Pengaruh Kuat Arus Dan Waktu Pengelasan Pada Proses Las Titik (Spot Welding) Terhadap Kekuatan Tarik Dan Mikrostuktur Hasil Las Dari Baja Fasa Ganda (Feritte-Martensite)

This research was conducted to investigate the appropiate spot welding variable to get the maximum tensile strength. The highest of tensile strength referred as good quality of weldment.The plate was made from low carbon steel with phase ferrite and martensite. The current of welding used 0.9 kA, 1.6 kA, dan 1.85 kA with welding time were 0.25, 0.5 , 0.75 and 1 second. Mechanical properties testing done involved tensile strength to know shear strength of weld joint. Microstructure test used optical microscope.The results show that spot welding with thecurrent of 1.85kA and welding time of 1 second has the highest tensile strength (about 237.04N/mm2). On the other hand, the lowest tensile strength (150 N/mm2) was produced by combination of 0.9 kA and 0.25 second welding time. It was caused by recrystallization phasedeformation on steel

Haplotype differences for copy number variants in the 22q11.23 region among human populations: a pigmentation-based model for selective pressure.

Two gene clusters are tightly linked in a narrow region of chromosome 22q11.23: the macrophage migration inhibitory factor (MIF) gene family and the glutathione S-transferase theta class. Within 120 kb in this region, two 30-kb deletions reach high frequencies in human populations. This gives rise to four haplotypic arrangements, which modulate the number of genes in both families. The variable patterns of linkage disequilibrium (LD) between these copy number variants (CNVs) in diverse human populations remain poorly understood. We analyzed 2469 individuals belonging to 27 human populations with different ethnic origins. Then we correlated the genetic variability of 22q11.23 CNVs with environmental variables. We confirmed an increasing strength of LD from Africa to Asia and to Europe. Further, we highlighted strongly significant correlations between the frequency of one of the haplotypes and pigmentation-related variables: skin color (R2=0.675, P<0.001), distance from the equator (R2=0.454, P<0.001), UVA radiation (R2=0.439, P<0.001), and UVB radiation (R2=0.313, P=0.002). The fact that all MIF-related genes are retained on this haplotype and the evidences gleaned from experimental systems seem to agree with the role of MIF-related genes in melanogenesis. As such, we propose a model that explains the geographic and ethnic distribution of 22q11.23 CNVs among human populations, assuming that MIF-related gene dosage could be associated with adaptation to low UV radiatio

The biological effects of diagnostic cardiac imaging on chronically exposed physicians: the importance of being non-ionizing

Ultrasounds and ionizing radiation are extensively used for diagnostic applications in the cardiology clinical practice. This paper reviewed the available information on occupational risk of the cardiologists who perform, every day, cardiac imaging procedures. At the moment, there are no consistent evidence that exposure to medical ultrasound is capable of inducing genetic effects, and representing a serious health hazard for clinical staff. In contrast, exposure to ionizing radiation may result in adverse health effect on clinical cardiologists. Although the current risk estimates are clouded by approximations and extrapolations, most data from cytogenetic studies have reported a detrimental effect on somatic DNA of professionally exposed personnel to chronic low doses of ionizing radiation. Since interventional cardiologists and electro-physiologists have the highest radiation exposure among health professionals, a major awareness is crucial for improving occupational protection. Furthermore, the use of a biological dosimeter could be a reliable tool for the risk quantification on an individual basis

Blood polymorphism frequencies in the T ofinu, the "Water Men" of Southern Benin

Informations on the genetic constitution (AcP, EsD, PGMl> AK, 6-PGD, Hb, Hp, Cp and Gc blood systems) of the Tofinu, a lacustrine population living in the pile-work of the Guinean coast (Southern Benin), are reported. The Tofinu gene fre¬quencies are much as would be expected from the geographical position of this country. The AcP, Hp and Hb fJ gene frequencies are compared with those of the other eth¬nic groups of Southern Benin as the Goun, Fon, Djedje, and Nago, using the contingen¬cy chi-square test of homogeneity. On the average, the five groups do not show any sig¬nificant differences. Thus it results that there seems to be a common genetic origin and that the cultural-linguistic differentiation followed the evolutive biological process for the populations of this country

The determination of the Cp and Hp polymorphisms

The phenotypes of the Cp and Hp serum polvmorphisms were de¬termined on a total of 22 Macaca fuscata fuscata. For the Cp types a single band was observed with a fast mobility in respect to the human Cp B band. Referring to the Hp system for some samples, in addition to the usual single band corresponding to the human Hp 1-1, one additional faint band which migrated in the approximate position of the slower¬moving human Hp 2-1 band was observed. Such a result is discussed

Deletion polymorphism of GSTT1 gene as protective marker for allergic rhinitis

Background and Aims: Allergic rhinitis (AR) is one of the most common respiratory diseases among human populations. Strong evidence suggests that genetic predisposition and environmental factors could contribute to the development of this complex disease. Glutathione S-transferases (GSTs) are biomarkers of inflammation and oxidative stress. These phase II enzymes play a significant role in detoxifying xenobiotic compounds. To analyze the role of GST gene polymorphisms in AR pathogenesis in a case-control population of 103 patients affected by AR and 200 healthy non-allergic subjects. Methods: We screened genomic DNA extracted from buccal cells for GSTM1 positive/null, GSTP1*I105V (rs1695) and GSTT1 positive/null polymorphisms. The X2-test, odds ratio (OR) and logistic regression were used as statistical analyses. Results: Significant differences in null genotype distribution between AR patients (13%) and healthy controls (30%) were found for the GSTT1 null genotype (OR=0.30, 95% confidence interval=0.14-0.65; P=0.001). GSTM1 and GSTP1 polymorphisms did not show any significant results. Conclusion: Our data indicated that GSTT1 may be a susceptibility locus for AR. Specifically, the positive/null polymorphism of GSTT1 may be involved in an oxidative stress-related mechanism that may enhance pathogenic pathways related to AR. Moreover, beside GSTT1, this deletion polymorphism affects also another gene potentially related to AR phenotype, LOC391322. This gene belongs to MIF (macrophage migration inhibitory factor) gene family and several studies indicated the role of this gene in several immunology-related phenotypes. Therefore, two different scenarios may explain the observed genetic association

A bio-anthropological study on the Central African Mbugu, Sango and Yakpa: some genetic erythrocyte and serum polymorphisms

According to the population census of 1975, the Central Afric2n Republic counts 1.713.000 inhabitants. The mean density is of 4 inhab./km ,but there is a great disproportion between the northern region and the central - sout¬hern one, more densely populated /0. M. S., 1977/. In this area 53 % of the population are represented by the Banda, settled about in the XVIII century to escape the Nubian slave - raids from the east. The Banda belong to the equatqrial branch of the eastern Nigritic peoples /Murdock, 1959/. In the south they adjoin to the Ngbandi-Yakoma river popu¬lations, who live along the right /Central Africa/ and left /Zaire/ banks of the Upper and Middle Ubangui river. The Ngbandi-Yakoma are a very homogene-ous fisher group speaking a Sudanic language of the eastern stock. Their eastern neighbours are the N•Zakara and Azande. The "Basse Kotto" District is included in the savanna belt, l.n the sou¬thern country of the central area. It is prevalently inhabited by the Yakpa, and Banda tribes, busy at farming /cotton, coffee, food growing to family use, manioc, sesame and peanut/, by the Mbugu, farmer populations too, with an uncertain ethnic-linguistic position and by the Sango, belonging to the Ngbandi-Yakoma group. The language of this population is the most diffused in the Ubangui region since 1930. The Yakpa, Mbugu and Sango are unknown from the bio - anthropological viewpoint. For this reason we have considered very interesting to carry out such a survey to verify on biological basis too, the Mbugu•s ethnic-linguis¬tic position among the residual groups, descendants by the ancient Neolithic Cushitic immigrants, at present settled isolatedly north of the Lake Tanga¬nyika /Murdock, 1959; Biasutti, 1967/ or their position among the Banda /Cirard, 1901/. For this purpose we have compared the Mbugu with the Yakpa and Sango of the "Basse Kotto" regarding to the distribution of several genetic polymor¬phisms