Graphene Decorated with Silver Nanoparticles as a Low-Temperature Methane Gas Sensor.

This paper is devoted to an investigation on the methane sensing properties of graphene (G), decorated with silver nanoparticles (AgNPs), under ambient conditions. To do so, we first present an effective modification in the standard manner of decorating graphene by AgNPs. From structural analysis of the product (AgNPs/G), it is concluded that graphene is indeed decorated by AgNPs of a mean size 29.3 nm, free of aggregation, with a uniform distribution. The so-produced material is then used, as a resistivity-based sensor, to examine its response to the presence of methane gas. Our measurements are performed at relatively low temperatures, for various silver-to-graphene mass ratios (SGMRs) and methane concentrations. To account for the effects of humidity, we have made the measurements, at room temperature, for different levels of humidity. Our results demonstrate that an increase in the SGMR enhances the response of AgNPs/G to methane with an optimum value of SGMR ≅ 12%. It is also illustrated that for methane concentrations less than 2000 ppm, the maximal response increases linearly and rapidly, even at room temperature. Moreover, we demonstrate that AgNPs/G is of low limit of detection, highly stable, selective, reversible, repeatable, and sensor-to-sensor reproducible, for methane sensing. The results thus promise a low-cost and simple-to-fabricate methane sensing device.

Pulmonary function tests in ulcerative colitis.

BACKGROUND: Pulmonary impairment in patients suffering ulcerative colitis (UC) has been suggested by several investigators using standard pulmonary function tests (PFTs). This changes in pulmonary function associated with minimal respiratory symptoms have been documented, especially in patients with active disease. The aim of this prospective study was to determine airway resistance and lung volumes in patients with UC who have no respiratory symptoms in comparisons to a healthy control group. MATERIALS AND METHODS: We evaluated a total of 30 patients with UC by means of spirometry, body plethysmography, and impulse oscillometry. The patients were not complaining of any pulmonary symptoms and did not present any history of previous respiratory diseases. As controls we examined 30 healthy subjects matched for gender, age, and smoking status. The relationship between PFT, lung volume, and airway resistance; and the activity, localization, and duration of the UC disease were analyzed. RESULTS: There was a significant difference between airway resistances (kPa/L/s) measured by body plethysmography in patients with UC and those of the controls (R5hz; 0.60 ± 0.44 vs. 0.39 ± 0.13; P < 0.001) and R20hz (0.37 ± 0.19 vs. 0.29 ± 0.1, P = 0.02). There were no correlation between PFT, airway resistance and site and scoring activity (P > 0.05). CONCLUSION: Despite the lack of pulmonary symptoms, increased airway resistance was found in UC patients. We also have not found correlation between PFT, lung volume and airway resistance values and scoring of UC activity.

Sample survey of chronic obstructive pulmonary disease and associated risk factors in isfahan, iran.

BACKGROUND: The purpose of this cross-sectional study was to estimate the number of individuals with chronic bronchitis and/or chronic obstructive pulmonary disease in Isfahan. Our study results were compared with those of previous studies in Iran and similar studies in other countries. MATERIALS AND METHODS: As a part of a population-based, cross-sectional study, 2,200 randomly selected individuals aged 40 years or older were asked to take part in the survey; among whom, 1308 individuals (59.45%) agreed to fill out the respiratory questionnaire. This group consisted of 636 (48.6%) males and 672 (51.4%) females. Spirometric measurements were performed in 279 cases. COPD was defined by the "Global Initiative for Obstructive Lung Disease" criteria. RESULTS: One hundred-seven individuals (8.1%) fulfilled the clinical criteria for chronic bronchitis as the main sign of COPD. Multivariate analysis revealed that age and smoking were independent predictors for chronic obstructive pulmonary disease. CONCLUSION: It is concluded that the prevalence of chronic bronchitis symptoms is approximately the same in our population as compared with western countries. The frequency of clinical chronic bronchitis has risen in comparison to a previous study in Isfahan.

Arm span as an independent predictor of pulmonary function parameters: validation and reference values.

BACKGROUND AND OBJECTIVES: To determine if arm span can be used as a measure of body length in developing prediction equations for lung function and to compare these equations with height-derived equations. METHODS: Standing height and arm span were measured for all study subjects. Spirometry measurements included FVC, FEV(1), FEV(1)/FVC ratio, PEFR, FEF(25), FEF(50), FEF(75) and FEF(25-75). These data were used to develop prediction equations using multiple regression analysis based on age, gender and arm span. An independent group (225 subjects) was used to evaluate the accuracy of the equations. Predicted values for each parameter were calculated separately for arm span and height and compared with the measured values. RESULTS: Study subjects comprised 1865 healthy non-smoking Persian volunteers. Arm span-based equations accurately predicted all of the spirometric parameters. The standard errors of the estimate for prediction equations based on arm span were slightly smaller than those based on standing height. Average predicted values based on height predicted from arm span did not consistently agree with the measured values. CONCLUSIONS: Predicting pulmonary parameters using equations based on arm span is as reliable as using equations based on standing height and are more accurate for patients in whom height cannot be measured reliably.

Normative reference values for lung transfer factor in Isfahan, Iran.

OBJECTIVES AND BACKGROUND: Transfer factor or carbon monoxide diffusing capacity (DL(CO)) is a particularly valuable test of the appropriateness of gas exchange across the alveolocapillary membrane. The purpose of this study is to derive predictive equations for DL(CO) and its derivative volume-corrected DL(CO) (DL(CO)/VA) measured by single-breath method in a large non-smoking population sample in Isfahan. METHODOLOGY: We evaluated 1429 randomly selected subjects (732 men, aged 5-85 years). Gender-specific linear prediction equations were developed by multiple regression analysis; with measured DL(CO), and DL(CO)/VA values (mmol/min/kPa), as dependent variables regressed against age (A), height (H) and body surface area (BSA). RESULTS: For both genders, age had negative effects on DL(CO), while height had a positive effect on DL(CO) and DL(CO)/VA (P < 0.01). The prediction equations for DL(CO) and DL(CO)/VA are: '0.152 x height - 0.056 x age - 11.595' and '-0.12 x age + 2.467', for men and: '-0.035 x age - 0.133 x height - 10.707' and '-0.012 x age - 0.02 x height + 2.755', for women, respectively. CONCLUSIONS: Our results therefore provide an original frame of reference for either DL(CO) or DL(CO)/VA in Iranian population, obtained from a standardized single-breath technique.

Association between Asthma and Body Mass Index in Children.

Obesity has been reported to be associated with an increase in asthma in children. If there is any association, it could be attributed to an effect of obesity on lung volume and thus airway's obstruction. Data from 2413 children aged 7-12 years in Isfahan were analyzed. The subjects were included in this study if data were available for: height, weight, age, lung volume, and any measure of asthma, including history of diagnosed asthma, wheeze, chronic cough, and medication as obtained by questionnaire. Body mass index (BMI) percentiles, divided into quintiles per year age, were used as a measure of standardized weight.After adjusting for, sex, age, smoking and family history, BMI was a significant risk factor for wheeze ever (p = 0.000) and asthma ever (p = 0.000), diagnosed asthma (P=0.000) and current asthma (p = 0.000). There was no significant correlation between BMI and obstructive spirometry. Increased BMI was significantly associated with an increased airway resistance.Despite the fact that higher BMI is a risk factor for, wheeze ever, wheeze and dyspnea in the last 12 months, and diagnosed asthma, higher BMI is not a risk factor for obstructive pattern in pulmonary function test.

Indoor women jobs and pulmonary risks in rural areas of Isfahan, Iran, 2000.

The prevalence rate of chronic airway's diseases in women and associated risk factors in developing countries are not well clarified. We evaluated the role of indoor duties in the prevalence of asthma, chronic bronchitis, and related symptoms among females in Isfahan suburbs. In three randomly selected villages, 561 responder females (response rate=95.25%) were evaluated through medical interview and physical examinations. Symptoms, signs, occupational and smoking histories, indoor and farming duties, possible outdoor jobs, housing and farming conditions were assessed. The observed respiratory morbidities were: current asthma (11.2%), history of asthma (1.3%), using asthma medications in life (15.2%), chronic bronchitis (3.4%), exercise-induced dyspnea and/or cough (16.2%), and frequent night coughs and/or dyspnea (15.3%). Age, childhood pulmonary infection, bread baking, carpet weaving and using biomass fuels were significant risk factors for all the pulmonary morbidities (P<0.05 to <0.001). Poultry feeding, using kerosene and gas fuels, were less strong risk factors for asthma and chronic bronchitis, respectively Only seven women were current or ex-smokers. Indoor respirable particulate matters were two to four folds more concentrated than outdoors. Women doing indoor jobs in Iran are potential risk factors for development of chronic obstructive pulmonary disease.

Common causes of pleural effusion in referral hospital in Isfahan, Iran 1997-1998.

During a one-year period to September 1998, data were collected from all 213 patients referred with pleural effusion. There were 132 males and 81 females; their ages ranged from 18 to 85 years. The most common etiologies of effusion were congestive heart failure (39.4%), malignancy (27.2%), pneumonia (8%), empyema (5.2%), and tuberculosis (5.2%). Pleural effusions are frequent in Iran, and the causes are fairly similar to those reported by European authors, but with slightly more tuberculosis cases, mostly among Afghan refugees.

Prevalence of self-reported respiratory symptoms in rural areas of Iran in 2000.

OBJECTIVES: The aims of the present study were to measure the population prevalence of symptoms of asthma, chronic bronchitis, obstructive lung disease and non-specific respiratory symptoms in randomly selected rural communities in south-west Isfahan, Iran. METHODOLOGY: Nine hundred and ninety-four subjects from a total of 1127 villagers (88.2% response rate) took part in a medical interview conducted by interns from the Isfahan Medical School. RESULTS: The mean (+/-SD) age of the population surveyed was 25.21 +/- 17.55 years and the smoking rate was 7.2%. The self-reported prevalence rates for current asthma, chronic bronchitis, non-specific exercise-induced cough and night cough were 6.1, 4.4, 13.3 and 11.3%, respectively. CONCLUSION: Asthma, chronic bronchitis and other respiratory disorders in rural Isfahan are more prevalent than expected for a young rural population with low smoking rates. The cause of this should be investigated.