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Related Concept Videos

Resistivity01:22

Resistivity

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When a voltage is applied to a conductor, an electrical field is generated, and charges in the conductor feel the force due to the electrical field. The current density that results depends on the electrical field and the properties of the material. In some materials, including metals at a given temperature, the current density is approximately proportional to the electrical field. In these cases, the current density can be modeled as:
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Resistance01:19

Resistance

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When a current moves through any conductor, the conductor causes some level of difficulty for the current to flow. The measure of that difficulty is known as the resistance of the material and is represented by R. Every material has its own resistance. In the case of conductors, heat is emitted whenever a current passes through them. Resistance depends on the resistivity of the material. Resistivity is a characteristic of the material used to fabricate electrical components, whereas the...
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Equivalent Resistance01:16

Equivalent Resistance

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In circuit analysis, situations often arise where resistors are neither in series nor parallel configurations. To tackle such scenarios, three-terminal equivalent networks like the wye (Y) (Figure 1 (a)) or tee (T) and delta (Δ) (Figure 1 (b)) or pi (π) networks come into play. These networks offer versatile solutions and are frequently encountered in various applications, including three-phase electrical systems, electrical filters, and matching networks.
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Resistance and Conductance01:25

Resistance and Conductance

517
A conductor's DC resistance at a given temperature is influenced by its resistivity, length, and cross-sectional area. Resistivity is an inherent property of the conductor material, with annealed copper serving as the international standard for measurement. For instance, the resistivity of hard-drawn aluminum at 20 degrees Celsius is 61% of the standard conductivity of annealed copper.
Various factors impact the resistance of a conductor. Spiraling in stranded conductors increases their...
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Rolling Resistance01:21

Rolling Resistance

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When a solid cylinder rolls steadily on a rigid surface, the normal force applied by the surface on the cylinder is perpendicular to the tangent at the contact point. However, since no materials are entirely rigid, the surface's reaction to the cylinder involves a range of normal pressures.
For instance, imagine a hard cylinder rolling on a comparatively soft surface. The cylinder's weight compresses the surface beneath it. As the cylinder moves, the material in front of it slows down due to...
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Vascular Resistance01:20

Vascular Resistance

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Vascular resistance is a critical concept in understanding blood flow dynamics in the circulatory system. It refers to the resistance that blood encounters as it flows through the blood vessels. This resistance is a key factor in determining blood pressure and cardiac workload.
The primary determinants of vascular resistance are vessel diameter, blood viscosity, and vessel length. Among these, vessel diameter plays the most significant role due to the fourth power relationship described by...
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Resistance to β-lactams in enterococci.

Paula Gagetti1, Laura Bonofiglio2, Gabriela García Gabarrot3

  • 1Grupo STREP de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas (SADEBAC), División de la Asociación Argentina de Microbiología, Argentina; Servicio Antimicrobianos, Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas (INEI), ANLIS "Dr Carlos G. Malbrán", Ciudad Autónoma de Buenos Aires, Argentina.

Revista Argentina De Microbiologia
|September 24, 2018
PubMed
Summary

High-level ampicillin resistance in Enterococcus faecium is a growing concern, primarily caused by alterations in the PBP5 protein. This resistance spreads through bacterial clonal expansion and horizontal gene transfer.

Keywords:
Antimicrobial resistanceEnterococciEnterococcus faecalisEnterococcus faeciumEnterococosResistenciaβ-Lactamsβ-Lactámicos

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Area of Science:

  • Microbiology
  • Antimicrobial Resistance
  • Molecular Biology

Background:

  • Enterococci exhibit intrinsic resistance to antimicrobials and readily acquire new resistance mechanisms.
  • Beta-lactam antibiotics are crucial for treating enterococcal infections, making resistance a significant clinical challenge.
  • Ampicillin resistance is infrequent in Enterococcus faecalis but prevalent in hospital-associated Enterococcus faecium.

Purpose of the Study:

  • To investigate the primary mechanisms driving high-level ampicillin resistance in Enterococcus faecium.
  • To understand the genetic basis and dissemination routes of ampicillin resistance in this pathogen.

Main Methods:

  • Analysis of PBP5 protein production and genetic polymorphisms in ampicillin-resistant Enterococcus faecium isolates.
  • Investigation of clonal spread and horizontal gene transfer as dissemination mechanisms.

Main Results:

  • High-level ampicillin resistance in Enterococcus faecium is predominantly linked to enhanced production of PBP5 and/or mutations in its beta subunit.
  • Both the clonal spread of strains with mutated pbp5 genes and horizontal gene transfer contribute to the dissemination of this resistance.

Conclusions:

  • Alterations in PBP5 are the key drivers of high-level ampicillin resistance in Enterococcus faecium.
  • Understanding these mechanisms and dissemination routes is vital for combating antimicrobial resistance in clinical settings.