bluuebunny/crossref_metadata_2025 huggingface dataset:
A standard video‐rate confocal laser‐scanning reflection and fluorescence microscope
Authors: Draaijer A. , Houpt P. M.
Published: August 2011

A confocal laser‐scanning microscope (CLSM) differs from a conventional microscope by affording an extreme depth discrimination, as well as a slightly improved resolution. These features afford improved imaging, and make possible new imaging techniques. The CLSM developed at TNO has standard video‐rate imaging, and is capable of working in reflection and in fluorescence mode simultaneously. Nonconfocally the laser‐scanning microscope can also be used in transmission mode. In addition to the evident advantages of a fast system when searching objects or studying living objects, the time needed to produce an image of extended depth of focus and high resolution is very short. Furthermore, the high‐speed averaging of many images at low laser‐power levels, and the short dwelling time of the focused laser beam (60 ns) obviate quenching effects in fluorescence microscopy and prevent damage to the object. In this article the TNO‐CLSM system is outlined. The most important specifications are summarized, and some representative micrographs obtained with the system are shown. Furthermore, the performance of the system is illustrated by some experimental results.
Imaging colloidal gold labels in LVSEM
Authors: Pawley J. , Albrecht R.
Published: August 2011

On biological samples, the topographic imaging capabilities of the new generation of scanning electron microscopes (SEM) (those having both field‐emission guns and low aberration lenses) rival those of the replica techniques. In addition, they permit the localization of specific molecules on the sample surface using one of several labeling techniques utilizing heavy metal colloids. Normally, colloidal gold can be detected in the SEM both by the secondary electron signal (shape) and by the backscattered electron signal (BSE, Z‐contrast). The new instruments seem to produce their best topographic images using low‐beam voltage (1–5 kV) where topographic contrast is higher and the required thickness of the metal coating is less (Haggis and Pawley 1988, Ris and Pawley 1988). Although the detection of backscattered electrons is more difficult at low‐beam voltage, we are able to show here that the secondary electron (SE) signal produced with a 2–5‐kV beam permits the unambiguous detection of gold particles as small as 5 nm on carbon‐coated specimens while a 1‐kV beam produces a high‐quality topographic image of the same sample.
Precision metrology of integrated circuit critical dimensions using in situ differential scanning electron microscopy
Authors: Sicignano A. , Vaez‐Iravani M.
Published: August 2011

A technique for performing precision measurements of critical dimensions (CD) on integrated circuit (IC) features using the scanning electron microscope (SEM) is presented. The method is based on obtaining true in situ differential SEM video signals of IC features. The technique is characterized by its high sensitivity to feature edges, and relative slopes. Results are presented on the application of this technique to SEM measurements of IC patterns in silicon, photoresist, and aluminum. The method affords the capability of accurate pattern alignment during SEM imaging preceding linewidth measurements.
Distribution of negative charges on the luminal surface of corneal endothelium
Authors: Gusev S. A. , Povaliyi T. M. , Volobueva T. M. , Zakharchenko V. N.
Published: August 2011

A method of marking the negatively charged sites in pieces of plasmalemma of rabbit corneal endothelium using colloidal nickel is described. The analysis of the distribution of negatively charged domains on the corneal surface was carried out using scanning electron microscopy. The normal distribution of negatively charged sites relative to topography is compared with the change after injecting adrenalin into the anterior chamber of the eye.
Specimen biasing to enhance or suppress secondary electron emission from charging specimens at low accelerating voltages,
Authors: Postek M. T. , Keery W. J. , Larrabee R. D.
Published: August 2011

Biasing of the specimen is shown to produce improved images in the scanning electron microscope at low beam energies (0.8–2.5 keV) when charging effects (induced by the primary electron beam), topographic effects, or detector shadowing effects would otherwise be present. Examples of such improvement are given for gallium arsenide field‐effect transistors (positive charging), patterned photoresist layers on silicon wafers (negative charging and shadowing in contact holes), fractured polymethylmethacrylate (negative charging), polyethylene wrapper material (positive charging), and polished diamond tools (positive charging). It is concluded that specimen biasing may be a simpler and more convenient way to achieve some of the advantages of the converted backscattered secondary electron (CBSE) technique for imaging, but without some of the fundamental disadvantages of that technique. Characterization of this backscattered electron‐derived image bears further investigation for possible metrological applications.
A new technique for imaging hard tissue by photothermal radiometric microscopy
Authors: Sheard S. J. , Boyde A.
Published: August 2011

Thermal wave imaging of hard tissue is demonstrated for the first time using a technique described as photothermal radiometric (PTR) microscopy. Images of human bone and whale dentine suggest that the thermal wave image reveals variations in tissue density and can provide similar information to microradiography or backscattered electron imaging, to which it is now an alternative requiring a minimum of sample preparation.
SEM observations of the sliding behavior of A12O3 and CBN against steel
Authors: Calabrese S. J. , Murray S. F.
Published: August 2011

Both aluminum oxide (A12O3) and cubic boron nitride (CBN) are being used as the abrasive medium in grinding wheels. To compare the effectiveness of these abrasives, a study was made, using the scanning electron microscope (SEM), to observe the sliding behavior and surface damage resulting from single particles of polycrystalline A12O3 and CBN sliding dry against hardened M‐50 tool steel. These experiments were run in the chamber of the SEM, which permitted direct observation of the contact areas at high magnifications. Friction force was monitored and videotape recordings were made continuously during these tests. Significantly lower friction and smoother wear tracks were obtained with the CBN. The A12O3 grit produced much sharper ridges and considerable microcracking on the ridges. These microcracks were formed perpendicular to the wear track. The wear tracks obtained in the SEM were compared with the surfaces produced by surface grinding hardened steel with both CBN and A12O3 wheels. At high magnifications, marked similarities between the ground surfaces and the surfaces produced by the basic sliding tests were noted. It is suggested that because of the large number of microcracks formed during the grinding process with the A12O3, the fatigue life of parts ground with an A12O3 wheel would be shorter than those ground with CBN. Practical experience indicates that this is true.
Increasing the versatility of an EMscope SP2000A sputter cryo system on a Hitachi S‐570 scanning electron microscope
Authors: Wergin W. P. , Erbe E. F.
Published: August 2011

The EMscope SP2000A Sputter Cryo System provides biologists with a quick and reproducible procedure to freeze, fracture, etch, and sputter coat biological samples, which are then transferred to a cold stage for scanning electron microscopic (SEM) observations. The standard specimen holder, which is supplied with the unit and referred to as a “stub,” will accommodate most specimens; however, fabricating a variety of additional holders to perform more specialized functions considerably increases the versatility of the cryounit and the resolution that can be achieved. For example, the adaptation of small hinged or hingeless gold holders, which are used in the freeze‐fracture technique, produces clean fractures, allows for storage of samples in liquid nitrogen and permits samples to be frozen much more rapidly than the large standard holder. A short working distance holder has been designed, which allows samples to be inserted into the final objective lens, thereby resulting in a negative working distance up to −3 mm. Use of this holder with the upper detector in the Hitachi S‐570 SEM, enhances the secondary electron signal and thereby increases resolution of frozen samples severalfold. Another specimen holder has been designed, which allows conventional SEM stubs to be observed without removal of the cryostage. This modification permits use of the EMscope stage and specimen transfer device at room temperature without any further alteration or adjustment. These and other types of modified holders allow investigators to store, manipulate, fracture, and observe biological samples at resolutions not normally attainable with a standard SEM cryostage.
The utility of an on‐line digital image recording system for SEM
Authors: Oho E. , Kanaya K.
Published: August 2011

An on‐line digital image processing system provides several useful functions to SEM users. It is especially convenient for general SEM image storing and filing, preferable to conventional methods using video monitor, camera, and film. When equipped with state‐of‐the‐art magneto‐optical disk unit (external memory) and a video copy processor for printout of a digital SEM image, its usefulness is enhanced. In order to validate this useful function, we compare a modern on‐line digital image recording system with a conventional one, from the viewpoint of the general SEM user.
Characterization of polymer blends and block copolymers by conventional and low voltage SEM
Authors: Himelfarb P. B. , Labat K. B.
Published: August 2011

Methods for characterizing block copolymers and polymer blends have been developed. Results from unstained and ruthenium tetroxide‐stained samples obtained by scanning electron microscopy at various acceleration voltage and by transmission electron microscopy are presented. The contrast in secondary images between components in stained polymer blends, where one component is preferentially stained, is maximized at higher acceleration voltage (10–25 keV). For measurement of particle size and shape, this is the preferred operating condition. To obtain high‐resolution images showing surface topography and fine structure, such as 20 nm domains in block copolymers, low‐voltage (<5 keV) imaging is preferred. Observation of the 20 nm domain structure in hydrogenated styrenebutadiene‐styrene shows that the spatial resolution now possible by scanning electron microscopy is comparable to that obtained by the traditional method of transmission electron microscopy.
Optimization of K‐ratio measurements for electron probe microanalysis
Authors: Schalkoord D. , Karduck P. , Rehbach W. P.
Published: August 2011

Electron probe microanalysis (EPMA) has developed over the past 35 years into a versatile and reliable tool for the quantitative analysis of microregions in solids. Recently its applicability has been extended to the determination of the composition and the thickness of thin layers or multilayers on substrates. Precise and reliable quantifications by EPMA presuppose that the x‐ray intensities are measured under optimized conditions. We discuss some of the important aspects concerning the exact measurement of x‐ray intensities with signal properties. The topics covered range from size of the excitation volume and aspects of the generation, absorption, and emission of x‐rays to instrumental stability, optimization of instrumental parameters, and sources of errors in EPMA.
Cryoscanning electron microscopy of a layer of extracellular polysaccharides produced by bacterial colonies
Authors: Van Doorn W. G. , Thiel F. , Boekestein A.
Published: August 2011

Cryo‐SEM allowed observation of a layer of extracellular polysaccharides that covered colonies of the bacterium Pseudomonas aeruginosa, growing on agar substrate. The layer was not found when using conventional preparation techniques and scanning electron microscopy. It disappeared partially as a result of glutaraldehyde fixation, but mainly during alcohol dehydration and critical point drying.
Use of the scanning electron acoustic microscopy (SEAM) for the study OF III–V compound semiconductors
Authors: Bresse J.‐F.
Published: August 2011

We present here examples of applications of SEAM for the characterization of III‐V compound semiconductors and the visualisation of defects in devices. The electron acoustic signal can be quantitatively correlated to the total incorporation of impurities in electrically active or nonactive sites. Both act to reduce the lattice thermal conductivity and can be correlated to the appearance of complexes giving rise to deep‐level emission in cathodoluminescence. Introduction of impurities and lattice defects by ion implantation induces a reduction in thermal conductivity. The recovery of lattice disorder by thermal annealing can be estimated from the SEAM signal evolution. In devices, SEAM is a unique nondestructive method to visualise, with submicron spatial resolution, interface compound formation between an ohmic contact and the semiconductor or zones of nonadherence of a metallic overlayer to a semiconductor.
Investigation of urinary stones by colour cathodoluminescent scanning electron microscopy (CCL‐SEM)
Authors: Saparin G. V. , Obyden S. K. , Golovanov S. A.
Published: August 2011

The ability of colour cathodoluminescent SEM (CCL‐SEM) to detect chemical substances on the surface of urinary stones was demonstrated. CCL‐SEM combined with conventional scanning electron microscopy (SEM) provides more detailed characterization of the ultrastructure and chemical composition on the surface of urinary calculi. The technique enables the identification of functionally active zones for investigation of stone formation.
A semiautomated image analysis procedure for the quantification of dental microwear
Authors: Ungar P. S. , Simon J.‐C. , Cooper J. W.
Published: August 2011

Different diets have been shown to leave characteristic patterns of microwear on the teeth of various mammalian species. The quantification of microwear features facilitates the comparison of taxa, and allows the discrimination of wear patterns associated with specific diets. The current study reports on a semiautomated image analysis procedure designed to expedite microwear quantification by engaging an IBM PS/2 running OS/2 Presentation Manager to compute and record the density, dimensions, and orientations of features defined by a user employing a mouse‐driven cursor. This technique is used to distinguish microwear patterns on the maxillary central incisors (I1s) of four Sumatran primate species (n=5 per taxon) with known dietary differences (Hylobates lar, Macaca fascicularis, Pongo pygmaeus, and Presbytis thomasi). However, although developed for a particular problem area, the analytical routines described are of general interest.
Electron‐count imaging in SEM
Authors: Yamada S. , Ito T. , Gouhara K. , Uchikawa Y.
Published: August 2011

We propose a method and a system for counting secondary electrons and for displaying micrographs from the SEM in real time. Evaluating the images obtained by the new system, we confirm that electron counting images have a higher signal to noise ratio than analogue images. This tendency is remarkable when the secondary electron signal is weak. We present the method and show experimental results obtained with our novel system for the detection of the secondary electron signal.
Calculation of the depth distribution function for continuous radiation
Authors: August H.‐J. , Wernisch J.
Published: August 2011

A newly developed electron‐scattering model has been employed for calculating depth distribution functions for bremsstrahlung. A comparison with depth distribution functions used in connection with characteristic radiation reveals that the value of the surface radiation Φ(0) is comparatively smaller in cases of continuous radiation generation, while the centre of gravity of the bremsstrahlung curves is situated at larger mass depths, thus increasing the effect of radiation absorption phenomena. The discrepancies between both types of curves increase with decreases in atomic number and overvoltage ratio. In light of the present results the transformations of characteristic radiation curves for obtaining those for continuous radiation known so far are not likely to be physically realistic. Therefore, the principle of a new transformation is proposed.
Calculation of secondary electron production using a diffusion matrix
Authors: Czyżewski Z. , Joy D. C.
Published: August 2011

The diffusion matrix model proposed by Desai and Reimer (1990) has been investigated. After some modifications it appeared to be a powerful tool for rapid determination of the SE and BSE signals from two‐dimensional surface topographies. Results for low atomic number specimens show good agreement between experimental and theoretical data.
New method of cell membrane cholesterol marking for scanning electron microscopy
Authors: Povaliy T. M. , Popova E. G. , Gusev S. A. , Grigorieva M. E. , Zaitsev S. T. , Gritskova I. A.
Published: August 2011

A new method is proposed for marking cell membrane cholesterol for SEM. The specific cholesterol markers (SCM) used consisted of polystyrene microspheres with digitonin on the surface. Digitonin is a specific cholesterol ligand. This method allows the investigation of the cholesterol content of phospholipid layers of the model and cell membranes. We analysed the distribution and quantity of cholesterol in model bilayer phospholipid membranes, liposomes, and in endothelial cell plasmalemma in health and during atherosclerosis.
A comparison of different intensity gradient formulae for orientation analysis of electron micrographs
Authors: Tovey N. K. , Martinez M. D.
Published: August 2011

A detailed study of different intensity gradient formulae was conducted using 91 separate images covering a wide range of microfabric. It was found that a formula based on the 3 × 3 local pixel array gives almost identical results over all images with the standard formula based on 20 pixels forming a circular grouping within the 5 × 5 local array. Other formulae based on other groupings of pixels within the same pixel arrays give markedly different results. Computation times are reduced up to 45% when the 8,5 formula is used in place of the 20,14 one, and would thus seem to have advantages when large numbers of images are to be processed. While all formulae give somewhat similar domain‐segmented images when viewed visually, differences are noted both in the number of segmented domains as well as in the area of domains in each orientation sector. It is possible that the radius of the modal filter selected for the domain segmentation should be varied according to the formula type used.
Material analysis with cathodoluminescence standard spectra
Authors: Koschek G. , Lork A.
Published: August 2011

There are several cases where x‐ray analyses of material cannot yield the desired results (e.g., if materials of nearly identical chemical composition are considered.) Spectral cathodoluminescence (CL) investigations can be used to overcome these difficulties. For this purpose, CL standard spectra of different standard substances are presented here. The validity of these spectra is demonstrated by spectral analysis of a fireproof ceramic consisting of Al2O3 and of quartz and by an attempt to explain the origin of the CL properties of magmatic Zircon which is of significant importance in the field of geochronological investigations.
SEM‐CL studies of plastic deformation processes in crystals
Authors: Akchurin M. Sh. , Galstyan V. G. , Regel V. R.
Published: August 2011

Cathode luminescence investigation in the scanning electron microscope showed that, under a concentrated load, enormous stresses (near G) under the indenter relaxed due to the creation and movement of interstitials giving rise to structure reconstruction and the formation of an ultradispersed state. Such reconstruction is accompanied by significant changes in material stoichiomentry. The formation of a volume with nanocrystal structure affects microindentation activation energy. The formation and displacement of dislocations around the impression should be considered as a process secondary to stress relaxation, that is, as a result of the reorganization of material structure under the indenter tip described.
Fractal behaviour of electron scattering in solids
Authors: Gauvin Raynald , Drouin Dominique
Published: August 2011

The fractal behaviour of electron scattering in solids is studied with electron trajectories simulated by Monte Carlo simulations. More precisely, the box‐counting dimension of electron trajectories in C, Cu, Ag, and Au is determined. Then, the fractal dimension curve of the position of an electron in function of time simulated in a gold target shows that the first part of the electron trajectory is described by a persistent process and that the last part is described by random walk process. Finally, the multifractal behaviour of an electron trajectory simulated in gold is presented.
Cone‐beam reconstruction of plate‐like specimens
Authors: Wang G. , Lin T. H. , Cheng P. C. , Shinozaki D. M.
Published: August 2011

An x‐ray shadow projection microscope using a scannable point source of x‐rays is under development at AMIL‐ARTS, SUNY at Buffalo. Considering the characteristics of the x‐ray microscope of AMIL‐ARTS and the limitations of Feldkamp's cone‐beam reconstruction algorithm, a general cone‐beam image reconstruction algorithm has been developed. In x‐ray microscopy, many specimens are plate‐like. The reconstruction of a plate‐like specimen appears to be a limited angle problem. A novel method is presented to reconstruct a plate‐like specimen using the general cone‐beam reconstruction algorithm. Shepp and Logan's head phantom is used in validating this method. A method for synthesizing projection data of ellipsoids is described. Typical simulation results are given.
Investigation of nanoparticles by atomic and lateral force microscopy
Authors: Wurster R. , Ocker B.
Published: August 2011

Metallic nanoparticles have been produced on vitreous carbon substrates by means of thermal evaporation. From pictures of the particles, made by a high‐resolution scanning electron microscope (HRSEM), a semispherical shape is suggested due to the total mass of deposited material. Atomic force microscopy (AFM) has been applied to this sample in order to get direct topographic information. The AFM has been operated with normal and super tips, the latter having a smaller cone angle and radius, thus following more precisely the contours of an object. Simultaneously lateral‐force microscopic (LFM) images have been recorded. Major differences between the contents of HRSEM‐ and AFM‐images are considered, emphasizing the important influence of the tips' geometry. Both the AFM and LFM line scans have been compared with and have qualitatively agreed with those calculated under simplifying assumptions.
Very low energy microscopy in commercial SEMs
Authors: Müllerová I. , Frank L.
Published: August 2011

Minimum necessary adaptations are described that are sufficient for obtaining very low energy electron micrographs (VLEEMs) from commercially available routine scanning electron micrographs (SEMs) with the electrons accelerated to an energy of the order of tens of keV. A cathode lens inserted into the specimen chamber enables one to decelerate electrons in front of the specimen surface to a desired low landing energy, which can be freely varied even down to zero. When a potential slightly more negative than the accelerating voltage is applied, a scanning mirror electron microscopy mode can be effected. The achievable point resolution at very low energies proves to be not too dependent on the objective lens parameters, so that the physical limit of aberrations of the homogeneous field of the cathode lens is nearly attainable. The detection efficiency for the standard Everhart‐Thornley secondary electron detector is discussed, and results for the routine Tesla BS 340 SEM are presented.
The primary distribution of vacancies in the L‐shell after ionisation with electrons
Authors: Schiebl Christian , Wernisch Johann
Published: August 2011

The extraction of the relative distribution of the primary generated vacancies, which have been produced by ionisation with electrons, that is, the vacancy distribution prior to the appearance of Coster Kronig transitions, is presented for the L‐subshells. Only fundamental parameters such as fluorescence yields, Coster Kronig transition probabilities, and relative intensities were used for the derivation. Furthermore, a closer look is taken at the energy dependence of these relative primary vacancy distributions.
Direct STEM fabrication and characterization of self‐supporting carbon structures for nanoelectronics
Authors: Kislov N. A.
Published: August 2011

A quantitative model is proposed to interpret the experimental results concerning the observed anomalous behavior of the thickness of growing self‐supporting carbon‐containing rods: a decrease in the thickness with increasing beam current. The model is based on the surface diffusion of hydrocarbon molecules and takes into account their ionization and desorption from the positively charged end of the growing rod. Possible causes of self‐maintained oscillation instability of the rod growth are discussed. Procedures are recommended to optimize the fabrication of self‐supporting carbon‐containing structures of complicated configurations and to reduce the negative effect of the incident beam electrons during their testing.
Characterisation of electronic and structural properties of thin silicon dioxide films by scanned probe microscopy
Authors: Welland M. E. , Murrell M. P.
Published: August 2011

This paper concerns the application of scanned probe microscopy to the study of thin silicon dioxide films. We show how the formation of 7 nm diameter silicon carbide particles on a silicon surface during high temperature processing affects the quality of subsequently grown oxide. To measure the local dielectric properties of thin oxides we have developed a new type of probe measurement which allows high resolution surface imaging, based on an atomic force microscope, combined with local electrical measurements. The spatial resolution of the electrical measurements was shown to be < 40 nm. Applying the technique to 500 nm capacitors fabricated on device quality oxide it was shown that some capacitors broke down during imaging while others remained stable at electric fields up to 30 MVcm−1. This higher breakdown strength may have substantial impact on future electronic device reliablity and performance.
Scanning probe microscopy for industrial applications: Selected examples
Authors: Dammer U. , Anselmetti D. , Dreier M. , Frommer J. , Fünfschilling J. , Gerth G. , Güntherodt H.‐J. , Haefke H. , Hidber H.‐R. , Howald L. , Hug H. J. , Jung T. H. , Lang H. P. , Lüthi R. , Meyer E. , Moser A. , Parashikov I. , Reimann P. , Richmond T. , Rüetschi M. , Rudin H. , Schwarz U. D. , Staufer U. , Sum R.
Published: August 2011

Some examples are selected to demonstrate the variety of possible scanning probe microscopy application in industry. Magnetic and magneto‐optical storage media can be investigated by magnetic force microscopy, whereas a conventional scanning force microscope is used to examine surface features of many different materials, such as technical glasses, photosensitive materials, new superconductors, and biomolecules. Some other examples include the modification as well as the observation of liquid crystal devices, and the impact that scanning probe microscopy has on other techniques such as high precision stepping motors and high quality electron beam sources.
Recent advances in atomic force microscopy of DNA
Authors: Hansma Helen G. , Sinsheimer Robert L. , Groppe Jay , Bruice Thomas C. , Elings Virgil , Gurley Gus , Bezanilla Magdalena , Mastrangelo Iris A. , Hough Paul V. C. , Hansma Paul K.
Published: August 2011

Three advances involving DNA in atomic force microscopy (AFM) are reported here. First a HEPES‐Mg buffer has been used that improves the spreading of DNA and provides good DNA coverage with as little as 200–500 picograms per sample. Second, the new “tapping” mode has been used to improve the ease and resolution of AFM‐imaging of DNA in air. Finally, AFM images are presented of single‐stranded ΦX‐174 virion DNA with the gene 32 single‐stranded binding protein. A summary of the current state of the field and of the methods for preparing and imaging DNA in the AFM is also presented.
Investigation of the formation of transition layers during LPE growth of GaAs
Authors: Bruk A. S. , Govorkov A. V. , Milvidskii M. G. , Popova E. V. , Shlenskii A. A. , Yugova T. G.
Published: August 2011

The properties of the near surface region in GaAs substrates doped with Sn and Te are studied after annealing in H2 flow or under controlled As overpressure. The transition regions between the bulk and the surface are formed upon such annealing. Also, the distribution of recombination centres across these transition regions is governed by defects diffused from the substrate and generated in the epitaxial layer.
Panchromatic cathodoluminescence characterization of III‐V lattice‐mismatched heterostructures
Authors: Salviati G.
Published: August 2011

Some examples of the possibilities that panchromatic cathodoluminescence (PCL) offers in the scanning electron microscopy (SEM) characterization of III‐V semiconductors are presented. Investigations on lattice‐mismatched InGaAs/InP, InGaAs/ GaAs single heterostructures, and InGaAs/GaAs superlattices and GaAs/Ge and GaAs/InP single layers are shown. Further, the use of PCL as a support in the nondestructive determination of the sensitivity limit of Rutherford backscattering and x‐ray diffraction techniques in the study of strain release in some of the above mentioned heterostructures is presented. Finally, PCL on‐line study of dislocation movement induced by electron beam irradiation in the SEM, as evidence of InGaAs/GaAs superlattice metastability, is also presented.
Second‐order spatial analysis of epidermal nerve fibers
Authors: Waller Lance A. , Särkkä Aila , Olsbo Viktor , Myllymäki Mari , Panoutsopoulou Ioanna G. , Kennedy William R. , Wendelschafer‐Crabb Gwen
Published: August 2011

Breakthroughs in imaging of skin tissue reveal new details on the distribution of nerve fibers in the epidermis. Preliminary neurologic studies indicate qualitative differences in the spatial patterns of nerve fibers based on pathophysiologic conditions in the subjects. Of particular interest is the evolution of spatial patterns observed in the progression of diabetic neuropathy. It appears that the spatial distribution of nerve fibers becomes more ‘clustered’ as neuropathy advances, suggesting the possibility of diagnostic prediction based on patterns observed in skin biopsies. We consider two approaches to establish statistical inference relating to this observation. First, we view the set of locations where the nerves enter the epidermis from the dermis as a realization of a spatial point process. Secondly, we treat the set of fibers as a realization of a planar fiber process. In both cases, we use estimated second‐order properties of the observed data patterns to describe the degree and scale of clustering observed in the microscope images of blister biopsies. We illustrate the methods using confocal microscopy blister images taken from the thigh of one normal (disease‐free) individual and two images each taken from the thighs of subjects with mild, moderate, and severe diabetes and report measurable differences in the spatial patterns of nerve entry points/fibers associated with disease status. Copyright © 2011 John Wiley & Sons, Ltd.
Behaviour of steel‐to‐concrete joints – moment resisting joint of a composite beam to reinforced concrete wall
Authors: Henriques José , da Silva Luís Simões , Ozbolt Ana , Kuhlmann Ulrike , Žižka Jiří , Wald František
Published: August 2011

The studied joint configuration is illustrated in Fig. 1. Two different transfer areas may be distinguished. The upper area consists of a reinforced concrete slab where the longitudinal reinforcement is anchored in the reinforced concrete wall. The wall and the slab were concreted at different times and therefore, no shear is assumed to be transferred between these members. Any friction is neglected. Thus, only tension is transferred through this part of the joint. At the bottom area, the steel beam sits in a steel bracket welded to an anchor plate which is fastened the reinforced concrete wall. The fixation between anchor plate and wall is achieved by headed studs welded to the plate. On the outside of the steel bracket, a plate is welded creating a “nose” which avoids the slip of the beam out of the steel bracket. The end‐plate of the steel beam is used for this propose. This end‐plate transmits the shear load to the steel bracket. Finally, compression is transferred to the reinforced concrete wall using a contact plate between end‐plate and anchor plate. The flux of loads is schematically represented in Fig. 2 for a hogging bending moment.
Fire after earthquake robustness evaluation and design: Application to steel structures
Authors: Faggiano Beatrice , Mazzolani Federico M.
Published: August 2011

The occurrence of fires breaking out during a seismic event, or even delayed after an earthquake represents a common circumstance in earthquake prone Countries, which must be adequately taken into account as a possible design scenario. In fact the behaviour in fire of structures that have been damaged by earthquakes changes as respect to the undamaged ones, since the earthquake‐induced damage makes the structure more vulnerable to fire effects. In view of the current seismic design approach, where a certain extent of damage in case of severe earthquake is acceptable, the analysis of the behaviour of structures under the effect of fires in combination or following an earthquake is a significant research field, which is not yet fully explored. The robustness assessment under fire of structures already damaged to different extent by the seism, through a performance – based approach, is required. The procedure should be valuable as a design tool, as well as a vulnerability evaluation of the built heritage against FFE. In this paper the proposed general methodology is exemplified with regards to steel structures.
Power performance of wind energy converters characterized as stochastic process: applications of the Langevin power curve
Authors: Wächter Matthias , Milan Patrick , Mücke Tanja , Peinke Joachim
Published: August 2011

The power performance of a wind energy converter (WEC) commonly refers to the relation between the input source and the electrical output, i.e. the input wind speed u and the electrical power output P. The International Electrotechnical Commission defined a so‐called power curve P(u) that quantifies this relation. Recently, a novel approach was introduced based on the short‐time dynamical response of the WEC to high‐frequency wind fluctuations. The dynamical behavior of the WEC is quantified by a drift field and the corresponding Langevin power curve (LPC).

We present three applications of our method to wind energy based on the LPC. The first application consists of testing the power performance of WECs using LIDAR wind measurements. We then extend this test to the monitoring of the WEC performance over time. Finally, we apply the LPC to a simulation model for a WEC as a tool to characterize its performance. These applications illustrate the flexibility of the LPC as a relevant tool for performance testing and monitoring. Copyright © 2011 John Wiley & Sons, Ltd.
Modeling wake effects in large wind farms in complex terrain: the problem, the methods and the issues
Authors: Politis E. S. , Prospathopoulos J. , Cabezon D. , Hansen K. S. , Chaviaropoulos P. K. , Barthelmie R. J.
Published: August 2011

Computational fluid dynamic (CFD) methods are used in this paper to predict the power production from entire wind farms in complex terrain and to shed some light into the wake flow patterns. Two full three‐dimensional Navier–Stokes solvers for incompressible fluid flow, employing k − ϵ and k − ω turbulence closures, are used. The wind turbines are modeled as momentum absorbers by means of their thrust coefficient through the actuator disk approach. Alternative methods for estimating the reference wind speed in the calculation of the thrust are tested. The work presented in this paper is part of the work being undertaken within the UpWind Integrated Project that aims to develop the design tools for next generation of large wind turbines. In this part of UpWind, the performance of wind farm and wake models is being examined in complex terrain environment where there are few pre‐existing relevant measurements. The focus of the work being carried out is to evaluate the performance of CFD models in large wind farm applications in complex terrain and to examine the development of the wakes in a complex terrain environment. Copyright © 2011 John Wiley & Sons, Ltd.
On the Solid Solution Series Er15[(Fe1–xRux)8C25]: Site Preference for Substitution in the Range 0 ≤ x ≤ 0.625?
Authors: Davaasuren Bambar , Dashjav Enkhtsetseg , Doert Thomas , Kreiner Guido , Kniep Rüdiger
Published: August 2011

The solid solution series Er15[(Fe1–xRux)8C25] was prepared by arc‐melting of pressed pellets of mixtures of the elements, followed by annealing at 1173 K and quenching. Powder X‐ray patterns reveal the presence of a limited solid solution phase within the composition range 0 ≤ x ≤ 0.75 (trigonal, P321). Its crystal structure contains polyanionic slabs $\rm^2_\infty$[Fe1–xRux)8(C25)45–] stacked along [001] with Er3+ ions in between. The substitutions concern a planar triangular cluster made up of six transition metal atoms and a trigonal planar complex of composition [(Fe1–xRux)(C2)3]. The single crystal structure determination of Er15[Fe4.93(1)Ru3.07C25] clearly shows that the iron atoms forming the outer triangle of the planar cluster are not affected by substitution, resulting in the chemical composition Fe3(Fe0.19(3)Ru0.81)3for the intermetallic cluster unit. According to the chemical bonding analyses, the formation of Ru–Ru bonds seems to be the driving force for this preferential site occupation. The trigonal planar complex, again, is affected by substitution: [(Fe0.68(4)Ru0.32)(C2)3]. Assuming complete substitution except for the outer triangle of the intermetallic cluster, the limiting chemical composition for the series results inEr15[(Fe3Ru5)C25] (x = 0.625). The difference to the experimental value (x = 0.75) gives reason for further investigations. The end member Er15[Ru15C25] was not observed.
A tableau-based decision procedure for CTL*
Authors: Reynolds Mark
Published: August 2011

We present a sound, complete and implementable tableau method for deciding satisfiability of formulas in the propositional version of computation tree logic CTL*. This is the first such tableau. CTL* is an exceptionally important temporal logic with applications from hardware design to agent reasoning, but there is no easily automated reasoning approach to CTL*. The tableau here is a traditional tree-shaped or top-down style tableau, and affords the possibility of reasonably quick decisions on the satisfiability of medium-sized formulas and construction of small models for them. A straightforward subroutine is given for determining when looping allows successful branch termination, but much needed further development is left as future work. In particular, a more general repetition prevention mechanism is needed to speed up the task of tableau construction.
Spatial and temporal dynamics of the male effective population size in bumblebees (Hymenoptera: Apidae)
Authors: Wolf Stephan , Toev Theresa , Moritz Ruby L. V. , Moritz Robin F. A.
Published: August 2011

Eusociality and male haploidy of bumblebees (Bombus spp.) enhance the deleterious effects of population decline and aggravate the degeneration of population fitness compared to solitary and diploid species. The highly dispersive male sex may be the prime driver to connect otherwise isolated populations. We therefore studied the temporal and spatial structure of the male population of Bombus terrestris (Linnaeus 1758) and Bombus lapidarius (Linnaeus 1758) using microsatellite DNA markers. We found that the majority of the males in a 1000 m² sampling area originated from colonies located outside of the workers foraging range, which was consistent with the genetic distances among colonies. The analyses of temporal population sub‐structure based on both colony detection rate over time and the clustering software STRUCTURE consistently suggested one large and temporally unstructured male population. Our results indicate an extended male flight distance for both species. Though the range of queen dispersal remains to be studied, the effective size (Ne) of bumblebees is increased by extended male mating flight ranges (Am) exceeding worker foraging distance by factor 1.66 (Am = 69.75 km2) and 1.74 (Am = 13.41 km2), B. terrestris and B. lapidarius, respectively. Thus this behaviour may counteract genetic deprivation and its effects. All populations were genetically highly diverse and showed no signs of inbreeding. We discuss the implications of our findings in context of bumblebee population dynamics and conservation. We also highlight the effects and benefits of sampling both workers and males for population genetic studies.
Phenolic Characterization and Geographical Classification of Commercial Extra Virgin Olive Oils Produced in Turkey
Authors: Alkan Derya , Tokatli Figen , Ozen Banu
Published: August 2011

The aim of this research was to characterize the extra virgin olive oil samples from different locations in the Aegean coastal area of Turkey in terms of their phenolic compositions for two consecutive years to show the classification of oil samples with respect to harvest year and geography. Forty seven commercial olive oil samples were analyzed with HPLC–DAD, and 17 phenolic compounds were quantified. Hydroxytyrosol, tyrosol, vanillic acid, p‐coumaric acid, ferulic acid, cinnamic acid, luteolin and apigenin were the characteristic phenols observed in all oil samples for two harvest years. Syringic acid, vanillin and m‐coumaric acid were the phenolic compounds appeared in the olive oil depending on the harvest year. Partial least square‐discriminant analysis (PLS‐DA) of data revealed that oils from the north Aegean and south Aegean areas had different phenolic profiles. The phenolic compounds, which played significant roles in the discrimination of the olive oils, were tyrosol, oleuropein aglycon, cinnamic acid, apigenin and hydroxytyrosol to tyrosol ratio. The Aegean coastal region is the largest olive oil producer and exporter of Turkey. This study shows that the olive oils from different parts of the region have their own defining characteristics that can be used in the authentication studies and geographical labeling of Turkish olive oils.
SPACELIKE CAPILLARY SURFACES IN THE LORENTZ–MINKOWSKI SPACE
Authors: PYO JUNCHEOL , SEO KEOMKYO
Published: August 2011

For a compact spacelike constant mean curvature surface with nonempty boundary in the three-dimensional Lorentz–Minkowski space, we introduce a rotation index of the lines of curvature at the boundary umbilical point, which was developed by Choe [‘Sufficient conditions for constant mean curvature surfaces to be round’, Math. Ann.323(1) (2002), 143–156]. Using the concept of the rotation index at the interior and boundary umbilical points and applying the Poincaré–Hopf index formula, we prove that a compact immersed spacelike disk type capillary surface with less than four vertices in a domain of $\Bbb L^3$ bounded by (spacelike or timelike) totally umbilical surfaces is part of a (spacelike) plane or a hyperbolic plane. Moreover, we prove that the only immersed spacelike disk type capillary surface inside a de Sitter surface in $\Bbb L^3$ is part of (spacelike) plane or a hyperbolic plane.
Prevalence of vitamin D deficiency and secondary hyperparathyroidism during winter in pre-menopausal Bangladeshi and Somali immigrant and ethnic Finnish women: associations with forearm bone mineral density
Authors: Islam Md Zahirul , Viljakainen Heli T. , Kärkkäinen Merja U. M. , Saarnio Elisa , Laitinen Kalevi , Lamberg-Allardt Christel
Published: August 2011

Secondary hyperparathyroidism (SHPT) is one of the outcomes of vitamin D deficiency that negatively affects bone metabolism. We studied the ethnic differences in vitamin D status in Finland and its effect on serum intact parathyroid hormone (S-iPTH) concentration and bone traits. The study was done in the Helsinki area (60°N) during January–February 2008. A total of 143 healthy women (20–48 years of age) from two groups of immigrant women (Bangladeshi, n 34 and Somali, n 48), and a group of ethnic Finnish women (n 61) were studied in a cross-sectional setting. Serum concentrations of 25-hydroxyvitamin D (S-25OHD) and S-iPTH were measured. Peripheral quantitative computed tomography measurements were taken at 4 and 66 % of the forearm length. In all groups, the distribution of S-25OHD was shifted towards the lower limit of the normal range. A high prevalence of vitamin D insufficiency (S-25OHD < 50 nmol/l) was observed (89·6 %) in the Somali group. The prevalence of SHPT (S-iPTH>65 ng/l) was higher (79·1 %) in Somali women than in Finnish women (16 %). There was a significant association between S-25OHD and S-iPTH (r − 0·49, P < 0·001). Ethnicity and S-25OHD together explained 30 % of the variation in S-iPTH. The total bone mass at all sites of the forearm, fracture load and stress–strain index was higher (P < 0·001) in Bangladeshi and Finnish women than in Somali women. The high prevalence of hypovitaminosis D, SHPT and low bone status in Somali women indicates a higher risk of osteoporosis.