Effect of surface hydrogen on the anomalous surface segregation behavior of Cr in Fe-rich Fe-Cr alloys

The segregation behavior of Cr in dilute Fe-Cr alloys is known to be anomalous since the main barrier for surface segregation of Cr in these alloys arises not from the topmost surface layer but from the subsurface layer where the solution energy of Cr is much more endothermic as compared to the topmost surface layer. The Fe-Cr alloys are candidate structural materials for the new generation of nuclear reactors. The surfaces of these alloys will be exposed to hydrogen or its isotopes in these reactors, and although hydrogen is soluble neither in Fe nor in Fe-Cr alloys, it is known that the adsorption energy of hydrogen on the surface of iron is not only exothermic but relatively large. This clearly raises the question of the effect of the hydrogen adsorbed on the surface of iron on the segregation behavior of chromium towards the surface of iron. In this paper we show, on the basis of our ab initio density functional theory calculations, that the presence of hydrogen on the surface of iron leads to a considerably reduced barrier for Cr segregation to both the topmost surface layer and the subsurface layer, but the subsurface layer still controls the barrier for surface segregation. This reduction in the barrier for surface segregation is due to the nature of the Cr-H couple that acts in a complex and synergistic manner. The presence of Cr enhances the exothermic nature of hydrogen adsorption that in turn leads to a reduced barrier for surface segregation. These results should be included in the multiscale modeling of Fe-Cr alloys

The implementation of decentralised biogas plants in Assam, NE India: the impact and effectiveness of the National Biogas and Manure Management Programme

The Indian Government’s National Biogas and Manure Management Programme (NBMMP) aims to deliver renewable energy services to households across the country by incentivising the deployment of family-sized (<6m3) anaerobic (biogas) digesters. We investigated how NBMMP policy is implemented at three levels, from government and state nodal agency, via private contractors to households. We analysed the scheme across two districts in Assam, north-east India, interviewing stakeholders in rural households, state and non-state institutions. We found a top-down, supply-side approach which enables central government to set targets and require individual states to deploy the scheme. Participation in the NBMMP was found to deliver improved energy service outcomes to a majority of households that can afford to participate, although the level of knowledge and understanding of the technology amongst users was limited. Improved training of householders, and particularly women, is needed in relation to the maintenance of digesters, feedstock suitability and the environmental and potential livelihood benefits of digestate. A policy revision which highlights the contextual and demand-side issues around adopting the technology, may deliver monetary benefits from market competition and enable development of community-focused microfinance schemes to improve the affordability of biogas systems

Assessment of epidermal growth factor receptor (EGFR) expression in primary colorectal carcinomas and their related metastases on tissue sections and tissue microarray

Metastatic colorectal carcinomas (CRC) resistant to chemotherapy may benefit from targeting monoclonal therapy cetuximab when they express the epidermal growth factor receptor (EGFR). Because of its clinical implications, we studied EGFR expression by immunohistochemistry on tissue sections of primary CRC (n=32) and their related metastases (n=53). A tissue microarray (TMA) was generated from the same paraffin blocks to determine whether this technique could be used for EGFR screening in CRC. On tissue sections, 84% of the primary CRC and 94% of the metastases were EGFR-positive. When matched, they showed a concordant EGFR-positive status in 78% of the cases. Moreover, staining intensity and extent of EGFR-positive cells in the primary CRC correlated with those observed in the synchronous metastases. On TMA, 65% of the primary CRC, 66% of the metastases, and 43% of the matched primary CRC metastases were EGFR-positive. There was no concordant EGFR status between the primary and the metastatic sites. A strong discrepancy of EGFR status was noted between TMA and tissue sections. In conclusion, EGFR expression measured in tissue sections from primary CRC and their related metastases was found to be similar and frequent, but it was significantly underestimated by the TMA technique

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society