Permeability evolution during progressive development of deformation bands in porous sandstones

[1] Triaxial deformation experiments were carried out on large (0.1 m) diameter cores of a porous sandstone in order to investigate the evolution of bulk sample permeability as a function of axial strain and effective confining pressure. The log permeability of each sample evolved via three stages: (1) a linear decrease prior to sample failure associated with poroelastic compaction, (2) a transient increase associated with dynamic stress drop, and (3) a systematic quasi-static decrease associated with progressive formation of new deformation bands with increasing inelastic axial strain. A quantitative model for permeability evolution with increasing inelastic axial strain is used to analyze the permeability data in the postfailure stage. The model explicitly accounts for the observed fault zone geometry, allowing the permeability of individual deformation bands to be estimated from measured bulk parameters. In a test of the model for Clashach sandstone, the parameters vary systematically with confining pressure and define a simple constitutive rule for bulk permeability of the sample as a function of inelastic axial strain and effective confining pressure. The parameters may thus be useful in predicting fault permeability and sealing potential as a function of burial depth and faul

Scaling of the superfluid density in severely underdoped YBa2Cu3O6+y

Recent measurements on extremely-underdoped YBa2Cu3O6+y [Phys. Rev. Lett. 99, 237003 (2007)] have allowed the critical temperature (T_c), superfluid density [rho_0 (T << T_c)] and dc conductivity [sigma_dc (T ~ T_c)] to be determined for a series of electronic dopings for T_c ~ 3 - 17 K. The general scaling relation rho_0/8 ~ 4.4 sigma_dc T_c is observed, extending the validity of both the ab-plane and c-axis scaling an order of magnitude and creating a region of overlap. This suggests that severely underdoped materials may constitute a Josephson phase; as the electronic doping is increased a more uniform superconducting state emerges.Comment: 5 pages, 3 figure

Reservoir theory for studying the geochemical evolution of soils

[1] Linking mineral weathering rates measured in the laboratory to those measured at the landscape scale is problematic. In laboratory studies, collections of minerals are exposed to the same weathering environment over a fixed amount of time. In natural soils, minerals enter, are mixed within, and leave the soil via erosion and dissolution/leaching over the course of soil formation. The key to correctly comparing mineral weathering studies from laboratory experiments and field soils is to consistently define time. To do so, we have used reservoir theory. Residence time of a mineral, as defined by reservoir theory, describes the time length between the moment that a mineral enters (via soil production) and leaves (via erosion and dissolution/leaching) the soil. Age of a mineral in a soil describes how long the mineral has been present in the soil. Turnover time describes the time needed to deplete a species of minerals in the soil by sediment efflux from the soil. These measures of time are found to be sensitive to not only sediment flux, which controls the mineral fluxes in and out of a soil, but also internal soil mixing that controls the probability that a mineral survives erosion. When these measures of time are combined with published data suggesting that a mineral’s dissolution reaction rate decreases during the course of weathering, we find that internal soil mixing, by partially controlling the age distribution of minerals within a soil, might significantly alter the soil’s mass loss rate via chemical weathering. Citation: Mudd, S. M., and K. Yoo (2010), Reservoir theory for studying the geochemical evolution of soils, J. Geophys. Res., 115, F03030, doi:10.1029/2009JF001591. 1

Influence of chemical denudation on hillslope morphology

[1] Models of hillslope evolution involving diffusion-like sediment transport are conventionally presented as an equation in which the changes in land-surface elevation or soil thickness are balanced by the divergence of soil transport and tectonic uplift, soil production, or both. These models typically do not include the loss or gain of mass in hillslope soils due to processes of chemical weathering and deposition. We formulate a more general depth-integrated equation for the conservation of soil mass on a hillslope that includes a term representing chemical deposition or denudation. This general depth-integrated equation is then simplified to determine the one-dimensional form of a steady state hillslope which experiences both mechanical and chemical denudation. The differences in morphology between hillslopes only experiencing diffusion-like mechanical sediment transport and hillslopes experiencing both diffusion-like mechanical sediment transport and chemical denudation are explored. Under the conditions of a downslope increase in local soil lowering rate due to chemical weathering the hillslope profile will depart from the parabolic shape predicted by models that incorporate only linear diffusion-like mechanical sediment transport. In addition, hillslopes that experience both chemica

Regional variations in the diffusion of triggered seismicity

[1] We determine the spatiotemporal characteristics of interearthquake triggering in the International Seismological Centre catalogue on regional and global scales. We pose a null hypothesis of spatially clustered, temporally random seismicity, and determine a residual pair correlation function for triggered events against this background. We compare results from the eastern Mediterranean, 25 Flinn-Engdahl seismic regions, and the global data set. The null hypothesis cannot be rejected for distances greater than 150 km, providing an upper limit to triggering distances that can be distinguished from temporally uncorrelated seismicity in the stacked data at present. Correlation lengths L andmean distances between triggered events hri are on the order of 10–50 km, but can be as high as 100 km in subduction zones. These values are not strongly affected by magnitude threshold, but are comparable to seismogenic thicknesses, implying a strong thermal control on correlation lengths. The temporal evolution of L and hri is well fitted by a power law, with an exponent H 0.1 ± 0.05. This is much lower than the value H = 0.5 expected for Gaussian diffusion in a homogenous medium. We observe clear regional variations in L, hri and H that appear to depend on tectonic setting. A detectable transition to a more rapid diffusion regime occurs in some cases at times greater than 100–200 days, possibly due to viscoelastic processes in the ductile lower crust

A spatially continuous magnetization model for Mars

[1] Using a three-component magnetic field data set at over 100,000 satellite points previously compiled for spherical harmonic analysis, we have produced a continuously varying magnetization model for Mars. The magnetized layer was assumed to be 40 km thick, an average value based on previous studies of the topography and gravity field. The severe nonuniqueness in magnetization modeling is addressed by seeking the model with minimum root-mean-square (RMS) magnetization for a given fit to the data, with the trade-off between RMS magnetization and fit controlled by a damping parameter. Our preferred model has magnetization amplitudes up to 20 A/m. It is expressed as a linear combination of the Green’s functions relating each observation to magnetization at the point of interest within the crust, leading to a linear system of equations of dimension the number of data points. Although this is impractically large for direct solution, most of the matrix elements relating data to model parameters are negligibly small. We therefore apply methods applicable to sparse systems, allowing us to preserve the resolution of the original data set. Thus we produce more detailed models than any previously published, although they share many similarities. We find that tectonism in the Valles Marineris region has a magnetic signature, and we show that volcanism south of the dichotomy boundary has both a magnetic and gravity signature. The method can also be used to downward continue magnetic data, and a comparison with other leveling techniques at Mars ’ surface is favorable

Charge order, metallic behavior and superconductivity in La_{2-x}Ba_xCuO_4 with x=1/8

The ab-plane optical properties of a cleaved single crystal of La_{2-x}Ba_xCuO_4 for x=1/8 (T_c ~ 2.4 K) have been measured over a wide frequency and temperature range. The low-frequency conductivity is Drude-like and shows a metallic response with decreasing temperature. However, below ~ 60 K, corresponding to the onset of charge-stripe order, there is a rapid loss of spectral weight below about 40 meV. The gapping of single-particle excitations looks surprisingly similar to that observed in superconducting La_{2-x}Sr_{x}CuO_4, including the presence of a residual Drude peak with reduced weight; the main difference is that the lost spectral weight moves to high, rather than zero, frequency, reflecting the absence of a bulk superconducting condensate.Comment: 4 pages, with 1 table and 3 figure

Risk, commercialism and social purpose: Repositioning the English housing association sector

Originally seen as the ‘third arm’ of UK housing policy, the independent, not-for-profit housing association sector had long been seen as effective in ‘filling the gap’ where the state or market were unable to provide for households in need. Since the 1980s in particular, successive governments had viewed housing associations in favourable terms as efficient, semi-autonomous social businesses, capable of leveraging significant private funding. By 2015, in contrast, central government had come to perceive the sector as inefficient, bureaucratic and wasteful of public subsidy. Making use of institutional theory, this paper considers this paradigm shift and examines the organisational responses to an increasingly challenging operating environment. By focusing, in particular, on large London housing associations, the paper analyses their strategic decision-making to address the opportunities and threats presented. The paper argues that in facing an era of minimal subsidy, low security and high risk, the 2015 reforms represent a critical juncture for the sector. Housing organisations face a stark dilemma about whether to continue a strategy of ‘profit for purpose’ or to embrace an unambiguously commercial ethos. The article contends that the trajectory of decision-making (although not unidirectional) leads ultimately towards an increased exposure to risk and vulnerability to changes in the housing market. More fundamentally, the attempt to reconcile social and commercial logics is likely to have wider consequences for the legitimacy of the sector

THE DETERMINANTS OF USING VASECTOMY CONTRACEPTION IN SOMBA OPU DISTRICT, INDONESIA

Background: MOP (Male Operation Method) is an alternative family planning method for men who have decided they don't want to have more children by undergoing minor surgery on the sperm duct by blocking or blocking the way for the sperm to prevent fertilization.Objective: The purpose of this study was to determine the determinants of the use of MOP (Male Operation Method) / Vasectomy contraception in Somba Opu District, Gowa Regency.Method: This research is quantitative research with analytics method by using cross sectional study,The sampling technique used was proportional random sampling with a sample size of99 respondents. The data collection employed was a questionnaire, and the data was analyzed using the chi-square test.Result: The results showed that there was an influence between income (p = 0.002), knowledge (p = 0.003), attitude (p = 0.004), wife's support (p = 0.004) with the use of MOP contraception and there was no influence between age (p = 0.082), education (p = 0.465), the number of children (p = 0.204), the number of children wanted (p = 0.876), PLKB (p = 0.267) with the use of MOP contraception.Conclusion: This study is expected to gain a clear understanding of contraceptives and can easily determine their choice of family planning, especially male FP (Male Operation Method)

QUALITATIVE STUDY OF INPATIENT MANAGEMENT IN IMPROVING SERVICE QUALITY AT RSUD TRIKORA SALAKAN INDONESIA

Background:The implementation of the management function requires the competence of the head of the room as the main manager in the inpatient room to improve the quality of service in the hospital.Objective:This research aimed to know the management competence of inpatient room heads in improving service quality at Trikora Salakan General Hospital.Method:The research method was descriptive with a qualitative approach, with did a deep interview to head of nursing medical and head of the room in improving the quality of service.Result:The result of the research showed that the management competence of the head of the room at Trikora Salakan Hospital was still not optimal, this was influence by the management competence of the head of the room in making room planning, organizing, implementing, and evaluating so that the head of the room needed to improve and maintain his role as head of the room so that the implementation of management competence in the inpatient room was still carried out by both by management standards.Conclusion: Planning competence, some of the heads of the room who do not know about the hospital development plan, no one arranges planning in the room by looking at the strategic plan of the hospital-based only on the needs of the roo