Imaging acoustic standing waves in the presence of flowing gas.

A method for imaging an acoustic standing wave in the presence of flowing gas is described. The optical power at the acoustic frequency in each pixel of a series of high-speed transmission electronic speckle pattern interferograms is used to map the steady-state pressure variations of an acoustic standing wave. The utility of the process is demonstrated by imaging the standing wave inside a transparent organ pipe.

Visualization of exhaled breath by transmission electronic speckle pattern interferometry.

A method for visualizing the air flow from the mouths of vocalists and wind musical instruments is presented. The method is based on a modification of electronic speckle pattern interferometry that incorporates the interference of a transmitted object beam rather than the standard method using a reflected object beam. The resulting whole-field real-time images are a valuable resource for both scientific and pedagogical use.

Do "brassy" sounding musical instruments need increased safe distancing requirements to minimize the spread of COVID-19?

Brass wind instruments with long sections of cylindrical pipe, such as trumpets and trombones, sound "brassy" when played at a fortissimo level due to the generation of a shock front in the instrument. It has been suggested that these shock fronts may increase the spread of COVID-19 by propelling respiratory particles containing the SARS-CoV-2 virus several meters due to particle entrainment in the low pressure area behind the shocks. To determine the likelihood of this occurring, fluorescent particles, ranging in size from 10-50 µm, were dropped into the shock regions produced by a trombone, a trumpet, and a shock tube. Preliminary results indicate that propagation of small airborne particles by the shock fronts radiating from brass wind instruments is unlikely.

Structural contributions to phantom partial generation in the piano.

The results of experiments designed to determine the origin of the anomalous frequency components in the sound of the piano commonly referred to as phantom partials are reported. It is shown that these overtones, which occur at the sum and difference frequencies associated with the transverse string motion, are produced by nonlinearities in both the string and the wooden components of the piano. However, the contribution from the string is significantly smaller than the contributions from other components.

The production of phantom partials due to nonlinearities in the structural components of the piano.

Phantom partials are anomalous overtones in the spectrum of the piano sound that occur at sum and difference frequencies of the natural overtones of the string. Although they are commonly assumed to be produced by forced longitudinal waves in the string, analysis of the sound of a piano produced by mechanically vibrating the soundboard while all the strings are damped indicates that phantom partials can occur in the absence of string motion. The magnitude of the effect leads to the conclusion that nonlinearity in the non-string components may be responsible for some of the power in the phantom partials.

Risk of gestational hypertension and preeclampsia in women who discontinued or continued antidepressant medication use during pregnancy.

PURPOSE: This study aimed to examine the association between discontinued and continued use of antidepressants and risk for gestational hypertension (GH) and preeclampsia (PE). METHODS: Data from the MotherToBaby pregnancy studies from 2004 to 2014 were analyzed to compare women who discontinued antidepressant use ˂20 weeks of gestation (discontinuers) and women who continued antidepressant use ≥20 weeks of gestation (continuers) to non-users for risk of GH (blood pressure ≥140/90 mmHg on two or more occasions at ≥20 weeks of gestation) and PE (GH with proteinuria). Maternal data, including exposures and study outcomes, were collected through multiple phone interviews. Medical records were used to validate outcomes. Odds ratios (ORs) and 95 % confidence intervals were estimated using logistic regression. Risk for GH and PE were also assessed within antidepressant drug classes. RESULTS: Data from 3471 women were analyzed. Continuers were significantly at risk for GH (adjusted odds ratios (aOR) 1.83; 95 % CI 1.05, 3.21) after adjustment. Analyses by drug class showed that continued use of serotonin-norepinephrine reuptake inhibitors (SNRI) increased risk for GH; however, of the 21 women who continued to use SNRI, only 3 developed GH. Continuers who used two or more antidepressant drug classes had increased risk for PE. Selective serotonin reuptake inhibitors or other antidepressant use was not associated with increased risk for GH or PE. No significant associations with PE or GH were found for discontinuers. CONCLUSIONS: Results suggest that women who continued to use antidepressants in the second half of pregnancy are at risk for GH and PE. No significant association was found among discontinuers.

Changes in Postpartum Insulin Requirements for Patients with Well-Controlled Type 1 Diabetes.

Objective To compare postpartum with preconception insulin doses in well-controlled (HbA1c ≤ 7.4%) type 1 diabetes mellitus (T1DM) and to characterize differences in postpartum insulin dosing based on infant feeding. Study Design The primary outcome in this retrospective cohort was the change in total daily insulin (TDI) from preconception to postpartum. Insulin administration (continuous subcutaneous insulin infusion [CSII] vs. multiple daily injections [MDI]), HbA1c, body mass index (BMI), and infant feeding were abstracted. Results We identified 44 women with T1DM and HbA1c ≤ 7.4%. Preconception mean BMI was 24.6 ± 3.6 kg/m(2) and median (interquartile range [IQR]) HbA1c was 6.4 (6.0-6.9)%. Of these, 73% used CSII and 27% used MDI. Additionally, 80% of patients reported exclusive breastfeeding, 7% were exclusively formula feeding, and 13% used both breast milk and formula. Median (IQR) preconception TDI was 0.64 (0.49-0.69) U/kg/day, and postpartum: 0.39 (0.30-0.50) U/kg/day. Postpartum TDI was 34% lower than preconception TDI (p = 0.02). There was no difference in the postpartum TDI in patients who were breast versus formula feeding or when comparing CSII with MDI. Conclusion There was a significant decrease in the TDI required postpartum when compared with preconception. Dosages do not seem to be impacted by administration route or breastfeeding. These findings warrant consideration when dosing postpartum insulin in patients with T1DM.

Early Second Trimester Weight Gain in Obese Women Predicts Excessive Gestational Weight Gain in Pregnancy.

OBJECTIVE: To assess gestational weight gain (GWG) in obese women to determine an inflection point that identifies women at risk for excessive weight gain. STUDY DESIGN: This is an observational prospective cohort study of pregnancies managed through the UC San Diego Maternal Weight and Wellness Program from 2011 to 2014. The primary outcome was total gestational weight gain. GWG was categorized as inadequate (<11 pounds), adequate (11-20 pounds), and excessive (>20 pounds) based on Institute of Medicine (IOM) recommendations. Other outcomes were GWG by trimester and postpartum weight retention. Bivariate and multivariate analyses were used to assess factors associated with GWG. RESULTS: Ninety-five patients had a mean prepregnancy body mass index (BMI) of 41.9 ± 8.9 kg/m(2) and a net weight gain of 21.9 ± 19 pounds. First trimester GWG was -0.3 ± 4.9 pounds, second trimester was 10.4 ± 10.8 pounds, and third trimester was 11.4 ± 8.5 pounds for all participants. Women who exceeded IOM recommendations accelerated weight gain at 12-14 weeks and gained a majority of weight during the second trimester. Weight gain of more than two pounds at 12-14 weeks had a 96 % positive predictive value (95 % CI 79-99) for excessive GWG. Postpartum women with excessive GWG retained more weight than those with inadequate GWG (10.7 ± 15.6 pounds compared with -13.6 ± 10.9 pounds, P < 0.001). On multiple linear regression GWG by trimester was predictive of total GWG with second and third trimester GWG having the greatest effect on total GWG. Prepregnancy BMI and gestational diabetes were not predictors of total GWG. CONCLUSIONS: Obese women at risk for excessive GWG may be identified as early as 12-14 weeks and gain most weight during the second trimester. GWG less than 11 pounds resulted in significant postpartum weight loss among obese women.

Continuous Subcutaneous Insulin Infusion versus Multiple Daily Injections of Insulin for the Management of Type 1 Diabetes Mellitus in Pregnancy: Association with Neonatal Chemical Hypoglycemia.

OBJECTIVE: We hypothesized that patients with type 1 diabetes mellitus (T1DM) who were managed during their pregnancy with a continuous subcutaneous insulin infusion (CSII) would have a lower incidence of neonatal hypoglycemia (NH) than patients managed with multiple daily injections (MDI) of insulin. STUDY DESIGN: This was a retrospective cohort of 95 women with T1DM who delivered singleton, term neonates between 2007 and 2014. The primary outcome was incidence of NH (capillary plasma glucose ≤ 45 mg/dL) in the first 24 hours after birth. RESULTS: The incidence of NH was 66.0% (62/95). The NH rate was significantly higher in women managed with CSII versus MDI (62 vs. 38%, p = 0.024). Neonates with NH had a higher birth weight (3,867 ± 658 vs. 3,414 ± 619 g, p = 0.002). When analyzing intrapartum glucose management, mothers of neonates with NH had significantly less time managed on an insulin infusion (median interquartile range 7 [3.5-30.5] vs. 17.5 [2.0-17.5] hours, p = 0.014). In multivariable analysis, only maternal body mass index (BMI) (p = 0.035) and time on an insulin infusion (p = 0.043) were significantly associated with NH. CONCLUSION: In our population of patients with T1DM, CSII was more prevalent in the NH group; however, when controlling for other factors, intrapartum glucose management and early maternal BMI were the only variables associated with NH.

Coupling of transverse and longitudinal waves in piano strings.

The existence of longitudinal waves in vibrating piano strings has been previously established, as has their importance in producing the characteristic sound of the piano. Modeling of the coupling between the transverse and longitudinal motion of strings indicates that the amplitude of the longitudinal waves are quadratically related to the transverse displacement of the string, however, experimental verification of this relationship is lacking. In the work reported here this relationship is tested by driving the transverse motion of a piano string at only two frequencies, which simplifies the task of unambiguously identifying the constituent signals. The results indicate that the generally accepted relationship between the transverse motion and the longitudinal motion is valid. It is further shown that this dependence on transverse displacement is a good approximation when a string is excited by the impact of the hammer during normal play.

Axial vibrations of brass wind instrument bells and their acoustical influence: Experiments.

It has recently been proposed that the effects of structural vibrations on the radiated sound of brass wind instruments may be attributable to axial modes of vibration with mode shapes that contain no radial nodes [Kausel, Chatziioannou, Moore, Gorman, and Rokni, J. Acoust. Soc. Am. 137, 3149-3162 (2015)]. Results of experiments are reported that support this theory. Mechanical measurements of a trumpet bell demonstrate that these axial modes do exist in brass wind instruments. The quality factor of the mechanical resonances can be on the order of 10 or less, making them broad enough to encompass the frequency range of previously reported effects attributed to bell vibrations. Measurements of the input impedance show that damping bell vibrations can result in impedance changes of up to 5%, in agreement with theory. Measurements of the acoustic transfer function demonstrate that the axial vibrations couple to the internal sound field as proposed, resulting in changes in the transfer function of approximately 1 dB. In agreement with theory, a change in the sign of the effect is observed at the frequency of the structural resonance.

Axial vibrations of brass wind instrument bells and their acoustical influence: Theory and simulations.

Previous work has demonstrated that structural vibrations of brass wind instruments can audibly affect the radiated sound. Furthermore, these broadband effects are not explainable by assuming perfect coincidence of the frequency of elliptical structural modes with air column resonances. In this work a mechanism is proposed that has the potential to explain the broadband influences of structural vibrations on acoustical characteristics such as input impedance, transfer function, and radiated sound. The proposed mechanism involves the coupling of axial bell vibrations to the internal air column. The acoustical effects of such axial bell vibrations have been studied by extending an existing transmission line model to include the effects of a parasitic flow into vibrating walls, as well as distributed sound pressure sources due to periodic volume fluctuations in a duct with oscillating boundaries. The magnitude of these influences in typical trumpet bells, as well as in a complete instrument with an unbraced loop, has been studied theoretically. The model results in predictions of input impedance and acoustical transfer function differences that are approximately 1 dB for straight instruments and significantly higher when coiled tubes are involved or when very thin brass is used.

Normal modes of a small gamelan gong.

Studies have been made of the normal modes of a 20.7 cm diameter steel gamelan gong. A finite-element model has been constructed and its predictions for normal modes compared with experimental results obtained using electronic speckle pattern interferometry. Agreement was reasonable in view of the lack of precision in the manufacture of the instrument. The results agree with expectations for an axially symmetric system subject to small symmetry breaking. The extent to which the results obey Chladni's law is discussed. Comparison with vibrational and acoustical spectra enabled the identification of the small number of modes responsible for the sound output when played normally. Evidence of non-linear behavior was found, mainly in the form of subharmonics of true modes. Experiments using scanning laser Doppler vibrometry gave satisfactory agreement with the other methods.

A midwifery-led in-hospital birth center within an academic medical center: successes and challenges.

The University of California San Diego Community Women's Health Program (CWHP) has emerged as a successful and sustainable coexistence model of women's healthcare. The cornerstone of this midwifery practice is California's only in-hospital birth center. Located within the medical center, this unique and physically separate birth center has been the site for more than 4000 births. With 10% cesarean delivery and 98% breast-feeding rates, it is an exceptional example of low-intervention care. Integrating this previously freestanding birth center into an academic center has brought trials of mistrust and ineffectual communication. Education, consistent leadership, and development of multidisciplinary guidelines aided in overcoming these challenges. This collaborative model provides a structure in which residents learn to be respectful consultants and appreciate differences in medical practice. The CWHP and its Birth Center illustrates that through persistence and flexibility a collaborative model of maternity services can flourish and not only positively influence new families but also future generations of providers.

The behavior of standing waves near the end of an open pipe with low mean flow.

The acoustic standing wave near the end of an open pipe is investigated using spectrally analyzed high-speed transmission electronic speckle pattern interferometry. It is shown that the standing wave extends beyond the open end of the pipe and the amplitude decays exponentially with distance from the end. Additionally, a pressure node is observed near the end of the pipe in a position that is not spatially periodic with the other nodes in the standing wave. A sinusoidal fit to the amplitude of the standing wave inside the pipe indicates that the end correction is well predicted by current theory.

Management of diabetes in pregnancy.

The link between diabetes and poor pregnancy outcomes is well established. As in the non-pregnant population, pregnant women with diabetes can experience profound effects on multiple maternal organ systems. In the fetus, morbidities arising from exposure to diabetes in utero include not only increased congenital anomalies, fetal overgrowth, and stillbirth, but metabolic abnormalities that appear to carry on into early life, adolescence, and beyond. This article emphasizes the newest guidelines for diabetes screening in pregnancy while reviewing their potential impact on maternal and neonatal complications that arise in the setting of hyperglycemia in pregnancy.

Insulin pump dosing across gestation in women with well-controlled type 1 diabetes mellitus.

OBJECTIVE: We hypothesized that bolus and basal insulin doses in women with type 1 diabetes mellitus who use insulin pumps would increase 2-fold to maintain hemoglobin A1c <6.5% across gestation. STUDY DESIGN: This was a retrospective study of 9 women with type 1 diabetes mellitus with preconceptional hemoglobin A1c ≤ 7.4% using insulin pumps. The primary outcome was absolute and percentage change of basal and bolus insulin from preconception to delivery. RESULTS: Total daily dose of insulin increased from 33.3 ± 7.8 U/d before conception to 93.5 ± 27.9 U/d at delivery. Basal rates rose modestly (50% increase, from 16.2 ± 6.5 U/d to 24.0 ± 9 U/d); bolus insulin doses quadrupled from 17.1 ± 6.1 U/d to 69.5 ± 29.6 U/d (P = .0001). Bolus insulin increased from approximately 50% of total daily dose of insulin before conception to 75% of total daily dose of insulin at 36 weeks' gestation. CONCLUSION: In well-controlled type 1 diabetes mellitus, insulin requirements increased 3-fold from before conception to 36 weeks' gestation. Most of this requirement was attributed to an increase in bolus rates that are required for control with meals.

Preoperative intravascular balloon catheters and surgical outcomes in pregnancies complicated by placenta accreta: a management paradox.

OBJECTIVE: The objective of the study was to compare outcomes between patients who did and did not receive preoperative uterine artery balloon catheters in the setting placenta accreta. STUDY DESIGN: This was a retrospective case-control study of patients with placenta accreta from 1990 to 2011. RESULTS: Records from 117 patients with pathology-proven accreta were reviewed. Fifty-nine patients (50.4%) had uterine artery balloons (UABs) placed preoperatively. The mean estimated blood loss (EBL) was lower (2165 mL vs 2837 mL; P = .02) for the group that had UABs compared with the group that did not. There were more cases with an EBL greater than 2500 mL and massive transfusions of packed red blood cells (>6 units) in the group that did not have UABs. Percreta was diagnosed more often on final pathology in the group with UABs. Surgical times did not differ between the 2 groups. Two patients (3.3%) had complications related to the UABs. CONCLUSION: Preoperative placement of UABs is relatively safe and is associated with a reduced EBL and fewer massive transfusions compared with a group without UABs.

Predicting adverse outcomes following trauma in pregnancy.

OBJECTIVE: To identify variables predicting adverse maternal or fetal outcome following trauma and to establish a composite morbidity model to predict poor obstetrical outcomes. STUDY DESIGN: A retrospective study of pregnant women following major and minor trauma from a single institution from 1985-2007 was performed. Abstracted data included maternal demographics, Injury Severity Score (ISS), laboratory and radiology studies,fetal monitoring and delivery information. Linear algorithm and logistic regression analysis estimated predictors of adverse obstetrical outcomes. Accuracy of composite morbidity models was tested using receiver operating characteristic. RESULTS: A total of 292 pregnant trauma patients were analyzed. Forty-eight (13%) women had an ISS > or = 10. Adverse pregnancy outcomes occurred in 71 patients (24%). Predictors of poor outcomes included trauma in the third trimester, length of stay (LOS) >2 days, abdominal trauma, ISS >2 and a positive Kleihauer-Betke (KB) test. Composite morbidity models resulted in sensitivity and specificity ranging from 54.3% to 70.4% and 59.5% to 87.5%, respectively. CONCLUSION: Predicting adverse perinatal outcomes following major trauma remains challenging. Composite morbidity models using a combination of third trimester trauma, LOS > 2 days, abdominal trauma, ISS >2 or a positive KB test improves identification of those at risk for adverse perinatal outcomes.

A simple and inexpensive optical technique to help students visualize mode shapes.

An imaging technique is introduced that is suitable for visualizing the mode shapes of vibrating structures in an educational setting. The method produces images similar to those obtained using electronic speckle pattern interferometry (ESPI), but it can be implemented for less than 1/10 the cost of a commercial ESPI system, and the apparatus is simple enough that it can be constructed by undergraduate students. This technique allows for real-time visualization of the normal modes and deflection shapes of harmonically vibrating structures, including those with shapes that make generating Chladni patterns with sand or powder impossible. The theory of operation and construction details are discussed.