666 research outputs found
On the averaging principle for one-frequency systems. Seminorm estimates for the error
We extend some previous results of our work [1] on the error of the averaging
method, in the one-frequency case. The new error estimates apply to any
separating family of seminorms on the space of the actions; they generalize our
previous estimates in terms of the Euclidean norm. For example, one can use the
new approach to get separate error estimates for each action coordinate. An
application to rigid body under damping is presented. In a companion paper [2],
the same method will be applied to the motion of a satellite around an oblate
planet.Comment: LaTeX, 23 pages, 4 figures. The final version published in Nonlinear
Dynamic
Poisson-Lie group of pseudodifferential symbols
We introduce a Lie bialgebra structure on the central extension of the Lie
algebra of differential operators on the line and the circle (with scalar or
matrix coefficients). This defines a Poisson--Lie structure on the dual group
of pseudodifferential symbols of an arbitrary real (or complex) order. We show
that the usual (second) Benney, KdV (or GL_n--Adler--Gelfand--Dickey) and KP
Poisson structures are naturally realized as restrictions of this Poisson
structure to submanifolds of this ``universal'' Poisson--Lie group.
Moreover, the reduced (=SL_n) versions of these manifolds (W_n-algebras in
physical terminology) can be viewed as subspaces of the quotient (or Poisson
reduction) of this Poisson--Lie group by the dressing action of the group of
functions.
Finally, we define an infinite set of functions in involution on the
Poisson--Lie group that give the standard families of Hamiltonians when
restricted to the submanifolds mentioned above. The Poisson structure and
Hamiltonians on the whole group interpolate between the Poisson structures and
Hamiltonians of Benney, KP and KdV flows. We also discuss the geometrical
meaning of W_\infty as a limit of Poisson algebras W_\epsilon as \epsilon goes
to 0.Comment: 64 pages, no figure
Problem detection in legislative oversight:An analysis of legislative committee agendas in the U.K. and U.S.
This paper outlines a dynamic problem-detection model of legislative oversight where legislative committees engage in information-gathering to identify emerging policy problems. It is argued that activities of legislative committees are responsive to indicators of problem status across a range of policy domains. This enables committees to react to problems before, or at least simultaneously to, citizens. Our analyses use a new dataset on the policy agenda of UK Parliamentary Select Committees in combination with directly comparable data on US Congressional hearings. Aggregate measures of problem status (e.g. GDP, crime rates) and public opinion on the �most important problem� facing the country are used as independent variables. The comparison between a well-established and developing committee system offers insights into common dynamics across institutional contexts. The findings show that committee agendas in both the UK and US are responsive to problem status for the majority of issues
Deformations of conformal theories and non-toric quiver gauge theories
We discuss several examples of non-toric quiver gauge theories dual to
Sasaki-Einstein manifolds with U(1)^2 or U(1) isometry. We give a general
method for constructing non-toric examples by adding relevant deformations to
the toric case. For all examples, we are able to make a complete comparison
between the prediction for R-charges based on geometry and on quantum field
theory. We also give a general discussion of the spectrum of conformal
dimensions for mesonic and baryonic operators for a generic quiver theory; in
the toric case we make an explicit comparison between R-charges of mesons and
baryons.Comment: 51 pages, 12 figures; minor corrections in appendix B, published
versio
Classe de Mathématiques, réalité et communication
This study focuses on an inquiry-based teaching experience in mathematics, with 5th grade students in which we have established a strong connection with reality and intensified student’s ability to communicate, while promoting problem solving and mathematical reasoning. Mathematics lessons are organized into four phases: (i) Launching the task for students; (ii) Development of the task; (iii) Discussion of the task; and (iv) Systematization of mathematical learning. To prepare task discussion, the teacher implements a “gallery of tasks” through which students have their first contact with their colleague’s resolutions: they can ask questions and make comments in the presented sheets. This article presents the results of a lesson on percentages, in which students worked on the task entitled “Discount at Bit- @ - Byte”. The analysis of this task and the results of similar tasks of reality made throughout the school year shows that the inquiry-based teaching allows improvements in mathematics, namely learning concepts and capabilities such as reasoning, communication and problem solving
Quantitative importance of staminodes for female reproductive success in Parnassia palustris under contrasting environmental conditions.
The five sterile stamens, or staminodes, in Parnassia palustris act both as false and as true nectaries. They attract pollinators with their conspicuous, but non-rewarding tips, and also produce nectar at the base. We removed staminodes experimentally and compared pollinator visitation rate and duration and seed set in flowers with and without staminodes in two different populations. We also examined the relative importance of the staminode size to other plant traits. Finally, we bagged, emasculated, and supplementary cross-pollinated flowers to determine the pollination strategy and whether reproduction was limited by pollen availability. Flowers in both populations were highly dependent on pollinator visitation for maximum seed set. In one population pollinators primarily cross-pollinated flowers, whereas in the other the pollinators facilitated self-pollination. The staminodes caused increased pollinator visitation rate and duration to flowers in both populations. The staminodes increased female reproductive success, but only when pollen availability constrained female reproduction. Simple linear regression indicated a strong selection on staminode size, multiple regression suggested that selection on staminode size was mainly caused by correlation with other traits that affected female fitness. [ABSTRACT FROM AUTHOR
National Beef Quality Audit-2016: Transportation, mobility, and harvest-floor assessments of targeted characteristics that affect quality and value of cattle, carcasses, and by-products
The National Beef Quality Audit-2016 (NBQA-2016) was conducted to assess current transportation, mobility, and quality characteristics of U.S. fed steers and heifers. Data were collected at 17 beef processing facilities between March and November 2016. About 8,000 live cattle were evaluated for transportation and mobility, and about 25,000 carcasses were evaluated on the slaughter floor. Cattle were in transit to the slaughter facility for a mean duration of 2.7 h from a mean distance of 218.5 km using trailers with dimensions ranging from 17.84 m2 to 59.09 m2. Area allotted per animal averaged 1.13 m2 and ranged from 0.85 m2 to 2.28 m2. A total of 96.8% of cattle received a mobility score of 1 (walks easily, no apparent lameness). Identification types (35.1% had multiple) were lot visual tags (61.5%), individual tags (55.0%), electronic tags (16.9%), metal-clip tags (9.2%), bar-coded tags (0.05%), wattles (0.01%), and other (2.6%). Cattle were black-hided (57.8%), Holstein (20.4%), red-hided (10.5%), yellow-hided (4.8%), gray-hided (2.9%), brown-hided (1.3%), and white-hided (1.1%). Unbranded hides were observed on 74.3% of cattle; 18.6% had brands located on the butt, 6.3% on the side, and 1.3% on the shoulder (values exceed 100% due to multiple brands). For hide-on carcasses, 37.7% displayed no mud or manure; specific locations for mud or manure were legs (40.8%), belly (33.0%), tail region (15.5%), side (6.8%), and top-line (3.9%). Cattle without horns represented 83.3% of the sample, and cattle that did have horns measured: \u3c 2.54 cm (5.5%), 2.54 to 12.7 cm (8.3%), and \u3e 12.7 cm (2.9%). Carcasses without bruises represented 61.1% of those sampled, whereas 28.2% had 1, 8.2% had 2, 2.1% had 3, and 0.3% had 4 bruises. Of those carcasses with a bruise, the bruise was located on the loin (29.7%), round (27.8%), chuck (16.4%), rib (14.4%), and brisket/plate/flank (11.6%). Frequencies of offal condemnations were livers (30.8%), lungs (18.2%), viscera (16.3%), hearts (11.1%), heads (2.7%), and tongues (2.0%). Compared to NBQA-2011, fewer cattle were identified for traceability, fewer were black-hided, a greater number were Holstein cattle, more with no brand and no horns, fewer without bruises, more liver, lung, and viscera condemnations, and fewer heads and tongues were condemned. The NBQA remains an influential survey for the U.S. beef industry to provide benchmarks and strategic plans for continued improvement of beef quality and consistency
Construction and physiochemical characterisation of a multi-composite, potential oral vaccine delivery system (VDS)
An increasing human population requires a secure food supply and a cost effective, oral vaccine delivery system for livestock would help facilitate this end. Recombinant antigen adsorbed onto silica beads and coated with myristic acid, was released (∼15% (w/v)) over 24 h at pH 8.8. At pH 2, the myristic acid acted as an enteric coating, protecting the antigen from a variety of proteases. The antigen adsorbed onto silica particles, coated in myristic acid had a conserved secondary structure (measured by circular dichroism (CD) spectroscopy) following its pH-triggered release. Small angle neutron scattering (SANS) was used to measure the thickness of the adsorbed antigen, finding that its adsorbed conformation was slightly greater than its solution radius of gyration, i.e. 120–160 Å. The addition of myristic acid led to a further increase in particle size, with scattering data consistent with an acid thickness slightly greater than a monolayer of fully extended alkyl chains and a degree of hydration of around 50%. Whilst adsorbed onto the silica and coated in myristic acid, the protein was stable over 14 days at 42 °C, indicating a reduced need for cold chain storage. These data indicate that further investigation is warranted into the development of this technology
Tevatron Run-1 Z Boson Data and Collins-Soper-Sterman Resummation Formalism
We examine the effect of the Z-boson transverse momentum distribution
measured at the Run-1 of the Tevatron on the nonperturbative function of the
Collins-Soper-Sterman (CSS) formalism, which resums large logarithmic terms
from multiple soft gluon emission in hadron collisions. The inclusion of the
Tevatron Run-1 Z-boson data strongly favors a Gaussian form of the CSS
nonperturbative function, when combined with the other low energy Drell-Yan
data in a global fit.Comment: Published version; minor modifications, three references added; 19
pages, 7 figure
- …