Children's solution processes in elementary arithmetic problems: Analysis and improvement.

Using error analysis and individual interviews, the problem-solving actions of 176 1st and 2nd graders were analyzed in Exp I. Shortcomings of Ss' knowledge and solution strategies were discovered. It seemed that these shortcomings could be overcome by instruction; therefore, a teaching experiment (Exp II; 52 2nd graders) was undertaken wherein instruction was given for 2 wks to an experimental class, while in a control group, the usual arithmetic program was taught. Experimental instruction related mainly to 3 topics: the equality sign, the part–whole relation, and verification of the outcome of an arithmetic operation. Results show that the experimental teaching program led to a decrease in Ss' thinking errors on elementary addition and subtraction problems. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Engineering camel single-domain antibodies and immobilization chemistry for human prostate-specific antigen sensing

The specificity and affinity characteristics of antibodies make them excellent probes in biosensor applications. Unfortunately, their large size, unstable behavior, and random immobilization properties create numerous problems. The single-domain antigen-binding fragment derived from heavy-chain antibodies of camelids (termed VHH) offers special advantages in terms of size, stability, and ease of generating different antibody constructs. In this study, we show the potential of those VHHs in sensing human prostate-specific antigen (hPSA) by SPR technology. Different VHH constructs were immobilized onto commercial and custom-built sensor surfaces by metal chelation, biotin-streptavidin interaction, or covalent coupling. The detection of subnanogram per milliliter hPSA concentrations could be attained on a covalently coupled three-dimensional dextran surface. Moreover, the ratio of different hPSA isoform concentrations could be assessed via a sandwich assay and resulted in the detection of clinically significant antigen concentrations within 15 min. In addition, for the first time, the intrinsic protein stability is presented as an important probe design factor, since our results reveal that higher intrinsic stability offers higher resistance to harsh regeneration conditions. In conclusion, we present VHHs as a novel class of biosensor probes rivaling conventional antibodies and their derived antibody fragments.     

Crop mapping in countries with small-scale farming: a case study for West Shewa,Ethiopia

Remote sensing is nowadays considered to be a valuable input for the annual collection of crop statistics. Derived crop maps can serve as a baseline for yield or area estimation or to target next year's census. For subsistence farming, where small parcels are mixed with other land use, crop mapping remains very challenging. This article evaluates the potential of discriminating crops in West Shewa, an area with small-scale farming in central Ethiopia. A hard classification of high-resolution (30 m) images, yielding good results for commercial farming, could not deal with mixed pixels due to the small parcels. Very high resolution (4 m) images have a more appropriate pixel size, although they only cover subsets of the region. The very high resolution classification was used to calibrate a neural network for sub-pixel classification of the high resolution images. The accuracies were not satisfactory, but did at least demonstrate the potential of this approach.     

Logarithmic barriers for sparse matrix cones

Algorithms are presented for evaluating gradients and Hessians of logarithmic barrier functions for two types of convex cones: the cone of positive semidefinite matrices with a given sparsity pattern and its dual cone, the cone of sparse matrices with the same pattern that have a positive semidefinite completion. Efficient large-scale algorithms for evaluating these barriers and their derivatives are important in interior-point methods for nonsymmetric conic formulations of sparse semidefinite programs. The algorithms are based on the multifrontal method for sparse Cholesky factorization.     

Evaluation of an injectable,photopolymerizable three-dimensional scaffold based on <Emphasis Type="SmallCaps">d</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactide and ɛ-caprolactone in a tibial goat model

An in situ crosslinkable, biodegradable, methacrylate-encapped porous bone scaffold composed of D: ,L: -lactide, varepsilon-caprolactone, 1,6-hexanediol and poly(ortho-esters), in which crosslinkage is achieved by photoinitiators, was developed for bone tissue regeneration. Three different polymer mixtures (pure polymer and 30% bioactive glass or alpha-tricalcium phosphate added) were tested in a uni-cortical tibial defect model in eight goats. The polymers were randomly applicated in one of four (6.0 mm diameter) defects leaving a fourth defect unfilled. Biocompatibility and bone healing properties were evaluated by serial radiographies, histology and histomorphometry. The pure polymer clearly showed excellent biocompatibility and moderate osteoconductive properties. The addition of alpha-TCP increased the latter characteristics. This product offers potentials as a carrier for bone healing promoter substances.     

Gate-induced insulating state in bilayer graphene devices

The potential of graphene-based materials consisting of one or a few layers of graphite for integrated electronics originates from the large room-temperature carrier mobility in these systems (approximately 10,000 cm2 V(-1) s(-1)). However, the realization of electronic devices such as field-effect transistors will require controlling and even switching off the electrical conductivity by means of gate electrodes, which is made difficult by the absence of a bandgap in the intrinsic material. Here, we demonstrate the controlled induction of an insulating state--with large suppression of the conductivity--in bilayer graphene, by using a double-gate device configuration that enables an electric field to be applied perpendicular to the plane. The dependence of the resistance on temperature and electric field, and the absence of any effect in a single-layer device, strongly suggest that the gate-induced insulating state originates from the recently predicted opening of a bandgap between valence and conduction bands.     

Iterative methods for the canonical decomposition of multi-way arrays: Application to blind underdetermined mixture identification

Two main drawbacks can be stated in the alternating least square (ALS) algorithm used to fit the canonical decomposition (CAND) of multi-way arrays. First its slow convergence caused by the presence of collinearity between factors in the multi-way array it decomposes. Second its blindness to Hermitian symmetries of the considered arrays. Enhanced line search (ELS) scheme was found to be a good way to cope with the slow convergence of the ALS algorithm together with a partial use of the Hermitian symmetry. However, to our knowledge, required equations to perform the latter scheme are only given in the case of third and fifth order arrays. Therefore, our first contribution consists in generalizing the ELS procedure to the case of complex arrays of any order greater than three. Our second contribution is another improvement of the ALS scheme, able to profit from Hermitianity and positive semi-definiteness of the considered arrays. It consists in resorting to the CAND first of a third order array having one unitary loading matrix and second of several rank-1 arrays. An iterative algorithm is then proposed alternating between Procrustes problem solving and the computation of rank-one matrix approximations in order to achieve the CAND of the third order array.     

Optimisation of the amino–carboxy coupling of oligonucleotides to beads used in liquid arrays

Interest is increasing in the multiplexed bead‐based method to detect nucleic acid quantities, using oligonucleotides (oligos) coupled to micrometre‐sized polystyrene beads. This paper describes an evaluation of this coupling step by examining different buffers at various pHs and the effect of changing the oligo concentration. The use of 2‐(N‐morpholino)ethanesulfonic acid (MES)–borate buffer (pH 4.5) during the effective coupling step yielded the best coupling efficiency. The addition of 15 pmol of oligo to 10⁵ beads resulted in the highest number of coupled oligos per bead (～336 ± 28 oligos µm^?2). In addition, an alternative method to calibrate the fluorescence intensity by using FloSense Rainbow Calibration Particles was evaluated. In this way, it was possible to compare data independently of the type of flow cytometer used or the photomultiplier tube settings. Copyright © 2005 Society of Chemical Industry     

Metallothioneins (MTs) and delta-aminolevulinic acid dehydratase (ALAd) as biomarkers of metal pollution in great tits (Parus major) along a pollution gradient

Biomonitoring allows an integrated evaluation of different aspects of exposure, accumulation and effects to environmental pollution, simultaneously accounting for the natural variety between individuals in an ecosystem. In this study, the effects of increased metal accumulation were evaluated at the biochemical level in terms of two biomarker responses in the great tit (Parus major), a small insectivorous songbird, along an established metal pollution gradient. Metal concentrations in internal tissues (liver and kidney) and blood indicated that lead and cadmium were the most important metals in the pollution gradient under study. At the biochemical level, induction of metal binding protein metallothionein (MT) in liver and kidney reflected cadmium concentrations in these tissues (R(2)=0.42 and R(2)=0.94 respectively, n=19), although in kidney, MT induction was not sufficient to complex all cadmium present. Secondly, the activity of the enzyme delta-aminolevulinic acid dehydratase (ALAd) in blood decreased exponentially in response to increased lead accumulation (R(2)=0.70, n=18) and represents therefore a specific effect marker for lead exposure. In the highest polluted area, an ALAd inhibition of 85% was reported. Since a higher metal exposure resulted in an increased metal accumulation and subsequent biomarker responses in a dose-dependent way, this study indicates the applicability of ALAd and MT levels in great tits for biomonitoring responses to heavy metal pollution.