6,700 research outputs found
The Data Big Bang and the Expanding Digital Universe: High-Dimensional, Complex and Massive Data Sets in an Inflationary Epoch
Recent and forthcoming advances in instrumentation, and giant new surveys,
are creating astronomical data sets that are not amenable to the methods of
analysis familiar to astronomers. Traditional methods are often inadequate not
merely because of the size in bytes of the data sets, but also because of the
complexity of modern data sets. Mathematical limitations of familiar algorithms
and techniques in dealing with such data sets create a critical need for new
paradigms for the representation, analysis and scientific visualization (as
opposed to illustrative visualization) of heterogeneous, multiresolution data
across application domains. Some of the problems presented by the new data sets
have been addressed by other disciplines such as applied mathematics,
statistics and machine learning and have been utilized by other sciences such
as space-based geosciences. Unfortunately, valuable results pertaining to these
problems are mostly to be found only in publications outside of astronomy. Here
we offer brief overviews of a number of concepts, techniques and developments,
some "old" and some new. These are generally unknown to most of the
astronomical community, but are vital to the analysis and visualization of
complex datasets and images. In order for astronomers to take advantage of the
richness and complexity of the new era of data, and to be able to identify,
adopt, and apply new solutions, the astronomical community needs a certain
degree of awareness and understanding of the new concepts. One of the goals of
this paper is to help bridge the gap between applied mathematics, artificial
intelligence and computer science on the one side and astronomy on the other.Comment: 24 pages, 8 Figures, 1 Table. Accepted for publication: "Advances in
Astronomy, special issue "Robotic Astronomy
Role of HOX Genes in Stem Cell Differentiation and Cancer.
HOX genes encode an evolutionarily conserved set of transcription factors that control how the phenotype of an organism becomes organized during development based on its genetic makeup. For example, in bilaterian-type animals, HOX genes are organized in gene clusters that encode anatomic segment identity, that is, whether the embryo will form with bilateral symmetry with a head (anterior), tail (posterior), back (dorsal), and belly (ventral). Although HOX genes are known to regulate stem cell (SC) differentiation and HOX genes are dysregulated in cancer, the mechanisms by which dysregulation of HOX genes in SCs causes cancer development is not fully understood. Therefore, the purpose of this manuscript was (i) to review the role of HOX genes in SC differentiation, particularly in embryonic, adult tissue-specific, and induced pluripotent SC, and (ii) to investigate how dysregulated HOX genes in SCs are responsible for the development of colorectal cancer (CRC) and acute myeloid leukemia (AML). We analyzed HOX gene expression in CRC and AML using information from The Cancer Genome Atlas study. Finally, we reviewed the literature on HOX genes and related therapeutics that might help us understand ways to develop SC-specific therapies that target aberrant HOX gene expression that contributes to cancer development
An APC:WNT Counter-Current-Like Mechanism Regulates Cell Division Along the Human Colonic Crypt Axis: A Mechanism That Explains How APC Mutations Induce Proliferative Abnormalities That Drive Colon Cancer Development.
APC normally down-regulates WNT signaling in human colon, and APC mutations cause proliferative abnormalities in premalignant crypts leading to colon cancer, but the mechanisms are unclear at the level of spatial and functional organization of the crypt. Accordingly, we postulated a counter-current-like mechanism based on gradients of factors (APC;WNT) that regulate colonocyte proliferation along the crypt axis. During crypt renewal, stem cells (SCs) at the crypt bottom generate non-SC daughter cells that proliferate and differentiate while migrating upwards. The APC concentration is low at the crypt bottom and high at the top (where differentiated cells reside). WNT signaling, in contrast, is high at the bottom (where SCs reside) and low at the top. Given that WNT and APC gradients are counter to one another, we hypothesized that a counter-current-like mechanism exists. Since both APC and WNT signaling components (e.g., survivin) are required for mitosis, this mechanism establishes a zone in the lower crypt where conditions are optimal for maximal cell division and mitosis orientation (symmetric versus asymmetric). APC haploinsufficiency diminishes the APC gradient, shifts the proliferative zone upwards, and increases symmetric division, which causes SC overpopulation. In homozygote mutant crypts, these changes are exacerbated. Thus, APC-mutation-induced changes in the counter-current-like mechanism cause expansion of proliferative populations (SCs, rapidly proliferating cells) during tumorigenesis. We propose this mechanism also drives crypt fission, functions in the crypt cycle, and underlies adenoma development. Novel chemoprevention approaches designed to normalize the two gradients and readjust the proliferative zone downwards, might thwart progression of these premalignant changes
Low input weed management in field peas
Two trials were conducted on a Templeton silt loam soil at Lincoln University, New Zealand (43 ° 38' S, 172 ° 28' E.) in 2007/08. The aim was to compare the competitive ability of different pea canopy architectures as influenced by genotype, population, sowing date and their interaction as a means of low input weed control strategy. The first experiment had three sowing dates, two pea genotypes and two herbicide treatments. Experiment 2 treatments were a factorial combination of four pea populations and three sown artificial weed populations. A significant sowing date x pea genotype interaction showed that in the August sowing genotype had no effect on seed yield. However, in September sown plots Pro 7035 yielded 559 g m⁻², which was 40% more than Midichi, and in the October sowing, the difference was 87% more. Herbicide-sprayed peas produced 19% more seed (508 g m⁻²) than the unsprayed plants. When no weeds were sown, the highest pea total dry matter (TDM) of 1,129 g m⁻² occurred at 200 plants m⁻². This was more than twice (513 g m⁻²) the yield of the lowest population (50 plants m⁻²). There was distinct variation in the weed spectrum over time. Coronopus didymus, Stellaria media and Lolium spp were present in relatively large numbers throughout the season. Some weeds only occurred late in the season meaning they could be successfully controlled by early sowing. It could be concluded that it is possible to obtain high pea yields by using the right sowing date and appropriate seed rate as a means of low input weed management strategy.Lincoln University Research Committee funded this research. Plant Research New
Zealand limited provided the pea seed and the fungicides that were used for all the trials
Necklace Radio Transmitter Attachment For Pheasants
We tested a pre-assembled, necklace-radio-transmitter-attachment design on female ring-necked pheasants (Phasianus colchicus) in northern Iowa. Birds were captured by nightlighting and bait trapping between September 1989 and March 1990. Radio transmitters were attached to 128 using a wire necklace. Two birds had problems adapting to the necklace, and 3 birds removed them. Twenty-three birds were still alive and wearing necklaces at the end of the study, for an average of 318 (SD= ± 52) days. Ease of attachment, long durability, light weight, and minimal bulk make the necklace an effective alternative to harness and poncho mounts
Institutionalization of a Software Process Innovation in Large Financial Services Organization: A Case of Re-Invention of a Requirements Inspection Process
Failed software development projects are expensive for society and individual companies. Studies indicate defects in requirements specification are the cause of many of these failures. A large financial services company recently implemented a software requirements inspection process based on the Fagan model with the assistance of the authors. Subsequently, the process was re-invented by users to be less formal, and the organization changed the official process to be consistent with the new process to encourage institutionalization. This change formed a natural experiment. The authors examined inspection documentation under both versions of the process to determine if there were any significant differences in the effectiveness of the versions or their implementation. They found that unplanned implementation effects of the new approach made it impossible to determine whether it was more effective than the original approach. Policy implications are discussed
Reliability Modeling for the Advanced Electric Power Grid
The advanced electric power grid promises a self-healing infrastructure using distributed, coordinated, power electronics control. One promising power electronics device, the Flexible AC Transmission System (FACTS), can modify power flow locally within a grid. Embedded computers within the FACTS devices, along with the links connecting them, form a communication and control network that can dynamically change the power grid to achieve higher dependability. The goal is to reroute power in the event of transmission line failure. Such a system, over a widespread area, is a cyber-physical system. The overall reliability of the grid is a function of the respective reliabilities of its two major subsystems, namely, the FACTS network and the physical components that comprise the infrastructure. This paper presents a mathematical model, based on the Markov chain imbeddable structure, for the overall reliability of the grid. The model utilizes a priori knowledge of reliability estimates for the FACTS devices and the communications links among them to predict the overall reliability of the power grid
The anti-cancer effect of retinoic acid signaling in CRC occurs via decreased growth of ALDH+ colon cancer stem cells and increased differentiation of stem cells
Background: Tumorigenesis is driven by stem cell (SC) overpopulation. BecauseALDH is both a marker for SCs in many tissues and a key enzyme in retinoid acid (RA)signaling, we studied RA signaling in normal and malignant colonic SCs.Hypothesis: RA signaling regulates growth and differentiation of ALDH+ colonicSCs dysregulation of RA signaling contributes to SC overpopulation and colorectalcancer (CRC) development.Methods: We analyzed normal and malignant colonic tissues and CRC cell linesto see if retinoid receptors (RXR &RAR) are exclusively expressed in ALDH+ SCs,and if RA signaling changes during CRC development. We determined whether RAsignaling regulates cancer SC (CSC) proliferation, differentiation, sphere formation,and population size.Results: RXR &RAR were expressed in ALDH+ colonic SCs, but not in MCM2+proliferative cells. Western blotting/immunostaining of CRCs revealed that RAsignaling components become overexpressed in parallel with ALDH overexpression,which coincides with the known overpopulation of ALDH+ SCs that occurs during,and drives, CRC development. Treatment of SCs with all-trans retinoic acid (ATRA)decreased proliferation, sphere formation and ALDH+ SC population size, and induceddifferentiation along the neuroendocrine cell (NEC) lineage.Conclusions: Retinoid signaling, by regulating ALDH+ colonic CSCs, decreases SCproliferation, sphere formation, and population size, and increases SC differentiation toNECs. Dysregulation of RA signaling in colonic SCs likely contributes to overpopulationof ALDH+ SCs and CRC growth.Implications: That retinoid receptors RXR and RAR are selectively expressed inALDH+ SCs indicates RA signaling mainly occurs via ALDH+ SCs, which provides amechanism to selectively target CSCs. © 2018 Impact Journals LLC. All rights reserved
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