Babylonian solar theory on the Antikythera mechanism

This article analyzes the angular spacing of the degree marks on the zodiac scale of the Antikythera mechanism and demonstrates that over the entire preserved 88° of the zodiac, the marks are systematically placed too close together to be consistent with a uniform distribution over 360°. Thus, in some other part of the zodiac scale (not preserved), the degree marks have been spaced farther apart. By contrast, the day marks on the Egyptian calendar scale are spaced uniformly, apart from minor errors. A solar equation of center is apparent which rises by nearly 2.7° over the preserved portion of the zodiac. The placement of the degree marks indicates that, in the preserved portion of the zodiac, the Sun was considered to run at a uniform pace of about 30° per synodic month, which is consistent with the Sun’s speed in the fast zone of the Babylonian solar theory of System A.

     

Three-dimensional illusory contours and surfaces.

Under general viewing conditions, objects are often partially camouflaged, obscured or occluded, thereby limiting information about their three-dimensional position, orientation and shape to incomplete and variable image cues. When presented with such partial cues, observers report perceiving 'illusory' contours and surfaces (forms) in regions having no physical image contrast. Here we report that three-dimensional illusory forms share three fundamental properties with 'real' forms: (1) the same forms are perceived using either stereo or motion parallax cues (cue invariance); (2) they retain their shape over changes in position and orientation relative to an observer (view stability); and (3) they can take the shape of general contours and surfaces in three dimensions (morphic generality). We hypothesize that illusory contours and surfaces are manifestations of a previously unnoticed visual process which constructs a representation of three-dimensional position, orientation and shape of objects from available image cues.     

Essential role for the peroxiredoxin Prdx1 in erythrocyte antioxidant defence and tumour suppression

Reactive oxygen species are involved in many cellular metabolic and signalling processes and are thought to have a role in disease, particularly in carcinogenesis and ageing. We have generated mice with targeted inactivation of Prdx1, a member of the peroxiredoxin family of antioxidant enzymes. Here we show that mice lacking Prdx1 are viable and fertile but have a shortened lifespan owing to the development beginning at about 9 months of severe haemolytic anaemia and several malignant cancers, both of which are also observed at increased frequency in heterozygotes. The haemolytic anaemia is characterized by an increase in erythrocyte reactive oxygen species, leading to protein oxidation, haemoglobin instability, Heinz body formation and decreased erythrocyte lifespan. The malignancies include lymphomas, sarcomas and carcinomas, and are frequently associated with loss of Prdx1 expression in heterozygotes, which suggests that this protein functions as a tumour suppressor. Prdx1-deficient fibroblasts show decreased proliferation and increased sensitivity to oxidative DNA damage, whereas Prdx1-null mice have abnormalities in numbers, phenotype and function of natural killer cells. Our results implicate Prdx1 as an important defence against oxidants in ageing mice.     

Agar diffusion plates: The recording of experimental data

Zusammenfassung Ein Auswertungsverfahren der Antigen-Antikörper-Analyse mittels der Geléediffusionsmethode vonOuchterlony wird beschrieben.Die Muster des Niederschlags im Versuch werden angefärbt und der Agar-Gelée-Nährboden mit dem Muster wird durch Austrocknung konserviert.So gefärbte und getrocknete Präparate können, visuell geprüft, als Negative oder Diapositive verwendet werden.     

Cerebellar decussation of fibres from the nucleus reticularis tegmenti pontis in the brain of the albino rat

Summary The existence of a cerebellar decussation of fibres from the medial portion of each nucleus reticularis tegmenti pontis (Rtp) of the albino rat is indicated. Definite cell loss in the medial aspect, of the most rostral third of Rtp is detectable after cerebellar hemisection involving parts or the entire depth of sublobule VIb. Cell loss in the medial aspect of the caudal half of Rtp is evident as a consequence of experimental lesions which damage both sublobules IIb and III.This work was supported by the Medical Research Council of New Zealand.Acknowledgments. A. special acknowledgment to. Mrs Heather Reid for her excellent preparation of the histological specimens. Grateful thanks to Mrs Maureen Owen for her careful typing assistance.     

大熊猫发情期繁殖行为的研究

本文从圈养大熊猫的活动节律、活动量、食欲、叫声、遗留气味标志、蹭阴频率和方式的变化;雌体独自抬尾出现的时间和频率、阴阜膨肿度和颜色、阴道角化细胞百分比的变化;雌雄个体相互影响和引诱等行为方面,探索大熊猫行为与发情高潮的关系。     

Two problems in Aristarchus’s treatise on the sizes and distances of the sun and moon

The book of Aristarchus of Samos, On the distances and sizes of the sun and moon, is one of the few pre-Ptolemaic astronomical works that have come down to us in complete or nearly complete form. The simplicity and cleverness of the basic ideas behind the calculations are often obscured in the reading of the treatise by the complexity of the calculations and reasoning. Part of the complexity could be explained by the lack of trigonometry and part by the fact that Aristarchus appears unwilling to make some simplifications that could be simply taken for granted. But an important part of the complexities is due to some unnecessary inconsistencies, as recently discovered by Berggren and Sidoli (Arch Hist Exact Sci 61:213–254, 2007). In the first part of this paper, I will try to show that some of these inconsistencies are just apparent. But the complexity of the calculations and reasoning is not the only reason that could disturb a reader of the treatise. The great inaccuracy—even for the measurement methods and instruments available at those times—of one of the three input values of the treatise is really astonishing. In the sixth and last hypothesis, Aristarchus states that the moon’s apparent size is equal to 2 $^{\circ }$ , while the correct value is one-fourth of that. Some attempts have been made in order to explain such a big value, but all of them have problems. In the second part of this paper, I will propose a new speculative but plausible explanation of the origin of this value.     

The planetary increase of brightness during retrograde motion: An explanandum constructed ad explanantem

In Ancient Greek two models were proposed for explaining the planetary motion: the homocentric spheres of Eudoxus and the Epicycle and Deferent System. At least in a qualitative way, both models could explain the retrograde motion, the most challenging phenomenon to be explained using circular motions. Nevertheless, there is another explanandum: during retrograde motion the planets increase their brightness. It is natural to interpret a change of brightness, i.e., of apparent size, as a change in distance. Now, while according to the Eudoxian model the planet is always equidistant from the earth, according to the epicycle and deferent system, the planet changes its distance from the earth, approaching to it during retrograde motion, just as observed. So, it is usually affirmed that the main reason for the rejection of Eudoxus' homocentric spheres in favor of the epicycle and deferent system was that the first cannot explain the manifest planetary increase of brightness during retrograde motion, while the second can. In this paper I will show that this historical hypothesis is not as firmly founded as it is usually believed to be.     

Rounding numbers: Ptolemy’s calculation of the Earth–Sun distance

In this article, I analyze the coincidence of the prediction of the Earth–Sun distance carried out by Ptolemy in his Almagest and the one he carried out, with another method, in the Planetary Hypotheses. In both cases, the values obtained for the Earth–Sun distance are very similar, so that the great majority of historians have suspected that Ptolemy altered or at least selected the data in order to obtain this agreement. In this article, I will provide a reconstruction of some way in which Ptolemy could have altered or selected the data and subsequently will try to argue in favor of its historical plausibility.     

The electrons of the dinosaurs and the center of the Earth: comments on D.D. Turner’s ‘The past vs. the tiny: historical science and the abductive arguments for realism’

Turner [The past vs. the tiny: Historical science and the abductive arguments for realism. Studies in History and Philosophy of Science 35A (2004) 1] claims that the arguments in favor of realism do not support with the same force both classes of realism, since they supply stronger reasons for experimental realism than for historical realism. I would like to make two comments, which should be seen as amplifications inspired by his proposal, rather than as a criticism. First, it is important to highlight that Turner’s distinction between ‘tiny’ and ‘past unobservables’ is neither excluding nor exhaustive. Second, even if we agreed with everything that Turner says regarding the arguments for realism and their relative weight in order to justify the experimental or historical version, there is an aspect that Turner does not consider and that renders historical realism less problematic than experimental realism.