The directed three-dimensional self-assembly of microstructures and nanostructures through the selective hybridization of DNA is the focus of great interest toward the fabrication of new materials. Single-stranded DNA is covalently attached to polystyrene latex microspheres. Single-stranded DNA can function as a sequence-selective Velcro by only bonding to another strand of DNA that has a complementary sequence. The attachment of the DNA increases the charge stabilization of the microspheres and allows controllable aggregation of microspheres by hybridization of complementary DNA sequences. In a mixture of microspheres derivatized with different sequences of DNA, microspheres with complementary DNA form aggregates, while microspheres with noncomplementary sequences remain suspended. The process is reversible by heating, with a characteristic "aggregate dissociation temperature" that is predictably dependent on salt concentration, and the evolution of aggregate dissociation with temperature is observed with optical microscopy.

Predicting the phase of precipitation is fundamental to water supply and hazard forecasting. Phase prediction methods (PPMs) are used to predict snow fraction, or the ratio of snowfall to total precipitation. Common temperature‐based regression (Dai method) and threshold at freezing (0°C) PPMs had comparable accuracy to a humidity‐based PPM (TRH method) using 6 and 24 h observations. Using a daily climate data set from 1980 to 2015, the TRH method estimates 14% and 6% greater precipitation‐weighted snow fraction than the 0°C and Dai methods, respectively. The TRH method predicts four times less area with declining snow fraction than the Dai method (2.1% and 8.1% of the study domain, respectively) from 1980 to 2015, with the largest differences in the Cascade and Sierra Nevada mountains and southwestern U.S. Future Representative Concentration Pathway (RCP) 8.5 projections suggest warming temperatures of 4.2°C and declining relative humidity of 1% over the 21st century. The TRH method predicts a smaller reduction in snow fraction than temperature‐only PPMs by 2100, consistent with lower humidity buffering declines in snow fraction caused by regional warming.

Changes in borehole water levels and remotely triggered seismicity occur in response to near and distant earthquakes at locations around the globe, but the mechanisms for these phenomena are not well understood. Experiments were conducted to show that seismically initiated gas bubble growth in groundwater can trigger a sustained increase in pore fluid pressure consistent in magnitude with observed coseismic borehole water level rise, constituting a physically plausible mechanism for remote triggering of secondary earthquakes through the reduction of effective stress in critically loaded geologic faults. A portion of the CO 2 degassing from the Earth's crust dissolves in groundwater where seismic Rayleigh and P waves cause dilational strain, which can reduce pore fluid pressure to or below the bubble pressure, triggering CO 2 gas bubble growth in the saturated zone, indicated by a spontaneous buildup of pore fluid pressure. Excess pore fluid pressure was measured in response to the application of 0.1-1.0 MPa, 0.01-0.30 Hz confining stress oscillations to a Berea sandstone core flooded with initially subsaturated aqueous CO 2 , under conditions representative of a confined aquifer. Confining stress oscillations equivalent to the dynamic stress of the 28 June 1992 M w 7.3 Landers, California, earthquake Rayleigh wave as it traveled through the Long Valley caldera, and Parkfield, California, increased the pore fluid pressure in the Berea core by an average of 36 ± 15 cm and 23 ± 15 cm of equivalent freshwater head, respectively, in agreement with 41.8 cm and 34 cm rises recorded in wells at those locations.1. Background Coseismic Borehole Water Level RiseWater levels in some wells respond to near and distant earthquakes [Roeloffs et al., 1995Roeloffs, 1998;Woodcock and Roeloffs, 1996;Liu et al., 1989;Zones, 1957;Leggette and Taylor, 1934;Sterns, 1928]. The water level can increase or decrease in response to a change in static stress, but the coseismic water level changes in a subset of wells always have the same sign, regardless of the sign of the local static stress change. In wells that exhibit coseismic water level rise, the increase in water level scales with the earthquake magnitude, and inversely as the square of the distance to the hypocenter [Roeloffs, 1998]. Coseismic water level rise typically begins within minutes of the passage of the seismic surface wave train and builds to a peak over hours to days then slowly declines to or near pre-earthquake level within hours to weeks. The largest coseismic water level rise in a given well tends to occur when the pre-earthquake water level is at or near a seasonal low [Roeloffs, 1998]. The 28 June 1992 M w 7.3 Landers, California, earthquake induced water level changes ranging from À180 cm to +300 cm in wells in Parkfield, Long Valley caldera, and Southern California (Figure 1), and caused borehole water level oscillations in Oregon and Nevada [Roeloffs et al., 1995].The Bourdieu Valley well, 435 km from the Landers hypocenter, responded with a 34 cm incre...

We measured the pore pressure response due to carbon dioxide (CO 2 ) gas bubble nucleation and growth in a Berea sandstone core flooded with an initially subsaturated aqueous solution of CO 2 , in response to a rapid drop in confining stress, under conditions representative of a confined aquifer. A portion of the CO 2 in the Earth's crust, derived from volcanic, magmatic, and biogenic sources, dissolves in groundwater. Sudden reductions in confining stress in the Earth's crust occur due to dilational strain generated by the propagation of seismic Rayleigh and P waves, or aseismic slip in the near field of earthquakes. A drop in confining stress produces a proportional drop in pore fluid pressure. When the pore fluid contains dissolved CO 2 , the pore pressure responds to a drop in confining stress like it does in the dissolved gas-free case, until the pore pressure falls below the bubble pressure. Gas bubble nucleation and diffusive growth in the pore space trigger spontaneous, transient buildup of the pore fluid pressure, and reduction of effective stress. We measured the rate of pore fluid pressure buildup in the 100 s immediately following the confining stress drop, as a function of the saturation with respect to CO 2 at the lowest pore pressure realized during the confining stress drop, using five different CO 2 partial pressures. The rate scales with the saturation with respect to dissolved CO 2 , from 10 kPa/min at 1.25 to 166 kPa/min at 1.8. The net pore pressure rise was as large as 0.7 MPa (100 psi) over 5 h.