Md. Arifur Rahman

Screening for gestational diabetes mellitus and its prevalence in Bangladesh

BACKGROUND The prevalence of gestational diabetes mellitus (GDM) has important health complications for both mother and child and is increasing all over the world. Although prevalence estimates for GDM are not new in developed and many developing countries, data are lacking for many low-income countries like Bangladesh. OBJECTIVE To evaluate the prevalence of GDM in Bangladesh. RESEARCH DESIGN AND METHODS This cross-sectional study included 3447 women who consecutively visited the antenatal clinics with an average gestation age of 26 weeks. GDM was defined according to WHO criteria (fasting plasma glucose [FPG] ≥7.0 mmol/L or 2-h ≥7.8 mmol/L) and the new ADA criteria (FPG ≥5.3 mmol/L or 2-h ≥8.6 mmol/L OGTT). We also calculated overt diabetes as FPG ≥7.0 mmol/L. RESULTS Prevalence of GDM was 9.7% according to the WHO criteria and 12.9% according to the ADA criteria in this study population. Prevalence of overt diabetes was 1.8%. Women with GDM were older, higher educated, had higher household income, higher parity, parental history of diabetes, and more hypertensive, compared with non-GDM women. CONCLUSION This study demonstrates a high prevalence of GDM in Bangladesh. These estimates for GDM may help to formulate new policies to prevent and manage diabetes.

Nonlinearity analysis, modeling and compensation in PZT micro actuator of dual-stage actuator system

A dual-stage actuator system consists of a coarse actuator for large motion and a micro-actuator facilitating small but precise motion to improve tracking performance. Piezoelectric micro-actuator made from PZT (Lead-Zirconium-Titanium) has been a popular choice as the secondary stage. However, the advantage gained by the precision of secondary actuator is somewhat lost by the inherent hysteresis nonlinearity of PZT actuator, if not compensated. This paper presents a rigorous analysis and modeling of the hysteresis of PZT actuator and its compensation in a dual-stage servo system. For the controller of dual-stage, a simple design approach is followed. The coarse actuator loop is first designed for basic performance and stability, using composite nonlinear feedback control. The compensator for the micro-actuator is then designed to achieve better performance of the overall system and it also includes the hysteresis compensator. Simulation results underscore the effectiveness of the design.

Significant reversal of cardiac upregulated endothelin-1 system in a rat model of sepsis by landiolol hydrochloride.

AIMS Landiolol hydrochloride, an ultra-short-acting highly cardio-selective β-1 blocker, has become useful for various medical problems. Recent studies have demonstrated that co-treatment with landiolol protects against acute lung injury and cardiac dysfunction in rats of lipopolysaccharide (LPS)-induced systemic inflammation, and was also associated with a significant reduction in serum levels of the inflammation mediator HMGB-1 and histological lung damage. Endothelin (ET)-1, a potent vasoconstrictor, has been implicated in pathogenesis of sepsis and sepsis-induced multiple organ dysfunction syndrome. Here, we investigated whether landiolol hydrochloride can play important roles in ameliorating LPS-induced alterations in cardiac ET system of septic rats. MAIN METHODS Eight-week-old male Wistar rats were administered LPS only for 3 h and the rest were treated with LPS as well as with landiolol non-stop for 3 h. KEY FINDINGS At 3 h after LPS (only) administration, circulatory tumor necrosis factor (TNF)-α level, blood lactate concentration and percentage of fractional shortening of heart were significantly increased. In addition, LPS induced a significant expression of various components of cardiac ET-1 system compared to control. Finally, treatment of LPS-administered rats with landiolol for 3 h normalized LPS-induced blood lactate levels and cardiac functional compensatory events, without altering levels of plasma TNF-α and ET-1. Most strikingly, landiolol treatment significantly normalized various components of cardiac ET-1 signaling system in septic rat. SIGNIFICANCE Taken together, these data led us to conclude that landiolol may be cardio-protective in septic rats by normalizing the expression of cardiac vasoactive peptide such as ET, without altering the circulatory levels of inflammatory cytokines.

Rate dependent direct inverse hysteresis compensation of piezoelectric micro-actuator used in dual-stage hard disk drive head positioning system

The head positioning servo system in hard disk drive is implemented nowadays using a dual-stage actuator—the primary stage consisting of a voice coil motor actuator providing long range motion and the secondary stage controlling the position of the read/write head with fine resolution. Piezoelectric micro-actuator made of lead zirconate titanate (PZT) has been a popular choice for the secondary stage. However, PZT micro-actuator exhibits hysteresis—an inherent nonlinear characteristic of piezoelectric material. The advantage expected from using the secondary micro-actuator is somewhat lost by the hysteresis of the micro-actuator that contributes to tracking error. Hysteresis nonlinearity adversely affects the performance and, if not compensated, may cause inaccuracy and oscillation in the response. Compensation of hysteresis is therefore an important aspect for designing head-positioning servo system. This paper presents a new rate dependent model of hysteresis along with rigorous analysis and identification of the model. Parameters of the model are found using particle swarm optimization. Direct inverse of the proposed rate-dependent generalized Prandtl-Ishlinskii model is used as the hysteresis compensator. Effectiveness of the overall solution is underscored through experimental results.

Analysis and compensation of hysteresis of PZT micro–actuator used in high precision dual–stage servo system

Piezoelectric micro–actuator made from (PZT) has been a suitable choice as the secondary actuator of a dual–stage actuator system. However, like any other piezoelectric actuator, this secondary PZT micro–actuator also exhibits hysteresis which is the inherent nonlinearity characteristic of piezoelectric material. Therefore, the advantage gained by the precision of secondary actuator is somewhat lost by this hysteresis, if not compensated. This paper proposes a rigorous technique for analysing, identifying and compensating the hysteresis of PZT actuator used in dual–stage actuator system. Identification and compensation are the two parts of the paper. In the first part of the paper, the parameters of generalised Prandtl–Ishlinskii (GPI) model are identified offline by particle swarm optimisation (PSO) technique. In compensation part, inverse GPI as the hysteresis compensator is obtained from the identified hysteresis model. Then in case of parameter uncertainty, PSO–based online tuning method is employed to adaptively adjust the parameters of inverse GPI model. For the linear controller of dual–stage, a simple design approach is followed. Simulation results show that the proposed technique can be efficiently used for the identification and compensation of hysteresis of PZT micro–actuator.

Dual-Stage Nanopositioning Scheme for 10 Tbit/in Hard Disk Drives With a Shear-Mode Piezoelectric Single-Crystal Microactuator

A dual-stage piezoelectric shear-mode actuation scheme aiming at high-density hard disk drive applications is designed, simulated, and experimentally evaluated. In this actuation scheme, a shear-mode piezoelectric single-crystal microactuator is installed between a suspension and a slider for realizing magnetic head nanopositioning in hard disk drives. The piezoelectric single-crystal-based shear-mode microactuator is dedicatedly designed and made of (1-x)Pb(Zn1/3Nb2/3)O3PbTiO3 (x=0.06-0.07) material to meet the technical specifications of servo control for 10 Tbit/in2 hard disk drives. The shear displacement of this microactuator under a constant voltage is independent of the dimensions of the microactuator, which has the great promise for further miniaturization and excellent performance consistency control. Theoretical analysis shows that the first intrinsic resonance of the microactuator is around 143 kHz. The shear-mode microactuator has a displacement of 25.4-30.7 nm at 12 V at frequencies up to 60 kHz. After it is installed between a suspension and a slider, and tested on a spin stand, the shear-mode microactuator exhibits a working frequency of 39.1 kHz and a displacement of more than 22 nm at 12 V under the disk flying condition. The technical feature and performance as achieved show that the dual-stage nanopositioning scheme using a shear-mode piezoelectric single-crystal microactuator is promising to meet the requirements of servo control for 10 Tbit/in2 hard disk drives.

Suppression of resonance in hard disk drive servo system with feedback resonant controller: a benchmark model study

In order to achieve the precision desired, the bandwidth of the read-write head positioning servomechanism of hard disk drive (HDD) is required to be very high to minimise the effects of external disturbances. However, any attempt to increase the bandwidth is hindered by increased gain in frequencies of mechanical resonances leading to oscillatory response. If not compensated properly, excessive or unbounded oscillation may even lead to instability. Cascade compensation is the popular method for compensating multiple resonant modes. However, this method requires a very precisely identified plant model. On the contrary, feedback controller works better in such situation which does not require a very accurate plant model. This paper presents a feedback resonant controller designed in a simple way to suppress the resonant modes of voice coil motor (VCM) actuator used in HDD servo system. Simulation results substantiate the effectiveness of the proposed design methodology.

Circulatory Level of Endothelin-1 and Hypertension in Rural Women in Bangladesh: A Potential Association Evidenced From a Community Based Cross-Sectional Study

Objective: High blood pressure is one of the primary risk factor for heart disease,stroke and chronic kidney disease and the leading cause of death worldwide. About 20% of adult populations are hypertensive in Bangladesh. Endothelin-1 (ET-1), a potential marker of endothelial dysfunction has been shown to be elevated in hypertensive subjects. No study yet has investigated the circulatory level of ET-1 and hypertension in a country from South Asia. As racial differences exist in plasma level of ET-1, more research addressing the association between ET-1 and hypertension among other races needs to be investigated. As such, the present study assessed circulating levels of ET-1 in subjects with or without hypertension and further examined the association of ET-1 with clinical and metabolic parameters. Methods: A total of 2052 rural Bangladeshi women with mean age of 44.46years were studied using a cross-sectional survey. Multiple regressions were used to examinethe association between circulatory ET-1 level and hypertension. Results: The prevalence of hypertensionwas30.3%. ET-1 levels were significantly higher in hypertensive (mean 3.08 pg/ml, SE ± 0.19) than non-hypertensive subjects (mean 2.01 pg/ml, SE ± 0.30) (p = <0.001). In univariateanalysis after adjusting for age, ET-1 had significant positive associations with diastolic blood pressure (DBP) (p = 0.002), systolic blood pressure (SBP) (p = <0.001), fasting blood glucose (p = 0.002), mean arterial pressure (MAP) (p = 0.001)and a negative significant association with high-density lipoprotein cholesterol (HDL) (p = 0.030). Unlike blood pressures, other variables including, triglycerides, body mass index, and waist circumference were not associated with ET-1. In multiple linear regression analysis after adjusting for age, ET-1 had significant positive associations with fasting blood glucose (p = 0.012) and mean arterial pressure (MAP) (p = 0.05)only. When we performed multiple logistic regression analysis considering hypertension status as dependent variable, hypertensive had significant positive associations with age (p = 0.015), waist circumference (p = <0.001), fasting blood glucose (p = 0.009), triglyceride (p = 0.001) and endothelin-1 (0.026). In tertile analysis, subjects with hypertension significantly increase as levels of ET-1 increase (P for trend = 0.02). Conclusions: Thus the present study demonstrates that there is higher concentration of ET-1 among hypertensive subjects of apparently healthy population in Bangladeshi rural women who did not know they were hypertensive. The relation of ET-1 and hypertension needs further investigations to define the clinical utility and predictive value of serum ET-1 levels in hypertension for South Asian population.

Interconnected systems with “mixed” passivity and negative-imaginary properties: A stability analysis in discrete-time

This paper briefly presents a stability analysis of interconnected systems with mixed passivity and negative-imaginary properties in discrete-time. These results are analogous to previously established continuous-time case. As discretization of the system or discrete-time design is an important issue for control system design, this paper provides a base for discretization of “mixed” system with passivity and negative imaginary properties. Numerical example and simulation results demonstrate the effectiveness of the proposed analysis.

Design of resonant controller for hard disk drive servo system using a mixed passivity and small-gain approach

Effective compensation of mechanical resonant modes is one of the design challenges in read/write head-positioning servomechanism of hard disk drive (HDD) servo. Resonant modes create oscillation in the system response and may lead to instability if not compensated properly. This paper presents a resonant controller designed in a simple and yet efficient way to suppress the effects of resonant modes of Voice Coil Motor (VCM) actuator used in HDD. The design is based on a mixed passivity and small gain approach to an unstable plant model. Since the original theorem is for stable systems, therefore a stabilizable controller is used for the design. Experimental results substantiate the effectiveness of the controller.