Rubidium spacecraft atomic timing system Final report

Rubidium 87 atomic time and frequency reference system for manned space fligh

Electrochemical titration of the S = 32 and S = 12 states of the iron protein of nitrogenase

AbstractThe iron protein of nitrogenase delivers electrons and ATP to the iron-molybdenum protein, which in turn reduces dinitrogen to ammonia. The iron protein contains a single four-iron, four-sulfur prosthetic group, detectable by ESR spectroscopy m its reduced form. Until recently, spin quantitations suggested that only a portion of the reduced iron protein was being detected by ESR, but recent work in several laboratories has shown that there is a spin = 32 signal near g = 5 in addition to the well characterized spin = 12 signal near g = 1.94. In this paper we characterize the redox properties of both states in the presence and absence of ATP and ADP, and find that the new spin state has identical redox properties to those previously determined for the spin = 12 state

Synthesis of N-Substituted Diamino-Propanols and their Physiological Effects

The p-toluiclinc-epichlorohydrin 1:1 addition compound has been reacted with pipericline, pyrrolicline, and morpholine to give disubstitutecl 2-propanols. 1-(p-Toluiclino)-3-pyrrolidino-2-propanol was fed to male rats and organ and body weights measured. The data do not permit us to evaluate adequately the physiological effects of the compound, but differences were observed in the size of the heart, kidneys, and thymus of the test animals

Super congruences and Euler numbers

Let $p>3$ be a prime. We prove that $$\sum_{k=0}^{p-1}\binom{2k}{k}/2^k=(-1)^{(p-1)/2}-p^2E_{p-3} (mod p^3),$$ $$\sum_{k=1}^{(p-1)/2}\binom{2k}{k}/k=(-1)^{(p+1)/2}8/3*pE_{p-3} (mod p^2),$$ $$\sum_{k=0}^{(p-1)/2}\binom{2k}{k}^2/16^k=(-1)^{(p-1)/2}+p^2E_{p-3} (mod p^3)$$, where E_0,E_1,E_2,... are Euler numbers. Our new approach is of combinatorial nature. We also formulate many conjectures concerning super congruences and relate most of them to Euler numbers or Bernoulli numbers. Motivated by our investigation of super congruences, we also raise a conjecture on 7 new series for $\pi^2$, $\pi^{-2}$ and the constant $K:=\sum_{k>0}(k/3)/k^2$ (with (-) the Jacobi symbol), two of which are $$\sum_{k=1}^\infty(10k-3)8^k/(k^3\binom{2k}{k}^2\binom{3k}{k})=\pi^2/2$$ and $$\sum_{k>0}(15k-4)(-27)^{k-1}/(k^3\binom{2k}{k}^2\binom{3k}k)=K.$

On the structure and function of nitrogenase from W5

Molybdoferredoxin from W5 was fractionated into MoFd with two atoms of molybdenum per 220,000 daltons and a specific activity of 2.6 [mu]moles C2H2 reduced/min/mg protein and into a catalytically inactive species with an identical protein moiety but an incomplete active centre. Native MoFd is a tetramer composed of two 50,000 and two 60,000 dalton subunits. At low protein concentrations the tetramer is in equilibrium with a dimer. Under low ionic strength and at low pH further dissociation into monomers occurs. MoFd and azoferredoxin have distinct electron paramagnetic resonance spectra. The EPR spectrum of AzoFd and that of the combination of the two nitrogenase components undergoes characteristic changes upon addition of MgATP2-.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34037/1/0000314.pd

From Demonstrations to Task-Space Specifications:Using Causal Analysis to Extract Rule Parameterization from Demonstrations

Learning models of user behaviour is an important problem that is broadly applicable across many application domains requiring human-robot interaction. In this work, we show that it is possible to learn generative models for distinct user behavioural types, extracted from human demonstrations, by enforcing clustering of preferred task solutions within the latent space. We use these models to differentiate between user types and to find cases with overlapping solutions. Moreover, we can alter an initially guessed solution to satisfy the preferences that constitute a particular user type by backpropagating through the learned differentiable models. An advantage of structuring generative models in this way is that we can extract causal relationships between symbols that might form part of the user's specification of the task, as manifested in the demonstrations. We further parameterize these specifications through constraint optimization in order to find a safety envelope under which motion planning can be performed. We show that the proposed method is capable of correctly distinguishing between three user types, who differ in degrees of cautiousness in their motion, while performing the task of moving objects with a kinesthetically driven robot in a tabletop environment. Our method successfully identifies the correct type, within the specified time, in 99% [97.8 - 99.8] of the cases, which outperforms an IRL baseline. We also show that our proposed method correctly changes a default trajectory to one satisfying a particular user specification even with unseen objects. The resulting trajectory is shown to be directly implementable on a PR2 humanoid robot completing the same task.Comment: arXiv admin note: substantial text overlap with arXiv:1903.0126

Kinetic and Spectroscopic Analysis of the Inactivating Effects of Nitric Oxide on the Individual Components of Azotobacter vinelandii Nitrogenase

The effects of nitric oxide (NO) on the individual components of Azotobacter vinelandii nitrogenase have been examined by kinetic and spectroscopic methods. Incubation of the Fe protein (Av2) for 1 h with stoichiometries of 4- and 8-fold molar excesses of NO to Av2 dimer resulted in a complete loss of activity of Av2 in C2H2-reduction assays. The kinetics of inactivation indicated that the minimum stoichiometry of NO to Av2 required to fully inactivate Av2 lies between 1 and 2. The rate of inactivation of Av2 activity by NO was stimulated up to 2-fold by the presence of MgATP and MgADP but was unaffected by the presence of sodium dithionite. Unexpectedly, complete inactivation of Av2 by low ratios of NO to Av2 also resulted in a complete loss of its ability to bind MgATP and MgADP. UV-visible spectroscopy indicated that the effect of NO on Av2 involves oxidation of the [4Fe-4S] center. EPR spectroscopy revealed that the loss of activity during inactivation of Av2 by NO correlated with the loss of the S = 1/2 and S = 3/2 signals. Appearance of the classical and intense iron-nitrosyl signal (g = 2.03) was only observed when Av2 was incubated with large molar excesses of NO and the appearance of this signal did not correlate with the loss of Av2 activity. The effects of NO on the MoFe protein (Avl) were more complex than for Av2. A time-dependent inactivation of Avl activity (C2H2 reduction) was observed which required considerably higher concentrations of NO than those required to inactivate Av2 (up to 10 P a ) . In addition, the effects of NO on Avl were significantly affected by the presence of sodium dithionite. In fact, kinetic evidence suggests that an Avl-catalyzed, NO-dependent consumption of dithionite occurs before Avl is inactivated by NO. A correlation between UV-visible and EPR spectral features and the extent of NO inactivation has been established. The inactivation of either nitrogenase component by NO did not lead to aggregation or dissolution into their constitutive subunits. However, NO inactivation did cause changes in both proteins since neither NO-treated protein inhibited C2H2-reducing activity in assays containing equimolar concentrations of untreated protein. The effects of NO on both nitrogenase components are interpreted in terms of the known reactivity of NO with Fe-S centers

International Commercial Arbitration: Fifty Years After the New York Convention

a one-day conference held at the Dean Rusk Center on January 30, 2009. The event, co-sponsored by the Georgia Journal of International and Comparative Law, featured Gary Born as keynote speaker and other leaders in the field of international commercial arbitration including Robert Davidson, Executive Director of JAMS Arbitration Practice; William K. Slate, II, President, American Arbitration Association; and Anne Marie Whitesell, Former Secretary General of the ICC International Court of Arbitration