Enhanced Multi-MeV Photon Emission by a Laser-Driven Electron Beam in a Self-Generated Magnetic Field.

We use numerical simulations to demonstrate that a source of collimated multi-MeV photons with high conversion efficiency can be achieved using an all-optical single beam setup at an intensity of 5×10^{22} W/cm^{2} that is already within reach of existing laser facilities. In the studied setup, an unprecedented quasistatic magnetic field (0.4 MT) is driven in a significantly overdense plasma, coupling three key aspects of laser-plasma interactions at high intensities: relativistic transparency, direct laser acceleration, and synchrotron photon emission. The quasistatic magnetic field enhances the photon emission process, which has a profound impact on electron dynamics via radiation reaction and yields tens of TW of directed MeV photons for a PW-class laser.

A microfabricated magnetic force transducer-microaspiration system for studying membrane mechanics.

The application of forces to cell membranes is a powerful method for studying membrane mechanics. To apply controlled dynamic forces on the piconewton scale, we designed and characterized a microfabricated magnetic force transducer (MMFT) consisting of current-carrying gold wires patterned on a sapphire substrate. The experimentally measured forces applied to paramagnetic and ferromagnetic beads as a function of applied current agree well with theoretical models. We used this device to pull tethers from microaspirated giant unilamellar vesicles and measure the threshold force for tether formation. In addition, the interlayer drag coefficient of the membrane was determined from the tether-return velocity under magnetic force-free conditions. At high levels of current, vesicles expanded as a result of local temperature changes. A finite element thermal model of the MMFT provided absolute temperature calibration, allowing determination of the thermal expansivity coefficient of stearoyl-oleoyl-phosphatidycholine vesicles (1.7 ± 0.4 × 10(-3) K(-1)) and characterization of the Joule heating associated with current passing through the device. This effect can be used as a sensitive probe of temperature changes on the microscale. These studies establish the MMFT as an effective tool for applying precise forces to membranes at controlled rates and quantitatively studying membrane mechanical and thermo-mechanical properties.

Dynamics of fracture in drying suspensions.

We investigate the dynamics of fracture in drying films of colloidal silica. Water loss quenches the nanoparticle dispersions to form a liquid-saturated elastic network of particles that relieves drying-induced strain by cracking. These cracks display intriguing intermittent motion originating from the deformation of arrested crack tips and aging of the elastic network. The dynamics of a single crack exhibits a universal evolution, described by a balance of the driving elastic power with the sum of interfacial power and the viscous dissipation rate of flowing interstitial fluid.

Ocular injuries caused by magpies.

This paper presents a series of six patients with ocular injuries resulting from magpie attacks. Five cases involved children. In two cases the penetration was overlooked initially. In one case the keratitis was caused by Bacillus cereus. Full ophthalmic examination, including indirect ophthalmoscopy and microbiological studies, must be undertaken initially to identify unrecognised eye injuries and to prevent the possible sight-threatening complications of vitreal fibrosis with subsequent retinal detachment or endophthalmitis.

Assessment of the Queensland School Health Service vision screening programme.

Despite the widespread acceptance of vision screening programmes as a means of detecting ocular disorders in children, there has been little formal assessment of their validity and reliability. One such screening programme is conducted in Queensland State Primary Schools by the Division of School Health Services of the State Department of Health. A group of 877 children was screened by the Service and subsequently subjected to a formal independent ophthalmological examination. A comparison of the results of these procedures revealed that the visual screen as performed by the Service was highly accurate in the determination of distant visual acuity. Detection of manifest strabismus was less satisfactory, with between 30 and 74% of sufferers being detected. There is no evidence to suggest that a more complex protocol will improve the detection of ocular disorders. Rather, a more effective implementation of the current screening procedure is required.

Further investigation of a strabismus model.

Computer models of strabismus have been available for about ten years. Such models are computer programs which perform a set of calculations based on an interpretation of the oculomotor system as a system of two spheres each with six adjustable springs. The effects of pathology and surgery can be simulated by altering the parameters of the springs. However, such models have not yet met with wide practical acceptance. One reason for this lack of interest is that previous investigators have neglected to apply strabismus models to concomitant strabismus. In this paper the application of a strabismus model to concomitant strabismus is demonstrated and data are generated which should be clinically useful. Another reason for lack of acceptance of computer models results from the expectation that they may be unreliable because of biological variability. The model developed here is tested for its sensitivity to a wide range of biological variations and proves to be very robust. Therefore, information on concomitant squint surgery given by the model should be applicable to most patients.

A corneal abnormality associated with trisomy 8 mosaicism syndrome.

Eye abnormalities are a significant feature of trisomy 8 mosaicism syndrome. This paper gives the first account of the specific histopathology of a corneal opacity which is characteristic of this syndrome. The importance of early recognition is stressed because of potential therapeutic visual improvement. The necessity of including mosaic trisomy 8 in the differential diagnosis of such corneal opacities is illustrated by this case.

Pre-school vision screening-a pilot study.

The importance of early vision screening in children is well known, but also are the difficulties of choosing a satisfactory programme and its implementation. This paper describes the reasons for the programme being implemented and discusses the method by examination and the co-operation required to carry it out. More than 10,000 children were screened by more than 350 voluntary family doctors. The examinations were carried out throughout Queensland in pre-school centres. The family doctors were fundamental in the success of the programme, as they had the considerable task of examining the children. The scheme was made possible by the co-operation of the family doctors through the help of the Royal Australian College of General Practitioners, The Family Medicine Programme and the Australian Medical Association. These organisations, together with the Division of School Health, Queensland, and The Royal Australian College of Ophthalmologists were responsible for the organisation of the scheme. The results of the Pilot Study and the requirements for an on-going programme are discussed.

The incidence and the results of active treatment of acute retrolental fibroplasia.

Over a four year period three hundred and thirty-nine (339) "at risk" premature neonates were examined, and sixty-five (65) cases of acute R.L.F. (19%) were detected. The overall observed incidence of acute R.L.F. in these surviving babies under 1000 gms birthweight was 47%, in those whose birthweight was 1001-1500 gms the incidence was 22%. The incidence of acute R.L.F., in those babies whose birthweight was greater than 1501-2000 gms was 4.0%. Most of the cases of acute R.L.F. that were detected occurred in those infants with a birth weight less than 1500 gms. Seventy-eight per cent (78%) of these cases of acute R.L.F. were mild and resolved spontaneously. Severe cases occurred only in those babies with a very low birthweight (less than 1100 gms). Active treatment with cryopexy or photocoagulation was undertaken in 15 eyes of 9 infants. Thirteen (13) of the fifteen (15) eyes treated resolved, and there were no blind patients in the series at the end of the study.

Electrophysiological assessment of compressive lesions of anterior visual pathways.

The findings in the pattern reversal V.E.C.P.'s have been examined in thirteen (13) patients, with proven or suspected pituitary tumours. Three (3) of these cases have been examined in detail, to highlight the unique capabilities of the pattern reversal V.E.C.P. in the assessment of conduction abnormalities of optic nerve and chiasma, due to compression by pituitary tumours. The V.E.C.P. is shown to be a uniquely sensitive procedure, which yields objective and quantitative data about the functional status of the anterior visual pathways, in cases of suspected compression by pituitary tumours. It is suggested that subclinical optic nerve compression is best detected by serially monitoring optic nerve conduction with the pattern reversal V.E.C.P.

Retrolental fibroplasia today.

The incidence of retrolental fibroplasia (RLF, retinopathy of prematurity) is increasing, as more premature infants of lower birth weight are surviving. Currently, about 17% of premature neonates at risk will develop this condition, although in 85% of these cases it will undergo spontaneous resolution. This paper reviews our current knowledge and management of RLF, and aims to remind us that sophisticated monitoring techniques have not eliminated the problems of hyperoxia.