3,398 research outputs found
Architected lattices for simultaneous broadband attenuation of airborne sound and mechanical vibrations in all directions
Phononic crystals and acoustic metamaterials are architected lattices
designed to control the propagation of acoustic or elastic waves. In these
materials, the dispersion properties and the energy transfer are controlled by
selecting the lattices' geometry and their constitutive material properties.
Most designs, however, only affect one mode of energy propagation, transmitted
either as acoustic, airborne sound or as elastic, structural vibrations. Here,
we present a design methodology to attenuate both acoustic and elastic waves
simultaneously in all polarizations. We experimentally realize the first
three-dimensional, load bearing, architected lattice, composed of a
single-material, that responds in a broadband frequency range in all
directions
Relating prepotentials and quantum vacua of N=1 gauge theories with different tree-level superpotentials
We consider N=1 supersymmetric U(N) gauge theories with Z_k symmetric
tree-level superpotentials W for an adjoint chiral multiplet. We show that (for
integer 2N/k) this Z_k symmetry survives in the quantum effective theory as a
corresponding symmetry of the effective superpotential W_eff(S_i) under
permutations of the S_i. For W(x)=^W(h(x)) with h(x)=x^k, this allows us to
express the prepotential F_0 and effective superpotential W_eff on certain
submanifolds of the moduli space in terms of an ^F_0 and ^W_eff of a different
theory with tree-level superpotential ^W. In particular, if the Z_k symmetric
polynomial W(x) is of degree 2k, then ^W is gaussian and we obtain very
explicit formulae for F_0 and W_eff. Moreover, in this case, every vacuum of
the effective Veneziano-Yankielowicz superpotential ^W_eff is shown to give
rise to a vacuum of W_eff. Somewhat surprisingly, at the level of the
prepotential F_0(S_i) the permutation symmetry only holds for k=2, while it is
anomalous for k>2 due to subtleties related to the non-compact period
integrals. Some of these results are also extended to general polynomial
relations h(x) between the tree-level superpotentials.Comment: 27 pages, 10 figures, modified version to appear in JHEP, discussion
of the physical meaning of the Z_k symmetry adde
KCNQ channels regulate age-related memory impairment:KCNQ regulates age-related memory
In humans KCNQ2/3 heteromeric channels form an M-current that acts as a brake on neuronal excitability, with mutations causing a form of epilepsy. The M-current has been shown to be a key regulator of neuronal plasticity underlying associative memory and ethanol response in mammals. Previous work has shown that many of the molecules and plasticity mechanisms underlying changes in alcohol behaviour and addiction are shared with those of memory. We show that the single KCNQ channel in Drosophila (dKCNQ) when mutated show decrements in associative short- and long-term memory, with KCNQ function in the mushroom body α/βneurons being required for short-term memory. Ethanol disrupts memory in wildtype flies, but not in a KCNQ null mutant background suggesting KCNQ maybe a direct target of ethanol, the blockade of which interferes with the plasticity machinery required for memory formation. We show that as in humans, Drosophila display age-related memory impairment with the KCNQ mutant memory defect mimicking the effect of age on memory. Expression of KCNQ normally decreases in aging brains and KCNQ overexpression in the mushroom body neurons of KCNQ mutants restores age-related memory impairment. Therefore KCNQ is a central plasticity molecule that regulates age dependent memory impairment
Autonomous Deployment of a Solar Panel Using an Elastic Origami and Distributed Shape Memory Polymer Actuators
Deployable mechanical systems such as space solar panels rely on the
intricate stowage of passive modules, and sophisticated deployment using a
network of motorized actuators. As a result, a significant portion of the
stowed mass and volume are occupied by these support systems. An autonomous
solar panel array deployed using the inherent material behavior remains
elusive. In this work, we develop an autonomous self-deploying solar panel
array that is programmed to activate in response to changes in the surrounding
temperature. We study an elastic "flasher" origami sheet embedded in a circle
of scissor mechanisms, both printed with shape memory polymers. The scissor
mechanisms are optimized to provide the maximum expansion ratio while
delivering the necessary force for deployment. The origami sheet is also
optimized to carry the maximum number of solar panels given space constraints.
We show how the folding of the "flasher" origami exhibits a bifurcation
behavior resulting in either a cone or disk shape both numerically and in
experiments. A folding strategy is devised to avoid the undesired cone shape.
The resulting design is entirely 3D printed, achieves an expansion ratio of
1000% in under 40 seconds, and shows excellent agreement with simulation
prediction both in the stowed and deployed configurations.Comment: 12 pages, 12 figure
Multi-Component KdV Hierarchy, V-Algebra and Non-Abelian Toda Theory
I prove the recently conjectured relation between the -matrix
differential operator , and a certain non-linear and non-local
Poisson bracket algebra (-algebra), containing a Virasoro subalgebra, which
appeared in the study of a non-abelian Toda field theory. Here, I show that
this -algebra is precisely given by the second Gelfand-Dikii bracket
associated with . The Miura transformation is given which relates the second
to the first Gelfand-Dikii bracket. The two Gelfand-Dikii brackets are also
obtained from the associated (integro-) differential equation satisfied by
fermion bilinears. The asymptotic expansion of the resolvent of
is studied and its coefficients yield an infinite sequence of
hamiltonians with mutually vanishing Poisson brackets. I recall how this leads
to a matrix KdV hierarchy which are flow equations for the three component
fields of . For they reduce to the ordinary KdV
hierarchy. The corresponding matrix mKdV equations are also given, as well as
the relation to the pseudo- differential operator approach. Most of the results
continue to hold if is a hermitian -matrix. Conjectures are made
about -matrix -order differential operators and
associated -algebras.Comment: 20 pages, revised: several references to earlier papers on
multi-component KdV equations are adde
Relationship between Service Quality, Customer Retention and the role of Social Media- Case study Premier Inn Hotel (UK)
The aim of this research is to critically evaluate the relationship between service quality and customer retention in Premier Inn Croydon. The objectives studies the concept of service quality in relevance with its characteristics, the objectives also evaluates the significance of customer retention for an organization. The researchers have also analysed and estimated the relationship between the two determinants which are service quality and customer retention of the company Premier Inn Croydon. Researchers have used positivism philosophy, survey strategy, explanatory design and deductive approach for the assessment and evaluation of the relationship between service quality and customer retention. The researchers have employed qualitative and quantitative both type of data obtained through circulating questionnaires and conducting interviews. Through non-probability sampling method and convenience based sampling technique; the sample was of 50 customers, 50 employees and 4 managers of Premier Inn Corydon. The successful completion of this very study has uncovered some area for the future studies especially the role of social media.
Along with this, a set of recommendations are also highlighted by the study for the selected company and for the future investigators
Enhancing pharmaceutical packaging through a technology ecosystem to facilitate the reuse of medicines and reduce medicinal waste
The idea of reusing dispensed medicines is appealing to the general public provided its benefits are illustrated, its risks minimized, and the logistics resolved. For example, medicine reuse could help reduce medicinal waste, protect the environment and improve public health. However, the associated technologies and legislation facilitating medicine reuse are generally not available. The availability of suitable technologies could arguably help shape stakeholders’ beliefs and in turn, uptake of a future medicine reuse scheme by tackling the risks and facilitating the practicalities. A literature survey is undertaken to lay down the groundwork for implementing technologies on and around pharmaceutical packaging in order to meet stakeholders’ previously expressed misgivings about medicine reuse (’stakeholder requirements’), and propose a novel ecosystem for, in effect, reusing returned medicines. Methods: A structured literature search examining the application of existing technologies on pharmaceutical packaging to enable medicine reuse was conducted and presented as a narrative review. Results: Reviewed technologies are classified according to different stakeholders’ requirements, and a novel ecosystem from a technology perspective is suggested as a solution to reusing medicines. Conclusion: Active sensing technologies applying to pharmaceutical packaging using printed electronics enlist medicines to be part of the Internet of Things network. Validating the quality and safety of returned medicines through this network seems to be the most effective way for reusing medicines and the correct application of technologies may be the key enabler
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