Optical properties of the iron-pnictide analog BaMn2As2

We have investigated the infrared and Raman optical properties of BaMn2As2 in the ab-plane and along the c-axis. The most prominent features in the infrared spectra are the Eu and A2u phonon modes which show clear TO-LO splitting from the energy loss function analysis. All the phonon features we observed in infrared and Raman spectra are consistent with the calculated values. Compared to the iron-pnictide analog AFe2As2, this compound is much more two-dimensional in its electronic properties. For E || c-axis, the overall infrared reflectivity is insulating like. Within the ab-plane the material exhibits a semiconducting behavior. An energy gap 2{\Delta}=48 meV can be clearly identified below room temperature.Comment: 5 pages, 7 figure

MLDS: Maximum Likelihood Difference Scaling in R

The MLDS package in the R programming language can be used to estimate perceptual scales based on the results of psychophysical experiments using the method of difference scaling. In a difference scaling experiment, observers compare two supra-threshold differences (a,b) and (c,d) on each trial. The approach is based on a stochastic model of how the observer decides which perceptual difference (or interval) (a,b) or (c,d) is greater, and the parameters of the model are estimated using a maximum likelihood criterion. We also propose a method to test the model by evaluating the self-consistency of the estimated scale. The package includes an example in which an observer judges the differences in correlation between scatterplots. The example may be readily adapted to estimate perceptual scales for arbitrary physical continua

MLDS: Maximum Likelihood Difference Scaling in R

The MLDS package in the R programming language can be used to estimate perceptual scales based on the results of psychophysical experiments using the method of difference scaling. In a difference scaling experiment, observers compare two supra-threshold differences (a,b) and (c,d) on each trial. The approach is based on a stochastic model of how the observer decides which perceptual difference (or interval) (a,b) or (c,d) is greater, and the parameters of the model are estimated using a maximum likelihood criterion. We also propose a method to test the model by evaluating the self-consistency of the estimated scale. The package includes an example in which an observer judges the differences in correlation between scatterplots. The example may be readily adapted to estimate perceptual scales for arbitrary physical continua.

Spectroscopy of PTCDA attached to rare gas samples: clusters vs. bulk matrices. I. Absorption spectroscopy

The interaction between PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) and rare gas or para-hydrogen samples is studied by means of laser-induced fluorescence excitation spectroscopy. The comparison between spectra of PTCDA embedded in a neon matrix and spectra attached to large neon clusters shows that these large organic molecules reside on the surface of the clusters when doped by the pick-up technique. PTCDA molecules can adopt different conformations when attached to argon, neon and para-hydrogen clusters which implies that the surface of such clusters has a well-defined structure and has not liquid or fluxional properties. Moreover, a precise analysis of the doping process of these clusters reveals that the mobility of large molecules on the cluster surface is quenched, preventing agglomeration and complex formation

Greenhouse gas production in degrading ice-rich permafrost deposits in northeastern Siberia

Permafrost deposits have been a sink for atmospheric carbon for millennia. Thaw-erosional processes, however, can lead to rapid degradation of ice-rich permafrost and the release of substantial amounts of organic carbon (OC). The amount of the OC stored in these deposits and their potential to be microbially decomposed to the greenhouse gases carbon dioxide (CO2) and methane (CH4) depends on climatic and environmental conditions during deposition and the decomposition history before incorporation into the permafrost. Here, we examine potential greenhouse gas production in degrading ice-rich permafrost deposits from three locations in the northeast Siberian Laptev Sea region. The deposits span a period of about 55 kyr from the last glacial period and Holocene interglacial. Samples from all three locations were incubated under aerobic and anaerobic conditions for 134 days at 4 °C. Greenhouse gas production was generally higher in deposits from glacial periods, where 0.2–6.1% of the initially available OC was decomposed to CO2. In contrast, only 0.1–4.0% of initial OC were decomposed in permafrost deposits from the Holocene and the late glacial transition. Within the deposits from the Kargin interstadial period (Marine Isotope Stage 3), local depositional environments, especially soil moisture, also affected the preservation of OC. Sediments deposited under wet conditions contained more labile OC and thus produced more greenhouse gases than sediments deposited under drier conditions. To assess the greenhouse gas production potentials over longer periods, deposits from two locations were incubated for a total of 785 days. However, more than 50% of total CO2 production over 785 days occurred within the first 134 days under aerobic conditions while even 80% were produced over the same period under anaerobic conditions, which emphasizes the non-linearity of the OC decomposition processes. Methanogenesis was generally observed in active layer samples but only sporadically in permafrost samples and was several orders of magnitude smaller than CO2 production

Charge Order Breaks Magnetic Symmetry in Molecular Quantum Spin Chains

Charge order affects most of the electronic properties but is believed not to alter the spin arrangement since the magnetic susceptibility remains unchanged. We present electron-spin-resonance experiments on quasi-one-dimensional (TMTTF)2X salts (X= PF6, AsF6 and SbF6), which reveal that the magnetic properties are modified below TCO when electronic ferroelectricity sets in. The coupling of anions and organic molecules rotates the g-tensor out of the molecular plane creating magnetically non-equivalent sites on neighboring chains at domain walls. Due to anisotropic Zeeman interaction a novel magnetic interaction mechanism in the charge-ordered state is observed as a doubling of the rotational periodicity of Delta H.Comment: 9 pages, 13 figure

Detection of Food-Borne Pathogens Using Nanozyme Technology

The recurrent outbreak of E. coli necessitates the need of rapid and sensitive technology to detect bacteria in the food samples. E. coli O157:H7 is infectious at very low CFU counts (10-100 viable cells). Herein, we report a unique combination of magnetic and plasmonic properties in a single nanoplatform, which have superior peroxidase-like activity. This new nanosensor platform, magneto-plasmonic nanosensor (MPnS), is composed of superparamagnetic iron oxide nanoparticles (IONPs) and gold nanoparticles (GNPs) and stabilized with polyacrylic acid polymer, providing surface -COOH functional groups. By using EDC/NHS bioconjugation chemistry, the surface of MPnS is decorated with E. coli O157:H7-specific antibodies. We compared the catalytic activities of MPnS with that of GNPs, IONPs and traditional HRP and calculated Michaelis-Menten kinetics, which showed highest catalytic activity for MPnS. The ELISA-like experiments were performed using MPnS to detect E. coli within 30 min with higher sensitivity. We extended this detection study using milk and spinach samples. Various spectrophotometric and colorimetric experimental results in the specific detection of E. coli will be detailed in this presentation

Putting Knowledge into Practice: Low-Income Women Talk about Food Choice Decisions

Insights into barriers and facilitators for healthy eating are needed to improve low-income women’s diets and to decrease disease risk. The study objectives were to explore women’s qualitative perceptions of influences on their food choices such as food security, their knowledge of nutrition-related health risk factors and self-efficacy for diet change, and their dietary intakes in practice. Thirty-six women, aged 19–50, who were eligible to receive income-based assistance were recruited in central Iowa. Focus group discussions on defining healthy foods, influences on food choice, and nutrition information sources were analyzed using a socioecological model framework. Demographics, nutrient intake estimates, food security status, health behaviors, and self-efficacy for nutrition behavior change were collected by survey. Most participants were White (61%), single (69%), food insecure (69%), and living with children (67%). Few women met dietary recommendations. Barriers to healthy eating include cost, convenience/preparation time, family taste preferences, and limitations of federal food assistance programs. Facilitators are high self-efficacy for nutrition change and health knowledge on average. These results challenge the strategy of using nutrition education to improve healthy eating and instead show that intervention messaging should focus on limited, achievable steps to improve dietary choices that fit within cost, convenience, and taste constraints

Passive phloem loading and long-distance transport in a synthetic tree-on-a-chip

Vascular plants rely on differences of osmotic pressure to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). In this process, known as M\"unch pressure flow, the loading of sugars from photosynthetic cells to the export conduit (the phloem) is crucial, as it sets the pressure head necessary to power long-distance transport. Whereas most herbaceous plants use active mechanisms to increase phloem concentration above that of the photosynthetic cells, in most tree species, for which transport distances are largest, loading seems to occur via passive symplastic diffusion from the mesophyll to the phloem. Here, we use a synthetic microfluidic model of a passive loader to explore the nonlinear dynamics that arise during export and determine the ability of passive loading to drive long-distance transport. We first demonstrate that in our device, phloem concentration is set by the balance between the resistances to diffusive loading from the source and convective export through the phloem. Convection-limited export corresponds to classical models of M\"unch transport, where phloem concentration is close to that of the source; in contrast, diffusion-limited export leads to small phloem concentrations and weak scaling of flow rates with the hydraulic resistance. We then show that the effective regime of convection-limited export is predominant in plants with large transport resistances and low xylem pressures. Moreover, hydrostatic pressures developed in our synthetic passive loader can reach botanically relevant values as high as 10 bars. We conclude that passive loading is sufficient to drive long-distance transport in large plants, and that trees are well suited to take full advantage of passive phloem loading strategies