Review of fan efficiency for meat chicken sheds

This report is all about ventilation fans (exhaust fans) used on tunnel ventilated meat chicken sheds. The report has two themes: reviewing the performance and efficiency of new fans currently available in Australia; and identifying methods to assess fans and help to identify fans that are underperforming

‘How to’ guide for measuring fan performance and efficiency in meat chicken sheds

This ‘how to’ guide provides readers with method to measure fan performance and energy efficiency of fans installed in meat chicken sheds. These methods are also useful for identifying fans that are under-performing or require maintenance. For more information about fan energy efficiency, a complementary report is available on the RIRDC website ‘Review of fan efficiency in meat chicken sheds’ (RIRDC Publication No. 15/018). A spreadsheet was also developed under this project for comparing and ranking fans against others in terms of energy efficiency, air flow and costs (‘Tunnel Ventilation Fan Comparison Spreadsheet’), and is available on the RIRDC website

‘How to’ guide for measuring fan performance and efficiency in meat chicken sheds

This ‘how to’ guide provides readers with method to measure fan performance and energy efficiency of fans installed in meat chicken sheds. These methods are also useful for identifying fans that are under-performing or require maintenance. For more information about fan energy efficiency, a complementary report is available on the RIRDC website ‘Review of fan efficiency in meat chicken sheds’ (RIRDC Publication No. 15/018). A spreadsheet was also developed under this project for comparing and ranking fans against others in terms of energy efficiency, air flow and costs (‘Tunnel Ventilation Fan Comparison Spreadsheet’), and is available on the RIRDC website

When can gravitational-wave observations distinguish between black holes and neutron stars?

Gravitational-wave observations of compact binaries have the potential to uncover the distribution of masses and angular momenta of black holes and neutron stars in the universe. The binary components' physical parameters can be inferred from their effect on the phasing of the gravitational-wave signal, but a partial degeneracy between the components' mass ratio and their angular momenta limits our ability to measure the individual component masses. At the typical signal amplitudes expected by the Advanced Laser Interferometer Gravitational-wave Observatory (signal-to-noise ratios between 10 and 20), we show that it will in many cases be difficult to distinguish whether the components are neutron stars or black holes. We identify when the masses of the binary components could be unambiguously measured outside the range of current observations: a system with a chirp mass $\mathcal{M} \le 0.871$ M$_\odot$ would unambiguously contain the smallest-mass neutron star observed, and a system with \mathcal{M} \ge 2.786 \Msun must contain a black hole. However, additional information would be needed to distinguish between a binary containing two 1.35 M$_\odot$ neutron stars and an exotic neutron-star--black-hole binary. We also identify those configurations that could be unambiguously identified as black-hole binaries, and show how the observation of an electromagnetic counterpart to a neutron-star--black-hole binary could be used to constrain the black-hole spin.Comment: 5 pages, 4 figures. Final version to be published in Ap.J.Let

Does the degree of preoperative mitral regurgitation predict survival or the need for mitral valve repair or replacement in patients with anomalous origin of the left coronary artery from the pulmonary artery?

BackgroundAnomalous origin of the left coronary artery from the pulmonary artery causes severe myocardial ischemia, global left ventricular dysfunction, and annular dilatation producing varying degrees of mitral regurgitation. Mitral regurgitation secondary to the left ventricular or papillary muscle dysfunction in infants will usually improve in the absence of ongoing ischemia. The aim of this study is to determine the influence of the degree of preoperative mitral regurgitation on the early and late outcomes of patients with anomalous origin of the left coronary artery from the pulmonary artery who underwent coronary reimplantation.MethodsTwenty-five patients underwent coronary reimplantation and 1 early patient had ligation during a 30-year period (median age, 4 months; range, 1 month to 16 years), with a median follow-up of 7 years (range, 4 months to 25 years). Before repair, 7 infants (27%) presented in extremis requiring ventilatory and inotropic support, and 17 patients (65%) presented with heart failure. Mitral regurgitation was present in all patients: trivial in 6 patients, mild in 12 patients, moderate in 5 patients, and severe in 3 patients. No patient underwent mitral valve repair or replacement at the time of anomalous origin of the left coronary artery from the pulmonary artery repair.ResultsHospital survival was 92%. Three patients underwent mitral valve repair or replacement at the mean time of 3.5 years (all with severe preoperative mitral regurgitation). The degree of mitral regurgitation gradually improved in all remaining patients with preoperative mild and moderate mitral regurgitation. Echocardiographic studies demonstrated improvement in left ventricular function in all children. None of the patients showed any evidence of supravalvar pulmonary stenosis as a result of their pulmonary artery reconstruction.ConclusionLong-term clinical outcome and left ventricular function are good despite severe left ventricular dysfunction at presentation. Mitral valve repair or replacement is generally not necessary at the time of anomalous origin of the left coronary artery from the pulmonary artery repair. Significant residual mitral regurgitation is present in some patients and can usually be managed surgically at a later date depending on its degree of severity

Anterior pericardial tracheoplasty for long-segment tracheal stenosis: Long-term outcomes

ObjectiveAlthough several techniques have been described for the treatment of tracheal stenosis, including slide tracheoplasty, tracheal autograft, rib grafting, and use of a pericardial patch, the optimal repair remains controversial because of a lack of long-term follow-up data. The purpose of this study is to examine the long-term results of anterior pericardial tracheoplasty.MethodsTo assess the long-term outcomes of patients who underwent repair of tracheal stenosis with anterior pericardial tracheoplasty, we reviewed the case histories of 26 consecutive patients (1984–present). All but 5 had long-segment tracheal stenosis with more than 10 complete tracheal rings. Twenty-one had significant cardiac disease, and 10 had their cardiac lesions repaired at the time of their tracheoplasty. The median age was 6 months (range, 2 days–25 years). All patients underwent anterior pericardial tracheoplasty through a median sternotomy during normothermic cardiopulmonary bypass. We have previously described our tracheoplasty technique. An average of 14 tracheal rings (range, 5–22) was divided anteriorly, and a patch of fresh autologous pericardium was used to enlarge the trachea to 1.5 times the predicted diameter for age and weight.ResultsThere were 3 hospital deaths (at 1, 2, and 7 months, respectively) and 2 late deaths (at 2 and 13 years postoperatively, respectively). No deaths were related to airway obstruction. Two survivors required tracheostomy postoperatively, one after formation of granulation tissue and stenosis and the other after failure to wean from mechanical ventilation. All survivors remain asymptomatic, with minimal to no evidence of airway obstruction. Median follow-up is 11 years (range, 3 months–22 years).ConclusionAnterior pericardial tracheoplasty for tracheal stenosis provides excellent results in the majority of patients at long-term follow-up

Vasoactive-ventilation-renal score reliably predicts hospital length of stay after surgery for congenital heart disease

Objectives We aimed to further validate the vasoactive-ventilation-renal score as a predictor of outcome in patients recovering from surgery for congenital heart disease. We also sought to determine the optimal time point within the early recovery period at which the vasoactive-ventilation-renal score should be measured. Methods We prospectively reviewed consecutive patients recovering from cardiac surgery within our intensive care unit between January 2015 and June 2015. The vasoactive-ventilation-renal score was calculated at 6, 12, 24, and 48 hours postoperatively as follows: vasoactive-ventilation-renal score = ventilation index + vasoactive-inotrope score + Δ creatinine [change in serum creatinine from baseline*10]. Primary outcome of interest was prolonged hospital length of stay, defined as length of stay in the upper 25%. Receiver operating characteristic curves were generated, and areas under the curve with 95% confidence intervals were calculated for all time points. Multivariable logistic regression modeling also was performed. Results We reviewed 164 patients with a median age of 9.25 months (interquartile range, 2.6-58 months). Median length of stay was 8 days (interquartile range, 5-17.5 days). The area under the curve value for the vasoactive-ventilation-renal score as a predictor of prolonged length of stay (>17.5 days) was greatest at 12 hours postoperatively (area under the curve = 0.93; 95% confidence interval, 0.89-0.97). On multivariable regression analysis, after adjustment for potential confounders, the 12-hour vasoactive-ventilation-renal score remained a strong predictor of prolonged hospital length of stay (odds ratio, 1.15; 95% confidence interval, 1.10-1.20). Conclusions In a heterogeneous population of patients undergoing surgery for congenital heart disease, the novel vasoactive-ventilation-renal score calculated in the early postoperative recovery period can be a strong predictor of prolonged hospital length of stay

On choosing the start time of binary black hole ringdown

The final stage of a binary black hole merger is ringdown, in which the system is described by a Kerr black hole with quasinormal mode perturbations. It is far from straightforward to identify the time at which the ringdown begins. Yet determining this time is important for precision tests of the general theory of relativity that compare an observed signal with quasinormal mode descriptions of the ringdown, such as tests of the no-hair theorem. We present an algorithmic method to analyze the choice of ringdown start time in the observed waveform. This method is based on determining how close the strong field is to a Kerr black hole (Kerrness). Using numerical relativity simulations, we characterize the Kerrness of the strong-field region close to the black hole using a set of local, gauge-invariant geometric and algebraic conditions that measure local isometry to Kerr. We produce a map that associates each time in the gravitational waveform with a value of each of these Kerrness measures; this map is produced by following outgoing null characteristics from the strong and near-field regions to the wave zone. We perform this analysis on a numerical relativity simulation with parameters consistent with GW150914- the first gravitational wave detection. We find that the choice of ringdown start time of $3\,\mathrm{ms}$ after merger used in the GW150914 study to test general relativity corresponds to a high dimensionless perturbation amplitude of $\sim 7.5 \times 10^{-3}$ in the strong-field region. This suggests that in higher signal-to-noise detections, one would need to start analyzing the signal at a later time for studies that depend on the validity of black hole perturbation theory.Comment: 23+4 pages, 22 figure

Shockwaves in converging geometries

Plate impact experiments are a powerful tool in equation of state (EOS) development, but are inherently limited by the range of impact velocities accessible to the gun. In an effort to dramatically increase the range of pressures which can be studied with available impact velocities, a new experimental technique is being developed. The possibility of using a confined converging target to focus Shockwaves and produce a large amplitude pressure pulse is examined. When the planar shock resulting from impact enters the converging target the impedance mismatch at the boundary of the confinement produces reflected Mach waves and the subsequent wave interactions produce a diffraction cycle resulting in increases in the shock strength with each cycle. Since this configuration is limited to relatively low impedance targets, a second technique is proposed in which the target is two concentric cylinders designed such that the inner cylinder will have a lower shock velocity than the much larger shock velocity in the outer cylinder. The resulting dispersion in the wave front creates converging shocks, which will interact and eventually result in a steady Mach configuration with an increase in pressure in the Mach disk. Numerical simulations indicate a significant increase in pressure for both methods and show promise for the proposed concepts