Problems in the Lifshitz Theory of Atom-Wall Interaction

Problems in the Lifshitz theory of atom-wall interaction arise when the dc conductivity of dielectric wall is included into the model of the dielectric response. We review the low-temperature behavior of the free energy and entropy of dispersion interaction for both dielectric and metallic walls. Consistency of the obtained results with thermodynamics and experimental data is analyzed. Recent attempts to include the screening effects and diffusion currents into the Lifshitz theory are considered. It is shown that this leads to the violation of the Nernst heat theorem for wide classes of wall materials. The physical reasons for the emergence of thermodynamic and experimental inconsistencies are elucidated.Comment: 12 pages, 2 figures, style file ws-ijmpa.cls is use

Van der Waals interaction between microparticle and uniaxial crystal with application to hydrogen atoms and multiwall carbon nanotubes

The Lifshitz theory of the van der Waals force is extended for the case of an atom (molecule) interacting with a plane surface of an uniaxial crystal or with a long solid cylinder or cylindrical shell made of isotropic material or uniaxial crystal. For a microparticle near a semispace or flat plate made of an uniaxial crystal the exact expressions for the free energy of the van der Waals and Casimir-Polder interaction are presented. An approximate expression for the free energy of microparticle- cylinder interaction is obtained which becomes precise for microparticle-cylinder separations much smaller than cylinder radius. The obtained expressions are used to investigate the van der Waals interaction between hydrogen atoms (molecules) and graphite plates or multiwall carbon nanotubes. To accomplish this the behavior of graphite dielectric permittivities along the imaginary frequency axis is found using the optical data for the complex refractive index of graphite for the ordinary and extraordinary rays. It is shown that the position of hydrogen atoms inside multiwall carbon nanotubes is energetically preferable compared with outside.Comment: 23 pages, 8 figures, 2 tables. Minor corrections are made and new references added. Accepted for publication in Phys. Rev.

The role of cytokines in the development of systemic inflammation in chronic obstructive pulmonary disease and obesity

Patients with chronic obstructive pulmonary disease (COPD) are characterized by a variety of comorbid conditions, including both somatic (arterial hypertension, atherosclerosis, coronary heart disease, bronchial asthma, malignant  neoplasms, diabetes mellitus, obesity, etc.) and mental (depressive disorders, suicide attempts). Against the background  of various chronic diseases of the respiratory system, endocrine, metabolic disorders, the risks of exacerbations of COPD increase.The leading  unifying  mechanism  of these conditions  is systemic subclinical  inflammation. Its excessive activity leads to the loss of the physiological functions of inflammation, which is accompanied  by an imbalance  in the endocrine system and the release of high concentrations of hormones and neurotransmitters. The result of this response is the uncoupling of cytokine mechanisms, which leads to an imbalance in the system of pro- and anti-inflammatory cytokines.The article describes the role of the pro-inflammatory chemokine  IL-8 (interleukin 8), which is responsible for the migration of neutrophils to the site of inflammation. This is how the neutrophilic type of inflammation is formed. IL-4 and IL-10 are considered, which occupy a leading position in the formation of CD4+ type of immunoreactivity, which is observed in bronchial asthma. Attention is focused on the significance of IL-6, because it is an integral component of local and systemic inflammation. An increase in its concentration and, as a result, a potential risk of damage to the respiratory epithelium is the remodeling of the bronchial tree, resulting in a decrease in the elasticity of the epithelium of the respiratory tract. This mechanism leads to the formation of pulmonary emphysema and further potentiation of pathophysiological processes in patients with COPD.Since IL-6 is a cytokine with anti-inflammatory  properties, its molecular activity is achieved by interacting  with a special receptor complex consisting  of two subunits: IL-6R and gp130. The former mediates IL-6 binding, while the latter triggers the JAK/STAT or MAPK signaling  cascade pathways. The result of the reaction of IL-6 with the effector cell directly depends on the type of signaling.The paper describes three mechanisms of signal transduction into the target cell: classical, cluster, and transsignaling.Thus, by studying  the role of cytokines in the systemic inflammatory response, we have shown the cross-talk between adipose tissue and the lungs in obesity, highlighting the main inflammatory mediators, which may indicate new therapeutic targets for preventing pulmonary dysfunction

Van der Waals and Casimir interactions between atoms and carbon nanotubes

The van der Waals and Casimir interactions of a hydrogen atom (molecule) with a single-walled and a multiwalled carbon nanotubes are compared. It is shown that the macroscopic concept of graphite dielectric permittivity is already applicable for nanotubes with only two or three walls. The absorption of hydrogen atoms by a nanotube at separations below one nanometer is considered. The lateral force due to exchange repulsion moves the atom to a position above the cell center, where it is absorbed by the nanotube because the repulsive force cannot balance the van der Waals attraction.Comment: 9 pages, 2 figures, Proceedings of QFEXT07, to appear in J. Phys.

Exact Casimir-Polder potential between a particle and an ideal metal cylindrical shell and the proximity force approximation

We derive the exact Casimir-Polder potential for a polarizable microparticle inside an ideal metal cylindrical shell using the Green function method. The exact Casimir-Polder potential for a particle outside a shell, obtained recently by using the Hamiltonian approach, is rederived and confirmed. The exact quantum field theoretical result is compared with that obtained using the proximity force approximation and a very good agreement is demonstrated at separations below 0.1$R$, where $R$ is the radius of the cylinder. The developed methods are applicable in the theory of topological defects.Comment: 8 pages, 4 figures, Accepted for publication in Eur. Phys. J.