Magnetic resonance imaging in the prenatal diagnosis of neural tube defects

OBJECTIVE: To assess the role of magnetic resonance imaging (MRI) in the prenatal diagnosis of neural tube defects (NTDs). BACKGROUND: NTDs comprise a heterogeneous group of congenital anomalies that derive from the failure of the neural tube to close. Advances in ultrasonography and MRI have considerably improved the diagnosis and treatment of NTDs both before and after birth. Ultrasonography is the first technique in the morphological study of the fetus, and it often makes it possible to detect or suspect NTDs. Fetal MRI is a complementary technique that makes it possible to clear up uncertain ultrasonographic findings and to detect associated anomalies that might go undetected at ultrasonography. The progressive incorporation of intrauterine treatments makes an accurate diagnosis of NTDs essential to ensure optimal perinatal management. The ability of fetal MRI to detect complex anomalies that affect different organs has been widely reported, and it can be undertaken whenever NTDs are suspected. CONCLUSION: We describe the normal appearance of fetal neural tube on MRI, and we discuss the most common anomalies involving the structures and the role of fetal MRI in their assessment. KEY POINTS: • To learn about the normal anatomy of the neural tube on MRI • To recognise the MR appearance of neural tube defects • To understand the value of MRI in assessing NTD

Environment-driven reactivity of H2 on PdRu surface alloys

The dissociative adsorption of molecular hydrogen on PdxRu1−x/Ru(0001) (0 ≤ x ≤ 1) has been investigated by means of He atom scattering, Density Functional Theory and quasi-classical trajectory calculations. Regardless of their surroundings, Pd atoms in the alloy are always less reactive than Ru ones. However, the reactivity of Ru atoms is enhanced by the presence of nearest neighbor Pd atoms. This environment-dependent reactivity of the Ru atoms in the alloy provides a sound explanation for the striking step-like dependence of the initial reactive sticking probability as a function of the Pd concentration observed in experiments. Moreover, we show that these environment-dependent effects on the reactivity of H2 on single atoms allow one to get around the usual constraint imposed by the Brønsted–Evans–Polanyi relationship between the reaction barrier and chemisorption energy.Fil: Ramos Acevedo, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Minniti, M.. Universidad Autónoma de Madrid; EspañaFil: Díaz, C.. Universidad Autónoma de Madrid; EspañaFil: Farias, D.. Universidad Autónoma de Madrid; EspañaFil: Miranda, R.. Universidad Autónoma de Madrid; España. Instituto Madrileño de Estudios Avanzados en Nanociencia; EspañaFil: Martín, F.. Universidad Autónoma de Madrid; España. Instituto Madrileño de Estudios Avanzados en Nanociencia; EspañaFil: Martinez, Alejandra Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; ArgentinaFil: Busnengo, Heriberto Fabio. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentin

Numerical study of dark current dynamics in a high-gradient backward travelling wave accelerating cavity using the electromagnetic simulation software CST studio.

High-Gradient accelerating cavities are one of the main research lines in the development of compact linear colliders. However, the operation of such cavities is currently limited by nonlinear effects that are intensified at high electric fields, such as dark currents and radiation emission or RF breakdowns. A new normal-conducting High-Gradient S-band Backward Travelling Wave accelerating cavity for medical application (v=0.38c) designed and constructed at Conseil Européen pour la Recherche Nucléaire (CERN) is being tested at Instituto de Física Corpuscular (IFIC) High Power RF Laboratory. The objective consists of studying its viability in the development of compact linear accelerators for hadrontherapy treatments in hospitals. Due to the high surface electric field in the cavity, electrons are emitted following Fowler- Nordheim equation, also known as dark currents. The emission and dynamic of these electrons are of fundamental importance on different phenomena such as RF Breakdowns or radiation dose emission. In this work, 3D electromagnetic numerical simulations have been performed using the computer simulation technology software CST Studio Suite. Then, the resulting EM field maps are used to study the emission and electron dynamics inside the cavity. The simulation results are compared with experimental data and first conclusions discussed

Novel reaction force for ultra-relativistic dynamics of a classical point charge

The problem of the electromagnetic radiation of an accelerated charged particle is one of the most controversial issues in Physics since the beginning of the last century, representing one of the most popular unsolved problems of the Modern Physics. Different equations of motion have been proposed throughout history for a point charge including the electromagnetic radiation emitted, but all these expressions show some limitations. An equation based on the principle of conservation of energy is proposed in this work for the ultra-relativistic motion. Different examples are analyzed showing that the energy lost by the charge agrees with the Li\'enard formula. This proposed equation has been compared with the Landau-Lifshitz equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula.Comment: 9 pages, 10 figure

Relativistic particle motion of a charge including the radiation reaction

The problem of the electromagnetic radiation of an accelerated charged particle is one of the most controversial issues in Physics since the beginning of the last century representing one of the most popular unsolved problems of the Modern Physics. Different equations of motion for a point charge including the electromagnetic radiation emitted have been proposed throughout history, but all these expressions show some limitations. An equation based on the principle of conservation of energy is proposed for the ultra-relativistic motion. Different examples are analyzed showing that the energy lost by the charge agrees with the relativistic generalization of the Larmor formula. This proposed equation has been compared with the Landau-Lifshitz equation obtaining a good agreement in the range of application of the Landau-Lifshitz formula. Finally, it is discussed a possible variation of the typical relativistic particle integrators (e.g. Boris, Vay or Higuera-Cary methods) in order to include the radiation reaction

Molecular prevalence of Coxiella burnetii in bulk-tank milk from bovine dairy herds : systematic review and meta-analysis

Coxiella burnetii is an obligate intracellular zoonotic bacterium that causes Q fever. Ruminants, including cattle, are broadly known to be reservoirs for this bacterium. Since 2006, many research groups have evaluated the herd-level prevalence of C. burnetii in cattle by molecular techniques on composite milk samples. This study explored the global C. burnetii herd-level prevalence from studies done on bovine bulk-tank milk (BTM) samples using PCR-based analysis. Also, moderators were investigated to identify sources of heterogeneity. Databases (CAB Abstracts, Medline via Ovid, PubMed, Web of Science and Google Scholar) were searched for index articles on C. burnetii prevalence in BTM samples by PCR published between January-1973 and November-2018. Numerous studies (1054) were initially identified, from which seventeen original publications were included in the meta-analysis based on the pre-defined selection criteria. These studies comprised 4031 BTM samples from twelve countries. A random-effects model was used because of considerable heterogeneity (I2 = 98%) to estimate the herd-level prevalence of C. burnetii as 37.0%(CI95%25.2–49.5%). The average herd size appeared to account for a high level of the heterogeneity. No other moderators (geographic location, gross national income or notification criteria for Q fever) seemed to be determinant. This systematic evaluation demonstrated a high molecular prevalence of C. burnetii in BTM samples both in European and non-European countries, evidencing a widespread herd-level circulation of this agent in bovine dairy farms around the world. Meta-regression showed herd size as the most relevant moderator with the odds of a BTM sample testing positive doubling with every unit increase

Tuning the size, composition and structure of Au and Co50Au50 Nanoparticles by High-Power Impulse Magnetron Sputtering in gas-phase Synthesis

Gas-phase synthesis of nanoparticles with different structural and chemical distribution is reported using a circular magnetron sputtering in an ion cluster source by applying high-power impulses. The influence of the pulse characteristics on the final deposit was evaluated on Au nanoparticles. The results have been compared with the more common direct current approach. In addition, it is shown for the first time that high-power impulses in magnetron based gas aggregation sources allows the growth of binary nanoparticles, CoAu in this case, with a variety of crystalline and chemical arrangements which are analyzed at the atomic level

Study of the RF pulse heating phenomenon in high gradient accelerating devices by means of analytical approximations

The main objective of this work is to present a simple method, based on analytical expressions, for obtaining a quick approximation of the temperature rise due to the Joule effect inside the metallic walls of an RF accelerating device. This proposal relies on solving the 1D heat-transfer equation for a thick wall, where the heat sources inside the wall are the ohmic losses produced by the RF electromagnetic fields penetrating the metal with finite electrical conductivity. Furthermore, it is discussed how the theoretical expressions of this method can be applied to obtain an approximation to the temperature increase in realistic 3D RF accelerating structures, taking as an example the cavity of an RF electron gun. These theoretical results have been benchmarked with numerical simulations carried out with commercial finite-element method codes, finding good agreement among them

Two-dimensional simulation of the electron transport in a photomultiplier tube

Photomultiplier tubes are widely used in experimental physics because they convert small light signals into a measurable electric current. Although their working principle is well known, it is very difficult to find simulations of the electron transport in these devices. For this reason, the electron transport in the Hamamatsu R13408-100 photomultiplier tube has been simulated in 2D. The software SUPERFISH is used for calculating the electrostatic fields and the Boris method for the effective electron dynamics. The secondary electron emission in the dynodes is implemented using an effective electron model and the modified Vaughan’s model. Some figures of merit for photomultiplier tubes (e.g. the gain, the electron transit time or the transit time spread) in function of the supply voltage and an external magnetic field have been studied obtaining a good qualitative accordance with the Hamamatsu datasheet. In further studies, we are going to compare our simulations with experimental measurements