Pore fluids affect the brittle failure strength of rocks by physico-chemical interactions between solids and fluids and by mechanisms associated with changes in effective stress controlled by ...drainage conditions. The two classes of mechanisms are often hard to separate in the field and in the laboratory. We performed triaxial deformation experiments at different strain rates that allowed for a systematic variation of the drainage state with the aim to identify the contribution of physico-chemical effects on the failure characteristics of three sandstone varieties (Ruhr sst, Wilkeson sst and Fontainebleau sst) covering a range of porosities, hydraulic properties and mineralogical compositions. The applied strain rates ranged from 10−7 to 10−3 s−1 comprising the critical strain rates for internal drainage estimated from experimentally determined hydraulic properties. Tests were performed at room temperature and an effective pressure of 20 MPa. Under these conditions all samples exhibited brittle failure and hence dilatancy hardening occurred when deformation proceeded too fast to maintain effective drainage. The strain rates observed for the onset of dilatancy hardening agreed within an order of magnitude with calculated critical strain rates. At strain rates low enough to ensure internal drainage the physico-chemical effects on strength were deduced from the comparison of tests on dry and saturated samples. The relative weakness of saturated samples was similar for the three sandstones and rather moderate. We did not find a distinct relationship between the weakening effect of water and the presence of clays. The peak in work performed on a sample systematically preceded that of the applied axial stress potentially pointing to an irreversible micromechanical instability before actual macroscopic failure. Considering work in addition to axial stress may provide valuable complementary constraints for a micromechanical interpretation of processes related to different states of internal drainage.
Periodic pumping tests are now being used to characterize subsurface hydraulic parameters owing to several advantages over conventional tests, for example, option of superposing periodic excitations ...on transients by the data processing in the frequency domain. We derive an analytical model of periodic pumping tests using a double‐packer system to isolate an injection interval in a borehole penetrating either a confined or unconfined anisotropic aquifer. The model, which is apt for injectivity analysis and axial interference analysis, was evaluated by comparing it to previously presented solutions of the hydraulic diffusion equation considering appropriate limits regarding interval length, storage capacity of the interval, and the aquifer specific yield. The axial interference analysis constrains the ratio of axial‐to‐radial hydraulic conductivity. Radial conductivity and specific storage are constrained by the injectivity analysis prescribing conductivity anisotropy ratios. The combination of the two analyses narrows down the range of estimated hydraulic properties. The application of our model to field data from a fault zone in crystalline rocks yields a subvertical conductivity at least 10 times greater than the horizontal value, which agrees qualitatively with the fault geometry. By proper choice of the pumping period, axial interference analysis can be used to not only assess the integrity of packers and their immediate surrounding but also to extend our understanding of subsurface features.
Key Points
Periodic pumping tests using a double‐packer system exploit pressure records above and below a double‐packer
Periodic pumping tests constrain hydraulic characteristics beyond conventional tests, including the axial‐to‐radial anisotropy ratio
A
bstract
The European Spallation Source (ESS), presently well on its way to completion, will soon provide the most intense neutron beams for multi-disciplinary science. Fortuitously, it will also ...generate the largest pulsed neutrino flux suitable for the detection of Coherent Elastic Neutrino-Nucleus Scattering (CE
ν
NS), a process recently measured for the first time at ORNL’s Spallation Neutron Source. We describe innovative detector technologies maximally able to profit from the order-of-magnitude increase in neutrino flux provided by the ESS, along with their sensitivity to a rich particle physics phenomenology accessible through high-statistics, precision CE
ν
NS measurements.
Central serotonin (5-hydroxytryptophan, 5-HT) modulates somatosensory transduction, but how it achieves sensory modality-specific modulation remains unclear. Here we report that enhancing ...serotonergic tone via administration of 5-HT potentiates itch sensation, whereas mice lacking 5-HT or serotonergic neurons in the brainstem exhibit markedly reduced scratching behavior. Through pharmacological and behavioral screening, we identified 5-HT1A as a key receptor in facilitating gastrin-releasing peptide (GRP)-dependent scratching behavior. Coactivation of 5-HT1A and GRP receptors (GRPR) greatly potentiates subthreshold, GRP-induced Ca2+ transients, and action potential firing of GRPR+ neurons. Immunostaining, biochemical, and biophysical studies suggest that 5-HT1A and GRPR may function as receptor heteromeric complexes. Furthermore, 5-HT1A blockade significantly attenuates, whereas its activation contributes to, long-lasting itch transmission. Thus, our studies demonstrate that the descending 5-HT system facilitates GRP-GRPR signaling via 5-HT1A to augment itch-specific outputs, and a disruption of crosstalk between 5-HT1A and GRPR may be a useful antipruritic strategy.
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•Central 5-HT signaling facilitates itch transmission•5-HT1A potentiates GRPR-mediated itch signaling•5-HT1A and GRPR are present in close proximity•Blockade of 5-HT1A function reduces chronic itch
How does the itch-scratch cycle occur? Zhao et al. show that scratching of mice produces serotonin to inhibit pain; paradoxically, serotonin also enhances itch through a crosstalk between its receptor 5-HT1A and GRPR, an itch receptor in the spinal cord.
Summary Objective To estimate the lifetime risk of symptomatic hip osteoarthritis (OA). Design We analyzed data from the Johnston County Osteoarthritis Project a longitudinal population-based study ...of OA in North Carolina, United States ( n = 3068). The weighted baseline sample comprised 18% blacks and 54% women, and the mean age was 63 years (range = 45–93). Symptomatic hip OA was defined as a Kellgren–Lawrence (K–L) radiographic score of ≥2 (anterior–posterior pelvis X-rays) and pain, aching or stiffness on most days, or groin pain, in the same hip. Lifetime risk, defined as the proportion who developed symptomatic hip OA in at least one hip by age 85, among people who live to age 85, was modeled using logistic regression with repeated measures (through generalized estimating equations). Results Lifetime risk of symptomatic hip OA was 25.3% 95% confidence interval (CI) = 21.3–29.3. Lifetime risk was similar by sex, race, highest educational attainment, and hip injury history. We studied lifetime risk by body mass index (BMI) in three forms: at age 18; at baseline and follow-up; and at age 18, baseline and follow-up and found no differences in estimates. Conclusion The burden of symptomatic hip OA is substantial with one in four people developing this condition by age 85. The similar race-specific estimates suggest that racial disparities in total hip replacements are not attributable to differences in disease occurrence. Despite increasing evidence that obesity predicts an increased risk of both hip OA and joint replacement, we found no association between BMI and lifetime risk.
A
bstract
The
Neutrino Experiment with a Xenon TPC
(NEXT) searches for the neutrinoless double-beta (0
νββ
) decay of
136
Xe using high-pressure xenon gas TPCs with electroluminescent amplification. ...A scaled-up version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of 0
νββ
decay better than 10
27
years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.
Summary
The newly introduced Nexfin® device allows analysis of the blood pressure trace produced by a non‐invasive finger cuff. We compared the cardiac output derived from the Nexfin and PiCCO, using ...transcardiopulmonary thermodilution, during cardiac surgery. Forty patients with preserved left ventricular function undergoing elective coronary artery bypass graft surgery were studied after induction of general anaesthesia and until discharge to the intensive care unit. There was a significant correlation between Nexfin and PiCCO before (r2 = 0.81, p < 0.001) and after (r2 = 0.56, p < 0.001) cardiopulmonary bypass. Bland–Altman analysis demonstrated the mean bias of Nexfin to be −0.1 (95% limits of agreement −0.6 to +0.5, percentage error 23%) and −0.1 (−0.8 to +0.6, 26%) l.min−1.m−2, before and after cardiopulmonary bypass, respectively. After a passive leg‐raise was performed, there was also good correlation between the two methods, both before (r2 = 0.72, p < 0.001) and after (r2 = 0.76, p < 0.001) cardiopulmonary bypass. We conclude that the Nexfin is a reliable method of measuring cardiac output during and after cardiac surgery.
To investigate the impact of knee osteoarthritis (OA) and/or knee pain on excess mortality.
We analyzed data from 4,182 participants in a community-based prospective cohort study of African American ...and Caucasian men and women aged ≥45 years. Participants completed knee radiographs and questionnaires at baseline and at up to three follow-ups to determine knee OA (rOA), knee pain and covariate status. Mortality was determined through 2015. We used Cox proportional hazards regression with time-varying covariates (TVC) to estimate hazard ratios (HR) and 95% confidence intervals (CI). Additional analyses stratified by sex, race and age were carried out.
Median follow-up time was 14.6 years during which 1822 deaths occurred. Baseline knee radiographic osteoarthritis (rOA) was 27.7%, 38.8% at first follow-up, 52.6% at second follow-up and 61.9% at the third follow-up. Knee rOA with pain and knee pain alone were both associated with a >15% increase in premature all-cause mortality. In analyses stratified by sex, race and age, associations between knee pain, with or without knee rOA, and all-cause death were found among women, Caucasians, those ≤65 years of age, and those with a body mass index (BMI)≥30, with observed increased risks of death between 21% and 65%. We observed similar, somewhat attenuated, results for cardiovascular disease (CVD) deaths.
In models taking into account variables that change over time, individuals who had knee pain, alone or with knee rOA, had increased mortality. These effects were particularly strong among those obese. Effective interventions to reduce knee pain, particularly those including weight management and prevention of comorbidities, could reduce mortality.
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