Designing black mirrors.

Black mirrors, or total absorbers, are related to neutral density (ND) filters. ND filters are primarily concerned with transmittance, whereas a black mirror has no transmittance and endeavors to reduce the reflectance to zero in the wavelength band of interest by absorbing all the light. Metal layers must be used for the absorptance capabilities and dielectric layers to create the interference phases, which maximize the electric field at the absorbing layers. Very thin metal layers, whose indices of refraction vary with the thickness and require special software handling in the design process, are required. The procedures and an additional viewpoint on designing black mirrors are discussed here.

Model-free approach to finding index of refraction values of optical coatings from spectral measurements.

Mathematical models for fitting the refractive index versus the wavelength, such as the Cauchy, Sellmeier, and Drude equations, or physical models, such as the Lorentz model, are commonly used to fit the index properties of measured spectra of optical thin film witness samples for use in the design and production of optical interference coatings. The degree of agreement of the coating reflectance and transmittance with the design when the coatings are produced with these data will depend on the accuracy of the spectral measurements and index fittings. As thin-film coating technology has progressed, many cases are now encountered where no simple model is adequate to fit the actual index dispersion. This work shows an approach to finding the refractive index versus wavelength, which is independent of any mathematical or physical models.

Designing with very thin optical films.

There is increasing interest in the design of films with thicknesses on the order of 10 nm and less for a variety of applications, such as nanoparticles, plasmonics, quantum dots, solar reflectors, black mirrors, etc. The indices of refraction (n and k) for the effective media of such coatings depend on the materials with which such "layers" interface and the specific process parameters used to produce those films. The structures may typically be nucleating island structures and may also be continuous films. A key factor is that the n and k values vary in thickness until some thickness is obtained, usually >20nm. Heretofore, to the best of our knowledge, films have not taken into account thickness index variations during the design process. Software has now been developed where the index at a given thickness is computed at each iteration of the design optimization process. This allows more realistic design results utilizing the full representation of the behavior of the layers in question; the resulting coatings, when produced, are in better agreement with the designs. Including n and k versus wavelength and thickness in the design process is here referred to as double dispersion.

Optimization of Ta2O5 optical thin film deposited by radio frequency magnetron sputtering.

Radio frequency magnetron sputtering has been used here to find the parameters at which to deposit Ta2O5 optical thin films with negligible absorption in the visible spectrum. The design of experiment methodology was employed to minimize the number of experiments needed to find the optimal results. Two independent approaches were used to determine the index of refraction n and k values.

Effect of Pore Structure on CO2 Adsorption Characteristics of Aminopolymer Impregnated MCM-36.

The CO2 adsorption characteristics of a pillared 2-dimensional porous silicate material impregnated with amine containing polymers have been investigated. It was determined that the introduction of amine polymer deteriorates the CO2 capture kinetics of the MCM-36 supported amine adsorbents compared to that of the bare material, due to the fact that with the addition of a higher loading of amine polymer the diffusion of CO2 through the 2-dimensional interlayer mesoporous channels of MCM-36 becomes greatly hindered. This pore blocking sets an upper limit to the CO2 capture performance of the polymer impregnated MCM-36 and greatly reduces the utility of using this sort of amine-solid adsorbent for carbon capture. Interestingly, these results suggest that for 2-D channel solid supports there is an optimal amine loading which is not likely to be equal to the maximum loading, and which can be determined and utilized to obtain the maximum improvement over the original materials. The study performed in this work for the MCM-36 material could therefore be applied to other porous supports to determine these optimum loadings and be used to more easily compare and contrast the alterations to capture characteristics which occur upon amine loading for a wide range of materials. It is believed this will make it more straightforward to determine which solid supports hold the promise for greatly improved capture characteristics upon amine loading and allow the field to more quickly determine avenues for fruitful development. These results also suggest the need for a new sort of support structure for amine loaded solids, one which can allow us to decouple amine loading from increasing diffusion resistance so that high amine efficiency can be maintained throughout the range of increased amine loadings.

Simulation comparisons of monitoring strategies in narrow bandpass filters and antireflection coatings.

This study compares and quantifies the simulated effects of noise, index errors, and photometric level errors on different optical monitoring layer termination strategies. A computer program to simulate optical thin film monitoring has been written for this work. The study looked at these termination methods: quartz crystal monitoring, photometric level cut, two types of turning point termination, and percent of optical extrema monitoring. A narrow bandpass filter and a four-layer antireflection coating design were simulated as examples.

Witness sample preparation for measuring antireflection coatings.

Measurement of antireflection coating of witness samples from across the worldwide industry has been shown to have excess variability from a sampling taken for the OSA Topical Meeting on Optical Interference Coatings: Measurement Problem. Various sample preparation techniques have been discussed with their limitations, and a preferred technique is recommended with its justification, calibration procedures, and limitations. The common practice of grinding the second side to reduce its reflection is less than satisfactory. One recommended practice is to paint the polished second side, which reduces its reflection to almost zero. A method to evaluate the suitability of given paints is also described.

Recombination-mediated changes in coreceptor usage confer an augmented pathogenic phenotype in a nonhuman primate model of HIV-1-induced AIDS.

Evolution of the env gene in transmitted R5-tropic human immunodeficiency virus type 1 (HIV-1) strains is the most widely accepted mechanism driving coreceptor switching. In some infected individuals, however, a shift in coreceptor utilization can occur as a result of the reemergence of a cotransmitted, but rapidly controlled, X4 virus. The latter possibility was studied by dually infecting rhesus macaques with X4 and R5 chimeric simian simian/human immunodeficiency viruses (SHIVs) and monitoring the replication status of each virus using specific primer pairs. In one of the infected monkeys, both SHIVs were potently suppressed by week 12 postinoculation, but a burst of viremia at week 51 was accompanied by an unrelenting loss of total CD4+ T cells and the development of clinical disease. PCR analyses of plasma viral RNA indicated an env gene segment containing the V3 region from the inoculated X4 SHIV had been transferred into the genetic background of the input R5 SHIV by intergenomic recombination, creating an X4 virus with novel replicative, serological, and pathogenic properties. These results indicate that the effects of retrovirus recombination in vivo can be functionally profound and may even occur when one of the recombination participants is undetectable in the circulation as cell-free virus.

Further guidance for broadband antireflection coating design.

Recent investigations have added to and refined the understanding of the behavior of broadband antireflection coating designs and provided further guidance for achieving more nearly optimal designs. The ability to optimize designs wherein the overall optical thickness of the design is constrained to a specific value has allowed this investigation. A broader bandwidth than previously reported has been studied and statistically fit more precisely by a polynomial equation, and also two linear equations for routine approximations have been derived. It has also been found that the optimal number of layers in the design can be predicted as a function of the bandwidth.

Expanded viewpoint for broadband antireflection coating designs.

Examining spectral regions outside of the band where an antireflection coating is specified can aid in finding optimal design solutions. The reflectance versus wavenumber plots at low frequencies indicate the overall thickness of the design. These plots also point to whether the design will provide the minimum possible average reflectance in the specified band. It has been discovered that these patterns are nearly replicated by the plot of a quarter-wave stack at peak frequency. It is also found that optimal solutions exist only at quantized intervals.

Generation of the pathogenic R5-tropic simian/human immunodeficiency virus SHIVAD8 by serial passaging in rhesus macaques.

A new pathogenic R5-tropic simian/human immunodeficiency virus (SHIV) was generated following serial passaging in rhesus macaques. All 13 animals inoculated with SHIV(AD8) passaged lineages experienced marked depletions of CD4(+) T cells. Ten of these infected monkeys became normal progressors (NPs) and had gradual losses of both memory and naïve CD4(+) T lymphocytes, generated antiviral CD4(+) and CD8(+) T cell responses, and sustained chronic immune activation while maintaining variable levels of plasma viremia (10(2) to 10(5) RNA copies/ml for up to 3 years postinfection [p.i.]). To date, five NPs developed AIDS associated with opportunistic infections caused by Pneumocystis carinii, Mycobacterium avium, and Campylobacter coli that required euthanasia between weeks 100 and 199 p.i. Three other NPs have experienced marked depletions of circulating CD4(+) T lymphocytes (92 to 154 cells/microl) following 1 to 2 years of infection. When tested for coreceptor usage, the viruses isolated from four NPs at the time of their euthanasia remained R5 tropic. Three of the 13 SHIV(AD8)-inoculated macaques experienced a rapid-progressor syndrome characterized by sustained plasma viremia of >1 x 10(7) RNA copies/ml and rapid irreversible loss of memory CD4(+) T cells that required euthanasia between weeks 19 and 23 postinfection. The sustained viremia, associated depletion of CD4(+) T lymphocytes, and induction of AIDS make the SHIV(AD8) lineage of viruses a potentially valuable reagent for vaccine studies.

Neutralizing antibody titers conferring protection to macaques from a simian/human immunodeficiency virus challenge using the TZM-bl assay.

We previously reported that passive transfer of polyclonal neutralizing antibodies (NAbs) sufficient to generate a titer of 1:38 in the plasma would confer sterilizing protection to 99% of macaques challenged intravenously with 75 TCID(50) of SHIV(DH12). Neutralizing activity in that study was measured in an MT4 cell assay in which infection was completely blocked (EC(100)). In the current study, the TZM-bl system was used to measure EC(50) neutralizing titers in several of the same macaque plasma samples and the relationship between these titers and in vivo protection was determined. The antiviral EC(50) NAb titers measured in individual plasma samples were higher than those previously obtained in the MT4 system. Furthermore, the geometric mean EC(50) NAb titers against pseudotyped SHIV(DH12) were 33-fold greater than the EC(100) titers measured in the MT4 cell assay against the replication-competent SHIV(DH12) inoculated into animals. An augmented probit regression model was used to generate curves relating TZM-bl EC(50) NAb titers and protection from a virus challenge; estimated titers conferring various levels of protection were then determined. In TZM-bl assays using pseudotyped SHIV(DH12), representative percent in vivo protection/estimated EC(50) titers were 99%/1:4467, 90%/1:1175, 80%/1:676, 50%/1:234, and 33%/1:141. Because it is likely that contributions from other arms of the immune system will contribute to vaccine-induced control, the range of EC(50) NAb titers we have derived may be more informative for evaluating the protective value of NAb activity from TZM-bl assays.

Monitoring error compensation in general optical coatings.

Error compensation in optical monitoring was demonstrated many years ago for narrow bandpass and edge filters. It is shown here that the compensation effects can apply to a broader range of more general coatings. This is illustrated with a very broadband antireflection coating design of 20 layers and a ramp design of 13 layers. The choice of monitoring wavelength and monitoring strategy are important, and suggestions are made concerning those choices. The results are derived from and demonstrated by computer simulations of the monitoring processes. The importance of monitoring directly on only one part and with one wavelength throughout the process in order to obtain the benefits of error compensation is emphasized.

Non-turning-point monitoring improves narrow bandpass filters.

Historic practice has been to optically monitor narrow bandpass filters by the termination of each layer at a turning point. The problem is that turning points are the least sensitive points to the change of the optical signal with thickness and, thereby, those points are most prone to errors. It is shown that better performance in the production results can be achieved by designing and monitoring in order to terminate layers at non-turning points. A further advantage has been discovered wherein nonoptical monitoring of some layers is used to achieve even better stability in the production result. Simulation programs have been applied to such designs and demonstrate the advantages as compared to the historical approach.

Building blocks for nonpolarizing optical coatings.

The problem of designing nonpolarizing beam splitters with as broad a spectral band as practical has not been clearly understood. The effort of the work reported here has been to glean understanding from the various results of a contest for such designs and further studies of what might be the underlying principles and behaviors that are involved in such designs. A few key layer patterns have been observed, and the importance of symmetry in these patterns has been discovered. Four-layer building blocks have been found that relate to the two quarter-wave optical thickness pairs used as building blocks in normal-incidence designs.

Monitoring thin films of the fence post design and its advantages for narrow bandpass filters.

A fence post design, when viewed on a plot of index of refraction versus film thickness, has thin (usually of equal thickness) high-index posts that stand above a broad low-index ground. Monitoring fence post and related posthole designs offers error compensation and error reduction. There tend to be two or more extrema within the optical monitoring trace of each layer between the fence posts that aid in the calibration and control of film thickness. This also leads to a potentially improved control during deposition of narrow bandpass filters that have been designed with nonquarterwaves at the passband wavelength.

Using fence post designs to speed the atomic layer deposition of optical thin films.

Atomic layer deposition (ALD) at this time is much slower than conventional optical thin-film deposition techniques. A more rapid ALD process for SiO(2) has been developed than for other ALD materials. A fence post design for optical thin films has thin layers of high-index posts standing above a broad low-index ground. If a design for ALD can be predominantly composed of SiO(2) layers with thin high-index layers, the deposition times can be correspondingly shortened, and it is shown that the required performance can still be nearly that of more conventional designs with high- and low-index layers of equal thickness. This combination makes the ALD benefits of conformal coating and precise thickness control more practical for optical thin-film applications.

Design of blocking filters of any narrow bandwidth.

A design approach is described to achieve spectral blocking filters of any spectral width and optical density for narrow blocking bands. The ratio of the thickness of the high-index material to the low-index material in the layer pairs is adjusted to obtain the desired bandwidth in the first-harmonic reflection band. The number of layer pairs is adjusted to provide the required optical density. Equations are provided for estimating the ratios and number of layer pairs needed to achieve a given bandwidth and optical density. This approach can be useful for laser line blocking filters, night vision filters, and other general applications.

N-terminal acetylation and protonation of individual hemoglobin subunits: position-dependent effects on tetramer strength and cooperativity.

The presence of alanine (Ala) or acetyl serine (AcSer) instead of the normal Val residues at the N-terminals of either the alpha- or the beta-subunits of human adult hemoglobin confers some novel and unexpected features on the protein. Mass spectrometric analysis confirmed that these substitutions were correct and that they were the only ones. Circular dichroism studies indicated no global protein conformational changes, and isoelectric focusing showed the absence of impurities. The presence of Ala at the N-terminals of the alpha-subunits of liganded hemoglobin results in a significantly increased basicity (increased pK(a) values) and a reduction in the strength of subunit interactions at the allosteric tetramer-dimer interface. Cooperativity in O(2) binding is also decreased. Substitution of Ala at the N-terminals of the beta-subunits gives neither of these effects. The substitution of Ser at the N terminus of either subunit leads to its complete acetylation (during expression) and a large decrease in the strength of the tetramer-dimer allosteric interface. When either Ala or AcSer is present at the N terminus of the alpha-subunit, the slope of the plot of the tetramer-dimer association/dissociation constant as a function of pH is decreased by 60%. It is suggested that since the network of interactions involving the N and C termini of the alpha-subunits is less extensive than that of the beta-subunits in liganded human hemoglobin disruptions there are likely to have a profound effect on hemoglobin function such as the increased basicity, the effects on tetramer strength, and on cooperativity.

Control of viremia and prevention of simian-human immunodeficiency virus-induced disease in rhesus macaques immunized with recombinant vaccinia viruses plus inactivated simian immunodeficiency virus and human immunodeficiency virus type 1 particles.

An effective vaccine against the human immunodeficiency virus type 1 (HIV-1) will very likely have to elicit both cellular and humoral immune responses to control HIV-1 strains of diverse geographic and genetic origins. We have utilized a pathogenic chimeric simian-human immunodeficiency virus (SHIV) rhesus macaque animal model system to evaluate the protective efficacy of a vaccine regimen that uses recombinant vaccinia viruses expressing simian immunodeficiency virus (SIV) and HIV-1 structural proteins in combination with intact inactivated SIV and HIV-1 particles. Following virus challenge, control animals experienced a rapid and complete loss of CD4(+) T cells, sustained high viral loads, and developed clinical disease by 17 to 21 weeks. Although all of the vaccinated monkeys became infected, they displayed reduced postpeak viremia, had no significant loss of CD4(+) T cells, and have remained healthy for more than 15 months postinfection. CD8(+) T-cell and neutralizing antibody responses in vaccinated animals following challenge were demonstrable. Despite the control of disease, virus was readily isolated from the circulating peripheral blood mononuclear cells of all vaccinees at 22 weeks postchallenge, indicating that immunologic control was incomplete. Virus recovered from the animal with the lowest postchallenge viremia generated high virus loads and an irreversible loss of CD4(+) T-cell loss following its inoculation into a naïve animal. These results indicate that despite the protection from SHIV-induced disease, the vaccinated animals still harbored replication-competent and pathogenic virus.