Displaying publications 41 - 60 of 390 in total

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  1. Ethnicity as a determinant of asthma-related quality of life in a multiracial country
    Loh LC, Teh PN, Seth KD, Raman S, Vijayasingham P, Thayaparan T
    Asia Pac J Public Health, 2006;18(1):49-55.
    PMID: 16629438 DOI: 10.1177/10105395060180010801
    In a multiracial country like Malaysia, ethnicity may influence the measurement of health-related quality of life (HRQL) in asthmatic patients. We invited 131 adult patients [44 Malays, 42 Chinese and 45 Indians; mean (95% CI) age: 43 (40.2-45.7) yrs; 28.2% male] with moderate-to-severe persistent asthma followed up in an urban-based hospital outpatient clinic to complete a disease-specific HRQL questionnaire [St Georges' Respiratory Questionnaire (SGRQ)] and to provide socio-demographic and asthma-related data. Indians reported significantly worse SGRQ total score, compared to Malays [mean (95% CI) difference: 10.15 (0.51-19.78); p = 0.037] and SGRQ activity score, compared to Malays [13.50 (1.95-25.05); p = 0.019] and Chinese [11.88 (0.19-25.05); p = 0.046]. Further analysis using multivariate linear regression showed that Indian ethnicity remained independently associated with SGRQ scores. Our finding highlights the relevance of ethnicity in assessing HRQL of asthmatic patients in a multiracial country such as Malaysia.

    Study site: chest clinic of an urban-based
    university teaching hospital
    Matched MeSH terms: Linear Models
  2. Fulltext Linguistic context effects in the speech perfection of Malay-speaking normal hearing young adults
    Cila Umat, Nahazatul Islia Jamari
    Jurnal Sains Kesihatan Malaysia, 2006;4(1):9-20.
    MyJurnal
    The study examined the use of linguistic contextual cues among native, Malay-speaking normal hearing young adults. Ten undergraduate students of Universiti Kebangsaan Malaysia participated in the study. All subjects had normal hearing with the average hearing threshold levels for the overall left and the right ears of 7.8 dB (SD 4.1). The Malay Hearing in Noise Test (MyHINT) materials were employed and presented to the subjects at an approximately 65 dBA presentation level. Testing was conducted in a sound field in three different listening conditions: in quiet, in noise with +5 dB signal-to-noise ratio (SNR) and 0 dB SNR. In every test condition, three lists of MyHINT were administered to each subject. The magnitude of context effects was measured using the j factor, which was derived from measurements of recognition probabilities for whole sentences (13,) and the constituent words in the sentences (PP) in which j = log P./ log P P. Results showed that all subjects scored 100% identification of words in sentences and whole sentences in quiet listening condition, while subjects' performances in 0 dB SNR were significantly poorer than that in quiet and in +5 dB SNR (p < 0.001). The j-values were significantly correlated with the probability of recognizing words in the sentences (r = 0.515, p = 0.029) in which lower j values were associated with lower P ps. Subjects were not significantly different from each other in their use of contextual cues in adverse listening conditions [F(9, 7) = 1.34, p = 0.359]. Using the linear regression function for j on word recognition probabilities, the predicted P. were calculated. It was found that the predicted and measured probabilities of recognizing whole sentences were highly correlated: r = 0.973, p < 0.001. The results suggested that linguistic contextual information become increasingly important for recognition of sentences by normal hearing young adult listeners as SNR deteriorates.
    Matched MeSH terms: Linear Models
  3. Fulltext Case mix and cost drivers for cardiology cases in Hospital UKM Cheras Kuala Lumpur
    Amrizal, M.N., Rohaizat, Y.B., Saperi, S., SyedMohamed Aljunid
    Malaysian Journal of Public Health Medicine, 2006;6(1):11-16.
    MyJurnal
    Hospital UKM is the first hospital to implement case·mix system in Malaysia. The objective of the programme is to utilise case-mix system as a tool in improving efficiency and quality of care. From July 2002 to June 2004, a total of 35,568 cases were grouped using IRDRG-Version 1.1 case-mix grouper. Out of these, 3,622 cases or 10.2 % were cardiology cases in MDC 05 (Diseases and Disorders of the Circulatory System). Medical Cardiology cases consist of 86.5% and the remaining 13.5% were Surgical Cardiology. Most of the cases were in severity level one (43.4%), 29.5 % in severity level two and 27.1% in severity level three. The mortality rates for severity level one, two and three were 1.0%, 2.6% and 11.5% respectively. Top three cardiology cases were Acute Myocardial Infarction Without Comorbidity and Complication (IRDRG 05331) (8.4%), Acute Myocardial Infarction With Major Comorbidity and Complication (IRDRG 05333) (7.6%) and Cardiac Catheterization for Ischemic Heart Disease Without Comorbidity and Complication (IRDRG 05311) (7.4%). Step-down costing was carried out to obtain the cost for each DRG group. The mean cost per episode of care for Medical Cardiology cases was RM 3,562 (SD= RM 2, 1 19) with average LOS of 6.4 days (SD= 3 .8days) . For the Surgical Cardiology cases, the mean cost per episode ofcare was RM 6,526 (SD= RM 4,585) and average LOS of5.8 days (SD= 4.1 days). The main components of cost for Medical Cardiology cases are ICU cost (28.8%), pharmacy (17.3%) and Ward Services (15.3%). In Surgical Cardiology, the biggest component of cost was for Operation Theatre (27.9%), followed by Ward Services (25 .4%) and pharmacy (8.5%). Multivariate analysis using multiple linear regression showed that factors which significantly influence the treatment cost of cardiology cases were length of stay, age of the patient, discharge outcome, case type ('surgical partition') and severity level.
    Matched MeSH terms: Linear Models
  4. Modelling exchange rates using regime switching models
    Mohd Tahir Ismail, Zaidi Isa
    Sains Malaysiana, 2006;35:55-62.
    The behaviour of many financial time series cannot be modeled solely by linear time series model. Phenomena such as mean reversion, volatility of stock markets and structural breaks cannot be modelled implicitly using simple linear time series model. Thus, to overcome this problem, nonlinear time series models are typically designed to accommodate these nonlinear features in the data. In this paper, we use portmanteau test and structural change test to detect nonlinear feature in three ASEAN countries exchange rates (Malaysia, Singapore and Thailand). It is found that the null hypothesis of linearity is rejected and there is evidence of structural breaks in the exchange rates series. Therefore, the decision of using regime switching model in this study is justified. Using model selection criteria (AIC, SBC, HQC), we compare the in-sample fitting between two types of regime switching model. The two regime switching models we considered were the Self-Exciting Threshold Autoregressive (SETAR) model and the Markov switching Autoregressive (MS-AR) model where these models can explain the abrupt changes in a time series but differ as how they model the movement between regimes. From the AIC, SBC and HQC values, it is found that the MS -AR model is the best fitted model for all the return series. In addition, the regime switching model also found to perform better than simple autoregressive model in in-sample fitting. This result justified that nonlinear model give better in-sample fitting than linear model.
    Matched MeSH terms: Linear Models
  5. Fulltext Risk factors associated with low bone mineral content in very low birth weight infants
    Rohana J, Hasmawati J, Zulkifli SZ
    Singapore Med J, 2007 Mar;48(3):191-4.
    PMID: 17342285
    We report part of the findings of a study conducted to determine the correlation between bone mineral content (BMC) and biochemical bone markers in very low birth weight (VLBW) infants.
    Matched MeSH terms: Linear Models
  6. Modeling the relationship between the main emulsion components and stability, viscosity, fluid behavior, zeta-potential, and electrophoretic mobility of orange beverage emulsion using response surface methodology
    Mirhosseini H, Tan CP, Hamid NS, Yusof S
    J Agric Food Chem, 2007 Sep 19;55(19):7659-66.
    PMID: 17708646
    The possible relationships between the main emulsion components (namely, Arabic gum, xanthan gum, and orange oil) and the physicochemical properties of orange beverage emulsion were evaluated by using response surface methodology. The physicochemical emulsion property variables considered as response variables were emulsion stability, viscosity, fluid behavior, zeta-potential, and electrophoretic mobility. The independent variables had the most and least significant ( p < 0.05) effect on viscosity and zeta-potential, respectively. The quadratic effect of orange oil and Arabic gum, the interaction effect of Arabic gum and xanthan gum, and the main effect of Arabic gum were the most significant ( p < 0.05) effects on turbidity loss rate, viscosity, viscosity ratio, and mobility, respectively. The main effect of Arabic gum was found to be significant ( p < 0.05) in all response variables except for turbidity loss rate. The nonlinear regression equations were significantly ( p < 0.05) fitted for all response variables with high R (2) values (>0.86), which had no indication of lack of fit. The results indicated that a combined level of 10.78% (w/w) Arabic gum, 0.56% (w/w) xanthan gum, and 15.27% (w/w) orange oil was predicted to provide the overall optimum region in terms of physicochemical properties studied. No significant ( p > 0.05) difference between the experimental and the predicted values confirmed the adequacy of response surface equations.
    Matched MeSH terms: Linear Models
  7. Classification of vascular function in upper limb using bilateral photoplethysmographic signals
    Shariati NH, Zahedi E, Jajai HM
    Physiol Meas, 2008 Mar;29(3):365-74.
    PMID: 18367811 DOI: 10.1088/0967-3334/29/3/007
    Bilateral PPG signals have been used for comparative study of two groups of healthy (free from any cardiovascular risk factors) and diabetic (as cardiovascular disease risk group) subjects in the age-matched range 40-50 years. The peripheral blood pulsations were recorded simultaneously from right and left index fingers for 90 s. Pulses have been modeled with the ARX440 model in the interval of 300 sample points with 100 sample points overlap between segments. Model parameters of three segments based on the highest fitness (higher than 80%) of modeled segments were retained for each subject. Subsequently, principal component analysis (PCA) was applied to the parameters of retained segments to eliminate the existing correlation among parameters and provide uncorrelated variables. The first principal component (contains 78.2% variance of data) was significantly greater in diabetic than in control groups (P < 0.0001, 0.74 +/- 2.01 versus -0.53 +/- 1.66). In addition the seventh principal component, which contains 0.02% of the data variance, was significantly lower in diabetic than in control groups (P < 0.05, -0.007 +/- 0.03 versus 0.005 +/- 0.03). Finally, linear discrimination analysis (LDA) was used to classify the subjects. The classification was done using the robust leaving-one-subject-out method. LDA could classify the subjects with 71.7% sensitivity and 70.2% specificity while the male subjects resulted in a highly acceptable result for the sensitivity (81%). The present study showed that PPG signals can be used for vascular function assessment and may find further application for detection of vascular changes before onset of clinical diseases.
    Matched MeSH terms: Linear Models
  8. Fulltext Quality of life among women with breast cancer from Universiti Kebangsaan Malaysia Medical Centre, Malaysia
    Redhwan, A.A., Md Idris, M.N., Zaleha, M.I., Robert, C., Fuad, I., Sami, R.A.
    Malaysian Journal of Community Health, 2008;14(2):46-55.
    MyJurnal
    Introduction : The purpose of this study was to determine the quality of life (QOL) of breast cancer survivors based on socio-demographic and clinical characteristics.
    Methods : A cross-sectional study was performed on 125 breast cancer survivors from the outpatient clinics. FACT-B (Functional Assessment of Cancer Therapy-Breast) questionnaire was used to assess survivors’ QOL.
    Results : Survivors with low body mass index (BMI) (underweight) were found to have the lowest overall QOL. Those who were overweight had a higher overall QOL, and those who were normal-weight had the highest QOL. Low educational level, being underweight and low monthly household income were significantly associated with lower overall QOL Tamoxifen use and employment status were significantly associated with QOL in some domains. Time since diagnosis to QOL interview was significantly associated with greater scores in emotional well-being (EWB). Multiple linear regression indicated that age, marital status, monthly household income, surgery and histological grade were indicative of the patients QOL.
    Conclusion : The four primary factors related to better QOL were high educational level, high income, normal body weight and greater duration from the time of diagnosis to the time of interview. Age, marital status, income, lumpectomy and histological grade were indicative of the patient QOL.
    Study site: Oncology and Surgical clinics; Pusat Perubatan Universiti Kebangsaan Malaysia (PPUKM), Kuala Lumpur, Malaysia
    Matched MeSH terms: Linear Models
  9. Pemodelan dan analisis data penyerapan logam berat oleh sayuran berdaun terpilih
    Ahmad Mahir Razali, Khairiah Jusoh, Nor Asyikin A, Siti Adyani S, Wardatun Aathirah M, Maimon Abdullah, et al.
    Sains Malaysiana, 2008;37.
    Kajian yang dijalankan adalah berkaitan dengan penentuan model yang sesuai serta analisis data penyerapan logam berat oleh sayuran berdaun yang terpilih iaitu kangkung (Ipomea aquatica), sawi bunga (Brassica chinensis var parachinensis), bayam (Amaranthus oleraceus L) dan sawi putih (Brassica chinensis L.). Kajian ini bertujuan untuk menentukan dan membandingkan kandungan serta corak pengambilan logam berat yang diserap oleh sayuran dan juga bahagian-bahagiannya yang meliputi daun, batang dan akar. Penentuan model yang dibuat bertujuan bagi melihat corak penyerapan logam berat oleh sayuran atau bahagian sayuran tertentu. Logam berat yang dikaji terdiri daripada kadmium , kromium, kuprum, ferum , mangan, plumbum dan zink. Plot serakan digunakan bagi menentukan corak pengambilan logam berat dalam sayuran dan bahagian-bahagiannya. Selain itu ujian Kruskal-Wallis digunakan bagi membuat perbandingan median di antara logam berat yang diserap oleh sayuran yang dikaji. Nilai khi-kuasa dua dan juga nilai-p digunakan bagi menentukan sama ada sesuatu logam berat yang diserap itu berkait rapat dengan jenis sayuran secara signifikan. Secara umum bolehlah dikatakan bahawa logam Fe, Mn dan Zn adalah dominan dalam semua bahagian sayuran yang dikaji. Selain itu, melalui ujian Kruskal-Wallis didapati penyerapan kesemua logam berat pada setiap bahagian sayuran adalah berbeza secara signifikan. Penyuaian model regresi linear, kuadratik, kubik atau eksponen telah dilakukan terhadap data ini dan didapati kebanyakan data dapat disuaikan dengan baik oleh model kuadratik dan kubik berdasarkan nilai pekali penentuan (R2).
    Matched MeSH terms: Linear Models
  10. Enantioselective analysis of primaquine and its impurity quinocide by capillary electrophoresis
    Elbashir AA, Saad B, Ali AS, Saleh MI, Aboul-Enein HY
    Biomed Chromatogr, 2009 Mar;23(3):295-301.
    PMID: 18816453 DOI: 10.1002/bmc.1113
    A capillary electrophoretic (CE) method for the baseline separation of the enantiomers of primaquine diphosphate (PQ) and quinocide (QC) (a major contaminant) in pharmaceutical formulations is proposed. Both components were separated under the following conditions: 50 mm tris phosphate buffer (pH 3.0) containing 15 mm hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as background electrolyte; applied voltage, 16 kV; capillary temperature, 25 degrees C; detection wavelength, 254 nm; hydrostatic injection, 10 s. The separations were conducted using a 35 cm length and 50 microm i.d. uncoated fused silica capillary column. Under the optimized conditions, the components were successfully separated in about 5 min. Intraday precision of migration time and corrected peak areas when expressed as relative standard deviation ranged from 0.17 to 0.45 and 2.60 to 3.94%, respectively, while the interday precision ranged from 2.59 to 4.20 and 3.15 to 4.21%, respectively. After the validation exercise, the proposed method was applied for the determination of QC impurity in PQ formulations.
    Matched MeSH terms: Linear Models
  11. Determination of quinocide as impurity in primaquine tablets by capillary zone electrophoresis
    Elbashir AA, Saad B, Ali AS, Saleh MI, Aboul-Enein HY
    Biomed Chromatogr, 2009 May;23(5):464-71.
    PMID: 19016231 DOI: 10.1002/bmc.1137
    A capillary zone electrophoretic method has been developed and validated for the determination of the impurity quinocide (QC) in the antimalarial drug primaquine (PQ). Different buffer additives such as native cyclodextrins and crown ethers were evaluated. Promising results were obtained when either beta-cyclodextrin (beta-CD) or 18-crown-6 ether (18C6) were used. Their separation conditions such as type of buffer and its pH, buffer additive concentration, applied voltage capillary temperature and injection time were optimized. The use of 18C6 offers slight advantages over beta-CD such as faster elution times and improved resolution. Nevertheless, migration times of less than 5 min and resolution factors (R(s)) in the range of 2-4 were obtained when both additives were used. The method was validated with respect to selectivity, linearity, limits of detection and quantitation, analytical precision (intra- and inter-day variability) and repeatability. Concentrations of 2.12 and 2.71% (w/w) of QC were found in pharmaceutical preparations of PQ from two different manufacturers. A possible mechanism for the successful separation of the isomers is also discussed.
    Matched MeSH terms: Linear Models
  12. The application of empirical mode decomposition for the enhancement of cardiotocograph signals
    Krupa BN, Mohd Ali MA, Zahedi E
    Physiol Meas, 2009 Aug;30(8):729-43.
    PMID: 19550027 DOI: 10.1088/0967-3334/30/8/001
    Cardiotocograph (CTG) is widely used in everyday clinical practice for fetal surveillance, where it is used to record fetal heart rate (FHR) and uterine activity (UA). These two biosignals can be used for antepartum and intrapartum fetal monitoring and are, in fact, nonlinear and non-stationary. CTG recordings are often corrupted by artifacts such as missing beats in FHR, high-frequency noise in FHR and UA signals. In this paper, an empirical mode decomposition (EMD) method is applied on CTG signals. A recursive algorithm is first utilized to eliminate missing beats. High-frequency noise is reduced using EMD followed by the partial reconstruction (PAR) method, where the noise order is identified by a statistical method. The obtained signal enhancement from the proposed method is validated by comparing the resulting traces with the output obtained by applying classical signal processing methods such as Butterworth low-pass filtering, linear interpolation and a moving average filter on 12 CTG signals. Three obstetricians evaluated all 12 sets of traces and rated the proposed method, on average, 3.8 out of 5 on a scale of 1(lowest) to 5 (highest).
    Matched MeSH terms: Linear Models
  13. Fulltext Prevalence and factors associated with stress among secondary school teachers in Kota Bharu, Kelantan, Malaysia
    Abdul Hadi A, Naing NN, Daud A, Nordin R, Sulong MR
    Southeast Asian J. Trop. Med. Public Health, 2009 Nov;40(6):1359-70.
    PMID: 20578472
    The teaching profession is an occupation at high risk for stress. This research attempted to determine the prevalence of stress and the associated factors contributing to stress among teachers in Malaysia. A cross-sectional study was conducted on 580 secondary school teachers in Kota Bharu District. The instrument used to carry out the study was adopted and modified from the Depression, Anxiety and Stress Scale (DASS 21) and Job Content Questionnaire (JCQ). The questionnaire consisted of two parts: Part I consisting non-job factors (socio-demographic characteristics) and Part II consisting of psychosocial factors contributing to stress. Simple and multiple linear regression analysis were carried out. The prevalence of stress was reported as 34.0%. Seventeen point four percent of teachers experienced mild stress. Age, duration of work and psychological job demands were significantly associated with stress level. This study indicates job-related factors did not contribute much to stress among secondary school teachers. Non-job-related factors should be further studied to determine methods for stress reduction in teachers in Malaysia.
    Matched MeSH terms: Linear Models
  14. Knowledge of HIV/AIDS and attitudes towards people living with HIV among the general staff of a public university in Malaysia
    Tee Y, Huang M
    SAHARA J, 2009 Dec;6(4):179-87.
    PMID: 20485857
    Stigma and discrimination towards people living with HIV have been widely documented, and have extended their impact into the workplace. Stigmatising attitudes towards people living with HIV (PLHIV) in the workplace significantly hinder HIV prevention efforts and indirectly affect national development. This cross-sectional study was designed to determine the level of knowledge about HIV and AIDS and assess attitudes towards PLHIV among the general staff of Universiti Putra Malaysia (UPM), as well as to identify factors that are associated with it. Self-administered questionnaires were posted to a total of 344 general staff from six randomly selected faculties, and they were a given a week to return the questionnaires. The response rate was 38%. Data were analysed using Pearson's correlation, independent t-test and multiple linear regression. The respondents showed a considerably high level of knowledge about HIV/AIDS (mean knowledge score of 15.57+/-1.93 out of 18 points) although there were some misconceptions (N=129). Likert scale responses to 20 attitude statements revealed that respondents generally had moderately positive attitudes toward PLHIV (average score of 69.65+/-10.08 out of 100 points). Attitudes were inconsistent when it involved direct contact and interaction with PLHIV. Factors significantly associated with level of knowledge and attitudes included age, education and income. There was no difference in mean score for knowledge and attitudes by gender. Further efforts are necessary to improve attitudes of the general staff towards PLHIV, particularly in areas of direct contact with PLHIV.
    Matched MeSH terms: Linear Models
  15. The relationship between psychosocial work factors, work stress and computer-related musculoskeletal discomforts among computer users in Malaysia
    Zakerian SA, Subramaniam ID
    Int J Occup Saf Ergon, 2009;15(4):425-34.
    PMID: 20003776
    Increasing numbers of workers use computer for work. So, especially among office workers, there is a high risk of musculoskeletal discomforts. This study examined the associations among 3 factors, psychosocial work factors, work stress and musculoskeletal discomforts. These associations were examined via a questionnaire survey on 30 office workers (at a university in Malaysia), whose jobs required an extensive use of computers. The questionnaire was distributed and collected daily for 20 days. While the results indicated a significant relationship among psychosocial work factors, work stress and musculoskeletal discomfort, 3 psychosocial work factors were found to be more important than others in both work stress and musculoskeletal discomfort: job demands, negative social interaction and computer-related problems. To further develop study design, it is necessary to investigate industrial and other workers who have experienced musculoskeletal discomforts and work stress.
    Matched MeSH terms: Linear Models
  16. Impact of nutritional status on the quality of life of advanced cancer patients in hospice home care
    Shahmoradi N, Kandiah M, Peng LS
    Asian Pac J Cancer Prev, 2009;10(6):1003-09.
    PMID: 20192573
    BACKGROUND: Cancer patients frequently experience malnutrition and this is an important factor in impaired quality of life.

    OBJECTIVE: This cross-sectional study examined the association between global quality of life and its various subscales with nutritional status among 61 (33 females and 28 males) advanced cancer patients cared for by selected hospices in peninsular Malaysia.

    METHODS: The Patient Generated-Subjective Global Assessment (PG-SGA) and the Hospice Quality of Life Index (HQLI) were used to assess nutritional status and quality of life, respectively.

    RESULTS: Nine (14.7%) patients were well-nourished, 32 (52.5%) were moderately or suspected of being malnourished while 20 (32.8%) of them were severely malnourished. The total HQLI mean score for these patients was 189.9-/+51.7, with possible scores ranging from 0 to 280. The most problem areas in these patients were in the domain of functional well-being and the least problems were found in the social/spiritual domain. PG-SGA scores significantly correlated with total quality of life scores (r2= 0.38, p<0.05), psychophysiological well-being (r2= 0.37, p<0.05), functional well-being (r2= 0.42, p<0.05) and social/ spiritual well-being (r2= 0.07, p<0.05). Thus, patients with a higher PG-SGA score or poorer nutritional status exhibited a lower quality of life.

    CONCLUSION: Advanced cancer patients with poor nutritional status have a diminished quality of life. These findings suggest that there is a need for a comprehensive nutritional intervention for improving nutritional status and quality of life in terminally ill cancer patients under hospice care.

    Matched MeSH terms: Linear Models
  17. Fulltext Smoking beliefs and behavior among youth in Malaysia and Thailand
    Parkinson CM, Hammond D, Fong GT, Borland R, Omar M, Sirirassamee B, et al.
    Am J Health Behav, 2009 Jul-Aug;33(4):366-75.
    PMID: 19182982
    To characterize smoking beliefs among Thai and Malaysian youth and to examine associations with gender, antismoking media exposure, and smoking status.
    Matched MeSH terms: Linear Models
  18. Fulltext Production of carbon dioxide using direct pyrolysis-combustion from Aquilariella Malaccensis or karas woods under argon atmosphere
    Noraishah Othman, Siti Kartom Kamarudin, Muhd Noor Md Yunus, Abd. Halim Shamsuddin, Siti Rozaimah, Zahirah Yaakob
    Pertanika Journal of Science & Technology, 2009;17(2):-.
    MyJurnal
    The production of carbon dioxide from Karas woods under argon atmosphere was investigated using a direct pyrolysis-combustion approach. Direct burning was used in this study, using argon for yrolysis and oxygen during combustion to look at the yield of carbon dioxide, produced at different parameters, such as the temperature, retention time and flow rate of argon, as the carrier gas. In this study, a new methodology, 23 response surface central composite design was successfully employed for the experimental design and analysis of results. Central composite experimental design and response surface method were utilized to determine the best operating condition for a maximum carbon dioxide production. Appropriate predictable empirical linear model was developed by incorporating interaction effects of all the variables involved. The results of the analysis revealed that linear equation models fitted well with the experimental for carbon dioxide yield. Nevertheless, the R-Squared obtained using the direct pyrolysis-combustion was 0.7118, indicating that the regression line was not at the best-fitted line.
    Matched MeSH terms: Linear Models
  19. Thermal noise due to surface-charge effects within the Debye layer of endogenous structures in dendrites
    Poznanski RR
    Phys Rev E Stat Nonlin Soft Matter Phys, 2010 Feb;81(2 Pt 1):021902.
    PMID: 20365590
    An assumption commonly used in cable theory is revised by taking into account electrical amplification due to intracellular capacitive effects in passive dendritic cables. A generalized cable equation for a cylindrical volume representation of a dendritic segment is derived from Maxwell's equations under assumptions: (i) the electric-field polarization is restricted longitudinally along the cable length; (ii) extracellular isopotentiality; (iii) quasielectrostatic conditions; and (iv) homogeneous medium with constant conductivity and permittivity. The generalized cable equation is identical to Barenblatt's equation arising in the theory of infiltration in fissured strata with a known analytical solution expressed in terms of a definite integral involving a modified Bessel function and the solution to a linear one-dimensional classical cable equation. Its solution is used to determine the impact of thermal noise on voltage attenuation with distance at any particular time. A regular perturbation expansion for the membrane potential about the linear one-dimensional classical cable equation solution is derived in terms of a Green's function in order to describe the dynamics of free charge within the Debye layer of endogenous structures in passive dendritic cables. The asymptotic value of the first perturbative term is explicitly evaluated for small values of time to predict how the slowly fluctuating (in submillisecond range) electric field attributed to intracellular capacitive effects alters the amplitude of the membrane potential. It was found that capacitive effects are almost negligible for cables with electrotonic lengths L>0.5 , contributes up to 10% of the signal for cables with electrotonic lengths in the range between 0.25
    Matched MeSH terms: Linear Models
  20. Comparison of signal-to-noise, blank determination, and linear regression methods for the estimation of detection and quantification limits for volatile organic compounds by gas chromatography
    Sanagi MM, Ling SL, Nasir Z, Hermawan D, Ibrahim WA, Abu Naim A
    J AOAC Int, 2010 2 20;92(6):1833-8.
    PMID: 20166602
    LOD and LOQ are two important performance characteristics in method validation. This work compares three methods based on the International Conference on Harmonization and EURACHEM guidelines, namely, signal-to-noise, blank determination, and linear regression, to estimate the LOD and LOQ for volatile organic compounds (VOCs) by experimental methodology using GC. Five VOCs, toluene, ethylbenzene, isopropylbenzene, n-propylbenzene, and styrene, were chosen for the experimental study. The results indicated that the estimated LODs and LOQs were not equivalent and could vary by a factor of 5 to 6 for the different methods. It is, therefore, essential to have a clearly described procedure for estimating the LOD and LOQ during method validation to allow interlaboratory comparisons.
    Matched MeSH terms: Linear Models
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