3,494 research outputs found
Forming the Moon from terrestrial silicate-rich material
Recent high-precision measurements of the isotopic composition of lunar rocks
demonstrate that the bulk silicate Earth and the Moon show an unexpectedly high
degree of similarity. This is inconsistent with one of the primary results of
classic dynamical simulations of the widely accepted giant impact model for the
formation of the Moon, namely that most of the mass of the Moon originates from
the impactor, not Earth.
Resolution of this discrepancy without changing the main premises of the
giant impact model requires total isotopic homogenisation of Earth and impactor
material after the impact for a wide range of elements including O, Si, K, Ti,
Nd and W. Even if this process could explain the O isotope similarity, it is
unlikely to work for the much heavier, refractory elements. Given the
increasing uncertainty surrounding the giant impact model in light of these
geochemical data, alternative hypotheses for lunar formation should be
explored. In this paper, we revisit the hypothesis that the Moon was formed
directly from terrestrial mantle material. We show that the dynamics of this
scenario requires a large amount of energy, almost instantaneously generated
additional energy. The only known source for this additional energy is nuclear
fission. We show that it is feasible to form the Moon through the ejection of
terrestrial silicate material triggered by a nuclear explosion at Earths
core-mantle boundary (CMB), causing a shock wave propagating through the Earth.
Hydrodynamic modelling of this scenario shows that a shock wave created by
rapidly expanding plasma resulting from the explosion disrupts and expels
overlying mantle and crust material.Comment: 26 pages, 5 figures, 1 tabl
A risk evaluation of traces of packaging materials in former food products intended as feed materials
Meta-analysis of risk of developing malignancy in congenital choledochal malformation
BackgroundCholedochal malformations comprise various congenital cystic dilatations of the extrahepatic and/or intrahepatic biliary tree. Choledochal malformation is generally considered a premalignant condition, but reliable data on the risk of malignancy and optimal surgical treatment are lacking. The objective of this systematic review was to assess the prevalence of malignancy in patients with choledochal malformation and to differentiate between subtypes. In addition, the risk of malignancy following cystic drainage versus complete cyst excision was assessed. MethodsA systematic review of PubMed and Embase databases was performed in accordance with the PRISMA statement. A meta-analysis of the risk of malignancy following cystic drainage versus complete cyst excision was undertaken in line with MOOSE guidelines. Prevalence of malignancy was defined as the rate of biliary cancer before resection, and malignant transformation as new-onset biliary cancer after surgery. ResultsEighteen observational studies were included, reporting a total of 2904 patients with a median age of 36 years. Of these, 312 in total developed a malignancy (107 per cent); the prevalence of malignancy was 73 per cent and the rate of malignant transformation was 34 per cent. Patients with types I and IV choledochal malformation had an increased risk of malignancy (P = 0016). Patients who underwent cystic drainage had an increased risk of developing biliary malignancy compared with those who had complete cyst excision, with an odds ratio of 397 (95 per cent c.i. 240 to 655). ConclusionThe risk of developing malignancy among patients with choledochal malformation was almost 11 per cent. The malignancy risk following cystic drainage surgery was four times higher than that after complete cyst excision. Complete surgical resection is recommended in patients with choledochal malformation. Choledochal cysts should be resecte
Post-silicon tuning capabilities of 45nm low-power CMOS digital circuits
Adaptive circuit techniques enable modification of power-performance efficient circuit operation. Yet it is unclear if such techniques remain effective in modern deep-submicron CMOS. In this paper we examine the technological boundaries of supply voltage scaling and body biasing in 45nm low-power CMOS. We demonstrate that there exists an effective tuning range for power-performance and performance variability control. Our analysis is supported by ring oscillator test-chip measurements
Comment on:Static cold storage compared with normothermic machine perfusion of the liver and effect on ischaemic-type biliary lesions after transplantation: a propensity score-matched study
Model infrared spectra of passively heated proto-planetary disks surrounding intermediate-mass pre-main-sequence stars
Interfacial tension and nucleation in mixtures of colloids and long ideal polymer coils
Mixtures of ideal polymers with hard spheres whose diameters are smaller than
the radius of gyration of the polymer, exhibit extensive immiscibility. The
interfacial tension between demixed phases of these mixtures is estimated, as
is the barrier to nucleation. The barrier is found to scale linearly with the
radius of the polymer, causing it to become large for large polymers. Thus for
large polymers nucleation is suppressed and phase separation proceeds via
spinodal decomposition, as it does in polymer blends.Comment: 4 pages (v2 includes discussion of the scaling of the interfacial
tension along the coexistence curve and its relation to the Ginzburg
criterion
- …