Mean Refractive Index Research Articles

The Prevalence and Severity of Myopia among Suburban Schoolchildren in Taiwan

We aimed to determine the prevalence and severity of myopia in suburban schoolchildren. The refractive error, best corrected visual acuity (BCVA) and other ocular indices of 6069 schoolchildren (aged 6 to 15 years) from elementary and junior high schools in Chiayi County, Taiwan were examined in 2013-2015. Spherical equivalent (SE) was stratified into 4 categories: emmetropia, mild myopia, moderate myopia, and high myopia for underlying analysis. Chi-squared (χ2) tests were used to determine significant associations between myopia and BCVA and age levels. To compare statistical significance among different age levels, P values of Bonferroni tests were calculated. Receiver operating characteristic (ROC) curves and correlation coefficient were calculated to assess the correlation between myopia and each ocular index. The youngest subject diagnosed with myopia was a 7-year-old. Myopia had significant associations with both BCVA and age levels (95% confidence intervals [CI] = 2.553, 2.713 and -0.284, -0.248, respectively), under P <0.05. Among the calculated ROC values, BCVA had the highest area of 0.676 with myopia. This further confirmed that BCVA was highly correlated with myopia in schoolchildren. Other ocular indices like intraocular pressure (IOP), pupil distance, ocular alignments, or ocular height had ROC curves below 0.5 to myopia. This study concluded that the onset of myopia started earlier and progressively worsened with years of investigation among the suburban schoolchildren. Myopia had significant associations with BCVA and age levels. To effectively reduce the prevalence and severity of myopia, it is time to take actions on eye care education for suburban schoolchildren.

Effect of Cataract Surgery on the Refractive Index of the Cornea Estimated by Optical Pachymetry.

To noninvasively estimate the refractive index (RI) of the central cornea along the antero-posterior direction before and after routine phacoemulsification. Using 2 setups for a standard optical pachymeter, the ratio of observed optical section widths (OSWs) is a function of the RI. Thus, the corneal RI could be estimated using a calibration equating OSW ratios with known RI values. The OSW was measured by 2 observers for 1) normal subjects for estimating interoperator errors and effects of sex and age on the RI and 2) before and after patients underwent routine phacoemulsification. First, the average interoperator difference (ΔRI) was +0.0005 (SD = ±0.0044, 95% confidence limit, -0.0002 to +0.0012). The root mean square difference between measurements obtained by the observers was 0.0032. There was a significant correlation between the ΔRI and the mean of each pair of measured values (r = -0.172, n = 153, P = 0.003). The mean RI (±SD) was 1.435 (±0.005, n = 82) for females and 1.429 (±0.005, n = 71) for males. There was no significant between-sex difference or association between the RI and age (mean age, ±SD, and range, 44.31, 20.38, and 19-88 years, respectively). Second, the difference (y) between the preoperative (x) and postoperative RI was, y = 0.844x - 1.203 (r = 0.694, n = 31, P ≤ 0.001) according to observer 1 and according to observer 2, y = 0.755x - 1.108 (r = 0.681, n = 31, P ≤ 0.001). The RI of the human cornea along the antero-posterior axis can be estimated using a modified application of traditional optical pachymetry. The average values for the corneal RI were higher compared with those reported in previous reports. The change in the RI after phacoemulsification could be predicted from the preoperative value.

Investigation of the surface, morphological and optical properties of boron– doped ZnO thin films deposited by thermionic vacuum arc technique

In this study, boron—doped ZnO (ZnO:B) thin films have been deposited on amorphous glass and polyethylene terephthalate (PET) substrates by thermionic vacuum arc (TVA) technique. The surface, morphology, microstructure, optical properties, and chemical analysis of B doped ZnO thin films were investigated. To determine the subjected properties, atomic force microscopy (AFM), field emission electron microscopy (FESEM), x–ray diffraction (XRD), UV–Vis spectrophotometer, Raman and Fourier transform infrared spectroscopy measurements have been carried out. The thicknesses values of the films were measured as to be 50 nm and 60 nm on glass and PET substrates. XRD results show that polycrystalline nature of the deposited thin films on the PET substrate is higher than the deposited films on glass substrate. All films are in polycrystalline structure. The deposited thin films are including ZnO crystalline formations. According to the Scherrer’s formula, the crystallite sizes were calculated approximately 20 nm for ZnO crystallites. Atomic force microscopy and field emission electron microscopy images revealed the formation of fine—dispersed, homogeneous, uniform and granular structure on the surface of the films. Optical studies show that the average transmittance values of the ZnO:B films were obtained to be 62% and 83% on glass and PET substrates, respectively. The mean refractive index of the films also obtained as 1.69 and 1.65 on glass and PET substrate, respectively. In order to the Tauc’s relation and photoluminescence measurements, the optical band gap values of the boron doped films were found to be 3.2 and 3.3 eV on glass and PET substrates, respectively. Raman spectra are also support the boron doped ZnO structures deposited onto glass and PET substrate.

Graftonite-(Mn), ideallyM1MnM2,M3Fe2(PO4)2, and graftonite-(Ca), ideallyM1CaM2,M3Fe2(PO4)2, two new minerals of the graftonite group from Poland

AbstractTwo new minerals of the graftonite group, graftonite-(Mn), ideallyM(1)MnM(2),M(3)Fe2(PO4)2, and graftonite-(Ca), ideallyM(1)CaM(2),M(3)Fe2(PO4)2, were discovered in phosphate nodules of two beryl–columbite–phosphate pegmatites at Lutomia and Michałkowa, respectively, in the Góry Sowie Block, Lower Silesia, southwest Poland. Graftonite-(Mn) is pinkish brown, whereas graftonite-(Ca) shows more brownish colouration. Both minerals have a vitreous lustre, a good cleavage observed along (010) and irregular fracture; both are transparent and neither of them is fluorescent. They are brittle and have a Mohs hardness of ~5. The minerals are non-pleochroic, colourless in all orientations, biaxial (+), with mean refractive indices α = 1.710(2) and 1.690(2), β = 1.713(2) and 1.692(2), and γ = 1.725(2) and 1.710(5), respectively. With complete order of Ca at theM(1) site, the formulae of the holotype crystals areM(1)(Mn0.70Ca0.30)M(2),M(3)(Fe1.34Mn0.60Mg0.06Zn0.01)Σ3(PO4)2for graftonite-(Mn) andM(1)(Ca0.98Mn0.02)M(2),M(3)(Fe1.38Mn0.56Mg0.05)Σ3(PO4)2for graftonite-(Ca). Both crystal chemistry and crystal-structure refinement (R1= 2.34 and 1.63%, respectively) indicate that theM(1) site is occupied dominantly by Mn in graftonite-(Mn) and by Ca in graftonite-(Ca), and theM(2) andM(3) sites are occupied by Fe2+and Mn2+, with Fe2+dominant over Mn2+at the aggregateM(2) +M(3) sites. Graftonite-(Mn) and graftonite-(Ca) are isostructural with graftonite,M(1)FeM(2),M(3)Fe2(PO4)2(monoclinic system; space-group symmetryP21/c), with the unit-cell parametersa= 8.811(2) Å,b= 11.494(2) Å,c= 6.138(1) Å, β = 99.23(3)° and V = 613.5(4) Å3, anda= 8.792(2) Å,b= 11.743(2) Å,c= 6.169(1) Å, β = 99.35(3)° andV= 628.5(1) Å3, respectively. The densities calculated on the basis of molar weights and unit-cell volumes are 3.793 g/cm3for graftonite-(Mn) and 3.592 g/cm3for graftonite-(Ca). The eight strongest lines in powder X-ray diffraction patterns on the basis of single-crystal data are, respectively [d, Å,I(hkl)]: 2.874, 100, (230 + 040); 2.858, 79, (221); 3.506, 73, (130); 2.717, 79, ($\bar{3}$11); 2.952, 55, (131); 2.916, 53, ($\bar{1}$12); 2.899, 44, (300); 3.016, 35, ($\bar{1}$02); and 3.654, 100, (130); 2.979, 85, (221); 3.014, 77, (230); 3.042, 76, (040 +$\bar{1}$12); 2.834, 68, ($\bar{3}$11); 3.097, 57, (131); 3.133, 56, ($\bar{1}$02); 2.542, 30, (311). Both minerals are common primary phosphates in phosphate nodules, occurring as lamellar intergrowths with sarcopside ± triphylite/lithiophilite, products of exsolution from a (Li,Ca)-rich graftonite-like parent phase crystallized at high temperature from P-bearing hydrosaline melts.

Fiber-based optic sensor for detecting human blood clot: present and future revival

Sustaining human’s life-frame away from being impeded by the clot - ghost term, we attempt to approach a mobile fiber-based optical sensor (f-s) for detecting blood clot in a blood vessel (intra-arteries/veins). Blood vessels are the part of the circulatory system that transport blood throughout the human body, thus their significance of being protected arise to the monograph focus. MRI (magnetic resonance imaging), X-rays and other medical instruments are diagnostic immobility techniques with a slackest interval. The corer causation of fiber-based optical sensor is to detect a clump of blood in the bloodstream by providing a prompt mobile diagnostic intervals preserving last-minutes-breath of human’s life. The detector (f-s) has been etched by diluting sulphuric acid ~10% at certain zone to sensate its function. The in-vitro monograph peaks its maximal monitoring when the sensor is attached to Raman Spectroscopy (RS) setup. RS quantifies the relative intensities of fibrinogen bond, which is the first type of blood coagulation elements of blood plasma. Blood coagulation parameters are the major concern of the monograph investigation, such as total haemoglobin (tHb), clotting reaction time (t), clot progression time (t2), maximum clot amplitude (ma) and mean refractive index (r). A blood sample will be drawn from the patient and after centrifugation to separate blood plasma from its constituents, then an immediate sloshing of blood plasma in the (f-s) packet which has its plug-in to RS. Estimating the quantitative analysis of blood sample concentration, RS will determine the presence of coagulation in terms of intensity and medical procedures will dominate the treatment process. Thus, the suggestive monograph provides a definite instrument for investigating blood coagulation intra-arteries/veins promptly.

Folvikite, Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4, a new oxyborate mineral from the Kitteln mine, Nordmark ore district, Värmland, Sweden: description and crystal structure

ABSTRACTFolvikite, Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4, is a new oxyborate mineral from the Kitteln mine, Värmland, Sweden, where it occurs as a primary skarn mineral embedded in calcite. It forms striated prismatic crystals up to 0.3 mm, and is black to dark reddish-brown with submetallic lustre and a reddish-brown streak. It is brittle, has a Mohs hardness of 6, and the calculated density is 4.14 g/cm3. Folvikite is biaxial with indeterminate optic sign due to pervasive twinning. The optic axial angle is 68.9(4)°. Refractive indices were not measured; the calculated mean refractive index is 1.85. Strong pleochroism was observed in plane-polarized light: AB = brown (intermediate), OB = dark brown (maximum) and ON = honey brown (minimum). Folvikite is monoclinic, space group P2, a = 5.3767(10), b = 6.2108(10), c = 10.9389(18) Å, β = 94.399(9)°, V = 364.22(16) Å3 and Z = 1. Chemical analysis by electron microprobe gave Sb2O5 18.15, MgO 24.11, MnO 29.73, Mn2O3 11.62, Al2O3 0.27, Fe2O3 0.45, B2O3 15.27, sum 99.60 wt.%. The B2O3 content was assigned as B = 4 apfu and the Mn2O3 / (MnO + Mn2O3) ratio was determined from the crystal structure. The empirical formula was normalized on the basis of 20 anions pfu: (Sb5+1.02Mn3+1.34Al0.05Fe3+0.05Mg5.46Mn2+3.82□0.26)Σ12O8(BO3)4. A simplified formula may be written as Sb5+Mn3+(Mg,Mn2+)10O8(BO3)4 with Z = 1. The crystal structure was solved by direct methods and refined to an R1 index of 4.1%. Folvikite is a member of the (3 Å) zigzag wallpaper-borate structures in which chains of edge-sharing octahedra extend along the c axis and are cross-linked by BO3 groups. There are five X sites partly occupied by Mn2+ &gt; Mg, one octahedrally coordinated M-site occupied by Sb5+ &gt; Mg, two M sites occupied by Mg ≥ Mn &gt; Sb5+, two M sites occupied by Mn3+ &gt; Mn2+, two M sites occupied by Mg &gt; Mn2+, and one M-site occupied by Mg &gt; □; plus two [3]-coordinated B sites occupied by B. As with the other zigzag borates, the polyhedra are arranged in F-walls, C-walls and S-columns.

The investigation of the Cr doped ZnO thin films deposited by thermionic vacuum arc technique

Cr doped ZnO thin films were prepared onto glass and polyethylene terephthalate (PET) substrates using thermionic vacuum arc. XRD patterns show the polycrystalline nature of the films. Cr, Zn, ZnO and Cr2O3 were detected in the layers. The mean crystallite sizes of the films were calculated about 20 nm for the films onto glass and PET substrates. The maximum dislocation density and internal strain values of the films are calculated. According to the optical analysis, the average transmittance and reflectance of the films were found to be approximately 53% and 16% for glass and PET substrates, respectively. The mean refractive index of the layer decreased to 2.15 from 2.38 for the PET substrate. The band gap values of the Cr-doped ZnO thin films were determined as 3.10 and 3.13 eV for glass and PET substrates.

Melcherite, trigonal Ba2Na2Mg[Nb6O19]·6H2O, the second natural hexaniobate, from Cajati, São Paulo, Brazil: Description and crystal structure

ABSTRACTMelcherite (IMA2015-018), ideally Ba2Na2Mg[Nb6O19]·6H2O, occurs as a vug mineral in the carbonatite of the Jacupiranga mine, Cajati county, São Paulo state, Brazil, associated with dolomite, calcite, magnetite, pyrrhotite, tochilinite, ‘pyrochlore’ and fluorapatite. This is also the type locality for zirkelite, quintinite, menezesite and pauloabibite. The mineral forms irregular, tabular crystals up to 200 µm in maximum dimension. Melcherite is transparent and displays a vitreous lustre; it is beige with a white streak. It is non-fluorescent. The mineral displays perfect cleavage on {001}. Chemical composition varies from Ba2Na2Mg[Nb6O19].6H2O to (BaK)(NaCa)Mg[Nb6O19].6H2O. Empirical formulae for the first and the second compositions are: (Ba1.75K0.19)Σ1.94(Na1.80Ca0.19)Σ1.99(Mg0.96Mn0.02Al0.02)Σ1.00Nb6.02O19.00·6H2O and (Ba0.99K1.00)Σ1.99(Na1.02Ca0.96)Σ1.98(Mg0.95Mn0.05)Σ1.00Nb6.02O19.00·6H2O, respectively. Data for a single crystal with the second composition are: trigonal, R$\bar 3$, a = 9.0117(6) Å, c = 23.3986(16) Å, V = 1645.64(19) Å3 and Z = 3. Calculated density for this formula is 3.733 g/cm3, and the calculated mean refractive index is 1.924. Melcherite is a hexaniobate that has structural layers parallel to the xy plane that stack along the c axis with simultaneous 1/3 [110] displacement so as to produce an R lattice. The melcherite structure is built by layers of [(Ba,K)(O,H2O)9] polyhedra and the [Nb6O19]8− super-octahedron (Lindqvist anion) interconnected by [(Na,Ca)O6] polyhedra. Cations of Mg2+ are bonded to six water molecules each and are not associated with Lindqvist oxygen ions. The mineral is named in honour of Geraldo Conrado Melcher (1924–2011), a pioneer in Jacupiranga carbonatite studies.

Improved Stability of Porous Silicon in Aqueous Media via Atomic Layer Deposition of Oxides

In this work, porous silicon (PSi) samples were conformally coated with ultrathin films of aluminum oxide (Al2O3) and hafnium oxide (HfO2) using atomic layer deposition (ALD) to passivate their internal surface and improve their overall stability in aqueous media. Their porosity and optical properties were characterized before and after ALD treatment. The stability over time in aqueous media of the ALD passivated porous layers was then evaluated and compared to PSi layers oxidized at 800 °C (PSiO2), which is a treatment widely used in the literature for biosensing applications. The ALD oxide-covered samples performed equally to the oxidized PSi samples, but exhibited a higher mean refractive index, which results in a better contrast. These improved optical properties resulted in a signal exhibiting a significantly decreased noise. This in turn leads to a theoretical limit of detection improved by a factor 13 and 16 for PSi/Al2O3 and PSi/HfO2, respectively, compared to the standard PSiO2. This could thus r...

Lensing effects in a random inhomogeneous medium

Curvature of the refractive index profile can cause the focusing or defocusing of a propagating beam. Such lensing can have detrimental effects on, for example, imaging through the atmosphere, where it can cause features to appear stretched or regions to appear artificially bright. We consider the problem of describing propagation in the presence of both curvature and stochastic fluctuations in the refractive index profile. For different scenarios motivated by atmospheric propagation data, we derive concise, robust formulas for the mean ray paths that include the effects of turbulence. In addition, for the case of a local maximum of the mean refractive index, we show that the focal length associated with the mean trajectories in the random medium is smaller than in the deterministic setting.

Determination of the refractive index of dehydrated cells by means of digital holographic microscopy

Spatial distributions of the integral refractive index in dehydrated cells of human oral cavity epithelium are obtained by means of digital holographic microscopy, and mean refractive index of the cells is determined. The statistical analysis of the data obtained is carried out, and absolute errors of the method are estimated for different experimental conditions.

Empirical electronic polarizabilities: deviations from the additivity rule. I. M2+SO4·nH2O, blödite Na2M2+(SO4)2·4H2O, and kieserite-related minerals with sterically strained structures

Empirical electronic polarizabilities allow the prediction of total mineral polarizabilities and mean refractive indices of the vast majority of minerals and synthetic oxides. However, deviations from the valence-sum rule at cations in some minerals are associated with large deviations of observed from calculated total polarizabilities. We have identified several groups of minerals and compounds where deviations from the valence-sum rule at cations lead to polarizability deviations of 2–5%: M(SO4)·nH2O, n = 1–6, blodite-group minerals [Na2M2+(SO4)2·4H2O], and the kieserite-related minerals: isokite, panasqueiraite and tilasite. In these minerals, the environment of the M ions contains both O and H2O: Mg[O4(H2O)2] in kieserite, szmikite, and szomolnokite; Mg[O2(H2O)4] in starkeyite, ilesite, and rozenite, and Mg[(H2O)6] in hexahydrite. In compounds where the ligands are only H2O, deviations from the valence-sum rule at the M(H2O)6 groups are not accompanied by significant polarizability deviations. This is the case for epsomite, MgSO4·7H2O; bieberite, CoSO4·7H2O; goslarite, ZnSO4·7H2O, six silicofluorides, MSiF6·6H2O; eighteen Tutton’s salts, M2M′(SO4)2·6H2O, where M = K, Rb, Cs and M′ = Mg, Mn, Fe, Co, Ni, Cu, and Zn; and eleven MM′(SO4)2·12H2O alums, where M = Na, K, Rb and Cs, and M′ = Al, Cr, Ga and In. This is also the case for the sulfates alunogen, Al2(SO4)3·17H2O and halotrichite, FeAl2(SO4)4·22H2O; three hydrated nitrates; one phosphate; three antimonates and two hydrated perchlorates. A possible explanation for this different behavior is that the bond-valence model treats O and H separately, whereas polarizability calculations treat the polarizability of the entire H2O molecule.

Refractive indices of minerals and synthetic compounds

This is a comprehensive compilation of refractive indices of 1933 minerals and 1019 synthetic compounds including exact chemical compositions and references taken from 30 compilations and many mineral and synthetic oxide descriptions. It represents a subset of about 4000 entries used by Shannon and Fischer (2016) to determine the polarizabilities of 270 cations and anions after removing 425 minerals and compounds containing the lone-pair ions (Tl + , Sn 2+ , Pb 2+ , As 3+ , Sb 3+ , Bi 3+ , S 4+ , Se 4+ , Te 4+ , Cl 5+ , Br 5+ , I 5+ ) and uranyl ions, U 6+ . The table lists the empirical composition of the mineral or synthetic compound, the ideal composition of the mineral, the mineral name or synthetic compound, the Dana classes and subclasses extended to include beryllates, aluminates, gallates, germanates, niobates, tantalates, molybdates, tungstates, etc., descriptive notes, e.g., structure polytypes and other information that helps define a particular mineral sample, and the locality of a mineral when known. Finally, we list n x , n y , n z , n Dobs > (all determined at 589.3 nm), n Dcalc >, deviation of observed and calculated mean refractive indices, molar volume V m , corresponding to the volume of one formula unit, anion molar volume V an , calculated from V m divided by the number of anions (O 2− , F − , Cl − , OH − ) and H 2 O in the formula unit, the total polarizability AE >, and finally the reference to the refractive indices for all 2946 entries. The total polarizability of a mineral, AE >, is a useful property that reflects its composition, crystal structure, and chemistry and was calculated using the Anderson-Eggleton relationship α AE = ( n D 2 - 1 ) V m 4 π + ( 4 π 3 - c ) ( n D 2 - 1 ) where c = 2.26 is the electron overlap factor. The empirical polarizabilities and therefore, the combination of refractive indices, compositions, and molar volumes of the minerals and synthetic oxides in the table were verified by a comparison of observed and calculated total polarizabilities, AE > derived from individual polarizabilities of cations and anions. The deviation between observed and calculated refractive indices is

Computation of refractive index and optical retardation in stretched polymer films.

Functional polymer films are key components in the display industry, and the theoretical prediction of the optical properties of stretched polymer films is important. In this study, we try to establish the theoretical calculation process without an empirical database to predict the refractive index, including wavelength dispersions and optical retardation of stretched polymer films using several commercial simulation tools. The polarizability tensor and molecular volume for periodic units of polymers are accurately simulated, resulting in the accurate prediction of the mean refractive index and its dispersion for raw polymer materials. The birefringence of stretched films is also calculated to predict reasonably accurate optical properties of stretched films. The simulation method is an effective way that requires a relatively short time and low cost to develop new types of polymer films.

Żabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, a new mineral of the titanite group from the Piława Górna pegmatite, the Góry Sowie Block, southwestern Poland

AbstractŻabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, was found in a Variscan granitic pegmatite at Piława Górna, Lower Silesia, SW Poland. The mineral occurs along with (Al,Ta,Nb)- and (Al,F)-bearing titanites, a pyrochlore-supergroupmineral and a K-mica in compositionally inhomogeneous aggregates, ∼120 μm × 70 μm in size, in a fractured crystal of zircon intergrown with polycrase-(Y) and euxenite-(Y). Żabińskiite is transparent, brittle, brownish, with a white streak, vitreous lustre and a Mohs hardness of ∼5. The calculated density for the refined crystal is equal to 3.897 g cm–3, but depends strongly on composition. The mineral is non-pleochroic, biaxial (–), with mean refractive indices ≥1.89. The (Al,Ta,Nb)-richest żabińskiite crystal,(Ca0.980Na0.015)∑=0.995(Al0.340Fe3+0.029Ti0.298V0.001Zr0.001Sn0.005Ta0.251Nb0.081)∑=1.005[(Si0.988Al0.012)O4.946F0.047(OH)0.007)∑=5.000];60.7 mol.% Ca[Al0.5(Ta,Nb)0.5](SiO4)O; is close in composition to previously described synthetic material. Żabińskiite is triclinic (space group symmetryA1) and has unit-cell parametersa= 7.031(2) Å,b= 8.692(2) Å,c= 6.561(2) Å, α = 89.712(11)°, β = 113.830(13)°, γ = 90.352(12)° andV= 366.77 (11) Å3. It is isostructural with triclinic titanite and bond-topologically identical with titanite and other minerals of the titanite group.Żabińskiite crystallized along with (Al,Ta,Nb)-bearing titanites at increasing Ti and Nb, and decreasing Ta activities, almost coevally with polycrase-(Y) and euxenite-(Y) from Ca-contaminated fluxed melts or early hydrothermal fluids.

Stochastic mirage phenomenon in a random medium.

In the framework of geometric optics, we consider the problem of characterizing the ray trajectory in a random medium with a mean refractive index gradient. Such a gradient results in the mirage phenomenon where an object's observed location is displaced from its actual location. We derive formulas for the mean ray path in both the situation of isotropic stochastic fluctuations and an important anisotropic case. For the isotropic model, the mean squared displacement is also given by a simple formula. Our results could be useful for applications involving the propagation of electromagnetic waves through the atmosphere, where larger-scale mean gradients and smaller-scale stochastic fluctuations are both present.

Refractive and birefringent properties of 4-alkyl-4′-oxycyanobiphenyls at direct and reverse phase transitions

ABSTRACTStudies of temperature behavior of the mean refractive index, ordinary and extraordinary refractive indices, and birefringence have been carried out for three nematogens. The thermo-morphologic properties of the biphasic regions of the direct nematic-isotropic liquid and reverse isotropic liquid-nematic phase transitions have been investigated. The 4-n-alkyl-4′-oxycyanobiphenyls (n = 5, 6, 7) were objects of our study. Studies have been carried out for the circular cycle as the heating-cooling. Temperature behavior of the order parameter in nematic mesophase and at the nematic-isotropic liquid and isotropic liquid-nematic phase transition is discussed.

Refractive Index Sensor Based on Fano Resonances in Metal-Insulator-Metal Waveguides Coupled with Resonators.

A surface plasmon polariton refractive index sensor based on Fano resonances in metal–insulator–metal (MIM) waveguides coupled with rectangular and ring resonators is proposed and numerically investigated using a finite element method. Fano resonances are observed in the transmission spectra, which result from the coupling between the narrow-band spectral response in the ring resonator and the broadband spectral response in the rectangular resonator. Results are analyzed using coupled-mode theory based on transmission line theory. The coupled mode theory is employed to explain the Fano resonance effect, and the analytical result is in good agreement with the simulation result. The results show that with an increase in the refractive index of the fill dielectric material in the slot of the system, the Fano resonance peak exhibits a remarkable red shift, and the highest value of sensitivity (S) is 1125 nm/RIU, RIU means refractive index unit. Furthermore, the coupled MIM waveguide structure can be integrated with other photonic devices at the chip scale. The results can provide a guide for future applications of this structure.

Reflection statistics of weakly disordered optical medium when its mean refractive index is different from an outside medium

Statistical properties of light waves reflected from a one-dimensional (1D) disordered optical medium [n(x) = n0+ dn(x), <dn(x)>=0] have been well studied, however, most of the studies have focused on the situation when the mean refractive index of the optical medium matched with the outside medium, i.e., n0= nout=1. Further, considering dn(x) as a Gaussian color noise refractive index medium with exponential spatial correlation decay length lc and k as the incident wave vector, it has been shown that for smaller correlation length limit, i.e., klc <<1, both the mean reflection coefficient <r> and std of r, σ(r), have same value, and they follow the relation <r>= σ(r) ∝ <dn2> lc. However, when the refractive index of the sample medium is different from the outside medium, the reflection statistics may have interesting features, which has not been well studied or understood. We studied the reflection statistics of a 1D weakly disordered optical medium with the mean background refractive index n0 being different from the outside medium nout (≠n0), to see the effect of mismatching (i.e., value of n0- nout) on the reflection statistics. In the mismatched case, the results show that the mean reflection coefficient <r> follows a form similar to that of the matched refractive-index case, i.e., <r(dn, lc)>∝ <dn2> lc, with a linear increased shift, which is due to 1D uniform background reflection from a slab. However, σ(r) is shown to be σ(r) ∝ (<dn2>lc)1/2, which is different from the matched case. This change in std of r is attributed to the interference between the mismatched-crerated edge mediated multiple scattering that are coupled with the random scattering. Applications to light scattering from random layered media and biological cells are discussed.

Delhuyarite-(Ce)–Ce4 Mg(Fe3+ 2W) [] (Si2 O7)2O6 (OH)2 – a new mineral of the chevkinite group, from the Nya Bastnäs Fe–Cu–REE deposit, Sweden

Delhuyarite-(Ce) is a new mineral (IMA no. 2016-091) with ideal formula Ce 4 Mg(Fe 3+ 2 W)□(Si 2 O 7 ) 2 O 6 (OH) 2 . It is named after Juan and Fausto de Elhuyar (Delhuyar), chemists and metallurgists, who in 1783 isolated tungsten metal for the first time. Associated minerals in the only known sample, from the Nya Bastnas Fe–Cu–REE deposit (Vastmanland, Sweden), include cerite-(Ce), tremolite–actinolite, percleveite-(Ce), bastnasite-(Ce), ferriallanite-(Ce), tornebohmite-(Ce), magnetite, chalcopyrite, quartz and scheelite. Delhuyarite-(Ce), which forms subhedral crystals up to 0.3 mm long, is brown–black with a dark brown streak and translucent with an adamantine lustre. It is pleochroic in black to rust red and optically biaxial (−). Calculated density and mean refractive index are 5.20 g cm −3 and 1.94, respectively. Chemical analyses (electron microprobe) gave (in wt%) La 2 O 3 14.58, Ce 2 O 3 23.29, Pr 2 O 3 1.89, Nd 2 O 3 6.13, Sm 2 O 3 0.74, Gd 2 O 3 0.37, Dy 2 O 3 0.03, Er 2 O 3 0.04, Yb 2 O 3 0.12, Y 2 O 3 0.22, CaO 0.76, Fe 2 O 3 12.86, MgO 2.43, Al 2 O 3 0.73, SiO 2 18.16, TiO 2 0.09, WO 3 15.53, H 2 O calc 1.33, F 0.05, Cl 0.03, O=(F, Cl) −0.03, sum 99.35, corresponding to an empirical formula: (Ce 1.89 La 1.19 Nd 0.48 Pr 0.15 Sm 0.06 Gd 0.03 Y 0.03 Ca 0.18 ) Σ4.01 (Fe 3+ 2.14 W 0.89 Mg 0.80 Al 0.19 Ti 0.02 ) Σ4.04 Si 4.01 O 20 (OH 1.96 F 0.04 ) Σ2 , based on 22 O atoms per formula unit (apfu). The presence of H 2 O is confirmed by IR-spectroscopy, from a strong absorption band at 3495 cm −1 . Delhuyarite-(Ce) is monoclinic, space group C 2 /m , with unit-cell parameters a =13.6020(6) A, b = 5.7445(3) A, c = 10.9996(5) A, β = 100.721(4)°, V = 844.47 (6) A 3 and Z = 2 (data for natural crystal). The crystal structure was refined to an R 1 index of 3.9% (natural crystal) and 1.8% (annealed). Delhuyarite-(Ce) has the same structural topology as chevkinite-subgroup minerals, e.g . chevkinite-(Ce). It is the only mineral of the group with a significant content of W 6+ = 0.89 apfu. In delhuyarite-(Ce), Mg is dominant at the M 1 site as in polyakovite-(Ce); the composition of the M 2, M 3 and M 4 sites is [(Fe 3+ 2 W□], with M 2 being 50% vacant.