Omnibus Sequences, Coupon Collection, and Missing Word Counts

In this paper, we study the properties of k-omnisequences of length n, defined to be strings of length n that contain all strings of smaller length k embedded as (not necessarily contiguous) subsequences. We start by proving an elementary result that relates our problem to the classical coupon collector problem. After a short survey of relevant results in coupon collection, we focus our attention on the number M of strings (or words) of length k that are not found as subsequences of an n string, showing that there is a gap between the probability threshold for the emergence of an omnisequence and the zero-infinity threshold for ${\mathbb E}(M)$ .     

Spectroscopic investigation on europium complexation with humic acid and its model compounds

Time resolved fluorescence spectroscopy (TRFS) of Eu(III) (an analogue of trivalent actinides) complexation with humic acid (HA) and its model compounds, namely phthalic acid (PA), mandelic acid (MA) and succinic acid (SA) has been carried out at varying concentration ratios of ligand to metal ion. The emission spectra were recorded in the range of 550–650 nm by exciting at an appropriate wavelength. The intensity of the 616 nm peak of Eu(III) was found to be sensitive to complexation. The ratio of the intensities of 616 and 592 nm peaks was used to determine the stability constants of Eu-phthalate, Eu-mandelate and Eu-succinate complexes. In the case of model compounds, the life-time was found to increase with increasing ligand to metal ratio (L/M) indicating the decrease in quenching of the fluorescence by coordinated water molecules with increasing complexation. On the other hand in the case of HA, the life-time was found to be constant at least up to L/M of 5, indicating the formation of outer sphere complex. Beyond L/M = 5 the life-time value was found to increase which can be attributed to the binding of the metal ion to the higher affinity sites in the HA macromolecule.     

Bioremediation of soil contaminated with organic compounds with special reference to acrylonitrile

Enrichment of acrylonitrile (AN) degrading bacterial culture from contaminated soil resulted in the isolation of two cultures which were identified as gram negative small rods (C1) and gram positive cocci (C2). One of the cultures (C1) was identified as Citrobacter fruendii on the basis of biochemical and physiological tests. Both the cultures (C1 and C2) were able to utilize acrylonitrile up to a concentration of 2000 mg/l as the sole source of carbon and nitrogen. The studies also confirmed that the acrylonitrile contaminated soil when ploughed with well mixed AN degrading culture, diammonium phosphate and farmyard manure, could be completely remediated within two months from the date of soil amendment.     

Carrier distillation-ICAP approach for trace metal assay of U3O8 powder

Summary A new approach for the trace metal assay of U₃O₈ powder has been described. The carrier distillation technique used for selective volatilization of trace metals in U₃O₈ with d.c. arc excitation is adapted for the release of analytes from the solid sample into the ICAP source by inductively heating the sample. The experimental parameters have been optimised for the direct determination of Cd, Cu, K, Na, Ni and Pb. The performance of the method developed here is tested for the precision and accuracy of determinations by analysing spiked U₃O₈ samples and NBL U₃O₈ reference standards (standard deviation 2–9%). The method appears promising to be developed as a highly precise analytical optical emission spectrometric method as it adds to the ingenuity of the carrier distillation method, the advantages of ICAP.

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Bestimmung von Metallspuren in U₃O₈-Pulver durch Trägerdestillation/ICAP

Zusammenfassung Das Trägerdestillationsverfahren zur selektiven Verdampfung von Spurenmetallen in U₃O₈ im Gleichstrombogen wurde mit induktiver Probeerhitzung für ICAP angepaßt. Die experimentellen Parameter wurden für die direkte Bestimmung von Cd, Cu, K, Na, Ni und Pb optimiert. Die Leistungsfähigkeit des Verfahrens wurde mit Hilfe von Proben mit bestimmten Zusätzen sowie mit zertifiziertem Referenzmaterial überprüft (Standardabweichung 2–9%). Durch die Verbindung der Vorteile von Trägerdestillation und ICAP bietet sich eine Methode von hoher Präzision.

     

Low energy constraints on N = 2 supersymmetric models

We derive constraints on the masses of mirror particles in N = 2 supersymmetric theories. We consider the K_L?K_S mass difference, the π → ev/π → μv branching ratio and the anomalous magnetic moment of the muon. The K_L?K_S mass difference gives a lower bound of 15 TeV on the mirror gauge scalar and mirror gauge fermion masses, under suitable assumptions.     

A model for like sign dimuons-detailed analysis

A detailed account of a model for like sign dimuons, recently proposed by us, is presented and compared with all the like sign dimuon data available. It can naturally account for the rate and all the kinematic features of these events, as given by the CHARM, CFRR and CFNRR experiments. The predicted event distributions are shown for the CHARM experiment, since it has sufficient number of events for a meaningful comparison. The implication of the model for other processes like neutrino induced trimuons and charm hadroproduction are also discussed.     

Persistent supersolid phase of hard-core bosons on the triangular lattice

We study hard-core bosons with unfrustrated hopping (t) and nearest neighbor repulsion (U) (spin S=1/2 XXZ model) on the triangular lattice. At half filling, the system undergoes a zero temperature (T) quantum phase transition from a superfluid phase at small U to a supersolid at Uc approximately 4.45 in units of 2t. This supersolid phase breaks the lattice translation symmetry in a characteristic sqrt[3] x square root of 3 pattern, and is remarkably stable--indeed, a smooth extrapolation of our results indicates that the supersolid phase persists for arbitrarily large U/t.     

Anomalous <Emphasis Type="Italic">VVH</Emphasis> interactions at a linear collider

We examine, in a model independent way, the sensitivity of a linear collider to the couplings of a light Higgs boson to a pair of gauge bosons, including the possibility of CP violation. We construct several observables that probe the various possible anomalous couplings. For an intermediate mass Higgs, a collider operating at a center of mass energy of 500 GeV and with an integrated luminosity of 500 fb⁻¹ is shown to be able to constrain the ZZH vertex at the few per cent level, with even higher sensitivity for some of the couplings. However, lack of sufficient number of observables as well as contamination from the ZZH vertex limits the precision to which anomalous part of the WWH coupling can be probed.