Optical forces in the T-matrix formalism

Le pinzette ottiche, fasci laser fortemente focalizzati, sono uno strumento cruciale per la manipolazione e lo studio senza contatto meccanico di particelle micro- e nanoscopiche di diversa natura. Presentano tantissime applicazioni interdisciplinari ma, solo di recente, si è riusciti a sviluppare una modellizzazione teorica accurata per il range della mesoscala che vada oltre le forti approssimazioni utilizzate per il calcolo delle forze ottiche su particelle molto più piccole (approssimazione di dipolo) o molto più grandi (ottica geometrica) della lunghezza d'onda della luce. In questo ambito di ricerca si inserisce il nostro lavoro di tesi che si basa sull'utilizzo del metodo della matrice di transizione (T-matrix) per il calcolo delle forze ottiche su particelle sferiche e nanofili alla mesoscala. Il formalismo della T-matrix costituisce attualmente uno dei metodi più accurati per il calcolo dello scattering elettromagnetico da particelle non-sferiche, sia isolate che interagenti in strutture composite. L'idea di espandere i campi incidenti e diffusi in armoniche sferiche vettoriali e di connettere i coefficienti di espansione attraverso una matrice di transizione si è dimostrato estremamente efficace anche nell'ambito della modellizzazione delle forze ottiche. In questo lavoro di tesi, abbiamo studiato le forze ottiche su nano e microstrutture intrappolate. In primo luogo, abbiamo studiato la dipendenza delle forze dalle dimensioni di particelle di morfologia sferica e filiformi (nanofili) di polistirene. Successivamente, abbiamo dimostrato per la prima volta come, rompendo la simmetria cilindrica in nanofili di ossido di zinco, possa essere evidenziata una componente di forza non conservativa legata all'elicità della luce e proporzionale al momento lineare di Belinfante. Gli effetti di questa forza ottica trasversa, tradizionalmente ritenuta 'virtuale', sono stati di recente misurati in esperimenti con onde evanescenti e nell'intrappolamento di nanofili

The 2014 Egyptian constitution: balancing leadership with civil rights (al - madaniyya)

In 2013, in the aftermath of the military coup d'état, many ‘Islamized’ articles have been banned from the 2012 Egyptian constitution and almost one hundred firmly inclined towards the respect of human rights and the absolutim on freedom of belief have been added. This latter issue did cause pragmatisms on the freedom of worship and on the nature of the new leadership, which remains intrinsically unstated in the 2014 text. Essential questions concerning the conceptualization of citizenship and its extension (al-wataniyya,) as well as the pluralism of the concept of ‘madaniyya’ (as right to the city) still remain unanswered. Based on the critical discourse analysis and in person observations dating back to 2012, this article will attempt to address and understand to what extent by changing the meaning of wataniyya the future of Egypt can change accordingly

Hepatic regeneration and growth factors

Nessun abstrac

Riqualificazione del parco urbano della cittadella vecchia di Pisa

Proposta decostruttivista per un centro culturale ipoge

Differential Dynamics at Glycosidic Linkages of an Oligosaccharide as Revealed by 13C NMR Spin Relaxation and Stochastic Modeling

Among biomolecules, carbohydrates are unique in that not only can linkages be formed through different positions but the structures may also be branched. The trisaccharide \uf062-D-Glcp-(1\uf0ae3)[\uf062-D-Glcp-(1\uf0ae2)]-\uf061-D-Manp-OMe represents a model of a branched vicinally disubstituted structure. A 13C site-specific isotopologue with labeling in each of the two terminal glucosyl residues enabled acquisition of high-quality 13C NMR relaxation parameters T1, T2 and heteronuclear NOE, with standard deviations of \uf0a3 0.5%. For interpretation of the experimental NMR data a diffusive chain model was used in which the dynamics of the glycosidic linkages is coupled to the global reorientation motion of the trisaccharide. Brownian dynamics simulations relying on the potential of mean force at the glycosidic linkages were employed to evaluate spectral densities of the spin probes. Calculated NMR relaxation parameters showed very good agreement with experimental data, deviating < 3%. The resulting dynamics is described by correlation times of 196 ps and 174 ps for the \uf062-(1\uf0ae2)- and \uf062-(1\uf0ae3)-linked glucosyl residues, respectively, i.e., different and linkage dependent. Notably, the devised computational protocol was performed without any fitting of parameters

Small‐for‐size liver transplanted into larger recipient: A model of hepatic regeneration

Orthotopic liver transplantation was performed in 60 recipient rats weighing 200 to 250 gm. Sixty rats of the same strain were used as liver donors, 30 weighing 100 to 140 gm (small for size) and the other 30 weighing 200 to 250 gm (same size). After 1, 2, 3, 4, 7 and 14 days (n = 5 each) DNA synthesis, nuclear thymidine labeling and mitoses were increased in both the small‐for‐size and same‐size groups, but significantly more in the former. These changes were maximal after 48 to 72 hr, similar to but later than the well‐known regeneration response after partial hepatectomy, which peaks at 24 hr in rats. Indirect indexes of regeneration of the transplanted livers also were measured: plasma or serum ornithine decarboxylase; insulin and glucagon serum levels; estradiol and testosterone serum levels (and their nuclear and cytosolic receptors); and transforming growth factor‐ß, c‐Ha‐ras and c‐jun mRNA expressions. With the small‐for‐size transplantation, these followed the same delayed pattern as the direct regeneration parameters. The small livers gradually increased in size over the course of 1 to 2 wk and achieved a volume equal to that of the liver originally present in the recipient. In contrast, no significant liver weight gain occurred in the transplanted livers from same‐size donors despite the evidence of regeneration by direct indexes, but not by most of the surrogate parameters, including ornithine decarboxylase. (Hepatology 1993;19:210–216). Copyright © 1994 American Association for the Study of Liver Disease

A dog model for acetaminophen-induced fulminant hepatic failure.

The development of a large animal model of fulminant hepatic failure produced with acetaminophen that should be useful in the development and evaluation of potential medical therapies for the important clinical problem of fulminant hepatic failure is described. Acetaminophen in dimethyl sulfoxide (600 mg/ml) given as three subcutaneous injections, with the first dose (750 mg/kg body wt) being given at noon, the second dose (200 mg/kg body wt) being given 9 h later, and the third dose (200 mg/kg body wt) being given 24 h after the initial dose consistently produces fulminant hepatic failure in dogs. The dimethyl sulfoxide vehicle, injected intramuscularly, does not influence either animal survival or hepatic function in control-treated dogs. No deaths occur within the first 36 h. By 72 h after initial drug administration, the mortality is 90%. Histopathological and biochemical investigations demonstrate a high degree of hepatocellular necrosis in nonsurviving animals without appreciable damage to the kidneys, lungs, or heart. The drug schedule and preparation outlined avoids the administration of large volumes of vehicle and results in prolonged high levels of acetaminophen in the blood sufficient to induce severe hepatic injury. Ranitidine (120 mg/kg body wt i.m.) given 30 min before each acetaminophen dose significantly reduces the mortality and hepatic necrosis produced using this model. This model satisfies all criteria established by Miller et al. for the production of a suitable large animal model of fulminant acute hepatic failure

The roto-conformational diffusion tensor as a tool to interpret molecular flexibility

Stochastic modeling approaches can be used to rationalize complex molecular dynamical behaviours in solution, helping to interpret the coupling mechanisms among internal and external degrees of freedom, providing insight into reaction mechanisms and extracting structural and dynamical data from spectroscopic observables. However, the definition of comprehensive models is usually limited by (i) the difficulty in defining – without resorting to phenomenological assumptions – a representative reduced ensemble of molecular coordinates able to capture essential dynamical properties and (ii) the complexity of numerical or approximate treatments of the resulting equations. In this paper, we address the first of these two issues. Building on a previously defined systematic approach to construct rigorous stochastic models of flexible molecules in solutions from basic principles, we define a manageable diffusive framework leading to a Smoluchowski equation determined by one main tensorial parameter, namely the scaled roto-conformational diffusion tensor, which accounts for the influence of both conservative and dissipative forces and describes the molecular mobility via a precise definition of internal–external and internal–internal couplings. We then show the usefulness of the roto-conformational scaled diffusion tensor as an efficient gauge of molecular flexibility through the analysis of a set of molecular systems of increasing complexity ranging from dimethylformamide to a protein domain