6,455 research outputs found
Bose-Einstein Condensation of Sr Through Sympathetic Cooling with Sr
We report Bose-Einstein condensation of Sr, which has a small,
negative s-wave scattering length (\,). We overcome the poor
evaporative cooling characteristics of this isotope by sympathetic cooling with
Sr atoms. Sr is effective in this role in spite of the fact that
it is a fermion because of the large ground state degeneracy arising from a
nuclear spin of , which reduces the impact of Pauli blocking of
collisions. We observe a limited number of atoms in the condensate
() that is consistent with the value of and the
optical dipole trap parameters.Comment: 4 pages, 4 figure
Runaway evaporation for optically dressed atoms
Forced evaporative cooling in a far-off-resonance optical dipole trap is
proved to be an efficient method to produce fermionic- or bosonic-degenerated
gases. However in most of the experiences, the reduction of the potential
height occurs with a diminution of the collision elastic rate. Taking advantage
of a long-living excited state, like in two-electron atoms, I propose a new
scheme, based on an optical knife, where the forced evaporation can be driven
independently of the trap confinement. In this context, the runaway regime
might be achieved leading to a substantial improvement of the cooling
efficiency. The comparison with the different methods for forced evaporation is
discussed in the presence or not of three-body recombination losses
Degenerate Fermi Gas of Sr
We report quantum degeneracy in a gas of ultra-cold fermionic Sr
atoms. By evaporatively cooling a mixture of spin states in an optical dipole
trap for 10.5\,s, we obtain samples well into the degenerate regime with
. The main signature of degeneracy is a change in the
momentum distribution as measured by time-of-flight imaging, and we also
observe a decrease in evaporation efficiency below .Comment: 4 pages, 3 figure
Inelastic and elastic collision rates for triplet states of ultracold strontium
We report measurement of the inelastic and elastic collision rates for
^{88}Sr atoms in the (5s5p)^3P_0 state in a crossed-beam optical dipole trap.
This is the first measurement of ultracold collision properties of a ^3P_0
level in an alkaline-earth atom or atom with similar electronic structure.
Since the (5s5p)^3P_0 state is the lowest level of the triplet manifold, large
loss rates indicate the importance of principle-quantum-number-changing
collisions at short range. We also provide an estimate of the collisional loss
rates for the (5s5p){^3P_2} state.Comment: 4 pages 5 figure
Geometrical CP violation in multi-Higgs models
We introduce several methods to obtain calculable phases with geometrical
values that are independent of arbitrary parameters in the scalar potential.
These phases depend on the number of scalars and on the order of the discrete
non-Abelian group considered. Using these methods we present new geometrical CP
violation candidates with vacuum expectation values that must violate CP (the
transformation that would make them CP conserving is not a symmetry of the
potential). We also extend to non-renormalisable potentials the proof that more
than two scalars are needed to obtain these geometrical CP violation
candidates.Comment: 8 pages, 2 figures. v2: table added, accepted by JHE
Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2 - (5s4d)3D2 transition
We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms
using the (5s5p)3P2 - (5s4d)3D2 transition. Atom number in a magneto-optical
trap is enhanced by driving this transition because Sr atoms that have decayed
into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state.
Spectroscopy of 84Sr, 86Sr, 87Sr, and 88Sr improves the value of the (5s5p)3P2
- (5s4d)3D2 transition frequency for 88Sr and determines the isotope shifts for
the transition.Comment: 4 pages, 5 figure
Fish Welfare in Urban Aquaponics: Effects of Fertilizer for Lettuce (Lactuca sativa L.) on Some Physiological Stress Indicators in Nile Tilapia (Oreochromis niloticus L.)
The combination of hydroponics and aquaculture, or aquaponics, normally requires adding fertilizer to recirculated water to ensure optimal plant growth, but the effect of that fertilizer on fish welfare has not been studied in detail, especially for small urban and coupled aquaponic systems. In this study, a commercial fertilizer was placed in two small aquaponic systems (less than 250 liters each) to test its effect on the stress levels of Nile tilapia (Oreochromis niloticus) compared to controls without any fertilizer. Fish production parameters were not significantly different between treatments, nor were physiological indicators of fish stress (plasma cortisol, glucose, and triglycerides). On the other hand, lettuce growth (leaf and root weight and length) was up to three times higher in the treatment that received fertilizer. © 2022 by the authors. Licensee MDPI, Basel, Switzerland
Sesame meal as the first protein source in piglet starter diets and advantages of a phytase: a digestive study
Soybean meal (SBM) is the protein source that is used most in feeding piglets, but its high price has prompted a search for alternatives. One option is sesame meal (SM), a by-product of sesame oil. This study evaluated the effects of SM and phytase on the intestinal morphology, total trypsin activity (TTA) and specific trypsin activity (STA), apparent ileal digestibility (AID) of amino acids (AAs), and apparent total tract digestibility (ATTD) of phosphorus (P), calcium (Ca), and energy (E) in weaned piglets. Twenty piglets weaned at 17 days old were placed in metabolic cages in a temperature-controlled room. When the piglets were 21 days old, cannulas were fitted at the terminal ileum. From the fourth day after surgery, piglets received the experimental treatments for nine days, namely an SM or SBM diet, each with or without phytase. The protein source or phytase did not affect villus height, crypt depth, or TTA. However, phytase increased STA. The AID of dry matter (DM), E, crude protein (CP), and AA was similar among treatments, except for arginine, which was more digestible in the SM diets (85.8) than in the SBM ones (81.6). The ATTD of DM and E was higher in the SM than in the SBM diets. Phytase increased the ATTD of Ca (22.7 %) and P (27.9 %). The findings showed that SM can be used as a protein source for piglets and that its consumption increases arginine intake. The addition of phytase to the diet increases the ATTD of P and Ca.Keywords: Amino acids digestibility, arginine, piglets weaning, phosphorus digestibilit
- …