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Many animal species use stereotyped displays to attract the opposite sex and to intimidate same-sexed rivals. Research aimed at understanding display recognition, function, and usage can be aided through the use of animal robots that allow one side of signaler–receiver interactions to be controlled. Manipulation of displays in ways that do not occur in nature has the potential to determine the boundaries of display recognition, as well as to provide insights into the manner in which animal display contests are structured. We describe two experiments that extend previous work on display recognition in the lizard Anolis grahami. In the first experiment, we used robots to determine the relative importance of body coloration and headbob display structure for species recognition. The results showed that subjects responded more strongly to robots having both conspecific appearance and display structure than to robots that deviated in those characteristics from the conspecific stimulus. In the second ...

Previous studies of Schizocosa ocreata wolf spiders have shown that visual and vibration signals are equally capable of eliciting female receptivity, but that multimodal cues enhance female response. Studies also indicate that signals in both modes convey male quality information; females choose males with larger foreleg tufts or greater amplitude vibratory signals. Male spiders eavesdrop on both the visual and vibration signals of other males and exploit them to find mates. We examined female mate preferences and male eavesdropping using video-vibratory playback experiments. Female S. ocreata respond to playback of male courtship, showing responses to both visual and vibratory signals alone, as well as multimodal playback. Females also showed preference for male quality indicators in both sensory modes. Eavesdropping males responded to playback of male courtship with displays of their own, but responded to signal modes differently. Males displayed a higher rate of courtship tapping in response to isolated vibration signals compared to visual or multimodal stimuli. However, in choice tests, males responded with higher display rates with multimodal and visual stimuli. Results suggest that visual, vibratory and multimodal courtship signals provide information about potential mates and rivals, and that responses of males and females may differ depending on context.

The brain is that portion of the central nervous system (CNS) that lies within the skull. Three major subdivisions are recognized: the brainstem, the cerebellum, and the cerebrum. The cerebrum includes both the cerebral hemispheres and the diencephalon. Brainstem The brainstem is the rostral continuation of the spinal cord. The foramen magnum, the hole at the base of the skull, marks the junction of the spinal cord and brainstem. The brainstem consists of three subdivisions: the medulla, the pons, and the midbrain (Figure 2.1). Medulla The caudal limit of the medulla lies at the foramen magnum. The central canal of the spinal cord expands in the region of the medulla to form the fourth ventricle (IV in Figure 1.2). Cranial nerves associated with the medulla are the hypoglossal, spinal accessory, vagus, and the glossopharyngeal. Pons The pons lies above (rostral to) the medulla (see Figure 2.1). The bulk of the medulla is continuous with the pontine tegmentum. The tegmentum consists of nuclei and tracts that lie between the basilar pons and the floor of the fourth ventricle (IV in Figure 1.2; see Figure 10.2). The basilar pons consists of tracts along with nuclei that are associated with the cerebellum. The fourth ventricle narrows at the rostral end of the pons to connect with the cerebral aqueduct of the midbrain (see Figures 1.2, 10.2–10.4). Cranial nerves associated with the pons are the statoacoustic (previously known as the auditory), facial, abducens, and trigeminal.

Emil Kraepelin (1919) suggested that abnormalities in the frontal lobe were responsible for problems in reasoning and that damage to the temporal lobe resulted in delusions and hallucinations in patients with dementia praecox (schizophrenia). The classical findings of Kluver and Bucy in the 1930s clearly and strongly linked the temporal lobes to behavior. Their work provided the basis from which the concept of the limbic system has developed. The temporal lobe can be divided into two regions: lateral and ventromedial. The lateral region supports cognitive functions associated with several sensory systems. It is recognized as neocortex and is the focus of this chapter. The ventromedial region of the temporal lobe contains major portions of the limbic system and thus contributes significantly to emotional tone. The ventromedial, limbic temporal lobe is discussed in Chapter 11. It is now accepted that dysfunction of the dorsolateral region of the temporal lobe may be associated with several psychopathological states. Temporal lobe lesions due to a variety of neurological insults can lead a patient to present with signs and symptoms that are more consistent with a psychiatric diagnosis than with a traditional neurological one. Anatomy and behavioral considerations The temporal lobe lies ventral to the lateral fissure (of Sylvius) and the parietal lobe. It is rostral to the occipital lobe (Figure 5.1). The superior temporal sulcus and the lateral fissure lie above the superior temporal gyrus and are particularly deep.

Hypothalamus The hypothalamus is the region of the mammalian brain that is most important in the coordination of behaviors essential for the maintenance and continuation of the species. Although the hypothalamus occupies only about 0.15% of the volume of the human brain, it plays a major role in the regulation and release of hormones from the pituitary gland, maintenance of body temperature, and organization of goal-seeking behaviors such as feeding, drinking, mating, and aggression. It is the primary center for the control of autonomic function. It is also the region of the brain that is essential for behavioral adjustments to changes in the internal or external environment (Figure 8.1). The hypothalamus is a very old structure with striking similarity between humans and lower animals. It is made up of a number of nuclei and scattered cell groups. Some hypothalamic cell groups control specific functions (e.g., blood pressure, heart rate, etc.) through the coordinated action of short intrahypothalamic connections. Other nuclei operate by projections to structures outside the confines of the hypothalamus. Anatomical and behavioral considerations The hypothalamus lies on either side of the walls of the third ventricle below the level of the hypothalamic sulcus (Figure 8.2, see Figures 9.2, 9.3, and 14.6). It is bounded in front (rostrally) by the lamina terminalis and optic chiasm, laterally by the optic tracts, and behind by the mamillary bodies. Some hypothalamic nuclei are continuous across the floor of the third ventricle.

Several investigations into brain activation caused by pain have suggested that the multiple painful stimulations used in typical block designs may cause attenuation over time of the signal within activated areas. The effect this may have on pain investigations using multiple tasks has not been investigated. The signal decay across a task of four repeating pain stimulations and between two serial pain tasks separated by a 4-min interval was examined to determine whether signal attenuation may significantly confound pain investigations.The characteristics of the brain activation of six subjects were determined using whole brain blood oxygenation level-dependent functional magnetic resonance imaging on a 1.5-T scanner. Tasks included both tingling and pain induced by transcutaneous electrical stimulation of the median nerve. The average group maps were analyzed by general linear modeling with corrected cluster P values of less than 0.05. The time courses of individual voxels were further investigated by analysis of variance with P values of less than 0.05.Significant differences between pain and tingling were found in the ipsilateral cerebellum, contralateral thalamus, secondary somatosensory cortex, primary somatosensory cortex, and anterior cingulate cortex. Highly significant signal decay was found to exist across each single pain task, but the signal was found to be restored after a 4-min rest period.This work shows that serial pain tasks can be used for functional magnetic resonance imaging studies using electrical nerve stimulation as a stimulus, as long as sufficient time is allowed between the two tasks.

Reaction of 3 equiv of 2,6-diisopropylaniline with La[N(SiMe(3))(2)](3) produces the dimeric species La(2)(NHAr)(6) (1). X-ray crystallography reveals a centrosymmetric structure, where the dimeric unit is bridged by intermolecular eta(6)-arene interactions of a unique arylamide ligand attached to an adjacent metal center. Exposure of 1 to THF results in formation of the monomeric tris-THF adduct La(NHAr)(3)(THF)(3) (2), which was shown by X-ray crystallography to maintain a fac-octahedral structure in the solid state. (1)H NMR spectroscopy illustrates that the binding of THF to 1 to form 2 is reversible and removal of THF under vacuum regenerates dimeric 1. Addition of pyridine to 1 yields the monomeric bis-pyridine adduct La(NHAr)(3)(py)(2) (3), which exhibits a distorted trigonal-bipyramidal La metal center. Solution (1)H NMR, IR, and Raman spectroscopy indicate that the pi-arene-bridged dimeric structure of 1 is maintained in solution. Variable-temperature (1)H NMR spectroscopic investigations of 1 are consistent with a monomer-dimer equilibrium at elevated temperature. In contrast, variable-temperature (1)H NMR spectroscopic investigations of the aryloxide analogue La(2)(OAr)(6) (4) show that the bridging and terminal aryloxide groups exchange by a mechanism in which the dimeric nature of the compound is retained. Density functional theory (DFT) calculations were carried out on model compounds La(2)(OC(6)H(5))(6), La(2)(NHC(6)H(5))(6), and (C(6)H(5)R)La(XC(6)H(5))(3), where X = O or NH and R = H, OH, or NH(2). The formation of eta(6)-arene interactions is energetically favored over monomeric LaX(3) (X = OPh or NHPh) with the aryloxide pi-arene interaction being stronger than the arylamide pi-arene interaction. Calculation of vibrational frequencies reveals the origin of the observed IR spectral behavior of both La(2)(OC(6)H(5))(6) and La(2)(NHC(6)H(5))(6), with the higher energy nu(C=C) stretch due to terminal ligands and the lower energy stretch associated with the bridging ligands.

Pu L 3 XAFS measurements show that the excess oxygen in single phase PuO 2 + x occurs as oxo groups with Pu-O distances of 1.83-1.91 A. This distance and the energy of the edge (via comparison with a large number of related compounds) are more consistent with a Pu(IV/V) than a Pu(IV/VI) mixture. Analogous to Pu(IV) colloids, although the Pu-Pu pair distribution remains single site even when it shows substantial disorder, the Pu-O distribution can display a number of additional shells at specific distances up to 3.4 A even in high fired materials when no oxo groups are present, implying intrinsic H + /OH - (/H 2 O). The number of oxo atoms increases when samples are equilibrated with humid air at ambient temperature, indicating that the Pu reactivity in this solid system differs notably from that of isolated complexes and demonstrating the importance of nanoscale cooperative phenomena and total free energy in determining its chemical properties.

Reaction of equimolar quantities of Sm[N(SiMe(3))(2)](3) and Al(i-Bu)(3) with 6 equiv of iso-propyl alcohol in toluene leads to the formation of the mixed-metal alkoxide complex [[(i-Pr-O)(i-Bu)Al(mu-O-i-Pr)(2)Sm(O-i-Pr)(HO-i-Pr)](mu-O-i-Pr)](2) (1). An analogous reaction between 1:1 Sm[N(SiMe(3))(2)](3)/Al(i-Bu)(3) and 6 equiv of tert-butyl alcohol, followed by addition of THF, produces the THF adduct [(THF)(2)Sm(O-t-Bu)(2)(mu-O-t-Bu)(2)Al(i-Bu)(2)] (2). Compound 1 crystallizes in the space group P1 while 2 crystallizes in space group Cmcm. Cell parameters for 1: a = 11.028(2) A, b = 12.168(2) A, c = 12.879(2) A, alpha = 82.84(1) degrees, beta = 64.88(1) degrees, gamma = 70.80(1) degrees, Z = 1. Cell parameters for 2: a = 11.304(2) A, b = 22.429(4) A, c = 15.768(2) A, Z = 4. Attempts to prepare the bulkier derivatives result in the formation of lanthanide aryloxide species only; reaction between equimolar amounts of Ln[N(SiMe(3))(2)](3) (Ln = Sm, Nd) and Al(i-Bu)(3) with 6 equiv of HO-2,4,6-Me(3)C(6)H(2), followed by the addition of THF or pyridine, yields the Lewis base adducts Sm(OAr)(3)(THF)(3) (3) and [Nd(mu-OAr)(OAr)(2)(py)(2)](2) (4). Compound 3 crystallizes in the space group Pbca while 4 crystallizes in space group P2(1)/c. Cell parameters for 3: a = 16.5822(9) A, b = 15.5668(9) A, c = 29.902(2) A, Z = 8. Cell parameters for 4: a = 13.4496(8) A, b = 20.034(1) A, c = 16.206(1) A, beta = 113.782(1) degrees, Z = 2. Reaction of Al(2)(O-t-Bu)(6) with [Sm(OAr)(3)](2) (Ar = 2,6-i-Pr(2)C(6)H(3)) yields the adduct (ArO)(3)Sm[(mu-O-t-Bu)(2)Al(2)(O-t-Bu)(4)] (5), which crystallizes in the space group P2(1)/n. Cell parameters for 5: a = 14.0960(7) A, b = 27.3037(15) A, c = 16.7893(9) A, beta = 92.216(1) degrees, Z = 4.

Treatment of nitrobenzene and other various nitroarenes with 6 equiv of samarium(II) under strictly anhydrous conditions allows for the isolation of aniline or the corresponding arylamine. Reducing the number of samarium(II) equivalents allows for the isolation of intermediate species, e.g., azoarenes or hydrazines. Use of Sm[N(SiMe(3))(2)](2), in place of the typically used SmI(2), has allowed for the detailed examination of the aqueous and nonaqueous species formed in this reduction and has been instrumental in delineation of the stepwise reaction mechanism. This is the first time that the reaction intermediates of an organic reaction mediated by samarium(II) have been isolated and analyzed by (1)H NMR and X-ray crystallography.

Investigation of behavior of actinides in alkaline media containing AL(III) showed that no aluminate complexes of actinides in oxidation states (IIII-VIII) were formed in alkaline solutions. At alkaline precipitation IPH (10-14) of actinides in presence of AL(III) formation of aluminate compounds is not observed. However, in precipitates contained actinides (IIV)

Males of the dimorphic jumping spider (Maevia inclemens) differ in both their morphologies and courtship displays (i.e. phase I). The tufted morph stilts and waves from an average distance of 9 cm from a female, whereas the grey morph crouches and sidles from an average distance of 3 cm from a female. The objective of this study was to determine the significance of the different courtship displays using computeranimated versions of males performing phase I courtship in a Y-maze where first male movement and then the distance of the stimulus was controlled. Females selected the first male that they orientated to at the close distance of 4 cm and at the far distance of 16cm. However, there was no preference for the first male at the intermediate distance of 8 cm or the furthest distance of 24 cm. In addition, males have morph-specific advantages regarding the time it takes to attract female attention. Grey males attracted female attention in less time than tufted males at 4 and 8 cm. However, tufted males attracted female attention in less time than grey males at 16 cm. These results suggest a mechanism for the evolution of two different courtship displays whereby each morph has an advantage at different distances from the female.

1; R1 = H, R2 = (E)-SiMe3) [86422-21-1] C8H16O2Si (MW 172.33) InChI = 1S/C8H16O2Si/c1-8(9)10-6-5-7-11(2,3)4/h5,7H,6H2,1-4H3/b7-5+ InChIKey = KWDYUHNACUTFNF-FNORWQNLSA-N 2; R1 = H, R2 = (Z)-SiMe3) [86422-22-2] InChI = 1S/C8H16O2Si/c1-8(9)10-6-5-7-11(2,3)4/h5,7H,6H2,1-4H3/b7-5- InChIKey = KWDYUHNACUTFNF-ALCCZGGFSA-N (E + Z) [80401-14-5] InChI = 1S/C8H16O2Si/c1-8(9)10-6-5-7-11(2,3)4/h5,7H,6H2,1-4H3 InChIKey = KWDYUHNACUTFNF-UHFFFAOYSA-N 3; R1 = SiMe3, R2 = H) [80401-11-2] InChI = 1S/C8H16O2Si/c1-6-8(10-7(2)9)11(3,4)5/h6,8H,1H2,2-5H3 InChIKey = IAMQLXWPWSUFPI-UHFFFAOYSA-N (preparation of vinylsilanes via the corresponding allylmetal complexes;1 oxygenated allylsilane reagents for nucleophilic addition and substitution reactions2) Preparative Method: (i) from 3-trimethylsilyl-2-propyn-1-ol by reduction (Sodium Bis(2-methoxyethoxy)aluminum Hydride (Red-Al), 70%)3 and acetylation (Acetyl Chloride, Pyridine, 78%);4 (ii) from 3-trimethylsilyl-2-propyn-1-ol by reduction (P-2 Raney Nickel, H2, 86%)5 and acetylation; (iii) from allyloxytrimethylsilane by a metalation–rearrangement sequence (tert-Butyllithium, 90%)2a,6 and acetylation (Acetic Anhydride, Triethylamine, 76%).2a Handling, Storage, and Precautions: use in a fume hood.

[76524-71-5] C7H12O3 (MW 144.17) InChI = 1S/C7H12O3/c1-4-9-6(2)5-10-7(3)8/h2,4-5H2,1,3H3 InChIKey = PLNQLUGDZHDPRC-UHFFFAOYSA-N (preparation of enol ethers via the corresponding allylpalladium complexes;1 cyclopentenone annulation1) Alternate Name: 3-acetoxy-2-ethoxy-1-propene. Preparative Methods: by reaction of α-lithioethyl vinyl ether with Paraformaldehyde (40–50%) followed by acetylation (Acetic Anhydride, Pyridine).1 Handling, Storage, and Precautions: use in a fume hood.

[6149-41-3] C4H8O3 (MW 104.12) InChI = 1S/C4H8O3/c1-7-4(6)2-3-5/h5H,2-3H2,1H3 InChIKey = RVGLEPQPVDUSOJ-UHFFFAOYSA-N (preparation of α-substituted acrylate and hydracrylate derivatives;1 photochemical conjugate additions;2 protection of the carboxy group3) Alternate Names: methyl 3-hydroxypropanoate; methyl hydracrylate. Physical Data: bp 71–73 °C/9 mmHg.4 Analysis of Reagent Purity: 1H NMR and MS.5 Preparative Methods: two methods have been published: reaction of β-Propiolactone with Sodium Methoxide in MeOH (17–36%),5, 6 or treatment of 3-hydroxypropionitrile with HCl in aqueous MeOH (68%).4 The latter method appears to be more desirable based upon yield of product and the high cost and toxicity of β-propiolactone.

Increased survival of C57BL/6 renal allografts following portal vein donor-specific pretransplant immunization of C3H mice is associated with increased expression of the molecule OX2 seen on host dendritic cells, along with a marked polarization in cytokine production from lymphocytes harvested from the transplanted animals, with preferential production of IL-4, IL-10, and TGF-β on donor-specific restimulation in vitro, and decreased production of IL-2, IFN-γ, and TNF-α compared with non-portal vein-immunized control transplanted mice. The increased renal allograft survival and the altered cytokine production are abolished by infusion of anti-mouse OX2 mAb (3B6). Infusion of a soluble OX2:Fc immunoadhesin can itself produce significant prolongation of xeno- and allografts in mice. We have used FITC-conjugated OX2:Fc to characterize cells expressing a ligand (OX2L) for OX2, and provide evidence that subpopulations of LPS-stimulated splenic macrophages, Con A-activated splenic T cells, and the majority (>80%) of γδTCR+ T cells express this ligand. We show below that F4/80+, OX2L+ splenic macrophages, admixed with OX2:Fc, represent a potent immunosuppressive population capable of causing more profound inhibition of alloreactivity in vitro or in vivo than that seen using either OX2:Fc or OX2+ (or OX2L+) cells alone. Immunoregulation by this OX2L+ population occurs in an MHC-restricted fashion.

The question of why receivers accept a selfish signaller's message as reliable or 'honest' has fuelled ample controversy in discussions of communication. The handicap mechanism is now widely accepted as a potent constraint on cheating. Handicap signals are deemed reliable by their costs: signallers must choose between investing in the signal or in other aspects of fitness. Accordingly, resources allocated to the signal come to reflect the signaller's fitness budget and, on average, cheating is uneconomic. However, that signals may also be deemed reliable by their design, regardless of costs, is not widely appreciated. Here we briefly describe indices and amplifiers, reliable signals that may be essentially cost free. Indices are reliable because they bear a direct association with the signalled quality rather than costs. Amplifiers do not directly provide information about signaller quality, but they facilitate assessment by increasing the apparency of pre-existing cues and signals that are associated with quality. We present results of experiments involving a jumping spider (Plexippus paykulli) to illustrate how amplifiers can facilitate assessment of cues associated with physical condition without invoking the costs required for handicap signalling.

When Jean-Luc Marion published Dieu sans l’etre: Hors-texte in 1982, it was mistaken by some as another apocalyptic pronouncement on the death of God, one more in a series of obituaries characterizing post-modernity — the end of ‘Man’, the end of history, the end of metaphysics. Decisively answering these critics in the preface to the English translation, Marion argues instead that ‘Under the title God Without Being we do not mean to insinuate that God is not, or that God is not truly God. We attempt to meditate on what F.VV. Schelling called ‘the freedom of God with regard to his own existence’ (2).1 That Marion turns first to the German philosopher to speak on behalf of his work is telling, for Philosophical Inquiries into the Nature of Human Freedom (1809) — the text that Marion cites and the primary object of my analysis here — informs his argument in complex and pervasive ways that I will only be able to address briefly.2 Freedom for Marion, as for Schelling, begins with the liberation of God — a task whose outcome can never be guaranteed — from the lifeless Kantian and Cartesian abstractions or ‘idols’ with which European philosophical modernity has, in the name of the Enlightenment, peremptorily replaced the divine: “God” as ultimate foundation, with Leibnitz; “God” as “God of morality”, with Kant, Fichte … “God” finally and above all as causa sui with Descartes, Spinoza, and in the end all of metaphysics’ (64). Schelling will devote the first part of the treatise on freedom to parsing the same list of the divine names of God, rejecting each for saying too much or too little about him. Where God is concerned, especially where the philosopher’s and the theologian’s God is concerned, one always says too much or too little. Whatever and wherever God is, he is always otherwise and elsewhere, fundamentally in excess of our figures and places for him, otherwise even than the subtlest of idolatries: namely, ‘the basic condition that renders all other conditions possible and even necessary — for us, humans — the fact of Being’ (xx). But how can we designate that which is radically indifferent to Being, not only to the ontic differences between what is and what is not, but also, more fundamentally, to the unthought ontological difference that constitutes the opening of that ‘between’? A very Schellingian question to ask, as it turns out.

By utilizing X-ray absorption methods, e.g., extended x-ray absorption fine structure (EXAFS) and single crystal x-ray diffraction (XRD), as well as Raman, UV-Vis and fluorescence spectroscopy, we have shown that an equilibrium exists between the monomeric uranyl hydroxide species UO2(OH)42− and UO2(OH)53−, which is dependent upon hydroxide concentration. Upon further study of this system, we have now determined that a new hydrolysis product is present in equilibrium with the monomeric uranyl hydroxide species, which is favored at higher UO22+ concentrations.

The mammalian fetus has been perceived, paradoxically, as a successful allograft, a successful tumor, and a successful parasite. Success depends on fetal trophoblast cells, which form the interface with the mother. The maternal immune system is involved in the success of pregnancy and in its failure. The discovery that maternal gammadelta T cells may recognize and react to the fetal trophoblast and the definition of a vascular mechanism whereby their Th1 and Th2/3-type cytokines may abort embryos replaces confusion and debate with a new and simple clarity that enables further research.

Synthese de cis-2,3-divinyl epoxydes a partir d'enynols et rearrangement de Cope conduisant en cinq etapes au cycle 4,5-dihydrooxepine

Video and computer technology have emerged as a powerful tool for controlling visual stimuli and investigating questions about perception in a variety of animal taxa, including spiders (Clark and Uetz, 1990, 1992, 1994), birds (Evans and Marler, 1991; Evans et al., 1993a, 1993b), lizards (Macedonia et al., 1994; Macedonia and Stamps, 1994), anuran amphibians (Roster et al. 1995), and teleost fishes (Rosenthal et al., 1996; Rowland et al., 1995a, 1995b). Video playback and computer animation of test stimuli afford several benefits over

In a theoretical age often enamoured by the “playfulness” of the sign and the pleasure of the text, Paul de Man’s last writings stand out as darkly sobering, driven as they are by an almost ascetic desire to bring thinking into proximity with what he calls, after Walter Benjamin, “reine Sprache,” pure language, or, more precisely, that which is purely language.2 From the stringent and self-cancelling perspective afforded by de Man’s late essays, the affirmatively Nietzschean rhetoric of some recent, linguistically-oriented theory—Canadian postmodernism is the example that I will explore here—registers the work of a deeply rooted aesthetic ideology that determines the play of signs primarily as the play of meaningful signs, which is to say legible signs that are happily and familiarly available to comprehension. What is familiarly known about signification is not properly known, however, for the simple reason that familiarity has as its primary effect the refusal to admit the negative possibility that “Language is not exhausted by the thought of the human” (Redfield 51). It could be argued that postmodernism’s greatest insight is into the fundamental indeterminacy of sign-systems, whether graphic, phonic, psychological, political, sexual, or economic, but that this same insight tends strongly to blind it to language’s most unsettling features, blankly in-significant and in-human as such.

An infrared imaging system based on a high resolution platinum silicide detector has been developed. The detector is a 486 x 640 Schottky Barrier photodiode array with a CCD readout multiplexer. The imaging system includes signal processing electronics to correct the fixed pattern noise and implements a histogram projection algorithm for automatic gain and offset adjustment and dynamic range compression. The perfonnance of the pattern noise correction has been demonstrated to reduce the residual pattern noise below the image shot noise over a scene temperature range of more than 50°C. The effect of optical cmss talk in the imager has been examined. The magnitude of the side lobes has been found to be a factor of about 7 x 10' smaller than the central spot.

An infrared imaging system based on a high resolution platinum suicide detector has been developed. Thedetector is a 486 x 640 Schottky Barrier photodiode array with a CCD readout multiplexer. The imaging systemincludes signal processing electronics to correct the fixed pattern noise and implements a histogram projection algorithm for automatic gain and offset adjustment and dynamic range compression. The performance of the pattern noise correction has been demonstrated to reduce the residual pattern noise below the image shot noise over a scene temperature range of more than 50 The effect of optical cross talk in the imager has been ex-amined. The magnitude of the side lobes has been found to be a factor of about 7 x iO smaller than the centralspot. 1. INTRODUCTIONPlatinum silicide detectors can be produced that offer much higher resolution for staring infrared systems thanis economically feasible with competing technologies. Resolution as high as 486 x 640 has been available for overthree years and megapixel resolution devices are within the reach of current technology. PtSi systems also showvery low pattern noise and highly stable pixel response. In addition to the desirable performance capabilities of thedevices and imaging systems, low to moderate cost systems can be produced. These characteristics are a result ofthe application of mature silicon technology, the monolithic construction of the devices, and the simplicity of the

The ability of a system based on a high-speed area array detector to simultaneously track and receive data from multiple low-power optical communication beacons is demonstrated. Specifically, the MOCTR POC system has achieved tracking precision of order 0.1 pixel with 2.7 picowatts, the minimum beacon power for the assumed system architecture; a data rate of 1 kbps with BER of order 1 to 10 x 10 exp -5, readily correctable with forward error correction; tracking and communication with simulated maximum earth background in the detector FOV; and simultaneous tracking of asynchronously modulated beacons. Areas needed to be addressed before an operational system can be implemented include reduction in size, weight and power, the demonstration of independent acquisition of multiple beacons, and the implementation of a full tracking algorithm in firmware.

A proof-of-concept (POC) demonstration system has been developed which demonstrates acquisition, tracking and point-ahead angle sensing for a space optical communications terminal utilizing a single high speed area array detector. The detector is the 128 x 128 pixel Kodak HS-40 photodiode array. It has 64 parallel readout channels and can operate at frames rates up to 40,000 frames/sec with rms readout noise of 20 photoelectrons. A windowing scheme and special purpose digital signal processing electronics are employed to implement acquisition and tracking algorithms. The system operates at greater than 1 kHz sample (frame) rates. Acquisition can be performed in as little as 30 milliseconds with less than 1 picowatt of 0.85 micron beacon power on the detector. At the same power level, the rms tracking accuracy is approximately 1/16 pixel. Results of system analysis and measurements using the POC system are presented.

Improved methods for measuring low pressures in cryogenic systems are described. Pressure transducers and associated sensing lines are thermally coupled to the cryogen to eliminate thermo-acoustic-oscillations (TAO) caused by thermal gradients between the flow line and the transducer. The applications include flow and density measurement, and vapor bubble detection. Fully immersed and externally mounted transducers are used in these methods to reduce heat leak and measurement uncertainty. Implementation considerations are discussed, including transducer selection and temperature compensation.

Synthese de cis-2,3-divinyl epoxydes a partir d'enynols et rearrangement de Cope conduisant en cinq etapes au cycle 4,5-dihydrooxepine

Space based optical communications systems that communicate with several satellites need a method to simultaneously track multiple platforms and receive low rate data from each platform. The tracking and data link are required to manage the communications network and to facilitate rapid switching of a high data rate optical link. We will describe a proof-of-concept (POC) system that utilizes a high speed area array detector to simultaneously track and receive data from multiple optical communications beacons. The tracking has sufficient precision to permit rapid acquisition and tracking of any of the beacons by a high speed optical link. The sensitivity of the system is sufficient to permit open loop pointing of divergent beacons. The beacon can be modulated at kilobit/sec rates and the tracking system is capable of synchronizing and extracting the data from all the beacons being tracked.