6,371 research outputs found
Interaction induced dimerization in zigzag single wall carbon nanotubes
We derive a low-energy effective model of metallic zigzag carbon nanotubes at
half filling. We show that there are three important features characterizing
the low-energy properties of these systems: the long-range Coulomb interaction,
umklapp scattering and an explicit dimerization generated by interactions. The
ratio of the dimerization induced gap and the Mott gap induced by the umklapp
interactions is dependent on the radius of the nanotube and can drive the
system through a quantum phase transition with SU(2)_1 quantum symmetry. We
consider the physical properties of the phases on either side of this
transition which should be relevant for realistic nanotubes.Comment: 8 pages, 5 figure
Clinical and radiological midterm results from using the Fixion expandable intramedullary nail in transverse and short oblique fractures of femur and tibia
BACKGROUND: A locked nail is the principal method used to eliminate rotatory components in femoral and tibial fractures. Nevertheless, weight bearing is not directed onto the fracture site, slowing down the healing process; another possibility is to use a large-diameter nail and ream the canal to obtain as much adherence as possible and increase the grip, but this can cause a number of complications. The expandable nail is a new option that in theory should remove some problems with previous techniques. MATERIALS AND METHODS: This was a retrospective nonrandomized study encompassing 21 femoral fractures and 27 tibial fractures in 45 patients. They were classified according to the AO classification. Clinical and radiological checks were done at one, three, and six months and at one year from the surgery in order to check for signs of clinical and radiological healing. A good alignment was considered to be the presence of a deformity of less than 5° in the sagittal and lateral planes and the absence of rotatory clinically evident problems. This protocol was adhered to up to six months after surgery by all of the patients, while only 62.2% performed the last control. The mean follow-up was 15 months. A second group of 48 consecutive fractures (24 femural and 24 tibial) treated with locked nail was created to compare surgical times. RESULTS: Appropriate alignment was observed in all cases; the healing process appeared slower: radiological healing occurred in most cases at six months. The following complications were reported: a case of intraoperative fracture widening with no effect on the treatment; a case of a lesion of the tip of the nail with pneumatic system rupture that necessitated nail substitution; two cases of retarded consolidation at six months, with both tibial fractures treated successfully by intralesion platelet gel; a case of incarcerated nail on 17 removals, resolved by shearing. We had no cases of clinically evident compartment syndrome or pulmonary embolism. CONCLUSIONS: The expandable Fixion nail presents significant advantages in the treatment of transverse and short oblique fractures of femur and tibia because it is easy to use, involves minimal X-ray exposure and can control rotations. Nevertheless, it high cost limits its use. We consider it as an alternative to locked nail
Bulk one-point function on disk in one-matrix model
We consider bulk correlation numbers on disk in one-matrix model. Using the
recently found so-called resonance transformation from the KdV to the Liouville
frame, we obtain an explicit expression for the bulk one-point function. The
result is consistent with the form of FZZ one-point function in the boundary
Liouville Field Theory.Comment: 8 page
{\mu}Split: efficient image decomposition for microscopy data
We present {\mu}Split, a dedicated approach for trained image decomposition
in the context of fluorescence microscopy images. We find that best results
using regular deep architectures are achieved when large image patches are used
during training, making memory consumption the limiting factor to further
improving performance. We therefore introduce lateral contextualization (LC), a
memory efficient way to train powerful networks and show that LC leads to
consistent and significant improvements on the task at hand. We integrate LC
with U-Nets, Hierarchical AEs, and Hierarchical VAEs, for which we formulate a
modified ELBO loss. Additionally, LC enables training deeper hierarchical
models than otherwise possible and, interestingly, helps to reduce tiling
artefacts that are inherently impossible to avoid when using tiled VAE
predictions. We apply {\mu}Split to five decomposition tasks, one on a
synthetic dataset, four others derived from real microscopy data. LC achieves
SOTA results (average improvements to the best baseline of 2.36 dB PSNR), while
simultaneously requiring considerably less GPU memory.Comment: Published at ICCV 2023. 10 pages, 7 figures, 9 pages supplement, 8
supplementary figure
The Gravity Dual of the Ising Model
We evaluate the partition function of three dimensional theories of gravity
in the quantum regime, where the AdS radius is Planck scale and the central
charge is of order one. The contribution from the AdS vacuum sector can - with
certain assumptions - be computed and equals the vacuum character of a minimal
model CFT. The torus partition function is given by a sum over geometries which
is finite and computable. For generic values of Newton's constant G and the AdS
radius L the result has no Hilbert space interpretation, but in certain cases
it agrees with the partition function of a known CFT. For example, the
partition function of pure Einstein gravity with G=3L equals that of the Ising
model, providing evidence that these theories are dual. We also present
somewhat weaker evidence that the 3-state and tricritical Potts models are dual
to pure higher spin theories of gravity based on SL(3) and E_6, respectively.Comment: 42 page
Laser irradiated foam targets: absorption and radiative properties
An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminium targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target
Current fluctuations in stochastically resetting particle systems
We consider a system of non-interacting particles on a line with initial
positions distributed uniformly with density on the negative half-line.
We consider two different models: (i) each particle performs independent
Brownian motion with stochastic resetting to its initial position with rate
and (ii) each particle performs run and tumble motion, and with rate its
position gets reset to its initial value and simultaneously its velocity gets
randomised. We study the effects of resetting on the distribution of
the integrated particle current up to time through the origin (from
left to right). We study both the annealed and the quenched current
distributions and in both cases, we find that resetting induces a stationary
limiting distribution of the current at long times. However, we show that the
approach to the stationary state of the current distribution in the annealed
and the quenched cases are drastically different for both models. In the
annealed case, the whole distribution approaches its
stationary limit uniformly for all . In contrast, the quenched distribution
attains its stationary form for , while it
remains time-dependent for . We show that increases linearly with for large . On the scale where , we show that has an unusual large deviation
form with a rate function that has a third-order phase transition at the
critical point. We have computed the associated rate functions analytically for
both models. Using an importance sampling method that allows to probe
probabilities as tiny as , we were able to compute numerically
this non-analytic rate function for the resetting Brownian dynamics and found
excellent agreement with our analytical prediction.Comment: 26 pages, 6 figure
The two-boundary Temperley-Lieb algebra
We study a two-boundary extension of the Temperley-Lieb algebra which has
recently arisen in statistical mechanics. This algebra lies in a quotient of
the affine Hecke algebra of type C and has a natural diagrammatic
representation. The algebra has three parameters and, for generic values of
these, we determine its representation theory.
We use the action of the centre of the affine Hecke algebra to show that all
irreducible representations lie within a finite dimensional diagrammatic
quotient. These representations are fully characterised by an additional
parameter related to the action of the centre. For generic values of this
parameter there is a unique representation of dimension 2^N and we show that it
is isomorphic to a tensor space representation. We construct a basis in which
the Gram matrix is diagonal and use this to discuss the irreducibility of this
representation.Comment: 45 pages Latex, 21 eps figures, revised versio
Asymptotics of the instantons of Painleve I
The 0-instanton solution of Painlev\'e I is a sequence of complex
numbers which appears universally in many enumerative problems in algebraic
geometry, graph theory, matrix models and 2-dimensional quantum gravity. The
asymptotics of the 0-instanton for large were obtained by the
third author using the Riemann-Hilbert approach. For , the
-instanton solution of Painlev\'e I is a doubly-indexed sequence
of complex numbers that satisfies an explicit quadratic non-linear recursion
relation. The goal of the paper is three-fold: (a) to compute the asymptotics
of the 1-instanton sequence to all orders in by using the
Riemann-Hilbert method, (b) to present formulas for the asymptotics of
for fixed and to all orders in using resurgent analysis,
and (c) to confirm numerically the predictions of resurgent analysis. We point
out that the instanton solutions display a new type of Stokes behavior, induced
from the tritronqu\'ee Painlev\'e transcendents, and which we call the induced
Stokes phenomenon. The asymptotics of the 2-instanton and beyond exhibits new
phenomena not seen in 0 and 1-instantons, and their enumerative context is at
present unknown.Comment: 29 pages, 8 figure
Shape-specific microfabricated particles for biomedical applications: a review
The storied history of controlled the release systems has evolved over time; from degradable drug-loaded sutures to monolithic zero-ordered release devices and nano-sized drug delivery formulations. Scientists have tuned the physico-chemical properties of these drug carriers to optimize their performance in biomedical/pharmaceutical applications. In particular, particle drug delivery systems at the micron size regime have been used since the 1980s. Recent advances in micro and nanofabrication techniques have enabled precise control of particle size and geometry–here we review the utility of microplates and discoidal polymeric particles for a range of pharmaceutical applications. Microplates are defined as micrometer scale polymeric local depot devices in cuboid form, while discoidal polymeric nanoconstructs are disk-shaped polymeric particles having a cross-sectional diameter in the micrometer range and a thickness in the hundreds of nanometer range. These versatile particles can be used to treat several pathologies such as cancer, inflammatory diseases and vascular diseases, by leveraging their size, shape, physical properties (e.g., stiffness), and component materials, to tune their functionality. This review highlights design and fabrication strategies for these particles, discusses their applications, and elaborates on emerging trends for their use in formulations. GRAPHICAL ABSTRACT: [Image: see text
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