Concurrent polarization retrieval in multi-heterodyne scanning near-field optical microscopy: validation on silicon form-birefringent grating.

We demonstrate a concurrent polarization-retrieval algorithm based on a multi-heterodyne scanning near-field optical microscopy (MH-SNOM) measurement system. This method relies on calibration of the polarization properties of the MH-SNOM using an isotropic region of the sample in the vicinity of the nanostructures of interest. We experimentally show the effectiveness of the method on a silicon form-birefringent grating (FBG) with significant polarization diversity. Three spatial dimensional near-field measurements are in agreement with theoretical predictions obtained with rigorous coupled-wave analysis (RCWA). Pseudo-far-field measurements are performed to obtain the effective refractive index of the FBG, emphasizing the validity of the proposed method. This reconstruction algorithm makes the MH-SNOM a powerful tool to analyze concurrently the polarization-dependent near-field optical response of nanostructures with sub wavelength resolution as long as a calibration area is available in close proximity.

The use of silicone expander and cecal transposition after pelvic exenteration.

AIMS: Describe a new approach for pelvic floor treatment employing a temporary mechanical support device with silicone expander, with or without association to cecal transposition. METHODS: From January 2000 to June 2006, 106 patients were submitted to pelvic exenteration. A retrospective evaluation was done of the last 30 patients previously submitted to total pelvic exenteration without neither urinary nor faecal sphincter preservation who latter were submitted to a pelvic floor treatment with silicone expander with or without association to cecal rotation. RESULTS: Twenty-six patients were female and four male. The most common primary neoplasm site were of gynecological origin (20 cases). The median follow-up period was 12 months (0.36-38). Only one patient presented small intestine loops slipping after expander removal. No other patient had small intestine loops slippage into the pelvis, probably because of cecal transposition. All patients were submitted to a post-operative CT scan to confirm that intestinal loops remained out of the pelvis. Six patients presented pelvic hollow infection after device removal. All cases had complete resolution with local cleaning using physiological solution associated with systemic antibiotic therapy, except one who needed a trans-abdominal surgical approach. CONCLUSIONS: Pelvic floor treatment employing a temporary mechanical support device with silicone expander, associated or not to cecal transposition is a low-morbidity procedure. The most common complication is pelvic floor infection, but maintaining a cutaneous perineal hole allows easy access and treatment of possible pelvic abscesses as well as early recurrence diagnosis.

Observation of amplitude and phase in ridge and photonic crystal waveguides operating at 1.55 microm by use of heterodyne scanning near-field optical microscopy.

We apply heterodyne scanning near-field optical microscopy (SNOM) to observe with subwavelength resolution the amplitude and phase of optical fields propagating in several microfabricated waveguide devices operating around the 1.55 microm wavelength. Good agreement between the SNOM measurements and predicted optical mode propagation characteristics in standard ridge waveguides demonstrates the validity of the method. In situ observation of the subwavelength-scale distribution and propagation of optical fields in straight and 90 degrees bend photonic crystal waveguides facilitates a more detailed understanding of the optical performance characteristics of these devices and illustrates the usefulness of the technique for investigating nanostructured photonic devices.

Prognostic and predictive value of the thymidylate synthase expression in patients with non-metastatic colorectal cancer.

AIMS: To assess the value of thymidylate synthase (TS) expression as a predictive factor in the efficacy of adjuvant chemotherapy in colorectal cancer, as well as its independent prognostic value for survival. METHODS: We studied 114 high risk colorectal carcinoma patients (high risk stage II and stage III), distributed in two treatment groups: surgery alone (61 patients) or surgery followed by 5-FU-based chemotherapy (53 patients). TS protein expression in the tumour tissue was assessed by immunohistochemistry. RESULTS: In the surgery alone subgroup, overall survival (OS) at 5 years were 77.5% for the patients with low TS expression, against 57.7% for the patients with high TS expression (p=0.006). Among patients with low TS, there was no difference in OS as a result of whether adjuvant chemotherapy was carried out or not (65.8 vs 77.5%, p=0.29). Among the patients with high TS, there was a significant gain in OS in favor of chemotherapy (87.8 vs 57.7%, p=0.04). Analyzing the complete sample, TS expression was not shown as an independent prognostic factor for survival in the multivariate analysis. CONCLUSIONS: The immunohistochemical TS expression may be used for selecting patients for better adjuvant chemotherapy protocols. In this sample, TS expression was not an independent prognostic factor for survival.

Ultrashort pulse propagation in near-field periodic diffractive structures by use of rigorous coupled-wave analysis.

We present a method for near-field analysis of ultrashort optical pulse propagation in periodic structures-including subwavelength and resonant grating structures-based on the integration of Fourier spectrum decomposition and rigorous coupled-wave analysis (RCWA). We discuss the spectral decomposition, including considerations for computational efficiency, the application of the RCWA method to compute the internal and external fields of the structure, and the synthesis of the resulting fields to obtain the time-domain solution. We apply this tool to the analysis of two photonic structures: (1) a nanostructured polarization-selective mirror that exhibits the desired broadband performance characteristics when operated at the design wavelength but yields strongly diminished polarization selectivity and modulation of the pulse envelope at an offset wave-length and (2) a two-mode coupled waveguide structure that produces from one incident pulse two transmitted pulses whose temporal separation depends on the waveguide geometry. In both examples, we apply our new modeling tool to investigate the near fields and find that near-field effects are critical in determining the performance characteristics of nanostructured devices. Furthermore, detailed observation and understanding of near-field phenomena in nanostructures may be applied to the design of novel photonic devices.

Near-field localization of ultrashort optical pulses in transverse 1-D periodic nanostructures.

We present a transverse 1-D periodic nanostructure which exhibits lateral internal Thorneld localization for normally incident ultrashort pulses, and which may be applied to the enhancement of nonlinear optical phenomena. The peak intensity of an optical pulse propagating in the nanostructure is approximately 12 times that of an identical incident pulse propagating in a bulk material of the same refractive index. For second harmonic generation, an overall enhancement factor of approximately 10.8 is predicted. Modeling of pulse propagation is performed using Fourier spectrum decomposition and Rigorous Coupled-Wave Analysis (RCWA).

Treatment of severe actinic rectitis.

BACKGROUND: The authors report the treatment of three female patients with severe actinic rectitis, with stenosis or perforation, submitted to anterior proctosigmoidectomy and transanal coloanal anastomosis. METHODS: In all cases surgery consisted of total proctosigmoidectomy, mucosectomy of the anal canal, lowering of the left colon through the pelvis and transanal anastomosis performed manually at the level of the pectineal line using separate absorbable sutures. A protective intestinal shunt was performed in all cases. RESULTS: The three patients did not present transoperative or immediate postoperative complications, but the first patient developed deep venous thrombosis of the leg that was submitted to successful clinical treatment. The intestinal shunts were later closed in all three cases. Sphicter function was considered very good in the first case and regular in the remaining two. CONCLUSION: The surgical technique utilized was considered to be adequate for the cases reported and is the first option for the maintenance of transit in patients with severe actinic rectitis since the anastomosis is performed using non-irradiated colon with the pectineal line, practically outside the pelvis.

Radiation and chemotherapy instead of surgery for low infiltrative rectal adenocarcinoma: a prospective trial.

BACKGROUND: The objective of this prospective study was to determine the possibility of treatment based exclusively on chemotherapy and radiotherapy for patients with low infiltrative rectal tumors in an attempt to preserve sphincter function. METHODS: Sixteen patients with rectal adenocarcinoma up to 3 cm above the pectineal line with initial indications for abdominoperineal resection (APR) were submitted to a 5040-cGy (28 x 180 cGy) radiotherapy dose and chemotherapy during the first 3 and last 3 days of radiotherapy, using 425 mg/m2/day of 5-fluorouracil (5FU) and 20 mg/m2/day of folinic acid. Levamisole was used at 150 mg/day for 3 consecutive days at 2-week intervals throughout the period of therapy. Patients with a complete response were not submitted to APR, but received additional brachytherapy for curative purposes with doses from 2000 to 3000 cGy. Patients with recurrence after a complete response, with partial response, or with no response were submitted to APR. RESULTS: Six patients (37.5%) presented a complete response, five (31.25%) presented a partial response, and five (31.35%) did not respond. The disease-free interval ranged from 1 to 34 months (mean = 11 months) among the six patients with complete response, and only one patient not submitted to APR is currently asymptomatic. Among the 15 patients with an indication for APR, three refused surgery because of full improvement of clinical symptoms and currently have tumor activity in the rectum. Mean patient follow-up was 23.8 months (8 to 43 months), and ten patients (62.5%) showed no evidence of active disease at last follow-up. CONCLUSIONS: The therapeutic schedule used was not effective in preserving sphincter function in patients with low infiltrative rectal adenocarcinoma, because responses, although very frequent, were only temporary.