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Rowley JR, Rowley RL, Wilding WV. Estimation of the lower flammability limit of organic compounds as a function of temperature. JOURNAL OF HAZARDOUS MATERIALS 2011; 186:551-557. [PMID: 21144650 DOI: 10.1016/j.jhazmat.2010.11.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 10/01/2010] [Accepted: 11/09/2010] [Indexed: 05/30/2023]
Abstract
A new method of estimating the lower flammability limit (LFL) of general organic compounds is presented. The LFL is predicted at 298 K for gases and the lower temperature limit for solids and liquids from structural contributions and the ideal gas heat of formation of the fuel. The average absolute deviation from more than 500 experimental data points is 10.7%. In a previous study, the widely used modified Burgess-Wheeler law was shown to underestimate the effect of temperature on the lower flammability limit when determined in a large-diameter vessel. An improved version of the modified Burgess-Wheeler law is presented that represents the temperature dependence of LFL data determined in large-diameter vessels more accurately. When the LFL is estimated at increased temperatures using a combination of this model and the proposed structural-contribution method, an average absolute deviation of 3.3% is returned when compared with 65 data points for 17 organic compounds determined in an ASHRAE-style apparatus.
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Gabarayeva NI, Grigorjeva VV, Rowley JR. Sporoderm development in Acer tataricum (Aceraceae): an interpretation. PROTOPLASMA 2010; 247:65-81. [PMID: 20431899 DOI: 10.1007/s00709-010-0141-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Accepted: 03/24/2010] [Indexed: 05/29/2023]
Abstract
For the first time, the developmental events in the course of complicated exine structure establishment have been traced in detail with transmission electron microscope in the representative of Acer. A new look at unfolding events is suggested using the knowledge of a boundary field, colloid science. Our purpose was to find out whether the sequence of sporoderm developmental events represents, in essence, the sequence of self-assembling micellar mesophases, initiated by genomically given physicochemical parameters and induced by surfactant glycoproteins at increasing concentration. Indeed, the first units observed in the periplasmic space are globular ones (=spherical micelles) which become arranged into rod-like units (=cylindrical micelles). Then, twisted clusters of rodlets form a layer of procolumellae (middle micellar mesophase). The tectum emerges as an untwisting and merging of distal ends of procolumellae (distal untwist of micelle clusters). In the end of tetrad period, when a hydrophilic-hydrophobic switch occurs in the periplasmic space, the contrast reversal of the columellae corresponds to the change of normal micelles to reverse ones. The initiation of the foot layer and the endexine lamellae, with their typical central "white lines", corresponds to the next-"neat"-mesophase, with its typical central gaps between layers. Aperture sites during development show all the main micellar mesophases and their transitional forms. The data received have supported our previous hypothesis.
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Gabarayeva NI, Grigorjeva VV, Rowley JR. A new look at sporoderm ontogeny in Persea americana and the hidden side of development. ANNALS OF BOTANY 2010; 105:939-55. [PMID: 20400758 PMCID: PMC2876015 DOI: 10.1093/aob/mcq075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
BACKGROUND AND AIMS The phenomenon of self-assembly, widespread in both the living and the non-living world, is a key mechanism in sporoderm pattern formation. Observations in developmental palynology appear in a new light if they are regarded as aspects of a sequence of micellar colloidal mesophases at genomically controlled initial parameters. The exine of Persea is reduced to ornamentation (spines and gemmae with underlying skin-like ectexine); there is no endexine. Development of Persea exine was analysed based on the idea that ornamentation of pollen occurs largely by self-assembly. METHODS Flower buds were collected from trees grown in greenhouses over 11 years in order to examine all the main developmental stages, including the very short tetrad period. After fixing, sections were examined using transmission electron microscopy. KEY RESULTS AND CONCLUSIONS The locations of future spines are determined by lipid droplets in invaginations of the microspore plasma membrane. The addition of new sporopollenin monomers into these invaginations leads to the appearance of chimeric polymersomes, which, after splitting into two individual assemblies, give rise to both liquid-crystal conical 'skeletons' of spines and spherical micelles. After autopolymerization of sporopollenin, spines emerge around their skeletons, nested into clusters of globules. These clusters and single globules between spines appear on a base of spherical micelles. The intine also develops on the base of micellar mesophases. Colloidal chemistry helps to provide a more general understanding of the processes and explains recurrent features of pollen walls from remote taxa.
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Blackmore S, Wortley AH, Skvarla JJ, Rowley JR. Pollen wall development in flowering plants. THE NEW PHYTOLOGIST 2007; 174:483-498. [PMID: 17447905 DOI: 10.1111/j.1469-8137.2007.02060.x] [Citation(s) in RCA: 235] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The outer pollen wall, or exine, is more structurally complex than any other plant cell wall, comprising several distinct layers, each with its own organizational pattern. Since elucidation of the basic events of pollen wall ontogeny using electron microscopy in the 1970s, knowledge of their developmental genetics has increased enormously. However, self-assembly processes that are not under direct genetic control also play an important role in pollen wall patterning. This review integrates ultrastructural and developmental findings with recent models for self-assembly in an attempt to understand the origins of the morphological complexity and diversity that underpin the science of palynology.
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Rowley JR, Skvarla JJ, El-Ghazaly G. Transfer of material through the microspore exine from the loculus into the cytoplasm. ACTA ACUST UNITED AC 2003. [DOI: 10.1139/b03-095] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Our results and those we review indicate that the exine has a great capacity for modifications that enable nutrients to pass through from the anther loculus to the microspore cytoplasm. Avenues of passage include strands, some of which are viscin threads, from the tapetum to microspores in, for example, Betula, Fuchsia, and Epilobium. Micro channels in Lopezia, Gaura, and Gelsemium extend through the ectexine, endexine, and intine to the cytoplasm. The bulge regions in Epilobium represent portions of the endexine that become very greatly enlarged, forming conducting channels that transport materials into the microspore cytoplasm. Results with tracers such as colloidal iron and lanthanum have also shown that exines of microspores are permeable across areas lacking obvious channels.Key words: Betula, Epilobium, exine, Fuchsia, Gaura, Gelsemium, Lopezia, microchannels, pollen, tapetum, tufts, viscin threads.
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Skvarla JJ, Rowley JR, Hollowell VC, Chissoe WF. Annulus-pore relationship in Gramineae (Poaceae) pollen: the pore margin of Pariana. AMERICAN JOURNAL OF BOTANY 2003; 90:924-930. [PMID: 21659188 DOI: 10.3732/ajb.90.6.924] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Pariana, a primitive bamboo, is the only genus in the Gramineae (Poaceae) to have pollen grains without an annulus as part of its single aperture (porate) system. In contrast, the markedly thickened exine layer underlying the pore margin is similar to counterparts in all grass genera. Components of the future annulus in Gramineae pollen develop toward the cytoplasm (proximally) and begin to be pressed outward by an increase in the cytoplasm during the microspore vacuolate stage, culminating in an annulus by maturity. However, in some species of Pariana these components are either not sufficiently developed or the cytoplasmic expansion is not sufficient to press the components into an annular ring around the pore. The structural relationship of exine layering in this type of pollen grain in Gramineae and other families with similar apertures has not hitherto been extensively studied. A critical examination of the apertures in bambusoid grasses may clarify their systematic position within the Gramineae.
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Morbelli MA, Rowley JR, El-Ghazaly G. Stages in development of Selaginella diffusa megaspores. JOURNAL OF PLANT RESEARCH 2003; 116:57-64. [PMID: 12605300 DOI: 10.1007/s10265-002-0068-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2002] [Accepted: 10/03/2002] [Indexed: 05/24/2023]
Abstract
In mature megaspores of Selaginella diffusa (C. Presl) Spring the units of the exospore are ordered and become unordered toward the outer and inner surfaces. The exospore surface is coated with silica at maturity. The insertion of the future gap begins in early stages with formation of many minigaps within the inner part of the exospore distally. The mesospore, like the exospore, is resistant to the acetolysis reaction and can, thus, provisionally be considered to consist of sporopollenin. Unit structures within the outer part of the mesospore are unordered, but become ordered in the middle and inner parts. The inner surface of the mesospore appears verrucate. In maturing megaspores, the mesospore is mostly disintegrated and the inner exospore, which encapsulated the mesospore, remains as a somewhat isolated structure, and is again near the outer exospore. There are connecting strands across the gap between the inner surface of the outer exospore and the surface of the inner exospore. There are also spheres on the outer surface of the inner exospore.
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Claugher D, Rowley JR. Pollen exine substructure In Fagus (Fagaceae): role of tufts in exine expansion. ACTA ACUST UNITED AC 1990. [DOI: 10.1139/b90-286] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We compare results obtained from mature pollen of Fagus sylvatica L. using high-resolution scanning electron microscopy with fransmission electron microscopy images from several stages, from the early free microspore through to mature pollen grains. Exine processes (tufts) on young and mature grains are rodlike, with cross striations 10–15 nm wide. The total diameter of the tufts is 70–100 nm on exines of young microspores and up to 200–250 nm on mature exines. Tufts about 70 nm wide on the young microspores contain about five stacks of loops about 30 nm in diameter, whereas larger tufts on more mature exines have many stacks of the 30 nm wide loops. At maturity there is a mixture of large (200–250 nm wide) and small (70–100 nm wide) tufts and some tapering down from over 200 nm in width to less than 100 nm. There is continuity and a similar range of widths between the tufts as they occur as bacules and components of the tectum. We conclude that either new large-sized tufts are inserted during growth or some of the small (original sized) tufts increase in diameter from their bases toward the outer tip, or that both of these processes occur.
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Abstract
Serial sections for light microscopy or transmission electron microscopy of two Classopollis pollen tetrads show that the exine structure, except for the nexine, has radially arranged rodlike units interwoven with transverse subunits. The nexine consists of strands or thin sheets except in the equatorial infratectal striate band area, where it is up to ca. 1 μm thick. Nexine is absent in the areas of the distal cryptopore and the subequatorial circumpolar infratectal canal. It is very thin or absent in the tetrad scar. Native contrast and reactivity to stain disappeared on immersion of thin sections in 1 M NaOH or HCl or in water. Reactivity to stains was regained after oxidizing the sections in KMnO4. Reactivity to stains appears to be dependent upon non-sporopollenin molecules embedded within exines. The above immersions remove stain reactive sites. Oxidative etching of sporopollenin exposes new sites. The specimens of Classopollis classoides Pflug studied and illustrated were picked from an Upper Jurassic sample (CRC 31519-2) collected at Osmington Mills locality, Dorset, England.
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Tillberg JE, Rowley JR, Barnard T. X-ray microanalysis of leakage from polyphosphate granules in Scenedesmus. JOURNAL OF ULTRASTRUCTURE RESEARCH 1980; 72:316-24. [PMID: 7431483 DOI: 10.1016/s0022-5320(80)90067-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Abstract
SYNOPSISThe investigation described in this paper considers the influence of social class and the infant's birth order on maternal care, and then, in the light of these findings, examines the association between quality of maternal care and infant development. The study population comprised 89% of all births during an 18-month period in a defined administrative area in Glamorganshire. Possible explanations for the findings are discussed.
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Belin L, Rowley JR. Demonstration of birch pollen allergen from isolated pollen grains using immunofluorescence and a single radial immunodiffusion technique. INTERNATIONAL ARCHIVES OF ALLERGY AND APPLIED IMMUNOLOGY 1971; 40:754-69. [PMID: 4998093 DOI: 10.1159/000230460] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Immunofiuorescence (IF) and single radial immunodiffusion (SRID) methods were modified in order to study the relation of allergen to the surface of birch pollen. By absorption of the anti-birch pollen sera employed, it was ascertained that both methods demonstrated thermostable allergenic birch pollen antigen and not nonallergenic antigens. The allergen rapidly diffuses from unfixed, wetted grains. After an aldehyde treatment and wet heating of the grains this leakage which mainly occurs through the pollen apertures was not demonstrated. Birch pollen allergen was released in a similar way from pollen of all of the six tested species of birch.
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Abstract
In the early microspore wall of the grass Poa annua L., sporopollenin is arranged in bundles of anastomosing strands. Each bundle contains at least two strands, each about 50 A in diameter, which anastomose or intertwine and look like a meshwork with pores of the mesh up to 50 A in diameter. After the early microspore stage the exine becomes homogeneous; it is similar in this respect to the exines or ornamented parts of the exines of pollen of other angiosperms examined by electron microscopy.
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