Astrophysics on the GRAPE Family of Special Purpose Computers

The GRAPE-4, the world's fastest computer in 1995-1997, has produced some major scientific results, through a wide diversity of large-scale simulations in astrophysics. Applications have ranged from planetary formation, through the evolution of star clusters and galactic nuclei, to the formation of galaxies and clusters of galaxies.Comment: 15 pages, to apper in Scienc

Star Cluster Ecology: VII The evolution of young dense star clusters containing primordial binaries

We study the first 100Myr of the evolution of isolated star clusters initially containing 144179 stars, including 13107 (10%) primordial hard binaries. Our calculations include the effects of both stellar and binary evolution. Gravitational interactions among the stars are computed by direct N-body integration using high precision GRAPE-6 hardware. The evolution of the core radii and central concentrations of our simulated clusters are compared with the observed sample of young (about 100Myr) star clusters in the large Magellanic cloud. Even though our simulations start with a rich population of primordial binaries, core collapse during the early phase of the cluster evolution is not prevented. Throughout the simulations, the fraction of binaries remains roughly constant (about 10%). Due to the effects of mass segregation the mass function of intermediate-mass main-sequence stars becomes as flat as $\alpha=-1.8$ in the central part of the cluster (where the initial Salpeter mass function had $\alpha=-2.35$). About 6--12% of the neutron stars were retained in our simulations; the fraction of retained black holes is 40--70%. In each simulation about three neutron stars become members of close binaries with a main-sequence companion. Such a binary will eventually become an x-ray binary, when the main-sequence star starts to fill its Roche lobe. Black holes are found more frequently in binaries; in each simulated cluster we find about 11 potential x-ray binaries containing a black hole. Abstract abbreviated....Comment: MNRAS in pres

Distributed N-body Simulation on the Grid Using Dedicated Hardware

We present performance measurements of direct gravitational N -body simulation on the grid, with and without specialized (GRAPE-6) hardware. Our inter-continental virtual organization consists of three sites, one in Tokyo, one in Philadelphia and one in Amsterdam. We run simulations with up to 196608 particles for a variety of topologies. In many cases, high performance simulations over the entire planet are dominated by network bandwidth rather than latency. With this global grid of GRAPEs our calculation time remains dominated by communication over the entire range of N, which was limited due to the use of three sites. Increasing the number of particles will result in a more efficient execution. Based on these timings we construct and calibrate a model to predict the performance of our simulation on any grid infrastructure with or without GRAPE. We apply this model to predict the simulation performance on the Netherlands DAS-3 wide area computer. Equipping the DAS-3 with GRAPE-6Af hardware would achieve break-even between calculation and communication at a few million particles, resulting in a compute time of just over ten hours for 1 N -body time unit. Key words: high-performance computing, grid, N-body simulation, performance modellingComment: (in press) New Astronomy, 24 pages, 5 figure

Re-evaluation of waist circumference in metabolic syndrome: a comparison between Japanese men and women

We re-evaluated the criteria for waist circumference to predict the accumulation of the components of metabolic syndrome. We used data for 3,185 Japanese, aged 20-79 years. Metabolic syndrome has recently been redefined by a new criterion in Japan, in which waist circumference cutoff points, i.e. 85 cm for men and 90 cm for women, are employed. Among the 3,185 Japanese considered in the present study, 335 men (26.8%) and 69 women (3.6%) were diagnosed as having metabolic syndrome. A cutoff point as a predictor for 2 or more components of metabolic syndrome was evaluated by sensitivity/specificity and a receiver operating characteristic (ROC) curve. The optimal point was estimated as being approximately 85 cm of waist circumference in men and 75 cm in women. We therefore recommend a cutoff value, 75 cm of waist circumference, for the criterion of metabolic syndrome in women

Creation, storage, and on-demand release of optical quantum states with a negative Wigner function

Highly nonclassical quantum states of light, characterized by Wigner functions with negative values, have been created so far only in a heralded fashion. In this case, the desired output emerges rarely and randomly from a quantum-state generator. An important example is the heralded production of high-purity single-photon states, typically based on some nonlinear optical interaction. In contrast, on-demand single-photon sources were also reported, exploiting the quantized level structure of matter systems. These sources, however, lead to highly impure output states, composed mostly of vacuum. While such impure states may still exhibit certain single-photon-like features such as anti-bunching, they are not enough nonclassical for advanced quantum information processing. On the other hand, the intrinsic randomness of pure, heralded states can be circumvented by first storing and then releasing them on demand. Here we propose such a controlled release, and we experimentally demonstrate it for heralded single photons. We employ two optical cavities, where the photons are both created and stored inside one cavity, and finally released through a dynamical tuning of the other cavity. We demonstrate storage times of up to 300 ns, while keeping the single-photon purity around 50% after storage. This is the first demonstration of a negative Wigner function at the output of an on-demand photon source or a quantum memory. In principle, our storage system is compatible with all kinds of nonclassical states, including those known to be essential for many advanced quantum information protocols.Comment: 14 pages, 5 figure

Cell Cycle Abnormality in Metabolic Syndrome and Nuclear Receptors as an Emerging Therapeutic Target

In recent years, many researchers have emphasized the importance of metabolic syndrome based on its increasing prevalence and its adverse prognosis due to associated chronic vascular complications. Upstream of a cluster of metabolic and vascular disorders is the accumulation of visceral adipose tissue, which plays a central role in the pathophysiology. In the accumulation of adipose tissues, cell cycle regulation is tightly linked to cellular processes such as proliferation, hypertrophy and apoptosis. In addition, various cell cycle abnormalities have also been observed in other tissues, such as kidneys and the cardiovascular system, and they are critically involved in the progression of disease. Here, we discuss cell cycle abnormalities in metabolic syndrome in various tissues. Furthermore, we describe the role of nuclear receptors in cell growth and survival, and glucose and lipid metabolism in the whole body. Therapeutic strategies for modulating various cell cycles in metabolic disorders by targeting nuclear receptors may overcome obesity and its chronic vascular complications in the future

Hemostasis for Massive Hemorrhage during Cesarean Section

Arterial ligation for massive hemorrhage during cesarean section may often fail to achieve hemostasis because of abundant collateral circulation. In recent years, various methods of hemostasis have been used, of which the most common are compression sutures, uterine balloon tamponade. In cases of massive hemorrhage, patients must be kept in good systemic condition, and local hemostasis must be achieved while paying attention to the possible occurrence of coagulopathy under monitoring of fibrinogen levels. When concomitant coagulopathy is present, local hemostasis is difficult to achieve because of hemorrhagic tendency. In such a case, obstetrical damage control procedures should be performed. First, the hemorrhagic area should be compressed with a towel or balloon, and at the same time, the artery should be blocked or compressed to reduce the blood flow into the uterus. The following resuscitation must also be implemented for warming intervention; blood transfusion to maintain the circulating blood volume; and the treatment of coagulopathy by “triple C supplement,” such as combined administration of fresh-frozen plasma and concentrated coagulation factors promptly to obtain a blood fibrinogen level of at least 150–200 mg/dL. If coagulopathy is eliminated, the conventional hemostatic procedures become effective. Hysterectomy is the last measure for hemostasis

Laparoscopic removal of uterine vertical compression sutures

AbstractUterine compression suturing is a relatively easy and effective way of hemostasis during cesarean section and is becoming widely accepted. However, complications such as necrosis or synechiae have been reported. We firstly report a case of laparoscopic removal of vertical compression sutures and discuss its benefits and improvements to be made. This case report is of a 32-year-old woman with placenta previa who received uterine vertical compression sutures for controlling massive bleeding during cesarean section. Because she complained of unbearable pelvic pain, laparoscopic compression suture removal was performed. Her pain was relieved after the threads were removed, suggesting that the compression sutures were the cause of her pelvic pain due to uterine ischemia. Although the risks of reoperation during the early postpartum period still exist, compression suture thread removal should be considered in cases of suspected uterine ischemia