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Icterus, a phenomenon caused by bilirubin elevation in the blood, is a common endogenous interference in chemistry testing, occurring either spectrally or through chemical reactivity with assay reagents. Often, laboratories have few options other than to dilute or reject samples exceeding icteric thresholds. However, recent studies have optimized in vitro photoisomerization of bilirubin to a 17-minute bilirubin half-life using 500 nm light at 37 °C. Using an enzymatic creatinine assay as a model, due to its prevalence in routine laboratory testing and susceptibility to icteric interference, our study explores the usage of in vitro photoisomerization by replicating these conditions in a device, the Bilibox, as means of resolving icterus in laboratory testing. Left-over icteric and non-icteric clinical samples, collected by lithium heparin vacutainer (n = 10), were analyzed for baseline creatinine, diluted creatinine (1:4 0.9 % NaCl), total bilirubin, direct bilirubin, and hemolysis, icterus and lipemia (HIL) indices. Samples were then placed in the Bilibox in two intervals of 30 min with repeat measurements of the aforementioned analytes. On average, icteric-index, total bilirubin (TBIL), and direct bilirubin (DBIL) decreased by 33.5, 39.1 and 39.9 % respectively following 30 min of Bilibox treatment; and by 47.6 %, 63.7 % and 59.8 % following 60 min. The average percent difference between the pre-exposure diluted and undiluted creatinine was 5.8 %, demonstrating the icterus interference. Following Bilibox treatment, the difference between undiluted (post-exposure) and diluted (pre-exposure) creatinine decreased to 0.02 % (p = 0.0232) and 2.2 % (p = 0.0021) at 30 and 60 min of treatment respectively, demonstrating resolution of interference. Consequently, photoisomerization can be utilized as an additional and reasonably quick method for resolving icterus when dilutional methods cannot be applied.

La movilidad urbana en la ciudad de Guayaquil y en la interconexión con los cantones aledaños ha crecido de manera significativa debido al incremento poblacional y a las actividades que se realizan en los diferentes polos de desarrollo de la ciudad, lo que demanda recurrir a otros sistemas de transporte como es el fluvial siendo este una alternativa para el logro de movilización masiva hacia los cantones Durán y Samborondón.

Urine drug testing (UDT) monitors prescription compliance and/or drug abuse. However, interpretation of UDT results obtained by liquid chromatography-tandem mass spectrometry (LC-MS-MS) can be complicated by the presence of drug impurities that are detected by highly sensitive methods. Hydrocodone is a drug impurity that can be found as high as 1% in oxycodone pills.We evaluated the frequency and concentration of hydrocodone and its metabolite, hydromorphone, in patients taking oxycodone to check if the ratio of hydrocodone or hydromorphone to oxycodone could distinguish between oxycodone only use from those consuming additional opiates.We correlated LC-MS/MS results with medication records of 319 patients with positive oxycodone results over 7 months (4/2021-11/2021).Fifteen of 319 patients with positive oxycodone results were taking oxycodone only. For these 15 patients, the mean ratio of hydrocodone to oxycodone was 0.57% (range 0.05%-3.35%), and the mean ratio of hydromorphone to oxycodone was 0.81% (range 0.18-3.51%).Hydrocodone and/or hydromorphone are detectable in patients taking only oxycodone and can likely be identified as an impurity if their calculated ratio to oxycodone is1%. Further validation of the ratios in a larger sample size is recommended.

In 2017, the American College of Gastroenterology (ACG) and the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition published clinical guidelines recommending the use of alanine aminotransferase (ALT) upper reference limits (URL) of 33, 25, 26, and 22 U/l for men, women, boys, and girls, respectively. This was opposed by laboratory experts who advocated for the use of higher URL of 59, 41, 33, and 24 U/l instead. We suspected that the variable inclusion of individuals who consumed alcohol to be a major contributing source of URL variability and debate.Outpatient ALT data (n = 7379) were collected from unique individuals ≥13 y with BMIs of ≥19 and ≤25. A total of 222 (3%) were excluded due to suspected liver disease. Patients were split into a pediatric group (age 13-17 y), an alcohol-restricted adult group (age 18-20 y), and adults with access to alcohol by decade (i.e., age 21-29, 30-39, 40-49, 50-59, 60-69, 70-79, and ≥ 80 y). All ALT values were measured on Roche Cobas 8000 with pyridoxal phosphate and traceable to the IFCC-reference measurement procedure.We derived URL similar to CALIPER for our pediatric population, but closer to ACG-proposed URL in our alcohol-restricted adult group. The URL increased significantly in men and women for all other age groups.The discrepancy in ALT URL in clinical laboratories may be attributable in part due to the variable inclusion of individuals who recently consumed alcohol in local population derivation studies.

Laboratorians are left unguided by a paucity of literature on how to configure rules for the detection of intravenous (IV) fluid contamination in blood samples. We designed a study to determine the in vitro effect of increasing blood sample contamination from commonly used crystalloid solutions and how these observations can guide the derivation of multianalyte delta checks to detect such pre-analytical error.In this study, we spiked increasing volumes of commonly used IV fluids (normal saline (NS), lactated ringers (LR), and 5% dextrose) into blood samples that were collected from healthy donors. Routine chemistry analytes were measured and compared between neat and contrived samples. From these observations, we derived several permutations of multianalyte delta checks using the basic metabolic panel framework and evaluated rule performance using retrospective data.The wet chemistry experiments showed that increasing the volume of crystalloid solution contamination significantly changed several analytes. Subsequently derived multianalyte delta check procedures were applied to retrospective data. For all IV fluids tested, smaller magnitudes of analyte change resulted in more samples flagged.Multianalyte delta checks may be an effective method for the detection of IV fluid contamination.

Objective To perform validation of plasma sodium on blood gas analyzers to reflexively correct erroneous measurements by ion-selective electrodes (ISEs). Methods We compared remnant specimens of whole blood and plasma collected by lithium heparin vacutainer with normal protein concentrations and no lipemia. Whole-blood specimens were tested for sodium concentration on the ABL800 Flex blood gas analyzer, followed by centrifugation for plasma separation, and repeat sodium determination on an aliquot of the plasma only. Also, plasma specimens were analyzed by indirect ISE on the Cobas 8000 series and by direct ISE on the ABL800 Flex for instrument comparison. Results Plasma aliquots yielded comparable results to the parent whole-blood specimen, with an average change of −1.33 mmol/L (R2 = 0.9727). Comparison of indirect ISE to direct ISE similarly yielded comparable results, with an average change of + 0.8 mmol/L (R2 = 0.9016). Conclusion Plasma is a valid specimen matrix for use on blood gas analyzers for sodium determination, eliminating the need for re-collection of whole-blood specimens from patients with pseudohyponatremia.

AimsPneumatic tube systems (PTSs) are critical for modern hospital operations, allowing for rapid sample transport. Despite widespread use, PTSs can compromise specimen integrity and affect laboratory values. Our objective was to prove that rapid serum clot tubes (RST) provide protective benefits over plasma during PTS transport and can be a practical solution for certain PTS routes.MethodsIn this study, we compared the effects of PTS transport on cell lysis indicators: h-index, lactate dehydrogenase (LDH) and potassium (K+), in RST versus lithium heparin gel separator tubes using 10 volunteers.ResultsIn comparison with plasma, RST showed a median reduction in PTS-induced haemolysis of 80.4% (p=0.0049), with a reduction in post-PTS median LDH concentration (49.7%, p=0.04) and K+ concentration (50.0%, p=0.0273).ConclusionThis study demonstrates RST tubes can significantly reduce PTS-induced haemolysis and can be recommended for poor PTS routes.

Background Heart-type fatty acid binding protein (H-FABP), a low molecular weight protein found primarily in myocardial tissue, has been identified as a potential biomarker in the detection of acute coronary syndrome and acute kidney injury. To further investigate clinical utility, we sought to establish an upper reference limit (URL) of H-FABP within a healthy U.S. population. Methods Serum samples of healthy donors were acquired from the AACC Universal Sample Bank. We analyzed 355 samples for H-FABP concentration using the Randox Laboratories immunoturbidimetric assay on the Roche Cobas 8000 series analyzer. Results The final sample population consisted of individuals aged 18–74 y, with 170 males and 185 females. The distribution of the population exhibited a strong positive skew, affecting outlier analysis and URL determination. The 97.5th-percentile URL was found to be 7.4 ng/ml (95% CI: 6.3–9.2), while the 99th-percentile URL was 12.1 ng/ml (8.6–14.9). Conclusion As the URL for H-FABP is highly affected by population distribution and outlier removal, final determination for an assay cutoff should be made in the context of clinical utility, either as a standalone assay or in conjunction with other biomarkers, and the desired clinical sensitivity and specificity.

Background Pseudohyponatremia describes an artifactual decrease in plasma sodium result in samples with high proteins and/or lipids when measured by an indirect ion-selective electrode (ISE) method. We suspected that Intralipid®-based lipemia cutoffs are inappropriate for detecting interfering lipids in human samples and a major contributing factor to the existence of pseudohyponatremia. Methods We evaluated 2 approaches to derive a lipemia cutoff for sodium, one in which patient plasma samples were pooled and spiked to simulate hyperlipidemia using Intralipid® (commonly used approach by in-vitro diagnostics manufacturers), and another in which endogenous hyperlipidemic samples (n = 31) were measured by methods not affected by hyperlipidemia (i.e., direct ISE and post-ultracentrifugation indirect ISE). Triglycerides, lipemic index (L-index) and indirect ISE sodium concentrations of samples were measured on Roche Cobas® 8000 and direct ISE on Radiometer® ABL835 Flex analyzers. Endogenous hyperlipidemic samples were also ultracentrifuged on Beckman Coulter® Airfuge to clear excess lipids and re-analyzed for sodium by indirect ISE. Results We discovered that Intralipid® is not an accurate emulation of the lipemic interference seen in pseudohyponatremia because it showed no effect up to the maximum level of lipemia tested (L-index = 2000). By contrast, endogenous hyperlipidemic samples demonstrated significant deviations in sodium concentration (≥4 mmol/l) when L-index approached or exceeded 700, and a strong positive correlation between L-index and the difference between the indirect and direct methods (i.e., extent of pseudohyponatremia). Conclusions Clinical laboratories should lower their tolerance for lipemia from the currently recommended L-index cutoff of 2000 on Roche Cobas 8000®. We recommend reflexing to direct ISE when L-index exceeds 700. Manufacturers and laboratories with other indirect ISE methods should evaluate the effect of lipid interference on their method using hyperlipidemic human samples not Intralipid®.

The aim if this study was to carry out the blood evaluation of Cebus albifrons primates kept in captivity at the Centro de Atención y Valoración de Fauna Silvestre (C.A.V) in the city of Ibagué, Colombia. Blood (~2 ml) was drawn from the femoral or axillary veins under chemical restriction in nine males (six castrated) and five females. Results were obtained for haematocrit 40.75 ± 3.91%, haemoglobin 15.2 ± 1.4 g/dl, erythrocyte counts 5 200 714 ± 510 331/mm3, mean corpuscular haemoglobin [HCM] 29.22 ± 1.46 pg, mean corpuscular haemoglobin concentration [CHCM] 37.26 ± 0.73 g/dl, mean corpuscular volume [VCM] 78.61 ± 4.46 fl, white blood cell count 8328.6 ± 2993.7/mm3, segmented neutrophils 43.56 ± 10.31%, monocytes 28.11 ± 5.28%, lymphocytes 23.54 ± 7.45%, eosinophils 4.79 ± 1.14% and platelets 276 857 ± 71 889/mm3. There were no significant differences between males and females. El objetivo del presente estudio fue realizar la valoración hemática de primates Cebus albifrons mantenidos en cautiverio en el Centro de Atención y Valoración de Fauna Silvestre (C.A.V) de la ciudad de Ibagué, Colombia. Se extrajo sangre (~2 ml) mediante la punción de las venas femoral o axilar bajo restricción química en nueve machos (seis castrados) y cinco hembras. Se obtuvieron resultados para el hematocrito de 40.75±3.91%, hemoglobina 15.2±1.4 g/dl, recuentos eritrocitarios 5 200 714±510 331/mm3 , hemoglobina corpuscular media [HCM] 29.22±1.46 pg, concentración de hemoglobina corpuscular media [CHCM] 37.26±0.73 g/dl, volumen corpuscular medio [VCM] 78.61±4.46 fl, recuento leucocitario 8328.6±2993.7/mm3 , neutrófilos segmentados 43.56±10.31%, monocitos 28.11±5.28%, linfocitos 23.54±7.45%, eosinófilos 4.79±1.14% y plaquetas 276 857 ±71 889/mm3. No se evidenciaron diferencias significativas entre sexos.

Background The use of marijuana in the USA has been steadily increasing over the last 10 years. This study is the first to investigate the effect of marijuana use by live kidney donors upon outcomes in both donors and recipients. Methods Living kidney donor transplants performed between January 2000 and May 2016 in a single academic institution were retrospectively reviewed. Donor and recipient groups were each divided into two groups by donor marijuana usage. Outcomes in donor and recipient groups were compared using t-test, Chi-square and mixed linear analysis (P 0.05 for all comparisons). There was no difference in renal function between NMUD and MUD groups and no long-term difference in kidney allograft function between NMKR and MKR groups. Conclusions Considering individuals with a history of marijuana use for living kidney donation could increase the donor pool and yield acceptable outcomes.

The space radiation environment comprises all of the nuclei in the periodic table with energies that extend from a fraction of an MeV/n to TeV/n. The vast range of projectile–target and energy combinations necessitates highly efficient and accurate cross section codes for use in radiation transport codes. As particles in the space radiation environment impinge on shielding materials, nuclear reactions, such as nuclear fragmentation, occur. One way of estimating nuclear fragmentation cross sections is to use an abrasion–ablation model, which describes how nucleons are dislodged from the nuclei as a result of nuclear collisions and the mechanism by which excited pre-fragments decay via particle emission to more stable states. The well-known partial wave solution method cannot be used directly for the computation of abrasion cross sections. Instead, abrasion cross sections may be computed by slightly altering the Eikonal solution method, which is a high energy (small scattering angle) approximation that depends on the nucleus–nucleus optical potential. The aim of the current work is to present two efficient methods for the computation of the Eikonal phase shift function. Analytic formulas of the optical potential are presented in the position-space representation for nuclei that are well-represented by harmonic-well nuclear matter densities (A < 20), which reduces the Eikonal phase factor to an integration over a single dimension. Next, the Eikonal phase function is presented in the momentum-space representation, which is particularly useful when the Fourier transform of the position-space optical potential is known. These new methods increase the computational efficiency by three orders of magnitude and allow for rapid prediction of elastic differential, total, elastic, and reaction cross sections in the Eikonal approximation.

Introduction: Volume of renal parenchymal loss is known to affect postoperative renal function after partial nephrectomy (PN). We utilize a novel comparison using donor nephrectomy (DN) pa...

Objective: This report aims to describe unique manifestations of proboscis lateralis and highlight the importance of a multidisciplinary approach to address the problems that arise from this rare congenital anomaly. Methods: Study Design: Case Report Setting: Tertiary Government Hospital Patient: One Results: A 13 year-old girl diagnosed with proboscis lateralis presented with a trunk-like appendage projecting from the surface of the right supramedial canthal area. She also had clear nasal discharge, nasal congestion, mouth-breathing, and snoring since birth. Paranasal Sinus (PNS) CT scan with 3D reconstruction showed agenesis of the right paranasal sinuses, and expansile aeration of the left paranasal sinuses. Due to her condition, the drainage system of the paranasal sinuses was obstructed, causing chronic rhinosinusitis (CRS). This hindered plans for reconstructive surgery despite medical management, hence the patient underwent Endoscopic Sinus Surgery (ESS). Conclusion: Proboscis lateralis is a rare congenital anomaly that results in aesthetic problems as well as airway concerns, such as rhinosinusitis and obstructive sleep apnea syndrome (OSAS). Management entails a multidisciplinary approach to address functional and aesthetic problems of the patient. Keywords: proboscis lateralis, chronic rhinosinusitis, obstructive sleep apnea, endoscopic sinus surgery, multidisciplinary approach, plastic surgery, reconstructive surgery

Anecdotal reports have suggested that transplantation of hepatitis C virus (HCV) antibody positive (Ab+)/nucleic acid test negative (NAT-) donor kidneys into HCV negative recipients is not associated with HCV transmission. We reviewed our center's outcomes of 32 HCV negative patients who received kidney allografts from 25 donors who were HCV Ab+/NAT-. The mean recipient age was 56.9 ± 12.1 years and the mean donor age was 41.5 ± 14 years, with a median Kidney Donor Profile Index (KDPI) of 68%. Twelve donors (48%) met Public Health Service (PHS) increased risk status. All patients received antithymocyte globulin induction followed by tacrolimus, mycophenolate mofetil, and steroid maintenance immunosuppression. With a mean follow-up posttransplant of 10 ± 2.7 months, 1- and 3- month serum creatinine levels were 1.7 ± 0.8 and 1.3 ± 0.4, respectively, and patient and graft survival rates were 100% and 97%, respectively. Fourteen patients (44%) seroconverted and became HCV Ab+ posttransplant. However, all 32 patients were HCV RNA negative at 1- and 3- months posttransplant, and 27 and 8 patients tested at 6- and 12-months posttransplant, respectively, remain HCV RNA negative. In conclusion, transplantation of HCV Ab+/NAT- kidneys to HCV negative recipients frequently causes HCV Ab seroconversion but not HCV viremia.

Background A significant increase in industry support of professional medical associations coupled with data suggesting that gifts from industry have significant clinical influence have prompted calls from the Institute of Medicine and physician leaders to identify and manage conflicts of interest that stem from financial support of professional medical associations by industry. Study Design A joint task force of members appointed by the Association for Academic Surgery and the Society of University Surgeons was convened in July 2009. Recommendations were developed regarding management of all potential conflicts of interest that can arise within the context of an academic surgical society, with specific focus on relationships with industry. Task force members reached consensus around each recommendation and the guidelines were subsequently adopted by the Executive Councils of both societies. Results The committee identified 4 primary areas of need for transparent and definitive management of conflict of interest: 1) individual society activities, including general budget support, society endorsements, and journal affiliation; 2) individual personnel conflicts such as society leadership and standards for disclosure of conflict; 3) meeting activities including budgetary support, program committee associations, and abstract review process; and 4) foundation support and research and travel awards. The resulting guidelines aim to protect the societies and their membership from undue bias that may undermine the credibility and mission of these associations. Conclusions Policy guidelines to mitigate conflict of interest are necessary to protect the integrity of the work of academic surgical societies and their fiduciary duty to members and patients. Guidelines created and adopted by the Association for Academic Surgery and Society of University Surgeons form an effective model for academic surgical societies and their members.

Acoustic energy propagates effectively to long ranges in the ocean interior because of the physical properties of the marine environment. Sound propagation in the ocean is relevant to a variety of studies in communication, climatology and marine biology. Examples drawn from ocean acoustics, therefore, are compelling to students with a variety of interests. The dependence of sound speed on depth results in a waveguide that permits the detection of acoustic energy at ranges, in some experiments, of thousands of kilometres. This effect serves as an illustration of Snell's law with a continuously variable index of refraction. Acoustic tomography also offers a means for imaging the ocean's thermal structure, because of the dependence of sound speed on temperature. The ability to perform acoustic thermometry for large transects of the ocean provides an effective means of studying climate change. This application in an area of substantial popular attention allows for an effective introduction to concepts in ray propagation. Aspects of computational ocean acoustics can be productive classroom examples in courses ranging from introductory physics to upper-division mathematical methods courses.

A line-integral approximation to the acoustic path integral has been used to generate predictions for the characteristic length scale of horizontal, cross-range coherence in long-range ocean-acoustic propagation. These estimates utilize a single range-independent sound-speed profile and the mean variance, as a function of depth, of fractional sound-speed perturbations due to internal waves. The length scales predicted by the integral approximation have been compared to the values generated by parabolic-equation simulations through multiple realizations of Garrett-Munk internal waves. One of the simulation environments approximates the Slice89 experiment; transmissions from a 250-Hz source were simulated in a deep-water transect to a maximum range of 1000km. The second environment corresponds to one of the propagation paths in the North Pacific Acoustic Laboratory (NPAL) experiment. The source in this experiment was bottom-mounted near Kauai, Hawaii and the relevant receiver consisted of five vertical line...

A range-dependent field of sound speed in the ocean, c(x,z), caused by internal waves, can give rise to instabilities in acoustic ray paths. Past work has shown the importance of the background, range-independent, sound-speed profile; the ray initial conditions; the source-receiver geometry (depths and range); and the strength of the internal waves. However, in the past the time evolution of the internal waves has been ignored on the grounds that the speed of internal waves is much slower than the speed of the acoustic wave. It is shown here by numerical simulation that two rays with identical initial conditions, traveling through an ocean with the same background profile and the same random realization of internal waves, but with the internal waves frozen in one case and evolving in the other, travel significantly different trajectories. The dependence of this "frozen-unfrozen" difference on the initial ray launch angle, the background profile, and the strength of the internal-wave spectrum, is investigated. The launch-angle difference that generates similar arrival-depth differences to those induced by internal-wave time evolution is on the order of 100 microrad. The pattern of differences is measured here by the arrival depth at the final range of 1000 km. The observed pattern as a function of launch angle, change in the background profile, and change in internal-wave strength is found to be nearly the same for "frozen-unfrozen" change as for a slight change in launch angle.

Acoustic interaction with the seafloor can generate both compressional and elastic shear waves in the solid. Accurate models of shear propagation are often computationally expensive and difficult to apply to long-range propagation. When the sound field in the water is of primary interest, an equivalent-fluid model of the seafloor, with parameters chosen to match the reflection coefficient of the actual elastic solid, can sufficiently characterize the effect of the bottom on energy in the water. The effective density of the seafloor material in this approach can be a complex number. Prior methods for generating equivalent fluids were intended for low shear speeds and low grazing angles. Recent developments in the technique were intended to extend its validity to higher shear speeds and a wider range of angles. These efforts were initially motivated by the need to simulate bottom-interacting arrivals for the broadband Kauai source in the North Pacific Acoustic Laboratory experiment at megameter ranges. The work to be presented involves a more detailed examination of the performance of the method, including comparisons to benchmark models and to shorter range data from this Kauai source collected as part of the Basin Acoustic Seamount Scattering Experiment.

This study determines whether the recipient and donor characteristics that influence the cytomegalovirus (CMV) infection rate after liver transplantation have changed.The recipient and donor characteristics that may affect the rate of CMV infection were assessed in 232 liver transplant recipients at our institution during a 14-year period (1989-2003).Since 1989, the age of recipients (P=0.0001) and donors (P=0.0001) has increased significantly. Pretransplant CMV seropositivity in recipients has decreased significantly (P=0.0001, 86.4% [1989-1992] to 53.7% [2000-2003]), whereas donor CMV seropositivity has remained unchanged (P0.20). As a result, there has been a significant increase in the proportion of high-risk (CMV recipient-/donor+) patients (P=0.012); 10.6% of recipients from 1989 to 1992 versus 24.1% of recipients from 2000 to 2003 were CMV recipient-/donor+. The Child-Pugh scores of recipients have remained unchanged over time. However, the proportion of patients undergoing transplantation while being cared for in the intensive care unit has decreased significantly over time (P=0.0002). Despite an increase in the rate of CMV infection (P=0.09), the incidence of CMV disease has decreased significantly (P=0.0004).The proportion of high-risk patients (CMV recipient-/donor+) has increased significantly over time, attributable largely to a declining rate of CMV seropositivity in recipients before transplantation. These data have implications for guiding prophylactic practices and resource use after liver transplantation.

Line-integral approximations to the acoustic path integral have been used to estimate the magnitude of the fluctuations in an acoustic signal traveling through an ocean filled with internal waves. These approximations for the root-mean-square (rms) fluctuation and the bias of travel time, rms fluctuation in a vertical arrival angle, and the spreading of the acoustic pulse are compared here to estimates from simulations that use the parabolic equation (PE). PE propagations at 250 Hz with a maximum range of 1000 km were performed. The model environment consisted of one of two sound-speed profiles perturbed by internal waves conforming to the Garrett-Munk (GM) spectral model with strengths of 0.5, 1, and 2 times the GM reference energy level. Integral-approximation (IA) estimates of rms travel-time fluctuations were within statistical uncertainty at 1000 km for the SLICE89 profile, and in disagreement by between 20% and 60% for the Canonical profile. Bias estimates were accurate for the first few hundred kilometers of propagation, but became a strong function of time front ID beyond, with some agreeing with the PE results and others very much larger. The IA structure functions of travel time with depth are predicted to be quadratic with the form theta(2)vc0(-2)deltaz(2), where deltaz is vertical separation, c0 is a reference sound speed, and thetav is the rms fluctuation in an arrival angle. At 1000 km, the PE results were close to quadratic at small deltaz, with values of thetav in disagreement with those of the integral approximation by factors of order 2. Pulse spreads in the PE results were much smaller than predicted by the IA estimates. Results imply that acoustic tomography of internal waves at ranges up to 1000 km can use the IA estimate of travel-time variance with reasonable reliability.

To understand the behavior of a scalar field propagating in a waveguide with inhomogeneous, anisotropic, small-scale structure. Oceanographically, to connect the results of sound transmission and scattering experiments to known or hypothesized structures within the hydrosphere, such as internal tides, internal waves, or microstructure, with account taken of ocean anisotropy, inhomogeneity, and the sound channel.

Because its soundspeed characteristics differ substantially from seawater,the presence of oil in the water column might be expected to impact acousticpropagation in the ocean environment. Empirical expressions are employed forthe sound speed in oil; it depends on the API (a measure of density), temperature,and pressure. Environmental data taken in the vicinity of the Deepwater Horizonsite taken during the 2007 Littoral Acoustic Demonstration Center experimentare used to generate profiles of temperature, pressure, and sound speed. Differentvalues of API and different distributions for the weighting fraction of theoil on the total sound speed are employed in numerical simulations. The computed,received acoustic fields for different values and locations of oil concentrationare compared to the case where no oil is present in several sourcereceiverranges. These forward models are intended to examine the feasibility of acousticallytracking oil as it travels from a source upward through the water column,or in locating oil suspended in the water column. These computations can aidin identifying the limitations on a realistic experimental scenario.

Receptions were recorded from a bottom‐mounted broadband source (with a center frequency of 75 Hz) located near Kauai as part of the basin acoustic seamount scattering experiment (BASSEX). Travel times for arrivals from this source have been modeled at basin‐scale ranges using complex‐density equivalent fluids for the elastic seafloor material. The collection of acoustic data at shorter ranges as part of BASSEX allows for a more detailed examination of the accuracy attainable by an equivalent‐fluid representation of the seafloor. The use of equivalent fluids is intended to depict the conversion of acoustic energy into shear waves. The performance and stability of propagation models can be substantially improved if equivalent fluids can be used to accurately characterize bottom interaction. Simulations have been performed in order to search for the equivalent fluid that best explains received data at a range of a few kilometers. The reflection coefficient of this equivalent fluid can then be matched to par...

Geoacoustic inversion from data just off a volcanic island (Kauai) poses significant challenges. One of the significant challenges is to separate the effects of seafloor roughness and shear wave conversion in the basement. Lava flow fields are known to have significant roughness on several scales relevant to low‐frequency acoustic propagation (75 Hz). Basalt is known to have a very high‐compressional speed of 3000 m/s and a variable shear speed ranging from 500 to 2000 m/s. The combination of shear and roughness can lead to significant ambiguity while performing a geoacoustic inversion because both mechanisms can lead to attenuation of the coherent field. During the BASSEX 2004 experiment up to 20 transmissions from the fixed NPAL source (75 Hz, m‐seq with a 50‐Hz bandwidth) were received on a towed horizontal line array at many orientations and ranges from the source. In this paper we look at several short‐range transmissions and attempt to sort out the scattering effects of roughness with the attenuatio...

The NPAL98 experiment offered a unique opportunity to study horizontal coherence because of the deployment of a billboard array. The billboard consisted of five vertical line arrays with a 3600‐m horizontal aperture listening to a 75‐Hz acoustic signal 3500 km away. Original estimates of horizontal coherence were complicated by the bottom‐interacting sound field, which made it difficult to track individual arrivals. Thus, previous studies of the horizontal coherence in this experiment were limited to the arrival pattern in aggregate. By using a turning‐point filter and a rake correlator, it is now possible to track individual arrivals during the NPAL98 experiment. We can thus measure the coherence of individual early non‐bottom‐interacting arrivals. Results are compared to recent calculated predictions using both Monte Carlo and path‐integral methods for the same environment. [Work supported by ONR.]

Some of the characteristics of an acoustic signal propagating to basin‐scale ranges in the ocean can be estimated using line integrals along deterministic ray paths. These line‐integral approximations involve the statistics of the internal‐wave field. The success or failure of the integral expressions can be analyzed by comparison to parabolic‐equation simulations through multiple realizations of the stochastic internal‐wave field. One acoustic characteristic of interest is the length scale of acoustic horizontal (cross‐range) coherence. Recent work comparing integral predictions of horizontal coherence length to values from simulations of the North Pacific Acoustic Laboratory experiment yielded mixed results. Additional comparisons will be discussed for acoustic propagation paths that are not impacted by range‐dependence in the bathymetry or background sound‐speed profile. These simulations will employ a single sound‐speed profile and a deep, range‐independent bottom. The comparisons can yield some insig...

Wave theoretic modeling was applied to obtain sensitivity kernels representing the amount by which ocean acoustic observables, such as pressure, intensity, or arrival times, are affected by localized sound‐speed variations anywhere in the medium. These kernels can be derived using the first Born approximation, yielding an integral representation of observable perturbations as functionals of sound‐speed perturbations. The kernel in each integral represents the spatial sensitivity of the observable to sound‐speed perturbations in the medium. The travel‐time sensitivity kernel represents a full‐wave generalization of the highly localized ray kernel from geometric optics. This work extended recent wave‐theoretic results for the travel‐time sensitivity kernel for short‐range propagation in simple environments to long‐range transmissions in more complicated ocean environments relevant to ongoing propagation and inversion experiments. It was shown that the geometry of the wave‐theoretic sensitivity kernels is re...

Acoustic transmissions from a broadband source near Kauai with a center frequency of 75 Hz were recorded on a two‐dimensional receiver array at a range of 3900 km as part of the North Pacific Acoustic Laboratory (NPAL) experiment. The receiver array consisted of five vertical line arrays (VLAs), with separations transverse to the propagation path ranging from a few hundred meters to a few kilometers. The coherences derived from the data have been compared to two different numerical predictions based on sound‐speed perturbations due to internal waves. An approximation to the acoustic path integral yields a prediction for the length scale of horizontal coherence. Parabolic‐equation simulations of propagation from the source to each VLA through multiple realizations of a random internal‐wave field provide another estimate of the coherence at each horizontal separation. [Work supported by ONR.] a)J. A. Colosi, B. D. Cornuelle, B. D. Dushaw, M. A. Dzieciuch, B. M. Howe, J. A. Mercer, R. C. Spindel, and P. F. W...

Acoustic transmissions from a 75‐Hz source near Kauai to a vertical line array near California were recorded as part of the North Pacific Acoustic Laboratory (NPAL) experiment. Extensive environmental measurements were also performed as part of the experiment and were intended to ensure correspondence between numerical simulations and the data. Despite the availability of this information, the process of identifying the recorded arrivals with predictions has not been a simple one. Since the source is near the seafloor at about 800 m depth, and the depth at the receiver is approximately 1800 m, acoustic interaction with the bathymetry has been explored as a possible complication. Ray simulations that allow for specular reflection from the bottom indicate that fully‐refracted and bottom‐interacting paths can reach the receiver range (about 3900 km) at similar travel times. The simultaneous presence of both kinds of acoustic energy could contribute to the identification difficulties. A series of parabolic‐eq...

In order to use observations of the bias and variance of travel time, the length scale of acoustic coherence in depth, and the spreading of the acoustic pulse as information about the internal‐wave field in the ocean (all for identifiable rays at long range), a reliable method of calculation of these quantities in the presence of a specific internal‐wave model must be made. Attempts to use analytical methods having proven unreliable for long range, except for the variance of travel time; there are two possibilities: (1) restrict tomography of identifiable rays to travel‐time variance; or (2) use simulation by parabolic equation to calculate expected values. The former is restricted and the latter is computer intensive. The needed resources for the latter will be discussed.

A range‐dependent field of sound speed in the ocean can give rise to chaotic instabilities in acoustic ray paths. A model of internal waves is used as a range‐dependent effect on the speed of sound in numerical simulations. These simulations, performed over a 1000‐km range, demonstrate the sensitivity of ray paths to slight changes in the sound‐speed field or the initial conditions of their launch. Previous work [Simmen et al. (1999)] has shown the effect on arrival depth of slightly shifting the launch angle of each ray. The focus of this work is the effect of internal wave time dependence. Comparisons are made between simulations using a time‐dependent medium and those using a time‐independent (‘‘frozen’’) medium, and between simulations with different geophysical starting times. The resulting arrival depth differences are compared to those induced by launch angle shifts. The structure and magnitude of these differences are considered in the case of two different sound‐speed profiles: a Munk canonical profile and a profile from the Slice89 experiment.