Rolling behavior of a micro-cylinder in adhesional contact.

Understanding the rolling behavior of a micro-object is essential to establish the techniques of micro-manipulation and micro-assembly by mechanical means. Using a combined theoretical/computational approach, we studied the critical conditions of rolling resistance of an elastic cylindrical micro-object in adhesional contact with a rigid surface. Closed-form dimensionless expressions for the critical rolling moment, the initial rolling contact area, and the initial rolling angle were extracted after a systematic parametric study using finite element method (FEM) simulations. The total energy of this system is defined as the sum of three terms: the elastic energy stored in the deformed micro-cylinder, the interfacial energy within the contact area, and the mechanical potential energy that depends on the external moment applied to the cylindrical micro-object. A careful examination of the energy balance of the system surprisingly revealed that the rolling resistance per unit cylindrical length can be simply expressed by "work of adhesion times cylindrical radius" independent of the Young's modulus. In addition, extending a linear elastic fracture mechanics based approach in the literature, we obtained the exact closed-form asymptotic solutions for the critical conditions for initial rolling; these asymptotic solutions were found in excellent agreement with the full-field FEM results.

[A case of gastrointestinal stromal tumor with liver and bone metastases effectively treated with radiofrequency ablation and imatinib mesylate].

A 58-year-old man was admitted because of perforation of the small intestine by a gastrointestinal stromal tumor (GIST). First, the small intestine including a GIST was resected; and then 2 month later, a part of the liver (S5) conforming to metastatic lesion was surgically removed. Twelve months later, another liver metastases was found, and surgical treatment was recommended; but the patient requested non-surgical therapy, so a radiofrequency ablation (RFA) was successfully performed. After that, recurrence of liver metastasis was not observed, but another metastasis was observed on the fifth lumbar vertebra; so administration of imatinib mesylate was started. 28 months after the initial administration the metastatic liver lesion was still invisible, and the bone metastatic lesion had not grown. The patient is alive with good performance status. This report shows that multi-modality therapy by surgery, RFA and imatinib mesylate was effective for liver and bone metastases of GIST.

Anabolic five subunit-type pyruvate:ferredoxin oxidoreductase from Hydrogenobacter thermophilus TK-6.

The thermophilic, obligately chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, assimilates carbon dioxide via the reductive tricarboxylic acid cycle. A gene cluster, porEDABG, encoding pyruvate:ferredoxin oxidoreductase (POR), which plays a key role in this cycle, was cloned and sequenced. The nucleotide sequence and the gene organization were similar to those of the five subunit-type 2-oxoglutarate:ferredoxin oxidoreductase from this strain, although the anabolic POR had been previously reported to consist of four subunits. A small protein (8 kDa) encoded by porE, which had not been detected in the previous work, was identified in the purified recombinant POR expressed in Escherichia coli, indicating that the enzyme is also a five-subunit type. Incorporation of PorE in the wild-type POR enzyme was confirmed by immunological analysis. PorA, PorB, PorG, and PorE were similar to the alpha, beta, gamma, and delta subunits of the four subunit-type 2-oxoacid oxidoreductases, respectively, and had conserved specific motifs. PorD had no specific motifs but was essential for the expression of the active enzyme.