Optofluidics: a novel generation of reconfigurable and adaptive compact architectures

The integration of microfluidics and microphotonics brings the ability to tune and reconfigure ultra-compact optical devices. This flexibility is essentially provided by three characteristics of fluids that are scalable at the micron-scale: fluid mobility, large ranges of index modulation, and abrupt interfaces that can be easily reshaped. Several examples of optofluidic devices are presented here to illustrate the achievement of flexible devices on (semi) planar and compact platforms. First, we report an integrated geometry for a compact and tunable interferometer that exploits a sharp and mobile air/water interface. We then describe a class of optically controlled devices that rely on the actuation of optically trapped micron-sized objects within a fluid environment. The last architecture results from the infiltration of photonic crystal devices with fluids. This produces tunable and reconfigurable photonic devices, like optical switches. Higher degrees of functionality could be achieved with sophisticated optofluidic platforms that associate complex microfluidic delivery and mixing schemes with microphotonic devices. Moreover, optofluidics offers new opportunities for realizing highly responsive and compact sensors.     

Flexible decision control in an autonomous trading agent

Modern electronic commerce creates significant challenges for decision-makers. The trading agent competition for supply-chain management (TAC SCM) is an annual competition among fully-autonomous trading agents designed by teams around the world. Agents attempt to maximize profits in a supply-chain scenario that requires them to coordinate Procurement, Production, and Sales activities in competitive markets. An agent for TAC SCM is a complex piece of software that must operate in a competitive economic environment. We report on results of an informal survey of agent design approaches among the competitors in TAC SCM, and then we describe and evaluate the design of our MinneTAC trading agent. We focus on the use of evaluators – configurable, composable modules for data analysis, modeling, and prediction that are chained together at runtime to support agent decision-making. Through a set of examples, we show how this structure supports Sales and Procurement decisions, and how those decision process can be modified in useful ways by changing evaluator configurations.     

Toward a benchmarking framework for research into bio-inspired hardware-software artefacts

In this paper, we suggest that one of the more crucial tasks currently facing researchers into the field of autonomous mobile robotics is the provision of a common task, or set of tasks, as a means of evaluating different approaches to robot design and architecture, and the generation of a common set of experimental frameworks to facilitate these different approaches. This paper stars with a brief introduction to the field, and behavior-based control in particular. We then discuss the issue of animal versus robot behavior, and focus on simulated experimentation versus embodied robotics. Finally, we move to the feasibility of evaluating and benchmarking different architectures, with the aim of producing mobile robots of continuously higher utility, with specific reference to our current four-layered robot control architecture. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Molecular Biology to Radiation Oncology: A Model for Translational Research? Opportunities in basic and translational research. From a workshop sponsored by the National Cancer Institute, Radiation Research Program, January 26-28, 1997, Bethesda, Maryland

Many exciting discoveries are being made that are providing new insights into how molecules, cells and tissues respond to ionizing radiation. There remains a need, however, to translate these findings into more effective treatments for cancer patients, including those treated with radiation therapy. This complex task will require the collaboration of scientists studying molecular, cellular and tissue responses, and those performing clinical trials of emerging therapies. The Radiation Research Program of the National Cancer Institute sponsored a workshop entitled "Molecular Biology to Radiation Oncology: A Model for Translational Research?" to bring together basic scientists and clinicians to exchange ideas and fundamental concepts and to identify opportunities for future research and collaboration. Four broad topics were addressed: signal transduction and apoptosis, the cell cycle, repair of radiation damage, and the microenvironment. The development, selection and use of appropriate experimental models is crucial to finding and developing new therapies, and opportunities exist in this area as well. This paper and the accompanying paper by Coleman and Harris that provides the viewpoint of radiation oncologists (Radiat. Res. 150, 134-147, 1998) summarize the background concepts and opportunities for translational research identified by the workshop participants.     

Chronic electrical stimulation of the left ventrointermediate (Vim) thalamic nucleus for the treatment of pharmacotherapy-resistant Parkinson's disease: a differential impact on access to semantic and episodic memory?

Thalamotomy for medically refractory Parkinson's disease (PD) is considered to be efficacious and relatively safe. Because a minority of patients experience decrements in language and memory (often mild and transient) after thalamotomy, chronic thalamic deep brain stimulation (DBS) might be a safer treatment given its reversibility and the modifiability of stimulation parameters. Two preliminary studies support the relative cognitive safety of unilateral DBS of the ventral intermediate (Vim) thalamic nucleus, but it is unclear whether possibly subtle changes in language and memory represent effects of "microthalamotomy" or of stimulation per se. This report provides preliminary data concerning effects of left thalamic stimulation on information processing speed, semantic memory (verbal fluency and visual confrontation naming), and verbal episodic memory in a patient with PD. In addition to being evaluated before and 3 and 6 months after surgery, the patient was tested 18 months after surgery either on or off medications and with the stimulator turned either on or off (order counterbalanced across medication conditions). Test performance differences between the stimulation conditions were attenuated "off" as compared to "on" medication. Vim stimulation consistently, albeit subtly, improved semantic verbal fluency but interfered with immediate recall of word lists. Parallels to findings from acute, intraoperative thalamic stimulation studies are explored. The hypothesis is offered that left Vim stimulation might facilitate access to semantic memory, but interfere with episodic memory processes.     

Strategies for rare-event detection: an approach for automated fetal cell detection in maternal blood

This article explores the feasibility of the use of automated microscopy and image analysis to detect the presence of rare fetal nucleated red blood cells (NRBCs) circulating in maternal blood. The rationales for enrichment and for automated image analysis for "rare-event" detection are reviewed. We also describe the application of automated image analysis to 42 maternal blood samples, using a protocol consisting of one-step enrichment followed by immunocytochemical staining for fetal hemoglobin (HbF) and FISH for X- and Y-chromosomal sequences. Automated image analysis consisted of multimode microscopy and subsequent visual evaluation of image memories containing the selected objects. The FISH results were compared with the results of conventional karyotyping of the chorionic villi. By use of manual screening, 43% of the slides were found to be positive (>=1 NRBC), with a mean number of 11 NRBCs (range 1-40). By automated microscopy, 52% were positive, with on average 17 NRBCs (range 1-111). There was a good correlation between both manual and automated screening, but the NRBC yield from automated image analysis was found to be superior to that from manual screening (P=.0443), particularly when the NRBC count was >15. Seven (64%) of 11 XY fetuses were correctly diagnosed by FISH analysis of automatically detected cells, and all discrepancies were restricted to the lower cell-count range. We believe that automated microscopy and image analysis reduce the screening workload, are more sensitive than manual evaluation, and can be used to detect rare HbF-containing NRBCs in maternal blood.     

Relationship between efficacy of defibrillation shocks and frequency characteristics of shock waveforms

INTRODUCTION: Using the Fourier transform, it is possible to replace each time domain representation of a defibrillatory shock by a unique frequency domain representation in which the shock waveform is defined in terms of a complex number function of frequency and typically described as an amplitude in amperes per hertz (or, closely related, joules per hertz) and an associated frequency-dependent phase angle. METHODS AND RESULTS: The present article describes the conceptual basis of the Fourier transform, sketches a simplified mathematical framework for deriving frequency domain parameters, considers properties crucial to interpreting defibrillatory-type shocks when expressed in the frequency domain, and then presents a series of shock waveforms in the frequency domain. Although not definitive, knowledge of the energy distribution with frequency alone, usually presented in joules per hertz, is shown to yield considerable insight into the probable comparable efficacy of uniphasic/biphasic rectangular, untruncated/truncated uniphasic exponential, and various biphasic "single capacitor" waveforms. CONCLUSION: In general, efficacy in achieving ventricular defibrillation is improved by parameter changes that shift a larger percentage of the delivered energy into a mid-frequency range (very roughly, 40 to 160 Hz). With further study, the frequency domain approach may prove to be a useful tool in the a priori selection of optimal defibrillatory shock waveforms.     

Formation of porosity in sputtered amorphous hydrogenated carbon films

Results are reported of the porosity and the microstructure of amorphous hydrogenated carbon films produced by direct current (d.c.) sputtering. The as-deposited films were initially slightly mesoporous. Heating the material in a vacuum, however, produced a highly porous material. The amount of porosity and the pore size distribution were directly related to the quantity of material which was outgassed during heating. The dependence on the baking temperature of the degree of sp² hybridization in the films had the same form as the dependence of the porosity and of the quantity of outgassing. The plasmon-energy data for the films was related to the process of morphology and composition reconstruction during the heating. The outgassing quantity was strongly dependent on the oxygen content of the as-prepared material. The morphology changes in the material can be regarded as a carbon-activation process involving the incorporation of oxygen in the film during deposition, followed by the outgassing of carbon-oxygen compounds during heating in vacuum. Many of the properties of the hydrogenated amorphous carbon (a-CH) film were very similar to those exhibited by conventional activated carbons, and it is therefore concluded that the porous baked a-CH film is a form of activated carbon.     

Working Models of Attachment Shape Perceptions of Social Support: Evidence From Experimental and Observational Studies.

Two studies examined the association between attachment style and perceptions of social support. Study 1 (N = 95 couples) used an experimental paradigm to manipulate social support in the context of a stressful task. Insecure participants (anxious and avoidant) who received low-support messages appraised these messages more negatively, rated a prior behavioral interaction with their partner as having been less supportive, and performed significantly worse at their task compared with secure participants. Study 2 (N = 153 couples) used a similar paradigm except that partners were allowed to send genuine support messages. Insecure participants (especially fearful) perceived their partners' messages as less supportive, even after controlling for independent ratings of the messages and relationship-specific expectations. These studies provide evidence that individuals are predisposed to appraise their support experiences in ways that are consistent with their chronic working models of attachment, especially when the support message is ambiguous. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamics of surface diffeomorphisms relative to homoclinic and heteroclinic orbits

We show how to obtain information about the dynamics of a two-dimensional discrete-time system from its homoclinic and heteroclinic orbits. The results obtained are based on the theory of 'trellises', which comprise finite-length subsets of the stable and unstable manifolds of a collection of saddle periodic orbits. For any collection of homoclinic or heteroclinic orbits, we show how to associate a canonical 'trellis type' which describes the orbits. Given a trellis type, we show how to compute a 'graph representative' which gives a combinatorial invariant of the trellis type. The orbits of the graph give the dynamics forced by the homoclinic/heteroclinic orbits in the sense that every orbit of the graph representative is 'globally shadowed' by some orbit of the system, and periodic, homoclinic/heteroclinic orbits of the graph representative are shadowed by similar orbits.