bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid phase endocytosis investigated by fluorescence with trimethylamino‐diphenylhexatriene in L929 cells; the influence of temperature and of cytoskeleton depolymerizing drugs
Authors: Illinger Dominique , Poindron Philippe , Kuhry Jean‐Georges
Published: February 2003

Summry— The temperature‐dependence of fluid phase endocytosis was investigated in L929 cells, using a recently described fluorescence approach with trimethylamino‐diphenylhexatriene (TMA‐DPH) [7, 9]. In interaction with cells, this probe is rapidly incorporated into the plasma membrane and follows its intracellular traffic of internalization‐recycling, thus behaving as a suitable marker for fluid phase endocytosis. The kinetics of the process may be followed accurately by simple fluorescence intensity measurements, while complementary fluorescence anistropy and micrographic data may be obtained in parallel with the same probe. It was shown that the formation of endocytic vesicles was not inhibited by cooling the cells, even down to 4°C, but only reduced in a quasi‐linear way with temperature. Conversely the further fusion events between the vesicle and large vacuular bodies (endosomes, lysosomes) were strongly and discontinuously influenced: they were almost totally suppressed below 15°C. The evolution of the membrane fluidity during endocytosis, which was monitored by fluorescence anisotropy measurements, indicated that the fusion inhibition was probably correlated with the inability of the endocytic vesicles to shed their initial clathrin coat at low temperature. Moreover, microscopic observations showed that at low temperature the endocytic vesicles hardly moved from the place of their formation. Pretreatment of the cells with microtubule and microfilament depolymerizing drugs (cytochalasin B, vinblastin) led to the conclusion that the cytoskeleton played little role in the vesicle movements. Altogether, the results suggested that the progression of the vesicles towards the cell core resulted from successive fusion events, which explained why they were considerably showed down by cooling.
The intramembranous particles of resting and secreting gastric (H+, K+)‐ATPase membranes*
Authors: Péranzi Gabriel , Bayle Denis , Lewin Miguel J.M. , Soumarmon Annick
Published: February 2003

Summry— The fundic mucosa of resting and acid‐secreting rabbit stomachs were freeze‐fractured and replicated to compare the intramembranous particles on the parietal cell tubulovesicles (rest) and canaliculus (secretion). The particles were counted and their shadow diameters were measured using an image analysis program. The tubulovesicles bore 9 726 ± 400 particles per μm2 (mean ± SD), having a mean diameter of 8.4 nm (n = 2571). The canaliculus bore 8 369 ± 430 particles per μm2, having a mean diameter of 7.7 nm (n = 3259). The data were reproducible: three fractures of tubulovesicles and canaliculus gave essentially the same distributions of particle diameters. By contrast, the frequency distributions of tubulovesicle and of canaliculus particle diameters were significantly different (P < 0.0005). Neither the opposite curvatures of tubulovesicle and canaliculus microvillus fractures nor subpopulations populations of tubulovesicles with different particle diameters, were the cause of the difference, since there was only one population of tubulovesicles. We therefore postulate that the diameters of intramembranous particles of tubulovesicles and canaliculus are different and suggest, as a working hypothesis, that the difference could be due to a conformational change of the major intramembranous protein, the (H+, K+)‐ATPase.
Establishment of endometrial glandular epithelial cell subculture in a serum‐free, hormonally defined medium, on a basement membrane matrix
Authors: Mahfoudi Abderrahim , Nicollier Monique , Propper Alain Y. , Coumes‐Marquet Sylvianne , Adessi Gérard L.
Published: February 2003

Summary— Epithelial glands were isolated from guinea‐pig endometrium. In order to reduce the requirement for a serum supplement and the contamination by non epithelial cells in primary culture, various coatings of the culture dishes were tested using serumfree Ham's F12 containing defined chemicals including 17β‐estradiol. while epithelial glands seeded on culture dishes coated with Matrigel, a basement membrane matrix‐failed to spread, they formed on poly‐d‐lysine plus serum‐coated dishes, a subconfluent monolayer (5–7 days) enriched in cytokeratin‐immunostained cells (78%). Cells from subconfluent primary cultures, obtained on poly‐d‐lysine plus serum‐coated dishes in serum‐free hormonally defined medium, were passaged on Matrigel‐coated dishes in serum‐free hormonally defined medium. These subcultures contained, at confluence (4–5 days), a high percentage (> 95%) of cytokeratin‐immunostained cells. These monolayers consisted of well‐differentiated cells which exhibited ultrastructural features characteristics of endometrial epithelial cells. Moreover, these confluent cells contained 50% immunostained nuclei for progesterone receptors. Progesterone receptor amounts decreased in confluent subcultures treated with progesterone and became undectable after longterm treatment, suggesting responsiveness of these cells to progesterone. This culture system provides a well‐defined model for the study of protein synthesis and secretion by endometrial glandular cells under hormonal control.
Immunogold labelling of arabinoxylans in the plant cell walls of normal and bm3 mutant maize
Authors: Barry Patrick , Prensier Gérard , Grenet Elisabeth
Published: February 2003

Summary— Polyclonal antibodies directed against α, l‐1.2‐arabinofuranosyl poly‐β,d‐1.4‐xylopyranosyl (degree of polymerization 130) have been raised from rabbits. The immunogold labelling in transmission electron microscopy (TEM) evidenced the arabinoxylans of the plant cell walls. Comparison between the stems of normal and mutant bm3 maize demonstrated a greater accessibility of arabinoxylans in the walls of the mutant maize. The method, specific and swift, allows us to specify the repartition in the different parts of the stem: sclerenchyma, fibers, parenchyma.
Light responses of shade-tolerant tropical tree species in north-east Queensland: a comparison of forest- and shadehouse-grown seedlings
Authors: Bloor Juliette M. G.
Published: February 2003

Shadehouse design may have a significant influence on the results of shadehouse studies investigating the light responses of tropical seedlings. Shadehouse effects were investigated by examining the seedling growth and morphological properties of four shade-tolerant tree species from north-east Queensland in the forest and in neutral-density shadehouses for up to 1 y. Understorey plots were compared with 0.8% shadehouses, and single-treefall gaps were compared with 10% shadehouses. Seedlings of all species showed higher growth rates in the shadehouses compared with the equivalent forest treatments. Nonetheless, trends found between high- and low-light growth rates in the shadehouse seedlings were mirrored in forest-grown seedlings. Specific leaf area (SLA) values in the shadehouses provided a good approximation of SLA in the forest for species in both light treatments. In contrast, biomass allocation and leaf area ratios were only comparable for forest and shadehouse seedlings grown in the high-light treatment. Furthermore, seedlings grown in shadehouses differed significantly from forest-grown seedlings in terms of their root morphology. Despite the differences in absolute values of plant characters in the shadehouse and forest seedlings, 65% of significant differences detected between high- and low-light plant characters in shadehouse-grown seedlings were also found in the forest-grown plants.
Seasonal effects on soil organic carbon dynamics in a tropical deciduous forest ecosystem in western Mexico
Authors: García-Oliva Felipe , Sveshtarova Biserka , Oliva Magdalena
Published: February 2003

Our study examines the effect of seasonal rains on soil organic C dynamics in a tropical deciduous forest ecosystem in Western Mexico. At the end of the wet season, an accumulation of labile nutrient forms developed and was maintained during the dry season. This accumulation enhances microbial activity in the first rains of the wet season. For example, the litter samples of the dry season had a higher C and N mineralization than those of the wet season. Similarly, the January soil samples had higher C mineralization than October soil samples (55 and 34 μg C g-1 d-1, respectively). These results suggest that the quality of C is strongly affected by the seasonality of rains, which in turn influences microbial activity. This seasonality also influences nutrient redistribution between soil aggregate fractions. Chemical changes across seasons suggest that soil organic matter associated with macro-aggregates represents the main source of energy for microbial activity at the beginning of the wet season, while micro-aggregates protect the labile nutrient forms during the growing season.
Evidence for seed dispersal by the catfish Auchenipterichthys longimanus in an Amazonian lake
Authors: Mannheimer Simone , Bevilacqua Gabriela , Caramaschi Érica P. , Rubio Scarano Fábio
Published: February 2003

The annual flood pulses of central Amazonian rivers
inundate marginal forests to 10 m depth or more (Furch &
Otto 1987, Junk et al. 1989). The regularity of this
flooding seems to have promoted the development of a
complex relationship between forest plants and fishes that
consume their seeds (Goulding 1980). Several fish species
migrate into the flooded forests to feed on buoyant fruits
and seeds, and many plant species reach their fruiting
peak during the flood season. Fruits and seeds have been
reported to have adaptive features related to water
(hydrochory) and/or fish (ichthyochory) dispersal
(Araújo-Lima & Goulding 1998, Gottsberger 1978,
Goulding 1980, Kubitzki & Ziburski 1994, Scarano 1998,
Williamson 1999, Williamson & Costa 2000). Strong
multicuspidate teeth in frugivorous fishes, fruit/seed buoyancy
(Goulding 1980) and chemical signs released by
fallen fruit to attract fish (Araújo-Lima & Goulding 1998)
are mechanisms for the seed dispersal of the flooded forest community.
St Anthony's gift
Authors: BURGEN ARNOLD
Published: February 2003

Numerous outbreaks of a disease whose most prominent effects were gangrene and loss of limbs occurred in Europe in the Middle Ages. Sufferers sought relief at the shrine of St Anthony at Vienne in France. Quite early, it was recognized that the disease was a poisoning due to the consumption of bread prepared from rye contaminated with the fungus ergot. Many interesting substances have been isolated from ergot, some of which are used in medicine in migraine and in childbirth, but the most dramatic substance derived from ergot is LSD. The circumstance of some of these discoveries is recounted.
Jewish intellectual life and German scientific culture during the Weimar period: the case of the Kaiser Wilhelm Society
Authors: MARKL HUBERT
Published: February 2003

Weimar Germany was a great period in scientific development in which Jews played a prominent role. However, Nazi anti-Jewish policies led to the dismissal of many staff members and directors of the institutes of the Kaiser Wilhelm Society, who were forced to go abroad. In their new environment they became major leaders in science – notably in the new branches such as molecular biology – with a continuing loss to Germany.
Scare stories. Or some arguments for providing journalism with a licence to think
Authors: MEYER GITTE
Published: February 2003

Journalists are often blamed for producing scare stories. It seems to have been forgotten that many, perhaps most, modern scare stories are based on scientific risk calculations, and that journalists are not trained in scaring the wits out of people in that particular way. A more precise accusation might be that journalists are eager, unthinking and unquestioning conveyors of results from scientific risk calculations. Calculation of risk has become an important research product; a product fitting nicely into conventional journalistic storytelling, but the concept of risk tends to dilute value disagreement and conflict of interests into seemingly purely factual issues, leaving little room for political debate. Moreover, the cargo attitude of journalism is in conflict with the journalistic ideal of critical investigation and analysis on behalf of the public to stimulate common deliberation in the public sphere. Apparently, the production of scientific knowledge is excluded from the public sphere. Regarding discussions on science and technology, journalists will have to enquire into aspects of facts, values and social interests to live up to the ideal of investigation on behalf of the public. Several obstacles along this path can be identified, one of them being the commercialization of journalism in the media-industry and of scientific research in the knowledge-industry. Universities, in the search for a meaning of life, might consider providing a home for independent, reflexive journalism on science in a social context.
In whom can we trust?
Authors: ZIMAN JOHN
Published: February 2003

People need socially accredited but disinterested experts to give them reliable advice about risks. Traditionally, this role has been performed by academics, but academia is coming increasingly under the influence of commercial and political interests. How can ‘post-academic’ science be shaped to sustain its vital role as an independent organ of civil society?
Literary representations of risk: terror, crime and punishment
Authors: FOKKEMA DOUWE
Published: February 2003

All forms of terror seem to aim at the destruction of the individual experience and judgement of people. Part of our world is threatened by political terror (as represented first by Dostoevsky) or ethnic and cultural terror (as convincingly described by J. M. Coetzee), but it seems possible, at least in principle, to find an answer to these threats. Is religion the primary remedy against nihilism and, therefore, also against terrorism as Dostoevsky believes? Or is the quasi or semi-autonomous self the major antagonist of terrorism? The genetic manipulation of the human race, as sketched by Michel Houellebecq in his novel Les Particules élémentaires (1998), holds a threat that is irreversible. The cloning of human beings, which supposedly offers a solution to many of our problems, seems too high a risk to take.
Impacts of varying habitat quality on the physiological stress of spotted salamanders (Ambystoma maculatum)
Authors: Newcomb Homan Rebecca , Regosin Jonathan V. , Rodrigues Daniel M. , Reed J. Michael , Windmiller Bryan S. , Romero L. Michael
Published: February 2003

We sampled blood from free‐living spotted salamanders (Ambystoma maculatum) to test whether differences in the concentrations of a stress hormone (corticosterone) were associated with different qualities of breeding and migration habitat. Spotted salamanders are forest specialists that migrate to vernal pools to breed, and upland habitat degradation may have sub‐lethal effects on animals that lead to population declines. An individual's level of physiological stress may function as a biomonitor for sub‐lethal effects, and thus as a biomonitor for ecosystem quality. We compared unstressed (baseline) and stress‐induced corticosterone concentrations in spotted salamanders: (1) at sites that differed in amount of forest loss; (2) during breeding migration across forest habitat versus pavement; (3) in microhabitats that varied in soil drainage and canopy cover. Removal of large amounts of terrestrial habitat surrounding a breeding pond was correlated with lower baseline (in males) and stress‐induced corticosterone concentrations, which may indicate healthy individuals with a reduced ability to respond to additional stress or individuals experiencing chronic stress. Male salamanders migrating across pavement had elevated baseline corticosterone concentrations compared to animals migrating through a forest, consistent with an acute stress response. However, concentrations of corticosterone did not differ between individuals in microhabitats with canopy cover and well‐drained soil versus those in microhabitats with no canopy cover and/or swampy soil. This endocrinological technique may be one useful measure of a population's health, helping to identify populations where further ecological study is recommended to evaluate conservation concerns.
Why sparrow distributions do not match model predictions
Authors: Jenkins Clinton N. , Powell Robert D. , Bass Oron L. , Pimm Stuart L.
Published: February 2003

A companion paper in this issue describes the mapping of Cape Sable seaside sparrow (Ammodramus maritimus mirabilis) habitat using satellite imagery. In general, those maps are correct. However, testing against an independent survey of the sparrow population does identify errors. Those errors fall into two categories, model errors and bird errors. The model errors result from genuine problems with the model. More interesting for conservation are the bird errors, which are more numerous. They are of two types. (1) Commission errors: some suitable habitat does not contain birds. These are areas where prior events have depleted sparrow numbers, but because the sparrows do not disperse long distances, they cannot occupy it quickly. (2) Omission errors: some birds remain in unsuitable habitat that was formerly suitable. This results from the sparrow's very high site fidelity. Often, they will not leave an area even when it is no longer suitable. The consequences of these bird errors are that some habitat and some birds are not contributing to the species' survival. Thus, an estimate of only the amount of habitat or only the sparrow population may present an overly optimistic view of the sparrow's plight.
Biological determinants of extinction risk: why are smaller species less vulnerable?
Authors: Cardillo Marcel
Published: February 2003

It is becoming increasingly clear that species of smaller body size tend to be less vulnerable to contemporary extinction threats than larger species, but few studies have examined the mechanisms underlying this pattern. In this paper, data for the Australian terrestrial mammal fauna are used to ask whether higher reproductive output or smaller home ranges can explain the reduced extinction risk of smaller species. Extinct and endangered species do indeed have smaller litters and larger home ranges for their body size than expected under a null model. In multiple regressions, however, only litter size is a significant predictor of extinction risk once body size and phylogeny are controlled for. Larger litters contribute to fast population growth, and are probably part of the reason that smaller species are less extinction‐prone. The effect of litter size varies between the mesic coastal regions and the arid interior of Australia, indicating that the environment a species inhabits mediates the effect of biology on extinction risk. These results suggest that predicting extinction risk from biological traits is likely to be a complex task which must consider explicitly interactions between biology and environment.
Influence of excited singlet absorption on output power of cw dye lasers
Authors: Teschke O. , Dienes A.
Published: February 2003

The effects of the absorption of the pump light by the first excited singlet state on the output of a Rhodamine 6G cw dye laser are investigated. Experimental results show a change in the incremental photon efficiency with pump wavelength. Theoretical expressions are derived for the output power, including the effects of excited state absorption. By matching experimental and theoretical results, values for the excited state absorption cross sections are found at four different wavelengths.
High−sensitivity optical recording in KTN by two−photon absorption
Authors: von der Linde D. , Glass A. M. , Rodgers K. F.
Published: February 2003

Birefringence changes are induced in a cubic potassium tantalate niobate crystal with an external electric field by two−photon absorption of picosecond optical pulses. The recording sensitivity of 100 μJ/cm2 for elementary holograms with a few percent reconstruction efficiency is comparable to the sensitivity of holographic silver halide emulsions. The high sensitivity of KTN is shown to be due to efficient charge transport of photoexcited carriers.
Linear and nonlinear optical properties of lithium perchlorate trihydrate LiClO4⋅3H2O
Authors: Bergman J. G. , Williams Denise , Crane G. R. , Storey R. N.
Published: February 2003

Lithium perchlorate trihydrate (LiClO4⋅3H2O) is shown to be nearly noncritically phase matchable for a 0.53-μ pump, generating ultraviolet at 0.265 μ. The water white crystals are transparent out to 2100 Å. The nonlinear coefficients d33, d31, and d15 are (±0.79, ±0.68, ±0.77) ×d11(SiO2), respectively.
Nondestructive refractive-index profile measurements of clad optical fibers
Authors: Marhic M. E. , Ho P. S. , Epstein M.
Published: February 2003

An interferometric method in conjunction with Abel inversion is used to precisely measure the index of refraction profile of clad optical fibers without perturbing them. The sample is immersed in index-matching fluid, so that fiber index variations cause only small phase shifts for rays propagating perpendicular to the axis, making interferometric methods applicable.
Optimum diffusion condition in the fabrication of a plastic lenslike medium
Authors: Iga K. , Yokomori K. , Sakayori T.
Published: February 2003

The optimum fabrication condition has been found in the preparation of a plastic lenslike medium which has a parabolic dielectric constant distribution. The maximum possible value of the focusing constant g=0.21 mm−1 was obtained for diallyl isophthalate–methylmethacrylate combination with a rod radius r0=1.5 mm.
Comment on ’’Dynamic model of high-pressure rare-gas excimer lasers’’
Authors: Gerardo J. B. , Johnson A. Wayne
Published: February 2003

The model of the rare-gas excimer lasers that was recently proposed by Werner et al. is shown to be inconsistent with some experimental measurements of xenon dimer laser gain and laser intensity. Measurements of the laser intensity and laser-medium gain of a xenon dimer laser show that the laser pulse terminates well before the laser-medium gain falls below the prelasing losses of the optical resonator. The measured value of the stimulated-emission cross section for the xenon dimer laser is (1.05±0.2) ×10−25 A cm2 at 1720 Å, where A is the transition probability of the upper energy level of the laser.
Avalanche photodiodes with a gain-bandwidth product of more than 200 GHz
Authors: Berchtold K. , Krumpholz O. , Suri J.
Published: February 2003

The design and characteristics of avalanche photodiodes with a gain-bandwidth product in the range of 250 GHz are reported. The planar front-illuminated silicon diodes are of the n+-p-π-p+ reach-through type.
Residual defects in Si produced by recoil implantation of oxygen
Authors: Moline R. A. , Cullis A. G.
Published: February 2003

The defect structures remaining in Si wafers after implantation of O+ and As+ ions together with subsequent annealing treatment have been studied using the transmission electron microscope. For implantation of 1016 150-keV As+/cm2 through 430 Å of SiO2 and subsequent annealing at 1000 °C in dry N2, the resulting defect structures show many similarities to those obtained following a 1–2×1016 10-keV O+/cm2 implantation and annealing sequence. However, if 150-keV As+ ions are implanted into bare Si, the general lattice disorder remaining after annealing is much smaller and the residual defects are much more widely spaced. The differences between the residual defects produced by the different As+ implantations are interpreted with the proposal that the recoil of oxygen from SiO2 is an important by-product of implantations through SiO2 layers.
Holographic microinterferometry of laser-produced plasmas with frequency-tripled probe pulses
Authors: Attwood D. T. , Coleman L. W. , Sweeney D. W.
Published: February 2003

Holographic microinterferometry is used to study plasmas produced by high-intensity subnanosecond pulses from a Nd laser. The probing pulse is frequency tripled to 3547 Å in order to reduce refractive errors due to steep density gradients and to reduce spatial resolution requirements. Measured electron densities as high as one-fourth critical for 1.06 μm are presented. Factors concerning the extension of these measurement to 1021 electrons/cm3 are discussed.
Far-infrared superradiant laser action in methyl fluoride
Authors: Evans D. E. , Sharp L. E. , James B. W. , Peebles W. A.
Published: February 2003

Submillimeter laser pulses exceeding 1-MW power have been generated superradiantly in CH3F gas pumped by 200 MW of 9.55-μ CO2 TEA laser radiation. When far-infrared output was restricted to operation on the 496 line alone, 0.5 MW was achieved within a bandwidth of 100 MHz.
Tunable dye laser resonance excitation of the LaAlO3:Cr3+ vibronic spectrum
Authors: Aoki S. , Abella I. D.
Published: February 2003

A fluorescence spectrum of the vibronic sideband of Cr3+ in LaAlO3 has been obtained by means of pulsed tunable dye laser excitation on resonance with the zero-phonon line. This method of excitation offers improved resolution, while attenuating competing spectral features arising from impurity ion pair interactions.
Submillimeter detection using a Schottky diode with a long-wire antenna
Authors: Mizuno K. , Kuwahara R. , Ono S.
Published: February 2003

A Schottky diode originally made for use as a detector and a mixer in the millimeter-waveglength region has been used as a room-temperature fast detector in the submillimeter-wavelength region. A voltage responsivity of 2 V/W and an NEP of 1×10−7 W/Hz1/2 at 337 μm were obtained by using high-gain long-wire-antenna coupling. The experimental and theoretical responses of the antenna structure are compared.
Observation of a self-colliding beam
Authors: Maglich Bogdan , Mazarakis Michael , Robinson Barry , Galayda John , Gore Robert , Colleraine Anthony P.
Published: February 2003

A single beam of accelerated deuterium ions, D+2, of 108 keV, injected into a highly inhomogeneous magnetic field, decreasing quadratically with the radial distance from the center, was made to collide head-on with itself. The trajectory of the ’’self-colliding beam’’ is a precessing figure 8, with the ions moving clockwise in both (upper and lower) loops and colliding head-on in the center.
A Schottky-diode acoustic memory and correlator
Authors: Ingebrigtsen K. A. , Cohen R. A. , Mountain R. W.
Published: February 2003

Experiments demonstrate that images of acoustic signals can be stored for tens of msec in a matrix of Schottky diodes on a silicon surface adjacent to a lithium niobate surface-wave delay line. The experiments show charging times of the order of 10 nsec.
Observation of orthorhombic→tetragonal→cubic phase transitions in some PLZT ceramics
Authors: Keve E. T.
Published: February 2003

With increasing temperature the sequence of phase transitions orthorhombic→tetragonal→cubic is observed for a PLZT ceramic of 7.5/64/36 composition. At 20 °C the inverse sequence is seen as a function of poling field. The compositional dependence of the transition temperatures is reported over a limited range.
Bleustein-Gulyaev surface wave storage in CdS
Authors: Maerfeld C. , Tournois P.
Published: February 2003

Storage experiments of Bleustein-Gulyaev surface acoustic wave in CdS, carried out at room temperature, are described. Storage time varies from 40 μsec to 2.5 msec. A linear relationship between the stored pattern decay time and the sample resistivity has been experimentally found. The storage mechanism involves deep bulk traps.
Deep-level controlled lifetime and luminescence efficiency in GaP
Authors: Hamilton B. , Peaker A. R. , Bramwell S. , Harding W. , Wight D. R.
Published: February 2003

The influence of deep levels on the minority-carrier lifetime and relative cathodoluminescent efficiency of undoped GaP has been investigated. Evidence that both these parameters are deep-level controlled is presented. The dominant center was detected by thermal capture and emission of minority carriers optically injected into the depletion layer of Schottky barriers. This center was found to have a depth of ET−EV=0.75 eV and a hole capture cross section of approximately 4×10−14 cm2.
Thermal instability in high−power laser discharges
Authors: Jacob J. H. , Mani S. A.
Published: February 2003

The thermal and acoustic instabilities that could possibly cause arcing in high−power pulsed and cw gas lasers have been investigated. A cubic dispersion relation is obtained from linearization of the coupled hydrodynamic and Ohmic equations in which the electrical conductivity is dependent on the neutral density. We find that when the thermal wave is unstable the acoustic waves are damped, and vice versa. The growth rate of the instability is proportional to the power density for low input powers while it goes as the cube root of the power density for high input powers.
Anisotropic absorption saturation with picosecond pulses
Authors: Shank C. V. , Ippen E. P.
Published: February 2003

A new technique for measuring fast recovery of anisotropic absorption saturation is described. Picosecond pulses from a mode−locked cw dye laser are used to induce and probe absorption saturation in the organic dye DODCI. Orientational relaxation of DODCI is measured as a function of solvent viscosity.
Double heterostructure Pb1−xSnxTe waveguides at 10.6 μm
Authors: Ralston R. W. , Walpole J. N. , Harman T. C. , Melngailis I.
Published: February 2003

High−optical−quality planar waveguides have been fabricated in the Pb1−xSnxTe alloy system by molecular beam expitaxy. The structures consist of a 6−μm−thick low−carrier−concentration (≲4×1016 cm−3) Pb0.92Sn0.08Te layer vacuum deposited on an n−type PbTe substrate followed by a second 0.5−μm−thick epitaxial layer of n−type PbTe. The measured propagation loss of ⩽1.5 cm−1 (6.5 dB/cm) for TE−polarized 10.6−μm laser radiation in these waveguides at 77 K is sufficiently low for integrated optical circuits in this wavelength range, and the waveguide fabrication techniques are compatible with those used for lasers and detectors in Pb1−xSnxTe epitaxial layers.
Superconducting critical currents of small coils of multifilamentary V3Ga wire under pulsed current excitation
Authors: Itoh K. , Tachikawa K.
Published: February 2003

In this study, the critical currents of small coils wound by multifilamentary wire of A−15−type superconducting V3Ga have been measured in large exciting speeds. The critical currents of the coils do not degrade up to exciting speeds of over 200 kOe/sec. The results are compared with those of similar coils wound by multifilamentary Nb−Ti wire.
Dynamic conversion and bubble strip−out
Authors: Vella−Coleiro G. P. , Hagedorn F. B. , Blank S. L.
Published: February 2003

The translational motion of magnetic bubbles in a field gradient has been studied with high−speed photography. No change in the bubble diameter was observed as the bubble moved in the field gradient, when using the compensation technique of Vella−Coleiro and Tabor. Thus the suggestion made recently by Josephs, that bubble strip−out can account for the scatter in the bubble velocity, is not applicable to our measurements. Dynamic conversion is the most plausible explanation of the velocity scatter that we observe, and circuit operation results at high frequencies support this viewpoint.
High−angular−resolution secondary−electron spectroscopy: Kikuchi correlations for As (0001)
Authors: Rusch T. W. , Ellis W. P.
Published: February 2003

A high−angular−resolution retarding−grid minianalyzer has been constructed for studying the amplitudes of Auger electron signals as a function of emission angle. With a resolution of 2° in angle and 1% in energy, a correlation was established between the directions of maximum emission of the As 12−eV peak and the open crystallographic directions of the Kikuchi−like display from As (0001).
Heterostructure CdS1−xSex−CdS surface lasers for integrated optics
Authors: Kawabe Mitsuo , Kotani Hideo , Masuda Kohzoh , Namba Susumu
Published: February 2003

Heterostructure CdS1−xSex−CdS surface lasers which have a larger refractive index and a smaller band gap than CdS substrates were fabricated by vapor phase epitaxy and their laser characteristics at 80 K were studied by using a nitrogen gas laser excitation. The Se profiles which were deduced from the fluorescence wavelength were steplike but graded due to diffusion. The optical gain of the epitaxially grown surface layer was larger than that of CdS single crystal owing to optical confinement. By stripe geometry excitation, an intense axial single−mode output was observed up to the excitation intensity three times as high as the threshold 70 kW/cm2. Optical coupling between the active and passive layers was observed in the samples which have a double epitaxial layer.
A deep center associated with the presence of nitrogen in GaP
Authors: Smith B. L. , Hayes T. J. , Peaker A. R. , Wight D. R.
Published: February 2003

The deep−level thermal activation energy spectrum of N−doped liquid−phase−epitaxial (LPE) and liquid−encapsulated−Czochralski (LEC) −grown GaP has been investigated using Schottky barrier thermally stimulated−current (TSC) measurements. We detect a center at Ec−Et=0.42 eV whose presence in the lattice depends on the deliberate addition of N to the material. The concentration of this center varies approximately as (Nd−Na)2 in n−type material, and the value of electron capture cross section for the center (St≈7×10−15 cm2) indicates that it could be a strong recombination center in N−doped p−type GaP. Separate experiments suggest that this center is strongly localized, and that it is not a simple complex involving shallow donors and native defects.
Cadmium arsenide thin−film dynamic pressure sensor
Authors: Wl/odarski W.
Published: February 2003

Results are presented of studies on the application of Cd3As2 thin films to measurements of dynamic pressures up to 600 atm in liquid nonconducting media. A comparison is made between this sensor and the quartz pressure sensor in measuring dynamic pressures. The dynamic error involved in measuring pressure with a cadmium arsenide thin−film resistance sensor has been determined as less than 1.5%.
Magnetoelastic Rayleigh wave convolver
Authors: Robbins William P. , Lundstrom Mark S.
Published: February 2003

An epoxy−bonded LiNbO3−YIG−LiNbO3 composite structure has been constructed and operated as a magnetoelastic Rayleigh wave convolver with 50−MHz input signals. The acoustic signals were propagated on a (110) YIG surface and the convolution characteristics were studied as a function of the magnitude and direction of the applied magnetic field. Nonuniform demagnetizing fields limited convolution pulses to less than 1.5 μsec duration. Relatively efficient operation was observed corresponding to an internal efficiency Fint of −53 dBm.
SiO2 film overlays for temperature−stable surface acoustic wave devices
Authors: Parker T. E. , Schulz M. B.
Published: February 2003

Temperature−stable surface acoustic wave devices have been fabricated on YZ LiNbO3 and YZ LiTaO3 by the use of SiO2 film overlays. On LiNbO3, a temperature dependence similar to that of ST−cut quartz was obtained, but with a coupling constant k2 of at least 5.4%. On LiTaO3, a second−order temperature coefficient of delay that is 5 times smaller than and opposite in sign to that of ST quartz was observed. The coupling constant was measured to be approximately 1.6%.
Redistribution of boron in silicon after high−temperature proton irradiation
Authors: Baruch Pierre , Monnier Joel , Blanchard Bruno , Castaing Claude
Published: February 2003

We have measured the distribution of boron in silicon, using secondary ion mass spectroscopy or nuclear reactions, after irradiation at 850°C by protons of energy 250−450 keV. The fluence was 1×1017 to 6×1017 protons/cm2. Prediffused and uniformly doped samples have been studied. It is found that the boron distribution is considerably modified: the boron concentration shows a peak near the end of the proton range, where the defect creation rate is highest. This anomaly cannot be explained by using solely simple diffusion theory, and depends on boron−defect interactions, such as the formation of precipitates or complexes. As a consequence, the interpretations of radiation−enhanced diffusion experiments must be discussed again.
Negative resistance in ion−implanted Al−Al2O3−Au junctions
Authors: Hirano Mikio , Kuriki Shinya , Matsumoto Goro
Published: February 2003

Conduction has been investigated in Al−Al2O3−Au sandwiches whose oxide is implanted with O or Al ions. The results reveal that ion implantation gives a junction type which can be electroformed, and which exhibits negative resistance in air at atmospheric pressure.
Power increase of N2 uv and ir lasers by addition of SF6
Authors: Willett Colin S. , Litynski Daniel M.
Published: February 2003

The output power and energy per pulse of transversely excited (TE) nitrogen lasers operating well over threshold on the 0.3371−μm transition in the C3Πu−B3Πg second positive system, and on near−infrared transitions in the B3Πg−A3Σ+u first positive system, have been found to be increased by more than 100% with the addition of SF6 compared with those obtainable from N2 alone. It is hypothesized that the increase in power results from a modification of the electron energy distribution by the SF6 or discharge products of SF6, to one that favors more efficient excitation of the C3Πu and B3Πg states of molecular nitrogen.
Metal reflectivity under high−intensity optical radiation
Authors: Zavecz T. E. , Saifi M. A. , Notis M.
Published: February 2003

Single high−intensity (106−109 W/cm2) pulses of 1.06−μ radiation emitted from a Q−switched Nd : YAG laser have been used to study reflectivity behavior of single−crystal copper and tantalum samples. Metal reflectivity during irradiation undergoes a significant drop to values much lower than can be attributed to high−temperature effects. This reflectivity drop under high radiation intensity has two characteristic features. First, if vaporization is avoided, then during the rising portion of the laser pulse the reflectivity drops continuously until it reaches a constant low value. For copper this occurs at an intensity of 3×108 W/cm2 and has a reflectivity value of ≈0.64. The corresponding values for tantalum are I≈2.5×107 W/cm2 and R≈0.41. For still higher intensities a further drop in reflectivity beyond the plateau region is observed. This drop in reflectivity is always accompanied by heavy melting and followed by some vaporization. As suggested by Prokhorov et al. this further drop in reflectivity could be associated with dielectriclike behavior of the molten zone.
Induced focusing and defocusing of optical beams via a Raman−type nonlinearity
Authors: Owyoung Adelbert
Published: February 2003

Using a 5.7−MW single−mode ruby laser pulse at an intensity of 100 MW/cm2 through a 10−cm−long cell of benzene, we report the experimental observation of the induced focusing and defocusing of an externally generated Stokes probe beam on the high− and low−frequency side of the 992−cm−1 Raman line, respectively. This observation gives direct evidence of the dispersion in the real part of the nonlinear susceptibility tensor χ3 in the vicinity of a Raman mode.
Enhanced crystallinity of silicon film deposited at low temperature
Authors: Chang Chin−An , Siekhaus Wigbert J. , Kaminska Thomas , Huo Donald Tai−Chan
Published: February 2003

Silicon thin films were vacuum deposited onto fused quartz at 600 °C with a prior coating of ultrathin aluminum layer (∼ 500 Å). Significant increase in crystallinity was observed from both x−ray diffraction and transmission electron microscopy studies. The problem of handling aluminum film at this temperature in a vacuum of 1×10−6 Torr is discussed, and distribution of aluminum in the silicon film is studied using Auger spectroscopy.
Double−discharge arrangement for cw electrical excitation of supersonic flows
Authors: Blom J. H. , Hanson R. K.
Published: February 2003

A simple double−discharge electrode arrangement for the cw excitation of supersonic molecular gas flows is described. Stable discharges in N2 and N2/CO mixtures, with E/N of 2.0−2.5×10−16 V cm2 and a power loading of 2.6×10−2 eV/molecule, were achieved.
Aerosol size spectrum analysis using relaxation time measurement
Authors: Kirsch K. J. , Mazumder M. K.
Published: February 2003

An experimental method has been developed to measure the dynamic relaxation times of aerosol particles. The particle relaxation time (τp) is determined from the ratio of the velocity amplitude of an aerosol particle (vp) to the velocity amplitude of the medium (ug) while the aerosol is subjected to acoustic excitation of a known frequency. A differential laser Doppler velocimeter is used to measure vp, while a microphone is used to measure ug. From the value of τp, the aerodynamic diameter of the particle can be determined if the particle density is known. The method can be applied to real−time in situ measurement of size distribution of an aerosol containing both solid particles and liquid droplets in the range of 0.1−10.0−μm diameters.
Superconducting weak links formed by ion implantation
Authors: Arrington III C. H. , Deaver B. S.
Published: February 2003

The superconducting order parameter has been controllably reduced in a narrow band across a strip of Nb thin film by implanting iron ions into the film. The resulting weak link exhibits the Josephson effects and is exceptionally rugged, both physically and electrically.
Zinc oxide on silicon memory cells scanned by acoustic surface waves
Authors: Coldren L. A.
Published: February 2003

The use of parametrically mixed acoustic surface waves to remotely scan and process the contents of zinc−oxide−on−silicon charge storage cells is demonstrated. The write, erase, and store characteristics of the memory cells are investigated. The signal−processing capability of the device is illustrated by the correlation of a line of stored information with a biphase coded input signal.
Porous−wall BeO capillary waveguide laser
Authors: Papayoanou A. , Fujisawa A.
Published: February 2003

Small−bore capillary tubes exhibit very high optical gains and saturation intensities in flowing gas CO2 systems. However, these parameters may vary greatly in the axial direction due to the nonuniform axial pressure distribution. Use of porous−wall BeO capillary tubes makes it possible to attain a more uniform pressure distribution and to usefully scale capillary waveguide amplifiers to longer lengths.
Phase−matching condition for scattering from acoustic surface reflective arrays
Authors: Otto O. W.
Published: February 2003

A phase−matching condition for scattering from acoustic surface reflective arrays is derived with velocity slowing of the reflective stripes taken into account. Propagation in a periodic region is described in terms of waves with sawtooth−shaped phase fronts. Stored energy is proposed as a mechanism for altering the effective velocity anisotropy between incident and scattered waves. The theory is tested against measured transmission resonances for metallic (Al) gratings on Y−cut LiNbO3.
Evidence for electronic stopping in ion implantation: Shallower profile of lighter isotope 10B in Si
Authors: Ohmura Y. , Koike K.
Published: February 2003

It has been observed by C−V measurements that randomly implanted 10B has shallower profiles in Si than 11B for the acceleration energy range from 50 to 200 keV. This effect can be explained only in terms of electronic stopping in LSS’s theory.
Reliability of DH GaAs lasers at elevated temperatures
Authors: Hartman R. L. , Dixon R. W.
Published: February 2003

Data from accelerated aging tests on continuously operating stripe−geometry double−heterostructure GaAs lasers are presented. By extrapolating data obtained in dry−nitrogen ambients at temperatures of 90, 70, and 50 °C, it is concluded that continuous room−temperature operation of these devices as lasers with power outputs exceeding 1 mW per laser face for times in excess of 100000 h is possible.
Reversible photoinduced change in intermolecular distance in amorphous As2S3 network
Authors: Tanaka K.
Published: February 2003

A reversible photoinduced change in the intermolecular distance has been observed in a well−annealed As2S3 film using a detailed x−ray diffraction technique. This phenomenon is strongly related to the reversible optical absorption edge shift (i.e., photodarkening) by successive cycles of band−gap illumination and annealing. A quantitative interpretation is given for both phenomena in connection with the pressure−induced optical absorption edge shift.
Defect structure of degraded heterojunction GaAlAs−GaAs lasers
Authors: Hutchinson P. W. , Dobson P. S. , O’Hara S. , Newman D. H.
Published: February 2003

Transmission electron microscopy has been used to study the defects associated with the degradation of broad−contact geometry double−heterostructure lasers. Two different types of dislocation networks have been observed close to the active region of the degraded device having Burgers vectors of (a/2) 〈011〉 and a〈001〉. Both networks have been shown to be of interstitial character.
Energy transfer from Ce3+ to Tm3+ in borate and phosphate glasses
Authors: Reisfeld R. , Eckstein Y.
Published: February 2003

Energy transfer from Ce3+ to Tm3+ is reported in borate and phosphate glasses. It was found that the 1D2→3H4 blue emission of thulium could be increased manyfold when excited through 4f−5d absorption of Ce3+. It is suggested that the energy transfer process is of multipolar type.
Fast imaging process in PbI2 films
Authors: Tolle H. J. , Memming R.
Published: February 2003

Images were formed in PbI2 layers covered with a polymer film by laser pulses in the nanosecond range. The local vapor pressure of PbI2 due to the resulting local heating led to the formation of bubbles which act as scattering centers for transmitted light.
Direct nuclear pumping of a helium−xenon laser
Authors: Helmick H. H. , Fuller J. L. , Schneider R. T.
Published: February 2003

Excitation of a He−Xe laser was achieved by nuclear pumping, i.e., fission products interacted directly with the lasing gas and a portion of their energy was emitted as laser light. The transition observed is most likely the Xe 5d[7/2]03−6p[5/2]2, 3.508 μm. The He−Xe gas mixture ratio was 20 : 1 at a total pressure of 200 Torr. The light output exhibited a threshold effect and had the same characteristic waveform as the fission fragment flux above the threshold level. Laser output duration was approximately 150 μsec.
Enhancement of cw laser melt-through of opaque solid materials by supersonic transverse gas flow
Authors: Robin James E. , Nordin Paul
Published: February 2003

The effects of a supersonic transverse gas flow over an opaque solid surface irradiated by a high−power cw laser is investigated. The motion of the gas parallel to the laser−induced melt layer produces two effects. The first is to feed energy into unstable surface disturbances. These instabilities do not grow indefinitely but become steady periodic waves. The second is the exertion of a shear stress at the gas/melt interface which in turn establishes a velocity profile in the melt. It is this second effect which results in melt removal at the trailing edge of the melt region. This removal increases the recession rate of the melt/solid boundary propagating through the solid. It is this shear−stress removal mechanism that is investigated. The analysis considers both gas and liquid viscosity.
Varistorlike I−V characteristics in sputtered carbon films
Authors: Morisaki H. , Iwasaki H. , Yazawa K.
Published: February 2003

Varistorlike I−V characteristics have been observed in sputtered carbon films sandwiched by Al electrodes. The threshold voltage of the Al−C−Al varistors is controlled by the sputtering time and not by the rf input power for sputtering if other parameters are unchanged. Auger analysis of the films has clarified that the nonlinear characteristics are strongly influenced by anomalous profiles of tungsten atoms migrated from Al.