Fast Algorithms at Low Temperatures via Markov Chains

For spin systems, such as the hard-core model on independent sets weighted by fugacity lambda>0, efficient algorithms for the associated approximate counting/sampling problems typically apply in the high-temperature region, corresponding to low fugacity. Recent work of Jenssen, Keevash and Perkins (2019) yields an FPTAS for approximating the partition function (and an efficient sampling algorithm) on bounded-degree (bipartite) expander graphs for the hard-core model at sufficiently high fugacity, and also the ferromagnetic Potts model at sufficiently low temperatures. Their method is based on using the cluster expansion to obtain a complex zero-free region for the partition function of a polymer model, and then approximating this partition function using the polynomial interpolation method of Barvinok. We present a simple discrete-time Markov chain for abstract polymer models, and present an elementary proof of rapid mixing of this new chain under sufficient decay of the polymer weights. Applying these general polymer results to the hard-core and ferromagnetic Potts models on bounded-degree (bipartite) expander graphs yields fast algorithms with running time O(n log n) for the Potts model and O(n^2 log n) for the hard-core model, in contrast to typical running times of n^{O(log Delta)} for algorithms based on Barvinok\u27s polynomial interpolation method on graphs of maximum degree Delta. In addition, our approach via our polymer model Markov chain is conceptually simpler as it circumvents the zero-free analysis and the generalization to complex parameters. Finally, we combine our results for the hard-core and ferromagnetic Potts models with standard Markov chain comparison tools to obtain polynomial mixing time for the usual spin system Glauber dynamics restricted to even and odd or "red" dominant portions of the respective state spaces

Privacy & security in the Cloud

Privacy and security issues are frequently presented as major inhibitors of cloud adoption. Some of these are operational issues and others relate to regulatory and compliance requirements that vary by industry and location. There is a growing body of guidance that seeks to clarify the implications of these concerns for various parts of the cloud supply chain. This paper provides a review of the business and legal risks associated with cloud computing and critically reviews the guidance available. It pays particular attention to the implications of the PRISM revelations for the development of a cloud marketplace that aims to keep data private and secure. A number of responses to cloud risks are available, including technological fixes and business responses. Each response has its own costs and requirements in terms of organisational capability and the paper evaluates the various responses that potential cloud adopters can use to manage the risks associated with cloud computing

Knowledge of Postgraduate Dental Students on Evidence-based Dentistry and Research Methodology. An International Survey

PURPOSE To assess the knowledge of postgraduate dental students about evidence-based methodology pertaining to the design, conduct, and critical appraisal of clinical trials. MATERIALS AND METHODS Senior postgraduate students were surveyed from the dental schools of three universities in Athens (Greece), Boston (USA), and Zürich (Switzerland). The proportion of students correctly answering each of the 10 questions of the survey, as well as the cumulative scores, were analysed statistically with descriptive statistics and logistic/linear regression analysis at α = 5%. RESULTS A total of 96 students with a mean age of 30.0 years attained an overall correct score of 45.6% ± 15.0%, with correct answers to each question ranging from 13.5% to 86.5%. The questions most frequently answered incorrectly pertained to characterising sensitivity/specificity (13.5%), the number needed to treat (14.0%), the credibility of trial synthesis in meta-analysis (23.7%), and publication bias (29.5%). The vast majority of postgraduate students could correctly identify the role of statistical power of a trial (63.8%), random allocation sequence in a randomised trial (76.0%), and blinding in a randomised trial (86.5%). Paediatric dentistry postgraduate students scored better than students from other departments (+15.1%; 95% CI: 3.0% to 27.1%; p = 0.02). CONCLUSIONS Postgraduate students in orthodontics and other dental specialties possessed moderate knowledge on evidence-based methodology and clinical trials. Efforts should be made to integrate such subjects in university postgraduate curricula, so that future dental specialists can critically appraise such research papers

The mass and density of the dwarf planet (225088) 2007 OR10

The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e$\approx$0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused by the Kozai mechanism. Dynamical considerations also suggest that the moon is small, D$_{eff}$ $<$ 100 km. Based on the newly determined system mass of 1.75x10$^{21}$ kg, 2007 OR10 is the fifth most massive dwarf planet after Eris, Pluto, Haumea and Makemake. The newly determined orbit has also been considered as an additional option in our radiometric analysis, provided that the moon orbits in the equatorial plane of the primary. Assuming a spherical shape for the primary this approach provides a size of 1230$\pm$50 km, with a slight dependence on the satellite orbit orientation and primary rotation rate chosen, and a bulk density of 1.75$\pm$0.07 g cm$^{-3}$ for the primary. A previous size estimate that assumed an equator-on configuration (1535$^{+75}_{-225}$ km) would provide a density of 0.92$^{+0.46}_{-0.14}$ g cm$^{-3}$, unexpectedly low for a 1000 km-sized dwarf planet.Comment: Accepted for publication in Icaru

The Role of Apparent Competition in Facilitating Ecological Release of a Range-expanding Insect

Due to anthropogenic climate change, species are expanding their historical natural ranges. However, interacting species will not shift synchronously and range-expanding species are likely to lose interactions and pick up novel ones in their expanded range. If antagonistic interactions, such as with competitors or enemies are lost, range-expanding species may experience “ecological release” and have impacts in their expanded range. Of the parasitoid wasps that attack phytophagous insects, some are specialists and some are generalists attacking alternative hosts (competitors). Range-expanding species may lose enemies if their specialists fail to follow from their native range and if generalist enemies fail to switch from competitors in the expanded range (“release from apparent competition”). We study a poleward range-expansion of a phytophagous gall-forming insect Neuroterus saltatorius that expanded its range from mainland western North America to Vancouver Island, BC, where it is outbreaking on its plant Querucs garryana. N. saltatorius co-occurs with several other gall-formers on its host, including Andricus opertus, throughout its native and expanded range. Here, we ask if A. opertus acts as an apparent competitor (shares enemies) with N. saltatorius, and if apparent competition is weaker in the expanded range. These two host species were collected from 18 sites that span the range of Q. garryana. We reared parasitoid wasps from them and identified parasitoids to morphospecies using taxonomic keys. We identified 16 parasitoids from N. saltatorius and 39 from A. opertus. Of these, 13 species of parasitoids are shared between the two host species in all regions, and we will calculate the rate of shared overlap to see if there are fewer shared species in the expanded range. This result would suggest that release from apparent competition contributes to ecological release. Understanding how biotic interactions change under range expansions is important to predict species responses to climate change.https://orb.binghamton.edu/research_days_posters_2021/1095/thumbnail.jp

Heritability of facial soft tissue growth in mono- and dizygotic twins at 12 and 17 years of age: A retrospective cohort study

OBJECTIVE The purpose of this investigation of untreated monozygotic and dizygotic twins was to identify the genetic and environmental components to the facial soft tissue growth. SETTINGS AND SAMPLE POPULATION The sample consisted of 52 untreated monozygotic twins (36 male and 16 female) and 46 untreated dizygotic twins (23 male and 23 female) from the Forsyth Moorrees Twin Study (1959-1975). MATERIALS AND METHODS Lateral cephalograms were taken at 12 and 17 years of age and traced to analyse facial convexity, nasolabial angle, upper and lower lip thickness, upper and lower lip profile and nose prominence. The genetic and environmental components of variance were analysed with structural equation modelling for multilevel mixed-effects model. RESULTS At 12 years of age, strong additive genetic influence was seen for facial convexity (70%), upper lip profile (66%) and nose prominence (65%), whereas strong dominant genetic components were found for upper lip thickness (56%). Nevertheless, under unique environment influence were nasolabial angle (58%), lower lip profile (51%) and lower lip thickness (64%). At 17 years of age, only upper lip thickness (55%) and nose prominence (84%) were under strong additive genetic control, while the rest of the variables were under strong dominant genetic control. The only exception was lower lip thickness (61%), which is still influenced by the unique environment. CONCLUSION Although monozygotic/dizygotic twins share at least part of their genome, at both times either additive, dominant or environmental components were found. Nevertheless, at 17 years of age most of the variables are either under additive or dominant genetic influence

Cephalometric Variability Among Siblings: A Pilot Study

Objective:To determine whether multiple siblings resemble one another in their craniofacial characteristics as measured on cephalometric radiographs.Methods:This study was conducted retrospectively using the Forsyth Moorrees twin sample. A total of 32 families were included, each with ≥4 postpubertal siblings, totaling 142 subjects. Only 1 monozygotic twin was included per family. Headfilms were digitized, skeletal landmarks were located, and 6 parameters that indicated sagittal jaw relationships and vertical status were measured. Diverse statistical approaches were used. Dixon’s Q-test detected outliers in a family for a given parameter. Manhattan Distance quantified similarity among siblings per parameter. Scatter plots visually displayed subject’s measure relative to the mean and standard deviation of each parameter to assess the clinical relevance of the differences.Results:A total of 11 families (34.4%) had no outliers on any parameter, 13 families (40.6%) had outliers on 1 parameter, and 8 families (25%) had outliers on ≥2 parameters. We identified 29 individuals with at least 1 outlying measure (20.4%). Among these, only 2 individuals (1.4%) were significantly different from their siblings for more than 1 measurement. Although the majority of the families did not demonstrate any statistical outlier, the ranges of the measurements were clinically relevant as they might suggest different treatment. For example, the mean range of SNB (Sella-Nasion-B point) angles was 7.23°, and the mean range of MPA was 9.42°.Conclusion:Although families are generally not dissimilar in their craniofacial characteristics, measurements from siblings cannot be used to predict the measurements of another sibling in a clinically meaningful way