomes quite troublesome in deep-penetration problems, and advanced variance reduction techniques are required to obtain reasonable uncertainties over large areas. The CADIS (Consistent Adjoint Driven Importance Sampling) methodology has been shown to very efficiently optimize the calculation of a response (flux or dose) for a single point or a small region using weight windows and a biased source based on the adjoint of that response. This has been incorporated into codes such as ADVANTG (based on MCNP) and the new sequence MAVRIC, which will be available in the next release of SCALE. In an effort to compute lower uncertainties everywhere in the problem, Larsen's group has also developed several methods to help distribute particles more evenly, based on forward estimates of flux. This paper focuses on the use of a forward estimate to weight the placement of the source in the adjoint calculation used by CADIS, which we refer to as a forward-weighted CADIS (FW-CADIS)

  4. A pattern recognition approach to transistor array parameter variance

    Science.gov (United States)

    da F. Costa, Luciano; Silva, Filipi N.; Comin, Cesar H.

    2018-06-01

    The properties of semiconductor devices, including bipolar junction transistors (BJTs), are known to vary substantially in terms of their parameters. In this work, an experimental approach, including pattern recognition concepts and methods such as principal component analysis (PCA) and linear discriminant analysis (LDA), was used to experimentally investigate the variation among BJTs belonging to integrated circuits known as transistor arrays. It was shown that a good deal of the devices variance can be captured using only two PCA axes. It was also verified that, though substantially small variation of parameters is observed for BJT from the same array, larger variation arises between BJTs from distinct arrays, suggesting the consideration of device characteristics in more critical analog designs. As a consequence of its supervised nature, LDA was able to provide a substantial separation of the BJT into clusters, corresponding to each transistor array. In addition, the LDA mapping into two dimensions revealed a clear relationship between the considered measurements. Interestingly, a specific mapping suggested by the PCA, involving the total harmonic distortion variation expressed in terms of the average voltage gain, yielded an even better separation between the transistor array clusters. All in all, this work yielded interesting results from both semiconductor engineering and pattern recognition perspectives.

  5. Dominance genetic variance for traits under directional selection in Drosophila serrata.

    Science.gov (United States)

    Sztepanacz, Jacqueline L; Blows, Mark W

    2015-05-01

    In contrast to our growing understanding of patterns of additive genetic variance in single- and multi-trait combinations, the relative contribution of nonadditive genetic variance, particularly dominance variance, to multivariate phenotypes is largely unknown. While mechanisms for the evolution of dominance genetic variance have been, and to some degree remain, subject to debate, the pervasiveness of dominance is widely recognized and may play a key role in several evolutionary processes. Theoretical and empirical evidence suggests that the contribution of dominance variance to phenotypic variance may increase with the correlation between a trait and fitness; however, direct tests of this hypothesis are few. Using a multigenerational breeding design in an unmanipulated population of Drosophila serrata, we estimated additive and dominance genetic covariance matrices for multivariate wing-shape phenotypes, together with a comprehensive measure of fitness, to determine whether there is an association between directional selection and dominance variance. Fitness, a trait unequivocally under directional selection, had no detectable additive genetic variance, but significant dominance genetic variance contributing 32% of the phenotypic variance. For single and multivariate morphological traits, however, no relationship was observed between trait-fitness correlations and dominance variance. A similar proportion of additive and dominance variance was found to contribute to phenotypic variance for single traits, and double the amount of additive compared to dominance variance was found for the multivariate trait combination under directional selection. These data suggest that for many fitness components a positive association between directional selection and dominance genetic variance may not be expected. Copyright © 2015 by the Genetics Society of America.

  6. Simultaneous Monte Carlo zero-variance estimates of several correlated means

    International Nuclear Information System (INIS)

    Booth, T.E.

    1998-01-01

    Zero-variance biasing procedures are normally associated with estimating a single mean or tally. In particular, a zero-variance solution occurs when every sampling is made proportional to the product of the true probability multiplied by the expected score (importance) subsequent to the sampling; i.e., the zero-variance sampling is importance weighted. Because every tally has a different importance function, a zero-variance biasing for one tally cannot be a zero-variance biasing for another tally (unless the tallies are perfectly correlated). The way to optimize the situation when the required tallies have positive correlation is shown

  7. Variance Swaps in BM&F: Pricing and Viability of Hedge

    Directory of Open Access Journals (Sweden)

    Richard John Brostowicz Junior

    2010-07-01

    Full Text Available A variance swap can theoretically be priced with an infinite set of vanilla calls and puts options considering that the realized variance follows a purely diffusive process with continuous monitoring. In this article we willanalyze the possible differences in pricing considering discrete monitoring of realized variance. It will analyze the pricing of variance swaps with payoff in dollars, since there is a OTC market that works this way and thatpotentially serve as a hedge for the variance swaps traded in BM&F. Additionally, will be tested the feasibility of hedge of variance swaps when there is liquidity in just a few exercise prices, as is the case of FX optionstraded in BM&F. Thus be assembled portfolios containing variance swaps and their replicating portfolios using the available exercise prices as proposed in (DEMETERFI et al., 1999. With these portfolios, the effectiveness of the hedge was not robust in mostly of tests conducted in this work.

  8. Calculation of the Carbon Footprint to Determine Sustainability Status: A Comparative Analysis of Some Selected Planned and Unplanned Areas of Dhaka Megacity

    Science.gov (United States)

    Iqbal, S. M. S.

    2015-12-01

    Resource scarcity is considered to be one of the most serious issues plaguing Dhaka city. Because of the massive pressure of increasing population (15.931 million), a very unsustainable situation is waiting for this city in the upcoming future. It is inevitable to know how far this city is from being sustainable. This paper embodies the comparative analysis of the carbon footprint of four different areas in Dhaka city. It is considered as one of the most important key indicators of sustainability. It calculates the amount of biologically productive land in order to produce all the resources consumed by an individual or a particular community. This research has been conducted in both the planned and unplanned areas of this city. Among compound, component and direct method, component method was used to calculate the carbon footprint. Primary data were collected from door to door questionnaire survey. Total 371 samples were drawn from all the study areas at 95 % confidence level and 5% confidence interval. After finishing data analysis it was clear that the per capita carbon footprint of the selected study areas exceeds the per capita biocapacity of Dhaka city. And there exists a huge variation between the planned and unplanned areas of Old Dhaka and New Dhaka. Per capita carbon footprint of Gulshan & Jhigatola (part of New Dhaka) is higher than the per capita carbon footprint of Gandaria & Wari (part of Old Dhaka) that means resource stress is higher in Gulshan & Jhigatola in comparison with Gandaria & Wari because of the difference of daily consumption pattern. One of the most important findings of this study is that the per capita carbon footprint is the highest in Gulshan (1.2407 gha) among all the study areas and it is 85.56 times greater than the per capita biocapacity of Dhaka city (0.0145 gha) that means a single resident of this area needs 1.2407 gha land in order to support his/her demand on nature but only 0.0145 gha land (in an average) is available for

  9. Concordance between intention to use and current use of contraceptives among six-month postpartum women in Brazil: The role of unplanned pregnancy.

    Science.gov (United States)

    Borges, Ana Luiza Vilela; Dos Santos, Osmara Alves; Fujimori, Elizabeth

    2018-01-01

    to examine the effect of pregnancy planning status in the concordance between intention to use and current use of contraceptives among postpartum women. a prospective study was conducted in 12 primary health care facilities in São Paulo, Brazil, from November 2013 to September 2014. A total of 264 woman aged 15-44 years old completed a face-to-face interview when they were pregnant (baseline), and were interviewed by phone at 6 months postpartum. At baseline, participants were questioned about the contraceptive method they would prefer to be using at 6 months postpartum. At 6 months postpartum, they answered about the contraceptive method they were currently using. Pregnancy planning status was measured using the Brazilian Portuguese London Measure of Unplanned Pregnancy. We conducted logistic regression, considering contraceptive preference-use concordance as the dependent variable and the main covariate as pregnancy planning status. Only 28.9% of postpartum women were using the method they preferred to use when they were pregnant. The agreement between preference and contraceptive use was higher for injectables (60.9%) and lowest for IUD, as nobody who preferred it was actually using it. Women who were not sure about what method they intended to use after childbirth more frequently reported no use at six months postpartum. Multivariate logistic regression showed that postpartum women whose pregnancy was unplanned were less likely to use the contraceptive methods that they intended to use when they were pregnant [aOR=0.36; 95%CI=0.14-0.97]. Brazilian women were able to access contraceptives in the postpartum period. However, there is a considerable discordance between their contraceptive intention to use and use at the sixth postpartum month. A higher unmet demand for IUD and sterilization should be highlighted. The pregnancy planning status is associated to postpartum contraceptive preference-use concordance, so interventions before pregnancy may affect

  10. Improving precision in gel electrophoresis by stepwisely decreasing variance components.

    Science.gov (United States)

    Schröder, Simone; Brandmüller, Asita; Deng, Xi; Ahmed, Aftab; Wätzig, Hermann

    2009-10-15

    Many methods have been developed in order to increase selectivity and sensitivity in proteome research. However, gel electrophoresis (GE) which is one of the major techniques in this area, is still known for its often unsatisfactory precision. Percental relative standard deviations (RSD%) up to 60% have been reported. In this case the improvement of precision and sensitivity is absolutely essential, particularly for the quality control of biopharmaceuticals. Our work reflects the remarkable and completely irregular changes of the background signal from gel to gel. This irregularity was identified as one of the governing error sources. These background changes can be strongly reduced by using a signal detection in the near-infrared (NIR) range. This particular detection method provides the most sensitive approach for conventional CCB (Colloidal Coomassie Blue) stained gels, which is reflected in a total error of just 5% (RSD%). In order to further investigate variance components in GE, an experimental Plackett-Burman screening design was performed. The influence of seven potential factors on the precision was investigated using 10 proteins with different properties analyzed by NIR detection. The results emphasized the individuality of the proteins. Completely different factors were identified to be significant for each protein. However, out of seven investigated parameters, just four showed a significant effect on some proteins, namely the parameters of: destaining time, staining temperature, changes of detergent additives (SDS and LDS) in the sample buffer, and the age of the gels. As a result, precision can only be improved individually for each protein or protein classes. Further understanding of the unique properties of proteins should enable us to improve the precision in gel electrophoresis.

  11. Working Around Cosmic Variance: Remote Quadrupole Measurements of the CMB

    Science.gov (United States)

    Adil, Arsalan; Bunn, Emory

    2018-01-01

    Anisotropies in the CMB maps continue to revolutionize our understanding of the Cosmos. However, the statistical interpretation of these anisotropies is tainted with a posteriori statistics. The problem is particularly emphasized for lower order multipoles, i.e. in the cosmic variance regime of the power spectrum. Naturally, the solution lies in acquiring a new data set – a rather difficult task given the sample size of the Universe.The CMB temperature, in theory, depends on: the direction of photon propagation, the time at which the photons are observed, and the observer’s location in space. In existing CMB data, only the first parameter varies. However, as first pointed out by Kamionkowski and Loeb, a solution lies in making the so-called “Remote Quadrupole Measurements” by analyzing the secondary polarization produced by incoming CMB photons via the Sunyaev-Zel’dovich (SZ) effect. These observations allow us to measure the projected CMB quadrupole at the location and look-back time of a galaxy cluster.At low redshifts, the remote quadrupole is strongly correlated to the CMB anisotropy from our last scattering surface. We provide here a formalism for computing the covariance and relation matrices for both the two-point correlation function on the last scattering surface of a galaxy cluster and the cross correlation of the remote quadrupole with the local CMB. We then calculate these matrices based on a fiducial model and a non-standard model that suppresses power at large angles for ~104 clusters up to z=2. We anticipate to make a priori predictions of the differences between our expectations for the standard and non-standard models. Such an analysis is timely in the wake of the CMB S4 era which will provide us with an extensive SZ cluster catalogue.

  12. A Variance Distribution Model of Surface EMG Signals Based on Inverse Gamma Distribution.

    Science.gov (United States)

    Hayashi, Hideaki; Furui, Akira; Kurita, Yuichi; Tsuji, Toshio

    2017-11-01

    Objective: This paper describes the formulation of a surface electromyogram (EMG) model capable of representing the variance distribution of EMG signals. Methods: In the model, EMG signals are handled based on a Gaussian white noise process with a mean of zero for each variance value. EMG signal variance is taken as a random variable that follows inverse gamma distribution, allowing the representation of noise superimposed onto this variance. Variance distribution estimation based on marginal likelihood maximization is also outlined in this paper. The procedure can be approximated using rectified and smoothed EMG signals, thereby allowing the determination of distribution parameters in real time at low computational cost. Results: A simulation experiment was performed to evaluate the accuracy of distribution estimation using artificially generated EMG signals, with results demonstrating that the proposed model's accuracy is higher than that of maximum-likelihood-based estimation. Analysis of variance distribution using real EMG data also suggested a relationship between variance distribution and signal-dependent noise. Conclusion: The study reported here was conducted to examine the performance of a proposed surface EMG model capable of representing variance distribution and a related distribution parameter estimation method. Experiments using artificial and real EMG data demonstrated the validity of the model. Significance: Variance distribution estimated using the proposed model exhibits potential in the estimation of muscle force. Objective: This paper describes the formulation of a surface electromyogram (EMG) model capable of representing the variance distribution of EMG signals. Methods: In the model, EMG signals are handled based on a Gaussian white noise process with a mean of zero for each variance value. EMG signal variance is taken as a random variable that follows inverse gamma distribution, allowing the representation of noise superimposed onto this

  13. What factors are associated with unplanned return following transurethral resection of bladder tumor? An analysis of a large single institution's experience.

    Science.gov (United States)

    Ghali, Fady; Moses, Rachel A; Raffin, Eric; Hyams, Elias S

    2016-10-01

    This study sought to evaluate factors associated with unplanned hospital return (UR) following transurethral resection of bladder tumor (TURBT), the largest source of readmission among ambulatory urological procedures. A retrospective review of TURBTs at a single academic institution between April 2011 and August 2014 was performed. Demographics, comorbidities, length of stay, tumor size and multiple other factors were recorded. UR was recorded within 30 days of surgery. Bivariate and multivariable analyses were performed to determine factors associated with UR. Among 708 patients undergoing TURBT, 23.9% were female with a mean age of 70 years. The rate of UR was 10.9%. The most common cause of UR was gross hematuria, accounting for 70%. On bivariate analysis, Foley catheter placement in the operating room, non-aspirin anticoagulation and index length of stay longer than 24 h were associated with hematuria-related UR (p hematuria-related UR (p  0.05). On multivariable analysis, only Foley placement in the operating room remained associated with higher rates of hematuria-related UR, while preoperative antibiotics, female gender and aspirin therapy remained associated with a lower likelihood of this event. UR following TURBT is common and typically results from gross hematuria. Patients with postoperative Foley catheterization in the operating room may require additional counseling or supervision before discharge, and should be considered for discharge with a Foley rather than having a prompt voiding trial.

  14. Timing of planned repeat cesarean delivery after two or more previous cesarean sections--risk for unplanned cesarean delivery and pregnancy outcome.

    Science.gov (United States)

    Melamed, Nir; Hadar, Eran; Keidar, Liron; Peled, Yoav; Wiznitzer, Arnon; Yogev, Yariv

    2014-03-01

    objective: To assess the effect of the scheduled gestational age for a repeat planned cesarean section (CS) on the risk for adverse pregnancy outcome in women with two or more previous CS. A retrospective cohort study of all women after ≥2 previous CS who were scheduled for a repeat planned CS. Women were divided into two groups at which the planned CS was scheduled: 38-week group or 39-week group. Overall, 377 were enrolled, 264 (70.0%) and 113 (30.0%) in the 38-week and the 39-week groups, respectively. The rate of an unplanned CS was significantly higher in the 39-week versus the 38-week group (23.0% versus 13.3%, p = 0.02). A repeat planned CS scheduled to week 39 was associated with an increased risk of maternal adverse outcome (31.9% versus 21.6%, p = 0.03). There was no significant difference in the rate of adverse neonatal outcome between the two groups (20.8% versus 23.0%, p = 0.5). The lowest rate of any adverse outcome (maternal and/or neonatal) was observed when CS was scheduled to 38 + 1 weeks of gestation. In women after two cesarean sections, scheduling a planned CS at around 39 weeks compared with at around 38 weeks is associated with an increased risk for maternal adverse outcome with no apparent advantage in terms of neonatal outcome.

  15. Socio spatial adaptation as a resilience form of native unplanned settlement in confrontation with new planned settlement development pressure (case study: enclave native settlement in Serpong, Tangerang)

    Science.gov (United States)

    Ischak, Mohammad; Setioko, Bambang; Nurgandarum, Dedes

    2017-12-01

    Urban growth refers to expansion of a metropolitan into sub urban areas as the surrounding environment, with no exception of Jakarta city due to limited availability and high price of land within the city. The city of Jakarta, as a metropolitan, carries of expansion in its surrounding environment including Tangerang. Privat developers may an important role in this urban growth through their large scale of new settlement development project. The formation of establishment of enclave native unplanned sub urban settlement scattered within planned new settlement in Tangerang is to be an consequence of Jakarta urban growth. This fenomena could be comprehended as a form of resilience native settlement in confrontation with the new planned settlement pressure. The aim of this research, presented in this paper is to understand the socio-spatial concept of those enclave native settlement as an adaptation form to the new planned settlement pressure. Through descriptive qualitative research method, with indepth interview as a main research instrument, this research could depict or uncover the facts that there are various form of socio-spatial adaptation as the main theme of resilience native suburban settlement formation.

  16. A comparison between temporal and subband minimum variance adaptive beamforming

    Science.gov (United States)

    Diamantis, Konstantinos; Voxen, Iben H.; Greenaway, Alan H.; Anderson, Tom; Jensen, Jørgen A.; Sboros, Vassilis

    2014-03-01

    This paper compares the performance between temporal and subband Minimum Variance (MV) beamformers for medical ultrasound imaging. Both adaptive methods provide an optimized set of apodization weights but are implemented in the time and frequency domains respectively. Their performance is evaluated with simulated synthetic aperture data obtained from Field II and is quantified by the Full-Width-Half-Maximum (FWHM), the Peak-Side-Lobe level (PSL) and the contrast level. From a point phantom, a full sequence of 128 emissions with one transducer element transmitting and all 128 elements receiving each time, provides a FWHM of 0.03 mm (0.14λ) for both implementations at a depth of 40 mm. This value is more than 20 times lower than the one achieved by conventional beamforming. The corresponding values of PSL are -58 dB and -63 dB for time and frequency domain MV beamformers, while a value no lower than -50 dB can be obtained from either Boxcar or Hanning weights. Interestingly, a single emission with central element #64 as the transmitting aperture provides results comparable to the full sequence. The values of FWHM are 0.04 mm and 0.03 mm and those of PSL are -42 dB and -46 dB for temporal and subband approaches. From a cyst phantom and for 128 emissions, the contrast level is calculated at -54 dB and -63 dB respectively at the same depth, with the initial shape of the cyst being preserved in contrast to conventional beamforming. The difference between the two adaptive beamformers is less significant in the case of a single emission, with the contrast level being estimated at -42 dB for the time domain and -43 dB for the frequency domain implementation. For the estimation of a single MV weight of a low resolution image formed by a single emission, 0.44 * 109 calculations per second are required for the temporal approach. The same numbers for the subband approach are 0.62 * 109 for the point and 1.33 * 109 for the cyst phantom. The comparison demonstrates similar

  17. Study of the variance of a Monte Carlo calculation. Application to weighting; Etude de la variance d'un calcul de Monte Carlo. Application a la ponderation

    Energy Technology Data Exchange (ETDEWEB)

    Lanore, Jeanne-Marie [Commissariat a l' Energie Atomique - CEA, Centre d' Etudes Nucleaires de Fontenay-aux-Roses, Direction des Piles Atomiques, Departement des Etudes de Piles, Service d' Etudes de Protections de Piles (France)

    1969-04-15

    One of the main difficulties in Monte Carlo computations is the estimation of the results variance. Generally, only an apparent variance can be observed over a few calculations, often very different from the actual variance. By studying a large number of short calculations, the authors have tried to evaluate the real variance, and then to apply the obtained results to the optimization of the computations. The program used is the Poker one-dimensional Monte Carlo program. Calculations are performed in two types of fictitious environments: a body with constant cross section, without absorption, where all shocks are elastic and isotropic; a body with variable cross section (presenting a very pronounced peak and hole), with an anisotropy for high energy elastic shocks, and with the possibility of inelastic shocks (this body presents all the features that can appear in a real case)

  18. A Mean-Variance Criterion for Economic Model Predictive Control of Stochastic Linear Systems

    DEFF Research Database (Denmark)

    Sokoler, Leo Emil; Dammann, Bernd; Madsen, Henrik

    2014-01-01

    , the tractability of the resulting optimal control problem is addressed. We use a power management case study to compare different variations of the mean-variance strategy with EMPC based on the certainty equivalence principle. The certainty equivalence strategy is much more computationally efficient than the mean......-variance strategies, but it does not account for the variance of the uncertain parameters. Openloop simulations suggest that a single-stage mean-variance approach yields a significantly lower operating cost than the certainty equivalence strategy. In closed-loop, the single-stage formulation is overly conservative...... be modified to perform almost as well as the two-stage mean-variance formulation. Nevertheless, we argue that the mean-variance approach can be used both as a strategy for evaluating less computational demanding methods such as the certainty equivalence method, and as an individual control strategy when...

  19. Continuous-Time Mean-Variance Portfolio Selection under the CEV Process

    Directory of Open Access Journals (Sweden)

    Hui-qiang Ma

    2014-01-01

    Full Text Available We consider a continuous-time mean-variance portfolio selection model when stock price follows the constant elasticity of variance (CEV process. The aim of this paper is to derive an optimal portfolio strategy and the efficient frontier. The mean-variance portfolio selection problem is formulated as a linearly constrained convex program problem. By employing the Lagrange multiplier method and stochastic optimal control theory, we obtain the optimal portfolio strategy and mean-variance efficient frontier analytically. The results show that the mean-variance efficient frontier is still a parabola in the mean-variance plane, and the optimal strategies depend not only on the total wealth but also on the stock price. Moreover, some numerical examples are given to analyze the sensitivity of the efficient frontier with respect to the elasticity parameter and to illustrate the results presented in this paper. The numerical results show that the price of risk decreases as the elasticity coefficient increases.

  20. Is fMRI ?noise? really noise? Resting state nuisance regressors remove variance with network structure

    OpenAIRE

    Bright, Molly G.; Murphy, Kevin

    2015-01-01

    Noise correction is a critical step towards accurate mapping of resting state BOLD fMRI connectivity. Noise sources related to head motion or physiology are typically modelled by nuisance regressors, and a generalised linear model is applied to regress out the associated signal variance. In this study, we use independent component analysis (ICA) to characterise the data variance typically discarded in this pre-processing stage in a cohort of 12 healthy volunteers. The signal variance removed ...