Search Results - (Author, Cooperation:R. E. Lee)

2012-03-03

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

4-Aminobenzoic Acid/chemistry/metabolism ; Amino Acid Sequence ; Anti-Bacterial Agents/chemistry/metabolism/*pharmacology ; Bacillus anthracis/drug effects/enzymology ; Biocatalysis ; Catalytic Domain ; Crystallization ; Crystallography, X-Ray ; Dihydropteroate Synthase/*chemistry/genetics/*metabolism ; Diphosphates/chemistry/metabolism ; *Drug Resistance, Bacterial ; Magnesium/chemistry ; Models, Chemical ; Models, Molecular ; Molecular Sequence Data ; Mutagenesis ; Parabens/chemistry/metabolism ; Protein Conformation ; Sulfamethoxazole/chemistry/metabolism/*pharmacology ; Sulfathiazoles/chemistry/metabolism/*pharmacology ; Yersinia pestis/drug effects/enzymology

2018-04-27

The American Society for Microbiology (ASM)

0066-4804

1098-6596

Biology

Medicine

1089-7550

AIP Digital Archive

Physics

Experimental 120-turn thin-film inductive heads have been built. The key features of this head are the 6-μm pitch helical coils and an omega-shaped, planar yoke structure having dual easy axes. Hardbaked photoresist insulator layers are used to encapsulate the yoke and to smooth out the wafer surface topography. Micro-Kerr studies show that the easy axis remains in the transverse direction in the yokes after multiple anneals. The P1/G/P2 is 3.8/0.3/3.8 μm, and the yoke length is close to 1 mm. The helical coils were built with a novel process that combines yoke/stud coplating and a photoresist planarization process. The coil resistance is 68Ω and the inductance is 5.5 μH. The yoke saturates at 5 mA. The heads were tested over disks having Mrt of 2.5 memu/cm2 and Hc of 1500 Oe. The write threshold current is 5.3 mA (peak-to-peak) and the overwrite is 30 dB. The isolated pulse amplitude Vpp is 10.3 μV/(TwV), where track width Tw is in μm and the linear velocity V in m/s.

Electronic Resource

0007-1269

Psychology

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1572-817X

Springer Online Journal Archives 1860-2000

Electrical Engineering, Measurement and Control Technology

Physics

Abstract Experiments were carried out to measure the optical coherence of an argon laser beam in tap water, distilled water, ocean coastal water and in processed water with 3% sodium chloride added. Measurements were made for water path lengths up to 2.9 m using two different procedures. The first was Young's experiment and the second involved an optical geometry common to the Laser Doppler Velocimeter. Results showed no degradation in the normalized degree of coherence over the measured distances. However, local changes in the index of refraction did cause the interference fringes to have some motion (approximately one-fourth of a fringe width). Tests were also carried out using the Laser Doppler Velocimeter in the back-scatter mode to measure the centre line velocity of a submerged jet. Results agreed very well with independent measurements.

Electronic Resource

1570-7458

cold tolerance ; freezing temperatures ; cold shock ; supercooling points ; overwintering ; Dalbulus maidis ; corn leafhopper ; Baldulus tripsaci ; Homoptera ; Cicadellidae

Springer Online Journal Archives 1860-2000

Biology

Abstract Little is known about how adults of the corn leafhopper,Dalbulus maidis (DeLong & Wolcott), and its congeners survive subfreezing temperatures at high elevations during the dry winter in Mexico. In the laboratory, duration of survival at −5°C was measured for four MexicanDalbulus species:D. maidis, D. elimatus (Ball),D. gelbus DeLong andD. quinquenotatus DeLong & Nault; and a closely related North American species,Baldulus tripsaci Kramer & Whitcomb. Adult leafhoppers reared under environmental conditions that simulated the beginning of the dry winter season during October in Mexico (‘October-reared’) were at least twice as tolerant of −5°C than adults reared under environmental conditions that simulated the beginning of the wet summer season during June (‘June-reared’).Dalbulus species found primarily at high elevations, such asD. elimatus, were seven times more tolerant of −5°C thanD. quinquenotatus, a species which overwinters at low to mid elevations on itsTripsacum hosts. October-rearedD. maidis adults survived relatively short periods at −5°C (LT50=8.9h) compared to October-rearedD. elimatus adults (LT50=42.3h). This suggests that in Mexico,D. maidis either overwinters in protected habitats at higher elevations or it migrates to lower, frost-free regions. October-rearedB. tripsaci adults, which overwinter in the egg stage, were intolerant of −5°C (LT50=2.6h). A conditioning period for 1 h at +5°C before and after exposure to −5°C significantly improved survival forD. maidis. Supercooling points (SCPs) were between −23 and −20°C, indicating that mortality of these leafhoppers at −5°C was due to cold shock injury rather than internal ice formation.

Electronic Resource

1420-9071

Space flight ; reproduction ; longevity ; insect

Springer Online Journal Archives 1860-2000

Biology

Medicine

Summary After 7 days of space flight house flies,Musca domestica, exhibited similar longevity, but a reduction in reproductive output as compared to earthbound controls. This reduction was not observed in later generations. These data suggest that space flight directly alters the rate of ovarian development, but that this effect is not genetically transmitted.

Electronic Resource

1432-1998

Springer Online Journal Archives 1860-2000

Medicine

Abstract Liposarcoma in childhood is rare. A case of a myxoid liposarcoma arising at the porta hepatis is reported in a 3-year-old boy with initial favourable response to surgery combined with radio- and chemotherapy. Fatal recurrence occurred at age 15 years. The radiological and sonographic findings of liposarcomas are reviewed.

Electronic Resource

1432-1998

Springer Online Journal Archives 1860-2000

Medicine

Abstract Osteogenic sarcoma arising in the spine, and in particular the neural arch, is rare. We present the case of a 4-year-old girl with an osteogenic sarcoma arising in the left transverse process of the second lumbar vertebra. The child received chemotherapy and delayed surgical excision was performed following a favourable response. The radiological features and differential diagnosis are discussed.

Electronic Resource

1420-9098

Springer Online Journal Archives 1860-2000

Biology

Resume Des taux élevés de fructose, de glucose et de tréhalose ont été mesurés chezPolistes exclamans etP. annularis après traitement par le froid. Par contre la présence de glycérol n'a été détectée qu'après un traitement prolongé au froid ou pendant le milieu de l'hiver. En février, le point de surgélation chezP. exclamans était descendu à −12,9° C, tandis que chezP. annularis une température de −10,7° C a été relevée après acclimatation au laboratoire à une température de 5° C et jamais moins de −6,8° C dans l'habitat naturel. En toutes circonstances, la congélation s'est révélée léthale chez lesPolistes adultes. Les ouvrières et les fondatrices-filles furent séparées en se basant sur l'aspect de leur corps graisseux. ChezP. exclamans, seulement 17 % (N=29) des fondatrices-filles et 76 % (N=45) des ouvrières moururent après une incubation à +5° C pendant 15 jours. Les fondatrices-filles survivantes avaient, dans leur hémolymphe, un taux élevé de fructose, qui joue donc un rôle antigel. Ces expériences démontrent qu'il existe une différence entre les ouvrières et les fondatrices-filles récoltées en automne et que l'aspect de leur corps graisseux vu à travers sa membrane est un indice de caste sûr. La réaction au froid des mâles était la même que celle des fondatrices-filles, indiquant ainsi que leur activité reproductrice de l'automne peut se prolonger en hiver.

Summary Elevated fructose, glucose and trehalose levels were found inPolistes exclamans andP. annularis after exposure to cold. Glycerol was found only after extensive exposure to cold or in mid-winter. InP. exclamans mean supercooling points (SCP) decreased to a low of −12.9° C in February. InP. annularis SCP were never below −6.8° C in the field, but laboratory acclimation at +5° C resulted in SCP of −10.7° C. Freezing was lethal to adultPolistes under all circumstances. Workers and future queens were separated on the basis of the appearance of their fat bodies. ForP. exclamans, only 17 % of the future queens died during 15 days at +5° C (N=29) while 76 % of the workers died during identical cold exposure (N=45). The surviving future queens had elevated cryoprotectant levels consisting mainly of fructose in their hemolymph, while the few workers that survived did not. These experiments indicate that there are physiological differences between workers and future queens inPolistes collected in autumn and that fat body appearance determined using non-invasive techniques is a reliable indicator of caste. Males were similar to future queens in their response to cold indicating that autumn mating activity may extend into winter.

Electronic Resource

1432-198X

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1615-6102

Extrusomes ; Protists ; Ejectisomes ; Gun cells ; Polar filaments ; Rhoptries ; K2 bodies ; Spermatial vesicles ; Adhesion vesicles

Springer Online Journal Archives 1860-2000

Biology

Summary The ultrastructural features, biogenesis and functions of several selected protist extrusive organelles are discussed. Most of the review focuses on some common extrusive organelles that were not considered by Hausmann and several types which have been described since that review of 16 years ago. For convenience, extrusomes are categorized as projectile or mucocyst extrusomes. The projectile extrusomes are further subdivided into non-penetrating and cell penetrating extrusomes. This review is restricted to projectile extrusomes such as ejectisomes, the microsporidian invasion apparatus, and the gun cell of oomycetes. Mucocysts include the apicomplexan rhoptries, the K2 bodies of oomycetes, and the spermatial vesicles and adhesive vesicles of red algae. The possible phylogenetic importance of some extrusive organelles is briefly considered.

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

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

Abstract The cathode fall region of the glow discharge contains fast electrons and fast ions which are accelerated in the electric field between the cathode and a plasma at near anode potential. When operated at low pressure and high voltage (i.e. on the left-hand branch of the Paschen breakdown curve), the fast electrons tend to form a mono-energetic group, although the ions, owing to relatively large cross-sections for interaction with the gas, have their energies spread over a wide range and also give rise to fast neutrals by charge exchange. Both types of particle can be efficiently brought out of the discharge through orifices placed in the electrodes. Thin or broad beams or sheets of particles, converging or diverging, can be designed over a wide range of current and voltage. At lower voltages, electron beams may be applied to a target placed within the discharge. As the voltage is increased, extracted electron beams become penetrating and can be manipulated magnetically outside the discharge. The gas pressure required for operation depends on the gas, the anode to cathode distance, and voltage and current. By appropriate design, operation at a pressure of about 100 μm or more can usually be arranged thus demanding only the simplest vacuum techniques. Both electron and ion beams may be applied to insulating materials as well as conducting materials. This is possible because electrical charging difficulties are avoided owing to the associated presence of ionised gas. A number of different types of glow discharge gun of novel design have been constructed and their characteristics investigated. This paper discusses the design principles employed and illustrates applications in the fields of crystal growing, vapour deposition, welding, thermal milling and etching and milling by sputtering.

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

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

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

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

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

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

Abstract Unidirectional and cyclic tensile stress-strain testing has been carried out on continuous tungsten fibre reinforced copper composites, with fibre diameter from 11 to 48 Μm at a volume fraction of 0.37. In tensile tests the composites showed positive deviations from the rule of mixtures, the amount increasing with a decrease in fibre diameter and, therefore, interfibre spacing. This matrix strengthening continued to failure and was shown to be related in part to the matrix grain size. In the cyclic stress-strain tests the matrix strengthening was approximately the same for all the composites and was greater than for the tensile tests. The strengthening could be accounted for by the formation of a substructure during cycling of approximately 0.5 Μm cell size.

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

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

Abstract The tensile microstrain behaviour of a series of magnesium-lithium alloys, with lithium contents up to 12.5 wt %, has been studied. The strain hardening exponents in the microstrain region were found to depend on the lithium content, the increase in which led to a change in crystal structure from hcp to bcc. The onset of cross-slip in the bcc alloys was found to sharply reduce the strain hardening capacity of the materials.

Electronic Resource

1573-4803

Springer Online Journal Archives 1860-2000

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

Abstract Cyclic stress-strain curves have been obtained for a series of magnesium-lithium alloys with lithium contents up to 12. 5wt%. The results show that the cyclic strain hardening exponents for stresses leading to failure in excess of 104 cycles are similar for all the alloys, even though the structure changes from h c p to b c c with increasing lithium content. This was attributed to similar deformation processes being involved in the materials at the microstrain levels involved in high endurance fatigue. There is a tendency for the plastic strain amplitude leading to failure at a given life to increase with lithium content. The accumulated work to failure for all the materials studied increases with fatigue life.

Electronic Resource

1432-136X

Freeze tolerance ; Sciatic nerve ; Osmotic stress ; Cryoprotection ; Frog, Rana sylvatica

Springer Online Journal Archives 1860-2000

Biology

Medicine

Abstract We investigated the restoration of peripheral nerve function and simple neurobehavioral reflexes in the freeze-tolerant wood frog (Rana sylvatica). Thirty-two specimens, allowed to freeze for 39 h and ultimately cooled to-2.2°C, were sampled at various time intervals up to 60 h after thawing at 5°C was initiated. The sciatic nerves of treated frogs were initially unresponsive to stimulation, but usually regained excitability within 5 h. Except for a slight reduction in nerve excitability characteristics of the compound action potentials of treated frogs were indistinguishable from those of control frogs. Recovery times for the hindlimb retraction and righting reflexes were 8 h and 14 h, respectively. Concentrations of the cryoprotectant glucose increased 8.2-fold in the sciatic nerve and 10.5-fold in the underlying semimembranosis muscle of treated frogs, and remained elevated for at least 60 h after thawing was initiated. These organs lost 47.2% and 15.9%, respectively, of their water during freezing, but were rehydrated within 2 h of the onset of thawing. The accumulation of glucose and the withdrawal of tissue water apparently are cryoprotective responses which enable this species to survive freezing.

Electronic Resource