Lepton flavor violating decays of vector mesons

We estimate the rates of lepton flavor violating decays of the vector mesons $\rho, \omega, \phi \to e \mu$. The theoretical tools are based on an effective Lagrangian approach without referring to any specific realization of the physics beyond the standard model responsible for lepton flavor violation (\Lfv). The effective lepton-vector meson couplings are extracted from the existing experimental bounds on the nuclear $\mu^--e^-$ conversion. In particular, we derive an upper limit for the \Lfv branching ratio ${\rm Br}(\phi \to e \mu) \leq1.3 \times 10^{-21}$ which is much more stringent than the recent experimental result ${\rm Br}(\phi \to e \mu) < 2 \times 10^{-6}$ presented by the SND Collaboration. Very tiny limits on \Lfv decays of vector mesons derived in this letter make direct experimental observation of these processes unrealistic.Comment: 3 pages, 1 figure, accepted for publication in Phys. Rev.

New bounds on lepton flavor violating decays of vector mesons and the Z0 boson

We give an estimate for the upper bounds on rates of lepton flavor violating (LFV) decays M to mu(pm) + e(mp) of vector mesons M = rho0, omega, phi, J/psi, Upsilon and the Z0 boson in a model independent way, analyzing the corresponding lowest dimension effective operators. These operators also contribute to nuclear mu-e-conversion. Based on this observation and using the existing experimental limits on this LFV nuclear process, we show that the studied two-body LFV decays of vector bosons are strongly suppressed independent on the explicit realization of new physics. The upper limits on the rates of some of these decays are significantly more stringent than similar limits known in the literature. In view of these results experimental observation of the two-body LFV decays of vector bosons looks presently unrealistic.Comment: 4 pages, 1 figur

Narrowband spectroscopy by all-optical correlation of broadband pulses

High peak power ultrafast lasers are widely used in nonlinear spectroscopy but often limit its spectral resolution because of the broad frequency bandwidth of ultrashort laser pulses. Improving the resolution by achieving spectrally narrow excitation of, or emission from, the resonant medium by means of multi-photon interferences has been the focus of many recent developments in ultrafast spectroscopy. We demonstrate an alternative approach, in which high resolution is exercised by detecting narrow spectral correlations between broadband excitation and emission optical fields. All-optical correlation analysis, easily incorporated into the traditional spectroscopic setup, enables direct, robust and simultaneous detection of multiple narrow resonances with a single femtosecond pulse.Comment: 5 pages, 4 figures, submitted to PR

The effects of landscape modifications on the long-term persistence of animal populations

Background: The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition. Methodology/Principal Findings: Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place. Significance: Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology, which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses

CDS wide slit time-series of EUV coronal bright points

Wide slit (90" x 240" ) movies of four Extreme Ultraviolet coronal bright points (BPs) obtained with the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SoHO) have been inspected. The wavelet analysis of the He I 584.34 Å, O V 629.73 Å and Mg VII/IX 368 Å time-series confirms the oscillating nature of the BPs, with periods ranging between 600 and 1100 s. In one case we detect periods as short as 236 s. We suggest that these oscillations are the same as those seen in the chromospheric network and that a fraction of the network bright points are most likely the cool footpoints of the loops comprising coronal bright points. These oscillations are interpreted in terms of global acoustic modes of the closed magnetic structures associated with BPs

On Urabe's criteria of isochronicity

We give a short proof of Urabe's criteria for the isochronicity of periodical solutions of the equation $\ddot{x}+g(x)=0$. We show that apart from the harmonic oscillator there exists a large family of isochronous potentials which must all be non-polynomial and not symmetric (an even function of the coordinate x).Comment: 8 page

Imaging stress and magnetism at high pressures using a nanoscale quantum sensor

Pressure alters the physical, chemical and electronic properties of matter. The development of the diamond anvil cell (DAC) enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena ranging from the properties of planetary interiors to transitions between quantum mechanical phases. In this work, we introduce and utilize a novel nanoscale sensing platform, which integrates nitrogen-vacancy (NV) color centers directly into the culet (tip) of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging (~600 nm) of both stress fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from 25-340 K. For the former, we quantify all six (normal and shear) stress components with accuracy $<0.01$ GPa, offering unique new capabilities for characterizing the strength and effective viscosity of solids and fluids under pressure. For the latter, we demonstrate vector magnetic field imaging with dipole accuracy $<10^{-11}$ emu, enabling us to measure the pressure-driven $\alpha\leftrightarrow\epsilon$ phase transition in iron as well as the complex pressure-temperature phase diagram of gadolinium. In addition to DC vector magnetometry, we highlight a complementary NV-sensing modality using T1 noise spectroscopy; crucially, this demonstrates our ability to characterize phase transitions even in the absence of static magnetic signatures. By integrating an atomic-scale sensor directly into DACs, our platform enables the in situ imaging of elastic, electric and magnetic phenomena at high pressures.Comment: 18 + 50 pages, 4 + 19 figure

Surface superconducting states in a polycrystalline MgB2_{2} sample

We report results of dc magnetic and ac linear low-frequency study of a polycrystalline MgB$_2$ sample. AC susceptibility measurements at low frequencies, performed under dc fields parallel to the sample surface, provide a clear evidence for surface superconducting states in MgB$_2$.Comment: 4 pages and 5 figure

Microparticles as Immune Regulators in Infectious Disease – An Opinion

Despite their clear relationship to immunology, few existing studies have examined the potential role of microparticles (MP) in infectious disease. MP have a different size range from exosomes and apoptotic bodies, with which they are often grouped and arise by different mechanisms in association with inflammatory cytokine action or stress on the source cell. Infection with pathogens usually leads to the expression of a range of inflammatory cytokines and chemokines, as well as significant stress in both infected and uninfected cells. It is thus reasonable to infer that infection-associated inflammation also leads to MP production. MP are produced by most of the major cell types in the immune system, and appear to be involved at both innate and adaptive levels, potentially serving different functions in each. Thus, they do not appear to have a universal function; instead their functions are source- or stimulus-dependent, although likely to be primarily either pro- or anti-inflammatory. We argue that in infectious diseases, MP may be able to deliver antigen, derived from the biological cargo acquired from their cells of origin, to antigen-presenting cells. Another potential benefit of MP would be to transfer and/or disseminate phenotype and function to target cells. However, MP may also potentially be manipulated, particularly by intracellular pathogens, for survival advantage