Jose Luis Paz

National University of San Marcos | UNMSM · Departamento Académico de Química Inorgánica

An analysis of the scientific production of Ecuador is performed by means of the composite indicator computed for Ecuador-based authors as compared to their counterparts of other South American countries. The dataset employed was obtained from the Databricks platform of the ELSEVIER’s International Center for Science Research, ICSR. Therefore, this...

Cellular susceptibility to SARS-CoV-2 infection in the respiratory tract has been associated with the ability of the virus to interact with potential receptors on the host membrane. We have modeled viral dynamics by simulating various cellular systems and artificial conditions, including macromolecular crowding, based on experimental and transcript...

It has been reported that the susceptibility of cells to be infected by SARS-CoV-2 may be facilitated by various proteins that behave as potential receptors for the virus. To explore this, we have modeled viral dynamics by simulating various cellular systems (Vero E6, HeLa, HEK293 and CaLu3) in the presence and absence of drugs (anthelmintic, ARBs,...

The topological profiles of the nonlinear optical properties of a two-level molecular system involving simplified versions of intramolecular coupling immersed in a thermal reservoir have been studied in four-wave mixing (FWM) spectroscopy. Solvent effects have been explicitly considered by modeling the nonradiative interaction with the solute as a...

We determined the optical profiles of a molecular system coupled with a thermal bath in presence of intramolecular coupling. Solvent effects were explicitly considered as a random variable by modelling the non-radiative interaction with the solute. Optical susceptibilities of stochastic origin were solved through cumulant expansions in Gaussian dis...

The COVID-19 pandemic has accelerated the study of the potential of multi-target drugs (MTDs). The mixture of homologues called ivermectin (avermectin-B1a + avermectin-B1b) has been shown to be a MTD with potential antiviral activity against SARS-CoV-2 in vitro. However, there are few reports on the effect of each homologue on the flexibility and s...

The SARS-CoV-2 pandemic has accelerated the study of existing drugs. The mixture of homologs called ivermectin (avermectin-B1a [HB1a] + avermectin-B1b [HB1b]) has shown antiviral activity against SARS-CoV-2 in vitro. However, there are few reports on the behavior of each homolog. We investigated the interaction of each homolog with promising target...

Profiles of the nonlinear optical properties of a two-level system interacting with a thermal reservoir in Four-wave mixing have been studied. The model is a generalization of the conventional two-level approach, it includes a simplified description of the molecular structure and the explicit consideration of permanent dipole moment. The Born-Oppen...

In this study, the degradation mechanism of chloroacetanilide herbicides in the presence of four different nucleophiles, namely: Br−, I−, HS−, and S2O3−2, was theoretically evaluated using the dispersion-corrected hybrid functional wB97XD and the DGDZVP as a basis set. The comparison of computed activation energies with experimental data shows an e...

The occurrence, persistence, and accumulation of antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) represent a new environmental problem due to their harmful effects on human and aquatic life. A suitable absorbent for a particular type of pollutant does not necessarily absorb other types of compounds, so knowing the compatibility betwe...

Water pollution is an environmental problem in constant raising because of population growing, industrial development, agricultural frontier expansion, and principally because of the lack of wastewater treatment technology to remove organic recalcitrant and toxic pollutants from industrial and domestic wastewater. Recalcitrant compounds are a serio...

In the present study, the most favourable reaction mechanism in the flash vacuum pyrolysis of 2-[(2E)-2-benzylidenehydrazinyl]pyridine and analogous was theoretically studied using B3LYP-D3/6-311G(d,p) level. The influence of different substituents on the phenyl ring in the para position is evaluated at 500 K. A deep analysis of the mechanisms reve...

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs), together with cas genes, constitute the systems CRISPR-Cas, a novel type of innate defense system in prokaryotes for the destruction of exogenous elements (plasmids or phages). The genus Vibrio and Photobacterium represents one of the main responsible infectious agents in aquacult...

The pandemic caused by SARS-CoV-2 forces drug research to combat it. Ivermectin, an FDA approved antiparasitic drug formulated as a mixture 80:20 of the equipotent homologous 22,23 dihydro ivermectin (B1_a and B1_b), which is known to inhibit SARS-CoV-2 in vitro with a mechanism of action to be defined. It draws attention powerfully that the energe...

The clustered regularly interspaced short palindromic repeats (CRISPR) are genetic sequences that conventionally confer immunity to prokaryotes against invading genetic elements. The objective of this work was to perform an analysis of these sequences at the thermodynamic level, determining the minimum free formation energy (MFE) of the direct repe...

Introduction: Metallic ions release from orthodontic brackets and wires mostly depends on quality (chemical composition) and the medium to which it is exposed, e.g., acid, alkali, substances with high fluorine concentration, etc. This review addressed corrosion and wear of orthodontic brackets, wires and arches exposed to different media: beverages...

An analysis of the scientific production of Ecuador is performed by means of the composite indicator computed for Ecuador-based authors as compared to their counterparts of other South American countries. The dataset employed was obtained from the Databricks platform of the ELSEVIER's International Center for Science Research, ICSR. Therefore, this...

Glyphosate [N-(phosphonomethyl)-glycine] is a herbicide with several commercial formulations that are used generally in agriculture for the control of various weeds. It is the most used pesticide in the world and comprises multiple constituents (coadjutants, salts, and others) that help to effectively reach the action's mechanism in plants. Due to...

SARS-CoV-2 has caused millions of infections and more than 600,000 deaths worldwide. Despite the large number of studies to date, there is no specifically effective treatment available for SARS-CoV-2. However, it has been proposed to target reused drugs with potential antiviral activity to the interface between the angiotensin-converting enzymes 2...

We propose modifications of the conventional optical Bloch equations for a complex system, when we consider intermolecular coupling effects. We model the isolated molecule as Born-Oppenheimer energy curves consisting of two-electronic states described as harmonic potentials, with minima displaced in nuclear coordinates and energy. We consider two-v...

We analyze the statistical averages over a set of realizations of the random variable in the Stochastic Optical Bloch equations, using Novikov's sufficient condition theorem. We consider a system on an adiabatic basis interacting with an external field in the presence of a thermal reservoir. We analyzed both for delta-correlated functions (white no...

We consider the Four-Wave mixing (FWM) signal and the effects of the pump beam on the nonlinear optical responses of a two-level system where intramolecular coupling is modelled by two coupled harmonic electronic potentials, displaced both in their equilibrium minimum position and energy. We investigate the modifications introduced in the FWM signa...

La pandemia mundial del COVID-19 causada por el SARS-CoV-2 ha hecho necesario buscar alternativas de tratamiento. La OMS ha recomendado el fármaco aprobado por la FDA Remdesivir dirigido a la RNA polimerasa viral. Adicionalmente, se han evaluado computacionalmente compuestos naturales con propiedades antivirales. Sin embargo, estos estudios se cent...

Se evaluaron los efectos del acoplamiento intramolecular en las propiedades ópticas no lineales de colorantes orgánicos inmersos en un reservorio térmico empleando espectroscopia de mezcla de cuatro ondas. Se modeló la molécula aislada como curvas de energía Born-Oppenheimer consistiendo de dos estados electrónicos descritos como potenciales armóni...

The global pandemic caused by the new SARS-COV-2 coronavirus makes it necessary to search for drugs for its control. Within of this research it has been known that the ivermectin drug, a FDA-approved drugs which is formulated as an 80:20 mixture of ivermectin B1a and B1b and used commonly for parasitic infections, has an inhibitory effect on viruse...

The global pandemic caused by infections of the new coronavirus (COVID-19) makes it necessary to find possible less toxic and easily accessible therapeutic agents. In this study, we used strategies docking and molecular dynamics to analyze phytochemical compounds against FDA-approved antimalarial drugs recommended for the treatment of COVID-19. The...

Usando las ecuaciones Ópticas de Bloch y considerando un sistema molecular que interactúa con un reservorio térmico, derivamos expresiones analíticas para las propiedades ópticas no lineales en la espectroscopia de mezcla de cuatro ondas. En este trabajo se introducen diferentes metodologías para el estudio de las polarizaciones macroscópicas y sus...

Using the Optical Bloch equations, and considering a molecular system interacting with a thermal reservoir in Four-wave mixing spectroscopy, we derive analytical expressions for the nonlinear optical properties. In this work, we introduce different methodologies for the study of the macroscopic polarizations and nonlinear optical susceptibilities....

Effects of spectral diffusion on the third-order nonlinear susceptibility for two- and three-level quantum systems, immersed in a thermal reservoir, are evaluated with a four-wave mixing (FWM) signal through the density matrix formalism. For this, inhomogeneously broadened two- and three-level quantum systems are used. In these models, the distribu...

In this work, we analyze different levels of propagation of the Four-wave mixing signal in a strongly driven two-level system when the stochastic effects of the thermal bath, are considered. First approximation level, given by an analytical solution valid only for constant pump intensity along the optical path; a second approximation level as an an...

The effect of the presence of glucose and sucrose on the non-intrinsic contribution to partial molar volume hini of Bovine Serum Albumin (BSA) is determined by means of static and dynamic electronic polarizability measurements. For that aim, a combined strategy based on high-resolution refractometry, high exactitude densitometry, and synchronous uo...

A homemade multispectral scanner has been used to evaluate the decay and fading of ink entries on paper and to quantitatively evaluate biosensor readings. The reflected light from10 different LEDs is read by a compact optical spectrometer.

In this work we introduce a methodology for the determination of the longitudinal and transversal relaxation times in a two-level system using symmetry properties of the optical responses in the frequency space εΔ1,Δ2. Employing the density matrix formalism and a perturbative scheme for the incident field amplitudes in the Four-wave mixing spectros...

A poster presented at Industrial University of Santander in Bucaramanga, Colombia at the XV ENO VI CANCOA conference. This research was about my undergraduate thesis where we analyze the effects of spectral diffusion on the nonlinear optical properties of two and three states quantum systems under a four wave mixing signal. Webpage: http://eno2017....

Using the four-wave mixing spectroscopy, we analyze the nonlinear optical properties in a strongly driven two-level system, using a perturbative treatment where, the pump field is considered at all orders, second order in the probe, and first order for the signal field, when the stochastic effects of the solvent are considered. Significant variatio...

Carbon nanoparticles (CNPs) have been synthesized by laser ablation of polycrystalline graphite in water using a pulsed Nd:YAG laser (1064 nm) with a width of 8 ns. Structural and mesoscopic characterization of the CNPs in the supernatant by Raman spectroscopy provide evidence for the presence of mainly two ranges of particle sizes: 1-5 nm and 10-5...

Symmetries of the nonlinear optical properties (rotation, reflection, inversion) of a two-level molecular system coupled to the thermal reservoir and interacting with classical electromagnetic fields, are studied. The thermal reservoir induces a time-dependent shift of the two-level resonance frequency. A perturbative methodology based in cumulant...

Using interferometry and Fourier analysis, the photothermal phase map is obtained from the induced thermal lens effect in a liquid sample with high absorbance at the laser wavelength. The experimental setup consists of an adaptation of two beams thermal lens experiment, where both arms of a Sagnac's interferometer are used as probe beams. The inter...

This paper describes experimental results of thermal diffusivity measurements performed on different concentrations of aqueous Tartrazine solutions. The measurements are performed using the frequency-resolved thermal lensing technique and the results are compared with the thermal diffusivity value of pure water used as a solvent or host liquid. The...

Nonlinear optical properties of a two-level molecular system immersed in a thermal bath have been studied in the present work. Solvent effects were explicitly considered by modeling the non-radiative interaction with the solute as a random variable. The innovation of this treatment is that it allows us to take into account the environment, inducing...

The solvent effects over nonlinear optical properties of a two-level molecular system in presence of a classical electromagnetic field were modeled in this work. The collective effects proper of the thermal reservoir are modeled as a random Bohr frequency, whose manifestation is the broadening of the upper level according to a prescribed random fun...

Previous work by one of the authors has shown the dependence of the Rayleigh-type optical mixing (RTOM) signal intensity on the incident pump and probe frequencies for different values of the ratio of relaxation times k = T1 / T2. In this work an inverse problem methodology is defined to determine the ratio of the relaxation times k from sparse and...

In this work, the thermal reservoir effects over the absorptive and dispersive nonlinear optical properties of a two-level molecular system in presence of classical electromagnetic fields, were modeled. The collective effects proper of the thermal reservoir are modeled as a time dependent frequency, whose manifestation is the broadening of the uppe...

This work studies the spatial propagation of the Four-Wave Mixing (FWM) signal of a molecular system (malachite green) with two electronic levels immersed in a thermal bath, under a perturbative treatment at all order in the pump field and to first order in the probe and signal fields. Using the Optical Stochastic Bloch Equations OSBE, we present t...

Frequency-resolved thermal lensing (FRTL) is an approach used to measure thermal diffusivity coefficients of liquid samples. The theoretical model of this approach is based on thermal waves and the Fresnel diffraction approximation. This model predicts that only two experimental parameters are needed to estimate the thermal diffusivity of the sampl...

An experiment for measuring the thermal diffusivity of a liquid sample and nanoparticle colloidal systems using the thermal lens effect, induced by a frequency modulated laser diode, is proposed. The method consists in measuring the photothermal signal depending on the modulation frequency of the laser. From the experimental data is possible to est...

An experiment for measuring the thermal diffusivity of a liquid sample and nanoparticle colloidal systems using the thermal lens effect, induced by a frequency modulated laser diode, is proposed. The method consists in measuring the photothermal signal depending on the modulation frequency of the laser. From the experimental data is possible to est...

A study of the effects of relaxation times on the Four-Wave Mixing (FWM) signal response in frequency space for a two-level system is presented where the collisional effects of the solvent and the presence of the electromagnetic field are considered. The model is a generalization of the conventional two-level approach in that it includes a simplifi...

The study of a two-level molecular system with permanent dipole moments (PDM) immersed in a thermal bath and interacting with an electromagnetic field depends on the inclusion of the rotating wave approximation (RWA). A methodology based on cumulant expansions to obtain the average in the Fourier components associated with the coherences and popula...

We present a theoretical and experimental frequency-resolved thermal lensing approach based on the thermoreflectance and Fresnel diffraction theories. The approach is validated by measuring the thermal diffusion coefficients of classical solvent and dyes.

Absorptive and dispersive nonlinear optical properties have been studied considering a two-level molecular system with permanent dipole moments immersed in a thermal reservoir interacting with a classical electromagnetic field. Our model is based in a stochastic description, where the system–solvent interaction induces random shifts in the Bohr fre...

The inclusion of the permanent dipole moments and the solvent on the optical conventional Bloch equations (OCBE) allowed us to obtain analytical expressions for the optical properties of a two-level molecular system. We employed the methodology developed by Colmenares et al.1, in which they model the collisional effect of the solvent through a stoc...

El presente trabajo propone una reflexión en torno al sentido de la Universidad –fundamento último de su autonomía–, tal como modernamente se consolida en Occidente a partir del siglo xviii, los desplazamientos que opera sobre ella el presente de nuestras sociedades mundializadas y lo que podría seguir siendo su Razón de Ser en el marco de las tran...

This work studies the spatial propagation of the four-wave mixing signal of a molecular system with two electronic levels immersed in a thermal bath. Using the optical Bloch-Maxwell equations, we present three approximations, two of them are analytical solutions and the other is a numerical approach, where the effects of the variation of pump inten...

The inclusion of the permanent dipole moments and the solvent on the optical conventional Bloch equations (OCBE) allowed us to obtain analytical expressions for the optical properties of a two-level molecular system. We employed the methodology developed by Colmenares et al.1, in which they model the collisional effect of the solvent through a stoc...

In this work we studied the symmetry properties of the Rayleigh-type optical mixing signal, of a two-level molecular system immersed in a thermal bath and irradiated by a classical electromagnetic field. Taking into account that the solvent produces an inhomogeneous displacement of the Bohr frequency and, employing a cumulant expansion to solve the...

In this work are studied the symmetry properties of the Rayleigh-type optical mixing signal of a two-level molecular system immersed in a thermal bath and irradiated by a classical electromagnetic field. The solvent induces a random shift of the Bohr frequency in the molecular system. A methodology based in cumulant expansions is employed to obtain...

The stochastic effects of a thermal bath on a two-level molecular system interacting with a classical electromagnetic field are considered. The collective effects are modeled as a random Bohr frequency, whose manifestation is the broadening of the upper level according to a prescribed random function. A methodology based in cumulant expansions to o...

Analytic approximants for the eigenvalues of the one-dimensional Schrödinger equation with potentials of the form V(x) = xa + λxb are found using a multi-point quasi-rational approximation technique. This technique is based on the use of the power series and asymptotic expansion of the eigenvalues in λ, as well as the expansion at intermediate poin...

El propósito del presente estudio es examinar la creación, desarrollo, estado actual y las dinámicas de la investigación en el área de la química en Venezuela. Los objetivos son: 1) reseñar históricamente la actividad de la investigación química señalando los hitos en su proceso de consolidación en el país y establecer las dinámicas actuales. 2) An...

The coherence of a two-level system immersed in a thermal bath and irradiated with an electromagnetic field was calculated through the optical stochastical Bloch equations. The solvent effects are modeled as a stochastical shift of the system's Bohr frequency and the electromagnetic field includes both pump and probe fields. The methodology include...

We present in this note the analytical solution of the optical Bloch equations for different scenarios of the parameter space. Our method partially follows the reported by H-R. Noh and W. Jhe [Opt. Commun. 283, (2010) 2353]. However, it differs substantially with the analytical solution reported by these authors. We use the exact solution provided...

In this study, we determined the absorptive and dispersive optical profiles of a molecular system coupled with a thermal bath. Solvent effects were explicitly considered by modelling the non-radiative interaction with the solute as a random variable. The optical stochastical Bloch equations (OSBE) were solved using a time-ordered cumulant expansion...

The nonlinear optical properties are studied theoretically of a molecular system immersed in a thermal bath and interacting with a four-wave mixing signal. A methodology based on cumulant expansions to obtain the average in the Fourier components associated with the coherences and populations, calculated by the optical stochastic Bloch equations, i...

We make use of two different methodologies to study the transition probabilities in a molecular anharmonic system in the presence of an external perturbation. For the first method, we use a series expansion of the displacement coordinate keeping up to fourth order terms; for the second method we use a deformed algebra to approximate the anharmonic...

We have developed an analytical method to describe the optical properties of nanoparticles, whose results are in agreement with the observed experimental behavior according to the size of the nanoparticle under analysis. Our considerations to describe plasmonic absorption and dispersion are based on the combination of the two-level molecular system...

In this work, the absorptive and dispersive profiles of a molecular system have been calculated through a methodology based on the averaging of the coherence obtained by the resolution of the optical stochastic Bloch equations. To this aim, a generalized Lorentzian approximation to the Voigt function has been used as a probability distribution, whi...

Analytic approximations for the absorption coefficient and refraction index have been obtained for a two-level molecular system in the presence of a four-wave mixing signal. Stochastic collisions among solute–solvent molecules produce a broadening of the upper level of energy. In this work, we have used four generalized Lorentzian approximants of t...

Solute–solvent collisions for a two-level molecular system interacting with a four-wave mixing signal are analyzed in the present contribution. The system is described using the optical stochastic Bloch equations (OSBE), where Bohr’s frequency is treated a stochastic variable due to the random collisions with the solvent. The resulting equations fo...

The present contribution offers an educated guess of the electronic excitation spectrum of van der Waals complexes, which can be used to set up initial experimental conditions in laser induced fluorescence spectroscopy experiments. In particular, we present bound-state calculations and predicted vertical excitation energies of Li-CO, CO-Ar and CO-H...

The interaction between a two-level molecular system and a high intensity electric field under the influence of a solvent was analyzed through the OSBE. To solve these equations, the average of the coherence was performed, using a generalized Lorentzian approximation for the Voigt's function as a probability distribution. Applying the convolution t...

Analytic approximants for the eigenvalues of the one-dimensional Schr\"odinger equation with potentials of the form $V(x)= Ax^a + Bx^b$ are found using a multi-point quasi-rational approximation technique. This technique is based on the use of the power series and asymptotic expansion of the eigenvalues in $\lambda=A^{-\frac{b+2}{a+2}}B$, as well a...

The optical properties of a two-level molecular system immersed in a thermal reservoir and irradiated by an electromagnetic field were studied using the optical stochastic Bloch equations. The effect of the solvent is modeled as a stochastical shift of the system's Bohr frequency and the electromagnetic field includes both pump and probe fields. Th...

In this work we introduce deformed creation and annihilation operators which differ from the usual harmonic oscillator operators a, a{sup {dagger}} by a number operator function A circumflex = a circumflex f(n circumflex ), A circumflex {sup {dagger}} = f(n circumflex )a circumflex {sup {dagger}}. We construct the deformed coordinate and momentum i...

We construct nonlinear coherent states by the application of a deformed displacement operator acting upon the vacuum state and as approximate eigenstates of a deformed annihilation operator. These states are used to evaluate the temporal evolution of the average value of the momentum and the diplacement coordinate as well as their dispersions. We a...

Accurate energy eigenvalues for the H2 molecule are presented here using a new approximate technique. This technique is based on a recently published two-point quasi-rational approximation method, which is an extension of the well-known Padé procedure. Approximants of order nine for the ground and excited states (n=1,2) have been determined. More t...

Analytic approximations for the ground state eigenvalues and eigenfunctions of polynomial potentials are found using an extended two-point quasi-rational approximation technique. In this procedure, the approximants are obtained through the power series and asymptotic expansion of the logarithmic derivative of the ground state eigenfunction, leaving...

In the present contribution, we performed ab initio calculations at the CCSD(T) level of theory in the framework of the supermolecule approach on the weakly bound CO-Ar van der Waals (vdW) complex in its "near T-shaped" most-stable ground state structure. The corresponding vertical excitation energies from the ground CO(X-1 Sigma)-Ar(S-1) to the ex...

Using nonlinear coherent states defined as approximate eigenstates of a deformed annihilation operator, we evaluate the response to a classical pulsed electric field of a system supporting a finite number of bound states. We calculate the temporal evolution of the average value of several observables like the momentum and the diplacement coordinate...

In this work, we have studied the Four-wave mixing (FWM) absorptive and dispersive optical properties in a two-level molecular system interacting with a thermal reservoir. The nature of the molecular collision induces frequency shifts, which lead to stochastic modulation of the central frequency. This shift is represented in the present model by ξ(...

In this work, an analytical solution for the energy eigenvalues for Morse potential with centrifugal terms is presented. This solution is obtained using the two-point quasi-rational approximant technique. We have also shown the advantage of our results with respect to other approximated method.

We construct a deformed oscillator whose energy spectra is similar to that of a Morse potential. We obtain a convenient algebraic representation of the displacement and the momentum of a Morse oscillator by expanding them in terms of deformed creation and annihilation operators and we compute their average values between approximate coherent states...