2,315 research outputs found
Phenotypic and genomic characterization of the first alkaliphilic aceticlastic methanogens and proposal of a novel genus Methanocrinis gen.nov. within the family Methanotrichaceae
Highly purified cultures of alkaliphilic aceticlastic methanogens were collected for the first time using methanogenic enrichments with acetate from a soda lake and a terrestrial mud volcano. The cells of two strains were non-motile rods forming filaments. The mud volcano strain M04Ac was alkalitolerant, with the pH range for growth from 7.5 to 10.0 (optimum at 9.0), while the soda lake strain Mx was an obligate alkaliphile growing in the pH range 7.7â10.2 (optimum 9.3â9.5) in the presence of optimally 0.2â0.3 M total Na+. Genomes of both strains encoded all enzymes required for aceticlastic methanogenesis and different mechanisms of (halo)alkaline adaptations, including ectoine biosynthesis, which is the first evidence for the formation of this osmoprotectant in archaea. According to 16S rRNA gene phylogeny, the strains possessed 98.3â98.9% sequence identity and belonged to the obligately aceticlastic genus Methanothrix with M. harundinaceae as the most closely related species. However, a more advanced phylogenomic reconstruction based on 122 conserved single-copy archaeal protein-coding marker genes clearly indicated a polyphyletic origin of the species included in the genus Methanothrix. We propose to reclassify Methanothrix harrundinacea (type strain 8AcT) into a new genus, Methanocrinis gen. nov., with the type species Methanocrinis harrundinaceus comb. nov. We also propose under SeqCode the complete genome sequences of strain MxTs (GCA_029167045.1) and strain M04AcTs (GCA_029167205.1) as nomenclatural types of Methanocrinis natronophilus sp. nov. and Methanocrinis alkalitolerans sp. nov., respectively, which represent other species of the novel genus. This work demonstrates that the low energy aceticlastic methanogenesis may function at extreme conditions present in (halo)alkaline habitats
Worldline Superfield Actions for N=2 Superparticles
We propose doubly supersymmetric actions in terms of n=2(D-2) worldline
superfields for N=2 superparticles in D=3,4 and Type IIA D=6 superspaces. These
actions are obtained by dimensional reduction of superfield actions for N=1
superparticles in D=4,6 and 10, respectively. We show that in all these models
geometrodynamical constraints on target superspace coordinates do not put the
theory on the mass shell, so the actions constructed consistently describe the
dynamics of the corresponding N=2 superparticles. We also find that in contrast
to the IIA D=6 superparticle a chiral IIB D=6 superparticle, which is not
obtainable by dimensional reduction from N=1, D=10, is described by superfield
constraints which produce dynamical equations. This implies that for the IIB
D=6 superparticle the doubly supersymmetric action does not exist in the
conventional form.Comment: Latex, 20 pp. Minor corrections, acknowledgements adde
On the Difference in Action of the Laser Light with Wavelength Near 2mm on Biotissue in Gas and Water Media
It is shown that unlike action in the air environment, section of the biotissue in the water environment (physiological solution) is performed by the steam-gas stream which is formed as a result of superintensive boiling in thin (about 0.1 mm) a liquid layer in which absorbed laser radiation. Coagulation of the biotissue, adjacent to a section, happens due to heat which is produced via vapor condensation.
Keywords: laser radiation in urology, a laser enucleation of the BPH, laser removal of the bladder cancer
Lorentz harmonics and superfield action. D=10, N=1 superstring
We propose a new version of the superfield action for a closed D=10, N=1
superstring where the Lorentz harmonics are used as auxiliary superfields. The
incorporation of Lorentz harmonics into the superfield action makes possible to
obtain superfield constraints of the induced worldsheet supergravity as
equations of motion. Moreover, it becomes evident that a so-called 'Wess-Zumino
part' of the superfield action is basically a Lagrangian form of the
generalized action principle. We propose to use the second Noether theorem to
handle the essential terms in the transformation lows of hidden gauge
symmetries, which remove dynamical degrees of freedom from the Lagrange
multiplier superfield.Comment: 23 pages, latex, no figures. V.2, minor corrections, a reference
adde
Evidence for the classical integrability of the complete AdS(4) x CP(3) superstring
We construct a zero-curvature Lax connection in a sub-sector of the
superstring theory on AdS(4) x CP(3) which is not described by the
OSp(6|4)/U(3) x SO(1,3) supercoset sigma-model. In this sub-sector worldsheet
fermions associated to eight broken supersymmetries of the type IIA background
are physical fields. As such, the prescription for the construction of the Lax
connection based on the Z_4-automorphism of the isometry superalgebra OSp(6|4)
does not do the job. So, to construct the Lax connection we have used an
alternative method which nevertheless relies on the isometry of the target
superspace and kappa-symmetry of the Green-Schwarz superstring.Comment: 1+26 pages; v2: minor typos corrected, acknowledgements adde
Superparticle Models with Tensorial Central Charges
A generalization of the Ferber-Shirafuji formulation of superparticle
mechanics is considered. The generalized model describes the dynamics of a
superparticle in a superspace extended by tensorial central charge coordinates
and commuting twistor-like spinor variables. The D=4 model contains a
continuous real parameter and at a=0 reduces to the SU(2,2|1)
supertwistor Ferber-Shirafuji model, while at a=1 one gets an OSp(1|8)
supertwistor model of ref. [1] (hep-th/9811022) which describes BPS states with
all but one unbroken target space supersymmetries. When 0<a<1 the model admits
an OSp(2|8) supertwistor description, and when a>1 the supertwistor group
becomes OSp(1,1|8). We quantize the model and find that its quantum spectrum
consists of massless states of an arbitrary (half)integer helicity. The
independent discrete central charge coordinate describes the helicity spectrum.
We also outline the generalization of the a=1 model to higher space-time
dimensions and demonstrate that in D=3,4,6 and 10, where the quantum states are
massless, the extra degrees of freedom (with respect to those of the standard
superparticle) parametrize compact manifolds. These compact manifolds can be
associated with higher-dimensional helicity states. In particular, in D=10 the
additional ``helicity'' manifold is isomorphic to the seven-sphere.Comment: 32 pages, LATEX, no figure
Generalized action principle and extrinsic geometry for N=1 superparticle
It is proposed the generalized action functional for N=1 superparticle in
D=3,4,6 and 10 space-time dimensions. The superfield geometric approach
equations describing superparticle motion in terms of extrinsic geometry of the
worldline superspace are obtained on the base of the generalized action. The
off-shell superdiffeomorphism invariance (in the rheonomic sense) of the
superparticle generalized action is proved. It was demonstrated that the half
of the fermionic and one bosonic (super)fields disappear from the generalized
action in the analytical basis. Superparticle interaction with Abelian gauge
theory is considered in the framework of this formulation. The geometric
approach equations describing superparticle motion in Abelian background are
obtained.Comment: 31 pages. Late
Photoactivation experiment on 197Au and its implications for the dipole strength in heavy nuclei
The 197Au(gamma,n) reaction is used as an activation standard for
photodisintegration studies on astrophysically relevant nuclei. At the
bremsstrahlung facility of the superconducting electron accelerator ELBE
(Electron Linear accelerator of high Brilliance and low Emittance) of
Forschungszentrum Dresden-Rossendorf, photoactivation measurements on 197Au
have been performed with bremsstrahlung endpoint energies from 8.0 to 15.5 MeV.
The measured activation yield is compared with previous experiments as well as
with calculations using Hauser-Feshbach statistical models. It is shown that
the experimental data are best described by a two-Lorentzian parametrization
with taking the axial deformation of 197Au into account. The experimental
197Au(gamma,n) reaction yield measured at ELBE via the photoactivation method
is found to be consistent with previous experimental data using photon
scattering or neutron detection methods.Comment: 9 page
Superbrane Actions and Geometrical Approach
We review a generic structure of conventional (Nambu-Goto and
Dirac-Born-Infeld-like) worldvolume actions for the superbranes and show how it
is connected through a generalized action construction with a doubly
supersymmetric geometrical approach to the description of super-p-brane
dynamics as embedding world supersurfaces into target superspaces.Comment: Based on talks given by the authors at the Volkov Memorial Seminar
"Supersymmetry and Quantum field Theory" (Kharkov, January 5-7, 1997), LaTeX
file, 11 pages Misprints corrected, references adde
Higher Spins from Tensorial Charges and OSp(N|2n) Symmetry
It is shown that the quantization of a superparticle propagating in an N=1,
D=4 superspace extended with tensorial coordinates results in an infinite tower
of massless spin states satisfying the Vasiliev unfolded equations for free
higher spin fields in flat and AdS_4 N=1 superspace. The tensorial extension of
the AdS_4 superspace is proved to be a supergroup manifold OSp(1|4). The model
is manifestly invariant under an OSp(N|8) (N=1,2) superconformal symmetry. As a
byproduct, we find that the Cartan forms of arbitrary Sp(2n) and OSp(1|2n)
groups are GL(2n) flat, i.e. they are equivalent to flat Cartan forms up to a
GL(2n) rotation. This property is crucial for carrying out the quantization of
the particle model on OSp(1|4) and getting the higher spin field dynamics in
super AdS_4, which can be performed in a way analogous to the flat case.Comment: LaTeX, 21 page (JHEP style), misprints corrected, added comments on
the relation of results of hep-th/0106149 with hep-th/9904109 and
hep-th/9907113, references adde
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