Universidad Americana de Morelos

Abstract This study evaluates argon–helium shielding gas mixtures in tungsten inert gas-welded Al6061-T6 alloy. Five gas compositions, from pure argon to pure helium, were tested under constant welding parameters on 6 mm-thick plates. Microstructural analysis via optical and scanning electron microscopy revealed refinement from ASTM grain size 4 in the base material to ASTM 7 in helium-rich welds; the 25% Ar–75% He mixture (hereafter referred to as G4) produced the most homogeneous fusion zone. All welded joints showed reductions in tensile strength and microhardness, characteristic of precipitation-hardened aluminum alloys. G4 performed best, retaining ~ 70% of ultimate tensile strength (UTS), ~ 65% of yield strength, and ~ 73.5% of Vickers microhardness of the base material. Pure argon led to limited penetration and heterogeneity, while pure helium caused excessive heat input and grain coarsening in the fusion zone. These results show that balanced Ar–He mixtures greatly improve weld microstructure and mechanical integrity, offering a practical guideline for high-performance Al6061-T6 joining in aerospace. Graphical abstract

Abstract Predicted population growth and urbanization in low-elevation coastal zones threaten natural ecosystems, causing landscape fragmentation, biodiversity loss, and reduced ecosystem services, such as climate regulation, crucial for coastal communities. These impacts undermine the capacity of communities to cope with climate change, including rising urban temperatures. Ecosystem-based adaptation (EbA) can address ecological and social challenges simultaneously. This study aimed to identify areas where green infrastructure projects could maximize benefits for landscape connectivity and temperature regulation in Campeche, Gulf of Mexico. Between 1995 and 2023, 1,249 ha of urban vegetation were lost, reducing access to green areas to under 10% in a quarter of neighborhoods and decreasing functional landscape connectivity by over 54%. During the same period, average temperatures rose from 29.5°C to 33°C. Areas without forest cover and functional connectivity (439 ha) exhibited significantly higher mean temperatures (33.43°C, STD 0.52) than vegetated areas (31.84°C, STD 0.49). Priority intervention sites were identified, covering 8.4% of the urban area, allowing recovery of temperature regulation services and enhancing landscape connectivity. These findings provide actionable insights for urban planning and EbA strategies in coastal cities facing climate change, highlighting the importance of preserving and restoring urban vegetation to maintain ecological functions and human wellbeing.

La propuesta de investigación tiene el siguiente alcance. En relación, al objetivo general, se pretende modelar la evolución de la crisis climática a través del tiempo tomando como variables el calentamiento global, los gases de efectos invernaderos, temperatura de la atmosfera y temperatura de los océanos, así como también la continuidad de los fenómenos naturales en cuanto a su medición, temporalidad y proyección. Para lograr lo anterior, se plantea la descripción de los siguientes objetivos específicos: - Identificar las variables correspondientes a la crisis climática, su relación y correlación entre ellas; - Desarrollar modelos de proyección con arreglos matemáticos y estadísticos para proyectarlos en un tiempo determinado y de esta manera, - Proponer medidas de atenuación a los diferentes escenarios desfavorables. Las principales variables que actualmente están vinculada directamente con el Cambio Climático son: el CO2, el índice atmosférico, la precipitación, la temperatura y la velocidad del viento. La correlación que existe entre los elementos climáticos, es muy alta, tanto en el comportamiento histórico como el comportamiento proyectado al 2035, su correlación se estima en 0.90, 0.95, 0.93 y 91 respectivamente. Los modelos matemáticos ocupados para manipular el análisis histórico y proyectado de las variables estudiadas: son los arreglos normales, esto asegura que los valores se puedan usar a una escala en común; luego se tiene el análisis de las variables históricas utilizando la tendencia lineal, y finalmente se tiene el análisis de las variables proyectadas al año 2035 utilizando la tendencia polinómica. En ambas situaciones la relación directa de los gases de efecto invernadero principalmente el CO2 está directamente relacionado con las variaciones de las variables en el tiempo, lo cual es un resultado muy preocupante porque ya no se puede hablar de cambio climático, sino de CRISIS CLIMATICA. En gran medida se requiere del cambio de paradigma de explotación de los recursos de nuestra madre tierra. Alertar de manera SOS hacia las grandes potencias, que hagan un uso razonable de la tecnología, para ello se proponen medidas de atenuación.

Abstract We study the spectrum, eigenstates and transport properties of a simple P T -symmetric model consisting in a finite, complex, square well potential with a delta potential at the origin. We show that as the strength of the delta potential increases, the system exhibits exceptional points accompanied by an accumulation of density associated with the break in the P T -symmetry. We also obtain the density and energy density fluxes and analyze their transport properties. We find that in the P T -symmetric phase transport is efficient, in the sense that all the density that flows into the system at the source, flows out at the sink, which is sufficient to derive a generalized unitary relation for the transmission and reflection coefficients.

Abstract: The most economical and efficient route to prepare polypeptides from synthetic chemistry is through the Ring-opening Polymerization (ROP) of amino acids using Ncarboxyanhydride (NCA) monomers. Peptide polymers, in contrast to proteins, consist of repeated amino acid units and are comparatively simpler macromolecules. Despite their simplicity, these polypeptides offer a unique combination of beneficial traits found in both synthetic polymers (such as solubility, processability, and rubber elasticity) and natural proteins (including secondary structure, functionality, and biocompatibility). Nevertheless, NCA polymerization faces significant challenges, including intricate monomer purification and the necessity for processing toxic solvents. In this context, this review presents the fundamental principles of this polymer chemistry, the synthesis of NCA monomers, and the different methodologies to access polypeptides by ROP. It also explores the most recent advances in this field of research, with a focus on how new methods enable the use of more reactive initiators and the development of original processes, including the use of aqueous solvents.

The purpose of this study is to analyze the prevalence of variants of normality and pathology in the mucosa of the oral cavity by anatomical area in a controlled population in a university undergraduate stomatological clinic in the state of Mexico. This is a cross-sectional, descriptive and observational study of 542 patients, of which 62.7% (340) belonged to the female gender and 37.3% ( 202) to the male gender, the age was distributed in a range of two to 85 years with a mean of 28 years and was categorized in five age groups: 2 to 12, 13 to 18, 19 to 35, 36 to 69 and > 70 years. A specialist in oral pathology, a specialist in pediatric dentistry and an intern in stomatology who served as a research assistant participated in this study. Thirteen variants of normality and 52 lesions in total were identified and reported by anatomical area, age range and gender. The number of conditions and lesions diagnosed per patient ranged from one to five in 87.27% and none were detected in 12.73% of the population studied. The most frequent variants of normality or conditions were fissured tongue with 12.17%, mucous appendage in the vestibular frenulum with 11.25% and Fordyce granules with 10.88%. The most prevalent lesions by anatomical area were: intradermal nevus with 2.39% in upper and lower external lip; simple cheilitis with 11.43% in the interphase interface of skin and mucosa of the lips (vermilion border); traumatic ulcer with 3.87% in labial mucosa; abscess of dental origin with 1.42 in gingiva; frenulum with low insertion 1.84% in frenulum; traumatic ulcer with 5. 53% in buccal mucosa; chronic atrophic candidiasis with 5.53% in palate; hypertrophic tonsils with 8.11% in tonsillar area; hairy tongue with 1.66% in tongue; traumatic ulcer with 3.69% in floor of mouth; pyogenic granuloma with 0.18% in alveolar process and finally; hypertrophy of labial salivary glands with 0.55% associated with the presence of orthodontic appliances. Finally, a Pearson's χ 2 test was carried out to establish correlation between dependent and independent Cuapio OAA y cols. Lesiones en mucosa bucal y condición sistémica Revista ADM 2024; 81 (1): 26-38 www.medigraphic.com/adm χ 2 de Pearson para establecer correlación entre variables dependientes e independientes, encontrando significancia estadística de p < 0.000 entre lesiones de lengua y condición sistémica y edad en relación a lesiones de lengua, paladar y labios con p < 0.000. Palabras clave: condiciones, variantes, lesiones, normalidad, patología, mucosa bucal. variables, finding statistical significance of p < 0.000 between tongue lesions and systemic condition and age in relation to tongue, palate and lip lesions with a p < 0.000.

The merger of two very different microbes, an anaerobic archaeon and an aerobic bacterium, led to the birth of eukaryotic cells. Current models hypothesize that an archaeon engulfed bacteria through external protrusions that then fused together forming the membrane organelles of eukaryotic cells, including mitochondria. Images of cultivated Lokiarchaea sustain this concept, first proposed in the inside-out model which assumes that the membrane traffic system of archaea drove the merging with bacterial cells through membrane expansions containing inositol lipids, considered to have evolved first in archaea. This assumption has been evaluated here in detail. The data indicate that inositol lipids first emerged in bacteria, not in archaea. The implications of this finding for the models of eukaryogenesis are discussed.

Objetivo: Sensibilizar a comunidade escolar sobre a importância dos métodos contraceptivos para a prevenção de infecções sexualmente transmissíveis. Métodos: Estudo com adolescentes, de ambos os sexos, com faixa etária entre 13 e 20 anos, matriculados no Instituto Federal de Educação, Ciência e Tecnologia do Maranhão -IFMA Campus Caxias. O projeto foi realizado em três etapas: aplicação de questionário para verificar o nível de conhecimento dos adolescentes referente às IST; realização de palestras e rodas de conversa sobre IST e métodos contraceptivos e reaplicação do questionário para verificar o impacto no conhecimento dos adolescentes após a realização das oficinas. Resultados: Participaram 145 adolescentes regularmente matriculados, sendo 64 (44,1%) meninos e 81 (55,9%) meninas. Destes, 66,8% (97) disseram já ter participado de algum tipo de palestra e/ou oficina sobre IST. O local mais citado para realização dessas ações foi a escola, citada por 85,6% (83) dos participantes. Os dados mostram que o conhecimento dos adolescentes em relação aos métodos contraceptivos aumentou após a realização das oficinas. Conclusão: A utilização de oficinas educativas permitiu uma maior participação dos adolescentes, com acréscimo de informações seguras sobre os temas abordados, motivando a mudança no comportamento de risco e oportunizando a promoção do autocuidado.