Towards a First Vertical Prototyping of an Extremely Fine-Grained Parallel Programming Approach

Explicit multithreading (XMT) is a parallel programming approach for exploiting on-chip parallelism. XMT introduces a computational framework with (1) a simple programming style that relies on fine-grained PRAM-style algorithms; (2) hardware support for low-overhead parallel threads, scalable load balancing, and efficient synchronization. The missing link between the algorithmic-programming level and the architecture level is provided by the first prototype XMT compiler. This paper also takes this new opportunity to evaluate the overall effectiveness of the interaction between the programming model and the hardware, and enhance its performance where needed, incorporating new optimizations into the XMT compiler. We present a wide range of applications, which written in XMT obtain significant speedups relative to the best serial programs. We show that XMT is especially useful for more advanced applications with dynamic, irregular access patterns, where for regular computations we demonstrate performance gains that scale up to much higher levels than have been demonstrated before for on-chip systems.     

Finding Euler tours in parallel

The problem of finding Euler tours in directed and undirected Euler graphs is considered. O(log |V|) time algorithms are given using a linear number of processors on a concurrent-read concurrent-write parallel RAM.     

Turing degrees of reals of positive effective packing dimension

A relatively longstanding question in algorithmic randomness is Jan Reimann's question whether there is a Turing cone of broken dimension. That is, is there a real A such that contains no 1-random real, yet contains elements of nonzero effective Hausdorff dimension? We show that the answer is affirmative if Hausdorff dimension is replaced by its inner analogue packing dimension. We construct a minimal degree of effective packing dimension 1.This leads us to examine the Turing degrees of reals with positive effective packing dimension. Unlike effective Hausdorff dimension, this is a notion of complexity which is shared by both random and sufficiently generic reals. We provide a characterization of the c.e. array noncomputable degrees in terms of effective packing dimension.     

Exclusively Heteronuclear 13C‐Detected Amino‐Acid‐Selective NMR Experiments for the Study of Intrinsically Disordered Proteins (IDPs)

Carbon‐13 direct‐detection NMR methods have proved to be very useful for the characterization of intrinsically disordered proteins (IDPs). Here we present a suite of experiments in which amino‐acid‐selective editing blocks are encoded in CACON‐ and CANCO‐type sequences to give ¹³C‐detected spectra containing correlations arising from a particular type or group of amino acid(s). These two general types of experiments provide the complementary intra‐ and inter‐residue correlations necessary for sequence‐specific assignment of backbone resonance frequencies. We demonstrate the capabilities of these experiments on two IDPs: fully reduced Cox17 and WIP^C. The proposed approach constitutes an independent strategy to simplify crowded spectra as well as to perform sequence‐specific assignment, thereby demonstrating its potential to study IDPs.     

The nanostructure of an electrochemically deposited hydroxyapatite coating

The structure of an implant's coating can significantly affect its physical and chemical properties, and eventually – its clinical performance. In this paper, the nanostructure of an electrochemically deposited hydroxyapatite (EDHA) coating was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The X-ray analysis showed that the coating consisted predominantly of the stoichiometric HA phase. However, SEM and HRTEM revealed that EDHA coating is composed of two distinct regions: the upper layer consisted of platelet crystallites preferentially grown perpendicular to the substrate surface, while the lower layer was dense and uniform and consisted of nano-sized crystallites of HA. The possible effects of these different microstructures on the implant's after-implantation behavior are discussed.     

Electrodeposition of rhenium–tin nanowires

Rhenium (Re) is a refractory metal which exhibits an extraordinary combination of properties. Thus, nanowires and other nanostructures of Re-alloys may possess unique properties resulting from both Re chemistry and the nanometer scale, and become attractive for a variety of applications, such as in catalysis, photovoltaic cells, and microelectronics. Rhenium–tin coatings, consisting of nanowires with a core/shell structure, were electrodeposited on copper substrates under galvanostatic or potentiostatic conditions. The effects of bath composition and operating conditions were investigated, and the chemistry and structure of the coatings were studied by a variety of analytical tools. A Re-content as high as 77 at.% or a Faradaic efficiency as high as 46% were attained. Ranges of Sn-to-Re in the plating bath, applied current density and applied potential, within which the nanowires could be formed, were determined. A mechanism was suggested, according to which Sn nanowires were first grown on top of Sn micro-particles, and then the Sn nanowires reduced the perrhenate chemically, thus forming a core made of crystalline Sn-rich phase, and a shell made of amorphous Re-rich phase. The absence of mutual solubility of Re and Sn may be the driving force for this phase separation.     

Blood-flow models of the circle of Willis from magnetic resonance data

Detailed knowledge of the cerebral hemodynamics is important for a variety of clinical applications. Cerebral perfusion depends not only on the status of the diseased vessels but also on the patency of collateral pathways provided by the circle of Willis. Due to the large anatomical and physiologic variability among individuals, realistic patient-specific models can provide new insights into the cerebral hemodynamics. This paper presents an image-based methodology for constructing patient-specific models of the cerebral circulation. This methodology combines anatomical and physiologic imaging techniques with computer simulation technology. The methodology is illustrated with a finite element model constructed from magnetic resonance image data of a normal volunteer. Several of the remaining challenging problems are identified. This work represents a starting point in the development of realistic models that can be applied to the study of cerebrovascular diseases and their treatment.