Comparison of epoxy and braze-welded attachment methods for FBG strain gauges

This paper presents experimental results from fatigue and static loading tests performed on both epoxy and braze-welded FBG strain sensors. Most FBG attachment methods are relatively understudied, with epoxy the most commonly used. Long curing times and humidity sensitivity during curing render epoxy inappropriate for certain implementations. This work shows that a bespoke braze-welded attachment design is able to achieve a higher static failure limit of 22kN when compared to strain gauge epoxies, which fail at 20kN. Both methods demonstrate high fatigue life, with no significant deterioration after two million cycles. Epoxy swelling was observed when the sensors were held at a relative humidity of 96%, applying ~0.6 mϵ of tension to the FBG, whereas a braze-weld attachment was unaffected by humidity

Spin- and angle-resolved photoemission studies of the electronic structure of Si(110)"16x2" surfaces

The electronic structure of Si(110)"16 x 2" double-domain, single-domain and 1 x 1 surfaces have been investigated using spin- and angle-resolved photoemission at sample temperatures of 77 K and 300 K. Angle-resolved photoemission was conducted using horizontally- and vertically-polarised 60 eV and 80 eV photons. Band-dispersion maps revealed four surface states ($S_1$ to $S_4$) which were assigned to silicon dangling bonds on the basis of measured binding energies and photoemission intensity changes between horizontal and vertical light polarisations. Three surface states ($S_1$, $S_2$ and $S_4$), observed in the Si(110)"16 x 2" reconstruction, were assigned to Si adatoms and Si atoms present at the edges of the corrugated terrace structure. Only one of the four surface states, $S_3$, was observed in both the Si(110)"16 x 2" and 1 x 1 band maps and consequently attributed to the pervasive Si zigzag chains that are components of both the Si(110)"16 x 2" and 1 x 1 surfaces. A state in the bulk-band region was attributed to an in-plane bond. All data were consistent with the adatom-buckling model of the Si(110)"16 x 2" surface. Whilst room temperature measurements of $P_y$ and $P_z$ were statistically compatible with zero, $P_x$ measurements of the enantiomorphic A-type and B-type Si(110)"16 x 2" surfaces gave small average polarisations of around 1.5\% that were opposite in sign. Further measurements at 77 K on A-type Si(110)"16 x 2" surface gave a smaller value of +0.3\%. An upper limit of $\sim1\%$ may thus be taken for the longitudinal polarisation.Comment: Main paper: 12 pages and 11 figures. Supplemental information: 5 pages and 2 figure

Search for spin-polarized photoemission from GaAs using light with orbital angular momentum

Laser light with photon energy near the band gap of GaAs and in Laguerre-Gaussian modes with different amounts of orbital angular momentum was used to produce photoemission from unstrained GaAs. The degree of electron spin polarization was measured using a micro-Mott polarimeter and found to be consistent with zero with an upper limit of ∼3% for light with up to ±5h of orbital angular momentum. In contrast, the degree of spin polarization of 32.3 ± 1.4% using circularly polarized laser light at the as the same wavelength, which is typical for bulk GaAs photocathodes

Two Novel Approaches for Electron Beam Polarization from Unstrained GaAs

Two novel approaches to producing highly-polarized electron beams from unstrained GaAs were tested using a micro-Mott polarimeter. Based on a suggestion by Nakanishi [1]], twophoton photoemission with 1560 nm light was used with photocathodes of varying thickness: 625m, 0.32m, and 0.18m. For each of these photocathodes, the degree of spin polarization of the photoemitted beam was less than 50%. Polarization via two-photon absorption was highest from the thinnest photocathode sample and close to that obtained from one-photon absorption (using 778 nm light), with values 40.3±1.0% and 42.6±1.0%, respectively. The second attempt to produce highly-polarized electrons used one-photon emission with 778 nm light in Laguerre-Gaussian modes with different amounts of orbital angular momentum. The degree of electron spin polarization was consistent with zero, with an upper limit of ~3% for light with up to ±5ħ of orbital angular momentum. In contrast, the degree of spin polarization was 32.3±1.4% using circularly-polarized laser light at the same wavelength, which is typical for thick, unstrained GaAs photocathodes

Human genetic and metabolite variation reveals that methylthioadenosine is a prognostic biomarker and an inflammatory regulator in sepsis.

Sepsis is a deleterious inflammatory response to infection with high mortality. Reliable sepsis biomarkers could improve diagnosis, prognosis, and treatment. Integration of human genetics, patient metabolite and cytokine measurements, and testing in a mouse model demonstrate that the methionine salvage pathway is a regulator of sepsis that can accurately predict prognosis in patients. Pathway-based genome-wide association analysis of nontyphoidal Salmonella bacteremia showed a strong enrichment for single-nucleotide polymorphisms near the components of the methionine salvage pathway. Measurement of the pathway's substrate, methylthioadenosine (MTA), in two cohorts of sepsis patients demonstrated increased plasma MTA in nonsurvivors. Plasma MTA was correlated with levels of inflammatory cytokines, indicating that elevated MTA marks a subset of patients with excessive inflammation. A machine-learning model combining MTA and other variables yielded approximately 80% accuracy (area under the curve) in predicting death. Furthermore, mice infected with Salmonella had prolonged survival when MTA was administered before infection, suggesting that manipulating MTA levels could regulate the severity of the inflammatory response. Our results demonstrate how combining genetic data, biomolecule measurements, and animal models can shape our understanding of disease and lead to new biomarkers for patient stratification and potential therapeutic targeting

Predicting freeze-thaw damage using tipping point analysis of strain data

This paper demonstrates how Tipping Point Analysis can be used to predict the onset of structural strain, induced by ice formation. In civil structures, water-ice transitions present many potential issues that can lead to structural damage or plant shutdowns. Examples include freeze-thaw damage in concrete and masonry, and ice build-up on moving parts such as wind turbine blades. Early indication of ice formation could prevent irreparable damage if this information could be used to actuate de-icing procedures. The transition considered in this work is the strain induced in a polypropylene container by the volume change of water as it freezes, measured using surface-mounted fibre-optic strain sensors. This first order phase transition can be detected early on using degenerate fingerprinting, which identifies “slowing down” of the noise prior to the critical point of the transition. Water was supercooled which, at freezing, causes a rapid increase in temperature, presenting an identifiable specific transition point for reference. The analysis was able to consistently predict freezing around 5-10 minutes prior to the transition. A linear relationship was found between mass calculated from the calorimetric equation and mass from experimental measurements. Strain could not be estimated from this mass, since the random process of freezing in an open top container causes an irregular distribution of force. These tests will allow the method and the model to be continually developed towards a more practical application

Do Rhinoceros Auklet, Cerorhinca monocerata, Fledglings Fly to the Sea from their Natal Burrows?

The mode of departure of Rhinoceros Auklet fledglings from their nest burrows has remained uncertain. Both walk-down and fly-down hypotheses have been proposed. Here we use the unique geography of Protection Island, Washington, to evaluate the fly-down hypothesis. Some fledglings raised on Protection Island do appear to walk to the water, but our results suggest that many of the island\u27s fledgling Rhinoceros Auklets fly to the sea

Taphonomic Effects of pH and Temperature on Extant Avian Dinosaur Eggshell

Avian and non-avian dinosaur eggshell contains clues that are helpful in the reconstruction of ancient habitats and behaviors. Fossilized eggshell often shows signs of corrosion attributed to acid dissolution of the calcium carbonate, but this process has never been quantified in controlled experiments. In work reported here, extant avian dinosaur egg-shell fragments were placed in buffered solutions of varying pH and temperature for varying periods of time. Changes in the appearance, mass, surface area, and thickness were described and compared with naturally weathered eggshell. Treatment resulted in corrosion and pitting of the outer surface and corrosion of the mammillary structure of the inner surface. Fragment mass, surface area, and thickness generally decreased in response to decreased pH and to increased temperature and exposure time. A classification scheme for eggshell corrosion is proposed

Search for spin-polarized photoemission from GaAs using light with orbital angular momentum

Laser light with photon energy near the band gap of GaAs and in Laguerre-Gaussian modes with different amounts of orbital angular momentum was used to produce photoemission from unstrained GaAs. The degree of electron spin polarization was measured using a micro-Mott polarimeter and found to be consistent with zero with an upper limit of ∼3% for light with up to ±5h of orbital angular momentum. In contrast, the degree of spin polarization of 32.3 ± 1.4% using circularly polarized laser light at the as the same wavelength, which is typical for bulk GaAs photocathodes