This document provides a brief introduction to bioimpedance, which refers to the electrical properties of biological tissue measured when current flows through it. It discusses how resistance and capacitance are the two basic properties affecting bioimpedance. Resistance opposes the flow of current, while capacitance allows alternating but not direct current to pass through. When current passes through tissue, it encounters resistance in the extracellular space at low frequencies but both resistance and capacitance at higher frequencies as it can then enter cells. Cole-Cole plots are used to display how impedance changes with frequency based on the resistance and capacitance properties of tissue.
This document discusses body water, osmolality, and related topics. It begins by explaining that total body water decreases from around 90% of body weight in fetuses to around 65% in adult males and 55% in adult females. It then covers Starling forces that govern fluid movement between compartments, osmotic pressure, electrolyte composition differences between intracellular and extracellular fluid, Gibbs-Donnan equilibrium, and active transport mechanisms. The document defines osmolality and osmolarity, explains colligative properties, and discusses clinical significance and methods for measuring plasma and urine osmolality.
The document provides an overview of the patch clamp technique. It discusses the history, principle, method, configurations, instrumentation, and applications of patch clamp. Some key points include:
- Patch clamp allows the recording of currents through single ion channels in isolated patches of cell membrane.
- It was developed in 1976 by Erwin Neher and Bert Sakmann, who received the Nobel Prize for this work.
- Different configurations (whole-cell, outside-out, inside-out, cell-attached) are used depending on the question being studied.
- It is used to identify ion channels and study their properties like activation, permeability, and modulation by drugs.
Membrane transport and the membrane potentialChy Yong
1. The extracellular environment surrounds cells and includes body fluids like blood plasma, tissue fluid, and lymph. It provides nutrients and a place for cells to exchange waste and signals.
2. The extracellular matrix is a network of connective tissue that binds cells together and to surrounding structures. It contains fibers like collagen and elastic fibers embedded in ground substance.
3. Transport across the cell membrane can occur through passive diffusion down a concentration gradient or active transport against a gradient using energy. Specific carrier proteins facilitate transport of some substances.
MRA and MRV are used to visualize blood vessels in the brain and detect abnormalities. MRA uses magnetic resonance techniques without contrast or with gadolinium contrast to image arteries. MRV images veins. The document describes the normal anatomy of brain blood circulation including segments of arteries like the ICA, ACA, MCA, PCA and venous drainage. Common anatomical variants are discussed like fetal origin of PCA or asymmetric carotid circulation. The specific case showed normal arteries and veins on MRA and MRV without any aneurysms, stenoses, or thromboses.
Piezoelectricity, discovered in the 1880s by the Curie brothers using quartz crystals, allows certain materials to generate an electric charge when subjected to pressure. This piezoelectric effect has been used in diagnostic medical sonography since the late 1950s. Piezoelectric transducers, which contain crystals that convert electrical pulses to mechanical vibrations and vice versa, are at the heart of ultrasound transducers. They enable the transducers to both transmit ultrasound pulses into the body by converting electric signals to sound and receive echo signals by converting returning sound waves back into electrical signals.
The document discusses coronary bifurcation interventions. It defines a coronary bifurcation and describes the three vessel segments - proximal main vessel, distal main vessel, and side branch. It discusses laws governing the relationship between vessel diameters. Classification systems for bifurcation lesions are presented, including the Medina classification. Techniques for percutaneous coronary intervention of bifurcations are outlined, including the provisional approach. Key considerations for wiring branches and addressing difficult side branch access are provided.
this presentation on cellular electrophysiology carry the information of electrical properties of biophysiology in cellular level. i hope it help you all.
This document discusses body water, osmolality, and related topics. It begins by explaining that total body water decreases from around 90% of body weight in fetuses to around 65% in adult males and 55% in adult females. It then covers Starling forces that govern fluid movement between compartments, osmotic pressure, electrolyte composition differences between intracellular and extracellular fluid, Gibbs-Donnan equilibrium, and active transport mechanisms. The document defines osmolality and osmolarity, explains colligative properties, and discusses clinical significance and methods for measuring plasma and urine osmolality.
The document provides an overview of the patch clamp technique. It discusses the history, principle, method, configurations, instrumentation, and applications of patch clamp. Some key points include:
- Patch clamp allows the recording of currents through single ion channels in isolated patches of cell membrane.
- It was developed in 1976 by Erwin Neher and Bert Sakmann, who received the Nobel Prize for this work.
- Different configurations (whole-cell, outside-out, inside-out, cell-attached) are used depending on the question being studied.
- It is used to identify ion channels and study their properties like activation, permeability, and modulation by drugs.
Membrane transport and the membrane potentialChy Yong
1. The extracellular environment surrounds cells and includes body fluids like blood plasma, tissue fluid, and lymph. It provides nutrients and a place for cells to exchange waste and signals.
2. The extracellular matrix is a network of connective tissue that binds cells together and to surrounding structures. It contains fibers like collagen and elastic fibers embedded in ground substance.
3. Transport across the cell membrane can occur through passive diffusion down a concentration gradient or active transport against a gradient using energy. Specific carrier proteins facilitate transport of some substances.
MRA and MRV are used to visualize blood vessels in the brain and detect abnormalities. MRA uses magnetic resonance techniques without contrast or with gadolinium contrast to image arteries. MRV images veins. The document describes the normal anatomy of brain blood circulation including segments of arteries like the ICA, ACA, MCA, PCA and venous drainage. Common anatomical variants are discussed like fetal origin of PCA or asymmetric carotid circulation. The specific case showed normal arteries and veins on MRA and MRV without any aneurysms, stenoses, or thromboses.
Piezoelectricity, discovered in the 1880s by the Curie brothers using quartz crystals, allows certain materials to generate an electric charge when subjected to pressure. This piezoelectric effect has been used in diagnostic medical sonography since the late 1950s. Piezoelectric transducers, which contain crystals that convert electrical pulses to mechanical vibrations and vice versa, are at the heart of ultrasound transducers. They enable the transducers to both transmit ultrasound pulses into the body by converting electric signals to sound and receive echo signals by converting returning sound waves back into electrical signals.
The document discusses coronary bifurcation interventions. It defines a coronary bifurcation and describes the three vessel segments - proximal main vessel, distal main vessel, and side branch. It discusses laws governing the relationship between vessel diameters. Classification systems for bifurcation lesions are presented, including the Medina classification. Techniques for percutaneous coronary intervention of bifurcations are outlined, including the provisional approach. Key considerations for wiring branches and addressing difficult side branch access are provided.
this presentation on cellular electrophysiology carry the information of electrical properties of biophysiology in cellular level. i hope it help you all.
1. Sweat glands aid in thermoregulation by evaporative cooling when sweat reaches the skin surface. The tubuloglomerular feedback mechanism senses changes in tubular fluid concentration and regulates glomerular filtration rate and renal blood flow.
2. The juxtaglomerular apparatus senses changes in distal tubular fluid and regulates renin secretion, glomerular filtration rate, and renal blood flow via the tubuloglomerular feedback mechanism. Countercurrent multiplication in the loops of Henle and vasa recta helps concentrate urine by creating a hypertonic medullary interstitium. Diuresis refers to increased urine output.
Energetics of Skeletal Muscle ContractionUMAMAHISHAQ
There are three main energy systems that provide ATP for skeletal muscle contraction:
1) The phosphagen system provides energy for brief, intense bursts of activity lasting 8-10 seconds through the breakdown of ATP and creatine phosphate.
2) The glycolytic system provides energy for moderate activity lasting 1.3-1.6 minutes through the anaerobic breakdown of glycogen to lactic acid.
3) The aerobic system provides sustained energy for prolonged activity by completely oxidizing nutrients through the citric acid cycle and electron transport chain, allowing contraction for an unlimited time as long as nutrients are available.
Carotid artery disease is a major cause of stroke. Left untreated, carotid stenosis over 75% carries a risk of stroke of 2-5% per year. Carotid endarterectomy has been shown in clinical trials such as NASCET and ACAS to significantly reduce stroke risk compared to medical management alone, with perioperative stroke or death rates of less than 6% for symptomatic patients and 3% for asymptomatic patients. Carotid artery stenting is an alternative treatment that utilizes embolic protection devices and stent placement to treat carotid stenosis, but requires technical expertise to achieve outcomes comparable to surgery.
MR diffusion, perfusion, and artifacts are discussed. Diffusion imaging measures water mobility and is used to characterize tissues and pathology. Perfusion imaging measures blood flow and is used to assess diseases like stroke and tumors. Common artifacts include ghosts from motion, aliasing from small fields of view, truncation artifacts at tissue interfaces, and magnetic susceptibility artifacts at tissue boundaries. Clinical applications of diffusion, perfusion, and other sequences are also outlined.
This document summarizes coronary stents, including their purpose, types, history, procedure for placement, and future advancements. Stents are small mesh devices that are placed in arteries to keep them open and improve blood flow after balloon angioplasty. There are bare metal stents and drug-eluting stents, which combat re-narrowing after placement. The first coronary stent was placed in 1986, and drug-eluting stents were introduced in 2001 to further reduce re-narrowing. Placement involves threading a catheter through an artery to the blockage and expanding a balloon and stent to open the artery. Future advancements include bioresorbable polymers that dissolve after artery healing is complete.
This document provides information about computerized tomography (CT) scans. It defines CT scanning as a medical imaging method that generates 3D images of internal organs from a series of 2D X-ray images taken around a single axis of rotation. The history section describes how the first commercially viable CT scanner was invented in the 1970s in the UK and how subsequent innovations improved scanning speed and image quality. The document also summarizes different generations of CT scanners and their technical specifications.
Bone densitometry, also called a DEXA scan, uses low-dose X-rays to measure bone mineral density and assess osteoporosis risk. It is most often performed on the lower spine and hips. A DEXA scan provides a T-score comparing the patient's bone density to that of a young adult, and a Z-score comparing it to others of the same age, gender, and body size. Osteopenia and osteoporosis are diagnosed based on negative T-scores below -1 and -2.5, respectively. DEXA scanning is a quick, low-radiation procedure used to diagnose bone density issues and monitor treatment effectiveness.
This document provides an overview of bone densitometry and osteoporosis testing. It discusses the types of tests including plain films, SPA, DPA, DXA, QCT, and peripheral tests. DXA is described as the gold standard as it is highly precise, uses minimal radiation, and can monitor changes over time. The document outlines how to perform DXA scans of the lumbar spine and hip, including proper positioning and region of interest placement. It also discusses test results reporting using T-scores and Z-scores to evaluate bone mineral density.
Osmolarity and osmolality both measure the concentration of solute particles in a solution, but osmolarity is based on volume while osmolality is based on mass. Osmolality is preferred in physiological conditions because volume can change with temperature whereas mass remains stable.
The document discusses membrane potential and action potentials in neurons. It provides details on:
- The resting membrane potential is established by ion gradients maintained by the sodium-potassium pump. There is a net negative charge inside and positive outside the membrane.
- An action potential is initiated when the membrane reaches its threshold potential due to sodium influx. It involves stages of depolarization, repolarization and refractory periods.
- The all-or-none principle states that an action potential will only be generated if the threshold is reached. Speed and propagation depends on myelination.
- Different cell types like cardiac and smooth muscles exhibit variations in their action potential waveforms.
This document discusses the principles of Doppler ultrasound. It begins with a brief history of Doppler and how the Doppler effect was discovered. It then covers the basic physics of Doppler ultrasound including the Doppler equation. The remainder of the document discusses specific Doppler parameters and how to optimize the Doppler examination including:
- Adjusting spectral and color Doppler parameters
- Normal arterial and venous flow patterns
- Changes in flow related to stenosis
interventional cardiology, Guiding catheters, wires, and balloons equipment...salman habeeb
This document provides an overview of guiding catheters, guide wires, and balloons which are core equipment used in percutaneous coronary interventions (PCI). It describes the design characteristics, advantages, and disadvantages of over-the-wire and rapid exchange balloon catheters. Key attributes of balloons like entry, tracking, and compliance are defined. Guiding catheters are discussed in terms of size, shape, and selection for accessing different coronary arteries. Finally, guide wire features such as core material, coating, and tip design are reviewed alongside common wire types used in various clinical scenarios.
This document contains a question bank for a physiology exam covering topics in biophysics and biochemistry of cells, blood, the cardiovascular system, the central nervous system, comparative physiology, and the endocrine system. It includes over 100 short answer and essay questions on these topics, some with suggested point values or word counts for the answers.
Learn from our Slideshare about the differences between ultrasound transducers. We also cover tips on how to treat your probes and how to select the right one.
Non-invasive imaging plays an important role in the management of cardiovascular diseases. Different imaging modalities have advantages and limitations. Echocardiography is useful for assessing cardiac structure and function but limited for coronary artery disease evaluation. Nuclear imaging can evaluate perfusion and function but not coronary anatomy directly. CT and MRI can assess coronary anatomy in addition to function but CT involves radiation. The appropriate choice of imaging modality depends on the clinical question and no single test can replace all others for evaluating cardiovascular diseases. Integrating complementary information from different tests provides the most comprehensive assessment.
Glucose reabsorption in the renal tubules normally ensures that all 180g of glucose filtered by the kidneys each day is reabsorbed back into circulation. This occurs via a two-step process - sodium-glucose cotransporters in the tubule's apical membrane use active transport to bring glucose into tubule cells, followed by facilitated diffusion and active sodium extrusion to return glucose to the bloodstream. Two sodium-coupled carriers have been identified for this process, one with high capacity but low affinity and one with low capacity but high affinity.
This document discusses using point-of-care ultrasound to investigate the cause of undifferentiated shock in emergency department patients. It describes various ultrasound protocols that can be used to examine the heart, lungs, abdomen, and veins to identify causes of shock like hypovolaemia, cardiogenic shock, pulmonary embolism, tamponade, and sepsis. Studies have found ultrasound can reduce the time to diagnosis in shock, decrease the use of vasopressors, and lead to fewer ICU days and lower morbidity compared to clinical examination alone. The limitations of ultrasound include operator dependence and difficulty obtaining views in critically ill patients.
Diffusion potential. Large Nerve. Na -K ATPase. Guyton and Hall. Medical Physiology. Dr. Nusrat Tariq. Professor Of Physiology. M.I.M.D.C. GOLDMAN HODGKIN KATZ EQUATION
This document discusses coronary guidewires used in percutaneous coronary intervention (PCI). It begins by outlining the history of angioplasty and guidewire development. It then covers the purpose, components, classifications, and appropriate uses of guidewires. The main components include the core, tip, coils, covers, and coatings. Guidewires are classified based on flexibility, device support, and clinical usage. Complications like vessel perforation, pseudolesions, and entrapment are also discussed. Proper guidewire manipulation and strategies for difficult lesions are outlined to maximize safety and efficacy.
Simon Fessard is an urban planner from France with over 10 years of experience in urban design, mobility planning, and cycling infrastructure projects. He has a master's degree in urban systems engineering and has worked at several planning firms and NGOs in Europe. Currently, he works as an urban planning consultant at Mobycon in the Netherlands focusing on projects related to cycling, public transportation, and traffic analysis. He has significant experience managing international projects, conducting research, and presenting at conferences on topics of cycling policy, bike sharing systems, and urban design.
How Social Software Helps 350,000 Men's Wearhouse Customers Dress Better Ever...tibbr
Find out how The Men’s Wearhouse uses tibbr today to meet the challenges of a modern retail environment in “The Future Of Work ― A Retailer’s Perspective” from his breakout session presentation at TUCON 2013.
1. Sweat glands aid in thermoregulation by evaporative cooling when sweat reaches the skin surface. The tubuloglomerular feedback mechanism senses changes in tubular fluid concentration and regulates glomerular filtration rate and renal blood flow.
2. The juxtaglomerular apparatus senses changes in distal tubular fluid and regulates renin secretion, glomerular filtration rate, and renal blood flow via the tubuloglomerular feedback mechanism. Countercurrent multiplication in the loops of Henle and vasa recta helps concentrate urine by creating a hypertonic medullary interstitium. Diuresis refers to increased urine output.
Energetics of Skeletal Muscle ContractionUMAMAHISHAQ
There are three main energy systems that provide ATP for skeletal muscle contraction:
1) The phosphagen system provides energy for brief, intense bursts of activity lasting 8-10 seconds through the breakdown of ATP and creatine phosphate.
2) The glycolytic system provides energy for moderate activity lasting 1.3-1.6 minutes through the anaerobic breakdown of glycogen to lactic acid.
3) The aerobic system provides sustained energy for prolonged activity by completely oxidizing nutrients through the citric acid cycle and electron transport chain, allowing contraction for an unlimited time as long as nutrients are available.
Carotid artery disease is a major cause of stroke. Left untreated, carotid stenosis over 75% carries a risk of stroke of 2-5% per year. Carotid endarterectomy has been shown in clinical trials such as NASCET and ACAS to significantly reduce stroke risk compared to medical management alone, with perioperative stroke or death rates of less than 6% for symptomatic patients and 3% for asymptomatic patients. Carotid artery stenting is an alternative treatment that utilizes embolic protection devices and stent placement to treat carotid stenosis, but requires technical expertise to achieve outcomes comparable to surgery.
MR diffusion, perfusion, and artifacts are discussed. Diffusion imaging measures water mobility and is used to characterize tissues and pathology. Perfusion imaging measures blood flow and is used to assess diseases like stroke and tumors. Common artifacts include ghosts from motion, aliasing from small fields of view, truncation artifacts at tissue interfaces, and magnetic susceptibility artifacts at tissue boundaries. Clinical applications of diffusion, perfusion, and other sequences are also outlined.
This document summarizes coronary stents, including their purpose, types, history, procedure for placement, and future advancements. Stents are small mesh devices that are placed in arteries to keep them open and improve blood flow after balloon angioplasty. There are bare metal stents and drug-eluting stents, which combat re-narrowing after placement. The first coronary stent was placed in 1986, and drug-eluting stents were introduced in 2001 to further reduce re-narrowing. Placement involves threading a catheter through an artery to the blockage and expanding a balloon and stent to open the artery. Future advancements include bioresorbable polymers that dissolve after artery healing is complete.
This document provides information about computerized tomography (CT) scans. It defines CT scanning as a medical imaging method that generates 3D images of internal organs from a series of 2D X-ray images taken around a single axis of rotation. The history section describes how the first commercially viable CT scanner was invented in the 1970s in the UK and how subsequent innovations improved scanning speed and image quality. The document also summarizes different generations of CT scanners and their technical specifications.
Bone densitometry, also called a DEXA scan, uses low-dose X-rays to measure bone mineral density and assess osteoporosis risk. It is most often performed on the lower spine and hips. A DEXA scan provides a T-score comparing the patient's bone density to that of a young adult, and a Z-score comparing it to others of the same age, gender, and body size. Osteopenia and osteoporosis are diagnosed based on negative T-scores below -1 and -2.5, respectively. DEXA scanning is a quick, low-radiation procedure used to diagnose bone density issues and monitor treatment effectiveness.
This document provides an overview of bone densitometry and osteoporosis testing. It discusses the types of tests including plain films, SPA, DPA, DXA, QCT, and peripheral tests. DXA is described as the gold standard as it is highly precise, uses minimal radiation, and can monitor changes over time. The document outlines how to perform DXA scans of the lumbar spine and hip, including proper positioning and region of interest placement. It also discusses test results reporting using T-scores and Z-scores to evaluate bone mineral density.
Osmolarity and osmolality both measure the concentration of solute particles in a solution, but osmolarity is based on volume while osmolality is based on mass. Osmolality is preferred in physiological conditions because volume can change with temperature whereas mass remains stable.
The document discusses membrane potential and action potentials in neurons. It provides details on:
- The resting membrane potential is established by ion gradients maintained by the sodium-potassium pump. There is a net negative charge inside and positive outside the membrane.
- An action potential is initiated when the membrane reaches its threshold potential due to sodium influx. It involves stages of depolarization, repolarization and refractory periods.
- The all-or-none principle states that an action potential will only be generated if the threshold is reached. Speed and propagation depends on myelination.
- Different cell types like cardiac and smooth muscles exhibit variations in their action potential waveforms.
This document discusses the principles of Doppler ultrasound. It begins with a brief history of Doppler and how the Doppler effect was discovered. It then covers the basic physics of Doppler ultrasound including the Doppler equation. The remainder of the document discusses specific Doppler parameters and how to optimize the Doppler examination including:
- Adjusting spectral and color Doppler parameters
- Normal arterial and venous flow patterns
- Changes in flow related to stenosis
interventional cardiology, Guiding catheters, wires, and balloons equipment...salman habeeb
This document provides an overview of guiding catheters, guide wires, and balloons which are core equipment used in percutaneous coronary interventions (PCI). It describes the design characteristics, advantages, and disadvantages of over-the-wire and rapid exchange balloon catheters. Key attributes of balloons like entry, tracking, and compliance are defined. Guiding catheters are discussed in terms of size, shape, and selection for accessing different coronary arteries. Finally, guide wire features such as core material, coating, and tip design are reviewed alongside common wire types used in various clinical scenarios.
This document contains a question bank for a physiology exam covering topics in biophysics and biochemistry of cells, blood, the cardiovascular system, the central nervous system, comparative physiology, and the endocrine system. It includes over 100 short answer and essay questions on these topics, some with suggested point values or word counts for the answers.
Learn from our Slideshare about the differences between ultrasound transducers. We also cover tips on how to treat your probes and how to select the right one.
Non-invasive imaging plays an important role in the management of cardiovascular diseases. Different imaging modalities have advantages and limitations. Echocardiography is useful for assessing cardiac structure and function but limited for coronary artery disease evaluation. Nuclear imaging can evaluate perfusion and function but not coronary anatomy directly. CT and MRI can assess coronary anatomy in addition to function but CT involves radiation. The appropriate choice of imaging modality depends on the clinical question and no single test can replace all others for evaluating cardiovascular diseases. Integrating complementary information from different tests provides the most comprehensive assessment.
Glucose reabsorption in the renal tubules normally ensures that all 180g of glucose filtered by the kidneys each day is reabsorbed back into circulation. This occurs via a two-step process - sodium-glucose cotransporters in the tubule's apical membrane use active transport to bring glucose into tubule cells, followed by facilitated diffusion and active sodium extrusion to return glucose to the bloodstream. Two sodium-coupled carriers have been identified for this process, one with high capacity but low affinity and one with low capacity but high affinity.
This document discusses using point-of-care ultrasound to investigate the cause of undifferentiated shock in emergency department patients. It describes various ultrasound protocols that can be used to examine the heart, lungs, abdomen, and veins to identify causes of shock like hypovolaemia, cardiogenic shock, pulmonary embolism, tamponade, and sepsis. Studies have found ultrasound can reduce the time to diagnosis in shock, decrease the use of vasopressors, and lead to fewer ICU days and lower morbidity compared to clinical examination alone. The limitations of ultrasound include operator dependence and difficulty obtaining views in critically ill patients.
Diffusion potential. Large Nerve. Na -K ATPase. Guyton and Hall. Medical Physiology. Dr. Nusrat Tariq. Professor Of Physiology. M.I.M.D.C. GOLDMAN HODGKIN KATZ EQUATION
This document discusses coronary guidewires used in percutaneous coronary intervention (PCI). It begins by outlining the history of angioplasty and guidewire development. It then covers the purpose, components, classifications, and appropriate uses of guidewires. The main components include the core, tip, coils, covers, and coatings. Guidewires are classified based on flexibility, device support, and clinical usage. Complications like vessel perforation, pseudolesions, and entrapment are also discussed. Proper guidewire manipulation and strategies for difficult lesions are outlined to maximize safety and efficacy.
Simon Fessard is an urban planner from France with over 10 years of experience in urban design, mobility planning, and cycling infrastructure projects. He has a master's degree in urban systems engineering and has worked at several planning firms and NGOs in Europe. Currently, he works as an urban planning consultant at Mobycon in the Netherlands focusing on projects related to cycling, public transportation, and traffic analysis. He has significant experience managing international projects, conducting research, and presenting at conferences on topics of cycling policy, bike sharing systems, and urban design.
How Social Software Helps 350,000 Men's Wearhouse Customers Dress Better Ever...tibbr
Find out how The Men’s Wearhouse uses tibbr today to meet the challenges of a modern retail environment in “The Future Of Work ― A Retailer’s Perspective” from his breakout session presentation at TUCON 2013.
This document discusses developing a structured framework called a Project Management Knowledge Structure (PMKS) to organize the body of knowledge in project management. It explores challenges in classifying knowledge and proposes using conceptual models to help understand the complex relationships within project management. The document examines previous attempts to structure knowledge and argues a new PMKS is needed to facilitate identifying and conveying project management information in the 21st century.
Este documento presenta el plan de estudios de la asignatura "Gastronomía Molecular" de la Facultad de Farmacia y Bioquímica de la Universidad Nacional Mayor de San Marcos. La asignatura se enfoca en aplicar conocimientos básicos de química y física a la gastronomía para preparar y transformar platos utilizando técnicas moleculares. El plan describe los objetivos, contenidos, metodología, sistema de evaluación y cronograma de la asignatura dividida en teoría y prácticas de laboratorio.
El documento presenta una estrategia de segmentación de clientes para una empresa (AS) basada en variables como el nivel de satisfacción, fidelidad, valor monetario y comportamiento digital. Se propone aplicar un modelo RFM+D que clasifique a los clientes en segmentos como "AS", "BANQUILLO", "LA CANTERA" y "PENALTI" dependiendo de cómo puntúen en dichas variables. El objetivo es desarrollar acciones de marketing segmentadas para fidelizar a los clientes.
This document outlines marketing strategies for Leg Avenue, a company that sells sexy costumes. It discusses the brand's positioning as making women feel confident and sexy by transforming them into fantasy characters. 15 strategies are proposed to increase sales through the website, social media, public relations with TV news and conventions, video content, partnerships, and expanding product lines. The target demographic is primarily women ages 18-44 who want to feel empowered and turn heads through costume play.
Este documento presenta una compilación de poesías de François Villon traducidas por diferentes autores. Incluye las poesías contenidas en "El Testamento" de Villon traducidas por Rubén Abel Reches, así como otras poesías diversas traducidas por Reches, Luis Gregorich y Carlos Alvar. También incluye el cuento "Un alojamiento para la noche" traducido por Antonio Bonano. Se transcriben las notas de los traductores y se indican las fuentes de donde fueron tomados los textos. Finalmente, contiene un índice
LR Health & Beauty celebrates its 30th anniversary in 2015 and introduces several new products and partnerships. It welcomes Portuguese megastar Cristina Ferreira and fashion designer Guido Maria Kretschmer as new faces of its fragrance segment. It also launches a new product category called Zeitgard for innovative skincare technologies, starting with a facial cleansing brush. The company looks forward to continued growth and innovation in the future.
El documento presenta una serie de frases y citas atribuidas a diversos autores sobre temas como el amor, Dios, la verdad, la juventud, la pobreza y la naturaleza. Algunas de las citas destacadas son aquellas de Madre Teresa, Chesterton, San Juan Bosco y Confucio.
Heavy Duty Linear Actuators, Belt Driven Actuators: MXBTolomatic
Tolomatic's heavy duty linear actuator, the MXB electric belt driven actuator is designed to outlast every rodless actuator on the market.
The MXB belt driven actuators set a new standard for durability. Built with Endurance Technology materials, MXB belt driven actuators are available with 2 different carriers (carriages).
1) The MXB-P profiled rail offers high load and bending moment capacities in a low profile package.
2) The MXB-U is designed for applications where loads are externally guided and supported.
Features of the MXB belt driven actuators:
High speed and acceleration capabilities (up to 1200 in/sec2)
6 body sizes accommodate a wide range of forces and loads
Polyurethane belt with steel members resists stretching
Excellent repeatability, high duty cycle performance
Choose MXB belt drive for longer strokes than screw drive actuators
El documento describe nueve tipos de personalidad según el sistema de clasificación del eneagrama. Cada persona tiene un patrón de comportamiento único pero existen similitudes entre individuos. El eneagrama identifica nueve tipos de personalidad como el reformador, el ayudador, el triunfador, el romántico, el investigador, el leal, el entusiasta y el desafiador. Conocer los tipos de personalidad puede ayudar a la auto comprensión.
Cómo conseguir mayor productividad y competitividad a través de la dirección ...Elizabeth Ontaneda
Las técnicas de dirección de operaciones se aplican en todo el mundo en cualquier tipo de empresa. Da igual que se trate de una oficina, un hospital, un restaurante, un centro comercial o una fábrica: la producción de bienes y servicios requiere que haya una dirección de operaciones, que es la que se encarga de llevar a cabo una serie de actividades que crean valor al transformar los recursos en bienes y servicios. Y cuanto más eficiente seamos en la producción eficiente de bienes y servicios, mayor será nuestra productividad y competitividad.
En esta sesión, Emilio Gómez nos enseñará cómo aplicar eficazmente los conceptos, herramientas y técnicas de la dirección de operaciones para alcanzar una mayor productividad; y cómo sus operaciones pueden generar una ventaja competitiva para su empresa.
El documento presenta la estructura organizativa y curricular del nivel de educación secundaria en Nicaragua. Incluye el perfil del egresado de este nivel con competencias en tres categorías: desarrollo personal y ciudadano, científica para el desarrollo, y desarrollo cultural y comunicativo. También presenta la misión, visión y propósitos de la educación secundaria nicaragüense.
Learning Single page Application chapter 1Puguh Rismadi
This document provides an overview of single page applications (SPAs) and the MEAN stack. It discusses SPAs, the MVC and MVVM patterns, differences between SPAs and traditional web development, factors for choosing frameworks, and an introduction to the MEAN stack which is comprised of MongoDB, Express, AngularJS, and Node.js. It also briefly mentions tools for developing web applications and recommends an IDE along with providing example Indonesian tutorials.
Este documento describe los protocolos para el lavado de manos correcto en ambientes hospitalarios. Explica que el lavado de manos es la medida más importante para prevenir la propagación de microorganismos e infecciones intrahospitalarias. Detalla la diferencia entre la flora residente y transitoria de la piel, los objetivos del lavado de manos, los materiales necesarios y los pasos correctos para lavar y secar las manos adecuadamente.
CCNY's BIC foundational course Brand Experience, taught by Dee Solomon, challenged students to work against Ty Montague "True Story" 'metastory' branding framework to brainstorm a new metastory for a company that could benefit from a transformational new brand story.
After weeks of research and brainstorming in larger groups, each student then worked individually with the final shared metastory for their group's company, in my case - Revlon, and strategized around 3 brand experiences (physical, digital, and revenue-driving) that were natural extensions of the metastory.
Semester: Spring 2014
El documento resume los conceptos fundamentales de la Core-energética, una disciplina creada por John Pierrakos que trabaja con los niveles psicosomáticos, energéticos y espirituales del ser humano. Describe que la Core-energética se basa en tres fuerzas internas (amor, eros y sexualidad) y que al reprimir estas fuerzas se pueden ocasionar problemas emocionales y de salud. Finalmente, explica que la Core-energética busca la sanación a través de la movilización energética y la expansión de
El documento describe los conceptos clave de la dirección. La dirección implica conducir, guiar y supervisar los esfuerzos de los subordinados para ejecutar planes y lograr objetivos. Esto incluye funciones como la ejecución de planes, motivación, guía, comunicación y supervisión para alcanzar las metas de la organización. También se describen principios como la armonía de objetivos, impersonalidad de mando y supervisión directa que son importantes para una dirección efectiva.
Power Circuits and Transforers-Unit 3 Labvolt Student Manualphase3-120A
This document discusses determining equivalent capacitance for series and parallel capacitors. It explains that capacitance opposes changes in voltage across capacitor terminals and depends on factors like dielectric material and plate size/spacing. The exercise objectives are to calculate equivalent capacitance using circuit measurements and explain how capacitance values combine in series and parallel configurations.
Electrical properties of tissues can be passive or active. Passive properties refer to how tissues behave in an electric field, while active properties refer to electricity generated from tissue activity. Live tissue acts as a special conductor allowing electric currents from both external sources and internal plasma membranes. Current can be direct (DC) or alternating (AC). Tissue impedance depends on properties like cell membrane conductance and resistance that influence how electric currents flow.
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1. Appendix A
Brief introduction to bioimpedance
Bioimpedance refers to the electrical properties of a biological tissue, measured
when current flows through it. This impedance varies with frequency and
different tissue types, and varies sensitively with the underlying histology.
This appendix is a brief summary of its principles; we hope it will be useful
for any non-technical readers new to EIT. The section is unreferenced; a
suggested reading list is attached at the end.
A.1.
RESISTANCE AND CAPACITANCE
The resistance and the capacitance of tissue are the two basic properties in
bioimpedance.
Resistance (R) is a measure of the extent to which an element opposes
the flow of electrons or, in aqueous solution as in living tissue, the flow of
ions among its cells. The three fundamental properties governing the flow
of electricity are voltage, current and resistance. The voltage may be thought
of as the pressure exerted on a stream of charged particles to move down a
wire or migrate through an ionized salt solution. This is analogous to the
pressure in water flowing along a pipe. The current is the amount of
charge flowing per unit time, and is analogous to water flow in a pipe. Resistance is the ease or difficulty with which the charged particles can flow, and is
analogous to the width of a pipe through which water flows—the resistance is
higher if the pipe is narrower (figure A.1).
They are related by Ohm’s law:
V (voltage, Volts) ¼ I (current, Amps) Â R (resistance, Ohms ðÞÞ:
The above applies to steadily flowing, or ‘d.c.’ current (direct current).
Current may also flow backwards and forwards—‘a.c.’ (alternating current).
411
2. 412
Brief introduction to bioimpedance
Figure A.1.
Basic concepts—current, voltage and resistance. Analogy to water flow.
Resistance has the same effect on a.c. current as d.c. current. Capacitance (C)
is an expression of the extent to which an electronic component, circuit or
system, stores and releases energy as the current and voltage fluctuate with
each a.c. cycle. The capacitance physically corresponds to the ability of
plates in a capacitor to store charge. With each cycle, charges accumulate
and then discharge. Direct current cannot pass through a capacitor. A.c.
can pass because of the rapidly reversing flux of charge. The capacitance is
an unvarying property of a capacitive or more complex circuit. However,
the effect in terms of the ease of current passage depends on the frequency
of the applied current—charges pass backwards and forwards more rapidly
if the applied frequency is higher.
For the purposes of bioimpedance, a useful concept for current travelling through a capacitance is ‘reactance’ (X). The reactance is analogous to
resistance—a higher reactance has a higher effective resistance to alternating
current. Like resistance, its value is in Ohms, but it depends on the applied
frequency, which should be specified (figure A.2).
The relationship is
Reactance (Ohms) ¼ 1=ð2 Â Å Â Frequency ðHzÞ Â Capacitance ðFaradsÞÞ:
When a current is passing through a purely resistive circuit, the voltage
recorded across the resistor will coincide exactly with the timing, or phase,
of the applied alternating current, as one would expect. In the water flow
analogy, an increase in pressure across a narrowing will be instantly followed
by an increase in flow. When current flows across a capacitor, the voltage
recorded across it lags behind the applied current. This is because the back
and forth flow of current depends on repeated charging and discharging of
the plates of the capacitor. This takes a little time to develop. To pursue the
water analogy, a capacitor would be equivalent to a taut membrane stretched
3. Resistance and capacitance
Figure A.2.
413
Capacitance, reactance and effect of frequency.
across the pipe. No continuous flow could pass. However, if the flow is
constantly reversed, then for each new direction, a little water will flow as
the membrane bulges, and then flow back the other way when the flow
reverses. The development of pressure on the membrane will only build up
after some water has flowed into the membrane to stretch it. In terms of a
sine wave which has 3608 in a full cycle, the lag is one quarter of a cycle, or 908.
In practice, this is seen if an oscilloscope is set up as in figure A.3. An
ideal (confused with d.c.) current a.c. source passes current across a resistor
or capacitor. The current delivered by the source is displayed on the upper
trace. The voltage measured over the components is displayed on the lower
trace. When this is across a resistor, it is in phase—when across a capacitor,
it lags by 908 and is said to be ‘out-of-phase’. When the circuit contains a
mixture of resistance and capacitance, the phase is intermediate between 0
and 908, and depends on the relative contributions from resistance and
capacitance. As a constant current is applied, the total combination of
resistance or reactance, the impedance can be calculated by Ohm’s law
from the amplitude of the voltage at the peak of the sine wave.
4. 414
Brief introduction to bioimpedance
Figure A.3. The voltage that results from an applied current is in phase for a resistor (A)
and 908 out of phase for a capacitor.
Impedance is made of these two components, resistance or the real part
of the data, and reactance, the out-of-phase data. These are usually displayed
on a graph in which resistance is the x axis and reactance is the y axis. This is
termed the ‘complex’ impedance, and the graph is the ‘complex’ plane. For
mathematical reasons to do with solutions of the equations for the sine
waves of the a.c. voltages, the in-phase resistive component is considered
to be a ‘real’ or normal number. The out-of-phase, capacitative, component
is considered to be ‘imaginary’. This means that the amplitude of the
capacitative voltage, a real number such as 3.2 V, is multiplied by ‘j’, which
is the square root of minus 1. Thus, a typical complex impedance might be
written as
450 þ 370j:
This would mean that the resistance is 450 and the reactance is 370 , and
would be displayed on the complex plane as in figure A.4, with the resistance
on the x axis and reactance on the y axis. Another equivalent way is to
calculate the length of the impedance line, which passes from the origin of
the graph to the complex impedance point. This is termed the ‘modulus’ of
the impedance (Z), and means its total amplitude, irrespective of whether
6. 416
Brief introduction to bioimpedance
it is resistance or reactance. In practice, this is identical to the amplitude of
the sine wave of measured voltage, seen on an oscilloscope, as in figure
A.3, irrespective of the phase angle. The ‘phase angle’ is calculated from
the graph, and is given along with the modulus. The phase angle on the
graph is exactly the same as the lag in phase of the measured voltage
(figure A.4). For the above example,
450 þ 370j ðR þ jXÞ converts to 583 at 398ðZ þ Þ:
A.2. IMPEDANCE IN BIOLOGICAL TISSUE
Cells may be modelled as a group of electronic components. One of the
simplest employs just three components (figure A.5). The extracellular
space is represented as a resistor (Re), and the intracellular space and the
membrane is modelled as a resistor (Ri) and a capacitor (Cm) (figure
A.5(a)). Both the extracellular space and intracellular space are highly
conductive, because they contain salt ions. The lipid membrane of cells
is an insulator, which prevents current at low frequencies from entering the
cells. At lower frequencies, almost all the current flows through the
extracellular space only, so the total impedance is largely resistive and is
equivalent to that of the extracellular space. As this is usually about 20%
or less of the total tissue, the resulting impedance is relatively high. At
higher frequencies, the current can cross the capacitance of the cell
membrane and so enter the intracellular space as well. It then has access to
the conductive ions in both the extra- and intra-cellular spaces, so the overall
impedance is lower (figure A.6(a)).
Figure A.5. (a) The cell modelled as basic electronic circuit. Ri and Re are the resistances
of the intracellular- and extracellular-space, and Cm is the membrane capacitance. (b)
Cole–Cole plot of this circuit.
7. Impedance in biological tissue
417
Figure A.6. (a) The movement of current through cells at both low and high frequencies.
(b) Idealized Cole–Cole plot for tissue.
The movement of the current in the different compartments of the cellular
spaces at different frequencies, and the related resistance and reactance values
measured, is usefully displayed as a Cole–Cole plot. This is an extension of the
resistance/reactance plot in the complex plane. Instead of the single point for a
measurement at one frequency, as in figure A.4, the values for a range of
frequencies are all superimposed. For simple electronic components, the arc
will be a semicircle (figure A.5(b)). At low frequencies, the measurement is
only resistive, and corresponds to the extracellular resistance—no current
passes through the intracellular path because it cannot cross the cell membrane
capacitance. As the applied frequency increases, the phase angle gradually
increases as more current is diverted away from the extracellular resistance,
and passes through the capacitance of the intracellular route. At high frequencies, the intracellular capacitance becomes negligible, so current enters the
parallel resistances of the intracellular and extracellular compartments. The
cell membrane reactance is now nil, so the entire impedance again is just
resistive and so returns to the X axis. Between these, the current passing
through the capacitative path reaches a peak. The frequency at which this
8. 418
Brief introduction to bioimpedance
occurs is known as the centre frequency (Fc), and is a useful measure of the
properties of an impedance. In real tissue, the Cole–Cole plot is not exactly
semicircular, because the detailed situation is clearly much more complex;
the plot is usually approximately semicircular, but the centre of the circle
lies below the x-axis. Inspection of the Cole–Cole plot yields the high- and
low-frequency resistances, as the intercept with the x-axis, and the centre
frequency is the point at which the phase angle is greatest. The angle of depression of the centre of the semicircle is another means of characterizing the tissue
(figure A.6(b)).
Over the frequency ranges used for EIT and MIT, about 100 Hz to
100 MHz, the resistance and reactance of tissue gradually decreases. This is
due to the simple effect of increased frequency passing more easily across capacitance, but also because cellular and biochemical mechanisms begin to operate, which increases the ease of passage of the electrical current. A
remarkable feature of live tissue is an extraordinarily high capacitance, which
is up to 1000 times greater than inorganic materials, such as plastics used in
capacitors. This is because capacitance is provided by the numerous and closely
opposed cell membranes of cells, each of which behaves as a tiny capacitor.
Over this frequency range, there are certain frequency bands where the phase
angle increases, because mechanisms come into play which provide more capacitance. They may be seen as regions of an increased decrease of resistance in a
plot of resistance against frequency, and are termed ‘dispersions’. At the low
end of the frequency spectrum, the outer cell membrane of most cells is able
to charge and discharge fully. This region is known as the alpha dispersion
and is usually centred at about 100 Hz.
As the frequency increases, from 10 kHz–10 MHz, the membrane only
partially charges and the current charges the small intracellular space structures, which behave largely as capacitances. At these higher frequencies the
current can flow through the lipid cell membranes, introducing a capacitive
component. This makes the higher frequencies sensitive to intracellular
changes due to structural relaxation. This effect is largest around 100 kHz,
and is termed the ‘beta dispersion’. At the highest frequencies, dipolar
reorientation of proteins and organelles can occur, and affect the impedance
measurements of extra- and intracellular environments. This is the gamma
dispersion, and is due to the relaxation of water molecules and is centred
at 10 GHz. Most changes between normal and pathological tissues occur
in the alpha and beta dispersion spectrum.
A.3. OTHER RELATED MEASURES OF IMPEDANCE
A.3.1.
Unit values of impedance
Resistance and reactance, as described above, are fixed measures of individual components or samples. It is useful to be able to describe the general
9. Other related measures of impedance
Figure A.7.
measured.
419
The effect of changing the length or cross-sectional area of the tissue sample
properties of a material. The impedance of a sample increases, as one would
expect, with increasing length of the sample between the measuring electrodes. Somewhat counter-intuitively, it decreases if the area contacting the
measuring electrodes increases—this is because there is more conductive
material to carry the current. The individual values for resistance or
reactance can be converted to the general property—termed ‘resistivity’ or
‘reactivity’ by adjusting for these. Resistivity is given in :m and is the
ability of a material to resist the passage of electrical current for a defined
unit of tissue (figure A.7). It is calculated as
ð:mÞ ¼ ResistanceðÞ Â Area=Length:
The capacitative element of a material can be considered in the same way—
the ‘reactivity’ is also measured in :m and is the general resistance property
of a material, at a specified frequency.
A.3.2.
Other indices of impedance
The resistance and reactance fully describe the impedance of tissue, but there
are several other related measures which are, sometimes confusingly, used in
the EIT and Bioimpedance, literature. These arise because different, reciprocal, terms may be used to describe the ease, as opposed to the difficulty, of
passage of current. Secondly, with respect to capacitance, one can choose
to use the effective resistance at a given frequency—the reactance, or the
intrinsic property of the material, the capacitance, which is independent of
frequency. Each of the different measures may be suffixed with ‘-ivity’ to
yield its general property. Finally, the measure given may refer to the
complex impedance rather than the in- or out-of-phase component.
Not all permutations, fortunately, are widely used. These are the most
common: the conductivity is the inverse of resistivity and is given in
Siemens/m or, more usually, S/m. The admittance is the inverse of
impedance, and so is a combined measure of in- and out-of-phase ease of
10. 420
Brief introduction to bioimpedance
passage of current through a tissue. The capacitance of the tissue is the
capacity to store charge, and is given in Farads. The permittivity of a
tissue is the property of a dielectric material that determines how much
electrostatic energy can be stored per unit of volume when unit voltage is
applied, and is given in F/m. The dielectric constant is the permittivity
relative to a vacuum, and indicates how much greater the capacitance of a
capacitor would be if the sample was placed between the plates compared
to a vacuum.
A.4. IMPEDANCE MEASUREMENT
The impedance of samples is usually recorded with silver electrodes. The
simplest arrangement is to place electrodes at either end of a cylindrical or
cuboidal sample of the tissue. A constant current is passed and the
impedance is calculated from the measured voltage (figure A.7). The drawback of this method is that the impedance measured includes not only the
tissue sample, but also that of the electrodes. The method can be reliable,
but requires that a calibration procedure is performed first to establish the
electrode impedance. These then need to be subtracted from the overall
impedance recorded, and it should be a fair assumption that the electrode
impedances do not change between the calibration and test procedures (see
figure A.8).
Impedance is best measured using four electrodes, as this circumvents
the error of inadvertent inclusion of the electrode impedance with two
terminal recordings (figure A.9). The principle is that constant current is
Figure A.8. (a) The two-electrode measurement as a block diagram, and (b) modelled as a
simple electrical circuit. The two overlapping rings represent a constant current electrical
source.
11. Relevance to electrical impedance tomography
421
Figure A.9. The four-electrode measurement as (a) a block diagram, and (b) modelled as
a simple electrical circuit.
delivered to the electrodes through the two current electrodes; as it is
constant, the correct current is independent of the electrode impedance.
The voltage is recorded by high performance modern amplifiers, which are
not significantly affected by the series electrodes impedance between the
sample and amplifier (figure A.7). As a result, the impedance is ideally
unaffected by electrode impedance, although non-idealities in the electronics
may cause inaccuracies in practice. The main drawback of this method is that
the geometry of the sample is no longer clear cut, so that conversion to
resistivity needs careful modelling of the path of current flow through the
tissue.
A.5.
RELEVANCE TO ELECTRICAL IMPEDANCE
TOMOGRAPHY
The Sheffield mark 1, and the several similar systems which have been used to
make clinical and human EIT measurements, only record the in-phase,
resistive, component of the impedance. This is because unwanted capacitance
in the leads and electronics introduce errors. Fortunately, these are all out-ofphase and so can be largely discounted by throwing away the out-of-phase
data. For the same reason, images are generated of differences over time,
as subtraction like this minimizes errors. As a result, the great majority of
clinical EIT images are a unitless ratio between the reference and test
image data at a single frequency. More recently, systems have been
constructed and tested which can measure at multiple frequencies, and
provide absolute impedance data. As these are validated, and come into
wider clinical use, then we may expect to see more absolute bioimpedance
parameters, such as resistivity, admittivity, centre frequency, or ratio of
extra- to intracellular resistivity, in EIT image data.
12. 422
Brief introduction to bioimpedance
FURTHER READING
Duck F A 1990 Physical properties of tissue: a comprehensive reference book. London:
Academic Press
Gabriel C, Gabriel S and Corthout E 1996a The dielectric properties of biological tissues: I.
Literature survey Physics in Medicine and Biology 41 2231–2249
Gabriel S, Lau R and Gabriel C 1996b The dielectric properties of biological tissues: II.
Measurements in the frequency range 10 Hz to 20 GHz Physics in Medicine and Biology 41 2251–2269
Geddes L B L E 1967 The specific resistance of biological material—a compendium of data
for the biomedical engineer and physiologist Med. Biol. Eng. 5 271–293
Grimnes S and Martinsen Ø G 2000 Bioimpedance and bioelectricity basics. London:
Academic Press