4,005 research outputs found
On the fundamental group of the complement of a complex hyperplane arrangement
We construct two combinatorially equivalent line arrangements in the complex
projective plane such that the fundamental groups of their complements are not
isomorphic. The proof uses a new invariant of the fundamental group of the
complement to a line arrangement of a given combinatorial type with respect to
isomorphisms inducing the canonical isomorphism of the first homology groups.Comment: 12 pages, Latex2e with AMSLaTeX 1.2, no figures; this last version is
almost the same as published in Functional Analysis and its Applications 45:2
(2011), 137-14
Assessing the Benefits of Public Research Within an Economic Framework: The Case of USDA's Agricultural Research Service
Evaluation of publicly funded research can help provide accountability and prioritize programs. In addition, Federal intramural research planning generally involves an institutional assessment of the appropriate Federal role, if any, and whether the research should be left to others, such as universities or the private sector. Many methods of evaluation are available, peer review—used primarily for establishing scientific merit—being the most common. Economic analysis focuses on quantifying ultimate research outcomes, whether measured in goods with market prices or in nonmarket goods such as environmental quality or human health. However, standard economic techniques may not be amenable for evaluating some important public research priorities or for institutional assessments. This report reviews quantitative methods and applies qualitative economic reasoning and stakeholder interviewing methods to the evaluation of economic benefits of Federal intramural research using three case studies of research conducted by USDA’s Agricultural Research Service (ARS). Differences among the case studies highlight the need to select suitable assessment techniques from available methodologies, the limited scope for comparing assessment results across programs, and the inherent difficulty in quantifying benefits in some research areas. When measurement and attribution issues make it difficult to quantify these benefits, the report discusses how qualitative insights based on economic concepts can help research prioritization.Agricultural Research Service, Federal intramural research, publicly funded research, Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety, Livestock Production/Industries, Productivity Analysis,
Short-term emission line and continuum variations in Mrk110
We present results of a variability campaign of Mrk110 performed with the
9.2-m Hobby-Eberly Telescope (HET) at McDonald Observatory. The high S/N
spectra cover most of the optical range. They were taken from 1999 November
through 2000 May. The average interval between the observations was 7.3 days
and the median interval was only 3.0 days. Mrk110 is a narrow-line Seyfert 1
galaxy. During our campaign the continuum flux was in a historically low stage.
Considering the delays of the emission lines with respect to the continuum
variations we could verify an ionization stratification of the BLR. We derived
virial masses of the central black hole from the radial distances of the
different emission lines and from their widths. The calculated central masses
agree within 20%. Furthermore, we identified optical HeI singlet emission lines
emitted in the broad-line region. The observed line fluxes agree with
theoretical predictions. We show that a broad wing on the red side of the
[OIII]5007 line is caused by the HeI singlet line at 5016A.Comment: 11 pages, 16 figures, A&A Latex. Accepted for publication in A&A Main
Journa
Recommended from our members
The iPad six years on: progress and problems for enhancing mobile learning with special reference to fieldwork education
This paper summarises findings from 2010 involving mobile technologies in the Enhancing Fieldwork Learning project. We show, through practical involvement with students and higher education teaching practitioners, that iPads can be used to
facilitate innovative pedagogies and promote active learning in various field and outofclass situations. We also note that iPads and similar smart devices can be useful in
Higher Education in general. The acceptance of Bring Your Own Device (BYOD) is far less common in the HE system in the UK than at secondary level despite the range of apps and development of students’ individual Personal Learning Environments
Hubble Space Telescope Observations of UV Oscillations in WZ Sagittae During the Decline from Outburst
We present a time series analysis of Hubble Space Telescope observations of
WZ Sge obtained in 2001 September, October, November and December as WZ Sge
declined from its 2001 July superoutburst. Previous analysis of these data
showed the temperature of the white dwarf decreased from ~29,000 K to ~18,000
K. In this study we binned the spectra over wavelength to yield ultraviolet
light curves at each epoch that were then analyzed for the presence of the
well-known 27.87 s and 28.96 s oscillations. We detect the 29 s periodicity at
all four epochs, but the 28 s periodicity is absent. The origin of these
oscillations has been debated since their discovery in the 1970s and competing
hypotheses are based on either white dwarf non-radial g-mode pulsations or
magnetically-channelled accretion onto a rotating white dwarf. By analogy with
the ZZ Ceti stars, we argue that the non-radial g-mode pulsation model demands
a strong dependence of pulse period on the white dwarf's temperature. However,
these observations show the 29 s oscillation is independent of the white
dwarf's temperature. Thus we reject the white dwarf non-radial g-mode pulsation
hypothesis as the sole origin of the oscillations. It remains unclear if
magnetically-funnelled accretion onto a rapidly rotating white dwarf (or belt
on the white dwarf) is responsible for producing the oscillations. We also
report the detection of a QPO with period ~18 s in the September light curve.
The amplitudes of the 29 s oscillation and the QPO vary erratically on short
timescales and are not correlated with the mean system brightness nor with each
other.Comment: 20 pages, 3 figures, 1 table; accepted for publication in Ap
Error Avoiding Quantum Codes and Dynamical Stabilization of Grover's Algorithm
An error avoiding quantum code is presented which is capable of stabilizing
Grover's quantum search algorithm against a particular class of coherent
errors. This error avoiding code consists of states only which are factorizable
in the computational basis. Furthermore, its redundancy is smaller than the one
which is achievable with a general error correcting quantum code saturating the
quantum Hamming bound. The fact that this code consists of factorizable states
only may offer advantages for the implementation of quantum gates in the error
free subspace
Application of Volcano Plots in Analyses of mRNA Differential Expressions with Microarrays
Volcano plot displays unstandardized signal (e.g. log-fold-change) against
noise-adjusted/standardized signal (e.g. t-statistic or -log10(p-value) from
the t test). We review the basic and an interactive use of the volcano plot,
and its crucial role in understanding the regularized t-statistic. The joint
filtering gene selection criterion based on regularized statistics has a curved
discriminant line in the volcano plot, as compared to the two perpendicular
lines for the "double filtering" criterion. This review attempts to provide an
unifying framework for discussions on alternative measures of differential
expression, improved methods for estimating variance, and visual display of a
microarray analysis result. We also discuss the possibility to apply volcano
plots to other fields beyond microarray.Comment: 8 figure
The ability to accumulate deoxyuridine triphosphate and cellular response to thymidylate synthase (TS) inhibition
Thymidylate synthase (TS) is an important enzyme catalysing the reductive methylation of dUMP to dTMP that is further metabolized to dTTP for DNA synthesis. Loss of viability following TS inhibition occurs as a consequence of depleted dTTP pools and at least in some cell lines, accumulation of dUTP and subsequent misincorporation of uracil into DNA. The expansion in dUTP pools is largely determined by the expression of the pyrophosphatase, dUTPase. Our previous work has shown that following TS inhibition the ability to accumulate dUTP was associated with an earlier growth inhibitory effect. 3 human lung tumour cell lines and HT29 human colon tumour cells transfected with dUTPase have been used to investigate the relationship between loss of viability following TS inhibition and dUTP accumulation. Cell cycle arrest typical of TS inhibition was an early event in all cell lines and occurred irrespective of the ability to accumulate dUTP or p53 function. However, a large expansion of dUTP pools was associated with mature DNA damage (4 h) and an earlier loss of viability following TS inhibition compared to cells in which dUTP pools were not expanded. In A549 cells damage to mature DNA may have been exacerbated by significantly higher activity of the excision repair enzyme, uracil-DNA glycosylase. Consistent with results using different inhibitors of TS, transfection of dUTPase into HT29 cells significantly reduced the cytotoxicity of a 24 h but not 48 h exposure to ZD9331. Although loss of viability can be mediated through dTTP deprivation alone, the uracil misincorporation pathway resulted in an earlier commitment to cell death. The relevance of this latter pathway in the clinical response to TS inhibitors deserves further investigation. © 2001 Cancer Research Campaign http://www.bjcancer.co
Monotone functions and maps
In [S. Basu, A. Gabrielov, N. Vorobjov, Semi-monotone sets. arXiv:1004.5047v2
(2011)] we defined semi-monotone sets, as open bounded sets, definable in an
o-minimal structure over the reals, and having connected intersections with all
translated coordinate cones in R^n. In this paper we develop this theory
further by defining monotone functions and maps, and studying their fundamental
geometric properties. We prove several equivalent conditions for a bounded
continuous definable function or map to be monotone. We show that the class of
graphs of monotone maps is closed under intersections with affine coordinate
subspaces and projections to coordinate subspaces. We prove that the graph of a
monotone map is a topologically regular cell. These results generalize and
expand the corresponding results obtained in Basu et al. for semi-monotone
sets.Comment: 30 pages. Version 2 appeared in RACSAM. In version 3 Corollaries 1
and 2 were corrected. In version 4 Theorem 3 is correcte
Recommended from our members
Would Bring Your Own Device (BYOD) be welcomed by undergraduate students to support their learning during fieldwork?
This paper reports student perceptions of the benefits and challenges of Bring Your Own Device (BYOD) in a fieldwork context. Student perceptions from six field courses across two institutions have been gathered using questionnaires and focus groups. Whilst a number of studies have focused on BYOD in a classroom context, little research has been undertaken about BYOD in a fieldwork context. The key findings suggest that around one fifth of students were not willing to use their own device during fieldwork citing loss or damage as the main reason. This key challenge is different to that which are found in a classroom which generally focus on network security, connectivity etc. The findings also suggest that some students believe that BYOD can have a negative impact on group work. There is a misalignment here between student and practitioner thinking with previous literature which suggests that practitioners believe BYOD and smart devices can enhance group work. The one key challenge which is found regardless of learning environment is inequality between those who have a device and those who do not
- …