Evaluation of precision in optoacoustic tomography for preclinical imaging in living subjects.

Optoacoustic Tomography (OT) is now widely used in preclinical imaging, however, precision (repeatability and reproducibility) of OT has yet to be determined. METHODS: We used a commercial small animal OT system. Measurements in stable phantoms were used to independently assess the impact of system variables on precision (using coefficient of variation, COV), including acquisition wavelength, rotational position, frame averaging. Variables due to animal handling and physiology, such as anatomical placement and anesthesia conditions were then assessed in healthy nude mice using the left kidney and spleen as reference organs. Temporal variation was assessed by repeated measurements over hours and days both in phantoms and $\textit{in vivo}$. Sensitivity to small molecule dyes was determined in phantoms and $\textit{in vivo}$; precision was assessed $\textit{in vivo}$ using IRDye800CW. RESULTS: OT COV in a stable phantom was less than 2% across all wavelengths over 30 days. The factors with greatest impact on the signal repeatability in phantoms were rotational position and user experience, both of which still resulted in a COV of less than 4%. Anatomical ROI size showed the highest variation at 12% and 18% COV in the kidney and spleen respectively, however, functional SO₂ measurements based on a standard operating procedure showed exceptional reproducibility of <4% COV. COV for repeated injections of IRDye800CW was 6.6%. Sources of variability for $\textit{in vivo}$ data included respiration rate, user experience and animal placement. CONCLUSION: Data acquired with our small animal OT system was highly repeatable and reproducible across subjects and over time. Therefore, longitudinal OT studies may be performed with high confidence when our standard operating procedure is followed.This work was funded by: the EPSRC-CRUK Cancer Imaging Centre in Cambridge and Manchester (C197/A16465); CRUK (C14303/A17197, C47594/A16267); EU-FP7-agreement FP7-PEOPLE-2013-CIG-630729; and the University of Cambridge EPSRC Impact Acceleration Account

String goniometry by neutral currents

If a new neutral gauge boson exists at accelerator energies, the measurement of the mixing angle(s) fixing its current could to a large extent determine the (heterotic) string model at the Planck scale. In this paper we present the renormalization group predictions for this angle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26534/1/0000073.pd

TJP2 (tight junction protein 2 (zona occludens 2))

Review on TJP2 (tight junction protein 2 (zona occludens 2)), with data on DNA, on the protein encoded, and where the gene is implicated

Dynamics of Quintessence Models of Dark Energy with Exponential Coupling to the Dark Matter

We explore quintessence models of dark energy which exhibit non-minimal coupling between the dark matter and the dark energy components of the cosmic fluid. The kind of coupling chosen is inspired in scalar-tensor theories of gravity. We impose a suitable dynamics of the expansion allowing to derive exact Friedmann-Robertson-Walker solutions once the coupling function is given as input. Self-interaction potentials of single and double exponential types emerge as result of our choice of the coupling function. The stability and existence of the solutions is discussed in some detail. Although, in general, models with appropriated interaction between the components of the cosmic mixture are useful to handle the coincidence problem, in the present study the coincidence can not be evaded due to the choice of the solution generating ansatz.Comment: 10 pages, 7 figure

Phenomenology of symmetry breaking from extra dimensions

Motivated by the electroweak hierarchy problem, we consider theories with two extra dimensions in which the four-dimensional scalar fields are components of gauge boson in full space. We explore the Nielsen-Olesen instability for SU(N) on a torus, in the presence of a magnetic background. A field theory approach is developed, computing explicitly the minimum of the complete effective potential, including tri-linear and quartic couplings and determining the symmetries of the stable vacua. We also develop appropriate gauge-fixing terms when both Kaluza-Klein and Landau levels are present and interacting, discussing the interplay between the possible six and four dimensional choices. The equivalence between coordinate dependent and constant Scherk-Schwarz boundary conditions -associated to either continuous or discrete Wilson lines- is analyzed.Comment: 39 pages and 8 eps figures. Few changes in section

Magnetic order and disorder in nanomagnets probed by superconducting vortices

We have studied two nanomagnet systems with strong (Co/Pd multilayers) and weak (NdCo alloy films) stray magnetic fields by probing the out-of-plane magnetic states with superconducting vortices. The hybrid samples are made of array of nanomagnets embedded in superconducting Nb thin films. The vortex motion detects relevant magnetic state features, since superconducting vortices are able to discriminate between different magnetic stray field strengths and directions. The usual matching effect between the superconducting vortex lattice and the periodic pinning array can be quenched by means of disorder magnetic potentials with strong stray fields at random. Ordered stray fields retrieve the matching effect and yield asymmetry and shift in the vortex dissipation signal. Furthermore vortices can discriminate the sizes of the nanomagnet magnetic domains, detecting magnetic domain sizes as small as 70 nm. In addition, we observe that the vortex cores play the crucial role instead of the supercurrents around the vortex.Comment: 22 pages, 8 figure

A model of the Universe including Dark Energy accounted for by both a Quintessence Field and a (negative) Cosmological Constant

In this work we present a model of the universe in which dark energy is modelled explicitely with both a dynamical quintessence field and a cosmological constant. Our results confirm the possibility of a future collapsing universe (for a given region of the parameter space), which is necessary for a consistent formulation of string theory and quantum field theory. We have also reproduced the measurements of modulus distance from supernovae with good accuracy.Comment: 11 pages, 4 figures, only the results for the single exponential potential are preserved. One author added. Some changes in the reference section. Submitted to Physical Review

Providing Personalized Guidance in Arithmetic Problem Solving

Supervising a student's resolution of an arithmetic word problem is a cumbersome task. Di erent students may use di erent lines of reasoning to reach the nal solution, and the assistance provided should be consistent with the resolution path that the student has in mind. In addition, further learning gains can be achieved if the previous student's background is also considered in the process. In this paper, we outline a relatively simple method to adapt the hints given by an Intelligent Tutoring System to the line of reasoning that the student is currently following. We also outline possible extensions to build a model of the student's most relevant skills, by tracking user's actions

New Isotropic and Anisotropic Sudden Singularities

We show the existence of an infinite family of finite-time singularities in isotropically expanding universes which obey the weak, strong, and dominant energy conditions. We show what new type of energy condition is needed to exclude them ab initio. We also determine the conditions under which finite-time future singularities can arise in a wide class of anisotropic cosmological models. New types of finite-time singularity are possible which are characterised by divergences in the time-rate of change of the anisotropic-pressure tensor. We investigate the conditions for the formation of finite-time singularities in a Bianchi type $VII_{0}$ universe with anisotropic pressures and construct specific examples of anisotropic sudden singularities in these universes.Comment: Typos corrected. Published versio