resistance

Examples of resistance in the following topics:

• Resistance and Resistivity

  • Resistance and resistivity describe the extent to which an object or material impedes the flow of electric current.
  • Conductance and resistance are reciprocals .
  • What determines resistivity?
  • Its resistance to the flow of current is similar to the resistance posed by a pipe to fluid flow.
  • Identify properties of the material that are described by the resistance and resistivity

• Resistance to French Rule

• Dependence of Resistance on Temperature

  • Resistivity and resistance depend on temperature with the dependence being linear for small temperature changes and nonlinear for large.
  • The resistivity of all materials depends on temperature.
  • where ρ0 is the original resistivity and α is the temperature coefficient of resistivity.
  • is the temperature dependence of the resistance of an object, where R0 is the original resistance and R is the resistance after a temperature change T.
  • Compare temperature dependence of resistivity and resistance for large and small temperature changes

• Mechanisms of Resistance

  • Resistance can be mediated by the environment or the microorganism itself .
  • Intrinsic resistance is considered to be a natural and inherited property with high predictability.
  • Once the identity of the organism is known, the aspects of its anti-microbial resistance are also recognized.
  • On the other hand, acquired resistance results from a change in the organism's genetic makeup.
  • Describe the mechanisms bacteria use to develop antimicrobial resistance and the factors that can lead to it

• Factors Affecting Pulmonary Ventilation: Airway Resistance

  • Airway resistance refers to resistance in the respiratory tract to airflow.
  • Airway resistance can change over time, especially during an asthma attack when the airways constricts causing an increase in airway resistance.
  • Below is the equation for calculating airway resistance (R).
  • Therefore the resistance to air in the bronchi is greater than the resistance to air in the trachea.
  • Laminar flow (a) has orderly layers and low resistance.

• Cost and Prevention of Resistance

  • Antimicrobial resistance is a major public health and economic burden on patients, affected communities, and healthcare providers.
  • Patients who are infected with bacterial strains resistant to more than one type or class of drugs (multidrug-resistant organisms, MDRO) often have an increased risk of prolonged illness, extended hospital stay, and mortality.
  • Multidrug resistance forces healthcare providers to use antibiotics that are more expensive or more toxic to the patient.
  • Research and development of new drugs effective against resistant bacterial strains also comes at a cost.
  • Antibiotic misuse is a major cause of the staggering healthcare costs for the treatment of resistant bacterial strains.

• Relative Resistance of Microbes

  • Endospores are considered the most resistant structure of microbes .
  • They are resistant to most agents that would normally kill the vegetative cells from which they formed.
  • Certain bacterial species are more resistant to treatment than others.
  • Gram-negative bacteria have high natural resistance to some antibiotics.
  • Staphylococcus aureus is one of the major resistant pathogens.

• Resisitors in Series

  • The total resistance in the circuit with resistors connected in series is equal to the sum of the individual resistances.
  • A measure of this limit on charge flow is called resistance.
  • The total resistance in the circuit is equal to the sum of the individual resistances, since the current has to pass through each resistor in sequence through the circuit.
  • This implies that the total resistance in a series is equal to the sum of the individual resistances.
  • Since all of the current must pass through each resistor, it experiences the resistance of each, and resistances in series simply add up.

• Introduction to Blood Flow, Pressure, and Resistance

  • Resistance to flow must be overcome to push blood through the circulatory system.
  • If resistance increases, either pressure must increase to maintain flow, or flow rate must reduce to maintain pressure.
  • Numerous factors can alter resistance, but the three most important are vessel length, vessel radius, and blood viscosity.
  • With increasing length, increasing viscosity, and decreasing radius, resistance is increased.
  • The resistance offered by peripheral circulation is known as systemic vascular resistance (SVR), while the resistance offered by the vasculature of the lungs is known as pulmonary vascular resistance (PVR).

• Combination Circuits

  • This is commonly encountered, especially when wire resistances is considered.
  • In that case, wire resistance is in series with other resistances that are in parallel.
  • Essentially, wire resistance is a series with the resistor.
  • It thus increases the total resistance and decreases the current.
  • Each is identified and reduced to an equivalent resistance, and these are further reduced until a single equivalent resistance is reached.