Short-lived nuclides in the early solar system: the stellar connection

Fossil evidence for the presence of short-lived nuclides with half-life ranging from 100,000 years to 100 million years (Ma) in the early solar system has been found in primitive meteorites. The nuclides with half-life less than a couple of million years (41Ca, 26Al, 10Be, 60Fe) must have been produced either shortly before or during the very early evolution of the solar system. Two plausible sources of these nuclides are proposed; a single stellar source (e.g., a TP-AGB star, supernova or a W-R star) or energetic particle production in solar, presolar or stellar environments. The presence of 10Be, which is not a product of stellar nucleosynthesis, argues for an energetic particle production mechanism. However, correlated presence of 41Ca and 26Al with well-defined initial abundances in early solar system objects cannot be explained in the energetic particle production model and it also fails to account for the presence of 60Fe. Recent experimental data demonstrate that the source of 10Be is decoupled from that of 26Al and 41Ca and suggest that both a stellar source as well as energetic particle production contributed to the inventory of the short-lived nuclides in the early solar system. New data for initial abundance of 60Fe in the solar system tend to favor a SN source. The presence of freshly synthesized short-lived nuclides from an evolved star in the early solar system led to the hypothesis of a triggered origin of the solar system. Numerical simulation studies indicate dynamical feasibility of such a process and there are indirect observational evidences for triggered formation of sun-like stars

Precompaction irradiation effects: Particles from an early active sun?

Two recent studies have shown that solar flare irradiated grains from Murchison and Kapoeta have excess spallogenic Ne-21 compared to unirradiated grains, indicating large precompaction particle irradiation effects. The quantity of cosmogenic neon in these grains presents serious difficulties for either galactic cosmic ray or normal solar flare sources. In the first study it was suggested that the effect might be the result of exposure to an early active sun. The more recent experiment both confirms the earlier results and provides constraints on the characteristic energy spectrum on the irradiation. The first results were obtained from Murchison olivines and Kapoeta pyroxenes by mass spectrometric analysis of sets of grains selected on the basis of the presence or absence of solar flare particle tracks. In the second work plagioclase feldspar grains from Kapoeta were studied

Extension of potential predictability of Indian summer monsoon dry and wet spells in recent decades

An understanding of the limit on potential predictability is crucial for developing appropriate tools for extended-range prediction of active/break spells of the Indian summer monsoon (ISM). The global low-frequency changes in climate modulate the annual cycle of the ISM and can influence the intrinsic predictability limit of the ISM intraseasonal oscillations (ISOs). Using 104-year (1901-2004) long daily rainfall data, the change in potential predictability of active and break spells are estimated by an empirical method. It is found that the potential predictability of both active and break spells have undergone a rapid increase during the recent three decades. The potential predictability of active spells has shown an increase from one week to two weeks while that for break spells increased from two weeks to three weeks. This result is interesting and intriguing in the backdrop of recent finding that the potential predictability of monsoon weather has decreased substantially over the same period compared to earlier decades due to increased potential instability of the atmosphere. The possible role of internal dynamics and external forcing in producing this change has been explored. The changes in energy exchange between the synoptic and ISO scale and the different ISO modes as evidenced by energetics computations in frequency domain also support the increased potential predictability of ISO. Our finding provides optimism for improved and useful extended-range prediction of monsoon active and break spells

Evidence in meteorites for an active early Sun

The amounts of neon-21 found in meteorite particles indicate that the Sun experienced a period of intense solar flare activity approximately 4.5 billion years ago

IONS (ANURADHA): Ionization states of low energy cosmic rays

IONS (ANURADHA), the experimental payload designed specifically to determine the ionization states, flux, composition, energy spectra and arrival directions of low energy (10 to 100 MeV/amu) anomalous cosmic ray ions of helium to iron in near-Earth space, had a highly successful flight and operation Spacelab-3 mission. The experiment combines the accuracy of a highly sensitive CR-39 nuclear track detector with active components included in the payload to achieve the experimental objectives. Post-flight analysis of detector calibration pieces placed within the payload indicated no measurable changes in detector response due to its exposure in spacelab environment. Nuclear tracks produced by alpha-particles, oxygen group and Fe ions in low energy anomalous cosmic rays were identified. It is calculated that the main detector has recorded high quality events of about 10,000 alpha-particles and similar number of oxygen group and heavier ions of low energy cosmic rays

High Temperature Fatigue Crack Growth Behavior of Ti-6Al-4V

Experimental evaluation of high temperature, Fatigue Crack Growth Rate (FCGR) data for Ti-6A1-4V, a titanium alloy, is presented. The FCGR data were measured at room temperature, 175, 230, 290 and 345°C using the Direct Current Potential Difference (DCPD) technique. Compact Tension (CT) specimens were used in the program and crack growth rates (da/dN) vs. Mode I stress intensity factor ranges (ΔΚ) were plotted as a function of temperature. A temperature rise from 175 to 345°C did not cause a substantial increase in crack growth rates within the Stage II region where a linear relationship describes the behavior. Fonnation of secondary cracks, observed at higher temperatures, may have slowed the crack propagation as observed in the fractography

Predicting and explaining behavioral intention and hand sanitizer use among US Army soldiers

Citation: Naiqing Lin, Kevin R. Roberts, (2017) Predicting and explaining behavioral intention and hand sanitizer use among US Army soldiers, In American Journal of Infection Control, 45(4),396-400. https://doi.org/10.1016/j.ajic.2016.11.008.According to the Centers for Disease Control and Prevention and the World Health Organization, simple hand washing is one of the most effective methods to prevent the spread of infectious diseases.1,2,3 The literature shows a strong and consistent association between personal hand hygiene and reduced gastrointestinal disease, respiratory illness, and absenteeism in the work force.1,4,5 Hands are the primary mode of transmission for many infectious diseases, particularly among military personnel.6 Hand hygiene is a proven measure of controlling infection in military settings

Laser phase modulation approaches towards ensemble quantum computing

Selective control of decoherence is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion while the even terms lead to self-induced transparency. These results also hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse-width. Such results form the basis of a robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted