About this time Hansen, who had long been engaged in researches on the biology of the fungi of fermentation, demonstrated that yeast free from bacteria could nevertheless occasion diseases in beer.
Hansen set himself the task of studying the properties of the varieties of yeast, and to do this he had to cultivate each variety in a pure state.
Having found that some of the commonest diseases of beer, such as yeast turbidity and the objectionable changes in flavour, were caused not by bacteria but by certain species of yeast, and, further, that different species of good brewery yeast would produce beers of different character, Hansen argued that the pitching yeast should consist only of a single species - namely, that best suited to the brewery in question.
Pure Cultivation of Yeasts.-The methods which were first adopted by Hansen for obtaining pure cultures of yeast were similar in principle to one devised by J.
Hansen counted the number of yeast cells suspended in a drop of liquid diluted with sterilized water.
Hansen pointed out that this was by no means the case, for it is more difficult to separate the cells from each other in the gelatin than in the liquid.
Such, in brief, are the methods devised by that brilliant investigator Hansen; and these methods have not only been the basis on which our modern knowledge of the Saccharomycetes is founded, but are the only means of attack which the present-day observer has at his disposal.
Previously to Hansen's work the only way of differentiating I Hansen found there were three species of spore-bearing Saccharomycetes and that these could be subdivided into varieties.
Schwann in 1839) was studied by Hansen, who found that each species only developed spores between certain definite temperatures.
Hansen showed that the microscopic appearance of film cells of the same species of Saccharomycetes varies according to the temperature of growth; the limiting temperatures of film formation, as well as the time of its appearance for the different species, also vary.
Hansen of two new inequalities in the moon's motion.
After completing these reductions, Airy made inquiries, before engaging in any theoretical investigation in connexion with them, whether any other mathematician was pursuing the subject, and learning that Hansen had taken it in hand under the patronage of the king of Denmark, but that, owing to the death of the king and the consequent lack of funds, there was danger of his being compelled to abandon it, he applied to the admiralty on Hansen's behalf for the necessary sum.
Hansen (1893) and J.
Hansen (1:1,500,000), was published in 1907.
Hydrodynamical methods received increased attention and the investigation of the movements of the ocean by means of physico-mathematical devices developed as a result of the older work of Bjerknes, continued chiefly by Helland-Hansen and Sandstrom.
Helland-Hansen and Nansen showed later that it was improbable that variations in the northerly drift of Atlantic water could be traced directly to variations in the quantity of heat received by the sea from solar radiation.
The plankton is divided into (a) the Zoo-plankton (such as the minute crustacea and the eggs and larva of fishes and many other marine animals); and (b) the Phyto-plankton, that is, the minute algae, diatoms, peridinians, some flagellate protozoa, spores of alga, etc. The investigation of the plankton from a new point of view, begun by Hansen in 1889, was continued by Lohmann at Kiel, by Cleve in Sweden, by Gran and Ostenfeldt in Norway and Denmark, and by Herdman, Allen and others in England.
Doubt was first thrown on the accuracy of this number by an announcement from Hansen in 1862 that the observed parallactic inequality of the moon was irreconcilable with the accepted value of the solar parallax, and indicated the much larger value 8.97".
Hansen (10) has recognized that the " praegenital somite " persists in a rudimentary condition, forming a " waist " to the series of somites in the Pedipalpi and Araneae.
(Original drawing by Pocock and Pickard-Cambridge, after Hansen and Sorensen.) caudal support for the many-jointed flagelliform telson, as in the Urotricha.
- An extremely remarkable minute form originally described by Grassi (34) from Sicily, and since further described by Hansen (35).
Hansen and Sorensen, The Order Palpigradi, Thorell (Koenenia), and its Relationships with other Arachnida," Ent.
Hansen and Sorensen, On Two Orders of Arachnida (Cambridge, 1904); Sorensen, " Opiliones laniatores," Nat.
Hansen (1813-1891), finished in 1858; the Minorite church, a Gothic edifice of the 14th century, containing an admirable mosaic of Leonardo da Vinci's "Last Supper" by Raffaeli, executed in 1806-14 by order of Napoleon and placed here in 1846.
Hansen and G.
Von Siccardsburg (1813-1868), the sumptuous interior of which vies with that of Paris; the academy of art, built in 187276; the exchange, built in 1872-77, both by Hansen; and the Austrian museum of art and industry, an Italian Renaissance building erected by Ferstel in 1868-71.
During Nansen's expedition on the " Fram " in 1894-1895, Scott Hansen made observations with a Sterneck's half-seconds pendulum on the ice where the sea was more than 1600 fathoms deep and found only an insignificant deviation from the number of swings corresponding to a normal ellipsoid.
Hansen the freezing-point T ° C. varies with the degree of concentration according to the formula T = - 0.0086-0 0064-6330"o - o 0001055a02.
By a number of ingenious devices Hansen developed methods by which dt could be determined.
Hansen, therefore, shows how the radius vector is corrected so as to give that of the true planet.
Hansen in 1829 (Astr.
Hansen, Die Aufhebung der Leibeigenschaft in Schleswig and Holstein (1861); G.
Xylinum - have been thoroughly studied by Hansen and A.
Hansen and others form a distinct order Tanaidea for the decidedly anomalous group called by Sars Isopoda chelifera.
Hansen (Proc. Zool.
Hansen (PlanktonExpedition Report, 1895).
Hansen concludes that "they are all typically ground animals, and as yet no species has been taken under such conditions that it could be reckoned to the pelagic plankton."
20 1911 (with temp. - 5° to - 23° F.) Amundsen left again with four companions, Helmer Hansen, Oscar Wisting, Sverre Hassel and Olav Bjaaland, four sledges and 52 dogs.
Goethe (1904); P. Hansen and R.