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Defect Induced Photoluminescence from Dark Excitonic States in Individual Single-Walled Carbon Nanotubes
No full textSUMMARY We show that new low-energy photoluminescence (PL) bands can be created in
semiconducting single-walled carbon nanotubes by intense pulsed excitation. The
new bands are attributed to PL from different nominally dark excitons that are
"brightened" due to defect-induced mixing of states with different parity
and/or spin. Time-resolved PL studies on single nanotubes reveal a significant
reduction of the bright exciton lifetime upon brightening of the dark excitons.
The lowest energy dark state has longer lifetimes and is not in thermal
equilibrium with the bright state
Molecular vibrational cooling by Optical Pumping with shaped femtosecond pulses
No full textSUMMARY Some of us have recently reported in Science 321 232 (2008) vibrational
cooling of translationally cold Cs_2 molecules into the lowest vibrational
level v=0 of the singlet X 1Sigma_g ground electronic state. Starting from a
sample of cold molecules produced in a collection of vibrational levels of the
ground state, our method was based on repeated optical pumping by laser light
with a spectrum broad enough to excite all populated vibrational levels but
frequency-limited in such a way to eliminate transitions from v=0 level, in
which molecules accumulate. In this paper this method is generalized to
accumulate molecules into an arbitrary selected "target" vibrational level. It
is implemented by using ultrashort pulse shaping techniques based on Liquid
Crystal spatial light modulator. In particular a large fraction of the
initially present molecule is transferred into a selected vibrational level
such as v=1, 2 and 7. Limitations of the method as well as the possible
extension to rotational cooling are also discussed
Implication of phospholipase D in response of Hordeum vulgare root to a short-term potassium deprivation
No full textSUMMARY To verify a possible implication of lipids and some other compounds such as hydrogen peroxide (H2O2) and glyceraldehydes-3-phosphate dehydrogenase (G3PDH) in the response of Hordeum vulgare to an early potassium deprivation, plants were grown in hydroponics for 30 days with a modified Hewitt nutrient solution containing 3 mM K+ and then incubated for increasing time ranging from 2 h up to 36 h in the same medium deprived of K+. In contrast to leaves, root K+ concentration showed its greatest decrease after 6 h of treatment. The main lipids of the control barley roots were phospholipids (PL), representing more than 50% of the total lipids. PL did not change with treatment whereas free sterols (FS) amounts decreased following K+ deprivation, showing an about 17% reduction after 36 h. As regards the individual PL, 30 h K+ deprivation caused a reduction in phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidylinositol (PI) levels whereas phosphatidylglycerol (PG), phosphatidylethanolamine (PE) and phosphatidic acid (PA) increased. The maximum PA accumulation as well as the highest phospholipase D (PLD) activation, estimated by an accumulation of phosphatidylbutanol (PtBut), were observed after 24 h of K+ starvation. At the root level, after 6 h of incubation in –K solution, H2O2 level showed the maximum value. At the same time G3PDH activity reached the minimum. On the basis of a concomitant stimulation of PLD activity and, consequently, PA accumulation, enhancement of H2O2 production, and inhibition of G3PDH activity we can suggest a possible involvement of these three compounds in an early response to K+ deprivation
A Computational Comparison of Reformulations of the Perspective Relaxation: SOCP vs. Cutting Planes
No full textThe Perspective Reformulation is a general approach for constructing tight approximations to MINLP problems with semicontinuous variables. Two different reformulations have been proposed for solving it, one resulting in a Second-Order Cone Program, the other based on representing the perspective function by (an infinite number of) cutting planes. We compare the two reformulations on two sets of MIQPs to determine which one is most effective in the context of exact or approximate Branch-and-Cut algorithms
Incubi e sogni metropolitani: la città degli architetti espressionisti
Get PDFL'articolo presenta sinteticamente l'immagine della città tedesca di inizio Novecento, così come percepita dagli artisti espressionisti e come sognata e progettata dagli architetti aderenti all'avanguardia. This paper describes the Expressionist idea of city, urban images and utopias in Germany at the beginning of the XXth Century (1910-1930)
Conservation and actuality in ancient environments. From the 1931 Athens Charter to the 2008 Bethlehem Charter
Get PDFSin dal principio del XX secolo la conservazione dei contesti urbani storicizzati ha costituito argomento di riflessione nonché di analisi nell’ambito di Convenzioni e Carte internazionali destinate a chiarire i principi fondativi propri di un corretto intervento conservativo della città. Il rapporto tra monumento, paesaggio, cultura e società, valutato a scala urbana, giunge a definire la conservazione come azione finalizzata al rispetto dell’autenticità del bene nel quale la collettività nel suo complesso deve identificarsi. Questi principi sono alla base delle più recenti Convenzioni internazionali nelle quali si inserisce oggi anche la ‘Carta di Betlemme’. Sulla base di queste premesse il contributo ha come finalità quello di delineare un percorso culturale e allo stesso tempo metodologico per la salvaguardia delle città storiche che, a partire dalla Carta di Atene del 1931, costituisce parte integrante della politica economica e di sviluppo sociale delle nazioni. From the beginning of the twentieth century, the protection of urban historical contexts was the subject of reflection and analysis within international Charters and Agreements aimed at clarifying the founding principles of a proper conservative intervention on the city. The relationship among monument, landscape, culture and society, evaluated at an urban scale, comes to define the conservation as an action aimed at the respect of the monuments authenticity in which the community altogether must identify itself. These principles are the basis of the most recent international conventions in which the ‘Bethlehem Charter‘ inscribes. On this basis the contribution aims at outlining a cultural and methodological path for the protection of historical cities which, starting from the 1931 Athens Charter, is an integral part of the economic policy and social development of nations
FastFlow: Efficient Parallel Streaming Applications on Multi-core
No full textShared memory multiprocessors come back to popularity thanks to rapid spreading of commodity multi-core architectures. As ever, shared memory programs are fairly easy to write and quite hard to optimise; providing multi-core programmers with optimising tools and programming frameworks is a nowadays challenge. Few efforts have been done to support effective streaming applications on these architectures. In this paper we introduce FastFlow, a low-level programming framework based on lock-free queues explicitly designed to support high-level languages for streaming applications.
We compare FastFlow with state-of-the-art programming frameworks such as Cilk, OpenMP, and Intel TBB. We experimentally demonstrate that FastFlow is always more efficient than all of them in a set of micro-benchmarks and on a real world application; the speedup edge of FastFlow over other solutions might be bold for fine grain tasks, as an example +35% on OpenMP, +226% on Cilk, +96% on TBB for the alignment of protein P01111 against UniProt DB using Smith-Waterman algorithm
Image Analysis Methods in MRI Examinations of the Breast
No full textBreast cancer represents a real emergency in many European and North American countries. In order to detect the diseases as soon as it starts developing, many countries have organized screening programs aimed to women monitoring. Traditional imaging modalities, like X-Ray mammography, do not provide certain and reliable results on young women or in women who underwent surgical interventions. Three-dimensional breast MRI has proven to be a valuable tool for disambiguate uncertain mammographic findings and for the pre-operative planning. However, in order for MRI of the breast to be effective, a contrast agent, highlighting areas with a high degree of vascularization, needs to be used. The full breast volume needs to be acquired once before and several times after the contrast agent injection. A contrast-enhance MR examination of the breast contains hundreds of images that must be inspected carefully. Automatic approaches to breast cancer detection can help radiologists in this hard tasks and speed up the inspection process. In this paper we present a survey of automatic approaches to breast cancer detection in MRI. We discuss both registration algorithms needed to align corresponding images acquired at different instants in time and classification algorithms able to label a suspicious area according to features automatically computed from the images
Sub-Doppler spectroscopy of atoms excited in the regime of Rabi oscillations in a thin gas cell
No full textWe carried out theoretical investigation about velocity-selective atomic excitation on long–lived (metastable) levels of an atomic vapour in a thin cell by a monochromatic laser beam, running in the normal direction. The regime of coherent Rabi oscillations is considered on the light-induced transition from a sublevel of the ground quantum term to a metastable atomic level. On the basis of density matrix equations for the two-level system, we analysed the atomic population density of the metastable level, when the sample is irradiated by resonant monochromatic laser beam with an annular cross-section versus atomic velocities and versus the detuning, the amplitude, and the geometry of the laser beam. It is shown that, in the centre of the annular region, it can be obtained a population distribution on the metastable level as a function of the laser detuning, characterized by a sharp narrow resonance profile, whose width is reduced with respect to the thermal Doppler width roughly by the ratio between the diameter of the irradiated region and the inner thickness of the cell. We suggest high-sensitive schemes, in order to detect these sub-Doppler resonances, by probing the population of the metastable state with a second laser beam, resonant with a transition leaving from the metastable level. The case of 1S0?3P1 spin-forbidden transition of Ca is discussed in more detail
La chiesa dei SS Ranieri e Leonardo in via Pietro Maffi
Get PDFRIASSUNTO Il capitolo descrive la chiesa di S. Ranierino nelle forme attuali, risalenti alla seconda metà del XIX secolo. SUMMARY This chapter describes the church of S. Ranierino after its reconstruction in the second half of the XIXth Century