The synthesis of a new family of chiral tridentate monoanionic NNN-pincer ligands based on the 1,3-bis(2-pyridylimino)isoindoline (BPI) framework is reported. Ligands with substituents of varying ...steric demand were prepared starting from achiral and low priced materials. A kinetic enzymatic resolution was used as a key step for the preparation of enantiomerically pure ligands. In this way, both enantiomers of a given ligand could be produced enantioselectively (>99.5% ee). The corresponding cobalt alkyl complexes were obtained using a pyridine alkyl cobalt precursor complex and were applied in asymmetric hydrosilylation of several prochiral alkylaryl ketones with high yields (up to 100%) and enantioselectivity (up to 91% ee) to give the chiral alcohols after hydrolysis.
•Auditory spindle stimulation does not entrain spindle activity during slow oscillation up-states.•Auditory spindle stimulation acutely induces a slow oscillation with coupled spindle activity.•The ...acute oscillatory response to spindle stimulation does not suffice to enhance memory.
The consolidation of sleep-dependent memories is mediated by an interplay of cortical slow oscillations (SOs) and thalamo-cortical sleep spindles. Whereas an enhancement of SOs with auditory closed-loop stimulation has been proven highly successful, the feasibility to induce and boost sleep spindles with auditory stimulation remains unknown thus far.
Here we tested the possibility to enhance spindle activity during endogenous SOs and thereby to promote memory consolidation. Performing a sleep study in healthy humans, we applied an auditory Spindle stimulation and compared it with an Arrhythmic stimulation and a control condition comprising no stimulation (Sham).
With Spindle stimulation we were not able to directly entrain endogenous spindle activity during SO up-states. Instead, both Spindle and Arrhythmic stimulation evoked a resonant SO response accompanied by an increase in spindle power phase-locked to the SO up-state. Assessment of overnight retention of declarative word-pairs revealed no difference between all conditions.
Our Spindle stimulation produced oscillatory evoked responses (i.e., increases in SOs and spindle activity during SO up-states) quite similar to those observed after the auditory closed-loop stimulation of SOs in previous studies, lacking however the beneficial effects on memory retention.
Our findings put the endeavour for a selective enhancement of spindle activity via auditory pathways into perspective and reveal central questions with regard to the stimulation efficacy on both an electrophysiological and a neurobehavioral level.
Shape-writing (aka gesture typing or swiping) is a word-based text entry method for touchscreen keyboards. It works by landing the finger on (or close to) the first character of the desired word and ...then sliding over all the other character keys without lifting the finger until the last word character is reached. This generates a trajectory of swiped characters on the keyboard layout which can be translated to a meaningful word by a statistical decoder. We hypothesize that swiping carries rich information about the user, such as demographic (e.g., age or gender) and behavioral (e.g., swiping familiarity or input finger) information. To test our hypothesis, we trained several sequence classifiers using different recurrent neural network architectures to predict demographic and behavioral correlates of users from swipe trajectories. We show that our sequence classifiers are always performing better than a random classifier; therefore, we conclude that cognitive and motor control mechanisms are embodied and reflected in swipe trajectories, validating thus our research hypothesis. Taken together, our results have implications for user privacy. Currently swiping is supported by all mobile vendors and has millions of users, so people may be inadvertently profiled at an unprecedented granularity. Future work should consider new ways of addressing these issues without impacting the user’s swiping experience.
Since the first report in the early 1950s, 1,3‐bis(2‐pyridylimino)isoindolines (BPIs) have found widespread applications in organic, inorganic and materials chemistry. This microreview focuses on ...recent progress towards chiral BPI derivatives as ligands for enantioselective catalysis as well as developments in the use of BPI complexes in materials science, focusing on luminescent and birefringent materials.
This microreview focuses on the development of 1,3‐bis(2‐pyridylimino)isoindolines (BPI) from their synthesis over half a century ago through to their current diverse applications in organic, inorganic and materials chemistry.
Condensation of phthalodinitrile and 2-amino-5,6,7,8-tetrahydroquinoline gave the bis(2-pyridylimino)isoindole protioligand 1 (thqbpiH) in high yield. Deprotonation of thqbpiH (1) using LDA in THF at ...-78 °C yields the corresponding lithium complex Li(THF)(thqbpi) (2) in which the lithium atom enforces almost planar arrangement of the tridentate ligand, with an additional molecule of THF coordinated to Li. Reaction of cobalt(II) chloride or iron(II) chloride with one equivalent of the lithium complex 2 in THF led to formation of the metal complexes CoCl(THF)(thqbpi) (3a) and FeCl(THF)(thqbpi) (3b). The paramagnetic susceptibility of 3a,b in solution was measured by the Evans method (3a: μ(eff) = 4.17 μ(B); 3b: μ(eff) = 5.57 μ(B)). Stirring a solution of 1 and cobalt(II) acetate tetrahydrate in methanol yielded the cobalt(II) complex 4 which was also accessible by treatment of 3a with one equivalent of silver or thallium acetate in DMSO. Whereas 3a,b were found to be mononuclear in the solid state, the acetate complex 4 was found to be dinuclear, the two metal centres being linked by an almost symmetrically bridging acetate. For all transition metal complexes paramagnetic (1)H as well as (13)C NMR spectra were recorded at variable temperatures. The complete assignment of the paramagnetic NMR spectra was achieved by computation of the spin densities within the complexes using DFT. The proton NMR spectra of 3a and 3b displayed dynamic behaviour. This was attributed to the exchange of coordinating solvent molecules by an associative mechanism which was analysed using lineshape analysis (ΔS(≠)= -154 ± 25 J mol(-1) K(-1) for 3a and ΔS(≠) = -168 ± 15 J mol(-1) K(-1) for 3b).
Iron(II) and cobalt(II) alkyl complexes using tridentate bis(pyridylimino)isoindolates as ancillary ligands have been synthesized from the pyridine alkyl precursor complexes (py)2Fe(CH2SiMe3)2 and ...(py)2Co(CH2SiMe3)2. The extremely air- and moisture-sensitive compounds were structurally characterized in the solid state by X-ray diffraction as well as in solution by paramagnetic NMR spectroscopy. It is demonstrated that the paramagnetic shifts in the 13C NMR spectra are dominated by strong Fermi-contact interactions. All 13C NMR signals can be assigned by correlation with DFT-calculated spin-density distributions.
The anionic ligands X in BPI-copper complexes induce different degrees of coordination of the peripheral ether moieties in the complexation of the metal. Furthermore, the BPIs may act as monoanionic ...or neutral ligands depending on the protonation status in the isoindoline ligand backbone. This leads to a variety of structural motifs. Display omitted
Copper(II) complexes of a new family of chiral tridentate 1,3-bis(2-pyridylimino)isoindoline (BPIH) ligands bearing peripheral, potentially ligating ether groups have been prepared and structurally characterized by X-ray diffraction and EPR spectroscopy. The acetato, halogenido, and triflato complexes display different degrees of coordination of the ligand periphery in the complex structure, and the complex geometry varies by coordination of the oxygen atoms of the ether moieties of the ligand side arms. Furthermore, the BPIs may act as monoanionic or neutral ligands depending on the protonation status of the isoindoline ligand backbone. Formation of complexes with deprotonated or protonated ligands may be controlled by the presence or absence of a base during the complexation reaction.
Bacteria display an abundance of cellular forms and can change shape during their life cycle. Many plausible models regarding the functional significance of cell morphology have emerged. A greater ...understanding of the genetic programs underpinning morphological variation in diverse bacterial groups, combined with assays of bacteria under conditions that mimic their varied natural environments, from flowing freshwater streams to diverse human body sites, provides new opportunities to probe the functional significance of cell shape. Here we explore shape diversity among bacteria, at the levels of cell geometry, size, and surface appendages (both placement and number), as it relates to survival in diverse environments. Cell shape in most bacteria is determined by the cell wall. A major challenge in this field has been deconvoluting the effects of differences in the chemical properties of the cell wall and the resulting cell shape perturbations on observed fitness changes. Still, such studies have begun to reveal the selective pressures that drive the diverse forms (or cell wall compositions) observed in mammalian pathogens and bacteria more generally, including efficient adherence to biotic and abiotic surfaces, survival under low-nutrient or stressful conditions, evasion of mammalian complement deposition, efficient dispersal through mucous barriers and tissues, and efficient nutrient acquisition.
Cycling is very popular; however, it is often believed to be associated with below average bone mass. This study compared bone measures of sprint- and distance-trained cyclists competing at World ...Master Track Championships, along with sedentary controls (30-82 yr), and examined the associations of bone measures with age.
Radius and tibia epiphyseal and shaft bone mineral density (BMD), bone mineral content (BMC), and cross-sectional area along with shaft polar moment of resistance (RPol) and endocortical/periosteal circumferences were assessed by peripheral quantitative computed tomography. Intergroup differences were assessed by ANOVA and age relationships by correlation analyses.
Sprint cyclists had the largest bone shafts and bone strength surrogates; the difference in diaphyseal BMC, area, and RPol compared with controls being >or=10% in the tibia and >or=8% in the radius (P < 0.01). Distance cyclists versus control group differences were smaller (tibia: approximately 4-10%; radius: <2%), reaching statistical significance only for tibial BMC and area (P < 0.05). Generally, epiphyseal bone measures showed no group differences. In the radius, age correlations were negative for both the sprinters' and the controls' diaphyseal and the sprinters' epiphyseal BMD; they were positive for the controls' diaphyseal endocortical and periosteal circumferences (P < 0.05). In the cyclists' tibiae, neither epiphyseal nor diaphyseal bone measures were correlated with age.
Sprint cyclists and to a lesser extent distance cyclists had greater tibia and radius bone strength surrogates than the controls, with tibial bone measures being well preserved with age in all groups. This suggests that competition-based cycling and the associated training regime is beneficial in preserving average or above-average bone strength surrogates into old age in men.
Impaired heart rate recovery (HRR) is a strong predictor of overall mortality and cardio-metabolic risk. This study aimed at investigating (1) the effect of participation in a lifestyle-change ...programme for weight loss on HRR in overweight and obese children and (2) potential associations between the changes in one minute HRR (HRR1) and fitness, weight loss and cardio-metabolic risk.
The analysis included 429 individuals (169 boys) aged 13.9 ± 2.3 years who participated in an inpatient weight loss programme for four to six weeks. At baseline and the end of the programme clinical investigations were performed, including blood analyses, blood pressure, anthropometry and maximal cycle ergometer exercise testing with continuous heart rate (HR) monitoring. HRR was calculated as the difference between the highest exercising HR and HR at one, three and five minutes post-exercise.
Average body weight decreased from 90.7 ± 22.5 kg to 81.9 ± 20.0 kg and peak exercise capacity increased from 1.66 ± 0.38 W/kg to 2.05 ± 0.45 W/kg (p < 0.001). Cardio-metabolic risk factors improved (waist circumference, LDL-cholesterol, HOMA insulin ratio, blood pressure; p < 0.05). HDL-cholesterol and triglyceride levels remained unchanged. Compared with baseline, at follow-up the decline in HR was more pronounced (+32%, +18% and +11% for HRR1, HRR3 and HRR5; p < 0.001). Improvements in HRR1 were weakly correlated with changes in exercise capacity (p < 0.05; r < 0.13), but not with changes in body weight and cardio-metabolic risk factors.
HRR considerably improved after an inpatient weight loss programme in overweight and obese children. This was not associated with improvements in body weight and cardio-metabolic risk; hence HRR would be a valuable addition to cardiovascular risk assessment in this group.
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