Growth Initiation Time Research Articles

Numerical analysis of boiling on high heat-flux and high subcooling condition using MPS-MAFL

This paper shows the numerical simulation study on the growth of the bubble in the transient pool boiling using moving particle semi-implicit with meshless advection using flow-directional local grid (MPS-MAFL) method. The growth process of a bubble with the different initial radii is calculated in a high heat-flux and high subcooling condition. The smaller initial radius is, the earlier the growth starts. The initial bubble radius has little effect on the growth initiation time and the bubble departure radius.

Growth mechanism of selectively grown II–VI semiconductor photonic dots for short-wavelength light emitters

The growth mechanism of the ZnS and CdS semiconductor photonic dots grown by metalorganic molecular-beam epitaxy (MOMBE) was studied. In the initial growth process, the delay time of growth initiation was present for small-area ZnS selective growth. The lateral growth during the selective epitaxy was not linear to the growth time, which was explained by considering the diffusion of the Zn and Cd precursors on the {0 3 4} side facets to the (0 0 1) top plane during the growth. The calculation of this model was in good agreement with the experimental results. The apex of the grown structures was studied, and the apex of CdS was sharper than those of ZnS and Zn 0.9Cd 0.1S. This shows that it is possible to position the CdS layer which has a narrow bandgap only on the apex of the Zn(Cd)S photonic dot as a light-emitting layer.

Three dimensional cohesive-element analysis and experiments of dynamic fracture in C300 steel

The dynamic drop-weight test is taken as a convenient basis for assessing the fidelity and predictive ability of cohesive models of fracture in applications involving dynamic crack growth. In the experimental phase of the study, coherent gradient sensing (CGS) has been used to study dynamic fracture in C300 maraging steel. The specimens were subjected to three-point bend impact loading under a drop weight tower. High-speed photographs of the CGS interferograms were analyzed to determine the crack tip location, the velocity and the dynamic fracture toughness as a function of time. Post-mortem examination of the specimens revealed the fractography of the fracture surfaces, including the development of shear lips. In a parallel numerical phase of the study, fracture has been modeled by recourse to an irreversible cohesive law embedded into cohesive elements. These cohesive elements govern all aspects of the separation and closure of the incipient cracks. The cohesive behavior of the material is assumed to be rate independent. The finite element model is three dimensional and consists of quadratic ten-noded tetrahedra. The numerical simulations have proven highly predictive of a number of observed features, including: the crack growth initiation time; the trajectory of the propagating crack tip; and the formation of shear lips near the lateral surfaces. The simulations therefore establish the feasibility of using cohesive models of fracture and cohesive elements to predict dynamic crack-growth initiation and propagation in three dimensions.

Evaluation of Various Traits of 40 Selections and Cultivars of Red Maple and Freeman Maple Growing in Maryland

Abstract Thirty-seven red maple (Acer rubrum L.) and three Freeman maple (A. x freemanii E. Murray) selections and commercial cultivars were evaluated for six years in a replicated field plot at Glenn Dale, MD. Significant differences among clones occurred for growth rate; for time, intensity, and duration of autumn color; for time of growth initiation in the spring; and for injury sustained from potato leafhopper (PLH) [Empoasca fabae (Harris)] feeding. The red maple cultivars showing the best red color over three years time were ‘Autumn Flame,’ ‘Brandywine,’ ‘Cumberland,’ ‘Red Rocket,’ ‘Somerset,’ ‘Sun Valley,’ and ‘Van.’ The cultivar ‘Bowhall’ was the least reddish. Of the three Freeman maples evaluated, ‘ Jeffersred’ and ‘Indian Summer’ manifested the best red color and also low PLH injury; whereas ‘Armstrong’ consistently showed the least reddish color of all 40 clones tested, and intermediate PLH injury. Those cultivars and selections from northern seed sources reached their peak color the earliest, but often dropped their leaves more quickly after showing their best color, compared to clones originating in more southerly locations. The clones showing the least PLH injury over several years included the Freeman maples ‘Jeffersred’ and ‘Indian Summer,’ and red maple clones and cultivars selected by the U.S. National Arboretum either from full-sib progenies (e.g., ‘Brandywine,’ ‘Somerset,’ ‘Sun Valley’) or from an Ohio provenance-progeny test (e.g., ‘Cumberland,’ ‘Red Rocket’). Those clones initiating growth (or “flushing”) earliest in the spring generally showed the least PLH injury; correlations between lateness of flushing and degree of PLH injury were highly significant.

Variation Among Alnus Progenies Grown in Ohio

Seedlings grown in Ohio from seed collected from 12 native seed sources of Alnusglutinosa (European black alder) and one seed source of Alnus cordata (Italian alder) were outplantedin1981 in acombination provenance/family planting. Data were collected over a period of 11 years after planting. Results show highly significant variation among provenances in winter injury, time of growth initiation, rate of survival, leaf miner injury, and height and diameter growth. Italian alder seedlings showed the least leafminer injury and the earliest flushing, but showed the poorest survival of all groups tested, primarily because of winter injury. European black alder seedlings grown from seed collected in Iran also sustained major winter dieback and poor survival. Trees from West Germany, France, Denmark, and Yugoslavia seed sources were fastest-growing, whereas seedlings from some sources in southern Europe (Spain, Italy, Bulgaria) were slowest - growing. The genetic variation shown in this study is sufficient to allow for success in breeding for improved insect resistance, cold hardiness, and growth rate in alder.

モードＩ／変動モードＩＩ混合荷重下での遅れ破壊き裂進展開始挙動に及ぼす応力波形の影響

The crack growth initiation behavior in delayed failure under superposed cyclic mode II stress of various stress wave forms was investigated on the precracked specimens of Ni-Cr-Mo steel quenched and tempered at 673K. When the range of mode II cyclic stress intensity factor ΔKII was superposed on the static stress intensity factor KI, the crack growth initiation time tg decreased with an increase in ΔKII, the degree of which increased with an increase in applied stress increasing period at a constant frequency; i.e. tg decreased most under cyclic load with positive saw tooth wave, followed by those with negative saw tooth wave and trapezoid. The intergranular fracture ratio ψ of crack growth initiation surface was affected little by stress wave forms of ΔKII. The reason why the crack growth initiation time tg decreased when the stress wave form of mode II had a long stress increasing period seems to be that the corrosive reaction is activated during the stress increasing period, since the protective film in the vicinity of crack tip is destroyed mechanically by cyclic stress.

Mathematical modeling of fetal growth. III. Evaluation of head growth using the head profile area.

Growth of the fetal head has been reexamined in a longitudinal study of 32 normally growing fetuses using the head profile area (HA). The Rossavik growth model (characterized by the coefficients c, k, and s) fit these data very well (R2 [+/- SD] 99.6 [+/- 0.3]%), and regression analysis indicated that optimum results are obtained when the coefficient k is kept constant. Head area growth before 28 weeks was found to be related to the coefficient c, which was strongly correlated (R2 69.2%) with the time of HA growth initiation. These results suggest that c reflects the genetic factors controlling growth in the early part of pregnancy. The coefficient s was negatively correlated with c (R2 82.1%) and had two components, one associated with c (pred. s) and one not associated with c (s-residual). This linkage between c and s, together with the parallel head growth seen after 30 weeks, suggests the possibility of a maternal system in which genetically determined head size (c) can be sensed and modified by other factors (s) to maximize compatibility between the fetal head and maternal pelvis.

Optimum growth initiation time for shoot buds of deciduous plants in a temperate climate.

A model predicting optimum growth initiation times for shoot buds of deciduous plants has been derived from simple assumptions based on maximizing average annual photosynthesis as a function of photosynthetic rates, length of growing season and the probability of late frost. This formulation predicts that optimum bud initiation time is sensitive to the variance in the frost probability but is independent of the average photosynthetic rate. Predicted optimal initiation times are only slightly affected by substantial changes in the length of the growing season (over a considerable change in latitude) except when the growing season is very short. The advantage of maximum frost resistance is also greatest in very short growing seasons. It is pointed out that the optimum time of leaf senescence at the end of the growing season must be based on more complex criteria than the time of growth initiation. Certain difficulties in interpreting bud break data from tree transplant experiments are discussed.

Spontaneous tetraploidy in apomictic seedlings ofCitrus

Populations of apomictic seedlings of clones ofCitrus species,Citrus hybrids, andPoncirus in the sub-family Aurantioideae were examined for spontaneous tetraploids as a source of materials for use in breeding experiments. Diagnostic features found useful in identifying nucellar tetraploids were leaf shape, petiole blade shape, leaf blade thickness, leaf color, comparative size differences in leaf venation, oil glands, and stomata, stem thickness, and relative size and developmental pattern of the root system. In older or bearing-age plants, nucellar tetraploids may be identified by differences in growth habit, vigor, size, time of growth initiation and bloom, and flower and fruit characteristics. Data are given for tetraploid frequency in glasshouse-grown, first-year nucellar seedlings of 42 populations of 32 clones of different genetic and seed origin and for tetraploid frequency in commercialnursery nucellar seedlings of the Carrizo rootstock clone in two consecutive years. Comparative data are given for quantitative development of roots, stems, and leaves of tetraploids and similar diploid nucellar seedlings. The data suggest that the ability to produce tetraploid apomictic seedlings is a variable genetic trait present in all or nearly all clones able to reproduce by adventitious embryony. Aspects of tetraploid nucellar seedlings that might warrant their testing as tree-size-controlling rootstocks in commercial citrus growing are discussed.

Variation in balsam fir provenances planted in New England

After 3 years in the field, survival, date of shoot growth initiation, and total height of 15 provenances planted at three locations indicate moderate to large provenances effects. Relative provenance performance varied among locations for survival and total height but not for flushing date. Regression and correlation analyses indicated that both the temperature and moisture regimes at seed origin have acted as selective forces on the native population. Time of shoot growth initiation has been mainly influenced by the temperature regime, while total height was generally related to the moisture regime. Survival was not associated with any of the climatic variables used in the study.

Variation in seedling development of balsam fir associated with seed origin

Measurements of total height and frequency of frost damage on 5-year-old trees demonstrated moderate to large variation associated with seed origin. Total height was measured at three nurseries in Wisconsin and Minnesota. Frost damage was measured at one nursery in central Wisconsin. The tallest seedlings were from eastern provenances. The seedlings least damaged by spring frost were from Wisconsin and Michigan provenances. Periodic measurements of shoot elongation indicated that variation in rate of elongation was the chief determinant of variation in total shoot elongation. Variation in time of shoot growth initiation was one cause of observed variation in frequency of frost damage. Variation among maternal progenies from six populations in Wisconsin and Michigan was similar to variation among range-wide provenances.

Growing Seasons of Cottonwood and Sycamore as Related to Geographic and Environmental Factors

The hypothesis that variation in dates of the beginning and end of growing seasons of eastern cottonwood (Populus deltoides Bartr.) and American sycamore (Platanus occidentalis L.) can be attributed to variation in air temperature andphotoperiod was tested by using data collected during a single year (1963) from trees widely distributed throughout their natural ranges. Dates of bud breaking and winter-bud formation were used as the criteria for the beginning and end of growing seasons. Correlation and regression analyses were used to elicit the relationships of these dates with latitude, altitude, air temperature, photoperiod, and with the dates of frost occurrence at the locations of the sampled trees. The growing season in these two species was not confined to the period between killing frost in spring and fall. The lengths of growing seasons were inversely related to the latitude. With increasing latitude, growth began later and stopped earlier. Both air temperature and photoperiod at the time of growth initiation and cessation varied with latitude. At a given latitude between 30°N and 50°N cessation of growth occurred at higher temperature than that at initiation of growth, and growth cessation between 33°N and 50°N was associated with shorter photoperiods than those at growth initiation. Temperature and photoperiod, acting in combination, appeared to be important, although not exclusive, factors in controlling the initiation and cessation of growth of these species. The regression line of monthly mean temperature on photoperiod on the day of growth initiation appeared to delineate a boundary between the period of dormancy and the active growing season. The cessation of growth could not be as clearly defined.

Seasonal Basal Growth Area as an Expression of Competition in Northern Hardwoods

A 2—year study of basal area change of six tree species was conducted with vernier growth bands in the northern conifer—hardwood sub—formation in north—central Wisconsin. Curves of basal area change per unit of stem circumference satisfactorily expressed differences in initiation of stem expansion, rate and duration of growth, and winter shrinkage for various species and crown classes. Seasonal growth for all species and crown classes was represented by a sigmoid curve beginning with a short period of slow basal area increase in early spring and ending with a longer period of declining growth rates leading to relative stability through late summer and fall. Winter shrinkage, most marked in basswood, began in early winter and often exceeded total summer growth by midwinter. Recovery was complete by early spring. Hemlock began rapid growth earlier and ceased growth later than any other species studied. Basswood began and ceased growth later than sugar maple, white and yellow birch, and trembling aspen. Timing of rapid growth initiation was somewhat affected by weather and tree condition. The decreasing order of vigor in competition of the major species was (1) sugar maple, (2) hemlock, and (3) yellow birch and basswood. Differences in amounts of cambial growth of species and crown classes were traceable to differences in both rate and duration of growth. Delay of rapid stem expansion in lower crown classes was much less marked than in lower crown classes of pure coniferous stands studied elsewhere, probably because of less canopy shading in spring. Differences in times of cessation of growth of crown classes were more marked, with the most suppressed trees ceasing growth earliest. Effects of particular stand conditions were most evident in growth of suppressed crown classes.

The induced synthesis of β-galactosidase in E.coli I. Synthesis of enzyme under various experimental conditions

In E. coli the content of β-galactosidase in already adapted cells corresponds to a hydrolysis of about 2 μ M ONPG × min −1 per mg dry weight. In adpating cells the enzyme is synthesized during the lag phase, and during the early growth phase the amount of enzyme synthesized per mg dry weight of new cells considerably exceeds the value mentioned above. By growing the bacteria in the presence of both glucose and lactose (diauxie), it was shown that the time of growth initiation is not solely a function of the amount of enzyme present in the cells. Induction of β-galactosidase synthesis occurs even in the absence of any exogenous nitrogen source, at least when lactose is the only energy source. Under these conditions the extent of enzyme synthesis may be decreased by starvation, by extraction with water and by pretreatment with glucose. However, the synthetic capacity may be recovered, partly at least, by addition of nitrogen-containing substances such as alanine and ATP. The initial rate of enzyme synthesis in N-free medium is also reduced by starvation and by extraction with water. Addition of small amounts of glucose, alanine or ATP, as well as pre-treatment with glucose or lactose increases this rate.