Nonequilibrium dynamics of photoexcited electrons in graphene: Collinear scattering, Auger processes, and the impact of screening

We present a combined analytical and numerical study of the early stages (sub-100-fs) of the nonequilibrium dynamics of photoexcited electrons in graphene. We employ the semiclassical Boltzmann equation with a collision integral that includes contributions from electron-electron (e-e) and electron-optical phonon interactions. Taking advantage of circular symmetry and employing the massless Dirac fermion (MDF) Hamiltonian, we are able to perform an essentially analytical study of the e-e contribution to the collision integral. This allows us to take particular care of subtle collinear scattering processes - processes in which incoming and outgoing momenta of the scattering particles lie on the same line - including carrier multiplication (CM) and Auger recombination (AR). These processes have a vanishing phase space for two-dimensional MDF bare bands. However, we argue that electron-lifetime effects, seen in experiments based on angle-resolved photoemission spectroscopy, provide a natural pathway to regularize this pathology, yielding a finite contribution due to CM and AR to the Coulomb collision integral. Finally, we discuss in detail the role of physics beyond the Fermi golden rule by including screening in the matrix element of the Coulomb interaction at the level of the random phase approximation (RPA), focusing in particular on the consequences of various approximations including static RPA screening, which maximizes the impact of CM and AR processes, and dynamical RPA screening, which completely suppresses them. © 2013 American Physical Society.

Aiding classification of gene expression data with feature selection: a comparative study

C. Shang and Q. Shen. Aiding classification of gene expression data with feature selection: a comparative study. Computational Intelligence Research, 1(1):68-76.

Becoming a father of a child with an intellectual disability- a narrative inquiry of Irish fathers’ stories

Background: This thesis explored men’s experiences of becoming a father of a child with an intellectual disability in the early years. In Ireland, it is estimated that there are almost 97% (n= 9,914) children with intellectual disabilities living at home in the care of parents, siblings, relatives or foster parents. While mothers and fathers are the primary caregivers, mothers’ experiences are well documented in comparison to the dearth of reports on fathers’ experiences. This descriptive narrative study aims to redress this gap in knowledge and understanding of men’s experiences of becoming a father of a child with an intellectual disability in the early years. Method: Narrative inquiry was employed for this study as it allows stories told by fathers to be collected as a means of exploring men’s transition to becoming a father of a child with an intellectual disability. A sample of 10 fathers of children with intellectual disabilities aged between thirteen months and five years of age were recruited from a large intellectual disability Health Service Provider (HSP) in the South of Ireland. Data were collected through semi-structured interviews which were audio-recorded, transcribed, and analysed using a narrative thematic approach. Findings: Findings are presented in four themes: i) ‘becoming a father’, ii) ‘something wrong with my child’, iii) ‘entering the world of disability’ and iv) ‘living a different life’. For all 10 fathers the time of being told that their child had an intellectual disability was laden with negative emotional responses irrespective of whether the diagnosis was at birth or more gradual over the child’s early developmental period. When fathers found out that ‘something was wrong’ they spoke of ‘moving on’ and entering the world of disability. In their narratives, becoming the father of a child with an intellectual disability had changed their lives and would inevitably change their futures. Fathers’ positivity was clearly evident with many fathers identifying that the diagnosis of their child with an intellectual disability was not a life ending event but rather a life changing event. Conclusions: Healthcare professionals have a critical role in supporting fathers during the transition to becoming a father of a child with an intellectual disability. Factors which require consideration include recognising that each father’s experience is unique; that fathers require support; and that fathers achieve personal growth because of their experiences of their transition to becoming a father of a child with an intellectual disability in the early years.

HPV clearance and the neglected role of stochasticity.

Clearance of anogenital and oropharyngeal HPV infections is attributed primarily to a successful adaptive immune response. To date, little attention has been paid to the potential role of stochastic cell dynamics in the time it takes to clear an HPV infection. In this study, we combine mechanistic mathematical models at the cellular level with epidemiological data at the population level to disentangle the respective roles of immune capacity and cell dynamics in the clearing mechanism. Our results suggest that chance-in form of the stochastic dynamics of basal stem cells-plays a critical role in the elimination of HPV-infected cell clones. In particular, we find that in immunocompetent adolescents with cervical HPV infections, the immune response may contribute less than 20% to virus clearance-the rest is taken care of by the stochastic proliferation dynamics in the basal layer. In HIV-negative individuals, the contribution of the immune response may be negligible.

Critical care in childbearing for midwives

Many women who have higher–risk pregnancies, complications or medical conditions require specialist obstetric or multidisciplinary care. Increasingly women, whose condition deteriorates and becomes critical during childbirth, are being cared for by midwives in obstetric high dependency units within the labour ward, rather than being cared for by nurses in ITU. Critical Care in Childbearing for Midwives explores all aspects of management, support and care of childbearing women who become critically ill due to pre–existing conditions or who develop critical illness as a result of complications of childbearing. It examines predisposing factors which result in the need for critical care, addresses specialist monitoring technology and skills, and explores autonomous practice and team approaches to providing care for critically ill women in childbearing.

Addressing Bed Costs for the Elderly: A New Methodology for Modelling Patient Outcomes and Length of Stay

The proportion of elderly in the population has dramatically increased and will continue to do so for at least the next 50 years. Medical resources throughout the world are feeling the added strain of the increasing proportion of elderly in the population. The effective care of elderly patients in hospitals may be enhanced by accurately modelling the length of stay of the patients in hospital and the associated costs involved. This paper examines previously developed models for patient length of stay in hospital and describes the recently developed conditional phase-type distribution (C-Ph) to model patient duration of stay in relation to explanatory patient variables. The Clinics data set was used to demonstrate the C-Ph methodology. The resulting model highlighted a strong relationship between Barthel grade, patient outcome and length of stay showing various groups of patient behaviour. The patients who stay in hospital for a very long time are usually those that consume the largest amount of hospital resources. These have been identified as the patients whose resulting outcome is transfer. Overall, the majority of transfer patients spend a considerably longer period of time in hospital compared to patients who die or are discharged home. The C-Ph model has the potential for considering costs where different costs are attached to the various phases or subgroups of patients and the anticipated cost of care estimated in advance. It is hoped that such a method will lead to the successful identification of the most cost effective case-mix management of the hospital ward.

Welfare Regimes and “progressive” governments in Latin America: The cases of Venezuela, Ecuador and Bolivia

Several authors have applied the concept of Welfare Regimens for studying social policy in Latin America (Esping-Andersen, 1993 and 2000). Among others, Martínez Franzoni (2007) develops a typology, with fi eld work is at the turn of the millennium, and establishes three categories: State-productivist regime, state-protectionist and family orientated. Most countries in the region are placed in the latter category. The hypothesis of this article argues that with the emergence of governments considered “left” or “progressive” in several countries of the region from the late ‘90s and, more decisively, in 2000’, the map of welfare regimes models could have mutated substantively. The nationally transformative experiences are different (various socio-economic realities and political action in which they are located exists) but they have several contact points that can be summarized in a greater state intervention in different areas previously closed to their operating and recovery of important functions of welfare and care of the population by the government. The paper discusses with an exploratory and descriptive approach the welfare schemes that would shape in three countries that have constitutionalized the change from the neoliberal paradigm: Venezuela, Bolivia and Ecuador.

Teachers’ perception of visual deficiencies and their impact on students

The sense of vision is people’s main source of information acquisition, hence the importance of a right diagnosis and correction, if necessary, of any faults for proper learning, especially in the early years of schooling. This article discusses the results of a survey of teachers in Andalusian schools that aimed at highlighting their knowledge of their students’ possible visual deficiencies, and its possible impact on school performance. The results indicate that such knowledge is generally limited to the type of refractive anomalies, and that they think that such anomalies are well treated in their students. Despite the importance they attach to these deficiencies on school learning, they think that other factors may have a greater role. They also consider that better training on this topic is necessary.

Shared or unshared parental care in overwintering brent geese (Branta bernicla hrota)

We examine brood size effects on the behaviour of wintering parent and juvenile brent geese (Branta bernicla hrota) to test predictions of shared and unshared parental care models. The behaviour of both parents and offspring appear to be influenced by declining food availability over the winter. Parental vigilance increased with brood size and may be explained by vigilance having functions in addition to antipredator behaviour where the benefits are shared among the brood. There was no increase in parental aggression with brood size and this does not fit the prediction of shared care. Nevertheless, large families are able to monopolize better feeding areas compared with smaller families and large families static feed more but walk feed less than do small families, the former apparently being the preferred mode. The presence of additional young, rather than increasing the amount of parental aggression, seems to enhance the family's competitive ability. Because parents with large broods benefit from enhanced access to resources there is likely to be no additional significant cost in the parental care of larger broods (sensu Trivers 1972).

Modern management of head injuries

Management of the head-injured patient is designed to prevent secondary injury and to provide the neurosurgeon with a live patient who has some hope of recovery. This review sets out the background essentials for the non-neurosurgeon dealing with the initial care of a head-injured patient.