38,841 research outputs found
Cozymase. A study of purification methods
Cozymase is one of the essential components of the complex enzyme mixture which effects alcoholic fermentation in the absence of living cells. The separation of the mixture into zymase and cozymase was first accomplished by Harden and Young [1] by means of ultrafiltration through a gelatin-impregnated Chamberland filter candle. The residue and filtrate as thus prepared possessed, separately, no fermentative action, but when mixed were found to produce a rapid fermentation. The active constituent of the residue was named zymase, while that constituent of the filtrate responsible for the reactivation of the residue was named cozymase.
We studied the purification produced in our material by a variety of reagents. In the investigation we have repeated much of the work done by von Euler and Myrbäk [2], and several differences have been found, which appear difficult to explain solely upon the basis of the lower initial purity of our material. As certain of the experiments show distinct promise, we hope to be able to extend the work upon a material of considerably higher original purity, such as was employed by von Euler and Myrbäk
Bose-Einstein condensation in complex networks
The evolution of many complex systems, including the world wide web, business
and citation networks is encoded in the dynamic web describing the interactions
between the system's constituents. Despite their irreversible and
non-equilibrium nature these networks follow Bose statistics and can undergo
Bose-Einstein condensation. Addressing the dynamical properties of these
non-equilibrium systems within the framework of equilibrium quantum gases
predicts that the 'first-mover-advantage', 'fit-get-rich' and
'winner-takes-all' phenomena observed in competitive systems are
thermodynamically distinct phases of the underlying evolving networks
Impurity transport in a mixed-collisionality stellarator plasma
A potential threat to the performance of magnetically confined fusion plasmas
is the problem of impurity accumulation, which causes the concentration of
highly charged impurity ions to rise uncontrollably in the center of the plasma
and spoil the energy confinement by excessive radiation. It has long been
thought that the collisional transport of impurities in stellarators always
leads to such accumulation (if the electric field points inwards, which is
usually the case), whereas tokamaks, being axisymmetric, can benefit from
"temperature screening", i.e., an outward flux of impurities driven by the
temperature gradient. Here it is shown, using analytical techniques supported
by results from a new numerical code, that such screening can arise in
stellarator plasmas too, and indeed does so in one of the most relevant
operating regimes, where the impurities are highly collisional whilst the bulk
plasma is in any of the low-collisionality regimes.Comment: 11 pages, 3 figure
Impurity transport and bulk ion flow in a mixed collisionality stellarator plasma
The accumulation of impurities in the core of magnetically confined plasmas,
resulting from standard collisional transport mechanisms, is a known threat to
their performance as fusion energy sources. Whilst the axisymmetric tokamak
systems have been shown to benefit from the effect of temperature screening,
that is an outward flux of impurities driven by the temperature gradient,
impurity accumulation in stellarators was thought to be inevitable, driven
robustly by the inward pointing electric field characteristic of hot fusion
plasmas. We have shown in Helander et. al. (2017b) that such screening can in
principle also appear in stellarators, in the experimentally relevant mixed
collisionality regime, where a highly collisional impurity species is present
in a low collisionality bulk plasma. Details of the analytic calculation are
presented here, along with the effect of the impurity on the bulk ion flow,
which will ultimately affect the bulk contribution to the bootstrap current
Recent Developments in Osteogenesis Imperfecta
Osteogenesis imperfecta (OI) is an uncommon genetic bone disease associated with brittle bones and fractures in children and adults. Although OI is most commonly associated with mutations of the genes for type I collagen, many other genes (some associated with type I collagen processing) have now been identified. The genetics of OI and advances in our understanding of the biomechanical properties of OI bone are reviewed in this article. Treatment includes physiotherapy, fall prevention, and sometimes orthopedic procedures. In this brief review, we will also discuss current understanding of pharmacologic therapies for treatment of OI
A type system for components
In modern distributed systems, dynamic reconfiguration, i.e.,
changing at runtime the communication pattern of a program, is chal-
lenging. Generally, it is difficult to guarantee that such modifications will
not disrupt ongoing computations. In a previous paper, a solution to this
problem was proposed by extending the object-oriented language ABS
with a component model allowing the programmer to: i) perform up-
dates on objects by means of communication ports and their rebinding;
and ii) precisely specify when such updates can safely occur in an object
by means of critical sections. However, improper rebind operations could
still occur and lead to runtime errors. The present paper introduces a
type system for this component model that extends the ABS type system
with the notion of ports and a precise analysis that statically enforces
that no object will attempt illegal rebinding
Topology of evolving networks: local events and universality
Networks grow and evolve by local events, such as the addition of new nodes
and links, or rewiring of links from one node to another. We show that
depending on the frequency of these processes two topologically different
networks can emerge, the connectivity distribution following either a
generalized power-law or an exponential. We propose a continuum theory that
predicts these two regimes as well as the scaling function and the exponents,
in good agreement with the numerical results. Finally, we use the obtained
predictions to fit the connectivity distribution of the network describing the
professional links between movie actors.Comment: 13 pages, 3 figure
Constraining blazar distances with combined Fermi and TeV data: an empirical approach
We discuss a method to constrain the distance of blazars with unknown
redshift using combined observations in the GeV and TeV regimes. We assume that
the VHE spectrum corrected for the absorption through the interaction with the
Extragalactic Background Light can not be harder than the spectrum in the
Fermi/LAT band. Starting from the observed VHE spectral data we derive the
EBL-corrected spectra as a function of the redshift z and fit them with power
laws to be compared with power law fits to the LAT data. We apply the method to
all TeV blazars detected by LAT with known distance and derive an empirical law
describing the relation between the upper limits and the true redshifts that
can be used to estimate the distance of unknown redshift blazars. Using
different EBL models leads to systematic changes in the derived upper limits.
Finally, we use this relation to infer the distance of the unknown redshift
blazar PKS 1424+240.Comment: 5 pages, 4 figures, accepted for publication in MNRAS, minor revisio
Giant strongly connected component of directed networks
We describe how to calculate the sizes of all giant connected components of a
directed graph, including the {\em strongly} connected one. Just to the class
of directed networks, in particular, belongs the World Wide Web. The results
are obtained for graphs with statistically uncorrelated vertices and an
arbitrary joint in,out-degree distribution . We show that if
does not factorize, the relative size of the giant strongly
connected component deviates from the product of the relative sizes of the
giant in- and out-components. The calculations of the relative sizes of all the
giant components are demonstrated using the simplest examples. We explain that
the giant strongly connected component may be less resilient to random damage
than the giant weakly connected one.Comment: 4 pages revtex, 4 figure
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