This paper describes the design of the Gamma database machine and the techniques employed in its implementation. Gamma is a relational database machine currently operating on an Intel iPSC/2 hypercube with 32 processors and 32 disk drives. Gamma employs three key technical ideas which enable the architecture to be scaled to 100s of processors. First, all relations are horizontally partitioned across multiple disk drives enabling relations to be scanned in parallel. Second, novel parallel algorithms based on hashing are used to implement the complex relational operators such as join and aggregate functions. Third, dataflow scheduling techniques are used to coordinate multioperator queries. By using these techniques it is possible to control the execution of very complex queries with minimal coordination -a necessity for configurations involving a very large number of processors.In addition to describing the design of the Gamma software, a thorough performance evaluation of the iPSC/2 hypercube version of Gamma is also presented. In addition to measuring the effect of relation size and indices on the response time for selection, join, aggregation, and update queries, we also analyze the performance of Gamma relative to the number of processors employed when the sizes of the input relations are kept constant (speedup) and when the sizes of the input relations are increased proportionally to the number of processors (scaleup). The speedup results obtained for both selection and join queries are linear; thus, doubling the number of processors halves the response time for a query. The scaleup results obtained are also quite encouraging. They reveal that a nearly constant response time can be maintained for both selection and join queries as the workload is increased by adding a proportional number of processors and disks.
Maximally tolerated dose (MTD) and metronomic dose chemotherapeutic approaches alter the immune system and the angiogenic process in different yet potentially complementary ways. A combination of MTD doxorubicin (MTD-DOX) and metronomic cyclophosphamide (mCTX) protocol was evaluated for safety and effect on circulating regulatory T (Treg) cells. We found that mCTX can be safely administered with MTD-DOX in tumour-bearing dogs. Both combination DOX/mCTX and single-agent DOX resulted in significant depletions of circulating lymphocytes throughout the chemotherapy cycle without apparent selectivity for Tregs. The indiscriminant lymphocyte depletions were similar between dogs randomized to receive DOX and dogs randomized to receive DOX/mCTX, suggesting this effect is because of DOX alone. These findings may have implications as to the therapeutic benefit (or lack thereof) of concurrent combination MTD and metronomic protocols. Future investigations are required to determine the effects and indeed the efficacy of concurrent versus sequential applications of MTD and metronomic chemotherapy protocols.
The incidence of idiopathic IMHA in dogs presenting to specialty hospitals located in 2 different climates of southern California was different, suggesting environmental triggers may be involved. Larger, prospective studies are needed to determine whether environmental parameters or undetected infectious disease account for some cases of idiopathic IMHA in dogs.
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