ABSTRACT
Due to the enormous size of the chemical compound space, usually only small regions are traversed with traditional direct molecular design approaches making the discovery for novel functionalized molecules for nonlinear optical applications challenging. By applying inverse molecular design algorithms, we aim to efficiently explore larger regions of the compound space in search of promising hexaphyrin-based molecular switches as measured by their first-hyperpolarizability (ßHRS) contrast. We focus on the 28R â 30R switch with a functionalization pattern allowing for centrosymmetric OFF states yielding zero ßHRS response. This switch is particularly challenging as full meso-substitution with a single type of functional group or core-modifications result in almost no contrast enhancement. We carried out four inverse design procedures during which two sets of core-modifications and three sets of meso-substitutions sites were systematically optimized. All 4 optimal switches are characterized by a mix of meso-substitutions and core-modifications, of which the best performing switch yields a 10-fold improvement over the parent macrocycle. Throughout the inverse design procedures, we collected and analyzed a database biased towards high NLO contrasts that contains 277 different patterns for hexaphyrin-based switches. We derived three design rules to obtain highly functional 28R â 30R NLO switches: (I) a combination of 2 strong EWG and 1 EDG group is the ideal recipe for increasing the NLO contrast, though their position also plays an important role. (II) The type of core-modification is less important when only the diagonal positions are core-modified. Switches with 4 core-modifications show a clear preference for oxygen. (III) Keeping centrosymmetry in the OFF state remains highly beneficial given the investigated functionalization pattern. Finally, we have demonstrated that combining meso-substitutions with core-modifications can synergistically improve the NLO contrast.
ABSTRACT
PURPOSE: A novel, minimally invasive posture monitor which can monitor lumbar postures outside the laboratory has demonstrated excellent reliability, as well as concurrent validity compared to a surface marker-based motion analysis system. However, it is unclear if this device reflects underlying vertebral motion. METHODS: Twelve participants performed full range sagittal plane lumbo-pelvic movements during sitting and standing. Their posture was measured simultaneously using both this device (BodyGuard™) and digital videofluoroscopy. RESULTS: Strong correlations were observed between the two methods (all r (s) > 0.88). Similarly, the coefficients of determination were high (all r (2) > 0.78). The maximum mean difference between the measures was located in the mid-range of motion and was approximately 3.4° in sitting and 3.9° in standing. CONCLUSION: The BodyGuard™ appears to be a valid method for analysing vertebral motion in the sagittal plane and is a promising tool for long-term monitoring of spinal postures in laboratory and clinical settings in people with low back pain.
