An investigation of Stress corrosion cracking in MgAZ61 alloy in 3.5% NaCl + 2% K2CrO4 aqueous solution at room temperature

Effect of specimen orientation, heat treatment and applied potential on the stress corrosion susceptibility of magnesium AZ61 (Mg-6.3% Al-0.5% Zn-0.20% Mn) alloy in an aqueous 3.5% NaCl + 2% K₂CrO₄ solution at room temperature was investigated. Stress corrosion times to failure were measured at different values of initial stress intensities using single edge (pre) cracked sheet tensile specimens and a modified tensometer. It was observed that while the specimen orientation has a significant effect on the measured values of stress corrosion threshold stress intensity, K_Iscc, the effect of varying the quench rate during heat treatment was minimal. Polarization measurements both in stressed and unstressed conditions, failed to reveal any significant effect of the applied stress intensity on the anodic polarization behavior of the alloy. However, measurements made under four different potentiostatic conditions showed a considerable increase in stress corrosion times to failure of the alloy. The results, together with fractographic observations of fractured specimen are discussed in terms of the mechanisms of stress corrosion cracking, in magnesium alloys.     

Primary drug resistance to Mycobacterium tuberculosis in renal transplant recipients

The author describes artificial retention of the testicle caused by a technical mistake of the surgeon during surgery of an inguinal hernia or hydrocele. The author emphasizes the experience of the surgeon needed during "minor" operations in children.     

Identification of nucleation loci in emulsion polymerization processes. I. New information from spectroscopy studies

Particle nucleation is the forcing function in emulsion polymerization reactions and as such it plays a significant role in the development of most of the properties of the final latex. The locus of nucleation in emulsion polymerization remains a contentious issue. Recent developments in the spectroscopy of emulsions strongly suggest that the locus of particle nucleation is a population of small nano‐droplets of size range between 30–100 nanometers in diameter. These nano‐droplets are generated independently of the rate of initiator decomposition and appear to be functions only of the emulsification conditions. In this paper the simulation studies leading to the identification of the nano‐droplet population are described. The theoretical evidence suggesting that the nano‐droplets are the main loci of particle nucleation is presented and along with the recommendations for the experimental work. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2847–2857, 2006     

Mechanical properties and densification behavior of β‐spodumene/anorthite composites

Although β‐spodumene/anorthite composites are interesting systems, little research work has been done to study their properties. This study aims at investigating the preparation and properties of β‐spodumene/anorthite composites containing β‐spodumene proportions ranging between 10 and 25 mass %. X‐ray diffraction analysis (XRD), Scanning electron microscopy (SEM), and the coefficient of thermal expansion (CTE) were used to characterize the effect of addition of β‐spodumene on the phase relations, microstructure, and thermal expansion behavior of resultant composites. The results show that the presence of β‐spodumene significantly reduces the porosity and reduces the densification temperature. It reduces thermal expansion and enhances the mechanical properties of anorthite‐containing composites.     

Antibiotic resistance and incidence of Enterococcus species in Turkish white cheese

Thirty samples of Turkish white cheese were analysed for the presence of Enterococcus spp., and presumptive isolates were identified by morphological, cultural and biochemical tests and confirmed by the API 20 Strep System. Among the 101 isolates of Enterococcus spp., 62 were E. faecalis , 25 were E. faecium , seven were E. durans , five were E. mundtii and two were E. hirae/dispar . The resistance of the isolates to 13 different antibiotics was determined by the Kirby–Bauer disc diffusion test. Resistance to streptomycin, erythromycin, oxacillin and vancomycin was frequently found in these enterococci, and resistance to vancomycin was found in 96.8% of E. faecalis isolates and 76% E. faecium . The most effective antimicrobials were ampicillin (69.3% of isolates inhibited) and imipenem (76.3% of isolates inhibited). This examination confirmed the presence of enterococci, especially vancomycin-resistant strains, in Turkish white cheese, indicating poor sanitary conditions during production and processing and a significant health risk for consumers.     

Analysis of tanks-in-series model with backflow for free-radical polymerization

Free-radical polymerization in a flow reactor represented by the tanks-in-series model with backflow was considered. Conversions and molecular weight distributions were computed as functions of the backflow parameter, and the results were compared with the conversion and molecular weight distribution from a CSTR and those from a plug-flow reactor. Backflow was found to be undesirable for the polymerization mechanism under investigation. Values of the degree of segregation for the tanks-in-series model were calculated by using Zwietering's approach as a function of backflow.     

Design and Realization of a Microcontroller Based E-Test Strip Application Device

Abstract

In this study, a device that supplies a microcontroller controlled E-test strip application was developed. It was aimed to gather two devices which are needed for E-test strip application's stages, i.e., inoculation onto agar plate and placement of E-test strip, into a device to thus reduce the cost and time required for this application. A PIC16F877A microcontroller was used in the system and it was programmed in Microcode Studio Plus Editor by using the PIC Basic Programming Language. The circuit whose design was realized was tested under circumstances in the laboratory and real medium. The designed system is in a state that can be used in hospitals as it is.     

Toughness of as-cast and partially crystallized composites of a bulk metallic glass

The deformation and fracture response of a bulk metallic glass (BMG) post-annealing above the glass transition temperature is examined. The toughness of the glass-matrix composite exhibits a sharp transition beyond a critical volume fraction of crystallization to values as low as that of brittle silicate glass. Instrumented indentation tests supplemented by impact tests were used to study this ductile to brittle transition exhibited by the partially crystallized samples. Indentation on the anneal-embrittled specimens shows lateral cracks in addition to cracks along the corners. The applicability of the Poisson's ratio-toughness correlation with respect to partially crystallized samples is also investigated.     

Investigation of musculoskeletal symptoms and ergonomic risk factors among female sewing machine operators in Turkey

This cross-sectional study aimed to identify the prevalence of musculoskeletal symptoms and ergonomic risks in female sewing machine operators at a textile company. The study sample comprised all female sewing machine operators in the company. The sample included 283 sewing machine operators. Data were collected through the use of the adapted Nordic Musculoskeletal Questionnaire and by direct observations via the rapid upper limb assessment (RULA) to determine ergonomic risks. RULA is a validated tool for assessment of ergonomic risks. The mean age of the women was 30.2 (SD: 8.4) and the mean number of years of employment was 13.4 (SD: 5.5). The highest prevalence rates for the women’s musculoskeletal symptoms were in the trunk (62.5%), neck (50.5%), and shoulder (50.2%). Of the women, 65% had experienced musculoskeletal pain or discomfort over the last 6 months. Pain intensity of these symptoms was assessed with a visual analogue scale. The average pain intensity of the women was found to be 3.5 (SD: 2.8). Results of the RULA scores were found to be quite high. There were no employees who received RULA scores of 1–2, which indicates acceptable postures (all scores >5). The final RULA scores of 6.9 indicate that the participants’ postures at their work stations need to be investigated immediately.

Relevance to industry

This study based on the RULA method allowed to perform a rapid and quite correct evaluation tolls for SMOs. For this research population, the research findings provided fundamental data on the prevalence of musculoskeletal symptoms and ergonomic risks among Turkish female SMOs.     

Analyzing Weighted Round Robin policies with a stochastic comparison approach

We study queuing delays for Weighted Round Robin (WRR) scheduling policies. The delay characteristics of these policies can be estimated through worst-case bounds as other fair queuing scheduling policies. However, these deterministic bounds are in general not accurate and they require that the input process has been shaped. Under Markovian arrival hypothesis, the delay of WRR   policies can be evaluated through Markovian numerical analysis. Nevertheless, this analysis is limited to small parameter sizes because of the state space explosion problem. We propose to apply the stochastic comparison approach. We build a bounding model based on the aggregation of sessions, and we show that under the same arrivals, the packet delays in the bounding model are larger in the _?st${?}_{\mathrm{st}}$ stochastic order sense than the packet delays in the original model. Due to this aggregation, the state space size is drastically reduced and we are able to provide stochastic delay bounds for WRR policies. We discuss the accuracy of the proposed bounds through numerical examples.