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The Defense Advanced Research Projects Agency (DARPA) smart materials research programs past, present, and future are reviewed in this article. Several articles have been written about the history of smart materials at DARPA;1–4 therefore, discussions of past efforts are limited and present and future work is emphasized. More importantly, this article presents the authors’ vision of what is next in the smart materials arena, for it is their belief that the journey to truly smart materials and structures has really just begun.

An experiment was carried out to determine the pattern of follicular expression of mRNAs for aromatase, IGF-I receptor (IGF-IR), IGF-binding protein (IGFBP)-2, -4 and -5, leptin and the long form of the leptin receptor (Ob-Rb) in ten ewes infused with human recombinant leptin (n= 5; 1 μg/h) or saline (n= 5) for 72 h in the luteal phase of the oestrous cycle. At the end of infusion a follicular phase was induced with a luteolytic dose of a prostaglandin F2α analogue and the ovaries were collected 32 h later. One ovary from each ewe was serially sectioned at 10 μm using a cryostat at −20 °C. All follicles >1 mm in diameter were counted and probed with specific oligoprobes for aromatase, IGF-IR and IGFBP-2, -4 and -5 and specific riboprobes for leptin and Ob-Rb. Leptin mRNA was detected in theca and granulosa cells and Ob-Rb mRNA was detected only in granulosa cells, of some, but not all antral follicles. Leptin doubled the number of follicles with a diameter ≥3.5 mm (1.0 ± 0.36 (s.e.m.) vs 2.4 ± 0.24; control vs leptin;P< 0.02) but had no effect on the number of ≥1 < 3.5 mm follicles. Leptin had no effect on the number of follicles expressing aromatase mRNA but it decreased significantly the number of follicles expressing mRNA for IGF-IR (10.7 ± 0.79 vs 7.4 ± 0.81; control vs leptin;P< 0.05), IGFBP-2 (10.0 ± 0.82 vs 5.2 ± 0.87; control vs leptin;P< 0.05) and IGFBP-5 (5.2 ± 1.60 vs 1.2 ± 0.30; control vs leptin;P< 0.05). Leptin increased the diameter of IGFBP-2 mRNA-positive follicles (1.5 ± 0.15 vs 2.2 ± 0.31 mm; control vs leptin;P< 0.05) and increased follicular mRNA expression for IGFBP-2 (0.30 ± 0.021 vs 0.39 ± 0.027 arbitrary units; control vs leptin;P< 0.05) and IGFBP-5 (0.46 ± 0.019 vs 0.25 ± 0.053 arbitary units; control vs leptin;P< 0.05). The mRNA for IGFBP-4 was detected in the theca of only two follicles from the control group. Leptin increased the number of follicles expressing Ob-Rb mRNA (0.25 ± 0.25 vs 1.40 ± 1.17; control vs leptin;P< 0.05) but had no effect on the number expressing leptin mRNA. Leptin decreased plasma concentrations of oestradiol (P< 0.05) and increased concentrations of FSH (P< 0.001) and insulin (P< 0.001), with no effect on glucose concentrations. These data show that: (i) ovine granulosa cells express mRNA for Ob-Rb and leptin and (ii) leptin increased the number of follicles ≥3.5 mm. Furthermore, the data suggest that suppression of oestradiol production by leptin is not mediated by inhibition of aromatase gene expression. Finally, the data indicate that the action of leptin in ovarian follicles is mediated by the IGF system, because leptin increased mRNA expression of IGFBP-2 and -5. Leptin also decreased the number of follicles expressing IGF-IR and IGFBP-2 and -5. We suggest that these actions of leptin on the IGF system decrease the bioavailability of IGF-I, resulting in decreased oestradiol production.

The unique performance of biological systems across a wide spectrum of phylogenetic species has historically provided inspirations for roboticists in new designs and fabrication of new robotic platforms. Of particular interest to a number of important applications is to create dynamic robots able to adapt to a change in their world, unplanned events that are sometimes unexpected, and sometimes unstable, harsh conditions. It is likely that the exploring dynamics in biological systems will continue to provide rich solutions to attaining robots capable of more complex tasks for this purpose. This is because the long-term design process of evolution utilizes a natural selection process that responds to such changes. Recently, there have been significant advances across a number of interdisciplinary efforts that have generated new capabilities in biorobotics. Whole body dynamics that capture the force dynamics and functional stability of legged systems over rough terrain have been elucidated and applied in legged robotic systems. Exploying the force dynamics of flapping winged insect flight has provided key discoveries and enabled the fabrication of new micro air vehicles. New classes of materials are being developed that emulate the ability of natural muscle, capturing the compliant and soft subtle movement and performance of biological appendages. In addition, classes of new multifunctional materials are being developed to enable the design of biorobotics with the structural and functional efficiency of living organisms. Optical flow and other sensors based on the principles of invertebrate vision have been implemented on robotic platforms for autonomous robotic guidance and control. These fundamental advances have resulted in the emergence of a new generation of bioinspired dynamic robots which show significant performance improvements in early prototype testing and that could someday be useful in a number of significant applications such as search and rescue and entertainment.

Machine properties optimized in the mesoscale size regime include improved heat transfer, macroscopic electrostatic actuation, and chemical mixing. This manuscript describes the origin of these advantages along with the development of several energy-efficient meso-machines that exploit these properties. The advantages of direct-write mesoscale electronics are also presented. These include the ability to place the electronics on the physical structure of a machine to improve performance, reduce size and weight, and enhance durability.

The application of electroactive polymers (EAP) for mechanical actuation is discussed. A comparison is made between established actuation technologies and polymer actuators. In addition, mammalian muscle properties are compared to some of the observed polymer actuation properties. This paper attempts to analyze actuator performance metrics, as set for current technologies, to determine the feasibility of electroactive polymer actuators in various applications. In this analysis, different mechanical design approaches are reviewed for possible use in EAP actuator applications. Examples of EAP microactuators are presented.

The field of Electroactive Polymers has experienced a considerable amount of expansion over the last decade. Much of this work has been concentrated on developing polymeric materials that mimic biological systems or that exhibit electronic and optical properties similar to inorganic materials. This paper briefly reviews some of the nearer term applications that electroactive polymers might impact: image processing and sonar. In addition, a review of compliant actuators based on the unique properties inherent in electroactive polymers is provided. Emphasis will be placed on the mechanisms responsible for actuation and on the limited mechanical, electrical and chemical data current available. A comparison between mammalian muscle properties and electroactive polymer actuator properties is provided.

A second cluster of genes encoding the E1 alpha, E1 beta, and E2 subunits of branched-chain alpha-keto acid dehydrogenase (BCDH), bkdFGH, has been cloned and characterized from Streptomyces avermitilis, the soil microorganism which produces anthelmintic avermectins. Open reading frame 1 (ORF1) (bkdF, encoding E1 alpha), would encode a polypeptide of 44,394 Da (406 amino acids). The putative start codon of the incompletely sequenced ORF2 (bkdG, encoding E1 beta) is located 83 bp downstream from the end of ORF1. The deduced amino acid sequence of bkdF resembled the corresponding E1 alpha subunit of several prokaryotic and eukaryotic BCDH complexes. An S. avermitilis bkd mutant constructed by deletion of a genomic region comprising the 5' end of bkdF is also described. The mutant exhibited a typical Bkd- phenotype: it lacked E1 BCDH activity and had lost the ability to grow on solid minimal medium containing isoleucine, leucine, and valine as sole carbon sources. Since BCDH provides an alpha-branched-chain fatty acid starter unit, either S(+)-alpha-methylbutyryl coenzyme A or isobutyryl coenzyme A, which is essential to initiate the synthesis of the avermectin polyketide backbone in S. avermitilis, the disrupted mutant cannot make the natural avermectins in a medium lacking both S(+)-alpha-methylbutyrate and isobutyrate. Supplementation with either one of these compounds restores production of the corresponding natural avermectins, while supplementation of the medium with alternative fatty acids results in the formation of novel avermectins. These results verify that the BCDH-catalyzed reaction of branched-chain amino acid catabolism constitutes a crucial step to provide fatty acid precursors for antibiotic biosynthesis in S. avermitilis.

A lyotropic protein liquid crystal was studied experimentally to evaluate its potential as a selective liquid membrane. Concentrated solutions of fibrinogen had nematic like properties under shear and exhibited graded selectivities toward solutes of widely differing sizes when subjected to a two-dimensional velocity field. The magnitude of the selectivity differences was found to depend on the shear orientated direction of the liquid crystal layer. The selectivity seems to be both a solubility phenomena and a relative diffusion phenomena. These anisotropic layers may have potential as controlled variable selectivity membranes.

2-Fluorphenyllithium reacts with chloro-phenyl-phosphines Ph3-n PCl n , = 1, 2, 3 to give diphenyl-(2-fluorophenyl)phosphine 1. bis-(2-fluorophenyl)phenyl-phosphine 2 and tris-(2-fluorophenyl)phosphine 3. The new compounds and their oxides are characterized by 13C-, 31P-NMR and mass spectra. Reaction with bromine yields the dibromtriarylphosphoranes. These compounds form with o-aminophenols two permutation isomeric 2,2,2-triaryl-1,3,2Λ5-benzoxazaphospholes. 2-Fluorphenyllithium reagiert mit Chlor-phenyl-phosphinen Ph3-n PCl n n 1, 2, 3 zu Diphenyl-(2-fluorphenyl)phosphin 1, Bis-(2-fluorphenyl)phenylphosphin 2 und Tris-(2-fluorphenyl)phosphin 3. Die neuen Verbindungen und ihre Oxide werden durch die 13C-und 31P-NMR-sowie die Massenspektren charakterisiert. Umsetzung mit elementarem Brom liefert die Dibromtriarylphosphorane, die sich mit o-Aminophenolen zu den entsprechenden permutationsisomeren 2,2,2-Triaryl-1,3,2Λ5-benzoxazaphospholen umsetzen lassen.

o-Aminophenole oder o-Phenylendiamine reagieren mit 5,5-Dibromdibenzophospholen zu Spirophosphoranen 1–6. Die 31P-, 13C- und 1H-NMR-Spektren sind temperaturunabhangig, so das keine Hinweise fur eine Permutationsisomerisierung aufgefunden wurden. Die Struktur wurde am Beispiel des 4,6-Di-tert-butyl-1-ethyl-1,3-dihydro-2-phenylspiro[2H-1,3,2λ]5-benzodiazaphosphol-2,5′-λ5-dibenzophosphols (5) bestimmt. Die Verbindung kristallisiert in der Raumgruppe P212121 mit Z=4. Die Funfringe sind aquatorial-axial an den Phosphor gebunden. Der Phenylrest und die NH-Gruppe besetzen aquatoriale Positionen, der N–C2H5-Substituent ist axial gebunden. Damit konnen die NMR-Kopplungen zugeordnet werden. Die Spiroverbindungen 1–6 besitzen eine vergleichbare Geometrie. Synthesis and Structure of Spiro[1,3,2λ5-benzoxaza (diaza)phosphole-2,5′λ5-dibenzophospholes] o-Aminophenols or o-phenylenediamines react with 5,5-dibromodibenzophospholes to give spirophosphoranes 1–6. The 31P-, 13C- and 1H-NMR spectra are independent of temperature, therefore, no evidence of a permutation process was detectable. As an example the structure of the heterocyclic compound 4,6-di-tert-butyl-1-ethyl-1,3-dihydro-2-phenylspiro[2H-1,3,2λ5-benzodiazaphosphole-2,5′-λ5-dibenzophosphole] (5) was determined by X-ray crystallography. The compound crystallizes in the space group P212121 with Z=4. The five-membered rings are attached to the phosphorus in an equatorial-axial manner. The phenyl and the NH group occupy equatorial positions, the N–C2H5 substituent is axially located. According to the geometry determined an assignment of the NMR coupling constants was done. Spiro compounds 1–6 show a very similar geometry.

The preparation of various N-(aminophenyl)iminophosphoranes is described. The new compounds are characterized by the usual analytical methods and by 31P-NMR-spectroscopy. For some compounds the results indicate an equilibrium with 2,3-dihydro-1,3,2-λ5-benzodiazaphospholes. The equilibrium constants and the thermodynamic parameters δH, ΔG and ΔS are obtained by quantitative NMR measurements. The position of the equilibrium depends strongly on the substituents as well as on the solvent used. Die Herstellung verschiedener N-(Aminophenyl)iminophosphorane wird beschrieben. Diese neuen Verbindungen werden mit Hilfe der ublichen analytischen Methoden und durch 31P-NMR-Untersuchungen charakterisiert. Dabei zeigte sich, das einige Verbindungen im Gleichgewicht mit den entsprechenden 2,3-Dihydro-1,3,2 δ5-benzodiazaphospholen vorliegen. Die Gleichgewichtskonstanten und die thermodynamischen Parameter ΔH, ΔG and ΔS werden durch quantitative Auswertung der NMR-Spektren bestimmt. Die Lage des Gleichgewichts wi...

In an effort to help determine the feasibility of the Urea process for production of the amine fuels, AFRPL established an in-house program to develop a useful analytical technique for monitoring the critical DMU to UDMH reaction. It was the absence of such a technique that presented problems for Vicksburg Chemical Company during their production contract with AFLC. Using laboratory scale equipment, AFRPL produced UDMH using purified DMU. Analysis of both reaction mixture and distillate was accomplished during all of the synthesis runs. After a variety of attempts, it was concluded that analysis of the DMU to UDMH reaction is difficult and propably not useful. Thus, great care must be taken in the scale up of the Urea process.

This paper represents the major results and conclusions of an AFRPL in-house analysis program set up to verify the capabilities of the monopropellant option of the CONTAM computer code for predicting plume contamination on sensitive spacecraft surfaces. The data used for verification was acquired in an AFRPL sponsored program at JPL. In that program, quartz crystal microbalance surfaces were used to measure the net deposition rate from the plume of a 0.1 lbf hydrazine thruster operating at vacuum conditions. The CONTAM code was used to model the 0.1 lbf thruster and to calculate the net deposition rates measured in the JPL tests. A comparison of the results indicated that the CONTAM code, while predicting the correct trends, overpredicts the plume mass deposition rates. Possible explanations for this deviation as well as a discussion of future studies to further understand the model's limitations are presented.