Search results for "CONSTANT"

Riemann’s Result and Consequences for Physics and Philosophy

2020

Riemann commented on his main result as follows: “The common character of those manifolds whose curvature is constant may also be expressed thus: that figures may be viewed in them without stretching. For clearly figures could not be arbitrarily shifted and turned around in them if the curvature at each point were not the same in all directions at one point as at another, and consequently the same constructions can be made from it; whence it follows that in aggregates with constant curvature, figures may have any arbitrary position given them. The measure-relations of these manifolds depend only on the value of the curvature, and in relation to the analytic expression it may be remarked tha…

Correction of the deviations in the retention times with Chromolith columns associated to the flow rate: Implications in the modelling of the retenti…

2011

In a previous work (J. Sep. Sci. 2009, 32, 2793-2803), we reported an interpretive optimisation approach to achieve maximal resolution in minimal analysis time, based on models describing the retention and peak shape as a function of mobile phase composition and flow rate. The method was applied to the separation of a group of basic drugs in a Chromolith column. In that work, we found that the retention factors were sensitive to the flow rate. The reason of the observed deviations in retention times is the increase in the column volume at the applied pressure, which decreases the linear velocity inside the column. This behaviour forced to include a correction term in the model that describe…

A new mathematical tool for an exact treatment of open quantum system dynamics

2005

A new method to obtain an operatorial exact solution of a wide class of Markovian master equations is presented. Its key point is the existence of a constant of motion partitioning the Hilbert space into finite-dimensional subspaces. The consequent possibility of representing the reduced density operator as a block diagonal matrix is shown. Each “block operator” evolves under the action of a non-unitary operator explicitly derived. Our mathematical approach is illustrated applying it to simple physical systems.

Chemotaxis and Haptotaxis on Cellular Level

2018

Chemotaxis and haptotaxis have been a main theme in the macroscopic study of bacterial and cellular motility. In this work, we use a successful model that describes cellular motility and investigate the influence these processes have on the shape and motility of fast migrating cells. We note that, despite the biological and modelling differences of chemotaxis and haptotaxis, the cells exhibit many similarities in their migration. In particular, after an initial adjustment phase, the cells obtain a stable shape, similar in both cases, and move with constant velocity.

Constantine X Doukas (1059–1067) versus Uzes – about the Nomads on Boats on the Danube in 1064

2021

The reign of the Doukas dynasty in 1059–1078 was a time when new threats to the Byzantine Empire emerge in Europe and Asia. One of them was the increased activity of Turkmen who were penetrating the lands belonging to the Byzantines. A manifestation of these threats was visible during the rule of Constantine X Doukas (1059–1067) in 1064. We have there an invasion of the tribe of Uzes, who crossed the Danube. They ventured so far, as the vicinity of Thessalonica and the province of Hellas, plundering everything in their path. Their actions surprised the defense of the Byzantines. This attack on the empire was related to their crossing of the Danube, about which Michael Attaliates and Skylitz…

Distinta relazione di un caso assai funesto avvenuto in Costantinopoli

2019

Historia verdadera del emperador Constantino el Magno, Aparicion, e invencion de la SSma. Cruz de Christo, y virtudes de Santa Elena Sacada de Eusebi…

Data presa de Palau Sign.: [A]-B2, C[8 Reclams Grav. xil. a la port. avant del tít., representant al Emperador Constantí

Density as a constraint and the separation of internal excitation energy in TDHF

1985

We present a fast and efficient constrained Hartree-Fock iteration scheme which constraints the complete density distribution to remain constant. The scheme is particularly suited to a coordinate- or momentum-space representation. The technique is applied to separate the collective and the internal energy in a propagating TDHF state. We study the behavior of these two energies in an16O+16O collision.

Optimal growth and land preservation

1997

A model of optimal economic growth with a constant population subject to a constraint on the availability of land is presented. It takes account of the dual character of land as a production factor and as a consumption good (environmental amenities) by determining the optimal intertemporal allocation of land between productive and recreational uses. An extension of the analysis for the case of a growing population with endogenous growth based on human capital accumulation shows that if the rate of discount is not very low then there exists a set of balanced growth paths compatible with a constant allocation of land. En este trabajo se presenta un modelo de crecimiento económico óptimo con u…

Symmetry breaking in a constrained cheeger type isoperimetric inequality

2015

We study the optimal constant in a Sobolev inequality for BV functions with zero mean value and vanishing outside a bounded open set. We are interested in finding the best possible embedding constant in terms of the measure of the domain alone. We set up an optimal shape problem and we completely characterize the behavior of optimal domains.