UNITY: A low-field magnetic resonance neuroimaging initiative to characterize neurodevelopment in low and middle-income settings.

Measures of physical growth, such as weight and height have long been the predominant outcomes for monitoring child health and evaluating interventional outcomes in public health studies, including those that may impact neurodevelopment. While physical growth generally reflects overall health and nutritional status, it lacks sensitivity and specificity to brain growth and developing cognitive skills and abilities. Psychometric tools, e.g., the Bayley Scales of Infant and Toddler Development, may afford more direct assessment of cognitive development but they require language translation, cultural adaptation, and population norming. Further, they are not always reliable predictors of future outcomes when assessed within the first 12-18 months of a child's life. Neuroimaging may provide more objective, sensitive, and predictive measures of neurodevelopment but tools such as magnetic resonance (MR) imaging are not readily available in many low and middle-income countries (LMICs). MRI systems that operate at lower magnetic fields (< 100mT) may offer increased accessibility, but their use for global health studies remains nascent. The UNITY project is envisaged as a global partnership to advance neuroimaging in global health studies. Here we describe the UNITY project, its goals, methods, operating procedures, and expected outcomes in characterizing neurodevelopment in sub-Saharan Africa and South Asia.

Low-frequency pulse echo reflection of the fundamental shear horizontal mode from part-thickness elliptical defects in plates.

Defect characterization using guided ultrasonic waves remains a challenging subject and requires a full understanding of the interaction of guided waves with a realistic representation of the defect. The characteristics of pulse echo reflection of the SH0 mode from part-thickness elliptical defects in plates is studied via finite element analysis and experimental measurements. The study shows that the reflection ratio spectrum of the SH0 mode from an elliptical defect exhibits periodic pattern due to interference between reflections from the two edges of the defect. The pattern of the reflection ratio spectrum is determined by the ratio of defect length in the incidence direction to wavelength, while the magnitude is affected by the maximum depth and the effective aspect ratio of the defect. Both the pattern and magnitude of the reflection ratio spectrum are found to be highly sensitive to the incidence angle, and the form of the variation of the reflection with angle is a strong function of the defect shape. In addition, a study of circular defects with tapered depth profiles reveals that the reflection is a function of average length of the tapered defect to wavelength ratio, and the magnitude of the reflection diminishes as the ratio increases.

The scattering of the fundamental torsional mode from axi-symmetric defects with varying depth profile in pipes.

Guided ultrasonic waves have been successfully applied to detect defects and corrosion in plates and pipes; however, defect sizing remains challenging due to the complex profiles of the defects encountered in practice. A study of the reflection of the fundamental torsional mode T(0,1) from an axi-symmetric defect with varying depth profile has been carried out via finite element modeling and experimental validation. Defects with gradually varying depth are represented by a series of tapered steps. It is revealed that, for both tapered up- and down-steps, the wave packet is reflected only at the start and end of the steps. The reflections from the start and end of the step have been predicted, and the frequency dependence of the overall reflection from the step has been studied. The study shows that the reflection coefficient varies as a function of the ratio of the average length of the tapered defect to the wavelength due to the interference between the waves reflected from the two ends of the defect. The reflection coefficient maxima decrease as the slope of the taper becomes more gradual, this effect being more pronounced when the ratio of the average defect length to the wavelength increases.

Valvular regurgitation: does cardiovascular magnetic resonance provide additional information compared to echocardiography?

Surgical intervention for chronic aortic or mitral regurgitation in asymptomatic individuals is recommended on the basis of regurgitant severity and the hemodynamic consequences on the left ventricle (LV). Echocardiography is the standard tool in clinical practice for evaluation of adults with chronic regurgitation. Regurgitant volume (RV) and fraction (RF) can be determined as the difference between stroke volumes measured at two intracardiac sites: antegrade flow across the regurgitant valve compared to antegrade flow across a normal valve. Alternatively, these severity measures can be determined by imaging the proximal flow convergence. Regurgitant orifice area also can be determined. However, limitations do exist with echocardiography due to poor image quality, variability in measuring flow diameters and foreshortened views of the ventricle. Cardiac magnetic resonance (CMR) imaging is a promising modality which can also measure regurgitant severity and may provide additional information about LV size and function. Q-flow methods allow measurement of flow velocity and instantaneous volume flow rates in the aorta or pulmonary artery; this data can be integrated over the cardiac cycle to determine RV and RF. CMR also allows accurate measurement of left and right ventricular volumes; the difference in stroke volume between the two ventricles is regurgitant volume. The role of CMR in clinical management of adults with valve regurgitation merits further study. Currently, we find CMR helpful when regurgitant severity is indeterminant on echocardiography (particularly if LV dysfunction is present), when more accurate measures of LV function are needed and when aortic dilation is present.

Scattering of the fundamental shear horizontal mode in a plate when incident at a through crack aligned in the propagation direction of the mode.

A study of the scattering of the fundamental guided wave SH(0) at a through-thickness narrow notch directed along the wave's propagation in a plate is presented. The results are obtained from Finite Element simulations and experimental measurements. Good agreement is found between the simulations and the measurements. The results are shown for a range of crack lengths and shapes. The scattered wave field consists of the reflected and diffracted SH(0) mode and also contributions from mode conversions to the S(0) mode. It is found that the coefficient of direct reflection of the SH(0) mode has an undulating nature depending on the length of the crack. This is caused by interference phenomena that are related to the interaction of different surface wave types generated on the crack surfaces and their diffractions at both tips of the crack. It is shown that the dominating part of this reflection is generated by the delayed "Rayleigh type" surface waves reflected from the far tip of the crack.

Transdermal delivery of regular insulin to chronic diabetic rats: effect of skin preparation and electrical enhancement.

The efficacy of passive transdermal versus electrically-enhanced, or iontophoretic delivery of insulin was studied. The effect of skin pre-treatment on iontophoretic delivery of insulin was also investigated. Rectangular pulses of 0.25 mA/cm2 current amplitude, 2 kHz frequency, and 50% duty cycle were used as anodal stimulation for electrically enhanced transdermal delivery of insulin. Twenty (20) BB/Wor chronic diabetic adult male rats were shaved 48 h prior to the study, and some experimental groups had hair stubble removed with a depilatory lotion. The iontophoretic drug-containing electrode was filled with 3 ml of porcine regular insulin (100 IU/ml) which has been adjusted to an acidic pH of 3.68 using 0.1 M HCl. The iontophoretic electrodes were then adhered to the abdomen of the alert rat. Results of the iontophoretic procedure were quantified by monitoring changes in blood glucose levels. When insulin was placed on the shaved skin, blood glucose levels fell in the chronic diabetic rat. In general, glucose levels fell more quickly and more profoundly using an iontophoretic enhancement of transdermal insulin delivery. However, some skin preparations facilitated movement of insulin more efficiently. The most profound effect of lowered blood glucose occurred when a depilatory lotion was used on the day of the study in conjunction with iontophoresis, where blood glucose levels fell by 61% after 1 h of iontophoretic treatment. Results indicate that insulin was delivered passively at therapeutic levels when the skin had been treated with the depilatory lotion on the same day as the study, was measured through a reduction in blood glucose levels of 29% after 1 h of passive delivery. When the depilatory lotion was used 24 h prior to iontophoresis, blood glucose remained near initial blood glucose levels. In the groups that did not have the depilatory lotion applied, blood glucose levels fell by 8% after 1 h of iontophoretic insulin delivery. The experimental evidence indicates a substantial increase in the penetration of insulin with the same-day application of depilatory lotion in conjunction with iontophoretic enhancement.

Effect of lower extremity muscular fatigue on motor control performance.

PURPOSE: The purpose of this study was to determine whether lower extremity fatigue affects the ability of an individual to balance on an unstable platform. METHODS: Twenty healthy subjects (average age, 29 yr, range, 20 to 39 yr) were tested on an instrumented balance assessment system. Static tests were done on the limbs unilaterally and then bilaterally, and finally a dynamic test was performed in which the subject moved the platform in a circular manner to chase a moving object on a computer screen. After testing, subjects were fatigued using an isokinetic dynamometer, which imposes closed kinetic chain antagonistic exercise on the ankle, knee, and hip, similar to a stair stepper. No rest was allowed, and subjects were fatigued to less than 50% of their initial tested force. Subjects were then immediately retested on the unstable platform using the same testing protocol. All subjects completed the testing. RESULTS: Analysis of pre- and post-fatigue balance results demonstrated significant decreases in motor control performance on the three static tests following exercise to fatigue in all subjects (P < 0.001). CONCLUSIONS: Our findings support anecdotal evidence that fatigued individuals are at increased risk of injury because of loss of balance. Avoidance of fatigue and preconditioning may prevent injury.

Soft tissue reconstruction in the shoulder. Comparison of suture anchors, absorbable staples, and absorbable tacks.

We evaluated three mechanical soft tissue fixation devices (SuperAnchor, Suretac, and the Instrument Makar [IM] Bioabsorbable Staple) in a cadaveric model by examining ultimate tensile failure and modes of failure in simulated Bankart repairs. We attempted to realistically evaluate the strengths of soft tissue reattachment procedures at the anterior glenoid under worst-case conditions--load to failure. Twenty fresh-frozen cadaveric shoulders were used in this investigation. Each of the three techniques was performed in each anterior glenoid rim at one of three locations: superior, middle, or inferior. The subscapularis muscle-tendon was harvested, used in the repair, and loaded to failure. The mean load at failure for the SuperAnchor was 217.32 N; for the IM Staple, 132.32 N; and for the Suretac, 122.37 N. A two-sample t-test demonstrated that the load at failure for the SuperAnchor was statistically greater (P < 0.001) when compared with the IM Staple and Suretac. There was no statistical difference between load at failure for the Suretac and the IM Staple. The most common failure mode for the Mitek was suture breakage (71%). Anchor pullout from bone was the most common failure mode for the IM Staple (75%) and Suretac (94%).

Quadriceps muscle contraction protects the anterior cruciate ligament during anterior tibial translation.

The proposed skiing injury mechanism that suggests a quadriceps muscle contraction can contribute to anterior cruciate ligament rupture was biomechanically investigated. The effect of quadriceps muscle force on a knee specimen loaded to anterior cruciate ligament failure during anterior tibial translation was studied in a human cadaveric model. In both knees from six donors, average age 41 years (range, 31 to 65), the joint capsule and ligaments, except the anterior cruciate ligament, were cut. The quadriceps tendon, patella, patellar tendon, and menisci were left intact. One knee from each pair was randomly selected to undergo destructive testing of the anterior cruciate ligament by anterior tibial translation at a displacement rate of 30 mm/sec with a simultaneously applied 889 N quadriceps muscle force. The knee flexion during testing was 30 degrees. As a control, the contralateral knee was loaded correspondingly, but only 5 N of quadriceps muscle force was applied. The ultimate load for the knee to anterior cruciate ligament failure when tested with 889 N quadriceps muscle force was 22% +/- 18% higher than that of knees tested with 5 N of force. The linear stiffness increased by 43% +/- 30%. These results did not support the speculation that a quadriceps muscle contraction contributes to anterior cruciate ligament failure. In this model, the quadriceps muscle force protected the anterior cruciate ligament from injury during anterior tibial translation.

Comparison of rehabilitative knee braces. A biomechanical investigation.

A biomechanical comparison of eight popular commercially available rehabilitative knee braces was undertaken using a specially designed mechanical surrogate and computerized data acquisition system. Tests conducted included passive extension, valgus rotation, and anterior-posterior tibial translation. Most of the braces tested significantly reduced both translations and rotations compared to the unbraced limb under static test conditions. Braced versus braced performance varied and was found to depend upon a number of mechanical and design factors.

The current state of functional knee bracing research. A review of the literature.

This paper reviews recent research on functional knee bracing. Research is categorized by subject, approach, or technique. The authors conclude that, while there is a good deal of excellent research available, there is little data to assist the clinician in selecting an orthosis for a specific application. The authors recommend that future investigations address the physiologic aspects of functional knee bracing and that brace manufacturers assume more responsibility in the validation of both existing and future brace designs.

Impact biomechanics of lateral knee bracing. The anterior cruciate ligament.

We evaluated the effects of six different prophylactic braces on ACL ligament strain under dynamic valgus loads using a mechanical surrogate limb validated against human cadaveric specimens. Medical collateral ligament and anterior cruciate ligament peak forces, medial collateral ligament and anterior cruciate ligament tension initiation times, and impact safety factors were calculated for both braced and unbraced conditions. These tests were conducted to determine whether or not application of a prophylactic brace might provide protection to the anterior cruciate ligament under valgus loading conditions. The results of this study indicate that those braces that increased impact duration appear to differentially protect the anterior cruciate ligament more than the medial collateral ligament, and that most of the braces tested appear to provide some degree of protection to the anterior cruciate ligament under direct lateral impacts. These findings should be confirmed clinically.

Differences in friction and torsional resistance in athletic shoe-turf surface interfaces.

This study evaluated the shoe-surface interaction of 15 football shoes made by 3 manufacturers in both anterior translation and rotation using a specially designed pneumatic testing system. The shoes included traditional cleated football shoes, "court" shoes (basketball-style shoes), molded-cleat shoes, and turf shoes. Under an 11.35-kg (25-pound) axial load, all shoes were tested on synthetic turf under wet and dry conditions and on natural stadium grass. Test-retest reliability, as calculated using the Pearson Product-Moment Correlation test, was 0.85 for force of translation and 0.55 for the moment of rotation. The wet versus dry surface values on translation were significantly different for rotation about the tibial axis. Spatting, which is protective taping of the ankle and heel applied on the outside of the shoe, resulted in a reduction of forces generated in both translation and rotation. No overall difference between shoes on grass versus AstroTurf was noted. However, there were significant differences for cleated and turf shoes. Shoes tested in conditions for which they were not designed exhibited reproducible excessive or extreme minimal friction characteristics that may have safety implications. On the basis of this study, we urge shoe manufacturers to display suggested indications and playing surface conditions for which their shoes are recommended.

The interaction of Lamb waves with defects.

The interaction of individual Lamb waves with a variety of defects simulated by notches is investigated using finite-element analysis, and the results are checked experimentally. Excellent agreement is obtained. It is shown that a 2-D Fourier transform method may be used to quantify Lamb wave interactions with defects. The sensitivity of individual Lamb waves to particular notches is dependent on the frequency-thickness product, the mode type and order, and the geometry of the notch. The sensitivity of the Lamb modes a(1), alpha(0), and s(0) to simulated defects in different frequency-thickness regions is predicted as a function of the defect depth to plate thickness ratio and the results indicate that Lamb waves may be used to find notches when the wavelength to notch depth ratio is on the order of 40. Transmission ratios of Lamb waves across defects are highly frequency dependent.

In vitro activity of Melaleuca alternifolia (tea tree) oil against bacterial and Candida spp. isolates from clinical specimens.

This study investigates the in vitro activity of tea tree oil (TTO) against a range of wild strains of microorganisms isolated from clinical specimens of leg ulcers and pressure sores. The antimicrobial effectiveness of TTO is determined in terms of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) or minimum fungicidal concentration (MFC). The isolates include methicillin-resistant Staphylococcus aureus (MRSA), S. aureus, faecal streptococci, beta-haemolytic streptococci, coagulase-negative staphylococci, Pseudomonas spp. and coliform bacilli. Eleven Candida spp. isolates from skin and vaginal swabs also are tested. Using an agar dilution assay, the MICs of TTO in 88 out of 90 isolates was 0.5-1.0% (v/v), whilst with P. aeruginosa it was >2% (v/v). A broth microdilution method was used to determine MIC and minimum cidal concentration (MCC) of 80 isolates. In 64 isolates, TTO produced an inhibitory and cidal effect at 3% and 4% (v/v), respectively. S. aureus and Candida spp. were the most susceptible to TTO, with MICs and MBCs of 0.5% and 1%, respectively. P. aeruginosa and the faecal streptococci isolates, with MICs and MBCs of >8%, were resistant to TTO.

Rehabilitation of anterior cruciate ligament injuries.

Rehabilitation of the anterior cruciate ligament absent or reconstructed knee is becoming a true artform. Accelerated, but controlled rehabilitation, is becoming more commonplace. Scientific-based data along with clinical experiences are the basis of the rehabilitation guidelines brought forth in this article. Anterior cruciate ligament strain and implications for exercise, continuous passive motion, proprioceptive exercise, and the role of knee bracing are all discussed in relation to the overall rehabilitation program.

Choosing functional knee braces.

Choosing a functional brace for knee injury is a complex issue complicated by a lack of quantitative research on the subject and an increasing number of braces currently on the market. The correct brace decision will be facilitated by a better understanding of knee injury biomechanics and by a thorough understanding of the choices available. The ultimate selection of a brace should be based on sound mechanical criteria and individualized for each patient. The brace must be mechanically effectual and one the patient likes, has confidence in, and will tolerate. In combination with aggressive rehabilitation, the functional brace can make a significant contribution to returning individuals to functional activity.

Bordetella pertussis isolates studied at the National Health Institute, Wellington, between 1977 and 1981.

Between 1977 and 1982, 199 isolates of Bordetella pertussis were referred to the National Health Institute for confirmation of identity and from mid 1982 for serotyping. The information gained from cultures referred during 1982 has been of assistance to the New Zealand Department of Health in investigating the causes of the present outbreak and has also enabled comparison with the serotypes involved in the present outbreak in the United Kingdom.

In vitro antimicrobial susceptibility of Streptococcus pneumoniae in New Zealand.

Ninety-seven isolates of Streptococcus pneumoniae referred to the National Health Institute between January 1976 and March 1978 were tested for their susceptibility to 10 antimicrobials. All were susceptible to penicillin, erythromycin, chloramphenicol, vancomycin, clindamycin, cephalothin and rifampicin. Resistance to tetracycline was found in 9.3 percent of the isolates, and 9.7 percent were resistant to a combination of sulphamethoxazole and trimethoprim.

Vibrio parahaemolyticus-food poisoning: case report.

Symptoms of food poisoning occurred following the ingestion of raw shellfish purchased in the Auckland area. Vibrio parahaemolyticus was recoverer from the patient. The potential of this and closely related microorganisms to cause illness is reviewed.