Location of Pyridine Guest Molecules in an Electroneutral {^3_∞}[SiO_(4/2)] Host Framework: Single-Crystal Structures of the As-Synthesized and Calcined Forms of High-Silica Ferrierite

Single crystals (up to 580 × 480 × 20 μm) of highly silicious ferrierite (Si-FER, 1), suitable for single-crystal X-ray investigations, are synthesized under organothermal conditions. The structures of the as-synthesized (1a) and the calcined (1b) Si-FER are determined at room temperature. Both structures are refined in the orthorhombic space group Pnnm (No. 58, standard setting) with a = 743.0(1) pm, b = 1409.2(2) pm, c = 1882.0(2) pm, V = 1970.5(4) × 10^6 pm^3, Z = 1, R = 0.041 (1a) and a = 741.8(1) pm, b = 1407.0(2) pm, c = 1871.3(2) pm, V = 1953.1(4) × 10^6 pm^3, Z = 1, R = 0.037 (1b). The structure solution when combined with chemical analysis and ^1H and ^(13)C MAS NMR gives a unit cell content of [Si_(36)O_(72)]{py_(4-x) ap_x} (x = 0−1, py = pyridine, ap = 1-amino-n-propane) and [Si_(36)O_(72)] for 1a and 1b, respectively. The structure of 1a shows only weak host−guest interactions between the {^3_∞}[SiO_(4/2)] framework and the occluded, orientationally disordered pyridine molecules by means of relatively long organic-to-framework distances, d(C_(py)···O) ≥ 354(2) pm. ^(29)Si MAS NMR spectra from the organic-containing Si-FER 1a and the organic-free form 1b are in good agreement with the crystallographic results in that they conform to the well-known linear relationship between the cosine expression of the T−O−T angles and the chemical shift of the respective tetrahedral sites (T-sites). A new modification of this relationship is presented here and offers an improved linear correlation between the X-ray and NMR data for 1a and 1b, as well as for other high-silica microporous materials. Application of this new correlation to denser SiO_2 compounds is discussed

Structural and electrical properties of c-axis oriented Y1-xCaxBa2(Cu1-yZny)3O7-delta thin films grown by pulsed laser deposition

Ca- and Zn-subsituted Y1-xCaxBa2(Cu1-yZny)O7-delta (x = 0, 0.05 and y = 0, 0.02, 0.04, 0.05) thin films were grown on SrTiO3 (100) substrates using the pulsed laser deposition (PLD) technique. Effects of various growth parameters on the quality of the film were studied via X-ray diffraction (XRD), atomic force microscopy (AFM), and in-plane resistivity, rhoab(T), measurements. The deposition temperature and oxygen partial pressure were gradually increased to 820C and 1.20 mbar respectively. Films grown under these conditions exhibited good c-axis orientation (primarily limited by the grain size) and low values of the extrapolated residual resistivity, rho(0), at zero temperature. The planar hole content, p, was determined from the room temperature thermopower, S[290K], measurements and the effects of oxygen annealing were also studied. Fully oxygenated samples were found to be overdoped with p ~ 0.195. The Superconducting transition temperature Tc(p), and rho(T,p) showed the expected systematic variations with changing Zn content.Comment: Submitted to Physica C (2003

Quantification of periaortic adipose tissue in contrast-enhanced CT angiography: technical feasibility and methodological considerations

To examine the feasibility of the quantifcation of abdominal periaortic fat tissue (PaFT) (tissue within − 45 to − 195 HU) in enhanced CT-angiographies compared to unenhanced CT-scans and identify methodological issues afecting its clinical implementation. Using OsirixMD, PaFT volume and mean HU value were retrospectively measured within a 5 mm periaortic ring in paired unenhanced and enhanced abdominal aortic CT-scans. The correlation between PaFT values was examined in a derivation cohort (n=101) and linear regression analysis produced correction factors to convert values from enhanced into values from unenhanced CTs. The conversion factors were then applied to enhanced CTs in a diferent validation cohort (n=47) and agreement of corrected enhanced values with values from unenhanced scans was evaluated. Correlation between PaFT Volume und Mean HU from enhanced and unenhanced scans was very high (r >0.99 and r=0.95, respectively, p<0.0001 for both). The correction factors for PaFT Volume and Mean HU were 1.1057 and 1.0011. Potential confounding factors (CT-kilovoltage, slice thickness, mean intraluminal contrast density, aortic wall calcifcation, longitudinal variation of intraluminal contrast density, aortic diameter) showed no signifcant efect in a multivariate regression analysis (p>0.05). Bland-Altman analysis of corrected enhanced and unenhanced values showed excellent agreement and Passing–Bablok regression confrmed minimal/no residual bias. PaFT can be quantifed in enhanced CT-angiographies very reliably. PaFT Volume scores are very consistently slightly underestimated in enhanced scans by about 10%, while the PaFT Mean HU value remains practically constant and ofers distinct methodological advantages. However, a number of methodological issues remain to be addressed

Benzamidinium tetra­hydro­penta­borate sesquihydrate

The asymmetric unit of the title compound [systematic name: benzamidinium 3,3′,5,5′-tetra­hydr­oxy-1,1′-spirobi[2,4,6-trioxa-1,3,5-triboracyclo­hexa­ne](1−) sesquihydrate], C7H9N2 +·B5H4O10 −·1.5H2O, is composed of two protonated benzamidinium cations, two tetra­hydro­penta­borate anions and three water mol­ecules of crystallization. The ions and water molecules are associated in the crystal structure by an extensive three-dimensional hydrogen-bonding network, which consists mainly of cation-to-anion N—H⋯O and anion-to-anion O—H⋯O hydrogen bonds

The effect of sacubitril/valsartan compared to olmesartan on cardiovascular remodelling in subjects with essential hypertension: the results of a randomized, double-blind, active-controlled study

Aims: Progressive aortic stiffening eventually leads to left ventricular (LV) hypertrophy and heart failure if left untreated. Anti-hypertensive agents have been shown to reverse this to some extent. The effects of sacubitril/valsartan (LCZ696), a dual-action angiotensin receptor blocker (ARB), and neprilysin inhibitor, on arterial stiffness and LV remodelling have not been investigated. Methods and results: This was a randomized, multi-centre, double-blind, double-dummy, active-controlled, parallel group, study to compare the effects on cardiovascular remodelling of sacubitril/valsartan with those of olmesartan in patients with hypertension and elevated pulse pressure. Magnetic resonance imaging scans were used to assess LV mass and local aortic distensibility, at baseline and at 12 and 52 weeks after initiation of treatment. Central pulse and systolic pressure were determined using a SphymoCor® XCEL device at each time point. A total of 114 patients were included, with 57 in each treatment group. The mean age was 59.8 years, and 67.5% were male. Demographic characteristics did not vary between the two sets of patients. Left ventricular mass index decreased to a greater extent in the sacubitril/valsartan group compared to the olmesartan group from baseline to 12 weeks (−6.36 vs. −2.32 g/m2; P = 0.039) and from baseline to 52 weeks (−6.83 vs. −3.55 g/m2; P = 0.029). These differences remained significant after adjustment for systolic blood pressure (SBP) at follow-up (P = 0.036 and 0.019 at 12 and 52 weeks, respectively) and similar signals (though formally non-significant) were observed after adjusting for changes in SBP (P = 0.0612 and P = 0.0529, respectively). There were no significant differences in local distensibility changes from baseline to 12 or 52 weeks between the two groups; however, there was a larger reduction in central pulse pressure for the sacubitril/valsartan group compared to the olmesartan group (P = 0.010). Conclusion: Since LV mass change correlates with cardiovascular prognosis, the greater reductions in LV mass indicate valuable advantages of sacubitril/valsartan compared to olmesartan. The finding that LV mass index decrease might be to some extent independent of SBP suggests that the effect of the dual-acting agent may go beyond those due to its BP-lowering ability

Space charged region in GaN and InN nanocolumns investigated by Atomic Force Microscopy

High quality InN and GaN nanocolumns of different length and diameter grown by molecular beam epitaxy (MBE) were electrically characterized directly and non-destructively by Atomic Force Microscopy (AFM) as a function of the column diameter. The “exact” column diameter was determined from AFM images by Blind Tip Estimation (BTE) and subsequent image reconstruction in order to avoid artefacts due to the finite AFM tip radius. In GaN, the conductivity rises up to a “critical” diameter due to a depletion region at the surface of the nanocolumns and remains constant above. In contrast, the electron accumulation at the surface causes decreasing conductivity in InN nanocolumns with increasing diameter. Thus, the nanocolumn surface acts as the preferential conduction path. These facts prove that there is electron accumulation in as-grown non-polar InN surfaces, according to calculations of the Fermi level pinning in InN

Large Predicted Self-Field Critical Current Enhancements In Superconducting Strips Using Magnetic Screens

A transport current distribution over a wide superconducting sheet is shown to strongly change in a presence of bulk magnetic screens of a soft magnet with a high permeability. Depending on the geometry, the effect may drastically suppress or protect the Meissner state of the sheet through the enhancement or suppression of the edge barrier critical current. The total transport current in the magnetically screened Meissner state is expected to compete with the critical current of the flux-filled sheet only for samples whose critical current is initially essentially controlled by the edge barrier effect.Comment: 6 figure

Location of Pyridine Guest Molecules in an Electroneutral {^3_∞}[SiO_(4/2)] Host Framework: Single-Crystal Structures of the As-Synthesized and Calcined Forms of High-Silica Ferrierite

Single crystals (up to 580 × 480 × 20 μm) of highly silicious ferrierite (Si-FER, 1), suitable for single-crystal X-ray investigations, are synthesized under organothermal conditions. The structures of the as-synthesized (1a) and the calcined (1b) Si-FER are determined at room temperature. Both structures are refined in the orthorhombic space group Pnnm (No. 58, standard setting) with a = 743.0(1) pm, b = 1409.2(2) pm, c = 1882.0(2) pm, V = 1970.5(4) × 10^6 pm^3, Z = 1, R = 0.041 (1a) and a = 741.8(1) pm, b = 1407.0(2) pm, c = 1871.3(2) pm, V = 1953.1(4) × 10^6 pm^3, Z = 1, R = 0.037 (1b). The structure solution when combined with chemical analysis and ^1H and ^(13)C MAS NMR gives a unit cell content of [Si_(36)O_(72)]{py_(4-x) ap_x} (x = 0−1, py = pyridine, ap = 1-amino-n-propane) and [Si_(36)O_(72)] for 1a and 1b, respectively. The structure of 1a shows only weak host−guest interactions between the {^3_∞}[SiO_(4/2)] framework and the occluded, orientationally disordered pyridine molecules by means of relatively long organic-to-framework distances, d(C_(py)···O) ≥ 354(2) pm. ^(29)Si MAS NMR spectra from the organic-containing Si-FER 1a and the organic-free form 1b are in good agreement with the crystallographic results in that they conform to the well-known linear relationship between the cosine expression of the T−O−T angles and the chemical shift of the respective tetrahedral sites (T-sites). A new modification of this relationship is presented here and offers an improved linear correlation between the X-ray and NMR data for 1a and 1b, as well as for other high-silica microporous materials. Application of this new correlation to denser SiO_2 compounds is discussed