Actor-Critic or Critic-Actor? A Tale of Two Time Scales

We revisit the standard formulation of tabular actor-critic algorithm as a two time-scale stochastic approximation with value function computed on a faster time-scale and policy computed on a slower time-scale. This emulates policy iteration. We begin by observing that reversal of the time scales will in fact emulate value iteration and is a legitimate algorithm. We compare the two empirically with and without function approximation (with both linear and nonlinear function approximators) and observe that our proposed critic-actor algorithm performs better empirically though with a marginal increase in the computational cost

Teacher as learner: a personal reflection on a short course for South African university educators

Higher education is understood to play a critical role in ongoing processes of social transformation in post-apartheid South Africa through the production of graduates who are critical and engaged citizens. A key challenge is that institutions of higher education are themselves implicated in reproducing the very hierarchies they hope to transform. In this paper, I reflect critically on my experiences of a course aimed at transforming teaching through transforming teachers. In this paper, I foreground my own positionality as a white female educator as I draw on feminist theorising to reflect on my experiences as a learner in the Community, Self and Identity course. I suggest that we need to teach in ways that are more cognisant of the complexities of the constraints on personal freedom in the past if we are to contribute to the development of social justice in the future.IS

Decision-making in higher education and intercollegiate athletics: case study on the Big Ten Conference realignment

This study focuses on the decision-making institutional leaders use during the process of conference realignment at the Division I level. Intercollegiate athletics has existed within higher education for well over a century. Conflicting values and objectives have persisted between intercollegiate athletic departments and the institutions of higher education with which they are affiliated. The publicity an institution receives from intercollegiate athletics, however, is more than any academic achievement can provide, so how college presidents make decisions that involve intercollegiate athletics is critical to higher education. The literature reveals that the economic climate has little to no significant impact on institutions’ spending when it comes to intercollegiate athletics (Frank, 2004; Smith, 2008; Fisher, 2009). In fact, many institutions and athletic departments at the Division I level lose money every year (Knight Commission, 2010). Thus, if not financially, then how do decision-makers in higher education weigh the costs versus the perceived benefits when it comes to intercollegiate athletics? Intercollegiate athletics at the Division I level has recently seen a wave of change in conference memberships. Over a two and half year period (June 2010 to December 2012), 77 Division I institutions changed conference affiliations for either their entire athletic departments or at least their football programs. Traditionally, conference membership has been determined by geography and by shared institutional values and objectives, and so this high number of changes over a 30-month period is a departure from these traditions. Examining conference realignment sheds insight into the decision-making process institutional leaders use when analyzing the costs and benefits of intercollegiate athletics to higher education. Max Weber’s rational decision-making model (Weber 1956), which analyzed the cost-benefit value of alternatives as well as the extent to which the alternatives reflected shared cultural values and beliefs. This model evolved when March and Simon (1958) proposed the common model for rational decision-making, contending that actors enter into decision-making situations with known objectives and that the cost-benefit value for each of the alternatives is determined by those objectives. The actors gather information on alternative solutions and then select the optimal alternative. Chaffee (1983) suggested five criteria for examining the rational decision-making process. They are (1) values and objectives, (2) alternatives, (3) centralization of decision-making, (4) understanding of consequences, and (5) value maximizing choice. Chaffee’s criteria guided this case study on conference realignment in the Big Ten Conference. This study found that presidents identify values and objectives prior to making decisions of whether or not to realign and expand conference membership, and then they evaluate alternatives in terms of how well their institutions match Big Ten leaders’ stated values and objectives The affirmative decisions of the presidents studied resulted in increases in revenues and brands at each institution. This research contributes to the process of decision-making by leaders in intercollegiate athletics, particularly at the Division I level. From a broader scope, the results contribute to the rational decision-making model and the criteria used to test it

Solubility analysis of homologous series of amino acids and solvation energetics in aqueous potassium sulfate solution

In this study we estimated the solubilities of glycine, D,L-alanine, D,L-nor-valine and D,L-serine in aqueous mixtures of potassium sulfate (K2SO4) at 298.15 K using analytical ‘gravimetric method’. The experimental solubilities of homologous series of amino acids in aqueous K2SO4 mixture were discussed in terms of relative solubility, salting-in and salting-out effect by evaluating the influential constants. The effect of physicochemical and chemical factors on solubility were discussed briefly and correlated with the thermodynamics. Initially, the study of solvation energetics such as transfer Gibbs energies were evaluated based on the calculations from solubility data and relative stability of the experimental molecules was discussed under the experimental condition. © 2019 The Author(s

NASICON materials - a long neglected class of solid electrolytes

The so-called NASICON materials AT2P3O12 (A = alkaline metal, T = tetravalent transition metal) are known since the 1970s [1] and are derived from the first “Na+ super-ionic conductor”, Na3Zr2Si2PO12, of this group of materials. The aims of current investigations are on the one hand the better understanding of the ionic conduction and on the other hand the search for new materials with very high ionic conductivity. For this purpose, new and simple synthesis methods have been developed, which deliver very homogeneous powders with reduced temperatures for the preparation of ceramics. In this way a lithium ion conductor with the composition Li1.5Al0.5Ti1.5P3O12 was manufactured. After sintering to highly dense ceramics a total conductivity of 0.7 mS/cm was achieved at room temperature [2] and therefore this material belongs to the best known solid oxidic Li+ ion conductors. NMR and impedance spectroscopy investigations [3-5] have shown that the bulk conductivity amounts to 3-5 mS/cm and that the grain boundaries determine the quality of the material. In the case of Na+ ion conductors, the prototype Na3Zr2Si2PO12 was newly synthesized and gave a previously not achieved conductivity of 1 mS/cm [6]. The modification of the composition by substitution with scandium delivered conductivities of 0.8 mS/cm (Na3.4Sc2Si0.4P2.6O12) [7] and 4 mS/cm (Na3.4Zr1.6Sc0.4Si2PO12) [8]. The latter composition possesses one of the highest known Na+ ion conductivities of oxide ceramics and reaches the conductivity of liquid electrolytes. The mentioned compositions confirm the empirical criteria which are necessary for achieving high ionic conductivities in NASICON materials [9]. References: [1] H. Y. P. Hong, Mater. Res. Bull. 11 (1976) 173-182; H. Y. P. Hong, J. B. Goodenough, J. A. Kafalas, Mater. Res. Bull. 11 (1976) 203-220 [2] Q. Ma, Q. Xu, C.-L. Tsai, F. Tietz, O. Guillon, J. Am. Ceram. Soc., (2016), in press [3] V. Epp, Q. Ma, F. Tietz, M. Wilkening, Phys. Chem. Chem. Phys., 17 (2015) 32115-32121 [4] S. Breuer, D. Prutsch, V. Epp, Q. Ma, F. Preishuber-Pflügl, F. Tietz, M. Wilkening, J. Mater. Chem. A, 3 (2015) 21343-21350 [5] D. Rettenwander, A. Welzl, S. Pristat, F. Tietz, S. Taibl, G. J. Redhammer, J. Fleig, J. Chem. Mater. A, 4 (2016) 1506-1513 [6] S. Naqash, Q. Ma, Tietz, O. Guillon, in preparation [7] M. Guin, F. Tietz, O. Guillon, in preparation [8] Q. Ma, M. Guin, S. Naqash, C.-L. Tsai, F. Tietz, O. Guillon, in preparation [9] M. Guin, F. Tietz, J. Power Sources, 273 (2015) 1056-106

An alkyne linchpin strategy for drug:pharmacophore conjugation: Experimental and computational realization of a meta-selective inverse sonogashira coupling

The late-stage functionalization (LSF) of pharmaceutical and agrochemical compounds by the site-selective activation of C-H bonds offers immediate access to diverse structural analogs and expands the accessible chemical space. We report a C-H functionalization LSF strategy that hinges on the use of an alkyne linchpin to assemble conjugates of sp2-rich marketed pharmaceuticals and agrochemicals with sp3-rich 3D-fragments and natural products. This is accomplished through a template-assisted inverse Sonogashira reaction that displays high levels of selectivity for the meta-position. This protocol is also amenable to distal structural modifications of α-amino acids. The transformation of alkyne functionality to other functional groups further highlights the applicative potential. Computational and experimental mechanistic studies shed light on the detailed mechanism. Turnover-limiting 1,2-migratory insertion of the bromoalkyne coupling partner occurs after relatively fast C-H activation. While this insertion occurs unselectively, regioconvergence results from one of the adducts undergoing a 1,2-trialkylsilyl migration to form the alkynylated product. A heterobimetallic Pd-Ag TS, which is essential for product formation, is explicitly implicated in the β-bromide elimination step

Template‐free Electrosynthesis of Platinum Nano‐Cauliflowers for Catalysing Electron Transfer Reaction of Plutonium

A coupled-oxido-reductive multiple-potentiostatic pulse strategy was developed to electrochemically prepare platinum-nano-cauliflowers (PtNCFs) on indium-tin-oxide (ITO) coated glass electrode. The mechanism of electrocrystallization was studied during the formation of PtNCFs on ITO. By virtue of that synthesis strategy, the PtNCFs/ITO surface could catalyse the quasi-reversible electron transfer reaction of plutonium (Pu) (IV)/(III) redox couple in aqueous sulphuric acid solution compared to bare ITO

Giant Topological Hall Effect in the Noncollinear Phase of Two-Dimensional Antiferromagnetic Topological Insulator MnBi₄Te₇

Magnetic topological insulators provide an important platform for realizing several exotic quantum phenomena, such as the axion insulating state and the quantum anomalous Hall effect, owing to the interplay between topology and magnetism. MnBi4Te7 is a two-dimensional Z(2) antiferromagnetic (AFM) topological insulator with a Ne ' el temperature of similar to 13 K. In AFM materials, the topological Hall effect (THE) is observed owing to the existence of nontrivial spin structures. A material with noncollinearity that develops in the AFM phase rather than at the onset of the AFM order is particularly important. In this study, we observed that such an unanticipated THE starts to develop in a MnBi4Te7 single crystal when the magnetic field is rotated away from the easy axis (c-axis) of the system. Furthermore, the THE resistivity reaches a giant value of similar to 7 mu Omega-cm at 2 K when the angle between the magnetic field and the c-axis is 75 degrees. This value is significantly higher than the values for previously reported systems with noncoplanar structures. The THE can be ascribed to the noncoplanar spin structure resulting from the canted state during the spinflip transition in the ground AFM state of MnBi4Te7. The large THE at a relatively low applied field makes the MnBi4Te7 system a potential candidate for spintronic applications