12,224 research outputs found
A fluorometric method for the estimation of tryptophan
The various colorimetric methods now employed for the estimation of tryptophan are not specific for tryptophan but give colored products with many compounds containing the indole nucleus, including indole itself. In order to facilitate studies of the enzymatic synthesis of tryptophan from indole and serine by extracts of Neurospora (1), a search for a rapid, quantitative method for the estimation of tryptophan in the presence of indole was undertaken. Tauber (2) reported that tryptophan gives a green fluorescence when treated with 70 to 72 per cent perchloric acid at room temperature. Modification of this procedure has led to a method for the rapid estimation of tryptophan, without preliminary extraction of indole, in hydrolyzed or unhydrolyzed tryptophan-containing materials
Goal-setting And Achievement In Activity Tracking Apps: A Case Study Of MyFitnessPal
Activity tracking apps often make use of goals as one of their core
motivational tools. There are two critical components to this tool: setting a
goal, and subsequently achieving that goal. Despite its crucial role in how a
number of prominent self-tracking apps function, there has been relatively
little investigation of the goal-setting and achievement aspects of
self-tracking apps.
Here we explore this issue, investigating a particular goal setting and
achievement process that is extensive, recorded, and crucial for both the app
and its users' success: weight loss goals in MyFitnessPal. We present a
large-scale study of 1.4 million users and weight loss goals, allowing for an
unprecedented detailed view of how people set and achieve their goals. We find
that, even for difficult long-term goals, behavior within the first 7 days
predicts those who ultimately achieve their goals, that is, those who lose at
least as much weight as they set out to, and those who do not. For instance,
high amounts of early weight loss, which some researchers have classified as
unsustainable, leads to higher goal achievement rates. We also show that early
food intake, self-monitoring motivation, and attitude towards the goal are
important factors. We then show that we can use our findings to predict goal
achievement with an accuracy of 79% ROC AUC just 7 days after a goal is set.
Finally, we discuss how our findings could inform steps to improve goal
achievement in self-tracking apps
Practical applications of small-angle neutron scattering.
Recent improvements in beam-line accessibility and technology have led to small-angle neutron scattering (SANS) becoming more frequently applied to materials problems. SANS has been used to study the assembly, dispersion, alignment and mixing of nanoscale condensed matter, as well as to characterise the internal structure of organic thin films, porous structures and inclusions within steel. Using time-resolved SANS, growth mechanisms in materials systems and soft matter phase transitions can also be explored. This review is intended for newcomers to SANS as well as experts. Therefore, the basic knowledge required for its use is first summarised. After this introduction, various examples are given of the types of soft and hard matter that have been studied by SANS. The information that can be extracted from the data is highlighted, alongside the methods used to obtain it. In addition to presenting the findings, explanations are provided on how the SANS measurements were optimised, such as the use of contrast variation to highlight specific parts of a structure. Emphasis is placed on the use of complementary techniques to improve data quality (e.g. using other scattering methods) and the accuracy of data analysis (e.g. using microscopy to separately determine shape and size). This is done with a view to providing guidance on how best to design and analyse future SANS measurements on materials not listed below
Midcourse maneuver operations program
Midcourse Maneuver Operations Program /MMOP/ computes the required velocity change to correct a spacecraft trajectory. The program establishes the existence of maneuvers which satisfy spacecraft constraints, explores alternate trajectories in the event that some out-of-tolerance condition forces a change in plans, and codes the maneuvers into commands
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Hydrologic Data for Urban Studies in the Austin, Texas Metropolitan Area, 1980
This report includes drainage basin maps and information from a specific storm (May 12, 1980) for the 23rd and 38th street Waller Creek locations.Waller Creek Working Grou
Diatom culture media contain extracellular silica nanoparticles which form opalescent films
Diatoms are unicellular photosynthetic algae with enormous diversity of patterns in their silica structures at the nano- to micronscale. In this study, we present results, which support the hypothesis that silica nanoparticles are released into the diatom culture medium. Formation of an opalescent film by the self-assembly of silica nanoparticles produced in the growth medium of diatoms. This film was formed on the filter paper from the culture medium of a Coscinodiscus sp. culture. A number of diatoms with partially opened valves were observed on the film surface under light microscopy and SEM, which indicates that cell contents inside of diatoms had been released into the culture solution. AFM images of produced an opalescent films show ordered arrays of silica nanoparticles with different diameters depending on the colors observed by light microscopy. The film forming silica nanoparticles are either released by the diatoms during reproduction or after cell death This approach provides an environmentally friendly means for fabricating silica nanoparticles, decorative coatings and novel optical materials. © 2008 SPIE.Dusan Losic, James G. Mitchell, Nicolas H. Voelcke
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Effect of Silane Coupling Agent Chemistry on Electrical Breakdown across Hybrid Organic–Inorganic Insulating Films
Dielectric breakdown measurements were conducted on self-assembled monolayer (SAM)/native silicon oxide hybrid dielectrics using conductive atomic force microscopy (C-AFM). By depositing silane coupling agents (SCAs) through a diffusional barrier layer, SAM roughness was decoupled from chemistry to compare the chemical effects of exposed R-group functionality on dielectric breakdown. Using Weibull and current–voltage (I–V) analysis, the breakdown strength was observed to be independent of SCA R-group length, and the addition of a SAM was seen to improve the breakdown strength relative to native silicon oxide by up to 158%. Fluorinated SCAs were observed to suppress tunneling leakage and exhibited increased breakdown strength relative to their hydrocarbon analogs. Electron trapping, scattering, or attachment processes inherent to the fluorinated moieties are thought to be the origin of the improved breakdown properties.Engineering and Applied Science
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