2,532 research outputs found
Feeding stations and shelters for quail on Missouri farms
"May, 1940""On most Missouri farms under normal conditions, there is enough food and cover during the summer and fall for more quail than are usually found there. One reason -- perhaps the most important reason -- why these additional quail are not there is the great reduction in the amount and quality of food and cover during the day."--First paragraph.Werner O. Nagel and Rudolf Bennit
Creep on seismogenic faults: Insights from analogue earthquake experiments
Tectonic faults display a range of slip behaviors including continuous and episodic slip covering rates of more than 10 orders of magnitude (m/s). The physical control of such kinematic observations remains ambiguous. To gain insight into the slip behavior of brittle faults we performed laboratory stick-slip experiments using a rock analogue, granular material. We realized conditions under which our seismogenic fault analogue shows a variety of slip behaviors ranging from slow, quasi continuous creep to episodic slow slip to dynamic rupture controlled by a limited number of parameters. We explore a wide parameter space by varying loading rate from those corresponding to interseismic to postseismic rates and normal loads equivalent to hydrostatic to lithostatic conditions at seismogenic depth. The experiments demonstrate that significant interseismic creep and earthquakes may not be mutually exclusive phenomena and that creep signals vary systematically with the fault’s seismic potential. Accordingly, the transience of interseismic creep scales with fault strength and seismic coupling as well as with the maturity of the seismic cycle. Loading rate independence of creep signals suggests that mechanical properties of faults (e.g. seismic coupling) can be inferred from shortterm observations (e.g. aftershock sequences). Moreover, we observe the number and size of small episodic slip events to systematically increase towards the end of the seismic cycle providing an observable proxy of the relative shear stress state on seismogenic faults. Modelling the data suggest that for very weak faults in a late stage of their seismic cycle, the observed creep systematics may lead to the chimera of a perennially creeping fault releasing stress by continuous creep and/or transient slow slip instead of large earthquakes
Interseismic deformation transients and precursory phenomena: Insights from stick-slip experiments with a granular fault zone
The release of stress in the lithosphere along active faults shows a wide range of behaviors spanning several spatial and temporal scales. It ranges from short-term localized slip via aseismic slip transients to long-term distributed slip along large fault zones. A single fault can show several of these behaviors in a complementary manner often synchronized in time or space. To study the multiscale fault slip behavior with a focus on interseismic deformation transients we apply a simpli�ed analog model experiment using a rate-and-state-dependent frictional granular material (glass beads) deformed in a ring shear tester. The analog model is able to show, in a reproducible manner, the full spectrum of natural fault slip behavior including transient creep and slow slip events superimposed on regular stick-slip cycles (analog seismic cycles). Analog fault slip behavior is systematically controlled by extrinsic parameters such as the system sti�ness, normal load on the fault, and loading rate. Accordingly, interseismic creep and slow slip events increase quantitatively with decreasing normal load, increasing sti�ness and loading rate. We observe two peculiar features in our analog fault model: (1) Absence of transients in the �final stage of the stick-slip cycle ("preseismic gap") and (2) "scale gaps" separating small interseismic slow (aseismic) events from large (seismic) fast events. Concurrent micromechanical processes, such as dilation, breakdown of force chains and granular packaging a�ect the frictional properties of the experimental fault zone and control interseismic strengthening and coseismic weakening. Additionally, interseismic creep and slip transients have a strong e�ect on the predictability of stress drops and recurrence times. Based on the strong kinematic similiarity between our fault analog and natural faults, our observations may set important constraints for time-dependent seismic hazard models along single faults
Profile of major and emerging mycotoxins in sesame and soybean grains in the Federal Capital Territory, Abuja, Nigeria
The spectrum of major and emerging mycotoxins in sesame and soybean grains from the six zones of the Federal Capital Territory (FCT), Abuja, Nigeria was determined using Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS). A total of 47 samples (24 sesame and 23 soybean were collected from farmers’ stores. Seven regulated mycotoxins in sesame and five in soybean including aflatoxin B1 (AFB1), aflatoxin B2 (AFB2) and fumonisin B1 (FB1) were detected. However, concentrations were generally lower than regulatory limits set in the EU for raw grains with the exception of ochratoxin A (OTA) exhibiting a maximum concentration level of 23.1 µg kg-1 in one of the soybean samples. This is the first report concerning the contamination of sesame and soybean in Abuja, FCT-Nigeria with the emerging mycotoxins addressed by recent European Food Safety Authority (EFSA) opinion papers totalling 10 in number. These include beauvericin (BEA), moniliformin (MON), sterigmatocystin (STE), altertoxin-I (ATX-I), alternariol (AOH), alternariol methylether (AME) though at relatively low µg kg-1 range. This preliminary data indicate that sesame and soybean might be relatively safe commodities in view of the profile of mycotoxins.
DOI: http://dx.doi.org/10.5281/zenodo.130718
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