Probing Internal Stress and Crystallinity in Wet Foam via Raman Spectroscopy

In this article, we correlate the internal stress and the characteristics of a vibrational mode in wet foam. Using microscope images, we estimate the average size of the bubbles in wet foam, at specific time intervals, over a duration of twenty four hours. Raman spectra are also recorded at the same time intervals, over the same time frame. We show that the internal stress, originated from the macroscopic structural change of foam with ageing, can be related to the observed Raman shift of the low frequency methylene rocking mode of the constituent surfactant molecules in foam. In this report we also show the capability of the Raman spectroscopy to reveal the crystallinity in foamy materials, when studied for a longer period of time.Comment: 16 pages, 7 figure

A fixed angle double mirror filter for preparing a pink undulator beam at the Advanced Photon Source

Recent advances in X-ray Photon Correlation Spectroscopy (XPCS) use the full bandwidth of an undulator harmonic in order to maximize the coherent flux for small angle X-ray scattering experiments. X-ray mirrors and filters are typically used to select a given harmonic of the spectrum. At the University of Michigan/Howard University/Lucent Technologies, Bell Labs, Collaborative Access Team (MHATT-CAT) undulator beamline of the Advanced Photon Source, we have designed a fixed-angle Double Mirror Filter which will provide a “pink beam” (i.e., 2–3% bandwidth) for XPCS experiments. This device uses two small mirrors which vertically reflect a 0.1 mm×0.1 mm0.1mm×0.1mm white beam in a symmetric geometry. The doubly reflected beam propagates parallel to the incident white beam, but is offset vertically by 35 mm. Using the standard offset of the APS allows one to stop the white beam with a standard APS beam stop. In this report, we will describe our design considerations for this instrument. We also report the results of preliminary tests of the performance. The mirrors preserve the transverse coherence of the source, and filter the undulator spectrum as expected. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87429/2/238_1.pd

Domain Growth, Wetting and Scaling in Porous Media

The lattice Boltzmann (LB) method is used to study the kinetics of domain growth of a binary fluid in a number of geometries modeling porous media. Unlike the traditional methods which solve the Cahn-Hilliard equation, the LB method correctly simulates fluid properties, phase segregation, interface dynamics and wetting. Our results, based on lattice sizes of up to $4096\times 4096$, do not show evidence to indicate the breakdown of late stage dynamical scaling, and suggest that confinement of the fluid is the key to the slow kinetics observed. Randomness of the pore structure appears unnecessary.Comment: 13 pages, latex, submitted to PR

On the origin of the A1g_{1g} and B1g_{1g} electronic Raman scattering peaks in the superconducting state of YBa2_{2}Cu3_{3}O7−δ_{7-\delta}

The electronic Raman scattering has been investigated in optimally oxygen doped YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ single crystals as well as in crystals with non-magnetic, Zn, and magnetic, Ni, impurities. We found that the intensity of the A$_{1g}$ peak is impurity independent and their energy to $T_{c}$ ratio is almost constant ($2\Delta/k_{B}T_{c}\sim5$). Moreover, the signal at the B$_{1g}$ channel is completely smeared out when non-magnetic Zn impurities are present. These results are qualitatively interpreted in terms of the Zeyher and Greco's theory that relates the electronic Raman scattering in the A$_{1g}$ and B$_{1g}$ channels to \textit{d}-CDW and superconducting order parameters fluctuations, respectively.Comment: Submited to Phys. Rev. Let

Evidence for Two Superconducting Gaps in MgB2MgB_2

We have measured the Raman spectra of polycrystalline MgB$_{2}$ from 25 {\cm} to 1200 {\cm}. When the temperature was decreased below the superconducting transition temperature $T_c$, we observed a superconductivity-induced redistribution in the electronic Raman continuum. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. Furthermore, we have analyzed the measured spectra using a quasi two-dimensional model in which two s-wave superconducting gaps open on two sheets of Fermi surface. For the gap values we have obtained $\Delta_1 = 22 cm^{-1}$ (2.7 meV) and $\Delta_2 = 50 cm^{-1}$ (6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron $\sigma$ bands and is responsible for the superconductivity of MgB$_{2}$.Comment: 3 figure

The OptiMine feasibility study: a novel implementation strategy to electronically screen and signpost patients to health behaviour apps

Background: Behavior change apps have the potential to provide individual support on a population scale at low cost, but they face numerous barriers to implementation. Electronic health records (EHRs) in acute care hospitals provide a valuable resource for identifying patients at risk, who may benefit from behavior change apps. A novel, emerging implementation strategy is to use digital technologies not only for providing support to help-seeking individuals but also for signposting patients at risk to support services (also called proactive referral in the United States). Objective: The OptiMine study aimed to increase the reach of behavior change apps by implementing electronic signposting for smoking cessation and alcohol reduction in a large, at-risk population that was identified through an acute care hospital EHR. Methods: This 3-phase, mixed methods implementation study assessed the acceptability, feasibility, and reach of electronic signposting to behavior change apps by using a hospital’s EHR system to identify patients who are at risk. Phase 1 explored the acceptability of the implementation strategy among the patients and staff through focus groups. Phase 2 investigated the feasibility of using the hospital EHR to identify patients with target risk behaviors and contact them via SMS text message, email, or patient portal. Phase 3 assessed the impact of SMS text messages sent to patients who were identified as smokers or risky drinkers, which signposted them to behavior change apps. The primary outcome was the proportion of participants who clicked on the embedded link in the SMS text message to access information about the apps. The acceptability of the SMS text messages among the patients who had received them was also explored in a web-based survey. Results: Our electronic signposting strategy—using SMS text messages to promote health behavior change apps to patients at risk—was found to be acceptable and feasible and had good reach. The hospital sent 1526 SMS text messages, signposting patients to either the National Health Service Smokefree or Drink Free Days apps. A total of 13.56% (207/1526) of the patients clicked on the embedded link to the apps, which exceeded our 5% a priori success criterion. Patients and staff contributed to the SMS text message content and delivery approach, which were perceived as acceptable before and after the delivery of the SMS text messages. The feasibility of the SMS text message format was determined and the target population was identified by mining the EHR. Conclusions: The OptiMine study demonstrated the proof of concept for this novel implementation strategy, which used SMS text messages to signpost at-risk individuals to behavior change apps at scale. The level of reach exceeded our a priori success criterion in a non–help-seeking population of patients receiving unsolicited SMS text messages, disconnected from hospital visits. International Registered Report Identifier (IRRID): RR2-10.2196/2366

Novel implementation strategy to electronically screen and signpost patients to health behavior apps: Mixed methods implementation study (OptiMine study)

BACKGROUND: Behavior change apps have the potential to provide individual support on a population scale at low cost, but they face numerous barriers to implementation. Electronic health records (EHRs) in acute care hospitals provide a valuable resource for identifying patients at risk, who may benefit from behavior change apps. A novel, emerging implementation strategy is to use digital technologies not only for providing support to help-seeking individuals but also for signposting patients at risk to support services (also called proactive referral in the United States). OBJECTIVE: The OptiMine study aimed to increase the reach of behavior change apps by implementing electronic signposting for smoking cessation and alcohol reduction in a large, at-risk population that was identified through an acute care hospital EHR. METHODS: This 3-phase, mixed methods implementation study assessed the acceptability, feasibility, and reach of electronic signposting to behavior change apps by using a hospital\u27s EHR system to identify patients who are at risk. Phase 1 explored the acceptability of the implementation strategy among the patients and staff through focus groups. Phase 2 investigated the feasibility of using the hospital EHR to identify patients with target risk behaviors and contact them via SMS text message, email, or patient portal. Phase 3 assessed the impact of SMS text messages sent to patients who were identified as smokers or risky drinkers, which signposted them to behavior change apps. The primary outcome was the proportion of participants who clicked on the embedded link in the SMS text message to access information about the apps. The acceptability of the SMS text messages among the patients who had received them was also explored in a web-based survey. RESULTS: Our electronic signposting strategy-using SMS text messages to promote health behavior change apps to patients at risk-was found to be acceptable and feasible and had good reach. The hospital sent 1526 SMS text messages, signposting patients to either the National Health Service Smokefree or Drink Free Days apps. A total of 13.56% (207/1526) of the patients clicked on the embedded link to the apps, which exceeded our 5% a priori success criterion. Patients and staff contributed to the SMS text message content and delivery approach, which were perceived as acceptable before and after the delivery of the SMS text messages. The feasibility of the SMS text message format was determined and the target population was identified by mining the EHR. CONCLUSIONS: The OptiMine study demonstrated the proof of concept for this novel implementation strategy, which used SMS text messages to signpost at-risk individuals to behavior change apps at scale. The level of reach exceeded our a priori success criterion in a non-help-seeking population of patients receiving unsolicited SMS text messages, disconnected from hospital visits. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.2196/23669

Synthesis and properties of 2′-deoxy-2′,4′-difluoroarabinose-modified nucleic acids

© 2015 American Chemical Society. We report the synthesis, thermal stability, and RNase H substrate activity of 2′-deoxy-2′,4′-difluoroarabino-modified nucleic acids. 2′-Deoxy-2′,4′-difluoroarabinouridine (2,′4′-diF-araU) was prepared in a stereoselective way in six steps from 2′-deoxy-2′-fluoroarabinouridine (2′-F-araU). NMR analysis and quantum mechanical calculations at the nucleoside level reveal that introduction of 4′-fluorine introduces a strong bias toward the North conformation, despite the presence of the 2′-βF, which generally steers the sugar pucker toward the South/East conformation. Incorporation of the novel monomer into DNA results on a neutral to slightly stabilizing thermal effect on DNA-RNA hybrids. Insertion of 2′,4′-diF-araU nucleotides in the DNA strand of a DNA-RNA hybrid decreases the rate of both human and HIV reverse transcriptase-associated RNase H-mediated cleavage of the complement RNA strand compared to that for an all-DNA strand or a DNA strand containing the corresponding 2′-F-araU nucleotide units, consistent with the notion that a 4′-fluorine in 2′-F-araU switches the preferred sugar conformation from DNA-like (South/East) to RNA-like (North).Peer Reviewe

Coherent X-ray Scattering from Manganite Charge and Orbital Domains

We report coherent x-ray scattering studies of charge and orbital domains in manganite systems. The experiments were carried out on LaMnO_3 and Pr_{0.6}Ca_{0.4}MnO_3, with the incident photon energy tuned near the Mn K edge. At room temperature, the orbital speckle pattern of LaMnO_3 was observed to be constant over a timescale of at least minutes, which is indicative of static orbital domains on this timescale. For Pr_{0.6}Ca_{0.4}MnO_3, both charge and orbital speckle patterns were observed. The observation of the latter rules out the presence of fast orbital fluctuations, while long time series data-- on the order of several minutes-- were suggestive of slow dynamic behavior. In contrast, the charge order speckle patterns were static.Comment: 6 pages, 4 figure

Speckle from phase ordering systems

The statistical properties of coherent radiation scattered from phase-ordering materials are studied in detail using large-scale computer simulations and analytic arguments. Specifically, we consider a two-dimensional model with a nonconserved, scalar order parameter (Model A), quenched through an order-disorder transition into the two-phase regime. For such systems it is well established that the standard scaling hypothesis applies, consequently the average scattering intensity at wavevector _k and time t' is proportional to a scaling function which depends only on a rescaled time, t ~ |_k|^2 t'. We find that the simulated intensities are exponentially distributed, with the time-dependent average well approximated using a scaling function due to Ohta, Jasnow, and Kawasaki. Considering fluctuations around the average behavior, we find that the covariance of the scattering intensity for a single wavevector at two different times is proportional to a scaling function with natural variables mt = |t_1 - t_2| and pt = (t_1 + t_2)/2. In the asymptotic large-pt limit this scaling function depends only on z = mt / pt^(1/2). For small values of z, the scaling function is quadratic, corresponding to highly persistent behavior of the intensity fluctuations. We empirically establish a connection between the intensity covariance and the two-time, two-point correlation function of the order parameter. This connection allows sensitive testing, either experimental or numerical, of existing theories for two-time correlations in systems undergoing order-disorder phase transitions. Comparison between theory and our numerical results requires no adjustable parameters.Comment: 18 pgs RevTeX, to appear in PR