Periodic analogues of the Kerr solutions: a numerical study

In recent years black hole configurations with non standard topology or with non-standard asymptotic have gained considerable attention. In this article we carry out numerical investigations aimed to find periodic coaxial configurations of co-rotating 3+1 vacuum black holes, for which existence and uniqueness has not yet been theoretically proven. The aimed configurations would extend Myers/Korotkin-Nicolai's family of non-rotating (static) coaxial arrays of black holes. We find that numerical solutions with a given value for the area A and for the angular momentum J of the horizons appear to exist only when the separation between consecutive horizons is larger than a certain critical value that depends only on A and |J|. We also establish that the solutions have the same Lewis's cylindrical asymptotic as Stockum's infinite rotating cylinders. Below the mentioned critical value the rotational energy appears to be too big to sustain a global equilibrium and a singularity shows up at a finite distance from the bulk. This phenomenon is a relative of Stockum's asymptotic's collapse, manifesting when the angular momentum (per unit of axial length) reaches a critical value compared to the mass (per unit of axial length), and that results from a transition in the Lewis's class of the cylindrical exterior solution. This remarkable phenomenon seems to be unexplored in the context of coaxial arrays of black holes. Ergospheres and other global properties are also presented in detail.Comment: 25 page

Magnetic frustration, phase competition, and the magnetoelectric effect in NdFe3(BO3)4

PACS numbers: 75.85.+t, 75.25. j, 75.30.Et, 78.70.Ck.-- et al.We present an element selective resonant magnetic x-ray scattering study of NdFe3(BO3)4 as a function of temperature and applied magnetic field. Our measurements show that the magnetic order of the Nd sublattice is induced by the Fe spin order. When a magnetic field is applied parallel to the hexagonal basal plane, the helicoidal spin order is suppressed and a collinear ordering, where the moments are forced to align in a direction perpendicular to the applied magnetic field, is stabilized. This result excludes a noncollinear spin order as the origin of the magnetically induced electric polarization in this compound. Instead our data imply that magnetic frustration results in a phase competition, which is the origin of the magnetoelectric response.This work was supported by the DFG through the Emmy Noether Programme (Grant No. GE1647/2-1) and the European Community’s Seventh Framework Program (FP7/2007-2013) under Grant No. 226716.Peer reviewe

A U-Pb Study of Zircons from a Lower Crustal Granulite Xenolith of the Spanish Central System: A Record of Iberian Lithospheric Evolution from the Neoproterozoic to the Triassic

A U-Pb laser ablation inductively coupled plasma mass spectrometry and secondary ion mass spectrometry geochronological study has been performed on zircons from a felsic granulite xenolith from the lower crust under the Variscan belt of Iberia. The ages obtained reveal zircon-forming events that span from the late Neoproterozoic (Cadomian-Avalonian orogeny) to the early stages of the opening of the Atlantic Ocean in the Mesozoic, through Cambro-Ordovician rifting, Devono-Carboniferous Variscan-Alleghenian collision, and Permian-Triassic extension and uplift. The U-Pb age groups found in zircons from this single lower crustal xenolith (ca. 220, 250, 280–310, 460–490, 525, and 550–490 Ma) record at least one complete cycle of closing and opening of oceanic basins and collision of continental masses. Zircons from the felsic granulite xenolith contain a synthesis of the geochronological information found on the surface geology and record most but not all major lithospheric events in the region in a ca. 400-m.yr. period

Targeted Inactivation of the mecB Gene, Encoding Cystathionine-γ-Lyase, Shows that the Reverse Transsulfuration Pathway Is Required for High-Level Cephalosporin Biosynthesis inAcremonium chrysogenum C10 but Not for Methionine Induction of the Cephalosporin Genes

[EN] Targeted gene disruption efficiency in Acremonium chrysogenum was increased 10-fold by applying the double-marker enrichment technique to this filamentous fungus. Disruption of themecB gene by the double-marker technique was achieved in 5% of the transformants screened. Mutants T6 and T24, obtained by gene replacement, showed an inactive mecB gene by Southern blot analysis and no cystathionine-γ-lyase activity. These mutants exhibited lower cephalosporin production than that of the control strain, A. chrysogenum C10, in MDFA medium supplemented with methionine. However, there was no difference in cephalosporin production between parental strain A. chrysogenum C10 and the mutants T6 and T24 in Shen's defined fermentation medium (MDFA) without methionine. These results indicate that the supply of cysteine through the transsulfuration pathway is required for high-level cephalosporin biosynthesis but not for low-level production of this antibiotic in methionine-unsupplemented medium. Therefore, cysteine for cephalosporin biosynthesis in A. chrysogenum derives from the autotrophic (SH2) and the reverse transsulfuration pathways. Levels of methionine induction of the cephalosporin biosynthesis gene pcbC were identical in the parental strain and the mecB mutants, indicating that the induction effect is not mediated by cystathionine-γ-lyase.SIThis work was supported by a grant of the CICYT (BIO97-0289-C02-01). We thank A. Paszewski for providing Aspergillus nidulansstrains M63 and C47 and M. Mediavilla, B. Martı́n, R. Barrientos, and M. Corrales for excellent technical assistance

Clinical, radiological and therapeutic features of keratocystic odontogenic tumours: a study over a decade

Factors associated with the potential for recurrence of keratocystic odontogenic tumours (KCOT) still remain to be clearly determined and no consensus exists concerning the management of KCOT. The purpose of this study was to evaluate different clinical factors associated with KCOT and its treatment methods. A retrospective review was performed of 55 cases treated from 2001 to 2010. Of the 55 cases, 27% were associated with an impacted or semi- impacted tooth. The majority of the lesions (82%) were located in tooth-bearing areas, and the overall mandibular to maxilla ratio of tumour occurrence was 5:1. The treatment options included enucleation, marsupialisation, or peripheral ostectomy, with or without the use of Carnoy ?s solution. Recurrence was found in 14 cases (25%). No significant association was seen between recurrence and age, symptomatic cases, location of the lesion, or unilocu - lar or multilocular appearance. The recurrence rate was higher in the group with tooth involvement, more marked in cases with third molar involvement. Statistical analysis showed a significant relation between recurrence and the type of treatment, with higher rates in cases treated with enucleation associated with tooth extraction. In our series, those cases with a closer relation with dental tissues showed a higher risk of recurrence, suggesting the need for a distinct classification for peripheral variants of KCOT

Correlations between Elastic, Calorimetric, and Polar Properties of Ferroelectric PbSc0.5Ta0.5O3 (PST)

Calorimetric, elastic, and polar properties of ferrolectric lead scandium tantalate PbSc0.5Ta0.5O3 (PST) with 65% cation order have been investigated in the vicinity of the paraelectric-ferroelectric transition at Ttrans = 295K. Comparison of temperature dependencies of the excess specific heat and elastic properties indicate that both anomalies stem from ther- mal fluctuations of order parameters in three dimensions. These fluctuations are consistent with tweed microstructure. This transition is driven by several coupled thermodynamic order parameters, as evidenced by a strongly non-linear scaling of the excess entropy with the squared ferroelectric polarization.National Natural Science Foundation of China (51850410520, 51320105014 and 51621063

Influence of Syncron® and Nitroactive® on flowering and ripening time in two sweet cherry cultivars

1 Pag. extracted from the Abstracts Book of the International Symposium.In this work, the influence of Syncron® and Nitroactive® on flowering and ripening is evaluated in two sweet cherry cultivars, Earlise and Lapins. A combination of Syncron 2% and Nitroactive 20% were applied at three dates during dormancy in two consecutive years with different winter weather conditions.Peer reviewe

A pre-Rodinian ophiolite involved in the Variscan suture of Galicia (Cabo Ortegal Complex, NW Spain)

U–Pb dating of zircons from a metagabbro of the Purrido amphibolitic unit (Cabo Ortegal Complex, NW Iberian Massif) yielded an age of 1159 ± 39 Ma, interpreted to approximate the crystallization age of the gabbroic protolith. Considering the arc affinity of the metagabbroic rocks, the unit is interpreted as a pre-Rodinian ophiolite developed in a back-arc setting. It is suggested that the ophiolite was obducted over the West African terranes during the assembly of Rodinia. There, this terrane remained tectonically stable and facing an ocean for a long time, and eventually became part of the Gondwanan margin. The ophiolite was finally involved in the Variscan suture of Galicia where it is sandwiched between Palaeozoic rocks. The Purrido unit is so far the only example of a Mesoproterozoic ophiolite in the European Variscan belt, where pre-Neoproterozoic rocks are very scarce and restricted to small exposures

Application of cathodoluminescence microscopy to the study of native acceptors in gallium antimonide

Cathodoluminescence in the scanning electron microscope is used to ivestigate growth and prosess induced defects in GaSb crystals. In particular, luminescence emission has been used to study the nature of acceptor defects present after different annealing and irradiation treatments