Feature selection for chemical sensor arrays using mutual information

We address the problem of feature selection for classifying a diverse set of chemicals using an array of metal oxide sensors. Our aim is to evaluate a filter approach to feature selection with reference to previous work, which used a wrapper approach on the same data set, and established best features and upper bounds on classification performance. We selected feature sets that exhibit the maximal mutual information with the identity of the chemicals. The selected features closely match those found to perform well in the previous study using a wrapper approach to conduct an exhaustive search of all permitted feature combinations. By comparing the classification performance of support vector machines (using features selected by mutual information) with the performance observed in the previous study, we found that while our approach does not always give the maximum possible classification performance, it always selects features that achieve classification performance approaching the optimum obtained by exhaustive search. We performed further classification using the selected feature set with some common classifiers and found that, for the selected features, Bayesian Networks gave the best performance. Finally, we compared the observed classification performances with the performance of classifiers using randomly selected features. We found that the selected features consistently outperformed randomly selected features for all tested classifiers. The mutual information filter approach is therefore a computationally efficient method for selecting near optimal features for chemical sensor arrays

Ambient levels of volatile organic compounds in the vicinity of petrochemical industrial area of Yokohama, Japan

Urban ambient air concentrations of 39 aromatic (including benzene, toluene, and xylenes) and aliphatic volatile organic compounds (VOCs) were measured in Yokohama city, Japan. Yokohama city was selected as a case study to assess the amount of VOC released from Industrial area to characterize the ambient air quality with respect to VOC as well as to know the impact of petrochemical storage facilities on local air quality. For this purpose, ambient air samples were collected (from June 2007 to November 2008) at six selected locations which are designated as industrial, residential, or commercial areas. To find out the diurnal variations of VOC, hourly nighttime sampling was carried out for three nights at one of the industrial locations (Shiohama). Samples were analyzed using gas chromatographic system (GC-FID). Results show strong variation between day and nighttime concentrations and among the seasons. Aliphatic fractions were most abundant, suggesting petrochemical storage facilities as the major source of atmospheric hydrocarbons. High concentrations of benzene, toluene, ethyl benzene, and xylene (BTEX) were observed at industrial locations. BTEX showed strong diurnal variation which is attributed to change in meteorology. During our campaign, low ambient VOC concentrations were observed at the residential site

Dynamical Principles of Emotion-Cognition Interaction: Mathematical Images of Mental Disorders

The key contribution of this work is to introduce a mathematical framework to understand self-organized dynamics in the brain that can explain certain aspects of itinerant behavior. Specifically, we introduce a model based upon the coupling of generalized Lotka-Volterra systems. This coupling is based upon competition for common resources. The system can be regarded as a normal or canonical form for any distributed system that shows self-organized dynamics that entail winnerless competition. Crucially, we will show that some of the fundamental instabilities that arise in these coupled systems are remarkably similar to endogenous activity seen in the brain (using EEG and fMRI). Furthermore, by changing a small subset of the system's parameters we can produce bifurcations and metastable sequential dynamics changing, which bear a remarkable similarity to pathological brain states seen in psychiatry. In what follows, we will consider the coupling of two macroscopic modes of brain activity, which, in a purely descriptive fashion, we will label as cognitive and emotional modes. Our aim is to examine the dynamical structures that emerge when coupling these two modes and relate them tentatively to brain activity in normal and non-normal states

FGFR3, HRAS, KRAS, NRAS and PIK3CA Mutations in Bladder Cancer and Their Potential as Biomarkers for Surveillance and Therapy

Background: Fifty percent of patients with muscle-invasive bladder cancer (MI-BC) die from their disease and current chemotherapy treatment only marginally increases survival. Novel therapies targeting receptor tyrosine kinases or activated oncogenes may improve outcome. Hence, it is necessary to stratify patients based on mutations in relevant oncogenes. Patients with non-muscle-invasive bladder cancer (NMI-BC) have excellent survival, however two-thirds develop recurrences. Tumor specific mutations can be used to detect recurrences in urine assays, presenting a more patient-friendly diagnostic procedure than cystoscopy. Methodology/Principal Findings: To address these issues, we developed a mutation assay for the simultaneous detection of 19 possible mutations in the HRAS, KRAS, and NRAS genes. With this assay and mutation assays for the FGFR3 and PIK3CA oncogenes, we screened primary bladder tumors of 257 patients and 184 recurrences from 54 patients. Additionally, in primary tumors p53 expression was obtained by immunohistochemistry. Of primary tumors 64% were mutant for FGFR3, 11% for RAS, 24% for PIK3CA, and 26% for p53. FGFR3 mutations were mutually exclusive with RAS mutations (p = 0.001) and co-occurred with PIK3CA mutations (p = 0.016). P53 overexpression was mutually exclusive with PIK3CA and FGFR3 mutations (p≤0.029). Mutations in the RAS and PIK3CA genes were not predictors for recurrence-free, progression-free and disease-specific survival. In patients presenting with NMI-BC grade 3 and MI-BC, 33 and 36% of the primary tumors were mutant. In patients with low-grade NMI-BC, 88% of the primary tumors carried a mutation and 88% of the recurrences were mutant. Conclusions/Significance: The mutation assays present a companion diagnostic to define patients for targeted therapies. In addition, the assays are a potential biomarker to detect recurrences during surveillance. We showed that 88% of patients presenting with low-grade NMI-BC are eligible for such a follow-up. This may contribute to a reduction in the number of cystoscopical examinations

YONSEI MEDICAL JOURNAL

Purpose: In this study, the relationship between sex hormone levels and erectile dysfunction (ED), as well as the necessity of routinely measuring sex hormone levels were evaluated. Materials and Methods: This study included one hundred patients admitted to a urology clinic for sexual dysfunction. To determine the hormone levels, following the history (included IIEF-5 score) and physical examination, triple blood samples were collected at intervals of 15 minutes between 08:00 and 10:00 am. Total and free testosterone, prolactin, follicle stimulating hormone and luteinizing hormone levels were studied. Results: Mean age was 43 (23 - 80) years. IIEF-5 score was less than 21 [9.8 - 4.3 (3 - 19)] in all study groups. There was a statistically significant correlation between tT and FSH, as well as between LH and FSH in Pearson (r = - 0.513, p 0.05). Of the 100 patients, 18 (18%) had low tT, 77 (77%) had normal and 5 (5%) had high tT levels. No statistically significant correlation was found between decreased libido and tT levels (p > 0.05). Twelve (66.6%) of the 18 patients with low tT had normal libido. Conclusion: Analyzing the medical history in detail and performing a thorough physical examination can reduce the need for excessive studies and consultations, and enables patients to save time and costs

ONKOLOGIE

Aim: The aim of this study is to evaluate patients' tolerance to pain caused by urethrocystoscopy ( UCS) in both diagnosis and the period of follow- up in patients with superficial bladder cancer, and to evaluate these results with respect to quality of life. Patients and Methods: Between March 2003 and October 2004, 66 patients with bladder cancer or hematuria underwent UCS and recorded their overall pain level. Results: The mean age was 60.4 ( range 26 - 83) years. UCS was done only one time in 22 patients for the diagnosis of etiology of hematuria and was done 4 times in 44 patients every 3 months for bladder cancer follow- up. The mean pain scores on first, second, third, and fourth UCS were 4.3 +/- 2.2, 4.7 +/- 2.5, 4.68 +/- 2.45, and 5.1 +/- 2.5, respectively. Statistically significant differences were found among mean pain scores of patients on first, third, and forth cystoscopic examinations ( p 0.05). Conclusion: UCS is a painful surgical procedure and pain tolerance was not observed on repeated UCS. Therefore urologists need to use more effective anesthetic methods to provide better patients' tolerance to pain and quality of life during the endoscopic procedure

SCANDINAVIAN JOURNAL OF UROLOGY AND NEPHROLOGY

Objective: The aim of this study is to investigate the value of phosphate levels in serum and urine in patients with recurrent renal stone disease. Materials and methods: The patients (n: 60) were divided into two groups as first-time stone disease (group 1) and recurrent renal stone disease ( group 2). The demographical datas and their historical information were recorded and physical examination was done. The sera and urine for 24 hr were obtained from patients to measure electrolyte levels especially phosphorus. In addition, based on presenting serum phosphate levels, patients were divided into the hypophosphatemia group, less than 2.5 mg/dl; normophosphatemia group, between 2.5-5.2 mg/dl; and hyperphosphatemia group greater than 5.2 mg/dl. Results: The mean age of study group was 45 (21-70) years. Thirty-six patients (60%) were in group 1 and 24 patients (40%) were in group 2. No statistically correlation was found between stone recurrence and phosphate levels both in serum and urine. There was only a statistical association of K levels in 24-hour urine samples between group 1 and 2. Conclusion: There was no significant association between stone recurrence and initial phosphate levels in the serum or in urine. We do not propose to determine phosphate levels routinely in management of patients with stone disease