Use of the Spin-Trapping Method for the Study of Stable Radicals Produced in Solid Dihydrothymine

ESR spin-trapping method has been used for the study of radiation-induced radicals in· powdered dihydrothymine. Four approximately equal small proton couplings (AH\u27 = 0.35 mT), a larger proton coupling (AH = 0.195 mT) and a nitrogen coupling (AN = = 0.295 mT) are attributed to the nitroxide radical formed by reaction of the spin trap with 6-dihydrothymyl radical upon dissolving of dihydrothymine. In the pyrimidine bases of nucleic acid and a number of related compounds irradiated in solid state and dissolved, no signs of the trapped radicals were observed

Neutron Activation Analysis of Traces of Palladium, Gold, and Iridium in Supernates from the Refining of Precious Metals

In the refining of precious metals it is desirable to be able to determine amounts \u27of the elements remaining in solution after various precipitations. Neutron-activation analysis can be used advantageously in this field, and in the present report the application of the method for the determination of traces of palladium, gold and iridium is described. The nuclear reactor BEPO at Harwell was used as the source of neutrons and each of the three elements could be determined wHh high sensitivity in a 0.5-ml aliquot of a sample solution. Results of analyses of microgram and submicrogram quantities of palladium, gold and iridium in the solutions under investigation showed good precision

Symmetric and antisymmetric exchange anisotropies in quasi-one-dimensional CuSe2_2O5_5 as revealed by ESR

We present an electron spin resonance (ESR) study of single-crystalline spin chain-system CuSe$_2$O$_5$ in the frequency range between 9 GHz and 450 GHz. In a wide temperature range above the N\'{e}el temperature $T_N=17$ K we observe strong and anisotropic frequency dependence of a resonance linewidth. Although sizeable interchain interaction $J_{IC}\approx 0.1 J$ ($J$ is the intrachain interaction) is present in this system, the ESR results agree well with the Oshikawa-Affleck theory for one-dimensional $S=1/2$ Heisenberg antiferromagnet. This theory is used to extract the anisotropies present in CuSe$_2$O$_5$. We find that the symmetric anisotropic exchange $J_c=(0.04 \pm 0.01) \:J$ and the antisymmetric Dzyaloshinskii-Moriya (DM) interaction $D=(0.05\pm 0.01)\:J$ are very similar in size in this system. Staggered-field susceptibility induced by the presence of the DM interaction is witnessed in the macroscopic susceptibility anisotropy.Comment: 8 pages, 7 figures, 2 tables, published in Phys. Rev.

Linear compression behaviour of oil palm empty fruit bunches

Received: January 29th, 2021 ; Accepted: April 8th, 2021 ; Published: May 20th, 2021 ; Correspondence: [email protected] study describes the mechanical behaviour of oil palm empty fruit bunches (EFB) as a promising product for pyrolysis production. The EFB samples mixture of moisture content 6.3 ± 0.3 (% d.b.) were grouped into different fraction sizes of 10, 20, 40 and 100 mm. The initial pressing height of each fraction size was measured at 60 mm and compressed at a maximum force of 4,500 N and speed of 10 mm min-1 to obtain the force-deformation dependencies using the universal compression machine and pressing vessel of diameter 60 mm with a plunger. Deformation, deformation energy, volume energy and strain were calculated. While deformation decreased with fraction sizes, deformation energy increased. The deformation energies at fraction sizes from 10 mm to 100 mm indicated energy savings of approximately 23%. The optimal fraction size in relation to energy efficiency was observed at 10 mm. The tangent model accurately described the mechanical behaviour of the EFB samples mixture. The results provide useful information for the design of optimal technology for processing EFB for energy purposes

Utilization of image analysis for description of drying characteristics of selected tropical fruits

ArticleThis study is focused on the utilization of image analysis for description of dimensions, and colours changes of fruits during drying process. Selected tropical fruits such are banana (Musa acuminata), mango (Magnifera indica) and pineapple (Ananas comosus) originally from North Sumatera in Indonesia were used in this experiment. Sliced pieces of the fruits were dried in experimental oven under temperature 90 °C for period of time 180 min and image of fruits samples were recorded by digital camera with HD resolution continuously throughout drying process. With aid of image analysis using Image J software and regarding to drying characteristics the colours and dimensions of the samples were analysed

Theoretical analysis of force, pressure and energy distributions of bulk oil palm kernels along the screwline of a mechanical screw press FL 200

ArticleThe present study is a follow-up of the previously published study on the mathematical description of loading curves and deformation energy of bulk oil palm kernels under compression loading, aimed at determining theoretically the amounts of force, pressure and energy along the screw lamella positions of the screw press FL 200 by applying the tangent curve mathematical model and the screwline geometry parameters (screw shaft diameter, screw inner and outer diameters, screw pitch diameter and the screw thickness). The fitting curve value of the tangent mathematical model was further examined at = 2 and = 3 by identifying the force, deformation, stress and compression coefficients at varying vessel diameters and initial pressing heights of the bulk oil palm kernels. Based on the results of the stepwise regression analysis, the amounts of the theoretical deformation energy in linear pressing as well as the theoretical force , pressure and energy of the screw press FL 200 were statistically significant (P-value significance F) in relation to the predictors ( , , and ). The coefficient of determination (R2 ) values between 61 and 86 % were observed for the determined regression models indicating that the responses , , and can accurately be predicted by the corresponding predictors. The normal probability plots of the responses approximately showed a normal distribution

3D image analysis of the shapes and dimensions of several tropical fruits

ArticleT hree dimension virtual models of Avocado ( Persea americana ) , Salak ( Salacca zalacca ) , Dragon fruit ( Hylocereus undatus ) , Mango ( Mangifera indica ) , Coconut ( Cocos nucifera ) using 3D scanner Intel RealSense were determined. C alculated models based on arithmetic and geometric diameter were also determined. From statistically analysis implies that virtual models on significance level 0 .05 are significantly different with calculated values based on arithmetic or geometric diameter

Mathematical description of loading curves and deformation energy of bulk oil palm kernels

ArticleThe study aimed at describing the experimental and theoretical relationships between t he force and deformation curves as well as the deformation energy of bulk oil palm kernels under compression loading. V essel diameters of 60, 80 and 100 mm with initial pressing heights of the bulk kernels measured at 40, 60 and 80 mm were examined by appl ying a maximum compressive force of 200 kN and a speed of 5 mm min - 1 . For the theoretical description of the force and deformation curves, the tangent curve mathematical model was applied using the MathCAD 14 software where the force coefficient of mechani cal behaviour, A (kN), the deformation coefficient of mechanical behaviour, B (mm - 1 ) and the fitting curve function exponent, n ( - ) were determined respectively. The determined coefficients in addition to the maximum deformation values obtained from the co mpression test were used for the estimation of the theoretical or analytical deformation energy. The determined regression models expressing the deformation, numerical energy and theoretical energy as well as the tangent model coefficients A and B dependen t on the vessel diameter and pressing height were statistically significant ( P < 0.05) or ( F - ratio > F - critical) . Improving the mechanical pressing of oil extraction for both domestic and industrial applications still remain a concer n of researchers and en gineers

Site-selective quantum correlations revealed by magnetic anisotropy in the tetramer system SeCuO3

We present the investigation of a monoclinic compound SeCuO3 using x-ray powder diffraction, magnetization, torque and electron-spin-resonance (ESR). Structurally based analysis suggests that SeCuO3 can be considered as a 3D network of tetramers. The values of intra-tetramer exchange interactions are extracted from the temperature dependence of the susceptibility and amount to ~200 K. The inter-tetramer coupling leads to the development of long-range antiferromagnetic order at TN = 8 K. An unusual temperature dependence of the effective g-tensors is observed, accompanied with a rotation of macroscopic magnetic axes. We explain this unique observation as due to site-selective quantum correlations

Simulating H/V spectral ratios (HVSR) of ambient vibrations: a comparison among numerical models

The use of H/V spectral ratios (HVSR) of ambient vibrations to constrain the local seismo-stratigraphical configuration relies on numerical forward models able to connect observations with subsoil seismic properties. Several models were proposed to this purpose in the last decades, which are based on different assumptions about the nature of the ambient vibration wavefield. Performances of nine numerical tools implementing these models have been checked by considering 1600 realistic 1-D subsoil configurations mostly relative to A, B and C Eurocode8 soil classes. Resultant HVSR curves predicted by the models are quite similar both in their general shape and in predicting the resonant soil frequencies, possibly because all of them share the same basic representation of the subsoil as a 1-D stack of flat uniform viscoelastic layers. The common sensitivity to transmission/reflection matrices resulting from that representation explains the well-known correspondence of HVSR maxima to 1-D resonance frequency estimates, regardless of the physical assumptions (about source distribution, radiation pattern, dominating seismic phases, etc.) behind the computational model adopted for simulating HVSR curves. On the other hand, the computational models here considered provide quite different amplitudes for HVSR values corresponding to the resonance frequencies. However, since experimental HVSR amplitudes at the same site are affected by an inherent variability (e.g. due to the possible lack of ergodicity of the ambient vibration stochastic wavefield, non-ideal experimental settings, etc.) and uncertainty about the local seismo-stratigraphical profile (attenuation, 2-D/3-D effects, etc.) observations cannot be used for general scoring of the considered computational models on empirical basis. In this situation, the ‘optimal’ numerical tool to be considered for the forward HVSR modelling must be defined case by case