Quasi-Continuous Metasurface Beam Splitters Enabled by Vector Iterative Fourier Transform Algorithm

Quasi-continuous metasurfaces are widely used in various optical systems and their subwavelength structures invalidate traditional design methods based on scalar diffraction theory. Here, a novel vector iterative Fourier transform algorithm (IFTA) is proposed to realize the fast design of quasi-continuous metasurface beam splitters with subwavelength structures. Compared with traditional optimization algorithms that either require extensive numerical simulations or lack accuracy, this method has the advantages of accuracy and low computational cost. As proof-of-concept demonstrations, several beam splitters with custom-tailored diffraction patterns and a 7 × 7 beam splitter are numerically demonstrated, among which the maximal diffraction angle reaches 70° and the best uniformity error reaches 0.0195, showing good consistency with the target energy distribution and these results suggest that the proposed vector IFTA may find wide applications in three-dimensional imaging, lidar techniques, machine vision, and so forth.     

Ultrafast X-ray scattering offers a structural view of excited-state charge transfer

Intramolecular charge transfer and the associated changes in molecular structure in N,N′-dimethylpiperazine are tracked using femtosecond gas-phase X-ray scattering. The molecules are optically excited to the 3p state at 200 nm. Following rapid relaxation to the 3s state, distinct charge-localized and charge-delocalized species related by charge transfer are observed. The experiment determines the molecular structure of the two species, with the redistribution of electron density accounted for by a scattering correction factor. The initially dominant charge-localized state has a weakened carbon–carbon bond and reorients one methyl group compared with the ground state. Subsequent charge transfer to the charge-delocalized state elongates the carbon–carbon bond further, creating an extended 1.634 Å bond, and also reorients the second methyl group. At the same time, the bond lengths between the nitrogen and the ring-carbon atoms contract from an average of 1.505 to 1.465 Å. The experiment determines the overall charge transfer time constant for approaching the equilibrium between charge-localized and charge-delocalized species to 3.0 ps.

Understanding the dynamic process of photoinduced charge transfer is expected to lead to many practical applications, including efficient photovoltaic systems, the development of photocatalysts, and better materials for energy storage (1–3). Charge transfer redistributes the electrons in a molecule and is typically associated with changes in the molecular geometry (2). On the fastest time scale, electrons move so rapidly that the nuclei appear frozen, a phenomenon known as charge migration (4–10). When time scales approach the typical vibrational motions of molecules, that is, tens of femtoseconds (10⁻¹⁴ s), the nuclei can adjust their positions, often resulting in localization of electronic charge and permanent changes in molecular geometry (11). While exhibiting a rich phenomenology on different time scales, it is evident that electron charge transfer and nuclear dynamics are intrinsically coupled (12–17). An accurate determination of the changes in molecular structure during charge transfer is therefore of great interest from both applied and fundamental perspectives.New scientific technologies, in particular X-ray free-electron lasers (XFEL) (18, 19) and MeV ultrafast electron diffraction (20), have made it possible to study structural dynamics in the ultrafast regime. Recent femtosecond gas-phase scattering experiments have successfully tracked structural changes during chemical reactions (21–26) and probed specific signatures of excited electronic states (27, 28). Given the emerging ability of ultrafast gas-phase scattering to record both nuclear and electronic structure (25, 27, 28), we use time-resolved gas-phase X-ray scattering to study the photoinduced intramolecular charge transfer in an organic molecule, N,N′-dimethylpiperazine (DMP, C₆H₁₄N₂), shown in Fig. 1. In its ground electronic state, DMP has C_2h symmetry with two equivalent ionization centers, one on each nitrogen atom. Valence ionization, or in the present case excitation to an electronic Rydberg state (29), induces charge transfer between the two nitrogen atoms, making DMP a prototype for exploring electron lone-pair interactions and charge transfer (30–32).Open in a separate windowFig. 1.A schematic illustration of the experimental setup. The ground-state molecules (DMP) were excited by 200 nm ultraviolet pump pulses, and the transient structures were probed by 9.5 keV X-ray pulses at variable time delays. The scattering signals were recorded on a CSPAD detector. The inset shows the calculated spin density, which gives the difference in density of electrons with spin up and spin down, of the charge-localized DMP (3sL) and charge-delocalized DMP (3sD) in the 3s Rydberg states at isovalues of 0.1 electron/ų.Previously, energy relaxation pathways and charge transfer in electronically excited DMP were explored using Rydberg fingerprint spectroscopy (33), a form of photoelectron spectroscopy. As depicted in Scheme 1, the investigations by Deb et al. (33) found that optical excitation at 207 nm prepares the molecule in a 3p Rydberg state, creating a state with a localized charge in the molecular core (3pL). Internal conversion to 3s then leads to charge-localized (3sL) and charge-delocalized (3sD) conformers with 230 and 480 fs time constants, respectively. The charge transfer proceeds as the molecules explore the 3s potential energy surface. An equilibrium between 3sL and 3sD structures is eventually established with an overall time constant of 2.65 ps, with the forward and backward first-order kinetic time constants for the transformation 3.4 and 12.0 ps, respectively (33).Open in a separate windowScheme 1.Reaction pathway for Rydberg-excited DMP as determined previously (33).A limitation in the prior spectroscopic work is that the photoelectron peaks are assigned by comparing measured binding energies with computational results and that the molecular structures that underlie the calculations cannot not be independently determined in the experiments. This is compounded by the fact that theoretical calculation of charge-localized and charge-delocalized excited states is challenging. Widely used computational methods sometimes give unsatisfactory results (34), and even results from high-level computations can be controversial (35–37). This has led to interesting discussions about whether a stable charge-localized structure exists in the DMP cation at all and about the validity of different exchange functionals within density functional theory to study the charge localization in DMP molecules (34). Considering the general experimental and theoretical interest in this system, direct structural measurements would be invaluable. The current study uses ultrafast time-resolved X-ray scattering to observe the structural relaxation dynamics in DMP. This provides a wealth of information, making it possible to test key assumptions of the photoelectron study. Most importantly, we determine the molecular structures of the charge-localized and -delocalized excited states.     

Conformational dynamics of a crystalline protein from microsecond-scale molecular dynamics simulations and diffuse X-ray scattering

X-ray diffraction from protein crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering is limited to what is available in the mean electron density. The diffuse scattering arises from correlations in the electron density variations and therefore contains information about collective motions in proteins. Previous studies using molecular-dynamics (MD) simulations to model diffuse scattering have been hindered by insufficient sampling of the conformational ensemble. To overcome this issue, we have performed a 1.1-μs MD simulation of crystalline staphylococcal nuclease, providing 100-fold more sampling than previous studies. This simulation enables reproducible calculations of the diffuse intensity and predicts functionally important motions, including transitions among at least eight metastable states with different active-site geometries. The total diffuse intensity calculated using the MD model is highly correlated with the experimental data. In particular, there is excellent agreement for the isotropic component of the diffuse intensity, and substantial but weaker agreement for the anisotropic component. Decomposition of the MD model into protein and solvent components indicates that protein–solvent interactions contribute substantially to the overall diffuse intensity. We conclude that diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.Proteins explore many conformations while carrying out their functions in biological systems (1–3). X-ray crystallography is the dominant source of information about protein structure; however, crystal structure models usually consist of just a single major conformation and at most a small portion of the model as alternate conformations. Crystal structures therefore are missing many details about the underlying conformational ensemble (4).Proteins assembled in crystalline arrays, like proteins in solution, exhibit rich conformational diversity (4) and often can perform their native functions (5). Many methods have emerged for using Bragg data to model conformational diversity in protein crystals (6–17). The development of these methods has been important as conformational diversity can lead to inaccuracies in protein structure models (9, 18–20). A key limitation of using the Bragg data, however, is that different models of conformational diversity can yield the same mean electron density.Whereas the Bragg scattering only contains information about the mean electron density, diffuse scattering (diffraction resulting in intensity between the Bragg peaks) is sensitive to spatial correlations in electron density variations (21–28) and therefore contains information about the way that atomic positions vary together in protein crystals. Because models that yield the same mean electron density can yield different correlations in electron density variations, diffuse scattering provides a means to increase the accuracy of crystallography for determining protein conformational variations (29). Peter Moore (30) and Mark Wilson (31) have argued that diffuse scattering should be used to test models of conformational diversity in X-ray crystallography.Several pioneering studies used diffuse scattering to reveal insights into correlated motions in proteins (17, 30, 32–49). Some of these studies used diffuse scattering to experimentally validate predictions of correlated motions from molecular-dynamics (MD) simulations (35–37, 40, 42–44). These studies revealed important insights but were limited by inadequate sampling of the conformational ensemble, leading to lack of convergence of the diffuse scattering calculations (35). Microsecond-scale simulations of staphylococcal nuclease were predicted to be adequate for convergence of diffuse scattering calculations (42). Modern simulation algorithms and computer hardware now enable microsecond or longer MD simulations of protein crystals (50).Here, we present calculations of diffuse X-ray scattering using a 1.1-μs MD simulation of crystalline staphylococcal nuclease. The results demonstrate that we have overcome the past limitation of inadequate sampling. We chose staphylococcal nuclease because the experiments of Wall et al. (49) still represent the only complete, high-quality, 3D diffuse scattering data set from a protein crystal. The calculated diffuse intensity is very similar using two independent halves of the trajectory; the results therefore are reproducible and can be meaningfully compared with the experimental data. The MD simulation provides a rich picture of conformational diversity in the energy landscape of a protein crystal, consisting of at least eight metastable states. Like previous MD studies of crystalline staphylococcal nuclease (42–44), the agreement of the simulation with the total experimental diffuse intensity is excellent, supporting the use of MD simulations to model diffuse scattering data. Unlike previous MD studies, we separately compared the more finely structured, anisotropic component of the diffuse intensity with experimental data. The agreement is substantial but weaker than for the isotropic component, indicating there are inaccuracies in the MD models. Our results therefore point toward using diffuse scattering to improve MD models of protein motions.     

In situ small-angle X-ray scattering reveals solution phase discharge of Li–O2 batteries with weakly solvating electrolytes

Electrodepositing insulating lithium peroxide (Li₂O₂) is the key process during discharge of aprotic Li–O₂ batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved lithium superoxide governs whether Li₂O₂ grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, better understanding governing factors for Li₂O₂ packing density and capacity requires structural sensitive in situ metrologies. Here, we establish in situ small- and wide-angle X-ray scattering (SAXS/WAXS) as a suitable method to record the Li₂O₂ phase evolution with atomic to submicrometer resolution during cycling a custom-built in situ Li–O₂ cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multiphase systems. Surprisingly, we find that features are absent that would point at a Li₂O₂ surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li₂O₂ platelets potentially forming large toroidal particles. Li₂O₂ solution growth is further justified by rotating ring-disk electrode measurements and electron microscopy. Higher discharge overpotentials lead to smaller Li₂O₂ particles, but there is no transition to an electronically passivating, conformal Li₂O₂ coating. Hence, mass transport of reactive species rather than electronic transport through a Li₂O₂ film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in weakly solvating electrolytes. The currently accepted Li–O₂ reaction mechanism ought to be reconsidered.

Understanding formation, properties, and function of energy materials requires not only information about chemistry but even more so about structure from atomic to μm scales (1), which puts high demands on (in situ) analytical techniques (2). This is the more important as complex composites and transformations are concerned (3). Electrodeposition of insulators is an intriguing example, where anything between monolayers and micrometric layers may form, even though the process is, in principle, self-limited to the electron tunneling distance of the deposit (4, 5). Topical examples are Li–S batteries, where Li₂S/S₈ are electrodeposited on discharge/charge (6) and Li–O₂ batteries, where insoluble and insulating lithium peroxide (Li₂O₂) is electrodeposited on discharge and the process being reversed on charge (5). Li–O₂ batteries could surpass current Li-ion batteries in energy, sustainability, and cost (4). However, practically realizing high reversible capacities faces the challenges of forming/decomposing large amounts of Li₂O₂ while suppressing parasitic reactions (5, 7–11). These challenges are interrelated and require understanding the interplay between physical chemistry and structural evolution at the nanoscale (2, 12–16).Currently, the discharge process of Li–O₂ batteries is understood to proceed in between two limiting cases, governed by the electrolyte solubility of the lithium superoxide (LiO₂) intermediate (5, 17–22). If LiO₂ is soluble, it is mobile and disproportionates remote from the pore surface to form typically some 100 nm large particles, allowing for high capacities (17, 18, 22, 23). In electrolytes where LiO₂ is thought insoluble, Li₂O₂ would grow as thin passivating surface film (24–28), leading to poor rates and low capacity (SI Appendix, Fig. S1). The prevailing mechanism not only determines rate and capacity (5, 7, 17–19, 28–30) but also impacts parasitic chemistry (7, 17, 31–33). However, the extent to which these mechanisms prevail is still not clear, and so is the true capacity-limiting factor, which could be either e⁻ transport through a thin Li₂O₂ coating or mass transport (O₂, LiO₂, and Li⁺) through a porous particulate Li₂O₂ deposit (25, 28, 30, 34–36). Measures and governing factors for Li₂O₂ packing density and capacity still need refinement. Conclusively identifying capacity limitations requires real-time in situ metrologies with structural sensitivity from the atomic to submicron scale. Current techniques are strong in aspects but fail to seamlessly cover the required length scales in the crucial in situ fashion (2, 37). Small- and wide-angle X-ray scattering (SAXS/WAXS) could in principle afford this because of its sensitivity toward any means that generate electron density contrast on length scales from 0.1 to 100 nm. However, SAXS data analysis from complex systems is highly challenging.Here, we expand the possibilities of in situ SAXS by developing a data analysis strategy that makes accessible the rich quantitative information contained in the scattering data of the electrochemical multiphase systems. The strategy includes 1) generating a statistically representative three-dimensional (3D) model of the electrode and 2) growth of Li₂O₂ structures by a suitable growth model, which we validate against measured scattering curves. We start with showing that in a high surface area carbon, a heuristic nucleation and growth model of thin Li₂O₂ platelets fits the in situ SAXS data over a range of electrolytes, voltages, and currents including such thought to be prototypical for surface or solution growth. Crucially, this method allows widely excluding a conformal Li₂O₂ coating to grow even in poorly solvating electrolytes and at high overpotentials; conditions previously considered prototypical for surface growth. This implies the capacity to be conclusively limited by species (O₂, LiO₂, and Li⁺) transport through the porous particulate Li₂O₂ deposit rather than electronic transport limitation through a conformal Li₂O₂ coating. Rotating ring-disk electrode (RRDE) measurements and electron microscopy independently justify solution-mediated discharge in weakly solvating electrolytes. The study provides 1) unexpected insights linking the nanoscale structure with Li–O₂ mechanisms and performance and 2) the in situ metrology tool to quantitatively characterize morphologies and growth mechanisms in complex multiphase systems in general, not limited to batteries or electrochemistry.     

Use of carbon nanotube sensor for detecting postoperative abnormal respiratory waveforms

BackgroundThis feasibility study aimed to detect respiratory waveforms from thoracic movements and evaluate if postoperative complications could be predicted using a carbon nanotube sensor.MethodsFifty patients who underwent lung resection for lung tumors were enrolled. The lung monitoring system of the carbon nanotube sensor was placed on bilateral chest walls across the 6^th–9^th ribs to measure chest wall motion. We examined the respiratory waveform in relation to surgical findings, postoperative course, and complications using Hilbert transform and Fast Fourier Transform (FFT).ResultsOf 50 patients (37 males, 13 females), 22 were included in the normal lung function group and 28 were included in the low lung function group. The respiratory rate and waveform indicated a regular pattern in the normal lung function group and the respiratory rate could be detected. Conversely, irregular respiratory pattern was detected in 70% of patients in the low lung function group. There was no significant different overall envelope peak value between operated side and non-operated side (0.195±0.05 and 0.18±0.06). In contrast, there was significantly high peak value in the presence of postoperative complications (P<0.05). And there was a significantly higher peak value in air leakage presence than air leakage absence in operated side (P=0.045).ConclusionsThe present study confirmed the feasibility of the sensor. It is promising in visualizing the respiratory state and detecting respiratory changes postoperatively.     

Iterative categorization (IC): a systematic technique for analysing qualitative data

The processes of analysing qualitative data, particularly the stage between coding and publication, are often vague and/or poorly explained within addiction science and research more broadly. A simple but rigorous and transparent technique for analysing qualitative textual data, developed within the field of addiction, is described. The technique, iterative categorization (IC), is suitable for use with inductive and deductive codes and can support a range of common analytical approaches, e.g. thematic analysis, Framework, constant comparison, analytical induction, content analysis, conversational analysis, discourse analysis, interpretative phenomenological analysis and narrative analysis. Once the data have been coded, the only software required is a standard word processing package. Worked examples are provided.     

High-resolution,low-dose phase contrast X-ray tomography for 3D diagnosis of human breast cancers

Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ∼10–20% of palpable tumors are not detectable on mammograms and only about 40% of biopsied lesions are malignant. Here we report a high-resolution, low-dose phase contrast X-ray tomographic method for 3D diagnosis of human breast cancers. By combining phase contrast X-ray imaging with an image reconstruction method known as equally sloped tomography, we imaged a human breast in three dimensions and identified a malignant cancer with a pixel size of 92 μm and a radiation dose less than that of dual-view mammography. According to a blind evaluation by five independent radiologists, our method can reduce the radiation dose and acquisition time by ∼74% relative to conventional phase contrast X-ray tomography, while maintaining high image resolution and image contrast. These results demonstrate that high-resolution 3D diagnostic imaging of human breast cancers can, in principle, be performed at clinical compatible doses.     

Inelastic x-ray scattering of dense solid oxygen: evidence for intermolecular bonding

The detailing of the intermolecular interactions in dense solid oxygen is essential for an understanding of the rich polymorphism and remarkable properties of this element at high pressure. Synchrotron inelastic x-ray scattering measurements of oxygen K-edge excitations to 38 GPa reveal changes in electronic structure and bonding on compression of the molecular solid. The measurements show that O₂ molecules interact predominantly through the half-filled 1π_g* orbital <10 GPa. Enhanced intermolecular interactions develop because of increasing overlap of the 1π_g* orbital in the low-pressure phases, leading to electron delocalization and ultimately intermolecular bonding between O₂ molecules at the transition to the ε-phase. The ε-phase, which consists of (O₂)₄ clusters, displays the bonding characteristics of a closed-shell system. Increasing interactions between (O₂)₄ clusters develop upon compression of the ε-phase, and provide a potential mechanism for intercluster bonding in still higher-pressure phases.     

Fourier‐transform infrared spectrometric analysis for detecting colorectal carcinoma

OBJECTIVE : To assess the value of Fourier‐transform infrared (FT‐IR) spectroscopic analysis in detecting colorectal carcinoma. METHODS : Fifty pairs of specimens of exfoliated cells from patients with colorectal carcinoma, who had undergone colorectal resection, were analyzed by using FT‐IR spectrometry. Exfoliated cells were obtained by scraping off: (i) the foci of the colorectal carcinoma; and (ii) the normal mucosa more than 5 cm away from the foci. Cell specimens were fixed and smeared onto two slides: a gold‐coated slide for the infrared spectrometry and a conventional one for histopathological evaluation. The spectra from 28 pairs of specimens were analyzed by logistic regression with multiple factors to establish a statistical model for predicting the probability of colorectal cancers, and then the spectra of the remaining 22 pairs were judged according to the model. Their corresponding diagnostic accuracy was calculated. RESULTS : Substantial differences were found in the spectral properties of cancer and non‐cancer cells, which were evident in the frequency region of 1000–1350/cm. A shift of the phosphodiester groups of nucleic acids was noted: compared with the spectral features of non‐cancerous cells, the distance between VsPO₂^– and VasPO₂^– was shorter in cancerous cells. The C–O stretching bonds of cell proteins were significantly changed in the frequency region of 1140–1180/cm. In non‐cancerous cells, the peak intensity of 1155/cm was stronger than that of 1174/cm, whereas in cancerous cells the peak intensity of 1155/cm was weaker than that of 1174/cm; the peak intensity ratio of 1174/cm : 1155/cm was increased in cancerous cells. The spectral characteristics of the spectrometric data from the 22 pairs of specimens were consistent with those of the base‐model data. The other 22 pairs of specimens were analyzed according to the model, indicating that Fourier‐transform infrared spectrometry can be used to discriminate cancerous cells from non‐cancerous cells with a sensitivity of 90.91%, a specificity of 86.36%, a positive prediction value of 86.96% and a negative predictive value of 90.48%. CONCLUSIONS : Fourier‐transform infrared spectrometry is of value in detecting colorectal cancer cells and it could be used as a rapid method for the clinical screening of malignant cells.     

Application of Grazing-Incidence X-ray Methods to Study Terrace-Stepped SiC Surface for Graphene Growth

The synthesis of graphene by the graphitization of SiC surface has been driven by a need to develop a way to produce graphene in large quantities. With the increased use of thermal treatments of commercial SiC substrates, a comprehension of the surface restructuring due to the formation of a terrace-stepped nanorelief is becoming a pressing challenge. The aim of this paper is to evaluate the utility of X-ray reflectometry and grazing-incidence off-specular scattering for a non-destructive estimate of depth-graded and lateral inhomogeneities on SiC wafers annealed in a vacuum at a temperature of 1400–1500 °C. It is shown that the grazing-incidence X-ray method is a powerful tool for the assessment of statistical parameters, such as effective roughness height, average terrace period and dispersion. Moreover, these methods are advantageous to local probe techniques because a broad range of spatial frequencies allows for faster inspection of the whole surface area. We have found that power spectral density functions and in-depth density profiles manifest themselves differently between the probing directions along and across a terrace edge. Finally, the X-ray scattering data demonstrate quantitative agreement with the results of atomic force microscopy.     

A Structured Light Technique for Monitoring Bioprosthetic Heart Valve Leaflet Surface Contours

The structured light technique recently developed in our laboratory to investigate the dynamic leaflet surface contour of bioprosthetic heart valves (BHVs), has been applied in a pulsatile flow loop to investigate a 25 mm commercial BHV. To simulate the physiological condition closely, a pulsatile heart valve testing loop, which reproduce physiological aortic and ventricular pressures and flow, was employed. The aortic conduit has been modified by adding an optical window to facilitate the visualization of the valve surface. Transient optical fringes were projected through the window to create a fringe pattern on the leaflet surface. The time-varying image of the surface was captured by a CCD camera. By using Fourier transform technique, the recorded fringe pattern was analyzed and the surface contours were retrieved. Corresponding to the various phases in one cardiac cycle, sequences of valve surface contours were obtained for both the original and the improved models of the BHVs respectively. The results showed that the improved model has superior performance over its predecessor. The application has demonstrated that the newly developed metrological technique has adequate precision to be used to investigate the leaflet motion of BHV under simulated physiological conditions. By combining the present technique with the computational fluid dynamics and finite element method, this technique can be a useful tool for the design and improvement of new BHV.     

Pattern-recognition program for analysis of colon myoelectric and pressure data

A pattern-recognition program was developed which emulates visual scoring of colonic myoelectric and pressure recordings. It smoothes digitized data with a moving average filter, computes difference scores between successive groups of three data points, and uses the signs of these difference scores to detect the beginning and end of waves. Adjacent waves are merged if their means are closer than 1.67 times the sum of their standard deviations, and amplitude and duration criteria are used to exclude nonsignificant waves. When compared to four experienced human scorers on randomly selected records, the program agreed as well with the human scorers as they agreed with each other, and it approached the level of agreement of these observers with themselves when they were asked to rescore the same records blindly four to six weeks later. Human scorers agreed with themselves on 36–71% of myoelectric slow waves and on 42–88% of pressure waves, compared to 100% test-retest reliability for the pattern-recognition program. Frequency histograms of the duration of waves detected by the pattern-recognition program differed from the spectra generated by the fast Fourier transform (FFT) method. This pattern-recognition program provides an alternative to spectral analysis for the reliable and objective quantification of colonic myoelectric slow waves and pressure waves.Supported by grant AM31369 from the National Institute of Diabetes and Digestive and Kidney Diseases; and by Research Career Development Award MH00133 from the National Institute of Mental Health.     

Frequency analysis of first heart sound for the elderly

Frequency analysis of first heart sound in elderly and expired cases was performed to reveal changes of the cardiovascular system accompanying aging. The vibration was analyzed for isometric contraction phase or 0.06 seconds following the main vibration of first sound by means of fast Fourier transform technique, and main frequency was compared. Mean main frequencies were 43.0 +/- 15.4 cps (mean +/- SD) in 21 cases from 54 years to 69 years, 41.4 +/- 12.6 cps in 34 cases from 70 years to 79 years, 40.0 +/- 14.4 cps in 19 cases from 80 years to 89 years, and 44.2 +/- 4.5 cps in 4 cases from 90 years to 94 years. It was 44.4 +/- 8.0 cps in 6 cases with left ventricular hypertrophy (LVH) on ECG, and 37.2 +/- 7.5 cps in 18 cases without LVH. It was 35.7 +/- 6.5 cps in 9 cases who expired and 32.6 +/- 5.8 cps in cases of those who died within a year. Though mean main frequencies were almost equal in these groups, it is higher than that of younger subjects, which suggests stiffness of the cardiovascular system of the aged. It was suggested that the stiffness of the cardiovascular system is greater than the increase in cardiac weight of elderly subjects with LVH. Mean main frequency was low in subjects who dies within a year, which may be due to cardiomegaly.     

X-ray Raman scattering study of MgSiO3 glass at high pressure: implication for triclustered MgSiO3 melt in Earth's mantle

Silicate melts at the top of the transition zone and the core-mantle boundary have significant influences on the dynamics and properties of Earth's interior. MgSiO3-rich silicate melts were among the primary components of the magma ocean and thus played essential roles in the chemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in Earth's interior, such as density, viscosity, and crystal-melt partitioning, depend on their electronic and short-range local structures at high pressures and temperatures. Despite essential roles of silicate melts in many geophysical and geodynamic problems, little is known about their nature under the conditions of Earth's interior, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressures. Here, we have probed local electronic structures of MgSiO3 glass (as a precursor to Mg-silicate melts), using high-pressure x-ray Raman spectroscopy up to 39 GPa, in which high-pressure oxygen K-edge features suggest the formation of tricluster oxygens (oxygen coordinated with three Si frameworks; 3O) between 12 and 20 GPa. Our results indicate that the densification in MgSiO3 melt is thus likely to be accompanied with the formation of triculster, in addition to a reduction in nonbridging oxygens. The pressure-induced increase in the fraction of oxygen triclusters >20 GPa would result in enhanced density, viscosity, and crystal-melt partitioning, and reduced element diffusivity in the MgSiO3 melt toward deeper part of the Earth's lower mantle.     

The occludin and ZO-1 complex, defined by small angle X-ray scattering and NMR, has implications for modulating tight junction permeability

Tight junctions (TJs) are dynamic cellular structures that are critical for compartmentalizing environments within tissues and regulating transport of small molecules, ions, and fluids. Phosphorylation-dependent binding of the transmembrane protein occludin to the structural organizing protein ZO-1 contributes to the regulation of barrier properties; however, the details of their interaction are controversial. Using small angle X-ray scattering (SAXS), NMR chemical shift perturbation, cross-saturation, in vitro binding, and site-directed mutagenesis experiments. we define the interface between the ZO-1 PDZ3-SH3-U5-GuK (PSG) and occludin coiled-coil (CC) domains. The interface is comprised of basic residues in PSG and an acidic region in CC. Complex formation is blocked by a peptide (REESEEYM) that corresponds to CC residues 468-475 and includes a previously uncharacterized phosphosite, with the phosphorylated version having a larger effect. Furthermore, mutation of E470 and E472 reduces cell border localization of occludin. Together, these results localize the interaction to an acidic region in CC and a predominantly basic helix V within the ZO-1 GuK domain. This model has important implications for the phosphorylation-dependent regulation of the occludin:ZO-1 complex.     

The Application of Chitosan for Protection of Cultural Heritage Objects of the 15–16th Centuries in the State Tretyakov Gallery

Microorganisms are one of the main factors in the deterioration of cultural heritage, in particular art paintings. The antiseptics currently used in painting have significant limitations due to insufficient effectiveness or increased toxicity and interaction with art materials. In this regard, the actual challenge is the search for novel materials that effectively work against microorganisms in the composition with painting materials and do not change their properties. Chitosan has pronounced antimicrobial properties but was not used previously as an antiseptic for paintings. In our study we developed a number of mock layers based on sturgeon glue, supplemented which chitosan (molecular weight 25 kDa or 45 kDa), standard antiseptics for paintings (positive controls) or without additives (negative control). According to Fourier transform infrared spectroscopy and atomic force microscopy, the addition of chitosan did not significantly affect the optical and surface properties of this material. The ability of chitosan to effectively protect paintings was shown after inoculation on the created mock-up layers of 10 fungi-destructors of tempera painting, previously isolated from cultural heritage of the of the 15–16th centuries in the State Tretyakov Gallery, on the created mock layers. Our study demonstrated the principled opportunity of using chitosan in the composition of painting materials to prevent biodeterioration for the first time.