bluuebunny/crossref_metadata_2025 huggingface dataset:
THE GENECOLOGY OF LAWN WEEDS. V. THE ADAPTIVE SIGNIFICANCE OF DIFFERENT GROWTH HABIT IN LAWN AND ROADSIDE POPULATIONS OF PLANTAGO MAJOR L.
Authors: WARWICK S. I. , BRIGGS D.
Published: May 2006

The differential responses of two genetically‐determined growth forms of Plantago major L. ‐prostrate plants from lawns and erect plants from roadsides ‐ were studied in experiments involving clipping and reciprocal transplants.

Under a regime of clipping at 2 cm above soil level in a pot experiment, plants from roadsides were severely damaged and all reproductive structures were lost, whereas plants from lawns were able to produce several thousand seeds per plant. In a reciprocal transplant experiment of ‘mown’ and ‘tall grass’ plots, a small number of erect inflorescences of the roadside plants survived mowing and were able to produce a minute quantity of seed. Lawn plants in mown plots produced significantly more seeds. In the tall grass plots, the roadside plants exhibited significantly greater vegetative and reproductive dry wt than lawn plants.

Estimates of coefficients of selection were calculated for both experiments. Although values varied with different estimates of performance, in general: (1) selection against the roadside plants in the clipping treatment of the pot experiment and in the mown plots of the reciprocal transplant experiment was high (c.s. values based on reproductive features ranged from 078 to 1 00); and (2) coefficients of selection against lawn plants in the control of the pot experiment and in the tall grass plots of the reciprocal transplant experiment were also high (c.s. values in the reciprocal transplant experiment ranged from 0‐74 to 0‐77).

Plants from lawns flowered significantly earlier than those from roadsides, and both lawn and roadside plants flowered significantly later in tall grass plots than in mown plots.

Some problems and advantages of reciprocal transplant experiments are discussed.

Our experiments provide strong evidence that differences in growth habit in Plantago major are of adaptive significance.
THE ENERGETICS OF FRESHWATER ALGAE; ENERGY REQUIREMENTS FOR BIOSYNTHESIS AND VOLUME REGULATION
Authors: RAVEN JOHN A.
Published: May 2006

Freshwater algae have an intracellular osmolarity in excess of that of the medium. The tendency for water to enter the cells is resisted, in cells with a mechanically functional cell wall, by the ability of the wall to withstand a turgor pressure equivalent to the intracellular osmolarity; in cells lacking such a mechanically functional wall the water which enters is expelled by a contractile vacuole (or its functional equivalent). A comparison of the energy costs of cell volume regulation by these two mechanisms has been carried out making energy costings based on the minimum thermodynamic requirement and on plausible mechanisms for the two processes (wall synthesis and contractile vacuole function). This analysis yielded the following conclusions.

(1) Wall synthesis is a ‘growth’ process, while contractile vacuole operation is a’maintenance’process; other things being equal, a cell wall is a preferable mechanism of volume regulation in non‐growing cells.

(2) For a 5 μm radius cell with a specific growth rate of 8 × 10−6 s−1 and a 10 μm radius cell with a rate of 4 × 10−6 s−1 the energy input rate for contractile vacuole operation is considerably lower than for wall synthesis on the basis of minimum thermodynamic requirement; the plausible mechanism approach makes the two energy costs quite similar. Decreased growth rates favours the wall over the contractile vacuole mechanism.

(3) Increased cell size (10 μm radius rather than 5 μm) has similar effects on the energy costs of both volume regulation mechanisms, provided a (cell organic weight)−0.32 dependence of intrinsic growth rate is incorporated into the computations.

(4) Increased intracellular osmolarity (at constant extracellular osmolarity) causes a directly proportional increase in energy input rate for the cell wall mechanism, and a more than proportional increase in energy cost for the contractile vacuole mechanism.

(5) A non‐spherical shape increases the energy cost (at constant cell volume) for both the cell wall and the contractile vacuole mechanisms.

These conclusions may be used in the interpretation of such phenomena as the lower osmolarity of wall‐less than walled cells and the tendency for the resting stages of normally wall‐less and flagellate cells to have walls. It appears that the majority of freshwater algae have genetic capabilities to produce both walls and contractile vacuoles for cell volume regulation (e.g, the production of walled cysts by organisms which are normally flagellate, and the production of wall‐less motile spores and gametes by normally walled organisms).
THE IMPORTANCE OF QUANTITATIVE ANATOMY IN THE INTERPRETATION OF WHOLE LEAF BIOCHEMISTRY IN SPECIES OF TRITICUM, HORDEUM AND AVENA
Authors: JELLINGS A. J. , LEECH RACHEL M.
Published: May 2006

The quantitative internal leaf architecture of the first leaves of several cereals, including species of Triticum, Hordeum and Avena, is described. In all the species only between 50 and 60% of the cells are mesophyll cells, 30 to 40% are vascular cells and 10% epidermal cells. Interspecific differences were identified in cell density and in the amount and distribution of non‐cellular space. In Triticum monococcum and Triticum aestivum the cell densities were 394 × 103 cm−2 and 124 × 103 cm−2 and non‐cellular space 20 and 24% respectively. The implications of these findings in the interpretation of leaf biochemistry are discussed.
GROWTH OF SITKA SPRUCE SEEDLINGS WITH ROOTS DIVIDED BETWEEN SOILS OF UNEQUAL MATRIC POTENTIAL
Authors: COUTTS M. P.
Published: May 2006

Post‐dormant seedlings with dormant roots were grown with their roots divided between two containers of loam or peat soil corresponding to wet/wet, dry/dry and wet/dry; the soil matric potentials were: loam, minus 6 kPa (wet) and minus 60 kPa (dry); peat, minus 5 kPa (wet) and minus 30 kPa (dry). In both soils the wet/dry treatment had little effect on leaf water potential, or on total plant growth compared with the wet/wet, but produced very uneven root development. Most growth of primary and woody roots occurred in the wet soil. Water supplied to one‐half of the root system did not increase growth of the half in dry soil, compared with the dry/dry treatment. Fewer roots emerged from dormancy in the dry than in the wet soil and at any one time, fewer roots were growing in the dry soil. The extension of main root axes in the dry soil was only slightly slower than in the wet soil. However, in the dry soil some roots were dying while others were extending and at the final harvest no increase was recorded in total root length.

When both halves of the root system were in dry soil, leaf water potential was slightly reduced and shoot and root growth were significantly reduced compared with the wet/wet treatment.

Soil adhered strongly to roots grown in the dry soil and the significance of this in plant water relations is discussed.
THE DISTRIBUTION OF CARBON AND THE DEMAND OF THE FUNGAL SYMBIONT IN LEEK PLANTS WITH VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: SNELLGROVE R. C. , SPLITTSTOESSER W. E. , STRIBLEY D. P. , TINKER P. B.
Published: May 2006

Leek plants (Allium porrum) were grown on partially sterilized soil either inoculated (M) or not (NM) with the vesicular‐arbuscular mycorrhizal fungus, Glomus mosseae. They were pulse‐fed with 14CO2 in an apparatus which allowed CO2 subsequently respired either by the shoots or by the roots plus soil to be separately monitored. There were three experiments. In two, plants were harvested 48 h after labelling and in the third after 214 h. At harvest, the distribution of 14C between shoot, root, soil organic matter and root washings was measured.

Similar growth curves for M and NM plants were obtained by supplying extra phosphorus to the latter, so that C distributions for both treatments could be compared directly. In all three experiments, about 7 % more of the total fixed C was translocated from shoot to root in M plants compared to NM plants. In the third experiment, this extra translocate could be accounted for by increased root respiration plus increased loss of C to the soil but, despite this drain, M and NM plants had equal rates of C assimilation per unit of leaf area. However, shoots of M plants had a lower content of dry matter and hence higher assimilation rates expressed on a dry matter basis.

Increased hydration is suggested as a mechanism whereby leaf area and hence C assimilation increases in mycorrhizal plants and which offsets the effects of the drain imposed by the mycorrhizas.
SPATIAL STRUCTURE OF A POPULATION OF TRICHOLOMOPSIS PLATYPHYLLA IN A WOODLAND SITE
Authors: THOMPSON WENDY , RAYNER A. D. M.
Published: May 2006

Isolates of the mycelial cord‐forming agaric, Tricholomopsis platyphylla, were obtained from an oak stand and their mating and mycelial interactions studied. The fungus was found to have tetrapolar incompatibility and genetically different dikaryons were strongly mutually antagonistic in culture. On the basis of such antagonism, 22 mycelial types, each comprising from one to 15 isolates were identified amongst a random sample of 113 dikaryotic mycelial isolates from an area of 20·8 ha. Isolates belonging to the same mycelial type were frequently found in close proximity in areas from which other types were excluded. However, some were from samples as much as 150 m apart and separated by areas occupied by other mycelial types. The likely origin of this distribution is discussed in relation to the pattern of dispersal, establishment and spread of this saprophytic fungus in a woodland habitat.
THE INFLUENCE OF soil AERATION ON THE EFFICIENCY OF VESICULAR–ARBUSCULAR MYCORRHIZAS
Authors: SAIF S. R.
Published: May 2006

Summary

Low concentrations of soil CO2 increased but higher concentrations of CO2 decreased the dry matter of mycorrhizal and non‐mycorrhizal plants of Eupatorium odoratum L. Dry matter of Guizotia abyssinica (L.f.) Cass. decreased linearly with increasing CO2. Shoot dry weight of Sorghum tricolor (L.) Moench was unaffected by increasing soil CO2. Inoculation with Glomus macrocarpum increased the dry matter of E. odoratum and Guizotia abyssinica significantly at all CO2 concentrations. Mycorrhizal plants were more sensitive to soil CO2 than were the non‐mycorrhizal plants. Carbon dioxide at concentrations up to 8% had little effect on mineral uptake (except N) by E. odoratum but 16% CO2 decreased the mineral uptake significantly. Mineral uptake by Guizotia abyssinica decreased but the mineral concentration in the plant increased with rising CO2. The mineral uptake and concentration in 5. bicolor showed variable response to soil CO2. The efficiency of the mycorrhizal fungus Glomus macrocarpum in enhancing growth of its hosts was more affected by soil CO2 than was its development in roots.
THE INFLUENCE OF BURIAL AND DRY‐STORAGE UPON CYCLIC CHANGES IN DORMANCY, GERMINATION AND RESPONSE TO LIGHT IN SEEDS OF VARIOUS ARABLE WEEDS
Authors: FROUD‐WILLIAMS R. J. , DRENNAN D. S. H. , CHANCELLOR R.J.
Published: May 2006

Summary

Seeds of Alopecurus myosuroides, Bromus sterilis, Capsella bursa‐pastoris, Papaver rhoeas, Stellaria media, Veronica arvensis, Veronica persica and Viola arvensis were sown in soil at depths of 0, 25 and 150 mm. Seeds buried at 150 mm were exhumed at intervals of 3, 6, 12 and 15 months and incubated at an alternating temperature regime of 10/20 °C (16/8 h) or irradiated with light of various wavelengths prior to incubation.

In general, shallow burial (25 mm) reduced seedling emergence except in the case of B. sterilis, which also germinated at a depth of 150 mm but failed to emerge.

Cyclic changes in dormancy of buried seeds were observed. Although sensitivity to light was enchanced by burial, germination and response to light quality varied between seasons. Dormancy of most species, including the winter annuals A. myosuroides, Veronica persica and Viola arvensis, was least in autumn and most in summer. Papaver rhoeas was least dormant in spring and S. media was least dormant in summer. Generally, red light promoted germination whereas far‐red light or darkness was not stimulatory. However, A. myosuroides was more sensitive to far‐red light in autumn than at other times of the year.

Natural day‐light promoted germination of A. myosuroides, S. media and Veronica arvensis. Germination of B. sterilis was delayed in natural daylight. Transfer of A. myosuroides, Papaver rhoeas, Veronica arvensis and Viola arvensis from darkness to daylight increased germination above that obtained under natural daylight.

Germination of freshly collected seeds of Alopecurus myosuroides, Arrhenatherum elatius, Poa annua, Poa trivialis, Plantago major and Viola arvensis was promoted by short irradiations of red light. Dry‐storage did not affect germination of Alopecurus myosuroides, Poa annua, Plantago major or Viola arvensis, but did affect dormancy and light requirement of Poa trivialis. Burial of seeds of Alopecurus myosuroides, Poa trivialis and Plantago major increased their sensitivity to far‐red light.

It is concluded that cyclic changes in seed dormancy and associated light sensitivity are determined seasonally and result from changing environmental factors and that they are of adaptive importance for survival.
FRANKIA SOURCE AFFECTS GROWTH, NODULATION AND NITROGEN FIXATION IN CASUARINA SPECIES
Authors: REDDELL PAUL , BOWEN G. D.
Published: May 2006

Summary

Two species of Casuarina [C. equisetifolia ssp. incana (Benth.) L.J. and C. cunninghamiana Miq.] differed in growth responses to inoculation with Frankia from five sources. Casuarina equisetifolia ssp. incana formed nodules with all five Frankia inocula whereas C. cunninghamiana formed nodules with only two. A range of response from ineffectiveness in N2 fixation to high effectiveness was observed between Casuarina species ‐ Frankia source combinations. Strains of Frankia highly effective on one species were frequently ineffective on the other. Effectiveness was related to nodule development after infection and to the ability of developed nodules to fix N2.
FORMATION OF EXTERNAL HYPHAE IN SOIL BY FOUR SPECIES OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI
Authors: ABBOTT L. K. , ROBSON A. D.
Published: May 2006

Summary

The ability of several species of vesicular–arbuscular (VA) mycorrhizal fungi to form hyphae in soil was compared in two glasshouse experiments. We measured the length of hyphae in soil and related this to the length of infected root. Species of VA mycorrhizal fungi differed in the length of external hyphae produced per cm of infected root. Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe produced less external hyphae per cm infected root than did Gigaspora calospora (Nicol. and Gerd.) Gerd. at all harvest times and when inoculum was either placed in a band below the seed or mixed throughout the soil. Glomus tenue (Greenall) Hall and Acaulospora laevis Gerd. and Trappe both produced similar lengths of external hyphae per cm infected root to that formed by G. calospora.

Differences among isolates of VA mycorrhizal fungi in the distribution of hyphae in soil may be as important as differences in the length of external hyphae when selecting fungi that are effective at increasing nutrient uptake.
FUNCTIONING OF VESICULAR–ARBUSCULAR MYCORRHIZAS UNDER FIELD CONDITIONS
Authors: FITTER A. H.
Published: May 2006

Summary

Although VA mycorrhizas are easily demonstrated as mutualistic associations in pot culture, on the basis of reciprocal exchange of carbon and (mainly) phosphorus, unequivocal field demonstrations are less numerous. This may be due to incompetence of widely occurring fungal types, to inter‐plant connections by hyphae, which dissipate the benefit, to grazing of external hyphae, or to problems associated with root longevity. The action of mycorrhizal roots in improving plant water relations and promoting phosphate uptake under field conditions is considered in the light of these constraints. It is suggested that much greater effort is required in the investigation of mycorrhizal associations in the field.
EVIDENCE FOR AN ENDOGENOUS CYCLE OF DORMANCY IN DRY STORED SEEDS OF POA TRIVIALIS L.
Authors: FROUD‐WILLIAMS R. J. , HILTON JANET R. , DIXON J.
Published: May 2006

Summary

Seeds of Poa trivialis L. (rough meadow‐grass) were collected from two contrasting habitats during the summer of 1982. Collections from an arable population were obtained on three occasions and seeds from a grassland population were collected once. Although both populations responded similarly to various combinations of light, temperature and nitrate, the arable collections were markedly more dormant.

Loss of dormancy of the grassland and early arable populations one month after collection was rapid in seeds stored at ambient temperatures and at 4 °C but more delayed in those stored at 23 °C. Despite a gradual loss of dormancy during storage, cyclic changes in dormancy were also evident, especially at 23 °C. The percentage germination of the various collections 7 d after incubation following storage at 23 °C increased over the first three months, but declined following six and 12 months storage and increased again after 15 months storage. At 4 °C the late arable collection lost dormancy more slowly than the other two collections and germination was greatest after six months storage; a reduction in percentage germination occurred after twelve months.

Seeds buried at 5 and 15 cm showed cyclic changes of dormancy, being least dormant in autumn and spring, but most dormant in summer, corresponding to the natural periodicity of germination.

It is proposed that cyclic changes in dormancy are regulated by endogenous rhythms and seasonal changes of temperature. The ecological implications of the germination behaviour of this species in various habitats are discussed.
EROSION OF WAXES FROM LEAF SURFACES BY SIMULATED RAIN
Authors: BAKER E. A. , HUNT GRACE M.
Published: May 2006

Summary

Effects of simulated rain on the epicuticular wax of glaucous leaves have been studied. Droplets (250 to 400 μm) travelling at low or medium velocity (0.25 to 5 m s−1) fractured the dendrites and tubes on leaves of Brassica spp., the tubes on Eucalyptus globulus Labillardere and the ribbons on the adaxial surfaces of Pisum sativum L. and Fragaria ananassa Duchesne. Rates of erosion for Brassica and E. globulus leaves were high during an initial application equivalent to 1 mm rainfall but declined markedly with extended exposure. In contrast, erosion from P. sativum and F. ananassa proceeded at a fairly uniform rate throughout the exposure period. The composition of the detached wax deposits was identical with that of the intact leaf wax for Brassica species but differed for the other species. The practical consequences of wax erosion of field crops are considered.
CALCIUM‐CONTAINING CRYSTALS IN TELFAIRIA HOOKER (CUCURBITACEAE)
Authors: OKOLI 'BOSA E. , McEUEN A. R.
Published: May 2006

Summary

Polarized light and scanning electron microscopy were used to examine the distribution, location and form of crystals in the leaves, probracts, stems, flowers and seed‐coats of Telfairia pedata (Sims) Hooker and T. occidentalis Hooker fil. Energy‐dispersive X‐ray analysis showed that calcium is the primary crystal cation. Histochemical tests confirmed that the crystals are mainly calcium oxalate and these are particularly abundant around and within the vascular tissues. Cystolith ‐ like crystals of calcium carbonate are also numerous at the bases of macrohairs and as heavy incrustations within the midrib and major veins of mature leaves. The crystal types include solitary, acicular, druse (cluster) and combinations of two or more of these. Substantial amounts of soluble oxalate were also found to be present, especially in the leaf laminae of T. occidentalis. The total oxalate contents of the edible portions of T. occidentalis were determined and compared with values published for other vegetables.
MODIFICATION OF RESPIRATION AND CARBOHYDRATE STATUS OF BARLEY ROOTS BY SELECTIVE PRUNING
Authors: FARRAR J. F. , JONES C. L.
Published: May 2006

Summary

Barley plants were pruned selectively to give root systems with relative growth rates that varied two‐fold. Rates of elongation of the seminal root axes were unaffected. Respiration rate was highest in the fast‐growing roots, but there was no change in the proportion of carbon entering the root that was subsequently lost in respiration. Soluble sugar contents were greater in fast than in slow growing plants, but the rate of uptake of exogenously supplied sucrose and glutamine was highest where root growth rate was reduced by pruning of the shoot. Turnover of sugars in the vacuole was slower in roots with reduced growth rate.
ABSORPTION OF NITROGEN DIOXIDE BY SUNFLOWER PLANTS GROWN AT VARIOUS LEVELS OF NITRATE
Authors: OKANO K. , TOTSUKA T.
Published: May 2006

Summary

The effect of varied levels of nitrate on the absorption of atmospheric nitrogen dioxide (NO2) by sunflower (Helianthus annus L.) plants was investigated by using a 15N dilution method. Growth of the plants was greatest at 5 mM nitrate, with less growth at 15 mM nitrate and a considerable reduction at zero nitrate. The total amount of NO2‐nitrogen absorbed by the plant depended on the plant size and total leaf area.

Nitrate supply did not influence the rate of absorption of NO2 by the plants when exposed to 0.3 μl l−1 NO2. On the contrary, when the plants were exposed to 2.0 μl l−1 NO2, the absorption rate was significantly lower for the plants grown at zero nitrate compared with those grown at 5 or 15 mM nitrate. The lower rate of NO2 absorption in the nitrate‐deficient plants was not due to the changes in stomatal resistance or stomatal density of the leaves, but could have been due to an increase in mesophyll resistance resulting from accumulation of high levels of nitrite in the leaf tissues. Nitrogen dioxide at 0.3 μl l−1 exerted a nutritional effect on the nitrate‐deficient plants, while NO2 at 2.0 μl l−1 acted as a toxic air pollutant on the plants at all the levels of nitrate supplied.
PATTERNS IN THE GEOGRAPHICAL DISTRIBUTION OF THE EARLY FLANDRIAN CORYLUS RISE IN SOUTHWEST SCOTLAND
Authors: BOYD W. E. , DICKSON J. H.
Published: May 2006

Summary

The timing of the early Flandrian Corylus rise in southwest Scotland is discussed, with reference to radiocarbon dates from nine sites. These sites cover a range of geomorphological regions and sediment types.

The Corylus rise on the mainland of southwest Scotland appears to have occurred with some degree of synchroneity over a wide area at around 9200 to 9300 radiocarbon years before present. However, two dates from the island of Arran in the Firth of Clyde are considerably younger, and the Corylus rise on Arran appears to have occurred approximately half a millenium later than on the surrounding mainland. This is explicable in terms of the relative isolation of Arran from the mainland; the surrounding deep‐water troughs effectively halted the migration of Corylus. The later, apparently ‘normal’Corylus rise on Arran may relate to Mesolithic human activity. A similar, but shorter interval separates the date of the late Corylus rise on the island of Mull from that of the Corylus rise on the surrounding mainland.
Political opportunity structures and right‐wing extremist party success
Authors: ARZHEIMER KAI , CARTER ELISABETH
Published: May 2006

West European right‐wing extremist parties have received a great deal of attention over the past two decades due to their electoral success. What has received less coverage, however, is the fact that these parties have not enjoyed a consistent level of electoral support across Western Europe during this period. This article puts forward an explanation of the variation in the right‐wing extremist party vote across Western Europe that incorporates a wider range of factors than have been considered previously. It begins by examining the impact of socio‐demographic variables on the right‐wing extremist party vote. Then, it turns its attention to a whole host of structural factors that may potentially affect the extreme right party vote, including institutional, party‐system and conjunctural variables. The article concludes with an assessment of which variables have the most power in explaining the uneven electoral success of right‐wing extremist parties across Western Europe. The findings go some way towards challenging the conventional wisdom as to how the advance of the parties of the extreme right may be halted.
Capitalist junctures: Explaining economic openness in the transition countries
Authors: BODENSTEIN THILO , SCHNEIDER GERALD
Published: May 2006

Abstract.  Current transition theories attribute the varying economic openness of post‐communist countries to the lack of democracy or the inhibiting veto power of vested interests. In this article, the authors offer micro‐foundations for such claims and link the key changes in the foreign economic policy of these states to internal coalition building during the first stages of the political transformation. A simple game‐theoretic model demonstrates that the way in which ruling elites' responses to the competing demands of domestic stakeholders crucially shaped the chance of foreign economic liberalization years later. This ‘early starter’ hypothesis is contrasted with contending accounts of economic opening in multivariate tests using the ELITE data set (Economic Liberalization in Transition Economies). The regression models confirm that the scope of the political transformation process has fostered foreign economic openness, while the existence of veto players helps rather than inhibits the process of foreign economic liberalization.
Media Standing of Urban Parkland Movements: The Case of Los Angeles' Taylor Yard, 1985–2001
Authors: Roth Andrew L. , Vander Haar Emilie L.
Published: May 2006

What role does media coverage play in local communities' efforts to assert their stake in contests over urban land use? We focus this question by examining the case of Taylor Yard in Los Angeles, where community activists fought for a decade to avoid industrial development of a 100‐acre parcel of former rail yard in favor of creating much‐needed parkland. We analyze 446 direct quotations from 54 print news stories on the contest over land use at Taylor Yard between 1985 and 2001. We identify whom journalists covering Taylor Yard treated as newsworthy sources, and how rivals employed competing definitions of “the community” and its interests to frame the contest over land use at Taylor Yard. This analysis shows how park advocates' framing of the contest ultimately achieved prominence in print news coverage of Taylor Yard. Our findings suggest the need to rethink previous sociological accounts of the relationships among local news professionals, their favored sources, and coverage of urban development.
Incidence of Atrial Fibrillation in Heart Transplant Patients: Long‐Term Follow‐Up
Authors: KHAN MOHAMMED , KALAHASTI VIDYASAGAR , RAJAGOPAL VIVEK , KHAYKIN YAARIV , WAZNI OUSSAMA , ALMAHAMEED SOUFIAN , ZUZEK RYAN , SHAH TEHMEENA , LAKKIREDDY DHANUMJAYA , SALIBA WALID , SCHWEIKERT ROBERT , CUMMINGS JENNIFER , MARTIN DAVID O , NATALE ANDREA
Published: May 2006

Background: The incidence of atrial fibrillation (AF) in heart transplant patients has not been well documented.

Methods: To determine the incidence of AF in a cohort of patients undergoing cardiac transplantation, clinical data were obtained from a prospectively collected database for all consecutive orthotopic heart transplantation (OHT) patients and for all consecutive coronary artery bypass graft (CABG) surgery patients between January 1984 and March 2004 at our institution. A cohort of 1,714 OHT patients and low‐risk CABG (normal ejection fraction [EF] and no left ventricular hypertrophy [LVH]) patients were age‐ and sex‐matched.

Results: The average age in the two groups was 56 ± 7 years with 87% male and 81% white race and body mass index (BMI) of 26 ± 4. There were 3 cases of AF (0.3%) in the OHT group and 757 cases of AF (21%) in the low‐risk CABG group. The strongest independent predictor of freedom from postoperative AF was having had a transplant (odds ratio [OR] 96, 95% confidence interval [CI] 13–720). The incidence of AF, atrial flutter (AFL), and supraventricular tachycardia (SVT) in OHT was 0.33, 2.8%, and 1.3%, respectively. Given that incidence of AF, AFL, and SVT in historical post‐CABG population is 25%, 17%, and 4.3%, transplanted patients appear to have lower incidence of AF, AFL, and SVT than the reference population. Consistent with this, transplanted patients underwent few ablation procedures for atrial arrhythmias. Additionally, the three patients with AF had bicaval anastomoses suggesting the possibility of PACs originating in the donor superior vena cava (SVC) or IVC (inferior vena cava) initiating AF in these patients.

Conclusions: In a cohort study of transplant and low‐risk CABG patients, the strongest independent predictor of freedom from AF is having undergone transplant surgery. One potential explanation for the markedly lower incidence of AF may be effective isolation of thoracic veins with documented cases retaining the native SVC.
An Unusual Presentation of a Large Left Ventricular Pseudoaneurysm
Authors: Leitman Marina , Shmueli Ruth , Stamler Alon , Krakover Ricardo , Hendler Alberto , Vered Zvi
Published: May 2006

Left ventricle pseudoaneurysm is an infrequent complication of myocardial infarction, and is most commonly localized in the inferoposterior left ventricular segments. We describe a patient post anterior myocardial infarction, who presented with pulmonary edema and a large pseudoaneurysm of the anterolateral wall with involvement of the anterolateral papillary muscle, resulting in severe mitral regurgitation. The patient underwent successful operation and is currently well.
Usefulness of Live/Real Time Three‐Dimensional Transthoracic Echocardiography in the Characterization of Ventricular Septal Defects in Adults
Authors: Mehmood Farhat , Miller Andrew P. , Nanda Navin C. , Patel Vinod , Singh Anurag , Duncan Kurt , Rajdev Sanjay , Enar Sibel , Singh Vikram , Nunez Anthony , McGiffin David C. , Kirklin James K. , Pacifico Albert D.
Published: May 2006

In this report, we present 12 patients (range 14–76 years, mean 40 ± 22.7 years) who underwent surgical repair of a ventricular septal defect (VSD). Location, size, and surrounding anatomy of the VSD were assessed prior to intervention in all patients with live/real time three‐dimensional transthoracic echocardiography (3DTTE). In 9 patients, measurements of maximum dimension, circumference, and area by 3DTTE correlated well with the same measurements from intraoperative three‐dimensional transesophageal echocardiographic (3DTEE) reconstruction. 3DTTE measurement of maximum dimension of VSDs also agreed well with maximum dimension by surgery in 10 patients. Live/real time 3DTTE accurately defined VSD location, size, and surrounding anatomy in all patients studied by us. VSD characterization by live 3DTTE agreed well with surgery descriptions and 3DTEE measurements.
Dental implants placed in expanded narrow edentulous ridges with the Extension Crest® device
Authors: Chiapasco Matteo , Ferrini Francesco , Casentini Paolo , Accardi Stefano , Zaniboni Marco
Published: May 2006

Objective: This study has been designed to evaluate the capability of a new surgical device (Extension Crest®) to widen narrow edentulous alveolar ridges and to allow a correct placement of endosseous implants in horizontally atrophied sites.

Material and methods: Forty‐five patients, 20 males and 25 females, aged 20–66 years, affected by edentulism associated to horizontal resorption of the ridges, were treated by means of a sagittal osteotomy and expansion of the ridge with a new surgical device (Extension Crest®) to obtain a wider bony base for ideal implant placement. In the same procedure in 33 patients, and 1 week afterwards in 12 patients, 110 endosseous titanium implants (ITI TE®) were placed. Three to four months later, the patients were rehabilitated with implant‐supported prostheses.

Results: The success rate of the expansion technique was 97.8%. A total of 110 implants were inserted in the expanded ridges. The mean follow‐up after the start of prosthetic loading was 20.4 months. Three implants were removed before the start of prosthetic loading, because of non‐integration, while no other implants failed after the completion of the prosthetic rehabilitation. Three implants, although integrated and in function, did not fulfill success criteria: cumulative success and survival rates at the end of the observation period were 95.4% and 97.3%, respectively.

Conclusion: Within the limits of this study, this technique appeared to be reliable and simple, with reduction of morbidity and times of dental rehabilitation as compared with other techniques such as autogenous bone grafts and guided bone regeneration. Survival and success rates of implants placed in the treated areas are consistent with those placed in native bone.
Gnathostomiasis: Import from Laos
Authors: Hennies Felix , Jappe Uta , Kapaun Annette , Enk Alexander
Published: May 2006

Gnathostomiasis is a nematode infestation endemic in Southeast Asia, which can involve multiple organs including the liver, eyes, gastrointestinal tract and CNS. The most common manifestation is recurrent migratory subcutaneous swellings which can appear anywhere on the body and are accompanied by pruritus and systemic symptoms such as low‐grade fever, loss of appetite and nausea. The diagnosis is based on the clinical picture, history of travel, peripheral blood eosinophilia and the determination of agent‐specific antibody levels. The standard treatment is albendazole. We present a 37‐year‐old Laotian woman, who had lived in Germany for 17 years, but developed recurrent swelling of the cheek following a visit to Laos. Because of the typical clinical findings, the history of a visit to Laos, and the presence of specific anti‐Gnathostoma antibodies on Western blot, the diagnosis of cutaneous gnathostomiasis was made.
Carbon Fiber/Thermoplastic Overwrapped Gun Tube
Authors: Littlefield Andrew , Hyland Edward , Andalora Andrew , Klein Nathaniel , Langone Robert , Becker Robert
Published: May 2006

The emphasis on lightweight large-caliber weapons systems has placed the focus on the use of advanced composite materials. Using composite materials not only directly removes weight from the gun tube but, by better balancing the tube, allows the use of smaller gun stabilization drive systems, thus further enhancing system weight loss. Additionally, the use of high stiffness composites helps with pointing accuracy and alleviating the dynamic strain phenomenon encountered with high-velocity projectiles. Traditionally though, using composites has been difficult because of the coefficient of thermal expansion mismatch between the steel substrate and the composite jacket, which causes a gap after manufacturing. Dealing with this mismatch has greatly complicated the manufacturing process in the past to the point where mass-producing the barrels would be problematic at best. By using a thermoplastic resin and a cure on the fly process, the manufacturability of the barrels has been greatly improved and the gap has been eliminated. This is the first time that this approach has been applied to a large-caliber gun tube. A 120mm barrel has been manufactured using this process with IM7 fibers in a polyetheretherketone matrix and successfully test fired. This paper will present the design, manufacturing, and test firing of this barrel.
Probabilistic Modeling for Ceramic Lined Gun Barrels
Authors: Carter Robert H.
Published: May 2006

Designers of advanced gun systems have been tasked with increasing barrel life in the face of the extreme erosion and wear of the interior ballistics environment. The addition of refractory metal coatings, such as chromium or tantalum, have greatly boosted service life, but even with these applications the erosion resistance of the underlying gun steel is the service-life limiting factor. The U.S. Army Research Laboratory (ARL) is currently undertaking an effort to determine the feasibility of ceramic gun barrels. Ceramics are attractive for liner materials because of their high-temperature performance and erosion-resistance characteristics. Unfortunately, their drawbacks are low tensile strength, low fracture toughness, and brittle fracture. Previous research into the replacement of metals with a ceramic liner has met with limited success, at best, but advances in ceramic manufacturing technology, probabilistic design, and sheathing technology have led to renewed interest in this area. The work at ARL has focused on developing a material property database of commercially available ceramics, extensive finite element and analytic modeling, experimental verification, and, ultimately, demonstration of the ceramic gun barrel technology. This body of work will focus on the derivation of analytic models for an N-layered tube to calculate the Weibull failure probabilities for a ceramic liner. Model results are verified through high-pressure burst testing of blank and sheathed ceramic tubes. The application of the models as a design tool is explored by generating failure surface plots to investigate optimal geometries and prestress levels for a variety of different liner and sheath materials across various caliber systems.
Mechanistic Features of Short Fatigue Crack Growth Kinetics for High Strength Steels in Sea Water
Authors: Kim Kijoon , Hartt William H.
Published: May 2006

The importance of fatigue to the integrity of offshore structures is well documented. Also, it has been demonstrated that much of the service life of members and components such as tendons and risers is comprised of an extension of cracks from initial surface defects to a size of several millimeters. At the same time, the growth kinetics of such short cracks has been shown to be more rapid than those of long cracks; however, it is upon the latter that most historical studies have focused. In the present paper, the results of scanning electron microscope fractographic analyses performed upon five high strength steels fatigued in air and seawater are presented. These revealed fracture surface morphology distinctions that were a unique function of material, environment (air versus seawater), potential, and crack length, and that the enhanced fatigue crack growth rate in the short crack regime was relatable to these morphological features. Of particular importance were (1) the development of secondary cracks as a precursor for the short crack to long crack growth rate kinetics transition, and (2) a change in fracture mode, either from quasicleavage (QC) to microvoid coalescence (MVC) or from intergranular to QC or MVC with increasing crack length. The results are discussed within the context of (1) alloy development for applications where a significant portion of the fatigue life transpires while cracks are relatively short such that the enhanced growth rate kinetics apply; and (2) materials selection and fatigue design of riser and tendon systems for deep water offshore structures.
Aircraft noise effects on sleep: Application of the results of a large polysomnographic field study
Authors: Basner Mathias , Samel Alexander , Isermann Ullrich
Published: May 2006

The Institute of Aerospace Medicine at the German Aerospace Center (DLR) investigated the influence of nocturnal aircraft noise on sleep in polysomnographic laboratory and field studies between 1999 and 2004. The results of the field studies were used by the Regional Council of Leipzig (Germany) for the establishment of a noise protection plan in the official approval process for the expansion of Leipzig/Halle airport. Methods and results of the DLR field study are described in detail. Special attention is given to the dose-response relationship between the maximum sound pressure level of an aircraft noise event and the probability to wake up, which was used to establish noise protection zones directly related to the effects of noise on sleep. These protection zones differ qualitatively and quantitatively from zones that are solely based on acoustical criteria. The noise protection plan for Leipzig/Halle airport is presented and substantiated: (1) on average, there should be less than one additional awakening induced by aircraft noise, (2) awakenings recalled in the morning should be avoided as much as possible, and (3) aircraft noise should interfere as little as possible with the process of falling asleep again. Issues concerned with the representativeness of the study sample are discussed.
Coupling mechanism of electromagnetic acoustical transducers for ultrasonic generation
Authors: Jian X. , Dixon S. , Edwards R. S. , Reed J.
Published: May 2006

Electromagnetic acoustic transducers (EMATs) generate ultrasonic waves in metals through an electromagnetic coupling mechanism. A concept for EMAT generation, using a coil alone without a permanent magnet, but with a pulse generator and a sample, is introduced. A simplified equivalent coil circuit is given and has been validated by experimental measurements. Such an equivalent circuit can be used for variations in excitation current calculations, which have often been neglected in previous publications in this area but have proved to be of great importance in considering the efficiency and frequency characteristics of ultrasonic generation. The equivalent coil inductance is dependent on the distance between the coil and the sample, due to coil interactions with eddy currents and the Ampere current of the magnetization mechanism. Analytical solution for an annular coil above metal samples is given, and the influences of the lift-off, coil radius, material magnetic permeability and electrical conductivity on the equivalent coil inductance are discussed. Experimental measurements agree well with predictions.
A rule-based emotion-dependent feature extraction method for emotion analysis from speech
Authors: Hozjan Vladimir , Kačič Zdravko
Published: May 2006

This paper presents a rule-based method to determine emotion-dependent features, which are defined from high-level features derived from the statistical measurements of prosodic parameters of speech. Emotion-dependent features are selected from high-level features using extraction rules. The ratio of emotional expression similarity between two speakers is defined by calculating the number and values of the emotion-dependent features that are present for the two speakers being compared. Emotional speech from Interface databases is used for evaluation of the proposed method, which was used to analyze emotional speech from five male and four female speakers in order to find any similarities and differences among individual speakers. The speakers are actors that have interpreted six emotions in four different languages. The results show that all the speakers share some universal signs regarding certain emotion-dependent features of emotional expression. Further analysis revealed that almost all speakers in the analysis used unique sets of emotion-dependent features and each speaker used unique values for the defined emotion-dependent features. The comparison among speakers shows that the expressed emotions can be analyzed according to two criteria. The first criterion is a defined set of emotion-dependent features and the second is an emotion-dependent feature value.
A comparison of differences in highway noise barrier design using TNM 2.5 and STAMINA
Authors: Shu Ning , Cohn Louis , Harris Rowell , Kim Teak
Published: May 2006

In April 2004, the FHWA TNM 2.5 was released; all state transportation agencies are required to use it for all Federal funded projects by FHWA. TNM 2.5 has been modified from the previous versions to update the noise energy back to the source, and therefore influence the predicted insertion loss and absolute noise levels. The study was designed to compare the noise barrier design by both TNM 2.5 and TNM 2.0, as well as STAMINA 2.0. All these models were used to design noise barriers on the I-64 St. Louis, MO project with the length for the mainline of 11 mile.
Reducing the occlusion effect with active noise control
Authors: Ryan James G. , Rule Betty , Armstrong Stephen W
Published: May 2006

The occlusion effect refers to the build-up of low-frequency sound pressure in the ear canal when it is sealed by a hearing aid. Hearing aid wearers experiencing the occlusion effect often complain about the sound of their own voice. The traditional solution to this problem is to introduce a vent or opening through the hearing aid from the canal end to the faceplate. Unfortunately, the use of large vents, which is required for reducing occlusion, can result in significant feedback problems. This paper describes a solution for the occlusion problem that is based on active noise control techniques. This approach allows occlusion reduction without the feedback problems caused by large vents.
Diffusion of Green Fluorescent Protein in Three Cell Environments in
Escherichia Coli
Authors: Mullineaux Conrad W. , Nenninger Anja , Ray Nicola , Robinson Colin
Published: May 2006

Surprisingly little is known about the physical environment inside a prokaryotic cell. Knowledge of the rates at which proteins and other cell components can diffuse is crucial for the understanding of a cell as a physical system. There have been numerous measurements of diffusion coefficients in eukaryotic cells by using fluorescence recovery after photobleaching (FRAP) and related techniques. Much less information is available about diffusion coefficients in prokaryotic cells, which differ from eukaryotic cells in a number of significant respects. We have used FRAP to observe the diffusion of green fluorescent protein (GFP) in cells of
Escherichia coli
elongated by growth in the presence of cephalexin. GFP was expressed in the cytoplasm, exported into the periplasm using the twin-arginine translocation (Tat) system, or fused to an integral plasma membrane protein (TatA). We show that TatA-GFP diffuses in the plasma membrane with a diffusion coefficient comparable to that of a typical eukaryotic membrane protein. A previous report showed a very low rate of protein diffusion in the
E. coli
periplasm. However, we measured a GFP diffusion coefficient only slightly smaller in the periplasm than that in the cytoplasm, showing that both cell compartments are relatively fluid environments.
Ecf, an Alternative Sigma Factor from
Neisseria gonorrhoeae
, Controls Expression of
msrAB
, Which Encodes Methionine Sulfoxide Reductase
Authors: Gunesekere Ishara C. , Kahler Charlene M. , Ryan Catherine S. , Snyder Lori A. S. , Saunders Nigel J. , Rood Julian I. , Davies John K.
Published: May 2006

A DNA microarray was used to identify genes transcribed in
Neisseria gonorrhoeae
using Ecf, an alternative sigma factor. No differences between the transcriptional profiles of strain FA1090 and a mutant where
ecf
had been inactivated could be detected when both were grown in vitro. We therefore constructed a gonococcal strain in which Ecf can be overexpressed. Some differentially expressed genes are clustered with
ecf
on the genome and appear to form a single transcriptional unit. Expression of the gene encoding MsrAB, which possesses methionine sulfoxide reductase activity, was also dependent on Ecf, suggesting that the regulon responds to oxidative damage. Western blotting confirmed that the increased level of MsrAB protein is dependent on the presence of Ecf.