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Injured young athletes were older and spent more hours per week in organized sports. There is an independent risk of injury and serious overuse injury in young athletes who specialize in a single sport. Growth rate was not related to injury risk. The study data provide guidance for clinicians counseling young athletes and their parents regarding injury risks associated with sports specialization.

Robust methods to tune the unique electronic properties of graphene by chemical modification are in great demand due to the potential of the two dimensional material to impact a range of device applications. Here we show that carbon and nitrogen core-level resonant X-ray spectroscopy is a sensitive probe of chemical bonding and electronic structure of chemical dopants introduced in single-sheet graphene films. In conjunction with density functional theory based calculations, we are able to obtain a detailed picture of bond types and electronic structure in graphene doped with nitrogen at the sub-percent level. We show that different N-bond types, including graphitic, pyridinic, and nitrilic, can exist in a single, dilutely N-doped graphene sheet. We show that these various bond types have profoundly different effects on the carrier concentration, indicating that control over the dopant bond type is a crucial requirement in advancing graphene electronics.

We describe a series of highly soluble diketo pyrrolo-pyrrole (DPP)-bithiophene copolymers exhibiting field effect hole mobilities up to 0.74 cm(2) V(-1) s(-1), with a common synthetic motif of bulky 2-octyldodecyl side groups on the conjugated backbone. Spectroscopy, diffraction, and microscopy measurements reveal a transition in molecular packing behavior from a preferentially edge-on orientation of the conjugated plane to a preferentially face-on orientation as the attachment density of the side chains increases. Thermal annealing generally reduces both the face-on population and the misoriented edge-on domains. The highest hole mobilities of this series were obtained from edge-on molecular packing and in-plane liquid-crystalline texture, but films with a bimodal orientation distribution and no discernible in-plane texture exhibited surprisingly comparable mobilities. The high hole mobility may therefore arise from the molecular packing feature common to the entire polymer series: backbones that are strictly oriented parallel to the substrate plane and coplanar with other backbones in the same layer.

Materials and Measurements:1 H and 13 C NMR spectra were recorded on a Bruker AV-300 (300 MHz), using the residual solvent resonance of CDCl 3 as an internal reference and are given in ppm.Absorption spectra were collected by a Perkin Elmer Lamba 9 UV-VIS spectrophotometer. Microanalyses were obtained with an elementar vario EL analyzer.Mass spectra were obtained either from an Agilent GCMS using a 6890 series GC with a 5973 MSD (EI) or a Bruker Esquire 3000+ (ESI). Molecular weight determinations were carried out in chloroform solution on an Agilent 1100 series HPLC using two Polymer Laboratories mixed B columns in series, and the system was calibrated against narrow weight PL polystyrene calibration standards. DSC measurements were performed on a TA Q100 under nitrogen. Reactions utilising microwave heating were performed on an Emrys Creator from Personal Chemistry Ltd. All starting materials and reagents were purchased from Aldrich Chemicals and Lancaster Chemicals. Anhydrous solvents were purchased from Romil Ltd and transferred using standard Schlenk line techniques.Column chromatography and TLC were performed on silica gel 60 (70-230 mesh, Merck) and silica gel F 254 plates (Merck) respectively. 3-Hexadecylthiophene and 3octadecylthiophene were prepared according to the published route. 1 4,4'-Bis(hexadecyl)-2,2'-bithiophene, 4,4'-bis(octadecyl)-2,2'-bithiophene and 2,5-bis-trimethylstannylthieno[3,2-b]thiophene were prepared in analogy to the published procedures. 2 5,5'-Dibromo-4,4'-bis(hexadecyl)-2,2'-bithiophene.To a solution of 4,4'-bis(hexadecyl)-2,2'-bithiophene (4.08 g, 6.63 mmol) in dichloromethane (30 ml) and glacial acetic acid (50 ml) at 40°C in the dark was added Nbromosuccinimde (2.36 g, 13.3 mmol) portionwise over 1 h. Water (100 ml) was added and the resulting precipitate collected by filtration, washed with water and acetone.Recrystallisation from butanone (twice) afforded the product (3.8 g, 74%) as pale yellow crystals. M/Z 772 (M+).

In situ hard X-ray absorption spectroscopy (XAS) at metal K-edges and soft XAS at O K-edge and metal L-edges have been carried out during the first charging process for the layered Li1-xCo1/3Ni1/3Mn1/3O2 cathode material. The metal K-edge XANES results show that the major charge compensation at the metal site during Li-ion deintercalation is achieved by the oxidation of Ni2+ ions, while the manganese ions and the cobalt ions remain mostly unchanged in the Mn4+ and Co3+ state. These conclusions are in good agreement with the results of the metal K-edge EXAFS data. Metal L-edge XAS results at different charge states in both the FY and PEY modes show that, unlike Mn and Co ions, Ni ions at the surface are oxidized to Ni3+ during charge, whereas Ni ions in the bulk are further oxidized to Ni4+ during charge. From the observation of O K-edge XAS results, we can conclude that a large portion of the charge compensation during Li-ion deintercalation is achieved in the oxygen site. By comparison to our earlier results on the Li1-xNi0.5Mn0.5O2 system, we attribute the active participation of oxygen in the redox process in Li1-xCo1/3Ni1/3Mn1/3O2 to be related to the presence of Co in this system.

Organic semiconductors are emerging as a viable alternative to amorphous silicon in a range of thin‐film transistor devices. With the possibility to formulate these p‐type materials as inks and subsequently print into patterned devices, organic‐based transistors offer significant commercial advantages for manufacture, with initial applications such as low performance displays and simple logic being envisaged. Previous limitations of both air stability and electrical performance are now being overcome with a range of both small molecule and polymer‐based solution‐processable materials, which achieve charge carrier mobilities in excess of 0.5 cm2 V−1 s−1, a benchmark value for amorphous silicon semiconductors. Polymer semiconductors based on thienothiophene copolymers have achieved amongst the highest charge carrier mobilities in solution‐processed transistor devices. In this Progress Report, we evaluate the advances and limitations of this class of polymer in transistor devices.

Surfaces of novel block copolymers with amphiphilic side chains were studied for their ability to influence the adhesion of marine organisms. The surface-active polymer, obtained by grafting fluorinated molecules with hydrophobic and hydrophilic blocks to a block copolymer precursor, showed interesting bioadhesion properties. Two different algal species, one of which adhered strongly to hydrophobic surfaces, and the other, to hydrophilic surfaces, showed notably weak adhesion to the amphiphilic surfaces. Both organisms are known to secrete adhesive macromolecules, with apparently different wetting characteristics, to attach to underwater surfaces. The ability of the amphiphilic surface to undergo an environment-dependent transformation in surface chemistry when in contact with the extracellular polymeric substances is a possible reason for its antifouling nature. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) was used, in a new approach based on angle-resolved X-ray photoelectron spectroscopy (XPS), to determine the variation in chemical composition within the top few nanometers of the surface and also to study the surface segregation of the amphiphilic block. A mathematical model to extract depth-profile information from the normalized NEXAFS partial electron yield is developed.