Alfonso Leyva

• PhD
• Professor (Assistant) at Pontifical Xavierian University

We describe the trajectories of circular orbits of spinless and spinning test particles around a rotating body in equatorial and non-equatorial planes via the Mathisson-Papapetrou-Dixon equations. In this paper, these equations include the Ricci rotation coefficients with the purpose of describing not only the curvature of space time, but also the...

In Colombia, medical physics started formally about 3 decades ago. Two master’s programs in medical physics initiated activities at two different universities. In particular, the master’s program at the Pontificia Universidad Javeriana has been underway since 2012, and taking into account its projections, a team was established in 2015 in collabora...

We describe the trajectories of circular orbits of spinless and spinning test particles around of rotating bodies in equatorial and non-equatorial planes via the Mathisson-Papapetrou-Dixon equations which include the Ricci rotation coefficients with the purpose of describing not only the curvature of space time, but also the rotation of the spinnin...

Hydroxyapatite (HAp) is the most commonly used biomaterial in modern bone regeneration studies because of its chemical similarity to bone, biocompatibility with different polymers, osteoconductivity, low cost, and lack of immune response. However, to overcome the disadvantages of HAp, which include fragility and low mechanical strength, current stu...

El propósito principal en este trabajo es determinar evento por evento el conteo, la distribución de energía, la distribución de momento y la distribución angular de las partículas producidas en la reacción nuclear principal que tiene lugar en la terapia de captura neutrónica por boro (BNCT) [10B (n, α)7 Li]. Además de una breve revisión histórica,...

Mycobacterium tuberculosis represents one of the world’s most devastating infectious agents – with one third of the world’s population infected and 1.5 million people dying each year from this deadly pathogen. As part of an effort to identify targets for therapeutic intervention, we carried out the kinetic characterization of the product of gene rv...

Introducción. Fenómenos como la monitoria fetal y el repertorio T específico contra el alérgeno Poa p9 han sido evaluados con la ley de Zipf/Mandelbrot. Objetivo. Establecer una metodología de caracterización de la dinámica del dengue en Palmira, Valle del Cauca, Colombia, fundamentada en la ley de Zipf/Mandelbrot y aplicada al periodo 2001-2004....

Huntington disease results from an expanded polyglutamine region in the N terminus of the huntingtin protein. HD pathology is characterized by neuronal degeneration and protein inclusions containing N-terminal fragments of mutant huntingtin. Structural information is minimal, though it is believed that mutant huntingtin polyglutamine adopts β struc...

We provide analytical results for the O(α s ) corrections to the polar angle dependence of the longitudinal spin–spin correlation asymmetry in $e^{+}e^{-}\to q\bar{q}$ . For top quark pair production the O(α s ) corrections to the longitudinal spin–spin asymmetry are strongly polar angle dependent and can amount up to ≃4% in the q 2-range from a...

To couple the energy present in the electrochemical proton gradient, established across the mitochondrial membrane by the respiratory chain, to the formation of ATP from ADP and Pi, ATP-synthase goes through a sequence of coordinated conformational changes of its major subunits (alpha, beta). These changes are induced by the rotation of the gamma s...

HOXD13, the homeobox-containing gene located at the most 5' end of the HOXD cluster, plays a critical role in limb development. It has been shown that mutations in human HOXD13 can give rise to limb malformations, with variable expressivity and a wide spectrum of clinical manifestations. Polyalanine expansions in HOXD13 cause synpolydactyly, wherea...

We calculate the linear and circular polarization of gluons produced in conjunction with massive quarks in the annihilation process $e^+e^-\rightarrow q \bar q G$ . The linear polarization is calculated in the hadron event plane as well as in the gluon-beam plane. Beam polarization and polar orientation effects are included in our discussion. For...

We calculate the linear and circular polarization of gluons produced in conjunction with massive quarks in the annihilation process e+e- → qq̄G. The linear polarization is calculated in the hadron event plane as well as in the gluon-beam plane. Beam polarization and polar orientation effects are included in our discussion. For typical top pair prod...

We calculate the O(alphas) corrections to longitudinal spin-spin correlations in e+e--->qq¯. For top quark pair production the O(alphas) corrections to the longitudinal spin-spin asymmetry amount to less than 1% in the q2-range from above tt¯-threshold up to sqrt(q2)=1000 GeV. In the e+e--->bb¯ case the O(alphas) corrections reduce the asymmetry va...

We consider the effect of gluon radiation on the energy of top/antitop quarks and on the anticollinearity of top-antitop quark pairs produced in $e^+e^-$ annihilation. Our results are presented in terms of the $E_q$-dependence of the $t\bar tg$ cross section and the dependence on the cosine of the opening angle $\theta_{12}$ between top and antitop...

We calculate the linear polarization of gluons radiated off top quarks produced in e{sup +}e⁻ annihilations. For typical top quark pair production energies at the Next Linear Collider the degree of linear polarization remains close to its soft gluon value of 100% over almost the whole energy spectrum of the gluon. The massive quark results are co...

We calculate the linear polarization of gluons radiated off top quarks produced in e+e- annihilations. For typical top quark pair production energies at the Next Linear Collider the degree of linear polarization remains close to its soft gluon value of 100% over almost the whole energy spectrum of the gluon. The massive quark results are compared w...

We calculate the $O(\alpha_s)$ corrections to longitudinal spin-spin correlations in $e^+e^-\to q\bar q$. For top quark pair production the $O(\alpha_s)$ corrections to the longitudinal spin-spin asymmetry amount to less than 1% in the $q^2$-range from above $t\bar t$-treshold up to $\sqrt{q^2}= 1000 GeV$. In the $e^+e^-\to b\bar b$ case the $O(\al...

We calculate the contribution from left-right symmetric models to the anomalous magnetic dipole ({Delta}{kappa}) and quadrupole ({Delta}{ital Q}) moments of the light {ital W} gauge boson. We obtain that both {Delta}{kappa} and {Delta}{ital Q} are suppressed by the small mixing angle sin{zeta} with respect to the standard model result. {copyright}...