Peptide Vaccine Formulation Controls the Duration of Antigen Presentation and Magnitude of Tumor-Specific CD8+ T Cell Response

Despite remarkable progresses in vaccinology, therapeutic cancer vaccines have not achieved their full potential. We previously showed that an excessively long duration of Ag presentation critically reduced the quantity and quality of vaccination-induced T cell responses and subsequent antitumor efficacy. In this study, using a murine model and tumor cell lines, we studied l-tyrosine amino acid-based microparticles as a peptide vaccine adjuvant with a short-term Ag depot function for the induction of tumor-specific T cells. l-Tyrosine microparticles did not induce dendritic cell maturation, and their adjuvant activity was not mediated by inflammasome activation. Instead, prolonged Ag presentation in vivo translated into increased numbers and antitumor activity of vaccination-induced CD8⁺ T cells. Indeed, prolonging Ag presentation by repeated injection of peptide in saline resulted in an increase in T cell numbers similar to that observed after vaccination with peptide/l-tyrosine microparticles. Our results show that the duration of Ag presentation is critical for optimal induction of antitumor T cells, and can be manipulated through vaccine formulation.

Effects of rapid antigen degradation and VEE glycoprotein specificity on immune responses induced by a VEE replicon vaccine

Genetic vaccines are engineered to produce immunogens de novo in the cells of the host for stimulation of a protective immune response. In some of these systems, antigens engineered for rapid degradation have produced an enhanced cellular immune response by more efficient entry into pathways for processing and presentation of MHC class I peptides. VEE replicon particles (VRP), single cycle vaccine vectors derived from Venezuelan equine encephalitis virus (VEE), are examined here for the effect of an increased rate of immunogen degradation on VRP vaccine efficacy. VRP expressing the matrix capsid (MA/CA) portion of SIV Gag were altered to promote rapid degradation of MA/CA by various linkages to co-translated ubiquitin or by destabilizing mutations and were used to immunize BALB/c mice for quantitation of anti-MA/CA cellular and humoral immune responses. Rapid degradation by the N-end rule correlated with a dampened immune response relative to unmodified MA/CA when the VRP carried a glycoprotein spike from an attenuated strain of VEE. In contrast, statistically equivalent numbers of IFNgamma(+)T-cells resulted when VRP expressing unstable MA/CA were packaged with the wild-type VEE glycoproteins. These results suggest that the cell types targeted in vivo by VRP carrying mutant or wild type glycoprotein spikes are functionally different, and are consistent with previous findings suggesting that wild-type VEE glycoproteins preferentially target professional antigen presenting cells that use peptides generated from the degraded antigen for direct presentation on MHC.

Mid-infrared vibrational spectra of discrete acetone-ligated cerium hydroxide cations

Cerium(iii) hydroxy reactive sites are responsible for several important heterogeneous catalysis processes, and understanding the reaction chemistry of substrate molecules like CO, H(2)O, and CH(3)OH as they occur in heterogeneous media is a challenging task. We report here the first infrared spectra of model gas-phase cerium complexes and use the results as a benchmark to assist evaluation of the accuracy of ab initio calculations. Complexes containing [CeOH](2+) ligated by three- and four-acetone molecules were generated by electrospray ionization and characterized using wavelength-selective infrared multiple photon dissociation (IRMPD). The C[double bond, length as m-dash]O stretching frequency for the [CeOH(acetone)(4)](2+) species appeared at 1650 cm(-1) and was red-shifted by 90 cm(-1) compared to unligated acetone. The magnitude of this shift for the carbonyl frequency was even greater for the [CeOH(acetone)(3)](2+) complex: the IRMPD peak consisted of two dissociation channels, an initial elimination of acetone at 1635 cm(-1), and elimination of acetone concurrent with a charge separation producing [CeO(acetone)](+) at 1599 cm(-1), with the overall frequency centered at 1616 cm(-1). The increasing red shift observed as the number of acetone ligands decreases from four to three is consistent with transfer of more electron density per ligand in the less coordinated complexes. The lower frequency measured for the elimination/charge separation process is likely due to a combination of: (a) anharmonicity resulting from population of higher vibrational states, and (b) absorption by the initially formed photofragment [CeOH(acetone)(2)](2+). The C-C stretching frequency in the complexes is also influenced by coordination to the metal: it is blue-shifted compared to bare acetone, indicating a slight strengthening of the C-C bond in the complex, with the intensity of the absorption decreasing with decreasing ligation. Density functional theory (DFT) calculations using three different functionals (VWN, B3LYP, and PBE0) were used to predict the infrared spectra of the complexes. Calculated frequencies for the carbonyl stretch are within 40 cm(-1) of the IRMPD of the three-acetone complex measured using the single acetone loss, and within 60 cm(-1) of the measurement for the four-acetone complexes. The B3LYP functionals provided the best agreement with the measured spectra, with the VWN modestly lower and PBE0 modestly higher. The C-C stretching frequencies calculated using B3LYP are higher in energy than the measured values by approximately 30 cm(-1), and reproduce the observed trend which shows that the C-C stretching frequency decreases with increasing ligation. Agreement between C-C frequency and calculation was not as good using the VWN functional, but still within 70 cm(-1). The results provide an evaluation of changes in the acceptor properties of the metal center as ligands are added, and of the utility of DFT for modeling f-block coordination complexes.

A method for cryopreserving chicken primordial germ cells

This study established a method for preserving chicken primordial germ cells (PGC) that enables long-term storage in liquid N. Gonads were harvested from stage 27 chick embryos and pooled in groups of 5, 10 (10E), or 20 embryos, contributing gonads to the cell suspension. The gonadal cells, including PGC, were then frozen in 1 of the following cryoprotectant treatments: 2.5% dimethyl sulfoxide (DMSO), 5% DMSO, 10% DMSO, 2.5% ethylene glycol (EG), 5% EG, 10% EG, and 0% cryoprotectant as a control. The cells were liberated and frozen in a biosecure cryopreservation straw at a rate of -1 degrees C/min until reaching -85 degrees C and were then plunged into liquid N (-196 degrees C), in which they were stored until analysis. Flow cytometry was used to analyze the PGC post-thaw. The PGC marker stage-specific embryonic antigen-1, which was detected with goat antimouse IgM fluorescein isothiocyanate, was used to label all PGC, and propidium iodide was used to detect cells with compromised cell membranes. There was an interaction effect for the number of viable PGC per individual embryo (P < or = 0.05). The highest level (183.6 +/- 28.4) of viable PGC per individual embryo was observed for 10% EG with 10E and was significantly higher (P < or = 0.05) than cryopreservation in 2.5% DMSO with 10E and 20 embryos, 2.5% EG with 10E, 5% EG with 10E, and all 0% cryoprotectant treatments. No statistical interaction (P > 0.05) was observed for the percentage of viable PGC. However, the highest percentage (80.6%) was observed at 10% EG with 10E. It was demonstrated that PGC were successfully frozen, and the most effective treatment was 10% EG with 10 embryos/straw.

Early post-hatch fasting induces satellite cell self-renewal

Early post-hatch satellite cell kinetics are an important aspect of muscle development, and understanding the interplay between fasting and muscle development will lead to improvements in muscle mass following an illness, and optimal meat production. The objective of this experiment was to test the influence of immediate post-hatch fasting on satellite cells in the poult. Male Nicholas poults (Meleagris gallopavo) were placed into two treatments: a fed treatment with immediate access to feed and water upon placement and a fasted treatment without access to feed and water for the first three days post-hatch. 5-bromo-2'-deoxyuridine (BrdU) was injected intra-abdominally in all poults to label mitotically active satellite cells. The pectoralis thoracicus muscle was harvested two hours following the BrdU injection. Immunohistochemistry for BrdU, Pax7, Bcl-2, Pax7 with BrdU, and determining myofiber cross-sectional area along with computer-based image analysis was used to study muscle development. Fed poults had higher body masses throughout the experiment (P< or =0.01), and they had higher pectoralis thoracicus muscle mass (P< or =0.01) at ten days of age than the fasted poults. Fed poults had higher satellite cell mitotic activity at three days and four days of age (P< or =0.01) compared to the fasted poults. However, Pax7 labeling index was higher in the fasted poults (P< or =0.01) at three days, four days, and five days post-hatch than the fed group. Similarly Bcl-2 labeling was higher in the fasted than in the fed group at three days post-hatch. Therefore, fasting depleted proliferating satellite cells indicated by the lower BrdU labeling in the fasted poults compared to the fed poults, and conserved the satellite cell proliferative reserve indicated by the higher level of Pax7 labeling for the fasted poults compared to the fed poults.

The effect of early nutrition on satellite cell dynamics in the young turkey

Early posthatch satellite cell mitotic activity is an important aspect of muscle development. An understanding of the interplay between nutrition and satellite cell mitotic activity will lead to more efficient meat production. The objective of this study was to test the influence of the leucine metabolite, beta-hydroxy beta-methylbutyrate (HMB), and feed deprivation on muscle development in the early posthatch poult. Male Nicholas poults were placed on 1 of 4 treatments: immediately fed a starter diet with 0.1% HMB (IF-HMB), immediately fed a starter diet containing 0.1% Solka-Floc for a control (IF-No HMB), feed and water withheld for 48 h immediately posthatch and then fed the HMB diet (WF-HMB), and feed and water withheld for 48 h immediately posthatch and then fed the control starter diet (WF-No HMB). 5-bromo-2'-deoxyuridine (BrdU) was injected intra-abdominally into all poults to label mitotically active satellite cells. The pectoralis thoracicus was harvested 2 h after the BrdU injection. Immunohistochemistry for BrdU, Pax7, and laminin along with computer-based image analysis was used to study muscle development. IF-HMB poults had higher body weights (P < 0.01) at 48 h and 1 wk of age and had higher satellite cell mitotic activity at 48 h of age (P < 0.01) compared with the IF-No HMB and WF poults. Therefore, dietary supplementation of HMB may have an anabolic effect on early posthatch muscle.

Structures of HCN-Mgn (n=2–6) complexes from rotationally resolved vibrational spectroscopy andab initiotheory

High-resolution infrared laser spectroscopy has been used to determine the structures of HCN-Mgn complexes formed in helium nanodroplets. The magnesium atoms are first added to the droplets to ensure that the magnesium complexes are preformed before the HCN molecule is added. The vibrational frequencies, structures, and dipole moments of these complexes are found to vary dramatically with cluster size, illustrating the nonadditive nature of the HCN-magnesium interactions. All of the complexes discussed here have the nitrogen end of the HCN pointing towards the magnesium clusters. For Mg3, the HCN binds to the "threefold" site, yielding a symmetric top spectrum. Although the HCN-Mg4 complex also has C3v symmetry, the HCN sits "on-top" of a single magnesium atom. These structures are confirmed by both ab initio calculations and measurements of the dipole moments. Significant charge transfer is observed in the case of HCN-Mg4, indicative of charge donation from the lone pair on the nitrogen of HCN into the lowest unoccupied molecular orbital of the Mg4.

Hazard rate ratio and prospective epidemiological studies

Analysis of prospective follow-up data usually includes a Cox regression model. When a hazard rate ratio, obtained as the exponential of an estimated regression coefficient from the Cox model, is greater than 1.0, it consistently exceeds relative risk, and is exceeded by the odds ratio. The divergence of these distinct epidemiologic measures increases with the product of three factors: (1) the length of follow-up, (2) the average rate of the end point occurence over the follow-up period, and (3) the magnitude of risk, either above or below 1. Cornfield's rare disease assumption is basically the product of the first two of these factors. However, risks in excess of 2.5 have a powerful effect on the divergence of these measures, and this point has received less emphasis. Conversely, and as seen frequently in applications, relative risk, hazard rate ratio, and odds ratio numerically approximate one another with shorter follow-up, rarer end points, and risks closer to 1. Although the hazard rate ratio is not always distinguished from relative risk, it is commonly close to, and is always between, relative risk and the odds ratio. Consistent and accurate terminology would have us use hazard rate ratio with Cox regression and odds ratio with logistic regression. The term "relative risk" seems to be a default choice, regardless of the model being used. However, when relative risk is the object of the model chosen, as in a Poisson regression approximation of two binomial proportions or an equivalent weighted least squares, then for us, relative risk is the accurate terminology.

Birefringence in gradient-index rod lenses: a direct measurement method and interferometric polarization effects

Gradient-index (GRIN) media can contain stress birefringence resulting from the variation in material composition. Anisotropy in a GRIN rod lens affects ray propagation and can degrade image quality. A technique, believed to be new, for measuring birefringence in GRIN rod lenses has been developed. The change in optical path difference (OPD) for orthogonal polarizations is measured directly. With this method, effects on OPD from standard imaging aberrations are excluded. Birefringence measurements for various GRIN rod samples are presented. The data are compared with results obtained previously by use of a Twyman-Green measurement method. Also, the polarization effects on tilt fringes observed with the direct measurement method and the Twyman-Green method are presented and modeled theoretically. Tilt fringes for large birefringence test cases are also modeled.

Probing the structure of metal cluster-adsorbate systems with high-resolution infrared spectroscopy

High-resolution infrared laser spectroscopy was used to obtain rotationally resolved infrared spectra of adsorbate-metal complexes. The method involves forming the bare metal clusters in helium nanodroplets and then adding a molecular adsorbate (HCN) and recording the infrared spectrum associated with the C-H stretching vibration. Rotationally resolved spectra were obtained for HCN-Mg(n) (n = 1 to 4). The results suggest a qualitative change in the adsorbate-metal cluster bonding with cluster size.

The NIEHS Xenopus maternal EST project: interim analysis of the first 13,879 ESTs from unfertilized eggs

The sequencing of expressed sequence tags (ESTs) from Xenopus laevis has lagged behind efforts on many other common experimental organisms and man, partly because of the pseudotetraploid nature of the Xenopus genome. Nonetheless, large collections of Xenopus ESTs would be useful in gene discovery, oligonucleotide-based knockout studies, gene chip analyses of normal and perturbed development, mapping studies in the related diploid frog X. tropicalis, and for other reasons. We have created a normalized library of cDNAs from unfertilized Xenopus eggs. These cells contain all of the information necessary for the first several cell divisions in the early embryo, as well as much of the information needed for embryonic pattern formation and cell fate determination. To date, we have successfully sequenced 13,879 ESTs out of 16,607 attempts (83.6% success rate), with an average sequence read length of 508 bp. Using a fragment assembly program, these ESTs were assembled into 8,985 'contigs' comprised of up to 11 ESTs each. When these contigs were used to search publicly available databases, 46.2% bore no relationship to protein or DNA sequences in the database at the significance level of 1e-6. Examination of a sample of 100 of the assembled contigs revealed that most ( approximately 87%) were comprised of two apparent allelic variants. Expression profiles of 16 of the most prominent contigs showed that 12 exhibited some degree of zygotic expression. These findings have implications for sequence-specific applications for Xenopus ESTs, particularly the use of allele-specific oligonucleotides for knockout studies, differential hybridization techniques such as gene chip analysis, and the establishment of accurate nomenclature and databases for this species.

Quiet time: a nursing intervention to promote sleep in neurocritical care units

BACKGROUND

Patients in intensive care units are often sleep deprived, yet little research exists on the impact of nursing care on promoting sleep.

OBJECTIVES

To determine if implementing a "quiet time" protocol to reduce external environmental stimuli is associated with increased frequency of sleep among patients in a neurocritical care unit.

METHODS

Patients were observed 8 times each day before and after implementation of a protocol in which environmental sounds and lights were decreased from 2 AM to 4 AM and from 2 PM to 4 PM. Data collected at 2:45 AM, 3:30 AM, 2:45 PM, and 3:30 PM on patients with scores of 10 or greater on the Glasgow Coma Scale were analyzed. A total of 2975 observations were made on a total of 239 patients: 1446 observations on 118 patients in the control group and 1529 observations on 121 patients in the intervention group.

RESULTS

The percentage of patients observed asleep was significantly higher during the months the quite-time period was implemented than during the control period before the intervention was started. The increase in sleep behavior was associated with decreased sound and light levels achieved during the quiet time. Patients observed during the intervention period were 1.6 times more likely to be asleep during the quiet time than were patients observed during the control period (P < .001).

CONCLUSIONS

A concentrated effort by staff to reduce environmental stimuli at discrete preset intervals increases the likelihood of sleep during scheduled quiet time in the neurocritical care unit.

Quiet time: a nursing intervention to promote sleep in neurocritical care units

BACKGROUND: Patients in intensive care units are often sleep deprived, yet little research exists on the impact of nursing care on promoting sleep. OBJECTIVES: To determine if implementing a "quiet time" protocol to reduce external environmental stimuli is associated with increased frequency of sleep among patients in a neurocritical care unit. METHODS: Patients were observed 8 times each day before and after implementation of a protocol in which environmental sounds and lights were decreased from 2 AM to 4 AM and from 2 PM to 4 PM. Data collected at 2:45 AM, 3:30 AM, 2:45 PM, and 3:30 PM on patients with scores of 10 or greater on the Glasgow Coma Scale were analyzed. A total of 2975 observations were made on a total of 239 patients: 1446 observations on 118 patients in the control group and 1529 observations on 121 patients in the intervention group. RESULTS: The percentage of patients observed asleep was significantly higher during the months the quite-time period was implemented than during the control period before the intervention was started. The increase in sleep behavior was associated with decreased sound and light levels achieved during the quiet time. Patients observed during the intervention period were 1.6 times more likely to be asleep during the quiet time than were patients observed during the control period (P &lt; .001). CONCLUSIONS: A concentrated effort by staff to reduce environmental stimuli at discrete preset intervals increases the likelihood of sleep during scheduled quiet time in the neurocritical care unit.

Measurement and calibration of interferometric imaging aberrations

Phase-shifting interferometry is the standard method for testing figure error on optical surfaces. Instruments measuring spheres and flats are readily available, but the accurate measurement of aspheres requires null correction. One problem with the general (nonull) testing of aspheres is the loss of common path. Systematic errors are introduced into the measurement by the fringe imaging optics. The sources and types of error are reviewed, as well as their effect on a wave-front measurement. These nonnull errors are predicted generally, with third-order analytic expressions derived for a tilted or a defocused test surface. An interferometer is built to test the expressions. The imaging system is a single lens, nominally image telecentric. Measurements are performed on a test surface defocused from -5 to 5 mm. The resulting measurement bias is shown to be in good agreement with third-order aberration theory predictions.

The life readiness program: a physical rehabilitation program for patients on hemodialysis

Patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD) are typically sedentary and functionally limited as a consequence of their condition. The purpose of this study is to test the effect of a lifestyle physical rehabilitation program (The Life Readiness Program) on physical function in patients with ESRD undergoing HD. Physical function was measured by the Kidney Disease Quality of Life Short Form (KDQOL-SF) physical function score (range, 0 to 100). Eighty-two patients were randomly assigned to a 6-month rehabilitation program (intervention; n = 39) or to standard clinical management alone (control; n = 43). The groups were frequency matched by age, sex, ethnicity, and diabetes as the cause of ESRD. General linear modeling of the change in physical function score was used for multivariate analysis. Physical function scores were not different between groups at baseline. Change in physical function score increased significantly in the intervention group compared with the control group when data were adjusted for the matching variables and adequacy of dialysis (3.2, -3.6; P = 0.04). Additionally, the control group reported more problems with work or daily functions because of emotional problems (P: </= 0.05). In this brief 6-month intervention, The Life Readiness Program showed the therapeutic benefit of a lifestyle rehabilitation program on functional outcomes and health-related quality of life for patients with ESRD undergoing hemodialysis.

Design and manufacture of a gradient-index axicon

A gradient-index axicon with its initial focus offset from the back surface was designed with the thin-lens approximation. Two samples were fabricated by means of the time-varying boundary condition diffusion method, which is based on the modified quasi-chemical diffusion model. Intensity profile measurements were taken along the focal region of the axicons. The samples produced extended line foci. From the intensity measurements, the central spot widths and back focal lengths were determined. The peak widths matched theoretical predictions made with the diffraction theory for the samples and showed good agreement with the predicted widths for a pseudo-Bessel beam, showing that the axicon produced a pseudo-diffractionless beam.

Interference imaging for aspheric surface testing

Peak-valley accuracy of lambda/20 over a range of 2lambda is not unusual in an interferometric null test. For the larger dynamic ranges of a nonnull test, however, the fringe-imaging optics degrades the accuracy. We classify the errors introduced and analyze them in the context of both general and third-order aberration theory. We can predict the measurement error from known interferometer parameters, and we illustrate this for a single mirror. The errors are tabulated for the specific case of a fourth-order asphere with 100 mum of sag. We show that the third-order approximation is comparable with exact ray-trace results for this case.

Birefringence measurements in gradient-index rod lenses

Stress birefringence can be found in gradient-index (GRIN) materials because they contain a variation in composition. GRIN glass fabricated by ion exchange may contain stress from two different processes. These include a size difference between the exchange and the diffusing ions and a variation in the thermal-expansion coefficient across the gradient region. The optical properties of the stressed material are polarization dependent, and therefore image quality is directly affected. We examine birefringence in GRIN rod lenses that have lengths more than ten times greater than their diameters. The effects are more easily observed in long rod lenses because of the large optical path lengths.

Interferometric chromatic dispersion measurements of long, gradient-index rod lenses in the visible and the near infrared

A new procedure is presented for testing long, radial-gradient-index rod lenses in a phase-stepping Twyman-Green interferometer. In addition, a method for converting the measured optical phase data to the rod's index of refraction profile is reviewed. This procedure was used to measure refractive-index profile dispersions over the wavelength range of 441 to 1064 nm. These measurements provide the first data for refractive-index profiles of rod lenses in the infrared and show the existence of positive dispersion, negative dispersion, and near-infrared dispersion reversal in some samples. The dispersion results suggest the need for modifications to the current glass model.

Design of three-element night-vision goggle objectives

Night-vision goggle objectives are often composed of six or more conventional lens elements with spherical surfaces and homogeneous refractive indices. Special elements such as aspheres, diffractive optics, and gradient-index materials can be used to reduce the total number of lenses required to meet military design specifications. A study was performed to examine the use of various combinations of these special surfaces to determine the minimum number of elements that can be used to construct the objective system. We present and compare the best resulting designs.

Rigid endoscopic relay systems: a comparative study

Relay systems in rigid endoscopes can compensate for aberrations in the objective and the eyepiece. Five classes of rigid relay systems are examined: conventional; glass Hopkins; plastic lens, glass-rod Hopkins; modified Hopkins; and gradient index. First-order theory, including achromatization, is developed for these systems. Design results are presented, and aberration, vignetting, and system length trade-offs are analyzed.

Quantitative phase imaging in confocal microscopy by optical differentiation

The technique of optical differentiation is applied to confocal microscopy for the purpose of quantitative phase imaging. One-dimensional absorptive filters are placed in the pupil of the microscope objective to produce images related to the local phase slope in the object. With suitable signal processing and integration, a quantitative phase profile is obtained. This method is demonstrated in a reflection-based surface-profiling instrument.

Severe obesity: effects on foot mechanics during walking

The purpose of our study was to determine the effects of severe obesity on the foot mechanics of adult females. Twenty-nine adult females between the ages of 20 and 48 years volunteered as subjects for this investigation. The subjects were separated into a severely obese (O) group (body mass index = 41.14 +/- 2.61; N = 16) and a normal weight control group (body mass index = 20.84 +/- 0.47; N = 13). A Locam camera (100 Hz) positioned perpendicular to the subjects' posterior aspect was used to film the rearfoot movement of the subjects during the final 15 sec of a 10 min treadmill walk. The O group had a significantly greater touchdown angle (P = .05), more total eversion range of motion (P = .001), and a faster maximum eversion velocity (P < .001). Moreover, analysis of dynamic foot angles indicated that the O group had significantly (P = .003) more forefoot abduction. Finally, anthropometric data revealed statistically different (P < .001) Q angle measurements between the O and control groups. The results of this study suggest that severely obese females have significantly greater rearfoot motion, foot angle, and Q angle values than normal weight females.

Control of the radial gradient-index profile by leaching of a gel

A new method for controlling the shape and increasing the maximum index change in the radial gradient-index profile of sol-gel bodies is demonstrated. This is accomplished by modifying the relative rates of the intricate reactions responsible for forming the gradient. In practice the changes reported here are effected solely by varying the leaching conditions. Through the proper choice of a solution to arrest the leaching action, the index change can be maximized for a given shape to double that of the previous technique. A detailed composition analysis of the data reveals that dopant diffusion and precipitation are the dominant factors influencing the observed results.

Index profile control using Li(+) for Na(+) exchange in aluminosilicate glasses

Two new techniques for altering the gradient-index profile shape are presented using ion exchange of Li(+) for Na(+) in an aluminosilicate glass. By varying the alkali concentration in the base glass and salt melt, the functional form of the index profile is modified to range in shape from convex to concave. The success of these techniques is attributed to the unusual characteristics of the initial system, which are shown to be caused by a nonlinear dependence of refractive index on dopant concentration.

Third-order aberration theory for weak gradient-index lenses

A set of simple analytic expressions has been developed for calculating the third-order aberration coefficients in weak or nearly thin axial and radial gradient-index lenses.

Effects of axial and radial gradients on Cooke triplets

This study investigates the role of gradient-index materials in the design of Cooke triplets for use as 35-mm format photographic objectives. Cooke triplet designs are presented with different types of gradient-index profiles. Both linear axial and shallow radial gradients are shown to provide effective control of spherical aberration and astigmatism. In particular, a Cooke triplet with a combination of both linear axial and radial gradients attains performance comparable to a six-element double Gauss lens. In virtually all cases, the use of gradient-index components improves the Cooke triplets' performance significantly.

Axial and radial gradient-index titania flint glasses

A series of TiO(2) flint glasses has been developed for producing GRIN glass by ion exchange. Both positive and negative axial and radial gradients were fabricated in high index glasses by exchange of Li(+) for Na(+) and Na(+) for Li(+), respectively. Index changes to 0.05 and depths up to 6 mm were achieved and a wide variety of index profiles are shown.

Gradient-index profile control from mixed molten salt baths

The composition of the molten salt bath was shown to exert a strong influence on the gradient-index profile that resulted from the ion exchange of silver for sodium. Two types of additives were used to enhance the ion exchange from a base AgCl melt. Both techniques reduced the profile degradation that normally occurred with long diffusion times, while one technique also increased the refractive index change at 0.6328 microm in a regular fashion from 0.06 to 0.15.

Design and tolerancing of aspherical and gradient-index germanium singlets of equal performance

Two different aspherical singlets, four types of axial gradient-index singlet, and one radial gradient-index singlet achieving the same performance are toleranced for thickness, curvatures, base index, and special coefficient (aspheric or gradient) sensitivities. The results show that the singlet with the most relaxed tolerances has a linear axial gradient which extends through the lens, followed in order by a singlet with a parabolic radial gradient, a singlet with an aspheric surface on the front, and a singlet with a parabolic axial gradient crossing the first surface.

Radial gradient-index eyepiece design

Three- and four-element eyepiece designs are presented each with a different type of radial gradient-index distribution. Both quadratic and modified quadratic index profiles are shown to provide effective control of the field aberrations. In particular, the three-element design with a quadratic index profile demonstrates that the inhomogeneous power contribution can make significant contributions to the overall system performance, especially the astigmatism correction. Using gradient-index components has allowed for increased eye relief and field of view making these designs comparable with five- and six-element ones.

Real-time index profile measurement during GRIN glass fabrication

A new instrument for measuring the evolution of index profiles during diffusion in hot (500 degrees C) glass is presented. This instrument, called the oven interferometer, has a spatial resolution of 10 microm at 0.6471 microm and a phase resolution of lambda/50. The development of index profiles with both time-dependent and constant boundary conditions is shown.

Design, fabrication, and testing of a gradient-index binocular objective

A two-element axial gradient-index binocular objective has been designed and fabricated by the ion exchange technique. A prototype system has been assembled and tested.

Measurement of the refractive-index profile in polycrystalline germanium-silicon alloy GRIN crystals

The refractive index as a function of spatial coordinate in three Czochralski grown germanium-silicon alloy GRIN crystals has been measured using ac interferometric techniques. The interferometer is capable of high phase resolution and is computer controlled for real-time data processing. The measured refractive-index profiles were compared to theoretical profiles which were calculated from a model based on the segregation effect of silicon in germanium.