Geometrijska razmatranja o naizgled krivom nagibu polumjeseca

The following phenomenon is well-known and again and again appears as an unanswered question in literature and on internet platforms: If you see moon and sun in the sky at the same time, then the (bisector of the) crescent moon in most cases does not seem to be precisely directed at the sun. Particularly at sunset, when you would expect the bisector of the crescent moon to be horizontal, it mostly points upwards. To “prove” that, photos that seem to support this view are displayed. In this paper it is shown by means of geometry what the “wrong moon tilt” is all about and that an explanation is to be found in the nature of central or normal projections (photography is basically a central projection, at an extremely long focal length it is approximately a normal projection). The paper also deals with the reason why the seemingly wrong tilt is subjectively felt. The path of the light from the sun to the moon is in any case displayed straight (apart from minor deviations due to refraction close to the horizon), except one takes photos with a fish-eye lens.Sljedeći je fenomen dobro poznat i često se u literaturi i na internetu pojavljuje kao pitanje bez odgovora: Ako na nebu istovremeno vidite mjesec i sunce, onda simetrala polumjeseca u većini slučajeva ne izgleda usmjerena točno prema suncu. Posebno u doba sunčeva zalaska, kad očekujete da simetrala polumjeseca bude horizontalna, ona je uglavnom usmjerena prema gore. Da bismo to ”dokazali” prikazujemo fotografije koje podržavaju takav pogled. U ovom se članku posredstvom geometrije objašnjava pojava ”krivog nagiba mjeseca, a rješenje se nalazi u prirodi centralnog ili ortogonalnog projiciranja (naime, fotografija je temeljno centralna projekcija, ali kod izuzetno velike žarišne duljine približno je ortogonalna projekcija). U članku se također razmatra razlog zašto se naizgled krivi nagib subjektivno osjeća. Svjetlosna putanja od sunca do mjeseca u svakom se slučaju prikazuje ravno (osim kod malih odstupanja koja se javljaju zbog loma svjetlosti u blizini horizonta), i osim kod fotografija slikanih sa širokokutnim objektivom

Geoarchaeological Methods for Landscape Reconstruction at the Excavation Site of Naga, Central Sudan

The archaeological excavation site of Naga, remains of a Meroitic city, is located in the semiarid region along the fringe of the north-eastern Sahel and the south-eastern Sahara desert, in central Sudan, 150 km north of Khartoum and 40 km south of the Nile. During its heyday the city was a highly developed central place, with a large population and a booming economy. Naga has been the object of archaeological research for several decades – and of geoscientific investigation since 2008. The first step for the investigation was to select adequate methods that combine the advantages of various subdisciplines and approaches. The study presented employs techniques from terrain modelling, geophysics and environmental analytics to evaluate field data with the aim of a comprehensive landscape reconstruction

Exploiting Locally Imposed Anisotropies in (Ga,Mn)As: a Non-volatile Memory Device

Progress in (Ga,Mn)As lithography has recently allowed us to realize structures where unique magnetic anisotropy properties can be imposed locally in various regions of a given device. We make use of this technology to fabricate a device in which we study transport through a constriction separating two regions whose magnetization direction differs by 90 degrees. We find that the resistance of the constriction depends on the flow of the magnetic field lines in the constriction region and demonstrate that such a structure constitutes a non-volatile memory device

Saturated Ferromagnetism and Magnetization Deficit in Optimally Annealed (Ga,Mn)As Epilayers

We examine the Mn concentration dependence of the electronic and magnetic properties of optimally annealed Ga1-xMnxAs epilayers for 1.35% < x < 8.3%. The Curie temperature (Tc), conductivity, and exchange energy increase with Mn concentration up to x ~ 0.05, but are almost constant for larger x, with Tc ~ 110 K. The ferromagnetic moment per Mn ion decreases monotonically with increasing x, implying that an increasing fraction of the Mn spins do not participate in the ferromagnetism. By contrast, the derived domain wall thickness, an important parameter for device design, remains surprisingly constant.Comment: 8 pages, 4 figures, submitted for Rapid Communication in Phys Rev

AU-Rich Element-Mediated mRNA Decay Can Occur Independently of the miRNA Machinery in Mouse Embryonic Fibroblasts and Drosophila S2-Cells

AU-rich elements (AREs) are regulatory sequences located in the 3′ untranslated region of many short-lived mRNAs. AREs are recognized by ARE-binding proteins and cause rapid mRNA degradation. Recent reports claimed that the function of AREs may be – at least in part – relayed through the miRNA pathway. We have revisited this hypothesis using dicer knock-out mouse embryonic fibroblasts and cultured Drosophila cells. In contrast to the published results, we find no evidence for a general requirement of the miRNA pathway in the function of AREs. Endogenous ier3 mRNA, which is known to contain a functional ARE, was degraded rapidly at indistinguishable rates in wild type and dicer knock-out mouse embryonic fibroblasts. In cultured Drosophila cells, both ARE-containing GFP reporter mRNAs and the endogenous cecA1 mRNA were resistant to depletion of the mi/siRNA factors dcr-1, dcr-2, ago1 and ago2. Furthermore, the Drosophila miRNA originally proposed to recognize AU-rich elements, miR-289, is not detectably expressed in flies or cultured S2 cells. Even our attempts to overexpress this miRNA from its genomic hairpin sequence failed. Thus, this sequence cannot serve as link between the miRNA and the AU-rich element mediated silencing pathways. Taken together, our studies in mammalian and Drosophila cells strongly argue that AREs can function independently of miRNAs

Genome-Wide Assessment of AU-Rich Elements by the AREScore Algorithm

In mammalian cells, AU-rich elements (AREs) are well known regulatory sequences located in the 3′ untranslated region (UTR) of many short-lived mRNAs. AREs cause mRNAs to be degraded rapidly and thereby suppress gene expression at the posttranscriptional level. Based on the number of AUUUA pentamers, their proximity, and surrounding AU-rich regions, we generated an algorithm termed AREScore that identifies AREs and provides a numerical assessment of their strength. By analyzing the AREScore distribution in the transcriptomes of 14 metazoan species, we provide evidence that AREs were selected for in several vertebrates and Drosophila melanogaster. We then measured mRNA expression levels genome-wide to address the importance of AREs in SL2 cells derived from D. melanogaster hemocytes. Tis11, a zinc finger RNA–binding protein homologous to mammalian tristetraprolin, was found to target ARE–containing reporter mRNAs for rapid degradation in SL2 cells. Drosophila mRNAs whose expression is elevated upon knock down of Tis11 were found to have higher AREScores. Moreover high AREScores correlate with reduced mRNA expression levels on a genome-wide scale. The precise measurement of degradation rates for 26 Drosophila mRNAs revealed that the AREScore is a very good predictor of short-lived mRNAs. Taken together, this study introduces AREScore as a simple tool to identify ARE–containing mRNAs and provides compelling evidence that AREs are widespread regulatory elements in Drosophila

Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization.

The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD

Tinman/Nkx2-5 acts via miR-1 and upstream of Cdc42 to regulate heart function across species

Cdc42 regulates cardiac function in mice and flies downstream of a conserved Tinman/Nkx2-5–miR-1 signaling network