High-resolution Cross Sections Research Articles

New and improved infra-red absorption cross sections and ACE-FTS retrievals of carbon tetrachloride (CCl4)

Carbon tetrachloride (CCl4) is one of the species regulated by the Montreal Protocol on account of its ability to deplete stratospheric ozone. As such, the inconsistency between observations of its abundance and estimated sources and sinks is an important problem requiring urgent attention (Carpenter et al., 2014) [5]. Satellite remote-sensing has a role to play, particularly limb sounders which can provide vertical profiles into the stratosphere and therefore validate stratospheric loss rates in atmospheric models.This work is in two parts. The first describes new and improved high-resolution infra-red absorption cross sections of carbon tetrachloride/dry synthetic air over the spectral range 700–860cm−1 for a range of temperatures and pressures (7.5–760Torr and 208–296K) appropriate for atmospheric conditions. This new cross-section dataset improves upon the one currently available in the HITRAN and GEISA databases. The second describes a new, preliminary ACE-FTS carbon tetrachloride retrieval that improves upon the v3.0/v3.5 data products, which are biased high by up to ~20–30% relative to ground measurements. Making use of the new spectroscopic data, this retrieval also improves the microwindow selection, contains additional interfering species, and utilises a new instrumental lineshape; it will form the basis for the upcoming v4.0 CCl4 data product.

Exam 2: Association Between Advances in High-Resolution Cross-Section Imaging Technologies and Increase in Prevalence of Pancreatic Cysts From 2005 to 2014

Exam 2: Association Between Advances in High-Resolution Cross-Section Imaging Technologies and Increase in Prevalence of Pancreatic Cysts From 2005 to 2014

Incorporation of deformation band fault damage zones in reservoir models

Fault damage zones in porous sandstones commonly exhibit networks of deformation bands reflecting crushing and reorganization of grains associated with small-scale, localized displacement. Deformation bands introduce anisotropic, order-of-magnitude reduction of effective permeability, which will affect fluid flow in reservoir rocks. We here present a method for incorporating these features in industrial-type reservoir models. The method involves the use of a three-dimensional fault zone grid generation technique that allows property modeling on a discrete high-resolution fault zone grid without refining the entire reservoir model. Deformation band data from 106 outcrop scan lines of fault damage zones were classified into discrete fault facies defined according to deformation band density. The distributional pattern of fault facies in the data exhibits recurrent spatial relationships, which could be reproduced using truncated Gaussian simulation in the modeling process. The frequency distribution of deformation band density for each facies was analyzed, and average density values were assigned to each facies for calculating cell permeability. Permeability anisotropy was handled by approximating the relationship between deformation band densities in different directions based on published high-resolution fault zone maps and cross sections. Fluid-flow simulations were carried out on several damage zones models, and results were benchmarked against models with conventional fault rendering without damage zones. Simulation results show that flow paths, remaining oil distribution, and reservoir responses in models incorporating damage zones deviate from models employing conventional fault representation without damage zones, and these differences increase as deformation band permeability decreases.

Performance and retention characteristics of nanocrystalline Si floating gate memory with an Al2O3 tunnel layer fabricated by plasma-enhanced atomic layer deposition

The down-scaling of nanocrystal Si (nc-Si) floating gate memory must overcome the challenge of leakage current induced by the conventional ultra-thin tunnel layer. We demonstrate that an improved memory performance based on the Al/SiNx/nc-Si/Al2O3/Si structure can be achieved by adopting the Al2O3 tunnel layer fabricated by plasma-enhanced atomic layer deposition. A larger memory window of 7.9 V and better retention characteristics of 4.7 V after 105 s can be obtained compared with the devices containing a conventional SiO2 tunnel layer of equivalent thickness. The capacitance-voltage characteristic reveals that the Al2O3 tunnel layer has a smaller electron barrier height, which ensures that more electrons are injected into the nc-Si dots through the Al2O3/Si interface. The analysis of the conductance-voltage and high-resolution cross-section transmission microscopy reveals that the smaller nc-Si dots dominate in the charge injection in the nc-Si floating gate MOS device with an Al2O3 tunnel layer. With an increase of the nc-Si size, both nc-Si and the interface contribute to the charge storage capacity and retention. The introduction of the Al2O3 tunnel layer in nc-Si floating gate memory provides a method to achieve an improved performance of nc-Si floating gate memory.

Clinical utility of anterior segment swept-source optical coherence tomography in glaucoma.

Optical coherence tomography (OCT), a noninvasive imaging modality that uses low-coherence light to obtain a high-resolution cross-section of biological structures, has evolved dramatically over the years. The Swept-source OCT (SS-OCT) makes use of a single detector with a rapidly tunable laser as a light source. The Casia SS-1000 OCT is a Fourier-domain, SS-OCT designed specifically for imaging the anterior segment. This system achieves high resolution imaging of 10΅m (Axial) and 30΅m (Transverse) and high speed scanning of 30,000 A-scans per second. With a substantial improvement in scan speed, the anterior chamber angles can be imaged 360 degrees in 128 cross sections (each with 512 A-scans) in about 2.4 seconds. We summarize the clinical applications of anterior segment SS-OCT in Glaucoma. Literature search: We searched PubMed and included Medline using the phrases anterior segment optical coherence tomography in ophthalmology, swept-source OCT, use of AS-OCT in glaucoma, use of swept-source AS-OCT in glaucoma, quantitative assessment of angle, filtering bleb in AS-OCT, comparison of AS-OCT with gonioscopy and comparison of AS-OCT with UBM. Search was made for articles dating 1990 to August 2015.

Absolute single-photoionization cross sections ofSe2+: Experiment and theory

Absolute single-photoionization cross-section measurements for ${\mathrm{Se}}^{2+}$ ions were performed at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged-beams photo-ion technique. Measurements were made at a photon energy resolution of $24\ifmmode\pm\else\textpm\fi{}3$ meV in the photon energy range 23.5--42.5 eV, spanning the ground state and low-lying metastable state ionization thresholds. To clearly resolve the resonant structure near the ground-state threshold, high-resolution measurements were made from 30.0 to 31.9 eV at a photon energy resolution of $6.7\ifmmode\pm\else\textpm\fi{}0.7$ meV. Numerous resonance features observed in the experimental spectra are assigned and their energies and quantum defects tabulated. The high-resolution cross-section measurements are compared with large-scale, state-of-the-art theoretical cross-section calculations obtained from the Dirac Coulomb $R$-matrix method. Suitable agreement is obtained over the entire photon energy range investigated. These results are an experimental determination of the absolute photoionization cross section of doubly ionized selenium and include a detailed analysis of the photoionization resonance spectrum of this ion.

Optical coherence microscopy of living cells and bioengineered tissue dynamics in high-resolution cross-section.

Optical coherence tomography (OCT) is a valuable tool in the cross-sectional observation/analysis of three-dimensional (3-D) biological tissues, and that histological observation is important clinically. However, the resolution of the technology is approximately 10-20 μm. In this study, optical coherence microscopy (OCM), a tomographic system combining OCT technology with a microscopic technique, was constructed for observing cells individually with a resolution at the submicrometer level. Cells and 3-D tissues fabricated by cell sheet technology were observed by OCM. Importantly, the cell nuclei and cytoplasm could be clearly distinguished, and the time-dependent dynamics of cell-sheet tissues could be observed in detail. Additionally, the 3-D migration of cells in the bioengineered tissue was also detected using OCM and metal-labeled cells. Bovine aortic endothelial cells, but not NIH3T3 murine embryonic skin fibroblasts, actively migrated within the 3-D tissues. This study showed that the OCM system would be a valuable tool in the fields of cell biology, tissue engineering, and regenerative medicine. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 481-488, 2017.

High-resolution absorption cross sections of C2H6 at elevated temperatures

Infrared absorption cross sections near 3.3 µm have been obtained for ethane, C2H6. These were acquired at elevated temperatures (up to 773 K) using a Fourier transform infrared spectrometer and tube furnace with a resolution of 0.005 cm−1. The integrated absorption was calibrated using composite infrared spectra taken from the Pacific Northwest National Laboratory (PNNL). These new measurements are the first high-resolution infrared C2H6 cross sections at elevated temperatures.

Association Between Advances in High-Resolution Cross-Section Imaging Technologies and Increase in Prevalence of Pancreatic Cysts From 2005 to 2014.

Increasingly, pancreatic cysts are discovered incidentally in patients undergoing cross-sectional imaging for nonpancreatic reasons. It is unclear whether this increase is caused by improved detection by progressively more sophisticated cross-sectional imaging techniques or by a true increase in prevalence. We aimed to determine the prevalence of incidental pancreatic cysts in patients undergoing magnetic resonance imaging (MRI) for nonpancreatic indications on successive, increasingly sophisticated MRI systems. Also, we compared prevalence based on the demographic characteristics of the patients. We collected data from MRIs performed at the Mayo Clinic in Florida during the sample months of January and February, from 2005 to 2014. Each patient's clinical chart was reviewed in chronological order to include the first 50 MRIs of each year (500 total). Patients were excluded if they had pancreatic disease including cysts, pancreatic surgery, pancreatic symptoms, pancreatic indication for the imaging study, or previous abdominal MRIs. An expert pancreatic MRI radiologist reviewed each image, looking for incidental pancreatic cysts. Of the 500 patients analyzed, 208 patients (41.6%) were found to have an incidental cyst. Asignificant relationship was observed between pancreatic cysts and patient age (P < .0001), diabetes mellitus (P= .001), and nonpancreatic cancer (P= .01), specifically nonmelanoma skin cancer (P= .03) or hepatocellular carcinoma (P= .02). The multivariable model showed a strong association between hardware and software versions and detection of cysts (P < .0001); the old hardware detected pancreatic cysts in 30.3% of patients, whereas the newest hardware detected cysts in 56.3% of patients. Based on an analysis of data collected from 2005 through 2014, newer versions of MRI hardware and software corresponded with higher numbers of pancreatic cysts detected. Older age, diabetes, and the presence of nonpancreatic cancer (specifically nonmelanoma skin cancer and hepatocarcinoma) were also associated with the presence of cysts.

High-resolution absorption measurements of NH3 at high temperatures: 500–2100 cm−1

High-resolution absorption spectra of NH3 in the region 500–2100cm−1 at temperatures up to 1027°C and approximately atmospheric pressure (1013±20 mbar) are measured. NH3 concentrations of 1000ppm, 0.5% and 1% in volume fraction were used in the measurements. Spectra are recorded in high temperature gas flow cells using a Fourier Transform Infrared (FTIR) spectrometer at a nominal resolution of 0.09cm−1. Measurements at 22.7°C are compared to high-resolution cross sections available from the Pacific Northwest National Laboratory (PNNL). The higher temperature spectra are analysed by comparison to a variational line list, BYTe, and experimental energy levels determined using the MARVEL procedure. Approximately 2000 lines have been assigned, of which 851 are newly assigned to mainly hot bands involving vibrational states as high as v2=5.

High-performance polyvinylidene fluoride/poly(styrene–butadiene–styrene)/functionalized MWCNTs-SCN-Ag nanocomposite membranes

In this work, solution blending technique was used to fabricate nano-filtration membranes of polyvinylidene fluoride (PVDF) and poly(styrene–butadiene–styrene) (SBS) blend matrix and modified multi-walled carbon nanotubes (MWCNTs) as filler. In this regard, two types of nanofiller, thiocyanate-modified nanotubes (MWCNTs-SCN) and silver-modified nanotubes (MWCNTs-SCN-Ag), were used as reinforced nanofiller in PVDF/SBS blend to form PVDF/SBS-MWCNTs-SCN 0.01–0.1 and PVDF/SBS-MWCNTs-SCN-Ag 0.01–0.1 membranes. Fourier transform infrared; field emission scanning electron microscopy; transmission electron microscopy; X-ray photoelectron spectroscopy; Brunauer, Emmett and Teller; and tensile tests were used for the exploration of structural and physical properties. Morphology studies showed the dispersion of polymer-coated silver nanoparticles with smooth and homogeneous surface in the spongy matrix. Porous nature of membranes was also observed in high-resolution cross-section micrographs. Tensile strength of PVDF/SBS-MWCNTs-SCN 0.01–1 nanocomposite series increased from 10.2 to 13.9 MPa, while PVDF/SBS-MWCNTs-SCN-Ag 0.01–1 had values in the range of 12.6–20.1 MPa. According to TGA, PVDF/SBS-MWCNTs-SCN revealed maximum decomposition temperature around 550–580 °C, while PVDF/SBS-MWCNTs-SCN-Ag had T max of 567–599 °C. The influence of various filler content on membrane performance and structure was studied using pertinent methods and techniques. Percentage of water content of PVDF/SBS-MWCNTs-SCN 0.01–0.1 was estimated around 1.08–2.80 % and this value was further increased to 1.94–4.65 % in silver nanoparticle-modified system. Moreover, the porosity of silver nanoparticle-modified system was found superior compared with the other composites. Pure water flux, salt rejection, and recovery were also found optimal for 0.05 wt% silver nanoparticle-based modified system. According to the consequences, novel membranes have fine nano-filtration characteristics to be utilized in advance water treatment industrial units.

Relative high-resolution absorption cross sections of C2H6 at low temperatures

Synchrotron radiation has been used to record absorption cross sections of ethane, C2H6, in the far-infrared with very high spectral resolution (up to 0.00096cm−1). C2H6 is present in the atmospheres of the Gas Giant planets and Titan but the vapor pressure at relevant atmospheric temperatures (i.e., between 70 and 200K) is low. This makes laboratory measurements difficult. We demonstrate the effectiveness of a unique “enclosive flow” cold cell, located at the Australian Synchrotron, that enables high-resolution absorption cross sections of gaseous C2H6 to be recorded at 90K.

Su1477 Advances in High Resolution Cross Section Imaging and the Rising Prevalence of Pancreatic Cysts Over the Past Decade

Su1477 Advances in High Resolution Cross Section Imaging and the Rising Prevalence of Pancreatic Cysts Over the Past Decade

Dislocation reduction in GaN grown on nano-patterned templates

A nano-holes patterned GaN-on-patterned sapphire substrate template has been developed to reduce the threading dislocation (TD) density in homoepitaxy GaN layer grown by plasma-assisted molecular beam epitaxy. The grown layers characterized by high resolution x-ray diffraction, photoluminescence, and cross-section transmission electron microscopy confirm that the TD density of GaN epilayer has been successfully reduced an order of magnitude to ~107cm−2 by optimizing the depth and coverage area percentage of patterned nano-holes.

Retrieval of three-dimensional small-scale structures in upper-tropospheric/lower-stratospheric composition as measured by GLORIA

Abstract. The three-dimensional quantification of small-scale processes in the upper troposphere and lower stratosphere is one of the challenges of current atmospheric research and requires the development of new measurement strategies. This work presents the first results from the newly developed Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) obtained during the ESSenCe (ESa Sounder Campaign) and TACTS/ESMVal (TACTS: Transport and composition in the upper troposphere/lowermost stratosphere, ESMVal: Earth System Model Validation) aircraft campaigns. The focus of this work is on the so-called dynamics-mode data characterized by a medium-spectral and a very-high-spatial resolution. The retrieval strategy for the derivation of two- and three-dimensional constituent fields in the upper troposphere and lower stratosphere is presented. Uncertainties of the main retrieval targets (temperature, O3, HNO3, and CFC-12) and their spatial resolution are discussed. During ESSenCe, high-resolution two-dimensional cross-sections have been obtained. Comparisons to collocated remote-sensing and in situ data indicate a good agreement between the data sets. During TACTS/ESMVal, a tomographic flight pattern to sense an intrusion of stratospheric air deep into the troposphere was performed. It was possible to reconstruct this filament at an unprecedented spatial resolution of better than 500 m vertically and 20 × 20 km horizontally.

Integrated high-resolution chemostratigraphy and facies-based stratigraphic architecture of the Lower Cretaceous (Aptian), Shu’aiba Formation, Saudi Arabia

High-resolution carbon isotope signatures were integrated with core descriptions and gamma-ray logs and used as a correlation tool for better age control to refine the sequence-stratigraphic framework of the Shu’aiba Formation in Saudi Arabia. The carbon isotope variations of the shallow carbonate Shu’aiba Formation correlate well with the Tethyan pelagic record and indicate an original marine signature for the Lower Cretaceous (Aptian) Shu’aiba Formation. Carbon isotope values of the Shu’aiba Formation range from 1.5‰ to 6‰ with minimal or no diagenetic effects. Oxygen isotope values range from −2.7‰ to −6.7‰ but were reset during diagenesis and cannot be applied for chemostratigraphic analysis. The Shu’aiba strontium isotope records range from 0.707356 to 0.707454 and differ slightly from the standard Aptian record because of diagenesis. The Shu’aiba Formation platform is a large-scale composite sequence (∼7 m.y.) composed of seven lower Aptian high-frequency sequences and two additional upper Aptian prograding sequences. Carbon isotope data were calibrated with core descriptions and gamma-ray logs to construct two detailed high-resolution stratigraphic cross sections. Carbon isotope data help refine the internal stratigraphic architecture of the Shu’aiba Formation especially on the slope and open-marine settings across the lower to upper Aptian boundary. The carbon isotope values of the Hawar “dense” unit in the base of the Shu’aiba Formation record major depletion corresponding to the global dissociation of methane hydrates, followed by major positive excursion associated with the deposition of Lithocodium and Bacinella facies coeval with the global oceanic anoxic event 1a. The rudist buildups on the platform have a value of approximately 4.5‰ at their base in most wells with a general uniform carbon isotope trend, followed by a gradual depletion to the top of the Shu’aiba Formation. Although some variations are observed in carbon isotope values associated with the lateral facies change from lagoon, margin, slope, open-marine, and basinal settings, carbon isotope trends are still similar and can be correlated fieldwide. Little evidence exists of meteoric diagenesis associated with the depletion of carbon isotope values. However, oxygen isotope records were possibly affected by meteoric diagenesis associated with subaerial exposure surfaces but did not get affected by the late Aptian hiatus, despite the massive karstification observed in cores. The good correlation between the original carbon isotope fluctuations and the third-order sequence framework of the Shu’aiba Formation fits well with the established carbon isotope curves that have been used as a proxy for global sea level changes during the Early Cretaceous. This study also shows that small-scale parasequences (fifth-order or higher) can be calibrated with carbon isotope curves, but they most likely represent relative sea level changes with local effects instead of global signatures. Application of high-resolution carbon isotope stratigraphy for the Shu’aiba Formation significantly constrain the stratigraphic framework and will lead to better geologic and simulation models for reservoir characterization and development.

Investigations of stacking fault density in perpendicular recording media

In magnetic recording media, the grains or clusters reverse their magnetization over a range of reversal field, resulting in a switching field distribution. In order to achieve high areal densities, it is desirable to understand and minimize such a distribution. Clusters of grains which contain stacking faults (SF) or fcc phase have lower anisotropy, an order lower than those without them. It is believed that such low anisotropy regions reverse their magnetization at a much lower reversal field than the rest of the material with a larger anisotropy. Such clusters/grains cause recording performance deterioration, such as adjacent track erasure and dc noise. Therefore, the observation of clusters that reverse at very low reversal fields (nucleation sites, NS) could give information on the noise and the adjacent track erasure. Potentially, the observed clusters could also provide information on the SF. In this paper, we study the reversal of nucleation sites in granular perpendicular media based on a magnetic force microscope (MFM) methodology and validate the observations with high resolution cross-section transmission electron microscopy (HRTEM) measurements. Samples, wherein a high anisotropy CoPt layer was introduced to control the NS or SF in a systematic way, were evaluated by MFM, TEM, and magnetometry. The magnetic properties indicated that the thickness of the CoPt layer results in an increase of nucleation sites. TEM measurements indicated a correlation between the thickness of CoPt layer and the stacking fault density. A clear correlation was also observed between the MFM results, TEM observations, and the coercivity and nucleation field of the samples, validating the effectiveness of the proposed method in evaluating the nucleation sites which potentially arise from stacking faults.

Optical coherence tomography imaging of macular oedema

Macular oedema (ME) occurs in a wide variety of pathological conditions and accounts for different degrees of vision loss. Early detection of ME is therefore critical for diagnosis and therapeutic...

Dielectric/Si Interface Quality Characterization Using Room Temperature Photoluminescence

Advanced metal-oxide-semiconductor (MOS) and metal-insulator-semiconductor (MIS) devices employ ultra thin dielectric gate layers. The physical dimensions are in the range of single digit to double digit nanometers. The effective oxide thickness (EOT) is significantly less than 10 nm. Pure SiO2 or combinations of SiO2and SiN layers are typically used as gate dielectrics. High dielectric constant materials (high-k dielectrics) and metal gates are also frequently used, depending on chip design.Physical dimensions of dielectric layer(s) are typically measured using ellipsometry and high resolution cross-section transmission microscopy (HRXTEM). Electrical characteristics are typically characterized using either contact or non-contact C-V and I-V measurements tools. Non-contact characterization techniques are generally preferred for in-line monitoring applications. However, spatial resolution of non-contact C-V and I-V measurement techniques is in the range of a few millimeters, which are 3 orders of magnitude larger than typical dimensions of actual devices. High spatial resolution, non-contact dielectric/Si interface quality characterization techniques must be developed.In this paper, ultra thin (~7 nm) SiO2/Si and ultra thin SiN/SiO2/Si wafers were prepared by low pressure thermal chemical vapor deposition (CVD) and thermal oxidation. Dielectric/Si interface quality was characterized by room temperature spectroscopic photoluminescence (PL) measurements. The PL intensity and spectra from Si were measured under different excitation wavelengths which have different probing depths. PL is an optical characterization technique which does not require any sample preparation and physical contact. Typical spatial resolution is in the range of a few microns. Small variations in dielectric/Si interface quality modulates electronic carrier behaviors significantly which results in large variations in PL intensity and spectra. Significant variations in PL intensity and spectra were measured from ultra thin (~7 nm) SiO2/Si wafers prepared by and low pressure thermal CVD and thermal oxidation. Si wafers with thermal oxide films generally showed significantly stronger PL intensity than Si wafers with thermal CVD grown oxide films (Fig. 1). Trends in PL intensity and spectra indicate the SiO2/Si interface quality of the thermally oxidized SiO2/Si is superior to that of the thermal CVD grown SiO2/Si (Fig. 2). PL characterization is found to be very sensitive to the integrity of dielectric/Si interface and thus, is promising as an in-line, non-contact interface quality monitoring technique.The excitation wavelength dependence of PL intensity and spectra of SiO2/Si and SiN/SiO2/Si will be discussed along with conventional physical and electrical characterization results.

Isotope selective photodissociation of N2by the interstellar radiation field and cosmic rays

Photodissociation of 14N2 and 14N15N occurs in interstellar clouds, circumstellar envelopes, protoplanetary discs, and other environments due to UV radiation from stellar sources and the presence of cosmic rays. This source of N atoms initiates the formation of complex N-bearing species and influences their isotopic composition. To study the photodissociation rates of 14N15N by UV continuum radiation and both isotopologues in a field of cosmic ray induced photons. To determine the effect of these on the isotopic composition of more complex molecules. High-resolution photodissociation cross sections of N2 are used from an accurate and comprehensive quantum- mechanical model of the molecule based on laboratory experiments. A similarly high-resolution spectrum of H2 emission following interactions with cosmic rays has been constructed. The spectroscopic data are used to calculate dissociation rates which are input into isotopically differentiated chemical models, describing an interstellar cloud and a protoplanetary disc. The dissociation rate of 14N15N in a Draine field assuming 30K excitation is 1.73x10-10s-1 and the rate due to cosmic rays assuming an H2 ionisation rate of 10-16s-1 is about 10-15s-1, with up to a factor of 10 difference between isotopologues. Shielding functions for 14N15N by 14N2, H2, and H are presented. Incorporating these into an interstellar cloud model, an enhancement of the atomic 15N/14N ratio is obtained due to the self-shielding of external radiation at an extinction of about 1.5 mag. This effect is larger where grain growth has reduced the opacity of dust to ultraviolet radiation. The transfer of photolytic isotopic fractionation N2 to other molecules is significant in a disc model, and is species dependent with 15N enhancement approaching a factor of 10 for HCN.