272 research outputs found
Studies on the motility and cryopreservation of rainbow trout (Salmo gairdneri) spermatozoa
The very short duration of vigorous movement (1½ to 7 min) in fresh water and physiological solutions make trout spermatozoa difficult subjects for cryopreservation studies. Solutions consisting of 250 to 280 mmol sucrose and 5 to 12% dimethyl sulphoxide (DMSO) (4 parts) did not activate trout spermatozoa (1 part), but after dilution with fresh water vigorous motility could be fully restored. These sucrose·DMSO solutions were employed in cryopreservation studies. Using straws and a fast freezing - fast thawing procedure, post· thaw dilution with fresh water resulted in 25% - 60% of spero matozoa becoming motile, all with vigorous forward progression. Some existing methods for the cryopreservation of other freshwater fish spermatozoa were repeated on trout without success
Absolute Calibration of a 200 MeV Proton Polarimeter for Use with the Brookhaven Linac
This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit
Counter-propagating radiative shock experiments on the Orion laser and the formation of radiative precursors
We present results from new experiments to study the dynamics of radiative
shocks, reverse shocks and radiative precursors. Laser ablation of a solid
piston by the Orion high-power laser at AWE Aldermaston UK was used to drive
radiative shocks into a gas cell initially pressurised between and $1.0 \
bar with different noble gases. Shocks propagated at {80 \pm 10 \ km/s} and
experienced strong radiative cooling resulting in post-shock compressions of {
\times 25 \pm 2}. A combination of X-ray backlighting, optical self-emission
streak imaging and interferometry (multi-frame and streak imaging) were used to
simultaneously study both the shock front and the radiative precursor. These
experiments present a new configuration to produce counter-propagating
radiative shocks, allowing for the study of reverse shocks and providing a
unique platform for numerical validation. In addition, the radiative shocks
were able to expand freely into a large gas volume without being confined by
the walls of the gas cell. This allows for 3-D effects of the shocks to be
studied which, in principle, could lead to a more direct comparison to
astrophysical phenomena. By maintaining a constant mass density between
different gas fills the shocks evolved with similar hydrodynamics but the
radiative precursor was found to extend significantly further in higher atomic
number gases (\sim4$ times further in xenon than neon). Finally, 1-D and 2-D
radiative-hydrodynamic simulations are presented showing good agreement with
the experimental data.Comment: HEDLA 2016 conference proceeding
Fluctuating Nematic Elastomer Membranes: a New Universality Class
We study the flat phase of nematic elastomer membranes with rotational
symmetry spontaneously broken by in-plane nematic order. Such state is
characterized by a vanishing elastic modulus for simple shear and soft
transverse phonons. At harmonic level, in-plane orientational (nematic) order
is stable to thermal fluctuations, that lead to short-range in-plane
translational (phonon) correlations. To treat thermal fluctuations and relevant
elastic nonlinearities, we introduce two generalizations of two-dimensional
membranes in a three dimensional space to arbitrary D-dimensional membranes
embedded in a d-dimensional space, and analyze their anomalous elasticities in
an expansion about D=4. We find a new stable fixed point, that controls
long-scale properties of nematic elastomer membranes. It is characterized by
singular in-plane elastic moduli that vanish as a power-law eta_lambda=4-D of a
relevant inverse length scale (e.g., wavevector) and a finite bending rigidity.
Our predictions are asymptotically exact near 4 dimensions.Comment: 18 pages, 4 eps figures. submitted to PR
Low Q^2 Jet Production at HERA and Virtual Photon Structure
The transition between photoproduction and deep-inelastic scattering is
investigated in jet production at the HERA ep collider, using data collected by
the H1 experiment. Measurements of the differential inclusive jet
cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the
transverse energy and the pseudorapidity of the jets in the virtual
photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3
< y < 0.6. The interpretation of the results in terms of the structure of the
virtual photon is discussed. The data are best described by QCD calculations
which include a partonic structure of the virtual photon that evolves with Q2.Comment: 20 pages, 5 Figure
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
The structure of the Yang-Mills spectrum for arbitrary simple gauge algebras
The mass spectrum of pure Yang-Mills theory in 3+1 dimensions is discussed
for an arbitrary simple gauge algebra within a quasigluon picture. The general
structure of the low-lying gluelump and two-quasigluon glueball spectrum is
shown to be common to all algebras, while the lightest three-quasigluon
glueballs only exist when the gauge algebra is A, that is in
particular . Higher-lying glueballs are shown to
exist only for the A, D and E gauge
algebras. The shape of the static energy between adjoint sources is also
discussed assuming the Casimir scaling hypothesis and a funnel form; it appears
to be gauge-algebra dependent when at least three sources are considered. As a
main result, the present framework's predictions are shown to be consistent
with available lattice data in the particular case of an
gauge algebra within 't Hooft's large- limit.Comment: 21 pages, 4 figures; remarks added, typos corrected in v2. v3 to
appear in EPJ
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