Tephra isochrons and chronologies of colonisation

This paper demonstrates the use of tephrochronology in dating the earliest archaeological evidence for the settlement of Iceland. This island was one of the last places on Earth settled by people and there are conflicting ideas about the pace and scale of initial colonisation. Three tephra layers, the Landnám (‘land-taking’) tephra layer (A.D. 877 ± 1), the Eldgjá tephra (A.D. 939) and the recently dated V-Sv tephra (A.D. 938 ± 6) can be found at 58% of 253 securely-dated early settlement sites across the country. The presence of the tephras permits both a countrywide comparison, and a classification of these settlement sites into pre-Landnám, Landnám and post-Landnám. The data summarised here for the first time indicate that it will be possible to reconstruct the tempo and development of the colonisation process in decadal resolution by more systematically utilising the dating potential of tephrochronology

An Electron Paramagnetic Resonance (EPR) spectroscopy study on the γ-irradiation sterilization of the pharmaceutical excipient l-histidine: Regeneration of the radicals in solution

The effects of γ-radiation sterilization on the parenteral excipient L-histidine were analysed by means of EPR spectroscopy. The irradiation process was found to induce the formation of a deamination radical which was persistent in the solid state. The nature and reactivity of the radicals following dissolution in water was evaluated using spin-trapping EPR experiments. The deamination radical was found to regenerate in solution in the presence of trace metals, potentially leading to radical induced degradation reactions occurring up to an hour after the dissolution process. Understanding this process is significant for the improved design of parental pharmaceutical formulations in which unwanted radical reactions after γ radiation sterilization could lead to degradation of active ingredients

Ionization degree of the electron-hole plasma in semiconductor quantum wells

The degree of ionization of a nondegenerate two-dimensional electron-hole plasma is calculated using the modified law of mass action, which takes into account all bound and unbound states in a screened Coulomb potential. Application of the variable phase method to this potential allows us to treat scattering and bound states on the same footing. Inclusion of the scattering states leads to a strong deviation from the standard law of mass action. A qualitative difference between mid- and wide-gap semiconductors is demonstrated. For wide-gap semiconductors at room temperature, when the bare exciton binding energy is of the order of T, the equilibrium consists of an almost equal mixture of correlated electron-hole pairs and uncorrelated free carriers.Comment: 22 pages, 6 figure

Zitterbewegung in External Magnetic Field: Classic versus Quantum Approach

We investigate variations of the Zitterbewegung frequency of electron due to an external static and uniform magnetic field employing the expectation value quantum approach, and compare our results with the classical model of spinning particles. We demonstrate that these two so far compatible approaches are not in agreement in the presence of an external uniform static magnetic field, in which the classical approach breaks the usual symmetry of free particles and antiparticles states, i.e. it leads to CP violation. Hence, regarding the Zitterbewegung frequency of electron, the classical approach in the presence of an external magnetic field is unlikely to correctly describe the spin of electron, while the quantum approach does, as expected. We also show that the results obtained via the expectation value are in close agreement with the quantum approach of the Heisenberg picture derived in the literature. However, the method we use is capable of being compared with the classical approach regarding the spin aspects. The classical interpretation of spin produced by the altered Zitterbewegung frequency, in the presence of an external magnetic field, are discussed.Comment: 16 pages, no figure

Protecting the environment through insect farming as a means to produce protein for use as livestock, poultry, and aquaculture feed

Securing protein for the approximate 10 billion humans expected to inhabit our planet by 2050 is a major priority for the global community. Evidence has accrued over the past 30 years that strongly supports and justifies the sustainable use of insects as a means to produce protein products as feed for pets, livestock, poultry, and aquacultured species. Researchers and entrepreneurs affiliated with universities and industries, respectively, from 18 nations distributed across North and South America, Europe, Asia, Africa and Australia contributed to the development of this article, which is an indication of the global interest on this topic. A brief overview of insects as feed for the aquaculture industry along with a review of the black soldier fly, Hermetia illucens (Diptera: Stratiomyidae), as a model for such systems is provided

Cas12a target search and cleavage on force-stretched DNA

Using optical tweezers, we investigate target search and cleavage by CRISPR–Cas12a on force-stretched k-DNA. Cas12a uses fast, one-dimensional hopping to locate its target. Binding and cleavage occur rapidly and specifically at low forces (r5 pN), with a 1.8 nm rate-limiting conformational change. Mechanical distortion slows diffusion, increases off-target binding but hinders cleavage

Operating experience with the 50 MeV 10kA ATA power conditioning system

The Advanced Test Accelerator (ATA) has been operational for over one year and has achieved full parameters in the power conditioning system. The pulsed power system has been previously described, however, during the past year of operation a considerable amount of statistical data has been accumulated on the 211 gas blown spark gaps that perform the main switching function in the ATA. These spark gaps were designed for 250kV, 40 kA and 70ns pulse. The parameter that made this spark gap somewhat unique was the requirement that it be able to provide a burst of ten pulses at one kilohertz with an average repetition rate of 5Hz. 2 references, 7 figures

Patellar cartilage volume of the back leg versus the higher loaded front leg in current elite male english cricket fast bowlers

Patellar cartilage volume of the back leg versus the higher loaded front leg in current elite male english cricket fast bowler

How 14 C dates on wood charcoal increase precision when dating colonization: The examples of Iceland and Polynesia

Archaeological chronologies use many radiocarbon (14C) dates, some of which may be misleading. Strict ‘chronometric hygiene’ protocols, which aim to enhance the overall accuracy and precision of 14C datasets by removing all potentially problematic samples, mean that so few dates remain in some locations that accurate chronologies cannot be established. 14C dates on charcoal can be affected by an ‘old-wood’ effect, and so they are often removed from analyses, despite >40,000 being available worldwide, representing > $25 million. We show that when a Bayesian chronological model is used, which incorporates an Outlier Model specific to wood charcoal, the 14C dataset of Iceland's Viking Age settlement agrees well with ice core-dated tephrochronology and written sources. Greatest accuracy comes from an even temporal distribution of 14C dates and more dates lead to greater precision (<20 years). This shows how charcoal-based 14C chronologies can pinpoint the transformational human settlement of islands in the Atlantic, Oceania, and elsewhere.This project was funded by the Icelandic Centre for Research (Rannís 121153-0061), Watanabe Trust fund and National Science Foundation (USA, NSF 1202692 and NSF 1249313)

Temporal Trends and Prognosis of Physical Examination Findings in Patients with Acute Decompensated Heart Failure: The ARIC Study Community Surveillance

BACKGROUND: Bedside evaluation of congestion is a mainstay of heart failure (HF) management. Whether detected physical examination signs have changed over time as obesity prevalence has increased in HF populations, or if the associated prognosis differs for HF with reduced or preserved ejection fraction (HFrEF or HFpEF) is uncertain. METHODS: From 2005 to 2014, the ARIC study (Atherosclerosis Risk in Communities) conducted adjudicated hospital surveillance of acute decompensated HF. We analyzed trends in physical examination findings, imaging signs, and symptoms related to congestion, both over time and by obesity class, and associated 28-day mortality risks. RESULTS: Of 24 937 weighted hospitalizations for acute decompensated HF (mean age 75 years, 53% women, 32% Black), 47% had HFpEF. The prevalence of obesity increased from 2005 to 2014 for both HF types. With increasing obesity category, detected edema increased, while jugular venous distension decreased, and rales remained stable. Detected edema also increased over time, for both HF types. Associations between 28-day mortality and individual signs and symptoms of congestion were similar for HFpEF and HFrEF; however, the adjusted mortality risk with all 3 (edema, rales, and jugular venous distension) versus <3 physical examination findings was higher for patients with HFpEF (odds ratio, 2.41 [95% CI, 1.53-3.79]) than HFrEF (odds ratio, 1.30 [95% CI, 0.87-1.93]); P for interaction by HF type =0.02. CONCLUSIONS: In patients hospitalized with acute decompensated HF, detected physical examination findings differ both temporally and by obesity. Combined findings from the physical examination are more prognostic of 28-day mortality for patients with HFpEF than HFrEF