Synthetic-aperture imaging laser radar: laboratory demonstration and signal processing

The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope's aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system.     

Definition, meaning, and measurement of the polarization extinction ratio of fiber-based devices

We clarify the definition of the polarization extinction ratio-also called polarization cross talk--of fiber-based devices. Its strong wavelength dependence, even for simple devices such as a single-fiber patchcord, is highlighted. Thus white sources may not be used for most measurements. We also explain the weakness of measurements with a rotating polarizer and a monochromatic source. Only a polarimeter may be used if accuracy is required. We report measurements of connections (including two connectors and one mating sleeve) and show the importance of the mating sleeve in the result. Finally, we define the validity domain of the standardized method, which uses both a white source and a rotating polarizer.     

Linear Response Theory Around a Localized Impurity in the Pseudogap Regime of an Anisotropic Superconductor

We compare and contrast the polarizability of a d-wave superconductor in the pseudogap regime, within the precursor pairing scenario (dPG), and of a d-density-wave (dDW) state, characterized by a d-wave hidden order parameter, but no pairing. Our study is motivated by STM imaging experiments around an isolated impurity, which may in principle distinguish between precursor pairing and dDW order in the pseudogap regime of the high- superconductors. In both cases, the -dependence of the polarizability is characterized by an azimuthal modulation, consistent with the d-wave symmetry of the underlying state. However, only the dDW result shows the fingerprints of nesting, with nesting wave vector , albeit imperfect, due to a nonzero value of the hopping ratio in the band dispersion relation. As a consequence of nesting, the presence of hole pockets is also reflected by the dependence of the retarded polarizability.     

Effects of altering the energy and protein supply to dairy cows during the dry period. 2. Metabolic and hormonal responses

We offered 48 multiparous Holstein-Friesian cows one of three different dry-period diets for 6 wk before predicted calving: A) a grass silage and barley straw mix (60:40 on a dry-matter basis), with a low protein content; B) grass silage only (medium protein); or C) grass silage plus 0.5 kg of high protein corn gluten meal (high protein)/d. A standard grass silage-based diet was offered to all cows following calving. All animals were blood sampled at weekly intervals during the dry period, and at wk 1, 3, 5, 7, 13, 17, and 21 of lactation. Nitrogen balance was measured in a subset of 12 cows (four per treatment) at 3 wk before calving, and at wk 8 and 18 of lactation. Nitrogen balance in the dry period increased significantly as dietary protein supply increased [9, 34, and 50 g of N/d (SED 8.8) for the three diets, respectively]. We measured no residual effects of dry-period treatment on N balance during lactation. Plasma concentrations of growth hormone became significantly higher in the late dry period in cows offered the silage and straw diet, although treatment differences disappeared after calving. Insulin concentrations were significantly affected by treatment throughout the dry period and indicated inadequate nutrient supplies from the low protein diet, leading to losses in body reserves of energy and protein. The results indicate that animals offered the low protein diet accumulated less N per day than is required for fetal development, suggesting that protein must have been repartitioned from maternal tissues.     

Traumatic neurosis in the etiology of alcoholism: Viet Nam combat and other trauma

Traumatic neurosis from Viet Nam combat or other sources includes many symptoms that can be effectively self-medicated with alcohol, at least initially. These symptoms include chronic anxiety and restlessness, insomnia, and recurrent frightening dreams. Repeated self-medication with alcohol results in tolerance and a need to increase the amount consumed. Attempts to decrease consumption or to abstain can lead to alcohol withdrawal symptoms similar to and exacerbating the initial symptoms of traumatic neurosis. Continuing alcohol use, with the establishment of a vicious circle, can follow. The authors present three case examples. They note that treatment of alcoholism under the conditions described requires specific attention to the underlying traumatic neurosis.     

Mucocutaneous lymph node syndrome

In 1967, Kawasaki reported an acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes that afflicted infants and young children in Japan. He called the entity mucocutaneous lymph node syndrome. In 1974, the condition was reported in Hawaii, and several cases have been reported subsequently from the continental United States and other countries. One percent to two % of patients had died suddenly of cardiac failure. Rickettsia-like bodies have been demonstrated from skin and lymph node biopsy specimens, and the pathologic features suggest a relationship to infantile periarteritis nodosa.     

MR of hypoxic encephalopathy in children after near drowning: correlation with quantitative proton MR spectroscopy and clinical outcome

BACKGROUND AND PURPOSE: Quantitative MR spectroscopy has a proved role in the investigation of hypoxia caused by near drowning. To date, no studies have addressed the MR imaging changes that may also accompany this condition. The purpose of this study was to describe the MR imaging findings in children with hypoxic encephalopathy caused by near drowning and to compare these findings with the results of qualitative and quantitative proton MR spectroscopy and clinical outcome. METHODS: Twenty-two children (6 months to 11 years old) admitted to the pediatric intensive care unit after near drowning incidents underwent cerebral MR imaging and quantitative proton MR spectroscopy. Clinical and imaging studies were reviewed retrospectively, and subjects were grouped according to outcome: good result, persistent vegetative state, and death. Images were scored for edema, basal ganglia changes, and cortical changes, and were compared with MR spectra and outcome at days 1 to 2, 3 to 4, and 5 or more. RESULTS: Six patients had a good outcome, four remained in a persistent vegetative state, and 12 died. Generalized/occipital edema correlated with poor outcome. Indistinct lentiform nuclei margins on T1-weighted images were a frequent finding (78%). Basal ganglia T2 hyperintensity correlated with poor outcome, progressing from a patchy/peripheral distribution to diffuse high intensity. Patchy high T2 signal in the cortex or subcortical lines were specific but insensitive for poor outcome, as were brain stem infarcts. CONCLUSION: MR images in children with hypoxic encephalopathy after near drowning show a spectrum of changes. The most sensitive prognostic result may be achieved by combining MR imaging with qualitative and quantitative MR spectroscopic data.