1,382 research outputs found
Comparisons of Supergranule Characteristics During the Solar Minima of Cycles 22/23 and 23/24
Supergranulation is a component of solar convection that manifests itself on
the photosphere as a cellular network of around 35 Mm across, with a turnover
lifetime of 1-2 days. It is strongly linked to the structure of the magnetic
field. The horizontal, divergent flows within supergranule cells carry local
field lines to the cell boundaries, while the rotational properties of
supergranule upflows may contribute to the restoration of the poloidal field as
part of the dynamo mechanism that controls the solar cycle. The solar minimum
at the transition from cycle 23 to 24 was notable for its low level of activity
and its extended length. It is of interest to study whether the convective
phenomena that influences the solar magnetic field during this time differed in
character to periods of previous minima. This study investigates three
characteristics (velocity components, sizes and lifetimes) of solar
supergranulation. Comparisons of these characteristics are made between the
minima of cycles 22/23 and 23/24 using MDI Doppler data from 1996 and 2008,
respectively. It is found that whereas the lifetimes are equal during both
epochs (around 18 h), the sizes are larger in 1996 (35.9 +/- 0.3 Mm) than in
2008 (35.0 +/- 0.3 Mm), while the dominant horizontal velocity flows are weaker
(139 +/- 1 m/s in 1996; 141 +/- 1 m/s in 2008). Although numerical differences
are seen, they are not conclusive proof of the most recent minimum being
inherently unusual.Comment: 22 pages, 5 figures. Solar Physics, in pres
Weakly Coupled Motion of Individual Layers in Ferromagnetic Resonance
We demonstrate a layer- and time-resolved measurement of ferromagnetic
resonance (FMR) in a Ni81Fe19 / Cu / Co93Zr7 trilayer structure. Time-resolved
x-ray magnetic circular dichroism has been developed in transmission, with
resonant field excitation at a FMR frequency of 2.3 GHz. Small-angle (to 0.2
degree), time-domain magnetization precession could be observed directly, and
resolved to individual layers through elemental contrast at Ni, Fe, and Co
edges. The phase sensitivity allowed direct measurement of relative phase lags
in the precession oscillations of individual elements and layers. A weak
ferromagnetic coupling, difficult to ascertain in conventional FMR
measurements, is revealed in the phase and amplitude response of individual
layers across resonance.Comment: 22 pages, 6 figures submitted to Physical Review
Luttinger liquid superlattices
We calculate the correlation functions and the DC conductivity of Luttinger
liquid superlattices, modeled by a repeated pattern of interacting and free
Luttinger liquids. In a specific realization, where the interacting subsystem
is a Hubbard chain, the system exhibits a rich phase diagram with four
different phases: two metals and two compressible insulators. In general, we
find that the effective low energy description amalgamates features of both
types of liquids in proportion to their spatial extent, suggesting the
interesting possibility of `engineered' Luttinger liquids.Comment: RevTeX, 5 pages, 3 figure
Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24
Recently, using Greenwich and Solar Optical Observing Network sunspot group
data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I),
has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg
latitude interval of the Sun's northern hemisphere and in the time-interval of
-1.35 year to +2.15 year from the time of the preceding minimum of a solar
cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of
the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the
areas of the spot groups in 0-10 deg latitude interval of the southern
hemisphere and in the time-interval of 1.0 year to 1.75 year just after the
time of the maximum of the cycle n correlates very well (r=0.966) with the
amplitude of cycle n+1. Using these relations, (1) and (2), the values 112 + or
- 13 and 74 + or -10, respectively, were predicted in Paper I for the amplitude
of the upcoming cycle 24. Here we found that in case of (1), the north-south
asymmetry in the area sum of a cycle n also has a relationship, say (3), with
the amplitude of cycle n+1, which is similar to (1) but more statistically
significant (r=0.968) like (2). By using (3) it is possible to predict the
amplitude of a cycle with a better accuracy by about 13 years in advance, and
we get 103 + or -10 for the amplitude of the upcoming cycle 24. However, we
found a similar but a more statistically significant (r=0.983) relationship,
say (4), by using the sum of the area sum used in (2) and the north-south
difference used in (3). By using (4) it is possible to predict the amplitude of
a cycle by about 9 years in advance with a high accuracy and we get 87 + or - 7
for the amplitude of cycle 24.Comment: 21 pages, 7 figures, Published in Solar Physics 252, 419-439 (2008
Price and income policies
Discussion and objective debate is an important and necessary ingredient of social decision-making in a democracy. Only thus can the public, legislators, administrators and special interest groups inventory and understand the complete range of phenomena relevant for public decision. Discussion and analysis is a method of measurement, for a more complete inventory of goals and sub-goals of public policy and for expression of hypotheses and predictions in respect to outcomes of various policy means. Discussion is the most ancient and universal process for reasoned calculation in social policy, whether this be at the program committee of the 4-H Club or in presidential elections.https://lib.dr.iastate.edu/card_reports/1006/thumbnail.jp
Students as ecologists: Strategies for successful mentorship of undergraduate researchers
Guiding undergraduates through the ecological research process can be incredibly rewarding and present opportunities to break down barriers to inclusion and diversity in scientific disciplines. At the same time, mentoring undergraduate researchers is a complicated process that requires time and flexibility. While many academics receive extensive guidance on how to be successful in research endeavors, we pay much less attention to training in mentorship and working collaboratively with undergraduate students. This paper seeks to provide a framework for successfully collaborating with undergraduates including initial recruitment, development of a contract, fostering student ownership of research projects, and submission of a polished manuscript.While institutions worldwide encourage undergraduate research and publication, little training and professional development are provided to potential mentors. Our paper fills a critical gap in knowledge and provides a framework for academic mentors of all career stages to successfully guide students from question to publication.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149365/1/ece35090_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149365/2/ece35090.pd
The Undergraduate–Postgraduate–Faculty Triad: Unique Functions and Tensions Associated with Undergraduate Research Experiences at Research Universities
We present an exploratory study of how undergraduates' involvement in research influences postgraduates (i.e., graduate and postdoctoral researchers) and faculty. We used a qualitative approach to examine the relationships among undergraduates, postgraduates, and the faculty head in a research group. In this group, undergraduates viewed postgraduates as more approachable than the faculty head both literally and figuratively. Mentorship by postgraduates presented unique challenges for undergraduates, including unrealistic expectations and varying abilities to mentor. The postgraduates and faculty head concurred that undergraduates contributed to the group's success and served as a source of frustration. Postgraduates appreciated the opportunity to observe multiple approaches to mentoring as they saw the faculty head and other postgraduates interact with undergraduates. The faculty head viewed undergraduate research as important for propagating the research community and for gaining insights into undergraduates and their postgraduate mentors. These results highlight how the involvement of undergraduates and postgraduates in research can limit and enhance the research experiences of members of the undergraduate–postgraduate–faculty triad. A number of tensions emerge that we hypothesize are intrinsic to undergraduate research experiences at research universities. Future studies can focus on determining the generalizability of these findings to other groups and disciplines
Domesticating Fears and Fantasies of ‘the East’: integrating the Ottoman legacy within European heritage
'Europe' has no fixed geographical, historical, religious or cultural boundaries. Claims for the existence of European civilization as a discrete construct are continually made yet dissolve on close scrutiny. Here, we examine these claims at one of the grandest points of existential crisis and belonging for Europe, the relationship with the 'Other within': Turkey, the Balkans and Ottoman heritage in Europe. Through a hybrid semiotic and Foucauldian analysis of catalogues of eight high-profile exhibitions in the United Kingdom, Turkey, Belgium and Portugal we argue that an unsettled discursive struggle is at play, in which one 'Europe' articulates 'reconciliation' of profound civilizational difference while another, Ottoman, 'Europe' stakes a claim of right as an intrinsic component of what it means to be European in a contemporary context. We attempt to trace the role of museum marketing in the perennial accommodation/exclusion of the Ottoman Empire as an intrinsic component in the diversity of Europe’s cultural heritage
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