Second-order Branching Research Articles

Multiple origins of congested inflorescences in Cyperus s.s. (Cyperaceae): Developmental and structural evidence

The understanding of homoplasic structures becomes more relevant when they are complex and define large angiosperm taxa. Inflorescence architecture usually fulfills both features, as happens with Cyperus, a genus with two taxonomical subdivisions characterized either by alternative expressions of Kranz anatomy (C(3) or C(4)) or inflorescence shape (condensed or lax). Those subdivisions are not completely congruent because at least one of these presumed characters has evolved several times. We focused a SEM study on the inflorescence development in species with condensed inflorescences and different photosynthetic anatomy to test the possibility that condensed inflorescences of subgen. Anosporum (C(3) anatomy) have evolved independently from those of subgen. Cyperus (C(4) anatomy). Freshly collected inflorescences of C. entrerianus, C. eragrostis, C. oxylepis, and C. incomtus were studied using stereoscopic and scanning electron microscopy. Condensed inflorescences of Cyperus species with C(3) and C(4) anatomy had differences in structure and development: (1) mature structure, (2) position of second-order branching initiation in the first developmental stage of the inflorescence, (3) main axis development and elongation, and branching development, (4) types of ramifications, (5) phyllotaxis and symmetry. Results support multiple origins of condensed inflorescences in Cyperus, based especially on differences in timing during development and elongation of the main axis and branches, branching pattern and phyllotaxis. Structure and development may be the key to using inflorescence morphology as an external feature to distinguish large natural groups within Cyperus based on vegetative anatomy.

Living Donor Candidates for Right Hepatic Lobe Transplantation: Evaluation at CT Cholangiography—Initial Experience

To retrospectively evaluate computed tomographic (CT) cholangiography in the depiction of second-order biliary tract anatomy in living donor candidates for right hepatic lobe transplantation. Human research committee approval was obtained, informed consent was not required, and the study was compliant with the Health Insurance Portability and Accountability Act. The authors identified all living right-lobe liver donor candidates who underwent CT cholangiography at their institution between October 2001 (when CT cholangiography was introduced at the institution) and March 2003 (n = 62). There were 41 men (mean age, 36 years; range, 18-55 years) and 21 women (mean age, 40 years; range, 22-55 years). Two readers in consensus rated quality of second-order bile duct visualization at CT cholangiography on a four-point scale (0, not seen; 3, excellent visualization) and noted the presence of variant second-order biliary tract branching anatomy. CT cholangiography findings were compared with those at surgery in subjects who underwent right hepatic lobe retrieval (n = 24). In addition, adult donors who underwent right hepatic lobe retrieval between January 2000 and March 2003 (29 men, mean age, 35 years [range, 20-52 years]; 18 women, mean age, 38 years [range, 23-54 years]) were identified. Numbers of donors who underwent intraoperative cholangiography before and after the introduction of CT cholangiography were compared by using the Fisher exact test. The mean second-order bile duct score at CT cholangiography was 2.9 (range, 2-3). Of 24 subjects who underwent right lobe retrieval, biliary tract anatomy determined at CT cholangiography was concordant with findings at surgery in 23 (96%). Variant second-order branching anatomy was seen in 13 subjects (54%) at surgery; one variant branch was missed at CT cholangiography. Of 47 subjects who underwent right hepatic lobe retrieval, significantly fewer subjects required conventional intraoperative cholangiography after the introduction of CT cholangiography (three of 24 subjects [12%]) than before (23 of 23 subjects; P < .0001). CT cholangiography accurately depicts biliary tract anatomy in living donor candidates for right hepatic lobe transplantation, and donors who undergo preoperative CT cholangiography are unlikely to need conventional intraoperative cholangiography.

The propagation and inhibition of an exothermic branched-chain flame with an endothermic reaction and radical scavenging

The effects of the endothermic decomposition of an inhibitory species W to form a radical scavenger on a laminar, pre-mixed flame supported by an exothermic second-order branching reaction are considered. This work extends a previous study, where the effects of the radical scavenger S were ignored. Two cases are identified, dependent on a parameter β measuring the relative rate of the decomposition of W. These are described by an high-activation-energy asymptotic analysis and through numerical integration of the propagating-flame equations for representative parameter values. For larger values of β the effect of the radical scavenger is to introduce a critical value of the heat-loss parameter α for flame propagation. For smaller values of β, where there is a critical value of α without any S being produced, the effect is to lower this critical value. In both cases the effect of the radical scavenger is to reduce the propagation speed and, if sufficient amounts of S are produced from the decomposition of W, to totally suppress flame propagation, even without any heat loss.

Flame quenching through endothermic reaction

A laminar premixed flame model is considered in which there is a second-order branching reaction coupled with an endothermic decay of a chemical inhibitor. An analysis, based on high activation energies for the reactions, is performed and two distinct cases are found. These depend on dimensionless parameters representing the loss of heat relative to its production, α, and the consumption of inhibitor relative to that of fuel, β. With α∼β⋘1, extinction is achieved through a saddle-node bifurcation at a critical value of α. For α⋘β, no extinction is found though considerable reductions in wave speed over the adiabatic limit are seen. The asymptotic results are compared with numerical simulations of an initial-value problem for the model.

Execution of the auxin replacement apical dominance experiment in temperate woody species

The classic Thimann-Skoog or auxin replacement apical dominance test of exogenous auxin repression of lateral bud outgrowth was successfully executed in both seedlings and older trees of white ash, green ash, and red oak under the following conditions: (1) decapitation of a twig apex and auxin replacement were carried out during spring flush, (2) the decapitation was in the previous season's overwintered wood, and (3) the point of decapitation was below the upper large irrepressible lateral buds but above the lower repressible lateral buds. Although it has been suggested that neither auxin, the terminal bud, nor apical dominance have control over the outgrowth of the irrepressible buds during spring flush, there is evidence in the present study that indicates that such control over the repressible buds exists. In seedlings, second-order branching, which resulted from decapitation of elongating current shoots, was also inhibited by exogenous auxin in the three species. Hence, the auxin replacement experiments did work on year-old proleptic buds (of branches of older trees) that would have entered the bud bank and also on current buds of seedlings. Cytokinin treatments were ineffectual in promoting bud growth.

Mesenteric circulation: three-dimensional MR angiography with a gadolinium-enhanced multiecho gradient-echo technique.

To evaluate the mesenteric circulation with magnetic resonance (MR) angiography, the authors examined 16 individuals (12 patients, four volunteers) with a gadolinium-enhanced, breath-hold, fat-saturated, multiecho, three-dimensional, gradient-echo sequence. Twenty examinations were performed. Grades of 3 or 4 (on a five-point scale [4 = best seen, 0 = not seen]) were applicable to 17 (85%) of 20 MR angiograms obtained in superior mesenteric artery trunks, 15 (75%) in celiac arteries, five (25%) in inferior mesenteric arteries; 15 (75%) of first-order branching, 12 (60%) of second-order branching, and 10 (50%) of third-order branching; 17 (85%) in superior mesenteric veins; and 17 (85%) in portal veins. MR angiography with this technique depicted the mesenteric arterial and venous circulation and the portal vein with excellent resolution in a short time.

Relationship Between Inflorescence Size and Seed Production in Barnyardgrass (Echinochloa crus-galli)

Barnyardgrass inflorescence length ranged from less than 2 to over 20 cm. Inflorescences less than 4 cm long were a single first-order raceme, while the largest had 20 to 50 primary branch racemes. Inflorescences longer than about 12 cm and with more than about 12 racemes showed second-order branching. Air-dried structural biomass increased from less than 2 milligrams for the smallest to over 300 milligrams for the largest inflorescences. Inflorescence length and structural biomass were positively correlated (r2= 0.95). Floret numbers increased from about 15 for smallest inflorescences to over 2000 for largest inflorescences and were positively correlated with inflorescence length (r2= 0.94) and with inflorescence structural biomass (r2= 0.94). Biomass of caryopses plus aborted florets had the same relationships as those for floret number. Measurement of frequency distribution of size and determination of numbers of inflorescences per plant should provide a means to predict fecundity in barnyardgrass.

Polycyclic growth and branching in the upper crown in provenances of lodgepole pine

The percentage of shoots that originated from polycyclic growth in first-order branches and branch numbers in upper annual segments of leader growth were determined from trees of seven provenances of Pinuscontorta Dougl. ssp. latifolia Engelm. from British Columbia and the Yukon, growing in a provenance trial at Prince George, B.C. The number of first-order branches varied among provenances and year of growth and was related to the frequency of extra cycles. The percentage of polycyclic shoots was greatest in the 2nd to 4th years of branch growth, although this varied with year and provenance. Total branch numbers were influenced mostly by variation in first- and second-order branch numbers. Second-order branch numbers were greatest in the second and third segments of leader growth (from the top down), but this was influenced by year of growth and provenance. The high levels of second-order branching corresponded to the greater frequency of polycyclic branches in these positions. The fast-growing southern provenance had the most branches, while the slow-growing Yukon source had the least. The slower-growing provenances had the most first-order branches per unit height.

New Species and Records of Iguanura (Palmae) from Sarawak and Thailand

Caespitose palm with stem 1.5-3-5 m tall and 1*5 cm diam.; internodes 2-5 cm long. Leaf sheath tough and fibrous, 15 cm long, very densely rustytomentose; petiole 40-47 cm long; lamina 36-54 cm long with 3-5 pairs of pinnae; pinnae 21-28 x 2-5-8 cm, with lower veins and rachis densely rufous-hairy. Inflorescences borne among the leaves; prophyll as long as leaf sheath; second peduncular bract projecting 8 cm beyond the leaf sheath, densely brown-tomentose. Inflorescence to 49-57 cm long, with peduncle to 29 cm; rachillae 4-8 in number, 19-33 cm long, the lowermost rachillae sometimes with second-order branching. Staminate flower with calyx 1 mm long, corolla 3 mm long, ribbed; stamens with lobed anthers 1-5 mm long, tissue in the stomial region with conspicuous large raphides; pistillode columnar, 2-5 mm long. Pistillate flowers (immature) with calyx 1 mm long; corolla 2 mm long and ribbed; staminodes minute; ovary ovoid, 1.5 mm long. Fruit elongate, 1-5 cm long by 5-6 mm broad at the base, tapering to 3 mm at the apex, with 3 ribs on the dorsal side and 2 lateral ribs extending less than half way from the base of the fruit, apex curved towards the basal stylar remains; young fruit green, turning white and ripening red. Endosperm homogeneous, curved and smooth (without ribs).

Controlled potential electrolysis: Analysis of the e.c.e. mechanism with first- and second-order branching reactions

Controlled potential electrolysis: Analysis of the e.c.e. mechanism with first- and second-order branching reactions

Controlled potential electrolysis: Analysis of the E.C.E. mechanism with first-and second-order branching reac tions

Controlled potential electrolysis: Analysis of the E.C.E. mechanism with first-and second-order branching reac tions

Kinetics of the hydrogen/oxygen reaction II. The explosion region in salt- and alkali-coated vessels

The first, second and third explosion limits for the hydrogen/oxygen reaction have been examined over a wide range of temperature, mixture composition, vessel size and wall coating. An expression has been derived from general chain theory which can account for the observed features of the complete explosion region. It includes and relates previously given expressions for the individual limits. The reactions found to be necessary and apparently sufficient to account for the hydrogen/oxygen spontaneous ignition peninsula are those of chain destruction in triple collisions, destruction at the wall of three different chain carriers, first-order branching, second-order branching, the regeneration of ‘dead’ chains and a chain-initiating process.