Coding for the Optical Channel: the Ghost-Pulse Constraint

We consider a number of constrained coding techniques that can be used to mitigate a nonlinear effect in the optical fiber channel that causes the formation of spurious pulses, called ``ghost pulses.'' Specifically, if $b_1 b_2 ... b_{n}$ is a sequence of bits sent across an optical channel, such that $b_k=b_l=b_m=1$ for some $k,l,m$ (not necessarily all distinct) but $b_{k+l-m} = 0$, then the ghost-pulse effect causes $b_{k+l-m}$ to change to 1, thereby creating an error. We design and analyze several coding schemes using binary and ternary sequences constrained so as to avoid patterns that give rise to ghost pulses. We also discuss the design of encoders and decoders for these coding schemes.Comment: 13 pages, 6 figures; accepted for publication in IEEE Transactions on Information Theor

Treatment of acute cryptococcal meningitis in HIV infected adults, with an emphasis on resource-limited settings

BACKGROUND: Despite the advent and increasingly wide availability of antiretroviral therapy, cryptococcal meningitis (CM) remains a significant cause of mortality and morbidity amongst individuals with HIV infection in resource-limited settings. The ideal management of CM remains unclear. The aim of this review is to assess the evidence for deciding on which antifungal regimen to use as well as other modalities of management to utilise especially resource poor settings in order to achieve the best possible outcome and enable an individual with CM to survive their acute illness and benefit from antiretroviral therapy. OBJECTIVES: To determine the most effective initial and consolidation treatment strategy for CM in HIV infected adults. SEARCH STRATEGY: The Cochrane HIV/AIDS group search strategy was used. Key words in the search included, meningitis, cryptococcus neoformans, treatment, trial, human immunodeficiency virus, acquired immunodeficiency syndrome, antifungal agents, amphotericin, flucytosine, fluconazole, azole, lumbar puncture, cerebrospinal fluid (CSF) pressure and acetazolamide. SELECTION CRITERIA: Randomised of HIV-infected adults with a first episode of CM diagnosed on CSF examination, by India ink staining, CSF culture or cryptococcal antigen testing. DATA COLLECTION AND ANALYSIS: Data were extracted using standardised forms and analysed using Rev Man 4.2.7 software. MAIN RESULTS: Six studies are included in the review. Five of the studies compared antifungal treatments and one study addressed lowering intracranial pressure. This study was stopped early due to excess adverse effects. The results of the other five studies as summarised as follows.Mayanja-Kizza 1998 compared fluconazole to fluconazole with 5 flucytosine. The dose of fluconazole used 200mg initially is lower than the recommended initial dose of 400mg. No survival advantage was found with the use of 5 flucytosine in addition to fluconazole.Two studies Brouwer 2004 and van der Horst 1997 compared Amphotericin (AmB) to AmB with 5 flucytosine. Both drugs were given at currently recommended doses for 2 weeks. No survival difference was found at 14 days or at 10 weeks (only recorded in Brouwer 2004). There were significantly more patients with sterile CSF cultures at 14 days in the group that received AmB with flucytosine.Brouwer 2004 compared AmB given alone to AmB given with flucytosine and fluconazole alone or in combination. This was a small study and no differences in mortality were noted between the groups.Bicanic 2008 compared high to standard dose AmB both with flucytosine. There was no difference in mortality between the two groups or adverse events.Leenders 1997 compared standard AmB to liposomal AmB. There was no difference in death rates between the two groups. But there were significantly fewer side effects in the group treated with liposomal AmB. AUTHORS' CONCLUSIONS: The main aim of this review was to determine the best treatment for cryptococcal meningitis in resource-limited settings. In these settings usually only AmB and fluconazole are available. No studies suitable for inclusion in the review were found that compared these two drugs. Therefore we are unable to recommend either treatment as superior to the other. The recommended treatment for CM is a combination of AmB and flucytosine. The optimal dosing of AmB remains unclear. Liposomal AmB is associated with less adverse events than AmB and may be useful in selected patients where resources allow.Future research into the management of cryptococcal meningitis in resource-limited settings should focus on the most effective use of medications that are available in these settings.Flucytosine in combination with AmB leads to faster and increased sterilisation of CSF compared to using AmB alone. As Flucytosine is often not available in developing countries, policy makers and national departments of heath should consider procuring this drug for HIV treatment programmes.Publisher PDFPeer reviewe

Senior citizens and over the counter drugs: challenges in rural India

Background: The geriatric population is on a rise in India, which is accompanied by an increase in their health care needs. As they are prone to have multiple diseases simultaneously the tendency for over the counter (OTC) or non-prescription drugs is much higher among the elderly population. A thorough knowledge about the medication practices among elderly is indispensable since the chances for adverse drugs events; drug interactions etc. are higher among them. The primary objective of the present study was to measure the prevalence of over the counter drug usage among those aged 60 years or above residing in a rural block of North Tamilnadu, India.Methods: A community based cross sectional study was conducted among those aged 60 years or above using an interviewer administered questionnaire and data was collected from 100 consenting participants who were selected using multi stage sampling.Results: The prevalence of the usage of over the counter drugs among the elderly population was found to be 51% (95% CI 41.1-60.9). It was shown that the usage of OTC drugs was associated with higher socio economic status (p value 0.015) and literacy (p value 0.003).Conclusions: Further studies need to done to identify whether such high prevalence of OTC drug usage among elderly is a reflection of drug practices among general population and if proven otherwise should explore the various reasons for the same so that necessary measures can be implemented to alleviate the situation.

Heterosis in single cross inter and intra-specific hybrids of Desi cotton (Gossipium arboreum and G. herbaceaum) for their seed cotton yield, fibre quality and seed oil content

The present investigation was carried out to assess the expression of per se performance and heterotic effect for fibre quality and seed oil content besides seed cotton yield, studied involving ten desi cotton (Gossipium arboreum and G. herbaceaum) genotypes and their 45 cross combinations in half diallel analysis. F-1 hybrids GBhv-282 x G 27 (67.36%), GBhv- 287 x 824 (58.14%), GBhv- 282 x GAM- 173 (35.00%), GBhv- 286 x G 27 (20.50%), and GBhv- 283 x 824 (18.75%) recorded highest per se performance and significant positive standard heterosis while the maximum heterobeltiosis for seed cotton yield per plant was exhibited by the hybrid GBhv- 287 x 824(155.60 %) followed by GBhv- 282 x G 27 (151.29%) and GBhv- 282 x GAM- 173 (130.30%). Similar trend of heterosis for numbers of boll per plant were observed in above hybrids. For fibre quality traits none of the cross showed consistent high performance for all the characters. Cross GBhv- 283 x 824 was exhibited high standard heterosis for 2.5 % span length, fibre strength, fibre elongation percentage as well as for short fibre index (SFI) while cross GBhv- 286 x 824 were promising for 2.5 per cent span length, fibre strength and fibre fineness. In case of oil content intraarboreum crosses resulted as better crosses and among them cross combination 824 x GAM- 173 was best. Desi cotton hybrids are having lower fibre quality and yield. So, improvement for yield and fibre quality of diploid native varieties through heterosis breeding provided better hybrids for rainfed farming

Digital calculation of response spectra from strong-motion earthquake records

This report presents a numerical method for computing response spectra from strong-motion earthquake records. The method is based on the exact solution to the governing differential equation and gives a three to four-fold saving in computing time compared to a third order Runge-Kutta method of comparable accuracy. An analysis was made of the errors introduced at various stages in the calculation of spectra so that allowable errors could be prescribed for the numerical integration. Using the proposed method of computing or other methods of comparable accuracy, example calculations show that the errors introduced by the numerical procedures are much less than the errors inherent in the digitization of the acceleration record. Included as appendices to the report are computer programs in Fortran IV, with instructions for their use, for computing spectra, for correction of the baseline of the digitized record, and for the computation of ground velocity and displacement