Sharif Digital Repository

This chapter explains biomedical applications of cyclodextrin-polymers. Cyclodextrins (CDs) are a class of natural cyclic oligosaccharides with 6, 7, or 8 D-(+)-glucose units linked by α-1, 4-linkages. The geometry of CDs gives a hydrophobic internal cavity that various organic, inorganic and biological molecules can be fitted in it. Many hydroxyl groups are situated on the outer parts of the rings, which make some of CDs water-soluble. These unique physicochemical properties of CDs make them promising materials to design polymeric systems. In the present chapter, first, the effect of CDs on solubility, stability and bioavailability of drugs is described. Second, polymeric systems based on... 

Design techniques to enhance bandwidth and linearity of broadband multistage low-noise amplifiers (LNAs) are presented. A feedback amplifier circuit is proposed to compensate for transistor gain roll-off with frequency in other amplifier stages and extend overall bandwidth. Moreover, a transistor width tapering in a multistage LNA is applied to improve linearity. These techniques are adopted in a three-stage monolithic microwave integrated circuit (MMIC) LNA implemented in a 0.1-μm GaAs pHEMT process. The LNA features 18-43 GHz bandwidth, 21.6 dB average gain, and 1.8-2.7 noise figure (NF). It exhibits output 1-dB compression point of 11.5 dBm at 30 GHz and consumes 70 mA bias current from a... 

In recent high speed networks such as ATM, dealing with different kinds of traffics have become a promising goal.Due to the dynamic nature and burstiness of aggregation of these various traffics, which is shown to be self similar, network congestion would occur more probably. Thus congestion control mechanisms (e.g. connection admission control) should be applied to preserve the quality of service of traffics passing through the network. In this paper we present a connection admission control (CAC) algorithm for self-similar traffics based on case based reasoning (CBR) which is almost a new concept in applied artificial intelligence. CBR is used to correct the estimation of the number of... 

The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are necessary to increase the capacity of cellular systems. Cell splitting causes a cellular system to have mixed cell sizes. Calculation of the reverse link capacity of CDMA cellular systems with mixed cell sizes and imperfect power control is presented in this paper. When a macro cell is split into micro cells, the capacity of a non-uniform cellular system has been calculated, together with the calculation of micro and neighboring macro cell capacity. The computer simulation results show that with the reduction in radius of a micro cell, its capacity increases, while that of the... 

Polyrotaxanes consisting of cyclodextrin rings, polyethylene glycol axes and quantum dot (QD) stoppers were synthesized and characterized. The molecular self-assembly of polyrotaxanes led to spindlelike nano-objects whose shape, size and position were dominated by QD stoppers. Due to their well-defined molecular self-assemblies, carbohydrate backbone, high functionality and several types of functional groups together with the high luminescence yield, synthesized hybrid nanostructures were recognized as promising candidates for biomedical applications. The potential applications of the molecular self-assemblies as drug-delivery systems was investigated by conjugation of doxorubicin (DOX) to... 

Molecular self-assembly of cadmium selenide quantum dots-end-capped polyrotaxane hybrid nanostructures (PRCdSe QDs) was led to a new type of core-shell hybrid nanomaterials consisting of cadmium selenide quantum dot (CdSe QDs) core and polyrotaxane shell (PR@QDs). Structure of PR@QDs was characterized using various techniques. It has been observed that the size of PR@QDs was between 20-25 nm in which diameter of core and thickness of shell were between 15-20 and 2-3 nm, respectively. Short-term in vitro cytotoxicity tests, using MTT (3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, were conducted on mouse tissue connective fibroblast adhesive cell line (L929) in order to... 

An X-band core chip is designed and fabricated in 0.18-μm CMOS technology, which can significantly reduce the monolithic microwave integrated circuit count required for realizing an active beam-former T/R module. The core chip consists of two RX/TX paths, each of which includes a 6-b phase shifter, a 6-b attenuator, along with two input and output amplifiers. A new architecture for realizing such a core chip system and a low loss circuit for 5.625° phase shift block are proposed. The overall rms phase and gain errors are better than 2° and 0.25 dB, respectively, in both RX/TX paths. The gain of each path is around 12 dB, while the output 1-dB compression point is higher than 10 dBm over the... 

A systematic method to design high power and high efficiency mm-wave fundamental oscillators is presented. By using a linear time variant method, we first obtain the optimum conditions and show that these conditions can be significantly different for high power and high efficiency fundamental oscillation. Next, we propose a modified multistage ring oscillator with interstage passive networks to exploit the full capacity of the transistors in terms of output power or efficiency. Analytical expressions are also derived to determine the value of passive elements used in the oscillator. To verify the validity of the method, a 77-GHz two-stage (differential) VCO is designed in a 65-nm CMOS...