198,766 research outputs found
F. Millonig and M. Grothe, circa 1935
No full textNursing students F. Millonig and M. Grothe sit together outside the hospital, circa 1935
The impact of market structure on innovation incentives
No full textGrothe M. The impact of market structure on innovation incentives. Bielefeld: Universitätsbibliothek Bielefeld; 2014
Basic fibroblast growth factor (bFGF) in rodent testis
No full textWe have previously described a 30 kDa basic fibroblast growth factor (bFGF)-like protein in rodent testicular homogenates and have shown that pachytene spermatocytes are the sites of predominant immunoreactivity for this bFGF-like protein (Mayerhofer, A., Russell, L.D., Grothe, C., Rudolf, M. and Gratzl, M. (1991) Endocrinology 129, 921–924). We have now addressed the question whether this 30 kDa bFGF-like protein is a large bFGF form and whether it is produced by pachytene spermatocytes. We detected bFGF mRNA in homogenates of isolated mouse spermatocytes (which consisted mainly of pachytene spermatocytes) using S1 nuclease protection assays. As shown by Western blot analyses, the bFGF mRNA in mouse spermatocytes is translated into bFGF of an approximate molecular weight of 30 kDa. Neither bFGF mRNA, nor bFGF itself, was observed in isolated mouse Leydig cells. These results indicate that the immunoreactive bFGF-like protein observed previously in germ cells of the murine testis is identical to bFGF. Thus, germ cells of the testis produce bFGF, which may exert regulatory function in the process of spermatogenesis
Biological Ice Nucleation in the Atmosphere and the Biosphere
No full textFrom the thermodynamic point of view, ice and snow can form already at temperatures slightly below its melting point, i.e. below zero degrees Celsius. Actually, ultrapure, liquid water can be supercooled down to minus forty degrees Celsius without freezing. The reason is a kinetic activation barrier, which hinders the phase transition. However, water impurities, e.g. biological material or organic particles, can lower this activation barrier and can thus catalyze the phase transition. This process is called heterogeneous ice nucleation and it plays an important role in many biological, meteorological and technical processes, e.g. in the formation of atmospheric ice clouds [1].
The most effective ice nucleus is ice itself, since it provides the own hexagonal structure, on which water molecules from the liquid phase can be oriented to form further ice phase. The most effective heterogeneous ice nucleus is the bacterium pseudomonas syringae. The reason is a protein at its outer cell membrane, which exhibits a hexagonal, ice-like structure. Furthermore, many other bacteria, fungal spores, and pollens carry also very effective ice nuclei, many of which in fact are macromolecules.
Macromolecular ice nuclei have for a long time been neglected by atmospheric scientists. However, plants are known by biologists to produce macromolecular ice nuclei as a part of their low-temperature survival strategy. In the past, it has been shown by us that birch pollen exhibit ice nucleation active macromolecules at their surface [2, 3]. These molecules can be washed off from the pollen grains and nucleate ice independently. Only very recently, we found the same ice nuclei also on secondary and primary wood and on leafs of birch trees. The question remains if these biological ice nuclei can be dispersed through the atmosphere and can impact cloud glaciation processes.
[1] T. Bartels-Rausch, V. Bergeron, J. Cartwright, R. Escribano, J. Finney, H. Grothe, P. Gutierrez, J. Haapala, W. Kuhs, J. Pettersson, S. Price, C. Sainz-Dıaz, D Stokes, G. Strazzulla, E. Thomson, H. Trinks, and N. Uras-Aytemiz, Rev. Mod. Phys. 84 (2012)885.
[2] B.G. Pummer, H. Bauer, J. Bernardi, S. Bleicher, and H. Grothe, Atm. Chem. Phys., 12 (2012) 2541.
[3] B.G. Pummer, C. Budke, S. Augustin-Bauditz, D. Niedermeier, L. Felgitsch, C. Kampf, R. Huber, K. Liedl, T. Loerting, T. Moschen, M. Schauperl, M. Tollinger, C. Morris, H. Wex, H. Grothe, U. Pöschl, T. Koop, and J. Fröhlich-Nowoisky, Atm. Chem. Phys. 15 (2015) 4077
Biological Ice Nucleation in the Atmosphere and the Biosphere
No full textFrom the thermodynamic point of view, ice and snow can form already at temperatures slightly below its melting point, i.e. below zero degrees Celsius. Actually, ultrapure, liquid water can be supercooled down to minus forty degrees Celsius without freezing. The reason is a kinetic activation barrier, which hinders the phase transition. However, water impurities, e.g. biological material or organic particles, can lower the activation barrier and can thus catalyze the phase transition. This process is called heterogeneous ice nucleation and it plays an important role in many biological, meteorological and technical processes, e.g. in the formation of atmospheric ice clouds. The most effective ice nucleus is ice itself, since it provides the own hexagonal structure, on which water molecules from the liquid phase can be oriented in order to form further ice phase. The most effective heterogeneous ice nucleus is the bacterium Pseudomonas Syringae. The reason is a protein at its outer cell membrane, which exhibits a hexagonal, icelike structure. Furthermore, fungal spores, pollen, and carbonaceous particles are also very effective ice nuclei [1, 2]. In many cases, the physical and chemical reasons for the ice nucleation activity are understood only rudimentary. Thus, the search for the perfect ice nucleus is still an open issue [3].The talk will explain the fundamentals of heterogeneous ice nucleation and will give examples from the field and the laboratory.
[1] B.G. Pummer, H. Bauer, J. Bernardi, S. Bleicher, and H. Grothe, Atm. Chem. Phys., 12 2541 (2012).
[2] B.G. Pummer, C. Budke, S. Augustin-Bauditz, D. Niedermeier, L. Felgitsch, C. Kampf, R. Huber, K. Liedl, T. Loerting, T. Moschen, M. Schauperl, M. Tollinger, C. Morris, H. Wex, H. Grothe, U. Pöschl, T. Koop, and J. Fröhlich-Nowoisky, Atm. Chem. Phys. 15 4077 (2015).
[3] T. Bartels-Rausch, V. Bergeron, J. Cartwright, R. Escribano, J. Finney, H. Grothe, P. Gutierrez, J. Haapala, W. Kuhs, J. Pettersson, S. Price, C. Sainz-Diaz, D Stokes, G. Strazzulla, E. Thomson, H. Trinks, and N. Uras-Aytemiz, Rev. Mod. Phys. 84 885 (2012)
Interaction of excitation and inhibition in processing of pure tone and amplitude-modulated stimuli in the medial superior olive of the mustached bat
No full text 1. In mammals with good low-frequency hearing, the medial superior olive (MSO) processes interaural time or phase differences that are important cues for sound localization. Its cells receive excitatory projections from both cochlear nuclei and are thought to function as coincidence detectors. The response patterns of MSO neurons in most mammals are predominantly sustained. In contrast, the MSO in the mustached bat is a monaural nucleus containing neurons with phasic discharge patterns. These neurons receive projections from the contralateral anteroventral cochlear nucleus (AVCN) and the ipsilateral medial nucleus of the trapezoid body (MNTB). 2. To further investigate the role of the MSO in the bat, the responses of 252 single units in the MSO to pure tones and sinusoidal amplitude-modulated (SAM) stimuli were recorded. The results confirmed that the MSO in the mustached bat is tonotopically organized, with low frequencies in the dorsal part and high frequencies in the ventral part. The 61-kHz region is overrepresented. Most neurons tested (88%) were monaural and discharged only in response to contralateral stimuli. Their response could not be influenced by stimulation of the ipsilateral ear. 3. Only 11% of all MSO neurons were spontaneously active. In these neurons the spontaneous discharge rate was suppressed during the stimulus presentation. 4. The majority of cells (85%) responded with a phasic discharge pattern. About one-half (51%) responded with a level-independent phasic ON response. Other phasic response patterns included phasic OFF or phasic ON-OFF, depending on the stimulus frequency. Neurons with ON-OFF discharge patterns were most common in the 61-kHz region and absent in the high-frequency region. 5. Double tone experiments showed that at short intertone intervals the ON response to the second stimulus or the OFF response to the first stimulus was inhibited. 6. In neuropharmacological experiments, glycine applied to MSO neurons (n = 71) inhibited any tone-evoked response. In the presence of the glycine antagonist strychnine the response patterns changed from phasic to sustained (n = 35) and the neurons responded to both tones presented in double tone experiments independent of the intertone interval (n = 5). The effects of strychnine were reversible. 7. Twenty of 21 neurons tested with sinusoidally amplitude-modulated (SAM) signals exhibited low-pass or band-pass filter characteristics. Tests with SAM signals also revealed a weak temporal summation of inhibition in 13 of the 21 cells tested.(ABSTRACT TRUNCATED AT 400 WORDS) </jats:p
Nukleation, Wachstum und Phasenübergänge von NAD und NAT - Untersuchungen an einem Labormodel
No full textSalpeters¨aurehydrate sind wichtige Bestandteile von festen Partikeln
in Polaren Stratosph¨arischen Wolken (PSC) und in Zirruswolken.
Entsprechend dem Phasendiagramm kommen nur
hexagonales Eis und Salpeters¨auretrihydrat (&#946;-NAT) als thermodynamisch
stabile Festk¨orperphasen in Frage. Beide Strukturen
werden in der Stratosph¨are regelm¨aßig beobachtet. Daneben
k¨onnten aber auch eine Reihe metastabiler Modifikationen
existieren: &#945;-NAD (Dihydrat), &#946;-NAD, &#945;-NAT, NAP (Pentahydrat)
und kubisches Eis. Die Existenzm¨oglichkeit dieser metastabilen
Verbindungen in der Stratosph¨are ist bisher nicht gesichert
und wird diskutiert.
Im Labor haben wir ein spezielles Modellverfahren entwickelt,
um die metastabilen Strukturen m¨oglichst rein darzustellen und
untersuchen zu k¨onnen. Als Untersuchungsmethoden wurden
die R¨ontgenpulverdiffraktion [1, 2], die FTIR-Spektroskopie [3]
und die Ramanspektroskopie [4] eingesetzt. Ziel war es, mit
der Diffraktion die Phasenzusammensetzung der Proben abzusichern
und dann an entsprechenden Proben spektroskopische
Daten zu sammeln, die f¨ur Feldmessungen und Kammerexperimente
ben¨otigt werden.
Besonderes Interesse galt dem NAD, das spezielle Nukleationseigenschaften
zeigt. F¨ur NAD und NAT wurde die Kristallisationskinetik
der Phasen¨uberg¨ange bestimmt. Dabei konnte
gezeigt werden, dass in verd¨unnten Proben hexagonales Eis
den Phasen¨ubergang von &#945;- in &#946;-NAT hemmt. Somit kann &#945;-
NAT auch bei stratosph¨arischen Temperaturen (T > 180 K)
noch mehrere Stunden existieren. Erg¨anzend wurde in ESEMMessungen
(environmental scanning electron microsocopy) der
Einfluss von Eis auf die Morphologie der Kristallite beobachtet.
Deren Kenntnis ist entscheidend, um das Streuverhalten der
Kristalle und Partikel richtig zu verstehen.
[1] H. Tizek, E. Kn¨ozinger, H. Grothe, PCCP 4 (2002), 5128.
[2] H. Tizek, E. Kn¨ozinger, H. Grothe, PCCP 6 (2004), 972.
[3] H. Grothe, C. E. Lund Myhre, H. Tizek, Vibr. Spectr. 34
(2004), 55.
[4] H. Grothe, C. E. Lund Myhre, C. J. Nielsen, J. Phys. Chem.
A 110 (2006), 2, in print
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Sensitivity to interaural time differences in the medial superior olive of a small mammal, the Mexican free-tailed bat
No full textNeurons in the medial superior olive (MSO) are thought to encode interaural time differences (ITDs), the main binaural cues used for localizing low-frequency sounds in the horizontal plane. The underlying mechanism is supposed to rely on a coincidence of excitatory inputs from the two ears that are phase-locked to either the stimulus frequency or the stimulus envelope. Extracellular recordings from MSO neurons in several mammals conform with this theory. However, there are two aspects that remain puzzling. The first concerns the role of the MSO in small mammals that have relatively poor low-frequency hearing and whose heads generate only very small ITDs. The second puzzling aspect of the scenario concerns the role of the prominent binaural inhibitory inputs to MSO neurons. We examined these two unresolved issues by recording from MSO cells in the Mexican free-tailed bat. Using sinusoidally amplitude-modulated tones, we found that the ITD sensitivities of many MSO cells in the bat were remarkably similar to those reported for larger mammals. Our data also indicate an important role for inhibition in sharpening ITD sensitivity and increasing the dynamic range of ITD functions. A simple model of ITD coding based on the timing of multiple inputs is proposed. Additionally, our data suggest that ITD coding is a by-product of a neuronal circuit that processes the temporal structure of sounds. Because of the free-tailed bat's small head size, ITD coding is most likely not the major function of the MSO in this small mammal and probably other small mammals
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