Large-scale Bias and Efficient Generation of Initial Conditions for Non-Local Primordial Non-Gaussianity

We study the scale-dependence of halo bias in generic (non-local) primordial non-Gaussian (PNG) initial conditions of the type motivated by inflation, parametrized by an arbitrary quadratic kernel. We first show how to generate non-local PNG initial conditions with minimal overhead compared to local PNG models for a general class of primordial bispectra that can be written as linear combinations of separable templates. We run cosmological simulations for the local, and non-local equilateral and orthogonal models and present results on the scale-dependence of halo bias. We also derive a general formula for the Fourier-space bias using the peak-background split (PBS) in the context of the excursion set approach to halos and discuss the difference and similarities with the known corresponding result from local bias models. Our PBS bias formula generalizes previous results in the literature to include non-Markovian effects and non-universality of the mass function and are in better agreement with measurements in numerical simulations than previous results for a variety of halo masses, redshifts and halo definitions. We also derive for the first time quadratic bias results for arbitrary non-local PNG, and show that non-linear bias loops give small corrections at large-scales. The resulting well-behaved perturbation theory paves the way to constrain non-local PNG from measurements of the power spectrum and bispectrum in galaxy redshift surveys.Comment: 43 pages, 10 figures. v2: references added. 2LPT parallel code for generating non-local PNG initial conditions available at http://cosmo.nyu.edu/roman/2LP

Halo Sampling, Local Bias and Loop Corrections

We develop a new test of local bias, by constructing a locally biased halo density field from sampling the dark matter-halo distribution. Our test differs from conventional tests in that it preserves the full scatter in the bias relation and it does not rely on perturbation theory. We put forward that bias parameters obtained using a smoothing scale R can only be applied to computing the halo power spectrum at scales k ~ 1/R. Our calculations can automatically include the running of bias parameters and give vanishingly small loop corrections at low-k. Our proposal results in much better agreement of the sampling and perturbation theory results with simulations. In particular, unlike the standard interpretation of local bias in the literature, our treatment of local bias does not generate a constant power in the low-k limit. We search for extra noise in the Poisson corrected halo power spectrum at wavenumbers below its turn-over and find no evidence of significant positive noise (as predicted by the standard interpretation) while we find evidence of negative noise coming from halo exclusion for very massive halos. Using perturbation theory and our non-perturbative sampling technique we also demonstrate that nonlocal bias effects discovered recently in simulations impact the power spectrum only at the few percent level in the weakly nonlinear regime.Comment: 25 pages, 14 figures; V2: significant revision including more details about halo exclusion and low-k noise. Conclusions unchange

Analysis of two pairing-based three-party password authenticated key exchange protocols

Password-Authenticated Key Exchange (PAKE) protocols allow parties to share secret keys in an authentic manner based on an easily memorizable password. Recently, Nam et al. showed that a provably secure three-party password-based authenticated key exchange protocol using Weil pairing by Wen et al. is vulnerable to a man-in-the-middle attack. In doing so, Nam et al. showed the flaws in the proof of Wen et al. and described how to fix the problem so that their attack no longer works. In this paper, we show that both Wen et al. and Nam et al. variants fall to key compromise impersonation by any adversary. Our results underline the fact that although the provable security approach is necessary to designing PAKEs, gaps still exist between what can be proven and what are really secure in practice

Gravity and Large-Scale Non-local Bias

The relationship between galaxy and matter overdensities, bias, is most often assumed to be local. This is however unstable under time evolution, we provide proofs under several sets of assumptions. In the simplest model galaxies are created locally and linearly biased at a single time, and subsequently move with the matter (no velocity bias) conserving their comoving number density (no merging). We show that, after this formation time, the bias becomes unavoidably non-local and non-linear at large scales. We identify the non-local gravitationally induced fields in which the galaxy overdensity can be expanded, showing that they can be constructed out of the invariants of the deformation tensor (Galileons). In addition, we show that this result persists if we include an arbitrary evolution of the comoving number density of tracers. We then include velocity bias, and show that new contributions appear, a dipole field being the signature at second order. We test these predictions by studying the dependence of halo overdensities in cells of fixed matter density: measurements in simulations show that departures from the mean bias relation are strongly correlated with the non-local gravitationally induced fields identified by our formalism. The effects on non-local bias seen in the simulations are most important for the most biased halos, as expected from our predictions. The non-locality seen in the simulations is not fully captured by assuming local bias in Lagrangian space. Accounting for these effects when modeling galaxy bias is essential for correctly describing the dependence on triangle shape of the galaxy bispectrum, and hence constraining cosmological parameters and primordial non-Gaussianity. We show that using our formalism we remove an important systematic in the determination of bias parameters from the galaxy bispectrum, particularly for luminous galaxies. (abridged)Comment: 26 pages, 9 figures. v2: improved appendix

The knowledge evolution framework : a knowledge management perspective on the impact of knowledge segregation on product development projects

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (p. 199-216).Developing offerings faster, better and cheaper than competitors has become critical to success. In response to these commercial pressures, many industries have shifted from a sequential, functional development paradigm to a concurrent, team-based paradigm. Increasing the concurrence and cross-functional development, however, also dramatically increases the dynamic complexity of development projects. This is added complexity on top of the increasing technological complexity of offerings. Whilst traditional models based on tools such as the CPM and PERT have been used for the planning and management of such projects successfully in the past, the increase in complexity has shown that such tools are less capable of planning and predicting the outcome of projects. This is due to the dynamic nature of projects and the task-based approach used. Recent research using dynamic simulation tools such as system dynamics have indicated reasons that project duration and cost have been consistently underestimated. The differentiation is attributed to the ability of dynamic simulation tools to capture the iterative nature of work. Existing research has, however, concentrated on iteration as a result of errors, quality control and shifting targets. Although these factors do contribute to iteration, they seem almost exogenous factors where independent policies can be used to mitigate the need for iteration. Yet all texts on design and product development describe the process as an iterative one. There must, therefore, be some endogenous factors that result in an inherent need for iteration. With the level of complexity of projects, specialization becomes necessary. As a result, no individual within a project has 'lull" knowledge about the project and its current state of development. In other words, the information and knowledge is segregated to different parts of the project organization. This research proposes a shift towards a knowledge-evolution paradigm and uses it to investigate the impacts of such knowledge segregation on the performance of product development projects. This proposed framework acts, in part, to provide management levers and measurements in managing the knowledge within product development projects. These are measurements that the traditional task-based frameworks cannot directly provide. A dynamic simulation model of a development project with multiple persons was built using the system dynamics methodology. The model portrays the segregation of knowledge and studies its impact on the rate of development and iteration. The model was applied to projects with a scope defined by the Delta Design Game. Though simple, the Delta Design game provides the boundaries in understanding the interactions amongst participants in a typical process and has been used in the past primarily to demonstrate this aspect of design. The model simulation bore results that closely resembled real life behavior of the Delta Design project. The model was also applied to the investigation of differing policies for improved project performance. These policies include strategies involving conservatism in design, preemptive measures against iteration and reduction of knowledge segregation through the decoupling of the knowledge processes. The model structure provides insight as to the effectiveness of these strategies. The research finds that rework and iteration happens inherently in development projects and its prevalence is interwoven into the fabric of the system architecture and project organization structure. Finally, this research has shown value in the knowledge evolution paradigm by gathering insights through which task-based models could not. In so doing so, it is shown that there is value in developing this concby Jeffrey C. Chi.Ph.D

Desperate housewives: An analysis of the characterisations of female gamblers portrayed in gambling movies in Hong Kong

This article examines portrayals of female gamblers in recent Hong Kong movies. The authors report that the depiction of female gamblers is very different from that of male gamblers in the movies made in the same period. Whereas the male gamblers are pitching a lonely and desperate battle against the evil opponent, the female gamblers portrayed in the movies are housewives or small-time players who gamble only for their personal gain. A general negative overtone in portrayals of female gamblers was interpreted as a reflection of the traditional view that discourages women from gambling. The shift of gambling themes in the Hong Kong movies has been identified to reflect the most salient concerns among Hong Kong residents. Such changes are attributed to particular social and cultural changes in the community

A cultural study of administrative litigation in the People's Republic of China

The introduction of administrative litigation in the People's Republic of China in October 1990 initiated a new era in the Chinese ruled-rulers relationship. It broke through the entrenched ruled-rulers dichotomy and established a formal legal channel for ordinary citizens to defend their personal and property rights against any infringement by government officials' unlawful specific administrative acts. This thesis is the first empirical analysis of administrative litigation in the People's Republic of China to use a cultural approach. A microanalysis was conducted through interviews with 738 individual household proprietors and 152 government officials from the Hai Dian, Xi Cheng, and Xuan Wu districts of the Beijing municipality between mid-1996 and early 1997, with a four-page questionnaire to assess their administrative litigation cultures. Complemented by a macro analysis, the survey also examined the structure and problems of the PRC's administrative litigation through comprehensive literature reviews, in-depth personal interviews, and attendance in court hearings. The PRC's administrative litigation is a top-down contrivance of the rulers to uphold their rule. As such, it has never been a fully-fledged redress mechanism, but only a confined concession with restricted jurisdiction bound by a narrowly but cautiously construed Administrative Litigation Law. Implementation of the PRe's administrative litigation has been difficult and problematic. The resulting consequences are confined and biased towards the rulers. The overall usefulness of the mechanism is restricted. And its prospect is worrying. The empirical survey generates extraordinarily interesting findings. The affective orientation of both sample groups on the need for administrative litigation was found highly positive and supportive. Their evaluational orientation on the consequences of administrative litigation in the country was highly affirmative. And their expectational orientation towards the future of the PRC's administrative litigation was equally optimistic. The surveyed rulers were clearly better informed in their cognitive orientation, but more reserved in their jurisdictional orientation. Meanwhile, the majority of the surveyed ruled were clearly dismayed in their appraisal orientation regarding the usefulness of the PRC's administrative litigation. The latter is obviously below the acceptable threshold, and substantial improvement is needed if it is to help ameliorate the Chinese ruled-rulers relationship

Sleep State Modulates Resting-State Functional Connectivity in Neonates.

The spontaneous cerebral activity that gives rise to resting-state networks (RSNs) has been extensively studied in infants in recent years. However, the influence of sleep state on the presence of observable RSNs has yet to be formally investigated in the infant population, despite evidence that sleep modulates resting-state functional connectivity in adults. This effect could be extremely important, as most infant neuroimaging studies rely on the neonate to remain asleep throughout data acquisition. In this study, we combine functional near-infrared spectroscopy with electroencephalography to simultaneously monitor sleep state and investigate RSNs in a cohort of healthy term born neonates. During active sleep (AS) and quiet sleep (QS) our newborn neonates show functional connectivity patterns spatially consistent with previously reported RSN structures. Our three independent functional connectivity analyses revealed stronger interhemispheric connectivity during AS than during QS. In turn, within hemisphere short-range functional connectivity seems to be enhanced during QS. These findings underline the importance of sleep state monitoring in the investigation of RSNs

Lycium barbarum Extracts Protect the Brain from Blood-Brain Barrier Disruption and Cerebral Edema in Experimental Stroke

BACKGROUND AND PURPOSE: Ischemic stroke is a destructive cerebrovascular disease and a leading cause of death. Yet, no ideal neuroprotective agents are available, leaving prevention an attractive alternative. The extracts from the fruits of Lycium barbarum (LBP), a Chinese anti-aging medicine and food supplement, showed neuroprotective function in the retina when given prophylactically. We aim to evaluate the protective effects of LBP pre-treatment in an experimental stroke model. METHODS: C57BL/6N male mice were first fed with either vehicle (PBS) or LBP (1 or 10 mg/kg) daily for 7 days. Mice were then subjected to 2-hour transient middle cerebral artery occlusion (MCAO) by the intraluminal method followed by 22-hour reperfusion upon filament removal. Mice were evaluated for neurological deficits just before sacrifice. Brains were harvested for infarct size estimation, water content measurement, immunohistochemical analysis, and Western blot experiments. Evans blue (EB) extravasation was determined to assess blood-brain barrier (BBB) disruption after MCAO. RESULTS: LBP pre-treatment significantly improved neurological deficits as well as decreased infarct size, hemispheric swelling, and water content. Fewer apoptotic cells were identified in LBP-treated brains by TUNEL assay. Reduced EB extravasation, fewer IgG-leaky vessels, and up-regulation of occludin expression were also observed in LBP-treated brains. Moreover, immunoreactivity for aquaporin-4 and glial fibrillary acidic protein were significantly decreased in LBP-treated brains. CONCLUSIONS: Seven-day oral LBP pre-treatment effectively improved neurological deficits, decreased infarct size and cerebral edema as well as protected the brain from BBB disruption, aquaporin-4 up-regulation, and glial activation. The present study suggests that LBP may be used as a prophylactic neuroprotectant in patients at high risk for ischemic stroke.published_or_final_versio

Mixed-location cerebral microbleeds as a biomarker of neurodegeneration in a memory clinic population

Cerebral microbleeds (CMBs) in the lobar and deep locations are associated with two distinct pathologies: cerebral amyloid angiopathy and hypertensive arteriopathy. However, the role of mixed-location CMBs in neurodegeneration remains unexplored. We investigated the associations between strictly lobar, strictly deep and mixed-location CMBs with markers of neurodegeneration. This study recruited 477 patients from a memory clinic who underwent 3T MRI scans. CMBs were categorized into strictly lobar, strictly deep and mixed-location. Cortical thickness, white matter volume and subcortical structural volumes were quantified using Free-Surfer. Linear regression models were performed to assess the association between CMBs and cerebral atrophy, and the mean difference (β) and 95% confidence intervals (CIs) were reported. In the regression analyses, mixed-location CMBs were associated with smaller cortical thickness of limbic region [β=-0.01; 95% CI=-0.02,-0.00, p=0.007) as well as with smaller accumbens volume [β=-0.01; 95% CI=-0.02,-0.00, p=0.004) and presubiculum region of hippocampus [β=-0.01; 95% CI=-0.02,-0.00, p=0.002). Strictly lobar CMBs were associated with smaller total white matter volume [β=-0.03; 95% CI=-0.04,-0.01, p<0.001] and with region specific white mat