Explore the vast range of titles available.

In the Fluid Mosaic Model for biological membrane structure, proposed by Singer and Nicolson in 1972, the lipid bilayer is represented as a neutral two-dimensional solvent in which the proteins of the membrane are dispersed and distributed randomly. The model portrays the membrane as dominated by a membrane lipid bilayer, directly exposed to the aqueous environment, and only occasionally interrupted by transmembrane proteins. This view is reproduced in virtually every textbook in biochemistry and cell biology, yet some critical features have yet to be closely examined, including the key parameter of the relative occupancy of protein and lipid at the center of a natural membrane. Here we show that the area occupied by protein and lipid at the center of the human red blood cell (RBC) plasma membrane is at least [almost equal to]23% protein and less than [almost equal to]77% lipid. This measurement is in close agreement with previous estimates for the RBC plasma membrane and the recently published measurements for the synaptic vesicle. Given that transmembrane proteins are surrounded by phospholipids that are perturbed by their presence, the occupancy by protein of more than [almost equal to]20% of the RBC plasma membrane and the synaptic vesicle plasma membrane implies that natural membrane bilayers may be more rigid and less fluid than has been thought for the past several decades, and that studies of pure lipid bilayers do not fully reveal the properties of lipids in membranes. Thus, it appears to be the case that membranes may be more mosaic than fluid, with little unperturbed phospholipid bilayer.

The pH-selective insertion and folding of a membrane peptide, pHLIP [pH (low) insertion peptide], can be used to target acidic tissue in vivo, including acidic foci in tumors, kidneys, and inflammatory sites. In a mouse breast adenocarcinoma model, fluorescently labeled pHLIP finds solid acidic tumors with high accuracy and accumulates in them even at a very early stage of tumor development. The fluorescence signal is stable for >4 days and is approximately five times higher in tumors than in healthy counterpart tissue. In a rat antigen-induced arthritis model, pHLIP preferentially accumulates in inflammatory foci. pHLIP also maps the renal cortical interstitium; however, kidney accumulation can be reduced significantly by providing mice with bicarbonate-containing drinking water. The peptide has three states: soluble in water, bound to the surface of a membrane, and inserted across the membrane as an α-helix. At physiological pH, the equilibrium is toward water, which explains its low affinity for cells in healthy tissue; at acidic pH, titration of Asp residues shifts the equilibrium toward membrane insertion and tissue accumulation. The replacement of two key Asp residues located in the transmembrane part of pHLIP by Lys or Asn led to the loss of pH-sensitive insertion into membranes of liposomes, red blood cells, and cancer cells in vivo, as well as to the loss of specific accumulation in tumors. pHLIP nanotechnology introduces a new method of detecting, targeting, and possibly treating acidic diseased tissue by using the selective insertion and folding of membrane peptides.

Despite significant interest in their functional properties, the mechanical behavior of high-entropy oxides (HEOs) is not well studied, particularly at elevated temperatures. Bulk (Co,Cu,Mg,Ni,Zn)O (transition metal (TM)-HEO) samples were deformed under compression at applied stresses and temperatures ranging from 5 to 31 MPa and 600 to 850 °C, respectively. All of the deformation conditions result in creep stress exponents of n < 3, indicating that TM-HEO exhibits superplastic deformation. A transition from structural to solution-precipitation-based superplasticity is observed during deformation above 650 °C. Additionally, TM-HEO exhibits shear-thickening behavior when deformed at stresses above 9 MPa. The formation and behavior of a Cu-rich tenorite secondary phase during deformation is identified as a key factor underpinning the deformation mechanisms. The microstructure and phase state of TM-HEO before deformation also influenced the behavior, with finer grain sizes and increasing concentrations of Cu-rich tenorite, resulting in the increased prevalence of solution-precipitation deformation. While complex, the results of this study indicate that TM-HEO deforms through known superplastic deformation mechanisms. Superplasticity is a highly efficient manufacturing method and could prove to be a valuable strategy for forming HEO ceramics into complex geometries.

Additive manufacturing of solid-state batteries is advantageous for improving the power density by increasing the geometric complexity of battery components, such as electrodes and electrolytes. In the present study, bulk three-dimensional Li 1+ x Al x Ti 2− x (PO 4 ) 3 (LATP) electrolyte samples were prepared using the laser powder bed fusion (L-PBF) additive manufacturing method. Li 3 PO 4 (LPO) was added to LATP to compensate for lithium vaporization during processing. Chemical compositions included 0, 1, 3, and 5 wt. % LPO. Resulting ionic conductivity values ranged from 1.4 × 10 −6 –6.4 × 10 −8 S cm −1 , with the highest value for the sample with a chemical composition of 3 wt. % LPO. Microstructural features were carefully measured for each chemical composition and correlated with each other and with ionic conductivity. These features and their corresponding ranges include: porosity (ranging from 5% to 19%), crack density (0.09–0.15 mm mm −2 ), concentration of residual LPO (0%–16%), and concentration and Feret diameter of secondary phases, AlPO4 (11%–18%, 0.40–0.61 µ m) and TiO2 (9%–11%, 0.50–0.78). Correlations between the microstructural features and ionic conductivity ranged from −0.88 to 0.99. The strongest negative correlation was between crack density and ionic conductivity (−0.88), confirming the important role that processing defects play in limiting the performance of bulk solid-state electrolytes. The strongest positive correlation was between the concentration of AlPO4 and ionic conductivity (0.99), which is attributed to AlPO4 acting as a sintering aid and the role it plays in reducing the crack density. Our results indicate that additions of LPO can be used to balance competing microstructural features to design bulk three-dimensional LATP samples with improved ionic conductivity. As such, refinement of the chemical composition offers a promising approach to improving the processability and performance of functional ceramics prepared using binderless, laser-based additive manufacturing for solid-state battery applications.

High-entropy oxides (HEO) with entropic stabilization and compositional flexibility have great potential application in batteries and catalysis. In this work, HEO thin films were synthesized by pulsed laser deposition (PLD) from a rock-salt (Co 0.2 Ni 0.2 Cu 0.2 Mg 0.2 Zn 0.2 )O ceramic target. The films exhibited the target’s crystal structure, were chemically homogeneous, and possessed a three-dimensional (3D) island morphology with connected randomly shaped nanopores. The effects of varying PLD laser fluence on crystal structure and morphology were explored systematically. Increasing fluence facilitates film crystallization at low substrate temperature (300 °C) and increases film thickness (60–140 nm). The lateral size of columnar grains, islands (19 nm to 35 nm in average size), and nanopores (9.3 nm to 20 nm in average size) increased with increasing fluence (3.4 to 7.0 J/cm 2 ), explained by increased kinetic energy of adatoms and competition between deposition and diffusion. Additionally, increasing fluence reduces the number of undesirable droplets observed on the film surface. The nanoporous HEO films can potentially serve as electrochemical reaction interfaces with tunable surface area and excellent phase stability. Graphical abstract

War, natural disasters, and other emergencies regularly disrupt children’s education in developing countries. The digital divide has long since affected low-resource and rural schools’ responses to crises that necessitate distance learning, often excluding children in remote and rural parts of countries from internet-dependent online learning programmes. In no place is this truer than in Haiti where, prior to August 2020, political unrest combined with the COVID-19 pandemic caused learners to miss 60% of their scheduled days in the 2019–2020 school year with only 45% of Haitian households having access to a power source, let alone internet or a smart device, that would enable them to participate in online learning. This study presents findings from exploratory research on the readiness of the Haitian education system to withstand crises and the impact of COVID-19 on the system and its learners. Through analyses of secondary data and semi-structured interviews with a variety of education stakeholders, the research reveals gaps in the system’s readiness; identifies key challenges prompted by school closures in Haiti and shares a handful of innovative responses developed to respond to these challenges. Findings indicate that the COVID-19 health crisis has not created the need for educational reform in Haiti, but rather, by exacerbating pre-existing gaps and frailties within the system, the pandemic has heightened the urgency with which educational reform must be pursued. Salient gaps include a significant digital divide, financial instability and inattention to learning adjacent needs such as nutrition and psychosocial health for parents and children alike. While this initial research has exposed a series of significant gaps and inequalities in the Haitian education system, moving forward, more comprehensive research is needed to determine how such inequalities can be most effectively addressed. Although the Haitian government has a key role to play in addressing these inequalities, findings from this study reveal that governmental responses to COVID-19 school closures and broader digital learning inequalities, were ineffective in their reach and did not reflect the majority of Haitian learners and their families’ realities. Findings also identify numerous innovations and assets on the part of non-governmental actors striving to address these gaps. However, these mechanisms were limited in scope and lacked the coordination among one another and the government that would be required to have scalable or measurable impact. Therefore, more research is needed to determine what the most successful mechanisms for addressing inequalities in the Haitian education system are and how they can be most effectively leveraged and scaled to create a more resilient education system moving forward.

The rocksalt structured (Co,Cu,Mg,Ni,Zn)O entropy-stabilized oxide (ESO) exhibits a reversible phase transformation that leads to the formation of Cu-rich tenorite and Co-rich spinel secondary phases. Using atom probe tomography, kinetic analysis, and thermodynamic modeling, we uncover the nucleation and growth mechanisms governing the formation of these two secondary phases. We find that these phases do not nucleate directly, but rather they first form Cu-rich and Co-rich precursor phases, which nucleate in regions rich in Cu and cation vacancies, respectively. These precursor phases then grow through cation diffusion and exhibit a rocksalt-like crystal structure. The Cu-rich precursor phase subsequently transforms into the Cu-rich tenorite phase through a structural distortion-based transformation, while the Co-rich precursor phase transforms into the Co-rich spinel phase through a defect-mediated transformation. Further growth of the secondary phases is controlled by cation diffusion within the primary rocksalt phase, whose diffusion behavior resembles other common rocksalt oxides. Graphical abstract

The ITER Neutral Beam Test Facility (NBTF), called PRIMA (Padova Research on ITER Megavolt Accelerator), is hosted in Padova, Italy and includes the MITICA experiment – a full-scale prototype of the ITER heating neutral beam injector (HNB). The large cryopump is intended to absorb the gas used to neutralize the high energy beams of the MITICA experiment. The cryopump is cooled by a dedicated cryoplant based on a Helial LF refrigerator by Air Liquide Advanced Technologies. The plant delivers up to 800 W of cooling power at 4.5 K. A specifically designed Auxiliary Cold Box (ACB) is capable to provide a He flow of 220 g/s at 81 K & 40 g/s at 4.6 K to the thermal shields and the cryosorption panels respectively. This cryoplant has a high grade of versatility needed to cope with the highly variable heat loads as well as with the different modes of operation. This paper presents the design of the cryoplant and highlights the various stages of the installation, commissioning and final acceptance tests.

High entropy oxide (HEO) materials display a reversible entropy-driven phase transformation that gives rise to a phase state consisting of the entropic single-phase and controllable volume fractions of a secondary phase, which we call the ‘phase spectrum’. Consolidated HEO samples were prepared with grain sizes spanning several orders of magnitude and were heat treated to demonstrate the dramatic effect that grain size has on controlling the phase spectrum behavior. The volume fraction and morphology of the secondary phase, determined here to be a Cu-rich multicomponent tenorite phase, and the corresponding heat treatment conditions were significantly influenced by the grain size.