155 research outputs found
Macroscopic study of time unsteady noise of an aircraft engine during static tests
Static tests of aircraft engines can exhibit greater than 10 db random unsteadiness of tone noise levels because flow disturbances that prevail near test site facilities are ingested. Presumably such changes are related to installation and test site features. Some properties of unsteady noise observed during tests of a Lycoming YF-102 turbofan engine are presented. Time and spatial variations in tone noise obtained from closely spaced far field and inlet duct microphones are displayed. Long to extremely short intermittent tone bursts are observed. Unsteadiness of the tone, its harmonics, and the broadband noise show little similarity. In the far field, identity of tone bursts is retained over a directivity angle of less than 10 deg. In the inlet duct, tone bursts appear to propagate axially but exhibit little circumferential similarity. They show only slight relationship to tone bursts observed in the far field. The results imply an intermittent generation of random mixtures of propagating duct modes
Comparison of NASA and contractor results from aeroacoustic tests of QCSEE OTW engine
The aerodynamics and acoustics of the over-the-wing (OTW) Quiet, Clean, Short Haul Experimental Engine (QCSEE) were tested. A boilerplate (nonflight weight), high-throat Mach number, acoustically treated inlet and a D-shaped OTW exhaust nozzle with variable position side doors were used. Some acoustic directivity results for the type "D" nozzle and acoustic effects of variations in the nozzle side door positions are included. It was found that the results are in agreement with those previously obtained
Ground-State Electromagnetic Moments of Calcium Isotopes
High-resolution bunched-beam collinear laser spectroscopy was used to measure
the optical hyperfine spectra of the Ca isotopes. The ground state
magnetic moments of Ca and quadrupole moments of Ca were
measured for the first time, and the Ca ground state spin was
determined in a model-independent way. Our results provide a critical test of
modern nuclear theories based on shell-model calculations using
phenomenological as well as microscopic interactions. The results for the
neutron-rich isotopes are in excellent agreement with predictions using
interactions derived from chiral effective field theory including three-nucleon
forces, while lighter isotopes illustrate the presence of particle-hole
excitations of the Ca core in their ground state.Comment: Accepted as a Rapid Communication in Physical Review
Calculation of electrostatic fields using quasi-Green's functions: application to the hybrid Penning trap.
Penning traps offer unique possibilities for storing, manipulating and investigating charged particles with high sensitivity and accuracy. The widespread applications of Penning traps in physics and chemistry comprise e.g. mass spectrometry, laser spectroscopy, measurements of electronic and nuclear magnetic moments, chemical sample analysis and reaction studies. We have developed a method, based on the Green's function approach, which allows for the analytical calculation of the electrostatic properties of a Penning trap with arbitrary electrodes. The ansatz features an extension of Dirichlet's problem to nontrivial geometries and leads to an analytical solution of the Laplace equation. As an example we discuss the toroidal hybrid Penning trap designed for our planned measurements of the magnetic moment of the (anti)proton. As in the case of cylindrical Penning traps, it is possible to optimize the properties of the electric trapping fields, which is mandatory for high-precision experiments with single charged particles. Of particular interest are the anharmonicity compensation, orthogonality and optimum adjustment of frequency shifts by the continuous SternGerlach effect in a quantum jump spectrometer. The mathematical formalism developed goes beyond the mere design of novel Penning traps and has potential applications in other fields of physics and engineering
Q-Value and Half-Lives for the Double-Beta-Decay Nuclide 110Pd
The 110Pd double-beta decay Q-value was measured with the Penning-trap mass
spectrometer ISOLTRAP to be Q = 2017.85(64) keV. This value shifted by 14 keV
compared to the literature value and is 17 times more precise, resulting in new
phase-space factors for the two-neutrino and neutrinoless decay modes. In
addition a new set of the relevant matrix elements has been calculated. The
expected half-life of the two-neutrino mode was reevaluated as 1.5(6) E20 yr.
With its high natural abundance, the new results reveal 110Pd to be an
excellent candidate for double-beta decay studies
Spins, Electromagnetic Moments, and Isomers of 107-129Cd
The neutron-rich isotopes of cadmium up to the N=82 shell closure have been
investigated by high-resolution laser spectroscopy. Deep-UV excitation at 214.5
nm and radioactive-beam bunching provided the required experimental
sensitivity. Long-lived isomers are observed in 127Cd and 129Cd for the first
time. One essential feature of the spherical shell model is unambiguously
confirmed by a linear increase of the 11/2- quadrupole moments. Remarkably,
this mechanism is found to act well beyond the h11/2 shell
Comprehensive Characterization of the Complex lola Locus Reveals a Novel Role in the Octopaminergic Pathway via Tyramine Beta-Hydroxylase Regulation
Longitudinals lacking (lola) is one of the most complex genes in Drosophila melanogaster, encoding up to 20 protein isoforms that include key transcription factors involved in axonal pathfinding and neural reprogramming. Most previous studies have employed loss-of-function alleles that disrupt lola common exons, making it difficult to delineate isoform-specific functions. To overcome this issue, we have generated isoform-specific mutants for all isoforms using CRISPR/Cas9. This enabled us to study specific isoforms with respect to previously characterized roles for Lola and to demonstrate a specific function for one variant in axon guidance via activation of the microtubule-associated factor Futsch. Importantly, we also reveal a role for a second variant in preventing neurodegeneration via the positive regulation of a key enzyme of the octopaminergic pathway. Thus, our comprehensive study expands the functional repertoire of Lola functions, and it adds insights into the regulatory control of neurotransmitter expression in vivo
Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K
The recently confirmed neutron-shell closure at N = 32 has been investigated
for the first time below the magic proton number Z = 20 with mass measurements
of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide
investigated at the online mass spectrometer ISOLTRAP. The resulting
two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly
lower than for 52Ca, highlighting the doubly-magic nature of this nuclide.
Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations
are challenged by the new measurements but reproduce qualitatively the observed
shell effect.Comment: 5 pages, 5 figure
- âŠ