In this paper, we introduce the family of UCON ABC models for usage control (UCON), which integrate Authorizations (A), oBligations (B), and Conditions (C) . We call these core models because they address the essence of UCON, leaving administration, delegation, and other important but second-order issues for later work. The term usage control is a generalization of access control to cover authorizations, obligations, conditions, continuity (ongoing controls), and mutability. Traditionally, access control has dealt only with authorization decisions on users' access to target resources. Obligations are requirements that have to be fulfilled by obligation subjects for allowing access. Conditions are subject and object independent environmental or system requirements that have to be satisfied for access. In today's highly dynamic, distributed environment, obligations and conditions are also crucial decision factors for richer and finer controls on usage of digital resources. Although they have been discussed occasionally in recent literature, most authors have been motivated from specific target problems and thereby limited in their approaches. The UCON ABC model integrates these diverse concepts in a unified framework. Traditional authorization decisions are generally made at the time of requests but hardly recognize ongoing controls for relatively long-lived access or for immediate revocation. Moreover, mutability issues that deal with updates on related subject or object attributes as a consequence of access have not been systematically studied.Unlike other studies that have targeted on specific problems or issues, the UCON ABC model seeks to enrich and refine the access control discipline in its definition and scope. UCON ABC covers traditional access controls such as mandatory, discretionary, and role-based access control. Digital rights management and other modern access controls are also covered. UCON ABC lays the foundation for next generation access controls that are required for today's real-world information and systems security. This paper articulates the core of this new area of UCON and develops several detailed models.

SummaryImmune cells are somewhat unique in that activation responses can alter quantitative phenotypes upwards of 100,000-fold. To date little is known about the metabolic adaptations necessary to mount such dramatic phenotypic shifts. Screening for novel regulators of macrophage activation, we found nonprotein kinases of glucose metabolism among the most enriched classes of candidate immune modulators. We find that one of these, the carbohydrate kinase-like protein CARKL, is rapidly downregulated in vitro and in vivo upon LPS stimulation in both mice and humans. Interestingly, CARKL catalyzes an orphan reaction in the pentose phosphate pathway, refocusing cellular metabolism to a high-redox state upon physiological or artificial downregulation. We find that CARKL-dependent metabolic reprogramming is required for proper M1- and M2-like macrophage polarization and uncover a rate-limiting requirement for appropriate glucose flux in macrophage polarization.

Quillen et al. presented an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray-luminous clusters. They found that at least half of these sources have signs of excess IR emission. Here we discuss the nature of the IR emission and its implications for cool core clusters. The strength of the mid-IR excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-IR emission in the remaining brightest cluster galaxies is likely related to star formation. The mass of molecular gas (estimated from CO observations) is correlated with the IR luminosity as found for normal star-forming galaxies. The gas depletion timescale is about 1 Gyr. The physical extent of the IR excess is consistent with that of the optical emission-line nebulae. This supports the hypothesis that star formation occurs in molecular gas associated with the emission-line nebulae and with evidence that the emission-line nebulae are mainly powered by ongoing star formation. We find a correlation between mass deposition rates (Ṁ X ) estimated from the X-ray emission and the star formation rates estimated from the IR luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates, suggesting that the reheating of the intracluster medium is generally very effective in reducing the amount of mass cooling from the hot phase but not eliminating it completely.

We study diffusive shock acceleration (DSA) of protons and electrons at nonrelativistic, high Mach number, quasiparallel, collisionless shocks by means of self-consistent 1D particle-in-cell simulations. For the first time, both species are found to develop power-law distributions with the universal spectral index −4 in momentum space, in agreement with the prediction of DSA. We find that scattering of both protons and electrons is mediated by right-handed circularly polarized waves excited by the current of energetic protons via non-resonant hybrid (Bell) instability. Protons are injected into DSA after a few gyro-cycles of shock drift acceleration (SDA), while electrons are first pre-heated via SDA, then energized via a hybrid acceleration process that involves both SDA and Fermi-like acceleration mediated by Bell waves, before eventual injection into DSA. Using the simulations we can measure the electron/proton ratio in accelerated particles, which is of paramount importance for explaining the cosmic ray fluxes measured at Earth and the multi-wavelength emission of astrophysical objects such as supernova remnants, radio supernovae, and galaxy clusters. We find the normalization of electron power-law is 10 −2 that of the protons for strong nonrelativistic shocks.

O nline word-of-mouth (WOM) such as consumer opinions, user experiences, and product reviews has become a major information source in consumer purchase decisions. Prior research on online WOM effect has focused mostly on low-involvement products such as books or CDs. For these products, retailer-hosted (internal) WOM is shown to influence sales overwhelmingly. Numerous surveys, however, suggest consumers often conduct pre-purchase searches for high-involvement products (e.g., digital cameras) and visit external WOM websites during the search process. In this study, we analyze the relative impact of external and internal WOMs on retailer sales for high-involvement products using a panel of sales and WOM data for 148 digital cameras from Amazon.com and three external WOM websites (Cnet, DpReview, and Epinions) over a four-month period. The results suggest that a retailer's internal WOM has a limited influence on its sales of high-involvement products, while external WOM sources have a significant impact on the retailer's sales. The findings imply that external WOM sources play an important role in the information search process.

The recent usage control model (UCON) is a foundation for next-generation access control models with distinguishing properties of decision continuity and attribute mutability. A usage control decision is determined by combining authorizations, obligations, and conditions, presented as UCON ABC core models by Park and Sandhu. Based on these core aspects, we develop a formal model and logical specification of UCON with an extension of Lamport's temporal logic of actions (TLA). The building blocks of this model include: (1) a set of sequences of system states based on the attributes of subjects, objects, and the system, (2) authorization predicates based on subject and object attributes, (3) usage control actions to update attributes and accessing status of a usage process, (4) obligation actions, and (5) condition predicates based on system attributes. A usage control policy is defined as a set of temporal logic formulas that are satisfied as the system state changes. A fixed set of scheme rules is defined to specify general UCON policies with the properties of soundness and completeness. We show the flexibility and expressive capability of this formal model by specifying the core models of UCON and some applications.

Bone tissue engineering has been one of the most promising areas of research, providing a potential clinical application to cure bone defects. Recently, various stem cells including embryonic stem cells (ESCs), bone marrow-derived mesenchymal stem cells (BM-MSCs), umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs), adipose tissue-derived stem cells (ADSCs), muscle-derived stem cells (MDSCs) and dental pulp stem cells (DPSCs) have received extensive attention in the field of bone tissue engineering due to their distinct biological capability to differentiate into osteogenic lineages. The application of these stem cells to bone tissue engineering requires inducing in vitro differentiation of these cells into bone forming cells, osteoblasts. For this purpose, efficient in vitro differentiation towards osteogenic lineage requires the development of well-defined and proficient protocols. This would reduce the likelihood of spontaneous differentiation into divergent lineages and increase the available cell source for application to bone tissue engineering therapies. This review provides a critical examination of the various experimental strategies that could be used to direct the differentiation of ESC, BM-MSC, UCB-MSC, ADSC, MDSC and DPSC towards osteogenic lineages and their potential applications in tissue engineering, particularly in the regeneration of bone.

In this paper we develop the concept of Usage Control (UCON) that encompasses traditional access control, trust management, and digital rights management and goes beyond them in its definition and scope. While usage control concepts have been mentioned off and on in the security literature for some time, there has been no systematic treatment so far. By unifying these three areas UCON offers a promising approach for the next generation of access control. Traditional access control has focused on a closed system where all users are known and primarily utilizes a server-side reference monitor within the system. Trust management has been introduced to cover authorization for strangers in an open environment such as the Internet. Digital rights management has dealt with client-side control of digital information usage. Each of these areas is motivated by its own target problems. Innovations in information technology and business models are creating new security and privacy issues which require elements of all three areas. To deal with these in a systematic unified manner we propose the new UCON model. UCON enables finer-grained control over usage of digital objects than that of traditional access control policies and models. For example, print once as opposed to unlimited prints. Unlike traditional access control or trust management, it covers both centrally controllable environment and an environment where central control authority is not available. UCON also deals with privacy issues in both commercial and non-commercial environments. In this paper we first discuss access control, trust management, and digital rights management and describe general concepts of UCON in the information security discipline. Then we define components of the UCON model and discuss how authorizations and access controls can be applied in the UCON model. Next we demonstrate some applications of the UCON model and develop further details. We use several examples during these discussions to show the relevance and validity of our approach. Finally we identify some open research issues.