Bay-Substitution of Perylene Bisimides with Bidentate Nucleophiles: The Case of Aryloxide Anions.

In this study, we delve into the regioselectivity of nucleophilic reactions involving brominated perylene bisimides (PBIs) and various bidentate aryloxide anions, previously associated with an SRN1 mechanism. We present herein a new perspective, suggesting that a single-electron-transfer aromatic nucleophilic substitution (SeT-SNAr) mechanism is a more plausible scenario. Our study reveals the favorable impact of photostimulation on reaction yields, making our method a convenient approach for accessing O-arylated PBIs.

Evaluation of Three Vaccination Schemes Against Clostridium perfringens Alpha Toxin and Their Effects on the Performance, Level of Intestinal Lesions, and Serum Antibody Titers in Broilers.

The objective of the trial was to evaluate three vaccination schemes against Clostridium perfringens (CP) alpha-toxoid through drinking water to determine if they can protect against clinical signs of necrotic enteritis and coccidiosis in broiler chickens. Three hundred 1-day-old Cobb 500 male chicks were used in 4 treatments with 10 repetitions. Each group received 1 of the following treatments over the course of 29 days: T1, no vaccination; T2, vaccination on Day 1; T3, vaccination on Day 7; and T4, vaccination on Days 7 and 17. The birds were vaccinated with inactivated CP toxoid type A, administered via drinking water. During the first 14 days, a high-protein diet (27%) consisting of corn, soy, and fish meal was fed. On Day 14 Eimeria acervulina (EA), Eimeria maxima (EMx), Eimeria tenella (ET), Eimeria necatrix, and Eimeria brunetti were used in a coccidial challenge. The field isolate CP type A was then inoculated on Days 18, 19, and 20. Ten birds were slaughtered by treatment to obtain serology samples for antibody titers and intestine samples for CP and Eimeria lesion score and gut integrity indicators. Productive performance was assessed using complete randomized design and compared statistically using the Tukey test, whereas intestinal integrity variables and antibodies against CP alpha toxin were assessed using a Kruskal-Wallis nonparametric method. The results revealed that the treatments had an effect on productive performance (P < 0.05); T3 had better body weight and weight gain than T1. In terms of lesion score at Day 21, T4 had a lower lesion score by EA, EMx, and ET than T1. Cell desquamation in T2 was lower than in T4, and excess mucus (EM) in T1 was the worst in gut integrity indicators at Day 21. On the other hand, T2 had more EM than T3 and T4 at Day 25. In the measurement of antibodies, no statistical differences (P > 0.05) were found. These findings indicate that vaccination on Day 7 (T3) outperformed double vaccination on Days 7 and 17 (T4) and single on Day 1 (T2), in terms of productive performance, gut integrity, and lesion scores; and on the last day of the experiment T3 had the best performance in immunology response.

Evaluación de tres esquemas de vacunación contra la toxina alfa de Clostridium perfringens y sus efectos sobre el rendimiento, el nivel de lesiones intestinales y los títulos de anticuerpos séricos en pollos de engorde. El objetivo del ensayo fue evaluar tres programas de vacunación contra Clostridium perfringens (CP) con un alfa-toxoide a través del agua de bebida para determinar si protegían contra signos clínicos de enteritis necrótica y coccidiosis en pollos de engorde. Para ello se emplearon 300 pollitos machos Cobb 500 de un día de edad, distribuidos en 4 tratamientos con 10 repeticiones. Cada grupo recibió, durante 29 días, uno de los siguientes tratamientos: T1: sin vacunación; T2: vacunación en el día uno; T3: vacunación en el día siete y T4, vacunación en los días siete y 17. Las aves fueron vacunadas con toxoide inactivado de C. perfringens tipo A, que se administró en el agua de bebida. Durante los primeros 14 días se alimentó con una dieta alta en proteína (27%) que consistía en maíz, soya y harina de pescado. El desafío coccidial se realizó en el día 14 con Eimeria acervulina (EA), Eimeria maxima (EMx), Eimeria tenella (ET), Eimeria necatrix and Eimeria brunetti. Posteriormente, en los días 18, 19 y 20 se inoculó una cepa aislada de campo de C. perfringens tipo A. Se sacrificaron diez aves por tratamiento para obtener muestras de sueros para determinar los títulos de anticuerpos y muestras de intestino para determinar la puntuación de lesiones por C. perfringens, por Eimeria y los indicadores de integridad intestinal. El comportamiento productivo se analizó bajo un diseño completamente al azar (DCA) y la comparación estadística se realizó mediante la prueba de Tukey, mientras que para las variables de integridad intestinal y los títulos de anticuerpos contra alfa toxina de C. perfringens se utilizó el método no paramétrico Kruskal-Wallis. Los resultados mostraron que el comportamiento productivo fue influenciado por los tratamientos (P < 0.05); el tratamiento T3 mostró el mejor peso corporal y ganancia de peso en comparación con el tratamiento T1. Con relación al puntaje de lesiones en el día 21, el tratamiento T4 tuvo el menor puntaje de lesiones por E. acervulina, E. maxima y E. tenella en comparación con el tratamiento T1. La descamación celular en el tratamiento T2 fue menor que en el T4 y el exceso de moco en el tratamiento T1 fue peor entre los indicadores de integridad intestinal en el día 21. Por otro lado, el tratamiento T2 tenía más exceso de moco en comparación con los tratamientos T3 y T4 en el día 25. No se encontraron diferencias estadísticas (P > 0.05) en la medición de títulos de anticuerpos. Estos hallazgos indican que la vacunación en el día siete (T3) superó a la vacunación doble en los días 7 y 17 (T4) y única en el día uno (T2), en términos de rendimiento productivo, integridad intestinal y puntajes de lesiones, además en el último día del experimento, el tratamiento T3 tuvo el mejor desempeño en la respuesta inmunológica.

An internet-based self-applied rat phobia treatment using a Virtual Therapy Assistant: Study protocol for a randomized controlled trial.

Specific phobias are a common anxiety disorder that deteriorates the lives of people who suffer from them. To reduce the symptoms produced by this mental disorder exposure therapies have been used. However, low- and middle-income countries, including Mexico, have the lowest rate of treatment due to multiple barriers that prevent addressing mental health problems. Self-applied treatments have been explored in previous studies, nevertheless, high dropout rates are a common problem in this kind of treatment. An alternative is using immersive self-applied treatments that could help increase adherence to the treatment. This article aims to present a study protocol to explore the feasibility of an Internet self-applied exposure treatment for rat phobias, using four types of immersive multimedia elements: images, videos, video games, and 360° videos. Also, the satisfaction and perception of a Virtual Therapy Assistant (VTA) that provides information and support to the user are described. The study protocol will compare two groups of participants, one on the waiting list, and the other will receive the self-applied treatment for rat phobia supported by the VTA. For this study, 45 participants will be recruited and the evaluation measures will be taken at four different times: baseline, post-treatment, and follow-ups at 3 and 6 months. The levels of anxiety and avoidance of the user manifested during the exposure to the multimedia elements, the improvement of the user's clinical symptoms, the level of satisfaction, the perception of effectiveness, and ease of use of the self-applied system will be evaluated. This study is expected to support the viability of self-applied treatment for rat phobias and the use of a VTA, showing the impact on treatment adherence. To the best of our knowledge, this is the first study to explore an exposure treatment for rats using different multimedia elements with the support of a VTA. The work will serve as a basis for the development of new virtual assistants that help in the treatment of other types of specific phobias. This research has been registered in Clinical Trials NCT (NCT05081323).

Development of Narratives and Belief in a Just World in Victims of Bullying Due to Sexual and Gender Diversity Issues.

Students belonging to a sexual and gender minority go through experiences of injustice in their educational centers and are victims of school bullying. This research analyzes the relationship between these experiences and their influence on the development of the Belief in a Just World, as well as the impact of their experiences on the development of their narratives. Participants are students who have suffered from bullying due to sexual and gender diversity issues during their primary and secondary education stages (ages 15-40 years). Starting from a constructivist qualitative methodological approach, a semi-structured interview was developed as an instrument for collecting data on these aspects. The information extracted was contrasted with the results of the Personal and General Belief in a Just Word Scales. The results of the first interviews provide us with prior information on current identities and narratives and their representations of justice.

1-Substituted Perylene Derivatives by Anionic Cyclodehydrogenation: Analysis of the Reaction Mechanism.

Perylene derivatives constitute a promising class of compounds with technological applications mainly due to their optoelectronic properties. One mechanism proposed to synthesize them, starting from binaphthyl derivatives, is anionic cyclodehydrogenation (under reductive conditions). However, the scope of this reaction is limited. In the present study, we report a theoretical and experimental analysis of this particular reaction mechanism for its use in the synthesis of 1-substituted perylenes. Different substituents at position 2 of 1,1'-binaphthalene were evaluated: -OCH3, -OSi(CH3)2C(CH3)3, and -N(CH3)2. Based on density functional theory (DFT) calculations on the proposed mechanism, we suggest that the cyclization takes place from binaphthyl dianion instead of its radical anion. This dianion has an open-shell diradical nature, and this could be the species that was detected by EPR in previous studies. The O-substituted derivatives could not afford the perylene derivatives since their radical anions fragment and the necessary binaphthyl dianion could not be formed. On the other hand, 49% of N,N-dimethylperylen-1-amine was obtained starting from the N-substituted 2-binapthyl derivative as a substrate, employing a simpler experimental methodology.

Biological Activities of Seven Medicinal Plants Used in Chiapas, Mexico.

Seven medicinal plants from Chiapas, Mexico, used by Native Americans were analyzed, aiming to improve the understanding of their medicinal properties through the evaluation of various biological activities, i.e., bactericidal, antioxidant, α-glucosidase inhibition, and toxicity, to provide a scientific basis for the management of infectious and hyperglycemic diseases in the Mexican southeast. Plant extracts were obtained from Cordia dodecandra, Gaultheria odorata, Heliotropium angiospermum, Justicia spicigera, Leucaena collinsii spp. collinsii, Tagetes nelsonii, and Talisia oliviformis through maceration techniques using methanol and chloroform (1:1). Minimum Inhibitory Concentration (MIC) was employed to determine the antibacterial activity against Staphylococcus aureus, Enterobacter faecalis, Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae, Klebsiella pneumoniae, and Pseudomonas aeuroginosa. The antiradical/antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays and antihemolytic activity using the 2,2'-Azobis(2-amidinopropane) dihydrochloride radical (APPH). The anti-α-glucosidase activity was evaluated in vitro through the chromogenic PNPG assay. The toxicity was assessed using the brine shrimp lethality assay. The highest antimicrobial activity was displayed by T. nelsonii, mainly against E. faecalis and P. aeuroginosa. The extracts of L. collinsii, J. spicigera, and T. nelsonii possess antioxidant properties with EC50 < 50 µg/mL. J. spicigera and T. nelsonii extracts showed the highest antihemolytic activity with IC50 < 14 µg/mL. T. nelsonii exhibited a remarkable inhibitor effect on the α-glucosidase enzyme and the greatest toxic effect on Artemia salina with IC50 = 193 ± 20 µg/mL and LD50 = 14 ± 1 µg/mL, respectively. According to our results, G. odorata, J. spicigera, T. nelsonii, and T. oliviformis extracts contained active antimicrobial compounds. At the same time, T. nelsonii stands to be a possible source of effective antineoplastic and antihyperglycemic compounds.

Study of the Effect of Nitric Acid in Electrochemically Synthesized Silicon Nanocrystals: Tunability of Bright and Uniform Photoluminescence.

In this work, we show a correlation between the composition and the microstructural and optical properties of bright and uniform luminescent porous silicon (PSi) films. PSi films were synthesized by electrochemical etching using nitric acid in an electrolyte solution. PSi samples synthesized with nitric acid emit stronger (up to six-fold greater) photoluminescence (PL) as compared to those obtained without it. The PL peak is shifted from 630 to 570 nm by changing the concentration ratio of the HF:HNO3:(EtOH-H2O) electrolyte solution, but also shifts with the excitation energy, indicating quantum confinement effects in the silicon nanocrystals (Si-NCs). X-ray photoelectron spectroscopy analysis shows a uniform silicon content in the PSi samples that emit the strongest PL. High-resolution transmission electron microscopy reveals that the Si-NCs in these PSi samples are about ~2.9 ± 0.76 nm in size and are embedded in a dense and stoichiometric SiO2 matrix, as indicated by the Fourier transform infrared analysis. On the other hand, the PSi films that show PL of low intensity present an abrupt change in the silicon content depth and the formation of non-bridging oxygen hole center defects.

An Effective and Safe Enkephalin Analog for Antinociception.

Opioids account for 69,000 overdose deaths per annum worldwide and cause serious side effects. Safer analgesics are urgently needed. The endogenous opioid peptide Leu-Enkephalin (Leu-ENK) is ineffective when introduced peripherally due to poor stability and limited membrane permeability. We developed a focused library of Leu-ENK analogs containing small hydrophobic modifications. N-pivaloyl analog KK-103 showed the highest binding affinity to the delta opioid receptor (68% relative to Leu-ENK) and an extended plasma half-life of 37 h. In the murine hot-plate model, subcutaneous KK-103 showed 10-fold improved anticonception (142%MPE·h) compared to Leu-ENK (14%MPE·h). In the formalin model, KK-103 reduced the licking and biting time to ~50% relative to the vehicle group. KK-103 was shown to act through the opioid receptors in the central nervous system. In contrast to morphine, KK-103 was longer-lasting and did not induce breathing depression, physical dependence, and tolerance, showing potential as a safe and effective analgesic.

Infrared Multiple Photon Dissociation Spectroscopy of Protonated Cyameluric Acid.

The present study reports the first structural characterization of protonated cyameluric acid ([CA + H]+) in the gas phase, which paves the way for prospective bottom-up research on the condensed-phase chemistry of CA in the protonated form. A number of [CA + H]+ keto-enol isomers can a priori be produced as a result of protonation at available N and O positions of precursor neutral CA tautomers, yet ab initio computations predict different reduced [CA + H]+ isomer populations dominating the solution and gas phases that are involved in the ion generation process (i.e., electrospray ionization). Infrared multiple photon dissociation spectra were recorded in the 990-1900 and 3300-3650 cm-1 regions and compared with theoretical [B3LYP/6-311++G(d,p)] IR absorption spectra of several [CA + H]+ isomers, providing a satisfactory agreement for the most stable monohydroxy form in the gas phase, [1358a]+, yet the contribution of its nearly isoenergetic OH rotamer, [1358b]+, cannot be neglected. This is indicative of the occurrence of [CA + H]+ isomer interconversion reactions, assisted by protic solvent molecules, during their transfer into the gas phase. The results suggest that available O positions on neutral CA are energetically favored protonation sites in the gas phase.

High HIV prevalence among transgender women in Paraguay.

Transgender women have been understudied and underserved in Paraguay; data are urgently needed to understand their HIV prevention and care needs. To estimate HIV prevalence and related risk and preventive behaviors among trans women in Paraguay, we conducted a cross-sectional survey in 2017. We employed starfish sampling - a hybrid venue-based and peer-referral method combining recruitment at randomly sampled venues and randomly selected clients from program lists, followed by short-chain referrals of eligible peers. Among 304 trans women enrolled, HIV prevalence was 24.8% (95% confidence interval [CI] 18.5-31.2%), with risk increasing with age (adjusted odds ratio [AOR] 1.06 per year, 95% CI 1.03-1.10), residence in Asunción department (AOR 4.75, 95% CI 1.57-14.36), and cocaine use (AOR 2.09, 95% CI 1.11-3.95). Trans women in Paraguay need to be prioritized for interventions with high HIV prevention efficacy. Substance use interventions to address cocaine use may also yield prevention benefits for trans women in our context.

Arenium cation or radical cation? An insight into the cyclodehydrogenation reaction of 2-substituted binaphthyls mediated by Lewis acids.

Perylene and its derivatives are some of the most interesting chromophores in the field of molecular design. One of the most employed methodologies for their synthesis is the cyclodehydrogenation of binaphthyls mediated by Lewis acids. In this article, we investigated the cyclodehydrogenation reaction of 2-substituted binaphthyls to afford the bay-substituted perylene. By using AlCl3 as a Lewis acid and high temperatures (the Scholl reaction), two new products bearing NH2 and N(CH3)2 groups at position 2 of the perylene ring were synthesized. Under these conditions, we were also able to obtain terrylene from ternaphthalene in 38% yield after two cyclodehydrogenation reactions in a single step. The attempts to promote the formation of a radical cation (necessary intermediary for the oxidative aromatic coupling mechanism) by using FeCl3 or a strong oxidant like 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) did not yield the expected products. DFT calculations suggested that the lack of reaction for oxidative aromatic coupling is caused by the difference between the oxidation potentials of the donor/acceptor couple. In the case of the Scholl reaction, the regiochemistry involved in the formation of the σ-complex together with the activation energy of the C-C coupling reaction helped to explain the differences in the reactivity of the different substrates studied.

Lateral size reduction of graphene oxide preserving its electronic properties and chemical functionality.

Graphene oxide (GO) is widely considered as a graphene precursor when chemically reduced. Nevertheless, through the precise control of two parameters: lateral size and oxidation degree, GO can be useful in many applications as modified graphene oxide or functional reduced graphene oxide. Commonly, the decrease in GO lateral size, involves a change in the C/O ratio and therefore a modification in a large number of characteristics. Here, a simple but effective approach to synthesize GO with lateral dimensions below 100 nm and without modification of its chemical, optical and electronic features is presented. The use of a sonifier at low temperature allows to rapidly reduce the lateral size in ∼82% while preserving the C/O ratio and consequently the chemical stability, the band gap, the electronic energy levels and the functionality. This method will allow several applications from biomedicine to energy, where reliable reduced size of GO is required.

[Clinical characteristics of primary immunodeficiencies in children from a tertiary hospital]. / Características clínicas de las inmunodeficiencias primarias en niños de un hospital de tercer nivel.

BACKGROUND: Primary immunodeficiencies are diseases that are caused by one or more defects in the immune system. OBJECTIVE: The purpose of the article is to describe the characteristics of the immunodeficiencies that were diagnosed in a pediatric hospital, which forms a reference center in the West of Mexico. METHODS: A cross-sectional study of pediatric patients with primary immunodeficiency in a pediatric hospital in Guadalajara, Jalisco. RESULTS: 60 patients were registered, of which 21% were female, and 78% were male. Predominant immunodeficiencies of antibodies formed the largest group (46% of patients). X-linked agammaglobulinemia was the most frequent immunodeficiency (21%); other frequent diagnoses were common variable immunodeficiency, and IgG subclass deficiency. The average age of the patients that were diagnosed was of 6.3 years. The most common initial manifestations were infectious processes (46%), and pneumonia was the frequent diagnosis (30%). Autoimmune manifestations were observed in 13% of patients; 67% of the patients were found with immunoglobulin replacement therapy, with which a decrease in hospitalizations from 3.2 times to 0.13 times was observed. There were two deceased patients due to surgical complications of cardiac correction and intestinal reconnection. CONCLUSION: Knowing the behavior of primary immune deficiencies in our environment allows the opening of areas of opportunity in order to improve the survival and quality of life of our patients.

Antecedentes: Las inmunodeficiencias primarias son un grupo de enfermedades causadas por uno más defectos del sistema inmunitario. Objetivo: Describir las características de las inmunodeficiencias diagnosticadas en un hospital pediátrico de tercer nivel, que constituye un centro de referencia en el Occidente de México. Métodos: Estudio transversal de pacientes pediátricos con inmunodeficiencias primarias atendidos en un hospital pediátrico en Guadalajara, Jalisco. Resultados: Se registraron 60 pacientes, 21 % mujeres y 78 % hombres. Las inmunodeficiencias predominantes de anticuerpos constituyeron el grupo más numeroso (46 %). La agammaglobulinemia ligada al cromosoma X fue la inmunodeficiencia más frecuente, con 21 % del registro. Otros diagnósticos frecuentes fueron inmunodeficiencia común variable y deficiencia de subclases de IgG. El promedio de edad al diagnóstico fue de 6.3 años. Las manifestación inicial más común fueron los procesos infecciosos (46 %) y la neumonía fue el diagnóstico más frecuente (30 %). Las manifestaciones autoinmunes se observaron en 13 % de los pacientes; 67 % de los pacientes se encontró con sustitución de inmunoglobulina, con la cual se observó disminución en las hospitalizaciones: de 3.2 a 0.13 veces. Fallecieron dos pacientes por complicaciones quirúrgicas de corrección cardiaca y reconexión intestinal. Conclusión: El conocimiento del comportamiento de las inmunodeficiencias primarias en nuestro medio permite apertura de áreas de oportunidad a fin de mejorar la supervivencia y calidad de vida de los pacientes.

Assessment of users' acceptability of a mobile-based embodied conversational agent for the prevention and detection of suicidal behaviour.

The use of embodied conversational agents in mental health has increased in the last years. Several studies exist describing the benefits and advantages of this technology as a complement to psychotherapeutic interventions for the prevention and treatment of depression, anxiety, or post-traumatic stress disorder, to name a few. A small number of these works implement capabilities in the virtual agent focused on the detection and prevention of suicidality risks. The work presented in this paper describes the development of an embodied conversational agent used as the main interface in HelPath, a mobile-based application addressed to individuals detected with any of the suicidal behaviours: ideation, planning or attempt. The main objective of HelPath is to continuously collect user's information that, complemented with data from the electronic health record, supports the identification of risks associated with suicidality. Through the virtual agent, the users also receive information and suggestions based on cognitive behaviour therapy that would help them to maintain a healthy condition. The paper also presents the execution of an exploratory pilot to assess the acceptability, perception and adherence of users towards the virtual agent. The obtained results are presented and discussed, and some actions for further improvement of the embodied conversational agent are also identified.

Dosis de exposición a fluoruros por el consumo de diferentes tipos de leche en residentes de una zona con hidrofluorosis endémica en México / Level of exposure to fluorides by the consumption of different types of milk in residents from an area of Mexico with endemic hydrofluorosis

Introducción: Diversos estudios han demostrado la presencia de fluorosis (FD) en la dentición primaria, lo que puede indicar una exposición a los fluoruros (F-) en la primera infancia. La leche materna se recomienda como alimento exclusivo hasta los 6 meses de edad. Aunque se menciona que solo una pequeña cantidad de F- puede eliminarse por leche materna, estudios han demostrado la presencia de este elemento en leche de mujeres residentes de zonas contaminadas, así como en leche de fórmulas comerciales. El objetivo del proyecto fue evaluar la dosis de exposición a F- a través de leche en niños residentes de una zona con hidrofluorosis endémica. Metodología: Un total de 110 niños de entre 6 y 36 meses de edad del municipio de Lagos de Moreno, Jalisco, México, participaron en el estudio. Se colectaron muestras de agua de los hogares, leche y orina. Las muestras se cuantificaron con el electrodo de ion selectivo. Se calculó la dosis de exposición a F- a través del programa Oracle Crystal Ball. Resultados: Se observaron dosis superiores a la dosis de referencia para FD en la leche de fórmula reconstituida con agua de abastecimiento público, de vaca pasteurizada (entera) y de vaca sin tratamiento sanitario (cruda) en el percentil 90, 70 y 50, respectivamente, así como una correlación entre los niveles de F- en leche y F- en orina (r = 0,41; p < 0,001). Conclusiones: La identificación de fuentes de F- en etapas tempranas del desarrollo infantil podría reducir el riesgo de presentar FD

Introduction: Several studies have shown the presence of fluorosis (DF) in primary dentition, suggesting an exposure to fluorides (F-) in early childhood. Breast milk is recommended as an exclusive food until 6 months of age. Although it is mentioned that only a small amount of F- can be eliminated by breast milk, studies have shown the presence of this element in milk of women living in contaminated areas, as well as in infant formulas. The objective of this project was to evaluate the exposure level to F- through milk in children living in an area with endemic hydrofluorosis. Methodology: The study included 110 children between 6 and 36 months of age from the municipality of Lagos de Moreno, Jalisco. Water samples were collected from the homes, as well as samples of milk (maternal, formula, whole or raw), and urine. Measurments were made with a selective ion electrode. The exposure level of F- for milk intake was calculated using the Oracle Crystal Ball package. Results: Levels greater than the reference level for DF were observed in infant formula reconstituted with public supply water, pasteurised cow's milk (whole) and untreated cow's milk treatment (raw) in the 90th, 70th, and 50th percentile, respectively, with a correlation being found between the levels of F- in milk and F- in urine (r = 0.41, P < .001)

Adiabatic deprotonation as an important competing pathway to ESIPT in photoacidic 2-phenylphenols.

ESIPT (Excited State Intramolecular Proton Transfer) to C atom in 2-phenylphenol is known to be an intrinsically inefficient process. However, to the best of our knowledge, a structure-ESIPT efficiency relationship has not been elucidated yet. Here, we show that there exists a competitive interplay between photoacidity and ESIPT efficiency for the 2-phenylphenol system. The attachment of electron withdrawing groups to the phenol moiety promotes adiabatic deprotonation in the excited state and diminishes the charge transfer character of the excitations, and both these factors contribute in decreasing the ESIPT reaction yield. On the other hand, unfavorable conformational distribution in the ground state also appears as another important aspect responsible for the low ESIPT extent of 2-phenylphenol. A new derivative bearing electron donating, bulky substituents at ortho and para positions of the phenol ring shows an outstanding ESIPT performance, which demonstrates that the efficiency of the process can be significantly enhanced by modifying the substitution pattern. We anticipate that our results will help to guide the molecular designing of new compounds with high ESIPT efficiency.

[Level of exposure to fluorides by the consumption of different types of milk in residents from an area of Mexico with endemic hydrofluorosis]. / Dosis de exposición a fluoruros por el consumo de diferentes tipos de leche en residentes de una zona con hidrofluorosis endémica en México.

INTRODUCTION: Several studies have shown the presence of fluorosis (DF) in primary dentition, suggesting an exposure to fluorides (F-) in early childhood. Breast milk is recommended as an exclusive food until 6 months of age. Although it is mentioned that only a small amount of F- can be eliminated by breast milk, studies have shown the presence of this element in milk of women living in contaminated areas, as well as in infant formulas. The objective of this project was to evaluate the exposure level to F- through milk in children living in an area with endemic hydrofluorosis. METHODOLOGY: The study included 110 children between 6 and 36 months of age from the municipality of Lagos de Moreno, Jalisco. Water samples were collected from the homes, as well as samples of milk (maternal, formula, whole or raw), and urine. Measurments were made with a selective ion electrode. The exposure level of F- for milk intake was calculated using the Oracle Crystal Ball package. RESULTS: Levels greater than the reference level for DF were observed in infant formula reconstituted with public supply water, pasteurised cow's milk (whole) and untreated cow's milk treatment (raw) in the 90th, 70th, and 50th percentile, respectively, with a correlation being found between the levels of F- in milk and F- in urine (r=0.41, P<.001). CONCLUSIONS: The identification of sources of F- in the early stages of child development could reduce the risk of developing DF.

Photoinduced Synthesis of Dibenzofurans: Intramolecular and Intermolecular Comparative Methodologies.

The SRN1 reaction has been used as a powerful tool for the synthesis of heterocycles, and only a few studies about photoinduced intramolecular cyclization to generate a new C-O bond by a radical pathway have been reported. This work introduces two strategies for the synthesis of substituted dibenzofurans by electron transfer (eT) reactions. The first one is a three-step process that comprises bromination of o-arylphenols, Suzuki-Miyaura cross-coupling and photoinduced cyclization in order to obtain the above-mentioned products. The second one is a metal-free procedure and does not require any photocatalyst. Different solvents were tested, and the yields ranged from low to moderate. A comparison was established between both methodologies, showing that the second one is the most suitable for the synthesis of dibenzofurans.

Functionalization Effect on Polymer Nanocomposite Coatings Based on TiO2⁻SiO2 Nanoparticles with Superhydrophilic Properties.

In this study, a novel binary nanocomposite system based on TiO2-SiO2 was functionalized with trimethylolpropane triacrylate (TMPTA) and characterized by XPS and XRD. Results revealed that TiO2-SiO2 nanoparticles were covalently functionalized. Functionalized nanoparticles at low concentrations (0.1 wt % and 0.5 wt %) were dispersed in acrylic acid acting as a polymer matrix. Nanocomposite coatings analysis demonstrate to achieve superhydrophilic properties as well as very good optical characteristics. Water contact angle characterization showed the functionalization effect by achieving a superhydrophilic behavior with a contact angle less than 5°. UV-Vis measurements demonstrated high optical transmittance above 95% for the coatings. Based on the obtained results a mechanism describing the chemical interactions of the constituents responsible for the synergy in the nanocomposite as well as the morphological play role in the behavior are presented.

Photoinduced nucleophilic substitution of iodocubanes with arylthiolate and diphenylphosphanide ions. Experimental and computational approaches.

A new synthetic route to modify the cubane nucleus is reported here. Methyl-4-iodocubane-1-carboxylate (1) and 1,4-diiodocubane (2) were employed as reagents to react with arylthiolate and diphenylphosphanide ions under irradiation in liquid ammonia and dimethylsulphoxide. The reactions proceed to afford thioaryl- and diphenylphosphoryl- cubane derivatives in moderate to good yields. It is also found that the monosubstituted product with retention of the second iodine is an intermediate compound. Mechanistic aspects are supported by DFT calculations.