Rigid Body Motion Estimation based on the Lagrange-d'Alembert Principle

Stable estimation of rigid body pose and velocities from noisy measurements, without any knowledge of the dynamics model, is treated using the Lagrange-d'Alembert principle from variational mechanics. With body-fixed optical and inertial sensor measurements, a Lagrangian is obtained as the difference between a kinetic energy-like term that is quadratic in velocity estimation error and the sum of two artificial potential functions; one obtained from a generalization of Wahba's function for attitude estimation and another which is quadratic in the position estimate error. An additional dissipation term that is linear in the velocity estimation error is introduced, and the Lagrange-d'Alembert principle is applied to the Lagrangian with this dissipation. This estimation scheme is discretized using discrete variational mechanics. The presented pose estimator requires optical measurements of at least three inertially fixed landmarks or beacons in order to estimate instantaneous pose. The discrete estimation scheme can also estimate velocities from such optical measurements. In the presence of bounded measurement noise in the vector measurements, numerical simulations show that the estimated states converge to a bounded neighborhood of the actual states.Comment: My earlier submitted manuscript (arXiv:1508.07671), is an extended version of this work, containing detailed proofs and more elaborated numerical simulations, currently under review in Automatica. This paper will be cited in the extended journal version (arXiv:1508.07671) upon publicatio

Dynamics of an ”SAIQR” Influenza Model

Modifications or extensions of the classical Susceptible-Infected-Recovered (SIR) model that account for a Quarantine (Q) class have shown to be capable of supporting recurrent, that is, periodic disease outbreaks. The fact that in such outbreaks a significant proportion of individuals escape symptomatic or experience mild infections has not been explored extensively. Motivated by our interests on the transmission dynamics and evolution of influenza A in human populations, we proceed to explore the role of an asymptomatic class (A) of individuals on the long-term transmission dynamics of influenza. We focus on a Susceptible-Asymptomatic-Infectious-Quarantine-Recovered (SAIQR) model that limits the interactions of Q-individuals and assumes that A-individuals are infectious, possibly not as infectious as those with clear symptoms. The analysis is carried out taking advantage of the significant time scale differences provided by the demographic and epidemic processes involved. It is shown that SAIQR models with vital dynamics (births and deaths) support recurrent outbreaks under reasonable disease or intervention periods. Further, we show that recurrence is possible within regions of parameter space that are consistent with influenza A transmission in human populations

The Cold Peace: Russo-Western Relations as a Mimetic Cold War

In 1989–1991 the geo-ideological contestation between two blocs was swept away, together with the ideology of civil war and its concomitant Cold War played out on the larger stage. Paradoxically, while the domestic sources of Cold War confrontation have been transcended, its external manifestations remain in the form of a ‘legacy’ geopolitical contest between the dominant hegemonic power (the United States) and a number of potential rising great powers, of which Russia is one. The post-revolutionary era is thus one of a ‘cold peace’. A cold peace is a mimetic cold war. In other words, while a cold war accepts the logic of conflict in the international system and between certain protagonists in particular, a cold peace reproduces the behavioural patterns of a cold war but suppresses acceptance of the logic of behaviour. A cold peace is accompanied by a singular stress on notions of victimhood for some and undigested and bitter victory for others. The perceived victim status of one set of actors provides the seedbed for renewed conflict, while the ‘victory’ of the others cannot be consolidated in some sort of relatively unchallenged post-conflict order. The ‘universalism’ of the victors is now challenged by Russia's neo-revisionist policy, including not so much the defence of Westphalian notions of sovereignty but the espousal of an international system with room for multiple systems (the Schmittean pluriverse)

Total chemical synthesis, characterization, and immunological properties of an MHC class I model using the TASP concept for protein de novo design.

The design, total chemical synthesis, and immunological properties of a four-alpha-helix bundle template-assembled synthetic protein (TASP) mimicking some of the structural features of the major histocompatibility complex (MHC) class I is described. In a first approach, the native sequence 58-74 of the alpha 1 heavy chain domain of HLA-A2 was modeled in order to increase helix stability and amphiphilicity of the 17-mer peptide, preserving the residues for potential T-cell receptor (TcR) binding properties. According to the TASP concept, these helical segments were covalently attached to a cyclic template molecule designed for the induction of a four-helix-bundle topology of the assembled peptide blocks. After extensive HPLC purification, stepwise solid-phase synthesis resulted in a TASP molecule of high chemical purity as demonstrated by analytical HPLC, mass spectrometry, and amino acid analysis. CD spectroscopic investigations are consistent with the onset of a partial alpha-helical conformation in aqueous buffer as well as in TFE. Antibodies raised directly against this four-alpha-helix bundle TASP molecule (without prior conjugation to a carrier molecule) were detected by ELISA. Flow cytometry studies showed that these antibodies recognize the native MHC class I molecule on the surface of HLA-A2-positive cells. The results indicate that the TASP approach represents a versatile tool for mimicking conformational epitopes