CBCT-based volume of simulated root resorption - influence of FOV and voxel size.

AIM: To examine the influence of the field of view (FOV) and voxel size on the measurement of the volume of simulated internal root resorption (IRR) lesions through cone-beam computed tomography (CBCT). METHODOLOGY: Eleven single-rooted teeth with IRR simulated by acid demineralization were studied. CBCT images were acquired using large FOV (voxel sizes of 0.200, 0.250 and 0.300 mm) and limited FOV (voxel sizes of 0.076, 0.100 and 0.200 mm). The IRR volumes were calculated using the Dolphin(®) software. Volumetric measurements were validated using IRR silicone putty casts. The analysis of variance (anova) for randomized block design complemented with the Tukey's test was employed. RESULTS: IRR volumes obtained using voxel sizes of 0.200 and 0.250 mm were similar (P > 0.05). However, both these values were significantly different from that obtained using the 0.300-mm voxel (P < 0.05). There was no significant difference between IRR volumes measured through voxel sizes of 0.076 and 0.100 mm (P > 0.05), but both differed significantly from that obtained through the 0.200-mm voxel (P < 0.05). There was no significant difference between the volumetric measurements of the 0.200-mm voxel images of the restricted and large FOV protocols. The mean volumes of the silicone casts were smaller than those calculated using a 0.200-mm voxel, but were similar to those obtained using voxel sizes of 0.076 and 0.300 mm. CONCLUSIONS: Despite the FOV protocol, voxel size can influence measurement of simulated IRR volumes. The importance of standardization of CBCT image acquisition protocols is emphasized, especially during follow-up of an IRR lesion, to prevent misinterpretation of its extent, which can create a bias in clinical decisions.

Doping-induced conductivity transitions in molecular layers of polyaniline: optical studies of electronic state changes.

The doping-induced conductivity transitions in molecular layers of polyaniline have been studied by monitoring the correlated optical and spectroscopic changes using spectroscopic and single wavelength extinction ellipsometry, also in total internal reflection mode (TIRE), together with reflection spectrometry. The measurements were performed on deposited multilayers as well as on a Langmuir monolayer at the air-water interface, as a function of acidic doping. We found that the characteristic spectroscopic features of conducting and insulating polyaniline persisted down to the single layer, both in the solid state and at the air-water interface. We also investigated in real time the modulation of conductivity induced by the intercalation of Li ions in the polyaniline film, by a combination of time-resolved ellipsometry and reflectivity spectra measurements. In this case, the enhanced sensitivity provided by the TIRE geometry, combined with the relatively fast time scale accessible by the single wavelength ellipsometry, allowed us to follow in detail in real time the doping/dedoping process.

Doping-induced conductivity transitions in molecular layers of polyaniline: detailed structural study.

We report detailed structural investigations, by synchrotron X-ray reflectivity (XRR), grazing incidence diffraction (GID), and space-resolved grazing incidence X-ray-induced fluorescence (GIXF), on the structure of molecular layers of polyaniline (PANI) that can be converted from insulating to conducting state simply by doping. We first address the simpler, but more intriguing, system, i.e., a floating monolayer of PANI on different subphases, for which we found a typical thickness of 28(1) A, not much affected by the doping process. For the doped film we also found an internal lateral structure, with in-plane spacing of 3.5 A-albeit with a small coherence of 3-4 repeat units only-compatible with face-to-face interchain stacking of phenyl rings, in agreement with the literature. By GIXF we could confirm the crucial role of Cl(-) intercalation in the doping process of the PANI film: under doping conditions (0.1 M HCl subphase) the Cl(-) intake is 8 times larger than in nondoping conditions (0.1 M KCl subphase). Multilayers transferred onto solid substrate were studied also as a function of the applied voltage, as this system constitutes the core of an electrochemically controlled device whose strongly nonlinear characteristic make it useful for applications to adaptive networks for complex information processing. By the application of an electrostatic field of 140 V/m, Cl ionic migration was observed confined to the polymeric film surface.

Light-driven release from polymeric microcapsules functionalized with bacteriorhodopsin.

Bacteriorhodopsin was incorporated into the shell of polymeric capsules. Light-driven variation of intercapsule volume pH with successive pore opening was demonstrated by scanning electron microscopy. Release of the encapsulated dye molecules was studied by confocal fluorescence microscopy.

Balance in patients with anorexia and bulimia nervosa.

AIM: Neuro-muscular adaptations to the loss or increase in body weight may induce postural alterations. The aim of this study was to investigate the effect of body weight alterations on postural stability in patients with anorexia nervosa and bulimia. METHODS: The study enrolled 15 women affected by anorexia nervosa (AN), (mean body mass index [BMI] 15.8+/-1.8 kg/m(2)), 15 women affected by bulimia nervosa (BN), (mean BMI 20.1+/-2.9 kg/m(2)) and 11 healthy matched women (HC), (mean BMI 20.1+/-1 kg/m(2)). Two quiet standing conditions with eyes open (EO) and closed (EC) were analysed with an optoelectronic system (Vicon 460, Viconpeak, Oxford, UK) with passive markers to estimate the centre of mass (CoM) position. RESULTS: BN patients were more unstable than HC, showing statistically significant differences in antero-posterior CoM excursions and path length. AN patients showed non significant differences from HC. Only HC showed differences between EO and EC conditions, with significantly greater excursions in medio-lateral direction in EC condition (P<0.013) as well as an increased sway area (P<0.022). CONCLUSIONS: In BN, musculoskeletal factors seem to play a major role in the diminished postural control, which appear to be linked to body weight fluctuations rather than to BMI absolute values. No clear-cut postural instability was demonstrated in patients with AN as compared to HC. Visual input appears not to affect balance in patients with eating disorders. Possible further causes of postural instability in BN and implications for rehabilitation treatment are discussed.

Electrochemical control of the conductivity in an organic memristor: a time-resolved X-ray fluorescence study of ionic drift as a function of the applied voltage.

Grazing-incidence X-ray fluorescence measurements were applied for a time-resolved study of an organic memristor conductivity variation mechanism. A comparison of these results with electrical measurements has allowed us to conclude that the variation of the fluorescence intensity of Rb ions is directly connected to the ionic charge transferred between the conducting polymer and the solid electrolyte, which made up the device. In addition, the conductivity of the memristor was shown to be a function of the transferred ionic charge.

X-ray reflectivity measurements of layer-by-layer films at the solid/liquid interface.

In this Letter, we present a method for the decoration of layer-by-layer (LbL) structures by heavy metal ions, which allows X-ray reflectivity (XRR) measurements at the solid/water interface. The improved contrast has allowed us to obtain well-structured X-ray reflectivity curves from samples at the liquid/solid interface that can be used for the film structure modeling. The developed technique was also used to follow the formation of complexes between DNA and the LbL multilayer. The XRR data are confirmed by independent null-ellipsometric measurements at the solid/liquid interface on the very same architectures.

Microstructural analysis of the effects of incorporation of myelin basic protein in phospholipid layers.

We report an X-ray reflectivity study on the effects of adsorption of myelin basic protein (MBP) on Langmuir monolayers and on deposited Langmuir-Schaefer multilayers of the phospholipid dipalmitoyl phosphatidylglycerol (DPPG). We provide for the first time, direct microscopic evidence on the destructuring effects of MBP leading to plasticity of the DPPG layers supporting commonly accepted models of the stabilizing role of MBP in the myelin membrane. We also show how protein adsorption onto the layer is determined both by electrostatic and nonspecific hydrophobic interactions.

Electron beam irradiation for structuring of molecular assemblies.

Nontraditional applications of electron beam irradiation for patterning of molecular assemblies are considered. The electron beam can have the following effects on molecular layers: destruction of molecular structure under e-beam irradiation with a successive formation of new molecular system when the irradiation is stopped; variation of the properties of the layer after e-beam irradiation; crosslinking of molecules in the layer under irradiation; modification of the templates for the successive film growth, providing different growing conditions in irradiated and nonirradiated areas; and activation of the solid support surface and molecular systems in the film resulting in the increased adhesion of the layer to the substrate in irradiated areas. All these effects were used for patterning of thin layers of different compounds. Five classes of molecular systems were considered, namely, films of simple surfactant molecules, layers of charge-transfer complexes, films of conducting polymers, aggregated nanoparticulate layers and films of nanoengineered polymeric capsules. Characteristic features of patterning processes in each particular case are discussed.

Molecular relaxation and microscopic structure of multilayers and superlattices of a photosensitive liquid-crystalline polymer.

We report a detailed study of photoinduced changes in the microscopic structure of monolayers, multilayers, and superlattices of a photosensitive side chain liquid crystalline polymer, deposited by the Langmuir-Schaefer technique. We probe both out-of-plane and in-plane ordering and its changes due to optical pumping of the trans-cis photoisomerization transition of the azobenzene side chain in an azopolyacrylate. Microscopic structure was studied mainly by synchrotron radiation x-ray reflectometry and grazing incidence diffraction; we also used null-ellipsometry and atomic force microscopy. Our results provide a quantitative modeling of the structural changes and corresponding relaxation times taking place as a function of confinement, temperature and optical pumping, and in particular confirm previously reported ellipsometric results on such changes as a function of sample thickness. This allows a quantitative description of the effects of reduced dimensionality on the structural transitions in this glass-forming system.

Photoinduced dynamics in a photosensitive side chain polymeric liquid crystal by quasielastic and inelastic neutron scattering.

We report the first study by inelastic (INS) and quasielastic neutron scattering of photoinduced changes in the reorientational and vibrational dynamics of a liquid crystalline side chain polymer. We use the cis-trans photoisomerization transition to take the system out of equilibrium and determine the quasielastic (QE) and inelastic scattering laws on two distinct time windows, corresponding to the time-of-flight (IN6) and backscattering (IN16) spectrometers at Institut Laue Langevin (ILL) (Grenoble). Our investigation was focused on the dynamics of the coupling between the mesogenic side chains and the polymeric main chain, which is connected to the extensive optical writing and memory effects that have been demonstrated in this complex material. We report data on the QE broadening and Debye-Waller factors, as a function of temperature across the glass transition (T(g)=293 K). We also studied the dynamical coupling of side and main chains. We report photoinduced changes on the static structure factor, on the purely elastic scattering fraction, on the low frequency vibrational dynamics (around the boson peak region). In particular, we find that on the space-time scales accessible to the INS techniques there is a time structure in the coupling, and that over longer times and distances the two dynamics are decoupled.

Kinetic and structural study of the interaction of myelin basic protein with dipalmitoylphosphatidylglycerol layers.

The interaction of myelin basic protein (MBP) with dipalmitoylphosphatidylglycerol films has been investigated by means of a microgravimetric gauge sensitive to the changes in load and structural modifications of the layer deposited onto its surface. Fourier transform infrared spectroscopy, circular dichroism, and x-ray diffraction have confirmed protein uptake by the lipid phase along with a global disordering effect onto the lipid alkyl chains and have shown a temporal evolution of the structure of water penetrating the lipid phase together with the protein. These effects are clearly related to the temporal variation of the microgravimetric gauge signal. Finally, measurements carried out on pre-annealed samples point out the role of mesoscopic morphology in determining the pathways through which MBP penetrates the lipid multilayer. The results obtained in our model system could be useful in clarifying the mechanisms of the myelinating and demyelinating processes that take place in the natural membrane.

Raman spectroscopy and order in biological systems.

The Raman spectra in the low 5-200 cm-1 frequency region of metabolically active E. coli cells have been analyzed to determine whether they are indicators of a possible in vivo underlying order by applying standard concepts derived from the Raman spectroscopy of crystalline systems with varying degrees of order. The analysis suggests that in-vivo space-time ordered structures involving amino acids associated with DNA exist since the low frequency lines of metabolically active cells can be assigned to lines seen in the spectra of crystals of given amino acids known to associate with DNA early in the lifetime of a cell.