Atomistic Hydrodynamics and the Dynamical Hydrophobic Effect in Porous Graphene

Mirroring their role in electrical and optical physics, two-dimensional crystals are emerging as novel platforms for fluid separations and water desalination, which are hydrodynamic processes that occur in nanoscale environments. For numerical simulation to play a predictive and descriptive role, one must have theoretically sound methods that span orders of magnitude in physical scales, from the atomistic motions of particles inside the channels to the large-scale hydrodynamic gradients that drive transport. Here, we use constraint dynamics to derive a nonequilibrium molecular dynamics method for simulating steady-state mass flow of a fluid moving through the nanoscopic spaces of a porous solid. After validating our method on a model system, we use it to study the hydrophobic effect of water moving through pores of electrically doped single-layer graphene. The trend in permeability that we calculate does not follow the hydrophobicity of the membrane, but is instead governed by a crossover between two competing molecular transport mechanisms.Comment: 6 pages, 3 figure

Will Worldwide Adoption Of IFRS Improve Comparability? An Instructional Case Between Two Companies In Two Countries

One of the most compelling arguments for US companies to adopt IFRS is to increase comparability between companies and countries worldwide. This instructional case emphasizes to students that even though two companies both follow the same set of accounting rules (IFRS in this case), comparability of financial statements can still be difficult due to accounting choices, judgments, and estimates made by management. In this case, two start-up companies enter the renewable energy industry and begin retailing wind turbines. Students record identical first-year transactions for the two companies, record six additional transactions where each company makes different accounting choices when applying IFRS, prepare a set of financial statements, and calculate ratios. Through these tasks, students can see how accounting choices made by management affect comparability of the financial statements. This case also gives students an opportunity to discuss how culture and the general accounting environment in a country may influence the accounting choices made by management

IT Knowledge: What Do Accounting Students Think They Know? Do You Know More Than I Do? An Exploratory Study

In recognition of the growing role of information technology (IT) in teaching accounting, we surveyed students at three Midwestern universities to determine their self-reported knowledge levels of 36 specific information technologies and difference in those IT knowledge levels between universities.  Unlike other areas of accounting, there are no set standards for the IT curriculum for accounting education.  Because of this, we expect to find significant differences in IT knowledge between these three universities.  These findings are analyzed in light of authoritative guidance on appropriate accounting technology topics and research on the current status of IT in accounting education.  We find accounting students have a low level of self-perceived IT knowledge.  These students are not proficient in requisite technologies even after completing most of their undergraduate course work.  We also find that there are significant differences in IT knowledge between the three universities in the study.  These findings imply that we may be doing a disservice to accounting students and the accounting profession by not having a set IT curriculum.  We conclude that it is time to assess IT knowledge and IT skill requirements necessary for accounting students and develop a standard IT curriculum in accounting education

A Further Investigation Of Tables Versus Graphs For Decision-Making: Does Accounting Knowledge Make A Difference?

This research uses cognitive processing and cognitive induction theory to examine whether accounting knowledge affects a decision-maker’s performance when using tables or graphs to perform a bankruptcy prediction task.  A laboratory experiment was conducted using a 2x2 between-subjects design where accounting knowledge (low vs. high) is crossed with information presentation format (tabular vs. graphical).  The results suggest that accounting knowledge does affect the use of alternative information presentation formats

Strongly Refuting Random CSPs Below the Spectral Threshold

Random constraint satisfaction problems (CSPs) are known to exhibit threshold phenomena: given a uniformly random instance of a CSP with $n$ variables and $m$ clauses, there is a value of $m = \Omega(n)$ beyond which the CSP will be unsatisfiable with high probability. Strong refutation is the problem of certifying that no variable assignment satisfies more than a constant fraction of clauses; this is the natural algorithmic problem in the unsatisfiable regime (when $m/n = \omega(1)$). Intuitively, strong refutation should become easier as the clause density $m/n$ grows, because the contradictions introduced by the random clauses become more locally apparent. For CSPs such as $k$-SAT and $k$-XOR, there is a long-standing gap between the clause density at which efficient strong refutation algorithms are known, $m/n \ge \widetilde O(n^{k/2-1})$, and the clause density at which instances become unsatisfiable with high probability, $m/n = \omega (1)$. In this paper, we give spectral and sum-of-squares algorithms for strongly refuting random $k$-XOR instances with clause density $m/n \ge \widetilde O(n^{(k/2-1)(1-\delta)})$ in time $\exp(\widetilde O(n^{\delta}))$ or in $\widetilde O(n^{\delta})$ rounds of the sum-of-squares hierarchy, for any $\delta \in [0,1)$ and any integer $k \ge 3$. Our algorithms provide a smooth transition between the clause density at which polynomial-time algorithms are known at $\delta = 0$, and brute-force refutation at the satisfiability threshold when $\delta = 1$. We also leverage our $k$-XOR results to obtain strong refutation algorithms for SAT (or any other Boolean CSP) at similar clause densities. Our algorithms match the known sum-of-squares lower bounds due to Grigoriev and Schonebeck, up to logarithmic factors. Additionally, we extend our techniques to give new results for certifying upper bounds on the injective tensor norm of random tensors

On the Nature of Trapped-Hole States in CdS Nanocrystals and the Mechanism of their Diffusion

Recent transient absorption experiments on CdS nanorods suggest that photoexcited holes rapidly trap to the surface of these particles and then undergo diffusion along the rod surface. In this paper, we present a semiperiodic DFT model for the CdS nanocrystal surface, analyze it, and comment on the nature of both the hole-trap states and the mechanism by which the holes diffuse. Hole states near the top of the valence band form an energetic near continuum with the bulk, and localize to the non-bonding sp$^3$ orbitals on surface sulfur atoms. After localization, the holes form nonadiabatic small polarons that move between the sulfur orbitals on the surface of the particle in a series of uncorrelated, incoherent, thermally-activated hops at room temperature. The surface-trapped holes are deeply in the weak-electronic coupling limit and, as a result, undergo slow diffusion.Comment: 4 figure

Glycine supplementation extends lifespan of male and female mice.

Diets low in methionine extend lifespan of rodents, though through unknown mechanisms. Glycine can mitigate methionine toxicity, and a small prior study has suggested that supplemental glycine could extend lifespan of Fischer 344 rats. We therefore evaluated the effects of an 8% glycine diet on lifespan and pathology of genetically heterogeneous mice in the context of the Interventions Testing Program. Elevated glycine led to a small (4%-6%) but statistically significant lifespan increase, as well as an increase in maximum lifespan, in both males (p = 0.002) and females (p \u3c 0.001). Pooling across sex, glycine increased lifespan at each of the three independent sites, with significance at p = 0.01, 0.053, and 0.03, respectively. Glycine-supplemented females were lighter than controls, but there was no effect on weight in males. End-of-life necropsies suggested that glycine-treated mice were less likely than controls to die of pulmonary adenocarcinoma (p = 0.03). Of the 40 varieties of incidental pathology evaluated in these mice, none were increased to a significant degree by the glycine-supplemented diet. In parallel analyses of the same cohort, we found no benefits from TM5441 (an inhibitor of PAI-1, the primary inhibitor of tissue and urokinase plasminogen activators), inulin (a source of soluble fiber), or aspirin at either of two doses. Our glycine results strengthen the idea that modulation of dietary amino acid levels can increase healthy lifespan in mice, and provide a foundation for further investigation of dietary effects on aging and late-life diseases

Glycine supplementation extends lifespan of male and female mice.

Diets low in methionine extend lifespan of rodents, though through unknown mechanisms. Glycine can mitigate methionine toxicity, and a small prior study has suggested that supplemental glycine could extend lifespan of Fischer 344 rats. We therefore evaluated the effects of an 8% glycine diet on lifespan and pathology of genetically heterogeneous mice in the context of the Interventions Testing Program. Elevated glycine led to a small (4%-6%) but statistically significant lifespan increase, as well as an increase in maximum lifespan, in both males (p = 0.002) and females (p \u3c 0.001). Pooling across sex, glycine increased lifespan at each of the three independent sites, with significance at p = 0.01, 0.053, and 0.03, respectively. Glycine-supplemented females were lighter than controls, but there was no effect on weight in males. End-of-life necropsies suggested that glycine-treated mice were less likely than controls to die of pulmonary adenocarcinoma (p = 0.03). Of the 40 varieties of incidental pathology evaluated in these mice, none were increased to a significant degree by the glycine-supplemented diet. In parallel analyses of the same cohort, we found no benefits from TM5441 (an inhibitor of PAI-1, the primary inhibitor of tissue and urokinase plasminogen activators), inulin (a source of soluble fiber), or aspirin at either of two doses. Our glycine results strengthen the idea that modulation of dietary amino acid levels can increase healthy lifespan in mice, and provide a foundation for further investigation of dietary effects on aging and late-life diseases

Ontario Neurodegenerative Disease Research Initiative (ONDRI): Structural MRI Methods and Outcome Measures

The Ontario Neurodegenerative Research Initiative (ONDRI) is a 3 years multi-site prospective cohort study that has acquired comprehensive multiple assessment platform data, including 3T structural MRI, from neurodegenerative patients with Alzheimer\u27s disease, mild cognitive impairment, Parkinson\u27s disease, amyotrophic lateral sclerosis, frontotemporal dementia, and cerebrovascular disease. This heterogeneous cross-section of patients with complex neurodegenerative and neurovascular pathologies pose significant challenges for standard neuroimaging tools. To effectively quantify regional measures of normal and pathological brain tissue volumes, the ONDRI neuroimaging platform implemented a semi-automated MRI processing pipeline that was able to address many of the challenges resulting from this heterogeneity. The purpose of this paper is to serve as a reference and conceptual overview of the comprehensive neuroimaging pipeline used to generate regional brain tissue volumes and neurovascular marker data that will be made publicly available online

A Common Ca2+-Driven Interdomain Module Governs Eukaryotic NCX Regulation

Na+/Ca2+ exchanger (NCX) proteins mediate Ca2+-fluxes across the cell membrane to maintain Ca2+ homeostasis in many cell types. Eukaryotic NCX contains Ca2+-binding regulatory domains, CBD1 and CBD2. Ca2+ binding to a primary sensor (Ca3-Ca4 sites) on CBD1 activates mammalian NCXs, whereas CALX, a Drosophila NCX ortholog, displays an inhibitory response to regulatory Ca2+. To further elucidate the underlying regulatory mechanisms, we determined the 2.7 Å crystal structure of mammalian CBD12-E454K, a two-domain construct that retains wild-type properties. In conjunction with stopped-flow kinetics and SAXS (small-angle X-ray scattering) analyses of CBD12 mutants, we show that Ca2+ binding to Ca3-Ca4 sites tethers the domains via a network of interdomain salt-bridges. This Ca2+-driven interdomain switch controls slow dissociation of “occluded” Ca2+ from the primary sensor and thus dictates Ca2+ sensing dynamics. In the Ca2+-bound conformation, the interdomain angle of CBD12 is very similar in NCX and CALX, meaning that the interdomain distances cannot account for regulatory diversity in NCX and CALX. Since the two-domain interface is nearly identical among eukaryotic NCXs, including CALX, we suggest that the Ca2+-driven interdomain switch described here represents a general mechanism for initial conduction of regulatory signals in NCX variants