Dynamic photorheological analysis of photopolymerizable urethane dimethacrylate resins with varying diluent content and light fluence

The in situ measurement of dynamic changes in viscosity induced by illumination has been performed on a range of photosensitive urethane dimethacrylates (UDMA) evaluating the response at three different illuminations intensities (1, 2, and 5 W cm^?2) and at three different diluent concentrations (15, 30, and 50%), using 1,6‐hexanediol dimethacrylate (HDDMA). The initial viscosity value ranged between 1 and 10 Pa s for the mixtures with final viscosities approaching 1 × 10⁷ Pa s after illumination. The initial rise in viscosity was analyzed using an exponential model with an exponent ranging from 1.0 to 2.5 with time under exposure. Higher conversion rates were observed with both higher intensity and lower HDDMA content. The analytical approach taken here could aid in developing more sophisticated models that consider simultaneous flow and cure advancement in other thermosets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

In vivo local determination of tissue optical properties: applications to human brain

Local and superficial near-infrared (NIR) optical-property characterization of turbid biological tissues can be achieved by measurement of spatially resolved diffuse reflectance at small source-detector separations (<1.4 mm). However, in these conditions the inverse problem, i.e., calculation of localized absorption and the reduced scattering coefficients, is necessarily sensitive to the scattering phase function. This effect can be minimized if a new parameter of the phase function gamma, which depends on the first and the second moments of the phase function, is known. If gamma is unknown, an estimation of this parameter can be obtained by the measurement, but the uncertainty of the absorption coefficient is increased. A spatially resolved reflectance probe employing multiple detector fibers (0.3-1.4 mm from the source) is described. Monte Carlo simulations are used to determine gamma, the reduced scattering and absorption coefficients from reflectance data. Probe performance is assessed by measurements on phantoms, the optical properties of which were measured by other techniques [frequency domain photon migration (FDPM) and spatially resolved transmittance]. Our results show that changes in the absorption coefficient, the reduced scattering coefficient, and gamma can be measured to within +/-0.005 mm(-1), +/-0.05 mm(-1), and +/-0.2, respectively. In vivo measurements performed intraoperatively on a human skull and brain are reported for four NIR wavelengths (674, 811, 849, 956 nm) when the spatially resolved probe and FDPM are used. The spatially resolved probe shows optimum measurement sensitivity in the measurement volume immediately beneath the probe (typically 1 mm(3) in tissues), whereas FDPM typically samples larger regions of tissues. Optical-property values for human skull, white matter, scar tissue, optic nerve, and tumors are reported that show distinct absorption and scattering differences between structures and a dependence on the phase-function parameter gamma.     

Accuracy of continuous ice-core trace-element analysis by inductively coupled plasma sector field mass spectrometry

Trace elements trapped in glaciers are important indicators for the characterization of past biogeochemical cycles, the identification of numerous sources and their varying strength, and thus indirectly provide insight into past climate variations. However, this necessitates highly resolved and continuous records of trace elements in ice. To obtain records corresponding to these requirements, a continuous ice-core melting (CIM) device was coupled to an inductively coupled plasma sector field mass spectrometer (ICP-SFMS). Accuracy of this newly developed method was tested by replicate analysis of longitudinally cut ice-core sections (reproducibility) and by comparing results of the continuous method with the conventional decontamination and analysis procedure. The new, fast method is suited to accurately determine concentrations of a number of elements, such as Li, Na, Mg, Ca, Mn, Co, Br, Sr, Mo, and Tl. However, for 18 elements (including Al and lanthanides) observed concentrations were underestimated when analyzed using the continuous method. Possible explanations of these low concentrations are (i) incomplete dissolution of mineral dust particles contained in the ice resulting from a delayed acidification step and/or (ii) adsorption of dissolved trace elements or mineral dust particles on the surface of the ice melting device.     

False memory in aging: Effects of emotional valence on word recognition accuracy.

Memory is susceptible to distortions. Valence and increasing age are variables known to affect memory accuracy and may increase false alarm production. Interaction between these variables and their impact on false memory was investigated in 36 young (18-28 years) and 36 older (61-83 years) healthy adults. At study, participants viewed lists of neutral words orthographically related to negative, neutral, or positive critical lures (not presented). Memory for these words was subsequently tested with a remember-know procedure. At test, items included the words seen at study and their associated critical lures, as well as sets of orthographically related neutral words not seen at study and their associated unstudied lures. Positive valence was shown to have two opposite effects on older adults' discrimination of the lures: It improved correct rejection of unstudied lures but increased false memory for critical lures (i.e., lures associated with words studied previously). Thus, increased salience triggered by positive valence may disrupt memory accuracy in older adults when discriminating among similar events. These findings likely reflect a source memory deficit due to decreased efficiency in cognitive control processes with aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Locally switched and limited source-body bias and other leakage reduction techniques for a low-power embedded SRAM

A low-power embedded SRAM for a large range of applications has been implemented in a standard digital 0.18-/spl mu/m process. The leakage current in the cells is reduced by using a source-body bias not exceeding the value that guaranties safe data retention, and less leaking nonminimum length transistors. Locally short-circuiting this bias, speed and noise margin loss in active mode is avoided, especially for low supply voltages. The bias is generated internally at the carefully designed equilibrium between cell, switch, and diode limiter leakages averaged over the array. The leakage of the full SRAM, including an optimized periphery, is reduced more than 20 times. Used in an industrial RF transceiver, the measurements confirm its performances.     

Supplementary condition for STG-designed speed-independent circuits

Speed-independent CMOS circuits designed using a state transition graph (STG) method are speed-independent only if the delays of the input inverters are considered as zero-delays     

Embryonics: a new methodology for designing field-programmable gatearrays with self-repair and self-replicating properties

The growth and the operation of all living beings are directed through the interpretation, in each of their cells, of a chemical program, the DNA string or genome. This process is the source of inspiration for the Embryonics (embryonic electronics) project, whose final objective is the conception of very large scale integrated circuits endowed with properties usually associated with the living world: self-repair (cicatrization) and self-replication. We begin by showing that any logic system can be represented by an ordered binary decision diagram (OBDD), and then embedded into a fine-grained field-programmable gate array (FPGA) whose basic cell is a multiplexer with programmable connections. The cellular array thus obtained is perfectly homogeneous: the function of each cell is defined by a configuration (or gene) and all the genes in the array, each associated with a pair of coordinates, make up the blueprint (or genome) of the artificial organism. In the second part of the project, we add to the basic cell a memory and an interpreter to, respectively, store and decode the complete genome. The interpreter extracts from the genome the gene of a particular cell as a function of its position in the array (its coordinates) and thus determines the exact configuration of the relative multiplexer. The considerable redundancy introduced by the presence of a genome in each cell has significant advantages: self-replication (the automatic production of one or more copies of the original organism) and self-repair (the automatic repair of one or more faulty cells) become relatively simple operations. The multiplexer-based FPGA cell and the interpreter are finally embedded into an electronic module; an array of such modules make it possible to demonstrate self-repair and self-replication     

Mortality and platelet depletion occur independently of fibrinogen consumption in murine models of tumour necrosis factor-mediated systemic inflammatory responses

The link between left ventricular dysfunction and arrhythmogenesis is commonly known. However, so far, only the systolic left ventricular dysfunction has been evaluated. Because of the controversial results of those studies, we decided to assess if is there a link between late potentials (LP) and left ventricular diastolic dysfunction. Our material consisted of 56 patients: 11 women and 45 men, mean age was 61.12 +/- 10.07 years. Signal averaged ECG and ECHO were performed in each patient, 2-3 months after myocardial infarction. For high pass filter of 40 Hz, LP were defined as 2 or 3 abnormal SAECG variables (the averaged QRS > 114 ms, the low amplitude signal duration LAS > 38 ms and root mean square voltage of the terminal 40 ms RMS40 < 20 microV). During ECHO study, we assessed E and A waves E/A ratio, left ventricular end-diastolic volume (LVEDV), ejection fraction (EF), acceleration (AT) and deceleration times (DT). The patients were divided into 2 groups: group I-30 patients LP positive and group II-26 patients LP negative. There were no significant differences between the groups in terms of age, EF, and heart rate. We presented significant differences between group I and II in terms of E wave velocity (0.75 +/- 0.19 vs 0.64 +/- 0.19 p < 0.03) E/A ratio (2.13 +/- 1.56 vs 1.0 +/- 0.5 p < 0.05) respectively. We did not confirm significant differences as regards A wave velocity, AT, isovolumetric time (IVRT) and LVEDV between both tested groups. In group I we revealed a significant correlation between E wave (r = 0.45), E/A ratio (r = 0.62), AT (r = -0.42) E/A ratio (r = 0.56), DT (r = 0.55) and QRS, as well as DT and LPD (r = 0.40) and between IVRT and RMS40 (r = -0.43). The results of our study suggest that in patients after myocardial infarction: 1/incidence of LP depends on the degree of left ventricular filling pattern like in impaired relaxion, quite well correlated with filtered QRS time 3/in LP positive patients there was predominance of restrictive left ventricular filling pattern, quite well correlation with RMS40 amplitude.