Studies of dense cores with ALMA

Dense cores are the simplest star-forming sites that we know, but despite their simplicity, they still hold a number of mysteries that limit our understanding of how solar-type stars form. ALMA promises to revolutionize our knowledge of every stage in the life of a core, from the pre-stellar phase to the final disruption by the newly born star. This contribution presents a brief review of the evolution of dense cores and illustrates particular questions that will greatly benefit from the increase in resolution and sensitivity expected from ALMA.     

Continuous monitoring of nightside upper thermospheric mass densities in the martian southern hemisphere over 4 martian years using electron reflectometry

Details are presented of an improved technique to use atmospheric absorption of magnetically reflecting solar wind electrons to constrain neutral mass densities in the nightside martian upper thermosphere. The helical motion of electrons on converging magnetic field lines, through an extended neutral atmosphere, is modeled to enable prediction of loss cone pitch angle distributions measured by the Magnetometer/Electron Reflectometer (MAG/ER) experiment on Mars Global Surveyor at 400 km altitude. Over the small fraction of Mars' southern hemisphere (∼2.5%) where the permanent crustal magnetic fields are both open to the solar wind and sufficiently strong as to dominate the variable induced martian magnetotail field, spherical harmonic expansions of the crustal fields are used to prescribe the magnetic field along the electron's path, allowing least-squares fitting of measured loss cones, in order to solve for parameters describing the vertical neutral atmospheric mass density profile from 160 to 230 km. Results are presented of mass densities in the southern hemisphere at 2 a.m. LST at the mean altitude of greatest sensitivity, 180 km, continuously over four martian years. Seasonal variability in densities is largely explained by orbital and latitudinal changes in dayside insolation that impacts the nightside through the resulting thermospheric circulation. However, the physical processes behind repeatable rapid, late autumnal cooling at mid-latitudes and near-aphelion warming at equatorial latitudes is not fully clear. Southern winter polar warming is generally weak or nonexistent over several Mars years, in basic agreement with MGS and MRO accelerometer observations. The puzzling response of mid-latitude densities from 160° to 200° E to the 2001 global dust storm suggests unanticipated localized nightside upper thermospheric lateral and vertical circulation patterns may accompany such storms. The downturn of the 11-year cycle of solar EUV flux is likely responsible for lower aphelion densities in 2004 and 2006 (Mars years 27 and 28).     

High‐precision Determination of Gold Mass Fractions in Geological Reference Materials by Internal Standardisation

Determination of gold abundances in natural rock is critical for applications, but very challenging. Here, we report a method for determining gold with a very low mass fraction (> 0.01 ng g^?1) in rocks. The method involves Carius tube digestion with reverse aqua regia, chromatographic separation to remove most of the sample matrix and measurement by high‐sensitivity ICP‐MS. The mono‐isotopic element gold was quantified by external calibration using an internal standardisation of gold to platinum that was precisely determined by isotope dilution. The method is robust and the obtained results are indistinguishable (< 5–10%, 2s) from those independently obtained by a standard addition technique on the same solution. The results from reference materials TDB‐1 and GPt‐2 are consistent with the certified values and those determined by HF‐aqua regia digestion, confirming the validity of the method. TDB‐1 (n = 20), GPt‐2 (n = 6), BHVO‐2 (n = 9) and other mafic RMs are homogenous for gold (10–20%, 2s) at the 2 g test portion level; however, sample heterogeneity affects some RMs. Gold and platinum‐group elements also display different extents of sample heterogeneity for different RMs. Given the homogeneity observed for TDB‐1, GPt‐2 and BHOV‐2, they are recommended as well‐suited RMs for inter‐laboratory comparison studies of gold.     

Charge-density analysis of spodumene (LiAlSi<Subscript>2</Subscript>O<Subscript>6</Subscript>), from ab initio Hartree–Fock calculations

An ab initio Hartree–Fock study of spodumene structure has been performed, and the wave function was used for a topological analysis of the electron density. The three non-equivalent oxygen atoms (O1, O2 and O3) of spodumene differed mainly in their valence shell charge concentration (VSCC). In particular, O1 shows a maximum of charge concentration along the Si–O bond path, and two other maxima, which can be regarded as lone pairs, point in the opposite direction with respect to the silicon position. O2 shows a torus of local charge concentration, whose axis is parallel to the Al–Si direction, with a bulge on the external side of the Si–O2–Al angle; even if no maximum exists in the Si direction, the valence shell of O2 appears to be strongly polarized toward the silicon; a slight polarization also exists along the Al–O bond path. A similar situation is displayed by O3, whose charge concentration has a torus-like shape, with the axis parallel to the Si–Si direction, and a bulge on the external side of the Si–O3–Si angle; as in the case of O2, a significant polarization of the valence shell of O3 is observed, towards the two Si directions. By recasting the calculated electron distribution in terms of the valence bond theory, a correlation has been found between structural details (bond lengths) and the hybridization state of the oxygen atoms.     

Reappraisal of great historical earthquakes in the northern Chile and southern Peru seismic gaps

A critical reappraisal of great historical interplate earthquakes in the occidental margin of South America, including southern Peru and northern Chile, is carried out.A spacetime distribution of the earthquakes associated to the seismotectonics regions defined by the rupture zones of the greatest events (1868, Mw = 8.8 and 1877, Mw = 8.8) is obtained. Both regions are seismic gaps that are in the maturity state of their respective earthquake cycles. The region associated to the 1868 earthquake presents a notable seismic quiescence in the present century.     

Electromagnetic induction in geothermal fields and volcanic belts

This review covers electromagnetic studies in geothermal and volcanic regions presented in the literature since 1983. It has been arranged by geographical areas, emphasizing where possible the data gathering, the interpretation techniques and the results of each study. The main conclusions of this review are: In all the surveys, people are measuring the complete MT impedance tensor. However, in general, this information is not being used in the interpretation mainly because of the poor quality of the data. This unfortunate situation originates by the presence of strong noise in the surveyed area and generally, by the lack of use of the remote reference technique. Crews with equipment and techniques that can gather data of very good quality, generally perform very detailed interpretations using most of the gathered information. Other groups that collect noisy data oversimplify the interpretation by using only one mode or averaging the resistivity of both modes and interpreting the results using simplified 1-D interpretations. At the interpretation stage, most of the mid-crustal conductors identified are being associated to the presence of trapped water of magmatic origin. In general, magma chambers are not being detected, probably because either they are absent or because there is a lack or resolution of the electromagnetic methods to detect them.     

The anomalous ionospheric absorption on winter days

Summary Some results on ionospheric absorption measurements made at Genova-Monte Capellino in the years 1959 and 1960 are presented, deducing the behaviour of the mean diurnal variation. The abnormally high absorption during some days of January and February 1959 is then discussed, together with the treatment of data collected in various European and Asiatic stations; the geographical distribution of the phenomenon is studied, and the influence of meteors is also briefly considered.This paper has been read at the XII-Assembly of the I.G.G.U. in Helsinki (July–August 1960).     

La distribuzione del campo magnetico terrestre all'isola di Stromboli

Riassunto Si riferisce sul rilevamento geomagnetico dell'isola di Stromboli, eseguito nel 1940 (marzo-maggio) con 218 stazioni, nelle quali vennero determinate, mediante misure relative, le componenti verticale ed orizzontale del campo terrestre. I risultati ottenuti per la distribuzione di questi elementi (e di quelli subordinatiI edF) sono stati rappresentati graficamente nelle cartine allegate; essi rivelano l'esistenza di anomalie particolarmente intense, talune con valori di Z e di H maggiori di 5000 , le cui caratteristiche vengono discusse in funzione delle condizioni geologiche locali e cioè sopratutto dell'attività relativamente recente del vulcano.

---

Zusammenfassung Die Arbeit bezieht sich auf die geomagnetische Aufnahme, welche im Jahre 1940 (März–Mai) auf der Insel Stromboli mit 218 Stationen durchgeführt wurde. Damit wurden mittels relativen Messungen die vertikale und horizontale Komponenten des Erdfeldes bestimmt. Die für die Verteilung dieser Elemente (und der abzuleitenden GrössenI undF) erreichten Ergebnisse sind in untenstehenden Karten dargestellt. Es zeigt sich u.a das Vorhandensein von äusserst starken Anomalien, die z.B. Z- und H-Werte über 5000 zeigen, deren Eigentümlichkeiten in Funktion der geologischen örtlichen Bedingungen, d.h. in erster Linie der vergangenen und relativ rezenten Tätigkeit des Vulkans, besprochen werden.

---

---

con quattro tavole f.t.     

Globalstrahlung und Sonnenaktivität

Summary Using the highest global irradiance values (Sun plus sky) at noon derived from the records gathered during the years 1958 to 1963 at Genova, Monte Capellino and Sauze d'Oulx, it is demonstrated that the thermal energy which the Earth receives from the Sun is dependent from the Sun activity. Precisely, an increase of the thermal energy withR _Z occurs up toR _Z=160–170, whereas for greater values ofR _Z the thermal energy received decreases with the increase ofR _Z.

---

---

Herrn Prof. Dr.Hans Ertel zu seinem 60. Geburtstag gewidmet.     

Sulla genesi delle precipitazioni

Riassunto In base a diverse serie di osservazioni meteorologiche raccolte su alte montagne, specie delle Alpi, l'A. dimostra che la conservazione della nebbia sottoraffreddata e la genesi delle precipitazioni nevose, sono regolate dalle temperature intorno a –11°, –4°–5° e –19° C, in completo accordo con lo spettro dei nuclei di congelamento dedotto sperimentalmente. Il risultato ha validità generale. — Segue l'illustrazione di talune deduzioni, con considerazioni interpretative.

---

Summary Making use of different series of meterological observations carried out in high mountains, particularly in the Alps, the Author proves that the conservations-tendency of undercooled fog and the formation of snow are essentially controlled by the air-temperatures around –11°, –4°–5° and –19°C, in perfect agreement with the spectrum of freezing nuclei, known from laboratory work. The result is of general validity. — Some interpretations are presented.

---

Zusammenfassung Auf Grund verschiedenen, im Hochgebirge, besonders in den Alpen, gesammelten meteorologischen Beobachtungsreihen, beweist der Verf., das die Erhaltungstendenz des unterkühlten Nebels und die Schneebildung wesentlich mitbestimmt werden durch die Luft-Temperaturen um –11°, –4°–5° und –19° C, in vollkommener Uebereinstimmung mit dem experimentell abgeleiten Spektrum der Gefrierkerne. Das Ergebnis hat allgemeine Gültigkeit. — Es folgen einige erläuternde Betrachtungen.