On the influence of T-Stress on photoelastic analysis under pure mode II loading

According to the classical definition for in-plane modes of crack deformation, the constant stress term T exists only in the presence of mode I. However, recent studies show that this term can exist in mode II conditions as well, and significantly affect the elastic stress field around the crack tip. These effects can be visualized using the experimental method of photoelasticity. Based on the analytical studies, presence of the T-stress in mode II cracks transforms the isochromatic fringe patterns from symmetric closed loops to asymmetric and discontinuous shapes. In this paper, presence of the T-stress in mode II cracks and its effects on the fringe patterns is experimentally investigated. The test specimens are Brazilian disks containing very sharp central cracks: experimental results indicate that these specimens contain negative values of T-stress. Experimental values are then compared to numerical results. To better understand the differences between experimental and numerical values, a thee dimensional analysis is performed with the finite element method: results show the influence of the real geometry of the crack front on the stress intensity factors

On the influence of T-Stress on photoelastic analysis under pure mode II loading

According to the classical definition for in-plane modes of crack deformation, the constant stress term T exists only in the presence of mode I. However, recent studies show that this term can exist in mode II conditions as well, and significantly affect the elastic stress field around the crack tip. These effects can be visualized using the experimental method of photoelasticity. Based on the analytical studies, presence of the T-stress in mode II cracks transforms the isochromatic fringe patterns from symmetric closed loops to asymmetric and discontinuous shapes. In this paper, presence of the T-stress in mode II cracks and its effects on the fringe patterns is experimentally investigated. The test specimens are Brazilian disks containing very sharp central cracks: experimental results indicate that these specimens contain negative values of T-stress. Experimental values are then compared to numerical results. To better understand the differences between experimental and numerical values, a thee dimensional analysis is performed with the finite element method: results show the influence of the real geometry of the crack front on the stress intensity factors

Comparison the frequency of dry eye syndrome in patients with newly diagnosed rheumatoid arthritis with healthly people in Zahedan

زمینه و هدف: از شایع ترین تظاهرات درگیری چشم، سندرم چشم خشک می باشد. سندرم چشم خشک باعث افزایش خطر عفونت چشم و اختلال در میزان دقت بینایی می گردد. مطالعات مختلف نتایج متفاوتی در خصوص شیوع آرتریت روماتویید و سندرم چشم خشک نشان داده اند. به نظر می رسد یکی از علل تفاوت شیوع سندرم چشم خشک در مطالعات مختلف، تفاوت آب و هوایی در مناطق مورد مطالعه باشد. هدف از این مطالعه، بررسی میزان شیوع خشکی چشم در بیماران مبتلا به آرتریت روماتویید در مناطق با آب و هوای گرم و خشک در مقایسه با افراد سالم و همچنین بررسی میزان شیوع سندرم چشم خشک در مبتلایان به آرتریت روماتویید تازه تشخیص داده شده می باشد. روش بررسی: در این مطالعه مورد-شاهدی،60 نفر از مبتلایان به آرتریت روماتویید و 60 نفر از افراد سالم که از نظر سن و جنس همسان سازی شده بودند وارد مطالعه شدند و در آنها علاوه بر شرح حال و علایم بالینی تست های شیرمر، منیسک اشک، فلورسین و شکست اشک بررسی شد. در بیمارانی که یکی یا بیشتر از این تست ها مثبت بود، تشخیص سندرم چشم خشک داده می شد. داده ها با استفاده از آزمون آماری کای اسکوئر مورد تجزیه و تحلیل قرار گرفتند. یافته‌ها :از 60 نفر مبتلا به آرتریت روماتویید 32 نفر (53) مبتلا به سندرم چشم خشک قطعی و 15 نفر (25) مبتلا به سندرم چشم خشک احتمالی بودند و در گروه کنترل 6 نفر (10) سندرم چشم خشک داشتند بین دو گروه بیمار و کنترل از نظر وجود سندرم چشم خشک قطعی اختلاف آماری معنی داری وجود داشت (001/0

Association of FAS and FAS Ligand Genes Polymorphism and Risk of Systemic Lupus Erythematosus

FAS/FASL pathway plays a critical role in maintaining peripheral immune tolerance; therefore, the apoptosis genes, Fas and Fas ligand (FasL), could be suitable candidate genes in human SLE susceptibility. Materials and Methods. In this case-control study, 106 SLE patients and 149 sex, age, and ethnicity matched healthy controls were genotyped for the Fas A-670G and FasLC-844T polymorphisms by polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). Results. The frequency of -670AA genotype was significantly higher in SLE patients than control group and the risk of SLE was 2.1-fold greater in subjects with AA genotype (P=0.03). The frequency of -670A allele was significantly higher in SLE patients than in controls too (58% versus 49%, P=0.03). The -844CC genotype frequency was significantly higher in SLE patients than in healthy controls and the risk of SLE was 2.8-fold greater in these subjects (P=0.01). The C allele frequency was significantly higher in patients than in controls (69% versus 49%, P=0.001). Increased SLE risk was observed in individuals with combined effect of Fas-670AA and FasL-844CC genotypes (P=0.001). Conclusion. Fas-670AA and FasL-844CC genotypes were associated with SLE risk, and combined effect of -670AA and -844CC genotypes might increase SLE susceptibility

Prooxidant-Antioxidant Balance in Patients with Systemic Lupus Erythematosus and Its Relationship with Clinical and Laboratory Findings

Aim. This study was aimed at evaluating prooxidant-antioxidant balance (PAB) in patients with systemic lupus erythematosus (SLE) and its relationship with laboratory findings and clinical manifestations. Methods. In this case-control study, 60 patients with SLE and 60 healthy individuals were enrolled. The blood samples were collected and their sera were separated. Subsequently, the prooxidant-antioxidant balance value was evaluated using PAB assay for each sample. Results. The mean of PAB values in SLE patients was significantly higher than healthy controls (147.3±42 versus 84.8±32.2 HK, P<0.0001). Furthermore, in SLE patients, there was a positive significant correlation between the PAB and erythrocyte sedimentation rate (ESR) (r=0.492, P<0.001). In addition, the PAB values in patients with alopecia, discoid rash, oral ulcers, arthritis, and nephritis were significantly higher than those without these manifestations. Conclusion. The findings of current study showed that the mean of PAB was significantly higher in SLE patients and PAB was correlated with ESR. Moreover increased PAB was found in SLE patients with alopecia, discoid rash, oral ulcers, arthritis, and nephritis. These findings suggest that the measurement of PAB may be useful to show oxidative stress condition in SLE patients

Targeting enteroviral 2A protease by a 16-mer synthetic peptide: Inhibition of 2Apro-induced apoptosis in a stable Tet-on HeLa cell line

AbstractEnteroviridae such as coxsackievirus are important infectious agents causing viral heart diseases. Viral protease 2A (2Apro) initiates the virus life cycle, and is an excellent target for developing antiviral drugs. Here, to evaluate the validity of the 2Apro as a proper therapeutic target, and based on the existing information and molecular dynamics, a 16-mer peptide was designed to specifically target the active site of protease 2Apro in order to block the activity of CVB3 2Apro. We showed that the peptide could compete with endogenous substrate in a concentration-dependent manner. Further, we established a HeLa cell line that expressed 2Apro. Expression of 2Apro resulted in significant morphological alteration and eventual cell death. Western blot and viability assay showed that the 16-mer peptide (200 μg/ml) could significantly block 2Apro activity and its cytotoxic effect. Future modification of the 16-mer peptide can improve its affinity for 2Apro and therefore develop effective antiviral drug

On the Mechanical Properties of Chiral Carbon Nanotubes

Carbon nanotubes (CNTs) are specific structures with valuable characteristics. In general, the structure of each nanotube is defined by a unique chiral vector. In this paper, different structures of short single-walled CNTs are simulated and their mechanical properties are determined using finite element method. For this aim, a simple algorithm is presented which is able to model the geometry of single-walled CNTs with any desired structure based on nano-scale continuum mechanics approach. By changing the chiral angle from 0 to 30 degree for constant length to radius ratio, the effect of nanotube chirality on its mechanical properties is evaluated. It is observed that the tensile modulus of CNTs changes between 0.93-1.02 TPa for different structures, and it can be higher for chiral structures than zigzag and armchair ones. Also, for different chiral angles, the bending modulus changes between 0.76-0.82 TPa, while the torsional modulus varies in the range of 0.283-0.301TPa

Investigation of Chirality Effect on Axial and Torsional Buckling Behavior of SWCNTs Using Finite Element Method

In this paper, chirality effect on the buckling behavior of SWCNTs has been investigated. In order to explore the effect of chiral angle, all structures are used with the same length and diameter but different chiral angles. For modeling of chemical bonds between carbon atoms, potential energy of molecular mechanics theory and strain energies of a 3D beam element have been equalized. After calculating the element properties, the node coordinates have been determined using a computer code developed in MATLAB software. Then, ANSYS software is used to study the chirality effects on axial and torsional buckling load. Results show that the chiral angle has no significant influence on critical axial force. However, chiral angle is an effective parameter in torsional buckling. Chiral angle of 19.11 degree has the maximum critical torsional moment among all structures. In counter-clock-wise loading condition, chiral angle of 9.64 degree has the minimum critical torsional moment. Also, the direction of twisting (cw or ccw) is important and the difference between cw and ccw critical torsional moment reaches its maximum value for chiral angle of 15.48 degree

Evaluation of HLA-G 14 bp Ins/Del and +3142G>C Polymorphism with Susceptibility and Early Disease Activity in Rheumatoid Arthritis

Purpose/Background. Mounting evidence designates that HLA-G plays a role in the regulation of inflammatory processes and autoimmune diseases. There are controversial reports concerning the impact of HLA-G gene polymorphism on rheumatoid arthritis (RA). This study was aimed at examining the impact of 14 bp ins/del and +3142G>C polymorphism with susceptibility and early disease activity in RA patients in a sample of the Iranian population. Methods. This case-control study was done on 194 patients with RA and 158 healthy subjects. The HLA-G rs1063320 (+3142G>C) and rs66554220 (14 bp ins/del) variants were genotype by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFP) and PCR method, respectively. Results. The HLA-G +3142G>C polymorphism significantly decreased the risk of RA in codominant (OR = 0.61, 95% CI = 0.38–0.97, p=0.038, GC versus GG; OR = 0.36, 95% CI = 0.14–0.92, p=0.034, CC versus GG), dominant (OR = 0.56, 95% CI = 0.36–0.87, p=0.011, GC + CC versus GG), and allele (OR = 0.58, 95% CI = 0.41–0.84, p=0.004, C versus G) inheritance models tested. Our finding did not support an association between HLA-G 14 bp ins/del variant and risk/protection of RA. In addition, no significant association was found between the polymorphism and early disease activity. Conclusion. In summary, our results showed that HLA-G +3142G>C gene polymorphism significantly decreased the risk of RA in a sample of the Iranian population

Arg399Gln and Arg194Trp Polymorphisms and Risk of Systemic Lupus Erythematosus in an Iranian Population: A Pilot Study

Background. Evidences are suggesting that DNA damage is implicated in development of systemic lupus erythematosus (SLE). Therefore we focused on two common XRCC1 polymorphisms (Arg399Gln and Arg194Trp) in SLE susceptibility in South East of Iran. Methods. Peripheral blood DNA was extracted from 163 SLE patients and 180 healthy controls. PCR-restriction fragment length polymorphism method was used for genotyping of XRCC1 Arg399Gln and Arg194Trp polymorphisms. Results. The frequency of Arg/Gln genotype of the XRCC1 Arg399Gln polymorphism was significantly lower in SLE patients than controls. Moreover, lower frequency of Arg/Gln genotype was found in SLE patients with malar rash compared to patients without this manifestation. No association was observed between XRCC1 Arg194Trp polymorphism and increased risk of SLE in studied population. Haplotype analysis revealed no correlation between four haplotypes of XRCC1 Arg399Gln and Arg194Trp polymorphisms and SLE risk. Conclusion. These findings suggest that XRCC1 399 Arg/Gln heterozygous genotype plays a protective role in SLE susceptibility