A comparative study on life cycle assessment of micro and macro components

Micro manufacturing is an extremely demanding technological field where very special materials are used, extreme production condition like clean room, super high temperature, toxic chemicals, etc. are employed. Due to these facts, micro products can be environmentally damaging even after their smaller dimensional scale. So performing of LCA for micro products is equally important as it is for macro products. Keeping this motivation in mind, current paper systematically performs the LCA of a micro Socket used in hearing aids. The analysis makes a guide line about how to use the conventional knowledge about LCA and tools for the efficient LCA analysis of the micro parts. A comparative study is made in the paper by comparing two different sockets of hearing aid and it shows well how to make a comparative study for LCA when the manufacturer makes a new product to replace an old one. Another comparative study is made in the paper for micro and macro which shows that scaled up effect of the micro product compared to macro counterpart. The critical finding of this comparative study shows that the relative environmental damage done by micro product is higher than the macro product and that is confirmed by the net impact analysis. Finally, the LCA procedure presented in the paper, and the knowledge documented can be a valuable source of information for the researchers and scientists who work with the LCA of micro and macro products.     

Electrocatalytic Formation and Inactivation of Intermetallic Compounds in Electrorefining of Silicon

Silicon for solar cell purposes is today produced by an energy intensive process exhibiting high irreversible thermodynamic energy losses. The purity of the product; 99,9999999 pct (9N), far exceeds what is generally accepted to be the requirements for photovoltaic purposes (4-6N). According to thermodynamics, all elements except boron may be removed from silicon by three layer electrochemical refining above the melting point of Si. Boron, on the other hand, shows higher affinity to specific transition metals compared to silicon. This may be exploited by applying two principles in parallel; electrochemical refining and electrocatalyzed reaction-precipitation of transition metal borides as heavy, stable particles. In this study we report on the formation of such compounds at the cathode-electrolyte interface during electrochemical refining. The trends and mechanisms observed in the laboratory scale investigation indicate that high purity silicon may be produced in industrial scale reactors at low cost- and energy intensity.     

Effects of phosphate-based glasses on T lymphocytes in vitro

Host responses to implanted materials can lead to the production of inflammatory mediators and thereby induce potentially adverse reactions, including the activation of T lymphocytes. Although such cells are a central component of immune reactions and likely to be fundamental in determining the long-term clinical efficacy of implants, their response to biomaterials is not well known. This study has therefore examined the in vitro effects of phosphate-based glasses (PG), which can be produced with pre-determined solubility and may be promising materials for promoting the regeneration of new bone and other tissues. Extracts of PG which were modified by the addition of Ca, Co, Zn, and Fe oxides were found to cause only very low levels of activation of human peripheral blood T lymphocytes over a period of 6 days, as measured by changes in DNA synthesis. In contrast, the activation of these cells by concanavalin A, a potent T cell mitogen, was partially inhibited by extracts of a high-Ca PG and nearly totally ablated by the Co-derived extract. These studies show that, despite their apparent inability to activate immunologically responsive cells directly, substances which leach out of metal-containing PG implant materials have the potential to modulate inflammatory reactions.     

Computer simulation of equilibrium relations in managanese ferroalloy production

The complex heterogeneous equilibria associated with the production of manganese ferroalloys have been simulated using recently developed thermochemical databases. Over 600 measured equilibrium data have been used to verify and calibrate the model calculations. Good agreement is obtained for many important technical relations such as carbon solubility, equilibrium diagrams and phase relations, and element distribution as a function of temperature and composition. Experimental slag/metal and slag/metal/gas equilibria in MnO-SiO₂ binary, MnO-SiO₂-CaO and MnO-SiO₂-Al₂O₃ ternary, MnO-SiO₂-CaO-Al₂O₃ quaternary, and MnO-SiO₂-CaO-Al₂O₃-MgO quinary systems can be reproduced within experimental uncertainties. The influence of temperature, CO partial pressure, and slag chemistry on the Mn- and Si-distribution equilibria has been quantitatively evaluated. This leads to a sound basis for optimizing the manganese ferroalloy production processes.     

A continuous-flow polymerase chain reaction microchip with regional velocity control

This paper presents a continuous-flow polymerase chain reaction (PCR) microchip with a serpentine microchannel of varying width for "regional velocity control." Varying the channel width by incorporating expanding and contracting conduits made it possible to control DNA sample velocities for the optimization of the exposure times of the sample to each temperature phase while minimizing the transitional periods during temperature transitions. A finite element analysis (FEA) and semi-analytical heat transfer model was used to determine the distances between the three heating assemblies that are responsible for creating the denaturation (96/spl deg/C), hybridization (60/spl deg/C), and extension (72/spl deg/C) temperature zones within the microchip. Predictions from the thermal FEA and semi-analytical model were compared with temperature measurements obtained from an infrared (IR) camera. Flow-field FEAs were also performed to predict the velocity distributions in the regions of the expanding and contracting conduits to study the effects of the microchannel geometry on flow recirculation and bubble nucleation. The flow fields were empirically studied using micro particle image velocimetry (/spl mu/-PIV) to validate the flow-field FEA's and to determine experimental velocities in each of the regions of different width. Successful amplification of a 90 base pair (bp) bacillus anthracis DNA fragment was achieved.     

The sizes of peptides generated from protein by mammalian 26 and 20 S proteasomes. Implications for understanding the degradative mechanism and antigen presentation

Knowledge about the sizes of peptides generated by proteasomes during protein degradation is essential to fully understand their degradative mechanisms and the subsequent steps in protein turnover and generation of major histocompatibility complex class I antigenic peptides. We demonstrate here that 26 S and activated 20 S proteasomes from rabbit muscle degrade denatured, nonubiquitinated proteins in a highly processive fashion but generate different patterns of peptides (despite their containing identical proteolytic sites). With both enzymes, products range in length from 3 to 22 residues, and their abundance decreases with increasing length according to a log-normal distribution. Less than 15% of the products are the length of class I presented peptides (8 or 9 residues), and two-thirds are too short to function in antigen presentation. Surprisingly, these mammalian proteasomes, which contain two "chymotryptic," two "tryptic," and two "post-acidic" active sites, generate peptides with a similar size distribution as do archaeal 20 S proteasomes, which have 14 identical sites. Furthermore, inactivation of the "tryptic" sites altered the peptides produced without significantly affecting their size distribution. Therefore, this distribution is not determined by the number, specificity, or arrangement of the active sites (as proposed by the "molecular ruler" model); instead, we propose that proteolysis continues until products are small enough to diffuse out of the proteasomes.     

The effectiveness of early endoscopy for upper gastrointestinal hemorrhage: a community-based analysis

OBJECTIVES: The effectiveness of upper endoscopy in unselected patients with upper gastrointestinal hemorrhage has not been well studied. This study was undertaken to identify factors associated with the performance of early endoscopy (ie, within 1 day of hospitalization) and, after adjusting for these factors, to determine associations between early endoscopy and in-hospital mortality, length of stay, and performance of surgery. METHODS: Subjects in this observational cohort study were 3,801 consecutive admissions with upper gastrointestinal hemorrhage to 30 hospitals in a large metropolitan region. Demographic and clinical data were abstracted from hospital records. A multivariable model based on factors that potentially could relate to the decision to perform endoscopy was developed to determine the propensity (0 to 100%) for early endoscopy in each patient. RESULTS: Early endoscopy was performed in 2,240 patients (59%), and although it was not associated with mortality after adjusting for severity of illness among all patients, it was associated with a higher risk of death for patients in the lowest propensity group. Early endoscopy was associated with a lower likelihood of upper gastrointestinal surgery in all patients and in the two highest propensity groups and with a shorter length of stay in the entire cohort and in all subgroups. CONCLUSIONS: In the absence of specific contraindications, early endoscopy should be considered because of associated reductions in length of stay and surgical intervention. Further studies are needed to identify subgroups in whom the procedure may be associated with adverse effects on survival.