New Outlook on the Possible Existence of Superheavy Elements in Nature

A consistent interpretation is given to some previously unexplained phenomena seen in nature in terms of the recently discovered long-lived high spin super- and hyper-deformed isomeric states. The Po halos seen in mica are interpreted as due to the existence of such isomeric states in corresponding Po or nearby nuclei which eventually decay by gamma- or beta-decay to the ground states of 210Po, 214Po and 218Po nuclei. The low-energy 4.5 MeV alpha-particle group observed in several minerals is interpreted as due to a very enhanced alpha transition from the third minimum of the potential-energy surface in a superheavy nucleus with atomic number Z=108 (Hs) and atomic mass number around 271 to the corresponding minimum in the daughter.Comment: 8 pages, 8 figures, 5 tables. Paper presented at VII Int. School-Seminar on Heavy Ion Physics, May 27 - June 1, 2002, Dubna, Russi

Pair production by boost-invariant fields in comoving coordinates

We derive the pair-production probability in a constant electric field in Rindler coordinates in a quasi-classical approximation. Our result is different from the pair-production probability in an inertial frame (Schwinger formula). In particular, it exhibits non-trivial dependence on rapidity and deviation from Gaussian behavior at small transverse momenta. Our results can be important for analysis of particle production in heavy-ion collisions.Comment: 12 pages, 2 figures. Discussion added and typos fixe

Combustion behaviour of some biodesulphurized coals assessed by TGA/DTA

Thermal analysis, i.e. TGA/DTA is used to study the changes in the combustion behaviour of microbially treated coals. In view of their high sulphur content and industrial significance three samples are under consideration, i.e. one lignite and two subbituminous from different region in Bulgaria. The differences in burning profiles can be related to structural changes resulted from biological treatments. The overall biological treatment generates these changes probably due to the oxidation process. Concerning organic sulphur biodesulphurization there is no change in any drastic mannerof the thermal characteristic parameters. In general, applied biotreatments provoke a complex influence on combustion coal behaviour. From one side a better ignition performance, a minor decrease in higher heating value and diminishing peak temperature of maximum weight loss rate for all biotreated samples are observed. From other side some decrease in the combustibility indicated by an increase in the combustion time and the end of combustion temperature are obvious. Also well determined decrease of self-heating temperature after biotreatments evolves high risk of spontaneous unmanageable coal combustion

PAHs in fly ash from lignite combustion

Η έρευνα περιγράφει τον εντοπισμό και προσδιορισμό πολυκυκλικών αρωματικών υδρογονανθράκων (ΠΑΥ) σε ιπτάμενη τέφρα από την καύση λιγνιτών στο θερμοηλεκτρικό σταθμό Μαρίτσα Ίζτοκ- 2. Προσδιορίζεται συνολική περιεκτικότητα σε ΠΑΥ, ~17 pgr/kgr στερεάς ύλης. Περιγράφεται και η κατανομή των ΠΑ Υ ως προς τον αριθμό αρωματικών δακτυλίων (R). Εχει διαπιστωθεί ότι τα οργανικά εκχυλίσματα περιέχουν τρικυκλικούς/τετρακυκλικούς ΠΑ Υ και αλκυλιωμένα παράγωγα τους. Εχει υπολογιστεί και καρκινογόνο δυναμικό, 0,07385 σχετικά με το βενζοπυρένιο = 1. Μέσω αέριας χρωματογραφίας-φασματομετρίας μάζας και προτύπων δευτερίου προσδιορίστηκαν 17 ΠΑΥ, μερικοί από τους οποίους περιλαμβάνονται στη λίστα της USEPA. Οι τιμές που προσδιορίστηκαν είναι χαμηλότερες από τις οριακές τιμές ΠΑΥ σε έδαφος σύμφωνα με τη βουλγαρική νομοθεσία. Παρ 'όλα αυτά χρειάζεται να υπολογίζεται η περιεκτικότητα σε ΠΑ Υ στην ιπτάμενη τέφρα από την καύση λιγνιτών λόγω της τεράστιας ετήσιας παραγωγής υπολειμμάτων από την καύση ανθράκων.This paper describes state-of the art for isolation and determination of polycyclic aromatic hydrocarbons (PAHs) in fly ash from lignite combustion in Maritza East Thermal Power Plant, Bulgaria. Total sum of-17 microg/kg solid by-product PAHs was determined. The profile of PAHs distribution according to the number of aromatic rings in the molecule (R) was determined. Organic extracts were mainly composed by PAHs, their alkylated homologues and heteroatom containing counterparts with dominance of three/four cyclic aromatic compounds. Respectively, relative carcinogenic potency values for PAHs compared to Benzofajpyrene with TEFEPA =1 was not high - 0,07385. Seventeen PAHs, some of them in the list of USEPA for priority pollutants with expressed carcinogenic/mutagenic potential, were identified and quantified by mass spectroscopy (GC/MS/MS) and d-PAHs as internal standards. Determined values for contents of PAHs under regulation were lower than their backgrounds in Bulgarian soils. Nevertheless PAHs in combustion fly ash should be monitored because of high solid by-products annual production and problems of reus

Time-of-arrival distribution for arbitrary potentials and Wigner's time-energy uncertainty relation

A realization of the concept of "crossing state" invoked, but not implemented, by Wigner, allows to advance in two important aspects of the time of arrival in quantum mechanics: (i) For free motion, we find that the limitations described by Aharonov et al. in Phys. Rev. A 57, 4130 (1998) for the time-of-arrival uncertainty at low energies for certain mesurement models are in fact already present in the intrinsic time-of-arrival distribution of Kijowski; (ii) We have also found a covariant generalization of this distribution for arbitrary potentials and positions.Comment: 4 pages, revtex, 2 eps figures include

Path integrals on a flux cone

This paper considers the Schroedinger propagator on a cone with the conical singularity carrying magnetic flux (``flux cone''). Starting from the operator formalism and then combining techniques of path integration in polar coordinates and in spaces with constraints, the propagator and its path integral representation are derived. "Quantum correction" in the Lagrangian appears naturally and no a priori assumption is made about connectivity of the configuration space.Comment: LaTeX file, 9 page

Wave envelopes with second-order spatiotemporal dispersion : I. Bright Kerr solitons and cnoidal waves

We propose a simple scalar model for describing pulse phenomena beyond the conventional slowly-varying envelope approximation. The generic governing equation has a cubic nonlinearity and we focus here mainly on contexts involving anomalous group-velocity dispersion. Pulse propagation turns out to be a problem firmly rooted in frames-of-reference considerations. The transformation properties of the new model and its space-time structure are explored in detail. Two distinct representations of exact analytical solitons and their associated conservation laws (in both integral and algebraic forms) are presented, and a range of new predictions is made. We also report cnoidal waves of the governing nonlinear equation. Crucially, conventional pulse theory is shown to emerge as a limit of the more general formulation. Extensive simulations examine the role of the new solitons as robust attractors

Semiempirical Shell Model Masses with Magic Number Z = 126 for Superheavy Elements

A semiempirical shell model mass equation applicable to superheavy elements up to Z = 126 is presented and shown to have a high predictive power. The equation is applied to the recently discovered superheavy nuclei Z = 118, A = 293 and Z = 114, A = 289 and their decay products.Comment: 7 pages, including 2 figures and 2 table

Evidence for a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th

Evidence for the existence of a superheavy nucleus with atomic mass number A=292 and abundance (1-10)x10^(-12) relative to 232Th has been found in a study of natural Th using inductively coupled plasma-sector field mass spectrometry. The measured mass matches the predictions [1,2] for the mass of an isotope with atomic number Z=122 or a nearby element. Its estimated half-life of t1/2 >= 10^8 y suggests that a long-lived isomeric state exists in this isotope. The possibility that it might belong to a new class of long-lived high spin super- and hyperdeformed isomeric states is discussed.[3-6]Comment: 14 pages, 5 figure

Modeling approach to regime shifts of primary production in shallow coastal ecosystems

Pristine coastal shallow systems are usually dominated by extensive meadows of seagrass species, which are assumed to take advantage of nutrient supply from sediment. An increasing nutrient input is thought to favour phytoplankton, epiphytic microalgae, as well as opportunistic ephemeral macroalgae that coexist with seagrasses. The primary cause of shifts and succession in the macrophyte community is the increase of nutrient load to water; however temperature plays also an important role. A competition model between rooted seagrass (Zostera marina), macroalgae (Ulva sp), and phytoplankton has been developed to analyse the succession of primary producer communities in these systems. Successions of dominance states, with different resilience characteristics, are found when modifying the input of nutrients and the seasonal temperature and light intensity forcing.Comment: 33 pages, including 10 figures. To appear in Ecological Complexit