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Shampo, Marc A., Robert A. Kyle, and David P. Steensma. "Hans Geiger—German Physicist and the Geiger Counter." Mayo Clinic Proceedings 86, no. 12 (December 2011): e54. http://dx.doi.org/10.4065/mcp.2011.0638.
Dostal, K. P., and D. Hoffmann. "Hans Geiger — ein Pionier der Teilchenphysik." Isotopenpraxis Isotopes in Environmental and Health Studies 21, no. 9 (January 1985): 297–99. http://dx.doi.org/10.1080/10256018508623524.
Marques, Deividi Marcio. "Partículas alfa como projéteis subatômicos: os trabalhos de Hans Geiger." História da Ciência e Ensino: construindo interfaces 20 (December 29, 2019): 695–701. http://dx.doi.org/10.23925/2178-2911.2019v20espp695-701.
ResumoOs trabalhos para desvendar a estrutura da matéria no começo do século passado fizeram com que vários cientistas elaborassem diferentes experimentos de modo a permitir o entendimento e o arranjo atômico em diferentes metais. Um dos físicos que merece destaque foi Johannes Wilhelm Geiger (18821945), também conhecido como Hans Geiger, que desenvolveu uma maneira de estudar a estrutura dos metais utilizando partículas alfa provenientes de compostos de rádio. A técnica consistia em bombardear finas folhas de diferentes metais com partículas alfa e analisar seus desvios. Essa técnica possibilitou que, futuramente, fosse possível a elaboração de outro experimento que constatou, entre outros aspectos, o núcleo atômico. Será́ apresentado, portanto, neste artigo a tradução comentada do artigo On the Scattering of the α–Particles by Matter.Palavras-chave: Partícula alfa; espalhamento de partículas; Hans GeigerAbstractThe work to unravel the structure of matter at the beginning of the last century led several scientists to design different experiments to allow understanding and arrangement atomic metals. One of the prominent physicists was Johannes Wilhelm Geiger (18821945), also known as Hans Geiger, who developed a way to study the structure of metals using alpha particles from radio compounds. The technique consisted of bombarding thin sheets of different metals with alpha particles and analyzing their deviations. This technique made it possible, in the future, to develop another experiment that found, among other aspects, the atomic nucleus. Therefore, it will be presented in this paper how Hans Geiger elaborated his experiments, highlighting their results and difficulties. In addition, the importance of this historical episode in Basic Education will be discussed.Keywords: Alpha particles; scattering particle; Hans Geiger
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Geiger, Tim. "Landshut in Mogadischu. Das außenpolitische Krisenmanagement der Bundesregierung angesichts der terroristischen Herausforderung 1977." Vierteljahrshefte für Zeitgeschichte 57, no. 3 (July 15, 2009): 413–56. http://dx.doi.org/10.1524/vfzg.2009.0049.
Vorspann Somalia und Mogadischu waren nicht erste Wahl. Andreas Baader, der Chef der Roten Armee Fraktion, und seine Mitgefangenen wollten im Falle einer Freipressung in andere Länder ausreisen. Die Bundesregierung vereitelte diese Pläne und legte sich dann auch auf eine Politik der Unnachgiebigkeit fest, als ein palästinensisches Kommando die Lufthansa-Maschine „Landshut“ entführte und die Freilassung der Häftlinge in Stammheim verlangte. Der Historiker Tim Geiger vom Institut für Zeitgeschichte schildert diese Ereignisse und die geschickte Verhandlungstaktik von Hans-Jürgen Wischnewski in Somalia. Er zeigt aber auch, mit welchen Mitteln Bundeskanzler Helmut Schmidt und sein Mann vor Ort operierten, als sie die Regierung von Siad Barre zur Mithilfe veranlassten. Vor allem mit Blick auf die selbstauferlegte Verpflichtung, keine Waffen in Krisenregionen zu liefern, gingen sie bis hart an die Grenze des Erlaubten.
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Cepedello Boiso, José. "La Grundnorm de Hans Kelsen, el concepto de unvollendetes Recht de Theodor Geiger y la fuerza hegemónica de la frontera: acerca del poder de los fenómenos jurídicos marginales." SOCIOLOGIA DEL DIRITTO, no. 1 (April 2017): 103–26. http://dx.doi.org/10.3280/sd2017-001006.
Hammarström, Harald, and Tom Güldemann. "Quantifying Geographical Determinants of Large-Scale Distributions of Linguistic Features." Language Dynamics and Change 4, no. 1 (2014): 87–115. http://dx.doi.org/10.1163/22105832-00401002.
In the recent past the work on large-scale linguistic distributions across the globe has intensified considerably. Work on macro-areal relationships in Africa (Güldemann, 2010) suggests that the shape of convergence areas may be determined by climatic factors and geophysical features such as mountains, water bodies, coastlines, etc. Worldwide data is now available for geophysical features as well as linguistic features, including numeral systems and basic constituent order. We explore the possibility that the shape of areal aggregations of individual features in these two linguistic domains correlates with Köppen-Geiger climate zones. Furthermore, we test the hypothesis that the shape of such areal feature aggregations is determined by the contour of adjacent geophysical features like mountain ranges or coastlines. In these first basic tests, we do not find clear evidence that either Köppen-Geiger climate zones or the contours of geophysical features are major predictors for the linguistic data at hand.
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Fricke, Rudolf G. A., and Kristian Schlegel. "Julius Elster and Hans Geitel – Dioscuri of physics and pioneer investigators in atmospheric electricity." History of Geo- and Space Sciences 8, no. 1 (January 4, 2017): 1–7. http://dx.doi.org/10.5194/hgss-8-1-2017.
Abstract. Julius Elster and Hans Geitel contributed to the physics at the turn of the 19–20th century in many ways. We first summarize the life of these exceptional scientists. Then – owing to the topic of this journal – we focus on their atmospheric electricity research. With their experiments, careful evaluations and ingenious interpretation, Elster and Geitel made important contributions to precipitation electricity, the influence of solar radiation on the electric state of the atmosphere, the nature of charge carriers and the ionization of air by radioactivity. They proved their experimental skills by inventing new instruments with unprecedented accuracy and reliability. A very modern concept was their attitude to undertake long-term measurements at various locations. A section on their recognition in the physics community and their scientific distinctions concludes the paper.
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Carmichael, Stephen W. "Exocytosis at the Atomic Level." Microscopy Today 5, no. 4 (May 1997): 3–4. http://dx.doi.org/10.1017/s1551929500061332.
As reviewed in this column on previous occasions, the atomic force microscope (AFM) is steadily making headway as an instrument that can make important contributions to biologic observations. Although the AFM is capable of operating in an aqueous environment, relatively little use has been made of this property to examine cellular structures under conditions that resemble those in vivo. A breakthrough in this regard was recently made by Stefan Schneider, Kumudesh Sritharan, John Geibel, Hans Oberleithner, and Bhanu Jena. of Yale University and the University of Würzburg.
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Geiser, F., G. Körtner, and BS Law. "Daily Torpor In A Pregnant Common Blossom-Bat (Syconycteris Australis: Megachiroptera)." Australian Mammalogy 23, no. 1 (2001): 53. http://dx.doi.org/10.1071/am01053.
TORPOR and reproduction in mammals are widely viewed as mutually exclusive processes. For most mammals, different energetic and hormonal demands appear to require a temporal sequence of torpor and reproduction within the yearly schedule. Torpor is characterised by a pronounced fall in body temperature and metabolic rate, which results in an overall reduction of energy expenditure (Geiser and Ruf 1995) and in most mammals occurs during the non-reproductive season (Goldman et al. 1986; Barnes 1996). Reproduction, on the other hand, requires an increase of energy expenditure for acquiring, processing and transfer of nutrients to the growing offspring (Hoffman 1964; Goldman et al. 1986; Thompson and Nicoll 1986; Kenagy et al. 1989; Barnes 1996).
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Huang, Hsin-hui, Takeshi Nagashima, Tetsu Yonezawa, Yasutaka Matsuo, Soon Hock Ng, Saulius Juodkazis, and Koji Hatanaka. "Giant Enhancement of THz Wave Emission under Double-Pulse Excitation of Thin Water Flow." Applied Sciences 10, no. 6 (March 17, 2020): 2031. http://dx.doi.org/10.3390/app10062031.
Simultaneous measurements of THz wave and hard X-ray emission from thin and flat water flow when irradiated by double femtosecond laser pulses (800 nm, 35 fs/transform-limited, 0.5 kHz, delay times up to 15 ns) were carried out. THz wave measurements by time-domain spectroscopy and X-ray detection by Geiger counters were performed at the transmission and the reflection sides of the flow. THz wave emission spectra show their dynamic peak shifts toward the low frequency with the highest intensity enhancements more than 1.5 × 10 3 times in |E| 2 accumulated over the whole spectrum range of 0–3 THz at the delay time of 4.7 ns between the two pulses. On the other hand, X-ray intensity enhancements are limited to about 20 times at 0 ns under the same experimental conditions. The mechanisms for the spectral changes and the intensity enhancements in THz wave emission are discussed from the viewpoint of laser ablation on the water flow induced by the pre-pulse irradiation.
Dissertations / Theses on the topic "Hans Geiger":
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Abele, Johannes. "Zauberstab der Atomwissenschaft: Hans Geiger und die Magie der Kerntechnik." Technische Universität Dresden, 2001. https://tud.qucosa.de/id/qucosa%3A27879.
Biehler, Hans-Martin [Verfasser], Klaus [Akademischer Betreuer] Feldmann, Klaus [Gutachter] Feldmann, W. [Gutachter] Sauer, Klaus [Herausgeber] Feldmann, and Manfred [Herausgeber] Geiger. "Optimierungskonzepte für Qualitätsdatenverarbeitung und Informationsbereitstellung in der Elektronikfertigung / Hans-Martin Biehler ; Gutachter: Klaus Feldmann, W. Sauer ; Betreuer: Klaus Feldmann ; Herausgeber: Klaus Feldmann, Manfred Geiger." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 1999. http://d-nb.info/1209741113/34.
Ferrier, Esther. "Deutsche Übertragungen der Divina Commedia Dante Alighieris, 1960-1983 Ida und Walther von Wartburg, Benno Geiger, Christa Renate Köhler, Hans Werner Sokop : Vergleichende Analyse, Inferno XXXII, Purgatorio VIII, Paradiso XXXIII /." Berlin ; New York : W. de Gruyter, 1994. http://books.google.com/books?id=5i5ZAAAAMAAJ.
Morgenthaler, Jan. Der Mann mit der Hand im Auge: Die Lebensgeschichte von Karl Geiser, Bildhauer, Zeichner und Photograph. Zürich: Limmat Verlag, 1988.
Hans-Michael Geiger- Informational Efficiency in Speculative Markets- A Theoretical Investigation. Peter Lang D, 1989. http://dx.doi.org/10.3726/b14075.
Hans-Michael Geiger- Informational Efficiency in Speculative Markets- A Theoretical Investigation: Informational Efficiency in Speculative Markets. Bern: Peter Lang International Academic Publishers, 2018.
Ferrier, Esther. Deutsche Ubertragungen Der Divina Commedia Dante Alighieris 1960-1983: Ida Und Walther Von Wartburg, Benno Geiger, Christa Renate Kohler, Hans Werne (Quellen ... Der Germanischen Volker, Nf). Walter De Gruyter Inc, 1994.
der Wissenschaft, Wegbereiter. "Hans Geiger (1882–1945)." In “The shoulders on which we stand”-Wegbereiter der Wissenschaft, 34–37. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-642-18916-6_9.
Achilles, Manfred. "Hans Geiger und der Spitzenzähler." In Historische Versuche der Physik, 128–33. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-46683-0_18.
Hentschel, Klaus. "Hans Geiger: Experimental Physics [c. April 1939]." In Physics and National Socialism, 189–92. Basel: Birkhäuser Basel, 1996. http://dx.doi.org/10.1007/978-3-0348-9008-3_71.
Hentschel, Klaus. "Werner Heisenberg, Hans Geiger & Max Wien. Petition [Spring 1936]." In Physics and National Socialism, 137–40. Basel: Birkhäuser Basel, 1996. http://dx.doi.org/10.1007/978-3-0348-9008-3_49.
Karstedt, Susanne. "Die Feyerabend-Connection – Wenn sich zwei freie Geister treffen." In Begegnungen mit Hans Albert, 183–86. Wiesbaden: Springer Fachmedien Wiesbaden, 2018. http://dx.doi.org/10.1007/978-3-658-22690-9_38.
Schweitzer, Carl-Christoph, Dieter Haack, Annegret Krätschell, and Johannes Richter. "Hans Geisler, Dresden — in einem Interview für diesen Band." In Lebensläufe — hüben und drüben, 127–36. Wiesbaden: VS Verlag für Sozialwissenschaften, 1993. http://dx.doi.org/10.1007/978-3-322-99405-9_13.
Höfler, Elke, Gerald Geier, and Claudia Zimmermann. "How to Design a Mathematical Learning App Suitable for Children." In Advances in Educational Technologies and Instructional Design, 160–78. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1692-7.ch008.
This paper examines the main considerations that influenced the development and implementation of an educational application created for elementary school children, with the aim of helping them to practice long divisions. In addition to discussing design principles for technologies that are suitable for children, the authors take a closer look at the framework for designing and using digital applications in the classroom. The most important aspects in this regard include the institutional setting of the Austrian school system and the myth of digital natives, as well as the Mobile Seamless Learning and Adaptive Learning approaches. The lack of basic digital infrastructure in Austrian elementary schools, the fact that not every child younger than ten years owns or has access to mobile devices and the resulting problematic implementation of Mobile Seamless Learning settings and BYOD strategies in schools ask for more flexible learning applications. The divisiontrainer designed by Geier (2015) is presented as a good practice example that takes the identified challenges into account.
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O'Brien, William. "France and The Western Alps." In Prehistoric Copper Mining in Europe. Oxford University Press, 2014. http://dx.doi.org/10.1093/oso/9780199605651.003.0010.
The use of copper was first established in the western Alps during the late fifth/ early fourth millennia BC. There were several metal-using groups in what is now modern Switzerland during the fourth millennium, including the Cortaillod and Pfyn cultures, followed in the third millennium BC by groups of the Saône-Rhône culture (Strahm 1994). The first direct evidence of copper production, however, only dates from the Late Bronze Age. This is based on the dating of smelting slag heaps in the valley of Oberhalbstein in the canton of Graubünden (Fasnacht 2004). These slags derive from the smelting of chalcopyrite ore derived from pillow lavas of the ophiolite geology in that area (Geiger 1984). The ability to smelt iron-rich copper ore involved a furnace technology that seems to have been first developed in the eastern Alps (see Chapter 7). No prehistoric mines are known; however, their existence may be inferred from the smelting of local ore at Late Bronze Age sites such as Savognin-Padnal and Marmorera-Stausees in the Oberhalbstein valley. Potential mining sites have been identified (see Schaer 2003), however, these have yet to be investigated in any detail. There are numerous deposits of copper mineralization in many parts of France. These occur in Brittany, the Pyrenees, the Corbières, on the margins of the Massif Central, the Maures, and the Alps. Research over the past 30 years has identified prehistoric copper mines in several of these areas. Further discoveries are possible in the difficult terrain of the Alps and Pyrenees, and also in areas where early copper mines have not been discovered, such as Brittany where deposits of steam tin and gold are also known. The oldest metal objects in France are recorded in the Paris Basin, where a small number of sheet copper beads date to the second half of the fourth millennium BC. These include the burial at Vignely (Seine-et-Marne) where a necklace of nine such beads was found with the burial of a five-year old child dated to 3499–3123 BC (Allard et al. 1998).
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Goldstein, Inge F., and Martin Goldstein. "Childhood Leukemia Near Nuclear Plants." In How Much Risk? Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195139945.003.0009.
In 1983 a television crew was making a documentary film about the health of the employees of a nuclear fuels reprocessing plant in England on the coast of the Irish Sea. This plant had previously been the site of a facility for the production of plutonium for nuclear weapons until it was converted to fuels processing after a fire in the reactor in 1957, during which there had been some release of radioactive material to the environment. The crew, filming in a town called Seascale 3 kilometers from the plant, where a number of the employees lived, was shocked to learn from the townspeople that there had been a surprising number of cases of leukemia among their children. Childhood leukemia is a rare disease, but in this small town there had been five cases in the preceding few years, ten times the number of cases that would have been expected from the average rate elsewhere in Great Britain. The focus of the film was changed from the health of the staff of the nuclear facility to the childhood leukemia in Seascale. Shown on television later that year, it aroused national attention and concern, making its points forcefully with shots of rapidly clicking Geiger counters in the neighborhood of the plant, claims that the coastline there is “the most radioactive environment on earth,” interviews with the anguished parents of sick or deceased children, reports of cows on neighboring farms born with malformations, and scenes of children playing on the beach with the smokestacks of the plant in the immediate background. It also reported that there had been some 300 other accidents at the plant in which radiation had been released, though the amounts were all of lesser magnitude than in the 1957 fire. The process for recovering plutonium from spent fuel from power plants does not recover all the plutonium, and some has to be disposed of as waste, along with other radioactive elements. Those responsible for the design of the plant had made the decision, based on both economic considerations and what was then known about the health hazards of radiation, to discharge much of this radioactive waste into the Irish Sea.
Conference papers on the topic "Hans Geiger":
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Rajabi Moghadam, Sahar, Fereydoon Abbasi Davani, and Babak Shirani Bidabadi. "Calibration of Activation Counter by a 2.48 kJ Plasma Focus Device." In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-30323.
A silver activation counter has been constructed by plastic scintillator plates along with silver foils for determination the neutron yield of a 2.48kJ plasma focus device, SBUPF1. This counter was calibrated by source removal method with an Am-Be 5 Ci neutron source which was placed above the anode of plasma focus device. Deuterium gas up to 8mbar pressure was injected to this device, and the neutron yield produced by pulsed D-D fusion of plasma focus device was measured by the counter. the neutron yield of SBUPF1 in 8mbar pressure was obtained 3.71±0.32×107 neutrons per shot. This result has relatively agreed with the neutron yield measured by silver activation Geiger counters.
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Heeb, M. J., F. Espana, M. Geiger, D. Collen, D. C. Stump, and J. H. Griffin. "IMMUNOLOGICAL SIMILARITIES BETWEEN PLASMA AND URINARY PROTEIN C INHIBITORS (PCIs) AND URINARY UROKINASE INHIBITOR (UKI)." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643816.
Plasma PCIs have similar MW (∼ 57K), amino acid composition, and heparin dependence (Suzuki et al 1983, JBC 258:163) as urinary UKI (Stump et al 1986, JBC 261:12759). Urinary PCI of ∼ 50K MW has a similar heparin dependence and urokinase (UK) competes with activated protein C (APC) for this PCI (Geiger et al 1986, Circ. 74:11-234). For comparison, three forms of PCI, one from urine and two from plasma, were purified, and each exhibited heparin-dependent UK and APC inhibitory activity and formed heparin-dependent complexes with APC. The APC-PCI complexes were visible on immunoblots (nondenaturing gels) developed using: A) monoclonal anti-UKI + 125I-antimouse IgG; B) polyclonal anti-plasma PCI + 125I-plasma PCI; and C) monoclonal anti-protein C + 125I-protein C. The three forms of purified PCI were detected by methods A and B. Two new bands of APC-inhibitor complexes were seen upon incubation of plasma with APC in the presence of heparin, and the same pattern was visualized by methods A, B, and C. In the absence of heparin, only one APC-inhibitor band was visualized by methods A and B, but two bands were visualized by method C. Plasma immunodepleted of UKI by monoclonal anti-UKI-Sepharose showed no detectable antigen or complexes with APC as visualized by methods A and B. However, the UKI-depleted plasma contained components which formed a reduced amount of complexes with APC as visualized with protein C antibodies, i.e. method C. Heparin stimulates tenfold the PCI activity of normal plasma. Based on amidolytic assays of APC using S-2366, the UKI-depleted plasma was very deficient (< 15%) in heparin-dependent PCI activity, whereas the weak heparin-independent PCI activity was slightly reduced. This indicates that the majority of heparin-dependent PCI activity of plasma is immunologically.related to UKI. These studies suggest that the two slightly different forms of plasma PCI, the urinary UKI, and the urinary PCI are very similar if not identical proteins and that plasma may contain a minor heparin-independent PCI which is not immunologically related to these proteins.
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Langrana, Noshir, Dan Qiu, Guohua Wu, Kathryn Higgins, and Cheng Tiao Hsieh. "Design, Simulation and SFF Techniques for Functional Components." In ASME 2000 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/detc2000/mech-14205.
Abstract Development of Solid Freeform Fabrication (SFF) systems has created the opportunity for new approaches in design of functional components, which leverages the inherent strengths of both experiment and numerical simulation. This paper describes an approach in which the computational models are integrated with the rapid prototyping fabrication processes. The parts are fabricated using different materials including wax, PZT, silicone nitride, and 17-4PH stainless steel powders for the SFF hardware (Langrana et al, 2000, Qiu et al, 1999, Danforth et al, 1998) and Ciba-Geigy SL-resin for SLA hardware (Higgins and Langrana, 1998, Higgins and Langrana 1999). The components such as turbine blades, actuators, and fixtures have been designed, simulated and fabricated. The properties of parts have been and are being quantified in terms of accuracy and quality.
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Athayde, C. M., and M. C. Scrutton. "ROLE OF GUANINE NUCLEOTIDES IN Ca2+ - DEPENDENT LYSOSOMAL SECRETION FROM ELECTROPERMEABILISED PLATELETS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644513.
Previous studies have shown that the maximal extent of Ca2+ dependent secretion of β-N-acetylglucosaminidase (B-N-AcGlc) from electropermeabilised human platelets can be enhanced by addition of thrombin or of 1-oleyl-2-acetylglycerol or 12-0-tetradecanoyl phorbol-13-acetate without a significant alteration in the EC^q for Ca2+. (Knight et al. Europ. J. Biochem.,143337 (1984)). We have found a similar Ca2+ dependent increase in the maximal extent of β-N-AcGlc and β-galactosidase secretion on addition of metabolically stable analogues of GTP (GTPγS and GppNHp) in the absence of thrombin or of GTP added in the presence of a nonsaturating concentration of thrombin. The EC50 values for GTP and GppNHp do not differ significantly for β-N-AcGlc and 3H-5HT secretion, but GTPγS is significantly more effective for 3H-5HT secretion.The time course of β-N-AcGlc secretion induced by GTPγS shows a significant delay as compared with that induced by thrombin + Ca2+. No significant differences could be detected between the properties of β-N-AcGlc or β-galactosidase secretion in this system. The results are consistent with involvement of a GTP binding protein (Np) in receptor-phospholipase C coupling mediating lysosomal secretion, but provide no indication that an additional protein of this type (Ne) is involved as has been proposed for lysosomal secretion from neutrophils. We have thus far failed to find evidence for heterogeneity in lysosomal secretion in this system (supported by SERC and Ciba-Geigy).
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Poll, C. T., and J. Westwick. "THE ROLE OF IONISED INTRACELLULAR FREE CALCIUM ([Ca++]i) IN THROMBIN-INDUCED DENSE GRANULE SECRETION." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644475.
Fura 2 is one of a recently-introduced family of Ca++ indicators with improved fluorescent properties compared to quin 2 (Grynkiewicz et al 1985). This study has examined the role of [Ca++]i in thrombin-induced dense granule release using prostacyclin-washed human platelets loaded with either thedense granule marker 14C-5HT (5HT) alone or with 5HT together with quin 2 ([quin2]i = 0.8mM) or fura 2 ([fura 2]i 20-30µM). In the presence of ImM extracellular calcium concentration ([Ca++]i) the [Ca++]e in quin 2 and fura 2 loaded platelets was 93±2 (n=10 experiments) and 133±0.3nM (n=12 experiments) respectively. In either quin 2 or fura 2 loaded platelets suspended in the presence of ImM [Ca++]e, thrombin (0.23-23.InM) promoted a rapid (in secs)concentration-dependent elevation of [Ca++]i from basal values to levels l-2µM, together with a parallel release of dense granules almost identical to that obtained with thrombin in non dye loaded platelets. In fura 2 loaded cells, removal of [Ca++]e inhibited the elevation of [Ca++]i induced by a sub-maximal concentration of thrombin (0.77nM) by 43+5% (n=4) but interestingly had no significant effect (p<0.05) on the rise in [Ca++]i elicited by low thrombin doses (0.231nM). Neither did lowering [Ca++]e inhibit the release of 5HT evoked by thrombin ( 0.231-23.InM) from either fura 2 loaded or non dye loaded platelets. In contrast, in quin 2 loaded platelets, removal of [Ca++]e inhibited the thrombin (0.231-23.InM) stimulated rise in [Ca++]i-by 90% and the 5HT release response to either low (0.231nM), sub-maximal (0.77nM) or maximal (23.InM) thrombin by 100% (n=4), 87+2°/o (n=6)and 2+l°/o (n=4) respectively. Fura 2 but not quin 2 loaded cells suspended in ImM [Ca++]e exhibited a Ca++ response to thrombin concentrations >2.31nM which could be separated into a rapid phasic component and a more sustained 'tonic' like component inhibitable by removal of [Ca++]e or by addition of ImM Ni++ . These data suggest the use of fura 2 rather than quin 2 for investigating stimulus response coupling in platelets, particularly when [Ca++]e is less than physiological. We thank the British Heart Foundation and Ciba-Geigy USA for financial support.
