bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface topography and intracellular organization of human cells in suspension as revealed by scanning electron microscopy
Authors: Malecki Marek , Ris Hans
Published: August 2011

This report presents a new procedure to study the ultrastructure of human cells in suspension by means of scanning electron microscopy. Living cells were maintained in suspension within cell culture flasks located on a rotating tilting table within an incubator. These cells were injected into warm glutaraldehyde/formaldehyde fixative. After washing in buffer, fixed cells were attached to propylamine‐derived glass carriers. However, saturating free aldehyde groups of fixed cells and blocking amine groups of the derived glass carriers prevented cells from attachment to these carriers. Thus, we postulated that bonds between the fixed cell‐free aldehyde groups and the carrier amine groups were responsible for cell‐to‐carrier attachment. Fixed cells attached to the carriers were subsequently dehydrated, dried, and coated for surface topography studies. For studies of internal cell organization, these attached cells were immersed in agar or gelatin as extracellular embedments and infused with sucrose or polyvinyl‐pyrrolidone as cryoprotectants. Cells then were frozen and fractured. Fractured cells were either thawed, dehydrated, critical point dried, and ion beam sputter‐coated, or freeze‐substituted, dried, and planar magnetron sputter‐coated. Finally, cell preparations were observed in the scanning electron microscope. Due to high cell attachment yield, both approaches samples observed in the electron microscope were representative of the entire cell population.
Scanning microscopies of indented MgO crystals
Authors: Nazarova T. A. , Nazarov M. V. , Rau E. I. , Saparin G. V.
Published: August 2011

The combination of scanning electron microscopy (SEM) and scanning optical microscopy (SOM), including a computer‐controlled signal detection system, is promising in the study of a variety of materials, especially such alkaline‐earth oxides with a rock salt structure, such as MgO. Among the SEM modes of this technique used to investigate deformed zones in indented MgO single crystals are: secondary electrons (SE), cathodoluminescence (CL) (total, pointal, color), electron beam‐induced current (EBIC), electron beam‐induced voltage (EBIV), as well as both polarized and transmitted light modes in SOM. The present experiments were designed to clarify the correlation between the optical, luminescent, electrical, and plastic properties of deformed MgO. An attempt has been made to explain the results in terms of dislocations created during deformation.
Chemical preparation of dielectrics for studying their microtopography by the SEM
Authors: Dorozhkin S. V. , Nikolaev A. L. , Melikhov I. V. , Saparin G. V. , Bliadze V. G.
Published: August 2011

A procedure for the chemical preparation of dielectrics to make their surfaces conductive is proposed. Its simplicity and rapidity, as well as the possibility of using it to study etching kinetics of specimen surface morphology are noteworthy. The procedure is demonstrated by the interaction of F‐apatite with acids. The procedural steps include careful attention to the washing of the specimen following its interaction with an acid and to its drying thereafter. The composition of the washing solution and the washing time must be carefully controlled. Positive results are obtained for the interaction between F‐apatite and phosphoric, hydrochloric, nitric acids and between glass and hydrofluoric acid. Acetone was employed as the washing solution and in all cases sharp images of the specimen surface were obtained in the SEM. The subsequent washing of the specimen in water restored the dielectric properties of its surface. By sequentially etching, drying, and observing the specimen in the SEM, a series of images was obtained of an area of the surface as it was being etched. This series of images permitted determination of the growth rate of etched pits.
Confocal surface profiling utilizing chromatic aberration
Authors: Browne M. A. , Akinyemi O. , Boyde A.
Published: August 2011

A new method for surface profiling in the confocal microscope utilizing chromatic aberration is presented. An expression for the integrated spectral intensity in the new profilometer is derived and chromatic aberration in the confocal microscope is explained. Estimates of the minimum resolvable depth and the maximum depth that can be profiled are given utilizing a ratiometric signal detection scheme. Examples of ratio images illustrating the new surface profiling technique are presented, showing the scheme to be both simple to implement and effective.
SIMS analyses of rare earth elements in natural minerals and glasses: An investigation of structural matrix effects on ion yields
Authors: Bottazzi Piero , Ottolini Luisa , Vannucci Riccardo
Published: August 2011

An investigation of the influence of matrix structure upon secondary ion signals for rare earth elements (REEs) in various silicates (amphiboles, clinopyroxenes, garnets, and plagioclases) was carried out by means of conventional energy filtering technique (CEF). Such matrices were analysed both as natural crystals and fused glasses. Of the selected REEs for the different minerals, only La showed an intensity relatively higher than Si in glassy amphiboles and augites. The hypothesis proposed of an ionization behaviour of La that differs with respect to other REEs in silicates has not been confirmed in plagioclases. All other relative REE ion yields from crystals and glasses agreed within the statistics of measurement for all investigated matrices. Moreover, any difference between crystal and glass REE ionization appeared not to be attributable to varying charging conditions during analysis under O− primary beam bombardment. Laboratory contamination during glass preparation and/or the presence of residual light REE‐enriched micron‐scale accessory phases (e.g., apatite) could be responsible for the higher La/Si signal in augite and amphibole glasses. Results obtained show that the efficiency of REE ionization compared with that of Si. generally is not affected by the sample structure as far as high energy secondary ions are concerned; therefore, glasses obtained by fusing silicate minerals are suitable for analytical work and can be employed to calibrate REE ion signals for quantitative purposes.
DNA and RNA polymerase/DNA complex imaged by scanning force microscopy: Influence of molecular‐scale friction
Authors: Zenhausern F. , Adrian M. , Heggeler‐Bordier B. Ten , Eng L. M. , Descouts P.
Published: August 2011

Reproducible images of DNA and the interaction of RNA polymerase with supercoiled DNA on mica have been obtained by scanning force microscopy (SFM) in air. This technique allowed visualization of the assembly of distinct nucleoprotein complexes at specific sites which initiate DNA replication. Transmission electron microscopic controls were performed on the carbon‐coated replica of the same specimens previously scanned by scanning force microscope. Image contrast formation has been investigated and lateral friction forces have been qualitatively characterized with SFM on DNA‐covered samples.
Analysis of electron range versus energy relationship of insulators in low‐voltage scanning electron microscopy
Authors: Ishibashi Y. , Kodama T. , Oiwa H. , Uchikawa Y.
Published: August 2011

A theoretical analysis is made concerning the question of whether or not an insulator's surface is observable without the unstable disturbance due to negative charge‐up in the secondary electron mode of a low‐voltage scanning electron microscope. Introducing a simple modification into the elementary theory of secondary electron emission from solid materials, the threshold condition as to observability is formulated as a function of the energy Ep and the incident angle ϕp of the primary beam. It is shown that for insulators the material's constant n, which appears in the standard formula of the electron range (R) versus energy (Ep) relationship R Φ E, can be determined through experimental investigations into observability of the surface. Careful consideration is also given to the effectiveness of the present theoretical analysis.
Light transport in single‐crystal scintillation detectors in SEM
Authors: Schauer P. , Autrata R.
Published: August 2011

A Monte Carlo simulation method was developed to determine the efficiency of photon transport through a modified rotationally symmetric Everhart‐Thornley detector. The method makes use of the random generation of photon emission from a luminescent centre and describes the trajectory of photons and the efficiency of their transport toward the photocathode of the photomultiplier tube. The model includes photon generation in a point source, mirror reflection by a metal‐coated surface, Fresnel reflection by a metal‐uncoated surface, Fresnel passage through the boundary of different materials, diffusion reflection, and passage through a matted surface and optical absorption in material. For the simulation, an IBM‐PC‐compatible program was written and applied to detection systems with disc, conical, and hemispherical YAG:Ce single‐crystal scintillators with cylindrical or tapered light guides or without any light guide. The model was verified by measuring the efficiency of detection systems excited by the primary electron beam in the line‐scan SEM mode.
Automatic contrast adjustment for detail recognition in SEM images using on‐line digital image processing
Authors: Oho Eisaku
Published: August 2011

A new digital filter method has been developed for enhancement of detail recognition in SEM images of high signal‐to‐noise ratio using an on‐line digital image processing system. The filter allows an automated improvement of the presentation of SEM image information and utilizes a median filter of very large mask size and histogram equalization. Since the method can be performed without input of any processing parameters, the user simply pushes a button for obtaining the processing result similar to conventional photo recording. The method utilizes digital signal processors for establishing high speed, hence, the processing results can be immediately assessed. When Applied to a variety of field‐emission SEM images, there were no problems with inconvenient artifact encountered.
Determination of fixed electron‐beam‐induced positive oxide charge
Authors: Bernstein G. H. , Polchlopek S. W. , Kamath R. , Porod W.
Published: August 2011

Contrary to previous beliefs, electron‐beam‐induced positive charges in insulators persist where created for at least several weeks without discernible movement. Formerly, coating with a thin metal overlay was thought to allow the charge to leak away. Coating with a conductor is shown to shield electric fields from affecting the imaging probe, but to remove no charge from the specimen. A new technique is introduced for the evaluation of the properties of electron‐beam‐induced positive charges in metal‐oxide‐semiconductor (MOS) capacitors. MOS structures were subjected to partial area exposure in a scanning electron microscope. These exposures resulted in the creation of areas of localized positive charge within the oxide, which was observed as steps in the capacitance‐voltage data. A systematic study was performed. It related the exposed area to the step height and the amount of induced charge to the voltage shift of the step. A model describing the observed phenomenon is presented, followed by a comparison of theoretical and experimental results. The progress of the charge over time was studied by performing capacitance‐voltage analysis 30 min after electron beam exposure and up to 4 weeks later.
Electron‐specimen interactions in low‐voltage scanning electron microscopy
Authors: Böngeler R. , Golla U. , Kässens M. , Reimer L. , Schindler B. , Senkel R. , Spranck M.
Published: August 2011

Measurements of the electron range R, and the backscattering coefficient η and the secondary electron yield δ at normal and tilted incidence for different elements show characteristic differences for electron energies in the range of 0.5 to 5 keV, compared with energies larger than 5 keV. The backscattering coefficient does not increase monotonically with increasing atomic number; for example, the secondary electron yield shows a lesser increase with increasing tilt angle. This can be confirmed in back‐scattered electron (BSE) and secondary electron (SE) micrographs of test specimens.

The results are in rather good agreement with Monte Carlo simulations using elastic Mott cross‐sections and a continuous‐slowing‐down model with a Rao Sahib‐Wittry approach for the stopping power at low electron energies. Therefore, this method can be used to calculate quantities of BSE and SE emission, which need a larger experimental effort. Calculations of the angular distribution of BSEs show an increasing intensity with increasing atomic number at high takeoff angles than expected from a cosine law that describes the angular characteristics at high electron energies. When simulating the energy distribution of BSEs, the continuous‐slowing‐down model should be substituted by using an electron energy‐loss spectrum (EELS) that considers plasmon losses and inner‐shell ionizations individually (single‐scattering‐function model). The EELS can be approached via the theory for aluminium or from EELS spectra recorded in a transmission electron microscope for other elements.

Measurements of electron range Rα En of 1 to 10 keV electrons are obtained from transmission experiments with thin films of known mass thickness. In agreement with other authors the exponent n is lower than at higher electron energies.
Plastic lenticular three‐dimensional prints
Authors: Wergin William P. , Erbe Eric F. , Pooley Christopher D.
Published: August 2011

Methods and explanations are presented for obtaining a series of four scanning electron micrographs (SEMs) containing parallax information that can be incorporated into a single three‐dimensional (3‐D) plastic lenticular print. The explanation includes a brief discussion of tilt angles for optimum stereopsis and tilt compensation to correct for foreshortening. In addition, instructions are given on how the four prints must be arranged and rephotographed so that Nishika 3‐D, a commercial company, can produce the final plastic lenticular prints. These 3‐D prints, which can be black and white or color, do not require glasses or any additional aids to perceive stereopsis. They are believed to be an effective and economical format for displaying 3‐D data at scientific poster sessions. Furthermore, the format and procedure used to produce the prints are not limited to data obtained from the SEM but can be used to create 3‐D prints from micrographs or other data that originate with high and intermediate voltage transmission electron microscopy, confocal microscopy, scanned probe microscopies, magnetic resonance imaging, and molecular models.
An attachment to SEM for 3‐D surface topography measurements of uniform materials
Authors: Kazmiruk V. V. , Stepanov I. S.
Published: August 2011

The paper reports on a SEM‐based system for quantitative three‐dimensional (3‐D) surface topography measurements. In comparison with commercial line‐width measuring systems, this metrology instrument is designed to measure quantitatively both critical dimensions in horizontal plane and features height while allowing for full cross section reconstruction from backscattered electrons (BSE) signal. The philosophy behind this technique has been described previously, (Aristov et al. 1988, 1991). Now the system is operational at our Institute, and its characteristics just as design criteria, and some examples of application are presented.
The influence of oxide surface layers on bulk electron probe microanalysis of oxygen—application to Ti‐Si‐O compounds
Authors: Goldstein J. I. , Choi S. K. , Van Loo F. J. J. , Heijligers H. J. M. , Bastin G. F. , Sloof W. G.
Published: August 2011

This paper discusses a generalized method to measure with the electron probe microanalyzer (EPMA) the oxygen in a material containing a surface oxide layer. The continuum background is the most difficult to measure, particularly for materials in which oxygen‐free samples cannot be produced. The method depends on the preparation of either oxygen‐free samples or well characterized oxygen‐containing samples. Specific application of the method to the Ti‐Si‐O system is discussed. In addition, measurements of oxide surface‐layer thickness of 3.6–8.0 nm on Ti and Ti‐Si compounds were obtained using EPMA and a scanning Auger microprobe (SAM). The nature of the oxide surface layers was shown using x‐ray photoelectron spectroscopy (XPS).
Detectability: A new criterion for evaluation of the confocal microscope
Authors: Gan X. S. , Sheppard C. J. R.
Published: August 2011

We introduce a new criterion to explore the performance, with respect to signal‐noise ratio for fluorescent imaging, in the confocal microscope. This criterion, which we term detectability, has three forms: transverse, axial, and three‐dimensional. It describes the ease with which a small object can be detected in transverse images, axial images, and three‐dimensional images.
Modification of a commercial SEM with a computer controlled cathode stabilized power supply
Authors: Postek Michael T. , Keery William J. , Vladar Andras E.
Published: August 2011

Modification of the high‐voltage circuitry of the thermionic electron gun of a commercial scanning electron microscope (SEM) to a fully computer‐controlled, cathode‐stabilized system is described. The modification permits automatic filament saturation and monitoring. Using this system, variations and drifts in the emission current over time can be adjusted and compensated automatically with a feedback loop in the computer‐controlled system. This change also enables the accurate determination and setting of the primary electron beam energy. Therefore, the accelerating voltage is known for comparison to Monte Carlo computer modeling of the electron beam specimen interaction.
Failure analysis of encapsulated electronic devices by means of scanning ultrasonic microscopy technique
Authors: De Liso G. , Muschitiello M. , Stucchi M.
Published: August 2011

The ultrasonic (also improperly known as “acoustic”) microscopy technique can be successfully applied to the nondestructive detection of package defects and damages in a wide range of electronic components. This paper presents three examples of application of this technique to the failure analysis of electronic devices that completely differ in package type, size, and application. The same analyses were also attempted by the x‐ray technique; a comparison of results of these two techniques is reported, and the advantages of the ultrasonic microscopy regarding applicability, sensitivity, and resolution are highlighted.
The use of scanning electron microscopy to quantify the burden of particles released from clean‐room wiping materials
Authors: Bhattacharjee Himansu R. , Paley Steven J. , Pavlik Thomas J. , Atterbury Osmond
Published: August 2011

A procedure is described for the detection and direct enumeration of the number of particles that can potentially be released from wiping materials. The technique involves the use of a scanning electron microscope (SEM) to count the particles from a wiper, first by releasing them in deionized water and then filtering the entirety of the liquid through a submicron membrane filter. To obtain an accurate count, the filtration must produce a normal distribution of particles on the filter, and hence the details of the filtering technique must be performed in a very precise manner. The counting of the particles on the filter is accomplished by scanning a statistically representative number of fields and averaging the number of particles per field. The results can then be checked for statistical precision and accuracy. Our criterion for successful measurement was ± 10% accuracy at a 95% confidence level. We believe that the SEM method described in this article is sensitive enough to quantify very low levels of total particle burden without succumbing to the variability and limitations encountered with other enumeration techniques. Typically, this technique enables the accurate counting of particles of all shapes from below 0.1 μm to hundreds of micrometers. In addition, the SEM technique allows for morphologic identification of particles as well as chemical identification if an energy‐dispersive x‐ray system (EDS) is employed.
Cathodoluminescence from intermixed quantum‐well structures: Evidence of remote luminescence
Authors: Norman C. E. , Ghisoni M.
Published: August 2011

Cathodoluminescence (CL) in the scanning electron microscope is used to investigate the lateral extent of the transition region between areas of a GaAs/AlGaAs multi‐quantum well annealed with and without intentional introduction of group III vacancies from an SiO2 surface layer. The results show that in structures in which the band gap varies from area to area by, for example, tens of meV over distances of a few μm, carrier drift prior to radiative recombination is an important factor. This phenomenon, which we designate “luminescence after drift” has important implications, not only in CL studies of device structures and materials systems in which lateral band gap variations exist, but also in determining the lower‐limit size and separation of optoelectronic devices fabricated by techniques such as vacancy‐enhanced intermixing.
Determination of local deep‐levels homogeneity using SEM
Authors: Bruk A. S. , Govorkov A. V. , Milvidskij M. G. , Polyakov A. Y.
Published: August 2011

A method to study microhomogeneity of deep centres in high resistivity and low resistivity semiconductors is described herein. It uses measurements of current decay induced in Schottky diodes and p‐n junctions by a probing electron beam of an SEM and is closely related to a method of photoelectron relaxation spectroscopy. The advantages of this method are demonstrated for an example of dislocation‐related inhomogeneity in semi‐insulating GaAs.
Scanning‐DLTS, EBIC, and CL Investigations of Diamond Indentations in GaAs p+n Junctions
Authors: Breitenstein O. , Egger U. , Heydenreich J.
Published: August 2011

Diamond indentations have been carried out on Zn‐diffused GaAs p+n junctions on (100) oriented material. Electron‐beam induced current (EBIC) investigations revealed the well‐known dislocation slip bands in 〈110〉 directions. Scanning deep level transient spectroscopy (SDLTS) imaging proved a deformation‐induced point‐defect level at Ey + 0.5 eV, which is preferentially concentrated in the dislocation‐free regions between the slip bands rather than within the slip bands. Monochromatic cathodolumines‐cence (CL) imaging at 10K using different wavelengths revealed only the dislocation‐induced recombination activity but not any point‐defect luminescence corresponding to the 0.5 eV level found by SDLTS.
Ruthenium‐catalyzed cyclizations of enynes via a ruthenacyclopentene intermediate: Development of three novel cyclizations controlled by a substituent on alkyne of enyne
Authors: Saito Nozomi , Tanaka Daisuke , Mori Miwako , Sato Yoshihiro
Published: August 2011

Three novel ruthenium‐catalyzed cyclizations of enynes were developed. In each cyclization, a ruthenacyclopentene derived from enyne and Cp*RuCl(cod) is a common intermediate. When an enyne having an alkyl, an ester, or a formyl group on an alkyne was reacted with Cp*RuCl(cod) under ethylene gas, ethylene was inserted into the ruthenium‐sp2 carbon bond of ruthenacyclopentene to afford ruthenacycloheptene, and β‐hydrogen elimination followed by reductive elimination occurred to give a cyclic compound having a 1,3‐diene moiety. When an acyl group was placed on the alkyne, the carbonyl oxygen coordinated to the ruthenium metal of ruthenacyclopentene to produce a ruthenium carbene complex, which reacted with ethylene to give a cyclic compound having a cyclopropane ring on the substituent. On the other hand, when the substituent on the alkyne was pent‐4‐enyl, insertion of an alkene part into ruthenacyclopentene followed by reductive elimination gave a tricyclic compound by a ruthenium‐catalyzed [2 + 2 + 2] cyclization of diene and an alkyne. DOI 10.1002/tcr.201100003
Three Copper(II) Complexes of a “Tritopic” Hydrazone Ligand: Synthesis and Structural Characterization
Authors: Qin Suni , Nie Chuanli , Weng Zhehui , Chen Zilu , Liang Fupei
Published: August 2011

Three copper(II) complexes with the ligand bis[(2‐pyridyl)methylene]pyridine‐2,6‐dicarbohydrazone (H2L), {[Cu3(L)(ClO4)3(C2H5OH)2(H2O)]·(ClO4)·(H2O)}n (1), {[Cu3(L)(SO4)2(H2O)3]·4H2O}n(2), and [Cu6(L)2(CH3COO)6(OH)2]·2H2O (3), were synthesized and structurally characterized. In each compound, the L2– ligand coordinates to three copper ions to produce a trinuclear copper subunit. The trinuclear copper subunits in compound 1 are connected by the bridging of ClO4– groups to build a 1D triple‐chain structure, and those in compound 2 are linked into 1D chain structure by the bridging of SO42– groups. Compound 3 presents a hexanuclear copper cluster formed by two trinuclear copper units linked by two μ3‐OH bridges.
Steryl Glucoside and Acyl Steryl Glucoside Analysis of Arabidopsis Seeds by Electrospray Ionization Tandem Mass Spectrometry
Authors: Schrick Kathrin , Shiva Sunitha , Arpin James C. , Delimont Nicole , Isaac Giorgis , Tamura Pamela , Welti Ruth
Published: August 2011

Establishment of sensitive methods for the detection of cellular sterols and their derivatives is a critical step in developing comprehensive lipidomics technology. We demonstrate that electrospray ionization tandem (triple quadrupole) mass spectrometry (ESI‐MS/MS) is an efficient method for monitoring steryl glucosides (SG) and acyl steryl glucosides (ASG). Comparison of analysis of SG and ASG by ESI‐MS/MS with analysis by gas chromatography with flame ionization detection (GC–FID) shows that the two methods yield similar molar compositions. These data demonstrate that ESI‐MS/MS response per molar amount of sterol conjugate is similar among various molecular species of SG and ASG. Application of ESI‐MS/MS to seed samples from wild‐type Arabidopsis and a mutant deficient in two UDP‐glucose:sterol glucosyltransferases, UGT80A2 and UGT80B1, revealed new details on the composition of sitosteryl, campesteryl and stigmasteryl glucosides and ASG. SG were decreased by 86% in the ugt80A2,B1 double mutant, compared to the wild‐type, while ASG were reduced 96%. The results indicate that these glucosyltransferases account for much of the accumulation of the sterol conjugates in wild‐type Arabidopsis seeds.
Pineal cysts in children
Authors: Lacroix-Boudhrioua V. , Linglart A. , Ancel P. Y. , Falip C. , Bougnères P. F. , Adamsbaum C.
Published: August 2011

Objective

To describe the prevalence and characteristics of pineal cysts found on MRI in children.

Methods

This is a retrospective monocentric study of all brain magnetic resonance imaging (MRI) examinations performed under the same technical conditions for checking the idiopathic nature of short stature (ISS group, n = 116) and for the investigation of central precocious puberty (CPP) over a 3-year period (n = 56). Dimensions, wall and septal thickness, number of locules, signal intensity, and the presence of a solid component were analysed. Ten of 19 cysts were re-evaluated (follow-up interval 4–28 months). The prevalence of the pineal cysts was compared between the two groups using χ2 and Fisher’s exact tests, and a significance threshold of p < 0.05.

Results

The prevalence of cysts was comparable in the two groups, CPP (10.7%) and ISS (11.2%). Cyst characteristics were similar in the two groups and 74% had thin septations. None of the cysts changed on follow-up. None of the children with pineal cysts exhibited neurological signs.

Conclusion

Benign pineal cysts are a common finding in young children. High-resolution MRI demonstrates that these cysts are often septated. This pattern is a normal variant and does not require follow-up MR imaging or IV contrast media.
Contrast-enhanced ultrasound (CEUS) in Crohn’s disease: technique, image interpretation and clinical applications
Authors: Ripollés Tomás , Martínez-Pérez María J. , Blanc Esther , Delgado Fructuoso , Vizuete José , Paredes José M. , Vilar José
Published: August 2011

Background

Recent meta-analysis has demonstrated no significant differences in diagnostic accuracy among different imaging techniques (US, MRI and CT) in the evaluation of Crohn’s disease (CD). High-resolution bowel ultrasound has emerged as an alternative imaging technique for the diagnosis and follow-up of patients with CD, being as accurate as CT and MR for detecting intramural and extramural extension of the disease. B-Mode US can evaluate the localization and length of the affected intestinal segments and allow identification of transmural complications, stenosis and intestinal obstruction. Doppler techniques are tools that visualize and quantify bowel vascularization. Contrast-enhanced ultrasound (CEUS) is a new technique that involves IV administration of an ultrasound contrast agent with real-time examination, providing an accurate depiction of the bowel wall microvascularization and the perienteric tissues. The introduction of imaging quantification techniques enables an objective quantitative measurement of the enhancement.

Method and results

The article reviews the technique, sonographic findings, advantages and limitations, and clinical applications of contrast-enhanced US in the evaluation of Cohn’s disease. Current CEUS applications in CD are: CD activity assessment, evaluation of inflammatory masses, distinguishing phlegmons from abscesses, characterization of stenosis by differentiating fibrosis from inflammation, monitoring the efficacy of drug treatments and improving the detection of disease recurrence.

Conclusion

CEUS is an emerging technique that is part of the entire sonographic evaluation, with a role in the diagnosis and follow-up of CD, thus improving therapy planning and monitoring of the efficacy of treatment.
Exponential global attractors for semigroups in metric spaces with applications to differential equations
Authors: CARVALHO ALEXANDRE N. , CHOLEWA JAN W.
Published: August 2011

In this article semigroups in a general metric space V, which have pointwise exponentially attracting local unstable manifolds of compact invariant sets, are considered. We show that under a suitable set of assumptions these semigroups possess strong exponential dissipative properties. In particular, there exists a compact global attractor which exponentially attracts each bounded subset of V. Applications of abstract results to ordinary and partial differential equations are given.
Biological indicators of thein-uteroenvironment and their association with birth weight for gestational age
Authors: Talge N. M. , Holzman C. , Senagore P. K. , Klebanoff M. , Fisher R.
Published: August 2011

Birth weight for gestational age (BW/GA) has been associated with a risk of adverse health outcomes. Biological indices of pregnancy complications, maternal mid-pregnancy serum biomarkers and placental pathology may shed light on these associations, but at present, they are most often examined as single entities and offer little insight about overlap. In addition, these indices are typically assessed in relation to the extremes of the BW/GA distribution, leaving open the question of how they relate to the entire BW/GA distribution. Addressing issues such as these may help elucidate why postnatal health outcomes vary across the BW/GA continuum. In this study, we focused on a subset of women who participated in the Pregnancy Outcomes and Community Health Study (n= 1371). We examined BW/GA (i.e. gestational age and sex-referencedz-scores) in relation to obstetric complications, second trimester maternal serum screening results and histologic evidence of placental pathology along with maternal demographics, anthropometrics and substance use. In adjusted models, mean reductions in BW/GAz-scores were associated with preeclampsia (β= −0.70, 95% CI −1.04, −0.36), high maternal serum alpha fetoprotein (β= −0.28, 95% CI −0.43, −0.13), unconjugated estriol (β= −0.31/0.5 multiples of the median decrease, 95% CI −0.41, −0.21) and high levels of maternal obstructive vascular pathology in the placenta (β= −0.46, 95% CI −0.67, −0.25). The findings were similar when preterm infants, small-for-gestational age or large-for-gestational age infants were excluded. More research is needed to examine how the factors studied here might directly mediate or mark risk when evaluating the associations between BW/GA and postnatal health outcomes.
Epigenetic alterations and autoimmune disease
Authors: Renaudineau Y. , Beauvillard D. , Padelli M. , Brooks W. H. , Youinou P.
Published: August 2011

Recent advances in epigenetics have enhanced our knowledge of how environmental factors (UV radiation, drugs, infections, etc.) contribute to the development of autoimmune diseases (AID) in genetically predisposed individuals. Studies conducted in monozygotic twins discordant for AID and spontaneous autoimmune animal models have highlighted the importance of DNA methylation changes and histone modifications. Alterations in the epigenetic pattern seem to be cell specific, as CD4+ T cells and B cells are dysregulated in systemic lupus erythematosus, synovial fibroblasts in rheumatoid arthritis and cerebral cells in multiple sclerosis. With regard to lymphocytes, the control of tolerance is affected, leading to the development of autoreactive cells. Other epigenetic processes, such as the newly described miRNAs, and post-translational protein modifications may also be suspected. Altogether, a conceptual revolution is in progress, in AID, with potential new therapeutic strategies targeting epigenetic patterns.
Determinants of Hand Attractiveness—A Study Involving Digitally Manipulated Stimuli
Authors: Kościński Krzysztof
Published: August 2011

Although attractiveness of the human hand is of significance in the social and mating context, thus far it has attracted little scientific interest. In this study, young women and men were presented with pairs of digitally manipulated images of opposite-sex hands and asked to indicate the hand perceived to be the more attractive in each pair. The hands within a pair differed from one another by a single feature: shape averageness, femininity, finger length, second-to-fourth-digit ratio, or skin smoothness. All these features, with the exception of the digit ratio, were shown to increase hand attractiveness in each sex in both dorsal and ventral views. Skin smoothness was preferred more strongly in female than in male hands. Women also tended to prefer medium degrees of shape femininity and skin smoothness in male hands compared to both high and low levels. Adaptive and non-adaptive (related to perceptual bias) mechanisms underlying these preferences are discussed.
Wobbling Appearance of a Face Induced by Doubled Parts
Authors: Ueda Sayako , Kitaoka Akiyoshi , Suga Tetsuo
Published: August 2011

An illusion produced by duplicating facial parts, which can cause an unstable feeling for many observers, was investigated. We examined factors that contribute to the unstable feeling. The results suggest that this illusion is specific to face perception, and the unstable feeling may be generated by difficulty in keeping attention directed to either of the duplicated facial parts.
Inconsistent Locomotion Inhibits Vection
Authors: Seno Takeharu , Ito Hiroyuki , Sunaga Shoji
Published: August 2011

We measured the strength of illusory self-motion perception (vection) with and without locomotion on a treadmill. The results revealed that vection was inhibited by inconsistent locomotion, but facilitated by consistent locomotion.
Assessing the vulnerability of traditional maize seed systems in Mexico to climate change
Authors: Bellon Mauricio R. , Hodson David , Hellin Jon
Published: August 2011

Climate change is predicted to have major impacts on small-scale farmers in Mexico whose livelihoods depend on rain-fed maize. We examined the capacity of traditional maize seed systems to provide these farmers with appropriate genetic material under predicted agro-ecological conditions associated with climate change. We studied the structure and spatial scope of seed systems of 20 communities in four transects across an altitudinal gradient from 10–2,980 m above sea level in five states of eastern Mexico. Results indicate that 90% of all of the seed lots are obtained within 10 km of a community and 87% within an altitudinal range of ±50 m but with variation across four agro-climate environments: wet lowland, dry lowland, wet upper midlatitude, and highlands. Climate models suggest a drying and warming trend for the entire study area during the main maize season, leading to substantial shifts in the spatial distribution patterns of agro-climate environments. For all communities except those in the highlands, predicted future maize environments already are represented within the 10-km radial zones, indicating that in the future farmers will have easy access to adapted planting material. Farmers in the highlands are the most vulnerable and probably will need to acquire seed from outside their traditional geographical ranges. This change in seed sources probably will entail important information costs and the development of new seed and associated social networks, including improved linkages between traditional and formal seed systems and more effective and efficient seed-supply chains. The study has implications for analogous areas elsewhere in Mexico and around the world.
Microaerobic steroid biosynthesis and the molecular fossil record of Archean life
Authors: Waldbauer Jacob R. , Newman Dianne K. , Summons Roger E.
Published: August 2011

The power of molecular oxygen to drive many crucial biogeochemical processes, from cellular respiration to rock weathering, makes reconstructing the history of its production and accumulation a first-order question for understanding Earth’s evolution. Among the various geochemical proxies for the presence of O2in the environment, molecular fossils offer a unique record of O2where it was first produced and consumed by biology: in sunlit aquatic habitats. As steroid biosynthesis requires molecular oxygen, fossil steranes have been used to draw inferences about aerobiosis in the early Precambrian. However, better quantitative constraints on the O2requirement of this biochemistry would clarify the implications of these molecular fossils for environmental conditions at the time of their production. Here we demonstrate that steroid biosynthesis is a microaerobic process, enabled by dissolved O2concentrations in the nanomolar range. We present evidence that microaerobic marine environments (where steroid biosynthesis was possible) could have been widespread and persistent for long periods of time prior to the earliest geologic and isotopic evidence for atmospheric O2. In the late Archean, molecular oxygen likely cycled as a biogenic trace gas, much as compounds such as dimethylsulfide do today.
Arabidopsis
hybrid speciation processes
Authors: Schmickl Roswitha , Koch Marcus A.
Published: August 2011

The genus
Arabidopsis
provides a unique opportunity to study fundamental biological questions in plant sciences using the diploid model species
Arabidopsis thaliana
and
Arabidopsis lyrata
. However, only a few studies have focused on introgression and hybrid speciation in
Arabidopsis
, although polyploidy is a common phenomenon within this genus. More recently, there is growing evidence of significant gene flow between the various
Arabidopsis
species. So far, we know
Arabidopsis suecica
and
Arabidopsis kamchatica
as fully stabilized allopolyploid species. Both species evolved during Pleistocene glaciation and deglaciation cycles in Fennoscandinavia and the amphi-Beringian region, respectively. These hybrid studies were conducted either on a phylogeographic scale or reconstructed experimentally in the laboratory. In our study we focus at a regional and population level. Our research area is located in the foothills of the eastern Austrian Alps, where two
Arabidopsis
species,
Arabidopsis arenosa
and
A. lyrata
ssp.
petraea
, are sympatrically distributed. Our hypothesis of genetic introgression, migration, and adaptation to the changing environment during the Pleistocene has been confirmed: We observed significant, mainly unidirectional gene flow between the two species, which has given rise to the tetraploid
A. lyrata
. This cytotype was able to escape from the narrow ecological niche occupied by diploid
A. lyrata
ssp.
petraea
on limestone outcrops by migrating northward into siliceous areas, leaving behind a trail of genetic differentiation.
Genome-wide recombination drives diversification of epidemic strains of
Acinetobacter baumannii
Authors: Snitkin Evan S. , Zelazny Adrian M. , Montero Clemente I. , Stock Frida , Mijares Lilia ,   NISC Comparative Sequence Program, Murray Patrick R. , Segre Julie A. , Mullikin Jim , Blakesley Robert , Young Alice , Chu Grace , Ramsahoye Colleen , Lovett Sean , Han Joel , Legaspi Richelle , Sison Christina , Gregory Michael , Montemayor Casandra , Gestole Marie , Hargrove April , Johnson Taccara , Myrick Jerlil , Riebow Nancy , Schmidt Brian , Novotny Betsy , Gupta Jyoti , Benjamin Betty , Brooks Shelise , Coleman Holly , Ho Shi-ling , Schandler Karen , Smith Lauren , Stantripop Mal , Maduro Quino , Bouffard Gerry , Dekhtyar Mila , Guan Xiaobin , Masiello Cathy , Maskeri Baishali , McDowell Jenny , Park Morgan , Thomas Pamela
Published: August 2011

Acinetobacter baumannii
is an emerging human pathogen and a significant cause of nosocomial infections among hospital patients worldwide. The enormous increase in multidrug resistance among hospital isolates and the recent emergence of pan-drug–resistant strains underscores the urgency to understand how
A. baumannii
evolves in hospital environments. To this end, we undertook a genomic study of a polyclonal outbreak of multidrug-resistant
A. baumannii
at the research-based National Institutes of Health Clinical Center. Comparing the complete genome sequences of the three dominant outbreak strain types enabled us to conclude that, despite all belonging to the same epidemic lineage, the three strains diverged before their arrival at the National Institutes of Health. The simultaneous presence of three divergent strains from this lineage supports its increasing prevalence in international hospitals and suggests an ongoing adaptation to the hospital environment. Further genomic comparisons uncovered that much of the diversification that occurred since the divergence of the three outbreak strains was mediated by homologous recombination across 20% of their genomes. Inspection of recombinant regions revealed that several regions were associated with either the loss or swapping out of genes encoding proteins that are exposed to the cell surface or that synthesize cell-surface molecules. Extending our analysis to a larger set of international clinical isolates revealed a previously unappreciated ability of
A. baumannii
to vary surface molecules through horizontal gene transfer, with subsequent intraspecies dissemination by homologous recombination. These findings have immediate implications in surveillance, prevention, and treatment of
A. baumannii
infections.
Efficient transformation of an auditory population code in a small sensory system
Authors: Clemens Jan , Kutzki Olaf , Ronacher Bernhard , Schreiber Susanne , Wohlgemuth Sandra
Published: August 2011

Optimal coding principles are implemented in many large sensory systems. They include the systematic transformation of external stimuli into a sparse and decorrelated neuronal representation, enabling a flexible readout of stimulus properties. Are these principles also applicable to size-constrained systems, which have to rely on a limited number of neurons and may only have to fulfill specific and restricted tasks? We studied this question in an insect system—the early auditory pathway of grasshoppers. Grasshoppers use genetically fixed songs to recognize mates. The first steps of neural processing of songs take place in a small three-layer feed-forward network comprising only a few dozen neurons. We analyzed the transformation of the neural code within this network. Indeed, grasshoppers create a decorrelated and sparse representation, in accordance with optimal coding theory. Whereas the neuronal input layer is best read out as a summed population, a labeled-line population code for temporal features of the song is established after only two processing steps. At this stage, information about song identity is maximal for a population decoder that preserves neuronal identity. We conclude that optimal coding principles do apply to the early auditory system of the grasshopper, despite its size constraints. The inputs, however, are not encoded in a systematic, map-like fashion as in many larger sensory systems. Already at its periphery, part of the grasshopper auditory system seems to focus on behaviorally relevant features, and is in this property more reminiscent of higher sensory areas in vertebrates.
Human herpesvirus-6 entry into the central nervous system through the olfactory pathway
Authors: Harberts Erin , Yao Karen , Wohler Jillian E. , Maric Dragan , Ohayon Joan , Henkin Robert , Jacobson Steven
Published: August 2011

Viruses have been implicated in the development of neurodegenerative diseases, such as Alzheimer's, Parkinson’s, and multiple sclerosis. Human herpesvirus-6 (HHV-6) is a neurotropic virus that has been associated with a wide variety of neurologic disorders, including encephalitis, mesial temporal lobe epilepsy, and multiple sclerosis. Currently, the route of HHV-6 entry into the CNS is unknown. Using autopsy specimens, we found that the frequency of HHV-6 DNA in the olfactory bulb/tract region was among the highest in the brain regions examined. Given this finding, we investigated whether HHV-6 may infect the CNS via the olfactory pathway. HHV-6 DNA was detected in a total of 52 of 126 (41.3%) nasal mucous samples, showing the nasal cavity is a reservoir for HHV-6. Furthermore, specialized olfactory-ensheathing glial cells located in the nasal cavity were demonstrated to support HHV-6 replication in vitro. Collectively, these results support HHV-6 utilization of the olfactory pathway as a route of entry into the CNS.
Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites
Authors: Cooper George , Reed Chris , Nguyen Dang , Carter Malika , Wang Yi
Published: August 2011

Carbonaceous meteorites deliver a variety of organic compounds to Earth that may have played a role in the origin and/or evolution of biochemical pathways. Some apparently ancient and critical metabolic processes require several compounds, some of which are relatively labile such as keto acids. Therefore, a prebiotic setting for any such individual process would have required either a continuous distant source for the entire suite of intact precursor molecules and/or an energetic and compact local synthesis, particularly of the more fragile members. To date, compounds such as pyruvic acid, oxaloacetic acid, citric acid, isocitric acid, and α-ketoglutaric acid (all members of the citric acid cycle) have not been identified in extraterrestrial sources or, as a group, as part of a “one pot” suite of compounds synthesized under plausibly prebiotic conditions. We have identified these compounds and others in carbonaceous meteorites and/or as low temperature (laboratory) reaction products of pyruvic acid. In meteorites, we observe many as part of three newly reported classes of compounds: keto acids (pyruvic acid and homologs), hydroxy tricarboxylic acids (citric acid and homologs), and tricarboxylic acids. Laboratory syntheses using
13
C-labeled reactants demonstrate that one compound alone, pyruvic acid, can produce several (nonenzymatic) members of the citric acid cycle including oxaloacetic acid. The isotopic composition of some of the meteoritic keto acids points to interstellar or presolar origins, indicating that such compounds might also exist in other planetary systems.