Boosting the Electrostatic MEMS Converter Output Power by Applying Three Effective Performance-Enhancing Techniques

This current study aims to enhance the electrostatic MEMS converter performance mainly by boosting its output power. Three different techniques are applied to accomplish such performance enhancement. Firstly, the power is boosted by scaling up the technology of the converter CMOS accompanied circuit, the power conditioning, and power controlling circuits, from 0.35 µm to 0.6 µm CMOS technology. As the converter area is in the range of mm², there are no restrictions concerning the scaling up of the accompanied converter CMOS circuits. As a result, the maximum voltage of the system for harvesting energy, V_max, which is the most effective system constraint that greatly affects the converter's output power, increases from 8 V to 30 V. The output power of the designed and simulated converter based on the 0.6 µm technology increases from 2.1 mW to 4.5 mW. Secondly, the converter power increases by optimizing its technological parameters, the converter thickness and the converter finger width and length. Such optimization causes the converter output power to increase from 4.5 mW to 11.2 mW. Finally, the converter structure is optimized to maximize its finger length by using its wasted shuttle mass area which does not contribute to its capacitances and output power. The proposed structure increases the converter output power from 11.2 mW to 14.29 mW. Thus, the three applied performance enhancement techniques boosted the converter output power by 12.19 mW, which is a considerable enhancement in the converter performance. All simulations are carried out using COMSOL Multiphysics 5.4.

Validation and Evaluation of a Behavioral Circuit Model of an Enhanced Electrostatic MEMS Converter

In this current study, the validation and evaluation of a behavioral circuit model of electrostatic MEMS converters are presented. The main objective of such a model is to accurately find the converter behavior through the proper choice of its circuit elements. In this regard, the model enables the implementation of the electrostatic MEMS converter using commercially available off-shelf circuit elements. Thus, the overall vibration energy harvesting system can be implemented and tested without the need for fabricating the converter. As a result, the converter performance can be verified and evaluated before its fabrication which saves the expenses of fabricating trailed prototypes. To test the model, we apply it to an enhanced converter in which the conventional electrostatic MEMS converter is modified by depositing the tantalum pentoxide, Ta2O5, a high dielectric constant material, on its fingers’ sidewalls. Such a deposition technique causes an appreciable increase in the overall converter capacitance and, in turn, the output power, which is boosted from the range of µw to the range of mW. Next, the converter behavioral circuit model, which is based on representing its capacitances variations with respect to the input displacement, x caused by the vibration signal, C–x curve, is built up. The model is qualitatively validated and quantitatively evaluated. The enhanced converter performance is investigated through the interaction of its model with the power conditioning circuit. From the simulation results, it is revealed that the converter behavioral circuit model accurately accomplishes the vibration energy conversion operation. As a result, the specification of the required controlling pulses for the converter operation is accurately determined. Finally, the model accuracy is validated by calibrating its performance with a traditionally simulated and fabricated electrostatic MEMS converter.

Traumatic renal injury: Five-year experience at a major trauma centre in South Africa

BACKGROUND

This study is intended to assess the current optimal management of traumatic renal injuries (TRIs), with a focus on high-grade and penetrating injuries.

METHODS

The Pietermaritzburg Metropolitan Trauma Service registry was interrogated retrospectively for patients managed for TRI between 1 January 2012 and 31 December 2016.

RESULTS

Of 13,315 inured patients treated by the PMTS, 223 (1.7%) had TRIs with an incidence of 1.5 per 100,000 population per year. The majority were males between 20 and 39 years of age. The distribution of mechanism of injury was 56.1% (n = 125) blunt and 43.9% (n = 98) penetrating trauma with no association between mechanism and grade of injury. Penetrating trauma was associated with hollow viscus and diaphragm injuries and blunt trauma with solid organ injuries. A total of 118 patients (52.9%) were managed non-operatively, 60 (26.9%) were not explored at operation, 27 (12.1%) underwent initial nephrectomy and 8 (3.6%) underwent renorraphy. Low-grade injuries (AAST I and II) and high-grade injuries (AAST III-V) were managed without renal intervention (non-operatively or not explored at laparotomy for associated injuries) in 88.7% (n = 87) and 72.0% (n = 91) of cases respectively. Blunt and penetrating injuries were managed without renal intervention in 87.9% (n = 109) and 70% (n = 69) of cases respectively. The initial nephrectomy rate was 1% (n = 1) and 20.6% (n = 26) for low- and high-grade injuries respectively, and 6.5% (n = 8) and 19% (n = 19) for blunt and penetrating injuries respectively. High grade (AAST III-V) injury (OR 14.94; 95% CI 3.36 - 66.34; p<0.001), penetrating mechanism (OR 4.99; 95% CI 1.98 - 12.52; p = 0.001) and metabolic acidosis (OR 2.73; 95% CI 1.04 - 7.20; p = 0.042) were significant risk factors for nephrectomy. Four patients (1.8%) underwent ureteral stent insertion and 2 (0.9%) underwent embolisation. The failure rate of initial non-operative management was 1.1%. The mortality rate was 8.1% (n = 18), but no patients with solitary renal injuries died.

CONCLUSION

Even in high-grade injuries and penetrating trauma, the majority of patients with TRI can be managed non-operatively or with the assistance of endourological or endovascular techniques, with good outcomes. Risk factors for nephrectomy include the presence of high-grade injuries, penetrating trauma and metabolic acidosis on presentation.

Dissolution enhancement of gliclazide using ultrasound waves and stabilizers in liquid anti-solvent precipitation

The absorption rate of gliclazide is slow and variable among subjects probably due to poor dissolution from the dosage form. The objective of this study was to enhance the dissolution rate of gliclazide by reducing the particle size. Gliclazide was precipitated from an acetone solution by adding an antisolvent (water) containing stabilizers. A combination of jets (flow rate of 20 ml/min), ultrasound, HPMC 4000, and sodium dodecyl sulfate was used to control particle size and particle size distribution. The effects of concentration of stabilizers, initial drug concentration in solution, time of insonation, antisolvent-to-solvent ratio, and ultrasound power on particle size and particle size distribution were studied. Precipitated drug particles were characterized by laser diffraction particle size analysis, SEM, FTIR spectroscopy, DSC, powder x-ray diffraction and in-vitro dissolution. With increasing almost all the studied parameters, the particle size of gliclazide initially decreased, exhibited a minimum, and then increased. Drug particles of glicazide with a mean particle size of 1.56 ± 0.09 μm and a narrow size distribution (d10/d50/d90 = 0.67/1.67/2.26) were precipitated as compared to unprocessed gliclazide with a mean particle size of 10.67 ± 0.04 μm and a wide size distribution (d10/ds50/d90 = 4.53/9.88/18.03). SEM images indicated changes in the particle morphology. Powder x-ray diffraction patterns and DSC curves indicated no changes in the chemical properties but only decrease in crystallinity and/or particle size. The dissolution rate was enhanced 2.55-fold. In conclusion, drug particles with small size and narrow size distribution were precipitated by selecting favorable process conditions, and dissolution was enhanced several folds.

Formulation and release behavior of diclofenac sodium in Compritol 888 matrix beads encapsulated in alginate

Sustained-release polymer beads containing diclofenac sodium (DNa) dispersed in Compritol 888 and encapsulated in calcium alginate shell were prepared utilizing 2(3) factorial design. The effect of sodium alginate concentration, drug: Compritol 888 weight ratio and CaCl2 concentration on drug content (%), time for 50% and 80% of the drug to be released, and mean dissolution time (MDT) were evaluated with analysis of variance (ANOVA). An increase in the level of all these factors caused retardation in the release, and t50%, t80%, and MDT were increased. The drug release was dependent on the pH of the release media. A formula that gives a release comparable to commercial products was prepared.

Dissolution behaviour of sustained release formulations of indomethacin with Eudragit RS

This study investigates the kinetics of the release of indomethacin from Eudragit RS polymer. It involved the study of the dissolution behaviour of indomethacin from different combinations of the drug in a solid dispersion form, granules and physical mixtures. It was evident that Eudragit RS had a retardation effect on the release of indomethacin, this effect was dependent on the amount of Eudragit included. Inclusion of sodium lauryl sulphate (SLS) in the solid dispersion, granules and physical mixtures modified the release and made it comparable to the release from Indocid retard capsules. The kinetics of the release process was found to be best described by the Higuchi square root of time equation and the first order equation indicating that the release process is diffusion controlled and dependent on the initial drug concentration. The retarding effect Eudragit had on the release of indomethacin was attributed to the possible interaction of the ammonium groups of the polymer with the carboxylate anion of indomethacin and to the inclusion of the drug within the inert insoluble polymer matrix.

Dissolution kinetics of glibenclamide glass

This work examines the dissolution kinetics of glibenclamide crystalline state, form I, and glibenclamide glassy state, form II. This required determination of the pH-solubility profiles of the two forms, dissolution at different stirring rates, temperatures, and pHs. It was found that form II exhibited higher solubility and dissolution rate at all the studied pHs. However, a significant increase in dissolution and solubility of form II was noted at pH 6. Dissolution studies at different stirring rates confirmed that the dissolution process is diffusion controlled, zero order in nature and adheres to the Noyes and Whitney and Levich equations. Dissolution studies at different temperatures enabled calculation of the heat of dissolution, Ea, of both forms. Ea for form I and form II was found to be almost identical. Storing of form II for one week at different temperatures resulted in the partial transformation of form II to form I as indicated from dissolution studies. The extent of transformation and hence reduction in dissolution rate increased with the increase in storage temperature.

Bioequivalence study of two capsule formulations of omeprazole

Bioequivalency of Omeraz, a test-product of Arab Pharmaceutical Manufacturing Company (Jordan) and Losec, a reference product by Astra (Sweden), was evaluated by a randomised crossover study on 22 healthy male volunteers. Serum concentrations of omeprazole were measured by an HPLC assay. There were no statistically significant differences between the two products in terms of serum profile and pharmacokinetic parameters including AUC, Cmax, Tlag, Tmax, MRT, Ke and T1/2. The AUC ratios (Omeraz/Losec) for 24 hours and for infinity were respectively 1.02 with a 90% C.L. of 0.88-1.16 and 1.00 with a 90% C.L. of 0.88-1.14. The two products may be considered as bioequivalent in terms of the extent of absorption as indicated by the AUC ratios. However, the confidence limits of Cmax fall outside the FDA accepted range.

Bioequivalence of two oral dosage forms prepared from different polymorphic modifications of tenoxicam

The bioavailability of two pharmaceutical dosage forms formulated using different polymorphs of tenoxicam were compared. Serum levels of TNX were analysed using high performance liquid chromatography. The pharmacokinetic parameters were estimated following the oral administration of a single dose (20 mg) of the drug as two different polymorphs to 12 healthy volunteers. The differences between formulations were statistically insignificant.

High performance liquid chromatographic analysis of tetroxoprim and sulphadiazine in serum and urine

Quantitative determination of tetroxoprim and sulphadiazine in serum and urine was performed using reversed phase high performance liquid chromatography. Protein precipitation using 10% perchloric acid was utilized for purification of serum samples while urine samples were diluted prior to analysis. The mobile phase consisted of triethylammonium acetate buffer (85%), acetonitrile (12%) and methanol (3%), with a final pH of 4.2. The eluent was monitored at 280 nm. Benzoic acid was used as an internal standard. Standardization, validation and application of the method is described.

Microbial contamination and preservation efficacy of cough preparations

Cough syrups, manufactured by four different Jordanian pharmaceutical companies, were examined for microbial contents and efficacy of preservation from fungal and bacterial contamination. Five per cent of the tested samples were found to be contaminated by Candida albicans and 30% of the products examined did not comply with the pharmacopoeial requirements for optimal preservation from fungal contamination. All the products tested were free from bacteria and were efficiently preserved against accidental bacterial contamination.

High performance liquid chromatographic analysis of caffeine concentrations in plasma and saliva

A rapid high performance liquid chromatographic (HPLC) method for the analysis of caffeine in plasma and saliva is described. Samples of saliva and plasma were purified using zinc sulphate solution as protein precipitant. The supernatant was injected directly onto the column. The mobile phase consisted of ammonium acetate buffer:acetonitrile:methanol (82:15:3, v/v). Measurements were carried out at 254 nm. Acetanilide was used as the internal standard and analysis was completed in 10 min. No interference from endogenous components or other methylxanthines was observed. The coefficients of variation for within day and between day analysis for both saliva and plasma were less than 7.66%. Samples were collected from 20 volunteers. The correlation coefficient between plasma and saliva caffeine concentrations was found to be 0.98.