W.J.M. van der Kemp

A meta-analysis of the polyunsaturated fatty acid composition of erythrocyte membranes in schizophrenia

BACKGROUND Membrane abnormalities in polyunsaturated fatty acids (PUFAs) have been reported in schizophrenia and have been associated with brain tissue loss in normal ageing. Therefore PUFA may be involved in the excessive brain tissue loss reported in schizophrenia. METHODS A systematic MEDLINE database search was conducted to identify studies that compared PUFAs in erythrocyte membranes in patients and controls. Patients were categorized by medication regime in medication naive first-episode patients, and patients receiving typical or atypical antipsychotics. SAMPLE Fourteen studies were included, comprising a total of 429 patients with schizophrenia and 444 healthy control subjects. Cohens d effect sizes were calculated for PUFAs in erythrocyte membranes using the random-effects model. Combined Cohens d was calculated separately for patients on different medication regime. RESULTS Medication-naive patients and patients taking typical antipsychotics showed significantly (p<0.01) decreased concentrations of arachidonic (AA), docosahexaenoic (DHA), and docosapentaenoic (DPA) acid. In addition, patients taking typical antipsychotics showed decreased linoleic (LA), dihomo-γ-linolenic acid (DGLA), eicosapentaenoic (EPA) and docosatetraenoic (DTA) acid (p<0.01). Patients taking atypical antipsychotics showed decreased DHA (p<0.01) only. CONCLUSIONS PUFA concentrations in erythrocyte membranes are decreased in schizophrenia. Of particular importance in patients are lower concentrations of DHA and AA, two fatty acids that are abundant in the brain and important precursors in the cell-signalling cascade.

Binary alkaline earth oxide mixtures: Estimation of the excess thermodynamic properties and calculation of the phase diagrams

Abstract A survey of available experimental excess thermodynamic properties for the binary alkaline earth oxide mixtures is given. The known excess thermodynamic properties of the oxide mixtures are evaluated and missing values are estimated by analogy with the binary common-ion alkali halide mixtures. The phase diagrams of the oxide mixtures corresponding to the evaluated / estimated excess properties are calculated and compared with the available experimental phase diagrams.

In situ produced 14C by cosmic ray muons in ablating Antarctic ice

Abstract Samples of a core (52 m) of ablating Antarctic ice were analysed for 14CO and 14CO2 by accelerator mass spectrometry. The data were compared with a 14C in situ production model that includes muon capture in addition to oxygen spallation by neutrons. The analysis reveals significant in situ 14C at depths below 10 m, which we attribute to 14C production by cosmic ray muons. The age of the ice was determined as 9.3±0.4 14C ka BP.

Increase in SNR for 31P MR spectroscopy by combining polarization transfer with a direct detection sequence

The sensitivity of 31P MRS can be increased using higher magnetic fields, but also by using 1H to 31P polarization transfer techniques where the sensitivity is determined by the polarization of the proton spins and thus the signal‐to‐noise per unit time is unaffected by the slow T1 relaxation properties of the 31P spins. This implies that 31P spins can be manipulated during the T1 relaxation of the 1H spins without affecting the signal‐to‐noise of the 1H to 31P polarization transferred spins. It is shown here that by combining 1H to 31P polarization transfer with a direct 31P detection sequence in one repetition time, one can gain more signal‐to‐noise per unit of time as compared to a polarization transfer sequence alone. Proof of principle was demonstrated by phantom measurements and additionally the method was applied to the human calf muscle and to the human breast in vivo at 7T. Magn Reson Med, 2012.

On the estimation of thermodynamic excess properties of binary solid solutions

An empirical estimation method for the heat of formation of solid solutions of binary mixtures of non-metallic chemically coherent substances from the lattice enthalpies of the pure substances is described. The method was tested on binary mixtures of the following groups of chemically coherent substances: alkali halides, alkaline earth oxides, p-dihalobenzenes and the cryogenic noble gases. Irrespective of the type of substance (ionic, molecular, atomic), the heat of formation of the solid solution as a function of composition could be estimated in good agreement with the experimental heat of formation data. An empirical estimation method for the characteristic temperature, the ratio of excess enthalpy and excess entropy, of binary solid solutions is described.

Binary common-ion alkali halide mixtures; a uniform description of the liquid and solid state

Abstract Empirical relations for the thermodynamic excess behaviour of binary common-ion alkali halide mixtures were derived. For the liquid state this gave rise to G E(1) ( x , T g ) = 0.68 H E(1) ( x , T g ) and S E(1) ( x , T g )=0.32 H E(1) ( x , T g )/ T g , and for the solid state G E(1) ( x , T )= A (1− T / (2565 K)) x (1− x )(1+ B (1−2 x )), in which the A parameter can be calculated from relative differences in unit cell volumes of the pure solid components A calc (kJ mol −1 ) = 11.53(Δ V / V s )+ 89.40(Δ V / V s ) 2 and the B parameter which is a measure for the asymmetry can be calculated from the A parameter using B = 1.04 × 10 −2 ( A calc /kJ mol −1 ). The phase diagrams were calculated and compared with experimental phase diagram data for twenty binary common-ion alkali halide systems that show complete sub-solidus miscibility.

SCANNING FORCE MICROSCOPY OF CHOLESTEROL MULTILAYERS PREPARED WITH THE SPIN-COATING TECHNIQUE

Abstract Multilayers of amphiphilic molecules are often prepared by the repeated transfer of a substrate through a Langmuir monolayer at the air/water interface. The Langmuir-Blodgett technique is not a suitable method for the construction of multilayers of cholesterol. In this study, the application of the spin-coating technique to the preparation of cholesterol multilayers was investigated. Scanning force microscopy was used to examine the morphology and thickness of cholestrrol films as a function of the frequency with which the substrate was spun, the concentration of the solution used to spin-coat the substrate, and the type of solvent. It was found that the amount of cholesterol that was deposited on the substrate was proportional to the concentration of the solution and to the inverse of the square root of the spinning frequency. Experiments performed with different solvents showed that, in cholesterol films were deposited on the substrate if the vapour pressure of the solvent was higher than 10 kPa at 298 K. Our results suggest that well-ordered cholesterol multilayers with adjustable thicknesses can be prepared with the spin-coating technique.

Very little in situ produced radiocarbon retained in accumulating Antarctic ice

Ice samples from Dronning Maud Land, Antarctica, were analyzed for 14 CO2 and 14 CO by accelerator mass spectrometry. Only a small amount (2%) of in situ produced radiocarbon was detected. The calibrated radiocarbon ages, corrected for in situ produced 14 C, are in fair agreement with age estimates obtained from stratigraphical methods added to a gas inclusion model. The ages of the entrapped air range from recent to ca. 1200 AD. ” 2000 Elsevier Science B.V. All rights reserved.

Whole-body radiofrequency coil for (31) P MRSI at 7 T.

Widespread use of ultrahigh‐field 31P MRSI in clinical studies is hindered by the limited field of view and non‐uniform radiofrequency (RF) field obtained from surface transceivers. The non‐uniform RF field necessitates the use of high specific absorption rate (SAR)‐demanding adiabatic RF pulses, limiting the signal‐to‐noise ratio (SNR) per unit of time. Here, we demonstrate the feasibility of using a body‐sized volume RF coil at 7 T, which enables uniform excitation and ultrafast power calibration by pick‐up probes. The performance of the body coil is examined by bench tests, and phantom and in vivo measurements in a 7‐T MRI scanner. The accuracy of power calibration with pick‐up probes is analyzed at a clinical 3‐T MR system with a close to identical 1H body coil integrated at the MR system. Finally, we demonstrate high‐quality three‐dimensional 31P MRSI of the human body at 7 T within 5 min of data acquisition that includes RF power calibration. Copyright

In-situ radiocarbon production by neutrons and muons in an antarctic blue ice field at Scharffenbergbotnen: a status report

In the radiocarbon accelerator mass spectrometry ( (super 14) C AMS) analysis of gases obtained in a dry extraction from a 52-m Antarctic ice core, we observed (super 14) CO (sub 2) and (super 14) CO concentrations decreasing with depth. The concentrations are explained in terms of in-situ production by neutrons and captured muons in ablating ice. The ratio of the (super 14) CO (sub 2) concentration to that of (super 14) CO has been found to be constant at 1.9+ or -0.3. The ablation rates obtained of 42+ or -18 cm.yr (super -1) and 40+ or -13 cm.yr (super -1) for the neutron and muon components, respectively, are about three times higher than observed from stake readings. The discrepancy may point to an incomplete extraction of the dry extraction method. Using the constant ratio in (super 14) CO (sub 2) and (super 14) CO concentrations we correct for the in-situ component in the trapped (super 14) CO (sub 2) and deduce an age of 10,300+ or -900 BP for the ice core.