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The effect of Si/Al ratio on local and nanoscale water diffusion in H-ZSM-5: A quasielastic neutron scattering and molecular dynamics simulation study
Get PDFThe dynamics of water confined in H-ZSM-5 (protonated form of the Zeolite Socony Mobil – 5) has been studied using quasielastic neutron scattering (QENS) and classical molecular dynamics simulations (MD). QENS measurements probed water confined in ZSM-5 samples with Si/Al ratios of 15, 40 and 140 at 2.8 wt% loadings. In the lower silica samples, fitting of the elastic incoherent structure factor (EISF) showed that water diffusion was confined to a sphere (with radii ranging from 3.4 to 4.3 \uc5), suggesting the mobile water was located within the MFI (framework type of H-ZSM-5) channel intersections, giving localised diffusion coefficients in the range of ∼0.9–1.8
7 10−9 m2s−1. In the high silica zeolite, the diffusion was observed to be far less confined and more long range in nature, with diffusion coefficients significantly higher than in the lower silica systems (∼1.8–4.8
7 10−9 m2s−1). MD simulations further investigated the effect of the Si/Al ratio on water diffusivity at 2.8 wt% loading (9 molecules/unit cell (UC)) in H-ZSM-5 with Si/Al ratio = 15, 47, 95 and fully siliceous. The Si/Al ratio had a significant effect on the MD calculated nanoscale diffusivity of water, reducing the self-diffusion coefficient by a factor of 2 from a fully siliceous system to that with Si/Al = 15, due to the strong coordination and increased residence time of water molecules at the Br\uf8nsted acid sites which range from ∼5 ps to ∼2 ps in the Si/Al = 15 and Si/Al = 95 systems respectively. QENS observables, both the EISF and quasielastic line broadenings, were reproduced from the MD trajectories upon sampling the experimental timescale giving both qualitative and quantitative agreement with the QENS experiments. Fitting of the MD calculated EISF showed that the experimentally observed diffusion confined to a sphere of radii ranging from 3.5 to 6.8 \uc5 was also present in our simulations, with diffusion coefficients calculated to within a factor of 0.5 of experiment
Evaluation in pig of an intestinal administration device for oral peptide delivery
No full textThe bioavailability of peptides co-delivered with permeation enhancers following oral administration remains low and highly variable. Two factors that may contribute to this are the dilution of the permeation enhancer in the intestinal fluid, as well as spreading of the released permeation enhancer and peptide in the lumen by intestinal motility. In this work we evaluated an Intestinal Administration Device (IAD) designed to reduce the luminal dilution of drug and permeation enhancer, and to minimize movement of the dosage form in the intestinal lumen. To achieve this, the IAD utilizes an expanding design that holds immediate release mini tablets and places these in contact with the intestinal epithelium, where unidirectional drug release can occur. The expanding conformation limits movement of the IAD in the intestinal tract, thereby enabling drug release at a single focal point in the intestine. A pig model was selected to study the ability of the IAD to promote intestinal absorption of the peptide MEDI7219 formulated together with the permeation enhancer sodium caprate. We compared the IAD to intestinally administered enteric coated capsules and an intestinally administered solution. The IAD restricted movement of the immediate release tablets in the small intestine and histological evaluation of the mucosa indicated that high concentrations of sodium caprate were achieved. Despite significant effect of the permeation enhancer on the integrity of the intestinal epithelium, the bioavailability of MEDI7219 was of the same order of magnitude as that achieved with the solution and enteric coated capsule formulations (2.5–3.8%). The variability in plasma concentrations of MEDI7219 were however lower when delivered using the IAD as compared to the solution and enteric coated capsule formulations. This suggests that dosage forms that can limit intestinal dilution and control the position of drug release can be a way to reduce the absorptive variability of peptides delivered with permeation enhancers but do not offer significant benefits in terms of increasing bioavailability
Cell-cell metabolite exchange creates a pro-survival metabolic environment that extends lifespan
Get PDFMetabolism is deeply intertwined with aging. Effects of metabolic interventions on aging have been explained with intracellular metabolism, growth control, and signaling. Studying chronological aging in yeast, we reveal a so far overlooked metabolic property that influences aging via the exchange of metabolites. We observed that metabolites exported by young cells are re-imported by chronologically aging cells, resulting in cross-generational metabolic interactions. Then, we used self-establishing metabolically cooperating communities (SeMeCo) as a tool to increase metabolite exchange and observed significant lifespan extensions. The longevity of the SeMeCo was attributable to metabolic reconfigurations in methionine consumer cells. These obtained a more glycolytic metabolism and increased the export of protective metabolites that in turn extended the lifespan of cells that supplied them with methionine. Our results establish metabolite exchange interactions as a determinant of cellular aging and show that metabolically cooperating cells can shape the metabolic environment to extend their lifespan
A microfluidic perspective on conventional in vitro transcranial direct current stimulation methods
Get PDFTranscranial direct current stimulation (tDCS) is a promising non-invasive brain stimulation method to treat neurological and psychiatric diseases. However, its underlying neural mechanisms warrant further investigation. Indeed, dose–response interrelations are poorly understood. Placing explanted brain tissue, mostly from mice or rats, into a uniform direct current electric field (dcEF) is a well-established in vitro system to elucidate the neural mechanism of tDCS. Nevertheless, we will show that generating a defined, uniform, and constant dcEF throughout a brain slice is challenging. This article critically reviews the methods used to generate and calibrate a uniform dcEF. We use finite element analysis (FEA) to evaluate the widely used parallel electrode configuration and show that it may not reliably generate uniform dcEF within a brain slice inside an open interface or submerged chamber. Moreover, equivalent circuit analysis and measurements inside a testing chamber suggest that calibrating the dcEF intensity with two recording electrodes can inaccurately capture the true EF magnitude in the targeted tissue when specific criteria are not met. Finally, we outline why microfluidic chambers are an effective and calibration-free approach of generating spatiotemporally uniform dcEF for DCS in vitro studies, facilitating accurate and fine-scale dcEF adjustments. We are convinced that improving the precision and addressing the limitations of current experimental platforms will substantially improve the reproducibility of in vitro experimental results. A better mechanistic understanding of dose–response relations will ultimately facilitate more effective non-invasive stimulation therapies in patients
Reliability and stability of a statistical model to predict ground-based PM2.5 over 10\ua0years in Karachi, Pakistan, using satellite observations
No full textUnderstanding the complex mechanisms of climate change and its environmental consequences requires the collection and subsequent analysis of geospatial data from observations and numerical modeling. Multivariable linear regression and mixed-effects models were used to estimate daily surface fine particulate matter (PM2.5) levels in the megacity of Pakistan. The main parameters for the multivariable linear regression model were the 10-km-resolution satellite aerosol optical depth (AOD) and daily averaged meteorological parameters from ground monitoring (temperature, dew point, relative humidity, wind speed, wind direction, and planetary boundary layer height). Ground-based PM2.5 was measured in two stations in the city, Korangi (industrial/residential) and Tibet Center (commercial/residential). The initial linear regression model was modified using a stepwise selection procedure and adding interaction parameters. Finally, the modified model showed a strong correlation between the PM2.5–satellite AOD and other meteorological parameters (R2 = 0.88–0.92 and p-value = 10−7 depending on the season and station). The mixed-effect technique improved the model performance by increasing the R2 values to 0.99 and 0.93 for the Korangi and Tibet Center sites, respectively. Cross-validation methods were used to confirm the reliability of the model to predict PM2.5 after 10\ua0years
Two-dimensional strain field analysis of reinforced concrete D-regions based on distributed optical fibre sensors
Get PDFThe introduction of Distributed Optical Fibre Sensing in experimental testing of reinforced concrete structures has enabled the acquisition of measurements with an unparalleled level of detail, providing an accurate and ubiquitous description of cracking and deflections throughout an element. However, most of the available research using this technology has focused on the study of beam specimens and high quality data for the calibration and development of models that can describe accurately the behaviour of D-regions in service is still lacking. For that reason, the application of distributed optical fibre sensing in D-regions remains a subject of interest. In this work a method for the deployment of fibre sensors in a multilayer configuration is presented for a wall element. An interpolation approach is then proposed, which combined with the distributed nature of the sensors enabled the description of detailed heat maps for the global and principal strain fields. The results indicated that shear strains can reveal the position of shear cracks well before they are formed whereas the maximum and minimum principal strains clearly show the crack pattern and crack development as well as the load transfer mechanisms including, for the first time, the experimental identification of a secondary strut-and-tie mechanisms
Beamformed transmission using a precoder
No full textThere is provided mechanisms for beamformed transmission using a precoder. A method is performed by a radio transceiver device. The radio transceiver device comprises hard ware. The hardware impacts transmission of signals from the radio transceiver device. The method comprises acquiring channel conditions of a radio propagation channel between the radio transceiver device and at least one other radio transceiver device. The method comprises determining a precoder, in form of a linear precoding matrix, for beam formed transmission towards the at least one other radio transceiver device. The precoder is determined according to the channel conditions and a model of how the hardware impacts the transmission of signals from the radio transceiver device. The method comprises transmitting, using the precoder, a signal towards the at least one other radio transceiver device
Reconstruction of clipped signals
No full textUsing information contained in clipped samples from aualog-to-digital (ADC) conversion to improve receiver performance, by, for example, reducing the clipping distortion caused by ADCs due to its data resolution constraints. This provides an advantage over existing solutions, which perform suboptimally because the existing solution discard information in tire clipped samples
Handbook on Planning and Power
No full textDrawing on research from diverse thinkers in urban planning and the built environment, this Handbook articulates the cutting edge of contemporary understandings about power and its impact on planning. It identifies the current state of knowledge about planning and power, as well as emerging trajectories within this field of research.This comprehensive Handbook examines power relations in late capitalism and provides normative suggestions on how power might be utilised in planning. Chapters analyse the work of fundamental theoretical thinkers, including Marx, Foucault, Deleuze, and Lacan, as well as the history and practice of abolitionist housing justice in the United States, feminist and queer perspectives on planning and power, and the emerging autonomous Smart City. It demonstrates the effects of power within planning and the ways in which individuals, communities, and organisations are shaped and impacted positively and negatively by its practices.With case studies from a range of different geopolitical regions, this stimulating Handbook will be essential reading for students and scholars of architecture, community development, geography, urban and regional planning, urban design, and urban studies. It will also be beneficial for practitioners of planning and the built environment
A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe
Get PDFWe report a candidate of a low-luminosity active galactic nucleus (AGN) at z = 5 that was selected from the first near-infrared images of the JWST CEERS project. This source, named CEERS-AGN-z5-1 at absolute 1450 \uc5 magnitude M 1450 = −19.5 \ub1 0.3, was found via a visual selection of compact sources from a catalog of Lyman break galaxies at z > 4, taking advantage of the superb spatial resolution of the JWST/NIRCam images. The 20 photometric data available from CFHT, Hubble Space Telescope, Spitzer, and JWST suggest that the continuum shape of this source is reminiscent of that for an unobscured AGN, and there is a clear color excess in the filters where the redshifted Hβ+[O iii] and Hα are covered. The estimated line luminosity is L Hβ+[O III] = 1043.0 erg s−1 and L Hα = 1042.9 erg s−1 with the corresponding rest-frame equivalent width EWHβ+[O III] = 1100 \uc5 and EWHα = 1600 \uc5, respectively. Our spectral energy distribution fitting analysis favors the scenario that this object is either a strong broad-line emitter or even a super-Eddington accreting black hole (BH), although a possibility of an extremely young galaxy with moderate dust attenuation is not completely ruled out. The bolometric luminosity, L bol = 2.5 \ub1 0.3
7 1044 erg s−1, is consistent with those of z < 0.35 broad-line AGNs with M BH ∼ 106 M ⊙ accreting at the Eddington limit. This new AGN population in the first 1.1 billion years of the universe may close the gap between the observed BH mass range at high redshift and that of BH seeds. Spectroscopic confirmation is awaited to secure the redshift and its AGN nature