A brief review of diagnostic properties of point-of-care ultrasound for adult bowel intussusception: Making the case for ultrasound.

Undifferentiated abdominal pain in adults is a common chief complaint in acute care clinics and emergency departments worldwide, representing up to 10% of visits to emergency departments. Many patients have a non-specific presentation and an initial workup with labwork, urine analysis or X-ray might not reveal a specific diagnosis. Although bowel intussusception is a primarily pediatric disease, adult intussusception is a recognized but rare cause of bowel obstruction often requiring surgical intervention.

Limits of Directed Self-Assembly in Block Copolymers.

Understanding the conditions under which defects appear in self-assembling soft-matter systems is of great importance, for example, in the development of block-copolymer (BCP) nanolithography. Here, we explore the limits of the directed self-assembly of BCPs by deliberately adding random imperfections to the template. Our results show that defects emerge due to local "shear-like" distortions of the polymer-template system, a new mechanism that is fundamentally different from the canonical mechanisms of 2D melting.

On the Inclusion of Short-distance Bystander Effects into a Logistic Tumor Control Probability Model.

Currently, interactions between voxels are neglected in the tumor control probability (TCP) models used in biologically-driven intensity-modulated radiotherapy treatment planning. However, experimental data suggests that this may not always be justified when bystander effects are important. We propose a model inspired by the Ising model, a short-range interaction model, to investigate if and when it is important to include voxel to voxel interactions in biologically-driven treatment planning.

The role of interparticle interaction and environmental coupling in a two-particle open quantum system.

The effects of bath coupling on an interacting two-particle quantum system are studied using tools from information theory. Shannon entropies of the one (reduced) and two-particle distribution functions in position, momentum and separable phase-space are examined. Results show that the presence of the bath leads to a delocalization of the distribution functions in position space, and a localization in momentum space.

A correlated-polaron electronic propagator: open electronic dynamics beyond the Born-Oppenheimer approximation.

In this work, we develop an approach to treat correlated many-electron dynamics, dressed by the presence of a finite-temperature harmonic bath. Our theory combines a small polaron transformation with the second-order time-convolutionless master equation and includes both electronic and system-bath correlations on equal footing. Our theory is based on the ab initio Hamiltonian, and is thus well-defined apart from any phenomenological choice of basis states or electronic system-bath coupling model.

Quantum computing without wavefunctions: time-dependent density functional theory for universal quantum computation.

We prove that the theorems of TDDFT can be extended to a class of qubit Hamiltonians that are universal for quantum computation. The theorems of TDDFT applied to universal Hamiltonians imply that single-qubit expectation values can be used as the basic variables in quantum computation and information theory, rather than wavefunctions. From a practical standpoint this opens the possibility of approximating observables of interest in quantum computations directly in terms of single-qubit quantities (i.

Exciton coherence lifetimes from electronic structure.

We model the coherent energy transfer of an electronic excitation within covalently linked aromatic homodimers from first-principles. Our results shed light on whether commonly used models of the bath calculated via detailed electronic structure calculations can reproduce the key dynamics. For the systems we model, the time scales of coherent transport are experimentally known from time-dependent polarization anisotropy measurements, and so we can directly assess whether current techniques are predictive for modeling coherent transport.

Time-dependent density functional theory of open quantum systems in the linear-response regime.

Time-dependent density functional theory (TDDFT) has recently been extended to describe many-body open quantum systems evolving under nonunitary dynamics according to a quantum master equation. In the master equation approach, electronic excitation spectra are broadened and shifted due to relaxation and dephasing of the electronic degrees of freedom by the surrounding environment. In this paper, we develop a formulation of TDDFT linear-response theory (LR-TDDFT) for many-body electronic systems evolving under a master equation, yielding broadened excitation spectra.

Time-dependent density functional theory for open quantum systems with unitary propagation.

We extend the Runge-Gross theorem for a very general class of open quantum systems under weak assumptions about the nature of the bath and its coupling to the system. We show that for Kohn-Sham (KS) time-dependent density functional theory, it is possible to rigorously include the effects of the environment within a bath functional in the KS potential. A Markovian bath functional inspired by the theory of nonlinear Schrödinger equations is suggested, which can be readily implemented in currently existing real-time codes.

Revisiting Molecular Dissociation in Density Functional Theory: A Simple Model.

A two-electron one-dimensional model of a heteroatomic molecule composed of two open-shell atoms is considered. Including only two electrons isolates and examines the effect that the highest occupied molecular orbital has on the Kohn-Sham potential as the molecule dissociates. We reproduce the characteristic step and peak that previous high-level wave function methods have shown to exist for real molecules in the low-density internuclear region.

Long-range excitations in time-dependent density functional theory.

Adiabatic time-dependent density functional theory fails for excitations of a heteroatomic molecule composed of two open-shell fragments at large separation. Strong frequency dependence of the exchange-correlation kernel is necessary for both local and charge-transfer excitations. The root of this is the static correlation created by the step in the exact Kohn-Sham ground-state potential between the two fragments.