Hypoxia and Sturgeons: report to the Chesapeake Bay Program Dissolved Oxygen Criteria Team

In this essay, three lines of evidence are developed that sturgeons in the Chesapeake Bay and elsewhere are unusually sensitive to hypoxic conditions: 1. In comparison to other fishes, sturgeons have a limited behavioral and physiological capacity to respond to hypoxia. Basal metabolism, growth, and consumption are quite sensitive to changes in oxygen level, which may indicate a relatively poor ability by sturgeons to oxyregulate. 2. During summertime, temperatures >20 C amplify the effect of hypoxia on sturgeons and other fishes due to a temperature*oxygen "squeeze" (Coutant 1987)- In bottom waters, this interaction results in substantial reduction of habitat; in dry years, nursery habitats in the Chesapeake Bay may be particularly reduced or even eliminated. 3. While evidence for population level effects by hypoxia are circumstantial, there are corresponding trends between the absence of Atlantic sturgeon reproduction in estuaries like the Chesapeake Bay where summertime hypoxia predominates on a system-wide scale. Also, the recent and dramatic recovery of shortnose sturgeon in the Hudson River (4-fold increase in abundance from 1980 to 1995) may have been stimulated by improvement of a large portion of the nursery habitat that was restored from hypoxia to normoxia during the period 1973-1978. (PDF contains 26 pages

Exact welfare measurement: theory and application to recreation economics

Although the limitations of consumer surplus have become widely known, there exists a lack of studies which present in a coherent framework recent developments in estimating Hicksian welfare measures. This study attempts to fill partially this gap by analyzing some theoretical and empirical aspects in the estimation of exact welfare measures using market data. Analytical expressions of the "exact" welfare measures, compensating variation (CV) and equivalent variation (EV), for some frequently used single demand equations as well as flexible functional form demand systems are presented. The different magnitudes of benefit estimates generated for the same valuation problem have been a source of important criticism of market related valuation studies. This study compares different functional forms consistent with the restrictions required for the aggregation of consumers and commodities. The results for steelhead rivers in Oregon indicate that the definitional differences in welfare measure (ordinary versus compensated measures) are quite small, which is consistent with the small budget shares that these activities account for a representative household. The results also suggest that the welfare measures may be very sensitive to the formulation of the model. However, the almost ideal demand system (AIDS) and translog indirect utility function demand system (TLOG) produce very close welfare estimates when catch rate, trips and a composite good are considered the commodities yielding utility. The treatment of endogenous quality variables has been a widely discussed issue in the recreation economics and labor economics literatures. In this study, unlike that of Bockstael and McConnell (1981), the demand system is specified as a function of exogenous parameters rather than endogenous implicit prices, avoiding the simultaneity of the demand system and the identification problem. Our empirical results support the comparative static predictions on the price and income elasticities for catch rate per trip and number of trips. A limitation of this study is the restrictive form assumed for the production technology. However, following Strong (1984), our model can be extended to take into account substitution among inputs, non constant returns to scale, and exogenous quality variables. Future research should be directed to study the properties of "exact welfare measures associated with different flexible functional forms. For large economic welfare changes, a global approximation to the underlying utility function as provided by Fourier series might be preferable. The comparisons among different model specifications should be done using rigorous statistical methods including the construction of confidence intervals for the welfare estimates

Opinion of medical students compared with non-medical students about organ donation and its bioethical conflicts

Introduction and Purpose: Organ donation is controversial. Chilean legislation failed to increase donors. However, it seems that there is an enthusiasm to be an organ donor, so education is important. Therefore, medical students play an important role in educating, but the other students may not know these topics. Thus, the following work pretends to compare the opinions of medical students and non-medical students at the University of Concepción (UDEC) about organ donation and associated bioethical conflicts.Material and Method: Observational, descriptive, cross-sectional study with qualitative and quantitative variables. It was used a 16-question survey, applied in Argentina, adapted to the Chilean culture. The sample was 60 students: 30 medical students and 30 students from other fields, outside the health area. Microsoft Windows Excel program was used to process the data.Results: Mostly men were surveyed, on average 21.5 years. Engineering was more frequent after medicine, and mode was 4 years studied. The absence of belief predominated. In both groups the donation was considered good; that they would donate, because it is a way of giving a life; and what they would like to receive. In medicine they considered that those who donate are brave people, where the other group considered that they give their lives and are brave. Regarding the concepts of brain death and Chilean law number 20.413, knowledge was lower in the non-medical group.Conclusions: We observe that medical university students handle some concepts related to donation in more detail than those who pursue careers outside the health area. Organ donation it is an issue that needs to be brought to discussion that should include the government authorities, local authorities, and the community

Genetics and conservation of the southern South American conifers

Coniferous trees dominate many northern forests, and globally there are around 627 species of conifers, from eight families and 70 genera. Although the largest abundance of conifers is in the great boreal forests of Eurasia and North America, the species diversity increases further south, even though the land area is smaller. The conifer flora of Chile comprises only nine conifer species, but these include 3/8 extant conifer families (Araucariaceae, Cupressaceae, Podocarpaceae) and eight genera, with all of these species and four genera just restricted to southern South America. Chilean conifers are concentrated in the Chilean Temperate Rainforest, one of the world’s plants biodiversity hotspots. Although some species of Chilean conifer such as Araucaria araucana (Molina) K. Koch (Monkey Puzzle) have been subject to intensive research, most have not. Knowledge gaps in their basic biology represent a limitation in the development of effective conservation strategies. This is a pressing challenge given the extensive threat to plant biodiversity in the region (harvesting, climate change, pathogens, expanding plantation forestry and agriculture, and natural and human-induced fires). To address this challenge, this research project focuses on assessing population connectivity/differentiation in four emblematic endemic conifers from South America each with a restricted area of distribution: Saxegothaea conspicua Lindley, Prumnopitys andina (Poepp. ex Endl) de Laubenfels, Podocarpus salignus D. Don all members of the Podocarpaceae; and Fitzroya cupressoides (Molina) Johnston (Cupressaceae). Between seven and ten populations (per species) were included in this investigation, covering the entire natural distribution of each conifer species in Chile. Restriction site-associated DNA markers (RAD-seq) analysis was conducted. RAD-seq was first optimised (de novo assembly) to accommodate the large and complex genomes of conifers, before being deployed to assess patterns of population genetic structure. The main finding of population genetic analyses was a similar level of nucleotide diversity and low levels of genetic structure in all four conifer species. The low population structure over relatively large geographical distances was particularly noteworthy. This result is likely due to the extreme longevity of individuals of these species restricting divergence due to genetic drift, despite their currently fragmented ranges. A regeneration survey was also conducted for one of the conifer species involved in this project (Pr. andina), and supplemented with informal observations on regeneration for the other three species. Regeneration was frequent throughout most of the natural distribution of Pr. andina. However, a very low number of saplings was observed in all of the populations (most of them had no saplings at all). Informal observations on S. conspicua, P. salignus and F. cupressoides suggest that regeneration is common for all these species (both seedlings and saplings). How- ever, there was some variation and P. salignus showed a higher level of regeneration than S. conspicua and F. cupressoides. A field-based observation of threats was also undertaken for each conifer species, following the methodology proposed by the IUCN which is directed on recording and evaluating the impact of threats in situ. The most common threats with the highest impact were associated with land-conversion to exotic plantations and livestock. This work represents one of the very few studies optimising RAD-seq data for conifers and provides a combination of field and laboratory data to support conservation planning for these important and iconic species

Clinical, imaging and genetic analysis of double bilateral radix entomolaris

Background: Anatomy describes that first mandibular molars have two roots: 1 mesial, with 2 root canals, and 1 distal, with 1 root canal. The presence of three roots in these teeth is uncommon. Root anatomical variations have an impact, especially in endodontic, where the highest rates of nonsurgical treatment failures are due to the inability to identify and access roots and/or accessory canals. The aim of this research is to report a case of double three-rooted mandibular first molar through clinical, imaging and genetic analysis. Materials and methods: Using a panoramic radiography, the presence of three roots in teeth 36 and 46 was diagnosed in a female patient. Additionally, it was indicated a cone beam computed tomography. Moreover, leukocyte genomic DNA was obtained from a blood sample of the patient to determine her ethnicity through analysis of mitochondrial DNA haplogroups using polymerase chain reaction-length restriction fragment polymorphism (PCR-RFLP). Results: Both molars had three roots, 1 mesial (M), 1 distolingual (DL), also known as radix entomolaris (RE), and a distovestibular (DV). For both teeth, M root had 2 canals, and DV and DL roots presented just 1 canal. Mitochondrial DNA analysis determined presence of haplogroup C, corresponding to Amerindian ethnicity. Conclusions: The presence of RE is uncommon. This case report contributes to describe this rare anatomical variation. To our knowledge, this is the first molecular-genetic study applied to dental anatomy and gives basis to develop future research in the area

Incentivos Económicos para una Explotación Eficiente del Bosque

The problem of forest management with noncentralized land property seems of increasing importance, specially for developing countries. There is a need to design mechanisms that allow to obtain both commercial benefits from exploitation and purely social b

Expectativas de implicación académica: Validez y uso en el diagnóstico de ingreso a la educación superior

Conocer las características de entrada de los estudiantes que inician la educación superior, permite tener una primera imagen de éstos para tomar decisiones institucionales que respondan a sus necesidades. El presente trabajo busca aportar a los procesos de diagnóstico institucional en el área socioemocional, indagando en un componente clave de ésta: las expectativas de implicación académica, entendidas como lo que el estudiante espera hacer durante su vida universitaria; expectativas que pueden incidir en su permanencia en educación superior. En este estudio de carácter cuantitativo no experimental y transversal, se aplicó la traducción del Cuestionario de Implicación Académica en su forma A (CIA –A) que evalúa expectativas. Este fue aplicado a 2.334 estudiantes de la cohorte 2019 que ingresaron a la Universidad Católica de Temuco en Chile, como parte del proceso diagnóstico institucional.Se evaluó la estructura factorial del CIA-A mediante análisis factorial confirmatorio; se calculó la confiabilidad de los factores identificados y  se emplearon análisis de conglomerados jerárquico y no jerárquico. La solución de mejor ajuste respaldaba la existencia de cinco factores: Implicación vocacional, Implicación institucional, Implicación social, Utilización de recursos y Participación estudiantil (alfas entre 0,79 y 0,88). Desde el análisis de conglomerados jerárquicos, se identificaron dos conglomerados y al asignar los participantes a cada uno, empleando un análisis de conglomerado no jerárquico, se obtuvo un primer cluster con un 44,83% (n=1.002) de los casos y un segundo cluster con un 55,17% (n=1.233), asumiéndose la presencia de perfiles de expectativas. Al comparar los resultados de ambos perfiles en el CIA-A se encontró que el perfil 2 presentaba mayores puntajes que el perfil 1 en todos los factores de expectativas académicas, por lo que se le denominó: Perfil de Mayor Involucramiento Esperado (n=1.233; 55,17%), mientras que al otro grupo se le denominó Perfil de Menor Involucramiento Esperado (n=1.002; 44,83%). Al comparar el perfil actitudinal por sexo, se puede observar que las mujeres tienden a presentar un perfil de mayor involucramiento esperado (60,8%) en comparación con los hombres (46,4%). Y entre las facultades, los alumnos de Ciencias de la Salud, Ciencias Sociales y de Humanidades, tienen una mayor proporción de alumnos en el perfil de mayor involucramiento esperado. Esta investigación aporta respaldo de la validez y confiabilidad del CIA-A como instrumento para la identificación de perfiles de estudiantes, lo que puede ayudar a identificar perfiles de riesgo. Lo anterior es relevante, pues evaluar expectativas permitiría anticipar problemas de adaptación y podría constituirse como herramienta factible para la identificación de áreas críticas a intervenir institucionalmente a través de programas de acompañamiento a estudiantes iniciales, docencia universitaria y desarrollo estudiantil, que permitan afianzar la permanencia de los estudiantes en las Instituciones de Educación Superior