27 research outputs found
目次
We discuss the issue of separating contributions from mechanical and optical properties of a moderately scattering tissue phantom to the modulation depth (M) of intensity autocorrelation measured in an ultrasound-assisted optical tomography system using axial and transverse illuminations. For axial illumination, M is affected by both the displacement and absorption coefficient, more prominently by displacement. But transverse illumination has very little contribution from displacement of scattering centers. Since displacement is related to the elastic property of the insonified region, we show that there is a possibility of separating the contributions from elastic and optical properties of the insonified region using axial and transverse illuminations. The main conclusions of our study using moderately scattering phantoms are: 1. axial illumination is the best for mapping storage modulus inhomogeneities, but M is also affected by optical absorption; 2. transverse illumination is the best for mapping absorption inhomogeneities; and 3. for the practically relevant case of an inclusion with larger storage modulus and absorption, both illuminations produced large contrast in M. When the scattering coefficient is high, the angle dependence of illumination is lost and the present method is shown to fail to separate these contributions based on direction of illumination
An adaptive delayed acknowledgment strategy to improve TCP performance in multi-hop wireless networks.
In multi-hop wireless networks, transmission control protocol (TCP) suffers from performance deterioration due to poor wireless channel characteristics. Earlier studies have shown that the small TCP acknowledgments consume as much wireless resources as the long TCP data packets. Moreover, generating an acknowledgment (ACK) for each incoming data packet reduces the performance of TCP. The main factor affecting TCP performance in multi-hop wireless networks is the contention and collision between ACK and data packets that share the same path. Thus, lowering the number of ACKs using the delayed acknowledgment option defined in IETF RFC 1122 will improve TCP performance. However, large cumulative ACKs will induce packet loss due to retransmission time-out at the sender side of TCP. Motivated by this understanding, we propose a new TCP receiver with an adaptive delayed ACK strategy to improve TCP performance in multi-hop wireless networks. Extensive simulations have been done to prove and evaluate our strategy over different topologies. The simulation results demonstrate that our strategy can improve TCP performance significantly
Heavy metal resistant bacteria associated with the black clam Villorita cyprinoides var cochinensis (Hanley) and water collected from Cochin backwater
A total of 147 strains of heterotrophic bacteria, isolated from water and the black clam
Villorlia cyprinoides var conchinensis from Cochin backwater were subjected to heavy metal sensitivity
tests for five heavy metals viz. mercury. zinc, cadmium, copper and lead. In general, the isolates from
water showed higher resistance towards the heavy metals. Members of all the genera except Coryneform
group showed similar trend of resistance. The strains of Coryneform group isolated from animals were
more resistant than their counterparts isolated from water. Minimum inhibitory concentration (MIC) of
the metals varied. It may be concluded from the results that the habitat of the organisms plays a unique
role in the ecology of heavy metal resistant bacteria
Studies on the effect of the organophosphorus pesticide Eka(Rlu) x EC 25 on the bacterial flora of Villorita cyprinoides var. cochinensis (Han1ey)
The thesis is Studies on the Effect or the Obganophosphorus Pesticide Ekalux(R) EC 25 on the Bacterial Flora or Villorita Cyprinoides Var.Cochinensis (Hanley). For the present investigation, the black clam Villorita gyprinoides var. cochinensis (Hanley), a most common clam genus present in this estuarine system has been selected as test organaism and Ekalux (R) EC 25 as toxicant. The aspects dealt with are 1. Total heterotrophic bacterial population,
2. Generic composition, 3. Hydrolytic enzyme producing bacteria, 4. Antibiotic resistance,
5. Heavy metal resistance, 6. The effect of pesticide concentration on the growth of the bacteria and 7. Effect of temperature, pH and sodium chloride on the growth and phosphate release of selected isolates.The samples for the experiment were collected from the Vembanad Lake, near Kumbalam Island during the period of September 1985 to May '86. The THB of the estuarine water and clams contained 6.5 x I04/ml and 2.975 x l06/g respectively, immediately after collection. Untreated water and clam samples showed enormous increase in THB from 0 hr population. The treated samples (water and clams) contained higher THB than 0 hr. In general, THB was observed to increase tremendously in the samples treated with pesticide when compared to their native flora. With reference to various concentrations of pesticides, THB recorded an increase with increase of concentration in water and clam samples.Cochin University
of Science and TechnologySchool of Marine Sciences, Cochin University
of Science and Technolog
Not Available
Not AvailableA total of 147 strains of heterotrophic bacteria, isolated from water and the black clam
Villorlia cyprinoides var conchinensis from Cochin backwater were subjected to heavy metal sensitivity
tests for five heavy metals viz. mercury. zinc, cadmium, copper and lead. In general, the isolates from
water showed higher resistance towards the heavy metals. Members of all the genera except Coryneform
group showed similar trend of resistance. The strains of Coryneform group isolated from animals were
more resistant than their counterparts isolated from water. Minimum inhibitory concentration (MIC) of
the metals varied. It may be concluded from the results that the habitat of the organisms plays a unique
role in the ecology of heavy metal resistant bacteria.Not Availabl
Detection of optical and mechanical property inhomogeneities in tissue mimicking phantoms using an ultrasound assisted optical probe
We discuss the issue of separating contributions from mechanical and optical properties of a moderately scattering tissue phantom to the modulation depth (M) of intensity autocorrelation measured in an ultrasound-assisted optical tomography system using axial and transverse illuminations. For axial illumination, M is affected by both the displacement and absorption coefficient, more prominently by displacement. But transverse illumination has very little contribution from displacement of scattering centers. Since displacement is related to the elastic property of the insonified region, we show that there is a possibility of separating the contributions from elastic and optical properties of the insonified region using axial and transverse illuminations. The main conclusions of our study using moderately scattering phantoms are: 1. axial illumination is the best for mapping storage modulus inhomogeneities, but M is also affected by optical absorption; 2. transverse illumination is the best for mapping absorption inhomogeneities; and 3. for the practically relevant case of an inclusion with larger storage modulus and absorption, both illuminations produced large contrast in M. When the scattering coefficient is high, the angle dependence of illumination is lost and the present method is shown to fail to separate these contributions based on direction of illumination. (c) 2008 Society of Photo-Optical Instrumentation Engineers
Measurement of visco-elastic properties of breast-tissue mimicking materials using diffusing wave spectroscopy
Diffusing wave spectroscopy (DWS), without the use of tracer particles, has been used to study the internal dynamics of polyvinyl alcohol (PVA) phantoms, which mimic the properties of normal and malignant breast tissues. From the measured intensity autocorrelations, the mean square displacement (MSD) of phantom meshing is estimated, leading to the storage and loss moduli of the medium covering frequencies up to 10 KHz. These are verified with independent measurements from a dynamic mechanical analyzer (DMA) at low frequencies. We thus prove the usefulness of DWS to extract visco-elastic properties of the phantom and its possible application in detecting malignancy in soft tissues