Light Scattering by Cholesteric Skyrmions

We study the light scattering by localized quasi planar excitations of a Cholesteric Liquid Crystal known as spherulites. Due to the anisotropic optical properties of the medium and the peculiar shape of the excitations, we quantitatively evaluate the cross section of the axis-rotation of polarized light. Because of the complexity of the system under consideration, first we give a simplified, but analytical, description of the spherulite and we compare the Born approximation results in this setting with those obtained by resorting to a numerical exact solution. The effects of changing values of the driving external static electric (or magnetic) field is considered. Possible applications of the phenomenon are envisaged.Comment: 18 pages, 14 figure

Groundwater Flow andWater Quality – A Flowpath Study in the SeminoleWell Field, Cedar Rapids, Iowa

In Iowa, alluvial aquifers near major rivers are a source of water for many communities. The City of Cedar Rapids withdraws water from wells completed in the Cedar River alluvium, a shallow alluvial aquifer adjacent to the Cedar River. The City of Cedar Rapids is located within Linn County in east-central Iowa, and water for the City is supplied by four well fields (East, Northwest, Seminole, and West well fields) along the Cedar River. The City has a population of about 121,000, and several large industries are major water users. Currently, per capita water usage in the City is nearly three times the national average. The City is committed to providing both a high quality and quantity of water to its customers. The USGS and Cedar Rapids Water Department have been working together in an ongoing research program to better understand water quality and flow in the Cedar River and alluvial well fields. Work has been done on both a basin and well-field approach and has involved dye tracing/time-of-travel studies on the Cedar River, water-quality sampling, geochemical modeling, and groundwater-flow modeling

Frequency Shifts in Natural Vibrations in Pantographic Metamaterials under Biaxial Tests

In this paper a 2D continuum model, thought as the homogenized limit of a microstructured pantographic sheet, is studied. The microstructure is characterized by two families of parallel fibers, whose deformation measures account for bending, elongation and relative rotation of the fibers. The deformation energy density of the homogenized model depends on both first and second gradients of the displacement. Modal analysis is performed in order to assess the peculiarities of the dynamic behavior of higher gradient models, and in particular the difference, with respect to classical laminae, in the dependence of the eigenfrequencies on the stiffness

Grasp planning with a soft reconfigurable gripper exploiting embedded and environmental constraints

Grasping in unstructured environments requires highly adaptable and versatile hands together with strategies to exploit their features to get robust grasps. This paper presents a method to grasp objects using a novel reconfigurable soft gripper with embodied constraints, the Soft ScoopGripper (SSG). The considered grasp strategy, called scoop grasp, exploits the SSG features to perform robust grasps. The embodied constraint, i.e., a scoop, is used to slide between the object and a flat surface (e.g., a table or a wall) in contact with it. The fingers are first configured according to object geometry and then used to establish reliable contact with it. Given the object to be grasped, the proposed grasp planner chooses the best configuration of the fingers and the scoop based on the object point cloud and then suitably aligns the gripper to it

Do electrospray mass spectra of surfactants mirror their aggregation state in solution?

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The interaction of native DNA with Zn(II) and Cu(II) complexes of 5-triethyl ammonium methyl salicylidene orto-phenylendiimine

The interaction of native calf thymus DNA with the Zn(II) and Cu(II) complexes of 5-triethyl ammonium methyl salicylidene ortophenylendiimine (ZnL2+ and CuL2+), in 1 mM Tris-HCl aqueous solutions at neutral pH, has been monitored as a function of the metal complex-DNA molar ratio by UV absorption spectro photometry, circular dichroism (CD) and fluorescence spectroscopy. The results support for an intercalative interaction of both ZnL2+ and CuL2+ with DNA, showing CuL2+ an affinity of approximately 10 times higher than ZnL2+. In particular, the values of the binding constant, determined by UV spectrophotometric titration, equal to 7.3 x 10(4) and 1.3 x 10(6) M-1. for ZnL2+ and CuL2+, respectively, indicate the occurrence of a marked interaction with a binding size of about 0.7 in base pairs. The temperature dependence of the absorbance at 258 nm suggests that both complexes strongly increase the DNA melting temperature (Tm) already at metal complex-DNA molar ratios equal to 0.1. As evidenced by the quenching of the fluorescence of ethidium bromide-DNA solutions in the presence of increasing amounts of metal complex, ZnL2+ and CuL2+ are able to displace the ethidium cation intercalated into DNA. A tight ZnL2+-DNA and CuL2+-DNA binding has been also proven by the appearance, in both metal complex-DNA solutions, of a broad induced CD band in the range 350-450 nm. In the case of the CuL2+-DNA system, the shape of the CD spectrum, at high CuL2+ content, is similar to that observed for psi-DNA solutions. Such result allowed us to hypothesize that CuL2+ induces the formation of supramolecular aggregates of DNA in aqueous solutions

Fibrin clot adhesion to conditioned root surfaces: an in vitro study with scanning electron microscopy analysis

Aim: Periodontal regeneration is contingent on the adhesion and maturation of fibrin clot to a root surface exposed to periodontal disease. Root surface demineralization in vitro improves the formation of a stable union between the fibrin clot and the root surface. In scientific literature there are not studies of comparison that stand which demineralizing agent is the best in promoting fibrin clot adhesion. The aim of this study was to evaluate and compare the efficacy of six root conditionings in removing the smear layer and developing the fibrin clot in static and dynamic conditions. Methods: 36 single-root teeth extracted for periodontal disease were cut with a microtome in order to obtain 72 specimens that were divided in three groups: 24 samples not covered with blood, 24 covered with fresh human whole blood, 24 covered with blood and rinsed in a rotary shaker table (Vortex\uae). 4 specimens from each group were conditioned for 3 minutes with: physiological saline solution (FISIO) as the control group, saturated solution of citric acid 25% (AC), ethylenediaminetetraacetic acid 24% (EDTA), a solution of tetracycline 200mg/mL (TETRA), a solution of tetracycline and citric acid (TETRA+AC), Prefgel\uae and successively Emdogain\uae (EMD). Then the 48 samples from group 2 and 3 were covered with blood, which was allowed to coagulate for 20 minutes in a 37\ub0C chamber. The blocks were rinsed and dehydrated under standardized conditions; specimens of group 3 were vortexed (100rpm). All the blocks were then sputtered with gold and analyzed with SEM. SEM images were evaluated by two blinded examiners, starting from the cementoenamel junction (CEJ), at 5 standardized points 2 mm distant from each other. A statistical analysis was performed. Results: EMD samples showed a more disorganized smear layer, in which is probably present the residual vehicle (propylene glycol alginate). However, in the 90% of all the specimens smear layer was found. AC treated samples showed a firmly adherent fibrin clot that covered the surfaces for the 70% of the specimens (the data was statistically relevant). Same results were found in TETRA+AC samples. The conditioning with EDTA, TETRA and EMD resulted in a sparsely organized clot worsened by the application of tensile forces, especially in TETRA samples. Only few blood cells without any clot organization were found in the control group, confirming that conditioning root surfaces improves the fibrin clot adhesion. Conclusion: The best formation of fibrin clot was observed for AC treated samples; this is probably due to the increase of root surface wettability caused by AC. The other root conditioning agents, even if lead to results better than the control group, are more susceptible to external forces and do not promote a stable fibrin clot adhesion