Order-Revealing Encryption and the Hardness of Private Learning

An order-revealing encryption scheme gives a public procedure by which two ciphertexts can be compared to reveal the ordering of their underlying plaintexts. We show how to use order-revealing encryption to separate computationally efficient PAC learning from efficient $(\epsilon, \delta)$-differentially private PAC learning. That is, we construct a concept class that is efficiently PAC learnable, but for which every efficient learner fails to be differentially private. This answers a question of Kasiviswanathan et al. (FOCS '08, SIAM J. Comput. '11). To prove our result, we give a generic transformation from an order-revealing encryption scheme into one with strongly correct comparison, which enables the consistent comparison of ciphertexts that are not obtained as the valid encryption of any message. We believe this construction may be of independent interest.Comment: 28 page

Vocation, Belongingness, and Balance: A Qualitative Study of Veterinary Student Well-Being

An elevated risk for suicide among veterinarians has stimulated research into the mental health of the veterinary profession, and more recently attention has turned to the veterinary student population. This qualitative study sought to explore UK veterinary students' perceptions and experiences of university life, and to consider how these may affect well-being. Semi-structured interviews were conducted with 18 students from a single UK school who were purposively selected to include perspectives from male, female, graduate-entry, standard-entry (straight from high school), and widening participation students across all 5 years of the program. Three main themes were identified: a deep-rooted vocation, navigating belongingness, and finding balance. Participants described a long-standing goal of becoming a veterinarian, with a determination reflected by often circuitous routes to veterinary school and little or no consideration of alternatives. Although some had been motivated by a love of animals, others were intrinsically interested in the scientific and problem-solving challenges of veterinary medicine. Most expressed strong feelings of empathy with animal owners. The issue of belongingness was central to participants' experiences, with accounts reflecting their efforts to negotiate a sense of belongingness both in student and professional communities. Participants also frequently expressed a degree of acceptance of poor balance between work and relaxation, with indications of a belief that this imbalance could be rectified later. This study helps highlight future avenues for research and supports initiatives aiming to nurture a sense of collegiality among veterinary students as they progress through training and into the profession

Distance to school is associated with sedentary time in children: Findings from the URBAN study

Sedentary behavior is associated with overweight and obesity in children, and distance to school has been negatively associated with active commuting to school. It is not known how distance to school relates to sedentary behavior in children. The aim of this study was to investigate the association between distance to school and children's sedentary behavior during weekdays at times where children interact with the neighborhood environment. Children (5-13 years, n = 295) who participated in the understanding relationships between activity and neighborhoods study (2008-2010) across four New Zealand cities wore a hip-mounted accelerometer for 7 days. Minutes spent sedentary (accelerometer count <100 min-1) were derived for the school travel periods (0800-0859 and 1500-1559) and after school discretionary time (1600-1759). Shortest street network distance to school was calculated from residential addresses using geographical information systems and parsed into tertiles for analysis. Children completed a daily travel log including mode of transport to and from school, which was dichotomized into active (walking and cycling) and passive (motorized) modes. Children living in the second tertile of distance from school were the least sedentary during the school traveling periods (42 ± 10%, mean ± true between-child SD) compared to those living in the first or third distance tertiles (47 ± 10 and 49 ± 10%, respectively); the differences were clear and likely substantial (90% confidence limits ± 6%). Children who traveled by motorized transport were more sedentary for each of the distance tertiles (50 versus 44%, 46 versus 39%, and 54 versus 27% for first, second, and third tertiles, respectively; 90% confidence limits ± 7%). In the period of 1600-1759, girls in the third distance tertile were the most sedentary. The combined effects of 1-2 km distance from school and active commuting to school contributed to least sedentary time in children

Kids in the city study: research design and methodology

Background: Physical activity is essential for optimal physical and psychological health but substantial declines in children's activity levels have occurred in New Zealand and internationally. Children's independent mobility (i.e., outdoor play and traveling to destinations unsupervised), an integral component of physical activity in childhood, has also declined radically in recent decades. Safety-conscious parenting practices, car reliance and auto-centric urban design have converged to produce children living increasingly sedentary lives. This research investigates how urban neighborhood environments can support or enable or restrict children's independent mobility, thereby influencing physical activity accumulation and participation in daily life.Methods/Design: The study is located in six Auckland, New Zealand neighborhoods, diverse in terms of urban design attributes, particularly residential density. Participants comprise 160 children aged 9-11 years and their parents/caregivers. Objective measures (global positioning systems, accelerometers, geographical information systems, observational audits) assessed children's independent mobility and physical activity, neighborhood infrastructure, and streetscape attributes. Parent and child neighborhood perceptions and experiences were assessed using qualitative research methods.Discussion: This study is one of the first internationally to examine the association of specific urban design attributes with child independent mobility. Using robust, appropriate, and best practice objective measures, this study provides robust epidemiological information regarding the relationships between the built environment and health outcomes for this population

Building nonparametric nn-body force fields using Gaussian process regression

Constructing a classical potential suited to simulate a given atomic system is a remarkably difficult task. This chapter presents a framework under which this problem can be tackled, based on the Bayesian construction of nonparametric force fields of a given order using Gaussian process (GP) priors. The formalism of GP regression is first reviewed, particularly in relation to its application in learning local atomic energies and forces. For accurate regression it is fundamental to incorporate prior knowledge into the GP kernel function. To this end, this chapter details how properties of smoothness, invariance and interaction order of a force field can be encoded into corresponding kernel properties. A range of kernels is then proposed, possessing all the required properties and an adjustable parameter $n$ governing the interaction order modelled. The order $n$ best suited to describe a given system can be found automatically within the Bayesian framework by maximisation of the marginal likelihood. The procedure is first tested on a toy model of known interaction and later applied to two real materials described at the DFT level of accuracy. The models automatically selected for the two materials were found to be in agreement with physical intuition. More in general, it was found that lower order (simpler) models should be chosen when the data are not sufficient to resolve more complex interactions. Low $n$ GPs can be further sped up by orders of magnitude by constructing the corresponding tabulated force field, here named "MFF".Comment: 31 pages, 11 figures, book chapte

Substitution of adeno-associated virus Rep protein binding and nicking sites with human Chromosome 19 sequences

<p>Abstract</p> <p>Background</p> <p>Adeno-associated virus type 2 (AAV2) preferentially integrates its DNA at a ~2 kb region of human chromosome 19, designated <it>AAVS1 </it>(also known as <it>MBS85</it>). Integration at <it>AAVS1 </it>requires the AAV2 replication (Rep) proteins and a DNA sequence within <it>AAVS1 </it>containing a 16 bp Rep recognition sequence (RRS) and closely spaced Rep nicking site (also referred to as a terminal resolution site, or <it>trs</it>). The AAV2 genome is flanked by inverted terminal repeats (ITRs). Each ITR contains an RRS and closely spaced <it>trs</it>, but the sequences differ from those in <it>AAVS1</it>. These ITR sequences are required for replication and packaging.</p> <p>Results</p> <p>In this study we demonstrate that the <it>AAVS1 </it>RRS and <it>trs </it>can function in AAV2 replication, packaging and integration by replacing a 61 bp region of the AAV2 ITR with a 49 bp segment of <it>AAVS1 </it>DNA. Modifying one or both ITRs did not have a large effect on the overall virus titers. These modifications did not detectably affect integration at <it>AAVS1</it>, as measured by semi-quantitative nested PCR assays. Sequencing of integration junctions shows the joining of the modified ITRs to <it>AAVS1 </it>sequences.</p> <p>Conclusions</p> <p>The ability of these <it>AAVS1 </it>sequences to substitute for the AAV2 RRS and <it>trs </it>provides indirect evidence that the stable secondary structure encompassing the <it>trs </it>is part of the AAV2 packaging signal.</p

Phenotypic Variation and Bistable Switching in Bacteria

Microbial research generally focuses on clonal populations. However, bacterial cells with identical genotypes frequently display different phenotypes under identical conditions. This microbial cell individuality is receiving increasing attention in the literature because of its impact on cellular differentiation, survival under selective conditions, and the interaction of pathogens with their hosts. It is becoming clear that stochasticity in gene expression in conjunction with the architecture of the gene network that underlies the cellular processes can generate phenotypic variation. An important regulatory mechanism is the so-called positive feedback, in which a system reinforces its own response, for instance by stimulating the production of an activator. Bistability is an interesting and relevant phenomenon, in which two distinct subpopulations of cells showing discrete levels of gene expression coexist in a single culture. In this chapter, we address techniques and approaches used to establish phenotypic variation, and relate three well-characterized examples of bistability to the molecular mechanisms that govern these processes, with a focus on positive feedback.