Magmatic systems are composed of melt accumulations and crystal mush that evolve with melt transport, contributing to igneous processes, volcano dynamics, and eruption triggering. Geophysical studies of active volcanoes have revealed details of shallow-level melt reservoirs, but little is known about fine-scale melt distribution at deeper levels dominated by crystal mush. Here, we present new seismic reflection images from Axial Seamount, northeastern Pacific Ocean, revealing a 3–5-km-wide conduit of vertically stacked melt lenses, with near-regular spacing of 300–450 m extending into the inferred mush zone of the mid-to-lower crust. This column of lenses underlies the shallowest melt-rich portion of the upper-crustal magma reservoir, where three dike intrusion and eruption events initiated. The pipe-like zone is similar in geometry and depth extent to the volcano inflation source modeled from geodetic records, and we infer that melt ascent by porous flow focused within the melt lens conduit led to the inflation-triggered eruptions. The multiple near-horizontal lenses are interpreted as melt-rich layers formed via mush compaction, an interpretation supported by one-dimensional numerical models of porous flow in a viscoelastic matrix.

A temperature independent pH buffer has been develeloped from combination of buffers of oppositesign temperature coefficients, and utility in low temperature spectroscopy and storage of pH sensitive compounds is demonstrated.Storage and analysis of samples at low and cryogenic temperatures has become a routine practice in modern research, as these temperatures can preserve integrity of precious samples, and allow modern biophysical and bioanalytical techniques to provide information on biomolecules at an unprecedented level. [1][2][3][4][5][6][7] Buffers are invariably used in the sample storage and analysis process. It is widely known that the pH of a buffer solution can change at low temperatures, and this has been ascribed to enthalpic effects on the proton equilibrium as well as selective precipitation of buffer components upon cooling. [8][9][10][11] If left unaccounted for, these pH changes could lead to demage to the samples and erroneous conclusions about biomolecular structures and dynamics at physiological temperature.About 75 years ago, Finn and coworkers reported the denaturation of proteins contained in muscle juice due to the variation in hydrogen ion and salt concentrations upon freezing. 12 Thereafter, activity loss of aldolase, phosphofructokinase and several dehydrogenases in sodium and potassium phosphate buffer at lower temperatures has been observed and ascribed to pH effects. 13,14 Several strategies have been applied to measure the temperature-dependent pH characteristics, such as the measurement of electromotive force (emf) to determine temperature dependence of pK a values, or the use of pH-sensitive dyes to probe protonic activity at low temperatures. [15][16][17][18] It was reported that EPR (electron paramagnetic resonance) based estimates of apparent pH change from the observation of several pH-sensitive systems (such as the flavin adenine dinucleotide semiquinone radical (FADH•) in xanthine oxidase) coincide well with estimates based on indicator dye optical changes. 19 Despite broad awareness, and extensive research into the relevance and merits of cryotemperature studies on biological systems, 20, 21 no reports of strategies to obtain buffers that resist temperature-dependent pH changes have appeared in the literature. Here we address this long standing problem through combination of buffers exhibiting an increase in pH upon freezing with those exhibiting a decrease. The utility of these temperature-independent-pH (TIP) buffers in preserving the sample integrity upon freezing of pH-sensitive pharmaceutical drugs, and in spectroscopic studies of human methemoglobin (met-Hb) is also demonstrated. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptTo obtain the TIP buffer, the apparent pH changes of the two commonly used buffers, (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and potassium phosphate) and mixtures thereof were first measured at low temperature via ratiometric absorption spectroscopy. A 1:1 mixture of two pH-indicator dyes (b...

A recent compilation of methane plumes detected offshore Washington State includes 1,772 individual bubble streams issuing from 491 discrete vent sites. The majority of these plume sites form a narrow 10‐km‐wide band located shallower than 250‐m water depth, with most sites located near the 175‐m‐deep continental shelf break that tracks the head scarps of large submarine canyons. Archive multichannel seismic profiles over the Cascadia shelf and uppermost margin that were co‐located within a few hundred meters with active emission sites show that methane bubble streams arise from listric/normal faults and triangular‐shaped regions of disturbed seismic reflectors that intersect the seafloor and extend several kilometers into the subsurface. Geological processes were evaluated for producing the narrow emission site depths including nonuniform distribution of methane within the Cascadia accretionary sediment wedge and horizontal transfer of groundwater from onshore subaerial sources. A model of enhanced sediment permeability arising from a contrasting response between the inner and outer portions of the accretionary wedge deformation during a megathrust earthquake cycle appears the most likely mechanism. This faulting is generated during extension of the overriding plate during megathrust earthquake cycles, with semicontinuous permeability enhancement of the fluid pathways from excitation by contemporary incident seismic waves.

Infection in humans with Campylobacter jejuni is commonly associated with exposure to food animal fecal material. In this study, we report on the recovery, potential for virulence and antimicrobial resistance levels of C. jejuni isolated from food and companion animals. Three hundred and seventy-eight fecal samples from food and companion animals and surface swabs from beef carcasses were tested for the presence of C. jejuni. C. jejuni was isolated from 13.8% (11/80) of dogs, 5% (1/20) of goats, 28.3% (17/60) of dairy cattle, 0% (0/65) of range cattle, 73.5% (36/49) of feedlot cattle, and 94.7% (18/19) of beef carcasses. Beef cattle from a single Arizona herd showed a considerable increase in fecal shedding of C. jejuni from pasture to feedlot and over time on the feedlot. Forty-two isolates were tested for susceptibility to four antimicrobial agents, each representing a class of antimicrobial drug approved for use in both humans and animals. None of the isolates were found to be resistant to erythromycin or gentamicin, whereas 2.4% of isolates were resistant to ciprofloxacin and 28.6% of isolates were resistant to tetracycline. The presence of virulence traits among the 42 isolates was assessed using in vitro macrophage survival and epithelial cell adherence and invasion assays. Of the isolates examined, 17 were able to survive within macrophages through 72 h at viable counts of >/=10(3)/well and 12 were capable of invading epithelial cells at viable counts of >/=10(3)/well. Data from these studies suggests that many of the isolates recovered from the non-poultry animal sources have the capacity to cause disease if transmitted to humans.