Determination of the hydrodynamic performance of marine propellers using fibre Bragg gratings

Downloading of the abstract is permitted for personal use only. A critical aspect in the design of marine propellers is their hydrodynamic performance which, when evaluated experimentally, requires a number of parameters to be monitored at the same time, i.e.The thrust and torque a propeller generates as well as the propeller shaft and vessel speed. In this investigation, three of those parameters are measured using Fibre Bragg Grating-based sensors, thus allowing for computationally derived performance values to be verified. For that purpose, open water tests were carried out where an instrumented propeller shaft was installed into a research vessel and measurements taken, evaluated and the results compared favorably with advanced computer-based simulations

Limits of Binaries That Can Be Characterized by Gravitational Microlensing

Due to the high efficiency of planet detections, current microlensing planet searches focus on high-magnification events. High-magnification events are sensitive to remote binary companions as well and thus a sample of wide-separation binaries are expected to be collected as a byproduct. In this paper, we show that characterizing binaries for a portion of this sample will be difficult due to the degeneracy of the binary-lensing parameters. This degeneracy arises because the perturbation induced by the binary companion is well approximated by the Chang-Refsdal lensing for binaries with separations greater than a certain limit. For binaries composed of equal mass lenses, we find that the lens binarity can be noticed up to the separations of $\sim 60$ times of the Einstein radius corresponding to the mass of each lens. Among these binaries, however, we find that the lensing parameters can be determined only for a portion of binaries with separations less than $\sim 20$ times of the Einstein radius.Comment: 5 pages, 3 figures, 1 tabl

Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2

The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighbouring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP2 and MoP2, that are type-II Weyl semimetals with robust Weyl points. We present transport and angle resolved photoemission spectroscopy measurements, and first principles calculations. Our single crystals of WP2 display an extremely low residual low-temperature resistivity of 3 nohm-cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. These properties are likely a consequence of the novel Weyl fermions expressed in this compound. We observe a large suppression of charge carrier backscattering in WP2 from transport measurements.Comment: Appeared in Nature Communication

Genetic Modifiers of Systemic Lupus Erythematosus in FcγRIIB−/− Mice

FcγRIIB is a potent lupus susceptibility gene as demonstrated by the observation that mice deficient in this molecule develop spontaneous antinuclear antibodies (ANA) and fatal glomerulonephritis when on the C57BL/6 background. To determine the mechanisms underlying the epistasis displayed by this gene we have constructed hybrids between FcγRIIB−/− and the systemic lupus erythematosus (SLE) modifiers yaa and lpr and the susceptibility locus Sle1. Sle1 and B6.RIIB−/− are both physically and functionally coupled; compound heterozygotes of Sle1 and B6.RIIB−/− develop significant disease, while single heterozygotes display no evidence of autoimmunity or disease, indicating that these genes lie on the same genetic pathway resulting in the loss of tolerance to nuclear antigens. However, the generation of ANA in itself is insufficient to account for the severity of autoimmune disease in this model, as demonstrated by analysis of yaa and lpr hybrids. Thus, B6.RIIB−/−/lpr mice are protected from disease progression, despite equivalent titers of ANA. In contrast, B6.RIIB−/−/yaa mice have significantly enhanced disease despite reduced ANA titers. Yaa modifies the specificity and thus the pathogenicity of the B6. RIIB−/− ANA, by converting them to antinucleolar antibodies. In addition to these known modifier pathways, we have discovered two novel, recessive loci contributed by the C57BL/6 genome that are required for the ANA phenotype, further indicating the epistatic properties of this SLE model

Microlensing Detections of Planets in Binary Stellar Systems

We demonstrate that microlensing can be used for detecting planets in binary stellar systems. This is possible because in the geometry of planetary binary systems where the planet orbits one of the binary component and the other binary star is located at a large distance, both planet and secondary companion produce perturbations at a common region around the planet-hosting binary star and thus the signatures of both planet and binary companion can be detected in the light curves of high-magnification lensing events. We find that identifying planets in binary systems is optimized when the secondary is located in a certain range which depends on the type of the planet. The proposed method can detect planets with masses down to one tenth of the Jupiter mass in binaries with separations <~ 100 AU. These ranges of planet mass and binary separation are not covered by other methods and thus microlensing would be able to make the planetary binary sample richer.Comment: 5 pages, two figures in JPG forma

Logarithmic perturbation theory for quasinormal modes

Logarithmic perturbation theory (LPT) is developed and applied to quasinormal modes (QNMs) in open systems. QNMs often do not form a complete set, so LPT is especially convenient because summation over a complete set of unperturbed states is not required. Attention is paid to potentials with exponential tails, and the example of a Poschl-Teller potential is briefly discussed. A numerical method is developed that handles the exponentially large wavefunctions which appear in dealing with QNMs.Comment: 24 pages, 4 Postscript figures, uses ioplppt.sty and epsfig.st

C programs for solving the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap

We present C programming language versions of earlier published Fortran programs (Muruganandam and Adhikari, Comput. Phys. Commun. 180 (2009) 1888) for calculating both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation. The GP equation describes the properties of dilute Bose-Einstein condensates at ultra-cold temperatures. C versions of programs use the same algorithms as the Fortran ones, involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method. In a one-space-variable form of the GP equation, we consider the one-dimensional, two-dimensional, circularly-symmetric, and the three-dimensional spherically-symmetric harmonic-oscillator traps. In the two-space-variable form, we consider the GP equation in two-dimensional anisotropic and three-dimensional axially-symmetric traps. The fully-anisotropic three-dimensional GP equation is also considered. In addition to these twelve programs, for six algorithms that involve two and three space variables, we have also developed threaded (OpenMP parallelized) programs, which allow numerical simulations to use all available CPU cores on a computer. All 18 programs are optimized and accompanied by makefiles for several popular C compilers. We present typical results for scalability of threaded codes and demonstrate almost linear speedup obtained with the new programs, allowing a decrease in execution times by an order of magnitude on modern multi-core computers.Comment: 8 pages, 1 figure; 18 C programs included (to download, click other and download the source

Sonographic and genetic findings in a case of asymptomatic spontaneous uterine rupture

An asymptomatic 25-year-old G4P0120 with history significant for cervical insufficiency and classical cesarean delivery 12.5 months prior to conception underwent routine transabdominal ultrasound at 36w4d; umbilical cord was found to be protruding into a fluid-filled pouch extruding from the lower uterine segment. During emergent cesarean delivery, a full-thickness uterine rupture was confirmed; the fetal cranium and umbilical cord were extrauterine. Maternal genotype revealed greater than expected minor allele frequencies for several collagen genes. Maternal gene expression (mRNA) and corresponding microRNA expression of these collagen genes differed several-fold between her G3 (cervical insufficiency, classical cesarean delivery) and G4 (uterine rupture) pregnancies. This case highlights that (1) cervical insufficiency, poor myometrial wound healing, and uterine rupture may co-occur and pathophysiology may be related to collagen abnormalities and (2) asymptomatic uterine rupture can be detected sonographically, even in late pregnancy. Clinicians should remain vigilant for the possibility of uterine rupture, particularly among high-risk patients