Quality control of instruments for measuring the characteristics of bactericidal UV radiation

Influence of spectral and angular sensitivity on the readout of biological dosimeters

A wave optics model for the facet lens-rhabdomere system of fly eyes is used to analyze the dependence of the angular and spectral sensitivity of R1-6 photoreceptors on the pupil mechanism. This assembly of light-absorbing pigment granules in the soma interacts with the waveguide modes propagating in the rhabdomere. A fly rhabdomere carries two modes in the middle wavelength range and four modes at short wavelengths, depending on the rhabdomere diameter and the angle of the incident light flux. The extension of the mode to outside the rhabdomere strongly depends on wavelength, and this dependence plays a determinant role in the light control function of the pupil. The absorbance spectrum of the pigment in the pupil granules is severely depressed at short wavelengths by waveguide effects, resulting in a distinct blue peak. Accordingly, pupil closure suppresses the photoreceptor's spectral sensitivity much more in the blue-green than in the UV. The pupil only narrows the angular sensitivity at short wavelengths. The geometrical size of the rhabdomere governs the angular sensitivity of fly photoreceptors in the dark-adapted state, but diffraction takes over in the fully light-adapted state.

A long range surface plasmon-polariton resonance (LRSPPR) based refractive index sensor (for biomolecular interaction study applications) with ultrahigh sensitivity and extremely narrow resonance dips with very small full width at half maximum (FWHM, w) is proposed. The theoretical analysis of the sensitivity for spectral and angular interrogations is presented. The structure consists of a MgF2 prism and a plasmonic waveguide (consisting of a metal cladded high index dielectric waveguide) separated by a low index dielectric layer. It is shown that both angular and spectral sensitivities increase nonlinearly with increase in analyte index. Angular sensitivity with FWHM = 0.009°, ranges from 340°/RIU to 505°/RIU for analyte index variation from 1.360 to 1.368 and spectral sensitivity with FWHM = 3 nm, ranges from 1.79 × 105 nm RIU−1 to 2.60 × 105 nm RIU−1 for analyte index variation from1.361 00 to 1.361 10. The sensitivities (S) and the figures of Merit of the proposed sensor are the highest obtained so far (to our knowledge).

Although all-dielectric sensors exhibit minimal absorption and a high figure of merit (FOM), their sensitivity is significantly lower compared to plasmonic sensors. One approach to enhancing the sensitivity of dielectric sensors is to utilize bound states in the continuum (BICs), which are resonant states with an infinite radiative lifetime. These states are characterized by polarization vortices in the far field, whose winding number determines the topological charge. Here, we demonstrate that the position of a BIC polarization vortex in the k-space has a square-root dependence on changes in the refractive index of the medium, similar to an exceptional point. We compute the angular and spectral sensitivities of our structure and demonstrate that the angular sensitivity reaches values comparable to those of surface plasmon polariton (SPP)-based sensors. We observe a blue spectral shift of BICs as the refractive index of the surrounding medium increases. This behavior differs from the conventional spectral response typically expected under such perturbations. Additionally, we find a distinct BIC regime exhibiting a pronounced angular sensitivity, surpassing its spectral one. Our findings pave the way for the development of dielectric sensors with high angular sensitivity and facilitate the practical observation of the optical vortex dynamics.

Three optical components of a fly's eye determine the angular sensitivity of the photoreceptors: the light diffracting facet lens, the wave-guiding rhabdomere and the light-absorbing visual pigment in the rhabdomere. How the integrated optical system of the fly eye shapes the angular sensitivity curves is quantitatively analyzed in five steps: (1) scalar diffraction theory for low Fresnel-number lenses is applied to four different facet lenses, with diameter 10, 20, 40, and 80 micro m, respectively, assuming a constant F-number of 2.2; (2) optical waveguide theory is used to calculate waveguide modes propagating in circular cylindrical rhabdomeres with diameter 1.0, 2.0, and 4.0 micro m, respectively; (3) the excitation of waveguide modes is studied with the tip of the waveguide positioned in the focal plane as well as outside this plane; (4) the light absorption from the various propagated modes by the visual pigment in the rhabdomere is calculated as a function of the angle of the incident light wave; and (5) the angular sensitivity of the photoreceptor is obtained by normalizing the total light absorption. Four wavelengths are considered: 300, 400, 500 and 600 nm. The analysis shows that the wavelength dependency of the lens diffraction is strongly compensated by that of the waveguide modes, an effect which is further enhanced by the decrease in light absorption when the mode number increases. The angular sensitivity of fly photoreceptors is robust to defocus and largely wavelength independent for all except very slender rhabdomeres.

A wave-optical model for the integrated facet lens-rhabdomere system of fly eyes is used to calculate the effective light power in the rhabdomeres when the eye is illuminated with a point light source or with an extended source. Two rhabdomere types are considered: the slender rhabdomeres of R7,8 photoreceptors and the wider, but tapering R1-6 rhabdomeres. The angular sensitivities of the two rhabdomere types have been calculated as a function of F-number and wavelength by fitting Gaussian functions to the effective light power. For a given F-number, the angular sensitivity broadens with wavelength for the slender rhabdomeres, but it stays approximately constant for the wider rhabdomeres. The integrated effective light power increases with the rhabdomere diameter, but it is for both rhabdomere types nearly independent of the light wavelength and F-number. The results are used to interpret the small F-number of Drosophila facet lenses. Presumably the small head puts a limit to the size of the facet lens and favors a short focal length.

When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5º angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure.

1. In the compound eye of the maleChrysomyia megacephala the facets in the ventral part of the eye are only ca. 20 μm in diameter, but increase abruptly to ca. 80 μm above the equator of the eye. Correspondingly there is a large and abrupt increase in the rhabdomere diameter from 2 to as much as 5 urn. The far-field radiation pattern of the eye shows that, despite the large change in ommatidial dimensions, the resolution of the eye remains approximately constant across the equator: angular sensitivity of the photoreceptors and sampling raster are similar ventrally and dorsally. The main result of the large dorsal facets is a more than tenfold increase in light capture. Thus this eye provides a clear example of an insect where large dorsal facets have evolved not for higher acuity, but rather for higher light capture. 2. Sensitivity is increased even more by a seventh photoreceptor cell joining neural superposition, as reported before for the dorsal eye of male houseflies. All seven photoreceptors have the same spectral sensitivity. 3. Angular sensitivities in the dorsal eye are more Gaussian-shaped than the flat-topped profile expected for large rhabdomere diameters. This is explained by the anatomical finding that the dorsal rhabdomeres taper strongly. It is suggested that the combination of high photon capture and rounded angular sensitivities is advantageous for monitoring movement and position of small objects. 4. Finally some of the constraints involved in constructing specialized dorsal eye regions for detection of small objects are considered.

The angular sensitivity of single retinula cells of the eye ofCalliphoraandEristalishas been measured by standard methods over the range of wavelengths that are visible to these flies. The point of using different wavelengths is to test the dependence of the angular sensitivity upon the width of the Airy disk of light which is focused on the receptors. The width of the Airy disk is determined by diffraction and proportional to wavelength. The seven bestCalliphoraretinula cells had a mean acceptance angle of ∆ρv= 1.66 ± 0.22° s. d. in the vertical plane and ∆ρH= 1.44 ± 0.31° s. d. in the horizontal plane. The acceptance angle is independent of wavelength, and also approaches the theoretical lower limit inferred from the width of the Airy disk at 500 nm. This unexpected result is explained optically. In the droneflyEristalisthe retinula cells with a single spectral peak near 350 nm (and therefore inferred to be cell 7 or 8) have values of ∆ρH= 1.16 ± 0.23° s. d. and ∆ρv= 1.10 ± 0.17° s. d. at 350 nm and ∆ρH= 1.24 ± 0.31° s. d. and ∆ρv= 1.19 ± 0.26° s. d. at 450 nm. Retinula cells 1-6 ofEristalis, however, have a larger ∆ρwhich is independent of wavelength. The difference in ∆ρbetween the u. v. receptors and the cells 1-6 inEristalisis explained by the smaller rhabdomeres of the former, because the two types of receptors share a common lens. In the most distal transverse sections, rhabdomeres 1-6 ofEristalishave major and minor diameters of 1.32 ± 0.11 μm s. d. and 1.09 ± 0.06 um s. d. (N= 12). Rhabdomere 7 has major and minor diameters of 0.74 ± 0.06 μm s. d. and 0.64 ± 0.08 μm s. d (N= 12). The observed values of ∆ρfor cells 1-6 are predicted from a simple theory based on the width of the Airy disk and the receptor size (Kuiper 1966) which predicts that ∆ρis independent of wavelength. For cell 7 an additional factor is introduced whereby there is an effect of wavelength and the cross-section of the rhabdomere is effectively reduced at longer wavelengths.

Purpose: Commercially available surface diodes are found to have as great as ±12% change in sensitivity with the angle of incidence of radiation. This work is a study of the cause of angular dependence of diode sensitivity and how it can be decreased. Method and Materials: A number of different surface diodes were used in these measurements: a commercially available, CA, and two prototype diodes, D1 and D2. CA and D1 were mounted on a circuit board that had a plane of copper on its backside; D2 was not mounted on a circuit board but did have a metal contact‐pad on its back surface. Optically stimulated luminescent dosimeters, OSLDs, were used that were packaged in a plastic case. All detectors were mounted in a water equivalent cylindrical phantom that provided symmetric buildup. Irradiations were made with a 6 MV, 10×10 cm2 field of a linear accelerator. Results: CA, D1, and OSLD had angular dependence of sensitivity of ±12%, ±9%, and ±1%, respectively. It was hypothesized that the copper plane on the circuit board was the cause of the anisotropy in sensitivity of the diodes. When a copper disc was placed on the backside of the OSLD its angular sensitivity became similar to that of CA and D1. D2 was found to have an angular dependence of ±5%. Conclusion: The anisotropy in angular dependence of diode sensitivity is in part due to the mounting of the diode on a circuit board that has a plane of copper. Low energy electrons are back scattered at the high atomic number interface and this results in higher detector sensitivity to photons that enter from the directions of the front and back surfaces of the detector. Diodes that are modified and not mounted near a plane of copper have reduced angular dependence.

The butterfly Papilio xuthus has acute tetrachromatic color vision. Its eyes are furnished with eight spectral classes of photoreceptors, situated in three types of ommatidia, randomly distributed in the retinal mosaic. Here, we investigated early chromatic information processing by recording spectral, angular, and polarization sensitivities of photoreceptors and lamina monopolar cells (LMCs). We identified three spectral classes of LMCs whose spectral sensitivities corresponded to weighted linear sums of the spectral sensitivities of the photoreceptors present in the three ommatidial types. In ~ 25% of the photoreceptor axons, the spectral sensitivities differed from those recorded at the photoreceptor cell bodies. These axons showed spectral opponency, most likely mediated by chloride ion currents through histaminergic interphotoreceptor synapses. The opponency was most prominent in the processes of the long visual fibers in the medulla. We recalculated the wavelength discrimination function using the noise-limited opponency model to reflect the new spectral sensitivity data and found that it matched well with the behaviorally determined function. Our results reveal opponency at the first stage of Papilio’s visual system, indicating that spectral information is preprocessed with signals from photoreceptors within each ommatidium in the lamina, before being conveyed downstream by the long visual fibers and the LMCs.

1. The spectral, polarizational and angular sensitivities of photoreceptor cells In the honeybee compound eye are examined by intracellular electrophysiological recordings. The specific aim of this paper is to compare the characteristics of receptor cells in the anatomically specialized dorsal rim area of the eye (containing non-twisted retinulae which are composed of 9 long receptor cells) with those of receptors in the remainder of the eye (containing twisted retinulae which are composed of 8 long cells and 1 short cell). 2. The direction of the optical axis for each cell investigated was determined within a coordinate system of space that takes into consideration the head position of the flying bee. All the cells studied (except those in the frontal part of the eye) looked upwards in directions close to the zenith (Fig. 2). 3. The UV-cells of the dorsal rim area exhibit high polarizational sensitivities (PS). The actual PS values depend on the amount of coupling between UV- and green-cells (Fig. 5a): UV-cells having relative green-sensitivities of >10% exhibit an average PS of 3.8; if the green-sensitivity is <10% it is 5.6 and rises to more than 10 for cells which either do not respond or hyperpolarize to green light. The overall average PS is 6.6. In marked contrast to this finding, most UV-cells in the remainder of the eye (in twisted retinulae) have PS <2.0 (Fig. 5b). 4. Polarizational sensitivities of green-cells are only slightly higher in the dorsal rim area (PS =1.8) than in the other parts of the eye (PS=1.3) (Fig 5c, d). 5. By measuring the direction of maximal sensitivity to the e-vector of linearly polarized light (Φmax), two populations of UV-receptors have been found in the dorsal rim area; theirΦmax values differ by 90° (Fig. 6). 6. Angular sensitivity functions having unconventional shapes are measured in most receptors of the dorsal rim area. They show a relatively narrow peak in the center and a wide, flat brim in which the average sensitivity decreases from 8% at 7° off axis to 2% at 30° (Fig. 3b, d; 7). If UV-cells having this type of visual field are tested with off-axial (20–30°) stimuli, PS is still high andΦmax is the same as for on-axial stimulation. Thus, the UV-cells of the dorsal rim area are wide-field e-vector analyzers. Apparently, the wide visual fields are caused by corneal specializations in that part of the eye. Control experiments in other parts of the eye confirm the narrow visual fields as they have been described by former authors (Fig. 3a, c). 7. The results are discussed in the light of recent behavioral and anatomical investigations on polarization vision. It is concluded that e-vector detection in the honeybee is performed mainly by the UV-receptors of the dorsal rim area.

A surface plasmon resonance optical refractive index sensor (for aqueous medium) with high angular and spectral sensitivities S, very small full width at half maxima (FWHM) w (narrow resonance), and very high quality factor, χ = S/w, is proposed, which operates in both angular and spectral interrogation modes. The structure consists of a prism and a composite plasmonic waveguide consisting of a high-index dielectic layer and a thin metal (Ag) film, separated by a low-index layer. Above the metal film, the medium is analyte. It is shown that even with a prism of low index, the proposed sensor offers very small FWHM of reflection spectra, which improves the sensor performance. Numerically, an angular sensitivity of 168°RIU−1 and a quality factor χ = 1680 can be achieved for the proposed configuration. Spectral sensitivity comes out to be 6000 nm RIU−1.

1. In male houseflies (Musca domestica) the frontal dorsal region of the eye contains a unique class of central rhabdomere (R7/8) not found in other eye regions or in female flies (Fig. 1). The rhabdomeres may be recognised in vivo by their red autofluorescence, and are called here 7r and 8r respectively. 2. Difference spectra of 7r rhabdomeres, measured by microspectrophotometry of single rhabdomeres are indistinguishable from those of R1–6 (Fig. 2). 3. Intracellular recordings coupled with dye injections have established that: a) 7r cells are indistinguishable from the peripheral photoreceptors R1–6, at least with respect to spectral, angular and absolute sensitivities, response waveform and noise characteristics (Figs. 4, 5; Table 1); b) 8r cells however are clearly distinguishable by virtue of their spectral sensitivity (Fig. 6), noise characteristics and response waveform (Fig. 5). 4. Axonal profiles from cells stained intracellularly with the dye Lucifer yellow (Fig. 9) show that: a) 7r cells do not project to the medulla but terminate in the upper region of the lamina cartridge layer where they also project out one or more lateral branches; b) 8r cells project long axons through to the medulla. 5. Electron microscopic examinations of cells initially identified by their autofluorescence indicate that 7r cells approximate many features of R1–6 cells, including cell body, rhabdomere and axonal diameters. In these respects 8r cells differ and show the characteristic morphology of other R7 and R8 cells (Fig. 8, Table 2).

The article presents a model for evaluating the human factors influence on the results of laboratory measurements of military equipment samples, which allows to increase the accuracy and quality of laboratory measurements due to the leveling of the human factors influence on the measurements results. The model is developed on the basis of the correlation-regression analysis approach, which allows to compare influencing the factor signs of the errors occurrence caused by the human factor with the expected results of measurements and to remove the errors caused by the human factor from the resulting measurement value. The proposed model can be used to predict errors caused by the human factor during laboratory measurements in the process of testing military equipment samples. In the work it was analyzed the characteristics of the human factors impact on the errors occurrence both by groups and by species, which made it possible to identify factor characteristics that affect the results of measurements due to the presence of the human factor. Analytical evaluation characteristics of the results automation possibility in the measurement process are also presented, which made it possible to determine the samples of military equipment, on the measurement of which during the evaluation, the human factor has the highest influence. The proposed model takes into account the correlation of causal factors and types of military equipment, the measurement process of which cannot be automated, which allows to assess the influence of the human factor on the results of laboratory measurements of military equipment samples. The proposed model, in contrast to existing approaches to reducing the influence of the human factor on measurement results, can be used without the need to exclude human participation in the process of laboratory measurements, but to take into account the error caused by the human factor in the process of analyzing the measurement results.