188 research outputs found
Unexpected drop of dynamical heterogeneities in colloidal suspensions approaching the jamming transition
As the glass (in molecular fluids\cite{Donth}) or the jamming (in colloids
and grains\cite{LiuNature1998}) transitions are approached, the dynamics slow
down dramatically with no marked structural changes. Dynamical heterogeneity
(DH) plays a crucial role: structural relaxation occurs through correlated
rearrangements of particle ``blobs'' of size
\cite{WeeksScience2000,DauchotPRL2005,Glotzer,Ediger}. On approaching
these transitions, grows in glass-formers\cite{Glotzer,Ediger},
colloids\cite{WeeksScience2000,BerthierScience2005}, and driven granular
materials\cite{KeysNaturePhys2007} alike, strengthening the analogies between
the glass and the jamming transitions. However, little is known yet on the
behavior of DH very close to dynamical arrest. Here, we measure in colloids the
maximum of a ``dynamical susceptibility'', , whose growth is usually
associated to that of \cite{LacevicPRE}. initially increases with
volume fraction , as in\cite{KeysNaturePhys2007}, but strikingly drops
dramatically very close to jamming. We show that this unexpected behavior
results from the competition between the growth of and the reduced
particle displacements associated with rearrangements in very dense
suspensions, unveiling a richer-than-expected scenario.Comment: 1st version originally submitted to Nature Physics. See the Nature
Physics website fro the final, published versio
On the rigidity of a hard sphere glass near random close packing
We study theoretically and numerically the microscopic cause of the
mechanical stability of hard sphere glasses near their maximum packing. We show
that, after coarse-graining over time, the hard sphere interaction can be
described by an effective potential which is exactly logarithmic at the random
close packing . This allows to define normal modes, and to apply recent
results valid for elastic networks: mechanical stability is a non-local
property of the packing geometry, and is characterized by some length scale
which diverges at [1, 2]. We compute the scaling of the bulk and
shear moduli near , and speculate on the possible implications of these
results for the glass transition.Comment: 7 pages, 4 figures. Figure 4 had a wrong unit in abscissa, which was
correcte
Mars Regolith Simulant Ameliorated by Compost as In Situ Cultivation Substrate Improves Lettuce Growth and Nutritional Aspects
Heavy payloads in future shuttle journeys to Mars present limiting factors, making self-sustenance essential for future colonies. Therefore, in situ resources utilization (ISRU) is the path to successful and feasible space voyages. This research frames the concept of planting leafy vegetables on Mars regolith simulant, ameliorating this substrate’s fertility by the addition of organic residues produced in situ. For this purpose, two butterhead lettuce (Lactuca sativa L. var. capitata) cultivars (green and red Salanova®) were chosen to be cultivated in four dierent mixtures of MMS-1 Mojave Mars simulant:compost (0:100, 30:70, 70:30 and 100:0; v:v) in a phytotron open gas exchange growth chamber. The impact of compost rate on both crop performance and the nutritive value of green- and red-pigmented cultivars was assessed. The 30:70 mixture proved to be optimal in terms of crop performance, photosynthetic activity, intrinsic water use eciency and quality traits of lettuce. In particular, red Salanova® showed the best performance in terms of these quality traits, registering 32% more phenolic content in comparison to 100% simulant. Nonetheless, the 70:30 mixture represents a more realistic scenario when taking into consideration the sustainable use of compost as a limited resource in space farming, while still accepting a slight significant decline in yield and quality in comparison to the 30:70 mixture
Analisis Kesesuaian Arahan Fungsi Kawasan Terhadap Penggunaan Lahan Dengan Pemanfaatan SIG di Kabupaten Pati Tahun 2015
Research on the suitability of direction functions area on the use of land in the district Pati. The purpose of this study was to, (1) Knowing the direction of the area function (2) Knowing the condition of existing landuse, (3) Analysis of suitability direction functions area to landuse with utilization SIG in district Pati 2015.
The research method used is survey method with approach a quantitative analysis tiered. The survey method aims to determine the condition landuses of appropriate and not accordance with the direction of function of the area, while the analysis quantitative tiered used to obtain data on the direction functions area using data parameters such as rainfall, soil type and slope in Regency Pati. Taking sampling this study using purposive sampling method, which means in deliberate taking samples in accordance with the requirements of sample required. Spatial analysis that such as the Geographic Information System serves to identify suitability land appropriate and not accordance with the help of GIS software.
The result research is be obtained wide suitability landuse with direction functions area in Pati regency of 1253.96 km2 or 79.35% of the entire area, while the area of landuse that is not appropriate with direction functions area of 326.27 km2 or 20.65 % of total area is 1580.23 km2. Based on the results of landuse that are in Appropriate with referral function of the area must be maintained. Instead of land use that is not in accordance with direction functions area must be done monitoring by the local government in order not to harm the public harm the environment.
Keywords: Suitability, Direction Functions Area, Landuse, Regional Appropriate and Not Appropriat
Potentially toxic element availability and risk assessment of cadmium dietary exposure after repeated croppings of brassica juncea in a contaminated agricultural soil
Phytoextraction of potentially toxic elements (PTEs) is eco-friendly and cost-effective for remediating agricultural contaminated soils, but plants can only take up bioavailable forms of PTEs, thus meaning that bioavailability is the key for the feasibility of this technique. With the aims to assess the phytoextraction efficiency on an agricultural soil contaminated by Cr, Zn, Cd, and Pb and the changes induced by plants in PTE bioavailability and in human health risk due to dietary exposure, in this work we carried out a mesocosm experiment with three successive croppings of Brassica juncea, each followed by Rocket salad as bioindicator. Brassica juncea extracted more Zn and Cd than Cr and Pb, significantly reducing, after three repeated croppings, the bioavailable element concentrations in soil as a result of plant uptake and soil pH changes. For Cd, this reduction did not bring the bioavailable amounts obtained by soil extraction with NH4NO3 below the trigger value of 0.1 mg kg−1 set by some European countries. Nevertheless, the Hazard Quotient for Cd in Rocket salad decreased across three repeated croppings of Brassica juncea. This indicated the beginning of a re-equilibration process between soil PTE forms of different bioavailability, that are in a dynamic equilibrium, thus stressing the need to monitor the possible regeneration of the most readily bioavailable pool
Heterogeneous Dynamics, Marginal Stability and Soft Modes in Hard Sphere Glasses
In a recent publication we established an analogy between the free energy of
a hard sphere system and the energy of an elastic network [1]. This result
enables one to study the free energy landscape of hard spheres, in particular
to define normal modes. In this Letter we use these tools to analyze the
activated transitions between meta-bassins, both in the aging regime deep in
the glass phase and near the glass transition. We observe numerically that
structural relaxation occurs mostly along a very small number of
nearly-unstable extended modes. This number decays for denser packing and is
significantly lowered as the system undergoes the glass transition. This
observation supports that structural relaxation and marginal modes share common
properties. In particular theoretical results [2, 3] show that these modes
extend at least on some length scale where
corresponds to the maximum packing fraction, i.e. the jamming
transition. This prediction is consistent with very recent numerical
observations of sheared systems near the jamming threshold [4], where a similar
exponent is found, and with the commonly observed growth of the rearranging
regions with compression near the glass transition.Comment: 6 pages, improved versio
Keterlibatan Orang Tua Dalam Pendampingan Belajar Anak
This study is aimed to describe the parental involvement accompany learning with their children and changes curriculum. Informants in this study were parents who had children in elementary school consisting of father and mother. This study uses a phenomenological qualitative research design with a method of data collection used interviews and observations. Interviews conducted are semi-structured. The results of the study found that fathers and mothers shared roles in assisting children to learn while at home even though school activities were mostly carried out by mothers. This is based on the father as the breadwinner whose hour of return is erratic so that he entrustfully to the mother. The process of parental involvement encompasses the support of parents, participates in parents and strengthens the development of childrens learning. The position of child birth also has an impact on how parents treat children when learning takes place
The effect of novel biodegradable films on agronomic performance of zucchini squash grown under open-field and greenhouse conditions
The soil mulching is an important agricultural practice for increasing crop productivity and earliness. Mulching can be made with natural or synthetic materials. The common films being used these days are usually made of low density polyethylene (LDPE), but its disposal can represent a serious environmental and economic problem. The biodegradable mulching can overcome these problems. Two experiments were carried out comparing the effects of biodegradable and LDPE mulching films on yield and quality of zucchini (Cucurbita pepo L.) grown in two environments (open-field vs. greenhouse). In both the environments a randomized complete block design was adopted. The treatments composed of no-mulched crop (control), soil covered by 15 microns black biodegradable film (MB15) and soil covered by 50 microns black LDPE film. The results showed that MB15 was able to maintain discrete technical proprieties until the end of cycle, especially in greenhouse, assuring a sufficient heating of soil, similar to LDPE. The soil heating promoted crop development. Furthermore, earliness was increased (84 in greenhouse vs. 99 days in open air) in greenhouse. The early production of zucchini grown on MB15 was similar to the one in LDPE production in greenhouse. The total marketable yield of plants grown on both films was not different but it was lower in open air. The biodegradable film significantly improved fruits quality, with higher values of firmness and total soluble solid than fruits grown on LDPE
Static and dynamic heterogeneities in irreversible gels and colloidal gelation
We compare the slow dynamics of irreversible gels, colloidal gels, glasses
and spin glasses by analyzing the behavior of the so called non-linear
dynamical susceptibility, a quantity usually introduced to quantitatively
characterize the dynamical heterogeneities. In glasses this quantity typically
grows with the time, reaches a maximum and then decreases at large time, due to
the transient nature of dynamical heterogeneities and to the absence of a
diverging static correlation length. We have recently shown that in
irreversible gels the dynamical susceptibility is instead an increasing
function of the time, as in the case of spin glasses, and tends asymptotically
to the mean cluster size. On the basis of molecular dynamics simulations, we
here show that in colloidal gelation where clusters are not permanent, at very
low temperature and volume fractions, i.e. when the lifetime of the bonds is
much larger than the structural relaxation time, the non-linear susceptibility
has a behavior similar to the one of the irreversible gel, followed, at higher
volume fractions, by a crossover towards the behavior of glass forming liquids.Comment: 9 pages, 3 figure
Sweet basil functional quality as shaped by genotype and macronutrient concentration reciprocal action
Basil (Ocimum basilicum L.) is among the most widespread aromatic plants due to its versatility of use and its beneficial health properties. This aromatic plant thrives in hydroponics, which is a valid tool to improve the production and functional quality of crops, but nevertheless, it offers the possibility to de-seasonalize production. A floating raft system was adopted to test the production and quality potential during autumn season of three different genotypes of Genovese basil (Aroma 2, Eleonora and Italiano Classico) grown in three nutrient solutions with crescent electrical conductivity (EC: 1, 2 and 3 dS m−1). The aromatic and phenolic profiles were determined by GC/MS and HPLC analysis, respectively. The combination Aroma 2 and the EC 2 dS m−1 resulted in the highest production, both in terms of fresh weight and dry biomass. The 2 dS m−1 treatment determined the major phenolic content, 44%, compared to the other two EC. Italiano Classico showed a higher total polyphenolic content in addition to a different aromatic profile compared to the other cultivars, characterized by a higher percentage of Eucalyptol (+37%) and Eugenol (+107%) and a lower percentage of linalool (−44%). Correct management of the nutritional solution combined with adequate genetic material managed an improvement in the production and the obtainment of the desired aromatic and phenolic profiles
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