Electrospray printing: Unravelling the history of a support free three-dimensional additive manufacturing technology

In this perspective article the author highlights a revolutionary technology, which makes reality, the ability to print true three-dimensional architectures, containing self-standing and self-supporting overhangs in the nano and micrometer scale, without the need for supports of any kind. There have been many attempts to achieve this feature in the rapid prototyping/additive manufacturing fields but has been met with little or no success. Current approaches to three-dimensional printing of self-standing and overhanging architectures have been achieved with the use of some form of supporting mould, secondary process or structure which could be either in the form of a viscous liquid or a solid structure to the coupling of lasers, temperature etc. Unfortunately, the use of such methodologies brings with them many issues and limitations, while destroying the concept of additive manufacturing. Note the author here defines additive manufacturing as a technology able to add materials when required during the fabrication of a 3D architecture without the need for external assistance or supports. These limitations in classical fabrication processes, restricts the use of advanced materials such as living biological cells to sensitive biomolecules to many others, for the forming of three-dimensional biological and non-biological architectures, whilst also increasing the costs and materials waste, which are required for acting as moulds, supports etc

Flow behaviour of dielectric liquids in an electric field

A family of 10 silicone oils with electrical conductivity similar to 10(-13) S m(-1) (a regime hitherto systematically unexplored) and viscosities ranging from 1 to 2000mPas have been Subjected to an electrical field of up to 1.5kV mm(-1) during flow from a needle. The flow behaviour of these liquids is investigated experimentally in the flow rate regime 10(-8)-10(-12) m(3) s(-1) and we analyse the results using the Ohnesorge number. Due to the low electrical conductivity and high electrical relaxation time of the silicone oils, only unsteady transient jets were found. The onset of this type of jetting has been defined using current measurements and, in contrast to conducting liquids, the non-dimensional jet diameter increases with increase in Ohnesorge number. The time elapsed between the start and finish of jetting increases with increasing Ohnesorge number

Scandals from an Island: Testing Anglo-American Corporate Governance Frameworks

Purpose The purpose of this paper is to provide an account of banking scandals in relation to corporate governance (CG) failures in an emerging economy, arguing that Anglo-American ideas of CG are misplaced in traditional settings. Design/methodology/approach Semi-structured interviews were conducted with key stakeholders. Observations of annual general meetings (AGMs) and the personal working experience of one of the researchers, along with documentation, provided triangulating data on CG practices. Findings The authors have found that both of the banks studied had adopted CG practices contrary to the expectations of the Sri Lankan CG codes. Key features of CG practices that emerged from their investigations of these two scandals are ineffectual central bank regulations, familial boards of directors, ceremonial board meetings, biased auditing practices and manipulative AGMs, relying on traditional structures of accountability centred around families, kin and social networks. Research limitations/implications The authors argue, drawing on Weber (1958, 1961, 1968, 1978), that the traditionalist culture mediates the process of rationality in bank governance codes and regulatory frameworks Therefore, practices fall far short of expectations. Originality/value The paper builds on the extended critique of shareholder-centric CG models and their transferability to alien contexts. It contributes to the CG studies calling for more appreciation of the need to move beyond the conventional view of CG problems as simply down to conflicts of interests. The authors complement and advance the decoupling debate in CG studies drawing on the Weberian notion of traditionalism

Thoughts on scaffolds

Scaffolds are instrumental in the engineering of functional tissues, and therefore have been an intense area of interests within the regenerative biology and medicine areas of research and development. Many approaches exist for creating scaffolds with either natural or synthetic advanced materials, which are subsequently coupled with cells and other materials, and microintegrated with the aid of a bioreactor, finally forming a functional three-dimensional tissue. Although many advances have been made over the years, none of these have truly been successful as postulated by literature for either biomedical or clinical utility. For e.g. generated reconstructs, have many limitations, such as poor cell infiltration throughout the entire depth of the scaffold, to the associated cost and time for generating functional reconstructs mimicking native tissue. These and other roadblocks have truly limited the use of scaffolds as tissue engineering biomaterials/building blocks in regenerative medicine. However, these previously faced obstacles have recently been overcome with new scaffolding technologies unearthed and pioneered in 2005, which demonstrate the ability to directly handle large quantities of multiple cell types with both a biopolymer and other advanced materials for simultaneously forming a three-dimensional living reconstruct mimicking native tissues. These recently discovered platform biotechnologies will truly have significant ramifications to the engineering of a three-dimensional tissue and for regenerative medicine in general as these platforms are versatile

Characterisation of Electrospun PS/PU Polymer Blend Fibre Mat for Oil Sorption

Electrospun polystyrene (PS) fibre mat has been shown to have great potential as an oil sorbent due to its high sorption capacity and oil-water selectivity. Poor mechanical properties, due to the lack of inter-fibre bonding, has been a limiting factor in its use in such applications. In this study, mats of polymer blends of polystyrene (PS) and thermoplastic polyurethane (PU) fibres, in different polymer weight ratios, were produced and investigated for possible oil sorption application. A comprehensive physico-chemical, thermal, mechanical and sorption characterisation of the different polymer blends was undertaken, to examine the effect of blend ratio on the fibre mat. Characterisation was by field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX) spectroscopy, attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), thermo-gravimetric and differential analysis (TG-DTA), mechanical tensile testing, and by sorption analysis. The microstructural properties of the fibres appeared significantly dependent upon the relative blend ratio. DSC revealed that good interaction/miscibility existed between the two polymers. Tensile strength characterisation showed that a pure PS fibre mat had a poor tensile strength, but the value increased over one order of magnitude with the addition of PU in the polymer matrix, attributed to the formation of inter-fibre bonds. Conversely, the sorption capacity (SC) decreased with increasing PU addition. Modulating the blend ratio could therefore provide a balance between the desired sorption capacity and the mechanical behaviour of resultant mats. Sorption capacity is a complex interaction between fibre and mat characteristics but the polymer blend technique reported here offers a simple, effective and inexpensive method of addressing the poor mechanical properties of electrospun PS fibre, through enhancing micro/nano scale interactions between the two polymers in the blend

Bio-electrosprayed human neural stem cells are viable and maintain their differentiation potential [version 2; peer review: 2 approved, 1 approved with reservations]

BACKGROUND: Bio-electrospray (BES) is a jet-based delivery system driven by an electric field that has the ability to form micro to nano-sized droplets. It holds great potential as a tissue engineering tool as it can be used to place cells into specific patterns. As the human central nervous system (CNS) cannot be studied in vivo at the cellular and molecular level, in vitro CNS models are needed. Human neural stem cells (hNSCs) are the CNS building block as they can generate both neurones and glial cells. METHODS: Here we assessed for the first time how hNSCs respond to BES. To this purpose, different hNSC lines were sprayed at 10 kV and their ability to survive, grow and differentiate was assessed at different time points. RESULTS: BES induced only a small and transient decrease in hNSC metabolic activity, from which the cells recovered by day 6, and no significant increase in cell death was observed, as assessed by flow cytometry. Furthermore, bio-electrosprayed hNSCs differentiated as efficiently as controls into neurones, astrocytes and oligodendrocytes, as shown by morphological, protein and gene expression analysis. CONCLUSIONS: This study highlights the robustness of hNSCs and identifies BES as a suitable technology that could be developed for the direct deposition of these cells in specific locations and configurations

ASAS-SN follow-up of IceCube high-energy neutrino alerts

We report on the search for optical counterparts to IceCube neutrino alerts released between April 2016 and August 2021 with the All-Sky Automated Survey for SuperNovae (ASAS-SN). Despite the discovery of a diffuse astrophysical high-energy neutrino flux in 2013, the source of those neutrinos remains largely unknown. Since 2016, IceCube has published likely-astrophysical neutrinos as public realtime alerts. Through a combination of normal survey and triggered target-of-opportunity observations, ASAS-SN obtained images within 1 hour of the neutrino detection for 20% (11) of all observable IceCube alerts and within one day for another 57% (32). For all observable alerts, we obtained images within at least two weeks from the neutrino alert. ASAS-SN provides the only optical follow-up for about 17% of IceCube's neutrino alerts. We recover the two previously claimed counterparts to neutrino alerts, the flaring-blazar TXS 0506+056 and the tidal disruption event AT2019dsg. We investigate the light curves of previously-detected transients in the alert footprints, but do not identify any further candidate neutrino sources. We also analysed the optical light curves of Fermi 4FGL sources coincident with high-energy neutrino alerts, but do not identify any contemporaneous flaring activity. Finally, we derive constraints on the luminosity functions of neutrino sources for a range of assumed evolution models

Changes in Invasive Pneumococcal Disease Caused by Streptococcus pneumoniae Serotype 1 Following Introduction of PCV10 and PCV13: Findings from the PSERENADE Project.

Streptococcus pneumoniae serotype 1 (ST1) was an important cause of invasive pneumococcal disease (IPD) globally before the introduction of pneumococcal conjugate vaccines (PCVs) containing ST1 antigen. The Pneumococcal Serotype Replacement and Distribution Estimation (PSERENADE) project gathered ST1 IPD surveillance data from sites globally and aimed to estimate PCV10/13 impact on ST1 IPD incidence. We estimated ST1 IPD incidence rate ratios (IRRs) comparing the pre-PCV10/13 period to each post-PCV10/13 year by site using a Bayesian multi-level, mixed-effects Poisson regression and all-site IRRs using a linear mixed-effects regression (N = 45 sites). Following PCV10/13 introduction, the incidence rate (IR) of ST1 IPD declined among all ages. After six years of PCV10/13 use, the all-site IRR was 0.05 (95% credibility interval 0.04–0.06) for all ages, 0.05 (0.04–0.05) for <5 years of age, 0.08 (0.06–0.09) for 5–17 years, 0.06 (0.05–0.08) for 18–49 years, 0.06 (0.05–0.07) for 50–64 years, and 0.05 (0.04–0.06) for ≥65 years. PCV10/13 use in infant immunization programs was followed by a 95% reduction in ST1 IPD in all ages after approximately 6 years. Limited data availability from the highest ST1 disease burden countries using a 3+0 schedule constrains generalizability and data from these settings are needed