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Surface Perfluoroalkyl Chains Segregation: A Tool for Reducing Calcium Deposits in Medical Grade Poly(Methyl Methacrylate)

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j.urnal of Biomaterials and Nanobiotechnology 2017年第2期8卷 176-187页

作者： Balj.t K. Ghatora Peter j. S. Foot stephen j. barton Ravtej.S. Thatti Antonio Papagni Luca Vaghi Materials Research Centre SEC Faculty Kingston University Surrey UK Department of Materials Science University of Milano-Bicocca Milano Italy

Intraocular lenses can be manufactured from a wide variety of polymers, but due to the lost cost associated with the use of Poly (methyl methacrylate) (PMMA), it is still the preferred material used in the developing countries. However, a maj.r drawback to its use is the build-up of calcium containing deposits that are formed on the intraocular lens over a period of time. In an attempt to hinder this deposition, surface modification of medical grade PMMA has been carried out using perfluoroalkyl chain (1,2,4-trifluoro-3-(C10F21CH2O)-7-(N,N)-dimethylaminoacridine) segregation. The segregation was explored using a 1% 1,2,4-trifluoro-3-(C10F21CH2O)-7-(N,N)-dimethyla-minoacridine in two methods: film casting and spin-coating, a thin film onto preformed PMMA discs. Both methods were compared against control PMMA to determine which method provided the best hindrance against calcium containing deposits when immersed in a simulated aqueous humour solution. Characterisation of the surface using scanning electron microscopy coupled with energy;dispersive x-ray analysis indicated that the surface segregation of perfluoroalkyl chains had hindered calcification in both methods. This pleminary research shows promising results of employing perfluoroalkyl chains in the surface segregation of biomaterials that can be employed in intraocular lenses.

关键词： Poly(Methyl Methacrylate) (PMMA) Perfluoroalkyl Segregation Medical Polymers Wettability Calcium Deposits

On localization with robust power control for safety critical wireless sensor networks

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控制理论与应用（英文版） 2011年第1期9卷 83-92页

作者： Michael j. WALSH Anthony FEE j.hn barton Brendan O'FLYNN Martin j. HAYES Cian O'MATHUNA Clarity Center for Web Technologies Microsystems Centre-Tyndall National Institute Lee MaltingsUniversity College CorkCorkIreland Wireless Access Research Center University of LimerickLimerickIreland

A hybrid methodology is proposed for use in low power, safety critical wireless sensor network applications, where quality-of-service orientated transceiver output power control is required to operate in parallel with radio frequency-based localization. The practical implementation is framed in an experimental procedure designed to track a moving agent in a realistic indoor environment. An adaptive time synchronized approach is employed to ensure the positioning technique can operate effectively in the presence of dataloss and where the transmitter output power of the mobile agent is varying due to power control. A deterministic multilateration-based positioning approach is adopted and accuracy is improved by filtering signal strength measurements overtime to account for multipath fading. The location estimate is arrived at by employing least-squares estimation. Power control is implemented at two separate levels in the network topology. First, power control is applied to the uplink between the tracking reference nodes and the centralized access point. A number of algorithms are implemented highlighting the advantage associated with using additional feedback bandwidth, where available, and also the need for effective time delay compensation. The second layer of power control is implemented on the uplink between the mobile agent and the access point and here quantifiable improvements in quality of service and energy efficiency are observed. The hybrid paradigm is extensively tested experimentally on a fully compliant 802.15.4 testbed, where mobility is considered in the problem formulation using a team of fully autonomous robots.

关键词： Wireless sensor network Power control Localization

Understanding the need for pre-inj.ction from permeability measurements: What is the connection?

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j.urnal of Rock Mechanics and Geotechnical Engineering 2019年第3期11卷 576-597页

作者： Nick barton Eda Quadros Nick barton & Associates OsloNorway BGTech Soil and Rock Engineering Ltd. Sao PauloBrazil

Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is effectively *** helps to avoid settlement damage caused by consolidation of clay deposits beneath built-up areas,since towns tend to be built where terrain is more flat,due to the clay *** are so many instances of settlement damage that the profession needs to take note of the need for high-pressure pre-grouting,to use micro-cements and micro-silica *** use of highpressure inj.ction may cause j.int j.cking,but this is local in extent when the rapid pressure decay away from an inj.ction hole is *** effect is variable and depends on the geometrical parameters of the *** pressure-decay advantage must not be violated by maintaining high pressure when grout flow from the inj.ction hole has *** latter can cause damage to the grouting already *** methods of estimating mean hydraulic apertures(e)from Lugeon testing are described,and from more sophisticated three-dimensional(3D)permeability *** estimation of the larger mean physical j.int apertures(E)is based on the j.int roughness coefficient(j.C).Comparison is then made with the empirical aperture-particle size criterion E>4d95,where d95 represents almost the largest cement particle *** on j.int set orientations and on the available micro-cements,the decision must be made of which range of pre-inj.ction pressure should be aimed for,using successive reductions of the water-cement ratio w/*** simple estimation of permeability,also with depth dependence,can be made with the empirical link between a modified rock mass quality Q and permeability,which is termed *** value of this parameter can be based on core-logging or intunnel face *** 3D before-and-after-grouting permeability measurements have been use

关键词： Pre-grouting Micro-cement Hydraulic apertures Physical j.int apertures j.int roughness Particle size Anisotropic permeability

Risk of shear failure and extensional failure around over-stressed excavations in brittle rock

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j.urnal of Rock Mechanics and Geotechnical Engineering 2017年第2期9卷 210-225页

作者： Nick barton Baotang Shen Nick barton&Associates OsloNorway CSIRO Energy BrisbaneAustralia

The authors investigate the failure modes surrounding over-stressed tunnels in *** lines of investigation are employed:failure in over-stressed three-dimensional(3D) models of tunnels bored under 3D stress,failure modes in two-dimensional(2D) numerical simulations of 1000 m and 2000 m deep tunnels using FRACOD,both in intact rock and in rock masses with one or two j.int sets,and finally,observations in TBM(tunnel boring machine) tunnels in hard and medium hard massive *** reason for 'stress-induced' failure to initiate,when the assumed maximum tangential stress is approximately(0.4-0.5)σ_c(UCS,uniaxial compressive strength) in massive rock,is now known to be due to exceedance of a critical extensional strain which is generated by a Poisson's ratio ***,because similar 'stress/strength' failure limits are found in mining,nuclear waste research excavations,and deep road tunnels in Norway,one is easily misled into thinking of compressive stress induced *** of this,the empirical SRF(stress reduction factor in the Q-system) is set to accelerate as the estimated ratio σ_(θmax)/σ_c >> *** mining,similar 'stress/strength' ratios are used to suggest depth of *** reality behind the fracture initiation stress/strength ratio of '0.4' is actually because of combinations of familiar tensile and compressive strength ratios(such as 10) with Poisson's ratio(say0.25).We exceed the extensional strain limits and start to see acoustic emission(AE) when tangential stress σθ ≈ 0.4σc,due to simple *** combination of 2D theoretical FRACOD models and actual tunnelling suggests frequent initiation of failure by 'stable' extensional strain fracturing,but propagation in 'unstable' and therefore dynamic *** the case of very deep tunnels(and 3D physical simulations),compressive stresses may be too high for extensional strain fracturing,and shearing will dominate,both ahead of the face and following the *** shallower,the conc

关键词： Fracture propagation Tension Shear Poisson’s ratio Break-out Rock burst Deep tunnels FRACOD model

Shear strength criteria for rock,rock j.ints,rockfill and rock masses:Problems and some solutions

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j.urnal of Rock Mechanics and Geotechnical Engineering 2013年第4期5卷 249-261页

作者： Nick barton Nick barton & Associates OsloNorway

Although many intact rock types can be very strong,a critical confining pressure can eventually be reached in triaxial testing,such that the Mohr shear strength envelope becomes *** critical state has recently been better defined,and correct curvature or correct deviation from linear Mohr-Coulomb（MC） has finally been *** shear testing procedures for rock j.ints,using multiple testing of the same sample,in case of insufficient samples,can be shown to exaggerate apparent *** rough j.ints do not have any cohesion,but instead have very high friction angles at low stress,due to strong *** masses,implying problems of large-scale interaction with engineering structures,may have both cohesive and frictional strength ***,it is not correct to add these,following linear M-C or nonlinear Hoek-Brown（H-B） standard *** is broken at small strain,while friction is mobilized at larger strain and remains to the end of the shear *** criterion ＇c then σn tan φ＇ should replace ＇c plus σn tan φ＇ for improved fit to *** of principal stresses to a shear plane seems to ignore mobilized dilation,and caused great experimental difficulties until *** seems to be plenty of room for continued research,so that errors of j.dgement of the last 50 years can be corrected.

关键词： Rock masses Critical state Rock j.ints Shear strength Non-linear friction Cohesion Dilation Scale effects Numerical modelling Stress transforms

Advances in j.int roughness coefficient (j.C) and its engineering applications

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j.urnal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3352-3379页

作者： Nick barton Changshuo Wang Rui Yong Nick barton&Associates Fjordveien 65cHavik Oslo1363Norway School of Civil Engineeing Shijiazhuang Tiedao UniversityShijiazhuang050043China Rock Mechuanics Institute Ningbo UniversityNingbo315211China

The j.int roughness coefficient (j.C), introduced in barton (1973) represented a new method in rock mechanics and rock engineering to deal with problems related to j.int roughness and shear strength estimation. It has the advantages of its simple form, easy estimation, and explicit consideration of scale effects, which make it the most widely accepted parameter for roughness quantification since it was proposed. As a result, j.C has attracted the attention of many scholars who have developed j.C-related methods in many areas, such as geological engineering, multidisciplinary geosciences, mining mineral processing, civil engineering, environmental engineering, and water resources. Because of such a developing trend, an overview of j.C is presented here to provide a clear perspective on the concepts, methods, applications, and trends related to its extensions. This review mainly introduces the origin and connotation of j.C, j.C-related roughness measurement, j.C estimation methods, j.C-based roughness characteristics investigation, j.C-based rock j.int property description, j.C's influence on rock mass properties, and j.C-based rock engineering applications. Moreover, the representativeness of the j.int samples and the determination of the sampling interval for rock j.int roughness measurements are discussed. In the future, the existing j.C-related methods will likely be further improved and extended in rock engineering.

关键词： j.int roughness coefficient(j.C) Rock j.ints Roughness Shear strength Scale effect

Real-time ore sorting using color and texture analysis

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International j.urnal of Mining Science and Technology 2023年第6期33卷 659-674页

作者： David G.Shatwell Victor Murray Augusto barton Hochschild Mining PLC La Colonia 180Lima 15023Peru Department of Electrical Engineering Universidad de Ingenieria y Tecnologia-UTECLima 15063Peru j.hn A.Paulson School of Engineering and Applied Sciences Harvard UniversityCambridge 02134USA Department of Electrical and Computer Engineering University of New MexicoAlbuquerque 87131USA

Sensor-based ore sorting is a technology used to classify high-grade mineralized rocks from low-grade waste rocks to reduce operation *** ore-sorting algorithms using color images have been proposed in the past,but only some validate their results using mineral grades or optimize the algorithms to classify rocks in *** paper presents an ore-sorting algorithm based on image processing and machine learning that is able to classify rocks from a gold and silver mine based on their *** algorithm is composed of four main stages:(1)image segmentation and partition,(2)color and texture feature extraction,(3)sub-image classification using neural networks,and(4)a voting system to determine the overall class of the *** algorithm was trained using images of rocks that a geologist manually classified according to their mineral content and then was validated using a different set of rocks analyzed in a laboratory to determine their gold and silver *** proposed method achieved a Matthews correlation coefficient of 0.961 points,higher than other classification algorithms based on support vector machines and convolutional neural networks,and a processing time under 44 ms,promising for real-time ore sorting applications.

关键词： Ore sorting Image color analysis Image texture analysis Machine learning

A photogrammetric approach for quantifying the evolution of rock j.int void geometry under varying contact states

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International j.urnal of Mining Science and Technology 2024年第4期34卷 461-477页

作者： Rui Yong Changshuo Wang Nick barton Shigui Du Institute of Rock Mechanics Ningbo UniversityNingbo 315211China Nick barton&Associates Fjordveien 65cHøvik 1363Norway

Accurate measurement of the evolution of rock j.int void geometry is essential for comprehending the distribution characteristics of asperities responsible for shear and seepage ***,existing techniques often require specialized equipment and skilled operators,posing practical *** this study,a cost-effective photogrammetric approach is ***,local coordinate systems are established to facilitate the alignment and precise quantification of the relative position between two halves of a rock ***/pull tests are conducted on rock j.ints with varying roughness levels to induce different contact states.A high-precision laser scanner serves as a benchmark for evaluating the photogrammetry *** certain deviations exist,the measured evolution of void geometry is generally consistent with the qualitative findings of previous *** photogrammetric measurements yield comparable accuracy to laser scanning,with maximum errors of 13.2%for aperture and 14.4%for void *** j.int matching coefficient(j.C)measurement errors are below 20%.Larger measurement errors occur primarily in highly mismatched rock j.ints with j.C values below 0.2,but even in cases where measurement errors exceed 80%,the maximum j.C error is only ***,the proposed photogrammetric approach holds promise for widespread application in void geometry measurements in rock j.ints.

关键词： Rock j.int Void geometry evolution Photogrammetry Aperture Void volume j.int matching coefficient

Microvascular response to transfusion in elective spine surgery

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World j.urnal of Orthopedics 2017年第1期8卷 49-56页

作者： j.Matthias Walz Ottokar Stundner Federico P Girardi Bruce A barton Aimee R Koll-Desrosiers stephen O Heard Stavros G Memtsoudis Department of Anesthesi-ology and Perioperative Medicine UMass Memorial Healthcare Department of Anesthesiology Hospital for Special SurgeryWeill Cornell Medical Center Department of Anesthesiology PerioperativeMedicine and Intensive Care MedicineParacelsus Medical University Department of Orthopedic Surgery Hospital for Special SurgeryWeill Cornell Medical Center Department of Quantitative Health Sciences University of Massachusetts Medical School

AIM To investigate the microvascular(skeletal muscle tissue oxygenation; SmO_2) response to transfusion in patients undergoing elective complex spine *** After IRB approval and written informed consent, 20 patients aged 18 to 85 years of age undergoing > 3level anterior and posterior spine fusion surgery were enrolled in the study. Patients were followed throughout the operative procedure, and for 12 h postoperatively. In addition to standard American Society of Anesthesiologists monitors, invasive measurements including central venous pressure, continual analysis of stroke volume(SV), cardiac output(CO), cardiac index(CI), and stroke volume variability(SVV) was performed. To measure skeletal muscle oxygen saturation(SmO_2) during the study period, a non-invasive adhesive skin sensor based on Near Infrared Spectroscopy was placed over the deltoid muscle for continuous recording of optical spectra. All administration of fluids and blood products followed standard procedures at the Hospital for Special Surgery, without deviation from usual standards of care at the discretion of the Attending Anesthesiologist based on individual patient comorbidities, hemodynamic status, and laboratory data. Time stamps were collected for administration of colloids and blood products, to allow for analysis of SmO_2 immediately before, during, and after administration of these fluids, and to allow for analysis of hemodynamic data around the same time points. Hemodynamic and oxygenation variables were collected continuously throughout the surgery, including heart rate, blood pressure, mean arterial pressure, SV, CO, CI, SVV, and SmO_2. Bivariate analyses were conducted to examine the potential associations between the outcome of interest, SmO_2, and each hemodynamic parameter measured using Pearson's correlation coeffi-cient, both for the overall cohort and within-patients individually. The association between receipt of packed red blood cells and SmO_2 was performed by runni

关键词： Transfusion Complex spine surgery Near infrared spectroscopy Microvascular blood flow Hemodynamic monitoring