Microchips as Controlled Drug-Delivery Devices

Controlled-release systems are common in a number of product areas, including foods, cosmetics, pesticides, and paper. Microencapsulated systems, for example, are used for the release of flavors and vitamins in foods, fragrances in perfumes, and inks in carbonless copy paper. Controlled-release systems for drug delivery first appeared in the 1960s and 1970s. In the past three decades, the number and variety of controlled release systems for drug-delivery applications has increased dramatically. Many of these use polymers having particular physical or chemical characteristics such as biodegradability, biocompatibility, or responsiveness to pH or temperature changes. However, recent advances in the field of microfabrication have created the possibility of a new class of controlled-release systems for drug delivery, namely, that of small, programmable devices. Their small size, potential for integration with microelectronics, and ability to store and release chemicals on demand could make controlled-release microchips useful in a number of areas, including medical diagnostics, analytical chemistry, chemical detection, industrial process monitoring and control, combinatorial chemistry, microbiology, and fragrance delivery. More importantly, drug-delivery microchips resulting from this convergence of controlled release and microfabrication technologies may provide new treatment options to clinicians in their fight against disease.     

Invariant fibrations for some birational maps of ℂ2

Abstract

In this article, we extract and study the zero entropy subfamilies of a certain family of birational maps of the plane. We find these zero entropy mappings and give the invariant fibrations associated to them.     

Three-dimensional airflow over Sardinia

Summary By using Pielke and Mahrer 3D mesoscale model, the air-flow over Sardinia has been studied for three typical meteorological situations. North-westerly flow (Maestrale), characterized by dry cold wind, shows strong downdrought over the desertic part of the island. Southeasterly flow (Scirocco), in summer, shows little interaction between the large-scale flow and the lower atmospheric layer over land. Sea breezes are usually advected easterly by the prevailing winds. Comments on practical applications and on limitations in local weather forecasting follow.

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Riassunto Il flusso atmosferico sopra la Sardegna è stato studiato per tre tipiche situazioni meteorologiche, con il modello tridimensionale di Pielke e Mahrer. Il vento da nordovest (Maestrale) caratterizzato da aria fredda e secca, genera correnti discendenti nella regione desertica dell'isola. Il vento da sud-ovest (Scirocco), d'estate, mostra una debole interazione con la grande scala e con lo strato limite sull'isola. La circolazione di brezza è spostata a est dai venti prevalenti. Seguono commenti sull'uso pratico del modello per le previsioni meteorologiche locali.

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Резюме С помощью трехмерной модели Пилка и Махрера, исследуется атмосферный поток над Сардинией для трех типичных метеорологических ситуаций. Северо-западный поток (Мистраль), характеризующийся сухим холодным ветром, порождает потоки, спускающиеся в пустынные районы острова. Юго-восточный поток (Сирокко), летом, обнаруживает слабое взаимодействие между крупномасштабным потоком и ограниченным атмосферным слоем над островом. Морские бризы обычно смещаются на восток за счет превалирующих ветров. Высказываются замечания, касающиеся практического использования описанной модели для локального предсказания погоды.

     

Normal functions and a class of associated boundary functions

Letμ′ be the family of non-empty closed subsets of the Riemann sphere and Λ the family of continuous curves λ with values in the unit disk and lim _t→1 |λ(t)|=1. A meromorphic functionf in |z|<1 induces a mapping\(\hat f\) from Λ intoμ′ by setting\(\hat f\left( \lambda \right)\) equal to the cluster set off on λ. The authors show that if\(\hat f\) is continuous then existence of an asymptotic value ate ^iθ implies the existence of an angular limit. Further if the spherical derivative off iso(1/(1?|z|)) then\(\hat f\) is constant on every open disk in the space Λ.     

Global periodicity and complete integrability of discrete dynamical systems

Consider the discrete dynamical system generated by a map F. It is said that it is globally periodic if there exists a natural number p such that F ^p (x)=x for all x in the phase space. On the other hand, it is called completely integrable if it has as many functionally independent first integrals as the dimension of the phase space. In this paper, we relate both concepts. We also give a large list of globally periodic dynamical systems together with a complete set of their first integrals, emphasizing the ones coming from difference equations.