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Tissue engineered bone scaffolds are potential alternatives to bone allografts and autografts. Porous scaffolds based on triply periodic minimal surfaces (TPMS) are good candidates for tissue growth because they offer high surface-to-volume ratio, have tailorable stiffness, and can be easily fabricated by additive manufacturing. However, the range of TPMS scaffold types is extensive, and it is not yet clear which type provides the fastest cell or tissue growth while being sufficiently stiff to act as a bone graft. Nor is there currently an established methodology for TPMS bone scaffold design which can be quickly adopted by medical designers or biologists designing implants. In this study, we examine six TPMS scaffold types for use as tissue growth scaffolds and propose a general methodology to optimise their geometry. At the macro-scale, the optimisation routine ensures a scaffold stiffness within suitable limits for bone, while at the micro-scale it maximises the cell growth rate. The optimisation procedure also ensures the scaffold pores are of sufficient diameter to allow oxygen and nutrient delivery via capillaries. Of the examined TPMS structures, the Lidinoid and Split P cell types provide the greatest cell growth rates and are therefore the best candidates for bone scaffolds., (© 2021. The Author(s).)

This study aimed at assessing occupational radiation doses in different diagnostic, interventional and therapeutic services. Personal dose equivalent, Hp(10), of 116 medical radiation workers, all with 3 y of dose records (2015-18), were collected from the TLD dosimetry service at the Sultan Qaboos University Hospital-a 700-bed tertiary care teaching hospital in Oman. The doses were measured using calibrated thermo-luminescence dosemeters (TLD-100 (LiF:Mg,Ti)). Five occupational groups, diagnostic radiology, interventional radiology, nuclear medicine, medical physicists and nurses, were considered. Average, maximum and median cumulative doses were estimated and compared against the annual dose limit (20 mSv per y) and the local dose investigation level (DIL) (6 mSv per y). Personal doses (average:maximum:median) for diagnostic radiology, interventional radiology, nuclear medicine, medical physicists and nurses group were found to be 0.05:0.90:0.00, 0.05:0.50:0.00, 1.20:7.40:0.40, 0.16:1.40:0.00 and 0.10:2.10:0.00 mSv, respectively. The findings of this study suggest, at the exception of nuclear medicine, lower DILs for all occupational groups., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Recent advances in additive manufacturing have enabled fabrication of phononic crystals and metamaterials which exhibit spectral gaps, or stopbands, in which the propagation of elastic waves is prohibited by Bragg scattering or local resonance effects. Due to the high level of design freedom available to additive manufacturing, the propagation properties of the elastic waves in metamaterials are tunable through design of the periodic cell. In this paper, we outline a new design approach for metamaterials incorporating internal resonators, and provide numerical and experimental evidence that the stopband exists over the irreducible Brillouin zone of the unit cell of the metamaterial (i.e. is a three-dimensional stopband). The targeted stopband covers a much lower frequency range than what can be realised through Bragg scattering alone. Metamaterials have the ability to provide (a) lower frequency stopbands than Bragg-type phononic crystals within the same design volume, and/or (b) comparable stopband frequencies with reduced unit cell dimensions. We also demonstrate that the stopband frequency range of the metamaterial can be tuned through modification of the metamaterial design. Applications for such metamaterials include aerospace and transport components, as well as precision engineering components such as vibration-suppressing platforms, supports for rotary components, machine tool mounts and metrology frames.

We report on numerical modelling of three-dimensional lattice structures designed to provide phononic bandgaps. The examined lattice structures rely on two distinct mechanisms for bandgap formation: the destructive interference of elastic waves and internal resonance. Further to the effect of lattice type on the development of phononic bandgaps, we also present the effect of volume fraction, which enables the designer to control the frequency range over which the bandgaps exist. The bandgaps were identified from dispersion curves obtained using a finite element wave propagation modelling technique that provides high computational efficiency and high wave modelling accuracy. We show that lattice structures employing internal resonance can provide transmissibility reduction of longitudinal waves of up to -103 dB. Paired with the manufacturing freedom and material choice of additive manufacturing, the examined lattice structures can be tailored for use in wide-ranging applications including machine design, isolation and support platforms, metrology frames, aerospace and automobile applications, and biomedical devices.

Recent advances in the preparation, control and measurement of atomic gases have led to new insights into the quantum world and unprecedented metrological sensitivities, e.g. in measuring gravitational forces and magnetic fields. The full potential of applying such capabilities to areas as diverse as biomedical imaging, non-invasive underground mapping, and GPS-free navigation can only be realised with the scalable production of efficient, robust and portable devices. We introduce additive manufacturing as a production technique of quantum device components with unrivalled design freedom and rapid prototyping. This provides a step change in efficiency, compactness and facilitates systems integration. As a demonstrator we present an ultrahigh vacuum compatible ultracold atom source dissipating less than ten milliwatts of electrical power during field generation to produce large samples of cold rubidium gases. This disruptive technology opens the door to drastically improved integrated structures, which will further reduce size and assembly complexity in scalable series manufacture of bespoke portable quantum devices.

Molecular beam epitaxial growth of ferromagnetic MnSb(0001) has been achieved on high quality, fully relaxed Ge(111)/Si(111) virtual substrates grown by reduced pressure chemical vapor deposition. The epilayers were characterized using reflection high energy electron diffraction, synchrotron hard X-ray diffraction, X-ray photoemission spectroscopy, and magnetometry. The surface reconstructions, magnetic properties, crystalline quality, and strain relaxation behavior of the MnSb films are similar to those of MnSb grown on GaAs(111). In contrast to GaAs substrates, segregation of substrate atoms through the MnSb film does not occur, and alternative polymorphs of MnSb are absent.

Depth-dependent magnetism in MnSb(0001) epitaxial films has been studied by combining experimental methods with different surface specificities: polarized neutron reflectivity, x-ray magnetic circular dichroism (XMCD), x-ray resonant magnetic scattering and spin-polarized low energy electron microscopy (SPLEEM). A native oxide ∼4.5 nm thick covers air-exposed samples which increases the film's coercivity. HCl etching efficiently removes this oxide and in situ surface treatment of etched samples enables surface magnetic contrast to be observed in SPLEEM. A thin Sb capping layer prevents oxidation and preserves ferromagnetism throughout the MnSb film. The interpretation of Mn L(3,2) edge XMCD data is discussed.

Objectives: This study was conducted to assess whether the radiation exposure levels of Omani family members of thyrotoxic patients, if treated with radioiodine therapy as outpatients, are within the international and local radiation dose limits in order to allow them to be treated as outpatients., Methods: The study included 86 family members of 22 self-dependent thyrotoxic patients (29 children ≤ 16 yrs and 57 adults including 11 spouses and 8 parents). The mean age of the family members was 26.6 years (range 17 months - 75 years).They were treated with (131)I as outpatients and monitored for 10 days in 2007-2008 for radiation exposure using thermoluminescent dosimeters (TLDs). The mean administered activity of (131)I to patients (±SD) was 610 ±79MBq in the range 520-862 MBq. Oral and written radiation safety instructions were given to patients and family members before leaving the hospital., Results: The radiation doses received by family members were less than the annual recommended dose limit for general public of 1mSv, except for four children aged 19 months, 12, 13 and 15 years, who received radiation doses of 2.9, 1.2, 1.2 and 1.2 mSv respectively., Conclusion: In view of the low radiation doses received by the family members, we recommend treating thyrotoxic patients undergoing radioiodine therapy with administered activities up to 800 MBq as outpatients.