Detailed modeling of the video signal and optimal readout of charge-coupled devices

This article provides a practical design methodology to calculate an optimal filter for noise reduction in the readout of charge-coupled devices (CCDs) taking into account the charge transfer and feedthroughs due to capacitive coupling in the CCD. A detailed analysis of the dynamics of the video signal and charge transfer is presented, including the circuital modeling of the output stage of the CCD and the dynamics of the electronics in the video chain before the analog-to-digital (AD) converter. This model is used to compute an optimal filter that minimizes the variance of the pixel noise and uses the samples of the charge transfer, before the charge is fully settled. This is necessary to enhance the performance of previous results that also use optimal filters but do not use the transition samples, while also reducing the pixel readout time, resulting in faster readouts. As a proof of concept for the optimal filter, we present novel experimental results using a Skipper CCD, which has a floating sense node that allows to measure the charge packet an arbitrary number of times. However, this technique can be applied to any CCD that has a readout system that digitally samples the video signal.     

Seasonal variability of the reduction in estrogenic activity at a municipal WWTP

In vitro monitored estrogenicity of municipal wastewater influent/effluent samples (collected from September to December from a Northern Canadian biological nutrient removal (BNR) treatment plant serving an urban population of 750,000) were combined with operational, wastewater quality, and climate data to determine which of these latter variables may be related to the levels and reduction in the former parameter. Significant variability was present in operational and wastewater quality parameters throughout the sampling period including a 7 degrees C difference in wastewater temperature Most of the wastewater samples collected during this period show a considerable amount of recombinant yeast assay (RYA) activity with the greatest activity (estradiol (E2)-equivalents of 106-175ng/L) seen in the final effluents collected from mid-September to mid-October. Percent reduction in the levels of RYA measured E2-equivalents varied from -234% to 75%. No correlations were seen in RYA activity reduction with percent reduction in 5-day biochemical oxygen demand (BOD(5)), flow (i.e. inversely related to hydraulic retention time), solids retention time or even rainfall, and the reduction trends for RYA measured activity were explained best by ambient and effluent temperatures in an inverse fashion (% reduction in E2-equivalents=-10.8.(effluent temperature in degrees C)+191, p=0.005). Complementary instrumental analysis of select sample composites revealed that the free/conjugated estrogen ratio was indeed greater in the wastewater sampled during warmer temperatures.     

Diagrid structural systems for tall buildings: characteristics and methodology for preliminary design

Diagrid structural systems are emerging as structurally efficient as well as architecturally significant assemblies for tall buildings. This paper presents a simple methodology for determining preliminary member sizes. The methodology is applied to a set of building heights ranging from 20 to 60 stories, and parameters for the optimal values of the grid geometry are generated for representative design loadings. These values are shown to be useful for architects and engineers as guidelines for preliminary design. Associated architectural and constructability issues of diagrid structures are also discussed here. Copyright © 2007 John Wiley & Sons, Ltd.     

Criteria to optimise a dynamic flat detector system used for interventional radiology

An analysis of the relationship between image quality and incident air kerma has been carried out for a dynamic flat detector X-ray system used for interventional radiology. A phantom of polymethyl methacrylate (PMMA) to simulate patients and two different image test objects, Leeds TOR 18FG and NEMA XR 21, were used to evaluate the quality of the obtained images. Measurements were made simulating clinical configuration with different PMMA thicknesses (16, 20, 24 and 28 cm), available fields of view of 22, 31, 42 and 48 cm (diagonal dimension), in the three default fluoroscopy modes and in one of the most used digital subtraction angiography image acquisition modes. The obtained results are being used to help in the optimisation of clinical procedures.     

Structural and spatially resolved studies on the hardening of a commercial resin-modified glass-ionomer cement

A commercial photopolymerizable resin-modified glass-ionomer (Fuji II LC) was studied using a variety of nuclear magnetic resonance (NMR) techniques. ¹H and ¹⁹F stray-field imaging (STRAFI) enabled to follow the acid–base reaction kinetics in self-cured (SC) samples. Gelation and maturation processes with 25 min and 40 h average time constants, respectively, were distinguished. In self- & photo-cured (SPC) samples, two processes were also observed, which occurred with 2 s and 47 s average time constants. ¹H, ²⁷Al and ²⁹Si magic angle spinning (MAS) NMR, ¹³C cross-polarization (CP)/MAS NMR and ²⁷Al multiple quanta (MQ)MAS NMR spectroscopy were used to obtain structural information on the glass and cements that were either SC or SPC. The presence of methacrylate groups was identified in the solid component. Unreacted hydroxyl ethylmethacrylate (HEMA) was detected in self-cured cement. ²⁷Al data showed that approximately 28% and 20% of Al is leached out from glass particles in SC and SPC samples, respectively. The upfield shift detected in ²⁹Si MAS NMR spectra of the cements is consistent with a decrease in the number of Al species in the second coordination sphere of the silicon structures. Scanning electron microscopy (SEM) showed existence of 3D shrinkage of the cement matrix in photo-cured cements.     

Comparative study between two different sources of n-3 poliunsaturated fatty acids and it effect on thymus and lipid profile in rats

In the present paper we analyzed the effect caused by different recovery diets enriched with n-3 polyunsaturated fatty acids (PUFA n-3) on thymus and serum lipid pattern. Severe depleted weanling Wistar rats (D) were divided in three groups that received during 10 days a 20% casein diet supplemented with EPA+DHA (group Cas), a 20% protein milk diet prepared using a commercial reduced-fat product enriched with linolenic and linoleic acids (group L) and a 20% casein diet as control group C. Cas and L gave each other 24 mg/day of PUFA n-3 being the ratio n-6/n-3 8.1/1 and 7.6/1, respectively. Thymus was removed and weighted and cell number were determined; blood was recollected and Total cholesterol, triacylglycerol, HDL and LDL-cholesterol fractions and myristic, palmitic, stearic, oleic, linoleic, linolenic, araquidonic, EPA and DHA fatty acid concentrations were measured in serum. Statistical analysis was performed using Anova test. Cell number were higher (p<0.01) in Cas (44.48+/-8.20) and in L (56.45+/-14.72) when compared to group D (1.80+/-0.70) and group C (23.70+/-4.04). L presented lower values of cholesterol, HDL and LDL-cholesterol (p<0.01) and higher values of triacylglycerol (p<0.05) when compared to Cas, being EPA (p<0.05) and DHA (p<0.01) higher in Cas. Being PUFA n-3 contribution the same in Cas and L, both diets were able to reverse the thymic athropy presenting a different hipolipemic behavior due to the different sources of PUFA n-3 used in the diets.     

Topologically controlled growth of magnetic-metal-functionalized semiconductor oxide nanorods

Colloidal semiconductor-magnetic hybrid nanocrystals with topologically controlled composition are fabricated by heterogeneous nucleation of spherical epsilon-Co domains onto anatase TiO2 nanorods. The latter can be selectively decorated at either their tips or at multiple locations along their longitudinal sidewalls, forming lattice-matched heterointerfaces regardless of the metal deposition sites. The possibility of switching between either heterostructure growth modes arises from the facet-dependent chemical reactivity of the oxide seeds, which is governed mainly by selective adhesion of the surfactants rather than by small differences in misfit-induced interfacial strain at the relevant junction points.     

An organic donor/acceptor lateral superlattice at the nanoscale

A precise control of the nanometer-scale morphology in systems containing mixtures of donor/acceptor molecules is a key factor to improve the efficiency of organic photovoltaic devices. Here we report on a scanning tunneling microscopy study of the first stages of growth of 2-[9-(1,3-dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole, as electron donor, and phenyl-C61-butyric acid methyl ester, as electron acceptor, on a Au(111) substrate under ultrahigh vacuum conditions. Due to differences in bonding strength with the substrate and different interactions with the Au(111) herringbone surface reconstruction, mixed thin films spontaneously segregate into a lateral superlattice of interdigitated nanoscale stripes with a characteristic width of about 10-20 nm, a morphology that has been predicted to optimize the efficiency of organic solar cells.     

Robust control with uncertainty estimation for feedback linearizable systems: application to control of distillation columns

The goal of this paper is to describe a linearizing feedback adaptive control structure which leads to a high quality regulation of the output error in the presence of uncertainties and external disturbances. The controller consists of three elements: a nominal input–output linearizing compensator, a state observer and an uncertainty estimator, which provides the adaptive part of the control structure. In this way, the feedback controller, based on the disturbance observer, compensates for external disturbances and plant uncertainties. The effectiveness of the controller is demonstrated on a distillation column via numerical simulations. ©