A fast-neutron coincidence collar using liquid scintillators for fresh fuel verification

Journal of Radioanalytical and Nuclear Chemistry - The IAEA has developed a liquid scintillator-based system for the non-destructive assay of 235U in fresh fuel assemblies. The fast neutron...     

Iterative atmospheric correction scheme and the polarization color of alpine snow

Characterization of the Earth's surface is crucial to remote sensing, both to map geomorphological features and because subtracting this signal is essential during retrievals of the atmospheric constituents located between the surface and the sensor. Current operational algorithms model the surface total reflectance through a weighted linear combination of a few geometry-dependent kernels, each devised to describe a particular scattering mechanism. The information content of these measurements is overwhelmed by that of instruments with polarization capabilities: proposed models in this case are based on the Fresnel reflectance of an isotropic distribution of facets. Because of its remarkable lack of spectral contrast, the polarized reflectance of land surfaces in the shortwave infrared spectral region, where atmospheric scattering is minimal, can be used to model the surface also at shorter wavelengths, where aerosol retrievals are attempted based on well-established scattering theories.In radiative transfer simulations, straightforward separation of the surface and atmospheric contributions is not possible without approximations because of the coupling introduced by multiple reflections. Within a general inversion framework, the problem can be eliminated by linearizing the radiative transfer calculation, and making the Jacobian (i.e., the derivative expressing the sensitivity of the reflectance with respect to model parameters) available at output. We present a general methodology based on a Gauss–Newton iterative search, which automates this procedure and eliminates de facto the need of an ad hoc atmospheric correction.In this case study we analyze the color variations in the polarized reflectance measured by the NASA Goddard Institute of Space Studies Research Scanning Polarimeter during a survey of late-season snowfields in the High Sierra. This insofar unique dataset presents challenges linked to the rugged topography associated with the alpine environment and a likely high water content due to melting. The analysis benefits from ancillary information provided by the NASA Langley High Spectral Resolution Lidar deployed on the same aircraft.The results obtained from the iterative scheme are contrasted against the surface polarized reflectance obtained ignoring multiple reflections, via the simplistic subtraction of the atmospheric scattering contribution. Finally, the retrieved reflectance is modeled after the scattering properties of a dense collection of ice crystals at the surface. Confirming that the polarized reflectance of snow is spectrally flat would allow to extend the techniques already in use for polarimetric retrievals of aerosol properties over land to the large portion of snow-covered pixels plaguing orbital and suborbital observations.     

Pseudopeptide‐Based Hydrogels Trapping Methylene Blue and Eosin Y

We present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc‐l ‐Phe‐d ‐Oxd‐OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO‐loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO‐loaded hydrogel through π–π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO.     

Relaxation Dynamics and Magnetic Anisotropy in a Low‐Symmetry DyIII Complex

The magnetic behaviour of a Dy(LH)₃ complex (LH^? is the anion of 2‐hydroxy‐N′‐[(E)‐(2‐hydroxy‐3‐methoxyphenyl)methylidene]benzhydrazide) was analysed in depth from both theoretical and experimental points of view. Cantilever torque magnetometry indicated that the complex has Ising‐type anisotropy, and provided two possible directions for the easy axis of anisotropy due to the presence of two magnetically non‐equivalent molecules in the crystal. Ab initio calculations confirmed the strong Ising‐type anisotropy and disentangled the two possible orientations. The computed results obtained by using ab initio calculations were then used to rationalise the composite dynamic behaviour observed for both pure Dy^III phase and Y^III diluted phase, which showed two different relaxation channels in zero and non‐zero static magnetic fields. In particular, we showed that the relaxation behaviour at the higher temperature range can be correctly reproduced by using a master matrix approach, which suggests that Orbach relaxation is occurring through a second excited doublet.     

Existence of strong minimizers for the Griffith static fracture model in dimension two

We consider the Griffith fracture model in two spatial dimensions, and prove existence of strong minimizers, with closed jump set and continuously differentiable deformation fields. One key ingredient, which is the object of the present paper, is a generalization to the vectorial situation of the decay estimate by De Giorgi, Carriero, and Leaci. This is based on replacing the coarea formula by a method to approximate $SB{D}^p$ functions with small jump set by Sobolev functions, and is restricted to two dimensions. The other two ingredients will appear in companion papers and consist respectively in regularity results for vectorial elliptic problems of the elasticity type and in a method to approximate in energy $GSB{D}^p$ functions by $SB{V}^p$ ones.     

Probing the Structure of Lysozyme–Carbon‐Nanotube Hybrids with Molecular Dynamics

Lysozyme has been successfully used to solvate carbon nanotubes (CNT). Extensive molecular dynamics simulations show that 1) a favorite site of adsorption exists, 2) the protein–tube interaction region is located far from the active site, 3) two protein helices act as a tweezer that grips the nanotube, 4) a localized protein re‐arrangement hides the tube from the solvent, and 5) aminic and amidic moieties of lysozyme behave similarly to surfactants in the solvation of the tube.     

Protective Properties of Novel S‐Acyl‐Glutathione Thioesters Against Ultraviolet‐induced Oxidative Stress

UV‐induced toxicity is characterized by marked oxidative stress, accompanied by the depletion of key cellular antioxidants, particularly glutathione (GSH). Replenishing cellular GSH may represent a means of counteracting UV‐induced toxicity: however, treatment with free GSH is not therapeutically effective due to its unfavorable pharmacokinetic properties. In this study, we show that S‐acyl‐glutathione (acyl‐SG) derivatives, which consist of an acyl chain (of variable length and saturation) linked via a thioester bond to GSH, increase intracellular levels of reduced GSH in primary skin fibroblasts, adenocarcinoma HeLa and neuroblastoma SH‐SY5Y cells. Consistent with this, acyl‐SG derivatives protect against UV‐induced reactive oxygen species (ROS) production and UV‐B/C‐mediated lipid peroxidation and caspase‐3 activation in the analyzed cell lines, with unsaturated thioesters displaying a significantly greater protective effect. Taken together, our findings suggest that acyl‐SG thioesters may be therapeutically effective in the treatment of UV‐related skin disorders and oxidative stress‐mediated conditions in general.