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The cellular distribution of three dirhodium(ii) complexes with a paddlewheel structure was investigated using synchrotron-based X-ray fluorescence microscopy and cell viability studies. Complexes with vacant axial sites displayed cytotoxic activity and nuclear accumulation whereas complexes in which the axial positions were blocked showed little to no toxicity nor uptake. [ABSTRACT FROM AUTHOR]

Background A variety of selenium compounds have been observed to provide protection against oxidative stress, presumably by mimicking the mechanism of action of the glutathione peroxidases. However, the selenium chemistry that underpins the action of these compounds has not been unequivocally established. Methods The synchrotron based techniques, X-ray absorption spectroscopy and X-ray fluorescence microscopy were used to examine the cellular speciation and distribution of selenium in SH-SY5Y cells pretreated with one of two diphenyl diselenides, or ebselen, followed by peroxide insult. Results Bis(2-aminophenyl)diselenide was shown to protect against oxidative stress conditions which mimic ischemic strokes, while its nitro analogue, bis(2-nitrophenyl)diselenide did not. This protective activity was tentatively assigned to the reductive cleavage of bis(2-aminophenyl)diselenide inside human neurocarcinoma cells, SH-SY5Y, while bis(2-nitrophenyl)diselenide remained largely unchanged. The distinct chemistries of the related compounds were traced by the changes in selenium speciation in bulk pellets of treated SH-SY5Y cells detected by X-ray absorption spectroscopy. Further, bis(2-aminophenyl)diselenide, like the known stroke mitigation agent ebselen, was observed by X-ray fluorescence imaging to penetrate into the nucleus of SH-SY5Y cells while bis(2-nitrophenyl)diselenide was observed to be excluded from the nuclear region. Conclusions The differences in activity were thus attributed to the varied speciation and cellular localisation of the compounds, or their metabolites, as detected by X-ray absorption spectroscopy and X-ray fluorescence microscopy. Significance The work is significant as it links, for the first time, the protective action of selenium compounds against redox stress with particular chemical speciation using a direct measurement approach. [ABSTRACT FROM AUTHOR]

Recently, using synchrotron radiation X-ray fluorescence microscopy (SRXRF), the copper accumulation in rat aortic elastin and copper topography in human THP-1 cell monolayer have been described. However, it is necessary to locate more accurately cellular copper in the vascular cells and tissues. In the current study, SRXRF coupling with transmission electron microscopy (TEM) was used to image copper in sections of human THP-1 cells and mouse aorta. The results showed that sections of 1 µm thickness are required for SRXRF producing a correlative image with TEM between copper topography and cellular ultrastructure. As compared with SRXRF alone, coupling TEM with SRXRF can clearly identify the location of copper in the nucleus and nucleolus in non-dividing THP-1 cell sections, and can differentiate the copper location at elastic laminae from collagen in mouse aortic sections. Thus, these results revealed new information about the copper topography in vascular cells and tissues and highlighted the potential of TEM-SRXRF to investigate the role of copper in macrophage and aortic homeostasis. [ABSTRACT FROM AUTHOR]

The elemental composition of single cells of Nitrosomonas europaea 19718 was studied via synchrotron X-ray fluorescence microscopy (XFM) as a function of inhibition by divalent copper (Cu(II)) and batch growth phase. Based on XFM, the intracellular Cu concentrations in exponential phase cultures of N. europaea exposed to Cu(II) were statistically higher than in stationary phase cultures at the 95% confidence interval (α = 0.05). However, the impact of Cu inferred from specific oxygen uptake rate (sOUR) measurements at the two physiological states was statistically not dissimilar at the Cu(II) doses tested, except at 1000 μM Cu(II), at which exponential phase cultures were significantly more inhibited. Furthermore, the elemental composition in uninhibited exponential and stationary phase N. europaea cultures was similar. Notably, the molar fractions of Cu and Fe, relative to other elements in N. europaea cultures were statistically higher than those recently reported in Pseudomonas fluorescens possibly owing to the preponderance of metal cofactor rich catalytic enzymes (such as ammonia monooxygenase) and electron transport mechanisms in N. europaea. [ABSTRACT FROM AUTHOR]

Quantitative synchrotron X-ray fluorescence (SXRF) imaging of adherent mouse fibroblast cells deficient in antioxidant-1 (Atox1), a metallochaperone protein responsible for delivering Cu to cuproenzymes in the trans-Golgi network, revealed striking differences in the subcellular Cu distribution compared with wild-type cells. Whereas the latter showed a pronounced perinuclear localization of Cu, the Atox1-deficient cells displayed a mostly unstructured and diffuse distribution throughout the entire cell body. Comparison of the SXRF elemental maps for Zn and Fe of the same samples showed no marked differences between the two cell lines. The data underscore the importance of Atox1, not only as a metallochaperone for delivering Cu to cuproenzymes, but also as a key player in maintaining the proper distribution and organization of Cu at the cellular level. [ABSTRACT FROM AUTHOR]

Abstract: Dithiocarbamates are a commercially important class of compounds that can produce peripheral neuropathy in humans and experimental animals. Previous studies have supported a requirement for copper accumulation and enhanced lipid peroxidation in dithiocarbamate-mediated myelinopathy. The study presented here extends previous investigations in two areas. Firstly, although total copper levels have been shown to increase within the nerve it has not been determined whether copper is increased within the myelin compartment, the primary site of lesion development. Therefore, the distribution of copper in sciatic nerve was characterized using synchrotron X-ray fluorescence microscopy to determine whether the neurotoxic dithiocarbamate, N,N-diethyldithiocarbamate, increases copper levels in myelin. Secondly, because lipid peroxidation is an ongoing process in normal nerve and the levels of lipid peroxidation products produced by dithiocarbamate exposure demonstrated an unusual cumulative dose response in previous studies the biological impact of dithiocarbamate-mediated lipid peroxidation was evaluated. Experiments were performed to determine whether dithiocarbamate-mediated lipid peroxidation products elicit an antioxidant response through measuring the protein expression levels of three enzymes, superoxide dismutase 1, heme oxygenase 1, and glutathione transferase α, that are linked to the antioxidant response element promoter. To establish the potential of oxidative injury to contribute to myelin injury the temporal relationship of the antioxidant response to myelin injury was determined. Myelin structure in peripheral nerve was assessed using multi-exponential transverse relaxation measurements (MET2) as a function of exposure duration, and the temporal relationship of protein expression changes relative to the onset of changes in myelin integrity were determined. Initial assessments were also performed to explore the potential contribution of dithiocarbamate-mediated inhibition of proteasome function and inhibition of cuproenzyme activity to neurotoxicity, and also to assess the potential of dithiocarbamates to promote oxidative stress and injury within the central nervous system. These evaluations were performed using an established model for dithiocarbamate-mediated demyelination in the rat utilizing sciatic nerve, spinal cord and brain samples obtained from rats exposed to N,N-diethyldithiocarbamate (DEDC) by intra-abdominal pumps for periods of 2, 4, and 8 weeks and from non exposed controls. The data supported the ability of DEDC to increase copper within myelin and to enhance oxidative stress prior to structural changes detectable by MET2. Evidence was also obtained that the excess copper produced by DEDC in the central nervous system is redox active and promotes oxidative injury. [Copyright &y& Elsevier]

Abstract: Synchrotron-based X-ray fluorescence microscopy (microXRF) is a powerful tool to study the two-dimensional distribution of a wide range of biologically relevant elements in tissues and cells. By growing mouse fibroblast cells directly on formvar-carbon coated electron microscopy grids, microXRF elemental maps with well-defined subcellular resolution were obtained. In order to colocalize the elemental distribution with the location of specific cellular structures and organelles, we explored the application of a commercially available secondary antibody conjugated to FluoroNanogold, a dual-label that combines a regular organic fluorophore with a 1.4nm Au-cluster as xenobiotic label for microXRF imaging. Adherent mouse fibroblast cells were grown on silicon nitride windows serving as biocompatible XRF support substrate, and labeled with FluoroNanogold in combination with primary antibodies specific for mitochondria or the Golgi apparatus, respectively. Raster scanning of the in-air dried cells with an incident X-ray energy of 11.95keV, sufficient to ensure excitation of the Au Lα line, provided two-dimensional maps with submicron resolution for Au as well as for most biologically relevant elements. MicroXRF proved to be sufficiently sensitive to image the location and structural details of the Au-labeled organelles, which correlated well with the subcellular distribution visualized by means of optical fluorescence microscopy. [Copyright &y& Elsevier]

Background: In rodents, zinc deficiency potentiates the effects of certain nitrosamines that act as esophageal carcinogens. Studies of the association between zinc and esophageal squamous cell carcinoma in humans have been hampered by plasmazinc homeostasis,which obscuresindividualdifferences in total zinc stores, and by the uncertainty regarding zinc bio- availability when estimating dietary zinc intake because phytate from whole grains effectively prohibits zinc absorption. By using baseline tissue biopsy specimens collected in a prospective observational study, we determined the association between incident esophageal squamous cell carcinoma and baseline element concentrations in tissue sections from residents of Linzhou, China, participating in a nutrition intervention trial. Methods: We used x-ray fluorescence spec- troscopy to measure zinc, copper, iron, nickel, and sulfur concentrations in single 5-μm-thick sections from formalin-fixed, paraffin-embedded esophageal biopsy specimens collected in 1985 from 60 eventual case and 72 control subjects. Sub- jects were matched on baseline histology and followed for 16 years. We used Cox proportional hazards models to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between each element and risk of incident esophageal cancer. All statistical tests were two-sided. Results: The risk of developing esophageal cancer was much lower for subjects in the highest quartile of esophageal tissue zinc con- centration compared with those in the lowest quartile (HR = 0.21, 95% CI = 0.065 to 0.68). The association was statistically significant across quartiles (Ptrend = .015). Individuals in the highest quartile of sulfur concentration had a lower risk of esophageal cancer than individuals in the lowest quartile (HR = 0.29, 95% CI = 0.095 to 0.85), but the association across quartiles was not statistically significant (Ptrend = .081). There was no association between copper, iron, or nickel concentrations and risk of esophageal cancer. Conclusion: High tissue zinc concentration was strongly associated with a reduced risk of developing esophageal squamous cell carcinoma. X-ray fluorescence spectroscopy can be used to assess relationships among concentrations of both nutritional and toxic elements and disease risk in banked tissue specimens. [ABSTRACT FROM AUTHOR]

Discusses key issues concerning x-ray microscopy techniques in use at the Advanced Photon Source (APS). Wide use of fluorescence, microscopy, tomography and microdiffraction in APS; Analysis of pertinent topics and relevant issues; Implications on studies of synchrotron radiation.

Focusing 8 keV x rays to a spot size of 150 and 90 nm full width at half maximum has been demonstrated at the first- and third-order foci, respectively, of a phase zone plate at the Advanced Photon Source 2-ID-D x-ray microprobe experiment station [Yun et al., Rev. Sci. Instrum. 70, 2238 (1999)]. In order to perform an x-ray microprobe experiment with such a high spatial resolution, vibration control of the x-ray microprobe supporting system becomes a critical issue. Recently, we have designed and constructed a vibration-damping structure for the APS 2-ID-D x-ray microprobe experiment station. In this article the vibration-damping structure design as well as the vibration test results for the x-ray microprobe supporting system are presented. This is an essential improvement toward future operation of the microprobe at sub-100-nm spatial resolution. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Recently, diimine Re(I) tricarbonyl complexes have attracted great interest due to their promising cytotoxic effects. Here, we compare the cytotoxicity and cellular uptake of two Re(I) compounds fac-[(Re(CO)3(bpy)(H2O)](CF3SO3) (1) and Na(fac-[(Re(CO)3(bpy)(S2O3)])·H2O (bpy = 2,2′-bipyridine) (2). The Re-thiosulfate complex in 2 was characterized in two solvated crystal structures {Na(fac-[Re(CO)3(bpy)(S2O3)])·1.75H2O·C2H5OH}4 (2 + 0.75H2O + C2H5OH)4 and (fac-[Re(CO)3(bpy)(H2O)]) (fac-[Re(CO)3(bpy)(S2O3)])·4H2O (3). The cytotoxicity of 1 and 2 was tested in the MDA-MB-231 breast cancer cell line and compared with that of cisplatin. The cellular localization of the Re(I) complexes was investigated using synchrotron-based X-ray fluorescence microscopy (XFM). The results show that replacement of the aqua ligand with thiosulfate renders the complex less toxic most likely by distrupting its cellular entry. Therefore, thiosulfate could potentially have a similar chemoprotective effect against diimine fac-Re(CO)3 complexes as it has against cisplatin. [ABSTRACT FROM AUTHOR]

The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca2+ uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca2+. The best‐known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. Here, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X‐ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities. [ABSTRACT FROM AUTHOR]

The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca2+ uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca2+. The best‐known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. Here, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X‐ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities. [ABSTRACT FROM AUTHOR]

Biobanks containing formalin-fixed, paraffin-embedded (FFPE) tissues from animals and human atomic-bomb survivors exposed to radioactive particulates remain a vital resource for understanding the molecular effects of radiation exposure. These samples are often decades old and prepared using harsh fixation processes which limit sample imaging options. Optical imaging of hematoxylin and eosin (H&E) stained tissues may be the only feasible processing option, however, H&E images provide no information about radioactive microparticles or radioactive history. Synchrotron X-ray fluorescence microscopy (XFM) is a robust, non-destructive, semi-quantitative technique for elemental mapping and identifying candidate chemical element biomarkers in FFPE tissues. Still, XFM has never been used to uncover distribution of formerly radioactive micro-particulates in FFPE canine specimens collected more than 30 years ago. In this work, we demonstrate the first use of low-, medium-, and high-resolution XFM to generate 2D elemental maps of ~ 35-year-old, canine FFPE lung and lymph node specimens stored in the Northwestern University Radiobiology Archive documenting distribution of formerly radioactive micro-particulates. Additionally, we use XFM to identify individual microparticles and detect daughter products of radioactive decay. The results of this proof-of-principle study support the use of XFM to map chemical element composition in historic FFPE specimens and conduct radioactive micro-particulate forensics. [ABSTRACT FROM AUTHOR]

Trace metals play important roles in biological function, and x-ray fluorescence microscopy (XFM) provides a way to quantitatively image their distribution within cells. The faithfulness of these measurements is dependent on proper sample preparation. Using mouse embryonic fibroblast NIH/3T3 cells as an example, we compare various approaches to the preparation of adherent mammalian cells for XFM imaging under ambient temperature. Direct side-by-side comparison shows that plunge-freezing-based cryoimmobilization provides more faithful preservation than conventional chemical fixation for most biologically important elements including P, S, Cl, K, Fe, Cu, Zn and possibly Ca in adherent mammalian cells. Although cells rinsed with fresh media had a great deal of extracellular background signal for Cl and Ca, this approach maintained cells at the best possible physiological status before rapid freezing and it does not interfere with XFM analysis of other elements. If chemical fixation has to be chosen, the combination of 3% paraformaldehyde and 1.5 % glutaraldehyde preserves S, Fe, Cu and Zn better than either fixative alone. When chemically fixed cells were subjected to a variety of dehydration processes, air drying was proved to be more suitable than other drying methods such as graded ethanol dehydration and freeze drying. This first detailed comparison for x-ray fluorescence microscopy shows how detailed quantitative conclusions can be affected by the choice of cell preparation method. [ABSTRACT FROM AUTHOR]

Refractive and diffractive artifacts can dominate the spatial resolution and affect quantitative measurements by microtomography at the micron level. We have recently developed x-ray computed tomography methods that demonstrated 1 μm resolution in three dimension in the final reconstruction. The first method used a Fresnel zone plate to produce a submicron focal spot which was then rastered across the sample see W. Yun et al., Rev. Sci. Instrum. 70, 2238 (1999). The second method used a collimated beam and a high resolution charge coupled device camera to capture the absorption image of the sample in close proximity see A. Koch et al., J. Opt. Soc. Am. A 15, 1940 (1998). Both methods were applied to study the mineral ultrastructure of individual trabeculae. Using volumetric viewing, the volume, shape, and orientation of osteocyte lacunae and major cannaliculae can be observed. Quantitative measurements and comparison between the two methods will be presented. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Understanding the optoelectronic properties of optically active materials at the nanoscale often proves challenging due to the diffraction-limited resolution of visible light probes and the dose sensitivity of many optically active materials to high-energy electron probes. In this study, we demonstrate correlative synchrotron-based scanning x-ray excited optical luminescence (XEOL) and x-ray fluorescence (XRF) to simultaneously probe local composition and optoelectronic properties of halide perovskite thin films of interest for photovoltaic and optoelectronic devices. We find that perovskite XEOL stability, emission redshifting, and peak broadening under hard x-ray irradiation correlates with trends seen in photoluminescence measurements under continuous visible light laser irradiation. The XEOL stability is sufficient under the intense x-ray probe irradiation to permit proof-of-concept correlative mapping. Typical synchrotron XRF and nano-diffraction measurements use acquisition times 10–100 x shorter than the 5-second acquisition employed for XEOL scans in this study, suggesting that improving luminescence detection should allow correlative XEOL measurements to be performed successfully with minimal material degradation. Analysis of the XEOL emission from the quartz substrate beneath the perovskite reveals its promise for use as a real-time in-situ x-ray dosimeter, which could provide quantitative metrics for future optimization of XEOL data collection for perovskites and other beam-sensitive materials. Overall, the data suggest that XEOL represents a promising route towards improved resolution in the characterization of nanoscale heterogeneities and defects in optically active materials that may be implemented into x-ray nanoprobes to complement existing x-ray modalities. [ABSTRACT FROM AUTHOR]

Understanding the optoelectronic properties of optically active materials at the nanoscale often proves challenging due to the diffraction-limited resolution of visible light probes and the dose sensitivity of many optically active materials to high-energy electron probes. In this study, we demonstrate correlative synchrotron-based scanning x-ray excited optical luminescence (XEOL) and x-ray fluorescence (XRF) to simultaneously probe local composition and optoelectronic properties of halide perovskite thin films of interest for photovoltaic and optoelectronic devices. We find that perovskite XEOL stability, emission redshifting, and peak broadening under hard x-ray irradiation correlates with trends seen in photoluminescence measurements under continuous visible light laser irradiation. The XEOL stability is sufficient under the intense x-ray probe irradiation to permit proof-of-concept correlative mapping. Typical synchrotron XRF and nano-diffraction measurements use acquisition times 10–100 x shorter than the 5-second acquisition employed for XEOL scans in this study, suggesting that improving luminescence detection should allow correlative XEOL measurements to be performed successfully with minimal material degradation. Analysis of the XEOL emission from the quartz substrate beneath the perovskite reveals its promise for use as a real-time in-situ x-ray dosimeter, which could provide quantitative metrics for future optimization of XEOL data collection for perovskites and other beam-sensitive materials. Overall, the data suggest that XEOL represents a promising route towards improved resolution in the characterization of nanoscale heterogeneities and defects in optically active materials that may be implemented into x-ray nanoprobes to complement existing x-ray modalities. [ABSTRACT FROM AUTHOR]

Silver is a non-nutrient element that is readily taken up by diatoms. It exists in the ocean in pM concentrations and is known to accumulate in marine sediments underlying surface waters that support diatom blooms. Laboratory studies and open-ocean water column profiles of Ag versus Si have led to the hypothesis that diatoms accumulate Ag within their silica frustules, subsequently delivering Ag to underlying sediments as the organisms die and sink to the seafloor. Through this delivery mechanism, sedimentary Ag concentrations might serve as a useful record of past export production. However, the actual partitioning of Ag between diatom organic and frustule parts is unknown, and as such represents a considerable source of uncertainty in the development of Ag as a proxy for diatom paleoproductivity and in fully describing Ag biogeochemical cycling. In this study, we use a synchrotron XRF microprobe to map the location of Ag within the laboratory-grown diatom Thalassiosira pseudonana and show that diatoms primarily store Ag in their soft tissue, not in their frustules. Intracellular Ag appears to be concentrated in vacuoles, although the majority of Ag is widely distributed and may be associated with the cell membrane and/or cytoplasm. These results imply an alternate mechanism for Ag delivery to sediments whereby Ag is associated with decomposing organic particles rather than skeletal remains. Silver therefore continues to show promise as a qualitative paleoproductivity proxy. Quantitative use is unlikely, however, given variable uptake rates by diatoms in response to environmental conditions and the significant potential for remineralization with organic matter in the water column. • Ag and trace element concentrations in diatoms were measured using synchrotron μ-XRF. • Ag is taken up by diatoms and clusters in detectable hotspots within the cell. • Ag appears to be contained within vacuoles and cell membrane and/or cytoplasm. • Storage in soft parts implies a biogenic-scavenged model for delivery to sediments. [ABSTRACT FROM AUTHOR]

The intracellular developmental processes in plants, particularly concerning lignin polymer formation and biomass production are regulated by microRNAs (miRNAs). MiRNAs including miR397b are important for developing efficient and cost-effective biofuels. However, traditional methods of monitoring miRNA expression, like PCR, are time-consuming, require sample extraction, and lack spatial and temporal resolution, especially in real-world conditions. We present a novel approach using plasmonics nanosensing to monitor miRNA activity within living plant cells without sample extraction. Plasmonic biosensors using surface-enhanced Raman scattering (SERS) detection offer high sensitivity and precise molecular information. We used the Inverse Molecular Sentinel (iMS) biosensor on unique silver-coated gold nanorods (AuNR@Ag) with a high-aspect ratio to penetrate plant cell walls for detecting miR397b within intact living plant cells. MiR397b overexpression has shown promise in reducing lignin content. Thus, monitoring miR397b is essential for cost-effective biofuel generation. This study demonstrates the infiltration of nanorod iMS biosensors and detection of non-native miRNA 397b within plant cells for the first time. The investigation successfully demonstrates the localization of nanorod iMS biosensors through TEM and XRF-based elemental mapping for miRNA detection within plant cells of Nicotiana benthamiana. The study integrates shifted-excitation Raman difference spectroscopy (SERDS) to decrease background interference and enhance target signal extraction. In vivo SERDS testing confirms the dynamic detection of miR397b in Arabidopsis thaliana leaves after infiltration with iMS nanorods and miR397b target. This proof-of-concept study is an important stepping stone towards spatially resolved, intracellular miRNA mapping to monitor biomarkers and biological pathways for developing efficient renewable biofuel sources. [ABSTRACT FROM AUTHOR]

Increasing evidence suggests that metal dyshomeostasis plays an important role in human neurodegenerative diseases. Although distinctive metal distributions are described for mature hippocampus and cortex, much less is known about metal levels and intracellular distribution in individual hippocampal neuronal somata. To solve this problem, we conducted quantitative metal analyses utilizing synchrotron radiation X-Ray fluorescence on frozen hydrated primary cultured neurons derived from rat embryonic cortex (CTX) and two regions of the hippocampus: dentate gyrus (DG) and CA1. Comparing average metal contents showed that the most abundant metals were calcium, iron, and zinc, whereas metals such as copper and manganese were less than 10% of zinc. Average metal contents were generally similar when compared across neurons cultured from CTX, DG, and CA1, except for manganese that was larger in CA1. However, each metal showed a characteristic spatial distribution in individual neuronal somata. Zinc was uniformly distributed throughout the cytosol, with no evidence for the existence of previously identified zinc-enriched organelles, zincosomes. Calcium showed a peri-nuclear distribution consistent with accumulation in endoplasmic reticulum and/or mitochondria. Iron showed 2–3 distinct highly concentrated puncta only in peri-nuclear locations. Notwithstanding the small sample size, these analyses demonstrate that primary cultured neurons show characteristic metal signatures. The iron puncta probably represent iron-accumulating organelles, siderosomes. Thus, the metal distributions observed in mature brain structures are likely the result of both intrinsic neuronal factors that control cellular metal content and extrinsic factors related to the synaptic organization, function, and contacts formed and maintained in each region. [ABSTRACT FROM AUTHOR]

Rapidly-frozen hydrated (cryopreserved) specimens combined with cryo-scanning x-ray fluorescence microscopy provide an ideal approach for investigating elemental distributions in biological cells and tissues. However, because cryopreservation does not deactivate potentially infectious agents associated with Risk Group 2 biological materials, one must be concerned with contamination of expensive and complicated cryogenic x-ray microscopes when working with such materials. We employed ultraviolet germicidal irradiation to decontaminate previously cryopreserved cells under liquid nitrogen, and then investigated its effects on elemental distributions under both frozen hydrated and freeze dried states with x-ray fluorescence microscopy. We show that the contents and distributions of most biologically important elements remain nearly unchanged when compared with non-ultraviolet-irradiated counterparts, even after multiple cycles of ultraviolet germicidal irradiation and cryogenic x-ray imaging. This provides a potential pathway for rendering Risk Group 2 biological materials safe for handling in multiuser cryogenic x-ray microscopes without affecting the fidelity of the results. [ABSTRACT FROM AUTHOR]

It is widely accepted that micro- and nanoscale inhomogeneities govern the performance of many thin-film solar cell absorbers. These inhomogeneities yield material properties (e.g., composition, structure, and charge collection) that are challenging to correlate across length scales and measurement modalities. The challenge is compounded if a correlation is sought during device operation or in conditions that mimic aging under particular stressors (e.g., heat and electrical bias). Correlative approaches, particularly those based on synchrotron x-ray sources, are powerful since they can access several material properties in different modes (e.g., fluorescence, diffraction, and absorption) with minimal sample preparation. Small-scale laboratory x-ray instruments have begun to offer multi-modality but are typically limited by low x-ray photon flux, low spatial resolution, or specific sample sizes. To overcome these limitations, a characterization stage was developed to enable multi-scale, multi-modal operando measurements of industrially relevant photovoltaic devices. The stage offers compatibility across synchrotron x-ray facilities, enabling correlation between nanoscale x-ray fluorescence microscopy, microscale x-ray diffraction microscopy, and x-ray beam induced current microscopy, among others. The stage can accommodate device sizes up to 25 × 25 mm2, offering access to multiple regions of interest and increasing the statistical significance of correlated properties. The stage materials can sustain humid and non-oxidizing atmospheres, and temperature ranges encountered by photovoltaic devices in operational environments (e.g., from 25 to 100 °C). As a case study, we discuss the functionality of the stage by studying Se-alloyed CdTe photovoltaic devices aged in the stage between 25 and 100 °C. [ABSTRACT FROM AUTHOR]

The NASA Stardust spacecraft exposed an aerogel collector to the interstellar dust passing through the solar system. We performed X-ray fluorescence element mapping and abundance measurements, for elements 19 ≤ Z ≤ 30, on six 'interstellar candidates,' potential interstellar impacts identified by Stardust@Home and extracted for analyses in picokeystones. One, I1044,3,33, showed no element hot-spots within the designated search area. However, we identified a nearby surface feature, consistent with the impact of a weak, high-speed particle having an approximately chondritic ( CI) element abundance pattern, except for factor-of-ten enrichments in K and Zn and an S depletion. This hot-spot, containing approximately 10 fg of Fe, corresponds to an approximately 350 nm chondritic particle, small enough to be missed by Stardust@Home, indicating that other techniques may be necessary to identify all interstellar candidates. Only one interstellar candidate, I1004,1,2, showed a track. The terminal particle has large enrichments in S, Ti, Cr, Mn, Ni, Cu, and Zn relative to Fe-normalized CI values. It has high Al/Fe, but does not match the Ni/Fe range measured for samples of Al-deck material from the Stardust sample return capsule, which was within the field-of-view of the interstellar collector. A third interstellar candidate, I1075,1,25, showed an Al-rich surface feature that has a composition generally consistent with the Al-deck material, suggesting that it is a secondary particle. The other three interstellar candidates, I1001,1,16, I1001,2,17, and I1044,2,32, showed no impact features or tracks, but allowed assessment of submicron contamination in this aerogel, including Fe hot-spots having CI-like Ni/Fe ratios, complicating the search for CI-like interstellar/interplanetary dust. [ABSTRACT FROM AUTHOR]

Homogeneous self-assembled monolayers (SAMs) of alkanethiols (HS(CH2)nX) on Au(111) were used as substrates for crystallization of ferriprotoporphyrin IX (heme) in acidic aqueous solution. Different terminal functional groups (X = OH, COOH, NH2, CH3) were used on the SAMs as models of sites where heme crystallization takes place in blood-feeding organisms. Atomic force microscopy, X-ray diffraction (XRD), and X-ray absorption near edge spectroscopy (XANES) were employed to characterize particle morphology, density, crystallographic orientation, and the coordination environment. It was found that the morphology and extent of growth of particulates were strongly affected by the environment in which they crystallize. As has been previously observed, acicular crystals form in DMSO−methanol solution, whereas irregular aggregates of crystals form in acidic aqueous solution. Here tabular crystals were found to form on -NH2 and -OH terminated SAMs, whereas inclined crystals formed on -COOH and -CH3 terminated substrates. Particulate coverage on these SAMs decreased in the order of -NH2, -COOH, -CH3, and -OH. Chloroquine, a widely used antimalaria drug, slowed particle nucleation rate on the SAMs with varying efficacy but was most efficient on the -COOH SAM. XANES measurements showed that the coordination environment surrounding iron in the particles was found to be the same, regardless of the preparation method and matches existing spectra of hemozoin produced in vivo and synthetic β-hematin. Different crystallographic planes were found to be expressed depending on the identity of the SAM using XRD. The interaction between the terminal functional group of the SAM and the density and orientation of crystals is discussed. Homogeneous self-assembled monolayers (SAMs) of alkanethiols (HS(CH2)nX) on Au(111) were used as substrates for crystallization of ferriprotoporphyrin IX (heme) in acidic aqueous solution. Different terminal functional groups (X = OH, COOH, NH2, CH3) were used on the SAMs as models of sites where heme crystallization takes place in blood-feeding organisms. Atomic force microscopy, X-ray diffraction (XRD), and X-ray absorption near edge spectroscopy (XANES) were employed to characterize particle morphology, density, crystallographic orientation, and the coordination environment. [ABSTRACT FROM AUTHOR]

Owing to recent progress in analytical techniques, metallomics are evolving from detecting distinct trace metals in a defined state to monitor the dynamic changes in the abundance and location of trace metals in vitro and in vivo. Vascular metallomics is an emerging field that studies the role of trace metals in vasculature. This review will introduce common metallomics techniques including atomic absorption spectrometry, inductively coupled plasma-atomic emission spectrometry, inductively coupled plasma-mass spectrometry and X-ray fluorescence spectrometry with a summary table to compare these techniques. Moreover, we will summarize recent research findings that have applied these techniques to human population studies in cardiovascular diseases, with a particular emphasis on the role of copper in these diseases. In order to address the issue of interdisciplinary studies between metallomics and vascular biology, we will review the progress of efforts to understand the role of copper in neovascularization. This recent advance in the metallomics field may be a powerful tool to elucidate the signaling pathways and specific biological functions of these trace metals. Finally, we summarize the evidence to support the notion that copper is a dynamic signaling molecule. As a future direction, vascular metallomics studies may lead to the identification of targets for diagnosis and therapy in cardiovascular disease. [ABSTRACT FROM AUTHOR]

The intracellular distribution of transition metals in V79 Chinese hamster lung cells treated with subtoxic doses of the organometallic anticancer complexes Cp2MCl2, where Cp is η 5 -cyclopentadienyl and M is Mo, Nb, Ti, or V, has been studied by synchrotron-based X-ray fluorescence (XRF). While significantly higher concentrations of Mo and Nb were found in treated cells compared with control cells, distinct differences in the cellular distribution of each metal were observed. Analysis of thin sections of cells was consistent with some localization of Mo in the nucleus. Studies with a noncytotoxic thiol derivative of molybdocene dichloride showed an uneven distribution of Mo in the cells. For comparison, the low levels of Ti and V in cells treated with the more toxic titanocene and vanadocene complexes, respectively, resulted in metal concentrations at the detection limit of XRF. The results agree with independent chemical studies that have concluded that the biological chemistry of each of the metallocene dihalides is unique. [ABSTRACT FROM AUTHOR]

The photophysical and photochemical properties of two Pt(IV)Re(I) conjugates were studied via both experimental and computational methods. Both conjugates exhibit modest photocytotoxicity against ovarian cancer cells. X-ray fluorescence microscopy showed that Pt and Re colocalize in cells whether they had been irradiated or not. This work demonstrates the potential of photoactivated multilimetallic agents for combating cancer. [ABSTRACT FROM AUTHOR]

X-ray ptychography, a powerful scanning lensless imaging technique, has become attractive for nondestructively imaging internal structures at nanoscale. Stage positioning overhead in conventional step-scan ptychography is one of the limiting factors on the imaging throughput. In this work, we demonstrate the use of advanced fly scan ptychography to achieve high-resolution ptychograms of modern integrated circuits on a large field-of-view at millimeter scale. By completely removing stage overheads between scan points, the imaging time for millimeter-size sample can be significantly reduced. Furthermore, we implement the orthogonal probe relaxation technique to overcome the variation of illumination across the large scan area as well as local vibrations. The capability of x-ray ptychography shown here is broadly applicable for various studies, which requires both high spatial resolution and large scan area. [ABSTRACT FROM AUTHOR]

Background: Neuroblastoma is the most common extracranial solid malignancy in childhood which, despite the current progress in radiotherapy and chemotherapy protocols, still has a high mortality rate in high risk tumors. Nanomedicine offers exciting and unexploited opportunities to overcome the shortcomings of conventional medicine. The photocatalytic properties of Fe3O4 core-TiO2 shell nanocomposites and their potential for cell specific targeting suggest that nanoconstructs produced using Fe3O4 core-TiO2 shell nanocomposites could be used to enhance radiation effects in neuroblastoma. In this study, we evaluated bare, metaiodobenzylguanidine (MIBG) and 3,4-Dihydroxyphenylacetic acid (DOPAC) coated Fe3O4@TiO2 as potential radiosensitizers for neuroblastoma in vitro. Results: The uptake of bare and MIBG coated nanocomposites modestly sensitized neuroblastoma cells to ionizing radiation. Conversely, cells exposed to DOPAC coated nanocomposites exhibited a five-fold enhanced sensitivity to radiation, increased numbers of radiation induced DNA double-strand breaks, and apoptotic cell death. The addition of a peptide mimic of the epidermal growth factor (EGF) to nanoconjugates coated with MIBG altered their intracellular distribution. Cryo X-ray fluorescence microscopy tomography of frozen hydrated cells treated with these nanoconjugates revealed cytoplasmic as well as nuclear distribution of the nanoconstructs. Conclusions: The intracellular distribution pattern of different nanoconjugates used in this study was different for different nanoconjugate surface molecules. Cells exposed to DOPAC covered nanoconjugates showed the smallest nanoconjugate uptake, with the most prominent pattern of large intracellular aggregates. Interestingly, cells treated with this nanoconjugate also showed the most pronounced radiosensitization effect in combination with the external beam x-ray irradiation. Further studies are necessary to evaluate mechanistic basis for this increased radiosensitization effect. Preliminary studies with the nanoparticles carrying an EGF mimicking peptide showed that this approach to targeting could perhaps be combined with a different approach to radiosensitization – use of nanoconjugates in combination with the radioactive iodine. Much additional work will be necessary in order to evaluate possible benefits of targeted nanoconjugates carrying radionuclides. [ABSTRACT FROM AUTHOR]

Alkali addition in organic–inorganic perovskite has become the standard recipe for achieving solar cells with efficiencies exceeding 20%, but the mechanism is not well understood. We use non-contact carrier lifetime measurements, mobility measurements, and synchrotron-based x-ray characterization techniques to show that there is a unique benefit to adding hybrid perovskite samples with Rb and Cs simultaneously. When either Rb or Cs is added, charge carrier mobility increases with alkali concentration. Charge carrier lifetime benefits from alkali incorporation as well, but is optimized with only moderate concentration at 1%. When both Rb and Cs are introduced, however, the high mobility is maintained and the charge carrier lifetime increases considerably. Our results show that when incorporated alone, Rb and Cs have very similar roles in a perovskite crystal, but when co-added, halide distribution becomes homogenized correlating with improved charge transport properties. [ABSTRACT FROM AUTHOR]

Ptychography is a rapidly developing scanning microscopy which is able to view the internal structures of samples at a high resolution beyond the illumination size. The achieved spatial resolution is theoretically dose‐limited. A broadband source can provide much higher flux compared with a monochromatic source; however, it conflicts with the necessary coherence requirements of this coherent diffraction imaging technique. In this paper, a multi‐wavelength reconstruction algorithm has been developed to deal with the broad bandwidth in ptychography. Compared with the latest development of mixed‐state reconstruction approach, this multi‐wavelength approach is more accurate in the physical model, and also considers the spot size variation as a function of energy due to the chromatic focusing optics. Therefore, this method has been proved in both simulation and experiment to significantly improve the reconstruction when the source bandwidth, illumination size and scan step size increase. It is worth mentioning that the accurate and detailed information of the energy spectrum for the incident beam is not required in advance for the proposed method. Further, we combine multi‐wavelength and mixed‐state approaches to jointly solve temporal and spatial partial coherence in ptychography so that it can handle various disadvantageous experimental effects. The significant relaxation in coherence requirements by our approaches allows the use of high‐flux broadband X‐ray sources for high‐efficient and high‐resolution ptychographic imaging. [ABSTRACT FROM AUTHOR]

The article discusses the theoretical maximum power conversion efficiency of a hot carrier solar cell has as high as 66%, above the Shockley-Queisser limit. Topics include implementation of hot carrier solar cells requires preserving high carrier temperature as carriers migrate for the active layer; and the impressive progress, challenges remain in achieving high carrier temperature at reasonable carrier density maintaining thermal stability.

The potential chemotherapeutic properties coupled to photochemical transitions make the family of fac-[Re(CO)3(N,N)X]0/+ (N,N = a bidentate diimine such as 2,2′-bipyridine (bpy); X = halide, H2O, pyridine derivatives, PR3, etc.) complexes of special interest. We have investigated reactions of the aqua complex fac-[Re(CO)3(bpy)(H2O)](CF3SO3) (1) with potential anticancer activity with the amino acid l-cysteine (H2Cys), and its derivative N-acetyl-l-cysteine (H2NAC), as well as the tripeptide glutathione (H3A), under physiological conditions (pH 7.4, 37 °C), to model the interaction of 1 with thiol-containing proteins and enzymes, and the impact of such coordination on its photophysical properties and cytotoxicity. We report the syntheses and characterization of fac-[Re(CO)3(bpy)(HCys)]·0.5H2O (2), Na(fac-[Re(CO)3(bpy)(NAC)]) (3), and Na(fac-[Re(CO)3(bpy)(HA)])·H2O (4) using extended X-ray absorption spectroscopy, IR and NMR spectroscopy, electrospray ionization spectrometry, as well as the crystal structure of {fac-[Re(CO)3(bpy)(HCys)]}4·9H2O (2 + 1.75 H2O). The emission spectrum of 1 displays a variance in Stokes shift upon coordination of l-cysteine and N-acetyl-l-cysteine. Laser excitation at λ = 355 nm of methanol solutions of 1–3 was followed by measuring their ability to produce singlet oxygen (1O2) using direct detection methods. The cytotoxicity of 1 and its cysteine-bound complex 2 was assessed using the MDA-MB-231 breast cancer cell line, showing that the replacement of the aqua ligand on 1 with l-cysteine significantly reduced the cytotoxicity of the Re(I) tricarbonyl complex. Probing the cellular localization of 1 and 2 using X-ray fluorescence microscopy revealed an accumulation of 1 in the nuclear and/or perinuclear region, whereas the accumulation of 2 was considerably reduced, potentially explaining its reduced cytotoxicity. Replacing the aqua ligand with cysteine in the antitumor active fac-[Re(CO)3(bpy)(H2O)](CF3SO3) complex significantly reduced its cellular accumulation and cytotoxicity against the MDA-MB-213 breast cancer cell line, shifted its maximum emission to considerably higher energies, and decreased its fluorescence quantum yield. [ABSTRACT FROM AUTHOR]

A conjugate of a Mn-based superoxide dismutase mimic with a Re-based multimodal probe 1_; was studied in a cellular model of oxidative stress. Its speciation was investigated using Re and Mn X-fluorescence. Interestingly, 1_; shows a distribution different from its unconjugated analogue but a similar concentration in mitochondria and a similar bioactivity. [ABSTRACT FROM AUTHOR]

This manuscript concerns the application of infrared birefringence imaging (IBI) to quantify macroscopic and microscopic internal stresses in multicrystalline silicon (mc-Si) solar cell materials. We review progress to date, and advance four closely related topics. (1) We present a method to decouple macroscopic thermally-induced residual stresses and microscopic bulk defect related stresses. In contrast to previous reports, thermally-induced residual stresses in wafer-sized samples are generally found to be less than 5 MPa, while defect-related stresses can be several times larger. (2) We describe the unique IR birefringence signatures, including stress magnitudes and directions, of common microdefects in mc-Si solar cell materials including: β-SiC and β-Si3N4 microdefects, twin bands, nontwin grain boundaries, and dislocation bands. In certain defects, local stresses up to 40 MPa can be present. (3) We relate observed stresses to other topics of interest in solar cell manufacturing, including transition metal precipitation, wafer mechanical strength, and minority carrier lifetime. (4) We discuss the potential of IBI as a quality-control technique in industrial solar cell manufacturing. [ABSTRACT FROM AUTHOR]

Synchrotron-based microprobe techniques were used to obtain systematic information about the size distribution, spatial distribution, shape, electrical activity, chemical states, and origins of iron-rich impurity clusters in multicrystalline silicon (mc-Si) materials used for cost-effective solar cells. Two distinct groups of iron-rich cluster have been identified in both materials: (a) the occasional large (diameter >=1 μm) particles, either oxidized and/or present with multiple other metal species reminiscent of stainless steels or ceramics, which are believed to originate from a foreign source such as the growth surfaces, production equipment, or feedstock, and (b) the more numerous, homogeneously distributed, and smaller iron silicide precipitates (diameter <=800 nm, often <=100 nm), originating from a variety of possible formation mechanisms involving atomically dissolved iron in the melt or in the crystal. It was found that iron silicide nanoprecipitates account for bulk Fe concentrations as high as 1014–1015 cm-3 and can have a large negative impact on device performance because of their high spatial density and homogeneous distribution along structural defects. The large (diameter >=1 μm) particles, while containing elevated amounts—if not the majority—of metals, are low in spatial density and thus deemed to have a low direct impact on cell performance, although they may have a large indirect impact via the dissolution of Fe, thus assisting the formation of iron silicide nanoprecipitates. These results demonstrate that it is not necessarily the total Fe content that limits the mc-Si device performance but the distribution of Fe within the material. [ABSTRACT FROM AUTHOR]

In this study, synchrotron-based x-ray absorption microspectroscopy (μ-XAS) is applied to identify the chemical states of copper-rich clusters within a variety of silicon materials, including as-grown cast multicrystalline silicon solar cell material with high oxygen concentration and other silicon materials with varying degrees of oxygen concentration and copper contamination pathways. In all samples, copper silicide (Cu3Si) is the only phase of copper identified. It is noted from thermodynamic considerations that unlike certain metal species, copper tends to form a silicide and not an oxidized compound because of the strong silicon–oxygen bonding energy; consequently the likelihood of encountering an oxidized copper particle in silicon is small, in agreement with experimental data. In light of these results, the effectiveness of aluminum gettering for the removal of copper from bulk silicon is quantified via x-ray fluorescence microscopy, and a segregation coefficient is determined from experimental data to be at least (1–2)×103. Additionally, μ-XAS data directly demonstrate that the segregation mechanism of Cu in Al is the higher solubility of Cu in the liquid phase. In light of these results, possible limitations for the complete removal of Cu from bulk mc-Si are discussed. [ABSTRACT FROM AUTHOR]

Motivated by the advanced photon source upgrade, a new hard X-ray microscope called "Velociprobe" has been recently designed and built for fast ptychographic imaging with high spatial resolution. We are addressing the challenges of high-resolution and fast scanning with novel hardware designs, advanced motion controls, and new data acquisition strategies, including the use of high-bandwidth interferometric measurements. The use of granite, air-bearing-supported stages provides the necessary long travel ranges for coarse motion to accommodate real samples and variable energy operation while remaining highly stable during fine scanning. Scanning the low-mass zone plate enables high-speed and high-precision motion of the probe over the sample. With an advanced control algorithm implemented in a closed-loop feedback system, the setup achieves a position resolution (3σ) of 2 nm. The instrument performance is evaluated by 2D fly-scan ptychography with our developed data acquisition strategies. A spatial resolution of 8.8 nm has been demonstrated on a Au test sample with a detector continuous frame rate of 200 Hz. Using a higher flux X-ray source provided by double-multilayer monochromator, we achieve 10 nm resolution for an integrated circuit sample in an ultrafast scan with a detector's full continuous frame rate of 3000 Hz (0.33 ms per exposure), resulting in an outstanding imaging rate of 9 × 104 resolution elements per second. [ABSTRACT FROM AUTHOR]

Chemotherapy-induced peripheral neuropathy (CIPN) is a side effect of platinum-based chemotherapy and decreases the quality of life of cancer patients. We compared neuroprotective properties of several agents using an in vitro model of terminally differentiated human cells NT2-N derived from cell line NT2/D1. Sodium azide and an active metabolite of amifostine (WR1065) increase cell viability in simultaneous treatment with cisplatin. In addition, WR1065 protects the non-dividing neurons by decreasing cisplatin caused oxidative stress and apoptosis. Accumulation of Pt in cisplatin-treated cells was heterogeneous, but the frequency and concentration of Pt in cells were lowered in the presence of WR1065 as shown by X-ray fluorescence microscopy (XFM). Transition metals accumulation accompanied Pt increase in cells; this effect was equally diminished in the presence of WR1065. To analyze possible chemical modulation of Pt-DNA bonds, we examined the platinum LIII near edge spectrum by X-ray absorption spectroscopy. The spectrum found in cisplatin-DNA samples is altered differently by the addition of either WR1065 or sodium azide. Importantly, a similar change in Pt edge spectra was noted in cells treated with cisplatin and WR1065. Therefore, amifostine should be reconsidered as a candidate for treatments that reduce or prevent CIPN. [ABSTRACT FROM AUTHOR]

Zinc K‐edge X‐ray absorption near‐edge (XANES) spectroscopy was conducted on 40 zinc mineral samples and organic compounds. The K‐edge position varied from 9660.5 to 9666.0 eV and a variety of distinctive peaks at higher post‐edge energies were exhibited by the materials. Zinc is in the +2 oxidation state in all analyzed materials, thus the variations in edge position and post‐edge features reflect changes in zinc coordination. For some minerals, multiple specimens from different localities as well as pure forms from chemical supply companies were examined. These specimens had nearly identical K‐edge and post‐edge peak positions with only minor variation in the intensity of the post‐edge peaks. This suggests that typical compositional variations in natural materials do not strongly affect spectral characteristics. Organic zinc compounds also exhibited a range of edge positions and post‐edge features; however, organic compounds with similar zinc coordination structures had nearly identical spectra. Zinc XANES spectral patterns will allow identification of unknown zinc‐containing minerals and organic phases in future studies. [ABSTRACT FROM AUTHOR]

The role of the alkali metal cations in halide perovskite solar cells is not well understood. Using synchrotron-based nano–x-ray fluorescence and complementary measurements, we found that the halide distribution becomes homogenized upon addition of cesium iodide, either alone or with rubidium iodide, for substoichiometric, stoichiometric, and overstoichiometric preparations, where the lead halide is varied with respect to organic halide precursors. Halide homogenization coincides with long-lived charge carrier decays, spatially homogeneous carrier dynamics (as visualized by ultrafast microscopy), and improved photovoltaic device performance. We found that rubidium and potassium phase-segregate in highly concentrated clusters. Alkali metals are beneficial at low concentrations, where they homogenize the halide distribution, but at higher concentrations, they form recombination-active second-phase clusters. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid organometal halide perovskites are known for their excellent optoelectronic functionality as well as their wide‐ranging chemical flexibility. The composition of hybrid perovskite devices has trended toward increasing complexity as fine‐tuned properties are pursued, including multielement mixing on the constituents A and B and halide sites. However, this tunability presents potential challenges for charge extraction in functional devices. Poor consistency and repeatability between devices may arise due to variations in composition and microstructure. Within a single device, spatial heterogeneity in composition and phase segregation may limit the device from achieving its performance potential. This review details how the nanoscale elemental distribution and charge collection in hybrid perovskite materials evolve as chemical complexity increases, highlighting recent results using nondestructive operando synchrotron‐based X‐ray nanoprobe techniques. The results reveal a strong link between local chemistry and charge collection that must be controlled to develop robust, high‐performance hybrid perovskite materials for optoelectronic devices. [ABSTRACT FROM AUTHOR]

We investigate the types and origins of structural defects in thin (<100 µm) kerfless epitaxial single crystal silicon grown on top of reorganized porous silicon layers. Although the structural defect density is low (has average defect density < 10 4  cm −2 ), localized areas with a defect density > 10 5  cm −2 are observed. Cross-sectional and systematic plan-view defect etching and microscopy reveals that the majority of stacking faults and dislocations originate at the interface between the porous silicon layer and the epitaxial wafer. Localised dislocation clusters are observed in regions of collapsed/deformed porous silicon and at decorated stacking faults. In localized regions of high extended defect density, increased minority-carrier recombination activity is observed. Evidence for impurity segregation to the extended defects (internal gettering), which is known to exacerbate carrier recombination is demonstrated. The impact of the defects on material performance and substrate re-use is also discussed. [ABSTRACT FROM AUTHOR]

The inability to unambiguously distinguish the biogenicity of microfossil-like structures in the ancient rock record is a fundamental predicament facing Archean paleobiologists and astrobiologists. Therefore, novel methods for discriminating biological from nonbiological chemistries of microfossil-like structures are of the utmost importance in the search for evidence of early life on Earth. This, too, is important for the search for life on Mars by in situ analyses via rovers or sample return missions for future analysis here on Earth. Here, we report the application of synchrotron X-ray fluorescence imaging of vanadium, within thermally altered organic-walled microfossils of bona fide biological origin. From our data, we demonstrate that vanadium is present within microfossils of undisputable biological origin. It is well known in the organic geochemistry literature that elements such as vanadium are enriched and contained within crude oils, asphalts, and black shales that have been formed by diagenesis of biological organic material. It has been demonstrated that the origin of vanadium is due to the diagenetic alteration of precursor chlorophyll and heme porphyrin pigment compounds from living organisms. We propose that, taken together, microfossil-like morphology, carbonaceous composition, and the presence of vanadium could be used in tandem as a biosignature to ascertain the biogenicity of putative microfossil-like structures. Key Words: Microfossils-Synchrotron micro-X-ray fluorescence-Vanadium-Tetrapyrrole-Biosignature. Astrobiology 17, 1069-1076. [ABSTRACT FROM AUTHOR]

[RhIII(*Cp)Cl(X,Y)] n+ complexes {X, Y = Cl, PTA, n = 0 ( 2); X, Y = en, n = 1 ( 3, Cl- salt; 4, PF6- salt); X, Y = acac, n = 0 ( 5); X, Y = cur, n = 0 ( 6), where *Cp = pentamethylcyclopentadienato, curH = curcumin; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane; en = 1,2-ethanediamine; acac = acetylacetonato = 2,4-pentanedionato(1-)} were synthesized from [Rh(*Cp)(µ-Cl)Cl]2 ( 1). While 2- 5 were inactive against human epithelial A549 lung-cancer cells in assays of cytotoxicity, and antimetastatic and proapoptotic behaviors, 6 had a cytotoxic activity similar to that of curH over 72 h, but at 24 h in real-time cell migration assays, it was less active, showing slow release of curH. All complexes underwent ligand-exchange reactions with biomolecules and cells within the timeframes of the assays (X-ray absorption spectroscopy). Intracellular elemental distributions (X-ray fluorescence microscopy) showed that 6 effectively delivered curH to cells, where it was released. Other elemental distributions and caspase activities were consistent with preapoptotic activities. As such, 6 is a promising delivery agent for bioactive ligands, such as curH. However, pure curcumin itself showed a previously unrecognized ability to promote migration of A549 cells at subtoxic concentrations in the presence of endothelial growth factor, which may be a concern for its widespread use as a nutritional supplement and as a potential drug. This aspect warrants further research. [ABSTRACT FROM AUTHOR]

The glioblastoma (GBM) is characterized by a short median survival and an almost 100% tumor related mortality. GBM cells exhibit highly invasive behavior whose mechanisms are not yet fully understood. The present study explores application of X-ray and visible light microscopy to display the elemental and structural images of cells from 3 patient derived GMB samples and an established GMB cell line. Slight differences in elemental concentrations, in actin cytoskeleton organization and cell morphology were noted between all cells types by X-ray fluorescence and full field soft X-ray microscopy, as well as the Structured Illumination Super-resolution Microscope (SIM). Different sample preparation approaches were used to match each imaging technique. While preparation for SIM included cell fixation and staining, intact frozen hydrated cells were used for the trace element imaging by hard X-ray fluorescence and exploration of the structural features by soft X-ray absorption tomography. Each technique documented differences between samples with regard to morphology and elemental composition and underscored the importance of use of multiple patient derived samples for detailed GBM study. [ABSTRACT FROM AUTHOR]

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer-Lambert's law, formulae are presented in a general integral form and numerically applicable framework. The procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically. [ABSTRACT FROM AUTHOR]