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James Everett, Joanna F Collingwood, Vindy Tjendana-Tjhin, Jake Brooks, Frederik Lermyte, Germán Plascencia-Villa, Ian Hands-Portman, Jon Dobson, George Perry, Neil D Telling
Altered metabolism of biometals in the brain is a key feature of Alzheimer's disease, and biometal interactions with amyloid-β are linked to amyloid plaque formation. Iron-rich aggregates, including evidence for the mixed-valence iron oxide magnetite, are associated with amyloid plaques. To test the hypothesis that increased chemical reduction of iron, as observed in vitro in the presence of aggregating amyloid-β, may occur at sites of amyloid plaque formation in the human brain, the nanoscale distribution and physicochemical states of biometals, particularly iron, were characterised in isolated amyloid plaque cores from human Alzheimer's disease cases using synchrotron X-ray spectromicroscopy...
April 24, 2018: Nanoscale
Patricia M Valdespino-Castillo, Ping Hu, Martín Merino-Ibarra, Luz M López-Gómez, Daniel Cerqueda-García, Roberto González-De Zayas, Teresa Pi-Puig, Julio A Lestayo, Hoi-Ying Holman, Luisa I Falcón
Microbialites are modern analogs of ancient microbial consortia that date as far back as the Archaean Eon. Microbialites have contributed to the geochemical history of our planet through their diverse metabolic capacities that mediate mineral precipitation. These mineral-forming microbial assemblages accumulate major ions, trace elements and biomass from their ambient aquatic environments; their role in the resulting chemical structure of these lithifications needs clarification. We studied the biogeochemistry and microbial structure of microbialites collected from diverse locations in Mexico and in a previously undescribed microbialite in Cuba...
2018: Frontiers in Microbiology
Marine Cotte, Tiphaine Fabris, Juliette Langlois, Ludovic Bellot-Gurlet, Françoise Ploye, Natalie Coural, Clotilde Boust, Jean-Paul Gandolfo, Thomas Galifot, Jean Susini
Louis Ducos du Huron (1837-1920) dedicated his entire life to the elaboration of physical-chemical processes for color photography. This study aimed at highlighting his unique contribution to three-color printing through 1) an in-depth review of the many protocols he published and 2) the synchrotron-based IR and X-ray microanalysis of fragments sampled in three artworks. Ducos du Hauron's method relied on the preparation and assembly of three monochromes (red, blue, yellow). This study brings to light complex multistep recipes based on photochemistry (carbon print), organic, and inorganic chemistry...
March 20, 2018: Angewandte Chemie
Sandra Ruiz-Gómez, Lucas Pérez, Arantzazu Mascaraque, Adrian Quesada, Pilar Prieto, Irene Palacio, Laura Martín-García, Michael Foerster, Lucía Aballe, Juan de la Figuera
We have grown high quality magnetite microcrystals free from antiphase boundaries on Ru(0001) by reactive molecular beam epitaxy, conserving bulk magnetic properties below 20 nm thickness. Magnetization vector maps are obtained by X-ray spectromicroscopy and compared with micromagnetic simulations. The observed domain configurations are dictated purely by shape anisotropy, overcoming the possible influences of (magneto)crystalline anisotropy and defects, thus demonstrating the possibility of designing spin structures in ultrathin, magnetically soft magnetite at will...
March 9, 2018: Nanoscale
J I Pacold, A B Altman, K B Knight, K S Holliday, M J Kristo, S G Minasian, T Tyliszczak, C H Booth, D K Shuh
Synchrotron radiation spectromicroscopy provides a combination of submicron spatial resolution and chemical sensitivity that is well-suited to analysis of heterogeneous nuclear materials. The chemical and physical characteristics determined by scanning transmission X-ray microscopy (STXM) are complementary to information obtained from standard radiochemical analysis methods. In addition, microscopic quantities of radioactive material can be characterized rapidly by STXM with minimal sample handling and intrusion, especially in the case of particulate materials...
February 26, 2018: Analyst
Xiaying Xin, Guohe Huang, Chunjiang An, Charley Huang, Harold Weger, Shan Zhao, Yang Zhou, Scott Rosendahl
This study investigated the toxicity of triclosan to the green microalga Chlorococcum sp. under multiple environmental stressors. The interactions between triclosan and environmental stressors were explored through full two-way factorial, synchrotron-based Fourier transform infrared spectromicroscopy and principal component analyses. Phosphorus concentration, pH * phosphorus concentration, and temperature * pH * NaCl concentration were the most statistically significant factors under triclosan exposure. The variation of those factors would have a huge impact on biophysiological performances...
February 20, 2018: Environmental Science & Technology
Lucyano J A Macedo, Frank N Crespilho
IR spectroscopy is an excellent method for understanding surface redox chemistry. However, obtaining sufficient spatial resolution to analyze in situ surface redox reactions is difficult because the aqueous sampling environments provide some challenges for IR spectroscopy. These challenges arise because of the vibrational contribution of water. In this letter, we demonstrate a solution to this problem, where the key development enabling the coupling of spectromicroscopy with electrochemical measurements is a CaF2 /electrolyte/Au sandwich IR-sensitive sample holder that acts as an electrochemical cell...
February 6, 2018: Analytical Chemistry
Ie-Hong Hong, Hsin-Zan Hsu
The layered antiferromagnetism of parallel nanowire (NW) arrays self-assembled on Si(110) have been observed at room temperature by direct imaging of both the topographies and magnetic domains using spin-polarized scanning tunneling microscopy/spectroscopy (SP-STM/STS). The topographic STM images reveal that the self-assembled unidirectional and parallel NiSi NWs grow into the Si(110) substrate along the [Formula: see text] direction (i.e. the endotaxial growth) and exhibit multiple-layer growth. The spatially-resolved SP-STS maps show that these parallel NiSi NWs of different heights produce two opposite magnetic domains, depending on the heights of either even or odd layers in the layer stack of the NiSi NWs...
March 2, 2018: Nanotechnology
J Dionne, T Lefèvre, P Bilodeau, M Lamarre, M Auger
Spider silks exhibit remarkable properties, among which the so-called supercontraction, a physical phenomenon by which fibers undergo a longitudinal shrinkage and a radial swelling when exposed to water. The process is marked by a significant decrease in chain orientation resulting from plasticisation of the amorphous phase. Despite several studies that determined the Hermans orientation function, more quantitative data are required to be able to describe theoretically the macroscopic water-induced shrinkage from molecular reorganization...
November 29, 2017: Physical Chemistry Chemical Physics: PCCP
C Struzzi, M Scardamaglia, N Reckinger, H Sezen, M Amati, L Gregoratti, J-F Colomer, C Ewels, R Snyders, C Bittencourt
Plasma fluorination of graphene is studied using a combination of spectroscopy and microscopy techniques, giving insight into the yield and fluorination mechanism for functionalization of supported graphene with both CF4 and SF6 gas precursors. Ion acceleration during fluorination is used to probe the effect on grafting functionalities. Adatom clustering, which occurs with CF4 plasma treatment, is suppressed when higher kinetic energy is supplied to the ions. During SF6 plasma functionalization, the sulfur atoms tend to bond to bare copper areas instead of affecting the graphene chemistry, except when the kinetic energy of the ions is restricted...
November 29, 2017: Physical Chemistry Chemical Physics: PCCP
Felipe Weidenbach Degrazia, Bruna Genari, Vicente Castelo Branco Leitune, Rodrigo Alex Arthur, Santiago Arias Luxan, Susana Maria Werner Samuel, Fabrício Mezzomo Collares, Salvatore Sauro
OBJECTIVE: To evaluate the immediate enamel bond strength, in situ degree of conversion and the polymerisation rate of three experimental orthodontic adhesives containing triclosan-loaded halloysite nanotubes. The antibacterial and bioactivity properties of such experimental materials were also assessed. MATERIALS AND METHODS: Three experimental orthodontic adhesives were formulated by incorporating triclosan-loaded halloysite nanotubes (TCN-HNT) at different concentrations (5wt%, 10wt% and 20wt%) into a resin blend (Control)...
November 7, 2017: Journal of Dentistry
Majid Kazemian Abyaneh, Tohru Araki, Burkhard Kaulich
Gold nanorods (GNRs) have been fabricated by a novel polymer-immobilised seed mediated method using ultraviolet (UV) photoreduced gold-polymethylmethacrylate (Au-PMMA) nanocomposites as a seed platform and characterised at sub-micron scale regime with synchrotron-based techniques; near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray fluorescence (XRF) mapping. In this report, it is shown that investigating polymer nanocomposites using combination of XRF mapping and NEXAFS spectromicroscopy can help to see the growth phenomenon from different perspective than conventional characterisation techniques...
October 16, 2017: Nanomaterials
Nicholas Tallarida, Joonhee Lee, Vartkess Ara Apkarian
The tip is key to the successful execution of tip-enhanced Raman scattering (TERS) measurements in the single molecule limit. We show that nanoscopically smooth silver tips, batch produced through field-directed sputter sharpening, reliably attain TERS with enhancement factors that reach 1013 , as measured by the Raman spectra of single CO molecules attached to the tip apex. We validate the bare tips by demonstrating spectromicroscopy with submolecular spatial resolution and underscore that TERS is a near-field effect that does not obey simple selection rules...
November 28, 2017: ACS Nano
Joonhee Lee, Nicholas Tallarida, Xing Chen, Pengchong Liu, Lasse Jensen, Vartkess Ara Apkarian
Atomically terminated and nanoscopically smooth silver tips effectively focus light on the angstrom scale, allowing tip-enhanced Raman spectromicroscopy (TER-sm) with single molecule sensitivity and submolecular spatial resolution. Through measurements carried out on cobalt-tetraphenylporphyrin (CoTPP) adsorbed on Au(111), we highlight peculiarities of vibrational spectromicroscopy with light confined on the angstrom scale. Field-gradient-driven spectra, orientational fingerprinting, and sculpting of local fields by atomic morphology of the junction are elucidated through measurements that range from 2D arrays at room temperature to single molecule manipulations at 5 K...
November 28, 2017: ACS Nano
Suhas Kumar, Ziwen Wang, Noraica Davila, Niru Kumari, Kate J Norris, Xiaopeng Huang, John Paul Strachan, David Vine, A L David Kilcoyne, Yoshio Nishi, R Stanley Williams
Negative differential resistance behavior in oxide memristors, especially those using NbO2 , is gaining renewed interest because of its potential utility in neuromorphic computing. However, there has been a decade-long controversy over whether the negative differential resistance is caused by a relatively low-temperature non-linear transport mechanism or a high-temperature Mott transition. Resolving this issue will enable consistent and robust predictive modeling of this phenomenon for different applications...
September 22, 2017: Nature Communications
Sungchul Bae, Manabu Kanematsu, Daniel Hernández-Cruz, Juhyuk Moon, David Kilcoyne, Paulo J M Monteiro
The understanding and control of early hydration of tricalcium silicate (C₃S) is of great importance to cement science and concrete technology. However, traditional characterization methods are incapable of providing morphological and spectroscopic information about in situ hydration at the nanoscale. Using soft X-ray spectromicroscopy, we report the changes in morphology and molecular structure of C₃S at an early stage of hydration. In situ C₃S hydration in a wet cell, beginning with induction (~1 h) and acceleration (~4 h) periods of up to ~8 h, was studied and compared with ex situ measurements in the deceleration period after 15 h of curing...
December 1, 2016: Materials
Sungchul Bae, Rae Taylor, David Kilcoyne, Juhyuk Moon, Paulo J M Monteiro
This study assesses the quantitative effects of incorporating high-volume fly ash (HVFA) into tricalcium silicate (C₃S) paste on the hydration, degree of silicate polymerization, and Al substitution for Si in calcium silicate hydrate (C-S-H). Thermogravimetric analysis and isothermal conduction calorimetry showed that, although the induction period of C₃S hydration was significantly extended, the degree of hydration of C₃S after the deceleration period increased due to HVFA incorporation. Synchrotron-sourced soft X-ray spectromicroscopy further showed that most of the C₃S in the C₃S-HVFA paste was fully hydrated after 28 days of hydration, while that in the pure C₃S paste was not...
February 4, 2017: Materials
G S Figueiredo, S Bojic, P Rooney, S-P Wilshaw, C J Connon, R M Gouveia, C Paterson, G Lepert, H S Mudhar, F C Figueiredo, M Lako
The gold standard substrate for the ex vivo expansion of human limbal stem cells (LSCs) remains the human amniotic membrane (HAM) but this is not a defined substrate and is subject to biological variability and the potential to transmit disease. To better define HAM and mitigate the risk of disease transmission, we sought to determine if decellularisation and/or γ-irradiation have an adverse effect on culture growth and LSC phenotype. Ex vivo limbal explant cultures were set up on fresh HAM, HAM decellularised with 0...
October 1, 2017: Acta Biomaterialia
Shovik Bandyopadhyay, Junjie Li, Elie Traer, Jeffrey W Tyner, Amy Zhou, Stephen T Oh, Ji-Xin Cheng
Since the advent of tyrosine kinase inhibitors (TKIs) such as imatinib, nilotinib, and dasatinib, chronic myelogenous leukemia (CML) prognosis has improved greatly. However, ~30-40% of patients develop resistance to imatinib therapy. Although most resistance is caused by mutations in the BCR-ABL kinase domain, 50-85% of these patients develop resistance in the absence of new mutations. In these cases, targeting other pathways may be needed to regain clinical response. Using label-free Raman spectromicroscopy, we evaluated a number of leukemia cell lines and discovered an aberrant accumulation of cholesteryl ester (CE) in CML, which was found to be a result of BCR-ABL kinase activity...
2017: PloS One
Laura E Abramiuc, Liviu C Tănase, Alexei Barinov, Nicoleta G Apostol, Cristina Chirilă, Lucian Trupină, Lucian Pintilie, Cristian M Teodorescu
The stability of thin films of lead zirco-titanate (PZT) under intense soft X-ray beams is investigated by time-resolved photoelectron spectromicroscopy with a lateral resolution below 1 micrometer. Surface dissociation is observed when samples are irradiated with intense (5 × 10(23) photons per s per m(2)) soft X-rays, with promotion of reduced lead on the surface. On areas exhibiting outwards polarization (P((+))), the reduced lead is formed at the expense of P((+))-PZT. On areas presenting co-existing P((+)) states with areas without out-of-plane polarization (P((0))), the reduced lead is formed at the expense of the P((0))-PZT component, while the P((+))-PZT remains constant...
July 12, 2017: Nanoscale
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