Quantification of bond strength between cementitious materials and microbially-induced calcium carbonate precipitates

Researchers have recently demonstrated the capabilities of microbially-induced calcium carbonate precipitation to fill and seal cracks in cementitious materials. However, the mechanical strength of microbially-induced crack healing is seldom investigated, especially at the fundamental level. In an effort to aid future development of structural repairs using this technique, the research discussed herein examines the suitability of several test methods to quantify the mechanical bond between calcium carbonate bio-deposits and cementitious substrates. Tests are performed at laboratory- and nano-scale to study both realistic cracks and isolated interfaces created under ideal conditions. Resonant frequency and mechanical bending tests were performed on notched, damaged, and treated Portland cement mortar beams. Sporosarcina pasteurii in nutrient media was applied to cracked beams in two different environmental conditions. Several experimental control treatments lacking bacteria were applied to additional sets of beams. Furthermore, bio-deposits were grown on prepared surfaces of cement paste in order to analyze an isolated interface using nanoscratch tests. A low-viscosity epoxy repair system was studied alongside the bio-deposits at both scales to provide a benchmark for comparison. Due to the challenges encountered when analyzing nanoscratch test results for a porous, discretely crystalline coating, data analysis methods for nanoscratch experiments were first established using a simplified model system of calcium-silicate-hydrate corrosion products on soda-lime glass substrates. Over the course of a 28-day treatment period, mortar beams in nearly all treatment conditions recovered to 95-105% of their pre-cracked resonant frequency, though the rate of recovery varied. Beams healed autogenously through hydration of remaining cement, without addition of external water, recovered to only about 85% of their original resonant frequency. In mechanical testing, only the set of beams healed by epoxy was capable of recovering significant load-carrying capacity. Other treated beams exhibited marginal improvements in fracture toughness recovery, but again lagged far behind the epoxy-based repair used for comparison in this study. On the other hand, the stiffness recovery under nearly all treatment conditions was competitive with the epoxy investigated here. These results indicate that the bacteria-based treatment could produce a repair that is weak in tension on the laboratory scale, but that bridges cracks well enough to increase overall stiffness. Initial nanoscratch experiments studying the model system of corrosion products on glass were indeed capable of quantifying an empirically observed distinction in bond strengths. When isolating the interfacial mechanical bond on this smaller scale, we find that a bio-deposit coating on cement paste fails at similar critical loads as an epoxy coating. Therefore, while the beam tests on the laboratory scale indicate a weak bond, it is possible for nano-scale tests which better isolate the interface between bio-deposits and cementitious materials to measure a fundamental bond strength which approaches that of a conventional epoxy repair

Cannibalism by large tadpoles of Rhinophrynus dorsalis (Anura: Rhinophrynidae)

In June 2014, we captured approximately 100 R. dorsalis tadpoles in a net from a seasonal wetland in Palo Verde National Park (10.3428 N, 85.3375 W) in N, 85.3375 W) in northwestern Costa Rica. While rearing the tadpoles in the laboratory, we observed five events in which larger tadpoles (Stage 26; Gosner, 1960) fed on conspecifics at earlier stages. At first, we interpreted this behaviour as scavenging. However, after observing more closely during two subsequent events, we noticed that the predated individuals were still alive. We were not able to observe interactions with tadpoles in older stages at this time due to tadpole mortality. Then, during the first week of the rainy season (May to November annually) on 23 May 2018, we collected approximately 300 Rhinophrynus dorsalis tadpolesUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Evidence of maternal provisioning of alkaloid-based chemical defenses in the strawberry poison frog Oophaga pumilio

Many organisms use chemical defenses to reduce predation risk. Aposematic dendrobatid frogs sequester alkaloid-based chemical defenses from a diet of arthropods, but research on these defenses has been limited to adults. Herein, we investigate chemical defense across development in a dendrobatid frog, Oophaga pumilio. This species displays complex parental care: at hatching, mothers transport tadpoles to phytotelmata, and then return to supply them with an obligate diet of nutritive eggs for about six weeks. We collected eggs, tadpoles, juveniles, and adults of O. pumilio, and detected alkaloids in all life stages. The quantity and number of alkaloids increased with frog and tadpole size. We did not detect alkaloids in the earliest stage of tadpoles, but alkaloids were detected as trace quantities in nutritive eggs and as small quantities in ovarian eggs. Tadpoles hand-reared with eggs of an alkaloid-free heterospecific frog did not contain alkaloids. Alkaloids that are sequestered from terrestrial arthropods were detected in both adults and phytotelm-dwelling tadpoles that feed solely on nutritive eggs, suggesting that this frog may be the first animal known to actively provision post-hatch offspring with chemical defenses. Finally, we provide experimental evidence that maternally derived alkaloids deter predation of tadpoles by a predatory arthropod.Ministerio del Ambiente, Energía y Technologia/[10CR000024]/MINAET/Costa RicaThe Convention on International Trade in Endangered Species/[10CR000024]/CITES/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP

Integrating tropical research into biology education is urgently needed

Understanding tropical biology is important for solving complex problems such as climate change, biodiversity loss, and zoonotic pandemics, but biology curricula view research mostly via a temperatezone lens. Integrating tropical research into biology education is urgently needed to tackle these issues. The tropics are engines of Earth systems that regulate global cycles of carbon and water, and are thus critical for management of greenhouse gases. Compared with higher-latitude areas, tropical regions contain a greater diversity of biomes, organisms, and complexity of biological interactions. The tropics house the majority of the world’s human population and provide important global commodities from species that originated there: coffee, chocolate, palm oil, and species that yield the cancer drugs vincristine and vinblastine. Tropical regions, especially biodiversity hotspots, harbor zoonoses, thereby having an important role in emerging infectious diseases amidst the complex interactions of global environmental change and wildlife migration [1]. These well-known roles are oversimplified, but serve to highlight the global biological importance of tropical systems. Despite the importance of tropical regions, biology curricula worldwide generally lack coverage of tropical research. Given logistical, economic, or other barriers, it is difficult for undergraduate biology instructors to provide their students with field-based experience in tropical biology research in a diverse range of settings, an issue exacerbated by the Coronavirus Disease 2019 (COVID-19) pandemic. Even in the tropics, field-based experience may be limited to home regions. When tropical biology is introduced in curricula, it is often through a temperate- zone lens that does not do justice to the distinct ecosystems, sociopolitical histories, and conservation issues that exist across tropical countries and regions [2]. The tropics are often caricatured as distant locations known for their remarkable biodiversity, complicated species interactions, and unchecked deforestation. This presentation, often originating from a colonial and culturally biased perspective, may fail to highlight the role of tropical ecosystems in global environmental and social challenges that accompany rising temperatures, worldwide biodiversity loss, zoonotic pandemics, and the environmental costs of ensuring food, water, and other ecosystem services for humans [3]

Heterologous hyperimmune polyclonal antibodies against SARS-COV-2: A broad coverage, affordable, and scalable potential immunotherapy for Covid-19

The emergence and dissemination of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the resulting COVID-19 pandemic triggered a global public health crisis. Although several SARS-CoV-2 vaccines have been developed, demand far exceeds supply, access to them is inequitable, and thus, populations in low- and middle-income countries are unlikely to be protected soon (1). Furthermore, there are no specific therapies available, which is a challenge for COVID-19 patient care (2). Thus, the appearance of SARS-CoV-2 variants and reports of reinfections associated with immune escape (3, 4) highlight the urgent need for effective and broad coverage COVID-19 therapeutics. Intravenous administration of human or heterologous antibodies is a therapy successfully used in patients with viral respiratory diseases (5). Accordingly, formulations containing SARS-CoV-2 specific antibodies are an attractive therapeutic option for COVID-19 patients (6). SARS-CoV-2 specific antibodies could limit infection by direct virion neutralization and/or by targeting infected cells for elimination via complement or antibody-mediated cytotoxicity (6). Specific SARS-CoV-2 antibody-based therapeutics include convalescent plasma (CP), monoclonal antibodies (mAbs), human polyclonal IgG formulations purified from CP or transgenic animals, and heterologous hyperimmune polyclonal antibodies (pAbs) (6). Although the window for using antibody-based therapeutics varies, clinical data show that they are mainly effective if administered early after symptoms onset (6).Universidad de Costa Rica/[741-C0-198]/UCR/Costa RicaCaja Costarricense del Seguro Social/[]/CCSS/Costa RicaBanco Centroamericano de Integración Económica/[]/BCIE/Costa RicaGerman academic exchange services/[57592642]/DAAD/AlemaniaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)UCR::Vicerrectoría de Docencia::Salud::Facultad de Medicina::Escuela de MedicinaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Centro de Investigación en Enfermedades Tropicales (CIET

All's well that begins Wells: Celebrating 60 years of Animal Behaviour and 36 years of research on anuran social behaviour

The scientific study of frogs and toads as important systems in behavioural ecology traces its roots to an influential review published in this journal 36 years ago (Wells 1977a, ‘The social behaviour of anuran amphibians’, Animal Behaviour, 25, 666–693). In just 28 pages, Wells summarized the state of knowledge on important behaviours associated with anuran breeding and introduced an evolutionary framework ‘for understanding the relationship between social behaviour and ecology’ (page 666) that was largely lacking in earlier treatments of this group. Not only is Wells's review one of the most cited papers ever published in Animal Behaviour, it is also responsible for setting broad research agendas and shaping much of our current thinking on social behaviour in an entire order of vertebrates. As such, it is entirely appropriate that we honour Wells's review and its contributions to the study of animal behaviour in this inaugural essay celebrating 12 papers selected by the community as the most influential papers published in the 60-year history of Animal Behaviour. In our essay, we place Wells's review in historical context at the dawn of behavioural ecology, highlight the field's progress in answering some major research questions outlined in the review, and provide our own prospectus for future research on the social behaviour of anuran amphibians. Highlights ► This essay celebrates Kent Wells's (1977, Animal Behaviour, 25, 666–693) paper, ‘The social behaviour of anuran amphibians’. ► We place the article in historical context and outline its major contributions. ► We discuss progress on anuran social behaviour since its publication in 1977. ► We provide our own prospectus on the future of anuran behavioural ecology

The role of complex cues in social and reproductive plasticity

Phenotypic plasticity can be a key determinant of fitness. The degree to which the expression of plasticity is adaptive relies upon the accuracy with which information about the state of the environment is integrated. This step might be particularly beneficial when environments, e.g. the social and sexual context, change rapidly. Fluctuating temporal dynamics could increase the difficulty of determining the appropriate level of expression of a plastic response. In this review, we suggest that new insights into plastic responses to the social and sexual environment (social and reproductive plasticity) may be gained by examining the role of complex cues (those comprising multiple, distinct sensory components). Such cues can enable individuals to more accurately monitor their environment in order to respond adaptively to it across the whole life course. We briefly review the hypotheses for the evolution of complex cues and then adapt these ideas to the context of social and sexual plasticity. We propose that the ability to perceive complex cues can facilitate plasticity, increase the associated fitness benefits and decrease the risk of costly ‘mismatches’ between phenotype and environment by (i) increasing the robustness of information gained from highly variable environments, (ii) fine-tuning responses by using multiple strands of information and (iii) reducing time lags in adaptive responses. We conclude by outlining areas for future research that will help to determine the interplay between complex cues and plasticity

Toward improving carbon nanotube utilization in Portland cement mortar using novel processing techniques

Carbon nanotubes have the potential to enhance the strength, toughness, and self-sensing ability of Portland cement mortar and concrete. Two processing methods were studied to improve the dispersion and bonding of carbon nanotubes in cementitious composites. In the first method, silica functional groups were covalently bonded to carbon nanotubes before dispersing them in the mixing water. Two silica morphologies were used separately. Initially, agglomerated nanosilica spheres were produced, and later a semi-uniform coating was attached to the CNT surface. The flowability of the resulting Portland cement mortar mixtures was quantified and their flexural strengths were determined at various ages. Results indicate improvements to workability when the functional groups are used, but no change in flexural strength from mixtures containing pristine carbon nanotubes. Preliminary study was also performed on cement clinker with carbon nanotubes grown on it. The modified clinker was mixed into cement paste to observe the dispersion and test the hydration kinetics of the mixture. The particles clumped together within the specimen and the dense coating of carbon prevented hydration at the surface of the particles