1,952 research outputs found
Multivalent and Multifunctional Calixarenes in Bionanotechnology
Get PDFThe key features of calixarene derivatives as multivalent ligands for biomacromolecules and as multifunctional catalysts are reviewed herein. The ease of functionalization and the possibility to control the regio- and stereochemical disposition of multiple ligating units around a central core allow to obtain ligands with high affinity and selectivity especially for proteins and nucleic acids. The hydrophilic/lipophilic character can also be finely tuned, allowing to obtain monomeric hybrid derivatives or amphiphiles able to self-assemble alone or in co-formulation with lipids to give nanoparticles and liposomes that incorporate calixarenes. The knowledge acquired up to now sheds light on the future applications of calixarenes in bionanotechnology and nanomedicine
Energia gravitazionale in astrofisica
Get PDFCon il termine energia gravitazionale si fa riferimento all'energia potenziale
posseduta da un corpo dotato di massa all'interno di un campo gravitazionale.
In questa trattazione presenterò una breve introduzione alla teoria del potenziale
rimanendo nella teoria classica di gravitazione Newtoniana: ricaveremo l'equazione
di Poisson e in seguito un'espressione per l'energia potenziale.
Successivamente dedurremo il teorema del viriale, che fornisce una relazione tra
alcune energie in gioco in un sistema all'equilibrio ed è un teorema estremamente
importante in astrofisica e trova numerosissime applicazioni.
Poi, analizzeremo il caso di singola particella che spiraleggia attorno ad un buco
nero, per mostrare che nei Nuclei Galattici Attivi, Quasar e in alcuni classi di
stelle binarie collassate l'estrazione dell'energia gravitazionale dal materiale che
sta accrescendo su questi oggetti è un meccanismo potentissimo per la produzione
di radiazione elettromagnetica ad alte energie.
I calcoli ci mostreranno infatti che l'effiecienza di conversione da massa in energia
può raggiungere il 40%, mentre, per confronto, l'energia prodotta dalle reazioni di
fusioni nucleare, nel caso più efficiente, di idrogeno, è circa del 0:7%.
Nella seconda applicazione studieremo il problema dell'instabilità di Jeans, in cui
considereremo il caso di una nube molecolare sferica autogravitante il cui collasso
porta alla formazione di stelle.
Infine, applicheremo il teorema del viriale in astrofisica stellare, e vedremo come è
utile per descriverne l'evoluzione ed altre quantità di interesse.
I vari casi studiato saranno solo una breve e generale trattazione o introduzione
al problema, data l'impossibilità di approfondirne i particolari che esulano dallo
scopo di questo lavoro
Dried out but alive: how mosquitoes survive 8 months
Get PDFHow malaria mosquitoes persist during the dry season in the Sahel and rapidly rebound at the onset of rains is unclear. Recently, Faiman and colleagues demonstrated that aestivation, a summer dormancy mechanism, is a major persistence strategy of Anopheles mosquitoes, which could be targeted by vector control
Vitiligo and autoimmune thyroid disorders
Get PDFVitiligo represents the most common cause of acquired skin, hair and oral depigmentation, affecting 0.5-1% of the population worldwide. It is clinically characterized by the appearance of disfiguring circumscribed skin macules following melanocyte destruction by autoreactive cytotoxic T lymphocytes. Patients affected by vitiligo usually show a poorer quality of life and are more likely to suffer from depressive symptoms, particularly evident in dark-skinned individuals. Although vitiligo is a non-fatal disease, exposure of affected skin to UV light increases the chance of skin irritation and predisposes to skin cancer. In addition, vitiligo has been associated to other rare systemic disorders due to presence of melanocytes in other body districts, such as in the eyes, auditory, nervous and cardiac tissues, where melanocytes are thought to have roles different from that played in the skin.
Several pathogenetic models have been proposed to explain vitiligo onset and progression, but clinical and experimental findings point mainly to the autoimmune hypothesis as the most qualified one. In this context, it is of relevance the strong association of vitiligo with other autoimmune diseases, in particular with autoimmune thyroid disorders, such as Hashimoto thyroiditis and Graves’ disease. In this review, after a brief overview of vitiligo and its pathogenesis, we will describe the clinical association between vitiligo and autoimmune thyroid disorders and discuss the possible underlying molecular mechanism(s)
Towards an Integrated System as Point-of-Care Device for the Optical Detection of Sepsis Biomarkers
Get PDFSevere infection and sepsis are a common, expensive, and frequently fatal conditions in critically ill patients. The sepsis diagnosis is not trivial, since it is an extremely complex chain of events involving inflammatory and anti-inflammatory processes, cellular reactions, and circulatory disorders. For these reasons, delay in diagnosis and initiation of drug treatments have shown to be crucial for this pathology. Moreover, a multitude of biomarkers has been proposed, many more than for other pathologies. In order to select optimal treatments for the highly heterogeneous group of sepsis patients and to reduce costs, novel multiplexed tools that better characterize the patient and his or her specific immune response are highly desired. In order to achieve the fundament of drastically improved multi-analyte detection and to attain low limits of detection in diagnostics, the area of point-of-care testing (POCT) technology is developing quickly, leading to the production of instruments, the reliability of which is continuously increasing. For this purpose, a selection of two biomarkers—C-reactive protein (CRP) and neopterin (NP)—was studied in this paper and a fluorescence-based integrated optical system, suitable for future POCT applications, was implemented that is capable of performing the simultaneous measurement of the two different biomarkers in replicate. A limit of detection of 10 and 2.1 µg L−1 was achieved for CRP and NP spiked in commercially available human serum, respectively. Moreover, measurements on both biomarkers were also performed on serum samples collected from septic patients
Relationship between tibial baseplate design and rotational alignment landmarks in primary total knee arthroplasty
Get PDFThis study evaluated the influence of modern tibial baseplate designs when using the anterior tibial cortex as a primary rotational landmark for the tibial baseplate in TKA. Eighty patients undergoing TKA were randomized in two groups. Group 1 included 25 females and 15 males receiving a posterior-stabilized (PS) symmetric tibial baseplate while Group 2 included 24 females and 16 males receiving a PS anatomical tibial component. Identical surgical technique, including the use of the surgical transepicondylar femoral axis (sTEA) and the anterior tibial cortex (“Curve-on-Curve”) as rotational alignment landmarks, was used. All patients underwent CT evaluation performed with the knee in full extension. Three observers independently measured the rotational alignment of the tibial component in relation to the sTEA. The rotational alignment of the symmetric baseplate showed an average external rotation of 1.3° (minimum 5°, maximum −1°): 91% of the knees showed 0 ± 3° with respect to the surgical sTEA, being internally rotated in 20%. The rotational alignment of the anatomical baseplate showed an average external rotation of 4.1° (minimum 0.4°, maximum 8.9°): only 47.5% of the knees showed 0 ± 3°, being externally rotated in 100%. The difference between the two groups was statistically significant. This study confirms the reliability of the “Curve-on-Curve” technique as an adequate rotational alignment anatomical landmark in TKA: the use of an asymmetric tibial baseplate might lead to external rotation of the tibial component when this technique is intraoperatively chosen
Biosensing with optical fiber gratings
Get PDFAbstractOptical fiber gratings (OFGs), especially long-period gratings (LPGs) and etched or tilted fiber Bragg gratings (FBGs), are playing an increasing role in the chemical and biochemical sensing based on the measurement of a surface refractive index (RI) change through a label-free configuration. In these devices, the electric field evanescent wave at the fiber/surrounding medium interface changes its optical properties (i.e. intensity and wavelength) as a result of the RI variation due to the interaction between a biological recognition layer deposited over the fiber and the analyte under investigation. The use of OFG-based technology platforms takes the advantages of optical fiber peculiarities, which are hardly offered by the other sensing systems, such as compactness, lightness, high compatibility with optoelectronic devices (both sources and detectors), and multiplexing and remote measurement capability as the signal is spectrally modulated. During the last decade, the growing request in practical applications pushed the technology behind the OFG-based sensors over its limits by means of the deposition of thin film overlays, nanocoatings, and nanostructures, in general. Here, we review efforts toward utilizing these nanomaterials as coatings for high-performance and low-detection limit devices. Moreover, we review the recent development in OFG-based biosensing and identify some of the key challenges for practical applications. While high-performance metrics are starting to be achieved experimentally, there are still open questions pertaining to an effective and reliable detection of small molecules, possibly up to single molecule, sensing in vivo and multi-target detection using OFG-based technology platforms
Response of human bone marrow stromal cells to a resorbable P2O5-SiO2-CaO-MgO-Na2O-K2O phosphate glass ceramic for tissue engineering applications
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