Tag Archives: amc 7

The wave amplitude is given by Here is the amplitude

The wave amplitude is given by,Here, is the amplitude of the component wave of frequency ω at source point, is the propagation constant (=2πf/v), is the reflection co-efficient at water-reflector interface, is the reflection co-efficient at water-transducer interface, and x is the position measured from the transducer face. For simplicity, we take . In the present experiment, since a single transducer is used as the transmitter as well as the receiver, the response observed in the oscilloscope will be proportional to the wave displacement at x=0, i.e. .
The echo trains for n different sample lengths, l1, l2,… ,ln, are captured using digital oscilloscope DL 1640 and stored in PC for further analysis. From the average amc 7 Δt between successive echoes, ultrasound velocity v is determined (v=2ln/Δt) and k is calculated. From exponential fitting of the echo heights, effective attenuation αe is determined. To get the intrinsic attenuation constant α the following procedure is adopted. The Fast Fourier Transform (FFT) of the echo trains obtained for n lengths are determined. For each frequency component, n wave amplitudes are obtained for n different sample lengths. Oak Ridge and Oxford method for parameter fitting [8] is used to fit these n amplitudes according to relation (2) by adjusting the parameters k, r, α and . The computational method requires input guess values for k, r, α and . Input k is obtained from experimentally measured v, input α is the lowest value of αe obtained for large l, input r is calculated using the relation r=(ρ1v1−ρ2v2)/(ρ1v1+ρ2v2), ρ being the density, with suffixes 1 and 2 designating the reflector material and water respectively, and input is chosen arbitrarily. The experiment is repeated using steel, copper, brass, lead and glass reflectors.

Results and discussion
The velocities (v) and effective attenuation constants (αe) are determined for various lengths (l) of water columns in pulse-echo experiment with five different reflecting surfaces. The values for v are close to each other within experimental error. Average v is determined to be 1.4775×105cmsec−1. Fig. 1 shows the dependence of αe on l for glass reflector. We see that attenuation values are widely different particularly for small values of l. Similar variation in the attenuation constant has been reported by Martinez and co-workers [2]. Their work shows clearly that at short distances from the transmitting transducer, the attenuation values measured in pulse-echo method show wide variation. At long distances however, the results are consistent and it is possible to get an average value of 0.04417np/cm for the attenuation constant though it is not in agreement with other reported values [3–6]. Their measurement in through-transmission method uses two transducers aligned face-to-face, parallel to each other. By this the water medium in between behaves effectively like a bounded medium as in pulse-echo method and no better solution is obtained. The attenuation value obtained in this method is 0.04654np/cm.
Measurements with other four reflectors, viz., steel, copper, brass and lead show similar nature of variation of αe with l and this is illustrated in Fig. 2. No significant difference is noticed due to the differences in r because of the fact that fluctuation due to change in l is more prominent than the effect caused by the change in r. For longer l and smaller r the echo signals are weak and measurement of αe is more erroneous. The observed nature of Fig. 2 is also consistent with the numerical study presented in Ref. [1].
To determine the intrinsic attenuation constant α, FFT components are computed for pulse-echo signals captured for seven different column lengths (ln, n=1, 2,… ,7) under same exciting conditions. The exciting input is pulsed rf signal of carrier frequency 1MHz, peak-peak pulse height of ∼300V, pulse width of ∼3μs and pulse repetition time ∼2.45ms. Table 1 presents the liquid column lengths for different reflectors used to get pulse-echo signals. Fig. 3 shows representative echo signal captured with glass reflector for (a) l1=5.056cm and (b) l7=3.552cm and Fig. 4(a) and (b) shows their fft components respectively. In Fig. 4 unit frequency corresponds to 100MHz and relative amplitude is in arbitrary unit. The frequency range where the fft amplitudes are relatively high is shown in Fig. 4. The peak region is considered for computational parameter fitting. The error in experimental fft amplitudes is assumed to be within 10%. Best fit parameters with minimum χ2 error are determined using Oak Ridge and Oxford method [8]. In finding the best fit parameters, several factors have been taken into consideration. Firstly, Triassic Period is known that there is no dispersion for normal sound propagation in water [12] in the frequency domain of the present experiment. Usually, the transducer bandwidth is ∼10% of the central operating frequency, i.e. 0.95–1.05MHz for 1MHz transducer. So k remains constant for all frequencies in this range. Velocity measurement in pulse echo method gives reasonably accurate value and we take the experimental value of v to calculate k and vary k within experimental error. For input r, we depend on theoretical value and allow small variation around this theoretical value. αe determined from pulse-echo experiment is chosen as input α. We choose the particular set of values for the parameters for which χ2 error is minimum for maximum frequency components in the range considered. The best fit parameters along with their input values are presented in Table 2. The average k thus obtained is 42.74±0.03cm−1 giving v=(1.4693±0.0011)×105cmsec−1 and average α is 0.0435±0.0013np/cm. This value of α is more accurate and consistent with the measurement by Martinez et al. [2].

Rhinovirus has been associated with the exacerbation of chronic

Rhinovirus has been associated with the exacerbation of chronic lung diseases, including asthma, COPD, bronchiectasis, bronchiolitis obliterans organizing pneumonia and cystic fibrosis. Rhinovirus infection triggers more severe symptoms and greater reduction in airway obstruction in patients with amc 7 than non-asthmatic controls. Experimental rhinovirus infection in humans also induced COPD exacerbation.
Extrapulmonary complications are frequently seen in critically ill patients with rhinovirus infection. In our study on critically ill patients, seizure was identified in 23% of patients with rhinovirus infection. Other extrapulmonary complications include pulmonary edema, diabetic ketoacidosis and hyperosmolar coma.

Currently, reverse transcription-polymerase chain reaction (RT-PCR) is the most common method in the detection of rhinovirus from clinical specimens because it is much more sensitive than viral culture. A major problem in the molecular diagnosis of rhinovirus is the difficulty in differentiating rhinovirus from enterovirus. The 5′UTR is the most popular target for the detection of rhinovirus because of high sensitivity. However, RT-PCR targeting 5′UTR without sequencing cannot reliably differentiate between rhinovirus and enterovirus, because it is difficult to find primer target sites that are substantially different between rhinovirus and enterovirus but identical among all rhinovirus species. There is also some concern regarding the sensitivity in the detection of rhinovirus C. The sensitivity of detection seems to be lower for rhinovirus C than that for other rhinovirus species, which may be related to the highly variable target region.
Current commercially available multiplex PCR assays can detect rhinovirus. Since most multiplex PCR assays cannot reliably differentiate rhinovirus and enterovirus, the result is reported as rhinovirus/enterovirus. Some commercially available multiplex diagnostic platforms report rhinovirus separately from enterovirus. Anyplex II RV16 has shown good differentiation between rhinovirus and enterovirus for a limited number of rhinovirus and enterovirus species tested, but this assay has lower sensitivity than xTAG respiratory pathogen panel. Cross reactivity has been found for enterovirus 68 in the GenMark Diagnostics eSensor respiratory viral panel.
Since prolonged viral shedding can occur, the detection of rhinovirus may be related to a past infection rather than the current infection. However, in children <1 year old, it was found that prolonged viral shedding beyond 30 days is uncommon (<5%).
There is currently no approved treatment for rhinovirus infections. Pleconaril, a capsid-binding drug which prevents the interaction between virus and host cell receptor, was the first antiviral against rhinovirus which has undergone clinical trial. In two parallel randomized, double-blind, placebo-controlled trials, the duration of symptoms was significantly shorter than the placebo group if the drug is taken within the first 24 h of symptoms. However, the United States Food and Drug Administration advisory committee rejected the manufacturer\’s application. The safety concerns included menstrual disorders in women taking pleconaril and oral contraceptives, and two women became pregnant while taking pleconaril and oral contraceptives. Several capsid-binding drugs have been developed recently. WIN56921 can inhibit both rhinovirus-A16 and rhinovirus-C15, but not rhinovirus-B14.
Other potential antiviral targets are the protease proteins. Ruprintrivir is an inhibitor of the rhinovirus 3C protease. In double-blind placebo-controlled clinical trials, intranasal ruprintrivir spray was effective in both the prevention and treatment of experimental rhinovirus infection in humans. However, in subsequent natural infection studies, there was no significant reduction in viral load or disease severity.