Relating correlation measures: the importance of the energy gap

The concept of correlation is central to all approaches that attempt the description of many-body effects in electronic systems. Multipartite correlation is a quantum information theoretical property that is attributed to quantum states independent of the underlying physics. In quantum chemistry, however, the correlation energy (the energy not seized by the Hartree-Fock ansatz) plays a more prominent role. We show that these two different viewpoints on electron correlation are closely related. The key ingredient turns out to be the energy gap within the symmetry-adapted subspace. We then use a few-site Hubbard model and the stretched H$_2$ to illustrate this connection and to show how the corresponding measures of correlation compare.Comment: 6 pages, 3 figure

Excitations of Quantum Many-Body Systems via Purified Ensembles: A Unitary-Coupled-Cluster-based Approach

State-average calculations based on mixture of states are increasingly being exploited across chemistry and physics as versatile procedures for addressing excitations of quantum many-body systems. If not too many states should need to be addressed, calculations performed on individual states is also a common option. Here we show how the two approaches can be merged into one method, dealing with a generalized yet single pure state. Implications in electronic structure calculations are discussed and for quantum computations are pointed out.Comment: 9 pages, additional calculatio

Implications of pinned occupation numbers for natural orbital expansions. I: Generalizing the concept of active spaces

The concept of active spaces simplifies the description of interacting quantum many-body systems by restricting to a neighbourhood of active orbitals around the Fermi level. The respective wavefunction ansatzes which involve all possible electron configurations of active orbitals can be characterized by the saturation of a certain number of Pauli constraints $0 \leq n_i \leq 1$, identifying the occupied core orbitals ($n_i=1$) and the inactive virtual orbitals ($n_j=0$). In Part I, we generalize this crucial concept of active spaces by referring to the generalized Pauli constraints. To be more specific, we explain and illustrate that the saturation of any such constraint on fermionic occupation numbers characterizes a distinctive set of active electron configurations. A converse form of this selection rule establishes the basis for corresponding multiconfigurational wavefunction ansatzes. In Part II, we provide rigorous derivations of those findings. Moroever, we extend our results to non-fermionic multipartite quantum systems, revealing that extremal single-body information has always strong implications for the multipartite quantum state. In that sense, our work also confirms that pinned quantum systems define new physical entities and the presence of pinnings reflect the existence of (possibly hidden) ground state symmetries

EVALUACIÓN FINANCIERA Y SOCIAL DEL PROYECTO SILVO-PASTORIL EN EL MUNICIPIO DE CACHIPAY- CUNDINAMARCA

El nivel de incertidumbre que se experimenta al momento de configurar y estructurar la idea inicial de cualquier proyecto es bastante alto, lo cual representa en muchos casos una barrera bastante fuerte para la preparación y posterior ejecución del mismo; y es precisamente aquí donde se debe reconocer la importancia de evaluar diferentes aspectos que tienen repercusión directa en la manera como se piensa materializar el escenario de cambio que se desea alcanzar con el proyecto.&nbsp

Mobile Network QoE-QoS Decision Making Tool for Performance Optimization in Critical Web Service

Regardless of the type of service that a company offers the customer satisfaction is a factor for success, if these services are in a highly competitive environment. This situation encourages companies to develop strategies to improve the Quality of the Experience (QoE) of their users. Strategies include improving their processes, or infrastructure for provisioning the services. Take these kind of decisions is very difficult because they ignore how the Key Performance Indicators (KPI) services are correlated with the information about user experience. This problem is approached from the perspective of mobile telecom operators, who have addressed this challenge through the Quality of Service (QoS) concept. Unfortunately, the QoS is only characterized by technical aspects, the user’s criteria are not included. Into a highly competitive environment, the user’s loyalty is a key component to be considered in the operator’s development plan. Nowadays, the mobile telecom operators focus their efforts to ensure not only the QoS but also the QoE. The aim of this paper was the develop a decision making tool that allows the mobile telco operators support their determinations about the maintenance of network infrastructure, as well as the expansion of the same, specifically for their critical web services; based in a correlated information between QoS and QoE. This tool was developed on the basis of the Pseudo Subjective Quality Assessment (PSQA) methodology

Development of a Novel Perfusable Solution for ex vivo Preservation: Towards Photosynthetic Oxygenation for Organ Transplantation

Oxygen is the key molecule for aerobic metabolism, but no animal cells can produce it, creating an extreme dependency on external supply. In contrast, microalgae are photosynthetic microorganisms, therefore, they are able to produce oxygen as plant cells do. As hypoxia is one of the main issues in organ transplantation, especially during preservation, the main goal of this work was to develop the first generation of perfusable photosynthetic solutions, exploring its feasibility for ex vivo organ preservation. Here, the microalgae Chlamydomonas reinhardtii was incorporated in a standard preservation solution, and key aspects such as alterations in cell size, oxygen production and survival were studied. Osmolarity and rheological features of the photosynthetic solution were comparable to human blood. In terms of functionality, the photosynthetic solution proved to be not harmful and to provide sufficient oxygen to support the metabolic requirement of zebrafish larvae and rat kidney slices. Thereafter, isolated porcine kidneys were perfused, and microalgae reached all renal vasculature, without inducing damage. After perfusion and flushing, no signs of tissue damage were detected, and recovered microalgae survived the process. Altogether, this work proposes the use of photosynthetic microorganisms as vascular oxygen factories to generate and deliver oxygen in isolated organs, representing a novel and promising strategy for organ preservation