A Comparison of the Effects of Haptic and Visual Feedback on Presence in Virtual Reality

In the current consumer market, Virtual reality experiences are predominantly generated through visual and auditory feedback. Haptics are not yet well established, but are increasingly introduced to enhance the user’s sense of ‘reality’. With haptic (vibrotactile) feedback now part of the built-in mechanism of VR consumer devices, there is an urgent need to understand how different modalities work together to improve the user experience. This paper reports an experiment that explores the contributions made to participants’ sense of presence by haptic and visual feedback in a virtual environment. Participants experienced a virtual ball bouncing on a virtual stick resting across their avatar hands. We found that presence was enhanced when they could both see and feel the ball’s action; with a strong suggestion that haptic feedback alone gave rise to a greater sense of presence than visual alone. Similarly, whilst visual or bimodal feedback enhanced participants’ ability to locate where the ball bounced on the stick, our results suggest that the action itself was more readily discerned haptically than visually

Suspect screening of maternal serum to identify new environmental chemical biomonitoring targets using liquid chromatography-quadrupole time-of-flight mass spectrometry.

The use and advantages of high-resolution mass spectrometry (MS) as a discovery tool for environmental chemical monitoring has been demonstrated for environmental samples but not for biological samples. We developed a method using liquid chromatography-quadrupole time-of-flight MS (LC-QTOF/MS) for discovery of previously unmeasured environmental chemicals in human serum. Using non-targeted data acquisition (full scan MS analysis) we were able to screen for environmental organic acids (EOAs) in 20 serum samples from second trimester pregnant women. We define EOAs as environmental organic compounds with at least one dissociable proton which are utilized in commerce. EOAs include environmental phenols, phthalate metabolites, perfluorinated compounds, phenolic metabolites of polybrominated diphenyl ethers and polychlorinated biphenyls, and acidic pesticides and/or predicted acidic pesticide metabolites. Our validated method used solid phase extraction, reversed-phase chromatography in a C18 column with gradient elution, electrospray ionization in negative polarity and automated tandem MS (MS/MS) data acquisition to maximize true positive rates. We identified "suspect EOAs" using Agilent MassHunter Qualitative Analysis software, to match chemical formulas generated from each sample run with molecular formulas in our unique database of 693 EOAs assembled from multiple environmental literature sources. We found potential matches for 282 (41%) of the EOAs in our database. Sixty-five of these suspect EOAs were detected in at least 75% of the samples; only 19 of these compounds are currently biomonitored in National Health and Nutrition Examination Survey. We confirmed two of three suspect EOAs by LC-QTOF/MS using a targeted method developed through LC-MS/MS, reporting the first confirmation of benzophenone-1 and bisphenol S in pregnant women's sera. Our suspect screening workflow provides an approach to comprehensively scan environmental chemical exposures in humans. This can provide a better source of exposure information to help improve exposure and risk evaluation of industrial chemicals

Design of quantum well infrared photodetectors

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 268-281).QWIPs which respond to normally incident radiation without the need for an optical grating are of particular interest because they can be fabricated with fewer process steps and increased expected yield. An important contribution of this work is the demonstration of the first n-type QWIP (n-QWIP) which showed a significant detectivity of 4x101 cm-[square root of] H-z/Watt without the use of an optical grating. This detectivity corresponds to a conversion efficiency of 4 % or, equivalently, a responsivity of 270 mA/W. This detectivity is significant because it is large enough for focal plane array performance to be limited by the uniformity of processing rather than the size of the single pixel detectivity. An important part of this work was the development of numerically accurate physical models yielding simple analytical expressions for the QWIP leakage current and photocurrent. This physical model yielded analytical expressions for the number of, and the distance over which, carriers are depleted from quantum wells whenever the photocurrent is larger than leakage current. This depletion capacitance is expected to be important at high frequencies, in situations where the photocurrent is much larger than the leakage current, and in QWIPs designed with a small number of quantum wells (as when the quantum efficiency is large or an optical cavity is used). Studies of the microscopic physics of quantum wells are presented to elucidate the physical origin of the intersubband absorption of normally incident radiation. A key result of this work is the derivation within the framework of k p theory of selection rules for the intersubband absorption of normally incident radiation by hole subbands in a p-QWIP (p-doped QWIP) in the absence of an optical grating. It is found that the absorption of normally incident radiation by holes in a p-QWIP in the absence of an optical grating is largest for heavy hole to light hole transitions. The intersubband absorption of normally incident radiation by electrons in an n-QWIP in the absence of an optical grating is found within k p theory to be much smaller than that in a p-QWIP. It is also found that k p theory predicts that uniaxial strain does not have a large effect on the strength or the selection rules of intersubband absorption because the Hamiltonian describing uniaxial strain has the same (tetragonal) symmetry as that describing the confinement of carriers in the quantum wells along the growth direction. Nonuniformity of device parameters across an array of QWIPs is an important issue. High Resolution X-ray Diffraction (HRXRD) was used to measure the layer width variations of QWIPs grown by molecular beam epitaxy. The spread of the measured full-width-half-maxima of superlattice diffraction peaks with the diffraction order was used with Bragg's Law to obtain the measured layer width variation in the growth direction. It was found that the fractional layer width variation was about 2% for three example growths. This layer width variation is consistent with an effusion cell temperature variation of 1°C during growth. A theoretical study has been made of different noise mechanisms which contribute to QWIP performance. A key result found in this work is that when the signal-to-noise ratio (SNR) is limited by either fixed pattern noise or thermal leakage arrival noise, the optimal number of quantum wells for a maximum in the expected QWIP SNR is roughly ... , where ... is the quantum efficiency of a QWIP having only one quantum well. Common QWIP designs used in industry are evaluated. In particular, the commonly used n-QWIP design in which the confinement barriers are comprised of a semiconductor superlattice is considered. This QWIP design is intended to reduce thermionic leakage by pushing the three-dimensional continuum of energy further up in energy by making the miniband transport through the superlattice barrier the means of photocurrent conduction. A Kronig-Penney model presented in this thesis showed that this QWIP design, with a superlattice comprising the QWIP barriers, is expected to have a tunneling leakage which is, at best, commensurate with QWIP barriers which are made of a single semiconductor material but whose band edge is the average value of the band edges of the semiconductors comprising the actual barrier superlattice. The measured thermionic leakage was found to be in good agreement with a model in which the leakage depends exponentially on an activation energy which varies linearly with the applied bias. A deviation of the measured thermionic leakage from the idealized model is proposed as a quantitative measure of the amount of excessive leakage.by Janet Lin Pan.Ph.D

Perinatal Nutrition Misconceptions among Pregnant Adolescents in Northeastern Oklahoma

Food, Nutrition and Institution Administratio

The association between socioeconomic status and disability after stroke: Findings from the Adherence eValuation After Ischemic stroke Longitudinal (AVAIL) registry

Background Stroke is the leading cause of disability among adults in the United States. The association of patients’ pre-event socioeconomic status (SES) with post-stroke disability is not well understood. We examined the association of three indicators of SES—educational attainment, working status, and perceived adequacy of household income—with disability 3-months following an acute ischemic stroke. Methods We conducted retrospective analyses of a prospective cohort of 1965 ischemic stroke patients who survived to 3 months in the Adherence eValuation After Ischemic stroke – Longitudinal (AVAIL) study. Multivariable logistic regression was used to examine the relationship of level of education, pre-stroke work status, and perceived adequacy of household income with disability (defined as a modified Rankin Scale of 3–5 indicating activities of daily living limitations or constant care required). Results Overall, 58% of AVAIL stroke patients had a high school or less education, 61% were not working, and 27% perceived their household income as inadequate prior to their stroke. Thirty five percent of patients were disabled at 3-months. After adjusting for demographic and clinical factors, stroke survivors who were unemployed or homemakers, disabled and not-working, retired, less educated, or reported to have inadequate income prior to their stroke had a significantly higher odds of post-stroke disability. Conclusions In this cohort of stroke survivors, socioeconomic status was associated with disability following acute ischemic stroke. The results may have implications for public health and health service interventions targeting stroke survivors at risk of poor outcomes

Potential of a sequence-based antigenic distance measure to indicate equine influenza vaccine strain efficacy

The calculation of pepitope values, a sequence-based measure of antigenic distance between strains, was developed for human influenza. The potential to apply the pepitope value to equine influenza vaccine strain selection was assessed. There was a negative correlation between pepitope value and vaccine efficacy for pairs of vaccine and challenge strains used in cross-protection studies in ponies that just reached statistical significance (p = 0.046) only if one pair of viruses was excluded from the analysis. Thus the pepitope value has potential to provide additional data to consider in the decision-making process for updating equine influenza vaccine strains. However, further work is required to define the epitopes of the equine H3N8 haemagglutinin protein recognised by equine antibodies, which could lead to refinement of the pepitope value calculation. Furthermore, other factors such as vaccine potency and virulence of circulating strains may also influence vaccine efficacy

XTH31, Encoding an in Vitro XEH/XET-Active Enzyme, Regulates Aluminum Sensitivity by Modulating in Vivo XET Action, Cell Wall Xyloglucan Content, and Aluminum Binding Capacity in Arabidopsis

Xyloglucan endohydrolase (XEH) and xyloglucan endotransglucosylase (XET) activities, encoded by xyloglucan endotransglucosylase-hydrolase (XTH) genes, are involved in cell wall extension by cutting or cutting and rejoining xyloglucan chains, respectively. However, the physiological significance of this biochemical activity remains incompletely understood. Here, we find that an XTH31 T-DNA insertion mutant, xth31, is more Al resistant than the wild type. XTH31 is bound to the plasma membrane and the encoding gene is expressed in the root elongation zone and in nascent leaves, suggesting a role in cell expansion. XTH31 transcript accumulation is strongly downregulated by Al treatment. XTH31 expression in yeast yields a protein with an in vitro XEH:XET activity ratio of >5000:1. xth31 accumulates significantly less Al in the root apex and cell wall, shows remarkably lower in vivo XET action and extractable XET activity, has a lower xyloglucan content, and exhibits slower elongation. An exogenous supply of xyloglucan significantly ameliorates Al toxicity by reducing Al accumulation in the roots, owing to the formation of an Al-xyloglucan complex in the medium, as verified by an obvious change in chemical shift of (27)Al-NMR. Taken together, the data indicate that XTH31 affects Al sensitivity by modulating cell wall xyloglucan content and Al binding capacity