Multiple reflections from meteor trails and small-scale wind structure

Summary A new observational method for determining winds on extremely small scales in the upper mesosphere has been developed by radar observations of relatively rare, but long enduring trails of bright meteors, known as fireballs. The radar meteor system near Bologna enables to determine wind velocities at the points on the fireball trail, separated from each other in a time scale of 1 s and in a distance scale by 0.1 km. Results of investigation of the fireballs observed in Bologna during the EBC (Energy Budget Campaign) in November 1980, based on the analysis of multiple or double reflections from meteor trails show the variation of the wind velocity in very small areas. Fireball trains can provide several independent echoes, connected with the position, orientation, total duration of the trail and with the efficiency of the radar equipment used. More complex information on the atmospheric irregularities and on their occurrence can be derived during the observations of meteor showers, analysing simultaneously the motion of the effective reflection point on the trail from the range drift of echoes, and the Doppler shift wind measurements.

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Riassunto è stato sviluppato un nuovo metodo per determinare i venti nell'alta mesosfera su scale estremamente piccole, dall'osservazione radar di tracce di meteore luminose, relativamente rare e durevoli, conosciute come ?fireballs?. Il sistema radar di Budrio, nei pressi di Bologna, consente di determinare velocità del vento in punti sulla scia del fireball, separati nel tempo e nella distanza, rispettivamente di 1 secondo e di 0.1 km. I risultati di un'indagine sui fireballs osservati durante l'EBC (Energy Budget Campaign) nel novembre 1980, basata sull'analisi di riflessioni multiple da tracce di meteore, mostra che la velocità del vento varia su aree molto piccole. Le scie di fireballs possono fornire parecchi echi indipendenti associati, da una parte, alla posizione, orientazione e durata totale della traccia, e dall'altra, all'efficienza dell'apparato radar utilizzato. Informazioni più complesse su alcune irregolarità atmosferiche e sulla loro incidenza, possono essere desunte nel corso delle osservazioni di sciami di meteore, analizzando simultaneamente il moto del punto effettivo di riflessione sulla traccia (dalle deviazioni nelle distanze degli echi), nonché le misure Doppler di vento.

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Резюме Развивается новый метод для определения ветров с очень малыми масштабами в верхней мезосфере, используя радарные наблюдения относительно редких, но продолжительных хвостов ярких метеоров, известных как файерболы. Радарная система в Будрио, недалеко от Болоньи, позволяет определить скорости ветра в точках в кильваторе файербола, которые разделены друг от друга по времени в 1 секунду, а по расстоянию в 0.1 км. Результаты исследования файерболов, наблюденных в течение ЕВС, в ноябре 1980, основанные на анализе многократных отражений от метеорных хвостов, обнаруживают изменения скорости ветра в очень малых областях. Кильваторы файерболов могут образовывать несколько независимых эхо-сигналов, связанных, с одной стороны, с положением, ориентацией и полной длительностью хвоста, а, с другой стороны, с эффективностью используемого радарного оборудования. Более полную информацию об атмосферных нерегулярностях и их возникновении можно получить во время наблюдений метеорных ливней, анализируя одновременно движение эффективной точки отражения в хвосте (из дрейфа расстояния для эхо) и измерения ветра по доплеровскому сдвигу.

     

Radio echoes from long-enduring meteor trails as a tracer of small-scale internal gravity waves

Summary Radar data from long-enduring meteor trails observed during two different campaigns carried out at the CNR station in Budrio (45° N, 11° E) near Bologna in Autumn of 1980 and 1985 reveal that the wave field near the mesopause is composed of a superposition of wave motions to be connected possibly to propagating internal gravity waves. The measured vertical wavelengths ranged from 2 to 13 km with dominant wave activity at values between (2÷3) km and (6÷7) km. The observed small-scale wave activity suggests processes and effects of wave field saturation and of convective or dynamical instability.     

Teaching and Learning Mathematics With Interactive Spreadsheets

Learning to teach mathematics at the middle and secondary levels should include many opportunities for teachers to learn how to use technology to better understand mathematics themselves and promote students' learning of mathematical concepts with technology-enabled pedagogy. This article highlights work done in a variety of preservice and in-service mathematics teacher education courses to help teachers use commonly available spreadsheets as an interactive exploratory learning tool. Several examples of teachers' subsequent use of spreadsheets in their own teaching are also discussed.     

Teacher Rationales for Scoring Students' Problem Solving Work

This article presents the scores teachers assigned to samples of actual students' problem-solving work and the rationales teachers provided for these scores. These rationales may reflect teachers' values relative to aspects of mathematical problem solving. It may be that when teachers can express rationales for scoring students' work, they are able to justify their evaluation of what students can “know and do” in mathematics.     

An observational method for upper-atmospheric wind fluctuations on very small scales

Summary Irregular wind motions in the meteor region ((70÷120) km) on very small space-time scales have been tentatively deduced by radar observations of relatively rare, but long enduring ionized trails of bright meteors (fireballs). The method here presented seems to be proper for the study of the turbulent winds in the upper mesosphere and lower thermosphere.     

PDMS bonding by means of a portable, low-cost corona system

A hand-held corona treater is presented as an effective, inexpensive, and portable alternative for irreversible bonding of polydimethylsiloxane (PDMS) to glass.     

Detection system for electro-separation analytical methods

The paper provides information about the on-line monitoring of components analysed by capillary electrophoresis. For this purposes we developed a whole-capillary transverse scanning detection system, which helps to improve and control the separation processes. A picture from a colour line scanner was used as a source of basic information for autonomous control of the separation process by regulation of the high voltage source. The application and algorithms for machine vision were designed in the progressive graphic development system LabVIEW. Real-time control of the separation process was implemented in a compact control process logic controller. The performance of the detection system was evaluated and the function of the overall system was tested by performing isotachophoretic analysis of a model mixture.     

Examining Secondary Mathematics Teachers' Opportunities to Develop Mathematically in Professional Learning Communities

To make progress toward ambitious and equitable goals for students’ mathematical development, teachers need opportunities to develop specialized ways of knowing mathematics such as mathematical knowledge for teaching (MKT) for their work with students in the classroom. Professional learning communities (PLCs) are a common model used to support focused teacher collaboration and, in turn, foster teacher development, instructional improvement, and student outcomes. However, there is a lack of specificity in what is known about teachers’ work in PLCs and what teachers can gain from those experiences, despite broad claims of their benefit. We discuss an investigation of the work of secondary mathematics teachers in PLCs at two high schools to describe and explicate possible opportunities for teachers to develop the mathematical knowledge needed for the work of teaching and the ways in which these opportunities may be pursued or hindered. The findings show that, without pointed focus on mathematical content, opportunities to develop MKT can be rare, even among mathematics teachers. Two detailed images of teacher discussion are shared to highlight these claims. This article contributes to the ongoing discussion about the affordances and limitations of PLCs for mathematics teachers, considerations for their use, and how they can be supported.     

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