Le 7 equazioni che regolano la struttura stellare

In questa tesi sono analizzate le 7 equazioni che regolano una struttura stellare: si tratta di 4 equazioni differenziali a coefficienti non costanti e 3 relazioni caratteristiche. La struttura stellare è approssimata a una sfera di gas autogravitante in cui in ogni strato la forza di gravità è in equilibrio idrostatico con la pressione del gas (le forze elettromagnetiche sono di fatto trascurate). La stella è una struttura in quasi equilibrio, ovvero il tempo di rilassamento per deviazioni dallo stato di equilibrio è molto minore rispetto al tempo necessario per produrre variazioni significative

Coexistence of Ballistic and Fourier Regimes in the β Fermi-Pasta-Ulam-Tsingou Lattice

Commonly, thermal transport properties of one-dimensional systems are found to be anomalous. Here, we perform a numerical and theoretical study of the β-Fermi-Pasta-Ulam-Tsingou chain, considered a prototypical model for one-dimensional anharmonic crystals, in contact with thermostats at different temperatures. We give evidence that, in steady state conditions, the local wave energy spectrum can be naturally split into modes that are essentially ballistic (noninteracting or scarcely interacting) and kinetic modes (interacting enough to relax to local thermodynamic equilibrium). We show numerically that the well-known divergence of the energy conductivity is related to how the transition region between these two sets of modes shifts in k space with the system size L, due to properties of the collision integral of the system. Moreover, we show that the kinetic modes are responsible for a macroscopic behavior compatible with Fourier's law. Our work sheds light on the long-standing problem of the applicability of standard thermodynamics in one-dimensional nonlinear chains, testbed for understanding the thermal properties of nanotubes and nanowires

Toward fractioning of isomers through binding-induced acceleration of azobenzene switching

The E/Z isomerization process of a uracil-azobenzene derivative in which the nucleobase is conjugated to a phenyldiazene tail is studied in view of its ability to form triply-H-bonded complexes with a suitably complementary 2,6-diacetylamino-4-pyridine ligand. UV-Vis and 1H-NMR investigations of the photochemical and thermal isomerization kinetics show that the thermal Z→E interconversion is four-fold accelerated upon formation of the H-bonded complex. DFT calculations show that the formation of triple H-bonds triggers a significant elongation of the N=N double bond, caused by an increase of its πg∗ antibonding character. This results in a reduction of the N=N torsional barrier and thus in accelerated thermal Z→E isomerization. Combined with light controlled E→Z isomerization this enables controllable fractional tuning of the two configurational isomers

An Unprecedented High Content of the Bioactive Flavone Tricin in Huperzia Medicinal Species Used by the Saraguro in Ecuador.

The flavone tricin (5,7,4′-trihydroxy-3′,5′-dimethoxyflavone) is considered to be a selective potent inhibitor of different cancer cell lines and a potential colorectal cancer chemopreventive agent. In this paper we describe a reliable UHPLC-UV-ESIMS method for the determination of tricin in Huperzia plants used in the traditional medicine of the Saraguro community living in Southern Ecuador. An unusually high amount of tricin was found in H. brevifolia and H. compacta, which exceeded the content of this flavone determined so far in other plants

Two successful natural pregnancies in a patient with severe uterine prolapse: A case report

<p>Abstract</p> <p>Introduction</p> <p>Uterine prolapse is a common gynecologic condition that is rare during or before pregnancy. We report an exceptional case of two pregnancies in a totally prolapsed uterus.</p> <p>Case presentation</p> <p>A 36-year-old Caucasian woman with a history of uterine prolapse presented with pregnancy. A vaginal pessary was applied to keep her uterus inside the pelvis after manual reposition. The pessary was removed at the 24th week. The gravid uterus persisted in the abdominal cavity because of its increased volume.</p> <p>Conclusion</p> <p>Our case shows that pregnancy during uterine prolapse is possible and that careful assessment is required to prevent complications during delivery. According to our experience, an elective caesarean section near term could be the safest mode of delivery.</p

Structural Characterisation of Metabolites from Pholiota spumosa (Basidiomycetes)

Three compounds of different biosynthetic origin were isolated from the fruiting bodies of the gilled mushroom Pholiota spumosa (Basidiomycetes, Strophariaceae). Fasciculol E, a lanostane triterpenoid conjugated to a depsipeptide unit, was isolated for the first time from genus Pholiota. In addition, the first isolation of putrescine-1,4-dicinnamamide as a natural compound is reported: its structure was established by single crystal X-ray diffraction, and by spectroscopic methods. Crystallographic analysis indicated the presence of a co-crystallised related dicinnamamide, namely the new compound (E)-2,3-dehydroputrescine-1,4-dicinnamamide, whose occurrence was confirmed by LC-MS analysis. An interesting evolutionary issue arises, following the observation that the cinnamamides produced by Pholiota spumosa bear an unsubstituted benzene ring, contrarily to those found in plants, which have always phenolic functionalities, and as such perform a variety of biological roles

Two-dimensional ketone-driven metal-organic coordination on Cu(111)

Two-dimensional metal-organic nanostructures based on the binding of ketone groups and metal atoms were fabricated by depositing pyrene-4,5,9,10-tetraone (PTO) molecules on a Cu(111) surface. The strongly electronegative ketone moieties bind to either copper adatoms from the substrate or co-deposited iron atoms. In the former case, scanning tunnelling microscopy images reveal the development of an extended metal-organic supramolecular structure. Each copper adatom coordinates two ketone ligands of two neighbouring PTO molecules, forming chains that are linked together into large islands via secondary van der Waals interactions. Deposition of iron atoms leads to a transformation of this assembly resulting from the substitution of the metal centres. Density functional theory calculations reveal that the driving force for the metal substitution is primarily determined by the strength of the ketone-metal bond, which is higher for Fe compared to Cu. This second class of nanostructures displays a structural dependence on the rate of iron deposition

Debris flows and debris avalanches initiation and runout susceptibility assessment in Campania region (Italy)

Sectors of the Campania region (southern Italy), where pyroclastic airfall deposits cover carbonate slopes, have frequently experienced debris avalanches and debris flows. These landslides are triggered by heavy rainfall and in the last century caused severe destruction and hundreds of deaths. Their occurrence is controlled by the interaction of several factors, both natural and human induced. The initial failure is linked with the presence of morphological discontinuities such as rocky scarps and road cuts, which interrupt the stratigraphical continuity of an “infinite slope”. Here the main criteria for susceptibility analysis are defined trying to develop a procedure for identify highly-susceptible sources, runout and invasion areas

Quantitative protein sensing with germanium THz-antennas manufactured using CMOS processes

The development of a CMOS manufactured THz sensing platform could enable the integration of state-of-the-art sensing principles with the mixed signal electronics ecosystem in small footprint, low-cost devices. To this aim, in this work we demonstrate a label-free protein sensing platform using highly doped germanium plasmonic antennas realized on Si and SOI substrates and operating in the THz range of the electromagnetic spectrum. The antenna response to different concentrations of BSA shows in both cases a linear response with saturation above 20 mg/mL. Ge antennas on SOI substrates feature a two-fold sensitivity as compared to conventional Si substrates, reaching a value of 6 GHz/(mg/mL), which is four-fold what reported using metal-based metamaterials. We believe that this result could pave the way to a low-cost lab-on-a-chip biosensing platform