Event anisotropy in 4.2A GeV/c C+C collisions

The directed and elliptic flow of protons and negative pions in 4.2A GeV/c C+C collisions is studied using the Fourier analysis of azimuthal distributions. It is found that the protons exhibit pronounced directed flow, while the flow of pions is either non existent or too weak to be detected experimentally. Also, it is found that in the entire rapidity interval the elliptic flow is very small if not zero. These results are confirmed by the Quark-Gluon-String Model (QGSM) and the relativistic transport model (ART 1.0), except that these models predict very weak antiflow of pions. The more detailed comparison with the QGSM suggests that the decay of resonances and rescattering of secondaries dominantly determine the proton and negative pion flow at this energy.Comment: 7 pages, 3 figures, TeX file changed from double to single-spacin

Synchronising C/C++ and POWER

Shared memory concurrency relies on synchronisation primitives: compare-and-swap, load-reserve/store-conditional (aka LL/SC), language-level mutexes, and so on. In a sequentially consistent setting, or even in the TSO setting of x86 and Sparc, these have well-understood semantics. But in the very relaxed settings of IBM®, POWER®, ARM, or C/C++, it remains surprisingly unclear exactly what the programmer can depend on. This paper studies relaxed-memory synchronisation. On the hardware side, we give a clear semantic characterisation of the load-reserve/store-conditional primitives as provided by POWER multiprocessors, for the first time since they were introduced 20 years ago; we cover their interaction with relaxed loads, stores, barriers, and dependencies. Our model, while not officially sanctioned by the vendor, is validated by extensive testing, comparing actual implementation behaviour against an oracle generated from the model, and by detailed discussion with IBM staff. We believe the ARM semantics to be similar. On the software side, we prove sound a proposed compilation scheme of the C/C++ synchronisation constructs to POWER, including C/C++ spinlock mutexes, fences, and read-modify-write operations, together with the simpler atomic operations for which soundness is already known from our previous work; this is a first step in verifying concurrent algorithms that use load-reserve/store-conditional with respect to a realistic semantics. We also build confidence in the C/C++ model in its own terms, fixing some omissions and contributing to the C standards committee adoption of the C++11 concurrency model

CRAF/Cassini (C/C)

The Comet Rendezvous Asteroid Flyby (CRAF) is a mission to rendezvous with the comet Tempel 2 and to station-keep at the comet for a period of 2.6 years, including the comet perihelion. There is a flyby of the asteroid Mandeville prior to the arrival at Tempel 2. The Cassini is a mission to place a spacecraft in a highly elliptical orbit around the planet Saturn and deliver a probe to the surface of its satellite Titan. There is a flyby of the asteroid 1989 UR1 prior to arrival at Saturn. Coverage goals for the two missions are explained. Information is given in tabular form for frequency assignments, telemetry, command, navigation, and tracking support responsibility

Library abstraction for C/C++ concurrency

When constructing complex concurrent systems, abstraction is vital: programmers should be able to reason about concurrent libraries in terms of abstract specifications that hide the implementation details. Relaxed memory models present substantial challenges in this respect, as libraries need not provide sequentially consistent abstractions: to avoid unnecessary synchronisation, they may allow clients to observe relaxed memory effects, and library specifications must capture these. In this paper, we propose a criterion for sound library abstraction in the new C11 and C++11 concurrency model, generalising the standard sequentially consistent notion of linearizability. We prove that our criterion soundly captures all client-library interactions, both through call and return values, and through the subtle synchronisation effects arising from the memory model. To illustrate our approach, we verify implementations against specifications for the lock-free Treiber stack and a producer-consumer queue. Ours is the first approach to compositional reasoning for concurrent C11/C++11 programs. 1

Murahashi Cross‐Coupling at −78 °C:A One-Pot Procedure for Sequential C-C/C-C, C-C/C-N, and C-C/C-S Cross-Coupling of Bromo-Chloro-Arenes

The coupling of organolithium reagents, including strongly hindered examples, at cryogenic temperatures (as low as -78 degrees C) has been achieved with high-reactivity Pd-NHC catalysts. A temperature-dependent chemoselectivity trigger has been developed for the selective coupling of aryl bromides in the presence of chlorides. Building on this, a one-pot, sequential coupling strategy is presented for the rapid construction of advanced building blocks. Importantly, one-shot addition of alkyllithium compounds to Pd cross-coupling reactions has been achieved, eliminating the need for slow addition by syringe pump

Proton stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c

The shape of proton rapidity distributions is analysed in terms of their Gaussian components, and the average rapidity loss is determined in order to estimate the amount of stopping in C+C, d+C, C+Ta and d+Ta collisions at 4.2A GeV/c. Three Gaussians correspond to the nuclear transparency and describe well all peripheral and also C+C central collisions. Two-component shape is obtained in case of d+C and C+Ta central collisions. Finally one Gaussian, found in d+Ta central collisions, corresponds to the full stopping. The calculated values of the average rapidity loss support the qualitative relationship between the number of Gaussian components and the corresponding stopping power. It is also observed, in central collisions, that the average rapidity loss increases with the ratio of the number of target and the number of projectile participants.Comment: 9 pages REVTeX, 1 PS figure replaced, to be published in Phys.Rev.

Tandemly repeated C-C-C-C-A-A hexanucleotide of Tetrahymena rDNA is present elsewhere in the genome and may be related to the alteration of the somatic genome.

The ribosomal RNA genes of the Tetrahymena macronucleus exist as extrachromosomal, linear molecules. The termini of these molecules have been shown to contain the tandemly repeated hexanucleotide (C-C-C-C-A-A)n. In this study the same or related sequences were found in other locations of the genome. Using the depurination method, we showed that macronuclear DNA contained this sequence even after rDNA had been removed. The sequence was found mainly in the repetitive fraction of the DNA. The presence of this sequence in both the macronucleus and the micronucleus was also shown by Southern hybridization using C-C-C-C-A-A repeat as a probe. Comparison between the hybridization patterns of macronuclei and micronuclei reveals interesting differences. Whereas the two nuclei share the same genetic origin, the majority of the restriction enzyme digestion sites flanking the C-C-C-C-A-A repeat appear to be different. Such a difference was found to be specific for this sequence, because it was not detected when other sequences were used for hybridization. These results suggest that some kind of alteration has occurred in the genome during the formation of the macronucleus, and that the C-C-C-C-A-A repeat may be related to this process

Think global, act local: Burn care in a resource-limited setting

Summary The few studies that are available show that the burden of burn injuries remains disproportionally high in resource-limited settings. These settings have a high incidence of burns, and due to limited access to safe burn care the mortality and morbidity remains high in these settings. Of all fire-related cases of mortality worldwide, 95% occur in resource-limited settings. Patients who survive are likely to face serious complications, such as burn scar contractures. During my work as a global health specialist, we, the Tanzanian doctors and I, were indeed confronted with a high incidence of burn injuries. We had limited treatment options available and experienced high mortality and morbidity due to burns. From the literature it became evident that little evidence was available regarding burn care in resource-limited settings. Few studies are available on the outcomes of skin grafting procedures, no studies were available that showed how often burn scar contractures developed, and none of the studies were able to prove whether contracture release surgery was effective in the longer-term. There are valuable and useful treatment guidelines available from the International Society for Burn Injuries, specifically aimed for resource-limited settings. However, the Society also pointed out that the evidence for the guidelines was scarce and recommendations were frequently based on expert opinion. Outline of this thesis To evaluate the current state of burn care and to guide future improvements in burn care of underserved populations in resource-limited settings, insight into current treatment and its outcomes is of vital importance. The studies described in this thesis concentrate on three areas: short-term reconstructive surgical missions (Part I); acute burn care (Part II); and burn scar contracture release surgery (Part III)