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Search Results: 1 - 10 of 6023 matches for " Zachary Anderson "
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Preservice Teachers' Mathematical Task Posing: An Opportunity for Coordination of Perspectives
Zachary Rutledge,Anderson Norton
Mathematics Educator , 2008,
Abstract: This article provides detailed analysis, from a radical constructivist perspective, of a sequence of letter-writing exchanges between a preservice secondary mathematics teacher and a high school student. This analysis shows the ways in which the preservice teacher gained understanding of the high school student’s mathematics and attempted to pose tasks accordingly, leading to a fruitful mathematical exchange. In addition, this article also considers the same exchange from what could be considered broadly as a situated perspective towards learning. We conclude by suggesting that these perspectives could be considered compatible within this study if a distinction is made between the student’s point of view and the researcher’s.
Measuring Task Posing Cycles: Mathematical Letter Writing Between Preservice Teachers and Algebra Students
Anderson Norton,Zachary Rutledge
Mathematics Educator , 2009,
Abstract: In a secondary school mathematics teaching methods course, a research team engaged 22 preservice secondary teachers (PSTs) in designing and posing tasks to algebra students through weekly letter writing. The goal of the tasks was for PSTs to elicit responses that would indicate student engagement in the mathematical processes described by NCTM (2000) and Bloom’s taxonomy (Bloom, Englehart, Furst, Hill, & Krathwohl, 1956), as well as student engagement in the highest levels of cognitive activity described by Stein, Smith, Henningsen, and Silver (2000). This paper describes our efforts to design reliable measures that assess student engagement in those processes as a product of the evolving relationship within letter-writing pairs. Results indicate that some processes are easier to elicit and assess than others, but that the letter-writing pairs demonstrated significant growth in terms of elicited processes. Although it is impossible to disentangle student factors from teacher factors that contributed to that growth, we find value in the authenticity of assessing PSTs’ tasks in terms of student engagement rather than student-independent task analysis.
Finishing Cattle in All-Natural and Conventional Production Systems  [PDF]
Zachary K. Smith, Peter T. Anderson, Bradley J. Johnson
Open Journal of Animal Sciences (OJAS) , 2020, DOI: 10.4236/ojas.2020.102013
Abstract: Beef cattle producers in the North America have a variety of production and marketing options and must choose the best production system for their situation. This review describes considerations involved in choosing between feeding cattle conventionally versus feeding them in programs that prohibit the use of certain technologies. Data from peer-reviewed journals, extension publications, nutritional consultants, governmental organizations, and feed companies were used to construct this review. Most cattle in North America are fed in conventional production systems. Conventional beef production systems typically use steroidal implants, ionophores, and beta-adrenergic agonists to improve animal productivity; as well as feed grade and injectable antimicrobials to control, treat or prevent disease and improve animal health. These technologies have been shown to lower the cost of production, allowing for beef to be competitive in the global protein market. Some consumers have expressed a preference for beef produced without these technologies. These “All-natural” (AN) cattle may bring a premium price in the market. The economic impact of differing productions systems can be described in relation to 1) cost of production, 2) operating costs of the feedlot, 3) price paid for feeder calves, and 4) price received for fed cattle. Conventional production provides the most favorable outcome for factors 1, 2, and 3, while AN production provides the most favorable outcome for item 4. There are also industry wide and societal aspects related to differing beef production systems related to health and safety of beef, land use, and cost of production allowing for a greater share of the global protein market. Technologies used in conventional production are critical tools to North American beef production. Differences in efficiencies between each type of non-conventional production systems must be re-captured in added premiums when cattle are marketed and sold. Premiums for AN cattle are enticing, but the true differences in the cost of production between the AN and conventional cattle must be evaluated in order for a producer to make the correct decision for their operation.
In situ imaging of vortices in Bose-Einstein condensates
Kali E. Wilson,Zachary L. Newman,Joseph D. Lowney,Brian P. Anderson
Physics , 2014, DOI: 10.1103/PhysRevA.91.023621
Abstract: Laboratory observations of vortex dynamics in Bose-Einstein condensates (BECs) are essential for determination of many aspects of superfluid dynamics in these systems. We present a novel application of dark-field imaging that enables \texttt{\it in situ} detection of two-dimensional vortex distributions in single-component BECs, a step towards real-time measurements of complex two-dimensional vortex dynamics within a single BEC. By rotating a $^{87}$Rb BEC in a magnetic trap, we generate a triangular lattice of vortex cores in the BEC, with core diameters on the order of 400 nm and cores separated by approximately 9 $\mu$m. We have experimentally confirmed that the positions of the vortex cores can be determined without the need for ballistic expansion of the BEC.
Realization of an all-dielectric zero-index optical metamaterial
Parikshit Moitra,Yuanmu Yang,Zachary Anderson,Ivan I. Kravchenko,Dayrl P. Briggs,Jason Valentine
Physics , 2013, DOI: 10.1038/nphoton.2013.214
Abstract: Metamaterials offer unprecedented flexibility for manipulating the optical properties of matter, including the ability to access negative index, ultra-high index and chiral optical properties. Recently, metamaterials with near-zero refractive index have drawn much attention. Light inside such materials experiences no spatial phase change and extremely large phase velocity, properties that can be applied for realizing directional emission, tunneling waveguides, large area single mode devices, and electromagnetic cloaks. However, at optical frequencies previously demonstrated zero- or negative-refractive index metamaterials require the use of metallic inclusions, leading to large ohmic loss, a serious impediment to device applications. Here, we experimentally demonstrate an impedance matched zero-index metamaterial at optical frequencies based on purely dielectric constituents. Formed from stacked silicon rod unit cells, the metamaterial possesses a nearly isotropic low-index response leading to angular selectivity of transmission and directive emission from quantum dots placed within the material.
Laboratory Driven, Lean-to-Adaptive Prototyping in Parallel for Web Software Project Identification and Application Development in Health Science Research  [PDF]
Zachary Dwight, Alexa Barnes
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.52010
Abstract: Clinical research laboratories, bioinformatics core facilities, and health science organizations often rely on heavy planning based software development models to propose, build, and distribute software as a consumable product. Projects in non-agile software life cycles tend to have rigid “plan-design-build” milestones, increasing the amount of time needed for software development completion. Though the classic software development approach is needed for large-scale and organizational projects, clinical research laboratories can expedite software development while maintaining quality by using lean prototyping as a condition of project advancement to a committed adaptive software development cycle. Software projects benefit from an agile methodology due to the active and changing requirements often guided by experimental data driven models. We describe a lean to adaptive method used in parallel with laboratory bench work to develop quality software quickly that meets the requirements of a fast-paced research environment and reducing time to production, providing immediate value to the end user, and limiting unnecessary development practices in favor of results.
Data Stream Subspace Clustering for Anomalous Network Packet Detection  [PDF]
Zachary Miller, Wei Hu
Journal of Information Security (JIS) , 2012, DOI: 10.4236/jis.2012.33027
Abstract: As the Internet offers increased connectivity between human beings, it has fallen prey to malicious users who exploit its resources to gain illegal access to critical information. In an effort to protect computer networks from external attacks, two common types of Intrusion Detection Systems (IDSs) are often deployed. The first type is signature-based IDSs which can detect intrusions efficiently by scanning network packets and comparing them with human-generated signatures describing previously-observed attacks. The second type is anomaly-based IDSs able to detect new attacks through modeling normal network traffic without the need for a human expert. Despite this advantage, anomaly-based IDSs are limited by a high false-alarm rate and difficulty detecting network attacks attempting to blend in with normal traffic. In this study, we propose a StreamPreDeCon anomaly-based IDS. StreamPreDeCon is an extension of the preference subspace clustering algorithm PreDeCon designed to resolve some of the challenges associated with anomalous packet detection. Using network packets extracted from the first week of the DARPA '99 intrusion detection evaluation dataset combined with Generic Http, Shellcode and CLET attacks, our IDS achieved 94.4% sensitivity and 0.726% false positives in a best case scenario. To measure the overall effectiveness of the IDS, the average sensitivity and false positive rates were calculated for both the maximum sensitivity and the minimum false positive rate. With the maximum sensitivity, the IDS had 80% sensitivity and 9% false positives on average. The IDS also averaged 63% sensitivity with a 0.4% false positive rate when the minimal number of false positives is needed. These rates are an improvement on results found in a previous study as the sensitivity rate in general increased while the false positive rate decreased.
Breaking of valley degeneracy by magnetic field in monolayer MoSe2
David MacNeill,Colin Heikes,Kin Fai Mak,Zachary Anderson,Andor Kormányos,Viktor Zólyomi,Jiwoong Park,Daniel C. Ralph
Physics , 2014, DOI: 10.1103/PhysRevLett.114.037401
Abstract: Using polarization-resolved photoluminescence spectroscopy, we investigate valley degeneracy breaking by out-of-plane magnetic field in back-gated monolayer MoSe$_2$ devices. We observe a linear splitting of $-0.22 \frac{\text{meV}}{\text{T}}$ between luminescence peak energies in $\sigma_{+}$ and $\sigma_{-}$ emission for both neutral and charged excitons. The optical selection rules of monolayer MoSe$_2$ couple photon handedness to the exciton valley degree of freedom, so this splitting demonstrates valley degeneracy breaking. In addition, we find that the luminescence handedness can be controlled with magnetic field, to a degree that depends on the back-gate voltage. An applied magnetic field therefore provides effective strategies for control over the valley degree of freedom.
Formation of Mercury(II)-Glutathione Conjugates Examined Using High Mass Accuracy Mass Spectrometry  [PDF]
Zachary Fine, Troy D. Wood
International Journal of Analytical Mass Spectrometry and Chromatography (IJAMSC) , 2013, DOI: 10.4236/ijamsc.2013.12011
Abstract:

Maternal exposure to Hg(II) during pregnancy has been identified as a potential causal factor in the development of severe neurobehavioral disorders. Children with autism have been identified with lower reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios, and GSH is known to strongly bind Hg(II). In order to gain insight into the mechanism by which GSH binds Hg(II), high resolution mass spectrometry coupled with tandem mass spectrometry was utilized to examine the conjugation process. While the 1:1 Hg(II):GSH conjugate is not formed immediately upon mixing aqueous solutions of Hg(II) and GSH, two species containing Hg(II) are observed:the 1:2 Hg(II):GSH conjugate, [(GS)2 Hg + H+], and a second Hg(II)-containing species around m/z 544. Interestingly, this species at m/z 544 decreases in time while the presence of the 1:1 Hg(II):GSH conjugate increases, suggesting that m/z 544 is an intermediate in the formation of the 1:1 conjugate. Experiments using the high mass accuracy capability of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry coupled to an electrospray ionization source indicate that the intermediate species is [GSH + HgCl]+, andnotthe 1:1 conjugate [Hg(GSH) – H + 2H2O]+postulated in previous literature. Further confirmation of [GSH + HgCl]+ is supported by collisionofinduced dissociation experiments, which show neutral loss of HCl from the intermediate and loss of the N- and C-terminal amino acids, indicating binding of Hg(II) at the Cys residue.

Mycobacterium drug responses
Zachary Perlman
Genome Biology , 2000, DOI: 10.1186/gb-2000-1-1-reports037
Abstract: INH induces a significant increase in the transcription of 14 genes. These include a number of genes known, or indicated by homology, to be involved in fatty acid biosynthesis, a gene for a transporter protein of unknown substrate, and genes for four proteins of unknown function. The authors note that the transport protein, which is already known to be correlated with pathogenicity, might represent a particularly promising new candidate drug target. The same genes are upregulated in an INH-resistant strain in response to ethionamide, whereas other compounds toxic to the bacterium provoke different response profiles. The authors also observe similarities in the patterns of upregulation of a subset of the biosynthetic genes that are clustered in an operon-like fashion in the genome, and suggest roles for other genes on the basis of differences in the time-course of their induction.Information about the M. tuberculosis H37Rv genome project, along with some relevant links, is maintained at the Sanger Centre.The idea that transcriptional arrays might be useful in drug target identification has been postulated for a while, and this paper may come to be viewed as an important proof-of-principle towards this end. Wilson et al. also highlight the ability of whole-genome analysis to bring otherwise obscure genes into the spotlight of potential therapeutic interest.Proceedings of the National Academy of Sciences of the United States of AmericaM. tuberculosis H37Rv genome project
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