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In the current study, we investigated windows for enhanced learning of cognitive skills during adolescence. Six hundred thirty-three participants (11-33 years old) were divided into four age groups, and each participant was randomly allocated to one of three training groups. Each training group completed up to 20 days of online training in numerosity discrimination (i.e., discriminating small from large numbers of objects), relational reasoning (i.e., detecting abstract relationships between groups of items), or face perception (i.e., identifying differences in faces). Training yielded some improvement in performance on the numerosity-discrimination task, but only in older adolescents or adults. In contrast, training in relational reasoning improved performance on that task in all age groups, but training benefits were greater for people in late adolescence and adulthood than for people earlier in adolescence. Training did not increase performance on the face-perception task for any age group. Our findings suggest that for certain cognitive skills, training during late adolescence and adulthood yields greater improvement than training earlier in adolescence, which highlights the relevance of this late developmental stage for education.

Background The underlying cause of glenohumeral arthritis is poorly understood. Glenohumeral arthrosis patterns have been classified and described, and differential contact stresses within the joint have been implicated as a cause of joint degeneration, but the intrinsic cause of degeneration patterns in the glenohumeral joint (GHJ) remains largely unknown. Purpose/hypothesis The purpose of this study was to assess morphological and mechanical differences in articular cartilage (AC) and subchondral bone (SCB) of the glenoid and humeral head in matched cadaveric specimens. We hypothesized that there would be significant zone-dependent differences between the intrinsic characteristics (AC thickness, SCB thickness, compressive forces) of the glenoid and humeral head. Study design Descriptive laboratory study. Methods Ten human cadaveric GHJs (mean age, 60.2 years) were dissected to expose articular surfaces to facilitate biomechanical testing. A 2-mm and 6-mm osteochondral plug was harvested at 5 zones (central, anterior, posterior, inferior, superior) on the glenoid and humeral head (N = 200 plugs). Each 2-mm core was histologically sectioned and stained with hematoxylin and eosin. AC thickness measurements were taken using light microscopy. The 6-mm plugs were imaged using micro-computed tomography to measure SCB thickness. After imaging, AC specimens were removed from the SCB and tested in confined compression. The compressive aggregate modulus (HA0), compressive stiffening coefficient (β), and compressive modulus at 16% strain (HA0.16) and at 50% strain (HA0.50) were calculated. Results The overall AC thickness was significantly greater on the glenoid. The glenoid also had significantly thicker AC at the inferior, posterior, and superior zones as well as significantly higher SCB thickness overall and significantly greater SCB thickness at the anterior and central zones. The glenoid had significantly greater overall HA0.50 and HA0.50 values at the superior zone and had a significantly greater overall compressive stiffening coefficient (β). Conclusion The glenoid had thicker AC, thicker SCB, and greater compressive stiffness at high strain. Clinical relevance These intrinsic differences may help better elucidate the cause of differential degeneration patterns between the glenoid and humeral head.

The usefulness of the 2D-NMR techniques in the structure determination of the oligo epsilon-caprolactone ethyl glucopyranoside (oilgo(epsilon-CL) EGP) conjugate, synthesized by a lipase-catalyzed regioselective reaction, is described. Data from a 13C-13C COSY NMR spectrum of the ethyl glucopyranoside is used for complete and unambiguous assignments of the carbon resonances in the 13C NMR spectrum of the anomeric mixture of EGP. A comparison of the DEPT135 spectrum of the product oilgo(epsilon-CL) EGP conjugate with that of the starting material, ethyl glucopyranoside (EGP), led to the conclusion that the lipase-catalyzed ring-opening of epsilon-CL initiated by a multifunctional initiator, EGP, proceeded in a regioselective fashion. Also, a detailed analysis of the NMR data has allowed determination of the site for lipase-catalyzed ring-opening polymerization of epsilon-CL. Our study suggests that among the possible four initiation sites in EGP only the hydroxyl group on carbon C-6 took part in the initiation process.

There are several techniques and methods used to quantify the presence of low-level impurities in pharmaceutical compounds. At present it is a difficult task to determine their molecular structure unless the impurity is isolated from the pharmaceutical compound. A procedure, based on crystallization and nuclear magnetic resonance (NMR) analysis, is described for determining the molecular structure and concentration of an impurity in the presence of pharmaceutical compound, even though that impurity has not been isolated. Slow crystallization is done in order to enrich the impurity concentration to usable levels in either the solution or in some extracted powder or crystallites. High-resolution one- and two-dimensional NMR analysis of the original and enriched materials may then allow determination of the impurity's structure and its concentration in the original sample. A specific example illustrating the technique is described.

The structural and morphological changes occurring in high-density polyethylene when exposed to gamma-radiation have been investigated by high-resolution solid state 13C NMR. NMR measurements are used to study the effect of gamma-radiation on crystalline and amorphous components. In addition, resonance peaks due to direct cross-links have been detected. The changes in main chain unsaturation are also studied.

The enantiomer separation and the spectral simplification of overlapped resonances in a high-resolution 1H NMR spectrum of a model compound have been successfully accomplished with the use of paramagnetic shift reagent. Both 1H and 13C NMR have been applied to determine the composition of a mixture containing optically active enantiomers of (+/-)-2,2-dimethyl-1-phenyl-1-propanol.

One- and two-dimensional 19F NMR spectroscopy has been used to elucidate the molecular structure of a novel compound: fluoromethyl 1,1,3,3,3-pentafluoro-2-propenyl ether. A detailed investigation has provided a means of understanding the complex nature of the one-dimensional 19F NMR spectrum of this compound. In addition, J values are used to predict the molecular conformation.

One- and two-dimensional NMR experiments are used to study substituted piperidine derivatives in both free base and salt form. The investigation of 1-methyl-2-piperidine methanol has resulted in stereostructural elucidation of this compound in the salt form.

The combined use of high-power proton decoupling and magic angle sample spinning (MAS) provides high-resolution C-13 NMR spectra for solids. In our laboratory we use these techniques to characterize polymeric materials. Magic angle sample spinning at high speeds reduces the intensity of first-order sidebands as the inverse square of the angular velocity of the rotor. The rotor speed depends on the design and the material of the spinner. Various rotor designs are being used for spinning at the magic angle (54.7°) with respect to the static magnetic field. These include the Andrew-Beams design and a cylindrical design with two bearings for both electromagnets and superconducting magnets. It has been noted that Delrin (polyoxymethylene) and Kel-F (polytrifluorochloroethylene) are suitable materials for the rotor. These rotors must be very stable and should have a long life for routine use. Our experience with Kel-F spinners shows that they wear quickly on the edges. The Delrin rotor spins faster and is stronger than the Kel-F rotor, but it also has a drawback in that the polyoxymethylene C-13 resonance appears at 89.1 ppm downfield from TMS in the NMR spectra. This resonance may interfere with the resonances of the solid polymers of interest. Slow speed may complicate the spectra with sidebands for some resonances. Here, we report some modifications of the Andrew-Beams-type spinner to overcome the above-mentioned difficulties. The modified spinners are stable and have a longer life compared with the Kel-F rotors. We also report a solid methylsilsesquioxane as a useful chemical shift reference compound.