‎Physique‎

‎"SMOLUCHOWSKI, MARIAN von. - BROWNIAN MOVEMENTS‎

‎Zur kinetischen Theorie der Brownschen Molekularbewegung und der Suspensionen. (Bearbeitet nach einer am 9. Juli 1906 der Krakauer Akademie vorgelegten und demnächst in dem Bullet. Int. Crac. erschienenen Abhandlung).‎

‎(Leipzig, Barth, 1906). Without wrappers.. In: ""Annalen der Physik. Vierte Folge. Bd. 21, No. 14.. Pp. 509-780. (Entire issue offered No 14). Smoluchowski's paper: pp. 756-780. Clean and fine.‎

‎First appearance of the final form of Smoluchowski's rechearches on the Brownian Movements, hereby introducing the Statistical Theory of the Brownian Movements.""Smoluchowski began his 1906 paper (the paper offered) by referring to Einstein's two articles of 1905. ""The findings (of these papers) agree completely with some results which I had...obtained several years ago and which I consider since then as an importent argument for the kinetic nature of this phenomenon."" Then why had he not published earlier ? 'Although it has not been possible for me till now to undertake an experimental test of the consequences of this point of view, something I originally intended to do, I have decided to publish these considerations...' In support of this decision, he stated that his kinetic method seemed more direct, simpler, and therefore more convincing than Einstein's, in which collision kinetics plays no explicit role....In any case, Smoluchowski's paper IS AN OUTSTANDING CONTRIBUTION TO PHYSICSS,even though the priority of Einstein is beyond question (as Smoluchowski himself pointed out)."" (Pais ""Subtle is the Lord"", pp. 100 ff.‎

Referentie van de boekhandelaar : 43861

‎"SMOLUCHOWSKI, MARIAN.‎

‎Anzahl und Grösse der Moleküle und Atome.‎

‎Bologna, Nicola Zanichelli, 1913. 8vo. In the original printed wrappers (With both the regular journal issue wrappers and the offprint wrappers - as issued). Offprint from ""Scientia"", Band XIII, Jahr 7. (1913), N.XXVII-1. A very fine and clean copy. Pp. 1-(25) - 20-(44).‎

‎Offprint issue of Smoluchowski's paper on the number and size of mulecules and atoms.‎

Referentie van de boekhandelaar : 48719

‎"SMOLUCHOWSKI, MARIAN.‎

‎Beitrag zur Theorie der Opaleszenz von Gasen im Kritischen zustande.‎

‎Cracovie, Imprimerie de L'Université, 1911. 8vo. In the original printed wrappers. Offprint from ""Bulletin de L'Académie des Sciences de Cracovie"", Octobre 1911. Very fine and clean. Pp. (2), 493-502.‎

‎Offprint issue of Smoluchowski's second paper on the reasons behind the blue sky and how to reproduce it.""In 1910 Theodor Svedberg based his experiments on Smoluchowski's calculations, observing how many particles of a suspension can be seen in the field of vision of a microscope at a given time and experimentally confirming Smoluchowski's predictions to an astonishingly high degree Smoluchowski himself had previously proved the existence of fluctuations of density in a pure gas by demonstrating that they are responsible for the known but unexplained phenomenon of the opalescence of a gas at a critical state. His paper ""Teoria kinetyczna opalescencji gazów w stanie krytycznym"" (""kinetic Theory of Gas Opalescence at the Critical Stale"" 1907) shows why the critical point plays such an important role and states that the opalescence of pure gas also should be observable under normal conditions: ""Each of us has observed it innumerable times when admiring the blue of the sky or the glow of the rising sun."" Smoluchowski combined the theory of fluctuations with the results of Lord Rayleigh's researches on the blue of the sky"" his finding (Einstein also took part in the discussion) was that the blueness of the sky was caused by fluctuations in the density of the air. Smoiuchowski's laboratory production of sky blue closed the investigation to a certain extent."" (DSB).‎

Referentie van de boekhandelaar : 48721

‎"SMOLUCHOWSKI, MARIAN.‎

‎Bemerkung zu der Arbeit B. Baules: ""Theoretische Behandlung der Erscheinungen in verdünnten Gasen"". - [AUTHOR'S PRESENTATION OFFPRINT ISSUE]‎

‎Leipzig, Johann Ambrosius Barth, 1914. 8vo. In the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint from ""Annalen der Physik"", Vierte Folge, Band 45, 1914. Light miscolouring to left margin of front wrapper. A very fine and clean copy, near mint. Pp. 1098-1102.‎

‎First edition, in the scarce author's presentation offprint issue, of Smoluchowski's comment of B. Baules paper on theoretical treatment of phenomena in rarefied gases.‎

Referentie van de boekhandelaar : 48715

‎"SMOLUCHOWSKI, MARIAN.‎

‎Elektrische Endomose und Strömungsströme. - [AUTHOR'S PRESENTATION OFFPRINT ISSUE]‎

‎Leipzig, Johann Ambrosius Barth, 1914. 8vo. In the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint of Smoluchowski's chapter in ""Handbuch der Elektrizität und des Magnetismus"". Very fine and clean. Pp. 366-428.‎

‎Scarce offprint with the author's printed presentation statement of Smoluchowski's important contribution to the ""Handbuch der Elektrizität und des Magnetismus"" in which he developed his theory of electroosmotic flow.""From 1899 Smoluchowski worked at the University of Lvov. Appointed professor in 1900, he held the chair of mathematical physics there until 1913. His first works at Lvov concerned atmospheric physics, aerodynamics and hydrodynamics, electrophoresis, and the theory of mountain folding. Recognition for these specialized works was show by his being asked to write the chapter on endosmosis phenomena in Handbuch der Elektrizitätund des Magnetismus, edited by J. A. Barth (Leipzig, 1914)."" (DSB).‎

Referentie van de boekhandelaar : 48706

‎"SMOLUCHOWSKI, MARIAN.‎

‎Studien über Molekularstatistik von Emulsion und deren Zusammenhang mit der Brownschen Bewegung.‎

‎Wien, Alfred Hölder, 1915. 8vo. Unopened, uncut in the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint from ""Kaiserl. Akademie der Wissenschaften"", Bd. CXXIII, Abt. IIa, Dezember, 1914. A very fine and clean copy. 25 pp.‎

‎First printing of Smolukowski's important paper on molecule statistics, emulsion and their connection to Brownian Motion. Einstein and Smolukowski work simultaneously and independently in the beginning of the 1900ies Brownian Motion. Smolukowski continued his work in this field and he work is distinct from Einstein's since Einstein said nothing of the collisions between a Brownian particle and the surrounding molecules.""From about 1900 Smoluchowski worked on Brownian movement. He wished to use experimental data to verify the theory he had obtained desire complicated by the confused situation of experimental research. In the meantime Einstein, in papers of 1905 and 1906, had presented a solution to the problem. Smoluchowski then decided to publish his results in 1906, which presented his different method. Einstein started from general relations of statistical physics, an approach that was universal but did not lend itself to visualization. For example, Einstein said nothing of the collisions between a Brownian particle and the surrounding molecules. Smoluchowski started by examining the effects of successive collisions and obtained a final formula that differed little from Einstein's. Smoluchowski's further works in this field extend through an examination of the Brownian movement of a particle undergoing the influence of a quasi-elastic force to the Brownian movements of macroscopic bodies. At the Conference of Natural Scientists at Münster in 1912, Smoluchowski proposed the observation of the Brownian rotative movement of a small mirror suspended on a thin quartz fiber and the observation free end of a similar fiber. The first experiment was performed by W. Gerlach and E. Lehrer in 1927, and later by Eugen Kappler"" the second, by A Houdijk and P. Zeeman, and by E. Einthoven. In 1925, Both experiments confirmed Smoluchowski's calculations.""‎

Referentie van de boekhandelaar : 48663

‎"SMOLUCHOWSKI, MARIAN.‎

‎Sur la conductibilité calorifique des corps pulvérisés (+) Études sur la conductibilité calorifique des corps pulvérisés (suite). - [THERMAL CONDUCTIVITY]‎

‎Cracovie, Imprimerie de L'Université, 1910 + 1911. 8vo. In the original printed wrappers. Two offprints from ""Bulletin de L'Académie des Sciences de Cracovie"", Mai, 1910 & Octobre, 1911. Both very fine and clean. Pp. (2), 130-53"" Pp. (1), 549-57.‎

‎Scarce offprint of Smoluchowski's important paper in which he documented that a layer of smooth spherical particles in vacuum may be used as an effective thermal insulator.""This was discovered by M. Smoluchowski some forty years ago. He investigated both theoretically and experimentally the thermal conductivity of powders, and concluded that filling the space between the walls of a Dewar vessel with a suitable powder would provide improved insulation by reducing the convective currents as well as the radiation and, moreover, would improve the vacuum by absorption. His application for a patent resulted in a long argument with the German Patent Office, whose examiners were reluctant to admit that any material agent could provide a better insulation than 'absolute' vacuum. At that time a large metallic Dewar vessel with its interstice filled with powdered active carbon was built at the Physical Institute of the University in Lwów, and showed the expected high insulating properties."" (Klemensiewicz, Thermal Conductivity of Powders)‎

Referentie van de boekhandelaar : 48711

‎"SMOLUCHOWSKI, MARIAN.‎

‎Sur la formation des veines d'efflux dans les liquides.‎

‎Cracovie, Imprimerie de l'Universite, 1904. 8vo. In the original stapled printed wrappers. Offprint from ""Bulletin de L'Académie des Sciences de Cracovie"", Octobre, 1904. A very fine and clean copy. Pp. (2), 371-384.‎

‎Scarce offprint of Smoluchowski's paper on the flow of liquids.‎

Referentie van de boekhandelaar : 48781

‎"SMOLUCHOWSKI, MARIAN.‎

‎Sur les phénomènes aérodynamiques et les effets thermiques qui les accompagnent.‎

‎Cracovie, Imprimerie de L'Université, 1903. 8vo. In the original printed wrappers. Offprint from ""Bulletin de L'Académie des Sciences de Cracovie"", Mars, 1903. Very fine and clean copy. Pp. 143-182.‎

‎Scarce offprint of Smoluchowski early work on aerodynamics and the related thermal effects.‎

Referentie van de boekhandelaar : 48705

‎"SMOLUCHOWSKI, MARIAN.‎

‎Theoretische Bemerkungen über die Viskosität der Kolloide.‎

‎Dresden & Leipzig, Theodor Steinkopff, 1916. Royal8vo. In the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint from ""Kolloid-Zeitschrift"", Heft 5, Band XVIII. With a few nicks to front wrapper. A hole (1 cm2) going all the way through the issue, however, not affecting text. Pp. (2), 191-95.‎

‎First edition, in the scarce author's presentation offprint issue, of Smoluchowski's theoretical remarks on the viscosity of the colloids.‎

Referentie van de boekhandelaar : 48722

‎"SMOLUCHOWSKI, MARIAN.‎

‎Versuch einer mathematischen Theorie der Koagulationskinetik kolloidaler Lösungen.‎

‎Leipzig, Wilhelm Engelmann, 1917. 8vo. In the original printed wrappers. Offprint from: ""Zeitschrift für physicalische Chemie"", XCII band, 2. heft. Very fine and clean. Pp. 129-168.‎

‎Scarce offprint of Smoluchowski's important paper on the mathematics behind his seminal coagulation equation. ""The underlying model may be described as follows: Consider n particles in three-dimensional Euclidean space, each particle being surrounded by a sphere of influence of diameter R. The particles move independently of each other, according to a Brownian Motion, as long as their distance is greater than R. When two particles meet at a distance R they stick together and form a ""double particle"", which itself is again in Brownian motion - and so on. Smoluchowski found on a heuristic basis an explicit formula for the average concentration of single, double, triple etc. particles at a time t."" (Lang, Smoluchowski's Theory of Coagulation in Colloids Holds Rigorously in the Boltzmann-Grad-Limit)‎

Referentie van de boekhandelaar : 48704

‎"SMOLUCHOWSKI, MARIAN.‎

‎Zur Theorie der Zustandsgleichungen. - [AUTHOR'S PRESENTATION OFFPRINT ISSUE]‎

‎Leipzig, Johann Ambrosius Barth, 1915. 8vo. In the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint from ""Annalen der Physik"", Vierte Folge, Band 48, 1915. A very fine and clean copy, near mint. Pp. 1098-1102.‎

‎First edition, in the scarce author's presentation offprint issue, of Smoluchowski's paper on The Equation of State.‎

Referentie van de boekhandelaar : 48714

‎"SMOLUCHOWSKI, MARIAN.‎

‎Über Brownsche Molekularbewegung unter Einwirkung äusserer Kräfte und deren Zusammenhang mit der verallgemeinerten Diffusionsgleichung. - [THE SMOLUCHOWSKI EQUATION]‎

‎Leipzig, Barth, 1915. 8vo. In the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint from ""Annalen der Physik"", Vierte Folge, Band 48, 1915. A very fine copy, near mint. Pp. 1103-1112.‎

‎Scarce presentation offprint with the printed presentation of Smolukowski's important drift-diffusion equation or the Smoluchowski equation. Here he documented that In some cases, the average velocity field exists because of a force, for example, the equation might describe the flow of ions dissolved in a liquid, with an electric field pulling the ions in some direction. This is referred to as the drift-diffusion equation (not to be confused with the Einstein-Smoluchowski relation)‎

Referentie van de boekhandelaar : 48659

‎"SMOLUCHOWSKI, MARIAN.‎

‎Über die Wechselwirkung von Kugeln die Sich in einer Zähen Flüssigkeit Bewegen.‎

‎Cracovie, Imprimerie de L'Université, 1911. 8vo. In the original printed wrappers. Offprint from ""Bulletin de L'Académie des Sciences de Cracovie"", Janvier 1911. Very fine and clean. Pp. (2), 28-39.‎

‎Scarce offprint of Smoluchowski's paper on the interaction of spheres that moves in a viscous liquid.‎

Referentie van de boekhandelaar : 48717

‎"SMOLUCHOWSKI, MARIAN.‎

‎Über durchschnittliche maximale Abweichung bei Brown'scher Molekularbewegung und Brillouin's Diffusionsversuche.‎

‎Wien, Alfred Hölder, 1915. 8vo. Unopened, uncut in the original printed wrappers. Author's presentation offprint with the printed presentation statement on top of frontwrapper ""Überreicht vom Verfasser"" [i.e. ""Given by the author""]. Offprint from ""Kaiserl. Akademie der Wissenschaften"", Abteilung IIa, 124. Band, 3. und 4. Heft. A very fine and clean copy. 14 pp.‎

‎First printing of Smolukowski's important paper the Average deviation in Brownian motion in relation to Brillouin's experiments on diffusion.Einstein and Smolukowski work simultaneously and independently in the beginning of the 1900ies Brownian Motion. Smolukowski continued his work in this field and he work is distinct from Einstein's since Einstein relate it to diffusion. ""From about 1900 Smoluchowski worked on Brownian movement. He wished to use experimental data to verify the theory he had obtained desire complicated by the confused situation of experimental research. In the meantime Einstein, in papers of 1905 and 1906, had presented a solution to the problem. Smoluchowski then decided to publish his results in 1906, which presented his different method. Einstein started from general relations of statistical physics, an approach that was universal but did not lend itself to visualization. For example, Einstein said nothing of the collisions between a Brownian particle and the surrounding molecules. Smoluchowski started by examining the effects of successive collisions and obtained a final formula that differed little from Einstein's. Smoluchowski's further works in this field extend through an examination of the Brownian movement of a particle undergoing the influence of a quasi-elastic force to the Brownian movements of macroscopic bodies. At the Conference of Natural Scientists at Münster in 1912, Smoluchowski proposed the observation of the Brownian rotative movement of a small mirror suspended on a thin quartz fiber and the observation free end of a similar fiber. The first experiment was performed by W. Gerlach and E. Lehrer in 1927, and later by Eugen Kappler"" the second, by A Houdijk and P. Zeeman, and by E. Einthoven. In 1925, Both experiments confirmed Smoluchowski's calculations.""‎

Referentie van de boekhandelaar : 48662

‎"SMOLUCHOWSKI, MARIAN.‎

‎Über gewisse Mängel in der Begründung des Entropiesatzes sowie der Boltzmann'schen Grundgleichung in der kinetischen Gastheorie.‎

‎Cracovie, Imprimerie de L'Université, 1915. 8vo. In the original printed wrappers. Offprint from ""Bulletin de L'Académie des Sciences de Cracovie"", Juillet 1915. Very fine and clean, near mint. Pp. (2), 164-178.‎

‎Offprint issue of Smoluchowski's paper on certain deficiencies of the foundations of the law of entropy and the basic Boltzmann equation of the kinetic theory of gases.‎

Referentie van de boekhandelaar : 48720

‎"SODDY, F. (+) E. RUTHERFORD.‎

‎Intra-atomic Charge [Soddy] (+) The Structure of the Atom [Rutherford]. - [INTRODUCING THE CONCEPT AND COINING THE WORD ""ISOTOPE""]‎

‎London, Macmillan, 1913-1914. Royal8vo. Bound in contemporary half calf with two black leather title label to spine with gilt lettering. Five raised bands. In ""Nature"", Vol. 92, September - February, 1913-1914. Library stamp of Christ Church College, Oxford on first page of index with their bookplate on front free endpaper and that of Dr Lee's Laboratory, Christ Church, on front paste-down. Minor wear to extremities, otherwise a very fine and clean copy.‎

‎"SODDY, FREDERICK.‎

‎Der gegenwärtige Stand der Radioaktivität.‎

‎(Leipzig, S. Hirzel, 1906). No wrappers. In ""Jahrbuch der Radioaktivität und Elektronik"", 3. bd., Heft 1. Pp. 1-116 (entire issue offered). Soddy's paper: pp. 1-23.‎

‎"SODDY, FREDERICK.‎

‎Die Entwickelung der Elemente.‎

‎(Leipzig, S. Hirzel, 1906). No wrappers. In ""Jahrbuch der Radioaktivität und Elektronik"", 3. bd., Heft 3. Pp. 239-358 (entire issue offered). Soddy's paper: pp. 247-264.‎

‎"SOMMERFELD, A. - THE BOHR-SOMMERFELD MODEL OF THE ATOM.‎

‎Zur Quantentheorie der Spektrallinien. I-III. (I. Theorie der Balmerschen Serie. II. Die Feinstruktur der Wasserstoff- und der wasserstoffähnlichen Linien. III. Theorie der Röntgenspektren.‎

‎Leipzig, Johann Ambrosius Barth, 1916. Contemp. hcloth. Gilt lettering to spine. VIII,888 a. 4 plates. (entire volume offered). Sommerfelds paper: pp. 1-94 a. pp. 125-167. A stamp on verso of titlepage. Clean and fine.‎

‎"SOMMERFELD, ARNOLD.‎

‎Zur Relativitätstheorie. I. Vierdimensionale Vektoralgebra.‎

‎Leipzig, Ambrosius Barth, 1910. 8vo. In full black cloth with gilt lettering to spine. In ""Annalen der Physik"", Vierte Folge, Band 32. Entire volume offered. Library labels to front end papers and stamp to title page, otherwise fine and clean. Pp. 749-76. [Entire volume: VIII, 1112 pp. + 15 plates.].‎

‎"SOMMERFELD, ARNOLD. - SPATIAL QUANTIZATION AND FINE STRUCTURE - THE ATOMIC MODEL OF SOMMERFELD.‎

‎Zur Quantentheorie der Spektrallinien. (+) Fortzetzung. (2 Parts).‎

‎(Leipzig, Ambrosius Barth, 1918). Without wrappers in ""Annalen der Physik"", Vierte Folge, Bd. 51, No.17 a. 18. The entire issues offered. Pp. 1-124 a. pp. 125-236. Sommerfeld's papers: pp. 1-94 a. pp. 125-167. Punched in inner margins after cords. Clean and fine.‎

‎"SPOTTISWOODE, WILLIAM & J. FLETCHER MOULTON. - EARLY TELEVISION.‎

‎On the Sensitive State of Electrical Discharges through Rarified Gases. Received April 2, - Read May 8, 1879.‎

‎(London, Harrison and Sons, 1880). 4to. No wrappers as extracted from ""Philosophical Transactions"" 1879 - Vol. 170 - Part I. Pp. 165-229 a. 6 lithographed plates.‎

‎"STARK, J.‎

‎Über die Lichtemission der Kanalstrahlen in Wasserstoff.‎

‎(Leipzig, Johann Ambrosius Barth, 1906). 8vo. No wrappers. Extracted from ""Annalen der Physik"" Vierte Folge. Bd. 21. Entire issue no. 13 offered. Pp. 401-456. [Entire issue: Pp. 401-608].‎

‎First appearance of Stark's extensive paper and most detailed paper on the Doppler-effect. In 1919 he was awarded the Nobel Prize in physics: ""for his discovery of the Doppler effect in canal rays and the splitting of spectral lines in electric fields"".""With the relatively elaborate equipment available to him in his own laboratory at Aachen, Stark completed his research in progress, chiefly on the dissymmetry of Bremsstrahlung, and undertook new series of experiments on the splitting of spectral lines in an electric field. While at Göttingen he had been encouraged by Woldemar Voigt to investigate this electrical analogy to the magnetic Zeeman effect. Stark’s first preparatory experiment, at the beginning of 1906, had been a failure"" but he was successful in October 1913. He described the experiment in a short autobiographical account. Having procured all the necessary equipment -""a high-intensity spectrograph of rather large dispersion, high-tension sources, and Gaede pumps"" - he looked for the effect ""simultaneously in the hydrogen and helium lines."" An electric field of between 10,000 and 31,000 volts/cm, was established in the canal-ray tube."" (DSB)‎

Referentie van de boekhandelaar : 50376

‎"STARK, J. (JOHANNES). - DISCOVERING THE ""STARK-EFFECT""‎

‎Beobachtungen über den Effekt des elektrischen Feldes auf Spektrallinien. I-VI. (I. Quereffekt. II. Längseffekt (together with G. Wendt). III. Abhängigkeit von der Feldstärke (together with H. Kirschbaum). IV.Linienarten, Verbreitung (together with H....‎

‎Leipzig, Johann Ambrosius Barth, 1914 u. 1915. No wrappers. In: ""Annalen der Physik. Vierte Folge. Hrsg. von W. Wien und M. Planck."", Bd. 43., No 7,1914. Pp. 965-1116 a. 4 plates (entire issue offered) and. Bd. 48, No. 18. Pp. 145-272 a. 2 plates (entire issue offered).The blocks are punched in inner margins after cords. Stark's papers I-IV: pp. 965-1047 (Bd. 43) and V-VI: pp. 193-235 (Bd. 48). Both issues clean and fine.‎

‎First appearance of these 5 important papers in which Stark describes his researches on the effects of the electrical field on the spectral lines of hydrogen, thus discovering the splitting of the spectral lines, THE STARK-EFFECT. This effect was incorporated into quantum mexhanics by Paul Epstein in 1916, and it was shown to be consistent with wave mechanics by Schrödinger in 1926. In 1919 Stark was awarded the Nobel Prize for physics for his discovery of the Doppler effect in canal rays and of the splitting of spectral lines inan electric field (the papers offered). ""At the beginning of July 1913, several months before Stark’s discovery, Niels Bohr published his concept of a quantum-mechanical model of the atom. This provided, in principle, the possibility of understanding the reason for the Stark effect, which the classical theory was powerless to explain. Stark therefore had an opportunity to be doubly gratified, having also been one of the first, after Max Planck and Einstein, to stress the “fundamental significance” of Planck’s elementary law (since 1907). which he had championed in many polemical discussions. Yet, almost incomprehensibly, Stark denied himself the satisfaction of seeing his own experiments confirm a theory for which he had helped prepare the way conceptually, even if he had not directly participated in its creation. Apparently he always had to oppose the accepted point of view. Thus, as Bohr’s theory continued to gain adherents in 1914-1916."" (DSB)‎

Referentie van de boekhandelaar : 44891