Orientation Of Axis Research Articles

Deep learning for rapid analysis of cell divisions in vivo during epithelial morphogenesis and repair.

Cell division is fundamental to all healthy tissue growth, as well as being rate-limiting in the tissue repair response to wounding and during cancer progression. However, the role that cell divisions play in tissue growth is a collective one, requiring the integration of many individual cell division events. It is particularly difficult to accurately detect and quantify multiple features of large numbers of cell divisions (including their spatio-temporal synchronicity and orientation) over extended periods of time. It would thus be advantageous to perform such analyses in an automated fashion, which can naturally be enabled using deep learning. Hence, we develop a pipeline of deep learning models that accurately identify dividing cells in time-lapse movies of epithelial tissues in vivo. Our pipeline also determines their axis of division orientation, as well as their shape changes before and after division. This strategy enables us to analyse the dynamic profile of cell divisions within the Drosophila pupal wing epithelium, both as it undergoes developmental morphogenesis and as it repairs following laser wounding. We show that the division axis is biased according to lines of tissue tension and that wounding triggers a synchronised (but not oriented) burst of cell divisions back from the leading edge.

Deep learning for rapid analysis of cell divisions in vivo during epithelial morphogenesis and repair

Cell division is fundamental to all healthy tissue growth, as well as being rate-limiting in the tissue repair response to wounding and during cancer progression. However, the role that cell divisions play in tissue growth is a collective one, requiring the integration of many individual cell division events. It is particularly difficult to accurately detect and quantify multiple features of large numbers of cell divisions (including their spatio-temporal synchronicity and orientation) over extended periods of time. It would thus be advantageous to perform such analyses in an automated fashion, which can naturally be enabled using deep learning. Hence, we develop a pipeline of deep learning models that accurately identify dividing cells in time-lapse movies of epithelial tissues in vivo. Our pipeline also determines their axis of division orientation, as well as their shape changes before and after division. This strategy enables us to analyse the dynamic profile of cell divisions within the Drosophila pupal wing epithelium, both as it undergoes developmental morphogenesis and as it repairs following laser wounding. We show that the division axis is biased according to lines of tissue tension and that wounding triggers a synchronised (but not oriented) burst of cell divisions back from the leading edge.

An Approach to Gamma-Hadron Separation via Measurements of the Middle-UV Fraction of EAS emission by an Imaging Atmospheric Cherenkov Telescope with UV-Sensitive SiPM detectors

Abstract The operation of a small-size Cherenkov gamma-ray telescope TAIGA-IACT with camera on SiPMs OnSemi MicroFJ-60035 has been modelled by multiparticle Monte Carlo (MC) methods. The model implies that telescope camera is equipped with two specific types of filters of 290 - 590 nm (visible+NUV) and 220 - 320 nm (MUV+UVB)-bands, each covering half of the camera pixels in some uniform order. This allows one to measure the fraction of UV-radiation in total amount of Cherenkov radiation of an extensive air shower (EAS), that can be used for efficient gamma-hadron separation. The corresponding quality factor takes values up to 5.07 in the 10 - 100 TeV range depending on the distance to EAS axis and camera orientation.

The AllWISE Catalog as an Infrared Celestial Reference Frame in the Gaia Era

The launch of Gaia in 2013 December ushered in a new era of space astrometry, allowing for fundamental reference research at an unprecedented level of precision. The international celestial reference frames in the radio band and the Gaia celestial reference frame in the optical band have been established and are consistent within several microarcseconds for axes orientation. To bridge the gap between the visual and radio bands, an infrared reference frame should be investigated. We present a study aimed at constructing an infrared reference frame using the observations from the AllWISE catalog. It is compared with Gaia DR3 for approximately 0.57 million extragalactic sources and for a full set of 273 million sources. Systematic differences in positions and proper motions, such as magnitude or color equations and vector spherical harmonics, are derived. These systematic differences are comparable to the random errors of AllWISE measurements and can be used to improve the AllWISE source positions and proper motions, making the AllWISE catalog a valuable all-sky reference frame in the infrared band. Our investigation of the AllWISE catalog reveals that extragalactic sources and stars exhibit different astrometric properties. The global difference between the extragalactic source reference frame and the stellar reference frames is found to be 8.6 mas and 13.7 mas for global rotation and glide amplitudes, respectively. Such internal inconsistency should be considered when using AllWISE as an infrared reference frame. Finally, we determine the orientation of the mean Galactic plane using the calibrated source distribution of the AllWISE catalog.

Janus monolayers Fe2SSeX2(X = Ga, In, and Tl): Robust nontrivial topology with high Chern-number

Abstract High-performance quantum anomalous Hall (QAH) systems are the crucial materials to explore emerging quantum physics and magnetic topological phenomena. Inspired by layered FeSe materials with excellent superconducting properties, the Janus monolayers Fe2SSeX2 (X = Ga, In, and Tl) are built by the decoration of Ga, In, and Tl atoms in monolayer Fe2SSe. Using the first-principles calculations, the Fe2SSeX2 have stable structures and prefer ferromagnetic (FM) orders, which belong to the Weyl semimetal without spin-orbit coupling (SOC). For the out-of-plane (OOP) magnetic anisotropy, the large nontrivial gaps are opened, and the Fe2SSeX2 are predicted to be large-gap QAH insulators with high Chern-number C = 2, proved by two chiral edge states and Berry curvatures. When the magnetization is flipped, two chiral edge states can be simultaneously changed and C = -2 can be obtained, revealing one fascinating behavior of chiral spin-edge-state locking. It is found that the QAH properties of the Fe2SSeX2 are robust against the strain. Especially, the nontrivial topological quantum states can spontaneously appear for the Fe2SSeGa2 and Fe2SSeIn2, because the easy magnetic axis orientations are adjusted from in-plane to OOP by the biaxial strain. Our studies provide excellent candidate systems to realize the QAH properties with high Chern-number, and advocate more experimental explorations in the combination of superconductivity and topology.

Encryption-decryption scheme in a single-pixel system based on polarization and Laguerre-Gaussian mode modulation

Optical cryptosystems are crucial for ensuring the security of optical information transmission and storage. The indirect measurement mechanism of single-pixel imaging (SPI) offers a feasible implementation channel for optical cryptosystems. Illumination patterns are encryption keys projected onto the plaintext object, while the intensity collected by the single-pixel detector forms the ciphertext. However, the variations in the object's angular position during SPI measurement generally introduce certain inaccuracies in image reconstruction. And due to SPI's input-output linear mapping relationship, the plaintext is vulnerable to exposure. This proposes an encryption-decryption scheme in a single-pixel system based on polarization and Laguerre-Gaussian (LG) mode modulation. The inherent circular symmetry of LG mode makes the angular position of the object information that can be encrypted, while the intrinsic properties of the object can be represented by polarization. Our system characterizes various polarization parameters of samples serving as reliable plaintext with an error of less than 4.2%, including depolarization, diattenuation, and retardance. For encryption demonstration, LG modes are randomly divided into 5 groups, corresponding to an object at different rotational states. This, combined with 16 polarization modulations, constructs pattern-angle-polarization joint keys, enabling high-security encryption as well as high-fidelity decryption of the mask image, optical axis orientation, and retardance of the test sample. Experimental results demonstrate the effectiveness of our scheme in enhancing the security and information complexity of optical cryptography, offering valuable insights for optical communication and quantum information security.

Osmium(III) Acetylacetonate and Its Missing Polymorph: A Magnetic and Structural Investigation.

Despite the potential for their application, the magnetic behavior of complexes containing 4d and 5d metal ions is underexplored, evidencing the need for benchmark multi-technique studies on simple molecules. We report here a structural and magnetic study on osmium(III) acetylacetonate [Os(acac)3]. X-ray single crystal diffraction did not allow us to determine the structure of the β-polymorph of [Os(acac)3]. The combined magnetic (dc magnetic measurements on powder and cantilever torque magnetometry on single crystal) and spectroscopic (electron paramagnetic resonance, EPR) characterization is here used to provide further evidence that its structure is indeed the one of the orthorhombic "missing polymorph", analogous to the ruthenium(III) derivative. Our study shows that all acetylacetonate complexes of the eighth group of the periodic table show dimorphism and are isomorphic. The EPR characterization allowed the experimental assessment of the easy axis nature of the ground doublet and the determination of the first hyperfine coupling in an osmium complex. Torque magnetometry, applied here for the first time on an osmium-based molecule, determined the orientation of the easy axis along the pseudo C3 axis of the complex. Ac magnetometric measurements revealed in-field slow relaxation of the magnetization further slowed by the suppression of dipolar fields via magnetic dilution in the isostructural gallium(III) analogue.

Shape-controlled growth of beta-gallium oxide nanowires and experimental investigation on the origination of electrons

Diameter-controlled growth of monoclinic gallium oxide nanowires was performed by chemical vapor deposition technique. Prior to growth, a thin layer of Au films was fabricated, SEM images indicated that Au could converge nanoparticles to govern the growth of β-Ga2O3 nanowires. The SEM images revealed both diameter and length of β-Ga2O3 nanowires strongly depended on the growth temperature. Nanowires grown at 1100 °C temperature have the minimum diameters and uniform lengths, compared with those grown at 900 °C and 1000 °C. The reasons are that a combination and a competition of vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism occur in the growth process. High temperature would provide enough energy to make Ga and O atoms grow along one-dimensional axial orientation following the VLS mechanism. However, low temperature confines atoms at the nanowires interface and enhance sidewalls coalescence following the VS mechanism. X-ray diffraction (XRD) patterns and refinement indicated that the grown samples were of high crystallinity and had intrinsic oxygen vacancies. Photoluminescence spectra were examined and then followed by Gaussian fitting. Through analysis, the emission peaks were considered to originate from intrinsic oxygen vacancies and Ga-O vacancy pairs, consisting with the XRD refinement results. β-Ga2O3 nanowires was coated on the interdigitated electrode, the response to the ultraviolet light and oxygen was studied.

Методы монохроматизации синхротронного излучения (обзор исследований)

The paper presents an analysis of studies related to the monochromatization of X-ray radiation (XR) at synchrotron radiation sources. A review of monochromators based on of X-ray diffraction on crystals is given, and the peculiarities of their technical realization are considered. The ideas about monochromators which include multilayer structures are examined. The authors also study technical problems arising during designing devices and its possible solutions. Introduction. The possibilities of using X-rays in scientific research are described. The high efficiency of synchrotron radiation sources is noted, and its characterization is given. Elementary information about diffraction of X-rays. The paper describes the properties of X-ray radiation and the possibilities of its using while studying various materials. Degree of monochromaticity. The degree of monochromaticity is an important characteristic of the synchrotron radiation (SR). Depending on the width of the wavelength band, “white”, “pink” and monochromatic beams are distinguished. Monochromators based on multilayer structures are used to obtain “pink” beams. Monochromatic radiation is formed using monocrystals. When conducting experiments with “white” beams, the monochromator is not used. The authors also describe the factors that violate the ideal fulfillment of the Wolf-Bragg condition and affect the degree of monochromaticity (heat, vibration). The reflectivity values at different beam grazing angles are noted to have different widths. Monochromators based on multilayer structures. Periodic structures combining thin layers of two heterogeneous materials make it possible to obtain “pink” beams. The wavelength bandwidth of such devices is one or two orders of magnitude greater than that of monochromators using crystals as optical elements. Configurations and geometry of optical elements. There are two types of X-ray diffraction on a crystal: Bragg and Laue diffraction. Bragg diffraction refers to reflective geometry, Laue diffraction is based on the passage of beams through the crystal. The section provides examples of monochromators with different configurations of crystals and X-ray mirrors. The arrangement of optical elements in a monochromator plays an important role in the geometry of the beam path. When designing monochromators, it is necessary to take into account the methods of fixation and orientation of the rotation axes of optical elements. Examples of monochromators with different configurations of crystals and X-ray mirrors are given. Focusing monochromators. It is possible to provide sagittal and meridional types of deformation by bending the optical element of the monochromator. Due to the curved crystal surface the beam is not only monochromatized but also subjected to focusing. Modern focusing monochromators are equipped with adaptivity elements allowing it to change the radius of curvature of the optical element. Examples of practical realization of such monochromators are presented. Thermal load of SR on optical elements. The SR is characterized by high brightness and a wide spectrum of emitted wavelengths. While operating optical elements of SR stations absorb a large amount of thermal power. The problems of heat dissipation have a fundamental influence on the quality of synchrotron radiation monochromatization. Additional information about monochromators. Examples of special design solutions for monochromators are given. Conclusion. The design of monochromators is relevant to the synchrotron radiation source 4+ “SKIF” under construction in Novosibirsk.

Astigmatism among schoolchildren in Mumbai, India: a large, population-based study

Background: Astigmatism is a common refractive error. If left untreated, it may result in blurred or distorted vision. We determined the prevalence of astigmatism in schoolchildren aged 6–16 years in Mumbai, India. Methods: A cross-sectional study was conducted using a stratified cluster random sampling method. We included primary and secondary schoolchildren aged 6–16 years. All children underwent a comprehensive eye examination. Astigmatism was characterized as having a diopter cylinder (DC) power of 0.50 or more in at least one eye, and for prevalence estimation, we reported the number of children with astigmatism. Astigmatism severity was defined as mild (less than or equal to - 1.50 DC), moderate (- 1.50 DC to - 2.50 DC), and severe (> - 2.50 DC). Based on the axis orientation, astigmatism was categorized as with-the-rule, against-the-rule, and oblique. Results: A total of 3151 schoolchildren with a mean (standard deviation) age of 12.1 (2.9) years were screened; boys and girls accounted for 49.22% and 50.78%, respectively. Age groups of 6–9, 10–13, and 14–16 years accounted for 51.35%, 28.53%, and 20.12%, respectively. The overall prevalence of astigmatism was 11.46%, with no significant difference between sexes (P > 0.05). The prevalences of astigmatism in the groups aged 6–9-, 10–13-, and 14–16 years were 5.24%, 3.49%, and 2.73%, respectively. Prevalence differed significantly among age groups (P < 0.05), with a trend of decreasing prevalence with increasing age. No significant association was found between age and severity of astigmatism (P > 0.05). The prevalences of mild, moderate, and severe astigmatism were 6.51%, 3.11%, and 1.84%, respectively. Mild astigmatism was significantly more prevalent than moderate (P < 0.05) or severe astigmatism (P < 0.05). The prevalence of astigmatism differed significantly among the three orientations of axis (P < 0.001). The prevalences were 9.20%, 1.68%, and 0.57% for with-the-rule, against-the-rule, and oblique astigmatism, respectively. We found a statistically significant difference in the prevalences of astigmatism based on the axis orientation between boys and girls (P < 0.05) and between age groups (P < 0.001), with a decreasing trend observed with increasing age. Conclusions: We found a prevalence of 11.46% for astigmatism among schoolchildren aged 6–16 years in Mumbai, India. There was a decreasing trend in prevalence with increasing age, with no difference between sexes. The prevalence was the highest for mild astigmatism, followed by moderate and severe astigmatism. Prevalence differed significantly based on the axis orientation among the three subtypes, age groups, and between the two sexes, with a decreasing trend with increasing age. With-the-rule astigmatism was the most common, followed by against-the-rule astigmatism; oblique astigmatism was the least common.

Characterising the stellar differential rotation based on largest-spot statistics from ground-based photometry

Aims. Stellar spot distribution has consequences on the observable periodic signals in long-time baseline ground-based photometry. We model the statistics of the dominating spots of two young and active Solar-type stars, V889 Her and LQ Hya, in order to obtain information on the underlying spot distribution, rotation of the star, as well as the orientation of the stellar axis of spin. Methods. By calculating estimates for spot-induced periodicities in independent subsets of photometric data, we obtain statistics based on the dominating spots in each subset, giving rise to largest-spot statistics accounting for stellar geometry and rotation, including differential rotation. Results. Our simple statistical models are able to reproduce the observed distribution of photometric signals rather well. This also enables us to estimate the dependence of angular velocity of the spots as a function of latitude. Our results indicate that V889 Her has a non-monotonic differential rotation curve with a maximum angular velocity between latitudes of 37–40 deg and lower angular velocity at the pole than the equator. Our results for LQ Hya indicate that the star rotates much like a rigid body. Furthermore, the results imply that the monotonic Solar differential rotation curve may not be a universal model for other solar-type stars. Conclusions. The non-monotonicity of the differential rotation of V889 Her is commonly produced in magnetohydrodynamic simulations, which indicates that our results are realistic from a theoretical perspective.

High-Precision Determination of NMR Interaction Parameters by Measurement of Single Crystals: A Review of Classical and Advanced Methods.

In this review, the process of extracting precise values for NMR interaction tensors from single crystal samples is systematically explored. Starting with a description of the orientation dependence of the considered interactions, i.e., chemical shift, dipolar, and quadrupole interaction, the techniques for acquiring and analysing single-crystal spectra are outlined. This includes the 'classical' approach, which requires the acquisition of three rotation patterns around three rotation axes that are orthogonal to each other, as well as more recent strategies aimed at reducing the number of required NMR spectra. One such strategy is the 'single-rotation method', which exploits the symmetry relations between tensors in the crystal structure to reduce the necessary amount of orientation-dependent data. This concept may be extended to additionally include the orientation of the goniometer axis itself in the data fit, which may be termed the 'minimal-rotation method'. Other, more exotic schemes, such as the use of specialised probe designs or the investigation of single crystals under magic-angle-spinning, are also briefly discussed. Actual values of NMR interaction tensors as determined from the various single-crystal methods have been collected and are provided in tables for spin I=1/2, I=1, and half-integer spins with I>1/2.

Melting and freezing of a skyrmion lattice

We report comprehensive Monte-Carlo studies of the melting of skyrmion lattices (SkL) in systems of small, medium, and large sizes with the number of skyrmions ranging from 103to over 105. Large systems exhibit hysteresis similar to that observed in real experiments on the melting of SkLs. For sufficiently small systems which achieve thermal equilibrium, a fully reversible sharp solid-liquid transition on temperature with no intermediate hexatic phase is observed. A similar behavior is found on changing the magnetic field that provides the control of pressure in the SkL. We find that on heating the melting transition occurs via a formation of grains with different orientations of hexagonal axes. On cooling, the fluctuating grains coalesce into larger clusters until a uniform orientation of hexagonal axes is slowly established. The observed scenario is caused by collective effects involving defects and is more complex than a simple picture of a transition driven by the unbinding and annihilation of dislocation and disclination pairs.

New findings on the orientation of the mouse anterior-posterior (A-P) axis before and during the initiation of gastrulation using a more refined embryo staging

A clinically significant event of early mammalian embryogenesis is the generation and early development of the anterior-posterior (A-P) axis, the imaginary line along which the structures from head to tail will form. This axis not only appears before gastrulation but is also oriented in a specific way in relation to the long and short diameters of the bilaterally symmetric epiblast. In mice, the most widely used mammalian in vivo model of early embryogenesis, the A-P axis is normally aligned with the long epiblast diameter by the early streak (ES) stage, a time during early gastrulation around embryonic day 6.5 (E6.5). Incorrect orientation of the A-P axis by the ES stage, that is, being aligned with the short epiblast diameter, leads to failure in completing gastrulation and results in embryo death soon after. Knowing the orientation of this axis from when it forms before gastrulation (around E5.5) until just before the ES stage is crucial for: (a) understanding the ill-defined factors involved in its formation and early development since they must be spatially related to it, and (b) providing explanations for the underlying mechanism when it is incorrectly orientated. However, the orientation of the A-P axis in pre-ES embryos of the E5.5-E6.5 period remains unclear. Specifically, although it is thought that this axis initially aligns with the short epiblast diameter and subsequently changes its orientation to become aligned with the long diameter by an unidentified pre-gastrulation stage before the ES stage, this proposition remains unresolved. This is largely due to the lack of clearly defined morphological criteria for staging certain periods of pre-ES mouse embryos (especially when the A-P axis initiates and when gastrulation begins prior to the ES stage), which are a prerequisite for identifying A-P axis orientation at specific pre-ES stages. Furthermore, although the orientation of an extraembryonic trophoblast asymmetry, specifically the tilt of the ectoplacental cone (EPC), coincides with that of the A-P axis by the ES stage, it is unknown whether such an association also exists at pre-gastrulation stages during A-P axis formation. Knowing this would exclude or implicate this trophoblast asymmetry as an upstream factor in orientating the A-P axis when it forms. To address these issues, we established a more refined embryo staging for the E5.5-E6.5 period using a novel combination of live morphological criteria and used it to examine the orientation of the A-P axis and that of the EPC tilt at specific stages. First, contrary to current thinking, we show that when the A-P axis first appears at our newly described anterior visceral endoderm-1 (AVE-1) and AVE-2 stages, it aligns with the long epiblast diameter in all embryos. This orientation is maintained in most embryos at all subsequent pre-gastrulation stages, specifically at our AVE-3 and pre-streak stages (the remaining embryos of these stages had this axis aligned with the short epiblast diameter). Second, we identified for the first time the pre-ES stage when gastrulation initiates, which we named the nascent streak (NS) stage, and further subdivided it into NS-1 and NS-2. At variance with current belief, we provide evidence that the earliest stage just before the ES stage when all embryos align their A-P axis with the long epiblast diameter is not a pre-gastrulation stage, but the NS-2 stage (at NS-1, most but not all embryos had this A-P axis orientation). Third, we implicate the EPC tilt as a possible extraembryonic factor in promoting correct A-P axis orientation, as this tilt exists before the AVE-1 stage and its orientation coincided with that of the A-P axis in all embryos at AVE-1, AVE-2 and ES stages and almost all embryos at AVE-3, pre-streak and NS stages. Overall, our work: (a) identified the previously unresolved orientation of the mouse A-P axis within the epiblast before the ES stage during the E5.5-E6.5 period; (b) provides an alternative explanation for when this axis is incorrectly oriented by the ES stage, namely, its defective alignment with the short epiblast diameter by this stage could be due to its failure to align with the long epiblast diameter from the time of its formation; and (c) implicates the pre-existing orientation of the EPC tilt as a possible factor in orientating the newly formed A-P axis.

Rolling mechanism profundities on material removal mechanism of surface-textured GaN using Molecular dynamics simulation

Molecular dynamics simulation examines how the polishing tool's rotating velocity and axes affect surface nanotribological properties and material removal mechanism of patterned gallium nitride (GaN) substrates. Frictional coefficient and average contact area affect material removal rate (MRR) variance. Rotating speed increases the frictional coefficient and contact area, elevating MRR. Anticlockwise abrasives have substantially higher root-mean-square roughness (RMS) than clockwise ones. After polishing, increasing the rotating angle increases the frictional coefficient, average contact area, MRR, and RMS. MRR enhancement is maximum at −15 rad/ns, the only spinning velocity that improves MRR. RMS improvement ratio is highest when the polishing tool spins clockwise or the rotational axis orientation is lowered. Particularly, the MRR and RMS improvements after the polishing process can reach 103.8 % and 223.5 %, respectively. These findings help explain atomic-scale GaN-based material removal and deformation with frictional resistance and erosion by polishing.

Steepness-fragility insights from the temperature derivative analysis of dielectric data of a highly nonsymmetric liquid crystal dimer.

A comprehensive dynamic analysis of the dielectric relaxation-time data across a broad temperature range for both isotropic and nematic phases has been conducted on the CBO3O.Py liquid crystal dimer, the shorter chain-length compound within the highly nonsymmetric pyrene-based series of liquid crystal dimers (CBOnO.Py, with n ranging from 3 to 11). It was known from another previous study that in the nematic phase, three different relaxation processes contribute to the complex dielectric permittivity depending on the orientation of the alignment axis with respect to the probing electric field direction. The temperature-derivative analysis of the relaxation-time data using different analytic functions reveals that the critical-like description, through the dynamic scaling model, best portrays the relaxation-time data in the nematic phase as the system approaches the glass transition. A single glass transition temperature is obtained which is consistent with thermal stimulated depolarization currents experimental determinations published elsewhere. From temperature-dependent steepness index m(T), the activation-critical model is also considered as a more general analytic function from which the dynamic scaling model is a terminal approximation. Additionally, the critical-like parametrization provides insight into obtaining a universal description of the temperature-dependent steepness index m(T), for all liquid crystal compounds belonging to symmetry-selected glass formers, such as rodlike liquid crystal monomers.

DeepEMC-T2 mapping: Deep learning-enabled T2 mapping based on echo modulation curve modeling.

Echo modulation curve (EMC) modeling enables accurate quantification of T2 relaxation times in multi-echo spin-echo (MESE) imaging. The standard EMC-T2 mapping framework, however, requires sufficient echoes and cumbersome pixel-wise dictionary-matching steps. This work proposes a deep learning version of EMC-T2 mapping, called DeepEMC-T2 mapping, to efficiently estimate accurate T2 maps from fewer echoes. DeepEMC-T2 mapping was developed using a modified U-Net to estimate both T2 and proton density (PD) maps directly from MESE images. The network implements several new features to improve the accuracy of T2/PD estimation. A total of 67 MESE datasets acquired in axial orientation were used for network training and evaluation. An additional 57 datasets acquired in coronal orientation with different scan parameters were used to evaluate the generalizability of the framework. The performance of DeepEMC-T2 mapping was evaluated in seven experiments. Compared to the reference, DeepEMC-T2 mapping achieved T2 estimation errors from 1% to 11% and PD estimation errors from 0.4% to 1.5% with ten/seven/five/three echoes, which are more accurate than standard EMC-T2 mapping. By incorporating datasets acquired with different scan parameters and orientations for joint training, DeepEMC-T2 exhibits robust generalizability across varying imaging protocols. Increasing the echo spacing and including longer echoes improve the accuracy of parameter estimation. The new features proposed in DeepEMC-T2 mapping all enabled more accurate T2 estimation. DeepEMC-T2 mapping enables simplified, efficient, and accurate T2 quantification directly from MESE images without dictionary matching. Accurate T2 estimation from fewer echoes allows for increased volumetric coverage and/or higher slice resolution without prolonging total scan times.

Radially and Axially Oriented Ammonium Alginate Aerogels Modified with Clay/Tannic Acid and Crosslinked with Glutaraldehyde.

Lightweight materials that combine high mechanical strength, insulation, and fire resistance are of great interest to many industries. This work explores the properties of environmentally friendly alginate aerogel composites as potential sustainable alternatives to petroleum-based materials. This study analyzes the effects of two additives (tannic acid and montmorillonite clay), the orientation that results during casting, and the crosslinking of the biopolymer with glutaraldehyde on the properties of the aerogel composites. The prepared aerogels exhibited high porosities between 90% and 97% and densities in the range of 0.059-0.191 g/cm3. Crosslinking increased the density and resulted in excellent performance under loading conditions. In combination with axial orientation, Young's modulus and yield strength reached values as high as 305 MPa·cm3/g and 7 MPa·cm3/g, respectively. Moreover, the alginate-based aerogels exhibited very low thermal conductivities, ranging from 0.038 W/m·K to 0.053 W/m·K. Compared to pristine alginate, the aerogel composites' thermal degradation rate decreased substantially, enhancing thermal stability. Although glutaraldehyde promoted combustion, the non-crosslinked aerogel composites demonstrated high fire resistance. No flame was observed in these samples under cone calorimeter radiation, and a minuscule peak of heat release of 21 kW/m2 was emitted as a result of their highly efficient graphitization and fire suppression. The combination of properties of these bio-based aerogels demonstrates their potential as substituents for their fossil-based counterparts.

Three-dimensional fiber orientation mapping of the human brain at micrometer resolution.

The accurate measurement of three-dimensional (3D) fiber orientation in the brain is crucial for reconstructing fiber pathways and studying their involvement in neurological diseases. Comprehensive reconstruction of axonal tracts and small fascicles requires high-resolution technology beyond the ability of current in vivo imaging (e.g. diffusion magnetic resonance imaging). Optical imaging methods such as polarization-sensitive optical coherence tomography (PS-OCT) and polarization microscopy can quantify fiber orientation at micrometer resolution but have been limited to two-dimensional in-plane orientation or thin slices, preventing the comprehensive study of connectivity in 3D. In this work we present a novel method to quantify volumetric 3D orientation in full angular space with PS-OCT. We measure the polarization contrasts of the brain sample from two illumination angles of 0 and 15 degrees and apply a computational method that yields the 3D optic axis orientation and true birefringence. We further present 3D fiber orientation maps of entire coronal cerebrum sections and brainstem with 10 μm in-plane resolution, revealing unprecedented details of fiber configurations. We envision that our method will open a promising avenue towards large-scale 3D fiber axis mapping in the human brain as well as other complex fibrous tissues at microscopic level.

Stabilisation of the swing pattern of an anisotropic simple pendulum

The suppression of the effects of anisotropy on a pendulum by use of a rotating mount was initially envisaged by Léon Foucault, based on his observations of the vibrations of a rod clamped in a lathe. However, the method seems to never have been tried due to the practical difficulties involved. We report a computational study of the stabilisation of the swing pattern of a simple pendulum, showing anisotropic behaviour in a static configuration, by rotation of the system mount. When the mount is static, for most initial conditions the swing patterns quickly evolves into unstable, complex Lissajous-like patterns. When the pendulum mount is rotated faster than the pendulum frequency effects of anisotropy are suppressed, and the swing pattern stabilises to that of an isotropic 3D simple pendulum. Suppression of mount anisotropy influence occurs for relatively low rotation rates. We also study swing evolution in the presence of random variations in the orientation of the mount principal axes. The use of computational techniques confirms Foucault’s original observations and hypothesis and provides an interesting avenue for students to engage meaningfully with this historically important and inspiring experiment in a novel and challenging manner.