The nature of intermolecular interactions in pyridinium-anion-ß-hexachlorocyclohexane molecular crystals.

The nature of intermolecular interactions in different molecular crystal configurations formed by pyridinium cations, chloride or bromide anions as well as ß-hexachlorocyclohexane (ß-HCH) molecules has been investigated using high level ab initio quantum chemistry methods. Several molecular subsystems taken from the crystal unit cell were considered and their supramolecular energy stability was analyzed in detail using high level density-fitting local electron correlation (DF-LMP2 and DF-LCCSD(T)) methods together with the aug-cc-pVTZ basis set. In order to elucidate the nature of the intermolecular interactions between different fragments, the symmetry adapted perturbation theory (SAPT) method up to "2+3" truncation expansion was applied. The SAPT analysis has shown that the "simple" pair model of a halide anion-ß-HCH complex is not adequate to properly describe the stability of the crystals, since the charge polarization induced by the cation counterpart on the halide anion significantly changes the nature and the magnitude of the anion-ß-HCH interaction.

The use of alpha 2 agonists during idiopathic scoliosis repair : a narrative review of the literature.

Alpha 2 agonists are appreciated drugs designed for the peri-operative period, because of their anxiolytic, sedative and analgesic properties. However, they are usually avoided during scoliosis surgery, a longlasting major procedure involving healthy patients, because of their potential effects on Somatosensory and Motorevoked potentials. The absence ofrecommendations suggests that their effects on evoked potentials are still unclear. Thus, we tried in this narrative review to identify the literature representative of the effects of clonidine and dexmedetomidine on evoked potentials, on human beings, published between 1988 and 2015 in English or French, using GOOGLE SCHOLAR and PUBMED. Paucity of literature prevented any conclusion about Clonidine's effects on evoked potentials, but no data suggested a noxious effect of Clonidine on evoked potentials, used in oral premedication (300 µg) or during the procedure (2 to 5 µg/kg). If literature was more extensive for dexmedetomidine, studies were still controversial. Although the majority of the studies did not find statistically significant differences concerning the effects of this drug on evoked potentials (loading dose of 0.3 to 1 µg/ kg followed by continuous infusion of 0.3 to 0.8 µg/kg/h), 2 case reports and 2 studies described substantial decreases. However, dexmedetomidine's shorter duration of action allowed a quick return to basal situation within an hour. In conclusion, more studies are needed in order to evaluate the effects of alpha 2 agonists on evoked potentials and to assess the safety of their use in this setting.

Continuous regional anesthesia and inflammation: a new target.

Inflammation can be defined as the host response when confronted with an aggression. The purpose of the inflammatory reaction is the defense of the host for re-establishing the baseline homeostasis of the organism. Compared to the neuroendocrine changes associated to the stress response to injury, the inflammatory reaction is the major determinant of patient's recovery in the perioperative period. Perioperative inflammation is involved in the occurrence of various postoperative adverse outcomes other than only acute pain. By consequence, perioperative strategies which limit or control the inflammatory response might have beneficial effects on patient's recovery. The present review summarizes the current knowledges on the interactions between some of these strategies, specifically regional anesthesia (RA) techniques, and inflammation in the context of perioperative medicine. Regional anesthesia through its components i.e. local anesthetics and analgesic adjuvants like alpha-2 adrenergic agonists (clonidine, dexmedetomidine) modulates the inflammatory response consecutive to tissue injury by various mechanisms, at different levels. While experimental studies have shown that RA techniques modulate both local and systemic inflammatory reactions, in contrast, clinical findings are inconsistent as actual RA techniques fail to impact major patients' outcomes beyond immediate postoperative analgesia. The discrepancy between experimental findings and clinical observations asks questions and argues for a different view of perioperative inflammatory processes, in other words for an individualized management of the patients. Future developments of tools to quantify inflammatory and immune profile of patients might certainly lead to exciting findings and to major improvements in perioperative medicine.

Engineering generalized synchronization in chaotic oscillators.

We report a method of engineering generalized synchronization (GS) in chaotic oscillators using an open-plus-closed-loop coupling strategy. The coupling is defined in terms of a transformation matrix that maps a chaotic driver onto a response oscillator where the elements of the matrix can be arbitrarily chosen, and thereby allows a precise control of the GS state. We elaborate the scheme with several examples of transformation matrices. The elements of the transformation matrix are chosen as constants, time varying function, state variables of the driver, and state variables of another chaotic oscillator. Numerical results of GS in mismatched Rössler oscillators as well as nonidentical oscillators such as Rössler and Chen oscillators are presented.