Analysis of the linear oscillation dynamics of Fluidyne engines.

A Fluidyne engine is a liquid piston Stirling engine that uses thermally induced self-sustained oscillations of water and air that are filled in a looped tube and tuning column. It presents high potential for use as a low-temperature-difference Stirling engine with a simple structure. This study analyzes the linear oscillation dynamics of the Fluidyne from a thermoacoustic point of view, with particular emphasis on the local specific acoustic impedance of the working gas, which is given by the ratio of the complex amplitudes of the pressure and velocity oscillations in the regenerator of the Fluidyne. The frequency dependence of the specific acoustic impedance indicates that the gas in the regenerator region undergoes a thermodynamic cycle equivalent to the Stirling cycle when the oscillation frequency is equal to the natural oscillation frequency of the U-shaped liquid column in the Fluidyne. The analysis of the natural oscillation modes determined two key parameters for the desired specific acoustic impedance: the tuning column length and the connecting position to the loop. Experimental verification was achieved via measurements of the onset temperature ratio and acoustic field of a prototype Fluidyne engine.

Rising incidence of oral cancer in Ahmedabad city.

CONTEXT: In 1999, an increase in mouth cancer incidence among young men (< 50 years) in urban Ahmedabad was reported to be occurring along with decreasing mouth cancer incidence in older age groups and increasing oral submucous fibrosis incidence associated with areca nut consumption among young men in Gujarat. The aim was to investigate whether the increase in the incidence mouth cancer that had started among young men in the 1990 s was continuing. SETTINGS AND DESIGN: Ahmedabad urban population, comparison of reported mouth cancer cases in the population across four time period. METHODS: Age-specific incidence rates of mouth cancer (International Classification of Diseases [ICD]-9:143-5; ICD-10:C03-06) in five year age groups among men aged ≥ 15 years for the city of Ahmedabad for years 1985, 1995, 2007 and 2010 were extracted from published reports. For comparison, lung cancer (ICD-9:169; ICD-10:C33-C34) rates were also abstracted. STATISTICAL ANALYSIS USED: A cohort approach was used for further analysis of mouth cancer incidence. Age adjusted incidence rates of mouth and lung cancer for men aged ≥ 15 years were calculated and compared. RESULTS: The age specific incidence rates of mouth cancer among men increased over the 25-year period while lung cancer rates showed a net decrease. Using a cohort approach for mouth cancer, a rapid increase in younger age cohorts was found. CONCLUSIONS: Mouth cancer incidence increased markedly among men in urban Ahmedabad between 1985 and 2010, apparently due to increasing consumption of areca nut products, mawa and gutka. Gutka has now been banned all over India, but a more vigorous implementation is necessary.

Medical problems among dental patients at the school of dentistry, the university of the West Indies.

This study ascertained demographic information and prevalence rates of medical problems among 571 new and consecutive dental patients attending the emergency clinic of the School of Dentistry, The University of the West Indies. Patients were interviewed by specially trained and calibrated dental students and interns. Various medical problems of patients were recorded in individual open-ended case sheets, maintaining their privacy and confidentiality. This information was then transcribed into a specially designed and pretested form. The data were entered into a Microsoft Excel spreadsheet and analyzed using the SPSS statistical package to obtain the prevalence rates of medical conditions, which were then cross-tabulated with gender, age, ethnicity, and other variables. Significance of differences, if any, was evaluated by chi-square test. In all, 303 medical conditions were encountered in 239 individuals, giving a prevalence rate of 42 percent. Hypertension (12.6 percent), diabetes (6.1 percent), asthma (5.8 percent), arthritis (4.7 percent), and various allergies (8.3 percent) constituted an important segment of the problems. Gender, ethnic, and age differences were also evident for some diseases. In this study-which was the first of this kind in the West Indies-vital information on medical problems among dental patients was obtained by interviews conducted by dental students and interns, forming an important part of their dental education.

Accidental implantation of a bur tip in the elbow of a dentist. A possible pathway for inoculation with deadly infectious agent.

The most common source of occupational injury to dentists is percutaneous puncture of the hands from "sharps". We report a percutaneous injury involving a dentist where the tip of a dental bur became implanted in his elbow. The dentist had been vaccinated against Hepatitis B and both the patient and dentist were Hiv and Hepatitis B seronegative immediately after the incident. Surgical exploration of the dentist's elbow the following day was unsuccessful in locating the bur tip. The dentist remains healthy and is not incapacitated as a result of the injury, despite retention of the bur tip. This accident has implications for modifying the design of present and future dental units. We are not aware of a previous report of this type of injury.

Accidental implantation of a bur tip in the elbow of a dentist. A possible pathway for inoculation with deadly infectious agent

The most common source of occupational injury to dentists is percutaneous puncture of the hands from "sharps". We report a percutaneous injury involving a dentist where the tip of a dental bur became implanted in his elbow. The dentist had been vaccinated against Hepatitis B and both the patient and dentist were Hiv and Hepatitis B seronegative immediately after the incident. Surgical exploration of the dentist's elbow the following day was unsuccessful in locating the bur tip. The dentist remains healthy and is not incapacitated as a result of the injury, despite retention of the bur tip. This accident has implications for modifying the design of present and future dental units. We are not aware of a previous report of this type of injury.

Soft tissue recurrence of a mandibular ameloblastoma causing facial deformity in the temporal region: case report

Because of its locally invasive nature, Because of its locally invasive nature, the recurrence rates for ameloblastoma after treatment are rather high. Recurrence also seems to depend on the histologic type of the tumor and the treatment modalities used. Thus, curettage alone is reported to have led to a 90% recurrence rate for mandibular tumors and a 100% recurrence rate for maxillary tumors in one report. In a subsample of 327 cases in a large study, a 17.7% recurrence rate was noted after radical treatment and a rate of 22.6% was noted after conservative treatment; granular and follicular variants of ameloblastomas were noted to recur more frequently than the plexiform type. Most recurrences occur at the site of the primary tumor. However, lesions are also known to recur in bone grafts, and rarely, recurrence involves adjacent soft tissues. We present an unusual case of an ameloblatoma that originates in the right mandibular body and ramus that recurred 4 years after radical surgical excision via extension into the right temporal region, causing facial deformity.

An epidemiological study of tori among 667 dental outpatients in Trinidad & Tobago, West Indies.

AIM: To study the prevalence of tori amongst dental outpatients, the ethnic and sex variations in their distribution, and their clinical features. SETTING: The School of Dentistry, St. Augustine, Trinidad & Tobago. PARTICIPANTS: 667 consecutive dental outpatients representing three different ethnic groups of the country. METHODS: Clinical examination for and recording of tori indicating their location, extent and clinical features and the age, sex and ethnic grouping of the patient. RESULTS: The overall prevalence of tori was 12.3 per cent. CONCLUSIONS: There were no significant differences in the prevalence among the African, Indian or mixed ethnic groups of patients examined. There seemed to be strong link between the coexistence of palatal and mandibular tori.

Metastasis of breast carcinoma to mandibular gingiva.

Metastatic tumours to the oral region are rare but more often involve the jaws rather than the oral soft tissues. In this report, an infiltrative ductal carcinoma of the breast that metastasised to the mandibular gingiva is presented. The patient consulted her dentist for what she thought was a dental abscess in the bicuspid region of the lower left jaw. However, her dentist referred her for a specialist opinion of the lesion. The patient's medical history revealed that she had undergone a breast 'lumpectomy' 1 year previously. A provisional diagnosis of primary or metastatic malignancy was made, and a biopsy was performed. Microscopically, the lesion showed features of a poorly differentiated infiltrative ductal carcinoma. Subsequent microscopic review of the primary lesion also showed a poorly differentiated infiltrating ductal carcinoma of the breast identical to the features observed in the metastatic lesion.

Facial swelling and gingival enlargement in a patient with sickle cell disease.

Sickle cell anemia is a frequent hemoglobinopathy in the Caribbean. While vaso-occlusion induced tissue injury in sickle cell anemia is common in various organs, orofacial lesions are rare. A 14-year-old Afro-Trinidadian boy suffering from sickle cell anemia developed an acute facial swelling, mimicking facial cellulitis of dental origin, which was caused by sickle cell-related hemorrhage. He also exhibited gingival enlargement, considered to be an outcome of repeated hemorrhagic episodes and fibrous repair. A new finding is the presence of erythrocyte-filled intraepithelial blood vessels in the gingival epithelium. We hypothesize this phenomena is a tissue response to hypoxia that occurs in sickle cell disease.

Influence of dietary factors on oral precancerous lesions in a population-based case-control study in Kerala, India.

BACKGROUND: Although tobacco is the primary etiologic factor for oral precancerous lesions in India, evidence from other sources indicates that diet may modify risk. This case-control study was designed to minimize a variety of biases in its attempt to investigate the relation between diet and oral precancerous lesions. METHODS: In a house-to-house survey of 5056 tobacco users in a rural area of Ernakulam district in Kerala, India, 226 individuals (44 females and 182 males) were found to have precancerous lesions (cases), which in 4 cases proved to be cancer. From among the examinees, an equal number of controls who were free of oral mucosal lesions and were matched to the cases regarding age (+/-5 years), gender, ward of residence, and use of tobacco also were enrolled. Dietary data were obtained using a customized interviewer-administered food-frequency questionnaire. All subjects and interviewers were blinded to the disease status of the subject. RESULTS: After controlling for tobacco use, intake of fruits, vegetables, and beta-carotene evinced inverse trends in risk (P<0.05), with an average reduction of over 10% per quartile of exposure. Associations with certain micronutrients appeared to differ according to gender, with an apparent 20% reduction in risk per mg of zinc consumed per day among men and the suggestion of an increased risk among those women in the lowest quartile of iron intake (an increase of approximately 2.5-fold) and ascorbic acid intake (an increase of approximately 70% increase) compared with other women (P<0.10). CONCLUSIONS: Consumption of vegetables, fruits, and several micronutrients may inhibit precancerous lesions of the oral cavity.

p53 expression in oral precancer as a marker for malignant potential.

The potential of p53 protein expression as a marker for determining which oral precancerous lesions may transform to malignancy with time was assessed. We compared the p53 expression in archival formalin-fixed, paraffin-embedded tissues from 22 baseline biopsies of precancerous lesions that transformed to cancer in 4-25 years against that in 68 similar lesions that did not transform over the same time period. Twenty-nine percent of precancers that transformed were p53-positive at baseline, compared to 31% of the biopsies that did not transform to malignancy. When examined by immunohistochemical methods p53 expression failed to detect potential malignant status of oral precancer. Non-specificity of the assay may account for this result but overexpression of p53 due to DNA damage by tobacco/betel-quid in non-progressive lesions needs further study. Nine precancerous lesions became p53-immunoreactive from precancer to cancer. This may suggest p53 overexpression peaks close to the time of transition from precancer to cancer rather than early in the natural history of oral precancer.

Development and testing of a quantitative food frequency questionnaire for use in Kerala, India.

OBJECTIVE: To develop and test a food frequency questionnaire (FFQ) for use in rural areas of Kerala, India. DESIGN: Based on food use and market surveys of the study area, a quantitative 81-item interviewer-administered FFQ was developed. A validation study was conducted consisting of 24-h diet recalls (24HR) administered on 8 days randomly selected over an entire year and two administrations of the FFQ, one at the beginning of the 1-year period and the other at the end. FFQ and 24HR-derived nutrient scores were compared using correlation and regression analyses and by examining differences in the nutrient scores. SETTING: Rural villages in Ernakulum district, Kerala, South India. SUBJECTS: In each of 30 households, the male head of household and female food preparer were enrolled. RESULTS: Pearson (parametric) correlation coefficients (r(p)) averaged about 0.50 in comparing nutrient scores derived from the 24HR with those from the first FFQ and about 0.55 in comparing the second FFQ. On average, Spearman correlation coefficients (r(s)) were slightly lower than the r(p) in comparing the scores derived from the first FFQ, but virtually identical for the second FFQ. Regression analyses indicated better agreement in the comparison of the 24HR-derived scores with the first FFQ than the second FFQ. Difference scores, however, tended to be larger in comparing the first FFQ scores with the 24HR. CONCLUSIONS: This FFQ produces results broadly comparable to those used in Europe and North America, indicating its suitability for comparing exposures within a study population in reference to health-related endpoints.

Effects of storage, time, temperature, and composition of containers on biologic components of human milk.

Effects of steel and glass storage containers, duration of storage up to seven hours, and storage temperature on the concentration of humoral and cellular factors in 357 samples of human breastmilk were examined. Leukocytic functions were estimated by E-rosetting of sheep RBCs by T-lymphocytes and phagocytosis of S. cerevisieae by phagocytes. Immunoglobulin (Ig) levels were studied by single radial immunodiffusion technique (SRID). Viability and cell counts reduced during the storage period, but were greater than 60 percent of baseline values. IgG, IgA, and IgM levels in milk did not show significant decline after storage (p > 0.01). Milk stored in glass yielded a greater number of functional cells after storage at 4 degrees C.

Epidemiology of cancer by tobacco products and the significance of TSNA.

Globally, oral cancer is one of the ten common cancers. In some parts of the world, including the Indian subcontinent, oral cancer is a major cancer problem. Tobacco use is the most important risk factor for oral cancer. The most common form of tobacco use, cigarette smoking, demonstrates a very high relative risk--in a recent cohort study (CPS II), even higher than lung cancer. In areas where tobacco is used in a smokeless form, oral cancer incidence is generally high. In the West, especially in the U.S. and Scandinavia, smokeless tobacco use consists of oral use of snuff. In Central, South, and Southeast Asia smokeless tobacco use encompasses nass, naswar, khaini, mawa, mishri, gudakhu, and betel quid. In India tobacco is smoked in many ways; the most common is bidi, others being chutta, including reverse smoking, hooka, and clay pipe. A voluminous body of research data implicating most of these forms of tobacco use emanates from the Indian subcontinent. These studies encompass case and case-series reports, and case-control, cohort, and intervention studies. Collectively, the evidence fulfills the epidemiological criteria of causality: strength, consistency, temporality, and coherence. The biological plausibility is provided by the identification of several carcinogens in tobacco, the most abundant and strongest being tobacco-specific N-nitrosamines such as N-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These are formed by N-nitrosation of nicotine, the major alkaloid responsible for addiction to tobacco. The etiological relationship between tobacco use and oral cancer has provided us with a comprehensive model for understanding carcinogenesis.

Etiology of oral submucous fibrosis with special reference to the role of areca nut chewing.

Oral submucous fibrosis (OSF) is a high risk precancerous condition, predominantly affecting Indians. Consumption of chilli was hypothesized as an etiologic factor on the basis of ecological observations and a solitary animal experimental study. Subsequent epidemiologic studies that included case-series reports, large cross-sectional surveys, case-control studies, cohort and intervention studies have identified areca nut as the major etiologic agent. Tissue-culture studies involving human fibroblasts, areca nut extracts and areca nut alkaloids supported this etiologic hypothesis by showing fibroblastic proliferation and increased collagen formation. Currently, the role of genetic susceptibility and that of autoimmunity are receiving attention. The influence of nutritional factors, if any, remains unclear.

Effect of cessation of tobacco use on the incidence of oral mucosal lesions in a 10-yr follow-up study of 12,212 users.

OBJECTIVE: To study the effect of cessation of tobacco use on the incidence of lichen planus, leukoplakia and other oral mucosal lesions. DESIGN: A 10-yr cohort study in a rural population of Ernakulam district, Kerala, India. MATERIAL AND METHODS: Some 12,212 tobacco users were interviewed and examined in a baseline survey and re-examined annually for 10 years. At each examination they were exposed to health educational programs to encourage them to quit their tobacco use. The incidence rates were calculated using person-years method among those who stopped their tobacco use and all others. RESULTS: A total of 77,681 person-years of observation accrued among men and 32,544 among women. Among men 6.5% of these and among women 14.4% were in the stopped category. The incidence of oral lichen planus did not show any consistent association with cessation of tobacco habits (incidence ratio 1.35) but for leukoplakia there was a substantial drop in the incidence after cessation (incidence ratio 0.31). Several other tobacco-associated oral mucosal lesions such as oral lichen planus-like lesion, smoker's palate, preleukoplakia, central papillary atrophy of the tongue and leukoedema showed either zero, or very small incidence, after cessation. CONCLUSION: The reported association between tobacco use and lichen planus appears to be indirect but for all other lesions it is direct. The cessation of tobacco use led to a substantial fall in the incidence of leukoplakia and other lesions implying a reduced risk for oral cancer after cessation of tobacco use.

Case reports of chromomycosis.

Two cases of chromomycosis were diagnosed in B.Y.L. Nair Charitable Hospital during the years 1980-1989. Isolates were identified as Fonsecea compactum.

Serological characterisation of Neisseria gonorrhoeae by co-agglutination technique.

Antibiotic susceptibility pattern in cases of acute gonococcal urethritis, was studied by single disc diffusion technique and minimum inhibitory concentration (MIC) by agar dilution technique were determined for 5 antibiotics, viz penicillin, ampicillin, tetracycline, gentamicin and norfloxacin. All the penicillinase producing Neisseria gonorrhoeae (PPNG) and non-PPNG strains were sensitive to norfloxacin. 72% of the isolates belonged to serogroup WII/WIII by co-agglutination technique.

Primary prevention trial of oral cancer in india: a 10-year follow-up study.

Oral cancer is caused by chewing and smoking of tobacco. To assess the feasibility of primary prevention of oral cancer, two cohorts were studied in base-line surveys and then followed up annually for 10-yr in Ernakulam district of Kerala state. The intervention cohort consisted of 12212 tobacco users aged 15 yr and over, who were exposed to a concentrated program of education against tobacco use. The control cohort was a non-concurrent cohort of 6075 tobacco users studied using similar methods but with a minimal amount of advice against tobacco use. The stoppage of tobacco use increased and the incidence rate of leukoplakia decreased significantly and substantially in the intervention cohort compared to the control cohort. The decrease in the incidence of leukoplakia was indicative of the decrease in the risk of oral cancer since the two were intimately related. This study demonstrated feasibility of primary prevention of oral cancer.