427 research outputs found
Non-destructive evaluation of reclaimed asphalt cement concrete
Reclaimed asphalt (RA) has been increasingly used as an alternative aggregate in the manufacture of low to medium strength cement concrete. It is the aim here to investigate the behaviour and properties of concrete made with RA, using ultrasonic pulse velocity (UPV). Most previous investigations using UPV have been into gravel concrete starting between 1–7 days and up to 28 days. In this research, the application of UPV has been extended to cement concrete made with RA aggregate at the very early age, taken here as the period starting immediately after concrete mixing and up to 28 days. An early age test system for continuous ultrasonic monitoring of fresh concretes has been used to assess important properties, such as early age strength, using UPV measurements. Concrete mixes with different water/cement ratios (.4–.7) were used. Empirical models have been produced relating compressive strength and UPV for early age RA concrete
Superrigid subgroups and syndetic hulls in solvable Lie groups
This is an expository paper. It is not difficult to see that every group
homomorphism from the additive group Z of integers to the additive group R of
real numbers extends to a homomorphism from R to R. We discuss other examples
of discrete subgroups D of connected Lie groups G, such that the homomorphisms
defined on D can ("virtually") be extended to homomorphisms defined on all of
G. For the case where G is solvable, we give a simple proof that D has this
property if it is Zariski dense. The key ingredient is a result on the
existence of syndetic hulls.Comment: 17 pages. This is the final version that will appear in the volume
"Rigidity in Dynamics and Geometry," edited by M. Burger and A. Iozzi
(Springer, 2002
Discovery of cellular regulation by protein degradation
What follows is a story of some of the lab’s adventures mentioned above, including the inventions of new biochemical and genetic methods. This account stems, in part, from previous descriptions of the early history of the Ub field (31,32). Another antecedent is an interview I gave to Dr. Istvan Hargittai, a distinguished Hungarian chemist. It describes my life and science, including the early years in Moscow, the 1977 escape from the former Soviet Union, the essentially accidental hiring of me by MIT, and the work that ensued (33). The narrative below borrows from these sources, and mentions our more recent contributions as well
Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential
The S-wave effective range parameters of the neutron-deuteron (nd) scattering
are derived in the Faddeev formalism, using a nonlocal Gaussian potential based
on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy
eigenphase shift is sufficiently attractive to reproduce predictions by the
AV18 plus Urbana three-nucleon force, yielding the observed value of the
doublet scattering length and the correct differential cross sections below the
deuteron breakup threshold. This conclusion is consistent with the previous
result for the triton binding energy, which is nearly reproduced by fss2
without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy
Rewriting a Deep Generative Model
A deep generative model such as a GAN learns to model a rich set of semantic
and physical rules about the target distribution, but up to now, it has been
obscure how such rules are encoded in the network, or how a rule could be
changed. In this paper, we introduce a new problem setting: manipulation of
specific rules encoded by a deep generative model. To address the problem, we
propose a formulation in which the desired rule is changed by manipulating a
layer of a deep network as a linear associative memory. We derive an algorithm
for modifying one entry of the associative memory, and we demonstrate that
several interesting structural rules can be located and modified within the
layers of state-of-the-art generative models. We present a user interface to
enable users to interactively change the rules of a generative model to achieve
desired effects, and we show several proof-of-concept applications. Finally,
results on multiple datasets demonstrate the advantage of our method against
standard fine-tuning methods and edit transfer algorithms.Comment: ECCV 2020 (oral). Code at https://github.com/davidbau/rewriting. For
videos and demos see https://rewriting.csail.mit.edu
Generalization and fine mapping of red blood cell trait genetic associations to multiâ ethnic populations: The PAGE study
Red blood cell (RBC) traits provide insight into a wide range of physiological states and exhibit moderate to high heritability, making them excellent candidates for genetic studies to inform underlying biologic mechanisms. Previous RBC trait genomeâ wide association studies were performed primarily in Europeanâ or Asianâ ancestry populations, missing opportunities to inform understanding of RBC genetic architecture in diverse populations and reduce intervals surrounding putative functional SNPs through fineâ mapping. Here, we report the first fineâ mapping of 6 correlated (Pearson’s r range: |0.04â 0.92|) RBC traits in up to 19â 036 African Americans and 19â 562 Hispanic/Latino participants of the Population Architecture using Genomics and Epidemiology consortium. Transâ ethnic metaâ analysis of race/ethnicâ and studyâ specific estimates for approximately 11â 000 SNPs flanking 13 previously identified association signals as well as 150â 000 additional arrayâ wide SNPs was performed using inverseâ variance metaâ analysis after adjusting for study and clinical covariates. Approximately half of previously reported index SNPâ RBC trait associations generalized to the transâ ethnic study population (pâ <â 1.7 Ã 10â 4); previously unreported independent association signals within the ABO region reinforce the potential for multiple functional variants affecting the same locus. Transâ ethnic fineâ mapping did not reveal additional signals at the HFE locus independent of the known functional variants. Finally, we identified a potential novel association in the Hispanic/Latino study population at the HECTD4/RPL6 locus for RBC count (pâ =â 1.9 Ã 10â 7). The identification of a previously unknown association, generalization of a large proportion of known association signals, and refinement of known association signals all exemplify the benefits of genetic studies in diverse populations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145575/1/ajh25161_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145575/2/ajh25161.pd
Gene duplications and evolution of vertebrate voltage-gated sodium channels
Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Molecular Evolution 63 (2006): 208-221, doi:10.1007/s00239-005-0287-9.Voltage-gated sodium channels underlie action potential generation in excitable tissue.
To establish the evolutionary mechanisms that shaped the vertebrate sodium channel
a-subunit (SCNA) gene family and their encoded Nav1 proteins, we identified all SCNA
genes in several teleost species. Molecular cloning revealed that teleosts have eight
SCNA genes, comparable to the number in another vertebrate lineage, mammals.
Prior phylogenetic analyses had indicated that teleosts and tetrapods share four
monophyletic groups of SCNA genes and that tandem duplications selectively
expanded the number of genes in two of the four mammalian groups. However, the
number of genes in each group varies between teleosts and tetrapods suggesting
different evolutionary histories in the two vertebrate lineages. Our findings from
phylogenetic analysis and chromosomal mapping of Danio rerio genes indicate that
tandem duplications are an unlikely mechanism for generation of the extant teleost
SCNA genes. Instead, analysis of other closely mapped genes in D. rerio supports the
hypothesis that a whole genome duplication was involved in expansion of the SCNA
gene family in teleosts. Interestingly, despite their different evolutionary histories,
mRNA analyses demonstrated a conservation of expression patterns for SCNA
orthologues in teleosts and tetrapods, suggesting functional conservation.The authors’ work was supported by NIH grants (NS 38937; AEN,
ADT and ABR, NS 25513; HHZ and YL and NSF IBN 0236147; MCJ)
Patterns of Multimorbidity in the Aged Population. Results from the KORA-Age Study
Multimorbidity is a common problem in aged populations with a wide range of individual and societal consequences. The objective of the study was to explore patterns of comorbidity and multimorbidity in an elderly population using different analytical approaches. Data were gathered from the population-based KORA-Age project, which included 4,127 persons aged 65–94 years living in the city of Augsburg and its two surrounding counties in Southern Germany. Information on the presence of 13 chronic conditions was collected in a standardized telephone interview and a self-administered questionnaire. Patterns of comorbidity and multimorbidity were analyzed using prevalence figures, logistic regression models and exploratory tetrachoric factor analysis. The prevalence of multimorbidity (≥2 diseases) was 58.6% in the total sample. Hypertension and diabetes (Odds Ratio [OR] 2.95, 99.58% confidence interval [CI] [2.19–3.96]), as well as hypertension and stroke (OR 2.00, 99.58% CI [1.26–3.16]) most often occurred in combination. This association was independent of age, sex and the presence of other conditions. Using factor analysis, we identified four patterns of multimorbidity: the first pattern includes cardiovascular and metabolic diseases, the second includes joint, liver, lung and eye diseases, the third covers mental and neurologic diseases and the fourth pattern includes gastrointestinal diseases and cancer. 44% of the persons were assigned to at least one of the four multimorbidity patterns; 14% could be assigned to both the cardiovascular/metabolic and the joint/liver/lung/eye pattern. Further common pairs were the mental/neurologic pattern combined with the cardiovascular/metabolic pattern (7.2%) or the joint/liver/lung/eye pattern (5.3%), respectively. Our results confirmed the existence of co-occurrence of certain diseases in elderly persons, which is not caused by chance. Some of the identified patterns of multimorbidity and their overlap may indicate common underlying pathological mechanisms
Conserved Expression Signatures between Medaka and Human Pigment Cell Tumors
Aberrations in gene expression are a hallmark of cancer cells. Differential tumor-specific transcript levels of single genes or whole sets of genes may be critical for the neoplastic phenotype and important for therapeutic considerations or useful as biomarkers. As an approach to filter out such relevant expression differences from the plethora of changes noted in global expression profiling studies, we searched for changes of gene expression levels that are conserved. Transcriptomes from massive parallel sequencing of different types of melanoma from medaka were generated and compared to microarray datasets from zebrafish and human melanoma. This revealed molecular conservation at various levels between fish models and human tumors providing a useful strategy for identifying expression signatures strongly associated with disease phenotypes and uncovering new melanoma molecules
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