482 research outputs found
Tailoring pH-responsive acrylic acid microgels with hydrophobic crosslinks for drug release
Amphiphilic microgels based on the hydrophilic acrylic acid (AA) and hydrophobic crosslinks of different compositions were synthesised using a lab-on-a-chip device. The microgels were formed by polymerising hydrophobic droplets. The droplets were generated via a microfluidic platform and contained a protected form of AA, a hydrophobic crosslinker (ethylene glycol dimethacrylate, EGDMA) and a free radical initiator in an organic solvent. Following photopolymerisation and subsequent hydrolysis, AA based microgels of amphiphilic nature were produced and it was demonstrated that they can successfully deliver both hydrophilic as well as hydrophobic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the aqueous solution as well as the crosslinking density and hydrophobic content of the microgels
Microfluidically fabricated pH-responsive anionic amphiphilic microgels for drug release
© 2016 The Royal Society of Chemistry. Amphiphilic microgels of different composition based on the hydrophilic, pH-responsive acrylic acid (AA) and the hydrophobic, non-ionic n-butyl acrylate (BuA) were synthesised using a lab-on-a-chip device. Hydrophobic droplets were generated via a microfluidic platform that contained a protected form of AA, BuA, the hydrophobic crosslinker, ethylene glycol dimethacrylate (EGDMA), and a free radical initiator in an organic solvent. These hydrophobic droplets were photopolymerised within the microfluidic channels and subsequently hydrolysed, enabling an integrated platform for the rapid, automated, and in situ production of anionic amphiphilic microgels. The amphiphilic microgels did not feature the conventional core-shell structure but were instead based on random amphiphilic copolymers of AA and BuA and hydrophobic crosslinks. Due to their amphiphilic nature they were able to encapsulate and deliver both hydrophobic and hydrophilic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the surrounding aqueous solution and the hydrophobic content of the microgels
Quasi multipartite entanglement measure based on quadratic functions
We develop a new entanglement measure by extending Jaeger's Minkowskian norm
entanglement measure. This measure can be applied to a much wider class of
multipartite mixed states, although still "quasi" in the sense that it is still
incapable of dividing precisely the sets of all separable and entangled states.
As a quadratic scalar function of the system density matrix, the quasi measure
can be easily expressed in terms of the so-called coherence vector of the
system density matrix, by which we show the basic properties of the quasi
measure including (1) zero-entanglement for all separable states, (2)
invariance under local unitary operations, and (3) non-increasing under local
POVM (positive operator-valued measure) measurements. These results open up
perspectives in further studies of dynamical problems in open systems,
especially the dynamic evolution of entanglement, and the entanglement
preservation against the environment-induced decoherence effects.Comment: 10pages,1 figur
Decoherence Control in Open Quantum System via Classical Feedback
In this work we propose a novel strategy using techniques from systems theory
to completely eliminate decoherence and also provide conditions under which it
can be done so. A novel construction employing an auxiliary system, the bait,
which is instrumental to decoupling the system from the environment is
presented. Our approach to decoherence control in contrast to other approaches
in the literature involves the bilinear input affine model of quantum control
system which lends itself to various techniques from classical control theory,
but with non-trivial modifications to the quantum regime. The elegance of this
approach yields interesting results on open loop decouplability and Decoherence
Free Subspaces(DFS). Additionally, the feedback control of decoherence may be
related to disturbance decoupling for classical input affine systems, which
entails careful application of the methods by avoiding all the quantum
mechanical pitfalls. In the process of calculating a suitable feedback the
system has to be restructured due to its tensorial nature of interaction with
the environment, which is unique to quantum systems. The results are
qualitatively different and superior to the ones obtained via master equations.
Finally, a methodology to synthesize feedback parameters itself is given, that
technology permitting, could be implemented for practical 2-qubit systems to
perform decoherence free Quantum Computing.Comment: 17 pages, 4 Fig
Inverse Problems in a Bayesian Setting
In a Bayesian setting, inverse problems and uncertainty quantification (UQ)
--- the propagation of uncertainty through a computational (forward) model ---
are strongly connected. In the form of conditional expectation the Bayesian
update becomes computationally attractive. We give a detailed account of this
approach via conditional approximation, various approximations, and the
construction of filters. Together with a functional or spectral approach for
the forward UQ there is no need for time-consuming and slowly convergent Monte
Carlo sampling. The developed sampling-free non-linear Bayesian update in form
of a filter is derived from the variational problem associated with conditional
expectation. This formulation in general calls for further discretisation to
make the computation possible, and we choose a polynomial approximation. After
giving details on the actual computation in the framework of functional or
spectral approximations, we demonstrate the workings of the algorithm on a
number of examples of increasing complexity. At last, we compare the linear and
nonlinear Bayesian update in form of a filter on some examples.Comment: arXiv admin note: substantial text overlap with arXiv:1312.504
Lab-on-a-chip workshop activities for secondary school students
The ability to engage and inspire younger generations in novel areas of science is important for bringing new researchers into a burgeoning field, such as lab-on-a-chip. We recently held a lab-on-a-chip workshop for secondary school students, for which we developed a number of hands-on activities that explained various aspects of microfluidic technology, including fabrication (milling and moulding of microfluidic devices, and wax printing of microfluidic paper-based analytical devices, so-called μPADs), flow regimes (gradient formation via diffusive mixing), and applications (tissue analysis and μPADs). Questionnaires completed by the students indicated that they found the workshop both interesting and informative, with all activities proving successful, while providing feedback that could be incorporated into later iterations of the event
B814: Performance Evaluations of Potato Clones and Varieties in the Northeastern States - 1985
New potato clones and varieties must be tested against commercially accepted cultivars to determine If they possess advantages over existing varieties. Possible Improvements over the existing varieties could Include greater disease resistance or tolerance, higher yield, more uniform tuber size distribution, Improved storagability, good processing characteristics, etc. Often new cultivars are sought to fill local special-purpose needs. The cooperative potato variety trials reported In this bulletin were conducted to provide Information on the performance, adaptation, and performance stability of new potato clones under a wide range of geographic, climatic, soil, and cultural conditions. These tests are contributions to Regional Project NE-107 entitled, Breeding and Evaluation of New Potato Clones for the Northeast.
The objectives of this regional project are: 1). To develop high quality, widely adapted, productive, pest resistant potato varieties for use In the northeast; 2). To determine regional performance, quality, and storage characteristics for promising potato clones and new varieties; 3). To evaluate promising clones and varieties for special-purpose needs such as pest outbreaks, processing, export, specialized market opportunities and/or production situations; 4). To develop management practices such as plant population, fertilizer rate, disease, weed, and Insect control strategies that will I Improve the yield and/or quality of promising clones. Data presented In this report primarily address objectives 2 and 3.https://digitalcommons.library.umaine.edu/aes_bulletin/1118/thumbnail.jp
Analytic Controllability of Time-Dependent Quantum Control Systems
The question of controllability is investigated for a quantum control system
in which the Hamiltonian operator components carry explicit time dependence
which is not under the control of an external agent. We consider the general
situation in which the state moves in an infinite-dimensional Hilbert space, a
drift term is present, and the operators driving the state evolution may be
unbounded. However, considerations are restricted by the assumption that there
exists an analytic domain, dense in the state space, on which solutions of the
controlled Schrodinger equation may be expressed globally in exponential form.
The issue of controllability then naturally focuses on the ability to steer the
quantum state on a finite-dimensional submanifold of the unit sphere in Hilbert
space -- and thus on analytic controllability. A relatively straightforward
strategy allows the extension of Lie-algebraic conditions for strong analytic
controllability derived earlier for the simpler, time-independent system in
which the drift Hamiltonian and the interaction Hamiltonia have no intrinsic
time dependence. Enlarging the state space by one dimension corresponding to
the time variable, we construct an augmented control system that can be treated
as time-independent. Methods developed by Kunita can then be implemented to
establish controllability conditions for the one-dimension-reduced system
defined by the original time-dependent Schrodinger control problem. The
applicability of the resulting theorem is illustrated with selected examples.Comment: 13 page
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
Automatic Planning and Control of Robot Natural Motion Via Feedback
A feedback control strategy for the command of robot motion includes some limited automatic planning capabilities. These may be seen as sequential solution algorithms implemented by the robot arm interpreted as a mechanical analog computer. This perspective lends additional insight into the manner in which such control techniques may fail, and motivates a fresh look at requisite sensory capabilities.
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