High-frequency ultrasound sensors using polymer microring resonators

Polymer microring resonators are demonstrated as high-frequency, ultrasound detectors. An optical microring resonator consists of a ring waveguide closely coupled to a straight bus waveguide, serving as light input and output. Acoustic waves irradiating the ring induce strain, deforming the waveguide dimensions and changing the refractive index of the waveguide via the elasto-optic effect. These effects modify the effective refractive index of the guided mode inside the waveguide. The sharp wavelength dependence of the microring resonance can enhance the optical response to acoustic strain. Such polymer microring resonators are experimentally demonstrated in detecting broadband ultrasound pulses from a 50 MHz transducer. Measured frequency response shows that these devices have potential in high-frequency, ultrasound detection. Design guidelines for polymer microring resonators forming an ultrasound detector array are discussed.     

VC-Dimension Analysis of Object Recognition Tasks

We analyze the amount of data needed to carry out various model-based recognition tasks in the context of a probabilistic data collection model. We focus on objects that may be described as semi-algebraic subsets of a Euclidean space. This is a very rich class that includes polynomially described bodies, as well as polygonal objects, as special cases. The class of object transformations considered is wide, and includes perspective and affine transformations of 2D objects, and perspective projections of 3D objects.We derive upper bounds on the number of data features (associated with non-zero spatial error) which provably suffice for drawing reliable conclusions. Our bounds are based on a quantitative analysis of the complexity of the hypotheses class that one has to choose from. Our central tool is the VC-dimension, which is a well-studied parameter measuring the combinatorial complexity of families of sets. It turns out that these bounds grow linearly with the task complexity, measured via the VC-dimension of the class of objects one deals with. We show that this VC-dimension is at most logarithmic in the algebraic complexity of the objects and in the cardinality of the model library.Our approach borrows from computational learning theory. Both learning and recognition use evidence to infer hypotheses but as far as we know, their similarity was not exploited previously. We draw close relations between recognition tasks and a certain learnability framework and then apply basic techniques of learnability theory to derive our sample size upper bounds. We believe that other relations between learning procedures and visual tasks exist and hope that this work will trigger further fruitful study along these lines.     

Glucosinolate Desulfation by the Phloem-Feeding Insect <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Glucosinolates are plant secondary defense metabolites confined nearly exclusively to the order Brassicales. Upon tissue rupture, glucosinolates are hydrolyzed to various bioactive breakdown products by the endogenous plant enzyme myrosinase. As the feeding of chewing insect herbivores is associated with plant tissue damage, these insects have developed several independent strategies for coping with the glucosinolate-myrosinase defense system. On the other hand, our knowledge of how phloem-feeding insects interact with the glucosinolate-myrosinase system is much more limited. In fact, phloem feeders might avoid contact with myrosinase altogether so their susceptibility to intoxication by glucosinolate hydrolysis products is unclear. Previous studies utilizing Arabidopsis thaliana plants accumulating high levels of aliphatic- or indolic-glucosinolates indicated that both glucosinolate groups have moderate negative effects on the reproductive performance of Bemisia tabaci, a generalist phloem-feeding insect. To get a deeper understanding of the interaction between B. tabaci and glucosinolate-defended plants, adults were allowed to feed on artificial diet containing intact glucosinolates or on Brussels sprout and A. thaliana plants, and their honeydew was analyzed for the presence of possible metabolites. We found that B. tabaci is capable of cleaving off the sulfate group of intact glucosinolates, producing desulfoglucosinolates that cannot be activated by myrosinases, a mechanism described to date only in several chewing insect herbivores. The presence of desulfated glucosinolates in the honeydew of a generalist phloem-feeder may indicate the necessity to detoxify glucosinolates, likely due to some level of cellular damage during feeding, which results in glucosinolate activation, or as a mechanism to circumvent the non-enzymatic breakdown of indolic glucosinolates.     

Colour change with longitudinal compression supports hypothesis of multilayer interference as cause for meat iridescence

The mechanism of iridescence in meat and meat products is still not fully understood but a widely accepted hypothesis is that it originates from a multilayer interference from sarcomere discs. In multilayer interference, the reflected wavelength is affected by the refraction angles, the thicknesses and refractive indices of the intermittent layers. A variation of these factors should therefore cause a disappearance or shift of iridescent colours. To test this hypothesis, we progressively compressed iridescent rolled fillets of ham longitudinal to the long axes of the muscle fibres and measured the interference colours by reflection spectrophotometry. We observed an interference colour shift from longer to shorter wavelengths and reflection intensity decreased with increasing compression pressure. Our data indicate that the compression decreased the layer thickness, so that constructive interference occurred at shorter wavelengths. The results thus provide support for multilayer interference being a primary cause and mechanism for meat iridescence.     

Measuring academic influence using heterogeneous author-citation networks

Scientometrics - Academic influence has been traditionally measured by citation counts and metrics derived from it, such as H-index and G-index. PageRank based algorithms have been used to give...     

Evaluation of publication delays in the orthopedic surgery manuscript review process from 2010 to 2015

Scientometrics - A continued growth in the volume of scientific literature may strain the practice of peer review possibly leading to delays in publication. While this appears true anecdotally,...     

Finding the dimension of slow dynamics in a rhythmic system

Dynamical systems with asymptotically stable periodic orbits are generic models for rhythmic processes in dissipative physical systems. This paper presents a method for reconstructing the dynamics near a periodic orbit from multivariate time-series data. It is used to test theories about the control of legged locomotion, a context in which time series are short when compared with previous work in nonlinear time-series analysis. The method presented here identifies appropriate dimensions of reduced order models for the deterministic portion of the dynamics. The paper also addresses challenges inherent in identifying dynamical models with data from different individuals.     

Fast-Match: Fast Affine Template Matching

Fast-Match is a fast algorithm for approximate template matching under 2D affine transformations that minimizes the Sum-of-Absolute-Differences (SAD) error measure. There is a huge number of transformations to consider but we prove that they can be sampled using a density that depends on the smoothness of the image. For each potential transformation, we approximate the SAD error using a sublinear algorithm that randomly examines only a small number of pixels. We further accelerate the algorithm using a branch-and-bound-like scheme. As images are known to be piecewise smooth, the result is a practical affine template matching algorithm with approximation guarantees, that takes a few seconds to run on a standard machine. We perform several experiments on three different datasets, and report very good results.     

The interdisciplinary engineering knowledge genome

Parallel to the concept of the human genome and its impact on biology and other disciplines, we revealed a similar concept in engineering sciences, termed the ??Interdisciplinary Engineering Knowledge Genome??, which is an organized collection of system and method ??genes?? that encode instructions for generating new systems and methods in diverse engineering disciplines. Resting on the firm mathematical foundation of combinatorial representations, the Interdisciplinary Engineering Knowledge Genome unifies many engineering disciplines, providing a basis for transforming knowledge between them, supporting new educational practices, promoting inventions, aiding design, and bootstrapping new discoveries in engineering and science. Given the formal underlying combinatorial representations, these merits could be automated. This paper elucidates this new concept and demonstrates its value and power in engineering design.     

Phase Constitution and Dynamic Properties of Spark Plasma‐Sintered Alumina–Titanium Composites

Al₂O₃/Ti composites of various metal to ceramic ratios were fabricated by the spark plasma sintering (SPS) technique. The effects of titanium concentration in the initial mixture on phase composition, and on the static and dynamic (planar impact testing) mechanical properties of the SPS‐processed composites were investigated. It was observed that the significant alumina dissolution in titanium takes place during SPS treatment. The composites fabricated from starting alumina/titanium powder mixtures with a mass fraction of titanium less than 0.8 consisted of two phases, alumina and a solid solution of oxygen and aluminum in titanium. For starting mixtures with higher titanium content, the presence of a Ti₃Al intermetallic phase with a relatively low fraction of dissolved oxygen was detected. Changes in phase composition could explain the effect of titanium content in the starting mixture on physical and mechanical properties of the composites. Mechanisms governing the dynamic response of the composites under loading of different intensities are discussed.