Estimating haplotype effects for survival data

DEFF Research Database (Denmark)

Scheike, Thomas; Martinussen, Torben; Silver, J

2010-01-01

Genetic association studies often investigate the effect of haplotypes on an outcome of interest. Haplotypes are not observed directly, and this complicates the inclusion of such effects in survival models. We describe a new estimating equations approach for Cox's regression model to assess haplo...

Re-evaluating neonatal-age models for ungulates: does model choice affect survival estimates?

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Troy W Grovenburg

Full Text Available New-hoof growth is regarded as the most reliable metric for predicting age of newborn ungulates, but variation in estimated age among hoof-growth equations that have been developed may affect estimates of survival in staggered-entry models. We used known-age newborns to evaluate variation in age estimates among existing hoof-growth equations and to determine the consequences of that variation on survival estimates. During 2001-2009, we captured and radiocollared 174 newborn (≤24-hrs old ungulates: 76 white-tailed deer (Odocoileus virginianus in Minnesota and South Dakota, 61 mule deer (O. hemionus in California, and 37 pronghorn (Antilocapra americana in South Dakota. Estimated age of known-age newborns differed among hoof-growth models and varied by >15 days for white-tailed deer, >20 days for mule deer, and >10 days for pronghorn. Accuracy (i.e., the proportion of neonates assigned to the correct age in aging newborns using published equations ranged from 0.0% to 39.4% in white-tailed deer, 0.0% to 3.3% in mule deer, and was 0.0% for pronghorns. Results of survival modeling indicated that variability in estimates of age-at-capture affected short-term estimates of survival (i.e., 30 days for white-tailed deer and mule deer, and survival estimates over a longer time frame (i.e., 120 days for mule deer. Conversely, survival estimates for pronghorn were not affected by estimates of age. Our analyses indicate that modeling survival in daily intervals is too fine a temporal scale when age-at-capture is unknown given the potential inaccuracies among equations used to estimate age of neonates. Instead, weekly survival intervals are more appropriate because most models accurately predicted ages within 1 week of the known age. Variation among results of neonatal-age models on short- and long-term estimates of survival for known-age young emphasizes the importance of selecting an appropriate hoof-growth equation and appropriately defining intervals (i

Survival chance in papillary thyroid cancer in Hungary: individual survival probability estimation using the Markov method

International Nuclear Information System (INIS)

Esik, Olga; Tusnady, Gabor; Daubner, Kornel; Nemeth, Gyoergy; Fuezy, Marton; Szentirmay, Zoltan

1997-01-01

Purpose: The typically benign, but occasionally rapidly fatal clinical course of papillary thyroid cancer has raised the need for individual survival probability estimation, to tailor the treatment strategy exclusively to a given patient. Materials and methods: A retrospective study was performed on 400 papillary thyroid cancer patients with a median follow-up time of 7.1 years to establish a clinical database for uni- and multivariate analysis of the prognostic factors related to survival (Kaplan-Meier product limit method and Cox regression). For a more precise prognosis estimation, the effect of the most important clinical events were then investigated on the basis of a Markov renewal model. The basic concept of this approach is that each patient has an individual disease course which (besides the initial clinical categories) is affected by special events, e.g. internal covariates (local/regional/distant relapses). On the supposition that these events and the cause-specific death are influenced by the same biological processes, the parameters of transient survival probability characterizing the speed of the course of the disease for each clinical event and their sequence were determined. The individual survival curves for each patient were calculated by using these parameters and the independent significant clinical variables selected from multivariate studies, summation of which resulted in a mean cause-specific survival function valid for the entire group. On the basis of this Markov model, prediction of the cause-specific survival probability is possible for extrastudy cases, if it is supposed that the clinical events occur within new patients in the same manner and with the similar probability as within the study population. Results: The patient's age, a distant metastasis at presentation, the extent of the surgical intervention, the primary tumor size and extent (pT), the external irradiation dosage and the degree of TSH suppression proved to be

Annual survival estimation of migratory songbirds confounded by incomplete breeding site-fidelity: study designs that may help

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Marshall, M. R.

2004-06-01

surrounding areas to minimize bias. Therefore, as an alternative protocol, we analyzed the data with subsets of three progressively larger areas surrounding the core. The data subsets provided four estimates of apparent survival that asymptotically approached true survival. This study design and analytical approach is likely to be logistically feasible in field settings and yields estimates of true survival unbiased (bias < 0.03 by incomplete breeding site–fidelity over a range of inter–annual territory movement patterns. The third approach we investigated used a robust design data collection and analysis approach. This approach resulted in estimates of survival that were unbiased (bias < 0.02, but were very imprecise and likely would not yield reliable estimates in field situations. The fourth approach utilized a fixed study area size, but modeled detection probability as a function of bird proximity to the study plot boundary (e.g., those birds closest to the edge are more likely to emigrate. This approach also resulted in estimates of survival that were unbiased (bias < 0.02, but because the individual covariates were normalized, the average capture probability was 0.50, and thus did not provide an accurate estimate of the true capture probability. Our results show that the core–area with surrounding resight–only can provide estimates of survival that are not biased by the effects of incomplete breeding site–fidelity.

Estimates of annual survival probabilities for adult Florida manatees (Trichechus manatus latirostris)

Science.gov (United States)

Langtimm, C.A.; O'Shea, T.J.; Pradel, R.; Beck, C.A.

1998-01-01

The population dynamics of large, long-lived mammals are particularly sensitive to changes in adult survival. Understanding factors affecting survival patterns is therefore critical for developing and testing theories of population dynamics and for developing management strategies aimed at preventing declines or extinction in such taxa. Few studies have used modern analytical approaches for analyzing variation and testing hypotheses about survival probabilities in large mammals. This paper reports a detailed analysis of annual adult survival in the Florida manatee (Trichechus manatus latirostris), an endangered marine mammal, based on a mark-recapture approach. Natural and boat-inflicted scars distinctively 'marked' individual manatees that were cataloged in a computer-based photographic system. Photo-documented resightings provided 'recaptures.' Using open population models, annual adult-survival probabilities were estimated for manatees observed in winter in three areas of Florida: Blue Spring, Crystal River, and the Atlantic coast. After using goodness-of-fit tests in Program RELEASE to search for violations of the assumptions of mark-recapture analysis, survival and sighting probabilities were modeled under several different biological hypotheses with Program SURGE. Estimates of mean annual probability of sighting varied from 0.948 for Blue Spring to 0.737 for Crystal River and 0.507 for the Atlantic coast. At Crystal River and Blue Spring, annual survival probabilities were best estimated as constant over the study period at 0.96 (95% CI = 0.951-0.975 and 0.900-0.985, respectively). On the Atlantic coast, where manatees are impacted more by human activities, annual survival probabilities had a significantly lower mean estimate of 0.91 (95% CI = 0.887-0.926) and varied unpredictably over the study period. For each study area, survival did not differ between sexes and was independent of relative adult age. The high constant adult-survival probabilities estimated

Estimating the average treatment effect on survival based on observational data and using partly conditional modeling.

Science.gov (United States)

Gong, Qi; Schaubel, Douglas E

2017-03-01

Treatments are frequently evaluated in terms of their effect on patient survival. In settings where randomization of treatment is not feasible, observational data are employed, necessitating correction for covariate imbalances. Treatments are usually compared using a hazard ratio. Most existing methods which quantify the treatment effect through the survival function are applicable to treatments assigned at time 0. In the data structure of our interest, subjects typically begin follow-up untreated; time-until-treatment, and the pretreatment death hazard are both heavily influenced by longitudinal covariates; and subjects may experience periods of treatment ineligibility. We propose semiparametric methods for estimating the average difference in restricted mean survival time attributable to a time-dependent treatment, the average effect of treatment among the treated, under current treatment assignment patterns. The pre- and posttreatment models are partly conditional, in that they use the covariate history up to the time of treatment. The pre-treatment model is estimated through recently developed landmark analysis methods. For each treated patient, fitted pre- and posttreatment survival curves are projected out, then averaged in a manner which accounts for the censoring of treatment times. Asymptotic properties are derived and evaluated through simulation. The proposed methods are applied to liver transplant data in order to estimate the effect of liver transplantation on survival among transplant recipients under current practice patterns. © 2016, The International Biometric Society.

[Survival analysis with competing risks: estimating failure probability].

Science.gov (United States)

Llorca, Javier; Delgado-Rodríguez, Miguel

2004-01-01

To show the impact of competing risks of death on survival analysis. We provide an example of survival time without chronic rejection after heart transplantation, where death before rejection acts as a competing risk. Using a computer simulation, we compare the Kaplan-Meier estimator and the multiple decrement model. The Kaplan-Meier method overestimated the probability of rejection. Next, we illustrate the use of the multiple decrement model to analyze secondary end points (in our example: death after rejection). Finally, we discuss Kaplan-Meier assumptions and why they fail in the presence of competing risks. Survival analysis should be adjusted for competing risks of death to avoid overestimation of the risk of rejection produced with the Kaplan-Meier method.

An estimator of the survival function based on the semi-Markov model under dependent censorship.

Science.gov (United States)

Lee, Seung-Yeoun; Tsai, Wei-Yann

2005-06-01

Lee and Wolfe (Biometrics vol. 54 pp. 1176-1178, 1998) proposed the two-stage sampling design for testing the assumption of independent censoring, which involves further follow-up of a subset of lost-to-follow-up censored subjects. They also proposed an adjusted estimator for the survivor function for a proportional hazards model under the dependent censoring model. In this paper, a new estimator for the survivor function is proposed for the semi-Markov model under the dependent censorship on the basis of the two-stage sampling data. The consistency and the asymptotic distribution of the proposed estimator are derived. The estimation procedure is illustrated with an example of lung cancer clinical trial and simulation results are reported of the mean squared errors of estimators under a proportional hazards and two different nonproportional hazards models.

Survival analysis

International Nuclear Information System (INIS)

Badwe, R.A.

1999-01-01

The primary endpoint in the majority of the studies has been either disease recurrence or death. This kind of analysis requires a special method since all patients in the study experience the endpoint. The standard method for estimating such survival distribution is Kaplan Meier method. The survival function is defined as the proportion of individuals who survive beyond certain time. Multi-variate comparison for survival has been carried out with Cox's proportional hazard model

Estimating the joint survival probabilities of married individuals

NARCIS (Netherlands)

Sanders, Lisanne; Melenberg, Bertrand

We estimate the joint survival probability of spouses using a large random sample drawn from a Dutch census. As benchmarks we use two bivariate Weibull models. We consider more flexible models, using a semi-nonparametric approach, by extending the independent Weibull distribution using squared

Evaluating methodological assumptions of a catch-curve survival estimation of unmarked precocial shorebird chickes

Science.gov (United States)

McGowan, Conor P.; Gardner, Beth

2013-01-01

Estimating productivity for precocial species can be difficult because young birds leave their nest within hours or days of hatching and detectability thereafter can be very low. Recently, a method for using a modified catch-curve to estimate precocial chick daily survival for age based count data was presented using Piping Plover (Charadrius melodus) data from the Missouri River. However, many of the assumptions of the catch-curve approach were not fully evaluated for precocial chicks. We developed a simulation model to mimic Piping Plovers, a fairly representative shorebird, and age-based count-data collection. Using the simulated data, we calculated daily survival estimates and compared them with the known daily survival rates from the simulation model. We conducted these comparisons under different sampling scenarios where the ecological and statistical assumptions had been violated. Overall, the daily survival estimates calculated from the simulated data corresponded well with true survival rates of the simulation. Violating the accurate aging and the independence assumptions did not result in biased daily survival estimates, whereas unequal detection for younger or older birds and violating the birth death equilibrium did result in estimator bias. Assuring that all ages are equally detectable and timing data collection to approximately meet the birth death equilibrium are key to the successful use of this method for precocial shorebirds.

Postoperative Respiratory Function and Survival After Pneumonectomy in Dogs and Cats.

Science.gov (United States)

Majeski, Stephanie A; Steffey, Michele A; Mayhew, Philipp D; Hunt, Geraldine B; Holt, David E; Runge, Jeffrey J; Kass, Philip H; Mellema, Matthew

2016-08-01

To describe indications for, and outcomes after, pneumonectomy in dogs and cats, including assessment of immediate postoperative respiratory function in comparison to dogs undergoing single lung lobectomy. Retrospective case series. Dogs (n=16) and cats (n=7) with naturally occurring pulmonary disease. Medical records (1990-2014) of dogs and cats undergoing right or left pneumonectomy were reviewed. Data retrieved included signalment, history, preoperative diagnostics, operative descriptions, postoperative data including respiratory function, and postdischarge outcomes. For respiratory function comparisons, medical records of dogs having undergone a single lung lobectomy via median sternotomy (n=15) or intercostal thoracotomy (n=15) were reviewed. Twenty-three cases (16 dogs, 7 cats) were included. Pneumonectomy was performed for congenital (1 dog, 1 cat), neoplastic (8 dogs, 1 cat), and infectious (7 dogs, 5 cats) disease. Postoperative aspiration pneumonia occurred in 2 dogs; 15 of 16 dogs (94%) and 6/7 cats (86%) survived to hospital discharge. After pneumonectomy, dogs had a significantly higher postoperative PaO2 on 21% oxygen (P=.033) and lower postoperative A-a gradient (P=.004) compared to dogs undergoing single lung lobectomy. Survival times (right-censored at last follow-up) for dogs ranged from 2 days to 7 years (estimated median=1,868 days) and for cats from 1-585 days. Dogs and cats have acceptable respiratory function immediately postoperatively and most have protracted long-term survival after pneumonectomy for a variety of pulmonary diseases. © Copyright 2016 by The American College of Veterinary Surgeons.

Estimation of transfused red cell survival using an enzyme-linked antiglobulin test

International Nuclear Information System (INIS)

Kickler, T.S.; Smith, B.; Bell, W.; Drew, H.; Baldwin, M.; Ness, P.M.

1985-01-01

An enzyme-linked antiglobulin test (ELAT) method was developed to estimate survival of transfused red cells. This procedure is based on a principle analogous to that of the Ashby technique were antigenically distinct red cells are transfused and their survival studied. The authors compared the ELAT survival to the 51 Chromium method ( 51 Cr) in four patients. Three patients with hypoproliferative anemias showed T 1/2 by ELAT of 17.5, 18, and 17 days versus 18.5, 20, and 19 days by the 51 Cr method. A fourth patient with traumatic cardiac hemolysis had two studies performed. In this case, the ELAT showed a T 1/2 of 10 and 8.1 days while 51 Cr T 1/2 values were 11 and 10.5 days. The ELAT method for measuring red cell survival yielded data which agreed closely with the results of the 51 Cr method. Although 51 Cr is the accepted method for red cell survival, the ELAT method can be used to estimate transfused red cell survival

The Influence of Mark-Recapture Sampling Effort on Estimates of Rock Lobster Survival.

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Ziya Kordjazi

Full Text Available Five annual capture-mark-recapture surveys on Jasus edwardsii were used to evaluate the effect of sample size and fishing effort on the precision of estimated survival probability. Datasets of different numbers of individual lobsters (ranging from 200 to 1,000 lobsters were created by random subsampling from each annual survey. This process of random subsampling was also used to create 12 datasets of different levels of effort based on three levels of the number of traps (15, 30 and 50 traps per day and four levels of the number of sampling-days (2, 4, 6 and 7 days. The most parsimonious Cormack-Jolly-Seber (CJS model for estimating survival probability shifted from a constant model towards sex-dependent models with increasing sample size and effort. A sample of 500 lobsters or 50 traps used on four consecutive sampling-days was required for obtaining precise survival estimations for males and females, separately. Reduced sampling effort of 30 traps over four sampling days was sufficient if a survival estimate for both sexes combined was sufficient for management of the fishery.

The Influence of Mark-Recapture Sampling Effort on Estimates of Rock Lobster Survival

Science.gov (United States)

Kordjazi, Ziya; Frusher, Stewart; Buxton, Colin; Gardner, Caleb; Bird, Tomas

2016-01-01

Five annual capture-mark-recapture surveys on Jasus edwardsii were used to evaluate the effect of sample size and fishing effort on the precision of estimated survival probability. Datasets of different numbers of individual lobsters (ranging from 200 to 1,000 lobsters) were created by random subsampling from each annual survey. This process of random subsampling was also used to create 12 datasets of different levels of effort based on three levels of the number of traps (15, 30 and 50 traps per day) and four levels of the number of sampling-days (2, 4, 6 and 7 days). The most parsimonious Cormack-Jolly-Seber (CJS) model for estimating survival probability shifted from a constant model towards sex-dependent models with increasing sample size and effort. A sample of 500 lobsters or 50 traps used on four consecutive sampling-days was required for obtaining precise survival estimations for males and females, separately. Reduced sampling effort of 30 traps over four sampling days was sufficient if a survival estimate for both sexes combined was sufficient for management of the fishery. PMID:26990561

System-level analysis of genes and functions affecting survival during nutrient starvation in Saccharomyces cerevisiae.

Science.gov (United States)

Gresham, David; Boer, Viktor M; Caudy, Amy; Ziv, Naomi; Brandt, Nathan J; Storey, John D; Botstein, David

2011-01-01

An essential property of all cells is the ability to exit from active cell division and persist in a quiescent state. For single-celled microbes this primarily occurs in response to nutrient deprivation. We studied the genetic requirements for survival of Saccharomyces cerevisiae when starved for either of two nutrients: phosphate or leucine. We measured the survival of nearly all nonessential haploid null yeast mutants in mixed populations using a quantitative sequencing method that estimates the abundance of each mutant on the basis of frequency of unique molecular barcodes. Starvation for phosphate results in a population half-life of 337 hr whereas starvation for leucine results in a half-life of 27.7 hr. To measure survival of individual mutants in each population we developed a statistical framework that accounts for the multiple sources of experimental variation. From the identities of the genes in which mutations strongly affect survival, we identify genetic evidence for several cellular processes affecting survival during nutrient starvation, including autophagy, chromatin remodeling, mRNA processing, and cytoskeleton function. In addition, we found evidence that mitochondrial and peroxisome function is required for survival. Our experimental and analytical methods represent an efficient and quantitative approach to characterizing genetic functions and networks with unprecedented resolution and identified genotype-by-environment interactions that have important implications for interpretation of studies of aging and quiescence in yeast.

Relationships between mastitis and functional longevity in Danish Black and White dairy cattle estimated using survival analysis

NARCIS (Netherlands)

Neerhof, H.J.; Madsen, P.; Ducrucq, V.; Vollema, A.R.; Jensen, I.; Korsgaard, I.R.

2000-01-01

The relationship between mastitis and functional longevity was assessed with survival analysis on data of Danish Black and White dairy cows. Different methods of including the effect of mastitis treatment on the culling decision by a farmer in the model were compared. The model in which mastitis

Causal inference for long-term survival in randomised trials with treatment switching: Should re-censoring be applied when estimating counterfactual survival times?

OpenAIRE

Latimer, N.R.; White, I.R.; Abrams, K.R.; Sieburt, U.

2017-01-01

Treatment switching often has a crucial impact on estimates of effectiveness and cost-effectiveness of new oncology treatments. Rank preserving structural failure time models (RPSFTM) and two-stage estimation (TSE) methods estimate ‘counterfactual’ (i.e. had there been no switching) survival times and incorporate re-censoring to guard against informative censoring in the counterfactual dataset. However, re-censoring causes a loss of longer term survival information which is problematic when e...

BAYESIAN ESTIMATION OF THE SHAPE PARAMETER OF THE GENERALISED EXPONENTIAL DISTRIBUTION UNDER DIFFERENT LOSS FUNCTIONS

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SANKU DEY

2010-11-01

Full Text Available The generalized exponential (GE distribution proposed by Gupta and Kundu (1999 is an important lifetime distribution in survival analysis. In this article, we propose to obtain Bayes estimators and its associated risk based on a class of  non-informative prior under the assumption of three loss functions, namely, quadratic loss function (QLF, squared log-error loss function (SLELF and general entropy loss function (GELF. The motivation is to explore the most appropriate loss function among these three loss functions. The performances of the estimators are, therefore, compared on the basis of their risks obtained under QLF, SLELF and GELF separately. The relative efficiency of the estimators is also obtained. Finally, Monte Carlo simulations are performed to compare the performances of the Bayes estimates under different situations.

Apparent survival rates of forest birds in eastern Ecuador revisited: improvement in precision but no change in estimates.

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John G Blake

Full Text Available Knowledge of survival rates of Neotropical landbirds remains limited, with estimates of apparent survival available from relatively few sites and species. Previously, capture-mark-recapture models were used to estimate apparent survival of 31 species (30 passerines, 1 Trochilidae from eastern Ecuador based on data collected from 2001 to 2006. Here, estimates are updated with data from 2001-2012 to determine how additional years of data affect estimates; estimates for six additional species are provided. Models assuming constant survival had highest support for 19 of 31 species when based on 12 years of data compared to 27 when based on six; models incorporating effects of transients had the highest support for 12 of 31 species compared to four when based on 12 and six years, respectively. Average apparent survival based on the most highly-supported model (based on model averaging, when appropriate was 0.59 (± 0.02 SE across 30 species of passerines when based on 12 years and 0.57 (± 0.02 when based on six. Standard errors of survival estimates based on 12 years were approximately half those based on six years. Of 31 species in both data sets, estimates of apparent survival were somewhat lower for 13, somewhat higher for 17, and remained unchanged for one; confidence intervals for estimates based on six and 12 years of data overlapped for all species. Results indicate that estimates of apparent survival are comparable but more precise when based on longer-term data sets; standard error of the estimates was negatively correlated with numbers of captures (rs  = -0.72 and recaptures (rs  = -0.93, P<0.001 in both cases. Thus, reasonable estimates of apparent survival may be obtained with relatively few years of data if sample sizes are sufficient.

Simultaneous use of mark-recapture and radiotelemetry to estimate survival, movement, and capture rates

Science.gov (United States)

Powell, L.A.; Conroy, M.J.; Hines, J.E.; Nichols, J.D.; Krementz, D.G.

2000-01-01

Biologists often estimate separate survival and movement rates from radio-telemetry and mark-recapture data from the same study population. We describe a method for combining these data types in a single model to obtain joint, potentially less biased estimates of survival and movement that use all available data. We furnish an example using wood thrushes (Hylocichla mustelina) captured at the Piedmont National Wildlife Refuge in central Georgia in 1996. The model structure allows estimation of survival and capture probabilities, as well as estimation of movements away from and into the study area. In addition, the model structure provides many possibilities for hypothesis testing. Using the combined model structure, we estimated that wood thrush weekly survival was 0.989 ? 0.007 ( ?SE). Survival rates of banded and radio-marked individuals were not different (alpha hat [S_radioed, ~ S_banded]=log [S hat _radioed/ S hat _banded]=0.0239 ? 0.0435). Fidelity rates (weekly probability of remaining in a stratum) did not differ between geographic strata (psi hat=0.911 ? 0.020; alpha hat [psi11, psi22]=0.0161 ? 0.047), and recapture rates ( = 0.097 ? 0.016) banded and radio-marked individuals were not different (alpha hat [p_radioed, p_banded]=0.145 ? 0.655). Combining these data types in a common model resulted in more precise estimates of movement and recapture rates than separate estimation, but ability to detect stratum or mark-specific differences in parameters was week. We conducted simulation trials to investigate the effects of varying study designs on parameter accuracy and statistical power to detect important differences. Parameter accuracy was high (relative bias [RBIAS] inference from this model, study designs should seek a minimum of 25 animals of each marking type observed (marked or observed via telemetry) in each time period and geographic stratum.

Will Incremental Hemodialysis Preserve Residual Function and Improve Patient Survival?

Science.gov (United States)

Davenport, Andrew

2015-01-01

The progressive loss of residual renal function in peritoneal dialysis patients is associated with increased mortality. It has been suggested that incremental dialysis may help preserve residual renal function and improve patient survival. Residual renal function depends upon both patient related and dialysis associated factors. Maintaining patients in an over-hydrated state may be associated with better preservation of residual renal function but any benefit comes with a significant risk of cardiovascular consequences. Notably, it is only observational studies that have reported an association between dialysis patient survival and residual renal function; causality has not been established for dialysis patient survival. The tenuous connections between residual renal function and outcomes and between incremental hemodialysis and residual renal function should temper our enthusiasm for interventions in this area. PMID:25385441

Meta-analysis of single-arm survival studies: a distribution-free approach for estimating summary survival curves with random effects.

Science.gov (United States)

Combescure, Christophe; Foucher, Yohann; Jackson, Daniel

2014-07-10

In epidemiologic studies and clinical trials with time-dependent outcome (for instance death or disease progression), survival curves are used to describe the risk of the event over time. In meta-analyses of studies reporting a survival curve, the most informative finding is a summary survival curve. In this paper, we propose a method to obtain a distribution-free summary survival curve by expanding the product-limit estimator of survival for aggregated survival data. The extension of DerSimonian and Laird's methodology for multiple outcomes is applied to account for the between-study heterogeneity. Statistics I(2)  and H(2) are used to quantify the impact of the heterogeneity in the published survival curves. A statistical test for between-strata comparison is proposed, with the aim to explore study-level factors potentially associated with survival. The performance of the proposed approach is evaluated in a simulation study. Our approach is also applied to synthesize the survival of untreated patients with hepatocellular carcinoma from aggregate data of 27 studies and synthesize the graft survival of kidney transplant recipients from individual data from six hospitals. Copyright © 2014 John Wiley & Sons, Ltd.

Designing a monitoring program to estimate estuarine survival of anadromous salmon smolts: simulating the effect of sample design on inference

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Romer, Jeremy D.; Gitelman, Alix I.; Clements, Shaun; Schreck, Carl B.

2015-01-01

A number of researchers have attempted to estimate salmonid smolt survival during outmigration through an estuary. However, it is currently unclear how the design of such studies influences the accuracy and precision of survival estimates. In this simulation study we consider four patterns of smolt survival probability in the estuary, and test the performance of several different sampling strategies for estimating estuarine survival assuming perfect detection. The four survival probability patterns each incorporate a systematic component (constant, linearly increasing, increasing and then decreasing, and two pulses) and a random component to reflect daily fluctuations in survival probability. Generally, spreading sampling effort (tagging) across the season resulted in more accurate estimates of survival. All sampling designs in this simulation tended to under-estimate the variation in the survival estimates because seasonal and daily variation in survival probability are not incorporated in the estimation procedure. This under-estimation results in poorer performance of estimates from larger samples. Thus, tagging more fish may not result in better estimates of survival if important components of variation are not accounted for. The results of our simulation incorporate survival probabilities and run distribution data from previous studies to help illustrate the tradeoffs among sampling strategies in terms of the number of tags needed and distribution of tagging effort. This information will assist researchers in developing improved monitoring programs and encourage discussion regarding issues that should be addressed prior to implementation of any telemetry-based monitoring plan. We believe implementation of an effective estuary survival monitoring program will strengthen the robustness of life cycle models used in recovery plans by providing missing data on where and how much mortality occurs in the riverine and estuarine portions of smolt migration. These data

Estimation of survival of adult Florida manatees in the Crystal River, at Blue Spring, and on the Atlantic Coast

Science.gov (United States)

O'Shea, Thomas J.; Langtimm, Catherine A.; O'Shea, Thomas J.; Ackerman, B.B.; Percival, H. Franklin

1995-01-01

We applied Cormack-Jolly-Seber open population models to manatee (Trichechus manatus latirostris) photo-identification databases to estimate adult survival probabilities. The computer programs JOLLY and RECAPCO were used to estimate survival of 677 individuals in three study areas: Crystal River (winters 1977-78 to 1990-91), Blue Spring (winters 1977-78 to 1990-91), and the Atlantic Coast (winters 1984-85 to 1990-91). We also estimated annual survival from observations of 111 manatees tagged for studies with radiotelemetry. Survival estimated from observations with telemetry had broader confidence intervals than survival estimated with the Cormack-Jolly-Seber models. Annual probabilities of capture based on photo-identification records were generally high. The mean annual adult survival estimated from sighting-resighting records was 0.959-0.962 in the Crystal River and 0.936-0.948 at Blue Spring and may be high enough to permit population growth, given the values of other life-history parameters. On the Atlantic Coast, the estimated annual adult survival (range of means = 0.877-0.885) may signify a declining population. However, for several reasons, interpretation of data from the latter study group should be tempered with caution. Adult survivorship seems to be constant with age in all three study groups. No strong differences were apparent between adult survival ofmales and females in the Crystal River or at Blue Spring; the basis of significant differences between sexes on the Atlantic Coast is unclear. Future research into estimating survival with photo-identification and the Cormack-Jolly-Seber models should be vigorously pursued. Estimates of annual survival can provide an additional indication of Florida manatee population status with a stronger statistical basis than aerial counts and carcass totals.

Annual survival rate estimate of satellite transmitter–marked eastern population greater sandhill cranes

Science.gov (United States)

Fronczak, David L.; Andersen, David E.; Hanna, Everett E.; Cooper, Thomas R.

2015-01-01

Several surveys have documented the increasing population size and geographic distribution of Eastern Population greater sandhill cranes Grus canadensis tabida since the 1960s. Sport hunting of this population of sandhill cranes started in 2012 following the provisions of the Eastern Population Sandhill Crane Management Plan. However, there are currently no published estimates of Eastern Population sandhill crane survival rate that can be used to inform harvest management. As part of two studies of Eastern Population sandhill crane migration, we deployed solar-powered global positioning system platform transmitting terminals on Eastern Population sandhill cranes (n  =  42) at key concentration areas from 2009 to 2012. We estimated an annual survival rate for Eastern Population sandhill cranes from data resulting from monitoring these cranes by using the known-fates model in the MARK program. Estimated annual survival rate for adult Eastern Population sandhill cranes was 0.950 (95% confidence interval  =  0.885–0.979) during December 2009–August 2014. All fatalities (n  =  5) occurred after spring migration in late spring and early summer. We were unable to determine cause of death for crane fatalities in our study. Our survival rate estimate will be useful when combined with other population parameters such as the population index derived from the U.S. Fish and Wildlife Service fall survey, harvest, and recruitment rates to assess the effects of harvest on population size and trend and evaluate the effectiveness of management strategies.

Nonparametric Bayesian inference for mean residual life functions in survival analysis.

Science.gov (United States)

Poynor, Valerie; Kottas, Athanasios

2018-01-19

Modeling and inference for survival analysis problems typically revolves around different functions related to the survival distribution. Here, we focus on the mean residual life (MRL) function, which provides the expected remaining lifetime given that a subject has survived (i.e. is event-free) up to a particular time. This function is of direct interest in reliability, medical, and actuarial fields. In addition to its practical interpretation, the MRL function characterizes the survival distribution. We develop general Bayesian nonparametric inference for MRL functions built from a Dirichlet process mixture model for the associated survival distribution. The resulting model for the MRL function admits a representation as a mixture of the kernel MRL functions with time-dependent mixture weights. This model structure allows for a wide range of shapes for the MRL function. Particular emphasis is placed on the selection of the mixture kernel, taken to be a gamma distribution, to obtain desirable properties for the MRL function arising from the mixture model. The inference method is illustrated with a data set of two experimental groups and a data set involving right censoring. The supplementary material available at Biostatistics online provides further results on empirical performance of the model, using simulated data examples. © The Author 2018. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Timely disclosure of progress in long-term cancer survival: the boomerang method substantially improved estimates in a comparative study.

Science.gov (United States)

Brenner, Hermann; Jansen, Lina

2016-02-01

Monitoring cancer survival is a key task of cancer registries, but timely disclosure of progress in long-term survival remains a challenge. We introduce and evaluate a novel method, denoted "boomerang method," for deriving more up-to-date estimates of long-term survival. We applied three established methods (cohort, complete, and period analysis) and the boomerang method to derive up-to-date 10-year relative survival of patients diagnosed with common solid cancers and hematological malignancies in the United States. Using the Surveillance, Epidemiology and End Results 9 database, we compared the most up-to-date age-specific estimates that might have been obtained with the database including patients diagnosed up to 2001 with 10-year survival later observed for patients diagnosed in 1997-2001. For cancers with little or no increase in survival over time, the various estimates of 10-year relative survival potentially available by the end of 2001 were generally rather similar. For malignancies with strongly increasing survival over time, including breast and prostate cancer and all hematological malignancies, the boomerang method provided estimates that were closest to later observed 10-year relative survival in 23 of the 34 groups assessed. The boomerang method can substantially improve up-to-dateness of long-term cancer survival estimates in times of ongoing improvement in prognosis. Copyright © 2016 Elsevier Inc. All rights reserved.

Survival, complications and functional outcomes of cemented megaprostheses for high-grade osteosarcoma around the knee.

Science.gov (United States)

Zhang, Chunlin; Hu, Jianping; Zhu, Kunpeng; Cai, Tao; Ma, Xiaolong

2018-04-01

We initiated a retrospective study on the long-term survival of cemented endoprostheses for bone tumours around the knee to answer the following questions: (1) What was the survival of these patients? (2) What was the overall survival of cemented prostheses around the knee? (3) What types of failures were observed in these reconstructions? (4) Did the survival and complications vary according to the site of the implant? (5) What was the functional result after cemented prosthesis replacement around the knee? From January 2006 to December 2013, 108 consecutive patients with an average age of 25 years, who had mature bone development as evidenced by imaging examinations, underwent 108 cemented endoprosthetic knee replacements for osteosarcoma resection. All patients received neoadjuvant chemotherapy using a multi-drug protocol consisting of high dose methotrexate (HDMTX), doxorubicin (ADM), cisplatin (DDP) and high dose ifosfamide (HDIFO). When extensor mechanism reconstruction was required, we ran nonabsorbable sutures through designated holes in the tibial component to fix detached hamstrings and the remaining ligaments in an imbricated fashion as well as reinforced the reconstruction with a medial gastrocnemius flap. Seventy-two (72/108, 66.7%) lesions were located in the distal femur and 36 (36/108, 33.3%) lesions at the proximal tibias. Nineteen patients were staged as IIA and 89 as IIB according to the Enneking staging system. The average follow-up was 53.3 months (range 12-125 months), with a minimum oncological follow-up of one year. Survival, prosthetic failure, complications and functional outcomes were recorded and reassessed at every visit after the primary operation. At the final follow-up, the oncologic results showed that 33 patients died from metastases, and local recurrence occurred in ten patients. The estimated overall five-year and eight-year survival rates were 71% (95% CI: 62.4-79.65%) and 67.2% (95% CI: 58-76.4%), respectively. In this

Direct Survival Analysis: a new stock assessment method

Directory of Open Access Journals (Sweden)

Eduardo Ferrandis

2007-03-01

Full Text Available In this work, a new stock assessment method, Direct Survival Analysis, is proposed and described. The parameter estimation of the Weibull survival model proposed by Ferrandis (2007 is obtained using trawl survey data. This estimation is used to establish a baseline survival function, which is in turn used to estimate the specific survival functions in the different cohorts considered through an adaptation of the separable model of the fishing mortality rates introduced by Pope and Shepherd (1982. It is thus possible to test hypotheses on the evolution of survival during the period studied and to identify trends in recruitment. A link is established between the preceding analysis of trawl survey data and the commercial catch-at-age data that are generally obtained to evaluate the population using analytical models. The estimated baseline survival, with the proposed versions of the stock and catch equations and the adaptation of the Separable Model, may be applied to commercial catch-at-age data. This makes it possible to estimate the survival corresponding to the landing data, the initial size of the cohort and finally, an effective age of first capture, in order to complete the parameter model estimation and consequently the estimation of the whole survival and mortality, along with the reference parameters that are useful for management purposes. Alternatively, this estimation of an effective age of first capture may be obtained by adapting the demographic structure of trawl survey data to that of the commercial fleet through suitable selectivity models of the commercial gears. The complete model provides the evaluation of the stock at any age. The coherence (and hence the mutual “calibration” between the two kinds of information may be analysed and compared with results obtained by other methods, such as virtual population analysis (VPA, in order to improve the diagnosis of the state of exploitation of the population. The model may be

Modelling the joint distribution of competing risks survival times using copula functions

OpenAIRE

Kaishev, V. K.; Haberman, S.; Dimitrova, D. S.

2005-01-01

The problem of modelling the joint distribution of survival times in a competing risks model, using copula functions is considered. In order to evaluate this joint distribution and the related overall survival function, a system of non-linear differential equations is solved, which relates the crude and net survival functions of the modelled competing risks, through the copula. A similar approach to modelling dependent multiple decrements was applied by Carriere (1994) who used a Gaussian cop...

Survival Estimates for the Passage of Juvenile Chinook Salmon through Snake River Dams and Reservoirs, 1993 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Iwamoto, Robert N.; Sandford, Benjamin P.; McIntyre, Kenneth W.

1994-04-01

A pilot study was conducted to estimate survival of hatchery-reared yearling chinook salmon through dams and reservoirs on the Snake River. The goals of the study were to: (1) field test and evaluate the Single-Release, Modified-Single-Release, and Paired-Release Models for the estimation of survival probabilities through sections of a river and hydroelectric projects; (2) identify operational and logistical constraints to the execution of these models; and (3) determine the usefulness of the models in providing estimates of survival probabilities. Field testing indicated that the numbers of hatchery-reared yearling chinook salmon needed for accurate survival estimates could be collected at different areas with available gear and methods. For the primary evaluation, seven replicates of 830 to 1,442 hatchery-reared yearling chinook salmon were purse-seined from Lower Granite Reservoir, PIT tagged, and released near Nisqually John boat landing (River Kilometer 726). Secondary releases of PIT-tagged smolts were made at Lower Granite Dam to estimate survival of fish passing through turbines and after detection in the bypass system. Similar secondary releases were made at Little Goose Dam, but with additional releases through the spillway. Based on the success of the 1993 pilot study, the authors believe that the Single-Release and Paired-Release Models will provide accurate estimates of juvenile salmonid passage survival for individual river sections, reservoirs, and hydroelectric projects in the Columbia and Snake Rivers.

Survival estimates for the passage of juvenile chinook salmon through Snake River dams and reservoirs. Annual report 1993

International Nuclear Information System (INIS)

Iwamoto, R.N.; Muir, W.D.; Sandford, B.P.; McIntyre, K.W.; Frost, D.A.; Williams, J.G.; Smith, S.G.; Skalski, J.R.

1994-04-01

A pilot study was conducted to estimate survival of hatchery-reared yearling chinook salmon through dams and reservoirs on the Snake River. The goals of the study were to: (1) field test and evaluate the Single-Release, Modified-Single-Release, and Paired-Release Models for the estimation of survival probabilities through sections of a river and hydroelectric projects; (2) identify operational and logistical constraints to the execution of these models; and (3) determine the usefulness of the models in providing estimates of survival probabilities. Field testing indicated that the numbers of hatchery-reared yearling chinook salmon needed for accurate survival estimates could be collected at different areas with available gear and methods. For the primary evaluation, seven replicates of 830 to 1,442 hatchery-reared yearling chinook salmon were purse-seined from Lower Granite Reservoir, PIT tagged, and released near Nisqually John boat landing (River Kilometer 726). Secondary releases of PIT-tagged smolts were made at Lower Granite Dam to estimate survival of fish passing through turbines and after detection in the bypass system. Similar secondary releases were made at Little Goose Dam, but with additional releases through the spillway. Based on the success of the 1993 pilot study, the authors believe that the Single-Release and Paired-Release Models will provide accurate estimates of juvenile salmonid passage survival for individual river sections, reservoirs, and hydroelectric projects in the Columbia and Snake Rivers

Multiple imputation for estimating the risk of developing dementia and its impact on survival.

Science.gov (United States)

Yu, Binbing; Saczynski, Jane S; Launer, Lenore

2010-10-01

Dementia, Alzheimer's disease in particular, is one of the major causes of disability and decreased quality of life among the elderly and a leading obstacle to successful aging. Given the profound impact on public health, much research has focused on the age-specific risk of developing dementia and the impact on survival. Early work has discussed various methods of estimating age-specific incidence of dementia, among which the illness-death model is popular for modeling disease progression. In this article we use multiple imputation to fit multi-state models for survival data with interval censoring and left truncation. This approach allows semi-Markov models in which survival after dementia depends on onset age. Such models can be used to estimate the cumulative risk of developing dementia in the presence of the competing risk of dementia-free death. Simulations are carried out to examine the performance of the proposed method. Data from the Honolulu Asia Aging Study are analyzed to estimate the age-specific and cumulative risks of dementia and to examine the effect of major risk factors on dementia onset and death.

estimated glomerular filtration rate and risk of survival in acute stroke

African Journals Online (AJOL)

2014-03-03

Mar 3, 2014 ... ESTIMATED GLOMERULAR FILTRATION RATE AND RISK OF SURVIVAL IN ACUTE STROKE. E. I. Okaka, MBBS, FWACP, F. A. Imarhiagbe, MBChB, FMCP, F. E. Odiase, MBBS, FMCP, O. C. A. Okoye, MBBS, FWACP,. Department of Medicine, University of Benin Teaching Hospital, Benin City, Nigeria.

Survival Analysis of Patients with End Stage Renal Disease

Science.gov (United States)

Urrutia, J. D.; Gayo, W. S.; Bautista, L. A.; Baccay, E. B.

2015-06-01

This paper provides a survival analysis of End Stage Renal Disease (ESRD) under Kaplan-Meier Estimates and Weibull Distribution. The data were obtained from the records of V. L. MakabaliMemorial Hospital with respect to time t (patient's age), covariates such as developed secondary disease (Pulmonary Congestion and Cardiovascular Disease), gender, and the event of interest: the death of ESRD patients. Survival and hazard rates were estimated using NCSS for Weibull Distribution and SPSS for Kaplan-Meier Estimates. These lead to the same conclusion that hazard rate increases and survival rate decreases of ESRD patient diagnosed with Pulmonary Congestion, Cardiovascular Disease and both diseases with respect to time. It also shows that female patients have a greater risk of death compared to males. The probability risk was given the equation R = 1 — e-H(t) where e-H(t) is the survival function, H(t) the cumulative hazard function which was created using Cox-Regression.

Intra-annual patterns in adult band-tailed pigeon survival estimates

Science.gov (United States)

Casazza, Michael L.; Coates, Peter S.; Overton, Cory T.; Howe, Kristy H.

2015-01-01

Context: The band-tailed pigeon (Patagioenas fasciata) is a migratory species occurring in western North America with low recruitment potential and populations that have declined an average of 2.4% per year since the 1960s. Investigations into band-tailed pigeon demographic rates date back to the early 1900s, and existing annual survival rate estimates were derived in the 1970s using band return data.

SURVIVAL ESTIMATES OF BYCATCH INDIVIDUALS DISCARDED FROM BIVALVE DREDGES

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Francisco Leitão

2014-12-01

Full Text Available The fate of released bycatch is an issue of great interest for fisheries research and management. Survival experiments were carried out to assess the survival capacity of animals damaged and discarded during clam dredging operations. Three common bycatch species, two fish (Trachinus vipera; Dicologlossa cuneata and one crab (Polybius henslowii, were collected during the sorting of catches from a commercial dredging boat. An arbitrary score scale was used to quantify the type and extent of damage to the organisms. Onboard, damaged individuals were placed in tanks containing seawater which were subsequently transferred to the laboratory. Survival experiments were conducted during the subsequent 48h. D. cuneata exhibited the lowest mortality after 48h (54%, followed by P. henslowii (65% and T. vipera (81%. Despite the magnitude of the percentage mortalities determined, the average number of individuals estimated to die during a 15 minutes tow (standard commercial fishing time was relatively small: 1.2, 3.24 and 11 for D. cuneata, T. vipera and P. henslowii, respectively. Nevertheless, when these figures are extrapolated to cover all the dredging fleet the impact of this practice on the populations of the species studied can be significant, particulary for D. cuneata.

marine survival ecosystem indicators - Estimating the ecosystem indicators of anadromous salmonids in the Puget Sound region

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The objective of this project is to develop a simple approach for estimating the marine survival and causes of trends in survival. Data is a summary of ecosystem...

SURVIVAL ANALYSIS AND LENGTH-BIASED SAMPLING

Directory of Open Access Journals (Sweden)

Masoud Asgharian

2010-12-01

Full Text Available When survival data are colleted as part of a prevalent cohort study, the recruited cases have already experienced their initiating event. These prevalent cases are then followed for a fixed period of time at the end of which the subjects will either have failed or have been censored. When interests lies in estimating the survival distribution, from onset, of subjects with the disease, one must take into account that the survival times of the cases in a prevalent cohort study are left truncated. When it is possible to assume that there has not been any epidemic of the disease over the past period of time that covers the onset times of the subjects, one may assume that the underlying incidence process that generates the initiating event times is a stationary Poisson process. Under such assumption, the survival times of the recruited subjects are called “lengthbiased”. I discuss the challenges one is faced with in analyzing these type of data. To address the theoretical aspects of the work, I present asymptotic results for the NPMLE of the length-biased as well as the unbiased survival distribution. I also discuss estimating the unbiased survival function using only the follow-up time. This addresses the case that the onset times are either unknown or known with uncertainty. Some of our most recent work and open questions will be presented. These include some aspects of analysis of covariates, strong approximation, functional LIL and density estimation under length-biased sampling with right censoring. The results will be illustrated with survival data from patients with dementia, collected as part of the Canadian Study of Health and Aging (CSHA.

[Estimations of maternal mortality using the sisterhood survival method: Latin American experience].

Science.gov (United States)

Wong, L R; Simons, H; Graham, W; Schkolnik, S

1990-08-01

The method of surviving sisters for indirectly estimating maternal mortality is still under development but shows promise for countries lacking alternative sources of data and good statistics. This work uses census or survey data to apply the method to rural villages in Gambia; Mapuche settlements in Cautin, Chile; marginal populations on the outskirts of Lima, Peru; and rural villages of Avaroa, Bolivia. The method is explained in detail following presentation of the results. The necessary basic information is outlined, and the particularities of its application to each Latin American case are discussed. The surviving sisters method was developed by Graham and Brass to derive indicators of maternal mortality based on the proportion of sisters who arrive at fertile age and die during pregnancy, delivery, or the postpartum period. The method transforms the proportions of sisters who died of maternal causes obtained from a census or survey into conventional probabilities of death. The basic information required concerns the numbers of sisters entering the reproductive period (excluding the respondent is she is a woman), the number surviving and decreased at the survey data, and the number who died during pregnancy, delivery, or the postpartum period. The probabilities of dying from a maternal cause were estimated on the basis of the sister survival method at 1/98 in Lima, 1/53 in Cautin, 1/17 in Gambia, and 1/10 in Bolivia. These probabilities correspond to ratios of maternal mortality per 100,000 live births of 286 in Lima, 414 in Cautin, 1005 in Gambia, and 1379 in Bolivia. The results demonstrate great variability in maternal mortality rates. In the cases of Lima and Cautin there were significant differences between estimates derived from the sister survival method and those derived from vital statistics. The 4 cases demonstrated the familiar association between maternal and infant mortality, fertility, and overall female mortality expressed in life expectancy at

Survival estimates for the passage of juvenile salmonids through Snake River dams and reservoirs, 1996. Annual report

International Nuclear Information System (INIS)

Smith, S.G.; Muir, W.D.; Hockersmith, E.E.; Achord, S.; Eppard, M.B.; Ruehle, T.E.; Williams, J.G.

1998-02-01

In 1996, the National Marine Fisheries Service and the University of Washington completed the fourth year of a multi-year study to estimate survival of juvenile salmonids (Oncorhynchus spp.) passing through dams and reservoirs on the Snake River. Actively migrating smolts were collected near the head of Lower Granite Reservoir and at Lower Granite Dam, tagged with passive integrated transponder (PIT) tags, and released to continue their downstream migration. Individual smolts were subsequently detected at PIT-tag detection facilities at Lower Granite, Little Goose, Lower Monumental, McNary, John Day and Bonneville Dams. Survival estimates were calculated using the Single-Release (SR) and Paired-Release (PR) Models. Timing of releases of tagged hatchery steelhead (O. mykiss) from the head of Lower Granite Reservoir and yearling chinook salmon (O. tshawytscha) from Lower Granite Dam in 1996 spanned the major portion of their juvenile migrations. Specific research objectives in 1996 were to (1) estimate reach and project survival in the Snake River using the Single-Release and Paired-Release Models throughout the yearling chinook salmon and steelhead migrations, (2) evaluate the performance of the survival-estimation models under prevailing operational and environmental conditions in the Snake River, and (3) synthesize results from the 4 years of the study to investigate relationships between survival probabilities, travel times, and environmental factors such as flow levels and water temperature

Survival Estimates for the Passage of Juvenile Salmonids through Snake River Dams and Reservoirs, 1996 Annual Report

Energy Technology Data Exchange (ETDEWEB)

Smith, Steven G.

1998-02-01

In 1996, the National Marine Fisheries Service and the University of Washington completed the fourth year of a multi-year study to estimate survival of juvenile salmonids (Oncorhynchus spp.) passing through dams and reservoirs on the Snake River. Actively migrating smolts were collected near the head of Lower Granite Reservoir and at Lower Granite Dam, tagged with passive integrated transponder (PIT) tags, and released to continue their downstream migration. Individual smolts were subsequently detected at PIT-tag detection facilities at Lower Granite, Little Goose, Lower Monumental, McNary, John Day and Bonneville Dams. Survival estimates were calculated using the Single-Release (SR) and Paired-Release (PR) Models. Timing of releases of tagged hatchery steelhead (O. mykiss) from the head of Lower Granite Reservoir and yearling chinook salmon (O. tshawytscha) from Lower Granite Dam in 1996 spanned the major portion of their juvenile migrations. Specific research objectives in 1996 were to (1) estimate reach and project survival in the Snake River using the Single-Release and Paired-Release Models throughout the yearling chinook salmon and steelhead migrations, (2) evaluate the performance of the survival-estimation models under prevailing operational and environmental conditions in the Snake River, and (3) synthesize results from the 4 years of the study to investigate relationships between survival probabilities, travel times, and environmental factors such as flow levels and water temperature.

Estimation of Inbreeding Coefficient and Its Effects on Lamb Survival in Sheep

Directory of Open Access Journals (Sweden)

mohammad almasi

2016-04-01

Full Text Available Introduction The mating of related individuals produces an inbred offspring and leads to an increased homozygosity in the progeny, genetic variance decrease within families and increase between families. The ration of homozygosity for individuals was calculated by inbreeding coefficient. Inbred individuals may carry two alleles at a locus that are replicated from one gene in the previous generations, called identical by descent. The inbreeding coefficient should be monitored in a breeding program, since it plays an important role at decreasing of homeostasis, performance, reproduction and viability. The trend of inbreeding is an indicator for determining of inbreeding level in the herd. Inbreeding affects both phenotypic means of traits and genetic variances within population, thus it is an important factor for delimitations of genetic progress in a population. Reports showed an inbreeding increase led to decrease of phenotypic value in some of the productive and reproductive traits. Materials and Methods In the current study, the pedigree data of 14030 and 6215 records of Baluchi and Iranblack lambs that collected from 1984 to 2011 at the Abbasabad Sheep Breeding Station in Mashhad, Iran, 3588 records of Makoei lambs that collected from 1994 to 2011 at the Makoei sheep breeding station and 6140, records of Zandi lambs that collected from 1991 to 2011 at the Khejir Sheep Breeding Station in Tehran, Iran were used to estimating the inbreeding coefficient and its effects on lamb survival in these breeds. Lamb survival trait was scored as 1 and 0 for lamb surviving and not surviving at weaning weight, respectively. Inbreeding coefficient was estimated by relationship matrix algorithm (A=TDT' methodology using the CFC software program. Effects of inbreeding coefficient on lamb survival were estimated by restricted maximum likelihood (REML method under 12 different animal models using ASReml 3.0 computer programme. Coefficient of inbreeding for each

Patient function, long-term survival, and use of surgery in patients with kidney cancer.

Science.gov (United States)

Tan, Hung-Jui; Chamie, Karim; Daskivich, Timothy J; Litwin, Mark S; Hu, Jim C

2016-12-15

Beyond age and comorbidity, functionality can shape the long-term survival potential of patients with cancer. Accordingly, herein the authors compared mortality and receipt of cancer-directed surgery according to patient function among older adults with kidney cancer. Using Surveillance, Epidemiology, and End Results (SEER)-Medicare data from 2000 through 2009, the authors studied 28,326 elderly subjects with primary kidney cancer. Patient function was quantified using function-related indicators, claims indicative of dysfunction and disability. Adjusting for patient and cancer characteristics, competing risk regression was used to assess the relationship between function-related indicator count and cause-specific mortality and then generalized estimating equations were used to quantify the probability of surgery. A total of 13,619 adult patients (48.1%) with at least 1 function-related indicator were identified. A higher indicator category was associated with older age, greater comorbidity, female sex, unmarried status, lower socioeconomic status, and higher stage of disease (Pkidney cancer mortality varied minimally with patient function. Patients with ≥ 2 indicators received cancer-directed surgery less often than those without disability (odds ratio, 0.61; 95% CI, 0.56-0.66), although treatment probabilities remained high for patients with locoregional disease and low for those with metastatic cancer. Among older adults with kidney cancer, functional health stands as a significant predictor of long-term survival. However, receipt of cancer-directed surgery appears largely determined by cancer stage. Patient function should be considered more heavily when determining treatment for older adults with kidney cancer. Cancer 2016;122:3776-3784. © 2016 American Cancer Society. © 2016 American Cancer Society.

Estimating the concordance probability in a survival analysis with a discrete number of risk groups.

Science.gov (United States)

Heller, Glenn; Mo, Qianxing

2016-04-01

A clinical risk classification system is an important component of a treatment decision algorithm. A measure used to assess the strength of a risk classification system is discrimination, and when the outcome is survival time, the most commonly applied global measure of discrimination is the concordance probability. The concordance probability represents the pairwise probability of lower patient risk given longer survival time. The c-index and the concordance probability estimate have been used to estimate the concordance probability when patient-specific risk scores are continuous. In the current paper, the concordance probability estimate and an inverse probability censoring weighted c-index are modified to account for discrete risk scores. Simulations are generated to assess the finite sample properties of the concordance probability estimate and the weighted c-index. An application of these measures of discriminatory power to a metastatic prostate cancer risk classification system is examined.

Relationships between mastitis and functional longevity in Danish Black and White dairy cattle estimated using survival analysis.

Science.gov (United States)

Neerhof, H J; Madsen, P; Ducrocq, V P; Vollema, A R; Jensen, J; Korsgaard, I R

2000-05-01

The relationship between mastitis and functional longevity was assessed with survival analysis on data of Danish Black and White dairy cows. Different methods of including the effect of mastitis treatment on the culling decision by a farmer in the model were compared. The model in which mastitis treatment was assumed to have an effect on functional longevity until the end of the lactation had the highest likelihood, and the model in which mastitis treatment had an effect for only a short period had the lowest likelihood. A cow with mastitis had 1.69 times greater risk of being culled than did a healthy herdmate with all other effects being the same. A model without mastitis treatment was used to predict transmitting abilities of bulls for risk of being culled, based on longevity records of their daughters, and was expressed in terms of risk of being culled. The correlation between the risk of being culled and the national evaluations of the bulls for mastitis resistance was approximately -0.4, indicating that resistance against mastitis was genetically correlated with a lower risk of being culled and, thus, a longer functional length of productive life.

Instrumental variables estimation of exposure effects on a time-to-event endpoint using structural cumulative survival models.

Science.gov (United States)

Martinussen, Torben; Vansteelandt, Stijn; Tchetgen Tchetgen, Eric J; Zucker, David M

2017-12-01

The use of instrumental variables for estimating the effect of an exposure on an outcome is popular in econometrics, and increasingly so in epidemiology. This increasing popularity may be attributed to the natural occurrence of instrumental variables in observational studies that incorporate elements of randomization, either by design or by nature (e.g., random inheritance of genes). Instrumental variables estimation of exposure effects is well established for continuous outcomes and to some extent for binary outcomes. It is, however, largely lacking for time-to-event outcomes because of complications due to censoring and survivorship bias. In this article, we make a novel proposal under a class of structural cumulative survival models which parameterize time-varying effects of a point exposure directly on the scale of the survival function; these models are essentially equivalent with a semi-parametric variant of the instrumental variables additive hazards model. We propose a class of recursive instrumental variable estimators for these exposure effects, and derive their large sample properties along with inferential tools. We examine the performance of the proposed method in simulation studies and illustrate it in a Mendelian randomization study to evaluate the effect of diabetes on mortality using data from the Health and Retirement Study. We further use the proposed method to investigate potential benefit from breast cancer screening on subsequent breast cancer mortality based on the HIP-study. © 2017, The International Biometric Society.

Cognitive function in families with exceptional survival

DEFF Research Database (Denmark)

Barral, Sandra; Cosentino, Stephanie; Costa, Rosann

2012-01-01

members in the offspring generation demonstrate significantly better performance on multiple tasks requiring attention, working memory, and semantic processing when compared with individuals without a family history of exceptional survival, suggesting that cognitive performance may serve as an important......The authors investigated whether cognitive function may be used as an endophenotype for longevity by assessing the cognitive performance of a family-based cohort consisting of 1380 individuals from 283 families recruited for exceptional survival in field centers in Boston, New York, Pittsburgh......, and Denmark. Cognitive performance was assessed in the combined offspring of the Long Life Family Study (LLFS) probands and their LLFS siblings as compared with their spouses' cognitive performance. Our results indicate that the combined offspring of the LLFS probands and their siblings achieve significantly...

Heterosis and heritability estimates for the survival of the Pacific white shrimp (Litopenaeus vannamei) under the commercial scale ponds

Institute of Scientific and Technical Information of China (English)

LU Xia; LUAN Sheng; CAO Baoxiang; SUI Juan; DAI Ping; MENG Xianhong; LUO Kun; KONG Jie

2017-01-01

The aim of the present study is to detect the potential of the base population from diallel crosses of eight introduced strains of the Pacific white shrimp (Litopenaeus vannamei) for improving the yield. Heterosis and heritability were estimated for pond survival at commercial farm conditions for the base population that included 207 full-sib families from a nested mating design by artificial insemination. Among all the hybrids, the heterosis ranged from–11.37%(UA1×UA2) to 20.53%(UA3×SIN) with an average of 0.953%. The results showed that more than half of the hybrids (51.85%) have negative heterosis for survival rate, but most of the hybrids with positive heterosis have high estimates. The high proportion of negative heterosis for survival rate reminders us that the survival trait also should be considered in the crossbreeding program to avoid yield decrease. However, high positive heterosis manifested in most of the hybrids for survival indicates the usefulness of these hybrids for improving the survival to obtain higher yield by crossbreeding in this breeding program. The heritability estimate for pond survival was 0.092±0.043 when genetic groups were included in the pedigree, and it was significantly different from zero (P<0.05). The results from this study also indicated that significant improvement for survival is possible through selection in L. vannamei.

Improving Survival and Promoting Respiratory Motor Function After Cervical Spinal Cord Injury

Science.gov (United States)

2017-09-01

AWARD NUMBER: W81XWH-15-1-0378 TITLE: Improving Survival and Promoting Respiratory Motor Function After Cervical Spinal Cord Injury PRINCIPAL...TITLE AND SUBTITLE CordCorInjury 5a. CONTRACT NUMBER Improvi g Survival and Promoting Respiratory Motor Function After Cervical Spinal Cord...care. However, despite these drastic interventions, the cervical injured patient is still susceptible to death due to respiratory complications

Plasmodium strain determines dendritic cell function essential for survival from malaria.

Directory of Open Access Journals (Sweden)

Michelle N Wykes

2007-07-01

Full Text Available The severity of malaria can range from asymptomatic to lethal infections involving severe anaemia and cerebral disease. However, the molecular and cellular factors responsible for these differences in disease severity are poorly understood. Identifying the factors that mediate virulence will contribute to developing antiparasitic immune responses. Since immunity is initiated by dendritic cells (DCs, we compared their phenotype and function following infection with either a nonlethal or lethal strain of the rodent parasite, Plasmodium yoelii, to identify their contribution to disease severity. DCs from nonlethal infections were fully functional and capable of secreting cytokines and stimulating T cells. In contrast, DCs from lethal infections were not functional. We then transferred DCs from mice with nonlethal infections to mice given lethal infections and showed that these DCs mediated control of parasitemia and survival. IL-12 was necessary for survival. To our knowledge, our studies have shown for the first time that during a malaria infection, DC function is essential for survival. More importantly, the functions of these DCs are determined by the strain of parasite. Our studies may explain, in part, why natural malaria infections may have different outcomes.

On Functional Calculus Estimates

NARCIS (Netherlands)

Schwenninger, F.L.

2015-01-01

This thesis presents various results within the field of operator theory that are formulated in estimates for functional calculi. Functional calculus is the general concept of defining operators of the form $f(A)$, where f is a function and $A$ is an operator, typically on a Banach space. Norm

Biochemical Control With Radiotherapy Improves Overall Survival in Intermediate and High-Risk Prostate Cancer Patients Who Have an Estimated 10-Year Overall Survival of >90%

International Nuclear Information System (INIS)

Herbert, Christopher; Liu, Mitchell; Tyldesley, Scott; Morris, W. James; Joffres, Michel; Khaira, Mandip; Kwan, Winkle; Moiseenko, Vitali; Pickles, Thomas

2012-01-01

Purpose: To identify subgroups of patients with carcinoma of the prostate treated with radical radiotherapy that have improved overall survival when disease is biochemically controlled. Methods and Materials: A cohort of 1,060 prostate cancer patients treated with radical radiotherapy was divided into nine subgroups based on National Comprehensive Cancer Network risk category and estimated 10-year overall survival (eOS 10y) derived from the age adjusted Charlson Comorbidity Index. Patients with and without biochemical control were compared with respect to overall survival. Actuarial estimates of overall survival were calculated using the Kaplan-Meier method. Univariate and multivariate Cox proportional hazards models were used for analysis of overall survival. Results: Median follow-up was 125 months (range, 51–176 months). Only the subgroups with high or intermediate risk disease and an eOS 10y of >90% had a statistically significantly improved overall survival when prostate cancer was biochemically controlled. In all other groups, biochemical control made no significant difference to overall survival. In the subgroup with high-risk disease and eOS 10y >90%, actuarial overall survival was 86.3% (95% confidence interval [CI] 78.5%–94.1%) and 62.1% (95% CI 52.9%–71.3%) for patients with biochemical control and biochemical relapse respectively (p = 0.002). In the intermediate risk group with eOS >90%, actuarial overall survival was 95.3% (95% CI 89.0%–100%) and 79.8% (95% CI 68.0%–91.6%) for biochemically controlled and biochemically relapsed patients (p = 0.033). On multivariate analysis, National Comprehensive Cancer Network risk group (p = 0.005), biochemical control (p = 0.033) and eOS 10y (p 90%.

Survival Estimates for the Passage of Juvenile Salmonids through Snake River Dams and Reservoirs, 1994 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Muir, William D.

1995-02-01

In 1994, the National Marine Fisheries Service and the University of Washington completed the second year of a multi-year study to estimate survival of juvenile salmonids (Oncorhynchus spp.) passing through the dams and reservoirs of the Snake River. Actively migrating smolts were collected at selected locations above, at, and below Lower Granite Dam, tagged with passive integrated transponder (PIT) tags, and released to continue their downstream migration. Survival estimates were calculated using the Single-Release, Modified Single-Release, and Paired-Release Models.

A unified survival theory of the functioning of the hypocretinergic system.

Science.gov (United States)

Chase, Michael H

2013-10-01

This article advances the theory that the hypocretinergic (orexinergic) system initiates, coordinates, and maintains survival behaviors and survival-related processes (i.e., the Unified Survival Theory of the Functioning of the Hypocretinergic System or "Unified Hypocretinergic Survival Theory"). A priori presumptive support for the Unified Hypocretinergic Survival Theory emanates from the fact that neurons that contain hypocretin are located in the key executive central nervous system (CNS) site, the lateral hypothalamus, that for decades has been well-documented to govern core survival behaviors such as fight, flight, and food consumption. In addition, the hypocretinergic system exhibits the requisite morphological and electrophysiological capabilities to control survival behaviors and related processes. Complementary behavioral data demonstrate that all facets of "survival" are coordinated by the hypocretinergic system and that hypocretinergic directives are not promulgated except during survival behaviors. Importantly, it has been shown that survival behaviors are selectively impacted when the hypocretinergic system is impaired or rendered nonfunctional, whereas other behaviors are relatively unaffected. The Unified Hypocretinergic Survival Theory resolves the disparate, perplexing, and often paradoxical-appearing results of previous studies; it also provides a foundation for future hypothesis-driven basic science and clinical explorations of the hypocretinergic system.

Survival probabilities of loggerhead sea turtles (Caretta caretta estimated from capture-mark-recapture data in the Mediterranean Sea

Directory of Open Access Journals (Sweden)

Paolo Casale

2007-06-01

Full Text Available Survival probabilities of loggerhead sea turtles (Caretta caretta are estimated for the first time in the Mediterranean by analysing 3254 tagging and 134 re-encounter data from this region. Most of these turtles were juveniles found at sea. Re-encounters were live resightings and dead recoveries and data were analysed with Barker’s model, a modified version of the Cormack-Jolly-Seber model which can combine recapture, live resighting and dead recovery data. An annual survival probability of 0.73 (CI 95% = 0.67-0.78; n=3254 was obtained, and should be considered as a conservative estimate due to an unknown, though not negligible, tag loss rate. This study makes a preliminary estimate of the survival probabilities of in-water developmental stages for the Mediterranean population of endangered loggerhead sea turtles and provides the first insights into the magnitude of the suspected human-induced mortality in the region. The model used here for the first time on sea turtles could be used to obtain survival estimates from other data sets with few or no true recaptures but with other types of re-encounter data, which are a common output of tagging programmes involving these wide-ranging animals.

Estimation of failure criteria in multivariate sensory shelf life testing using survival analysis.

Science.gov (United States)

Giménez, Ana; Gagliardi, Andrés; Ares, Gastón

2017-09-01

For most food products, shelf life is determined by changes in their sensory characteristics. A predetermined increase or decrease in the intensity of a sensory characteristic has frequently been used to signal that a product has reached the end of its shelf life. Considering all attributes change simultaneously, the concept of multivariate shelf life allows a single measurement of deterioration that takes into account all these sensory changes at a certain storage time. The aim of the present work was to apply survival analysis to estimate failure criteria in multivariate sensory shelf life testing using two case studies, hamburger buns and orange juice, by modelling the relationship between consumers' rejection of the product and the deterioration index estimated using PCA. In both studies, a panel of 13 trained assessors evaluated the samples using descriptive analysis whereas a panel of 100 consumers answered a "yes" or "no" question regarding intention to buy or consume the product. PC1 explained the great majority of the variance, indicating all sensory characteristics evolved similarly with storage time. Thus, PC1 could be regarded as index of sensory deterioration and a single failure criterion could be estimated through survival analysis for 25 and 50% consumers' rejection. The proposed approach based on multivariate shelf life testing may increase the accuracy of shelf life estimations. Copyright © 2017 Elsevier Ltd. All rights reserved.

A versatile test for equality of two survival functions based on weighted differences of Kaplan-Meier curves.

Science.gov (United States)

Uno, Hajime; Tian, Lu; Claggett, Brian; Wei, L J

2015-12-10

With censored event time observations, the logrank test is the most popular tool for testing the equality of two underlying survival distributions. Although this test is asymptotically distribution free, it may not be powerful when the proportional hazards assumption is violated. Various other novel testing procedures have been proposed, which generally are derived by assuming a class of specific alternative hypotheses with respect to the hazard functions. The test considered by Pepe and Fleming (1989) is based on a linear combination of weighted differences of the two Kaplan-Meier curves over time and is a natural tool to assess the difference of two survival functions directly. In this article, we take a similar approach but choose weights that are proportional to the observed standardized difference of the estimated survival curves at each time point. The new proposal automatically makes weighting adjustments empirically. The new test statistic is aimed at a one-sided general alternative hypothesis and is distributed with a short right tail under the null hypothesis but with a heavy tail under the alternative. The results from extensive numerical studies demonstrate that the new procedure performs well under various general alternatives with a caution of a minor inflation of the type I error rate when the sample size is small or the number of observed events is small. The survival data from a recent cancer comparative study are utilized for illustrating the implementation of the process. Copyright © 2015 John Wiley & Sons, Ltd.

The Application of Extended Cox Proportional Hazard Method for Estimating Survival Time of Breast Cancer

Science.gov (United States)

Husain, Hartina; Astuti Thamrin, Sri; Tahir, Sulaiha; Mukhlisin, Ahmad; Mirna Apriani, M.

2018-03-01

Breast cancer is one type of cancer that is the leading cause of death worldwide. This study aims to model the factors that affect the survival time and rate of cure of breast cancer patients. The extended cox model, which is a modification of the proportional hazard cox model in which the proportional hazard assumptions are not met, is used in this study. The maximum likelihood estimation approach is used to estimate the parameters of the model. This method is then applied to medical record data of breast cancer patient in 2011-2016, which is taken from Hasanuddin University Education Hospital. The results obtained indicate that the factors that affect the survival time of breast cancer patients are malignancy and leukocyte levels.

Estimation of Correlation Functions by Random Decrement

DEFF Research Database (Denmark)

Asmussen, J. C.; Brincker, Rune

This paper illustrates how correlation functions can be estimated by the random decrement technique. Several different formulations of the random decrement technique, estimating the correlation functions are considered. The speed and accuracy of the different formulations of the random decrement...... and the length of the correlation functions. The accuracy of the estimates with respect to the theoretical correlation functions and the modal parameters are both investigated. The modal parameters are extracted from the correlation functions using the polyreference time domain technique....

Survival Estimates for the Passage of Spring-Migrating Juvenile Salmonids through Snake and Columbia River Dams and Reservoirs, 2001-2002 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Zabel, Richard; Williams, John G.; Smith, Steven G. (Northwest and Alaska Fisheries Science Center, Fish Ecology Division, Seattle, WA)

2002-06-01

In 2001, the National Marine Fisheries Service and the University of Washington completed the ninth year of a study to estimate survival and travel time of juvenile salmonids (Oncorhynchus spp.) passing through dams and reservoirs on the Snake and Columbia Rivers. All estimates were derived from passive integrated transponder (PIT)-tagged fish. We PIT tagged and released at Lower Granite Dam a total of 17,028 hatchery and 3,550 wild steelhead. In addition, we utilized fish PIT tagged by other agencies at traps and hatcheries upstream of the hydropower system and sites within the hydropower system. PIT-tagged smolts were detected at interrogation facilities at Lower Granite, Little Goose, Lower Monumental, McNary, John Day, and Bonneville Dams and in the PIT-tag detector trawl operated in the Columbia River estuary. Survival estimates were calculated using the Single-Release Model. Primary research objectives in 2001 were to: (1) estimate reach and project survival and travel time in the Snake and Columbia Rivers throughout the yearling chinook salmon and steelhead migrations; (2) evaluate relationships between survival estimates and migration conditions; and (3) evaluate the survival-estimation models under prevailing conditions. This report provides reach survival and travel time estimates for 2001 for PIT-tagged yearling chinook salmon and steelhead (hatchery and wild) in the Snake and Columbia Rivers. Results are reported primarily in the form of tables and figures with a minimum of text. More details on methodology and statistical models used are provided in previous reports cited in the text. Results for summer-migrating chinook salmon will be reported separately.

Predicting survival in oldest old people

NARCIS (Netherlands)

Taekema, Diana G.; Gussekloo, J.; Westendorp, Rudi G J; De Craen, Anton J M; Maier, Andrea B.

2012-01-01

Objective: Measures of physical performance are regarded as useful objective clinical tools to estimate survival in elderly people. However, oldest old people, aged 85 years or more, are underrepresented in earlier studies and frequently unable to perform functional tests. We studied the association

Factors predictive of survival and estimated years of life lost in the decade following nontraumatic and traumatic spinal cord injury.

Science.gov (United States)

Hatch, B B; Wood-Wentz, C M; Therneau, T M; Walker, M G; Payne, J M; Reeves, R K

2017-06-01

Retrospective chart review. To identify factors predictive of survival after spinal cord injury (SCI). Tertiary care institution. Multiple-variable Cox proportional hazards regression analysis for 759 patients with SCI (535 nontraumatic and 221 traumatic) included age, sex, completeness of injury, level of injury, functional independence measure (FIM) scores, rehabilitation length of stay and SCI cause. Estimated years of life lost in the decade after injury was calculated for patients vs uninjured controls. Median follow-up was 11.4 years. Population characteristics included paraplegia, 58%; complete injury, 11%; male sex, 64%; and median rehabilitation length of stay, 16 days. Factors independently predictive of decreased survival were increased age (+10 years; hazard ratio (HR (95% CI)), 1.6 (1.4-1.7)), male sex (1.3 (1.0-1.6)), lower dismissal FIM score (-10 points; 1.3 (1.2-1.3)) and all nontraumatic causes. Metastatic cancer had the largest decrease in survival (HR (95% CI), 13.3 (8.7-20.2)). Primary tumors (HR (95% CI), 2.5 (1.7-3.8)), vascular (2.5 (1.6-3.8)), musculoskeletal/stenosis (1.7 (1.2-2.5)) and other nontraumatic SCI (2.3 (1.5-3.6)) were associated with decreased survival. Ten-year survival was decreased in nontraumatic SCI (mean (s.d.), 1.8 (0.3) years lost), with largest decreases in survival for metastatic cancer and spinal cord ischemia. Age, male sex and lower dismissal FIM score were associated with decreased survival, but neither injury severity nor level was associated with it. Survival after SCI varies depending on SCI cause, with survival better after traumatic SCI than after nontraumatic SCI. Metastatic cancer and vascular ischemia were associated with the greatest survival reduction.

First Direct Evidence for Natal Wintering Ground Fidelity and Estimate of Juvenile Survival in the New Zealand Southern Right Whale Eubalaena australis.

Science.gov (United States)

Carroll, E L; Fewster, R M; Childerhouse, S J; Patenaude, N J; Boren, L; Baker, C S

2016-01-01

Juvenile survival and recruitment can be more sensitive to environmental, ecological and anthropogenic factors than adult survival, influencing population-level processes like recruitment and growth rate in long-lived, iteroparous species such as southern right whales. Conventionally, Southern right whales are individually identified using callosity patterns, which do not stabilise until 6-12 months, by which time the whale has left its natal wintering grounds. Here we use DNA profiling of skin biopsy samples to identify individual Southern right whales from year of birth and document their return to the species' primary wintering ground in New Zealand waters, the Subantarctic Auckland Islands. We find evidence of natal fidelity to the New Zealand wintering ground by the recapture of 15 of 57 whales, first sampled in year of birth and available for subsequent recapture, during winter surveys to the Auckland Islands in 1995-1998 and 2006-2009. Four individuals were recaptured at the ages of 9 to 11, including two females first sampled as calves in 1998 and subsequently resampled as cows with calves in 2007. Using these capture-recapture records of known-age individuals, we estimate changes in survival with age using Cormack-Jolly-Seber models. Survival is modelled using discrete age classes and as a continuous function of age. Using a bootstrap method to account for uncertainty in model selection and fitting, we provide the first direct estimate of juvenile survival for this population. Our analyses indicate a high annual apparent survival for juveniles at between 0.87 (standard error (SE) 0.17, to age 1) and 0.95 (SE 0.05: ages 2-8). Individual identification by DNA profiling is an effective method for long-term demographic and genetic monitoring, particularly in animals that change identifiable features as they develop or experience tag loss over time.

Long-term survival and function after suspected gram-negative sepsis.

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Perl, T M; Dvorak, L; Hwang, T; Wenzel, R P

1995-07-26

To determine the long-term (> 3 months) survival of septic patients, to develop mathematical models that predict patients likely to survive long-term, and to measure the health and functional status of surviving patients. A large tertiary care university hospital and an associated Veterans Affairs Medical Center. From December 1986 to December 1990, a total of 103 patients with suspected gram-negative sepsis entered a double-blind, placebo-controlled efficacy trial of monoclonal antiendotoxin antibody. Of these, we followed up 100 patients for 7667 patient-months. Beginning in May 1992, we reviewed hospital records and contacted all known survivors. We measured the health status of all surviving patients. The determinants of long-term survival (up to 6 years) were identified through two Cox proportional hazard regression models: one that included patient characteristics identified at the time of sepsis (bedside model) and another that included bedside, infection-related, and treatment characteristics (overall model). Of the 60 patients in the cohort who died at a median interval of 30.5 days after sepsis, 32 died within the first month of the septic episode, seven died within 3 months, and four more died within 6 months. In the bedside multivariate model constructed to predict long-term survival, large hazard ratios (HRs) were associated with severity of underlying illness as classified by McCabe and Jackson criteria (for rapidly fatal disease, HR = 30.4, P respiratory distress syndrome (HR = 2.3; P = .02) predicted patients most likely to die. The Acute Physiology and Chronic Health Evaluation II score was not a significant predictor of outcome when either model included the simpler McCabe and Jackson classification of underlying disease severity. We compared the health status scores with norms for the general population and found that patients with resolved sepsis reported more physical dysfunction (P bedridden), suggesting that the patients' physical function

Survival Function Analysis of Planet Size Distribution

OpenAIRE

Zeng, Li; Jacobsen, Stein B.; Sasselov, Dimitar D.; Vanderburg, Andrew

2018-01-01

Applying the survival function analysis to the planet radius distribution of the Kepler exoplanet candidates, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 Earth radii separates small exoplanets from large exoplanets above. When combined with the recently-discovered radius gap at 2 Earth radii, it supports the treatment of planets 2-4 Earth rad...

Estimating Function Approaches for Spatial Point Processes

Science.gov (United States)

Deng, Chong

Spatial point pattern data consist of locations of events that are often of interest in biological and ecological studies. Such data are commonly viewed as a realization from a stochastic process called spatial point process. To fit a parametric spatial point process model to such data, likelihood-based methods have been widely studied. However, while maximum likelihood estimation is often too computationally intensive for Cox and cluster processes, pairwise likelihood methods such as composite likelihood, Palm likelihood usually suffer from the loss of information due to the ignorance of correlation among pairs. For many types of correlated data other than spatial point processes, when likelihood-based approaches are not desirable, estimating functions have been widely used for model fitting. In this dissertation, we explore the estimating function approaches for fitting spatial point process models. These approaches, which are based on the asymptotic optimal estimating function theories, can be used to incorporate the correlation among data and yield more efficient estimators. We conducted a series of studies to demonstrate that these estmating function approaches are good alternatives to balance the trade-off between computation complexity and estimating efficiency. First, we propose a new estimating procedure that improves the efficiency of pairwise composite likelihood method in estimating clustering parameters. Our approach combines estimating functions derived from pairwise composite likeli-hood estimation and estimating functions that account for correlations among the pairwise contributions. Our method can be used to fit a variety of parametric spatial point process models and can yield more efficient estimators for the clustering parameters than pairwise composite likelihood estimation. We demonstrate its efficacy through a simulation study and an application to the longleaf pine data. Second, we further explore the quasi-likelihood approach on fitting

Rethinking plant functional types in Earth System Models: pan-tropical analysis of tree survival across environmental gradients

Science.gov (United States)

Johnson, D. J.; Needham, J.; Xu, C.; Davies, S. J.; Bunyavejchewin, S.; Giardina, C. P.; Condit, R.; Cordell, S.; Litton, C. M.; Hubbell, S.; Kassim, A. R. B.; Shawn, L. K. Y.; Nasardin, M. B.; Ong, P.; Ostertag, R.; Sack, L.; Tan, S. K. S.; Yap, S.; McDowell, N. G.; McMahon, S.

2016-12-01

Terrestrial carbon cycling is a function of the growth and survival of trees. Current model representations of tree growth and survival at a global scale rely on coarse plant functional traits that are parameterized very generally. In view of the large biodiversity in the tropical forests, it is important that we account for the functional diversity in order to better predict tropical forest responses to future climate changes. Several next generation Earth System Models are moving towards a size-structured, trait-based approach to modelling vegetation globally, but the challenge of which and how many traits are necessary to capture forest complexity remains. Additionally, the challenge of collecting sufficient trait data to describe the vast species richness of tropical forests is enormous. We propose a more fundamental approach to these problems by characterizing forests by their patterns of survival. We expect our approach to distill real-world tree survival into a reasonable number of functional types. Using 10 large-area tropical forest plots that span geographic, edaphic and climatic gradients, we model tree survival as a function of tree size for hundreds of species. We found surprisingly few categories of size-survival functions emerge. This indicates some fundamental strategies at play across diverse forests to constrain the range of possible size-survival functions. Initial cluster analysis indicates that four to eight functional forms are necessary to describe variation in size-survival relations. Temporal variation in size-survival functions can be related to local environmental variation, allowing us to parameterize how demographically similar groups of species respond to perturbations in the ecosystem. We believe this methodology will yield a synthetic approach to classifying forest systems that will greatly reduce uncertainty and complexity in global vegetation models.

Best lung function equations for the very elderly selected by survival analysis

DEFF Research Database (Denmark)

Miller, Martin R; Thinggaard, Mikael; Christensen, Kaare

2014-01-01

We evaluated which equations best predicted the lung function of a cohort of nonagenarians based on which best accounted for subsequent survival.In 1998, we measured lung function, grip strength and dementia score (Mini Mental State Examination (MMSE)) in a population-based sample of 2262 Danes...... with a hazard ratio for death of 1, 1.16, 1.32 and 1.60 respectively, compared with equations derived with the inclusion of elderly subjects.We conclude that extrapolating from NHANES III equations to predict lung function in nonagenarians gave better survival predictions from spirometry than when employing...... equations derived using very elderly subjects with possible selection bias. These findings can help inform how future lung function equations for the elderly are derived....

Genetic parameters and factors influencing survival to 24 hrs after birth in Danish meat sheep breeds

DEFF Research Database (Denmark)

Maxa, J; Sharifi, A R; Pedersen, J

2009-01-01

In this study, influential factors and (co)variance components for survival to 24 h after birth were determined and estimated for Texel, Shropshire, and Oxford Down, the most common sheep breeds in Denmark. Data from 1992 to 2006 containing 138,813 survival records were extracted from the sheep...... recording database at the Danish Agricultural Advisory Service. Estimation of (co)variance components was carried out using univariate animal models, applying logistic link functions. The logistic functions were also used for estimation of fixed effects. Both direct and maternal additive genetic effects......, as well as common litter effects, were included in the models. The mean survival to 24 h after birth was 92.5, 91.7, and 88.5% for Texel, Shropshire, and Oxford Down, respectively. There was a curvilinear relationship between survival to 24 h after birth and birth weight, with survival less for light...

Estimation of Unemployment Duration in Botoşani County Using Survival Analysis

Directory of Open Access Journals (Sweden)

Darabă Gabriel

2017-01-01

Full Text Available In this paper we aim at estimating the unemployment duration in Botosani County in order tostudy the impact of individual characteristics (gender, age, place of residence, unemploymentbenefit, etc. on the length of unemployment spells. We use Cox regression model to measure theeffects of gender, age, residential environment, etc. on the hazard rate of leaving unemploymentandKaplan-Meier estimator to compare survival probabilities among different categories ofunemployed persons. The study is carried out on a sample of 200 unemployment spellsregisteredwith the Employment Agency of Botoşani County from January 2012 to December 2015. Theresults reveal that place of residence, unemployment benefit and unemployed category have asignificant impact on unemployment spells.

Association of High-Dose Ibuprofen Use, Lung Function Decline, and Long-Term Survival in Children with Cystic Fibrosis.

Science.gov (United States)

Konstan, Michael W; VanDevanter, Donald R; Sawicki, Gregory S; Pasta, David J; Foreman, Aimee J; Neiman, Evgueni A; Morgan, Wayne J

2018-04-01

Cystic fibrosis deaths result primarily from lung function loss, so chronic respiratory therapies, intended to preserve lung function, are cornerstones of cystic fibrosis care. Although treatment-associated reduction in rate of lung function loss should ultimately improve cystic fibrosis survival, no such relationship has been described for any chronic cystic fibrosis therapy. In part, this is because the ages of most rapid lung function decline-early adolescence-precede the median age of cystic fibrosis deaths by more than a decade. To study associations of high-dose ibuprofen treatment with the rate of forced expiratory volume in 1 second decline and mortality among children followed in the Epidemiologic Study of Cystic Fibrosis and subsequently in the U.S. Cystic Fibrosis Foundation Patient Registry. We performed a matched cohort study using data from Epidemiologic Study of Cystic Fibrosis. Exposure was defined as high-dose ibuprofen use reported at ≥80% of encounters over 2 years. Unexposed children were matched to exposed children 5:1 using propensity scores on the basis of demographic, clinical, and treatment covariates. The rate of decline of percent predicted forced expiratory volume in 1 second during the 2-year follow-up period was estimated by mixed-effects modeling with random slopes and intercepts. Survival over 16 follow-up years in the U.S. Cystic Fibrosis Foundation Patient Registry was compared between treatment groups by using proportional hazards modeling controlling for matching and covariates. We included 775 high-dose ibuprofen users and 3,665 nonusers who were well matched on demographic, clinical, and treatment variables. High-dose ibuprofen users declined on average 1.10 percent predicted forced expiratory volume in 1 second/yr (95% confidence interval; 0.51, 1.69) during the 2-year treatment period, whereas nonusers declined at a rate of 1.76% percent predicted forced expiratory volume in 1 second/yr (95% confidence interval; 1.48, 2

Shifting paradigms in the estimation of survival for castration-resistant prostate cancer: A tertiary academic center experience.

Science.gov (United States)

Afshar, Mehran; Evison, Felicity; James, Nicholas D; Patel, Prashant

2015-08-01

Castration-resistant prostate cancer (CRPC) has retained a guarded prognosis, with historical survival estimates of 18 to 24 months. However, the landscape of available therapy has changed, and the emphasis has altered from supportive to active treatment. Few large series from real-world populations exist in the contemporary era with fully mature survival data to confirm the indication based on clinical trials that patients with CRPC are surviving far longer than the historical estimates. We aim to review a large patient cohort with CRPC and provide mature survival data. Using the electronic histopathology database at Queen Elizabeth Hospital, Birmingham, UK, all prostate-specific antigentest results between April 2006 and September 2007 were extracted, and patients satisfying the American Society for Radiation Oncology (ASTRO) definition of hormone failure were identified. Electronic records were reviewed and variables were collected, including survival, treatment, biochemistry, histopathology, and demographics. Probability of survival, and of developing metastasis or CRPC, was determined using the Kaplan-Meier method. Patients were stratified into 3 groups, namely, D0--no metastasis at diagnosis but later appearance, D1--no metastasis at diagnosis or at last follow-up, and D2--metastasis at diagnosis. From 8,062 patient-prostate-specific antigen episodes, we identified 447 patients meeting the criteria. A notes review revealed 147 patients with CRPC. Median overall survival (OS) from diagnosis was 84.7 months (95% CI: 73-89), and 129 deaths had occurred (88%). Median OS from diagnosis for D0, D1, and D2 patients was 100.4, 180.1, and 58.9 months, respectively (Pdata benefit clinicians and patients in understanding prognosis and treatment choices. Importantly, our patients were diagnosed before the current wave of novel therapeutics for CRPC, so survival for men diagnosed today may be more than our findings. Copyright © 2015 Elsevier Inc. All rights reserved.

A nonparametric approach to medical survival data: Uncertainty in the context of risk in mortality analysis

International Nuclear Information System (INIS)

Janurová, Kateřina; Briš, Radim

2014-01-01

Medical survival right-censored data of about 850 patients are evaluated to analyze the uncertainty related to the risk of mortality on one hand and compare two basic surgery techniques in the context of risk of mortality on the other hand. Colorectal data come from patients who underwent colectomy in the University Hospital of Ostrava. Two basic surgery operating techniques are used for the colectomy: either traditional (open) or minimally invasive (laparoscopic). Basic question arising at the colectomy operation is, which type of operation to choose to guarantee longer overall survival time. Two non-parametric approaches have been used to quantify probability of mortality with uncertainties. In fact, complement of the probability to one, i.e. survival function with corresponding confidence levels is calculated and evaluated. First approach considers standard nonparametric estimators resulting from both the Kaplan–Meier estimator of survival function in connection with Greenwood's formula and the Nelson–Aalen estimator of cumulative hazard function including confidence interval for survival function as well. The second innovative approach, represented by Nonparametric Predictive Inference (NPI), uses lower and upper probabilities for quantifying uncertainty and provides a model of predictive survival function instead of the population survival function. The traditional log-rank test on one hand and the nonparametric predictive comparison of two groups of lifetime data on the other hand have been compared to evaluate risk of mortality in the context of mentioned surgery techniques. The size of the difference between two groups of lifetime data has been considered and analyzed as well. Both nonparametric approaches led to the same conclusion, that the minimally invasive operating technique guarantees the patient significantly longer survival time in comparison with the traditional operating technique

Estimating state-contingent production functions

DEFF Research Database (Denmark)

Rasmussen, Svend; Karantininis, Kostas

The paper reviews the empirical problem of estimating state-contingent production functions. The major problem is that states of nature may not be registered and/or that the number of observation per state is low. Monte Carlo simulation is used to generate an artificial, uncertain production...... environment based on Cobb Douglas production functions with state-contingent parameters. The pa-rameters are subsequently estimated based on different sizes of samples using Generalized Least Squares and Generalized Maximum Entropy and the results are compared. It is concluded that Maximum Entropy may...

Up-to-date and projected estimates of survival for people with cystic fibrosis using baseline characteristics: A longitudinal study using UK patient registry data.

Science.gov (United States)

Keogh, Ruth H; Szczesniak, Rhonda; Taylor-Robinson, David; Bilton, Diana

2018-03-01

Cystic fibrosis (CF) is the most common inherited disease in Caucasians, affecting around 10,000 individuals in the UK today. Prognosis has improved considerably over recent decades with ongoing improvements in treatment and care. Providing up-to-date survival predictions is important for patients, clinicians and health services planning. Flexible parametric survival modelling of UK CF Registry data from 2011 to 2015, capturing 602 deaths in 10,428 individuals. Survival curves were estimated from birth; conditional on reaching older ages; and projected under different assumptions concerning future mortality trends, using baseline characteristics of sex, CFTR genotype (zero, one, two copies of F508del) and age at diagnosis. Male sex was associated with better survival, as was older age at diagnosis, but only in F508del non-homozygotes. Survival did not differ by genotype among individuals diagnosed at birth. Median survival ages at birth in F508del homozygotes were 46years (males) and 41years (females), and similar in non-homozygotes diagnosed at birth. F508del heterozygotes diagnosed aged 5 had median survival ages of 57 (males) and 51 (females). Conditional on survival to 30, median survival age rises to 52 (males) and 49 (females) in homozygotes. Mortality rates decreased annually by 2% during 2006-2015. Future improvements at this rate suggest median survival ages for F508del homozygous babies of 65 (males) and 56 (females). Over half of babies born today, and of individuals aged 30 and above today, can expect to survive into at least their fifth decade. Evidence before this study We searched PubMed with terms "(cystic fibrosis survival) and (projection OR model OR registry OR United Kingdom OR UK)" to identify relevant studies on survival estimates for individuals with cystic fibrosis (CF). We also considered the most recent annual report from the UK Cystic Fibrosis Registry (Cystic Fibrosis Trust, 2016), a review by Buzzetti and colleagues (2009), the chapter

A NEW METHOD FOR PREDICTING SURVIVAL AND ESTIMATING UNCERTAINTY IN TRAUMA PATIENTS

Directory of Open Access Journals (Sweden)

V. G. Schetinin

2017-01-01

Full Text Available The Trauma and Injury Severity Score (TRISS is the current “gold” standard of screening patient’s condition for purposes of predicting survival probability. More than 40 years of TRISS practice revealed a number of problems, particularly, 1 unexplained fluctuation of predicted values caused by aggregation of screening tests, and 2 low accuracy of uncertainty intervals estimations. We developed a new method made it available for practitioners as a web calculator to reduce negative effect of factors given above. The method involves Bayesian methodology of statistical inference which, being computationally expensive, in theory provides most accurate predictions. We implemented and tested this approach on a data set including 571,148 patients registered in the US National Trauma Data Bank (NTDB with 1–20 injuries. These patients were distributed over the following categories: (1 174,647 with 1 injury, (2 381,137 with 2–10 injuries, and (3 15,364 with 11–20 injuries. Survival rates in each category were 0.977, 0.953, and 0.831, respectively. The proposed method has improved prediction accuracy by 0.04%, 0.36%, and 3.64% (p-value <0.05 in the categories 1, 2, and 3, respectively. Hosmer-Lemeshow statistics showed a significant improvement of the new model calibration. The uncertainty 2σ intervals were reduced from 0.628 to 0.569 for patients of the second category and from 1.227 to 0.930 for patients of the third category, both with p-value <0.005. The new method shows the statistically significant improvement (p-value <0.05 in accuracy of predicting survival and estimating the uncertainty intervals. The largest improvement has been achieved for patients with 11–20 injuries. The method is available for practitioners as a web calculator http://www.traumacalc.org.

A new algorithm for finding survival coefficients employed in reliability equations

Science.gov (United States)

Bouricius, W. G.; Flehinger, B. J.

1973-01-01

Product reliabilities are predicted from past failure rates and reasonable estimate of future failure rates. Algorithm is used to calculate probability that product will function correctly. Algorithm sums the probabilities of each survival pattern and number of permutations for that pattern, over all possible ways in which product can survive.

Non-Parametric Estimation of Correlation Functions

DEFF Research Database (Denmark)

Brincker, Rune; Rytter, Anders; Krenk, Steen

In this paper three methods of non-parametric correlation function estimation are reviewed and evaluated: the direct method, estimation by the Fast Fourier Transform and finally estimation by the Random Decrement technique. The basic ideas of the techniques are reviewed, sources of bias are point...

Survival analysis approach to account for non-exponential decay rate effects in lifetime experiments

International Nuclear Information System (INIS)

Coakley, K.J.; Dewey, M.S.; Huber, M.G.; Huffer, C.R.; Huffman, P.R.; Marley, D.E.; Mumm, H.P.; O'Shaughnessy, C.M.; Schelhammer, K.W.; Thompson, A.K.; Yue, A.T.

2016-01-01

In experiments that measure the lifetime of trapped particles, in addition to loss mechanisms with exponential survival probability functions, particles can be lost by mechanisms with non-exponential survival probability functions. Failure to account for such loss mechanisms produces systematic measurement error and associated systematic uncertainties in these measurements. In this work, we develop a general competing risks survival analysis method to account for the joint effect of loss mechanisms with either exponential or non-exponential survival probability functions, and a method to quantify the size of systematic effects and associated uncertainties for lifetime estimates. As a case study, we apply our survival analysis formalism and method to the Ultra Cold Neutron lifetime experiment at NIST. In this experiment, neutrons can escape a magnetic trap before they decay due to a wall loss mechanism with an associated non-exponential survival probability function.

Survival analysis approach to account for non-exponential decay rate effects in lifetime experiments

Energy Technology Data Exchange (ETDEWEB)

Coakley, K.J., E-mail: kevincoakley@nist.gov [National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305 (United States); Dewey, M.S.; Huber, M.G. [National Institute of Standards and Technology, 100 Bureau Drive, Stop 8461, Gaithersburg, MD 20899 (United States); Huffer, C.R.; Huffman, P.R. [North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Triangle Universities Nuclear Laboratory, 116 Science Drive, Box 90308, Durham, NC 27708 (United States); Marley, D.E. [National Institute of Standards and Technology, 100 Bureau Drive, Stop 8461, Gaithersburg, MD 20899 (United States); North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Mumm, H.P. [National Institute of Standards and Technology, 100 Bureau Drive, Stop 8461, Gaithersburg, MD 20899 (United States); O' Shaughnessy, C.M. [University of North Carolina at Chapel Hill, 120 E. Cameron Ave., CB #3255, Chapel Hill, NC 27599 (United States); Triangle Universities Nuclear Laboratory, 116 Science Drive, Box 90308, Durham, NC 27708 (United States); Schelhammer, K.W. [North Carolina State University, 2401 Stinson Drive, Box 8202, Raleigh, NC 27695 (United States); Triangle Universities Nuclear Laboratory, 116 Science Drive, Box 90308, Durham, NC 27708 (United States); Thompson, A.K.; Yue, A.T. [National Institute of Standards and Technology, 100 Bureau Drive, Stop 8461, Gaithersburg, MD 20899 (United States)

2016-03-21

In experiments that measure the lifetime of trapped particles, in addition to loss mechanisms with exponential survival probability functions, particles can be lost by mechanisms with non-exponential survival probability functions. Failure to account for such loss mechanisms produces systematic measurement error and associated systematic uncertainties in these measurements. In this work, we develop a general competing risks survival analysis method to account for the joint effect of loss mechanisms with either exponential or non-exponential survival probability functions, and a method to quantify the size of systematic effects and associated uncertainties for lifetime estimates. As a case study, we apply our survival analysis formalism and method to the Ultra Cold Neutron lifetime experiment at NIST. In this experiment, neutrons can escape a magnetic trap before they decay due to a wall loss mechanism with an associated non-exponential survival probability function.

Predicting functional decline and survival in amyotrophic lateral sclerosis.

Science.gov (United States)

Ong, Mei-Lyn; Tan, Pei Fang; Holbrook, Joanna D

2017-01-01

Better predictors of amyotrophic lateral sclerosis disease course could enable smaller and more targeted clinical trials. Partially to address this aim, the Prize for Life foundation collected de-identified records from amyotrophic lateral sclerosis sufferers who participated in clinical trials of investigational drugs and made them available to researchers in the PRO-ACT database. In this study, time series data from PRO-ACT subjects were fitted to exponential models. Binary classes for decline in the total score of amyotrophic lateral sclerosis functional rating scale revised (ALSFRS-R) (fast/slow progression) and survival (high/low death risk) were derived. Data was segregated into training and test sets via cross validation. Learning algorithms were applied to the demographic, clinical and laboratory parameters in the training set to predict ALSFRS-R decline and the derived fast/slow progression and high/low death risk categories. The performance of predictive models was assessed by cross-validation in the test set using Receiver Operator Curves and root mean squared errors. A model created using a boosting algorithm containing the decline in four parameters (weight, alkaline phosphatase, albumin and creatine kinase) post baseline, was able to predict functional decline class (fast or slow) with fair accuracy (AUC = 0.82). However similar approaches to build a predictive model for decline class by baseline subject characteristics were not successful. In contrast, baseline values of total bilirubin, gamma glutamyltransferase, urine specific gravity and ALSFRS-R item score-climbing stairs were sufficient to predict survival class. Using combinations of small numbers of variables it was possible to predict classes of functional decline and survival across the 1-2 year timeframe available in PRO-ACT. These findings may have utility for design of future ALS clinical trials.

Survival analysis with functional covariates for partial follow-up studies.

Science.gov (United States)

Fang, Hong-Bin; Wu, Tong Tong; Rapoport, Aaron P; Tan, Ming

2016-12-01

Predictive or prognostic analysis plays an increasingly important role in the era of personalized medicine to identify subsets of patients whom the treatment may benefit the most. Although various time-dependent covariate models are available, such models require that covariates be followed in the whole follow-up period. This article studies a new class of functional survival models where the covariates are only monitored in a time interval that is shorter than the whole follow-up period. This paper is motivated by the analysis of a longitudinal study on advanced myeloma patients who received stem cell transplants and T cell infusions after the transplants. The absolute lymphocyte cell counts were collected serially during hospitalization. Those patients are still followed up if they are alive after hospitalization, while their absolute lymphocyte cell counts cannot be measured after that. Another complication is that absolute lymphocyte cell counts are sparsely and irregularly measured. The conventional method using Cox model with time-varying covariates is not applicable because of the different lengths of observation periods. Analysis based on each single observation obviously underutilizes available information and, more seriously, may yield misleading results. This so-called partial follow-up study design represents increasingly common predictive modeling problem where we have serial multiple biomarkers up to a certain time point, which is shorter than the total length of follow-up. We therefore propose a solution to the partial follow-up design. The new method combines functional principal components analysis and survival analysis with selection of those functional covariates. It also has the advantage of handling sparse and irregularly measured longitudinal observations of covariates and measurement errors. Our analysis based on functional principal components reveals that it is the patterns of the trajectories of absolute lymphocyte cell counts, instead of

Estimating Stochastic Volatility Models using Prediction-based Estimating Functions

DEFF Research Database (Denmark)

Lunde, Asger; Brix, Anne Floor

to the performance of the GMM estimator based on conditional moments of integrated volatility from Bollerslev and Zhou (2002). The case where the observed log-price process is contaminated by i.i.d. market microstructure (MMS) noise is also investigated. First, the impact of MMS noise on the parameter estimates from......In this paper prediction-based estimating functions (PBEFs), introduced in Sørensen (2000), are reviewed and PBEFs for the Heston (1993) stochastic volatility model are derived. The finite sample performance of the PBEF based estimator is investigated in a Monte Carlo study, and compared...... to correctly account for the noise are investigated. Our Monte Carlo study shows that the estimator based on PBEFs outperforms the GMM estimator, both in the setting with and without MMS noise. Finally, an empirical application investigates the possible challenges and general performance of applying the PBEF...

The effect of clinical performance on the survival estimates of direct restorations

Directory of Open Access Journals (Sweden)

Kyou-Li Kim

2013-02-01

Full Text Available Objectives In most retrospective studies, the clinical performance of restorations had not been considered in survival analysis. This study investigated the effect of including the clinically unacceptable cases according to modified United States Public Health Service (USPHS criteria into the failed data on the survival analysis of direct restorations as to the longevity and prognostic variables. Materials and Methods Nine hundred and sixty-seven direct restorations were evaluated. The data of 204 retreated restorations were collected from the records, and clinical performance of 763 restorations in function was evaluated according to modified USPHS criteria by two observers. The longevity and prognostic variables of the restorations were compared with a factor of involving clinically unacceptable cases into the failures using Kaplan-Meier survival analysis and Cox proportional hazard model. Results The median survival times of amalgam, composite resin and glass ionomer were 11.8, 11.0 and 6.8 years, respectively. Glass ionomer showed significantly lower longevity than composite resin and amalgam. When clinically unacceptable restorations were included into the failure, the median survival times of them decreased to 8.9, 9.7 and 6.4 years, respectively. Conclusions After considering the clinical performance, composite resin was the only material that showed a difference in the longevity (p < 0.05 and the significantly higher relative risk of student group than professor group disappeared in operator groups. Even in the design of retrospective study, clinical evaluation needs to be included.

Evaluation of the Weibull and log normal distribution functions as survival models of Escherichia coli under isothermal and non isothermal conditions.

Science.gov (United States)

Aragao, Glaucia M F; Corradini, Maria G; Normand, Mark D; Peleg, Micha

2007-11-01

Published survival curves of Escherichia coli in two growth media, with and without the presence of salt, at various temperatures and in a Greek eggplant salad having various levels of essential oil, all had a characteristic downward concavity when plotted on semi logarithmic coordinates. Some also exhibited what appeared as a 'shoulder' of considerable length. Regardless of whether a shoulder was noticed, the survival pattern could be considered as a manifestation of an underlying unimodal distribution of the cells' death times. Mathematically, the data could be described equally well by the Weibull and log normal distribution functions, which had similar modes, means, standard deviations and coefficients of skewness. When plotted in their probability density function (PDF) form, the curves also appeared very similar visually. This enabled us to quantify and compare the effect of temperature or essential oil concentration on the organism's survival in terms of these temporal distributions' characteristics. Increased lethality was generally expressed in a shorter mean and mode, a smaller standard deviation and increased overall symmetry as judged by the distributions' degree of skewness. The 'shoulder', as expected, simply indicated that the distribution's standard deviation was much smaller than its mode. Rate models based on the two distribution functions could be used to predict non isothermal survival patterns. They were derived on the assumption that the momentary inactivation rate is the isothermal rate at the momentary temperature at a time that corresponds to the momentary survival ratio. In this application, however, the Weibullian model with a fixed power was not only simpler and more convenient mathematically than the one based on the log normal distribution, but it also provided more accurate estimates of the dynamic inactivation patterns.

Modelling survival

DEFF Research Database (Denmark)

Ashauer, Roman; Albert, Carlo; Augustine, Starrlight

2016-01-01

The General Unified Threshold model for Survival (GUTS) integrates previously published toxicokinetic-toxicodynamic models and estimates survival with explicitly defined assumptions. Importantly, GUTS accounts for time-variable exposure to the stressor. We performed three studies to test...

Covariate analysis of bivariate survival data

Energy Technology Data Exchange (ETDEWEB)

Bennett, L.E.

1992-01-01

The methods developed are used to analyze the effects of covariates on bivariate survival data when censoring and ties are present. The proposed method provides models for bivariate survival data that include differential covariate effects and censored observations. The proposed models are based on an extension of the univariate Buckley-James estimators which replace censored data points by their expected values, conditional on the censoring time and the covariates. For the bivariate situation, it is necessary to determine the expectation of the failure times for one component conditional on the failure or censoring time of the other component. Two different methods have been developed to estimate these expectations. In the semiparametric approach these expectations are determined from a modification of Burke's estimate of the bivariate empirical survival function. In the parametric approach censored data points are also replaced by their conditional expected values where the expected values are determined from a specified parametric distribution. The model estimation will be based on the revised data set, comprised of uncensored components and expected values for the censored components. The variance-covariance matrix for the estimated covariate parameters has also been derived for both the semiparametric and parametric methods. Data from the Demographic and Health Survey was analyzed by these methods. The two outcome variables are post-partum amenorrhea and breastfeeding; education and parity were used as the covariates. Both the covariate parameter estimates and the variance-covariance estimates for the semiparametric and parametric models will be compared. In addition, a multivariate test statistic was used in the semiparametric model to examine contrasts. The significance of the statistic was determined from a bootstrap distribution of the test statistic.

Receiver function estimated by maximum entropy deconvolution

Institute of Scientific and Technical Information of China (English)

吴庆举; 田小波; 张乃铃; 李卫平; 曾融生

2003-01-01

Maximum entropy deconvolution is presented to estimate receiver function, with the maximum entropy as the rule to determine auto-correlation and cross-correlation functions. The Toeplitz equation and Levinson algorithm are used to calculate the iterative formula of error-predicting filter, and receiver function is then estimated. During extrapolation, reflective coefficient is always less than 1, which keeps maximum entropy deconvolution stable. The maximum entropy of the data outside window increases the resolution of receiver function. Both synthetic and real seismograms show that maximum entropy deconvolution is an effective method to measure receiver function in time-domain.

Osteocalcin protects pancreatic beta cell function and survival under high glucose conditions

Energy Technology Data Exchange (ETDEWEB)

Kover, Karen, E-mail: kkover@cmh.edu [Division of Endocrine/Diabetes, Children' s Mercy Hospital & Clinics, Kansas City, MO 64108 (United States); University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108 (United States); Yan, Yun; Tong, Pei Ying; Watkins, Dara; Li, Xiaoyu [Division of Endocrine/Diabetes, Children' s Mercy Hospital & Clinics, Kansas City, MO 64108 (United States); University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108 (United States); Tasch, James; Hager, Melissa [Kansas City University Medical Biosciences, Kansas City, MO (United States); Clements, Mark; Moore, Wayne V. [Division of Endocrine/Diabetes, Children' s Mercy Hospital & Clinics, Kansas City, MO 64108 (United States); University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108 (United States)

2015-06-19

Diabetes is characterized by progressive beta cell dysfunction and loss due in part to oxidative stress that occurs from gluco/lipotoxicity. Treatments that directly protect beta cell function and survival in the diabetic milieu are of particular interest. A growing body of evidence suggests that osteocalcin, an abundant non-collagenous protein of bone, supports beta cell function and proliferation. Based on previous gene expression data by microarray, we hypothesized that osteocalcin protects beta cells from glucose-induced oxidative stress. To test our hypothesis we cultured isolated rat islets and INS-1E cells in the presence of normal, high, or high glucose ± osteocalcin for up to 72 h. Oxidative stress and viability/mitochondrial function were measured by H{sub 2}O{sub 2} assay and Alamar Blue assay, respectively. Caspase 3/7 activity was also measured as a marker of apoptosis. A functional test, glucose stimulated insulin release, was conducted and expression of genes/protein was measured by qRT-PCR/western blot/ELISA. Osteocalcin treatment significantly reduced high glucose-induced H{sub 2}O{sub 2} levels while maintaining viability/mitochondrial function. Osteocalcin also significantly improved glucose stimulated insulin secretion and insulin content in rat islets after 48 h of high glucose exposure compared to untreated islets. As expected sustained high glucose down-regulated gene/protein expression of INS1 and BCL2 while increasing TXNIP expression. Interestingly, osteocalcin treatment reversed the effects of high glucose on gene/protein expression. We conclude that osteocalcin can protect beta cells from the negative effects of glucose-induced oxidative stress, in part, by reducing TXNIP expression, thereby preserving beta cell function and survival. - Highlights: • Osteocalcin reduces glucose-induced oxidative stress in beta cells. • Osteocalcin preserves beta cell function and survival under stress conditions. • Osteocalcin reduces glucose

Osteocalcin protects pancreatic beta cell function and survival under high glucose conditions

International Nuclear Information System (INIS)

Kover, Karen; Yan, Yun; Tong, Pei Ying; Watkins, Dara; Li, Xiaoyu; Tasch, James; Hager, Melissa; Clements, Mark; Moore, Wayne V.

2015-01-01

Diabetes is characterized by progressive beta cell dysfunction and loss due in part to oxidative stress that occurs from gluco/lipotoxicity. Treatments that directly protect beta cell function and survival in the diabetic milieu are of particular interest. A growing body of evidence suggests that osteocalcin, an abundant non-collagenous protein of bone, supports beta cell function and proliferation. Based on previous gene expression data by microarray, we hypothesized that osteocalcin protects beta cells from glucose-induced oxidative stress. To test our hypothesis we cultured isolated rat islets and INS-1E cells in the presence of normal, high, or high glucose ± osteocalcin for up to 72 h. Oxidative stress and viability/mitochondrial function were measured by H 2 O 2 assay and Alamar Blue assay, respectively. Caspase 3/7 activity was also measured as a marker of apoptosis. A functional test, glucose stimulated insulin release, was conducted and expression of genes/protein was measured by qRT-PCR/western blot/ELISA. Osteocalcin treatment significantly reduced high glucose-induced H 2 O 2 levels while maintaining viability/mitochondrial function. Osteocalcin also significantly improved glucose stimulated insulin secretion and insulin content in rat islets after 48 h of high glucose exposure compared to untreated islets. As expected sustained high glucose down-regulated gene/protein expression of INS1 and BCL2 while increasing TXNIP expression. Interestingly, osteocalcin treatment reversed the effects of high glucose on gene/protein expression. We conclude that osteocalcin can protect beta cells from the negative effects of glucose-induced oxidative stress, in part, by reducing TXNIP expression, thereby preserving beta cell function and survival. - Highlights: • Osteocalcin reduces glucose-induced oxidative stress in beta cells. • Osteocalcin preserves beta cell function and survival under stress conditions. • Osteocalcin reduces glucose-induced TXNIP

ESTIMATION OF FUNCTIONALS OF SPARSE COVARIANCE MATRICES.

Science.gov (United States)

Fan, Jianqing; Rigollet, Philippe; Wang, Weichen

High-dimensional statistical tests often ignore correlations to gain simplicity and stability leading to null distributions that depend on functionals of correlation matrices such as their Frobenius norm and other ℓ r norms. Motivated by the computation of critical values of such tests, we investigate the difficulty of estimation the functionals of sparse correlation matrices. Specifically, we show that simple plug-in procedures based on thresholded estimators of correlation matrices are sparsity-adaptive and minimax optimal over a large class of correlation matrices. Akin to previous results on functional estimation, the minimax rates exhibit an elbow phenomenon. Our results are further illustrated in simulated data as well as an empirical study of data arising in financial econometrics.

Atrioventricular valve repair in patients with functional single-ventricle physiology: impact of ventricular and valve function and morphology on survival and reintervention.

Science.gov (United States)

Honjo, Osami; Atlin, Cori R; Mertens, Luc; Al-Radi, Osman O; Redington, Andrew N; Caldarone, Christopher A; Van Arsdell, Glen S

2011-08-01

This study was to determine whether atrioventricular valve repair modifies natural history of single-ventricle patients with atrioventricular valve insufficiency and to identify factors predicting survival and reintervention. Fifty-seven (13.5%) of 422 single-ventricle patients underwent atrioventricular valve repair. Valve morphology, regurgitation mechanism, and ventricular morphology and function were analyzed for effect on survival, transplant, and reintervention with multivariate logistic and Cox regression models. Comparative analysis used case-matched controls. Atrioventricular valve was tricuspid in 67% and common in 28%. Ventricular morphology was right in 83%. Regurgitation mechanisms were prolapse (n = 24, 46%), dysplasia (n = 18, 35%), annular dilatation (n = 8, 15%), and restriction or cleft (n = 2, 4%). Postrepair insufficiency was none or trivial in 14 (26%), mild in 33 (61%), and moderate in 7 (13%). Survival in repair group was lower than in matched controls (78.9% vs 92.7% at 1 year, 68.7% vs 90.6% at 3 years, P = .015). Patients with successful repair and normal ventricular function had equivalent survival to matched controls (P = .36). Independent predictors for death or transplant included increased indexed annular size (P = .05), increased cardiopulmonary bypass time (P = .04), and decreased postrepair ventricular function (P = .01). Ventricular dilation was a time-related factor for all events, including failed repair. Survival was lower in single-ventricle patients operated on for atrioventricular valve insufficiency than in case-matched controls. Patients with little postoperative residual regurgitation and preserved ventricular function had equivalent survival to controls. Lower grade ventricular function and ventricular dilation correlated with death and repair failure, suggesting that timing of intervention may affect outcome. Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All

Quantifying discrimination of Framingham risk functions with different survival C statistics.

Science.gov (United States)

Pencina, Michael J; D'Agostino, Ralph B; Song, Linye

2012-07-10

Cardiovascular risk prediction functions offer an important diagnostic tool for clinicians and patients themselves. They are usually constructed with the use of parametric or semi-parametric survival regression models. It is essential to be able to evaluate the performance of these models, preferably with summaries that offer natural and intuitive interpretations. The concept of discrimination, popular in the logistic regression context, has been extended to survival analysis. However, the extension is not unique. In this paper, we define discrimination in survival analysis as the model's ability to separate those with longer event-free survival from those with shorter event-free survival within some time horizon of interest. This definition remains consistent with that used in logistic regression, in the sense that it assesses how well the model-based predictions match the observed data. Practical and conceptual examples and numerical simulations are employed to examine four C statistics proposed in the literature to evaluate the performance of survival models. We observe that they differ in the numerical values and aspects of discrimination that they capture. We conclude that the index proposed by Harrell is the most appropriate to capture discrimination described by the above definition. We suggest researchers report which C statistic they are using, provide a rationale for their selection, and be aware that comparing different indices across studies may not be meaningful. Copyright © 2012 John Wiley & Sons, Ltd.

Long-term trajectories of lower extremity function in older adults: estimating gender differences while accounting for potential mortality bias.

Science.gov (United States)

Botoseneanu, Anda; Allore, Heather G; Gahbauer, Evelyne A; Gill, Thomas M

2013-07-01

Gender-specific trajectories of lower extremity function (LEF) and the potential for bias in LEF estimation due to differences in survival have been understudied. We evaluated longitudinal data from 690 initially nondisabled adults age 70 or older from the Precipitating Events Project. LEF was assessed every 18 months for 12 years using a modified Short Physical Performance Battery (mSPPB). Hierarchical linear models with adjustments for length-of-survival estimated the intraindividual trajectory of LEF and differences in trajectory intercept and slope between men and women. LEF declined following a nonlinear trajectory. In the full sample, and among participants with high (mSPPB 10-12) and intermediate (mSPPB 7-9) baseline LEF, the rate-of-decline in mSPPB was slower in women than in men, with no gender differences in baseline mSPPB scores. Among participants with low baseline LEF (mSPPB ≤6), men had a higher starting mSPPB score, whereas women experienced a deceleration in the rate-of-decline over time. In all groups, participants who survived longer had higher starting mSPPB scores and slower rates-of-decline compared with those who died sooner. Over the course of 12 years, older women preserve LEF better than men. Nonadjustment for differences in survival results in overestimating the level and underestimating the rate-of-decline in LEF over time.

Discrimination measures for survival outcomes: connection between the AUC and the predictiveness curve.

Science.gov (United States)

Viallon, Vivian; Latouche, Aurélien

2011-03-01

Finding out biomarkers and building risk scores to predict the occurrence of survival outcomes is a major concern of clinical epidemiology, and so is the evaluation of prognostic models. In this paper, we are concerned with the estimation of the time-dependent AUC--area under the receiver-operating curve--which naturally extends standard AUC to the setting of survival outcomes and enables to evaluate the discriminative power of prognostic models. We establish a simple and useful relation between the predictiveness curve and the time-dependent AUC--AUC(t). This relation confirms that the predictiveness curve is the key concept for evaluating calibration and discrimination of prognostic models. It also highlights that accurate estimates of the conditional absolute risk function should yield accurate estimates for AUC(t). From this observation, we derive several estimators for AUC(t) relying on distinct estimators of the conditional absolute risk function. An empirical study was conducted to compare our estimators with the existing ones and assess the effect of model misspecification--when estimating the conditional absolute risk function--on the AUC(t) estimation. We further illustrate the methodology on the Mayo PBC and the VA lung cancer data sets. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Capture-recapture abundance and survival estimates of three cetacean species in Icelandic coastal waters using trained scientist-volunteers

Science.gov (United States)

Bertulli, Chiara G.; Guéry, Loreleï; McGinty, Niall; Suzuki, Ailie; Brannan, Naomi; Marques, Tania; Rasmussen, Marianne H.; Gimenez, Olivier

2018-01-01

Knowledge of abundance and survival of humpback whales, white-beaked dolphins and minke whales are essential to manage and conserve these species in Icelandic coastal shelf waters. Our main goal was to test the feasibility of employing inexpensive research methods (data collected by trained-scientist volunteers onboard opportunistic vessels) to assess abundance and apparent survival. No previous studies in Iceland have investigated these two demographic parameters in these three cetacean species using open capture-recapture models accounting for imperfect and possibly heterogeneous detection. A transient effect was accounted for whenever required to estimate the population of resident individuals. Identification photographs were collected by scientist-trained volunteers for 7 years (2006-2013) from onboard commercial whale-watching vessels in the coastal waters of Faxaflói (southwest coast, 4400 km2) and Skjálfandi (northeast coast, 1100 km2), Iceland. We estimated an average abundance of 83 humpback whales (Mn; 95% confidence interval: 54-130) in Skjálfandi; 238 white-beaked dolphins (La; [163-321]) in Faxaflói; and 67 minke whales (Ba; [53-82]) in Faxaflói and 24 (14-31) in Skjálfandi. We also found that apparent survival was constant for all three species (Mn: 0.52 [0.41-0.63], La: 0.79 [0.64-0.88], Ba-Faxaflói: 0.80 [0.67-0.88], Ba-Skjálfandi: 0.96 [0.60-0.99]). Our results showed inter-annual variation in abundance estimates which were small for all species, and the presence of transience for minke whales. A significant increase in abundance during the study period was solely found in minke whale data from Skjálfandi. Humpback whales and white-beaked dolphins showed lower apparent survival rates compared to similar baleen whale and dolphin populations. Our results show data collected by trained-scientist volunteers can produce viable estimates of abundance and survival although bias in the methods we employed exist and need to be addressed. With the

Temporal trends of functional dependence and survival among older adults from 1991 to 2010 in Sweden: toward a healthier aging.

Science.gov (United States)

Angleman, Sara B; Santoni, Giola; Von Strauss, Eva; Fratiglioni, Laura

2015-06-01

Declines in functional dependence among older adults were observed before the 1990s, but there is uncertainty about subsequent trends. Our study aimed to verify the temporal trends in disability during 1991-2010 in an older Swedish population and to estimate the associated changes in survival. Functional status in octogenarians and nonagenarians was assessed at seven occasions with intervals of 2-3 years. Sample size varied at each assessment with an average of 646 (range 212-1096). Disability was defined as difficulty in one or more of personal activities of daily living. We compared prevalence and incidence, as well as mortality, and survival associated with disability over the 20-year period. Sex-standardized prevalence of disability remained steady over time with a tendency toward a gradual decline, and a statistically significant decrease was present among nonagenarians. Sex-standardized cumulative incidence also remained steady. The proportion of people with prevalent disability who died <3 years remained stable, as did the survival time of people with incident disability. In contrast, among nondisabled persons, 3-year mortality decreased significantly, and for octogenarians median survival time was 1.3 years longer at the more recent assessment than a decade earlier. Both prevalence and incidence of disability remained stable over the last two decades in this urban Swedish population, with a trend toward a slow decline. Mortality remained steady among disabled persons but decreased among persons without disability, suggesting that increased life expectancy during the last two decades may be essentially driven by longer lives of functionally independent people. © The Author 2014. Published by Oxford University Press on behalf of the Gerontological Society of America. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Induction of Protective Genes Leads to Islet Survival and Function

Directory of Open Access Journals (Sweden)

Hongjun Wang

2011-01-01

Full Text Available Islet transplantation is the most valid approach to the treatment of type 1 diabetes. However, the function of transplanted islets is often compromised since a large number of β cells undergo apoptosis induced by stress and the immune rejection response elicited by the recipient after transplantation. Conventional treatment for islet transplantation is to administer immunosuppressive drugs to the recipient to suppress the immune rejection response mounted against transplanted islets. Induction of protective genes in the recipient (e.g., heme oxygenase-1 (HO-1, A20/tumor necrosis factor alpha inducible protein3 (tnfaip3, biliverdin reductase (BVR, Bcl2, and others or administration of one or more of the products of HO-1 to the donor, the islets themselves, and/or the recipient offers an alternative or synergistic approach to improve islet graft survival and function. In this perspective, we summarize studies describing the protective effects of these genes on islet survival and function in rodent allogeneic and xenogeneic transplantation models and the prevention of onset of diabetes, with emphasis on HO-1, A20, and BVR. Such approaches are also appealing to islet autotransplantation in patients with chronic pancreatitis after total pancreatectomy, a procedure that currently only leads to 1/3 of transplanted patients being diabetes-free.

Clustered survival data with left-truncation

DEFF Research Database (Denmark)

Eriksson, Frank; Martinussen, Torben; Scheike, Thomas H.

2015-01-01

Left-truncation occurs frequently in survival studies, and it is well known how to deal with this for univariate survival times. However, there are few results on how to estimate dependence parameters and regression effects in semiparametric models for clustered survival data with delayed entry....... Surprisingly, existing methods only deal with special cases. In this paper, we clarify different kinds of left-truncation and suggest estimators for semiparametric survival models under specific truncation schemes. The large-sample properties of the estimators are established. Small-sample properties...

[Survival functions and life tables at the origins of actuarial mathematics].

Science.gov (United States)

Spelta, D

1997-01-01

"In the determination of death probabilities of an insured subject one can use either statistical data or a mathematical function. In this paper a survey of the relationship between mortality tables and survival functions from the origins until the first half of the nineteenth century is presented. The author has tried to find the methodological grounds which have induced the actuaries to prefer either of these tools." (EXCERPT)

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.

Fusion probability and survivability in estimates of heaviest nuclei production

International Nuclear Information System (INIS)

Sagaidak, Roman

2012-01-01

A number of theoretical models have been recently developed to predict production cross sections for the heaviest nuclei in fusion-evaporation reactions. All the models reproduce cross sections obtained in experiments quite well. At the same time they give fusion probability values P fus ≡ P CN differed within several orders of the value. This difference implies a corresponding distinction in the calculated values of survivability. The production of the heaviest nuclei (from Cm to the region of superheavy elements (SHE) close to Z = 114 and N = 184) in fusion-evaporation reactions induced by heavy ions has been considered in a systematic way within the framework of the barrier-passing (fusion) model coupled with the standard statistical model (SSM) of the compound nucleus (CN) decay. Both models are incorporated into the HIVAP code. Available data on the excitation functions for fission and evaporation residues (ER) produced in very asymmetric combinations can be described rather well within the framework of HIVAP. Cross-section data obtained in these reactions allow one to choose model parameters quite definitely. Thus one can scale and fix macroscopic (liquid-drop) fission barriers for nuclei involved in the evaporation-fission cascade. In less asymmetric combinations (with 22 Ne and heavier projectiles) effects of fusion suppression caused by quasi-fission are starting to appear in the entrance channel of reactions. The P fus values derived from the capture-fission and fusion-fission cross-sections obtained at energies above the Bass barrier were plotted as a function of the Coulomb parameter. For more symmetric combinations one can deduce the P fus values semi-empirically, using the ER and fission excitation functions measured in experiments, and applying SSM model with parameters obtained in the analysis of a very asymmetric combination leading to the production of (nearly) the same CN, as was done for reactions leading to the pre-actinide nuclei formation

Estimating Functions with Prior Knowledge, (EFPK) for diffusions

DEFF Research Database (Denmark)

Nolsøe, Kim; Kessler, Mathieu; Madsen, Henrik

2003-01-01

In this paper a method is formulated in an estimating function setting for parameter estimation, which allows the use of prior information. The main idea is to use prior knowledge of the parameters, either specified as moments restrictions or as a distribution, and use it in the construction of a...... of an estimating function. It may be useful when the full Bayesian analysis is difficult to carry out for computational reasons. This is almost always the case for diffusions, which is the focus of this paper, though the method applies in other settings.......In this paper a method is formulated in an estimating function setting for parameter estimation, which allows the use of prior information. The main idea is to use prior knowledge of the parameters, either specified as moments restrictions or as a distribution, and use it in the construction...

Improved survival prediction from lung function data in a large population sample

DEFF Research Database (Denmark)

Miller, M.R.; Pedersen, O.F.; Lange, P.

2008-01-01

Studies relating tung function to survival commonly express lung function impairment as a percent of predicted but this retains age, height and sex bias. We have studied alternative methods of expressing forced expiratory volume in 1 s (FEV1) for predicting all cause and airway related lung disease.......1 respectively. Cut levels of lung function were used to categorise impairment and the HR for multivariate prediction of all cause and airway related lung disease mortality were 10 and 2044 respectively for the worst category of FEV1/ht(2) compared to 5 and 194 respectively for the worst category of FEV1PP....... In univariate predictions of all cause mortality the HR for FEV1/ht(2) categories was 2-4 times higher than those for FEV1PP and 3-10 times higher for airway related tung disease mortality. We conclude that FEV1/ht(2) is superior to FEV1PP for predicting survival. in a general population and this method...

Partitioning of excess mortality in population-based cancer patient survival studies using flexible parametric survival models

Directory of Open Access Journals (Sweden)

Eloranta Sandra

2012-06-01

Full Text Available Abstract Background Relative survival is commonly used for studying survival of cancer patients as it captures both the direct and indirect contribution of a cancer diagnosis on mortality by comparing the observed survival of the patients to the expected survival in a comparable cancer-free population. However, existing methods do not allow estimation of the impact of isolated conditions (e.g., excess cardiovascular mortality on the total excess mortality. For this purpose we extend flexible parametric survival models for relative survival, which use restricted cubic splines for the baseline cumulative excess hazard and for any time-dependent effects. Methods In the extended model we partition the excess mortality associated with a diagnosis of cancer through estimating a separate baseline excess hazard function for the outcomes under investigation. This is done by incorporating mutually exclusive background mortality rates, stratified by the underlying causes of death reported in the Swedish population, and by introducing cause of death as a time-dependent effect in the extended model. This approach thereby enables modeling of temporal trends in e.g., excess cardiovascular mortality and remaining cancer excess mortality simultaneously. Furthermore, we illustrate how the results from the proposed model can be used to derive crude probabilities of death due to the component parts, i.e., probabilities estimated in the presence of competing causes of death. Results The method is illustrated with examples where the total excess mortality experienced by patients diagnosed with breast cancer is partitioned into excess cardiovascular mortality and remaining cancer excess mortality. Conclusions The proposed method can be used to simultaneously study disease patterns and temporal trends for various causes of cancer-consequent deaths. Such information should be of interest for patients and clinicians as one way of improving prognosis after cancer is

Usng subjective percentiles and test data for estimating fragility functions

International Nuclear Information System (INIS)

George, L.L.; Mensing, R.W.

1981-01-01

Fragility functions are cumulative distribution functions (cdfs) of strengths at failure. They are needed for reliability analyses of systems such as power generation and transmission systems. Subjective opinions supplement sparse test data for estimating fragility functions. Often the opinions are opinions on the percentiles of the fragility function. Subjective percentiles are likely to be less biased than opinions on parameters of cdfs. Solutions to several problems in the estimation of fragility functions are found for subjective percentiles and test data. How subjective percentiles should be used to estimate subjective fragility functions, how subjective percentiles should be combined with test data, how fragility functions for several failure modes should be combined into a composite fragility function, and how inherent randomness and uncertainty due to lack of knowledge should be represented are considered. Subjective percentiles are treated as independent estimates of percentiles. The following are derived: least-squares parameter estimators for normal and lognormal cdfs, based on subjective percentiles (the method is applicable to any invertible cdf); a composite fragility function for combining several failure modes; estimators of variation within and between groups of experts for nonidentically distributed subjective percentiles; weighted least-squares estimators when subjective percentiles have higher variation at higher percents; and weighted least-squares and Bayes parameter estimators based on combining subjective percentiles and test data. 4 figures, 2 tables

Updated estimates of survival and cost effectiveness for imatinib versus interferon-alpha plus low-dose cytarabine for newly diagnosed chronic-phase chronic myeloid leukaemia.

Science.gov (United States)

Reed, Shelby D; Anstrom, Kevin J; Li, Yanhong; Schulman, Kevin A

2008-01-01

For trials in which participants are followed beyond the main study period to assess long-term outcomes, economic evaluations conducted using short-term data should be systematically updated to reflect new information. We used 60-month survival data from the IRIS (International Randomized study of Interferon vs STI571) trial to update previously published cost-effectiveness estimates, based on 19 months of follow-up, of imatinib versus interferon (IFN)-alpha plus low-dose cytarabine in patients with chronic-phase chronic myeloid leukaemia. For patients treated with imatinib, we used the 60-month data to calibrate the survival curves generated from the original cost-effectiveness model. We used historical data to model survival for patients randomized to IFNalpha. We updated costs for medical resources using 2006 Medicare reimbursement rates and applied average wholesale prices (AWPs) and wholesale acquisition costs (WACs) to study medications. Five-year survival for patients randomized to imatinib was better than predicted in the original model (89.4% vs 83.2%). We estimated remaining life expectancy with first-line imatinib to be 19.1 life-years (3.8 life-years over the original model) and 15.2 QALYs (3.1 QALYs over the original estimate). Estimates for IFNalpha remained at 9.1 life-years and 6.3 QALYs. When we applied AWPs to study medications, incremental cost-effectiveness ratios (ICERs) were $US 51,800-57,500 per QALY. When we applied WACs, ICERs were $US 42,000-46,200 per QALY. Although the analysis revealed that the original survival estimates were conservative, the updated cost-effectiveness ratios were consistent with, or slightly higher than, the original estimates, depending on the method for assigning costs to study medications.

Conditional survival of patients with diffuse large B-cell lymphoma

DEFF Research Database (Denmark)

Møller, Michael Boe; Pedersen, Niels Tinggaard; Christensen, Bjarne E

2006-01-01

BACKGROUND: Prognosis of lymphoma patients is usually estimated at the time of diagnosis and the estimates are guided by the International Prognostic Index (IPI). However, conditional survival estimates are more informative clinically, as they consider those patients only who have already survive...... survival probability provides more accurate prognostic information than the conventional survival rate estimated from the time of diagnosis.......BACKGROUND: Prognosis of lymphoma patients is usually estimated at the time of diagnosis and the estimates are guided by the International Prognostic Index (IPI). However, conditional survival estimates are more informative clinically, as they consider those patients only who have already survived...... a period of time after treatment. Conditional survival data have not been reported for lymphoma patients. METHODS: Conditional survival was estimated for 1209 patients with diffuse large B-cell lymphoma (DLBCL) from the population-based LYFO registry of the Danish Lymphoma Group. The Kaplan-Meier method...

Malware Function Estimation Using API in Initial Behavior

OpenAIRE

KAWAGUCHI, Naoto; OMOTE, Kazumasa

2017-01-01

Malware proliferation has become a serious threat to the Internet in recent years. Most current malware are subspecies of existing malware that have been automatically generated by illegal tools. To conduct an efficient analysis of malware, estimating their functions in advance is effective when we give priority to analyze malware. However, estimating the malware functions has been difficult due to the increasing sophistication of malware. Actually, the previous researches do not estimate the...

Optimal estimation of the intensity function of a spatial point process

DEFF Research Database (Denmark)

Guan, Yongtao; Jalilian, Abdollah; Waagepetersen, Rasmus

easily computable estimating functions. We derive the optimal estimating function in a class of first-order estimating functions. The optimal estimating function depends on the solution of a certain Fredholm integral equation and reduces to the likelihood score in case of a Poisson process. We discuss...

Thresholding projection estimators in functional linear models

OpenAIRE

Cardot, Hervé; Johannes, Jan

2010-01-01

We consider the problem of estimating the regression function in functional linear regression models by proposing a new type of projection estimators which combine dimension reduction and thresholding. The introduction of a threshold rule allows to get consistency under broad assumptions as well as minimax rates of convergence under additional regularity hypotheses. We also consider the particular case of Sobolev spaces generated by the trigonometric basis which permits to get easily mean squ...

Intracranial tumors in infants: long-term functional outcome, survival, and its predictors.

Science.gov (United States)

Pillai, Shibu; Metrie, Mary; Dunham, Christopher; Sargent, Michael; Hukin, Juliette; Steinbok, Paul

2012-04-01

Intracranial tumors are rare in the first year of life. This study evaluates survival rates and functional outcomes of survivors at least 5 years after diagnosis and the predictors of this outcome. A retrospective chart review of all infants with a primary intracranial tumor was carried out. Radiology and pathology were re-reviewed. Outcome was assessed at 5 years or more after diagnosis using Bloom's categories (Bloom 1-2 = good outcome, the rest = poor outcome) and late effects severity scoring. Age, tumor location, size, extent of tumor resection, type of adjuvant therapy given, and WHO grade of tumor histology were evaluated as predictors of outcome. Among 35 infants, 20 (57%) survived, with 12 (34%) having a good outcome. Deficits among the survivors included neurological dysfunction in 14 (70%), visual impairment in 9 (45%), endocrine dysfunction in 5 (25%), and auditory disability in 3 (15%). Ten of the 20 survivors were either attending regular school or were engaged in a skilled job. At presentation, older age and an infratentorial location of the tumor are predictors of poor outcome. After histopathological diagnosis, the WHO grading of tumor is the only independent predictor of survival (p = 0.002) and functional outcome (p brain tumors (34%) had a good functional outcome and approximately a quarter of them (28%) were able to attend regular school or take up a skilled job. After tissue diagnosis, histological grade of tumor is the only independent predictor associated with outcome.

Estimating freshwater productivity, overwinter survival, and migration patterns of Klamath River Coho Salmon

Science.gov (United States)

Manhard, Christopher V.; Som, Nicholas A.; Perry, Russell W.; Faukner, Jimmy; Soto, Toz

2018-01-01

An area of great importance to resource management and conservation biology in the Klamath Basin is balancing water usage against the life history requirements of threatened Coho Salmon. One tool for addressing this topic is a freshwater dynamics model to forecast Coho Salmon productivity based on environmental inputs. Constructing such a forecasting tool requires local data to quantify the unique life history processes of Coho Salmon inhabiting this region. Here, we describe analytical methods for estimating a series of sub-models, each capturing a different life history process, which will eventually be synchronized as part of a freshwater dynamics model for Klamath River Coho Salmon. Specifically, we draw upon extensive population monitoring data collected in the basin to estimate models of freshwater productivity, overwinter survival, and migration patterns. Our models of freshwater productivity indicated that high summer temperatures and high winter flows can both adversely affect smolt production and that such relationships are more likely in tributaries with naturally regulated flows due to substantial intraannual environmental variation. Our models of overwinter survival demonstrated extensive variability in survival among years, but not among rearing locations, and demonstrated that a substantial proportion (~ 20%) of age-0+ fish emigrate from some rearing sites in the winter. Our models of migration patterns indicated that many age-0+ fish redistribute in the basin during the summer and winter. Further, we observed that these redistributions can entail long migrations in the mainstem where environmental stressors likely play a role in cueing refuge entry. Finally, our models of migration patterns indicated that changes in discharge are important in cueing the seaward migration of smolts, but that the nature of this behavioral response can differ dramatically between tributaries with naturally and artificially regulated flows. Collectively, these analyses

A logistic regression estimating function for spatial Gibbs point processes

DEFF Research Database (Denmark)

Baddeley, Adrian; Coeurjolly, Jean-François; Rubak, Ege

We propose a computationally efficient logistic regression estimating function for spatial Gibbs point processes. The sample points for the logistic regression consist of the observed point pattern together with a random pattern of dummy points. The estimating function is closely related to the p......We propose a computationally efficient logistic regression estimating function for spatial Gibbs point processes. The sample points for the logistic regression consist of the observed point pattern together with a random pattern of dummy points. The estimating function is closely related...

Multiple Imputation for Estimating the Risk of Developing Dementia and Its Impact on Survival

OpenAIRE

Yu, Binbing; Saczynski, Jane S.; Launer, Lenore J.

2010-01-01

Dementia, Alzheimer’s disease in particular, is one of the major causes of disability and decreased quality of life among the elderly and a leading obstacle to successful aging. Given the profound impact on public health, much research has focused on the age-specific risk of developing dementia and the impact on survival. Early work has discussed various methods of estimating age-specific incidence of dementia, among which the illness-death model is popular for modeling disease progression. I...

PHAZE, Parametric Hazard Function Estimation

International Nuclear Information System (INIS)

2002-01-01

1 - Description of program or function: Phaze performs statistical inference calculations on a hazard function (also called a failure rate or intensity function) based on reported failure times of components that are repaired and restored to service. Three parametric models are allowed: the exponential, linear, and Weibull hazard models. The inference includes estimation (maximum likelihood estimators and confidence regions) of the parameters and of the hazard function itself, testing of hypotheses such as increasing failure rate, and checking of the model assumptions. 2 - Methods: PHAZE assumes that the failures of a component follow a time-dependent (or non-homogenous) Poisson process and that the failure counts in non-overlapping time intervals are independent. Implicit in the independence property is the assumption that the component is restored to service immediately after any failure, with negligible repair time. The failures of one component are assumed to be independent of those of another component; a proportional hazards model is used. Data for a component are called time censored if the component is observed for a fixed time-period, or plant records covering a fixed time-period are examined, and the failure times are recorded. The number of these failures is random. Data are called failure censored if the component is kept in service until a predetermined number of failures has occurred, at which time the component is removed from service. In this case, the number of failures is fixed, but the end of the observation period equals the final failure time and is random. A typical PHAZE session consists of reading failure data from a file prepared previously, selecting one of the three models, and performing data analysis (i.e., performing the usual statistical inference about the parameters of the model, with special emphasis on the parameter(s) that determine whether the hazard function is increasing). The final goals of the inference are a point estimate

Robust estimation of the expected survival probabilities from high-dimensional Cox models with biomarker-by-treatment interactions in randomized clinical trials

Directory of Open Access Journals (Sweden)

Nils Ternès

2017-05-01

Full Text Available Abstract Background Thanks to the advances in genomics and targeted treatments, more and more prediction models based on biomarkers are being developed to predict potential benefit from treatments in a randomized clinical trial. Despite the methodological framework for the development and validation of prediction models in a high-dimensional setting is getting more and more established, no clear guidance exists yet on how to estimate expected survival probabilities in a penalized model with biomarker-by-treatment interactions. Methods Based on a parsimonious biomarker selection in a penalized high-dimensional Cox model (lasso or adaptive lasso, we propose a unified framework to: estimate internally the predictive accuracy metrics of the developed model (using double cross-validation; estimate the individual survival probabilities at a given timepoint; construct confidence intervals thereof (analytical or bootstrap; and visualize them graphically (pointwise or smoothed with spline. We compared these strategies through a simulation study covering scenarios with or without biomarker effects. We applied the strategies to a large randomized phase III clinical trial that evaluated the effect of adding trastuzumab to chemotherapy in 1574 early breast cancer patients, for which the expression of 462 genes was measured. Results In our simulations, penalized regression models using the adaptive lasso estimated the survival probability of new patients with low bias and standard error; bootstrapped confidence intervals had empirical coverage probability close to the nominal level across very different scenarios. The double cross-validation performed on the training data set closely mimicked the predictive accuracy of the selected models in external validation data. We also propose a useful visual representation of the expected survival probabilities using splines. In the breast cancer trial, the adaptive lasso penalty selected a prediction model with 4

Efficient Estimating Functions for Stochastic Differential Equations

DEFF Research Database (Denmark)

Jakobsen, Nina Munkholt

The overall topic of this thesis is approximate martingale estimating function-based estimationfor solutions of stochastic differential equations, sampled at high frequency. Focuslies on the asymptotic properties of the estimators. The first part of the thesis deals with diffusions observed over...

Impact of Base Functional Component Types on Software Functional Size based Effort Estimation

OpenAIRE

Gencel, Cigdem; Buglione, Luigi

2008-01-01

Software effort estimation is still a significant challenge for software management. Although Functional Size Measurement (FSM) methods have been standardized and have become widely used by the software organizations, the relationship between functional size and development effort still needs further investigation. Most of the studies focus on the project cost drivers and consider total software functional size as the primary input to estimation models. In this study, we investigate whether u...

A flexible and coherent test/estimation procedure based on restricted mean survival times for censored time-to-event data in randomized clinical trials.

Science.gov (United States)

Horiguchi, Miki; Cronin, Angel M; Takeuchi, Masahiro; Uno, Hajime

2018-04-22

In randomized clinical trials where time-to-event is the primary outcome, almost routinely, the logrank test is prespecified as the primary test and the hazard ratio is used to quantify treatment effect. If the ratio of 2 hazard functions is not constant, the logrank test is not optimal and the interpretation of hazard ratio is not obvious. When such a nonproportional hazards case is expected at the design stage, the conventional practice is to prespecify another member of weighted logrank tests, eg, Peto-Prentice-Wilcoxon test. Alternatively, one may specify a robust test as the primary test, which can capture various patterns of difference between 2 event time distributions. However, most of those tests do not have companion procedures to quantify the treatment difference, and investigators have fallen back on reporting treatment effect estimates not associated with the primary test. Such incoherence in the "test/estimation" procedure may potentially mislead clinicians/patients who have to balance risk-benefit for treatment decision. To address this, we propose a flexible and coherent test/estimation procedure based on restricted mean survival time, where the truncation time τ is selected data dependently. The proposed procedure is composed of a prespecified test and an estimation of corresponding robust and interpretable quantitative treatment effect. The utility of the new procedure is demonstrated by numerical studies based on 2 randomized cancer clinical trials; the test is dramatically more powerful than the logrank, Wilcoxon tests, and the restricted mean survival time-based test with a fixed τ, for the patterns of difference seen in these cancer clinical trials. Copyright © 2018 John Wiley & Sons, Ltd.

Optimal Bandwidth Selection for Kernel Density Functionals Estimation

Directory of Open Access Journals (Sweden)

Su Chen

2015-01-01

Full Text Available The choice of bandwidth is crucial to the kernel density estimation (KDE and kernel based regression. Various bandwidth selection methods for KDE and local least square regression have been developed in the past decade. It has been known that scale and location parameters are proportional to density functionals ∫γ(xf2(xdx with appropriate choice of γ(x and furthermore equality of scale and location tests can be transformed to comparisons of the density functionals among populations. ∫γ(xf2(xdx can be estimated nonparametrically via kernel density functionals estimation (KDFE. However, the optimal bandwidth selection for KDFE of ∫γ(xf2(xdx has not been examined. We propose a method to select the optimal bandwidth for the KDFE. The idea underlying this method is to search for the optimal bandwidth by minimizing the mean square error (MSE of the KDFE. Two main practical bandwidth selection techniques for the KDFE of ∫γ(xf2(xdx are provided: Normal scale bandwidth selection (namely, “Rule of Thumb” and direct plug-in bandwidth selection. Simulation studies display that our proposed bandwidth selection methods are superior to existing density estimation bandwidth selection methods in estimating density functionals.

An enzyme-linked immunoabsorbent assay for estimating red cell survival of transfused red cells-validation using CR-51 labeling

International Nuclear Information System (INIS)

Drew, H.; Kickler, T.; Smith, B.; LaFrance, N.

1984-01-01

The survival time of transfused red cells antigenically distinct from the recipient's red cells was determined using an indirect enzyme linked antiglobulin test. These results were then compared to those determined by Cr-51 labeling. Three patients with hypoproliferative anemias and one patient (2 studies) with traumatic hemolytic anemia caused by a prosthetic heart valve were studied. Survival times were performed by transfusing a 5cc aliquot of Cr-51 labeled cells along with the remaining unit. One hour post transfusion, a blood sample was drawn and used as the 100% value. Subsequent samples drawn over a 2-3 week period were then compared to the initial sample to determine percent survival for both methods. The ELISA method for measuring red cell survival in antigenically distinct cells is in close agreement with the Cr-51 method. Although CR-51 labeling is the accepted method for red cell survival determination the ELISA method can be used when radioisotopes are unavailable or contraindicated or when the decision to estimate red cell survival is made after transfusion

Henslow's sparrow winter-survival estimates and response to prescribed burning

Science.gov (United States)

Thatcher, B.S.; Krementz, D.G.; Woodrey, M.S.

2006-01-01

Wintering Henslow's sparrow (Ammodramus henslowii) populations rely on lands managed with prescribed burning, but the effects of various burn regimes on their overwinter survival are unknown. We studied wintering Henslow's sparrows in coastal pine savannas at the Mississippi Sandhill Crane National Wildlife Refuge, Jackson County, Mississippi, USA, during January and February 2001 and 2002. We used the known-fate modeling procedure in program MARK to evaluate the effects of burn age (1 or 2 growing seasons elapsed), burn season (growing, dormant), and calendar year on the survival rates of 83 radiomarked Henslow's sparrows. We found strong evidence that Henslow's sparrow survival rates differed by burn age (with higher survival in recently burned sites) and by year (with lower survival rates in 2001 likely because of drought conditions). We found some evidence that survival rates also differed by bum season (with higher survival in growing-season sites), although the effects of burn season were only apparent in recently burned sites. Avian predation was the suspected major cause of mortality (causing 6 of 14 deaths) with 1 confirmed loggerhead shrike (Lanius ludovicianus) depredation. Our results indicated that recently burned savannas provide high-quality wintering habitats and suggested that managers can improve conditions for wintering Henslow's sparrows by burning a large percentage of savannas each year.

Bias-corrected estimation of stable tail dependence function

DEFF Research Database (Denmark)

Beirlant, Jan; Escobar-Bach, Mikael; Goegebeur, Yuri

2016-01-01

We consider the estimation of the stable tail dependence function. We propose a bias-corrected estimator and we establish its asymptotic behaviour under suitable assumptions. The finite sample performance of the proposed estimator is evaluated by means of an extensive simulation study where...

Unstable volatility functions: the break preserving local linear estimator

DEFF Research Database (Denmark)

Casas, Isabel; Gijbels, Irene

The objective of this paper is to introduce the break preserving local linear (BPLL) estimator for the estimation of unstable volatility functions. Breaks in the structure of the conditional mean and/or the volatility functions are common in Finance. Markov switching models (Hamilton, 1989......) and threshold models (Lin and Terasvirta, 1994) are amongst the most popular models to describe the behaviour of data with structural breaks. The local linear (LL) estimator is not consistent at points where the volatility function has a break and it may even report negative values for finite samples...

Biostatistics series module 9: Survival analysis

Directory of Open Access Journals (Sweden)

Avijit Hazra

2017-01-01

Full Text Available Survival analysis is concerned with “time to event“ data. Conventionally, it dealt with cancer death as the event in question, but it can handle any event occurring over a time frame, and this need not be always adverse in nature. When the outcome of a study is the time to an event, it is often not possible to wait until the event in question has happened to all the subjects, for example, until all are dead. In addition, subjects may leave the study prematurely. Such situations lead to what is called censored observations as complete information is not available for these subjects. The data set is thus an assemblage of times to the event in question and times after which no more information on the individual is available. Survival analysis methods are the only techniques capable of handling censored observations without treating them as missing data. They also make no assumption regarding normal distribution of time to event data. Descriptive methods for exploring survival times in a sample include life table and Kaplan–Meier techniques as well as various kinds of distribution fitting as advanced modeling techniques. The Kaplan–Meier cumulative survival probability over time plot has become the signature plot for biomedical survival analysis. Several techniques are available for comparing the survival experience in two or more groups – the log-rank test is popularly used. This test can also be used to produce an odds ratio as an estimate of risk of the event in the test group; this is called hazard ratio (HR. Limitations of the traditional log-rank test have led to various modifications and enhancements. Finally, survival analysis offers different regression models for estimating the impact of multiple predictors on survival. Cox's proportional hazard model is the most general of the regression methods that allows the hazard function to be modeled on a set of explanatory variables without making restrictive assumptions concerning the

An improved method for estimating the frequency correlation function

KAUST Repository

Chelli, Ali; Pä tzold, Matthias

2012-01-01

For time-invariant frequency-selective channels, the transfer function is a superposition of waves having different propagation delays and path gains. In order to estimate the frequency correlation function (FCF) of such channels, the frequency averaging technique can be utilized. The obtained FCF can be expressed as a sum of auto-terms (ATs) and cross-terms (CTs). The ATs are caused by the autocorrelation of individual path components. The CTs are due to the cross-correlation of different path components. These CTs have no physical meaning and leads to an estimation error. We propose a new estimation method aiming to improve the estimation accuracy of the FCF of a band-limited transfer function. The basic idea behind the proposed method is to introduce a kernel function aiming to reduce the CT effect, while preserving the ATs. In this way, we can improve the estimation of the FCF. The performance of the proposed method and the frequency averaging technique is analyzed using a synthetically generated transfer function. We show that the proposed method is more accurate than the frequency averaging technique. The accurate estimation of the FCF is crucial for the system design. In fact, we can determine the coherence bandwidth from the FCF. The exact knowledge of the coherence bandwidth is beneficial in both the design as well as optimization of frequency interleaving and pilot arrangement schemes. © 2012 IEEE.

An improved method for estimating the frequency correlation function

KAUST Repository

Chelli, Ali

2012-04-01

For time-invariant frequency-selective channels, the transfer function is a superposition of waves having different propagation delays and path gains. In order to estimate the frequency correlation function (FCF) of such channels, the frequency averaging technique can be utilized. The obtained FCF can be expressed as a sum of auto-terms (ATs) and cross-terms (CTs). The ATs are caused by the autocorrelation of individual path components. The CTs are due to the cross-correlation of different path components. These CTs have no physical meaning and leads to an estimation error. We propose a new estimation method aiming to improve the estimation accuracy of the FCF of a band-limited transfer function. The basic idea behind the proposed method is to introduce a kernel function aiming to reduce the CT effect, while preserving the ATs. In this way, we can improve the estimation of the FCF. The performance of the proposed method and the frequency averaging technique is analyzed using a synthetically generated transfer function. We show that the proposed method is more accurate than the frequency averaging technique. The accurate estimation of the FCF is crucial for the system design. In fact, we can determine the coherence bandwidth from the FCF. The exact knowledge of the coherence bandwidth is beneficial in both the design as well as optimization of frequency interleaving and pilot arrangement schemes. © 2012 IEEE.

Symbiotic Dinoflagellate Functional Diversity Mediates Coral Survival under Ecological Crisis.

Science.gov (United States)

Suggett, David J; Warner, Mark E; Leggat, William

2017-10-01

Coral reefs have entered an era of 'ecological crisis' as climate change drives catastrophic reef loss worldwide. Coral growth and stress susceptibility are regulated by their endosymbiotic dinoflagellates (genus Symbiodinium). The phylogenetic diversity of Symbiodinium frequently corresponds to patterns of coral health and survival, but knowledge of functional diversity is ultimately necessary to reconcile broader ecological success over space and time. We explore here functional traits underpinning the complex biology of Symbiodinium that spans free-living algae to coral endosymbionts. In doing so we propose a mechanistic framework integrating the primary traits of resource acquisition and utilisation as a means to explain Symbiodinium functional diversity and to resolve the role of Symbiodinium in driving the stability of coral reefs under an uncertain future. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ewe maternal behavior score to estimate lamb survival and performance during lactation

Directory of Open Access Journals (Sweden)

Andreia Barros de Moraes

2016-08-01

Full Text Available Mortality of perinatal lambs and low weight at weaning cause huge liabilities to farmers. Current study describes maternal-filial behavior and evaluates the use of maternal behavior score (MBS to estimate the behavior of ewes and lambs soon after birth, and correlate it with lamb mortality and performance during lactation. Thirty-seven Corriedale ewes were used in a completely randomized design. MBS was assessed up to 24 hours after birth, taking into consideration the distance of the ewe from the lamb at the approach of a person. Maternal behavior, placental weight, weight gain of the lambs until weaning and their survival rate were also evaluated until two hours after lambing. More than 90% of the ewes had adequate maternal behavior, with parental care, even though ewes were very sensitive to the presence of people. There was no significant correlation between MBS and maternal behavior, lamb mortality rate and live weight gain. Under these conditions, MBS was not a useful tool to estimate maternal behavior and performance of lambs.

Conditional survival is greater than overall survival at diagnosis in patients with osteosarcoma and Ewing's sarcoma.

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Miller, Benjamin J; Lynch, Charles F; Buckwalter, Joseph A

2013-11-01

Conditional survival is a measure of the risk of mortality given that a patient has survived a defined period of time. These estimates are clinically helpful, but have not been reported previously for osteosarcoma or Ewing's sarcoma. We determined the conditional survival of patients with osteosarcoma and Ewing's sarcoma given survival of 1 or more years. We used the Surveillance, Epidemiology, and End Results (SEER) Program database to investigate cases of osteosarcoma and Ewing's sarcoma in patients younger than 40 years from 1973 to 2009. The SEER Program is managed by the National Cancer Institute and provides survival data gathered from population-based cancer registries. We used an actuarial life table analysis to determine any cancer cause-specific 5-year survival estimates conditional on 1 to 5 years of survival after diagnosis. We performed a similar analysis to determine 20-year survival from the time of diagnosis. The estimated 5-year survival improved each year after diagnosis. For local/regional osteosarcoma, the 5-year survival improved from 74.8% at baseline to 91.4% at 5 years-meaning that if a patient with localized osteosarcoma lives for 5 years, the chance of living for another 5 years is 91.4%. Similarly, the 5-year survivals for local/regional Ewing's sarcoma improved from 72.9% at baseline to 92.5% at 5 years, for metastatic osteosarcoma 35.5% at baseline to 85.4% at 5 years, and for metastatic Ewing's sarcoma 31.7% at baseline to 83.6% at 5 years. The likelihood of 20-year cause-specific survival from the time of diagnosis in osteosarcoma and Ewing's sarcoma was almost 90% or greater after 10 years of survival, suggesting that while most patients will remain disease-free indefinitely, some experience cancer-related complications years after presumed eradication. The 5-year survival estimates of osteosarcoma and Ewing's sarcoma improve with each additional year of patient survival. Knowledge of a changing risk profile is useful in counseling

Bayesian error estimation in density-functional theory

DEFF Research Database (Denmark)

Mortensen, Jens Jørgen; Kaasbjerg, Kristen; Frederiksen, Søren Lund

2005-01-01

We present a practical scheme for performing error estimates for density-functional theory calculations. The approach, which is based on ideas from Bayesian statistics, involves creating an ensemble of exchange-correlation functionals by comparing with an experimental database of binding energies...

Estimating survival of dental fillings on the basis of interval-censored data and multi-state models

DEFF Research Database (Denmark)

Joly, Pierre; Gerds, Thomas A; Qvist, Vibeke

2012-01-01

We aim to compare the life expectancy of a filling in a primary tooth between two types of treatments. We define the probabilities that a dental filling survives without complication until the permanent tooth erupts from beneath (exfoliation). We relate the time to exfoliation of the tooth...... with all these particularities, we propose to use a parametric four-state model with three random effects to take into account the hierarchical cluster structure. For inference, right and interval censoring as well as left truncation have to be dealt with. With the proposed approach, we can conclude...... that the estimated probability that a filling survives without complication until exfoliation is larger for one treatment than for the other, for all ages of the child at the time of treatment....

Hypermetabolism in ALS is associated with greater functional decline and shorter survival.

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Steyn, Frederik J; Ioannides, Zara A; van Eijk, Ruben P A; Heggie, Susan; Thorpe, Kathryn A; Ceslis, Amelia; Heshmat, Saman; Henders, Anjali K; Wray, Naomi R; van den Berg, Leonard H; Henderson, Robert D; McCombe, Pamela A; Ngo, Shyuan T

2018-04-29

To determine the prevalence of hypermetabolism, relative to body composition, in amyotrophic lateral sclerosis (ALS) and its relationship with clinical features of disease and survival. Fifty-eight patients with clinically definite or probable ALS as defined by El Escorial criteria, and 58 age and sex-matched control participants underwent assessment of energy expenditure. Our primary outcome was the prevalence of hypermetabolism in cases and controls. Longitudinal changes in clinical parameters between hypermetabolic and normometabolic patients with ALS were determined for up to 12 months following metabolic assessment. Survival was monitored over a 30-month period following metabolic assessment. Hypermetabolism was more prevalent in patients with ALS than controls (41% vs 12%, adjusted OR=5.4; pALS. Mean lower motor neuron score (SD) was greater in hypermetabolic patients when compared with normometabolic patients (4 (0.3) vs 3 (0.7); p=0.04). In the 12 months following metabolic assessment, there was a greater change in Revised ALS Functional Rating Scale score in hypermetabolic patients when compared with normometabolic patients (-0.68 points/month vs -0.39 points/month; p=0.01). Hypermetabolism was inversely associated with survival. Overall, hypermetabolism increased the risk of death during follow-up to 220% (HR 3.2, 95% CI 1.1 to 9.4, p=0.03). Hypermetabolic patients with ALS have a greater level of lower motor neuron involvement, faster rate of functional decline and shorter survival. The metabolic index could be important for informing prognosis in ALS. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Combined treatment with atorvastatin and imipenem improves survival and vascular functions in mouse model of sepsis.

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Choudhury, Soumen; Kannan, Kandasamy; Pule Addison, M; Darzi, Sazad A; Singh, Vishakha; Singh, Thakur Uttam; Thangamalai, Ramasamy; Dash, Jeevan Ranjan; Parida, Subhashree; Debroy, Biplab; Paul, Avishek; Mishra, Santosh Kumar

2015-08-01

We have recently reported that pre-treatment, but not the post-treatment with atorvastatin showed survival benefit and improved hemodynamic functions in cecal ligation and puncture (CLP) model of sepsis in mice. Here we examined whether combined treatment with atorvastatin and imipenem after onset of sepsis can prolong survival and improve vascular functions. At 6 and 18h after sepsis induction, treatment with atorvastatin plus imipenem, atorvastatin or imipenem alone or placebo was initiated. Ex vivo experiments were done on mouse aorta to examine the vascular reactivity to nor-adrenaline and acetylcholine and mRNA expressions of α1D AR, GRK2 and eNOS. Atorvastatin plus imipenem extended the survival time to 56.00±4.62h from 20.00±1.66h observed in CLP mice. The survival time with atorvastatin or imipenem alone was 20.50±1.89h and 27.00±4.09h, respectively. The combined treatment reversed the hyporeactivity to nor-adrenaline through preservation of α1D AR mRNA/protein expression and reversal of α1D AR desensitization mediated by GRK2/Gβγ pathway. The treatment also restored endothelium-dependent relaxation to ACh through restoration of aortic eNOS mRNA expression and NO availability. In conclusion, combined treatment with atorvastatin and imipenem exhibited survival benefit and improved vascular functions in septic mice. Copyright © 2015 Elsevier Inc. All rights reserved.

Cross-validation and Peeling Strategies for Survival Bump Hunting using Recursive Peeling Methods

Science.gov (United States)

Dazard, Jean-Eudes; Choe, Michael; LeBlanc, Michael; Rao, J. Sunil

2015-01-01

We introduce a framework to build a survival/risk bump hunting model with a censored time-to-event response. Our Survival Bump Hunting (SBH) method is based on a recursive peeling procedure that uses a specific survival peeling criterion derived from non/semi-parametric statistics such as the hazards-ratio, the log-rank test or the Nelson--Aalen estimator. To optimize the tuning parameter of the model and validate it, we introduce an objective function based on survival or prediction-error statistics, such as the log-rank test and the concordance error rate. We also describe two alternative cross-validation techniques adapted to the joint task of decision-rule making by recursive peeling and survival estimation. Numerical analyses show the importance of replicated cross-validation and the differences between criteria and techniques in both low and high-dimensional settings. Although several non-parametric survival models exist, none addresses the problem of directly identifying local extrema. We show how SBH efficiently estimates extreme survival/risk subgroups unlike other models. This provides an insight into the behavior of commonly used models and suggests alternatives to be adopted in practice. Finally, our SBH framework was applied to a clinical dataset. In it, we identified subsets of patients characterized by clinical and demographic covariates with a distinct extreme survival outcome, for which tailored medical interventions could be made. An R package PRIMsrc (Patient Rule Induction Method in Survival, Regression and Classification settings) is available on CRAN (Comprehensive R Archive Network) and GitHub. PMID:27034730

Intrastriatal Grafting of Chromospheres: Survival and Functional Effects in the 6-OHDA Rat Model of Parkinson's Disease.

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Alejandra Boronat-García

Full Text Available Cell replacement therapy in Parkinson's disease (PD aims at re-establishing dopamine neurotransmission in the striatum by grafting dopamine-releasing cells. Chromaffin cell (CC grafts produce some transitory improvements of functional motor deficits in PD animal models, and have the advantage of allowing autologous transplantation. However, CC grafts have exhibited low survival, poor functional effects and dopamine release compared to other cell types. Recently, chromaffin progenitor-like cells were isolated from bovine and human adult adrenal medulla. Under low-attachment conditions, these cells aggregate and grow as spheres, named chromospheres. Here, we found that bovine-derived chromosphere-cell cultures exhibit a greater fraction of cells with a dopaminergic phenotype and higher dopamine release than CC. Chromospheres grafted in a rat model of PD survived in 57% of the total grafted animals. Behavioral tests showed that surviving chromosphere cells induce a reduction in motor alterations for at least 3 months after grafting. Finally, we found that compared with CC, chromosphere grafts survive more and produce more robust and consistent motor improvements. However, further experiments would be necessary to determine whether the functional benefits induced by chromosphere grafts can be improved, and also to elucidate the mechanisms underlying the functional effects of the grafts.

Nesting success and survival rates of suburban Olive Thrushes ...

African Journals Online (AJOL)

Reproductive rate, clutch size, nesting success and survival rate of dependent fledglings were estimated from breeding records in the Eastern Cape. These data were used to estimate survival rate of independent fledglings. The estimated adult survival rate in this region was high and the clutch size was small, compared to ...

The use of simple reparameterizations to improve the efficiency of Markov chain Monte Carlo estimation for multilevel models with applications to discrete time survival models.

Science.gov (United States)

Browne, William J; Steele, Fiona; Golalizadeh, Mousa; Green, Martin J

2009-06-01

We consider the application of Markov chain Monte Carlo (MCMC) estimation methods to random-effects models and in particular the family of discrete time survival models. Survival models can be used in many situations in the medical and social sciences and we illustrate their use through two examples that differ in terms of both substantive area and data structure. A multilevel discrete time survival analysis involves expanding the data set so that the model can be cast as a standard multilevel binary response model. For such models it has been shown that MCMC methods have advantages in terms of reducing estimate bias. However, the data expansion results in very large data sets for which MCMC estimation is often slow and can produce chains that exhibit poor mixing. Any way of improving the mixing will result in both speeding up the methods and more confidence in the estimates that are produced. The MCMC methodological literature is full of alternative algorithms designed to improve mixing of chains and we describe three reparameterization techniques that are easy to implement in available software. We consider two examples of multilevel survival analysis: incidence of mastitis in dairy cattle and contraceptive use dynamics in Indonesia. For each application we show where the reparameterization techniques can be used and assess their performance.

ESTIMATION OF PARAMETERS AND RELIABILITY FUNCTION OF EXPONENTIATED EXPONENTIAL DISTRIBUTION: BAYESIAN APPROACH UNDER GENERAL ENTROPY LOSS FUNCTION

Directory of Open Access Journals (Sweden)

Sanjay Kumar Singh

2011-06-01

Full Text Available In this Paper we propose Bayes estimators of the parameters of Exponentiated Exponential distribution and Reliability functions under General Entropy loss function for Type II censored sample. The proposed estimators have been compared with the corresponding Bayes estimators obtained under Squared Error loss function and maximum likelihood estimators for their simulated risks (average loss over sample space.

Overexpression of survival motor neuron improves neuromuscular function and motor neuron survival in mutant SOD1 mice.

Science.gov (United States)

Turner, Bradley J; Alfazema, Neza; Sheean, Rebecca K; Sleigh, James N; Davies, Kay E; Horne, Malcolm K; Talbot, Kevin

2014-04-01

Spinal muscular atrophy results from diminished levels of survival motor neuron (SMN) protein in spinal motor neurons. Low levels of SMN also occur in models of amyotrophic lateral sclerosis (ALS) caused by mutant superoxide dismutase 1 (SOD1) and genetic reduction of SMN levels exacerbates the phenotype of transgenic SOD1(G93A) mice. Here, we demonstrate that SMN protein is significantly reduced in the spinal cords of patients with sporadic ALS. To test the potential of SMN as a modifier of ALS, we overexpressed SMN in 2 different strains of SOD1(G93A) mice. Neuronal overexpression of SMN significantly preserved locomotor function, rescued motor neurons, and attenuated astrogliosis in spinal cords of SOD1(G93A) mice. Despite this, survival was not prolonged, most likely resulting from SMN mislocalization and depletion of gems in motor neurons of symptomatic mice. Our results reveal that SMN upregulation slows locomotor deficit onset and motor neuron loss in this mouse model of ALS. However, disruption of SMN nuclear complexes by high levels of mutant SOD1, even in the presence of SMN overexpression, might limit its survival promoting effects in this specific mouse model. Studies in emerging mouse models of ALS are therefore warranted to further explore the potential of SMN as a modifier of ALS. Copyright © 2014 Elsevier Inc. All rights reserved.

Estimation of direct effects for survival data by using the Aalen additive hazards model

DEFF Research Database (Denmark)

Martinussen, Torben; Vansteelandt, Stijn; Gerster, Mette

2011-01-01

We extend the definition of the controlled direct effect of a point exposure on a survival outcome, other than through some given, time-fixed intermediate variable, to the additive hazard scale. We propose two-stage estimators for this effect when the exposure is dichotomous and randomly assigned...... Aalen's additive regression for the event time, given exposure, intermediate variable and confounders. The second stage involves applying Aalen's additive model, given the exposure alone, to a modified stochastic process (i.e. a modification of the observed counting process based on the first...

Prolonged Delayed Graft Function Is Associated with Inferior Patient and Kidney Allograft Survivals.

Directory of Open Access Journals (Sweden)

Tainá Veras de Sandes-Freitas

Full Text Available It is unclear if there is an association between the duration of delayed graft function (DGF and kidney transplant (KT outcomes. This study investigated the impact of prolonged DGF on patient and graft survivals, and renal function one year after KT. This single center retrospective analysis included all deceased donor KT performed between Jan/1998 and Dec/2008 (n = 1412. Patients were grouped in quartiles according to duration of DGF (1-5, 6-10, 11-15, and >15 days, designated as prolonged DGF. The overall incidence of DGF was 54.2%. Prolonged DGF was associated with retransplantation (OR 2.110, CI95% 1.064-4.184,p = 0.033 and more than 3 HLA mismatches (OR 1.819, CI95% 1.117-2.962,p = 0.016. The incidence of acute rejection was higher in patients with DGF compared with those without DGF (36.2% vs. 12.2%, p<0.001. Compared to patients without DGF, DGF(1-5, DGF(6-10, and DGF(11-15, patients with prolonged DGF showed inferior one year patient survival (95.2% vs. 95.4% vs. 95.5% vs. 93.4% vs. 88.86%, p = 0.003, graft survival (91% vs. 91.4% vs. 92% vs. 88.7% vs. 70.5%, p<0.001, death-censored graft survival (95.7% vs. 95.4% vs. 96.4% vs. 94% vs. 79.3%, p<0.001, and creatinine clearance (58.0±24.6 vs. 55.8±22.2 vs. 53.8±24.1 vs. 53.0±27.2 vs. 36.8±27.0 mL/min, p<0.001, respectively. Multivariable analysis showed that prolonged DGF was an independent risk factor for graft loss (OR 3.876, CI95% 2.270-6.618, p<0.001, death censored graft loss (OR 4.103, CI95% 2.055-8.193, p<0.001, and death (OR 3.065, CI95% 1.536-6.117, p = 0.001. Prolonged DGF, determined by retransplantation and higher HLA mismatches, was associated with inferior renal function, and patient and graft survivals at one year.

Bayesian Nonparametric Mixture Estimation for Time-Indexed Functional Data in R

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Terrance D. Savitsky

2016-08-01

Full Text Available We present growfunctions for R that offers Bayesian nonparametric estimation models for analysis of dependent, noisy time series data indexed by a collection of domains. This data structure arises from combining periodically published government survey statistics, such as are reported in the Current Population Study (CPS. The CPS publishes monthly, by-state estimates of employment levels, where each state expresses a noisy time series. Published state-level estimates from the CPS are composed from household survey responses in a model-free manner and express high levels of volatility due to insufficient sample sizes. Existing software solutions borrow information over a modeled time-based dependence to extract a de-noised time series for each domain. These solutions, however, ignore the dependence among the domains that may be additionally leveraged to improve estimation efficiency. The growfunctions package offers two fully nonparametric mixture models that simultaneously estimate both a time and domain-indexed dependence structure for a collection of time series: (1 A Gaussian process (GP construction, which is parameterized through the covariance matrix, estimates a latent function for each domain. The covariance parameters of the latent functions are indexed by domain under a Dirichlet process prior that permits estimation of the dependence among functions across the domains: (2 An intrinsic Gaussian Markov random field prior construction provides an alternative to the GP that expresses different computation and estimation properties. In addition to performing denoised estimation of latent functions from published domain estimates, growfunctions allows estimation of collections of functions for observation units (e.g., households, rather than aggregated domains, by accounting for an informative sampling design under which the probabilities for inclusion of observation units are related to the response variable. growfunctions includes plot

Childhood craniopharyngioma: survival, local control, endocrine and neurologic function following radiotherapy

International Nuclear Information System (INIS)

Danoff, B.F.; Cowchock, F.S.; Kramer, S.

1983-01-01

Between 1961 and 1978, 19 patients with a diagnosis of childhood or teenage craniopharyngioma received supervoltage radiotherapy. All patients had previously undergone either partial surgical resection (10 patients), total gross resection (3 patients), or aspiration and biopsy (6 patients). Fourteen patients were treated primarily and five were treated for recurrence. The five-year survival was 73% with a 10-year survival of 64%. Sixteen percent developed a recurrence following radiotherapy. Long term effects were assesed in terms of neurologic, intellectual, psychological and endocrine function. Seventy-nine percent had none or minimal neurologic disability. The mean full scale IQ for the group was 90. There were no additional endocrine deficiencies that could be directly attributed to radiation. Behavioral disorders occurred in 50%. These results are at least comparable, if not superior, to those of surgery

Estimating movement and survival rates of a small saltwater fish using autonomous antenna receiver arrays and passive integrated transponder tags

Science.gov (United States)

Rudershausen, Paul J.; Buckel, Jeffery A.; Dubreuil, Todd; O'Donnell, Matthew J.; Hightower, Joseph E.; Poland, Steven J.; Letcher, Benjamin H.

2014-01-01

We evaluated the performance of small (12.5 mm long) passive integrated transponder (PIT) tags and custom detection antennas for obtaining fine-scale movement and demographic data of mummichog Fundulus heteroclitus in a salt marsh creek. Apparent survival and detection probability were estimated using a Cormack Jolly Seber (CJS) model fitted to detection data collected by an array of 3 vertical antennas from November 2010 to March 2011 and by a single horizontal antenna from April to August 2011. Movement of mummichogs was monitored during the period when the array of vertical antennas was used. Antenna performance was examined in situ using tags placed in wooden dowels (drones) and in live mummichogs. Of the 44 tagged fish, 42 were resighted over the 9 mo monitoring period. The in situ detection probabilities of the drone and live mummichogs were high (~80-100%) when the ambient water depth was less than ~0.8 m. Upstream and downstream movement of mummichogs was related to hourly water depth and direction of tidal current in a way that maximized time periods over which mummichogs utilized the intertidal vegetated marsh. Apparent survival was lower during periods of colder water temperatures in December 2010 and early January 2011 (median estimate of daily apparent survival = 0.979) than during other periods of the study (median estimate of daily apparent survival = 0.992). During late fall and winter, temperature had a positive effect on the CJS detection probability of a tagged mummichog, likely due to greater fish activity over warmer periods. During the spring and summer, this pattern reversed possibly due to mummichogs having reduced activity during the hottest periods. This study demonstrates the utility of PIT tags and continuously operating autonomous detection systems for tracking fish at fine temporal scales, and improving estimates of demographic parameters in salt marsh creeks that are difficult or impractical to sample with active fishing gear.

Estimating survival probabilities by exposure levels: utilizing vital statistics and complex survey data with mortality follow-up.

Science.gov (United States)

Landsman, V; Lou, W Y W; Graubard, B I

2015-05-20

We present a two-step approach for estimating hazard rates and, consequently, survival probabilities, by levels of general categorical exposure. The resulting estimator utilizes three sources of data: vital statistics data and census data are used at the first step to estimate the overall hazard rate for a given combination of gender and age group, and cohort data constructed from a nationally representative complex survey with linked mortality records, are used at the second step to divide the overall hazard rate by exposure levels. We present an explicit expression for the resulting estimator and consider two methods for variance estimation that account for complex multistage sample design: (1) the leaving-one-out jackknife method, and (2) the Taylor linearization method, which provides an analytic formula for the variance estimator. The methods are illustrated with smoking and all-cause mortality data from the US National Health Interview Survey Linked Mortality Files, and the proposed estimator is compared with a previously studied crude hazard rate estimator that uses survey data only. The advantages of a two-step approach and possible extensions of the proposed estimator are discussed. Copyright © 2015 John Wiley & Sons, Ltd.

Development on electromagnetic impedance function modeling and its estimation

Energy Technology Data Exchange (ETDEWEB)

Sutarno, D., E-mail: Sutarno@fi.itb.ac.id [Earth Physics and Complex System Division Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung (Indonesia)

2015-09-30

Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition

A taylor series approach to survival analysis

International Nuclear Information System (INIS)

Brodsky, J.B.; Groer, P.G.

1984-09-01

A method of survival analysis using hazard functions is developed. The method uses the well known mathematical theory for Taylor Series. Hypothesis tests of the adequacy of many statistical models, including proportional hazards and linear and/or quadratic dose responses, are obtained. A partial analysis of leukemia mortality in the Life Span Study cohort is used as an example. Furthermore, a relatively robust estimation procedure for the proportional hazards model is proposed. (author)

DOCK8 is critical for the survival and function of NKT cells.

Science.gov (United States)

Crawford, Greg; Enders, Anselm; Gileadi, Uzi; Stankovic, Sanda; Zhang, Qian; Lambe, Teresa; Crockford, Tanya L; Lockstone, Helen E; Freeman, Alexandra; Arkwright, Peter D; Smart, Joanne M; Ma, Cindy S; Tangye, Stuart G; Goodnow, Christopher C; Cerundolo, Vincenzo; Godfrey, Dale I; Su, Helen C; Randall, Katrina L; Cornall, Richard J

2013-09-19

Patients with the dedicator of cytokinesis 8 (DOCK8) immunodeficiency syndrome suffer from recurrent viral and bacterial infections, hyper-immunoglobulin E levels, eczema, and greater susceptibility to cancer. Because natural killer T (NKT) cells have been implicated in these diseases, we asked if these cells were affected by DOCK8 deficiency. Using a mouse model, we found that DOCK8 deficiency resulted in impaired NKT cell development, principally affecting the formation and survival of long-lived, differentiated NKT cells. In the thymus, DOCK8-deficient mice lack a terminally differentiated subset of NK1.1(+) NKT cells expressing the integrin CD103, whereas in the liver, DOCK8-deficient NKT cells express reduced levels of the prosurvival factor B-cell lymphoma 2 and the integrin lymphocyte function-associated antigen 1. Although the initial NKT cell response to antigen is intact in the absence of DOCK8, their ongoing proliferative and cytokine responses are impaired. Importantly, a similar defect in NKT cell numbers was detected in DOCK8-deficient humans, highlighting the relevance of the mouse model. In conclusion, our data demonstrate that DOCK8 is required for the development and survival of mature NKT cells, consistent with the idea that DOCK8 mediates survival signals within a specialized niche. Accordingly, impaired NKT cell numbers and function are likely to contribute to the susceptibility of DOCK8-deficient patients to recurrent infections and malignant disease.

DOCK8 is critical for the survival and function of NKT cells

Science.gov (United States)

Crawford, Greg; Enders, Anselm; Gileadi, Uzi; Stankovic, Sanda; Zhang, Qian; Lambe, Teresa; Crockford, Tanya L.; Lockstone, Helen E.; Freeman, Alexandra; Arkwright, Peter D.; Smart, Joanne M.; Ma, Cindy S.; Tangye, Stuart G.; Goodnow, Christopher C.; Cerundolo, Vincenzo; Godfrey, Dale I.; Su, Helen C.; Randall, Katrina L.

2013-01-01

Patients with the dedicator of cytokinesis 8 (DOCK8) immunodeficiency syndrome suffer from recurrent viral and bacterial infections, hyper–immunoglobulin E levels, eczema, and greater susceptibility to cancer. Because natural killer T (NKT) cells have been implicated in these diseases, we asked if these cells were affected by DOCK8 deficiency. Using a mouse model, we found that DOCK8 deficiency resulted in impaired NKT cell development, principally affecting the formation and survival of long-lived, differentiated NKT cells. In the thymus, DOCK8-deficient mice lack a terminally differentiated subset of NK1.1+ NKT cells expressing the integrin CD103, whereas in the liver, DOCK8-deficient NKT cells express reduced levels of the prosurvival factor B-cell lymphoma 2 and the integrin lymphocyte function-associated antigen 1. Although the initial NKT cell response to antigen is intact in the absence of DOCK8, their ongoing proliferative and cytokine responses are impaired. Importantly, a similar defect in NKT cell numbers was detected in DOCK8-deficient humans, highlighting the relevance of the mouse model. In conclusion, our data demonstrate that DOCK8 is required for the development and survival of mature NKT cells, consistent with the idea that DOCK8 mediates survival signals within a specialized niche. Accordingly, impaired NKT cell numbers and function are likely to contribute to the susceptibility of DOCK8-deficient patients to recurrent infections and malignant disease. PMID:23929855

Advanced statistical methods to study the effects of gastric tube and non-invasive ventilation on functional decline and survival in amyotrophic lateral sclerosis.

Science.gov (United States)

Atassi, Nazem; Cudkowicz, Merit E; Schoenfeld, David A

2011-07-01

A few studies suggest that non-invasive ventilation (1) and gastric tube (G-tube) may have a positive impact on survival but the effect on functional decline is unclear. Confounding by indication may have produced biased estimates of the benefit seen in some of these retrospective studies. The objective of this study was to evaluate the effects of G-tube and NIV on survival and functional decline using advanced statistical models that adjust for confounding by indications. A database of 331 subjects enrolled in previous clinical trials in ALS was available for analysis. Marginal structural models (MSM) were used to compare the mortality hazards and ALSFRS-R slopes between treatment and non-treatment groups, after adjusting for confounding by indication. Results showed that the placement of a G-tube was associated with an additional 1.42 units/month decline in the ALSFRS-R slope (p NIV had no significant effect on ALSFRS-R decline or mortality. In conclusion, marginal structural models can be used to adjust for confounding by indication in retrospective ALS studies. G-tube placement could be followed by a faster rate of functional decline and increased mortality. Our results may suffer from some of the limitations of retrospective analyses.

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.)

Survival of alpha particle irradiated cells as a function of the shape and size of the sensitive volume (nucleus)

International Nuclear Information System (INIS)

Stinchcomb, T.G.; Roeske, J.C.

1995-01-01

Microdosimetry is the study of the stochastic variation of energy deposited within sub-cellular targets. As such, the size and shape of the critical target (i.e. cell nucleus) are essential when considering microdosimetric quantities. In this work, a microdosimetric analysis examines the expected cell survival as a function of the size and shape of the cell nucleus under conditions of irradiation emitting alpha particles. The results indicate that, in general, cell survival is relatively insensitive to changes in the shape of the cell nucleus when the volume is held constant. However, cell survival is a strong function of the variation in the size of the target. These results are useful when analysing the results of cell survival experiments for alpha particle emitters. (Author)

Towards an Early Software Effort Estimation Based on Functional and Non-Functional Requirements

Science.gov (United States)

Kassab, Mohamed; Daneva, Maya; Ormandjieva, Olga

The increased awareness of the non-functional requirements as a key to software project and product success makes explicit the need to include them in any software project effort estimation activity. However, the existing approaches to defining size-based effort relationships still pay insufficient attention to this need. This paper presents a flexible, yet systematic approach to the early requirements-based effort estimation, based on Non-Functional Requirements ontology. It complementarily uses one standard functional size measurement model and a linear regression technique. We report on a case study which illustrates the application of our solution approach in context and also helps evaluate our experiences in using it.

Impact of Bystander Automated External Defibrillator Use on Survival and Functional Outcomes in Shockable Observed Public Cardiac Arrests.

Science.gov (United States)

Pollack, Ross A; Brown, Siobhan P; Rea, Thomas; Aufderheide, Tom; Barbic, David; Buick, Jason E; Christenson, James; Idris, Ahamed H; Jasti, Jamie; Kampp, Michael; Kudenchuk, Peter; May, Susanne; Muhr, Marc; Nichol, Graham; Ornato, Joseph P; Sopko, George; Vaillancourt, Christian; Morrison, Laurie; Weisfeldt, Myron

2018-02-26

Background - Survival following out-of-hospital cardiac arrest (OHCA) with shockable rhythms can be improved with early defibrillation. Although shockable OHCA accounts for only ≈25% of overall arrests, ≈60% of public OHCAs are shockable, offering the possibility of restoring thousands of individuals to full recovery with early defibrillation by bystanders. We sought to determine the association of bystander automated external defibrillator use with survival and functional outcomes in shockable observed public OHCA. Methods - From 2011 to 2015, the Resuscitation Outcomes Consortium prospectively collected detailed information on all cardiac arrests at 9 regional centers. The exposures were shock administration by a bystander-applied automated external defibrillator in comparison with initial defibrillation by emergency medical services. The primary outcome measure was discharge with normal or near-normal (favorable) functional status defined as a modified Rankin Score ≤2. Survival to hospital discharge was the secondary outcome measure. Results -Among 49 555 OHCAs, 4115 (8.3%) observed public OHCAs were analyzed, of which 2500 (60.8%) were shockable. A bystander shock was applied in 18.8% of the shockable arrests. Patients shocked by a bystander were significantly more likely to survive to discharge (66.5% versus 43.0%) and be discharged with favorable functional outcome (57.1% versus 32.7%) than patients initially shocked by emergency medical services. After adjusting for known predictors of outcome, the odds ratio associated with a bystander shock was 2.62 (95% confidence interval, 2.07-3.31) for survival to hospital discharge and 2.73 (95% confidence interval, 2.17-3.44) for discharge with favorable functional outcome. The benefit of bystander shock increased progressively as emergency medical services response time became longer. Conclusions - Bystander automated external defibrillator use before emergency medical services arrival in shockable observed

Estimating functions for inhomogeneous spatial point processes with incomplete covariate data

DEFF Research Database (Denmark)

Waagepetersen, Rasmus

and this leads to parameter estimation error which is difficult to quantify. In this paper we introduce a Monte Carlo version of the estimating function used in "spatstat" for fitting inhomogeneous Poisson processes and certain inhomogeneous cluster processes. For this modified estimating function it is feasible...

Estimating functions for inhomogeneous spatial point processes with incomplete covariate data

DEFF Research Database (Denmark)

Waagepetersen, Rasmus

2008-01-01

and this leads to parameter estimation error which is difficult to quantify. In this paper, we introduce a Monte Carlo version of the estimating function used in spatstat for fitting inhomogeneous Poisson processes and certain inhomogeneous cluster processes. For this modified estimating function, it is feasible...

Consistent Parameter and Transfer Function Estimation using Context Free Grammars

Science.gov (United States)

Klotz, Daniel; Herrnegger, Mathew; Schulz, Karsten

2017-04-01

This contribution presents a method for the inference of transfer functions for rainfall-runoff models. Here, transfer functions are defined as parametrized (functional) relationships between a set of spatial predictors (e.g. elevation, slope or soil texture) and model parameters. They are ultimately used for estimation of consistent, spatially distributed model parameters from a limited amount of lumped global parameters. Additionally, they provide a straightforward method for parameter extrapolation from one set of basins to another and can even be used to derive parameterizations for multi-scale models [see: Samaniego et al., 2010]. Yet, currently an actual knowledge of the transfer functions is often implicitly assumed. As a matter of fact, for most cases these hypothesized transfer functions can rarely be measured and often remain unknown. Therefore, this contribution presents a general method for the concurrent estimation of the structure of transfer functions and their respective (global) parameters. Note, that by consequence an estimation of the distributed parameters of the rainfall-runoff model is also undertaken. The method combines two steps to achieve this. The first generates different possible transfer functions. The second then estimates the respective global transfer function parameters. The structural estimation of the transfer functions is based on the context free grammar concept. Chomsky first introduced context free grammars in linguistics [Chomsky, 1956]. Since then, they have been widely applied in computer science. But, to the knowledge of the authors, they have so far not been used in hydrology. Therefore, the contribution gives an introduction to context free grammars and shows how they can be constructed and used for the structural inference of transfer functions. This is enabled by new methods from evolutionary computation, such as grammatical evolution [O'Neill, 2001], which make it possible to exploit the constructed grammar as a

Asymptotic normality of kernel estimator of $\\psi$-regression function for functional ergodic data

OpenAIRE

Laksaci ALI; Benziadi Fatima; Gheriballak Abdelkader

2016-01-01

In this paper we consider the problem of the estimation of the $\\psi$-regression function when the covariates take values in an infinite dimensional space. Our main aim is to establish, under a stationary ergodic process assumption, the asymptotic normality of this estimate.

DNA-dependent protein kinase catalytic subunit functions in metastasis and influences survival in advanced-stage laryngeal squamous cell carcinoma.

Science.gov (United States)

He, Sha-Sha; Chen, Yong; Shen, Xiao-Ming; Wang, Hong-Zhi; Sun, Peng; Dong, Jun; Guo, Gui-Fang; Chen, Ju-Gao; Xia, Liang-Ping; Hu, Pei-Li; Qiu, Hui-Juan; Liu, Shou-Sheng; Zhou, Yi-Xin; Wang, Wei; Hu, Wei-Han; Cai, Xiu-Yu

2017-01-01

Background: DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is known to function in several types of cancer. In this study, we investigated the expression and clinicopathologic significance of DNA-PKcs in laryngeal squamous cell carcinoma (LSCC). Methods: We conducted a retrospective study of 208 patients with advanced-stage LSCC treated at Sun Yat-sen University Cancer Center, Guangzhou, China. We assessed DNA-PKcs and p16INK4a (p16) status using immunohistochemistry. We examined the association between DNA-PKcs expression and clinicopathologic features and survival outcomes. To evaluate the independent prognostic relevance of DNA-PKcs, we used univariate and multivariate Cox regression models. We estimated overall survival (OS) and distant metastasis-free survival (DMFS) using the Kaplan-Meier method. Results: Immunohistochemical analyses revealed that 163/208 (78.4%) of the LSCC tissue samples exhibited high DNA-PKcs expression. High DNA-PKcs expression was significantly associated with survival outcomes ( P = 0.016) and distant metastasis ( P = 0.02; chi-squared test). High DNA-PKcs expression was associated with a significantly shorter OS and DMFS than low DNA-PKcs expression ( P = 0.029 and 0.033, respectively; log-rank test), and was associated with poor OS in the p16-positive subgroup ( P = 0.047). Multivariate analysis identified DNA-PKcs as an independent prognostic indicator of OS and DMFS in all patients ( P = 0.039 and 0.037, respectively). Conclusions : Our results suggest that patients with LSCC in whom DNA-PKcs expression is elevated have a higher incidence of distant metastasis and a poorer prognosis. DNA-PKcs may represent a marker of tumor progression in patients with p16-positive LSCC.

Genetic introgression and the survival of Florida panther kittens

Science.gov (United States)

Hostetler, Jeffrey A.; Onorato, David P.; Nichols, James D.; Johnson, Warren E.; Roelke, Melody E.; O'Brien, Stephen J.; Jansen, Deborah; Oli, Madan K.

2010-01-01

Estimates of survival for the young of a species are critical for population models. These models can often be improved by determining the effects of management actions and population abundance on this demographic parameter. We used multiple sources of data collected during 1982–2008 and a live-recapture dead-recovery modeling framework to estimate and model survival of Florida panther (Puma concolor coryi) kittens (age 0–1 year). Overall, annual survival of Florida panther kittens was 0.323 ± 0.071 (SE), which was lower than estimates used in previous population models. In 1995, female pumas from Texas (P. c. stanleyana) were released into occupied panther range as part of an intentional introgression program to restore genetic variability. We found that kitten survival generally increased with degree of admixture: F1 admixed and backcrossed to Texas kittens survived better than canonical Florida panther and backcrossed to canonical kittens. Average heterozygosity positively influenced kitten and older panther survival, whereas index of panther abundance negatively influenced kitten survival. Our results provide strong evidence for the positive population-level impact of genetic introgression on Florida panthers. Our approach to integrate data from multiple sources was effective at improving robustness as well as precision of estimates of Florida panther kitten survival, and can be useful in estimating vital rates for other elusive species with sparse data.

[Prognostic estimation in critical patients. Validation of a new and very simple system of prognostic estimation of survival in an intensive care unit].

Science.gov (United States)

Abizanda, R; Padron, A; Vidal, B; Mas, S; Belenguer, A; Madero, J; Heras, A

2006-04-01

To make the validation of a new system of prognostic estimation of survival in critical patients (EPEC) seen in a multidisciplinar Intensive care unit (ICU). Prospective analysis of a patient cohort seen in the ICU of a multidisciplinar Intensive Medicine Service of a reference teaching hospital with 19 beds. Four hundred eighty four patients admitted consecutively over 6 months in 2003. Data collection of a basic minimum data set that includes patient identification data (gender, age), reason for admission and their origin, prognostic estimation of survival by EPEC, MPM II 0 and SAPS II (the latter two considered as gold standard). Mortality was evaluated on hospital discharge. EPEC validation was done with analysis of its discriminating capacity (ROC curve), calibration of its prognostic capacity (Hosmer Lemeshow C test), resolution of the 2 x 2 Contingency tables around different probability values (20, 50, 70 and mean value of prognostic estimation). The standardized mortality rate (SMR) for each one of the methods was calculated. Linear regression of the EPEC regarding the MPM II 0 and SAPS II was established and concordance analyses were done (Bland-Altman test) of the prediction of mortality by the three systems. In spite of an apparently good linear correlation, similar accuracy of prediction and discrimination capacity, EPEC is not well-calibrated (no likelihood of death greater than 50%) and the concordance analyses show that more than 10% of the pairs were outside the 95% confidence interval. In spite of its ease of application and calculation and of incorporating delay of admission in ICU as a variable, EPEC does not offer any predictive advantage on MPM II 0 or SAPS II, and its predictions adapt to reality worse.

Concurrent Chemoradiotherapy Improves Survival in Patients With Hypopharyngeal Cancer

Energy Technology Data Exchange (ETDEWEB)

Paximadis, Peter, E-mail: ppaximad@med.wayne.edu [Department of Radiation Oncology, Wayne State University, Detroit, MI (United States); Yoo, George; Lin, Ho-Sheng; Jacobs, John [Department of Otolaryngology, Barbara Ann Karmanos Cancer Institute, Detroit, MI (United States); Sukari, Ammar [Department of Medical Oncology, Barbara Ann Karmanos Cancer Institute, Detroit, MI (United States); Dyson, Greg [Department of Oncology, Barbara Ann Karmanos Cancer Institute, Detroit, MI (United States); Christensen, Michael; Kim, Harold [Department of Radiation Oncology, Wayne State University, Detroit, MI (United States)

2012-03-15

Purpose: To retrospectively review our institutional experience with hypopharyngeal carcinoma with respect to treatment modality. Methods and Materials: A total of 70 patients with hypopharyngeal cancer treated between 1999 and 2009 were analyzed for functional and survival outcomes. The treatments included surgery alone (n = 5), surgery followed by radiotherapy (RT) (n = 3), surgery followed by chemoradiotherapy (CRT) (n = 13), RT alone (n = 2), CRT alone (n = 22), induction chemotherapy followed by RT (n = 3), and induction chemotherapy followed by CRT (n = 22). Results: The median follow-up was 18 months. The median overall survival and disease-free survival for all patients was 28.3 and 17.6 months, respectively. The 1- and 2-year local control rate for all patients was 87.1% and 80%. CRT, given either as primary therapy or in the adjuvant setting, improved overall survival and disease-free survival compared with patients not receiving CRT. The median overall survival and disease-free survival for patients treated with CRT was 36.7 and 17.6 months vs. 14.0 and 8.0 months, respectively (p < .01). Of the patients initially treated with an organ-preserving approach, 4 (8.2%) required salvage laryngectomy for local recurrence or persistent disease; 8 (16.3%) and 12 (24.5%) patients were dependent on a percutaneous gastrostomy and tracheostomy tube, respectively. The 2-year laryngoesophageal dysfunction-free survival rate for patients treated with an organ-preserving approach was estimated at 31.7%. Conclusions: Concurrent CRT improves survival in patients with hypopharyngeal cancer. CRT given with conventional radiation techniques yields poor functional outcomes, and future efforts should be directed at determining the feasibility of pharyngeal-sparing intensity-modulated radiotherapy in patients with hypopharyngeal tumors.

ASURV: Astronomical SURVival Statistics

Science.gov (United States)

Feigelson, E. D.; Nelson, P. I.; Isobe, T.; LaValley, M.

2014-06-01

ASURV (Astronomical SURVival Statistics) provides astronomy survival analysis for right- and left-censored data including the maximum-likelihood Kaplan-Meier estimator and several univariate two-sample tests, bivariate correlation measures, and linear regressions. ASURV is written in FORTRAN 77, and is stand-alone and does not call any specialized libraries.

Investigation of MLE in nonparametric estimation methods of reliability function

International Nuclear Information System (INIS)

Ahn, Kwang Won; Kim, Yoon Ik; Chung, Chang Hyun; Kim, Kil Yoo

2001-01-01

There have been lots of trials to estimate a reliability function. In the ESReDA 20 th seminar, a new method in nonparametric way was proposed. The major point of that paper is how to use censored data efficiently. Generally there are three kinds of approach to estimate a reliability function in nonparametric way, i.e., Reduced Sample Method, Actuarial Method and Product-Limit (PL) Method. The above three methods have some limits. So we suggest an advanced method that reflects censored information more efficiently. In many instances there will be a unique maximum likelihood estimator (MLE) of an unknown parameter, and often it may be obtained by the process of differentiation. It is well known that the three methods generally used to estimate a reliability function in nonparametric way have maximum likelihood estimators that are uniquely exist. So, MLE of the new method is derived in this study. The procedure to calculate a MLE is similar just like that of PL-estimator. The difference of the two is that in the new method, the mass (or weight) of each has an influence of the others but the mass in PL-estimator not

Efficient Estimating Functions for Stochastic Differential Equations

DEFF Research Database (Denmark)

Jakobsen, Nina Munkholt

The overall topic of this thesis is approximate martingale estimating function-based estimationfor solutions of stochastic differential equations, sampled at high frequency. Focuslies on the asymptotic properties of the estimators. The first part of the thesis deals with diffusions observed over...... a fixed time interval. Rate optimal and effcient estimators areobtained for a one-dimensional diffusion parameter. Stable convergence in distribution isused to achieve a practically applicable Gaussian limit distribution for suitably normalisedestimators. In a simulation example, the limit distributions...... multidimensional parameter. Conditions for rate optimality and effciency of estimatorsof drift-jump and diffusion parameters are given in some special cases. Theseconditions are found to extend the pre-existing conditions applicable to continuous diffusions,and impose much stronger requirements on the estimating...

Survival Estimates for the Passage of Juvenile Salmonids through Snake River Dams and Reservoirs, 1997 Annual Report.

Energy Technology Data Exchange (ETDEWEB)

Hockersmith, Eric E.

1999-03-01

This report consists of two parts describing research activities completed during 1997 under Bonneville Power Administration Project Number 93-29. Part 1 provides reach survival and travel time estimates for 1997 for PIT-tagged hatchery steelhead and yearling chinook salmon in the Snake and Columbia Rivers. The results are reported primarily in the form of tables and figures with a minimum of text. More detailed information on methodology and the statistical models used in the analysis are provided in previous annual reports cited in the text. Analysis of the relationships among travel time, survival, and environmental factors for 1997 and previous years of the study will be reported elsewhere. Part 2 of this report describes research to determine areas of loss and delay for juvenile hatchery salmonids above Lower Granite Reservoir.

Survival, Function, and Complications of Oral Implants Placed in Bone Flaps in Jaw Rehabilitation: A Systematic Review.

Science.gov (United States)

Zhang, Lei; Ding, Qian; Liu, Cunrui; Sun, Yannan; Xie, Qiufei; Zhou, Yongsheng

2016-01-01

This systematic review attempted to determine the survival rate of implants placed in bone flaps in jaw rehabilitation and the functional gains and the most common complications related to these implants. An electronic search was undertaken of PubMed, EMBASE, and CNKI records from 1990 through July 2014. Two independent examiners read the titles and abstracts of the results to identify studies that met the inclusion criteria. Subsequently, the reference lists of the selected publications were hand searched. Descriptive statistics were used to report all data related to the survival rate of implants placed in bone flaps in jaw rehabilitation, the functional gains, and complications. A total of 20 studies were included for systematic review without repetition. The mean follow-up time after implant placement ranged from 1.75 to 9.5 years. Within the limitations of available studies, the survival rate of implants placed in bone flaps in jaw rehabilitation ranged from 82.4% to 100%. Of the 20 included studies, 15 reported a survival rate higher than 90%. The cumulative survival rate was 93.2%, with the longest follow-up time being 12.9 years. The most common complications related to these implants were peri-implant bone resorption or peri-implant inflammation, and peri-implant soft tissue proliferation. The main factors associated with the survival rate of implants in bone flaps were reported as time of implant placement and radiotherapy. Despite some persistent soft tissue problems and implant loss, most patients reached a satisfactory functional and esthetic outcome, as evaluated by clinical examination and subjectively by the patients at interview. Implant-supported dental prosthetic rehabilitation in reconstructed jaws improved the quality of life in terms of speech, nutrition, oral competence, and facial appearance. Placement of implants in bone flaps in jaw rehabilitation was demonstrated to be a reliable technique with a high survival rate. Multicentered

Overhydration, Cardiac Function and Survival in Hemodialysis Patients.

Science.gov (United States)

Onofriescu, Mihai; Siriopol, Dimitrie; Voroneanu, Luminita; Hogas, Simona; Nistor, Ionut; Apetrii, Mugurel; Florea, Laura; Veisa, Gabriel; Mititiuc, Irina; Kanbay, Mehmet; Sascau, Radu; Covic, Adrian

2015-01-01

Chronic subclinical volume overload occurs very frequently and may be ubiquitous in hemodialysis (HD) patients receiving the standard thrice-weekly treatment. It is directly associated with hypertension, increased arterial stiffness, left ventricular hipertrophy, heart failure, and eventually, higher mortality and morbidity. We aimed to assess for the first time if the relationship between bioimpedance assessed overhydration and survival is maintained when adjustments for echocardiographic parameters are considered. A prospective cohort trial was conducted to investigate the impact of overhydration on all cause mortality and cardiovascular events (CVE), by using a previously reported cut-off value for overhydration and also investigating a new cut-off value derived from our analysis of this specific cohort. The body composition of 221 HD patients from a single center was assessed at baseline using bioimpedance. In 157 patients supplemental echocardiography was performed (echocardiography subgroup). Comparative survival analysis was performed using two cut-off points for relative fluid overload (RFO): 15% and 17.4% (a value determined by statistical analysis to have the best predictive value for mortality in our cohort). In the entire study population, patients considered overhydrated (using both cut-offs) had a significant increased risk for all-cause mortality in both univariate (HR = 2.12, 95%CI = 1.30-3.47 for RFO>15% and HR = 2.86, 95%CI = 1.72-4.78 for RFO>17.4%, respectively) and multivariate (HR = 1.87, 95%CI = 1.12-3.13 for RFO>15% and HR = 2.72, 95%CI = 1.60-4.63 for RFO>17.4%, respectively) Cox survival analysis. In the echocardiography subgroup, only the 17.4% cut-off remained associated with the outcome after adjustment for different echocardiographic parameters in the multivariate survival analysis. The number of CVE was significantly higher in overhydrated patients in both univariate (HR = 2.46, 95%CI = 1.56-3.87 for RFO >15% and HR = 3.67, 95%CI = 2

Overhydration, Cardiac Function and Survival in Hemodialysis Patients.

Directory of Open Access Journals (Sweden)

Mihai Onofriescu

Full Text Available Chronic subclinical volume overload occurs very frequently and may be ubiquitous in hemodialysis (HD patients receiving the standard thrice-weekly treatment. It is directly associated with hypertension, increased arterial stiffness, left ventricular hipertrophy, heart failure, and eventually, higher mortality and morbidity. We aimed to assess for the first time if the relationship between bioimpedance assessed overhydration and survival is maintained when adjustments for echocardiographic parameters are considered.A prospective cohort trial was conducted to investigate the impact of overhydration on all cause mortality and cardiovascular events (CVE, by using a previously reported cut-off value for overhydration and also investigating a new cut-off value derived from our analysis of this specific cohort. The body composition of 221 HD patients from a single center was assessed at baseline using bioimpedance. In 157 patients supplemental echocardiography was performed (echocardiography subgroup. Comparative survival analysis was performed using two cut-off points for relative fluid overload (RFO: 15% and 17.4% (a value determined by statistical analysis to have the best predictive value for mortality in our cohort.In the entire study population, patients considered overhydrated (using both cut-offs had a significant increased risk for all-cause mortality in both univariate (HR = 2.12, 95%CI = 1.30-3.47 for RFO>15% and HR = 2.86, 95%CI = 1.72-4.78 for RFO>17.4%, respectively and multivariate (HR = 1.87, 95%CI = 1.12-3.13 for RFO>15% and HR = 2.72, 95%CI = 1.60-4.63 for RFO>17.4%, respectively Cox survival analysis. In the echocardiography subgroup, only the 17.4% cut-off remained associated with the outcome after adjustment for different echocardiographic parameters in the multivariate survival analysis. The number of CVE was significantly higher in overhydrated patients in both univariate (HR = 2.46, 95%CI = 1.56-3.87 for RFO >15% and HR = 3

Comparison of hypertabastic survival model with other unimodal hazard rate functions using a goodness-of-fit test.

Science.gov (United States)

Tahir, M Ramzan; Tran, Quang X; Nikulin, Mikhail S

2017-05-30

We studied the problem of testing a hypothesized distribution in survival regression models when the data is right censored and survival times are influenced by covariates. A modified chi-squared type test, known as Nikulin-Rao-Robson statistic, is applied for the comparison of accelerated failure time models. This statistic is used to test the goodness-of-fit for hypertabastic survival model and four other unimodal hazard rate functions. The results of simulation study showed that the hypertabastic distribution can be used as an alternative to log-logistic and log-normal distribution. In statistical modeling, because of its flexible shape of hazard functions, this distribution can also be used as a competitor of Birnbaum-Saunders and inverse Gaussian distributions. The results for the real data application are shown. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Decreased function of survival motor neuron protein impairs endocytic pathways.

Science.gov (United States)

Dimitriadi, Maria; Derdowski, Aaron; Kalloo, Geetika; Maginnis, Melissa S; O'Hern, Patrick; Bliska, Bryn; Sorkaç, Altar; Nguyen, Ken C Q; Cook, Steven J; Poulogiannis, George; Atwood, Walter J; Hall, David H; Hart, Anne C

2016-07-26

Spinal muscular atrophy (SMA) is caused by depletion of the ubiquitously expressed survival motor neuron (SMN) protein, with 1 in 40 Caucasians being heterozygous for a disease allele. SMN is critical for the assembly of numerous ribonucleoprotein complexes, yet it is still unclear how reduced SMN levels affect motor neuron function. Here, we examined the impact of SMN depletion in Caenorhabditis elegans and found that decreased function of the SMN ortholog SMN-1 perturbed endocytic pathways at motor neuron synapses and in other tissues. Diminished SMN-1 levels caused defects in C. elegans neuromuscular function, and smn-1 genetic interactions were consistent with an endocytic defect. Changes were observed in synaptic endocytic proteins when SMN-1 levels decreased. At the ultrastructural level, defects were observed in endosomal compartments, including significantly fewer docked synaptic vesicles. Finally, endocytosis-dependent infection by JC polyomavirus (JCPyV) was reduced in human cells with decreased SMN levels. Collectively, these results demonstrate for the first time, to our knowledge, that SMN depletion causes defects in endosomal trafficking that impair synaptic function, even in the absence of motor neuron cell death.

Production Functions for Water Delivery Systems: Analysis and Estimation Using Dual Cost Function and Implicit Price Specifications

Science.gov (United States)

Teeples, Ronald; Glyer, David

1987-05-01

Both policy and technical analysis of water delivery systems have been based on cost functions that are inconsistent with or are incomplete representations of the neoclassical production functions of economics. We present a full-featured production function model of water delivery which can be estimated from a multiproduct, dual cost function. The model features implicit prices for own-water inputs and is implemented as a jointly estimated system of input share equations and a translog cost function. Likelihood ratio tests are performed showing that a minimally constrained, full-featured production function is a necessary specification of the water delivery operations in our sample. This, plus the model's highly efficient and economically correct parameter estimates, confirms the usefulness of a production function approach to modeling the economic activities of water delivery systems.

Design and Analysis of Salmonid Tagging Studies in the Columbia Basin, Volume XXI; A Summary of Methods for Conducting Salmonid Fry Mark-Recapture Studies for Estimating Survival in Tributaries, Technical Report 2005-2006.

Energy Technology Data Exchange (ETDEWEB)

Skalski, John

2007-02-01

Productivity and early fry survival can have a major influence on the dynamics of fish stocks. To investigate the early life history of fish, numerous methods have been developed or adapted to these much smaller fish. Some of the marking techniques provide individual identification; many others, only class identification. Some of the tagging techniques require destructive sampling to identify a mark; other methods permit benign examination and rerelease of captured fish. Sixteen alternative release-recapture designs for conducting fry survival investigations were examined. Eleven approaches were found capable of estimating survival parameters; five were not. Of those methods capable of estimating fry survival, five required unique marks, four required batch-specific marks, and two approaches required remarking and rereleasing captured fry. No approach based on a simple batch mark was capable of statistically estimating survival.

A comparison of dependence function estimators in multivariate extremes

KAUST Repository

Vettori, Sabrina; Huser, Raphaë l; Genton, Marc G.

2017-01-01

Various nonparametric and parametric estimators of extremal dependence have been proposed in the literature. Nonparametric methods commonly suffer from the curse of dimensionality and have been mostly implemented in extreme-value studies up to three dimensions, whereas parametric models can tackle higher-dimensional settings. In this paper, we assess, through a vast and systematic simulation study, the performance of classical and recently proposed estimators in multivariate settings. In particular, we first investigate the performance of nonparametric methods and then compare them with classical parametric approaches under symmetric and asymmetric dependence structures within the commonly used logistic family. We also explore two different ways to make nonparametric estimators satisfy the necessary dependence function shape constraints, finding a general improvement in estimator performance either (i) by substituting the estimator with its greatest convex minorant, developing a computational tool to implement this method for dimensions $$D\\ge 2$$D≥2 or (ii) by projecting the estimator onto a subspace of dependence functions satisfying such constraints and taking advantage of Bernstein–Bézier polynomials. Implementing the convex minorant method leads to better estimator performance as the dimensionality increases.

A comparison of dependence function estimators in multivariate extremes

KAUST Repository

Vettori, Sabrina

2017-05-11

Various nonparametric and parametric estimators of extremal dependence have been proposed in the literature. Nonparametric methods commonly suffer from the curse of dimensionality and have been mostly implemented in extreme-value studies up to three dimensions, whereas parametric models can tackle higher-dimensional settings. In this paper, we assess, through a vast and systematic simulation study, the performance of classical and recently proposed estimators in multivariate settings. In particular, we first investigate the performance of nonparametric methods and then compare them with classical parametric approaches under symmetric and asymmetric dependence structures within the commonly used logistic family. We also explore two different ways to make nonparametric estimators satisfy the necessary dependence function shape constraints, finding a general improvement in estimator performance either (i) by substituting the estimator with its greatest convex minorant, developing a computational tool to implement this method for dimensions $$D\\\\ge 2$$D≥2 or (ii) by projecting the estimator onto a subspace of dependence functions satisfying such constraints and taking advantage of Bernstein–Bézier polynomials. Implementing the convex minorant method leads to better estimator performance as the dimensionality increases.

Prediction of the survival and functional ability of severe stroke patients after ICU therapeutic intervention

Directory of Open Access Journals (Sweden)

Aoun-Bacha Zeina

2008-06-01

Full Text Available Abstract Background This study evaluated the benefits and impact of ICU therapeutic interventions on the survival and functional ability of severe cerebrovascular accident (CVA patients. Methods Sixty-two ICU patients suffering from severe ischemic/haemorrhagic stroke were evaluated for CVA severity using APACHE II and the Glasgow coma scale (GCS. Survival was determined using Kaplan-Meier survival tables and survival prediction factors were determined by Cox multivariate analysis. Functional ability was assessed using the stroke impact scale (SIS-16 and Karnofsky score. Risk factors, life support techniques and neurosurgical interventions were recorded. One year post-CVA dependency was investigated using multivariate analysis based on linear regression. Results The study cohort constituted 6% of all CVA (37.8% haemorrhagic/62.2% ischemic admissions. Patient mean(SD age was 65.8(12.3 years with a 1:1 male: female ratio. During the study period 16 patients had died within the ICU and seven in the year following hospital release. The mean(SD APACHE II score at hospital admission was 14.9(6.0 and ICU mean duration of stay was 11.2(15.4 days. Mechanical ventilation was required in 37.1% of cases. Risk ratios were; GCS at admission 0.8(0.14, (p = 0.024, APACHE II 1.11(0.11, (p = 0.05 and duration of mechanical ventilation 1.07(0.07, (p = 0.046. Linear coefficients were: type of CVA – haemorrhagic versus ischemic: -18.95(4.58 (p = 0.007, GCS at hospital admission: -6.83(1.08, (p = 0.001, and duration of hospital stay -0.38(0.14, (p = 0.40. Conclusion To ensure a better prognosis CVA patients require ICU therapeutic interventions. However, as we have shown, where tests can determine the worst affected patients with a poor vital and functional outcome should treatment be withheld?

New graphic AUC-based method to estimate overall survival benefit: pomalidomide reanalysis.

Science.gov (United States)

Fenix-Caballero, S; Diaz-Navarro, J; Prieto-Callejero, B; Rios-Sanchez, E; Alegre-del Rey, E J; Borrero-Rubio, J M

2016-02-01

Difference in median survival is an erratic measure and sometimes does not provide a good assessment of survival benefit. The aim of this study was to reanalyse the overall survival benefit of pomalidomide from pivotal clinical trial using a new area under curve (AUC)-based method. In the pivotal trial, pomalidomide plus low-dose dexamethasone showed a significant survival benefit over high-dose dexamethasone, with a difference between medians of 4.6 months. The new AUC method applied to the survival curves, obtained an overall survival benefit of 2.6 months for the pomalidomide treatment. This average difference in OS was calculated for the 61.5% of patients for whom the time to event is reliable enough. This 2-month differential would have major clinical and pharmacoeconomic implications, on both cost-effectiveness studies and on the willingness of the healthcare systems to pay for this treatment. © 2015 John Wiley & Sons Ltd.

Myosin light chain kinase knockout improves gut barrier function and confers a survival advantage in polymicrobial sepsis.

Science.gov (United States)

Lorentz, C Adam; Liang, Zhe; Meng, Mei; Chen, Ching-Wen; Yoseph, Benyam P; Breed, Elise R; Mittal, Rohit; Klingensmith, Nathan J; Farris, Alton B; Burd, Eileen M; Koval, Michael; Ford, Mandy L; Coopersmith, Craig M

2017-06-07

Sepsis-induced intestinal hyperpermeability is mediated by disruption of the epithelial tight junction, which is closely associated with the peri-junctional actin-myosin ring. Myosin light chain kinase (MLCK) phosphorylates the myosin regulatory light chain, resulting in increased permeability. The purpose of this study was to determine whether genetic deletion of MLCK would alter gut barrier function and survival from sepsis. MLCK -/- and wild type (WT) mice were subjected to cecal ligation and puncture and assayed for both survival and mechanistic studies. Survival was significantly increased in MLCK -/- mice (95% vs. 24%, p<0.0001). Intestinal permeability increased in septic WT mice compared to unmanipulated mice. In contrast, permeability in septic MLCK -/- mice was similar to that seen in unmanipulated animals. Improved gut barrier function in MLCK -/- mice was associated with increases in the tight junction mediators ZO-1 and claudin 15 without alterations in claudin 1, 2, 3, 4, 5, 7, 8, 13, occludin or JAM-A. Other components of intestinal integrity (apoptosis, proliferation and villus length) were unaffected by MLCK deletion as were local peritoneal inflammation and distant lung injury. Systemic IL-10 was decreased greater than 10-fold in MLCK -/- mice; however, survival was similar between septic MLCK -/- mice given exogenous IL-10 or vehicle. These data demonstrate that deletion of MLCK improves survival following sepsis, associated with normalization of intestinal permeability and selected tight junction proteins.

Economic evaluation of nivolumab for the treatment of second-line advanced squamous NSCLC in Canada: a comparison of modeling approaches to estimate and extrapolate survival outcomes.

Science.gov (United States)

Goeree, Ron; Villeneuve, Julie; Goeree, Jeff; Penrod, John R; Orsini, Lucinda; Tahami Monfared, Amir Abbas

2016-06-01

Background Lung cancer is the most common type of cancer in the world and is associated with significant mortality. Nivolumab demonstrated statistically significant improvements in progression-free survival (PFS) and overall survival (OS) for patients with advanced squamous non-small cell lung cancer (NSCLC) who were previously treated. The cost-effectiveness of nivolumab has not been assessed in Canada. A contentious component of projecting long-term cost and outcomes in cancer relates to the modeling approach adopted, with the two most common approaches being partitioned survival (PS) and Markov models. The objectives of this analysis were to estimate the cost-utility of nivolumab and to compare the results using these alternative modeling approaches. Methods Both PS and Markov models were developed using docetaxel and erlotinib as comparators. A three-health state model was used consisting of progression-free, progressed disease, and death. Disease progression and time to progression were estimated by identifying best-fitting survival curves from the clinical trial data for PFS and OS. Expected costs and health outcomes were calculated by combining health-state occupancy with medical resource use and quality-of-life assigned to each of the three health states. The health outcomes included in the model were survival and quality-adjusted-life-years (QALYs). Results Nivolumab was found to have the highest expected per-patient cost, but also improved per-patient life years (LYs) and QALYs. Nivolumab cost an additional $151,560 and $140,601 per QALY gained compared to docetaxel and erlotinib, respectively, using a PS model approach. The cost-utility estimates using a Markov model were very similar ($152,229 and $141,838, respectively, per QALY gained). Conclusions Nivolumab was found to involve a trade-off between improved patient survival and QALYs, and increased cost. It was found that the use of a PS or Markov model produced very similar estimates of expected cost

Robust estimates of environmental effects on population vital rates: an integrated capture–recapture model of seasonal brook trout growth, survival and movement in a stream network

Science.gov (United States)

Letcher, Benjamin H.; Schueller, Paul; Bassar, Ronald D.; Nislow, Keith H.; Coombs, Jason A.; Sakrejda, Krzysztof; Morrissey, Michael; Sigourney, Douglas B.; Whiteley, Andrew R.; O'Donnell, Matthew J.; Dubreuil, Todd L.

2015-01-01

Modelling the effects of environmental change on populations is a key challenge for ecologists, particularly as the pace of change increases. Currently, modelling efforts are limited by difficulties in establishing robust relationships between environmental drivers and population responses.We developed an integrated capture–recapture state-space model to estimate the effects of two key environmental drivers (stream flow and temperature) on demographic rates (body growth, movement and survival) using a long-term (11 years), high-resolution (individually tagged, sampled seasonally) data set of brook trout (Salvelinus fontinalis) from four sites in a stream network. Our integrated model provides an effective context within which to estimate environmental driver effects because it takes full advantage of data by estimating (latent) state values for missing observations, because it propagates uncertainty among model components and because it accounts for the major demographic rates and interactions that contribute to annual survival.We found that stream flow and temperature had strong effects on brook trout demography. Some effects, such as reduction in survival associated with low stream flow and high temperature during the summer season, were consistent across sites and age classes, suggesting that they may serve as robust indicators of vulnerability to environmental change. Other survival effects varied across ages, sites and seasons, indicating that flow and temperature may not be the primary drivers of survival in those cases. Flow and temperature also affected body growth rates; these responses were consistent across sites but differed dramatically between age classes and seasons. Finally, we found that tributary and mainstem sites responded differently to variation in flow and temperature.Annual survival (combination of survival and body growth across seasons) was insensitive to body growth and was most sensitive to flow (positive) and temperature (negative

Functional outcome and survival after radiotherapy of metastatic spinal cord compression in patients with cancer of unknown primary

International Nuclear Information System (INIS)

Rades, Dirk; Fehlauer, Fabian; Veninga, Theo; Stalpers, Lukas J.A.; Basic, Hiba; Hoskin, Peter J.; Rudat, Volker; Karstens, Johann H.; Schild, Steven E.; Dunst, Juergen

2007-01-01

Purpose: Patients with cancer of unknown primary (CUP) account for about 10% of patients with metastatic spinal cord compression (MSCC). This study aims to define the appropriate radiation regimen for these patients. Methods and Materials: Data of 143 CUP patients irradiated for MSCC were retrospectively evaluated. Short-course radiotherapy (RT) (1x8 Gy, 5x4 Gy, n = 68) and long-course RT (10x3 Gy, 15x2.5 Gy, 20x2 Gy, n = 75) plus 8 further potential prognostic factors (age, gender, performance status, visceral metastases, other bone metastases, number of involved vertebrae, ambulatory status, time of developing motor deficits before RT) were compared for functional outcome and survival. Results: Improvement of motor function occurred in 10% of patients, no further progression of motor deficits in 57%, and deterioration in 33%. On multivariate analysis, functional outcome was positively associated with slower development of motor deficits (p < 0.001), absence of visceral metastases (p = 0.008) and other bone metastases (p = 0.027), and ambulatory status (p = 0.054), not with the radiation regimen (p = 0.74). Recurrence of MSCC in the irradiated region occurred in 7 patients after median 6 months. Median survival was 4 months. On multivariate analysis, better survival was significantly associated with absence of visceral metastases (p < 0.001), absence of other bone metastases (p = 0.005), ambulatory status (p = 0.001), and slower development of motor deficits (p = 0.030). Conclusions: For MSCC treatment in patients with CUP, no significant difference was observed between short-course and long-course RT regarding functional outcome and survival. Short-course RT appears preferable, at least for patients with a poor predicted survival, as it is more patient convenient and more cost-effective

The survival rate of self-immolators in Kermanshah Province 2010- 2011

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Farid Najafi

2013-12-01

Full Text Available Background: Self-immolation is one of the most violent methods of suicide, which is spreading in Iran. The highest rate of deaths due to committing suicide and self-immolation in Iran is observed in Kermanshah province. This research was conducted to study the survival rate and the factors that influence survival among the ones who commit self-immolation in Kermanshah province. Methods: In this study, all the cases who did not survive, as well as all the ones who were hospitalized due to self-immolation in Kermanshah province during 2010 and 2011 were examined. The Kaplan-Meier method was used to estimate the survival function, and in order to do the comparisons, Logrank test and Cox Regression were employed using Stata 12 software. Results: The results indicated that during 2010 and 2011, 343 individuals committed self-immolation in Kermanshah Province, while, 288 (84% were women. Also, it was found that 184 (53% did not survive, the mean and median of survival time in those who committed suicide deliberately, were 33±2.6 and 11±2 days respectively. Estimation of survival rate using Logrank test indicated that survival rate had a significant relationship with age, mental disorders, drug addiction, and TBSA (Total Body Surface Area, while it did not suggest a statistically significant relationship with gender, marital status and cause of injury. After multivariate analysis using Cox regression, only two variables of age and TBSA could remain in the model and the other variables were excluded from the model. Conclusion: The death toll due to self-immolation is very high and the mean and median of survival time among the people who committed self-immolation is very low. Therefore, it is recommended that remedial action be performed quickly without wasting time.

On a family of Bessel type functions: Estimations, series, overconvergence

Science.gov (United States)

Paneva-Konovska, Jordanka

2017-12-01

A family of the Bessel-Maitland functions are considered in this paper and some useful estimations are obtained for them. Series defined by means of these functions are considered and their behaviour on the boundaries of the convergence domains is discussed. Using the obtained estimations, necessary and sufficient conditions for the series overconvergence, as well as Hadamard type theorem are proposed.

Development and validation of risk prediction equations to estimate survival in patients with colorectal cancer: cohort study

OpenAIRE

Hippisley-Cox, Julia; Coupland, Carol

2017-01-01

Objective: To develop and externally validate risk prediction equations to estimate absolute and conditional survival in patients with colorectal cancer. \\ud \\ud Design: Cohort study.\\ud \\ud Setting: General practices in England providing data for the QResearch database linked to the national cancer registry.\\ud \\ud Participants: 44 145 patients aged 15-99 with colorectal cancer from 947 practices to derive the equations. The equations were validated in 15 214 patients with colorectal cancer ...

On estimation of the intensity function of a point process

NARCIS (Netherlands)

Lieshout, van M.N.M.

2010-01-01

Abstract. Estimation of the intensity function of spatial point processes is a fundamental problem. In this paper, we interpret the Delaunay tessellation field estimator recently introduced by Schaap and Van de Weygaert as an adaptive kernel estimator and give explicit expressions for the mean and

Heritability Estimates of Endophenotypes of Long and Health Life: The Long Life Family Study

DEFF Research Database (Denmark)

Matteini, Amy M; Fallin, M Daniele; Kammerer, Candace M

2010-01-01

survival were identified and heritability estimates were calculated. Principal components (PCs) analysis was carried out using 28 physiologic measurements from five trait domains (cardiovascular, cognition, physical function, pulmonary, and metabolic). RESULTS: The five most dominant PCs accounted for 50......% of underlying trait variance. The first PC (PC1), which consisted primarily of poor pulmonary and physical function, represented 14.3% of the total variance and had an estimated heritability of 39%. PC2 consisted of measures of good metabolic and cardiovascular function with an estimated heritability of 27%. PC...

Estimating variability in functional images using a synthetic resampling approach

International Nuclear Information System (INIS)

Maitra, R.; O'Sullivan, F.

1996-01-01

Functional imaging of biologic parameters like in vivo tissue metabolism is made possible by Positron Emission Tomography (PET). Many techniques, such as mixture analysis, have been suggested for extracting such images from dynamic sequences of reconstructed PET scans. Methods for assessing the variability in these functional images are of scientific interest. The nonlinearity of the methods used in the mixture analysis approach makes analytic formulae for estimating variability intractable. The usual resampling approach is infeasible because of the prohibitive computational effort in simulating a number of sinogram. datasets, applying image reconstruction, and generating parametric images for each replication. Here we introduce an approach that approximates the distribution of the reconstructed PET images by a Gaussian random field and generates synthetic realizations in the imaging domain. This eliminates the reconstruction steps in generating each simulated functional image and is therefore practical. Results of experiments done to evaluate the approach on a model one-dimensional problem are very encouraging. Post-processing of the estimated variances is seen to improve the accuracy of the estimation method. Mixture analysis is used to estimate functional images; however, the suggested approach is general enough to extend to other parametric imaging methods

A generalized additive regression model for survival times

DEFF Research Database (Denmark)

Scheike, Thomas H.

2001-01-01

Additive Aalen model; counting process; disability model; illness-death model; generalized additive models; multiple time-scales; non-parametric estimation; survival data; varying-coefficient models......Additive Aalen model; counting process; disability model; illness-death model; generalized additive models; multiple time-scales; non-parametric estimation; survival data; varying-coefficient models...

Quasi-Newton methods for parameter estimation in functional differential equations

Science.gov (United States)

Brewer, Dennis W.

1988-01-01

A state-space approach to parameter estimation in linear functional differential equations is developed using the theory of linear evolution equations. A locally convergent quasi-Newton type algorithm is applied to distributed systems with particular emphasis on parameters that induce unbounded perturbations of the state. The algorithm is computationally implemented on several functional differential equations, including coefficient and delay estimation in linear delay-differential equations.

The design and analysis of salmonid tagging studies in the Columbia River. Volume 7: Monte-Carlo comparison of confidence internal procedures for estimating survival in a release-recapture study, with applications to Snake River salmonids

International Nuclear Information System (INIS)

Lowther, A.B.; Skalski, J.

1996-06-01

Confidence intervals for survival probabilities between hydroelectric facilities of migrating juvenile salmonids can be computed from the output of the SURPH software developed at the Center for Quantitative Science at the University of Washington. These intervals have been constructed using the estimate of the survival probability, its associated standard error, and assuming the estimate is normally distributed. In order to test the validity and performance of this procedure, two additional confidence interval procedures for estimating survival probabilities were tested and compared using simulated mark-recapture data. Intervals were constructed using normal probability theory, using a percentile-based empirical bootstrap algorithm, and using the profile likelihood concept. Performance of each method was assessed for a variety of initial conditions (release sizes, survival probabilities, detection probabilities). These initial conditions were chosen to encompass the range of parameter values seen in the 1993 and 1994 Snake River juvenile salmonid survival studies. The comparisons among the three estimation methods included average interval width, interval symmetry, and interval coverage

Headphone-To-Ear Transfer Function Estimation Using Measured Acoustic Parameters

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Jinlin Liu

2018-06-01

Full Text Available This paper proposes to use an optimal five-microphone array method to measure the headphone acoustic reflectance and equivalent sound sources needed in the estimation of headphone-to-ear transfer functions (HpTFs. The performance of this method is theoretically analyzed and experimentally investigated. With the measured acoustic parameters HpTFs for different headphones and ear canal area functions are estimated based on a computational acoustic model. The estimation results show that HpTFs vary considerably with headphones and ear canals, which suggests that individualized compensations for HpTFs are necessary for headphones to reproduce desired sounds for different listeners.

Smoothed Conditional Scale Function Estimation in AR(1-ARCH(1 Processes

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Lema Logamou Seknewna

2018-01-01

Full Text Available The estimation of the Smoothed Conditional Scale Function for time series was taken out under the conditional heteroscedastic innovations by imitating the kernel smoothing in nonparametric QAR-QARCH scheme. The estimation was taken out based on the quantile regression methodology proposed by Koenker and Bassett. And the proof of the asymptotic properties of the Conditional Scale Function estimator for this type of process was given and its consistency was shown.

Cross-Validation of Survival Bump Hunting by Recursive Peeling Methods.

Science.gov (United States)

Dazard, Jean-Eudes; Choe, Michael; LeBlanc, Michael; Rao, J Sunil

2014-08-01

We introduce a survival/risk bump hunting framework to build a bump hunting model with a possibly censored time-to-event type of response and to validate model estimates. First, we describe the use of adequate survival peeling criteria to build a survival/risk bump hunting model based on recursive peeling methods. Our method called "Patient Recursive Survival Peeling" is a rule-induction method that makes use of specific peeling criteria such as hazard ratio or log-rank statistics. Second, to validate our model estimates and improve survival prediction accuracy, we describe a resampling-based validation technique specifically designed for the joint task of decision rule making by recursive peeling (i.e. decision-box) and survival estimation. This alternative technique, called "combined" cross-validation is done by combining test samples over the cross-validation loops, a design allowing for bump hunting by recursive peeling in a survival setting. We provide empirical results showing the importance of cross-validation and replication.

Econometric estimation of the “Constant Elasticity of Substitution" function in R

DEFF Research Database (Denmark)

Henningsen, Arne; Henningsen, Geraldine

for estimating the traditional CES function with two inputs as well as nested CES functions with three and four inputs. Furthermore, we demonstrate how these approaches can be applied in R using the add-on package micEconCES and we describe how the various estimation approaches are implemented in the mic......EconCES package. Finally, we illustrate the usage of this package by replicating some estimations of CES functions that are reported in the literature....

A single model procedure for tank calibration function estimation

International Nuclear Information System (INIS)

York, J.C.; Liebetrau, A.M.

1995-01-01

Reliable tank calibrations are a vital component of any measurement control and accountability program for bulk materials in a nuclear reprocessing facility. Tank volume calibration functions used in nuclear materials safeguards and accountability programs are typically constructed from several segments, each of which is estimated independently. Ideally, the segments correspond to structural features in the tank. In this paper the authors use an extension of the Thomas-Liebetrau model to estimate the entire calibration function in a single step. This procedure automatically takes significant run-to-run differences into account and yields an estimate of the entire calibration function in one operation. As with other procedures, the first step is to define suitable calibration segments. Next, a polynomial of low degree is specified for each segment. In contrast with the conventional practice of constructing a separate model for each segment, this information is used to set up the design matrix for a single model that encompasses all of the calibration data. Estimation of the model parameters is then done using conventional statistical methods. The method described here has several advantages over traditional methods. First, modeled run-to-run differences can be taken into account automatically at the estimation step. Second, no interpolation is required between successive segments. Third, variance estimates are based on all the data, rather than that from a single segment, with the result that discontinuities in confidence intervals at segment boundaries are eliminated. Fourth, the restrictive assumption of the Thomas-Liebetrau method, that the measured volumes be the same for all runs, is not required. Finally, the proposed methods are readily implemented using standard statistical procedures and widely-used software packages

Survival and function of phagocytes in blood culture media

DEFF Research Database (Denmark)

Fischer, T K; Prag, J; Kharazmi, A

1999-01-01

The survival and function of human phagocytes in sterile aerobic and anaerobic blood culture media were investigated using neutrophil morphology, white blood cell count in a haemoanalyser, flow cytometry, oxidative burst response, and bactericidal effect in Colorbact and Septi-Chek blood culture...... media and Bact/Alert. When comparing agitation to stationary incubation no difference in phagocytic activity was found. The methods showed the same trends demonstrating that the phagocytes' viability and activity were prolonged by oxygen and shortened by anaerobic conditions and sodium polyethanol...... sulfonate (SPS). Best preserved activity and viability were found in the aerobic media containing less than 0.5 g/l SPS, in which significant phagocyte oxidative burst and bactericidal activity were found up to 4 days after inoculation. Considering that the majority of bacteremias are due to aerobic...

Patient-Reported Functional Status in Outpatients With Advanced Cancer: Correlation With Physician-Reported Scores and Survival.

Science.gov (United States)

Popovic, Gordana; Harhara, Thana; Pope, Ashley; Al-Awamer, Ahmed; Banerjee, Subrata; Bryson, John; Mak, Ernie; Lau, Jenny; Hannon, Breffni; Swami, Nadia; Le, Lisa W; Zimmermann, Camilla

2018-06-01

Performance status measures are increasingly completed by patients in outpatient cancer settings, but are not well validated for this use. We assessed performance of a patient-reported functional status measure (PRFS, based on the Eastern Cooperative Oncology Group [ECOG]), compared with the physician-completed ECOG, in terms of agreement in ratings and prediction of survival. Patients and physicians independently completed five-point PRFS (lay version of ECOG) and ECOG measures on first consultation at an oncology palliative care clinic. We assessed agreement between PRFS and ECOG using weighted Kappa statistics, and used linear regression to determine factors associated with the difference between PRFS and ECOG ratings. We used the Kaplan-Meier method to estimate the patients' median survival, categorized by PRFS and ECOG, and assessed predictive accuracy of these measures using the C-statistic. For the 949 patients, there was moderate agreement between PRFS and ECOG (weighted Kappa 0.32; 95% CI: 0.28-0.36). On average, patients' ratings of performance status were worse by 0.31 points (95% CI: 0.25-0.37, P statistic was higher for the average of PRFS and ECOG scores (0.619) than when reported individually (0.596 and 0.604, respectively). Patients tend to rate their performance status worse than physicians, particularly if they are younger or have greater symptom burden. Prognostic ability of performance status could be improved by using the average of patients and physician scores. Copyright © 2018 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.

Applied survival analysis using R

CERN Document Server

Moore, Dirk F

2016-01-01

Applied Survival Analysis Using R covers the main principles of survival analysis, gives examples of how it is applied, and teaches how to put those principles to use to analyze data using R as a vehicle. Survival data, where the primary outcome is time to a specific event, arise in many areas of biomedical research, including clinical trials, epidemiological studies, and studies of animals. Many survival methods are extensions of techniques used in linear regression and categorical data, while other aspects of this field are unique to survival data. This text employs numerous actual examples to illustrate survival curve estimation, comparison of survivals of different groups, proper accounting for censoring and truncation, model variable selection, and residual analysis. Because explaining survival analysis requires more advanced mathematics than many other statistical topics, this book is organized with basic concepts and most frequently used procedures covered in earlier chapters, with more advanced topics...

mBEEF-vdW: Robust fitting of error estimation density functionals

DEFF Research Database (Denmark)

Lundgård, Keld Troen; Wellendorff, Jess; Voss, Johannes

2016-01-01

. The functional is fitted within the Bayesian error estimation functional (BEEF) framework [J. Wellendorff et al., Phys. Rev. B 85, 235149 (2012); J. Wellendorff et al., J. Chem. Phys. 140, 144107 (2014)]. We improve the previously used fitting procedures by introducing a robust MM-estimator based loss function...... catalysis, including datasets that were not used for its training. Overall, we find that mBEEF-vdW has a higher general accuracy than competing popular functionals, and it is one of the best performing functionals on chemisorption systems, surface energies, lattice constants, and dispersion. We also show...

Estimation of parameters of constant elasticity of substitution production functional model

Science.gov (United States)

Mahaboob, B.; Venkateswarlu, B.; Sankar, J. Ravi

2017-11-01

Nonlinear model building has become an increasing important powerful tool in mathematical economics. In recent years the popularity of applications of nonlinear models has dramatically been rising up. Several researchers in econometrics are very often interested in the inferential aspects of nonlinear regression models [6]. The present research study gives a distinct method of estimation of more complicated and highly nonlinear model viz Constant Elasticity of Substitution (CES) production functional model. Henningen et.al [5] proposed three solutions to avoid serious problems when estimating CES functions in 2012 and they are i) removing discontinuities by using the limits of the CES function and its derivative. ii) Circumventing large rounding errors by local linear approximations iii) Handling ill-behaved objective functions by a multi-dimensional grid search. Joel Chongeh et.al [7] discussed the estimation of the impact of capital and labour inputs to the gris output agri-food products using constant elasticity of substitution production function in Tanzanian context. Pol Antras [8] presented new estimates of the elasticity of substitution between capital and labour using data from the private sector of the U.S. economy for the period 1948-1998.

Histopathological analysis of pre-implantation donor kidney biopsies: association with graft survival and function in one year post-transplantation

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Karla Lais Pêgas

2014-04-01

Full Text Available Introduction: Pre-implantation kidney biopsy is a decision-making tool when considering the use of grafts from deceased donors with expanded criteria, implanting one or two kidneys and comparing this to post-transplantation biopsies. The role of histopathological alterations in kidney compartments as a prognostic factor in graft survival and function has had conflicting results. Objective: This study evaluated the prevalence of chronic alterations in pre-implant biopsies of kidney grafts and the association of findings with graft function and survival in one year post-transplant. Methods: 110 biopsies were analyzed between 2006 and 2009 at Santa Casa de Porto Alegre, including live donors, ideal deceased donors and those with expanded criteria. The score was computed according to criteria suggested by Remuzzi. The glomerular filtration rate (GFR was calculated using the abbreviated MDRD formula. Results: No statistical difference was found in the survival of donors stratified according to Remuzzi criteria. The GFR was significantly associated with the total scores in the groups with mild and moderate alterations, and in the kidney compartments alone, by univariate analysis. The multivariate model found an association with the presence of arteriosclerosis, glomerulosclerosis, acute rejection and delayed graft function. Conclusion: Pre-transplant chronic kidney alterations did not influence the post-transplantation one-year graft survival, but arteriosclerosis and glomerulosclerosis is predictive of a worse GFR. Delayed graft function and acute rejection are independent prognostic factors.

Technical report. The application of probability-generating functions to linear-quadratic radiation survival curves.

Science.gov (United States)

Kendal, W S

2000-04-01

To illustrate how probability-generating functions (PGFs) can be employed to derive a simple probabilistic model for clonogenic survival after exposure to ionizing irradiation. Both repairable and irreparable radiation damage to DNA were assumed to occur by independent (Poisson) processes, at intensities proportional to the irradiation dose. Also, repairable damage was assumed to be either repaired or further (lethally) injured according to a third (Bernoulli) process, with the probability of lethal conversion being directly proportional to dose. Using the algebra of PGFs, these three processes were combined to yield a composite PGF that described the distribution of lethal DNA lesions in irradiated cells. The composite PGF characterized a Poisson distribution with mean, chiD+betaD2, where D was dose and alpha and beta were radiobiological constants. This distribution yielded the conventional linear-quadratic survival equation. To test the composite model, the derived distribution was used to predict the frequencies of multiple chromosomal aberrations in irradiated human lymphocytes. The predictions agreed well with observation. This probabilistic model was consistent with single-hit mechanisms, but it was not consistent with binary misrepair mechanisms. A stochastic model for radiation survival has been constructed from elementary PGFs that exactly yields the linear-quadratic relationship. This approach can be used to investigate other simple probabilistic survival models.

Disentangling the effects of tocilizumab on neutrophil survival and function.

Science.gov (United States)

Gaber, Timo; Hahne, Martin; Strehl, Cindy; Hoff, Paula; Dörffel, Yvonne; Feist, Eugen; Burmester, Gerd-Rüdiger; Buttgereit, Frank

2016-06-01

The synovial tissue in rheumatoid arthritis (RA) represents a hypoxic environment with up-regulated pro-inflammatory cytokines and cellular infiltrates including neutrophils. Although inhibition of the interleukin (IL)6 receptor pathway by tocilizumab is a potent treatment option for RA, it may also cause adverse effects such as an occasionally high-grade neutropenia. We analysed the impact of tocilizumab on survival, mediator secretion, oxidative burst, phagocytosis and energy availability of high-dose toll-like receptor (TLR)2/4-stimulated neutrophils (to mimic an arthritis flare) under normoxic versus hypoxic conditions. Human neutrophils were purified, pre-treated with varying doses of tocilizumab, dexamethasone or human IgG1 and high-dose-stimulated with lipopolysaccharide (LPS) alone-triggering TLR2/4-, LPS plus IL6, or left unstimulated. Cells were then incubated under normoxic (18 % O2) or hypoxic (1 % O2) conditions and subsequently analysed. Neutrophil survival and energy availability were significantly decreased by tocilizumab in a dose-dependent manner in high-dose TLR2/4-stimulated cells, but to a greater extent under normoxia as compared to hypoxia. We also found high-dose LPS-stimulated oxidative burst and phagocytosis of neutrophils to be higher under hypoxic versus normoxic conditions, but this difference was reduced by tocilizumab. Finally, we observed that tocilizumab affected neutrophil mediator secretion as a function of oxygen availability. Tocilizumab is known for both beneficial effects and a higher incidence of neutropenia when treating RA patients. Our results suggest that both effects can at least in part be explained by a reduction in neutrophil survival, a dose-dependent inhibition of hypoxia-induced NADPH oxidase-mediated oxidative burst and phagocytosis of infiltrating hypoxic neutrophils and an alteration of mediator secretion.

Modelling survival: exposure pattern, species sensitivity and uncertainty.

Science.gov (United States)

Ashauer, Roman; Albert, Carlo; Augustine, Starrlight; Cedergreen, Nina; Charles, Sandrine; Ducrot, Virginie; Focks, Andreas; Gabsi, Faten; Gergs, André; Goussen, Benoit; Jager, Tjalling; Kramer, Nynke I; Nyman, Anna-Maija; Poulsen, Veronique; Reichenberger, Stefan; Schäfer, Ralf B; Van den Brink, Paul J; Veltman, Karin; Vogel, Sören; Zimmer, Elke I; Preuss, Thomas G

2016-07-06

The General Unified Threshold model for Survival (GUTS) integrates previously published toxicokinetic-toxicodynamic models and estimates survival with explicitly defined assumptions. Importantly, GUTS accounts for time-variable exposure to the stressor. We performed three studies to test the ability of GUTS to predict survival of aquatic organisms across different pesticide exposure patterns, time scales and species. Firstly, using synthetic data, we identified experimental data requirements which allow for the estimation of all parameters of the GUTS proper model. Secondly, we assessed how well GUTS, calibrated with short-term survival data of Gammarus pulex exposed to four pesticides, can forecast effects of longer-term pulsed exposures. Thirdly, we tested the ability of GUTS to estimate 14-day median effect concentrations of malathion for a range of species and use these estimates to build species sensitivity distributions for different exposure patterns. We find that GUTS adequately predicts survival across exposure patterns that vary over time. When toxicity is assessed for time-variable concentrations species may differ in their responses depending on the exposure profile. This can result in different species sensitivity rankings and safe levels. The interplay of exposure pattern and species sensitivity deserves systematic investigation in order to better understand how organisms respond to stress, including humans.

Survival of adult martens in Northern Wisconsin

Science.gov (United States)

Nicholas P. McCann; Patrick A. Zollner; Jonathan H. Gilbert

2010-01-01

Low adult marten (Martes americana) survival may be one factor limiting their population growth >30 yr after their reintroduction in Wisconsin, USA. We estimated annual adult marten survival at 0.81 in northern Wisconsin, with lower survival during winter (0.87) than summer-fall (1.00). Fisher (Martes pennanti) and raptor kills...

Power estimation on functional level for programmable processors

Directory of Open Access Journals (Sweden)

M. Schneider

2004-01-01

Full Text Available In diesem Beitrag werden verschiedene Ansätze zur Verlustleistungsschätzung von programmierbaren Prozessoren vorgestellt und bezüglich ihrer Übertragbarkeit auf moderne Prozessor-Architekturen wie beispielsweise Very Long Instruction Word (VLIW-Architekturen bewertet. Besonderes Augenmerk liegt hierbei auf dem Konzept der sogenannten Functional-Level Power Analysis (FLPA. Dieser Ansatz basiert auf der Einteilung der Prozessor-Architektur in funktionale Blöcke wie beispielsweise Processing-Unit, Clock-Netzwerk, interner Speicher und andere. Die Verlustleistungsaufnahme dieser Bl¨ocke wird parameterabhängig durch arithmetische Modellfunktionen beschrieben. Durch automatisierte Analyse von Assemblercodes des zu schätzenden Systems mittels eines Parsers können die Eingangsparameter wie beispielsweise der erzielte Parallelitätsgrad oder die Art des Speicherzugriffs gewonnen werden. Dieser Ansatz wird am Beispiel zweier moderner digitaler Signalprozessoren durch eine Vielzahl von Basis-Algorithmen der digitalen Signalverarbeitung evaluiert. Die ermittelten Schätzwerte für die einzelnen Algorithmen werden dabei mit physikalisch gemessenen Werten verglichen. Es ergibt sich ein sehr kleiner maximaler Schätzfehler von 3%. In this contribution different approaches for power estimation for programmable processors are presented and evaluated concerning their capability to be applied to modern digital signal processor architectures like e.g. Very Long InstructionWord (VLIW -architectures. Special emphasis will be laid on the concept of so-called Functional-Level Power Analysis (FLPA. This approach is based on the separation of the processor architecture into functional blocks like e.g. processing unit, clock network, internal memory and others. The power consumption of these blocks is described by parameter dependent arithmetic model functions. By application of a parser based automized analysis of assembler codes of the systems to be estimated

Power estimation on functional level for programmable processors

Science.gov (United States)

Schneider, M.; Blume, H.; Noll, T. G.

2004-05-01

In diesem Beitrag werden verschiedene Ansätze zur Verlustleistungsschätzung von programmierbaren Prozessoren vorgestellt und bezüglich ihrer Übertragbarkeit auf moderne Prozessor-Architekturen wie beispielsweise Very Long Instruction Word (VLIW)-Architekturen bewertet. Besonderes Augenmerk liegt hierbei auf dem Konzept der sogenannten Functional-Level Power Analysis (FLPA). Dieser Ansatz basiert auf der Einteilung der Prozessor-Architektur in funktionale Blöcke wie beispielsweise Processing-Unit, Clock-Netzwerk, interner Speicher und andere. Die Verlustleistungsaufnahme dieser Bl¨ocke wird parameterabhängig durch arithmetische Modellfunktionen beschrieben. Durch automatisierte Analyse von Assemblercodes des zu schätzenden Systems mittels eines Parsers können die Eingangsparameter wie beispielsweise der erzielte Parallelitätsgrad oder die Art des Speicherzugriffs gewonnen werden. Dieser Ansatz wird am Beispiel zweier moderner digitaler Signalprozessoren durch eine Vielzahl von Basis-Algorithmen der digitalen Signalverarbeitung evaluiert. Die ermittelten Schätzwerte für die einzelnen Algorithmen werden dabei mit physikalisch gemessenen Werten verglichen. Es ergibt sich ein sehr kleiner maximaler Schätzfehler von 3%. In this contribution different approaches for power estimation for programmable processors are presented and evaluated concerning their capability to be applied to modern digital signal processor architectures like e.g. Very Long InstructionWord (VLIW) -architectures. Special emphasis will be laid on the concept of so-called Functional-Level Power Analysis (FLPA). This approach is based on the separation of the processor architecture into functional blocks like e.g. processing unit, clock network, internal memory and others. The power consumption of these blocks is described by parameter dependent arithmetic model functions. By application of a parser based automized analysis of assembler codes of the systems to be estimated the input

Unbiased estimators for spatial distribution functions of classical fluids

Science.gov (United States)

Adib, Artur B.; Jarzynski, Christopher

2005-01-01

We use a statistical-mechanical identity closely related to the familiar virial theorem, to derive unbiased estimators for spatial distribution functions of classical fluids. In particular, we obtain estimators for both the fluid density ρ(r) in the vicinity of a fixed solute and the pair correlation g(r) of a homogeneous classical fluid. We illustrate the utility of our estimators with numerical examples, which reveal advantages over traditional histogram-based methods of computing such distributions.

Survival pathways under stress

Indian Academy of Sciences (India)

First page Back Continue Last page Graphics. Survival pathways under stress. Bacteria survive by changing gene expression. pattern. Three important pathways will be discussed: Stringent response. Quorum sensing. Proteins performing function to control oxidative damage.

Tsc1 is a Critical Regulator of Macrophage Survival and Function

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Chunmin Fang

2015-07-01

Full Text Available Background/Aims: Tuberous sclerosis complex 1 (Tsc1 has been shown to regulate M1/M2 polarization of macrophages, but the precise roles of Tsc1 in the function and stability of macrophages are not fully understood. Here we show that Tsc1 is required for regulating the survival, migration and phagocytosis of macrophages. Methods: Mice with Tsc1 homozygous deletion in myeloid cells (LysMCreTsc1flox/flox; Tsc1 KO were obtained by crossing Tsc1flox/flox mice with mice expressing Cre recombinase under the control of Lysozyme promoter (LysMCre. The apoptosis and growth of macrophages were determined by flow cytometry and Real-time PCR (RT-PCR. The phagocytosis was determined using a Vybrant™ phagocytosis assay kit. The migration of macrophages was determined using transwell migration assay. Results: Peritoneal macrophages of Tsc1 KO mice exhibited increased apoptosis and enlarged cell size. Both M1 and M2 phenotypes in Tsc1-deficient macrophages were elevated in steady-state as well as in inflammatory conditions. Tsc1-deficient macrophages demonstrated impaired migration and reduced expression of chemokine receptors including CCR2 and CCR5. Phagocytosis activity and ROS production were enhanced in Tsc1-deficient macrophages. Furthermore, pharmacological inhibition of the mammalian target of rapamycin complex 1 (mTORC1 partially reversed the aberrance of Tsc1-deficient macrophages. Conclusion: Tsc1 plays a critical role in regulating macrophage survival, function and polarization via inhibition of mTORC1 activity.

The design and analysis of salmonid tagging studies in the Columbia Basin. Volume 2: Estimating salmonid survival with combined PIT-CWT tagging. Technical report

International Nuclear Information System (INIS)

Newman, K.

1997-06-01

Passive Integrated Transponder (PIT) tags and Coded Wire Tags (CWTs) in combination can provide information about salmonid survival that single tag releases may not. The release and recapture protocol affects which survival and recapture rates can be estimated and the precision of the estimates. For the particular case of Columbia river salmonids tagged with both PIT tags and CWTs, three different release and recapture protocols were evaluated. This report addresses the need to study the fate of salmon smolt in-river and their subsequent return as adults. Double-tagging procedures are investigated where PIT-tags would be used to provide in-river survival data during smolt outmigrations and coded-wire tags (CWT) used to provide adult return information. This report provides statistical models for the analysis of the joint data as well as recommendations on optimal tagging studies. Study costs and stress on smolt can be reduced by only PIT-tagging a subset of all the fish coded-wire-tagged, while retaining the information content and sampling precision

Surviving endoplasmic reticulum stress is coupled to altered chondrocyte differentiation and function.

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Kwok Yeung Tsang

2007-03-01

Full Text Available In protein folding and secretion disorders, activation of endoplasmic reticulum (ER stress signaling (ERSS protects cells, alleviating stress that would otherwise trigger apoptosis. Whether the stress-surviving cells resume normal function is not known. We studied the in vivo impact of ER stress in terminally differentiating hypertrophic chondrocytes (HCs during endochondral bone formation. In transgenic mice expressing mutant collagen X as a consequence of a 13-base pair deletion in Col10a1 (13del, misfolded alpha1(X chains accumulate in HCs and elicit ERSS. Histological and gene expression analyses showed that these chondrocytes survived ER stress, but terminal differentiation is interrupted, and endochondral bone formation is delayed, producing a chondrodysplasia phenotype. This altered differentiation involves cell-cycle re-entry, the re-expression of genes characteristic of a prehypertrophic-like state, and is cell-autonomous. Concomitantly, expression of Col10a1 and 13del mRNAs are reduced, and ER stress is alleviated. ERSS, abnormal chondrocyte differentiation, and altered growth plate architecture also occur in mice expressing mutant collagen II and aggrecan. Alteration of the differentiation program in chondrocytes expressing unfolded or misfolded proteins may be part of an adaptive response that facilitates survival and recovery from the ensuing ER stress. However, the altered differentiation disrupts the highly coordinated events of endochondral ossification culminating in chondrodysplasia.

The effect of heat on Na+/H+ antiport function and survival in mammalian cells

International Nuclear Information System (INIS)

Liu, F.-F.; Diep, Kim; Tannock, Ian F.; Hill, Richard P.

1996-01-01

Purpose: Because intracellular pH (pH i ) is a determinant of thermosensitivity, it is important to understand the relationship between heat cytotoxicity and the mechanisms responsible for pH i regulation, such as the Na + /H + antiport. The objective of this study is to elucidate the relationship between heat damage and Na + /H + antiport activity. Methods and Materials: Various cell lines, EMT6, RIF-1, and its thermoresistant variant TR-4, and CCL39, and its variant that lacks the Na + /H + antiport (PS120), were all heated using a water bath. Parallel assessments of antiport function and pH i were made using the fluorescent dye 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF). Results: Exposure of EMT6 cells to 43-46 deg. C for 30-60 min caused progressive decline in antiport activity, in parallel with cytotoxicity. When the same degree of cytotoxicity was induced by ionizing radiation, no alteration in Na + /H + antiport function was observed. Despite a 10-fold lower survival in RIF-1 compared to TR-4 cells after heating, there was no difference in the thermosensitivity of their antiports. Antiport activity in the TR-4 cells, however, was higher than that of RIF-1 cells both before and during heating. Intracellular pH for TR-4 cells decreased minimally during heating, in contrast to a decline of 1 pH unit in RIF-1 cells despite similar relative levels of antiport activity, suggesting that in this pair of cell lines, antiport activity does not play a major pH i regulatory role. PS120 and CCL39 cells had similar survival levels when heated at pH e 7.2 in the presence of NaHCO 3 , which allows function of the other major regulator of pH i , the Na + -dependent HCO 3 - /Cl - exchanger. This occurred despite a drop in pH i in the PS120 cells during heating. A reduced survival was observed, however, in PS120 cells after 43 deg. C for 30-60 min at either pH e 6.5 or pH e 7.2 in the absence of NaHCO 3 . Intracellular pH for both lines decreased with increasing

Modified Weighted Kaplan-Meier Estimator

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Mohammad Shafiq

2007-01-01

Full Text Available In many medical studies majority of the study subjects do not reach to the event of interest during the study period. In such situations survival probabilities can be estimated for censored observation by Kaplan Meier estimator. However in case of heavy censoring these estimates are biased and over estimate the survival probabilities. For heavy censoring a new method was proposed (Bahrawar Jan, 2005 to estimate the survival probabilities by weighting the censored observations by non-censoring rate. But the main defect in this weighted method is that it gives zero weight to the last censored observation. To over come this difficulty a new weight is proposed which also gives a non-zero weight to the last censored observation.

On Estimation of the CES Production Function - Revisited

DEFF Research Database (Denmark)

Henningsen, Arne; Henningsen, Geraldine

2012-01-01

Estimation of the non-linear Constant Elasticity of Scale (CES) function is generally considered problematic due to convergence problems and unstable and/or meaningless results. These problems often arise from a non-smooth objective function with large flat areas, the discontinuity of the CES...... function where the elasticity of substitution is one, and possibly significant rounding errors where the elasticity of substitution is close to one. We suggest three (combinable) solutions that alleviate these problems and improve the reliability and stability of the results....

Survival curves for irradiated cells

International Nuclear Information System (INIS)

Gibson, D.K.

1975-01-01

The subject of the lecture is the probability of survival of biological cells which have been subjected to ionising radiation. The basic mathematical theories of cell survival as a function of radiation dose are developed. A brief comparison with observed survival curves is made. (author)

Estimation of a monotone percentile residual life function under random censorship.

Science.gov (United States)

Franco-Pereira, Alba M; de Uña-Álvarez, Jacobo

2013-01-01

In this paper, we introduce a new estimator of a percentile residual life function with censored data under a monotonicity constraint. Specifically, it is assumed that the percentile residual life is a decreasing function. This assumption is useful when estimating the percentile residual life of units, which degenerate with age. We establish a law of the iterated logarithm for the proposed estimator, and its n-equivalence to the unrestricted estimator. The asymptotic normal distribution of the estimator and its strong approximation to a Gaussian process are also established. We investigate the finite sample performance of the monotone estimator in an extensive simulation study. Finally, data from a clinical trial in primary biliary cirrhosis of the liver are analyzed with the proposed methods. One of the conclusions of our work is that the restricted estimator may be much more efficient than the unrestricted one. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Insights from Machine Learning for Evaluating Production Function Estimators on Manufacturing Survey Data

OpenAIRE

Arreola, José Luis Preciado; Johnson, Andrew L.

2016-01-01

Organizations like census bureaus rely on non-exhaustive surveys to estimate industry population-level production functions. In this paper we propose selecting an estimator based on a weighting of its in-sample and predictive performance on actual application datasets. We compare Cobb-Douglas functional assumptions to existing nonparametric shape constrained estimators and a newly proposed estimated presented in this paper. For simulated data, we find that our proposed estimator has the lowes...

Bias Errors due to Leakage Effects When Estimating Frequency Response Functions

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Andreas Josefsson

2012-01-01

Full Text Available Frequency response functions are often utilized to characterize a system's dynamic response. For a wide range of engineering applications, it is desirable to determine frequency response functions for a system under stochastic excitation. In practice, the measurement data is contaminated by noise and some form of averaging is needed in order to obtain a consistent estimator. With Welch's method, the discrete Fourier transform is used and the data is segmented into smaller blocks so that averaging can be performed when estimating the spectrum. However, this segmentation introduces leakage effects. As a result, the estimated frequency response function suffers from both systematic (bias and random errors due to leakage. In this paper the bias error in the H1 and H2-estimate is studied and a new method is proposed to derive an approximate expression for the relative bias error at the resonance frequency with different window functions. The method is based on using a sum of real exponentials to describe the window's deterministic autocorrelation function. Simple expressions are derived for a rectangular window and a Hanning window. The theoretical expressions are verified with numerical simulations and a very good agreement is found between the results from the proposed bias expressions and the empirical results.

Clinical use of estimated glomerular filtration rate for evaluation of kidney function

DEFF Research Database (Denmark)

Broberg, Bo; Lindhardt, Morten; Rossing, Peter

2013-01-01

is a significant predictor for cardiovascular disease and may along with classical cardiovascular risk factors add useful information to risk estimation. Several cautions need to be taken into account, e.g. rapid changes in kidney function, dialysis, high age, obesity, underweight and diverging and unanticipated......Estimating glomerular filtration rate by the Modification of Diet in Renal Disease or Chronic Kidney Disease Epidemiology Collaboration formulas gives a reasonable estimate of kidney function for e.g. classification of chronic kidney disease. Additionally the estimated glomerular filtration rate...

Poor survival of treatment-related acute nonlymphocytic leukemia

International Nuclear Information System (INIS)

Neugut, A.I.; Nieves, J.; Murray, T.; Tsai, Weiyann; Robinson, E.

1990-01-01

Population-based data on more than 1 million patients registered in the Surveillance, Epidemiology, and End-Results Program of the National Cancer Institute, 1973-1984, were analyzed to determine the survival of patients with de novo acute nonlymphocytic leukemia (ANLL) and following a first primary tumor treated (with chemotherapy and/or radiation therapy) or untreated. Cases that occurred within 12 months of the first malignant neoplasm were excluded. Survival was estimated using Cox proportional-hazards modeling, with age, sex, and specific type of ANLL as covariates. The 6,271 patients with de novo ANLL had an estimated 12-month survival of 30%, while the 107 patients with treatment-related ANLL had an estimated 12-month survival of 10%. The authors conclude that ANLL that occurs after chemotherapy or radiation therapy is biologically more aggressive and/or resistant to therapy than spontaneous ANLL. This provides a rationale for current studies on treatment-induced cellular changes and on more aggressive therapy for these patients

Plasma Levels of Middle Molecules to Estimate Residual Kidney Function in Haemodialysis without Urine Collection.

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Enric Vilar

Full Text Available Residual Kidney Function (RKF is associated with survival benefits in haemodialysis (HD but is difficult to measure without urine collection. Middle molecules such as Cystatin C and β2-microglobulin accumulate in renal disease and plasma levels have been used to estimate kidney function early in this condition. We investigated their use to estimate RKF in patients on HD.Cystatin C, β2-microglobulin, urea and creatinine levels were studied in patients on incremental high-flux HD or hemodiafiltration(HDF. Over sequential HD sessions, blood was sampled pre- and post-session 1 and pre-session 2, for estimation of these parameters. Urine was collected during the whole interdialytic interval, for estimation of residual GFR (GFRResidual = mean of urea and creatinine clearance. The relationships of plasma Cystatin C and β2-microglobulin levels to GFRResidual and urea clearance were determined.Of the 341 patients studied, 64% had urine output>100 ml/day, 32.6% were on high-flux HD and 67.4% on HDF. Parameters most closely correlated with GFRResidual were 1/β2-micoglobulin (r2 0.67 and 1/Cystatin C (r2 0.50. Both these relationships were weaker at low GFRResidual. The best regression model for GFRResidual, explaining 67% of the variation, was: GFRResidual = 160.3 · (1/β2m - 4.2. Where β2m is the pre-dialysis β2 microglobulin concentration (mg/L. This model was validated in a separate cohort of 50 patients using Bland-Altman analysis. Areas under the curve in Receiver Operating Characteristic analysis aimed at identifying subjects with urea clearance≥2 ml/min/1.73 m2 was 0.91 for β2-microglobulin and 0.86 for Cystatin C. A plasma β2-microglobulin cut-off of ≤19.2 mg/L allowed identification of patients with urea clearance ≥2 ml/min/1.73 m2 with 90% specificity and 65% sensitivity.Plasma pre-dialysis β2-microglobulin levels can provide estimates of RKF which may have clinical utility and appear superior to cystatin C. Use of cut-off levels

Myocardial contractile function in survived neonatal piglets after cardiopulmonary bypass

Directory of Open Access Journals (Sweden)

Popov Aron-Frederik

2010-11-01

Full Text Available Abstract Background Hemodynamic function may be depressed in the early postoperative stages after cardiac surgery. The aim of this study was the analysis of the myocardial contractility in neonates after cardiopulmonary bypass (CPB and mild hypothermia. Methods Three indices of left ventricular myocardial contractile function (dP/dt, (dP/dt/P, and wall thickening were studied up to 6 hours after CPB in neonatal piglets (CPB group; n = 4. The contractility data were analysed and then compared to the data of newborn piglets who also underwent median thoracotomy and instrumentation for the same time intervals but without CPB (non-CPB group; n = 3. Results Left ventricular dP/dtmax and (dP/dtmax/P remained stable in CPB group, while dP/dtmax decreased in non-CPB group 5 hours postoperatively (1761 ± 205 mmHg/s at baseline vs. 1170 ± 205 mmHg/s after 5 h; p max and (dP/dtmax/P there were no statistically significant differences between the two groups. Comparably, although myocardial thickening decreased in the non-CPB group the differences between the two groups were not statistically significant. Conclusions The myocardial contractile function in survived neonatal piglets remained stable 6 hours after cardiopulmonary bypass and mild hypothermia probably due to regional hypercontractility.

Conical square function estimates in UMD Banach spaces and applications to H?-functional calculi

NARCIS (Netherlands)

Hytönen, T.; Van Neerven, J.; Portal, P.

2008-01-01

We study conical square function estimates for Banach-valued functions and introduce a vector-valued analogue of the Coifman-Meyer-Stein tent spaces. Following recent work of Auscher-M(c)Intosh-Russ, the tent spaces in turn are used to construct a scale of vector-valued Hardy spaces associated with

Coefficient Estimate Problem for a New Subclass of Biunivalent Functions

OpenAIRE

N. Magesh; T. Rosy; S. Varma

2013-01-01

We introduce a unified subclass of the function class Σ of biunivalent functions defined in the open unit disc. Furthermore, we find estimates on the coefficients |a2| and |a3| for functions in this subclass. In addition, many relevant connections with known or new results are pointed out.

Predicting long-term graft survival in adult kidney transplant recipients

Directory of Open Access Journals (Sweden)

Brett W Pinsky

2012-01-01

Full Text Available The ability to accurately predict a population′s long-term survival has important implications for quantifying the benefits of transplantation. To identify a model that can accurately predict a kidney transplant population′s long-term graft survival, we retrospectively studied the United Network of Organ Sharing data from 13,111 kidney-only transplants completed in 1988- 1989. Nineteen-year death-censored graft survival (DCGS projections were calculated and com-pared with the population′s actual graft survival. The projection curves were created using a two-part estimation model that (1 fits a Kaplan-Meier survival curve immediately after transplant (Part A and (2 uses truncated observational data to model a survival function for long-term projection (Part B. Projection curves were examined using varying amounts of time to fit both parts of the model. The accuracy of the projection curve was determined by examining whether predicted sur-vival fell within the 95% confidence interval for the 19-year Kaplan-Meier survival, and the sample size needed to detect the difference in projected versus observed survival in a clinical trial. The 19-year DCGS was 40.7% (39.8-41.6%. Excellent predictability (41.3% can be achieved when Part A is fit for three years and Part B is projected using two additional years of data. Using less than five total years of data tended to overestimate the population′s long-term survival, accurate prediction of long-term DCGS is possible, but requires attention to the quantity data used in the projection method.

Prognostic factors in metastatic spinal cord compression: a prospective study using multivariate analysis of variables influencing survival and gait function in 153 patients

International Nuclear Information System (INIS)

Helweg-Larsen, Susanne; Soerensen, Per Soelberg; Kreiner, Svend

2000-01-01

Purpose: Based on a very large patient cohort followed prospectively for at least a year or until death, we analyzed the prognostic significance of various clinical and radiological variables on posttreatment ambulatory function and survival. Methods and Materials: During a 3((1)/(2))-year period we prospectively included 153 consecutive patients with a diagnosis of spinal cord compression due to metastatic disease. The patients were followed with regular neurological examinations by the same neurologist for a minimum period of 11 months or until death. The prognostic significance of five variables on gait function and survival time after treatment was analyzed. Results: The type of the primary tumor had a direct influence on the interval between the diagnosis of the primary malignancy and the occurrence of spinal cord compression (p < 0.0005), and on the ambulatory function at time of diagnosis (p = 0.016). There was a clear correlation between the degree of myelographic blockage and gait function (p = 0.000) and between gait function and sensory disturbances (p = 0.000). The final gait was dependent on the gait function at time of diagnosis (p < 0.0005). Survival time after diagnosis depended directly on the time from primary tumor diagnosis until spinal cord compression (p = 0.002), on the ambulatory function at the time of diagnosis (p = 0.018), and on the ambulatory function after treatment. Conclusions: The pretreatment ambulatory function is the main determinant for posttreatment gait function. Survival time is rather short, especially in nonambulatory patients, and can only be improved by restoration of gait function in nonambulatory patients by immediate treatment

The regulation of function, growth and survival of GLP-1-producing L-cells

DEFF Research Database (Denmark)

Kuhre, Rune Ehrenreich; Holst, Jens Juul; Kappe, Camilla

2016-01-01

that regulate the growth, survival and function of these cells are largely unknown. We recently showed that prolonged exposure to high concentrations of the fatty acid palmitate induced lipotoxic effects, similar to those operative in insulin-producing cells, in an in vitro model of GLP-1-producing cells...... absorption and disposal, as well as cell proliferation and survival. In Type 2 Diabetes (T2D) reduced plasma levels of GLP-1 have been observed, and plasma levels of GLP-1, as well as reduced numbers of GLP-1 producing cells, have been correlated to obesity and insulin resistance. Increasing endogenous...... secretion of GLP-1 by selective targeting of the molecular mechanisms regulating secretion from the L-cell has been the focus of much recent research. An additional and promising strategy for enhancing endogenous secretion may be to increase the L-cell mass in the intestinal epithelium, but the mechanisms...

Estimation and Application of Ecological Memory Functions in Time and Space

Science.gov (United States)

Itter, M.; Finley, A. O.; Dawson, A.

2017-12-01

A common goal in quantitative ecology is the estimation or prediction of ecological processes as a function of explanatory variables (or covariates). Frequently, the ecological process of interest and associated covariates vary in time, space, or both. Theory indicates many ecological processes exhibit memory to local, past conditions. Despite such theoretical understanding, few methods exist to integrate observations from the recent past or within a local neighborhood as drivers of these processes. We build upon recent methodological advances in ecology and spatial statistics to develop a Bayesian hierarchical framework to estimate so-called ecological memory functions; that is, weight-generating functions that specify the relative importance of local, past covariate observations to ecological processes. Memory functions are estimated using a set of basis functions in time and/or space, allowing for flexible ecological memory based on a reduced set of parameters. Ecological memory functions are entirely data driven under the Bayesian hierarchical framework—no a priori assumptions are made regarding functional forms. Memory function uncertainty follows directly from posterior distributions for model parameters allowing for tractable propagation of error to predictions of ecological processes. We apply the model framework to simulated spatio-temporal datasets generated using memory functions of varying complexity. The framework is also applied to estimate the ecological memory of annual boreal forest growth to local, past water availability. Consistent with ecological understanding of boreal forest growth dynamics, memory to past water availability peaks in the year previous to growth and slowly decays to zero in five to eight years. The Bayesian hierarchical framework has applicability to a broad range of ecosystems and processes allowing for increased understanding of ecosystem responses to local and past conditions and improved prediction of ecological

The Influence of Tag Presence on the Mortality of Juvenile Chinook Salmon Exposed to Simulated Hydroturbine Passage: Implications for Survival Estimates and Management of Hydroelectric Facilities

Energy Technology Data Exchange (ETDEWEB)

Carlson, Thomas J.; Brown, Richard S.; Stephenson, John R.; Pflugrath, Brett D.; Colotelo, Alison HA; Gingerich, Andrew J.; Benjamin, Piper L.; Langeslay, Mike; Ahmann, Martin L.; Johnson, Robert L.; Skalski, John R.; Seaburg, Adam; Townsend, Richard L.

2012-05-01

Each year, millions of fish have telemetry tags (acoustic, radio, inductive) surgically implanted to assess their passage and survival through hydropower facilities. One route of passage of particular concern is through hydro turbines, in which fish may be exposed to a range of potential injuries, including barotraumas from rapid decompression. The change in pressure from acclimation to exposure (nadir) has been found to be an important factor in predicting the likelihood of mortality and injury for juvenile Chinook salmon undergoing rapid decompression associated with simulated turbine passage. The presence of telemetry tags has also been shown to influence the likelihood of injury and mortality for juvenile Chinook salmon. This research investigated the likelihood of mortality and injury for juvenile Chinook salmon carrying telemetry tags and exposed to a range of simulated turbine passage. Several factors were examined as predictors of mortal injury for fish undergoing rapid decompression, and the ratio of pressure change and tag burden were determined to be the most predictive factors. As the ratio of pressure change and tag burden increase, the likelihood of mortal injury also increases. The results of this study suggest that previous survival estimates of juvenile Chinook salmon passing through hydro turbines may have been biased due to the presence of telemetry tags, and this has direct implications to the management of hydroelectric facilities. Realistic examples indicate how the bias in turbine passage survival estimates could be 20% or higher, depending on the mass of the implanted tags and the ratio of acclimation to exposure pressures. Bias would increase as the tag burden and pressure ratio increase, and have direct implications on survival estimates. It is recommended that future survival studies use the smallest telemetry tags possible to minimize the potential bias that may be associated with carrying the tag.

Functional survival after acute care for severe head injury at a designated trauma center in Hong Kong

Directory of Open Access Journals (Sweden)

Benedict B.T. Taw

2012-07-01

Conclusion: Multidisciplinary neurorehabilitation service is an important component of comprehensive trauma care. Despite significant early mortalities, a proportion of severely head-injured patients who survive acute care may achieve good long-term functional recovery.

Physical training is beneficial to functional status and survival in patients with prolonged mechanical ventilation

Directory of Open Access Journals (Sweden)

Shiauyee Chen

2011-09-01

Conclusion: Six weeks physical therapy training plus 6 weeks unsupervised maintenance exercise enhanced functional levels and increased survival for the PMV patients compared with those with no such intervention. Early physical therapy interventions are needed for the PMV patients in respiratory care centers. [J Formos Med Assoc 2011; 110(X:XX–XX

Systematic review of survival time in experimental mouse stroke with impact on reliability of infarct estimation

DEFF Research Database (Denmark)

Klarskov, Carina Kirstine; Klarskov, Mikkel Buster; Hasseldam, Henrik

2016-01-01

infarcts with more substantial edema. Purpose: This paper will give an overview of previous studies of experimental mouse stroke, and correlate survival time to peak time of edema formation. Furthermore, investigations of whether the included studies corrected the infarct measurements for edema...... of reasons for the translational problems from mouse experimental stroke to clinical trials probably exists, including infarct size estimations around the peak time of edema formation. Furthermore, edema is a more prominent feature of stroke in mice than in humans, because of the tendency to produce larger...... of the investigated process. Our findings indicate a need for more research in this area, and establishment of common correction methodology....

Fusion probability and survivability in estimates of heaviest nuclei production

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Sagaidak Roman N.

2012-02-01

Full Text Available Production of the heavy and heaviest nuclei (from Po to the region of superheavy elements close to Z=114 and N=184 in fusion-evaporation reactions induced by heavy ions has been considered in a systematic way within the framework of the barrier-passing model coupled with the statistical model (SM of de-excitation of a compound nucleus (CN. Excitation functions for fission and evaporation residues (ER measured in very asymmetric combinations can be described rather well. One can scale and fix macroscopic (liquid-drop fission barriers for nuclei involved in the calculation of survivability with SM. In less asymmetric combinations, effects of fusion suppression caused by quasi-fission (QF are starting to appear in the entrance channel of reactions. QF effects could be semi-empirically taken into account using fusion probabilities deduced as the ratio of measured ER cross sections to the ones obtained in the assumption of absence of the fusion suppression in corresponding reactions. SM parameters (fission barriers obtained at the analysis of a very asymmetric combination leading to the production of (nearly the same CN should be used for this evaluation.

Survival of radio-marked mallard ducklings in northeastern California

Science.gov (United States)

Mauser, D.M.; Jarvis, R.L.; Gilmer, D.S.

1994-01-01

Estimates of duckling survival are necessary to accurately assess recruitment of mallards (Anas platyrhynchos), yet few reliable estimates exist. During 1988-90, we estimated survival rates for 127 radio-marked mallard ducklings from 64 broods on Lower Klamath National Wildlife Refuge, California. In 1988, we restricted the survival estimate to the first 10 days post-hatch (S = 0.18, SE = 0.07). Survival from hatching to 50 days was 0.37 (SE = 0.09) in 1989 and 0.34 (SE = 0.07) in 1990. Total brood loss differed among years (P < 0.05); 81.2% in 1988 (n = 16), 36.8% in 1989 (n = 19), and 37.5% in 1990 (n = 24). Ninety-three percent of mortality occurred during the first 10 days of life. We detected no differences in the proportion of radio-marked ducklings fledged from early-hatched versus late-hatched nests (P = 0.74). During 1989-90, 16 females appeared to lose their entire brood; however, 3 radio-marked ducklings from 2 of these broods were fledged by other brood hens. Of 29 radio-marked ducklings that reached 44 days of life, 6 (20.7%) joined other broods. Habitat enhancement is the key to improving duckling survival because the large number of predator species that consume ducklings makes predator control difficult.

Individual survival curves comparing subjective and observed mortality risks.

Science.gov (United States)

Bissonnette, Luc; Hurd, Michael D; Michaud, Pierre-Carl

2017-12-01

We compare individual survival curves constructed from objective (actual mortality) and elicited subjective information (probability of survival to a given target age). We develop a methodology to estimate jointly subjective and objective individual survival curves accounting for rounding on subjective reports of perceived survival. We make use of the long follow-up period in the Health and Retirement Study and the high quality of mortality data to estimate individual survival curves that feature both observed and unobserved heterogeneity. This allows us to compare objective and subjective estimates of remaining life expectancy for various groups and compare welfare effects of objective and subjective mortality risk using the life cycle model of consumption. We find that subjective and objective hazards are not the same. The median welfare loss from misperceptions of mortality risk when annuities are not available is 7% of current wealth at age 65 whereas more than 25% of respondents have losses larger than 60% of wealth. When annuities are available and exogenously given, the welfare loss is substantially lower. Copyright © 2017 John Wiley & Sons, Ltd.

Estimating the basilar-membrane input-output function in normal-hearing and hearing-impaired listeners

DEFF Research Database (Denmark)

Jepsen, Morten Løve; Dau, Torsten

To partly characterize the function of cochlear processing in humans, the basilar membrane (BM) input-output function can be estimated. In recent studies, forward masking has been used to estimate BM compression. If an on-frequency masker is processed compressively, while an off-frequency masker...... is transformed more linearly, the ratio between the slopes of growth of masking (GOM) functions provides an estimate of BM compression at the signal frequency. In this study, this paradigm is extended to also estimate the knee-point of the I/O-function between linear rocessing at low levels and compressive...... processing at medium levels. If a signal can be masked by a low-level on-frequency masker such that signal and masker fall in the linear region of the I/O-function, then a steeper GOM function is expected. The knee-point can then be estimated in the input level region where the GOM changes significantly...

Some aspects of the translog production function estimation

Directory of Open Access Journals (Sweden)

Florin-Marius PAVELESCU

2011-06-01

Full Text Available In a translog production function, the number of parameters practically öexplodesö as the number of considered production factors increases. Consequently, the shortcoming in the estimation of the respective production function is the occurrence of collinearity. Theoretically, the collinearity impact is minimum if a single production factor is taken into account. In this case, we can determine not only the output elasticity but also the elasticity of scale related to the respective production factor. In the present paper, we demonstrate that the relationship between the output elasticity and estimated average elasticity of scale depends on the dynamics trajectory of the production factor, underexponential and overexponential, respectively. At the end, a practical example is offered, dealing with the computation of the Gross Domestic Product elasticity and average elasticity of scale related to employed population in the United Kingdom and France during 1999-2009.

Relative effects of survival and reproduction on the population dynamics of emperor geese

Science.gov (United States)

Schmutz, Joel A.; Rockwell, Robert F.; Petersen, Margaret R.

1997-01-01

Populations of emperor geese (Chen canagica) in Alaska declined sometime between the mid-1960s and the mid-1980s and have increased little since. To promote recovery of this species to former levels, managers need to know how much their perturbations of survival and/or reproduction would affect population growth rate (λ). We constructed an individual-based population model to evaluate the relative effect of altering mean values of various survival and reproductive parameters on λ and fall age structure (AS, defined as the proportion of juv), assuming additive rather than compensatory relations among parameters. Altering survival of adults had markedly greater relative effects on λ than did equally proportionate changes in either juvenile survival or reproductive parameters. We found the opposite pattern for relative effects on AS. Due to concerns about bias in the initial parameter estimates used in our model, we used 5 additional sets of parameter estimates with this model structure. We found that estimates of survival based on aerial survey data gathered each fall resulted in models that corresponded more closely to independent estimates of λ than did models that used mark-recapture estimates of survival. This disparity suggests that mark-recapture estimates of survival are biased low. To further explore how parameter estimates affected estimates of λ, we used values of survival and reproduction found in other goose species, and we examined the effect of an hypothesized correlation between an individual's clutch size and the subsequent survival of her young. The rank order of parameters in their relative effects on λ was consistent for all 6 parameter sets we examined. The observed variation in relative effects on λ among the 6 parameter sets is indicative of how relative effects on λ may vary among goose populations. With this knowledge of the relative effects of survival and reproductive parameters on λ, managers can make more informed decisions about

Bayesian nonparametric inference on quantile residual life function: Application to breast cancer data.

Science.gov (United States)

Park, Taeyoung; Jeong, Jong-Hyeon; Lee, Jae Won

2012-08-15

There is often an interest in estimating a residual life function as a summary measure of survival data. For ease in presentation of the potential therapeutic effect of a new drug, investigators may summarize survival data in terms of the remaining life years of patients. Under heavy right censoring, however, some reasonably high quantiles (e.g., median) of a residual lifetime distribution cannot be always estimated via a popular nonparametric approach on the basis of the Kaplan-Meier estimator. To overcome the difficulties in dealing with heavily censored survival data, this paper develops a Bayesian nonparametric approach that takes advantage of a fully model-based but highly flexible probabilistic framework. We use a Dirichlet process mixture of Weibull distributions to avoid strong parametric assumptions on the unknown failure time distribution, making it possible to estimate any quantile residual life function under heavy censoring. Posterior computation through Markov chain Monte Carlo is straightforward and efficient because of conjugacy properties and partial collapse. We illustrate the proposed methods by using both simulated data and heavily censored survival data from a recent breast cancer clinical trial conducted by the National Surgical Adjuvant Breast and Bowel Project. Copyright © 2012 John Wiley & Sons, Ltd.

Characterization of Pediatric Acute Lymphoblastic Leukemia Survival Patterns by Age at Diagnosis

International Nuclear Information System (INIS)

Hossain, M. J.; Xie, L.; McCahan, S. M.; Hossain, M. J.

2014-01-01

Age at diagnosis is a key prognostic factor in pediatric acute lymphoblastic leukemia (ALL) survivorship. However, literature providing adequate assessment of the survival variability by age at diagnosis is scarce. The aim of this study is to assess the impact of this prognostic factor in pediatric ALL survival. We estimated incidence rate of mortality, 5-year survival rate, Kaplan-Meier survival function, and hazard ratio using the Surveillance Epidemiology and End Results (SEER) data during 1973-2009. There was significant variability in pediatric ALL survival by age at diagnosis. Survival peaked among children diagnosed at 1-4 years and steadily declined among those diagnosed at older ages. Infants (<1 year) had the lowest survivorship. In a multivariable Cox proportional hazard model stratified by year of diagnosis, those diagnosed in age groups 1-4, 5-9, 10-14, and 15-19 years were 82%, 75%, 57%, and 32% less likely to die compared to children diagnosed in infancy, respectively. Age at diagnosis remained to be a crucial determinant of the survival variability of pediatric ALL patients, after adjusting for sex, race, radiation therapy, primary tumor sites, immuno phenotype, and year of diagnosis. Further research is warranted to disentangle the effects of age-dependent biological and environmental processes on this association.

Data on empirically estimated corporate survival rate in Russia.

Science.gov (United States)

Kuzmin, Evgeny A

2018-02-01

The article presents data on the corporate survival rate in Russia in 1991-2014. The empirical survey was based on a random sample with the average number of non-repeated observations (number of companies) for the survey each year equal to 75,958 (24,236 minimum and 126,953 maximum). The actual limiting mean error ∆ p was 2.24% with 99% integrity. The survey methodology was based on a cross joining of various formal periods in the corporate life cycles (legal and business), which makes it possible to talk about a conventionally active time life of companies' existence with a number of assumptions. The empirical survey values were grouped by Russian regions and industries according to the classifier and consolidated into a single database for analysing the corporate life cycle and their survival rate and searching for deviation dependencies in calculated parameters. Preliminary and incomplete figures were available in the paper entitled "Survival Rate and Lifecycle in Terms of Uncertainty: Review of Companies from Russia and Eastern Europe" (Kuzmin and Guseva, 2016) [3]. The further survey led to filtered processed data with clerical errors excluded. These particular values are available in the article. The survey intended to fill a fact-based gap in various fundamental surveys that involved matters of the corporate life cycle in Russia within the insufficient statistical framework. The data are of interest for an analysis of Russian entrepreneurship, assessment of the market development and incorporation risks in the current business environment. A further heuristic potential is achievable through an ability of forecasted changes in business demography and model building based on the representative data set.

On approximation and energy estimates for delta 6-convex functions.

Science.gov (United States)

Saleem, Muhammad Shoaib; Pečarić, Josip; Rehman, Nasir; Khan, Muhammad Wahab; Zahoor, Muhammad Sajid

2018-01-01

The smooth approximation and weighted energy estimates for delta 6-convex functions are derived in this research. Moreover, we conclude that if 6-convex functions are closed in uniform norm, then their third derivatives are closed in weighted [Formula: see text]-norm.

Anti-inflammatory thalidomide improves islet grafts survival and functions in a xenogenic environment.

Directory of Open Access Journals (Sweden)

Chunguang Chen

Full Text Available Thalidomide possesses both anti-inflammatory and anti-angiogenic properties. This study investigates its potential application in islet transplantation with a xenogenic transplantation model. Transplantation was performed using C57Bl/6 mice and NMRI nu/nu mice as recipients of porcine islets. Moreover, islet graft vasculature and inflammation were investigated to identify the mechanisms of thalidomide action. In the immunocompetent environment of C57Bl/6 mice, a fast graft rejection was observed. The group treated with thalidomide 200 mg/kg BW per day achieved and maintained euglycemia in the complete observation period for 42 days. The treated mice had more functional islet graft mass with less leukocyte infiltration. The pro-inflammatory TNF-alpha and VEGF content in islet grafted kidneys was significantly lowered by the treatment. By comparison, thalidomide was not effective in improving graft survival in immunocompromised nude mice. It strongly inhibited the VEGF and TNF-alpha-induced endothelial proliferation of isolated pig islets in a dose dependent manner. The magnitude of thalidomide's inhibitory effect was nearly identical to the effect of VEGF- receptor 2 inhibitor SU416 and anti-TNF-receptor 1 neutralizing antibody, and was reversed by sphingosine-1-phosphate. In conclusion, the anti-inflammatory effect of thalidomide improved islet graft survival and function in a transplantation model with a maximum immune barrier.

Predicting Structure-Function Relations and Survival following Surgical and Bronchoscopic Lung Volume Reduction Treatment of Emphysema.

Science.gov (United States)

Mondoñedo, Jarred R; Suki, Béla

2017-02-01

Lung volume reduction surgery (LVRS) and bronchoscopic lung volume reduction (bLVR) are palliative treatments aimed at reducing hyperinflation in advanced emphysema. Previous work has evaluated functional improvements and survival advantage for these techniques, although their effects on the micromechanical environment in the lung have yet to be determined. Here, we introduce a computational model to simulate a force-based destruction of elastic networks representing emphysema progression, which we use to track the response to lung volume reduction via LVRS and bLVR. We find that (1) LVRS efficacy can be predicted based on pre-surgical network structure; (2) macroscopic functional improvements following bLVR are related to microscopic changes in mechanical force heterogeneity; and (3) both techniques improve aspects of survival and quality of life influenced by lung compliance, albeit while accelerating disease progression. Our model predictions yield unique insights into the microscopic origins underlying emphysema progression before and after lung volume reduction.

Androgen receptor agonists increase lean mass, improve cardiopulmonary functions and extend survival in preclinical models of Duchenne muscular dystrophy.

Science.gov (United States)

Ponnusamy, Suriyan; Sullivan, Ryan D; You, Dahui; Zafar, Nadeem; He Yang, Chuan; Thiyagarajan, Thirumagal; Johnson, Daniel L; Barrett, Maron L; Koehler, Nikki J; Star, Mayra; Stephenson, Erin J; Bridges, Dave; Cormier, Stephania A; Pfeffer, Lawrence M; Narayanan, Ramesh

2017-07-01

Duchenne muscular dystrophy (DMD) is a neuromuscular disease that predominantly affects boys as a result of mutation(s) in the dystrophin gene. DMD is characterized by musculoskeletal and cardiopulmonary complications, resulting in shorter life-span. Boys afflicted by DMD typically exhibit symptoms within 3-5 years of age and declining physical functions before attaining puberty. We hypothesized that rapidly deteriorating health of pre-pubertal boys with DMD could be due to diminished anabolic actions of androgens in muscle, and that intervention with an androgen receptor (AR) agonist will reverse musculoskeletal complications and extend survival. While castration of dystrophin and utrophin double mutant (mdx-dm) mice to mimic pre-pubertal nadir androgen condition resulted in premature death, maintenance of androgen levels extended the survival. Non-steroidal selective-AR modulator, GTx-026, which selectively builds muscle and bone was tested in X-linked muscular dystrophy mice (mdx). GTx-026 significantly increased body weight, lean mass and grip strength by 60-80% over vehicle-treated mdx mice. While vehicle-treated castrated mdx mice exhibited cardiopulmonary impairment and fibrosis of heart and lungs, GTx-026 returned cardiopulmonary function and intensity of fibrosis to healthy control levels. GTx-026 elicits its musculoskeletal effects through pathways that are distinct from dystrophin-regulated pathways, making AR agonists ideal candidates for combination approaches. While castration of mdx-dm mice resulted in weaker muscle and shorter survival, GTx-026 treatment increased the muscle mass, function and survival, indicating that androgens are important for extended survival. These preclinical results support the importance of androgens and the need for intervention with AR agonists to treat DMD-affected boys. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The design and analysis of salmonid tagging studies in the Columbia basin. Volume 8: A new model for estimating survival probabilities and residualization from a release-recapture study of fall chinook salmon (Oncorhynchus tschawytscha) smolts in the Snake River

International Nuclear Information System (INIS)

Lowther, A.B.; Skalski, J.

1997-09-01

Standard release-recapture analysis using Cormack-Jolly-Seber (CJS) models to estimate survival probabilities between hydroelectric facilities for Snake river fall chinook salmon (Oncorhynchus tschawytscha) ignore the possibility of individual fish residualizing and completing their migration in the year following tagging. These models do not utilize available capture history data from this second year and, thus, produce negatively biased estimates of survival probabilities. A new multinomial likelihood model was developed that results in biologically relevant, unbiased estimates of survival probabilities using the full two years of capture history data. This model was applied to 1995 Snake River fall chinook hatchery releases to estimate the true survival probability from one of three upstream release points (Asotin, Billy Creek, and Pittsburgh Landing) to Lower Granite Dam. In the data analyzed here, residualization is not a common physiological response and thus the use of CJS models did not result in appreciably different results than the true survival probability obtained using the new multinomial likelihood model

Functional Mixed Effects Model for Small Area Estimation.

Science.gov (United States)

Maiti, Tapabrata; Sinha, Samiran; Zhong, Ping-Shou

2016-09-01

Functional data analysis has become an important area of research due to its ability of handling high dimensional and complex data structures. However, the development is limited in the context of linear mixed effect models, and in particular, for small area estimation. The linear mixed effect models are the backbone of small area estimation. In this article, we consider area level data, and fit a varying coefficient linear mixed effect model where the varying coefficients are semi-parametrically modeled via B-splines. We propose a method of estimating the fixed effect parameters and consider prediction of random effects that can be implemented using a standard software. For measuring prediction uncertainties, we derive an analytical expression for the mean squared errors, and propose a method of estimating the mean squared errors. The procedure is illustrated via a real data example, and operating characteristics of the method are judged using finite sample simulation studies.

Factors related to respiration influencing survival and respiratory function in patients with amyotrophic lateral sclerosis: a retrospective study.

Science.gov (United States)

Leonardis, L; Dolenc Grošelj, L; Vidmar, G

2012-12-01

Various breathing abnormalities (Neurology 2009; 73: 1218) have been proposed as indicators for the introduction of non-invasive positive-pressure ventilation (NIV) in patients with amyotrophic lateral sclerosis (ALS). We were interested in the usefulness of symptoms of respiratory insufficiency and abnormal results of daytime arterial gas analyses (AGA) as predictors of survival and the effect of NIV on respiratory volumes and pressures. Reported symptoms, respiratory subscore of the ALS Functional Rating Scale (ALSFRS-r), Norris scale (Norris-r), and AGA were retrospectively analyzed in 189 ALS patients. Longitudinal follow-up of forced vital capacity (FVC), maximal inspiratory and expiratory pressure (MIP, MEP), and sniff nasal pressure (SNP) were analyzed with regard to the introduction of NIV. Respiratory symptoms were a bad prognostic sign (P = 0.007). Abnormalities in Norris-r, ALSFRS-r, pO(2), pCO(2), and oxygen saturation tended to be associated with a shorter survival, although they were not statistically significant. NIV prolonged survival and reduced the decline in FVC (P = 0.007), MIP, MEP, and SNP (the last three were not statistically significant). Symptoms, abnormal FVC, and AGA do not always coincide, and they can appear in a different sequence. Any respiratory abnormality should prompt the clinician to start discussing NIV with the patient. NIV prolongs survival and improves respiratory function. © 2012 The Author(s) European Journal of Neurology © 2012 EFNS.

Estimated conditional score function for missing mechanism model with nonignorable nonresponse

Institute of Scientific and Technical Information of China (English)

CUI Xia; ZHOU Yong

2017-01-01

Missing data mechanism often depends on the values of the responses,which leads to nonignorable nonresponses.In such a situation,inference based on approaches that ignore the missing data mechanism could not be valid.A crucial step is to model the nature of missingness.We specify a parametric model for missingness mechanism,and then propose a conditional score function approach for estimation.This approach imputes the score function by taking the conditional expectation of the score function for the missing data given the available information.Inference procedure is then followed by replacing unknown terms with the related nonparametric estimators based on the observed data.The proposed score function does not suffer from the non-identifiability problem,and the proposed estimator is shown to be consistent and asymptotically normal.We also construct a confidence region for the parameter of interest using empirical likelihood method.Simulation studies demonstrate that the proposed inference procedure performs well in many settings.We apply the proposed method to a data set from research in a growth hormone and exercise intervention study.

Design and Analysis of Salmonid Tagging Studies in the Columbia Basin : Evaluating Wetland Restoration Projects in the Columbia River Estuary using Hydroacoustic Telemetry Arrays to Estimate Movement, Survival, and Residence Times of Juvenile Salmonids, Volume XXII (22).

Energy Technology Data Exchange (ETDEWEB)

Perry, Russell W.; Skalski, John R.

2008-08-01

Wetlands in the Columbia River estuary are actively being restored by reconnecting these habitats to the estuary, making more wetland habitats available to rearing and migrating juvenile salmon. Concurrently, thousands of acoustically tagged juvenile salmonids are released into the Columbia River to estimate their survival as they migrate through the estuary. Here, we develop a release-recapture model that makes use of these tagged fish to measure the success of wetland restoration projects in terms of their contribution to populations of juvenile salmon. Specifically, our model estimates the fraction of the population that enter the wetland, survival within the wetland, and the mean residence time of fish within the wetland. Furthermore, survival in mainstem Columbia River downstream of the wetland can be compared between fish that remained the mainstem and entered the wetland. These conditional survival estimates provide a means of testing whether the wetland improves the subsequent survival of juvenile salmon by fostering growth or improving their condition. Implementing such a study requires little additional cost because it takes advantage of fish already released to estimate survival through the estuary. Thus, such a study extracts the maximum information at minimum cost from research projects that typically cost millions of dollars annually.

Fledgling survival increases with development time and adult survival across north and south temperate zones

Science.gov (United States)

Lloyd, Penn; Martin, Thomas E.

2016-01-01

Slow life histories are characterized by high adult survival and few offspring, which are thought to allow increased investment per offspring to increase juvenile survival. Consistent with this pattern, south temperate zone birds are commonly longer-lived and have fewer young than north temperate zone species. However, comparative analyses of juvenile survival, including during the first few weeks of the post-fledging period when most juvenile mortality occurs, are largely lacking. We combined our measurements of fledgling survival for eight passerines in South Africa with estimates from published studies of 57 north and south temperate zone songbird species to test three predictions: (1) fledgling survival increases with length of development time in the nest; (2) fledgling survival increases with adult survival and reduced brood size controlled for development time; and (3) south temperate zone species, with their higher adult survival and smaller brood sizes, exhibit higher fledgling survival than north temperate zone species controlled for development time. We found that fledgling survival was higher among south temperate zone species and generally increased with development time and adult survival within and between latitudinal regions. Clutch size did not explain additional variation, but was confounded with adult survival. Given the importance of age-specific mortality to life history evolution, understanding the causes of these geographical patterns of mortality is important.

Estimating cost-effectiveness of mass cardiopulmonary resuscitation training strategies to improve survival from cardiac arrest in private locations.

Science.gov (United States)

Swor, Robert; Compton, Scott

2004-01-01

Most cardiopulmonary resuscitation (CPR) trainees are young, and most cardiac arrests occur in private residences witnessed by older individuals. To estimate the cost-effectiveness of a CPR training program targeted at citizens over the age of 50 years compared with that of current nontargeted public CPR training. A model was developed using cardiac arrest and known demographic data from a single suburban zip code (population 36,325) including: local data (1997-1999) regarding cardiac arrest locations (public vs. private); incremental survival with CPR (historical survival rate 7.8%, adjusted odds ratio for CPR 2.0); arrest bystander demographics obtained from bystander telephone interviews; zip code demographics regarding population age and distribution; and 12.50 dollars per student for the cost of CPR training. Published rates of CPR training programs by age were used to estimate the numbers typically trained. Several assumptions were made: 1) there would be one bystander per. arrest; 2) the bystander would always perform CPR if trained; 3) cardiac arrest would be evenly distributed in the population; and 4) CPR training for a proportion of the population would proportionally increase CPR provision. Rates of arrest, bystanders by age, number of CPR trainees needed to result in increased arrest survival, and training cost per life saved for a one-year study period were calculated. There were 24.3 cardiac arrests per year, with 21.9 (90%) occurring in homes. In 66.5% of the home arrests, the bystander was more than 50 years old. To yield one additional survivor using the current CPR training strategy, 12,306 people needed to be trained (3,510 bystanders aged 50 years), which resulted in CPR provision to 7.14 additional patients. The training cost per life saved for a bystander aged 50 years was 785,040 dollars. Using a strategy of training only those cost of 53,383 dollars per life saved. Using these assumptions, current CPR training strategy is not a cost

Evaluating the Impact of Zimbabwe's Prevention of Mother-to-Child HIV Transmission Program: Population-Level Estimates of HIV-Free Infant Survival Pre-Option A.

Science.gov (United States)

Buzdugan, Raluca; McCoy, Sandra I; Watadzaushe, Constancia; Kang Dufour, Mi-Suk; Petersen, Maya; Dirawo, Jeffrey; Mushavi, Angela; Mujuru, Hilda Angela; Mahomva, Agnes; Musarandega, Reuben; Hakobyan, Anna; Mugurungi, Owen; Cowan, Frances M; Padian, Nancy S

2015-01-01

We estimated HIV-free infant survival and mother-to-child HIV transmission (MTCT) rates in Zimbabwe, some of the first community-based estimates from a UNAIDS priority country. In 2012 we surveyed mother-infant pairs residing in the catchment areas of 157 health facilities randomly selected from 5 of 10 provinces in Zimbabwe. Enrolled infants were born 9-18 months before the survey. We collected questionnaires, blood samples for HIV testing, and verbal autopsies for deceased mothers/infants. Estimates were assessed among i) all HIV-exposed infants, as part of an impact evaluation of Option A of the 2010 WHO guidelines (rolled out in Zimbabwe in 2011), and ii) the subgroup of infants unexposed to Option A. We compared province-level MTCT rates measured among women in the community with MTCT rates measured using program monitoring data from facilities serving those communities. Among 8568 women with known HIV serostatus, 1107 (12.9%) were HIV-infected. Among all HIV-exposed infants, HIV-free infant survival was 90.9% (95% confidence interval (CI): 88.7-92.7) and MTCT was 8.8% (95% CI: 6.9-11.1). Sixty-six percent of HIV-exposed infants were still breastfeeding. Among the 762 infants born before Option A was implemented, 90.5% (95% CI: 88.1-92.5) were alive and HIV-uninfected at 9-18 months of age, and 9.1% (95%CI: 7.1-11.7) were HIV-infected. In four provinces, the community-based MTCT rate was higher than the facility-based MTCT rate. In Harare, the community and facility-based rates were 6.0% and 9.1%, respectively. By 2012 Zimbabwe had made substantial progress towards the elimination of MTCT. Our HIV-free infant survival and MTCT estimates capture HIV transmissions during pregnancy, delivery and breastfeeding regardless of whether or not mothers accessed health services. These estimates also provide a baseline against which to measure the impact of Option A guidelines (and subsequently Option B+).

On approximation and energy estimates for delta 6-convex functions

Directory of Open Access Journals (Sweden)

Muhammad Shoaib Saleem

2018-02-01

Full Text Available Abstract The smooth approximation and weighted energy estimates for delta 6-convex functions are derived in this research. Moreover, we conclude that if 6-convex functions are closed in uniform norm, then their third derivatives are closed in weighted L2 $L^{2}$-norm.

estimating an aggregate import demand function for ghana

African Journals Online (AJOL)

Administrator

we estimate an import demand function for Ghana for the period 1970 to ... results also indicate that economic growth (real GDP) and depreciation in the ... 80% of shocks to real exchange rates, merchandise imports and GDP ... imports; capital goods, 43 percent; intermediate ... merchandise imports (World Bank, 2004). For.

Two-component mixture cure rate model with spline estimated nonparametric components.

Science.gov (United States)

Wang, Lu; Du, Pang; Liang, Hua

2012-09-01

In some survival analysis of medical studies, there are often long-term survivors who can be considered as permanently cured. The goals in these studies are to estimate the noncured probability of the whole population and the hazard rate of the susceptible subpopulation. When covariates are present as often happens in practice, to understand covariate effects on the noncured probability and hazard rate is of equal importance. The existing methods are limited to parametric and semiparametric models. We propose a two-component mixture cure rate model with nonparametric forms for both the cure probability and the hazard rate function. Identifiability of the model is guaranteed by an additive assumption that allows no time-covariate interactions in the logarithm of hazard rate. Estimation is carried out by an expectation-maximization algorithm on maximizing a penalized likelihood. For inferential purpose, we apply the Louis formula to obtain point-wise confidence intervals for noncured probability and hazard rate. Asymptotic convergence rates of our function estimates are established. We then evaluate the proposed method by extensive simulations. We analyze the survival data from a melanoma study and find interesting patterns for this study. © 2011, The International Biometric Society.

Towards an Early Software Effort Estimation Based on Functional and Non-Functional Requirements

NARCIS (Netherlands)

Kassab, M.; Daneva, Maia; Ormanjieva, Olga; Abran, A.; Braungarten, R.; Dumke, R.; Cuadrado-Gallego, J.; Brunekreef, J.

2009-01-01

The increased awareness of the non-functional requirements as a key to software project and product success makes explicit the need to include them in any software project effort estimation activity. However, the existing approaches to defining size-based effort relationships still pay insufficient

ON THE ESTIMATION OF DISTANCE DISTRIBUTION FUNCTIONS FOR POINT PROCESSES AND RANDOM SETS

Directory of Open Access Journals (Sweden)

Dietrich Stoyan

2011-05-01

Full Text Available This paper discusses various estimators for the nearest neighbour distance distribution function D of a stationary point process and for the quadratic contact distribution function Hq of a stationary random closed set. It recommends the use of Hanisch's estimator of D, which is of Horvitz-Thompson type, and the minussampling estimator of Hq. This recommendation is based on simulations for Poisson processes and Boolean models.

Cost function estimation

DEFF Research Database (Denmark)

Andersen, C K; Andersen, K; Kragh-Sørensen, P

2000-01-01

on these criteria, a two-part model was chosen. In this model, the probability of incurring any costs was estimated using a logistic regression, while the level of the costs was estimated in the second part of the model. The choice of model had a substantial impact on the predicted health care costs, e...

Methylenetetrahydrofolate reductase 677C>T and methionine synthase 2756A>G mutations: no impact on survival, cognitive functioning, or cognitive decline in nonagenarians

DEFF Research Database (Denmark)

Bathum, Lise; von Bornemann Hjelmborg, Jacob; Christiansen, Lene

2007-01-01

BACKGROUND: Several reports have shown an association between homocysteine, cognitive functioning, and survival among the oldest-old. Two common polymorphisms in the genes coding for methylenetetrahydrofolate reductase (MTHFR 677C>T) and methionine synthase (MTR 2756A>G) have an impact on plasma...... homocysteine level. METHODS: We examined the effect of the MTHFR 677C>T and MTR 2756A>G genotypes on baseline cognitive functioning, cognitive decline over 5 years measured in three assessments, and survival in a population-based cohort of 1581 nonagenarians. Cognitive functioning was assessed by using...

Multi-subject hierarchical inverse covariance modelling improves estimation of functional brain networks.

Science.gov (United States)

Colclough, Giles L; Woolrich, Mark W; Harrison, Samuel J; Rojas López, Pedro A; Valdes-Sosa, Pedro A; Smith, Stephen M

2018-05-07

A Bayesian model for sparse, hierarchical inverse covariance estimation is presented, and applied to multi-subject functional connectivity estimation in the human brain. It enables simultaneous inference of the strength of connectivity between brain regions at both subject and population level, and is applicable to fmri, meg and eeg data. Two versions of the model can encourage sparse connectivity, either using continuous priors to suppress irrelevant connections, or using an explicit description of the network structure to estimate the connection probability between each pair of regions. A large evaluation of this model, and thirteen methods that represent the state of the art of inverse covariance modelling, is conducted using both simulated and resting-state functional imaging datasets. Our novel Bayesian approach has similar performance to the best extant alternative, Ng et al.'s Sparse Group Gaussian Graphical Model algorithm, which also is based on a hierarchical structure. Using data from the Human Connectome Project, we show that these hierarchical models are able to reduce the measurement error in meg beta-band functional networks by 10%, producing concomitant increases in estimates of the genetic influence on functional connectivity. Copyright © 2018. Published by Elsevier Inc.

Adult survival and population growth rate in Colorado big brown bats (Eptesicus fuscus)

Science.gov (United States)

O'Shea, T.J.; Ellison, L.E.; Stanley, T.R.

2011-01-01

We studied adult survival and population growth at multiple maternity colonies of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado. We investigated hypotheses about survival using information-theoretic methods and mark-recapture analyses based on passive detection of adult females tagged with passive integrated transponders. We constructed a 3-stage life-history matrix model to estimate population growth rate (??) and assessed the relative importance of adult survival and other life-history parameters to population growth through elasticity and sensitivity analysis. Annual adult survival at 5 maternity colonies monitored from 2001 to 2005 was estimated at 0.79 (95% confidence interval [95% CI] = 0.77-0.82). Adult survival varied by year and roost, with low survival during an extreme drought year, a finding with negative implications for bat populations because of the likelihood of increasing drought in western North America due to global climate change. Adult survival during winter was higher than in summer, and mean life expectancies calculated from survival estimates were lower than maximum longevity records. We modeled adult survival with recruitment parameter estimates from the same population. The study population was growing (?? = 1.096; 95% CI = 1.057-1.135). Adult survival was the most important demographic parameter for population growth. Growth clearly had the highest elasticity to adult survival, followed by juvenile survival and adult fecundity (approximately equivalent in rank). Elasticity was lowest for fecundity of yearlings. The relative importances of the various life-history parameters for population growth rate are similar to those of large mammals. ?? 2011 American Society of Mammalogists.

An estimating function approach to inference for inhomogeneous Neyman-Scott processes

DEFF Research Database (Denmark)

Waagepetersen, Rasmus

2007-01-01

This article is concerned with inference for a certain class of inhomogeneous Neyman-Scott point processes depending on spatial covariates. Regression parameter estimates obtained from a simple estimating function are shown to be asymptotically normal when the "mother" intensity for the Neyman-Sc...

Measurement of temporal regional cerebral perfusion with single-photon emission tomography predicts rate of decline in language function and survival in early Alzheimer's disease

International Nuclear Information System (INIS)

Claus, J.J.; Walstra, G.J.M.; Hijdra, A.; Gool, W.A. van; Royen, E.A. van; Verbeeten, B. Jr.

1999-01-01

We determined the relationship between regional cerebral blood flow (rCBF) measured with single-photon emission tomography (SPET) and decline in cognitive function and survival in Alzheimer's disease. In a prospective follow-up study, 69 consecutively referred patients with early probable Alzheimer's disease (NINCDS/ADRDA criteria) underwent SPET performed at the time of initial diagnosis using technetium-99m-labelled hexamethylpropylene amine oxime. Neuropsychological function was assessed at baseline and after 6 months and survival data were available on all patients, extending to 5.5 years of follow-up. Lower left temporal (P<0.01) and lower left parietal (P<0.01) rCBF were statistically significantly related to decline in language function after 6 months. The association between left temporal rCBF and survival was also statistically significant (P<0.05) using Cox proportional hazards regression analysis. Performing analysis with quartiles of the distribution, we found a threshold effect for low left temporal rCBF (rCBF<73.7%, P<0.01) and high risk of mortality. In this lowest quartile, median survival time was 2.7 years (follow-up to 5.2 years), compared with 4.4 years in the other quartiles (follow-up to 5.5 years). Kaplan-Meier survival curves showed statistically significant (P<0.05, log rank test) survival curves for the lowest versus other quartiles of left temporal rCBF. All results were unaffected by adjustment for age, sex, dementia severity, duration of symptoms, education and ratings of local cortical atrophy. We conclude that left temporal rCBF predicts decline in language function and survival in patients with early probable Alzheimer's disease, with a threshold effect of low rCBF and high risk of mortality. (orig.)

Comparing performance level estimation of safety functions in three distributed structures

International Nuclear Information System (INIS)

Hietikko, Marita; Malm, Timo; Saha, Heikki

2015-01-01

The capability of a machine control system to perform a safety function is expressed using performance levels (PL). This paper presents the results of a study where PL estimation was carried out for a safety function implemented using three different distributed control system structures. Challenges relating to the process of estimating PLs for safety related distributed machine control functions are highlighted. One of these examines the use of different cabling schemes in the implementation of a safety function and its effect on the PL evaluation. The safety function used as a generic example in PL calculations relates to a mobile work machine. It is a safety stop function where different technologies (electrical, hydraulic and pneumatic) can be utilized. It was detected that by replacing analogue cables with digital communication the system structure becomes simpler with less number of failing components, which can better the PL of the safety function. - Highlights: • Integration in distributed systems enables systems with less components. • It offers high reliability and diagnostic properties. • Analogue signals create uncertainty in signal reliability and difficult diagnostics

Genetic architecture of rainbow trout survival from egg to adult

NARCIS (Netherlands)

Vehvilainen, H.; Kause, A.; Quiton, C.; Kuukka-Anttila, H.; Koskinen, H.; Paananen, T.

2010-01-01

Survival from birth to a reproductive adult is a challenge that only robust individuals resistant to a variety of mortality factors will overcome. To assess whether survival traits share genetic architecture throughout the life cycle, we estimated genetic correlations for survival within fingerling

Estimating quality adjusted progression free survival of first-line treatments for EGFR mutation positive non small cell lung cancer patients in The Netherlands

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Verduyn S

2012-09-01

Full Text Available Abstract Background Gefitinib, a tyrosine kinase inhibitor, is an effective treatment in advanced non-small cell lung cancer (NSCLC patients with an activating mutation in the epidermal growth factor receptor (EGFR. Randomised clinical trials showed a benefit in progression free survival for gefitinib versus doublet chemotherapy regimens in patients with an activated EGFR mutation (EGFR M+. From a patient perspective, progression free survival is important, but so is health-related quality of life. Therefore, this analysis evaluates the Quality Adjusted progression free survival of gefitinib versus three relevant doublet chemotherapies (gemcitabine/cisplatin (Gem/Cis; pemetrexed/cisplatin (Pem/Cis; paclitaxel/carboplatin (Pac/Carb in a Dutch health care setting in patients with EGFR M+ stage IIIB/IV NSCLC. This study uses progression free survival rather than overall survival for its time frame in order to better compare the treatments and to account for the influence that subsequent treatment lines would have on overall survival analysis. Methods Mean progression free survival for Pac/Carb was obtained by extrapolating the median progression free survival as reported in the Iressa-Pan-Asia Study (IPASS. Data from a network meta-analysis was used to estimate the mean progression free survival for therapies of interest relative to Pac/Carb. Adjustment for health-related quality of life was done by incorporating utilities for the Dutch population, obtained by converting FACT-L data (from IPASS to utility values and multiplying these with the mean progression free survival for each treatment arm to determine the Quality Adjusted progression free survival. Probabilistic sensitivity analysis was carried out to determine 95% credibility intervals. Results The Quality Adjusted progression free survival (PFS (mean, (95% credibility interval was 5.2 months (4.5; 5.8 for Gem/Cis, 5.3 months (4.6; 6.1 for Pem/Cis; 4.9 months (4.4; 5.5 for Pac/Carb and 8

An estimating function approach to inference for inhomogeneous Neyman-Scott processes

DEFF Research Database (Denmark)

Waagepetersen, Rasmus Plenge

“This paper is concerned with inference for a certain class of inhomogeneous Neyman-Scott point processes depending on spatial covariates. Regression parameter estimates obtained from a simple estimating function are shown to be asymptotically normal when the “mother” intensity for the Neyman-Scott...

Conditional net survival: Relevant prognostic information for colorectal cancer survivors. A French population-based study.

Science.gov (United States)

Drouillard, Antoine; Bouvier, Anne-Marie; Rollot, Fabien; Faivre, Jean; Jooste, Valérie; Lepage, Côme

2015-07-01

Traditionally, survival estimates have been reported as survival from the time of diagnosis. A patient's probability of survival changes according to time elapsed since the diagnosis and this is known as conditional survival. The aim was to estimate 5-year net conditional survival in patients with colorectal cancer in a well-defined French population at yearly intervals up to 5 years. Our study included 18,300 colorectal cancers diagnosed between 1976 and 2008 and registered in the population-based digestive cancer registry of Burgundy (France). We calculated conditional 5-year net survival, using the Pohar Perme estimator, for every additional year survived after diagnosis from 1 to 5 years. The initial 5-year net survival estimates varied between 89% for stage I and 9% for advanced stage cancer. The corresponding 5-year net survival for patients alive after 5 years was 95% and 75%. Stage II and III patients who survived 5 years had a similar probability of surviving 5 more years, respectively 87% and 84%. For survivors after the first year following diagnosis, five-year conditional net survival was similar regardless of age class and period of diagnosis. For colorectal cancer survivors, conditional net survival provides relevant and complementary prognostic information for patients and clinicians. Copyright © 2015 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Lean body mass predicts long-term survival in Chinese patients on peritoneal dialysis.

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Jenq-Wen Huang

Full Text Available BACKGROUND: Reduced lean body mass (LBM is one of the main indicators in malnutrition inflammation syndrome among patients on dialysis. However, the influence of LBM on peritoneal dialysis (PD patients' outcomes and the factors related to increasing LBM are seldom reported. METHODS: We enrolled 103 incident PD patients between 2002 and 2003, and followed them until December 2011. Clinical characteristics, PD-associated parameters, residual renal function, and serum chemistry profiles of each patient were collected at 1 month and 1 year after initiating PD. LBM was estimated using creatinine index corrected with body weight. Multiple linear regression analysis, Kaplan-Meier survival analysis, and Cox regression proportional hazard analysis were used to define independent variables and compare survival between groups. RESULTS: Using the median LBM value (70% for men and 64% for women, patients were divided into group 1 (n = 52; low LBM and group 2 (n = 51; high LBM. Group 1 patients had higher rates of peritonitis (1.6 vs. 1.1/100 patient months; p<0.05 and hospitalization (14.6 vs. 9.7/100 patient months; p<0.05. Group 1 patients also had shorter overall survival and technique survival (p<0.01. Each percentage point increase in LBM reduced the hazard ratio for mortality by 8% after adjustment for diabetes, age, sex, and body mass index (BMI. Changes in residual renal function and protein catabolic rate were independently associated with changes in LBM in the first year of PD. CONCLUSIONS: LBM serves as a good parameter in addition to BMI to predict the survival of patients on PD. Preserving residual renal function and increasing protein intake can increase LBM.

Functional Gain After Inpatient Stroke Rehabilitation: Correlates and Impact on Long-Term Survival.

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Scrutinio, Domenico; Monitillo, Vincenzo; Guida, Pietro; Nardulli, Roberto; Multari, Vincenzo; Monitillo, Francesco; Calabrese, Gianluigi; Fiore, Pietro

2015-10-01

Prediction of functional outcome after stroke rehabilitation (SR) is a growing field of interest. The association between SR and survival still remains elusive. We sought to investigate the factors associated with functional outcome after SR and whether the magnitude of functional improvement achieved with rehabilitation is associated with long-term mortality risk. The study population consisted of 722 patients admitted for SR within 90 days of stroke onset, with an admission functional independence measure (FIM) score of stroke onset to rehabilitation admission (PStroke Scale score at rehabilitation admission (P<0.001), and aphasia (P=0.021) were independently associated with FIM gain. The R2 of the model was 0.275. During a median follow-up of 6.17 years, 36.9% of the patients died. At multivariable Cox analysis, age (P<0.0001), coronary heart disease (P=0.018), atrial fibrillation (P=0.042), total cholesterol (P=0.015), and total FIM gain (P<0.0001) were independently associated with mortality. The adjusted hazard ratio for death significantly decreased across tertiles of increasing FIM gain. Several factors are independently associated with functional gain after SR. Our findings strongly suggest that the magnitude of functional improvement is a powerful predictor of long-term mortality in patients admitted for SR. © 2015 American Heart Association, Inc.

Bioclimatic Thresholds, Thermal Constants and Survival of Mealybug, Phenacoccus solenopsis (Hemiptera: Pseudococcidae) in Response to Constant Temperatures on Hibiscus

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Sreedevi, Gudapati; Prasad, Yenumula Gerard; Prabhakar, Mathyam; Rao, Gubbala Ramachandra; Vennila, Sengottaiyan; Venkateswarlu, Bandi

2013-01-01

Temperature-driven development and survival rates of the mealybug, Phenacoccussolenopsis Tinsley (Hemiptera: Pseudococcidae) were examined at nine constant temperatures (15, 20, 25, 27, 30, 32, 35 and 40°C) on hibiscus ( Hibiscus rosa -sinensis L.). Crawlers successfully completed development to adult stage between 15 and 35°C, although their survival was affected at low temperatures. Two linear and four nonlinear models were fitted to describe developmental rates of P . solenopsis as a function of temperature, and for estimating thermal constants and bioclimatic thresholds (lower, optimum and upper temperature thresholds for development: Tmin, Topt and Tmax, respectively). Estimated thresholds between the two linear models were statistically similar. Ikemoto and Takai’s linear model permitted testing the equivalence of lower developmental thresholds for life stages of P . solenopsis reared on two hosts, hibiscus and cotton. Thermal constants required for completion of cumulative development of female and male nymphs and for the whole generation were significantly lower on hibiscus (222.2, 237.0, 308.6 degree-days, respectively) compared to cotton. Three nonlinear models performed better in describing the developmental rate for immature instars and cumulative life stages of female and male and for generation based on goodness-of-fit criteria. The simplified β type distribution function estimated Topt values closer to the observed maximum rates. Thermodynamic SSI model indicated no significant differences in the intrinsic optimum temperature estimates for different geographical populations of P . solenopsis . The estimated bioclimatic thresholds and the observed survival rates of P . solenopsis indicate the species to be high-temperature adaptive, and explained the field abundance of P . solenopsis on its host plants. PMID:24086597

Bioclimatic thresholds, thermal constants and survival of mealybug, Phenacoccus solenopsis (hemiptera: pseudococcidae) in response to constant temperatures on hibiscus.

Science.gov (United States)

Sreedevi, Gudapati; Prasad, Yenumula Gerard; Prabhakar, Mathyam; Rao, Gubbala Ramachandra; Vennila, Sengottaiyan; Venkateswarlu, Bandi

2013-01-01

Temperature-driven development and survival rates of the mealybug, Phenacoccussolenopsis Tinsley (Hemiptera: Pseudococcidae) were examined at nine constant temperatures (15, 20, 25, 27, 30, 32, 35 and 40°C) on hibiscus (Hibiscusrosa -sinensis L.). Crawlers successfully completed development to adult stage between 15 and 35°C, although their survival was affected at low temperatures. Two linear and four nonlinear models were fitted to describe developmental rates of P. solenopsis as a function of temperature, and for estimating thermal constants and bioclimatic thresholds (lower, optimum and upper temperature thresholds for development: Tmin, Topt and Tmax, respectively). Estimated thresholds between the two linear models were statistically similar. Ikemoto and Takai's linear model permitted testing the equivalence of lower developmental thresholds for life stages of P. solenopsis reared on two hosts, hibiscus and cotton. Thermal constants required for completion of cumulative development of female and male nymphs and for the whole generation were significantly lower on hibiscus (222.2, 237.0, 308.6 degree-days, respectively) compared to cotton. Three nonlinear models performed better in describing the developmental rate for immature instars and cumulative life stages of female and male and for generation based on goodness-of-fit criteria. The simplified β type distribution function estimated Topt values closer to the observed maximum rates. Thermodynamic SSI model indicated no significant differences in the intrinsic optimum temperature estimates for different geographical populations of P. solenopsis. The estimated bioclimatic thresholds and the observed survival rates of P. solenopsis indicate the species to be high-temperature adaptive, and explained the field abundance of P. solenopsis on its host plants.

Islet graft survival and function: concomitant culture and transplantation with vascular endothelial cells in diabetic rats.

Science.gov (United States)

Pan, Xiaoming; Xue, Wujun; Li, Yang; Feng, Xinshun; Tian, Xiaohui; Ding, Chenguang

2011-12-15

Human islet transplantation is a great potential therapy for type I diabetes. To investigate islet graft survival and function, we recently showed the improved effects after co-culture and co-transplantation with vascular endothelial cells (ECs) in diabetic rats. ECs were isolated, and the viability of isolated islets was assessed in two groups (standard culture group and co-culture group with ECs). Then streptozotocin-induced diabetic rats were divided into four groups before islet transplantation as follows: group A with infusion of islet grafts; group B with combined vascular ECs and islet grafts; groups C and D as controls with single ECs infusion and phosphate-buffered saline injection, respectively. Blood glucose and insulin concentrations were measured daily. Expression of vascular endothelial growth factor was investigated by immunohistochemical staining. The mean microvascular density was also calculated. More than 90% of acridine orange-propidium iodide staining positive islets demonstrated normal morphology while co-cultured with ECs for 7 days. Compared with standard control, insulin release assays showed a significantly higher simulation index in co-culture group except for the first day (Ptransplantation, there was a significant difference in concentrations of blood glucose and insulin among these groups after 3 days (Pislet group (P=0.04). Co-culture with ECs in vitro could improve the survival and function of isolated rat islet, and co-transplantation of islets with ECs could effectively prolong the islet graft survival in diabetic rats.

Method for estimating modulation transfer function from sample images.

Science.gov (United States)

Saiga, Rino; Takeuchi, Akihisa; Uesugi, Kentaro; Terada, Yasuko; Suzuki, Yoshio; Mizutani, Ryuta

2018-02-01

The modulation transfer function (MTF) represents the frequency domain response of imaging modalities. Here, we report a method for estimating the MTF from sample images. Test images were generated from a number of images, including those taken with an electron microscope and with an observation satellite. These original images were convolved with point spread functions (PSFs) including those of circular apertures. The resultant test images were subjected to a Fourier transformation. The logarithm of the squared norm of the Fourier transform was plotted against the squared distance from the origin. Linear correlations were observed in the logarithmic plots, indicating that the PSF of the test images can be approximated with a Gaussian. The MTF was then calculated from the Gaussian-approximated PSF. The obtained MTF closely coincided with the MTF predicted from the original PSF. The MTF of an x-ray microtomographic section of a fly brain was also estimated with this method. The obtained MTF showed good agreement with the MTF determined from an edge profile of an aluminum test object. We suggest that this approach is an alternative way of estimating the MTF, independently of the image type. Copyright © 2017 Elsevier Ltd. All rights reserved.

Operational production of Geodetic Excitation Functions from EOP estimated values at ASI-CGS

Science.gov (United States)

Sciarretta, C.; Luceri, V.; Bianco, G.

2009-04-01

ASI-CGS is routinely providing geodetic excitation functions from its own estimated EOP values (at present SLR and VLBI; the current use of GPS EOP's is also planned as soon as this product will be fully operational) on the ASI geodetic web site (http://geodaf.mt.asi.it). This product has been generated and monitored (for ASI internal use only) in a long pre-operational phase (more than two years), including validation and testing. The daily geodetic excitation functions are now weekly updated along with the operational ASI SLR and VLBI EOP solutions and compared, whenever possible, with the atmospheric excitation functions available at the IERS SBAAM, under the IB and not-IB assumption, including the "wind" term. The work will present the available estimated geodetic function time series and its comparison with the relevant atmospheric excitation functions, deriving quantitative indicators on the quality of the estimates. The similarities as well as the discrepancies among the atmospheric and geodetic series will be analysed and commented, evaluating in particular the degree of correlation among the two estimated time series and the likelihood of a linear dependence hypothesis.

Evaluating the Impact of Zimbabwe’s Prevention of Mother-to-Child HIV Transmission Program: Population-Level Estimates of HIV-Free Infant Survival Pre-Option A

Science.gov (United States)

Buzdugan, Raluca; McCoy, Sandra I.; Watadzaushe, Constancia; Kang Dufour, Mi-Suk; Petersen, Maya; Dirawo, Jeffrey; Mushavi, Angela; Mujuru, Hilda Angela; Mahomva, Agnes; Musarandega, Reuben; Hakobyan, Anna; Mugurungi, Owen; Cowan, Frances M.; Padian, Nancy S.

2015-01-01

Objective We estimated HIV-free infant survival and mother-to-child HIV transmission (MTCT) rates in Zimbabwe, some of the first community-based estimates from a UNAIDS priority country. Methods In 2012 we surveyed mother-infant pairs residing in the catchment areas of 157 health facilities randomly selected from 5 of 10 provinces in Zimbabwe. Enrolled infants were born 9–18 months before the survey. We collected questionnaires, blood samples for HIV testing, and verbal autopsies for deceased mothers/infants. Estimates were assessed among i) all HIV-exposed infants, as part of an impact evaluation of Option A of the 2010 WHO guidelines (rolled out in Zimbabwe in 2011), and ii) the subgroup of infants unexposed to Option A. We compared province-level MTCT rates measured among women in the community with MTCT rates measured using program monitoring data from facilities serving those communities. Findings Among 8568 women with known HIV serostatus, 1107 (12.9%) were HIV-infected. Among all HIV-exposed infants, HIV-free infant survival was 90.9% (95% confidence interval (CI): 88.7–92.7) and MTCT was 8.8% (95% CI: 6.9–11.1). Sixty-six percent of HIV-exposed infants were still breastfeeding. Among the 762 infants born before Option A was implemented, 90.5% (95% CI: 88.1–92.5) were alive and HIV-uninfected at 9–18 months of age, and 9.1% (95%CI: 7.1–11.7) were HIV-infected. In four provinces, the community-based MTCT rate was higher than the facility-based MTCT rate. In Harare, the community and facility-based rates were 6.0% and 9.1%, respectively. Conclusion By 2012 Zimbabwe had made substantial progress towards the elimination of MTCT. Our HIV-free infant survival and MTCT estimates capture HIV transmissions during pregnancy, delivery and breastfeeding regardless of whether or not mothers accessed health services. These estimates also provide a baseline against which to measure the impact of Option A guidelines (and subsequently Option B+). PMID:26248197

Net survival after exposure to polychlorinated biphenyls and dioxins: the Yusho study.

Science.gov (United States)

Onozuka, Daisuke; Hirata, Teruaki; Furue, Masutaka

2014-12-01

Net survival is an important measure of the overall outcome of disease management. This net survival is the most appropriate for international comparisons of disease impact between countries or time periods with different patterns of all-cause mortality because it is not influenced by other causes of death. However, little information is available on net survival among Yusho patients, who were accidentally exposed to PCBs and other dioxin-related compounds. We estimated the net survival of 1664 Yusho patients (860 males, 804 females) as Yusho cohort subjects using the unbiased Pohar-Perme method. Among males, 1-, 5-, 10-, and 15-year net survival were 99.5% (95% confidence interval (CI): 97.9, 99.9), 99.1% (CI: 95.0, 99.9), 97.4% (CI: 86.5, 99.5), and 97.4% (CI: 84.2, 99.6), respectively. Among females, net survival remained almost constant. 1-, 5-, 10-, and 15-year net survival were generally higher in females than in males. This study provides the first unbiased estimations of net survival among Yusho patients. We confirmed that older male Yusho patients have experienced a significant decrease in net survival. Our results suggest that the excess hazard of PCBs and dioxins must be taken into account when evaluating unbiased estimates of net survival. Copyright © 2014 Elsevier Ltd. All rights reserved.

Bacterial genotoxin functions as immune-modulator and promotes host survival

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Riccardo Guidi

2016-07-01

Full Text Available Bacterial genotoxins are effectors that cause DNA damage in target cells. Many aspects of the biology of these toxins have been characterised in vitro, such as structure, cellular internalisation pathways and effects on the target cells. However, little is known about their function in vivo. Salmonella enterica serovar Typhi (S. Typhi is a Gram-negative, intracellular bacterium that causes typhoid fever, a debilitating disease infecting more than 20 million people every year. S. Typhi produce a genotoxin named typhoid toxin (TT, but its role in the contest of host infection is poorly characterized. The major obstacle in addressing this issue is that S. Typhi is exclusively a human pathogen. To overcome this limitation, we have used as model bacterium S. Typhimurium, and engineered it to produce endogenous levels of an active and inactive typhoid toxin, hereby named as TT (or genotoxic and cdtB (or control, respectively. To our surprise, infection with the genotoxin strain strongly suppressed intestinal inflammation, leading to a better survival of the host during the acute phase of infection, suggesting typhoid toxin may exert a protective role. The presence of a functional genotoxin was also associated with an increased frequency of asymptomatic carriers.

$L^{p}$-square function estimates on spaces of homogeneous type and on uniformly rectifiable sets

CERN Document Server

Hofmann, Steve; Mitrea, Marius; Morris, Andrew J

2017-01-01

The authors establish square function estimates for integral operators on uniformly rectifiable sets by proving a local T(b) theorem and applying it to show that such estimates are stable under the so-called big pieces functor. More generally, they consider integral operators associated with Ahlfors-David regular sets of arbitrary codimension in ambient quasi-metric spaces. The local T(b) theorem is then used to establish an inductive scheme in which square function estimates on so-called big pieces of an Ahlfors-David regular set are proved to be sufficient for square function estimates to hold on the entire set. Extrapolation results for L^p and Hardy space versions of these estimates are also established. Moreover, the authors prove square function estimates for integral operators associated with variable coefficient kernels, including the Schwartz kernels of pseudodifferential operators acting between vector bundles on subdomains with uniformly rectifiable boundaries on manifolds.

The risk function approach to profit maximizing estimation in direct mailing

NARCIS (Netherlands)

Muus, Lars; Scheer, Hiek van der; Wansbeek, Tom

1999-01-01

When the parameters of the model describing consumers' reaction to a mailing are known, addresses for a future mailing can be selected in a profit-maximizing way. Usually, these parameters are unknown and are to be estimated. Standard estimation are based on a quadratic loss function. In the present

Juvenile survival in a neotropical migratory songbird is lower than expected.

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Matthew I McKim-Louder

Full Text Available Attempts to estimate and identify factors influencing first-year survival in passerines, survival between fledging and the first reproductive attempt (i.e. juvenile survival, have largely been confounded by natal dispersal, particularly in long-distance migratory passerines. We studied Prothonotary Warblers (Protonotaria citrea breeding in nest boxes to estimate first-year survival while accounting for biases related to dispersal that are common in mark-recapture studies. The natal dispersal distribution (median = 1420 m; n = 429 and a distance-dependent recruitment rate, which controls for effects of study site configuration, both indicated a pattern of short-distance natal dispersal. This pattern was consistent with results of a systematic survey for birds returning outside the nest box study sites (up to 30 km in all directions within a majority (81% of total available bottomland forest habitat, further suggesting that permanent emigration outside of the study system was rare. We used multistate mark-recapture modeling to estimate first-year survival and incorporated factors thought to influence survival while accounting for the potential confounding effects of dispersal on recapture probabilities for warblers that fledged during 2004-2009 (n = 6093. Overall, the average first-year survival for warblers reared without cowbird nestmates was 0.11 (95% CI = 0.09-0.13, decreased with fledging date (0.22 early to 0.03 late and averaged 40% lower for warblers reared with a brood parasite nestmate. First-year survival was less than half of the rate thought to represent population replacement in migratory passerines (∼0.30. This very low rate suggests that surviving the first year of life for many Neotropical migratory species is even more difficult than previously thought, forcing us to rethink estimates used in population models.

Peritransplant Soluble CD30 as a Risk Factor for Slow Kidney Allograft Function, Early Acute Rejection, Worse Long-Term Allograft Function, and Patients' Survival.

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Trailin, Andriy V; Ostapenko, Tetyana I; Nykonenko, Tamara N; Nesterenko, Svitlana N; Nykonenko, Olexandr S

2017-01-01

We aimed to determine whether serum soluble CD30 (sCD30) could identify recipients at high risk for unfavorable early and late kidney transplant outcomes. Serum sCD30 was measured on the day of kidney transplantation and on the 4th day posttransplant. We assessed the value of these measurements in predicting delayed graft function, slow graft function (SGF), acute rejection (AR), pyelonephritis, decline of allograft function after 6 months, and graft and patient survival during 5 years of follow-up in 45 recipients. We found the association between low pretransplant serum levels of sCD30 and SGF. The absence of significant decrease of sCD30 on the 4th day posttransplant was characteristic for SGF, early AR (the 8th day-6 months), late AR (>6 months), and early pyelonephritis (the 8th day-2 months). Lower pretransplant and posttransplant sCD30 predicted worse allograft function at 6 months and 2 years, respectively. Higher pretransplant sCD30 was associated with higher frequency of early AR, and worse patients' survival, but only in the recipients of deceased-donor graft. Pretransplant sCD30 also allowed to differentiate patients with early pyelonephritis and early AR. Peritransplant sCD30 is useful in identifying patients at risk for unfavorable early and late transplant outcomes.

Peritransplant Soluble CD30 as a Risk Factor for Slow Kidney Allograft Function, Early Acute Rejection, Worse Long-Term Allograft Function, and Patients' Survival

Science.gov (United States)

Ostapenko, Tetyana I.; Nykonenko, Tamara N.; Nesterenko, Svitlana N.; Nykonenko, Olexandr S.

2017-01-01

Background We aimed to determine whether serum soluble CD30 (sCD30) could identify recipients at high risk for unfavorable early and late kidney transplant outcomes. Methods Serum sCD30 was measured on the day of kidney transplantation and on the 4th day posttransplant. We assessed the value of these measurements in predicting delayed graft function, slow graft function (SGF), acute rejection (AR), pyelonephritis, decline of allograft function after 6 months, and graft and patient survival during 5 years of follow-up in 45 recipients. Results We found the association between low pretransplant serum levels of sCD30 and SGF. The absence of significant decrease of sCD30 on the 4th day posttransplant was characteristic for SGF, early AR (the 8th day–6 months), late AR (>6 months), and early pyelonephritis (the 8th day–2 months). Lower pretransplant and posttransplant sCD30 predicted worse allograft function at 6 months and 2 years, respectively. Higher pretransplant sCD30 was associated with higher frequency of early AR, and worse patients' survival, but only in the recipients of deceased-donor graft. Pretransplant sCD30 also allowed to differentiate patients with early pyelonephritis and early AR. Conclusions Peritransplant sCD30 is useful in identifying patients at risk for unfavorable early and late transplant outcomes. PMID:28694560

Tug of War between Survival and Death: Exploring ATM Function in Cancer

Science.gov (United States)

Stagni, Venturina; Oropallo, Veronica; Fianco, Giulia; Antonelli, Martina; Cinà, Irene; Barilà, Daniela

2014-01-01

Ataxia-telangiectasia mutated (ATM) kinase is a one of the main guardian of genome stability and plays a central role in the DNA damage response (DDR). The deregulation of these pathways is strongly linked to cancer initiation and progression as well as to the development of therapeutic approaches. These observations, along with reports that identify ATM loss of function as an event that may promote tumor initiation and progression, point to ATM as a bona fide tumor suppressor. The identification of ATM as a positive modulator of several signalling networks that sustain tumorigenesis, including oxidative stress, hypoxia, receptor tyrosine kinase and AKT serine-threonine kinase activation, raise the question of whether ATM function in cancer may be more complex. This review aims to give a complete overview on the work of several labs that links ATM to the control of the balance between cell survival, proliferation and death in cancer. PMID:24681585

Tug of War between Survival and Death: Exploring ATM Function in Cancer

Directory of Open Access Journals (Sweden)

Venturina Stagni

2014-03-01

Full Text Available Ataxia-telangiectasia mutated (ATM kinase is a one of the main guardian of genome stability and plays a central role in the DNA damage response (DDR. The deregulation of these pathways is strongly linked to cancer initiation and progression as well as to the development of therapeutic approaches. These observations, along with reports that identify ATM loss of function as an event that may promote tumor initiation and progression, point to ATM as a bona fide tumor suppressor. The identification of ATM as a positive modulator of several signalling networks that sustain tumorigenesis, including oxidative stress, hypoxia, receptor tyrosine kinase and AKT serine-threonine kinase activation, raise the question of whether ATM function in cancer may be more complex. This review aims to give a complete overview on the work of several labs that links ATM to the control of the balance between cell survival, proliferation and death in cancer.

Symptomatic spinal metastasis: A systematic literature review of the preoperative prognostic factors for survival, neurological, functional and quality of life in surgically treated patients and methodological recommendations for prognostic studies.

Directory of Open Access Journals (Sweden)

Anick Nater

Full Text Available While several clinical prediction rules (CPRs of survival exist for patients with symptomatic spinal metastasis (SSM, these have variable prognostic ability and there is no recognized CPR for health related quality of life (HRQoL. We undertook a critical appraisal of the literature to identify key preoperative prognostic factors of clinical outcomes in patients with SSM who were treated surgically. The results of this study could be used to modify existing or develop new CPRs.Seven electronic databases were searched (1990-2015, without language restriction, to identify studies that performed multivariate analysis of preoperative predictors of survival, neurological, functional and HRQoL outcomes in surgical patients with SSM. Individual studies were assessed for class of evidence. The strength of the overall body of evidence was evaluated using GRADE for each predictor.Among 4,818 unique citations, 17 were included; all were in English, rated Class III and focused on survival, revealing a total of 46 predictors. The strength of the overall body of evidence was very low for 39 and low for 7 predictors. Due to considerable heterogeneity in patient samples and prognostic factors investigated as well as several methodological issues, our results had a moderately high risk of bias and were difficult to interpret.The quality of evidence for predictors of survival was, at best, low. We failed to identify studies that evaluated preoperative prognostic factors for neurological, functional, or HRQoL outcomes in surgical patients with SSM. We formulated methodological recommendations for prognostic studies to promote acquiring high-quality evidence to better estimate predictor effect sizes to improve patient education, surgical decision-making and development of CPRs.

Survival-variation within and between functional categories of the African multimammate rat

DEFF Research Database (Denmark)

Julliard, Romain; Leirs, Herwig; Stenseth, Nils Chr.

1999-01-01

in the population immediately after their first capture; (iv) subadults survival in later months is, however, positively related to density; and (v) adult survival shows negative density-dependence. 3. Both density-dependent and density-independent factors simultaneously determine stage-dependent survival variation...

The utility of harvest recoveries of marked individuals to assess polar bear (Ursus maritimus) survival

Science.gov (United States)

Peacock, Elizabeth; Laake, Jeff; Laidre, Kristin L.; Born, Erik W.; Atkinson, Stephen N.

2012-01-01

Management of polar bear (Ursus maritimus) populations requires the periodic assessment of life history metrics such as survival rate. This information is frequently obtained during short-term capture and marking efforts (e.g., over the course of three years) that result in hundreds of marked bears remaining in the population after active marking is finished. Using 10 additional years of harvest recovery subsequent to a period of active marking, we provide updated estimates of annual survival for polar bears in the Baffin Bay population of Greenland and Canada. Our analysis suggests a decline in survival of polar bears since the period of active marking that ended in 1997; some of the decline in survival can likely be attributed to a decline in springtime ice concentration over the continental shelf of Baffin Island. The variance around the survival estimates is comparatively high because of the declining number of marks available; therefore, results must be interpreted with caution. The variance of the estimates of survival increased most substantially in the sixth year post-marking. When survival estimates calculated with recovery-only and recapture-recovery data sets from the period of active marking were compared, survival rates were indistinguishable. However, for the period when fewer marks were available, survival estimates were lower using the recovery-only data set, which indicates that part of the decline we detected for 2003 – 09 may be due to using only harvest recovery data. Nevertheless, the decline in the estimates of survival is consistent with population projections derived from harvest numbers and earlier vital rates, as well as with an observed decline in the extent of sea ice habitat.

A note on reliability estimation of functionally diverse systems

International Nuclear Information System (INIS)

Littlewood, B.; Popov, P.; Strigini, L.

1999-01-01

It has been argued that functional diversity might be a plausible means of claiming independence of failures between two versions of a system. We present a model of functional diversity, in the spirit of earlier models of diversity such as those of Eckhardt and Lee, and Hughes. In terms of the model, we show that the claims for independence between functionally diverse systems seem rather unrealistic. Instead, it seems likely that functionally diverse systems will exhibit positively correlated failures, and thus will be less reliable than an assumption of independence would suggest. The result does not, of course, suggest that functional diversity is not worthwhile; instead, it places upon the evaluator of such a system the onus to estimate the degree of dependence so as to evaluate the reliability of the system

Hypothermic machine perfusion reduces delayed graft function and improves one-year graft survival of kidneys from expanded criteria donors: a meta-analysis.

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Baoping Jiao

Full Text Available BACKGROUND: Expanded criteria donors (ECDs are currently accepted as potential sources to increase the donor pool and to provide more chances of kidney transplantation for elderly recipients who would not survive long waiting periods. Hypothermic machine perfusion (HMP is designed to mitigate the deleterious effects of simple cold storage (CS on the quality of preserved organs, particularly when the donor is in a marginal status. METHODS: We compared the transplant outcomes in patients receiving ECD kidneys with either HMP or CS graft preservation. Articles from the MEDLINE, EMBASE and Cochrane Library databases were searched and all studies reporting outcomes from HMP versus CS methods of kidney preservation were included in this meta-analysis. The parameters analyzed included the incidence of delayed graft function (DGF, primary non-function (PNF and one-year graft and patient survival. RESULTS: A total of seven studies qualified for the review, involving 2374 and 8716 kidney grafts with HMP or CS preservation respectively, all from ECD donors. The incidence of delayed graft function (DGF was significantly reduced with an odd ratio(OR of 0.59 (95% CI 0.54-0.66, P<0.001 and one-year graft survival was significantly improved with an OR of 1.12 (95% CI 1.03-1.21, P = 0.005 in HMP preservation compared to CS. However, there was no difference in the incidence of PNF (OR 0.54, 95% CI 0.21-1.40, P = 0.20, and one-year patient survival (OR 0.98, 95% CI 0.94-1.02, P = 0.36 between HMP and CS preservation. CONCLUSIONS: HMP was associated with a reduced incidence of DGF and an with increased one-year graft survival, but it was not associated with the incidence of PNF and one-year patient survival.

Monitoring of Subyearling Chinook Salmon Survival and Passage at Bonneville Dam, Summer 2010

Energy Technology Data Exchange (ETDEWEB)

Ploskey, Gene R.; Weiland, Mark A.; Carlson, Thomas J.

2012-09-01

The purpose of this study was to estimate dam passage and route specific survival rates for subyearling Chinook salmon smolts to a primary survival-detection array located 81 km downstream of the dam, evaluate a BGS located in the B2 forebay, and evaluate effects of two spill treatments. The 2010 study also provided estimates of forebay residence time, tailrace egress time, spill passage efficiency (SPE), and spill + B2 Corner Collector (B2CC) efficiency, as required in the Columbia Basin Fish Accords. In addition, the study estimated forebay passage survival and survival of fish traveling from the forebay entrance array, through the dam and downstream through 81 km of tailwater.

Comparing adaptive procedures for estimating the psychometric function for an auditory gap detection task.

Science.gov (United States)

Shen, Yi

2013-05-01

A subject's sensitivity to a stimulus variation can be studied by estimating the psychometric function. Generally speaking, three parameters of the psychometric function are of interest: the performance threshold, the slope of the function, and the rate at which attention lapses occur. In the present study, three psychophysical procedures were used to estimate the three-parameter psychometric function for an auditory gap detection task. These were an up-down staircase (up-down) procedure, an entropy-based Bayesian (entropy) procedure, and an updated maximum-likelihood (UML) procedure. Data collected from four young, normal-hearing listeners showed that while all three procedures provided similar estimates of the threshold parameter, the up-down procedure performed slightly better in estimating the slope and lapse rate for 200 trials of data collection. When the lapse rate was increased by mixing in random responses for the three adaptive procedures, the larger lapse rate was especially detrimental to the efficiency of the up-down procedure, and the UML procedure provided better estimates of the threshold and slope than did the other two procedures.

Measurement of temporal regional cerebral perfusion with single-photon emission tomography predicts rate of decline in language function and survival in early Alzheimer`s disease

Energy Technology Data Exchange (ETDEWEB)

Claus, J.J.; Walstra, G.J.M.; Hijdra, A.; Gool, W.A. van [Department of Neurology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Royen, E.A. van [Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam (Netherlands); Verbeeten, B. Jr. [Department of Radiology, Academic Medical Center, University of Amsterdam (Netherlands)

1999-03-01

We determined the relationship between regional cerebral blood flow (rCBF) measured with single-photon emission tomography (SPET) and decline in cognitive function and survival in Alzheimer`s disease. In a prospective follow-up study, 69 consecutively referred patients with early probable Alzheimer`s disease (NINCDS/ADRDA criteria) underwent SPET performed at the time of initial diagnosis using technetium-99m-labelled hexamethylpropylene amine oxime. Neuropsychological function was assessed at baseline and after 6 months and survival data were available on all patients, extending to 5.5 years of follow-up. Lower left temporal (P<0.01) and lower left parietal (P<0.01) rCBF were statistically significantly related to decline in language function after 6 months. The association between left temporal rCBF and survival was also statistically significant (P<0.05) using Cox proportional hazards regression analysis. Performing analysis with quartiles of the distribution, we found a threshold effect for low left temporal rCBF (rCBF<73.7%, P<0.01) and high risk of mortality. In this lowest quartile, median survival time was 2.7 years (follow-up to 5.2 years), compared with 4.4 years in the other quartiles (follow-up to 5.5 years). Kaplan-Meier survival curves showed statistically significant (P<0.05, log rank test) survival curves for the lowest versus other quartiles of left temporal rCBF. All results were unaffected by adjustment for age, sex, dementia severity, duration of symptoms, education and ratings of local cortical atrophy. We conclude that left temporal rCBF predicts decline in language function and survival in patients with early probable Alzheimer`s disease, with a threshold effect of low rCBF and high risk of mortality. (orig.) With 3 figs., 3 tabs., 44 refs.

Neuregulin-1/erbB-activation improves cardiac function and survival in models of ischemic, dilated, and viral cardiomyopathy.

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Liu, Xifu; Gu, Xinhua; Li, Zhaoming; Li, Xinyan; Li, Hui; Chang, Jianjie; Chen, Ping; Jin, Jing; Xi, Bing; Chen, Denghong; Lai, Donna; Graham, Robert M; Zhou, Mingdong

2006-10-03

We evaluated the therapeutic potential of a recombinant 61-residue neuregulin-1 (beta2a isoform) receptor-active peptide (rhNRG-1) in multiple animal models of heart disease. Activation of the erbB family of receptor tyrosine kinases by rhNRG-1 could provide a treatment option for heart failure, because neuregulin-stimulated erbB2/erbB4 heterodimerization is not only critical for myocardium formation in early heart development but prevents severe dysfunction of the adult heart and premature death. Disabled erbB-signaling is also implicated in the transition from compensatory hypertrophy to failure, whereas erbB receptor-activation promotes myocardial cell growth and survival and protects against anthracycline-induced cardiomyopathy. rhNRG-1 was administered IV to animal models of ischemic, dilated, and viral cardiomyopathy, and cardiac function and survival were evaluated. Short-term intravenous administration of rhNRG-1 to normal dogs and rats did not alter hemodynamics or cardiac contractility. In contrast, rhNRG-1 improved cardiac performance, attenuated pathological changes, and prolonged survival in rodent models of ischemic, dilated, and viral cardiomyopathy, with the survival benefits in the ischemic model being additive to those of angiotensin-converting enzyme inhibitor therapy. In addition, despite continued pacing, rhNRG-1 produced global improvements in cardiac function in a canine model of pacing-induced heart failure. These beneficial effects make rhNRG-1 promising as a broad-spectrum therapeutic for the treatment of heart failure due to a variety of common cardiac diseases.

Local gradient estimate for harmonic functions on Finsler manifolds

OpenAIRE

Xia, Chao

2013-01-01

In this paper, we prove the local gradient estimate for harmonic functions on complete, noncompact Finsler measure spaces under the condition that the weighted Ricci curvature has a lower bound. As applications, we obtain Liouville type theorem on Finsler manifolds with nonnegative Ricci curvature.

Estimating Aggregate Import-Demand Function In Nigeria: A Co ...

African Journals Online (AJOL)

This paper investigates the behaviour of Nigeria's aggregate imports between the periods 1980-2005. In the empirical analysis of the aggregate import demand function for Nigeria, cointegration and Error Correction modeling approaches have been used. Our econometric estimates suggest that real GDP largely explains ...

Survival modeling for the estimation of transition probabilities in model-based economic evaluations in the absence of individual patient data: a tutorial.

Science.gov (United States)

Diaby, Vakaramoko; Adunlin, Georges; Montero, Alberto J

2014-02-01

Survival modeling techniques are increasingly being used as part of decision modeling for health economic evaluations. As many models are available, it is imperative for interested readers to know about the steps in selecting and using the most suitable ones. The objective of this paper is to propose a tutorial for the application of appropriate survival modeling techniques to estimate transition probabilities, for use in model-based economic evaluations, in the absence of individual patient data (IPD). An illustration of the use of the tutorial is provided based on the final progression-free survival (PFS) analysis of the BOLERO-2 trial in metastatic breast cancer (mBC). An algorithm was adopted from Guyot and colleagues, and was then run in the statistical package R to reconstruct IPD, based on the final PFS analysis of the BOLERO-2 trial. It should be emphasized that the reconstructed IPD represent an approximation of the original data. Afterwards, we fitted parametric models to the reconstructed IPD in the statistical package Stata. Both statistical and graphical tests were conducted to verify the relative and absolute validity of the findings. Finally, the equations for transition probabilities were derived using the general equation for transition probabilities used in model-based economic evaluations, and the parameters were estimated from fitted distributions. The results of the application of the tutorial suggest that the log-logistic model best fits the reconstructed data from the latest published Kaplan-Meier (KM) curves of the BOLERO-2 trial. Results from the regression analyses were confirmed graphically. An equation for transition probabilities was obtained for each arm of the BOLERO-2 trial. In this paper, a tutorial was proposed and used to estimate the transition probabilities for model-based economic evaluation, based on the results of the final PFS analysis of the BOLERO-2 trial in mBC. The results of our study can serve as a basis for any model

Nonparametric estimation of the stationary M/G/1 workload distribution function

DEFF Research Database (Denmark)

Hansen, Martin Bøgsted

2005-01-01

In this paper it is demonstrated how a nonparametric estimator of the stationary workload distribution function of the M/G/1-queue can be obtained by systematic sampling the workload process. Weak convergence results and bootstrap methods for empirical distribution functions for stationary associ...

Survival and maturation rates of the African rodent Mastomys natalensis

DEFF Research Database (Denmark)

Sluydts, Vincent; Crespin, Laurent; Davis, Stephen

2008-01-01

the model fit. On the other hand we showed that maturation rates were correlated negatively with density the previous month and positively to cumulative rainfall over the past three months. Survival estimates of both adults and subadults varied seasonally, with higher estimates during the increase phase......Survival and maturation rates of female Mastomys natalensis were analysed based on a ten-year onthly capture-recapture data set. We investigated whether direct and delayed density dependent and independent (rainfall) variables accounted for the considerable variation in demographic traits....... It was estimated that seasonal and annual covariates accounted for respectively 29 and 26% of the total variation in maturation rates and respectively 17 and 11% of the variation in survival rates. Explaining the between-year differences in maturation rates with annual past rainfall or density did not improve...

Quantitative pre-surgical lung function estimation with SPECT/CT

International Nuclear Information System (INIS)

Bailey, D. L.; Willowson, K. P.; Timmins, S.; Harris, B. E.; Bailey, E. A.; Roach, P. J.

2009-01-01

Full text:Objectives: To develop methodology to predict lobar lung function based on SPECT/CT ventilation and perfusion (V/Q) scanning in candidates for lobectomy for lung cancer. Methods: This combines two development areas from our group: quantitative SPECT based on CT-derived corrections for scattering and attenuation of photons, and SPECT V/Q scanning with lobar segmentation from CT. Eight patients underwent baseline pulmonary function testing (PFT) including spirometry, measure of DLCO and cario-pulmonary exercise testing. A SPECT/CT V/Q scan was acquired at baseline. Using in-house software each lobe was anatomically defined using CT to provide lobar ROIs which could be applied to the SPECT data. From these, individual lobar contribution to overall function was calculated from counts within the lobe and post-operative FEV1, DLCO and VO2 peak were predicted. This was compared with the quantitative planar scan method using 3 rectangular ROIs over each lung. Results: Post-operative FEV1 most closely matched that predicted by the planar quantification method, with SPECT V/Q over-estimating the loss of function by 8% (range - 7 - +23%). However, post-operative DLCO and VO2 peak were both accurately predicted by SPECT V/Q (average error of 0 and 2% respectively) compared with planar. Conclusions: More accurate anatomical definition of lobar anatomy provides better estimates of post-operative loss of function for DLCO and VO2 peak than traditional planar methods. SPECT/CT provides the tools for accurate anatomical defintions of the surgical target as well as being useful in producing quantitative 3D functional images for ventilation and perfusion.

Analyzing survival curves at a fixed point in time for paired and clustered right-censored data

Science.gov (United States)

Su, Pei-Fang; Chi, Yunchan; Lee, Chun-Yi; Shyr, Yu; Liao, Yi-De

2018-01-01

In clinical trials, information about certain time points may be of interest in making decisions about treatment effectiveness. Rather than comparing entire survival curves, researchers can focus on the comparison at fixed time points that may have a clinical utility for patients. For two independent samples of right-censored data, Klein et al. (2007) compared survival probabilities at a fixed time point by studying a number of tests based on some transformations of the Kaplan-Meier estimators of the survival function. However, to compare the survival probabilities at a fixed time point for paired right-censored data or clustered right-censored data, their approach would need to be modified. In this paper, we extend the statistics to accommodate the possible within-paired correlation and within-clustered correlation, respectively. We use simulation studies to present comparative results. Finally, we illustrate the implementation of these methods using two real data sets. PMID:29456280

System Coordination of Survivability and Safety of Complex Engineering Objects Operation

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Nataliya Pankratova

2014-11-01

Full Text Available A system strategy to estimation the guaranteed survivability and safety of complex engineering objects (CEO operation is proposed. The principles that underlie the strategy of the guaranteed safety of CEO operation provide a flexible approach to timely detection, recognition, forecast, and system diagnostics of risk factors and situations, to formulation and implementation of a rational decision in a practicable time within an unremovable time constraint. Implementation of the proposed strategy is shown on example of diagnostics of electromobile-refrigerator functioning in real mode.

Cancer Cell-derived Exosomes Induce Mitogen-activated Protein Kinase-dependent Monocyte Survival by Transport of Functional Receptor Tyrosine Kinases*

Science.gov (United States)

Song, Xiao; Ding, Yanping; Liu, Gang; Yang, Xiao; Zhao, Ruifang; Zhang, Yinlong; Zhao, Xiao; Anderson, Gregory J.; Nie, Guangjun

2016-01-01

Tumor-associated macrophages (TAM) play pivotal roles in cancer initiation and progression. Monocytes, the precursors of TAMs, normally undergo spontaneous apoptosis within 2 days, but can subsist in the inflammatory tumor microenvironment for continuous survival and generation of sufficient TAMs. The mechanisms underlying tumor-driving monocyte survival remain obscure. Here we report that cancer cell-derived exosomes were crucial mediators for monocyte survival in the inflammatory niche. Analysis of the survival-promoting molecules in monocytes revealed that cancer cell-derived exosomes activated Ras and extracellular signal-regulated kinases in the mitogen-activated protein kinase (MAPK) pathway, resulting in the prevention of caspase cleavage. Phosphorylated receptor tyrosine kinases (RTKs), such as phosphorylated epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2), were abundantly expressed in cancer cell-derived exosomes. Knock-out of EGFR or/and HER-2, or alternatively, inhibitors against their phosphorylation significantly disturbed the exosome-mediated activation of the MAPK pathway, inhibition of caspase cleavage, and increase in survival rate in monocytes. Moreover, the deprived survival-stimulating activity of exosomes due to null expression of EGFR and HER-2 could be restored by activation of another RTK, insulin receptor. Overall, our study uncovered a mechanism of tumor-associated monocyte survival and demonstrated that cancer cell-derived exosomes can stimulate the MAPK pathway in monocytes through transport of functional RTKs, leading to inactivation of apoptosis-related caspases. This work provides insights into the long sought question on monocyte survival prior to formation of plentiful TAMs in the tumor microenvironment. PMID:26895960

Measuring survival time: a probability-based approach useful in healthcare decision-making.

Science.gov (United States)

2011-01-01

In some clinical situations, the choice between treatment options takes into account their impact on patient survival time. Due to practical constraints (such as loss to follow-up), survival time is usually estimated using a probability calculation based on data obtained in clinical studies or trials. The two techniques most commonly used to estimate survival times are the Kaplan-Meier method and the actuarial method. Despite their limitations, they provide useful information when choosing between treatment options.

Lipschitz estimates for convex functions with respect to vector fields

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Valentino Magnani

2012-12-01

Full Text Available We present Lipschitz continuity estimates for a class of convex functions with respect to Hörmander vector fields. These results have been recently obtained in collaboration with M. Scienza, [22].

Overall survival and disease-free survival in endometrial cancer: prognostic factors in 276 patients

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Tejerizo-García A

2013-09-01

Full Text Available Álvaro Tejerizo-García,1 Jesús S Jiménez-López,1 José L Muñoz-González,1 Sara Bartolomé-Sotillos,1 Laura Marqueta-Marqués,1 Gregorio López-González,1 José F Pérez-Regadera Gómez21Service of Obstetrics and Gynecology, 2Radiation Oncology Service, Hospital Universitario 12 de Octubre, Madrid, SpainObjective: The aim of the study reported here was to assess the disease-free survival and overall survival of patients with endometrial cancer and to determine independent factors affecting the prognosis.Materials and methods: This was a retrospective study of a single-center clinical series of 276 patients (mean age 64 years with histologically confirmed cancer of the corpus uteri. The standard treatments were extrafascial total hysterectomy and bilateral salpingo-oophorectomy with selective pelvic/para-aortic node dissection, according to risk for recurrence. Actuarial overall survival and disease-free survival were estimated according to the Kaplan–Meier method. Univariate and multivariate Cox proportional hazards analyses were used to assess the prognostic significance of the different variables.Results: The estimated median follow-up, determined using the inverse Kaplan–Meier method, was 45 months (95% confidence interval [CI] 41.2–48.8 for disease-free survival and 46 months (95% CI 43.0–49.0 for overall survival. The statistically significant variables affecting disease-free survival and overall survival were age, serous-papillary and clear-cell histological types, outer-half myometrial invasion, advanced International Federation of Gynecology and Obstetrics (FIGO stage, tumor grades G2 and G3, incomplete surgical resection, positive lymph nodes, lymphovascular space invasion, tumor remnants of >1 cm after surgery, and high-risk group. In the multivariate Cox regression model, predictors of tumor recurrence included advanced FIGO stage (hazard ratio [HR] 4.90, 95% CI 2.57–9.36, P < 0.001 and tumor grades G2 (HR 4.79, 95

Source Estimation for the Damped Wave Equation Using Modulating Functions Method: Application to the Estimation of the Cerebral Blood Flow

KAUST Repository

Asiri, Sharefa M.; Laleg-Kirati, Taous-Meriem

2017-01-01

In this paper, a method based on modulating functions is proposed to estimate the Cerebral Blood Flow (CBF). The problem is written in an input estimation problem for a damped wave equation which is used to model the spatiotemporal variations

Conditional survival of cancer patients: an Australian perspective

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Yu Xue

2012-10-01

Full Text Available Abstract Background Estimated conditional survival for cancer patients diagnosed at different ages and disease stage provides important information for cancer patients and clinicians in planning follow-up, surveillance and ongoing management. Methods Using population-based cancer registry data for New South Wales Australia, we estimated conditional 5-year relative survival for 11 major cancers diagnosed 1972–2006 by time since diagnosis and age and stage at diagnosis. Results 193,182 cases were included, with the most common cancers being prostate (39,851, female breast (36,585 and colorectal (35,455. Five-year relative survival tended to increase with increasing years already survived and improvement was greatest for cancers with poor prognosis at diagnosis (lung or pancreas and for those with advanced stage or older age at diagnosis. After surviving 10 years, conditional 5-year survival was over 95% for 6 localised, 6 regional, 3 distant and 3 unknown stage cancers. For the remaining patient groups, conditional 5-year survival ranged from 74% (for distant stage bladder cancer to 94% (for 4 cancers at different stages, indicating that they continue to have excess mortality 10–15 years after diagnosis. Conclusion These data provide important information for cancer patients, based on age and stage at diagnosis, as they continue on their cancer journey. This information may also be used by clinicians as a tool to make more evidence-based decisions regarding follow-up, surveillance, or ongoing management according to patients' changing survival expectations over time.

Estimating the probability of survival of individual shortleaf pine (Pinus echinata mill.) trees

Science.gov (United States)

Sudip Shrestha; Thomas B. Lynch; Difei Zhang; James M. Guldin

2012-01-01

A survival model is needed in a forest growth system which predicts the survival of trees on individual basis or on a stand basis (Gertner, 1989). An individual-tree modeling approach is one of the better methods available for predicting growth and yield as it provides essential information about particular tree species; tree size, tree quality and tree present status...

Acylcarnitines profile best predicts survival in horses with atypical myopathy.

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François Boemer

Full Text Available Equine atypical myopathy (AM is caused by hypoglycin A intoxication and is characterized by a high fatality rate. Predictive estimation of survival in AM horses is necessary to prevent unnecessary suffering of animals that are unlikely to survive and to focus supportive therapy on horses with a possible favourable prognosis of survival. We hypothesized that outcome may be predicted early in the course of disease based on the assumption that the acylcarnitine profile reflects the derangement of muscle energetics. We developed a statistical model to prognosticate the risk of death of diseased animals and found that estimation of outcome may be drawn from three acylcarnitines (C2, C10:2 and C18 -carnitines with a high sensitivity and specificity. The calculation of the prognosis of survival makes it possible to distinguish the horses that will survive from those that will die despite severe signs of acute rhabdomyolysis in both groups.

Acylcarnitines profile best predicts survival in horses with atypical myopathy

Science.gov (United States)

Detilleux, Johann; Cello, Christophe; Amory, Hélène; Marcillaud-Pitel, Christel; Richard, Eric; van Galen, Gaby; van Loon, Gunther; Lefère, Laurence; Votion, Dominique-Marie

2017-01-01

Equine atypical myopathy (AM) is caused by hypoglycin A intoxication and is characterized by a high fatality rate. Predictive estimation of survival in AM horses is necessary to prevent unnecessary suffering of animals that are unlikely to survive and to focus supportive therapy on horses with a possible favourable prognosis of survival. We hypothesized that outcome may be predicted early in the course of disease based on the assumption that the acylcarnitine profile reflects the derangement of muscle energetics. We developed a statistical model to prognosticate the risk of death of diseased animals and found that estimation of outcome may be drawn from three acylcarnitines (C2, C10:2 and C18 -carnitines) with a high sensitivity and specificity. The calculation of the prognosis of survival makes it possible to distinguish the horses that will survive from those that will die despite severe signs of acute rhabdomyolysis in both groups. PMID:28846683

Impact of surgical volume on functional results and cardiospecific survival rates in patients with clinically localized renal cancer

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M. I. Volkova

2014-11-01

Full Text Available Objective: to analyze the impact of surgical volume on functional results and cardiospecific survival rates in patients with clinically localized renal carcinoma.Subjects and methods. Four hundred and fifty-three patients with pT1–3aN0M0 renal cell carcinoma and normally functioning secondkidney who had undergone radical nephrectomy (n = 226 (49.9 % or kidney resection (n = 227 (50.1 % were selected for the investigation. The patient groups who had undergone different-volume operations were matched for gender, age, body mass index (BMI, side of involvement, tumor sizes, and baseline glomerular filtration rate (GFR (p > for all. The median baseline Charlson index and the rate of ASA classes III–IV operative risk were significantly higher in candidates for radical nephrectomy (p < 0.05 for all, the rate of diseases affecting kidney function, pT1a category, and G1 anaplasia were higher in the kidney resection group (p < 0.0001. The median follow-up was 50 (12–224 months.Results. Within 28 days postsurgery, the rate of acute renal dysfunction (ARD was 36.2 %. The independent risk factors of ARD were kidney resection (risk ratio (RR = 0.210; 95 % confidence interval (CI 0.115–0.288; р < 0.0001 and ischemia time (RR = 0.012; 95 % CI 0.004–0.021; p = 0.004. The degree of ARD after kidney resection was significantly lower than that following radical nephrectomy (p < 0.0001. In the late postoperative period, the incidence of chronic kidney disease (CKD Stage ≥ III was 38.4 %. Its independent risk factors were low baseline GFR (RR = 0.003; 95 % CI 0.002–0.005; p < 0.0001, radical nephrectomy (RR = 0.195; 95 % CI 0.093–0.298; p < 0.0001, and ARD (RR = 0.281; 95 % CI 0.187–0.376; p = 0.0001. Ten-year specific and cardiospecific survival rates in all the patients were 98.5 and 94.9 %, respectively, and unrelated to surgical volume. The independent predictors of poor cardiospecific survival were BMI, Charlson index, and ASA risk

Impact of surgical volume on functional results and cardiospecific survival rates in patients with clinically localized renal cancer

Directory of Open Access Journals (Sweden)

M. I. Volkova

2014-01-01

Full Text Available Objective: to analyze the impact of surgical volume on functional results and cardiospecific survival rates in patients with clinically localized renal carcinoma.Subjects and methods. Four hundred and fifty-three patients with pT1–3aN0M0 renal cell carcinoma and normally functioning secondkidney who had undergone radical nephrectomy (n = 226 (49.9 % or kidney resection (n = 227 (50.1 % were selected for the investigation. The patient groups who had undergone different-volume operations were matched for gender, age, body mass index (BMI, side of involvement, tumor sizes, and baseline glomerular filtration rate (GFR (p > for all. The median baseline Charlson index and the rate of ASA classes III–IV operative risk were significantly higher in candidates for radical nephrectomy (p < 0.05 for all, the rate of diseases affecting kidney function, pT1a category, and G1 anaplasia were higher in the kidney resection group (p < 0.0001. The median follow-up was 50 (12–224 months.Results. Within 28 days postsurgery, the rate of acute renal dysfunction (ARD was 36.2 %. The independent risk factors of ARD were kidney resection (risk ratio (RR = 0.210; 95 % confidence interval (CI 0.115–0.288; р < 0.0001 and ischemia time (RR = 0.012; 95 % CI 0.004–0.021; p = 0.004. The degree of ARD after kidney resection was significantly lower than that following radical nephrectomy (p < 0.0001. In the late postoperative period, the incidence of chronic kidney disease (CKD Stage ≥ III was 38.4 %. Its independent risk factors were low baseline GFR (RR = 0.003; 95 % CI 0.002–0.005; p < 0.0001, radical nephrectomy (RR = 0.195; 95 % CI 0.093–0.298; p < 0.0001, and ARD (RR = 0.281; 95 % CI 0.187–0.376; p = 0.0001. Ten-year specific and cardiospecific survival rates in all the patients were 98.5 and 94.9 %, respectively, and unrelated to surgical volume. The independent predictors of poor cardiospecific survival were BMI, Charlson index, and ASA risk

Transoral endoscopic esophageal myotomy based on esophageal function testing in a survival porcine model.

Science.gov (United States)

Perretta, Silvana; Dallemagne, Bernard; Donatelli, Gianfranco; Diemunsch, Pierre; Marescaux, Jacques

2011-01-01

The most effective treatment of achalasia is Heller myotomy. To explore a submucosal endoscopic myotomy technique tailored on esophageal physiology testing and to compare it with the open technique. Prospective acute and survival comparative study in pigs (n = 12; 35 kg). University animal research center. Eight acute-4 open and 4 endoscopic-myotomies followed by 4 survival endoscopic procedures. Preoperative and postoperative manometry; esophagogastric junction (EGJ) distensibility before and after selective division of muscular fibers at the EGJ and after the myotomy was prolonged to a standard length by using the EndoFLIP Functional Lumen Imaging Probe (Crospon, Galway, Ireland). All procedures were successful, with no intraoperative and postoperative complications. In the survival group, the animals recovered promptly from surgery. Postoperative manometry demonstrated a 50% drop in mean lower esophageal sphincter pressure (LESp) in the endoscopic group (mean preoperative LESp, 22.2 ± 3.3 mm Hg; mean postoperative LESp, 11.34 ± 2.7 mm Hg; P open procedure group (mean preoperative LESp, 24.2 ± 3.2 mm Hg; mean postoperative LESp, 7.4 ± 4 mm Hg; P myotomy is feasible and safe. The lack of a significant difference in EGJ distensibility between the open and endoscopic procedure is very appealing. Were it to be perfected in a human population, this endoscopic approach could suggest a new strategy in the treatment of selected achalasia patients. Copyright © 2011 American Society for Gastrointestinal Endoscopy. Published by Mosby, Inc. All rights reserved.

Acoustic Telemetry Evaluation of Juvenile Salmonid Passage and Survival at John Day Dam, 2010

Energy Technology Data Exchange (ETDEWEB)

Weiland, Mark A.; Woodley, Christa M.; Ploskey, Gene R.; Hughes, James S.; Kim, Jin A.; Deng, Zhiqun; Fu, Tao; Fischer, Eric S.; Skalski, J. R.; Townsend, Richard L.; Duncan, Joanne P.; Hennen, Matthew J.; Wagner, Katie A.; Arntzen, Evan V.; Miller, Benjamin L.; Miracle, Ann L.; Zimmerman, Shon A.; Royer, Ida M.; Khan, Fenton; Cushing, Aaron W.; Etherington, D. J.; Mitchell, T. D.; Elder, T.; Batton, George; Johnson, Gary E.; Carlson, Thomas J.

2013-05-01

This report presents survival, behavioral, and fish passage results for yearling and subyearling Chinook salmon smolts and juvenile steelhead tagged with JSATS acoustic micro-transmitters as part of a survival study conducted at John Day Dam during 2010. This study was designed to evaluate the passage and survival of yearling and subyearling Chinook salmon and juvenile steelhead to assist managers in identifying dam operations for compliance testing as stipulated by the 2008 Federal Columbia River Power System Biological Opinion and the 2008 Columbia Basin Fish Accords. Survival estimates were based on a single-release survival estimate model.

Estimating unsaturated hydraulic conductivity from soil moisture-tim function

International Nuclear Information System (INIS)

El Gendy, R.W.

2002-01-01

The unsaturated hydraulic conductivity for soil can be estimated from o(t) function, and the dimensionless soil water content parameter (Se)Se (β - βr)/ (φ - θ)), where θ, is the soil water content at any time (from soil moisture depletion curve l; θ is the residual water content and θ, is the total soil porosity (equals saturation point). Se can be represented as a time function (Se = a t b ), where t, is the measurement time and (a and b) are the regression constants. The recommended equation in this method is given by

Estimation of Correlation Functions by the Random Decrement Technique

DEFF Research Database (Denmark)

Brincker, Rune; Krenk, Steen; Jensen, Jakob Laigaard

responses simulated by two SDOF ARMA models loaded by the same bandlimited white noise. The speed and the accuracy of the RDD technique is compared to the Fast Fourier Transform (FFT) technique. The RDD technique does not involve multiplications, but only additions. Therefore, the technique is very fast......The Random Decrement (RDD) Technique is a versatile technique for characterization of random signals in the time domain. In this paper a short review of the theoretical basis is given, and the technique is illustrated by estimating auto-correlation functions and cross-correlation functions on modal...

Estimation of Correlation Functions by the Random Decrement Technique

DEFF Research Database (Denmark)

Brincker, Rune; Krenk, Steen; Jensen, Jacob Laigaard

1991-01-01

responses simulated by two SDOF ARMA models loaded by the same band-limited white noise. The speed and the accuracy of the RDD technique is compared to the Fast Fourier Transform (FFT) technique. The RDD technique does not involve multiplications, but only additions. Therefore, the technique is very fast......The Random Decrement (RDD) Technique is a versatile technique for characterization of random signals in the time domain. In this paper a short review of the theoretical basis is given, and the technique is illustrated by estimating auto-correlation functions and cross-correlation functions on modal...

Estimation of Correlation Functions by the Random Decrement Technique

DEFF Research Database (Denmark)

Brincker, Rune; Krenk, Steen; Jensen, Jakob Laigaard

1992-01-01

responses simulated by two SDOF ARMA models loaded by the same bandlimited white noise. The speed and the accuracy of the RDD technique is compared to the Fast Fourier Transform (FFT) technique. The RDD technique does not involve multiplications, but only additions. Therefore, the technique is very fast......The Random Decrement (RDD) Technique is a versatile technique for characterization of random signals in the time domain. In this paper a short review of the theoretical basis is given, and the technique is illustrated by estimating auto-correlation functions and cross-correlation functions on modal...

A dose-surviving fraction curve for mouse colonic mucosa

International Nuclear Information System (INIS)

Tucker, S.L.; Thames, H.D. Jr.; Withers, H.R.; Mason, K.A.

1983-01-01

A dose-surviving fraction curve representing the response of the mouse colonic mucosa to single doses of 137 Cs gamma radiation was obtained from the results of a multifraction in vivo colony assay. Construction of the curve required an estimated of the average number of clonogens initially present per colonic crypt. The estimated clonogen count (88) was determined by a statistical method based on the use of doses per fraction common to different fractionation protocols. Parameters for the LQ and TC models of cell survival were obtained by weighted least-squares fits to the data. A comparison of the survival characteristics of cells from the mouse colonic and jejunal crypts suggested that the epithelium of the colon is less radiosensitive than that of the jejunum. (author)

Modulating Function-Based Method for Parameter and Source Estimation of Partial Differential Equations

KAUST Repository

Asiri, Sharefa M.

2017-10-08

Partial Differential Equations (PDEs) are commonly used to model complex systems that arise for example in biology, engineering, chemistry, and elsewhere. The parameters (or coefficients) and the source of PDE models are often unknown and are estimated from available measurements. Despite its importance, solving the estimation problem is mathematically and numerically challenging and especially when the measurements are corrupted by noise, which is often the case. Various methods have been proposed to solve estimation problems in PDEs which can be classified into optimization methods and recursive methods. The optimization methods are usually heavy computationally, especially when the number of unknowns is large. In addition, they are sensitive to the initial guess and stop condition, and they suffer from the lack of robustness to noise. Recursive methods, such as observer-based approaches, are limited by their dependence on some structural properties such as observability and identifiability which might be lost when approximating the PDE numerically. Moreover, most of these methods provide asymptotic estimates which might not be useful for control applications for example. An alternative non-asymptotic approach with less computational burden has been proposed in engineering fields based on the so-called modulating functions. In this dissertation, we propose to mathematically and numerically analyze the modulating functions based approaches. We also propose to extend these approaches to different situations. The contributions of this thesis are as follows. (i) Provide a mathematical analysis of the modulating function-based method (MFBM) which includes: its well-posedness, statistical properties, and estimation errors. (ii) Provide a numerical analysis of the MFBM through some estimation problems, and study the sensitivity of the method to the modulating functions\\' parameters. (iii) Propose an effective algorithm for selecting the method\\'s design parameters

Cancer Cell-derived Exosomes Induce Mitogen-activated Protein Kinase-dependent Monocyte Survival by Transport of Functional Receptor Tyrosine Kinases.

Science.gov (United States)

Song, Xiao; Ding, Yanping; Liu, Gang; Yang, Xiao; Zhao, Ruifang; Zhang, Yinlong; Zhao, Xiao; Anderson, Gregory J; Nie, Guangjun

2016-04-15

Tumor-associated macrophages (TAM) play pivotal roles in cancer initiation and progression. Monocytes, the precursors of TAMs, normally undergo spontaneous apoptosis within 2 days, but can subsist in the inflammatory tumor microenvironment for continuous survival and generation of sufficient TAMs. The mechanisms underlying tumor-driving monocyte survival remain obscure. Here we report that cancer cell-derived exosomes were crucial mediators for monocyte survival in the inflammatory niche. Analysis of the survival-promoting molecules in monocytes revealed that cancer cell-derived exosomes activated Ras and extracellular signal-regulated kinases in the mitogen-activated protein kinase (MAPK) pathway, resulting in the prevention of caspase cleavage. Phosphorylated receptor tyrosine kinases (RTKs), such as phosphorylated epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2), were abundantly expressed in cancer cell-derived exosomes. Knock-out of EGFR or/and HER-2, or alternatively, inhibitors against their phosphorylation significantly disturbed the exosome-mediated activation of the MAPK pathway, inhibition of caspase cleavage, and increase in survival rate in monocytes. Moreover, the deprived survival-stimulating activity of exosomes due to null expression of EGFR and HER-2 could be restored by activation of another RTK, insulin receptor. Overall, our study uncovered a mechanism of tumor-associated monocyte survival and demonstrated that cancer cell-derived exosomes can stimulate the MAPK pathway in monocytes through transport of functional RTKs, leading to inactivation of apoptosis-related caspases. This work provides insights into the long sought question on monocyte survival prior to formation of plentiful TAMs in the tumor microenvironment. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

On Improving Density Estimators which are not Bona Fide Functions

OpenAIRE

Gajek, Leslaw

1986-01-01

In order to improve the rate of decrease of the IMSE for nonparametric kernel density estimators with nonrandom bandwidth beyond $O(n^{-4/5})$ all current methods must relax the constraint that the density estimate be a bona fide function, that is, be nonnegative and integrate to one. In this paper we show how to achieve similar improvement without relaxing any of these constraints. The method can also be applied for orthogonal series, adaptive orthogonal series, spline, jackknife, and other ...

Estimation of Nonlinear Functions of State Vector for Linear Systems with Time-Delays and Uncertainties

Directory of Open Access Journals (Sweden)

Il Young Song

2015-01-01

Full Text Available This paper focuses on estimation of a nonlinear function of state vector (NFS in discrete-time linear systems with time-delays and model uncertainties. The NFS represents a multivariate nonlinear function of state variables, which can indicate useful information of a target system for control. The optimal nonlinear estimator of an NFS (in mean square sense represents a function of the receding horizon estimate and its error covariance. The proposed receding horizon filter represents the standard Kalman filter with time-delays and special initial horizon conditions described by the Lyapunov-like equations. In general case to calculate an optimal estimator of an NFS we propose using the unscented transformation. Important class of polynomial NFS is considered in detail. In the case of polynomial NFS an optimal estimator has a closed-form computational procedure. The subsequent application of the proposed receding horizon filter and nonlinear estimator to a linear stochastic system with time-delays and uncertainties demonstrates their effectiveness.

Estimation of Multiple Point Sources for Linear Fractional Order Systems Using Modulating Functions

KAUST Repository

Belkhatir, Zehor; Laleg-Kirati, Taous-Meriem

2017-01-01

This paper proposes an estimation algorithm for the characterization of multiple point inputs for linear fractional order systems. First, using polynomial modulating functions method and a suitable change of variables the problem of estimating

Dehydration survival of crop plants and its measurement.

Science.gov (United States)

Blum, Abraham; Tuberosa, Roberto

2018-01-08

Dehydration survival under drought stress is defined in this review as the transition from plant activity into a quiescent state of life preservation, which will be terminated by either recovery or death, depending on the stress regime and the plant's resilience. Dehydration survival is a popular phenotype by which functional genomics attempts to test gene function in drought resistance and survival. The available reports on phenotyping and genotyping of dehydration survival in genomic studies indicate that the measurement of this trait is often biased to the extent that misguided interpretations are likely to occur. This review briefly discusses the physiological basis of dehydration survival in resurrection plants and crop plants, and concludes that in phenotyping dehydration survival there is a need to distinguish between dehydration avoidance and dehydration tolerance (also termed desiccation tolerance) in affecting survival and recovery. Without this distinction, functional genomics studies of the trait might be biased. Survival due to dehydration avoidance is expressed by the capacity to maintain a relatively high plant water status as the plant is desiccated. Survival due to dehydration tolerance is expressed by delayed mortality (mortality at a relatively low plant water status) as affected by the resilience of plant metabolism. The common test of dehydration survival, using the relative recovery after a given number of stress days, is therefore insufficient because it is mainly driven by dehydration avoidance and so ignores a possible role for dehydration tolerance. Conceivable methods for more accurate phenotyping of the two components of dehydration survival are proposed and discussed. © The Author(s) 2018. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Machine Learning Estimation of Atom Condensed Fukui Functions.

Science.gov (United States)

Zhang, Qingyou; Zheng, Fangfang; Zhao, Tanfeng; Qu, Xiaohui; Aires-de-Sousa, João

2016-02-01

To enable the fast estimation of atom condensed Fukui functions, machine learning algorithms were trained with databases of DFT pre-calculated values for ca. 23,000 atoms in organic molecules. The problem was approached as the ranking of atom types with the Bradley-Terry (BT) model, and as the regression of the Fukui function. Random Forests (RF) were trained to predict the condensed Fukui function, to rank atoms in a molecule, and to classify atoms as high/low Fukui function. Atomic descriptors were based on counts of atom types in spheres around the kernel atom. The BT coefficients assigned to atom types enabled the identification (93-94 % accuracy) of the atom with the highest Fukui function in pairs of atoms in the same molecule with differences ≥0.1. In whole molecules, the atom with the top Fukui function could be recognized in ca. 50 % of the cases and, on the average, about 3 of the top 4 atoms could be recognized in a shortlist of 4. Regression RF yielded predictions for test sets with R(2) =0.68-0.69, improving the ability of BT coefficients to rank atoms in a molecule. Atom classification (as high/low Fukui function) was obtained with RF with sensitivity of 55-61 % and specificity of 94-95 %. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

LARF: Instrumental Variable Estimation of Causal Effects through Local Average Response Functions

Directory of Open Access Journals (Sweden)

Weihua An

2016-07-01

Full Text Available LARF is an R package that provides instrumental variable estimation of treatment effects when both the endogenous treatment and its instrument (i.e., the treatment inducement are binary. The method (Abadie 2003 involves two steps. First, pseudo-weights are constructed from the probability of receiving the treatment inducement. By default LARF estimates the probability by a probit regression. It also provides semiparametric power series estimation of the probability and allows users to employ other external methods to estimate the probability. Second, the pseudo-weights are used to estimate the local average response function conditional on treatment and covariates. LARF provides both least squares and maximum likelihood estimates of the conditional treatment effects.

Impact of work-related cancers in Taiwan-Estimation with QALY (quality-adjusted life year) and healthcare costs.

Science.gov (United States)

Lee, Lukas Jyuhn-Hsiarn; Lin, Cheng-Kuan; Hung, Mei-Chuan; Wang, Jung-Der

2016-12-01

This study estimates the annual numbers of eight work-related cancers, total losses of quality-adjusted life years (QALYs), and lifetime healthcare expenditures that possibly could be saved by improving occupational health in Taiwan. Three databases were interlinked: the Taiwan Cancer Registry, the National Mortality Registry, and the National Health Insurance Research Database. Annual numbers of work-related cancers were estimated based on attributable fractions (AFs) abstracted from a literature review. The survival functions for eight cancers were estimated and extrapolated to lifetime using a semi-parametric method. A convenience sample of 8846 measurements of patients' quality of life with EQ-5D was collected for utility values and multiplied by survival functions to estimate quality-adjusted life expectancies (QALEs). The loss-of-QALE was obtained by subtracting the QALE of cancer from age- and sex-matched referents simulated from national vital statistics. The lifetime healthcare expenditures were estimated by multiplying the survival probability with mean monthly costs paid by the National Health Insurance for cancer diagnosis and treatment and summing this for the expected lifetime. A total of 3010 males and 726 females with eight work-related cancers were estimated in 2010. Among them, lung cancer ranked first in terms of QALY loss, with an annual total loss-of-QALE of 28,463 QALYs and total lifetime healthcare expenditures of US$36.6 million. Successful prevention of eight work-related cancers would not only avoid the occurrence of 3736 cases of cancer, but would also save more than US$70 million in healthcare costs and 46,750 QALYs for the Taiwan society in 2010.

Estimation of cost function in the natural gas industry

Energy Technology Data Exchange (ETDEWEB)

Kim, Young Duk [Korea Energy Economics Institute, Euiwang (Korea)

1999-02-01

The natural gas industry in Korea has characteristics of a dual industrial structure with wholesale and retail and a regional monopoly of city gas company. Recently there have been discussions on the restructuring of gas industry and the problems arising from such industrial organization. At this point, the labor and capital cost of KOGAS were analyzed to find out efficiency of KOGAS, the wholesaler and the cost function focusing on distribution was estimated to find out effect of scale of city gas company, the retailer. As a result, in the case of KOGAS, it is prove that enhancing competitive power is needed by improving labor productivity through stabilization of labor structure and by maximizing value-added through stability of capital combination. From the estimation of cost function of city gas companies, the existing regional monopoly of city gas company have effects on its scale only when the area of operation and end users used the same amount per end user are increased. (author). 31 refs., 10 figs., 43 tabs.

Bayesian Estimation of the Scale Parameter of Inverse Weibull Distribution under the Asymmetric Loss Functions

Directory of Open Access Journals (Sweden)

Farhad Yahgmaei

2013-01-01

Full Text Available This paper proposes different methods of estimating the scale parameter in the inverse Weibull distribution (IWD. Specifically, the maximum likelihood estimator of the scale parameter in IWD is introduced. We then derived the Bayes estimators for the scale parameter in IWD by considering quasi, gamma, and uniform priors distributions under the square error, entropy, and precautionary loss functions. Finally, the different proposed estimators have been compared by the extensive simulation studies in corresponding the mean square errors and the evolution of risk functions.

On the robust nonparametric regression estimation for a functional regressor

OpenAIRE

Azzedine , Nadjia; Laksaci , Ali; Ould-Saïd , Elias

2009-01-01

On the robust nonparametric regression estimation for a functional regressor correspondance: Corresponding author. (Ould-Said, Elias) (Azzedine, Nadjia) (Laksaci, Ali) (Ould-Said, Elias) Departement de Mathematiques--> , Univ. Djillali Liabes--> , BP 89--> , 22000 Sidi Bel Abbes--> - ALGERIA (Azzedine, Nadjia) Departement de Mathema...

Hepatocyte nuclear factor 4A improves hepatic differentiation of immortalized adult human hepatocytes and improves liver function and survival.

Science.gov (United States)

Hang, Hua-Lian; Liu, Xin-Yu; Wang, Hai-Tian; Xu, Ning; Bian, Jian-Min; Zhang, Jian-Jun; Xia, Lei; Xia, Qiang

2017-11-15

Immortalized human hepatocytes (IHH) could provide an unlimited supply of hepatocytes, but insufficient differentiation and phenotypic instability restrict their clinical application. This study aimed to determine the role of hepatocyte nuclear factor 4A (HNF4A) in hepatic differentiation of IHH, and whether encapsulation of IHH overexpressing HNF4A could improve liver function and survival in rats with acute liver failure (ALF). Primary human hepatocytes were transduced with lentivirus-mediated catalytic subunit of human telomerase reverse transcriptase (hTERT) to establish IHH. Cells were analyzed for telomerase activity, proliferative capacity, hepatocyte markers, and tumorigenicity (c-myc) expression. Hepatocyte markers, hepatocellular functions, and morphology were studied in the HNF4A-overexpressing IHH. Hepatocyte markers and karyotype analysis were completed in the primary hepatocytes using shRNA knockdown of HNF4A. Nuclear translocation of β-catenin was assessed. Rat models of ALF were treated with encapsulated IHH or HNF4A-overexpressing IHH. A HNF4A-positive IHH line was established, which was non-tumorigenic and conserved properties of primary hepatocytes. HNF4A overexpression significantly enhanced mRNA levels of genes related to hepatic differentiation in IHH. Urea levels were increased by the overexpression of HNF4A, as measured 24h after ammonium chloride addition, similar to that of primary hepatocytes. Chromosomal abnormalities were observed in primary hepatocytes transfected with HNF4A shRNA. HNF4α overexpression could significantly promote β-catenin activation. Transplantation of HNF4A overexpressing IHH resulted in better liver function and survival of rats with ALF compared with IHH. HNF4A improved hepatic differentiation of IHH. Transplantation of HNF4A-overexpressing IHH could improve the liver function and survival in a rat model of ALF. Copyright © 2017 Elsevier Inc. All rights reserved.

Development of fragility functions to estimate homelessness after an earthquake

Science.gov (United States)

Brink, Susan A.; Daniell, James; Khazai, Bijan; Wenzel, Friedemann

2014-05-01

Immediately after an earthquake, many stakeholders need to make decisions about their response. These decisions often need to be made in a data poor environment as accurate information on the impact can take months or even years to be collected and publicized. Social fragility functions have been developed and applied to provide an estimate of the impact in terms of building damage, deaths and injuries in near real time. These rough estimates can help governments and response agencies determine what aid may be required which can improve their emergency response and facilitate planning for longer term response. Due to building damage, lifeline outages, fear of aftershocks, or other causes, people may become displaced or homeless after an earthquake. Especially in cold and dangerous locations, the rapid provision of safe emergency shelter can be a lifesaving necessity. However, immediately after an event there is little information available about the number of homeless, their locations and whether they require public shelter to aid the response agencies in decision making. In this research, we analyze homelessness after historic earthquakes using the CATDAT Damaging Earthquakes Database. CATDAT includes information on the hazard as well as the physical and social impact of over 7200 damaging earthquakes from 1900-2013 (Daniell et al. 2011). We explore the relationship of both earthquake characteristics and area characteristics with homelessness after the earthquake. We consider modelled variables such as population density, HDI, year, measures of ground motion intensity developed in Daniell (2014) over the time period from 1900-2013 as well as temperature. Using a base methodology based on that used for PAGER fatality fragility curves developed by Jaiswal and Wald (2010), but using regression through time using the socioeconomic parameters developed in Daniell et al. (2012) for "socioeconomic fragility functions", we develop a set of fragility curves that can be

Postfledging survival of Grasshopper Sparrows in grasslands managed with fire and grazing

Science.gov (United States)

Hovick, Torre J.; Miller, James R.; Koford, Rolf R.; Engle, David M.; Debinski, Diane M.

2011-01-01

More accurate estimates of survival after nestlings fledge are needed for population models to be parameterized and population dynamics to be understood during this vulnerable life stage. The period after fledging is the time when chicks learn to fly, forage, and hide from predators. We monitored postfledging survival, causespecific mortality, and movements of Grasshopper Sparrows (Ammodramus savannarum) in grassland managed with fire and grazing. In 2009, we attached radio transmitters to 50 nestlings from 50 different broods and modeled their survival in response to climatic, biological, and ecological variables. There was no effect of treatment on survival. The factor most influencing postfledging survival was age; no other variable was significant. The majority of chicks (74%) died within 3 days of radio-transmitter attachment. We attributed most mortality to mesopredators (48%) and exposure (28%). Fledglings' movements increased rapidly for the first 4 days after they left the nest and were relatively stable for the remaining 10 days we tracked them. On average, fledglings took flight for the first time 4 days after fledging and flew ≥10 m 9 days after fledging. Our data show that the Grasshopper Sparrow's survival rates may be less than most models relying on nest-success estimates predict, and we emphasize the importance of incorporating estimates of survival during the postfledging period in demographic models.

Uncontrolled non-heartbeating donors (types i-ii) with normothermic recirculation vs. heartbeating donors: evaluation of functional results and survival.

Science.gov (United States)

Miranda-Utrera, N; Medina-Polo, J; Pamplona-Casamayor, M; Passas-Martínez, J B; Rodríguez-Antolín, A; de la Rosa Kehrmann, F; Duarte-Ojeda, J M; Tejido-Sánchez, A; Villacampa Aubá, F; Andrés Belmonte, A

2015-09-01

Non-heartbeating donors (NHBD) are an alternative to heartbeating donors (HBD). Our objective was to compare functional results and kidney survival from NHBDs and HBDs. A retrospective study comparing the results of 236 normothermically preserved kidneys from type i and ii type NHBDs with the results of 250 from HBDs that were transplanted in our center between 2005 and 2012. Homogeneity between groups was tested and we evaluated the presence of delayed graft function (DGF) associated with pretransplant variables of the donor and recipient. Both groups show homogeneity in pretransplant characteristics in terms of: age, HLA incompatibilities, and recipient hemodialysis time. Average follow-up time was 33 months (range 0-87) for NHBDs and 38 months (range 0-90) for HBDs. 5.5% of NHBDs showed primary non-function (PNF) vs. 4% of HBDs (P=.42) and 80.9% of DGF vs. 46.8% of HBDs (P<.001). At the end of the follow-up, there were no statistically significant differences in the survival of grafts (92.8% for NHBD vs. 93.6% for HBD, P=.71) and recipients (99.1% NHBD vs. 98.6% HBD, P=.28). Although the DGF percentage was greater for NHBDs, final creatinine as well as graft and recipient survival were similar for both groups. Therefore, in our experience, kidneys from NHBDs have similar results to those from HBDs and are an excellent source of organs for transplantation. Copyright © 2014 AEU. Publicado por Elsevier España, S.L.U. All rights reserved.

The evaluation of the long term survival and functions in the autonomic nerve-sparing operation with pre-operative radiotherapy for rectal cancer

International Nuclear Information System (INIS)

Saito, Norio; Sarashina, Hiromi; Nunomura, Masao; Koda, Keiji; Takiguchi, Nobuhiro; Soda, Hiroaki; Ozaki, Kazuyoshi; Sugaya, Yoshiki; Nakajima, Nobuyuki

1997-01-01

One hundred and ninety five patients have been received autonomic nerve-sparing operations for rectal cancer in our department since 1984. These patients were classified into two groups, those with preoperative irradiation (irradiated group) and those with surgery alone. The survival rates and the local recurrence rates for these patients were compared, and post-operative urinary and male sexual functions were discussed. The overall cumulative five-year and nine-year survival rates were 80.3% and 66.5%, whereas those in the irradiated group were 84.0% and 77.7%, and those in the surgery alone group were 74.6% and 62.9%. Local recurrence rates were 9.6% all, 5.6% in the irradiated groups, and 11.9% in the surgery alone group. Maintenance of urinary function was successful in almost all patients with bilateral and unilateral pelvic nerve plexus. But the sexual function in males especially ejaculation was preserved in only 54.5% of the patients with bilateral hypogastric nerve and pelvic plexus, and in only 14.3% of the patients with unilateral saving. There was no significant deference in the outcome of the two group, but there was a tendency to obtain the better survival and to decrease the local recurrence in the irradiated group. It was difficult to preserve the sexual function by the nerve-sparing operation with lymphadevectomy. (author)

A composite likelihood approach for spatially correlated survival data

Science.gov (United States)

Paik, Jane; Ying, Zhiliang

2013-01-01

The aim of this paper is to provide a composite likelihood approach to handle spatially correlated survival data using pairwise joint distributions. With e-commerce data, a recent question of interest in marketing research has been to describe spatially clustered purchasing behavior and to assess whether geographic distance is the appropriate metric to describe purchasing dependence. We present a model for the dependence structure of time-to-event data subject to spatial dependence to characterize purchasing behavior from the motivating example from e-commerce data. We assume the Farlie-Gumbel-Morgenstern (FGM) distribution and then model the dependence parameter as a function of geographic and demographic pairwise distances. For estimation of the dependence parameters, we present pairwise composite likelihood equations. We prove that the resulting estimators exhibit key properties of consistency and asymptotic normality under certain regularity conditions in the increasing-domain framework of spatial asymptotic theory. PMID:24223450

A composite likelihood approach for spatially correlated survival data.

Science.gov (United States)

Paik, Jane; Ying, Zhiliang

2013-01-01

The aim of this paper is to provide a composite likelihood approach to handle spatially correlated survival data using pairwise joint distributions. With e-commerce data, a recent question of interest in marketing research has been to describe spatially clustered purchasing behavior and to assess whether geographic distance is the appropriate metric to describe purchasing dependence. We present a model for the dependence structure of time-to-event data subject to spatial dependence to characterize purchasing behavior from the motivating example from e-commerce data. We assume the Farlie-Gumbel-Morgenstern (FGM) distribution and then model the dependence parameter as a function of geographic and demographic pairwise distances. For estimation of the dependence parameters, we present pairwise composite likelihood equations. We prove that the resulting estimators exhibit key properties of consistency and asymptotic normality under certain regularity conditions in the increasing-domain framework of spatial asymptotic theory.

A survival model for fractionated radiotherapy with an application to prostate cancer

Energy Technology Data Exchange (ETDEWEB)

Zaider, Marco [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY (United States)]. E-mail: Zaiderm@mskcc.org; Zelefsky, Michael J.; Leibel, Steven A. [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Hanin, Leonid G. [Department of Mathematics, Idaho State University, Pocatello, ID (United States); Tsodikov, Alexander D.; Yakovlev, Andrei Y. [Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT (United States)

2001-10-01

This paper explores the applicability of a mechanistic survival model, based on the distribution of clonogens surviving a course of fractionated radiation therapy, to clinical data on patients with prostate cancer. The study was carried out using data on 1100 patients with clinically localized prostate cancer who were treated with three-dimensional conformal radiation therapy. The patients were stratified by radiation dose (group 1: <67.5 Gy; group 2: 67.5-72.5 Gy; group 3: 72.5-77.5 Gy; group 4: 77.5-87.5 Gy) and prognosis category (favourable, intermediate and unfavourable as defined by pre-treatment PSA and Gleason score). A relapse was recorded when tumour recurrence was diagnosed or when three successive prostate specific antigen (PSA) elevations were observed from a post-treatment nadir PSA level. PSA relapse-free survival was used as the primary end point. The model, which is based on an iterated Yule process, is specified in terms of three parameters: the mean number of tumour clonogens that survive the treatment, the mean of the progression time of post-treatment tumour development and its standard deviation. The model parameters were estimated by the maximum likelihood method. The fact that the proposed model provides an excellent description both of the survivor function and of the hazard rate is prima facie evidence of the validity of the model because closeness of the two survivor functions (empirical and model-based) does not generally imply closeness of the corresponding hazard rates. The estimated cure probabilities for the favourable group are 0.80, 0.74 and 0.87 (for dose groups 1-3, respectively); for the intermediate group: 0.25, 0.51, 0.58 and 0.78 (for dose groups 1-4, respectively) and for the unfavourable group: 0.0, 0.27, 0.33 and 0.64 (for dose groups 1-4, respectively). The distribution of progression time to tumour relapse was found to be independent of prognosis group but dependent on dose. As the dose increases the mean progression

Survival analysis II: Cox regression

NARCIS (Netherlands)

Stel, Vianda S.; Dekker, Friedo W.; Tripepi, Giovanni; Zoccali, Carmine; Jager, Kitty J.

2011-01-01

In contrast to the Kaplan-Meier method, Cox proportional hazards regression can provide an effect estimate by quantifying the difference in survival between patient groups and can adjust for confounding effects of other variables. The purpose of this article is to explain the basic concepts of the

Volunteering is associated with increased survival in able-bodied participants of the English Longitudinal Study of Ageing.

Science.gov (United States)

Rogers, Nina Trivedy; Demakakos, Panayotes; Taylor, Mark Steven; Steptoe, Andrew; Hamer, Mark; Shankar, Aparna

2016-06-01

Volunteering has been linked to reduced mortality in older adults, but the mechanisms explaining this effect remain unclear. This study investigated whether volunteering is associated with increased survival in participants of the English Longitudinal Study of Ageing and whether differences in survival are modified by functional disabilities. A multivariate Cox Proportional Hazards model was used to estimate the association of volunteering with survival over a period of 10.9 years in 10 324 participants, while controlling for selected confounders. To investigate effect modification by disability, the analyses were repeated in participants with and without self-reported functional disabilities. Volunteering was associated with a reduced probability of death from all causes in univariate analyses (HR=0.65, CI 0.58 to 0.73, pvolunteers had significantly increased survival compared with able-bodied non-volunteers (HR=0.81, 95% CI 0.69 to 0.95, p=0.009). There was no significant survival advantage among disabled volunteers, compared with disabled non-volunteers (HR=1.06, CI 0.88 to 1.29, p=0.53). Volunteering is associated with reduced mortality in older adults in England, but this effect appears to be limited to volunteers who report no disabilities. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Effect of gamma-irradiation on mouse pancreatic islet-allograft survival

International Nuclear Information System (INIS)

Kanai, T.; Porter, J.; Gotoh, M.; Monaco, A.P.; Maki, T.

1989-01-01

Elimination or inactivation of lymphoid tissue in the pancreatic islet preparation achieves prolongation of islet-allograft survival. In this study we examined the effect of gamma-irradiation on mouse islet-allograft survival. In a B6AF1 isograft model, irradiation up to 2400 rad did not induce deterioration of islet function over 200 days, but greater doses caused cessation of graft function between 83 and 186 days. When DBA/2 crude islets were transplanted into B6AF1 recipients, all nonirradiated allografts were acutely rejected. Marked prolongation of allograft survival was achieved by islet irradiation with doses between 800 and 12,000 rad. With higher doses, significant numbers of allografts survived beyond the controls, but many lost function between 78 and 180 days, with none surviving greater than 200 days. Irradiation with 16,000 rad caused acute radiation damage. Because most secondary islet allografts in recipient mice that lost primary islet-graft function between 84 and 195 days survived greater than 100 days, late functional loss was probably due to the radiation injury. Combined use of recipient treatment with cyclosporin A and graft irradiation (2400 rad) achieved prolongation of DBA/2 islets in B6AF1 mice

Juvenile survival in a tropical population of roseate terns: Interannual variation and effect of tick parasitism

Science.gov (United States)

Monticelli, David; Ramos, Jaime A.; Hines, James E.; Nichols, James D.; Spendelow, Jeffrey A.

2008-01-01

Many demographic studies on long-lived seabirds have focused on the estimation of adult survival, but much less is known about survival during the early years of life, especially in tropical species. We report analyses of a capture–recapture dataset of 685 roseate terns ringed as fledglings and adults between 1998 and 2005 on Aride Island, Seychelles, and recaptured/resighted at the same colony site over a 5 yr (2002 to 2006) period. A multistate model was used to estimate survival for different age classes, including juvenile (first-year) birds returning as non-breeding prospectors. The effect of infestation by parasites (ticks) on survival was also examined. Overall, the estimated return of first-year individuals to the natal colony was very variable, ranging from 2 to 22%. Conditioned on survival, the probability of returning from Age 2 yr onwards increased to 70%. Survival rates were best modeled as time-specific, with estimates varying from 0.02 to 1.00 (mean 0.69) in first-year birds with a marked negative effect of tick infestation. In older birds (minimum age of 2 yr), the annual estimates fell between 0.69 and 0.86 (mean 0.77). Using a components of variance approach for estimation of year-to-year variation, we found high temporal variability for first-year individuals (coefficient of variation [CV] = 65%) compared to much less variation in the survival rate of older birds (CV = 9%). These findings agree with the life-history prediction that demographic rates of juveniles are usually lower and more variable than those of older individuals. Our results are also consistent with the predicted negative effect of tick parasitism on juvenile survival. Compared with data from other roseate tern populations, survival over the first 2 yr (Age 0 to 2 yr) was 18 to 40% higher in this study, suggesting that a high ‘young’ survival rate may be an important demographic trait in this tropical population to compensate for the low annual reproductive success. Our

Linking age, survival, and transit time distributions

Science.gov (United States)

Calabrese, Salvatore; Porporato, Amilcare

2015-10-01

Although the concepts of age, survival, and transit time have been widely used in many fields, including population dynamics, chemical engineering, and hydrology, a comprehensive mathematical framework is still missing. Here we discuss several relationships among these quantities by starting from the evolution equation for the joint distribution of age and survival, from which the equations for age and survival time readily follow. It also becomes apparent how the statistical dependence between age and survival is directly related to either the age dependence of the loss function or the survival-time dependence of the input function. The solution of the joint distribution equation also allows us to obtain the relationships between the age at exit (or death) and the survival time at input (or birth), as well as to stress the symmetries of the various distributions under time reversal. The transit time is then obtained as a sum of the age and survival time, and its properties are discussed along with the general relationships between their mean values. The special case of steady state case is analyzed in detail. Some examples, inspired by hydrologic applications, are presented to illustrate the theory with the specific results. This article was corrected on 11 Nov 2015. See the end of the full text for details.

Estimating the Partition Function Zeros by Using the Wang-Landau Monte Carlo Algorithm

Energy Technology Data Exchange (ETDEWEB)

Kim, Seung-Yeon [Korea National University of Transportation, Chungju (Korea, Republic of)

2017-03-15

The concept of the partition function zeros is one of the most efficient methods for investigating the phase transitions and the critical phenomena in various physical systems. Estimating the partition function zeros requires information on the density of states Ω(E) as a function of the energy E. Currently, the Wang-Landau Monte Carlo algorithm is one of the best methods for calculating Ω(E). The partition function zeros in the complex temperature plane of the Ising model on an L × L square lattice (L = 10 ∼ 80) with a periodic boundary condition have been estimated by using the Wang-Landau Monte Carlo algorithm. The efficiency of the Wang-Landau Monte Carlo algorithm and the accuracies of the partition function zeros have been evaluated for three different, 5%, 10%, and 20%, flatness criteria for the histogram H(E).

Landscape‐level patterns in fawn survival across North America

Science.gov (United States)

Gingery, Tess M.; Diefenbach, Duane R.; Wallingford, Bret D.; Rosenberry, Christopher S.

2018-01-01

A landscape‐level meta‐analysis approach to examining early survival of ungulates may elucidate patterns in survival not evident from individual studies. Despite numerous efforts, the relationship between fawn survival and habitat characteristics remains unclear and there has been no attempt to examine trends in survival across landscape types with adequate replication. In 2015–2016, we radiomarked 98 white‐tailed deer (Odocoileus virginianus) fawns in 2 study areas in Pennsylvania. By using a meta‐analysis approach, we compared fawn survival estimates from across North America using published data from 29 populations in 16 states to identify patterns in survival and cause‐specific mortality related to landscape characteristics, predator communities, and deer population density. We modeled fawn survival relative to percentage of agricultural land cover and deer density. Estimated average survival to 3–6 months of age was 0.414 ± 0.062 (SE) in contiguous forest landscapes (no agriculture) and for every 10% increase in land area in agriculture, fawn survival increased 0.049 ± 0.014. We classified cause‐specific mortality as human‐caused, natural (excluding predation), and predation according to agriculturally dominated, forested, and mixed (i.e., both agricultural and forest cover) landscapes. Predation was the greatest source of mortality in all landscapes. Landscapes with mixed forest and agricultural cover had greater proportions and rates of human‐caused mortalities, and lower proportions and rates of mortality due to predators, when compared to forested landscapes. Proportion and rate of natural deaths did not differ among landscapes. We failed to detect any relationship between fawn survival and deer density. The results highlight the need to consider multiple spatial scales when accounting for factors that influence fawn survival. Furthermore, variation in mortality sources and rates among landscapes indicate the potential for

Survival and Functionality of hESC-Derived Retinal Pigment Epithelium Cells Cultured as a Monolayer on Polymer Substrates Transplanted in RCS Rats.

Science.gov (United States)

Thomas, Biju B; Zhu, Danhong; Zhang, Li; Thomas, Padmaja B; Hu, Yuntao; Nazari, Hossein; Stefanini, Francisco; Falabella, Paulo; Clegg, Dennis O; Hinton, David R; Humayun, Mark S

2016-05-01

To determine the safety, survival, and functionality of human embryonic stem cell-derived RPE (hESC-RPE) cells seeded on a polymeric substrate (rCPCB-RPE1 implant) and implanted into the subretinal (SR) space of Royal College of Surgeons (RCS) rats. Monolayers of hESC-RPE cells cultured on parylene membrane were transplanted into the SR space of 4-week-old RCS rats. Group 1 (n = 46) received vitronectin-coated parylene membrane without cells (rMSPM+VN), group 2 (n = 59) received rCPCB-RPE1 implants, and group 3 (n = 13) served as the control group. Animals that are selected based on optical coherence tomography screening were subjected to visual function assays using optokinetic (OKN) testing and superior colliculus (SC) electrophysiology. At approximately 25 weeks of age (21 weeks after surgery), the eyes were examined histologically for cell survival, phagocytosis, and local toxicity. Eighty-seven percent of the rCPCB-RPE1-implanted animals showed hESC-RPE survivability. Significant numbers of outer nuclear layer cells were rescued in both group 1 (rMSPM+VN) and group 2 (rCPCB-RPE1) animals. A significantly higher ratio of rod photoreceptor cells to cone photoreceptor cells was found in the rCPCB-RPE1-implanted group. Animals with rCPCB-RPE1 implant showed hESC-RPE cells containing rhodopsin-positive particles in immunohistochemistry, suggesting phagocytic function. Superior colliculus mapping data demonstrated that a significantly higher number of SC sites responded to light stimulus at a lower luminance threshold level in the rCPCB-RPE1-implanted group. Optokinetic data suggested both implantation groups showed improved visual acuity. These results demonstrate the safety, survival, and functionality of the hESC-RPE monolayer transplantation in an RPE dysfunction rat model.

Drawbacks of the use of indirect estimates of renal function to evaluate the effect of risk factors on renal function

NARCIS (Netherlands)

Verhave, JC; Gansevoort, RT; Hillege, HL; De Zeeuw, D; Curhan, GC; De Jong, PE

Many epidemiologic studies presently aim to evaluate the effect of risk factors on renal function. As direct measurement of renal function is cumbersome to perform, epidentiologic studies generally use an indirect estimate of renal function. The consequences of using different methods of renal

Multinational Companies, Technology Spillovers, and Plant Survival

OpenAIRE

Holger Görg; Eric Strobl

2003-01-01

This paper examines the effect of the presence of multinational companies on plant survival in the host country. We postulate that multinational companies can impact positively on plant survival through technology spillovers. We study the nature of the effect of multinationals using a Cox proportional hazard model which we estimate using plant level data for Irish manufacturing industries. Our results show that the presence of multinationals has a life enhancing effect only on indigenous plan...

The statistical treatment of cell survival data

International Nuclear Information System (INIS)

Boag, J.W.

1975-01-01

The paper considers the sources of experimental error in cell survival experiments and discusses in simple terms how these combine to influence the accuracy of single points and the parameters of complete survival curves. Cell sampling and medium-dilution errors are discussed at length and one way of minimizing the former is examined. The Monte-Carlo method of estimating the distribution of derived parameters in small samples is recommended and illustrated. (author)

Extensions and Applications of the Cox-Aalen Survival Model

DEFF Research Database (Denmark)

Scheike, Thomas H.; Zhang, Mei-Jie

2003-01-01

Aalen additive risk model; competing risk; counting processes; Cox model; cumulative incidence function; goodness of fit; prediction of survival probability; time-varying effects......Aalen additive risk model; competing risk; counting processes; Cox model; cumulative incidence function; goodness of fit; prediction of survival probability; time-varying effects...

SEMI-COMPETING RISKS ON A TRIVARIATE WEIBULL SURVIVAL MODEL

Directory of Open Access Journals (Sweden)

Jenq-Daw Lee

2008-07-01

Full Text Available A setting of a trivairate survival function using semi-competing risks concept is proposed, in which a terminal event can only occur after other events. The Stanford Heart Transplant data is reanalyzed using a trivariate Weibull distribution model with the proposed survival function.

Causal Mediation Analysis for the Cox Proportional Hazards Model with a Smooth Baseline Hazard Estimator.

Science.gov (United States)

Wang, Wei; Albert, Jeffrey M

2017-08-01

An important problem within the social, behavioral, and health sciences is how to partition an exposure effect (e.g. treatment or risk factor) among specific pathway effects and to quantify the importance of each pathway. Mediation analysis based on the potential outcomes framework is an important tool to address this problem and we consider the estimation of mediation effects for the proportional hazards model in this paper. We give precise definitions of the total effect, natural indirect effect, and natural direct effect in terms of the survival probability, hazard function, and restricted mean survival time within the standard two-stage mediation framework. To estimate the mediation effects on different scales, we propose a mediation formula approach in which simple parametric models (fractional polynomials or restricted cubic splines) are utilized to approximate the baseline log cumulative hazard function. Simulation study results demonstrate low bias of the mediation effect estimators and close-to-nominal coverage probability of the confidence intervals for a wide range of complex hazard shapes. We apply this method to the Jackson Heart Study data and conduct sensitivity analysis to assess the impact on the mediation effects inference when the no unmeasured mediator-outcome confounding assumption is violated.

Linear estimates of structure functions from deep inelastic lepton-nucleon scattering data. Part 1

International Nuclear Information System (INIS)

Anikeev, V.B.; Zhigunov, V.P.

1991-01-01

This paper concerns the linear estimation of structure functions from muon(electron)-nucleon scattering. The expressions obtained for the structure functions estimate provide correct analysis of the random error and the bias The bias arises because of the finite number of experimental data and the finite resolution of experiment. The approach suggested may become useful for data handling from experiments at HERA. 9 refs

A recursive Monte Carlo method for estimating importance functions in deep penetration problems

International Nuclear Information System (INIS)

Goldstein, M.

1980-04-01

A pratical recursive Monte Carlo method for estimating the importance function distribution, aimed at importance sampling for the solution of deep penetration problems in three-dimensional systems, was developed. The efficiency of the recursive method was investigated for sample problems including one- and two-dimensional, monoenergetic and and multigroup problems, as well as for a practical deep-penetration problem with streaming. The results of the recursive Monte Carlo calculations agree fairly well with Ssub(n) results. It is concluded that the recursive Monte Carlo method promises to become a universal method for estimating the importance function distribution for the solution of deep-penetration problems, in all kinds of systems: for many systems the recursive method is likely to be more efficient than previously existing methods; for three-dimensional systems it is the first method that can estimate the importance function with the accuracy required for an efficient solution based on importance sampling of neutron deep-penetration problems in those systems

Modulation transfer function estimation of optical lens system by adaptive neuro-fuzzy methodology

Science.gov (United States)

Petković, Dalibor; Shamshirband, Shahaboddin; Pavlović, Nenad T.; Anuar, Nor Badrul; Kiah, Miss Laiha Mat

2014-07-01

The quantitative assessment of image quality is an important consideration in any type of imaging system. The modulation transfer function (MTF) is a graphical description of the sharpness and contrast of an imaging system or of its individual components. The MTF is also known and spatial frequency response. The MTF curve has different meanings according to the corresponding frequency. The MTF of an optical system specifies the contrast transmitted by the system as a function of image size, and is determined by the inherent optical properties of the system. In this study, the adaptive neuro-fuzzy (ANFIS) estimator is designed and adapted to estimate MTF value of the actual optical system. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system. The back propagation learning algorithm is used for training this network. This intelligent estimator is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.

Cancer survival among Alaska Native people.

Science.gov (United States)

Nash, Sarah H; Meisner, Angela L W; Zimpelman, Garrett L; Barry, Marc; Wiggins, Charles L

2018-03-26

Recent cancer survival trends among American Indian and Alaska Native (AN) people are not well understood; survival has not been reported among AN people since 2001. This study examined cause-specific survival among AN cancer patients for lung, colorectal, female breast, prostate, and kidney cancers. It evaluated whether survival differed between cancers diagnosed in 1992-2002 (the earlier period) and cancers diagnosed in 2003-2013 (the later period) and by the age at diagnosis (<65 vs ≥65 years), stage at diagnosis (local or regional/distant/unknown), and sex. Kaplan-Meier and Cox proportional hazards models were used to estimate univariate and multivariate-adjusted cause-specific survival for each cancer. An improvement was observed in 5-year survival over time from lung cancer (hazard ratio [HR] for the later period vs the earlier period, 0.83; 95% confidence interval [CI], 0.72-0.97), and a marginally nonsignificant improvement was observed for colorectal cancer (HR, 0.81; 95% CI, 0.66-1.01). Site-specific differences in survival were observed by age and stage at diagnosis. This study presents the first data on cancer survival among AN people in almost 2 decades. During this time, AN people have experienced improvements in survival from lung and colorectal cancers. The reasons for these improvements may include increased access to care (including screening) as well as improvements in treatment. Improving cancer survival should be a priority for reducing the burden of cancer among AN people and eliminating cancer disparities. Cancer 2018. © 2018 American Cancer Society. © 2018 American Cancer Society.

Introduction to SURPH.1 analysis of release-recapture data for survival studies

International Nuclear Information System (INIS)

Smith, S.G.; Skalski, J.R.; Schlechte, J.W.; Hoffmann, A.; Cassen, V.

1994-12-01

Program SURPH is the culmination of several years of research to develop a comprehensive computer program to analyze survival studies of fish and wildlife populations. Development of this software was motivated by the advent of the PIT-tag (Passive Integrated Transponder) technology that permits the detection of salmonid smolt as they pass through hydroelectric facilities on the Snake and Columbia Rivers in the Pacific Northwest. Repeated detections of individually tagged smolt and analysis of their capture-histories permits estimates of downriver survival probabilities. Eventual installation of detection facilities at adult fish ladders will also permit estimation of ocean survival and upstream survival of returning salmon using the statistical methods incorporated in SURPH.1. However, the utility of SURPH.1 far exceeds solely the analysis of salmonid tagging studies. Release-recapture and radiotelemetry studies from a wide range of terrestrial and aquatic species have been analyzed using SURPH.1 to estimate discrete time survival probabilities and investigate survival relationships. The interactive computing environment of SURPH.1 was specifically developed to allow researchers to investigate the relationship between survival and capture processes and environmental, experimental and individual-based covariates. Program SURPH.1 represents a significant advancement in the ability of ecologists to investigate the interplay between morphologic, genetic, environmental and anthropogenic factors on the survival of wild species. It is hoped that this better understanding of risk factors affecting survival will lead to greater appreciation of the intricacies of nature and to improvements in the management of wild resources. This technical report is an introduction to SURPH.1 and provides a user guide for both the UNIX and MS-Windows reg-sign applications of the SURPH software

On the analysis of clonogenic survival data: Statistical alternatives to the linear-quadratic model

International Nuclear Information System (INIS)

Unkel, Steffen; Belka, Claus; Lauber, Kirsten

2016-01-01

the extraction of scores of radioresistance, which displayed significant correlations with the estimated parameters of the regression models. Undoubtedly, LQ regression is a robust method for the analysis of clonogenic survival data. Nevertheless, alternative approaches including non-linear regression and multivariate techniques such as cluster analysis and principal component analysis represent versatile tools for the extraction of parameters and/or scores of the cellular response towards ionizing irradiation with a more intuitive biological interpretation. The latter are highly informative for correlation analyses with other types of data, including functional genomics data that are increasingly beinggenerated

Acoustic Telemetry Studies of Juvenile Chinook Salmon Survival at the Lower Columbia Projects in 2006

Energy Technology Data Exchange (ETDEWEB)

Ploskey, Gene R.; Weiland, Mark A.; Hughes, James S.; Zimmerman, Shon A.; Durham, Robin E.; Fischer, Eric S.; Kim, Jina; Townsend, Richard L.; Skalski, John R.; McComas, Roy L.

2008-02-01

The Portland District of the U.S. Army Corps of Engineers contracted with the Pacific Northwest National Laboratory (PNNL) to conduct three studies using acoustic telemetry to estimate detection probabilities and survival of juvenile Chinook salmon at three hydropower projects on the lower Columbia River. The primary goals were to estimate detection and survival probabilities based on sampling with JSATS equipment, assess the feasibility of using JSATS for survival studies, and estimate sample sizes needed to obtain a desired level of precision in future studies. The 2006 JSATS arrays usually performed as well or better than radio telemetry arrays in the JDA and TDA tailwaters, and underperformed radio arrays in the BON tailwater, particularly in spring. Most of the probabilities of detection on at least one of all arrays in a tailwater exceeded 80% for each method, which was sufficient to provide confidence in survival estimates. The probability of detection on one of three arrays includes survival and detection probabilities because fish may die or pass all three arrays undetected but alive.

Working Conditions and Factory Survival: Evidence from Better Factories Cambodia

OpenAIRE

Robertson, Raymond; Brown, Drusilla; Dehejia, Rajeev

2016-01-01

A large and growing literature has identified several conditions, including exporting, that contribute to plant survival. A prevailing sentiment suggests that anti-sweatshop activity against plants in developing countries adds the risk of making survival more difficult by imposing external constraints that may interfere with optimizing behavior. Using a relatively new plant-level panel dataset from Cambodia, this paper applies survival analysis to estimate the relationship between changes in ...

Using Survival Analysis to Evaluate Medical Equipment Battery Life.

Science.gov (United States)

Kuhajda, David

2016-01-01

As hospital medical device managers obtain more data, opportunities exist for using the data to improve medical device management, enhance patient safety, and evaluate costs of decisions. As a demonstration of the ability to use data analytics, this article applies survival analysis statistical techniques to assist in making decisions on medical equipment maintenance. The analysis was performed on a large amount of data related to failures of an infusion pump manufacturer's lithium battery and two aftermarket replacement lithium batteries from one hospital facility. The survival analysis resulted in statistical evidence showing that one of the third-party batteries had a lower survival curve than the infusion pump manufacturer's battery. This lower survival curve translates to a shorter expected life before replacement is needed. The data suggested that to limit unexpected failures, replacing batteries at a two-year interval, rather than the current industry recommendation of three years, may be warranted. For less than $5,400 in additional annual cost, the risk of unexpected battery failures can be reduced from an estimated 28% to an estimated 7%.

Audit in radiation therapy: long-term survival and cost of treatment

International Nuclear Information System (INIS)

Stevens, G.; Firth, I.

1997-01-01

In order to determine the cost of radiation treatment and the survival rate of a cohort of patients treated in a 6 month period in 1988, estimates of the capital and recurrent costs of this service were made for the calendar year 1988, expressed as $A(1988). Data collected prospectively included workload statistics (including number of attendances), field treated and complexity of treatment. Patient and tumour-related data included tumour site, intent of treatment and survival. The survival rate of patients during this period was determined in June 1995. The cost per field in 1988 was estimated at $A44.32. The 1988 costs of courses of definitive, adjuvant and palliative radiation therapy were estimated at $A2545, $A2482 and $A929, respectively. The major contributor to the cost of salaries and consumables within the Radiation Oncology Department (81.6%), with capital costs accounting for 13.5%, overheads accounting for 4.5% of the costs and planned admissions accounting for 0.2%. The median survival time of 580 patients with malignant disease treated during this period in 1988 was 12.4 months. The overall 5 year survival rate was 27%. For 105 patients treated definitively with radiation therapy, the median and 5 year survival rate figures were 26.0 months and 40%. For 149 patients treated with adjuvant radiation therapy, the 5 year survival rate was 62% (median survival rate not reached). For 279 patients treated palliatively, median and 5 year survival rate figures were 5.2 months and 3%. The cost per month of survival for all patients with malignancy was $A67; the figures for definitive , adjuvant and palliative treatments being $A74, $A48 and $A105, respectively. A sensitivity analysis indicated that these figures were robust. The cost of radiation treatment per field was comparable to reports for other centres and emphasizes the utility of radiation therapy as a cost-effective cancer treatment modality. 7 refs., 6 tabs., 2 figs

Postoperative Insulin-Like Growth Factor 1 Levels Reflect the Graft's Function and Predict Survival after Liver Transplantation.

Directory of Open Access Journals (Sweden)

Daniele Nicolini

Full Text Available The reduction of insulin-like growth factor 1 (IGF-1 plasma levels is associated with the degree of liver dysfunction and mortality in cirrhotic patients. However, little research is available on the recovery of the IGF-1 level and its prognostic role after liver transplantation (LT.From April 2010 to May 2011, 31 patients were prospectively enrolled (25/6 M/F; mean age±SEM: 55.2±1.4 years, and IGF-1 serum levels were assessed preoperatively and at 15, 30, 90, 180 and 365 days after transplantation. The influence of the donor and recipient characteristics (age, use of extended criteria donor grafts, D-MELD and incidence of early allograft dysfunction on hormonal concentration was analyzed. The prognostic role of IGF-1 level on patient survival and its correlation with routine liver function tests were also investigated.All patients showed low preoperative IGF-1 levels (mean±SEM: 29.5±2.1, and on postoperative day 15, a significant increase in the IGF-1 plasma level was observed (102.7±11.7 ng/ml; p65 years or extended criteria donor grafts. An inverse correlation between IGF-1 and bilirubin serum levels at day 15 (r = -0.3924, p = 0.0320 and 30 (r = -0.3894, p = 0.0368 was found. After multivariate analysis, early (within 15 days IGF-1 normalization [Exp(b = 3.913; p = 0.0484] was the only prognostic factor associated with an increased 3-year survival rate.IGF-1 postoperative levels are correlated with the graft's quality and reflect liver function. Early IGF-1 recovery is associated with a higher 3-year survival rate after LT.

Depression and Liver Transplant Survival.

Science.gov (United States)

Meller, William; Welle, Nicole; Sutley, Kristen; Thurber, Steven

Patients who underwent liver transplantation and experienced clinical depression have heretofore evinced lower survival rates when compared to nondepressed counterparts. To investigate the hypothesis that transplant patients who seek and obtain medical treatment for depression would circumvent the prior reduced survival findings. A total of 765 patients with liver transplants were scrutinized for complications following transplantation. Further, 104 patients experienced posttransplant depression as manifested by diagnosis and treatment by medical personnel. Survival analyses were conducted comparing hazard and survival curves for these selected individuals and the remainder of transplant patients. Contrary to prior data and consistent with the aforementioned hypothesis, median survival durations, survival curves, and hazard functions (controlling for age and prolonged posttransplant survival for the depressed patients were better. The improved survival for the depressed patients may simply be related to an amelioration of depressed symptoms via antidepressant medications. However, this interpretation would only be congruent with reduced hazard, not elevated survival, beyond the norm (median) for other transplant participants. Assuming the reliability and generalization of our findings, perhaps a reasonable and compelling interpretation is that combined with the effectiveness of antidepressant medications, the seeking and receiving treatment for depression is a type of proxy measure of a more global pattern of adherence to recommended posttransplant medical regimens. Copyright © 2017 The Academy of Psychosomatic Medicine. Published by Elsevier Inc. All rights reserved.

Iohexol clearance is superior to creatinine-based renal function estimating equations in detecting short-term renal function decline in chronic heart failure.

Science.gov (United States)

Cvan Trobec, Katja; Kerec Kos, Mojca; von Haehling, Stephan; Anker, Stefan D; Macdougall, Iain C; Ponikowski, Piotr; Lainscak, Mitja

2015-12-01

To compare the performance of iohexol plasma clearance and creatinine-based renal function estimating equations in monitoring longitudinal renal function changes in chronic heart failure (CHF) patients, and to assess the effects of body composition on the equation performance. Iohexol plasma clearance was measured in 43 CHF patients at baseline and after at least 6 months. Simultaneously, renal function was estimated with five creatinine-based equations (four- and six-variable Modification of Diet in Renal Disease, Cockcroft-Gault, Cockcroft-Gault adjusted for lean body mass, Chronic Kidney Disease Epidemiology Collaboration equation) and body composition was assessed using bioimpedance and dual-energy x-ray absorptiometry. Over a median follow-up of 7.5 months (range 6-17 months), iohexol clearance significantly declined (52.8 vs 44.4 mL/[min ×1.73 m2], P=0.001). This decline was significantly higher in patients receiving mineralocorticoid receptor antagonists at baseline (mean decline -22% of baseline value vs -3%, P=0.037). Mean serum creatinine concentration did not change significantly during follow-up and no creatinine-based renal function estimating equation was able to detect the significant longitudinal decline of renal function determined by iohexol clearance. After accounting for body composition, the accuracy of the equations improved, but not their ability to detect renal function decline. Renal function measured with iohexol plasma clearance showed relevant decline in CHF patients, particularly in those treated with mineralocorticoid receptor antagonists. None of the equations for renal function estimation was able to detect these changes. ClinicalTrials.gov registration number: NCT01829880.

School District Inputs and Biased Estimation of Educational Production Functions.

Science.gov (United States)

Watts, Michael

1985-01-01

In 1979, Eric Hanushek pointed out a potential problem in estimating educational production functions, particularly at the precollege level. He observed that it is frequently inappropriate to include school-system variables in equations using the individual student as the unit of observation. This study offers limited evidence supporting this…

Functional survival after acute care for severe head injury at a designated trauma center in Hong Kong.

Science.gov (United States)

Taw, Benedict B T; Lam, Alan C S; Ho, Faith L Y; Hung, K N; Lui, W M; Leung, Gilberto K K

2012-07-01

Severe head injury is known to be a major cause of early mortalities and morbidities. Patients' long-term outcome after acute care, however, has not been widely studied. We aim to review the outcome of severely head-injured patients after discharge from acute care at a designated trauma center in Hong Kong. This is a retrospective study of prospectively collected data of patients admitted with severe head injuries between 2004 and 2008. Patients' functional status post-discharge was assessed using the Extended Glasgow Outcome Score (GOSE). Of a total of 1565 trauma patients, 116 had severe head injuries and 41 of them survived acute hospital care. Upon the last follow-up, 23 (56.1%) of the acute-care survivors had improvements in their GOSE, six (11.8%) experienced deteriorations, and 12 (23.5%) did not exhibit any change. The greatest improvement was observed in patients with GOSE of 5 and 6 upon discharge, but two of the 16 patients with GOSE 2 or 3 also had a good recovery. On logistic regression analysis, old age and prolonged acute hospital stay were found to be independent predictors of poor functional outcome after a mean follow-up duration of 42 months. Multidisciplinary neurorehabilitation service is an important component of comprehensive trauma care. Despite significant early mortalities, a proportion of severely head-injured patients who survive acute care may achieve good long-term functional recovery. Copyright © 2012, Asian Surgical Association. Published by Elsevier Taiwan LLC. All rights reserved.