bluuebunny/crossref_metadata_2025 huggingface dataset:
Strikingly different propulsive forces generated by different dynein‐deficient mutants in viscous media
Authors: Minoura Itsushi , Kamiya Ritsu
Published: February 2005

The propulsive force generated by Chlamydomonas mutants deficient in flagellar dynein was estimated from their swimming velocities in viscous media. The force produced by wild‐type cell increased by 30–40% when viscosity was raised from 0.9 to 2 cP but decreased as viscosity was further raised above 6 cP. The biphasic dependence of force generation on viscosity was also observed in the mutant idal, which lacks the II component of the inner‐arm dynein. The mutant ida4, which lacks the inner‐arm 12 component, was extremely susceptible to viscosity and stopped swimming at 6 cP, at which other mutants could swim. In contrast, odal, which lacks the entire dynein outer arm, produced a fairly constant force of about one‐third of the wild‐type value, over a viscosity range of 0.9–11 cP. In demembranated and reactivated cell models of the wild type, the propulsive force decreased monotonically as viscosity increased. Thus the increase in force generation at about 2 cP observed in live cells may be caused by some unknown mechanism that is lost in cell models. The cell models of odal, in contrast, did not show a marked change in force generation with the change in viscosity. These results indicate that the force generation by the outer‐arm dynein greatly depends on viscosity or the velocity of movement, whereas the complete set of inner‐arm dynein present in the odal axoneme produces a fairly constant force at different viscosities. These different properties of inner and outer dynein arms should be important in the mechanism that produces flagellar beating.
Novel mode of hyper‐oscillation in the paralyzed axoneme of a chlamydomonas mutant lacking the central‐pair microtubules
Authors: Yagi Toshiki , Kamiya Ritsu
Published: February 2005

The flageliar axoneme of the mutant pf18 lacking the central pair does not beat, but undergoes a nanometer‐scale, high‐frequency oscillation (hyper‐oscillation) in the presence of ATP [Yagi et al., 1994: Cell Motil, Cytoskeleton 29:177–185]. The present study demonstrates that the amplitude of the hyper‐oscillation increases significantly in the simultaneous presence of ATP and ADP. In addition, the hyper‐oscillation under these conditions sometimes takes on an exceptionally simple asymmetric pattern, in which the maximal shearing velocity exceeds 50 μm/sec, much higher than the maximal velocity of ordinary dynein‐microtubule sliding. The asymmetric oscillation thus appears to be at least partly driven by an internal elastic force. Its amplitude suggests that the axoneme has an elastic component that can be stretched by as long as 0.1 μm. Analyses of the asymmetric pattern further suggests that the axonemal dyneins have a tendency to attach to and detach from the doublets cooperatively and that the mechanochemical cycle of dynein has an inherent refractory period of about 2 msec, during which dynein cannot interact with microtubules.
Traction forces in locomoting cells
Authors: Oliver Tim , Jacobson Ken , Dembo Micah
Published: February 2005

A means of determining quantitative maps of the tractions exerted by locomoting cells on a substratum has been developed. This method is similar to the Harris silicone substratum assay [Harris et al., 1980: Science 208:177–179], but uses an improved non‐wrinkling film that deforms more predictably in response to traction forces. The method also utilizes a mathematical analysis of rubber deformation to produce the final map of the distribution of tractions. The resulting maps consistently showed that fish keratocytes exert a steady‐state “pinching” on the substratum, perpendicular to the cell's direction of locomotion. No significant rearward tractions were detected at or near the front edge of the cell. Likewise, no significant forward tractions associated with peeling of adhesions were found at the back of the cell. A second assay uses deflection of a lightly attached glass microneedle to measure the total force exerted by locomoting cells. Forces of approximately 4.5 × 10−3 dyn were required to “stall” locomoting keratocytes. The implications of these findings for cell movement are discussed.
Porcine brain neurofilament‐H tail domain kinase: Its identification as cdk5/p26 complex and comparison with cdc2/cyclin B kinase
Authors: Hisanaga Shin‐Ichi , Uchiyama Massashi , Hosoi Tomoko , Yamada Keisuke , Honma Naoyuki , Ishiguro Koichi , Uchida Tsuneko , Dahl Doris , Ohsumi Keita , Kishimoto Takeo
Published: February 2005

Using dephosphorylated neurofilament (NF) proteins as substrates, the kinase with a higher activity for in the dephosphorylated NF‐H than the phosphorylated form of NF‐H was searched for in the porcine brain extract. Most NF‐H kinase activity in the brain extract pelleted with microtubules. The NF‐H kinase purified from a high salt extract of the microtubule pellets was composed of cdk5 and a 26 kDa protein, a fragment of the 35 kDa regulatory subunit of cdk5. In contrast to the association of the active kinase with microtubules, each of uncomplexed cdk5 and the 35 kDa regulatory subunit was differently distributed in the supernatant fraction and the pellet, respectively, by ultracentrifugation of the brain extract. Dephosphorylated forms of NF‐H and NF‐M became reactive to antibodies recoginizing in vivo phosphorylation sites (SM131, 34, and 36, JJ31 and 51) by phosphorylation with cdk5/p26. cdk5/p26 showed similar enzymatic properties to p34cdc2/cyclin B kinase; the substrate specificity and inhibition by a p34cdc2 kinase specific inhibitor, butyrolactone I. However, p34cdc2/cyclin B kinase was distinguished from cdk5/p26 by its binding to p13suc1 protein and by its reactivity to anti‐p34cdc2 antibodies. In spite of similar enzymatic properties of cdk5/p26 and p34cdc2/cyclin B kinase, cdk5/26 did not display M‐phase promoting activity when assayed with a cell‐free system of Xenopus egg extract. © 1995 Wiley‐Liss, Inc.
Cytoskeleton of the Drosophila egg chamber: New observations on microfilament distribution during oocyte growth
Authors: Riparbelli Maria Giovanna , Callaini Giuliano
Published: February 2005

The distribution of microfilaments in Drosophila egg chambers stained with rhodamine (Rh)‐conjugated phallcidin was studied by laser scanning confocal microscopy and transmission electron microscopy. These techniques revealed new details in the pattern of microfilament localization. We observed in stage 1–3 egg chambers accumulation of filamentous actin in the oocyte cytoplasm between the ring canals connecting the oocyte with adjacent nurse cells. Starting from stages 6–7 short microfilament bundles arranged in basket‐like structures were associated with the side of the ring canals facing the nurse cell cytoplasm. We also observed a dramatic decrease in the actin network associated with the cortex of the oocyte in stage 10. During stage 10B the nurse cell cytoplasm was crossed by radial actin bundles that showed a sarcomeric‐like cross striation after Rh‐phalloidin staining. The ring canals also did not uniformly stain but showed a punctate labeling. The implications of the actin cytoskeleton during oocyte growth are discussed. © 1995 Wiley‐Liss, Inc.
Structural and biological consequences of increased vimentin expression in simple epithelial cell types
Authors: Andreoli Jeanne M. , Trevor Katrina T.
Published: February 2005

Cytoskeletal intermediate filaments (IFs) constitute a diverse family of proteins whose members are expressed in tissue‐specific patterns. Although vimentin IFs are normally restricted to mesenchyme, a variety of cell types express vimentin alone or together with cell‐specific IFs during growth, differentiation, and neoplasia. In this study, we have investigated the influence of increased vimentin expression on the simple epithelial cell phenotype. An expression vector encoding a human vimentin cDNA was transfected into the murine HR9 endoderm and F9 embryonal carcinoma cell lines, which serve as models for early extraembryonic epithelial differentiation. Stable clones that expressed varying levels of the human vimentin were characterized by immunofluorescence and biochemical analysis. A relatively high level of vimentin expression in HR9 and differentiated F9 epithelial cells resulted in aberrant vimentin structures with a co‐collapss of keratin K8/K18 filaments and lowered amounts of keratin protein. In F9 epithelial cells, the desmosomal proteins DP I/II did not appear to localize to cell surface desmosomes but rather co‐aggregated with the perturbed IFs. Although overall cell morphology was not dramatically altered, individual nuclei were distorted by excess intracellular vimentin. Furthermore, cell proliferation as well as the cell spreading response time were slowed. There appears to be a threshold effect regarding overall vimentin levels as cells that expressed lower amounts of the human vimentin exhibited no obvious structural nor biological effects. Our results demonstrate that wild‐type vimentin can act as a “mutant” protein when present at high intracellular levels, inducing a variety of phenotypic changes. © 1995 Wiley‐Liss, Inc.
Genomic structure of a cytoplasmic dynein heavy chain gene from the nematode Caenorhabditis elegans
Authors: Lye R. John , Wilson Richard K. , Waterston Robert H.
Published: February 2005

We report the cloning and sequencing of genomic DNA encoding a cytoplasmic dynein heavy chain from the nematode Caenorhabditis elegans. In a contiguous stretch of 35,103 bp of DNA from the left arm of linkage group I, we have found a gene that is predicted to encode a protein of 4,568 amino acids. This gene is composed of 15 exons and 14 relatively short introns, and it has significant homology of the other dynein heavy chains in the databases. The deduced molecular mass of the derived polypeptide is 512,624 Da. As with other dynein heavy chains that have been sequenced to date, it contains four GXXGXGK(S/T) motifs that form part of the consensus sequence for nucleotide triphosphate‐binding domains. Comparison of axonemal and cytoplasmic dynein heavy chains shows that regions of homology among all dyneins are clustered in the carboxyl terminal two‐thirds of the polypeptide, whereas the amino terminal one‐third of the heavy chains may contain domains that specify functions that differ between axonemal and cytoplasmic forms of the dynein heavy chain. © 1995 Wiley‐Liss, Inc.
Multiple protein kinase activities required for activation of sperm flagellar motility
Authors: Chaudhry Prem S. , Creagh Susan , Yu Nam , Brokaw Charles J.
Published: February 2005

A specific peptide inhibitor of the cyclic AMP (cAMP)‐dependent protein kinase (PKI‐peptide) is a very effective inhibitor of the cAMP‐dependent activation of motility of Ciona spermatozoa, when the PKI‐peptide is present at the beginning of incubation of demembranated spermatozoa with cAMP and ATP. Under conditions where approximately 120 sec is required for full activation of motility, the window of sensitivity to the PKI‐peptide lasts for only 25–30 sec. Examination of sperm pellet proteins labeled with 32P ATP during activation reveals a major 25 kDa phosphoprotein and 2 minor phosphoproteins whose phosphorylation is highly sensitive to inhibition by the PKI‐peptide and essentially complete during this early phase. These sperm proteins appear to be immediate substrates for cAMP‐dependent protein kinase, and phosphorylation of one or more of these appears to be required, but not sufficient, for activation of motility. The phosphorylation of other proteins is reduced or eliminated when PKI‐peptide is present at the beginning of incubation, but is unaffected by later addition of PKI‐peptide. Some of these substrates appear to be likely candidates for axonemal proteins that must be phosphorylated during the later stages of incubation in order to complete the activation process. This selection is based upon a high degree of inhibition by inclusion of PKI‐peptide or other inhibitors at the start of the incubation process, on near‐completion of their phosphorylation by the end of the 2 min incubation period required for activation of motility, and evidence that these proteins are phosphorylated during in vivo activation of motility. Although these observations suggest the presence of a second kinase activity that is upregulated by the initial activation of the cAMP‐dependent protein kinase, assays using exogenous substrates have not yet been able to identify such a kinase activity. © 1995 Wiley‐Liss, Inc.
Exploring the function of inner and outer dynein arms with Chlamydomonas mutants
Authors: Kamiya Ritsu
Published: February 2005

Chlamydomonas flagella contain as many as 11 different dynein heavy chains, three in the outer arm and eight in the inner. Several lines of evidence suggest that these different dyneins are functionally diverse. This diversity may be important for the generation of axonemal undulating movement.
Regulation of dynein‐driven microtubule sliding by an axonemal kinase and phosphatase in Chlamydomonas flagella
Authors: Habermacher Geoffrey , Sale Winfield S.
Published: February 2005

The following is a summary of physiological and pharmacological studies of the regulation of dynein‐driven microtubule sliding in Chlamydomonas flagella. The experimental basis for the study is described, and data indicating that an axonemal cAMP‐dependent protein kinase can regulate inner arm dynein activity are reviewed. In addition, preliminary data are summarized indicating that an axonemal type 1 phosphatase can also regulate dynein‐drive microtubule sliding velocity. It is predicted that the protein kinase, phosphatase, and an inner dynein arm component form a regulatory complex in the axoneme.
Biophysical aspects and modelling of ciliary motility
Authors: Holwill M. E. J. , Foster G. F. , Hamasaki T. , Satir P.
Published: February 2005

The dominance of viscous forces in the generation of propulsive thrust by cilia is emphasised. Fourier analysis indicates that ciliary bends consist of circular arcs joined by linear segments; this arc‐line shape appears to be a property associated with the molecular mechanism responsible for bending the cilium and is unchanged by variations in the external viscous loading on the organelle. The flexibility of a computer‐generated model of axonemal structure is demonstrated by the incorporation of recent data concerning the surface lattice of the microtubules. Computer simulations using the model show that predictions based on stochastic, rather than co‐ordinated, dynein arm activity provide a qualitative match to experimental observations of microtubules gliding over fields of dynein molecules.
Functional dissection of the dynein motor domain
Authors: Eshel Dan
Published: February 2005

The highly conserved lysine residue in the putative hydrolytic ATP‐binding motif of the yeast cytoplasmic dynein heavy chain was replaced with leucine. The mutation was generated by a two‐stage transformation method designed for genomic site‐directed mutagenesis. Preliminary observations show that the effects of this alteration on the cellular roles of dynein are indistinguishable from those of a disruption mutation in which the entire motor domain is not expressed. © 1995 Wiley‐Liss, Inc.
Recombinant expression of the brush border myosin I heavy chain
Authors: Collins Kathleen , Matsudaira Paul T.
Published: February 2005

Although the specific functions of myosin I motors are not known, their localization to membrane structures suggests a function in membrane motility. Different myosin I isoforms in the same cell or in different cells can possess different localizations. To determine if the localization and biochemical activity of the best‐characterized mammalian myosin I, chicken intestinal epithelium brush border myosin I, was dependent on determinants of the membrane or actin cytoskeleton specific to epithelial cells, we transfected the cDNA for the heavy chain of this myosin into COS cells. Transient transfection of COS cells with the chicken brush border myosin I heavy chain resulted in the production of recombinant myosin I. Recombinant brush border myosin I localized to protrusions of the plasma membrane, particularly at spreading cell edges, and also to unknown cytoplasmic structures. Some cells expressing particularly high levels of brush border myosin I possessed a highly irregular surface. Recombinant brush border myosin I purified from COS cells bound to actin filaments in an ATP‐dependent manner and decorated actin filaments to form a characteristic appearance. The recombinant myosin also catalyzed calcium‐sensitive, actin‐activated MgATPase activity similar to that of the native enzyme. Thus, any cellular factor required for the general membrane localization or biochemical activity of brush border myosin I is present in COS cells as well as intestinal epithelium.
Centripetal transport of microtubules in motile cells
Authors: Mikhailov Alexei V. , Gundersen Gregg G.
Published: February 2005

The Study of microtubule (MT) dynamics in cells has largely been restricted to events occurring over relatively short periods in nonmotile or stationary cell in culture. By using the antioxidant, Oxyrase, we have reduced the sensitivity of fluorescent MTs to photodamage and this has allowed us to image fluorescent MTs with good temporal resolution over much longer periods of time. We have used our enhanced imaging capabilities to examine MT dynamics in fibroblasts moving directionally into a wound. We found that MTs in these cells exhibited dynamic instability similar to that reported for other cells. More interestingly, we found a novel dynamic behavior of the MTs in wihch entire MTs were moved inward from the leading edge toward the cell nucleus. This centripetal transport (CT) of MTs only occurred to those MTs that were oriented with their long axis parallel to the leading edge; radially oriented MTs were not transported centripetally. Both small bundles of MTs and individual MTs were observed to undergo CT at a rate of 0.63 × 0.37 μm/min. This rate was similar to the rate of CT of latex beads applied to the cell surface and of endogenous pinocytotic vesicles in the cytoplasm. When we imaged both MTs and pinocytotic vesicles, we found that the pinocytotic vesicles were ensheathed by a small group of parallel MTs that moved centripetally in concert with the vesicles. Conversely, we found many instances of MTs moving centripetally without associated vesicles. When cells were treated with nocodazole to depolymerize MTs rapidly, the rate of pinocytotic vesicle CT was inhibited by 75%. This suggests that centripetal transport of MTs may be involved in the movement of pinocytotic vesicles in cells. In conclusion, our results show that MTs in motile cells are redistributed by a novel mechanism, CT, that does not require changes in polymer length. The centripetally transported MTs may play a role in transporting pinocytotic vesicles in the cell. © 1995 Wiley‐Liss, Inc.
Visualization of the transverse cytoskeletal network in insect‐flight muscle by scanning‐electron microscopy
Authors: Trombitás Karoly , Pollack Gerald H.
Published: February 2005

Located at the level of the Z‐line, the transverse cytoskeletal network of insectflight muscle interconnects adjacent myofibrils with one another, and interconnects peripheral myofibrils with the cell membrane. This network has been presumed to keep myofibrils in register, or to distribute tension laterally among myofibrils. In this study, we used scanning‐electron microscopy to reveal details of the three‐dimensional arrangement of this network. The network is seen to interconnect longitudinal elements of the cytoskeletal network which surround each myofibril. The arrangement is not unlike that seen in vertebrate skeletal muscle. Interestingly, the transverse network makes contact with cell components such as dense bodies and mitochondria. Such contacts imply potential roles over and above those noted above. The network may be involved not only in mechanical function, but possibly also in intracellular communication. © 1995 Wiley‐Liss, Inc.
Changes of cell behavior by near‐infrared signals
Authors: Albrecht‐Buehler Guenter
Published: February 2005

3T3 mouse fibroblasts responded differently to specific near‐infered signals than epithelial CV1 cell. Furthermore, signals with the same wavelength and energy changed the percentages of attracted and repelled 3T3 cells if their intensity modulation was altered. I found this result in a 22 month long study which established a spectrum of motile responses of 781 individual 3T3 cells and 148 CV1 cells to the near‐infrared emissions of microscopic, pulsating light sources using the infrared spot‐irradiation phase‐contrast (IRSIP) microscopic [Albrecht‐Buehler, 1991: J. Cell Biol. 114:493–502]. Thus the response of cultured, mammalian cells to near‐infrared light signals is not merely a matter of total energy absorption by cirtain cytoplasmic componets. Since it seems to depend on the cell type and the temporal pattern in which the light energy is emitted, it appears to imply the existence of a new kind of cellular information. © 1995 Wiley‐Liss, Inc.
Recent progress in lateral overgrowth of semiconductor structures from the liquid phase
Authors: Zytkiewicz Z. R. , Dobosz D. , Liu Y. C. , Dost S.
Published: February 2005

The article presents a short review of recent developments in epitaxial lateral overgrowth (ELO) of thin layers of III‐V compound semiconductors by liquid phase epitaxy (LPE) and also by liquid phase electroepitaxy (LPEE). The focus is on the relative contributions of various transport processes involved in ELO toward the growth of high quality, dislocation free thin layers of semiconductors with large width/thickness ratios. Results of our experimental and modelling studies on lateral overgrowth by LPE are used as examples. Furthermore, the application of LPEE for lateral overgrowth of compound semiconductors, a new emerging area of ELO technology, is discussed, and some experimental and numerical results are presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Monte Carlo study of the dependence of the habits of Kossel crystal on dynamic parameters during two‐dimensional growth
Authors: Prywer J. , Krukowski S.
Published: February 2005

We present the Monte Carlo simulation results, demonstrating that the habit of two‐dimensional growth of Kossel crystals depends on supersaturation and surface diffusion barrier. It is shown that at very small supersaturation, the surface diffusion plays dominant role and controls the resulting growth shapes. At higher supersaturation the growth habit is universal and does not depend on surface diffusion rates. Further increase of the supersaturation leads to unstable growth morphologies. These Monte Carlo results are analyzed using SHAPE package in order to derive the relative growth rates along different crystallographic directions. Using these data the dependence of the growth habit on the energetic parameters: bond energy and temperature and dynamic parameters: supersaturation and surface diffusion is given. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of growth conditions and structure of SrAl0.5Ta0.5O3 : LaAlO3 : CaAl0.5Ta0.5O3 crystals
Authors: Aleksiyko R. , Berkowski M. , Fink‐Finowicki J. , Diduszko R. , Byszewski P. , Kikalejshvili‐Domukhovska R.
Published: February 2005

(SrAl0.5Ta0.5O3)1‐x‐y(LaAlO3)x(CaAl0.5Ta0.5O3)y perovskite crystals of general formula ABO3 (where A = Sr1‐x‐yLaxCay and B = Al1/2+x/2Ta1/2‐x/2) were grown by the Czochralski and floating zone methods in wide a composition range. The experiments allowed us to determine regions on the composition diagram where solid solution crystals exist. The structure of the crystals at room temperatures was investigated by X‐ray measurements. Structure of the crystals at constant radius of B‐ions depends on the volume of a primitive perovskite unit cell. Thus, the structure undergoes transition from the cubic lattice of Fm3m + Pm3m space group symmetry through tetragonal (P4/mbm) to orthorhombic (Pbnm) with decreasing the primitive perovskite unit cell volume. One expects that with changing the temperature the crystals undergo second order structural phase transitions but no heat effects by differential scanning calorimetry were observed. There were no twins detected in the crystals with the cubic and tetragonal structures. The range of the lattice parameters variation and the high melting point indicate that these crystals may be used as substrates for HTSc, manganites or GaN epitaxial layers because of their high thermal and chemical stability.
Growth and optical characterization of Cd1‐xBexSe and Cd1‐xMgxSe crystals
Authors: Firszt F. , Wronkowska A. A. , Wronkowski A. , Łęgowski S. , Marasek A. , Męczyńska H. , Pawlak M. , Paszkowicz W. , Strzałkowski K. , Zakrzewski A. J.
Published: February 2005

Cd1‐xBexSe and Cd1‐xMgxSe solid solutions were grown from the melt by the high pressure Bridgman method. Optical, luminescence and photothermal properties of these materials were investigated. Spectroscopic ellipsometry was applied for determination of the spectral dependence of the complex dielectric function $ \tilde \varepsilon $(E) and refractive index n(E) at room temperature in the photon energy range 0.75‐6.5 eV for samples with optic axis (c‐axis) perpendicular to the air‐sample interface. The critical point (CP) parameters for E0 and E1 transitions were determined using a standard excitonic CP function to fit the numerically calculated differential spectra ∂2ε2/∂E2. The dispersion of the refractive index of the alloys was modelled using a Sellmeier‐type relation. The values of fundamental and exciton band‐gap energies were estimated from the ellipsometric and photoluminescence measurements. The origin of luminescence in Cd1‐xBexSe and Cd1‐xMgxSe was discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of semi‐insulating InP co‐doped with Ti and various acceptors for use in X‐ray detection
Authors: Zdansky K. , Pekarek L. , Gorodynskyy V. , Kozak H.
Published: February 2005

Semi‐insulating InP single crystals co‐doped with Zn and Ti and co‐doped with Ti and Mn were grown by Czochralski technique. Wafers of these crystals were annealed for a long time at a high temperature and cooled slowly. The samples were characterized by temperature dependent resistivity and Hall coefficient measurements. The binding energies of Ti in semi‐insulating InP co‐doped with Ti and Zn and co‐doped with Ti and Mn were found to differ which shows that Ti may occupy different sites in InP. The curves of Hall coefficient vs. reciprocal temperature deviate from straight lines at low temperatures due to electron and hole mixed conductance. The value of resistivity of the annealed semi‐insulating InP co‐doped with Ti and Mn reaches high resistivity at a reduced temperature easily achievable by thermo‐electric devices which could make this material useable in X‐ray detection. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study on shaped single crystal growth and scintillating properties of Bi‐doped rare‐earth garnets
Authors: Novoselov A. , Yoshikawa A. , Nikl M. , Solovieva N. , Fukuda T.
Published: February 2005

Shaped single crystals of Bi:Gd3Ga5O12 (Bi = 0.102, 0.126 and 0.141 mol.%) and Bi:Y3Ga5O12 (Bi = 0.041, 0.047 and 0.061 mol.%) were grown by the micro‐pulling‐down method. Measured optical absorption spectra show an absorption band round 290 nm ascribed to the lowest energy 6s2→6s6p transition of Bi3+. Difference in the position of the emission spectra of Bi‐related bands in Gd3Ga5O12 (470 nm) and Y3Ga5O12 (314 nm) was explained by the lower local distortion of Bi polyhedron in Y3Ga5O12 host leading to smaller Stokes shift of only 0.36 eV. Unsuitability of Bi‐doping in the Gd3Ga5O12 host to get energy transfer from Gd3+ towards Bi3+ centers was concluded, while Bi‐doped Y3Ga5O12 could compete against Bi4Ge3O12 scintillator. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FTIR absorption study of hydroxyl ions in KHo(WO4)2 single crystals
Authors: Kovács L. , Borowiec M. T. , Majchrowski A. , Baraldi A. , Capelletti R.
Published: February 2005

The presence of hydroxyl ions has been detected in as‐grown KHo(WO4)2 double tungstate single crystals by Fourier Transform Infrared (FTIR) spectroscopy. The absorption bands of the stretching vibration of OH– ions have been observed between 8–300 K in the 3450–3650 cm–1 wave number range. The temperature and polarization dependences of several intense narrow absorption lines corresponding to hydroxyl ions in different environments have been studied in detail. All lines were shifted, broadened and their intensity was decreased by increasing temperature due to phonon coupling. The band intensities strongly depended on the light propagation and polarization directions, allowing the determination of the orientation of OH– dipoles with respect to the crystallographic axes. The isotopic replicas of several OH– bands have been detected between 2550–2650 cm–1 in crystals treated in D2O water vapour at 873 K. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Behaviour of surface phonons in LiCsSO4 crystal at phase transition
Authors: Trzaskowska A. , Mielcarek S. , Mroz B.
Published: February 2005

The paper reports results of Brillouin spectroscopy study performed on surface phonons in different crystallographic surfaces of crystals, in a wide temperature range but with particular emphasis on the temperatures covering the phase transition. The main aim of the study is to establish in which way the ferroelastic phase transition related to a strong soft bulk mode is reflected in the near‐surface region of the ferroelastic crystals. Results of the Brillouin scattering of the surface phonons propagating in the ferroelastic crystal LiCsSO4 in the temperature range covering its phase transition are presented. Surface acoustic phonons in different planes and at various depths from the surface have been studied. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of bismuth triborate single crystal using Brillouin and Raman spectroscopy
Authors: Kasprowicz D. , Runka T. , Szybowicz M. , Ziobrowski P. , Majchrowski A. , Michalski E. , Drozdowski M.
Published: February 2005

The bismuth triborate (BiB3O6; BIBO) single crystal has been studied by Brillouin and Raman spectroscopy. Using Brillouin spectroscopy the propagation of the acoustic phonons in [100], [010], [001], [110] and [011] directions has been analyzed. The influence of birefringent and optical activity of BIBO crystal on some acoustic phonons has been discussed. The Raman spectra of the crystal in different scattering geometries have been recorded in the 50–1500 cm‐1 spectral range at room temperature. The number and symmetry of Raman active modes was determined on the basis of site symmetry group analysis. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hologram characteristics of Mn, Tb co‐doped stoichiometric LiNbO3 single crystals
Authors: Lee H. J. , Shin T. I. , Lee S. M. , Yoon D. H.
Published: February 2005

Mn, Tb co‐doped stoichiometric LiNbO3 (Mn:Tb:SLN) single crystals of 0.5∼1.0 mm in diameter and 30∼35 mm in length were grown using the micro‐pulling down (µ‐PD) method. Mn:Tb:SLN single crystals were also grown to 20‐25 mm in diameter and 30‐35 mm in length using the Czochralski (CZ) method. The homogeneous distributions of Mn and Tb concentration were confirmed by the EPMA and defects were observed by optical microscopy. We investigated the photoluminescence (PL) and hologram grating properties of Mn:Tb:SLN single crystals. The effect of concentration of dopant MnO2 and Tb4O7 on the luminescnce properties of the Mn:Tb:LiNbO3 single crystals excited by laser line 325 nm, 488 nm and 514 nm is reported. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of Al‐Cu‐Co single quasicrystals by X‐ray topography
Authors: Bogdanowicz W.
Published: February 2005

Al‐Cu‐Co single quasicrystals were studied by the reflective X‐ray topography. It was found that on the surfaces of the single quasicrystals, which were parallel to (00001) decagonal plane, the contrast associated with screw dislocation occurs. In the topograms taken from other surfaces of the single quasicrystals the bands of contrast appear. This contrast comes from the antiphase domains and depends on the conditions of the single quasicrystals growth process. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Early stages of low temperature epitaxial growth of InSb on GaAs
Authors: Borowska A. , Gutek J. , Czajka R. , Oszwaldowski M. , Richter A.
Published: February 2005

Early stages of the growth of the low‐temperature InSb under‐layer in the two‐stage method of the heteroepitaxial growth of InSb layers on GaAs substrates are studied. The investigated orientations are: (100), (111)A, (111)B, (110) planes and (110) plane misoriented by 3° towards the <100> direction. The investigated deposits are prepared by the flash evaporation method. InSb deposits having an average layer thickness between 2 nm and 10 nm consist of separate grains with a grain diameter of around 30 nm. Independent of the substrate orientation, they are oriented in conformity with the substrate, confirming that the initial mode of the growth is that of Stransky‐Krastanov. Annealing of the layers at 470 °C improves the crystallinity of the grains. The same annealing of 30 nm thick layers results in a decrease in their resistance and the surface roughness. The greatest changes are observed in the (100) oriented layers, and the smallest changes are observed in the (110) oriented layers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aqueous Phase One‐Electron Reduction of Sulfonium, Selenonium and Telluronium Salts
Authors: Eriksson Per , Engman Lars , Lind Johan , Merényi Gabor
Published: February 2005

Triorganylsulfonium, ‐selenonium and ‐telluronium salts were reduced by carbon dioxide radical anions/solvated electrons produced in aqueous solution by radiolysis. The radical expulsion accompanying reduction occurred with the expected leaving group propensities (benzyl > secondary alkyl > primary alkyl > methyl > phenyl), although greater than expected loss of the phenyl group was often observed. Diorganyl chalcogenides formed in the reductions were conveniently isolated by extraction with an organic solvent. Product yields based on the amount of reducing radicals obtained from the γ‐source were often higher than stoichiometric (up to 1800 %) in the reduction of selenonium and telluronium compounds; it is likely that this result can be accounted for in terms of a chain reaction with carbon‐centred radicals/formate serving as the chain transfer agent. The product distribution was essentially independent of the reducing species for diphenyl alkyl telluronium salts, whereas significant variations were seen for some of the corresponding selenonium salts. This would suggest the intermediacy of telluranyl radicals in the one‐electron reduction of telluronium salts. However, pulse radiolysis experiments indicated that the lifetimes of such a species (the triphenyltelluranyl radical) would have to be less than 1 μs. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthesis of Functionalized Nitrogen Heterocycles by Radical Decarboxylation of β‐ and γ‐Amino Acids
Authors: Boto Alicia , Hernández Rosendo , de León Yolanda , Murguía José R. , Rodriguez‐Afonso Abigail
Published: February 2005

Iodinated or oxygenated nitrogen heterocycles are obtained by radical decarboxylation of β‐ and γ‐amino acids. This mild, versatile reaction is applied to the synthesis of bioactive products, such as 4‐arylpiperidines, hydroxylated piperidines, and new antifungal agents.
Parallel‐recording systems for electron energy loss spectroscopy (EELS)
Authors: Egerton R. F.
Published: February 2005

The present report paper deals with the use of a photodiode array for recording electron energy loss spectra in a transmission electron microscope. Important properties of the array are outlined, together with a description of the circuitry needed for interfacing the output to a multichannel analyser.

In the direct‐exposure mode, the device can easily detect a single (80 or 100 keV) electron, allowing inner‐shell energy losses between 200 eV and 2000 eV to be recorded in about 10 seconds. By signal averaging a large number of readouts, a dynamic range of at least 105 is possible. Irradiation damage to the array can be controlled by cooling the array and by various anealing procedures. Sensitivity and DQE are lower, but the dynamic range is higher in the indirect mode, where a fluorescent screen is used to convert the electrons into visible photons, which are then imaged onto the diodes. The choice of screen material and of optical coupling to the array are discussed. Several spectral artifacts are described, together with spectrum‐processing techniques designed to remove them.
The usefulness of glutaraldehyde‐carbohydrazide copolymerization in biological specimen stabilization for scanning electron microscopy
Authors: Gunning William T. , Crang Richard E.
Published: February 2005

Biological specimens can be prepared for scanning electron microscopy by means of copolymerizing the fixing agent glutaraldehyde with carbohydrazide prior to air drying. Such preparations are more stable in the electron microscope, show less internal cellular disruption and retain more of their native elemental composition than specimens prepared by means of dehydration and critical‐point drying. Specimens observed in the scanning electron microscope can often be recovered for thin sectioning with no additional embedment, and can then be observed by means of transmission elecltron microscopy. The preparation (termed GACH) can be performed in almost any laboratory with no specialized equipment and, for the most part, may be carried out at room temperature. The technique appears to provide the promise of further research applications in scanning electron microscopy which may employ conjugated procedures of immunocytochemistry and cathodoluminescence as well as X‐ray microanalysis in limited situations.
Energy‐dispersive X‐ray microanalysis of aqueous biologic samples on bulk supports
Authors: Roman Richard J. , Hatchell Marion
Published: February 2005

The present investigation describes a modification of the liquid droplet technique that allows for the quantitative elemental analysis of small volumes (< 100 picoliters) of aqueous biologic samples using a scanning transmission electron microscope (Philips 400 HTG‐STEM) equipped with an EDAX energy dispersive detector. Aliquots of samples and standards were micropipetted onto solid beryllium supports under paraffin oil. The oil was washed with organic solvents and the samples frozen and freeze‐dried. The samples were excited in a Philips 400‐HTG‐STEM by scanning a 1‐μm, 20‐kV electron beam over the surface of the droplets, and the X‐ray spectra were collected. Measured X‐ray intensities in characteristic peaks were found to be linearly related to the concentration of various elements in the sample. This work demonstrates the feasibility of performing quantitative elemental analysis of minute samples and cells in a scanning transmission electron microscope equipped with an energy dispersive X‐ray detector.
Intelligent interface for a microprocessor controlled scanning transmission electron microscope with x‐ray imaging
Authors: Kowarski David
Published: February 2005

An intelligent interface has been designed to perform synchronous digital image acquistion and scan generation (SDIASG interface) for a microprocessor controlled Scanning Transmission Electron Microscope (S(T)EM) with x‐ray imaging. The SDIASG interface connects an LSI‐11/2 microprocessor to a Philips EM400 electron microscope. The LSI‐11/2 microprocessor is part of a DeAnza VC5000 digital image display system. A system using the SDIASG interface is described. The system takes advantage of the SDIASG interface and a DeAnza VC5000 digital image display system to realize new capabilities that optimize conditions for x‐ray mapping.

A low characteristic x‐ray count rate is generated by the ultrathin specimens from which high resolution x‐ray maps can be obtained (Shuman et al, 1976; Somlyo and Shuman, 1982). This low count rate necessitates a long image accumulation time, which in turn makes drift correction essential for maintaining spatial resolution. The new capabilities of the system described here consist of real‐time display and summation of consecutive image and x‐ray maps, and automatic return to a high speed imaging mode between consecutive x‐ray map passes. The new capabilities combine to allow frequent correction for specimen drift between consecutive x‐ray mapping passes while still permitting a long total accumulation time for the x‐ray maps.
A procedure for rupture‐free preparation of confluently grown monolayer cells for scanning electron microscopy
Authors: Schroeter Dieter , Spiess Eberhard , Paweletz Neidhard , Benke Rosemarie
Published: February 2005

Monolayers of PtK‐1 and HeLa cells grown on glass or plastic supports are extremely susceptible to lacerations, e.g., splits and cracks caused mainly by shrinkage when prepared for scanning electron microscopy (SEM). We find that a four‐step fixation procedure including glutaraldehyde, OsO4, tannic acid, and uranylacetate application, in combination with critical point drying, drastically reduces these structural damages. In addition, the conductivity of the specimens is enhanced, so that they can be investigated without gold coating. Transmission electron microscopy (TEM) investigation of perpendicular sections in the area of lacerations provides evidence that the subcortical cytoskeletal elements are of crucial importance in maintaining cell membrane stability during the preparations. Our relatively quick and simple procedure results in an improved structural appearance of the cells.
Protein A‐gold electron microscopic immunocytochemistry: Methods, applications, and limitations
Authors: Bendayan Moïse
Published: February 2005

The postembedding protein A‐gold immunocytochemical approach has been introduced as an alternative to other techniques for the ultrastructural localization of antigenic sites. The present review deals with the development, the theoretical background, and technical approach of the protein A‐gold method as well as the different modifications introduced in order to enhance the resolution of the results and to perform double labelings on the same section. Various examples demonstrate the reliability and the wide range of application of this technique. In addition, some problems, pitfalls, and limitations particular to this method are reported.
Application of the Laplacian filter to high‐resolution enhancement of SEM images
Authors: Oho Eisaku , Baba Norio , Katoh Masaru , Nagatani Takashi , Osumi Masako , Amako Kazunobu , Kanaya Koichi
Published: February 2005

Certain digital image‐processing methods, which are useful for nonperiodic structural images, have been applied to high‐resolution SEM images for the improvement of resolution. Samples utilized in the present study consisted of magnetic tape coated with gold, T4 phage coated with gold‐palladium, and uncoated specimens of Prolamellar body (PLB) in Cucurbita moschata. These images were blurred and otherwise disturbed by electronic noise, though the images were taken at the limit of efficiency of intrinsic instrument. The major image‐processing tool was the Laplacian filter, which subtracts the Laplacian from the original image. Noise, which is a serious problem in digital processing of high‐resolution SEM images, was suppressed by the nonlinear type smoothing method. Also, the noise was evaluated by an autocorrelation function and a power spectrum of the image. By using these methods of “deblurring” and noise removal, we achieved better resolution, and structural details of our biological specimens were revealed.
Electron crystal structure analysis of small organic molecules
Authors: Dorset Douglas L.
Published: February 2005

Electron crystallography of small organic molecules, i.e., electron diffraction crystal structure analysis, has been long recognized to possess definite advantages over neutron and x‐ray diffraction techniques for the investigation of microcrystalline preparations. Quantitative application of the technique to real structural problems, on the other hand, had been hindered initially by an inadequate theoretical model. Yet, as demonstrated in this review of the methodology, the adequate recognition of limiting factors due to n‐beam dynamical scattering and crystal deformation permits design of optimal diffraction experiments which yield intensity data suitable for ab initio structure analysis. Representative crystallographic analyses discussed here underscore the utility of this technique as a probe of organic molecular structure at atomic resolution.
Localization of proteins on viral nucleocapsids using immunoelectron microscopy
Authors: Murti K. G. , Portner A. , Troughton K. , Deshpande K.
Published: February 2005

We have described an indirect immunoelectron microscope method to localize individual proteins on viral nucleocapsids using monoclonal antibodies and colloidal gold‐conjugated second antibodies. The procedure provides good binding and retention of antibodies, good resolution(< 24nm), and negligible nonspecific binding of antibodies to the background. In addition, the method is compatible with both negative and positive staining, the two staining procedures commonly used to derive ultrastructural information on viral chromosomes. We have illustrated the procedure by localizing the NP (nucleoprotein, ≈︁ 2,600 copies) and P (polymerase‐associated protein, ≈︁ 300 copies) proteins on the nucleocapsid of Sendai virus, a paramyxovirus.
Cautions, common sense, and rationale for the electron microscopy laboratory
Authors: Smithwick Eleanor B.
Published: February 2005

This paper is a condensation of precautions, general information, and common‐sense tips designed to assist students in electron microscopy. Although not all circumstances are included and many of the recommendations are common sense, this handout has proven invaluable to beginners in two different multiuser electron microscopy facilities. When integrated by discussion and testing into the initial training period, this information will save the neophyte, lab manager, and others working in a multiuser facility untold hours of frustration, of wasted time, effort, and supplies, and of exposure to the myriad environmental hazards inherent in the performance of electron microscopy. The rationale for these suggestions is included, enhancing problem‐solving in situations not covered directly in this presentation.
Structural and electron diffraction data for sapphire (α‐al2o3)
Authors: Lee W. E. , Lagerlof K. P. D.
Published: February 2005

Crystallographic and electron diffraction data for sapphire (α‐Al2O3) are presented which enable ready and unique identification of TEM diffraction patterns and facilitate image analysis. Crystallographic data is presented in the form of stereographic projections and in figures listing angles between planes and angles between zones. Electron diffraction data consist of computer‐simulated diffraction patterns and tables of extinction distances calculated using atomic and ionic electron scattering factors.