50 research outputs found
Mode-selective optical sensing using asymmetric waveguide junctions
AbstractMeasuring a single analyte in a highly absorptive microfluidic channel has always been a challenge. Even with a highly selective sensing layer, other chemical species can affect the interrogation of the analyte. Matching the evanescent tail with the sensing layer thickness is difficult in case of evanescent field sensing. The tail typically extends beyond the sensing layer, introducing noise and spurious errors in the measurement, which scales up with analyte concentration. In this work therefore, we propose the use of a simple multimode evanescent waveguide sensor that eliminates such common spurious effects. The proposed mode-selective sensing system exploits the sensitivity differences between the different guided modes in detecting the effects of the outer medium in the sensor response. The operation of the sensor device relies on the use of an asymmetric waveguide junction, which enable efficient separation of waveguide modes and therefore detection of their differences in behaviour. The proposed device is shown through simulations to achieve very small estimation errors below 5%, even for very high absorption coefficients of the outer medium of up to 80 times larger than that of the sensing layer
Recommended from our members
Biochemical sensing using Siloxane polymer waveguides
The objective of this work presented here is to extend the capabilities of
siloxane waveguide technology in the field of biochemical sensing. Recent
advances in the integration of polymeric optical waveguides with electronics onto
standard printed circuit boards (PCBs) allow the formation of cost-effective lab-on-achip
modules suitable for mass production. This technology has been primarily
designed for on-board data communication. The focus of this research is to investigate
the possibility of realising a Siloxane polymer based lab-on-chip sensor.
Different siloxane-polymer-based optical waveguide sensor structures have been
designed and analysed from the aspect of biochemical sensing. An evanescent-wave
absorption sensor based on mode-selective asymmetric waveguide junctions is
proposed for the first time. The device mitigates the common optical effect of
spurious response in absorption sensors due to the analyte transport fluid.
Head injury is the leading cause of death in the population of people under 40 years.
Currently, 3 out of 5 deaths in emergency rooms are due to severe brain injuries
in the developed world. Researchers at the Neurosciences Critical Care Unit
(NCCU) at Addenbrooke’s Hospital have managed to correlate biochemical
changes with the severeness of the injury and the likelihood of patient recovery.
Considerable progress has been made to develop a lab-on-chip sensor capable of
continuously monitoring glucose, lactate and pyruvate concentrations in the brain
fluid, hence the contribution to the current trend in the advancement of portable
lab-on-chip technologies for the deployment of point-of-care diagnostic tools. A
novel recognition layer has been developed based on porphyrin in combination with
glucose, lactate and pyruvate oxidase for measuring all the analytes, enabling fast
and reversible chemical reactions to be monitored by optical interrogation. The
operational wavelength of the developed recognition layer is 425 nm, which
required the formation of polymer features that were beyond the fabrication
capabilities at the time. Through considerable process development and the
adoption of nanoimprinting lithography, siloxane polymer based optical
waveguides were fabricated allowing the realisation of highly sensitive optical
sensors. Based on the results that are presented here, it can be concluded the
functionalization of siloxane polymer waveguide have a potential for realising
biochemical sensors in the future. The new fabrication technique will allow the
formation of more robust and complex lab-on-chip sensors based on this material.ESPR
Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts
We outline the scientific motivation behind a search for gravitational waves
associated with short gamma ray bursts detected by the InterPlanetary Network
(IPN) during LIGO's fifth science run and Virgo's first science run. The IPN
localisation of short gamma ray bursts is limited to extended error boxes of
different shapes and sizes and a search on these error boxes poses a series of
challenges for data analysis. We will discuss these challenges and outline the
methods to optimise the search over these error boxes.Comment: Methods paper; Proceedings for Eduardo Amaldi 9 Conference on
Gravitational Waves, July 2011, Cardiff, U
All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run
We present results from a search for gravitational-wave bursts in the data
collected by the LIGO and Virgo detectors between July 7, 2009 and October 20,
2010: data are analyzed when at least two of the three LIGO-Virgo detectors are
in coincident operation, with a total observation time of 207 days. The
analysis searches for transients of duration < 1 s over the frequency band
64-5000 Hz, without other assumptions on the signal waveform, polarization,
direction or occurrence time. All identified events are consistent with the
expected accidental background. We set frequentist upper limits on the rate of
gravitational-wave bursts by combining this search with the previous LIGO-Virgo
search on the data collected between November 2005 and October 2007. The upper
limit on the rate of strong gravitational-wave bursts at the Earth is 1.3
events per year at 90% confidence. We also present upper limits on source rate
density per year and Mpc^3 for sample populations of standard-candle sources.
As in the previous joint run, typical sensitivities of the search in terms of
the root-sum-squared strain amplitude for these waveforms lie in the range 5
10^-22 Hz^-1/2 to 1 10^-20 Hz^-1/2. The combination of the two joint runs
entails the most sensitive all-sky search for generic gravitational-wave bursts
and synthesizes the results achieved by the initial generation of
interferometric detectors.Comment: 15 pages, 7 figures: data for plots and archived public version at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=70814&version=19, see
also the public announcement at
http://www.ligo.org/science/Publication-S6BurstAllSky
Search for long-lived gravitational-wave transients coincident with long gamma-ray bursts
Long gamma-ray bursts (GRBs) have been linked to extreme core-collapse supernovae from massive stars. Gravitational waves (GW) offer a probe of the physics behind long GRBs. We investigate models of long-lived (~10–1000 s) GW emission associated with the accretion disk of a collapsed star or with its protoneutron star remnant. Using data from LIGO’s fifth science run, and GRB triggers from the Swift experiment, we perform a search for unmodeled long-lived GW transients. Finding no evidence of GW emission, we place 90% confidence-level upper limits on the GW fluence at Earth from long GRBs for three waveforms inspired by a model of GWs from accretion disk instabilities. These limits range from F<3:5 ergs cm⁻2 to F<1200 ergs cm⁻2, depending on the GRB and on the model, allowing us to probe optimistic scenarios of GW production out to distances as far as ≈ 33 Mpc. Advanced detectors are expected to achieve strain sensitivities 10× better than initial LIGO, potentially allowing us to probe the engines of the nearest long GRBs.J. Aasi ... D.J. Hosken ... W. Kim ... E.J. King ... J. Munch ... D. J. Ottaway ... P. J. Veitc
A directed search for gravitational waves from Scorpius X-1 with initial LIGO
19 pages, 8 figuresInternational audienceWe present results of a search for continuously-emitted gravitational radiation, directed at the brightest low-mass X-ray binary, Scorpius X-1. Our semi-coherent analysis covers 10 days of LIGO S5 data ranging from 50-550 Hz, and performs an incoherent sum of coherent -statistic power distributed amongst frequency-modulated orbital sidebands. All candidates not removed at the veto stage were found to be consistent with noise at a 1% false alarm rate. We present Bayesian 95% confidence upper limits on gravitational-wave strain amplitude using two different prior distributions: a standard one, with no a priori assumptions about the orientation of Scorpius X-1; and an angle-restricted one, using a prior derived from electromagnetic observations. Median strain upper limits of 1.3e-24 and 8e-25 are reported at 150 Hz for the standard and angle-restricted searches respectively. This proof of principle analysis was limited to a short observation time by unknown effects of accretion on the intrinsic spin frequency of the neutron star, but improves upon previous upper limits by factors of ~1.4 for the standard, and 2.3 for the angle-restricted search at the sensitive region of the detector
FOOD PURCHASE HABITS IN FIELD OF DIRECT SALES
The growing popularity of direct sales is promoted and caused by increasing numbers of factors. A trend, for instance, is that as a result of alleged and real food scandals of recent years, trust of consumers in modern food industry has started shrinking. Consequently, on a consumer side, the demand for safety and transparency is rising. Consumers would like to have information on the origin of the product they purchase. This need is possible to be satisfied by direct sales. A research on consumer habits connected to direct sales is in the centre of the study. Influencing factors in food purchase are being examined and consumer groups defined by a cluster analysis based on the importance of influencing factors in food purchase are also being introduced. Amongst others, behaviour of individual consumer groups in a direct sales context is being highlighted, too
Mutation in Mpzl3, a Gene Encoding a Predicted the Adhesion Protein, in the Rough Coat (rc) Mice with Severe Skin and Hair Abnormalities
The rough coat (rc), an autosomal-recessive mutation, arose spontaneously in C57BL/6J mice. Homozygous rc mice develop severe skin and hair abnormalities, including cyclic and progressive hair loss and sebaceous gland hypertrophy. The rc locus was previously mapped to Chromosome 9. To elucidate the genetic basis underlying the rc phenotype development, we carried out positional cloning, and mapped the rc locus to a 246-kb interval. We identified a missense mutation within a novel open reading frame in the rc/rc mice, which is predicted to encode a cell adhesion molecule with the highest homology to myelin protein zero (MPZ) and myelin protein zero-like 2 (MPZL2, also called epithelial V-like antigen). We therefore named this gene Mpzl3 (myelin protein zero-like 3). The mutation in the rc/rc mice occurred at a highly conserved residue within the conserved Ig-like V-type domain, thus likely altering the MPZL3 protein function. Reverse transcriptase-PCR and Western blot analyses revealed expression of the Mpzl3 gene in various adult organs, including the skin. Using indirect immunofluorescence, we detected MPZL3 protein in the keratinocytes and sebocytes in the skin. Results from this study identified a novel gene encoding a predicted adhesion protein whose mutation in the rc/rc mice likely caused the rc phenotype