A Model of Pulsed Eddy Current Crack Detection

As its name implies, the pulsed eddy current (PEC) method makes use of a short burst of excitation current, rather than continuous sinusoidal (CW) current as is the case with conventional eddy current probes. Reflected fields, including flaw signal fields, are therefore time-dependent in the pulsed case, and are characterized by peak signal amplitude, pulse arrival time and signal decay parameters, rather than amplitude and phase as in the CW case

Axisymmetric Waves in Layered Anisotropic Fibers and Composites

The complicated morphology of the new generation of advanced fibrous composites gave further impetus to the study of the interaction of ultrasonic waves with multilayered concentric cylindrical systems. Typically, the fiber consists of a cylindrical core embedded in a cladding region followed by a distinct interface zone separating the fiber system from the host (matrix) region. In addition, the cladding region itself often consists of subregions which can be identified as distinct layers. Each individual layer can posses certain degree of microscopic anisotropy adding to the macroscopic anisotropy produced by the presence of layering and imperfect interfaces. Relatively few efforts have been spent upon the study of free and immersed homogeneous anisotropic rods [1–5]. These works are insufficient to model real situations encountered in materials characterization of advanced fibrous composites. In order to better model advanced fibrous composites at least three major effects need to be accounted for. These are the inhomogeneous nature of the structure as reflected in its multilayering, the inherent microscopic anisotropy of some of the constituents and finally the quality of the interfaces. In this paper we briefly describe a unified analytical treatment of wave propagation along the fiber direction of multilayered coaxial fibrous systems embedded in a host material. A more detailed discussion of this general treatment will be presented elsewhere [6]. Figure 1 shows typical geometric situations including (a) a single multilayered fiber, (b) a single multilayered fiber either immersed in an infinite fluid or embedded in an infinite solid, and an infinite composite material with periodically distributed multilayered fiber

Quasi-normal frequencies: Key analytic results

The study of exact quasi-normal modes [QNMs], and their associated quasi-normal frequencies [QNFs], has had a long and convoluted history - replete with many rediscoveries of previously known results. In this article we shall collect and survey a number of known analytic results, and develop several new analytic results - specifically we shall provide several new QNF results and estimates, in a form amenable for comparison with the extant literature. Apart from their intrinsic interest, these exact and approximate results serve as a backdrop and a consistency check on ongoing efforts to find general model-independent estimates for QNFs, and general model-independent bounds on transmission probabilities. Our calculations also provide yet another physics application of the Lambert W function. These ideas have relevance to fields as diverse as black hole physics, (where they are related to the damped oscillations of astrophysical black holes, to greybody factors for the Hawking radiation, and to more speculative state-counting models for the Bekenstein entropy), to quantum field theory (where they are related to Casimir energies in unbounded systems), through to condensed matter physics, (where one may literally be interested in an electron tunelling through a physical barrier).Comment: V1: 29 pages; V2: Reformatted, 31 pages. Title changed to reflect major additions and revisions. Now describes exact QNFs for the double-delta potential in terms of the Lambert W function. V3: Minor edits for clarity. Four references added. No physics changes. Still 31 page

Cytomegalovirus Infection of the Cervix Detected By Cytology and Histology: A Report of Five Cases

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72846/1/j.1365-2303.1993.tb00094.x.pd

Dissolution dominating calcification process in polar pteropods close to the point of aragonite undersaturation

Thecosome pteropods are abundant upper-ocean zooplankton that build aragonite shells. Ocean acidification results in the lowering of aragonite saturation levels in the surface layers, and several incubation studies have shown that rates of calcification in these organisms decrease as a result. This study provides a weight-specific net calcification rate function for thecosome pteropods that includes both rates of dissolution and calcification over a range of plausible future aragonite saturation states (Omega_Ar). We measured gross dissolution in the pteropod Limacina helicina antarctica in the Scotia Sea (Southern Ocean) by incubating living specimens across a range of aragonite saturation states for a maximum of 14 days. Specimens started dissolving almost immediately upon exposure to undersaturated conditions (Omega_Ar,0.8), losing 1.4% of shell mass per day. The observed rate of gross dissolution was different from that predicted by rate law kinetics of aragonite dissolution, in being higher at Var levels slightly above 1 and lower at Omega_Ar levels of between 1 and 0.8. This indicates that shell mass is affected by even transitional levels of saturation, but there is, nevertheless, some partial means of protection for shells when in undersaturated conditions. A function for gross dissolution against Var derived from the present observations was compared to a function for gross calcification derived by a different study, and showed that dissolution became the dominating process even at Omega_Ar levels close to 1, with net shell growth ceasing at an Omega_Ar of 1.03. Gross dissolution increasingly dominated net change in shell mass as saturation levels decreased below 1. As well as influencing their viability, such dissolution of pteropod shells in the surface layers will result in slower sinking velocities and decreased carbon and carbonate fluxes to the deep ocean

'A hidden disorder until the pieces fall into place' - a qualitative study of vaginal prolapse

<p>Abstract</p> <p>Background</p> <p>Vaginal prolapse affects quality of life negatively and is associated with urinary, bowel, and sexual symptoms. Few qualitative studies have explored women's experiences of vaginal prolapse. The objective of the study was to elucidate the experiences of living with prolapse and its impact on daily life, prior to surgical intervention.</p> <p>Methods</p> <p>In-depth interviews were conducted with 14 women with vaginal prolapse, prior to surgical treatment. Recruitment of the informants was according to 'purposive sampling'. An interview guide was developed, including open-ended questions addressing different themes, which was processed and revised during the data collection and constituted part of a study-emergent design. Data were collected until 'saturation' was achieved, that is, when no significant new information was obtained by conducting further interviews. Interviews were audiotaped, transcribed verbatim, and analyzed according to manifest and latent content analysis.</p> <p>Results</p> <p>The theme defining the process of living with prolapse and women's experiences was labelled 'process of comprehension and action'. The findings constitute two categories: obstacles and facilitators to seeking health care. The category <it>obstacles </it>comprises six subcategories that define the factors restraining women from seeking health care: absence of information, blaming oneself, feeling ignored by the doctor, having a covert condition, adapting to successive impairment, and trivializing the symptoms and de-prioritizing own health. The category <it>facilitators </it>include five subcategories that define the factors promoting the seeking of health care: confirmation and support by others, difficulty in accepting an ageing body, feeling sexually unattractive, having an unnatural body, and reaching the point of action.</p> <p>Conclusion</p> <p>The main theme identified was the 'process of comprehension and action'. This process consisted of factors functioning as either obstacles or facilitators to seeking health care. The main obstacles described by the participants were lack of information and confirmation. The main facilitators constituted feeling sexually unattractive and impaired physical ability due to prolapse. Information on prolapse should be easily accessible, to improve the possibility for women to gain knowledge about the condition and overcome obstacles to seeking health care. Health care professionals have a significant role in facilitating the process by confirming and informing women about available treatment.</p

Libbie Hyman

66 p. : ill. ; 26 cm.Study of invertebrates at the American Museum of Natural History / Neil H. Landman and Judith E. Winston -- Libbie Hyman and the American Museum of Natural History / Judith E. Winston -- Libbie Hyman at the University of Chicago / Jane Maienschein -- Libbie Hyman and comparative vertebrate anatomy / Marvalee H. Wake -- Contributions of Libbie H. Hyman to knowledge of land planarians: relating personal experiences (Tricladida: Terricola) / Robert E. Ogren -- Libbie Henrietta Hyman: her influence on teaching and research in invertebrate zoology / M. Patricia Morse -- Systematics of the flatworms- Libbie Hyman's influence on current views of the Platyhelminthes / Seth Tyler.Includes bibliographical references."This issue of Novitates consists of papers presented at a symposium on the life and work of American zoologist Dr. Libbie Henrietta Hyman, 1888-1969, held at the annual meeting of the American Society of Zoologists in Atlanta, Georgia, December 1991. Judith E. Winston provides an introduction to Libbie Hyman's early years. Growing up in Fort Dodge, Iowa, young Libbie demonstrated a love of nature and a drive for learning that eventually led to a scholarship at the University of Chicago, where she majored in zoology. Jane Maienschein covers Libbie Hyman's Chicago period. During that period Libbie gained experience in experimental biology by participation in Charles Manning Child's research program on metabolic gradients, which applied the "Chicago style" of biology. The lack of good manuals for the comparative anatomy and zoology labs she taught as a graduate student led Libbie to develop her own laboratory manuals, published by the University of Chicago Press. Marvalee Wake discusses Libbie Hyman's interactions with the press about these guides. Hyman's correspondence with press officials revealed her growing frustration as she desired more time to work on invertebrates, but was persuaded to revise vertebrate anatomy texts instead. Despite her protests, her seminal ideas and approaches to learning vetebrate anatomy were profoundly important. Judith Winston discusses Libbie's productive career at the American Museum of Natural History. In 1930, Dr. Hyman left Chicago to pursue the invertebrate work that interested her most-and found a welcome in G. K. Noble's Department of Experimental Biology at the AMNH. With his help she obtained an unpaid position as a research associate, office space, and use of the AMNH library, vital to her project, a treatise on invertebrate zoology. Her 6 volume treatise, The Invertebrates, was published between 1940 and 1967 by McGraw-Hill. In 1943 she transferred to the AMNH Department of Invertebrates. Neil Landman outlines the history of that Department in the Museum, and Libbie's connection with it. M. Patricia Morse discusses Dr. Hyman's influence on invertebrate zoology in general. Her treatise set the tone for invertebrate zoology courses and the publication of books on the subject. Each volume was eagerly received by zoologists, not only for thorough coverage of the literature (including non-English language literature), but also for uniformity of approach, comprehensive illustrations, and thoughtful synthesis of phylogenetic relationships for each group covered. Robert Ogren discusses Libbie Hyman's contributions to land planarian taxonomy. Hyman was the first American zoologist recognized as an authority on Turbellaria, Tricladida, and Terricola. Contributions began after her 1937 appointment as research associate at the American Museum of Natural History and continued for 25 years, resulting in 11 taxonomic papers, the last published in 1962. Seth Tyler discusses Libbie Hyman's overall influence on the systematics of turbellarian flatworms, especially through the comprehensive review of flatworms published in Volume II of The Invertebrates. The system of classification she adopted for the phylum Platyhelminthes was that of Bresslau, dating to 1933. Modern systematists have clarified the phylogenetic relationships of flatworm groups, in particular by using characters discerned with electron microscopy; and application of principles of cladistic systematics has been important in grouping turbellarians and the major groups of parasitic flatworms into supraordinal taxa. A number of competing systems for these higher-level groupings have been proposed, and these are being tested with molecular techniques comparing nucleic-acid sequences. Still, the current best-accepted system clearly bears Hyman's stamp; her views of evolution in the phylum and its taxonomy are still relevant"--P. 2