2,368 research outputs found
l-Amino Acid Production by a Immobilized Double-Racemase Hydantoinase Process: Improvement and Comparison with a Free Protein System
Protein immobilization is proving to be an environmentally friendly strategy for manufacturing biochemicals at high yields and low production costs. This work describes the optimization of the so-called “double-racemase hydantoinase process,” a system of four enzymes used to produce optically pure l-amino acids from a racemic mixture of hydantoins. The four proteins were immobilized separately, and, based on their specific activity, the optimal whole relation was determined. The first enzyme, d,l-hydantoinase, preferably hydrolyzes d-hydantoins from d,l-hydantoins to N-carbamoyl-d-amino acids. The remaining l-hydantoins are racemized by the second enzyme, hydantoin racemase, and continue supplying substrate d-hydantoins to the first enzyme. N-carbamoyl-d-amino acid is racemized in turn to N-carbamoyl-l-amino acid by the third enzyme, carbamoyl racemase. Finally, the N-carbamoyl-l-amino acid is transformed to l-amino acid by the fourth enzyme, l-carbamoylase. Therefore, the product of one enzyme is the substrate of another. Perfect coordination of the four activities is necessary to avoid the accumulation of reaction intermediates and to achieve an adequate rate for commercial purposes. The system has shown a broad pH optimum of 7–9, with a maximum activity at 8 and an optimal temperature of 60 °C. Comparison of the immobilized system with the free protein system showed that the reaction velocity increased for the production of norvaline, norleucine, ABA, and homophenylalanine, while it decreased for l-valine and remained unchanged for l-methionine
Efficiently Storing Well-Composed Polyhedral Complexes Computed Over 3D Binary Images
A 3D binary image I can be naturally represented
by a combinatorial-algebraic structure called cubical complex
and denoted by Q(I ), whose basic building blocks are
vertices, edges, square faces and cubes. In Gonzalez-Diaz
et al. (Discret Appl Math 183:59–77, 2015), we presented a
method to “locally repair” Q(I ) to obtain a polyhedral complex
P(I ) (whose basic building blocks are vertices, edges,
specific polygons and polyhedra), homotopy equivalent to
Q(I ), satisfying that its boundary surface is a 2D manifold.
P(I ) is called a well-composed polyhedral complex over the
picture I . Besides, we developed a new codification system
for P(I ), encoding geometric information of the cells
of P(I ) under the form of a 3D grayscale image, and the
boundary face relations of the cells of P(I ) under the form
of a set of structuring elements. In this paper, we build upon
(Gonzalez-Diaz et al. 2015) and prove that, to retrieve topological
and geometric information of P(I ), it is enough to
store just one 3D point per polyhedron and hence neither
grayscale image nor set of structuring elements are needed.
From this “minimal” codification of P(I ), we finally present
a method to compute the 2-cells in the boundary surface of
P(I ).Ministerio de Economía y Competitividad MTM2015-67072-
Spatiotemporal Barcodes for Image Sequence Analysis
Taking as input a time-varying sequence of two-dimensional
(2D) binary images, we develop an algorithm for computing a spatiotemporal
0–barcode encoding lifetime of connected components on the image
sequence over time. This information may not coincide with the one provided
by the 0–barcode encoding the 0–persistent homology, since the
latter does not respect the principle that it is not possible to move backwards
in time. A cell complex K is computed from the given sequence,
being the cells of K classified as spatial or temporal depending on whether
they connect two consecutive frames or not. A spatiotemporal path is
defined as a sequence of edges of K forming a path such that two edges
of the path cannot connect the same two consecutive frames. In our
algorithm, for each vertex v ∈ K, a spatiotemporal path from v to the
“oldest” spatiotemporally-connected vertex is computed and the corresponding
spatiotemporal 0–bar is added to the spatiotemporal 0–barcode.Junta de Andalucía FQM-369Ministerio de Economía y Competitividad MTM2012-3270
Encoding Specific 3D Polyhedral Complexes Using 3D Binary Images
We build upon the work developed in [4] in which we presented
a method to “locally repair” the cubical complex Q(I) associated
to a 3D binary image I, to obtain a “well-composed” polyhedral complex
P(I), homotopy equivalent to Q(I). There, we developed a new codification
system for P(I), called ExtendedCubeMap (ECM) representation,
that encodes: (1) the (geometric) information of the cells of P(I) (i.e.,
which cells are presented and where), under the form of a 3D grayscale
image gP ; (2) the boundary face relations between the cells of P(I),
under the form of a set BP of structuring elements.
In this paper, we simplify ECM representations, proving that geometric
and topological information of cells can be encoded using just a 3D
binary image, without the need of using colors or sets of structuring
elements. We also outline a possible application in which well-composed
polyhedral complexes can be useful.Junta de Andalucía FQM-369Ministerio de Economía y Competitividad MTM2012-32706Ministerio de Economía y Competitividad MTM2015-67072-
Characterising epithelial tissues using persistent entropy
In this paper, we apply persistent entropy, a novel topological statis-
tic, for characterization of images of epithelial tissues. We have found
out that persistent entropy is able to summarize topological and geomet-
ric information encoded by -complexes and persistent homology. After
using some statistical tests, we can guarantee the existence of signi cant
di erences in the studied tissues.Ministerio de Economía y Competitividad MTM2015-67072-
Persistent entropy: a scale-invariant topological statistic for analyzing cell arrangements
In this work, we develop a method for detecting differences in the topological distribution of cells forming epithelial tissues. In particular, we extract topological information from their images using persistent homology and a summary statistic called persistent entropy. This method is scale invariant, robust to noise and sensitive to global topological features of the tissue. We have found significant differences between chick neuroepithelium and epithelium of Drosophila wing discs in both, larva and prepupal stages. Besides, we have tested our method, with good results, with images of mathematical tesselations that model biological tissues
A new manual wheelchair propulsion system with self-locking capability on ramps
A wheelchair user faces many difficulties in their everyday attempts to use ramps, especially those
of some length. The present work describes the design and build of a propulsion system for manual wheelchairs
for use in ascending or descending long ramps. The design is characterized by a self-locking mechanism that
activates automatically to brake the chair when the user stops pushing. The system consists of a planetary transmission
with a self-locking capacity coupled to a push rim with which the user moves the system. Different
transmission ratios are proposed, adapted to the slope and to the user’s physical capacity (measured as the power
the user can apply over ample time periods). The design is shown to be viable in terms of resistance, and approximate
dimensions are established for the height and width of the propulsion system. Also, a prototype was built
in order to test the self-locking system on ramps
A game-based approach to the teaching of object-oriented programming languages
Students often have difficulties when trying to understand the concepts of object-oriented programming
(OOP). This paper presents a contribution to the teaching of OOP languages through a game-oriented
approach based on the interaction with tangible user interfaces (TUIs). The use of a specific type of
commercial distributed TUI (Sifteo cubes), in which several small physical devices have sensing, wireless
communication and user-directed output capabilities, is applied to the teaching of the C# programming
language, since the operation of these devices can be controlled by user programs written in C#. For our
experiment, we selected a sample of students with a sufficient knowledge about procedural programming,
which was divided into two groups: The first one had a standard introductory C# course, whereas
the second one had an experimental C# course that included, in addition to the contents of the previous
one, two demonstration programs that illustrated some OOP basic concepts using the TUI features.
Finally, both groups completed two tests: a multiple-choice exam for evaluating the acquisition of basic
OOP concepts and a C# programming exercise. The analysis of the results from the tests indicates that the
group of students that attended the course including the TUI demos showed a higher interest level (i.e.
they felt more motivated) during the course exposition than the one that attended the standard introductory
C# course. Furthermore, the students from the experimental group achieved an overall better
mark. Therefore, we can conclude that the technological contribution of Sifteo cubes – used as a
distributed TUI by which OOP basic concepts are represented in a tangible and a visible way – to the
teaching of the C# language has a positive influence on the learning of this language and such basic
concepts
The DOCENTIA Programme: basis, development and implications
Este artículo responde al objetivo de mostrar el desarrollo histórico de un
programa de apoyo para la evaluación de la actividad docente del profesorado
universitario denominado DOCENTIA, desde su origen, sus objetivos y su desarrollo en
las instituciones de educación superior españolas. En primer lugar, comenzamos con
la exposición de los antecedentes sobre evaluación docente en las instituciones de
educación superior, ligadas al desarrollo de la Ley de Reforma Universitaria, hasta la
aprobación de la vigente Ley de Universidades (LOMLOU, 2007). A continuación,
describimos la naturaleza y sentido de la herramienta DOCENTIA en el nuevo contexto
universitario, adaptado a las exigencias de garantía de calidad de las instituciones.
Posteriormente, presentamos un análisis comparado de los diecisiete modelos de
evaluación de la actividad docente certificados hasta diciembre de 2017 por las
agencias de evaluación, a partir de criterios objetivos. A continuación, exponemos el
desarrollo que ha seguido el programa en términos cuantitativos y cualitativos en la
Universidad española. Finalizamos, planteando una reflexión sobre las implicaciones
que en la práctica ha producido la aplicación de la herramienta de evaluación docente
DOCENTIA, en la mejora de la función docente de la actividad universitaria.This paper aims to show the historical development of a programme
supporting the assessment of the teaching activities of university professors called
DOCENTIA, covering its origins, aims, and implementation within Spanish higher
education institutions. Firstly, we will explain the antecedents on teacher assessment
in higher education institutions, which are linked to the development of the University
Reform Act, and up to the current Act on Universities (LOMLOU, 2007). Next, we will
describe the nature of DOCENTIA as a tool adapted to the quality assurance demands
in the new university context. Following this, we will present an analysis comparing the
seventeen models of teacher assessment which were certified as of December 2017 by
the assessment agencies based on objective
criteria. Then, we will explain the development of the programme in both qualitative
and quantitative terms within the Spanish university system. We will finish off by
reflecting on the practical implications of the teaches assessment tool DOCENTIA in the
improvement of the teaching practice within Spanish universities
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