Electronic structure of C60 / graphite

We report temperature-dependent photoelectron spectra for a monolayer of C_60 adsorbed on HOPG, as well as C 1s x-ray absorption. This extends a previous report which showed the close similarity between the spectrum of the HOMO for the two-dimensional overlayer and that of C_60 in the gas phase. The present work shows that intermolecular and molecule-substrate vibrations contribute strongly to the spectral lineshape at room temperature. Thus, vibrational effects are shown to be crucial for the proper understanding of photoelectron spectra, and thus the charge transport properties, for C_60 in contact with graphite and graphite-like materials.Comment: Proc. of the XV. Int. Winterschool on Electronic Properties of Novel Materials, Kirchberg/Tirol, Austria, 200

GEOTHERMAL EXPLORATION IN THE ALEXANDRIA AREA, THESSALONIKI BASIN (MACEDONIA, NORTHERN GREECE)

Η περιοχή της Αλεξάνδρειας βρίσκεται στη Λεκάνη Θεσσαλονίκης, η οποία έχει πληρωθεί με ιζήματα πάχους άνω των 4 km. To 1980, κατασκευάσθηκε βόρεια της πόλης της Αλεξάνδρειας η γεώτρηση έρευνας υδρογονανθράκων AL-1, βάθους 1705 m, στην οποία καταγράφηκαν οι θερμοκρασίες των 39 και 65oC σε βάθη 700 και 1705 m αντίστοιχα. Μεταξύ 1996 και 2000, ανορύχθηκαν δύο γεωθερμικές ερευνητικές γεωτρήσεις, βάθους 532 και 620 m, οι οποίες διέτρησαν Τεταρτογενή και Πλειοκαινικά ιζήματα και στις οποίες μετρήθηκαν θερμοκρασίες 30.1 και 33.4oC σε βάθη 500 και 611 m αντίστοιχα. Η προκαταρκτική γεωθερμική έρευνα οδήγησε την κατασκευή της πρώτης παραγωγικής γεώτρησης (ΓΝ-1Π). Ανορύχθηκε μέχρι βάθος 805 m διατρύοντας αργίλους, άμμους, τόφφους, μάργες, αργιλο-μάργες, μαργαϊκούς ασβεστόλιθους, χάλικες, ψαμμίτες και κροκαλοπαγή. Η γεώτρηση σωληνώθηκε μέχρι τα 805 m και φίλτρα τοποθετήθηκαν σε διάφορα βάθη κάτω από τα 607 m. Τιμές θερμοκρασίας και ηλεκτρικής αγωγιμότητας 35.1-37.2oC και 5100-8200 μS/cmαντίστοιχα καταγράφηκαν σε βάθη 607-800 m. Η γεώτρηση παρουσιάζει αρτεσιανή ροή με 30-40 m3/h νερών των 34.1oC και παρέχει με άντληση 130 m3/h νερών θερμοκρασίας 35.5oC. Το παραγόμενο γεωθερμικό νερό με ΣΔΑ 2.18 g/l είναι του τύπου Na-Cl και διαφοροποιείται από τα ρηχά νερά. Η θερμική ισχύς της γεώτρησης ΓΝ-1Π υπολογίζεται σε 1.65 MWt.The area of Alexandria is located in the Thessaloniki basin that has been filled with more than 4 km of sediments. In 1980, oil exploration borehole AL-1, 1,705 m deep, was drilled north of the town of Alexandria and the temperatures of 39 and 65oC were recorded at depths of 700 and 1,705 m respectively. During 1996-2000, two geothermal exploration boreholes were drilled at depths of 532 and 620 m penetrating Quaternary and Pliocene sediments and the temperatures of 30.1 and 33.4oC were measured at 500 and 611 m respectively. The preliminary geothermal investigation resulted in the construction of the first production well (GN-1P). It was drilled to a depth of 805 m penetrating clays, sands, tuffs, marls, clayey marls, marly limestones, gravels, sandstones and conglomerates. The borehole was cased down to 805 m and screens were placed at various depths below 607 m. Temperature and electrical conductivity values of 35.1-37.2oC and 5,100-8,200 μS/cm respectively were recorded at depths of 607-800 m. This well discharges 30-40 m3/h waters at 34.1oC with artesian flow and provides 130 m3/h waters at 35.5oC with pumping. The produced geothermal water with TDS of 2.18 g/l belongs to the Na-Cl type differentiated from the shallow waters. The thermal capacity of well GN-1P is calculated to be 1.65 MWt

PRELIMINARY GEOTHERMAL INVESTIGATION IN THE BASIN OF KATERINI (NORTHERN GREECE)

Η παρούσα εργασία περιγράφει τα αποτελέσματα της προκαταρκτικής γεωθερμικής έρευνας που διενεργήθηκε από το ΙΓΜΕ στην λεκάνη της Κατερίνης (Β. Ελλάδα). Οι ερευνητικές εργασίες κατά κύριο λόγο περιελάμβαναν θερμομετρήσεις στην κεφαλή 73 υπαρχουσών υδρογεωτρήσεων, μέτρηση της θερμοκρασίας σε συνάρτηση με το βάθος στο εσωτερικό πέντε (5) γεωτρήσεων και χημικές αναλύσεις 18 δειγμάτων από επιλεγμένες θέσεις. Με βάση τα στοιχεία που προέκυψαν από την κατανομή των θερμοκρασιών, διακρίνονται τρεις επιμέρους περιοχές γεωθερμικού ενδιαφέροντος. Ως σημαντικότερη κρίνεται αυτή του Κάτω Αγίου Ιωάννη (νότια τμήμα της λεκάνης), όπου μετρήθηκαν θερμοκρασίες της τάξης των 27oC σε βάθος 340m. Εν τούτοις, για τη λεπτομερή διερεύνηση των γεωθερμικών συνθηκών στη λεκάνη Κατερίνης, απαιτείται περαιτέρω συστηματική έρευνα και κατασκευή τουλάχιστον μίας ερευνητικής γεωθερμικής γεώτρησης μεγάλου βάθους.This paper describes the results of the preliminary surface geothermal exploration conducted by IGME in the basin of Katerini (Northern Greece). It mainly regards temperature measurements at the wellhead of 73 wells and in the interior of five boreholes, as well as sampling and chemical analyses from 18 selected sites. Based on the collected data, three sub-regions of geothermal interest can be distinguished, the most important of which is the area of Kato Agios Ioannis (to the south of the basin), with temperatures around 27oC at the depth of 340m. Nonetheless, the detailed geothermal investigation of this basin requires further systematic research as well as the drilling of at least one deep geothermal exploration borehole

Chiral Symmetry Breaking in QCD: A Variational Approach

We develop a "variational mass" expansion approach, recently introduced in the Gross--Neveu model, to evaluate some of the order parameters of chiral symmetry breakdown in QCD. The method relies on a reorganization of the usual perturbation theory with the addition of an "arbitrary quark mass $m$, whose non-perturbative behaviour is inferred partly from renormalization group properties, and from analytic continuation in $m$ properties. The resulting ansatz can be optimized, and in the chiral limit $m \to 0$ we estimate the dynamical contribution to the "constituent" masses of the light quarks $M_{u,d,s}$; the pion decay constant $F_\pi$ and the quark condensate $< \bar q q >$.Comment: 10 pages, no figures, LaTe

Optimized Perturbation Theory for Wave Functions of Quantum Systems

The notion of the optimized perturbation, which has been successfully applied to energy eigenvalues, is generalized to treat wave functions of quantum systems. The key ingredient is to construct an envelope of a set of perturbative wave functions. This leads to a condition similar to that obtained from the principle of minimal sensitivity. Applications of the method to quantum anharmonic oscillator and the double well potential show that uniformly valid wave functions with correct asymptotic behavior are obtained in the first-order optimized perturbation even for strong couplings.Comment: 11 pages, RevTeX, three ps figure

Element specific characterization of heterogeneous magnetism in (Ga,Fe)N films

We employ x-ray spectroscopy to characterize the distribution and magnetism of particular alloy constituents in (Ga,Fe)N films grown by metal organic vapor phase epitaxy. Furthermore, photoelectron microscopy gives direct evidence for the aggregation of Fe ions, leading to the formation of Fe-rich nanoregions adjacent to the samples surface. A sizable x-ray magnetic circular dichroism (XMCD) signal at the Fe L-edges in remanence and at moderate magnetic fields at 300 K links the high temperature ferromagnetism with the Fe(3d) states. The XMCD response at the N K-edge highlights that the N(2p) states carry considerable spin polarization. We conclude that FeN{\delta} nanocrystals, with \delta > 0.25, stabilize the ferromagnetic response of the films.Comment: 4 pages, 3 figures, 1 tabl

Lewis J. Sundquist: Augustana Alum of 1886

Lewis J. Sundquist graduated from Augustana in 1886. We will discuss his career as a pastor, his family history, and his genealogy