Error correction/masking for digital voice transmission over theland mobile satellite system

The development of a 2400-b/s speech digitizer which provides an acceptable level of intelligibility and quality over land mobile satellite channels is described. Performance tests over simulated channels in the UHF band (800 MHz) are presented. The voice digitizer is a linear prediction (LPC) vocoder which uses a channel error correction and concealment procedure tailored to error statistics for a minimum-shift keyed (MSK) downlink to a moving vehicle. The error-handling technique is based on perceptual criteria and utilizes the parametric nature of LPC representation of speech. A single-error-correcting, single-burst-detecting (28, 20) fire code is shown to be the best choice for the application. The intelligibility of the vocoder is measured and compared to the standard LPC-10 algorithm. The major remaining sources of speech quality degradation due to channel errors are determined and ranked     

Bone tumors of the coracoid process of the scapula

Bone tumors of the coracoid process of the scapula are rare, and diagnosis and treatment often are delayed. The records of 18 patients with bone tumors of the coracoid process were reviewed. Histologic types included eight cases of ordinary chondrosarcoma, three cases of dedifferentiated chondrosarcoma, two cases of osteoid osteoma, and one case each of osteosarcoma, plasmacytoma, lymphoma, giant cell tumor, and aneurysmal bone cyst. All 18 patients had shoulder pain, and eight of them had been treated with steroid injections for nonneoplastic conditions. Radiologically, chondrosarcoma did not always show clear cortical destruction, and one giant cell tumor had features mimicking those of chondrosarcoma. Five patients (three with dedifferentiated chondrosarcoma, one with chondrosarcoma, one with plasmacytoma) died of disease. The coracoid process was the site with a markedly high proportion of chondrosarcomas. Bone tumors of the coracoid process may be difficult to detect on plain radiographs. In the patient with persistent shoulder pain unresponsive to the selected treatment, additional imaging studies should be considered to eliminate the possibility of a bone lesion.     

Outcome of hypertension management in Asian Americans

BACKGROUND: Ethnic and/or racial differences in drug response to antihypertensive agents have been recognized, yet the prescribing practices and the information on efficacy of various agents rely mainly on the response of whites to drugs. OBJECTIVES: To assess the management of hypertension in Asian Americans and to compare it with an age- and sex-matched group of white patients with hypertension. METHODS: The patients' medical records were used as the primary source of information for the data collection. The observational period was a 12-month window and included 200 patients of Asian origin with hypertension and 196 white patients with hypertension whose medical records were randomly selected. RESULTS: The study describes the pattern of use of antihypertensive agents and the differences in response to antihypertensive agents between Asian Americans and whites. The preferred antihypertensive agents in both Asian and white patients included monotherapy with either calcium channel blockers or angiotensin-converting enzyme inhibitors. However, medication changes, dose reduction, and the experience of side effects were all significantly more frequently recorded in Asian patients than in white patients (P < .001, P < .008, and P < .002, respectively). CONCLUSIONS: These findings are supportive of some previous reports on ethnic differences in drug response to antihypertensive agents. The findings also point to the need for further prospective studies on the outcome of hypertension management in Asian American patients.     

Maximum-likelihood diversity combining in partial-band noise

Maximum-likelihood diversity combining is investigated for an FFH/MFSK spread spectrum system in partial-band noise (PBN). The structure of maximum-likelihood diversity reception in PBN plus white Gaussian noise is derived. It is shown that signal-to-noise ratio and the noise variance at each hop have to be known to implement this optimum diversity combiner. Several suboptimum diversity combining schemes are also considered. The performance of the optimum combining scheme is evaluated. It is shown that adaptive gain control diversity combining actually achieves the optimum performance when interference is not very weak     

Prospective study of high grade anal squamous intraepithelial neoplasia in a cohort of homosexual men: influence of HIV infection, immunosuppression and human papillomavirus infection

OBJECTIVE: To determine the risk of developing high grade anal squamous intraepithelial neoplasia (HG-AIN) in relation to HIV infection and immunosuppression, after controlling for the effects of human papillomavirus (HPV) infection. DESIGN: Prospective cohort study of 158 HIV-seropositive and 147 HIV-seronegative homosexual men presenting to a community-based clinic with initially negative anal cytologic and colposcopic findings. METHODS: Subjects completed self-administered questionnaires, underwent cytologic screening, and standardized unaided and colposcopic examination of the proximal anal canal for presence of abnormalities suggestive of AIN. Anal specimens were screened for HPV DNA. RESULTS: HG-AIN developed in eight (5.4%) and 24 (15.2%) HIV-seronegative and -seropositive men, respectively. Risk of HG-AIN among HIV-seronegative men was associated with detection of anal HPV types 16 or 18 by Southern transfer hybridization (STH), detection of HPV 16 or 18 at the lower levels by polymerase chain reaction but not by STH, and with number of positive HPV tests; HG-AIN risk among HIV-seropositive men was associated with detection of HPV 16 or 18 only by STH, detection of HPV types other than 16 or 18, CD4 count < or = 500 x 10(6)/l, and number of positive HPV tests. HIV-induced immunosuppression remained an independent predictor of HG-AIN after adjusting for type and level of detection of HPV; HIV infection predicted HG-AIN risk after adjustment for number of positive HPV tests. CONCLUSIONS: The association of HG-AIN with HIV, independent of HPV type, level of HPV detection and number of positive HPV tests, suggests that this increased risk cannot be entirely explained by an effect of HIV on HPV detection. Future studies focusing on factors more specific to the local microenvironment in the anal canal should help clarify these issues.     

Outcome of plasma exchange therapy in thrombotic microangiopathy after renal transplantation

Thrombotic microangiopathy (TMA) in renal transplant recipients is commonly associated with calcineurin inhibitors (CNIs), though several factors such as vascular rejection, viral infections and other drugs may play a contributory role. We report a series of 29 patients with TMA, all of whom were on CNIs. Though plasma exchange (PEx) is widely used to treat TMA, therapeutic guidelines are not well defined. All our patients were treated with PEx and discontinuation of CNIs. Thrombotic microangiopathy was diagnosed at a median of 7 days post-transplant. The mean decrease in Hgb and platelets during TMA was 66% and 64%, respectively, and peak serum creatinine during TMA was 7.4 +/- 2.9 mg%. Mean duration of PEx therapy was 8.5 (range 5-23) days. Recovery of platelet count to 150K/mcL and Hgb to 8-10 g/dL were used as endpoints for PEx. Twenty-three/29 (80%) patients recovered graft function after PEx. Twenty/23 (87%) patients who recovered were placed back on CNl. Nineteen/20 (95%) patients tolerated reinstitution of CNl without recurrence of TMA. In post-transplant TMA, PEx was associated with a graft salvage rate of 80%, reversal of hematological changes can be used as the endpoint for PEx therapy and CNl can be reintroduced without risk of recurrence in the majority of patients.