Scanning Electron Microscopy Research Papers (original) (raw)

In spite of numerous, substantial advances in equine reproduction, many stages of embryonic and fetal morphological development are poorly understood, with no apparent single source of comprehensive information. Hence, the objective of the present study was to provide a complete macroscopic and microscopic description of the equine embryo/fetus at various gestational ages. Thirty-four embryos/fetuses were aged based on their crown rump length (CRL), and submitted to macroscopic description, biometry, light and scanning microscopy, as well as the alizarin technique. All observed developmental changes were chronologically ordered and described. As examples of the main observed features, an accentuated cervical curvature was observed upon macroscopic examination in all specimens. In the nervous system, the encephalic fourth ventricle and the encephalic vesicles forebrain, midbrain, and hindbrain, were visualized from Day 19 (ovulation ϭ Day 0). The thoracic and pelvic limbs were also visualized; their extremities gave rise to the hoof during development from Day 27. Development of other structures such as pigmented optical vesicle, liver, tail, cardiac area, lungs, and dermal vascularization started on Days 25, respectively. Light and scanning microscopy facilitated detailed examinations of several organs, e.g., heart, kidneys, lungs, and intestine, whereas the alizarin technique enabled visualization of ossification. Observations in this study contributed to the knowledge regarding equine embryogenesis, and included much detailed data from many specimens collected over a long developmental interval.

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- Embryology, Scanning Electron Microscopy, Embryo, Fetal development

Previous studies of hair cell regeneration and hearing recovery in birds after acoustic overstimulation have involved relatively few species. Studies of the effects of acoustic overexposure typically report high variability. Though it is impossible to tell, the data so far also suggest there may be considerable species differences in the degree of damage and the time course and extent of recovery. To examine this issue, we exposed four species of birds (quail, budgerigars, canaries, and zebra finches) to identical conditions of acoustic overstimulation and systematically analyzed changes in hearing sensitivity, basilar papilla morphology, and hair cell number. Quail and budgerigars showed the greatest susceptibility to threshold shift and hair cell loss after overstimulation with either pure tone or bandpass noise, while identical types of overstimulation in canaries and zebra finches resulted in much less of a threshold shift and a smaller, more diffuse hair cell loss. All four species showed some recovery of threshold sensitivity and hair cell number over time. Canary and zebra finch hearing and hair cell number recovered to within normal limits while quail and budgerigars continued to have an approximately 20 dB threshold shift and incomplete recovery of hair cell number. In a final experiment, birds were exposed to identical wide-band noise overstimulation under conditions of artificial middle ear ventilation. Hair cell loss was substantially increased in both budgerigars and canaries suggesting that middle ear air pressure regulation and correlated changes in middle ear transfer function are one factor influencing susceptibility to acoustic overstimulation in small birds. ß 1999 Elsevier Science B.V. All rights reserved. 0378-5955 / 99 / $^see front matter ß 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 -5 9 5 5 ( 9 9 ) 0 0 0 2 2 -2

- by Micheal Dent and +1
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- Scanning Electron Microscopy, Hearing, Noise, Birds

d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 600-607 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a a b s... more

d e n t a l m a t e r i a l s 2 6 ( 2 0 1 0 ) 600-607 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a a b s t r a c t Objectives. Resin-modified glass ionomers (RMGI) have demonstrated clinical success providing immediate and long-term relief from root sensitivity. RMGIs have been recently introduced as paste-liquid systems for convenience of clinical usage. The objective of this study was to measure the ability of a new paste-liquid RMGI to reduce fluid flow through human dentin, compared to an established single-bottle nanofilled total etch resin adhesive indicated for root desensitization.

- by Kelli Agee
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- Engineering, Glass, Scanning Electron Microscopy, Dental Materials

The fabrication of composites formed by alumina grains (95 vol%) in the micrometer size range and aluminium titanate nanoparticles (5 vol%) by reaction sintering of alumina (Al 2 O 3 ) and titania (TiO 2 ) is investigated. The green bodies were constituted by mixtures of sub-micrometric alumina and nano-titania obtained from freeze-drying homogeneous water based suspensions, and pressing the powders. The optimization of the colloidal processing variables was performed using the viscosity of the suspensions as control parameter. Different one step and two step sintering schedules using as maximum dwell temperatures 1300 and 1400 8C were established from dynamic sintering experiments. Specimens cooled at 5 8C/min as well as quenched specimens were prepared and characterized in terms of crystalline phases, by X-ray diffraction, and microstructure by scanning electron microscopy of fracture surfaces.

- by Isabel Santacruz and +1
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- Engineering, Scanning Electron Microscopy, Ceramics, Cooling Rate

Direct foaming of colloidal suspensions is a simple and versatile approach for the fabrication of macroporous ceramic materials. Wet foams produced by this method can be stabilized by longchain surfactants or by colloidal particles. In this work, we investigate the processing of particle-stabilized wet foams into crack-free macroporous ceramics. The processing steps are discussed with particular emphasis on the consolidation and drying process of wet foams. Macroporous alumina ceramics prepared using different consolidation and drying methods are compared in terms of their final microstructure, porosity, and compressive strength. Consolidation of the wet foam by particle coagulation before drying resulted in porous alumina with a closed-cell structure, a porosity of 86.5%, an average cell size of 35 lm, and a remarkable compressive strength of 16.3 MPa. On the other hand, wet foams consolidated via gelation of the liquid within the foam lamella led to porous structures with interconnected cells in the size range from 100 to 150 lm. The tailored microstructure and high mechanical strength of the macroporous ceramics can be of interest for the manufacture of bio-scaffolds, thermal insulators, impact absorbers, separation membranes, and light weight ceramics.

Ordered (SBA-15) and disordered (KIL-2) mesoporous silica supports have been synthesized and used for incorporation of titania with different Ti/Si molar ratios (1/2, 1/1, 2/1) via sol–gel impregnation method. Titanium isopropoxide and aqueous titania sol prepared by low-temperature sol–gel processing were used as a source of titania. Characterization by powder X-ray diffraction (XRD), nitrogen sorption measurements, scanning electron microscopy (SEM) and UV–vis–NIR diffuse reflectance spectroscopy (DRS) has been carried out to investigate the chemical framework and morphology of powders. The photocatalytic degradation of isopropanol in the gaseous medium was selected as a probe reaction to test the photoactivity of powders and to verify the potential application of these materials for air remediation. It was found that the titania source, Ti/Si molar ratio and the type of silica support influenced the functional properties of the material, which were evaluated by adsorption capacity and photocatalytic activity in the gas–solid reactor. The adsorption capacity of isopropanol was the highest in the presence of the SBA-15-supported materials. The photoactivity results indicated that the powders which were prepared using SBA-15 as a silica support and a Ti/Si molar ratio of 1/1 were the most active towards isopropanol oxidation monitored in situ by FT-IR spectroscopy.

- by Urška Štangar
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- Engineering, Scanning Electron Microscopy, Titanium, Biological Sciences

In this work, we report on the electrodeposition of ZnO thin films on n-Si (1 0 0) and glass substrates. The influence of the deposition time on the morphology of ZnO thin films was investigated. The ZnO thin films were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDS) and scanning electron microscopy (SEM). The results show a variation of ZnO texture from main (0 0 2) at 10 min to totally (1 0 1) at 15 min deposition time. The photoluminescence (PL) studies show that both UV (∼382 nm) and blue (∼432 nm) luminescences are the main emissions for the electrodeposited ZnO films. In addition, the film grown at 15 min indicates an evident decrease of the yellow-green (∼520 nm) emission band comparing with that of 10 min. Finally, transmittance spectra show a high transmission value up to 85% in the visible wavelength range. Such results would be very interesting for solar cells applications.

- by Nadia Ahmed
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- Materials Science, Solar Cell, Scanning Electron Microscopy, Multidisciplinary

To prepare miscible polyethylene glycol diacrylate/polyvinylidene fluoride ͑PEGDA/PVdF͒ blend gel polymer electrolytes, low molecular weight (M ϭ 742) liquid PEGDA oligomer was mixed with PVdF-HFP dissolved in ethylene carbonate/dimethyl carbonate/LiPF 6 liquid electrolytes, and then cured under ultraviolet irradiation. Room temperature conductivity of PEGDA/PVdF blend films was found to be comparable to that of PVdF-HFP gel polymer electrolytes, and they were electrochemically stable up to 4.6 V vs. Li/Li ϩ. Scanning electron micrographs revealed that PEGDA/PVdF blend electrolytes have pore size intermediate between dense PEGDA and highly porous PVdF-HFP. It was confirmed by weight change measurement that liquid electrolyte was likely to evaporate through large pores in PVdF-HFP at 80°C, while PEGDA/PVdF blend showed better liquid electrolyte retention ability. This result was in good agreement with more stable interfacial properties of PEGDA/PVdF blend at 80°C in ac impedance analysis. Consequently, both PVdF-HFP and PEGDA/PVdF gel polymer electrolytes delivered similar discharge capacity at room temperature, but PEGDA/PVdF blend gel polymer electrolyte showed much better cycle performance than pure PVdF-HFP at 80°C.

- by Hester Vismer
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- Medical Microbiology, Scanning Electron Microscopy, Medical Mycology, South Africa

Aim To evaluate marginal seal, water sorption, solubility and loss of mass after brushing of several temporary filling materials.Methodology For marginal seal, Class I cavities, including endodontic access preparations, were made in human molar teeth and restored using one or other of several temporary filling materials (n = 10): zinc oxide/calcium sulphate-based cement (Cavit, 3M,ESPE, St. Paul, MN, USA), zinc oxide/eugenol cement (IRM, Dentsply Caulk, Milford, DE, USA), glass ionomer cement (Vidrion R, SSWhite, Rio de Janeiro, RJ, Brazil) or a dimethacrylate-based filling (Bioplic, Biodinâmica, Londrina, PR, Brazil). Dye penetration was assessed after thermocycling and immersion in 0.5% basic fuchsine solution. For water sorption, solubility and loss of mass analyses, disc-shaped specimens were made. Water sorption and solubility were evaluated by mass alteration after storage in distilled water for 7 days (n = 7). Loss of mass was calculated based on the difference of mass after abrasion with a toothbrush (n = 5), and surfaces were analysed by SEM. Data of water sorption, solubility and loss of mass were submitted to anova and Tukey’s test, and marginal sealing data to Kruskal–Wallis test (P < 0.05).Results Statistically significant differences were observed for marginal sealing (P < 0.0001), water sorption (P < 0.01), solubility (P < 0.01) and loss of mass (P < 0.05). Bioplic had the best marginal seal. Cavit had the greatest water sorption and solubility. Vidrion R and Bioplic had the lowest solubility. Loss of mass after brushing was higher for Cavit, followed by Bioplic, IRM and Vidrion R. Cavit and Vidrion R were worn aggressively by brushing.Conclusions The resin-based temporary filling Bioplic produced the best marginal seal, and was associated with the lowest water sorption, solubility and loss of mass.

- by Rafael rodrigues moraes
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- Dentistry, Water, Scanning Electron Microscopy, Adsorption

The complex Co 2 (CO) 6 [l-g 2 -(H 3 CC"CCH 2 CH 2 OH)] (1) with the ligand 3-pentyn-1-ol (pol) has been synthesized following established procedures. Its structure has been determined by X-ray analysis. The complex Co 2 (CO) 6 (mbo) (mbo = 2-methyl-3-butyn-2-ol, HC"CC(CH 3 ) 2 OH), (3), along with the already known Co 2 (CO) 6 (bud) (bud = 1,4-butyn-diol, HOCH 2 C"CCH 2 OH) (2), and Co 2 (CO) 8 were reacted with 2(diphenylphosphino)ethyl-triethoxysilane [Ph 2 PCH 2 CH 2 Si(OCH 2 CH 3 ) 3 ] (dpts) and tris(hydroxymethyl)phosphine [P(CH 2 OH) 3 ] (thp). With dpts, mono-and di-substituted complexes were obtained: these were characterized by analytical and spectroscopic techniques. The structures of Co 2 (CO) 6 (dpts) 2 (5) and of Co 2 (CO) 4 -(pol)(dpts) 2 (8) have been determined by X-ray analysis.

- by Fabio Carniato and +1
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- Inorganic Chemistry, Organic Chemistry, Scanning Electron Microscopy, Organometallic Chemistry

Response surface methodology (RSM) was used to optimize the conditions for the production of endo ␤-1,4 glucanase, a component of cellulase by Aspergillus nidulans MTCC344 under solid state fermentation, using bagasse as the chief substrate. A four-factor-five-level central composite design was employed for experimental design and analysis of the results. Maximum cellulase activity (CMCase was 28.96 U g −1) can be attained at the optimum conditions, 16.8 mm bagasse bed height, 60% moisture content, pH 4.25 and temperature 40 • C in the solid state fermenter. These data were rather close to the experimental results obtained (CMCase was 28.84 U g −1). A. nidulans MTCC344 was able to hydrolyze pretreated bagasse completely after 8 days of incubation with significant endo ␤-1,4 glucanase activities. The results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) of bagasse showed structural changes through pretreatment, in favor of enzymatic hydrolysis. Bagasse with alkali pretreatment using sodium hydroxide is a source of lignocelluloses able to improve the yield of endo ␤-1,4 glucanase by the strain of A. nidulans. The endo ␤-1,4 glucanase produced during the bioconversion of cellulose to glucose by A. nidulans MTCC344 is strongly dependent on the pretreatment given before hydrolysis.

Biological and technical failures of implants have already been reported. Mechanical factors are certainly of importance in implant failures, even if their exact nature has not yet been established. The abutment screw fracture or loosening represents a rare, but quite unpleasant failure. The aim of the present research is an analysis and structural examination of screw thread or abutment loosening compared with screw threads or abutment without loosening. The loosening of screw threads was compared to screw thread without loosening of three different implant systems; Branemark (Nobel Biocare, Gothenburg, Sweden), T.B.R. implant systems (Benax, Ancona, Italy) and Restore (Lifecore Biomedical, Chaska, Minnesota, USA). In this study broken screws were excluded. A total of 16 screw thread loosenings were observed (Group I) (4 Branemark, 4 T.B.R and 5 Restore), 10 screw threads without loosening were removed (Group II), and 6 screw threads as received by the manufacturer (unused) (Group ...

In the treatment of photoaged skin, glycolic acid works by removing superficial portions of the epidermis and stimulating dermis regeneration. Vitamins A, C, and E should stimulate collagen production and antioxidants should prevent free radical damage and skin aging. However, the effectiveness of different therapies has often relied on subjective methods of assessment. Histologic analysis has seldom been used because of the drawback of permanent scarring. In the literature, the use of a quantitative method for the assessment of facial rejuvenation has been described: the silicone replica technique. The authors' aim was to promote and recommend the use of this technique and, in particular, to test the effect of glycolic acid and multivitamin- and antioxidant-based products on skin texture. The authors performed a prospective, randomized, double-blind, controlled study on 30 women treated topically in the outer canthal region (crow's-feet area). Patients were divided into thr...

The aim of this work was to formulate sodium alginate nanospheres of amphotericin B by controlled gellification method and to evaluate the role of the nanospheres as a "passive carrier" in targeted antifungal therapy. Methods: Sodium alginate nanospheres of amphotericin B were prepared by controlled gellification method, and the particle size analysis was carried out by scanning electron microscopy. The carrier capacity of sodium alginate was evaluated in terms of drug to polymer ratio. In vitro release study was carried out on all drug loaded nanospheres by the dialysis method. Release kinetics of drug from different drug loaded nanospheres was also determined. The in vivo antifungal efficacy of nanospheres bound drug vis-à-vis the free drug was evaluated in candidiasis-induced mice models. Results: Preparation of nanospheres through controlled gellification method yielded particles with a size range of 419.6 ± 0.28 nm. Studies on drug to polymer ratio showed a linear relationship between concentration of drug and drug loading capacity. In vitro release kinetic study revealed that the release of drug from the nanospheres followed Fickian diffusion. In vivo studies showed that the nanospherebound drug produced a higher antifungal efficacy than the free drug. Conclusion: The formulated sodium alginate nanospheres containing amphotericin B was found to have better antifungal activity when compared to the free drug and also yielded sustained in vitro release.

N-acetyl-β-D-hexosaminidase was purified from wheat bran and characterized. The purified enzyme showed two protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with molecular mass of 75 and 78 kDa. The enzyme exhibited optimum pH and temperature at 5.0 and 50 o C, respectively. The enzyme was active on the substrates of p-nitrophenyl-Nacetyl-β-D-glucosaminide (pNP-GlcNAc) and p-nitrophenyl-Nacetyl-β-D-galactosaminide (pNP-GalNAc), whereas inactive on pNP-β-D-glucopyranoside, pNP-β-D-galactopyranoside, swollen chitin, and colloidal chitin, suggesting high substrate specificity. The enzyme activity for pNP-GlcNAc was stable at pH 3-6 and under 50 o C. The K m , V max and K cat for pNP-GlcNAc were 0.014 mM, 0.05 µmol/min, and 3.01×10 6 min −1 , respectively. The enzyme could be completely inhibited at 1-10 mM HgCl 2 and AgNO 3, suggesting that the intact thiol group is essential for activity. β-N-Acetylhexosaminidase from wheat bran could inhibit the conidial germination and digest the hyphae of Fusarium solani.

- by Hans Salinas
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- Engineering, Genetics, Microbiology, Organic Chemistry

CaP ceramic has been widely used as coating on metals in orthopedics and oral dentistry. Variations in CaP composition can lead to different dissolution/precipitation behavior and may also affect the bone response. In the present study calcium pyrophosphate and hydroxylapatite coatings were successfully prepared by RF magnetron sputtering deposition. The phase composition, morphological properties, and the dissolution in SBF were characterized by using XRD, FTIR, EDS, SEM, and spectrophotometry. The results showed that all the sputtered coatings were amorphous and changed into a crystal structure after IR-radiation. The temperature for the crystallization of the amor-phous coatings is lower for the hydroxylapatite coating (550°C), compared to the calcium pyrophosphate coating (650°C). All sputtered amorphous coatings were instable in SBF and dissolved partially within 4 wks of incubation. The heat-treated coatings appeared to be stable after incubation. These results showed that magnetron sputtering of calcium pyrophosphate coating is a promising method for forming a biocompatible ceramic coating.

- by Joop Wolke
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- Engineering, Scanning Electron Microscopy, Biological Sciences, Crystal structure

Nanocrystalline zinc oxide-thin films have drawn the attention of researchers due to its attractive properties like transparency in visible region, abundance in nature and gas sensitivity. Nanostructured Zinc oxide (ZnO) thin films were grown on silicon, alumina and glass substrates at various substrate temperatures using a 6 kW electron beam evaporation technique. The effects of film thickness, growth temperature and substrate on the crystallinity of deposited ZnO films were investigated using X-ray diffraction, scanning electron microscopy, optical absorption and photoluminescence studies. Our studies show that good quality films are obtained for silicon substrate for a growth temperature of 2508 8 8 8 8C. Film thickness plays an important role on the evolution of the nanostructures. SEM studies combined with XRD analysis reveal that ultrathin nanorods are grown with (002), (101) and (102) orientations. All the ZnO films show room temperature photoluminescence emission bands at 394 nm and 468 nm. Optical absorption studies show strong absorption at 377 nm. Details of the structure and optical properties correlation will be presented and potential of a simple technique such as e-beam deposition to grown ZnO nanostructures suitable for optoelectronic application will be assessed.

- by Dr. Keyur Patel
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- Inorganic Chemistry, Scanning Electron Microscopy, Nanotechnology, Zinc Oxide

HDPE Aspergillus tubingensis VRKPT1 Aspergillus flavus VRKPT2 Fourier transformed infra-red spectroscopy Scanning electron microscopy a b s t r a c t High density polyethylene (HDPE) is the most commonly found non-degradable solid waste among the polyethylene. In this present study, HDPE degrading various fungal strains were isolated from the polyethylene waste dumped marine coastal area and screened under in vitro condition. Based on weight loss and FT-IR Spectrophotometric analysis, two fungal strains designated as VRKPT1 and VRKPT2 were found to be efficient in HDPE degradation. Through the sequence analysis of ITS region homology, the isolated fungi were identified as Aspergillus tubingensis VRKPT1 and Aspergillus flavus VRKPT2. The biofilm formation observed under epifluorescent microscope had shown the viability of fungal strains even after one month of incubation. The biodegradation of HDPE film nature was further investigated through SEM analysis. HDPE poses severe environmental threats and hence the ability of fungal isolates was proved to utilize virgin polyethylene as the carbon source without any pre-treatment and pro-oxidant additives.

- by Robert Antony
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- Biofilms, Carbon, Scanning Electron Microscopy, Multidisciplinary

Ahs~ract-Morphological studies on graphite surfaces by scanning electron microscopy are presented for tubes made from total pyrolytic graphite (TPG). The inner surface of TPG tubes was found to be fairly rough due to adhering residues of the polycrystalline electrographite substrate on which they were deposited. These residues were vaporized on subsequent dry heating of the tube and recondensed on the tube surface in the form of nodules and flakes. The residues disappeared entirely when the tube was heated with an analyte solution. All experiments were continued for about 550 atomization cycles, and all tubes appeared to be in good condition at that point. The sensitivity for vanadium in dilute nitric acid and for molybdenum in iron, however, had decreased by about 50% during the experiment. The signal for phosphorus in the presence of lanthanum as the modifier disappeared almost entirely and that for copper in perchloric acid was very erratic throughout the experiment. However, it was not always possible to correlate a change in analytical performance with a visible corrosion pattern. The absence of any secondary carbon coating on the inner surface of the TPG tubes was considered to be the main reason for the inconsistency of analytical signals. Primary faults caused by irregular crystal growth were found to be the most likely locations for corrosive attack. Delamination, exfoliation and pitting were the types of corrosion found in all tubes, the extent, however, was dependent on the matrix used in a particular experiment.

The prominent nitric oxide (NO) donor [Ru(terpy)(bdqi)NO](PF 6 ) 3 has been synthesized and evaluated with respect to noteworthy biological effects due to its NO photorelease, including vascular relaxation and melanoma cell culture toxicity. The potential for delivering NO in therapeutic quantities is tenable since the nitrosyl ruthenium complex (NRC) must first reach the "target tissue" and then release the NO upon stimulus. In this context, NRC-loaded lipid carriers were developed and characterized to further explore its topical administration for applications such as skin cancer treatment. NRC-loaded solid lipid nanoparticles (SLN) and nanostructured lipid carriers were prepared via the microemulsification method, with average diameters of 275 ± 15 nm and 211 ± 31 nm and zeta potentials of −40.7 ± 10.4 mV and −50.0 ± 7.5 mV, respectively. In vitro kinetic studies of NRC release from nanoparticles showed sustained release of NRC from the lipid carriers and illustrated the influence of the release medium and the lyophilization process. Stability studies showed that NO is released from NRC as a function of temperature and time and due to skin contact. The encapsulation of NRC in SLN followed by its lyophilization, significantly improved the complex stability. Furthermore, of particular interest was the fact that in the NO photorelease study, the NO release from the NRC-loaded SLN was approximately twice that of just NRC in solution. NRC-loaded SLN performs well enough at releasing and protecting NO degradation in vitro that it is a promising carrier for topical delivery of NO.

- by Renata Fonseca Vianna Lopez and +1
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- Analytical Chemistry, Kinetics, Photochemistry, Scanning Electron Microscopy

The aim of the present study was to prepare, optimize and characterize ketoprofen proniosomes. The niosomes were prepared using a slurry method followed by in vitro evaluation after embedding the proniosomes-derived niosomes into a carbopol matrix. A central, composite Box-Wilson design was used for the optimization with the total lipid concentration (X 1 ), surfactant loading (X 2 ) and amount of drug (X 3 ) as the independent variables. Prepared proniosomes were characterized for percentage drug entrapment (PDE) and mean volume diameter (MVD). Multiple regression analysis and contour plots were used to relate the dependent and independent variables. Checkpoint batches were also prepared to prove the validity of the evolved mathematical model and contour plots. The optimization model predicted the levels of X 1 , X 2 and X 3 (-1, -0.3 and 0.92, respectively), for a maximized response of PDE with constraints of ≤ 5 μm on MVD. Optimized batch was used to prepare a niosomal gel, which showed significantly higher cumulative amount of drug permeated and steady state transdermal flux compared to plain gel. This work has demonstrated the use of the central composite Box-Wilson design, regression analysis, and contour plots in optimizing ketoprofen proniosomes. Developed niosomal gel formulation has also demonstrated permeation enhancement of ketoprofen compared to plain gel.

- by Craig Bunt
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- Engineering, Chemical Engineering, Analytical Chemistry, Biomedical Engineering

The mechanical properties of reinforced thermoplastics depend on such characteristics of the filler as granulometry, orientation and dispersion. These d@erent microtextural parameters were determined by using a single tool: image analysis, which was coupled with optical and electron microscopies. The dtflerent materials tested were based on polypropylene obtained by extrusion and injection steps. For the deferent samples analysed, the processing conditions and the filler concentration were constant, and variability was due to the dtflerent average lengths of the$ller incorporated in the matrix. The dtrerent filler parameters were determined with particular emphasis on the techniques of dispersion characterisation. The techniques developed in this study were based on image analysis. They enabled us to estimate filler-size distribution and development of the three-dimensional orientation inside the material and between direrent samples. The development of the filler dispersion was also made apparent. In addition, the relationships obtained between the direrent microtextural parameters were investigated. The general conclusion is that image analysis is very suitable for characterisation of this kind of material. 0 1998 Elsevier Science Ltd. All rights reserved

- by Luc Avérous and +1
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- Engineering, Electron Microscopy, Image Analysis, Scanning Electron Microscopy
- by Brian Sommerlad
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- Scanning Electron Microscopy, Adolescent, Pediatric Surgery, Connective tissue

SnS is of interest for use as an absorber layer and the wider energy bandgap phases e.g. SnS 2 , Sn 2 S 3 and Sn/S/ O alloys of interest as Cd-free buffer layers for use in thin film solar cells. In this work thin films of tin sulphide have been thermally evaporated onto soda-lime glass substrates with the aim of optimising the properties of the material for use in superstrate configuration device structures. The thin films were characterised using energy dispersive X-ray analysis (EDS) to determine the film composition, X-ray diffraction (XRD) to determine the phases present and structure of each phase, transmittance versus wavelength measurements to determine the energy bandgap and scanning electron microscopy (SEM) to observe the surface topology and topography. These properties were then correlated to the deposition parameters. Using the optimised conditions it is possible to produce thin films of tin sulphide that are pinhole free and conformal to the substrate that are suitable for use in thin film solar cell structures.

- by Ian Forbes
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- Engineering, Materials Science, Technology, Solar Cell

Scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) is a widely applied elemental microanalysis method capable of identifying and quantifying all elements in the periodic table except H, He, and Li. By following the "k-ratio" (unknown/standard) measurement protocol development for electron-excited wavelength dispersive spectrometry (WDS), SEM/EDS can achieve accuracy and precision equivalent to WDS and at substantially lower electron dose, even when severe X-ray peak overlaps occur, provided sufficient counts are recorded. Achieving this level of performance is now much more practical with the advent of the highthroughput silicon drift detector energy dispersive Xray spectrometer (SDD-EDS). However, three measurement issues continue to diminish the impact of SEM/EDS: (1) In the qualitative analysis (i.e., element identification) that must precede quantitative analysis, at least some current and many legacy software systems are vulnerable to occasional misidentification of major constituent peaks, with the frequency of misidentifications rising significantly for minor and trace constituents. (2) The use of standardless analysis, which is subject to much broader systematic errors, leads to quantitative results that, while useful, do not have sufficient accuracy to solve critical problems, e.g. determining the formula of a compound. (3) EDS spectrometers have such a large volume of acceptance that apparently credible spectra can be obtained from specimens with complex topography that introduce uncontrolled geometric factors that modify X-ray generation and propagation, resulting †This article is a U.S. government work and, as such, is in the public domain in the United States of America.

Crystalline Cd(OH) 2 /CdCO 3 nanowires, having lengths in the range from 0.3 up to several microns and 5-30 nm in diameter, were synthesized by a microwave-assisted wet chemical route and used as a precursor to obtain CdO nanostructures after a suitable thermal treatment in air. The morphology and microstructure of the as-synthesized and annealed materials have been investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and thermogravimetry-differential scanning calorimetry. The change in morphology and electrical properties with temperature has revealed a wire-to-rod transformation along with a decreases of electrical resistance.

- by A. Stassi and +1
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- Carbon Dioxide, Scanning Electron Microscopy, Transmission Electron Microscopy, Nanotechnology

Electrospinning was utilized to create lightweight, electrically responsive wing skins for micro-air vehicle (MAV) wing frame designs. Various compositions of an electroactive polymer were investigated to determine the appropriate electrospinning conditions for these materials. Electrospun mats of these materials were characterized via optical microscopy and scanning electron microscopy. Tensile properties of the electrospun fibers were also measured. An optimal polymer composition was electrospun onto MAV wing frames to create a bird wing-like texture. Preliminary testing of electroactivity of these prototype MAV wings is reported here. q

- by poovizhi paramasivam
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- Engineering, Scanning Electron Microscopy, Polymer, Optical microscopy

Ultrastructural Studies of Conidiogenesis of Ascochyta rabiei, the Causal Organism of Chickpea Blight EJ. Singh, a Mahendra Pal 2 and Nam Prakash a Studies employing transmission (TEM) and scanning (SEM) electron microscopy revealed that conidiogenous cells of the chickpea blight fungus, Ascochyta rabiei (Pass.) Labr., resembled phialides in most of their features. The phialides were generally of a simple type, but occasionally they proliferated in a percurrent fashion. There is enough evidence to suggest that the fungus is better placed in genus Phoma. SEM has been employed for the first time to study internal details of fructifications of a closed type in coelomycete fungi. KEY WORDS: Ascochyta rabiei; chickpea blight; ultrastructure; taxonomy; chickpea; scanning electron microscopy; transmission electron microscopy. however, there are many gaps in our knowledge on the taxonomy of this important pathogen. In deuteromycete taxonomy, recently, emphasis is laid particularly on the mode of conidiogenesis. Development is reported to be phialidic in Phoma spp. but annellidic in Ascochyta spp. (4). Therefore, keeping this developmental aspect in mind, studies were performed under transmission (TEM) and scanning (SEM) electron microscopes to reveal the mode of conidiogenesis in the fungus A. rabiei. MATERIALS AND METHODS Medium The culture of A. rabiei was raised on potato dextrose-chickpea seed-agar medium, PDCA (peeled potatoes, 200 g; dextrose, 20 g; agar-agar, 20 g; water to make 1 l; split chickpea seeds with testa intact, two per test tube), at 20+1~

- by Premjit Singh
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- Electron Microscopy, Plant Biology, Biology, Scanning Electron Microscopy
- by Michael Sela
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- Dentistry, Scanning Electron Microscopy, Polymers, Medicine

Teeth of seven patients from the Brandywine isolate who had dentinogenesis imperfecta (DI) type III were evaluated by clinical, radiologic, and scanning electron microscopic techniques. The deciduous and permanent teeth were opalescent, and there was marked attrition. Enamel pitting was present on some permanent teeth. Anterior open bites were found in all persons with complete permanent dentitions. Pulps of developing teeth were larger than normal during early development but rapidly became almost completely obliterated. There was increased constriction at the cementoenamel junctions. While radiolucencies were noted at the apices of teeth which had pulp exposures due to attrition, several patients had similar radiolucencies which could not be attributed to caries or attrition. Scanning electron microscopy showed a significant reduction in the number of dentin tubules on fractured dentin surfaces; calcospherites at the calcification front were either irregularly shaped or absent. A single tooth from a patient with DI type II was studied and had similar abnormalities on scanning electron microscopy, although tubules were easier to find and calcospherites at the calcification front were more regular than in DI type Ill. The findings in DI type Ill of enamel pitting, enlarged pulps early in tooth development, and radiolucencies at the apices of teeth without pulp exposures support the hypothesis that DI type II and DI type Ill are different disorders.

- by Scott Leaf
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- Scanning Electron Microscopy, Adolescent, Medicine, Oral and Maxillofacial Surgery

We report our investigations on the embryonic development of Gryllus assimilis, with particular attention to the head. Significant findings revealed with scanning electron microscopy (SEM) images include: (1) the pre-antennal lobes represent the anterior-most segment that does not bear any appendages; (2) each of the lobes consists of central and marginal regions; (3) the central region thereof develops into the protocerebrum and the optic lobes, whereas the marginal region thereof becomes the anterior portion of the head capsule; (4) the initial position of the antennal segment is posterior to the mouth region; (5) appendage anlagen are transitorily present in the intercalary segment, and they later vanish together with the segment itself; (6) a bulged sternum appears to develop from the ventral surface of the mandibular, maxillary and labial segments. Embryonic features are then compared across the Insecta and further extended to the embryos of a spider (Araneae, Chelicerata). Striking similarities shared by the anterior-most region of the insect and spider embryos lead the authors to conclude that such comparison should be further undertaken to cover the entire Euarthropoda. This will help us to understand the embryology and evolution of the arthropod head.

- by Dieter Waloszek
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- Zoology, Embryology, Biology, Scanning Electron Microscopy

In the past several years, there has been a trend in the sunscreen/ cosmetics industry to replace micron-sized titanium dioxide (TiO 2) particles with nanoscale materials. The increased use of nanoscale TiO 2 has resulted in questions about these and other nanoproducts. This study examines the effects of using nanoscale TiO 2 on ultraviolet (UV) attenuation in simple to complex sunscreen formulations. UV light attenuation, product stability, and potential damage to the skin barrier were examined with both nanoscale and microscale TiO 2 particles. Results indicate that none of the formulations decreased the barrier function of the skin and the best UV attenuation occurs when the TiO 2 particles are stabilized with a coating and evenly distributed such as with non-agglomerated coated nanoscale materials. This indicates that nanoscale TiO 2 may have better efficacy while lacking toxicity. Ré sumé Au cours des dernières années, nous avons constaté une tendance dans l'industrie solaire/cosmétique pour le remplacement des particules micron-taille de dioxyde de titane (TiO 2) avec des matériaux de nano-échelle. L'utilisation accrue des particules de TiO 2 l'échelle du nanométre a engendré des questions sur tous les produits contenant des matériaux nano-échelle. Cette étude examine les effets de l'utilisation de particule de TiO 2 a l'échelle du nanomètre sur l'atténuation des rayons UV dans les formulations de crème solaire simple et complexe. Nous avons étudié l'atténuation de la luminosité ultraviolet (UV), la stabilité du produit et les effets sur la fonction barrière de la peau, avec les particules de TiO 2 nano-échelle et micro-échelle. Les résultats indiquent que les particules a l'échelle du nanométre, enduits et non-aggloméré, fournissent une excellente atténuation UV, sans diminuer la fonction barrière de la peau. Ceci suggére que les particules de TiO 2 a l'échelle du nanométre ont une meilleure efficacité, sans poser des inquiétudes en ce qui concerne leur securité.

- by Bill Doub
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- Nanoparticle, Scanning Electron Microscopy, Morphology, Titanium

Phosphate-based glasses have been examined in many studies as a potential biomaterial for bone repair because of its degradation properties, which can be controlled and allow the release of various elements to promote osteogenic tissue growth. However most of these experiments studied either tertiary or quaternary glass systems. This study investigated a qinternary system that included titanium dioxide for degradation rate control and zinc that is considered to have a role in bone formation. Zinc and titanium phosphate glass discs of different compositions were melt synthesized and samples of each composition was tested for different physical, chemical and biological characteristics via density measurement, X-ray diffraction, differential thermal analysis, mass loss, ion release, scanning electron microscopy, biocompatibility studies via live/dead assays at three time points (day 1, 4, and 7). The results showed that the glass was amorphous and that the all thermal variables decreas...

Uroplakins, cytokeratins and the apical plasma membrane were studied in the epithelia of mouse urinary tract. In the simple epithelium covering the inner medulla of the renal pelvis, no uroplakins or cytokeratin 20 were detected and cells had microvilli on their apical surface. The epithelium covering the inner band of the outer medulla became pseudostratified, with the upper layer consisting of large cells with stalks connecting them to the basal lamina. Uroplakins and cytokeratin 20 were not expressed in these cells. However, some superficial cells appeared without connections to the basal lamina; these cells expressed uroplakins Ia, Ib, II and III and cytokeratin 20, they contained sparse small uroplakin-positive cytoplasmic vesicles and their apical surface showed both microvilli and ridges. Cytokeratin 20 was seen as dots in the cytoplasm. This epithelium therefore showed partial urothelial differentiation. The epithelium covering the outer band of the outer medulla gradually changed from a twolayered to a three-layered urothelium with typical umbrella cells that contained all four uroplakins. Cytokeratin 20 was organized into a complex network. The epithelium possessed an asymmetric unit membrane at the apical cell surface and fusiform vesicles. Umbrella cells were also observed in the ureter and urinary bladder. In males and females, the urothelium ended in the bladder neck and was continued by a non-keratinized stratified epithelium in the urethra in which no urothelial cell differentiation markers were detected. We thus show here the expression, distribution and organization of specific proteins associated with the various cell types in the urinary tract epithelium.

- by Rok Romih
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- Scanning Electron Microscopy, Immunohistochemistry, Cell Differentiation, Mice

Acid mine drainage (AMD) – characterized by high acidity and elevated sulfate and metal concentrations – represents a big environmental concern. Biological sulfate reduction has become an alternative to the classical physicochemical methods. In this study, domestic wastewater (DW) was tested as a cost-effective carbon-source for the remediation of AMD. Sediments from Tinto River, an extreme acidic environment with an elevated concentration of metals, were used as inoculum. Three anaerobic bioreactors with different microbial supports were fed with a 1:10 (v:v) mixture of synthetic AMD:DW. Around 50% of the organic matter present in the DW co-precipitated with the metals from the AMD previous to feeding the reactor. Therefore, the reactors had to be supplemented with an extra carbon-source (acetate) to achieve higher S elimination. Elevated removal efficiencies of chemical oxygen demand (COD) (>88%), sulfate (>75%), Fe (>85%) and other dissolved metals (>99% except for Mn...

Joining of dissimilar materials is of increasing interest for a wide range of industrial applications. The automotive industry, in particular, views dissimilar materials joining as a gateway for the implementation of lightweight materials. Specifically, the introduction of aluminum alloy parts into a steel car body requires the development of reliable, efficient and economic joining processes. Since aluminum and steel demonstrate

In order to overcome the high price, weight and volume of non-porous graphite bipolar plates, metallic bipolar plates are being investigated as a substitute material. However, metallic materials can corrode under proton exchange membrane fuel cell (PEMFC) working conditions, leading to a degradation in the performance of the membrane. Previous work had shown that a polypyrrole coating on SS316L can significantly increase the corrosion resistance of the base material. In this study, a Taguchi design of experiment method was used to optimize the process parameters for the polypyrrole coating so as to produce the maximum corrosion resistance. Potentiodynamic and potentiostatic tests were used to determine the corrosion resistance of the polypyrrole-coated SS316L. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) was used to characterize the coating thickness and coating appearance. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to determine the metal ion concentration in the solution after corrosion. The interfacial contact resistance of SS316L with carbon paper was measured both before and after coating with polypyrrole.

- by D. Northwood
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- Engineering, Performance, Scanning Electron Microscopy, Corrosion

The fabrication, evaluation and attractive performance of multiwall carbon nanotube(MWCNT)/ polysulfone biocomposite membrane modified thick-film screen-printed electrochemical biosensors are reported. The fabricated carbon nanotube/polysulfone (CNT/PS) strips combine the attractive advantages of carbon nanotube materials, polysulfone matrix and disposable screen-printed electrodes. Such thick-film carbon nanotubes/polysulfone sensors have a well defined performance, are mechanically stable, and exhibit high electrochemical activity. Furthermore, biocompatibility of CNT/PS composite allows easy incorporation of biological functional moiety of horseradish peroxidase by phase inversion technique. The comparison of graphite with MWCNT as conductor material is described in this paper. The proposed H 2 O 2 biosensor exhibited a linear range (applied potential, 20.2 V) from 0.02 to 0.5 mM and a K M app of 0.71 mM.

Background: The effectiveness of aerosol therapy is significantly reduced by the mucus layer covering the airways of the tracheobronchial tree. According to the present concept, drug particles are delivered to the lung together with the functional carrier particle that facilitates both the drug transport into the lungs and the penetration of deposited particles through the mucus. The approach of manufacturing multicomponent powders with mucoactive compounds and anti-asthmatic medicines (DSCG) bound together in a single particle is additionally considered. Methods: Powders were produced with the spray-drying technique from aqueous precursor solutions containing pure low molecular weight dextran, pure mannitol and dextran/mannitol-N-acetyl cysteine (NAC) mixtures (4:1 and 1:1). NAC has been selected for this purpose as a compound, which is known to be mucolytic. Dextran and mannitol are potentially applicable in the field of inhalation drug delivery. They have been used as stabilizers of functional carrier particles. Powders were characterized for their yield and physicochemical properties including: morphology (SEM), moisture content and thermal properties (DSC). Aerosol performance was determined with NGI impactor after standardized aerosolization of the produced powders in a commercial DPI. Results: Particle size distributions of dextran-NAC powders were characterized by high fine particle fraction (45-62%), which assures good particle deposition in the lower airways. The thermodynamic properties of the powders based on the temperature of the glass transition T g (50-63 • C) suggest the required stability during storage at moderate humidity. Conclusions: Preliminary examination of the required properties of these particles confirms their potential as functional carriers for pulmonary drug delivery.

- by Tomasz Sosnowski
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- Thermodynamics, Scanning Electron Microscopy, Aerosols, Pharmaceutics

A new approach for studying the effect of temperature on anodic oxide growth on aluminium is presented in this paper. Using an in-house developed electrode holder, anodizing is performed under conditions of applied and controlled electrode temperature. The influence of temperature on the process is evaluated by experiments in a broad temperature range for both the electrode and the electrolyte temperature. The electrochemical behaviour of the aluminium electrodes is demonstrated to be more susceptible to variations of the electrode temperature than to variations of the electrolyte temperature. Concerning the morphology of the anodic film it is shown that by cooling the electrode a normal oxide layer could be grown at high electrolyte temperatures, whereas anodizing in a cool electrolyte at high electrode temperature results in a collapsed porous structure at the oxide surface. Furthermore, the electrode temperature affects the formation ratio of the oxide to a larger extent than the electrolyte temperature, indicating its important influence even on the level of the ionic conductivity during anodic oxide growth. All observations indicate that merely considering the electrolyte temperature upon studying the influence of temperature on the process is not sufficient; the electrode temperature is much more determining.

- by Jean-baptiste Jorcin
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- Engineering, Scanning Electron Microscopy, Morphology, Comparative Study

One of the current challenges for application of PEM fuel cell is to find corrosion resistant, electrically conductive, light weight, cost competitive bipolar plate material. Low temperature carburization (LTC) of stainless steels is a novel, patented process by Swagelok Company. This paper addresses the corrosion resistance characteristics of LTC SS 316 for polymer electrolyte membrane fuel cell (PEMFC) bipolar plate applications. Corrosion properties of this material were studied using potentiodynamic and potentiostatic tests in simulated (1 M H 2 SO 4 + 2 ppm HF, 0.5 M H 2 SO 4 , pH: 4.0, and 5% HCl + 5% Na 2 SO 4) PEMFC conditions. LTC SS 316 showed excellent corrosion resistance in these conditions compared to SS 316. The mechanism of anodic dissolution and general corrosion of LTC SS 316 was observed to be similar to SS 316 however the extent of LTC SS 316 corrosion was less. LTC SS 316 showed corrosion currents well below 16 A cm −2 in anodic and cathodic atmospheres under potentiostatic conditions. The potentiostatic current rapidly falls to ∼4.0 and ∼1.5 A cm −2 under anodic and cathodic conditions, respectively. LTC SS 316 was observed to form a thinner oxide layer as compared to SS 316 after 24 h of potentiostatic testing. Moreover LTC SS 316 lowered the interfacial contact resistance by approximately 24% as compared to SS 316 after corrosion testing. Hence this study clearly states the performance advantage of using LTC SS 316 as bipolar plate material as compared to conventional materials.

- by Gerhard Schiroky
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- Engineering, Corrosion Science, Scanning Electron Microscopy, Morphology

Embolism is responsible for half of cerebral infarctions, yet few animal models were developed due to the unpredictability of the embolus-induced infarcts. We manufactured artificial embolic particles by blending chitin and poly(D,L-Lactide-co-glycolide) (chitin/PLGA) for their good biocompatibility and rapid hydration expansion property. We subdivided the chitin/PLGA microparticles into 10 size groups (from 38e45 mm to 255e350 mm) and injected them through the external carotid artery toward the bifurcation of the common carotid artery in the rat. Reduced blood flow of the ipsilateral hemisphere was evident immediately after the injection of particles. The spherical appearance of the particle was critical in occluding the cerebral vessels. Particle 212e250mm produced the greatest diffuse infarction in the ipsilateral hemisphere, including the cortex, hippocampus, basal ganglion, thalamus, midbrain and cerebellum. Particle 75-90mm induced single or sparse isolated infarcts mainly located in the subcortical region, resembling lacunar stroke observed in humans. Particle 38e45mm frequently crossed to the contralateral hemisphere and induced diffuse infarctions in both hemispheres. The cortex infarct volumes were positively correlated to neurologic score and seizure incidence. In conclusion, we have established embolic stroke animal models, including a novel model that mainly expresses lacunar infarction, by intravenous injection of chitin/PLGA microparticles.

- by Yu-min Kuo
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- Biomaterials, Scanning Electron Microscopy, Multidisciplinary, Stroke

Epiphytic lichens are efficient air pollution bio monitors as they obtain nutrients, water and pollutants from the atmosphere. The aim of this study was at analyzing the surface of hyphae and the surface of the lichens Evernia prunastri (unwashed and washed in distilled water). Mass percentage of 26 selected elements: C, O, Na, Mg, Al, Si, P, S, Cl, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Sn, Sb, Hg, Pb and Bi was determined by scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS). Mass percentage of: Na, Mg, V, Cr, Mn, Co, Ni, Zn, As, Cd, Sn, Sb, Hg, Pb was below the limit of detection of the applied method. The mass percentage of all other determined elements on the hyphae and surface of lichen was higher in unwashed samples, except for C, O, P, Fe, Cl, Ca and Cu. The elemental analysis of the unwashed lichen surface showed the prevalence of: O, C, Si, Cu and
Bi. Results obtained in the unwashed and washed lichen samples showed that the cleaning with water can be used in order to eliminate adhering materials. Indeed, most of elements of interest for the environmental contamination accumulated by the lichens were not
removed. SEM images showed particles that are flat, with irregular shape and edges, generally smooth and rounded indicating that the particles deposited were dry aerosol particles.

We aimed to compare the apical sealing ability of two experimental retrograde root-filling cements and mineral trioxide aggregate using a fluid filtration method. X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF) were used to evaluate structural and qualitative characteristics. Thirty single-rooted extracted teeth were treated, root-end prepared, and obturated using MTA and two experimental cements. Fluid filtration was measured during a 5-minute period after 4, 24, and 48 hours and 1, 2, and 12 weeks. The results were statistically compared by using a two-way analysis of variance (p Ͻ 0.05). The marginal adaptation was evaluated by using a SEM replica technique. XRD analyses showed similar patterns. XRF showed lower amounts of SiO 2 and FeO 3 in the experimental cements. All cements showed a reduced fluid flow rate over time. No significant differences were found between the cements. The SEM replica indicated a good marginal adaptation to dentinal walls. Both experimental cements showed suitable properties as retrograde rootfilling materials. (J Endod 2007;33:742-745)

- by Johan Hoebeke
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- Physiology, Kinetics, Scanning Electron Microscopy, Adsorption

Background: 1E10 monoclonal antibody is a murine anti-idiotypic antibody that mimics N-glycolyl-GM3 gangliosides. This antibody has been tested as an anti-idiotypic cancer vaccine, adjuvated in Al(OH) 3 , in several clinical trials for melanoma, breast, and lung cancer. During early clinical development this mAb was obtained in vivo from mice ascites fluid. Currently, the production process of 1E10 is being transferred from the in vivo to a bioreactor-based method.

- by Adolfo Castillo
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- Engineering, Thermodynamics, Organic Chemistry, Physical Chemistry

The exoskeleton of the lobster Homarus americanus is a multiphase biological composite material which consists of an organic matrix (crystalline α-chitin fibers and various types of non-crystalline proteins) and minerals (mainly calcite). In this study we discuss experimental data about the mesoscopic structure and the crystallographic texture (orientation distribution) of the α-chitin–protein fiber network in this material. The synchrotron measurements reveal very strong crystallographic textures of the α-chitin. According to these data, a large fraction of the α-chitin lattice cells is arranged with their longest axis parallel to the normal of the surface of the exoskeleton. Additionally, a smaller fraction of the α-chitin cells is oriented with their longest axis perpendicular to the cuticle surface. These structural investigations reveal the pronounced role of crystallographic orientation distributions in mineralized biological composite materials which may be of relevance for an improved understanding of biological and bio-inspired nano-composites.

- by Dierk Raabe
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- Materials Engineering, Mechanical Engineering, Materials Science, Crystallography

Epidermal changes caused by a chytridiomycete fungus (Chytridiomycota; Chytridiales) were found in sick and dead adult anurans collected from montane rain forests in Queensland (Australia) and Panama during mass mortality events associated with significant population declines. We also have found this new disease associated with morbidity and mortality in wild and captive anurans from additional locations in Australia and Central America. This is the first report of parasitism of a vertebrate by a member of the phylum Chytridiomycota. Experimental data support the conclusion that cutaneous chytridiomycosis is a fatal disease of anurans, and we hypothesize that it is the proximate cause of these recent amphibian declines.

- by dip putradi
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- Tropical Ecology, Australia, Scanning Electron Microscopy, Population Dynamics