A flexible method for rapid force computation in elliptical magnets

The design of open-access elliptical cross-section magnet systems has recently come under consideration. Obtaining values for the forces generated within these unusual magnets is important to progress the designs towards feasible instruments. This paper presents a novel and flexible method for the rapid computation of forces within elliptical magnets. The method is demonstrated by the analysis of a clinical magnetic resonance imaging magnet of elliptical cross-section and open design. The analysis reveals the non-symmetric nature of the generated Maxwell forces, which are an important consideration, particularly in the design of superconducting systems.

Rapid diagnosis in pediatric infectious diseases: The past, the present and the future

The focus of rapid diagnosis of infectious diseases of children in the last decade has shifted from variations of the conventional laboratory techniques of antigen detection, microscopy and culture to that of molecular diagnosis of infectious agents. Pediatricians will need to be able to interpret the use, limitations and results of molecular diagnostic techniques as they are increasingly integrated into routine clinical microbiology laboratory protocols. PCR is the best known and most successfully implemented diagnostic molecular technology to date. It can detect specific infectious agents and determine their virulence and antimicrobial genotypes with greater speed, sensitivity and specificity than conventional microbiology methods. Inherent technical limitations of PCR are present, although they are reduced in laboratories that follow suitable validation and quality control procedures. Variations of PCR together with advances in nucleic acid amplification technology have broadened its diagnostic capabilities in clinical infectious disease to now rival and even surpass traditional methods in some situations. Automation of all components of PCR is now possible. The completion of the genome sequencing projects for significant microbial pathogens, in combination with PCR and DNA chip technology, will revolutionize the diagnosis and management of infectious diseases.

Rapid isolation of total RNA and genomic DNA from Hakea actities

Tissues of the Australian native plant species Hakea actities (Proteaceae) contain numerous metabolites and structural compounds that hinder the isolation of nucleic acids. Separate RNA and genomic DNA extraction procedures were developed to isolate high quality nucleic acids from H. actities. Total RNA was extracted from leaves, roots and cluster roots of H. actities grown in low nutrient levels. Cluster root formation in H. actities only occurs when the plants are grown in low nutrient concentrations. However, under these conditions, nucleic acid extraction becomes increasingly difficult. The new procedures are faster than many of the published nucleic acid extraction protocols, and avoid the use of hazardous chemicals. The RNA extraction method was used successfully on another Australian species and a crop species, suggesting that the procedure is useful for molecular studies of a broad range of plants.

A rapid screen of the severity of mild traumatic brain injury

This study investigated the sensitivity of information processing, recall and orientation tasks to the presence of mild Traumatic Brain Injury (mTBI). Fifty-six (40 male, 16 female) mTBI patients and 85 (57 male and 28 female) controls with orthopaedic injuries were tested within 24 hr of injury in the Department of Emergency Medicine. mTBI patients answered fewer orientation questions and recalled fewer words in delayed recall than orthopaedic patients. mTBI patients judged fewer sentences in 2 min than orthopaedic controls, and female mTBI patients judged fewer sentences than male mTBI patients. Male mTBI patients correctly recalled fewer words during immediate memory and learning than female mTBI patients and orthopaedic controls. Those mTBI patients with a history of previous head injuries did not perform more poorly than those mTBI patients without previous head injuries. These results indicate that tests of speed of information processing, word learning and orientation questions are sensitive to the acute effects of mTBI.

Quadriceps concentric and eccentric exercise 1: Changes in contractile and electrical activity following eccentric and concentric exercise

The purpose of this study was to determine whether or not losses of strength or endurance following eccentric and concentric exercise are associated with reduced excitation. The effects of eccentric and concentric work on maximal voluntary isometric contraction (MVC) and surface electromyogram (EMG) of the quadriceps were studied in 10 healthy male subjects following bench-stepping for 20 min with a constant leading leg. Prior to stepping and at 0, 0.25, 0.50, 0.75, 1, 3. 24 and 48 h afterwards the subjects performed a 30 s leg extension MVC with each leg during which the isometric force and the root mean square voltage of the EMG were recorded. In the eccentrically exercised muscles (ECC), MVC0-3 (force during the first 3 s of contraction) fen immediately after the bench-stepping exercise to 88 +/- 2% (mean SE) of the pre-exercise value and remained significantly lower than the concentrically exercised muscles (p < 0.05). The muscle weakness in the ECC could not be attributed to central fatigue as surface EMG amplitude at MVC0-3 increased during the recovery period. Muscle weakness after eccentric exercise appears to be due to contractile failure, which is not associated with a reduction in excitation as assessed by surface EMG. Muscular fatigue over 30 s did not change in the two muscle groups after exercise (p = 0.79), indicating that the ECC were weaker but not more fatiguable after exercise.

Deep and superficial fibers of the lumbar multifidus muscle are differentially active during voluntary arm movements

AB Study Design. A cross-sectional study was conducted. Objective. To determine the activity of the deep and superficial fibers of the lumbar multifidus during voluntary movement of the arm. Summary of Background Data. The multifidus contributes to stability of the lumbar spine. Because the deep and superficial parts of the multifidus are near the center of lumbar joint rotation, the superficial fibers are well suited to control spine orientation, and the deep fibers to control intervertebral movement. However, there currently are limited in vivo data to support this distinction. Methods. Electromyographic activity was recorded in both the deep and superficial multifidus, transversus abdominis, erector spinae, and deltoid using selective intramuscular electrodes and surface electrodes during single and repetitive arm movements. The latency of electromyographic onset in each muscle during single movements and the pattern of electromyographic activity during repetitive movements were compared between muscles. Results. With single arm movements, the onset of electromyography in the erector spinae and superficial multifidus relative to the deltoid was dependent on the direction of movement, but the onset in the deep multifidus and transversus abdominis was not. With repetitive arm movements, peaks in superficial multifidus and erector spinae electromyography occurred only during flexion for most subjects, whereas peaks in deep multifidus electromyography occurred during movement in both directions. Conclusions. The deep and superficial fibers of the multifidus are differentially active during single and repetitive movements of the arm. The data from this study support the hypothesis that the superficial multifidus contributes to the control of spine orientation, and that the deep multifidus has a role in controlling intersegmental motion. (C) 2002 Lippincott Williams & Wilkins, Inc.

The influence of a concurrent cognitive task on the compensatory stepping response to a perturbation in balance-impaired and healthy elders

This study investigated the influence of a concurrent cognitive task on the compensatory stepping response in balance-impaired elders and the attentional demand of the stepping response. Kinetic, kinematic and neuromuscular measures of a forward recovery step were investigated in 15 young adults, 15 healthy elders and 13 balance-impaired elders in a single task (postural recovery only) and dual task (postural recovery and vocal reaction time task) situation. Results revealed that reaction times were longer in all subjects when performed concurrently with a compensatory step, they were longer for a step than an in-place response and longer for balance-impaired older adults compared with young adults. An interesting finding was that the latter group difference may be related to prioritization between the two tasks rather than attentional demand, as the older adults completed the step before the reaction time, whereas the young adults could perform both concurrently. Few differences in step characteristics were found between tasks, with the most notable being a delayed latency and reduced magnitude of the early automatic postural response in healthy and balance-impaired elders with a concurrent task. (C) 2002 Elsevier Science B.V. All rights reserved.

New W-isotope evidence for rapid terrestrial accretion and very early core formation

The short-lived Hf-182-W-182-isotope system is an ideal clock to trace core formation and accretion processes of planets. Planetary accretion and metal/silicate fractionation chronologies are calculated relative to the chondritic Hf-182-W-182-isotope evolution. Here, we report new high-precision W-isotope data for the carbonaceous chondrite Allende that are much less radiogenic than previously reported and are in good agreement with published internal Hf-W chronometry of enstatite chondrites. If the W-isotope composition of terrestrial rocks, representing the bulk silicate Earth, is homogeneous and 2.24 epsilon(182W) units more radiogenic than that of the bulk Earth, metal/silicate differentiation of the Earth occurred very early. The new W-isotope data constrain the mean time of terrestrial core formation to 34 million years after the start of solar system accretion. Early terrestrial core formation implies rapid terrestrial accretion, thus permitting formation of the Moon by giant impact while Hf-182 was still alive. This could explain why lunar W-isotopes are more radiogenic than the terrestrial value. Copyright (C) 2002 Elsevier Science Ltd.

Rapid field calculations for the effect of ferromagnetic material in MRI magnet design

Magnetic resonance imaging (MRI) magnets have very stringent constraints on the homogeneity of the static magnetic field that they generate over desired imaging regions. The magnet system also preferably generates very little stray field external to its structure, so that ease of siting and safety are assured. This work concentrates on deriving, means of rapidly computing the effect of 'cold' and 'warm' ferromagnetic material in or around the superconducting magnet system, so as to facilitate the automated design of hybrid material MR magnets. A complete scheme for the direct calculation of the spherical harmonics of the magnetic field generated by a circular ring of ferromagnetic material is derived under the conditions of arbitrary external magnetizing fields. The magnetic field produced by the superconducting coils in the system is computed using previously developed methods. The final, hybrid algorithm is fast enough for use in large-scale optimization methods. The resultant fields from a practical example of a 4 T, clinical MRI magnet containing both superconducting coils and magnetic material are presented.

A rapid PCR protocol for marker assisted detection of heterozygotes in segregating generations involving 1BL/1RS translocation and normal wheat lines

A rapid and reliable polymerase chain reaction (PCR)-based protocol was developed for detecting zygosity of the 1BL/1RS translocation in hexaploid wheat. The protocol involved a multiplex PCR with 2 pairs of oligonucleotide primers, rye-specific Ris-1 primers, and consensus 5S intergenic spacer (IGS) primers, and digestion of the PCR products with the restriction enzyme, MseI. A small piece of alkali-treated intact leaf tissue is used as a template for the PCR, thereby eliminating the necessity for DNA extraction. The test is simple, highly sensitive, and rapid compared with the other detection systems of 1BS1RS heterozygotes in hexaploid wheat. PCR results were confirmed with AFLP analyses. Diagnostic tests for 1BL/1RS translocation based on Sec-1-specific ELISA, screening for chromosome arm 1RS controlled rust resistance locus Yr9, and the PCR test differed in their ability to detect heterozygotes. The PCR test and rust test detected more heterozygotes than the ELISA test. The PCR test is being used to facilitate S1 family recurrent selection in the Germplasm Enhancement Program of the Australian Northern Wheat Improvement Program. A combination of the PCR zygosity test with other markers currently being implemented in the breeding program makes this test economical for 1BL/1RS characterisation of S1 families.

Rapid genotyping of loci involved in antifolate drug resistance in Plasmodium falciparum by primer extension

Current methods used to genotype point mutations in Plasmodium falciparum genes involved in resistance to antifolate drugs include restriction digestion of PCR products, allele-specific amplification or sequencing. Here we demonstrate that known point mutations in dihydrofolate reductase and dihydropteroate synthase can be scored quickly and accurately by single-nucleotide primer extension and detection of florescent products on a capillary sequencer. We use this method to genotype parasites in natural infections from the Thai-Myanmar border. This approach could greatly simplify large-scale screening of resistance mutations of the type required for evaluating and updating antimalarial drug treatment policies. The method can be easily adapted to other P. falciparum genes and will greatly simplify scoring of point mutations in this and other parasitic organisms. © 2002 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.

Auditor conservatism and voluntary disclosure: Evidence from the Year 2000 systems issue

This study further examines the phenomenon of conservative auditor behaviour by considering the level of voluntary disclosure of Year 2000 remediation information in company annual reports. Previous studies have provided evidence of conservative auditor behaviour by examining the link between Big 6 auditor choice and accruals (Francis and Krishnan 1999; Becker et al., 1998; Defond and Subramanyam 1998). Protecting their reputation capital increases Big 6 auditor incentives to act conservatively to avoid litigation risk. We propose and find that Big 6 auditor clients disclose more Year 2000 remediation information than non–Big 6 auditor clients.

Rapid colour changes in multilayer reflecting stripes in the paradise whiptail, Pentapodus paradiseus

The Paradise whiptail (Pentapodus paradiseus) has distinct reflective stripes on its head and body. The reflective stripes contain a dense layer of physiologically active iridophores, which act as multilayer reflectors. The wavelengths reflected by these stripes can change from blue to red in 0.25 s. Transmission electron microscopy revealed that the iridophore cells contain plates that are, on average, 51.4 nm thick. This thickness produces a stack, which acts as an ideal quarter-wavelength multilayer reflector (equal optical thickness of plates and spaces) in the blue, but not the red, region of the spectrum. When skin preparations were placed into hyposmotic physiological saline, the peak wavelength of the reflected light shifted towards the longer (red) end of the visible spectrum. Hyperosmotic saline reversed this effect and shifted the peak wavelength towards shorter (blue/UV) wavelengths. Norepinephrine (100 mumol l(-1)) shifted the peak wavelength towards the longer end of the spectrum, while adenosine (100 mumol l(-1)) reversed the effects of norepinephrine. The results from this study show that the wavelength changes are elicited by a change of similar to70 nm in the distance between adjacent plates in the iridophore cells.

A rapid method for determining recent sunscreen use in field studies

The role of sunscreens in preventing skin cancer and melanoma is the focus of ongoing research. Currently, there is no objective measure which can be used in field studies to determine whether a person has applied sunscreen to their skin, and researchers must use indirect assessments such as questionnaires. We sought to develop a rapid, non-invasive method for identifying sunscreen on the skin for use in epidemiological studies. Our basic method is to swab the skin, elute any residues which have been adsorbed onto the swab by rinsing in ethanol, and submit the eluted washings for spectrophotometric analysis. In a controlled study, we applied 0.1 ml of sunscreen to a 50 cm(2) grid on both forearms of 21 volunteers. Each forearm was allocated one of 10 different sunscreen brands. The skin was swabbed after intervals of 20 min, 1 h, 2 h and 4 h. In a field study conducted among 12 children aged 2-4 years attending a child care centre, sunscreen was applied to the faces of half the children. Swabs were then taken from the face and back of all children without knowledge of sunscreen status. In the controlled study, sunscreen was clearly detectable up to 2 h after application for all brands containing organic sunscreen, and marginally detectable at 4 h. In the field study, this method correctly identified all children with and without sunscreen. We conclude that spectrophotometric analysis of skin swabs can reliably detect the presence of sunscreen on the skin for up to 2 It after application. (C) 2002 Elsevier Science B.V. All rights reserved.