Raman microscopy of formamide-intercalated kaolinites treated by controlled-rate thermal analysis technology

Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is reported. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm-1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm-1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl-stretching band of the inner hydroxyl is observed at 3621 cm-1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide.

In Situ Observation of the Thermal Decomposition of Weddelite by Heating Stage Environmental Scanning Electron Microscopy

The morphological and chemical changes occurring during the thermal decomposition of weddelite, CaC2O4·2H2O, have been followed in real time in a heating stage attached to an Environmental Scanning Electron Microscope operating at a pressure of 2 Torr, with a heating rate of 10 °C/min and an equilibration time of approximately 10 min. The dehydration step around 120 °C and the loss of CO around 425 °C do not involve changes in morphology, but changes in the composition were observed. The final reaction of CaCO3 to CaO while evolving CO2 around 600 °C involved the formation of chains of very small oxide particles pseudomorphic to the original oxalate crystals. The change in chemical composition could only be observed after cooling the sample to 350 °C because of the effects of thermal radiation.

Raman microscopy of the molybdate minerals koechlinite, iriginite and lindgrenite

A series of molybdate bearing minerals including wulfenite, powellite, lindgrenite and iriginite have been analysed by Raman microscopy. These minerals are closely related and often have related paragenesis. Raman microscopy enables the selection of individual crystals of these minerals for spectroscopic analysis even though several of the minerals can be found in the same matrix because of the paragenetic relationships between the minerals. The molybdenum bearing minerals lindgrenite, iriginite and koechlinite were studied by scanning electron microscopy and compositionally analysed by EDX methods using an electron probe before Raman spectroscopic analyses. The Raman spectra are assigned according to factor group analysis and related to the structure of the minerals. These minerals have characteristically different Raman spectra.

Corneal sensitivity and slit scanning in vivo confocal microscopy of the subbasal nerve plexus of the normal central and peripheral human cornea

Purpose: To determine the subbasal nerve density and tortuosity at 5 corneal locations and to investigate whether these microstructural observations correlate with corneal sensitivity. Method: Sixty eyes of 60 normal human subjects were recruited into 1 of 3 age groups, group 1: aged ,35 years, group 2: aged 35–50 years, and group 3: aged .50 years. All eyes were examined using slit-lamp biomicroscopy, noncontact corneal esthesiometry, and slit scanning in vivo confocal microscopy. Results: The mean subbasal nerve density and the mean corneal sensitivity were greatest centrally (14,731 6 6056 mm/mm2 and 0.38 6 0.21 millibars, respectively) and lowest in the nasal mid periphery (7850 6 4947 mm/mm2 and 0.49 6 0.25 millibars, respectively). The mean subbasal nerve tortuosity coefficient was greatest in the temporal mid periphery (27.3 6 6.4) and lowest in the superior mid periphery (19.3 6 14.1). There was no significant difference in mean total subbasal nerve density between age groups. However, corneal sensation (P = 0.001) and subbasal nerve tortuosity (P = 0.004) demonstrated significant differences between age groups. Subbasal nerve density only showed significant correlations with corneal sensitivity threshold in the temporal cornea and with subbasal nerve tortuosity in the inferior and nasal cornea. However, these correlations were weak. Conclusions: This study quantitatively analyzes living human corneal nerve structure and an aspect of nerve function. There is no strong correlation between subbasal nerve density and corneal sensation. This study provides useful baseline data for the normal living human cornea at central and mid-peripheral locations

In vivo confocal microscopy of the palpebral conjunctiva and tarsal plate

Purpose The aim of this work is to develop a more complete understanding of the in vivo histology of the human palpebral conjunctiva and tarsal plate. Methods. The upper eyelids of 11 healthy human volunteer subjects were everted, and laser scanning confocal microscopy was used to examine the various tissue layers of the palpebral conjunctiva and tarsal plate. Results The superficial and basal epithelial layers are composed of cells with gray cytoplasm and thick, light gray borders.Nuclei can not be seen. The stroma has a varied appearance; fibrous tissue is sometimes observed, interspersed with dark,amorphous lacunae, and crevases. Numerous single white or gray cells populate this tissue, and fine blood vessels are seen traversing the field. Occasional conjunctival microcysts and Langerhans cells are observed. The tarsal plate is dark and amorphous, and meibomian gland acini with convoluted borders are clearly observed. Acini are composed of an outer lining of large cuboidal cells, and differentiated secretory cells can be seen within the acini lumen. Conclusions Laser scanning confocal microscopy is capable of studying the human palpebral conjunctiva, tarsal plate, and acini of meibomian glands in vivo. The observations presented here may provide useful supplementary anatomical information relating to the morphology of this tissue.

Corneal confocal microscopy : a novel noninvasive means to diagnose neuropathy in patients with Fabry disease

ABSTRACT: Neuropathy is a cause of significant disability in patients with Fabry disease, yet its diagnosis is difficult. In this study we compared the novel noninvasive techniques of corneal confocal microscopy (CCM) to quantify small-fiber pathology, and non-contact corneal esthesiometry (NCCA) to quantify loss of corneal sensation, with established tests of neuropathy in patients with Fabry disease. Ten heterozygous females with Fabry disease not on enzyme replacement therapy (ERT), 6 heterozygous females, 6 hemizygous males on ERT, and 14 age-matched, healthy volunteers underwent detailed quantification of neuropathic symptoms, neurological deficits, neurophysiology, quantitative sensory testing (QST), NCCA, and CCM. All patients with Fabry disease had significant neuropathic symptoms and an elevated Mainz score. Peroneal nerve amplitude was reduced in all patients and vibration perception threshold was elevated in both male and female patients on ERT. Cold sensation (CS) threshold was significantly reduced in both male and female patients on ERT (P < 0.02), but warm sensation (WS)and heat-induced pain (HIP) were only significantly increased in males onERT (P<0.01). However, corneal sensation assessed withNCCAwas significantly reduced in female (P < 0.02) and male (P < 0.04) patients on ERT compared with control subjects. According to CCM, corneal nerve fiber and branch density was significantly reduced in female (P < 0.03) and male (P < 0.02) patients on ERT compared with control subjects. Furthermore, the severity of neuropathic symptoms and the neurological component of the Mainz Severity Score Index correlated significantly with QSTand CCM. This study shows that CCM and NCCA provide a novel means to detect early nerve fiber damage and dysfunction, respectively, in patients with Fabry disease.

In vivo confocal microscopy of the bulbar conjunctiva

Background: The aim of this work is to develop a more complete qualitative and quantitative understanding of the in vivo histology of the human bulbar conjunctiva. Methods: Laser scanning confocal microscopy (LSCM) was used to observe and measure morphological characteristics of the bulbar conjunctiva of 11 healthy human volunteer subjects. Results: The superficial epithelial layer of the bulbar conjunctiva is seen as a mass of small cell nuclei. Cell borders are sometimes visible. The light grey borders of basal epithelial cells are clearly visible, but nuclei can not be seen. The conjunctival stroma is comprised of a dense meshwork of white fibres, through which traverse blood vessels containing cellular elements. Orifices at the epithelial surface may represent goblet cells that have opened and expelled their contents. Goblet cells are also observed in the deeper epithelial layers, as well as conjunctival microcysts and mature forms of Langerhans cells. The bulbar conjunctiva has a mean thickness of 32.9 1.1 mm, and a superficial and basal epithelial cell density of 2212 782 and 2368 741 cells/ mm2, respectively. Overall goblet and mature Langerhans cell densities are 111 58 and 23 25 cells/mm2, respectively. Conclusions: LSCM is a powerful technique for studying the human bulbar conjunctiva in vivo and quantifying key aspects of cell morphology. The observations presented here may serve as a useful marker against which changes in conjunctival morphology due to disease, surgery, drug therapy or contact lens wear can be assessed.

Smectite flocculation structure modified by AI13 macromolecules; as revealed by the Transmission X-ray Microscopy (TXM)

The aggregate structure which occurs in aqueous smectitic suspensions is responsible for poor water clarification, difficulties in sludge dewatering and the unusual rheological behaviour of smectite rich soils. These macroscopic properties are dictated by the 3-D structural arrangement of smectite finest fraction within flocculated aggregates. Here, we report results from a relatively new technique, Transmission X-ray Microscopy (TXM), which makes it possible to investigate the internal structure and 3-D tomographic reconstruction of the smectite clay aggregates modified by Al13 keggin macro-molecule [Al13(O)4(OH)24(H2O)12 ]7+. Three different treatment methods were shown resulted in three different micro-structural environments of the resulting flocculation.

Raman microscopy of haidingerite Ca(AsO3OH)•H2O and brassite Mg(AsO3OH)•4H2O

Raman spectroscopy has been used to study the arsenate minerals haidingerite Ca(AsO3OH)•H2O and brassite Mg(AsO3OH)•4H2O. Intense Raman bands in haidingerite spectrum observed at 745 and 855 cm-1 are assigned to the (AsO3OH)2- ν3 antisymmetric stretching and ν1 symmetric stretching vibrational modes. For brassite two similarly assigned intense bands are found at 809 and 862 cm-1. The observation of multiple Raman bands in the (AsO3OH)2- stretching and bending regions suggests that the arsenate tetrahedrons in the crystal structures of both minerals studied are strongly distorted. Broad Raman bands observed at 2842 cm-1 for haidingerite and 3035 cm-1 for brassite indicate strong hydrogen bonding of water molecules in the structure of these minerals. OH…O hydrogen bond lengths were calculated from the Raman spectra based on empiric relations.

Investigation of inclusions trapped inside Libyan Desert glass by Raman microscopy

Several specimens of Libyan Desert Glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species, rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.