197 research outputs found
Magneto-plasmonic heterodimers: Evaluation of different synthesis approaches
Nanomedicine has gained huge attention in recent years with new approaches in medical diagnosis and therapy. Particular consideration has been devoted to the nanoparticles (NPs) in theranostic field with specific interest for magnetic and gold NPs (MNPs and GNPs) due to their peculiar properties under exposition to electromagnetic fields. In this paper, we aim to develop magneto-plasmonic heterodimer by combining MNPs and GNPs through a facile and reproducible synthesis and to investigate the influence of different synthesis parameters on their response to magnetic and optical stimuli. In particular, various syntheses were performed by changing the functionalization step and using or not a reducing agent to obtain stable NP suspensions with tailored properties. The obtained heterodimers were characterized through physical, chemical, optical, and magnetic analysis, in order to evaluate their size, shape, plasmonic properties, and superparamagnetic behavior. The results revealed that the shape and dimensions of the nanocomposites can be tuned by MNPs surface functionalization, as well as by the use of a reducing agent, giving rise to nanoplatform suitable for biomedical application, exploiting the gold absorbing peak in the specific gold absorbing range of GNPs, while maintaining the superparamagnetic behavior typical of the MNPs. The obtained nanocomposites can be proposed as potential candidates for cancer theranostics
Membrane Sigma-Models and Quantization of Non-Geometric Flux Backgrounds
We develop quantization techniques for describing the nonassociative geometry
probed by closed strings in flat non-geometric R-flux backgrounds M. Starting
from a suitable Courant sigma-model on an open membrane with target space M,
regarded as a topological sector of closed string dynamics in R-space, we
derive a twisted Poisson sigma-model on the boundary of the membrane whose
target space is the cotangent bundle T^*M and whose quasi-Poisson structure
coincides with those previously proposed. We argue that from the membrane
perspective the path integral over multivalued closed string fields in Q-space
is equivalent to integrating over open strings in R-space. The corresponding
boundary correlation functions reproduce Kontsevich's deformation quantization
formula for the twisted Poisson manifolds. For constant R-flux, we derive
closed formulas for the corresponding nonassociative star product and its
associator, and compare them with previous proposals for a 3-product of fields
on R-space. We develop various versions of the Seiberg-Witten map which relate
our nonassociative star products to associative ones and add fluctuations to
the R-flux background. We show that the Kontsevich formula coincides with the
star product obtained by quantizing the dual of a Lie 2-algebra via convolution
in an integrating Lie 2-group associated to the T-dual doubled geometry, and
hence clarify the relation to the twisted convolution products for topological
nonassociative torus bundles. We further demonstrate how our approach leads to
a consistent quantization of Nambu-Poisson 3-brackets.Comment: 52 pages; v2: references adde
Influence of Analysis Technique on Measurement of Diffusion Tensor Imaging Parameters
We compared results from various methods of analysis of diffusion tensor imaging (DTI) data from a single data set consisting of 10 healthy adolescents
Affect in mathematics education
There are two different uses for the word “affect” in behavioral sciences. Often it is used as an overarching umbrella concept that covers attitudes, beliefs, motivation, emotions, and all other noncognitive aspects of human mind. In this article, however, the word affect is used in a more narrow sense, referring to emotional states and traits. A more technical definition of emotions, states, and traits will follow later.Peer reviewe
Mindfulness-based interventions for young offenders: a scoping review
Youth offending is a problem worldwide. Young people in the criminal justice system have frequently experienced adverse childhood circumstances, mental health problems, difficulties regulating emotions and poor quality of life. Mindfulness-based interventions can help people manage problems resulting from these experiences, but their usefulness for youth offending populations is not clear. This review evaluated existing evidence for mindfulness-based interventions among such populations. To be included, each study used an intervention with at least one of the three core components of mindfulness-based stress reduction (breath awareness, body awareness, mindful movement) that was delivered to young people in prison or community rehabilitation programs. No restrictions were placed on methods used. Thirteen studies were included: three randomized controlled trials, one controlled trial, three pre-post study designs, three mixed-methods approaches and three qualitative studies. Pooled numbers (n = 842) comprised 99% males aged between 14 and 23. Interventions varied so it was not possible to identify an optimal approach in terms of content, dose or intensity. Studies found some improvement in various measures of mental health, self-regulation, problematic behaviour, substance use, quality of life and criminal propensity. In those studies measuring mindfulness, changes did not reach statistical significance. Qualitative studies reported participants feeling less stressed, better able to concentrate, manage emotions and behaviour, improved social skills and that the interventions were acceptable. Generally low study quality limits the generalizability of these findings. Greater clarity on intervention components and robust mixed-methods evaluation would improve clarity of reporting and better guide future youth offending prevention programs
D1-Strings in Large RR 3-Form Flux, Quantum Nambu Geometry and M5-Branes in C-Field
We consider D1-branes in a RR flux background and show that there is a low
energy - large flux double scaling limit where the D1-branes action is
dominated by a Chern-Simons-Myers coupling term. As a classical solution to the
matrix model, we find a novel quantized geometry characterized by a quantum
Nambu 3-bracket. Infinite dimensional representations of the quantum Nambu
geometry are constructed which demonstrate that the quantum Nambu geometry is
intrinsically different from the ordinary Lie algebra type noncommutative
geometry. Matrix models for the IIB string, IIA string and M-theory in the
corresponding backgrounds are constructed. A classical solution of a quantum
Nambu geometry in the IIA Matrix string theory gives rise to an expansion of
the fundamental strings into a system of multiple D4-branes and the fluctuation
is found to describe an action for a non-abelian 3-form field strength which is
a natural non-abelian generalization of the PST action for a single D4-brane.
In view of the recent proposals of the M5-branes theory in terms of the
D4-branes, we suggest a natural way to include all the KK modes and propose an
action for the the multiple M5-branes in a constant C-field. The worldvolume of
the M5-branes in a C-field is found to be described by a quantum Nambu geometry
with self-dual parameters. It is intriguing that our action is naturally
formulated in terms of a 1-form gauge field living on a six dimensional quantum
Nambu geometry.Comment: 34 pages. LaTe
G<sub>2</sub>-structures and quantization of non-geometric M-theory backgrounds
We describe the quantization of a four-dimensional locally non-geometric
M-theory background dual to a twisted three-torus by deriving a phase space
star product for deformation quantization of quasi-Poisson brackets related to
the nonassociative algebra of octonions. The construction is based on a choice
of -structure which defines a nonassociative deformation of the addition
law on the seven-dimensional vector space of Fourier momenta. We demonstrate
explicitly that this star product reduces to that of the three-dimensional
parabolic constant -flux model in the contraction of M-theory to string
theory, and use it to derive quantum phase space uncertainty relations as well
as triproducts for the nonassociative geometry of the four-dimensional
configuration space. By extending the -structure to a -structure,
we propose a 3-algebra structure on the full eight-dimensional M2-brane phase
space which reduces to the quasi-Poisson algebra after imposing a particular
gauge constraint, and whose deformation quantisation simultaneously encompasses
both the phase space star products and the configuration space triproducts. We
demonstrate how these structures naturally fit in with previous occurences of
3-algebras in M-theory.Comment: 41 pages; v2: Final version published in JHE
Light and tree size influence belowground development in yellow birch and sugar maple
The effects of light and tree size on the root architecture and mycorrhiza of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh) growing in the understory of deciduous forests in southern Qu
Extended generalized geometry and a DBI-type effective action for branes ending on branes
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