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1.
Sci Rep ; 9(1): 18857, 2019 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-31827165

RESUMO

Combining micro-X-ray absorption spectroscopy (µXAS) and micro-X-ray fluorescence spectroscopy (µXRF) is a promising approach for the investigation of complex multi-phase systems. In this work, we have employed this approach to investigate natural sphalerite, the most common form of Zinc Sulfide. Spatially resolved elemental distribution maps of common 3d metal atoms (Zn, Cu, Ni, Co, and Fe) are superimposed with chemical speciation and structural parameter maps in order to understand the sphaleriteore-formation process and metamorphosis. Chemical speciation and structural parameters have been obtained by analyzing the µXAS spectra collected in several representative points of the sample, after µXRF mapping. In the present case, this X-ray based approach has permitted to determine the spatial distribution of the Zn species in sphalerite. The presence of two main zincite and smithsonite inclusions has been established, with the latter located close to copper impurity center. Since copper is known to remarkably reduce the corrosion resistance of zinc, resulting in the formation of carbonate as the corrosion product, this implies a possible role of Cu in the growth of the carbonate inclusions. The results obtained highlight the efficiency of this method in univocally identifying the spatial distribution of phases in complex systems, thanks to the simultaneous access to complementary information.

2.
Int J Mol Sci ; 20(19)2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31554226

RESUMO

Selenocompounds (SeCs) are well-known nutrients and promising candidates for cancer therapy; however, treatment efficacy is very heterogeneous and the mechanism of action is not fully understood. Several SeCs have been reported to have albumin-binding ability, which is an important factor in determining the treatment efficacy of drugs. In the present investigation, we hypothesized that extracellular albumin might orchestrate SeCs efficacy. Four SeCs representing distinct categories were selected to investigate their cytotoxicity, cellular uptake, and species transformation. Concomitant treatment of albumin greatly decreased cytotoxicity and cellular uptake of SeCs. Using both X-ray absorption spectroscopy and hyphenated mass spectrometry, we confirmed the formation of macromolecular conjugates between SeCs and albumin. Although the conjugate was still internalized, possibly via albumin scavenger receptors expressed on the cell surface, the uptake was strongly inhibited by excess albumin. In summary, the present investigation established the importance of extracellular albumin binding in determining SeCs cytotoxicity. Due to the fact that albumin content is higher in humans and animals than in cell cultures, and varies among many patient categories, our results are believed to have high translational impact and clinical implications.


Assuntos
Albuminas/química , Sequestrantes/química , Sequestrantes/farmacologia , Albuminas/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Estrutura Molecular , Espécies Reativas de Oxigênio/metabolismo , Análise Espectral
3.
Nat Mater ; 18(8): 866-873, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31263227

RESUMO

Subnanometric metal species (single atoms and clusters) have been demonstrated to be unique compared with their nanoparticulate counterparts. However, the poor stabilization of subnanometric metal species towards sintering at high temperature (>500 °C) under oxidative or reductive reaction conditions limits their catalytic application. Zeolites can serve as an ideal support to stabilize subnanometric metal catalysts, but it is challenging to localize subnanometric metal species on specific sites and modulate their reactivity. We have achieved a very high preference for localization of highly stable subnanometric Pt and PtSn clusters in the sinusoidal channels of purely siliceous MFI zeolite, as revealed by atomically resolved electron microscopy combining high-angle annular dark-field and integrated differential phase contrast imaging techniques. These catalysts show very high stability, selectivity and activity for the industrially important dehydrogenation of propane to form propylene. This stabilization strategy could be extended to other crystalline porous materials.

4.
Angew Chem Int Ed Engl ; 58(38): 13550-13555, 2019 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-31309662

RESUMO

Metal-organic frameworks (MOFs) capable of mobility and manipulation are attractive materials for potential applications in targeted drug delivery, catalysis, and small-scale machines. One way of rendering MOFs navigable is incorporating magnetically responsive nanostructures, which usually involve at least two preparation steps: the growth of the magnetic nanomaterial and its incorporation during the synthesis of the MOF crystals. Now, by using optimal combinations of salts and ligands, zeolitic imidazolate framework composite structures with ferrimagnetic behavior can be readily obtained via a one-step synthetic procedure, that is, without the incorporation of extrinsic magnetic components. The ferrimagnetism of the composite originates from binary oxides of iron and transition metals such as cobalt. This approach exhibits similarities to the natural mineralization of iron oxide species, as is observed in ores and in biomineralization.

5.
J Phys Chem Lett ; 10(12): 3359-3368, 2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31141374

RESUMO

Lithium-rich transition-metal-oxide cathodes are among the most promising materials for next generation lithium-ion-batteries because they operate at high voltages and deliver high capacities. However, their cycle-life remains limited, and individual roles of the transition-metals are still not fully understood. Using bulk-sensitive X-ray absorption and emission spectroscopy on Li[Li0.2Ni0.16Mn0.56Co0.08]O2, we inspect the behavior of Mn, generally considered inert upon the electrochemical process. During the first charge Mn appears to be redox-active showing a partial transformation from high-spin Mn4+ to Mn3+ in both high and low spin configurations, where the latter is expected to favor reversible cycling. The Mn redox-state with cycling continues changing in opposition to the expected charge compensation and is correlated with Ni oxidation/reduction, also spatially. The findings suggest that strain induced on the Mn-O sublattice by Ni oxidation triggers Mn reduction. These results unravel the Mn role in controlling the electrochemistry of Li-rich cathodes.

6.
Inorg Chem ; 58(8): 4935-4944, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30920816

RESUMO

Iron is an essential nutrient for nearly all forms of life, although scarcely available due to its poor solubility in nature and complex formation in higher eukaryotes. Microorganisms have evolved a vast array of strategies to acquire iron, the most common being the production of high-affinity iron chelators, termed siderophores. The opportunistic bacterial pathogen Pseudomonas aeruginosa synthesizes and secretes two siderophores, pyoverdine (PVD) and pyochelin (PCH), characterized by very different structural and functional properties. Due to its chemical similarity with Fe(III), Ga(III) interferes with several iron-dependent biological pathways. Both PVD and PCH bind Fe(III) and Ga(III). However, while the Ga-PCH complex is more effective than Ga(III) in inhibiting P. aeruginosa growth, PVD acts as a Ga(III) scavenger and protects bacteria from Ga(III) toxicity. To gain more insight into the different outcomes of the biological paths observed for the Fe(III) and Ga(III)-siderophore complexes, better knowledge is needed of their coordination geometries that directly influence the metal complexes chemical stability. The valence state and coordination geometry of the Ga-PCH and Fe-PCH complexes has recently been investigated in detail; as for PVD complexes, several NMR structural studies of Ga(III)-PVD are reported in the literature, using Ga(III) as a diamagnetic isosteric substitute for Fe(III). In this work, we applied up-to-date spectroscopic techniques as synchrotron-radiation-induced X-ray photoelectron spectroscopy (SR-XPS) and X-ray absorption fine structure (XAFS) spectroscopy coupled with molecular modeling to describe the electronic structure and coordination chemistry of Fe and Ga coordinative sites in PVD metal complexes. These techniques allowed us to unambiguously determine the oxidation state of the coordinative ions and to gather interesting information about the similarities and differences between the two coordination compounds as induced by the different metal.

7.
Phys Chem Chem Phys ; 20(36): 23783-23788, 2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30199083

RESUMO

The local structure of correlated spin-orbit insulator Sr2-xMxIrO4 (M = K, La) has been investigated by Ir L3-edge extended X-ray absorption fine structure measurements. The measurements were performed as a function of temperature for different dopings induced by substitution of Sr with La or K. It is found that Ir-O bonds have strong covalency and they hardly show any change across the Néel temperature. In the studied doping range, neither Ir-O bonds nor their dynamics, measured by their mean square relative displacements, show any appreciable change upon carrier doping, indicating the possibility of nanoscale phase separation in the doped system. On the other hand, there is a large increase of the static disorder in Ir-Sr correlation, larger for K doping than La doping. Similarities and differences with respect to the local lattice displacements in cuprates are briefly discussed.

8.
Phys Chem Chem Phys ; 20(22): 15288-15292, 2018 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-29790510

RESUMO

We have investigated the nanostructuring effects on the local structure of V2O5 cathode material by means of temperature dependent V K-edge X-ray absorption fine structure measurements. We have found that the nanostructuring largely affects V-O and V-V bond characteristics with a general softening of the local V-O and V-V bonds. The obtained bond strengths correlate with the specific capacity shown by the different systems, with higher capacity corresponding to softer atomic pairs. The present study suggests the key role of local atomic displacements in the diffusion and storage of ions in cathodes for batteries, providing important information for designing new functional materials.

9.
Polymers (Basel) ; 10(8)2018 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-30960838

RESUMO

The physicochemical and mechanical properties of new alkaline anion-exchange membranes (AAEMs) based on chitosan (CS) and poly(vinyl alcohol) (PVA) polymers doped with unsupported copper nanoparticles (NPs) and copper exchanged over different porous materials were investigated regarding ion-exchange capacity (IEC), OH- conductivity, water uptake (WU), water vapor permeability (WVP), and thermal and mechanical resistance. The influence of the type of filler included in different morphologies and filler loading has been explored using copper exchanged materials such as the layered porous titanosilicate AM-4, layered stannosilicate UZAR-S3, and zeolites Y, MOR, and BEA. Compared to commercially available anion-exchange membranes, the best performing membranes in terms of WU, IEC, OH- conductivity and WVP in this study were those containing 10 wt % of Cu-AM-4 and Cu-UZAR-S3, although 10 wt % Cu-MOR provided better mechanical strength at close values of WVP and anion conductivity. It was also observed that when Cu was exchanged in a porous silicate matrix, its oxidation state was lower than when embedded as unsupported metal NPs. In addition, the statistical analysis of variance determined that the electrochemical properties of the membranes were noticeably affected by both the type and filler loading, and influenced also by the copper oxidation state and content in the membrane, but their hydrophilic properties were more affected by the polymers. The largest significant effects were noticed on the water sorption and transport properties, which gives scope for the design of AAEMs for electrochemical and water treatment applications.

10.
J Synchrotron Radiat ; 24(Pt 2): 545-546, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-28244452

RESUMO

Corrections to the paper by Honkanen et al. (2014). [J. Synchrotron Rad. 21, 104-110] are made.

11.
Psychooncology ; 26(10): 1444-1454, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27246348

RESUMO

BACKGROUND: There is increasing recognition of the unique physical and psychosocial concerns of the growing population of cancer survivors. An emerging literature demonstrates that fear of cancer recurrence (FCR) is a problematic long-term and late effect for cancer survivors. In fact, FCR is a top concern, and this article provides a necessary synthesis of the extant research evidence and theory. METHODS: Literature searches were conducted using databases including MEDLINE and PsychINFO using specified search terms including 'fear of recurrence' and 'worry about recurrence'. A comprehensive narrative review summarizes early empirical findings on FCR including current definitions, assessment tools, clinical presentations, quality of life impact, prevalence, trajectory and risk factors. This paper also critically reviews the relevant theoretical frameworks to best understand these findings and considers multiple psychosocial treatment models that may have relevance for addressing FCR in the clinical setting. RESULTS: There is evidence of substantial prevalence and quality of life impact of FCR. Several theories (e.g. self-regulation model of illness, a family-based model, uncertainty in illness theory, social-cognitive processing theory, terror management theory) directly or indirectly help conceptualize FCR and inform potential treatment options for those with clinically significant distress or impairment resulting from FCR. CONCLUSIONS: Further investigation into FCR is warranted to promote evidence-based care for this significant cancer survivorship concern.


Assuntos
Medo/psicologia , Recidiva Local de Neoplasia/psicologia , Qualidade de Vida , Ansiedade/psicologia , Humanos , Transtornos Fóbicos , Prevalência , Fatores de Risco , Sobreviventes , Incerteza
12.
Rev Sci Instrum ; 87(11): 115103, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27910538

RESUMO

We have developed a helium gas flow cryostat for use on synchrotron tender to hard X-ray beamlines. Very efficient sample cooling is achieved because the sample is placed directly in the cooling helium flow on a removable sample holder. The cryostat is compact and easy to operate; samples can be changed in less than 5 min at any temperature. The cryostat has a temperature range of 2.5-325 K with temperature stability better than 0.1 K. The very wide optical angle and the ability to operate in any orientation mean that the cryostat can easily be adapted for different X-ray techniques. It is already in use on different beamlines at the European Synchrotron Radiation Facility (ESRF), ALBA Synchrotron Light Facility (ALBA), and Diamond Light Source (DLS) for inelastic X-ray scattering, powder diffraction, and X-ray absorption spectroscopy. Results obtained at these beamlines are presented here.

13.
Materials (Basel) ; 9(12)2016 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-28774148

RESUMO

The synthesis, characterization and assessment of the antibacterial properties of hydrophilic silver nanoparticles (AgNPs) were investigated with the aim to probe their suitability for innovative applications in the field of nanobiotechnology. First, silver nanoparticles were synthetized and functionalized with two capping agents, namely 3-mercapto-1-propansulfonate (3MPS) and 1-ß-thio-d-glucose (TG). The investigation of the structural and electronic properties of the nano-systems was carried out by means of X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). XPS data provided information about the system stability and the interactions between the metallic surface and the organic ligands. In addition, XPS data allowed us to achieve a deep understanding of the influence of the thiols stoichiometric ratio on the electronic properties and stability of AgNPs. In order to shed light on the structural and electronic local properties at Ag atoms sites, XAS at Ag K-Edge was successfully applied; furthermore, the combination of Dynamic Light Scattering (DLS) and XAS results allowed determining AgNPs sizes, ranging between 3 and 13 nm. Finally, preliminary studies on the antibacterial properties of AgNPs showed promising results on four of six multidrug-resistant bacteria belonging to the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp.).

14.
Rev Sci Instrum ; 85(8): 084105, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25173285

RESUMO

We demonstrate the use of commercially available fused silica capillary and fittings to construct a cell for operando X-ray absorption spectroscopy (XAS) for the study of heterogeneously catalyzed reactions under high pressure (up to 200 bars) and high temperature (up to 280 °C) conditions. As the first demonstration, the cell was used for CO2 hydrogenation reaction to examine the state of copper in a conventional Cu/ZnO/Al2O3 methanol synthesis catalyst. The active copper component of the catalyst was shown to remain in the metallic state under supercritical reaction conditions, at 200 bars and up to 260 °C. With the coiled heating system around the capillary, one can easily change the length of the capillary and control the amount of catalyst under investigation. With precise control of reactant(s) flow, the cell can mimic and serve as a conventional fixed-bed micro-reactor system to obtain reliable catalytic data. This high comparability of the reaction performance of the cell and laboratory reactors is crucial to gain insights into the nature of actual active sites under technologically relevant reaction conditions. The large length of the capillary can cause its bending upon heating when it is only fixed at both ends because of the thermal expansion. The degree of the bending can vary depending on the heating mode, and solutions to this problem are also presented. Furthermore, the cell is suitable for Raman studies, nowadays available at several beamlines for combined measurements. A concise study of CO2 phase behavior by Raman spectroscopy is presented to demonstrate a potential of the cell for combined XAS-Raman studies.

15.
J Psychosoc Oncol ; 32(6): 727-34, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25157545

RESUMO

International research suggests that many women with gynecological cancers have unmet supportive care needs that often correlate with greater psychological distress and poorer quality of life. The United States has a diverse population and evolving health care system, so this study aims to identify the support needs of women with gynecologic cancer in this geographic region. Furthermore, there are numerous health disparities with regards to cancer care; therefore, a second aim of this study is to explore health disparities in unmet support needs. Fifty-one women with gynecologic cancers completed an adapted version of the Supportive Care Needs Survey. Sociodemographic and cancer-related information were also collected. Findings revealed a high frequency of unmet support needs, particularly in the psychological, physical, and practical domains. Additionally, disparities in levels of support needs were found to be dependent on income and minority status. Specifically, unmet needs in the physical/daily living and practical domains were dependent on income, and minorities reported significantly higher support needs in the sexuality and psychological need domains than their majority counterparts. These results highlight the potential benefits of enhanced multidisciplinary services to better assess and address patients' needs. Nonetheless even with enhanced services, the findings, consistent with other health disparities research, suggest lower income affects access to care, so more research is needed on how to overcome these barriers.


Assuntos
Neoplasias dos Genitais Femininos/psicologia , Neoplasias dos Genitais Femininos/terapia , Disparidades em Assistência à Saúde , Determinação de Necessidades de Cuidados de Saúde , Apoio Social , Feminino , Pesquisas sobre Serviços de Saúde , Humanos , Pessoa de Meia-Idade , Fatores Socioeconômicos , Estados Unidos
16.
J Phys Chem B ; 118(29): 8750-5, 2014 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-25007231

RESUMO

The microscopic structure of the hydrogen-bond network of water-alcohol mixtures was studied using X-ray Raman scattering (XRS). To systematically examine how the hydrogen-bond network of water is affected by an increasing size of the hydrophobic group, small linear alcohols (methanol, ethanol, and propanol) in constant mole fractions were studied. The oxygen K-edge spectra were not altered upon hydration of the alcohols beyond a simple superposition of signals from alcohol and water. The experiment thus indicates that alcohols do not have a substantial effect on the structure of the hydrogen-bond network of water. In particular, no apparent breaking or forming of the hydrogen bonds is observed to take place in the overall structure. In addition, there is no indication of changes in the tetrahedrality of the hydrogen-bond network of water in the vicinity of alcohol molecules.


Assuntos
Álcoois/química , Interações Hidrofóbicas e Hidrofílicas , Água/química , Ligação de Hidrogênio , Conformação Molecular , Simulação de Dinâmica Molecular , Difração de Raios X
17.
J Synchrotron Radiat ; 21(Pt 4): 762-7, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24971972

RESUMO

Wavelength-dispersive high-resolution X-ray spectrometers often employ elastically bent crystals for the wavelength analysis. In a preceding paper [Honkanen et al. (2014). J. Synchrotron Rad. 21, 104-110] a theory for quantifying the internal stress of a macroscopically large spherically curved analyser crystal was presented. Here the theory is applied to compensate for the corresponding decrease of the energy resolution. The technique is demonstrated with a Johann-type spectrometer using a spherically bent Si(660) analyser in near-backscattering geometry, where an improvement in the energy resolution from 1.0 eV down to 0.5 eV at 9.7 keV incident photon energy was observed.

18.
J Phys Condens Matter ; 26(13): 135501, 2014 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-24614302

RESUMO

We report a study on charge-neutral crystal-field (dd) excitations in NiO as a function of applied pressure up to 55 GPa, using resonant inelastic x-ray scattering spectroscopy at the Ni K edge. We find distinct signatures of the pressure-induced modifications to the 3d orbital energies as a function of pressure. These modifications are experimentally evidenced by a subtle splitting of the dd-excitation resonance energies. We compare the experimental results to a charge-transfer cluster-model calculation, and a LSDA + U calculation of the ground state as a function of lattice constant. We thus show how resonant inelastic x-ray scattering spectroscopy is able to give insights into the manifold of excited states even in conditions that are difficult to access with many traditional experimental techniques.

19.
J Synchrotron Radiat ; 21(Pt 1): 104-10, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24365923

RESUMO

Theoretical and experimental studies are presented on properties of spherically bent analyser crystals for high-resolution X-ray spectrometry. A correction to the bent-crystal strain field owing to its finite surface area is derived. The results are used to explain the reflectivity curves and anisotropic properties of Si(660) and Si(553) analysers in near-backscattering geometry. The results from the calculation agree very well with experimental results obtained using an inelastic X-ray scattering synchrotron beamline.

20.
Proc Natl Acad Sci U S A ; 110(16): 6301-6, 2013 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-23479639

RESUMO

We report on the microscopic structure of water at sub- and supercritical conditions studied using X-ray Raman spectroscopy, ab initio molecular dynamics simulations, and density functional theory. Systematic changes in the X-ray Raman spectra with increasing pressure and temperature are observed. Throughout the studied thermodynamic range, the experimental spectra can be interpreted with a structural model obtained from the molecular dynamics simulations. A spatial statistical analysis using Ripley's K-function shows that this model is homogeneous on the nanometer length scale. According to the simulations, distortions of the hydrogen-bond network increase dramatically when temperature and pressure increase to the supercritical regime. In particular, the average number of hydrogen bonds per molecule decreases to ≈ 0.6 at 600 °C and p = 134 MPa.


Assuntos
Temperatura Alta , Pressão , Água/química , Ligação de Hidrogênio , Modelos Químicos , Simulação de Dinâmica Molecular , Análise Espectral Raman , Termodinâmica
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