Pancharatnam and Berry Phases in Three-Level Photonic Systems

A theoretical analysis of Pancharatnam and Berry phases is made for biphoton three-level systems, which are produced via frequency degenerate co-linear spontaneous parametric down conversion (SPDC). The general theory of Pancharatnam phases is discussed with a special emphasis on geodesic 'curves'in Hilbert space. Explicit expressions for Pancharatnam, dynamical and geometrical phases are derived for the transformations produced by linear phase-converters. The problem of gauge invariance is treated along all the article

Improperly obtained evidence in the Commonwealth: lessons for England and Wales?

English law's traditional approach to the admissibility of improperly obtained evidence is currently being rethought in response to a range of domestic and international pressures. With the position in England and Wales following the House of Lords' decision in A and Others (2005) firmly in mind, this article undertakes a selective review of comparative approaches to the admissibility of improperly obtained evidence in Australia, Canada and New Zealand. Having analysed relevant legislation and case law in each jurisdiction, general principles are derived to guide future developments in English law, in conformity with the European Convention on Human Rights

Phase Dynamics of Two Entangled Qubits

We make a geometric study of the phases acquired by a general pure bipartite two level system after a cyclic unitary evolution. The geometric representation of the two particle Hilbert space makes use of Hopf fibrations. It allows for a simple description of the dynamics of the entangled state's phase during the whole evolution. The global phase after a cyclic evolution is always an entire multiple of $\pi$ for all bipartite states, a result that does not depend on the degree of entanglement. There are three different types of phases combining themselves so as to result in the $n \pi$ global phase. They can be identified as dynamical, geometrical and topological. Each one of them can be easily identified using the presented geometric description. The interplay between them depends on the initial state and on its trajectory and the results obtained are shown to be in connection to those on mixed states phases.Comment: 9 figures, slightly different version from the accepted on

The twistor geometry of three-qubit entanglement

A geometrical description of three qubit entanglement is given. A part of the transformations corresponding to stochastic local operations and classical communication on the qubits is regarded as a gauge degree of freedom. Entangled states can be represented by the points of the Klein quadric ${\cal Q}$ a space known from twistor theory. It is shown that three-qubit invariants are vanishing on special subspaces of ${\cal Q}$. An invariant vanishing for the $GHZ$ class is proposed. A geometric interpretation of the canonical decomposition and the inequality for distributed entanglement is also given.Comment: 4 pages RevTeX

Preferences for Prenatal Tests for Cystic Fibrosis: A Discrete Choice Experiment to Compare the Views of Adult Patients, Carriers of Cystic Fibrosis and Health Professionals

As new technologies enable the development of non-invasive prenatal diagnosis (NIPD) for cystic fibrosis (CF), research examining stakeholder views is essential for the preparation of implementation strategies. Here, we compare the views of potential service users with those of health professionals who provide counselling for prenatal tests. A questionnaire incorporating a discrete choice experiment examined preferences for key attributes of NIPD and explored views on NIPD for CF. Adult patients (n = 92) and carriers of CF (n = 50) were recruited from one children’s and one adult NHS specialist CF centre. Health professionals (n = 70) were recruited via an e-mail invitation to relevant professional bodies. The key attribute affecting service user testing preferences was no miscarriage risk, while for health professionals, accuracy and early testing were important. The uptake of NIPD by service users was predicted to be high and includes couples that would currently decline invasive testing. Many service users (47%) and health professionals (55.2%) thought the availability of NIPD for CF would increase the pressure to undergo prenatal testing. Most service users (68.5%) thought NIPD for CF should be offered to all pregnant women, whereas more health professionals (68.2%) thought NIPD should be reserved for known carrier couples. The implications for clinical practice are discussed

Gait Extraction and Description by Evidence-Gathering

Using gait as a biometric is of increasing interest, yet there are few model-based, parametric, approaches to extract and describe moving articulated objects. One new approach can detect moving parametric objects by evidence gathering, hence accruing known performance advantages in terms of performance and occlusion. Here we show how that the new technique can be extended not only to extract a moving person, but also to extract and concurrently provide a gait signature for use as a biometric. We show the natural relationship between the bases of these approaches, and the results they can provide. As such, these techniques allow for gait extraction and description for recognition purposes, and with known performance advantages of a well-established vision technique

Geomorphic Effects of Engineered Log Structures and Response to a Catastrophic Flood Event in a Missouri Ozarks River

Engineered log structures (ELSs) composed of local tree logs have been installed in river channels throughout the Pacific Northwest as a restoration technique. However, ELSs have not been tested for use in the Ozark Highlands until recently. In October 2016 the U.S. Forest Service installed four ELSs to stabilize banks along the North Fork of the White River in Ozark County, Missouri. The purpose here is to report on monitoring studies of pre- and post-restoration channel conditions and to assess geomorphic responses to floods. Over a ten-day period in April 2017 there were two bankfull floods, and on April 30, 2017 a catastrophic flood event classified as a \u3e500-year flood occurred with a stage of 12.8 m that was greater than 4 m above the previous record flood in 1985. The flood toppled the riparian forest and caused geomorphic changes throughout the study reach. Key findings of this study are: 1) One structure was buried by greater than 3 meters of bar sediment, 2) large woody debris pieces more than doubled from 96 pieces in 2016 to 209 pieces in 2017 in the 1,100 m reach where ELSs enhanced recruitment, 3) a planform change occurred where the thalweg migrated to the opposite side of the channel, and 4) Structures 3 and 4 trapped fluvial wood and enhanced sedimentation in targeted areas on a lateral bar feature. Conclusions of this study are: 1) During the high-magnitude flood, the floodplain acted as a point-bar where floodplain chutes were carved and sediment deposited over the normal floodplain surface; 2) Structures 3 and 4 enhanced LWD recruitment by creating flow separation between the channel and the mouth of a floodplain chute; 3) Managers should incorporate shallow bedrock typically present in the Ozarks into future ELS designs and; 4) Cables helped ELS logs remain in their installed location due to the added shear resistance. The use of ELSs in this research were designed to recruit fluvial wood and enhance sedimentation under more frequent flow conditions but withstood a historic flood. Therefore, further investigation is needed to determine suitability of using ELSs in Ozarks streams under lower magnitude, more frequent flows

BooksDealing with life difficulties

Cognitive Psychotherapy: Theory and Practice. Ed by C. Perris, I. M. Blackburn and H. Perris. Pp. viii +422. Illustrated. DM 148. Berlin: Springer-Verlag