摘要:

The diastatic activity of wheat flour has been definitely resolved into two independent variable factors: (1) concentration and activity of the enzyme, (2) resistance of starch to hydrolysis. The method for the measurement of starch resistance involves the inactivation of the natural diastase with sodium tungstate, washing out the excess precipitant, and the addition of a fixed amount of taka-diastase. By the use of this method it has been found that continued grinding or extraction with ether decreases the resistance of the starch. Both diastatic activity and starch resistance are affected by the conditions under which the wheat is grown. The increase in diastatic activity when wheat is sprouted is due mainly to a change in the quantity or nature of the enzyme. Several modifications in Rumsey's method for diastatic activity are recommended.

ISSN:1923-4287    

DOI:10.1139/cjr29-007

出版商:NRC Research Press    

年代:1929

数据来源: NRC

摘要:

The steam-curing of Portland Cement Mortars in saturated steam at 100°, 125°, 150°, 175° and 200 °C. was studied both as to variations in the tensile strength of 2-day and 28-day mortar briquets and as to the changes which occurred in the crystalline matter in the cement. The rate of hydration of the cement, as shown by the disappearance of the original crystalline material, increased with the temperature of the saturated steam. Crystals of calcium hydroxide appeared almost at once, but after reaching a maximum decreased again in amount. At the same time, a new crystalline product appeared and increased in quantity as the amount of hydrated lime decreased. Some of the chemical properties of the new crystals are given. The stability of the new crystals when exposed to solutions of sulphates indicates that the great increase in the resistance of Portland cement mortars to alkali action produced by steam-curing is connected with the production of this crystalline material.

ISSN:1923-4287    

DOI:10.1139/cjr29-008

出版商:NRC Research Press    

年代:1929

数据来源: NRC

摘要:

A rapid method of estimating the moisture in a sample of wheat is described. This method depends on the effect produced in a specially arranged radio circuit in which an alternating current of high frequency is generated. When a container holding some of the wheat under examination is introduced into the rapidly alternating electric field, a change occurs in the strength of the current which may be measured by an ammeter in the circuit and which may be immediately interpreted as a measure of the moisture content of the wheat.

ISSN:1923-4287    

DOI:10.1139/cjr29-009

出版商:NRC Research Press    

年代:1929

数据来源: NRC

摘要:

A genetical study of resistance of wheat to black stem rust, and a plant breeding attack on the rust problem are described. A large F2population of the cross Vernal (T.dicoccum) × Marquis (T.vulgare) was grown under severe natural epidemic conditions in the field and hundreds of F3progenies were exposed in the seedling stage, under controlled conditions, to pure physiologic forms of rust. In the field Vernal is highly resistant and Marquis susceptible to most forms of stem rust. Resistance in the field proved incompletely dominant and appeared to be governed by a single genetic factor. Marquis and Vernal were found to differ by one main genetic factor, Rb, for seedling reaction to form 21. This factor Rb, carried by Vernal, also governs seedling resistance to forms 17, 29 and 36 and appears to be responsible for the slight seedling resistance of Vernal to form 27. There was some evidence that the factor Rbis the same factor that controls the resistance of the F2plants to the forms of rust in the field (forms 17, 21, 29 and 36 were known to be present.) A different factor Racauses the resistance of Marquis seedlings to form 27. Vernal resistance was not found to be associated closely with the seed shape of that variety nor with its adherence of glumes to the seed.

ISSN:1923-4287    

DOI:10.1139/cjr29-010

出版商:NRC Research Press    

年代:1929

数据来源: NRC

摘要:

Observations on the color changes ofLepus americanusare recorded and discussed. Melanin is shown to be lacking in the white winter hair but plentiful in the dark summer hair, especially in the roots, thereby protecting the animal from sunburn. In view of the observations on experimental animals it is considered that the color changes ofLepus americanusare due, not to local environmental factors, but to an inherited habit. The conclusion is reached that color changes are primarily for the summer exclusion and winter retention of heat and for protection against ultra-violet light. (G.B.T.)

ISSN:1923-4287    

DOI:10.1139/cjr29-011

出版商:NRC Research Press    

年代:1929

数据来源: NRC