Searching Signals in Chinese Ancient Records for the 14^{14}C Increases in AD 774-775 and in AD 992-993

According to the analysis of the $^{14}$C content of two Japanese trees over a period of approximately 3000 years at high time resolution, Miyake (2012) found a rapid increase at AD 774-775 and later on at AD 992-993 (Miyake 2013). This corresponds to a high-energy event happened within one year that input $\gamma$-ray energy about 7$\times{}$10$^{24}$erg to the Earth, leaving the origin a mystery. Such strong event should have an unusual optical counterpart, and have been recorded in historical literature. We searched Chinese historical materials around AD 744-775 and AD 992-993, but no remarkable event was found except a violent thunderstorm in AD 775. However, the possibility of a thunderstorm containing so much energy is still unlikely. We conclude the event caused the $^{14}$C increase is still unclear. This event most probably has no optical counterpart, and short gamma-ray burst, giant flare of a soft gamma-ray repeater and terrestrial $\gamma$-ray flash may all be the candidates.Comment: 8 pages, 3 figure

Auditor type, firm ownership and auditor reporting under a joint audit requirement : exploratory evidence from India

India is one of the largest developing countries in the world. Although many issues and phenomena arising from its transitional economy are worthy of research from an accounting perspective, the Indian accounting market is a field that remains relatively unexplored in the extant literature. One of the institutional features of India is that while it is mandatory for public sector companies and banks to have joint auditors, their appointment is voluntary for other companies. In a thesis motivated by this and other institutional features and the absence of related accounting and auditing studies conducted in an Indian setting, I examine the relations of auditor type and firm ownership with the types of auditor opinions issued under the joint audit requirement. Using a sample of 1,142 firm-year observations from the major Indian stock exchanges from 2006-2008, I develop an auditor opinion model to examine the relations between firm ownership, auditor type and auditor opinions under the joint-audit requirement that applies in India. Companies’ self-selection bias for auditors is also considered and corrected using the Heckman 2-step method. Based on the empirical results, I report as follows. First, Big 4 auditors are more likely to issue modified opinions than local Indian auditors. Second, the Indian government assumes a supervisory role rather than a collusive role and the joint-audit requirement is associated with a higher level of auditor reporting quality. Finally, companies audited by joint auditors are more likely to receive modified opinions than companies audited by a single auditor. The findings provide evidence of the importance of understanding the pattern of auditor opinion in India and the incentives of joint auditors, as well as the influence this pattern has on auditor reporting quality in a transitional economy

Constraining the Mass of the Photon with Gamma-Ray Bursts

One of the cornerstones of modern physics is Einstein's special relativity, with its constant speed of light and zero photon mass assumptions. Constraint on the rest mass m_{\gamma} of photons is a fundamental way to test Einstein's theory, as well as other essential electromagnetic and particle theories. Since non-zero photon mass can give rise to frequency-(or energy-) dependent dispersions, measuring the time delay of photons with different frequencies emitted from explosive astrophysical events is an important and model-independent method to put such a constraint. The cosmological gamma-ray bursts (GRBs), with short time scales, high redshifts as well as broadband prompt and afterglow emissions, provide an ideal testbed for m_{\gamma} constraints. In this paper we calculate the upper limits of the photon mass with GRB early time radio afterglow observations as well as multi-band radio peaks, thus improve the results of Schaefer (1999) by nearly half an order of magnitude.Comment: 25 pages, 2 tables, Accepted by Journal of High Energy Astrophysic

On the development of computer network management technology in the new era

with the development of science and technology in China, network technology has been used in various fi elds of society, and plays an important role. With the development of the times, it has gradually become an important part of people’s life and production process. However, in the new era, there are still many problems that are diffi cult to solve in the process of computer network management in China. In view of this, this paper analyzes the development of computer network management technology in the new era in detail, hoping to provide some valuable references for teachers and friends

Controlled Levofloxacin Release and Antibacterial Properties of β-Cyclodextrins-Grafted Polypropylene Mesh Devices for Hernia Repair.

Mesh infection is a major complication of hernia repair. After knitted mesh implantation, bacteria can grow within textile structures causing infection. In this work, polypropylene (PP) mesh devices were two-step grafted with hexamethylene diisocyanate (HDI) and β⁻cyclodexrins (CD) and then loaded with suitable antimicrobial levofloxacin HCL for hernia mesh-infection prevention. First, oxygen plasma was able to create surface roughness, then HDI was successfully grafted onto PP fiber surfaces. Afterwards, CD was covalently grafted onto the HDI treated PP meshes, and levofloxacin HCL (LVFX) was loaded into the CD cavity of the modified meshes. The modified devices were evaluated for sustained antibiotic properties and drug-release profiles in a phosphate buffer, and sustained drug release was observed between interfaces of meshes and aqueous environment. The antibiotic-loaded PP mesh samples demonstrated sustained antibacterial properties for 7 and 10 days, respectively, against both Gram-negative and Gram-positive bacteria. The CD-captured levofloxacin HCL showed burst release after 6 h but later exhibited sustained release for the next 48 h. Among all samples, the modified mesh LVFX-6 was more stable and showed more sustained drug release and could be employed in future clinical applications

A novel process for nutrients removal and phosphorus recovery from domestic wastewater by combining BNR with induced crystallization

An excessive discharge of phosphorus from wastewater to water bodies may potentially contribute to eutrophication. On the other hand, mineral phosphorus resources will be depleted in the near future, because of difficulty to automatically recycle from water to land, unlike nitrogen. A new process for nutrients removal coupled with phosphorus recovery was proposed in this study by combining biological nutrients removal (BNR) with induced crystallization (IC), BNR-IC for short later, differently from conventional phosphorus recovery process. Our results showed that the BNR-IC system can maintain not only high and stable carbon, nitrogen and phosphorus removal efficiencies, all presenting above 90%, but also good phosphorus recovery performance from synthetic domestic wastewater, displaying about 70.2% of phosphorus recovery rate. When the COD, TN, NH4–N and P concentrations of 250 mg L−1, 42 mg L−1, 40 mg L−1, and 10 mg L−1, respectively were given in the influent, a stable removal efficiencies of 92.5% COD, 78.6% TN, 85.9% NH4–N and 95.2% P were obtained for the BNR-IC process and correspondingly the COD, TN, NH4–N and P concentrations of 18.75 mg L−1, 8.99 mg L−1, 5.64 mg L−1, 0.42 mg L−1 were monitored in the effluent, meeting the Chinese National Class I (grade A) Sewage Discharge Standard. Analyses of SEM and EDS, moreover, also demonstrated that the surface of seed crystal (calcite used here) was completely covered by hydroxyl calcium phosphate (HAP) produced during the induced crystallization process to recover phosphorus. Although our study involved only a small-scale trial, the proposed BNR-IC process here may be a promising technology, and can potentially aid in improvement of the effluent quality from WWTP and in recycle of mineral phosphorus resources when applied to practice

Teaching reform of computer network security course in Colleges and Universities

Under the background of the rapid development of information technology, the application scope of e-commerce has been continuously improved, which also improves the application degree of computer. In order to conform to the characteristics of the development of the times, colleges and universities should strengthen the personnel training work, and cultivate students with strong quality and ability, and master systematic and comprehensive computer network knowledge in the new era. Therefore, teachers need to teach students the basic concepts, theories and technical methods of network security knowledge to ensure that they meet the characteristics and requirements of higher education. Based on this, this paper analyzes and studies the teaching reform of computer network security course in Colleges and universities, expounds the necessity of teaching reform of computer network security course in Colleges and universities, analyzes the characteristics of computer network security classroom in Colleges and universities, and puts forward the teaching reform strategies of computer network security course in colleges and universities on this basis, for reference