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Head and neck arteriovenous malformations are the commonest extracranial vascular malformations but demonstrate a unique challenge in the limited available surgical options secondary to their intimate association to vital structures. We present a case of middle-aged female patient who presented with threatened upper-airway obstruction and bleeding secondary to a slowly enlarging parapharyngeal arteriovenous malformations. She was treated with an endovascular-only approach with the proximal arteriole branches selectively undergoing embolo-sclerotherapy with an optimal radiological and clinical outcome. We also demonstrate the utility of elective tracheostomy prior to intervention.

The appropriate identification and localization of a nidus of a high flow arteriovenous malformation is crucial to guide targeted interventional therapy. However, the nidus of a complex or previously treated HFAVM can be difficult to non–invasively demonstrate on magnetic resonance imaging alone. We describe a unique case of a 56-year-old female with a complex high flow arteriovenous malformation in which we demonstrated the feasibility of fluorodeoxyglucose positron emission tomography/computed tomography to non–invasively delineate the nidus which subsequently guided successful targeted interventional therapy.

Self-Compacting Concrete (SCC) is a flowable concrete that exerts high pressure on formwork. SCC is the most commonly used concrete worldwide for construction applications due to its cost-effectiveness. The high flow of SCC reduces both the number of workers and the casting time required. It also eliminates vibration and removes noise pollution. This study is a review of previous investigations into the pressure exerted by fresh-state SCC on formwork. The paper discussed various factors that affect lateral pressure on formwork. These factors are included theoretical predictions, the effect of temperature, casting rate, rheology, types of pressure sensors, geometry and workability. Considering these various factors, the paper discussed major factors related to lateral pressure of SCC at early ages. However, internal temperature measurement of concrete effects at fresh state appears to be an important factor.

Renal arteriovenous fistulas (AVFs) are rare vascular abnormalities. Their high-flow nature may result in increased cardiac output and lead to heart failure. Transcatheter endovascular management of renal AVFs with various embolization materials has been the treatment of choice in recent years. Embolization of large renal AVFs poses a risk of embolization through the AVF to the pulmonary circulation. Herein, we present the case of a patient whose large high-flow renal AVF was treated by a novel method involving the use of a bare stent and detachable metallic coils—called a wire-trapping technique—as well as compare this method with vascular plugs. Keywords: Transcatheter embolization, Arteriovenous fistula, Across-stent wire trapping

Vascular anomalies are often poorly understood and misdiagnosed. Their diagnosis and treatment depend on a thorough understanding of the subtypes of vascular anomalies that exist. Both arteriovenous malformations and vascular tumors are classified as high-flow vascular anomalies. Most vascular tumors are infantile hemangiomas, which do not require interventional management, but other rarer vascular tumors may require emergent embolization if causing cardiovascular compromise. The different pathologic subtypes and their clinical presentation are discussed. The percutaneous treatment of high-flow vascular malformations (arteriovenous malformations) is discussed in detail, including the importance of the various anatomic subtypes and the approaches to embolization.

The introduction of expanded endonasal approaches to the tumors of the skull base allows for meningiomas to be approached through a transnasal corridor. The resulting defects create high flow cerebrospinal fluid leaks with the need to obtain a durable closure along the anterior skull base, sphenoid planum, or clivus. The nasal septal flap has become the workhorse for endoscopic reconstruction of these defects. This chapter reviews the history, anatomy, and outcomes of the use of the nasal septal flap.

Recently, heated humidified high-flow nasal cannula (HHHFNC) has been introduced and applied as a noninvasive respiratory support in neonates. Although HHHFNC is widely used in neonates presenting with respiratory distress, the efficiency and safety when compared with nasal continuous positive airway pressure or noninvasive positive pressure ventilation are still controversial. This review aims to evaluate the performance and applications of HHHFNC in neonates.

With high construction efficiency and large usable volumes, underground TWH caverns in rock salt formations provide optimal storage for large-scale compressed natural gas. Previous studies of SWV cavern construction indicate that different water injection methods will result in different leaching rates and will therefore form different cavern geometries. Therefore the influence of the water injection method on the TWH cavern construction process and geometries were thoroughly evaluated in this study. Based on the leaching numerical simulation code TWHSMC V2.0, we conducted a series of simulation experiments. The results illustrate that under the same water injection rate, the cavern construction speed of the alternate injection method is faster than the unidirectional injection method. Using the unidirectional method will form asymmetrical triangular pyramidal caverns. In contrast, using the alternate method will form symmetrical elliptical cone caverns. Under repeated alternating “Injection” and “Withdrawal” operations, the larger the flow rate, the shorter the cavern construction time, and the smaller the H/L ratio coefficient, as well as the closer the cavern geometry is to the horizontal cavern. Thus, during construction of a TWH-cavern in thinly-bedded rock salt (halite) deposits, repeated and alternating injections and withdrawals with high flow rates are necessary., The authors would gratefully like to acknowledge the financial support from the National Natural Science Foundation of China Project (No. 11705255), Chinese Academy of Sciences “Light of West China” Program (No. 29Y728010) and PetroChina Scientific Research and Technology Development Project (No. 2019B-3205)

Pool–riffle sequences are easily recognized vertical undulations in rivers with gradients

For the purposes of layout design, solids dryers may be considered in two classes. In the first, there is a low airflow, only needed to carry away evolved vapor. Heating is by indirect heat transfer into the material being dried. Such dryers tend to be compact standard units, mounted essentially on one floor level. The second type of dryer has a medium to high flow of heated air or inert gas as the drying medium. Their air-heating systems, exhaust-gas cleaning, and handling systems are often as large as the dryer itself.

One of the philosophies that lies behind Process Safety Management (PSM) programs is that each chemical process is unique. Therefore, it is not possible to have a prescriptive standard that tells design and operating companies what to do. Instead, companies have to identify the unique hazards associated with their facility and then implement corrective actions based on a risk-ranking methodology. For this reason, facilities covered by PSM standards have to conduct Process Hazards Analyses (PHAs), often using the Hazard and Operability (HAZOP) methodology.

The steam generator tube rupture (SGTR) scenarios project was carried out in the EU 5th framework programme in the field of nuclear safety during years 2000–2002. The first objective of the project was to generate a comprehensive database on fission product retention in a steam generator. The second objective was to verify and develop predictive models to support accident management interventions in steam generator tube rupture sequences, which either directly lead to severe accident conditions or are induced by other sequences leading to severe accidents. The models developed for fission product retention were to be included in severe accident codes. In addition, it was shown that existing models for turbulent deposition, which is the dominating deposition mechanism in dry conditions and at high flow rates, contain large uncertainties. The results of the project are applicable to various pressurised water reactors, including vertical steam generators (western PWR) and horizontal steam generators (VVER). © 2004 Elsevier B.V. All rights reserved.

The present work is focused on the multiobjective optimization of integrated multistage reverse osmosis membrane cascades applied to the ultrapurification of chemicals for the semiconductor industry. The membrane systems were formulated adding product quality metrics to economic criteria to result a bi-criteria nonlinear programming (NLP) problem. The Pareto solutions to the problem were generated via the epsilon constraint method. On the one hand, maximum economic profit solutions corresponded with the configurations applying bypass. The bypass from the feed stream of the last stage was preferred over other proposed options. On the other hand, maximum quality solutions were obtained by low recovery rates (specifically in the last stages of the cascade) and the consequent high flow (and low metallic content) streams recirculated to previous stages.

Publisher Summary This chapter talks about air jet milling. The first versions, developed in the late 19th century, used a jet of compressed air to project solids against a target. Such devices have the severe disadvantage of target wear and subsequent contamination of the products but have lead to the development of other versions with opposed jets, tangential intersecting jets and more recently opposed jets in a fluidized bed. Air jet milling, or more correctly fluid energy milling, uses high velocity jets of gas to impart energy to particles for size reduction. Air jet mills have mainly been developed for producing fine particles of below 50 mm. Most models are available in many sizes from lab-size versions (as low as to 1 gram/h) up to industrial versions (up to 6 tonne/h), making for easy testing and scale-up. However, a disadvantage is that air jet mills require ancillary air compressors that can assure high flow rates at pressures up to about 10 bars. In addition, the chapter also discusses different types of air jet mills.

This chapter is designed to discuss clogging of the pipe system. Clogging is partial or total obstruction and hence, the hindrance of the function of pipe system. Plastic pipes have smooth inner walls that promote high flow rates and resistance to the formation of deposits, thus preventing clogging. Through clogging, the flow of fluid inside the pipe is reduced or totally stopped and hence, the main functional requirement of the pipeline is jeopardized. Moreover, clogging can lead to other side effects with far severe consequences. Clogging can be caused by the buckling collapse of the pipe, detachment of pipe pieces, and clogging of the pipe by the external solid objects. The washed-in soil can also cause clogging of the pipe. Another cause of clogging is the longitudinal sagging, partial settlements, and upheaval of the pipe. In plastic pipes, buckling and large deformations are the main causes of clogging. Another common cause of clogging is the intrusion of tree root tips and growth of plants into the pipe system. This chapter also presents a basic set of guidelines for failure investigation of plastic pipes.

Publisher Summary This chapter highlights that hydrogeological mapping was completed on a 50,000 km2 area around the IEA Weyburn CO2 monitoring and storage project site to identify the directions and rates of formation fluid flow through aquifers, assess the competence of aquitards, and define the necessary boundary conditions for the risk analysis system models. Formation pressures and hydraulic heads indicate mostly lateral flow through the aquifers. A wide range of total dissolved solids occurs laterally within individual aquifers as well as vertically throughout the section. A strong regional aquitard separates the deep hydrogeological systems, including the Midale Aquifer, from a shallow active hydrogeologic system. For geochemical modeling and risk assessment: the deep hydrogeological regime beneath the reservoir may be neglected in order to simplify the system models; the steep salinity gradient across the CO2 injection area must be accounted for in modeling; and, high flow velocities in overlying aquifers are important input parameters to the system model for scenario analysis of any CO2 leakage into overlying horizons. Hydrogeological mapping demonstrates that the Weyburn Field is a good site to sequester CO2 from a hydrogeological perspective.

Polymers are greatly modified by the use of additives, by the wide range of plastics materials made from polyvinyl chloride (PVC). It is convenient to consider materials based on a general chemical structure as a generic group. It is also useful to consider distinctive variants of such a generic group as sub-generic groups. In the case of polycarbonates, one well-known software package identifies nine sub-generic groups for polycarbonates, including standard grades, structural foam, high flow, glass or carbon reinforced (PTFE)-lubricated, ultraviolet-stabilized, and fire-retardant. Even this is a considerable simplification, since in 1993, one manufacturer alone was offering 88 grades of polycarbonate. Indeed, in recent years, there has been an increase in the use of blends of polymers as a less expensive way of extending the spectrum of properties available, rather than that of developing highly specialized polymers. The selection of material for a particular application is not a simple exercise. The range of values of selected properties that can be obtained with a specific grade of material in a given injection mould simply by varying processing parameters such as melt temperature, injection time, and injection pressure. Such a variation may well be greater than the difference in properties shown between materials under consideration. An intelligent use of the molding process may well be more effective and more economical than the use of a more expensive material.

Publisher Summary Interest in miniaturization is increasing with the growing environmental concerns over waste disposal and the high cost of many biological samples. Because of high resolution, selectivity, sensitivity, and speed, high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) have become the methods of choice for a vast array of analytical separations. Miniaturization of these techniques offers many advantages. This chapter presents an overview of the advantages and disadvantages of various types of miniaturization, and the requirements they impose on instrument design. One advantage is that HPLC, which uses high pressure and high flow rates, can be more readily interfaced with spectroscopic identification techniques such as mass spectrometry, which require much lower flow rates. Interest in the miniaturization of CE has progressed in the direction of CE on a silicon chip.

Publisher Summary If asked to give the most desirable attributes of a chromatographic system or in fact any modern instrument, few life scientists would list “speed” or “analysis time.” This is surprising in view of the fact that high-performance chromatographic separations of one hour or less have revolutionized biochemistry and biotechnology. Purification of a protein or peptide could consume the bulk of a student's time in graduate school during that era. High-performance liquid chromatography (HPLC) is now a preferred alternative to soft gels for many biological applications. It is shown here that new technologies allow chromatographic separations of macromolecules to be achieved more rapidly than by HPLC, and perhaps two orders of magnitude faster than with soft gel materials. This discussion focuses on the need for greater separation speed, phenomena that limit the speed of chromatographic separations, various techniques for overcoming these limitations and the applications of high-speed separations. This chapter tries to trace the history of fast separations for proteins. It has been shown that there are multiple methods to achieve faster separations. Use of small (1 to 3 txm) nonporous particles increases the speed of separations, but suffers from high back pressure. This problem is solved by operating the columns at high temperature, but it has been shown that this leads to denaturation of proteins and in case of silica-based supports a loss of bonded phase from the support material. Corefilled supports are another means of performing faster separations. Still another method is the use of peffusion chromatography, in which the pore geometry enables the use of high flow rates, with a modest back pressure.

Past experience at JET, with a graphite first wall, has shown that substantial quantities of gas could be retained and released into the vessel during plasma pulses. Hence the gas introduction system was required only to top-up with gas to achieve a required plasma density. With freshly-conditioned graphite and particularly with a beryllium first wall there is continued pumping throughout the pulse and the gas introduction system can be called upon to inject several times the gas content of the plasma at high flow rates. Technically, this has required several developments of the gas introduction system (new valves and improved control). The gas economy has been examined in some detail with a gas collection system. The gas retention and release characteristics of different first walls (carbon and beryllium) have been studied. These developments and studies are described in this paper.

Two types of phase separators for use on the Superfluid Helium On-Orbit Transfer (SHOOT) Flight Experiment are being developed. One has the ability to phase separate normal liquid helium as well as superfluid. The other is designed to phase separate superfluid with a low flow impedance for high flow rates.

The flow stress of Ni1+xAl1-x(0

Publisher Summary This chapter describes the different aspects of heterogeneities and O2 transport. It discusses the ability to distinguish between diffusion shunt and perfusion shunt through high flow capillaries in which three conditions are considered: (1) in the region of low ratio of flow, diffusion shunting might occur, (2) a middle region where exchange is completely flow limited over the range of flows, and (3) a higher flow of diffusion region where permeation of a barrier or diffusion into tissue begins to limit the local blood tissue exchange at some point along the capillary. When two indicators have differing diffusivity in the tissue but have identical indicator dilution curves when injected simultaneously into the inflow and become separated when the flow is raised, then the one of lower diffusivity is pushed into a region showing its partial barrier or diffusion limitation to exchange. When the two tracers become separated by lowering the flow and not by raising it, then the one with the higher diffusivity participates in diffusional shunting between inflow and outflow. Thus, water at low flow in the heart shows a smaller amount of diffusional shunting that is not evident at higher flows when its curves are indentical to those of antipyrine.

An exhaust fan apparatus was developed by the author to directly measure the excess thermal energy produced by attached greenhouses. The accuracy of this experimental technique is verified under controlled conditions and then applied to a full scale attached greenhouse. The full scale testing indicates that given suitably high flow rates, 43% of the shortwave radiation transmitted into a greenhouse can be extracted as low grade heat (i.e. 30 to 40°C). It is concluded that the critical factor affecting the thermal performance of an attached greenhouse is not necessarily the total amount of heat produced but rather how that heat is managed.

There is substantial interest in the flow and heat exchange of a gas moving through multilayered porous structures. The flow through a porous medium is usually represented by the Ergun equation, often in reduced form for either low or high flow rates. However, there are physical situations (i.e in the iron blast furnace) where the whole flow range is covered so that it is necessary to develop a formulation which copes with this. This paper describes a formulation of flow through multilayered porous media using the full Ergun equation. In particular, the new formulation is compared with existing equations and their differences rationalised in terms of the physical approximations inherent in each representation.

The further development and evaluation of an electropositive pleated cartridge filter (Virozorb 1MDS) for concentrating small quantities of viruses from large volumes of water at ambient pH levels up to 7.5 without added salts is described. 1MDS filters efficiently adsorbed viruses at high flow rates, and the adsorbed viruses retained their infectivity on filters stored at 4° for as long as 12.5 days prior to elution with beef extract-glycine. In comparative trials virus recoveries with 1MDS filters were equivalent to or greater than those with electronegative Filterite filters.

Fifteen well-operated activated sludge treatment plants were studied to characterize the causes and nature of process upsets. Records several years long for each plant were analyzed. Upsets were tentatively identified by preliminary statistical analyses. The tentatively identified upsets were then corroborated by visiting the treatment plants and checking the logbook and interviewing the opera-tors. About nine percent of days were affected by some kind of an upset. The frequency and duration of upsets were quantified. Most upsets were short; the average duration was about 3.5 days, and many lasted only one or two days. The most common causes were low DO, high flow, low MLSS, and solids handling; these four categories accounted for more than sixty percent of the upsets. Operational problems and influent variables were much more important than mechanical failures or maintenance shutdowns. Most upsets appear and disappear too quickly to be detected by traditional sampling and monitoring methods.