Cooperative diversity using MIMO systems

Multipath fading is one of the primary factors for degrading the performance in a wireless network. Information theoretic and past research suggest the use various diversity techniques to combat fading in wireless networks. Antenna diversity, a form of diversity technique, when incorporated in a wireless transceiver increases the system capacity and is one of the effective methods to combat fading in wireless systems. Also, recent research by Laneman et.al., Sendonaris et.al. suggests that cooperation among users in a wireless networks is an effective approach for a better signal reception in multipath fading environments. The diversity gains obtained by cooperation among the users of a wireless network is termed as cooperative diversity . Although, prior research in cooperative diversity considers users equipped with single antenna, in practical scenarios users may be able to accommodate multiple antennas due to the recent advanced research in semiconductor industry. Hence, the primary purpose of this thesis is to design, simulate and analyze an end-end performance of multi-antenna wireless systems employing cooperative multi antenna relay nodes so as to exploit the cooperative diversity and antenna diversity simultaneously in a wireless networks. Three main contributions to the area of cooperative multiple-input multiple-output (MIMO) wireless systems is presented in this thesis. First, we perform information theoretic analysis to study the impact of antenna arrays on cooperative wireless networks and propose the best possible distribution of antenna arrays among the three terminals of a simple three terminal cooperative relay network. Second, we design, simulate, and analyze a cooperative multiple-input multiple-output (MIMO) wireless systems employing orthogonal space-time block codes as proposed by Alamouti in 1998 with a decode-and-forward (DF) relay terminal. We implement a maximal ratio combining receiver that provides almost twice the diversity gain with respect to point-point multiple input multiple output link. Finally, we implement a practical receiver for cooperative reception using multiple antennas at all nodes based on Bell-Labs Layered Space Time architecture (BLAST). We incorporate a practical adaptive decode-and-forward (DF) relaying technique for reliable signal retransmission for both Alamouti space-time coding and the BLAST schemes. Results presented in terms of bit error rates and throughput show that remarkable performance gains are achievable by combining the concepts drawn from space-time coding, cooperative relaying and array processing

Association between components of metabolic syndrome and elevated intraocular pressure

Background: Glaucoma is a group of eye diseases which result in damage to the optic nerve and ultimately vision loss. Elevated intraocular pressure (IOP) remains as the one major known risk factor for both the development and progression of glaucoma. Metabolic syndrome (MS) have been found to relate to elevated IOP. The aim of the study is to examine the association between MS and IOP by comparing central corneal thicknesses (CCT).Methods: The study was carried out with 169 subjects consists of 94 were clinically diagnosed MS patients and 75 are healthy controls. Serum fasting glucose, triglyceride and HDL cholesterol levels were measured, and waist circumference, body mass index and blood pressure of all patients were recorded. Ophthalmological examinations, including IOP and CCT measurements were done on everyone.Results: Higher IOP was observed in subjects with MS than those without MS. There was significant difference in the CCT values between the groups with and without MS (p<0.05). Most of the MS components were associated with IOP and CCT (p<0.05).Conclusions: The study concludes that components of MS have strong association with IOP and CCT. The prevalence of MS is increasing rapidly in developing countries and the main cause for MS is sedentary lifestyle. Since there is relationship between MS and IOP, lifestyle intervention might have therapeutic potential to reduce IOP. Further studies are warranted to bring about the possible underlying relationship between components of MS and IOP

Marine pollution - its effects on living resources with special reference to aquaculture

Due to large scale industrialisation and indiscriminate discharge of effluents with high BOD, toxic chemicals and particulate matter reach the aquatic environment, either directly or indirectly. Enrichment of the coastal waters through nutrients and minerals lead to immediate and long term effects on the biota and fishery resources causing severe eutrophication or mass mortality. Among a large variety of pollutants which reach the aquatic environment, the domestic sewage, agricultural pesticides, industrial wastes, oil and oil dispersants, radioactive wastes and the polluted water from the coconut retting zones causes deleterious effects in the inshore and fish fanning areas

ASSOCIATION OF SERUM URIC ACID AND LIPID PROFILE IN TYPE 2 DIABETIC PATIENTS WITH AND WITHOUT DIABETIC RETINOPATHY

Objectives: Diabetic retinopathy (DR) is one of the microvascular complications in type 2 diabetes (T2D).  Elevated serum uric acid (SUA) has been shown to play a significant role in diabetic neuropathy and nephropathy but there is little information on retinopathy. Therefore, the present study was aimed to investigate the SUA and lipid profile in T2D patients with and without DR and the association between SUA and severity of DR.Methods: The study was conducted in the ophthalmology OPD at Sri Lakshmi Narayana Institute of Medical Sciences. The presence of T2D was confirmed by investigating fasting blood glucose level (normal limit &lt; 110 mg/dl) in all the individuals. DR was examined by detailed dilated fundoscopic examination. Based on the fundus examination, patients were divided in to diabetes with signs of DR and those without signs of DR. Age and sex matched healthy were taken as controls. Fasting blood sugar, SUA and lipid profile were investigated for these groups. Results: The study found elevated SUA and abnormal lipid profile in DR group when compared to non-DR and control groups. We also found the significant association between SUA and severity of DR particularly in males.Conclusion: We found a significant association between SUA and severity of DR in T2D patients. Further studies with large sample size are needed to establish the role of elevated SUA and the mechanism involved in the pathogenesis of retinopathy in diabetic patients. Regular measurements of SUA level could be advised to the diabetic patients for the early management

Lysis-deficient phages as novel therapeutic agents for controlling bacterial infection

<p>Abstract</p> <p>Background</p> <p>Interest in phage therapy has grown over the past decade due to the rapid emergence of antibiotic resistance in bacterial pathogens. However, the use of bacteriophages for therapeutic purposes has raised concerns over the potential for immune response, rapid toxin release by the lytic action of phages, and difficulty in dose determination in clinical situations. A phage that kills the target cell but is incapable of host cell lysis would alleviate these concerns without compromising efficacy.</p> <p>Results</p> <p>We developed a recombinant lysis-deficient <it>Staphylococcus aureus </it>phage P954, in which the endolysin gene was rendered nonfunctional by insertional inactivation. P954, a temperate phage, was lysogenized in <it>S. aureus </it>strain RN4220. The native endolysin gene on the prophage was replaced with an endolysin gene disrupted by the chloramphenicol acetyl transferase (<it>cat</it>) gene through homologous recombination using a plasmid construct. Lysogens carrying the recombinant phage were detected by growth in presence of chloramphenicol. Induction of the recombinant prophage did not result in host cell lysis, and the phage progeny were released by cell lysis with glass beads. The recombinant phage retained the endolysin-deficient genotype and formed plaques only when endolysin was supplemented. The host range of the recombinant phage was the same as that of the parent phage. To test the <it>in vivo </it>efficacy of the recombinant endolysin-deficient phage, immunocompromised mice were challenged with pathogenic <it>S. aureus </it>at a dose that results in 80% mortality (LD₈₀). Treatment with the endolysin-deficient phage rescued mice from the fatal <it>S. aureus </it>infection.</p> <p>Conclusions</p> <p>A recombinant endolysin-deficient staphylococcal phage has been developed that is lethal to methicillin-resistant <it>S. aureus </it>without causing bacterial cell lysis. The phage was able to multiply in lytic mode utilizing a heterologous endolysin expressed from a plasmid in the propagation host. The recombinant phage effectively rescued mice from fatal <it>S. aureus </it>infection. To our knowledge this is the first report of a lysis-deficient staphylococcal phage.</p

Stratifying low level Isoniazid resistance using additional intermediate drug concentration

AbstractIsoniazid (INH) susceptibility testing for 100 Mycobacterium tuberculosis performed by conventional minimum inhibitory concentration (MIC) method was stratified using additional drug concentrations. Introduction of additional drug concentrations did not greatly improve the discriminatory capacity, but can be used in specialized studies pertaining to cross resistance between structural analogues of INH

Optimization of the conventional minimum inhibitory concentration method for drug susceptibility testing of ethionamide

AbstractEvaluation of newer methods and optimization of existing methods for the susceptibility testing of second-line drugs, especially ethionamide, are essential when treatment of multidrug-resistant tuberculosis (MDR-TB) is warranted. The ideal method must clearly demarcate sensitive from resistant strains. Hence, optimization of the conventional minimum inhibitory concentration (MIC) method was attempted using diluted inoculum. The optimized MIC method was evaluated using 206 Mycobacterium tuberculosis strains isolated from new and previously treated tuberculosis patients and were compared with the conventional MIC method and proportion sensitivity (PST) method. The sensitivity and specificity of the optimized MIC method in comparison with the PST method was 74% and 90%. Assessment of the optimized MIC method with the conventional MIC method gave a sensitivity of and specificity of 73% and 98%. Overall agreement between the methods was found to be ⩾80%. Endowed with the ability to identify the resistant strains precisely, the optimized MIC method can be used for screening resistance to ethionamide

Effect of temperature on storage of ethionamide during susceptibility testing

Objective: Ethionamide being thermolabile in nature, effect of temperature on the drug and its stability in liquid andsolid media during susceptibility testing procedures was assessed to understand the inconsistency in DST formats.Methods: Working solution of ethionamide and Lowenstein- Jensen (LJ) media incorporated with ethionamide werepreincubated at 4°C and 37°C prior to DST methods was incubated till 4 weeks at different temperatures and utilizedfor DST in MGIT 960.Results: Degradation of ethionamide working solution was observed at 37°C after 3 weeks of incubation. Ethionamideincorporated LJ media can be stored without compromise on susceptibility up to 5 weeks. But, a week of prior incubationat 37°C has deleterious effect on the DST profile. Ethionamide was found to degrade at 37°C after different timepoints when stored as solution or as LJ media.Conclusion: Use of DST formats that provide results within 2 weeks can be recommended for ethionamide susceptibilitytesting. J Microbiol Infect Dis 2013; 3(3): 128-132Key words: Degradation; Ethionamide; LJ medium; MGIT 960; Mycobacterium tuberculosi

Revisiting the susceptibility testing of Mycobacterium tuberculosis to ethionamide in solid culture medium.

BACKGROUND & OBJECTIVES Increase in the isolation of drug resistant phenotypes of Mycobacterium tuberculosis necessitates accuracy in the testing methodology. Critical concentration defining resistance for ethionamide (ETO), needs re-evaluation in accordance with the current scenario. Thus, re-evaluation of conventional minimum inhibitory concentration (MIC) and proportion sensitivity testing (PST) methods for ETO was done to identify the ideal breakpoint concentration defining resistance. METHODS Isolates of M. tuberculosis (n=235) from new and treated patients were subjected to conventional MIC and PST methods for ETO following standard operating procedures. RESULTS With breakpoint concentration set at 114 and 156 µg/ml, an increase in specificity was observed whereas sensitivity was high with 80 µg/ml as breakpoint concentration. Errors due to false resistant and susceptible isolates were least at 80 µg/ml concentration. INTERPRETATION & CONCLUSIONS Performance parameters at 80 µg/ml breakpoint concentration indicated significant association between PST and MIC methods