Photodisintegration of light nuclei for testing a correlated realistic interaction in the continuum

An exact calculation of the photodisintegration cross section of 3H, 3He and 4He is performed using as interaction the correlated Argonne V18 potential, constructed within the Unitary Correlation Operator Method (VUCOM). Calculations are carried out using the Lorentz Integral Transform method in conjunction with an hyperspherical harmonics basis expansion. A comparison with other realistic potentials and with available experimental data is discussed. The VUCOM potential leads to a very similar description of the cross section as the Argonne V18 interaction with the inclusion of the Urbana IX three-body force for photon energies 45< w < 120 MeV, while larger differences are found close to threshold.Comment: 9 pages, 6 figure

Quantifying mixing using magnetic resonance imaging.

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media (1, 2). The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile (1)H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products

Multi-material topology optimization of adhesive backing layers via J-integral and strain energy minimizations

Strong adhesives rely on reduced stress concentrations, often obtained via specific geometry or composition of materials. In many examples in nature and engineering prototypes, the adhesive performance relies on structural rigidity being placed in specific locations. A few design principles have been formulated, based on parametric optimization, while a general design tool is still missing. We propose to use topology optimization to achieve optimal stiffness distribution in a multi-material adhesive backing layer, reducing stress concentration at specified locations. The method involves the minimization of a linear combination of J-integral and strain energy. While the J-integral minimization is aimed at reducing stress concentration, we observe that the combination of these two objectives ultimately provides the best results. We analyze three cases in plane strain conditions, namely (i) double-edged crack and (ii) center crack in tension and (iii) edge crack under shear. Each case evidences a different optimal topology with (i) and (ii) providing similar results. The optimal topology allocates stiffness in regions that are far away from the crack tip, intuitively, but the allocation of softer materials over stiffer ones can be non-trivial. To test our solutions, we plot the contact stress distribution across the interface. In all observed cases, we eliminate the stress singularity at the crack tip. Stress concentrations might arise in locations far away from the crack tip, but the final results are independent of crack size. Our method ultimately provides optimal, flaw tolerant, adhesives where the crack location is known

Photonuclear sum rules and the tetrahedral configuration of 4^4He

Three well known photonuclear sum rules (SR), i.e. the Thomas-Reiche-Kuhn, the bremsstrahlungs and the polarizability SR are calculated for 4He with the realistic nucleon-nucleon potential Argonne V18 and the three-nucleon force Urbana IX. The relation between these sum rules and the corresponding energy weighted integrals of the cross section is discussed. Two additional equivalences for the bremsstrahlungs SR are given, which connect it to the proton-neutron and neutron-neutron distances. Using them, together with our result for the bremsstrahlungs SR, we find a deviation from the tetrahedral symmetry of the spatial configuration of 4He. The possibility to access this deviation experimentally is discussed.Comment: 13 pages, 1 tabl

π0\pi^0-Photoproduction on the deuteron via Δ\Delta-excitation using the Lorentz Integral Transform

The Lorentz Integral Transform method (LIT) is extended to pion photoproduction in the $\Delta$-resonance region. The main focus lies on the solution of the conceptual difficulties which arise if energy dependent operators for nucleon resonance excitations are considered. In order to demonstrate the applicability of our approach, we calculate the inclusive cross section for $\pi^0$-photoproduction off the deuteron within a simple pure resonance model.Comment: 4 pages, EPJA styl

The six-nucleon Yakubovsky equations for 6He

The six-nucleon problem for the bound state is formulated in the Yakubovsky scheme. Hints for a numerical implementation are provided.Comment: 25 pages, 0 figure

Total Photoabsorption Cross Sections of A=6 Nuclei with Complete Final State Interaction

The total photoabsorption cross sections of 6He and 6Li are calculated microscopically with full inclusion of the six-nucleon final state interaction using semirealistic nucleon-nucleon potentials. The Lorentz Integral Transform (LIT) method and the effective interaction approach for the hyperspherical formalism are employed. While 6Li has a single broad giant resonance peak, there are two well separated peaks for 6He corresponding to the breakup of the neutron halo and the alpha core, respectively. The comparison with the few available experimental data is discussed.Comment: LaTeX, 8 pages, 3 ps figure

Mealybugs in roots of coffee and its associated herbaceous plants in the departament of Nariño

Objetivos: En esta investigación se estudiaron las chinches harinosas (Hemiptera: Pseudococcidae y Putoidae) presentes en las raíces de café (Coffea arabica L.) y de arvenses asociadas a este cultivo. Alcance: En los municipios de Sandoná, Consacá, La Unión, San Pablo y San José de Albán, departamento de Nariño, Colombia. Metodología: Se recogieron 114 muestras a partir de raíces de café y de 17 especies de plantas arvenses asociadas a este cultivo, pertenecientes a las familias botánicas Asclepidaceae, Asteraceae, Commelinaceae, Cyperaceae, Poaceae, Plantaginaceae, Polygonaceae, Solanaceae. Los insectos se colectaron de forma manual, en raíces de plantas que presentaran alguna sintomatología asociada al ataque de estos insectos tales como clorosis y debilitamiento. La identificación taxonómica se realizó a partir de ejemplares montados en lámina para microscopía después de diferentes procesos, con base en la comparación de la morfología externa de las hembras adultas con las claves establecidas para el grupo. Principales resultados: Se identificaron por primera vez en Nariño en el cultivo de café, dos especies pertenecientes a los géneros Puto Signoret ( Putoidae) y Dysmicoccus Ferris (Pseudococcidae). Conclusión: Esta información es importante para incorporarla dentro de planes de manejo integrado de plagas en zonas productoras de café en Nariño y en Colombia. Con este trabajo se aumenta el conocimiento en la distribución de las especies de insectos escama del café en el país.Objectives: The mealybugs (Hemiptera: Pseudococcidae and Putoidae) present in roots of coffee (Coffea arabica L.) and herbaceous plants associated to this crop were studied in this research. Scope: This research was carried out in Sandoná, Consacá, La Union, San Pablo and San José de Albán, municipalities of the Department of Nariño. Methodology: A total of 114 samples were collected from roots of coffee and 17 species of herbaceous plants associated with this crop, belonging to the botanical families Asclepidaceae, Asteraceae, Commelinaceae, Cyperaceae, Poaceae, Plantaginaceae, Polygonaceae and Solanaceae. The specimens were collected manually in roots of plants that presented some symptomatology such as chlorosis and weakening associated with the attack of these insects. The taxonomic identification was made from specimens placed in microscope slides after different processes based on the comparison of the external morphology of the adult female with de taxonomic codes established for the group. Main results: Two species belonging to the genus Puto Signoret (Putoidae family) and Dysmicoccus Ferris (Pseudococcidae family) were identified for the first time in coffee crops in Nariño. Conclusion: This information is important to be incorporated into integrated pest management plans in coffee producing areas in Nariño and in Colombia. The knowledge in the distribution of the species of mealybugs of coffee in the country is enriched with this work

alpha-particle photoabsorption with a realistic nuclear force

The 4He total photoabsorption cross section is calculated with the realistic nucleon-nucleon potential Argonne V18 and the three-nucleon force (3NF) Urbana IX. Final state interaction is included rigorously via the Lorentz Integral Transform method. A rather pronounced giant resonance with peak cross sections of 3 (3.2) mb is obtained with (without) 3NF. Above 50 MeV strong 3NF effects, up to 35%, are present. Good agreement with experiment is found close to threshold. A comparison in the giant resonance region is inconclusive, since present data do not show a unique picture.Comment: 13 pages, 4 figures; corrected experimental data in Fig.4b and slightly modified discussion of Fig.4