Search results for "PLL"

Sterilization of macroscopic poly(l-lactic acid) porous scaffolds withdense carbon dioxide: Investigation of the spatial penetration of thetreatment …

2016

Abstract In this work the sterilization with dense carbon dioxide of poly( l -lactic acid) (PLLA) porous scaffolds intended for tissue engineering applications was investigated with the main objective of confirming the three-dimensional efficacy of the treatment and of analysing the scaffold properties after CO2 treatment. For this purpose the scaffold was contaminated with a conventional bacterium (Escherichia coli) and with spores (Streptomyces coelicolor), a species more fascinating and difficult to inactivate. Contamination was performed in such a way to soak the whole matrix with bacteria and spores. The effect of pressure and treatment time on the efficacy of the sterilization was eva…

Development of a novel in vitro system for biomedical applications

2022

Nella ricerca scientifica e medica, l'uso degli animali ha apportato notevoli benefici all’uomo. Sebbene la loro fisiologia non imiti perfettamente il corpo umano, essi agiscono come perfetti "modelli" per lo studio delle malattie umane e lo sviluppo di nuovi farmaci e trattamenti. Tuttavia, secondo la Food and Drug Administration (FDA), solo l'8% dei farmaci testati sugli animali è considerato sicuro ed efficace per l'uso sull’essere umano, il 92% non lo è. Questi tassi di fallimento estremamente elevati nello sviluppo di farmaci, insieme ai costi in forte aumento, hanno portato molti ricercatori a rivalutare il valore degli studi in vivo sugli animali. Questo è stato il motivo per cui, ne…

Procedimento di preparazione di scaffolds polimerici preangiogenizzati.

2009

In vitro bioactivity study of composite scaffold prepared via thermally induced phase separation

Among porous materials suitable for Bone Tissue Engineering (BTE) scaffolds, bioactive ceramics (hydroxyapatite, HA) and bioactive glasses (BG) have been used for their excellent biocompatibility, bioactivity and efficient osteointegration (1). However, their major limitations are brittleness, low mechanical stability and low dissolution rate (2). Recent evidences suggest that composite scaffold based on biodegradable polymers (e.g. Poly-lacticacid (PLLA)) simultaneously loaded with HA and BG hold promising potential as efficient osteoconductive implants (3, 4). In this work we investigated the possibility to produce composite PLLA-HA-BG scaffolds via Thermally Induced Phase Separation (TIP…

BIOGLASS® integration in Poly-L-Lactic-Acid scaffolds produced via Thermally Induced Phase Separation (TIPS).

In this work, a method of integration of BG particles in polymeric scaffold was developed with a trial and error procedure. The main purpose was to obtain highly porous and mechanically stable bioactive devices.

Stability of charge-pump phase-locked loops : the hold-in and pull-in ranges

2020

The problem of design and analysis of synchronization control circuits is a challenging task for many applications: satellite navigation, digital communication, wireless networks, and others. In this article the Charge-Pump Phase-Locked Loop (CP-PLL) electronic circuit, which is used for frequency synthesis and clock generation in computer architectures, is studied. Analysis of CP-PLL is not trivial: full mathematical model, rigorous definitions, and analysis still remain open issues in many respects. This article is devoted to development of a mathematical model, taking into account engineering aspects of the circuit, interpretation of core engineering problems, definition in relation to m…

Nonlinear Analysis of Charge-Pump Phase-Locked Loop : The Hold-In and Pull-In Ranges

2021

In this paper a fairly complete mathematical model of CP-PLL, which reliable enough to serve as a tool for credible analysis of dynamical properties of these circuits, is studied. We refine relevant mathematical definitions of the hold-in and pull-in ranges related to the local and global stability. Stability analysis of the steady state for the charge-pump phase locked loop is non-trivial: straight-forward linearization of available CP-PLL models may lead to incorrect conclusions, because the system is not smooth near the steady state and may experience overload. In this work necessary details for local stability analysis are presented and the hold-in range is computed. An upper estimate o…

Nonlinear dynamical model of Costas loop and an approach to the analysis of its stability in the large

2015

The analysis of the stability and numerical simulation of Costas loop circuits for highfrequency signals is a challenging task. The problem lies in the fact that it is necessary to simultaneously observe very fast time scale of the input signals and slow time scale of phase difference between the input signals. To overcome this difficult situation it is possible, following the approach presented in the classical works of Gardner and Viterbi, to construct a mathematical model of Costas loop, in which only slow time change of signal's phases and frequencies is considered. Such a construction, in turn, requires the computation of phase detector characteristic, depending on the waveforms of the…

Nonlinear dynamical model of Costas loop and an approach to the analysis of its stability in the large

2015

The analysis of the stability and numerical simulation of Costas loop circuits for high-frequency signals is a challenging task. The problem lies in the fact that it is necessary to simultaneously observe very fast time scale of the input signals and slow time scale of phase difference between the input signals. To overcome this difficult situation it is possible, following the approach presented in the classical works of Gardner and Viterbi, to construct a mathematical model of Costas loop, in which only slow time change of signal?s phases and frequencies is considered. Such a construction, in turn, requires the computation of phase detector characteristic, depending on the waveforms of th…

Composite Scaffolds with a Hydrohyapatite Spatial Gradient for Osteochondral Defect Repair

2018

Osteochondral defects derived by traumatic injury or aging related disease are often associated with severe joint pain and progressive loss of joint functions for millions of people worldwide and represent a major challenge for the orthopedic community. Tissue engineering offers new therapeutic approach to repair the osteochondral defects, through the production of scaffolds manufactured to mimic their complex architecture, which consists of cartilage and bone layers. Composite scaffolds based on a PLLA polymeric matrix containing hydroxyapatite (HA) as a filler were prepared through a modified thermally induced phase separation (TIPS) protocol. A suspension was prepared by adding sieved HA…