Biomineralizaciones de sílice amorfa en secuencias pedosedimentarias del sudeste bonaerense: tafonomía, biogeoquímica e importancia paleoambiental

Las secuencias pedosedimentarias del Cenozoico tardío del sudeste bonaerense, expuestas en las barrancas costeras entre Mar del Plata y Miramar, constituyen uno de los registros de mamíferos continentales más importantes de Sudamérica. Si bien las condiciones paleoambientales en las que se depositaron han sido ampliamente estudiadas, la evolución de la paleovegetación previa al Holoceno ha sido un tema poco abordado debido a la limitada capacidad de preservación de macrorestos vegetales y polen. A pesar de esto, otros bioindicadores capaces de aportar información paleoambiental, como las biomineralizaciones de sílice amorfa, se han mencionado con recurrencia en descripciones microscópicas de las barrancas costeras, y solo han sido estudiadas de forma exploratoria. Estos cuerpos de sílice hidratada (SiO2·nH2O) de entre 5 y 200 μm, son precipitados en espacios intra, inter o extracelulares por organismos que capturan ácido monosilícico (Si(OH)4) del ambiente para cumplir diversas funciones, principalmente protección y sostén. La magnitud de este fenómeno impacta de forma directa en el ciclo biogeoquímico del Si y, por lo tanto, en el equilibrio de los sistemas naturales. En el ámbito continental, se encuentran cuatro tipos de organismos que biomineralizan esta sustancia: diatomeas (algas pardas), que producen su pared celular con dos tecas de sílice amorfa caracterizadas por una intrincada ornamentación; crisofitas (algas doradas) que forman quistes de sílice amorfa como estructuras de resistencia; poríferos de agua dulce que producen espículas de sílice amorfa, que junto con espongina componen su esqueleto; y numerosas familias de plantas vasculares que forman cuerpos de sílice amorfa llamados silicofitolitos, que pueden presentar diferentes morfologías o morfotipos, cuyo valor taxonómico puede alcanzar el nivel de subfamilia. Luego de la muerte y descomposición de los organismos, las biomineralizaciones de sílice amorfa pueden degradarse constituyendo una de las principales fuentes de Si en el medio terrestre, o pueden preservarse en suelos y sedimentos por millones de años, formando parte del registro microfósil. En este trabajo se describieron en secuencias pedosedimentarias representativas del Cenozoico tardío del sudeste bonaerense, los ensambles de biomineralizaciones de sílice amorfa. Dentro de los cuales se incluyó a los presentes en suelos y sedimentos actuales, y a los formados a lo largo del Cenozoico tardío en dos perfiles tipo de las barrancas costeras. Con ello se buscó evaluar la capacidad de los ensambles actuales de representar a las especies formadoras e indirectamente el tipo de ambiente; reconocer cambios composicionales dentro del registro formado durante el Cenozoico tardío y posibilitar su comparación con ensambles de ambientes análogos actuales. Adicionalmente, se analizaron los procesos tafonómicos que pudieron afectar a las biomineralizaciones en estos depósitos, para así lograr un análisis integral de los resultados y establecer su relevancia paleoambiental. La prospección de unidades de estudio de las secuencias pedosedimentarias se realizó en base a criterios preestablecidos. Los ambientes actuales representativos del sudeste bonaerense se eligieron en áreas con bajo impacto antrópico. Se muestrearon suelos (Argiudol típico) mediante excavación de calicata y ambientes lénticos (lagunas someras) por recuperación de testigos. Mientras que los perfiles de las barrancas costeras analizados (Perfil Escalera Barranca Los Lobos y Perfil Punta San Andrés), fueron seleccionados en base a su buena resolución temporal, accesibilidad y preexistencia de control cronoestratigráfico. Los perfiles se dividieron en secciones muestreales delimitadas en base a diferencias morfológicas observadas en campo y complementadas por análisis de laboratorio. Para cada sección se obtuvieron muestras de sectores espaciados lateralmente. En total, fueron analizadas 18 muestras de ambientes actuales y 72 muestras de los perfiles. Sobre las cuales también se midió la concentración de sílice disuelta en solución mediante espectrofotometría. El contenido de biomineralizaciones de sílice amorfa fue descrito en microscopio óptico de forma cuantitativa y cualitativa. Se estimaron abundancias por peso de muestra total y se calcularon las abundancias relativas con sus respectivos intervalos de confianza para silicofitolitos, diatomeas, quistes de crisofitas y espículas de esponjas. En base a los resultados, se establecieron zonas con diferencias significativas mediante análisis de agrupamiento y se determinó el grado de similitud entre ensambles actuales y fósiles mediante análisis de escalamiento multidimensional no métrico (NMDS). En ambientes actuales se encontraron biomineralizaciones de sílice amorfa formando ensambles abundantes, en promedio la cantidad por miligramo fue de 14 883 en suelos y 20 649 en sedimentos de ambientes lénticos; constituyendo registros distintivos y representativos de las especies formadoras. Los silicofitolitos dominaron los ensambles del suelo, principalmente constituidos por los morfotipos RONDEL y ELONGADO ENTERO; mientras que en las lagunas someras también se encontraron los morfotipos BILOBADO, ELONGADO DENTADO y CRENADO. Los ensambles de ambientes lénticos también presentaron diversidad de diatomeas en buen estado de preservación. Lo que posibilitó la delimitación de zonas en los testigos de cada laguna, con períodos de profundización representados por especies planctónicas como Cyclotella meneghiniana y Aulacoseira granulata, y períodos de somerización y desecación indicados por especies epífitas como Gomphonema spp. y aerófitas como Hantzschia amphyoxis y Luthicola mutica. También se hallaron en los testigos analizados 14 tipos de quistes de crisofitas, que constituyen el primer registro en lagunas someras del sudeste bonaerense. Uno de los cuales tiene afinidad biológica conocida, por lo que puede ser asignado a Uroglena volvox Ehrenberg. Por su parte, las espículas de esponja fueron halladas como un elemento muy poco frecuente, y asignables a Ephydatia fluviatilis, la única especie actual registrada. En los perfiles de las barrancas costeras, la cantidad promedio por miligramo de microfósiles máxima fue de 10 500, mientras que en promedio fue de 6600 en perfil Escalera Barranca Los Lobos y de 4250 en perfil Punta San Andrés. En los ensambles hallados, los silicofitolitos fueron los únicos microfósiles en cantidades suficientes como para admitir análisis cuantitativos. Por su abundancia a lo largo de las secuencias y su mayor capacidad de disolución en relación con la sílice inorgánica, serían una importante fuente de Si en el ciclo biogeoquímico continental local. Su aporte se concentraría especialmente en paleosuelos argílicos, donde se encontraron los ensambles más numerosos y las concentraciones de sílice disuelta más altas. El análisis de la tafonomía de los silicofitolitos respaldó su relevancia como bioindicador para este registro, por lo que la abundancia por peso de muestra total y frecuencia relativa de morfotipos se utilizó para reconstruir la paleovegetación, e indirectamente la intensidad de pedogénesis y condiciones paleoclimáticas. Para contextualizar los resultados se utilizó el esquema aloestratigráfico más reciente y estudios de magnetoestratigrafía previos como control cronológico indirecto. El estudio del perfil Escalera Barranca Los Lobos permitió reconstruir la paleovegetación del área durante el Plioceno medio/tardío y Pleistoceno, donde el registro de silicofitolitos indica cuatro cambios en la cobertura vegetal. Los ensambles hallados en la Alofm. Playa San Carlos indican una paleovegetación dominada por pastizales tipo flechillar y arecáceas. En la Alofm. Punta Martínez de Hoz se observó un cambio interno en los ensambles, los cuales indican una cobertura vegetal dominada por pastizales de régimen semiárido templado/frío en la sección inferior, y húmedo en la superior. Este aumento de la disponibilidad hídrica es a su vez respaldada por la presencia de diatomeas y quistes de crisofitas. Por último, en la Alofm. Punta San Andrés se registran ensambles homologables a la cobertura vegetal típica de ambientes lénticos actuales. El análisis del perfil Punta San Andrés permitió completar la reconstrucción de ambientes durante la depositación de la Alofm. Punta San Andrés con mayor detalle. El perfil presentó dos secciones con contenidos anormalmente bajos de silicofitolitos, sugiriendo paleoambientes áridos con escasa cobertura vegetal, que habrían alternado con períodos con buen desarrollo de pastizales de composición similar a los actuales. Estos resultados refuerzan la interpretación de condiciones áridas en el sudeste pampeano alrededor de los 2,5 Ma, como ha sido previamente inferido a partir de la presencia de taxones específicamente adaptados a climas áridos de la biozona Ctenomys chapadmalensis. Los resultados de este trabajo destacan el potencial uso de los silicofitolitos como bioindicadores en las secuencias pedosedimentarias del Cenozoico tardío del sudeste bonaerense, donde la litología y mineralogía homogénea ha sido un obstáculo para la comprensión de la evolución paleoambiental de la región. Mientras que las diatomeas, componentes importantes en los ensambles de las lagunas pampeanas someras actuales, se encuentran en escasa cantidad en las secuencias pedosedimentarias y por lo tanto carecen de relevancia paleoambiental en este registro. Su escasez no implica la inexistencia de paleohumedales en la historia geológica del área, sino que responde a condiciones de preservación adversas. Los quistes de crisofitas constituyen un componente poco abundante, aunque con presencia constante a lo largo de las secuencias pedosedimentarias. Si bien tienen escasa relevancia paleoambiental para este registro, la continuidad en su investigación permitirá homologar la antigua taxonomía local al reciente sistema numérico internacional y ampliar el conocimiento de su distribución nacional y mundial. De los quistes hallados en este trabajo, 6 son mencionados por primera vez en Argentina. Finalmente, las espículas de esponjas se encuentran en bajas cantidades y solo representadas por fragmentos de megaescleras. Debido a la ausencia de condiciones óptimas para el desarrollo de esponjas tanto en el presente como durante el Cenozoico tardío, se infiere que no ha sido un filo prolífico ni diverso en el área. Por ello, puede considerarse que las espículas no poseen relevancia paleoambiental para este registro.Doctor en Ciencias NaturalesUniversidad Nacional de La PlataFacultad de Ciencias Naturales y Muse

Epigenetics of Lipid Phenotypes

Dyslipidemia is a well-established risk factor for cardiovascular disease, the main cause of death worldwide. Blood lipid profiles are patterned by both genetic and environmental factors. In recent years, epigenetics has emerged as a paradigm that unifies these influences. In this review, we have summarized the latest evidence implicating epigenetic mechanisms—DNA methylation, histone modification, and regulation by RNAs—in lipid homeostasis. Key findings have emerged in a number of novel epigenetic loci located in biologically plausible genes (eg, CPT1A, ABCG1, SREBF1, and others), as well as microRNA-33a/b. Evidence from animal and cell culture models suggests a complex interplay between different classes of epigenetic processes in the lipid-related genomic regions. Although epigenetic findings hold the potential to explain the interindividual variability in lipid profiles as well as the underlying mechanisms, they have yet to be translated into effective therapies for dyslipidemia

Small Farmers’ Use of Social Media and Other Channels for Marketing their Agricultural Products

We examined small farmers’ use of and preference for different channels for marketing agricultural products and explored differences by gender, age group, and education level. Farmers markets and social media were preferred channels, with participants under age 55 being more likely than those 55 and over to prefer and use social media and agree that social media would be useful for promoting products and increasing sales. While selling via social media could provide a larger market, one challenge is that the average age of Mississippi farm operators is 59. Therefore, Extension must consider multiple approaches for delivering training on marketing

S14: Factors Affecting Dental Students’ Comfort with Online Synchronous Learning

Background: The COVID-19 pandemic has caused many universities to expand the use of videoconferencing technology to continue academic coursework. This study examines dental students’ experience with videoconferencing technology, comfort levels, and perceptions of using videoconferencing technology. Methods: 54 out of 100 second-year dental students enrolled in a course on local anesthesia, 54 completed a survey following an online synchronous lecture given in September 2020. Survey questions asked about prior experience with videoconferencing, comfort levels, and reasons for not turning on their video (showing their face). Results: Overall, 48.2% had little or no prior experience with videoconferencing prior to March 2020. The Regression analyses showed there were significant positive associations between ratings of experience and comfort with answering questions and interacting in breakouts (r=.55, p=.04 and r=.54, p=0.03, respectively). Students were significantly more comfortable interacting with each other more during in-person than on-line breakout sessions than on-line breakout sessions (p=0.003). Although not significant, students were more comfortable in-person than on-line for all other classroom parameters. The main reasons students did not turn on their for not using the video feature were that they did not want to dress up (48.1%), others were not using their video (46.3%), and feeling that they did not look good (35.5%). Conclusion: Students who had prior experience with videoconferencing technology were more comfortable actively participating in online synchronous lectures. Students reported feeling more comfortable interacting during in-person breakout groups than in online breakout groups. The most significant reasons for students not using the video feature (showing their face) relate to inconvenience, peers not using the video feature, and self-consciousness

Ecohealth interventions limit triatomine reinfestation following insecticide spraying in La Brea, Guatemala

In this study, we evaluate the effect of participatory Ecohealth interventions on domestic reinfestation of the Chagas disease vector Triatoma dimidiata after village-wide suppression of the vector population using a residual insecticide. The study was conducted in the rural community of La Brea, Guatemala between 2002 and 2009 where vector infestation was analyzed within a spatial data framework based on entomological and socio-economic surveys of homesteads within the village. Participatory interventions focused on community awareness and low-cost home improvements using local materials to limit areas of refuge and alternative blood meals for the vector within the home, and potential shelter for the vector outside the home. As a result, domestic infestation was maintained at ≤ 3% and peridomestic infestation at ≤ 2% for 5 years beyond the last insecticide spraying, in sharp contrast to the rapid reinfestation experienced in earlier insecticide only interventions. Copyright © 2013 by The American Society of Tropical Medicine and Hygiene

Heavy Metals in Soil and Salad in the Proximity of Historical Ferroalloy Emission

Emissions of manganese (Mn), lead (Pb), iron (Fe), zinc (Zn), copper (Cu) from ferro-alloy operations has taken place in Valcamonica, a pre-Alp valley in the province of Brescia, Italy, for about a century until 2001. Metal concentrations were measured in the soil of local home gardens and in the cultivated vegetables. Soil analysis was carried out using a portable X-Ray Fluorescence (XRF) spectrometer in both surface soil and at 10 cm depth. A subset of soil samples (n = 23) additionally was analysed using the modified BCR sequential extraction method and ICP-OES for intercalibration with XRF (XRF Mn = 1.33 * total OES Mn – 71.8; R = 0.830, p < 0.0001). Samples of salads (Lactuca sativa and Chichorium spp.) were analyzed with a Total Reflection X-Ray Fluorescence (TXRF) technique. Vegetable and soil metal measurements were performed in 59 home gardens of Valcamonica, and compared with 23 gardens from the Garda Lake reference area. Results indicate significantly higher levels of soil Mn (median 986 ppm vs 416 ppm), Pb (median 46.1 ppm vs 30.2 ppm), Fe (median 19,800 ppm vs 13,100 ppm) in the Valcamonica compared to the reference area. Surface soil levels of all metals were significantly higher in surface soil compared to deeper soil, consistent with atmospheric deposition. Significantly higher levels of metals were shown also in lettuce from Valcamonica for Mn (median 53.6 ppm vs 30.2) and Fe (median 153 vs 118). Metals in Chichorium spp. did not differ between the two areas. Surface soil metal levels declined with increasing distance from the closest ferroalloy plant, consistent with plant emis- sions as the source of elevated soil metal levels. A correlation between Mn concentrations in soil and lettuce was also observed. These data show that historic ferroalloy plant activity, which ended nearly a decade before this study, has contributed to the persistence of increased Mn levels in locally grown vegetables. Further research is needed to assess whether this increase can lead to adverse effects in humans and plants especially for Mn, an essential element that can be toxic in humans when exceeding the homeostatic ranges

Chytridiomycosis and Amphibian Population Declines Continue to Spread Eastward in Panama

Chytridiomycosis is a globally emerging disease of amphibians and the leading cause of population declines and extirpations at species-diverse montane sites in Central America. We continued long-term monitoring efforts for the presence of the fungal pathogen Batrachochytrium dendrobatidis (Bd) and for amphibian populations at two sites in western Panama, and we began monitoring at three new sites to the east. Population declines associated with chytridiomycosis emergence were detected at Altos de Campana National Park. We also detected Bd in three species east of the Panama Canal at Soberanía National Park, and prevalence data suggests that Bd may be enzootic in the lowlands of the park. However, no infected frogs were found further east at Tortí (prevalence <7.5% with 95% confidence). Our results suggest that Panama's diverse and not fully described amphibian communities east of the canal are at risk. Precise predictions of future disease emergence events are not possible until factors underlying disease emergence, such as dispersal, are understood. However, if the fungal pathogen spreads in a pattern consistent with previous disease events in Panama, then detection of Bd at Tortí and other areas east of the Panama Canal is imminent. Therefore, development of new management strategies and increased precautions for tourism, recreation, and biology are urgently neede

Upper bounds on the superfluid stiffness and superconducting TcT_c: Applications to twisted-bilayer graphene and ultra-cold Fermi gases

Understanding the material parameters that control the superconducting transition temperature $T_c$ is a problem of fundamental importance. In many novel superconductors, phase fluctuations determine $T_c$, rather than the collapse of the pairing amplitude. We derive rigorous upper bounds on the superfluid phase stiffness for multi-band systems, valid in any dimension. This in turn leads to an upper bound on $T_c$ in two dimensions (2D), which holds irrespective of pairing mechanism, interaction strength, or order-parameter symmetry. Our bound is particularly useful for the strongly correlated regime of low-density and narrow-band systems, where mean field theory fails. For a simple parabolic band in 2D with Fermi energy $E_F$, we find that $k_BT_c \leq E_F/8$, an exact result that has direct implications for the 2D BCS-BEC crossover in ultra-cold Fermi gases. Applying our multi-band bound to magic-angle twisted bilayer graphene (MA-TBG), we find that band structure results constrain the maximum $T_c$ to be close to the experimentally observed value. Finally, we discuss the question of deriving rigorous upper bounds on $T_c$ in 3D.Comment: Revised figures, includes estimates from another model of MA-TBG, published version of manuscrip

Duration of adjuvant chemotherapy for stage III colon cancer

BACKGROUND Since 2004, a regimen of 6 months of treatment with oxaliplatin plus a fluoropyrimidine has been standard adjuvant therapy in patients with stage III colon cancer. However, since oxaliplatin is associated with cumulative neurotoxicity, a shorter duration of therapy could spare toxic effects and health expenditures. METHODS We performed a prospective, preplanned, pooled analysis of six randomized, phase 3 trials that were conducted concurrently to evaluate the noninferiority of adjuvant therapy with either FOLFOX (fluorouracil, leucovorin, and oxaliplatin) or CAPOX (capecitabine and oxaliplatin) administered for 3 months, as compared with 6 months. The primary end point was the rate of disease-free survival at 3 years. Noninferiority of 3 months versus 6 months of therapy could be claimed if the upper limit of the two-sided 95% confidence interval of the hazard ratio did not exceed 1.12. RESULTS After 3263 events of disease recurrence or death had been reported in 12,834 patients, the noninferiority of 3 months of treatment versus 6 months was not confirmed in the overall study population (hazard ratio, 1.07; 95% confidence interval [CI], 1.00 to 1.15). Noninferiority of the shorter regimen was seen for CAPOX (hazard ratio, 0.95; 95% CI, 0.85 to 1.06) but not for FOLFOX (hazard ratio, 1.16; 95% CI, 1.06 to 1.26). In an exploratory analysis of the combined regimens, among the patients with T1, T2, or T3 and N1 cancers, 3 months of therapy was noninferior to 6 months, with a 3-year rate of disease-free survival of 83.1% and 83.3%, respectively (hazard ratio, 1.01; 95% CI, 0.90 to 1.12). Among patients with cancers that were classified as T4, N2, or both, the disease-free survival rate for a 6-month duration of therapy was superior to that for a 3-month duration (64.4% vs. 62.7%) for the combined treatments (hazard ratio, 1.12; 95% CI, 1.03 to 1.23; P=0.01 for superiority). CONCLUSIONS Among patients with stage III colon cancer receiving adjuvant therapy with FOLFOX or CAPOX, noninferiority of 3 months of therapy, as compared with 6 months, was not confirmed in the overall population. However, in patients treated with CAPOX, 3 months of therapy was as effective as 6 months, particularly in the lower-risk subgroup. (Funded by the National Cancer Institute and others.

Urinary, Gastrointestinal, and Sexual Dysfunctions after Chemotherapy, Radiotherapy, Radical Surgery or Multimodal Treatment in Women with Locally Advanced Cervical Cancer: A Multicenter Retrospective Study

Background: Different strategies have been proposed for the treatment of locally advanced cervical cancer (LACC), with different impacts on patient's quality of life (QoL). This study aimed to analyze urinary, bowel, and sexual dysfunctions in a series of LACC patients who underwent chemotherapy, radiotherapy, radical surgery, or a combination of these treatments. Methods: Patients with LACC who underwent neoadjuvant radio-chemotherapy (NART/CT; n = 35), neoadjuvant chemotherapy (NACT; n = 17), exclusive radio-chemotherapy (ERT/CT; n = 28), or upfront surgery (UPS; n = 10) from November 2010 to September 2019 were identified from five oncological referral centers. A customized questionnaire was used for the valuation of urinary, gastrointestinal, and sexual dysfunctions. Results: A total of 90 patients were included. Increased urinary frequency (&gt;8 times/day) was higher in ERT/CT compared with NACT/RT (57.1% vs. 28.6%; p = 0.02) and NACT (57.1% vs. 17.6%; p = 0.01). The use of sanitary pads for urinary leakage was higher in ERT/CT compared with NACT/RT (42.9% vs. 14.3%; p = 0.01) and NACT (42.9% vs. 11.8%; p = 0.03). The rate of reduced evacuations (&lt;3 times a week) was less in UPS compared with NACT/RT (50% vs. 97.1%; p &lt; 0.01), NACT (50% vs. 88.2, p &lt; 0.01), and ERT/CT (50% vs. 96.4%; p &lt; 0.01). A total of 52 women were not sexually active after therapy, and pain was the principal reason for the avoidance of sexual activity. Conclusions: The rate and severity of urinary, gastrointestinal, and sexual dysfunction were similar in the four groups of treatment. Nevertheless, ERT/CT was associated with worse sexual and urinary outcomes