A Downward-looking Three-dimensional Imaging Method for Airborne FMCW SAR Based on Array Antennas

AbstractWith regard to problems in conventional synthetic aperture radar (SAR), such as imaging distortion, beam limitation and failure in acquiring three-dimensional (3-D) information, a downward-looking 3-D imaging method based on frequency modulated continuous wave (FMCW) and digital beamforming (DBF) technology for airborne SAR is presented in this study. Downward-looking 3-D SAR signal model is established first, followed by introduction of virtual antenna optimization factor and discussion of equivalent-phase-center compensation. Then, compensation method is provided according to reside video phase (RVP) and slope term for FMCW SAR. As multiple receiving antennas are applied to downward-looking 3-D imaging SAR, range cell migration correction (RCMC) turns to be more complex, and corrective measures are proposed. In addition, DBF technology is applied in realizing cross-track resolution. Finally, to validate the proposed method, magnitude of slice, peak sidelobe ratio (PSLR), integrated sidelobe ratio (ISLR) and two-dimensional (2-D) contour plot of impulse response function (IRF) of point target in three dimensions are demonstrated. Satisfactory performances are shown by simulation results

Study on macromolecular structure of different types of contact metamorphic coals

Contact metamorphism occurs when magma intrudes into the coal seam, resulting in changes to the microfraction, grade, chemical composition, physico-chemical structure and process properties of the coal. Different types of contact metamorphic products are formed under different tectonic-thermal conditions. In order to reveal the variability of different types of contact metamorphic coals and their controlling factors from the macromolecular structure scale, a comparative study of natural coke series samples from the Tashan mine in Datong, Shanxi Province and coal-based graphite series samples from the Lutang mine in Hunan Province was carried out using industrial analysis, elemental analysis, reflectance determination, X-ray diffraction (XRD) and Raman spectroscopy (Raman) test methods, and combined with geological background analysis. The results show that the small shallow-formed rocks have a short thermal action time, poor thermal confinement conditions, belong to high temperature and low pressure condition, narrow contact metamorphic zone, and develop natural coke - thermal transformation coal sequence; the series is in the carbonation stage, and the coal macromolecular structure is dominated by chemical changes, with aromatization and ring condensation dominating. It shows carbon enrichment, dehydrogenation, deoxygenation, reduction of defects in the active sites such as side chains and functional groups, growth of aromatic structural units leading to an increase in defects within the aromatic level, and the aromatic lamellae are not ordered. The acidic and moderately acidic deep-formed rock bodies such as strains and bases intruded in a regional extrusive tectonic setting are well heated, thermally confined and under high temperature and pressure conditions, and the contact metamorphic width can exceed 1km, developing graphite-semi-graphite-anthracite metamorphic sequences; the chemical composition of the coal-based graphite series is highly mature and less variable, and the macromolecular structure is dominated by physical changes, mainly occurring as collagenesis and rank physicochemical interactions. The non-oriented aromatic lamellae are spliced and stacked and rotated and oriented by forces, with a continuous reduction of defects and a transition to a three-dimensional ordered crystal structure

Dermal Fibroblast CCN1 Expression in Mice Recapitulates Human Skin Dermal Aging

The aging process deleteriously alters the structure and function of dermal collagen. These alterations result in thinning, fragility, wrinkles, laxity, impaired wound healing, and a microenvironment conducive to cancer. However, the key factors responsible for these changes have not been fully elucidated and relevant models for the study of skin aging progression are lacking. CCN1, a secreted extracellular matrix (ECM) associated matricellular protein, is elevated in dermal fibroblasts in aged human skin. Towards constructing a mouse model to study key factors involved in skin aging progression, we demonstrate that transgenic mice, with selective expression of CCN1 in dermal fibroblasts (COL1A2-CCN1), display accelerated skin dermal aging. The aged phenotype in COL1A2-CCN1 mice resembles aged human dermis: the skin is wrinkled, and the dermis is thin and composed of loose, disorganized, and fragmented collagen fibrils. These dermal alterations reflect reduced production of collagen due to impaired TGF-β signaling and increased expression of matrix metalloproteinases, driven up induction of c-Jun/AP-1. Importantly, similar mechanisms drive human dermal aging. Taken together, the data demonstrate that elevated expression of CCN1 by dermal fibroblasts functions as a key mediator of dermal aging. The COL1A2-CCN1 mouse model provides a novel tool for understanding and studying mechanisms of skin aging and age-related skin disorders

A panel of induced pluripotent stem cells from chimpanzees: A resource for comparative functional genomics

Comparative genomics studies in primates are restricted due to our limited access to samples. In order to gain better insight into the genetic processes that underlie variation in complex phenotypes in primates, we must have access to faithful model systems for a wide range of cell types. To facilitate this, we generated a panel of 7 fully characterized chimpanzee induced pluripotent stem cell (iPSC) lines derived from healthy donors. To demonstrate the utility of comparative iPSC panels, we collected RNA-sequencing and DNA methylation data from the chimpanzee iPSCs and the corresponding fibroblast lines, as well as from 7 human iPSCs and their source lines, which encompass multiple populations and cell types. We observe much less withinspecies variation in iPSCs than in somatic cells, indicating the reprogramming process erases many inter-individual differences. The low within-species regulatory variation in iPSCs allowed us to identify many novel inter-species regulatory differences of small magnitude

A large scale hearing loss screen reveals an extensive unexplored genetic landscape for auditory dysfunction

The developmental and physiological complexity of the auditory system is likely reflected in the underlying set of genes involved in auditory function. In humans, over 150 non-syndromic loci have been identified, and there are more than 400 human genetic syndromes with a hearing loss component. Over 100 non-syndromic hearing loss genes have been identified in mouse and human, but we remain ignorant of the full extent of the genetic landscape involved in auditory dysfunction. As part of the International Mouse Phenotyping Consortium, we undertook a hearing loss screen in a cohort of 3006 mouse knockout strains. In total, we identify 67 candidate hearing loss genes. We detect known hearing loss genes, but the vast majority, 52, of the candidate genes were novel. Our analysis reveals a large and unexplored genetic landscape involved with auditory function

Synthesis, characterization and dielectric properties of a novel temperature stable (1-x)CoTiNb2O8-xZnNb(2)O(6) ceramic

(1-x)CoTiNb2O8-xZnNb(2)O(6) microwave dielectric ceramics were prepared via the conventional solid-state reaction route with the aim of reducing the (f) value and improving the thermal stability. The phase composition and the microstructure were investigated using X-ray diffraction, Raman spectra, and scanning electron microscopy. A set of phase transitions which were induced by composition had been confirmed via the sequence: rutile structurecoexistence of rutile and columbite phasecolumbite phase. For (1-x)CoTiNb2O8-xZnNb(2)O(6) microwave dielectric ceramics, the addition of ZnNb2O6 content (x = 0-1) led to the decrease of epsilon(r) from 62.98 to 23.94. As a result of the high Q x f of ZnNb2O6 ceramics, the increase of ZnNb2O6 content also led to the lower sintering temperatures and the higher Q x f values. The (f) value was reduced from +108.04 (x = 0) to - 49.31 ppm/degrees C (x = 1). Among them, high density 0.5CoTiNb(2)O(8)-0.5ZnNb(2)O(6) ceramics were obtained at 1175 degrees C with excellent microwave dielectric properties of epsilon(r) 39.2, Q x f 40013 GHz, and (f)+3.57 ppm/degrees C

Structural, Raman spectroscopic and microwave dielectric studies on (1-x) NiZrNb2O8 - x ZnTa2O6

(1 - x) NiZrNb2O8 - x ZnTa2O6 microwave dielectric ceramics were prepared via the conventional solid-state reaction route. Structural and lattice parameters of the (1 - x) NiZrNb2O8 - x ZnTa2O6 ceramics were analyzed through X-ray diffraction, Raman spectra, and scanning electron microscopy. The results showed that there were serious ionic diffusion and solid solution reaction in the composite ceramics. The substitution of Ni2+, Zr4+, and Zn2+ at A-sites and the substitution of Nb5+ and Ta5+ at B-sites led to the change of the lattice parameters. There was a gradual transformation in crystal structure from monoclinic phase into Tri-alpha PbO2 phase with the increasing ZnTa2O6 content. With the increase of x value from 0 to 1, the epsilon (r) value increased from 23.76 to 35.71 and the Q x AE' value increased from 32107 to 46709 GHz. The temperature frequency resonance coefficient near zero could be obtained at x = 0.8. The 0.2NiZrNb(2)O(8) - 0.8ZnTa(2)O(6) ceramics were obtained at 1275 A degrees C with excellent microwave dielectric properties: epsilon (r) similar to 33.69, Q x AE' similar to 37,529 GHz and tau(AE') similar to + 2.56 ppm/A degrees C

synthesischaracterizationanddielectricpropertiesofanoveltemperaturestable1xcotinb2o8xznnb2o6ceramic

(1–x)CoTiNb_2O_8 –xZnNb_2O_6 microwave dielectric ceramics were prepared via the conventional solid-state reaction route with the aim of reducing the τ_f value and improving the thermal stability. The phase composition and the microstructure were investigated using X-ray diffraction, Raman spectra, and scanning electron microscopy. A set of phase transitions which were induced by composition had been confirmed via the sequence: rutile structure→coexistence of rutile and columbite phase→columbite phase. For (1–x)CoTiNb_2O_8 –xZnNb_2O_6 microwave dielectric ceramics, the addition of ZnNb_2O_6 content (x =0–1) led to the decrease of ε_r from 62.98 to 23.94. As a result of the high Q ×? of ZnNb_2O_6 ceramics, the increase of ZnNb_2O_6 content also led to the lower sintering temperatures and the higher Q ×? values. The τ_f value was reduced from+108.04 (x =0) to – 49.31 ppm/℃ (x = 1). Among them, high density 0.5CoTiNb_2O_8 -0.5ZnNb_2O_6 ceramics were obtained at 1175 ℃ with excellent microwave dielectric properties of ε_r 39.2, Q ×? 40013 GHz, and τ_f+ 3.57 ppm/℃

Synthesis, characterization and dielectric properties of a novel temperature stable (1-x)CoTiNb2O8-xZnNb(2)O(6) ceramic

(1-x)CoTiNb2O8-xZnNb(2)O(6) microwave dielectric ceramics were prepared via the conventional solid-state reaction route with the aim of reducing the (f) value and improving the thermal stability. The phase composition and the microstructure were investigated using X-ray diffraction, Raman spectra, and scanning electron microscopy. A set of phase transitions which were induced by composition had been confirmed via the sequence: rutile structurecoexistence of rutile and columbite phasecolumbite phase. For (1-x)CoTiNb2O8-xZnNb(2)O(6) microwave dielectric ceramics, the addition of ZnNb2O6 content (x = 0-1) led to the decrease of epsilon(r) from 62.98 to 23.94. As a result of the high Q x f of ZnNb2O6 ceramics, the increase of ZnNb2O6 content also led to the lower sintering temperatures and the higher Q x f values. The (f) value was reduced from +108.04 (x = 0) to - 49.31 ppm/degrees C (x = 1). Among them, high density 0.5CoTiNb(2)O(8)-0.5ZnNb(2)O(6) ceramics were obtained at 1175 degrees C with excellent microwave dielectric properties of epsilon(r) 39.2, Q x f 40013 GHz, and (f)+3.57 ppm/degrees C