Magnitude Of Imbalance Research Articles

Static and Dynamic Stress of the Combined Rotor with Curvic Couplings Considering the Rough Three-Dimensional Interface at Extreme Operating Conditions

The curvic coupling, as one of the common connecting structures for gas turbine combined rotors, is more susceptible to various dynamic and static loads at extreme operating conditions. But, traditional combined rotor models tend to neglect the influence of the connection structure, especially failing to consider the contribution of the curvic coupling interfaces. To address this problem, this paper establishes a solid geometric model of the combined rotor with curvic couplings considering the rough three-dimensional interfaces. The effectiveness of the proposed model method is indirectly verified through the compression tests and modal tests. Subsequently, combined with finite element calculations, the mechanical properties of the rotor with curvic couplings considering the rough interface are analyzed under static and dynamic load conditions. The results indicate that the roughness of the interface significantly affects the deformation of the contact surface under static load, but its impact on the overall deformation of the rotor is relatively insignificant. The dynamic stress at the interface exhibits periodic variations at the resonance speed. At the maximum operating speed, the dynamic stress is influenced by the magnitude of imbalance. The aforementioned methods and conclusions provide a reference for the design research and engineering application of combined rotors.

Linking whole-body angular momentum and step placement during perturbed human walking.

Human locomotion is remarkably robust to environmental disturbances. Previous studies have thoroughly investigated how perturbations influence body dynamics and what recovery strategies are used to regain balance. Fewer studies have attempted to establish formal links between balance and the recovery strategies that are executed to regain stability. We hypothesized that there would be a strong relationship between the magnitude of imbalance and recovery strategy during perturbed walking. To test this hypothesis, we applied transient ground surface translations that varied in magnitude, direction and onset time while 11 healthy participants walked on a treadmill. We measured stability using integrated whole-body angular momentum (iWBAM) and recovery strategy using step placement. We found the strongest relationships between iWBAM and step placement in the frontal plane for earlier perturbation onset times in the perturbed step (R2=0.52, 0.50) and later perturbation onset times in the recovery step (R2=0.18, 0.25), while correlations were very weak in the sagittal plane (all R2≤0.13). These findings suggest that iWBAM influences step placement, particularly in the frontal plane, and that this influence is sensitive to perturbation onset time. Lastly, this investigation is accompanied by an open-source dataset to facilitate research on balance and recovery strategies in response to multifactorial ground surface perturbations, including 96 perturbation conditions spanning all combinations of three magnitudes, eight directions and four gait cycle onset times.

Bicuculline restores frequency-dependent hippocampal I/E ratio and circuit function in PGC-1ɑ null mice

Altered inhibition/excitation (I/E) balance contributes to various brain disorders. Dysfunctional GABAergic interneurons enhance or reduce inhibition, resulting in I/E imbalances. Differences in short-term plasticity between excitation and inhibition cause frequency-dependence of the I/E ratio, which can be altered by GABAergic dysfunction. However, it is unknown whether I/E imbalances can be rescued pharmacologically using a single dose when the imbalance magnitude is frequency-dependent. Loss of PGC-1α (peroxisome proliferator activated receptor γ coactivator 1α) causes transcriptional dysregulation in hippocampal GABAergic interneurons. PGC-1α-/- slices have enhanced baseline inhibition onto CA1 pyramidal cells, causing increased I/E ratio and impaired circuit function. High frequency stimulation reduces the I/E ratio and recovers circuit function in PGC-1α-/- slices. Here we tested if using a low dose of bicuculline that can restore baseline I/E ratio can also rescue the frequency-dependent I/E imbalances in these mice. Remarkably, bicuculline did not reduce the I/E ratio below that of wild type during high frequency stimulation. Interestingly, bicuculline enhanced the paired-pulse ratio (PPR) of disynaptic inhibition without changing the monosynaptic inhibition PPR, suggesting that bicuculline modifies interneuron recruitment and not GABA release. Bicuculline improved CA1 output in PGC-1α-/- slices, enhancing EPSP-spike coupling to wild type levels at high and low frequencies. Our results show that it is possible to rescue frequency-dependent I/E imbalances in an animal model of transcriptional dysregulation with a single treatment.

Common scale minimal sufficient balance: An improved method for covariate‐adaptive randomization based on the Wilcoxon‐Mann‐Whitney odds ratio statistic

Minimal sufficient balance (MSB) is a recently suggested method for adaptively controlling covariate imbalance in randomized controlled trials in a manner which reduces the impact on randomness of allocation over other approaches by only intervening when the imbalance is sufficiently significant. Despite its improvements, the approach is unable to consider the relative clinical importance or magnitude of imbalance in each covariate weight, and ignores any imbalance which is not statistically significant, even when these imbalances may collectively justify intervention. We propose the common scale MSB (CS‐MSB) method which addresses these limitations, and present simulation studies comparing our proposed method to MSB. We demonstrate that CS‐MSB requires less intervention than MSB to achieve the same level of covariate balance, and does not adversely impact either statistical power or Type‐I error.

Synergistic effects between data corpora properties and machine learning performance in data pipelines

To analyse data, a computationally feasible pipeline must be developed for data modelling. Corpora properties affect performance variability of machine learning (ML) techniques in pipelines; however, this has not been thoroughly investigated using simulation methodologies. A Monte Carlo study is used to compare differences in the area under the curve (AUC) metric for large-n-small-p-corpora examining: 1) the choice of ML algorithm; 2) size of the training database; 3) measurement error; 4) class imbalance magnitude; 5) missing data pattern. Our simulations are consistent with established results under which these algorithms and corpora properties perform best, while providing insights into their synergistic effects. Measurement error negatively impacted pipeline performance across all corpora factors and ML algorithms. A larger training corpus ameliorated the decrease in predictive efficacy resulting from measurement error, class imbalance magnitudes, and missing data patterns. We discuss the implications of these findings for designing pipelines to enhance prediction performance.

Design and Statistical Methods for Handling Covariates Imbalance in Randomized Controlled Clinical Trials: Dilemmas Resolved

Introduction In practice, between groups baseline imbalance following randomization not only opens effect estimate to bias in controlled trials, it also has certain ethical consequences. Both design and statistical approaches to ensure balanced treatment groups in prognostic factors are not without their drawbacks. This article identified potential limitations associated with design and statistical approaches for handling covariate imbalance in randomized controlled clinical trials (RCTs) and proffered solutions to them. Methods A careful review of literatures coupled with a robust appraisal of statistical models of methods involved in a way that compared their strength and weaknesses in trial environments, was adopted. Results Stratification breaks down in small sample size trials and may not accommodate more than two stratification factors in practice. On the other hand, minimization that balances for multiple prognostic factors even in small trials is not a pure random procedure and in addition, could present with complexities in computations. Overall, either minimization or stratification factors should be included in the model for statistical adjustment. Statistically, estimate of effect by change score analysis (CSA) is susceptible to direction and magnitude of imbalance. Only analysis of covariance (ANCOVA) yields unbiased effect estimate in all trial scenarios including situations with baseline imbalance in known and unknown prognostic covariates. Conclusion Design methods for balancing covariates between groups are not without their limitations. Both direction and size of baseline imbalance also have profound consequence on effect estimate by CSA. Only ANCOVA yields unbiased treatment effect and is recommended at all trial scenarios, whether or not between groups covariate imbalance matters.

Design and analysis of CMOS baluns for 94 GHz image radar and 28 GHz 5G communication system

Two W-band CMOS elliptical baluns (i.e. balun-1 and balun-2) for 94 GHz image radar, and one miniature Ka-band CMOS square balun (i.e. balun-3) with short-terminal and input capacitor (for elimination of the inductive imaginary part of the input impedance at the input port) for 28 GHz 5G communication system are demonstrated. These baluns are applicable to a down-conversion mixer for conversion of the single RF and LO input signals to differential signals. They are also applicable to a phase shifter for conversion of the single I and Q signals (from the quadrature coupler) to differential I (i.e. I + and I −) and Q (i.e. Q + and Q −) signals. Instead of the traditional balun structure that uses three sections of thin M5 (or M8) interconnection lines (underneath the thick top M6 (or top M9) main structure), the proposed balun structures use only one section of thin M5 (or M8) interconnection line to enhance S21 and S31. Balun-2 (with M9 main structure thickness of 3.4 μm) attains S21 of − 4.98 to − 4.57 dB, S31 of − 4.85 to − 4.59 dB, amplitude imbalance magnitude (AIM) smaller than 0.15 dB and phase difference deviation (PDD) smaller than 4° for 90–100 GHz. Balun-3 (with M6 main structure thickness of 2.34 μm) occupies a small chip area of 0.042 mm2, and achieves S21 of − 4.97 to − 4.44 dB, S31 of − 4.68 to − 4.29 dB, AIM smaller than 0.28 dB and PDD smaller than 2.3° for 27–29 GHz. The prominent results of these baluns indicate that they are suitable for W-band and Ka-band systems.

Oxidative stress in patients with diabetes mellitus type 2

Background: Diabetes mellitus (DM) refers to a group of common metabolic disorders that share the phenotype of hyperglycemia. Depending on the etiology of the DM, factors contributing to hyperglycemia include reduced insulin secretion, decreased glucose utilization, and increased glucose production. India is one of the epicenters of the global DM pandemic. Oxidative stress which is classically defined as an event resulting from the magnitude of imbalance between oxidant and antioxidant substances, generated in a setting of oxidation-reduction reactions, is hypothesized to play an important role in the development of DM. Aims and Objectives: This study aims to assess lipid peroxidation by estimating serum malondialdehyde (MDA) and antioxidant status by assaying paraoxonase-1 (PON-1) in Type 2 diabetes patients and healthy controls and also to study the correlation between MDA and PON-1 levels in patients with Type 2 diabetes. Materials and Methods: A cross-sectional comparative study was conducted in 152 participants, which were divided into two groups as patients with type 2 diabetes (n = 76) and control (n = 76) non-diabetic, healthy, age- and sex-matched individuals. The study was conducted in Government Medical College, Kozhikode, after the approval of the Institutional Ethical Committee. All the subjects who satisfied the inclusion and exclusion criteria and who gave informed consent were included in a consecutive manner till sample size is achieved. Serum MDA and PON-1 were estimated using spectrophotometry. The data were analyzed using Statistical Package for the Social Sciences (SPSS) version 18. Results: Oxidative stress was increased in type 2 diabetic patients as evidenced by significantly elevated MDA and reduced PON-1 than the normal controls. Conclusion: Oxidative stress is an important pathophysiological process for the development of type 2 diabetes. This study reveals the importance of screening all diabetes patients for oxidative stress. Dietary management and antioxidant supplementation would help them to prevent development of complications following diabetes, which, in turn, improve their quality of life.

NOMERICAL ANALYSIS OF UMBALANCED ROTOR

The article presents the research results of the vibrational characteristics of the designed rotor system, namely, the amplitude-frequency characteristicsare constructed in different frequency ranges and at various unbalanced masses. The main stages of conducting dynamic analysis in ANSYS arehighlighted on the example of harmonic analysis. The critical frequencies for unbalanced rotor are determined at which resonance is observed. Thevalues of the displacement amplitudes at critical frequencies and at the operating frequency under different imbalance values are observed. The plot ofamplitude dependence is constructed on the imbalance magnitude at the pump operating frequency. The obtained values are compared with the maximum allowable gap between the rotor and stator pump parts, and with that in mind, the permissible values of the unbalance values for the designed pump are determined. On the basis of the research, practical recommendations for the pump dynamic balancing have been developed for agiven permissible imbalance magnitude.

The Effects of Surface Heterogeneity Scale on the Flux Imbalance under Free Convection

AbstractIt is well known that the available energy (i.e., the net radiation minus the ground heat flux) is often 10–30% larger than the sum of turbulent fluxes measured by the eddy‐covariance method. Although field observations and previous large‐eddy simulation studies have shown that surface heterogeneity can induce flux imbalance, the relationship between the flux imbalance magnitude and the surface heterogeneity scale remains to be investigated in more detail. Here we examine the flux imbalance over landscapes characterized by different surface heterogeneity scales in a dry freely convective boundary layer. We reveal that the flux imbalance initially increases with increasing surface heterogeneity scale. However, when the surface heterogeneity scale becomes larger than the boundary layer height, the surface starts to behave locally homogeneous, which leads to a lower flux imbalance. Based on large‐eddy simulation results, we propose a conceptual model to explain how the domain average flux imbalance is influenced by surface heterogeneity. The flux imbalance is found to be controlled by the ratio of the boundary layer height to the Obukhov length (−zi/L), the integral length scale of vertical velocity (lw), the mean horizontal speed (U), and the time averaging interval (T). Among these four variables, lw determines the size of turbulent coherent structures (i.e., large eddies), whereas −zi/L affects the form of these large eddies. Meanwhile, the U and T determine how many these large eddies can be sampled by the eddy covariance. This finding indicates that it may be possible to diagnose the flux imbalance using these four variables under convective conditions.

Design and implementation of 75~110 GHz elliptical dual balun in 90 nm CMOS for W-Band transceiver

ABSTRACTWe demonstrate an elliptical dual balun structure for 94 GHz image radar transceiver. The results of two prototypes with small chip size of 0.0256 mm2 are reported. For the first one (i.e. dual balun 1), the input couple-line width is 4 mm and coupled-line space is 2 µm. That is, the distance between the output couple-lines is 8 mm. For the second one (i.e. dual balun 2), the input couple-line width is 2 mm and coupled-line space is 3 mm. The distance between output couple-lines is also 8 mm. The other geometric parameters of the two dual baluns are the same. In a star double-balanced mixer or a four-way power amplifier, the dual balun is applicable for four-way power splitting. Over the 92 ~ 96 GHz, dual balun 1 attains prominent S11 of −14.4~ −16.4 dB, S21 of −7.61~ −7.67 dB, S31 of −8.78~ −8.93 dB, S41 of −7.43~ −7.6 dB, S51 of −9.68~ −9.89 dB, amplitude imbalance magnitude (AIM) smaller than 2.39 dB, and phase difference deviation (PDD) smaller than 3.6°. Furthermore, dual balun 2 attains remarkable S11 of −13.8~ −14.8 dB, S21 of −7.8~ −7.95 dB, S31 of −8~ −8.39 dB, S41 of −7.46~ −7.72 dB, S51 of −8.18~ −8.54 dB, AIM smaller than 0.95 dB, and PDD smaller than 3.8°, close to those of dual balun 1.

Improving safety in workplaces when operating the compressor units for the account of noise reduction and vibration

Purpose. Increase of safety at working places due to introduction in manufacture of author's methods and means of decrease in vibration and noise in the sources which are a part of compressor devices. Method. System analysis in the field of fundamental research of oscillatory processes, vibration and noise; application of standard and proposed calculation and experimental methods for studying oscillatory systems with unbalanced rotors of compressor units; mathematical modeling of processes. Results. The work of compressor plants is associated with increased levels of noise and vibration. These harmful production factors adversely affect the person and act on it both directly and indirectly. Without the timely use of preventive measures, the risks of the above hazards will increase dramatically. In the course of the study, it became apparent that methods and means of eliminating the causes of increased vibration and noise in compressor plants to date have not been fully understood. The main sources of increased mechanical noise and vibration at low frequencies are unbalanced rotors of compression blocks. Unbalanced rotors are the cause of increased vibration and mechanical noise. In all considered sources, the imbalance of the rotors is the cause of increased vibration and mechanical noise. The appearance of vibration in the rotation of an unbalanced rotor is due to the presence of vibration forces whose frequency coincides with the rotational frequency, and the module is proportional to the magnitude of imbalance (imbalance). The level of noise from the vibrating surface depends on its shape, area and vibration velocity. In general, the unbalance of a hard rotor has two components: static and momentary. Different methods are used to balance the rotors, the essence of which is to adjust the unbalanced masses. This can be achieved by removing or adding a certain mass in correction planes by drilling, staining, soldering, welding or gluing. The process of measuring and eliminating the disequilibrium of the rotors is called balancing. Currently, several types of balancing machines are used. The most common are resonant and after resonance balancing machines, on which the corresponding measuring methods (before resonance and after resonance) are realized. In operation of compressor plants, operational imbalances often arise due to the impact of an aggressive environment (dust, caustic substances and other factors). Both of the considered machine tools (the method) have drawbacks, which limit their efficiency and the possibility of using on repair sites of construction industry enterprises. These include the need for pre-setting the machine, limited accuracy of measurement at one start, the effect of external and internal interference on the measurement result. High speed and the presence of rotary rotor drives during the balancing process are the cause of a high risk of injury to people. Balancing rotors in specialized machine-building enterprises usually requires high financial and time costs. As a result, compressor installations are used for complete wear with increased noise and vibration. Currently developed and patented vibration methods and instruments for measuring the imbalance of rotors, based on measuring the frequency of free fading oscillations of the swivel frames. Different methods are used to balance the rotors, the essence of which is to adjust the unbalanced masses. This can be achieved by removing or adding a certain mass in correction planes by drilling, staining, soldering, welding or gluing. In operation of compressor plants, operational imbalances often arise due to the impact of an aggressive environment (dust, caustic substances and other factors). High speed and the presence of rotary rotor drives during the balancing process are the cause of a high risk of injury to people. The proposed methods and means can be implemented not only at the enterprises producing compressor plants, but also on repair sites of enterprises that operate compressor plants, for example, construction industry enterprises. Scientific novelty. It is the presentation of new methods and means of measuring imbalances, which, in the opinion of the authors of the article, are not inferior to the analogues in efficiency and are safer. Practical meaningfulness. It consists in the possibility of using the proposed methods and tools directly on the repair sites of the construction industry enterprises. This will reduce the time and financial costs of repairing compressor plants, thereby reducing noise and vibration during their operation. Ultimately, the introduction of the proposed methods and tools will increase the safety of the enterprises in the construction industry associated with the operation of compressor plants.

Stabilisation times after transitions to standing from different working postures

Transitioning to standing after maintaining working postures may result in imbalance and could elicit a fall. The objective of this study was to quantify the magnitude of imbalance using a stabilisation time metric. Forty-five male participants completed three replications of conditions created by one of four working postures (bent at waist, squat, forward kneel, reclined kneel) and three durations within posture. Participants transitioned to quiet standing at a self-selected pace. Stabilisation time, based on changes in centre of pressure velocity, was used to indicate the initiation of steady state while standing. Stabilisation time was significantly affected by static postures but not duration within posture. The largest stabilisation times resulted from transitions initiated from a bent at waist posture. The smallest were associated with the kneeling postures, which were not significantly different from each other. Findings may lead to recommendations for redesign of tasks, particularly in high-risk environments such as construction.Statement of Relevance: Task performance on the jobsite often requires individuals to maintain non-erect postures. This study suggests that working posture affects stabilisation during transition to a standing position. Bending at the waist and squatting resulted in longer stabilisation times, whereas both kneeling postures evaluated resulted in greater imbalance but for a shorter duration.

Evaluation of Antioxidant Status in Myocardial Infarction in Diabetic and Non-diabetic Subjects: A Comparative Study

Cellular oxidative stress is the leading cause of the worst outcome of myocardial infarction (MI) in diabetes. Diabetes Mellitus is one of the important risk factors for heart pathology, because of increased production of Reactive oxygen Species(ROS).The present study was designed to find out the antioxidant status in diabetic and non-diabetic MI Patients.100 MI patients were grouped into 50 Diabetic MI(group 2) and 50 Non diabetic MI(group 3) and was compared with age matched 50 controls (group1). Malondialdehyde(MDA) or Thiobarbituric acid reactive substances (TBARs), antioxidant enzymes Superoxide Dismutase(SOD) &Catalase were measured in erythrocytes and Vitamin C in plasma was measured. The result showed that there is a significant decrease in the antioxidant status in diabetic and non-diabetic MI patients and a simultaneous significant increase in the lipid peroxidation .Thus there is an imbalance between oxidant and antioxidant molecules in MI patients, and magnitude of imbalance is greater in diabetic MI patients, possibly because of greater oxidative stress in diabetic patients. Potentially antioxidant therapy may play a critical role in reducing morbidity and mortality in MI.

Rebalancing: Evidence from Current Account Adjustment in Europe

After the 2003-2007 economic boom, European countries with large pre-crisis current account imbalances are undergoing adjustments. Countries are adjusting at different paces and ways reflecting the source and magnitude of imbalances, availability of financing, competitiveness of the tradable sector and external environment. While emerging European countries with large pre-crisis imbalances and a fixed exchange rate regime have seen sharp current account adjustments and a rebound in growth, adjustment in the euro zone periphery countries, which are also carrying a legacy of pre-crisis CA imbalances, has been gradual with difficulties bringing back growth. This paper is an empirical investigation of current account adjustment in Europe with a focus on these two groups, looking at contributions from cyclical and other factors, and seeking to draw policy conclusions.

Rebalancing: Evidence from Current Account Adjustment in Europe

After the 2003-2007 economic boom, European countries with large pre-crisis current account imbalances are undergoing adjustments. Countries are adjusting at different paces and ways reflecting the source and magnitude of imbalances, availability of financing, competitiveness of the tradable sector and external environment. While emerging European countries with large pre-crisis imbalances and a fixed exchange rate regime have seen sharp current account adjustments and a rebound in growth, adjustment in the euro zone periphery countries, which are also carrying a legacy of pre-crisis CA imbalances, has been gradual with difficulties bringing back growth. This paper is an empirical investigation of current account adjustment in Europe with a focus on these two groups, looking at contributions from cyclical and other factors, and seeking to draw policy conclusions.

On Imbalance Generated by Vortical Flows in a Two-Layer Spherical Boussinesq Primitive Equation Model

Abstract The spontaneous adjustment emission of inertia–gravity waves is investigated by examining the amount of imbalance generated during the evolution of unstable jets in an isentropic two-layer primitive equation model on the sphere. To determine the balance and thus the imbalance, potential vorticity (PV) inversion by means of the first-, second-, and third-order plain-δδ, plain-δγ, and plain-γγ balance relations, as well as the Bolin–Charney balance relations, is applied. Five sets of experiments are carried out by (i) changing the upper-layer potential temperature with a fixed initial jet speed and (ii) changing the initial jet speed with a fixed upper-layer potential temperature. For each set, the relation between the optimal measure of imbalance with the corresponding measure of balanced vortical flow is sought at the peak of instability. The minimal imbalance obtained by 1 of the above 10 PV inversion procedures is considered as the optimal. The focus herein is on the magnitude of imbalance and its scaling with various measures of balanced flow. It is shown that for the magnitude of imbalance it is always possible to find the proper measure with an exponentially small scaling. For the imbalance-to-balance ratio, however, a power law is obtained when either the jet or the stratification is weak. The latter difference in scaling behavior of the imbalance and imbalance-to-balance ratio may be an artifact of the inevitable numerical errors whose effects are felt more strongly when the signature of vortical flow is weak.

Bifurcations in the response of a rigid rotor supported by load sharing between magnetic and auxiliary bearings

Auxiliary bearings are utilized in practical installations of magnetically suspended rotating machines with the main functions to provide support to the rotating machines during their non-operational period, and to protect the magnetic bearings and the rotating assembly from being damaged due to power loss during operation. The relatively small clearances of these bearings, which are typically half of that of the magnetic bearings, may at time cause contact between the rotor and these bearings to occur even during normal operation of the rotating machines. The work presented herein examines the bifurcations in the response of a rigid rotor supported by load sharing between magnetic and auxiliary bearings, which occurs during contact between the rotor and the auxiliary bearings. Numerical results revealed the occurrence of period-doubling bifurcation resulting in vibrations of period-2, -4, -8, -16 and -32, as well as quasi-periodic and chaotic vibrations. The results further showed that for a relatively small rotor imbalance magnitude, which is within the prescribed level of certain classes of practical rotating machinery, such nonlinear dynamical phenomena would not have been discovered had the auxiliary bearings forces been omitted in the model of the rotor-bearing system. As these bearings are essential elements in practical installations of magnetically supported rotating machines, failure to include them in the rotor-bearing model may result in incorrect prediction of the rotor’s vibration response.

Blinded sample size recalculation in multicentre trials with normally distributed outcome

The internal pilot study design enables to estimate nuisance parameters required for sample size calculation on the basis of data accumulated in an ongoing trial. By this, misspecifications made when determining the sample size in the planning phase can be corrected employing updated knowledge. According to regulatory guidelines, blindness of all personnel involved in the trial has to be preserved and the specified type I error rate has to be controlled when the internal pilot study design is applied. Especially in the late phase of drug development, most clinical studies are run in more than one centre. In these multicentre trials, one may have to deal with an unequal distribution of the patient numbers among the centres. Depending on the type of the analysis (weighted or unweighted), unequal centre sample sizes may lead to a substantial loss of power. Like the variance, the magnitude of imbalance is difficult to predict in the planning phase. We propose a blinded sample size recalculation procedure for the internal pilot study design in multicentre trials with normally distributed outcome and two balanced treatment groups that are analysed applying the weighted or the unweighted approach. The method addresses both uncertainty with respect to the variance of the endpoint and the extent of disparity of the centre sample sizes. The actual type I error rate as well as the expected power and sample size of the procedure is investigated in simulation studies. For the weighted analysis as well as for the unweighted analysis, the maximal type I error rate was not or only minimally exceeded. Furthermore, application of the proposed procedure led to an expected power that achieves the specified value in many cases and is throughout very close to it.

Free radicals and antioxidant status in acute myocardial infarction patients with and without diabetes mellitus

In this study we investigated the oxidative stress, antioxidants and inflammatory molecules in patients of acute myocardial infarction (AMI) with diabetes (n = 50) and non-diabetes (n = 50). Fifty healthy subjects were taken as control. The levels of plasma TBARS and ceruloplasmin levels were significantly high in diabetic and non-diabetic AMI patients as compared with control. On the other hand, the activities of both enzymatic and non-enzymatic antioxidants were significantly decreased in diabetic and non-diabetic AMI patients as compared with control. Inflammatory markers showed significant rise in diabetic patients as compared with controls. Our results show increased inflammation and oxidative stress in patients with AMI, and magnitude of imbalance is greater in diabetic AMI patients, possibly because of greater inflammation in diabetic patients.