Dielectric Responses in Multilayer C_f/Si₃N₄ as High-Temperature Microwave-Absorbing Materials

High-temperature microwave-absorbing materials are in great demand in military and aerospace vehicles. The high-temperature dielectric behavior of multilayer Cf/Si3N4 composites fabricated by gelcasting has been intensively investigated at temperature coverage up to 800°C in the X-band (8.2–12.4 GHz). Experimental results show that the permittivity of Si3N4 matrix exhibits excellent thermo-stability with temperature coefficient lower than 10−3°C−1. Taking temperature-dependent polarized bound charge and damping coefficient into consideration, a revised dielectric relaxation model with Lorentz correction for Si3N4 ceramics has been established and validated by experimental results. Besides, a general model with respect to permittivity as a function of temperature and frequency has been established with the help of nonlinear numerical analysis to reveal mechanisms of temperature-dependent dielectric responses in Cf/Si3N4 composites. Temperature-dependent permittivity has been demonstrated to be well distributed on circular arcs with centers actually kept around the real ( ε ′ ) axis in the Cole-Cole plane. Furthermore, space charge polarization and relaxation are discussed. These findings point to important guidelines to reveal the mechanism of dielectric behavior for carbon fiber functionalized composites including but not limited to Cf/Si3N4 composites at high temperatures, and pave the way for the development of high-temperature radar absorbing materials

6-Isopropyl-5-meth­oxy-3-phenyl-3H-1,2,3-triazolo[4,5-d]pyrimidin-7(6H)-one

In the title compound, C14H15N5O2, the whole mol­ecule apart from the terminal C atoms of the isopropyl group is located on a crystallographic mirror plane. An intra­molecular C—H⋯N hydrogen-bonding inter­action may stabilize the mol­ecular conformation. The crystal packing features weak slipped π–π inter­actions between the pyrimidine and the phenyl rings of symmetry-related mol­ecules [centroid–centroid distance = 3.746 (1)Å, slippage of 1.574 Å]

6-Butyl-5-(4-methoxy­phen­oxy)-3-phenyl-3H-1,2,3-triazolo[4,5-d]pyrimidin-7(6H)-one

The asymmetric unit of the title compound, C21H21N5O3, consists of two geometrically similar mol­ecules. The fused rings of the triazolo[4,5-d]pyrimidine system are nearly coplanar, making dihedral angels of 1.48 (18) and 1.34 (16)°, and the phenyl rings are twisted by 12.3 (1) and 8.7 (1)° with respect to the triazolopyrimidine plane. The ethyl groups of the n-butyl side chains are disordered over two sites in each of the independent mol­ecules, the ratios of occupancies being 0.60:0.40 and 0.61:0.39

3,3,3′,3′-Tetra­methyl-6,6′-bis­[(pyridin-4-yl)meth­oxy]-1,1′-spiro­biindane ­monohydrate

The asymmetric unit in the title compound, C33H34N2O2·H2O, consists of a V-shaped mol­ecule and a water mol­ecule to which it is hydrogen bonded. The angle between the mean planes of the two spiro-connected indane groups is 77.06 (5)°. The two five-membered rings of the indane groups have envelope conformations with the methyl­ene atoms adjacent to the spiro C atom forming the flaps. They have deviations from the mean plane of the other four atoms in the rings of 0.374 (4) and 0.362 (4) Å. In the crystal, molecules are linked to form inversion dimers via O—H⋯N hydrogen bonds involving the pyridine N atoms and the solvent water mol­ecule. The dimers are linked into a chain along the b axis by π–π stacking inter­actions between a pyridine ring and its centrosymmetrically related ring in an adjacent dimer. The centroid–centroid distance between the planes is 3.7756 (17) Å, the perpendicular distance is 3.4478 (11) Å and the offset is 1.539 Å

6-Isopropyl-3-phenyl-5-(p-tol­yloxy)-3H-1,2,3-triazolo[4,5-d]pyrimidin-7(6H)-one: whole-mol­ecule disorder

The title compound, C20H19N5O2, exhibits whole-mol­ecule disorder the refined ratios of the two components being 0.57 (2):0.43 (2). In the major component, the essentially planar [maximum deviation 0.033 (17) Å] fused pyrimidine and triazole ring system forms a dihedral angle of 10.5 (3)° with the phenyl ring, while in the minor component of disorder this angle is 27.5 (5)°. The crystal structure is stabilized by π–π stacking inter­actions between symmetry-related triazole and pyrimidine rings, with centroid–centroid distances of 3.594 (10) Å

6-Butyl-5-(4-methyl­phen­oxy)-3-phenyl-3H-1,2,3-triazolo[4,5-d]pyrimidin-7(6H)-one

In the title compound, C21H21N5O2, the triazolopyrimidine ring system is essentially planar [maximum displacement = 0.021 (4) Å] and forms dihedral angles of 41.17 (9) and 67.99 (8)° with the phenyl and benzene rings, respectively. The n-butyl side chains is disordered over two positions with an ccupancy ratio of 0.77:0.23. An intra­molecular C—H⋯O hydrogen-bonding inter­action stabilizes the mol­ecular conformation. In the crystal, mol­ecules are linked by inter­molecular C—H⋯O and C—H⋯N hydrogen bonds into a three-dimensional network. In addition, π–π stacking inter­actions involving the triazole and pyrimidine rings of adjacent mol­ecules are observed, with centroid–centroid distances of 3.545 (1) Å

Chloridobis(1,10-phenanthroline-κ2 N,N′)copper(II) tetra­kis­(nitrato-κ2 O,O′)(1,10-phenanthroline-κ2 N,N′)terbate(III)

The title complex salt, [CuCl(C12H8N2)2][Tb(NO3)4(C12H8N2)], consists of discrete [CuCl(phen))2]+ cations and [Tb(NO3)4(phen)]− anions (phen is 1,10-phenanthroline). The [CuCl(phen))2]+ cation contains a five-coordinate Cu2+ ion, ligated by two bidentate phen ligands and one Cl− ion, exhibiting a distorted CuN4Cl trigonal–bipyramidal geometry. In the [Tb(NO3)4(phen)]− anion, the Tb3+ ion is coordinated by one chelating phen ligand and four chelating nitrates, forming a distorted TbN2O8 bicapped dodeca­hedral configuration. The anions and cations are assembled into a three-dimensional network by weak C—H⋯Cl and C—H⋯O hydrogen bonds. There is also a significant π–π stacking inter­action, with a centroid–centroid distance of 3.635 (2) Å

Superresolution Reconstruction of Single Image for Latent features

In recent years, Deep Learning has shown good results in the Single Image Superresolution Reconstruction (SISR) task, thus becoming the most widely used methods in this field. The SISR task is a typical task to solve an uncertainty problem. Therefore, it is often challenging to meet the requirements of High-quality sampling, fast Sampling, and diversity of details and texture after Sampling simultaneously in a SISR task.It leads to model collapse, lack of details and texture features after Sampling, and too long Sampling time in High Resolution (HR) image reconstruction methods. This paper proposes a Diffusion Probability model for Latent features (LDDPM) to solve these problems. Firstly, a Conditional Encoder is designed to effectively encode Low-Resolution (LR) images, thereby reducing the solution space of reconstructed images to improve the performance of reconstructed images. Then, the Normalized Flow and Multi-modal adversarial training are used to model the denoising distribution with complex Multi-modal distribution so that the Generative Modeling ability of the model can be improved with a small number of Sampling steps. Experimental results on mainstream datasets demonstrate that our proposed model reconstructs more realistic HR images and obtains better PSNR and SSIM performance compared to existing SISR tasks, thus providing a new idea for SISR tasks

Ethyl (2,5-dioxo-1-phenyl-2,3-dihydro-1H,5H-1-benzofuro[3,2-d]imidazo[1,2-a]pyrimidin-3-yl)acetate

In the title compound, C22H17N3O5, synthesized via the aza-Wittig reaction of ethyl 3-(phenyl­imino­methyl­ene­amino)­benzofuran-2-carboxyl­ate, benzene isocyanate and diethyl 2-amino­succinate, the imidazo[1,2-a]benzo[4,5]furo[2,3-d]pyrim­idine ring system is essentially planar (r.m.s. deviation for all 16 non-H atoms = 0.020 Å). The phenyl ring is twisted with respect to this ring system, making a dihedral angle of 54.23 (4)°. The crystal packing is stabilized by weak inter­molecular C—H⋯O inter­actions

Carotid and cerebrovascular disease in symptomatic patients with type 2 diabetes: assessment of prevalence and plaque morphology by dual-source computed tomography angiography

<p>Abstract</p> <p>Background</p> <p>Plaque morphology directly correlates with risk of embolism and the recently developed dual-source computed tomography angiography (DSCTA) may help to detect plaques more precisely. The aim of our study was to evaluate the prevalence and morphology of carotid and cerebrovascular atherosclerotic plaques in patients with symptomatic type 2 diabetes mellitus (DM) by DSCTA.</p> <p>Methods</p> <p>From July 2009 to August 2010, DSCTA was prospectively performed in 125 consecutive patients with symptomatic type 2 DM. We retrospectively analyzed plaque type, distribution, and extensive and obstructive natures were determined for each segment for all patients.</p> <p>Results</p> <p>Atherosclerotic plaques were detected in 114 (91.2%) patients. Relatively more noncalcified (45%) and calcified (39%) plaques and less mixed (16%) plaques were observed (p < 0.001). Noncalcified plaques were found mainly in the intracranial arteries (81.8%), mixed plaques in the intracranial arteries (25.2%) and intracranial internal carotid artery (ICA) (56.1%). Calcified plaques were found mainly in the intracranial ICA (65.9%) and extracranial arteries (28.2%) (for all, p < 0.001). Extension of plaques from the 1^stto 5^thsegments was observed in 67 (58.8%) patients and from the 6^thto 10^thsegments in 35 (30.7%) patients. The most common site of all detected plaques was the cavernous segment. Regarding stenosis, there were significantly more nonobstructive than obstructive stenosis (91% vs. 9%, p < 0.001).</p> <p>Conclusion</p> <p>DSCTA detected a high prevalence of plaques in patients with symptomatic type 2 DM. A relatively high proportion of plaques were noncalcified, as well as with nonobstructive stenosis. The distribution of plaques was extensive, with the cavernous portion of ICA being the most common site.</p