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Malthusian Locks
Abstract: Applications running in modern multithreaded environments are sometimes
\emph{over-threaded}. The excess threads do not improve performance, and in
fact may act to degrade performance via \emph{scalability collapse}. Often,
such software also has highly contended locks. We opportunistically leverage
the existence of such locks by modifying the lock admission policy so as to
intentionally limit the number of threads circulating over the lock in a given
period. Specifically, if there are more threads circulating than are necessary
to keep the lock saturated, our approach will selectively cull and passivate
some of those threads. We borrow the concept of \emph{swapping} from the field
of memory management and intentionally impose \emph{concurrency restriction}
(CR) if a lock is oversubscribed. In the worst case CR does no harm, but it
often yields performance benefits. The resultant admission order is unfair over
the short term but we explicitly provide long-term fairness by periodically
shifting threads between the set of passivated threads and those actively
circulating. Our approach is palliative, but often effective.
Distributed, Parallel, and Cluster Computing (cs.DC)
ACM&classes:
D.4.1; D.1.3
[cs.DC] for this version)
Submission history
From: David Dice []
Thu, 19 Nov :31 GMT
Sun, 28 Feb :21 GMT
Wed, 13 Jul :47 GMT
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热敏灸治疗膝骨性关节炎的临床疗效及静息态功能磁共振研究
目的　　观察热敏灸治疗膝骨性关节炎(knee osteoarthritis，KOA)的临床疗效，运用静息态脑功能磁共振成像(resting-state functional MagneticResonance Imaging，rfMRI)技术，研究热敏灸KOA患者左侧犊鼻穴前后的静息态脑功能变化，探索这种新艾灸方法可能的脑机制。　　方法　　1.将60例左侧KOA患者，随机分成热敏灸一组和常规艾灸组，每组30例，均选取双侧犊鼻、阳陵泉、足三里及患侧鹤顶穴，热敏灸一组进行回旋、雀啄、往返、温和灸，常规艾灸组对准应灸的腧穴部位距离皮肤2～3 cm进行温和灸。采用Lysholm膝关节功能评分表评价疗效，比较两组治疗前后关节疼痛、晨僵、关节部位肿胀、步行能力评分。　　2.选择30例左侧KOA患者3为rfMRI研究组(即热敏灸二组)，在热敏灸前和热敏灸后分别进行rfMRI扫描，采用比率低频振幅(fractional amplitude of low frequency fluctions，fALFF)和局部一致性(regional homogeneity，ReHo)的分析方法观测静息态脑功能的变化。　　结果　　1.热敏灸一组的关节疼痛分值为(1.12±0.62)，晨僵分值为(0.62±0.61)，关节肿胀分值为(0.89±0.76)，步行能力分值为(1.7±1.56)；常规艾灸组的关节疼痛分值为(1.97±0.66)，晨僵分值为(0.69±0.61)，关节肿胀分值为(0.93±0.74)，步行能力分值为(2.75±1.61)；热敏灸一组各指标与常规艾灸组相比差异均具有显著性(均P<0.01)，尤其以关节疼痛的缓解和步行能力的提高为显(均P<0.01)。热敏灸一组显效率为90.0％，常规艾灸组为73.3％，热敏灸一组显效率明显优于常规艾灸组(P<0.01)。　　2.rfMRI研究组在热敏灸后，患者右大脑、外核、左小脑、左大脑、白质区的fALFF值较灸前增高，中央前回、额叶、枕叶的fALFF值较灸前降低(P<0.05，K值≥85)；患者丘脑、外核、顶叶脑区的ReHo值较灸前显著增高，右大脑、左大脑、额叶的ReHo值较灸前降低(P<0.05，K值≥85)。　　结论　　1.热敏灸疗法的总体疗效优于常规艾灸疗法，而且能更好地改善KOA患者的症状和体征，值得临床推广和应用。　　2.热敏灸后影响多个脑区的显著变化基本符合躯体的痛温传导路径，而躯体感觉系统的激活可能是经络感传现象的客观依据；热敏灸的脑功能调节并非通过单一的脑区而是由多个脑区共同组成的网络来实现。
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, July–August 2013, Pages
Research reportAbnormal network connectivity in frontotemporal dementia: Evidence for prefrontal isolation, , , , , , , , , , , , , , , , , , , , , , a Rotman Research Institute, Baycrest Centre, Toronto, Ontario, Canadab Division of Neurology, University of Toronto, Toronto, Ontario, Canadac University Health Network Memory Clinic, Toronto Western Hospital, Toronto, Ontario, Canadad Sunnybrook Health Sciences Centre, Toronto, Ontario, Canadae Centre for Addiction and Mental Health, Toronto, Ontario, Canadaf Department of Psychology, University of Toronto, Toronto, Ontario, CanadaIntroductionDegraded social function, disinhibition, and stereotypy are defining characteristics of frontotemporal dementia (FTD), manifesting in both the behavioral variant of frontotemporal dementia (bvFTD) and semantic dementia (SD) subtypes. Recent neuroimaging research also associates FTD with alterations in the brain's intrinsic connectivity networks. The present study explored the relationship between neural network connectivity and specific behavioral symptoms in FTD.MethodsResting-state functional magnetic resonance imaging was employed to investigate neural network changes in bvFTD and SD. We used independent components analysis (ICA) to examine changes in frontolimbic network connectivity, as well as several metrics of local network strength, such as the fractional amplitude of low-frequency fluctuations, regional homogeneity, and seed-based functional connectivity. For each analysis, we compared each FTD subgroup to healthy controls, characterizing general and subtype-unique network changes. The relationship between abnormal connectivity in FTD and behavior disturbances was explored.ResultsAcross multiple analytic approaches, both bvFTD and SD were associated with disrupted frontolimbic connectivity and elevated local connectivity within the prefrontal cortex. Even after controlling for structural atrophy, prefrontal hyperconnectivity was robustly associated with apathy scores. Frontolimbic disconnection was associated with lower disinhibition scores, suggesting that abnormal frontolimbic connectivity contributes to positive symptoms in dementia. Unique to bvFTD, stereotypy was associated with elevated default network connectivity in the right angular gyrus. The behavioral variant was also associated with marginally higher apathy scores and a more diffuse pattern of prefrontal hyperconnectivity than SD.ConclusionsThe present findings support a theory of FTD as a disorder of frontolimbic disconnection leading to unconstrained prefrontal connectivity. Prefrontal hyperconnectivity may represent a compensatory response to the absence of affective feedback during the planning and execution of behavior. Increased reliance upon prefrontal processes in isolation from subcortical structures appears to be maladaptive and may drive behavioral withdrawal that is commonly observed in later phases of neurodegeneration.KeywordsFrontotemporal dementia; Intrinsic connectivity networks; Resting state; Salience network; Systems neuroscience; Default network
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