Ni and Cu incorporated mesoporous nanocomposite catalytic materials

Nickel and copper incorporated MCM-41-like mesoporous nanocomposite materials prepared by the direct hydrothermal synthesis and the impregnation procedures showed highly attractive pore structure and surface area results for catalytic applications. The XRD patterns showed that characteristic MCM-41 structure was preserved for the materials synthesized following an impregnation procedure before the calcination step. The surface area of the Cu impregnated material with a quite high Cu/Si atomic ratio (0.19) was 631 m2/g. Very narrow pore size distributions with an average pore diameter of about 2.7 nm were obtained as a result of plugging of some of the smaller pores by Cu nanoballs. For lower metal to Si ratios (for instance for Ni/Si = 0.06) much higher surface area values (1130 m2/g) were obtained. In the case of nanocomposite materials synthesized by the direct hydrothermal route, MCM-41 structure was not destroyed for samples containing metal to Si atomic ratios as high as 0.12. In the case of materials containing Cu/Si and Ni/Si ratios over 0.2 wider pore size distributions and some decrease of surface area were observed.     

Stability of phase-contrast tomography

Phase-contrast tomography (PCT) allows three-dimensional imaging of objects that display insufficient contrast for conventional absorption-based tomography. We prove that PCT is stable with respect to high-frequency noise in experimental phase-contrast data, unlike conventional tomography, which is known to be mildly unstable. We use known properties of the three-dimensional x-ray transform and transport-of-intensity equation to construct a matrix representation of the forward PCT operator. We then invert this formula to show that, under natural boundary conditions, the PCT reconstruction operator exists and leads to a unique solution. We show that the singular values s(n) of the reconstruction operator have asymptotic behavior s(n)=O(n(-3/2)), guaranteeing the mathematical stability of the reconstruction process.     

Activity Comparison of Different Solid Acid Catalysts in Etherification of Glycerol with tert-Butyl Alcohol in Flow and Batch Reactors

In the presented work, etherification of glycerol with TBA was investigated in a continuous flow and also in a batch reactor using nine different commercial solid acid catalysts, namely Amberlyst-15, Amberlyst-36, Amberlyst-35, Amberlyst-16, Relite EXC8D, Lewatit K2629, H-Beta, H-Mordenite and Nafion SAC-13. Results proved the advantages of flow reactor to achieve quite high glycerol conversion values in very short residence times, due to efficient contact of reactants with the solid catalyst, which was caused by higher catalyst to reactant ratio within the reactor. Results of batch reactor experiments obtained in the temperature range of 80–200 °C proved the importance of operating temperature on the catalytic performance of these materials. Amberlyst-15, which has the highest Brønsted acidity, gave the highest glycerol conversion at 90–100 °C. However, this material is unstable at temperatures higher than 110 °C. Performances of Amberlyst-36 and Relite EXC8D were the best in the range of 110–150 °C, which started to become unstable at 150 °C. Although the catalytic performance of Nafion-SAC-13 was not as good as Amberlyst type resins at temperatures up to 150 °C, its thermal stability was higher and could be used up to 200 °C. Although Brønsted acidity was the most important property of these materials in the etherification reaction of glycerol, results also proved the importance of diffusion resistance on the observed conversion values, which limited the penetration of glycerol to the active acid sites, especially in the catalysts with smaller pore diameters and at lower temperatures. Increased significance of swelling at higher temperatures, especially with Amberlyst-36 which had lower cross-linking in its structure and less rigidity, contributed to the penetration of the reactants to the active sites. Water produced during the etherification reaction was also shown to cause deactivation of the catalysts by reversible adsorption on the acid sites.     

Oxidative dehydrogenation of ethane over a monolith coated by molybdenum-vanadium-niobium mixed-oxide catalyst

Oxidative dehydrogenation of ethane to ethylene was investigated using Mo 0.71 V 0.21 Nb 0.08 mixed-oxide catalyst, in powder form and coated over a monolith. At 570°C and with a feed stream containing an O 2 /C 2 H 6 mole ratio of one, ethylene selectivity value reaching to 96% was obtained at a conversion level of about 5% with the monolith-supported catalyst. DRIFTS studies indicated the presence of adsorbed ethoxide species. The proposed reaction scheme for the production of ethylene includes the elimination of g -hydrogen of adsorbed species by the lattice oxygen.     

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

Bifunctional monodispersed Fe₃O₄ particles coated with an ultrathin Y₂O₃:Tb³⁺ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe₃O₄ core and outer Y₂O₃:Tb³⁺ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging.     

Carbon Dots-Mediated Fluorescent Scaffolds: Recent Trends in Image-Guided Tissue Engineering Applications

Regeneration of damaged tissues or organs is one of the significant challenges in tissue engineering and regenerative medicine. Many researchers have fabricated various scaffolds to accelerate the tissue regeneration process. However, most of the scaffolds are limited in clinical trials due to scaffold inconsistency, non-biodegradability, and lack of non-invasive techniques to monitor tissue regeneration after implantation. Recently, carbon dots (CDs) mediated fluorescent scaffolds are widely explored for the application of image-guided tissue engineering due to their controlled architecture, light-emitting ability, higher chemical and photostability, excellent biocompatibility, and biodegradability. In this review, we provide an overview of the recent advancement of CDs in terms of their different synthesis methods, tunable physicochemical, mechanical, and optical properties, and their application in tissue engineering. Finally, this review concludes the further research directions that can be explored to apply CDs in tissue engineering.     

Endometriosis and Cancer: Exploring the Role of Macrophages

Endometriosis and cancer have much in common, notably their burgeoning of cells in hypoxic milieus, their invasiveness, and their capacity to trigger remodeling, vascularization, and innervation of other tissues. An important role in these processes is played by permissive microenvironments inhabited by a variety of stromal and immune cells, including macrophages. Remarkable phenotypical plasticity of macrophages makes them a promising therapeutic target; some key issues are the range of macrophage phenotypes characteristic of a particular pathology and the possible manners of its modulation. In both endometriosis and cancer, macrophages guard the lesions from immune surveillance while promoting pathological cell growth, invasion, and metastasis. This review article focuses on a comparative analysis of macrophage behaviors in endometriosis and cancer. We also highlight recent reports on the experimental modulation of macrophage phenotypes in preclinical models of endometriosis and cancer.     

Observation of Electrically Tunable van Hove Singularities in Twisted Bilayer Graphene from NanoARPES

The possibility of triggering correlated phenomena by placing a singularity of the density of states near the Fermi energy remains an intriguing avenue toward engineering the properties of quantum materials. Twisted bilayer graphene is a key material in this regard because the superlattice produced by the rotated graphene layers introduces a van Hove singularity and flat bands near the Fermi energy that cause the emergence of numerous correlated phases, including superconductivity. Direct demonstration of electrostatic control of the superlattice bands over a wide energy range has, so far, been critically missing. This work examines the effect of electrical doping on the electronic band structure of twisted bilayer graphene using a back-gated device architecture for angle-resolved photoemission measurements with a nano-focused light spot. A twist angle of 12.2° is selected such that the superlattice Brillouin zone is sufficiently large to enable identification of van Hove singularities and flat band segments in momentum space. The doping dependence of these features is extracted over an energy range of 0.4 eV, expanding the combinations of twist angle and doping where they can be placed at the Fermi energy and thereby induce new correlated electronic phases in twisted bilayer graphene.     

BankXX: Supporting legal arguments through heuristic retrieval

The BankXX system models the process of perusing and gathering information for argument as a heuristic best-first search for relevant cases, theories, and other domain-specific information. As BankXX searches its heterogeneous and highly interconnected network of domain knowledge, information is incrementally analyzed and amalgamated into a dozen desirable ingredients for argument (called argument pieces), such as citations to cases, applications of legal theories, and references to prototypical factual scenarios. At the conclusion of the search, BankXX outputs the set of argument pieces filled with harvested material relevant to the input problem situation.This research explores the appropriateness of the search paradigm as a framework for harvesting and mining information needed to make legal arguments. In this article, we describe how legal research fits the heuristic search framework and detail how this model is used in BankXX. We describe the BankXX program with emphasis on its representation of legal knowledge and legal argument. We describe the heuristic search mechanism and evaluation functions that drive the program. We give an extended example of the processing of BankXX on the facts of an actual legal case in BankXX's application domain — the good faith question of Chapter 13 personal bankruptcy law. We discuss closely related research on legal knowledge representation and retrieval and the use of search for case retrieval or tasks related to argument creation. Finally we review what we believe are the contributions of this research to the understanding of the diverse disciplines it addresses.This research was supported in part by grant No. 90-0359 from the Air Force Office of Sponsored Research and NSF grant No. EEC-9209623 State/University/Industry Cooperative Research on Intelligent Information Retrieval.