1,648 research outputs found
N-qubit states as points on the Bloch sphere
We show how the Majorana representation can be used to express the pure
states of an N-qubit system as points on the Bloch sphere. We compare this
geometrical representation of N-qubit states with an alternative one, proposed
recently by the present authors.Comment: 9 pages, 2 figures, contribution to CEWQO 2009 proceedings. v2: Minor
changes, published versio
Spacetime Foam Model of the Schwarzschild Horizon
We consider a spacetime foam model of the Schwarzschild horizon, where the
horizon consists of Planck size black holes. According to our model the entropy
of the Schwarzschild black hole is proportional to the area of its event
horizon. It is possible to express geometrical arguments to the effect that the
constant of proportionality is, in natural units, equal to one quarter.Comment: 16 pages, 2 figures, improved and extended version with some
significant changes. Accepted for publication in Phys.Rev.
Microscopic Black Hole Pairs in Highly-Excited States
We consider the quantum mechanics of a system consisting of two identical,
Planck-size Schwarzschild black holes revolving around their common center of
mass. We find that even in a very highly-excited state such a system has very
sharp, discrete energy eigenstates, and the system performs very rapid
transitions from a one stationary state to another. For instance, when the
system is in the 100th excited state, the life times of the energy eigenstates
are of the order of s, and the energies of gravitons released in
transitions between nearby states are of the order of eV.Comment: 22 pages, 3 figures, uses RevTe
Explicit expressions for the topological defects of spinor Bose-Einstein condensates
In this paper we first derive a general method which enables one to create
expressions for vortices and monopoles. By using this method we construct
several order-parameters describing the vortices and monopoles of Bose-Einstein
condensates with hyperfine spin F=1 and F=2. We concentrate on defects which
are topologically stable in the absence of an external magnetic field. In
particular we show that in a ferromagnetic condensate there can be a vortex
which does not produce any superfluid flow. We also point out that the
order-parameter space of the cyclic phase of F=2 condensate consists of two
disconnected sets. Finally we examine the effect of an external magnetic field
on the vortices of a ferromagnetic F=1 condensate and discuss the experimental
preparation of a vortex in this system.Comment: 17 pages, partly rewritten to improve clarity, conclusions unchange
Application of CRISPR/Cas9 Tools for Genome Editing in the White-Rot Fungus Dichomitus squalens
Dichomitus squalens is an emerging reference species that can be used to investigate white-rot fungal plant biomass degradation, as it has flexible physiology to utilize different types of biomass as sources of carbon and energy. Recent comparative (post-) genomic studies on D. squalens resulted in an increasingly detailed knowledge of the genes and enzymes involved in the lignocellulose breakdown in this fungus and showed a complex transcriptional response in the presence of lignocellulose-derived compounds. To fully utilize this increasing amount of data, efficient and reliable genetic manipulation tools are needed, e.g., to characterize the function of certain proteins in vivo and facilitate the construction of strains with enhanced lignocellulolytic capabilities. However, precise genome alterations are often very difficult in wild-type basidiomycetes partially due to extremely low frequencies of homology directed recombination (HDR) and limited availability of selectable markers. To overcome these obstacles, we assessed various Cas9-single guide RNA (sgRNA) ribonucleoprotein (RNP) -based strategies for selectable homology and non-homologous end joining (NHEJ) -based gene editing in D. squalens. We also showed an induction of HDR-based genetic modifications by using single-stranded oligodeoxynucleotides (ssODNs) in a basidiomycete fungus for the first time. This paper provides directions for the application of targeted CRISPR/Cas9-based genome editing in D. squalens and other wild-type (basidiomycete) fungi
Application of CRISPR/Cas9 Tools for Genome Editing in the White-Rot Fungus Dichomitus squalens
Dichomitus squalens is an emerging reference species that can be used to investigate white-rot fungal plant biomass degradation, as it has flexible physiology to utilize different types of biomass as sources of carbon and energy. Recent comparative (post-) genomic studies on D. squalens resulted in an increasingly detailed knowledge of the genes and enzymes involved in the lignocellulose breakdown in this fungus and showed a complex transcriptional response in the presence of lignocellulose-derived compounds. To fully utilize this increasing amount of data, efficient and reliable genetic manipulation tools are needed, e.g., to characterize the function of certain proteins in vivo and facilitate the construction of strains with enhanced lignocellulolytic capabilities. However, precise genome alterations are often very difficult in wild-type basidiomycetes partially due to extremely low frequencies of homology directed recombination (HDR) and limited availability of selectable markers. To overcome these obstacles, we assessed various Cas9-single guide RNA (sgRNA) ribonucleoprotein (RNP) -based strategies for selectable homology and non-homologous end joining (NHEJ) -based gene editing in D. squalens. We also showed an induction of HDR-based genetic modifications by using single-stranded oligodeoxynucleotides (ssODNs) in a basidiomycete fungus for the first time. This paper provides directions for the application of targeted CRISPR/Cas9-based genome editing in D. squalens and other wild-type (basidiomycete) fungi
Interplanetary shocks lacking type II radio bursts
We report on the radio-emission characteristics of 222 interplanetary (IP)
shocks. A surprisingly large fraction of the IP shocks (~34%) is radio quiet
(i.e., the shocks lacked type II radio bursts). The CMEs associated with the RQ
shocks are generally slow (average speed ~535 km/s) and only ~40% of the CMEs
were halos. The corresponding numbers for CMEs associated with radio loud (RL)
shocks are 1237 km/s and 72%, respectively. The RQ shocks are also accompanied
by lower peak soft X-ray flux. CMEs associated with RQ (RL) shocks are
generally accelerating (decelerating). The kinematics of CMEs associated with
the km type II bursts is similar to those of RQ shocks, except that the former
are slightly more energetic. Comparison of the shock The RQ shocks seem to be
mostly subcritical and quasi-perpendicular. The radio-quietness is predominant
in the rise phase and decreases through the maximum and declining phases of
solar cycle 23. The solar sources of the shock-driving CMEs follow the sunspot
butterfly diagram, consistent with the higher-energy requirement for driving
shocks
Radio-loud CMEs from the disk center lacking shocks at 1 AU
A coronal mass ejection (CME) associated with a type II burst and originating
close to the center of the solar disk typically results in a shock at Earth in
2-3 days and hence can be used to predict shock arrival at Earth. However, a
significant fraction (about 28%) of such CMEs producing type II bursts were not
associated with shocks at Earth. We examined a set of 21 type II bursts
observed by the Wind/WAVES experiment at decameter-hectometric (DH) wavelengths
that had CME sources very close to the disk center (within a central meridian
distance of 30 degrees), but did not have a shock at Earth. We find that the
near-Sun speeds of these CMEs average to ~644 km/s, only slightly higher than
the average speed of CMEs associated with radio-quiet shocks. However, the
fraction of halo CMEs is only ~30%, compared to 54% for the radio-quiet shocks
and 91% for all radio-loud shocks. We conclude that the disk-center radio-loud
CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks
only close to the Sun and dissipate before arriving at Earth. There is also
evidence for other possible processes that lead to the lack of shock at 1 AU:
(i) overtaking CME shocks merge and one observes a single shock at Earth, and
(ii) deflection by nearby coronal holes can push the shocks away from the
Sun-Earth line, such that Earth misses these shocks. The probability of
observing a shock at 1 AU increases rapidly above 60% when the CME speed
exceeds 1000 km/s and when the type II bursts propagate to frequencies below 1
MHz.Comment: 33 pages, 11 figures, 2 table
Identification of an l-Arabitol Transporter from Aspergillus niger
l-arabitol is an intermediate of the pentose catabolic pathway in fungi but can also be used as a carbon source by many fungi, suggesting the presence of transporters for this polyol. In this study, an l-arabitol transporter, LatA, was identified in Aspergillus niger. Growth and expression profiles as well as sugar consumption analysis indicated that LatA only imports l-arabitol and is regulated by the arabinanolytic transcriptional activator AraR. Moreover, l-arabitol production from wheat bran was increased in a metabolically engineered A. niger mutant by the deletion of latA, indicating its potential for improving l-arabitol-producing cell factories. Phylogenetic analysis showed that homologs of LatA are widely conserved in fungi
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