The Circumference of the Earth and Ptolemy’s World Map

The interlink between the determination of the circumference of the Earth and the geographical mapping performed by Ptolemy in his Geography (c. 150 AD) is discussed. As Ptolemy himself stated, he used the value of 180,000 stades for the circumference of the Earth which is in stark contrast to the famous result of Eratosthenes, i.e. 252,000 stades. Many scholars see these different values as a result of the diverse definitions of a stade used by both ancient authors. Such a view cannot, nevertheless, explain the excessive distortion of Ptolemy's world map along the east-west direction. We have treated the problem with the methods of spherical trigonometry and have shown that many features of Ptolemy’s map can be easily explained and corrected under the presupposition that the length of the stade used by Ptolemy coincides with that of Eratosthenes. The latitudinal distortion in Ptolemaic map is caused by his underestimating of the size of the Earth in combination with his efforts to keep the known latitudes of the localities. Another mathematical consequence is a significant longitudinal displacement of the localities lying approximately on the same meridian (so-called antikemenoi poleis), as in the case Carthage in relation to Rome. It is shown that a simple transformation of the Ptolemaic coordinates to the circumference of the Earth measured by Eratosthenes drastically improves the positions of the locations given in Ptolemy´s catalogue. The comparison of the recalculated positions of the identified localities with their actual positions confirmed a very high precision of Eratosthenes' result for the circumference of the Earth.Untersucht wird der Zusammenhang zwischen der Bestimmung des Erdumfangs und dem kartographischen Verfahren, das Ptolemaios in seiner Geographie (ca. 150 n. Chr.) anwendet. Wie Pto-lemaios selbst behauptet, verwendet er statt des Resultats der berühmten Erdumfangsmessung des Eratosthenes (252 000 Stadien) den Wert von 180 000 Stadien für die Erdgröße. Die meisten Forscher heute führen diesen Unterschied auf unterschiedliche Stadien-Längen zurück. Eine solche Ansicht kann aber z. B. nicht die starke Ost-West-Überdehnung der Oikumene erklären, wie sie aus der Erdkarte des Ptolemaios bekannt ist. Wir haben daher dieses Problem mit den Methoden der Sphärischen Trigonometrie behandelt und können nun zeigen, dass sich viele Verzerrungen leicht erklären und korrigieren lassen, wenn wir annehmen, dass das Ptolemaische Stadion mit dem des Eratosthenes identisch ist. Vielmehr wird die Überdehnung der Oikumene durch den zu geringen Erdumfang bei Ptolemaios in Verbindung mit seinem Bestreben, die überlieferten Breitenangaben für bekannte Orte zu bewahren, verursacht. Eine andere mathematische Konsequenz ist die signifikante Nord-Süd-Verlagerung von Orten, die auf dem gleichen Meridian liegen (so genannte antikemenoi poleis), wie die von Karthago gegenüber Rom. Wir können nachweisen, dass durch eine Rekalkulation der Ptolemaischen Koordinaten in Bezug auf die “richtige” Erdgröße des Eratosthenes die Positionen der Orte in seinem Katalog dramatisch verbessert werden. Ein Vergleich zwischen den rekalkulierten und modernen Koordinaten bestätigt außerdem die Genauigkeit der Eratosthenischen Erdmessung

Current Star Formation in the Ophiuchus and Perseus Molecular Clouds: Constraints and Comparisons from Unbiased Submillimeter and Mid-Infrared Surveys. II

We present a census of the population of deeply embedded young stellar objects (YSOs) in the Ophiuchus molecular cloud complex based on a combination of Spitzer Space Telescope mid-infrared data from the "Cores to Disks" (c2d) legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. We have applied a method developed for identifying embedded protostars in Perseus to these datasets and in this way construct a relatively unbiased sample of 27 candidate embedded protostars with envelopes more massive than our sensitivity limit (about 0.1 M_sun). Embedded YSOs are found in 35% of the SCUBA cores - less than in Perseus (58%). On the other hand the mid-infrared sources in Ophiuchus have less red mid-infrared colors, possibly indicating that they are less embedded. We apply a nearest neighbor surface density algorithm to define the substructure in each of the clouds and calculate characteristic numbers for each subregion - including masses, star formation efficiencies, fraction of embedded sources etc. Generally the main clusters in Ophiuchus and Perseus (L1688, NGC1333 and IC348) are found to have higher star formation efficiencies than small groups such as B1, L1455 and L1448, which on the other hand are completely dominated by deeply embedded protostars. We discuss possible explanations for the differences between the regions in Perseus and Ophiuchus, such as different evolutionary timescales for the YSOs or differences, e.g., in the accretion in the two clouds.Comment: Accepted for publication in ApJ (56 pages, 13 figures; abstract abridged). Version with full-resolution figures available at http://www.astro.uni-bonn.de/~jes/paper120.pd

Discovery of a Wide Low-mass Binary System in Upper Scorpius

Using the near-infrared spectrometer SpeX and its slit-viewing camera at the IRTF, I have resolved a low-mass member of the Upper Scorpius OB association into a double star. From K-band images of the pair, DENIS-P J161833.2-251750.4 A and B, I measure a separation of 0.96" and a magnitude difference of dK=0.42 mag. I present resolved 0.8-2.5 micron spectroscopy of the two objects, both of which exhibit signatures of youth in the shape of their H- and K-band continua, demonstrating that both are members of Upper Scorpius rather than field stars. In addition, through a comparison to optically-classified pre-main-sequence objects, I derive a spectral type near M5 for each component, corresponding to a mass of ~0.15 Msun with the evolutionary models of Chabrier and Baraffe. The probability that this pair is composed of unrelated M-type members of Upper Scorpius is ~10^-5. When added to the recent discoveries of other wide, easily disrupted low-mass binaries, this new system further establishes that the formation of low-mass stars and brown dwarfs does not require ejection from multiple systems. These observations also indicate that wide low-mass binaries can form in OB associations as well as in smaller clusters where the previously known wide pairs have been found. Thus, the available data show no perceptible effect of star-forming environment on the prevalence of loosely bound low-mass systems.Comment: 5 page

Triggered Star Formation by Massive Stars

We present our diagnosis of the role that massive stars play in the formation of low- and intermediate-mass stars in OB associations (the Lambda Ori region, Ori OB1, and Lac OB1 associations). We find that the classical T Tauri stars and Herbig Ae/Be stars tend to line up between luminous O stars and bright-rimmed or comet-shaped clouds; the closer to a cloud the progressively younger they are. Our positional and chronological study lends support to the validity of the radiation-driven implosion mechanism, where the Lyman continuum photons from a luminous O star create expanding ionization fronts to evaporate and compress nearby clouds into bright-rimmed or comet-shaped clouds. Implosive pressure then causes dense clumps to collapse, prompting the formation of low-mass stars on the cloud surface (i.e., the bright rim) and intermediate-mass stars somewhat deeper in the cloud. These stars are a signpost of current star formation; no young stars are seen leading the ionization fronts further into the cloud. Young stars in bright-rimmed or comet-shaped clouds are likely to have been formed by triggering, which would result in an age spread of several megayears between the member stars or star groups formed in the sequence.Comment: 2007, ApJ, 657, 88

Three very young HgMn stars in the Orion OB1 Association

We report the detection of three mercury-manganese stars in the Orion OB1 association. HD 37886 and BD-0 984 are in the approximately 1.7 million year old Orion OB1b. HD 37492 is in the approximately 4.6 million year old Orion OB1c. Orion OB1b is now the youngest cluster with known HgMn star members. This places an observational upper limit on the time scale needed to produce the chemical peculiarities seen in mercury-manganese stars, which should help in the search for the cause or causes of the peculiar abundances in HgMn and other chemically peculiar upper main sequence stars.Comment: 8 pages including 1 figure. To appear in Astrophysical Journal Letter

Hot Organic Molecules Toward a Young Low-Mass Star: A Look at Inner Disk Chemistry

Spitzer Space Telescope spectra of the low mass young stellar object (YSO) IRS 46 (L_bol ~ 0.6 L_sun) in Ophiuchus reveal strong vibration-rotation absorption bands of gaseous C2H2, HCN, and CO2. This is the only source out of a sample of ~100 YSO's that shows these features and the first time they are seen in the spectrum of a solar-mass YSO. Analysis of the Spitzer data combined with Keck L- and M-band spectra gives excitation temperatures of > 350 K and abundances of 10(-6)-10(-5) with respect to H2, orders of magnitude higher than those found in cold clouds. In spite of this high abundance, the HCN J=4-3 line is barely detected with the James Clerk Maxwell Telescope, indicating a source diameter less than 13 AU. The (sub)millimeter continuum emission and the absence of scattered light in near-infrared images limits the mass and temperature of any remnant collapse envelope to less than 0.01 M_sun and 100 K, respectively. This excludes a hot-core type region as found in high-mass YSO's. The most plausible origin of this hot gas rich in organic molecules is in the inner (<6 AU radius) region of the disk around IRS 46, either the disk itself or a disk wind. A nearly edge-on 2-D disk model fits the spectral energy distribution (SED) and gives a column of dense warm gas along the line of sight that is consistent with the absorption data. These data illustrate the unique potential of high-resolution infrared spectroscopy to probe organic chemistry, gas temperatures and kinematics in the planet-forming zones close to a young star.Comment: 4 pages, 4 figures; To appear in Astrophysical Journal Letter

Far-Ultraviolet Dust Albedo Measurements in the Upper Scorpius Cloud Using the SPINR Sounding Rocket Experiment

The Spectrograph for Photometric Imaging with Numeric Reconstruction (SPINR) sounding rocket experiment was launched on 2000 August 4 to record far-ultraviolet (912-1450 A) spectral and spatial information for the giant reflection nebula in the Upper Scorpius region. The data were divided into three arbitrary bandpasses (912-1029 A, 1030-1200 A, and 1235-1450 A) for which stellar and nebular flux levels were derived. These flux measurements were used to constrain a radiative transfer model and to determine the dust albedo for the Upper Scorpius region. The resulting albedos were 0.28+/-0.07 for the 912-1029 A bandpass, 0.33+/-0.07 for the 1030-1200 A bandpass, and 0.77+/-0.13 for the 1235-1450 A bandpass

Vitamin D deficiency as a risk factor for infection, sepsis and mortality in the critically ill: systematic review and meta-analysis

INTRODUCTION: In Europe, vitamin D deficiency is highly prevalent varying between 40% and 60% in the healthy general adult population. The consequences of vitamin D deficiency for sepsis and outcome in critically ill patients remain controversial. We therefore systematically reviewed observational cohort studies on vitamin D deficiency in the intensive care unit.METHODS: Fourteen observational reports published from January 2000 to March 2014, retrieved from Pubmed and Embase, involving 9,715 critically ill patients and serum 25-hydroxyvitamin D3 (25 (OH)-D) concentrations, were meta-analysed.RESULTS: Levels of 25 (OH)-D less than 50 nmol/L were associated with increased rates of infection (risk ratio (RR) 1.49, 95% (confidence interval (CI) 1.12 to 1.99), P = 0.007), sepsis (RR 1.46, 95% (CI 1.27 to 1.68), P <0.001), 30-day mortality (RR 1.42, 95% (CI 1.00 to 2.02), P = 0.05), and in-hospital mortality (RR 1.79, 95% (CI 1.49 to 2.16), P <0.001). In a subgroup analysis of adjusted data including vitamin D deficiency as a risk factor for 30-day mortality the pooled RR was 1.76 (95% CI 1.37 to 2.26, P <0.001).CONCLUSIONS: This meta-analysis suggests that vitamin D deficiency increases susceptibility for severe infections and mortality of the critically ill

SCUBA Mapping of Spitzer c2d Small Clouds and Cores

We present submillimeter observations of dark clouds that are part of the Spitzer Legacy Program, From Molecular Cores to Planet-Forming Disks (c2d). We used the Submillimetre Common User's Bolometer Array to map the regions observed by Spitzer by the c2d program to create a census of dense molecular cores including data from the infrared to the submillimeter. In this paper, we present the basic data from these observations: maps, fluxes, and source attributes. We also show data for an object just outside the Perseus cloud that was serendipitously observed in our program. We propose that this object is a newly discovered, evolved protostar.Comment: 37 pages, accepted to The Astronomical Journa

Resilience in the face of uncertainty: early lessons from the COVID-19 pandemic

The transboundary dynamics of COVID-19 present an unprecedented test of organisational resilience. In the UK, the National Health Service (NHS), a talisman of collective fortitude against disease and illness, has struggled to cope with inadequate provision of virus tests, ventilators, and personal protective equipment needed to fight the pandemic. In this paper, we reflect on the historic dynamics and strategic priorities that have undermined the NHS's attempts to navigate these troubled times. We invoke the organisational resilience literature to address 'the good, the bad and the ugly' of preparedness in readiness and response to the current pandemic. In particular, we draw on Meyer's (1982) seminal work on 'adaptation to jolts', excavating current preparedness failings. We argue an overreliance on perceived efficiency benefits of 'lean production' and 'just in time' continuity planning superseded strategic redundancy and slack in the system. This strategic focus was not simply the result of a failure in foresight, but rather a failure to act adaptively on knowledge of the known threats and weaknesses spotlighted by earlier projections of an inevitable pandemic threat. In conclusion, we consider how the UK Government and NHS must now undergo a phase of 'readjustment' in Meyer's terms, in light of these failings. We suggest that independent responsibility for national future preparedness should be handed to the NHS free from political interference. This would operate under the umbrella of a national emergency preparedness, resilience and response public body, enshrined in law, and similar in governance to the current Bank of England. This will help ensure that foresight is accompanied by durability and fortitude in safeguarding the UK against future pandemic threats