676 research outputs found
Optical Frequency Optimization of a High Intensity Laser Power Beaming System Utilizing VMJ Photovoltaic Cells
An effective form of wireless power transmission (WPT) has been developed to enable extended mission durations, increased coverage and added capabilities for both space and terrestrial applications that may benefit from optically delivered electrical energy. The high intensity laser power beaming (HILPB) system enables long range optical 'refueling" of electric platforms such as micro unmanned aerial vehicles (MUAV), airships, robotic exploration missions and spacecraft platforms. To further advance the HILPB technology, the focus of this investigation is to determine the optimal laser wavelength to be used with the HILPB receiver, which utilizes vertical multi-junction (VMJ) photovoltaic cells. Frequency optimization of the laser system is necessary in order to maximize the conversion efficiency at continuous high intensities, and thus increase the delivered power density of the HILPB system. Initial spectral characterizations of the device performed at the NASA Glenn Research Center (GRC) indicate the approximate range of peak optical-to-electrical conversion efficiencies, but these data sets represent transient conditions under lower levels of illumination. Extending these results to high levels of steady state illumination, with attention given to the compatibility of available commercial off-the-shelf semiconductor laser sources and atmospheric transmission constraints is the primary focus of this paper. Experimental hardware results utilizing high power continuous wave (CW) semiconductor lasers at four different operational frequencies near the indicated band gap of the photovoltaic VMJ cells are presented and discussed. In addition, the highest receiver power density achieved to date is demonstrated using a single photovoltaic VMJ cell, which provided an exceptionally high electrical output of 13.6 W/sq cm at an optical-to-electrical conversion efficiency of 24 percent. These results are very promising and scalable, as a potential 1.0 sq m HILPB receiver of similar construction would be able to generate 136 kW of electrical power under similar conditions
Comparison of Square and Radial Geometries for High Intensity Laser Power Beaming Receivers
In an effort to further advance a realizable form of wireless power transmission (WPT), high intensity laser power beaming (HILPB) has been developed for both space and terrestrial applications. Unique optical-to-electrical receivers are employed with near infrared (IR-A) continuous-wave (CW) semiconductor lasers to experimentally investigate the HILPB system. In this paper, parasitic feedback, uneven illumination and the implications of receiver array geometries are considered and experimental hardware results for HILPB are presented. The TEM00 Gaussian energy profile of the laser beam presents a challenge to the effectiveness of the receiver to perform efficient photoelectric conversion, due to the resulting non-uniform illumination of the photovoltaic cell arrays. In this investigation, the geometry of the receiver is considered as a technique to tailor the receiver design to accommodate the Gaussian beam profile, and in doing so it is demonstrated that such a methodology is successful in generating bulk receiver output power levels reaching 25 W from 7.2 sq cm of photovoltaic cells. These results are scalable, and may be realized by implementing receiver arraying and utilizing higher power source lasers to achieve a 1.0 sq m receiver capable of generating over 30 kW of electrical power. This type of system would enable long range optical "refueling" of electric platforms, such as MUAV s, airships, robotic exploration missions and provide power to spacecraft platforms which may utilize it to drive electric means of propulsion. In addition, a smaller HILPB receiver aperture size could be utilized to establish a robust optical communications link within environments containing high levels of background radiance, to achieve high signal to noise ratios
Large scale shell model calculations for odd-odd Mn isotopes
Large scale shell model calculations have been carried out for odd-odd
Mn isotopes in two different model spaces. First set of calculations
have been carried out in full shell valence space with two recently
derived shell interactions namely GXPF1A and KB3G treating Ca
as core. The second set of calculations have been performed in
valence space with the interaction treating Ca as core and
imposing a truncation by allowing up to a total of six particle excitations
from the 0f orbital to the upper orbitals for protons and
from the upper orbitals to the 0g orbital for neutron. For
low-lying states in Mn, the KB3G and GXPF1A both predicts good results
and for Mn, KB3G is much better than GXPF1A. For negative parity and
high-spin positive parity states in both isotopes interaction is
required. Experimental data on Mn is sparse and therefore it is not
possible to make any definite conclusions. More experimental data on negative
parity states is needed to ascertain the importance of 0g and higher
orbitals in neutron rich Mn isotopes.Comment: 5 pages, 4 figures, Submitted to Eur. Phys. J.
Probing shell structure and shape changes in neutron-rich sulfur isotopes through transient-field g factor measurements on fast radioactive beams of 38S and 40S
The shell structure underlying shape changes in neutron-rich nuclei near N=28
has been investigated by a novel application of the transient field technique
to measure the first-excited state g factors in 38S and 40S produced as fast
radioactive beams. There is a fine balance between proton and neutron
contributions to the magnetic moments in both nuclei. The g factor of deformed
40S does not resemble that of a conventional collective nucleus because spin
contributions are more important than usual.Comment: 10 pages, 6 figures, accepted in PR
Shell structure underlying the evolution of quadrupole collectivity in S-38 and S-40 probed by transient-field g-factor measurements on fast radioactive beams
The shell structure underlying shape changes in neutron-rich nuclei between
N=20 and N=28 has been investigated by a novel application of the transient
field technique to measure the first-excited state g factors in S-38 and S-40
produced as fast radioactive beams. Details of the new methodology are
presented. In both S-38 and S-40 there is a fine balance between the proton and
neutron contributions to the magnetic moments. Shell model calculations which
describe the level schemes and quadrupole properties of these nuclei also give
a satisfactory explanation of the g factors. In S-38 the g factor is extremely
sensitive to the occupation of the neutron p3/2 orbit above the N=28 shell gap
as occupation of this orbit strongly affects the proton configuration. The g
factor of deformed S-40 does not resemble that of a conventional collective
nucleus because spin contributions are more important than usual.Comment: 10 pages, 36 figures, accepted for publication in Physical Review
Shell structure at N=28 near the dripline: spectroscopy of Si, P and S
Measurements of the N=28 isotones 42Si, 43P and 44S using one- and two-proton
knockout reactions from the radioactive beam nuclei 44S and 46Ar are reported.
The knockout reaction cross sections for populating 42Si and 43P and a 184 keV
gamma-ray observed in 43P establish that the d_{3/2} and s_{1/2} proton orbits
are nearly degenerate in these nuclei and that there is a substantial Z=14
subshell closure separating these two orbits from the d_{5/2} orbit. The
increase in the inclusive two-proton knockout cross section from 42Si to 44S
demonstrates the importance of the availability of valence protons for
determining the cross section. New calculations of the two-proton knockout
reactions that include diffractive effects are presented. In addition, it is
proposed that a search for the d_{5/2} proton strength in 43P via a higher
statistics one-proton knockout experiment could help determine the size of the
Z=14 closure.Comment: Phys. Rev. C, in pres
Variation with mass of \boldmath{B(E3; 0_1^+ \to 3_1^-)} transition rates in even-mass xenon nuclei
transition matrix elements have been measured for
even-mass Xe nuclei using sub-barrier Coulomb excitation in inverse
kinematics. The trends in energy and
excitation strengths are well reproduced using phenomenological models based on
a strong coupling picture with a soft quadrupole mode and an increasing
occupation of the intruder orbital.Comment: 5 pages, 4 figures, PRC in pres
Synthesis and Quantitative StructureâActivity Relationship of Imidazotetrazine Prodrugs with Activity Independent of O6-Methylguanine-DNA-methyltransferase, DNA Mismatch Repair and p53.
The antitumor prodrug Temozolomide is compromised by its dependence for activity on DNA mismatch repair (MMR) and the repair of the chemosensitive DNA lesion, O6-methylguanine (O6-MeG), by O6-methylguanine-DNA-methyltransferase (EC 2.1.1.63, MGMT). Tumor response is also dependent on wild-type p53. Novel 3-(2-anilinoethyl)-substituted imidazotetrazines are reported that have activity independent of MGMT, MMR and p53. This is achieved through a switch of mechanism so that bioactivity derives from imidazotetrazine-generated arylaziridinium ions that principally modify guanine-N7 sites on DNA. Mono- and bi-functional analogs are reported and a quantitative structure-activity relationship (QSAR) study identified the p-tolyl-substituted bi-functional congener as optimized for potency, MGMT-independence and MMR-independence. NCI60 data show the tumor cell response is distinct from other imidazotetrazines and DNA-guanine-N7 active agents such as nitrogen mustards and cisplatin. The new imidazotetrazine compounds are promising agents for further development and their improved in vitro activity validates the principles on which they were designed
OdreÄivanje trans-resveratrola u pokoĆŸici groĆŸÄa tijekom sazrijevanja i u vinu pomoÄu metode HPLC
Trans-resveratrol (3,5,4â-trihydroxy-trans-stilbene) is naturally present in the skin of grapes and therefore is expected to occur in grape products. Recently, there has been a renewal of interest in wine as medical treatment for various disorders. In this study, berry skins of five red grape varieties were analysed at weekly intervals for trans-resveratrol production, during 2012 and 2013 harvest. The obtained wines were also evaluated. Quantification of trans resveratrol in grape skin extracts and wines was carried out by high-performance liquid chromatography. Favourable viticultural climate during harvest in 2012 resulted in a higher content of trans-resveratrol. The highest trans-resveratrol content was in Pinot Noir and Feteasca Neagra grape varieties, both in berry skins and wines, while the lowest amounts were identified in Cabernet Sauvignon variety. We can conclude that there was a significant correlation between the content of trans-resveratrol in grape skins and that in the respective wine.Trans-resveratrol (3,5,4\u27-trihidroksi-trans-stilben) je prirodni fenol, koji se nalazi u pokoĆŸici groĆŸÄa i iz nje dospijeva u proizvode od groĆŸÄa. U novije se vrijeme ponovno javlja interes za primjenu vina u lijeÄenju razliÄitih zdravstvenih poremeÄaja. U ovom je radu tjedno praÄen udjel trans-resveratrola u pokoĆŸici pet sorata crnog groĆŸÄa tijekom uzgoja 2012. i 2013. godine. Nakon toga su analizirana i vina proizvedena iz tih sorata. Za odreÄivanje koliÄine trans-resveratrola u ekstraktu pokoĆŸice i vinu upotrijebljena je viskodjelotvorna tekuÄinska kromatografija. VeÄi je udjel trans-resveratrola pronaÄen u groĆŸÄu i vinu iz 2012. godine, i to zbog povoljnijih klimatskih uvjeta. NajviĆĄe je trans-resveratrola bilo u groĆŸÄu i vinu sorata Pinot Noir i Feteasca Neagra, a najmanje u onima sorte Cabernet Sauvignon. ZakljuÄeno je da postoji znaÄajna korelacija izmeÄu koliÄine trans-resveratrola u pokoĆŸici groĆŸÄa i u vinu, i to kod svih sorata
- âŠ