Hydrodesulfurization of Dibenzothiophene: A Machine Learning Approach.

The hydrodesulfurization (HDS) process is widely used in the industry to eliminate sulfur compounds from fuels. However, removing dibenzothiophene (DBT) and its derivatives is a challenge. Here, the key aspects that affect the efficiency of catalysts in the HDS of DBT were investigated using machine learning (ML) algorithms. The conversion of DBT and selectivity was estimated by applying Lasso, Ridge, and Random Forest regression techniques. For the estimation of conversion of DBT, Random Forest and Lasso offer adequate predictions. At the same time, regularized regressions have similar outcomes, which are suitable for selectivity estimations. According to the regression coefficient, the structural parameters are essential predictors for selectivity, highlighting the pore size, and slab length. These properties can connect with aspects like the availability of active sites. The insights gained through ML techniques about the HDS catalysts agree with the interpretations of previous experimental reports.

Activated layered double hydroxides: assessing the surface anion basicity and its connection with the catalytic activity in the cyanoethylation of alcohols.

Layered double hydroxides (LDHs) act as catalysts in several reactions like in the cyanoethylation of alcohols with acrylonitrile to produce alkoxypropionitriles. Here we report an experimental and theoretical study in which it is shown that the experimental catalytic activity of LDHs in the cyanoethylation of 2-propanol and methanol correlates with the predicted strength of the basicity of the adsorbed surface species. First, it is shown that using activated LDHs containing Mg2+ and Al3+ (MgAl-LDH), Mg2+ and Ga3+ (MgGa-LDH), and Mg2+, Al3+ and Ga3+ (MgAlGa-LDH) great conversions to alkoxypropionitriles in high yields are obtained. Next, the basicity of these LDHs is estimated by means of the local softness, a local reactivity index calculated using density functional theory and appropriate surface models. For that, the adsorption of hydroxide and methoxide anions at the (001) surface of MgAl and MgGa-LDHs is investigated. We include LDHs containing Zn2+ and Al3+ (ZnAl-LDH) and Zn2+ and Ga3+ (ZnGa-LDH) in this part of the study to account for the effect of changing the divalent and trivalent metal composition on the basicity. It is found that hydroxide anions adsorbed on the MgGa-LDH surface and methoxide anions adsorbed on the MgAl-LDH surface are the most basic ones. This basicity trend correlates with our experimental findings about the catalytic activity of the activated LDHs. Further analyzing the connection between the LDH composition and the anion basicity, it is argued that the key steps dictating the LDH catalytic activity are the alcohol deprotonation in the cyanoethylation of 2-propanol, as it has been previously suggested, and the methoxide anion attack to the acrylonitrile double bond in the methanol cyanoethylation reaction.

Using a non-spin flip model to rationalize the irregular patterns observed in the activation of the C-H and Si-H bonds of small molecules by CpMCO (M = Co, Rh) complexes.

The activation of the C-H and Si-H bonds of CH(CH3)3 and SiH(CH3)3 molecules by organometallic compounds CpMCO (M = Co, Rh) has been investigated through DFT and CASSCF-MRMP2 calculations. In particular, we have analyzed the pathways joining the lowest-lying triplet and singlet states of the reactants with the products arising from the insertion of the metal atom into the C-H or Si-H bonds of the organic molecules. Channels connecting the reactants with the inserted structure Cp(CO)H-M-C(CH3)3 through the oxidative addition of the C-H bond of the organic molecule to the metal fragment were found only for the reaction CpRhCO + CH(CH3)3. However, inserted structures could also be obtained for the interactions of SiH(CH3)3 with CpCoCO and CpRhCO by two sequential reactions involving the formation and rebounding of the radical fragments Cp(CO)H-M + Si(CH3)3. According to this two-step reaction scheme, the complex CpCoCO is unable to activate the C-H bond of the CH(CH3)3 molecule due to the high energy at which the radical fragments Cp(CO)H-M + C(CH3)3 are located. The picture attained for these interactions is consistent with the available experimental data for this kind of reaction and allows rationalization of the differences in the reactivity patterns determined for them without using spin-flip models, as has been proposed in previous studies.

A two-step reaction scheme leading to singlet carbene species that can be detected under matrix conditions for the reaction of Zr(3F) with either CH3F or CH3CN.

The results obtained from CASSCF-MRMP2 calculations are used to rationalize the singlet complexes detected under matrix-isolation conditions for the reactions of laser-ablated Zr((3)F) atoms with the CH3F and CH3CN molecules, without invoking intersystem crossings between electronic states with different multiplicities. The reaction Zr((3)F) + CH3 F evolves to the radical products ZrF· + ·CH3. This radical asymptote is degenerate to that emerging from the singlet channel of the reactants Zr((1)D) + CH3 F because they both exhibit the same electronic configuration in the metal fragment. Hence, the caged radicals obtained under cryogenic-matrix conditions can recombine through triplet and singlet paths. The recombination of the radical species along the low-multiplicity channel produces the inserted structures H3C-Zr-F and H2C=ZrHF experimentally detected. For the Zr((3)F) + CH3 CN reaction, a similar two-step reaction scheme involving the radical fragments ZrNC· + ·CH3 explains the presence of the singlet complexes H C-Zr-NC and H2 C=Zr(H)NC revealed in the IR-matrix spectra upon UV irradiation.

Manifestaciones dermatológicas en el síndrome de inmunodeficiencia adquirida: estudio de 46 pacientes / Dermatological manifestations of the acquired immunodeficiency syndrome: study of 46 patients

Estudio dermatológico e histopatológico en 46 pacientes con infección VIH/SIDA. Se hizo clasificación clínica y de su subpoblaciones de linfocitos de acuerdo con los criterios del CDC, pero no se encontró relación estadísticamente significativa. Las dermatosis se presentaron en 77 por ciento de los casos y las más frecuentes fueron: sarcoma de Kaposi (18.9 por ciento), molusco contagioso (16.8 por ciento), dermatitis seborreica (12.6 por ciento), herpes zoster (10.5 por ciento), reacciones a fármacos (10.5 por ciento) y candidosis oral (8.4 por ciento)

Estudio de factibilidad: ácido 13-cisretinoico, interferón Ó-2a y radioterapia concurrentes en el tratamiento de 23 pacientes con carcinoma epidermoide cervicouterino avanzado / Factibility study: acid 13-cis retinoic, interferon Ó-2a and radiotherapy concurrents in the treatment of 23 patients with advanced, epidermoid, cervicouterine carcinoma

Se confirma la importante actividad terapéutica de 13.cRA y del IFNÓ-2a en el carcinoma de células escamosas del cervix sin tratamiento previo. Un resultado inesperado fue la toxicidad temprana de los agentes biológicos sobre la mucosa del colon cuando se combinan con radioterapia

Mucormicosis rinocerebral por Rhizopus sp / Cerebral mucormycosis by Rhizopus sp

Masculino de 24 años de edad con diabetes mellitus insulino-dependiente descompensada, cetoacidosis y mucormicosis rinocerebral por Rhizopus sp. Se trató en forma multidisciplinaria con control metabólico, anfotericina B y extensa debridación del área necrótica. El resultado fue satisfactorio; se planeó reconstrucción quirúrgica

Pancreatitis aguda: experiencia en el Hospital General Dr. Manuel Gea González / Acute pancreatitis: experience in the Hospital General Dr. Manuel Gea Gonzalez

La pancreatitis aguda es una enfermedad con elevada prevalencia en nuestro medio, la cual provoca complicaciones que pueden desencadenar la muerte del paciente que la padece. En el presente estudio, en 2 años obtuvimos una muestra de 83 pacientes a los que observamos en forma prospectiva, estableciendo el comportamiento de la enfermedad en cada uno encontrando resultados importantes, los cuales concuerdan con los reportes a nivel mundial

Glicosilación de hemoglobinas / Glycosylated hemoglobin

En el organismo existe una gran variedad de proteínas cuyas funciones biológicas son muy diversas. Estas funciones dependen en gran parte del tipo de aminoácidos que las constituyen. Normalmente las proteínas se modifican después de su síntesis. Entre esas modificaciones está la que resulta de la unión de diversos carbohidratos con ciertos aminoácidos a través de reacciones enzimáticas y no enzimáticas. La unión de los carbohidratos a las proteínas se conoce como glicosilación y depende de la concentración de aquellos. Una proteína típica que sufre este fenómeno es la hemoglobina, que se emplea como parámetro para evaluar a largo plazo (cuatro a ocho semanas), el control metabólico de los pacientes con diabetes mellitus y se conoce como hemoglobina glicosilada

Bases para el uso combinado de los interferones y de los retinoides en oncología clínica / Basis for the combined use of interferon and retinoid in clinical oncology

El acido retinoico y el interferón alfa tienen actividad limitada en el tratamiento de cáncer avanzado. La información obtenida de los cultivos celulares indican que, en combinación, estos agentes tienen incremento de la actividad biológica modulando el crecimiento y la diferenciación en un número de tipos celulares malignos. Trabajos clínicos recientes sobre el tratamiento de algunos carcinomas avanzados de células escamosas informan actividad terapéutica con este régimen. Este artículo revisa los datos preclínicos obtenidos al evaluar el ácido retinoico en combinación con interferones