Reconnection Electric Field and Hardness of X-Ray Emission of Solar Flares

Magnetic reconnection is believed to be the prime mechanism to trigger solar flares and accelerate electrons up to energies of MeV. In the classical two-dimensional reconnection model, the separation motion of chromospheric ribbons manifests the successive reconnection that takes place higher up in the corona. Meanwhile, downward traveling energetic electrons bombard the dense chromosphere and create hard X-ray (HXR) emissions, which provide a valuable diagnostic of electron acceleration. Analyses of ribbon dynamics and HXR spectrum have been carried out separately. In this Letter, we report a study of the comparison of reconnection electric field measured from ribbon motion and hardness (spectral index) of X-ray emission derived from X-ray spectrum. Our survey of the maximum average reconnection electric field and the minimum overall spectral index for 13 two-ribbon flares show that they are strongly anti-correlated. The former is also strongly correlated with flare magnitude measured using the peak flux of soft X-ray emissions. These provide strong support for electron acceleration models based on the electric field generated at reconnecting current sheet during flares.Comment: 5 pages, 2 figures. Accepted to Astrophysical Journal Letters 2009 Mar 2

A New Method for Figuring the Number of Hidden Layer Nodes in BP Algorithm

In the field of artificial neural network, BP neural network is a multi-layer feed-forward neural network. Because it is difficult to figure the number of hidden layer nodes in a BP neural network, the theoretical basis and the existing methods for BP network hidden layer nodes are studied. Then based on traditional empirical formulas, we propose a new approach to rapidly figure the quantity of hidden layer nodes in two-layer network. That is, with the assistance of experience formulas, the horizon of unit number in hidden layer can be confirmed and its optimal value will be found in this horizon. Finally, a new formula for figuring the quantity of hidden layer codes is obtained through fitting input dimension, output dimension and the optimal value of hidden layer codes. Under some given input dimension and output dimension, efficiency and precision of BP algorithm may be improved by applying the proposed formula

Optimization of 3D ZnO brush-like nanorods for dye-sensitized solar cells

© 2018 The Royal Society of Chemistry This is an Open Access article, distributed under the terms of the Creative Commons Attribution Unported 3.0 license (CC BY 3.0), https://creativecommons.org/licenses/by/3.0/ which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly citedIn a dye-sensitized solar cell (DSSC) the amount of adsorbed dye on the photoanode surface is a key factor that must be maximized in order to obtain enhanced DSSC performance. In this study 3D ZnO nanostructures, named brush-like, are demonstrated as alternative photoanodes. In these structures, long ZnO nanorods are covered with a metal-organic precursor, known as a layered-hydroxide zinc salt (LHZS), which is subsequently converted to crystalline ZnO using two-step annealing. The LHZS is able to easily grow on any surface, such as the ZnO nanorod surface, without needing the assistance of a seed-layer. Brush-like structures synthesized using different citrate concentrations in the growth solutions and different annealing conditions are characterized and tested as DSSC photoanodes. The best-performing structure reported in this study was obtained using the highest citrate concentration (1.808 mM) and the lowest temperature annealing condition in an oxidative environment. Conversion efficiency as high as 1.95% was obtained when these brush-like structures were employed as DSSC photoanodes. These results are extremely promising for the implementation of these innovative structures in enhanced DSSCs, as well as in other applications that require the maximization of surface area exposed by ZnO or similar semiconductors, such as gas- or bio-sensing or photocatalysis.Peer reviewedFinal Published versio

Mutational Analysis of GATA4 and NKX2.5 Genes in Dilated Cardiomyopathy Patients

Purpose: To evaluate the lipid profile abnormalities and association of the GATA4 (1232 C→T) and NKX 2.5 (73C→T) gene polymorphisms with Dilated cardiomyopathy (DCM) among Chinese population.Methods: The blood samples were collected from the Outpatient Department (OPD) of Cardiology Unit, Zhengzhou Central Hospital, China for a period of three years from 2010 – 2013. Dilated cardiomyopathy cases (n = 270) and healthy controls (n = 290) were genotyped using polymerase chain reaction (PCR), restriction fragment length polymorphism, (RFLP) denaturing high-performance liquid chromatography (DHPLC) and sequencing.Results: Evaluation of the age and sex of the patients indicated that DCM was more prevalent among males (71.1 %) than in females (28.9 %). Mean (± SD) values of the serum total cholesterol and serum LDL-cholesterol were higher in DCM patients (4.37 ± 0.16 and 3.19 ± 0.14 mmol/L, respectively) compared to the control group (4.29 ± 0.18 and 3.06 ± 0.19 mmol/L, respectively), while as there was significantly lower serum mean (± SEM) HDL-cholesterol levels in patients with DCM than in controls (p < 0.001). Exon 1 region of NKX 2.5 gene was screened for variations at 73C→T keeping in view both parameters (age and sex) among healthy controls and DCM patients. The results indicate that the homozygous mutant (TT) and heterozygous mutant (CT) nucleotides were significantly higher in DCM patients than in controls. Further analysis of GATA4 gene revealed that five DCM patients had 1232C/T variant, whereas, it was absent in the control group.Conclusion: GATA4 1232C/T and NKX 2.5 73C→T polymorphisms and high levels of serum triglycerides (TG) may be associated with the pathogenesis of DCM in the studied populationKeywords: Dilated cardiomyopathy, Congestive heart failure, Polymerase chain reaction, Restrictionfragment length polymorphism, Denaturing high-performance liquid chromatograph

On the Momentum Dependence of the Flavor Structure of the Nucleon Sea

Difference between the $\bar u$ and $\bar d$ sea quark distributions in the proton was first observed in the violation of the Gottfried sum rule in deep-inelastic scattering (DIS) experiments. The parton momentum fraction $x$ dependence of this difference has been measured over the region $0.02 < x < 0.35$ from Drell-Yan and semi-inclusive DIS experiments. The Drell-Yan data suggested a possible sign-change for $\bar d(x)-\bar u(x)$ near $x \sim 0.3$, which has not yet been explained by existing theoretical models. We present an independent evidence for the $\bar d(x)-\bar u(x)$ sign-change at $x \sim 0.3$ from an analysis of the DIS data. We further discuss the $x$-dependence of $\bar d(x)-\bar u(x)$ in the context of meson cloud model and the lattice QCD formulation.Comment: 5 pages, 5 figures, final versio

Circular Ribbon Flares and Homologous Jets

Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), which has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a circular ribbon have rarely been reported, although it is expected in the fan--spine magnetic topology involving reconnection at a three-dimensional (3D) coronal null point. We present five circular ribbon flares with associated surges, using high-resolution and high-cadence halpha blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory. In all the events, a central parasitic magnetic field is encompassed by the opposite polarity, forming a circular PIL traced by filament material. Consequently, a flare kernel at the center is surrounded by a circular flare ribbon. The four homologous jet-related flares on 1991 March 17 and 18 are of particular interest, as (1) the circular ribbons brighten sequentially, with co-spatial surges, rather than simultaneously, (2) the central flare kernels show an intriguing "round-trip" motion and become elongated, and (3) remote brightenings occur at a region with the same magnetic polarity as the central parasitic field and are co-temporal with a separate phase of flare emissions. In another flare on 1991 February 25, the circular flare emission and surge activity occur successively, and the event could be associated with magnetic flux cancellation across the circular PIL. We discuss the implications of these observations combining circular flare ribbons, homologous jets, and remote brightenings for understanding the dynamics of 3D magnetic restructuring.Comment: Ap.J., accepte

Effective Dynamic Range in Measurements with Flash Analog-to-Digital Convertor

Flash Analog to Digital Convertor (FADC) is frequently used in nuclear and particle physics experiments, often as the major component in big multi-channel systems. The large data volume makes the optimization of operating parameters necessary. This article reports a study of a method to extend the dynamic range of an 8-bit FADC from the nominal $\rm{2^8}$ value. By comparing the integrated pulse area with that of a reference profile, good energy reconstruction and event identification can be achieved on saturated events from CsI(Tl) crystal scintillators. The effective dynamic range can be extended by at least 4 more bits. The algorithm is generic and is expected to be applicable to other detector systems with FADC readout.Comment: 19 pages, 1 table, 10 figure

2-Isopropyl-5-methyl­cyclo­hexyl N-cyclo­hexyl-P-phenyl­phospho­namidate

The title compound, C22H36NO2P, features a P atom bonded to a phenyl ring, a cyclo­hexyl­amine unit and the O atom of a menthyl group. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds connect mol­ecules into a one-dimensional chain in the b direction