On-Surface Synthesis of Square-Type Porphyrin Tetramers with Central Antiaromatic Cyclooctatetraene Moiety.

The synthesis of two-dimensionally extended polycyclic heteroatomic molecules keeps attracting considerable attention. In particular, frameworks bearing planar cyclooctatetraenes (COT) moieties can display intriguing properties, including antiaromaticity. Here, we present an on-surface chemistry route to square-type porphyrin tetramers with a central COT ring, coexisting with other oligomers. This approach employing temperature-induced dehydrogenative porphyrin homocoupling in an ultrahigh vacuum environment provides access to surface-supported, unsubstituted porphyrin tetramers that are not easily achievable by conventional synthesis means. Specifically, monomeric free-base (2H-P) and Zn-metalated (Zn-P) porphines (P) were employed to form square-type free-base and Zn-functionalized tetramers on Ag(100). An atomic-level characterization by bond-resolved atomic force microscopy and scanning tunneling microscopy and spectroscopy is provided, identifying the molecular structures. Complemented by density functional theory modeling, the electronic structure is elucidated, indeed revealing antiaromaticity induced by the COT moiety. The present study thus gives access, and insights, to a porphyrin oligomer, representing both a model system for directly fused porphyrins and a potential building block for conjugated, extended two-dimensional porphyrin sheets.

Tuning the Diradical Character of Pentacene Derivatives via Non-Benzenoid Coupling Motifs.

The development of functional organic molecules requires structures of increasing size and complexity, which are typically obtained by the covalent coupling of smaller building blocks. Herein, with the aid of high-resolution scanning tunneling microscopy/spectroscopy and density functional theory, the coupling of a sterically demanded pentacene derivative on Au(111) into fused dimers connected by non-benzenoid rings was studied. The diradical character of the products was tuned according to the coupling section. In particular, the antiaromaticity of cyclobutadiene as the coupling motif and its position within the structure play a decisive role in shifting the natural orbital occupancies toward a stronger diradical electronic character. Understanding these structure-property relations is desirable not only for fundamental reasons but also for designing new complex and functional molecular structures.

Steering Large Magnetic Exchange Coupling in Nanographenes near the Closed-Shell to Open-Shell Transition.

The design of open-shell carbon-based nanomaterials is at the vanguard of materials science, steered by their beneficial magnetic properties like weaker spin-orbit coupling than that of transition metal atoms and larger spin delocalization, which are of potential relevance for future spintronics and quantum technologies. A key parameter in magnetic materials is the magnetic exchange coupling (MEC) between unpaired spins, which should be large enough to allow device operation at practical temperatures. In this work, we theoretically and experimentally explore three distinct families of nanographenes (NGs) (A, B, and C) featuring majority zigzag peripheries. Through many-body calculations, we identify a transition from a closed-shell ground state to an open-shell ground state upon an increase of the molecular size. Our predictions indicate that the largest MEC for open-shell NGs occurs in proximity to the transition between closed-shell and open-shell states. Such predictions are corroborated by the on-surface syntheses and structural, electronic, and magnetic characterizations of three NGs (A[3,5], B[4,5], and C[4,3]), which are the smallest open-shell systems in their respective chemical families and are thus located the closest to the transition boundary. Notably, two of the NGs (B[4,5] and C[4,3]) feature record values of MEC (close to 200 meV) measured on the Au(111) surface. Our strategy for maximizing the MEC provides perspectives for designing carbon nanomaterials with robust magnetic ground states.

Highly entangled polyradical nanographene with coexisting strong correlation and topological frustration.

Open-shell nanographenes exhibit unconventional π-magnetism arising from topological frustration or strong electron-electron interaction. However, conventional design approaches are typically limited to a single magnetic origin, which can restrict the number of correlated spins or the type of magnetic ordering in open-shell nanographenes. Here we present a design strategy that combines topological frustration and electron-electron interactions to fabricate a large fully fused 'butterfly'-shaped tetraradical nanographene on Au(111). We employ bond-resolved scanning tunnelling microscopy and spin-excitation spectroscopy to resolve the molecular backbone and reveal the strongly correlated open-shell character, respectively. This nanographene contains four unpaired electrons with both ferromagnetic and anti-ferromagnetic interactions, harbouring a many-body singlet ground state and strong multi-spin entanglement, which is well described by many-body calculations. Furthermore, we study the magnetic properties and spin states in the nanographene using a nickelocene magnetic probe. The ability to imprint and characterize many-body strongly correlated spins in polyradical nanographenes paves the way for future advancements in quantum information technologies.

Mycobacteriosis in wild birds: the potential risk of disseminating a little-known infectious disease.

Avian mycobacteriosis is important for animal and human health; wild birds play an important role in mycobacterial species' ecology and movement. This review was aimed at reporting the role of birds in the spread of avian mycobacteriosis in human and animal populations at risk and thus a systematic review was made of PubMed, Science Direct, Scielo and Scirus databases. Mycobacteria are classified into the Mycobacterium tuberculosis complex and non-tuberculous mycobacteria; the Mycobacterium avium complex represents the most important part of the latter because it is primarily responsible for mycobacterial infection in wild birds and is a potential pathogen for mammals, especially for immunocompromised patients. The clinical signs in birds are variable as it is a chronic and debilitating disease, involving emaciated carcasses, white nodules in different organs and microscopically it presents granulomatosous multifocal inflammation. Diagnosis begins by suspicion based on clinical signs and finishes with microbiological confirmation. New diagnostic techniques include testing with DNA-RNA probes. No effective treatment is currently available and chemoprophylaxis on suspicion of infection is not recommended at the start; these factors increase the potential risk of mycobacteriosis becoming one of the most frequently documented zoonotic diseases which is difficult to treat in birds and humans. Recent concern regarding mycobacterial infection lies in the increased frequency of these opportunistic infections occurring in immunocompromised individuals and these infections' potential impact on bird conservation, this being increased by greater contact between humans and wild and captive birds.

Mycobacteriosis in wild birds: the potential risk of disseminating a little-known infectious disease / Micobacteriosis en aves silvestres: riesgo potencial de diseminación de una infección poco conocida en el mundo

Avian mycobacteriosis is important for animal and human health; wild birds play an important role in mycobacterial species' ecology and movement. This review was aimed at reporting the role of birds in the spread of avian mycobacteriosis in human and animal populations at risk and thus a systematic review was made of PubMed, Science Direct, Scielo and Scirus databases. Mycobacteria are classified into the Mycobacterium tuberculosis complex and non-tuberculous mycobacteria; the Mycobacterium avium complex represents the most important part of the latter because it is primarily responsible for mycobacterial infection in wild birds and is a potential pathogen for mammals, especially for immunocompromised patients. The clinical signs in birds are variable as it is a chronic and debilitating disease, involving emaciated carcasses, white nodules in different organs and microscopically it presents granulomatosous multifocal inflammation. Diagnosis begins by suspicion based on clinical signs and finishes with microbiological confirmation. New diagnostic techniques include testing with DNA-RNA probes. No effective treatment is currently available and chemoprophylaxis on suspicion of infection is not recommended at the start; these factors increase the potential risk of mycobacteriosis becoming one of the most frequently documented zoonotic diseases which is difficult to treat in birds and humans. Recent concern regarding mycobacterial infection lies in the increased frequency of these opportunistic infections occurring in immunocompromised individuals and these infections' potential impact on bird conservation, this being increased by greater contact between humans and wild and captive birds.

La micobacteriosis aviar es de importancia para la salud animal y humana. El objetivo de esta revisión fue reportar el papel de las aves en la diseminación de la micobacteriosis aviar en poblaciones vulnerables. Se realizó una revisión sistemática en las bases de datos PubMed, Science Direct, Scielo and Scirus. Las aves silvestres juegan un papel importante en la ecología y movimiento de micobacterias. Estas se clasifican en el Complejo Mycobacterium tuberculosis y las micobacterias no tuberculosas, dentro de este último grupo se destaca el Complejo Mycobacterium avium , principal responsable de micobacteriosis en aves silvestres y patógeno potencial para los mamíferos principalmente pacientes inmunosuprimidos. Los signos clínicos son variables, siendo una enfermedad debilitante y crónica, e involucra carcasas emaciadas, nódulos blanquecinos en diferentes órganos, microscópicamente presenta inflamaciones granulomatosas multifocales. El diagnóstico inicia por la sospecha basada en los síntomas clínicos y termina con la confirmación microbiológica. Adicionalmente, las nuevas técnicas diagnósticas incluyen pruebas con sondas de ADN-ARN. Actualmente, no existe un tratamiento efectivo y no se recomienda iniciar quimioprofilaxis; estos factores incrementan el riesgo potencial para convertir la micobacteriosis aviar en una enfermedad zoonótica más frecuente de lo documentado y de difícil tratamiento en aves y humanos. La reciente preocupación de las infecciones micobacterianas, radica en el aumento de la frecuencia de estas infecciones oportunistas en personas inmunocomprometidas y el impacto potencial de estas infecciones sobre la conservación de las especies de aves, favorecido por el mayor contacto entre humanos y aves tanto silvestres como cautivas.

Aspectos toxicológicos y Clínicos de la mordedura por serpientes venenosas en animales domésticos / Toxic and clinical aspects os poisonous snakes bite in domestic animals

Las mordeduras por serpientes venenosas en animales domésticos en Colombia son muy poco reportadas, y su principal causa es la invasión de los hábitats naturales por parte del hombre. Las serpientes venenosas se caracterizan por tener el órgano de Jacobson, la lengua bífida, las fosas termorreceptoras y las glándulas productoras de veneno con cuatro diferentestipos de colmillos inoculadores. En Colombia se encuentran dos familias, Viperidae y Elapidae, con siete y cuatro géneros, respectivamente. Los componentes y mecanismos de acción de los venenos (toxinas) son muy variados, donde se encuentran componentes no proteicos (inorgánicos y orgánicos) y proteicos, con acción necrotizante, coagulante o hemorrágica.Su mordedura causa efectos locales y sistémicos, con diversas secuelas, además de una variedad de disturbios hematológicos y bioquímicos, los cuales en la mayoría de los casos llevan a la muerte. Los hallazgos postmortem macroscópicos y microscópicos son característicos. Su diagnóstico depende de la historia y los signos clínicos; y su tratamiento se basa en controlar los efectos de las toxinas y en brindar un soporte hemodinámico al paciente mientras las toxinas son eliminadas del organismo...

Visión retrospectiva de las malformaciones anorectales Hospital Central de San Cristobal decenio 1988-1998 / Vision retroespective of the malformation anorectal Central Hospital of San Cristobal deceni 1988-1998

Obtener una visión objetiva de la problemática que representan las malformaciones anorectales. Realizamos una investigación documental y restrospectiva basada en los casos de malformaciones anorectales registrados en el Hospital Central de San Cristobal durante 10 años. La incidencia fue de 25000 nacidos vivos; con predominio del sexo masculino (61 por ciento). La malformación más frecuente la atrevia anal baja (26 por ciento). El invertograma se realizó en 82 por ciento, y la colostomía derivativa fue realizada en el 38 por ciento. Se concluye que las MAR no son infrecuentes por lo cual preciso afinar el diagnóstico clínico y brindarle mayor apoyo psicológico a pacientes y sus padres