Reference Point

We use six decades of catch-at-age data for perch (Perca fluviatilis) and pike (Esox lucius) in Windermere (UK) to estimate age-and sex-specific population sizes, natural mortalities and catchabilities in both species. Population sizes are estimated by fitting age structured population models to the catch-at-age data using standard maximum likelihood methods. We validate our methods using data simulations, and use our estimates of vital rates (natural mortality, recruitment and catahability) to address important aspects of fisheries biology. ...

Sexual maturity is marked by morphological changes in freshwater anomuran crabs. Specific modifications to the dorsal and ventral forms of the cephalothorax and the coxa of the fifth pereiopod in males indicate reproductive maturity. Here, we describe changes in cephalothorax and coxa that develop during sexual maturity in the freshwater anomuran, Aegla uruguayana. To evaluate shape, the dorsal and ventral cephalothorax and the coxa of the fifth pereiopod of this species were digitally photographed. With specific landmarks as reference points, the crab shape was analyzed for each of the three body parts. Relative warps analysis were performed revealing shape differences among the size forms and sexes. The dorsal cephalothorax and the coxa of the fifth pereiopod are different between juveniles, males and females. Individuals of 12–16 mm cephalothorax length have a shape closest to the “consensus configuration” in the population, which is correlated with the onset of sexual maturity in males. Additionally, there are size and shape differences among juveniles and adult individuals of the population. The shape differences were observed mainly in the coxa of the fifth pereiopod of males, as the length of the sexual tube increases during sexual development. Moreover, sexual maturity occurred simultaneously with cephalothorax and coxa development. These results show that multiple cohorts of A. uruguayana coexist in the population and that individuals can have a different reproductive capacity within the active sexual population.

Preparation for surgery for thoracic intraspinal lesions commonly involves rather difficult X-ray procedures in the operating room. The object of this report is to inform neurosurgeons about a modified technique for preoperative surface localization of intraspinal thoracic pathology. Adhesive, disposable radiographic skin markers placed at the presumed level of an intraspinal lesion are visualized along with the lesion on sagittal magnetic resonance scans of the thoracic spine. The lesion and the skin markers were clearly identified within the same field of view. The lesion itself rather than the vertebral body becomes the reference point for localization. Preoperative imaging with adhesive skin markers facilitates positioning and draping for surgery for thoracic intraspinal lesions. It may even replace intra-operative X-ray procedures in selected cases.

The pelvic organ prolapse quantification (POPQ) system is currently the most common and specific system describing different prolapse stages. Nevertheless, its use is not yet accepted worldwide in routine care. Our aim was to develop a simple teaching tool for the POPQ system capable of simulating different stages of uterovaginal prolapse for use in medical education with hands on training. We constructed a moveable and flexible tool with an inverted Santa Claus’ cap, which simulated the vaginal cuff and the tassel at the end representing the cervix. A wooden embroidery frame fixed the cap and served as the hymen, the reference point for all measurements. Inside the cap, we sewed buttons to define the anatomic landmark points Aa and Ap located 3 cm distal from the frame. After explaining the device to the students, we used the three-by-three grid for recording the quantitative description of the pelvic organ support. First, each student had to demonstrate a specific prolapse with his cap device. Then, a prolapse was simulated on the cap, and the student had to take the relevant measurements and record them in the POPQ grid. The main training effect to understand the POPQ system seems to be the possibility for each trainee to simulate a three-dimensional prolapse with this flexible vagina model.

Abstract. The identification of the user's intention or interest through queries that they submit to a search engine can be very useful to offer them more adequate results. In this work we present a framework for the identification of user's interest in an automatic way, based on the ...

... G. Bitelli, VA Girelli, MA Tini, L. Vittuari DISTART – University of Bologna, Viale Risorgimento 2 – 40136 Bologna, Italy e-mail: (gabriele.bitelli, valentina.girelli, mariaalessandra.tini, luca.vittuari)@mail.ing.unibo.it ... I. Bitelli G., Capasso M., Davoli P., Pernigotti S., Vittuari L., 2003b. ...

Teaching and learning fractions has traditionally been one of the most problematic areas in primary school mathematics. Several studies have suggested that one of the main factors contributing to this complexity is that fractions comprise a multifaceted notion encompassing five interrelated subconstructs (i.e., part-whole, ratio, operator, quotient, and measure). Kieren was the first to establish that the concept of fractions is not a single construct, but consists of several interrelated subconstructs. Later on, in the early 1980s, Behr et al. built on Kieren’s conceptualization and suggested a theoretical model linking the five subconstructs of fractions to the operations of fractions, fraction equivalence, and problem solving. In the present study we used this theoretical model as a reference point to investigate students’ constructions of the different subconstructs of fractions. In particular, using structural equation modeling techniques to analyze data of 646 fifth and sixth graders’ performance on fractions, we examined the associations among the different subconstructs of fractions as well as the extent to which these subconstructs explain students’ performance on fraction operations and fraction equivalence. To a great extent, the data provided support to the associations included in the model, although, they also suggested some additional associations between the notions of the model. We discuss these findings taking into consideration the context in which the study was conducted and we provide implications for the teaching of fractions and suggestions for further research.