Combining EGM2008 and SRTM/DTM2006.0 residual terrain model data to improve quasigeoid computations in mountainous areas devoid of gravity data

A global geopotential model, like EGM2008, is not capable of representing the high-frequency components of Earth?s gravity field. This is known as the omission error. In mountainous terrain, omission errors in EGM2008, even when expanded to degree 2,190, may reach amplitudes of10cm and more for height anomalies. The present paper proposes the utilisation of high-resolution residual terrain model (RTM) data for computing estimates of the omission error in rugged terrain. RTM elevations may be constructed as the difference between the SRTM (Shuttle Radar Topography Mission) elevation model and the DTM2006.0 spherical harmonic topographic expansion. Numerical tests, carried out in the German Alps with a precise gravimetric quasigeoid model (GCG05) and GPS/levelling data as references, demonstrate that RTM-based omission error estimatesimprove EGM2008 height anomaly differences by 10cm in many cases. The comparisons of EGM2008-only height anomalies and the GCG05 model showed 3.7 cm standard deviation after a bias-fit. Applying RTM omission error estimates to EGM2008 reduces the standard deviation to 1.9 cm which equates to a significant improvement rate of 47%. Using GPS/levelling data strongly corroborates thesefindings with an improvement rate of 49%. The proposed RTM approach may be of practical value to improve quasigeoid determination in mountainous areas without sufficient regional gravity data coverage, e.g., in parts of Asia, South America or Africa. As a further application, RTMomission error estimates will allow refined validation of global gravity field models like EGM2008 from GPS/levelling data

Indirect evaluation of Mars Gravity Model 2011 using a replication experiment on Earth

Curtin University’s Mars Gravity Model 2011 (MGM2011) is a high-resolution composite set of gravity field functionals that uses topography-implied gravity effects at medium- and short-scales (~125 km to ~3 km) to augment the space-collected MRO110B2 gravity model. Ground-truth gravity observations that could be used for direct validation of MGM2011 are not available on Mars’s surface. To indirectly evaluate MGM2011 and its modelling principles, an as-close-as-possible replication of the MGM2011 modelling approach was performed on Earth as the planetary body with most detailed gravity field knowledge available. Comparisons among six ground-truth data sets (gravity disturbances, quasigeoid undulations and vertical deflections) and the MGM2011-replication over Europe and North America show unanimously that topography-implied gravity information improves upon space-collected gravity models over areas with rugged terrain. The improvements are ~55% and ~67% for gravity disturbances, ~12% and ~47% for quasigeoid undulations, and ~30% to ~50% for vertical deflections. Given that the correlation between space-collected gravity and topography is higher for Mars than Earth at spatial scales of a few 100 km, topography-implied gravity effects are more dominant on Mars. It is therefore reasonable to infer that the MGM2011 modelling approach is suitable, offering an improvement over space-collected Martian gravity field models

The Price of Low Communication in Secure Multi-Party Computation

Traditional protocols for secure multi-party computation among n parties communicate at least a linear (in n) number of bits, even when computing very simple functions. In this work we investigate the feasibility of protocols with sublinear communication complexity. Concretely, we consider two clients, one of which may be corrupted, who wish to perform some “small” joint computation using n servers but without any trusted setup. We show that enforcing sublinear communication complexity drastically affects the feasibility bounds on the number of corrupted parties that can be tolerated in the setting of information-theoretic security. We provide a complete investigation of security in the presence of semi-honest adversaries---static and adaptive, with and without erasures---and initiate the study of security in the presence of malicious adversaries. For semi-honest static adversaries, our bounds essentially match the corresponding bounds when there is no communication restriction---i.e., we can tolerate up to t < (1/2 - \epsilon)n corrupted parties. For the adaptive case, however, the situation is different. We prove that without erasures even a small constant fraction of corruptions is intolerable, and---more surprisingly---when erasures are allowed, we prove that t < (1- \sqrt(0.5) -\epsilon)n corruptions can be tolerated, which we also show to be essentially optimal. The latter optimality proof hinges on a new treatment of probabilistic adversary structures that may be of independent interest. In the case of active corruptions in the sublinear communication setting, we prove that static “security with abort” is feasible when t < (1/2 - \epsilon)n, namely, the bound that is tight for semi-honest security. All of our negative results in fact rule out protocols with sublinear message complexity

MPC with Synchronous Security and Asynchronous Responsiveness

Two paradigms for secure MPC are synchronous and asynchronous protocols. While synchronous protocols tolerate more corruptions and allow every party to give its input, they are very slow because the speed depends on the conservatively assumed worst-case delay $\Delta$ of the network. In contrast, asynchronous protocols allow parties to obtain output as fast as the actual network allows, a property called responsiveness, but unavoidably have lower resilience and parties with slow network connections cannot give input. It is natural to wonder whether it is possible to leverage synchronous MPC protocols to achieve responsiveness, hence obtaining the advantages of both paradigms: full security with responsiveness up to $t$ corruptions, and extended security (full security or security with unanimous abort) with no responsiveness up to $T \ge t$ corruptions. We settle the question by providing matching feasibility and impossibility results: -For the case of unanimous abort as extended security, there is an MPC protocol if and only if $T + 2t < n$. -For the case of full security as extended security, there is an MPC protocol if and only if $T < n/2$ and $T + 2t < n$. In particular, setting $t = n/4$ allows to achieve a fully secure MPC for honest majority, which in addition benefits from having substantial responsiveness

Three-dimensional CFD simulations with large displacement of the geometries using a connectivity-change moving mesh approach

This paper deals with three-dimensional (3D) numerical simulations involving 3D moving geometries with large displacements on unstructured meshes. Such simulations are of great value to industry, but remain very time-consuming. A robust moving mesh algorithm coupling an elasticity-like mesh deformation solution and mesh optimizations was proposed in previous works, which removes the need for global remeshing when performing large displacements. The optimizations, and in particular generalized edge/face swapping, preserve the initial quality of the mesh throughout the simulation. We propose to integrate an Arbitrary Lagrangian Eulerian compressible flow solver into this process to demonstrate its capabilities in a full CFD computation context. This solver relies on a local enforcement of the discrete geometric conservation law to preserve the order of accuracy of the time integration. The displacement of the geometries is either imposed, or driven by fluid–structure interaction (FSI). In the latter case, the six degrees of freedom approach for rigid bodies is considered. Finally, several 3D imposed-motion and FSI examples are given to validate the proposed approach, both in academic and industrial configurations

Posterior translacrimal approach to the maxillary sinus

Background: This study aimed to compare the view into the maxillary sinus using the posterior translacrimal approach compared with grade 3 antrostomy. Methods: Grade 3 antrostomy followed by a posterior translacrimal approach was performed on four cadavers. The maximum intramaxillary view was documented endoscopically guided by electromagnetic navigation. Representative screenshots were evaluated in a blinded manner by three independent sinus surgeons. In addition, a prospective investigation of specific complications in the post-operative course of consecutive patients was performed. Results: In the cadaver study, the posterior translacrimal approach provided a significantly better view into the maxillary sinus compared with grade 3 antrostomy. In the clinical study, only 1 out of 20 patients reported on a minor problem with lacrimal drainage at 6 months. Conclusion: The posterior translacrimal approach to visualising the maxillary sinus should be considered a strong alternative to more radical techniques

Evaluation and pharmacovigilance of projects promoting cultivation and local use of Artemisia annua for malaria

<p>Abstract</p> <p>Background</p> <p>Several non-governmental organisations (NGOs) are promoting the use of <it>Artemisia annua </it>teas as a home-based treatment for malaria in situations where conventional treatments are not available. There has been controversy about the effectiveness and safety of this approach, but no pharmacovigilance studies or evaluations have been published to date.</p> <p>Method</p> <p>A questionnaire about the cultivation of <it>A. annua</it>, treatment of patients, and side-effects observed, was sent to partners of the NGO Anamed in Kenya and Uganda. Some of the respondents were then selected purposively for more in-depth semi-structured interviews.</p> <p>Results</p> <p>Eighteen partners in Kenya and 21 in Uganda responded. 49% reported difficulties in growing the plant, mainly due to drought. Overall about 3,000 cases of presumed malaria had been treated with <it>A. annua </it>teas in the previous year, of which about 250 were in children and 54 were in women in the first trimester of pregnancy. The commonest problem observed in children was poor compliance due to the bitter taste, which was improved by the addition of sugar or honey. Two miscarriages were reported in pregnant patients. Only four respondents reported side-effects in other patients, the commonest of which was vomiting. 51% of respondents had started using <it>A. annua </it>tea to treat illnesses other than malaria.</p> <p>Conclusions</p> <p>Local cultivation and preparation of <it>A. annua </it>are feasible where growing conditions are appropriate. Few adverse events were reported even in children and pregnant women. Where ACT is in short supply, it would make sense to save it for young children, while using <it>A. annua </it>infusions to treat older patients who are at lower risk. An ongoing pharmacovigilance system is needed to facilitate reporting of any adverse events.</p

I Blame Therefore it Was: Rape Myth Acceptance, Victim Blaming, and Memory Reconstruction

We examined the causal order of relationships between rape myth acceptance (RMA), victim blaming, and memory reconstruction. In Study 1, RMA-congruent memory (or alternatively, victim blaming) mediated the relationship between RMA and victim blaming (memory reconstruction). In Study 2, similar relationships emerged between RMA, victim blaming, and memory reconstruction. Although no mediation of RMA occurred in Study 2 independently, a mini meta-analysis of Studies 1 and 2 data replicated both patterns of mediation observed in Study 1. In Study 3, memory accuracy for neutral details of a rape scenario was unrelated to RMA. Manipulating memory to be more (vs. less) RMA congruent had no effect on victim blaming (Study 4), although manipulating perceived victim blameworthiness (Studies 5 and 6) produced RMA-congruent memory reconstruction when the victim was more (vs. less) blameworthy. The results suggest that, via victim blaming, RMA motivates a memory reconstruction process that explains and justifies victim blaming after the fact