Acoustic energy harvesting using an electromechanical Helmholtz resonator

This paper presents the development of an acoustic energy harvester using an electromechanical Helmholtz resonator (EMHR). The EMHR consists of an orifice, cavity, and a piezoelectric diaphragm. Acoustic energy is converted to mechanical energy when sound incident on the orifice generates an oscillatory pressure in the cavity, which in turns causes the vibration of the diaphragm. The conversion of acoustic energy to electrical energy is achieved via piezoelectric transduction in the diaphragm of the EMHR. Moreover, the diaphragm is coupled with energy reclamation circuitry to increase the efficiency of the energy conversion. Lumped element modeling of the EMHR is used to provide physical insight into the coupled energy domain dynamics governing the energy reclamation process. The feasibility of acoustic energy reclamation using an EMHR is demonstrated in a plane wave tube for two power converter topologies. The first is comprised of only a rectifier, and the second uses a rectifier connected to a flyback converter to improve load matching. Experimental results indicate that approximately 30 mW of output power is harvested for an incident sound pressure level of 160 dB with a flyback converter. Such power level is sufficient to power a variety of low power electronic devices.

Application of CYP3A4 in vitro data to predict clinical drug-drug interactions; predictions of compounds as objects of interaction

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Numerous retrospective analyses have shown the utility of in vitro systems for predicting potential drug-drug interactions (DDIs). Prediction of DDIs from in vitro data is commonly obtained using estimates of enzyme K(i), inhibitor and substrate concentrations and absorption rate for substrate and inhibitor.

WHAT THIS STUDY ADDS

Using a generic approach for all test compounds, the findings from the current study showed the use of recombinant P450s provide a more robust in vitro measure of P450 contribution (fraction metabolized, f(m)) than that achieved when using chemical inhibitors in combination with human liver microsomes, for the prediction of potential CYP3A4 drug-drug interactions prior to clinical investigation. The current study supported the use of SIMCYP(R), a modelling and simulation software in utilizing the in vitro measures in the prediction of potential drug-drug interactions.

AIMS

The aim of this study was to explore and optimize the in vitro and in silico approaches used for predicting clinical DDIs. A data set containing clinical information on the interaction of 20 Pfizer compounds with ketoconazole was used to assess the success of the techniques.

METHODS

The study calculated the fraction and the rate of metabolism of 20 Pfizer compounds via each cytochrome P450. Two approaches were used to determine fraction metabolized (f(m)); 1) by measuring substrate loss in human liver microsomes (HLM) in the presence and absence of specific chemical inhibitors and 2) by measuring substrate loss in individual cDNA expressed P450s (also referred to as recombinant P450s (rhCYP)) The fractions metabolized via each CYP were used to predict the drug-drug interaction due to CYP3A4 inhibition by ketoconazole using the modelling and simulation software SIMCYP.

RESULTS

When in vitro data were generated using Gentest supersomes, 85% of predictions were within two-fold of the observed clinical interaction. Using PanVera baculosomes, 70% of predictions were predicted within two-fold. In contrast using chemical inhibitors the accuracy was lower, predicting only 37% of compounds within two-fold of the clinical value. Poorly predicted compounds were found to either be metabolically stable and/or have high microsomal protein binding. The use of equilibrium dialysis to generate accurate protein binding measurements was especially important for highly bound drugs.

CONCLUSIONS

The current study demonstrated that the use of rhCYPs with SIMCYP provides a robust in vitro system for predicting the likelihood and magnitude of changes in clinical exposure of compounds as a consequence of CYP3A4 inhibition by a concomitantly administered drug.

Application of CYP3A4 in vitro data to predict clinical drug-drug interactions; predictions of compounds as objects of interaction

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Numerous retrospective analyses have shown the utility of in vitro systems for predicting potential drug-drug interactions (DDIs). Prediction of DDIs from in vitro data is commonly obtained using estimates of enzyme K(i), inhibitor and substrate concentrations and absorption rate for substrate and inhibitor.

WHAT THIS STUDY ADDS

Using a generic approach for all test compounds, the findings from the current study showed the use of recombinant P450s provide a more robust in vitro measure of P450 contribution (fraction metabolized, f(m)) than that achieved when using chemical inhibitors in combination with human liver microsomes, for the prediction of potential CYP3A4 drug-drug interactions prior to clinical investigation. The current study supported the use of SIMCYP(R), a modelling and simulation software in utilizing the in vitro measures in the prediction of potential drug-drug interactions.

AIMS

The aim of this study was to explore and optimize the in vitro and in silico approaches used for predicting clinical DDIs. A data set containing clinical information on the interaction of 20 Pfizer compounds with ketoconazole was used to assess the success of the techniques.

METHODS

The study calculated the fraction and the rate of metabolism of 20 Pfizer compounds via each cytochrome P450. Two approaches were used to determine fraction metabolized (f(m)); 1) by measuring substrate loss in human liver microsomes (HLM) in the presence and absence of specific chemical inhibitors and 2) by measuring substrate loss in individual cDNA expressed P450s (also referred to as recombinant P450s (rhCYP)) The fractions metabolized via each CYP were used to predict the drug-drug interaction due to CYP3A4 inhibition by ketoconazole using the modelling and simulation software SIMCYP.

RESULTS

When in vitro data were generated using Gentest supersomes, 85% of predictions were within two-fold of the observed clinical interaction. Using PanVera baculosomes, 70% of predictions were predicted within two-fold. In contrast using chemical inhibitors the accuracy was lower, predicting only 37% of compounds within two-fold of the clinical value. Poorly predicted compounds were found to either be metabolically stable and/or have high microsomal protein binding. The use of equilibrium dialysis to generate accurate protein binding measurements was especially important for highly bound drugs.

CONCLUSIONS

The current study demonstrated that the use of rhCYPs with SIMCYP provides a robust in vitro system for predicting the likelihood and magnitude of changes in clinical exposure of compounds as a consequence of CYP3A4 inhibition by a concomitantly administered drug.

Comparison of dose estimation from occupational exposure to 239Pu using different modelling approaches

Several approaches are available for bioassay interpretation when assigning Pu doses to Mayak workers. First, a conventional approach is to apply ICRP models per se. An alternative method involves individualised fitting of bioassay data using Bayesian statistical methods. A third approach is to develop an independent dosimetry system for Mayak workers by adapting ICRP models using a dataset of available bioassay measurements for this population. Thus, a dataset of 42 former Mayak workers, who died of non-radiation effects, with both urine bioassay and post-mortem tissue data was used to test these three approaches. All three approaches proved to be adequate for bioassay and tissue interpretation, and thus for Pu dose reconstruction purposes. However, large discrepancies are observed in the resulting quantitative dose estimates. These discrepancies can, in large part, be explained by differences in the interpretation of Pu behaviour in the lungs in the context of ICRP lung model. Thus, a careful validation of Pu lung dosimetry model is needed in Mayak worker dosimetry systems.

The use of Biobrane by burn units in the United Kingdom: a national study

Biobrane is a biosynthetic wound dressing, first used by Woodruff in 1979, which has many of the ideal properties of a dressing as outlined by Pruitt and Levine [Pruitt Jr BA, Levine NS. Characteristics and uses of biologic dressings and skin substitutes. Arch Surg 1984;119(3):312-22]. It is becoming increasingly popular in the management of superficial and moderate depth partial thickness burns and a range of other conditions. When used appropriately, it has been shown to reduce pain levels, healing time, inpatient stay and nursing requirements when compared to traditional dressings. We present the results of a national study concerning the use of Biobrane in the United Kingdom, highlight variations in practice, discuss the pertinent issues, make suitable recommendations and highlight the versatility of Biobrane as a wound dressing.

Resuscitation burn card—A useful tool for burn injury assessment

It is well recognised that the initial assessment of body surface area affected by a burn is often over estimated in Accident and Emergency Departments. A useful aide-memoir in the acute setting is Wallace's "rule of nines" or using the patients' palmar surface of the hand, which approximates 1% of the total body surface area, as a method of assessment. Unfortunately, as with every system, limitations apply. Factors such as patient size and the interpretation of what is exactly the 'palmar surface' may significantly influence burn size estimations and subsequently fluid resuscitation. Our aim is to develop a simple, quick and easy reproducible method of calculating burn injuries for medical professionals in the acute setting. Worldwide, the dimensions of a credit card are standardized (8.5 cm x 5.3 cm), thus producing a surface area of 45 cm2. We created a resuscitation burn card (RBC) using these exact same proportions, upon which a modified body surface area (BSA) nomogram was printed. Knowing the patient height and weight, we calculated the surface area of the card as percentage of total body surface area (TBSA). On the opposite site of the RBC, a Lund and Browder chart was printed, as well as the Parkland formula and a formula to calculate paediatric burn fluid requirements. The plastic, flexible RBC conformed well to the body contour and was designed for single use. We used the resuscitation burn card in the initial assessment of simulated burns in a Regional Burn Centre and in an Accident and Emergency Department. The information present on the card was found to be clear and straightforward to use. The evaluation of burn extent was found to be more accurately measured than the estimation obtained without the RBC. The resuscitation burn card can be a valuable tool in the hands of less experienced medical professionals for the early assessment and fluid resuscitation of a burn.

Burns inflicted by self or by others—An 11 year snapshot

INTRODUCTION

In the United Kingdom, the incidence of assault by burning and of self inflicted burns increased significantly over the last decade. This has major implications both for service providers and society as a whole. Our aim was to investigate the differences in patients' characteristics, management and outcome following a burn sustained by either an assault or self immolation.

METHODS

Acute admissions to a tertiary Burn Centre were retrospectively reviewed over an 11 year period (1994-2005). Demographic data and information regarding the circumstances surrounding the incident, burn severity, treatment and outcomes of the patients were collected.

RESULTS

Over an 11 year period, 1745 patients were admitted to the tertiary Burn Centre. Of this total, 41 patients (mean age 29 years+/-16) sustained burns following an assault, a further 86 patients (mean age of 37 years+/-12) had self inflicted burn injuries; males were preponderant in both groups. In this series, a history of alcohol or substance abuse was present in 25% of both cohorts, 63% of the patients with self inflicted injuries having a previously diagnosed psychiatric disorder. Petrol, accelerants and other flammable liquids were the main agents chosen to inflict injury in both the assault and self inflicted groups. The burn depth and surface area distribution was greater in the self inflicted group compared to those assaulted (29% versus 21%). A difference was also noted in the pattern of distribution of burns between the two groups, as well as between genders although this difference was not significant. Two-thirds (67.4%) of the self immolated patients and 56% of the assaulted group required surgery. The length of hospital stay was similar for both groups, averaging 20 days. The crude mortality for the self inflicted group was 29%, whereas in the assaulted patients, the overall mortality was 4.9%.

CONCLUSION

Although the incidence of burns caused either by assault or attempted suicide is low, the affected patients require a multidisciplinary approach. Their management requires significant medical, psychological occupational and social support. Increased awareness and education of those vulnerable individuals maybe of benefit to help prevent self inflicted injuries by burning.

Reliability of the ICRP'S dose coefficients for members of the public: IV. basis of the human alimentary tract model and uncertainties in model predictions

The biokinetic and dosimetric model of the gastrointestinal (GI) tract applied in current documents of the International Commission on Radiological Protection (ICRP) was developed in the mid-1960s. The model was based on features of a reference adult male and was first used by the ICRP in Publication 30, Limits for Intakes of Radionuclides by Workers (Part 1, 1979). In the late 1990s an ICRP task group was appointed to develop a biokinetic and dosimetric model of the alimentary tract that reflects updated information and addresses current needs in radiation protection. The new age-specific and gender-specific model, called the Human Alimentary Tract Model (HATM), has been completed and will replace the GI model of Publication 30 in upcoming ICRP documents. This paper discusses the basis for the structure and parameter values of the HATM, summarises the uncertainties associated with selected features and types of predictions of the HATM and examines the sensitivity of dose estimates to these uncertainties for selected radionuclides. Emphasis is on generic biokinetic features of the HATM, particularly transit times through the lumen of the alimentary tract, but key dosimetric features of the model are outlined, and the sensitivity of tissue dose estimates to uncertainties in dosimetric as well as biokinetic features of the HATM are examined for selected radionuclides.

Power Converters for Piezoelectric Energy Extraction

Passive circuits and active circuits (i.e., switched-mode power converters) for vibration-energy harvesting are reviewed, focusing on power-extraction efficiency (PEE). Optimal battery voltage and resistance are given for maximal power extraction by passive circuits. Switched-mode converters are reviewed as means to match the actual battery voltage or load resistance to the optimal ones. To emulate the optimal battery voltage or load resistor, these converters could be controlled by pulse-width modulation (PWM) or by resonance, could operate in continuous or discontinuous conduction modes (CCM or DCM), and could leverage the piezoelectric (PZT) impedances in the energy extraction process. The large filter capacitor usually found after the bridge rectifier actually degrades the PEE. Resonance between the output capacitor of the PZT and the converter inductor improves the PEE at the expense of higher voltage and current stresses.

The development of a national standardized approach for the enumeration of residual leucocytes in blood components

BACKGROUND AND OBJECTIVES

The UK Blood Transfusion Services implemented universal leucocyte depletion of the blood supply in November 1999. To provide statistical process monitoring of these processes, automated methods were introduced to count residual leucocytes (white blood cells) in blood components.

MATERIALS AND METHODS

Initially in the National Blood Service (NBS) England, protocols were standardized on the use of LeucoCount reagents with either Becton-Dickinson or Beckman Coulter flow cytometers.

RESULTS

Standardization of protocols resulted in a decreased intersite variability of red cell samples (from 36% to 9% at a level of 11 and 10 cells/ micro l, respectively), and 100% of sites (n = 11) fulfilled the validation criteria. However, we also evaluated the use of alternative reagents with the result that reagents from either Becton-Dickinson or Beckman Coulter, used on either a Becton-Dickinson or Beckman Coulter flow cytometer, passed our validation criteria.

CONCLUSIONS

It is critical to include samples from filtered products containing white blood cells in validations of leucocyte enumeration methodology, as results may differ between methods using these samples but not using spiked or fixed material. Standardized gating strategies and optimization methods for flow cytometers are critical for obtaining equivalent results with different reagents and instruments.

Classification models of child molesters utilizing the Abel Assessment for sexual interest

OBJECTIVE

The aims of this study are to demonstrate 1) the criterion validity of the Abel Assessment for sexual interest (AASI) based on its ability to discriminate between non child molesters and admitting child molesters, and 2) its resistance to falsification based on its ability to discriminate between liar-denier child molesters and non child molesters.

METHOD

A group of 747 participants matched by age, race, and income was used to develop three logistic regression equations. The models compare a group of non child molesting patients under evaluation for other paraphilias to three groups: 1) a group of admitting molesters of girls under 14 years of age, 2) a group of admitting molesters of boys under 14 years of age, and 3) a group believed to be concealing or denying having molested.

RESULTS

Both of the equations designed to discriminate between admitting child molesters and non child molesters were statistically significant. The equation contrasting child molesters attempting to conceal or deny their behavior and non child molesting patients was also statistically significant.

CONCLUSIONS

The models classifying admitting child molesters versus non child molesters demonstrate criterion validity, while the third model provides evidence of the AASI's resistance to falsification and its utility as a tool in the detection of child molesters who deny the behavior. Results of the equations are reported and suggestions for their use are discussed.

Occipital hypoperfusion on SPECT in dementia with Lewy bodies but not AD

OBJECTIVE

To compare regional cerebral blood flow (rCBF) changes using 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) SPECT in subjects with dementia with Lewy bodies (DLB) and AD and in normal age-matched control subjects; to examine the utility of SPECT changes in the differential diagnosis of AD and DLB.

METHOD

Whole-brain SPECT scans were acquired using a single-headed rotating gamma camera (IGE CamStar XR/T) in elderly subjects with consensus criteria DLB (n = 23; mean age = 79.4 years), National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association AD (n = 50; 81.9 years), and normal control subjects (n = 20; 78.1 years) after injection with 500 MBq of 99mTc-HMPAO. Region-of-interest analysis was performed using a SPECT template registered in Talairach space, with rCBF normalized to cerebellum.

RESULTS

Both DLB and AD subjects had significantly reduced rCBF in parietal and temporal regions compared with the control subjects. The AD group also showed a significant reduction in rCBF in the frontal and medial temporal regions and the DLB in the occipital areas compared with control subjects. AD and DLB groups differed only in occipital perfusion (p < 0.01). SPECT measures (occipital and medial temporal) correctly classified 69% of all subjects, with a 65% sensitivity and 87% specificity for DLB against AD and control subjects.

CONCLUSION

Temporoparietal hypoperfusion on SPECT is common to both AD and DLB. Occipital hypoperfusion is more frequently seen in DLB. Although not diagnostically specific in individual cases, occipital hypoperfusion on SPECT should raise suspicion that DLB may be the cause of dementia, prompting careful search for other features of the disorder.

Dosimetric models for thorium and practical problems in assessing intakes

An overview is given of the models recommended by the International Commission on Radiological Protection (ICRP) for assessing intakes and doses, and summarises biokinetic data obtained after the deposition of different chemical compounds of thorium in the rat lung. The results emphasise the importance of using material-specific data rather than default reference values for absorption into blood. The limitations of external monitoring of the chest or urine analysis are discussed, and comments made on alternative strategies for radiological protection of the worker.

Pathogenicity induced by feline leukemia virus, Rickard strain, subgroup A plasmid DNA (pFRA)

A new provirus clone of feline leukemia virus (FeLV), which we named FeLV-A (Rickard) or FRA, was characterized with respect to viral interference group, host range, complete genome sequence, and in vivo pathogenicity in specific-pathogen-free newborn cats. The in vitro studies indicated the virus to be an ecotropic subgroup A FeLV with 98% nucleotide sequence homology to another FeLV-A clone (F6A/61E), which had also been fully sequenced previously. Since subgroup B polytropic FeLVs (FeLV-B) are known to arise via recombination between ecotropic FeLV-A and endogenous FeLV (enFeLV) env elements, the in vivo studies were conducted by direct intradermal inoculation of the FRA plasmid DNA so as to eliminate the possibility of coinoculation of any FeLV-B which may be present in the inoculum prepared by propagating FeLV-A in feline cell cultures. The following observations were made from the in vivo experiments: (i) subgroup conversion from FeLV-A to FeLV-A and FeLV-B, as determined by the interference assay, appeared to occur in plasma between 10 and 16 weeks postinoculation (p.i.); (ii) FeLV-B-like recombinants (rFeLVs), however, could be detected in DNA isolated from buffy coats and bone marrow by PCR as early as 1 to 2 weeks p.i.; (iii) while a mixture of rFeLV species containing various amounts of N-terminal substitution of the endogenous FeLV-derived env sequences were detected at 8 weeks p.i., rFeLV species harboring relatively greater amounts of such substitution appeared to predominate at later infection time points; (iv) the deduced amino acid sequence of rFeLV clones manifested striking similarity to natural FeLV-B isolates, within the mid-SU region of the env sequenced in this work; and (v) four of the five cats, which were kept for determination of tumor incidence, developed thymic lymphosarcomas within 28 to 55 weeks p.i., with all tumor DNAs harboring both FeLV-A and rFeLV proviruses. These results provide direct evidence for how FeLV-B species evolve in vivo from FeLV-A and present a new experimental approach for efficient induction of thymic tumors in cats, which should be useful for the study of retroviral lymphomagenesis in this outbred species.

Evidence-based management of patients with burns

A review of the evidence for the management of burn wounds

A comparative study of silicone net dressing and paraffin gauze dressing in skin-grafted sites

This prospective randomized study has compared paraffin gauze dressing (n = 19) with silicone net dressing (Mepitel, n = 19) applied as the first layer to newly grafted burn wounds. At the first postoperative dressing visual analogue pain scores were greater in the paraffin gauze group (mean 4.4) than in the silicone net group (mean 1.4, P < 0.01). All patients in the paraffin gauze group experienced some degree of pain on dressing removal, whereas 53 per cent of patients in the silicone net group experienced no pain. Overall graft take was similar in both groups, (silicone net mean 95.7 per cent; paraffin gauze mean 94.3 per cent). Dressings were harder to remove in the paraffin gauze group as assessed by a simple scoring system (P < 0.001). In conclusion silicone net dressing confers advantages over conventional paraffin gauze, especially in reducing patient discomfort during dressing changes.

Matrix-assisted UV-laser desorption/ionization mass spectrometric analysis of monoclonal antibodies for the determination of carbohydrate, conjugated chelator, and conjugated drug content

The chemically averaged molecular weights of a variety of native and conjugated monoclonal antibodies, approximately 150,000, were measured by matrix-assisted UV-laser desorption/ionization mass spectrometry. The average mass of the carbohydrate present in a monoclonal antibody was estimated from the difference between the measured mass of the monoclonal antibody and the mass of the protein present in the monoclonal antibody computed from the amino acid translation of the DNA sequence. The loading of chelators and anticancer drugs conjugated to a monoclonal antibody was quantitated from the difference in the measured masses for the conjugated and untreated monoclonal antibody relative to the expected mass change upon conjugation of 1 mol of chelator or drug. The loading results obtained by mass spectrometry were consistent in most cases with measurements obtained by radioactivity trace assay or UV spectrometry. Similar matrix-assisted UV-laser desorption/ionization mass spectrometric studies were also made after reducing untreated and conjugated monoclonal antibodies with dithiothreitol to determine the distribution of carbohydrate and chelator between the light and heavy chains of the molecules. Matrix-assisted UV-laser desorption/ionization mass spectra were used to compute loading values for covalently bound drugs and proteins, while the loading values obtained by use of gel-filtration HPLC and UV spectrometry cannot distinguish between covalently and noncovalently bound drugs and proteins.