Search Results (4)

Currently, ultrasonic methods for assessing the fatigue lifetime of various structural materials are being actively developed. Many steel constructions are made by welding. The weld heat-affected zone is the weak point of the construction, as it is most susceptible to destruction. Therefore, it is actually important to search for acoustic parameters that uniquely characterize the structural damage accumulation in the heat-affected zone of a welded joint in order to predict failure. In this work, the specimens were made from the base metal and the welded joint’s heat-affected zone. The specimens were subjected to uniaxial tension–compression under a symmetrical cycle in the region of low-cycle fatigue with control of the strain amplitude. The propagation bulk velocities of longitudinal, shear waves and subsurface longitudinal critically refracted (LCR) waves during cyclic loading were studied. The acoustic birefringence of shear waves was calculated, and a similar parameter was proposed for longitudinal and LCR waves. The dependence of the elastic modulus ratio on the cycle ratio was obtained. It was shown that the acoustic parameters change most intensively in the heat-affected zone. According to the data of the C₃₃/C₅₅ ratio changes measured through the ultrasonic method, a formula for calculating the remaining fatigue life in the heat-affected zone was proposed. Full article

Hypertrophic cardiomyopathy (HCM), caused by mutations in thin filament proteins, manifests as moderate cardiac hypertrophy and is associated with sudden cardiac death (SCD). We identified a new de novo variant, c.656A>T (p.D219V), in the TPM1 gene encoding cardiac tropomyosin 1.1 (Tpm) in a young SCD victim with post-mortem-diagnosed HCM. We produced recombinant D219V Tpm1.1 and studied its structural and functional properties using various biochemical and biophysical methods. The D219V mutation did not affect the Tpm affinity for F-actin but increased the thermal stability of the Tpm molecule and Tpm-F-actin complex. The D219V mutation significantly increased the Ca²⁺ sensitivity of the sliding velocity of thin filaments over cardiac myosin in an in vitro motility assay and impaired the inhibition of the filament sliding at low Ca²⁺ concentration. The molecular dynamics (MD) simulation provided insight into a possible molecular mechanism of the effect of the mutation that is most likely a cause of the weakening of the Tpm interaction with actin in the "closed" state and so makes it an easier transition to the “open” state. The changes in the Ca²⁺ regulation of the actin-myosin interaction characteristic of genetic HCM suggest that the mutation is likely pathogenic. Full article

Arylazoimidazoles are important dyes which were intensively studied in the past. In contrast, triarylazoimidazoles (derivatives which carry aryl substituents at the imidazole core) received almost no attention in the scientific literature. Here, we report a new family of simple and easily accessible triarylazoimidazole-group 12 metal complexes, which feature highly efficient photo-luminescence emission (Φ up to  0.44). Novel compounds exhibit bright red emission in solution, which could be excited with a visible light. Full article

Background and Objective. Variation of osteoporosis in the population is the result of an interaction between the genotype and the environment, and the genetic causes of osteoporosis are being widely investigated. The aim of this study was to analyze the association between the polymorphisms of the vitamin D receptor (VDR), type I collagen (COL1A1), and lactase (LCT) genes and severe postmenopausal osteoporosis as well as bone mineral density (BMD).
Material and Methods. A total of 54 women with severe postmenopausal osteoporosis and 77 controls (mean age, 58.3 years [SD, 6.2] and 56.7 years [SD, 7.42], respectively) were included into the study. The subjects were recruited at the City Center for Osteoporosis Prevention (Minsk, Belarus). Dual-energy x-ray absorptiometry was used to measure bone mineral density at the lumbar spine and the femoral neck. Severe osteoporosis was diagnosed in the women with the clinical diagnosis of postmenopausal osteoporosis and at least 1 fragility fracture. The control group included women without osteoporosis. Polymorphic sites in osteoporosis predisposition genes (ApaI, BsmI, TaqI, and Cdx2 of the VDR gene, G2046T of the COL1A1 gene, and T-13910C of the LCT gene) were determined using the polymerase chain reaction on the deoxyribonucleic acid isolated from dried bloodspots.
Results. The data showed that the ApaI and BsmI polymorphisms of the VDR gene and T- 13910C of the LCT gene were associated with severe postmenopausal osteoporosis in the analyzed Belarusian women (P<0.01). A statistically significant positive correlation between the VDR risk genotypes ApaI and TaqI and bone mineral density was found (P<0.05).
Conclusions. The findings of this study suggest that at least the ApaI and BsmI polymorphisms of the VDR gene and T-13910C of the LCT gene are associated with the risk of postmenopausal osteoporosis in our sample of the Belarusian women. Full article