Antibiofilm surface functionalization of catheters by magnesium fluoride nanoparticles

The ability of bacteria to colonize catheters is a major cause of infection. In the current study, catheters were surface-modified with MgF2 nanoparticles (NPs) using a sonochemical synthesis protocol described previously. The one-step synthesis and coating procedure yielded a homogenous MgF2 NP layer on both the inside and outside of the catheter, as analyzed by high resolution scanning electron microscopy and energy dispersive spectroscopy. The coating thickness varied from approximately 750 nm to 1000 nm on the inner walls and from approximately 450 nm to approximately 580 nm for the outer wall. The coating consisted of spherical MgF2 NPs with an average diameter of approximately 25 nm. These MgF2 NP-modified catheters were investigated for their ability to restrict bacterial biofilm formation. Two bacterial strains most commonly associated with catheter infections, Escherichia coli and Staphylococcus aureus, were cultured in tryptic soy broth, artificial urine and human plasma on the modified catheters. The MgF2 NP-coated catheters were able to significantly reduce bacterial colonization for a period of 1 week compared to the uncoated control. Finally, the potential cytotoxicity of MgF2 NPs was also evaluated using human and mammalian cell lines and no significant reduction in the mitochondrial metabolism was observed. Taken together, our results indicate that the surface modification of catheters with MgF2 NPs can be effective in preventing bacterial colonization and can provide catheters with long-lasting self-sterilizing properties

Shape-Dependence of Spontaneous Photon Emission by Quantum Electron Wavepackets and the QED Origin of Bunched Electron Beam Superradiance

It has been shown that the spontaneous emission rate of photons by free electrons, unlike stimulated emission, is independent of the shape or modulation of the quantum electron wavefunction (QEW). Nevertheless, here we show that the quantum state of the emitted photons is non-classical and does depend on the QEW shape. This non-classicality originates from the shape dependent off-diagonal terms of the photon density matrix. This is manifested in the Wigner distribution function and would be observable experimentally through Homodyne detection techniques as a squeezing effect. Considering a scheme of electrons interaction with a single microcavity mode, we present a QED formulation of spontaneous emission by multiple modulated QEWs through a build-up process. Our findings indicate that in the case of a density modulated QEWs beam, the phase of the off-diagonal terms of the photon state emitted by the modulated QEWs is the harbinger of bunched beam superradiance, where the spontaneous emission is proportional to N_e^2. This observation offers a potential for enhancement of other quantum electron interactions with quantum systems by a modulated QEWs beam carrying coherence and quantum properties of the modulation.Comment: 52 pages, 6 figures,Suppl. Mater. 25 pages, Suppl. Mater. 5 figures, 1 tabl

The Sample Complexity of Dictionary Learning

A large set of signals can sometimes be described sparsely using a dictionary, that is, every element can be represented as a linear combination of few elements from the dictionary. Algorithms for various signal processing applications, including classification, denoising and signal separation, learn a dictionary from a set of signals to be represented. Can we expect that the representation found by such a dictionary for a previously unseen example from the same source will have L_2 error of the same magnitude as those for the given examples? We assume signals are generated from a fixed distribution, and study this questions from a statistical learning theory perspective. We develop generalization bounds on the quality of the learned dictionary for two types of constraints on the coefficient selection, as measured by the expected L_2 error in representation when the dictionary is used. For the case of l_1 regularized coefficient selection we provide a generalization bound of the order of O(sqrt(np log(m lambda)/m)), where n is the dimension, p is the number of elements in the dictionary, lambda is a bound on the l_1 norm of the coefficient vector and m is the number of samples, which complements existing results. For the case of representing a new signal as a combination of at most k dictionary elements, we provide a bound of the order O(sqrt(np log(m k)/m)) under an assumption on the level of orthogonality of the dictionary (low Babel function). We further show that this assumption holds for most dictionaries in high dimensions in a strong probabilistic sense. Our results further yield fast rates of order 1/m as opposed to 1/sqrt(m) using localized Rademacher complexity. We provide similar results in a general setting using kernels with weak smoothness requirements

A blocking monoclonal antibody to CCL24 alleviates liver fibrosis and inflammation in experimental models of liver damage

Background & Aims: C-C motif chemokine ligand 24 (CCL24) is a chemokine that regulates inflammatory and fibrotic activities through its receptor, C-C motif chemokine receptor (CCR3). The aim of the study was to evaluate the involvement of the CCL24-CCR3 axis in liver fibrosis and inflammation and to assess the potential of its blockade, by a monoclonal anti-CCL24 antibody, as a therapeutic strategy for non-alcoholic steatohepatitis (NASH) and liver fibrosis. Methods: Expression of CCL24 and CCR3 was evaluated in liver biopsies and blood samples. CCL24 involvement in NAFLD/NASH pathogenesis was assessed in Ccl24 knockout mouse using the methionine-choline deficient (MCD) diet experimental model. Antifibrotic and anti-inflammatory effects of CM-101 were tested in the MCD and STAM mouse models and in the thioacetamide (TAA) model in rats. Liver enzymes, liver morphology, histology and collagen deposition, as well as fibrosis- and inflammation-related protein expression were assessed. Activation of hepatic stellate cells (HSCs) was evaluated in the human LX2 cell line. Results: Patients with NASH and advanced NAFLD exhibited significant expression of both CCL24 and CCR3 in liver and blood samples. In the experimental MCD-diet model, Ccl24 knockout mice showed an attenuated liver damage response compared to wild-type mice, exhibiting reduced histological NAFLD activity scores and fibrosis, as well as lower levels of liver enzymes. Blocking CCL24 using CM-101 robustly reduced liver damage in 3 experimental animal models (MCD, STAM and TAA), as demonstrated by attenuation of liver fibrosis and NAFLD activity score. Furthermore, blocking CCL24 by CM-101 significantly inhibited CCL24-induced HSC motility, α-SMA expression and pro-collagen I secretion. Conclusion: Our results reveal that blocking CCL24 significantly attenuates liver fibrosis and inflammation and may have a potential therapeutic effect in patients with NASH and/or liver fibrosis. Lay summary: CCL24 is a chemokine that regulates inflammation and fibrosis. It was found to be significantly expressed in patients with non-alcoholic steatohepatitis, in whom it regulates profibrotic processes in the liver. Herein, we show that blockade of CCL24 using a monoclonal antibody robustly attenuated liver fibrosis and inflammation in animal models, thus suggesting a potential therapeutic role for an anti-CCL24 agent

Theory and design consideration of a THz superradiant waveguide FEL

We present theoretical analysis and design considerations of a THz superradiant FEL. We derive analytical expressions for the spectral parameter of THz radiation, emitted superradiantly in a rectangular waveguide using a Longitudinal Section Magnetic mode expansion. The results compare well with numerical simulations using UCLA GPTFEL code. GPT simulations of the accelerator e-beam transport show that the chirp provided by a hybrid photocathode RF gun, can produce tight bunching at the undulator site below σ = 100fs. This enables intense superradiant emission up to 3THz, limited by the beam bunching factor. Phase-space analysis of the beam transport indicates that keeping the beam bunching parameter small enough for higher THz frequency operation is limited by the energy spread of the beam in the gun

Geodetic Brane Gravity

Within the framework of geodetic brane gravity, the Universe is described as a 4-dimensional extended object evolving geodetically in a higher dimensional flat background. In this paper, by introducing a new pair of canonical fields {lambda, P_{lambda}}, we derive the quadratic Hamiltonian for such a brane Universe; the inclusion of matter then resembles minimal coupling. Second class constraints enter the game, invoking the Dirac bracket formalism. The algebra of the first class constraints is calculated, and the BRST generator of the brane Universe turns out to be rank-1. At the quantum level, the road is open for canonical and/or functional integral quantization. The main advantages of geodetic brane gravity are: (i) It introduces an intrinsic, geometrically originated, 'dark matter' component, (ii) It offers, owing to the Lorentzian bulk time coordinate, a novel solution to the 'problem of time', and (iii) It enables calculation of meaningful probabilities within quantum cosmology without any auxiliary scalar field. Intriguingly, the general relativity limit is associated with lambda being a vanishing (degenerate) eigenvalue.Comment: 23 pages, 1 figure, minor change

Cooperative greedy pursuit strategies for sparse signal representation by partitioning

Cooperative Greedy Pursuit Strategies are considered for approximating a signal partition subjected to a global constraint on sparsity. The approach aims at producing a high quality sparse approximation of the whole signal, using highly coherent redundant dictionaries. The cooperation takes place by ranking the partition units for their sequential stepwise approximation, and is realized by means of i)forward steps for the upgrading of an approximation and/or ii) backward steps for the corresponding downgrading. The advantage of the strategy is illustrated by approximation of music signals using redundant trigonometric dictionaries. In addition to rendering stunning improvements in sparsity with respect to the concomitant trigonometric basis, these dictionaries enable a fast implementation of the approach via the Fast Fourier Transfor

Coherent Excitation of Bound Electron Quantum State With Quantum Electron Wavepackets

We present a fully quantum model for the excitation of a bound electron based on the “free-electron bound-electron resonant interaction” (FEBERI) scheme. The bound electron is modeled as a quantum two-level system (TLS) at any initial quantum (qubit) state, and the free electron is presented as a pre-shaped quantum electron wavepacket (QEW). In the case that the QEW is short or modulated at optical frequency, the TLS quantum state may be coherently controlled with multiple modulation-correlated QEWs. For this case, we derive the transition probability of the TLS due to interaction with a multi-particle beam based on an analytical approximate solution of the Schrodinger equation that amounts to using Born’s probabilistic interpretation of the quantum electron wavefunction. We verify the credibility of the analytical model at its validity ranges using a fully quantum density matrix computation procedure. It is shown that the transition probability can grow quadratically with the number of correlated QEWs and exhibit Rabi oscillation. The study indicates a possibility of engineering the quantum state of a TLS by utilizing a beam of shaped QEWs