Late Holocene expansion of ponderosa pine (\u3ci\u3ePinus ponderosa\u3c/i\u3e) in the Central Rocky Mountains, USA

Aim: Ponderosa pine (Pinus ponderosa) experienced one of the most extensive and rapid post-glacial plant migrations in western North America. We used plant macrofossils from woodrat (Neotoma) middens to reconstruct its spread in the Central Rocky Mountains, identify other vegetation changes coinciding with P. ponderosa expansion at the same sites, and relate P. ponderosa migrational history to both its modern phylogeography and to a parallel expansion by Utah juniper (Juniperus osteosperma). Location: Central Rocky Mountains, Wyoming and Montana, and Black Hills, Wyoming and South Dakota, USA. Methods: Plant macrofossils were analysed in 90 middens collected at 14 widely separated sites in the northern part of the range of P. ponderosa var. scopulorum. Middens with and without P. ponderosa were 14C dated to pinpoint time of appearance at each site. Sensitivity experiments using a bioclimatic model were used to evaluate potential climatic drivers of late Holocene expansion. Results: Pinus ponderosa colonized the Black Hills region by at least 3850 yr bp (all ages given in calendar years before present). It expanded into the eastern Bighorn Mountains of northern Wyoming by 2630 yr bp, quickly spreading north in the western Bighorns from 1400 to 1000 yr bp. Concurrent with the latter expansion, P. ponderosa spread c. 350 km to the Little Belt and Big Belt Mountains in western Montana, establishing its northern limit and the modern introgression zone between var. scopulorum and var. ponderosa. Expansion in the Central Rockies of P. ponderosa involved two known haplotypes

Interband electron Raman scattering in a quantum wire in a transverse magnetic field

Electron Raman scattering (ERS) is investigated in a parabolic semiconductor quantum wire in a transverse magnetic field neglecting by phonon-assisted transitions. The ERS cross-section is calculated as a function of a frequency shift and magnetic field. The process involves an interband electronic transition and an intraband transition between quantized subbands. We analyze the differential cross-section for different scattering configurations. We study selection rules for the processes. Some singularities in the Raman spectra are found and interpreted. The scattering spectrum shows density-of-states peaks and interband matrix elements maximums and a strong resonance when scattered frequency equals to the "hybrid" frequency or confinement frequency depending on the light polarization. Numerical results are presented for a GaAs/AlGaAs quantum wire.Comment: 8 pages, 5 figure

Noise Assessment/Survey at ERAU Fleet Maintenance Hanger

One of the many hazards associated with aviation, and conducting aircraft maintenance, is the issuance of noise hazards. Federal agencies such as Occupational Health and Safety Administration have incorporated standards pertaining to threshold limit values and permissible exposure limits surrounding noise in the workplace. Our objective is to assist the work environment in the Embry-Riddle aviation hangar to assure personnel are protected from lasting effects of noise through this research. The method used for research in this paper was a combination of sound monitoring of the maintenance hangar using a sound level meter, noise dosimeter and the NIOSH Sound Level Meter application as well as using relevant previous research studies. The results of the sound monitoring determined that the noise level within the maintenance hangar was well below the OSHA Time Weighted Average of 85 dB, and the noise level peaked at 115.4 dB for a single impulse. It has been concluded that the maintenance hangar does not require a hearing conservation program at this time as the data indicates that noise levels are well within OSHA standards. However, the current data does not include the engine run-up operations

New Measurements and Quantitative Analysis of Electron Backscattering in the Energy Range of Neutron Beta-Decay

We report on the first detailed measurements of electron backscattering from plastic scintillator targets, extending our previous work on beryllium and silicon targets. The scintillator experiment posed several additional experimental challenges associated with charging of the scintillator target, and those challenges are addressed in detail. In addition, we quantitatively compare the energy and angular distributions of this data, and our previous data, with electron transport simulations based on the Geant4 and Penelope Monte Carlo simulation codes. The Penelope simulation is found globally to give a superior description of the data. Such information is crucial for a broad array of weak-interaction physics experiments, where electron backscattering can give rise to the dominant detector-related systematic uncertainty.Comment: 7 pages, 3 figure

Relación del conocimiento del etiquetado “Semáforo Nutricional” en el estado nutricional de adolescentes ecuatorianos/List of labeling knowledge: "Nutritional traffic light" in the nutritional status of Ecuadorian adolescents

El semáforo nutricional (SN) es un tipo de etiquetado de alimentos creado para mejorar la comprensión del contenido de nutrientes (sodio, azúcar y grasa) en los alimentos procesados. En Ecuador, el SN es de uso obligatorio desde el año 2012. Objetivo: Evaluar la relación del conocimiento del etiquetado SN en el estado nutricional de adolescentes ecuatorianos. Métodos: Estudio transversal. Con 599 adolescentes (14- 18 años). Se recopilaron datos antropométricos, actividad física (IPAQ-A) e ingesta alimentaria utilizando 3 encuestas de recordatorio de 24 horas, el conocimiento del SN se evaluó con un cuestionario preparado para este fin: puntuaciones >5 significaron adecuado conocimiento (AC). Las relaciones entre las variables se determinaron mediante prueba t de student, utilizando el software STATA-14. Resultados: 55% de los adolescentes presentaron diagnóstico de sobrepeso, el 28% obesidad, según los indicadores IMC//Edad, el 48% un AC. Los adolescentes que mostraron inadecuado conocimiento evidenciaron medias más altas de IMC//edad, circunferencia de la cintura, circunferencia de la cadera y porcentaje de masa grasa (p<0.001), no se encontró diferencias en la ingesta alimentaria y conocimiento del SN. Conclusiones: El conocimiento del SN puede estar relacionado con el sobrepeso-obesidad en adolescentes, se necesita realizar más estudios para conocer cuál es el impacto de SN sobre el estado nutricional de la población en general. Nutritional traffic light (NT) is a type of food labeling created to improve the understanding of nutrient content (sodium, sugar and fat) in industrialized foods. In Ecuador, the TN is mandatory since 2012. Objective: To evaluate the relationship of NT labeling knowledge in the nutritional status of Ecuadorian adolescents. Methods: cross-sectional study. With 600 teenagers (14-18 years old). Anthropometric data, physical activity (IPAQ-A), and food intake were collected using 3 reminder surveys of 24 hours. Knowledge of NT was assessed with a questionnaire prepared for this purpose: scores> 5 meant adequate knowledge (AK). The relationships between the variables were determined by student’s T-test, using the STATA-14 software. Results: 55% of the adolescents presented a diagnosis of overweight and 28% of the adolescents presented a diagnosis of obesity according to the BMI indicators // age 48% presented a AK. Adolescents who presented inadequate knowledge presented higher means of BMI // age, waist circumference, hip circumference and percentage of fat mass (p <0.001), no differences were found in food intake and NT knowledge. Conclusions: Knowledge of NT may be related to overweight-obesity in adolescents, more studies are needed to establish these associations. Palabras clave: Semáforo nutricional, estado nutricional, adolescentes, Ecuador. Keywords: Nutritional traffic light, nutritional status, adolescents, Ecuador

Formic Acid Ionization and Fragmentation by Multiphoton Absorption

Multiphoton absorption is an intensity dependent nonlinear effect related to the excitation of virtual intermediate states. In the present work, multiphoton ionization and dissociation of the formic acid molecule (HCOOH) by the interaction with photons from 532 Nd: YAG laser at different intensities are discussed, using different carrier gases. The induced fragmentation-ionization patterns show up to 17 fragments and dissociation channels are proposed. Some evidence of small clusters formation and conformational memory from the ratio of the detected products, CO+ and CO2+, on the light of the available results, it is possible to conclude that they arise from trans and cis formic acid. Our results are compared with those obtained in other laboratories under different experimental conditions, some of them show only partial agreement and differences are discussed. Following the Keldysh description it is possible, from our experimental parameters, characterize our results, in the multiphoton absorption regime

Thermodynamics of protein folding: a random matrix formulation

The process of protein folding from an unfolded state to a biologically active, folded conformation is governed by many parameters e.g the sequence of amino acids, intermolecular interactions, the solvent, temperature and chaperon molecules. Our study, based on random matrix modeling of the interactions, shows however that the evolution of the statistical measures e.g Gibbs free energy, heat capacity, entropy is single parametric. The information can explain the selection of specific folding pathways from an infinite number of possible ways as well as other folding characteristics observed in computer simulation studies.Comment: 21 Pages, no figure

HIV-exposed uninfected children. A systematic review on psychological well-being and association with school performances in Africa

There is a growing number of children affected by HIV in Africa. Research on HIV-exposed uninfected children (HEU) is also growing. This systematic review focuses on the psychological well-being of HEU and its association with school intervention, outcomes, and enrollment in the African context, which is where the rate of HIV reaches its highest levels. Research on public databases was conducted according to PRISMA standards. Only studies on HEU primary school children in Africa, both quantitative and qualitative, were included. Out of 1510 papers retrieved, 50 met the inclusion criteria. These studies demonstrate that HEU children are more likely to perform worse in school compared to their counterparts who were not exposed to HIV and to show poorer concentration in the classroom. Children with parents suffering from AIDS are worried for them and have to take household responsibility, resulting in school dropouts, juvenile work, and risky behaviors. Few interventions have been conducted in the school environment with some of them being successful; therefore, future research should involve schools to create an inclusive environment where HEU children could enhance their potential and improve their psychological health

Local Extinction and Unintentional Rewilding of Bighorn Sheep (Ovis canadensis) on a Desert Island

Bighorn sheep ( Ovis canadensis) were not known to live on Tiburón Island, the largest island in the Gulf of California and Mexico, prior to the surprisingly successful introduction of 20 individuals as a conservation measure in 1975. Today, a stable island population of ∼500 sheep supports limited big game hunting and restocking of depleted areas on the Mexican mainland. We discovered fossil dung morphologically similar to that of bighorn sheep in a dung mat deposit from Mojet Cave, in the mountains of Tiburón Island. To determine the origin of this cave deposit we compared pellet shape to fecal pellets of other large mammals, and extracted DNA to sequence mitochondrial DNA fragments at the 12S ribosomal RNA and control regions. The fossil dung was 14C-dated to 1476-1632 calendar years before present and was confirmed as bighorn sheep by morphological and ancient DNA (aDNA) analysis. 12S sequences closely or exactly matched known bighorn sheep sequences; control region sequences exactly matched a haplotype described in desert bighorn sheep populations in southwest Arizona and southern California and showed subtle differentiation from the extant Tiburón population. Native desert bighorn sheep previously colonized this land-bridge island, most likely during the Pleistocene, when lower sea levels connected Tiburón to the mainland. They were extirpated sometime in the last ∼1500 years, probably due to inherent dynamics of isolated populations, prolonged drought, and (or) human overkill. The reintroduced population is vulnerable to similar extinction risks. The discovery presented here refutes conventional wisdom that bighorn sheep are not native to Tiburón Island, and establishes its recent introduction as an example of unintentional rewilding, defined here as the introduction of a species without knowledge that it was once native and has since gone locally extinct

Structure of an Early Intermediate in the M-State Phase of the Bacteriorhodopsin Photocycle

AbstractThe structure of an early M-intermediate of the wild-type bacteriorhodopsin photocycle formed by actinic illumination at 230K has been determined by x-ray crystallography to a resolution of 2.0Å. Three-dimensional crystals were trapped by illuminating with actinic light at 230K, followed by quenching in liquid nitrogen. Amide I, amide II, and other infrared absorption bands, recorded from single bacteriorhodopsin crystals, confirm that the M-substate formed represents a structure that occurs early after deprotonation of the Schiff base. Rotation about the retinal C13—C14 double bond appears to be complete, but a relatively large torsion angle of 26° is still seen for the C14—C15 bond. The intramolecular stress associated with the isomerization of retinal and the subsequent deprotonation of the Schiff base generates numerous small but experimentally measurable structural changes within the protein. Many of the residues that are displaced during the formation of the late M (MN) substate formed by three-dimensional crystals of the D96N mutant (Luecke et al., 1999b) are positioned, in early M, between their resting-state locations and the ones which they will adopt at the end of the M phase. The relatively small magnitude of atomic displacements observed in this intermediate, and the well-defined positions adopted by nearly all of the atoms in the structure, may make the formation of this structure favorable to model (simulate) by molecular dynamics