Tapered transmission line technique based graded matching layers for thickness mode piezoelectric transducers

Conventionally, in order to acoustically match thickness mode piezoelectric transducers to a low acoustic impedance load medium, multiple quarter wavelength (QW) matching layers are employed at the front face of the device. Typically a number of layers, 2-4 in number, are employed resulting in discrete impedance steps within the acoustic matching scheme. This can result in impedance matching with limited bandwidth characteristics. This paper investigates the application of tapered transmission line filter theory to implement a graded impedance profile, through the thickness of the matching layer scheme, to solve the impedance mismatch problem whilst accounting for enhanced transducer sensitivity and bandwidth

A pop-up float recovery system for coastal oceanographic tripods

The recovery package described here was used as the primary retrieval system to recover tripod instrument platforms from a depth of 90 meters. The device uses dual in-line burn wires, one of which is acoustically commanded from the surface ship. The other is set to release by back-up timer, ensuring recovery in the event of a poor acoustic command channel. The burn wire activates spring loaded cam latches which release the float package and pull a ~ inch Dacron line to the surface. The float package is recovered and the line is used to winch the tripod to the surface for recovery by the ship's crane. Major benefits of the system are reliability, low cost, light weight, and use of many off-the-shelf components. The float package provides 50 pounds of buoyancy and is fabricated using commercial fish trawl net floats. The retrieval line container is separate from the float assembly, and is fabricated from plastic storage containers. The line is coiled and restricted to prevent unpackaging due to waves or current action. The system described here is not appropriate in areas of high current or great depth due to drag and dead weight of the lift line.Funding was provided by the Office of Naval Research under contract No. N00014-89.J-1058

Two distinct Do-Not-Resuscitate protocols leaving less to the imagination: an observational study using propensity score matching

BACKGROUND: Do-Not-Resuscitate (DNR) patients tend to receive less medical care after the order is written. To provide a clearer approach, the Ohio Department of Health adopted the Do-Not-Resuscitate law in 1998, indicating two distinct protocols of DNR orders that allow DNR patients to choose the medical care: DNR Comfort Care (DNRCC), implying DNRCC patients receive only comfort care after the order is written; and DNR Comfort Care-Arrest (DNRCC-Arrest), implying that DNRCC-Arrest patients are eligible to receive aggressive interventions until cardiac or respiratory arrest. The aim of this study was to examine the medical care provided to patients with these two distinct protocols of DNR orders. METHODS: Data were collected from August 2002 to December 2005 at a medical intensive care unit in a university-affiliated teaching hospital. In total, 188 DNRCC-Arrest patients, 88 DNRCC patients, and 2,051 non-DNR patients were included. Propensity score matching using multivariate logistic regression was used to balance the confounding variables between the 188 DNRCC-Arrest and 2,051 non-DNR patients, and between the 88 DNRCC and 2,051 non-DNR patients. The daily cost of intensive care unit (ICU) stay, the daily cost of hospital stay, the daily discretionary cost of ICU stay, six aggressive interventions, and three comfort care measures were used to indicate the medical care patients received. The association of each continuous variable and categorical variable with having a DNR order written was analyzed using Student’s t-test and the χ(2) test, respectively. The six aggressive interventions and three comfort care measures performed before and after the order was initiated were compared using McNemar’s test. RESULTS: DNRCC patients received significantly fewer aggressive interventions and more comfort care after the order was initiated. By contrast, for DNRCC-Arrest patients, the six aggressive interventions provided were not significantly decreased, but the three comfort care measures were significantly increased after the order was initiated. In addition, the three medical costs were not significantly different between DNRCC and non-DNR patients, or between DNRCC-Arrest and non-DNR patients. CONCLUSIONS: When medical care provided to DNR patients is clearly indicated, healthcare professionals will provide the medical care determined by patient/surrogate decision-makers and healthcare professionals, rather than blindly decreasing medical care. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12916-014-0146-x) contains supplementary material, which is available to authorized users

Oceanic forcing of interannual and multidecadal climate variability in the southwestern Indian Ocean: evidence from a 160 year coral isotopic record (La Réunion, 55°E, 21°S)

We have developed a new 163-year bimonthly coral δ18O record from La Réunion (55°E, 21°S). Interannual variations in coral δ18O are coherent with the Southern Oscillation Index but not with regional sea surface temperature (SST). Correlations with the global SST field suggest more negative seawater δ18O (δ18Osw) during La Niña years. We propose that the signal results from changes in the strength of the South Equatorial Current and the Indonesian throughflow, which carry low salinity water. Multidecadal variations in coral δ18O are coherent with regional SST, but the sign is of opposite sense as expected from the coral δ18O-temperature relationship. This requires multidecadal changes in salinity large enough to overprint the SST contribution in the coral δ18O record. Our results suggest that multidecadal salinity variations result from modulations in the transport of the South Equatorial Current, which varies in response to the surface wind field and/or the Indonesian throughflow

A Station-Based Southern Annular Mode Index from 1884 to 2005

Atmospheric pressure observations from the Southern Hemisphere are used to estimate monthly and annually averaged indexes of the southern annular mode (SAM) back to 1884. This analysis groups all relevant observations in the following four regions: one for Antarctica and three in the subtropical zone. Continuous surface pressure observations are available at a number of locations in the subtropical regions since the end of the nineteenth century. However, year-round observations in the subpolar region near the Antarctic continent began only during the 1940-60 period. The shorter Antarctic records seriously compromise the length of a traditionally estimated SAM index. To improve the situation "proxy'' estimates of Antarctic sea level pressure anomalies are provided based on the concept of atmospheric mass conservation poleward of 208S. This allows deriving a longer SAM index back to 1884. Several aspects of the new record, its statistical properties, seasonal trends, and the regional pressure anomaly correlations, are presented

Constitutions and Bills of Rights:Invigorating or Placating Democracy?

Champions of constitutions and bills of rights regularly portray them as possessing significant, sometimes mysterious, powers. One characterisation is that newly implemented constitutions may invigorate a democracy, particularly at the ballot box. This paper challenges that notion by scrutinising a relatively unexplored area of constitutional performance: voter turnout. In particular, it examines a number of jurisdictions that have recently implemented constitutions and bill of rights, finding that in many of them, voter turnout decreased after passage, sometimes significantly. As the argument for a codified British constitution endures, the findings of this paper provide provisional evidence that those advocating for such a device should be wary of touting its potentially invigorating democratic effects. Ultimately, however, the paper calls for more research into the area of constitutions and democratic performance, such as voter turnout

Risk of placenta previa in second birth after first birth cesarean section: a population-based study and meta-analysis.

OBJECTIVE: To compare the risk of placenta previa at second birth among women who had a cesarean section (CS) at first birth with women who delivered vaginally. METHODS: Retrospective cohort study of 399,674 women who gave birth to a singleton first and second baby between April 2000 and February 2009 in England. Multiple logistic regression was used to adjust the estimates for maternal age, ethnicity, deprivation, placenta previa at first birth, inter-birth interval and pregnancy complications. In addition, we conducted a meta-analysis of the reported results in peer-reviewed articles since 1980. RESULTS: The rate of placenta previa at second birth for women with vaginal first births was 4.4 per 1000 births, compared to 8.7 per 1000 births for women with CS at first birth. After adjustment, CS at first birth remained associated with an increased risk of placenta previa (odds ratio = 1.60; 95% CI 1.44 to 1.76). In the meta-analysis of 37 previously published studies from 21 countries, the overall pooled random effects odds ratio was 2.20 (95% CI 1.96-2.46). Our results from the current study is consistent with those of the meta-analysis as the pooled odds ratio for the six population-based cohort studies that analyzed second births only was 1.51 (95% CI 1.39-1.65). CONCLUSIONS: There is an increased risk of placenta previa in the subsequent pregnancy after CS delivery at first birth, but the risk is lower than previously estimated. Given the placenta previa rate in England and the adjusted effect of previous CS, 359 deliveries by CS at first birth would result in one additional case of placenta previa in the next pregnancy.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are