Real-time, large-depth holographic 3D head-up display: selected aspects.

Today's state-of-the-art automotive head-up displays (HUD) possess single- or double layer focal planes that limit the observers' eye focus to these planes when crucial information is shown. Other visual 3D cues such as motion parallax also suffer from this limitation. The resulting viewing experience contradicts the natural way of viewing during driving or interaction, when alerts and hints should appear at the correct projection depth where real objects of interest are located. Here we present a real-time holographic HUD with continuous depth that supports the intuitive and natural way of viewing and interacting with virtual environments outside and inside the car. We demonstrate full-color, 3D real-time encoding within a field-of-view of 5∘×3∘.

Doubly Dressed Bosons: Exciton Polaritons in a Strong Terahertz Field.

We demonstrate the existence of a novel quasiparticle, an exciton in a semiconductor doubly dressed with two photons of different wavelengths: a near infrared cavity photon and terahertz (THz) photon, with the THz coupling strength approaching the ultrastrong coupling regime. This quasiparticle is composed of three different bosons, being a mixture of a matter-light quasiparticle. Our observations are confirmed by a detailed theoretical analysis, treating quantum mechanically all three bosonic fields. The doubly dressed quasiparticles retain the bosonic nature of their constituents, but their internal quantum structure strongly depends on the intensity of the applied terahertz field.

[A rare coagulation disorder. Diagnostics and management in cases of hereditary dysfibrinogenemia]. / Seltene Ursache einer hämorrhagischen Diathese. Diagnostik und perioperatives Management bei hereditärer Dysfibrinogenämie.

Before elective surgery, it is mandatory that a precise history be taken to detect increased hemorrhagic diathesis and that thrombocytes, Quick/INR, and aPTT be determined. If pathological levels are found, further laboratory tests are necessary after frequent causes (e.g., liver cirrhosis) have been excluded. Single-factor analysis for the von Willebrand's factor antigen and if necessary further tests to check for von Willebrand's syndrome (multimeric analysis) as well as platelet function tests should be performed.Dysfibrinogenemia is a rare coagulation disorder, which causes elevated INR. It shows a wide spectrum of clinical manifestations including thrombophilia, excessive bleeding, and even asymptomatic cases. We present a 72-year-old patient with asymptomatic dysfibrinogenemia who needed hip replacement due to arthrosis. Lowered fibrinogen levels were substituted prior to operation and the clinical course afterwards was uneventful under additional prophylactic anticoagulation in order to prevent thrombosis. The case report illustrates the interdisciplinary teamwork which is very important in the management of patients with coagulation disorders.

Clinical outcomes after treatment of intra-bony defects with an EMD/synthetic bone graft or EMD alone: a multicentre randomized-controlled clinical trial.

OBJECTIVES: Comparison of the outcomes of a combination of an enamel matrix derivative and a synthetic bone graft (EMD/SBC) with EMD alone in wide intra-bony defects. MATERIAL AND METHODS: Seventy-three patients with chronic periodontitis were recruited in five centres in Germany. All patients had one wide intra-bony defect of >/=4 mm. Surgical procedures involved microsurgical technique and the modified papilla preservation flap. After debridement, defects were randomly assigned to EMD/SBC (test) or EMD (control). Assessments at baseline and after 6 months included bone sounding, attachment levels, probing pocket depths, bleeding on probing and recessions. Early wound-healing, adverse effects and patients' perceptions were also recorded. RESULTS: Both treatment modalities led to significant clinical improvements. Change in bone fill 6 months after surgery was 2.0 mm (+/- 2.1) in the test group and 2.1 mm (+/- 1.2) in the control group. A gain in clinical attachment of 1.3 mm (+/- 1.8) in the test group and 1.8 mm (+/- 1.6) in the control group was observed. One week after surgery, primary closure was maintained in 95% of the test sites and 100% of the control sites. No differences in patients' perceptions were found. CONCLUSION: The results of the present study showed similar clinical outcomes following both treatment modalities.

Volatile and Within-Needle Terpene Changes to Douglas-fir Trees Associated With Douglas-fir Beetle (Coleoptera: Curculionidae) Attack.

Mass attack by tree-killing bark beetles (Curculionidae: Scolytinae) brings about large chemical changes in host trees that can have important ecological consequences. For example, mountain pine beetle (Dendroctonus ponderosae Hopkins) attack increases emission of terpenes by lodgepole pine (Pinus contorta Dougl. ex Loud.), affecting foliage flammability with consequences for wildfires. In this study, we measured chemical changes to Douglas-fir (Pseudotsuga menziesii var. glauca (Mirb.) Franco) foliage in response to attack by Douglas-fir beetles (Dendroctonus pseudotsugae Hopkins) as trees die and crowns transitioned from green/healthy, to green-infested (year of attack), to yellow (year after attack), and red (2 yr after attack). We found large differences in volatile and within-needle terpene concentrations among crown classes and variation across a growing season. In general, emissions and concentrations of total and individual terpenes were greater for yellow and red needles than green needles. Douglas-fir beetle attack increased emissions and concentrations of terpene compounds linked to increased tree flammability in other conifer species and compounds known to attract beetles (e.g., [Formula: see text]-pinene, camphene, and D-limonene). There was little relationship between air temperature or within-needle concentrations of terpenes and emission of terpenes, suggesting that passive emission of terpenes (e.g., from dead foliage) does not fully explain changes in volatile emissions. The potential physiological causes and ecological consequences of these bark beetle-associated chemical changes are discussed.

Quantum holography.

We propose to make use of quantum entanglement for extracting holographic information about a remote 3-D object in a confined space which light enters, but from which it cannot escape. Light scattered from the object is detected in this confined space entirely without the benefit of spatial resolution. Quantum holography offers this possibility by virtue of the fourth-order quantum coherence inherent in entangled beams.

Spatial correlations of spontaneously down-converted photon pairs detected with a single-photon-sensitive CCD camera.

A single-photon-sensitive intensified charge-coupled-device (ICCD) camera has been used to simultaneously detect, over a broad area, degenerate and nondegenerate photon pairs generated by the quantum-optical process of spontaneous parametric down-conversion. We have developed a new method for determining the quantum fourth- order correlations in spatially extended detection systems such as this one. Our technique reveals the expected phase-matching-induced spa- tial correlations in a 2-f Fourier-transform system.

Spectral characteristics of the responses of primary auditory-nerve fibers to amplitude-modulated signals.

The spectral responses of cat single primary auditory nerve fibers to sinusoidal amplitude-modulated (AM) and double-sideband (DSB) acoustic signals applied to the ear were examined. DSB is an amplitude-modulated signal with a suppressed carrier. Period histograms were compiled from the neural spike-train data, and the frequency spectrum was determined by Fourier transforming these histograms. For DSB signals, spectral components were found to be present at the frequencies of the stimulus as well as at certain combination frequencies. For AM signals, several clusters of spectral components were present. The lowest-frequency cluster consisted of components at DC, at the modulation frequency, and at its harmonics. A higher frequency cluster occurs around a component with the frequency of the carrier. The components of cluster are separated from the carrier by the modulation frequency and its harmonics. Yet higher-frequency clusters appear around multiples of the carrier frequency with components at frequencies separated from these multiples by the modulation frequency and its harmonics. The magnitudes of these spectral components were determined for carrier frequencies located below, at, and above the characteristic frequency of the units, and for different stimulus levels, modulation frequencies, and modulation depths. The low-frequency components present in the neural spike train appear to be the result of demodulation taking place in the inner ear. The demodulated components are strong and are present over a wide range of sound levels, carrier frequencies, modulation frequencies, and nerve-fiber characteristics. This demodulation may be significant for speech recognition.

Spectral characteristics of the responses of primary auditory-nerve fibers to frequency-modulated signals.

The spectral responses of cat single primary auditory nerve fibers to sinusoidal frequency-modulated acoustic signals applied to the ear are examined. Period histograms were constructed from the neural spike-train data, and the frequency spectrum was determined by Fourier transforming these histograms. Several clusters of spectral components were present. The lowest-frequency cluster consists of components at DC, at the modulation frequency, and at its harmonics. In the next cluster, components surround the carrier frequency and are separated from it by the modulation frequency and its harmonics. Higher-frequency clusters surround frequencies that are twice and three times the carrier frequency. The components in each cluster are separated from the multiples of the carrier frequency by the modulation frequency and its harmonics. The magnitudes of the spectral components were investigated for carrier frequencies located below, at, and above the unit characteristic frequency, and for different signal levels, modulation frequencies, and modulation indices. The components at the modulation frequency and its harmonics were strong and present over a wide range of signal levels, carrier frequencies, modulation frequencies, and nerve-fiber characteristics. The presence of components at the modulation frequency indicates that a demodulation process is occurring. This process may be significant for speech recognition.

Rate fluctuations and fractional power-law noise recorded from cells in the lower auditory pathway of the cat.

The noise properties of the sequence of action potentials recorded from adult-cat auditory nerve fibers and lateral superior olivary units have been investigated under various stimulus conditions. Large fluctuations exhibited by the spike rate, and spike clusters evident in the pulse-number distribution, both indicate an unusual underlying sequence of neural events. We present results demonstrating that (i) the firing rate calculated with different averaging times can exhibit self-similar behavior; (ii) the pulse-number distribution remains irregular even for large numbers of samples; (iii) the spike-number variance-to-mean ratio increases with the counting time T in fractional power-law fashion for sufficiently large T; and (iv) the exponent in the power law generally depends on the stimulus level. The results obtained in our laboratories support the notion that all auditory-nerve and LSO units exhibit fractal neural firing patterns, as indicated earlier by Teich (IEEE Trans. Biomed. Eng. 36, 150-160, 1989).

Fractal character of the auditory neural spike train.

Long-counting-time pulse-number distributions (PND's) were measured from a broad variety of cat primary auditory fibers using different tone and noise stimuli, counting times T, and number of samples NT. Whereas short-counting-time PND's (T approximately 50 ms) manifest the presence of spike pairs (an enhancement of even over odd-count probabilities), the irregular shapes of the long-counting-time PND's (T approximately greater than 0.1 s) reveal that the underlying sequence of action potentials consists of spike clusters when viewed on a longer time scale. For all units measured, the count variance-to-mean ratio (Fano factor) F(T) varied little over some 90 dB change in the stimulus level. On the other hand, F(T) increased substantially as T and/or NT were increased, corresponding to the capture of larger and larger spike clusters in the counting time. A relationship is developed between the Fano-time function F(T) and the normalized coincidence rate function, g(tau) versus delay time tau. A plausible form for g(tau) leads to a Fano-time function in good accord with the data. The observed power-law growth of the Fano factor for large counting times [F(T) approximately T alpha where 0 less than alpha less than 1] is accompanied by a power-law decay of the coincidence rate for large delay times [g(tau) approximately tau alpha -1] and a power-law form for the power spectral density at low frequencies [S(f) approximately f -alpha]. The behavior of the PND's and the scale invariance implicit in these fractional-power-law relationships suggest that the neural events on all primary auditory fibers exhibit fractal behavior for sufficiently large times (sufficiently low frequencies). The spike pairs and spike clusters in the PND's are natural consequences of this behavior. The fractal dimension D identical to alpha is estimated to be in the range of 0.3 approximately less than D approximately less than 0.9 for counting times in the range 0.1-10 s. The fractal dimension provides a measure of the degree of event clustering, or irregularity of a sequence of events, that is preserved over different time scales. PND's from low-skew vestibular units, in contrast, do not exhibit fractal behavior. It is suggested that auditory neural-firing patterns may serve to efficiently sample natural fractal noises.

Spontaneous cellular vibrations in the guinea-pig cochlea.

Mechanical vibrations of Hensen cells were measured with a laser-heterodyne interferometer in the third turn of the guinea-pig temporal-bone preparation without the application of an external stimulus. Smoothed periodograms (spectral-density estimates vs frequency) were constructed from the velocity vs time waveforms recorded from individual cells. For some cells, several peaks appear in the periodograms at levels as high as 10 dB above the noise floor, indicating the presence of spontaneous vibrations. The frequencies at which the peaks are located differ in different preparations, indicating that the observed peaks are not caused by the presence of ambient noise or ambient vibrations. It is demonstrated that smoothed-periodogram analysis is superior to fast-Fourier-transform analysis for discerning these spontaneous spectral components. The frequency tuning curves of cells from which spontaneous vibrations were measured (determined by applying an external stimulus to the ear) have single principal peaks. When the spontaneous spectral features are present, their frequencies lie, for the most part, within the principal-peak region of the tuning curve. We propose that these spontaneous vibrations originate at the outer hair cells and are the source of spontaneous otoacoustic emissions in the ear.

Hollow fibre liquid-phase microextraction of functionalised carboxylic acids from atmospheric particles combined with capillary electrophoresis/mass spectrometric analysis.

A method was developed to enrich various mono- and dicarboxylic acids from aqueous extracts of atmospheric particles by three-phase hollow fibre liquid-phase microextraction. Analysis was performed by capillary electrophoresis/electrospray ionisation mass spectrometry applying a previously reported separation method. Several extraction parameters (pH of donor and acceptor phase, composition of supported liquid membrane, shaking speed, and extraction time) were tested for their influence on analyte recovery. A strong dependence of the recovery on the acceptor phase pH was observed. The final method consisted of 10% (w/v) trioctylphosphine oxide in dihexylether as supported liquid membrane, 1.8 ml aqueous particle extract, acidified by sulfuric acid to a pH of 2 as donor phase, and 15 µl of 50 mM aqueous ammonia solution as acceptor phase. The extraction devices were shaken at 2200 rpm for 2 h. With this method, the recoveries from aqueous standards were between 10 and 80% with a repeatability of 4-14% for most compounds. Generally, more polar compounds were extracted less efficient than less polar ones. A few of the most polar compounds showed recoveries <10% with a repeatability of 20-55%. The enrichment factor was typically 10-100. The analyte recovery from real samples was found to strongly depend on the sample matrix due to co-extraction of mineral acids and organic acidic material present in atmospheric particles. Quantification was achieved by the method of standard addition. The easy handling of the hollow fibre devices, the low costs per extraction and the possibility to do many extractions in parallel allowed for an application of the developed method to a large set of real samples.

Role of the doubly stochastic Neyman type-A and Thomas counting distributions in photon detection.

The Neyman type-A and Thomas counting distributions provide a useful description for a broad variety of phenomena from the distribution of larvas on small plots of land to the distribution of galaxies in space. They turn out to provide a good description for the counting of photons generated by multiplied Poisson processes, as long as the time course of the multiplication is short compared with the counting time. Analytic expressions are presented for the probability distributions, moment generating functions, moments, and variance-to-mean ratios. Sums of Neyman type-A and Thomas random variables are shown to retain their form under the constraint of constant multiplication parameter. Conditions under which the Neyman type-A and Thomas converge in distribution to the fixed multiplicative Poisson and to the Gaussian are presented. This latter result is most important for it provides a ready solution to likelihood-ratio detection, estimation, and discrimination problems in the presence of many kinds of signal and noise. The doubly stochastic Neyman type-A, Thomas, and fixed multiplicative Poisson distributions are also considered. A number of explicit applications are presented. These include (1) the photon counting scintillation detection of nuclear particles, when the particle flux is low, (2) the photon counting detection of weak optical signals in the presence of ionizing radiation, (3) the design of a star-scanner spacecraft guidance system for the hostile environment of space, (4) the neural pulse counting distribution in the cat retinal ganglion cell at low light levels, and (5) the transfer of visual signal to the cortex in a classical psychophysics experiment. A number of more complex contagious distributions arising from multiplicative processes are also discussed, with particular emphasis on photon counting and direct-detection optical communications.

Three-Frequency Nonlinear Heterodyne Detection. 1: cw Radar and Analog Communications.

Though heterodyne detection provides a valuable technique for detecting small signals, the conventional system has several inherent disadvantages. In applications such as communications and radar, obtaining a reasonably high signal-to-noise ratio (SNR) requires (1) a good knowledge of the velocity of the transmitter or target, (2) a stable yet tunable local oscillator, and (3) a target or source that presents a minimum of frequency broadening. These conditions are frequently not adhered to by real systems, particularly in the ir and optical, giving rise to detection capabilities far below optimum. Calculations are presented for the use and operation of a three-frequency nonlinear heterodyne system that eliminates many of the stringent conditions required for conventional heterodyne detection, while maintaining its near-ideal SNR. The technique, which is similar in principle to heterodyne radiometry, makes use of a two-frequency transmitter and a nonlinear second detector and is particularly useful for signal acquisition; for signals of unknown Doppler shift, in fact, performance is generally superior to that of the conventional system. Although primary emphasis is on the ir and optical because of the large Doppler shifts encountered there, application of the principle in the microwave and radiowave is also discussed. For cw radar and analog communications, the SNR, power spectral density (PSD), and minimum detectable power (MDP) are obtained and compared with the standard configuration. Both sinewave and Gaussian input signals are treated. A variety of specific cases are discussed including the optimum performance case, the typical radar case, and the AM and FM communications case. Evaluation of the technique for pulsed radar and digital communications applications (both in the absence and in the presence of the lognormal atmospheric channel) is reserved for Part 2 of this paper [Appl. Opt. 14, 680 (1975)].

Three-frequency nonlinear heterodyne detection. 2: digital communications and pulsed radar.

Part 1 of this paper [Appl. Opt. 14, 666 (1975)] dealt with the cw radar and analog communications uses of three-frequency nonlinear heterodyne detection. In this paper, we evaluate the technique for a number of specific pulsed radar and digital communications applications. Both the vacuum channel and the lognormal turbulent atmospheric channel are considered. It is found that the advantages of the technique in the pulsed/digital system are similar to those obtained in the cw/analog system. Computer generated error probability curves as a function of the input signal-to-noise ratio are presented for a variety of binary receiver parameters and configurations and for various levels of atmospheric turbulence. Orthogonal and nonorthogonal signaling schemes, as well as dependent and independent fading, are considered. When Doppler information is poor, performance is generally superior to that of the conventional heterodyne system.

Computer simulation of superposed coherent and chaotic radiation.

A computer simulation technique useful for generating superposed coherent and chaotic radiation of arbitrary spectral shape is described. Its advantages over other techniques include flexibility and ease of implementation, as well as the capability of incorporating spectral characteristics that cannot be generated by other methods. We discuss the implementation of the technique and present results to demonstrate its validity. The technique can be used to obtain numerical solutions to photon statistics problems through computer simulation. We furthermore argue that experiments involving photon statistics can be carried out using a wideband source in place of an amplitude-stabilized source whenever the spectral characteristics of the source are not important. Experimental results that corroborate the argument are presented.