Why electrons pass through very tiny wires less smoothly than expected: Light shed on 20-year-old mystery

Aug. 29, 2013 — Groningen scientists have found an explanation for a mystery that has been puzzling the physics community since 1995. In the journal Nature on Aug. 28, they explain why electrons pass through very tiny wires (known as quantum point contacts) less smoothly than expected.The observations of the group led by Prof. C.H. (Caspar) van der Wal of the Zernike Institute for Advanced Materials of the University of Groningen will affect electronics on a nanoscale: ‘Our thinking about this has been too naïve so far.’The mystery concerns nano wires that are about a hundred atoms wide. As early as 1988, the Dutch physicist Bart van Wees, currently a professor at the Zernike Institute, discovered a remarkable effect in this kind of wire. When he made them wider, the flow did not increase gradually but in a stepwise manner. Van der Wal: ‘This could be explained by quantum effects that occurred in the wires. There is a formula that describes precisely how these steps occur.’Unexpected peakHowever, in the first step, with the thinnest wires, a tiny exception in the gradual increase was consistently found. …

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No danger of cancer through gene therapy virus, study suggests

June 19, 2013 — In fall 2012, the European Medicines Agency (EMA) approved the modified adeno-associated virus AAV-LPL S447X as the first ever gene therapy for clinical use in the Western world. uniQure, a Dutch biotech company, had developed AAV-LPL S447X for the treatment of a rare inherited metabolic disease called lipoprotein lipase deficiency (LPLD) which affects approximately one or two out of one million people. The disease causes severe, life-threatening inflammations of the pancreas. Afflicted individuals carry a defect in the gene coding for the lipoprotein lipase enzyme which is necessary for breakdown of fatty acids. AAV-LPLS447X shall be used as a viral vector to deliver an intact gene copy to affected cells.The viruses modified for gene therapy cannot integrate their DNA into the host cell genome, because they lack a particular enzyme needed for this. Nevertheless, integration may happen occasionally. “We had to exclude that AAV-LPLS447X tends to integrate at sites in the genome where this integration might activate cancer-promoting genes. This is exactly what had been observed with a virus used for gene therapy,” says Dr. Manfred Schmidt, a molecular biologist. Schmidt leads a research group at NCT Heidelberg and DKFZ that studies the safety of gene-therapeutic methods.In collaboration with scientists from uniQure, the Heidelberg researchers analyzed the genome of five LPLD patients who had been treated with AAV-LPLS447X . …

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Severe maternal complications less common during home births, study suggests

June 14, 2013 — Women with low risk pregnancies who choose to give birth at home have a lower risk of severe complications than women who plan a hospital birth, finds a new study.However, the authors stress that the overall risk of severe problems is small and the results are significant only for women who have previously given birth — not for first-time mums.The relative safety of planned home births is a topic of continuous debate, but studies have so far been too small to compare severe maternal complications between planned home and planned hospital birth among low risk women.Of all Western countries, the Netherlands has the highest percentage of home births, assisted by a primary care midwife.So a team of Dutch researchers decided to test whether low risk women at the onset of labour with planned home birth have a higher rate of rare but severe outcomes (known as severe acute maternal morbidity or SAMM) than those with planned hospital births.This was defined as admission to an intensive care unit, uterine rupture, eclampsia or major obstetric haemorrhage (requiring a large blood transfusion). Other adverse complications included postpartum haemorrhage (severe loss of blood after delivery) and manual removal of the placenta. Using data from a national study into maternal morbidity and national birth registry data from 1 August 2004 to 1 August 2006, they identified over 146,000 low risk women in primary care at the onset of labour.Results were adjusted for several factors including gestational age, maternal age, ethnic background and socioeconomic status.Of the 146,752 women included in the study, 92,333 (63%) had a planned home birth and 54,419 (37%) a planned hospital birth.For women having their first baby (nulliparous women), the rate of severe outcomes for a planned home birth was 2.3 per 1000 compared with 3.1 per 1000 for a planned hospital birth. The rate of postpartum haemorrhage was 43.1 per 1000 for a planned home compared with 43.3 per 1000 for a planned hospital birth.For women who had previously given birth (parous women), the rate of severe outcomes for a planned home birth was 1 per 1000 compared with 2.3 per 1000 for a planned hospital birth. The rate of postpartum haemorrhage was 19.6 per 1000 for a planned home compared with 37.6 per 1000 for a planned hospital birth.Adverse outcomes were less common among planned home births than among planned hospital births but differences were only statistically significant for women who had previously given birth.The researchers emphasise that their findings may only apply to regions where midwives are well trained to assist women at home births and where facilities for transfer of care and transportation in case of emergencies are adequate.However, they say the fact that they did not find higher rates of severe complications among planned home births “should not lead to complacency” and that “every avoidable adverse maternal outcome is one too many.”Overall, they conclude: “Low risk women in primary care with planned home birth at the onset of labour had a lower rate of severe acute maternal morbidity, postpartum haemorrhage, and manual removal of placenta than those with planned hospital birth. These differences were statistically significant for parous women.”

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Building 3-D fractals on a nano scale

May 31, 2013 — It starts with one 3D structure with eight planes, an octahedron. This repeats itself to smaller octahedra: 625 after just four steps. At every corner of a new octahedron, a successive octahedron is formed. A truly fascinating 3D fractal ‘building’ is formed on the micro and nano scale. It can be used for high performance filtering, for example.Share This:Scientists of the MESA+ Institute for Nanotechnology of the University of Twente in The Netherlands present these structures in the Journal of Micromechanics and Microengineering (JMM).A fractal is a geometric structure that can repeat itself towards infinity. Zooming in on a fragment of it, the original structure becomes visible again. A major advantage of a 3D fractal is that the effective surface rises with every next step. Looking at the octahedra, after four steps the final structure is not much bigger than the original octahedron, but the effective surface has been multiplied by 6.5. The smallest octahedra are 300 nanometers in size, with on every corner a nano pore of 100 nanometer. Having 625 of these nano pores on a limited surface area, a very effective filer with low flow resistance is formed. …

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