Needle Morphology Research Articles

Microstructure and mechanical properties of modified and non-modified stir-cast Al-Si hypoeutectic alloys

The microstructure and mechanical properties of modified and non-modified stir-cast commercial aluminium alloys A-S7G03 and A-S4G have been investigated. Stir casting of these alloys resulted in spherical and/or rosette shape primary α-phase, and the eutectic silicon was broken into miniature needle morphology. This stir-cast structure slightly improved the mechanical properties in comparison to those of conventionally cast alloys, however the fracture of the stir-cast alloys revealed intergranular brittle fracture. The addition of 0.02% strontium, in the form of Al-5 mass% Sr master alloy, during stir casting modified the eutectic silicon into a very fine spheroidal morphology, while the α-phase particle showed the same morphology as the stir-cast alloys. This novel structure resulted in significant improvement of mechanical properties. The elongation of the modified stir-cast alloys was five times greater than that of the non-modified one. A transgranular mode of fracture was observed for the modified stircast alloys, moreover smooth ripple and dimple patterns were observed reflecting the high ductility of the modified stir-cast alloys.

Estimating the surface area of spruce and pine foliage from displaced volume and length

Accurate determination of the surface area of needle-leaved trees is a basic requirement for many types of physiological or growth analysis studies in forest research. While many methods are available to estimate surface area, there is still a need for an accurate, rapid measurement technique for species with three- or four-sided needle morphology. I propose a regression technique with length and displaced volume as the independent variables. The regression technique is an improvement over the use of displaced volume and length in direct geometric calculation as it does not assume a constant needle morphology. The regression technique gives more accurate results than direct calculation, is comparable in precision, and is necessary to counter bias where variation in the cross-sectional shape of foliage is related to the treatment or variable under study. Use of regression, however, requires that a subsample of foliage, representing the range of conditions to be studied, be sectioned and measured directly for surface area to develop the estimation equation.

Allometric relations of deciduous (Larixoccidentalis) and evergreen conifers (Pinuscontorta and Pseudotsugamenziesii) of the Cascade Mountains in central Washington

Logarithmic equations for estimating component biomass and projected leaf area from stem diameter and (or) sapwood cross-sectional area were computed for western larch (Larixoccidentalis Nutt.), lodgepole pine (Pinuscontorta Dougl.), and Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) in a mixed conifer stand in the Cascades of central Washington. Regression equations for estimating foliage biomass reported in this study did not compare favorably with foliage biomass allometric relations from other studies. For a given diameter, western larch supported a greater current foliage mass than lodgepole pine or Douglas-fir (P < 0.001); however, the total foliage mass of lodgepole pine was significantly greater (P < 0.001) than western larch. Despite lodgepole pine supporting a total foliage mass approximately twofold greater than western larch, allometric relations between foliage area and stem diameter were not different (P > 0.05) between the deciduous and evergreen conifer. Western larch supports a needle morphology that provides a greater photosynthetic surface area per unit of carbon invested than evergreen conifers in this environment.

Chemical and petrological properties of some liptinite-rich coals from British Columbia

Chemical and petrological analyses were carried out on several British Columbia coals which are known as ‘needle’ coals because of the pine needle morphology exhibited on weathering. The object was to determine the nature of the precursor and thus to identify the component maceral as resinitic or algal. Infrared spectroscopy, saturate fraction gas chromatography, pyrolysis chromatography, gas chromatography-mass spectrometry, organic elemental analysis and reflectance and fluorescence microscopy were used. While the i.r. properties are consistent with previously published results on resinite, the other chemical results suggest that the present materials are not obviously related to any given member of the liptinite group of macerals. High concentrations of extractable hopanoid hydrocarbons are interpreted as resulting from high contribution to the biomass by bacterial debris. The petrological results suggest that the main constituent of the ‘needles’ can be best described as bituminite II or III derived from non-algal lipids. This conclusion is also supported by the observed associations of the other identifiable macerals. The results indicate that the ‘needles’ have been chemically and petrologically homogenized from a liptinite-rich precursor with minimal algal input. The present morphology may have been preserved from resin rodlets which have been severely altered by catagenetic or biological mechanisms or both.

Isolation, characterization, and preliminary X-ray diffraction data for a serine protease from Penicillium cyclopium.

The major extracellular protein of Penicillium cyclopium has been isolated from its culture media and purified by ammonium sulfate fractionation, gel, and ion-exchange chromatography. We show this secreted protein to be endopeptidase. The molecular weight is approximately 32,000, the pI is 5.0, and the pH optimum using a variety of protein and synthetic substrates is around 7.0. Inhibition studies show that the protease is not inhibited by pepstatin nor by p-chloromercuribenzoic acid, indicating, respectively, that it is not an aspartyl protease nor a thiol protease. Complete inhibition is observed, however, with phenylmethanesulfonyl fluoride. Three crystal forms suitable for high resolution x-ray diffraction studies have been obtained from this purified protease with reflections being observed to well beyond 3.0 A resolution. One form having a needle morphology is of the orthorhombic crystal class and has space group P2(1)2(1)2(1). The unit cell dimensions are a = 41.9 A, b = 43.2 A, and c = 111.5 A with 1 molecule of the protease occurring in the asymmetric unit. The second form grown at pH values less than 6.0 has a plate morphology, is of orthorhombic space group P2(1)2(1)2(1), and has unit cell dimensions a = 59.12 A, b = 62.33 A, and c = 70.62 A. The third form is polyhedral in habit, is also of space group P2(1)2(1)2(1), and appears when the pH of the mother liquor is greater than 7.0. The cell dimensions of this crystal form are a = 57.07 A, b = 58.82 A, c = 70.79 A, and again there is 1 molecule/asymmetric unit. Three-dimensional structural analysis by x-ray diffraction is now underway. All crystal forms are somewhat denser than the norm having mass to volume ratios of 1.58, 2.00, and 1.85 A3/dalton, respectively.

Monoterpenoid and morphological differentiation within Pinus cembroides

Wood of Pinus cembroides from 232 trees sampled in 23 localities throughout its range in the United States and Mexico has been analysed for monoterpenes. With a few exceptions the trees of the continental populations from the state of Hidalgo northward produced α-pinene as the main monoterpene. The majority of trees of the southern populations (subsp. orizabensis) from the state of Puebla and adjoining regions of the neighboring Veracruz and Tlaxcala produced 3-carene in appreciable amounts. The population from Baja California (subsp. lagunae) produced monoterpenes of the sabinene family (thujene, sabinene, γ-terpinene, terpinolene and p- cymene ) as the main constituents. The variations in morphological characters, including number of needles per fascicle, number of stomatal rows in needles, number of resin canals in needles, as well as other characters of the internal needle morphology, needle length and thickness, needle retention, thickness of seed shells, bark and cone characteristics, rate of growth and cotyledon number either paralleled or did not contradict the chemical variations. The evolution of the southern populations (subsp. orizabensis) into a separate group most likely resulted from geographic separation and climatic differences, while the evolutionary separation of the Baja California trees (subsp. lagunae) was connected with northwestern movement of the California coastal region from Miocene onward and the formation of Sierra Madre Occidental resulting in separation of this population from the mainland populations by the gap of the Gulf of California and the coastal mountain ranges.

Food Quality Induced Variance in Larval Performance: Comparison between Rare and Common Pine-Feeding Sawflies (Diprionidae)

This paper is a contribution towards a better understanding of why some monophagous diprionid sawflies have outbreaks while others seem to be always rare. We reared larvae of four northern European species, Neodiprion sertifer, Diprion pini, Gilpinia verticalis, and G. socia, on pine twigs collected from five habitats: deciduous forest, field edge, rock, plantation, and bog. The sawflies span from the serious pest N. sertifer to an always rare species G. socia; the pine twigs differed in e.g. needle morphology and nitrogen content, from 1.6% of dry wt in deciduous forest to 0.9% in bog. Larval mortality was higher in common than rare species. In a between-species analysis, production efficiency (cocoon weight divided by consumption) was positively correlated with nitrogen assimilation efficiency and larval growth rate. Neodiprion sertifer had the highest nitrogen assimilation efficiency and the second highest production efficiency, but this may be as well a consequence than a cause of outbreaks. The two outbreak species, N. sertifer and D. pini, showed less variation between the pine types in cocoon weight, production efficiency and larval mortality than the two Gilpinia species, suggesting that the continuous rarity of the latter species is strengthened by their sensitivity to food quality. Cocoon predation may nonetheless be a more important factor preventing outbreaks than plant defences.

INTRASPECIFIC VARIATION IN ABIES LASIOCARPA FROM BRITISH COLUMBIA AND WASHINGTON

Sixteen natural stands of Abies lasiocarpa (Hook.) Nutt. were sampled from British Columbia and Washington to investigate patterns of intraspecific variation in this species and to evaluate Hunt and von Rudloff's recognition of two species of subalpine fir. Principal components analysis and canonical variates analysis were performed separately on seed‐cone data, needle morphology data, and needle flavonoid data. Analysis of cone data indicated no geographical patterning of populations, but eastern and western groups of populations were segregated in both the needle morphology and flavonoid analyses. With the exception of the Vancouver Island population, three geographic groups were discerned based on their needle morphology: 1) populations from the coastal mountains of British Columbia, 2) those from the Cascade Mountains of Washington, and 3) those from the eastern interior of British Columbia. Although the Vancouver Island population was grouped with the interior British Columbia populations based on needle morphology, it was similar to the other coastal populations based on flavonoid data. These inconsistent results among the three different types of taxonomic evidence underscore the need to consider a variety of traits when drawing taxonomic conclusions in Abies. Although the delineation of eastern and western groups is not wholly consistent for the different data sets, the results support recognition of coastal and interior varieties of subalpine fir.

Intraspecific Variation in Abies lasiocarpa from British Columbia and Washington

Sixteen natural stands of Abies lasiocarpa (Hook.) Nutt. were sampled from British Columbia and Washington to investigate patterns of intraspecific variation in this species and to evaluate Hunt and von Rudloff's recognition of two species of subalpine fir. Principal components analysis and canonical variates analysis were performed separately on seed-cone data, needle morphology data, and needle flavonoid data. Analysis of cone data indicated no geographical patterning of populations, but eastern and western groups of populations were segregated in both the needle morphology and flavonoid analyses. With the exception of the Vancouver Island population, three geographic groups were discerned based on their needle morphology: 1) populations from the coastal mountains of British Columbia, 2) those from the Cascade Mountains of Washington, and 3) those from the eastern interior of British Columbia. Although the Vancouver Island population was grouped with the interior British Columbia populations based on needle morphology, it was similar to the other coastal populations based on flavonoid data. These inconsistent results among the three different types of taxonomic evidence underscore the need to consider a variety of traits when drawing taxonomic conclusions in Abies. Although the delineation of eastern and western groups is not wholly consistent for the different data sets, the results support recognition of coastal and interior varieties of subalpine fir.

Changes in needle morphology, anatomy, and mineral content during the recovery of protected balsam fir trees initially defoliated by the spruce budworm

Morphological, anatomical, and chemical changes in foliage of 25- to 30-year-old balsam fir trees (Abiesbalsamea (L.) Mill.) that had been completely defoliated in 1977 by the spruce budworm (Choristoneurafumiferana (Clem.)) and then protected for 5 years by insecticide, were compared with foliage from adjacent undefoliated trees. The comparison showed that in 1978, the 1st year of refoliation, needle length, weight, and width were greater in the defoliated trees, while in 1979 they were less. In 1980, needle length was again less, but no difference was observed in needle weight and width. Needle length, weight, and width were similar in the defoliated and undefoliated trees in 1981 and 1982. Needle density in the defoliated trees was lower in 1978, but greater in 1979, while no difference occurred in 1980–1982. Foliar nitrogen content was higher in the defoliated trees in 1978–1980. Foliar phosphorus and potassium content were higher in the defoliated trees only in 1978. Needle and mesophyll cross-sectional areas in the defoliated trees were larger in 1978, but were smaller in 1979. There were no differences during 1980–1982. Mesophyll and needle cross-sectional areas were positively correlated throughout 1978–1982. Relative amounts of total protein were higher, whereas those of total insoluble carbohydrates were lower in 1978–1980 needles from undefoliated trees.

Structural characterization of laser-processed molybdenum steel

Experiments were performed to study the effects of rapid melting and subsequent quenching on the microstructure and microhardness of laser-processed molybdenum steel. Molybdenum was flame sprayed onto the surface of an AISI 6150 (low alloy) steel substrate to a thickness of 25 μm; the surface of the steel was then melted using a 1200 W continuous wave CO 2 laser to produce an alloy containing 15% Mo to a penetration depth of 200 μm. Multiple-pass laser melting was employed with a distance of 0.25 mm between successive passes. The microstructure, characterized by scanning and thin foil transmission electron microscopy, consisted of δ ferrite cells with two types of carbide precipitation. Selected area diffraction investigations together with dark field microscopy studies identified these carbides as M 6C and Mo 2C. Fine Mo 2C carbide having the characteristic needle morphology was observed within the ferrite cells. The solidification carbide, namely M 6C, was found to occur in large quantities both at the intercellular boundaries and within the matrix. The matrix M 6C carbide exhibited spherical and rhombohedral morphologies while the cell boundary M 6C carbide had a lamellar morphology. The size of M 6C carbide varied from 0.05 to 0.2 μm. It is proposed that these microstructural features enhanced the microhardness of the laser-alloyed fusion zone to 455 kgf mm −2 (44 HRC).

Growth of Cr Needle Crystals Induced by Field Electron Emission

This paper describes the growth of needle crystals of Cr on a field cathode operating in Cr(CO)6 vapor at 2–5×10-2 Torr. The products are classified into two categories depending on the magnitude of the applied potential; (1) thickly-distributed, tree-like needles obtained at 0.5–5 kV and (2) sparsely-distributed, fibrous needles obtained at higher potentials. The former needle growth is possibly promoted by Cr+ ions from a corona plasma while the latter is promoted by the same ions from an arc plasma. The needle morphology is sensitive to temperature in the former and to field strength in the latter. Both types of needle consist of agglomerated crystallites oriented randomly, and their structure can be an fcc one with a lattice spacing of about 4.14 Å. It is hypothesized that this fcc structure is attributable to the growth mode of the needles in an extremely strong electric field.

Adaptation and Dimorphism in Eastern Hemlock, Tsuga canadensis (L.) Carr

Eastern hemlock's (Tsuga canadensis (L.) Carr.) habitat distribution, and variations in its growth rate response to macroclimatic variation, sensitivity to climatic and topographic variation, and gross needle and branch morphology, were quantified in eight major geographical areas throughout the species' range in the eastern United States. The results revealed two apparent sympatric ecotypes or morphs which occur throughout most of the species' range; these ecotypes may be differentiated by habitat preference, growth rates, sensitivity to moisture and temperature, and certain gross morphological characters. The "high-response" hemlock prefers mesophytic habitats, and exhibits a high growth rate, high sensitivity to moisture, and low sensitivity to temperature. The "low-response" type also occurs in mesic sites, but is more common on subxeric slopes; it exhibits a low growth rate, low sensitivity to moisture, and high sensitivity to temperature. Throughout southern Canada and New England, the two ecotypes are distinct in terms of growth rate, morphology, and response to macroclimatic variation, despite their sympatric occurrence in mesophytic habitats; only limited intergradation is observed. In the Alleghenies and southern Appalachians, the two types broadly intergrade, providing a spectrum of phenotypes, the extremes of which correspond to the two New England ecotypes. Only the high-response type was found in the Cumberland Mountains and Plateau, while the disjunct populations studied in Indiana were composed entirely of intermediate individuals. Differentiation into ecotypes and subsequent introgression between the two ecotypes appear to confirm a competitive advantage to T. canadensis, giving it a phenotypic elasticity which allows it to occupy a broad range of habitats. However, there also appears to be sufficient divergent selection against the intermediates to prevent the two ecotypes' convergence or fusion into a single phenotype.

Growth kinetics of bainite plates and widmanstÄtten needles in theΒ′ phase of a Ag-45at. pct Cd alloy

The morphology of bainite plates and widmanstAtten needles formed in the Β′ phase of a Ag-45 at. pet Cd alloy at temperatures 160 to 300‡C was studied by optical and scanning electron microscopy. Both precipitate forms were similar in appearance to precipitates reported for Cu-Zn alloys. The growth kinetics of both bainite plates and widmanstAtten needles were measured by interrupted annealing and scanning electron microscopy. Using the bainite thickening kinetics measured at 160, 200 and 240‡C, the Frank-Zener model for growth of planar precipitates, and supersaturation data obtained from the Ag-Cd metastable phase diagram enabled the effective chemical diffusivities, Deff, to be calculated for the three transformation temperatures. The results were in good agreement with the expected diffusivities. The lengthening kinetics of bainite plates at 160‡C and of widmanstAtten needles at 240‡C were analyzed using Trivedi’s model for diffusion-controlled growth. Deff obtained from the lengthening kinetics of the needles was in good agreement with the Deff value obtained from the thickening kinetics of the plates, indicating that widmanstAtten needles lengthened and bainite plates thickened at a rate controlled by volume diffusion. Bainite plates lengthened only in the early stage of growth and at a rate approximately 180 times larger than that permitted by volume diffusion. Possible reasons for such behavior were discussed.

Variation and selection in western montane species II. Variation within and between populations of white firon an elevational transect

Four populations of Abies concolor, white fir, were sampled along an elevational transect in the central Sierra Nevada mountains of California. This paper is based on data taken during the first two years' growth in a nearby nursery at Placerville, California. Ten of the thirteen growth, size, and needle morphological characteristics had significant differences between population samples, while eleven characteristics had significant differences between open-pollinated families within the population samples. High-elevation population samples were smaller in size and needle measurements, had fewer adaxial stomatal rows, blunter needle tips, and a shorter growing season. Most characteristic values were distributed ecotypically between the two lower- and the two higher-elevation population samples. Analyses of the patterns of variation demonstrated that characteristics of size and growth showed greater differentiation between population samples than did characteristics of needle morphology. It was concluded that the differences between characteristic patterns were caused by the more intense selection pressures acting upon the characteristics of size and growth. No consistent differences were discovered between these population samples in terms of total amounts of within-population genetic variation. The failure to find differences in intra-population variation may be due to the high rates of migration that probably exist within such a transect, and the fact that none of the populations included in this study are truly marginal. There were large differences between characteristics for total within-population variation; a positive but non-significant correlation was found between high coefficients of variation and those characteristics with much differentiation between populations. It is postulated that the maintenance of this intra-population variation was caused by microhabitat adaptations and gene flow. Evidence for increased genetic variation within open-pollinated families due to pollen immigration is presented, and its implications discussed.

Local Variation in Intergrading Abies grandis-Abies concolor Populations in the Central Oregon Cascades: Needle Morphology and Periderm Color

In the central Oregon Cascades, grand fir morphology varies from that of typical Abies grandis to that of populations with a variety of morphological types, some closely resembling A. concolor Low-elevation populations west of the Cascade crest, mostly on river terraces, resemble A grandis. High-elevation west-side populations, disjunct from those at low elevations and occupying ridge tops and steep, dry slopes, include trees with some traits of A. concolor. Populations on the east flank of the Cascades show a greater but widely variable influence of A. concolor. East-side populations vary locally with aspect, being most like A. grandis on north slopes, but they do not clearly vary with elevation. Incidence of characteristics resembling A. concolor increases from north to south within the study area, although this pattern shows deviations not associated with obvious changes in topography Periderm color and needle morphology show the same general relationships between the populations sampled. Either "maximum number of adaxial stomatal rows" or "percentage of length of needle with adaxial stomata" can be used to describe the extent of adaxial stomata Needle notch depth is not consistently correlated with stomatal characteristics on a tree-to-tree basis, but shows a similar, less distinct, geographic and habitat pattern. The variation within populations is greater in the intermediate populations than in those of "typical" A. grandis. This is consistent with the origin of the intermediate populations being introgression, as proposed by earlier workers. The described patterns of morphological variation provide a basis from which ecological and physiological variation in these intergrading populations may be studied

A study by X-ray diffraction of the deformation of AGSI alloys

Abstract : The deformation of two-phase Ag-Si alloys has been studied by X-ray line broadening. Equiaxed and needle Si morphologies were examined. The Si particles do not deform. The dislocation densities in the Ag matrix are higher with the needle morphology, in agreement with Ashby's predictions. (Author)

The growth of large SbSI crystals: Control of needle morphology

SbSI crystals have been grown by many techniques, all of which yield long thin needles because of an inherent growth rate anisotropy greater than 50:1. A modified flux technique using excess SbI 3 as the solvent was devised to circumvent this difficulty. Nucleation is initiated in a large temperature gradient in a narrow extension of the growth vessel. The main part of the growth vessel is essentially isothermal. As the temperature is lowered a few crystals grow from the nucleation region into the main part of the growth vessel. In the absence of further nucleation these crystals are forced to grow in thickness, yielding crystals up to 1 cm in diameter.

The Effects of Position in Crown on the Morphology of Needles of Loblolly Pine (Pinus taeda L.)

The Effects of Position in Crown on the Morphology of Needles of Loblolly Pine (Pinus taeda L.)

Variation in Lodgepole Pine with reference to Provenances Planted in Great Britain and Ireland

Variation in growth habit and bark type of lodgepole pine (Pinus contorta Douglas) in its native habitat is described and illustrated with photographs. Needle morphology is assessed from plantation samples and some of the problems associated with the assessment of variation are discussed. The problem of ensuring that imported seed is collected from the right stands is considered.