347 research outputs found
Investigation of the diversity and safety of the predominant Bacillus pumilus sensu lato and other Bacillus species involved in the alkaline fermentation of cassava leaves for the production of Ntoba Mbodi
The objective of the study was to investigate the identity, diversity, and safety of the Bacillus population involved in the fermentation of cassava (Manihot esculenta Crantz) leaves for the production of Ntoba Mbodi, a Congolese food.
Ninety bacteria were identified by phenotyping and genotyping using ITS-PCR, rep-PCR, and sequencing of the 16S rRNA, gyrA, gyrB and rpoB genes. Moreover, the isolates were screened for the presence of genes coding for haemolytic (HblC, HblD) and non-haemolytic enterotoxins (NheA, NheB and NheC), cytotoxin K (CytK) and emetic toxin (EM1) as well as their ability to produce haemolysin.
The investigations revealed the predominance (72.21 %) of species of the Bacillus pumilus group i.e. B. safensis (48), B. pumilus (7), and B. pumilus sensu lato (10). Other species of Bacillus including B. cereus sensu lato (11), B. megaterium (4), B. subtilis (4), B. amyloliquefaciens (2), B. siamensis (2), B. licheniformis (1) and Lysinibacillus louembei were also identified. Haemolytic, non-haemolytic and cytokin toxin genes were detected in the B. cereus strains which were also able to produce haemolysin. The emetic toxin gene was not detected in any isolates. The toxin genes screened were not detected in any of the non B. cereus species
The excitation spectrum for weakly interacting bosons in a trap
We investigate the low-energy excitation spectrum of a Bose gas confined in a
trap, with weak long-range repulsive interactions. In particular, we prove that
the spectrum can be described in terms of the eigenvalues of an effective
one-particle operator, as predicted by the Bogoliubov approximation.Comment: LaTeX, 32 page
SOX2 is the determining oncogenic switch in promoting lung squamous cell carcinoma from different cells of origin
Lung squamous cell carcinoma (LSCC) is a devastating malignancy with no effective treatments, due to its complex genomic profile. Therefore, preclinical models mimicking its salient features are urgently needed. Here we describe mouse models bearing various combinations of genetic lesions predominantly found in human LSCC. We show that SOX2 but not FGFR1 overexpression in tracheobronchial basal cells combined with Cdkn2ab and Pten loss results in LSCC closely resembling the human counterpart. Interestingly, Sox2;Pten;Cdkn2ab mice develop LSCC with a more peripheral location when Club or Alveolar type 2 (AT2) cells are targeted. Our model highlights the essential role of SOX2 in commanding the squamous cell fate from different cells of origin and represents an invaluable tool for developing better intervention strategies
Phase space formalisms of quantum mechanics with singular kernel
The equivalence of the Rivier-Margenau-Hill and Born-Jordan-Shankara phase
space formalisms to the conventional operator approach of quantum mechanics is
demonstrated. It is shown that in spite of the presence of singular kernels the
mappings relating phase space functions and operators back and forth are
possible.Comment: 15 pages, no figures, LATE
A multidisciplinary scientific investigation of the 1916 Hawthorn Mine Crater, Beaumont Hamel, Somme, Northern France
Hawthorn Crater is a prominent feature of the former Somme battlefield near Beaumont Hamel, Northern France. It resulted from the detonation of arguably the most famous of nine mines that the British had prepared below German lines on 1 July 1916, as part of the opening day of the Battle of the Somme. However, the crater has not been studied scientifically, as was in private land until recently taken over by the Hawthorn Crater Association. This paper documents three field seasons of multi-disciplinary site investigations. Methods included: remote sensing, drones, ground-based-LiDAR and surface surveys, geophysics and archaeological investigations. Magnetic anomalies were identified as: still-intact German fire pits, barbed wire and equipment, as the crater became the frontline after formation, and Allied shell craters. This study provided a rare opportunity to study a First World War mine crater, and highlighting modern science can assist detection and characterisation of significant archaeological sites
Optical properties of the pseudogap state in underdoped cuprates
Recent optical measurements of deeply underdoped cuprates have revealed that
a coherent Drude response persists well below the end of the superconducting
dome. In addition, no large increase in optical effective mass has been
observed, even at dopings as low as 1%. We show that this behavior is
consistent with the resonating valence bond spin-liquid model proposed by Yang,
Rice, and Zhang. In this model, the overall reduction in optical conductivity
in the approach to the Mott insulating state is caused not by an increase in
effective mass, but by a Gutzwiller factor, which describes decreased coherence
due to correlations, and by a shrinking of the Fermi surface, which decreases
the number of available charge carriers. We also show that in this model, the
pseudogap does not modify the low-temperature, low-frequency behavior, though
the magnitude of the conductivity is greatly reduced by the Gutzwiller factor.
Similarly, the profile of the temperature dependence of the microwave
conductivity is largely unchanged in shape, but the Gutzwiller factor is
essential in understanding the observed difference in magnitude between ortho-I
and -II YBaCuO.Comment: 9 pages, 6 figures, submitted to Eur. Phys. J.
Transformation of in-plane in at fixed oxygen content
This paper reveals the origin of variation in the magnitude and temperature
dependence of the normal state resistivity frequently observed in different
YBCO single crystal or thin film samples with the same . We investigated
temperature dependence of resistivity in thin films
with 7- and 6.90, which were subjected to annealing in argon at
400-420 K (). Before annealing these films exhibited a non-linear
, with a flattening below 230 K, similar to and
observed in untwinned and twinned YBCO crystals, respectively.
For all films the annealing causes an increase of resistivity and a
transformation of from a non-linear dependence towards a more
linear one (less flattening). In films with 7- the increase of
resistivity is also associated with an increase in . We proposed the
model that provides an explanation of these phenomena in terms of thermally
activated redistribution of residual O(5) oxygens in the chain-layer of YBCO.
Good agreement between the experimental data for , where t is
the annealing time, and numerical calculations was obtained.Comment: 8 pages, 9 figures, submitted to PR
Hidden dimers and the matrix maps: Fibonacci chains re-visited
The existence of cycles of the matrix maps in Fibonacci class of lattices is
well established. We show that such cycles are intimately connected with the
presence of interesting positional correlations among the constituent `atoms'
in a one dimensional quasiperiodic lattice. We particularly address the
transfer model of the classic golden mean Fibonacci chain where a six cycle of
the full matrix map exists at the centre of the spectrum [Kohmoto et al, Phys.
Rev. B 35, 1020 (1987)], and for which no simple physical picture has so far
been provided, to the best of our knowledge. In addition, we show that our
prescription leads to a determination of other energy values for a mixed model
of the Fibonacci chain, for which the full matrix map may have similar cyclic
behaviour. Apart from the standard transfer-model of a golden mean Fibonacci
chain, we address a variant of it and the silver mean lattice, where the
existence of four cycles of the matrix map is already known to exist. The
underlying positional correlations for all such cases are discussed in details.Comment: 14 pages, 2 figures. Submitted to Physical Review
The 3D Structure of N132D in the LMC: A Late-Stage Young Supernova Remnant
We have used the Wide Field Spectrograph (WiFeS) on the 2.3m telescope at
Siding Spring Observatory to map the [O III] 5007{\AA} dynamics of the young
oxygen-rich supernova remnant N132D in the Large Magellanic Cloud. From the
resultant data cube, we have been able to reconstruct the full 3D structure of
the system of [O III] filaments. The majority of the ejecta form a ring of
~12pc in diameter inclined at an angle of 25 degrees to the line of sight. We
conclude that SNR N132D is approaching the end of the reverse shock phase
before entering the fully thermalized Sedov phase of evolution. We speculate
that the ring of oxygen-rich material comes from ejecta in the equatorial plane
of a bipolar explosion, and that the overall shape of the SNR is strongly
influenced by the pre-supernova mass loss from the progenitor star. We find
tantalizing evidence of a polar jet associated with a very fast oxygen-rich
knot, and clear evidence that the central star has interacted with one or more
dense clouds in the surrounding ISM.Comment: Accepted for Publication in Astrophysics & Space Science, 18pp, 8
figure
Coherent states for exactly solvable potentials
A general algebraic procedure for constructing coherent states of a wide
class of exactly solvable potentials e.g., Morse and P{\"o}schl-Teller, is
given. The method, {\it a priori}, is potential independent and connects with
earlier developed ones, including the oscillator based approaches for coherent
states and their generalizations. This approach can be straightforwardly
extended to construct more general coherent states for the quantum mechanical
potential problems, like the nonlinear coherent states for the oscillators. The
time evolution properties of some of these coherent states, show revival and
fractional revival, as manifested in the autocorrelation functions, as well as,
in the quantum carpet structures.Comment: 11 pages, 4 eps figures, uses graphicx packag
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