893 research outputs found
On the variation of leaf border in Rhizomnium (Cinclidiaceae)
In the genus Rhizomnium T. Kop. most taxa have a strong leaf border several cells broad and bi- to tristratose. Rhizomnium striatulum (Mitt.) T. Kop. belongs to that group. In Northeast China one population of R. striatulum was found with a very weak leaf border, and also the costa of these plants is weaker than is characteristic for the species. The deviating population is figured and its significance discussed. The distribution of R. striatulum is mapped
Fermi condensates for dynamic imaging of electro-magnetic fields
Ultracold gases provide micrometer size atomic samples whose sensitivity to
external fields may be exploited in sensor applications. Bose-Einstein
condensates of atomic gases have been demonstrated to perform excellently as
magnetic field sensors \cite{Wildermuth2005a} in atom chip
\cite{Folman2002a,Fortagh2007a} experiments. As such, they offer a combination
of resolution and sensitivity presently unattainable by other methods
\cite{Wildermuth2006a}. Here we propose that condensates of Fermionic atoms can
be used for non-invasive sensing of time-dependent and static magnetic and
electric fields, by utilizing the tunable energy gap in the excitation spectrum
as a frequency filter. Perturbations of the gas by the field create both
collective excitations and quasiparticles. Excitation of quasiparticles
requires the frequency of the perturbation to exceed the energy gap. Thus, by
tuning the gap, the frequencies of the field may be selectively monitored from
the amount of quasiparticles which is measurable for instance by
RF-spectroscopy. We analyse the proposed method by calculating the
density-density susceptibility, i.e. the dynamic structure factor, of the gas.
We discuss the sensitivity and spatial resolution of the method which may, with
advanced techniques for quasiparticle observation \cite{Schirotzek2008a}, be in
the half a micron scale.Comment: 10 pages, 4 figure
Random l-colourable structures with a pregeometry
We study finite -colourable structures with an underlying pregeometry. The
probability measure that is used corresponds to a process of generating such
structures (with a given underlying pregeometry) by which colours are first
randomly assigned to all 1-dimensional subspaces and then relationships are
assigned in such a way that the colouring conditions are satisfied but apart
from this in a random way. We can then ask what the probability is that the
resulting structure, where we now forget the specific colouring of the
generating process, has a given property. With this measure we get the
following results: 1. A zero-one law. 2. The set of sentences with asymptotic
probability 1 has an explicit axiomatisation which is presented. 3. There is a
formula (not directly speaking about colours) such that, with
asymptotic probability 1, the relation "there is an -colouring which assigns
the same colour to and " is defined by . 4. With asymptotic
probability 1, an -colourable structure has a unique -colouring (up to
permutation of the colours).Comment: 35 page
The size of the pion from full lattice QCD with physical u, d, s and c quarks
We present the first calculation of the electromagnetic form factor of the Ï meson at physical light
quark masses. We use configurations generated by the MILC collaboration including the effect of u, d, s and c sea quarks with the Highly Improved Staggered Quark formalism. We work at three values of the lattice spacing on large volumes and with u/d quark masses going down to the physical value. We study scalar and vector form factors for a range in space-like q2 from 0.0 to -0.13 GeV2 and from their shape we extract mean square radii. Our vector form factor agrees well with experiment and we find hr2iV = 0:403(18)(6) fm2. For the scalar form factor we include quark-line disconnected
contributions which have a significant impact on the radius. We give the first results for SU(3) flavour-singlet and octet scalar mean square radii, obtaining: hr2isinglet
S = 0:506(38)(53)fm2 and hr2ioctet S = 0:431(38)(46)fm2. We discuss the comparison with expectations from chiral perturbation theory
The cave spider Meta menardi (Araneae, Tetragnathidae) â occurrence in Finland and notes on its biology
Fifteen years ago the cave spider Meta menardi (Latreille, 1804) was known in Finland in two locations only. Partly due to extensive search it is to date known from 20 sites, all however located in the south-westernmost parts of the country. M. menardi is known to prefer stable and relatively warm subterranean habitats. Our temperature data from a cave on the Ă
land Islands in Finland indicates that the populations of M. menardi on the northern limit of its distribution could be more cold tolerant than the previously studied populations in Central Europe. In this paper all known locations in Finland are mapped and presented in a table with habitat data. A note on the strategy for catching mosquitoes with the orb web is given and the possible importance of the prey-catching function of the orb web is briefly discussed
Tunability of the optical absorption in small silver cluster-polymer hybrid systems
We have calculated the absorption characteristics of different hybrid systems
consisting of Ag, Ag2 or Ag3 atomic clusters and poly(methacrylic acid) (PMAA)
using the time-dependent density-functional theory. The polymer is found to
have an extensive structural-dependency on the spectral patterns of the hybrid
systems relative to the bare clusters. The absorption spectrum can be `tuned'
to the visible range for hybrid systems with an odd number of electrons per
silver cluster, whereas for hybrid systems comprising an even number of
electrons, the leading absorption edge can be shifted up to about 4.5 eV. The
results give theoretical support to the experimental observations on the
absorption in the visible range in metal cluster-polymer hybrid structures.Comment: Updated layout and minor changes in versions 2 and
The mass of the b-quark from lattice NRQCD and lattice perturbation theory
We present a determination of the b-quark mass accurate through O(\alpha_s^2)
in perturbation theory and including partial contributions at O(\alpha_s^3).
Nonperturbative input comes from the calculation of the Upsilon and B_s
energies in lattice QCD including the effect of u, d and s sea quarks. We use
an improved NRQCD action for the b-quark. This is combined with the heavy quark
energy shift in NRQCD determined using a mixed approach of high-beta simulation
and automated lattice perturbation theory. Comparison with experiment enables
the quark mass to be extracted: in the MS bar scheme we find m_b(m_b) =
4.166(43) GeV.Comment: v2 - corrected some typos and an error in the summary plo
Mangora acalypha new to Finland, with notes on other araneid species spreading northwards (Araneae, Araneidae)
Two specimens of Mangora acalypha (Walckenaer, 1802) were found in a rich pine fen in Hammarland on the Ă
land Islands in 2015. The possible connection of global climate change with five recently (within the last 15 years) recorded araneid species as new to Finland is discussed. These are, in addition to M. acalypha, Agalenatea redii (Scopoli, 1763), Argiope bruennichi (Scopoli, 1772), Larinioides sclopetarius (Clerck, 1757), Neoscona adianta (Walckenaer, 1802)
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