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The study begins with a comprehensive experimental investigation into the cutting capability of SS 431 steel using abrasive water jet machining (AWJM), focusing on optimizing the process through a response surface methodology (RSM-BBD) approach. Parametric analysis of the AWJM process identified the key factors affecting the cutting performance, such as the abrasive water pressure, standoff distance, and traverse speed. An increase in the water jet pressure and standoff distance which improves the material removal rate by 42.25%. As the standoff distance decreased, surface quality was improved by 7.89%. The surface characteristics and material removal rate results correlated with the optimized machining parameters, providing insights into the trade-off machining efficiency.

The study begins with a comprehensive experimental investigation into the cutting capability of SS 431 steel using abrasive water jet machining (AWJM), focusing on optimizing the process through a response surface methodology (RSM-BBD) approach. Parametric analysis of the AWJM process identified the key factors affecting the cutting performance, such as the abrasive water pressure, standoff distance, and traverse speed. An increase in the water jet pressure and standoff distance which improves the material removal rate by 42.25%. As the standoff distance decreased, surface quality was improved by 7.89%. The surface characteristics and material removal rate results correlated with the optimized machining parameters, providing insights into the trade-off machining efficiency. [ABSTRACT FROM AUTHOR]

In this work, radioactivity levels and distributions of natural radionuclides in selected fertilizer samples from Tiruvannamalai locality, Tamil Nadu, India were investigated. Various types of chemical fertilizer samples such as calcium nitrate (CN), Urea (U), Sulphur (S), Complex Fertilizer (CF) and Spic Surabi (SS) were collected from the manufacturers and suppliers of Tiruvannamalai locality, Tamil Nadu, India. Activity concentration of natural radionuclides in different fertilizer samples were measured by gamma counting system. Hazard parameters have been calculated for different studied samples. The following parameters were studied: Radium Equivalent Activity (Raeq), Absorbed dose rate (DR), Annual Effective Dose Rate (AEDR), Gamma Index (Iγ), External Hazard Index (Hex), Activity utilisation index (AUI), and Cancer risk (CR). The mean activity concentrations of uranium, thorium and potassium were 188.56, 27.06 and 579.0 Bq.kg−1 respectively. Obtained activity concentrations as well as hazard parameters were compared with world recommended values. Results shown that hazard parameters for studied samples were less than the international recommended values except AUI and CR. [ABSTRACT FROM AUTHOR]

We report on the properties of defects in exfoliated graphene on SiO2 produced by electron irradiation at 25 keV and dosages from 4.96 × 1015 to 9.56 × 1017 electrons/cm2. With increasing dosage, graphene exhibits the two-stage amorphization trajectory reported for the Ar ion bombardment of graphene. Initially, the ratio of the D-peak height, ID, to the G peak height, IG, increases as new defects are formed. In the second stage, ID/IG decreases as defects cover most of the sample. In the second stage, we find that the full width at half maximum of the Raman 2D, D, and G peaks increases by 3, 3, and 6 cm−1, respectively. These values are less by factors of about 10, 5, and 10, respectively, than those reported for amorphous graphene produced by Ar ion bombardment. We find that ID/IG monotonically decreases in the second stage as the annealing temperature increases from 80 to 220 °C. Assuming that ID/IG is proportional to the defect density, we find an activation energy for defect healing, Ea = 0.48 eV, which is significantly less than Ea = 0.95 eV reported for vacancies and closer to Ea = 0.29 and 0.58 eV reported for hydrogen and hydroxyl group adsorbates, respectively. We propose that, in the second stage, graphene does not become amorphous, and the defects responsible for the D peak are adsorbates. [ABSTRACT FROM AUTHOR]

This study investigated [Ca.sup.2+]-cycling properties of sarcoplasmic reticulum (SR) in right ventricle (RV) and left ventricle (LV) of normal rat myocardium. Intracellular [Ca.sup.2+] transients and contractile function were monitored in freshly isolated myocytes from RV and LV. SR in RV displayed nearly fourfold lower rates of ATP-energized [Ca.sup.2+] uptake in vitro than SR of LV. The [Ca.sup.2+] concentration required for half-maximal activation of [Ca.sup.2+] transport was nearly twofold higher in SR of RV. The lower [Ca.sup.2+]-sequestering activity of SR in RV was accompanied by a matching decrement in [Ca.sup.2+]-induced phosphoenzyme formation during the catalytic cycle of the [Ca.sup.2+]-pumping ATPase (SERCA2). Western immunoblot analysis showed that protein levels of [Ca.sup.2+]-ATPase and its inhibitor phospholamban (PLN) were only ~15% lower in SR of RV than in SR of LV. Coimmunoprecipitation experiments revealed that PLN-bound, functionally inert [Ca.sup.2+]-ATPase molecules in SR of RV greatly exceed (>50%) that in SR of LV. Endogenous [Ca.sup.2+]/calmodulin-dependent protein kinase-mediated phosphorylation of SR substrates did not abolish the huge disparity in SR [Ca.sup.2+] pump function between RV and LV. Intracellular [Ca.sup.2+] transients, evoked by electrical field stimulation, were significantly prolonged in RV myocytes compared with LV myocytes, mainly because of slow decay of intracellular [Ca.sup.2+] concentration. The slow decay of intracellular [Ca.sup.2+] concentration in RV and consequent decrease in the speed of RV relaxation may promote temporal synchrony of the end of diastole in RV and LV. The preponderance of functionally silent SR [Ca.sup.2+] pumps in RV reflects a higher diastolic reserve required to protect and maintain RV function in the face of a sudden rise in afterload or resistance in the pulmonary circulation. calcium-adenosinetriphosphatase; phospholamban; phosphoenzyme; calcium transient; diastolic reserve