Physical Modelling of Stress-dependent Permeability in Fractured Rocks

This paper presents the results of laboratory experiments conducted to study the impact of stress on fracture deformation and permeability of fractured rocks. The physical models (laboratory specimens) consisted of steel cubes simulating a rock mass containing three sets of orthogonal fractures. The laboratory specimens were subjected to two or three cycles of hydrostatic loading/unloading followed by the measurement of displacement and permeability. The results show a considerable difference in both deformation and permeability trends between the first loading and the subsequent loading/unloading cycles. However, the micrographs of the contact surfaces taken before and after the tests show that the standard deviation of asperity heights of measured surfaces are affected very little by the loadings. This implies that both deformation and permeability are rather controlled by the highest surface asperities which cannot be picked up by the conventional roughness characterization technique. We found that the dependence of flow rate on mechanical aperture follows a power law with the exponent n smaller or larger than three depending upon the loading stage. Initially, when the maximum height of the asperities is high, the exponent is slightly smaller than 3. The first loading, however, flattens these asperities. After that, the third loading and unloading yielded the exponent of around 4. Due to the roughness of contact surfaces, the flow route is no longer straight but tortuous resulting in flow length increase.     

Power-spectrum normalization from the local abundance of rich clusters of galaxies

The number density of rich galaxy clusters still provides the most robust way of normalizing the power spectrum of dark matter perturbations on scales relevant to large-scale structure. We revisit this constraint in the light of several recent developments: (1) the availability of well-defined samples of local clusters with relatively accurate X-ray temperatures; (2) new theoretical mass functions for dark matter haloes, which provide a good fit to large numerical simulations; (3) more accurate mass–temperature relations from larger catalogues of hydrodynamical simulations; (4) the requirement to consider closed as well as open and flat cosmologies to obtain full multiparameter likelihood constraints for CMB and SNe studies. We present a new sample of clusters drawn from the literature and use this sample to obtain improved results on σ ₈, the normalization of the matter power spectrum on scales of 8  h ⁻¹ Mpc, as a function of the matter density and cosmological constant in a universe with general curvature. We discuss our differences with previous work, and the remaining major sources of uncertainty. Final results on the normalization, approximately independent of power spectrum shape, can be expressed as constraints on σ at an appropriate cluster normalization scale R _Cl. We provide fitting formulas for R _Cl and σ ( R _Cl) for general cosmologies, as well as for σ ₈ as a function of cosmology and shape parameter Γ. For flat models we find approximately σ ₈≃(0.495_−0.037^+0.034)Ω_M^−0.60 for Γ=0.23, where the error bar is dominated by uncertainty in the mass–temperature relation.     

Glacier changes in the Tien Shan as determined from topographic and remotely sensed data

This research presents a precise evaluation of the Tien Shan glacier's recession based on data of geodetic surveys 1861–1869, aerial photographs from 1943, 1963, 1977, 1981, 1:25,000 scale topographic maps, SRTM, and ASTER data from 2000/2003 for the Akshiirak glacierized massif in the central Tien Shan with 178 glaciers covering 317.6 km², and for the Ala Archa glacier basin in the northern Tien Shan with 48 glaciers covering 36.31 km².The Tien Shan glaciers retreated as much as 3 km from the 1860s to 2003. From 1943 to 1977, Akshiirak and Ala Archa shrunk 4.2% and 5.1% respectively, and from 1977 to 2003 the area shrunk 8.6% and 10.6%, respectively. The volume of the Akshiirak glaciers was reduced by 3.566 km³ from 1943 to 1977 and 6.147 km³ from 1977 to 2000.The total reduction of the Tien Shan glacier is 14.2% during the last 60 yr. The northern and central Tien Shan have not experienced a significant increase of precipitation during the last 100 yr, but they have experienced an increase in summer air temperatures, especially observable since the 1970s, which caused an acceleration of the Tien Shan glaciers recession.     

Evolution of the X-ray luminosity and metallicity of starburst blown superbubbles

We have modelled the evolution of hot superbubbles in starbursts, taking into account the rapid changes in the chemical composition of the interior of the superbubbles resulting from the large stellar mass loss, i.e. stellar winds from massive young stars and type II supernovae. We have followed in detail the time-dependent production and mixing of oxygen and iron in the interior of the hot superbubbles and showed that while the oxygen abundance rapidly climbs to over solar values in less than 10 Myr, iron abundance remains always under solar. This highly enhanced oxygen metallicity boosts the early X-ray luminosity of superbubbles while keeping the iron abundance subsolar. This brings theory and X-ray observations of the luminosity and metal content of young starbursts closer together.     

Early Norian flora from Partizansk River Basin of Primorye, Russia

An early Norian flora from the Partizansk River Basin of Primorye, Far-East of Russia, is described in detail for the first time, in which over 25 taxa are reported. The flora is dominated by cycadoalean, bennettitalean and coniferous plants, associated with a lot of ferns and czekanowskialean plants, and with a few ginkgoalean. In floristic characteristics, the flora can be well comparable with Late Triassic Mongugai flora of southwestern Primorye and its neighboring Tianqiaoling flora of eastern Jilin, China, as well with the Yamanoi and Nariwa floras from southwestern Japan. As the plant-bearing strata are sandwiched in the lower Norian marine beds yielding marine fauna, the age of the Partizansk flora is well evidenced as the early Norian. Paleophytogeographically, the flora appears to be in the ecotone of the Medio-Triassic and Arcto-Triassic floristic regions in Eurasia, and indicates probably warm temperate or subtropic vegetation in nature. Four new species are reported in this paper, including Ctenis elegantus sp. nov, Ixostrobus pacificus sp. nov., Elatocladus elegantus sp. nov. and E. prynadae sp. nov.     

Mv Lyr: Transition from Low to High Brightness State

We present results of multicolour photometry of the nova-like binary MV Lyr in the years 2002–2003, corresponding to the transition of the star from its low (V = 17.8) to high (V = 12.3) brightness state. The transition lasted at most 200 days. During the first ∼50 days MV Lyr brightened at the rate 0.06 mag/day, and during the next ∼150 days at the rate 0.01 mag/day. The brightening was accompanied by a blue shift from 0.45 to 0.05 in V−R, interpreted as an increase of the accretion disk contribution to the total light. During the transition MV Lyr displayed well-known ‘quasi-orbital’ light variations and fast quasi-periodic oscillations with a typical time scale of tens of minutes.