Synchrotron radiation from the Crab Nebula discriminates between models of space–time foam

It has been argued by Jacobson, Liberati and Mattingly that synchrotron radiation from the Crab Nebula imposes a stringent constraint on any modification of the dispersion relations of the electron that might be induced by quantum gravity. We supplement their analysis by deriving the spectrum of synchrotron radiation from the coupling of an electrically charged particle to an external magnetic fields in the presence of quantum-gravity effects of the general form (E/M_QG). We find that the synchrotron constraint from the Crab Nebula practically excludes 1.74 for M_QGm_P=1.2×10¹⁹ GeV. On the other hand, this analysis does not constrain any modification of the dispersion relation of the photon that might be induced by quantum gravity. We point out that such quantum-gravity effects need not obey the equivalence principle, a point exemplified by the Liouville-string D-particle model of space–time foam. This model suggests a linear modification of the dispersion relation for the photon, but not for the electron, and hence is compatible with known constraints from the Crab Nebula and elsewhere.     

The Hybrid Nature of 0846＋51W1： a BL Lac Object with a Narrow Line Seyfert 1 Nucleus

We found a NLS1 nucleus in the extensively studied eruptive BL Lac object, 0846+51W1, out of a large sample of NLS1s compiled from the spectroscopic dataset of SDSS DR1. Its optical spectrum can be well decomposed into three components: a power law component from the relativistic jet, a stellar component from the host galaxy, and a component from a typical NLS1 nucleus. The emission line properties of 0846+51W1, FWHM     

Absorption of nuclear γ-rays on the starlight radiation in FR I sources: the case of Centaurus A

Several BL Lac objects are confirmed sources of variable and strongly Doppler-boosted TeV emission produced in the nuclear portions of their relativistic jets. It is more than probable that also many of the Fanaroff–Riley type I (FR I) radio galaxies, believed to be the parent population of BL Lacs, are TeV sources, for which Doppler-hidden nuclear γ-ray radiation may be only too weak to be directly observed. Here we show, however, that about 1 per cent of the total time-averaged TeV radiation produced by the active nuclei of low-power FR I radio sources is inevitably absorbed and re-processed by photon–photon annihilation on the starlight photon field, and the following emission of the created and quickly isotropized electron–positron pairs. In the case of the radio galaxy Centaurus A, we found that the discussed mechanism can give a distinctive observable feature in the form of an isotropic γ-ray halo. It results from the electron–positron pairs injected to the interstellar medium of the inner parts of the elliptical host by the absorption process, and upscattering starlight radiation via the inverse-Compton process mainly to the GeV–TeV photon energy range. Such a galactic γ-ray halo is expected to possess a characteristic spectrum peaking at ∼0.1 TeV photon energies, and the photon flux strong enough to be detected by modern Cherenkov Telescopes and, in the future, by GLAST. These findings should apply as well to the other nearby FR I sources.     

Estimation of net accumulation rate at a Patagonian glacier by ice core analyses using snow algae

Snow algae in a 45.97-m-long ice core from the Tyndall Glacier (50°59′05″S, 73°31′12″W, 1756 m a.s.l.) in the Southern Patagonian Icefield were examined for potential use in ice core dating and estimation of the net accumulation rate. The core was subjected to visual stratigraphic observation and bulk density measurements in the field, and later to analyses of snow algal biomass, water isotopes (¹⁸O, D), and major dissolved ions. The ice core contained many algal cells that belonged to two species of snow algae growing in the snow near the surface: Chloromonas sp. and an unknown green algal species. Algal biomass and major dissolved ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, SO₄²⁻) exhibited rapid decreases in the upper 3 m, probably owing to melt water elution and/or decomposition of algal cells. However, seasonal cycles were still found for the snow algal biomass, ¹⁸O, D-excess, and major ions, although the amplitudes of the cycles decreased with depth. Supposing that the layers with almost no snow algae were the winter layers without the melt water essential to algal growth, we estimated that the net accumulation rate at this location was 12.9 m a^− 1 from winter 1998 to winter 1999, and 5.1 m from the beginning of winter to December 1999. These estimates are similar to the values estimated from the peaks of ¹⁸O (17.8 m a^− 1 from summer 1998 to summer 1999 and 11.0 m from summer to December 1999) and those of D-excess (14.7 m a^− 1 from fall 1998 to fall 1999 and 8.6 m a^− 1 from fall to December 1999). These values are much higher than those obtained by past ice core studies in Patagonia, but are of the same order of magnitude as those predicted from various observations at ablation areas of Patagonian glaciers.     

北京同步辐射装置准直测量控制网的设计与优化

在北京同步辐射装置升级改造中,为提高元件的安装精度,同时兼顾未来新增光束线的建设需要,在实验大厅建立了准直测量控制网,作为设备定位、调校、安装和变形监测等工作的基础。本文重点介绍该控制网的设计、优化与观测结果分析,特别阐述了激光精密测量技术的应用,以及对点位密度、测量精度及可靠性的控制。     

顾及多尺度分割参数的FNEA面向对象分类

首先对分形网络演化（FNEA）算法做了介绍,通过试验对比4种分割方法棋盘分割、四叉树分割、多尺度分割、光谱差异分割的效果。此外,通过eCognition Developer 8.7分析软件对影像进行多尺度分割预处理,从5开始,以5为单位向上递增,共选取12组参数进行分割试验,采用面向对象CART分类器对分割后影像分类。对比分类效果图可知,小尺度分割参数对分类效果能有较好的提升;对比总体精度及Kappa系数可知,小尺度分割参数分类精度优于大尺度分割参数,且当分割参数Scale为10时,分类精度达到最好的级别。     

基于热流固耦合的增强型地热有机朗肯循环发电系统性能分析

本文建立了耦合井筒、热储、有机朗肯循环发电系统的详细数学模型, 包括三维非稳态热流固耦合模型和有机朗肯循环发电系统热动力学模型, 参考青海省共和县恰卜恰干热岩体地热地质特征, 包括压裂储层、围岩、裂隙、井筒等特征参数, 研究了注入流量、注入温度和井间距对系统净输出功、年均净输出功和热效率的影响规律。结果表明: 在一定的注入流量、注入温度和净间距下, 随着时间的推移, 岩石孔隙压力和热应力作用使得裂隙渗透率增大, 注入泵功耗是降低的, 净输出功和热效率也是降低的。注入流量的增大提高了膨胀机轴功、注入泵功耗和生产温度衰减速率, 进而导致热效率降低, 存在最优的注入流量50 kg/s, 使得年均净输出功达到最大值1 470.1 kW。注入温度的增大可以提高系统热效率, 降低净输出功的年均衰减速率, 当注入温度为60 ℃时, 年均净输出功最大。井间距的增大减缓了生产温度的衰减速率, 有利于热效率的提高, 但是也同时也增大了膨胀机轴功和注入泵功耗。当分支井间距为450 m时, 年均净输出功达到最大值1 497.3 kW。此研究可为增强地热发电系统的开发利用提供指导。     

随机Petri网在地震应急协同能力定量评价与动态分析中的应用

地震应急是一个复杂动态的过程,需要各部门协同配合方能高效开展应急工作。本文通过调研分析历史地震应急处置案例,提出了Ⅰ、Ⅱ级应急响应下多主体地震应急协同的一般流程,构建了相应的随机Petri网模型,并基于Petri网可能出现的状态集同构马尔科夫链,在计算各应急状态稳定概率的基础上,定量评价应急协同能力。同时,将应急过程中利用率高的变迁所对应的应急行为,作为应急处置的关键环节。通过调整各关键环节的应急速率,进一步对应急协同能力进行动态分析,进而提出有效提高应急协同联动能力的相关建议,为科学开展地震应急处置工作提供支持。     

Extinctions, Morphological Gaps, Major Transitions, Stem Groups, and the Origin of Major Clades, with a Focus on Early Animals

Systematic extinctions can leave major morphological gaps between living crown-group clades. Such morphological gaps would be perceived, from a neontological point of view, as major evolutionary transitions. In order to fill these morphological gaps and to map the evolutionary steps toward major evolutionary transitions, we need to integrate extinct stem-group taxa in phylogenetic studies. However, the recognition of stem group has not been widely adopted in the study of early animal fossils, despite that all fossils are stem groups at one level or another. Part of the difficulty is that stem groups may not have all features that collectively diagnose the respective crown group, and they can have unique (autapomorphic) features, making them tantalizingly similar to and frustratingly different from the crown group (e.g., stem-group eukaryotes can be prokaryotic and stem-group animals can be protistan). The need to embrace stem groups and to implement the PhyloCode, in order to achieve phylogenetic clarity and to offer key paleontological insights into the origin and early animal evolution, is illustrated in debates on several controversial Ediacaran and Cambrian fossils.     

Identification of Milankovitch Cycles and Calculation of Net Primary Productivity of Paleo-peatlands using Geophysical Logs of Coal Seams

Individual coal seams formed in paleo-peatlands represent sustained periods of terrestrial carbon accumulation and a key environmental indicator attributed to this record is the rate of carbon accumulation. Determining the rate of carbon accumulation requires a measure of time contained within the coal. This study aimed to determine this rate via the identification of Milankovitch orbital cycles in the coals. The geophysical log is an ideal paleoclimate proxy and has been widely used in the study of sedimentary records using spectral analysis. Spectral analyses of geophysical log from thick coal seams can be used to identify the Milankovitch cycles and to calculate the period of the coal deposition. By considering the carbon loss during coalification, the long-term average carbon accumulation rate and net primary productivity (NPP) of paleo-peatlands in coal seams can be obtained. This review paper presents the procedures of analysis, assessment of results and interpretation of geophysical logs in determining the NPP of paleo-peatlands.