Understanding the behavioral and neurocognitive relation between mind wandering and learning

In the last decade, tremendous advances have been made in the effort to understand mind wandering, yet many questions remain unanswered. Chief among them is how mind wandering relates to learning. Insofar as mind wandering has been linked to poor learning, finding ways to reduce the propensity to mind wander could potentially improve learning. Two experiments were conducted to examine this. The first experiment evaluated how difficulty of the to-be-learned materials affected one’s tendency to mind wander and revealed that people mind wandered when there was a mismatch between their level of expertise and the difficulty of materials studied. The second experiment compared whether participants were more likely to mind wander in blocked or interleaved conditions and showed that participants were more likely to mind wander when materials were presented in a blocked fashion. Together, these results indicate that techniques such as studying materials specific to one’s own level of mastery or changing the way in which one studies might reduce mind wandering and improve learning. Of equal importance is the question of what happens on in the brain when a person mind wanders. While the effect of mind wandering on early sensory processing is known, the impact it has on learning-related processing is not. In two event-related potential (ERP) experiments, participants were asked to report whether they were mind wandering or not while studying materials they were later tested on. Analyses revealed that elaborative semantic processing – indexed by a late, sustained slow wave that was maximal at posterior parietal electrode sites – was attenuated when participants mind wandered. Crucially, the pattern when people were on task rather than mind wandering was similar to the subsequent memory effect previously reported by other memory researchers, suggesting that mind wandering disrupts the deep level of processing required for learning

Surface-passivated plasmonic nano-pyramids for bulk heterojunction solar cell photocurrent enhancement

This is the published version. ©Copyright 2012 Royal Society of ChemistryWe report that self-assembled gold (Au) nanopyramid arrays can greatly enhance the photocurrent of narrow bandgap organic solar cells using their plasmonic near-field effect. The plasmonic enhanced power conversion efficiency exhibited up to 200% increase under the AM 1.5 solar illumination

Toward better public health reporting using existing off the shelf approaches: The value of medical dictionaries in automated cancer detection using plaintext medical data

Objectives Existing approaches to derive decision models from plaintext clinical data frequently depend on medical dictionaries as the sources of potential features. Prior research suggests that decision models developed using non-dictionary based feature sourcing approaches and “off the shelf” tools could predict cancer with performance metrics between 80% and 90%. We sought to compare non-dictionary based models to models built using features derived from medical dictionaries. Materials and methods We evaluated the detection of cancer cases from free text pathology reports using decision models built with combinations of dictionary or non-dictionary based feature sourcing approaches, 4 feature subset sizes, and 5 classification algorithms. Each decision model was evaluated using the following performance metrics: sensitivity, specificity, accuracy, positive predictive value, and area under the receiver operating characteristics (ROC) curve. Results Decision models parameterized using dictionary and non-dictionary feature sourcing approaches produced performance metrics between 70 and 90%. The source of features and feature subset size had no impact on the performance of a decision model. Conclusion Our study suggests there is little value in leveraging medical dictionaries for extracting features for decision model building. Decision models built using features extracted from the plaintext reports themselves achieve comparable results to those built using medical dictionaries. Overall, this suggests that existing “off the shelf” approaches can be leveraged to perform accurate cancer detection using less complex Named Entity Recognition (NER) based feature extraction, automated feature selection and modeling approaches

Comparison of negative and positive ion electrospray tandem mass spectrometry for the liquid chromatography tandem mass spectrometry analysis of oxidized deoxynucleosides

AbstractOxidized deoxynucleosides are widely used as biomarkers for DNA oxidation and oxidative stress assessment. Although gas chromatography mass spectrometry is widely used for the measurement of multiple DNA lesions, this approach requires complex sample preparation contributing to possible artifactual oxidation. To address these issues, a high performance liquid chromatography (HPLC)-tandem mass spectrometric (LC-MS/MS) method was developed to measure 8-hydroxy-2′-deoxyguanosine (8-OH-dG), 8-hydroxy-2′-deoxyadenosine (8-OH-dA), 2-hydroxy-2′-deoxyadenosine (2-OH-dA), thymidine glycol (TG), and 5-hydroxymethyl-2′-deoxyuridine (HMDU) in DNA samples with fast sample preparation. In order to selectively monitor the product ions of these precursors with optimum sensitivity for use during quantitative LC-MS/MS analysis, unique and abundant fragment ions had to be identified during MS/MS with collision-induced dissociation (CID). Positive and negative ion electrospray tandem mass spectra with CID were compared for the analysis of these five oxidized deoxynucleosides. The most abundant fragment ions were usually formed by cleavage of the glycosidic bond in both positive and negative ion modes. However, in the negative ion electrospray tandem mass spectra of 8-OH-dG, 2-OH-dA, and 8-OH-dA, cleavage of two bonds within the sugar ring produced abundant S1 type ions with loss of a neutral molecule weighing 90 u, [M − H − 90]−. The signal-to-noise ratio was similar for negative and positive ion electrospray MS/MS except in the case of thymidine glycol where the signal-to-noise was 100 times greater in negative ionization mode. Therefore, negative ion electrospray tandem mass spectrometry with CID would be preferred to positive ion mode for the analysis of sets of oxidized deoxynucleosides that include thymidine glycol. Investigation of the fragmentation pathways indicated some new general rules for the fragmentation of negatively charged oxidized nucleosides. When purine nucleosides contain a hydroxyl group in the C8 position, an S1 type product ion will dominate the product ions due to a six-membered ring hydrogen transfer process. Finally, a new type of fragment ion formed by elimination of a neutral molecule weighing 48 (CO2H4) from the sugar moiety was observed for all three oxidized purine nucleosides

Doped graphene nanohole arrays for flexible transparent conductors

Graphene nanohole arrays (GNAs) were fabricated using nanoimprint lithography. The improved optical transmittance of GNAs is primarily due to the reduced surface coverage of graphene from the nanohole fabrication. Importantly, the exposed edges of the nanoholes provided effective sites for chemical doping using thionyl chloride was shown to enhance the conductance by a factor of 15–18 in contrast to only 2-4 for unpatterned graphene. GNAs can provide a unique scheme for improving both optical transmittance and electrical conductivity of graphene-based transparent conductors

Enhanced energy density with a wide thermal stability in epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 thin films

High-quality epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films of thickness of 880 nm were fabricated using pulsed laser deposition on (001) Nb doped SrTiO3 (Nb:STO) substrates. Besides a confirmation of the epitaxial relationship [100]PLZT//[100]Nb:STO and (001)PLZT//(001)Nb:STO using X-ray diffraction, a transmission electron microscopy study has revealed a columnar structure across the film thickness. The recoverable energy density (Wrec) of the epitaxial PLZT thin film capacitors increases linearly with the applied electric field and the best value of 31 J/cm3 observed at 2.27 MV/cm is considerably higher by 41% than that of the polycrystalline PLZT film of a comparable thickness. In addition to the high Wrec value, an excellent thermal stability as illustrated in a negligible temperature dependence of the Wrec in the temperature range from room temperature to 180 C is achieved. The enhanced Wrec and the thermal stability are attributed to the reduced defects and grain boundaries in epitaxial PLZT thin films, making them promising for energy storage applications that require both high energy density, power density, and wide operation temperatures

Atomically Thin Al2O3 Films for Tunnel Junctions

Metal-insulator-metal tunnel junctions are common throughout the microelectronics industry. The industry standard AlOx tunnel barrier, formed through oxygen diffusion into an Al wetting layer, is plagued by internal defects and pinholes which prevent the realization of atomically thin barriers demanded for enhanced quantum coherence. In this work, we employ in situ scanning tunneling spectroscopy along with molecular-dynamics simulations to understand and control the growth of atomically thin Al2O3 tunnel barriers using atomic-layer deposition. We find that a carefully tuned initial H2O pulse hydroxylated the Al surface and enabled the creation of an atomically thin Al2O3 tunnel barrier with a high-quality M−I interface and a significantly enhanced barrier height compared to thermal AlOx. These properties, corroborated by fabricated Josephson junctions, show that atomic-layer deposition Al2O3 is a dense, leak-free tunnel barrier with a low defect density which can be a key component for the next generation of metal-insulator-metal tunnel junctions

Second-harmonic generation induced by electric currents in GaAs

We demonstrate a new, nonlinear optical effect of electric currents. First, a steady current is generated by applying a voltage on a doped GaAs crystal. We demonstrate that this current induces second-harmonic generation of a probe laser pulse. Second, we optically inject a transient current in an undoped GaAs crystal by using a pair of ultrafast laser pulses, and demonstrate that it induces the same second-harmonic generation. In both cases, the induced second-order nonlinear susceptibility is proportional to the current density. This effect can be used for nondestructive, noninvasive, and ultrafast imaging of currents. These advantages are illustrated by the real-time observations of a coherent plasma oscillation and spatial resolution of current distribution in a device. This new effect also provides a mechanism for electrical control of the optical response of materials.Comment: 5 pages, 3 figure

Ulcerative colitis-risk loci on chromosomes 1p36 and 12q15 found by genome-wide association study.

Ulcerative colitis is a chronic inflammatory disease of the colon that presents as diarrhea and gastrointestinal bleeding. We performed a genome-wide association study using DNA samples from 1,052 individuals with ulcerative colitis and preexisting data from 2,571 controls, all of European ancestry. In an analysis that controlled for gender and population structure, ulcerative colitis loci attaining genome-wide significance and subsequent replication in two independent populations were identified on chromosomes 1p36 (rs6426833, combined P = 5.1 x 10(-13), combined odds ratio OR = 0.73) and 12q15 (rs1558744, combined P = 2.5 x 10(-12), combined OR = 1.35). In addition, combined genome-wide significant evidence for association was found in a region spanning BTNL2 to HLA-DQB1 on chromosome 6p21 (rs2395185, combined P = 1.0 x 10(-16), combined OR = 0.66) and at the IL23R locus on chromosome 1p31 (rs11209026, combined P = 1.3 x 10(-8), combined OR = 0.56; rs10889677, combined P = 1.3 x 10(-8), combined OR = 1.29)