Equilibrium Crystal Shapes by Virtual Work

A formulation on equilibrium crystal shape determination based on the principle of virtual work is presented. The treatment is restricted to two dimensions. A corresponding discrete solution method is given. Some example cases are presented.     

Determination of 234U/238U ratio: comparison of multi-collector ICPMS and ICP-QMS for water, hair and nails samples, and comparison with alpha-spectrometry for water samples

The (234)U/(238)U ratio in water, hair and nails samples was determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) and by alpha-spectrometry for the water samples only. A correlation of 0.99 was found between the two ICPMS methods and of 0.98 with alpha-spectrometry. The range of activity ratios was between 0.9 and 2.6 according to the MC-ICPMS measurements. The reproducibility of both ICPMS techniques was better than 4% for water samples containing 1 mug l(-1) of uranium and a (234)U/(238)U atom ratio of 54.9 x 10(-6). Sample preparation for the ICPMS consisted of dilution of water samples containing >10 microg l(-1) of uranium and measurement time was approximately 1 min, while alpha-spectrometry involved pre-concentration and separation of the uranium and counting times of 1,000 min.     

Configurable parallel memory architecture for multimedia computers

This paper presents a novel parallel memory architecture for multimedia computers. Applying a configurable or programmable addressing circuitry capable of parallel memory accesses, the memory management of multimedia applications can be enhanced. Necessary computer architecture changes to virtual address representation, paging, virtual memory, address computation circuitry and data permutation are discussed. These changes allow the memory to be partitioned for different access functions. In addition, the same memory area can be accessed by multiple access patterns. Therefore, a general-purpose computing system that is capable of exploiting the repeating memory access patterns in its applications can be built. Performance of the configurable parallel memory architecture (CPMA) is analyzed in the case of a selection of algorithms from a video encoder. These motion estimation algorithms and zigzag scanning benefit from the multiple memory access functions, which is apparent from the comparisons to the traditional sequential memory accesses.     

Effects of interstimulus interval on somatosensory evoked magnetic fields (SEFs): a hypothesis concerning SEF generation at the primary sensorimotor cortex

Cerebral responses evoked by peripheral stimuli are known to depend critically on the interstimulus interval (ISI). Here we report on the effects of ISI on somatosensory evoked magnetic fields (SEFs) to right median nerve stimulation, obtained in 9 healthy adults with ISIs of 0.15 0.3, 1,3 and 5 s. At the contralateral (left) primary sensorimotor cortex (SMI), the first cortical response, N20m, was stable between the ISIs 0.3 and 5 s, but slightly attenuated at the shortest ISI of 0.15 s. In contrast, the P35m and P60m deflections were very sensitive to changes of the ISI, declining steadily with shortening of the ISI throughout the entire range. These deflections were frequently undetectable at the shortest ISI of 0.15 s. Concomitant with the reductions of P35m and P60m, an N45m deflection was enhanced toward the short ISIs. Responses from second somatosensory cortex (SII) and posterior parietal cortex (PPC) were seen only with ISIs of 1 s or greater, being strongest at the 5 s ISI. Based on known effects of the ISI on intracellular evoked potentials, we present the following tentative model for the generation mechanism of the SMI response: N20m represents early excitatory postsynaptic potentials (EPSPs), P35m early inhibitory postsynaptic potentials (IPSPs), N45m secondary EPSPs and P60m late IPSPs in pyramidal neurones of area 3b. For practical purposes, SEFs from SMI can be obtained with short ISIs, while responses from SII and PPC require an ISI of at least 1 s.     

Assessment of occupational exposure to uranium by indirect methods needs information on natural background variations

Urine monitoring is the preferred method to determine exposure to soluble compounds of uranium in workplaces. The interpretation of uranium contents in workers bioassay samples requires knowledge on uranium excretion and its dependence on intake by diet. Exceptionally high concentrations of natural uranium in private drinking water sources have been measured in the granite areas of Southern Finland. Consequently, high concentrations of natural uranium have been observed in the urine and hair samples of people using water from their own drilled wells. Natural uranium content in urine and hair samples of family members, who use uranium-rich household water, have been analyzed by using ICP-MS. The uranium concentrations both in urine and hair samples of the study subjects were significantly higher than the world-wide average values. In addition, gammaspectrometric methods have been tested for determining uranium in hair samples. This method can be used only for samples with highly elevated uranium concentrations.     

The concept of fictitious loading

The concept of fictitious external loading being in exact equilibrium with the internal stresses in a structure is introduced. It is employed in conjunction with the principle of virtual work in an effort to examine certain details of the finite element displacement method in an alternative way.     

Cancer in the offspring of fathers in hydrocarbon-related occupations

Thirteen patients with bulbar urethral strictures were treated by excision of the stricture and end to end anastomosis of the urethra with uniformly good results.