Iterative maximum-likelihood reconstruction in quantum homodyne tomography

I propose an iterative expectation maximization algorithm for reconstructing a quantum optical ensemble from a set of balanced homodyne measurements performed on an optical state. The algorithm applies directly to the acquired data, bypassing the intermediate step of calculating marginal distributions. The advantages of the new method are made manifest by comparing it with the traditional inverse Radon transformation technique

Using Facebook for travel decision-making: an international study of antecedents

Purpose: This study investigates antecedents of using non-travel-specific social media (specifically Facebook) for travel decision-making before a leisure trip. Design/methodology/approach: Based on an online survey of 426 young travel consumers from Italy and Sweden, this work applies structural equation modeling and multi-group analysis. Findings: The study finds support for most of the conventional TAM-related constructs: perceived usefulness, perceived enjoyment, and intention, while ease of use is not found relevant in this context. Research limitations/implications: Results shed light on the antecedents of using non-travel-specific social media in two countries. Future research might focus on validating the factors identified and add others that might shape usage in the selected countries. Future studies could further investigate possible differences arising from culture, country of origin and age. The analysis can also be extended to other countries. Practical implications: The analysis might help managers in the hospitality and tourism sector by providing an understanding of the cognitive factors which determine travelers’ decision to use Facebook for trip planning. Thus, managers should get to know these factors in their effort to influence social media in hospitality and tourism settings. Originality/value: The findings offer interesting perspectives on the applicability of conventional models to the context of non-travel-specific social media platforms. The exploration of cross-cultural differences also adds to the extant body of knowledge

Results from Shell Model Monte Carlo Studies

We review results obtained using Shell Model Monte Carlo (SMMC) techniques. These methods reduce the imaginary-time many-body evolution operator to a coherent superposition of one-body evolutions in fluctuating one-body fields; the resultant path integral is evaluated stochastically. After a brief review of the methods, we discuss a variety of nuclear physics applications. These include studies of the ground-state properties of pf-shell nuclei, Gamow-Teller strength distributions, thermal and rotational pairing properties of nuclei near N=Z, $\gamma$-soft nuclei, and $\beta\beta$-decay in ^{76}Ge. Several other illustrative calculations are also reviewed. Finally, we discuss prospects for further progress in SMMC and related calculations

An action principle for the quantization of parametric theories and nonlinear quantum cosmology

By parametrizing the action integral for the standard Schrodinger equation we present a derivation of the recently proposed method for quantizing a parametrized theory. The reformulation suggests a natural extension from conventional to nonlinear quantum mechanics. This generalization enables a unitary description of the quantum evolution for a broad class of constrained Hamiltonian systems with a nonlinear kinematic structure. In particular, the new theory is applicable to the quantization of cosmological models where a chosen gravitational degree of freedom acts as geometric time. This is demonstrated explicitly using three cosmological models: the Friedmann universe with a massless scalar field and Bianchi type I and IX models. Based on these investigations, the prospect of further developing the proposed quantization scheme in the context of quantum gravity is discussed.Comment: 14 page

Entanglement generation in continuously coupled parametric generators

We investigate a compact source of entanglement. This device is composed of a pair of linearly coupled nonlinear waveguides operating by means of degenerate parametric downconversion. For the vacuum state at the input the generalized squeeze variance and logarithmic negativity are used to quantify the amount of nonclassicality and entanglement of output beams. Squeezing and entanglement generation for various dynamical regimes of the device are discussed.Comment: 6 pages, 7 figure

The experiences of inpatient nursing staff caring for young people with early psychosis

Background: Early intervention services aim to improve outcomes for people with first episode psychosis and, where possible, to prevent psychiatric hospital admission. When hospitalisation does occur, inpatient staff are required to support patients and families who may be less familiar with services, uncertain about possible outcomes, and may be experiencing a psychiatric hospital for the first time. Aims: Our study aimed to understand the process of hospitalisation in early psychosis, from the perspective of inpatient nursing staff. We were particularly interested in their experiences of working with younger people in the context of adult psychiatric wards. Methods: Nine inpatient nursing staff took part in semi-structured interviews, which were transcribed and then analysed using interpretative phenomenological analysis. Results: Five themes are outlined: ‘it’s all new and it’s all learning’; the threatening, unpredictable environment; care and conflict within the intergenerational relationship; motivation and hope; and coping and self-preservation. Conclusions: The phenomenological focus of our approach throws the relational component of psychiatric nursing into sharp relief. We reflect on the implications for organisations, staff, families and young people. We suggest that the conventional mode of delivering acute psychiatric inpatient care is not likely to support the best relational and therapeutic outcomes

Review of catch trends and changes in fish species composition of the Volta lake during its 45 years of existence

Existing catch data for the whole of the Volta lake from 1969 to 2004 and those for certain segments of the lake (Strata II, III, and IV) covering various periods were analysed in relation to lake levels, to find out changes in catch trends and species composition. The study was undertaken as a baseline activity aimed at enhancing fisheries productivity and  management of the lake. Higher catches were made at the inception of the lake, with about 65,000 t being recorded in 1969. This dropped and  fluctuated between 36,000 anct48,000 t from 1971 to 1994. Catches kept increasing rapidly from 1995 with about 80,000 t being recorded in 1999, the highest in the history of the lake. In relation to annual fake water level fluctuations, high catches were made during periods of low water level compared to periods of high water level. On the long term, decreasing lake water level corresponded with higher fish catches. There was a change frominsectivorous fish species (e.g., Chrysichthys, Schilhe and Synodontis) at the initial stages of the formation of the lake to those with vegetarian food habits dominated by the tilapias. The dominance oftilapias in catches, which persisted till the early parts of the 1990s, has given way to Chrysichthys spp., suggesting that the composition of fish species in the lake is still undergoing changes 45 years after its formation

Perinatal or neonatal mortality among women who intend at the onset of labour to give birth at home compared to women of low obstetrical risk who intend to give birth in hospital: A systematic review and meta-analyses

Background: More women are choosing to birth at home in well-resourced countries. Concerns persist that out-of-hospital birth contributes to higher perinatal and neonatal mortality. This systematic review and meta-analyses determines if risk of fetal or neonatal loss differs among low-risk women who begin labour intending to give birth at home compared to low-risk women intending to give birth in hospital. Methods: In April 2018 we searched five databases from 1990 onward and used R to obtain pooled estimates of effect. We stratified by study design, study settings and parity. The primary outcome is any perinatal or neonatal death after the onset of labour. The study protocol is peer-reviewed, published and registered (PROSPERO No.CRD42013004046). Findings: We identified 14 studies eligible for meta-analysis including ~ 500,000 intended home births. Among nulliparous women intending a home birth in settings where midwives attending home birth are well-integrated in health services, the odds ratio (OR) of perinatal or neonatal mortality compared to those intending hospital birth was 1.07 (95% Confidence Interval [CI], 0.70 to 1.65); and in less integrated settings 3.17 (95% CI, 0.73 to 13.76). Among multiparous women intending a home birth in well-integrated settings, the estimated OR compared to those intending a hospital birth was 1.08 (95% CI, 0.84 to 1.38); and in less integrated settings was 1.58 (95% CI, 0.50 to 5.03). Interpretation: The risk of perinatal or neonatal mortality was not different when birth was intended at home or in hospital. Funding: Partial funding: Association of Ontario Midwives open peer reviewed grant. Research in Context: Evidence before this study Although there is increasing acceptance for intended home birth as a choice for birthing women, controversy about its safety persists. The varying responses of obstetrical societies to intended home birth provide evidence of contrasting views. A Cochrane review of randomised controlled trials addressing this topic included one small trial and noted that in the absence of adequately sized randomised controlled trials on the topic of intended home compared to intended hospital birth, a peer reviewed protocol be published to guide a systematic review and meta-analysis including observational studies. Reviews to date have been limited by design or methodological issues and none has used a protocol published a priori.Added value of this study Individual studies are underpowered to detect small but potentially important differences in rare outcomes. This study uses a published peer-reviewed protocol and is the largest and most comprehensive meta-analysis comparing outcomes of intended home and hospital birth. We take study design, parity and jurisdictional support for home birth into account. Our study provides much needed information to policy makers, care providers and women and families when planning for birth.Implications of all the available evidence Women who are low risk and who intend to give birth at home do not appear to have a different risk of fetal or neonatal loss compared to a population of similarly low risk women intending to give birth in hospital

Theory for the electromigration wind force in dilute alloys

A multiple scattering formulation for the electromigration wind force on atoms in dilute alloys is developed. The theory describes electromigration via a vacancy mechanism. The method is used to calculate the wind valence for electromigration in various host metals having a close-packed lattice structure, namely aluminum, the noble metals copper, silver and gold and the $4d$ transition metals. The self-electromigration results for aluminum and the noble metals compare well with experimental data. For the $4d$ metals small wind valences are found, which make these metals attractive candidates for the experimental study of the direct valence.Comment: 18 pages LaTeX, epsfig, 8 figures. to appear in Phys. Rev. B 56 of 15/11/199