scholarly journals Exponentially selective molecular sieving through angstrom pores

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
P. Z. Sun ◽  
M. Yagmurcukardes ◽  
R. Zhang ◽  
W. J. Kuang ◽  
M. Lozada-Hidalgo ◽  
...  
Keyword(s):  
Gas Transport ◽  
High Flow ◽  
Effective Diameter ◽  
Two Dimensional ◽  
Next Generation ◽  
Activation Barriers ◽  
Flow Rates ◽  
Low Intensity ◽  
Molecular Separation ◽  
Molecular Sieving

AbstractTwo-dimensional crystals with angstrom-scale pores are widely considered as candidates for a next generation of molecular separation technologies aiming to provide extreme, exponentially large selectivity combined with high flow rates. No such pores have been demonstrated experimentally. Here we study gas transport through individual graphene pores created by low intensity exposure to low kV electrons. Helium and hydrogen permeate easily through these pores whereas larger species such as xenon and methane are practically blocked. Permeating gases experience activation barriers that increase quadratically with molecules’ kinetic diameter, and the effective diameter of the created pores is estimated as ∼2 angstroms, about one missing carbon ring. Our work reveals stringent conditions for achieving the long sought-after exponential selectivity using porous two-dimensional membranes and suggests limits on their possible performance.

scholarly journals Shocks in sand flowing in a silo

2002 ◽  
Vol 452 ◽  
pp. 293-301 ◽  
Author(s):  
AZADEH SAMADANI ◽  
L. MAHADEVAN ◽  
A. KUDROLLI
Keyword(s):  
Granular Material ◽  
Newtonian Fluid ◽  
Hydraulic Jump ◽  
High Flow ◽  
Experimental Results ◽  
Two Dimensional ◽  
Flow Rates ◽  
Typical Response ◽  
Sharp Discontinuity

We study the formation of shocks on the surface of a granular material draining through an orifice at the bottom of a quasi-two-dimensional silo. At high flow rates, the surface is observed to deviate strongly from a smooth linear inclined profile, giving way to a sharp discontinuity in the height of the surface near the bottom of the incline, the typical response of a choking flow such as encountered in a hydraulic jump in a Newtonian fluid like water. We present experimental results that characterize the conditions for the existence of such a jump, describe its structure and give an explanation for its occurrence.

Construction of graphene oxide based mixed matrix membranes with CO2-philic sieving gas-transport channels through strong π–π interactions

2018 ◽  
Vol 6 (37) ◽  
pp. 17854-17860 ◽  
Author(s):  
Shenzhen Cong ◽  
Hui Li ◽  
Xiangjian Shen ◽  
Jing Wang ◽  
Junyong Zhu ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Gas Transport ◽  
Mixed Matrix Membranes ◽  
Two Dimensional ◽  
High Permeability ◽  
Mixed Matrix ◽  
Π Interactions ◽  
Technological Challenge ◽  
Transport Channels ◽  
Molecular Sieving

Two-dimensional nanomaterials can be used to create innovative membranes with high permeability and selectivity, but precise manipulation of laminar stacking and the construction of ordered, CO2-philic molecular sieving channels remains a technological challenge.

scholarly journals Spheres in the vicinity of a bifurcation: elucidating the Zweifach–Fung effect

2011 ◽  
Vol 674 ◽  
pp. 359-388 ◽  
Author(s):  
V. DOYEUX ◽  
T. PODGORSKI ◽  
S. PEPONAS ◽  
M. ISMAIL ◽  
G. COUPIER
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Initial Distribution ◽  
High Flow ◽  
High Flow Rate ◽  
Low Flow ◽  
Two Dimensional ◽  
Flow Rates ◽  
Low Flow Rate

The problem of the splitting of a suspension in bifurcating channels divided into two branches of non-equal flow rates is addressed. As has long been observed, in particular in blood flow studies, the volume fraction of particles generally increases in the high-flow-rate branch and decreases in the low-flow-rate branch. In the literature, this phenomenon is sometimes interpreted as the result of some attraction of the particles towards this high-flow-rate branch. In this paper, we focus on the existence of such an attraction through microfluidic experiments and two-dimensional simulations and show clearly that such an attraction does not occur but is, on the contrary, directed towards the low-flow-rate branch. Arguments for this attraction are given and a discussion on the sometimes misleading arguments found in the literature is given. Finally, the enrichment of particles in the high-flow-rate branch is shown to be mainly a consequence of the initial distribution in the inlet branch, which shows necessarily some depletion near the walls.

Monitoring Effects of Catchment Management Practices on Phosphorus Loads into the Eutrophic Peel-Harvey Estuary, Western Australia

1986 ◽  
Vol 18 (4-5) ◽  
pp. 53-61 ◽  
Author(s):  
P. B. Birch ◽  
G. G. Forbes ◽  
N. J. Schofield
Keyword(s):  
Management Practices ◽  
Major Change ◽  
High Flow ◽  
Catchment Management ◽  
Flow Rates ◽  
Early Results ◽  
Phosphorus Loads ◽  
Time Of Year ◽  
High Runoff

Early results from monitoring runoff suggest that the programme to reduce application of superphosphate to farmlands in surrounding catchments has been successful in reducing input of phosphorus to the eutrophic Peel-Harvey estuary. In the estuary this phosphorus fertilizes algae which grow in abundance and accumulate and pollute once clean beaches. The success of the programme has been judged from application of an empirical statistical model, which was derived from 6 years of data from the Harvey Estuary catchment prior to a major change in fertilizer practices in 1984. The model relates concentration of phosphorus with rate of flow and time of year. High phosphorus concentrations were associated with high flow rates and with flows early in the high runoff season (May-July). The model predicted that the distribution of flows in 1984 should have resulted in a flow-weighted concentration of phosphorus near the long-term average; the observed concentration was 25% below the long-term average. This means that the amount of phosphorus discharged into the Harvey Estuary could have been about 2 5% less than expected from the volume of runoff which occurred. However several more years of data are required to confirm this trend.

Functional Two-Dimensional Black Phosphorus Nanostructures towards Next-Generation Devices

2021 ◽  
Author(s):  
Mengke Wang ◽  
Jun Zhu ◽  
You Zi ◽  
Zheng-Guang Wu ◽  
Haiguo Hu ◽  
...  
Keyword(s):  
Surface Area ◽  
Biomedical Applications ◽  
Black Phosphorus ◽  
Large Surface Area ◽  
Two Dimensional ◽  
Next Generation

In recent years, two-dimensional (2D) black phosphorus (BP) has been widely applied in many fields, such as (opto)electronics, transistors, catalysis and biomedical applications due to its large surface area, tunable...

scholarly journals ‘Tanned’ gelatin spheres and granules for exclusion chromatography

1968 ◽  
Vol 108 (4) ◽  
pp. 641-646 ◽  
Author(s):  
A. Polson ◽  
W. Katz
Keyword(s):  
Molecular Weight ◽  
Polyethylene Glycol ◽  
High Molecular Weight ◽  
Weight Fraction ◽  
High Flow ◽  
High Molecular Weight Fraction ◽  
Flow Rates ◽  
Protein Molecules ◽  
Exclusion Chromatography

1. The preparation of tanned gelatin spheres and granules from high-molecular-weight gelatin is described. This material is comparatively hard, giving high flow rates, is insoluble in water at temperatures between 0° and 100° and is resistant to digestion by trypsin and chymotrypsin. The high-molecular-weight fraction of gelatin was prepared by precipitation with polyethylene glycol, and the spheres and granules prepared from this fraction were hardened and insolubilized by tanning with either formalin or chromium salts or both. 2. The spheres and granules were used successfully for the separation of protein molecules and other protein-aceous materials ranging in molecular weight from 200 to greater than 6000000. This gel exclusion material has several properties superior to those of other products used for similar purposes. Further, it was noticed that the porosity of the spheres differed considerably from that of the granules.

scholarly journals Evaluation of a Humidified Nasal High-Flow Oxygen System, Using Oxygraphy, Capnography and Measurement of Upper Airway Pressures

2011 ◽  
Vol 39 (6) ◽  
pp. 1103-1110 ◽  
Author(s):  
J. E. Ritchie ◽  
A. B. Williams ◽  
C. Gerard ◽  
H. Hockey
Keyword(s):  
Healthy Volunteers ◽  
Airway Pressure ◽  
Gas Flow ◽  
Air Entrainment ◽  
High Flow ◽  
Positive Pressure ◽  
Mean Airway Pressure ◽  
Flow Rates ◽  
Oxygen Fraction ◽  
Airway Pressures

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO2 and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow™ humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order. FiO2, FEO2, FECO2 and airway pressures were measured. Calculation of FiO2 from FEO2 and FECO2 was later performed. Calculated FiO2 approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cmH2O. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.

Two-dimensional graphene oxide based membranes for ionic and molecular separation: Current status and challenges

2021 ◽  
pp. 105605
Author(s):  
Shania Sharif ◽  
Khuram Shahzad Ahmad ◽  
Faisal Rehman ◽  
Zubeda Bhatti ◽  
Khalid Hussain Thebo
Keyword(s):  
Graphene Oxide ◽  
Current Status ◽  
Two Dimensional ◽  
Molecular Separation

Ferromagnetic Dirac Half-Metallicity in Transition Metal Embedded Honeycomb Borophene

2021 ◽  
Author(s):  
Yanxia Wang ◽  
Xue Jiang ◽  
Yi Wang ◽  
Jijun Zhao
Keyword(s):  
Transition Metal ◽  
First Principles ◽  
Valence Electron ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Next Generation ◽  
Half Metallicity ◽  
Counting Rule ◽  
Spintronic Devices ◽  
Electron Counting

Exploring two-dimensional (2D) ferromagnetic materials with intrinsic Dirac half-metallicity is crucial for the development of next-generation spintronic devices. Based on first-principles calculations, here we propose a simple valence electron-counting rule...

scholarly journals Water friction in nanofluidic channels made from two-dimensional crystals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ashok Keerthi ◽  
Solleti Goutham ◽  
Yi You ◽  
Pawin Iamprasertkun ◽  
Robert A. W. Dryfe ◽  
...  
Keyword(s):  
Hexagonal Boron Nitride ◽  
Slip Length ◽  
Two Dimensional ◽  
Water Flows ◽  
Nanofluidic Channels ◽  
Molecular Separation ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Biological Channels ◽  
Atomically Flat

AbstractMembrane-based applications such as osmotic power generation, desalination and molecular separation would benefit from decreasing water friction in nanoscale channels. However, mechanisms that allow fast water flows are not fully understood yet. Here we report angstrom-scale capillaries made from atomically flat crystals and study the effect of confining walls’ material on water friction. A massive difference is observed between channels made from isostructural graphite and hexagonal boron nitride, which is attributed to different electrostatic and chemical interactions at the solid-liquid interface. Using precision microgravimetry and ion streaming measurements, we evaluate the slip length, a measure of water friction, and investigate its possible links with electrical conductivity, wettability, surface charge and polarity of the confining walls. We also show that water friction can be controlled using hybrid capillaries with different slip lengths at opposing walls. The reported advances extend nanofluidics’ toolkit for designing smart membranes and mimicking manifold machinery of biological channels.

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