2,984 research outputs found
Metabolomics on integrated circuit
We have demonstrated a chip-based diagnostics tool for the quantification of metabolites, using specific enzymes, to study enzyme kinetics and calculate the Michaelis-Menten constant. An array of 256×256 ion-sensitive field effect transistors (ISFETs) fabricated in a complementary metal oxide semiconductor (CMOS) process is used for this prototype. We have used hexokinase enzyme reaction on the ISFET CMOS chip with glucose concentration in the physiological range of 0.05 mM – 231 mM and successfully studied the enzyme kinetics of hexokinase in detail. This will promote future research towards multiplexing enzyme-based metabolite quantification on a single chip, ultimately opening a pathway towards a personal metabolome machine
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Content retrieval and mobile users: An outdoor investigation of an ambient travel guide
People's information needs change as they encounter new situations. The need for an ambient information environment becomes more evident in the case of the mobile traveller where situated information access is one of the main challenges.
The motivation for this work has been to provide relevant information to the right situation and user in an ambient manner. Our way to solve this is to deliver personalised and context-aware information to the mobile user. To this end we have developed a platform, and prototype applications for travellers, and tourists. The system integrates our own tag technology with information from content service providers covering both general travel guide and local information.
The development methodology is user-centred, iterative, and progressive in nature. It combines information retrieval (IR) test and evaluation techniques with iterative and user-centred development techniques at the test and evaluation phase. Combining the two disciplines gives us the ability to test and evaluate both the information aspects and the interaction aspects of any information system in parallel. Another advantage would be that one can develop content and software in parallel.
This paper focuses on the IR test and evaluation framework that has been used in conjunction with the user-centred development. We emphasize the importance of performing IR test and evaluation for mobile systems in terms of users’ situations and tasks. The paper presents the results of some of the findings from a preliminary user test in an outdoor scenario. The test took place in a popular tourist destination in Spain
Review of overall parameters of giant radio pulses from the Crab pulsar and B1937+21
We present a review of observed parameters of giant radio pulses, based on
the observations conducted by our group during recent years. The observations
cover a broad frequency range of about 3 octaves, concentrating between 600 and
4850 MHz. Giant pulses of both the Crab pulsar and the millisecond pulsar
B1937+21 were studied with the 70-m Tidbinbilla, the 100-m GBT, 64-m Kalyazin
and Westerbork radio telescopes. We discuss pulse energy distribution,
dependence of peak flux density from the pulse width, peculiarities of radio
spectra, and polarization properties of giant radio pulses.Comment: 3 pages, 4 figures, to be published in the Proceedings of the
conference "40 Years of Pulsars: Millisecond Pulsars, Magnetars, and More"
held on August 12-17, 2007, McGill University, Montreal, Canad
The role of mobile technology in promoting social inclusion among adults with intellectual disabilities
Background: Mobile technology has the potential to assist adults with intellectual disabilities to initiate and maintain social connections in important areas of their lives, such as family, friends and work/volunteering. Method: The present study investigated how specific aspects of mobile device/app use are associated with the social inclusion of people with intellectual disabilities. The study also examined what background attributes were associated with particular patterns of mobile device/app use and social inclusion. Results: The findings revealed that the use of mobile technology among adults with intellectual disabilities was positively associated with their social inclusion with family, friends and work/volunteering. There were also some key background attributes associated with participants’ use of mobile technology and the extent to which mobile technology assisted their social inclusion. Conclusions: Implications for practice and policy are discussed
Periodic Thermonuclear X-ray Bursts from GS 1826-24 and the Fuel Composition as a Function of Accretion Rate
We analyze 24 type I X-ray bursts from GS 1826-24 observed by the Rossi X-ray
Timing Explorer between 1997 November and 2002 July. The bursts observed
between 1997-98 were consistent with a stable recurrence time of 5.74 +/- 0.13
hr. The persistent intensity of GS 1826-24 increased by 36% between 1997-2000,
by which time the burst interval had decreased to 4.10 +/- 0.08 hr. In 2002
July the recurrence time was shorter again, at 3.56 +/- 0.03 hr. The bursts
within each epoch had remarkably identical lightcurves over the full approx.
150 s burst duration; both the initial decay timescale from the peak, and the
burst fluence, increased slightly with the rise in persistent flux. The
decrease in the burst recurrence time was proportional to Mdot^(-1.05+/-0.02)
(where Mdot is assumed to be linearly proportional to the X-ray flux), so that
the ratio alpha between the integrated persistent and burst fluxes was
inversely correlated with Mdot. The average value of alpha was 41.7 +/- 1.6.
Both the alpha value, and the long burst durations indicate that the hydrogen
is burning during the burst via the rapid-proton (rp) process. The variation in
alpha with Mdot implies that hydrogen is burning stably between bursts,
requiring solar metallicity (Z ~ 0.02) in the accreted layer. We show that
solar metallicity ignition models naturally reproduce the observed burst
energies, but do not match the observed variations in recurrence time and burst
fluence. Low metallicity models (Z ~ 0.001) reproduce the observed trends in
recurrence time and fluence, but are ruled out by the variation in alpha. We
discuss possible explanations, including extra heating between bursts, or that
the fraction of the neutron star covered by the accreted fuel increases with
Mdot.Comment: 9 pages, 6 figures, accepted by ApJ. Minor revisions following the
referee's repor
A Search for Pulsed and Bursty Radio Emission from X-ray Dim Isolated Neutron Stars
We have carried out a search for radio emission from six X-ray dim isolated
neutron stars (XDINSs) observed with the Robert C. Byrd Green Bank Radio
Telescope (GBT) at 820 MHz. No bursty or pulsed radio emission was found down
to a 4sigma significance level. The corresponding flux limit is 0.01-0.04 mJy
depending on the integration time for the particular source and pulse duty
cycle of 2%. These are the most sensitive limits yet on radio emission from
these objects.Comment: 3 pages, 3 figures, to be appeared in the Proceedings of the
conference "40 Years of Pulsars: Millisecond Pulsars, Magnetars, and More"
held on August 12-17, 2007, McGill University, Montreal, Canad
Osteosarcoma is characterised by reduced expression of markers of osteoclastogenesis and antigen presentation compared with normal bone
BACKGROUND: Osteosarcoma (OS) is the most common primary bone tumour in children and adolescents. Patients who respond poorly to chemotherapy have a higher risk of metastatic disease and 5-year survival rates of only 10-20%. Therefore, identifying molecular targets that are specific for OS, or more specifically, metastatic OS, will be critical to the development of new treatment strategies to improve patient outcomes
Evaluation of different time domain peak models using extreme learning machine-based peak detection for EEG signal
Various peak models have been introduced to detect and analyze peaks in the time domain analysis of electroencephalogram (EEG) signals. In general, peak model in the time domain analysis consists of a set of signal parameters, such as amplitude, width, and slope. Models including those proposed by Dumpala, Acir, Liu, and Dingle are routinely used to detect peaks in EEG signals acquired in clinical studies of epilepsy or eye blink. The optimal peak model is the most reliable peak detection performance in a particular application. A fair measure of performance of different models requires a common and unbiased platform. In this study, we evaluate the performance of the four different peak models using the extreme learning machine (ELM)-based peak detection algorithm. We found that the Dingle model gave the best performance, with 72 % accuracy in the analysis of real EEG data. Statistical analysis conferred that the Dingle model afforded significantly better mean testing accuracy than did the Acir and Liu models, which were in the range 37–52 %. Meanwhile, the Dingle model has no significant difference compared to Dumpala model
The double pulsar: evolutionary constraints from the system geometry
The double pulsar system PSR J0737-3039A/B is a highly relativistic double
neutron star (DNS) binary, with a 2.4-hour orbital period. The low mass of the
second-formed NS, as well the low system eccentricity and proper motion, point
to a different evolutionary scenario compared to other known DNS systems. We
describe analysis of the pulse profile shape over 6 years of observations, and
present the resulting constraints on the system geometry. We find the recycled
pulsar in this system, PSR J0737-3039A, to have a low misalignment between its
spin and orbital angular momentum axes, with a 68.3% upper limit of 6.1
degrees, assuming emission from both magnetic poles. This tight constraint
lends credence to the idea that the supernova that formed the second pulsar was
relatively symmetric, possibly involving electron-capture onto an O-Ne-Mg core.Comment: 5 page, 2 figures; To appear in the conference proceedings "40 Years
of Pulsars: Millisecond Pulsars, Magnetars, and More", August 12-17, 2007, at
McGill University, Montreal, Canada. Version with full-resolution figures can
be found at http://www.phas.ubc.ca/~ferdman/ferdman.0737_geo.full.ps.gz;
typos corrected, some rewording, and references adde
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