140 research outputs found
Electron-impact spectroscopy of acetaldehyde
Acetaldehyde has been studied by the technique of lowâenergy variableâangle electron energyâloss spectroscopy. With this method the lowâlying spinâforbidden transitions have been located via the behavior of the relative differential cross sections, providing the first identification by this technique of such states in acetaldehyde. Highâlying states were also investigated and some assignments of dipole symmetryâforbidden/quadrupole symmetryâallowed excitations were made on the basis of characteristic angular behavior, evident for the asymmetric molecule acetaldehyde just as for the symmetric molecules formaldehyde and acetone. Through a comparison of the acetaldehyde results with those for formaldehyde and acetone the trends in the allowed and forbidden transition energies were examined as a function of methyl substitution and found to be relatively linear
Nova Scarred: The Implications of an International Ferry\u27s Floating Jurisdiction on the Law of the Sea, the Lands, and the Flag
Regardless of whether the Nova Star is labeled as a âferryâ or âcruiseâ or a hybrid of the two, legal questions remain concerning application of law and jurisdiction to a foreign vessel traveling daily between two foreign ports during the summer months. The law forming the backdrop to possible legal claims is shaped by general maritime law, the laws of a vesselâs origin, state regulations, and a United States federal statute originating in 1920. The Merchant Marine Act of 1920, better known as the Jones Act, regulates maritime law and commerce in United States ports and between United States and foreign ports, and further provides legal claims for workers at sea. As this comment discusses further, the law that an employee or passenger falls under changes fluidly with uncertainty based upon several factors, including their role on the vessel, the location of circumstance that gave rise to their claim, and the origin of the vessel. These sometimes overlapping and sometimes conflicting laws already have an impact on how vessels like the Nova Star operate and could have an even further impact on the pending life of the Nova Star, including implications on wages, on-board injury, and liability. This comment addresses the struggles facing an international ferry in northeast North America, the issue of legal application of jurisdictional law touched by an international ferry, and the ferryâs likelihood of success. Part II provides a background of international ferries, particularly those that have serviced the coastline between Canada and Maine. It then discusses the revival of the Nova Star and its current state, and the international relations between the United States and Canada, as well as Maine and Nova Scotia. Part III delves deeper into the current state of the law surrounding a round-trip maritime route between Canadian and U.S. ports and the legal remedies available for those aboard the ferry. Part III further analyzes the factor determination employed by the courts and discusses whether the remedies would be available for a ferry cruise service like the Nova Star, given the competing laws at hand. Part IV concludes with a recommendation for clearer and more consistent application of maritime choice of law determinations to those employed on international ferries, made available through either judicial or legislative action
Spin and orbital fluctuations in non-equilibrium transport through quantum dots: A renormalisation-group analysis
We study non-equilibrium current and occupation probabilities of a
two-orbital quantum dot. The couplings to the leads are allowed to be
asymmetric and orbital dependent as it is generically the case in transport
experiments on molecules and nanowires. Starting from a two-orbital Anderson
model, we perform a generalised Schrieffer-Wolff transformation to derive an
effective Kondo model. This generates an orbital potential scattering
contribution which is of the same order as the spin exchange interaction. In a
first perturbative analysis we identify a regime of negative differential
conductance and a cascade resonance in the presence of an external magnetic
field, which both originate from the non-equilibrium occupation of the
orbitals. We then study the logarithmic enhancement of these signatures by
means of a renormalisation-group treatment. We find that the orbital potential
scattering qualitatively changes the renormalisation of the spin exchange
couplings and strongly affects the differential conductance for asymmetric
couplings.Comment: 6 pages, 4 figures, revised version as publishe
Transconductance of a double quantum dot system in the Kondo regime
We consider a lateral double-dot system in the Coulomb blockade regime with a
single spin-1/2 on each dot, mutually coupled by an anti-ferromagnetic exchange
interaction. Each of the two dots is contacted by two leads. We demonstrate
that the voltage across one of the dots will have a profound influence on the
current passing through the other dot. Using Poor Man's scaling, we find that
the Kondo-effect can lead to a strong enhancement of this {\it
transconductance}.Comment: updated to published versio
Overcoming barriers to effective early parenting interventions for attention-deficit hyperactivity disorder (ADHD): parent and practitioner views
BackgroundThe importance of early intervention approaches for the treatment of attention-deficit hyperactivity disorder (ADHD) has been increasingly acknowledged. Parenting programmes (PPs) are recommended for use with preschool children with ADHD. However, low take-up' and high drop-out' rates compromise the effectiveness of such programmes within the community.
MethodsThis qualitative study examined the views of 25 parents and 18 practitioners regarding currently available PPs for preschool children with ADHD-type problems in the UK. Semi-structured interviews were undertaken to identify both barriers and facilitators associated with programme access, programme effectiveness, and continued engagement.
Results and conclusionsMany of the themes mirrored previous accounts relating to generic PPs for disruptive behaviour problems. There were also a number of ADHD-specific themes. Enhancing parental motivation to change parenting practice and providing an intervention that addresses the parents' own needs (e.g. in relation to self-confidence, depression or parental ADHD), in addition to those of the child, were considered of particular importance. Comparisons between the views of parents and practitioners highlighted a need to increase awareness of parental psychological barriers among practitioners and for better programme advertising generally. Clinical implications and specific recommendations drawn from these findings are discussed and presented
Transport through a Kondo quantum dot: Functional RG approach
We apply the functional renormalization group (FRG) method to calculate the
conductance of a quantum dot in the Kondo regime. Starting from the exact FRG
equations in Keldysh formulation for the Kondo exchange Hamiltonian in
pseudo-fermion (pf) representation, we solve the coupled equations for the pf
self energy and the coupling function, neglecting three-particle and higher
correlation functions. The conductance as a function of temperature and
bias voltage is calculated using a renormalized Golden Rule expression. The
limiting behavior at and/or ( : Kondo temperature)
agrees with known results. The difficulties when approaching strong coupling
are analyzed and improvements are suggested.Comment: accepted for publication in Ann. Phys. (Berlin
Non-Equilibrium Electron Transport through a Double Quantum Dot System: Study of Two Exchange Coupled Quantum Dots in a 4-Terminal Geometry
In this thesis we study two exchange-coupled quantum dots with an emphasis on non-equilibrium physics. Assuming a single electron on each quantum dot, the double quantum dot system is characterized by an interplay between the Kondo spin coupling of the dots with the leads and the spin-exchange coupling between the dots. We find that a finite voltage on one quantum dot drives the other quantum dot out of equilibrium
Nonequilibrium Cotunneling through a Three-Level Quantum Dot
We calculate the nonlinear cotunneling conductance through a quantum dot with
3 electrons occupying the three highest lying energy levels. Starting from a
3-orbital Anderson model, we apply a generalized Schrieffer-Wolff
transformation to derive an effective Kondo model for the system. Within this
model we calculate the nonequilibrium occupation numbers and the corresponding
cotunneling current to leading order in the exchange couplings. We identify the
inelastic cotunneling thresholds and their splittings with applied magnetic
field, and make a qualitative comparison to recent experimental data on carbon
nanotube and InAs quantum-wire quantum dots. Further predictions of the model
like cascade resonances and a magnetic-field dependence of the orbital level
splitting are not yet observed but within reach of recent experimental work on
carbon nanotube and InAs nanowire quantum dots.Comment: 12 pages, 13 figure
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