4,281 research outputs found
Mass Spectra of N=2 Supersymmetric SU(n) Chern-Simons-Higgs Theories
An algebraic method is used to work out the mass spectra and symmetry
breaking patterns of general vacuum states in N=2 supersymmetric SU(n)
Chern-Simons-Higgs systems with the matter fields being in the adjoint
representation. The approach provides with us a natural basis for fields, which
will be useful for further studies in the self-dual solutions and quantum
corrections. As the vacuum states satisfy the SU(2) algebra, it is not
surprising to find that their spectra are closely related to that of angular
momentum addition in quantum mechanics. The analysis can be easily generalized
to other classical Lie groups.Comment: 17 pages, use revte
Self-DUal SU(3) Chern-Simons Higgs Systems
We explore self-dual Chern-Simons Higgs systems with the local and
global symmetries where the matter field lies in the adjoint
representation. We show that there are three degenerate vacua of different
symmetries and study the unbroken symmetry and particle spectrum in each
vacuum. We classify the self-dual configurations into three types and study
their properties.Comment: Columbia Preprint CU-TP-635, 19 page
Maxwell Chern-Simons Solitons from Type IIB String Theory
We study various three-dimensional supersymmetric Maxwell Chern-Simons
solitons by using type IIB brane configurations. We give a systematic
classification of soliton spectra such as topological BPS vortices and
nontopological vortices in supersymmetric Maxwell
Chern-Simons system via the branes of type IIB string theory. We identify the
brane configurations with the soliton spectra of the field theory and obtain a
nice agreement with field theory aspects. We also discuss possible brane
constructions for BPS domain wall solutions.Comment: 23 pages, Latex, 4 figures; (q_1,q_2)-string convention changed,
minor correction
Antibacterial PMMA Composite Cements with Tunable Thermal and Mechanical Properties
PMMA-based cements are the most used bone cements in vertebroplasty and total hip arthroplasty. However, they present several drawbacks, including susceptibility to bacterial infection, monomer leakage toxicity, and high polymerization temperature, which can all lead to damage to the surrounding tissues and their failure. In the present study, silver nanowires (AgNWs) have been introduced to bestow antibacterial properties; chitosan (CS) to promote porosity and to reduce the polymerization temperature, without negatively affecting the mechanical performance; and methacryloyl chitosan (CSMCC) to promote cross-linking with methyl methacrylate (MMA) and reduce the quantity of monomer required for polymerization. Novel PMMA cements were formulated containing AgNWs (0 and 1% w/w) and CS or CSMCC at various concentrations (0, 10, 20, and 30% w/w), testing two different ratios of powder and MMA (P/L). Mechanical, thermal, antibacterial, and cytotoxic properties of the resulting composite cements were tested. Cements with concentrations of CS > 10% presented a significantly reduced polymerization temperature. The mechanical performances were affected for concentrations > 20% with a P/L concentration equal to 2:1. Concentrations of AgNWs as low as 1% w/w conferred antimicrobial activity against S. aureus, whereas biofilm formation on the surface of the cements was increased when CS was included in the preparation. The combination of CS and AgNWs allowed a higher concentration of Ag+ to be released over time with enhanced antimicrobial activity. Inclusion of AgNWs did not affect cell viability on the scaffolds. In conclusion, a combination of CS and AgNWs may be beneficial for reducing both polymerization temperature and biofilm formation, without significantly affecting mesenchymal stem cell proliferation on the scaffolds. No advantages have been noticed as a result of the reducing P/L ratio or using CSMCC instead of CS
Skeletal disproportion in glucocorticoid-treated boys with Duchenne muscular dystrophy
We aimed to compare body segment and bone lengths in glucocorticoid-treated boys with Duchenne muscular dystrophy (DMD) with healthy controls using dual-energy absorptiometry (DXA) images. Total height (Ht), sitting height (SH), leg length (LL) and bone lengths (femur, tibia) in boys with DMD and age-matched control boys were measured using DXA. Thirty boys with DMD (median age 10.0 years (6.1, 16.8)) were compared with 30 controls. SH in DMD was 3.3 cm lower (95% CI − 6.1, − 0.66; p = 0.016). LL in DMD was 7.3 cm lower (95% CI − 11.2, − 3.4; p < 0.0001). SH:LL of boys with DMD was higher by 0.08 (95% CI 0.04, 0.12; p < 0.0001). Femur length in DMD was 2.4 cm lower (95% CI − 4.6, − 0.12; p = 0.04), whereas tibial length in DMD was 4.8 cm lower (95% CI − 6.7, − 2.9; p < 0.0001). SH:LL was not associated with duration of glucocorticoid use (SH:LL β = 0.003, 95% CI − 0.01 to 0.002, p = 0.72).
Conclusion: Glucocorticoid-treated boys with DMD exhibit skeletal disproportion with relatively shorter leg length and more marked reduction of distal long bones. As glucocorticoid excess is not associated with such disproportion, our findings raise the possibility of an intrinsic disorder of growth in DMD
Inverse Melting of an Electronic Liquid Crystal
Inverse melting refers to the rare thermodynamic phenomenon in which a solid
melts into a liquid upon cooling, a transition that can occur only when the
ordered (solid) phase has more entropy than the disordered (liquid) phase, and
that has so far only been observed in a handful of systems. Here we report the
first experimental observation for the inverse melting of an electronic liquid
crystalline order in strontium-doped lanthanum nickelate, a compound
isostructural with the superconducting cuprates, with a hole doping
concentration of 1/3. Using x-ray scattering, we demonstrate that the isotropic
charge modulation is driven to nematic order by fluctuating spins and shows an
inverse melting transition. Using a phenomenological Landau theory, we show
that this inverse melting transition is due to the interlayer coupling between
the charge and spin orders. This discovery points to the importance of the
interlayer correlations in the system, and provides a new perspective to study
the intricate nature of the electronic liquid crystal phases in strongly
correlated electronic systems, including possibly the Cu- and Fe-based high-Tc
superconductors.Comment: 7 pages, 7 figure
Inverse order-disorder transition of charge stripes
We report an unusual transition behavior of charge stripes in La1.67Sr0.33NiO4 using x-ray scattering. The segregated holes in La1.67Sr0.33NiO4 are observed to form anisotropic stripes in the a × b plane of the crystal space below the transition temperature T 238 K, and at the same time, display an unusual inverse order-disorder transition along the c axis. Using a phenomenological Landau theory, we show that this inverse transition is due to the interlayer coupling between the charge and spin orders. This discovery points to the importance of the interlayer correlations in the strongly correlated electrons system
Proficient brain for optimal performance: the MAP model perspective
Background. The main goal of the present study was to explore theta and alpha event-related desynchronization/synchronization (ERD/ERS) activity during shooting performance. We adopted the idiosyncratic framework of the multi-action plan (MAP) model to investigate different processing modes underpinning four types of performance. In particular, we were interested in examining the neural activity associated with optimal-automated (Type 1) and optimal-controlled (Type 2) performances. Methods. Ten elite shooters (6 male and 4 female) with extensive international experience participated in the study. ERD/ERS analysis was used to investigate cortical dynamics during performance. A 4 × 3 (performance types × time) repeated measures analysis of variance was performed to test the differences among the four types of performance during the three seconds preceding the shots for theta, low alpha, and high alpha frequency bands. The dependent variables were the ERD/ERS percentages in each frequency band (i.e., theta, low alpha, high alpha) for each electrode site across the scalp. This analysis was conducted on 120 shots for each participant in three different frequency bands and the individual data were then averaged. Results. We found ERS to be mainly associated with optimal-automatic performance, in agreement with the “neural efficiency hypothesis.” We also observed more ERD as related to optimal-controlled performance in conditions of “neural adaptability” and proficient use of cortical resources. Discussion. These findings are congruent with the MAP conceptualization of four performance states, in which unique psychophysiological states underlie distinct performance-related experiences. From an applied point of view, our findings suggest that the MAP model can be used as a framework to develop performance enhancement strategies based on cognitive and neurofeedback technique
Conformal Dimensions from Topologically Massive Quantum Field Theory
We discuss the evaluation of observables in two-dimensional conformal field
theory using the topological membrane description. We show that the spectrum of
anomalous dimensions can be obtained perturbatively from the topologically
massive quantum field theories by computing radiative corrections to
Aharonov-Bohm scattering amplitudes for dynamical charged matter fields. The
one-loop corrections in the case of topologically massive Yang-Mills theory are
shown to coincide with the scaling dimensions of the induced ordinary and
supersymmetric WZNW models. We examine the effects of the dressing of a
topologically massive gauge theory by topologically massive gravity and show
that the one-loop contributions to the Aharonov-Bohm amplitudes coincide with
the leading orders of the KPZ scaling relations for two-dimensional quantum
gravity. Some general features of the description of conformal field theories
via perturbative techniques in the three-dimensional approach are also
discussed.Comment: 48 pages Latex; Uses macro package FEYNMAN.te
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