Ultrahigh vacuum Raman spectroscopy for the preparation of III-V semiconductor surfaces.

Raman spectroscopy is well-suited for the characterization of semiconductor materials. However, due the weakness of the Raman signal, the studies of thin semiconductor layers in complex environments, such as ultrahigh vacuum, are rather scarce. Here, we have designed a Raman apparatus based on the use of a fiber optic probe, with a lens collecting the backscattered light directly inserted in ultrahigh vacuum.

Oxa-Michael-initiated cascade reactions of levoglucosenone.

The reactions of aromatic aldehydes and levoglucosenone promoted by methoxide gives bridged α,β-unsaturated ketones, formed by a series of oxa-Michael-initiated cascade reactions in yields of up to 91% (14 examples). A complex series of equilibria operate during the reaction, and the formation of the bridged species is thermodynamically favored, except in the case of 5-methylfurfural and pyrrole-2-carboxaldehyde. This is the first report detailing this type of aldol/Michael cascade involving oxa-Michael initiation.

Assessing the insulating properties of an ultrathin SrTiOshell grown around GaAs nanowires with molecular beam epitaxy.

We have studied electronic transport in undoped GaAs/SrTiOcore-shell nanowires standing on their Si substrate with two-tip scanning tunneling microscopy in ultrahigh vacuum. The resistance profile along the nanowires is proportional to the tip separation with resistances per unit length of a few GΩ/m. Examination of the different transport pathways parallel to the nanowire growth axis reveals that the measured resistance is consistent with a conduction along the interfacial states at the GaAs{110} sidewalls, the 2 nm thick SrTiOshell being as much as resistive, despite oxygen deficient growth conditions.

Transport Properties of Methyl-Terminated Germanane Microcrystallites.

Germanane is a two-dimensional material consisting of stacks of atomically thin germanium sheets. It's easy and low-cost synthesis holds promise for the development of atomic-scale devices. However, to become an electronic-grade material, high-quality layered crystals with good chemical purity and stability are needed.

ChronoRoot: High-throughput phenotyping by deep segmentation networks reveals novel temporal parameters of plant root system architecture.

Background: Deep learning methods have outperformed previous techniques in most computer vision tasks, including image-based plant phenotyping. However, massive data collection of root traits and the development of associated artificial intelligence approaches have been hampered by the inaccessibility of the rhizosphere. Here we present ChronoRoot, a system that combines 3D-printed open-hardware with deep segmentation networks for high temporal resolution phenotyping of plant roots in agarized medium.

The Diversity of Volatile Compounds in Australia's Semi-Desert Genus (Scrophulariaceae).

Australia's endemic desert shrubs are commonly aromatic, with chemically diverse terpenes and phenylpropanoids in their headspace profiles. Species from the genus (Scrophulariaceae ex. Myoporaceae) are the most common, with 215 recognised taxa and many more that have not yet been described, widely spread across the arid parts of the Australian continent.

Site-Specific Mutations of GalR Affect Galactose Metabolism in Streptococcus pneumoniae.

(the pneumococcus) is a formidable human pathogen that is capable of asymptomatically colonizing the nasopharynx. Progression from colonization to invasive disease involves adaptation to distinct host niches, which vary markedly in the availability of key nutrients such as sugars. We previously reported that cell-cell signaling via the autoinducer 2 (AI-2)/LuxS quorum-sensing system boosts the capacity of to utilize galactose as a carbon source by upregulation of the Leloir pathway.

Biomimetic Synthesis of Mitchellenes B-H from the Abundant Biological Precursor 14-Hydroxy-6,12-muuroloadien-15-oic Acid.

A step-economic biomimetic synthesis of mitchellenes B-H found in has been achieved. Starting from the putative muurolane biological precursor, redox isomerization of the allylic alcohol gave an epimeric mixture of aldehydes, which could be used as a handle for cyclization onto the C6 position, using BuSnH-mediated radical cyclization or NHC-catalyzed Stetter reaction. The NHC-mediated approach was superior as the epimeric mixture underwent a dynamic kinetic resolution during the reaction, and reduction of the mixture with NaBH selectively formed the mitchellene ring system in 56% yield for the three steps.

Revision of the Phytochemistry of Eremophila sturtii and E. mitchellii.

Eremophila sturtii and E. mitchellii are found in the arid and temperate regions of Australia and, because of their similar appearances, are often confused. Previous phytochemical investigations have described mitchellene sesquiterpenes (1-5) reported from E.

Climate warming: a loss of variation in populations can accompany reproductive shifts.

The most documented response of organisms to climate warming is a change in the average timing of seasonal activities (phenology). Although we know that these average changes can differ among species and populations, we do not know whether climate warming impacts within-population variation in phenology. Using data from five study sites collected during a 13-year survey, we found that the increase in spring temperatures is associated with a reproductive advance of 10 days in natural populations of common lizards (Zootoca vivipara).

Oxygen isotope fractionation between bird bone phosphate and drinking water.

Oxygen isotope compositions of bone phosphate (δO) were measured in broiler chickens reared in 21 farms worldwide characterized by contrasted latitudes and local climates. These sedentary birds were raised during an approximately 3 to 4-month period, and local precipitation was the ultimate source of their drinking water. This sampling strategy allowed the relationship to be determined between the bone phosphate δO values (from 9.

The genealogical decomposition of a matrix population model with applications to the aggregation of stages.

Matrix projection models are a central tool in many areas of population biology. In most applications, one starts from the projection matrix to quantify the asymptotic growth rate of the population (the dominant eigenvalue), the stable stage distribution, and the reproductive values (the dominant right and left eigenvectors, respectively). Any primitive projection matrix also has an associated ergodic Markov chain that contains information about the genealogy of the population.

The Iridoid Myodesert-1-ene and Elemol/Eudesmol are found in Distinct Chemotypes of the Australian Aboriginal Medicinal Plant Eremophila dalyana (Scrophulariaceae).

The strongly aromatic Australian desert species Eremophila dalyana is an Aboriginal medicinal plant that continues to be used today in Central Australia in the treatment of respiratory complaints and Sarcoptes scabiei infestation. Using hydrodistillation of aerial parts of the plant, the new natural product myodesert-l- ene was isolated in two disjunct populations at up to 98% of the volatiles present in the hydrodistilled oils. Weak antimicrobial activities were observed for whole oils and myodesert-l-ene.

Investigating the Influence of Climate Changes on Rodent Communities at a Regional-Scale (MIS 1-3, Southwestern France).

Terrestrial ecosystems have continuously evolved throughout the Late Pleistocene and the Holocene, deeply affected by both progressive environmental and climatic modifications, as well as by abrupt and large climatic changes such as the Heinrich or Dansgaard-Oeschger events. Yet, the impacts of these different events on terrestrial mammalian communities are poorly known, as is the role played by potential refugia on geographical species distributions. This study examines community changes in rodents of southwestern France between 50 and 10 ky BP by integrating 94 dated faunal assemblages coming from 37 archaeological sites.

A new approach to the generation time in matrix population models.

The generation time is commonly defined as the mean age of mothers at birth. In matrix population models, a general formula is available to compute this quantity. However, it is complex and hard to interpret.

Trophic groups and modules: two levels of group detection in food webs.

Within food webs, species can be partitioned into groups according to various criteria. Two notions have received particular attention: trophic groups (TGs), which have been used for decades in the ecological literature, and more recently, modules. The relationship between these two group concepts remains unknown in empirical food webs.

Isotopic and anatomical evidence of an herbivorous diet in the Early Tertiary giant bird Gastornis. implications for the structure of Paleocene terrestrial ecosystems.

The mode of life of the early Tertiary giant bird Gastornis has long been a matter of controversy. Although it has often been reconstructed as an apex predator feeding on small mammals, according to other interpretations, it was in fact a large herbivore. To determine the diet of this bird, we analyze here the carbon isotope composition of the bone apatite from Gastornis and contemporaneous herbivorous mammals.

Density-dependent life history and the dynamics of small populations.

1. Small population dynamics depend importantly on the strength and shape of density dependence. Unfortunately, the lack of reliable life-history data often prevents to make accurate demographic predictions for populations regulated by density dependence.

Ecological emergence of thermal clines in body size.

The unprecedented rate of global warming requires a better understanding of how ecosystems will respond. Organisms often have smaller body sizes under warmer climates (Bergmann's rule and the temperature-size rule), and body size is a major determinant of life histories, demography, population size, nutrient turnover rate, and food-web structure. Therefore, by altering body sizes in whole communities, current warming can potentially disrupt ecosystem function and services.

The co-evolution of multiply-informed dispersal: information transfer across landscapes from neighbors and immigrants.

Dispersal plays a key role in natural systems by shaping spatial population and evolutionary dynamics. Dispersal has been largely treated as a population process with little attention to individual decisions and the influence of information use on the fitness benefits of dispersal despite clear empirical evidence that dispersal behavior varies among individuals. While information on local density is common, more controversial is the notion that indirect information use can easily evolve.

Eco-evolutionary feedbacks, adaptive dynamics and evolutionary rescue theory.

Adaptive dynamics theory has been devised to account for feedbacks between ecological and evolutionary processes. Doing so opens new dimensions to and raises new challenges about evolutionary rescue. Adaptive dynamics theory predicts that successive trait substitutions driven by eco-evolutionary feedbacks can gradually erode population size or growth rate, thus potentially raising the extinction risk.

Evolutionary entropy predicts the outcome of selection: Competition for resources that vary in abundance and diversity.

Competition between individuals for resources which are limited and diverse in composition is the ultimate driving force of evolution. Classical studies of this event contend that the outcome is a deterministic process predicted by the growth rate of the competing types-a tenet called the Malthusian selection principle. Recent studies of competition indicate that the dynamics of selection is a stochastic process, regulated by the population size, the abundance and diversity of the resource, and predicted by evolutionary entropy-a statistical parameter which characterizes the rate at which the population returns to the steady state condition after a random endogenous or exogenous perturbation.

New beam line for time-of-flight medium energy ion scattering with large area position sensitive detector.

A new beam line for medium energy ion mass scattering (MEIS) has been designed and set up at the Ångström laboratory, Uppsala University, Sweden. This MEIS system is based on a time-of-flight (ToF) concept and the electronics for beam chopping relies on a 4 MHz function generator. Repetition rates can be varied between 1 MHz and 63 kHz and pulse widths below 1 ns are typically obtained by including beam bunching.

Biodiversity is not (and never has been) a bed of roses!

Over the last decades, the critical study of fossil diversity has led to significant advances in the knowledge of global macroevolutionary patterns of biodiversity. The deep-time history of life on Earth results from background originations and extinctions defining a steady-state, nonstationary equilibrium occasionally perturbed by biotic crises and "explosive" diversifications. More recently, a macroecological approach to the large-scale distribution of extant biodiversity offered new, stimulating perspectives on old theoretical questions and current practical problems in conservation biology.