Long-term drying shrinkage of self-compacting concrete: experimental and analytical investigations

YesThe present study investigated long-term drying shrinkage strains of self-compacting concrete (SCCs). For all SCCs mixes, Portland cement was replaced with 0–60% of fly ash (FA), fine and course aggregates were kept constant with 890 kg/m3 and 780 kg/m3, respectively. Two different water binder ratios of 0.44 and 0.33 were examined for both SCCs and normal concrete (NCs). Fresh properties of SCCs such as filling ability, passing ability, viscosity and resistance to segregation and hardened properties such as compressive and flexural strengths, water absorption and density of SCCs and NCs were also determined. Experimental results of drying shrinkage were compared to five existing models, namely the ACI 209R-92 model, BSEN-92 model, ACI 209R-92 (Huo) model, B3 model, and GL2000. To assess the quality of predictive models, the influence of various parameters (compressive strength, cement content, water content and relative humidity) effecting on the drying shrinkage strain as considered by the models are studied. The results showed that, using up to 60% of FA as cement replacement can produce SCC with a compressive strength as high as 30 MPa and low drying shrinkage strain. SCCs long-term drying shrinkage from 356 to 1000 days was higher than NCs. ACI 209R-92 model provided a better prediction of drying shrinkage compared with the other models.Financial support of Higher Education of Libya (469/2009)

J D Bernal: philosophy, politics and the science of science

This paper is an examination of the philosophical and political legacy of John Desmond Bernal. It addresses the evidence of an emerging consensus on Bernal based on the recent biography of Bernal by Andrew Brown and the reviews it has received. It takes issue with this view of Bernal, which tends to be admiring of his scientific contribution, bemused by his sexuality, condescending to his philosophy and hostile to his politics. This article is a critical defence of his philosophical and political position

J D Bernal: philosophy, politics and the science of science

This paper is an examination of the philosophical and political legacy of John Desmond Bernal. It addresses the evidence of an emerging consensus on Bernal based on the recent biography of Bernal by Andrew Brown and the reviews it has received. It takes issue with this view of Bernal, which tends to be admiring of his scientific contribution, bemused by his sexuality, condescending to his philosophy and hostile to his politics. This article is a critical defence of his philosophical and political position

Spectroscopic Characterization of the Ground and Low-Lying Electronic States of Ga2N via Anion Photoelectron Spectroscopy.

Anion photoelectron spectra of Ga2N− were measured at photodetachment wavelengths of 416nm(2.978eV), 355nm(3.493eV), and 266nm(4.661eV). Both field-free time-of-flight and velocity-map imaging methods were used to collect the data. The field-free time-of-flight data provided better resolution of the features, while the velocity-map-imaging data provided more accurate anisotropy parameters for the peaks. Transitions from the ground electronic state of the anion to two electronic states of the neutral were observed and analyzed with the aid of electronic structure calculations and Franck-Condon simulations. The ground-state band was assigned to a transition between linear ground states of Ga2N−(XΣg+1) and Ga2N(XΣu+2), yielding the electron affinity of Ga2N, 2.506±0.008eV. Vibrationally resolved features in the ground-state band were assigned to symmetric and antisymmetric stretch modes of Ga2N, with the latter allowed by vibronic coupling to an excited electronic state. The energy of the observed excited neutral state agrees with that calculated for the AΠu2 state, but the congested nature of this band in the photoelectron spectrum is more consistent with a transition to a bent neutral state

Peptide-Based Supramolecular Systems Chemistry

Peptide-based supramolecular systems chemistry seeks to mimic the ability of life forms to use conserved sets of building blocks and chemical reactions to achieve a bewildering array of functions. Building on the design principles for short peptide-based nanomaterials with properties, such as self-assembly, recognition, catalysis, and actuation, are increasingly available. Peptide-based supramolecular systems chemistry is starting to address the far greater challenge of systems-level design to access complex functions that emerge when multiple reactions and interactions are coordinated and integrated. We discuss key features relevant to systems-level design, including regulating supramolecular order and disorder, development of active and adaptive systems by considering kinetic and thermodynamic design aspects and combinatorial dynamic covalent and noncovalent interactions. Finally, we discuss how structural and dynamic design concepts, including preorganization and induced fit, are critical to the ability to develop adaptive materials with adaptive and tunable photonic, electronic, and catalytic properties. Finally, we highlight examples where multiple features are combined, resulting in chemical systems and materials that display adaptive properties that cannot be achieved without this level of integration

The role of depression in the association between mobilisation timing and live discharge after hip fracture surgery: Secondary analysis of the UK National Hip Fracture Database

Purpose The aim was to compare the probability of discharge after hip fracture surgery conditional on being alive and in hospital between patients mobilised within and beyond 36-hours of surgery across groups defined by depression. Methods Data were taken from the National Hip Fracture Database and included patients 60 years of age or older who underwent hip fracture surgery in England and Wales between 2014 and 2016. The conditional probability of postsurgical live discharge was estimated for patients mobilised early and for patients mobilised late across groups with and without depression. The association between mobilisation timing and the conditional probability of live discharge were also estimated separately through adjusted generalized linear models. Results Data were analysed for 116,274 patients. A diagnosis of depression was present in 8.31% patients. In those with depression, 7,412 (76.7%) patients mobilised early. In those without depression, 84,085 (78.9%) patients mobilised early. By day 30 after surgery, the adjusted odds ratio of discharge among those who mobilised early compared to late was 1.79 (95% CI: 1.56–2.05, p<0.001) and 1.92 (95% CI: 1.84–2.00, p<0.001) for those with and without depression, respectively. Conclusion A similar proportion of patients with depression mobilised early after hip fracture surgery when compared to those without a diagnosis of depression. The association between mobilisation timing and time to live discharge was observed for patients with and without depression

Stabilization of GABAA Receptors at Endocytic Zones Is Mediated by an AP2 Binding Motif within the GABAA Receptor β3 Subunit

The strength of synaptic inhibition can be controlled by the stability and endocytosis of surface and synaptic GABAA receptors (GABAARs), but the surface receptor dynamics that underpin GABAAR recruitment to dendritic endocytic zones (EZs) have not been investigated. Stabilization of GABAARs at EZs is likely to be regulated by receptor interactions with the clathrin-adaptor AP2, but the molecular determinants of these associations remain poorly understood. Moreover, although surface GABAAR downmodulation plays a key role in pathological disinhibition in conditions such as ischemia and epilepsy, whether this occurs in an AP2-dependent manner also remains unclear. Here we report the characterization of a novel motif containing three arginine residues (405RRR407) within the GABAAR β3-subunit intracellular domain (ICD), responsible for the interaction with AP2 and GABAAR internalization. When this motif is disrupted, binding to AP2 is abolished in vitro and in rat brain. Using single-particle tracking, we reveal that surface β3-subunit-containing GABAARs exhibit highly confined behavior at EZs, which is dependent on AP2 interactions via this motif. Reduced stabilization of mutant GABAARs at EZs correlates with their reduced endocytosis and increased steady-state levels at synapses. By imaging wild-type or mutant super-ecliptic pHluorin-tagged GABAARs in neurons, we also show that, under conditions of oxygen–glucose deprivation to mimic cerebral ischemia, GABAARs are depleted from synapses in dendrites, depending on the 405RRR407 motif. Thus, AP2 binding to an RRR motif in the GABAAR β3-subunit ICD regulates GABAAR residency time at EZs, steady- state synaptic receptor levels, and pathological loss of GABAARs from synapses during simulated ischemia

Maximal work extraction from quantum systems

Thermodynamics teaches that if a system initially off-equilibrium is coupled to work sources, the maximum work that it may yield is governed by its energy and entropy. For finite systems this bound is usually not reachable. The maximum extractable work compatible with quantum mechanics (``ergotropy'') is derived and expressed in terms of the density matrix and the Hamiltonian. It is related to the property of majorization: more major states can provide more work. Scenarios of work extraction that contrast the thermodynamic intuition are discussed, e.g. a state with larger entropy than another may produce more work, while correlations may increase or reduce the ergotropy.Comment: 5 pages, 0 figures, revtex

The role of carbon capture, utilization, and storage for economic pathways that limit global warming to below 1.5°C

The 2021 Intergovernmental Panel on Climate Change (IPCC) report, for the first time, stated that CO2 removal will be necessary to meet our climate goals. However, there is a cost to accomplish CO2 removal or mitigation that varies by source. Accordingly, a sensible strategy to prevent climate change begins by mitigating emission sources requiring the least energy and capital investment per ton of CO2, such as new emitters and long-term stationary sources. The production of CO2-derived products should also start by favoring processes that bring to market high-value products with sufficient margin to tolerate a higher cost of goods

Weekly variability of hydrography and transport of northwestern inflows into the northern North Sea

Quantifying the variability of North Sea inflows and understanding the temporal variability of their physical properties are essential for understanding, modelling and managing the ecosystems of the North Sea. The Joint North Sea Information System (JONSIS) line hydrographic section crosses the path of the main inflows of Atlantic water into the northwestern North Sea. We use observations from an autonomous underwater glider to observe the inflows at high spatial and temporal resolutions. The glider completed 10 partial sections of the JONSIS line in October and November of 2013. Key water masses of the inflow are identified; their spatial distribution varies greatly from section to section. This is not apparent from long-running ship surveys of the JONSIS line, which are generally several months apart. In particular, the distribution of water of most recent Atlantic origin varies as summer stratification decays throughout autumn: at the start of the deployment it is present as a thin layer beneath the thermocline; at the end of the deployment, it occupies the full depth of the water column. Thermohaline flow, i.e. that which is driven by horizontal density gradients, is focused into three or four jets (approximately 10 km wide). Jets as narrow as these have not previously been observed in the region. We also observe baroclinic eddies. The thermohaline transport of the inflows is compared with the absolute transport that is derived by referencing geostrophic shear to the glider's dive-average current. Thermohaline transport (approximately 0.2 Sv) is consistently smaller than absolute transport (approximately 0.5 Sv). The week-to-week variability in hydrography and flow structure identified in this study is relevant to on-going efforts to define a background state against which the nature of anthropogenic changes can be assessed, and future modelling efforts should represent the spatial and temporal variability that we have identified