High-resolution Density Research Articles

Fast quantitative fluorescence authentication of milk powder and vanillin by a line-scan hyperspectral system.

We present a fast hyperspectral line-scan fluorescence imaging system to verify the feasibility of quantitative fluorescence authentication of powders. Vanillin, which is restricted for use in milk powder, especially in milk powder for infants, is mixed with milk powder in different mass concentrations (5%, 10%, 30%, 50%, 70%, and 90%). Mixed powders are located on a motorized linear stage. A 405nm line laser is utilized to excite the fluorescence of the sample. Based on galvo scanning, we can generate a laser line with high spatial resolution and high-intensity density on the samples. An imaging spectrometer with a complementary metal-oxide semiconductor (CMOS) camera as detector is built. The spectral range of the spectrometer is 365-810nm, with about 1nm spectral resolution. One snapshot of the CMOS can acquire the fluorescent spatial and spectral information of a line region in 100ms. By scanning the motorized linear stage, we obtain the fluorescence hypercube of the sample. A 100×1926×1216 hypercube, which covers an area of 15 mm×5 mm, is obtained in 50s. The imaging speed can be enhanced further by increasing the intensity of the excitation laser and the sensitivity of the area camera. Fully constrained least squares, a linear spectral mixture analysis, is utilized to analyze the hypercube obtained by our homemade imaging spectrometer, thus obtaining the pixel concentration of vanillin in each mixed powder. Linear regression analysis is used for the pixel concentration and mass concentration of vanillin. A linear relationship with coefficient of determination R2 equal to one is observed, which demonstrates the capability of fluorescence hyperspectral quantitative analysis in powders.

High-fidelity geometry models for improving the consistency of CHAMP, GRACE, GOCE and Swarm thermospheric density data sets

During the last two decades, accelerometers on board of the CHAMP, GRACE, GOCE and Swarm satellites have provided high-resolution thermosphere density data to improve our knowledge on atmospheric dynamics and coupling processes in the thermosphere-ionosphere region. Most users of the data have focused on relative density variations. Scale differences between datasets and models have been largely neglected or removed using ad hoc scale factors. The origin of these scale differences arises from errors in the aerodynamic modelling, specifically in the modelling of the satellite outer surface geometry and of the gas-surface interactions. Therefore, the first step to remove the scale differences is to enhance the geometry modelling. This work forms the foundation for the future improvement of characterization of satellite aerodynamics and gas-surface interactions models at TU Delft, as well as for extending the use of sideways and angular accelerations in the aerodynamic analysis of accelerations and derivation of thermosphere datasets. Although work to improve geometry and aerodynamic force models by other authors has focused on CHAMP and GRACE, this paper includes the GOCE and Swarm satellites as well. In addition, it uses a density determination algorithm that is valid for arbitrary attitude orientations, enabling a validation making use of attitude manoeuvres. The results show an improvement in the consistency of density data between these four missions, and of data obtained before, during and after attitude manoeuvres of CHAMP and Swarm. The new models result in larger densities, compared to the previously used panel method. The largest average rescaling of density, by switching to the new geometry models is reached for Swarm at 32%, the smallest for GRACE at 5%. For CHAMP and GOCE, mean differences of 11% and 9% are obtained respectively. In this paper, an overview of the improvements and comparisons of data sets is provided together with an introduction to the next research phase on the gas-surface interactions.

Arbitrary-order Hilbert Spectral Analysis and Intermittency in Solar Wind Density Fluctuations

Abstract The properties of inertial- and kinetic-range solar wind turbulence have been investigated with the arbitrary-order Hilbert spectral analysis method, applied to high-resolution density measurements. Due to the small sample size and to the presence of strong nonstationary behavior and large-scale structures, the classical analysis in terms of structure functions may prove to be unsuccessful in detecting the power-law behavior in the inertial range, and may underestimate the scaling exponents. However, the Hilbert spectral method provides an optimal estimation of the scaling exponents, which have been found to be close to those for velocity fluctuations in fully developed hydrodynamic turbulence. At smaller scales, below the proton gyroscale, the system loses its intermittent multiscaling properties and converges to a monofractal process. The resulting scaling exponents, obtained at small scales, are in good agreement with those of classical fractional Brownian motion, indicating a long-term memory in the process, and the absence of correlations around the spectral-break scale. These results provide important constraints on models of kinetic-range turbulence in the solar wind.

44‐1: Distinguished Student Paper: Motion‐blur‐free LCD for High Resolution Virtual Reality Displays

A new liquid crystal display device with fast response time, high transmittance, and low voltage for virtual reality is reported. When driven at 90Hz with 17% duty ratio, the motion picture response time is 1.5 ms, similar to CRT, leading to indistinguishable motion blur. Moreover, this device enables high resolution density because only one thin‐film transistor per pixel is needed and it has a built‐in storage capacitor.

Imprints of the large-scale structure on AGN formation and evolution

Black hole masses are found to correlate with several global properties of their host galaxies, suggesting that black holes and galaxies have an intertwined evolution and that active galactic nuclei (AGN) have a significant impact on galaxy evolution. Since the large-scale environment can also affect AGN, this work studies how their formation and properties depend on the environment. We have used a reconstructed three-dimensional high-resolution density field obtained from a Bayesian large-scale structure reconstruction method applied to the 2M++ galaxy sample. A web-type classification relying on the shear tensor is used to identify different structures on the cosmic web, defining voids, sheets, filaments, and clusters. We confirm that the environmental density affects the AGN formation and their properties. We found that the AGN abundance is equivalent to the galaxy abundance, indicating that active and inactive galaxies reside in similar dark matter halos. However, occurrence rates are different for each spectral type and accretion rate. These differences are consistent with the AGN evolutionary sequence suggested by previous authors, Seyferts and Transition objects transforming into low-ionization nuclear emission line regions (LINERs), the weaker counterpart of Seyferts. We conclude that AGN properties depend on the environmental density more than on the web-type. More powerful starbursts and younger stellar populations are found in high densities, where interactions and mergers are more likely. AGN hosts show smaller masses in clusters for Seyferts and Transition objects, which might be due to gas stripping. In voids, the AGN population is dominated by the most massive galaxy hosts.

Validation of an MRI Protocol for Routine Quantitative Assessment of Tunnel Position in Anterior Cruciate Ligament Reconstruction

Background: No standardized methodology and objective criteria currently exist to accurately and objectively assess tunnel placement and consequent graft orientation in anterior cruciate ligament (ACL) reconstruction (ACLR) through a single imaging modality. Advances in magnetic resonance imaging (MRI) technology have enabled the use of volumetric high spatial and contrast resolution proton density–weighted sequencing, which allows precise delineation of graft orientation, tunnel position, and quantitative assessment of tunnel position relationship to adjacent reproducible anatomic landmarks. Purpose: To establish an MRI protocol that would provide an accurate alternative to 3-dimensional computed tomography (3D-CT) for standardized assessment of bone tunnel placement in ACLR, as a component of assessing ACLR outcomes and to assist in presurgical planning for revision ACLR. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Twenty-four participants diagnosed with a failed ACLR underwent MRI and 3D-CT per the imaging protocols of the Sydney Orthopaedic Research Institute, in which the acquired data were converted to 3D models. The bone tunnels of the previous ACLR were then intraoperatively digitized at the tunnel aperture and along the length of the tunnel (barrel) and used as the reference standard to evaluate the accuracy of high-resolution MRI and 3D-CT. Differences in geometry between the image-based model and the reference point cloud were calculated through point-to-point comparison. Results: At the tunnel apertures, no significant differences were detected between the MRI and 3D-CT models versus the reference models for the femur (P = .9472) and tibia (P = .5779). Mean ± SD tunnel barrel deviations between MRI and 3D-CT were 0.48 ± 0.28 mm (femur) and 0.46 ± 0.27 mm (tibia). No significant differences were detected between the MRI and 3D-CT models versus the reference models for the femoral (P = .5730) and tibial (P = .3002) tunnel barrels. Conclusion: This study demonstrated that, in addition to being the optimum modality for assessment of soft tissue injury of the knee, a high-resolution 3D turbo spin echo proton density sequence can provide an accurate assessment of tunnel placement, without the use of ionizing radiation. Therefore, this protocol provides the foundation for an objective standardized platform to quantitatively evaluate the location of ACL bone tunnels and graft orientation for routine postoperative assessment, presurgical planning, and evaluation of clinical outcomes.

Empirical reproducibility, sensitivity, and optimization of acquisition protocol, for Neurite Orientation Dispersion and Density Imaging using AMICO

Neurite Orientation Dispersion and Density Imaging (NODDI) has been gaining prominence for estimating multiple diffusion compartments from MRI data acquired in a clinically feasible time. To establish a pathway for adoption of NODDI in clinical studies, it is important to understand the sensitivity and reproducibility of NODDI metrics on empirical data in the context of acquisition protocol and brain anatomy. Previous studies addressed reproducibility across the 3 T scanners and within session and between subject reproducibility at 1.5 T and 3 T. However, empirical reproducibility on the performance of NODDI metrics based on b-value and diffusion-sensitized directions has not yet been addressed. In this study, we investigate a high angular resolution dataset with 11 repeats of a study with five b-values shells (1000, 1500, 2000, 2500 and 3000 s/mm2) and 96 directions per shell on a single subject. We validated the findings with a dataset from second subject with 10 repeats and 3 b-value shells (1000, 2000, 3000 s/mm2). The NODDI model was estimated using Accelerated Microstructure Imaging via Convex Optimization (AMICO) for different b-values and gradient directions on two-shell High Angular Resolution Density Imaging (HARDI) data fixing the lower shell at b = 1000 s/mm2. NODDI model applied to all acquired imaging data was used as a baseline gold standard for comparison. Additionally, we characterize orientation dispersion index (ODI) reproducibility using single-shell data. The experimental findings confirmed the sensitivity of intracellular volume fraction (Vic) with the choice of outer shell b-value more than with the choice of gradient directions. On the other hand, ODI is more sensitive to the number of gradient directions compared to b-value selection. Single-shell results for ODI are more comparable to 2-shell data at lower b-values than higher b-values. Recommended settings by region of interest and acquisition time are reported for the researchers considering using NODDI in human studies and/or comparing results across acquisition protocols.

Cryo-EM Studies of Pre-mRNA Splicing: From Sample Preparation to Model Visualization.

The removal of noncoding introns from pre-messenger RNA (pre-mRNA) is an essential step in eukaryotic gene expression and is catalyzed by a dynamic multi-megadalton ribonucleoprotein complex called the spliceosome. The spliceosome assembles on pre-mRNA substrates by the stepwise addition of small nuclear ribonucleoprotein particles and numerous protein factors. Extensive remodeling is required to form the RNA-based active site and to mediate the pre-mRNA branching and ligation reactions. In the past two years, cryo-electron microscopy (cryo-EM) structures of spliceosomes captured in different assembly and catalytic states have greatly advanced our understanding of its mechanism. This was made possible by long-standing efforts in the purification of spliceosome intermediates as well as recent developments in cryo-EM imaging and computational methodology. The resulting high-resolution densities allow for de novo model building in core regions of the complexes. In peripheral and less ordered regions, the combination of cross-linking, bioinformatics, biochemical, and genetic data is essential for accurate modeling. Here, we summarize these achievements and highlight the critical steps in obtaining near-atomic resolution structures of the spliceosome.

Metallosupramolecular Architectures Formed with Ferrocene-Linked Bis-Bidentate Ligands: Synthesis, Structures, and Electrochemical Studies.

The self-assembly of ligands of different geometries with metal ions gives rise to metallosupramolecular architectures of differing structural types. The rotational flexibility of ferrocene allows for conformational diversity, and, as such, self-assembly processes with 1,1'-disubstituted ferrocene ligands could lead to a variety of interesting architectures. Herein, we report a small family of three bis-bidentate 1,1'-disubstituted ferrocene ligands, functionalized with either 2,2'-bipyridine or 2-pyridyl-1,2,3-triazole chelating units. The self-assembly of these ligands with the (usually) four-coordinate, diamagnetic metal ions Cu(I), Ag(I), and Pd(II) was examined using a range of techniques including 1H and DOSY NMR spectroscopies, high-resolution electrospray ionization mass spectrometry, X-ray crystallography, and density functional theory calculations. Additionally, the electrochemical properties of these redox-active metallosupramolecular assemblies were examined using cyclic voltammetry and differential pulse voltammetry. The copper(I) complexes of the 1,1'-disubstituted ferrocene ligands were found to be coordination polymers, while the silver(I) and palladium(II) complexes formed discrete [1 + 1] or [2 + 2] metallomacrocyclic architectures.

Hemispheric asymmetries in the orientation and location of the lateral geniculate nucleus in dyslexia.

Human brain asymmetry reflects normal specialization of functional roles and may derive from evolutionary, hereditary, developmental, experiential, and pathological factors (Toga & Thompson, 2003). Geschwind and Galaburda (1985) suggested that processing difficulties in dyslexia are due to structural differences between hemispheres. Because of its potential significance to the controversial magnocellular theory of dyslexia, we investigated hemispheric differences in the human lateral geniculate nucleus (LGN), the primary visual relay and control nucleus in the thalamus, in subjects with dyslexia compared to normal readers. We acquired and averaged multiple high-resolution proton density (PD) weighted structural magnetic resonance imaging (MRI) volumes to measure in detail the anatomical boundaries of the LGN in each hemisphere. We observed hemispheric asymmetries in the orientation of the nucleus in subjects with dyslexia that were absent in controls. We also found differences in the location of the LGN between hemispheres in controls but not in subjects with dyslexia. Neither the precise anatomical differences in the LGN nor their functional consequences are known, nor is it clear whether the differences might be causes or effects of dyslexia.

A flexible hybridized electromagnetic-triboelectric multi-purpose self-powered sensor

This paper presents a novel hybridized flexible electromagnetic-triboelectric generator that consists of a round/square shaped coil and magnet, and also, highly flexible, mechanically and thermally durable, and cost-effective polymeric materials. The reported hybridized nano generator is capable of converting external mechanical load to electricity. Using a systematic optimization approach results in an optimal configuration and size for the electromagnetic components of the self-powered sensor. Combination of the electromagnetic and triboelectric components provides several advantages for the proposed self-powered device including high resolution and power density even in low frequency and small amplitude of the excitations. We probe the sensitivity of the fabricated self-powered sensor considering different amplitude and frequency of excitations as well as external resistors. After providing a general performance analysis for the proposed self powered sensor, we show its potential for different specific applications including human motion based energy harvesting and sensing, tire condition monitoring, and pressure sensing. The utilization of the proposed self-powered sensor can provide a sustainable energy source for wireless sensor nodes, and also overcomes the battery capacity limitation that restricts the life time durability of mobile electrical devices.

Real-space evidence of Watson-Crick and Hoogsteen adenine-uracil base pairs on Au(111).

From the interplay of high-resolution scanning tunneling microscopy imaging and density functional theory calculations, we show the real-space evidence of the formation of Watson-Crick and Hoogsteen adenine-uracil base pairs on an Au(111) surface with the employment of base derivatives, and further investigate the relative stability of the two types of adenine-uracil base pairs.

Unmanned aerial vehicle (UAV)-based monitoring of a landslide: Gallenzerkogel landslide (Ybbs-Lower Austria) case study.

In the present study, UAV-based monitoring of the Gallenzerkogel landslide (Ybbs, Lower Austria) was carried out by three flight missions. High-resolution digital elevation models (DEMs), orthophotos, and density point clouds were generated from UAV-based aerial photos via structure-from-motion (SfM). According to ground control points (GCPs), an average of 4cm root mean square error (RMSE) was found for all models. In addition, light detection and ranging (LIDAR) data from 2009, representing the prefailure topography, was utilized as a digital terrain model (DTM) and digital surface model (DSM). First, the DEM of difference (DoD) between the first UAV flight data and the LIDAR-DTM was determined and according to the generated DoD deformation map, an elevation difference of between - 6.6 and 2m was found. Over the landslide area, a total of 4380.1m3 of slope material had been eroded, while 297.4m3 of the material had accumulated within the most active part of the slope. In addition, 688.3m3 of the total eroded material had belonged to the road destroyed by the landslide. Because of the vegetation surrounding the landslide area, the Multiscale Model-to-Model Cloud Comparison (M3C2) algorithm was then applied to compare the first and second UAV flight data. After eliminating both the distance uncertainty values of higher than 15cm and the nonsignificant changes, the M3C2 distance obtained was between - 2.5 and 2.5m. Moreover, the high-resolution orthophoto generated by the third flight allowed visual monitoring of the ongoing control/stabilization work in the area.

Intermetallic: A Pseudoelement for Catalysis.

A clear correlation between electronic structure and CO2 selectivity for steam reforming of methanol (SRM) was obtained with PdZn, PtZn, NiZn, and PdCd intermetallics on the basis of experiments and calculations. In order to rule out the effects of oxide supports, the intermetallic powders were simply prepared by alloying in an arc furnace followed by crushing in a mortar. PdZn and PdCd exhibit valence electronic densities of states similar to that of Cu and significant chemical shifts (larger than 1 eV) of Pd 3d states with respect to pure Pd, as verified by high-resolution hard X-ray photoelectron spectroscopy (HXPS) measurements and density functional theory (DFT) calculations. Consequently, they show the similar high selectivity of CO2 for the SRM reaction. However, this is not the case for PtZn and NiZn because of the slight differences in their valence electronic structures from that of PdZn. The interval between the Fermi level and the top of the d band is closely related to the selectivity of CO2 for the SRM: the larger the interval is, the higher is the selectivity of CO2. According to DFT calculations for bulk PdZn performed by Chen et al. ( Phys. Rev. B 2003 , 68 , 075417 ), the (111) and (100) surfaces exposing Zn and Pd in an equimolar ratio are more stable than the (001) or (110) surfaces terminated by alternative Zn or Pd layers. First-principles slab calculations for PdZn, PtZn, and NiZn show that bond breaking on the surface leads to a reduction in the d bandwidth but that the d band for stable (111) or (100) surfaces remains essentially unchanged from that of the bulk. It is intriguing that PdZn and PdCd do not contain Cu but show similar valence electronic structure and catalytic selectivity, and hence, a concept is proposed where PdZn and PdCd are regarded as pseudoelements of Cu. The basis of this concept is like electronic structure, like catalysis, which has been demonstrated by experiments and calculations. This is a logical way to enable us to look for new catalysts in which precious metals are partially or completely replaced by base metals. We do not expect that this concept can be applied to all catalytic reactions, but this approach is one of most promising ways to derive a better understanding of the origin of catalytic mechanisms and eventually allow us to design useful catalysts intentionally in the future. This Account reviews the authors' published works on this topic.

Alumina-Supported CoFe Alloy Catalysts Derived from Layered-Double-Hydroxide Nanosheets for Efficient Photothermal CO2 Hydrogenation to Hydrocarbons.

A series of novel CoFe-based catalysts are successfully fabricated by hydrogen reduction of CoFeAl layered-double-hydroxide (LDH) nanosheets at 300-700 °C. The chemical composition and morphology of the reaction products (denoted herein as CoFe-x) are highly dependent on the reduction temperature (x). CO2 hydrogenation experiments are conducted on the CoFe-x catalysts under UV-vis excitation. With increasing LDH-nanosheet reduction temperature, the CoFe-x catalysts show a progressive selectivity shift from CO to CH4 , and eventually to high-value hydrocarbons (C2+ ). CoFe-650 shows remarkable selectivity toward hydrocarbons (60% CH4 , 35% C2+ ). X-ray absorption fine structure, high-resolution transmission electron microscopy, Mössbauer spectroscopy, and density functional theory calculations demonstrate that alumina-supported CoFe-alloy nanoparticles are responsible for the high selectivity of CoFe-650 for C2+ hydrocarbons, also allowing exploitation of photothermal effects. This study demonstrates a vibrant new catalyst platform for harnessing clean, abundant solar-energy to produce valuable chemicals and fuels from CO2 .

High-resolution charge density of metal hexaborides

High-resolution charge density of metal hexaborides

On-Surface Synthesis of Adenine Oligomers via Ullmann Reaction.

Despite the fact that DNA bases have been well-studied on surface, the on-surface synthesis of one-dimensional DNA analogs through in situ reactions is still an interesting topic to be investigated. Herein, from the interplay of high-resolution scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations, we have delicately designed a halogenated derivative of adenine as precursor to realize the combination of DNA bases and Ullmann reaction, and then successfully synthesized adenine oligomers on Au(111) via Ullmann coupling. This model system provides a possible bottom-up strategy of fabricating adenine oligomers on surface, which may further give access to man-made DNA strands with multiple bases.

Mechanistic Study of Copper-Catalyzed C-H Hydroxylation/C-S Coupling by ESI-HR MS and DFT Calculations.

The reaction mechanism of Cu-catalyzed C-H hydroxylation/C-S coupling was studied using electrospray ionization high resolution mass spectrometry (ESI-HR MS) and density functional theory calculations (DFT). Notably, a series of CuI and CuIII complexes were observed as key intermediates and identified using ESI-HR MS. Furthermore, a catalyst cycle involving proton abstraction/oxidative addition/reductive elimination was proposed. This study is important and valuable with respect to C-H functionalization.

Model-based local density sharpening of cryo-EM maps.

Atomic models based on high-resolution density maps are the ultimate result of the cryo-EM structure determination process. Here, we introduce a general procedure for local sharpening of cryo-EM density maps based on prior knowledge of an atomic reference structure. The procedure optimizes contrast of cryo-EM densities by amplitude scaling against the radially averaged local falloff estimated from a windowed reference model. By testing the procedure using six cryo-EM structures of TRPV1, β-galactosidase, γ-secretase, ribosome-EF-Tu complex, 20S proteasome and RNA polymerase III, we illustrate how local sharpening can increase interpretability of density maps in particular in cases of resolution variation and facilitates model building and atomic model refinement.

HP2 survey

We present new high resolution and dynamic range dust column density and temperature maps of the California Molecular Cloud derived from a combination of Planck and Herschel dust-emission maps, and 2MASS NIR dust-extinction maps. We used these data to determine the ratio of the 2.2 micron extinction coefficient to the 850 micron opacity and found the value to be close to that found in similar studies of the Orion B and Perseus clouds but higher than that characterizing the Orion A cloud, indicating that variations in the fundamental optical properties of dust may exist between local clouds. We show that over a wide range of extinction, the column density probability distribution function (PDF$_N$) of the cloud can be well described by a simple power law with an index that represents a steeper decline with column density than found in similar studies of the Orion and Perseus clouds. Using only the protostellar population of the cloud and our extinction maps we investigate the Schmidt relation within the cloud. We show that the protostellar surface density, $\Sigma_*$, is directly proportional to the ratio of the protostellar and cloud pdfs. We use the cumulative distribution of protostars to infer the functional forms for both $\Sigma_*$ and PDF$_*$. We find that $\Sigma_*$ is best described by two power-law functions with steeper indicies than found in other local GMCs. We find that the protostellar pdf is a declining function of extinction also best described by two power-laws whose behavior mirrors that of $\Sigma_*$. Our observations suggest that variations both in the slope of the Schmidt relation and in the sizes of the protostellar populations between GMCs are largely driven by variations in the slope of the cloud pdf. This confirms earlier studies suggesting that cloud structure plays a major role in setting the global star formation rates in GMCs.