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Hole-containing silicon has been regarded as a viable candidate thermoelectric material because of its low thermal conductivity. However, because voids are efficient scattering centers not just for phonons but also for charge carriers, achievable power factors (PFs) are normally too low for its most common form, i.e. porous silicon, to be of practical interest. In this communication we report that high PFs can, indeed, be achieved with nanoporous structures obtained from highly doped silicon. High PFs, up to a huge 22 mW K m (more than six times higher than values for the bulk material), were observed for heavily boron-doped nanocrystalline silicon films in which nanovoids (NVs) were generated by He ion implantation. In contrast with single-crystalline silicon in which He implantation leads to large voids, in polycrystalline films implantation followed by annealing at 1000°C results in homogeneous distribution of NVs with final diameters of approximately 2 nm and densities of the order of 10 cm with average spacing of 10 nm. Study of its morphology revealed silicon nanograins 50 nm in diameter coated with 5-nm precipitates of SiB. We recently reported that PFs up to 15 mW K m could be achieved for silicon-boron nanocomposites (without NVs) because of a simultaneous increase of electrical conductivity and Seebeck coefficient. In that case, the high Seebeck coefficient was achieved as a result of potential barriers on the grain boundaries, and high electrical conductivity was achieved as a result of extremely high levels of doping. The additional increase in the PF observed in the presence of NVs (which also include SiB precipitates) might have several possible explanations; these are currently under investigation. Experimental results are reported which might clarify the reason for this paradoxical effect of NVs on silicon PF. [ABSTRACT FROM AUTHOR]

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Introduction: The aim of the present study was to compare the restaging results obtained by transrectal ultrasound (TRUS), computed tomography (CT), and magnetic resonance imaging (MRI) performed after preoperative chemoradiation with pathologic staging of the operative specimen. Methods: From January 2008 to December 2009, all the consecutive patients with locally advanced rectal cancer that underwent neoadjuvant therapy at our department were evaluated. The results of diagnostic examinations and the definitive pathological examination were considered and compared. Results: Thirty-seven patients were included in the study (27 males, 73%), mean age was 65.5 years (range 45-82 years). In all the patients TRUS and CT and in 20 patients MRI were performed before and after the treatment. Concerning the depth of invasion after treatment TRUS agreed with histopathology in 25/37 patients (67.5%), CT agreed in 22/37 cases (59.5%), and MRI in 12/20 cases (60%). Considering only neoplasia with stage T3, TRUS agreed in 23/24 cases (96%), CT in 19 cases (79%), and MRI in 10/12 cases (83.5%). Considering the tumors that did not exceed the rectal wall (T0, T1, and T2), TRUS agreed with histology in 2/13 cases (15.5%), CT in 3/13 cases (23%), and MRI 2/8 cases (25%). Concerning the presence of positive lymph nodes TRUS agreed with histology in 28/37 cases (75.5%), while CT agreed in 21/37 cases (56.5%) and MRI in 11/20 cases (55%). The concordance between the techniques was found to be low. Conclusions: Transrectal ultrasonography resulted as the most accurate method to determine neoplastic wall infiltration and lymph node involvement even after radiochemotherapy. In most cases, considering the poor correlation between the diagnostic procedures and the disagreement of the results, a restaging performed only with TRUS could be proposed, limiting the use of the other imaging methods to selected cases. [ABSTRACT FROM AUTHOR]

Background: Selective re-creation of a new internal anal sphincter could be indicated when the natural one is irreversibly damaged or excised. Methods: In this preliminary experimental work, surgical techniques of internal anal sphincter replacement in pigs were investigated. After preoperative anorectal manometry, surgical procedure was done in two phases: abdominal, mobilization of the colon-rectum to the pelvic floor; and perianal, dissection of the anal canal from the external anal sphincter through the intersphincteric space. The fully mobilized anorectal segment, including the internal anal sphincter, was pulled down through the anus and resected. The distal colonic stump was then demucosated and two types of plications of the demucosated segment were accomplished, each type in three animals. The plicated segment was then returned into the anal canal, inside the external sphincter. Short-term follow-up with clinical and manometric evaluations was performed and, subsequently, histological analysis of the plicated segment, after the animals were sacrificied. Results: None of the animals became incontinent. Anal manometry identified a high-pressure zone and relaxation reflex in the new anal canal. Histologic studies showed hypertrophy of smooth muscle layers without degenerative changes. Conclusion: This study indicates that a plication of colonic smooth muscle wall can re-create a high-pressure zone in the anal canal after the internal anal sphincter has been excised. [ABSTRACT FROM AUTHOR]