Joint inversion of Rayleigh wave phase velocity and ellipticity using USArray: Constraining velocity and density structure in the upper crust

Rayleigh wave ellipticity, or H/V ratio, observed on the surface is particularly sensitive to shallow earth structure. In this study, we jointly invert measurements of Rayleigh wave H/V ratio and phase velocity between 24–100 and 8–100 sec period, respectively, for crust and upper mantle structure beneath more than 1000 USArray stations covering the western United States. Upper crustal structure, in particular, is better constrained by the joint inversion compared to inversions based on phase velocities alone. In addition to imaging Vs structure, we show that the joint inversion can be used to constrain Vp/Vs and density in the upper crust. New images of uppermost crustal structure (<3 km depth) are in excellent agreement with known surface features, with pronounced low Vs, low density, and high Vp/Vs anomalies imaged in the locations of several major sedimentary basins including the Williston, Powder River, Green River, Denver, and San Juan basins. These results demonstrate not only the consistency of broadband H/V ratios and phase velocity measurements, but also that their complementary sensitivities have the potential to resolve density and Vp/Vs variations

Designing Visible Light-Cured Thiol-Acrylate Hydrogels for Studying the HIPPO Pathway Activation in Hepatocellular Carcinoma Cells

Various polymerization mechanisms have been developed to prepare peptide-immobilized poly(ethylene glycol) (PEG) hydrogels, a class of biomaterials suitable for studying cell biology in vitro. Here, a visible light mediated thiol-acrylate photopolymerization scheme is reported to synthesize dually degradable PEG-peptide hydrogels with controllable crosslinking and degradability. The influence of immobilized monothiol pendant peptide is systematically evaluated on the crosslinking of these hydrogels. Further, methods are proposed to modulate hydrogel crosslinking, including adjusting concentration of comonomer or altering the design of multifunctional peptide crosslinker. Due to the formation of thioether ester bonds, these hydrogels are hydrolytically degradable. If the dithiol peptide linkers used are susceptible to protease cleavage, these thiol-acrylate hydrogels can be designed to undergo partial proteolysis. The differences between linear and multiarm PEG-acrylate (i.e., PEGDA vs PEG4A) are also evaluated. Finally, the use of the mixed-mode thiol-acrylate PEG4A-peptide hydrogels is explored for in situ encapsulation of hepatocellular carcinoma cells (Huh7). The effects of matrix stiffness and integrin binding motif (e.g., RGDS) on Huh7 cell growth and HIPPO pathway activation are studied using PEG4A-peptide hydrogels. This visible light poly-merized thiol-acrylate hydrogel system represents an alternative to existing light-cured hydrogel platforms and shall be useful in many biomedical applications

3-D crustal structure of the western United States: application of Rayleigh-wave ellipticity extracted from noise cross-correlations

We present a new 3-D seismic model of the western United States crust derived from a joint inversion of Rayleigh-wave phase velocity and ellipticity measurements using periods from 8 to 100 s. Improved constraints on upper-crustal structure result from use of short-period Rayleigh-wave ellipticity, or Rayleigh-wave H/V (horizontal to vertical) amplitude ratios, measurements determined using multicomponent ambient noise cross-correlations. To retain the amplitude ratio information between vertical and horizontal components, for each station, we perform daily noise pre-processing (temporal normalization and spectrum whitening) simultaneously for all three components. For each station pair, amplitude measurements between cross-correlations of different components (radial–radial, radial–vertical, vertical–radial and vertical–vertical) are then used to determine the Rayleigh-wave H/V ratios at the two station locations. We use all EarthScope/USArray Tranportable Array data available between 2007 January and 2011 June to determine the Rayleigh-wave H/V ratios and their uncertainties at all station locations and construct new Rayleigh-wave H/V ratio maps in the western United States between periods of 8 and 24 s. Combined with previous longer period earthquake Rayleigh-wave H/V ratio measurements and Rayleigh-wave phase velocity measurements from both ambient noise and earthquakes, we invert for a new 3-D crustal and upper-mantle model in the western United States. Correlation between the inverted model and known geological features at all depths suggests good resolution in five crustal layers. Use of short-period Rayleigh-wave H/V ratio measurements based on noise cross-correlation enables resolution of distinct near surface features such as the Columbia River Basalt flows, which overlie a thick sedimentary basin

Hidden Trends in 90 Years of Harvard Business Review

In this paper, we demonstrate and discuss results of our mining the abstracts of the publications in Harvard Business Review between 1922 and 2012. Techniques for computing n-grams, collocations, basic sentiment analysis, and named-entity recognition were employed to uncover trends hidden in the abstracts. We present findings about international relationships, sentiment in HBR's abstracts, important international companies, influential technological inventions, renown researchers in management theories, US presidents via chronological analyses.Comment: 6 pages, 14 figures, Proceedings of 2012 International Conference on Technologies and Applications of Artificial Intelligenc

Comparative study of visible light polymerized gelatin hydrogels for 3D culture of hepatic progenitor cells

Photopolymerization techniques have been widely used to create hydrogels for biomedical applications. Visible light-based photopolymerizations are commonly initiated by type II (i.e., noncleavage-type) photoinitiator in conjunction with a coinitiator. On the other hand, type I photoinitiators (i.e., cleavage type) are rarely compatible with visible light-based initiation due to their limited molar absorbability in the visible light wavelengths. Here, we report visible light initiated orthogonal photoclick crosslinking to fabricate gelatin-norbornene and poly(ethylene glycol)-tetra-thiol hydrogels using either cleavage-type (i.e., lithium acylphosphinate, LAP) or noncleavage-type photoinitiator (i.e., eosin-Y, EY) without the use of a coinitiator. Regardless of the initiator type, the step-growth gelatin-PEG hybrid hydrogels crosslinked and degraded similarly. While both systems exhibited similar cytocompatibility for hepatic progenitor HepaRG cells, gelation initiated by noncleavage-type initiator EY afforded slightly higher degree of hepatic gene expression

How University Departmens respond to the Rise of Academic Entrepreneurship? The Pasteur's Quadrant Explanation

This paper examines how universities can develop a new organizational structure to cope with the rise of academic entrepreneurship. By deploying the Pasteurian quadrant framework, knowledge creation and knowledge utilization in universities are measured. The relationships between university antecedents, Pasteurian orientation, and research performance are analyzed. A survey of university administrators and faculty members collected 634 responses from faculty members in 99 departments among 6 universities. The findings indicate that university antecedents of strategic flexibility and balancing commitment contribute to a greater Pasteurian orientation in university departments. The higher degree of Pasteurian orientation has significantly positive impacts on the performance both of knowledge creation and knowledge utilization. Moreover, the Pasteurian orientation acts as a mediator between university antecedents and research performance. Using cluster analysis, the departments are categorized into four groups. The differences between university- and department- factors in these four groups are examined and discussed. We conclude that not all university departments should move toward the Pasteurian group, and there are specific organizational and disciplinary factors resulting in mobility barriers among groups. Policies to encourage academic entrepreneurship should consider these mobility barriers, along with this new governance of science.Academic entrepreneurship, Pasteur’s quadrant, research excellence, research commercialization

Thiol-ene hydrogels as desmoplasia-mimetic matrices for modeling pancreatic cancer cell growth, invasion, and drug resistance

The development of pancreatic ductal adenocarcinoma (PDAC) is heavily influenced by local stromal tissues, or desmoplasia. Biomimetic hydrogels capable of mimicking tumor niches are particularly useful for discovering the role of independent matrix cues on cancer cell development. Here, we report a photo-curable and bio-orthogonal thiol-ene (i.e., cross-linked by mutually reactive norbornene and thiol groups via photoinitiation) hydrogel platform for studying the growth, morphogenesis, drug resistance, and cancer stem cell marker expression in PDAC cells cultured in 3D. The hydrogels were prepared from multi-arm poly(ethylene glycol)-norbornene cross-linked with protease-sensitive peptide to permit cell-mediated matrix remodeling. Collagen 1 fibrils were incorporated into the covalent network while cytokines (e.g., EGF and TGF-β1) were supplemented in the culture media for controlling cell fate. We found that the presence of collagen 1 enhanced cell proliferation and Yes-associated protein (YAP) translocation to cell nuclei. Cytokines and collagen 1 synergistically up-regulated MT1-MMP expression and induced cell spreading, suggestive of epithelial-mesenchymal transition (EMT) in the encapsulated cells. Furthermore, PDAC cells cultured in 3D developed chemo-resistance even in the absence of collagen 1 and cytokines. This phenotype is likely a consequence of the enrichment of pancreatic cancer stem cells that expressed high levels of CD24, sonic hedgehog (SHH), and vascular endothelial growth factor (VEGF)

Amplification and Attenuation across USArray using Ambient Noise Wavefront Tracking

As seismic traveltime tomography continues to be refined using data from the vast USArray data set, it is advantageous to also exploit the amplitude information carried by seismic waves. We use ambient noise cross correlation to make observations of surface wave amplification and attenuation at shorter periods (8–32 s) than can be observed with only traditional teleseismic earthquake sources. We show that the wavefront tracking approach can be successfully applied to ambient noise correlations, yielding results quite similar to those from earthquake observations at periods of overlap. This consistency indicates that the wavefront tracking approach is viable for use with ambient noise correlations, despite concerns of the inhomogeneous and unknown distribution of noise sources. The resulting amplification and attenuation maps correlate well with known tectonic and crustal structure; at the shortest periods, our amplification and attenuation maps correlate well with surface geology and known sedimentary basins, while our longest period amplitudes are controlled by crustal thickness and begin to probe upper mantle materials. These amplification and attenuation observations are sensitive to crustal materials in different ways than traveltime observations and may be used to better constrain temperature or density variations. We also value them as an independent means of describing the lateral variability of observed Rayleigh wave amplitudes without the need for 3-D tomographic inversions