SummaryTo

Introduction. The YciO protein of Escherichia coli is a member of a family of proteins that also includes YrdC, HypF in E. coli, YwlC in Bacillus subtilis, and Sua5 in Saccharomyces cerevisiae (PF01300 family in PFAM database 1). Sequences similar to YciO are found either as (a) independent proteins, (b) with C-terminal extensions, or (c) as domains in larger proteins (PFAM). The proteins YwlC from B. subtilis and Sua5 from S. cerevisiae are examples of the second category. Sua5 has been identified as having an essential role for normal growth on lactate or glycerol medium, although the precise function of the Sua5 protein remains unclear. 2 HypF represents the third category where this domain is located in the middle of the linear sequence. The hypF and hydN genes form the hydA locus in E. coli, which encodes functions necessary for the formation of hydrogenase activity. HypF, the hydrogenase maturation protein, most likely participates in the maturation of all three E. coli hydrogenase isozymes 1, 2, and 3 from their inactive precursor forms. 3 Both crystallographic and nucleic acid binding studies with E. coli YrdC revealed that this protein might exert its function through binding to double-stranded RNA. 4 This would imply a role for YciO/YrdC and their homologous domains in larger proteins as functioning in the regulation of either transcription or translation. To gain further insight into this family of proteins, we have determined the crystal structure of E. coli YciO at 2.1 Å resolution. Materials and Methods. The gene encoding E. coli yciO was cloned, and the protein was expressed and purified as an N-terminal His 6-tag fusion with a thrombin cleavage site as described previously for E. coli MoeA. 5 Crystals of the fusion protein were obtained by the hanging drop vapor diffusion method by equilibrating drops containing 2 L of protein (15 mg/mL) in buffer (20 mM Tris, pH 7.5, 40 mM NH 4 SO 4 , 60 mM NH 4 Ac, 5 mM 2-mercaptoethanol) and 2 L of reservoir solution (10% [w/v] PEG3350, 0.1 M MES buffer, pH 6.5, 0.1 M MgAc 2 , 5% [v/v] ethylene glycol) suspended over 0.5 mL of reservoir solution. The crystals belong to the orthorhombic system, space group P2 1 2 1 2 1 with unit cell dimensions a ϭ 48.40, b ϭ 68.77, c ϭ 94.77 Å and one molecule in the asymmetric unit. Before data collection, the crystal was soaked for ϳ15 s in a cryoprotecting solution of 23% (w/v) PEG3350, 0.1 M MES, pH 6.5, 0.1 M MgAc 2 , 5% (v/v)

SMod2.6 SUMMARYA new method of calculating synthetic seismograms of primary reflections or backscattering for surface reflection surveying is introduced using the De Wolf MFSB approximation and phase-screen one-way propagation. Two versions of algorithm are presented, both of which use the dual domain technique for computational efficiency. One is the direct use of MFSB approximation, in which the step length of calculating the backscattered waves uses the grid spacing, but the step length of forward propagation uses the screen interval which is much greater than the grid spacing. The other version is the screen approximation for both the forward and backward scattered waves and therefore both step lengths can adopt the screen interval, resulting in great computational efficiency. The screen-approximation involves small-angle approximation and may have some effects on largeangle backscattered waves. Numerical examples using both versions of algorithm show good results. Good agreements with finite difference calculation on the second example indicate that even though the screen approximation involves the small-angle approximation, satisfactory results can be obtained for many practical applications with a great computational efficiency. INTRODUCTIONFast modeling methods and algorithms in complex heterogeneous media, especially for 3-D media, are crucial to the development of imaging and inversion methods, interpretations and applications of seismic methods for complex structures. Finite difference and finite element methods, which in principle can model wave propagation in arbitrarily heterogeneous media, are time consuming, even formidable in the case of large 3-D elastic wave problems. In this study we develop a new method based on multiple-forescattering single-backscattering (MFSB) approximation, i.e. the De Wolf approximation for calculating the backscattered field in the configuration of surface reflection surveying. A dual domain formulation is derived for fast implementation of the method. When the scales of heterogeneities are greater than the dominant wavelength, the theory can be further approximated by the thin-slab scattering approximation and the screen scattering approximation. It is shown that the screen approximation can substantially reduce the computation time. Finally two numerical examples are given to demonstrate the validity of the method.

The EGS Collab project, supported by the US Department of Energy, is performing intensively monitored rock stimulation and flow tests at the 10-m scale in an underground research laboratory to address challenges in implementing enhanced geothermal systems (EGS). Data and observations from the field tests are compared to simulations to understand processes and build confidence in numerical modeling of the processes. We have completed Experiment 1 (of 3), which examined hydraulic fracturing in a well-characterized underground fractured phyllite test bed at a depth of approximately 1.5 km at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. Testbed characterization included fracture mapping, borehole acoustic and optical televiewers, full waveform sonic, conductivity, resistivity, temperature, campaign p- and s-wave investigations and electrical resistance tomography. Borehole geophysical techniques including passive seismic, continuous active source seismic monitoring, electrical resistance tomography, fiber-based distributed strain, distributed temperature, and distributed acoustic monitoring, were used to carefully monitor stimulation events and flow tests. More than a dozen stimulations and nearly one year of flow tests were performed. Quality data and detailed observations were collected and analyzed during stimulation and water flow tests using ambient temperature and chilled water. We achieved adaptive control of the tests using real-time monitoring and rapid dissemination of data and near-real-time simulation. More detailed numerical simulation was performed to answer key experimental design questions, forecast fracture propagation trajectories and extents, and analyze and evaluate results. Data are freely available from the Geothermal Data Repository. Experiment 2 examines the potential for hydraulic shearing in amphibolite at a depth of about 1.25 km at SURF. This site has a different set of stress and fracture conditions than Experiment 1. The Experiment 2 testbed consists of nine subhorizontal boreholes configured in two fans of two boreholes which surround the testbed and contain grouted-in electrical resistance tomography, seismic sensors, active seismic sources and distributed fiber sensors. A "five-spot" set of test wells that extends from a custom mined alcove includes an injection well and four production/monitoring wells. The testbed was characterized geophysically and hydrologically, and three stimulations have been performed using the Step-Rate Injection Method for Fracture In-Situ Properties (SIMFIP) tool to measure strains, and a new strain quantifying tool (downhole robotic strain analysis tool -DORSA) was deployed in a monitoring hole during stimulation. Real-time data were broadcast during stimulations to allow real-time response to arising issues.

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