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Sampling Rate (sampling + rate)
Selected AbstractsImpact of the Sampling Rate on the Estimation of the Parameters of Fractional Brownian MotionJOURNAL OF TIME SERIES ANALYSIS, Issue 3 2006Zhengyuan Zhu Primary 60G18; secondary 62D05, 62F12 Abstract., Fractional Brownian motion is a mean-zero self-similar Gaussian process with stationary increments. Its covariance depends on two parameters, the self-similar parameter H and the variance C. Suppose that one wants to estimate optimally these parameters by using n equally spaced observations. How should these observations be distributed? We show that the spacing of the observations does not affect the estimation of H (this is due to the self-similarity of the process), but the spacing does affect the estimation of the variance C. For example, if the observations are equally spaced on [0, n] (unit-spacing), the rate of convergence of the maximum likelihood estimator (MLE) of the variance C is . However, if the observations are equally spaced on [0, 1] (1/n -spacing), or on [0, n2] (n -spacing), the rate is slower, . We also determine the optimal choice of the spacing , when it is constant, independent of the sample size n. While the rate of convergence of the MLE of C is in this case, irrespective of the value of ,, the value of the optimal spacing depends on H. It is 1 (unit-spacing) if H = 1/2 but is very large if H is close to 1. [source] Curve skeleton skinning for human and creature charactersCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2006Xiaosong Yang Abstract The skeleton driven skinning technique is still the most popular method for animating deformable human and creature characters. Albeit an industry de facto due to its computational performance and intuitiveness, it suffers from problems like collapsing elbow and candy wrapper joint. To remedy these problems, one needs to formulate the non-linear relationship between the skeleton and the skin shape of a character properly, which however proves mathematically very challenging. Placing additional joints where the skin bends increases the sampling rate and is an ad hoc way of approximating this non-linear relationship. In this paper, we propose a method that is able to accommodate the inherent non-linear relationships between the movement of the skeleton and the skin shape. We use the so-called curve skeletons along with the joint-based skeletons to animate the skin shape. Since the deformation follows the tangent of the curve skeleton and also due to higher sampling rates received from the curve points, collapsing skin and other undesirable skin deformation problems are avoided. The curve skeleton retains the advantages of the current skeleton driven skinning. It is easy to use and allows full control over the animation process. As a further enhancement, it is also fairly simple to build realistic muscle and fat bulge effect. A practical implementation in the form of a Maya plug-in is created to demonstrate the viability of the technique. Copyright © 2006 John Wiley & Sons, Ltd. [source] Out-of-core compression and decompression of large n -dimensional scalar fieldsCOMPUTER GRAPHICS FORUM, Issue 3 2003Lawrence Ibarria We present a simple method for compressing very large and regularly sampled scalar fields. Our method is particularlyattractive when the entire data set does not fit in memory and when the sampling rate is high relative to thefeature size of the scalar field in all dimensions. Although we report results foranddata sets, the proposedapproach may be applied to higher dimensions. The method is based on the new Lorenzo predictor, introducedhere, which estimates the value of the scalar field at each sample from the values at processed neighbors. The predictedvalues are exact when the n-dimensional scalar field is an implicit polynomial of degreen, 1. Surprisingly,when the residuals (differences between the actual and predicted values) are encoded using arithmetic coding,the proposed method often outperforms wavelet compression in anL,sense. The proposed approach may beused both for lossy and lossless compression and is well suited for out-of-core compression and decompression,because a trivial implementation, which sweeps through the data set reading it once, requires maintaining only asmall buffer in core memory, whose size barely exceeds a single (n,1)- dimensional slice of the data. Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Compression, scalar fields,out-of-core. [source] Dynamic Changes of Ictal High-Frequency Oscillations in Neocortical Epilepsy: Using Multiple Band Frequency AnalysisEPILEPSIA, Issue 2 2007Ayako Ochi Summary:,Purpose: To characterize the spatial and temporal course of ictal high-frequency oscillations (HFOs) recorded by subdural EEG in children with intractable neocortical epilepsy. Methods: We retrospectively studied nine children (four girls, five boys; 4,17 yr) who presented with intractable extrahippocampal localization-related epilepsy and who underwent extraoperative video subdural EEG (1000 Hz sampling rate) and cortical resection. We performed multiple band frequency analysis (MBFA) to evaluate the frequency, time course, and distribution of ictal HFOs. We compared ictal HFO changes before and after clinical onset and postsurgical seizure outcomes. Results: Seventy-eight of 79 seizures showed HFOs. We observed wide-band HFOs (,250Hz, ,120 electrodes) in six patients either with partial seizures alone (three patients) or with epileptic spasms (three patients). Three patients with partial seizures that secondarily generalized had wide-band HFOs (,170 Hz) before clinical onset and sustained narrow-band HFOs (60,164 Hz) with electrodecremental events after clinical onset (,28 electrodes). In four postoperatively seizure-free patients, more electrodes recorded higher-frequency HFOs inside the resection area than outside before and after clinical seizure onset. In five patients with residual seizures, electrodes recorded more HFOs that were of higher or equal frequency outside the surgical area than inside after clinical onset. Conclusion: For partial seizures alone and epileptic spasms, more electrodes recorded only wide-band HFOs; for partial seizures that secondarily generalized, fewer electrodes recorded wide-band HFOs, but in these seizures electrodes also recorded subsequent sustained narrow-band ictal HFOs. Resection of those brain regions having electrodes with ictal, higher HFOs resulted in postsurgical seizure-free outcomes. [source] Design of a near-optimal adaptive filter in digital signal processor for active noise controlINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2008S. M. Yang Abstract Adaptive filter has been applied in adaptive feedback and feedforward control systems, where the filter dimension is often determined by trial-and-error. The controller design based on a near-optimal adaptive filter in digital signal processor (DSP) is developed in this paper for real-time applications. The design integrates the adaptive filter and the experimental design such that their advantages in stability and robustness can be combined. The near-optimal set of controller parameters, including the sampling rate, the dimension of system identification model, the dimension (order) of adaptive controller in the form of an FIR filter, and the convergence rate of adaptation is shown to achieve the best possible system performance. In addition, the sensitivity of each design parameter can be determined by analysis of means and analysis of variance. Effectiveness of the adaptive controller on a DSP is validated by an active noise control experiment. Copyright © 2007 John Wiley & Sons, Ltd. [source] Adaptive sliding mode control of air,fuel ratio in internal combustion enginesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 6 2004Jason S. Souder Abstract A simplified model of an internal combustion engine is used to derive a sliding mode control law. Adaptive update laws are derived for two fueling parameters that describe fuel flow into the cylinders, and a third parameter that describes air flow into the cylinders. The update laws allow the sliding mode control gain, which is usually increased to overcome model uncertainty, to be reduced. This improves the tracking performance of the sliding mode controller in the presence of the feedback time delays. The parameter update laws are modified to bound the parameter values and allow all three parameter update laws to run simultaneously. The effect of the sampling rate on the adaptive sliding mode controller performance and air,fuel ratio biasing via gain selection are also addressed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Simultaneous Optical Mapping of Transmembrane Potential and Intracellular Calcium in Myocyte CulturesJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2000VLADIMIR G. FAST Ph.D. Simultaneous Mapping of Vm and Cai2+. Introduction: Fast spatially resolved measurements of transmembrane potential (Vm) and intracellular calcium (Cai2+) are important for studying mechanisms of arrhythmias and defibrillation. The goals of this work were (1) to develop an optical technique for simultaneous multisite optical recordings of Vm and Cai2+, and (2) to determine the relationship between Vm and Cai2+ during normal impulse propagation in myocyte cultures. Methods and Results: Monolayers of neonatal rat myocytes were stained with fluorescent dye RH-237 (Vm) and Fluo-3AM (Cai2+). Both dyes were excited at the same wavelength range. The emitted fluorescent was optically separated into components corresponding to changes in Vm, and Cai2+ and measured using two 16 × 16 photodiode arrays at a spatial resolution of up to 27.5 ,m per diode and sampling rate of 2.5 kHz. The optical setup was adjusted so that there was no optical cross-talk between the two types of measurements, which was validated in experiments involving staining with either RH-237 or Fluo-3. The amplitude of Fluo-3 signals rapidly decreased during experiments due to dye leakage. Dye leakage was substantially reduced by application of 1 mM probenecid, a blocker of organic anion transport, which had no effect on action potential duration and only minor effect on conduction velocity. In double-stained preparations, during regular pacing Cai2+ transients had a rise time of 14.2 ± 2 msec, and they followed Vm upstrokes with a delay of 5.3 ± 1 msec (n = 9). Durations of Vm, and Cai2+ transients determined at 50% level of signal recovery were 54.6 ± 10 msec and 136 ± 8 msec, respectively. Application of 2 ,M nifedipine reduced the amplitude and duration of Cai2+ transients without significantly affecting conduction velocity. Conclusion: The results demonstrate feasibility of simultaneous optical recordings of Vm and Cai2+ transients with high spatial and temporal resolution. [source] Determination of propafenone hydrochloride by flow-injection analysis coupled with resonance light scattering detectionLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 2 2009Xiaoli Hu Abstract A simple, sensitive and rapid flow injection analysis (FIA) method with resonance light scattering (RLS) was described for the determination of propafenone (PPF). The method was based on the ion-association reaction of 12-tungstophosphoric acid (TP) with propafenone. In pH 1.0 acidic medium, TP reacted with PPF to form an ion-associate complex, which resulted in a significant enhancement of RLS intensity. The maximum scattering peak was located at 340 nm, the RLS intensity was proportional to the concentration of PPF in the range 0.003,9.0 µg/mL, and the detection limit (3,) of 1.0 ng/mL was obtained at a sampling rate of 60 samples/h. The feasible reaction conditions and FIA parameters for the system were optimized. The method proposed in this paper shows satisfactory reproducibility with a relative standard deviation (RSD) of 2.1% for 10 successive determinations of 2.0 µg/mL PPF. The present method had been successfully applied to the determination of PPF in serum samples and pharmaceutical samples. The results obtained were in agreement with the method used in the Chinese Pharmacopoeia. Copyright © 2008 John Wiley & Sons, Ltd. [source] GLITP optical monitoring of QSO 0957+561: VR light curves and variabilityMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003A. Ullán ABSTRACT The Gravitational Lenses International Time Project (GLITP) collaboration observed the first gravitational lens system (QSO 0957+561) from 2000 February 3 to March 31. The daily VR observations were made with the 2.56-m Nordic Optical Telescope at Roque de los Muchachos Observatory, La Palma, Spain. We have derived detailed and robust VR light curves of the two components Q0957+561A and Q0957+561B. In spite of the excellent sampling rate, we have not found evidence in favour of true daily variability. With respect to variability on time-scales of several weeks, we measure VR gradients of about ,0.8 mmag d,1 in Q0957+561A and +0.3 mmag d,1 in Q0957+561B. The gradients are very probably originated in the far source. Thus, adopting this reasonable hypothesis (intrinsic variability), we compare them to the expected gradients during the evolution of a compact supernova remnant at the redshift of the source quasar. The starburst scenario is roughly consistent with some former events, but the new gradients do not seem to be caused by supernova remnant activity. [source] Technical Note: Effect of contact lenses on measurement of the accommodation microfluctuationsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Mhairi Day Abstract Aim:, Dynamic measurement of accommodation in subjects with myopia usually involves recording through soft contact lenses (CLs) to correct the refractive error. Conversely, dynamic accommodation measurement in emmetropic control subjects is generally undertaken without any corrective lenses. The aim of this experiment was to determine whether CL correction affects the measurement of accommodation microfluctuations using infrared refractometry, and whether this needs to be considered in studies which attempt to compare accommodation responses between the two groups. Methods:, Ten young emmetropic subjects viewed a high contrast Maltese cross target monocularly using the right eye at a target vergence of 0 D. The subjects viewed the target under two conditions: with CL condition and without CL condition, where the subjects viewed the target with the eye only. Accommodation responses of the right eye were recorded continuously for 2 min at a sampling rate of 52 Hz using the Shin-Nippon SRW-5000 autorefractor. Results:, No significant difference (two-tailed paired t -test, t9 = ,1.499, p = 0.168) was found in mean accommodation response between the with CL (mean ± S.D. = ,0.02 ± 0.24 D) and without CL conditions (mean ± S.D. = +0.01 ± 0.25 D). No significant (two-tailed paired t -test, t9 = 0.151, p = 0.883) difference in the magnitude of the accommodation microfluctuations was found between the with CL (mean ± S.D. = 0.162 ± 0.04 D) and without CL condition (mean ± S.D. = 0.169 ± 0.04 D). Power spectrum analysis revealed no differences in the characteristics of the microfluctuations waveform between the two conditions. A control experiment carried out on a subgroup of five subjects using a negative (,3 D) CL demonstrated that there was no significant effect of the dioptric power of the CL on the magnitude of the accommodation microfluctuations (anova: F3,15 = 0.254, p = 0.782). Conclusion:, Thin soft CLs do not affect the magnitude or frequency characteristics of accommodation microfluctuations when measured using the Shin-Nippon SRW-5000. [source] Refractive group differences in accommodation microfluctuations with changing accommodation stimulusOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2006Mhairi Day Abstract Purpose:, Microfluctuations of accommodation are known to increase in magnitude with increasing accommodation stimulus. Reduced sensitivity to blur in myopic subjects could also lead to increases in the magnitude of the microfluctuations. The aim of this study is to examine the effect of variations in accommodation stimulus upon the microfluctuations in different refractive groups. Methods:, Thirty-six subjects were divided into three groups depending upon their refractive error and age of onset of their myopia; 12 emmetropes (EMMs), 12 early onset myopes (EOMs) and 12 late-onset myopes (LOMs). Steady-state accommodation responses were recorded continuously for 2 min using the Shin-Nippon SRW-5000 autorefractor at a sampling rate of 52 Hz while viewing targets at accommodation stimuli levels of 0, 1, 2, 3 and 4 D in a Badal (+5 D) optical system. Results:, The EMMs and EOMs showed systematic increases in the root mean square (r.m.s.) value of the microfluctuations with increasing accommodation stimulus. In contrast, no systematic variation with accommodation stimulus was found for the LOMs. Power spectrum analysis demonstrated that increases in the size of the microfluctuations were mediated by increases in the power of the low frequency components of the accommodation response. Conclusions:, The magnitude of the microfluctuations in the EMMs and EOMs may be influenced primarily by accommodation response-induced zonular relaxation effects or to changes in the physical properties of the accommodation plant with increasing accommodation response. The LOMs may have an increased baseline neural blur threshold, which appears to modulate the magnitude of the accommodative microfluctuations for low accommodation levels. At higher accommodation demands, the changes in the physical properties of the accommodation plant or the zonular relaxation effects appear to exceed the blur threshold, and the known association between microfluctuations and accommodation stimulus level is restored. [source] High-frequency electroencephalographic oscillations correlate with outcome of epilepsy surgery,ANNALS OF NEUROLOGY, Issue 2 2010Julia Jacobs MD Objective High-frequency oscillations (HFOs) in the intracerebral electroencephalogram (EEG) have been linked to the seizure onset zone (SOZ). We investigated whether HFOs can delineate epileptogenic areas even outside the SOZ by correlating the resection of HFO-generating areas with surgical outcome. Methods Twenty patients who underwent a surgical resection for medically intractable epilepsy were studied. All had presurgical intracerebral EEG (500Hz filter and 2,000Hz sampling rate), at least 12-month postsurgical follow-up, and a postsurgical magnetic resonance imaging (MRI). HFOs (ripples, 80,250Hz; fast ripples, >250Hz) were identified visually during 5 to 10 minutes of slow-wave sleep. Rates and extent of HFOs and interictal spikes in resected versus nonresected areas, assessed on postsurgical MRIs, were compared with surgical outcome (Engel's classification). We also evaluated the predictive value of removing the SOZ in terms of surgical outcome. Results The mean duration of follow-up was 22.7 months. Eight patients had good (Engel classes 1 and 2) and 12 poor (classes 3 and 4) surgical outcomes. Patients with a good outcome had a significantly larger proportion of HFO-generating areas removed than patients with a poor outcome. No such difference was seen for spike-generating regions or the SOZ. Interpretation The correlation between removal of HFO-generating areas and good surgical outcome indicates that HFOs could be used as a marker of epileptogenicity and may be more accurate than spike-generating areas or the SOZ. In patients in whom the majority of HFO-generating tissue remained, a poor surgical outcome occurred. ANN NEUROL 2010;67:209,220 [source] T-Wave Variability Detects Abnormalities in Ventricular Repolarization: A Prospective Study Comparing Healthy Persons and Olympic AthletesANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2009Lara Heinz M.D. Background: Sudden cardiac death in athletes is more common than in the general population. Routine screening procedures are performed to identify competitors at risk. A new Holter-based parameter analyzes variation of the ventricular repolarization (TVar). The aim of this study was to evaluate differences in electrocardiogram (ECG), Echo, and Holter (H) in competitive athletes compared to a healthy control group consisting of medical students (MS). Methods: A total of 40 athletes (19 females, Olympic team, Luxembourg) and 40 MS (22 females) were examined by means of a resting ECG, treadmill exercise (TE), echocardiogram (Echo), as well as H recordings during a routine screening visit. To analyze TVar, a 20-minute H recording at rest (sampling rate 1000 per second) was performed. Moreover, heart rate variability (HRV) as well as HR turbulence (HRT) was computed. Results: No differences in demographic variables were detected. Quantification of HRV detected a significant increase in the vagal component of autonomic cardiac modulation. In contrast, no differences for HRT were found. Echo parameter demonstrated a thicker septal wall without differences of the posterior wall. TVar values were normal in range, but did differ significantly between the two groups. No correlation between TVar and echo as well as Holter parameters was detected. Conclusions: TVar was able to demonstrate significant differences in terms of alterations of ventricular activation. This might indicate an early change of myocardial repolarization representing a substrate for life-threatening arrhythmia. Larger studies on the predictive value of TVar including follow-up are necessary to confirm this preliminary finding. [source] A model-based approach to quality control of paper productionAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 3 2004Patrick E. Brown Abstract This paper uses estimated model parameters as inputs into multivariate quality control charts. The thickness of paper leaving a paper mill is measured at a high sampling rate, and these data are grouped into successive data segments. A stochastic model for paper is fitted to each data segment, leading to parameter estimates and information-based standard errors for these estimates. The estimated model parameters vary by more than one can be explained by the information-based standard errors, suggesting that the ,true' underlying parameters are not constant over time. A model is formulated for the true parameters in which the information matrix dictates the distribution for the observed parameters given the true parameters. Copyright © 2004 John Wiley & Sons, Ltd. [source] A Mass Spectrometry Plate Reader: Monitoring Enzyme Activity and Inhibition with a Desorption/Ionization on Silicon (DIOS) PlatformCHEMBIOCHEM, Issue 7 2004Zhouxin Shen Dr. Abstract A surface-based laser desorption/ionization mass spectrometry assay that makes use of Desorption/Ionization on Silicon Mass Spectrometry (DIOS-MS) has been developed to monitor enzyme activity and enzyme inhibition. DIOS-MS has been used to characterize inhibitors from a library and then to monitor their activity against selected enzyme targets, including proteases, glycotransferase, and acetylcholinesterase. An automated DIOS-MS system was also used as a high-throughput screen for the activity of novel enzymes and enzyme inhibitors. On two different commercially available instruments, a sampling rate of up to 38 inhibitors per minute was accomplished, with thousands of inhibitors being monitored. The ease of applying mass spectrometry toward developing enzyme assays and the speed of surface-based assays such as DIOS for monitoring inhibitor effectiveness and enzyme activity makes it attractive for a broad range of screening applications. [source] 2453: Optic disc in the picture: novel imaging techniquesACTA OPHTHALMOLOGICA, Issue 2010W DREXLER Purpose Advances in light sources and detection technologies enabled a paradigm shift in retinal OCT imaging performance. ,Snap-shot OCT' enabling isotropic sampling over 512x512x1024 voxels with 600 frames/second in less than a second is now possible. Methods The resolution advantage in conjunction with full volumetric sampling has enabled the development of more informative indices of axonal damage in glaucoma compared with measurements of RNFL thickness and cup to disc ratio provided by other devices. A novel mapping method was developed, the three-dimensional minimal distance (3D-MDM) as the optical correlate of true retinal nerve fiber layer thickness around the optic nerve head region. In a preliminary study relation between the cross-sectional areas of the retinal nerve fiber layer and the optic nerve was found to be a sensitive measure of axon loss. Results In addition to all the major layers of the retina, the entire choroid down to the lamina cribrosa and sclera can now be visualized. This enables unprecedented information about choroidal vasculature without any contrast agents, choroidal thickness and will enable quantification of choroidal blood flow in the near future. Furthermore this technique allows tissue to be imaged in vitro with an image resolution better than 1-2 µm, allowing to image single cells and detect pre-apoptotic signatures using OCT. RGC-5 cells were imaged using a sampling rate 1024x512x1024 voxel at 800 nm central wavelength and a bandwidth of 230 nm, enabling the detection of optical signatures at different pre-stages of programmed cell death. Conclusion Significantly increased OCT imaging speed and tissue penetration might enable novel insights and diagnostic opportunities in the diagnosis and therapy monitoring of glaucoma. Commercial interest [source] Sampling in the Great Lakes for pharmaceuticals, personal care products, and endocrine-disrupting substances using the passive polar organic chemical integrative samplerENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010Hongxia Li Abstract The passive polar organic chemical integrative sampler in the pharmaceutical configuration (i.e., pharmaceutical-POCIS) was calibrated for sampling at water temperatures of 5, 15 and 25°C to determine the influence of temperature on chemical-specific sampling rates (RS), thus providing more robust estimates of the time-weighted average concentrations of pharmaceuticals and personal care products (PPCPs) and endocrine-disrupting substances (EDS) in surface water. The effect of water temperature and flow on the RS of these analytes was evaluated in the laboratory with a static system. The loss of the test compounds from water by uptake into POCIS was linear over an 8-d period, and these experimental data yielded RS values in the range of 0.07 to 2.46 L/d across the temperature range for the 30 compounds tested. Water temperature and flow influenced POCIS uptake rates, but these effects were relatively small, which is consistent with the theory for uptake into POCIS samplers. Therefore, under a narrow range of water temperatures and flows, it may not be necessary to adjust the RS for POCIS. Except for acidic drugs and sulfonamide antibiotics, RS values were positively correlated with octanol,water partition coefficients (log KOW) of the test compounds. A linear relationship was also observed between RS and chromatographic retention times on a C18 reversed-phase column. These observations may provide a rapid method for estimating the RS of additional chemicals in the POCIS. The application of the RS to POCIS deployed for one month in Lake Ontario, Canada, during the summers of 2006 and 2008 yielded estimates of PPCP and EDS concentrations that are consistent with conventional concentration measurements of these compounds in Lake Ontario surface water. Environ. Toxicol. Chem. 2010;29:751,762. © 2009 SETAC [source] What are daily maximum and minimum temperatures in observed climatology?INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2008X. Lin Abstract Instrumental daily maximum and minimum temperatures are reported and archived from various surface thermometers along with different average algorithms in historical and current U.S. surface climate networks. An instrumental bias in daily maximum and minimum temperatures caused by surface temperature sensors due to the different sampling rates, average algorithms, and sensor's time constants was examined using a Gaussian-distributed function of surface air temperature fluctuations in simulation. In this study, the field observations were also included to examine the effects of average algorithms used in reporting daily maximum and minimum temperatures. Compared to the longest-recorded and standard liquid-in-glass maximum and minimum thermometers, some surface climate networks produced a systematic warming (cooling) bias in daily maximum (minimum) temperature observations, thus, resulting biases made the diurnal temperature range (DTR) more biased in extreme climate studies. Our study clarified the ambiguous concepts on daily maximum and minimum temperature observations defined by the World Meteorological Organization (WMO) in terms of sensor's time constants and average lengths and an accurate description of daily maximum and minimum temperatures is recommended to avoid the uncertainties occurred in the observed climatology. Copyright © 2007 Royal Meteorological Society [source] Theory & Methods: Bias due to Ignoring the Sample Design in Case,Control StudiesAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2002John M. Neuhaus Case,control studies allow efficient estimation of the associations of covariates with a binary response in settings where the probability of a positive response is small. It is well known that covariate,response associations can be consistently estimated using a logistic model by acting as if the case,control (retrospective) data were prospective, and that this result does not hold for other binary regression models. However, in practice an investigator may be interested in fitting a non,logistic link binary regression model and this paper examines the magnitude of the bias resulting from ignoring the case,control sample design with such models. The paper presents an approximation to the magnitude of this bias in terms of the sampling rates of cases and controls, as well as simulation results that show that the bias can be substantial. [source] | |||||||||||||||||||||||||||||||