densitometer

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densitometer

(den-să-tom -ĕ-ter) An instrument for measuring the density of exposure of a photographic emulsion. Densitometers have a light source and photocell to measure the transmission (or reflection) of the sample. They are used in obtaining quantitative measurements from photographic records of spectra, diffraction experiments, etc.

Densitometer

A photometer for measuring the optical density (the opposite of transmittance) of materials.

Densitometer

 

a device for measuring the optical density of developed photographic materials. They are classified according to the method of measurement (direct readout and the comparison principle), the type of light receiver (the eye, a photocell, or a photomultiplier), the type of output data (nonrecording devices and automatic recording devices), and the magnitude of the field being measured (densitometers proper, as compared with microdensitometers, which are sometimes referred to as microphotometers).

In devices with direct readout, a single light beam whose initial strength Φ0 is compared with the strength Φ of the beam after passage through a photosensitive layer is usually used. Devices whose operation is based on the comparison method have two light beams originating from the same source, one of which is the measuring beam and the other is the reference beam. In the most widely used type of photoelectric densitometer, the two beams are directed at two photoelectric receivers that are in a difference-reading circuit (that is, if the strength of the two beams is equal, the signal of the two receivers is zero) or are alternately connected to the same receiver. The difference signal, which is caused by unequal strength of the two beams, is brought to a zero reading with the aid of a variable light attenuator (for instance, a gray photometer wedge) inserted into one of the beams being compared and calibrated in units of optical density D = log Φ0/Φ.

The accuracy of densitometer measurements averages ±0.02 optical density units over the entire measurement range. For the best models the range is 5-6 density units; for relatively simple devices it is 2.5-3.0 density units (transmission coefficients of 10-5-10-6 and 0.003-0.001, respectively). The most typical densitometer models made in the USSR are the DFE-10 nonrecording wedge densitometer with selenium photocells (Dmax = 3.0) and the IFO-451 recording wedge microdensitometer with a photomultiplier, which is capable of measuring optical densities up to 2.5 units.

REFERENCE

Gorokhovskii, Iu. N., and T. M. Levenberg. Obshchaia sensitometriia: Teoriia i praktika. Moscow, 1963.

IU. N. GOROKHOVSKII

densitometer

[‚den·sə′täm·əd·ər]
(engineering)
An instrument which measures optical density by measuring the intensity of transmitted or reflected light; used to measure photographic density.

densitometer

i. An instrument for measuring the density or specific gravity of fuel. Also called a densimeter.
ii. An instrument for measuring the optical density (photographic transmission, photographic reflection, visual transmission, etc.) of a material, generally of a photographic image.

densitometer

A device that calibrates the relative strength of a color using complementary filters. Contrast with colorimeter.
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A 2-year prospective densitometric study on the influence of Fok-I gene polymorphism in young patients with thalassaemia major.
Lix et al., "High fracture probability with FRAX[R] usually indicates densitometric osteoporosis: implications for clinical practice," Osteoporosis International, vol.
The analysis of densitometric findings showed no difference in FAT and LEAN SDS according to FTO genotype (Table S7).
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Caption: Figure 3: Densitometric profile and SDS-PAGE of a pool of 15 myofibrillar extracts obtained from beef, lamb, and chicken samples extracted with denaturing (a) and nondenaturing (b) solutions (1 = myosin heavy chain; 2 = 180-110 kDa; 3 = [alpha]-actinin; 4 = 95-55 kDa; 5 = desmin; 6 = 51-47 kDa; 7 = actin; 8 = 39 kDa; 9 = troponin T; 10 = tropomyosin; 11 = 33-23 kDa; 12 = myosin light chain 1; 13 = 21-18 kDa; 14 = troponin C; 15 = myosin light chain 2; 16 = 14-10 kDa).
Figure 4(b) shows the densitometric quantification of nestin and actin expression from images shown in Figure 4(a), and these values have been plotted on a graphic that shows the association of nestin and actin expression.
(b) Western blotting and densitometric analysis of CD36 and [beta]-actin (loading control) in macrophage extracts.
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The intensity of the bands was evaluated by densitometric analysis; the values from a representative experiment were normalized, expressed as fold increase with respect to the untreated sample (CTRL) and reported as a graph.
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