Spontaneous Conversion from Virtual to Real Photons in the Ultrastrong Coupling Regime

We show that a spontaneous release of virtual photon pairs can occur in a quantum optical system in the ultrastrong coupling regime. In this regime, which is attracting interest both in semiconductor and superconducting systems, the light-matter coupling rate {\Omega}R becomes comparable to the bare resonance frequency of photons {\omega}0. In contrast to the dynamical Casimir effect and other pair creation mechanisms, this phenomenon does not require external forces or time dependent parameters in the Hamiltonian.Comment: To appear on Phys. Rev. Let

Molecular Bremsstrahlung Radiation at GHz Frequencies in Air

A detection technique for ultra-high energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular Bremsstrahlung radiation emitted by low-energy ionization electrons left after the passage of the showers in the atmosphere. In this article, a detailed estimate of the spectral intensity of photons at ground level originating from this radiation is presented. The spectral intensity expected from the passage of the high-energy electrons of the cascade is also estimated. The absorption of the photons in the plasma of electrons/neutral molecules is shown to be negligible. The obtained spectral intensity is shown to be $2\times10^{-21}$W cm$^{-2}$ GHz$^{-1}$ at 10 km from the shower core for a vertical shower induced by a proton of $10^{17.5}$ eV. In addition, a recent measurement of Bremsstrahlung radiation in air at gigahertz frequencies from a beam of electrons produced at 95 keV by an electron gun is also discussed and reasonably reproduced by the model.Comment: 20 pages, 9 figures, figures (2,4,7) improved in v2, accepted by Phys. Rev.

Microenvironment in neuroblastoma: Isolation and characterization of tumor-derived mesenchymal stromal cells

Background: It has been proposed that mesenchymal stromal cells (MSCs) promote tumor progression by interacting with tumor cells and other stroma cells in the complex network of the tumor microenvironment. We characterized MSCs isolated and expanded from tumor tissues of pediatric patients diagnosed with neuroblastomas (NB-MSCs) to define interactions with the tumor microenvironment. Methods: Specimens were obtained from 7 pediatric patients diagnosed with neuroblastoma (NB). Morphology, immunophenotype, differentiation capacity, proliferative growth, expression of stemness and neural differentiation markers were evaluated. Moreover, the ability of cells to modulate the immune response, i.e. inhibition of phytohemagglutinin (PHA) activated peripheral blood mononuclear cells (PBMCs) and natural killer (NK) cytotoxic function, was examined. Gene expression profiles, known to be related to tumor cell stemness, Wnt pathway activation, epithelial-mesenchymal transition (EMT) and tumor metastasis were also evaluated. Healthy donor bone marrow-derived MSCs (BM-MSC) were employed as controls. Results: NB-MSCs presented the typical MSC morphology and phenotype. They showed a proliferative capacity superimposable to BM-MSCs. Stemness marker expression (Sox2, Nanog, Oct3/4) was comparable to BM-MSCs. NB-MSC in vitro osteogenic and chondrogenic differentiation was similar to BM-MSCs, but NB-MSCs lacked adipogenic differentiation capacity. NB-MSCs reached senescence phases at a median passage of P7 (range, P5-P13). NB-MSCs exhibited greater immunosuppressive capacity on activated T lymphocytes at a 1:2 (MSC: PBMC) ratio compared with BM-MSCs (p = 0.018). NK cytotoxic activity was not influenced by co-culture, either with BM-MSCs or NB-MSCs. Flow-cytometry cell cycle analysis showed that NB-MSCs had an increased number of cells in the G0-G1 phase compared to BM-MSCs. Transcriptomic profiling results indicated that NB-MSCs were enriched with EMT genes compared to BM-MSCs. Conclusions: We characterized the biological features, the immunomodulatory capacity and the gene expression profile of NB-MSCs. The NB-MSC gene expression profile and their functional properties suggest a potential role in promoting tumor escape, invasiveness and metastatic traits of NB cancer cells. A better understanding of the complex mechanisms underlying the interactions between NB cells and NB-derived MSCs should shed new light on potential novel therapeutic approaches

CdO-based nanostructures as novel CO2 gas sensors

Crystalline Cd(OH)2/CdCO3 nanowires, having lengths in the range from 0.3 up to several microns and 5–30 nm in diameter, were synthesized by a microwave-assisted wet chemical route and used as a precursor to obtain CdO nanostructures after a suitable thermal treatment in air. The morphology and microstructure of the as-synthesized and annealed materials have been investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and thermogravimetry–differential scanning calorimetry. The change in morphology and electrical properties with temperature has revealed a wire-to-rod transformation along with a decreases of electrical resistance. Annealed samples were printed on a ceramic substrate with interdigitated contacts to fabricate resistive solid state sensors. Gas sensing properties were explored by monitoring CO2 in synthetic air in the concentration range 0.2–5 v/v% (2000–50 000 ppm). The effect of annealing temperature, working temperature and CO2 concentration on sensing properties (sensitivity, response/recovery time and stability) were investigated. The results obtained demonstrate that CdO-based thick films have good potential as novel CO2 sensors for practical applications

A versatile ultrasound system for in vitro experiments

Objective One of the most difficult tasks to achieve with the available instrumentations used to study the interaction between ultrasound (US) and cellular model systems is to design an experiment, where only the effects of one physical parameter at a time is evaluated, while all the others are kept constant. The set-ups are usually custom-made, often by means of clinical instrument intended for a different therapeutic purpose. Furthermore, the results are not strictly comparable with others obtained with techniques considered standard in molecular and cellular biology at this time, because there is the need to use non-standard devices to contain biological samples. Sterility, as well as temperature, is not well controlled and reproducibility is usually a major concern. In our study we show the effects of ultrasound treatments on different cellular systems. The experiments are performed with a versatile bench-top US apparatus to be adapted for several in vitro experiments and that allows easy and robust reproducibility using standard set-ups for the cell samples. Methods One main feature of our bench-top US system is that it has been designed in order to use standard plasticware commonly used in molecular biology labs, ensuring the temperature control and sterility conditions needed in the field. We present a set-up where the simultaneous use of a set of transducers operating at different frequencies on the same plate, allows the comparison of the deposition of the same acoustic pressure, whilst evaluating the effect of frequency alone on the readout of the cell experiments. The apparatus modular design also allows the use of a set of transducers operating at the same frequency, in experiments where the throughput is a relevant factor. We demonstrate that it is possible to define the position of the target within all the achievable areas of the acoustic field with sub-millimetric accuracy. Tests for several applications based on biologic effects by ultrasound have been carried out by varying the acoustic parameters such as power, frequency range, sonication time and duty cycle, all controlled within robust protocols executed in automation. Results The resulting data proves that it is possible to perform in vitro experiments for different purposes (i.e. drug delivery, cellular sonoporation, nanoparticles or microbubbles swelling, tissue regeneration, neuronal cell stimulation etc.) keeping the relevant physical parameters of sonication constant, for instance acoustic pressure, but varying the others parameters (i.e. frequency, pulse length or duty cycle etc) one at the time. Conclusions We show that with our apparatus it is possible to obtain robust and reproducible results on cellular experiments, using all the standard devices that are commonly available in biological labs. The improvement on the side of reproducibility and portability of the experiments allows a straightforward comparison between our results and those obtained with other techniques

TEMPERATURE AND LEVEL DENSITY PARAMETER OF EVAPORATION RESIDUES PRODUCED IN THE REACTION 165Ho + 600 MeV 20Ne

Evaporative and preequilibrium neutrons emitted from evaporation residues in the reaction Ho + 600 MeV neon are exploited to deduce the thermal excitation energy E* and temperature T of the residues. From these quantities the level density parameter is deduced at a temperature of 4.1 MeV

Cytotoxicity of Libyan Juniperus phoenicea against Human Cancer Cell Lines A549, EJ138, Hepg2 and MCF7

Background: The current study was undertaken to assess the cytotoxicity of the leaves of Libyan Juniperus phoenicea (Cupressaceae) against human cancer cell lines. Methods: The cytotoxicity of the n-hexane, dichloromethane (DCM) and methanol (MeOH) extracts of the leaves of J. phoenicea (JP), obtained from sequential Soxhlet extractions, was assessed against four human cancer cell lines: EJ138 (human bladder carcinoma), HepG2 (human liver hepatocellular carcinoma), A549 (human lung carcinoma) and MCF7 (human breast adenocarcinoma) using the MTT assay. Results: The cell line A549 was the most sensitive to the JP extracts, with the highest level of cytotoxicity with the IC50 values of 16, 13 and 100 μg/mL for the DCM, n-hexane and MeOH extracts, respectively. However, generally the most potent cytotoxic extract across the other cells tested was the n-hexane extract, followed by the DCM extract, whilst the MeOH extracts showed little or no cytotoxicity. The percentage of viability of cells decreased as the concentration of test compounds increased. The cytotoxicity of various chromatographic fractions from the extracts was also studied against the A459 cells. For the n-hexane fractions, the IC50 values were 160, 62, 90, 30, 9.5 and 40 μg/mL for fractions 1 to 5 and 7, respectively. Fractions 4 and 5 showed the greatest effect. DCM fractions 2, 3 and 4 had the IC50 values of 60, 92 and 19 μg/mL, respectively, and DCM fractions 5 to 8 were non-cytotoxic. Fractions 1 and 2 of the MeOH extract were non-cytotoxic, whereas cytotoxicity was observed for fractions 3 and 4 with IC50 values of 50 and 85 μg/mL, respectively. Conclusion: The outcome of the present study suggested that the JP leaves possess cytotoxic activities. The high level of cytotoxicity of the n-hexane and DCM extracts suggested that lipophilicity might affect the cytotoxicity of JP, where the less polar compounds had the strongest cytotoxicity

Detection of the Cherenkov light diffused by Sea Water with the ULTRA Experiment

The study of Ultra High Energy Cosmic Rays represents one of the most challenging topic in the Cosmic Rays and in the Astroparticle Physics fields. The interaction of primary particles with atmospheric nuclei produces a huge Extensive Air Shower together with isotropic emission of UV fluorescence light and highly directional Cherenkov photons, that are reflected/diffused isotropically by the impact on the Earth's surface or on high optical depth clouds. For space-based observations, detecting the reflected Cherenkov signal in a delayed coincidence with the fluorescence light improves the accuracy of the shower reconstruction in space and in particular the measurement of the shower maximum, giving a strong signature for discriminating hadrons and neutrinos, and helping to estimate the primary chemical composition. Since the Earth's surface is mostly covered by water, the ULTRA (UV Light Transmission and Reflection in the Atmosphere)experiment has been designed to provide the diffusing properties of sea water, overcoming the lack of information in this specific field. A small EAS array, made up of 5 particle detectors, and an UV optical device, have been coupled to detect in coincidence both electromagnetic and UV components. The detector was in operation from May to December, 2005, in a small private harbor in Capo Granitola (Italy); the results of these measurements in terms of diffusion coefficient and threshold energy are presented here.Comment: 4 pages, 3 figures, PDF format, Proceedings of 30th ICRC, International Cosmic Ray Conference 2007, Merida, Yucatan, Mexico, 3-11 July 200