-Parallel I/O prefetching is considered to be effective in improving I/O performance. However, the effectiveness depends on determining patterns among future I/O accesses swiftly and fetching data in time, which is difficult to achieve in general. In this study, we propose an I/O signature-based prefetching strategy. The idea is to use a predetermined I/O signature of an application to guide prefetching. To put this idea to work, we first derived a classification of patterns and introduced a simple and effective signature notation to represent patterns. We then developed a toolkit to trace and generate I/O signatures automatically. Finally, we designed and implemented a thread-based client-side collective prefetching cache layer for MPI-IO library to support prefetching. A prefetching thread reads I/O signatures of an application and adjusts them by observing I/O accesses at runtime. Experimental results show that the proposed prefetching method improves I/O performance significantly for applications with complex patterns.

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Aggregation-induced emission (AIE) nanoparticles have been shown promise for fluorescence bioimaging and photodynamic therapy due to the good combination of nanoparticles and organic dyes or photosensitizers. Among several kinds of AIE nanoparticles, those that are capsulated with nanographene oxides (NGO) are easy to make, size-tunable, and have proven to be very stable in deionized water. However, the stability in saline solution still needs improvement for further applications in chemical or biomedical fields, and the efficacy of photodynamic therapy using NGO-capsulate AIE photosensitizers has not been evaluated yet. Herein, we modified NGO with polyethylene glycol (PEG) to improve the stability of NGO-capsulated AIE nanoparticles in phosphate buffer saline. Furthermore, by combining this modification method with a dual-functional molecule which has both typical AIE property and photosensitizing ability, we performed both two-photon fluorescence bioimaging and photodynamic therapy in vitro and in vivo. Our work shows that AIE nanoparticles capsulated with PEGylated nanographene oxide can be a powerful tool for future bioimaging and photodynamic therapy applications.

Aggregation-induced emission nanoparticles, TPE-red–PSMA, were prepared and used as photosensitizers for two-photon excited photodynamic therapy under 1040 nm fs laser excitation.

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Parallel file systems have become a common component of modern high-end computers to mask the ever-increasing gap between disk data access speed and CPU computing power. However, while working well for certain applications, current parallel file systems lack the ability to effectively handle concurrent I/O requests with data synchronization needs, whereas concurrent I/O is the norm in data-intensive applications. Recognizing that an I/O request will not complete until all involved file servers in the parallel file system have completed their parts, in this paper we propose a serverside I/O coordination scheme for parallel file systems. The basic idea is to coordinate file servers to serve one application at a time in order to reduce the completion time, and in the meantime maintain the server utilization and fairness. A window-wide coordination concept is introduced to serve our purpose. We present the proposed I/O coordination algorithm and its corresponding analysis of average completion time in this study. We also implement a prototype of the proposed scheme under the PVFS2 file system and MPI-IO environment. Experimental results demonstrate that the proposed scheme can reduce average completion time by 8% to 46%, and provide higher I/O bandwidth than that of default data access strategies adopted by PVFS2 for heavy I/O workloads. Experimental results also show that the server-side I/O coordination scheme has good scalability.

Pyropheophorbide‐a methyl ester (MPPa) is a semisynthetic photosensitizer derived from chlorophyll a. The absorption peak of MPPa in organic solvent and in cells was at 667 and 674 nm, respectively. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide reduction assay showed that MPPa had no dark cytotoxicity. In vitro photodynamic activity was extensively evaluated using a human lung carcinoma cancer cell line (NCI‐h446). MPPa exhibited no genotoxicity, as assayed by single‐cell gel electrophoresis. Using confocal laser scanning microscopy and organelle‐specific fluorescent probes, MPPa was found to localize in the intracellular membrane system, namely the endoplasmic reticulum, Golgi apparatus, lysosomes and mitochondria, in the NCI‐h446 cells. Furthermore, nuclear staining and DNA gel electrophoresis revealed that DNA condensation and fragmentation occurred post–photodynamic therapy, indicating the cell death was in the apoptotic mode.

I/O data access is a recognized performance bottleneck of high-end computing. Several commercial and research parallel file systems have been developed in recent years to ease the performance bottleneck. These advanced file systems perform well on some applications but may not perform well on others. They have not reached their full potential in mitigating the I/O-wall problem. Data access is application dependent. Based on the application-specific optimization principle, in this study we propose a cost-intelligent data access strategy to improve the performance of parallel file systems. We first present a novel model to estimate data access cost of different data layout policies. Next, we extend the cost model to calculate the overall I/O cost of any given application and choose an appropriate layout policy for the application. A complex application may consist of different data access patterns. Averaging the data access patterns may not be the best solution for those complex applications that do not have a dominant pattern. We then further propose a hybrid data replication strategy for those applications, so that a file can have replications with different layout policies for the best performance. Theoretical analysis and experimental testing have been conducted to verify the newly proposed cost-intelligent layout approach. Analytical and experimental results show that the proposed cost model is effective and the application-specific data layout approach achieved up to 74% performance improvement for data-intensive applications.