Characterization of a defective PbWO4 crystal cut along the a-c crystallographic plane: structural assessment and a novel photoelastic stress analysis

Among scintillators, the PWO is one of the most widely used, for instance in CMS calorimeter at CERN and PANDA project. Crystallographic structure and chemical composition as well as residual stress condition, are indicators of homogeneity and good quality of the crystal. In this paper, structural characterization of a defective PbWO4 (PWO) crystal has been performed by X-ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Photoelasticity in the unusual a-c crystallographic plane. XRD and EDS analysis have been used to investigate crystallographic orientation and chemical composition, while stress distribution, which indicates macroscopic inhomogeneities and defects, has been obtained by photoelastic approaches, in Conoscopic and Sphenoscopic configuration. Since the sample is cut along the a-c crystallographic plane, a new method is proposed for the interpretation of the fringe pattern. The structural analysis has detected odds from the nominal lattice dimension, which can be attributed to the strong presence of Pb and W. A strong inhomogeneity over the crystal sample has been revealed by the photoelastic inspection. The results give reliability to the proposed procedure which is exploitable in crystals with other structures.Comment: 18 pages, 10 figures, revised versio

Bandgap Narrowing in Quantum Wires

In this paper we consider two different geometry of quasi one-dimensional semiconductors and calculate their exchange-correlation induced bandgap renormalization (BGR) as a function of the electron-hole plasma density and quantum wire width. Based on different fabrication scheme, we define suitable external confinement potential and then leading-order GW dynamical screening approximation is used in the calculation by treating electron-electron Coulomb interaction and electron-optical phonon interaction. Using a numerical scheme, screened Coulomb potential, probability of different states, profile of charge density and the values of the renormalized gap energy are calculated and the effects of variation of confinement potential width and temperature are studied.Comment: 17 Pages, 4 Figure

Additive energy forward curves in a Heath-Jarrow-Morton framework

One of the peculiarities of power and gas markets is the delivery mechanism of forward contracts. The seller of a futures contract commits to deliver, say, power, over a certain period, while the classical forward is a financial agreement settled on a maturity date. Our purpose is to design a Heath-Jarrow-Morton framework for an additive, mean-reverting, multicommodity market consisting of forward contracts of any delivery period. The main assumption is that forward prices can be represented as affine functions of a universal source of randomness. This allows us to completely characterize the models which prevent arbitrage opportunities: this boils down to finding a density between a risk-neutral measure $\mathbb{Q}$, such that the prices of traded assets like forward contracts are true $\mathbb{Q}$-martingales, and the real world probability measure $\mathbb{P}$, under which forward prices are mean-reverting. The Girsanov kernel for such a transformation turns out to be stochastic and unbounded in the diffusion part, while in the jump part the Girsanov kernel must be deterministic and bounded: thus, in this respect, we prove two results on the martingale property of stochastic exponentials. The first allows to validate measure changes made of two components: an Esscher-type density and a Girsanov transform with stochastic and unbounded kernel. The second uses a different approach and works for the case of continuous density. We apply this framework to two models: a generalized Lucia-Schwartz model and a cross-commodity cointegrated market.Comment: 28 page

Decoration of nanovesicles with pH (low) insertion peptide (pHLIP) for targeted delivery

Acidity at surface of cancer cells is a hallmark of tumor microenvironments, which does not depend on tumor perfusion, thus it may serve as a general biomarker for targeting tumor cells. We used the pH (low) insertion peptide (pHLIP) for decoration of liposomes and niosomes. pHLIP senses pH at the surface of cancer cells and inserts into the membrane of targeted cells, and brings nanomaterial to close proximity of cellular membrane. DMPC liposomes and Tween 20 or Span 20 niosomes with and without pHLIP in their coating were fully characterized in order to obtain fundamental understanding on nanocarrier features and facilitate the rational design of acidity sensitive nanovectors. The samples stability over time and in presence of serum was demonstrated. The size, ζ-potential, and morphology of nanovectors, as well as their ability to entrap a hydrophilic probe and modulate its release were investigated. pHLIP decorated vesicles could be useful to obtain a prolonged (modified) release of biological active substances for targeting tumors and other acidic diseased tissues

Percolation of Partially Interdependent Scale-free Networks

We study the percolation behavior of two interdependent scale-free (SF) networks under random failure of 1-$p$ fraction of nodes. Our results are based on numerical solutions of analytical expressions and simulations. We find that as the coupling strength between the two networks $q$ reduces from 1 (fully coupled) to 0 (no coupling), there exist two critical coupling strengths $q_1$ and $q_2$, which separate three different regions with different behavior of the giant component as a function of $p$. (i) For $q \geq q_1$, an abrupt collapse transition occurs at $p=p_c$. (ii) For $q_2<q<q_1$, the giant component has a hybrid transition combined of both, abrupt decrease at a certain $p=p^{jump}_c$ followed by a smooth decrease to zero for $p < p^{jump}_c$ as $p$ decreases to zero. (iii) For $q \leq q_2$, the giant component has a continuous second-order transition (at $p=p_c$). We find that $(a)$ for $\lambda \leq 3$, $q_1 \equiv 1$; and for $\lambda > 3$, $q_1$ decreases with increasing $\lambda$. $(b)$ In the hybrid transition, at the $q_2 < q < q_1$ region, the mutual giant component $P_{\infty}$ jumps discontinuously at $p=p^{jump}_c$ to a very small but non-zero value, and when reducing $p$, $P_{\infty}$ continuously approaches to 0 at $p_c = 0$ for $\lambda 0$ for $\lambda > 3$. Thus, the known theoretical $p_c=0$ for a single network with $\lambda \leqslant 3$ is expected to be valid also for strictly partial interdependent networks.Comment: 20 pages, 17 figure

Minimal Scales from an Extended Hilbert Space

We consider an extension of the conventional quantum Heisenberg algebra, assuming that coordinates as well as momenta fulfil nontrivial commutation relations. As a consequence, a minimal length and a minimal mass scale are implemented. Our commutators do not depend on positions and momenta and we provide an extension of the coordinate coherent state approach to Noncommutative Geometry. We explore, as toy model, the corresponding quantum field theory in a (2+1)-dimensional spacetime. Then we investigate the more realistic case of a (3+1)-dimensional spacetime, foliated into noncommutative planes. As a result, we obtain propagators, which are finite in the ultraviolet as well as the infrared regime.Comment: 16 pages, version which matches that published on CQ

Tumor Location in the Head/Uncinate Process and Presence of Fibrosis Impair the Adequacy of Endoscopic Ultrasound-Guided Tissue Acquisition of Solid Pancreatic Tumors

Endoscopic ultrasound-guided tissue acquisition (EUS-TA) of solid pancreatic tumors shows optimal specificity despite fair sensitivity, with an overall suboptimal diagnostic yield. We aim to quantify the adequacy and accuracy of EUS-TA and assess predictive factors for success, focusing on the presence and degree of specimen fibrosis. All consecutive EUS-TA procedures were retrieved, and the specimens were graded for sample adequacy and fibrosis. The results were evaluated according to patients’ and tumor characteristics and the EUS-TA technique. In total, 407 patients (59% male, 70 [63–77] year old) were included; sample adequacy and diagnostic accuracy were 90.2% and 94.7%, respectively. Fibrosis was significantly more represented in tumors located in the head/uncinate process (p = 0.001). Tumor location in the head/uncinate (OR 0.37 [0.14–0.99]), number of needle passes ≥ 3 (OR 4.53 [2.22–9.28]), and the use of cell block (OR 8.82 [3.23–23.8]) were independently related to adequacy. Severe fibrosis was independently related to false negative results (OR 8.37 [2.33–30.0]). Pancreatic tumors located in the head/uncinate process showed higher fibrosis, resulting in EUS-TA with lower sample adequacy and diagnostic accuracy. We maintain that three or more needle passes and cell block should be done to increase the diagnostic yield

Effect of autonomic blocking agents on the respiratory-related oscillations of ventricular action potential duration in humans

Ventricular action potential duration (APD) is an important component of many physiological functions including arrhythmogenesis. APD oscillations have recently been reported in humans at the respiratory frequency. This study investigates the contribution of the autonomic nervous system to these oscillations. In 10 patients undergoing treatment for supraventricular arrhythmias, activation recovery intervals (ARI; a conventional surrogate for APD) were measured from multiple left and right ventricular (RV) endocardial sites, together with femoral artery pressure. Respiration was voluntarily regulated and heart rate clamped by RV pacing. Sympathetic and parasympathetic blockade was achieved using intravenous metoprolol and atropine, respectively. Metroprolol reduced the rate of pressure development (maximal change in pressure over time): 1,271 (± 646) vs. 930 (± 433) mmHg/s; P < 0.01. Systolic blood pressure (SBP) showed a trend to decrease after metoprolol, 133 (± 21) vs. 128 (± 25) mmHg; P = 0.06, and atropine infusion, 122 (± 26) mmHg; P < 0.05. ARI and SBP exhibited significant cyclical variations (P < 0.05) with respiration in all subjects with peak-to-peak amplitudes ranging between 0.7 and 17.0 mmHg and 1 and 16 ms, respectively. Infusion of metoprolol reduced the mean peak-to-peak amplitude [ARI, 6.2 (± 1.4) vs. 4.4 (± 1.0) ms, P = 0.008; SBP, 8.4 (± 1.6) vs. 6.2 (± 2.0) mmHg, P = 0.002]. The addition of atropine had no significant effect. ARI, SBP, and respiration showed significant coupling (P < 0.05) at the breathing frequency in all subjects. Directed coherence from respiration to ARI was high and reduced after metoprolol infusion [0.70 (± 0.17) vs. 0.50 (± 0.23); P < 0.05]. These results suggest a role of respiration in modulating the electrophysiology of ventricular myocardium in humans, which is partly, but not totally, mediated by β-adrenergic mechanisms

Proton-counting radiography for proton therapy: a proof of principle using CMOS APS technology

Despite the early recognition of the potential of proton imaging to assist proton therapy (Cormack 1963 J. Appl. Phys. 34 2722), the modality is still removed from clinical practice, with various approaches in development. For proton-counting radiography applications such as computed tomography (CT), the water-equivalent-path-length that each proton has travelled through an imaged object must be inferred. Typically, scintillator-based technology has been used in various energy/range telescope designs. Here we propose a very different alternative of using radiation-hard CMOS active pixel sensor technology. The ability of such a sensor to resolve the passage of individual protons in a therapy beam has not been previously shown. Here, such capability is demonstrated using a 36 MeV cyclotron beam (University of Birmingham Cyclotron, Birmingham, UK) and a 200 MeV clinical radiotherapy beam (iThemba LABS, Cape Town, SA). The feasibility of tracking individual protons through multiple CMOS layers is also demonstrated using a two-layer stack of sensors. The chief advantages of this solution are the spatial discrimination of events intrinsic to pixelated sensors, combined with the potential provision of information on both the range and residual energy of a proton. The challenges in developing a practical system are discussed