13,416 research outputs found
First Evaluation of Dynamic Aperture at Injection for FCC-hh
In the Hadron machine option, proposed in the context of the Future Circular
Colliders (FCC) study, the dipole field quality is expected to play an
important role, as in the LHC. A preliminary evaluation of the field quality of
dipoles, based on the NbSn technology, has been provided by the magnet
group. The effect of these field imperfections on the dynamic aperture, using
the present lattice design, is presented and first tolerances on the b and
b multipole components are evaluated
Regular Incidence Complexes, Polytopes, and C-Groups
Regular incidence complexes are combinatorial incidence structures
generalizing regular convex polytopes, regular complex polytopes, various types
of incidence geometries, and many other highly symmetric objects. The special
case of abstract regular polytopes has been well-studied. The paper describes
the combinatorial structure of a regular incidence complex in terms of a system
of distinguished generating subgroups of its automorphism group or a
flag-transitive subgroup. Then the groups admitting a flag-transitive action on
an incidence complex are characterized as generalized string C-groups. Further,
extensions of regular incidence complexes are studied, and certain incidence
complexes particularly close to abstract polytopes, called abstract polytope
complexes, are investigated.Comment: 24 pages; to appear in "Discrete Geometry and Symmetry", M. Conder,
A. Deza, and A. Ivic Weiss (eds), Springe
Optimal Control for Generating Quantum Gates in Open Dissipative Systems
Optimal control methods for implementing quantum modules with least amount of
relaxative loss are devised to give best approximations to unitary gates under
relaxation. The potential gain by optimal control using relaxation parameters
against time-optimal control is explored and exemplified in numerical and in
algebraic terms: it is the method of choice to govern quantum systems within
subspaces of weak relaxation whenever the drift Hamiltonian would otherwise
drive the system through fast decaying modes. In a standard model system
generalising decoherence-free subspaces to more realistic scenarios,
openGRAPE-derived controls realise a CNOT with fidelities beyond 95% instead of
at most 15% for a standard Trotter expansion. As additional benefit it requires
control fields orders of magnitude lower than the bang-bang decouplings in the
latter.Comment: largely expanded version, superseedes v1: 10 pages, 5 figure
Status report of the baseline collimation system of CLIC. Part II
Important efforts have recently been dedicated to the characterisation and
improvement of the design of the post-linac collimation system of the Compact
Linear Collider (CLIC). This system consists of two sections: one dedicated to
the collimation of off-energy particles and another one for betatron
collimation. The energy collimation system is further conceived as protection
system against damage by errant beams. In this respect, special attention is
paid to the optimisation of the energy collimator design. The material and the
physical parameters of the energy collimators are selected to withstand the
impact of an entire bunch train. Concerning the betatron collimation section,
different aspects of the design have been optimised: the transverse collimation
depths have been recalculated in order to reduce the collimator wakefield
effects while maintaining a good efficiency in cleaning the undesired beam
halo; the geometric design of the spoilers has been reviewed to minimise
wakefields; in addition, the optics design has been optimised to improve the
collimation efficiency. This report presents the current status of the the
post-linac collimation system of CLIC. Part II is mainly dedicated to the study
of the betatron collimation system and collimator wakefield effects.Comment: 25 pages, 13 figure
Language difficulties in first year Science
A key goal of the study entitled ‘A cross-disciplinary approach to language support for first year students in the science disciplines’, funded by the Carrick Institute for Learning and Teaching in Higher Education, is to examine the role of language in the learning of science by first-year university students. The disciplines involved are Physics, Chemistry and Biology. This national project also aims to transfer active learning skills, which are widely used in language teaching, to the teaching of science in first year. The paper discusses the background to the study, reports on some of the preliminary results on the language difficulties faced by first year student cohorts in science from data collected in 2008, and describes the framework we have established for the organization and delivery of first year science courses to be implemented in semester one 2009
Embedding in-discipline language support for first year students in the sciences
This paper reports on a project which aims at addressing the need to cater for the language needs of a diverse student body (both domestic and international student body) by embedding strategic approaches to learning and teaching in first year sciences in tertiary education. These strategies consist of active learning skills which are widely used in language learning. The disciplines covered by the project are Biology, Chemistry and Physics and involves the University of Canberra (UC), University of Sydney (USyd), University of Tasmania (UTAS), University of Technology, Sydney (UTS) and University of Newcastle (Newcastle) in Australia. This project is funded by the Australian Learning and Teaching Council (ALTC). The paper discusses the background to the study and reports on results on the language difficulties faced by first year science student cohorts from data collected in 2008 as well as qualitative data was also collected on 2008 students’ attitudes towards online science learning. It will also report on the results on the implementation of the learning strategies at UTS and UTAS in Physics and Chemistry disciplines in 2009. Keywords: First year science teaching, role of language in science teaching, active learning skill
Microscopic theory for the light-induced anomalous Hall effect in graphene
We employ a quantum Liouville equation with relaxation to model the recently
observed anomalous Hall effect in graphene irradiated by an ultrafast pulse of
circularly polarized light. In the weak-field regime, we demonstrate that the
Hall effect originates from an asymmetric population of photocarriers in the
Dirac bands. By contrast, in the strong-field regime, the system is driven into
a non-equilibrium steady state that is well-described by topologically
non-trivial Floquet-Bloch bands. Here, the anomalous Hall current originates
from the combination of a population imbalance in these dressed bands together
with a smaller anomalous velocity contribution arising from their Berry
curvature. This robust and general finding enables the simulation of electrical
transport from light-induced Floquet-Bloch bands in an experimentally relevant
parameter regime and creates a pathway to designing ultrafast quantum devices
with Floquet-engineered transport properties
Effects of Dietary Fat Source on Performance of Lactating Dairy Cows Fed a Pre-mixed Concentrate
Inclusion of a pre-blended concentrate (OneTrak®, Cargill Inc., Blair, NE) in the total mixed ration (TMR) for dairy cows can simplify the daily mixing of dietary ingredients. A cow’s response to fat supplementation can be affected by other dietary ingredients; however, little is known about production responses to dietary fat in diets with high concentrations of non-forage fiber. This study evaluated cow performance in response to fat sources when the ration contained a pre-blended concentrate composed largely of a non-forage fiber source. Six pens of mid-lactation cows were studied; the addition of saturated fat (Energy Booster 100) and rumen-protected unsaturated fat (Megalac) were compared to a control diet with no added fat. Milk yield tended to increase with both fat sources. Protein concentration decreased with fat supplementation but protein yield did not differ. Efficiency of conversion of feed to milk tended to increase for Megalac compared with Energy Booster. These responses to dietary fat are comparable to those for diets without OneTrak®, suggesting that no unusual dietary interactions with fat supplements are apparent with OneTrak® feeding programs
A call to safeguard sexual and reproductive health information and services during Ebola outbreaks
The recent Ebola virus disease (EVD) outbreaks in 2021 exemplify how sexual and reproductive health services are too often considered unessential during health emergencies. Bleeding for reasons other than EVD, such as pregnancy complications or rape, can be construed as EVD symptoms, reinforcing fear and stigmatisation, and delaying timely access to adequate care. In this commentary, we urgently call on all humanitarian actors to integrate the Minimum Initial Services Package for Sexual and Reproductive Health in Crisis Situations into current and future EVD preparedness and response efforts
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