3,250 research outputs found
A Handheld low-mass, impact instrument to measure nondestructive firmness of fruit
A portable, handheld impact firmness sensor was designed for nondestructive measurement of fruit firmness while the fruit remain attached to the tree or for use in other remote locations where the use of a benchtop instrument would be impractical. The instrument design was based on the low-mass, constant velocity, impact-type measurement concept. Validation tests of the handheld sensor using `Bartlett' pears from orchards in California and Washington showed excellent agreement (r2 = 0.92 and 0.96, respectively) with both ASAE Standard method S368.2 for determining the apparent modulus of intact fruit and the impact firmness scores from a commercial benchtop impact firmness instrument
Muscle Oxygen Demands of the Vastus Lateralis in Back and Front Squats
International Journal of Exercise Science 13(6): 734-743, 2020. In resistance training squats are often used to strengthen the muscles of the lower extremities and core muscles. There are two common forms of squats that use a barbell for loading, the back squat and the front squat. The technique and loading of each squat differ markedly. However, the energetic demands on the muscle between the two forms are not well understood. The purpose of this study was to investigate the difference in energy demands between front and back squats by measuring the change in skeletal muscle oxygen saturation (SmO2) through the use of near infrared spectroscopy (NIRS). Methods: Eleven resistance trained individuals, (5 female, 6 male) with an average age of 23.7 ± 1.4, completed 3 sets of 15 repetitions at 70% of their 1-RM weight for both back and front squats. Skeletal muscle oxygen saturation (SmO2) of the vastus lateralis was measured using a wireless NIRS device. Results: The ΔSmO2 was not significantly different between back and front squats but was different between sets 1-3 (44.76 ± 3.24% vs. 55.19 ± 2.75% vs. 56.30 ± 2.63%), main effect p ≤ 0.0001 . The recovery of SmO2 was significantly different between back (42.5 ± 3.4 sec) and front squats (30.9 ± 2.8 sec), main effect p ≤ 0.05. Conclusions: The findings of this study suggest that the energetic demands placed on the vastus lateralis during both front and back squats are similar with a slower recovery of energetics in the back squat
A geometric approach to time evolution operators of Lie quantum systems
Lie systems in Quantum Mechanics are studied from a geometric point of view.
In particular, we develop methods to obtain time evolution operators of
time-dependent Schrodinger equations of Lie type and we show how these methods
explain certain ad hoc methods used in previous papers in order to obtain exact
solutions. Finally, several instances of time-dependent quadratic Hamiltonian
are solved.Comment: Accepted for publication in the International Journal of Theoretical
Physic
Van Hove Singularity and D-Wave Pairing in Disordered Superconductors
We apply the coherent potential approximation (CPA) to a simple model for
disordered superconductors with d-wave pairing. We demonstrate that whilst the
effectiveness of an electronic Van Hove singularity to enhance the transition
temperature T is reduced by disorder it is not eliminated. In fact we give
a qualitative account of changes in the T vs. doping curve with increasing
disorder and compare our results with experiments on the
Y_{0.8}Ca_{0.2}Ba_2(Cu_{1-c}Zn_c)_{3}O_{7-\delta} alloys.Comment: 4 pages of text and 7 postscript file
Z' Decays into Four Fermions
If a new is discovered with a mass at LHC/SSC, its (rare)
decays into two charged leptons plus missing transverse energy will probe the
coupling to the lepton doublet and to , allowing
further discrimination among extended electroweak models.Comment: 9 pages plus 1 figure (not included but available), UG-FT-22/9
A Closed Class of Hydrodynamical Solutions for the Collective Excitations of a Bose-Einstein Condensate
A trajectory approach is taken to the hydrodynamical treatment of collective
excitations of a Bose-Einstein condensate in a harmonic trap. The excitations
induced by linear deformations of the trap are shown to constitute a broad
class of solutions that can be fully described by a simple nonlinear matrix
equation. An exact closed-form expression is obtained for the solution
describing the mode {n=0, m=2} in a cylindrically symmetric trap, and the
calculated amplitude-dependent frequency shift shows good agreement with the
experimental results of the JILA group.Comment: RevTex, 4 pages, 1 eps figure, identical to the published versio
Weak force detection using a double Bose-Einstein condensate
A Bose-Einstein condensate may be used to make precise measurements of weak
forces, utilizing the macroscopic occupation of a single quantum state. We
present a scheme which uses a condensate in a double well potential to do this.
The required initial state of the condensate is discussed, and the limitations
on the sensitivity due to atom collisions and external coupling are analyzed.Comment: 12 pages, 2 figures, Eq.(41) has been correcte
Colorless States in Perturbative QCD: Charmonium and Rapidity Gaps
We point out that an unorthodox way to describe the production of rapidity
gaps in deep inelastic scattering, recently proposed by Buchm\"uller and
Hebecker, suggests a description of the production of heavy quark bound states
which is in agreement with data. The approach questions the conventional
treatment of the color quantum number in perturbative QCD.Comment: 14 pages, plain Latex, 9 postscript figures included. Uses epsf.sty.
Postscript file of paper with figures also available at
http://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-919.ps.Z or at
ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-919.ps.
Spin and orbital ordering in double-layered manganites
We study theoretically the phase diagram of the double-layered perovskite
manganites taking into account the orbital degeneracy, the strong Coulombic
repulsion, and the coupling with the lattice deformation. Observed spin
structural changes as the increased doping are explained in terms of the
orbital ordering and the bond-length dependence of the hopping integral along
-axis. Temperature dependence of the neutron diffraction peak corresponding
to the canting structure is also explained. Comparison with the 3D cubic system
is made.Comment: 7 figure
- …