Dynamic sound scattering: Field fluctuation spectroscopy with singly scattered ultrasound in the near and far fields.

Dynamic sound scattering (DSS) is a powerful acoustic technique for investigating the motion of particles or other inclusions inside an evolving medium. In DSS, this dynamic information is obtained by measuring the field autocorrelation function of the temporal fluctuations of singly scattered acoustic waves. The technique was initially introduced 15 years ago, but its technical aspects were not adequately discussed then. This paper addresses the need for a more complete account of the method by describing in detail two different implementations of this sound scattering technique, one of which is specifically adapted to a common experimental situation in ultrasonics. The technique is illustrated by the application of DSS to measure the mean square velocity fluctuations of particles in fluidized suspensions, as well as the dynamic velocity correlation length. By explaining the experimental and analytical methods involved in realizing the DSS technique in practice, the use of DSS will be facilitated for future studies of particulate suspension dynamics and particle properties over a wide range of particle sizes and concentrations, from millimeters down to nanometers, where the use of optical techniques is often limited by the opacity of the medium.

Fibrous ingluvial foreign bodies in 33 cockatiels (Nymphicus hollandicus).

The presentation, treatment and outcomes of 33 ingluvial fibrous foreign bodies in cockatiels (Nymphicus hollandicus) are described. Vomiting, lethargy and weight loss were the most common presenting signs. Diagnosis was made on palpation of a mass in the crop (ingluvies). Both surgical and non-surgical treatment regimens were evaluated. The overall mortality rate was 33%, suggesting fibrous materials are not safe for cockatiels to groom or ingest and should not be offered as cage accessories.

Herpesvirus in a captive Australian Krefft's river turtle (Emydura macquarii krefftii).

CASE REPORT: A mature, captive Krefft's river turtle (Emydura macquarii krefftii) was presented with severe proliferative and ulcerative lesions of the skin and shell. The areas were biopsied and histopathological examination demonstrated orthokeratotic hyperkeratosis with keratinocytes containing eosinophilic intranuclear inclusions. Molecular diagnostics confirmed the presence of a herpesvirus in the affected tissues. CONCLUSION: This is the first recorded case of herpesvirus infection in an Australian freshwater turtle species.

Granuloma formation and suspected neuropathic pain in a domestic pigeon (Columba livia) secondary to an oil-based, inactivated Newcastle disease vaccine administered for protection against pigeon paramyxovirus-1.

CASE REPORT: A domestic pigeon developed a sterile granuloma following vaccination with an oil-adjuvant, inactivated La Sota strain of Newcastle disease. The aim of vaccination was to provide protection against pigeon paramyxovirus-1 (PPMV-1), a disease previously considered exotic to Australia. Granuloma formation is considered a rare complication of vaccination against PPMV-1 in pigeons. Clinical signs consistent with neuropathic pain became apparent during the extensive management of the granuloma, which included surgical removal of foreign material, control of the pain and inflammation and protection against antimicrobial contamination. CONCLUSION: PPMV-1 is now considered endemic in Australia and protecting pigeons with vaccination is important. Until a product is registered for use, vaccination remains off-label and the risk of adverse reaction, including sterile granuloma, must be considered.

Osteosarcoma in a woma python (Aspidites ramsayi).

Osteosarcoma of the axial skeleton in an 18-month-old woma python (Aspidites ramsayi) is described. A subcutaneous mass overlying the costal arches enlarged progressively over a period of 5 months and, in that time, became ulcerated and more invasive of surrounding tissues. A punch biopsy of the lesion under general anaesthesia provided tissue for histopathology and diagnosis of low-grade osteosarcoma.

Clostridium difficile-associated disease acquired in the neurocritical care unit.

BACKGROUND: Clostridium difficile is an important cause of nosocomial infection on the intensive care unit. Little is known about infection rates on the neurocritical care unit (NICU). The purpose of this study was to determine the prevalence, severity, and outcome associated with Clostridium difficile-associated disease (CDAD) acquired on the NICU. METHODS: Patients on NICU with a positive stool Clostridium difficile toxin assay, from August 2004 to February 2008, were identified by the Department of Microbiology. Each patient's medical notes and charts were reviewed in turn. Patients with a positive assay within 48 h of NICU admission were excluded. RESULTS: Twenty-one (0.6%) NICU patients developed CDAD. All were emergency admissions, 18 (86.0%) were neurosurgical. Subarachnoid hemorrhage was the most common diagnosis, 5 (23.8%) patients. Median age and APACHE II score on admission were 55 (IQR 40-66) and 21 (IQR 16-24), respectively. Thirteen (61.9%) patients were female. Median interval between NICU admission and diarrhea onset and CDAD diagnosis were 5 (3-8) days and 7 (4-12) days, respectively. At the time of diagnosis most, 11 (52.4%) patients, had moderate CDAD. Previously identified risk factors for ICU-acquired CDAD comprised: age > 65 (6), antibiotics (21), and medical device requirements (21). Five (23.8%) patients deteriorated clinically as a result of CDAD. The overall in-hospital mortality for those with NICU acquired CDAD was 19%. CONCLUSIONS: Although CDAD is rarely acquired on the NICU, up to one quarter of affected patients may experience complications. Prospective validation of severity definitions and treatment guidelines may help to reduce the complication rates.

Outcomes of critically ill patients with cirrhosis admitted to intensive care: an important perspective from the non-transplant setting.

BACKGROUND: Hospital admissions for cirrhosis have been increasing in the United Kingdom, leading to increased pressure on intensive care (ICU) services. Outcome data for patients admitted to ICU are currently limited to transplant centre reports, with mortality rates exceeding 70%. These tertiary reports could fuel a negative bias when patients with cirrhosis are reviewed for ICU admission in secondary care. AIMS: To determine whether disease severity and mortality rates in non-transplant general ICU are less severe than those reported by tertiary datasets. METHODS: A prospective dual-centre non-transplant ICU study. Admissions were screened for cirrhosis and physiological and biochemical data were collected. Disease-specific and critical illness scoring systems were evaluated. RESULTS: Cirrhosis was present in 137/4198 (3.3%) of ICU admissions. ICU and hospital mortality were 38% and 47%, respectively; median age 50 [43-59] years, 68% men, 72% alcoholic cirrhosis, median Child Pugh Score (CPS) 10 [8-11], Model for End-Stage Liver Disease (MELD) 18 [12-24], Acute Physiology and Chronic Health Evaluation II score (APACHE II) 16 [13-22]. CONCLUSIONS: Mortality rates and disease staging were notably lower than in the published literature, suggesting that patients have a more favourable outlook than previously considered. Transplant centre data should therefore be interpreted with caution when evaluating the merits of intensive care admission for patients in general secondary care ICUs.

The increasing hospital disease burden of haemochromatosis in England.

BACKGROUND: Hereditary haemochromatosis is a preventable cause of liver disease with an increasing disease burden. AIMS: To investigate time trends for hospital admission ascribed to haemochromatosis in England during the period from 1989/1990 to 2002/2003 and mortality from 1979 to 2005. METHODS: Hospital admission data, relating to both in-patients and day-cases, were obtained from the Hospital Episodes Statistics service. Mortality rates for England and Wales were provided by the Office for National Statistics. RESULTS: Haemochromatosis is an uncommon cause for hospital admission. Age-standardized in-patient admission rates increased over the study period by 269% in men and by 290% in women: (from 0.64 to 2.36 and from 0.21 to 0.81 per year per 100 000). The increase in age-standardized day-case admission rates was even higher (men: from 2.78 to 34.9 per year per 100 000, 1155%; women: from 0.58 to 11.67 per year per 100 000, 1924%). Haemochromatosis was recorded as an uncommon cause of death. CONCLUSIONS: Hospital in-patient and day case admissions for haemochromatosis increased markedly over the study period while mortality remained low. Both admission rates and mortality were higher in men than in women. The increase in admission rate may reflect improved recognition and diagnosis of iron overload disorders following identification of the HFE gene.

'Liver function tests' on the intensive care unit: a prospective, observational study.

AIMS: To evaluate the prevalence, patterns and significance of deranged liver function tests (LFT) in critically ill patients. METHODS: A prospective, observational data collection of the LFT [bilirubin, alanine aminotransferase (ALT), alkaline phosphatase (AKP), gamma glutaryl transferase (gammaGT)] and critical care parameters in all admissions to the general intensive care unit (ICU) of our institution. Prevalence of abnormal LFT on the day of ITU admission is described and the relationship of abnormal LFT to clinical events and 30-day mortality analysed. RESULTS: Of 263 first admissions without hepatobiliary disease, 61% demonstrated an abnormal LFT at the point of admission. The majority of abnormalities were less than twice the upper limit of normal. Episodes of ventilation, haemofiltration and hypotension during the first 48 h were associated with an abnormal ALT on day 3. The presence of an abnormal ALT [odds ratio 2.7 (1.2-6.0)], AKP [OR 2.8 (1.1-7.3)] or gammaGT [OR 3.9 (1.9-8.3)] was associated with an increased risk of death within 30 days of admission. When adjusted for APACHE II score, LFTs were not independent predictors of mortality. DISCUSSION: Low-grade abnormalities of LFT are a significant entity in critically ill patients and show an association with mortality outcomes and clinical events on ICU. They are likely to represent part of a spectrum of liver injury associated with critical illness and should not be disregarded.

Temperature dependence of the two-dimensional infrared spectrum of liquid H2O.

Two-dimensional infrared photon-echo measurements of the OH stretching vibration in liquid H2O are performed at various temperatures. Spectral diffusion and resonant energy transfer occur on a time scale much shorter than the average hydrogen bond lifetime of approximately 1 ps. Room temperature measurements show a loss of frequency and, thus, structural correlations on a 50-fs time scale. Weakly hydrogen-bonded OH stretching oscillators absorbing at high frequencies undergo slower spectral diffusion than strongly bonded oscillators. In the temperature range from 340 to 274 K, the loss in memory slows down with decreasing temperature. At 274 K, frequency correlations in the OH stretch vibration persist beyond approximately 200 fs, pointing to a reduction in dephasing by librational excitations. Polarization-resolved pump-probe studies give a resonant intermolecular energy transfer time of 80 fs, which is unaffected by temperature. At low temperature, structural correlations persist longer than the energy transfer time, suggesting a delocalization of OH stretching excitations over several water molecules.

Mesoscopic phase statistics of diffuse ultrasound in dynamic matter.

Temporal fluctuations in the phase of waves transmitted through a dynamic, strongly scattering, mesoscopic sample are investigated using ultrasonic waves, and compared with theoretical predictions based on circular Gaussian statistics. The fundamental role of phase in diffusing acoustic wave spectroscopy is revealed, and phase statistics are also shown to provide a sensitive and accurate way to probe scatterer motions at both short and long time scales.

Ultrafast noncollinear optical parametric chirped pulse amplification in KTiOAsO4.

Amplification of femtosecond pulses at 1.56 microm based on noncollinear parametric chirped pulse amplification in a potassium titanyl arsenate (KTA) crystal with pumping at 1.05 microm is reported. The 100 fs pulses of an erbium fiber laser are parametrically amplified while synchronously pumped by an amplified mode-locked Nd:YLF laser. This amplifier has a saturated gain of 65 dB with 30% conversion efficiency and has produced 160 fs pulses with peak powers of up to 0.75 GW. The system produced 380 mW before compression and can be readily scaled to the multiwatt range with bandwidths to support sub-100 fs pulses.

Anharmonic couplings underlying the ultrafast vibrational dynamics of hydrogen bonds in liquids.

The multilevel structure and vibrational couplings of O-H stretching transitions in intermolecular hydrogen bonds of acetic acid dimers are determined by femtosecond two-dimensional photon-echo spectroscopy in the infrared. Combining experiment and theoretical calculations, we separate Fermi resonances with combination tones of fingerprint modes from anharmonic couplings to underdamped low-frequency modes of the dimer. A multilevel density matrix approach based on density functional theory calculations reproduces the experimental results and reveals coupling strengths of both mechanisms on the order of 40-150 cm(-1).

Ultrafast memory loss and energy redistribution in the hydrogen bond network of liquid H2O.

Many of the unusual properties of liquid water are attributed to its unique structure, comprised of a random and fluctuating three-dimensional network of hydrogen bonds that link the highly polar water molecules. One of the most direct probes of the dynamics of this network is the infrared spectrum of the OH stretching vibration, which reflects the distribution of hydrogen-bonded structures and the intermolecular forces controlling the structural dynamics of the liquid. Indeed, water dynamics has been studied in detail, most recently using multi-dimensional nonlinear infrared spectroscopy for acquiring structural and dynamical information on femtosecond timescales. But owing to technical difficulties, only OH stretching vibrations in D2O or OD vibrations in H2O could be monitored. Here we show that using a specially designed, ultrathin sample cell allows us to observe OH stretching vibrations in H2O. Under these fully resonant conditions, we observe hydrogen bond network dynamics more than one order of magnitude faster than seen in earlier studies that include an extremely fast sweep in the OH frequencies on a 50-fs timescale and an equally fast disappearance of the initial inhomogeneous distribution of sites. Our results highlight the efficiency of energy redistribution within the hydrogen-bonded network, and that liquid water essentially loses the memory of persistent correlations in its structure within 50 fs.

Focusing of sound in a 3D phononic crystal.

We present a combined experimental and theoretical study of phonon focusing phenomena in a pass band above the complete band gap in a 3D phononic crystal. Wave propagation was found to depend dramatically on both frequency and incident direction. This propagation anisotropy leads to very large negative refraction, which can be used to focus a diverging ultrasonic beam into a narrow focal spot with a large focal depth. The experimental field patterns are well explained using a Fourier imaging technique, based on the 3D equifrequency surfaces calculated from multiple scattering theory.

Observation of the cascaded atomic-to-global length scales driving protein motion.

Model studies of the ligand photodissociation process of carboxymyoglobin have been conducted by using amplified few-cycle laser pulses short enough in duration (<10 fs) to capture the phase of the induced nuclear motions. The reaction-driven modes are observed directly in real time and depict the pathway by which energy liberated in the localized reaction site is efficiently channeled to functionally relevant mesoscale motions of the protein.

Diffusing acoustic wave spectroscopy.

We have developed a technique in ultrasonic correlation spectroscopy called diffusing acoustic wave spectroscopy (DAWS). In this technique, the motion of the scatterers (e.g., particles or inclusions) is determined from the temporal fluctuations of multiply scattered sound. In DAWS, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the autocorrelation function of the temporal field fluctuations to be related to the dynamics of the multiply scattering medium. The expressions relating the temporal field autocorrelation function to the motion of the scatterers are derived, focusing on the types of correlated motions that are most likely to be encountered in acoustic measurements. The power of this technique is illustrated with ultrasonic data on fluidized suspensions of particles, where DAWS provides a sensitive measure of the local relative velocity and strain rate of the suspended particles over a wide range of time and length scales. In addition, when combined with the measurements of the rms velocity of the particles using dynamic sound scattering, we show that DAWS can be used to determine the spatial extent of the correlations in the particle velocities, thus indirectly measuring the particle velocity correlation function. Potential applications of diffusing acoustic wave spectroscopy are quite far reaching, ranging from the ultrasonic nondestructive evaluation of the dynamics of inhomogeneous materials to geophysical studies of mesoscopic phenomena in seismology.

Ultrasound tunneling through 3D phononic crystals.

We report the study of ultrasound tunneling in 3D phononic crystals, consisting of fcc arrays of close-packed tungsten carbide beads in water. The transmission coefficient, phase velocity, and group velocity were measured along the [111] direction, allowing us to systematically investigate the tunneling of ultrasound at frequencies in the lowest band gap. Our experimental data are interpreted using multiple scattering theory, which provides a good explanation of our results. The effect of absorption and the difference between the tunneling of classical waves and quantum waves are discussed.