5,573 research outputs found
catena-Poly[[[aqua(1,10-phenanthroline-κ2 N,N′)cadmium(II)]-μ-pyridine-2,3-dicarboxylato-κ4 N,O 2:O 3,O 3′] dihydrate]
The title complex, {[Cd(C7H3NO4)(C12H8N2)(H2O)]·2H2O}n, is a one-dimensional coordination polymer, wherein the Cd atom is seven-coordinated by two 1,10-phenanthroline N atoms, one N and three O atoms from two different pyridine-2,3-dicarboxylate ligands, and one water molecule. It is further extended to a two-dimensional layer structure by hydrogen bonds and π–π stacking interactions [centroid-centroid distances of 3.560 (2) and 3.666 (2) Å]. There is a C4 water chain in the structure whose repeat unit contains four water molecules with O⋯O distances in the range 2.748 (3)–2.795 (4) Å. One of the two H atoms of each water of hydration is statistically distributed over two positions with equal occupancy
Genetic and clinical features of hemoglobin H disease in Chinese patients
Background. Normally, one pair of each of the two α-globin genes, α1 and α2, resides on each copy of chromosome 16. In hemoglobin H disease, three of these four α-globin genes are affected by a deletion, a mutation, or both. We studied the α-globin gene abnormalities and the clinical and hematologic features of Chinese patients with hemoglobin H disease in Hong Kong. Methods. We assessed the clinical features, hematologic values, serum ferritin levels, and liver function of 114 patients with hemoglobin H disease. We also performed echocardiography and magnetic resonance imaging of the liver and examined the two pairs of α-globin genes. Results. Hemoglobin H disease in 87 of the 114 patients (76 percent) was due to the deletion of three of the four α-globin genes (--/-α), a combination termed the deletional type of hemoglobin H. The remaining 27 patients (24 percent) had the nondeletional type of hemoglobin H disease, in which two α-globin genes are deleted and a third is mutated (--/αα(T)). All 87 patients with the deletional type of hemoglobin H were double heterozygotes in whom there was a deletion of both α-globin genes from one chromosome, plus a deletion of the α1 or α2 gene from the other chromosome (--/α- or --/-α). A variety of mutated α-globin genes was found in the patients with nondeletional type of hemoglobin H disease. Patients with the nondeletional type of the H disease had more symptoms at a younger age, more severe hemolytic anemia, and larger spleens and were more likely to require transfusions than patients with deletional hemoglobin H disease. The severity of iron overload was not related to the genotype. Conclusions. Chinese patients in Hong Kong with the nondeletional type of hemoglobin H disease have more severe disease than those with the deletional type of the disease. Iron overload is a major cause of disability in both forms of the disease. (C) 2000, Massachusetts Medical Society.published_or_final_versio
Hydroxonium 1-ammonioethane-1,1-diyldiphosphonate
The title complex, H3O+·NH3C(CH3)(PO3H)2
−, contains a hydroxonium ion and an NH3C(CH3)(PO3H)2
− anion. The three H atoms of H3O+ form a pseudo-tetrahedron by being distributed over four positions with occupation factors of 0.75. Multiple N—H⋯O and O—H⋯O hydrogen bonds in the crystal structure form an intricate three-dimensional supramolecular network
Singular Cucker-Smale Dynamics
The existing state of the art for singular models of flocking is overviewed,
starting from microscopic model of Cucker and Smale with singular communication
weight, through its mesoscopic mean-filed limit, up to the corresponding
macroscopic regime. For the microscopic Cucker-Smale (CS) model, the
collision-avoidance phenomenon is discussed, also in the presence of bonding
forces and the decentralized control. For the kinetic mean-field model, the
existence of global-in-time measure-valued solutions, with a special emphasis
on a weak atomic uniqueness of solutions is sketched. Ultimately, for the
macroscopic singular model, the summary of the existence results for the
Euler-type alignment system is provided, including existence of strong
solutions on one-dimensional torus, and the extension of this result to higher
dimensions upon restriction on the smallness of initial data. Additionally, the
pressureless Navier-Stokes-type system corresponding to particular choice of
alignment kernel is presented, and compared - analytically and numerically - to
the porous medium equation
Atomically dispersed Pt-N-4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction
Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt-N-4 sites doped on a carbon nanotube (Pt-1/CNT) can catalyse the CER with excellent activity and selectivity. The Pt-1/CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt-1/CNT exhibits near 100% CER selectivity even in acidic media, with low Cl- concentrations (0.1M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl- on Pt-N-4 sites during the CER. Density functional theory calculations suggest the PtN4C12 site as the most plausible active site structure for the CER
Structural and Biochemical Bases for the Inhibition of Autophagy and Apoptosis by Viral BCL-2 of Murine γ-Herpesvirus 68
All gammaherpesviruses express homologues of antiapoptotic B-cell lymphoma-2 (BCL-2) to counter the clearance of infected cells by host antiviral defense machineries. To gain insights into the action mechanisms of these viral BCL-2 proteins, we carried out structural and biochemical analyses on the interactions of M11, a viral BCL-2 of murine γ-herpesvirus 68, with a fragment of proautophagic Beclin1 and BCL-2 homology 3 (BH3) domain-containing peptides derived from an array of proapoptotic BCL-2 family proteins. Mainly through hydrophobic interactions, M11 bound the BH3-like domain of Beclin1 with a dissociation constant of 40 nanomole, a markedly tighter affinity compared to the 1.7 micromolar binding affinity between cellular BCL-2 and Beclin1. Consistently, M11 inhibited autophagy more efficiently than BCL-2 in NIH3T3 cells. M11 also interacted tightly with a BH3 domain peptide of BAK and those of the upstream BH3-only proteins BIM, BID, BMF, PUMA, and Noxa, but weakly with that of BAX. These results collectively suggest that M11 potently inhibits Beclin1 in addition to broadly neutralizing the proapoptotic BCL-2 family in a similar but distinctive way from cellular BCL-2, and that the Beclin1-mediated autophagy may be a main target of the virus
Response Surface Methodology to Optimize Enzymatic Preparation of Deapio-Platycodin D and Platycodin D from Radix Platycodi
In the present work, we reported the enzymatic preparation of deapio-platycodin D (dPD) and platycodin D (PD) optimized by response surface methodology (RSM) from Radix Platycodi. During investigation of the hydrolysis of crude platycosides by various glycoside hydrolases, snailase showed a strong ability to transform deapio-platycoside E (dPE) and platycoside E (PE) into dPD and PD with 100% conversion. RSM was used to optimize the effects of the reaction temperature (35–45 °C), enzyme load (5–20%), and reaction time (4–24 h) on the conversion process. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of dPD and PD conversion yield. The optimum preparation conditions were as follows: temperature, 43 °C; enzyme load, 15%; reaction time, 22 h. The biotransformation pathways were dPE→dPD3→dPD and PE→PD3→PD, respectively. The determined method may be highly applicable for the enzymatic preparation of dPD and PD for medicinal purposes and also for commercial use
The Kondo effect in ferromagnetic atomic contacts
Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk,
electronic conduction in these materials takes place mainly through the and
electrons, whereas the magnetic moments are mostly in the narrow
-electron bands, where they tend to align. This general picture may change
at the nanoscale because electrons at the surfaces of materials experience
interactions that differ from those in the bulk. Here we show direct evidence
for such changes: electronic transport in atomic-scale contacts of pure
ferromagnets (iron, cobalt and nickel), despite their strong bulk
ferromagnetism, unexpectedly reveal Kondo physics, that is, the screening of
local magnetic moments by the conduction electrons below a characteristic
temperature. The Kondo effect creates a sharp resonance at the Fermi energy,
affecting the electrical properties of the system;this appears as a Fano-Kondo
resonance in the conductance characteristics as observed in other artificial
nanostructures. The study of hundreds of contacts shows material-dependent
lognormal distributions of the resonance width that arise naturally from Kondo
theory. These resonances broaden and disappear with increasing temperature,
also as in standard Kondo systems. Our observations, supported by calculations,
imply that coordination changes can significantly modify magnetism at the
nanoscale. Therefore, in addition to standard micromagnetic physics, strong
electronic correlations along with atomic-scale geometry need to be considered
when investigating the magnetic properties of magnetic nanostructures.Comment: 7 pages, 5 figure
Control of LED Emission with Functional Dielectric Metasurfaces
The improvement of light-emitting diodes (LEDs) is one of the major goals of
optoelectronics and photonics research. While emission rate enhancement is
certainly one of the targets, in this regard, for LED integration to complex
photonic devices, one would require to have, additionally, precise control of
the wavefront of the emitted light. Metasurfaces are spatial arrangements of
engineered scatters that may enable this light manipulation capability with
unprecedented resolution. Most of these devices, however, are only able to
function properly under irradiation of light with a large spatial coherence,
typically normally incident lasers. LEDs, on the other hand, have angularly
broad, Lambertian-like emission patterns characterized by a low spatial
coherence, which makes the integration of metasurface devices on LED
architectures extremely challenging. A novel concept for metasurface
integration on LED is proposed, using a cavity to increase the LED spatial
coherence through an angular collimation. Due to the resonant character of the
cavity, extending the spatial coherence of the emitted light does not come at
the price of any reduction in the total emitted power. The experimental
demonstration of the proposed concept is implemented on a GaP LED architecture
including a hybrid metallic-Bragg cavity. By integrating a silicon metasurface
on top we demonstrate two different functionalities of these compact devices:
directional LED emission at a desired angle and LED emission of a vortex beam
with an orbital angular momentum. The presented concept is general, being
applicable to other incoherent light sources and enabling metasurfaces designed
for plane waves to work with incoherent light emitters.Comment: 29 pages, 6 figure
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