SCYM (ASCP) ACTUAL
EXAM 2025 -2026 WITH
100% CORRECT
ANSWERS
Generation of differential pressure (syringe pump, pressure based) - ANSWER --Low
differential pressure allows the cells to move past the interrogation point one at a time. .... One
kind involves generating pressure using a pump and regulator system ... Differential pressure
based fluidic system. ... peristaltic and/or syringe pumps to deliver the sample into the
instrument.
Characterization of syringe-pump-driven induced pressure - ANSWER --In syringe-pump-
driven microfluidic systems, pressure fluctuations are observed in an elastic microchannel. The
syringe pump is driven by an electrical stepper motor, from which mechanical oscillations are
expected to generate flow-rate fluctuations and in turn leads to the pressure fluctuations in the
channel flow.
Hydrodynamic Focusing - ANSWER --Most modern flow cytometers tightly position the
sample for optical analysis via hydrodynamic focusing. Here, a carrier fluid called the sheath
fluid is used to position the sample of cells into a single file for optical interrogation.
Hydordynamic focusing and sheath fluids - ANSWER --The central stream (sample stream)
is focused and surrounded by the secondary slower stream (sheath fluid). The shape and size of
,the flow cell is crucial to hydrodynamic focusing, and traditionally the cell is nozzle shaped. ... In
a flow cytometer, the sheath fluid pressure is constant while the sample fluid is adjusted
Sample Pressure and the Sheath Pressure - ANSWER --The difference between the sample
pressure and the sheath pressure is the differential pressure. This controls the width of the core
stream and the total number of cells passing the laser intercept.
differential pressure based flow cytometers - ANSWER --Differential pressure based flow
cytometers currently dominate the market. These systems have two pressure regulators. The
first is at a constant pressure that sets how fast the fluids runs at. The second is regulated by the
investigator (like on this LSR-II control panel).
Optical Filters - ANSWER --Filters are pieces of glass coated on both sides that allow light
of a certain collection, or band, of wavelengths to pass through while absorbing or interfering
with photons of other wavelengths. These come in bandpass, longpass, and shortpass flavors
Band Pass Optical Filter - ANSWER --A filter that allows light between a set wavelength to
pass through and reflects light above and below the set wavelength. For example, a bandpass
filter with a wavelength of 550/40nm would allow light between 530nm and 570nm to pass
through, but reflect light below 530nm and above 570nm.
Longpass Filter - ANSWER --wavelength above 650nM
Shortpass Filter - ANSWER --wavelength below 488nM
dichroics mirrors - ANSWER --Dichroic mirrors can block light by phased reflection
allowing certain light to pass through and interfering with other wavelengths. For example, a
500LP dichroic mirror would transmit light above 500 nm and reflect the light below 500 nm in a
different direction. A 525SP dichroic mirror would transmit all light below 525 nm and reflect all
light above 525 nm in a different direction. These dichroic mirrors are critical in the directing
and capturing of light by the detectors.
, neutral density filter - ANSWER --filter that reduces or modifies the intensity of all
wavelengths, or colors, of light equally, giving no changes in hue of color rendition
polarization filter - ANSWER --Polarization of scatter and fluorescence signals in flow
cytometry. ... depending on the light source(s), the optical layout, and the types of mirrors and
filters used.
Dichroic Filters - ANSWER --Dichroic filters (sometimes called beam splitters) are used in
the flow cytometer at an angle often of 45°. Short wavelength pass (SWP) filters transmit light
below a given wavelength and reflect light of longer wavelengths. Long wavelength pass (LWP)
filters work in the reverse fashion. Their important parameters are the wavelength for 50%
transmission (the cut off for LWP or the cut-on wavelength for SWP), the peak transmission and
the slope at the cut-on or cut-off wavelength. Their properties depend on the angle at which
they are used.
Optical Pathyway with fibers - ANSWER --Optical fibers are used to deliver lasers to the
interrogation point on some cytometers. This strategy also provides a space-saving benefit in
terms of where the lasers can be positions in the instrument. However, a downside to this
approach is that there can be significant power loss between the laser output and the
interrogation point as laser light travels through the fiber. Additionally, fibers are not compatible
with higher energy light, especially UV wavelengths, which can degrade the material of the fiber
over time and require frequent replacement.
Optical Pathyway with Lens and Fibers using optical gel - ANSWER --Some cytometers use
the lens and the fibers, which are directly coupled using an optical gel which may minimize light
loss due to refraction. As light passes through different types of mediums (water, quartz, and
air), it bends at the media interfaces. The degree to which this occurs depends on the difference
in refractive index between the two mediums: the greater the difference, the more refraction
occurs. By coupling the lens, which is typically glass or quartz, to material with a similar
refractive index, like gel, there may be less loss as light transitions between the mediums. The
EXAM 2025 -2026 WITH
100% CORRECT
ANSWERS
Generation of differential pressure (syringe pump, pressure based) - ANSWER --Low
differential pressure allows the cells to move past the interrogation point one at a time. .... One
kind involves generating pressure using a pump and regulator system ... Differential pressure
based fluidic system. ... peristaltic and/or syringe pumps to deliver the sample into the
instrument.
Characterization of syringe-pump-driven induced pressure - ANSWER --In syringe-pump-
driven microfluidic systems, pressure fluctuations are observed in an elastic microchannel. The
syringe pump is driven by an electrical stepper motor, from which mechanical oscillations are
expected to generate flow-rate fluctuations and in turn leads to the pressure fluctuations in the
channel flow.
Hydrodynamic Focusing - ANSWER --Most modern flow cytometers tightly position the
sample for optical analysis via hydrodynamic focusing. Here, a carrier fluid called the sheath
fluid is used to position the sample of cells into a single file for optical interrogation.
Hydordynamic focusing and sheath fluids - ANSWER --The central stream (sample stream)
is focused and surrounded by the secondary slower stream (sheath fluid). The shape and size of
,the flow cell is crucial to hydrodynamic focusing, and traditionally the cell is nozzle shaped. ... In
a flow cytometer, the sheath fluid pressure is constant while the sample fluid is adjusted
Sample Pressure and the Sheath Pressure - ANSWER --The difference between the sample
pressure and the sheath pressure is the differential pressure. This controls the width of the core
stream and the total number of cells passing the laser intercept.
differential pressure based flow cytometers - ANSWER --Differential pressure based flow
cytometers currently dominate the market. These systems have two pressure regulators. The
first is at a constant pressure that sets how fast the fluids runs at. The second is regulated by the
investigator (like on this LSR-II control panel).
Optical Filters - ANSWER --Filters are pieces of glass coated on both sides that allow light
of a certain collection, or band, of wavelengths to pass through while absorbing or interfering
with photons of other wavelengths. These come in bandpass, longpass, and shortpass flavors
Band Pass Optical Filter - ANSWER --A filter that allows light between a set wavelength to
pass through and reflects light above and below the set wavelength. For example, a bandpass
filter with a wavelength of 550/40nm would allow light between 530nm and 570nm to pass
through, but reflect light below 530nm and above 570nm.
Longpass Filter - ANSWER --wavelength above 650nM
Shortpass Filter - ANSWER --wavelength below 488nM
dichroics mirrors - ANSWER --Dichroic mirrors can block light by phased reflection
allowing certain light to pass through and interfering with other wavelengths. For example, a
500LP dichroic mirror would transmit light above 500 nm and reflect the light below 500 nm in a
different direction. A 525SP dichroic mirror would transmit all light below 525 nm and reflect all
light above 525 nm in a different direction. These dichroic mirrors are critical in the directing
and capturing of light by the detectors.
, neutral density filter - ANSWER --filter that reduces or modifies the intensity of all
wavelengths, or colors, of light equally, giving no changes in hue of color rendition
polarization filter - ANSWER --Polarization of scatter and fluorescence signals in flow
cytometry. ... depending on the light source(s), the optical layout, and the types of mirrors and
filters used.
Dichroic Filters - ANSWER --Dichroic filters (sometimes called beam splitters) are used in
the flow cytometer at an angle often of 45°. Short wavelength pass (SWP) filters transmit light
below a given wavelength and reflect light of longer wavelengths. Long wavelength pass (LWP)
filters work in the reverse fashion. Their important parameters are the wavelength for 50%
transmission (the cut off for LWP or the cut-on wavelength for SWP), the peak transmission and
the slope at the cut-on or cut-off wavelength. Their properties depend on the angle at which
they are used.
Optical Pathyway with fibers - ANSWER --Optical fibers are used to deliver lasers to the
interrogation point on some cytometers. This strategy also provides a space-saving benefit in
terms of where the lasers can be positions in the instrument. However, a downside to this
approach is that there can be significant power loss between the laser output and the
interrogation point as laser light travels through the fiber. Additionally, fibers are not compatible
with higher energy light, especially UV wavelengths, which can degrade the material of the fiber
over time and require frequent replacement.
Optical Pathyway with Lens and Fibers using optical gel - ANSWER --Some cytometers use
the lens and the fibers, which are directly coupled using an optical gel which may minimize light
loss due to refraction. As light passes through different types of mediums (water, quartz, and
air), it bends at the media interfaces. The degree to which this occurs depends on the difference
in refractive index between the two mediums: the greater the difference, the more refraction
occurs. By coupling the lens, which is typically glass or quartz, to material with a similar
refractive index, like gel, there may be less loss as light transitions between the mediums. The
