Improving formaldehyde removal from water and wastewater by fenton, photo-fenton and ozonation/fenton processes through optimization and modeling

This study aimed to assess, optimize and model the efficiencies of Fenton, photo-Fenton and ozonation/Fenton processes in formaldehyde elimination from water and wastewater using the response surface methodology (RSM) and artificial neural network (ANN). A sensitivity analysis was used to determine the importance of the independent variables. The influences of different variables, including H2O2 concentration, initial formaldehyde concentration, Fe dosage, pH, contact time, UV and ozonation, on formaldehyde removal efficiency were studied. The optimized Fenton process demonstrated 75% formaldehyde removal from water. The best performance with 80% formaldehyde removal from wastewater was achieved using the combined ozonation/Fenton process. The developed ANN model demonstrated better adequacy and goodness of fit with a R2 of 0.9454 than the RSM model with a R2 of 0. 9186. The sensitivity analysis showed pH as the most important factor (31%) affecting the Fenton process, followed by the H2O2 concentration (23%), Fe dosage (21%), contact time (14%) and formaldehyde concentration (12%). The findings demonstrated that these treatment processes and models are important tools for formaldehyde elimination from wastewater

Dynamic temporary blood facility location-allocation during and post-disaster periods

The key objective of this study is to develop a tool (hybridization or integration of different techniques) for locating the temporary blood banks during and post-disaster conditions that could serve the hospitals with minimum response time. We have used temporary blood centers, which must be located in such a way that it is able to serve the demand of hospitals in nearby region within a shorter duration. We are locating the temporary blood centres for which we are minimizing the maximum distance with hospitals. We have used Tabu search heuristic method to calculate the optimal number of temporary blood centres considering cost components. In addition, we employ Bayesian belief network to prioritize the factors for locating the temporary blood facilities. Workability of our model and methodology is illustrated using a case study including blood centres and hospitals surrounding Jamshedpur city. Our results shows that at-least 6 temporary blood facilities are required to satisfy the demand of blood during and post-disaster periods in Jamshedpur. The results also show that that past disaster conditions, response time and convenience for access are the most important factors for locating the temporary blood facilities during and post-disaster periods

Revisiting herbage sample collection and preparation procedures to minimise risks of trace element contamination

A renewed interest in trace elements (TE), as micronutrients as well as potentially toxic elements, and new options for multi-element analysis has led to an increased number of scientists engaging in TE studies. Accreditation, certification and quality control of TE analyses often applies only to the last step in the sample chain when prepared samples are sent to the laboratory for digestion/extraction and subsequent analysis. However, all stages of the chain from initial sampling to final analysis require an understanding of the specific challenges involved in TE studies and an awareness of the contamination risks as well as approaches to limit these. Contamination can potentially be introduced during all stages of handling and preparation of plant samples, e.g. through dust and the materials that make up the different work surfaces, tools and containers used. Milling devices originally used during preparation of two sets of archived herbage samples were tested to indicate the degree of contamination that can arise from milling. For example, some of the milling devices tested showed effects on several TE concentrations while also increasing the variability between samples. A titanium knife mill which was included for comparison gave the best results, showing no measurable contamination by TE of primary interest, while it allowed a high throughput of samples. To enhance the quality of data on TE in bulky plant material such as herbage and to ensure future usability of newly archived samples, we suggest that field handbooks and sample preparation protocols (where needed) are revised to include precautions against TE contamination in all handling steps. This will ensure reliable data on concentrations of micronutrients and potential toxic TE in plant material

Evaluation of the reasons for the extraction among patients referred to the Oral Surgery Department,Faculty of Dentistry, Tehran University of Medical Sciences

Statement of Problem: Tooth extraction is always considered as the final treatment option in dentistry."nConsidering the numerous advances in dentistry, nowadays the preservation of the permanent teeth until old"nage is common. However, in most economically poor countries or those without security service insurance,"nthe high rate of extraction, particularly among restorable teeth, is regrettable."nPurpose: The aim of the present study was to determine the reasons for tooth extraction among patients"nreferred to the faculty of Dentistry, Tehran University of Medical Sciences in 2002."nMaterials and Methods: This descriptive and cross-sectional study was conducted on 320 patients. The"ninformation about patient's general knowledge, oral health status, tooth location and causes of extraction were"ncollected and recorded in a questionnaire. The data were submitted to statistical Chi-Square test."nResults: No statistically significant difference was found between two genders in their mentioned causes for"nextraction. The most prevalent reasons were as follows: Caries (50%), Periodontal diseases (16.6%). Absence"nof an acceptable occlusion, prosthetic problems, patient's request, etc... make up the remaining 33.4% of the"nreasons."nConclusion: According to this study, it is suggested to investigate extraction etiology at the society level and"nif similar results are obtained, necessary steps should be taken to prevent caries and periodontal problems as"nthe major mentioned causes for tooth extraction

Flexibility of Shape-Persistent Molecular Building Blocks Composed of p-Phenylene and Ethynylene Units

Jeschke G, Sajid M, Schulte M, et al. Flexibility of Shape-Persistent Molecular Building Blocks Composed of p-Phenylene and Ethynylene Units. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. 2010;132(29):10107-10117.Ethynylene and p-phenylene are frequently employed constitutional units in constructing the backbone of nanoscopic molecules with specific shape and mechanical or electronic function. How well these properties are defined depends on the flexibility of the backbone, which can be characterized via the end-to-end distance distribution. This distribution is accessible by pulse electron paramagnetic resonance (EPR) distance measurements between spin labels that are attached at the backbone. Four sets of oligomer with different sequences of p-phenylene and ethynylene units and different spin labels were prepared using polar tagging as a tool for simple isolation of the targeted compounds. By variation of backbone length, of the sequence of p-phenylene and ethynylene units, and of the spin labels a consistent coarse-grained model for backbone flexibility of oligo(p-phenyleneethynylene)s and oligo(p-phenylenebutadiynylene)s is obtained. The relation of this harmonic segmented chain model to the worm-like chain model for shape-persistent polymers and to atomistic molecular dynamics simulations is discussed. Oligo(p-phenylene butadiynylene)s are found to be more flexible than oligo(p-phenyleneethynylene)s, but only slightly so. The end-to-end distance distribution measured in a glassy state of the solvent at a temperature of 50 K is found to depend on the glass transition temperature of the solvent. In the range between 91 and 373 K this dependence is in quantitative agreement with expectations for flexibility due to harmonic bending. For the persistence lengths at 298 K our data predict values of (13.8 +/- 1.5) nm for poly(p-phenyleneethynylene)s and of (11.8 +/- 1.5) nm for poly(p-phenylenebutadiynylene)s