scholarly journals A time-dependent multi-layered mathematical model of filtration and solute exchange, the revised Starling principle and the Landis experiments

2017 ◽  
Vol 6 (3) ◽  
Author(s):  
Laura Facchini ◽  
Alberto Bellin ◽  
Eleuterio F. Toro
Keyword(s):  
Blood Stream ◽  
Solute Concentration ◽  
Blood Capillary ◽  
Transient Model ◽  
Solute Exchange ◽  
Cell Life ◽  
External Pressures ◽  
Plasma Filtration ◽  
Microvessel Wall

Cell oxygenation and nutrition is vitally important for human and animal life. Oxygen and nutrients are transported by the blood stream and cross microvessel walls to penetrate the cell’s membrane. Pathological alterations in the transport of oxygen, and other nutrition elements, across microvessel walls may have serious consequences to cell life, possibly leading to localized cell necrosis. We present a transient model of plasma filtration and solute transport across microvessel walls by coupling flow and transport equations, the latter being non-linear in solute concentration. The microvessel wall is modeled through the superimposition of two or more membranes with different physical properties, representing key structural elements. With this model, the combined effect of the endothelial cells, the glycocalyx and other coating membranes specific of certain microvessels, can be analyzed. We investigate the role of transient external pressures in the study of trans-vascular filtration and solute exchange during the drop of blood capillary pressure due to the pathological decrease of blood volume called hypovolaemia, as well as hemorrhage. We discuss the advantage of using a multi-layered model, rather than a model considering the microvessel wall as a single and homogeneous membrane.

scholarly journals Why do informal markets remain informal: the role of tacit knowledge in an Indian footwear cluster

2021 ◽  
Author(s):  
Yugank Goyal ◽  
Klaus Heine
Keyword(s):  
Tacit Knowledge ◽  
Informal Markets ◽  
Market Institutions ◽  
Market Structures ◽  
Long Run ◽  
External Pressures ◽  
Propositional Form ◽  
The City

AbstractWhy do informal markets resist formalizing, even when the gains of doing so outweigh its costs in the long run? While a number of responses to this question have been advanced, we discover that part of the reason could be located in the tacit knowledge (attributed to Polanyi, Hayek) embedded in the marketplace, on which market institutions run. This factor is not fully explored yet. Tacit (idiosyncratic, inarticulate, nonconscious) knowledge is acquired personally through experience and cannot be transferred or conveyed to anyone. This is the knowledge we use to act without knowing it in a propositional form. We present the case of one of India’s largest informal footwear cluster, located in the city of Agra. We show that informal markets, hinged on tacit knowledge, cannot evolve easily and therefore may remain locked-in, despite external pressures or incentives to formalize. The study shows that efforts to overcome informality and reaping the benefits of formalized market structures cannot be done without taking cognizance of the sticky intangible knowledge on which these markets rest.

The role of microRNA-33 as a key regulator in hepatic lipogenesis signaling and a potential serological biomarker for NAFLD with excessive dietary fructose consumption in C57BL/6N mice

2021 ◽  
Author(s):  
Jeong Hoon Pan ◽  
Hanvit Cha ◽  
Jingsi Tang ◽  
Seoyoon Lee ◽  
Suk Hee Lee ◽  
...  
Keyword(s):  
Fatty Liver ◽  
Blood Stream ◽  
Hepatic Lipogenesis ◽  
Dietary Fructose

Fructose-induced hepatic miR-33 suppression lead to fatty liver via upregulation of SREBP1. Additionally, fructose-induced hepatic ferroptosis may cause a spill-over of miR-33 into blood stream, which could be a potential serological biomarker for fructose-induced NAFLD.

Pressure-flow relations in coronary circulation

1990 ◽  
Vol 70 (2) ◽  
pp. 331-390 ◽  
Author(s):  
J. I. Hoffman ◽  
J. A. Spaan
Keyword(s):  
Coronary Vessels ◽  
Good Evidence ◽  
The Body ◽  
Vascular Compression ◽  
Exact Nature ◽  
Coronary Veins ◽  
Collapsible Tubes ◽  
External Pressures ◽  
Flow Through

The blood vessels that run on the surface of the heart and through its muscle are compliant tubes that can be affected by the pressures external to them in at least two ways. If the pressure outside these vessels is higher than the pressure at their downstream ends, the vessels may collapse and become Starling resistors or vascular waterfalls. If this happens, the flow through these vessels depends on their resistance and the pressure drop from their inflow to the pressure around them and is independent of the actual downstream pressure. In the first part of this review, the physics of collapsible tubes is described, and the possible occurrences of vascular waterfalls in the body is evaluated. There is good evidence that waterfall behavior is seen in collateral coronary arteries and in extramural coronary veins, but the evidence that intramural coronary vessels act like vascular waterfalls is inconclusive. There is no doubt that in systole there are high tissue pressures around the intramyocardial vessels, particularly in the subendocardial muscle of the left ventricle. The exact nature and values of the forces that act at the surface of the small intramural vessels, however, are still not known. We are not certain whether radial (compressive) or circumferential and longitudinal (tensile) stresses are the major causes of vascular compression; the role of collagen struts in modifying the reaction of vessel walls to external pressures is unknown but possibly important; direct examination of small subepicardial vessels has failed to show vascular collapse. One of the arguments in favor of intramyocardial vascular waterfalls has been that during a long diastole the flow in the left coronary artery decreases and reaches zero when coronary arterial pressure is still high: it can be as much as 50 mmHg in the autoregulating left coronary arterial bed and approximately 15-20 mmHg even when the vessels have been maximally dilated. These high zero flow pressures, especially during maximal vasodilatation, have been regarded as indicating a high back pressure to flow that is due to waterfall behavior of vessels that are exposed to tissue pressures.(ABSTRACT TRUNCATED AT 400 WORDS)

How to survive in the age of artificial intelligence? Exploring the intelligent transformations of SMEs in central China

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Jinqiang Wang ◽  
Yaobin Lu ◽  
Si Fan ◽  
Peng Hu ◽  
Bin Wang
Keyword(s):  
Artificial Intelligence ◽  
Small And Medium Enterprises ◽  
Policy Support ◽  
Central China ◽  
Limited Resources ◽  
Text Data ◽  
Content Type ◽  
External Pressures ◽  
Medium Enterprises

PurposeThe purpose of the research is to explore how small and medium enterprises (SMEs) in central China achieve intelligent transformation through the use of artificial intelligence (AI). Because of unequal resource allocation, constraints on the intelligent transformation of SMEs in central China are different from those in economically and technologically well-developed coastal provinces. Hence, the authors focus on SMEs in central China to identify drivers of and barriers to intelligent transformation.Design/methodology/approachThe interview data were collected from 66 SMEs across 20 industries in central China. To verify the validity of the data collection method, the authors used two methods to control for retrospective bias: multi-level informants and enterprises' AI project application materials (Wei and Clegg, 2020). The final data were validated without conflicts. Next, the authors cautiously followed a two-step approach recommended by Venkatesh et al. (2010) and used NVivo 11.0 to analyze the collected text data.FindingsSMEs in central China are enthusiastic about intelligent transformation while facing both internal and external pressures. SMEs need to pay attention to both internal (enterprise development needs, implementation cost, human resources and top management involvement) and external factors (external market pressure, convenience of AI technology and policy support) and their different impacts on intelligent transformation. However, constrained by limited resources, SMEs in central China have been forced to take a step-by-step intelligent transformation strategy based on their actual needs with the technological flexibility method in the short term.Originality/valueConsidering the large number of SMEs and their importance in promoting China's economic development and job creation (SME Bureau of MIIT, 2020), more research on SMEs with limited resources is needed. In the study, the authors confirmed that enterprises should handle “social responsibility” carefully because over-emphasizing it will hinder intelligent transformation. However, firms should pay attention to the role of executives in promoting intelligent transformation and make full use of policy support to access more resources.

The role of Staphylococcus lugdunensis as a pathogen in children: a multicentre retrospective study

2021 ◽  
Vol 70 (5) ◽  
Author(s):  
Noa Hurvitz ◽  
Lea Ohana Sarna Cahan ◽  
Itai Gross ◽  
Daniel Grupel ◽  
Orli Megged ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Blood Culture ◽  
Otitis Media ◽  
Paediatric Population ◽  
Blood Stream ◽  
Staphylococcus Lugdunensis ◽  
Content Type ◽  
Link Type ◽  
Putative Role

Introduction: Staphylococcus lugdunensis (SL), a tube coagulase negative Staphylococcus , is known to be pathogenic in adults, causing mainly skin infections. Gap Statement: Previous studies assessing SL's role in paediatric populations are sparse and are mainly limited to case reports. Aim: Present the clinical characteristics consistent with SL infections and its putative role as a pathogen in the paediatric population. Methodology: A retrospective multicentre study was conducted in four paediatric medical centres in Israel. Patients with isolates of SL presenting between 2009–2019 were included. Results: SL was isolated from 40 patients. Average (±SD) age at presentation was 5.9 (±6.2) years, with 22 (55 %) being female. Skin, soft tissue and musculoskeletal infections were the most common (n=20, 50%) followed by ear infections (n=13, 32.5%). Five cases of urine isolates and two isolates from blood culture samples were also reported. Skin abscess was the most common infection among skin and soft tissue isolates, reported in 17 children (85%) with SL being the only pathogen in 15 (75%). Otitis media was the most common ear infection accounting for 12 (92%) of all cases with SL as the only isolate reported in 6 (46%). Five cases of SL isolates from urine specimens were reported, all of which with poor growth of bacteria and normal urinalysis. Two cases of SL growth in blood culture were found in children presenting with signs and symptoms consistent with invasive blood stream infection. Conclusions: In the paediatric population, studied infections caused by SL are increasingly observed. The results of this study highlight its role as a pathogen in soft tissue infections and its putative role in otitis media and invasive blood stream infections. However, the role of SL as an uropathogen was not established.

scholarly journals Shedding Light on the Role of the Skin in Vaccine-Induced Protection against the Malaria Sporozoite

mBio ◽  
2018 ◽  
Vol 9 (6) ◽  
Author(s):  
Johanna Patricia Daily
Keyword(s):  
Plasmodium Falciparum ◽  
Blood Vessels ◽  
Blood Stream ◽  
Mosquito Vectors ◽  
Protective Mechanisms ◽  
Partial Protection ◽  
Content Type ◽  
Shed Light ◽  
In Infants And Children

ABSTRACT The most advanced vaccine against Plasmodium falciparum malaria, RTS,S/AS01, provides partial protection in infants and children living in areas of malaria endemicity. Further understanding its mechanisms of protection may allow the development of improved second-generation vaccines. The RTS,S/AS01 vaccine targets the sporozoites injected by mosquito vectors into the dermis which then travel into the blood stream to establish infection in the liver. Flores-Garcia et al. (Y. Flores-Garcia, G. Nasir, C. S. Hopp, C. Munoz, et al., mBio 9:e02194-18, 2018, https://doi.org/10.1128/mBio.02194-18) shed light on early protective responses occurring in the dermis in immunized animals. They demonstrated that immunization impairs sporozoite motility and entry into blood vessels. Furthermore, they established that challenge experiments performed using a dermal route conferred greater protection than intravenous challenge in immunized mice. Thus, the dermal challenge approach captures the additional protective mechanisms occurring in the dermis that reflect the natural physiology of infection. Those studies highlighted the fascinating biology of skin-stage sporozoites and provided additional insights into vaccine-induced protection.

scholarly journals THE ROLE OF SUBSURFACE FLOW DYNAMIC ON SPATIAL AND TEMPORAL VARIATION OF WATER CHEMISTRY IN A HEADWATER CATCHMENT

2016 ◽  
Vol 8 (1) ◽  
pp. 17
Author(s):  
Tadashi Tanaka
Keyword(s):  
Water Chemistry ◽  
Temporal Variation ◽  
Random Process ◽  
Riparian Zone ◽  
Subsurface Flow ◽  
Solute Concentration ◽  
Spatial And Temporal Variation ◽  
Flow Dynamic ◽  
Headwater Catchment

Variation of water chemistry does not merely occur due to in situ chemical process, but also transport process. The study was carried out to address the role of subsurface flow dynamic on spatial and temporal variation of water chemistry in a headwater catchment. Hydrometric and hydrochemistry measurements were done in transect with nested piezometers, tensiometers, and suction samplers at different depths across hillslope and riparian zone in a 5.2 ha first-order drainage of the Kawakami experimental basin, Nagano, Central Japan from August 2000 to August 2001. Spatial variation of solute concentration was defined by the standard deviation and coefficient of variation of the seasonal observed concentrations. Autocorrelation analysis was performed to define temporal variation of solute concentration. The results showed that spatial variation of water chemistry was mainly influenced by the variation of subsurface flow through the hillslope and riparian zone. Solute concentration in the deep riparian groundwater was almost three times higher than that in the hillslope segment. A prominent downward flow in deep riparian groundwater zone provided transport of solutes to the deeper layer. Time series analysis showed that in the deep riparian groundwater, Ca2+, Mg2+, SO42- and HCO3- concentrations underwent a random process, Na+ concentration of a random process superimposed by a trend process, and SiO2 of a random process superimposed by a periodic process. Near the riparian surface, SO42- concentration was composed of a random process superimposed by a periodic process, whereas other solutes were mainly in a random process. In the hillslope soil water, there was no trend observed for the Na+ concentration, but there were for Ca2+ and Mg2+. The magnitude and direction of subsurface flow across hillslope and riparian zone created transport and deposition processes that changed solute concentration spatially and temporally.

The Northern and Western Borderlands of the Sasanian Empire: Contextualising the Roman/Byzantine and Sasanian Frontier

2017 ◽  
pp. 99-125 ◽  
Author(s):  
Dan Lawrence ◽  
Tony J. Wilkinson
Keyword(s):  
Roman Empire ◽  
Military Installations ◽  
Mountain Ranges ◽  
Sasanian Empire ◽  
North East ◽  
Eastern Iran ◽  
External Pressures ◽  
North Eastern ◽  
Southern Caucasus

This chapter investigates the archaeological landscapes of the frontiers of the Sasanian Empire. Drawing on evidence from current and archived archaeological surveys, in combination with high-resolution remote sensing datasets such as CORONA spy photography, we compare the organisation of settlements and defensive structures of the Sasanian frontier zones in response to a variety of external pressures. These varied from the Roman Empire in the west to less centralised entities, including nomadic groups, in the south-west and north-east. Following a general discussion of the multiple manifestations of Sasanian frontiers drawn from southern Mesopotamia (Iraq), northern Syria and north-eastern Iran, the main focus of the chapter is on the complex frontier landscape of the southern Caucasus, particularly the area of modern Azerbaijan, Georgia and Daghestan. We discuss the role of linear barriers, including the Gorgan Wall in north-eastern Iran and the Ghilghilchay and Derbent Walls in the Caucasus, irrigation systems, and alignments of fortifications and settlements in shaping their local landscapes. By placing the archaeological remains of the Sasanian Empire in a wider context we are able to examine the relationships between military installations, settlement patterns, infrastructure and geographical features such as mountain ranges and rivers. Comparing the different case studies allows us to conclude with some general statements on the nature of Sasanian power in the frontier territories of the empire.

scholarly journals Incumbents in the Transition Towards the Bioeconomy: The Role of Dynamic Capabilities and Innovation Strategies

2019 ◽  
Vol 11 (18) ◽  
pp. 5044 ◽  
Author(s):  
Nhat Strøm-Andersen
Keyword(s):  
Dynamic Capabilities ◽  
Management Strategies ◽  
Transition Process ◽  
Organizational Restructuring ◽  
Meat Processing ◽  
Sustainability Transition ◽  
External Pressures ◽  
Business Dynamics ◽  
Multi Level

This study explored incumbents’ roles in the transition towards the bioeconomy by examining what goes on inside firms, what strategies they practiced, and how these affected the way incumbents engaged in the transition, as well as their ability to innovate. The study focused on the Norwegian meat-processing sector, investigating how dynamic capabilities affected incumbent firms in the transition process, and the management strategies adopted in response to external pressures (local and global) and to innovation opportunities. The analytical approach builds on two theoretical pillars: Multi-level perspective and dynamic capabilities. The findings showed that the incumbent exercised different modes of behavior—first-into-niche and follow-into-niche—in response to innovation pathways during the transition, mobilizing various dynamic capabilities—learning, financing, and organizational restructuring. The study sheds light on the underlying business dynamics of incumbent firms within a given regime and on intra-regime dynamics concerning innovation opportunities, and notes the proactive roles of incumbents in the sustainability transition.

scholarly journals An Investigation of the Basic Physics of Irrigation in Urology and the Role of Automated Pump Irrigation in Cystoscopy

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Dwayne Chang ◽  
Rustom P. Manecksha ◽  
Konstantinos Syrrakos ◽  
Nathan Lawrentschuk
Keyword(s):  
Flow Rate ◽  
External Pressure ◽  
Flow Rates ◽  
Pumping System ◽  
External Pressures ◽  
Basic Physics ◽  
Traditional Irrigation ◽  
Irrigation Solution ◽  
Bladder Fullness

Objective. To investigate the effects of height, external pressure, and bladder fullness on the flow rate in continuous, non-continuous cystoscopy and the automated irrigation fluid pumping system (AIFPS).Materials. Each experiment had two 2-litre 0.9% saline bags connected to a continuous, non-continuous cystoscope or AIFPS via irrigation tubing. Other equipment included height-adjustable drip poles, uroflowmetry devices, and model bladders.Methods. In Experiment 1, saline bags were elevated to measure the increment in flow rate. In Experiment 2, saline bags were placed under external pressures to evaluate the effect on flow rate. In Experiment 3, flow rate changes in response to variable bladder fullness were measured.Results. Elevating saline bags caused an increase in flow rates, however the increment slowed down beyond a height of 80 cm. Increase in external pressure on saline bags elevated flow rates, but inconsistently. A fuller bladder led to a decrease in flow rates. In all experiments, the AIFPS posted consistent flow rates.Conclusions. Traditional irrigation systems were susceptible to changes in height of irrigation solution, external pressure application, and bladder fullness thus creating inconsistent flow rates. The AIFPS produced consistent flow rates and was not affected by any of the factors investigated in the study.

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