Standard map in magnetized relativistic systems: fixed points and regular acceleration

We investigate the concept of a standard map for the interaction of relativistic particles and electrostatic waves of arbitrary amplitudes, under the action of external magnetic fields. The map is adequate for physical settings where waves and particles interact impulsively, and allows for a series of analytical result to be exactly obtained. Unlike the traditional form of the standard map, the present map is nonlinear in the wave amplitude and displays a series of peculiar properties. Among these properties we discuss the relation involving fixed points of the maps and accelerator regimes.Comment: Work to appear in Phys. Rev. E. 2 figure

Alternate islands of multiple isochronous chains in wave-particle interactions

We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinite number of perturbative terms with the same winding number, which may generate islands in the same region of phase space. As a consequence, the number of isochronous island chains varies as a function of the wave parameters. We observe that in all the resonances, the number of chains is related to the amplitude of the various resonant terms. We determine analytically the position of the periodic points and the number of island chains as a function of the wave number and wave period. Such information is very important when one is concerned with regular particle acceleration, since it is necessary to adjust the initial conditions of the particle to obtain the maximum acceleration.Comment: Submitte

Nickel (0) complexes as promising chemosensors for detecting the “cork taint” in wine

2,4,6-Trichloroanisole (TCA) is well recognized as one of the most responsible molecules of cork taint, an organoleptic defect of wine which represents a serious problem for wine industries. Up to now, very few examples of TCA-biosensors have been developed and we report herein a promising nickel (0) complex that can be employed as chemosensor for the TCA detection in cork stoppers. Among the three Ni (0) complexes studied in this work, complex Ni(0)(BINAP)(η2-PhCN) (2) showed the best reactivity towards pure TCA affording the oxidative addition product 4 in four hours at room temperature. Compound 4 represents an appealing probe for the indirect quantification of TCA due to the presence of the characteristic UV-adsorption band at 444 nm. Statistical studies on real samples confirmed that the presence of TCA can be detected by employing UV-Visible spectroscopy, as demonstrated by PCA analyses which allowed distinguishing TCA-contaminated samples from non-contaminated ones. Even if the present study has to be considered a preliminary approach for the realization of a chemosensor usable in real systems, the here reported Ni (0)-based sensing procedure represents the first examples of TCA chemical detection

Hyperbaric oxygen therapy improves the osteogenic and vasculogenic properties of mesenchymal stem cells in the presence of inflammation in vitro

Hyperbaric oxygen (HBO) therapy has been reported to be beneficial for treating many conditions of inflammation-associated bone loss. The aim of this work was to in vitro investigate the effect of HBO in the course of osteogenesis of human Mesenchymal Stem Cells (MSCs) grown in a simulated pro-inflammatory environment. Cells were cultured with osteogenic differentiation factors in the presence or not of the pro-inflammatory cytokine Tumor Necrosis Factor-α (TNF-α), and simultaneously exposed daily for 60 min, and up to 21 days, at 2,4 atmosphere absolute (ATA) and 100% O2. To elucidate osteogenic differentiation-dependent effects, cells were additionally pre-committed prior to treatments. Cell metabolic activity was evaluated by means of the MTT assay and DNA content quantification, whereas osteogenic and vasculogenic differentiation was assessed by quantification of extracellular calcium deposition and gene expression analysis. Metabolic activity and osteogenic properties of cells did not differ between HBO, high pressure (HB) alone, or high oxygen (HO) alone and control if cells were pre-differentiated to the osteogenic lineage. In contrast, when treatments started contextually to the osteogenic differentiation of the cells, a significant reduction in cell metabolic activity first, and in mineral deposition at later time points, were observed in the HBO-treated group. Interestingly, TNF-α supplementation determined a significant improvement in the osteogenic capacity of cells subjected to HBO, which was not observed in TNF-α-treated cells exposed to HB or HO alone. This study suggests that exposure of osteogenic-differentiating MSCs to HBO under in vitro simulated inflammatory conditions enhances differentiation towards the osteogenic phenotype, providing evidence of the potential application of HBO in all those processes requiring bone regeneration

Statistical Mechanics of Unbound Two Dimensional Self-Gravitating Systems

We study, using both theory and molecular dynamics simulations, the relaxation dynamics of a microcanonical two dimensional self-gravitating system. After a sufficiently large time, a gravitational cluster of N particles relaxes to the Maxwell-Boltzmann distribution. The time to reach the thermodynamic equilibrium, however, scales with the number of particles. In the thermodynamic limit, $N\to\infty$ at fixed total mass, equilibrium state is never reached and the system becomes trapped in a non-ergodic stationary state. An analytical theory is presented which allows us to quantitatively described this final stationary state, without any adjustable parameters

Advances in Materials and Technologies for Gas Sensing from Environmental and Food Monitoring to Breath Analysis

Gas sensing research experiences a worldwide revival in the last years. From one side, the emergence of novel sensing materials enables unprecedented capacities for improving the device performances. From the other, the increasing opportunities for applications impacting current societal priorities highly motivate further studies. Here, this field is reviewed with special attention to the emerging approaches and the most recent breakthroughs, challenges, and perspectives. In particular, this study focuses on: 1) the sensing layers analyzing recent trends toward nanostructured, low-dimensional and composite materials; and 2) the latest achievements and targets in terms of applications, from environmental monitoring to food aroma identification and quality control up to the healthcare sector with breath analysis and diseases diagnosis

Hyphal morphology, molecular genetics and phylogenetic relationships among commensal and pathogenic vulvovaginal isolates of Candida albicans

Vaginal candidiasis is a common disorder in women of childbearing age, caused primarily by Candida albicans. Since C. albicans is a commensal fungus of the vaginal mucosa, a long-standing question is how the fungus switches from being a harmless commensal to a virulent pathogen. Clinical studies and murine vaginitis models suggest that host inflammatory processes drive the onset of symptomatic infection. In previous work with fresh clinical samples, we found that the pro-inflammatory cell wall polysaccharide β-glucan is largely masked from immune recognition during vulvovaginal infection. Enhanced β-glucan availability was only found in hyphae from symptomatic patients with strong neutrophil infiltration. There was high variability in levels of β-glucan exposure and hyphal morphology among colonizing and infection-associated isolates, and we reasoned that this could be explained by fungal-intrinsic factors and/or host-associated traits. We assayed several aspects of C. albicans isolated from symptomatic and asymptomatic individuals to determine any associations between fungal-intrinsic traits and virulence: MLST analysis, sequencing of the gene encoding the candidalysin toxin, and propensity to form hyphal cells. Preliminary results suggest that none of these indicators correlates with isolates causing symptomatic infection, indicating that host-intrinsic mechanisms may play the most important role in the occurrence of symptomatic infections

POMC and TP53 genetic variability and risk of basal cell carcinoma of skin: Interaction between host and genetic factors.

Background: Basal cell carcinoma (BCC) of the skin is the most common neoplasm among the Caucasian population of the western world. Ultraviolet (UV) radiation-induced p53 activation promotes cutaneous pigmentation by increasing transcriptional activity of pro-opiomelanocortin (POMC) in the skin. Induction of POMC/-melanocyte-stimulating hormone (α-MSH) activates the melanocortin 1 receptor (MC1R), resulting in skin pigmentation. The tumor suppressor p53 is a key player in stress responses that preserve genomic stability, responding to a variety of insults including DNA damage, hypoxia, metabolic stress and oncogene activation. Malfunction of the p53 pathway is an almost universal hallmark of human tumors. Polymorphisms in the gene encoding p53 (TP53) alter its transcriptional activity, which in turn may influence the UV radiation-induced tanning response. Objective: The aim of the present work is to test association between POMC and TP53 genetic variability, the possible interplay with host factors and the risk of basal cell carcinoma of skin. Methods: We covered the variability of the two genes we used 17 tagging polymorphisms in 529 BCC cases and 532 healthy controls. We have also tested the possible interactions between the genetic variants and three known risk factors for BCC: skin complexion, sun effect and skin response to sun exposure. Results: We did not observe any statistically significant association between SNPs in these two genes and BCC risk overall, nor interactions of SNPs with known BCC risk factors. However we found that, in the group of subjects with lower sun exposure, carriers of one copy of the C allele of the TP53 SNP rs12951053 had a decreased risk of BCC (OR = 0.28, 95% CI 0.12-0.62, P= 0.002). Conclusions: We have observed that the interplay of an environmental risk factor and one polymorphism in TP53 gene could modulate the risk of BCC

Role of OPRM1, clinical and anthropometric variants in neonatal pain reduction

An increased awareness on neonatal pain-associated complications has led to the development of pain scales adequate to assess the level of pain experienced by newborns such as the ABC score. A commonly used analgesic procedure is to administer a 33% oral dextrose solution to newborns prior to the painful intervention. Although this procedure is very successful, not in all subjects it reaches complete efficacy. A possible explanation for the different response to the treatment could be genetic variability. We have investigated the genetic variability of the OPRM1 gene in 1077 newborns in relation to non-pharmacologic pain relief treatment. We observed that the procedure was successful in 966 individuals and there was no association between the genotypes and the analgesic efficacy when comparing individuals that had an ABC score = 0 and ABC score >0. However, considering only the individuals with ABC score>0, we found that the homozygous carriers of the G allele of the missense variant SNP rs1799971 (A118G) showed an interesting association with higher ABC score. We also observed that individuals fed with formula milk were more likely to not respond to the analgesic treatment compared to those that had been breastfed