Properties of anionic polymerized ε‐caprolactam in the presence of carbon nanotubes

The results of the investigations of the relations between structure, physical and usage properties of polyamide 6 (PA6) reinforced with multiwall carbon nanotubes (MWNTs) are presented. A method of in situ anionic bulk polymerization of ε‐caprolactam in the presence of MWNTs was used for the preparation of reinforced PA6. The polymerization product was crushed, and the pellets of PA6 and PA6/MWNTs composites were injection molded to produce the standard test specimens for various measurements. The surface morphology (SEM), thermal (DSC, TGA, DMTA), and mechanical properties (tensile strength, Charpy's notched impact strength) of these materials were examined. Some differences between our specimens and those obtained by hydrolytic polymerization of ε‐caprolactam (CL) were found. It was found that a small amount of carbon nanotube decreases the crystallinity degree of PA6 matrix in the composites. The thermal stability was higher than that for neat PA6. DMTA results showed that the magnitudes of the storage modulus are higher for the PA6/MWNTs composites than for the unmodified PA6 in the temperature range between ?90 and 200°C. The tensile strength and tensile modulus are higher compared with the neat PA6. The elongation at break showed no noticeable change in the range of MWNTs loading considered, while the Charpy's notched impact strength slightly decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

An integrated approach for coal tailings management

A detailed study on an integrated process featuring three distinct mechanisms (i.e., hydrophobic extraction, coagulation and flocculation) is presented. In this process, fine coals in the tailings stream are extracted into a mineral oil by hydrophobic extraction, while coagulant and flocculant are used to aid effluent clarification by coagulation/flocculation. With a single stage process, a coal‐in‐oil mixture is produced as a potential fuel, while clarifying the water for recycling. The hydrophobicity of coal is found to be a key parameter in coal extraction. The addition of mineral oil prior to flocculant and coagulant, especially in the presence of fine clays, is beneficial for recovering weakly hydrophobic fine coals. Fine clays are found to stabilize coal‐rich oil droplets, reducing coal recovery. The presence of hydrophobic coal enhances droplet coalescence and improves process performance. In a case study using a tailings stream from OBED coal preparation plant, it was found that re‐grinding of original tailings is necessary to expose fresh hydrophobic surfaces. Applying this single stage unit operation to a tailings containing 52% ash, a combustible recovery greater than 85% in the form of coal‐in‐oil mixture at product ash content less than 14 wt% was achieved.     

Intelligent Modeling: Advances in Open Pit Mine Design and Optimization Research

Design and optimization of pit layouts yield the mineable ore reserves and minimum waste to maximize the net pit value and to ensure optimum location of surface facilities. Many algorithms and their modifications, derived from stripping ratio concepts, displacement of conic volumes, dynamic programming and graph theory, have been developed to design and optimize pit layouts. These algorithms have assisted engineers in making design decisions but they are limited in dealing with pit design stochastic processes. Large information and database and the requirement for complete rerun of these algorithms with information and data changes result in long computations and CPU times. Current algorithms do not provide analysts with intelligent design options to deal with structural, hydrological and tectonics problems of mine design. In this paper, the authors discuss current state-of-the-art technology and research in intelligent modeling. Current and future research frontiers in intelligent modeling are also addressed with emphasis on developing efficient and user-friendly technology for pit design and optimization.     

The “model minority myth”: Internalized racialism of positive stereotypes as correlates of psychological distress, and attitudes toward help-seeking.

Stereotypes associated with Asian Americans (model minority group) are, at times, positive. Endorsement of these stereotypes (i.e., internalized racialism) might contribute to Asian's distress and their attitudes toward seeking services. The purpose of this study was to use the theory of “status-based rejection sensitivity” as a way to examine the relationship between internalized racialism (i.e., endorsement and/or internalization of positive Asian stereotypes) and psychological distress, and attitudes toward help-seeking among 291 Asian Americans. Results indicated that higher levels of endorsement of positive Asian stereotypes were related to higher levels of psychological distress and more negative attitudes toward help-seeking. No evidence was found for the moderating roles of internalized racialism in the endorsement of positive Asian stereotypes–distress/help-seeking links. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

PIXE analysis of chromium phytoaccumulation by the aquatic macrophytes Eicchornia crassipes

The uptake of hexavalent chromium in free living floating aquatic macrophytes Eicchornia crassipes cultivated in non-toxic chromium-doped hydroponic solutions is presented. A Cr-uptake bioaccumulation experiment was carried out using healthy macrophytes grown in a temperature controlled greenhouse. Six samples of nutrient media and plants were collected during the 23 day experiment. Roots and leaves were acid digested with the addition of an internal Gallium standard, for thin film sample preparation and quantitative Cr analysis by PIXE method. The Cr⁶⁺ mass uptake by the macrophytes reached up to 70% of the initial concentration, comparable to former results and literature data. The Cr-uptake data were described using a non-structural first order kinetic model. Due to low cost and high removal efficiency, living aquatic macrophytes E. crassipes are a viable biosorbent in an artificial wetland of a water effluent treatment plant.     

Rapid brain autopsy. The Joseph and Kathleen Bryan Alzheimer's Disease Research Center experience

OBJECTIVE: To develop a system for retrieving brain tissue within 1 hour after death in an effective and useful manner. DESIGN: Nurse clinicians were employed as study co-ordinators and were available to families 24 hours each day. SETTING: Autopsies were performed at Duke University Medical Center, Durham, NC, from 1985 through 1995. PARTICIPANTS: Neuropathology faculty, fellows, and residents, autopsy technicians; and brain bank staff. RESULTS: Fifty-one rapid autopsies with a postmortem interval of less than 1 hour have been performed. Four of these were normal controls, three were disease controls, and 44 represented Alzheimer's disease patients. Tissue retrieved at rapid autopsy has been distributed to 93 research teams, 30 of these located at Duke University Medical Center. Many researchers have received multiple shipments of tissue. CONCLUSIONS: The Bryan Alzheimer's Disease Research Center Rapid Autopsy Program at Duke University Medical Center has been successful in retrieving tissue from individuals with dementia and also from controls within 1 hour of death. The critical features of the success of this program have been the use of nurse clinicians who work closely with patients and their families to ensure a successful autopsy at the time of death and the maintenance of a 24-hour call schedule for nurses and neuropathology staff. Similar programs can be implemented for experimental work into the pathogenesis of a wide variety of human diseases in which the examination of human tissue is required.     

(5′S) 5′,8-cyclo-2′-deoxyadenosine Cannot Stop BER. Clustered DNA Lesion Studies

As a result of external and endocellular physical-chemical factors, every day approximately ~10⁵ DNA lesions might be formed in each human cell. During evolution, living organisms have developed numerous repair systems, of which Base Excision Repair (BER) is the most common. 5′,8-cyclo-2′-deoxyadenosine (cdA) is a tandem lesion that is removed by the Nucleotide Excision Repair (NER) mechanism. Previously, it was assumed that BER machinery was not able to remove (5′S)cdA from the genome. In this study; however, it has been demonstrated that, if (5′S)cdA is a part of a single-stranded clustered DNA lesion, it can be removed from ds-DNA by BER. The above is theoretically possible in two cases: (A) When, during repair, clustered lesions form Okazaki-like fragments; or (B) when the (5′S)cdA moiety is located in the oligonucleotide strand on the 3′-end side of the adjacent DNA damage site, but not when it appears at the opposite 5′-end side. To explain this phenomenon, pure enzymes involved in BER were used (polymerase β (Polβ), a Proliferating Cell Nuclear Antigen (PCNA), and the X-Ray Repair Cross-Complementing Protein 1 (XRCC1)), as well as the Nuclear Extract (NE) from xrs5 cells. It has been found that Polβ can effectively elongate the primer strand in the presence of XRCC1 or PCNA. Moreover, supplementation of the NE from xrs5 cells with Polβ (artificial Polβ overexpression) forced oligonucleotide repair via BER in all the discussed cases.     

The new Melbourne nuclear microprobe system

The spatial resolution in a nuclear microprobe system has been stalled at around 1 μm for many years. In Melbourne we are presently constructing a new facility which aims to break this barrier. The key ingredients of the new facility are: (i) a novel magnetic quadrupole lens quintuplet probe forming system that is a further optimised version of the CSIRO/MARC system presently in operation in Sydney, (ii) high solid angle detectors for particles, X-rays and secondary electrons and (iii) a fast data acquisition system able to cope with greater than 20 kHz count rates from up to four detectors with full deadtime correction. This paper describes the optimised probe forming lens system which is comprised of four thin lenses and one thick lens to produce an orthomorphic probe forming lens system with a demagnification of 150.