The analysis of the lactation curve into maximum yield and persistency

1930 ◽  
Vol 20 (2) ◽  
pp. 145-185 ◽  
Author(s):  
H. G. Sanders
Keyword(s):  
Mammary Gland ◽  
Negative Selection ◽  
Maximum Yield ◽  
The Body ◽  
External Factors ◽  
The Other ◽  
Lactation Curve ◽  
Nutritional Factor ◽  
The Mean ◽  
Selection For

An attempt has been made to analyse the lactation yield into its two components, maximum yield and persistency; the latter has been defined as the ratio of lactation to maximum yield, and has been measured by a S.F. calculated from , where R is the mean ratio for the month of calving concerned.Whilst, when corrections for external factors are applied, maximum and persistence are equally constant throughout the cow's life, these factors cause wider individual fluctuations with persistency; maximum yield is subject to a more rigid limit and may be largely determined by the area of the mammary gland, but persistency seems to be chiefly a nutritional factor—that is to say, it depends on the success of the mammary gland in competing with the other tissues of the body for the available nutriment. This leads to the view that persistency is higher in the dairy type of cow; it also appears to be associated with high constitution, for very definite positive selection is apparent with persistency, as compared to marked negative selection for maximum—this is attributed to pathological attrition falling more heavily on cows with high initial yield and low persistency.

IV. On the expansion by heat of metals and alloys

1867 ◽  
Vol 15 ◽  
pp. 220-222
Keyword(s):  
Specific Gravity ◽  
Metals And Alloys ◽  
The Body ◽  
The Other ◽  
Different Temperatures ◽  
The Mean

In a paper “ On the Expansion by Heat of Water and Mercury” *, a method of determining the expansion of bodies is described, by which good results can be obtained with comparatively small quantities of the substances to be experimented with. This method, that of weighing the body in water at different temperatures, has been employed for the present research. The results obtained are given in the following Tables:— From the above the following conclusion is drawn-namely, that just as it may be said that the specific gravity of an alloy is approximately equal to the mean specific gravities of the component metals , so also from the foregoing we may deduce that the volume which an alloy will occupy at any temperature between 0° and 100° is approximately equal to the mean of the volumes o f the component metals at the same temperature, or, in the other words, the cubical or linear coefficients o f expansion by heat of an alloy between 0° and 100° are approximately equal to the mean of the cubical or linear coefficients of expansion by heat o f the component metals .

scholarly journals Evolution of crabs – history and deconstruction of a prime example of convergence

2014 ◽  
Vol 83 (2) ◽  
pp. 87-105 ◽  
Author(s):  
Gerhard Scholtz
Keyword(s):  
Body Shape ◽  
Sea Urchins ◽  
The Body ◽  
External Factors ◽  
The Other ◽  
Compact Body ◽  
Body Shapes ◽  
Definition Of ◽  
Internal And External Factors

Compared with the elongate bodies of shrimps or lobsters, crabs are characterised by a compact body organisation with a depressed, short carapace and a ventrally folded pleon. The evolutionary transformation from a lobster-like crustacean towards a crab is called ‘carcinization’ and has been interpreted as a dramatic morphological change. Nevertheless, the crab-shape evolved convergently in a number of lineages within Decapoda. Accordingly, numerous hypotheses about internal and external factors have been presented, which all try to explain these frequent convergent carcinization events despite the seemingly fundamental changes in the body organisation. However, what a crab is lies greatly in the eye of the beholder and most of the hypotheses about the lobster/crab transformation are biased by untested assumptions. Furthermore, there are two meanings of the word ‘crab’ within decapods: one, the phylogenetic meaning, refers to the clade Brachyura; the other, more general and typological use of the word crab, describes decapods with a certain body shape. These two meanings should not be confused when the issue of carcinization is discussed. Here, I propose a definition of what a crab is, i.e. what is meant when we speak about carcinization. I show that not all Brachyura are crabs in the typological sense. Carcinization occurred at least twice within the clade. Among Anomala there is further evidence that crab-shaped Lithodidae derived from a hermit-crab like ancestor. Carcinization is not restricted to Anomala plus Brachyura (Meiura) but is also found in Achelata, namely in slipper lobsters. A deconstruction of the crab-shape reveals that parts of it appear in various combinations among all decapod groups. Only a certain threshold of number and quality of crab-features makes us call an animal a ‘crab’. This reveals that carcinization does not involve such dramatic changes in morphology as has been suggested. Moreover similar alterations of body shapes appear frequently in other crustacean taxa and in various animal groups as diverse as sharks and sea urchins. Hence morphological constraints, macroevolution, trends, tendencies, or underlying synapomorphies of any kind are not necessary assumptions for the explanation of the evolution of crabs.

FERTILITY OF BARLEY AUTOTETRAPLOIDS: II. THE RELATIONSHIP OF ANEUPLOIDY, DWARFING AND FERTILITY IN FOUR AUTOTETRAPLOID BARLEY VARIETIES

1961 ◽  
Vol 41 (1) ◽  
pp. 124-133 ◽  
Author(s):  
E. Reinbergs ◽  
L. H. Shebeski
Keyword(s):  
Continuous Selection ◽  
The Other ◽  
High Fertility ◽  
Chromosome Distribution ◽  
Apparent Relationship ◽  
Identical Number ◽  
The Mean ◽  
Selection For ◽  
Relationship Of ◽  
The Relationship

A considerable number of dwarf plants (16.4 to 85.7 per cent) was found in C2 to C5 generations of four artificially-induced barley autotetraploids from the varieties OA.C. 21, Brant, York and Montcalm.The Montcalm tetraploid, which was the lowest in mean fertility, had the highest percentage of dwarfs. In the other three tetraploids there was no apparent relationship between the frequency of dwarfs and the mean per cent fertility. In the O.A.C. 21 tetraploid continuous selection for plants with high fertility did not reduce the occurrence of dwarfs.Most of the dwarf plants were aneuploids with 26, 27, 29, 30 or 31 chromosomes, but plants with identical number of chromosomes often showed differences in phenotype. Among the aneuploids 29-chromosome plants were most frequently found. The 26- and 31-chromosome plants were completely sterile. Only a low percentage of the other aneuploid plants produced seed. By considering the observed percentages of dwarf plants and the ratio of hypoploids to hyperploids produced, the largest part of sterility in the four barley autotetraploids could be attributed to irregular chromosome distribution.

scholarly journals Integration of Proprioceptive and Visual Position-Information: An Experimentally Supported Model

1999 ◽  
Vol 81 (3) ◽  
pp. 1355-1364 ◽  
Author(s):  
Robert J. van Beers ◽  
Anne C. Sittig ◽  
Jan J. Denier van der Gon
Keyword(s):  
Visual Information ◽  
The Body ◽  
The Other ◽  
Proprioceptive Information ◽  
Position Information ◽  
Left Hand ◽  
The Mean ◽  
The Right ◽  
Variable Errors ◽  
Available Information

Integration of proprioceptive and visual position-information: an experimentally supported model. To localize one’s hand, i.e., to find out its position with respect to the body, humans may use proprioceptive information or visual information or both. It is still not known how the CNS combines simultaneous proprioceptive and visual information. In this study, we investigate in what position in a horizontal plane a hand is localized on the basis of simultaneous proprioceptive and visual information and compare this to the positions in which it is localized on the basis of proprioception only and vision only. Seated at a table, subjects matched target positions on the table top with their unseen left hand under the table. The experiment consisted of three series. In each of these series, the target positions were presented in three conditions: by vision only, by proprioception only, or by both vision and proprioception. In one of the three series, the visual information was veridical. In the other two, it was modified by prisms that displaced the visual field to the left and to the right, respectively. The results show that the mean of the positions indicated in the condition with both vision and proprioception generally lies off the straight line through the means of the other two conditions. In most cases the mean lies on the side predicted by a model describing the integration of multisensory information. According to this model, the visual information and the proprioceptive information are weighted with direction-dependent weights, the weights being related to the direction-dependent precision of the information in such a way that the available information is used very efficiently. Because the proposed model also can explain the unexpectedly small sizes of the variable errors in the localization of a seen hand that were reported earlier, there is strong evidence to support this model. The results imply that the CNS has knowledge about the direction-dependent precision of the proprioceptive and visual information.

scholarly journals XVIII. On the direction assumed by plants

1848 ◽  
Vol 138 ◽  
pp. 253-275
Keyword(s):  
Solid Body ◽  
The Body ◽  
The Other ◽  
External Object ◽  
Metallic Wire ◽  
Slight Tendency ◽  
The Family ◽  
The Mean ◽  
Perennial Herbs

The plants with tendrils are very numerous. According to Mr. Palm there are about five hundred, divided into seventeen families. Of these, one hundred and sixty have a ligneous stem, eighty-three are perennial herbs, and one hundred and seventeen are annuals. My experiments on the mode of curling-up of these organs were made on the tendrils of the Tamus comunis , a plant of the family of the Asparageæ. The tendrils of this plant seem to be a thread-like degeneration of the footstalk of a leaf, whose place they occupy on the stem of the plant. They are at first straight, and are implanted perpendicularly on the stem, so as to form almost a right angle with it; the extreme end of the tendril only has a slight tendency to bend towards the stem. When the tendril of the Tamus is touched by any solid body whatever on a point of its surface not too far from the extremity, it contracts itself from the outside inwards, forming at first a hook and then a curl, so as to embrace the body closely if that body be circular; if angular, the knot is only tight on the angles, and bulges out on the surfaces. When a first knot is tied, the end of the tendril continues to roll itself up in a coil, though not in contact with the body in that part, and the coil slides over the external object, coming nearer and nearer to it so as to embrace it several times: in the mean while, the other end of the tendril continues also to contract itself. In this way as many as seven or eight knots are formed. I have frequently seen three tied before my eyes within the space of a quarter of an hour on a metallic wire, small branches of wood, a pencil, my finger, &c. The contact of any solid body whatever is sufficient to produce this effect; so much so, that although the tendril is evidently destined by nature to support the creeper to which it belongs, by means of the urrounding plants, yet if it chances to meet a part of the very same plant of Tamus of which it is itself a portion, the contact causes it immediately to roll itself up around that portion.

scholarly journals Threshold selection for rust resistance in hybrid poplar: Population response to mass selection

2011 ◽  
Vol 60 (1-6) ◽  
pp. 266-276 ◽  
Author(s):  
B. J. Stanton
Keyword(s):  
Rust Resistance ◽  
Polynomial Regression ◽  
Hybrid Poplar ◽  
Directional Selection ◽  
The Other ◽  
Quadratic Functions ◽  
Mass Selection ◽  
Selection Intensity ◽  
The Mean ◽  
Selection For

AbstractElevenPopulus×generosapopulations were developed in the Pacific Northwest by annual controlled hybridization ofP. deltoidesandP. trichocarpabetween 1991 and 2001. Mass selection forMelampsoraleaf rust resistance was observed in the field as a threshold character in identifying seedling phenotypes for clonally replicated evaluation. The effectiveness of the approach was assessed for each annual population by comparing the distribution of phenotypes in unselected seedling populations with the distribution of selected genotypes in the clonal field tests established in successive years and evaluated at the approximate same level of disease severity using two selection thresholds corresponding to chlorotic and healthy tissue. Bi-directional selection was used as an initial check on the efficacy of the procedure and resulted in a wide separation in liability between the positive (0.06 threshold units (T.U.)) and negative (−2.45 T.U.) selection groups when tested as clones. The other 10 seedling populations that were subjected solely to directional selection exhibited a mean increase in incidence above the first selection threshold at the clonal stage (47 versus 81%) that was accompanied by an improvement in population liability (−0.06 versus 0.50 T.U.) and a reduction in population standard deviation (0.83 versus 0.54 T.U.). The change in liability was strongly related by polynomial regression to selection intensity and a grouping of populations based on infection-season precipitation (r2=0.98). The mean liability of four of the 10 seedling populations observed during years of high infection-season rainfall was six-fold lower than the mean liability of those populations observed during the other six years of lower infection-season rainfall (−0.12 T.U. versus −0.02 T.U., respectively), indicating that populations undergoing evaluation during years of heavy precipitation experienced more intense rust exposure. Moreover, quadratic functions showed that populations undergoing rust evaluation during years of high rainfall were more responsive to increases in selection intensity above the vertex of the function (i.e. 13.20 versus 3.43 T.U.). Realized heritability averaged 0.63 for all ten populations subjected solely to directional selection.

scholarly journals Eye Movements and Body Images

1964 ◽  
Vol 9 (4) ◽  
pp. 336-344 ◽  
Author(s):  
E. Llewellyn Thomas ◽  
Eugene Stasiak
Keyword(s):  
Eye Movements ◽  
Visual Attention ◽  
Eye Movement ◽  
Psychiatric Patients ◽  
External World ◽  
The Body ◽  
The Other ◽  
Body Images ◽  
The Face ◽  
The Mean

The eye-movement patterns of nine hospitalized psychiatric patients were compared with those of ten non-patients when looking at pictures of themselves and others. There were highly significant differences between both the mean fixation times of the two groups and also between the area of the body to which they paid the most attention. The mean fixation times of all the non-patients grouped closely around 0.61 seconds whereas the patients varied between 0.12 seconds and 0.47 seconds and 0.72 seconds and 1.04 seconds. Non-patients looked at all body levels, but spent much more time looking at the face. Patients on the other hand paid much more visual attention to the body and tended to avoid the face. It is suggested that the variability in the fixation times and the tendency to avoid the face reflects a mechanism in the patient which is tending to avoid receiving information about certain aspects of the external world.

The shape of the lactation curve

1923 ◽  
Vol 13 (2) ◽  
pp. 169-179 ◽  
Author(s):  
H. G. Sanders
Keyword(s):  
Environmental Factors ◽  
Total Yield ◽  
Maximum Yield ◽  
Genetic Characteristic ◽  
Dry Period ◽  
Significant Relation ◽  
Genetic Character ◽  
Lactation Curve ◽  
The Mean

(1) The ratio of the total lactation yield to the maximum yield, divided by the mean ratio (in the particular district) for the month of calving in which the lactation commenced, has been selected to represent the shape of each individual cow's lactation curve, and has been called the shape figure (S.F.).(2) The variation of individual S.F.'s was found to be less than that of all cows taken together—i.e. the shape of the curve, though largely determined by environmental factors, is due partly to a genetic characteristic of the cow.(3) The S.F.'s of 1st calvers are high (about 11 per cent, above those of subsequent lactations); i.e. heifers give a small maximum relative to their total yield.(4) No significant relation was found between the length of the dry period preceding calving, and the ratio of the total to the maximum yield in the subsequent lactation.(5) S.F.'s rise markedly and definitely as we pass from low to moderate, and from moderate to high, yielders; i.e. in good milkers the maximum is lower relative to the total yield than in bad milkers. Though there is variation from herd to herd (due probably to the system of management), this rise was shown between bad and good cows within the same herd, and seems to be a definite genetic character.

Effects of Hypothermia and Hyperthermia on Fertilization in Rat Eggs

1956 ◽  
Vol 33 (2) ◽  
pp. 348-357
Author(s):  
C. R. AUSTIN
Keyword(s):  
Body Temperature ◽  
The Body ◽  
The Other ◽  
Direct Influence ◽  
Body Temperatures ◽  
Slowing Down ◽  
Other Hand ◽  
The Mean ◽  
Rat Eggs ◽  
G 13

The chilling of rats to body temperatures down to 4-7° C. before and during the time of ovulation had little effect upon the subsequent penetration of the eggs by spermatozoa. With a hypothermia of 0-1° C, however, there was almost complete and apparently permanent inhibition of spermatozoon entry. There seemed to be no reason to ascribe this effect to direct influence of cold on eggs or spermatozoa. Probably the failure of penetration arose largely from delay of ovulation, coupled perhaps with some derangement of the tubal environment. Hypothermia after ovulation but before and during the time of spermatozoon entry into the eggs temporarily but completely inhibited penetration when the body temperature was kept below 33° C. The likely explanation appears to be that ‘capacitation’ is prevented or greatly slowed by such temperatures. Hyperthermia, induced before and during the time of ovulation, somewhat reduced the mean number of eggs ovulated (from 10.5 to 7.5) and the proportion penetrated by spermatozoa (from 97 to 66%). The proportion of eggs penetrated by two or more spermatozoa was increased (from 19 to 28%), but the frequency of polyspermic fertilization did not change significantly. Hyperthermia after ovulation but before and during the time of spermatozoon entry also led to a greater proportion of eggs containing two or more spermatozoa (31%), but in addition it increased the incidence of polyspermy (from 2.5 to21.2%). Larger rats (170-200 g.) subjected to hyperthermia showed a higher frequency of polyspermy (34%) than smaller rats (100-130 g.; 13% polyspermy). Evidently the processes involved in the ‘zona reaction’ are reduced in efficiency by hyperthermia whether applied before or after ovulation. On the other hand, the block to polyspermy depends on processes that are much more sensitive to heat after ovulation. It is considered that the slowing down of the block to polyspermy is associated with ageing of the egg, that the ageing is accelerated by hyperthermia and that this effect is promoted in older rats.

Hairiness in wool and a method for selection based on the nature of the fibres and the distribution of halo hairs of the lamb's tail

1957 ◽  
Vol 49 (1) ◽  
pp. 1-18 ◽  
Author(s):  
F. M. Labban
Keyword(s):  
Fibre Diameter ◽  
The Body ◽  
The Other ◽  
Significant Difference ◽  
Mean Diameter ◽  
Wide Variability ◽  
The Mean ◽  
Highly Correlated ◽  
Different Parts

Hairiness in wool of Suffolk sheep as a fault was found to be associated with other defects like coarseness of wool fibres, hairiness of the britch, and the occurrence of pigmented fibres. The presence of these various defects was studied in the lamb's tail at docking time, and subsequently evaluated and correlated with the fleece.The tails were graded according to the nature of the fibres and the spread of halo hairs from the tip to the base into four principal grades which by further subgrading could be made into seven grades. The results were as follows:(1) There was wide variability in grades of tails within each flock.(2) Average grade of tails followed in general the mean quality of the adult fleece.(3) When Border Leicester were crossed with Welsh Mountain the tails of the two reciprocal crosses were found to be of hairy type of tail and nearly like the Welsh Mountain type.(4) The percentage of coloured tails in the least hairy grades was found to be inversely related to the quality of the tail grade and indirectly to the fleece quality.(5) The diameter of the wool fibres on the base of the tail is highly correlated with the diameter of fibres from the britch regions or mean fibre diameter from four regions of the body (mid-shoulder, midside, hip and britch).(6) The mean diameter of the wool fibres obtained from four different parts of the tail was correlated with those of the britch regions only.(7) The diameter and variability of fibres increased from shoulder to britch in the body and from base to tip in the tails.(8) The britch and tails of two groups of sheep, one group characterized by coarse and the other by fine britch and tail wool, were studied histologically. There were significant or highly significant differences in the following characteristics in the britch of the two groups: (a) total number of follicles, (b) primary follicles with no medulla, (c) total number of secondary follicles, (d) secondaries with no medulla, (e) secondaries with large medulla. The only type of follicle where a significant difference was found in the tail was in the number of secondary follicles with no medulla.

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