Is it possible to reduce the expected response time of every request at a web server, simply by changing the order in which we schedule the requests? That is the question we ask in this paper.This paper proposes a method for improving the performance of web servers servicing static HTTP requests. The idea is to give preference to requests for small files or requests with short remaining file size, in accordance with the SRPT (Shortest Remaining Processing Time) scheduling policy.The implementation is at the kernel level and involves controlling the order in which socket buffers are drained into the network. Experiments are executed both in a LAN and a WAN environment. We use the Linux operating system and the Apache and Flash web servers.Results indicate that SRPT-based scheduling of connections yields significant reductions in delay at the web server. These result in a substantial reduction in mean response time and mean slowdown for both the LAN and WAN environments. Significantly, and counter to intuition, the requests for large files are only negligibly penalized or not at all penalized as a result of SRPT-based scheduling.

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We report on the immobilization of gold nanoparticles on end-functionalized and solvent responsive polystyrene brushes, grafted on an underlying substrate. The presence of gold nanoparticles on polystyrene brushes was confirmed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The resulting polystyrene−Au nanoassemblies have been used as the nanosensors for the detection of a variety of organic solvents in surrounding media. The sensing mechanism is based upon the change in the proximity of the immobilized gold nanoparticles as a consequence of the solvent induced reversible swelling−deswelling of polystyrene chains. The sensing ability was demonstrated by a simple analytic tool, i.e., UV−vis spectroscopy, through a shift in plasmon resonance band of immobilized Au nanoparticles. A dramatic blue shift of 32 nm in the surface resonance band was observed as the surrounding media of Au immobilized polystyrene brushes (Au−PS) was changed from air to the toluene. The described approach is facile and versatile in nature, which can be used for the fabrication of a variety of nanosensors based on the polymer brushes−nanoparticle assemblies.

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A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2‐(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self‐initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6 × 106.

The present study reports on a versatile method of the preparation of polystyrene−ZnO composite particles with core−shell or raspberry-like morphology. SEM analysis revealed that ZnO has been deposited on the surface of functionalized polystyrene beads as either a continuous thin layer or small clusters, depending on the reaction parameters. We propose that the interaction between ZnO nanoparticles and β-diketone groups, present on the surface of polystyrene beads, is the driving force for the preparation of these composite particles. IR spectroscopy was used to prove the interaction between ZnO nanoparticles and β-diketone groups. X-ray diffraction of the PS/ZnO particles revealed diffraction peaks corresponding to wurtzite ZnO crystalline phase. TGA results demonstrated that the ZnO contents of composite particles can be varied by changing the concentration of Zn(Ac)2·2H2O salt prior to reaction. The composite particles produced are envisioned to have applications as the building blocks for fabrication of sensors, transducers, actuators, UV detectors, and optoelectronic devices.

In this study, we report on the fabrication of the nanoassemblies consisting of the poly(N-isopropyl acrylamide) (PNIPAAm) brushes immobilized with gold nanoparticles (Au NPs). The employed process involves grafting of the carboxyl terminated PNIPAAm chains on an underlying substrate in a brush conformation followed by the immobilization of surface functionalized Au NPs by means of physical interaction (hydrogen bonding). Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy have been employed to characterize the prepared PNIPAAm-Au nanoassemblies. Polymer brushes have been found to suppress the nanoparticles' aggregation and, hence, facilitate the complete surface coverage. Furthermore, we demonstrated the application of resulting PNIPAAm-Au nanoassemblies in the fabrication of the temperature nanosensors. The employed approach is simple and highly versatile for the modification of macroscopic surfaces with a wide range of NPs.

In the present study, we report a method for preparing a fluorescent thermosensitive hybrid material based on monodisperse, thermosensitive poly( N-isopropyl acrylamide) (PNIPAM) microgels covered with CdTe nanocrystals of 3.2 nm diameter. The CdTe nanocrystals were covalently immobilized on the surface of PNIPAM microgels. The chemical environment around the CdTe nanocrystals was modified by changing the temperature and inducing the microgel volume-phase transition. This change provoked a steep variation in the nanocrystal photoluminescence (PL) intensity in such a way that when the temperature was under the low critical solution temperature (LCST) of the polymer (36 degrees C) the PL of the nanocrystals was strongly quenched, whereas above the LCST the PL intensity was restored.