Probing plasma fluorinated graphene via spectromicroscopy.

Plasma fluorination of graphene is studied using a combination of spectroscopy and microscopy techniques, giving insight into the yield and fluorination mechanism for functionalization of supported graphene with both CF4 and SF6 gas precursors. Ion acceleration during fluorination is used to probe the effect on grafting functionalities. Adatom clustering, which occurs with CF4 plasma treatment, is suppressed when higher kinetic energy is supplied to the ions. During SF6 plasma functionalization, the sulfur atoms tend to bond to bare copper areas instead of affecting the graphene chemistry, except when the kinetic energy of the ions is restricted. Using scanning photoelectron microscopy, with a 100 nm spatial resolution, the chemical bonding environment is evaluated in the fluorinated carbon network at selected regions and the functionalization homogeneity is controlled in individual graphene flakes.

Probing the interaction between 2,2'-bithiophene-5-carboxylic acid and TiO2 by photoelectron spectroscopy: A joint experimental and theoretical study.

The interaction between 2,2'-bithiophene-5-carboxylic acid (PT2) sublimed under ultra-high vacuum conditions and anatase (101) and rutile (110) TiO2 single crystal surfaces is investigated by studying the electronic spectral density near the Fermi level with synchrotron-based spectroscopy. The experimental results are compared to density functional theory calculations of the isolated PT2 molecule and of the molecule adsorbed on an anatase TiO2 (101) cluster. The relative concentrations of Ti, C, and S atoms indicate that the adsorbed molecule remains intact upon deposition, which is typical of a Stranski-Krastanov growth mode. The analysis of the O1s spectrum suggests a predominant bidentate geometry of the adsorption with both rutile and anatase surfaces, as supported by previous theoretical simulations. It is also theoretically and experimentally demonstrated that the PT2 adsorption causes the appearance of new electronic states in the gap near the TiO2 valence band. A pinning effect of the LUMO level of the dye is also theoretically predicted.

Growth control, structure, chemical state, and photoresponse of CuO-CdS core-shell heterostructure nanowires.

The growth of single-crystal CuO nanowires by thermal annealing of copper thin films in air is studied. We show that the density, length, and diameter of the nanowires can be controlled by tuning the morphology and structure of the copper thin films deposited by DC magnetron sputtering. After identifying the optimal conditions for the growth of CuO nanowires, chemical bath deposition is employed to coat the CuO nanowires with CdS in order to form p-n nanojunction arrays. As revealed by high-resolution TEM analysis, the thickness of the polycrystalline CdS shell increases when decreasing the diameter of the CuO core for a given time of CdS deposition. Near-edge x-ray absorption fine-structure spectroscopy combined with transmission x-ray microscopy allows the chemical analysis of isolated nanowires. The absence of modification in the spectra at the Cu L and O K edges after the deposition of CdS on the CuO nanowires indicates that neither Cd nor S diffuse into the CuO phase. We further demonstrate that the core-shell nanowires exhibit the I-V characteristic of a resistor instead of a diode. The electrical behavior of the device was found to be photosensitive, since increasing the incident light intensity induces an increase in the collected electrical current.

Combining mass spectrometry diagnostic and density functional theory calculations for a better understanding of the plasma polymerization of ethyl lactate.

The focus of this work is on the growth mechanism of ethyl lactate-based plasma polymer film (ELPPF) that could be used as barrier coatings. In such an application, the ester density of the plasma polymer has to be controlled to tune the degradation rate of the material. Our strategy consists of correlating the plasma chemistry evaluated by RGA mass spectrometry and understanding, via DFT calculations, the chemistry of the synthesized thin films. The theoretical calculations helped us to understand the plasma chemistry in plasma ON and OFF conditions. From these data it is unambiguously shown that the signal m/z 75 can directly be correlated with the precursor density in the plasma phase. The combination of XPS and chemical derivatization experiments reveal that the ester content in the ELPFF can be tailored from 2 to 18 at. % by decreasing the RF power, which is perfectly correlated with the evolution of the plasma chemistry. Our results also highlight that the ELPPF chemistry, especially the ester content, is affected by the plasma mode of operation (continuous or pulsed discharge, at similar injected mean power) for similar ester content in the plasma. This could be related to different energy conditions at the interface of the growing films that could affect the sticking coefficient of the ester-bearing fragments.

Derivatization of free radicals in an isopropanol plasma polymer film: the first step toward polymer grafting.

Plasma-polymerized films (PPF) synthesized by plasma-enhanced chemical vapor deposition (PECVD) find increasing applications in biomedicine and differ in many ways from conventional polymers. One of the most specific properties of the PPF is the high reactivity of its free-radical-rich surface, arising from the deposition mechanism. Although generally considered as a disadvantage leading to the aging of the PPF, reactivity of the plasma-treated polymers and PPF surfaces can be beneficially employed, for example, for grafting of a specific chemical functionality or short polymer chains. The quantitative evaluation of the surface radical density of the PPF is thus considered as the necessary preparatory step toward any subsequent grafting reaction. In the present study, the surface radical density of an isopropanol-based PPF was quantitatively determined by a combination of NO chemical derivatization and X-ray photoelectron spectroscopy (XPS). Once the derivatization conditions were optimized, the radical density, derived from at % N determined by XPS, was evaluated as a function of the deposition power. It was found out that the surface density of free radicals presents a maximum for the deposition power of 200 W (~2.3 × 10(14) spin/cm(2)) and it stabilizes (~2.1 × 10(14) spin/cm(2)) with further power increase. XPS findings were supported by in situ FTIR measurements that provided additional information about the degree of plasma fragmentation denoting fragmentation saturation for a deposition power of 200 W. By fitting the N1s peak it was possible to identify primary, secondary and ternary radicals and to study their respective evolutions with different deposition conditions. Angle-resolved XPS analysis allowed the in-depth distribution of radicals to be addressed, revealing that on the top surface, primary, and secondary radicals are dominating, whereas more tertiary radicals are present in the subsurface region. Finally, some preliminary chemical grafting experiments have allowed the relevance of derivatization results to be cross-checked.

Microanatomic analysis of the trigeminal nerve and potential nerve graft donor sites.

A histologic study was undertaken to define the microanatomic characteristics of two commonly injured peripheral trigeminal nerve branches (lingual and mandibular nerves) and the two nerves most frequently procured for use in their interpositional graft repair (sural and greater auricular nerves). Nerves, obtained from fresh human cadavers, were evaluated for total fascicular area, fascicle number, axon number, axon size, and axon density. The peripheral branches of the trigeminal nerve (third division) were morphometrically similar, with only a slight decrease in axon density in the lingual nerve. Comparisons between the donor nerves, however, showed numerous discrepancies at the axonal level. While the fascicular area of the sural nerve was only slightly smaller, axon numbers and densities were only one-half that of the trigeminal nerves. Although the greater auricular nerve was appreciably smaller in overall size, a much better correlation existed with the trigeminal nerve in axonal qualities. These microanatomic findings raise questions about the potential capability of these graft choices to optimally restore axonal connections between nerve ends in trigeminal nerve repair.

Negatively charged resins stimulate bone formation in subperiosteal sites in rats. The effect of age.

The osteogenic response to subperiosteal injection of negatively charged ion exchange resins was compared in the tibiae of one-month and 16- to 22-month-old rats. The resins were administered either in the form of beads (CM Sephadex) or as particles (CM cellulose, carboxymethylcellulose), and the animals were killed at two weeks and at one month after injection. Histologically, the resins did not produce an inflammatory response. Periosteal bone formation was observed wherever resin was in contact with bone, and in the resin bed the connective tissues that invested the charged materials ossified within the first month. Marrow spaces commonly formed where periosteal growth was most rapid. The osteogenic effect was independent of resin conformation, and it was more pronounced in the younger rats.

Efficacy of nerve growth factor in regeneration of the mandibular nerve: a preliminary report.

An experimental study evaluating the potential utility of nerve growth factor (NGF) on sensory nerve regeneration was conducted in a rabbit mandibular nerve model. In 10 animals, bilateral 7-mm nerve gaps were created and repaired with the placement of 10-mm Silastic (American Scientific Products, McGaw Park, IL) conduits into which NGF (left side) and a control solution (cytochrome C, right side) was instilled. After 90 days, the nerve repairs were removed and the two sides compared by clinical appearance, and histologic and electrophysiologic assessment. The conduits instilled with control solution failed to result in nerve regeneration in any of the animals. The conduits with NGF solution, however, consistently displayed neural connections between the proximal and distal ends with the presence of slowed, but recordable, conduction velocities. The axonal numbers in the NGF repairs were significantly less than those of the normal nerve, but when adjusted for fascicular size, the axonal densities were comparable. In addition, osteoid tissue was observed around many of the NGF-induced nerve regenerates, but not on the control solution side, suggesting a possible influence of this protein on bone formation.

Effects of nerve growth factor on craniofacial onlay bone graft survival: preliminary findings.

A study was undertaken to evaluate the effects of nerve growth factor (NGF), which had previously demonstrated bone formation around mandibular nerve regenerates, on resorption of onlay bone grafts to the rabbit skull. Iliac grafts were onlayed on the parietal bone bilaterally and immobilized with wire ligatures in 15 animals. NGF and a control solution were introduced into the grafts through subcutaneous osmotic pumps. After 60 days, graft survival was compared by weights, histology, and fluorochrome labels. NGF-treated grafts were characterized by an average of 88.4% weight retention, preservation of the outer cortical plate with firm fixation to the underlying calvarium, and fluorescent labels localized to the inner cortex. Conversely, control grafts had an average weight retention of 42.8% (p < 0.01), nearly complete outer cortical plate loss with increased mobility of the residual inner cortex, and a lack of fluorescence in any part of the grafts. Despite the incongruous name, NGF exhibited a beneficial effect on onlay bone graft volume maintenance in this study. Although the mechanism and the long-term effects are unknown, inhibition of graft resorption rather than enhancement of bone formation is suggested.

Autologous facial fat transplantation: improved graft maintenance by microbead bioactivation.

An alternative approach to the management of free fat transplantation resorption was evaluated in a rat facial model. Fat grafts obtained from the inguinal region were transferred to subcutaneous lateral facial sites in 20 animals. The grafts were mixed with either basic fibroblast growth factor (bFGF) alone or dextran beads that had been pretreated with bFGF. The grafts were then compared by weight and histology at 1 and 6 months postoperatively. Although graft weights were nearly comparable at 1 month, substantial differences were seen at 6 months, with the bead-containing grafts exhibiting near complete weight maintenance and better overall graft form. Histologically, the bead-containing grafts had extensive intercellular collagen formation and a heterogeneity of adipocyte cell sizes, particularly after 1 month. These findings suggest that the addition of cell-specific bioactive peptides that affect either the preadipocyte cell line and/or the fibroblastic components of the recipient site improve postoperative fat graft weight maintenance. Delivery of the biochemical agent appears to require a carrier system to exert its effects.

Enhancement of repair in experimental calvarial bone defects using calcium sulfate and dextran beads.

Granular medical-grade calcium sulfate hemihydrate (MGCSH) and negatively charged dextran beads (DB) were evaluated both separately and in combination in cranial defects. Thirty-six rats received bilateral parietal inlay reconstructions using MGCSH, MGCSH plus DB, or DB alone or the defects were left unfilled. Postoperative evaluation at 45, 90, and 135 days was done by visual inspection, caliper measurements of defect thickness, and histologic examination. The best fibro-osseous repair of the defects occurred with the use of MGCSH in combination with DB. Repair tissue, which was confluent with the adjacent cranium, was noted to have good thickness, and a high bone content. By contrast, defects repaired with either DB or MGCSH alone had poorer quality repair tissue, with concavities, voids, bead migration, decreased thickness, and minimal bony replacement/ingrowth. Unfilled control defects showed only a thin, friable, translucent connective tissue layer of repair. No method produced complete bony closure.

[Systematic antepartum fetal evaluation ("Safe"). A concept for diagnosis of fetal function in threatened hypoxia]. / Systematische antepartuale fetale Erhebungen ("Safe"). Ein Konzept für die fetale Funktionsdiagnostik bei drohender Hypoxie.

TARGET: The significant aim of the study was to prove whether it makes sense to apply the classical approach of diagnostic procedures to the fetus. PATIENTS AND METHODS: In a group of a total of 534 singleton pregnancies we examined the value of various biochemical and biophysical tests for detecting the risk of perinatal hypoxia. The sequence and combination of the most decisive tests was considered as well as the different approach within the observation period. RESULTS: Maternal laboratory findings like HPL and E3 were significantly less predictive of growth disturbance and compromise than any biophysical test. A small fetal abdomen detected by ultrasound ("observation") is up to now the earliest and most reliable predictor of foetal growth disturbance, followed by Doppler measurements of the uteroplacental circulation ("examination of the chronic respiratory function"). Examination of the foetal heart-circulatory function with pulsed Doppler and the foetal cardiac frequency (CTG) are the procedures of choice to determine the risk of perinatal hypoxia following pre-selection of foetuses, which are too old or too thin. In these patients, additional stress tests have neither medical nor a diagnostic advantage compared to the published function tests. Amongst the variety of biophysical tests, the Apgar score ("fetal Apgar score") was superior to all other tests in predicting prenatal or perinatal hypoxia and might even prevent invasive procedures. CONCLUSION: The sequence from non-invasive biophysical tests, including the fetal Apgar score, to invasive procedures is recommended for screening and follow-up of preselected pregnancies at risk for perinatal hypoxia. This approach might be applied to other risk groups and will hopefully be supplemented by new noninvasive diagnostic tools allowing early prognosis and prevention of fetal and neonatal disease.