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We demonstrate a synchronously pumped fiber optical parametric oscillator tunable from 795 nm to 860 nm. The FOPO operates in the normal dispersion regime and generates highly chirped pulses at the output allowing for significant pulse energy scaling without pulse breaking. The FOPO was able to generate up to 3.9 nJ pulses compressible to 173 fs by a photonic crystal fiber compressor.

To address the need for a high quality data set based upon field observations suitable for parameterization, calibration, and validation of terrestrial biosphere models, we have developed a comprehensive global database on net primary productivity (NPP). We have compiled field measurements of biomass and associated environmental data for multiple study sites in major grassland types worldwide. Where sufficient data were available, we compared aboveground and total NPP estimated by six computational methods (algorithms) for 31 grassland sites. As has been found previously, NPP estimates were 2–5 times higher using methods which accounted for the dynamics of dead matter, compared with what is still the most commonly applied estimate of NPP (maximum peak live biomass). It is suggested that assumptions such as the use of peak biomass as an indicator of NPP in grasslands may apply only within certain subbiomes, e.g. temperate steppe grasslands. Additional data on belowground dynamics, or other reliable estimates of belowground productivity, are required if grasslands are to be fully appreciated for their role in the global carbon cycle.

Consistent data on terrestrial net primary productivity (NPP) are urgently needed to constrain model estimates of carbon fluxes and hence to refine our understanding of ecosystem responses to climate change. The NPP data have been collected in a coordinated manner for the past 30 years, but comprehensive summaries are rare. We report on the development and availability of a global NPP database that is suitable for modeling of the terrestrial carbon cycle at global and regional scales, for validation of remote sensing data, and for other applications. These data were obtained from the literature on ecophysiological field work and from detailed consultation with the scientific community. Data on NPP, biomass, and associated environmental variables are now publicly available for 53 detailed study sites, of which more than half have data for belowground biomass or biomass dynamics. Aboveground NPP ranges from 35 to 2320 g m–2a–1 (dry matter) and total NPP from 182 to 3538 g m–2a–1. Well-known but previously unobtainable compilations of data, such as the "Osnabrück Data Set" and the International Biological Program (IBP) Woodlands Data Set, are also incorporated in this database. Preliminary exploration of relationships between NPP and mean annual precipitation and temperature suggests that the new 53-site data collection, as well as the Osnabrück and IBP data, are all consistent with the historic "Miami" statistical model. These data are available from the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) for biogeochemical dynamics (see http://www.daac.ornl.gov/NPP/).Key words: net primary productivity, grasslands, forests, biogeochemical dynamics, global carbon cycle, model validation.

The three objectives of this paper were: to summarize net primary production (NPP) and carbon allocation patterns for boreal forests, to examine relationships between climatic and biological variables and NPP, and to examine carbon allocation coefficients for all boreal forests or types of boreal forests that can be used to estimate NPP from easily measured components of NPP. Twenty-four Class I stands (complete NPP budgets) and 45 Class II boreal forest stands (aboveground NPP [NPPA] and budget only) were identified. The geographic distribution of the Class I stands was not uniform; 46% of the stands were from two studies in North America, and only one stand was from the important larch forests of Eurasia. Total (above- and belowground) net primary production (NPPT) ranged from 52 to 868 g C·m−2·yr−1 and averaged 424 g C·m−2·yr−1. NPPA was consistently larger for deciduous than for evergreen boreal forests in each of the major boreal regions, especially for boreal forests in Alaska. Belowground net prima...

The Earth Observing System (EOS) instrument teams must validate the operational products they produce from the Terra spacecraft data. As a pilot for future validation activities, four EOS teams (MODIS, MISR, ASTER, and Landsat-7) and community experts conducted an 11-day field campaign in May 1997 near Las Cruces, NM. The goals of the Prototype Validation Exercise (PROVE) included (1) gaining experience in the collection and use of field data for EOS product validation; (2) developing coordination, measurement, and data-archiving protocols; and (3) compiling a synoptic land and atmospheric data set for testing algorithms. PROVE was held at the USDA-Agricultural Research Service's (ARS) Jornada Experimental Range, an expansive desert plateau hosting a complex mosaic of grasses and shrubs. Most macroscopic variables affecting the radiation environment were measured with ground, air-borne (including AVIRIS and laser altimeter), and space-borne sensors (including AVHRR, Landsat TM, SPOT, POLDER, and GOES). The Oak Ridge Distributed Active Archive Center (DAAC) then used campaign data sets to prototype Mercury, its Internet-based data harvesting and distribution system. This article provides general information about PROVE and assesses the progress made toward the campaign goals. Primary successes included the rapid campaign formulation and execution, measurement protocol development, and the significant collection, reduction, and sharing of data among participants. However, the PROVE data were used primarily for arid-land research and model validation rather than for validating satellite products, and the data were slow to reach the DAAC and hence public domain. The lessons learned included: (1) validation campaigns can be rapidly organized and implemented if there are focused objectives and on-site facilities and expertise; (2) data needs, organization, storage, and access issues must be addressed at the onset of campaign planning; and (3) the end-to-end data collection, release, and publication environment may need to be readdressed by program managers, funding agencies, and journal editors if rapid and comprehensive validation of operational satellite products is to occur.

Reducing uncertainty in predictions of regional-scale models depends on meaningful contrasts with field measurements. This paper introduces a two-stage process that works from the premise that an appropriate goal for regional models is to produce reasonable behavior over dominant environmental gradients. We demonstrate two techniques for contrasting models with data, one based on the shape of modeled relationships (functional contrasts) and the other based on an examination of the residuals (residual contrasts) between the model and an empirically derived surface fit to field data. Functional contrasts evaluated the differences between the response of simulated net primary production (NPP) to climate variables and the response observed in field measurements of NPP. Residual contrasts compared deviations of NPP from the empirical surface to identify groupings (for example, vegetation classes, geographic regions) with model deviations different from those of the field data. In all model–data contrasts, we assigned sample weights to field measurements to ensure unbiased representation of the region, and we included both constructive comparisons and formal statistical tests. In general, we learned more from constructive methods designed to reveal structure or pattern in discrepancy than we did from statistical tests designed to falsify models. Although our constructive methods were more subjective and less concise, they succeeded in revealing gaps in our understanding of regional-scale processes that can guide future efforts to reduce scientific uncertainty. This was best illustrated by NPP predictions from the Biome-BGC model, which showed a stronger response to precipitation than apparently operates in the field. In another case, differences revealed in savanna and dry woodlands had insufficient field-data support, suggesting a need for future field studies to improve understanding in this, and other, poorly studied ecosystems.

The synthesis and modeling of ecological processes at multiple spatial and temporal scales involves bringing together and sharing data from numerous sources. This article describes a data and information system model that facilitates assembling, managing, and sharing diverse data from multiple disciplines, scales, and sites to support integrated ecological studies. Cross-site scientific-domain working groups coordinate the development of data associated with their particular scientific working group, including decisions about data requirements, data to be compiled, data formats, derived data products, and schedules across the sites. The Web-based data and information system consists of nodes for each working group plus a central node that provides data access, project information, data query, and other functionality. The approach incorporates scientists and computer experts in the working groups and provides incentives for individuals to submit documented data to the data and information system.

Progress in modeling the global carbon cycle is inhibited by the lack of a high-quality data set based upon field observations of net primary productivity (NPP) with which to calibrate, parameterize, and evaluate terrestrial biosphere models. Under the auspices of the Global Primary Production Data Initiative (GPPDI), an activity endorsed by the International Geosphere–Biosphere Program’s Data and Information System, a small international workshop was held in Cincinnati, Ohio, USA, in December 1996 to address the problem of extrapolating sparse field observations of NPP to produce a consistent database representative of major biomes. We report the conclusions of this workshop and the goals of GPPDI—to further expand the existing data compilation, to agree upon consistent standards for cross-site comparisons and allometric relationships for various biome types, and to document methodologies for spatial extrapolation from point measurements to grid cells. The resulting NPP database will also have intrinsic ...

An electron cyclotron resonance (ECR) reactor was used to develop a low damage CF{sub 4}/O{sub 2}/Ar etch process for patterning submicron features in SiN{sub x} films on GaAs substrates. Statistically designed experiments were performed to optimize the process with regard to the following response variables (in order of importance): plasma damage tl the underlying GaAs substrate, sidewall profile (anisotropy), selectivity to photoresist, uniformity, and SiN{sub x} etch rate. Damage, as measured by the change in sheet carrier concentration of uniformly doped epilayers, increased with decreasing chamber pressure. Langmuir probe measurements indicated that the ion saturation current increased with decreasing chamber pressure. Further analysis of the data revealed that damage was strongly correlated with ion current density. Dependence of damage on ion energy was found to be a second-order effect. These findings indicate that in an ECR ion flux, not ion energy, plays the major role in introducing damage to the substrate. The addition of low level RF power was necessary to provide sidewall profile control. The data suggest that a high resolution, low damage plasma etch process can be uniquely achieved using an ECR reactor.

A microdialysis method is described which allows for the quantitative determination of extracellular analyte concentration under transient conditions. The method provides the extracellular concentration and the in vivo probe recovery as a function of time. The technique is based on the method for steady-state conditions but differs in the use of a between-group rather than a within-group design. Following cocaine and amphetamine administration, a significantly greater increase in extracellular DA was found than was estimated from the dialysate using conventional microdialysis methods. The discrepancy is due to microdialysis probe recovery decreasing concurrently with the increase observed in extracellular DA following cocaine and amphetamine injections. The method estimates the extracellular concentration independently of any changes in recovery.

Forest structure and composition influence patterns of insect outbreaks and can be explained on the Walker Branch watershed by past land use (timber harvest and agriculture), soils, aspect, and slope. In particular, pine bark beetles caused large losses of pine on sites that had been used for agriculture, on Fullerton silt loam soils, and on north-to-northeast and east-to-southeast exposures. Hickory bark beetles had a high impact on hickory biomass on Bodine soil areas that were forested in 1935 and sloped greater than 11%. Thus, prior land use can have an indirect effect on future disturbances.

Fluorescent oligonucleotide hybridization probes were used to label bacterial cells for analysis by flow cytometry. The probes, complementary to short sequence elements within the 16S rRNA common to phylogenetically coherent assemblages of microorganisms, were labeled with tetramethylrhodamine and hybridized to suspensions of fixed cells. Flow cytometry was used to resolve individual target and nontarget bacteria (1 to 5 microns) via probe-conferred fluorescence. Target cells were quantified in an excess of nontarget cells. The intensity of fluorescence was increased additively by the combined use of two or three fluorescent probes complementary to different regions of the same 16S rRNA.

FLUXNET is a “network of regional networks” created by international scientists to coordinate regional and global analysis of observations from micrometeorological tower sites. The flux tower sites use eddy covariance methods to measure the exchanges of carbon dioxide (CO2), water vapor, and energy between terrestrial ecosystems and the atmosphere. FLUXNET’S goals are to aid in understanding the mechanisms controlling the exchanges of CO2, water vapor, and energy across a range of time (0.5 hours to annual periods) and space scales. FLUXNET provides an infrastructure for the synthesis and analysis of world-wide, long-term flux data compiled from various regional flux networks. Information compiled by the FLUXNET project is being used to validate remote sensing products associated with the National Aeronautics and Space Administration (NASA) Terra and Aqua satellites. FLUXNET provides access to ground information for validating estimates of net primary productivity, and energy absorption that are being generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. In addition, this information is also used to develop and validate ecosystem models.

Acrysoftrade mark (Alcon) foldable lenses (IOLs) have been shown to be highly biocompatible and exhibit a low incidence of posterior capsular opacification. However, minute vacuoles or 'glistenings' have been observed in some Acrysof IOLs. The clinical relevance of vacuole formation is presently unclear. To help clarify the influence of factors present under in vivo conditions on vacuole formation, the present experimental study examines the influence of aqueous humor components on the occurrence of vacuoles in Acrysof IOLs.A total of 12 sterile Acrysof IOLs (Alcon, MA60BM) were incubated at body temperature (37 degrees C) for 3 or 6 months in anterior-chamber aqueous humor with or without human serum. The center portion was cut from two unconditioned, unhydrated, sterile control IOLs and the 12 conditioned IOLs and examined using light microscopy for vacuole formation. A third unconditioned, hydrated control IOL was examined using light and scanning electron microscopy.The incidence of vacuoles was quantified by two independent investigators using light microscopy. After hydration with balanced salt solution, the surface quality of a control IOL was examined using scanning electron microscopy.The control IOLs exhibited no or very few vacuoles. Scanning electron microscopy revealed that the control IOLs had normal surface texture without any surface vacuoles. IOLs that had been conditioned in aqueous humor without serum exhibited no great increase in the number of vacuoles, whereas IOLs conditioned in aqueous humor with serum exhibited a greater number of vacuoles that increased over time.The number of vacuoles increases with incubation time in aqueous humor containing serum. The addition of serum increased the proportion of lipids and proteins in the solution, which also occurs with a breakdown in the blood-aqueous barrier. The results of the present study point to a physiological factor that may lead to vacuole formation in IOLs and may aid clinicians in identifying risk factors involved in the formation of vacuoles.

To describe the visual complaints of a series of patients implanted with the AcrySof(R) (Alcon Surgical) acrylic intraocular lens (IOL) that resolved with IOL exchange.Jules Stein Eye Institute, Los Angeles, California, and John A. Moran Eye Center, Salt Lake City, Utah, USA.This was a retrospective review of patients who had AcrySof IOL exchange from January 1997 to December 1998.Eight patients (9 eyes) with bothersome visual symptoms following AcrySof IOL implantation were identified. Problems included glare, halos around point light sources, and peripheral arcs of light, often worse at night. In each case, the IOL was well-centered in the capsular bag and there was no significant posterior capsule opacification. Six patients (7 eyes) had the MA30BA model with a 5.5 mm optic, and 2 patients (2 eyes) had the MA60BM model with a 6.0 mm optic. No extralenticular reasons for the patients' complaints could be identified. Exchanging the AcrySof IOLs with silicone or poly(methyl methacrylate) IOLs alleviated most symptoms. In 5 of 8 patients, dysphotopsias resolved completely.A small number of patients implanted with AcrySof IOLs have specific complaints of glare, halos, and peripheral arcs of light. Optical considerations that may help explain these symptoms include the high refractive index of the IOL material and the truncated design of the optic. Patients who are highly observant and those with large pupils may be particularly symptomatic. Intraocular lens exchange may be necessary in some cases.

To determine the relationship between various intraocular lens (IOL) types and the incidence of unwanted light images.The Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.A telephone questionnaire was administered to 302 postoperative patients who had received 1 of 6 commonly used IOLs between January and September 1998. Patients were included only if they had uneventful cataract surgery, no additional ocular pathology, and a postoperative best corrected visual acuity of 20/25 or better. A control group of 50 patients with the diagnosis of presbyopia only also participated in the questionnaire. Patients reported on incidence of glare, light sensitivity, and unwanted images. The data were analyzed for statistically significant relationships between incidence of photopsias and IOL type.The AcrySof 5.5 mm, AcrySof 6.0 mm, and SI-40 groups reported significantly more unwanted images than the control group (P =.0014). The 2 AcrySof groups also reported a greater incidence of light to the side causing a central flash, and the SI-40 group, a higher incidence of glare. The control group was more likely to experience symptoms of glare than any pseudophakic group. Overall, a mean of 49% of patients reported some light-related phenomenon postoperatively. The majority in all groups reported being satisfied with their eyesight despite the light-related problems.A significant number of pseudophakic patients reported symptoms of dysphotopsia. Patients who received an acrylic IOL with flattened edges were at increased risk of experiencing images associated with edge reflections. The SI-40 lens group, although less than the AcrySof groups, reported a higher incidence of glare than the non-AcrySof groups; however, it also had the highest number of patients still driving at night. The phakic population commonly experienced glare reported as more severe than several of the IOL groups.

Active fluorescence techniques are becoming commonly used to monitor the state of the photosynthetic apparatus in natural populations of phytoplankton, but at present these are bulk water measurements that average all the fluorescent material in each sample. Here we describe two instruments that combine individual-cell "pump-during-probe" (PDP) measurements of chlorophyll (Chl) fluorescence induction, on the time scale of 30 to 100 micros, with flow cytometric or visual characterization of each cell.In the PDP flow cytometer, we measure Chl fluorescence yield as a function of time during a 150 micros excitation flash provided by an argon ion laser; each particle is subsequently classified as in a conventional flow cytometer. In the PDP microfluorometer, individual cells in a sample chamber are visually identified, and fluorescence excitation is provided by a blue light-emitting diode that can be configured to provide a saturating flash and also a subsequent series of short flashlets. This sequence allows both saturation and relaxation kinetics to be monitored.Phytoplankton from natural samples and on-deck iron-enrichment incubation experiments in the Southern Ocean were examined with each PDP instrument, providing estimates of the potential quantum yield of photochemistry and the functional absorption cross section for photosystem 2, for either individuals (for cells larger than a few micrometers) or populations (for smaller cells).Results from initial field applications indicate that single-cell PDP measurements can be a powerful tool for investigating the nutritional state of phytoplankton cells and the regulation of phytoplankton growth in the sea.

The authors conducted a 3-year randomized trial to compare silicone intraocular lenses (IOLs) with polymethylmethacrylate (PMMA) IOLs, to determine any differences in laser capsulotomy rates, capsular opacification light scatter, and subjective scoring.A total of 119 patients were enrolled, 84 of whom were examined at 3 years. The authors designed a prospective, masked, and randomized trial to compare the objective (lens opacity meter), subjective (slit-lamp scoring), and clinical parameters of the posterior capsular opacification (PCO) of these patients.The silicone group had less PCO than the PMMA group, according to objective (8.6% vs. 10.4%; P = .02, Student's t test) and subjective scoring (0.88 vs. 1.79; P = .0001, Student's t test). The laser capsulotomy rate was 24% for the silicone group and 33% for the PMMA group; however, this difference was not statistically significant.The silicone IOL was associated with less PCO than the PMMA IOL.

Posterior capsular opacification (PCO) is a frequent complication following phacoemulsification with intraocular lens (IOL) implantation. A series of consecutive patients receiving capsular bag-fixated, silicone IOL implants were assessed for both incidence of PCO and the administration of intraoperative miotics.During a 5-year period, 477 consecutive eyes were retrospectively evaluated. Surgeries were grouped according to intraoperative miotic agent: 0.01% carbachol or 1.0% acetylcholine. Patients receiving no miotic drug served as a control group. Yttrium-aluminum-garnet (YAG) laser posterior capsulotomy was performed on patients with clinically significant PCO.The percentage of eyes requiring YAG laser capsulotomy was similar for the three groups: 21.6% (25 of 91) for the carbachol group, 18.4% (14 of 62) for the acetylcholine group, and 18.6% (53 of 232) for the control group. A chi-squared analysis indicated that the difference among the groups was not statistically significant. The three groups also had similar average follow-up times between surgery and YAG capsulotomy (carbachol group = 52.2 weeks, acetylcholine group = 47.5 weeks, and control group = 48.3 weeks).Intraocular miotics do not increase the incidence of PCO.

An extensive compilation of more than 700 field estimates of net primary productivity of natural and agricultural ecosystems worldwide was synthesized in Germany in the 1970s and early 1980s. Although the Osnabrueck data set has not been updated since the 1980s, it represents a wealth of information for use in model development and validation. This report documents the development of this data set, its contents, and its recent availability on the Internet from the Oak Ridge National Laboratory Distributed Active Archive Center for Biogeochemical Dynamics. Caution is advised in using these data, which necessarily include assumptions and conversions that may not be universally applicable to all sites.

We report five cases of sudden shallowing of the anterior chamber associated with irrigation under the iris. We suspect that irrigation in this context forces fluids through the zonules into the posterior chamber, where it becomes trapped, causing anterior chamber shallowing. In our cases, this phenomenon was most commonly associated with irrigation during cortex removal in cases in which the cornea was open (associated with corneal transplantation) and with zonular dehiscence.

We present a patient who underwent bilateral radial keratotomy (RK) followed by a bilateral revisional RK for undercorrection. After the second procedure, the patient had a severely flattened left cornea, with marked hyperopia and irregular astigmatism. The right eye, however, remained myopic, causing extreme anisometropia. We hypothesize that the different results in these two eyes may have been due to a critical number of damaged left corneal stromal fibers. Patients undergoing revisional RK or requiring additional incisions may be at increased risk for such a complication.

Phacoemulsification combined with pars plana vitrectomy was performed on seven patients with both cataracts and vitreoretinal disease. Six of the seven had a posterior chamber intraocular lens (PC-IOL) placed in the capsular bag following cataract extraction. Visual acuities ranging from light perception to hand movement preoperatively, postoperatively ranged from hand movement to 20/25. There were no perioperative complications. During an average follow-up of more than 6 months, neovascular glaucoma developed in one patient, and a conjunctival cyst in another. The PC-IOLs were well tolerated. The small limbal incision used in phacoemulsification allows better control during the vitrectomy procedure and ensures a water-tight wound. In addition, with the limbal approach, the posterior lens capsule is maintained, with all the attendant advantages.

We sought to determine whether, given the decreasing rate of complications associated with cataract surgery and IOL implantation, postoperative restrictions placed on patients undergoing these procedures could be significantly and safely relaxed. We reviewed the charts of 216 patients who had undergone capsulorhexis or "can-opener" capsulotomy, phacoemulsification, and insertion of an oval IOL over a 3-year period, noting any operative or postoperative complications. All of these patients had been examined the day after surgery and, if no complications were noted, had been instructed only to refrain from activities that produced pain. No shield was required, and no instructions were given to restrict showering, hair washing, or any other normal physical activity. We found no complications related to any postoperative activity. These results suggest that current postoperative instructions typically restricting such patients' activities should be reevaluated.

Corneal rust rings are common findings after removal of a metallic foreign body. These rings should be removed to prevent inflammation and scarring. We compared the corneal damage in rabbit eyes caused by rust-ring removal using two different methods: a small-gauge hypodermic needle and a hand-held electric ophthalmic drill. No significant difference was found in the amount of corneal scarring as graded by a masked observer. However, there was a trend toward deeper stromal damage in the drill-treated subjects (207 +/- 73 microns) than in the needle-treated subjects (172 +/- 61 microns). In light of this finding, we suggest caution in removing central rust rings with an electric drill since an avoidable, permanent scar may result.

An extensive compilation of nearly 700 field estimates of net primary productivity of natural and agricultural ecosystems worldwide was synthesized in Germany in the 1970s and early 1980s. The literature cited dates from 1869 to 1982, with the majority of references from the 1960s and 1970s. Although the Osnabruck data set has not been updated since the 1980s, it represents a wealth of information for use in model development and validation. This data paper documents the development of this data set, its contents, and its recent availability on the Internet, both in Ecological Archives on the Ecological Society of America's web site, and in a “mirror” copy at the Oak Ridge National Laboratory Distributed Active Archive Center for Biogeochemical Dynamics. The version presented here (version 2.0) incorporates amendments suggested by data users over the past two years. Caution is advised in using these data, which necessarily include assumptions that may not be universally applicable to all study sites and records. Nevertheless, we consider these “Class III” data to be useful, even though they may not meet the “Gold Standards” which are being developed for this type of data (mainly because the documentation may be incomplete, not because the numbers themselves are of poor quality).

The effect of a girth-weld-induced residual stress field on the linear elastic fracture mechanics of a thin-walled pipe is examined. The procedure for using the residual stress distribution to compute KI and KII for a circumferential crack which is growing radially is described. In addition to the two-pass girth weld, stress intensity factors are computed for a residual stress distribution in a flat plate and for a hypothetical residual stress state in a second thin-walled pipe. The computed stress intensity factor for the flat plate geometry and its residual stress distribution are compared with a solution from the literature as a check on the computational procedure. The through-the-thickness residual stress distribution due to the two-pass girth weld is similar to a half-cosine wave. For purposes of comparison, the hypothetical through-the-thickness distribution selected for the second pipe is similar to a full cosine wave. The stress intensity factor is presented as a function of crack depth for a crack initiating on the inner surface of the pipe. The redistribution of residual stresses due to crack growth is also shown for selected crack lengths. The study shows that residual stress-induced crack growth in pipes can be significantly different from that in flat plates due to the possibility of locked-in residual bending moments in the pipe. These locked-in moments can have effects similar to externally applied loads and can either promote or restrain crack growth. A residual stress distribution is illustrated in which crack growth, if initiated, would continue through the entire wall. Also, a residual stress distribution is illustrated for which the crack could arrest after a certain amount of growth.

L'echantillonnage porte sur une large collection d'invertebres, poissons et mammiferes des eaux cotieres du sud de la Californie et des eaux pelagiques entre Costa Rica et l'ile Cocos. Mise en evidence d'un leger mais progressif accroissement du 13 C/ 12 C dans les tissus des animaux (muscle) lorsque croit le niveau trophique. Interet de ces resultats dans l'etude des biocenoses

The radiation response of the RSN54L series of low power TTL logic circuits was observed after exposure to Flash X-ray, neutron and electron beam environtnents. Several matching types of memory and non-memory SN54L circuits were irradiated in the Flash X-ray environments forming a transient hardness comparison of the hardened and standard low power families. Both DC and switching electrical specification measurements were made on four hundred and eighty (480) RSN54L gate circuits. These terminal measurements served as a monitor for the permanent degradation effects from neutron irradiation. Wide pulse and catastrophic failure tests were run using the electron beam. The RSN54L circuits were found to survive a neutron fluence of 1×1014 n/cm2 (1 MeV equivalent) at full fanout. They sugvived a total dose in the electron beam of 1×108 Rad(Si) and had a transient failure threshold higher than 3×109 Rad(Si)/s.

Presence of aromatic hydrocarbons in meteorites using chromatographic separation techniques

A radiation hardened nonvolatile MNOS RAM (SA2998) is being developed at Sandia National Laboratories. The memory organization is 128 × 8 bits and utilizes two p-channel MNOS transistors per memory cell. The peripheral circuitry is constructed with CMOS metal gate and is processed with standard Sandia rad-hard processing techniques. The device requires +10 V and +25 V for operation. The devices have memory retention after a dose-rate exposure of lE12 rad(Si)/s, are functional after total dose exposure of 1E6 rad(Si), and are dose-rate upset resistant to levels of 7E8 rad(Si)/s.

Parallel running 10-0 and 11-0 nylon sutures were used in 76 consecutive penetrating keratoplasties on patients with keratoconus. Removal of the 10-0 suture at eight to 12 weeks allowed for early visual rehabilitation postoperatively. The use of various trephine sizes and the use of a bridle suture versus a scleral ring were evaluated by several visual parameters. The incidence of complications with the double running suture was not greater than that obtained with other suture techniques.

The question of whether or not phacoemulsification causes significant corneal endothelial damage has been studied in many ways. In this study, we used videotaped specular microscopy and nitroblue tetrazolium (NBT) staining to assess cell damage under conditions in which the two most commonly blamed sources of damage--probe tip trauma and lens fragments--cannot be implicated. After 15 minutes of irrigation, aspiration, and ultrasound in a modified corneal viewing and storage (CVS) chamber, the four test corneas showed less than 5% cell damage as assessed by NBT staining, which was no more than in the control. In one case, an unexpected air bubble on the endothelium caused a loss of endothelial cells. Because small air bubbles are common during phacoemulsification, and because such air bubbles may represent a cause of endothelial cell loss, the endothelial damage caused by air bubbles during phacoemulsification merits further study.

We examined 291 cases of IOL implantation in order to evaluate differences between males and females for several factors. We found that women have shorter axial lengths, older age at time of surgery, greater preoperative corneal curvature, higher power of IOL implanted, more surgically induced astigmatism, and a higher rate of complications. Insignificant differences between the two groups included pre- and postoperative refraction, preoperative astigmatism, visual acuity, type of IOL implanted, corneal thickness, endothelial cell count, and percent of patients requiring discissions.

To examine the effect of trephine tilting and scleral ring placement on wound size, five corneas from McCarey-Kaufman medium and ten whole eyes were trephined centrally under controlled conditions and the major and minor axes measured. It was found that, even with great care taken to hold the trephine perpendicular to the cornea, a fair amount of disparity between the major and minor axes of the donor tissue was seen. The scleral fixation ring produced much distortion, although removal allowed the peripheral cornea to return to more normal configuration. The relationship between amount of trephine tilting and increase in the major axis of the cornea is examined, and all of these concepts are discussed in terms of current keratoplasty technique.

Corneal transplantation has become increasingly successful as a result of improved methods of tissue procurement and preservation, refined surgical techniques, better medical care, heightened public awareness and an expanded network of eye banks. Vision improves within a day of surgery and continues to improve for six months to one year. Careful screening of donors and donor corneal tissue is essential. Causes of transplantation failure include rejection, glaucoma and recurrent infections.

Rosenthal et al. [1] recently reported a series of patients with pulmonary uptake of bone imaging tracer. All patients in that series had evidence of renal failure, and the majority had hypercalcemia as factors relating to their metastatic pulmonary calcification . We recently studied a patient with pulmonary alveolar microlithiasis without abnormal laboratory values who also demonstrated diffuse intense uptake of bone tracer in the lung.

An intraocular lens without loops was inserted in a cat eye using a suture through the iris and holes in the superior lens haptic for fixation. Excellent results were obtained in 37 of 54 implanted intraocular lenses. Among the 17 with complications, 5 eyes were lost because of death. One case of probable endophthalmitis and one of wound rupture occurred. The remaining ten problems were related to contact between intraocular lens and cornea. The mean cell loss in 21 eyes with intraocular lenses and no postsurgical corneal touch was 24%. In ten control eyes (wound only, no lens insertion) the mean cell change was +4%. This difference was statistically significant. This technique may be useful in testing the lens-cornea endothelial toxicity of other intraocular lens modifications.

Spatial data files covering energy, environmental, and socioeconomic themes at Oak Ridge National Laboratory (ORNL) are described. The textual descriptions are maintained by the Regional and Urban Studies Information Center (RUSTIC) within the Data Management and Analysis Group, Energy Division, as part of the Oak Ridge Computerized Hierarchical Information System (ORCHIS) and are available for online retrieval using the ORLOOK program. Descriptions provide abstracts, geographic coverage, original data source, availability limitations, and contact person. Most of the files described in this document are available on a cost-recovery basis.

A corneal punch used for making circular holes in the aorta was tried on pig eyes to check for efficacy and accuracy. This approach was rejected as being clinically useless because the incision necessary to introduce the punch was larger than the diameter of the cut, intraocular trauma was felt to be inevitable due to the large amount of effort necessary to punch, the tissue removed was oval and the internal diameter was much larger than the external diameter of the tissue cut.

One hundred twenty-seven cultures were taken from donor eyes in McCarey Kaufman (M-K) media and 60 from anterior chamber cultures of whole eyes. From the 127 eyes, 17 positive culture were obtained, 13 of which came from anterior chamber cultures of the whole eye and 4 from the M-K media. Of the 16 eyes used for corneal transplantation, there was 1 successfully treated clinical corneal infection. It is concluded that patients with chronic debilitating disease possibly have terminal bacteremia and donor contamination. It is our current recommendations that all corneas obtained in tissue culture media be cultured by the eye bank upon arrival and that eyes prepared for M-K media and refrigerated whole eyes have an anterior chamber culture. Any positive results should then be sent to the primary surgeon as soon as the culture results are ascertained.