Some topics in the theory of generalized fc-groups

2009 - 2010A finiteness condition is a group-theoretical property which is possessed by all finite groups: thus it is a generalization of finiteness. This embraces an immensely wide collection of properties like, for example, finiteness, finitely generated, the maximal condition and so on. There are also numerous finiteness conditions which restrict, in some way, a set of conjugates or a set of commutators in a group. Sometimes these restrictions are strong enough to impose a recognizable structure on the group. R. Baer and B.H. Neumann were the first authors to discuss groups in which there is a limitation on the number of conjugates which an element may have. An element x of a group G is called FC-element of G if x has only a finite number of conjugates in G, that is to say, if |G : CG(x)| is finite or, equivalently, if the factor group G/CG(⟨x⟩G) is finite. It is a basic fact that the FC-elements always form a characteristic subgroup. An FC-element may be thought as a generalization of an element of the center of the group, because the elements of the latter type have just one conjugate. For this reason the subgroup of all FC-elements is called the FC-center and, clearly, always contains the center. A group G is called an FC-group if it equals its FC-center, in other words, every conjugacy class of G is finite. Prominent among the FC-groups are groups with center of finite index: in such a group each centralizer must be of finite index, because it contains the center. Of course in particular all abelian groups and all finite groups are FC-groups. Further examples of FC-groups can be obtained by noting that the class of FC-groups is closed with respect to forming subgroups, images and direct products. The theory of FC-groups had a strong development in the second half of the last century and relevant contributions have been given by several important authors including R. Baer, B.H. Neumann, Y.M. Gorcakov, Chernikov,L.A. Kurdachenko, and many others. We shall use the monographs , as a general reference for results on FC-groups. The study of FC-groups can be considered as a natural investigation on the properties common to both finite groups and abelian groups. A particular interest has been devoted to groups having many FC-subgroups or many FC-elements. [edited by the author]IX n.s

A spherical model with directional interactions: I. Static properties

We introduce a simple spherical model whose structural properties are similar to the ones generated by models with directional interactions, by employing a binary mixture of large and small hard spheres, with a square-well attraction acting only between particles of different size. The small particles provide the bonds between the large ones. With a proper choice of the interaction parameters, as well as of the relative concentration of the two species, it is possible to control the effective valence. Here we focus on a specific choice of the parameters which favors tetrahedral ordering and study the equilibrium static properties of the system in a large window of densities and temperatures. Upon lowering the temperature we observe a progressive increase in local order, accompanied by the formation of a four-coordinated network of bonds. Three different density regions are observed: at low density the system phase separates into a gas and a liquid phase; at intermediate densities a network of fully bonded particles develops; at high densities -- due to the competition between excluded volume and attractive interactions -- the system forms a defective network. The very same behavior has been previously observed in numerical studies of non-spherical models for molecular liquids, such as water, and in models of patchy colloidal particles. Differently from these models, theoretical treatments devised for spherical potentials, e.g. integral equations and ideal mode coupling theory for the glass transition can be applied in the present case, opening the way for a deeper understanding of the thermodynamic and dynamic behavior of low valence molecules and particles.Comment: 11 pages, 11 figure

Age-related variations in the growth hormone response to growth hormone secretagogues

Growth hormone (GH) secretagogues are synthetic peptidyl and non-peptidyl molecules which possess a strong, dose-dependent and reproducible GH-releasing effect after intravenous and even oral administration in humans. This effect is probably mediated via the activation of specific receptors, mainly present at the pituitary and hypothalamic level; a human pituitary GH secretogogue receptor has already been cloned, pointing to the existence of an endogenous GH secretagogue-like ligand. The GH-releasing effect of GH secretagogues is gender-independent but undergoes marked age-related variations. In fact, the effect is low at birth, increases markedly at puberty, persists at a similar level in adulthood and decreases thereafter, being already similar in middle age to that in elderly subjects. It is likely that the reduced activity of GH secretagogues in aging reflects the age-related changes in the neural control of somatotrope function. These could include the hypothetical impairment in the activity of the p..

Preliminary study on kinetics of pyroglutamic acid formation in fermented milk

Pyroglutamic acid (pGlu) influences the aromatic and sensory properties of foods and has several benefits for human health. The presence and kinetics of pGlu formation in fermented milk samples were investigated from a chemical point of view. Plain yoghurt, kefir and other probiotic fermented milk products available on the market were analysed to quantify lactic acid and pGlu. The pGlu concentrations in fermented milks ranged from 51.65 to 277.37 mg 100 g-1 dry matter. Laboratory- scale fermented milk was produced, and samples were taken at different times of fermentation and storage to construct the kinetics curve. At the beginning of the fermentation process, pGlu was already present in UHT milk (188.69 mg 100 g-1 dry matter) used to elaborate fermented milk, and its content increased not only during fermentation but during storage as well, reaching up to 403.56 mg 100 g-1 dry matter after 30 days

Self-assembly scenarios of patchy colloidal particles

The rapid progress in precisely designing the surface decoration of patchy colloidal particles offers a new, yet unexperienced freedom to create building entities for larger, more complex structures in soft matter systems. However, it is extremely difficult to predict the large variety of ordered equilibrium structures that these particles are able to undergo under the variation of external parameters, such as temperature or pressure. Here we show that, by a novel combination of two theoretical tools, it is indeed possible to predict the self-assembly scenario of patchy colloidal particles: on one hand, a reliable and efficient optimization tool based on ideas of evolutionary algorithms helps to identify the ordered equilibrium structures to be expected at T = 0; on the other hand, suitable simulation techniques allow to estimate via free energy calculations the phase diagram at finite temperature. With these powerful approaches we are able to identify the broad variety of emerging self-assembly scenarios for spherical colloids decorated by four patches and we investigate and discuss the stability of the crystal structures on modifying in a controlled way the tetrahedral arrangement of the patches.Comment: 11 pages, 7 figures, Soft Matter Communication (accepted

Chlamydia pneumoniae clinical isolate from gingival crevicular fluid: a potential atherogenic strain

Chlamydia pneumoniae has been associated to atherosclerotic cardiovascular diseases. The aim of our study was to characterize, for the first time, a C. pneumoniae strain isolated from the gingival crevicular fluid of a patient with chronic periodontitis, described as a risk factor for cardiovascular diseases. C. pneumoniae isolate was characterized and compared to the respiratory AR-39 strain by VD4-ompA genotyping and by investigating the intracellular growth in epithelial and macrophage cell lines and its ability to induce macrophage-derived foam cells. Inflammatory cytokine levels were determined in the gingival crevicular fluid sample. C. pneumoniae isolate showed a 99% similarity with the AR-39 strain in the VD4-ompA gene sequence and shared a comparable growth kinetic in epithelial cells and macrophages, as evidenced by the infectious progeny and by the number of chlamydial genomic copies. C. pneumoniae isolate significantly increased the number of foam cells as compared to uninfected and LDL-treated macrophages (45 vs. 6%, P = 0.0065) and to the AR-39 strain (45 vs. 30%, P = 0.0065). Significantly increased levels of interleukin 1-β (2.1 ± 0.3 pg/μL) and interleukin 6 (0.6 ± 0.08 pg/μL) were found. Our results suggest that C. pneumoniae may harbor inside oral cavity and potentially be atherogenic, even though further studies will be needed to clarify the involvement of C. pneumoniae in chronic periodontitis as a risk factor for cardiovascular diseases

A Screen for Kinetochore-Microtubule Interaction Inhibitors Identifies Novel Antitubulin Compounds

Protein assemblies named kinetochores bind sister chromatids to the mitotic spindle and orchestrate sister chromatid segregation. Interference with kinetochore activity triggers a spindle checkpoint mediated arrest in mitosis, which frequently ends in cell death. We set out to identify small compounds that inhibit kinetochore-microtubule binding for use in kinetochore-spindle interaction studies and to develop them into novel anticancer drugs

Frontiers of light manipulation in natural, metallic, and dielectric nanostructures

AbstractThe ability to control light at the nanoscale is at the basis of contemporary photonics and plasmonics. In particular, properly engineered periodic nanostructures not only allow the inhibition of propagation of light at specific spectral ranges or its confinement in nanocavities or waveguides, but make also possible field enhancement effects in vibrational, Raman, infrared and fluorescence spectroscopies, paving the way to the development of novel high-performance optical sensors. All these devices find an impressive analogy in nearly-periodic photonic nanostructures present in several plants, animals and algae, which can represent a source of inspiration in the development and optimization of new artificial nano-optical systems. Here we present the main properties and applications of cutting-edge nanostructures starting from several examples of natural photonic architectures, up to the most recent technologies based on metallic and dielectric metasurfaces

Cell Toxicity Study of Antiseptic Solutions Containing Povidone-Iodine and Hydrogen Peroxide

The increasing incidence of periprosthetic joint infections (PJIs) has led to a growing interest in developing strategies to prevent and treat this severe complication. The surgical site's application of antiseptic solutions to eliminate contaminating bacteria and eradicate the bacterial biofilm has been increasing over time. Even though it has been proven that combining antimicrobials could enhance their activities and help overcome acquired microbial resistance related to the topical use of antibiotics, the toxicity of integrated solutions is not well described. This study aimed to evaluate the cytotoxicity of solutions containing povidone-iodine (PI) and hydrogen peroxide (H2O2), alone or in combination, after 1.3 and 5 min of exposure. Chondrocytes, tenocytes, and fibroblast-like synoviocytes were used for cytotoxicity analysis. Trypan blue stain (0.4% in PBS) was applied to evaluate the dead cells. All solutions tested showed a progressive increase in toxicity as exposure time increased except for PI at 0.3%, which exhibited the lowest toxicity. The combined solutions reported a reduced cellular killing at 3 and 5 min than H2O2 at equal concentrations, similar results to PI solutions

Health technology assessment of pathogen reduction technologies applied to plasma for clinical use

Although existing clinical evidence shows that the transfusion of blood components is becoming increasingly safe, the risk of transmission of known and unknown pathogens, new pathogens or re-emerging pathogens still persists. Pathogen reduction technologies may offer a new approach to increase blood safety. The study is the output of collaboration between the Italian National Blood Centre and the Post-Graduate School of Health Economics and Management, Catholic University of the Sacred Heart, Rome, Italy. A large, multidisciplinary team was created and divided into six groups, each of which addressed one or more HTA domains.Plasma treated with amotosalen + UV light, riboflavin + UV light, methylene blue or a solvent/detergent process was compared to fresh-frozen plasma with regards to current use, technical features, effectiveness, safety, economic and organisational impact, and ethical, social and legal implications. The available evidence is not sufficient to state which of the techniques compared is superior in terms of efficacy, safety and cost-effectiveness. Evidence on efficacy is only available for the solvent/detergent method, which proved to be non-inferior to untreated fresh-frozen plasma in the treatment of a wide range of congenital and acquired bleeding disorders. With regards to safety, the solvent/detergent technique apparently has the most favourable risk-benefit profile. Further research is needed to provide a comprehensive overview of the cost-effectiveness profile of the different pathogen-reduction techniques. The wide heterogeneity of results and the lack of comparative evidence are reasons why more comparative studies need to be performed