Comparative Monte Carlo Efficiency by Monte Carlo Analysis

We propose a modified power method for computing the subdominant eigenvalue $\lambda_2$ of a matrix or continuous operator. Here we focus on defining simple Monte Carlo methods for its application. The methods presented use random walkers of mixed signs to represent the subdominant eigenfuction. Accordingly, the methods must cancel these signs properly in order to sample this eigenfunction faithfully. We present a simple procedure to solve this sign problem and then test our Monte Carlo methods by computing the $\lambda_2$ of various Markov chain transition matrices. We first computed ${\lambda_2}$ for several one and two dimensional Ising models, which have a discrete phase space, and compared the relative efficiencies of the Metropolis and heat-bath algorithms as a function of temperature and applied magnetic field. Next, we computed $\lambda_2$ for a model of an interacting gas trapped by a harmonic potential, which has a mutidimensional continuous phase space, and studied the efficiency of the Metropolis algorithm as a function of temperature and the maximum allowable step size $\Delta$. Based on the $\lambda_2$ criterion, we found for the Ising models that small lattices appear to give an adequate picture of comparative efficiency and that the heat-bath algorithm is more efficient than the Metropolis algorithm only at low temperatures where both algorithms are inefficient. For the harmonic trap problem, we found that the traditional rule-of-thumb of adjusting $\Delta$ so the Metropolis acceptance rate is around 50% range is often sub-optimal. In general, as a function of temperature or $\Delta$, $\lambda_2$ for this model displayed trends defining optimal efficiency that the acceptance ratio does not. The cases studied also suggested that Monte Carlo simulations for a continuum model are likely more efficient than those for a discretized version of the model.Comment: 23 pages, 8 figure

Food-conditioned odour rejection in the late stages of the meal, mediating learnt control of meal volume by aftereffects of food consumption

In a two-bottle choice test, rats drank more of the fluid having a novel odour than that having an odour which had previously been presented in the later part of meals on concentrated maltodextrin solution. Rats are normally more averse to a novel odour than to a familiar odour; therefore, the conditioned reaction to the odour acquired in these circumstances is likely to be an ingestive aversion, rather than merely a lack of preference. Furthermore, this learnt odour rejection was seen only in the second half of the meal, indicating that it is dependent on an ingestion-induced state of repletion. Together then, these observations are evidence that the volume of meals rich in carbohydrate can be controlled by learnt rejection of particular food flavours in the presence of visceral cues specific to repletion (previously dubbed "conditioned satiety"), the only known mechanism by which aftereffects of ingested energy could reduce meal volume

The Weight of Opinion - The early childhood sector's perceptions about childhood overweight and obesty

Early childhood is a critical time in a child’s development when the foundations for good or poor eating habits and self-regulation of appetite are laid. Because long day care centres and preschools structure the daily environment in which the children in their care play and learn, the early childhood sector can make an important contribution to preventing and (sometimes) dealing with childhood overweight and obesity. Whether through the direct provision of food at child care or rules/suggestions surrounding the food that children are to bring to preschool, they exert some control over what children consume while in their care. Similarly, they control the amount of active play time that is available during the day. Long day care centres and preschools may also incorporate messages about healthy eating and the benefits of active play into their curriculum, and may provide modelling of good eating habits by the teachers/workers during snack or meal times. They may also regulate the kinds of fundraising opportunities used to support their preschools/centres (e.g. no chocolates or donut fundraisers), and provide parents with information and support regarding the development of healthy habits. This report presents the findings from a series of in-depth interviews on the perceptions of early childhood staff about the issue of childhood overweight and obesity and their role in supporting healthy eating and active play.Interviews were conducted with eleven directors and staff members from four long day care centres and four preschools, located in three areas within metropolitan Sydney and one area in rural NSW. The results show that the early childhood educators recognise childhood overweight and obesity as a serious issue and appreciate the complexity of the causes of the increasing prevalence of overweight. They viewed these issues as part of their core mission as early childhood educators, and worked under a philosophy of close partnership with families (and, in some cases, with local health professionals). All of the participants also acknowledged that parents can be sensitive about their children’s weight, that there can be uncertainty surrounding definitions of overweight among young children, and that there can be emotions around the provision of food and children’s eating patterns. At the same time, interviewees recognised that the early childhood sector can only do so much by themselves and that their efforts need to be complemented by efforts to support parents and change cultural and environmental factors that make it difficult to eat healthy foods and get adequate physical activity, especially considering the fact that not all children have access to or participate in early childhood education. However, given the large proportion of children and parents who do have contact with the early childhood sector, the potential to strengthen the role of the sector in preventing childhood overweight and obesity and promoting healthy eating and active play was highlighted in the research. The interviewees gave practical suggestions for how that could occur. They wanted more early childhood-friendly games, activities, books, songs, and posters about healthy eating and physical activity, more resources they could give directly to parents, more guidance on optimal nutrition policies (for preschools), more training for themselves (including information on when to be concerned about children’s weight and what to do about it), and more access to health professionals who could come and speak to them and the parents.This research was funded by NSW Health and The Ross Family Trust. Principal Investigators: Dr Michael Booth and Lesley King. The authors would like to thank Louise Erickson for her valuable contribution to this project, as well as all the preschools and child care centres who participated in the study

Ultrareliable, fault-tolerant control systems: A conceptual description

An Ultrareliable, Fault-Tolerant, Control-System (UFTCS) concept is described using a systems design philosophy which allows development of system structures containing virtually no common elements. Common elements limit achievable system reliability and can cause catastrophic loss of fault-tolerant system function. The UFTCS concept provides the means for removing common system elements by permitting the elements of the system to operate as independent, uncoupled entities. Multiple versions of the application program are run on dissimilar hardware. Fault tolerance is achieved through the use of static redundancy management

Effects of Adverse Childhood Experiences on High Risk Inpatients Criminal Behavior

Adverse childhood experiences (ACEs) play a role in the development of chronic mental and physical diseases in adulthood. These experiences include adversities such as: emotional/verbal abuse, sexual abuse, physical abuse, and household dysfunction. In this study, we hypothesize that forensic mental health offenders will have higher ACE scores than community participants. Secondly, we hypothesize that these participants will show higher rates of and earlier incidences of offending, arrest, incarceration, and hospitalization as a result of their ACE scores. Further, we hypothesize that males and females will be affected by ACEs differently. Using archival data from a secure forensic psychiatric facility in the Midwestern US, data were collected from 211 participants, of which 80% were males and 18% females. The ages of the participants ranged from 23 to 72 with a median age of 43. Using SPSS software, we were able to determine frequency of the ten categories of abuse, maltreatment, and familial dysfunction as included in the original ACE research. Correlations were run to determine the relationship between ACEs and criminal behavior. Statistical comparisons were also run to examine the differences between males and females. ACE score significantly correlated with age at first psychiatric admission. Males and females were significantly different with regard to ACE score. However, other variables were not significant and suggest that future research need to more deeply examine these differences, and additional variables that may determine criminal outcomes in high-risk samples

Self-contained Kondo effect in single molecules

Kondo coupling of f and conduction electrons is a common feature of f-electron intermetallics. Similar effects should occur in carbon ring systems(metallocenes). Evidence for Kondo coupling in Ce(C8H8)2 (cerocene) and the ytterbocene Cp*2Yb(bipy) is reported from magnetic susceptibility and L_III-edge x-ray absorption spectroscopy. These well-defined systems provide a new way to study the Kondo effect on the nanoscale, should generate insight into the Anderson Lattice problem, and indicate the importance of this often-ignored contribution to bonding in organometallics.Comment: 4 pages, 5 figures (eps

Quantifying structural damage from self-irradiation in a plutonium superconductor

The 18.5 K superconductor PuCoGa5 has many unusual properties, including those due to damage induced by self-irradiation. The superconducting transition temperature decreases sharply with time, suggesting a radiation-induced Frenkel defect concentration much larger than predicted by current radiation damage theories. Extended x-ray absorption fine-structure measurements demonstrate that while the local crystal structure in fresh material is well ordered, aged material is disordered much more strongly than expected from simple defects, consistent with strong disorder throughout the damage cascade region. These data highlight the potential impact of local lattice distortions relative to defects on the properties of irradiated materials and underscore the need for more atomic-resolution structural comparisons between radiation damage experiments and theory.Comment: 7 pages, 5 figures, to be published in PR

Explaining anomalous responses to treatment in the Intensive Care Unit

The Intensive Care Unit (ICU) provides treatment to critically ill patients. When a patient does not respond as expected to such treatment it can be challenging for clinicians, especially junior clinicians, as they may not have the relevant experience to understand the patient’s anomalous response. Datasets for 10 patients from Glasgow Royal Infirmary’s ICU have been made available to us. We asked several ICU clinicians to review these datasets and to suggest sequences which include anomalous or unusual reactions to treatment. Further, we then asked two ICU clinicians if they agreed with their colleagues’ assessments, and if they did to provide possible explanations for these anomalous sequences. Subsequently we have developed a system which is able to replicate the clinicians’ explanations based on the knowledge contained in its several ontologies; further the system can suggest additional explanations which will be evaluated by the senior consultant

Horizon energy and angular momentum from a Hamiltonian perspective

Classical black holes and event horizons are highly non-local objects, defined in terms of the causal past of future null infinity. Alternative, (quasi)local definitions are often used in mathematical, quantum, and numerical relativity. These include apparent, trapping, isolated, and dynamical horizons, all of which are closely associated to two-surfaces of zero outward null expansion. In this paper we show that three-surfaces which can be foliated with such two-surfaces are suitable boundaries in both a quasilocal action and a phase space formulation of general relativity. The resulting formalism provides expressions for the quasilocal energy and angular momentum associated with the horizon. The values of the energy and angular momentum are in agreement with those derived from the isolated and dynamical horizon frameworks.Comment: 39 pages, 3 figures, Final Version : content essentially unchanged but many small improvements made in response to referees, a few references adde