Highly Transparent Ka-/W-Band Electromagnetic Shielding Films Based on Double-Layered Metal Meshes.

An electromagnetic (EM) wave-shielding film exhibiting high performance in high-frequency bands, such as the Ka- and W-bands, was fabricated by using double-layered metal meshes. The double-layered shielding (DLS) film consists of metallic micromesh and nanomesh electrodes (NMEs) on the upper and lower surfaces of a poly(ethylene terephthalate) (PET) film, respectively. The micromesh electrodes (MMEs) were fabricated such that they possessed a thickness higher than the line width, and they thus exhibited excellent electromagnetic wave-shielding performance in addition to optical transmittance. Moreover, the nanomesh electrodes helped prevent the deterioration of the shielding performance owing to the increase in frequency, which was possible by decreasing the aperture size of the mesh-type electrodes. The shielding effectiveness (SE) of the double-layered metal-mesh film was evaluated by using a shielding measurement system that is optimized for high frequencies. In addition, optical transmittance and flexibility tests were conducted. The results confirm that the double-layered shielding film exhibited a shielding effectiveness of more than 50 dB at an optical transmittance of 90% and a stable bending resistance of up to 5000 cycles at a radius of curvature of 6 mm. Double-layered metal-mesh films with such excellent performance are expected to be widely used in diverse applications such as the automobile, medical, and military industries.

Micrometer Scale Resolution Limit of a Fiber-Coupled Electro-Optic Probe.

We present the practical resolution limit of a fine electrical structure based on a fiber-coupled electro-optic probing system. The spatial resolution limit was experimentally evaluated on the sub-millimeter to micrometer scale of planar electrical transmission lines. The electrical lines were fabricated to have various potential differences depending on the dimensions and geometry. The electric field between the lines was measured through an electro-optic probe, which was miniaturized up to the optical bare fiber scale so as to investigate the spatial limit of electrical signals with minimal invasiveness. The experimental results show that the technical resolution limitation of a fiber-coupled probe can reasonably approach a fraction of the mode field diameter (~10 µm) of the fiber in use.

Correlative 3D x-ray fluorescence and ptychographic tomography of frozen-hydrated green algae.

Accurate knowledge of elemental distributions within biological organisms is critical for understanding their cellular roles. The ability to couple this knowledge with overall cellular architecture in three dimensions (3D) deepens our understanding of cellular chemistry. Using a whole, frozen-hydrated Chlamydomonas reinhardtii cell as an example, we report the development of 3D correlative microscopy through a combination of simultaneous cryogenic x-ray ptychography and x-ray fluorescence microscopy. By taking advantage of a recently developed tomographic reconstruction algorithm, termed GENeralized Fourier Iterative REconstruction (GENFIRE), we produce high-quality 3D maps of the unlabeled alga's cellular ultrastructure and elemental distributions within the cell. We demonstrate GENFIRE's ability to outperform conventional tomography algorithms and to further improve the reconstruction quality by refining the experimentally intended tomographic angles. As this method continues to advance with brighter coherent light sources and more efficient data handling, we expect correlative 3D x-ray fluorescence and ptychographic tomography to be a powerful tool for probing a wide range of frozen-hydrated biological specimens, ranging from small prokaryotes such as bacteria, algae, and parasites to large eukaryotes such as mammalian cells, with applications that include understanding cellular responses to environmental stimuli and cell-to-cell interactions.

Joint reconstruction of x-ray fluorescence and transmission tomography.

X-ray fluorescence tomography is based on the detection of fluorescence x-ray photons produced following x-ray absorption while a specimen is rotated; it provides information on the 3D distribution of selected elements within a sample. One limitation in the quality of sample recovery is the separation of elemental signals due to the finite energy resolution of the detector. Another limitation is the effect of self-absorption, which can lead to inaccurate results with dense samples. To recover a higher quality elemental map, we combine x-ray fluorescence detection with a second data modality: conventional x-ray transmission tomography using absorption. By using these combined signals in a nonlinear optimization-based approach, we demonstrate the benefit of our algorithm on real experimental data and obtain an improved quantitative reconstruction of the spatial distribution of dominant elements in the sample. Compared with single-modality inversion based on x-ray fluorescence alone, this joint inversion approach reduces ill-posedness and should result in improved elemental quantification and better correction of self-absorption.

Nanoscale x-ray imaging of circuit features without wafer etching.

Modern integrated circuits (ICs) employ a myriad of materials organized at nanoscale dimensions, and certain critical tolerances must be met for them to function. To understand departures from intended functionality, it is essential to examine ICs as manufactured so as to adjust design rules, ideally in a non-destructive way so that imaged structures can be correlated with electrical performance. Electron microscopes can do this on thin regions, or on exposed surfaces, but the required processing alters or even destroys functionality. Microscopy with multi-keV x-rays provides an alternative approach with greater penetration, but the spatial resolution of x-ray imaging lenses has not allowed one to see the required detail in the latest generation of ICs. X-ray ptychography provides a way to obtain images of ICs without lens-imposed resolution limits, with past work delivering 20-40 nm resolution on thinned ICs. We describe a simple model for estimating the required exposure, and use it to estimate the future potential for this technique. Here we show for the first time that this approach can be used to image circuit detail through an unprocessed 300 µm thick silicon wafer, with sub-20 nm detail clearly resolved after mechanical polishing to 240 µm thickness was used to eliminate image contrast caused by Si wafer surface scratches. By using continuous x-ray scanning, massively parallel computation, and a new generation of synchrotron light sources, this should enable entire non-etched ICs to be imaged to 10 nm resolution or better while maintaining their ability to function in electrical tests.

Effects of exercise on mature or precursor brain­derived neurotrophic factor pathways in ovariectomized rats.

Ovariectomy (OVX) is a method used to block estrogen in female rats that induces hippocampal dysfunction and affects brain­derived neurotrophic factor (BDNF) pathways. The majority of previous studies investigating OVX focused on BDNF expression in the hippocampus and cognitive function. The present study focused on the pathways of each BDNF type, precursor (proBDNF) and mature (mBDNF), and the effects of regular exercise in the hippocampus of ovariectomized rats. Female Sprague­Dawely rats were used and OVX surgery was performed. After 1 week of recovery from surgery, two groups of rats that received OVX surgery were subjected to regular treadmill exercise for 8 weeks. The results of protein levels by western blotting indicated that the expression of proBDNF, p75 neurotrophin receptor (p75NTR) and c­Jun N­terminal protein kinase (JNK) was increased, and mBDNF, tropomyosin­related kinase B (TrkB) and nuclear factor­κB expression was significantly reduced in the OVX control group compared with the sham control group SC (P<0.05). Thus, the survival pathway by mBDNF was impaired and the pro­apoptotic response was activated by increased JNK expression due to proBDNF­p75NTR binding in the hippocampus of ovariectomized rats. By contrast, exercise reduced activation of the pro­apoptotic response and increased mBDNF­TrkB expression in the hippocampus of ovariectomized rats. Thus, regular exercise may increase the activation of survival pathways via mBDNF and reducing the activation of the pro­apoptotic pathway of proBDNF in the hippocampus of ovariectomized rats.

Synchrotron-based X-ray fluorescence microscopy enables multiscale spatial visualization of ions involved in fungal lignocellulose deconstruction.

The role of ions in the fungal decay process of lignocellulose biomaterials, and more broadly fungal metabolism, has implications for diverse research disciplines ranging from plant pathology and forest ecology, to carbon sequestration. Despite the importance of ions in fungal decay mechanisms, the spatial distribution and quantification of ions in lignocellulosic cell walls and fungal hyphae during decay is not known. Here we employ synchrotron-based X-ray fluorescence microscopy (XFM) to map and quantify physiologically relevant ions, such as K, Ca, Mn, Fe, and Zn, in wood being decayed by the model brown rot fungus Serpula lacrymans. Two-dimensional XFM maps were obtained to study the ion spatial distributions from mm to submicron length scales in wood, fungal hyphae with the dried extracellular matrix (ECM) from the fungus, and Ca oxalate crystals. Three-dimensional ion volume reconstructions were also acquired of wood cell walls and hyphae with ECM. Results show that the fungus actively transports some ions, such as Fe, into the wood and controls the distribution of ions at both the bulk wood and cell wall length scales. These measurements provide new insights into the movement of ions during decay and illustrate how synchrotron-based XFM is uniquely suited study these ions.

Field-calibrated magneto-optic sensor based on off-axis optical probing of intense magnetic fields.

We present a magneto-optic sensing system based on the "off-axis" optical probing technique to control the measurement sensitivity of magnets with various field strengths. The magnetic field is experimentally investigated in the absolute scale through a photonic calibration method with a standard electromagnet. Our all-dielectric magnetic field probe has a wide dynamic range (20 mT-3 T) with good responsivity and low probe invasiveness against the magnetic field being measured. Utilizing this magnetic-field-calibrated probing system, we obtain the magnetic field distribution of permanent magnets. Subsequently, we compare our results with numerical analyses to confirm the effectiveness of the probing system. Finally, we measure the intense magnetic field inside the bore of a 3.0-T clinical magnetic resonance imaging system with our probe.

Two-tier calibrated electro-optic sensing system for intense field characterization of high-power W-band gyrotron.

We present a field-calibrated electro-optic sensing system for measurement of the electric field radiating from a high-power vacuum oscillator at ~95 GHz. The intense electric field is measured in absolute scale via two probe-calibration steps, associated with a photonic heterodyne scheme. First, a micro-electro-optic probe, fabricated to less than one-tenth the oscillation wavelength scale to minimize field-perturbation due to the probe, is placed on the aperture of a field-calculable WR-10 waveguide to calibrate the probe in V/m scale. Then, using this arrangement as a calibrated reference probe at the first-tier position, another probe-bulkier, and thus more robust and sensitive but not accessible to the aperture-is calibrated at the second-tier position away from the waveguide aperture. This two-tier calibrated probe was utilized to diagnose the sub-MV/m scale of intense electric fields and emissions from a high-power W-band gyrotron. The experimental results obtained proved consistent with calculated analytical results-verifying the efficacy of the developed system.

Treadmill exercise after social isolation increases the levels of NGF, BDNF, and synapsin I to induce survival of neurons in the hippocampus, and improves depression-like behavior.

PURPOSE: We investigated the effects of 8 weeks of treadmill exercise on nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and synapsin I protein expression and on the number of 5-bromo-2'-deoxyuridine-5'-mono-phosphate (BrdU)-positive cells in the dentate gyrus of the hippocampus in socially isolated rats. Additionally, we examined the effects of exercise on the number of serotonin (5-HT)- and tryptophan hydroxylase (TPH)-positive cells in the raphe nuclei and on depression behaviors induced by social isolation. METHODS: Forty male Sprague-Dawley rats were divided into four groups: (1) group housing and control group (GCG, n = 10); (2) group housing and exercise group (GEG, n = 10); (3) isolated housing and control group (ICG, n = 10); and (4) isolated housing and exercise group (IEG, n = 10). After 1 week of housing under the normal condition of 3 animals per cage, rats were socially isolated via transfer to individual cages for 8 weeks. Rats were then subjected to treadmill exercise for 5 days per week for 8 weeks during which time the speed of the treadmill was gradually increased. RESULTS: Compared to the GCG, levels of NGF, BDNF, and synapsin I were significantly decreased in the ICG and significantly increased in the IEG (p < 0.001 respectively). Significantly more BrdU-positive cells in the GEG were present as compared to the GCG and ICG, and more BrdU-positive cells were found in the IEG as compared to the ICG (p < 0.001). 5-HT-positive cells in the GEG were significantly increased compared to the GCG and ICG, and more of these cells were found in the IEG as compared to the ICG (p < 0.01). TPH-positive cells in the GEG were significantly increased compared to those in the GCG and ICG (p < 0.05). In the forced swim test, immobility time was significantly increased in the ICG and significantly decreased in the IEG as compared to the ICG (p < 0.01). CONCLUSION: These results showed that regular treadmill exercise following social isolation not only increased the levels of NGF, BDNF, and synapsin I to induce survival of neurons in the hippocampus but also improved depression by increasing the number of serotonergic cells in the raphe nuclei.

A New Workflow for x-ray fluorescence tomography: MAPSToTomoPy.

X-ray fluorescence tomography involves the acquisition of a series of 2D x-ray fluorescence datasets between which a specimen is rotated. At the Advanced Photon Source at Argonne National Laboratory, the workflow at beamlines 2-ID-E and 21-ID-D (the Bionanoprobe, a cryogenic microscope system) has included the use of the program MAPS for obtaining elemental concentrations from 2D images, and the program TomoPy which was developed to include several tomographic reconstruction methods for x-ray transmission data. In the past, fluorescence projection images from an individual chemical element were hand-assembled into a 3D dataset for reconstruction using interactive tools such as ImageJ. We describe here the program MAPSToTomoPy, which provides a graphical user interface (GUI) to control a workflow between MAPS and TomoPy, with tools for visualizing the sinograms of projection image sequences from particular elements and to use these to help correct misalignments of the rotation axis. The program also provides an integrated output of the 3D distribution of the detected elements for subsequent 3D visualization packages.

Scientific data exchange: a schema for HDF5-based storage of raw and analyzed data.

Data Exchange is a simple data model designed to interface, or `exchange', data among different instruments, and to enable sharing of data analysis tools. Data Exchange focuses on technique rather than instrument descriptions, and on provenance tracking of analysis steps and results. In this paper the successful application of the Data Exchange model to a variety of X-ray techniques, including tomography, fluorescence spectroscopy, fluorescence tomography and photon correlation spectroscopy, is described.

Alignment of low-dose X-ray fluorescence tomography images using differential phase contrast.

X-ray fluorescence nanotomography provides unprecedented sensitivity for studies of trace metal distributions in whole biological cells. Dose fractionation, in which one acquires very low dose individual projections and then obtains high statistics reconstructions as signal from a voxel is brought together (Hegerl & Hoppe, 1976), requires accurate alignment of these individual projections so as to correct for rotation stage runout. It is shown here that differential phase contrast at 10.2 keV beam energy offers the potential for accurate cross-correlation alignment of successive projections, by demonstrating that successive low dose, 3 ms per pixel, images acquired at the same specimen position and rotation angle have a narrower and smoother cross-correlation function (1.5 pixels FWHM at 300 nm pixel size) than that obtained from zinc fluorescence images (25 pixels FWHM). The differential phase contrast alignment resolution is thus well below the 700 nm × 500 nm beam spot size used in this demonstration, so that dose fractionation should be possible for reduced-dose, more rapidly acquired, fluorescence nanotomography experiments.

Mechanistic studies of water electrolysis and hydrogen electro-oxidation on high temperature ceria-based solid oxide electrochemical cells.

Through the use of ambient pressure X-ray photoelectron spectroscopy (APXPS) and a single-sided solid oxide electrochemical cell (SOC), we have studied the mechanism of electrocatalytic splitting of water (H2O + 2e(-) → H2 + O(2-)) and electro-oxidation of hydrogen (H2 + O(2-) → H2O + 2e(-)) at ∼700 °C in 0.5 Torr of H2/H2O on ceria (CeO2-x) electrodes. The experiments reveal a transient build-up of surface intermediates (OH(-) and Ce(3+)) and show the separation of charge at the gas-solid interface exclusively in the electrochemically active region of the SOC. During water electrolysis on ceria, the increase in surface potentials of the adsorbed OH(-) and incorporated O(2-) differ by 0.25 eV in the active regions. For hydrogen electro-oxidation on ceria, the surface concentrations of OH(-) and O(2-) shift significantly from their equilibrium values. These data suggest that the same charge transfer step (H2O + Ce(3+) <-> Ce(4+) + OH(-) + H(•)) is rate limiting in both the forward (water electrolysis) and reverse (H2 electro-oxidation) reactions. This separation of potentials reflects an induced surface dipole layer on the ceria surface and represents the effective electrochemical double layer at a gas-solid interface. The in situ XPS data and DFT calculations show that the chemical origin of the OH(-)/O(2-) potential separation resides in the reduced polarization of the Ce-OH bond due to the increase of Ce(3+) on the electrode surface. These results provide a graphical illustration of the electrochemically driven surface charge transfer processes under relevant and nonultrahigh vacuum conditions.

Photocatalysis and hydrophilicity of doped TiO2 thin films.

TiO(2) thin films were prepared using the dip-coating method with a polymeric sol including additives such as Al, W, and Al+W to examine two major properties: photocatalysis and hydrophilicity. W-doped films showed the best photocatalytic efficiency, while Al-doped film was poorer than undoped samples. However, good hydrophilicity in terms of saturation contact angle and surface conversion rate was found in Al- and (Al+W)-mixed-doped films. It was found that deep electron-hole traps and high surface acidity of W-doped TiO(2) thin film were the major factors in high photocatalytic efficiency. In addition, low surface acidities of Al- and (Al+W)-doped films provided better hydrophilicity than W-doped ones. However, the amount of [Ti(3+)] point defects on the surface was another major factor, probably the most important, in getting the best hydrophilicity. Conclusively, it seemed that many parts of the photocatalysis mechanism depend more on bulk-related properties than do those of hydrophilicity, which can be defined as an interfacial (surface) or near-surface-restricted process.