An Investigation of Vertical Turbulent Transport Processes in Coastal Regions Using Tower Observations

High-resolution tower observations of turbulent transport processes in the coastal atmospheric surface layer show that the exchange coefficients for momentum, enthalpy, and moisture behave differently for different environmental and atmospheric conditions. The drag coefficient is closely tied to wind speed and turbulent intensity. The exchange coefficient for enthalpy shows a dependence on stability. Analysis of the turbulent kinetic energy budget yields a new parameterization framework that well explains the observed variation of the drag coefficient, particularly at low wind speeds.

Pressure Induced Structural Changes and Gas Diffusion Pathways in Monomeric Fluorescent Proteins

Fluorescent proteins (FPs) are extremely valuable biochemical markers which have found a wide range of applications in cellular and molecular biology research. The monomeric variants of red fluorescent proteins (RFPs), known as mFruits, have been especially valuable for in vivo applications in mammalian cell imaging. Fluorescent proteins consist of a chromophore caged in the beta-barrel protein scaffold. The photophysical properties of an FP is determined by its chromophore structure and its interactions with the protein barrel. Application of hydrostatic pressure on FPs results in the modification of the chromophore environment which allows a systematic study of the role of the protein-chromophore interactions on photophysical properties of FPs. Using Molecular Dynamics (MD) computer simulations, I investigated the pressure induced structural changes in the monomeric variants mCherry, mStrawberry, and Citrine. The results explain the molecular basis for experimentally observed pressure responses among FP variants. It is found that the barrel flexibility, hydrogen bonding interactions and chromophore planarity of the FPs can be correlated to their contrasting photophysical properties at vaious pressures. I also investigated the oxygen diffusion pathways in mOrange and mOrange2 which exhibit marked differences in oxygen sensitivities as well as photostability. Such computational identifications of structural changes and oxygen diffusion pathways are important in guiding mutagenesis efforts to design fluorescent proteins with improved photophysical properties.

The spectral albedo of sea ice and salt crusts on the tropical ocean of Snowball Earth: II. Optical modeling

During the Snowball Earth events of the Neoproterozoic, tropical regions of the ocean could have developed a precipitated salt lag deposit left behind by sublimating sea ice. The major salt would have been hydrohalite, NaCl•2H2O. The crystals in such a deposit can be small and highly scattering, resulting in an allwave albedo similar to that of snow. The snow-free sea ice from which such a crust could develop has a lower albedo, around 0.5, so the development of a crust would substantially increase the albedo of tropical regions on Snowball Earth. Hydrohalite crystals are much less absorptive than ice in the near- infrared part of the solar spectrum, so their presence at the surface would increase the overall albedo as well as altering its spectral distribution. In this paper, we use laboratory measurements of the spectral albedo of a hydrohalite lag deposit, in combination with a radiative transfer model, to infer the inherent optical properties of hydrohalite as functions of wavelength. Using this result, we model mixtures of hydrohalite and ice representing both artificially created surfaces in the laboratory and surfaces relevant to Snowball Earth. The model is tested against sequences of laboratory measurements taken during the formation and the dissolution of a lag deposit of hydrohalite. We present a parameterization for the broadband albedo of cold, sublimating sea ice as it forms and evolves a hydrohalite crust, for use in climate models of Snowball Earth.

Is the maximum velocity of carboxylation (Vcmax) well adjusted for deciduous shrubs in DGVMs: a case study for the Caatinga Biome in Brazil.

Vcmax is the rate of maximum velocity of carboxylation of plants and is considered one of the most critical parameters for changes in vegetation in face of global changes and it has a direct impact on gross primary productivity. Physiological processes are considered the main sources of uncertainties in dynamic global vegetation models (DGVMs). The Caatinga biome, in the semiarid region of northeastern Brazil, is extremely important due to its biodiversity and endemism. In a field work realized in an area of preserved Caatinga forest, measurements of carbon assimilation (in response to light and CO2) were performed on 11 individuals of a native species. These results of Vcmax measurements in Caatinga were compared with parameterization of models, revealing that Vcmax is not well adjusted in several DGVMs. Also, the values obtained in the Caatinga field experiments were very close to empirical values obtained in the Northern hemisphere (Austria). These ecophysiological measurements can contribute in understanding of this biome

6-(Methylsulfonyl) hexyl isothiocyanate as potential chemopreventive agent: molecular and cellular profile in leukaemia cell lines

Despite numerous therapeutic interventions cancer is still today the second leading cause of death. A growing interest has been addressed to isothiocytanates and more recently, the 6- (methylsulfonyl) hexyl isothiocyanate (6-MITC), the main constituent of the rhizome of Wasabia Japonica, has stimulated the interest of researchers. Aim of the research was to study if 6-MITC is able to modulate the main mechanisms underlying chemopreventive process in leukemic cells lines, verify the selectivity of action and the safety of use in terms of mutagenicity. The study was conducted on different cell types. In particular, Jurkat and HL-60 cells were treated with increasing concentrations of 6-MITC and cell viability, induction of apoptosis, cell cycle analysis, autophagy modulation and stimulation of differentiation were evaluated by flow cytometry. PBL, the non-transformed counterparty of leukemia cells, was used to analyse the selectivity of action by studying the same mechanisms previously indicated. Finally, safety of use and antimutagenicity were studied in TK6 cells adopting an automated protocol in flow cytometry. The achieved results have demonstrated that isothiocyanate modulates many signaling pathways involved in chemopreventive mechanism. In fact, 6-MITC induces apoptosis of both transformed cells, limits tumor growth by slowing down the cell cycle of Jurkat cells and blocks HL-60 cell cycle, increases the autophagic flux and induces cytodifferentiation of promyelocytic HL-60 into macrophage and granulocytic phenotypes. Furthermore, the results obtained with 6-MITC on PBL from healthy donors suggest that the isothiocyante is a good selective cytotoxic agent. Essential feature of a good chemopreventive agent is selectivity toward cancer cells and low toxicity towards non-transformed cells. Finally, the analysis of the micronuclei revealed that 6-MITC is not mutagenic, ensuring safe use, and that instead, it is able to counteract the mutagenic activity of the aneuploidogen Vinblastine, demonstrating another important and interesting chemopreventive activity.

A comparison between vertical mixing parameterizations in the Levantine Sea

The goal of this thesis was the study of an optimal vertical mixing parameterization scheme in a mesoscale dominated field characterized from a strong vorticity and the presence of a layer of colder, less saline water at about 100 m depth (Atlantic Waters); in these conditions we compared six different experiments, that differ by the turbulent closure schemes, the presence or not of an enhanced diffusion parameterization and the presence or not of a double diffusion mixing parameterization. To evaluate the performance of the experiments and the model we compared the simulations with the ARGO observations of temperature and salinity available in our domain, in our period of interest. The conclusions were the following: • the increase of the resolution gives better results in terms of temperature in all the considered cases, and in terms of salinity. • The comparisons between the Pacanovski-Philander and the TKE turbulent closure schemes don’t show significant differences when the simulations are compared to the observations. • The removing of the enhanced diffusion parameterization in presence of the TKE turbulent closure submodel doesn’t give positive results, and show limitations in the resolving of gravitational instabilities near the surface • The k-ϵ turbulent closure model utilized in all the GLS experiments, is the best performing closure model among the three considered, with positive results in all the salinity comparison with the in situ observation and in most of the temperature comparisons. • The double mixing parameterization utilized in the k-ϵ closure submodel improves the results of the experiments improving both the temperature and salinity in comparison with the ARGO data.

Progettazione di un kit di supporto ai corsi Project Based Learning: il ruolo del tutor nel modello Tech to Market.

L’istruzione superiore in Europa è stata oggetto di un significativo processo di riforma: è aumentato l’interesse per un modello di apprendimento intorno ai progetti, centrato sullo studente, che favorisse lo sviluppo di competenze trasversali – il project-based learning (PBL). Inserire il PBL nelle Università richiede un processo di innovazione didattica: il curriculum di un corso PBL e le competenze richieste all’insegnante si differenziano dall’apprendimento tradizionale. Senza un'adeguata attenzione ai metodi di supporto per insegnanti e studenti, questi approcci innovativi non saranno ampiamente adottati. L’obiettivo di questo studio è determinare in che modo sia possibile implementare un corso PBL non presenziato da figure esperte di PBL. Le domande della ricerca sono: è possibile implementare efficacemente un approccio PBL senza il coinvolgimento di esperti dei metodi di progettazione? come si declinano i ruoli della facilitazione secondo questa configurazione: come si definisce il ruolo di tutor d’aula? come rafforzare il supporto per l’implementazione del corso? Per rispondere alle domande di ricerca è stata utilizzata la metodologia AIM-R. Viene presentata la prima iterazione dell’implementazione di un corso di questo tipo, durante la quale sono state svolte attività di ricerca e raccolta dati. L’attività di facilitazione è affidata a tre figure diverse: docente, tutor d’aula e coach professionisti. Su questa base, sono stati definiti gli elementi costituenti un kit di materiale a supporto per l’implementazione di corsi PBL. Oltre a un set di documenti e strumenti condivisi, sono stati elaborati i vademecum per guidare studenti, tutor e docenti all’implementazione di questo tipo di corsi. Ricerche future dovranno essere volte a identificare fattori aggiuntivi che rendano applicabile il kit di supporto per corsi basati su un modello diverso dal Tech to Market o che utilizzino strumenti di progettazione diversi da quelli proposti durante la prima iterazione.