Quiescent consistency: Defining and verifying relaxed linearizability

Concurrent data structures like stacks, sets or queues need to be highly optimized to provide large degrees of parallelism with reduced contention. Linearizability, a key consistency condition for concurrent objects, sometimes limits the potential for optimization. Hence algorithm designers have started to build concurrent data structures that are not linearizable but only satisfy relaxed consistency requirements. In this paper, we study quiescent consistency as proposed by Shavit and Herlihy, which is one such relaxed condition. More precisely, we give the first formal definition of quiescent consistency, investigate its relationship with linearizability, and provide a proof technique for it based on (coupled) simulations. We demonstrate our proof technique by verifying quiescent consistency of a (non-linearizable) FIFO queue built using a diffraction tree. © 2014 Springer International Publishing Switzerland

Verifying linearizability on TSO architectures

Linearizability is the standard correctness criterion for fine-grained, non-atomic concurrent algorithms, and a variety of methods for verifying linearizability have been developed. However, most approaches assume a sequentially consistent memory model, which is not always realised in practice. In this paper we define linearizability on a weak memory model: the TSO (Total Store Order) memory model, which is implemented in the x86 multicore architecture. We also show how a simulation-based proof method can be adapted to verify linearizability for algorithms running on TSO architectures. We demonstrate our approach on a typical concurrent algorithm, spinlock, and prove it linearizable using our simulation-based approach. Previous approaches to proving linearizabilty on TSO architectures have required a modification to the algorithm's natural abstract specification. Our proof method is the first, to our knowledge, for proving correctness without the need for such modification

Race, Class, And Gender In Boys\u27 Education: Repositioning Intersectionality Theory

Boys\u27 identities are distinctly gendered, racialized, and classed across disparate social and cultural contexts. Related intersectional identity processes are associated with boys\u27 academic success. While intersectionality has been utilized throughout boys\u27 education scholarship, a limited, light touch approach is often enacted. As a critical logic of interpretation, intersectionality theory accounts for race, class, and gender within equity-based empirical studies. The authors contend insufficient engagement with intersectionality may lead educational research on boys\u27 social and learner identities to become static. Examining boys\u27 identities through intersectional approaches reveals more complex insights particularly related to their school engagement. Critical of the recent boy crisis literature, this article strives to compel theorists of boys\u27 education to more fully leverage the history, constructs, and epistemologies of intersectionality

Diffractive deeply inelastic scattering of hadronic states with small transverse size

Diffractive deeply inelastic scattering from a hadron is described in terms of diffractive quark and gluon distributions. If the transverse size of the hadronic state is sufficiently small, these distributions are calculable using perturbation theory. We present such a calculation and discuss the underlying dynamics. We comment on the relation between this dynamics and the pattern of scaling violation observed in the hard diffraction of large-size states at HERA.Comment: 8 pages including 3 figures, REVTE

Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry

Organic phosphates and phosphonates are present in a number of cellular components that can be damaged by exposure to ionizing radiation. This work reports femtosecond time-resolved mass spectrometry (FTRMS) studies of three organic phosphonate radical cations that model the DNA sugar-phosphate backbone: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and diisopropyl methylphosphonate (DIMP). Upon ionization, each molecular radical cation exhibits unique oscillatory dynamics in its ion yields resulting from coherent vibrational excitation. DMMP has particularly well-resolved 45 fs (732 ± 28 cm−1) oscillations with a weak feature at 610–650 cm−1, while DIMP exhibits bimodal oscillations with a period of ∼55 fs and two frequency features at 554 ± 28 and 670–720 cm−1. In contrast, the oscillations in DEMP decay too rapidly for effective resolution. The low- and high-frequency oscillations in DMMP and DIMP are assigned to coherent excitation of the symmetric O–P–O bend and P–C stretch, respectively. The observation of the same ionization-induced coherently excited vibrations in related molecules suggests a possible common excitation pathway in ionized organophosphorus compounds of biological relevance, while the distinct oscillatory dynamics in each molecule points to the potential use of FTRMS to distinguish among fragment ions produced by related molecules

Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry

Organic phosphates and phosphonates are present in a number of cellular components that can be damaged by exposure to ionizing radiation. This work reports femtosecond time-resolved mass spectrometry (FTRMS) studies of three organic phosphonate radical cations that model the DNA sugar-phosphate backbone: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and diisopropyl methylphosphonate (DIMP). Upon ionization, each molecular radical cation exhibits unique oscillatory dynamics in its ion yields resulting from coherent vibrational excitation. DMMP has particularly well-resolved 45 fs (732 ± 28 cm−1) oscillations with a weak feature at 610–650 cm−1, while DIMP exhibits bimodal oscillations with a period of ∼55 fs and two frequency features at 554 ± 28 and 670–720 cm−1. In contrast, the oscillations in DEMP decay too rapidly for effective resolution. The low- and high-frequency oscillations in DMMP and DIMP are assigned to coherent excitation of the symmetric O–P–O bend and P–C stretch, respectively. The observation of the same ionization-induced coherently excited vibrations in related molecules suggests a possible common excitation pathway in ionized organophosphorus compounds of biological relevance, while the distinct oscillatory dynamics in each molecule points to the potential use of FTRMS to distinguish among fragment ions produced by related molecules

From Community College Faculty to Dean: Using Schlossberg’s Transition Theory to Understand the Transition Experience.

Succession planning and the pending vacancies in leadership are both important topics in higher education in general and community colleges specifically. Faculty have historically played an important role in filling the leadership pipeline in community colleges, with the first step in this transition being from faculty to academic deans. However, there is little research focused on the role of the academic dean, let alone that transition from faculty to administration, in the community college setting. The purpose of this qualitative study was to understand the perceptions of faculty who have transitioned into academic dean roles on two-year college campuses. Through the interviews with the seven participants, we began to understand how one perceives the transition from faculty to administrator in the community college setting. Schlossberg’s transition theory (1981) was the theoretical framework that was used and modified to create the four major factors labeled the Four S\u27s, in an attempt to understand an individual’s capacity to transition (Goodman, 2006; Schlossberg, 2008; Schlossberg, Lynch, & Chickering, 1989). This study found there is a wide range of motivations that prompt faculty to move into administration. Two themes emerged around the perceptions of the transition. The first was the fast-paced nature of the change, and the second was the changing relationship with faculty members. The participants were able to use their assets of situation, self, and strategies to overcome the liabilities of support to move into their new role. Implications for practice include: building a support system for new deans, developing practical training for deans, creating a greater sense of community among deans, and encouraging self-care