257 research outputs found
ADICI 3N DE ROCA FOSF 3RICA Y CAMBIOS EN LAS FRACCIONES DE P EN SUELOS CON DIFERENTE HUMEDAD Y PER\uedODOS DE INCUBACI 3N
El objetivo de este trabajo fue comparar la disoluci\uf3n de la roca fosf\uf3rica (RF) Monte Fresco en dos suelos \ue1cidos muy contrastantes en caracter\uedsticas f\uedsico-qu\uedmicas, mediante un esquema de fraccionamiento a diferentes per\uedodos de incubaci\uf3n y contenidos de humedad. El suelo Iguana es muy arenoso, de baja fertilidad natural y baja capacidad de retenci\uf3n de fosfatos, mientras que el suelo Bram\uf3n es mucho m\ue1s \ue1cido y mayor contenido de Al cambiable pero con mayor fertilidad natural y alta capacidad de retenci\uf3n de fosfatos. En el suelo Iguana la RF se disolvi\uf3 en una mayor proporci\uf3n que en el suelo Bram\uf3n, ya que este suelo, a pesar de su fuerte acidez present\uf3 altos niveles de P (total y disponible) y Ca intercambiable los cuales generaron condiciones menos apropiadas para la reacci\uf3n de la RF. A lo largo de la incubaci\uf3n con RF, como resultado de la redistribuci\uf3n de las fracciones mayores de P (P-HCl y P-residual) originalmente presentes en la RF, ocurri\uf3 un incremento significativo para la fracciones P-resina y P-microbiano en el suelo Iguana, y de P-resina, P-microbiano, NaOH-Pi y Po en el suelo Bram\uf3n, en este caso, posiblemente asociado con sus mayores niveles de C. Un mayor contenido de humedad disminuy\uf3 los valores de las fracciones m\ue1s l\ue1biles (resina y NaHCO3) en ambos suelos, lo que implica, una mayor adsorci\uf3n del P al establecerse un mayor contacto entre las superficies adsorbentes y el f\uf3sforo reci\ue9n liberado de la roca fosf\uf3rica.
Palabras clave adicionales: Adsorci\uf3n de P, biomasa microbiana, fraccionamiento de P, suelos \ue1cidos.
ABSTRACT
The objective of this study was to compare the dissolution of the phosphate rock (PR) Monte Fresco in two acidic soils very contrasting in physicochemical characteristics, through a scheme of fractionation at different periods of incubation and moisture contents. Iguana, a very sandy soil with a low natural fertility and low phosphate retention; and much more acid Bram\uf3n soil with a higher exchangeable Al content but with greater natural fertility and high capacity of phosphate retention. Iguana soil dissolved the PR in a greater proportion than the soil Bram\uf3n, since this soil, despite its strong acidity presented high levels of P (total and available) and exchangeable Ca which generated less appropriate conditions for the reaction of the PR. During incubation with PR, as a result of the redistribution of the major fractions of P (P-HCl and P-residual) originally present in the PR, occurred a significant increase for the P-resin and microbial-P fractions in Iguana soil; and in P-resin, microbial-P, NaOH-Pi and Po for Bram\uf3n soil, in this case, possibly associated with its higher C content. Higher moisture contents decreased more labile P-fractions (resin and NaHCO3) values in both soils, which implies, a higher adsorption of P due to a greater contact between the adsorbent surfaces and newly released P from the PR.
Additional key words: Acid soils, microbial biomass, P-adsorption, P-fractionation. <br
Expression, purification and thermal stability evaluation of an engineered amaranth protein expressed in Escherichia coli
Background: The acidic subunit of amarantin (AAC)\u2014the predominant
amaranth seed storage protein\u2014has functional potential and its
third variable region (VR) has been modified with antihypertensive
peptides to improve this potential. Here, we modified the C-terminal in
the fourth VR of AAC by inserting four VY antihypertensive peptides.
This modified protein (AACM.4) was expressed in Escherichia coli. In
addition, we also recombinantly expressed other derivatives of the
amarantin protein. These include: unmodified amarantin acidic subunit
(AAC); amarantin acidic subunit modified at the third VR with four VY
peptides (AACM.3); and amarantin acidic subunit doubly modified, in the
third VR with four VY peptides and in the fourth VR with the RIPP
peptide (AACM.3.4). Results: E. coli BL21-CodonPlus (DE3)-RIL was the
most favorable strain for the expression of proteins. After 6 h of
induction, it showed the best recombinant protein titer. The AAC and
AACM.4 were obtained at higher titers (0.56 g/L) while proteins
modified in the third VR showed lower titers: 0.44 g/L and 0.33 g/L for
AACM.3 and AACM.3.4, respectively. As these AAC variants were mostly
expressed in an insoluble form, we applied a refolding protocol. This
made it possible to obtain all proteins in soluble form. Modification
of the VR 4 improves the thermal stability of amarantin acidic subunit;
AAC manifested melting temperature (Tm) at 34\ub0C and AACM.4 at
37.2\ub0C. The AACM.3 and AACM.3.4 did not show transition curves.
Conclusions: Modifications to the third VR affect the thermal stability
of amarantin acidic subunit
Fast evaluation of the adsorption energy of organic molecules on metals via graph neural networks
Modeling in heterogeneous catalysis requires the extensive evaluation of the energy of molecules adsorbed on surfaces. This is done via density functional theory but for large organic molecules it requires enormous computational time, compromising the viability of the approach. Here we present GAME-Net, a graph neural network to quickly evaluate the adsorption energy. GAME-Net is trained on a well-balanced chemically diverse dataset with C1–4 molecules with functional groups including N, O, S and C6–10 aromatic rings. The model yields a mean absolute error of 0.18 eV on the test set and is 6 orders of magnitude faster than density functional theory. Applied to biomass and plastics (up to 30 heteroatoms), adsorption energies are predicted with a mean absolute error of 0.016 eV per atom. The framework represents a tool for the fast screening of catalytic materials, particularly for systems that cannot be simulated by traditional methods
Schwartz - Zippelov teorem i neke njegove primjene
U ovom radu izložen je rezultat poznat pod nazivom Schwartz - Zippelova lema ili Schwartz - Zippelov teorem. Tema rada pripada pretežno algebri, ali ima značajne primjene u drugim matematičkim područjima kao što je na primjer teorija algoritama, te kombinatorika. Rad se sastoji od tri poglavlja. U uvodu je ukratko opisana tema i cilj rada. Prvo poglavlje sadrži kratku povijest nastanka teorema, različite oblike rezultata pojedinih autora, te kratki opis pojmova korištenih u samom radu. Drugo poglavlje sastoji se od iskaza i dokaza Schwartz - Zippelovog teorema, a u trećem poglavlju izložene su neke primjene tog teorema na probleme koji se mogu svesti na testiranje jednakosti polinoma. Takvi su, primjerice, problem postojanja savršenog sparivanja u grafu i ispitivanje svojstva asocijativnosti u grupoidu. Uz svaku primjenu navedeni su i prikladni primjeri.In this diploma thesis we present the result usually called the Schwartz-Zippel lemma or the Schwartz-Zippel theorem. The nature of this theorem is basically algebraic, but it has significant applications in other areas of mathematics, such as the theory of algorithms and combinatorial theory. The thesis consists of three chapters. The main theme and objective are briefly described in the introduction. The first chapter contains a short history of the theorem’s origins, various forms of the main results by different authors and some comments of basic concepts related to this topic. The statement and a proof of the Schwartz-Zippel theorem are given in the second chapter, together with the general outline of its applications. The third and final chapter consists of some applications to problems which can be reduced to polynomial identity testing, including the existence of a perfect matching in a graph and testing of the associativity property in a groupoi
Scaling-up batch conditions for efficient sucrose hydrolysis catalyzed by an immobilized recombinant Pichia pastoris cells in a stirrer tank reactor
Background: Invert sugar is used greatly in food and pharmaceutical
industries. This paper describes scaling-up batch conditions for
sucrose inversion catalyzed by the recombinant Pichia pastoris BfrA4X
whole cells expressing Thermotoga maritima invertase entrapped in
calcium alginate beads. For the first time, we describe the application
of a kinetic model to predict the fractional conversion expected during
sucrose hydrolysis reaction in both, a model and a prototype bioreactor
with 0.5- and 5-L working volume, respectively. Results: Different
scaled-up criteria used to operate the 0.5-L bioreactor were analyzed
to explore the invert sugar large scale production. After model
inversion studies, a 5-L scaled-up reaction system was performed in a
7-L stirred reactor. Both scaled-up criteria, immobilized biocatalyst
dosage and stirring speed, were analyzed in each type of bioreactors
and the collected data were used to ensure an efficient scale-up of
this biocatalyst. Conclusions: To date, there is not enough information
to describe the large-scale production of invert sugar using different
scaled-up criteria such as dose of immobilized biocatalyst and stirring
speed effect on mass transfer. The present study results constitute a
valuable tool to successfully carry out this type of high-scale
operation for industrial purposes
Optimization of worm-bed leachate for culturing of tomato ( Lycopersicon esculentum Mill) inoculated with Glomus fasciculatum and Pseudomonas fluorescens
A response surface technique was used to analyze the effect of Glomus
fasciculatum , Pseudomonas fluorescens and worm-bed leachate (WBL)
on growth, yield and characteristics of tomato ( Lycopersicon
esculentum Mill). The treatments combined inoculation with or without
P. fluorescens or G. fasciculatum and the application of WBL at 20%
(v/v) each day or every three days. Plant height, number of leaves and
yield of tomato fruits was not affected by the factors studied.
However, plants with foliar application of WBL each day developed wider
stems than those with an application every three days. The pH of the
fruits was lower when WBL was applied every three days compared to a
daily application. The soluble solids content of the fruits was higher
when WBL was applied daily compared to those sprayed every three days.
Plant development was not affected by addition of P. fluorescens, G.
fasciculatum or WBL, but WBL changed fruit characteristics
Catalytical properties of N-glycosylated Gluconacetobacter diazotrophicus levansucrase produced in yeast
The influence of N-glycosylation on the kinetic and catalytical
properties of a bacterial fructosyltransferase (LsdA) produced in
Pichia pastoris was studied. The glycosylated enzyme behaved
similarly to non-glycosylated LsdA when substrate specificity,
fructo-oligosaccharide (FOS) production, sucrose hydrolysis or levan
formation reactions were carried out under different experimental
conditions. The kinetic parameters for native or yeast-expressed LsdA
determined at 60\ub0C, condition for the highest hydrolytic activity,
followed a conventional Michaelis-Menten kinetics. Synthase activity of
this levansucrase increased in water-restricted environments by
addition of salt or organic solvent to the reaction mixtures
VALES VI: ISM enrichment in star-forming galaxies up to z0.2 using CO(1-0), CO(1-0) and CO(1-0) line luminosity ratios
We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations
towards 27 low-redshift () star-forming galaxies taken from the
Valpara\'iso ALMA/APEX Line Emission Survey (VALES). We perform stacking
analyses of the CO(), CO() and CO()
emission lines to explore the (CO())/(CO()))
(hereafter (CO)/(CO)) and
(CO())/(CO()) (hereafter
(CO)/(CO) line luminosity ratio dependence as a function
of different global galaxy parameters related to the star formation activity.
The sample has far-IR luminosities L and stellar
masses of M corresponding to typical star-forming and
starburst galaxies at these redshifts. On average we find a
(CO)/(CO) line luminosity ratio value of 16.12.5.
Galaxies with evidences of possible merging activity tend to show higher
(CO)/(CO) ratios by a factor of two, while variations of
this order are also found in galaxy samples with higher star formation rates or
star formation efficiencies. We also find an average
(CO)/(CO) line luminosity ratio of 2.50.6, which is
in good agreement with those previously reported for starburst galaxies. We
find that galaxy samples with high , SFR and SFE show low
(CO)/(CO) line luminosity ratios with high
(CO)/(CO) line luminosity ratios, suggesting that these
trends are produced by selective enrichment of massive stars in young
starbursts.Comment: 16 pages, 10 figures to be published in MNRA
Synthesis of Densely Packaged, Ultrasmall Pt02Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Temperature
The gram\u2010scale synthesis, stabilization, and characterization of well\u2010defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X\u2010ray snapshots of Pt02 clusters, homogenously distributed and densely packaged within the channels of a metal\u2013organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140\u2009\ub0C), energetically costly industrial reactions in the gas phase such as HCN production, CO2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less\u2010dangerous industrial reactions
Are there changes in the nutritional status of children of Oportunidades families in rural Chiapas, Mexico? A cohort prospective study
Background: In Mexico, despite that the fact that several social
programs have been implemented, chronic undernutrition is still a
public health problem affecting 1.5 million children of <5 years.
Chiapas ranks first in underweight and stunting at national level with
a stunting prevalence of 31.4 % whereas for its rural population is
44.2 %. The purpose of this paper is to determine if the nutritional
status of a cohort of children living in poor rural communities under
Oportunidades has changed. We were interested in assessing the
nutrition evolution of the children who were initially diagnosed as
stunted and of those who were diagnosed as normal. Oportunidades is an
anti-poverty program of the Mexican government consisting mainly in
monetary transfers to the families living in alimentary poverty.
Methods: A 9-year cohort prospective study was conducted with
nutritional evaluations of 222 children. Anthropometric indices were
constructed from measurements of weight, height, and age of the
children whose nutritional status was classified following WHO
standards. Results: The results showed that although these children
were Oportunidades beneficiaries for 9 years and their families
improved their living conditions, children still had a high prevalence
of stunting (40.1 %) and 69.6 % had not recovered yet. Children who
were initially diagnosed with normal nutritional status and became
stunted 2 years later had a higher risk (relative risk (RR) 5.69,
2.95\u201310.96) of continuing stunted at school age and adolescence.
Conclusions: Oportunidades has not impacted, as expected, the
nutritional status of the study population. These findings pose the
question: Why has not the nutritional status of children improved,
although the living conditions of their families have significantly
improved? This might be the result of an adaptation process achieved
through a decrease of growth velocity. It is important to make efforts
to watch the growth of the children during their first 3 years of age,
to focus on improving the diet of women at fertile age and pay special
attention to environmental conditions to break the vicious cycle of
malnutrition
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