| 1. |
- Glas, Gerie J., et al.
(författare)
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Ventilation practices in burn patients-an international prospective observational cohort study
- 2021
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Ingår i: BURNS & TRAUMA. - : Oxford University Press. - 2321-3868 .- 2321-3876. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: It is unknown whether lung-protective ventilation is applied in burn patients and whether they benefit from it. This study aimed to determine ventilation practices in burn intensive care units (ICUs) and investigate the association between lung-protective ventilation and the number of ventilator-free days and alive at day 28 (VFD-28). Methods: This is an international prospective observational cohort study including adult burn patients requiring mechanical ventilation. Low tidal volume (V-T) was defined as V-T <= 8 mL/kg predicted body weight (PBW). Levels of positive end-expiratory pressure (PEEP) and maximum airway pressures were collected. The association between V-T and VFD-28 was analyzed using a competing risk model. Ventilation settings were presented for all patients, focusing on the first day of ventilation. We also compared ventilation settings between patients with and without inhalation trauma. Results: A total of 160 patients from 28 ICUs in 16 countries were included. Low V-T was used in 74% of patients, median V-T size was 7.3 [interquartile range (IQR) 6.2-8.3] mL/kg PBW and did not differ between patients with and without inhalation trauma (p= 0.58). Median VFD-28 was 17 (IQR 0-26), without a difference between ventilation with low or high V-T (p= 0.98). All patients were ventilated with PEEP levels >= 5 cmH(2)O; 80% of patients had maximum airway pressures <30 cmH(2)O. Conclusion: In this international cohort study we found that lung-protective ventilation is used in the majority of burn patients, irrespective of the presence of inhalation trauma. Use of low V-T was not associated with a reduction in VFD-28.
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| 2. |
- Hollmann, Jochen, 1970, et al.
(författare)
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An Evaluation of Document Prefetching in a Distributed Digital Library
- 2003
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Ingår i: Research and AdvancedTechnology for Digital Libraries / Lecture Notes In Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. - 9783540407263 ; 2769, s. 276-287
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Latency is a fundamental problem for all distributed systems including digital libraries. To reduce user perceived delays both caching -- keeping accessed objects for future use -- and prefetching -- transferring objects ahead of access time -- can be used. In a previous paper we have reported that caching is not worthwhile for digital libraries due to low re-access frequencies. In this paper we evaluate our previous findings that prefetching can be used instead. To do this we have set up an experimental prefetching proxy which is able to retrieve documents from remote fulltext archives before the user demands them. Using a simple prediction to keep the overhead of unnecessarily transfered data limited, we find that it is possible to cut the user perceived average delay a factor of two.
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| 3. |
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| 4. |
- Hollmann, Jochen, et al.
(författare)
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Effectiveness of caching in a distributed digital library system
- 2007
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Ingår i: Journal of Systems Architecture. - : Elsevier BV. - 1383-7621. ; 53:7, s. 403-416
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Tidskriftsartikel (refereegranskat)abstract
- Today independent publishers are offering digital libraries with fulltext archives. In an attempt to provide a single user-interface to a large set of archives, the studied Article-Database-Service offers a consolidated interface to a geographically distributed set of archives. While this approach offers a tremendous functional advantage to a user, the fulltext download delays caused by the network and queuing in servers make the user-perceived interactive performance poor. This paper studies how effective caching of articles at the client level can be achieved as well as at intermediate points as manifested by gateways that implement the interfaces to the many fulltext archives. A central research question in this approach is: What is the nature of locality in the user access stream to such a digital library? Based on access logs that drive the simulations, it is shown that client-side caching can result in a 20% hit rate. Even at the gateway level temporal locality is observable, but published replacement algorithms are unable to exploit this temporal locality. Additionally, spatial locality can be exploited by considering loading into cache all articles in an issue, volume, or journal, if a single article is accessed. But our experiments showed that improvement introduced a lot of overhead. Finally, it is shown that the reason for this cache behavior is the long time distance between re-accesses, which makes caching quite unfeasible.
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| 5. |
- Hollmann, Jochen, 1970, et al.
(författare)
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Empirical Observations regarding Predictability in User Access-Behavior in a Distributed Digital Library System
- 2003
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Today document archives are geographically distributed but often not replicated. This can potentially result in a low quality of service in terms of reduced availability and long user-perceived access times. Instead of indiscriminate replication we study the effectiveness of caching techniques such as prefetching and selective preloading. Our technique analyzes whether user access behavior is predictable enough to guess what articles to prefetch or to preload based on access logs from DADS, a digital library system for scientific journal articles developed at DTV, the Technical Knowledge Center of Denmark. We have found that once a literature search has been narrowed to up to ten articles, there is a high likelihood that some of them will be eventually downloaded. This suggests that prefetching can be used to hide the article transfer latency. We have also found that 80% of the article downloads are confined to less than 20% of the journals, so preloading a small fraction of the digital library database could significantly shorten the access latency and improve the availability.
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| 6. |
- Hollmann, Jochen, 1970, et al.
(författare)
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Empirical Observations regarding Predictability in User Access-Behavior in a Distributed Digital Library System
- 2002
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Ingår i: Proceedings of the 16th International Parallel and Distributed Processing Symposium. - 0769515738 ; , s. 221-228
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Konferensbidrag (refereegranskat)abstract
- Document archives are today geographicallydistributed but often not replicated. This canpotentially result in a low quality of service interms of reduced availability and long user-perceivedaccess times, especially during peakhours. Indiscriminate replication is not feasible dueto the sheer size of the database and itsadministration. In an ongoing project, the goal is tostudy the effectiveness of caching techniques likeprefetching and selective preloading to improvequality of service of digital library systems.In this paper, we analyze whether user accessbehavior is predictable enough to use it to guesswhat articles to prefetch or to preload based on useraccess logs from DADS, a digital library systemdeveloped at the Technical Knowledge Center ofDenmark, DTV. We have found that once a literaturesearch has been narrowed down to less than tenarticles, there is a high likelihood that some ofthem will be eventually downloaded. This suggeststhat prefetching can be used to hide the articletransfer latency. We have also found that as many as80% of the article downloads are confined to lessthan 20% of the journals. This suggests thatpreloading a small fraction of the digital librarydatabase can significantly shorten the access latencyas well as improving the availability.
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| 7. |
- Hollmann, Jochen, 1970, et al.
(författare)
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Enhancing Garbage Collection Synchronization using Explicit Bit Barriers
- 2015
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Ingår i: 44th International Conference on Parallel Processing, ICPP 2015, Beijing, China, 1-4 September. - 0190-3918. - 9781467375870 ; 2015-December, s. 769 - 778
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Konferensbidrag (refereegranskat)abstract
- Multicore architectures offer a convenient way to unlock concurrency between application (called mutator) and garbage collector, yet efficient synchronization between the two by means of barriers is critical to unlock this concurrency. Hardware Transactional Memory (HTM), now commercially available, opens up new ways for synchronization with dramatically lower overhead for the mutator. Unfortunately, HTM-based schemes proposed to date either require specialized hardware support or impose severe overhead through invocation of OS-level trap handlers. This paper proposes Explicit Bit Barriers (EBB), a novel approach for fast synchronization between the mutator and HTM-encapsulated relocation tasks. We compare the efficiency of EBBs with read barriers based on virtual memory that rely on OS-level trap handlers. We show that EBBs are nearly as efficient as those needing specialized hardware, but run on commodity Intel processors with TSX extensions.
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| 8. |
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| 9. |
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| 10. |
- Hollmann, Jochen, et al.
(författare)
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Prospects of caching in a distributed digital library
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Many independent publishers are today offering digital libraries with fulltext archives. In an attempt to provide a single user-interface to a large set of archives, DTVs Article Database Service, offers a consolidatedinterface to a geographically distributed set of archives. While this approach offers a tremendous functional advantage to a user, the delays caused by the network and queuing delays in servers make the user-perceived interactive performance poor. In this paper, we study the prospects of caching articles at the client level as wel as intermediate points as manifested by gateways that implement the interfaces to the many fulltext archives. A central research question is what the nature of the locality is in the user accesses to such a digital library. Based on access logs to drive simulations, we find that client side caching can result in a 20% hitrate. However, at the gateway level, where multiple users may access the same article, the temporal locality is poor and caching is not so relevant. We have also studied whether spatial locality can be exploited by considering to load into cache all articles in an issue, volume, or journal, if a single article is accessed, but found that spatial locality is quite poor.
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