Physical limitations on quantum nonlocality in the detection of gamma photons emitted from positron/electron annihilation

Recent experimental measurements of the time interval between detection of the two photons emitted in positron/electron annihilation have indicated that collapse of the spatial part of the photon's wavefunction, due to detection of the other photon, does not occur. Although quantum nonlocality actually occurs in photons produced through parametric down-conversion, the recent experiments give strong evidence against measurement-induced instantaneous spatial-localization of high-energy gamma photons. A new quantum-mechanical analysis of the EPR problem is presented which may help to explain the observed differences between photons produced through parametric down-conversion and photons produced through positron/electron annihilation. The results are found to concur with the recent experiments involving gamma photons.Comment: accepted for publication, Phys. Rev.

Improving IEC 61850 interoperability and simplifying IED configuration through the standardisation of protection settings

One of the key benefits of IEC 61850 is that it can facilitate interoperability between Intelligent Electronic Devices (IEDs) from different vendors. However, at present, the scope of interoperability is constrained to communications data, such as Sampled Value (SV) and Generic Object Oriented Substation Events (GOOSE) messaging, and has not been extended to protection setting information. The protection functions are implemented using proprietary parameters and are typically stored in vendor-specific binary files, which make it very difficult to manipulate these data directly from external applications. Engineers must also understand the meaning and implications of modification of all proprietary setting parameters and often need to be trained in the use of vendor-specific tools, which is time consuming and potentially increases the risk of introducing protection setting errors. Furthermore, the existing IED configuration process is complex, involves many steps, and requires the use of various software tools. To address these problems, this paper proposes the use of the IEC 61850 data model and System Configuration description Language (SCL) to represent protection settings. The proprietary protection settings data are mapped to the IEC 61850 standardised data and saved as SCL files. The common representation of protection settings in SCL files can also be interpreted and converted back to proprietary settings, thus achieving protection setting interoperability. A prototype tool that implements the process has been developed and demonstrated by the authors. In the paper, the entire process is described using examples. The SCL files, based on an XML syntax that can be easily manipulated automatically by applications such as protection coordination tools, are used to streamline the existing IED configuration process. A simplified IED configuration process using the SCL based setting files is proposed in the paper. Compared with the existing process, the new process is significantly streamlined, and permits an IED-independent system configuration tool to carry out the entire configuration process. No proprietary software or communications are needed. It also allows the protection settings to be performed at a system level, rather than individually on a “per device” basis. The key challenges that must be addressed in order for the proposed process to be widely adopted are: the IEC 61850 data model for protection settings is not complete; vendors may prefer to maintain proprietary formats; the data model should have the capability to be extended for future protection functions. This paper reports the progress towards addressing these challenges

Cholesterol granuloma in the wall of a mandibular dentigerous cyst: a rare case report

Cholesterol granuloma is an inflammatory reaction to cholesterol crystals deposition. It may develop in a variety of sites including the middle ear, mastoid process or even paranasal sinuses. Very few cases of cholesterol granuloma occurring in the jaws were reported. This report presents a rare case of cholesterol granuloma that developed in the wall of a large mandibular dentigerous cyst. The condition was treated with hemimandibulectomy followed by reconstruction with a free fibular flap

Separability and entanglement in 2x3xN composite quantum systems

The separability and entanglement of quantum mixed states in \Cb^2 \otimes \Cb^3 \otimes \Cb^N composite quantum systems are investigated. It is shown that all quantum states $\rho$ with positive partial transposes and rank $r(\rho)\leq N$ are separable.Comment: Latex, 15 page

Transition to smart card technology : how transit operators can encourage the take-up of smart card technology

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.Includes bibliographical references (p. 181-184).This thesis explores and evaluates the essential strategies needed for transit agencies to switch from traditional fare collection systems to smart cards. More transit agencies today are investing in smart card technology as part of their new automated fare collection (AFC) systems. Although the benefits of switching to smart card systems have been well-researched and acknowledged by transit agencies, it is unclear how a transit agency should go about implementing a smart card system in order to achieve optimum customer acceptance and to reap maximum benefits from the system. Recent experience has shown that a range of implementation policy decisions can go a long way towards speeding or slowing down the adoption of the technology by customers. A case study approach is used here to identify and evaluate the effectiveness and impacts of policies used by five transit agencies that currently employ smart cards. These policies fall into two categories: 1) distribution, operational and usage policies, and 2) fare policies. Distribution, operational and usage policies must be designed to facilitate and enhance customer adoption of smart cards, especially in the case where alternative fare media will co-exist.(cont.) Fare policies are designed to differentiate smart cards from other fare media through differential pricing strategies, frequent-use bonuses and low price guarantees. The thesis also examines the use of fare models in assisting transit agencies to predict ridership and revenue, especially focusing on the features needed in these models to predict the usage rates of smart cards and their associated unique fare options. Finally, the findings from the research are integrated and used to develop a set of guidelines for use by a transit agency that is switching to a smart card fare payment system. The main topics of these guidelines were identified as: 1) the use of fare policy incentives, 2) balance between restrictions and alternatives with respect to co-existing fare media, 3) accessibility to smart card support services, 4) capitalizing on the superiority of smart card technology, and 5) the use of a single card. To illustrate the usefulness of the guidelines, they were applied to a case study of the Massachusetts Bay Transportation Authority (MBTA)'s new AFC program, the CharlieCard.by Yi Hong.S.M

Summer pruning effect on tree growth and fruit production of persimmon

This paper reviews the effect of summer pruning in persimmon (Diospyros kaki Thunb.) with regard to its positive and negative aspects on tree growth and fruit production. In order for this practice to be of a significant value, a clear understanding is needed to appreciate the fact that so many variables are involved and much remains to be substantiated. Major reasons for summer pruning of persimmon are to improve fruit quality by enhancing light penetration into the tree canopy and to restrict vegetative shoot growth. Summer pruning generally suppresses tree growth even though it elevates leaf activity. Positive effects of summer pruning on skin color, soluble solids, and appearance of fruits are observed mainly in those orchards where the trees are heavily dormant-pruned to lower tree height and to secure space in high density plantings. Secondary shoot pruning and topping could also improve fruit quality, increasing flower bud formation of remaining shoots. Summer-pruning effects are highly dependent on its severity and timing to affect tree growth, shoot regrowth, reserve accumulation, and fruit quality

Quantum Cryptography Using Single Particle Entanglement

A quantum cryptography scheme based on entanglement between a single particle state and a vacuum state is proposed. The scheme utilizes linear optics devices to detect the superposition of the vacuum and single particle states. Existence of an eavesdropper can be detected by using a variant of Bell's inequality.Comment: 4 pages, 3figures, revte

Optically opaque color-flavor locked phase inside compact stars

The contribution of thermally excited electron-positron pairs to the bulk properties of the color-flavor locked quark phase inside compact stars is examined. The presence of these pairs causes the photon mean free path to be much smaller than a typical core radius ($R_0 \simeq 1$ km) for all temperatures above 25 keV so that the photon contribution to the thermal conductivity is much smaller than that of the Nambu-Goldstone bosons. We also find that the electrons and positrons dominate the electrical conductivity, while their contributions to the total thermal energy is negligible.Comment: 3 pages, 2 figures. Published versio

Quantum Conductance in Silver Nanowires: correlation between atomic structure and transport properties

We have analyzed the atomic arrangements and quantum conductance of silver nanowires generated by mechanical elongation. The surface properties of Ag induce unexpected structural properties, as for example, predominance of high aspect ratio rod-like wires. The structural behavior was used to understand the Ag quantum conductance data and the proposed correlation was confirmed by means of theoretical calculations. These results emphasize that the conductance of metal point contacts is determined by the preferred atomic structures and, that atomistic descriptions are essential to interpret the quantum transport behavior of metal nanostructures.Comment: 4 pages, 4 figure

Skeletal Shape Correspondence Through Entropy

We present a novel approach for improving the shape statistics of medical image objects by generating correspondence of skeletal points. Each object's interior is modeled by an s-rep, i.e., by a sampled, folded, two-sided skeletal sheet with spoke vectors proceeding from the skeletal sheet to the boundary. The skeleton is divided into three parts: the up side, the down side, and the fold curve. The spokes on each part are treated separately and, using spoke interpolation, are shifted along that skeleton in each training sample so as to tighten the probability distribution on those spokes' geometric properties while sampling the object interior regularly. As with the surface/boundary-based correspondence method of Cates et al., entropy is used to measure both the probability distribution tightness and the sampling regularity, here of the spokes' geometric properties. Evaluation on synthetic and real world lateral ventricle and hippocampus data sets demonstrate improvement in the performance of statistics using the resulting probability distributions. This improvement is greater than that achieved by an entropy-based correspondence method on the boundary points