Hybrid quadrupole mass filter∕quadrupole ion trap∕time-of-flight-mass spectrometer for infrared multiple photon dissociation spectroscopy of mass-selected ions

We present a laboratory-constructed mass spectrometer optimized for recording infrared multiple photon dissociation (IRMPD) spectra of mass-selected ions using a benchtop tunable infrared optical parametric oscillator∕amplifier (OPO∕A). The instrument is equipped with two ionization sources, an electrospray ionization source, as well as an electron ionization source for troubleshooting. This hybrid mass spectrometer is composed of a quadrupole mass filter for mass selection, a reduced pressure (～10(-5) Torr) quadrupole ion trap (QIT) for OPO irradiation, and a reflectron time-of-flight drift tube for detecting the remaining precursor and photofragment ions. A helium gas pulse is introduced into the QIT to temporarily increase the pressure and hence enhance the trapping efficiency of axially injected ions. After a brief pump-down delay, the compact ion cloud is subjected to the focused output from the continuous wave OPO. In a recent study, we implemented this setup in the study of protonated tryptophan, TrpH(+), as well as collision-induced dissociation products of this protonated amino acid [W. K. Mino, Jr., K. Gulyuz, D. Wang, C. N. Stedwell, and N. C. Polfer, J. Phys. Chem. Lett. 2, 299 (2011)]. Here, we give a more detailed account on the figures of merit of such IRMPD experiments. The appreciable photodissociation yields in these measurements demonstrate that IRMPD spectroscopy of covalently bound ions can be routinely carried out using benchtop OPO setups.     

A temperature programmed desorption study of non-thermal plasma modified γ-Al2O3

In this paper, the effect of non-thermal RF plasma modification on the point of zero charge (PZC) of γ-Al₂O₃ has been explored. Samples of alumina were first modified with air, CO₂, N₂ or Ar plasma and then measurements of the PZC were taken. In order to determine the mechanism behind PZC shift, the surface area and crystal phase were measured for each sample using nitrogen physisorption (BET) and X-ray diffraction (XRD). Additionally, the presence of plasma gas on the surface of alumina was determined qualitatively using a modified temperature programmed desorption (TPD) technique. Air and CO₂ modification of alumina powder decreased the PZC from 7.48 to 4.86 and 6.57 respectively. However, N₂ and Ar modification did not result in any PZC shift. BET and XRD measurements showed no significant surface area or phase changes occurred due to non-thermal plasma modification. TPD profiles for air and CO₂ modified samples showed new peaks corresponding to the adsorption of plasma ions on the alumina surface. These results demonstrate that PZC changes in a support after plasma treatment is caused by the adsorption of plasma species.     

Evaluating top faculty researchers and the incentives that motivate them

We survey tenure-track faculty members employed in three fields in colleges of agriculture at land-grant universities—agricultural economics, agronomy, and food science—to evaluate the effects of different employment structures and incentives on research productivity. These evaluations include conducting statistical tests to assess any effects of different academic appointments and developing a regression model to measure the effects of these and other attributes on individual research productivity, as defined by the number of publications in the Thomson ISI Web of Science. We find faculty who hold larger teaching and extension appointments produce fewer publications; we also find positive effects on the number of publications for grants and university funding, multi-institutional research collaboration, and number of graduate students advised.     

Anxiety enhances threat processing without competition among multiple inputs: A diffusion model analysis.

Enhanced processing of threatening information is a well established phenomenon among high-anxious individuals. This effect is most reliably shown in situations where 2 or more items compete for processing resources, suggesting that input competition is a critical component of the effect. However, it could be that there are small effects in situations without input competition, but the dependent measures typically used are not sensitive enough to detect them. The present study analyzed data from a noncompetition task, single-string lexical decision, with the diffusion model, a decision process model that provides a more direct measure of performance differences than either response times or accuracy alone. The diffusion model analysis showed a consistent processing advantage for threatening words in high-anxious individuals, whereas traditional comparisons showed no significant differences. These results challenge the view that input competition is necessary for enhanced threat processing. Implications for theories of anxiety are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Critical variables in the alignment of electrospun PLLA nanofibers

Electrospun polymer nanofibers show promise as components of scaffolds for tissue engineering because of their ability to orient regenerating cells. Our research focuses on aligned electrospun fiber scaffolds for nerve regeneration. Critical to this are highly aligned fibers, which are frequently difficult to manufacture reproducibly. Here we show that three variables: the distance between the spinneret tip and collector, the addition of DMF to the solvent, and placement of an aluminum sheet on the spinneret together greatly improve the alignment of electrospun poly-L-lactide (PLLA) nanofibers. We identified the most important variable as tip-to-collector distance. Nanofiber alignment was maximal at 30 cm compared to shorter distances. DMF:chloroform (1:9) improved nanofiber uniformity and was integral to maintaining a uniform stream over the 30 cm tip-to-collector distance. Other ratios caused splattering of the solution or flattening or beading of the fibers and non-uniform fiber diameter. The aluminum sheet helped to stabilize the electric field and improve fiber alignment provided that it was placed at 1 cm behind the tip, while other distances destabilized the stream and worsened alignment. This study demonstrates that control of these variables produces dramatic improvement in reproducibly obtaining high alignment and uniform morphology of electrospun PLLA nanofibers.     

Heliostat field optimization: A new computationally efficient model and biomimetic layout

In this article, a new model and a biomimetic pattern for heliostat field layout optimization are introduced. The model, described and validated herein, includes a detailed calculation of the annual average optical efficiency accounting for cosine losses, shading and blocking, aberration and atmospheric attenuation. The model is based on a discretization of the heliostats and can be viewed as ray tracing with a carefully selected distribution of rays. The prototype implementation is sufficiently fast to allow for field optimization. Parameters are introduced for the radially staggered layout and are optimized with the objective of maximizing the annual insolation weighted heliostat field efficiency. In addition, inspired by the spirals of the phyllotaxis disc pattern, a new biomimetic placement heuristic is described and evaluated, which generates layouts of both higher insolation-weighted efficiency and higher ground coverage than radially staggered designs. Specifically, this new heuristic is shown to improve the existing PS10 field by 0.36% points in efficiency while simultaneously reducing the land area by 15.8%. Moreover, the new pattern achieves a better trade-off between land area usage and efficiency, i.e., it can reduce the area requirement significantly for any desired efficiency. Finally, the improvement in area becomes more pronounced with an increased number of heliostats, when maximal efficiency is the objective. While minimizing the levelized cost of energy (LCOE) is typically a more practical objective, results of the case study presented show that it is possible to both reduce the land area (i.e. footprint) of the plant and number of heliostats for fixed energy collected. By reducing the capital cost of the plant at no additional costs, the effect is a reduction in LCOE.     

Increasing feedback seeking in public contexts: It takes two (or more) to tango.

Two studies examined the effects of the feedback-seeking context on the feedback-seeking process. Previous research has suggested that the publicness of the feedback-seeking context influences the degree to which individuals seek performance feedback (S. J. Ashford & G. B. Northcraft (1992; P. E. Levy, M. D. Albright, B. D. Cawley, & J. R. Williams, 1995). The current 2 studies extend the feedback-seeking model outlined by P. E. Levy et al. (1995) by examining the influence that contextual manipulations (i.e., source supportiveness and peer reactions) have on feedback seeking in the public context. Overall results suggest that the frequency of feedback seeking can be increased substantially in a public setting if the supportiveness of source and peer reactions are positive. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Puzzle of RNAs that Target Gene Promoters

Setting the right target : Most researchers who use small RNAs in mammalian cells assume that mRNA will be the target. Recent studies suggest that small RNAs can also target chromosomal DNA.