Synthesis and processing of nanoscaled ceramics by chemical routes

Nanocrystalline boehmite and TiN powders have been used as model systems for testing the conception of small-molecule surface modification for the preparation of processable nanoscaled slips and pastes with a high solid content. It was found that after surface modification of boehmite with carboxylic acids like acetic or propionic acid and the addition of 5 to 6 vol.-% of organic processing additives pastes with a solid content of about 45 vol.-% can be prepared. The nanocrystalline pastes have been extruded to tubes which after drying exhibit green densities of about 55 to 60 % of the theory. In the case of TiN it was shown that deagglomeration with short-chained organic bases gives low viscous slips with a solid content of 40 wt.-%. Green bodies with a green density of about 50 % of the theory have been prepared by vacuum-assisted pressure filtration. The nanocrystalline material exhibits a very high sintering activity so that a density above 96 % of the theory could be achieved at 1150°C leading to a microstructure consisting of an average grain size of about 50 nm. This clearly demonstrates the potential of nanosized starting material for separating the densification regime from the grain growth regime in the sintering step

Images of Crust Beneath Southern California Will Aid Study of Earthquakes and Their Effects

The Whittier Narrows earthquake of 1987 and the Northridge earthquake of 1991 highlighted the earthquake hazards associated with buried faults in the Los Angeles region. A more thorough knowledge of the subsurface structure of southern California is needed to reveal these and other buried faults and to aid us in understanding how the earthquake-producing machinery works in this region

Understanding earthquake hazards in southern California - the "LARSE" project - working toward a safer future for Los Angeles

The Los Angeles region is underlain by a network of active faults, including many that are deep and do not break the Earth’s surface. These hidden faults include the previously unknown one responsible for the devastating January 1994 Northridge earthquake, the costliest quake in U.S. history. So that structures can be built or strengthened to withstand the quakes that are certain in the future, the Los Angeles Region Seismic Experiment (LARSE) is locating hidden earthquake hazards beneath the region to help scientists determine where the strongest shaking will occur

Design and Fabrication of Vertically-Integrated CMOS Image Sensors

Technologies to fabricate integrated circuits (IC) with 3D structures are an emerging trend in IC design. They are based on vertical stacking of active components to form heterogeneous microsystems. Electronic image sensors will benefit from these technologies because they allow increased pixel-level data processing and device optimization. This paper covers general principles in the design of vertically-integrated (VI) CMOS image sensors that are fabricated by flip-chip bonding. These sensors are composed of a CMOS die and a photodetector die. As a specific example, the paper presents a VI-CMOS image sensor that was designed at the University of Alberta, and fabricated with the help of CMC Microsystems and Micralyne Inc. To realize prototypes, CMOS dies with logarithmic active pixels were prepared in a commercial process, and photodetector dies with metal-semiconductor-metal devices were prepared in a custom process using hydrogenated amorphous silicon. The paper also describes a digital camera that was developed to test the prototype. In this camera, scenes captured by the image sensor are read using an FPGA board, and sent in real time to a PC over USB for data processing and display. Experimental results show that the VI-CMOS prototype has a higher dynamic range and a lower dark limit than conventional electronic image sensors

Global temperature calibration of the alkenone unsaturation index (UK′37) in surface waters and comparison with surface sediments

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 7 (2006): Q02005, doi:10.1029/2005GC001054.In this paper, we compile the current surface seawater C37 alkenone unsaturation (UK′37) measurements (n=629, −1 to 30°C temperature range) to derive a global, field-based calibration of UK′37 with alkenone production temperature. A single nonlinear “global” surface water calibration of UK′37 accurately predicts alkenone production temperatures over the diversity of modern-day oceanic environments and alkenone-synthesizing populations (T=−0.957 + 54.293(UK′37) − 52.894(UK′37)2 + 28.321(UK′37)3, r2=0.97, n=567). The mean standard error of estimation is 1.2°C with insignificant bias in estimated production temperature among the different ocean regions sampled. An exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients (e.g., the Brazil-Malvinas Confluence). In contrast to the surface water data, the calibration of UK′37 in surface sediments with overlying annual mean sea surface temperature (AnnO) is best fit by a linear model (AnnO=29.876(UK′37) − 1.334, r2=0.97, n=592). The standard error of estimation (1.1°C) is similar to that of the surface water production calibration, but a higher degree of bias is observed among the regional data sets. The sediment calibration differs significantly from the surface water calibration. UK′37 in surface sediments is consistently higher than that predicted from AnnO and the surface water production temperature calibration, and the magnitude of the offset increases as the surface water AnnO decreases. We apply the global production temperature calibration to the coretop UK′37 data to estimate the coretop alkenone integrated production temperature (coretop IPT) and compare this with the overlying annual mean sea surface temperature (AnnO). We use simple models to explore the possible causes of the deviation observed between the coretop temperature signal, as estimated by UK′37, and AnnO. Our results indicate that the deviation can best be explained if seasonality in production and/or thermocline production as well as differential degradation of 37:3 and 37:2 alkenones both affect the sedimentary alkenone signal.C.R. acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG)

Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers

: Modern humans have populated Europe for more than 45,000 years1,2. Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period3. Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe4, but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants

Palaeogenomics of Upper Palaeolithic to Neolithic European hunter-gatherers

Publisher Copyright: © 2023, The Author(s).Modern humans have populated Europe for more than 45,000 years1,2. Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period3. Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe4, but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants.Peer reviewe