1-Acute Control of Local Blood Flow
... leads to formation of the vascular growth factors (also called "angiogenic factors").They cause new vessels to sprout from other small vessels. So oxygen is important not only for acute control of local blood flow but also for long-term control. One example of this is increased vascularity in tissue ...
... leads to formation of the vascular growth factors (also called "angiogenic factors").They cause new vessels to sprout from other small vessels. So oxygen is important not only for acute control of local blood flow but also for long-term control. One example of this is increased vascularity in tissue ...
12. THE LAWS OF THERMODYNAMICS Key Words
... From (12-9), we can clearly understand the basic idea behind any heat engine: mechanical work can be obtained from thermal energy only when heat is allowed to flow from a high temperature TH to a low temperature TC. In this process, some of the heat can be transformed into mechanical work. Equation ...
... From (12-9), we can clearly understand the basic idea behind any heat engine: mechanical work can be obtained from thermal energy only when heat is allowed to flow from a high temperature TH to a low temperature TC. In this process, some of the heat can be transformed into mechanical work. Equation ...
How long does it take to boil an egg?
... egg, namely: (a) at what temperature the white and the yolk cook and (b) what their thermal conductivities (κ) and specific heats (ce ) are. The first question can be easily solved experimentally by cooking a small amount of egg (e.g., at the bottom of a test tube) in a water bath whose temperature ...
... egg, namely: (a) at what temperature the white and the yolk cook and (b) what their thermal conductivities (κ) and specific heats (ce ) are. The first question can be easily solved experimentally by cooking a small amount of egg (e.g., at the bottom of a test tube) in a water bath whose temperature ...
Unit 5 Student Packet
... 8. *Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 40.0 cm3. If the combustion of this mixture released 950.0J of energy, to what volume will the gases expand against a constant pressure of 650.0 torr if all of the energy of combustion is converted i ...
... 8. *Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 40.0 cm3. If the combustion of this mixture released 950.0J of energy, to what volume will the gases expand against a constant pressure of 650.0 torr if all of the energy of combustion is converted i ...
chapter 21 electrolyte balance
... 21.5: Acid-Base Balance • Electrolytes that ionize in water and release hydrogen ions are acids • Substances that combine with hydrogen ions are bases • Acid-base balance entails regulation of the hydrogen ion concentrations of body fluids • This is important because slight changes in hydrogen ion ...
... 21.5: Acid-Base Balance • Electrolytes that ionize in water and release hydrogen ions are acids • Substances that combine with hydrogen ions are bases • Acid-base balance entails regulation of the hydrogen ion concentrations of body fluids • This is important because slight changes in hydrogen ion ...
Countercurrent exchange
Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some component, between two flowing bodies flowing in opposite directions to each other. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. For example, in a distillation column, the vapors bubble up through the downward flowing liquid while exchanging both heat and mass.The maximum amount of heat or mass transfer that can be obtained is higher with countercurrent than co-current (parallel) exchange because countercurrent maintains a slowly declining difference or gradient (usually temperature or concentration difference). In cocurrent exchange the initial gradient is higher but falls off quickly, leading to wasted potential. For example, in the diagram at the right, the fluid being heated (exiting top) has a higher exiting temperature than the cooled fluid (exiting bottom) that was used for heating. With cocurrent or parallel exchange the heated and cooled fluids can only approach one another. The result is that countercurrent exchange can achieve a greater amount of heat or mass transfer than parallel under otherwise similar conditions. See: flow arrangement.Countercurrent exchange when set up in a circuit or loop can be used for building up concentrations, heat, or other properties of flowing liquids. Specifically when set up in a loop with a buffering liquid between the incoming and outgoing fluid running in a circuit, and with active transport pumps on the outgoing fluid's tubes, the system is called a Countercurrent multiplier, enabling a multiplied effect of many small pumps to gradually build up a large concentration in the buffer liquid.Other countercurrent exchange circuits where the incoming and outgoing fluids touch each other are used for retaining a high concentration of a dissolved substance or for retaining heat, or for allowing the external buildup of the heat or concentration at one point in the system.Countercurrent exchange circuits or loops are found extensively in nature, specifically in biologic systems. In vertebrates, they are called a Rete mirabile, originally the name of an organ in fish gills for absorbing oxygen from the water. It is mimicked in industrial systems. Countercurrent exchange is a key concept in chemical engineering thermodynamics and manufacturing processes, for example in extracting sucrose from sugar beet roots.Countercurrent multiplication is a similar but different concept where liquid moves in a loop followed by a long length of movement in opposite directions with an intermediate zone. The tube leading to the loop passively building up a gradient of heat (or cooling) or solvent concentration while the returning tube has a constant small pumping action all along it, so that a gradual intensification of the heat or concentration is created towards the loop. Countercurrent multiplication has been found in the kidneys as well as in many other biological organs.