1,625 research outputs found
Reply to "Comment on 'Piezonuclear decay of thorium' [Phys. Lett. A 373 (2009) 1956]" [Phys. Lett. A 373 (2009) 3795]
No full textIn a paper appearing in this issue of Physics Letters A, Ericsson et al. raise some critical comments on the experiment [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956] we carried out by cavitating a solution of thorium-228, which evidenced its anomalous decay behaviour, thus confirming the results previously obtained by Urutskoev et al. by explosion of titanium foils in solutions. In this Letter, we reply to these comments. In our opinion, the main shortcomings of the criticism by the Swedish authors are due to their omitting of inserting our experiment in the wider research stream of piezonuclear reactions, and to the statistical analysis they used, which does not comply with the rules generally accepted for samples with small numbers. However, apart from any possible theoretical speculation, there is the basic fact that two different experiments (ours and that by Urutskoev et al.), carried out independently and by different means, highlight an analogous anomaly in the decay of thorium subjected to pressure waves. Such a convergence of results shows that it is worth to further carry on experimental investigations, in order to get either a confirmation or a disproof of the induced-pressure anomalous behaviour of radioactive nuclides even different from thorium. (C) 2009 Elsevier B.V. All rights reserved
A new species of the genus Odonteus (Coleoptera: Geotrupidae) from Northern Pakistan
No full textA remarkable new species, Odonteus gandhara Carpaneto & Mignani, n. sp., is described from
northern Pakistan. The holotype (adult male) and the paratype (adult female) are illustrated and
compared with O. armiger (Scopoli, 1772) and O. orientalis Mittal, 1998, the only two species of
this genus recognized in the Old World. Both O. armiger and O. orientalis have the eye not completely
divided by the canthus and have a sensory area on the external side of the last antennomere
(this character has never been discussed in the literature until now). These two character states in O.
armiger and O. orientalis compel emendations to the definition of the genus. The new species has a
great zoogeographical relevance because similar species occur in North America (O. obesus
LeConte, 1859 and O. falli Wallis, 1928), and probably represents a relict species endemic to the
Himalayan range.
Key words: Odonteus, systematics, new species, zoogeography, Pakistan, Himalayan range, Palearctic
Regio
NON-HERMITIAN REALIZATION OF A LIE-DEFORMED HEISENBERG ALGEBRA
No full textWe discuss the non-Hermitian realization of a Lie-deformed, non-canonical Heisenberg algebra. We show that it essentially amounts to the case of a Q-deformed algebra with complex deformation parameter. The (real) energy eigenvalues of the corresponding oscillator are derived, whose deformed spectrum has, among the others, a ground state energy lower than that of the usual harmonic oscillator. The non-Hermitian deformed SU(2) algebra is also constructed
An item response theory model for students ability evaluation using computer-automated test results
No full textReply to the comment on “Piezonuclear decay of thorium” [Phys. Lett. A 373 (2009) 1956] by G. Ericsson et al. (2009)
No full textBOSE REALIZATION OF A NONCANONICAL HEISENBERG ALGEBRA
No full textWe find out the Bose realization of a generalized Heisenberg algebra, in which the bracket of the annihilation and creation operators is proportional to a polynomial function of the number operator. The eigenvalues of the corresponding oscillator are derived in a special case. We stress also the connection between non-canonical commutation relations and q-algebras
A time-variable, phase-dependent emission line in the X-ray spectrum of the isolated neutron star RXJ0822–4300
No full textRX J0822−4300 is the central compact object associated with the Puppis A supernova remnant. Previous X-ray observations suggested RX J0822−4300 to be a young neutron star with a weak dipole field and a peculiar surface temperature distribution dominated by two antipodal spots with different temperatures and sizes. An emission line at 0.8 keV was also detected. We performed a very deep (130-ks) observation with XMM–Newton, which allowed us to study in detail the phase-resolved properties of RX J0822−4300. Our new data confirm the existence of a narrow spectral feature, best modelled as an emission line, only seen in the ‘soft’-phase interval – when the cooler region is best aligned to the line of sight. Surprisingly, comparison of our recent observations to the older ones yields evidence for a variation in the emission-line component, which can be modelled as a decrease in the central energy from ∼0.80 keV in 2001 to ∼0.73 keV in 2009–10. The line could be generated via cyclotron scattering of thermal photons in an optically-thin layer of gas, or, alternatively, it could originate in low-rate accretion by a debris disc. In any case, a variation in energy, pointing to a variation of the magnetic field in the line-emitting region, cannot be easily accounted for
LANDAU-ZENER-LIKE TRANSITIONS OF A DRIVEN CALDIROLA-KANAI OSCILLATOR
No full textWe discuss the generalized tunneling through a dynamical barrier for a damped and forced oscillator of the Caldirola-Kanai type. The Landau-Zener-like probability transition from the oscillator ground state to the nth energy level is exactly evaluated by using the Wei-Norman algebraic form of the time evolution operator. Considering a specific example, we show that an increase of the friction parameter gamma implies a decrease of the occupation probability
QUANTUM TUNNELING OF A DAMPED AND DRIVEN, INVERTED HARMONIC-OSCILLATOR
No full textUsing the evolution operator method, we derive the exact propagator of the generalized parametric oscillator in its more general form. This result is exploited to obtain the exact wavefunction of a damped and driven, inverted harmonic oscillator of the Caldirola-Kanai type, taking a Gaussian wavepacket as the initial state. We discuss the tunnelling process of such a system. The probability density and the persistence probability are evaluated. The expression for the sojourn time is derived for a small external force, and is the sum of two terms, whose explicit forms are obtained in the case of an extended wavepacket. The first term is an increasing function of the dissipation parameter gamma, whereas the second one is strictly due to the presence of the driving force
- …
