Temperature dependence of the magnetic volume susceptibility of human breast fat tissue: an NMR study

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Proton resonance frequency shift (PRFS)-based MR thermometry (MRT) is hampered by heat-induced susceptibility changes when applied in tissues containing fat, e.g., the human breast. In order to assess the impact of fat susceptibility changes on PRFS-based MRT during thermal therapy in the human breast, reliable knowledge of the temperature dependence of the magnetic volume susceptibility of fat, dχ_fat/dT, is a prerequisite. In this work we have measured dχ_fat/dT of human breast fat tissue, using a double-reference method to ensure invariance to temperature-induced changes in the proton electron screening constant.     

Characterization of the packing of aggregate in concrete by a discrete element approach

Aggregate roughly takes up three-quarters of the volume of concrete, so it plays an important role in the properties of concrete. A particle packing phenomenon exists in a wide range of fields as well as in concrete technology. A spherical grain shape is generally adopted in conventional discrete element simulation (DES) systems, despite imposing serious limitations. In this paper, a flexible simulation strategy is presented for the simulation of arbitrary-shaped aggregate grains used in concrete technology. This simulation approach is also incorporated in a concurrent algorithm-based DES system. Furthermore, a method has been developed for the assessment of properties pertaining to arbitrary shaped particles, such as mass, centre of mass, and moment of inertia. Some trials of particle packing with different shapes are also revealed and discussed in this paper.     

Ultrafast gas chromatographic separation of organophosphor and organosulfur compounds utilizing a microcountercurrent flame photometric detector

A microcountercurrent flame photometric detector (microcc-FPD) was adapted and optimized for ultrafast gas chromatographic (GC) separation and detection of organophosphor (OP) and organosulfur (OS) compounds on short chromatographic columns. Air and hydrogen are introduced to the microcc-FPD from opposite directions, creating a hydrogen-rich flame. In this microcc-FPD, combustion takes place between the burner tips without touching them. The separation between the tips and the flame reduces heat loss from the flame to the surrounding environment, resulting in low hydrogen consumption and a compact flame. The microcc-FPD is capable of detecting very narrow (13 ms) chromatographic peaks. An ultrafast GC separation of a group of six OP and OS compounds is achieved within less than 5 s using fast temperature programming of a 0.5-m-long microbore column. Very fast separations are also demonstrated on a 1-m-long microfabricated column consisting of 150-microm-wide, 240-microm-deep channels, etched in a 1.9-cm square silicon chip, covered with a Pyrex wafer, and statically coated with dimethyl polysiloxane. With a hydrogen flow rate of 10 mL/min, the detection limit for OP is 12 pg of P/s and 3 ng of S/s for OS compounds at a signal-to-noise ratio of 2. The coupling of a microfabricated column and a miniature FPD is an important step toward the development of a miniaturized GC-FPD capable of ultrafast detection of low levels of OP and OS compounds.     

A psychophysiological study of the use of partial information in stimulus-response translation.

Ss performed a hybrid go/no-go reaction task in which colored letters were assigned in various ways to 4 finger responses, 2 on each hand. In addition to reaction time (RT), psychophysiological measures were used to assess the duration of stimulation and the onset of central and peripheral motor activity. The results suggest that response selection can begin on the basis of 1 stimulus dimension (e.g., color), while the other dimension (e.g., letter form) has not yet been identified. Other results are discussed with regard to "selection for action" (D. A. Allport, 1987) and the importance of stimulus–response translation strategies in the use of partial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wait-free linearization with a mechanical proof

Summary The correctness of a program for wait-free linearization ofan arbitrary shared data object in bounded memory is verified mechanically. The program uses atomic read-write registers, an array of consensus registers and one compare and swap register. In the program, a number of processes concurrently inspect and modify a pointer structure without waiting. Consequently, the proof of correctness is very delicate. The theorem prover NQTHM of Boyer and Moore has been used to mechanically certify the correctress. Wim H. Hesselink received his Ph.D. in mathematics from the University of Utrecht in 1975. After ten years of research in Lie algebras he turned to computer science. In 1986/1987 he was on leave with the Department of Computer Sciences of the University of Texas at Austin. Currently, he is chairman of the Department of Computing Science at the University of Groningen. His research interests include distributed programming, design and correctness of algorithms, mechanicaltheorem proving, and predicate transformation semantics of recursive procedures with nondeterminacy of various flavors.     

Bounded delay for a free address

 The problem is to let n processes concurrently and repeatedly search for free addresses in a range of m addresses. The search must be wait-free: a searching process finds an address in a bounded number of steps. Three solutions are presented. The first one has large atomic actions. The second one is only correct if m≧(r+1) ⋅ n where r is the maximum number of used addresses. The third solution is always partially correct. It is wait-free if m>r+2 ⋅ n. This solution has a worst-case waiting time quadratic in n and an amortized waiting time linear in n, even linear in the number of active processes. Received February 2, 1994/January 24, 1995