Self-assembly provides the basis for a procedure used to organize millimeter-scale objects into regular, three-dimensional arrays ("crystals") with open structures. The individual components are designed and fabricated of polyurethane by molding; selected faces are coated with a thin film of liquid, metallic alloy. Under mild agitation in warm, aqueous potassium bromide solution, capillary forces between the films of alloy cause self-assembly. The structures of the resulting, self-assembled arrays are determined by structural features of the component parts: the three-dimensional shape of the components, the pattern of alloy on their surfaces, and the shape of the alloy-coated surfaces. Self-assembly of appropriately designed chiral pieces generates helices.

No abstract

ABSTRACT. In the last years, RF power amplifiers are taking advantage of the switched dc-dc converters to use them in several architectures that may improve the efficiency of the amplifier, keeping a good linearity. The use of linearization techniques such as Envelope Elimination and Restoration (EER) and Envelope Tracking (ET) requires a very fast dc-dc power converter to provide variable voltage supply to the power amplifier but theoretically the efficiency can be much higher than using the classical amplifiers belonging to classes A, B or AB.The purpose of this paper is to analyze the state of the art of the power converters used as envelope amplifiers in this application where a fast output voltage variation is required. The power topologies will be explored and several important parameters such as efficiency, bandwidth and output voltage range will be discussed.

No abstract

Objective To review our experience in management of residual masses after chemotherapy for metastatic seminoma. Patients and methods The study comprised a review of 107 patients with metastatic seminoma, treated with initial chemotherapy from 1978 to 1996. Forty‐three patients had residual masses detected by computed tomography after chemotherapy, while 64 achieved a complete response. Residual masses were classified radiologically as <3 cm or ≥3 cm and as well‐ or poorly defined. Of the patients with residual masses, 19 underwent surgery, while 24 were observed. Results Viable cancer was present in six of 11 patients with well‐defined residual masses of ≥3 cm (positive histology in three of six undergoing surgery and site relapses in three of five observed), one of 14 patients with poorly defined masses of ≥3 cm (negative histology in nine undergoing surgery and site relapse in one of five observed), and in none of 17 patients with residual masses of <3 cm (negative histology in four undergoing surgery and no site relapses in 13 observed; one additional patient in this group died from treatment complications). Conclusion Patients with a complete response after chemotherapy, a residual mass of <3 cm and a poorly defined residual mass of ≥3 cm can be observed, reserving intervention for recurrent or progressive disease. Well‐defined residual masses of ≥3 cm should be resected because there is a 55% likelihood of persistent tumour.