OBJECTIVE . We assessed the value of sonography in predicting intraoperative difficulties for patients undergoing laparoscopic cholecystectomy and in identifying indicators for conversion to conventional cholecystectomy. SUBJECTS AND METHODS . Upper abdominal sonography was performed (according to a checklist) in 75 consecutive patients before laparoscopic cholecystectomy. Sonographic findings were verified by the surgeon in the operating room.RESULTS . Conversion from laparoscopic surgery to laparotomy was performed in five patients (6.7%). Of 75 patients, 19 had sonograms revealing gallbladder wall thickening (>4 mm); surgical preparation difficulties in 16 of these patients led to laparotomy in four patients. Sensitivity, specificity, positive predictive value, and accuracy of wall thickening as an indicator of technical difficulties were 66.7%, 94.1%, 84.2%, and 85.3%, respectively. Sensitivity, specificity, positive predictive value, and accuracy of wall thickening as an indicator of surgical conversion were 80.0%, 78.6%, 21.1%, and 78.7%, respectively. Technical difficulties at laparoscopy occurred in all five patients with pericholecystic fluid on sonography (sensitivity, 20.8%; specificity, 100%; positive predictive value, 100%; accuracy, 74.7%) and led to laparotomy in three patients (sensitivity 60.0%, specificity 97.1%, positive predictive value 60%, accuracy 94.7%). The accuracy of sonography for cholecystolithiasis was 100%.CONCLUSION . On sonography, gallbladder wall thickening is the most sensitive indicator and pericholecystic fluid is the most specific indicator of technical difficulties during laparoscopic cholecystectomy. Such difficulties may require conversion to laparotomy.

This article presents a possible framework for the cooperation of mathematics and physics education research domains. Moreover, the potential topics for such a scientific collaboration are explained by means of a structuring qualitative content analysis of current handbooks and conference proceedings in Germany and Vietnam. These topics can form a basis for further projects on the connection of subject-related didactics. One of these projects is an interdisciplinary course in teacher training at the Hanoi National University of Education (HNUE) as part of the Inter TeTra project between the HNUE and the University of Siegen.

Observation is widely regarded as a fundamental way of studying nature. However, due to its complexity, proposing a comprehensive characterization is challenging. Observation is a method of studying nature that can be divided into several dimensions. Each of these dimensions can be presented as a pair of terms, which are elaborated in this paper based on the epistemological, philosophical, and educational literature. In addition, the dimensions can be assigned to two levels, which can be used to group the individual dimensions. This epistemological perspective on the method is enriched by historical examples from different periods in physics and astronomy to substantiate and illustrate the classifications. The aim of the paper is to provide an overview of the epistemological features of the method in terms of these dimensions, which may be helpful for discussions in teacher training courses.

The Earth’s albedo, as the fraction of sunlight that is directly reflected back into space from the surface or clouds, is a key factor in modeling Earth’s climate. In tasks such as the simplified estimation of the mean temperature, it is usually given as a constant, without mentioning its determination and the associated difficulties. In fact, the albedo can be determined by a basically simple procedure based on the observation of a well-known phenomenon: Earth’s shine. A comparison of the intensities between the directly illuminated side of the Moon and the side illuminated by Earth’s shine provides the mean albedo for a large part of the Earth’s surface. In this paper, the procedure will be reproduced using simple instruments. Assuming the reflection properties of a Lambert sphere—an ideal diffuse reflecting body—for the Earth, and using measurements of the phase function—as a description for the angular distribution of the scattered light—of the Moon, the Earth’s albedo is determined from self-acquired data. Even with these simple conditions it is possible to come quite close to the value of the Earth’s albedo.

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