855 research outputs found
The smallest space miners: principles of space biomining
As we aim to expand human presence in space, we need to find viable approaches to achieve independence from terrestrial resources. Space biomining of the Moon, Mars and asteroids has been indicated as one of the promising approaches to achieve in-situ resource utilization by the main space agencies. Structural and expensive metals, essential mineral nutrients, water, oxygen and volatiles could be potentially extracted from extraterrestrial regolith and rocks using microbial-based biotechnologies. The use of bioleaching microorganisms could also be applied to space bioremediation, recycling of waste and to reinforce regenerative life support systems. However, the science around space biomining is still young. Relevant differences between terrestrial and extraterrestrial conditions exist, including the rock types and ores available for mining, and a direct application of established terrestrial biomining techniques may not be a possibility. It is, therefore, necessary to invest in terrestrial and space-based research of specific methods for space applications to learn the effects of space conditions on biomining and bioremediation, expand our knowledge on organotrophic and community-based bioleaching mechanisms, as well as on anaerobic biomining, and investigate the use of synthetic biology to overcome limitations posed by the space environments
Effets de la frequence de nourrissage sur les parametres zootechniques et le taux de masculinisation des larves de la souche « Bresil » du tilapia du nil Oreochromis niloticus (Linnee, 1758) pendant et apres le traitement...
Full French Title: Effets de la frequence de nourrissage sur les parametres zootechniques et le taux de masculinisation des larves de la souche « Bresil » du tilapia du nil Oreochromis niloticus (Linnee, 1758) pendant et apres le traitement avec le 17- α -methyltestosterone
En larviculture la survie et la croissance peuvent être influencées par divers paramètres parmi lesquels la fréquence d’alimentation. L’effet de ce paramètre sur les larves de la souche « Brésil » du tilapia du Nil Oreochromis niloticus au cours de la période de traitement (5, 6, 7 et 8 repas / jour) et post-traitement (3, 4, 5 et 6 repas / jour) avec le 17-α -méthyltestostérone a été testé. La durée de chacune des périodes a été de 21 jours. La ration quotidienne distribuée a été établie sur la base du poids moyen initial avec un taux d’alimentation de 50 % de la biomasse par jour, ce dernier a été ajusté chaque semaine en fonction de la croissance des poissons. Après les 21 jours de la période de traitement hormonale, les meilleures performances de croissance (411,33 ± 21,19 mg) ont été enregistrées chez les larves nourries 6 fois par jour. Les plus fortes croissances (1617,44 ± 90,34 mg) au cours de la période post-traitement ont été obtenues chez les alevins ayant reçu 5 repas par jour. Les fréquences de nourrissage de 6 et 5 repas quotidiens sont donc optimales respectivement en période de traitement et post- traitement avec le 17-α -méthyltestostérone. Concernant, le taux de masculinisation, les poissons nourris aux fréquences de 6, 7 et 8 repas par jour ont obtenues des valeurs similaires mais supérieurs (p-value < 0,05) à celle de la fréquence de 5 repas par jour. Ainsi, pour obtenir un pourcentage élevé de mâle lors de l’inversion hormonale du sexe chez le tilapia du Nil en milieu d’élevage, une fréquence d’au moins 6 repas par jour est recommandée.
Mots clés: Oreochromis niloticus, fréquence d’alimentation, Post-traitement, larves, paramètres zootechniques
English Title: Effects of feeding frequency on zootechnical parameters and masculinization rate of Oreochromis niloticus (Linnaeus, 1758) «Brazil» strain larvae during and after the treatment with 17-alpha-methyltestosterone
English Abstract
In larval culture the survival and growth can be influenced by various parameters of which the feeding frequency. The effect of this parameter on ‘’ Brazil ‘’ strain larvae of Nile tilapia Oreochromis niloticus during (5, 6, 7 and 8 meals / day) and after (3, 4, 5 and 6 meals / day) 17-α -methyltestosterone treatment, was tested. The duration of each period was 21 days. The daily ration distributed was 50% of the biomass during the first week. It was adjusted for total biomass at the end of each control fishery. After the 21 days of the hormonal treatment period, the best growth performances (411.33 ± 21.19 mg) were recorded in the larvae fed 6 times per day. The highest growth (1617.44 ± 90.34 mg) after treatment was obtained in fry fed 5 meals per day. The feeding frequencies of 6 and 5 daily meals are therefore optimal during treatment and aftertreatment with 17- α-methyltestosterone respectively. Concerning the masculinization rate, fish fed at the frequencies of 6, 7 and 8 meals per day obtained similar values but higher (p-value < 0.05) than the frequency of 5 meals per day. A feeding of at least 6 meals per day is recommended during the inversion of the sex in the larvae of the ‘’ Brazil ‘’ strain of Nile tilapia in breeding environment. Regarding the rate of masculinization, fish fed at frequencies of 6, 7 and 8 meals per day obtained similar but higher values (p-value < 0.05) than the frequency of 5 meals per day. Thus, to obtain a high percentage of males during the hormonal inversion of sex in the Nile tilapia in the rearing environment, a frequency of at least 6 meals per day is recommended.
Keywords: Oreochromis niloticus, feeding frequency, post-treatment, larvae, zootechnical parameter
Matrix Assisted Formation of Ferrihydrite Nanoparticles in a Siloxane/Poly(Oxyethylene) Nanohybrid
Matrix-assisted formation of ferrihydrite, an iron oxide hydroxide analogue
of the protein ferritin-core, in a sol-gel derived organic-inorganic hybrid is
reported. The hybrid network (named di-ureasil) is composed of
poly(oxyethylene) chains of different average polymer molecular weights grafted
to siloxane domains by means of urea cross-linkages and accommodates
ferrihydrite nanoparticles. Magnetic measurements, Fourier transform infrared
and nuclear magnetic resonance spectroscopy reveal that the controlled
modification of the polymer molecular weight allows the fine-tuning of the
ability of the hybrid matrix to assist and promote iron coordination at the
organic-inorganic interface and subsequent nucleation and growth of the
ferrihydrite nanoparticles whose core size (2-4 nm) is tuned by the amount of
iron incorporated. The polymer chain length, its arrangement and crystallinity,
are key factors on the anchoring and formation of the ferrihydrite particles.Comment: 7 pages, 6 figures. To be published in J. Mater. Che
Pengembangan Perangkat Pembelajaran Matematika dengan Model Pembelajaran Berbasis Masalah pada Materi Kubus dan Balok untuk Siswa Kelas VIII Smp/mts
The background of this study is the restrict of mathematics learning instruments as supporting learning referring to 2013 Curriculum. This study aimed to develop mathematics learning instruments with problem based learning's model on cubes and cuboids for 8th grade SMP/MTs. Learning instruments in this study are syllabus, lesson plans, and student worksheet. This study method used is 4D model by Thiagarajan, Dorothy S. Semmel, and Melvyn I. Semmel that consist of define, design, development, and disseminate, but the study was limited only to development step. Based on the data analysis, it can be conclude that mathematics learning instruments is very valid with mean score of syllabus is 4,53, mean score of lesson plans is 4,26, and mean score of student worksheet is 4,21. This student worksheet has also reached the practical qualification with mean percentage of student responses is 97,33 on a small test group
Minimal Algorithmic Information Loss Methods for Dimension Reduction, Feature Selection and Network Sparsification
We introduce a family of unsupervised, domain-free, and (asymptotically)
model-independent algorithms based on the principles of algorithmic probability
and information theory designed to minimize the loss of algorithmic
information, including a lossless-compression-based lossy compression
algorithm. The methods can select and coarse-grain data in an
algorithmic-complexity fashion (without the use of popular compression
algorithms) by collapsing regions that may procedurally be regenerated from a
computable candidate model. We show that the method can preserve the salient
properties of objects and perform dimension reduction, denoising, feature
selection, and network sparsification. As validation case, we demonstrate that
the method preserves all the graph-theoretic indices measured on a well-known
set of synthetic and real-world networks of very different nature, ranging from
degree distribution and clustering coefficient to edge betweenness and degree
and eigenvector centralities, achieving equal or significantly better results
than other data reduction and some of the leading network sparsification
methods. The methods (InfoRank, MILS) can also be applied to applications such
as image segmentation based on algorithmic probability.Comment: 23 pages in double column including Appendix, online implementation
at http://complexitycalculator.com/MILS
Progress on lanthanide-based organic–inorganic hybrid phosphors
Research on organic–inorganic hybrid materials containing trivalent lanthanide ions (Ln3+) is a very active field that has rapidly shifted in the last couple of years to the development of eco-friendly, versatile and multifunctional systems, stimulated by the challenging requirements of technological applications spanning domains as diverse as optics, environment, energy, and biomedicine. This tutorial review offers a general overview of the myriad of advanced Ln3+-based organic–inorganic hybrid materials recently synthesised, which may be viewed as a major innovation in areas of phosphors, lighting, integrated optics and optical telecommunications, solar cells, and biomedicin
Evidence of random magnetic anisotropy in ferrihydrite nanoparticles based on analysis of statistical distributions
We show that the magnetic anisotropy energy of antiferromagnetic ferrihydrite
depends on the square root of the nanoparticles volume, using a method based on
the analysis of statistical distributions. The size distribution was obtained
by transmission electron microscopy, and the anisotropy energy distributions
were obtained from ac magnetic susceptibility and magnetic relaxation. The
square root dependence corresponds to random local anisotropy, whose average is
given by its variance, and can be understood in terms of the recently proposed
single phase homogeneous structure of ferrihydrite.Comment: 6 pages, 2 figure
Chitosan membranes containing micro or nano-size bioactive glass particles : evolution of biomineralization followed by in-situ dynamic mechanical analysis
A newfamilyofbiodegradablepolymer/bioactiveglass(BG)compositematerialshas
emergedbasedontheavailabilityofnano-sizedbioactiveparticles.Suchnovelbiocompo-
sites canhaveenhancedperformance,intermsofmechanicalpropertiesandbioactivity,
and theycanbedesignedtobeusedinboneregenerationapproaches.
In thiswork,membranesofchitosan(CTS)andchitosanwithbioactiveglass(BG)both
micron andnanosizedparticles(CTS/mBG,CTS/nBG,respectively)werepreparedby
solvent casting.Microstructuralandmechanicalpropertieswereevaluatedinorderto
compare theeffectsoftheincorporationofmicro(mBG) andnano(nBG)particlesinthe
chitosan matrix. In vitro bioactivity testswereperformedtocharacterizetheapatitelayer
that isformedonthesurfaceofthematerialafterbeingimmersedinsimulatedbodyfluid
(SBF). Thebiomineralizationprocessonthebiomaterialswasalsofollowedusingnon-
conventionaldynamicmechanicalanalysis(DMA),bothonlineandoffline.InsuchDMA
experiments,thechangeinthestoragemodulus, E0, andthelossfactor,tan d, were
measured asafunctionoftheimmersiontimeinSBF.TheresultsdemonstratedthatCTS/
nBG membranespossessenhancedmechanicalpropertiesandhigherbioactivityin
comparisonwiththeCTS/mBG membranes.SuchresultssuggestthepotentialofnBGfor
the developmentofbioactivecompositesforboneregenerationapplications.This work was financially supported by Foundation for Science and Technology (FCT) by the projects PTDC/QUI/69263/2006, PTDC/CTM-BPC/112774/2009 and, through the scholarship SFRH/BD/64601/2009 granted to Sofia G. Caridade. The authors acknowledge Dr D. Mohn and Prof. W. Stark (Em Zurich) for providing the nBG particles used
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