Plane-polarized Light Research Articles

Lavoisierite, Mn2+ 8[Al10(Mn3+Mg)][Si11P]O44(OH)12, a new mineral from Piedmont, Italy: the link between “ardennite” and sursassite

The new mineral species lavoisierite, ideally Mn2+ 8[Al10(Mn3+Mg)][Si11P]O44(OH)12, has been discovered in piemontite-bearing micaschists belonging to the Piedmontese Nappe from Punta Gensane, Viu Valley, Western Alps, Italy. It occurs as yellow-orange acicular to prismatic-tabular crystals up to a few millimeters in length, with white streak and vitreous luster, elongated along [010] and flattened on {001}. Lavoisierite is associated with quartz, “mica,” sursassite, piemontite, spessartine, braunite, and “tourmaline.” Calculated density is 3.576 g cm−3. In plane-polarized light, it is transparent, pleochroic, with pale yellow parallel to [010] and yellow-orange normal to this direction; extinction is parallel and elongation is positive. Birefringence is moderate; the calculated average refraction index n is 1.750. Lavoisierite is orthorhombic, space group Pnmm, with a 8.6891(10), b 5.7755(3), c 36.9504(20) A, V 1854.3(2) A3, Z = 2. Calculated main diffraction lines of the X-ray powder diffraction pattern are [d in A, (I), (hkl); relative intensities are visually estimated]: 4.62 (m) (112), 2.931 (vs) (1110), 2.765 (s) (1111), 2.598 (s) (310), 2.448 (ms) (028). Chemical analyses by electron microprobe give (in wt%) P2O5 2.08, V2O5 0.37, SiO2 34.81, TiO2 0.13, Al2O3 22.92, Cr2O3 0.32, Fe2O3 0.86, Mn2O3 6.92, MnO 19.09, MgO 5.73, CaO 1.94, Na2O 0.01, H2O 5.44, sum 100.62 wt%. H2O content was calculated from structure refinement. The empirical formula, based on 56 anions, is (Mn 5.340 2+ Mg1.810Ca0.686Na0.006)Σ=7.852(Al8.921Mn 1.739 3+ Mg1.010Fe 0.214 3+ Cr0.084Ti0.032)Σ=12.000(Si11.496P0.582V0.081)Σ=12.159O43.995(OH)12.005. The crystal structure of lavoisierite was solved by direct methods and refined on the basis of 1743 observed reflections to R 1 = 4.6 %. The structure is characterized by columns of edge-sharing octahedra running along [010] and linked to each other by means of [SiO4], [Si2O7], and [Si3O10] groups. Lavoisierite, named after the French chemist and biologist Antoine-Laurent de Lavoisier (1743–1794), displays an unprecedented kind of structure, related to those of “ardennite” and sursassite.

Methane-derived authigenic carbonates from modern and paleoseeps on the Cascadia margin: Mechanisms of formation and diagenetic signals

Authigenic carbonate precipitation occurs within marine sediments where sulfate-dependent anaerobic methane oxidation occurs. Geochemical and isotopic analyses of authigenic carbonates are commonly used as indicators of carbon sources and environmental conditions present during carbonate formation, but burial diagenesis and recrystallization can overprint these signals. Plane polarized light (PPL) and cathodoluminescent (CL) petrography allows for detailed characterization of carbonate phases and their subsequent alteration. Petrographic, isotopic, and geochemical characteristics of modern offshore authigenic carbonates from central and northern Cascadia are compared with Oligocene–Pliocene fossil seep carbonates uplifted on the Olympic Peninsula. Coupled analyses show the value and complexity of separating primary vs. secondary signals with relevance to understanding fluid-burial history in methane seep provinces on tectonically active convergent margins.The modern, offshore, near-seafloor diagenetic environment (S. Hydrate Ridge and Barkley Canyon) is dominated by acicular and microcrystalline aragonite and high-Mg calcite (HMC, >12mol % Mg). PPL and CL data illustrate that aragonite and HMC phases recrystallize to intermediate-Mg calcite (IMC, 5–12mol% Mg) during burial and diagenesis and eventually to low-Mg calcite (LMC, <5mol% Mg). This diagenetic progression is accompanied by a decrease in Mg/Ca and Sr/Ca ratios. Typically an increase in Ba/Ca is consistent with a high-barium content of the methane-bearing pore fluids that drive recrystallization. CL images also discern primary carbonates with high Mn/Ca ratios, including biogenic peloids, from secondary phases related to deep fluid migration through high permeability conduits. In the secondary phases, the Mn/Ca reflects Mn-enrichment that characterizes deep sourced fluids venting at Barkley Canyon. Mn-enrichment is accompanied by depletion in 18O attributable to elevated fluid temperatures during recrystallization.

Fluor-elbaite, Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F, a new mineral species of the tourmaline supergroup

Fluor-elbaite, Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F, is a new mineral of the tourmaline supergroup. It is found in miarolitic cavities in association with quartz, pink muscovite, lepidolite, spodumene, spessartine, and pink beryl in the Cruzeiro and Urubu mines (Minas Gerais, Brazil), and apparently formed from late-stage hydrothermal solutions related to the granitic pegmatite. Crystals are blue-green with a vitreous luster, sub-conchoidal fracture and white streak. Fluor-elbaite has a Mohs hardness of approximately 7.5, and has a calculated density of about 3.1 g/cm3. In plane-polarized light, fluor-elbaite is pleochroic (O = green/bluish green, E = pale green), uniaxial negative. Fluor-elbaite is rhombohedral, space group R 3 m, a = 15.8933(2), c = 7.1222(1) A, V = 1558.02(4) A3, Z = 3 (for the Cruzeiro material). The strongest eight X-ray-diffraction lines in the powder pattern [ d in A( I )( hkl )] are: 2.568(100)(051), 2.939(92)(122), 3.447(67)(012), 3.974(58)(220), 2.031(57)(152), 4.200(49)(211), 1.444(32)(642), and 1.650(31)(063). Analysis by a combination of electron microprobe, secondary ion mass spectrometry, and Mossbauer spectroscopy gives SiO2 = 37.48, Al2O3 = 37.81, FeO = 3.39, MnO = 2.09, ZnO = 0.27, CaO = 0.34, Na2O = 2.51, K2O = 0.06, F = 1.49, B2O3 = 10.83, Li2O = 1.58, H2O = 3.03, sum 100.25 wt%. The unit formula is: X(Na0.78□0.15Ca0.06K0.01)Y(Al1.15Li1.02Fe2+0.46Mn2+0.28Zn0.03) ZAl6T(Si6.02O18)B(BO3)3V(OH)3W(F0.76OH024). The crystal structure of fluor-elbaite was refined to statistical indices R 1 for all reflections less then 2% using Mo K α X-ray intensity data. Fluor-elbaite shows relations with elbaite and tsilaisite through the substitutions WF ↔ WOH and Y(Al + Li) + WF ↔ 2YMn2+ + WOH, respectively.

High precision magnetic linear dichroism measurements in (Ga,Mn)As

Investigation of magnetic materials using the first-order magneto-optical Kerr effects (MOKEs) is well established and is frequently used. On the other hand, the utilization of the second-order (or quadratic) magneto-optical (MO) effects for the material research is rather rare. This is due to the small magnitude of quadratic MO signals and the fact that the signals are even in magnetization (i.e., they do not change a sign when the magnetization orientation is reversed), which makes it difficult to separate second-order MO signals from various experimental artifacts. In 2005 a giant quadratic MO effect-magnetic linear dichroism (MLD)-was observed in the ferromagnetic semiconductor (Ga,Mn)As. This discovery not only provided a new experimental tool for the investigation of in-plane magnetization dynamics in (Ga,Mn)As using light at normal incidence, but it also motivated the development of experimental techniques for the measurement of second-order MO effects in general. In this paper we compare four different experimental techniques that can be used to measure MLD and to separate it from experimental artifacts. We show that the most reliable results are obtained when we monitor the polarization of reflected light while the magnetization of the sample is rotated by applying an external magnetic field. Using this technique we measure the MLD spectra of (Ga,Mn)As in a broad spectral range from 0.1 eV to 2.7 eV and we observe that MLD has a magnitude comparable to the polar MOKE signals in this material.

New insights on the red alga Archaeolithophyllum and its preservation from the Pennsylvanian of the Cantabrian Zone (NW Spain)

The new species Archaeolithophyllum asymmetricum nov. sp., from the Bachende Formation (Pennsylvanian, Cantabrian Zone, NW Spain), is described herein using cathodoluminescence microscopy. Under plane-polarized light, A. asymmetricum occurs as elongate and arcuate sheets preserved as calcitic mosaics of tiny anhedral to subhedral crystals. Cathodoluminescence has revealed that skeletal walls are composed of dull-bright (locally bright) luminescent calcite that contrasts sharply with the nonluminescent cements filling the intraskeletal pores. Skeletal walls are currently composed of low-Mg calcite (0.5–2 mol % MgCO3) with low Sr content (average 415 ppm). A. asymmetricum shows a strong asymmetry of the thallus organization. The internal tissue is well differentiated into a thick medullar hypothallus and a thin upper cortical perithallus, the latter being composed of nearly rectangular cells arranged in rows perpendicular to the external surface. Cell fusions commonly occur in the perithallial tissue whereas conceptacles exhibit a highly arched geometry lacking any preserved aperture. A. asymmetricum accumulations display a growth pattern similar to that reported from Late Paleozoic “phylloid algae”, and also resemble Miocene frameworks of the corallinacean Mesophyllum. These accumulations of A. asymmetricum formed micrite-rich bioherms with abundant shelter porosities, which are filled up with radiaxial-fibrous calcite (originally high-Mg calcite) and subsequent blocky spar. They constructed a rigid framework that was basically a combination of the foliaceous growth form, crust fusion and division, and synsedimentary marine cementation. Paleontological and sedimentological evidence suggests that A. asymmetricum thrived in an outer platform environment with relative quiet conditions. The exceptional preservation of these algae was favored by a rapid cementation of the intraskeletal pores under oxidizing conditions in a marine phreatic environment, protecting skeletons from early dissolution and recrystallization. Although the resulting neomorphic microsparite fabric suggests an aragonite precursor, the morphological similarities (especially reproductive organs) between Archaeolithophyllum and Recent calcitic corallinaceans, and the similar trace element composition of the algal thalli and the surrounding high-Mg radiaxial-fibrous cements, suggest that originally, Archaeolithophyllum was probably composed of high-Mg calcite. Based on the morphologic features, framework strategies (crust fusion and division) and growth modes, it is suggested that Archaeolithophyllum might be phylogenetically related to the modern coralline algae.

Paseroite, PbMn2+(Mn2+,Fe2+)2(V5+,Ti,Fe3+,〈)18O38, a new member of the crichtonite group

Paseroite, ideally PbMn 2þ (Mn 2þ ,Fe 2þ )2(V 5þ ,Ti,Fe 3þ ,&)18O38, is a new mineral (IMA2011-069) from fossil wood in the upper part of the Molinello mine, Val Graveglia, Italy. Paseroite occurs in direct association with quartz, chalcocite, volborthite, metatyuyamunite and pyrophanite, and was also found as zones within V-rich senaite crystals with which it forms a solid-solution series. Paseroite forms as isolated submetallic, dark grey to black, elongated scalenohedral crystals between 50 and 100mm in length, with the forms {001} and {102} present. The tenacity is brittle, the fracture conchoidal, and the streak is black. The Vickers hardness is 847 kg mm � 2 (load 500g), which is equivalent to 6-6.5 on the Mohs scale. The calculated density is 4.315 g/cm 3 (on the basis of the empirical formula). In plane-polarised incident light, paseroite is greyish in colour, weakly bireflectant and non-pleochroic. Internal reflections are absent. Between crossed polars, paseroite is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) are: 18.4 %, 18.2 % (471.1 nm); 17.9 %, 17.7 % (548.3 nm); 17.6 %, 17.3 % (586.6 nm); and 17.0 %, 16.8 % (652.3 nm), respectively. The empirical formula, calculated on the basis of 38 O atoms pfu is: (Pb0.61Sr0.39)1.00 (V 5þ 7.78Ti 4þ 7.03Mn 2þ 1.86Fe 2þ 0.67Fe 3þ 0.37Zn0.24Na0.19U0.02Mg0.02&2.82)21.00O38. According to the structural results, the simplified formula is: PbMn 2þ (Mn 2þ ,Fe 2þ )2(V 5þ ,Ti,Fe 3þ ,&)18O38. Structurally, paseroite crystallises in the space group R3, with the unit-cell parameters a ¼ 10.3894(5), c ¼ 20.8709(8) A u , V ¼ 1950.98(15) A u 3 and Z ¼ 3. The crystal structure was refined to R ¼ 0.0234 for 632 reflections with Io . 2s(Io) and is isostructural with senaite and all other members of the crichtonite group. The eight strongest X-ray powder-diffraction lines (d in A u (I/I0 )( hkl)) are: 3.417 (100) (024), 3.012 (21) (300), 2.896 (61) (216), 2.858 (36) (214), 2.765 (27) (303), 2.260 (85) (144), 2.149 (65) (415) and 1.809 (57) (418). The name is after Marco Pasero (b. 1958), Professor of Mineralogy at the University of Pisa.

Formation of surface relief grating in polymers with pendant azobenzene chromophores as studied by AFM/UFM

We studied peculiarities of the structural reconstruction within holographically recorded gratings on the surface of several different amorphous azobenzene-containing polymers. Under illumination with a light interference pattern, two processes take place in this type of polymer. The first process is the light-induced orientation of azobenzene units perpendicular to the polarization plane of the incident light. The second one is a transfer of macromolecules along the grating vector (i.e. perpendicular to the grating lines). These two processes result in the creation of a volume orientation grating (alternating regions of different direction or degree of molecular orientation) and a surface relief grating (SRG)—i.e. modulation of film thickness. One can assume that both orientation of molecules and their movement might change the local mechanical properties of the material. Therefore, formation of the SRG is expected to result also in modulation of the local stiffness of the polymer film. To reveal and investigate these stiffness changes within the grating, spin-coated polymer films were prepared and the gratings were recorded on them in two different ways: with an orthogonal circular or orthogonal linear polarization of two recording light beams. A combination of atomic force microscopy (AFM) and ultrasonic force microscopy (UFM) techniques was applied for SRG development monitoring. We demonstrate that formation of the phase gratings depends on the chemical structure of polymers being used, polymer film thickness, and recording parameters, with the height of grating structures (depth of modulation) increasing with both the exposure time and the film thickness. UFM images suggest that the slopes of the topographic peaks in the phase gratings exhibit an increased stiffness with respect to the grating depressions.

Experimental Research on Measuring Two-Dimensional Stress Field Using Digital Holographic Photo-Elastic Method

According to the holographic optical theory, based on the method of rotating reference light polarization plane, through the simultaneous solution of light intensity equations transformed by the hologram, the digital holographic nondestructive testing of two-dimensional stress field is introduced. This technology does not require additional experimental means and numerical method for separate fringes, determining fringe order and solving stress. It is a convenient, accurate and non-destructive measurement of two-dimensional stress field. The paper first introduces the basic theory of digital holographic photo-elastic method, and then verifies it by experiments and simulation. Light intensity images are obtained through the comparative experiments and theoretical solutions. The results prove the strong feasibility of the method in experiments, and lay the foundation for further experimental study.

Oxy-chromium-dravite, NaCr3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup

Oxy-chromium-dravite, NaCr3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O, is a new mineral of the tourmaline supergroup. It is found in metaquartzites of the Pereval marble quarry (Sludyanka, Lake Baikal, Russia) in association with quartz, calcite, chromphyllite, eskolaite, chromite, uvarovite, chromian phlogopite, and pyroxenes of the diopside-kosmochlor series, Cr-bearing tremolite, Cr-bearing titanite, Cr-bearing rutile, and pyrite. Crystals are emerald green, transparent with a vitreous luster, green streak, and conchoidal fracture. Oxy-chromium-dravite has a VHN hardness of 14 540 MPa, a Mohs hardness of approximately 7½, and a calculated density of 3.3 g/cm3. In plane-polarized light, oxy-chromiumdravite is pleochroic (O = dark green, E = yellow green) and uniaxial negative: ω = 1.765(5), ε = 1.715(5). Oxy-chromium-dravite is rhombohedral, space group R3m, with the unit-cell parameters a = 16.1121(3), c = 7.3701(1) Å, V = 1656.95(5) Å3, Z = 3. The chemical characterization resulted in: SiO2 = 31.73, TiO2 = 0.31, B2O3 = 9.35, Al2O3 = 3.61, Cr2O3 = 36.25, V2O3 = 5.81, MgO = 7.49, Na2O = 2.78, K2O = 0.08, F = 0.78, H2O = 2.16, sum 100.01 wt%. The unit formula is

Tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3OH, a new mineral species of the tourmaline supergroup from Grotta d'Oggi, San Pietro in Campo, island of Elba, Italy

Tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3OH, is a long-expected new mineral of the tourmaline supergroup. It occurs in an aplitic dike of a LCT-type pegmatite body from Grotta d’Oggi, San Pietro in Campo, island of Elba, Italy, in association with quartz, K-feldspar, plagioclase, elbaite, and schorl. Crystals are greenish yellow with a vitreous luster, a white streak, and show no fluorescence. Tsilaisite has a Mohs hardness of approximately 7; it is brittle with a sub-conchoidal fracture, and has a calculated density of 3.133 g/cm3. In plane-polarized light, tsilaisite is pleochroic, O = pale greenish yellow, E =very ale greenish yellow; it is uniaxial negative, ω = 1.645(5), Ɛ = 1.625(5). Tsilaisite is rhombohedral, space group R3m, a = 15.9461(5), c = 7.1380(3) Å, V = 1571.9(1) Å3, Z = 3. The strongest eight ‑raydiffraction lines in the powder pattern [d in Å(I)(hkl)] are: 3.974(100)(220), 2.942(94)(122), 2.570(79) (051), 2.034(49)(152), 4.205(41)(211), 6.329(22)(101), 2.377(21)(003), and 1.592(21)(550). Analysis by a combination of electron microprobe, secondary ion mass spectrometry, and optical absorption spectroscopy gives SiO2 = 36.10(3), TiO2 = 0.32(4), Al2O3 = 37.10(5), MnO = 9.60(10), CaO = 0.09(4), Na2O = 2.11(7), K2O = 0.03(1), F = 0.79(3), B2O3 = 10.2(6), Li2O = 0.8(1), H2O = 3.1(2), sum 99.95 wt%. The unit formula is X(Na0.67⃞0.30Ca0.02K0.01)Y(Mn2+1.34Al1.14Li0.54Ti0.04)ZAl6T(Si5.94Al0.06)B2.91O27V(OH)3W(OH0.39F0.41O0.20). The structure, refined also taking into account the positional disorder of the O1 and O2 anions, converged to statistical indices R1 for all reflections of about 2%. The resulting site populations indicate that the Z site is occupied by Al and that the Y site is dominated by Mn2+. Aluminum is incorporated at Y through two types of substitutions: YAl+WO2- → YMn2++WOH, which has the result of replacing OH at the W site by O2-, and Y(Al+Li)+WF → 2YMn2++WOH, which relates fluor-elbaite to the tsilaisite component. Infrared absorption spectra measured in the principal OH-stretching region were interpreted on the basis of local arrangements consistent with the short-range bond-valence requirements. A compositional trend from fluor-elbaite to tsilaisite is observed in samples from Elba Island. The occurrence of tsilaisite is very rare in nature, as a consequence of both the requirement of extraordinary petrogenetic conditions and limited structural stability.

ELDRAGONITE, Cu6BiSe4(Se2), A NEW MINERAL SPECIES FROM THE EL DRAGON MINE, POTOSI, BOLIVIA, AND ITS CRYSTAL STRUCTURE

Eldragonite, with the simplified formula Cu 6 BiSe 4 (Se 2 ), is a new mineral species discovered in a telethermal vein-type deposit with selenides at the El Dragon mine, Province of Quijarro, Department of Potosi, Bolivia. It forms inclusions in krut’aite, and is associated with clausthalite, klockmannite, umangite and tiemannite, as well as with watkinsonite, petrovicite and two unnamed phases in the system Cu–Pb–Hg–Bi–Se. The unique vein of eldragonite-bearing krut’aite is hosted within sandstones and shales of Devonian age. Eldragonite occurs in anhedral grains and polycrystalline aggregates attaining a size of up to 100 × 80 μm. Megascopically, the mineral has a brownish to light-maroon color, is opaque and lacks internal reflections. It has a metallic luster and a brownish black streak, is brittle with an uneven to conchoidal fracture, without observable cleavage. The VHN 15 values range between 212 and 243 (mean 225) kg/mm 2 , corresponding to a Mohs hardness of ~3 ½. In plane-polarized light, eldragonite is distinctly bireflectant and pleochroic, from light grayish brown to cream; it is strongly anisotropic with rotation tints in shades of orange and blue-black. The reflectances (in air and oil, respectively) for the COM standard wavelengths are: 32.5–34.5, 17.7–19.7 (470 nm), 32.95–36.3, 18.0–21.4 (546 nm), 33.3–36.8, 18.3–21.6 (589 nm), 34.0–36.9, 19.1–21.7 (650 nm). Electron-microprobe analyses gave (mean of 24 analyses): Cu 35.9, Fe 1.25, Ni 0.35, Bi 20.3, Se 42.5, total 100.3 wt.%, corresponding to (Cu 5.98 Fe 0.24 Ni 0.06 ) ∑6.28 Bi 1.03 Se 5.70 . The ideal formula is Cu 6 BiSe 4 (Se 2 ), which requires Cu 35.84, Bi 19.64, Se 44.52 wt.%. Eldragonite has an orthorhombic cell, space group Pmcn , with a 4.0341(4), b 27.056(3), c 9.5559(9) A, V 1043.0(3) A 3 , and Z = 4. The calculated density is 6.76 g/cm 3 . The strongest X-ray powder-diffraction lines [ d in A ( I ) hkl ] are: 6.547(58)031, 3.579(100)052, 3.253(48)141, 3.180(77)081, 3.165(56)013, 3.075(84)102, 3.065(75)151,112, 2.011(53)200, 1.920(76)154, 1.846(52)1103. The crystal structure was solved from single-crystal data, and was refined to R 1 = 0.026 on the basis of 1731 unique reflections. There are one Bi and six Cu positions. Among the six Se positions, two Se atoms form a Se 2 pair [d(Se–Se) = 2.413 A]; eldragonite is thus a mixed selenide–diselenide compound. The crystal structure is organized according to two slabs alternating along a . The thin slab with formula Cu 6 Se 6 is a zigzag layer derived from the CaF 2 archetype; the thick slab, Cu 6 Bi 2 Se 6 , is similar to that of wittichenite, Cu 3 BiS 3 . The Se 2 pair is at the junction between these two slabs. This new mineral species is named after the location where it was discovered.

JACUTINGAITE, Pt2HgSe3, A NEW PLATINUM-GROUP MINERAL SPECIES FROM THE CAUE IRON-ORE DEPOSIT, ITABIRA DISTRICT, MINAS GERAIS, BRAZIL

Jacutingaite, Pt 2 HgSe 3 , is a new species of platinum-group mineral discovered at the Caue iron-ore deposit, Itabira district, Minas Gerais, Brazil. Observed in a polished section, the mineral is about 50 μm across and occurs on an aggregate of atheneite, potarite and hematite. The new mineral is partly altered to a Pt–O phase. Synthetic jacutingaite is megascopically grey in color, has a metallic luster and a grey streak. The mineral is brittle, with a very good {001} cleavage. Values of VHN 10 (15 indentations on five grains of synthetic Pt 2 HgSe 3 ) are between 119 and 245 kg/mm 2 , with a mean value of 169 kg/mm 2 , corresponding to a Mohs hardness of approximately 3½. Under plane-polarized light, jacutingaite is light grey, has a moderate to distinct bireflectance, a bluish grey to rusty brown pleochroism, and a weak to distinct anisotropy; it does not exhibit internal reflections. Reflectance values of synthetic jacutingaite in air (R max , R min , in %) are: 51.1, 47.4 at 470 nm, 50.5, 48.2 at 546 nm, 49.6, 48.0 at 589 nm, and 47.8, 47.1 at 650 nm. Three electron-microprobe analyses of natural jacutingaite gave an average composition: Pt 37.30, Pd 5.91, Hg 25.72, Ag 0.16, Cu 0.82, and Se 31.48, total 101.39 wt.%, corresponding to the empirical formula (Pt 1.46 Pd 0.42 Cu 0.10 Ag 0.01 ) ∑1.99 Hg 0.98 Se 3.04 based on six atoms; the average result of nine analyses of synthetic jacutingaite is: Pt 47.14, Hg 24.24, and Se 28.62, for a total of 100.00 wt.%, corresponding to Pt 2.00 Hg 1.00 Se 3.00 . The mineral is trigonal, space group P 3 m 1, with a 7.3477(2), c 5.2955(1) A, V 247.59(1) A 3 and Z = 2. The crystal structure was solved and refined from the powder X-ray-diffraction data on synthetic Pt 2 HgSe 3 . Jacutingaite is isostructural with Pt 4 Tl 2 X 6 ( X = S, Se, or Te); no structural analogue is known as a mineral. Jacutingaite is structurally related to sudovikovite. The strongest lines in the X-ray powder-diffraction pattern of synthetic jacutingaite [ d in A(I) hkl ] are: 5.2917(100)001, 2.7273(16)201, 2.4443(10)012, 2.0349(18)022, 1.7653(37)003, 1.3240(11)004 and 1.0449(11)025. The mineral is named after the specular-hematite-rich vein-type mineralization locally known as “jacutinga”, in which it occurs.

Polarised light-induced orientation and reorientation processes and unexpected ‘memory effect’ in side-chain azobenzene-containing LC polymers

Photoorientation phenomena in thin films of side-chain azobenzene-containing polymethacrylates having different length of spacer (4, 6 and 10 methylene units) were studied in detail. Irradiation of these films with polarised blue light (473 nm) leads to photoorientation of photochromic side groups in a direction perpendicular to the polarisation plane of the incident light. It was shown that values of photoinduced dichroism increase with the lengthening of the methylene spacer. Annealing of the polymers films at a temperature higher than glass transition results in an additional growth of dichroism. However, the degree of uniaxial order of the annealed films was almost the same. The reorientation phenomena in irradiated and annealed films were studied by the irradiation of these films with the light of the same wavelength (473 nm) but polarisation rotated by 90° with respect to the first irradiation cycle. A study of the kinetics of the reorientation showed that the polymers with a spacer having four and six methylenic groups undergo the fast complete reorientation, whereas the polymer with 10 methylenic units is characterised by a much slower reorientation process. Moreover, an unusual ‘memory effect’ was found for the polymer films deposited on quartz substrates; annealing of the films after reorientation restores an initial orientation state achieved by the first irradiation cycle, whereas the films spin-coated on mica surface do not demonstrate this phenomenon. The ‘memory effect’ is probably associated with the roughness of the quartz substrates.

Palytoxin detection and quantification using the fluorescence polarization technique

Palytoxin (PLT) is a highly toxic nonpeptidic marine natural product, with a complex chemical structure. Its mechanism of action targets Na,K-ATPase. Fluorescence polarization (FP) is a spectroscopic technique that can be used to determine molecular interactions. It is based on exciting a fluorescent molecule with plane-polarized light and measuring the polarization degree of the emitted light. In this study, FP was used to develop a detection method based on the interaction between the Na,K-ATPase and the PLT. The Na,K-ATPase was labeled with a reactive succinimidyl esther of carboxyfluorescein, and the FP of protein–dye conjugate was measured when the amount of PLT in the medium was modified. The assay protocol was first developed using ouabain as a binding molecule. The final result was a straight line that correlates FP units and PLT concentration. Within this line the PLT equivalents in a natural sample can be quantified. A selective cleaning procedure to mussel samples and dinoflagellates cultures was also developed to avoid the matrix effect. The LOQ (limit of quantification) of the method is 10nM and the LOD (limit of detection) is 2nM. This new PLT detection method is easier, faster, and more reliable than the other methods described to date.

Menchettiite, AgPb2.40Mn1.60Sb3As2S12, a new sulfosalt belonging to the lillianite series from the Uchucchacua polymetallic deposit, Lima Department, Peru

Menchettiite, ideally AgPb 2.40 Mn 1.60 Sb 3 As 2 S 12 , is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as black, anhedral to subhedral grains up to 200 μm across, closely associated with orpiment, tennantite/tetrahedrite, other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S, and calcite. Menchettiite is opaque with a metallic luster and possesses a black streak. It is brittle, with uneven fracture; the Vickers microhardness (VHN 100 ) is 128 kg/mm 2 (range 119-136) (corresponding to a Mohs hardness of 2½-3). The calculated density is 5.146 g/cm 3 (on the basis of the empirical formula). In plane-polarized incident light, menchettiite is weakly to moderately bireflectant and weakly pleochroic from dark gray to a dark green. Internal reflections are absent. Between crossed polarizers, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (R min and R max ) for the four standard COM wavelengths are 33.1, 39.8 (471.1 nm), 31.8, 38.0 (548.3 nm), 30.9, 37.3 (586.6 nm), and 29.0, 35.8 (652.3 nm), respectively. Menchettiite is monoclinic, space group P2 1 /n, with unit-cell parameters: a = 19.233(2), b = 12.633(3), c = 8.476(2) Å, β = 90.08(2)°, V = 2059.4(8) Å 3 , a: b: c 1.522:1:0.671, Z = 2, and it is twinned on {100}. The crystal structure was refined to R = 0.0903 for 2365 reflections with Fo &gt; 4σ(Fo) and it resulted to be topologically identical to those of ramdohrite, uchucchacuaite, and fizélyite. The six strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.4066 (39) ( 3̅12), 3.4025 (39) (312), 3.2853 (100) (520), 2.8535 (50) ( 2̅32), 2.8519 (47) (232), and 2.1190 (33) (004). Electron-microprobe analyses gave the chemical formula Ag 1.95 Cu 0.01 Pb 4.81 Mn 3.20 Fe 0.02 Zn 0.01 Sb 6.09 As 3.94 Bi 0.01 S 23.95 Se 0.01 , on the basis of 44 atoms and according to the structure refinement results. Menchettiite can be classified among the Sb-rich members of the lillianite homeotypic series, which are described with the general formula Ag x Pb 3-2x Sb 2+x S 6 . Besides the heterovalent substitution 2Pb 2+ → Ag + + Sb 3+ taken into consideration by the above formula, two isovalent substitutions relate menchettiite to the other lillianite homeotypes, i.e., Mn 2+ → Pb 2+ and As 3+ → Sb 3+ . The name is after Silvio Menchetti (1937-), Professor of Mineralogy and Crystallography at the University of Florence. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2011-009).

Cosserat gyro-birefringence. An introduction to nonsymmetrical photoelasticity

Mechanical couple stresses modify at a microscopic level optical properties of some materials so they can display gyro-birefringence phenomena. The Optical Cosserat medium is defined and optical rotation tensor relative to couple stress is introduced. The generalized tensor of the dielectric permittivity is written for the Cosserat medium. Split of the plane-polarized light wave on passing through the Cosserat medium is shown and rotation of the azimuth of polarization is expressed by components of the couple stress tensor.

Polarímetro virtual: desenvolvimento, utilização e avaliação de um software educacional

Optical activity is the ability of chiral substances to rotate the plane of plane-polarized light and is measured using an instrument called a polarimeter. An educational software application to explore, both interactively and visually, the concepts related to polarimetry to facilitate their understanding was developed. The software was field-tested and a questionnaire evaluating the graphics interface, usability and the software as an educational tool, was answered by students. The results characterized the computer application developed as an auxiliary tool for assisting teachers in lectures and students in the learning process.

How pharmacokinetic can help to choose the right local anesthetics during epidural infusion

Abstract Local anesthetics (LA) are used for the prevention and relief of both acute and chronic pain. The local anesthetic molecule consists of three components; each of these contributes distinct properties to the molecule. The onset of action is determined by tissue pH, the pKa of the particular agent used, and the amount of nonionized drug available in the tissue. The duration of action depends on the length of time that the drug binds to the membrane. Most local anesthetics were produced as enantiomeric mixtures known as racemates, although it is recognized that each enantiomer possesses quite different pharmacological properties. All amide-type local anesthetics, except for lidocaine, contain a chiral center, meaning that two enantiomers exist. Enantiomers have the same physicochemical properties and differ only in the way that they rotate plane-polarized light. However, their biological behavior, in terms of pharmacokinetic and pharmacodynamic characteristics, can be very different. The clinical response to a particular local anesthetic or its toxicity may vary substantially from patient to patient; dosing often requires careful titration. Interindividual variability is caused by several factors including the pharmacokinetics features of the drug, pharmacodynamic properties or patient’s characteristics.

경반층 토양인 장원통의 미세형태학적 및 광물학적 특성

본 연구지역인 장원통은 자연 경반층을 함유하는 토양으로 명시되어 있다. 따라서, 장원통의 물리 화학적, 광물학적 그리고 미세형태학적 분석을 통해 경반층의 생성원인을 규명하고자 하였다. 토양의 층위별로 토양을 채취하여 물리화학적 광물학적 특성을 분석하였다. 토성분석은 피펫법으로 측정하였다. 점토광물은 <TEX>$</TEX><TEX><</TEX><TEX>2{\mu}m$</TEX> 이하로 분리한 후 정방위법으로 X-선 회절기를 이용하여 동정하였다. 미세형태학적 특성을 살펴보기 위해 불교란 시료를 채취하여 0.03mm 이하로 박편을 제작한 후 편광현미경을 이용하여 분석하였다. 장원통 시료에 대한 물리 화학적 특성을 분석한 결과, 토양조성은 모든 층위가 미사질 양토로 도시되었다. 점토의 함량이 약 19.3-20.6% 범위이고, 미사는 약 58.3-61.5%로 미사의 함량이 높게 분포하고 있으며 상부보다는 하부로 내려갈수록 미사의 함량이 더 높게 분포하였다. 표토의 pH는 4.9-4.8로 우리나라 밭 토양의 평균치 5.59 보다 낮게 분포 하고 있었다. 점토광물은 일라이트, 카올리나이트, 녹니석 그리고 질석이 동정되었다. 본 지역의 미세형태학적 특성을 관찰하기 위해 박편을 제작하여 편광현미경 하에서 박편을 관찰한 결과, 사장석과 석영반정이 주위에 미사크기의 각괴상 토양 입자가 우상-좌상방향으로 미약한 층을 이루고 있으나 기질과 경계가 명확하고 토양 기질 간에 미사 크기의 띠를 관찰할 수 있었다. 점토광물은 점토 집적층에서 공극을 채우는 형태로 존재하는 것이 아니라 일차광물에서 변질된 이차광물로 존재하고 있다. 따라서 장원통의 경반층은 점토집적 보다는 미사집적에 의한 영향이 더 크다고 볼 수 있다. 따라서 현재의 토양통 설명서에서 분류된 Typic Fragiochrepts의 해석이 올바르다고 판단된다. This study was carry out on a Jang-Won series (fine loamy, mixed, mesic family of typic fragipan) that were established and classified as a fragipan soil in Korea. The morphological, physical, chemical and minerals characteristics of Jang-Won series were studied to determine the genesis of fragipan soils in natural environment. Each sample was analyzed for its physical, chemical and mineralogical characteristics. The particle size distribution of samples was measured using pipette method. Clay minerals were investigated on parallel-oriented specimens of the clay fraction (<TEX>$</TEX><TEX><</TEX><TEX>2{\mu}m$</TEX>) from each horizon, separated by sieving and centrifugation, using X-ray diffraction (XRD) analysis. Micromorphological observations were made on thin sections prepared from soil blocks impregnated with Crystic Resin, cut and ground to less than <TEX>$30{\mu}m$</TEX> in thickness, and finally polished with diamond paste. Most horizons have pH values in the range of fewer than 5.0 and have very low base-saturation values. Their textural classification ranges from silt loam to loam, the lower horizons being the finer. The clay fraction revealed the occurrence of illite, kaolinite, chlorite and vermiculite. The micro-morphological analysis carries out thin sections from each soil profile. The silt concentrations occur as extremely dense and homogenous bands or zones of silt-sized materials, brownish in colour in plane-polarized light and anisotropic in cross-polarized light, surrounding or adhering to skeleton grains. The genesis of fragipan in the Jangweon series assumed composition of clay fraction rather than silt concentration. Therefore, this results suggested an authentic interpretation which Jangweon series is classification as Typic Fragiochrepts.

Photosensitivity control of an isotropic medium through polarization of light pulses with tilted intensity front

We present the first experimental evidence of anisotropic photosensitivity of an isotropic homogeneous medium under uniform illumination. Our experiments reveal fundamentally new type of light induced anisotropy originated from the hidden asymmetry of pulsed light beam with a finite tilt of intensity front. We anticipate that the observed phenomenon, which enables employing mutual orientation of a light polarization plane and pulse front tilt to control interaction of matter with ultrashort light pulses, will open new opportunities in material processing.