Search Results - (Author, Cooperation:L. Barton)

2018-02-28

Genetics Society of America (GSA)

0016-6731

Biology

2018-10-02

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-09-04

Rockefeller University Press

0022-1007

1540-9538

Medicine

Infectious Disease and Host Defense

2015-01-17

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Acclimatization ; Agriculture/*history ; *Altitude ; Archaeology ; Climate ; History, Ancient ; Humans ; Radiometric Dating ; Temperature ; Tibet

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The possible importance of crop volume was investigated in a series of experiments in which the crop weights of and amounts of water imbibed by flies mounted on waxed sticks were determined at intervals during the 10-h period after the flies had been allowed to drink to repletion. The results of ...

Electronic Resource

1572-8889

blowfly ; mating ; sexual receptivity ; housing conditions

Springer Online Journal Archives 1860-2000

Biology

Abstract Sexual receptivity in sugar-and-water-fed females of the anautogenous blowfly Lucilia cuprinawas low when they had been housed in groups but high when they had been housed singly. Females were completely unreceptive on the second and third days after emergence, irrespective of housing conditions. There after receptivity increased but more rapidly in the singly housed females. Experiments in which females were housed singly for some days and then in groups, or vice versa, showed that receptivity could be influenced by housing conditions experienced both over the first 5 days after emergence and later in life.

Electronic Resource

1572-8889

Lucilia cuprina ; blowfly ; mating ; readiness to lay ; oviposition

Springer Online Journal Archives 1860-2000

Biology

Abstract Virgin females of Lucilia cuprinararely lay eggs, whereas mated females do so readily. This effect of mating is due entirely to increased readiness to lay, and not to any effect on ovarian development. An investigation was made of how readiness to lay was affected by matings which differed in terms of the male's chemical and mechanical contribution. Individual males were mated, during 1 day, to a succession of females whose readiness to lay was determined 1 or 8 days after mating. On both days, the proportion of females laying was inversely related to the number of females with which the male had previously mated. A high proportion of females that had mated with previously unmated or oncemated males laid at both 1 and 8 days after mating. However, this proportion tended to decline between day 1 and day 8 in females that had mated with males with two or more previous matings, and this effect was most evident in females mated with males that had previously mated with four or more females. When matings were manually terminated as soon as coupling had occurred, the proportion laying remained as low as in virgins. This proportion progressively increased as mating duration increased from 2 to 6 min. The proportion that laid after mating terminated at 6 or 8 min was as high as that for females from full-term matings (mean duration, 12.5 min). The results are generally similar to those obtained in parallel experiments on the effect of mating on sexual receptivity in this species and, therefore, indicate that the physiological bases for the two effects of mating might be the same.

Electronic Resource

1570-7458

Springer Online Journal Archives 1860-2000

Biology

Zusammenfassung Die Wirkung von DDT-Behandlung auf die elektrische Reaktion der Neuronen von chemorezeptorischen Labellenhaaren bei Reizung mit Kochsalz wurde bei Stubenfliegen (Musca domestica L.) eines DDT-resistenten (HR) und eines nichtresistenten Stammes (ES) untersucht. Das Eintauchen einzelner Rezeptorhaare in wässrige DDT-Suspensionen vor der Reizung und Registrierung der Neuronenaktivität durch einen Kochsalz-Elektrolyten bewirkte den Ersatz der normalen Einzelimpulse durch Gruppen von 2 oder mehr Impulsen bei beiden Stämmen. Bei dem resistenten Stamm steigerte sich die Reaktion — gemessen am mittleren Grade der Impuls-Vervielfachung — während der ersten 10–15 Minuten; danach zeigte signifikante Abnahme der Vervielfachung die Erholung der Neurone von den DDT-Wirkungen an. Bei nichtresistenten Fliegen zeigten die Neurone keine signifikante Erholung. Bevor die Erholung deutlich wurde, waren die Chemorezeptorhaare resistenter Fliegen — gemessen an der Konzentration der angewendeten Suspension — 3,9 bis 8,5mal weniger empfindlich gegen DDT als diejenigen der nichtresistenten Fliegen. Das Verhältnis steigerte sich infolge der Erholung in den nächsten 15 Minuten auf mehr als das 15fache. In einer Paralleluntersuchung der DDT-Vergiftung ganzer Fliegen der beiden Stämme wurden einzeln begiftete Fliegen nach dem Grade der Vergiftung geordnet, den sie zu verschiedenen Zeiten nach der Behandlung aufwiesen. Alle nichtresistenten Fliegen, bei denen deutliche Vergiftungserscheinungen auftraten, wurden zunehmend mehr beeinflußt und starben. Es überlebten nur diejenigen, bei denen klare Anzeichen einer Vergiftung zu keinem Zeitpunkt auftraten. Die resistenten Fliegen waren zu einer völligen Erholung von fortgeschrittenen Stadien der Vergiftung fähig. Bei Dosen, die einen gewissen Grad der Erholung gestatteten, stieg in Gruppen resistenter Fliegen der mittlere Grad der Vergiftung nur während der ersten Stunde an, dann fiel er wieder, sobald sich einige Fliegen erholten. Die Relationen — für die beiden Stämme — gleich giftiger Dosen zeigten, bevor die Erholung in Erscheinung trat, daß die resistenten Fliegen 2- bis 6mal weniger empfindlich gegen DDT-Begiftung waren als die nichtresistenten. Erholung der resistenten Fliegen vergrößerte die Relation auf das mehr als 15fache. So ergaben die Untersuchungen an Chemorezeptorhaaren und an ganzen Fliegen sehr ähnliche Werte für die relative Empfindlichkeit der Stämme gegenüber DDT-Begiftung und für das große Ausmaß, in welchem die Widerstandsfähigkeit der Fliegen des HR-Stammes von der Fähigkeit zur Erholung von DDT-Vergiftungen abhängt. Es kann gefolgert werden, daß die Resistenz der Fliegen des HR-Stammes gegenüber DDT vollständig ausgedrückt werden kann auf dem Niveau der chemorezeptorischen Haare auf ihren Labellen. Es wird vermutet, daß Dehydrochlorierung des DDT, welche vermutlich den Mechanismus der Erholung gestattet, auch mit geringerer Sensibilität dieses Stammes gegenüber DDT-Vergiftung in Verbindung gebracht werden kann.

Abstract Two characteristics of DDT-resistance in houseflies (Musca domestica L.), namely, a significantly higher threshold to DDT and the ability to recover from DDT-poisoning, were found to be detectable quantitatively at the level of the neurones of the labellar chemoreceptor hairs. Treatment of the chemoreceptor hairs with DDT resulted in replacement of the normal single impulses by groups of 2 or more. Hairs of resistant (HR) flies showed some recovery from this effect after 10–15 minutes, but those of non-resistant (ES) flies did not. Whole flies topically dosed with DDT solutions were rated for the degree of intoxication shown at various times after treatment. In the resistant strain, flies that survived began to recover from intoxication at about 1 hour, but no recovery was observed in the non-resistant strain. The ratios of equi-effective concentrations or dosages for the two strains were found to be very similar in the chemoreceptor hair and whole fly tests. Up to the onset of recovery they were between 3.9 and 8.5 for the hairs and between 2.0 and 6.0 for the whole flies. After recovery commenced, the ratios increased to more than 15 for both the hairs and the whole flies. It was concluded that the resistance of strain HR flies is fully expressed at the level of the chemoreceptor hairs on their labella, and is mainly due to the ability to recover from DDT-poisoning.

Electronic Resource

1570-7458

Musca domestica ; feeding ; sex ; reproductive state

Springer Online Journal Archives 1860-2000

Biology

Résumé Les choix alimentaires de 3 catégories de M. domestica: femelles n'ayant pas consommé de protéines, femelles à ovaires développés alimentées sur protéines, mâles n'ayant pas consommé de protéines, ont été examinés par leur absorption de solutions dans une paire de ‘potomètres’. Elles avaient le choix entre, d'une part une solution de sucrose et, d'autre part une solution de L. leucine ou d'un tampon de phosphate de soude. Pour les expériences où les femelles non préalablement alimentées sur protéines ne présentent aucune préférence, les femelles alimentées sur protéines et les mâles préfèrent nettement la solution de sucrose. Les résultats montrent que les femelles non alimentées sur protéines répondent plus que les femelles mûres et les mâles à la fois à la solution de L. leucine et au tampon de phosphate qu'au sucrose. Ceci suggère que l'impulsion sensorielle provoquée par ces deux breuvages est perçue par les femelles n'ayant pas consommé de protéines comme un indicateur d'aliments indispensables au développement ovarien.

Abstract Comparisons were made of the preferences shown by non-protein-fed females, protein-fed gravid females, and non-protein-fed males of the house fly, given choices between sucrose solution and either l-leucine or sodium phosphate buffer. In choice tests where non-protein-fed females showed little preference, protein-fed females and males both showed a strong preference for the sucrose solution. The findings suggest that l-leucine and sodium phosphate buffer are recognised by non-protein-fed females as indicators of nutrients for ovarian development.

Electronic Resource

1570-7458

Lucilia cuprina ; Diptera ; Calliphoridae ; oocyte resorption

Springer Online Journal Archives 1860-2000

Biology

Résumé Chez Lucilia cuprina Wied., le nombre d'ovarioles, et ainsi le nombre maximum d'oeufs développés au cours de chaque cycle ovarien, est une fonction linéaire de la taille de l'adulte (largeur de la tête). La largeur moyenne de la tête des femelles de la nature est 3 mm (2,3 à 3,5) et la fécondité potentielle moyenne par cycle de 232 oeufs (111 à 318). La fécondité réelle est influencée par la qualité et la quantité de protéines dans le régime alimentaire. Toutes les femelles de la nature semblent avoir les mêmes exigences minimales en protéines pour la maturation des ovocytes, c'est à dire que quelle que soit leur taille (fécondité potentielle) les femelles doivent obtenir les protéines suffisantes à la formation d'au moins 110 ovocytes pour devenir gravides. Les femelles dont l'absorption de protéines dépasse ce minimum, mais est insuffisant pour permettre la maturation de la totalité de leurs ovocytes, en résorbent quelques uns et conduisent à maturité le reste. Puisque la fécondité potentielle augmente avec la taille des mouches, les grosses femelles résorbent plus d'ovocytes que les petites avec un régime suboptimal en protéines, c'est à dire que la proportion d'ovocytes résorbés augmente avec la taille des mouches. Dans les conditions de la nature, la totalité des ovocytes parvient rarement à maturité, ce qui indique une limitation générale en aliments riches en protéines. La réduction moyenne de la fécondité chez les femelles de la nature a été au cours de cette étude de 53.4 oeufs par cycle (23,2%).

Abstract In the Australian sheep blowfly, Lucilia cuprina, the number of ovarioles, and hence the maximum number of eggs developed in each ovarian cycle, is a linear function of adult size (headwidth). Field females have a mean headwidth of 3.0 mm (range=2.30–3.50 mm) and a mean potential fecundity/cycle of 232 eggs (range=111–318 eggs). Realised fecundity is influenced by the quality and amount of protein in the adult diet. All field females appear to have the same minimum protein requirement for egg maturation, i.e., whatever their size (potential fecundity) females must obtain sufficient protein to mature at least 110 eggs in order to become gravid. Females whose protein intake exceeds this minimum but falls short of the amount needed for maturation of their full egg complements resorb some of their oocytes and mature the remainder. Since potential fecundity increases with fly size, large females resorb more oocytes than small females under suboptimal protein regimes, i.e., the proportion of oocytes resorbed increases with fly size. Under field conditions, females rarely matured full complements of eggs, which indicates a general shortage of protein-rich material. The mean reduction in fecundity of field females during these studies was 53.4 eggs/cycle (23.2%).

Electronic Resource

1570-7458

Lucilia cuprina ; blowfly ; autogenous ; anautogenous ; survival ; food deprivation ; females

Springer Online Journal Archives 1860-2000

Biology

Résumé La grande majorité des femelles de L. cuprina est anautogène. Cependant, l'observation de femelles autogènes dans la nature, et la sélection au laboratoire d'une lignée autogène à partir d'une souche anautogène indique que cette espèce est susceptible de devenir autogène. Le stade de développement ovarien des femelles capturées dans la nature montre que l'habitat est généralement carencé en aliments riches en protéines susceptibles de permettre le développement ovarien de L. cuprina. Dans de telles conditions, les femelles autogènes devraient être avantagées; leur très grande rareté indique que certains désavantages doivent être associés au génotype autogène. On a constaté que les femelles autogénes qui viennent d'émerger ont une teneur en eau plus faible que les anautogènes; ceci suggère que l'un des coûts possibles de l'autogénie pourraît être une aptitude réduite à supporter les périodes de privation d'eau suivant l'émergence. Pour cette raison, la survie de femelles sauvages anautogènes a été comparée à celles de lignées autogènes sélectionnées au laboratoire, en absence de sucrose, en présence ad lib. de sucrose, ou sans eau ni sucre. Pouvues uniquement de sucrose, les femelles anautogènes survivent 12 heures de plus que les autogènes, tandis qu'en présence exclusive d'eau les femelles autogènes survivent 19 heures de plus. En absence de sucrose et d'eau les femelles anautogènes survivent environ 5 heures de plus. Il semble que la mortalité des femelles autogènes privées totalement d'aliments est due principalement à un stress hydrique, tandis que le sucrose et le stress hydrique ensemble paraissent jouer un rôle dans la mort des femelles anautogènes. Ces résultats montrent que l'autogénie des femelles peut être un désavantage lors des conditions sèches fréquentes dans l'aire de cette espèce.

Abstract The vast majority of wild-type females of Lucilia cuprina are anautogenous. The survival of wild-type anautogenous females following emergence was compared with that of females from laboratory-selected autogenous strains, when deprived of sucrose and given ad lib access to water, deprived of water and given ad lib access to sucrose, or deprived of both water and sucrose. Anautogenous females survived substantially longer than autogenous females when only sucrose was supplied, but the opposite applied when the flies were supplied with water only. Anautogenous females survived somewhat longer than autogenous females in the absence of both sucrose and water. Thus, autogenous females might be at a disadvantage in the dry conditions which often prevail in areas occupied by the species.

Electronic Resource

1570-7458

Sheep blowfly ; Lucilia cuprina ; readiness to lay ; oviposition site-deprivation ; egg-load

Springer Online Journal Archives 1860-2000

Biology

Résumé L'effet de la privation de lieu de ponte a été étudié en comparant les pontes de femelles isolées ayant formé leurs œufs mûrs dans les 24 heures précédentes, à celles de femelles ayant atteint leur maturité sexuelle 8 jours avant. La rétention ovocytaire est provoquée en faisant consommer aux femelles de cette espèce anautogène différentes quantités d'aliments riches en protéines. La ponte de femelles dont le contingent total de leurs ovocytes s'est développé, — c'est-à-dire 260 —, après consommation ad libitum de foie de mouton pendant 48 heures, a été comparée à celle de femelles ayant formé 190 ovocytes mûrs après ingestion d'une quantité limitée de jus de foie. Dans des expériences sans choix, les femelles isolées de différences catégories ont eu accès pendant 4 heures au substrat de ponte trempé: 1) dans du jus de foie, 2) dans du jus dilué 16 fois, 3) dans du jus de foie non dilué mais contenant NaCl (inhibiteur de la ponte) à la concentration de 2 M. Le jus non dilué a provoqué une forte stimulation, induisant la ponte de 80% des femelles. Le jus dilué et celui contenant NaCl n'ont induit la ponte que de 40% des femelles avec des niveaux de stimulation bien plus faibles. La date d'introduction du lieu de ponte et le taux de rétention des ovocytes mûrs n'ont eu auçun effet sur la proportion de femelles réagissant à ces 3 types de stimulation.

Abstract Oviposition by Lucilia cuprina Wiedemann (Diptera, Calliphoridae) was examined in relation to period of oviposition site-deprivation and egg-load. Effects of oviposition site-deprivation were examined by comparing oviposition performance of individual females that had matured their batch of oocytes within the previous 24 h with that of females which had reached ovarian maturity 8 days previously. Egg-load was manipulated by causing females of this anautogenous species to consume different amounts of protein-rich material. In no-choice experiments, individual females of the different categories were given access for 4 h to oviposition substrate, soaked with (i) liver exudate, (ii) the exudate diluted 16-fold or (iii) the undilated exudate containing the oviposition deterrent sodium chloride at a concentration of 2 M. These solutions elicited oviposition from different proportions of females, but neither these proportions, nor the interval between introduction of the oviposition site and the initiation of oviposition, was significantly affected by the period of oviposition site-deprivation or the number of eggs matured by the females.

Electronic Resource

2018-01-11

American Physical Society (APS)

1098-0121

1095-3795

Physics

Magnetism

2018-12-06

American Physical Society (APS)

1539-3755

1550-2376

Physics

Statistical Physics

1089-7666

AIP Digital Archive

Physics

A nominally plane turbulent jet is synthesized by the interactions of a train of counter-rotating vortex pairs that are formed at the edge of an orifice by the time-periodic motion of a flexible diaphragm in a sealed cavity. Even though the jet is formed without net mass injection, the hydrodynamic impulse of the ejected fluid and thus the momentum of the ensuing jet are nonzero. Successive vortex pairs are not subjected to pairing or other subharmonic interactions. Each vortex of the pair develops a spanwise instability and ultimately undergoes transition to turbulence, slows down, loses its coherence and becomes indistinguishable from the mean jet flow. The trajectories of vortex pairs at a given formation frequency scale with the length of the ejected fluid slug regardless of the magnitude of the formation impulse and, near the jet exit plane, their celerity decreases monotonically with streamwise distance while the local mean velocity of the ensuing jet increases. In the far field, the synthetic jet is similar to conventional 2D jets in that cross-stream distributions of the time-averaged velocity and the corresponding rms fluctuations appear to collapse when plotted in the usual similarity coordinates. However, compared to conventional 2D jets, the streamwise decrease of the mean centerline velocity of the synthetic jet is somewhat higher (∼x−0.58), and the streamwise increase of its width and volume flow rate is lower (∼x0.88 and ∼x0.33, respectively). This departure from conventional self-similarity is consistent with the streamwise decrease in the jet's momentum flux as a result of an adverse streamwise pressure gradient near its orifice. © 1998 American Institute of Physics.

Electronic Resource

1089-7658

AIP Digital Archive

Mathematics

Physics

It is shown that the interaction part of the symmetric energy-momentum tensor for a system of charged particles is integrable over any forward light cone. A covariant definition of the mechanical momentum is then given and conservation of momentum is shown.

Electronic Resource

1089-7658

AIP Digital Archive

Mathematics

Physics

It is shown that the interaction part of the electromagnetic angular momentum density of a system of charged particles is integrable over any forward light cone. A covariant definition of the mechanical momentum is then given and it is shown that angular momentum is conserved.

Electronic Resource

1089-7658

AIP Digital Archive

Mathematics

Physics

The electromagnetic linear and angular momenta are defined as an integral of the appropriate density over a forward lightcone. It will be shown how to relate the electromagnetic momenta, for a system of charged point particles, as an integral over finite segments of each world line. Other treatments of this problem, where the momenta is defined as the integral over a spacelike hyperplane, require the integral over infinite segments of the world lines. In general, these integrals diverge for point particles. However, the integrals over the forward lightcones are finite. Several examples are worked.

Electronic Resource

1550-7408

Blackwell Publishing Journal Backfiles 1879-2005

Biology

SYNOPSIS. Experimentally induced precystic stages and mature cysts from 3 clones of Tetrahymena rostrata were examined by light and electron microscopy. It was demonstrated by cytochemical staining and fine-structural observations that precystic stages release mucocyst material that provides for the production of a cyst wall. Early and late cysts also contain numerous autophagous vacuoles. In late cysts there is a replacement of depleted mucocyst organelles. The developmental evidence obtained from sampling of sequential developmental stages suggests an ∼24-h timetable of cytoplasmic events associated with encystment in this organism.

Electronic Resource

1089-7658

AIP Digital Archive

Mathematics

Physics

In the early 1950s, Lundquist showed the significance of electromagnetic fields with a vanishing Lorentz force density to magnetohydrostatic fluids. Today, these fields are known as force-free electromagnetic fields. Later that decade, Lüst and Schlüter demonstrated that cosmic magnetic fields are force-free and Chandrasekhar and Kendall then constructed a large class of force-free fields whose electric charge density field is also vanishing. In this article, we constructed force-free fields without assuming that the electric charge density vanishes, and in some cases we established a connection between force-free fields and nonlinear Schrödinger equations. © 2002 American Institute of Physics.

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