Note on fault-slip motion inferred from a study of micro-cataclastic particles from an underground shear rupture

Mining of a highly-stressed remnant in a deep South African gold mine was accompanied by considerable seismic activity and some significant rockbursts. The larger seismic events were registered some 60 km away at a WSSN station and several shear ruptures corresponding to these events were encountered during mining operations.A careful study based on detailed exploration of two of these ruptures proved them to be the source of two of the larger rockbursts.Certain striking features revealed by a scanning electron microscopic study of some of the fresh cataclastic rock-flour forming part of the comminuted filling of these ruptures provide strong evidence of violent shock rebound phenomena in the faulting process. This interpretation could provide useful insight into earthquake source mechanisms and also has practical significance in the understanding of mine rockbursts.     

两种方法诱导太平洋牡蛎三倍体在生产上的应用效果

本文就太平洋牡蛎三倍体育苗中，常用的低温休克法和6－DMAP法进行了生产性试验比较。其结果为：在三倍体诱导率方面，低温休克的三倍体率低且不稳定，6－DMAP法诱导三倍体率高且稳定；在生长方面，低温休克法诱导的三倍体在养成期的生长和成活均差于6－DMAP法诱导的，三倍体率差异明显，但在幼虫期二者差异不显著。     

冲击波时差法原理及其应用

文章旨在解决某些水中兵器在运动中爆炸瞬时的空间位置的测定问题，提出了利用靶船布阵并通过测定冲击波掠过各阵元的时差确定瞬时炸点位置的方法。作者通过海上模拟动态爆炸试验验证了这种方法在工程上实现的有效性。     

利用咖啡因和热休克诱导太平洋牡蛎三倍体

报道采用咖啡因和热休克相结合的方法 ,抑制受精卵第二极体释放诱导太平洋牡蛎三倍体的优化方案。实验结果表明 ,三倍体诱导率随着咖啡因浓度的增高而增高 ,D形幼虫的孵化率却随着咖啡因浓度的增高而降低 ;所进行 30～ 36℃热休克温度试验 ,其对三倍体诱导率影响不大 ,但对孵化率影响明显。在 2 3～ 2 5℃条件下 ,当 50 %受精卵出现第一极体时 ,用浓度为 2 g/ L的咖啡因 ,结合 33℃± 1℃的热休克 ,处理牡蛎受精卵 15min,三倍体诱导率达 80 %以上 ,孵化率在 4 5%左右。通过此法诱导的三倍体群幼虫的成活与生长情况与其二倍体群体无明显差异。     

Perturbative analysis of two-temperature radiative shocks with multiple cooling processes

The structure of the hot downstream region below a radiative accretion shock, such as that of an accreting compact object, may oscillate because of a global thermal instability. The oscillatory behaviour depends on the functional forms of the cooling processes, the energy exchanges of electrons and ions in the shock-heated matter, and the boundary conditions. We analyse the stability of a shock with unequal electron and ion temperatures, where the cooling consists of thermal bremsstrahlung radiation which promotes instability, plus a competing process which tends to stabilize the shock. The effect of transverse perturbations is considered also. As an illustration, we study the special case in which the stabilizing cooling process is of order 3/20 in density and 5/2 in temperature, which is an approximation for the effects of cyclotron cooling in magnetic cataclysmic variables. We vary the efficiency of the second cooling process, the strength of the electron–ion exchange and the ratio of electron and ion pressures at the shock, to examine particular effects on the stability properties and frequencies of oscillation modes.     

Variability of the extreme z = 4.72 blazar, GB 1428+4217

On 1998 May 9–11, the highly variable, low-luminosity Seyfert 1 galaxy NGC 4051 was observed in an unusual low-flux state by BeppoSAX , RXTE and EUVE . We present fits of the 4–15 keV RXTE spectrum and BeppoSAX MECS spectrum obtained during this observation, which are consistent with the interpretation that the source had switched off, leaving only the spectrum of pure reflection from distant cold matter. We place this result in context by showing the X-ray light curve of NGC 4051 obtained by our RXTE monitoring campaign over the past two and a half years, which shows that the low state lasted for ∼150 d before the May observations (implying that the reflecting material is >10¹⁷ cm from the continuum source) and forms part of a light curve showing distinct variations in long-term average flux over time-scales > months. We show that the long-time-scale component to X-ray variability is intrinsic to the primary continuum and is probably distinct from the variability at shorter time-scales. The long-time-scale component to variability maybe associated with variations in the accretion flow of matter on to the central black hole . As the source approaches the low state, the variability process becomes non-linear. NGC 4051 may represent a microcosm of all X-ray variability in radio-quiet active galactic nuclei (AGNs), displaying in a few years a variety of flux states and variability properties which more luminous AGNs may pass through on time-scales of decades to thousands of years.     

Spiral patterns with straight arm segments

The phenomenon of 'rows', which are straight geometrical segments in the spiral arms of galaxies, is studied. The Whirlpool nebula, Messier 51 (NGC 5194) in Canes Venatici, is considered to be an example of a giant grand design galaxy. Optical photographs, H α , ultraviolet and far-ultraviolet images, CO, 21-cm and synchrotron emission maps, and a K _s-band mosaic of M51 are studied. With this observational material, multiple rows can be recognized in the spiral arms of the galaxy. The rows comprise a major part of the arms. The lengths of the rows increase almost linearly with distance from the centre. They intersect one another at an (average) angle ≈2π/3. A possible physical explanation of the phenomenon of rows is discussed on the basis of the assumption that the formation of straight arm segments might be due to the gas-dynamical effect of stability of flat shock fronts, and the tendency of a slightly curved shock front to become flat. A quantitative flattening criterion enables an explanation of the geometrical properties of the arm patterns found in M51 and also in M101. A brief list of spirals with rows is given.     

The structure of steady detonation waves in Type Ia supernovae: pathological detonations in C–O cores

The structure of steady, one-dimensional detonation waves in C–O is investigated for initial densities in the range 2×10⁷ to 1×10⁹ g cm⁻³. At these and greater densities, the self-supporting detonation wave is of the pathological type. For such waves the detonation speed is an eigenvalue of the steady equations, and the reaction zone contains an internal frozen sonic point where the thermicity vanishes. The self-supporting flow downstream of this singular point is supersonic, and is very different from that in supported (overdriven) detonations. A method for determining the structure of pathological detonation waves is described. These waves are examined, and the self-sustaining wave is compared with and contrasted to the supported detonations considered previously by Khokhlov. We show that the thickness of the self-sustaining detonation is a few times the thickness of supported detonations, and that the self-sustaining detonation produces more of the iron-peak and less of the intermediate mass elements than do supported detonations. Implications for the cellular detonation instability are also discussed.     

Characteristics of ≥ 290 keV magnetosheath ions

We performed a statistical analysis of 290–500 keV ion data obtained by IMP-8 during the years 1982–1988 within the earth’s magnetosheath and analysed in detail some time periods withdistinct ion bursts. These studies reveal the following characteristics for magnetosheath 290–500 keV energetic ions: (a) the occurrence frequency and the flux of ions increase with increasing geomagnetic activity as indicated by the Kp index; the occurrence frequency was found to be as high as P ≥ 42% for Kp ≥ 2, (b) the occurrence frequency in the dusk magnetosheath was found to be slightly dependent on the local time and ranged between ≈30% and ≈46% for all Kp values; the highest occurrence frequency was detected near the dusk magnetopause (21 LT), (c) the high energy ion bursts display a dawn-dusk asymmetry in their maximum fluxes, with higher fluxes appearing in the dusk magnetosheath, and (d) the observations in the dusk magnetosheath suggest that there exist intensity gradients of energetic ions from the bow shock toward the magnetopause. The statistical results are consistent with the concept that leakage of magnetospheric ions from the dusk magnetopause is a semi-permanent physical process often providing the magnetosheath with high energy (290–500 keV) ions.     

基于煤层巷道开挖卸荷效应的底板冲击孕育过程研究

采用相似模拟和数值模拟研究了河南义马煤田跃进矿采掘影响下巷道底板的应力及变形规律,揭示底板冲击矿压发生前的孕育过程。研究表明,巷道底板冲击受煤层埋深、顶板条件、巷道施工布置方式等多因素影响。在巨厚坚硬上覆砾岩影响下,工作面开采增加了相邻工作面的应力水平。在厚煤层中巷道沿顶板布置留底煤,巷道开挖后,一定范围的煤层底板中的水平应力升高,垂直应力降低,增加了煤层失稳破坏的可能性。巷道开挖卸荷过程中,底板由于没有支护,垂直位移增加,底板的塑性区范围大于两帮,并产生了明显的拉伸破坏,容易使底板成为冲击破坏突破口。