Brief announcement: passive and active attacks on audience response systems using software defined radios

Audience response systems, also known as clickers, are used at many academic institutions to offer active learning environments. Since these systems are used to administer graded assignments, and sometimes even exams, it is crucial to assess their security. Our work seeks to exploit and document potential vulnerabilities of clickers. For this purpose, we use software defined radios to perform jamming, sniffing and spoofing attacks on an audience response system in production, which provide different possible methods of cheating. The results of our study demonstrate that clickers are easily exploitable. We build a prototype and show that it is practically possible to covertly steal or forge answers of a peer or even an entire classroom, with high levels of confidence. Additionally, we find that the receivers software of the system lacks protection against unexpected answers, which allows our spoofer to submit any ASCII character and opens the receiver up to possible fuzzing attacks. As a result of this study, we discourage using clickers for high-stake assessments, unless they provide proper security protection..http://people.bu.edu/staro/SSS2017_Brief_v0.pdfhttp://people.bu.edu/staro/SSS2017_Brief_v0.pdfhttp://people.bu.edu/staro/SSS2017_Brief_v0.pdfAccepted manuscrip

Dune field pattern formation and recent transporting winds in the Olympia Undae Dune Field, north polar region of Mars

High-Resolution Imaging Science Experiment (HiRISE) imagery of the central Olympia Undae Dune Field in the north polar region of Mars shows a reticulate dune pattern consisting of two sets of nearly orthogonal dune crestlines, with apparent slipfaces on the primary crests, ubiquitous wind ripples, areas of coarse-grained wind ripples, and deflated interdune areas. Geomorphic evidence and dune field pattern analysis of dune crest length, spacing, defect density, and orientation indicates that the pattern is complex, representing two constructional generations of dunes. The oldest and best-organized generation forms the primary crestlines and is transverse to circumpolar easterly winds. Gross bed form-normal analysis of the younger pattern of crestlines indicates that it emerged with both circumpolar easterly winds and NE winds and is reworking the older pattern. Mapping of secondary flow fields over the dunes indicates that the most recent transporting winds were from the NE. The younger pattern appears to represent an influx of sediment to the dune field associated with the development of the Olympia Cavi reentrant, with NE katabatic winds channeling through the reentrant. A model of the pattern reformation based upon the reconstructed primary winds and resulting secondary flow fields shows that the development of the secondary pattern is controlled by the boundary condition of the older dune topography

Direct Observation of the Dynamics of Ylide Solvation by Hydrogen-bond Donors using Time-Resolved Infrared Spectroscopy

[Image: see text] The photoexcitation of α-diazocarbonyl compounds produces singlet carbene intermediates that react with nucleophilic solvent molecules to form ylides. The zwitterionic nature of these newly formed ylides induces rapid changes in their interactions with the surrounding solvent. Here, ultrafast time-resolved infrared absorption spectroscopy is used to study the ylide-forming reactions of singlet carbene intermediates from the 270 nm photoexcitation of ethyl diazoacetate in various solvents and the changes in the subsequent ylide–solvent interactions. The results provide direct spectroscopic observation of the competition between ylide formation and C–H insertion in reactions of the singlet carbene with nucleophilic solvent molecules. We further report the specific solvation dynamics of the tetrahydrofuran (THF)-derived ylide (with a characteristic IR absorption band at 1636 cm(–1)) by various hydrogen-bond donors and the coordination by lithium cations. Hydrogen-bonded ylide bands shift to a lower wavenumber by −19 cm(–1) for interactions with ethanol, −14 cm(–1) for chloroform, −10 cm(–1) for dichloromethane, −9 cm(–1) for acetonitrile or cyclohexane, and −16 cm(–1) for Li(+) coordination, allowing the time evolution of the ylide–solvent interactions to be tracked. The hydrogen-bonded ylide bands grow with rate coefficients that are close to the diffusional limit. We further characterize the specific interactions of ethanol with the THF-derived ylide using quantum chemical (MP2) calculations and DFT-based atom-centered density matrix propagation trajectories, which show preferential coordination to the α-carbonyl group. This coordination alters the hybridization character of the ylidic carbon atom, with the greatest change toward sp(2) character found for lithium-ion coordination

Orthopedic Screwdriver Design

Design an adjustable mechanical clutch screwdriver suitable for driving Orthopedic Screws into bones. The clutch would prevent over tightening and damaging bone material. The prototype design must demonstrate the function and ergonomics of the device and it must be suitable for modification into a medical device. Specify material changes and design details that would be needed for the ultimate production model

Vibration Isolation for Scanning Tunneling Microscope

Scanning Tunneling Microscopy (STM) works by scanning a fine metal wire over a conductive sample in order to image samples on the atomic level. The microscope uses a feedback loop with a PID controller to maintain a constant tunneling current between the sample and the tip. In order to obtain clear imaging at the atomic level, the microscope and the sample need to be isolated from external vibrations in a vacuum chamber. The scope for this project is to build and test a single-stage vibration isolation system that effectively attenuates the amplitude of external vibrations acting on the microscope. This document summarizes the preliminary design process, including the customer interviews we performed, the background research we collected about existing patents and designs, and the technical journal articles dealing with this subject that we read. In addition, this project defines the final design along with manufacturing and testing results to validate the design. The final design includes a final design description, design justification, manufacturing results, as well as the testing plan and results. These sections serve to overview the process for our final design selection and the results of the manufacturing and testing phases of the final design

Loop quantum cosmology of Bianchi type IX models

The loop quantum cosmology "improved dynamics" of the Bianchi type IX model are studied. The action of the Hamiltonian constraint operator is obtained via techniques developed for the Bianchi type I and type II models, no new input is required. It is shown that the big bang and big crunch singularities are resolved by quantum gravity effects. We also present the effective equations which provide modifications to the classical equations of motion due to quantum geometry effects.Comment: 20 page

An Evolving Understanding of Enigmatic Large Ripples on Mars

Two scales of ripples form in fine sand on Mars. The larger ripples were proposed to have an equilibrium size set by an aerodynamic process, making them larger under thinner atmospheres and distinct from smaller impact ripples. Sullivan et al. (2020) show that large ripples can develop in a numerical model due to Mars’ low atmospheric pressure. Although their proposed growth‐limiting mechanism is consistent with an aerodynamic process, they argue that the ripples in their model are simply large versions of impact ripples, not a separate class of ripples. Here, we explore this debate by synthesizing recent advances in large‐ripple formation. Although significant knowledge gaps remain, it is clear that large martian ripples are larger under thinner atmospheres, and thus remain a powerful paleoclimate indicator