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Dynamic behavior and damping capacity of auxetic foam pads
A novel set of auxetic (negative Poisson's ratio) open cell polyurethane foam has been developed and tested under dynamic
loading conditions to assess the viscoelastic response under white noise random excitation and compressive cycling. Foam pads
normalized to standard ISO 13753 have been tested at room temperature and frequency bandwidth 10-500 Hz to assess
transmissibility characteristics for possible antivibration glove applications. The results show that the ISO 13753 normalized
transmissibility for these foams falls below 0.6 above 100 Hz, with lower peak maximum stresses under indentation compared to
conventional open cell solids. These results suggest possible use of the auxetic foam for pads or linens against « white fingers«
vibration applications. Further tests have been conducted on cyclic compressive loading up to 3 Hz and loading ratios of 0.95 for
loading histories up to 100000 cycles. The damping capacity of the auxetic foams showed and increase by a factor 10 compared
to the conventional foams used to manufacture the negative Poisson's ratio ones, and stiffness degradation stabilized after few tens on cycles
The Near-IR-Optical-UV Emission of BL Lacertae Objects
Near--infrared, optical and ultraviolet quasi--simultaneous observations of
11 BL Lacertae objects are reported. For all but one source the dereddened
spectral flux distribution in the Hz frequency
range can be described by a single power law f with
average spectral index = 0.88 0.42 (standard deviation) plus,
where relevant, the contribution of the host galaxy. In most cases the non
simultaneous soft X--ray fluxes obtained by the {\it Einstein Observatory} lie
on or below the extrapolation of the power law. The results are compared with
the average spectral properties of other samples of BL Lacs studied separately
in the IR--optical and in the UV bands. The implications for existing models of
the objects are shortly discussed.Comment: 23 pages, latex file, 2 figures available as postscript files
appended at the end of the latex text file, Ref. S.I.S.S.A. 31/94/
The outskirts of globular clusters as modified gravity probes
In the context of theories of gravity modified to account for the observed
dynamics of galactic systems without the need to invoke the existence of dark
matter, a prediction often appears regarding low acceleration systems: wherever
falls below one should expect a transition from the classical to
the modified gravity regime.This modified gravity regime will be characterised
by equilibrium velocities which become independent of distance, and which scale
with the fourth root of the total baryonic mass, . The two
above conditions are the well known flat rotation curves and Tully-Fisher
relations of the galactic regime. Recently however, a similar phenomenology has
been hinted at, at the outskirts of Galactic globular clusters, precisely in
the region where . Radial profiles of the projected velocity
dispersion have been observed to stop decreasing along Keplerian expectations,
and to level off at constant values beyond the radii where . We have
constructed gravitational equilibrium dynamical models for a number of globular
clusters for which the above gravitational anomaly has been reported, using a
modified Newtonian force law which yields equilibrium velocities equivalent to
MOND. We find models can be easily constructed having an inner Newtonian region
and an outer modified gravity regime, which reproduce all observational
constraints, surface brightness profiles, total masses and line of sight
velocity dispersion profiles. Through the use of detailed single stellar
population models tuned individually to each of the globular clusters in
question, we derive estimates of the total masses for these systems.
Interestingly, we find that the asymptotic values of the velocity dispersion
profiles are consistent with scaling with the fourth root of the total masses,
as expected under modified gravity scenarios.Comment: Accepted in ApJ, 13 pages, 7 figure
Blazar properties: an update from recent results
After a brief critical overview of the main properties of blazars and their
classification, some significant results from recent multiwavelength
observations are summarized, in the context of the jet physics.Comment: 5 pages, 2 figures. Invited talk at the 2nd Heidelberg workshop:
"High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", January
13-16, 2009, to be published in Int. J. Mod. Phys. D. Updated reference
The Importance of Property Rights In The Developing World: A study and comparison of Zimbabwe and Botswana
What is the redshift of the gamma- ray BL Lac source S4 0954+65?
High signal-to-noise ratio spectroscopic observations of the BL Lac object S4
0954+65 at the alleged redshift z = 0.367 are presented. This source was
detected at gamma frequencies by MAGIC (TeV) and FERMI (GeV) telescopes during
a remarkable outburst that occurred in February 2015, making the determination
of its distance particularly relevant for our understanding of the properties
of the Extragalactic Background Light. Contrary to previous reports on the
redshift, we found that the optical spectrum is featureless at an equivalent
width limit of \sim 0.1 Ang. A critical analysis of the existing observations
indicates that the redshift is still unknown. Based on the new data we estimate
a lower limit to the redshift at z \geq 0.45.Comment: Minor comment and accepted for publication in Astronomical Journa
S-adenosylmethionine and superoxide dismutase 1 synergistically counteract Alzheimer's disease features progression in tgCRND8 mice
Recent evidence emphasizes the role of dysregulated one-carbon metabolism in Alzheimer's Disease (AD). Exploiting a nutritional B-vitamin deficiency paradigm, we have previously shown that PSEN1 and BACE1 activity is modulated by one-carbon metabolism, leading to increased amyloid production. We have also demonstrated that S-adenosylmethionine (SAM) supplementation contrasted the AD-like features, induced by B-vitamin deficiency. In the present study, we expanded these observations by investigating the effects of SAM and SOD (Superoxide dismutase) association. TgCRND8 AD mice were fed either with a control or B-vitamin deficient diet, with or without oral supplementation of SAM + SOD. We measured oxidative stress by lipid peroxidation assay, PSEN1 and BACE1 expression by Real-Time Polymerase Chain Reaction (PCR), amyloid deposition by ELISA assays and immunohistochemistry. We found that SAM + SOD supplementation prevents the exacerbation of AD-like features induced by B vitamin deficiency, showing synergistic effects compared to either SAM or SOD alone. SAM + SOD supplementation also contrasts the amyloid deposition typically observed in TgCRND8 mice. Although the mechanisms underlying the beneficial effect of exogenous SOD remain to be elucidated, our findings identify that the combination of SAM + SOD could be carefully considered as co-adjuvant of current AD therapies
Reclassification of the nearest quasar pair candidate: SDSS J15244+3032 - RXS J15244+3032
We present optical spectroscopy of the nearest quasar pair listed in the 13th
edition of the Veron-Cetty & Veron catalogue, i.e. the two quasars SDSS
J15244+3032 and RXS J15244+3032 (redshift z~0.27, angular separation ~7 arcsec,
and line-of-sight velocity difference ~1900 km/s). This system would be an
optimal candidate to investigate the mutual interaction of the host galaxies
with ground based optical imaging and spectroscopy. However, new optical data
demonstrate that RXS J15244+3032 is indeed a star of spectral type G.
This paper includes data gathered with the Asiago 1.82m telescope (Cima Ekar
Observatory, Asiago, Italy).Comment: 5 pages, 2 figures, 1 table. Accepted for publication in APS
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