Voice-band modems: A device to transmit data over telephone networks

Over the last 40 years, there has been continuous evolution in the design of voice-band modems-starting at a data rate of 300 bits per second in late 1950s, a rate of 33,600 bits per second has been achieved in 1995. Realising such high data rates over the voice band of 3400 Hz is a remarkable feat made possible by combining sophisticated techniques from three disciplines, communication theory, signal processing and information theory. In this article, we begin with a brief introduction of voice-band modems and then introduce the basic principles of data transmission.     

Serum alpha-1-antitrypsin in smokers and non-smokers

Serum alpha-1-antitrypsin assay was carried out in 21 smokers (mean age 44±8 yrs) and in 25 nonsmokers (mean age 44±7 yrs). The levels of serum alpha-1-antitrypsin expressed in umol/mt/ml were 2.97±0.85 for smokers and 3.08±0.37 for non-smokers and analysis of variance revealed no significant difference between these two groups. However in five smokers reduced levels (<80% of the lower limit of non-smokers) were seen and four of them were bus drivers. This study advises monitoring of serum alpha-1-antitrypsin levels in smokers with possible therapy to those with reduced levels.     

Some Theorems on sum Separability of Multivariable Reactance and Positive Real Functions

New necessary and sufficient conditions, which are also algorithmic in nature, are obtained for the decomposition of a multivariable reactance function or a multivariable positive real function into a sum of several single variable reactance functions or several single variable positive real functions, respectively.     

Adenosine deaminase and protein tyrosine phosphatase activities in liver and peritoneal macrophages of streptozotocin induced diabetic mice

Adenosine deaminase and protein tyrosine phosphatase activities in liver and peritoneal macrophages were estimated in control, streptozotocin induced diabetes and insulin treated diabetic groups of Swiss albino mice. Both the enzyme levels were elevated while glycogen content decreased in the liver of diabetic group of animals as compared to controls, while in insulin treated group, they were comparable to control levels. In macrophages also, both adenosine deaminase which plays an important role in their maturation and protein tyrosine phosphatase enzyme involved in their activation were high in diabetic group, whereas in insulin treated diabetic group, the values were comparable to control levels. *** DIRECT SUPPORT *** A00FN011 00003     

Serum calcium levels in patients with essential hypertension and their first degree relatives

Calcium plays an important role in the pathophysiology of essential hypertension. Serum calcium levels were measured in 117 subjects with essential hypertension and 77 first-degree relatives. The results showed that serum calcium levels were significantly (p<0.01) decreased in both males and females with essential hypertension and their first-degree relatives when compared with the normotensive controls. This is the first study in Indian population.     

Evaluation of FSH,LH and testosterone levels in different subgroups of infertile males

Gonadotropins (FSH, LH) and testosterone are the prime regulators of germ cell development. Abnormal spermatogenesis is often associated with altered serum gonadotropins and testosterone. FSH, LH and testosterone levels were estimated in 96 infertile men of whom 35 were azoospermic, 35 were oligozoospermic, 11 were with varicocele and 15 were with histopathological abnormalities like hypospermatogenesis, spermatid arrest and sertoli-cell only syndrome. Results showed statistically significant (p<0.05), increase in the mean FSH and LH levels in all the infertile males studied when compared with the fertile controls (n=35). However, there is no significant difference in the mean levels of testosterone between the infertile and fertile men.     

<Emphasis Type="Italic">In vitro</Emphasis> released antigens in diagnosis and immunomonitoring of filaria and tuberculosis

In vitro released antigens by living parasites or bacteria underin vitro maintenance or short term culture showing specific humoral immune response have been explored in development of immunodiagnostics for infectious diseases such as filariasis and tuberculosis in our laboratory. ELISA usingB. malayi mf ES antigen has been explored for detecting IgG antibody by Indirect ELISA and antigen by Inhibition ELISA and in immunomonitoring of carriers as well as clinical filarial cases. A ten year follow up of mf carriers with DEC therapy showed disapperance of antigen and antibody followed by reappearance in few cases in an endemic area. None of the cases followed developed clinical symptoms suggesting the need for long term monitoring and treatment of microfilaraemic carriers. Further immunomonitoring was found to be useful in confirming filaria aetiology in the absence of microfilaremia and determining appropriate period of treatment of acute, early clinical and occult filarial infections for clinical relief and cure.Indirect Stick Penicillinase ELISA system using Mtb EST-6 antigen for detecting tuberculous IgG antibody and a Sandwich Penicillinase ELISA system using affinity purified antibody for detecting circulating antigen were explored in tuberculosis. A combination of both the assay systems with a sensitivity of 70% and specificity of 98% was found to be promising in the precise diagnosis of pulmonary tuberculosis. Further antigen detection was found to be useful in bone and joint tuberculosis.     

Filarial antibody and antigen detection in different clinical conditions in an endemic area

The study was conducted in filarial endemic area for various clinical presentations and diagnosis of occult filariasis. A total of 157 cases of various clinical presentations namely tropical pulmonary eosinophilia, monoarthritis, polyarthritis, glomerulonephropathy, tenosynovitis, inguinal lymphadenopathy, generalised lymphadenopathy, retroperitonial lymphadenopathy, endomyocardial fibrosis and acute conjunctivitis were screened for filarial antigen and antibody by enzyme linked immunosorbent assay (ELISA). Out of 157 cases, 107 cases were positive for antigen or antibody, suggesting the role of filarial infection in these clinical presentations. All the 107 cases were treated with diethylcarbamazine citrate (DEC) and some of the patients who were followed showed relief in signs and symptoms. Hence assay of filarial antigen and/or antibody may be useful for diagnosing occult filarial syndromes for better management and further appropriate treatment.     

Assay of tubercular antibody, circulating free and immune complexed antigen in the diagnosis of pulmonary tuberculosis

Analysis of tubercular antibody, circulating free and immune complexed antigen (CIC-Ag) was done in confimed pulmonary tuberculosis sera by ELISA, using ES-31 antigen and affinity purified anti ES-31 antibody. Twenty three of 25 (92%) tuberculosis sera were positive for IgG antibody to ES-31 antigen. Using anti ES-31 antibody, free tubercular antigen could be detected in 20 of 25 (80%) cases whereas circulating immune complexed antigen (CIC-Ag) in 18 of 25 (72%) cases by sandwich ELISA. Of the two sera showing absence of antibody, one showed presence of free and CIC-Ag whereas the other showed the presence of free antigen. Thus antigen assay may be used as an adjunct tool for confirmation of pulmonary tuberculosis.