X-ray Diffraction Mapping for Cultural Heritage Science: a Review of Experimental Configurations and Applications

X-ray diffraction (XRD) mapping consists in the acquisition of XRD patterns at each pixel (or voxel) of an area (or volume). The spatial resolution ranges from the micrometer (μXRD) to the millimeter (MA-XRD) scale, making the technique relevant for tiny samples up to large objects. Although XRD is primarily used for the identification of different materials in (complex) mixtures, additional information regarding the crystallite size, their orientation, and their in-depth distribution can also be obtained. Through mapping, these different types of information can be located on the studied sample/object. Cultural heritage objects are usually highly heterogeneous, and contain both original and later (degradation, conservation) materials. Their structural characterization is required both to determine ancient manufacturing processes and to evaluate their conservation state. Together with other mapping techniques, XRD mapping is increasingly used for these purposes. Here, the authors review applications as well as the various configurations for XRD mapping (synchrotron/laboratory X-ray source, poly-/monochromatic beam, micro/macro beam, 2D/3D, transmission/reflection mode). On-going hardware and software developments will further establish the technique as a key tool in heritage science.     

Inelastic neutron scattering study of dynamical properties of bioprotectant solutions against temperature

In this work inelastic neutron scattering (INS) collected at different temperature values by the IN4 and IN6 spectrometers at the Institute Laue Langevin (ILL, Grenoble, France) on mixtures of two glass-forming bioprotectant systems, i.e. trehalose and glycerol, as a function of concentration are presented. The data analyses show that in the investigated mixtures the fast local dynamics, measured by INS, exhibits a switching-off maximum at very low glycerol content both at very low and very high temperature. This effect can be accounted for by a not-ideal mixing process of the pure constituents which gives rise to an increased hydrogen bonding network strength.     

Novel synthetic route for covalent coupling of biomolecules on super‐paramagnetic hybrid nanoparticles

The immobilization of biomolecules on magnetic nanoparticles is an issue with high potential in different fields. We describe herein a new strategy to immobilize biomolecules on super‐paramagnetic nanoparticles based on the reactivity of vinyl sulfone groups with naturally occurring functional groups present in biomolecules (amine and thiol). A new monomer containing a polymerizable methacryloyl group and a secondary amine group was synthesized and used to prepare super‐paramagnetic hybrid nanoparticles (SP‐HNPs) by two‐step miniemulsion polymerization. The Michael addition reaction of divinyl sulfone (DVS) to the secondary amine groups localized on the nanoparticles surface allows the introduction of the vinyl sulfone function in the SP‐HNPs (SP‐HNPs‐VS). The morphology of the functionalized SP‐HNPs was characterized by transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), dynamic light scattering, and magnetic susceptibility. The capacity of SP‐HNPs‐VS for the immobilization of biomolecules was evaluated with three model proteins: avidin, invertase, and horseradish peroxidase (HRP). The model proteins were successfully immobilized in mild aqueous conditions compatible with the biological nature of the enzymes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Unraveling the Composition of Rembrandt's Impasto through the Identification of Unusual Plumbonacrite by Multimodal X‐ray Diffraction Analysis

Rembrandt (1606–1669) is renowned for his impasto technique, involving his use of lead white paint with outstanding rheological properties. This paint was obtained by combining lead white pigment (a mixture of cerussite PbCO₃ and hydrocerussite Pb₃(CO₃)₂(OH)₂) with an organic binding medium, but the exact formulation used by Rembrandt remains a mystery. A powerful combination of high‐angle and high‐lateral resolution x‐ray diffraction was used to investigate several microscopic paint samples from four Rembrandt masterpieces. A rare lead compound, plumbonacrite (Pb₅(CO₃)₃O(OH)₂), was detected in areas of impasto. This can be considered a fingerprint of Rembrandt's recipe and is evidence of the use of an alkaline binding medium, which sheds a new light on Rembrandt's pictorial technique.     

Global Hypoellipticity for a Class of Pseudo-differential Operators on the Torus

We show that an obstruction of number-theoretical nature appears as a necessary condition for the global hypoellipticity of the pseudo-differential operator \(L=D_t+(a+ib)(t)P(D_x)\) on \(\mathbb {T}^1_t\times \mathbb {T}_x^{N}\). This condition is also sufficient when the symbol \(p(\xi )\) of \(P(D_x)\) has at most logarithmic growth. If \(p(\xi )\) has super-logarithmic growth, we show that the global hypoellipticity of L depends on the change of sign of certain interactions of the coefficients with the symbol \(p(\xi ).\) Moreover, the interplay between the order of vanishing of coefficients with the order of growth of \(p(\xi )\) plays a crucial role in the global hypoellipticity of L. We also describe completely the global hypoellipticity of L in the case where \(P(D_x)\) is homogeneous. Additionally, we explore the influence of irrational approximations of a real number in the global hypoellipticity.

     

X-ray structurally characterized Mo (VI), Fe (III) and Cu (II) complexes of amide-imine conjugate: (bio)catalytic and histidine recognition studies

An amide-imine conjugate, (E)-N′-((2-hydroxybenzen-1-yl) methylene)-4-methylbenzohydrazide (H₂L^PTASAL), derived from 4-methyl-benzoic acid hydrazide (PTA) and 2-hydroxybenzaldehyde is used to prepare Mo (VI), Cu (II) and Fe (III) complexes. The X-ray structurally characterized complexes have been explored as catalyst for amine assisted asymmetric ring opening (ARO) of epoxide, carbon-heteroatom cross-coupling and ethyl benzene oxidation. In addition, their catecholase like activities have thoroughly been investigated. Moreover, the Cu (II) complex selectively recognizes histidine by fluorescence spectroscopy.     

A Process-Based Pore Network Model Construction for Granular Packings Under Large Plastic Deformations

Transport in Porous Media - We propose a process-based method for constructing a pore network model of granular packings under large deformations. The method uses the radical Voronoi tessellation...     

Numerical modeling of the immune response to human papillomavirus infection

In this work, we develop mathematical models describing the interactions between Human papillomavirus (HPV)-infected cells and the immune system. We start with simple models in order to capture the most important features of such interactions. Then, we proceed to consider fundamental immunological characteristics for the models. For the numerical counterpart, we develop and implement efficient numerical discretizations of our models in order to illustrate the behavior of the schemes using different initial conditions, which represent the degree of infection of the disease. Understanding such interactions is of paramount importance for the prevention and the potential eradication of the infection. One main goal of this research is to analyze how and under what circumstances the immune system succeeds in eliminating HPV-infected cells.     

Measuring the efficiency of highway maintenance contracting strategies: A bootstrapped non-parametric meta-frontier approach

Highly deteriorated US road infrastructure, major budgetary restrictions and the significant growth in traffic have led to an emerging need for improving performance of highway maintenance practices. Privatizing some portions of road maintenance operations by state Departments of Transportation (DOTs) under the auspices of performance-based contracts has been one of the innovative initiatives in response to such a need. This paper adapts the non-parametric meta-frontier framework to the two-stage bootstrapping technique to develop an analytical approach for evaluating the relative efficiency of two highway maintenance contracting strategies. The first strategy pertains to the 180 miles of Virginia’s Interstate highways maintained by Virginia DOT using traditional maintenance practices. The second strategy pertains to the 250 miles of Virginia’s Interstate highways maintained via a Public Private Partnership using a performance-based maintenance approach. The meta-frontier approach accounts for the heterogeneity that exists among different types of highway maintenance contracts due to different limitations and regulations. The two-stage bootstrapping technique accounts for the large set of uncontrollable factors that affect the highway deterioration processes. The preliminary findings, based on the historical data for the state of Virginia, suggest that road authorities (counties) that have used traditional contracting for transforming the maintenance expenditures into the improvement of the road conditions seem to be more efficient than road authorities that have used the performance-based contracting. This paper recommends that road authorities use hybrid contracting approaches that include best practices of both traditional and performance-based highway maintenance contracting.     

Balancing life with glycoconjugates: monitoring unfolded protein response-mediated anti-angiogenic action of tunicamycin by Raman Spectroscopy

Asparagine-linked protein glycosylation is a hallmark for glycoprotein structure and function. Its impairment by tunicamycin [a competitive inhibitor of N-acetylglucosaminyl 1-phosphate transferase (GPT)] has been known to inhibit neo-vascularization (i.e., angiogenesis) in humanized breast tumor due to an induction of ER stress-mediated unfolded protein response (UPR). The studies presented here demonstrate that (i) tunicamycin (i) inhibits capillary endothelial cell proliferation in a dose dependent manner; (ii) treated cells are incapable of forming colonies upon its withdrawal; and (iii) tunicamycin treatment causes nuclear fragmentation. Tunicamycin-induced ER stress-mediated UPR event in these cells was studied with the aid of Raman spectroscopy, in particular, the interpretation of bands at 1672, 1684 and 1694 cm(-1), which are characteristics of proteins and originate from C=O stretching vibrations of mono-substituted amides. In tunicamycin-treated cells these bands decreased in area as follows: at 1672 cm(-1) by 41.85% at 3 h and 55.39% at 12 h; at 1684 cm(-1) by 20.63% at 3 h and 40.08% at 12 h; and also at 1994 cm(-1) by 33.33% at 3 h and 32.92% at 12 h, respectively. Thus, in the presence of tunicamycin, newly synthesized protein chains fail to arrange properly into their final secondary and/or tertiary structures, and the random coils they form had undergone further degradation.