Phase aberration correction using near-field signal redundancy. II. Experimental results

For pt.I see ibid., vol.44, no.2, pp.355-71. A phase-aberration correction algorithm using near-field signal redundancy was proposed in part I. Here, this algorithm is tested on data collected from phantoms and volunteers. A linear array transducer was used with a synthetic-aperture scanning system. A wedge of plastic gel was used to introduce phase aberrations when collecting data from a phantom. About 40 sets of RF data were collected from eight volunteers. Results from both phantom and volunteer data have shown that the near-field signal redundancy algorithm can improve image quality by correcting phase aberrations when they are present. The results also show that this algorithm is robust.     

Compact diode-laser based rubidium frequency reference

The performance of a simple microwave frequency reference based on Raman scattering in an atomic vapor is examined. This reference has the potential to be compact, low-power, and insensitive to acceleration. Several design architectures have been evaluated with a table-top experiment in order to guide the future development of a compact system. Fractional frequency deviations of 相似文献   

PVDF reference hydrophone development in the UK-from fabrication and lamination to use as secondary standards

During the last 30 yrs, PVDF has been used extensively as a sensor material. Over this period, the GEC-Marconi Research Centre has developed a wide range of devices based on PVDF as a piezoelectric transducer material. The ability to create laminated structures has led to an enhancement in performance and has allowed innovative designs to be realized. This paper describes the development of the laminated PVDF structure and its benefits, such as increased sensitivity and improved signal to noise ratio. Examples of devices utilizing the lamination process are given in the form of both a bilaminar-shielded membrane hydrophone and a PVDF sonar hydrophone. Performance properties of both types of hydrophones are presented along with a discussion of their use as secondary standard hydrophones at the National Physical Laboratory (NPL).     

Characterization of Lunar Dust for Toxicological Studies. II: Texture and Shape Characteristics

The morphology (shape and texture) of dust fractions of five Apollo lunar soils and a lunar dust simulant, JSC-1Avf, was studied using scanning electron microscopy. Shape (aspect ratio and complexity) of particles was described based on the two-dimensional projection images. The distributions of aspect ratio and complexity of particles are reported. It was determined that the Apollo lunar dust particles consist mainly of impact-produced glass, with complicated morphologies, extensive surface areas per grain, and sharp, jagged edges. Importantly, many grains contain elaborate vesicular textures, representing minute agglutinates. Dust simulant JSC-1Avf also has similar shapes as lunar dust, but differs in surface texture and area (smooth and nonvesicular). These data provide information for toxicity studies of lunar dust and for selecting a suitable lunar dust simulant.     

Field and Laboratory Evaluation of the Impact of Tall Fescue on Polyaromatic Hydrocarbon Degradation in an Aged Creosote-Contaminated Surface Soil

A field study was initiated in 1997 to assess the ability of tall fescue grass to remediate an aged creosote-contaminated surface soil. Field monitoring was combined with aerobic microcosm experiments, microbial enumerations, and plant tissue analysis to determine the impact of tall fescue on the degradation of six polycyclic aromatic hydrocarbons (PAHs), acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene, and chrysene, and to elucidate the mechanisms of remediation. Fescue grass had a beneficial impact on the degradation of all PAHs except phenanthrene. Mean concentrations of the three-ring PAHs, acenaphthene and fluorene, were lower in fescue cells compared to unvegetated cells after 36 months. In microcosms with soil from fescue cells, acenaphthene had a significantly higher degradation rate and lower final concentration after 180 days than in microcosms prepared with soil from unvegetated cells. Mean concentrations of the four-ring PAHs, fluoranthene, pyrene, and chrysene, were statistically similar in the field study; however, the 10th and 20th percentile concentrations were lower in fescue cells during all sampling periods. Microcosm studies showed increased degradation of fluoranthene and pyrene in soil samples taken from tall fescue rhizosphere compared to unvegetated soil and abiotic controls. Degradation of four-ring PAHs was enhanced in the shallow zones (10–15 cm below ground surface) of vegetated cells. The root mass was approximately 35% greater in shallow zones than in medium depth zones (15–21 cm below ground surface). Microbial populations on solid mineral media plates with pyrene and chrysene as the sole carbon source were two times higher in soils from tall fescue plots than from unvegetated soils, suggesting that the increased PAH degradation was a result of increased microbial activity in the rhizosphere. Gas chromatography/mass spectrometry analysis of fescue shoots indicated that no uptake or translocation of PAHs or PAH degradation intermediates into the shoots was occurring.     

Structured play therapy: A model for choosing topics and activities.

This article presents a model to be used for structured play therapy for use with adolescents and children ages 7 yrs and older. Structured play therapy is a form of play therapy that is directive and uses planned, structured activities in almost every session. This model was developed to provide a framework for appropriate timing and sequence of structured activities. This article describes structured play therapy and how it differs from nondirective play, presents a structured play therapy model, presents specific guidelines for choosing appropriate structured activities and exercises, and presents a case study demonstrating application of the model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Belief and feeling: Evidence for an accessibility model of emotional self-report.

This review organizes a variety of phenomena related to emotional self-report. In doing so, the authors offer an accessibility model that specifies the types of factors that contribute to emotional self-reports under different reporting conditions. One important distinction is between emotion, which is episodic, experiential, and contextual, and beliefs about emotion, which are semantic, conceptual, and decontextualized. This distinction is important in understanding the discrepancies that often occur when people are asked to report on feelings they are currently experiencing versus those that they are not currently experiencing. The accessibility model provides an organizing framework for understanding self-reports of emotion and suggests some new directions for research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overt and relational aggression in Russian nursery-school-age children: parenting style and marital linkages

Maternal and paternal parenting styles and marital interactions linked to childhood aggressive behavior as described in Western psychological literature were measured in an ethnic Russian sample of 207 families of nursery-school-age children. Results corroborated and extended findings from Western samples. Maternal and paternal coercion, lack of responsiveness, and psychological control (for mothers only) were significantly correlated with children's overt aggression with peers. Less responsiveness (for mothers and fathers) and maternal coercion positively correlated with relational aggression. Some of these associations differed for boys versus girls. Marital conflict was also linked to more overt and relational aggression for boys. When entered into the same statistical model, more marital conflict (for boys only), more maternal coercion, and less paternal responsiveness were found to be the most important contributors to overt and relational aggression in younger Russian children.     

Theonellapeptolide IIIe, a new cyclic peptolide from the New Zealand deep water sponge, Lamellomorpha strongylata

The structure, stereochemistry, and conformation of theonellapeptolide IIIe (1), a new 36-membered ring cyclic peptolide from the New Zealand deep-water sponge Lamellomorpha strongylata, is described. The sequence of the cytotoxic peptolide was determined through a combination of NMR and MS-MS techniques and confirmed by X-ray crystal structure analysis, which, with chiral HPLC, established the absolute stereochemistry.     

Exposure to prenatal nicotine transiently increases neuronal nicotinic receptor subunit alpha7, alpha4 and beta2 messenger RNAs in the postnatal rat brain

This study determined the effects of prenatal nicotine exposure (2 mg/kg/day) in Sprague Dawley CD rats via subcutaneously implanted osmotic minipumps, during gestational days 7-21, on postnatal levels of neuronal nicotinic receptor alpha4, alpha7 and beta2 subunit messenger RNAs. Northern analysis of postnatal day 1, 7, 14 and 28 hippocampal/septal and cortical total RNA using alpha-[32P]dCTP-labeled alpha4, alpha7 and beta2 complementary DNA probes identified a single (5.7-kb) alpha7 messenger RNA, three (2.4-, 3.8- and 8.0-kb) alpha4 messenger RNAs and four (3.7-, 5.0-, 7.5- and 10.0-kb) beta2 messenger RNAs. In comparison to prenatal saline, prenatal nicotine produced several significantly higher messenger RNA levels (cortical: 5.7-kb alpha7, 2.4-, 3.8- and 8.0-kb alpha4, 10.0-kb beta2; hippocampal/septal: 2.4- and 8.0-kb alpha4); these increases occurred predominantly on, but were not restricted to, postnatal day 14. Effects of nicotine were generally resolved by postnatal day 28. Collapsing the data across sex and age, a significant treatment effect indicated that hippocampal/septal and cortical 8.0-kb alpha4 messenger RNA levels and 10.0-kb beta2 messenger RNA levels were significantly higher following prenatal nicotine exposure. This is the first study indicating that prenatal nicotine produces alterations in developing postnatal rat neuronal nicotinic receptor messenger RNA levels, possibly by premature stimulation of neuronal nicotinic receptors. These results further implicate the teratogenic potential of nicotine in postnatal neuronal development.