Absolute pore size distributions from NMR

NMR measurements on core samples saturated with brine returns valuable information on the porous structure of the rock core. Monitoring a single fluid component in a relaxation experiment reflects the pore size distribution and thus the degree of sorting of the porous rock. The basic assumptions are that the mobility of the component confined in the porous rock is of such a value that a small fraction of the probing molecules experience the surfaces of the pores and that the surface relaxation strength is fairly independent of pore size. Then one may combine diffusion measurements at short observation times returning a value for the average surface to volume ratio with ordinary relaxation time measurements to obtain an absolute pore size distribution instead of the standard T2 distributions or T1-T2 correlated two dimensional distributions

Contrast Enhanced Magnetic Resonance Imaging of Amyloid-β Plaques in a Murine Alzheimer's Disease Model

Background: Early detection of amyloid-β (Aβ) aggregates is a critical step to improve the treatment of Alzheimer’s disease (AD) because neuronal damage by the Aβ aggregates occurs before clinical symptoms are apparent. We have previously shown that luminescent conjugated oligothiophenes (LCOs), which are highly specific towards protein aggregates of Aβ, can be used to fluorescently label amyloid plaque in living rodents. Objective: We hypothesize that the LCO can be used to target gadolinium to the amyloid plaque and hence make the plaque detectable by T1-weighted magnetic resonance imaging (MRI). Methods: A novel LCO-gadolinium construct was synthesized to selectively bind to Aβ plaques and give contrast in conventional T1-weighted MR images after intravenous injection in Tg-APPSwe mice. Results: We found that mice with high plaque-burden could be identified using the LCO-Gd constructs by conventional MRI. Conclusion: Our study shows that MR imaging of amyloid plaques is challenging but feasible, and hence contrast-mediated MR imaging could be a valuable tool for early AD detection.publishedVersio

Effect of powder metallurgy synthesis parameters for pure aluminium on resultant mechanical properties

In this work, pure aluminium powders of different average particle size were compacted, sintered into discs and tested for mechanical strength at different strain rates. The effects of average particle size (15, 19, and 35 μm), sintering rate (5 and 20 °C/min) and sample indentation test speed (0.5, 0.7, and 1.0 mm/min) were examined. A compaction pressure of 332 MPa with a holding time of six minutes was used to produce the green compacted discs. The consolidated green specimens were sintered with a holding time of 4 h, a temperature of 600 °C in an argon atmosphere. The resulting sintered samples contained higher than 85% density. The mechanical properties and microstructure were characterized using indentation strength measurement tests and SEM analysis respectively. After sintering, the aluminium grain structure was observed to be of uniform size within the fractured samples. The indentation test measurements showed that for the same sintering rate, the 35 μm powder particle size provided the highest radial and tangential strength while the 15 μm powder provided the lowest strengths. Another important finding from this work was the increase in sintered sample strength which was achieved using the lower sinter heating rate, 5 °C/min. This resulted in a tangential stress value of 365 MPa which was significantly higher than achieved, 244 MPa, using the faster sintering heating rate, 20 °C/min

Maternal smoking during pregnancy and subcutaneous fat mass in early childhood. The Generation R Study

Maternal smoking during pregnancy increases the risk of obesity in the offspring. Not much is known about the associations with other measures of body composition. We assessed the associations of maternal smoking during pregnancy with the development of subcutaneous fat mass measured as peripheral and central skinfold thickness measurements in early childhood, in a population-based prospective cohort study from early fetal life onward in the city of Rotterdam, The Netherlands. The study was performed in 907 mothers and their children at the ages of 1.5, 6 and 24 months. As compared to non-smoking mothers, mothers who continued smoking during pregnancy were more likely to have a younger age and a lower educational level. Their children had a lower birth weight, higher risk of small size for gestational age and were breastfed for a shorter duration (P-values <0.01). We did not observe differences in peripheral, central and total subcutaneous fat mass between the offspring of non-smoking mothers, mothers who smoked in first trimester only and mothers who continued smoking during pregnancy (P > 0.05). Also, the reported number of cigarettes smoked by mothers in both first and third trimester of pregnancy were not associated with peripheral, central and total subcutaneous fat mass in the offspring at the ages of 1.5, 6 and 24 months. Our findings suggest that fetal exposure to cigarette smoke during pregnancy does not influence subcutaneous fat mass in early childhood. Follow-up studies are needed in children at older ages and to identify associations of maternal smoking during pregnancy with other measures of body composition

Bruno Touschek: particle physicist and father of the electron-positron collider

This article gives a brief outline of the life and works of the Austrian physicist Bruno Touschek, who conceived, proposed and, 50 years ago, brought to completion the construction of AdA, the first electron-positron storage ring. The events which led to the approval of the AdA pro ject and the Franco-Italian collaboration which con- firmed the feasibility of electron-positron storage rings will be recalled. We shall illustrate Bruno Touschek's formation both as a theoretical physicist and as an expert in particle accelerators during the period be- tween the time he had to leave the Vienna Staat Gymnasium in 1938, because of his Jewish origin from the maternal side, until he arrived in Italy in the early 1950s and, in 1960, proposed to build AdA, in Frascati. The events which led to Touschek's collaboration with Rolf Wideroe in the construction of the first European betatron will be de- scribed. The article will make use of a number of unpublished as well as previously unknown documents, which include an early correspon- dence with Arnold Sommerfeld and Bruno Touschek's letters to his family in Vienna from Italy, Germany and Great Britain. The impact of Touschek's work on students and collaborators from University of Rome will be illustrated through his work on QED infrared radiative corrections to high energy e+e- experiments and the book Meccanica Statistica.Comment: To be published in EPJ

Maternal smoking during pregnancy and offspring overweight : is there a dose–response relationship? An individual patient data meta-analysis

We want to thank the funders of the individual studies: the UK Medical Research Council and the Wellcome Trust (Grant ref: 102215/2/13/2) and the University of Bristol, the Danish National Research Foundation, Pharmacy Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation, and the Health Foundation, the US NICHD (contracts no. 1-HD-4-2803 and no. 1-HD-1-3127, R01 HD HD034568), the NHMRC, the CNPq (Portuguese acronym for the National Research Council—grant 523474/96-2) and FAPESP (Portuguese acronym for the São Paulo State Research Council—grant 00/0908-7). We would like to thank the participating families of all studies for the use of data. For the ASPAC study, we want to thank the midwives for their help in recruiting families, and the whole ALSPAC team, which includes interviewers, computer and laboratory technicians, clerical workers, research scientists, volunteers, managers, receptionists, and nurses. This work was supported by the Deutschen Forschungsgesellschaft (German Research Foundation, DFG) [KR 1926/9-1, KU1443/4-1]. Dr. Gilman’s contribution was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.Peer reviewedPostprin

Absolute pore size distributions from NMR

NMR measurements on core samples saturated with brine returns valuable information on the porous structure of the rock core. Monitoring a single fluid component in a relaxation experiment reflects the pore size distribution and thus the degree of sorting of the porous rock. The basic assumptions are that the mobility of the component confined in the porous rock is of such a value that a small fraction of the probing molecules experience the surfaces of the pores and that the surface relaxation strength is fairly independent of pore size. Then one may combine diffusion measurements at short observation times returning a value for the average surface to volume ratio with ordinary relaxation time measurements to obtain an absolute pore size distribution instead of the standard T2 distributions or T1-T2 correlated two dimensional distributions

PROBING THE CONNECTIVITY BETWEEN PORES IN ROCK CORE SAMPLES

ABSTRACT By Nuclear Magnetic Resonance (NMR) measurements of relaxation and diffusion at a predefined observation time in 100 % brine saturated rock core samples it is possible to probe the connectivity between the pores within the sample. By plotting the observation time dependent diffusion coefficients as a function of the surface-to-volume ratio characteristic for each sample, it is possible to compare the connectivity between rock core samples

Absolute pore size distributions from NMR

NMR measurements on core samples saturated with brine returns valuable information on the porous structure of the rock core. Monitoring a single fluid component in a relaxation experiment reflects the pore size distribution and thus the degree of sorting of the porous rock. The basic assumptions are that the mobility of the component confined in the porous rock is of such a value that a small fraction of the probing molecules experience the surfaces of the pores and that the surface relaxation strength is fairly independent of pore size. Then one may combine diffusion measurements at short observation times returning a value for the average surface to volume ratio with ordinary relaxation time measurements to obtain an absolute pore size distribution instead of the standard T2 distributions or T1-T2 correlated two dimensional distributions