471 research outputs found
The Effectiveness Of Errorless Learning For Teaching Concepts And Comments To Children With Autism
Inferring land use from mobile phone activity
Understanding the spatiotemporal distribution of people within a city is
crucial to many planning applications. Obtaining data to create required
knowledge, currently involves costly survey methods. At the same time
ubiquitous mobile sensors from personal GPS devices to mobile phones are
collecting massive amounts of data on urban systems. The locations,
communications, and activities of millions of people are recorded and stored by
new information technologies. This work utilizes novel dynamic data, generated
by mobile phone users, to measure spatiotemporal changes in population. In the
process, we identify the relationship between land use and dynamic population
over the course of a typical week. A machine learning classification algorithm
is used to identify clusters of locations with similar zoned uses and mobile
phone activity patterns. It is shown that the mobile phone data is capable of
delivering useful information on actual land use that supplements zoning
regulations.Comment: To be presented at ACM UrbComp201
PREPARATION OF WATER-RESISTANT SUBSTANCES FOR ECOTOXICOLOGICAL TESTING
Sažetak
Metode za određivanje toksičnosti kemijskih tvari na vodene organizme, propisane organizacijama kao što su OECD, EU ili ISO odnose se na kemijske supstancije s točnim generičkim opisom, tj. propisuju ispitivanje vodotopljivih, kemijski stabilnih i nehlapljivih tvari. Međutim, ako se te metode primjenjuju za tvari koje ne podliježu navedenim svojstvima (tvari koje su samo djelomično ili slabo topljive u vodi, nestabilne, hlapljive ili kompleksnog sastava), mogu se očekivati teškoće u procjeni toksičnosti.
Prema sadašnjim saznanjima najbolja raspoloživa metoda za ispitivanje toksičnosti u vodi slabo topljivih kemijskih tvari je WAF metodologija (Water Accommodated Fraction). WAF predstavlja vodeni medij koji sadrži frakciju supstancije zaostale u vodenom mediju nakon miješanja i odvajanja faza.
Predmet naših ispitivanja su maziva teško topljiva u vodi od kojih neka imaju svojstvo intenzivnog prijanjanja uz podlogu i maziva ulja koja s vodom stvaraju emulziju. Prema svom sastavu to su maziva na osnovi sintetičkih estera i biljnih ulja različito ugušćeni sa sapunima ili organofilnim bentonitima. Ispitivana maziva miješana su s deioniziranom vodom i mineralnim medijem pomoću elektromagnetske mješalice i u vremenskom razdoblju od 24-96 sati miješanja praćeni su određeni parametri (koncentracija lipofilnih tvari, totalni organski ugljik i prisutnost organskih kiselina eventualno nastalih hidrolizom estera).Abstract
Test methods for assessment toxicity chemical substances to aquatic organisms have been described by various organizations including the OECD, EU or ISO. Those test methods are typically designed for substances with precise generic description and substances, which are readily water soluble, chemically stable and non-volatile. When test methods are applied to substances with different chemical properties (sparingly soluble, unstable or volatile substances or those of a complex composition) it is possible to expect some difficulties in toxicity evaluation.
According to present knowledge the best test method for toxicity examination of water-resistant substances is WAF methodology (Water Accommodated Fraction). WAF is an aqueous medium containing only that fraction of a substance which remains in the aqueous phase after mixing and phase separation.
The subjects for our examination were water-resistant greases (some of them have very strong adhesive characteristics) and lubricant oils which form emulsion with water. According to their chemical composition there are synthetic based esters and plant oils thickned with soaps and organophylic bentonits. The greases were mixed with deionised water and mineral media on magnetic stirrer and during the time period of 24-96 hours some parameters were defined (concentration of lipophylic substances, total organic carbon and organic acids eventually made by ester hydrolyzis)
Direct radiocarbon dating of fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) from Long Point, Coorong, South Australia
Accelerator Mass Spectrometry (AMS) radiocarbon dates (n=20) determined on fish otoliths from mulloway (Argyrosomus japonicus) and black bream (Acanthopagrus butcheri) are reported from five sites at Long Point, Coorong, South Australia. The dates range from 2938–2529 to 326–1 cal. BP, extending the known period of occupation of Long Point. Previous dating at the sites indicated intensive occupation of the area from 2455–2134 cal. BP. Results provide a detailed local chronology for the region, contributing to a more comprehensive understanding of Aboriginal use of Ngarrindjeri lands and waters. This study validates the use of fish otoliths for radiocarbon dating and reveals how dating different materials can result in different midden chronologies
Immunolocalization of dually phosphorylated MAPKs in dividing root meristem cells of Vicia faba, Pisum sativum, Lupinus luteus and Lycopersicon esculentum
Key message In plants, phosphorylated MAPKs display
constitutive nuclear localization; however, not all
studied plant species show co-localization of activated
MAPKs to mitotic microtubules.
Abstract The mitogen-activated protein kinase (MAPK)
signaling pathway is involved not only in the cellular
response to biotic and abiotic stress but also in the regulation
of cell cycle and plant development. The role of
MAPKs in the formation of a mitotic spindle has been
widely studied and the MAPK signaling pathway was
found to be indispensable for the unperturbed course of cell
division. Here we show cellular localization of activated
MAPKs (dually phosphorylated at their TXY motifs) in
both interphase and mitotic root meristem cells of Lupinus
luteus, Pisum sativum, Vicia faba (Fabaceae) and Lycopersicon esculentum (Solanaceae). Nuclear localization
of activated MAPKs has been found in all species. Colocalization
of these kinases to mitotic microtubules was
most evident in L. esculentum, while only about 50 % of
mitotic cells in the root meristems of P. sativum and V.
faba displayed activated MAPKs localized to microtubules
during mitosis. Unexpectedly, no evident immunofluorescence
signals at spindle microtubules and phragmoplast
were noted in L. luteus. Considering immunocytochemical
analyses and studies on the impact of FR180204 (an
inhibitor of animal ERK1/2) on mitotic cells, we hypothesize
that MAPKs may not play prominent role in the
regulation of microtubule dynamics in all plant species
Experimental Study of the Inductance of Pinned Vortices in Superconducting YBa2Cu3O7-d Films
Using a two-coil mutual inductance method, we have measured the complex
resistivity, rho_v(T,Be), of pinned vortices in c-axis pulsed laser deposited
YBa2Cu3O7-d films with magnetic field Be applied perpendicular to the film. At
low frequencies, (<100 kHz), rho_v is inductive and is inversely proportional
to the Labusch parameter, the average vortex pinning force constant, kappa_exp.
The observed weakening of kappa_exp with Be is consistent with a simple model
based on linear pinning defects. Adding classical thermal fluctuations to the
model in a simple way describes the observed linear T dependence of rho_v,
below ~15 K and provides reasonable values for the effective radius (.3 nm to
>.8 nm) of the defects and the depth of the pinning potential. The success of
this model implies that thermal supercurrent (phase) fluctuations have their
full classical amplitude down to 5 K for frequencies below the characteristic
depinning frequency. To date, no sufficient theory exists to explain the data
between ~15 K and the vortex glass melting temperature.Comment: 31 pages, 8 figures. Subm. to PR
Pair breaking by impurities in the two-dimensional t-J model
Pair breaking mechanisms by impurities are investigated in the
two-dimensional t-J model by exact diagonalization techniques. Analysis of
binding energies, pairing correlations, dynamical spin and pair
susceptibilities shows that non-magnetic impurities are more effective in
suppressing pairing than magnetic ones in agreement with experimental studies
of Zn- and Ni- substituted High-Tc superconductors.Comment: 4 pages, Revtex v3.0, 4 figures uuencoded, ask for hardcopies at
[email protected] A missleading statement in the introduction was correcte
Interplay of disorder and magnetic field in the superconducting vortex state
We calculate the density of states of an inhomogeneous superconductor in a
magnetic field where the positions of vortices are distributed completely at
random. We consider both the cases of s-wave and d-wave pairing. For both
pairing symmetries either the presence of disorder or increasing the density of
vortices enhances the low energy density of states. In the s-wave case the gap
is filled and the density of states is a power law at low energies. In the
d-wave case the density of states is finite at zero energy and it rises
linearly at very low energies in the Dirac isotropic case
(\alpha_D=t/\Delta_0=1, where t is the hopping integral and \Delta_0 is the
amplitude of the order parameter). For slightly higher energies the density of
states crosses over to a quadratic behavior. As the Dirac anisotropy increases
(as \Delta_0 decreases with respect to the hopping term) the linear region
decreases in width. Neglecting this small region the density of states
interpolates between quadratic and back to linear as \alpha_D increases. The
low energy states are strongly peaked near the vortex cores.Comment: 12 REVTeX pages, 15 figure
Combinatorial molecular optimization of cement hydrates
Despite its ubiquitous presence in the built environment, concrete’s molecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete’s environmental footprint have provided strong motivation to develop new concrete with greater specific stiffness or strength (for structures with less material). Herein, a combinatorial approach is described to optimize properties of cement hydrates. The method entails screening a computationally generated database of atomic structures of calcium-silicate-hydrate, the binding phase of concrete, against a set of three defect attributes: calcium-to-silicon ratio as compositional index and two correlation distances describing medium-range silicon-oxygen and calcium-oxygen environments. Although structural and mechanical properties correlate well with calcium-to-silicon ratio, the cross-correlation between all three defect attributes reveals an indentation modulus-to-hardness ratio extremum, analogous to identifying optimum network connectivity in glass rheology. We also comment on implications of the present findings for a novel route to optimize the nanoscale mechanical properties of cement hydrate.National Ready Mixed Concrete Association (Research sponsorship)Education Foundation (N.J.) (Research sponsorship)Portland Cement Association (Research sponsorship
Coherent Potential Approximation for `d - wave' Superconductivity in Disordered Systems
A Coherent Potential Approximation is developed for s-wave and d-wave
superconductivity in disordered systems. We show that the CPA formalism
reproduces the standard pair-breaking formula, the self-consistent Born
Approximation and the self-consistent T-matrix approximation in the appropriate
limits. We implement the theory and compute T_c for s-wave and d-wave pairing
using an attractive nearest neighbor Hubbard model featuring both binary alloy
disorder and a uniform distribution of scattering site potentials. We determine
the density of states and examine its consequences for low temperature heat
capacity. We find that our results are in qualitative agreement with
measurements on Zn doped YBCO superconductors.Comment: 35 pages, 23 figures, submitted to Phys Rev.
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