bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro binding and survival assays of Leishmania parasites to peripherical blood monocytes and monocyte-derived macrophages isolated from dogs naturally and experimentally infected with Leishmania (Leishmania) chagasi
Authors: Sampaio Weverton M , Moura Eliane P , Arruda Felipe CS , Ribeiro Raul R , Alves Cíntia F , Melo Ferdinan A , Fernandes Ana Paula SM , Michalick Marilene SM , Melo Maria N , Tafuri Washington L , Tafuri Wagner L
Published: May 2007

Background

There are a few works considering the characterization of canine monocyte-derived macrophages as well as a standardized procedure for isolation, culture, and infection of these cells withLeishmania. We have performed several modifications in order to improve the canine monocyte-derived macrophage cultures. In addition, we have done a comparative study between monocytes and monocyte-derived macrophages from dogs naturally and experimentally infected withL. chagasi.

Results

In the presence of exogenous serum, opsonizedLeishmaniapromastigotes binds better to monocytes/macrophages than without serum. Otherwise, this binding occurs due to the strict correlation between the opsonized biologic particles with the third receptor of the complement (CR3-CD11b/CD18). In fact, our assays with CD11b confirmed the importance of this receptor for canine cells and theL. chagasiexperimental system. Moreover, monocytes obtained from naturally infected dogs have shown a higher number of monocytes bounded to promastigotes. The experimental results regarding survival have shown that promastigote forms of opsonizedL. chagasiwere more infective, because we found higher numbers of promastigotes bound to the different cells. As a consequence, after forty-eight hours of binding, higher numbers of amastigotes appeared inside monocyte-macrophages.

Conclusion

These studies have given support to continue comparative studies involving canine monocytes, monocyte-derived macrophages and peritoneal macrophages. Since we have standardized the canine cell culture, we are looking forward to determining the phenotypic properties of these cells before and afterL. chagasiinfection using flow cytometry.
Priorities in Colorectal Cancer Research: Recommendations From the Gastrointestinal Scientific Leadership Council of the Coalition of Cancer Cooperative Groups
Authors: O'Dwyer Peter J. , Eckhardt S. Gail , Haller Daniel G. , Tepper Joel , Ahnen Dennis , Hamilton Stanley , Benson Al B. , Rothenberg Mace , Petrelli Nicholas , Lenz Heinz-Joseph , Diasio Robert , DuBois Raymond , Sargent Daniel , Sloan Jeff , Johnson C. Daniel , Comis Robert L. , O'Connell Michael J.
Published: May 2007

Emerging technologies have greatly expanded our ability to detect, characterize, and treat colorectal cancer. The Coalition of Cancer Cooperative Groups convened a multidisciplinary panel, the Scientific Leadership Council in GI cancer, to discuss and advise on the priorities and opportunities to advance current and future approaches into the clinical arena to impact most rapidly the morbidity and mortality from this disease. The Council's recommendations for research priorities are the result of engagement of community and academic oncologists, patient advocacy groups, and other stakeholders including the pharmaceutical industry and governmental agencies. We detail some key prospects for investigation in the areas of colon cancer detection, prevention, and surgical and medical management. Many are in early or definitive clinical trials, and a focus on rapid accrual is urged. The implementation of biology-directed laboratory investigations, both in association with ongoing clinical trials and as a separate developmental strategy for targeted therapies, is supported as the route to individualized therapy.
Image as Trace: Speculations about an Undead Paradigm
Authors: Geimer Peter
Published: May 2007

Translated by Kata Gellen

peter geimer is an art historian and assistant professor at the Swiss Federal Institute of Technology (eth) Zürich. His major scholarly interests are the history of photography, image science, the “living image,” and visualization in the natural sciences. Publications in English include the editing of UnDead: Relations between the Living and the Lifeless (Preprint, Max Planck Institute for the History of Science, Berlin 2003; forthcoming Kadmos, 2007).

kata gellen is a PhD candidate in the Department of German at Princeton University. She is currently writing her dissertation on the figure of noise in modern German literature. Her essay “The Opaque Voice: Canetti's Foreign Tongues” is forthcoming in a collection of essays edited by William Donahue and Julian Preece called The Worlds of Elias Canetti (Cambridge Scholars Press, 2007).
Regulated Nodal signaling promotes differentiation of the definitive endoderm and mesoderm from ES cells
Authors: Takenaga Masanori , Fukumoto Miki , Hori Yuichi
Published: May 2007

Nodal signaling induces the formation of the endoderm and mesoderm during gastrulation. Nodal expression persists until the definitive endoderm progenitor has completely formed, and disappears thereafter. A tightly regulated Nodal expression system is essential for the differentiation of embryonic stem (ES) cells into distinct tissue lineages. On this basis, we established an ES cell differentiation system with the tetracycline-regulated expression of Nodal. The upregulated Nodal signaling pathway and its downstream transcriptional targets induced the specification of ES cells into definitive endoderm and mesoderm derivatives, and the subsequent downregulation of Nodal signaling promoted further maturation of the gut tube both in vitro and in vivo. Sustained expression of the Nodal gene inhibited the maturation of the definitive endoderm owing to persistent Oct3 and/or Oct4 expression and teratoma formation. Furthermore, quantitative single cell analysis by flow cytometry using CXCR4, VEGFR2 and PDGFR-α indicated that this protocol for definitive endoderm and mesoderm differentiation is superior to any other available protocol. Our findings also indicated that the Nodal or Nodal-related molecules secreted from Nodal-expressing ES cells could cause genetically unmanipulated ES cells to induce the expression of the Nodal signaling pathway and its downstream targets, which consequently leads to the differentiation of the ES cells into definitive endoderm and mesoderm. Our differentiation system, using tightly regulated Nodal expression, enabled us to investigate the mechanism of ES cell differentiation into definitive endoderm or mesoderm derivatives. Our findings also demonstrate that Nodal-expressing ES cells might be a source of highly active proteins that could be used for developing endoderm or mesoderm tissues in regenerative medicine.
Ear tag induced Staphylococcus infection in mice
Authors: Cover C. E. , Keenan C. M. , Bettinger G. E.
Published: May 2007

Mice used in a 2-year oral toxicity study developed a progressive, moist dermatitis. The initial lesions were seen around the ears in which metal identification tags had been placed and usually progressed to include the skin of the neck and shoulder. Clinically, the mice were pruritic, lost weight, had rough coats, and became moribund. The predominant finding at necropsy was pale brown kidneys with irregular granular surfaces. Histologically, there was inflammation and focal-to-diffuse necrosis in the visceral organs and affected skin. The predominant organism isolated from the skin, kidneys and heart blood was Staphylococcus aureus. This bacterium is a common inhabitant of the skin of conventionally housed mice and its isolation from the kidneys and blood suggested that the portal of entry was the wound caused by the insertion of the metal ear tag.
Efficacy of a commercial bacterin in protecting Strain 13 guineapigs against Bordetella bronchiseptica pneumonia
Authors: Stephenson E. H. , Trahan C. J. , Ezzell J. W. , Mitchell W. C. , Abshire T. G. , Oland D. D. , Nelson G. O.
Published: May 2007

Bordetella bronchiseptica is known to be endemic in many guineapig ( Cavia porcellus) colonies, and periodically is the aetiological agent of fatal epizootics of bronchopneumonia. A commercial, non-adjuvant B. bronchiseptica bacterin, which is approved for use in canines, was evaluated for induction of a protective immune response in Strain 13/N guineapigs against an airborne challenge of virulent B. bronchispeptica in small-particle aerosol. Seronegative animals were vaccinated on days 0 and 21 with intramuscular injections of 0·2 ml of bacterin. Humoral antibody titres of the vaccinated animals, as determined by ELISA, ranged from 128-1024 on day 49. On day 30 following the second dose of bacterin (study day 51), 12 vaccinated and 12 PBS sham-vaccinated animals were exposed to an inhaled dose of 4·3 × 105 CFU of B. bronchiseptica (325 LD50). Vaccinated, challenged animals remained clinically normal, although each guineapig did develop a localized upper respiratory infection. The rate of weight gain as well as rectal temperature of these animals were analogous to those exhibited by the control groups. Examination of 4 of the vaccinated, challenged animals on day 7 after exposure showed bacteria present in moderate to high numbers in the larynx and trachea but only minimally detectable in the lungs; by 30 days after exposure, the numbers of bacteria in the larynx and trachea were diminshed, with none being detected in the lungs. Pathological alterations induced by B. bronchiseptica were not detected at either day 7 or day 30 after challenge in any of the vaccinated, challenged animals. Protection induced in Strain 13/N guineapigs by the commercial canine bacterin was sufficient to preclude the development of pulmonary disease, even in animals presented with a massive challenge of virulent bacteria in a small-particle aerosol.
Carbon dioxide as a short-term restraint anaesthetic in rats with subclinical respiratory disease
Authors: Fenwick D. C. , Blackshaw J. K.
Published: May 2007

The use of carbon dioxide (CO2) with, and without, oxygen (O2) as a short-term restraint anaesthetic for Wistar rats in which subclinical respiratory disease was endemic, was assessed in 3 separate experiments. In the first, rats were placed in a CO2 atmosphere generated from solid CO2 chips in a 701 plastic bin, and removed at time intervals ranging from 0 to 120 s after disappearance of the pedal reflex. Eight of 25 rats died, including 2 which were removed immediately the pedal reflex disappeared; it was concluded that CO2 without O2 was not a suitable short-term anaesthetic for rats. In a second study, rats were anaesthetized in atmospheres of 50 : 50 and 80 : 20 (CO2 : O2) provided from commercially available cylinders, in 2 different environments-a 3·41 glass jar and a 171 plastic bin. Rats became excited in the plastic bin but not the glass jar. Rats in the glass jar displayed visible depression and cessation of whiskers movement significantly more quickly in the 80 : 20 (CO2 : O2) than in the 50 : 50 mixture (4·2±0·98 s, n = 6, and 66·0±4·9 s, n = 6 vs 13·8±2·77 s, n = 5 and 1520±20·8 s, n = 5, respectively). Rats in the 171 plastic bin lost their pedal reflexes in a mean 41·5±4·55 s ( n = 11) in the 50 : 50 mixture and in a mean 30·9±6·38 s ( n = 11) in the 80 : 20 (CO2 : O2) group. Those left in the 50 : 50 mixture for 60 sand 180 s after disappearance of their pedal reflexes, recovered these reflexes in 20·2±0·44 s and 21·5±7·23 s respectively after removal from the gas. Respiration and heart beat ceased in one rat remaining in the 50 : 50 mixture after 13 min 10 s. No untoward effects occurred in rats left in the 50 : 50 mixture for 180 s after disappearance of the pedal reflex, but 2 died when left for an equivalent period in the 80 : 20 mixture. In the third study, examples of the practical use of a 50 : 50 mixture as a short term restraint anaesthetic are described. It was concluded that this mixture was a cheap, safe, and effective means of short-term restraint for rats with subclinical respiratory disease, when the minimal time of exposure to the gases was employed.
Effect of Humic Acid on the Sorption and Kinetic Desorption of Radiocaesium Ions on/from Na-Rectorite Studied by the Batch Technique and a Chelating Resin
Authors: Wu W.S. , Fan Q.H. , Lu S. , Niu S. , Wang X.
Published: May 2007

The sorption of radiocaesium ions onto Na-rectorite was studied at a pH value of 5.0 ± 0.2 using the batch technique under ambient conditions. The effect of humic acid on the Cs+ ion sorption was also investigated. The results indicated that the presence of humic acid significantly enhanced the sorption of Cs+ ions onto rectorite. The kinetic desorption of Cs+ ions from bare and HA-bound rectorite, respectively, was studied by the addition of a chelating resin. The results obtained indicated that Cs+ ion sorption onto rectorite generated reversible and irreversible sorption sites, with the irreversible sorption sites consisting of at least two kinds, i.e. “weak” and “strong”. With increasing ageing time, surface-sorbed Cs+ ions on solid colloids can move from “weak” sites to “strong” sites, whereas that corresponding to irreversible sorption are incapable of movement irrespective of the length of the aging time. The results obtained are important for the evaluation of the behaviour of radionuclides in the natural environment.
2D Numerical Simulation of a Wind Turbine De-Icing System, Using Cycled Heating
Authors: Battisti L. , Fedrizzi R.
Published: May 2007

At cold climate sites, the icing of the turbine components, mainly the blades, affects the system's performance and safety due to the ice accretion and shedding. Consequently, the economic sustainability of wind turbine utilization in adverse climates needs some special requirements, such as anti-icing or de-icing equipment for the blades. This paper gives a numerical investigation of a new approach, consisting of cyclically de-icing the wind turbine blades by the intermittent warming of the surfaces. De-icing simulations were carried out for a MW-class rotor blade section. A parametric study investigated the sustainability and effectiveness of warm air de-icing systems, in terms of the heating cycle duration and the heating energy consumption.
Aspects of the Dynamic Response of a Small Wind Turbine Blade in Highly Turbulent Flow: Part 1 Measured Blade Response
Authors: Wilson S. V. R. , Clausen P. D.
Published: May 2007

This paper presents some dynamic measurements acquired from the surface of a composite constructed test blade on an operating 400W three-bladed wind turbine. The structural design of the composite blade was modified from the original design to reduce its stiffness in flapwise bending. Signals from 10 strain gauges attached to the blade were acquired every 45° in the azimuthal domain and at a fixed rate of 140Hz in the time domain. The test turbine was located at a highly turbulent site with the turbulence intensity between 0.3 and 0.5 at all wind speeds. Signals from the gauges show the cyclic response of the blade was dominated by the 1P frequency with influences from 2P, 3P and 4P frequencies increasing with the radial position of the gauge on the blade. Cyclic variation in the root bending moment was nearly sinusoidal, with a small plateau in the peak possibly due to the effects of large yaw angle on the blade bending moment. The blade's response to yaw was investigated for both normal yaw events, i.e. those experienced by the turbine many times during a typical day, and for extreme yaw events, i.e. which occurred infrequently. During a normal yaw event with a yaw rate of 70°/s, the cyclic variation in blade strain near the hub connection increased from 210 μstrain1 before the event to 1500 μstrain at the peak of the event. An extreme yaw event produced a yaw rate of 160°/s with the cyclic variation in strain increasing from 200 μstrain to 2600 μstrain.
Hippocampal Metaplasticity Induced by Deficiency in the Extracellular Matrix Glycoprotein Tenascin-R
Authors: Bukalo Olena , Schachner Melitta , Dityatev Alexander
Published: May 2007

Predisposition of synapses to undergo plastic changes can be dynamically adjusted according to the history of synaptic activity (i.e., synapses are metaplastic). In search of a molecular mechanism underlying metaplasticity, we investigated mice deficient in the glycoprotein tenascin-R (TNR), based on the observations that this mutant exhibits elevated basal excitatory synaptic transmission and reduced perisomatic GABAergic inhibition. TNR is a major extracellular matrix glycoprotein of the CNS and carries the HNK-1 carbohydrate (human natural killer cell glycan), which has been identified as the functional epitope mediating regulation of GABAergic transmission via GABABreceptors. Here, we used patch-clamp recordings in hippocampal slices to determine the critical levels of postsynaptic neuron depolarization necessary for induction of long-term potentiation (LTP) at CA3–CA1 synapses and found that deficiency in TNR leads to a metaplastic increase in the threshold for induction of LTP. Reconstitution of slices from TNR-deficient mice with an HNK-1 glycomimetic or pharmacological treatment with either a GABAAreceptor agonist, a GABABreceptor antagonist, an L-type voltage-dependent Ca2+channel blocker, or an inhibitor of protein serine/threonine phosphatases restored LTP to the levels seen in wild-type mice. We propose that a chain of events initiated by reduced GABAergic transmission and proceeding via Ca2+entry into cells and elevated activity of phosphatases mediates homeostatic adjustment of hippocampal plasticity in the absence of TNR. These data uncover a novel mechanism by which an extracellular matrix molecule and its associated carbohydrate provide conditions beneficial for induction of LTP in the CA1 region of the hippocampus.
Presynaptic G-Protein-Coupled Receptors Regulate Synaptic Cleft Glutamate via Transient Vesicle Fusion
Authors: Schwartz Eric J. , Blackmer Trillium , Gerachshenko Tatyana , Alford Simon
Published: May 2007

When synaptic vesicles fuse with the plasma membrane, they may completely collapse or fuse transiently. Transiently fusing vesicles remain structurally intact and therefore have been proposed to represent a form of rapid vesicle recycling. However, the impact of a transient synaptic vesicle fusion event on neurotransmitter release, and therefore on synaptic transmission, has yet to be determined. Recently, the molecular mechanism by which a serotonergic presynaptic G-protein-coupled receptor (GPCR) regulates synaptic vesicle fusion and inhibits synaptic transmission was identified. By making paired electrophysiological recordings in the presence and absence of low-affinity antagonists, we now demonstrate that activation of this presynaptic GPCR lowers the peak synaptic cleft glutamate concentration independently of the probability of vesicle fusion. Furthermore, this change in cleft glutamate concentration differentially inhibits synaptic NMDA and AMPA receptor-mediated currents. We conclude that a presynaptic GPCR regulates the profile of glutamate in the synaptic cleft through altering the mechanism of vesicle fusion leading to qualitative as well as quantitative changes in neural signaling.
Targeting Sensory Axon Regeneration in Adult Spinal Cord
Authors: Tang Xiao-Qing , Heron Paula , Mashburn Charles , Smith George M.
Published: May 2007

Extensive regeneration of sensory axons into the spinal cord can be achieved experimentally after dorsal root injury, but no effort has been made to target regenerating axons and restore a normal lamina-specific projection pattern. Ectopic axon growth is potentially associated with functional disorders such as chronic pain and autonomic dysreflexia. This study was designed to target regenerating axons to normal synaptic locations in the spinal cord by combining positive and negative guidance molecules. Previously, we observed that, after dorsal rhizotomy, overexpression of NGF leads to robust regeneration and sprouting of calcitonin gene-related peptide (CGRP)-positive nociceptive axons throughout dorsal horn and ventral horns. To restrict these axons within superficial laminas, adenovirus expressing semaphorin 3A was injected into the ventral spinal cord 3 d after NGF virus injection. Semaphorin 3A expression was observed in deep dorsal and ventral cord regions and limited axon growth to laminas I and II, shaping axonal regeneration toward the normal distribution pattern. NGF and semaphorin 3A treatment also targeted the regeneration of substance P-positive nociceptive axons but had no effect on injured isolectin B4-binding nociceptive axons. Axon regeneration led to functional restoration of nociception in both NGF- and NGF/semaphorin 3A-treated rats. Although no significant difference in behavior was found between these two groups, confocal microscopy illustrated ectopic synaptic formations in deeper laminas in NGF/green fluorescent protein-treated rats. The results suggested that antagonistic guidance cues can be used to induce and refine regeneration within the CNS, which is important for long-term, optimal functional recovery.
Cell Cycle Regulator E2F4 Is Essential for the Development of the Ventral Telencephalon
Authors: Ruzhynsky Vladimir A. , McClellan Kelly A. , Vanderluit Jacqueline L. , Jeong Yongsu , Furimsky Marosh , Park David S. , Epstein Douglas J. , Wallace Valerie A. , Slack Ruth S.
Published: May 2007

Early forebrain development is characterized by extensive proliferation of neural precursors coupled with complex structural transformations; however, little is known regarding the mechanisms by which these processes are integrated. Here, we show that deficiency of the cell cycle regulatory protein, E2F4, results in the loss of ventral telencephalic structures and impaired self-renewal of neural precursor cells. The mechanism underlying aberrant ventral patterning lies in a dramatic loss of Sonic hedgehog (Shh) expression specifically in this region. The E2F4-deficient phenotype can be recapitulated by interbreeding mice heterozygous for E2F4 with those lacking one allele of Shh, suggesting a genetic interaction between these pathways. Treatment of E2F4-deficient cells with a Hh agonist rescues stem cell self-renewal and cells expressing the homeodomain proteins that specify the ventral telencephalic structures. Finally, we show that E2F4 deficiency results in impaired activity of Shh forebrain-specific enhancers. In conclusion, these studies establish a novel requirement for the cell cycle regulatory protein, E2F4, in the development of the ventral telencephalon.
Dissociating Task Performance from fMRI Repetition Attenuation in Ventral Visual Cortex
Authors: Xu Yaoda , Turk-Browne Nicholas B. , Chun Marvin M.
Published: May 2007

Repeated visual stimuli elicit reduced neural responses compared with novel stimuli in various brain regions (repetition attenuation). This effect has become a powerful tool in fMRI research, allowing researchers to investigate the stimulus-specific neuronal representations underlying perception and cognition. Repetition attenuation is also commonly associated with behavioral priming, whereby response accuracy and speed increase with repetition. This raises the possibility that repetition attenuation merely reflects decreased processing time. Here, we report a full dissociation between repetition attenuation and behavioral performance by varying the task performed on identical visual stimuli. In the scene task, observers judged whether two photographs came from the same scene, and in the image task, they judged whether the two photographs were identical pixel for pixel. The two tasks produced opposite patterns of behavioral performance: in the scene task, responses were faster and more accurate when the photographs were very similar, whereas, in the image task, responses were faster and more accurate when the photographs were less similar. However, in the parahippocampal place area (PPA), a scene-selective region of ventral cortex, identical repetition attenuation was observed in both tasks: lower neural responses for the very similar pairs relative to the less similar pairs. Whereas the PPA was impervious to task modulation, responses from two frontal regions mirrored behavioral performance, consistent with their role in decision-making. Thus, although repetition attenuation and performance are often correlated, they can be dissociated, suggesting that attenuation in ventral visual areas reflects stimulus-specific processing independent of task demands.
A Retrospective: Reflections on the Tenth Anniversary of Nova Religio
Authors: Lucas Phillip Charles
Published: May 2007

Nova Religio came into being to provide a growing cohort of scholars of new religions with a dedicated forum within which to publish their research. The title, Nova Religio, was chosen to convey the journal's focus on new religious phenomena across historical periods. The description, The Journal of Alternative and Emergent Religions, signified that Nova Religio would have as its purview religious communities and movements that fall outside the "established, or dominant, religious institutions and traditions of a given nation or culture." The journal has published a number of important symposia during its first decade and established itself as the journal of record for scholars of new and minority religions. Three initiatives are suggested to help the field of new religions studies (NRS) achieve its full potential in the academy: 1) continued outreach to colleagues in interdisciplinary fields; 2) a transition from frames that see new religions as "social problems," to frames that sees these movements as "social phenomena"; and 3) the building of stronger organizational foundations within the academy.
Computer‐vision determination of 3‐D geometric parameters of LDL particles via cryogenic transmission electron microscopy
Authors: Collier W. Lewis , Martin Lenore M. , Van Antwerpen Rik
Published: May 2007

Abstract— Previous research has shown that the size of the LDL macromolecules can have an effect on cardiovascular health and that LDL macromolecules may be non‐spherical in shape. Some of these studies, however, used methods that are not conducive to automatic determination of the 3‐D parameters of the particles. In particular, the prior methods used for determination of geometric‐parameter determination were either centrifugal separations or manual determination of parameters from cryogenic transmission electron micrographs. An application of computer‐vision techniques to automatically determine the 3‐D parameters from cryogenic transmission electron microscopy (CTEM) images will be described. Correlation of computer‐generated geometric models to the orthonormal projection CTEM imagery were investigated to determine the applicability of finding the pertinent geometric parameters of the expected discoid shape of the LDL particles. The processing showed that the discoid shape can be verified using small‐angle rotations that are more amenable to the limitations of CTEM imaging.
Transnational Cultural Policy and European Cosmopolitanism
Authors: Robins Kevin
Published: May 2007

This article is concerned with cultural policy for diversity in contemporary European societies. What it argues for is the need now to move beyond the national frame within which diversity policy has been hitherto conceived. A key development comes from the global migrations that have been occurring through the last twenty years, and which have brought a new cultural complexity to the European space. What this article suggests is that this complexity might actually be a productive resource for European culture generally. And what it maintains is that, in order to realize this potential, there is a need to address cultural policy from a perspective that is both transnational and transcultural. Transcultural diversity policy is crucial to the elaboration of a new European cosmopolitanism.
Principles of the tool Rockfor.net for quantifying the rockfall hazard below a protection forest
Authors: Berger Frédéric , Dorren Luuk K.A.
Published: May 2007

There are presently no clear rules for determining optimal rockfall protection forests, taking into account forest and site characteristics as well as the size and energy of the falling rock. To provide a tool that meets these requirements and quantifies the protective capacity, we have developed Rockfor.net (www.rockfor.net). This paper explains the underlying principles as well as the calculation methods used. Furthermore, it presents case studies which provide validation.
Design of Nanocomposite Low‐Friction Coatings
Authors: Wilhelmsson O. , Råsander M. , Carlsson M. , Lewin E. , Sanyal B. , Wiklund U. , Eriksson O. , Jansson U.
Published: May 2007

Friction and wear between moving surfaces is unavoidable and is an important reason for failure of mechanical components. A wear‐resistant and low‐friction coating can prolong the lifetime of an engineered component. Here we demonstrate a new concept for the design of low‐friction nanocomposite carbide coatings with an intrinsic driving force to form amorphous carbon (C–C bonds). Ti–Al–C has been chosen as a model system, but the idea is general and should be applicable to a wide class of materials. The ability to intrinsically form amorphous carbon is achieved by a substitutional solid solution of the weak‐carbide‐forming metal (Al) into the thermodynamically stable monocarbide (TiC). This creates, in a controllable manner, a driving force for phase separation of carbide particles embedded in a matrix of amorphous carbon. In a tribological contact the amorphous carbon can be further graphitized and thereby lower the friction coefficient. Consequently, the model system has a self‐lubricating mechanism but at the same time a tunable share of the two phases, which gives excellent possibilities to design wear resistance and toughness. In this paper we show that the friction coefficient can be lowered by more than 50 % for Al‐containing TiC coatings without severe loss in mechanical characteristics.
Covalent Functionalization of Carbon Nanohorns with Porphyrins: Nanohybrid Formation and Photoinduced Electron and Energy Transfer
Authors: Pagona G. , Sandanayaka A. S. D. , Araki Y. , Fan J. , Tagmatarchis N. , Charalambidis G. , Coutsolelos A. G. , Boitrel B. , Yudasaka M. , Iijima S. , Ito O.
Published: May 2007

The covalent attachment of carbon nanohorns (CNHs) to α‐5‐(2‐aminophenyl)‐α‐15‐(2‐nitrophenyl)‐10,20‐bis(2,4,6‐trimethyl‐phenyl)‐porphyrin (H2P) via an amide bond is accomplished. The resulting CNH–H2P nanohybrids form a stable inklike solution. High‐resolution transmission electron microscopy (HRTEM) images demonstrate that the original dahlia‐flowerlike superstructure of the CNHs is preserved in the CNH–H2P nanohybrids. Steady‐state and time‐resolved fluorescence studies show efficient quenching of the excited singlet state of H2P, suggesting that both electron and energy transfer occur from the singlet excited state of H2P to CNHs, depending on the polarity of the solvent. In the case of electron transfer, photoexcitation of H2P results in the reduction of the nanohorns and the simultaneous oxidation of the porphyrin unit. The formation of a charge‐separated state, CNH•––H2P•+, has been corroborated with the help of an electron mediator, hexyl‐viologen dication (HV2+), in polar solvents. Moreover, the charge‐separated CNH•––H2P•+ states have been identified by transient absorption spectroscopy.
A one‐step preparation of compatibilized polypropylene‐nanocomposites by reactive extrusion processing
Authors: Rzaev Z. M. O. , Yilmazbayhan A. , Alper E.
Published: May 2007

We have developed a one‐step method for preparing nanocomposites based on powdered isotactic polypropylene (i‐PP) as a matrix polymer (melt‐flow index (MFI) = 7.2 g 10 min−1), oligo(i‐PP‐g‐MA) (MFI = 35–70 g 10 min−1) as a reactive compatibilizer and docecylamine‐surface‐modified montmorillonite clay (organo‐MMT). This method includes grafting maleic anhydride (MA) onto i‐PP chains in the melt state under the controlled thermal degradation conditions and intercalative compounding of the obtained oligo(i‐PP‐g‐MA) with i‐PP and organo‐MMT by reactive extrusion. The effect of extrusion parameters on MFI, composition and properties of the grafted i‐PPs, and mechanism of formation and properties of PP/oligo(PP‐g‐MA)s/organo‐MMT nanocomposites were investigated by FTIR, XRD, and thermal analysis (DSC, TGA, and DTA). The results indicate that the formation of nanostructured morphologies proceeds through the formation of strong H‐bonding and amidization/imidization reactions between the anhydride units of exfoliated grafted i‐PP chain and alkylamine within the organo‐MMT interlayers. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:41–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20082
Ueber die höchsten hörbaren und unhörbaren Töne von c5 = 4096 Schwingungen (ut7 = 8192 v s), bis über f9 (fa11), zu 90 000 Schwingungen (180 000 v s), nebst Bemerkungen über die Stosstöne ihrer Intervalle, und die durch sie erzeugten Kundt'schen Staubfiguren
Authors: Koenig Rudolph
Published: May 2007

II. Ueber die höchsten Töne, welche man ohne directes Stimmen mit den verschiedenen tönenden Körpern nach der Berechnung ihrer Dimensionen und auch durch mechanisch erzeugte Impulse herstellen kann.
Die Einwirkung magnetischer Felder auf das Wärmeleitvermögen von Gasen. I
Authors: Senftleben Hermann , Pietzner Joachim
Published: May 2007

Das Wärmeleitvermögen paramagnetischer Gase wird durch Einwirkung magnetischer Felder herabgesetzt. Die Versuchsanordnung zum Nachweis und zur quantitativen Messung dieses Effektes wird beschrieben. Die Ergebnisse der Messungen werden mitgeteilt und diskutiert.
Die Reibung, Wärmeleitung und Diffusion in Gasmischungen. XXVI. Die innere Reibung von Propylen und β‐Butylen und von ihren Mischungen mit He oder H2
Authors: Trautz Max , Husseini Ishaq
Published: May 2007

I. Messungsverfahren. ‐ II. Ergebnisse: a) Reingase; b) Gemische. ‐ III. Zusammenfassung.
Ein Zustandsdiagramm für Gemische aus beliebig vielen Bestandteilen
Authors: Fischer V.
Published: May 2007

Es wird ein ebenes orthogonales Diagramm für Gemische aus beliebig vielen Bestandteilen entwickelt. Am Beispiel des Gemisches Stickstoff‐Sauerstoff‐Argon‐Kohlenoxyd wird gezeigt, wie sich in einem solchen Diagramm die Gleichgewichtsisobaren des Vierstoffgemisches darstellen lassen.
Zur Theorie der Kikuchilinien
Authors: v. Laue M.
Published: May 2007

Die Kikuchilinien entstehen durch Streuung unter Energieabgabe an Elektronen, die an bestimmte Atome gebunden sind. Leitungselektronen hingegen ergeben bei dieser Streuung keine derartigen Linien.
Über die Energieabsorption von schnellen Kathodenstrahlen
Authors: Gentner Konrad
Published: May 2007

Es wird die Energieabsorption in Al für 25,6 kV‐Elektronen in Abhängigkeit von der Schichtdicke untersucht. Darüber hinaus geben die hierzu notwendigen Messungen Gelegenheit, die Gesetzmäßigkeiten zu prüfen: 1. über die Rückdiffusion, 2. über die Abhängigkeit der Elektronenzahl und ‐Geschwindigkeit vom Streuwinkel, 3. über den Absorptionskoeffizienten und Einzelheiten des Absorptionsvorganges. Weiterhin wurden mehrere bekannte Zusammenhänge neu bestätigt: 1. das Whiddingtonsche Gesetz, 2. der wahrscheinlichste Ablenkungswinkel für die Streustrahlung.
Über die Frage der praktischen Verwendbarkeit von Christiansenfitern
Authors: von Fragstein Konrad
Published: May 2007

In dieser Zeitschrift wurde von mir vor einiger Zeit ein Christiansenfilter zur Aussonderung von schmalen Spektralbezirken im Ultraviolett beschrieben. Im folgenden soll noch über einige Verbesserungen berichtet werden, die an dem Filter angebracht wurden, und schließlich wird noch eine Betrachtung über die mit Christiansenfiltern zu erzielenden Beleuchtungsstärken angestellt.
Die Bremsung der Magnetisierung durch mikroskopische Wirbelströme
Authors: Becker R.
Published: May 2007

Für das Magnetfeld, welches durch die mikroskopischen Wirbelströme bei einer gegebenen Änderung der Magnetisierung im Innern eines Ferromagnetikums erzeugt wird, läßt sich eine allgemeine Formel angeben. Diese wird für den Fall einer 180° ‐Wand näher diskutiert. Man gewinnt dadurch einen quantitativen Ansatz zu Deutung des Ausbleibens der ferromagnetischen Suszeptibilität bei hohen Frequenzen.
Ein neuer und fundamentaler Versuch zur Totalreflexion
Authors: Goos F. , Hänchen H.
Published: May 2007

Die Maxwellsche Theorie lehrt, daß bei Totalreflexion Lichtenergie in das dünnere Medium eindringt. Experimentell wurde bisher diese Energie immer nur im dünneren Medium selbst nachgewiesen, dadurch Licht abgezapft und somit die totale Reflexion zunichte gemacht. Es soll nun hier ein neues Experiment beschrieben werden, bei dem die Lichtbewegung im dünneren Medium nachgewiesen wird durch ein Phänomen, welches sich im dichteren Medium abspielt, nachdem das Licht bereits das dünnere Medium durchlaufen und dieses wieder verlassen hat. Dabei wird die totale Reflexion in keiner Weise gestört. Das Phänomen wird quantitativ in Beziehung gesetzt zur Maxwellschen Theorie.
Über die Fraunhoferschen Linien und ihre Mitte‐Rand‐Variation auf der Sonnenscheibe
Authors: Unsöld A.
Published: May 2007

Nach einer zusammenfassenden Darstellung der Entwicklung unserer heutigen Vorstellungen über die Entstehung der Fraunhoferlinien im Sonnenspektrum wird eine einfache und übersichtliche Methode zur Berechnung der Intensität und Mitte‐Rand‐Variation für schwache Linien und die Flügel starker Linien entwickelt. Ein für einige charakteristische Modelle durchgeführter Vergleich mit der früher vom Verf. angegebenen „Gewichtsfunktionenmethode”︁ ergibt gute Übereinstimmung. An Hand eines von B. Strömgren berechneten Modells der Sonnenatmosphäre wird sodann gezeigt, wie man die Beobachtungen über die Mitte‐Rand‐Variation von Adam, Minnaert und Redman für schwache Linien sowie von Houtgast für die Flügel starker Fraunhoferlinien in anschaulicher Weise deuten kann. Beiläufig wird der Bereich der Anwendbarkeit der üblichen planparallel geschichteten Atmosphärenmodelle durch eine einfache geometrische Betrachtung abgegrenzt. Auf die Notwendigkeit weiterer Untersuchungen über den Verlauf von Temperatur und Druck in den äußersten Sonnenschichten wird hingewiesen.
Ionisation und Anregung in den Sonnenprotuberanzen
Authors: Wurm Karl
Published: May 2007

Es wird eine Analyse der Ionisations‐ und Anregungsverhältnisse der Sonnenprotuberanzen durchgeführt, die im Gegensatz zu der bisher vorliegenden Protuberanzentheorie auf jede Verwendung der Saha‐ und Boltzmann ‐ Gleichung verzichtet. Die Benutzung der letzteren verbietet sich, da in den Protuberanzenatmosphären nachweislich extreme Abweichungen von einem thermischen Gleichgewichtszustand vorliegen. Die Ausführungen erstrecken sich in erster Linie auf die Bestimmung folgender Größen: Elektronendichte Ne, Gesamtdichte N, Ionisationsgrad des H‐Atoms NHII/NHI, Elektronentemperatur Te sowie die relative Besetzung der Balmerterme n = 2, n = 3. Es wird weiterhin eine Methode angegeben, welche die Intensität der Ly α‐Strahlung zu ermitteln gestattet.
Der Zusammenhang der vier‐ und fünfdimensionalen Metrik
Authors: Jordan P.
Published: May 2007

Es wird eine sehr vereinfachte Herleitung gegeben für die Formeln, welche die Beziehungen zwischen der fünfdimensionalen Metrik g μν und der vierdimensionalen gkl zum Ausdruck bringen.
Kritische Reynoldssche Zahl für Rohrströmung und Entropieprinzip
Authors: Meißner Walther , Schubert Gerhard U.
Published: May 2007

In der Einleitung wird dargelegt, daß der Umschlag von laminarer zu turbulenter Strömung als eine Frage der Wahrscheinlichkeit der Strömungsart aufgefaßt und daher mit Hilfe des Entropieprinzips behandelt werden kann. In Teil 1 ist zunächst eine Lösung der exakten phänomenologischen gaskinetischen Grundgleichungen für den Fall der laminaren Strömung eines idealen Gases in einem rotationssymmetrischen schwach‐konischen Rohr durch Reihenentwicklungen gegeben. In Teil 2 sind möglichst genaue Formeln für die „ideale turbulente Strömung”︁ (genügend lange Anlauf‐ und Auslaufstrecken!) im gleichartigen Rohr abgeleitet. In Teil 3 wird mit Hilfe der in den beiden ersten Teilen gewonnenen Ergebnisse der Verlauf der über dem Rohrquerschnitt gemittelten Entropie für die laminare und ideale turbulente Strömung und zwar für beide oberhalb und unterhalb der kritischen Reynoldsschen Zahl berechnet. Die für die beiden Strömungsarten als Funktion des Abstandes vom Rohrende aufgetragenen Entropiekurven schneiden sich nahezu an der der kritischen Reynoldsschen Zahl entsprechenden Stelle. Oberhalb des Schnittpunktes ist die Entropie für die ideale turbulente Strömung größer als für die laminare, unterhalb des Schnittpunktes ist umgekehrt die Entropie für die laminare Strömung die größere. Der Umschlag bei der kritischen Reynoldsschen Zahl ist also thermodynamisch bedingt. Im Schlußteil ist die Frage, wie der universelle Wert der kritischen Reynoldsschen Zahl zu erklären ist und wie die Verhältnisse bei andersartigen Strömungen als der Rohrströmung liegen, erörtert.
Elektrischer Widerstand, magnetische Widerstandsänderung und Hall‐Effekt der Alkalimetalle
Authors: Justi Eduard
Published: May 2007

An Proben von Alkalimetallen bisher nicht verfügbarer Reinheit, die zudem sorgfältig entgast waren, wurden Messungen der Temperaturabhängigkeit des elektrischen Widerstandes bei H = 0, Messungen der Beeinflussung des elektrischen Widerstandes durch magnetische Längs‐ und Querfelder bis über 40000 Gauß, sowie Messungen des Halleffektes im Bereich zwischen Zimmertemperatur und 0,73° abs durchgeführt.

Der Widerstand des reinsten Na, der am He‐Siedepunkt nur noch 0,244% des Eispunktswiderstandes beträgt, fällt bei Abkühlung auf 0,73° abs auf 0,17%. Ähnlich nimmt das Widerstandsverhältnis einer reinen K‐Probe bei Abkühlung von 4,22° auf 0,77° von rT = 0,475% auf 0,056% ab. Es erscheint als möglich, daß es sich hierbei um Anzeichen beginnender Supraleitung handelt. Rb und Cs zeigen im He‐Siedebereich ebenfalls noch einen geringen Widerstandsabfall.

In der Meßgenauigkeit der magnetischen Widerstandsänderungen der Alkalien wurden solche Fortschritte erzielt, daß diese nunmehr in Abhängigkeit von T und H zuverlässig festgelegt werden konnten; die relativen Widerstandsänderungen erreichen bei Na 50%. Nach Kohler werden die gemessenen ΔϱH,T/ϱH = 0, T als Funktion des Quotienten Feldstärke/reduziertes Widerstandsverhältnis H/(RT/Rθ) dargestellt. Dabei ergibt sich, daß alle gemessenen Widerstandsänderungen für alle Alkalien in einem bandförmigen Bereich liegen, der sich als untere Begrenzung an das ähnliche Band für die reinen Metalle der ungeradzahligen Gruppen des Periodischen Systems anschmiegt. Die Höhe dieses Bandes, in dem sämtliche Metalle enthalten sind, deren Widerstand durch ein Querfeld nicht unbegrenzt vermehrt wird, beträgt weniger als 1 Größenordnung von ΔϱH/ϱ.

Schließlich wird über die ersten Ergebnisse noch weiterzuführender Messungen des Halleffektes der Alkalien berichtet; die Hallkonstante ist in weiten T‐ und H‐Bereich unveränderlich.

Die bei diesen Versuchen angewendeten tiefen Temperaturen bis zu 0,73° abs konnten mit wesentlich geringerem Aufwand als bisher bekannt erreicht werden, indem der Siededruck des Heliums statt durch eine Diffusionspumpe, durch eine Hg‐Dampfstrahlpumpe erniedrigt wurde. Es wird gezeigt, inwiefern diese Pumpenanordnung der bisherigen überlegen ist.
Eine quantitative Deutung der elektrischen und lichtelektrischen Leitfähigkeit von Zinkoxyd auf Grund des Massenwirkungsgesetzes
Authors: Mollwo E. , Stöckmann F.
Published: May 2007

Diese Arbeit versucht, die in den vorhergehenden Arbeiten mitgeteilten Gesetzmäßigkeiten über die elektrische und lichtelektrische Leitung von ZnO quantitativ zu deuten. Es wird angenommen, daß bei Zimmertemperatur leitendes ZnO stöchiometrisch überschüssiges Zn enthält. Dieses dissoziiert thermisch in Zn+ und ein Elektron. Durch Lichtabsorption wird vom Zn+ ein weiteres Elektron abgespalten. Auf beide Reaktionen werden das Massenwirkungsgesetz sowie die Gesetze der chemischen Reaktionskinetik angewandt und dadurch Beziehungen für die Konzentration von freien Elektronen erhalten, die die Beobachtungen richtig wiedergeben.
Über lichtelektrische Leitung am Bleisulfid
Authors: Pick Heinz
Published: May 2007

Dünne Schichten aus Bleisulfid werden als spiegelnder Niederschlag aus einer chemischen Fällungsreaktion gewonnen. Nach einem geeigneten Formierungsprozeß zeigen diese Schichten hohe lichtelektrische Empfindlichkeit in einem Gebiet zwischen 0,3 und 3,5 μ. Der Zusammenhang zwischen Bestand an lichtelektrischen Elektronen und Bestrahlungsstärke wird experimentell für verschiedene Temperaturen ermittelt und durch eine empirische Formel quantitativ erfaßt. Der zeitliche Verlauf der Änderung des Elektronenbestandes bei Beginn und Ende einer Belichtung wird durch Oszillogramme bei verschiedenen Bestrahlungsstärken und Temperaturen registriert. Die experimentellen Ergebnisse werden gedeutet und die Brauchbarkeit der Vorstellung durch quantitativen Vergleich mit den Messungen festgestellt. Der wesentliche Punkt dieser Vorstellung ist, daß die lichtelektrischen Elektronen sowohl durch ihre eigenen Ursprungsorte als auch — mit einer anderen Wahrscheinlichkeit — durch die Ursprungsorte der thermisch abdissoziierten Elektronen wieder eingefangen werden können. Ihre Lebensdauer nimmt mit der Bestrahlungsstärke, d. h. dem Elektronenbestand, ab.
Die Elektronendiffusion in der Ionosphäre
Authors: Seeliger R.
Published: May 2007

Es werden allgemeine Überlegungen angestellt zu der Frage, wieweit die Diffusion der Elektronen für die Aufbaustruktur des Ionosphärenplasmas eine Rolle spielen kann. Nicht unwesentlich ist dabei, daß sich hier eindringlich zeigt: Selbst für derartige abschätzende Betrachtungen steht noch nicht genügend zuverlässiges Material zu bündigen quantitativen Folgerungen zur Verfügung.
Anregung von Leuchtstoffen durch die energiereichen Kerntrümmer der Uranspaltung. (Mit 3 Abbildungen)
Authors: Broser I. , Kallmann H.
Published: May 2007

Es wird die Anregung von Leuchtstoffen durch einzelne hochgeladene energiereiche Teilchen, die bei der Uranspaltung ausgesandt werden, mit Hilfe des Leuchtmassenzählers (bestehend aus Leuchtstoffschirm und Sekundär‐Elektronenvervielfacher) untersucht. Der nachweis schwerer Kerntrümmer mit dieser Methode gestaltet sich, auch bei Gegenwart einer starken γ‐Strahlung, sehr einfach. Der Beweis, daß es sich bei den beobachteten Lichtblitzen großer Intensität tatsächlich um Urantrümmer handelt, wird auf verschiedene Weise geführt. Für die Leuchtstoffphysik ergibt sich aus den Messungen die absolute Energieausbeute und die Zeitdauer der Lichtblitze für ZnSAg bei Anregung durch einzelne schwere geladene Kerne.
Über die Berechnung des Schallfeldes von kreisförmigen Membranen in starrer Wand. (Mit 3 Abbildungen)
Authors: Stenzel H.
Published: May 2007

Zur Bestimmung der für den Schalldruck im Aufpunkt (r, γ) charakteristischen Funktion 𝓇 (r, γ) werden die speziellen Funktionen 𝓇 (∞, γ) (Aufpunkt im Unendlichen) und 𝓇 (r, o) (Aufpunkt auf der Mittelachse) eingeführt. Mit Hilfe der Differentialgleichung für die Legendreschen Kugelfunktionen Pn (z) wird gezeigt, daß die Koeffizienten der nach fallenden Potenzen von r fortschreitenden Reihe von 𝓇 (r, γ) durch eine auf die Funktion 𝓇 (∞, γ) ausgeübte Differentialoperation gegeben sind. Ist insbesondere 𝓇 (∞, γ) als Potenzreihe von z (z = cos γ) gegeben, so wird 𝓇 (r, γ) ebenfalls durch eine Reihe dargestellt, die nach Potenzen von cos γ fortschreitet.

In analoger Weise ergibt sich mit Hilfe der Differentialgleichung der Rayleighschen Funktion fn (ikr) die Bestimmung der Koeffizienten der nach Potenzen von sin γ fortschreitenden Reihe von 𝓇 (r, γ) durch eine auf die Funktion 𝓇 (r, o) ausgeübte Differentialoperation.

Die Tragweite der abgeleiteten Formeln wird an Hand von Beispielen für die Kolbenmembran erläutert.
Druck‐ und Temperaturverschiebung der Absorptionskante von Cadmiumsulfid. (Mit 4 Abbildungen)
Authors: Höhler G.
Published: May 2007

Im ersten Teil der Arbeit wird ein Versuch beschrieben, aus dem sich eine Verschiebung der Absorptionskante von Cadmiumsulfid bei isothermer Kompression um 0,01 Å pro atm ergibt. Die Diskussion im zweiten Teil behandelt den allgemeineren Fall der Kantenverschiebung bei Temperaturänderung. Es wird versucht zu zeigen, daß sowohl die Stoßverbreiterung als auch die Verschiebung der Bandränder durch thermische Ausdehnung zu diesem Effekt beitragen. Für CdS verhalten sich die Anteile wie 4:1.