The influence of build strategies in selective inhibition sintering (SIS)

Selective Inhibition Sintering of metal alloys (SIS-metal) has been proven effective in the additive manufacture (AM) of low resolution bronze parts. Recent advancements in the use of a high-precision inkjet print head represented an order of magnitude improvement in SIS-metal resolution. However, the fabrication of complex three-dimensional metallic parts required new SIS-metal compatible, cross-sectional image generation based on the part boundary profile. In the proposed study, five candidate layer-processing approaches were identified and validated for basic geometries. These approaches were chosen from previous research as well as preliminary investigations and were applied to a modified SIS-metal process for validation. The validation criteria were based upon the amount of powder waste produced, the ability to handle complex geometries, printing speed, extraction (post-processing) speed, and part integrity. Results are discussed for implementation of the five candidate layer processing approaches in the fabrication of basic shapes. A preliminary evaluation is presented for their use on more complex geometries. Two approaches were then chosen for the construction of more complex geometries, the results of which are presented.     

Four Novel p.N385K,p.V36A,c.1033–1034insT and c.1417–1418delCT Mutations in the Sphingomyelin Phosphodiesterase 1 (SMPD1) Gene in Patients with Types A and B Niemann-Pick Disease (NPD)

Background: Types A and B Niemann-Pick disease (NPD) are autosomal-recessive lysosomal storage disorders caused by the deficient activity of acid sphingomyelinase due to mutations in the sphingomyelin phosphodiesterase 1 (SMPD1) gene. Methods: In order to determine the prevalence and distribution of SMPD1 gene mutations, the genomic DNA of 15 unrelated Iranian patients with types A and B NPD was examined using PCR, DNA sequencing and bioinformatics analysis. Results: Of 8 patients with the p.G508R mutation, 5 patients were homozygous, while the other 3 were heterozygous. One patient was heterozygous for both the p.N385K and p.G508R mutations. Another patient was heterozygous for both the p.A487V and p.G508R mutations. Two patients (one homozygous and one heterozygous) showed the p.V36A mutation. One patient was homozygous for the c.1033–1034insT mutation. One patient was homozygous for the c.573delT mutation, and 1 patient was homozygous for the c.1417–1418delCT mutation. Additionally, bioinformatics analysis indicated that two new p.V36A and p.N385K mutations decreased the acid sphingomyelinase (ASM) protein stability, which might be evidence to suggest the pathogenicity of these mutations. Conclusion: with detection of these new mutations, the genotypic spectrum of types A and B NPD is extended, facilitating the definition of disease-related mutations. However, more research is essential to confirm the pathogenic effect of these mutations.     

Fabrication,characterization, and thermal property evaluation of silver nanofluids

Silver nanoparticles were successfully prepared in two different solvents using a microwave heating technique, with various irradiation times. The silver nanoparticles were dispersed in polar liquids (distilled water and ethylene glycol) without any other reducing agent, in the presence of the stabilizer polyvinylpyrrolidone (PVP). The optical properties, thermal properties, and morphology of the synthesized silver particles were characterized using ultraviolet-visible spectroscopy, photopyroelectric technique, and transmission electron microscopy. It was found that for the both solvents, the effect of microwave irradiation was mainly on the particles distribution, rather than the size, which enabled to make stable and homogeneous silver nanofluids. The individual spherical nanostructure of self-assembled nanoparticles has been formed during microwave irradiation. Ethylene glycol solution, due to its special properties, such as high dielectric loss, high molecular weight, and high boiling point, can serve as a good solvent for microwave heating and is found to be a more suitable medium than the distilled water. A photopyroelectric technique was carried out to measure thermal diffusivity of the samples. The precision and accuracy of this technique was established by comparing the measured thermal diffusivity of the distilled water and ethylene glycol with values reported in the literature. The thermal diffusivity ratio of the silver nanofluids increased up to 1.15 and 1.25 for distilled water and ethylene glycol, respectively.     

A new optimization approach for nozzle selection and component allocation in multi-head beam-type SMD placement machines

This paper addresses a highly challenging scheduling problem faced in multi-head beam-type surface mounting devices (SMD) machines. An integrated mathematical model is formulated aiming to balance workloads over multiple heads as well as improving the traveling speed of the robotic arm by incorporating the appropriateness factors in the model to evaluate the compatibility of component-nozzle pairs. The proposed model is a bi-objective mixed integer nonlinear programming one, which is first converted into a linearized model and then directly solved by using the augmented epsilon constraint method for small problem instances. As the model is turned out to be NP-hard, we also develop a Multi-Objective Particle Swarm Optimization (MOPSO) algorithm to solve the model for medium and large-sized problem instances. The parameters of the proposed MOPSO are tuned by using the Taguchi Method and corresponding numerical results are provided.     

Role of hormonal and environmental factors on early incidence of breast cancer in Iran

Although the probability of having breast cancer increases with the age in general, this malignancy affects Iranian women at least one decade younger than their counterparts in other countries. However the underlying risk factors for the discrepancy have not been identified. The aryl hydrocarbon receptor (AhR) mediates the effects of many environmental endocrine disruptors and contributes to the loss of normal ovarian function in polluted environments. This study was aimed to compare the interactions between AhR and other fundamental genes (p53, K-Ras, ER, PgR) in a clinical setting. To conduct the immunohistochemical studies using appropriate monoclonal antibodies, 25 premenopausal invasive ductal carcinoma, 29 postmenopausal invasive ductal carcinoma and 30 breast fibroadenoma were selected retrospectively from 2004 to 2007 in the pathology department of Imam Khomeini hospital complex of Tehran University of Medical Sciences . Higher levels of AhR in epithelial cells of premenopausal patients and breast fibroadenoma emphasized the susceptibility of these cells to environmental-induced tumors. AhR overexpression contributed to ER-/PgR-immunophenotype in young/premenopausal patients but the same pattern was not observed in benign and postmenopausal malignant tumors. It seems that early incidence of breast cancer in Iran is the result of interactions between hormonal and environmental factors.     

Secrecy performance analysis of CIOD–OFDM systems over wireless fading channels

Wireless Networks - Space–time block codes from coordinate interleaved orthogonal designs (CIODs) have been attracted attention due to their capability for full-diversity and full-rate...     

Novel solution for acceleration motion of a vertically falling non-spherical particle by VIM–Padé approximant

In this paper, the acceleration motion of a vertically falling non-spherical particle in incompressible Newtonian media was investigated. The velocity and acceleration were carried out using analytical solution techniques i.e., the variational iteration method (VIM) and a Padé approximant. The results were also compared with VIM and the established fourth order Runge–Kutta method in order to verify the accuracy of the proposed method. It was shown that this method can lead into more accurate results compared with VIM.