Non-linear Regression Curves Research Articles

Achieving Real-World Saturated Hydraulic Conductivity: Practical and Theoretical Findings from Using an Exponential One-Phase Decay Model

Obtaining accurate values of saturated hydraulic conductivity (Ksat) is very important for managing all natural or artificial processes involving water flow into soils. Double-ring infiltration (DRI) is one of the easiest-to-work-with techniques commonly used for Ksat determination. Unfortunately, when improperly used, it leads to important variations and inaccurate results. This study was designed to investigate the necessary conditions to reach the true-value or real-world saturated hydraulic conductivity (Ksat-real-world) in the field. For this purpose, the effects of two factors—namely, the measured infiltration data type (cumulative, instant rate, and average rate) and the related non-linear regression equation type—were analyzed. Measurements with DRI were performed with samples from 106 locations in three West African countries, namely, Burkina Faso, Mali, and Cote d’Ivoire. The soils were composed of loam, sandy loam, and sandy clay loam. The results show that when infiltration rates are used rather than cumulative infiltration non-linear regression curves, the variability between the measured Ksat and the real-world saturated hydraulic conductivity (Ksat-real-world) could reach from 2.2% to 58.8%. This variability was caused by the approximate amplification—according to the procedure used—of time-increment measurement errors. Extending the test duration to more than 4 h, especially when clay soils were involved, and using the exponential one-phase decay non-linear regression of the cumulative infiltration data based on a clear measurement protocol provided the Ksat values that were closest to Ksat-real-world.

S1098 Learning Curve of Transoral Incisionless Fundoplication: A Proficiency Study

Introduction: Transoral incisionless fundoplication (TIF) is a minimally invasive endoscopic procedure for treatment of gastroesophageal reflux disease. Performing TIF requires unique training to achieve proficiency. This study aims to evaluate the learning curve of performing TIF in relation to patient and procedure-specific characteristics. Methods: This is a retrospective study of consecutive TIF procedures performed by a single experienced gastroenterologist to assess the procedure learning curve. Historical and procedural characteristics were recorded, and the learning curve was estimated by cumulative sum of means (CUSUM) analysis. Proficiency was defined as reliably achieving a procedure length less than 45 minutes. Results: 77 consecutive TIF procedures (68 patients) were included. The average age of patients was 52.35 ± 15.74 years (32.4% male). The estimated learning plateaus for procedure time and number of fasteners were 41 minutes and 24 fasteners, respectively. Twelve procedures were required to reliably achieve a procedure length of 45 minutes or less. There was no significant correlation between the length of the TIF procedure and number of fasteners (p=0.091) or Hill classification (I vs II/III) (p=0.483). There was no relationship between the Hill classification (I vs. II/III) and number of fasteners (p=0.475). We observed a significant increase in average number of fasteners used over time from 18.5 ± 2.28 during the first quartile of procedures to 29.82 ± 4.61 in the last quartile (p=0.01). There was no relationship between procedure length, ASA score, number of fasteners, and hospital length of stay. Conclusion: Proficiency in performing TIF in less than 45 minutes can be achieved after independently performing 12 procedures.Figure 1.: Non-linear regression curves for proficiency of procedure duration and number of fasteners Table 1. - Baseline patient characteristics and procedural outcomes Patient summary characteristics: Gender (Female) 67.6% (n=46) Age [mean ± SD] 52.35 ± 15.74 Race White 79.41% (n=54) Non-Hispanic 67.65% (n=46) BMI [mean ± SD] 27.7 ± 5.1 ASA Score II 69.1% (n=47) III 29.4% (n=20) IV 1.5% (n=1) Prior history of Barrett’s ablation 4.4% (n=3) Prior esophageal surgical intervention Nissen Fundoplication 8.8% (n=6) POEM- Nissen Fundoplication 1.5% (n=1) POEM 2.9% (n=2) Indication for TIF GERD 83.82% (n=57) Chronic cough +/- GERD 16.17% (n=11) Hernia HILL grade (if available): 1 25% (n=14) 2 62.5% (n=35) 3 8.9% (n=5) 4 3.6% (n=1) Longitudinal length of hernia ≥ 2cm (available value; n=56) 26.78% (n=15) PH impedance or Bravo test (uninterpreTable; n=1, not performed due to presence of BE/esophagitis=5) Acid 82.26% (n=51) Non-acid 17.74% (n=11) Procedure characteristics: Total TIF procedures (n=77) Median procedure length(minutes) [min, max] 41 [26,91] Number of fasteners [mean ± SD] 23.1 ± 6.2 Number of fasteners original TIF per Quartiles [mean ± SD] First 18.5 ± 2.28 Second 21.53 ± 3.12 Third 24.71 ± 3.53 Forth 29.82 ± 4.61 Median Hospital LOS (days) [min, max] 1 [0,10]

The wasting-associated metabolite succinate disrupts myogenesis and impairs skeletal muscle regeneration.

Muscle wasting is a debilitating co-morbidity affecting most advanced cancer patients. Alongside enhanced muscle catabolism, defects in muscle repair/regeneration contribute to cancer-associated wasting. Among the factors implicated in suppression of muscle regeneration are cytokines that interfere with myogenic signal transduction pathways. Less understood is how other cancer/wasting-associated cues, such as metabolites, contribute to muscle dysfunction. This study investigates how the metabolite succinate affects myogenesis and muscle regeneration. We leveraged an established ectopic metabolite treatment (cell permeable dimethyl-succinate) strategy to evaluate the ability of intracellular succinate elevation to 1) affect myoblast homeostasis (proliferation, apoptosis), 2) disrupt protein dynamics and induce wasting-associated atrophy, and 3) modulate in vitro myogenesis. In vivo succinate supplementation experiments (2% succinate, 1% sucrose vehicle) were used to corroborate and extend in vitro observations. Metabolic profiling and functional metabolic studies were then performed to investigate the impact of succinate elevation on mitochondria function. We found that in vitro succinate supplementation elevated intracellular succinate about 2-fold, and did not have an impact on proliferation or apoptosis of C2C12 myoblasts. Elevated succinate had minor effects on protein homeostasis (~25% decrease in protein synthesis assessed by OPP staining), and no significant effect on myotube atrophy. Succinate elevation interfered with in vitro myoblast differentiation, characterized by significant decreases in late markers of myogenesis and fewer nuclei per myosin heavy chain positive structure (assessed by immunofluorescence staining). While mice orally administered succinate did not exhibit changes in overall body composition or whole muscle weights, these mice displayed smaller muscle myofiber diameters (~6% decrease in the mean of non-linear regression curves fit to the histograms of minimum feret diameter distribution), which was exacerbated when muscle regeneration was induced with barium chloride injury. Significant decreases in the mean of non-linear regression curves fit to the histograms of minimum feret diameter distributions were observed 7 days and 28 days post injury. Elevated numbers of myogenin positive cells (3-fold increase) supportive of the differentiation defects observed in vitro were observed 28 days post injury. Metabolic profiling and functional metabolic assessment of myoblasts revealed that succinate elevation caused both widespread metabolic changes and significantly lowered maximal cellular respiration (~35% decrease). This study broadens the repertoire of wasting-associated factors that can directly modulate muscle progenitor cell function and strengthens the hypothesis that metabolic derangements are significant contributors to impaired muscle regeneration, an important aspect of cancer-associated muscle wasting.

Frog somatic indices: Importance of considering allometric scaling, relation with body condition and seasonal variation in the frog Leptodactylus latrans

• Scaled somatic indices should be employed in Leptodactylus latrans. • Scaled liver index best correlated with body condition. • Scaled fat index and scaled gonad present opposite variations. • Carcass-related energy reserves are of importance for body condition. • No single somatic index can solely illustrate body condition. Snout-vent length (SVL) and liver, gonad, fat bodies and carcass weight data from 661 individual Leptodactylus latrans frogs collected over ten years in the Pampa Region of Argentina were analyzed to evaluate the best approach for expressing the corresponding somatic indices. The seasonal variation of these indices and their respective correlation with body condition was also examined. Results obtained demonstrated that the weight of all examined tissues and organs vary in an allometric manner in function of SVL, which implies that scaled somatic indices should be employed in this species. The study also highlights the fact that size-independent somatic indices are more easily obtained if the scaling exponent is defined through a non-linear regression of mass on length rather than by performing a standardized major axis regression of lnweight on lnlength. In the case of liver, fat and carcass, the non-linear regression curves were not statistically different amongst sexes and so a single relationship was described for both males and females L. latrans . Logically, the relationships between SVL and male and female gonad weight varied on distinct scale, and so it was necessary to analyze ovaries and testis separately. Scaling factors equal to 5.03, 3.11 and 2.75 were calculated to respectively estimate fat (SFI), liver (SLI) and carcass (SCI) scaled indices of L. latrans. In the case of the scaled gonadal index (SGI), scaling factors equal to 3.81 and 6.49 were used to calculate male and female indices. In both sexes, the seasonal variation in SFI and SGI was perfectly opposite, SGI being at its maximum in the spring when SFI was near zero, and reaching its lowest values in February-March when SFI increased. The amplitude of these changes was, nevertheless greater in females, representing a 4–5 times order of variation, in contrast to a 2–3 times order of change in males. In both sexes, SLI exhibited a 30% drop from October to December, although this loss was completely recovered in the second half of the summer (December to March). SLI was the somatic index that best correlated with the 14–18% natural variation in body condition that was observed over the spring-summer season. Nevertheless, carcass-related energy reserves were also of significant importance for frog metabolism as SCI varied very closely with body condition, explaining 75–80% of is variation. Results obtained illustrate the fact that no single somatic index can solely illustrate body condition because of the intricate relationship existing between SGI and SFI, and the importance of carcass-related energy reserves. In view of all the above, body condition comes out as the ideal monitoring endpoint for acquiring information on frog energy status.

Procoagulant in vitro effects of clinical cellular therapeutics in a severely injured trauma population.

Clinical trials in trauma populations are exploring the use of clinical cellular therapeutics (CCTs) like human mesenchymal stromal cells (MSC) and mononuclear cells (MNC). Recent studies demonstrate a procoagulant effect of these CCTs related to their expression of tissue factor (TF). We sought to examine this relationship in blood from severely injured trauma patients and identify methods to reverse this procoagulant effect. Human MSCs from bone marrow, adipose, and amniotic tissues and freshly isolated bone marrow MNC samples were tested. TF expression and phenotype were quantified using flow cytometry. CCTs were mixed individually with trauma patients' whole blood, assayed with thromboelastography (TEG), and compared with healthy subjects mixed with the same cell sources. Heparin was added to samples at increasing concentrations until TEG parameters normalized. Clotting time or R time in TEG decreased relative to the TF expression of the CCT treatment in a logarithmic fashion for trauma patients and healthy subjects. Nonlinear regression curves were significantly different with healthy subjects demonstrating greater relative decreases in TEG clotting time. In vitro coadministration of heparin normalized the procoagulant effect and required dose escalation based on TF expression. TF expression in human MSC and MNC has a procoagulant effect in blood from trauma patients and healthy subjects. The procoagulant effect is lower in trauma patients possibly because their clotting time is already accelerated. The procoagulant effect due to MSC/MNC TF expression could be useful in the bleeding trauma patient; however, it may emerge as a safety release criterion due to thrombotic risk. The TF procoagulant effect is reversible with heparin.

Outcomes of transmastoid resurfacing for superior canal dehiscence using a cartilage overlay technique.

Superior semicircular canal dehiscence is a well-described syndrome with potentially debilitating symptoms. We report on the audiologic and long-term symptom outcomes of 10 patients (12 ears) undergoing a cartilage overlay transmastoid resurfacing technique. Retrospective chart review and cross-sectional outcomes recall survey were used. A mailed questionnaire quantifying the effect of surgery on symptom severity and patient satisfaction were used. Nonlinear regression curves of pre-/postoperative air and bone pure-tone audiometric data were used to evaluate postoperative changes in hearing. Surgical failure was defined as requiring revision surgery, and rates were estimated over time using a Kaplan-Meier analysis. Most patients reported improved symptoms postoperatively and were satisfied overall with the surgical outcomes. However, four of 12 ears (33%) had a second (revision) surgery before achieving these results. Postoperatively, hearing through air and bone conduction tended to decrease at frequencies greater than 2500 Hz. The chance of avoiding a re-operation at 36 months (and up to 120 months) was estimated to be 57.1% (95% confidence interval [confidence interval]: 100%, 32.6%). The most common surgical complication was intraoperative cerebrospinal fluid (CSF) leak, encountered exclusively during dural elevation, seen in four of 12 ears (33%). Although subjectively successful at reducing symptoms, in our small sample this surgical approach did not provide a long-term stable repair and was frequently associated with intraoperative CSF leak. Offering transmastoid resurfacing to patients should involve a detailed discussion on the potential for revision surgery and risks of diminished hearing and CSF leak. 4 Laryngoscope, 129:2164-2169, 2019.

USE OF STATISTICAL CORRELATION FOR ENERGY MANAGEMENT IN OFFICE PREMISES ADOPTING TECHNIQUES OF THE INDUSTRY 4.0

We present a statistical analysis of correlations between carbon dioxide concentration and energy consumption in workplaces, with the goal of enabling its eventual programming in energy platforms In Cloud for improving management and enhancing automation and control in the service sector industry. A low-cost system is used to measure and transmit the data of buildings and the information can be analyzed by any remote device. The study includes data measured during one year in two offices located at Sada (A Coruña, Spain) and Clayton (Panama). We present linear and nonlinear regression curves, show that there are significant positive correlations and discuss seasonal and climate-related aspects. We argue that this kind of analysis can provide useful information for the design and operation in the service industry, through web-based energy platforms for control and automation. Keywords: Industry 4.0, intelligent energy platforms, energy consumption, statistical analysis, automation of facilities, control of facilities.

Validation of Novel Metrics from the Accommodative Dynamic Profile.

Objective and subjective methods of assessing time taken for accommodative change (ToAC) include accommodative dynamics (AD) and accommodative facility (AF). This study investigates the validity of novel metrics derived from the AD-profile and explores their relationship with AF. AD were assessed using a modified open-field autorefractor in 43 healthy adults. Non-linear regression curves were fitted to the data to derive: latency-of-accommodation (nLoA) and -disaccomodation (nLoD), Time-for-accommodation (ToA) and -disaccommodation (ToD), and objective-ToAC (oToAC). Latencies were also calculated through visual inspection of the AD data as in previous studies (pLoA and pLoD). AF was used to assess subjective-ToAC. Statistical analysis explored the relationships between the AD-metrics and AF. Subjects were assessed on three visits to examine intra- and inter-observer repeatability. nLoA and nLoD were greater than pLoA (p = 0.001) and pLoD (p = 0.004) respectively. nLoA and nLoD also demonstrated greater intra- and inter-observer repeatability than pLoA and pLoD. AF demonstrated a moderate, inverse correlation with ToA (p = 0.02), ToD (p = 0.007), and oToAC (p = 0.007). ToD was the single best accommodative predictor of AF (p = 0.011). The novel method for deriving latency was more repeatable, but not interchangeable with the techniques used in previous studies. ToD was the most repeatable metric with the greatest association with AF.

Simultaneous confidence bands for contrasts between several nonlinear regression curves

We propose simultaneous confidence bands of the hyperbolic-type for the contrasts between several nonlinear (curvilinear) regression curves. The critical value of a confidence band is determined from the distribution of the maximum of a chi-square random process defined on the domain of explanatory variables. We use the volume-of-tube method to derive an upper tail probability formula of the maximum of a chi-square random process, which is asymptotically exact and sufficiently accurate in commonly used tail regions. Moreover, we prove that the formula obtained is equivalent to the expectation of the Euler–Poincaré characteristic of the excursion set of the chi-square random process, and hence conservative. This result is therefore a generalization of Naiman’s inequality for Gaussian random processes. As an illustrative example, growth curves of consomic mice are analyzed.

Abstract 318: Enhancing drug discovery and development throughput without sacrificing predictivity: ex vivo 3D drug response profiling (DRP) using patient-derived xenografts (PDX)

Abstract Background: PDX have become critical elements of preclinical drug development as they better reflect the heterogeneity, molecular and histopathologic signatures of the original tumor than cell lines or genetically engineered mouse models, and their drug response profiles correlate with clinical response. While PDX models have become a powerful tool in drug discovery and development, limitations include low throughput for broad drug screening, lack of dose-response curves, high cost and progressive loss of human-derived stromal elements over serial passages, restricting utility for certain therapeutic classes. A potential mechanism to overcome the low throughput and high cost of PDX models is the incorporation of ex vivo 3D (EV3D) DRP on cells isolated from early passage PDX models. Thus, we correlated DRP results using PDX with genetic mutations and drug response of PDX tested in vivo. Materials & Methods: Cells were isolated from low-passage triple negative breast, invasive bladder, and non-small cell lung PDX tumors propagated in NSG mice and cultured as 3D spheroids. 3D spheroid cultures were exposed to 15 clinically-relevant chemotherapy and targeted agents and assayed for cell viability over a range of concentrations. Non-linear regression curves were generated and relative IC50s estimated. In vivo response with limited numbers of agents at clinically relevant concentrations (3 including controls) was assessed. Results: 3D cultures and testing were successfully established across all PDX and IC50s were successfully generated in 98% of drugs tested. EV3D DRP of PDX tumors differentiated activity of cytotoxic and targeted agents across tumors of similar histologic site of origin. Gemcitabine (IC50 = .007 versus 27 uM) and docetaxel (0.2 versus 40uM) activity was highly correlated with in vivo response in bladder and breast cancers, respectively, whereas cisplatin was equally active across all tumor types (IC50 = 3-8uM). hENT1 mRNA expression was not predictive of gemcitabine activity. EV3D DRP data correlated with PDX and clinical outcome. It identified Erlotinib as being relatively inactive (3 uM) against lung cancer PDX with an EGFR e19del, T790M mutation which correlated with the outcome seen in the PDX mouse and the clinical patient outcome in which the patient became nonresponsive to erlotinib. Trametinib was highly active against lung cancer PDX with a KRAS G12C mutation (IC50 6.7 × 10-6 versus 1.1 × 10-3) and will be used to perform efficacy studies in the KRAS mutant lung PDX model Conclusions: EV3D DRP predicts in vivo response and correlates with pathway activating mutations. EV3D DRP using PDX may represent a novel high throughput and predictive drug response platform that enables compound ranking for preclinical and clinical applications. Citation Format: Tessa M. DesRochers, Christina Mattingly, Stephen Shuford, Matthew Gevaert, David Orr, Carol Bult, Susie Airhart, Mingshan Cheng, Minan Wang, James Keck, Howland Crosswell. Enhancing drug discovery and development throughput without sacrificing predictivity: ex vivo 3D drug response profiling (DRP) using patient-derived xenografts (PDX). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 318. doi:10.1158/1538-7445.AM2015-318

PTU-293 Hes data for ulcerative colitis demonstrates the critical role of the ibd nurse specialist in preventing a&e attendance

<h3>Introduction</h3> A key role for an Inflammatory Disease Nurse (IBD) nurse specialist is to act as a first point of contact with secondary care, and as an alternative to the Emergency Department (ED), for a patient with IBD who thinks they may be experiencing a relapse. This opportunistic and observational study allowed the potentially crucial importance of this component of the IBD nurse specialist role to be evaluated. <h3>Method</h3> Using hospital episode statistic (HES) data for 2013 (source and acknowledgement….) we analysed the month-by-month variation in ED visits for UC across three NHS Trusts in our region. At Trust 1, a single-handed IBD nurse has been in post since 2002, with a temporary loss of service experienced in April–May 2013, then a planned evaluation of a nurse-led telephone helpline May–Nov 2013 only. At Trust 2, a single-handed IBD nurse was appointed in January 2013 while Trust 3 maintained a stable, hierarchical service with a lead nurse and two junior team members. Comparison of non-linear (cubic) regression curves was with the extra sum of squares F test (GraphPad Prism v4.0). <h3>Results</h3> In 2013, there were 144 episodes recorded at Trust 1, 129 at Trust 2 and 90 at Trust 3. The Figure 1below shows the pattern of ED attendances over the year. Trust 1 recorded zero admissions in Jan-Mar, with a dramatic peak in April coinciding with the loss of service, then settling with the provision of the telephone helpline and rising again with the planned withdrawal of this service (periods shown by shaded bar at top of graph). Trust 2 experienced a gradual decline in attendances (IBD nurse post start denoted by vertical arrow). Trust 3 experienced a stable rate of attendances. A statistically significant difference was observed, and analysing data as a proportion of OP activity or number of medical beds did not affect this analysis. <h3>Conclusion</h3> The loss of an IBD nurse specialist is associated with a dramatic rise in ED attendance, while new provision appears to reduce this KPI. Data were not available for 2012, but will be forthcoming for 2014 to determine the durability and magnitude of the trends observed in this study. <h3>Disclosure of interest</h3> None Declared.

Analysis of flowering dynamics heritability in the perennial warm‐season grass Paspalum dilatatum

AbstractUnderstanding the flowering cycles of perennial warm‐season grass species may be very important to the design of management practices and breeding. However, developmental dynamics are not well understood. As most plant traits associated with flowering dynamics do not follow a normal distribution, the use of general linear models to describe and compare these variables might be misleading. The aims of this study were (i) to find a methodology to compare panicle accumulation curves and (ii) to estimate heritabilities for flowering curve attributes. Panicle counts were recorded during a complete flowering cycle on a diverse collection of dallisgrass (Paspalum dilatatum). We compared the efficiency of different linear mixed models based on whole plot or individual plant data; then, we adjusted nonlinear regression curves for individual plants to estimate several curve attributes and compared this approach to the area under the curve. Finally, we calculated the broad‐sense heritabilities of the estimated curve parameters. The following reproductive curve attributes were obtained: panicle production potential, panicle accumulation rate and days until 3, 5, 10 and 15 panicles. We found that monitoring individual plants is more efficient when studying flowering attributes. Significant differences among genotypes for several flowering cycle attributes were found. Heritabilities were very high for all flowering cycle initiation and duration attributes. We also showed that the number of days until the emergence of a given low number of panicles can be used as a highly heritable measure to characterize flowering cycles.

English

The species Jurema-imbira ( Mimosa ophthalmocentra ) is typical of the Caatinga of Northeast Brazil and has medicinal properties; besides being also used by timber industry. The study aimed at assessing effects of irrigation water salinity on emergence and early development of seedlings of jurema-imbira ( Mimosa ophthalmocentra Mart. ex Benth.). For this, seeds were manually extracted from the pods of matrix plants and sown under greenhouse conditions in polystyrene trays and irrigated with brackish solutions calibrated to electrical conductivity of 1.5, 2.5, 3.5, 4.5 and 5.5 dS m -1 ; and a treatment with tap water with salinity level of 0.5 dS m -1 was used as control. The experiment was conducted in October 2013. Parameters assessed were: seedling emergence, emergence speed, seedling height, root length, stem diameter, dry mass of shoots, dry mass of roots and total dry mass of seedling. A completely randomized design was used with six treatments, and four replications each consisting of of 25 seeds per treatment. Adjustment of nonlinear and polynomial regression curves, which was used to estimate behavior of variables assessed was performed with aid of software Sigmaplot®. Salinity negatively affects all variables directly proportional to its increase in the irrigation water, with the greatest seedling development at a dose of 1.5 dS m -1 .

Modeling Wildfire Spread in Mountain Pine Beetle-Affected Forest Stands, British Columbia, Canada

AbstractThe mountain pine beetle (Dendroctonus ponderosaeHopkins; MPB) has killed lodgepole pines (Pinus contortaDougl. ex Loud.) across 20 million hectares of central British Columbia, Canada, since the late 1990s, challenging land managers as well as fire management personnel. Although recent studies have used models to simulate how MPB might affect fire spread, very little fire behaviour has been documented in MPB-affected stands. We documented rate of spread (ROS) in experimental fires and wildfires in recent MPB-killed stands in British Columbia using interpretations of oblique photographs, airborne measurements of wildfire spread, and experimental burns. Fire spread observations were used to develop ROS models following the empirical approach of the Canadian Forest Fire Danger Rating System (CFFDRS). Sixteen fire runs were examined that occurred in mature MPB-affected pine stands from 1 to 5 years since peak attack. Observations of ROS were associated with corresponding weather measurements from nearby weather stations and non-linear regression curves were fit to paired ROS and Initial Spread Index (ISI) data according to CFFDRS convention. Although the dataset is less robust than a strictly experimental approach, fires had faster spread and more crown fire than predicted, with a linear average of 2.7 times higher ROS in best fit models than expected for unaffected pine. The most likely crown fire initiation threshold (P= 0.5) was ISI 5.5. Fire intensity is likely higher in early post-MPB stands due to increased ROS, lower crowning thresholds, and greater consumption of fine dead branches. Further studies on fire behaviour in MPB-affected stands are needed, but the present findings can help reduce uncertainty in fire and land management decisions in the interim.

Diminishing marginal disutility of hypoglycaemic events: results from a time trade-off survey in five countries.

The negative impact of hypoglycaemic events on health-related quality of life (HRQoL) may be evaluated by attaching published disutilities to these events. It is suggested that the marginal negative impact of individual hypoglycaemic events on HRQoL may decrease as the overall frequency increases. Using disutility values from a large-scale (>8,000 respondents), time trade-off (TTO) study, nonlinear regression curves were fitted to the total disutility of different frequencies of non-severe daytime and nocturnal hypoglycaemic events. Nonparametric bootstrapping was applied to characterise the uncertainty of the marginal disutility. Power function regression curves were estimated at U d = 0.0141x (0.3393) and U d = 0.0221x (0.3277). An increase from 0 to 1 hypoglycaemic event per year produced a utility decrease of 0.0141 and 0.0221 for non-severe daytime and nocturnal events, respectively. An increase from 25 to 26 events per year produced a marginal impact of 0.0006 and 0.0008 for non-severe daytime and nocturnal events, respectively. These data concur with the noted phenomenon of "first being worst" as regards hypoglycaemic events. This finding may reflect a coping mechanism on the part of patients, a maximum limit for trading off remaining lifetime or the nature of the study. Applying nonlinear functions to the TTO data might improve the precision of the measured impact of hypoglycaemic events.

Lactation curve of Beetal goats in Pakistan

Abstract. This study was accomplished with the objective to determine parameters of lactation curves in Beetal goats using Wood’s model. Therefore, milk yield data on 127 Beetal goats maintained at five different government farms were recorded from post-kidding to drying off of does. Wood model parameters were estimated using non-linear regression and individual curves were fitted. The characteristics/parameters of lactation curve were computed. The mean initial yield »a«, rate of increase »b« and rate of decline »c« parameters in Wood’s model for Beetal were 1,214.97, 0.3690 and 0.1196, respectively with R2 value of 98.2 %. The value of percent squared bias (PSB) and the persistency were 0.13 and 60.2%, respectively with mean square error value of 38.45. Flock effect was a significant (P&lt;0.01) source of variation for all the lactation curve parameters, PSB and persistency. Parity did not affect significantly any of the parameters. Type of birth significantly influenced parameter »a«, Time to reach peak (TPY) and lactation milk yield (LMY). Sex of kid also did not affect significantly any of the parameters. Age of doe was significant for parameters »a«, »b«, »c«. Quadratic effect of age was non-significant for all parameters and characteristics. Lactation length significantly affected parameter »a«, »b« and LMY.

Derivation of Inflection Points of Nonlinear Regression Curves - Implications to Statistics

In this paper, we derive inflection points for the commonly known growth curves, namely, generalized logistic, Richards, Von Bertalanffy, Brody, logistic, Gompertz, generalized Weibull, Weibull, Monomolecular and Mitscherlich functions. The functions often represent the mean part of non-linear regression models in Statistics. Inflection point of a growth curve is the point on the curve at which the rate of growth gets maximum value and it represents an important physical interpretation in the respective application area. Not only the model parameters but also the inflection point of a growth curve is of high statistical interests.

A generalization of the bivariate Beta-Binomial distribution

This paper presents a new bivariate discrete distribution that generalizes the bivariate Beta-Binomial distribution. It is generated by Appell hypergeometric function F 1 and can be obtained as a Binomial mixture with an Exton's Generalized Beta distribution. The model has different marginal distributions which are, together with the conditional distributions, more flexible than the Beta-Binomial distribution. It has non-linear regression curves and is useful for random variables with positive correlation. These features make the model very adequate to fit observed data as the two applications included show.

Prediction of very high cycle fatigue failure for high strength steels, based on the inclusion geometrical properties

This article deals with the experimental and predicted fatigue endurance of the high strength steels, European 100C6 (martensitic and bainitic) and the Japanese SUJ2 in the gigacycle regime. Tests were carried out with stress ratio R = −1 in tension–compression condition at room temperature. To attain the high number of cycles required in a reasonable period of time, an ultrasonic test machine working at 20 KHz was used to obtaining 1.7 × 10 9 cycles in approximately 24 h. The relationship between the geometrical properties of inclusions associated with fatigue failure and the fatigue life of these steels was studied. Thereafter, with basis on a simplified evaluation of the highest stress in the elliptical inclusion for fatigue Mode I, three models to predict the fatigue life for these high strength steels were proposed adjusting non-linear regression curves to the corresponding experimental results.

The Anesthetic Effects of Etomidate: Species-Specific Interaction with α2-Adrenoceptors

The IV anesthetic, etomidate, has structural and clinical similarities to specific alpha2-adrenoceptor agonists such as dexmedetomidine. We investigated whether the sedative effects of etomidate may be mediated by alpha2-adrenoceptors. The anesthetic potency of etomidate (1-20 microM) was determined in Xenopus laevis tadpoles in the absence and presence of the specific alpha2-adrenoceptor antagonist atipamezole (10 microM). Anesthesia was defined as loss of righting reflex. Nonlinear logistic regression curves were fitted to the data and half-maximal effective concentrations and the slopes of the curves were calculated. Additionally, sedative/ hypnotic effects of etomidate (8 mg/kg IP) were studied by rotarod test in wild-type (WT) mice and mice carrying targeted deletions of the alpha2A-adrenoceptor gene (alpha2A-KO). Data are presented as mean +/- sem. The fraction of anesthetized tadpoles increased with increasing concentrations of etomidate. Atipamezole significantly increased the half-maximal effective concentration of etomidate (4.5 +/- 0.2 microM; slope: 2.6 +/- 0.3) to 8.4 +/- 0.4 microM (slope: 2.3 +/- 0.3). Etomidate resulted in time-dependent sedative effects in all mice, as assessed by rotarod performance. In WT mice, the sedative effects of etomidate were not decreased by atipamezole (2 mg/kg). Consistently, etomidate-induced sedation was not reduced in alpha2A-KO animals compared with WT mice. The sedative effects of etomidate exhibit a species-specific interaction with alpha2-adrenoceptors. Although the decrease in potency of etomidate by atipamezole may be caused by an interaction with alpha2-adrenoceptors in X. laevis tadpoles, results in mice indicate that the hypnotic effect of etomidate does not require alpha2-adrenoceptors.