Papers by Luis campos cuellar Campos
Código de Responsabilidad Civil Legislación Comentarios y Jurisprudencia
arXiv (Cornell University), May 19, 2020
The solution in hyperspherical coordinates for N dimensions is given for a general class of parti... more The solution in hyperspherical coordinates for N dimensions is given for a general class of partial differential equations of mathematical physics including the Laplace, wave, heat and Helmholtz, Schrödinger, Klein-Gordon and telegraph equations and their combinations. The starting point is the Laplacian operator specified by the scale factors of hyperspherical coordinates. The general equation of mathematical physics is solved by separation of variables leading to the dependencies: (i) on time by the usual exponential function; (ii) on longitude by the usual sinusoidal function; (iii) on radius by Bessel functions of order generally distinct from cylindrical or spherical Bessel functions; (iv) on one latitude by associated Legendre functions; (v) on the remaining latitudes by an extension, namely the hyperspherical associated Legendre functions. The original associated Legendre functions are a particular case of the Gaussian hypergeometric functions, and the hyperspherical associated Legendre functions are also a more general particular case of the Gaussian hypergeometric functions so that it is not necessary to consider extended Gaussian hypergeometric functions.
Aerospace
The separation of aircraft in cruising flight in air corridors is based on the assurance of an ex... more The separation of aircraft in cruising flight in air corridors is based on the assurance of an extremely low probability of collision due to position inaccuracy caused by navigation errors, atmospheric disturbances, or other factors. The appropriate standard is the International Civil Aviation Organization (ICAO) Target Level of Safety (TLS) of frequency of collision less than 5 × 10−9 per flight hour. An upper bound for the collision probability per unit distance is the probability of coincidence, in the case of aircraft flying at the same speed along parallel tracks in the same direction. This leads to the case of two aircraft flying at a constant separation, for which at least three probabilities of coincidence can be calculated: (i) the maximum probability of coincidence at the most likely point; (ii) the cumulative probability of coincidence integrated along the flight path; and (iii) the cumulative probability of coincidence integrated over all space. These three probabilities...
A blended-wing-body is an example of an aircraft configuration with multiple control surfaces. Th... more A blended-wing-body is an example of an aircraft configuration with multiple control surfaces. The most effective use of these control surfaces, e.g. to minimize cruise drag due to pitch trim, or to maximize pitching moment at low speed in an engine-out condition, leads to optimization problems. The method investigated is this paper is applied to multiple control surfaces, taking into account their mutual interactions and also the influence of shifts of center of gravity. It is shown in a particular case that it is possible to achieve pitch trim in cruise with drag reduction relative to the untrimmed case.
A key aspect of Air Traffic Management in the future is to determine (i) the technical requiremen... more A key aspect of Air Traffic Management in the future is to determine (i) the technical requirements to (ii) ensure safety with (iii) increased capacity. The methods to calculate collision probabilities have been applied to reduced vertical separation minima, to lateral separation, to crossing aircraft to free flight and to flight in terminal areas. In the present paper the cumulative probability of coincidence (CPC) is calculated for comparison with the ICAO Alternative Target Level of Safety (ATLS) probability of collision per nautical mile. The comparison of the CPC with the ATLS is made for four typical cruise flight conditions.
The noise of jet and rocket engines involves the coupling of sound to swirling flows and to heat ... more The noise of jet and rocket engines involves the coupling of sound to swirling flows and to heat exchanges leading in the more complex cases of triple interactions to acoustic-vorticalentropy (AVE) waves. The present paper presents as far as the authors are aware the first derivation of the AVE equation for axisymmetric linear non-dissipative perturbations of a compressible, non-isentropic, swirling mean flow, with constant axial velocity and constant angular velocity. The axisymmetric AVE wave equation is obtained for the radial velocity perturbation, specifying its radial dependence for a given frequency and axial wavenumber. The AVE wave equation in the case of zero axial wavenumber has only one singularity at the critical radius, where the isothermal Mach number for the swirl velocity is unity. The exact solution of the AVE wave equation is obtained as series expansions of Gaussian hypergeometric type valid inside, outside and around the critical layer, thus: (i) covering the wh...
Aerospace, 2021
The coupling of the longitudinal and lateral stability modes of an aeroplane is considered in two... more The coupling of the longitudinal and lateral stability modes of an aeroplane is considered in two cases: (i) weak coupling, when the changes in the frequency and damping of the phugoid, short period, dutch roll, and helical modes are small, i.e., the square of the deviation is negligible compared to the square of the uncoupled value; (ii) strong coupling, when the coupled values may differ significantly from the uncoupled values. This allows a comparison of three values for the frequency and damping of each mode: (i) exact, i.e., fully coupled; (ii) with the approximation of weak coupling; (iii) with the assumption of decoupling. The comparison of these three values allows an assessment of the importance of coupling effects. The method is applied to two flying wing designs, concerning all modes in a total of eighteen flight conditions. It turns out that lateral-longitudinal coupling is small in all cases, and thus classical handling qualities criteria can be applied. The handling qu...
Journal of Advanced Transportation, 2018
The paper presents methods to determine the time, positions, and distance of closest approach for... more The paper presents methods to determine the time, positions, and distance of closest approach for two vehicles following arbitrary trajectories in two or three dimensions. The distance of closest approach of two vehicles following arbitrary curved trajectories is determined by two conditions: (i) the relative velocity must be orthogonal to the relative position in order for the distance to be a nonzero extremum; (ii) the radial acceleration including centripetal terms must have a direction that increases the separation for the extremum to be a minimum. This theorem on the distance of closest approach simplifies in the case of uniform motion along rectilinear trajectories. Three examples are given: (i) the two-dimensional motion of surface vehicles changing the velocity of one of them so as to enforce a given minimum separation distance; (ii) the three-dimensional motion of two aircraft, one flying horizontally and the other climbing, changing the vertical velocity of the latter to e...
Nefrología, 2016
Background: Albuminuria was widely considered as the first clinical sign of diabetic kidney disea... more Background: Albuminuria was widely considered as the first clinical sign of diabetic kidney disease (DKD), which is why it has traditionally been used as a screening test for DKD. However, increasing evidence has shown that a significant number of type 2 diabetes mellitus (DM) patients have a decreased glomerular filtration rate (GFR) without significant albuminuria, known as non-albuminuric DKD (NA-DKD). The aim of this study was to determine the prevalence and the demographic and clinical characteristics of patients with NA-DKD. Methods: This was a 1-year retrospective study that included 146 type 2 diabetic patients with GFR < 75 mL/min followed-up in a diabetes outpatient department. Patients were divided into two groups according to their ACR status -NA-DKD and albuminuric DKD (A-DKD). Results: Of the 146 patients included in the study, 53.4% had A-DKD and 46.6% had NA-DKD. According to the multivariable analysis performed, patients with NA-DKD tended to be older (p = 0.021), female (p = 0.045) and with a lower GFR (p = 0.004) than A-DKD patients. There was no difference between the groups in terms of body mass index, metabolic control of DM, duration of DM diagnosis and prevalence of metabolic syndrome. The majority of patients with DKD had albuminuria, but a significant proportion had a non-albuminuric phenotype (46.6% in this population). These patients exhibit distinct clinical features that could have screening, therapeutic and prognosis implications.
Proceedings 35th Annual Simulation Symposium. SS 2002
A novel simulation framework is described that uses a client-server paradigm combined with a disc... more A novel simulation framework is described that uses a client-server paradigm combined with a discrete event simulator to allow the simulation modules to be distributed around a centralized core. The framework also simplifies the creation of new simulations by achieving the goals of being general purpose, easily extensible, modular, and distributed. A prototype of the Client-Server Discrete Event Simulator (CS-DEVS) has been developed as a proof of concept. Two examples are presented to demonstrate the power of the new paradigm and prove the correctness of CS-DEVS. The first example is a modeling of the classical bank queuing simulation. The second example models the simulation of a distributed computing system, with complete modules for workload generation, architecture description, and scheduling and load balancing algorithms.
A lower bound for dynamic scheduling of data parallel programs
Lecture Notes in Computer Science, 1998
Page 1. A Lower Bound for Dynamic Scheduling of Data Parallel Programs Fabricio Alves Barbosa da ... more Page 1. A Lower Bound for Dynamic Scheduling of Data Parallel Programs Fabricio Alves Barbosa da Silva2⋆ , Luis Miguel Campos1⋆⋆ , and Isaac D. Scherson1,2⋆⋆⋆ 1 Information and Comp. Science, University of California ...
Cytochrome c 6 (Cyt) from the thermophilic cyanobacterium Phormidium laminosum has been purified ... more Cytochrome c 6 (Cyt) from the thermophilic cyanobacterium Phormidium laminosum has been purified and characterized. It is a mildly acidic protein, with physicochemical properties very similar to those of plastocyanin (Pc). This is in agreement with the functional interchangeability of the two metalloproteins as electron donors to Photosystem I (PS I). The kinetic analyses of the interaction of Pc and Cyt with Photosystem I show that both metalloproteins reduce PS I with similar efficiencies, according to an oriented collisional kinetic model involving repulsive electrostatic interactions. The thermostability study of the Phormidium Pc/PS I system compared with those from mesophilic cyanobacteria (Synechocystis, Anabaena and Pseudanabaena) reveals that Pc is the partner limiting the thermostability of the Phormidium couple. The cross-reactions between Pc and PS I from different organisms demonstrate not only that Phormidium Pc enhances the stability of the Pc/PS I system using PS I from mesophilic cyanobacteria, but also that Phormidium PS I possesses a higher thermostability than the other photosystems.
Framework for personal tv
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2009
Journal of managed care pharmacy : JMCP, 2007
Colony-stimulating factors (CSFs) significantly decrease the risk of febrile neutropenia (FN), a ... more Colony-stimulating factors (CSFs) significantly decrease the risk of febrile neutropenia (FN), a common complication of myelosuppressive chemotherapy. Pegfilgrastim (6 mg), introduced in 2002, has a sustained duration of action, with a single dose comparable in efficacy to daily injections of filgrastim (5 g per kg per day) for 10 to 11 days; both agents should be initiated 24 hours after completing chemotherapy. To (1) describe the use of pegfilgrastim and filgrastim in oncology practices throughout the United States and (2) compare their effectiveness in actual practice as measured by the outcome of febrile neutropenia in patients who received chemotherapy regimens administered every 3 to 4 weeks for breast, lung, ovarian, colon cancer, or lymphoma and who received a CSF prior to developing FN. Data were retrospectively obtained from the medical records of a cohort of adult patients aged 18 years or older treated in 99 community oncology practices in the United States in 2001 and ...
PloS one, 2013
A battery of thermodynamic, kinetic, and structural approaches has indicated that the small α-hel... more A battery of thermodynamic, kinetic, and structural approaches has indicated that the small α-helical protein BBL folds-unfolds via the one-state downhill scenario. Yet, single-molecule fluorescence spectroscopy offers a more conflicting view. Single-molecule experiments at pH 6 show a unique half-unfolded conformational ensemble at mid denaturation, whereas other experiments performed at higher pH show a bimodal distribution, as expected for two-state folding. Here we use thermodynamic and laser T-jump kinetic experiments combined with theoretical modeling to investigate the pH dependence of BBL stability, folding kinetics and mechanism within the pH 6-11 range. We find that BBL unfolding is tightly coupled to the protonation of one of its residues with an apparent pKa of ~ 7. Therefore, in chemical denaturation experiments around neutral pH BBL unfolds gradually, and also converts in binary fashion to the protonated species. Moreover, under the single-molecule experimental conditi...
Protein Science, 2002
Electrostatic contributions to the conformational stability of apoflavodoxin were studied by meas... more Electrostatic contributions to the conformational stability of apoflavodoxin were studied by measurement of the proton and salt-linked stability of this highly acidic protein with urea and temperature denaturation. Structure-based calculations of electrostatic Gibbs free energy were performed in parallel over a range of pH values and salt concentrations with an empirical continuum method. The stability of apoflavodoxin was higher near the isoelectric point (pH 4) than at neutral pH. This behavior was captured quantitatively by the structure-based calculations. In addition, the calculations showed that increasing salt concentration in the range of 0 to 500 mM stabilized the protein, which was confirmed experimentally. The effects of salts on stability were strongly dependent on cationic species: K + , Na + , Ca 2+ , and Mg 2+ exerted similar effects, much different from the effect measured in the presence of the bulky choline cation. Thus cations bind weakly to the negatively charged surface of apoflavodoxin. The similar magnitude of the effects exerted by different cations indicates that their hydration shells are not disrupted significantly by interactions with the protein. Site-directed mutagenesis of selected residues and the analysis of truncation variants indicate that cation binding is not site-specific and that the cation-binding regions are located in the central region of the protein sequence. Three-state analysis of the thermal denaturation indicates that the equilibrium intermediate populated during thermal unfolding is competent to bind cations. The unusual increase in the stability of apoflavodoxin at neutral pH affected by salts is likely to be a common property among highly acidic proteins.
Protein Science, 2006
Although core residuesc an sometimesb er eplacedb ys horter ones withouti ntroducing significant ... more Although core residuesc an sometimesb er eplacedb ys horter ones withouti ntroducing significant changes in protein structure, the energetic consequences are typically large andd estabilizing. Many efforts have been devoted to understand and predict changes in stabilityf rom analysis of the environment of mutatedr esidues,b ut the relationshipsp roposed fori ndividualp roteins have often failed to describe additionaldata. We report here 17 apoflavodoxin large-to-small mutations that cause overall protein destabilizations of 0.6-3.9k cal.mol ÿ 1 .B yc omparing two-state urea andt hree-state thermal unfolding data, the overall destabilizations observed are partitioned intoe ffects on the N-to-I ando nt he I-to-U equilibria. In allc ases, thee quilibriumi ntermediate exerts a' 'buffering''e ffect that reduces thei mpact of the overall destabilization on theN-to-I equilibrium. Thep erformance of several structure-energeticsr elationships, proposed to explain the energetics of hydrophobic shortening mutations, hasb een evaluated by using an apoflavodoxin data setc onsisting of 14 mutations involving branching-conservative aliphatic side-chain shortenings andalarger data set, including similar mutations implemented in sevenmodel proteins. Our analysis showsthat the stability changes observed for anyofthe differenttypes of mutations (LA, IA, IV,and VA )ineither data set arebest explained by ac ombination of differential hydrophobicity ando ft he calculated volume of the modeled cavity (as previously observed for LA andI Am utations in lysozyme T4). In contrast, sequence conservation within the flavodoxin family,w hich is ag oodp redictorf or charge-reversal stabilizing mutations, does notp erform so well fora liphatic shortening ones.
Journal of Molecular Biology, 2004
The vast majority of our knowledge on protein stability arises from the study of simple two-state... more The vast majority of our knowledge on protein stability arises from the study of simple two-state models. However, proteins displaying equilibrium intermediates under certain conditions abound and it is unclear whether the energetics of native/intermediate equilibria is well represented in current knowledge. We consider here that the overall conformational stability of three-state proteins is made of a "relevant" term and a "residual" one, corresponding to the free energy differences of the native to intermediate (N-to-I) and intermediate to denatured (I-to-D) equilibria, respectively. The N-to-I free energy difference is considered to be the relevant stability because protein-unfolding intermediates are likely devoid of biological activity. We use surface charge optimisation to first increase the overall (N-to-D) stability of a model three-state protein (apoflavodoxin) and then investigate whether the stabilisation obtained is realised into relevant or into residual stability. Most of the mutations designed from electrostatic calculations or from simple sequence conservation analysis produce large increases in the overall stability of the protein. However, in most cases, this simply leads to similarly large increases of the residual stability. Two mutations, nevertheless, show a different trend and increase the relevant stability of the protein substantially. When all the mutations are mapped onto the structure of the apoflavodoxin thermal-unfolding intermediate (obtained independently by equilibrium f-analysis and NMR) they cluster perfectly so that the mutations increasing the relevant stability appear in the small unstructured region of the intermediate and the others in the native-like region. This illustrates the need for specific investigation of N-to-I equilibria and the structure of protein intermediates, and indicates that it is possible to rationally stabilise a protein against partial unfolding once the structure of the intermediate conformation is known, even if at low resolution.
Journal of Molecular Biology, 2004
Protein intermediates in equilibrium with native states may play important roles in protein dynam... more Protein intermediates in equilibrium with native states may play important roles in protein dynamics but, in cases, can initiate harmful aggregation events. Investigating equilibrium protein intermediates is thus important for understanding protein behaviour (useful or pernicious) but it is hampered by difficulties in gathering structural information. We show here that the f-analysis techniques developed to investigate transition states of protein folding can be extended to determine low-resolution threedimensional structures of protein equilibrium intermediates. The analysis proposed is based solely on equilibrium data and is illustrated by determination of the structure of the apoflavodoxin thermal unfolding intermediate. In this conformation, a large part of the protein remains close to natively folded, but a 40 residue region is clearly unfolded. This structure is fully consistent with the NMR data gathered on an apoflavodoxin mutant designed specifically to stabilise the intermediate. The structure shows that the folded region of the intermediate is much larger than the proton slow-exchange core at 25 8C. It also reveals that the unfolded region is made of elements whose packing surface is more polar than average. In addition, it constitutes a useful guide to rationally stabilise the native state relative to the intermediate state, a far from trivial task.
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Papers by Luis campos cuellar Campos