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Your search keyword '"Althubiti, Numa A."' showing total 27 results
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27 results on '"Althubiti, Numa A."'

2. Hadronic loop effects to excited scalar charmed mesons revisited

Author

Alhakami, Mohammad H., Althubiti, Numa A., and Al-shammari, Nwuyer A.

Subjects
High Energy Physics - Phenomenology
Abstract

We re-examine the hadronic loop effects to the masses of $D^*_0$ and $D^*_{s0}$ calculated in quark models in the framework of heavy meson chiral perturbation theory (HMCHPT). The inaccuracy in the choice of the argument of the chiral loop functions in previous works is corrected. Our calculations consider the full one-loop corrections that appear at leading order in the chiral expansion of the effective Lagrangian. Unlike previous approaches, ours leads to satisfactory results in explaining the low mass of the observed scalar charm states reported by the Particle Data Group (PDG). It is found that the mass shift of bare $D^*_{s0}$ ($D^*_{0}$) state is mainly due to the $DK$ ($D\pi$) loop corrections for values of the couplings that are compatible with the measured ones. We show why previous approaches of using HMCHPT in studying mass shift effects due to chiral loops gave unsatisfactory results.

Published
2022
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12. Tracking the neutron νi13/2 orbital in the neutron-deficient polonium isotopes with the high-precision ISOLTRAP mass spectrometer at CERN-ISOLDE

Author

Althubiti, Numa, Billowes, Jonathan, and Flanagan, Kieran

Subjects
500
Abstract

The measurements that will be presented investigate the neutron-deficient polonium isotopes in the region of A = 195-199, with a special emphasis on 195Po and 197Po. These isotopes were produced at ISOLDE/CERN and delivered to the ISOLTRAP experiment where mass measurements and α-decay spectroscopy were performed. The decay-spectroscopy studies were carried out for the first time at ISOLTRAP with the support of the multi reflection time-of-flight mass spectrometer (MR-TOF MS). The masses of (195,197)g,mPo were measured precisely with Penning-trap mass spectrometry, from which the state ordering and the energy of the 13/2⁺ states in 195,197Po were determined for the first time. Furthermore, the state ordering and the energy of the 13/2⁺ state in lead, radon, and radium were obtained through α-decay chains. The new data complete the knowledge of the energy systematics in this region. The presented mass measurements provide information on the behaviour of the 13/2⁺ states in the lead region near N = 104, which remain excited states. Additionally, 195Po half-life measurements were performed in isobarically pure conditions. The resulting 195gPo half-life value is in agreement with the one in the literature, with improving in the precision of the value, whereas the 195mPo half-life value is significantly smaller than the literature value.

Published
2018

18. Influence of the dwell time in the polarization hysteresis of polymer electrolyte membrane fuel cells

Author

Iranzo Paricio, Jose Alfredo, Navas Herrera, Sergio Jesús, Pino Lucena, Francisco Javier, Althubiti, Numa A., Berber, Mohamed R., Universidad de Sevilla. Departamento de Ingeniería Energética, Universidad de Sevilla. TEP143: Termotecnia, Ministry of Education in Saudi Arabia Project No. 375213500, Spanish Ministry of Science, Innovation and Universities Grant ENE2017-91159-EXP, Spanish Ministry of Science, Innovation and Universities Grant PID2019-104441RB-I0, Spanish Ministry of Economy and Competitiveness Grant UNSE15-CE2962, and Consejería de Economía, Conocimiento, Empresas y Universidad (Junta de Andalucía) co-funded with ERDF funds PY20 RE026 AICIA

Subjects
Equivalent circuit, Fuel cell, Voltage hysteresis, Dwell time, Electrochemical impedance spectroscopy
Abstract

The extent of the cell voltage hysteresis observed in polarization curves of PEM fuel cells and the origins causing this effect are investigated by performing experimental polarization curves with different dwell times for a 50 cm2 PEM fuel cell. Electrochemical Impedance Spectroscopy measurements are carried out in order to determine the relative contributions of the different polarizations (ohmic, activation, and concentration polarization). Equivalent circuits were obtained from the impedance spectra, where the interpretation of the circuit parameters enabled the analysis of the origin and extent of the cell voltage hysteresis. It was identified that the cause of the cell voltage hysteresis is actually dominated by the changes in the concentration polarization at low current densities, and by the changes in the activation polarization at high current densities. The cell ohmic resistance (and consequently the membrane hydration) presents a minor effect on the cell voltage hysteresis. The effect of the dwell time in the cell voltage hysteresis (with values ranging from 15 to 25 mV) presents a mixed trend, with an initial decrease for increasing dwell times from 120 to 600 s, and a later increase and a final almost constant hysteresis for longer dwell times.

Published
2022

19. Influence of the dwell time in the polarization hysteresis of polymer electrolyte membrane fuel cells

Author

Universidad de Sevilla. Departamento de Ingeniería Energética, Universidad de Sevilla. TEP143: Termotecnia, Ministry of Education in Saudi Arabia Project No. 375213500, Spanish Ministry of Science, Innovation and Universities Grant ENE2017-91159-EXP, Spanish Ministry of Science, Innovation and Universities Grant PID2019-104441RB-I0, Spanish Ministry of Economy and Competitiveness Grant UNSE15-CE2962, Consejería de Economía, Conocimiento, Empresas y Universidad (Junta de Andalucía) co-funded with ERDF funds PY20 RE026 AICIA, Iranzo Paricio, José Alfredo, Navas Herrera, Sergio Jesús, Pino Lucena, Francisco Javier, Althubiti, Numa A., Berber, Mohamed R., Universidad de Sevilla. Departamento de Ingeniería Energética, Universidad de Sevilla. TEP143: Termotecnia, Ministry of Education in Saudi Arabia Project No. 375213500, Spanish Ministry of Science, Innovation and Universities Grant ENE2017-91159-EXP, Spanish Ministry of Science, Innovation and Universities Grant PID2019-104441RB-I0, Spanish Ministry of Economy and Competitiveness Grant UNSE15-CE2962, Consejería de Economía, Conocimiento, Empresas y Universidad (Junta de Andalucía) co-funded with ERDF funds PY20 RE026 AICIA, Iranzo Paricio, José Alfredo, Navas Herrera, Sergio Jesús, Pino Lucena, Francisco Javier, Althubiti, Numa A., and Berber, Mohamed R.

Abstract

The extent of the cell voltage hysteresis observed in polarization curves of PEM fuel cells and the origins causing this effect are investigated by performing experimental polarization curves with different dwell times for a 50 cm2 PEM fuel cell. Electrochemical Impedance Spectroscopy measurements are carried out in order to determine the relative contributions of the different polarizations (ohmic, activation, and concentration polarization). Equivalent circuits were obtained from the impedance spectra, where the interpretation of the circuit parameters enabled the analysis of the origin and extent of the cell voltage hysteresis. It was identified that the cause of the cell voltage hysteresis is actually dominated by the changes in the concentration polarization at low current densities, and by the changes in the activation polarization at high current densities. The cell ohmic resistance (and consequently the membrane hydration) presents a minor effect on the cell voltage hysteresis. The effect of the dwell time in the cell voltage hysteresis (with values ranging from 15 to 25 mV) presents a mixed trend, with an initial decrease for increasing dwell times from 120 to 600 s, and a later increase and a final almost constant hysteresis for longer dwell times.

Published
2022

22. Structural and dielectric properties of ion beam irradiated polymer/silver composite films

Author

Althubiti, Numa A, Atta, Ali, Alotaibi, Badriah M, and Abdelhamied, Mostufa M

Abstract

In this work, flexible nanocomposite films that are composed of silver (Ag) nanoparticles, polyaniline (PANI) and methylcellulose (MC) were manufactured using the casting solution fabrication technique. The manufactured films were characterized using X-ray diffraction and Fourier transform infrared spectroscopy, which confirming the preparation of the composite samples. The MC/PANI/silver films were then irradiated with oxygen (O)-ion beams at a range of fluences (8 × 1017, 16 × 1017and 24 × 1017 ions/cm2). The electrical conductivity, complex impedance behavior, electric modulus and energy density of pure and irradiated films were determined throughout the frequency range 100 Hz–5 MHz. The oxygen-beam irradiation of MC/PANI/silver films caused a significant modification in dielectric parameters. Also, the dielectric constant ′ improved from 0.68 to 3.17, and the conductivity was modified from 1.47 × 10−6to 25.9 × 10−6 S/cm. The findings of the present study will pave the way for the use of irradiated MC/PANI/silver nanocomposite films in a variety of applications, including microelectronic devices, batteries and supercapacitors.

Published
2022
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24. Mass spectrometry of neutron-rich nuclides into the N=40 'island of inversion'

Author

Althubiti, Numa, Ascher, Pauline, Atanasov, Dinko, Beck, Dietrich, Blaum, Klaus, Breitenfeldt, Martin, Cakirli, Burcu, Cocolios, Thomas Elias, Eliseev, Sergey, Eronen, Tommi, George, Sebastian, Herfurth, Frank, Herlert, Alexander, Kowalska, Magdalena, Kreim, Susanne, Litvinov, Yuri A, Lunney, David, Manea, Vladimir, Minaya Ramirez, Enrique, Naimi, Sarah, Neidherr, Dennis, Rosenbusch, Marco, de Roubin, Antoine, Schweikhard, Lutz, Welker, Andre, Wienholtz, Frank, Wolf, Robert Norbert, and Zuber, Kai

Subjects
Detectors and Experimental Techniques
Published
2015

26. Identification of Family Non-universal Gauge Bosons in High-energy Electron-positron Collisions.

Author

Bagneid, Ali A. and Althubiti, Numa A.

Subjects
*BOSONS, *ELECTRON-positron interactions, *SUPERSYMMETRY, *POLARIZATION (Nuclear physics), *ELECTROWEAK interactions, *SCATTERING (Physics), *STANDARD model (Nuclear physics)
Abstract

We examine effects on measurable observables in e+e- collisions resulting from the existence of additional neutral gauge bosons originating in extensions of the standard model. In particular, we consider family non-universal neutral gauge bosons occurring in the minimal supersymmetric standard model and in the Sp(6)L x U(1)Y model, as well as other theoretically motivated popular neutral gauge bosons. We show how the proper employment of the generation-dependent couplings of the extra gauge boson, and the appropriate adjustment of the beam polarization, not only improved the identification of the models but also enhanced the discovery potential of the family non-universal extra gauge bosons. [ABSTRACT FROM AUTHOR]

Published
2011
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