1,106 research outputs found
Ethnic Studies in Academe: Challenges and Prospects for the 21st Century. NAES Plenary Session , Kansas City,1995 Missouri, March 19, 1994
The primary intent of organizing the plenary that follows was to engage a number of dedicated and experienced ethnic studies scholar-activists in a focused conversation on the current state of ethnic studies in the academy. At this point many of us have been involved in ethnic studies for more than twenty years. The perspectives and observations offered in this monograph are transcribed from the recordings of the plenary. It offers the reader a far-ranging discussion of the field, its history, its struggles, its pedagogy, and some of its underlying principles
Phase imaging with intermodulation atomic force microscopy
Intermodulation atomic force microscopy (IMAFM) is a dynamic mode of atomic
force microscopy (AFM) with two-tone excitation. The oscillating AFM cantilever
in close proximity to a surface experiences the nonlinear tip-sample force
which mixes the drive tones and generates new frequency components in the
cantilever response known as intermodulation products (IMPs). We present a
procedure for extracting the phase at each IMP and demonstrate phase images
made by recording this phase while scanning. Amplitude and phase images at
intermodulation frequencies exhibit enhanced topographic and material contrast.Comment: 6 pages, 6 page
Formation of Halonitromethanes and Iodo-Trihalomethanes in Drinking Water Summary
The main purpose of this study was to examine the conditions and precursors involved in the formation of two emerging classes of disinfection by-products (DBPs), halonitromethanes (HNMs) and iodo-trihalomethanes (I-THMs), which are not currently regulated but have been observed in some drinking water systems
The Role of Nonlinear Dynamics in Quantitative Atomic Force Microscopy
Various methods of force measurement with the Atomic Force Microscope (AFM)
are compared for their ability to accurately determine the tip-surface force
from analysis of the nonlinear cantilever motion. It is explained how
intermodulation, or the frequency mixing of multiple drive tones by the
nonlinear tip-surface force, can be used to concentrate the nonlinear motion in
a narrow band of frequency near the cantilevers fundamental resonance, where
accuracy and sensitivity of force measurement are greatest. Two different
methods for reconstructing tip-surface forces from intermodulation spectra are
explained. The reconstruction of both conservative and dissipative tip-surface
interactions from intermodulation spectra are demonstrated on simulated data.Comment: 25 pages (preprint, double space) 7 figure
Involvement of AmphiREL, a Rel-like gene identified in Brachiastoma belcheri, in LPS-induced response: Implication for evolution of Rel subfamily genes
AbstractRel/NF-ÎşB family genes are important transcriptional factors regulating vital activities of immunity response, but no Rel/NF-ÎşB gene has been identified in amphioxus. In this study, we have not only identified and characterized a Rel-like gene from Brachiastoma belcheri, but also extensively studied the evolution of Rel gene subfamily. We found that: 1) the amphioxus genome contains an AmphiREL gene encoding a Rel/NF-ÎşB homolog, and AmphiREL gene was involved in the innate immune response of LPS stimulation in amphioxus. 2) Gene synteny comparison and structure comparison suggested that AmphiREL is an orthologous gene of human RELB, and is a paralogous gene of human RELA and REL. 3) Structural changes of Rel subfamily proteins are diverse during the evolution process, and imply their functional diversity. 4) The Rel subfamily genes have undergone very strong purifying selection. Together, our results provide important clues for understanding the evolution and function of Rel subfamily genes
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Bayesian Inference of Spatial Organizations of Chromosomes
Knowledge of spatial chromosomal organizations is critical for the study of transcriptional regulation and other nuclear processes in the cell. Recently, chromosome conformation capture (3C) based technologies, such as Hi-C and TCC, have been developed to provide a genome-wide, three-dimensional (3D) view of chromatin organization. Appropriate methods for analyzing these data and fully characterizing the 3D chromosomal structure and its structural variations are still under development. Here we describe a novel Bayesian probabilistic approach, denoted as “Bayesian 3D constructor for Hi-C data” (BACH), to infer the consensus 3D chromosomal structure. In addition, we describe a variant algorithm BACH-MIX to study the structural variations of chromatin in a cell population. Applying BACH and BACH-MIX to a high resolution Hi-C dataset generated from mouse embryonic stem cells, we found that most local genomic regions exhibit homogeneous 3D chromosomal structures. We further constructed a model for the spatial arrangement of chromatin, which reveals structural properties associated with euchromatic and heterochromatic regions in the genome. We observed strong associations between structural properties and several genomic and epigenetic features of the chromosome. Using BACH-MIX, we further found that the structural variations of chromatin are correlated with these genomic and epigenetic features. Our results demonstrate that BACH and BACH-MIX have the potential to provide new insights into the chromosomal architecture of mammalian cells.Statistic
Improving Multiple-CMP Systems Using Token Coherence
Improvements in semiconductor technology now enable Chip Multiprocessors (CMPs). As many future computer systems will use one or more CMPs and support shared memory, such systems will have caches that must be kept coherent.
Coherence is a particular challenge for Multiple-CMP (M-CMP) systems. One approach is to use a hierarchical protocol that explicitly separates the intra-CMP coherence protocol from the inter-CMP protocol, but couples them hierarchically to maintain coherence. However, hierarchical protocols are complex, leading to subtle, difficult-to-verify race conditions. Furthermore, most previous hierarchical protocols use directories at one or both levels, incurring indirections—and thus extra latency—for sharing misses, which are common in commercial workloads.
In contrast, this paper exploits the separation of correctness substrate and performance policy in the recently-proposed token coherence protocol to develop the first M-CMP coherence protocol that is flat for correctness, but hierarchical for performance. Via model checking studies, we show that flat correctness eases verification. Via simulation with micro-benchmarks, we make new protocol variants more robust under contention. Finally, via simulation with commercial workloads on a commercial operating system, we show that new protocol variants can be 10-50% faster than a hierarchical directory protocol
Interaction imaging with amplitude-dependence force spectroscopy
Knowledge of surface forces is the key to understanding a large number of
processes in fields ranging from physics to material science and biology. The
most common method to study surfaces is dynamic atomic force microscopy (AFM).
Dynamic AFM has been enormously successful in imaging surface topography, even
to atomic resolution, but the force between the AFM tip and the surface remains
unknown during imaging. Here, we present a new approach that combines high
accuracy force measurements and high resolution scanning. The method, called
amplitude-dependence force spectroscopy (ADFS) is based on the
amplitude-dependence of the cantilever's response near resonance and allows for
separate determination of both conservative and dissipative tip-surface
interactions. We use ADFS to quantitatively study and map the nano-mechanical
interaction between the AFM tip and heterogeneous polymer surfaces. ADFS is
compatible with commercial atomic force microscopes and we anticipate its
wide-spread use in taking AFM toward quantitative microscopy
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