Keystroke dynamics in the pre-touchscreen era

Biometric authentication seeks to measure an individual’s unique physiological attributes for the purpose of identity verification. Conventionally, this task has been realized via analyses of fingerprints or signature iris patterns. However, whilst such methods effectively offer a superior security protocol compared with password-based approaches for example, their substantial infrastructure costs, and intrusive nature, make them undesirable and indeed impractical for many scenarios. An alternative approach seeks to develop similarly robust screening protocols through analysis of typing patterns, formally known as keystroke dynamics. Here, keystroke analysis methodologies can utilize multiple variables, and a range of mathematical techniques, in order to extract individuals’ typing signatures. Such variables may include measurement of the period between key presses, and/or releases, or even key-strike pressures. Statistical methods, neural networks, and fuzzy logic have often formed the basis for quantitative analysis on the data gathered, typically from conventional computer keyboards. Extension to more recent technologies such as numerical keypads and touch-screen devices is in its infancy, but obviously important as such devices grow in popularity. Here, we review the state of knowledge pertaining to authentication via conventional keyboards with a view toward indicating how this platform of knowledge can be exploited and extended into the newly emergent type-based technological contexts

Displacement operators: the classical face of their quantum phase

In quantum mechanics, the operator representing the displacement of a system in position or momentum is always accompanied by a path-dependent phase factor. In particular, two non-parallel displacements in phase space do not compose together in a simple way, and the order of these displacements leads to different displacement composition phase factors. These phase factors are often attributed to the nonzero commutator between quantum position and momentum operators, but such a mathematical explanation might be unsatisfactory to students who are after more physical insight. We present a couple of simple demonstrations, using classical wave mechanics and classical particle mechanics, that provide some physical intuition for the phase associated with displacement operators.Comment: 14 pages, 4 figures, reorganized and reformatte

Strain-induced gauge and Rashba fields in ferroelectric Rashba lead chalcogenide PbX monolayers (X = S, Se, Te)

One of the exciting features of two-dimensional (2D) materials is their electronic and optical tunability through strain engineering. Previously, we found a class of 2D ferroelectric Rashba semiconductors PbX (X = S, Se, Te) with tunable spin-orbital properties. In this work, based on our previous tight-binding (TB) results, we derive an effective low-energy Hamiltonian around the symmetry points that captures the effects of strain on the electronic properties of PbX. We find that strains induce gauge fields which shift the Rashba point and modify the Rashba parameter. This effect is equivalent to the application of in-plane magnetic fields. The out-of-plane strain, which is proportional to the electric polarization, is also shown to modify the Rashba parameter. Overall, our theory connects strain and spin splitting in ferroelectric Rashba materials, which will be important to understand the strain-induced variations in local Rashba parameters that will occur in practical applications

Two-dimensional square buckled Rashba lead chalcogenides

We propose the lead sulphide (PbS) monolayer as a two-dimensional semiconductor with a large Rashba-like spin-orbit effect controlled by the out-of-plane buckling. The buckled PbS conduction band is found to possess Rashba-like dispersion and spin texture at the M and Γ points, with large effective Rashba parameters of λ∼5 eV Å and λ∼1 eV Å, respectively. Using a tight-binding formalism, we show that the Rashba effect originates from the very large spin-orbit interaction and the hopping term that mixes the in-plane and out-of-plane p orbitals of Pb and S atoms. The latter, which depends on the buckling angle, can be controlled by applying strain to vary the spin texture as well as the Rashba parameter at Γ and M. Our density functional theory results together with tight-binding formalism provide a unifying framework for designing Rashba monolayers and for manipulating their spin properties.P.Z.H., H.S.P., and D.K.C. acknowledge the support of the Physics and Mechanical Engineering Department at Boston University. P.Z.H. is grateful for the hospitality of the NUS Centre for Advanced 2D Materials and Graphene Research Centre where this work was initiated. D.K.C. acknowledges the hospitality of the Aspen Center for Physics, which is supported by the US National Science Foundation Grant No. PHY-1607611. A.S.R., A.C.,and A.H.C.N. acknowledge support by the National Research Foundation, Prime Minister Office, Singapore, under its Medium Sized Centre Programme and CRP award "Novel 2D materials with tailored properties: Beyond graphene" (Grant No. R-144-000295-281). (Physics and Mechanical Engineering Department at Boston University; PHY-1607611 - US National Science Foundation; R-144-000295-281 - National Research Foundation, Prime Minister Office, Singapore, under its Medium Sized Centre Programme and CRP award "Novel 2D materials with tailored properties: Beyond graphene")Published versio

Second-harmonic generation microscopy analysis reveals proteoglycan decorin is necessary for proper collagen organization in prostate.

Collagen remodeling occurs in many prostate pathologies; however, the underlying structural architecture in both normal and diseased prostatic tissues is largely unexplored. Here, we use second-harmonic generation (SHG) microscopy to specifically probe the role of the proteoglycan decorin (Dcn) on collagen assembly in a wild type (wt) and Dcn null mouse (Dcn  -    /    -  ). Dcn is required for proper organization of collagen fibrils as it regulates size by forming an arch-like structure at the end of the fibril. We have utilized SHG metrics based on emission directionality (forward-backward ratio) and relative conversion efficiency, which are both related to the SHG coherence length, and found more disordered fibril organization in the Dcn  -    /    -  . We have also used image analysis readouts based on entropy, multifractal dimension, and wavelet transforms to compare the collagen fibril/fiber architecture in the two models, where all these showed that the Dcn  -    /    -   prostate comprised smaller and more disorganized collagen structures. All these SHG metrics are consistent with decreased SHG phase matching in the Dcn  -    /    -   and are further consistent with ultrastructural analysis of collagen in this model in other tissues, which show a more random distribution of fibril sizes and their packing into fibers. As Dcn is a known tumor suppressor, this work forms the basis for future studies of collagen remodeling in both malignant and benign prostate disease

An exact solution of the five-dimensional Einstein equations with four-dimensional de Sitter-like expansion

We present an exact solution to the Einstein field equations which is Ricci and Riemann flat in five dimensions, but in four dimensions is a good model for the early vacuum-dominated universe.Comment: 6 pages; to appear in Journal of Mathematical Physics; v2: reference 3 correcte

Gathering Teacher Feedback to Improve Informal Education

The educational programs offered at the Center for Education and Research in Environmental Strategies (CERES)in Australia, provide informal education opportunities for students learning about sustainability. However, without information about teachers\u27 needs, they are unsure how to develop and evolve their programs. This project gathered feedback to better inform the development and evolution of these programs. We surveyed and interviewed Victorian teachers which led to recommendations regarding the design of their programs and pricing model, and to the creation of teacher feedback gathering tools: a program evaluation and survey for prospective schools. By establishing communication with teachers, CERES can design their programs to meet teacher\u27s needs

Spatially optimized gene transfection by laser-induced breakdown of optically trapped nanoparticles

We demonstrate laser-induced breakdown of an optically trapped nanoparticle with a nanosecond laser pulse. Controllable cavitation within a microscope sample was achieved, generating shear stress to monolayers of live cells. This efficiently permeabilize their plasma membranes. We show that this technique is an excellent tool for plasmid-DNA transfection of cells with both reduced energy requirements and reduced cell lysis compared to previously reported approaches. Simultaneous multisite targeted nanosurgery of cells is also demonstrated using a spatial light modulator for parallelizing the technique.Publisher PDFPeer reviewe