The zonal architecture of human articular cartilage described by T2 relaxation time in the presence of Gd-DTPA2-

The depth-wise variation of T(2) relaxation time is known to reflect the collagen network architecture in cartilage, while the delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) technique is sensitive to tissue proteoglycan (PG) concentration. As the cartilage PG content varies along the tissue depth, the depth-dependent accumulation of the contrast agent may affect the inherent T(2) of cartilage in a nonconstant manner. Therefore, T(2) and dGEMRIC are typically measured in separate MRI sessions. In the present in vitro MRI study at 9.4 T, depth-wise T(2) profiles and collagenous zone thicknesses as determined from T(2) maps in the absence and presence of Gd-DTPA(2-) (T(2) and T(2Gd), respectively) were compared in samples of intact human articular cartilage (n=65). These T(2) measures were further correlated with birefringence (BF) of polarized light microscopy (PLM) to quantify the ability of MRI to predict the properties of the collagen fibril network. The reproducibility of the T(2) measurement in the current setup was also studied. Typical tri-laminar collagen network architecture was observed both with and without Gd-DTPA(2-). The inverse of BF (1/BF) correlated significantly with both T(2) and T(2Gd) (r=0.91, slope=0.56 and r=0.90, slope=0.63), respectively. The statistically significant linear correlations between zone thicknesses as determined from T(2) and T(2Gd) were r=0.55 (slope=0.49), r=0.74 (slope=0.71) and r=0.95 (slope=0.94) for superficial, middle and deep tissue zones, respectively. Reproducibility of the T(2) measurement was worst for superficial cartilage. Consistent with PLM, T(2) and T(2Gd) measurements reveal highly similar depth-dependent information on collagen network in intact human cartilage. Thus, dGEMRIC and T(2) measurements in one MRI session are feasible for intact articular cartilage in vitro.     

Pitch-Synchronous Changes in the Anterior Cricothyroid Space During Singing

Pitch-synchronous changes in the anterior cricothyroid (CT) space were registered with ultrasonography (USG) for ten healthy subjects (5 males, 5 females) during the production of musical fifths throughout the whole voice range. One of the males and one of the females were trained amateur singers, the other subjects were choir singers. The average decrease in CT space per a musical fifth was 1.3-2.4 mm for the males and 1.0-1.8 mm for the females; the average decrease was smaller in the middle of the pitch range for both genders. The results suggest that (1) USG can be used for detection of pitch-synchronous changes in the CT space; (2) these changes are dependent on pitch range; and (3) more trained singers tend to have somewhat smaller changes than less trained subjects at certain frequencies. The results seem to indicate that F0 control mechanism varies according to pitch range and register, and possibly according to individual structure and vocal technique related differences.     

Solution properties of an aqueous poly(methacryl oxyethyl trimethylammonium chloride) and its poly(oxyethylene) grafted analog

Cationic poly(methacryl oxyethyl trimethylammonium chloride), PMOTAC, and its poly(oxyethylene), POE, grafted analog have been synthesised. The molar mass of the POE grafts was M_w = 200 g/mol, and the grafting degrees of the synthesised copolymers were 2, 5, and 15 mol %. The effect of the POE grafts on the solution properties and the conformation of the polycation has been investigated in aqueous NaNO₃ by means of dynamic and static light scattering, viscometry, and Raman spectroscopy. It was found that the polyelectrolyte properties are more pronounced for the homopolymer than for the POE‐grafted copolymers. The increase of the POE‐grafting degree dramatically decreases the hydrodynamic radius of individual macromolecules and causes intermolecular association. It also suppresses the conformational response of the copolymers upon changing the ionic strength with respect to that of the homopolymer. DFT calculations have been used to estimate a possible mechanism of interaction between the POE grafts and the MOTAC repeating units. It has been revealed that the POE grafts are capable of forming intramolecular hydrogen bonds with the MOTAC groups. The latter was confirmed experimentally; addition of free POE chains to a solution of PMOTAC results in formation of intermolecular PMOTAC/POE complexes. Increasing the POE concentration decreases the solution viscosity. At the same time, the bimodal distributions of the hydrodynamic radius, which are typical for polyelectrolytes in salt‐free solutions, become monomodal representing the PMOTAC/POE complexes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 547–557, 2008     

Stable isotope profiles of nitrogen gas indicate denitrification in oxygen-stratified humic lakes

Mid-summer N(2) profiles were analyzed from nine oxygen-stratified, humic-acid-rich lakes using a continuous flow isotope ratio mass spectrometer and a Gasbench II device. Sample preparation steps were performed under water to avoid air contamination. The instrument precision for the δ(15)N measurement was high (0.03‰), but for the whole sampling and analysis procedure the mean deviation between replicate samples was 0.13‰ for the δ(15)N measurements and 5.5% for the N(2) gas concentration analysis. The results show that the Gasbench peripheral was suitable for measurement of the (15)N natural abundance of dissolved nitrogen gas, with denitrification indicated by the oversaturation and slightly (<1‰) depleted δ(15)N values of the dissolved N(2) gas in the suboxic zones of some of the study lakes. Calculated values for the denitrified (excess) N(2) varied between -5.3 and 0.7‰. The denitrification potential was determined using the (15)N tracer method, with results showing nitrate-inducible denitrification and no signs of anaerobic ammonium oxidation (anammox).     

Frequent Hypercyclicity of Random Entire Functions for the Differentiation Operator

We study the random entire functions defined as power series \(f(z) = \sum _{n=0}^\infty (X_n/n!) z^n\) with independent and identically distributed coefficients \((X_n)\) and show that, under very weak assumptions, they are frequently hypercyclic for the differentiation operator \(D: H({\mathbb {C}}) \rightarrow H({\mathbb {C}}),\,f \mapsto Df = f'\) . This gives a very simple probabilistic construction of \(D\) -frequently hypercyclic functions in \(H({\mathbb {C}})\) . Moreover we show that, under more restrictive assumptions on the distribution of the \((X_n)\) , these random entire functions have a growth rate that differs from the slowest growth rate possible for \(D\) -frequently hypercyclic entire functions at most by a factor of a power of a logarithm.     

Critical Mandelbrot Cascades

We study Mandelbrot’s multiplicative cascade measures at the critical temperature. As has been recently shown by Barral et al. (C R Acad Sci Paris Ser I 350:535–538, 2012), an appropriately normalized sequence of cascade measures converges weakly in probability to a nontrivial limit measure. We prove that these limit measures have no atoms and give bounds for the modulus of continuity of the cumulative distribution function of the measure. Using the earlier work of Barral and Seuret (Adv Math 214:437–468, 2007), we compute the multifractal spectrum of the measures. We also extend the result of Benjamini and Schramm (Commun Math Phys 289:653–662, 2009), in which the KPZ formula from quantum gravity is validated for the high temperature cascade measures, to the critical and low temperature cases.     

Atomic layer deposition of crystalline molybdenum oxide thin films and phase control by post-deposition annealing

Molybdenum forms a range of oxides with different stoichiometries and crystal structures, which lead to different properties and performance in diverse applications. Herein, crystalline molybdenum oxide thin films with controlled phase composition are deposited by atomic layer deposition. The MoO₂(thd)₂ and O₃ as precursors enable well-controlled growth of uniform and conformal films at 200–275 °C. The as-deposited films are rough and, in most cases, consist of a mixture of α- and β-MoO₃ as well as an unidentified suboxide MoO_x (2.75 ≤ x ≤ 2.89) phase. The phase composition can be tuned by changing deposition conditions. The film stoichiometry is close to MoO₃ and the films are relatively pure, the main impurity being hydrogen (2–7 at-%), with ≤1 at-% of carbon and nitrogen. Post-deposition annealing is studied in situ by high-temperature X-ray diffraction in air, O₂, N₂, and forming gas (10% H₂/90% N₂) atmospheres. Phase-pure films of MoO₂ and α-MoO₃ are obtained by annealing at 450 °C in forming gas and O₂, respectively. The ability to tailor the phase composition of MoO_x films deposited by scalable atomic layer deposition method represents an important step towards various applications of molybdenum oxides.     

Assessment of interstitial water content of articular cartilage with T1 relaxation

The interstitial water content typically increases in the early degeneration of articular cartilage. Previously, T₂ relaxation has been related to water content, yet it is known to be strongly affected by the collagen orientation. Articular cartilage plugs from the bovine patella, femur and tibia (N=20) were mapped for T₁ and T₂ at 9.4 T to test the ability of T₁ relaxation to reflect cartilage water content. As a reference, water and proteoglycan (PG) contents were determined. Significant (P<.01) linear associations were demonstrated between the relaxation rates and tissue water content (R₁: r=−.81, R₂: r=−.60) and PG content (R₁: r=.75). After adjustment for the tissue water content, partial correlation analysis did not show significant associations between the relaxation rates and tissue PG content. After the effect of PGs was removed, significant (P<.05) linear correlation between the relaxation rates and tissue water content (R₁: r=−.48, R₂: r=−.50) was observed. Thus, the spin-lattice relaxation rate is proposed to provide a biomarker for water content in articular cartilage.     

Diffusion tensor imaging of native and degenerated human articular cartilage

Diffusion tensor imaging (DTI) is potentially sensitive to collagen degeneration in cartilage. In this study, DTI was measured on human cartilage samples with interventions of trypsin and collagenase. The measured preferred diffusion direction was consistent with the zonal structure of collagen network. The glycosaminoglycan concentration decreased and apparent diffusion coefficient increased with both interventions. The fractional anisotropy (FA) was not affected by trypsin and showed a slight increase with combined trypsin and collagenase intervention. DTI in cartilage is technically challenging due to the low FA and the almost undetectable change with collagen disruption seen here.     

Bile acid alkylamide derivatives as low molecular weight organogelators: systematic gelation studies and qualitative structural analysis of the systems

A series of amino- and hydroxyalkyl amides of bile acids have been synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), (1)H and (13)C nuclear magnetic resonance spectroscopy (NMR), as well as electrospray ionization mass spectrometry (ESI-MS) measurements. The ability of the synthesized molecules to promote gel formation was systematically investigated. Out of 396 combinations formed by 11 compounds and 36 different solvents, 22 gel-containing systems were obtained with 1% (w/v) gelator concentration. Apart from one exception, the gelator compounds were lithocholic acid derivatives. This challenges the general trend of bile acid-based physical gelators, according to which the gelation ability of lithocholic acid derivatives is poor. A correlation between the values of Kamlet-Taft parameters and solvent preferences for gelators was observed. The morphologies of the solid and gel structures studied with scanning electron microscopy (SEM) showed variability from fibers to spherical microscale aggregates, the latter of which are unique among bile acid-based organogels. The gels exhibited more complex behavior than was previously established with bile acid derivatives, judging by the microscale diversity present in gelating and non-gelating systems and the tendency for polymorphism. This study underlines the importance of both the molecular and colloidal scale aspects of the gelation phenomenon.