STUDY THE SUSTAIN RELEASE EFFECT OF DIFFERENT POLYMERS USED IN THE FORMULATION OF ASPIRIN-ROSUVASTATIN TABLETS

Objective: Low permeability of rosuvastatin calcium faces a problem of low bioavailability (absolute bioavailability 20%) as its permeation is the rate limiting factor. Rosuvastatin calcium is a selective competitive inhibitor of HMG-CoA reductase and it lowers plasma cholesterol level. Aspirin is an anti-platelet agent with half-life of 6-7 h. Frequency of dosing of both drugs is high to maintain the desired plasma drug concentration so it is selected to formulate a sustained release tablet of aspirin and rosuvastatin calcium, which release the drug in a sustained manner over a period of time by using various polymers and study the effect of polymers on the release pattern of both drugs. This approach will also enhance the residence time of rosuvastatin calcium at the absorption site and enhance permeation by the effect of the polymers used and this in turn will enhance bioavailability. Methods: Tablets contain aspirin plus rosuvastatin calcium were prepared by direct compression method. The sustained release of the tablets was obtained by using different polymers (xanthan gum, microcrystalline cellulose, HPMC K4M and chitosan) incorporated in the tablet and responsible for the release of both drugs from each tablet. Tablets were evaluated for weight variation, drug content, friability, hardness and thickness for all batches (F1 to F12). In-vitro dissolution was studied for all batches (F1 to F12) according to the type and ratio of each polymer used within these formulas i.e. (10 mg, 20 mg and 30 mg) respectively. Results: The release of aspirin and rosuvastatin calcium from sustained release tablets varied according to the type and amount (ratio) of each polymer used. After the 7 h release study; (F1, F2, F3) that uses xanthan gum as the sustain release polymer showed the most sustained formulations than other polymers. The sustained release of drugs from tablet enhanced by increasing the amount of polymer, so F3 for example, which contain 30 mg xanthan gum had most sustained release than F1 and F2 which contain (10 mg and 20 mg) of the polymer respectively, this due to polymer related viscosity, swelling and binding mechanisms.Conclusion: Using suitable polymer for sustained release will enhance the pharmacokinetics and efficacy of drugs and increase patient complains about combination therapy.Â

Error models for digital channels and applications to wireless communication systems

Digital wireless channels are extremely prone to errors that appear in bursts or clusters. Error models characterise the statistical behaviour of bursty profiles derived from digital wireless channels. Generative error models also utilise those bursty profiles in order to create alternatives, which are more efficient for experimental purposes. Error models have a tremendous value for wireless systems. They are useful for the design and performance evaluation of error control schemes, in addition to higher layer protocols in which the statistical properties of the bursty profiles are greatly functional. Furthermore, underlying wireless digital channels can be substituted by generated error profiles. Consequently, computational load and simulation time can be significantly reduced when executing experiments and performing evaluation simulations for higher layer communications protocols and error control strategies. The burst error statistics are the characterisation metrics of error models. These statistics include: error-free run distribution; error-free burst distribution; error burst distribution; error cluster distribution; gap distribution; block error probability distribution; block burst probability distribution; bit error correlation function; normalised covariance function; gap correlation function; and multigap distribution. These burst error statistics scrutinise the error models and differentiate between them, with regards to accuracy. Moreover, some of them are advantageous for the design of digital components in wireless communication systems. This PhD thesis aims to develop accurate and efficient error models and to find applications for them. A thorough investigation has been conducted on the burst error statistics. A breakdown of this thesis is presented as follows. Firstly, an understanding of the different types of generative error models, namely, Markovian based generative models, context-free grammars based generative models, chaotic models, and deterministic process based generative models, has been presented. The most widely used models amongst the generative models have been compared with each other consulting the majority of burst error statistics. In order to study generative error models, error burst profiles were obtained mainly from the Enhanced General Packet Radio Service (EGPRS) system and also the Long Term Evolution (LTE) system. Secondly, more accurate and efficient generative error models have been proposed. Double embedded processes based hidden Markov model and three-layered processes based hidden Markov model have been developed. The two types of error profiles, particularly the bit-level and packet-level error profiles were considered. Thirdly, the deterministic process based generative models’ parameters have been tuned or modified in order to generate packet error sequences rather than only bit error sequences. Moreover, a modification procedure has been introduced to the same models to enhance their generation process and to make them more desirable. Fourthly, adaptive generative error models have been built in order to accommodate widely used generative error models to different digital wireless channels with different channel conditions. Only a few reference error profiles have been required in order to produce additional error profiles in various conditions that are beneficial for the design and performance evaluation of error control schemes and higher layer protocols. Finally, the impact of the Hybrid Automatic Repeat reQuest (HARQ) on the burst error statistics of physical layer error profiles has been studied. Moreover, a model that can generate predicted error sequences with burst error statistics similar to those of error profiles when HARQ is included has been proposed. This model is constructive in predicting the behaviour of the HARQ in terms of a set of higher order statistics rather than only predicting a first order statistic. Moreover, the whole physical layer is replaced by adaptively generated error profiles in order to check the performance of the HARQ protocol. The developed generative error models as well as the developed adaptive generative error models are expected to benefit future research towards the testing of many digital components in the physical layer as well as the wireless protocols of the link and transport layers for many existing and emerging systems in the field of wireless communications

EFFECT OF NATURAL AND SYNTHETIC POLYMERS ON THE PROPERTIES OF CANDESARTAN CILEXETIL MATRIX TABLET PREPARED BY DRY GRANULATION

ABSTRACTObjective: The objective of this study is to develop a controlled release matrix tablet of candesartan cilexetil to reduce the frequency of administration,enhance bioavailability and improve patient compliance; a once daily sustained release formulation of candesartan cilexetil is desirable.Methods: The prepared tablets from F1 to F24 were evaluated with different evaluation parameters like weight variation, drug content, friability,hardness, thickness and swelling ability. In vitro release for all formulas were studied depends on the type and amount of each polymer, i.e. (16 mg,32 mg and 48 mg) respectively beside to the combination effect of polymers on the release of the drug from the tablet.Results: In vitro release showed that formula 13 had the faster release (100% after 4 h) which contained acacia (1:1) and the lowest sustain releasewas showed for F7 (73% after 8 h) which contained HPMC K100M (1:1). Formula 1 was an 89 % release after 8 h which contain eudragit RS100; F4was a 100 % release after 5 h which contain Na CMC, F10 was a 100% after 8 h which contain xanthan gum and F16 was a 100 % release after 5 hwhich contain tragacanth polymer. Formula 9 had a lower release than F7 and F8 respectively. Formula 7 can be used for sustain oral drug delivery ofcandesartan cilexetil while Formula 13 can be used in contrary as fast release tablets for faster response.Conclusion: Controlled drug delivery system is promising for less dosing and higher patient compliance.Keywords: Angiotensin II receptor antagonist, Hypertension, Matrix system, Control release

Fabrication of PVC Enrofloxacin-Selective Electrodes for Estimating Enrofloxacin in Pure Form and as Preparation Formula:

أوجدت هذه الدراسة تطورا" لخصائص الاستجابة الكهروكيميائية للأقطاب الكهربائية الانتقائية للإينروفلوكساسين باستخدام الراسب والمعتمد على إنتاج الفوسفوتونجستيك ,بعد أستخدام مزيج من البولي فاينيل هيدروكلورايد (PVC) وداي بيوتيل فثاليت أوداي بيوتيل فوسفيت كمواد ملدنة. كانت أغشية المتحسسات الناتجة عبارة عن قطب كهربائي إنروفلوكساسين-فوسفوتونجستيك (متحسس1) ENR-DBPH-PTAوالقطب (متحسس2) .ENR-DOP-PTA  الاستجابات الخطية لأقطاب (ENR-DBPH-PTA)  و(ENR-DOP-PTA)  كانت ضمن المديات التركيزية 2.1×10-6- 10-1 و3.0×10-6- 10-2مول .لتر-1على التوالي, والتي تم ملاحظتها لكلا المتحسسين. الانحدارات كانت 0.24±51.61 و39.40±0.16  ملي فولت/حقبة.  ومديات الدالة الحامضية مساوية الى   8.5-2.5و2.0-9.0 التي لوحظت للمتحسسات 1و2 ,على التوالي. أظهرت أجهزة الاستشعار التي تم إنشاؤها معاملات انتقائية هائلة لعقار ENR.كما أظهرت أجهزة الاستشعار المقترحة خصائص علمية مفيدة لتقدير ENR في جرعة الدواء والشكل النقي.This study explored the development and qualities of the response of electrochemical properties of enrofloxacin-selective electrodes using precipitation based on producing phosphotungstic, after utilizing a matrix of polyvinyl chloride (PVC) and dibutyl phthalate or dibutyl phosphate as a plasticizer. The resulting membrane sensors were an enrofloxacin-phosphotungstic electrode (sensors 1) and an ENR-DOP-PTA electrode (sensors 2). Linear responses of (ENR-DBPH-PTA) and (ENR-DOP-PTA) within the concentration ranges of 2.1×10-6-10-1 and 3.0×10-6-10-2 mol. L-1, respectively, for both sensors were observed. Slopes of 51.61±0.24 and 39.40± 0.16 mV/decade and pH ranges equal to 2.5-8.5 and 2.0-9.0 were observed for sensors 1 and 2, respectively. The coefficients of selectivity of the created sensors demonstrated phenomenal selectivity for ENR. The proposed sensors showed useful scientific properties for the assurance of ENR in drug dosage and pure form

Heat generation, plastic deformation and residual stresses in friction stir welding of aluminium alloy

The interactions among thermal history, plastic deformation and residual stresses in the friction stir welding (FSW) process under different welding parameters have been widely considered a crucial issue and still not fully understood. In the present study, a novel three-dimensional fully coupled thermo-mechanical finite element (FE) model based on coupled Eulerian-Lagrangian approach (CEL) has been developed to simulate the FSW process of aluminium alloy AA 6082-T6 and to analyse the thermo-mechanical interaction mechanisms under different welding conditions. The numerical model successfully simulates the plunge, dwell, and welding steps in FSW and captures the evolution of temperature, plastic deformation, and residual stresses in the welded joint. The obtained results were validated by experimental testing with observed cross-weld thermal history, optical macrography and residual stress measurement using the neutron diffraction technique. The results reveal that the tool rotation speed governs the temperature evolution; the peak temperature increased from 740 to 850 °K when the tool rotation speed rose from 800 to 1100 rpm. The rotational speed also affected the plastic deformation, material flow, and the volume of material being stirred during the welding process. Higher plastic deformation is formed in the stirring zone by increasing the tool angular velocity. This behaviour led to an increase in the stirring effect of the welding tool, reduction of the tunnel defect size and enhancing the quality of weldments. The distribution of residual stresses in different zones of the FSW joints has been found to have an M-shaped profile. A significant tensile residual stress is characterised in the edge of the nugget zone in both longitudinal and transverse directions, balanced by compressive stresses in the thermo-mechanically affected zone, heat-affected zone and base metal. The presented FE modelling provides a reliable insight into the effects of the welding parameters on the weld quality of FSW joints and process optimisation with minimised experimental trials

Microstructure and mechanical properties of friction stir welded AA6092/SiC metal matrix composite

There is a need for improved understanding on the effects of friction stir welding (FSW) on the metallurgical and mechanical properties of aluminium matrix composite (AMC). In this study, AA6092/SiC/17.5p-T6 AMC joints were produced by using FSW with varying tool rotation and traverse speeds. The microstructural characterisation by scanning electron microscopy equipped with electron backscattered diffraction (EBSD) system revealed a substantial grain refinement and a homogeneous distribution of reinforcement particles in the nugget zone. The grain size of the nugget zone was greatly influenced by weld pitch, as a key indicator to control the amount of heat input, exposure time and cooling rate. Vickers microhardness profile across the welding zone revealed a significant difference in microhardness among the base metals, heat affected zone, thermo-mechanically affected zone and nugget zone. The tensile strength of the cross-weld specimens showed a high joint efficiency of about 75% of the base metal combined with relatively high ductility. Low-cycle fatigue properties were investigated in the axial total strain-amplitude control mode (from 0.3% to 0.5%) wit

The mycobiota of herbal drug plants in Oman and possible decontamination by gamma radiation

The mycobiota of seven herbal plant species were surveyed: Nigella sativa, Zataria multiflora, Trigonella foenum-graecum, Rhazya stricta (seeds and leaves), Haplophyllum tuberculatum, Aristolochia bracteolata and Teucrium muscatense. A total of 24 species of fungi were isolated from the plants (seeds, leaves, flowers and/or stems). No significant differences were found between the mycobiota of the herbal plant species or between the six samples of each plant. Aspergillus niger and Penicillium sp. were the most common species, followed by A. flavus and Rhizopus spp. A. flavus was found in all herbal plants except R. stricta (leaves) and Z. multiflora. Aflatoxins were extracted from a number of herbal plants. Some strains of A. flavus isolated from the plants were aflatoxigenic. Gamma radiation at 905.4 Gy showed an average percent inhibition of fungi on some herbal plants between 88.6 and 99.1%. Complete inhibition was obtained at 1836 Gy

Water-stable zirconium-based metal-organic framework material with high-surface area and gas-storage capacities.

We designed, synthesized, and characterized a new Zr-based metal-organic framework material, NU-1100, with a pore volume of 1.53 ccg(-1) and Brunauer-Emmett-Teller (BET) surface area of 4020 m(2) g(-1) ; to our knowledge, currently the highest published for Zr-based MOFs. CH4 /CO2 /H2 adsorption isotherms were obtained over a broad range of pressures and temperatures and are in excellent agreement with the computational predictions. The total hydrogen adsorption at 65 bar and 77 K is 0.092 g g(-1) , which corresponds to 43 g L(-1) . The volumetric and gravimetric methane-storage capacities at 65 bar and 298 K are approximately 180 vSTP /v and 0.27 g g(-1) , respectively.OKF, JTH and RQS thank DOE ARPA-E and the Stanford Global Climate and Energy Project for support of work relevant to methane and CO2, respectively. TY acknowledges support by the U. S. Department of Energy through BES Grant No. DE-FG02-08ER46522. WB acknowledges support from the Foundation for Polish Science through the “Kolumb” Program. DFJ acknowledges the Royal Society (UK) for a University Research Fellowship. This material is based upon work supported by the National Science Foundation (grant CHE-1048773).This is the accepted manuscript. The final version is available as 'Water-Stable Zirconium-Based Metal–Organic Framework Material with High-Surface Area and Gas-Storage Capacities' from Wiley at http://onlinelibrary.wiley.com/doi/10.1002/chem.201402895/abstract

The global burden of adolescent and young adult cancer in 2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In estimating the global burden of cancer, adolescents and young adults with cancer are often overlooked, despite being a distinct subgroup with unique epidemiology, clinical care needs, and societal impact. Comprehensive estimates of the global cancer burden in adolescents and young adults (aged 15–39 years) are lacking. To address this gap, we analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, with a focus on the outcome of disability-adjusted life-years (DALYs), to inform global cancer control measures in adolescents and young adults. Methods: Using the GBD 2019 methodology, international mortality data were collected from vital registration systems, verbal autopsies, and population-based cancer registry inputs modelled with mortality-to-incidence ratios (MIRs). Incidence was computed with mortality estimates and corresponding MIRs. Prevalence estimates were calculated using modelled survival and multiplied by disability weights to obtain years lived with disability (YLDs). Years of life lost (YLLs) were calculated as age-specific cancer deaths multiplied by the standard life expectancy at the age of death. The main outcome was DALYs (the sum of YLLs and YLDs). Estimates were presented globally and by Socio-demographic Index (SDI) quintiles (countries ranked and divided into five equal SDI groups), and all estimates were presented with corresponding 95% uncertainty intervals (UIs). For this analysis, we used the age range of 15–39 years to define adolescents and young adults. Findings: There were 1·19 million (95% UI 1·11–1·28) incident cancer cases and 396 000 (370 000–425 000) deaths due to cancer among people aged 15–39 years worldwide in 2019. The highest age-standardised incidence rates occurred in high SDI (59·6 [54·5–65·7] per 100 000 person-years) and high-middle SDI countries (53·2 [48·8–57·9] per 100 000 person-years), while the highest age-standardised mortality rates were in low-middle SDI (14·2 [12·9–15·6] per 100 000 person-years) and middle SDI (13·6 [12·6–14·8] per 100 000 person-years) countries. In 2019, adolescent and young adult cancers contributed 23·5 million (21·9–25·2) DALYs to the global burden of disease, of which 2·7% (1·9–3·6) came from YLDs and 97·3% (96·4–98·1) from YLLs. Cancer was the fourth leading cause of death and tenth leading cause of DALYs in adolescents and young adults globally. Interpretation: Adolescent and young adult cancers contributed substantially to the overall adolescent and young adult disease burden globally in 2019. These results provide new insights into the distribution and magnitude of the adolescent and young adult cancer burden around the world. With notable differences observed across SDI settings, these estimates can inform global and country-level cancer control efforts. Funding: Bill & Melinda Gates Foundation, American Lebanese Syrian Associated Charities, St Baldrick's Foundation, and the National Cancer Institute