Contrast Formation in Kelvin Probe Force Microscopy of Single π-Conjugated Molecules

We report the contrast formation in the local contact potential difference (LCPD) measured by Kelvin probe force microscopy (KPFM) on single charge-transfer complexes (CTCs) on a NaCl bilayer on Cu(111). At different tip heights, we found quantitatively different LCPD contrasts that characterize different properties of the molecule. In the small distance regime, the tip penetrates the electron density of the molecule, and the contrast is related to the size and topography of the electron shell of the molecule. For larger distances, the LCPD contrast corresponds to the electrostatic field above the molecule. However, in the medium-distance regime, that is, for tip heights similar to the size of the molecule, the nonspherical distribution of π- and σ-electrons often conceals the effect of the partial charges within the molecule. Only for large distances does the LCPD map converge toward the simple field of a dipole for a polar molecule.

Evaluation of HA-fibrin-based hydrogel for restoration of degenerated intervertebral disc

Introduction: Intervertebral disc degeneration is associated with loss of nucleus pulposus (NP) tissue and reduced disc height[1]. A number of therapies, including synthetic and natural biomaterials, have been developed to restore full disc function and to minimize the pain and disability caused by this disease. Fibrin-based biomaterials are used as a replacement for NP or as a cell carrier for tissue engineering approaches[2]. While the behavior of such gels is well-characterized from a material point of view, little is known about their contribution to intervertebral disc (IVD) restoration under dynamic loads. The aim of the present study is the evaluation of a hyaluronic acid fibrin-based hydrogel (ProCore) used to repair an in vitro model of disc degeneration under dynamic loading. Methods: In vitro model of disc degeneration was induced in intact coccygeal bovine IVD by papain digestion of the NP as previously described[3]. In order to characterize fibrin hydrogels, four experimental groups were considered: 1) intact IVD (control), 2) IVD injected with PBS, 3) injection of hydrogels in degenerative IVD and 4) injection of hydrogels in combination with human bone marrow-derived mesenchymal stem cells (MSC) in degenerative IVD. All of the groups were subjected to dynamic loading protocols consisting of 0.2MPa static compression superimposed with ±2° torsion at 0.2Hz for 8h per day and maintained for 7 days. Additionally, one group consisted of degenerative IVD injected with hydrogel and subjected to static compression. Disc heights were monitored after the duration of the loading and compared to the initial disc height. The macrostructure of the formed tissue and the cellular distribution was evaluated by histological means. Results: After one week of loading, the degenerative IVD filled with hydrogel in combination with MSC (dynamic load), hydrogels (dynamic load) and hydrogels (static load) showed a reduction in height by 30%, 15% and 20%, respectively, as compared to their initial disc height. Histological sections showed that the HA-fibrin gel fully occupied the nucleotomized region of the disc and that fibrin was effective in filling the discontinuities of the cavity region. Furthermore, the cells were homogenously distributed along the fibrin hydrogels after 7 days of loading. Discussion: In this study, we showed that fibrin hydrogels showed a good integration within the papain-induced model of disc degeneration and can withstand the applied loads. Fibrin hydrogels can contribute to disc restoration by possibly maintaining adequate stiffness of the tissue and thus preventing disorganization of the surrounding IVD. References: 1. Jarman, J.P., Arpinar, V.E., Baruah, D., Klein, A.P., Maiman, D.J., and Tugan Muftuler, L. (2014). Intervertebral disc height loss demonstrates the threshold of major pathological changes during degeneration. Eur Spine J . 2. Colombini, A., Ceriani, C., Banfi, G., Brayda-Bruno, M., and Moretti, M. (2014). Fibrin in intervertebral disc tissue engineering. Tissue Eng Part B Rev . 3. Chan, S.C., Bürki, A., Bonél, H.M., Benneker, L.M., and Gantenbein-Ritter, B. (2013). Papain-induced in vitro disc degeneration model for the study of injectable nucleus pulposus therapy. Spine J 13, 273-283. Acknowledgement We thank the Swiss National Science Foundation SNF #310030_153411 for funding.

Density-dependent dynamics of a dominant rain forest tree change with juvenile stage and time of masting

Although negative density dependence (NDD) can facilitate tree species coexistence in forests, the underlying mechanisms can differ, and rarely are the dynamics of seedlings and saplings studied together. Herein we present and discuss a novel mechanism based on our investigation of NDD predictions for the large, grove-forming ectomycorrhizal mast fruiting tree, Microberlinia bisulcata (Caesalpiniaceae), in an 82.5-ha plot at Korup, Cameroon. We tested whether juvenile density, size, growth and survival decreases with increasing conspecific adult basal area for 3245 ‘new’ seedlings and 540 ‘old’ seedlings (< 75-cm tall) during an approximately 4-year study period (2008–2012) and for 234 ‘saplings’ (≥ 75-cm tall) during an approximately 6-year study period (2008–2014). We found that the respective densities of new seedlings, old seedlings and saplings were positively, not and negatively related to increasing BA. Maximum leaf numbers and heights of old seedlings were negatively correlated with increasing basal areas, as were sapling heights and stem diameters. Whereas survivorship of new seedlings decreased by more than one-half with increasing basal area over its range in 2010–2012, that of old seedlings decreased by almost two-thirds, but only in 2008–2010, and was generally unrelated to conspecific seedling density. In 2010–2012 relative growth rates in new seedlings’ heights decreased with increasing basal area, as well as with increasing seedling density, together with increasing leaf numbers, whereas old seedlings’ growth was unrelated to either conspecific density or basal area. Saplings of below-average height had reduced survivorship with increasing basal area (probability decreasing from approx. 0.4 to 0.05 over the basal area range tested), but only sapling growth in terms of leaf numbers decreased with increasing basal area. These static and dynamic results indicate that NDD is operating within this system, possibly stabilizing the M. bisulcata population. However, these NDD patterns are unlikely to be caused by symmetric competition or by consumers. Instead, an alternative mechanism for conspecific adult–juvenile negative feedback is proposed, one which involves the interaction between tree phenology and ectomycorrhizal linkages.

Gingival labial recessions and the post-treatment proclination of mandibular incisors

INTRODUCTION A prerequisite for development of gingival recession is the presence of alveolar bone dehiscence. Proclination of mandibular incisors can result in thinning of the alveolus and dehiscence formation. OBJECTIVE To assess an association between proclination of mandibular incisor and development of gingival recession. METHODS One hundred and seventeen subjects who met the following inclusion criteria were selected: 1. age 11-14 years at start of orthodontic treatment (TS), 2. bonded retainer placed immediately after treatment (T0), 3. dental casts and lateral cephalograms available pre-treatment (TS), post-treatment (T0), and 5 years post-treatment (T5), and 4. post-treatment (T0) lower incisor inclination (Inc_Incl) <95° or >100.5°. Two groups were formed: non-proclined (N = 57; mean Inc_Incl = 90.8°) and proclined (N = 60; mean Inc_Incl = 105.2°). Clinical crown heights of mandibular incisors and the presence of gingival recession sites in this region were assessed on plaster models. Fisher's exact tests, t-tests, and regression models were computed for analysis of inter-group differences. RESULTS The mean increase of clinical crown heights (from T0 to T5) of mandibular incisors ranged from 0.75 to 0.83mm in the non-proclined and proclined groups, respectively (P = 0.273). At T5, gingival recession sites were present in 12.3% and 11.7% patients from the non-proclined and proclined groups, respectively. The difference was also not significant (P = 0.851). CONCLUSIONS The proclination of mandibular incisors did not increase a risk of development of gingival recession during five-year observation in comparison non-proclined teeth.

Retrievability of implant-supported crowns when using three different cements: a controlled clinical trial

PURPOSE The purpose of this study was to analyze the removal of implant-supported crowns retained by three different cements using an air-accelerated crown remover and to evaluate the patients' response to the procedure. MATERIALS AND METHODS This controlled clinical trial was conducted with 21 patients (10 women, 11 men; mean age: 51 ± 10.2 years) who had received a total of 74 implants (all placed in the posterior zone of the mandible). Four months after implant surgery, the crowns were cemented on standard titanium abutments of different heights. Three different cements (two temporary: Harvard TEMP and Improv; and one definitive: Durelon) were used and randomly assigned to the patients. Eight months later, one blinded investigator removed all crowns. The number of activations of the instrument (CORONAflex, KaVo) required for crown removal was recorded. The patients completed a questionnaire retrospectively to determine the impact of the procedure and to gauge their subjective perception. A linear regression model and descriptive statistics were used for data analysis. RESULTS All crowns could be retrieved without any technical complications or damage. Both abutment height (P = .019) and cement type (P = .004) had a significant effect on the number of activations, but the type of cement was more important. An increased total number of activations had no or only a weak correlation to the patients' perception of concussion, noise, pain, and unwillingness to use the device. CONCLUSIONS Cemented implant crowns can be removed, and the application of an air-accelerated device is a practicable method. A type of cement with appropriate retention force has to be selected. The impact on the patients' subjective perception should be taken into account.

Geomorphology of the Imhotep region on comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Context. Since August 2014, the OSIRIS Narrow Angle Camera (NAC) onboard the Rosetta spacecraft has acquired high spatial resolution images of the nucleus of comet 67P/Churyumov-Gerasimenko, down to the decimeter scale. This paper focuses on the Imhotep region, located on the largest lobe of the nucleus, near the equator. Aims. We map, inventory, and describe the geomorphology of the Imhotep region. We propose and discuss some processes to explain the formation and ongoing evolution of this region. Methods. We used OSIRIS NAC images, gravitational heights and slopes, and digital terrain models to map and measure the morphologies of Imhotep. Results. The Imhotep region presents a wide variety of terrains and morphologies: smooth and rocky terrains, bright areas, linear features, roundish features, and boulders. Gravity processes such as mass wasting and collapse play a significant role in the geomorphological evolution of this region. Cometary processes initiate erosion and are responsible for the formation of degassing conduits that are revealed by elevated roundish features on the surface. We also propose a scenario for the formation and evolution of the Imhotep region; this implies the presence of large primordial voids inside the nucleus, resulting from its formation process.

Effects of shape Rosmarinus officinalis neighbors on resprouting of shape Erica multiflora individuals

To study the effects of competition in Mediterranean shrubland regeneration following disturbance, we used a neighborhood approach to assess the influence of mature Rosmarinus officinalis neighbors on the resprouting of Erica multiflora individuals after clipping. Sprout biomass of target plants 2 years after clipping was regressed against various measures of neighbor abundance within a 2 m radius around target E. multiflora individuals in which all vegetation except R. officinalis had been removed. The largest single influence on the biomass of sprouts produced was the previous biomass of the resprouting plant. The abundance of R. officinalis neighbors had a weak but detectable effect on resprouting of E. multiflora. Abundance of neighbors within 60 cm from target plants was the best predictor of regrowth. At this distance, two simple measures of neighbor abundance within the neighborhood, the number of neighbors and the sum of their heights, were significant in accounting for variation in resprouted biomass. None of the combinations of neighbor variables performed significantly better than single variables. The best models accounted for around 24 percent of the variation in resprout biomass. As in other studies, angular dispersion of neighbors never had a significant effect on performance of target plants. The weak but significant response of resprouting to variation in R. officinalis abundance suggests that the intensity of competition in the experiment was low because of the removal of other species.