120 research outputs found
Entropy driven key-lock assembly
The effective interaction between a sphere with an open cavity (lock) and a
spherical macroparticle (key), both immersed in a hard sphere fluid, is studied
by means of Monte Carlo simulations. As a result, a 2d map of the key-lock
effective interaction potential is constructed, which leads to the proposal of
a self-assembling mechanism: there exists trajectories through which the
key-lock pair could assemble avoiding trespassing potential barriers. Hence,
solely the entropic contribution can induce their self-assembling even in the
absence of attractive forces. This study points out the solvent contribution
within the underlying mechanisms of substrate-protein assembly/disassembly
processes, which are important steps of the enzyme catalysis and protein
mediated transport
Analysis of the Process Parameter Influence in Laser Cladding of 316L Stainless Steel
Laser Cladding is one of the leading processes within Additive Manufacturing technologies, which has concentrated a considerable amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in the laser cladding processing of single and compound volumes (solid forms) made from AISI 316L stainless steel powders and using a coaxial nozzle for their deposition. Process speed, applied laser power and powder flow are considered to be the main variables affecting the laser cladding in single clads, whereas overlap percentage and overlapping strategy also become relevant when dealing with multiple clads. By setting appropriate values for each process parameter, the main goal of this paper is to develop a processing window in which a good metallurgical bond between the delivered powder and the substrate is obtained, trying simultaneously to maintain processing times at their lowest value possible. Conventional metallography techniques were performed on the cross sections of the laser tracks to measure the effective dimensions of clads, height and width, as well as the resulting dilution value. Besides the influence of the overlap between contiguous clads and layers, physical defects such as porosity and cracks were also evaluated. Optimum process parameters to maximize productivity were defined as 13 mm/s, 2500 W, 30% of overlap and a 25 g/min powder feed rat
Estrategias de emprendimiento y emociones de mujeres empresarias: Propuestas innovadoras en el contexto económico andaluz
El presente trabajo tiene como objetivo identificar en los discursos de mujeres empresarias diferentes acciones estratégicas de emprendimiento y diversas emociones que ponen en valor el funcionamiento facilitador de propuestas innovadoras. Partimos de la idea de que existen emociones asociadas a estrategias de emprendimiento. Para investigarlo se usa una metodología de corte cualitativo, seleccionando ocho mujeres empresarias a través de la Asociación de Empresarias de Sevilla, para la realización de dos grupos de discusión. Los resultados muestran la presencia de diferentes acciones estratégicas que concretan y caracterizan a otras estrategias generales como la gestión empresarial, la innovación y el liderazgo y el impacto social. Las emociones dan sentido a las formas de hacer empresa por parte de estas mujeres, detectando tanto emociones facilitadoras como bloqueadoras. Resultando clave la formación de la mujer como empresaria y emprendedora, reconociendo las necesidades de educación emociona
Ion pairing in model electrolytes: A study via three particle correlation functions
A novel integral equations approach is applied for studying ion pairing in
the restricted primitive model (RPM) electrolyte, i. e., the three point
extension (TPE) to the Ornstein-Zernike integral equations. In the TPE
approach, the three-particle correlation functions are obtained. The TPE results are compared to molecular
dynamics (MD) simulations and other theories. Good agreement between TPE and MD
is observed for a wide range of parameters, particularly where standard
integral equations theories fail, i. e., low salt concentration and high ionic
valence. Our results support the formation of ion pairs and aligned ion
complexes.Comment: 43 pages (including 18 EPS figs) - RevTeX 4 - J. Chem. Phys. (in
press
AMMO-Prot: amine system project 3D-model finder
BACKGROUND: Amines are biogenic amino acid derivatives, which play pleiotropic and very important yet complex roles in animal physiology. For many other relevant biomolecules, biochemical and molecular data are being accumulated, which need to be integrated in order to be effective in the advance of biological knowledge in the field. For this purpose, a multidisciplinary group has started an ontology-based system named the Amine System Project (ASP) for which amine-related information is the validation bench. RESULTS: In this paper, we describe the Ontology-Based Mediator developed in the Amine System Project (http://asp.uma.es) using the infrastructure of Semantic Directories, and how this system has been used to solve a case related to amine metabolism-related protein structures. CONCLUSIONS: This infrastructure is used to publish and manage not only ontologies and their relationships, but also metadata relating to the resources committed with the ontologies. The system developed is available at http://asp.uma.es/WebMediator
New interfacial microtubule inhibitors of marine origin, PM050489/PM060184, with potent antitumor activity and a distinct mechanism
We have investigated the target and mechanism of action of a new family of cytotoxic small molecules of marine origin. PM050489 and its dechlorinated analogue PM060184 inhibit the growth of relevant cancer cell lines at subnanomolar concentrations. We found that they are highly potent microtubule inhibitors that impair mitosis with a distinct molecular mechanism. They bind with nanomolar affinity to unassembled αβ-tubulin dimers, and PM050489 binding is inhibited by known Vinca domain ligands. NMR TR-NOESY data indicated that a hydroxyl-containing analogue, PM060327, binds in an extended conformation, and STD results define its binding epitopes. Distinctly from vinblastine, these ligands only weakly induce tubulin self-association, in a manner more reminiscent of isohomohalichondrin B than of eribulin. PM050489, possibly acting like a hinge at the association interface between tubulin heterodimers, reshapes Mg2+-induced 42 S tubulin double rings into smaller 19 S single rings made of 7 ± 1 αβ-tubulin dimers. PM060184-resistant mutants of Aspergillus nidulans map to β-tubulin Asn100, suggesting a new binding site different from that of vinblastine at the associating β-tubulin end. Inhibition of assembly dynamics by a few ligand molecules at the microtubule plus end would explain the antitumor activity of these compounds, of which PM060184 is undergoing clinical trials.We wish to thank J. M. Fernandez Sousa (PharmaMar) for useful discussions and support, E. Hamel (NCI) for providing eribulin, C. Scazzocchio and G. Diallinas for useful advice on mutant screening, H. N. Arst for advice on mutant screening and mapping and for kindly providing strains MAD3688 and MAD4655, T. J. Fitzgerald (A&M University) for MTC and C. Alfonso (CIB) for AUC analysis. We also thank Rhône Poulenc Rorer Aventis for supplying docetaxel and Matadero Municipal Vicente de Lucas de Segovia for providing the calf brains for tubulin purification. B.P. had a contract from Comunidad de Madrid, and A.C. had a Ramon y Cajal contract, J.R.-S. had a fellowship from “Programa de Cooperación Científica entre el Ministerio de Ciencia, Tecnologías y Medio Ambiente de la República de Cuba (CITMA) y el CSIC”. This work was supported by grants BIO2010-16351 (J.F.D.), BQU2009-08536 (J.J.-B.), CAM S2010/BMD-2457 (J.F.D.), CAM S2010/BMD-2353 (J.J.-B., J.M.A.), IPT-2011-0752-900000 and BIO2012-30965 (M.A.P.), BFU2011-23416 (J.M.A.) and PharmaMar-CSIC contracts
The circumnuclear environment of the peculiar galaxy NGC 3310
Gas and star velocity dispersions have been derived for eight circumnuclear
star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC3310
using high resolution spectroscopy in the blue and far red. Stellar velocity
dispersions have been obtained from the CaII triplet in the near-IR, using
cross-correlation techniques, while gas velocity dispersions have been measured
by Gaussian fits to the Hb 4861A and [OIII]5007A emission lines.
The CNSFRs stellar velocity dispersions range from 31 to 73 km/s. These
values, together with the sizes measured on archival HST images, yield upper
limits to the dynamical masses for the individual star clusters between 1.8 and
7.1 x 10 M, for the whole CNSFR between 2 x 10 and 1.4 x 10
M, and 5.3 x 10 M for the nucleus inside the inner 14.2 pc.
The masses of the ionizing stellar population responsible for the HII region
gaseous emission have been derived from their published Ha luminosities and are
found to be between 8.7 x 10 and 2.1 x 10 M for the
star-forming regions, and 2.1 x 10 M for the galaxy nucleus; they
therefore constitute between 1 and 7 per cent of the total dynamical mass.
The ionized gas kinematics is complex; two different kinematical components
seem to be present as evidenced by different line widths and Doppler shifts.Comment: 24 pages, accepted by MNRA
Kinematics of gas and stars in the circumnuclear starforming ring of NGC 3351
We have measured gas and stellar velocity dispersions in 5 circumnuclear
starforming regions (CNSFRs) and the nucleus of the barred spiral galaxy NGC
3351. The stellar dispersions have been obtained from high resolution spectra
of the CaT lines at 8494, 8542, 8662 \AA, while the gas
velocity dispersions have been measured by Gaussian fits to the H
4861 \AA line on high dispersion spectra.
The CNSFRs, with sizes of about 100 to 150 pc in diameter, are seen to be
composed of several individual star clusters with sizes between 1.7 and 4.9 pc
on an HST image. Using the stellar velocity dispersions, we have derived
dynamical masses for the entire starforming complexes and for the individual
star clusters. Values of the stellar velocity dispersions are between 39 and 67
km s. Dynamical masses for the whole CNSFRs are between 4.9
10 and 4.3 10 M and between 1.8 and 8.7
10 M for the individual star clusters.
Stellar and gas velocity dispersions are found to differ by about 20 km
s with the H lines being narrower than both the stellar lines and
the [O{\sc iii}] 5007 \AA lines. We have found indications for the
presence of two different kinematical components in the ionised gas of the
regions. The radial velocity curve shows deviation from circular motions for
the ionised hydrogen consistent with its infall towards the central regions of
the galaxy at a velocity of about 25 km s. To disentangle the origin of
these two components it will be necessary to map these regions with high
spectral and spatial resolution and much better S/N in particular for the
O lines.Comment: 17 pages, 13 figures, 7 tables - Accepted by MNRA
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