Fabrication of gap-optimized CMUT

A recently introduced set up of capacitive micromachined ultrasonic transducers (cMUT) combines a conductive membrane above a structured sacrificial layer. All previous approaches either require an additional metallic electrode or do not possess a structured sacrificial layer and, consequently, may make exact adjustment of the membrane dimensions difficult. The present set ups are especially suited for the fabrication of cMUT with gap heights ranging between 50 nm and 2 /spl mu/m between the electrodes. Large gaps are a prerequisite to enabling sufficient deflections of the membrane and, therewith, to generating high pressure gradients. On the other hand, small gap sizes are desirable for detecting weak ultrasonic sources. This paper focuses on the fabrication process of cMUT to realize electrode separation above 500 nm and, in addition, on the manufacturing of cMUT with gaps below 500 nm. The successful realization has been proven by some basic experimental investigations. Finally, the fundamental equations of a frequently chosen simulation model are documented, as a number of ambiguities exist in the common literature.     

Apolipoprotein (apo) B and apoII gene expression are both estrogen-responsive in chick embryo liver but only apoII is estrogen-responsive in kidney

Estrogen regulates the hepatic synthesis of a variety of proteins required for egg yolk production in oviparous vertebrates. In chickens, two of these proteins, apolipoprotein (apo) B and apoII, comprise the major protein components of specialized very low density lipoprotein particles that transport triacylglycerols and cholesterol to the developing egg yolk. In the adult, apoB is synthesized constitutively in liver, small intestine, and kidney but is estrogen-responsive only in the liver. In this work we have examined the embryonic expression of the apoB and apoII genes in yolk sac, liver, kidney, and small intestine. The 14 kb apoB mRNA was first detected at day 3 of development in vascular yolk sac, a tissue involved in the transfer of yolk lipids into the embryonic circulation. Constitutive apoB mRNA expression was detectable in liver at day 6.5 and in kidney at day 7.5, but in intestine was barely detectable before hatching. The hepatic apoB gene acquired estrogen-responsiveness at day 6.5 and its hormone-dependent expression increased throughout development in concert with the estrogen-responsive expression of the apoII gene. In contrast, the constitutively expressed apoB gene in kidney remained unresponsive to estrogen. Surprisingly, the apoII gene was found to be responsive to estrogen in both the embryonic kidney and small intestine. ApoII mRNA induction by estrogen in kidney at day 11 was at 10% of the level in the liver but estrogen-responsiveness decreased later in development and was low in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)     

Supporting reflection and dialogue in a community of machine setters: Lessons learned from design and use of a hypermedia type training material

The debate about experience-based or tacit knowledge has focused much attention on the limits to formalisation of work process knowledge. A main line of argument has been that, for example, industrial work even with highly advanced technical equipment can only be performed adequately when the worker through experience on the job has gained a feel for the functioning of the machinery and the properties and behaviour of the materials. In this debate links tend to be created between on the one hand formalised-abstracted-verbal knowledge as opposed to on the other hand informalised-concrete-tacit knowledge. We have worked for some years with the design of training materials which at its core have video documentation of best practice as we have found it at work. In this paper we will present and discuss experience with design and use of a hypermedia type training material, SPRING to be used by new machine setters in the spring industry. Based on our own experience we will argue for the relevance of this type of training materials as a means of supporting reflection and dialogue in the community of practitioners.     

"In situ" anesthetics and experimental cryotumorectomy

The results obtained by testing 3127 mink sera as well as the analysis of families completely confirmed that the Lpm allotype system of very high density proteins is under genetic control, as postulated earlier. The polymorphism of the first five allotypes is due to the genetic units Lpm1, Lpm4, Lpm1,2, Lpm3,4 and Lpm2,4,5, which behave as Mendelian alleles. The data obtained suggest the existence of an additional gene, LpmX, which, in the homozygous state, determines a very rare phenotype, negative for the first five markers.     

Leg function after radiotherapy for Ewing's sarcoma

Twenty-nine patients with Ewing's sarcoma of the lower extremity who survived for two or more years following therapy (5000 rad locally and systemic chemotherapy) were studied to assess functional status of the affected leg. Twenty-two of twenty-nine were alive and were reexamined; the deceased patients were evaluated by record review. Twenty-two of the twenty-nine had serial radiographs, which were reviewed to assess growth change induced by radiation. The living patients were divided on the basis of clinical examination into four functional groups with Group I comprising patients with minor functional limitations and leg length discrepancy 1.5 cm or less. Group II patients had moderate functional limitations with 2.5-cm leg-length discrepancy or less. Group III patients had severe functional limitations with up to 4-cm leg length discrepancy. Group IV patients had severe complications, sufficient enough to warrant amputation. Thirteen of twenty-two patients were classified as functional Group I, five as Group II, three as Group III, and one as Group IV. Radiographic changes in growing bone did not correlate with functional results. Although a femoral fracture and an age less than 16 years at diagnosis were found to be less favorable prognostic factors for the functional treatment result, these results show that neither femoral location nor young age justify primary amputation for Ewing's sarcoma of the lower leg extremity.     

The Regional Dimension of Knowledge Transfers—A Behavioral Approach

Innovations are inherently connected to knowledge transfers. The need of face-to-face contacts to transfer tacit knowledge is commonly argued to cause a regional dimension of innovative activities. The paper presents an alternative explanation based on a model of boundedly rational actors who search for knowledge. It is shown that a regional dimension exists in these processes that results from a regional bias in an actor's search activities. Social embeddedness, a shared regional identity and limited spatial mobility foster this bias. We argue that insights from research on these topics can help to define the geographic size of a region.     

Losses and forces due to eddy currents in a magnetically non-linear conductive half space

A simple soft magnetically non-linear moving conductor model (“iron”) as “half-space” is presented under the inducing effect of a sinusoidal distributed current loading at different current amplitudes, covering the low to very high saturation level of 1–4 T. Eddy current losses, penetration depth of field and tangential braking and normal attractive forces are compared with the results for a linear conductor with constant saturation (relative permeability 100) for a velocity range, described by magnetic Reynolds numbers 1–300. Eddy current losses and the braking force are bigger for the non-linear case (typically 160–200%) and the penetration depth is bigger by 200–400%. The attractive force is smaller, first due to field compression at higher velocity, second due to the increased saturation level, which gives lower relative permeability values than the assumed constant value of 100 in the linear case. For a rough estimate of either eddy current effects in eddy current brakes and linear induction motors with massive secondary or of eddy current losses in electrical machines and apparatus often a constant saturation is assumed. The here presented results allow a preliminary correction due to the non-linear conductor effect, before a detailed non-linear numerical analysis of the investigated geometry is done.     

Magnetic and Temperature‐Sensitive Release Gels from Supramolecular Polymers

Supramolecular gels consisting of trivalent polyisobutylene and bivalent poly(ethylene oxide) are generated. Strong hydrogen bonding interactions, affixed to the end‐group moieties of the respective polymers (binding constant K_assn = 10⁵ M ^–1), serve as molecular glue, leading to the formation of weak gels. Two different gels were prepared: one, with a short telechelic poly(ethylene glycol) (PEG) segment (gel A), and one with a longer PEG segment (number‐average molecular weight M_n = 2000 g mol^–1) (gel B). Both gels show a significant increase in viscosity upon mixing of the two polymeric components, with a lag time of several minutes, indicative of nucleation mechanisms as the formation principle. However, only gel A displays classical gel‐like behavior, with a loss modulus G′ larger than the storage modulus G″ after formation. Both gels display microphase‐separated behavior with a spacing between 4–5 nm as probed via small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) measurements. The incorporation of magnetic nanoparticles (Fe₂O₃; radius r = 3.5 nm) is successfully achieved, generating new magnetic gels with strongly thermoresponsive properties, displaying a strong temperature‐dependent release profile of included dye molecules. Magnetic measurements indicate a superparamagnetic behavior of the incorporated nanoparticles, prospecting the application as magneto‐sensitive delivery gels for pharmaceutical purposes.