Design and numerical simulation of an optofluidic pressure sensor.

We present a numerical design procedure for an all-optical compact sensor by means of integrating the optofluidic switch polymer interferometers to measure the microfluidic air pressure and flow rate. The design is based on a flexible air gap optical cavity that can generate an interference pattern when illuminated by a monochromatic light. The optical interference pattern directly depends on the pressure. In our numerical simulations, we take the effects of fluid flow rate, solid deformation, and the light interference into account. We use the beam propagation method for simulating the optics and the finite element method for simulating the mechanics. The significance of the proposed sensor lies with its low power consumption, compactness, low cost, and short length. This sensor can operate under pressure range of 0-60±6% Pa at a constant temperature of 20 °C.

Recurrence in breast cancer. Analysis with frailty model.

OBJECTIVE: To determine the value of known prognostic factors for metastasis in breast cancer by accounting for patient-specific effect of patients who received surgical treatment followed by adjuvant treatment using the frailty model. METHODS: One hundred seventeen women with breast cancer who underwent surgery followed by adjuvant therapy at 3 hospitals in Tehran, Iran between 1995 and 2003 were enrolled in this study. Women with defined breast cancer with no distant metastases at time of diagnosis that have undergone modified radical mastectomy or breast-conserving surgery were enrolled. Tumors were classified according to the Tumor, Node, Metastasis (TNM) system of the American Joint Committee on cancer. Grading was performed according to Scarff-Bloom-Richardson method. Estrogen receptor (ER) was measured by immunohistochemistry method. The patients have been followed regularly by routine clinical laboratory profile, serologic markers (CEA, CA15-3) and para-clinical examinations; furthermore, we have followed missing materials by other access ways such as calling. RESULTS: Median follow up time for patients was 26 months after surgery. During the follow up time 44 (38%) patients developed metastasis and 20 (45%) of these 44 patients experienced the second metastasis. The median disease-free survival for patients in the study was 49.6 month. The median time to experience second metastasis after the first one was 22.5 months. Risk of occurrence of a metastasis in the first year after surgery was 12%. Risk of experience a metastasis up to the second year was 32% and up to fifth years was 69%. Result of fitting a frailty model to data showed that size of tumor, number of positive lymph nodes and histologic grade had a significant effect on the risk of metastasis (p<0.05). Patients with tumor size larger than 5 cm were in higher risk of metastasis compared with others. Increase in the number of positive lymph nodes to more than 10, increased risk of metastasis. Patients with moderate or undifferentiated histologic grade were in higher risk of metastasis to well differentiated patients. Age, family history, lymph node stage, and ER had no significant effect. It was found that there was heterogeneity between patients after adjusting for other covariates because variance of frailty was 0.315. It means that based on the variance of the distribution of frailty, the relative risk of high-risk patients to low-risk patients was 7.2, wherein high-risk group is defined as a cluster at the 95th percentile and low-risk to a cluster of 5th percentile of the frailty distribution. CONCLUSION: Known risk factors describe the risk of metastasis partly and other unknown or unmeasured factors, such as genetics or environmental factors are important to describe the risk of metastasis in breast cancer.

Postoperative life expectancy in gastric cancer patients and its associated factors.

OBJECTIVE: In recent years, the patterns of mortality have changed in Iran, and cancers are playing a greater role in this regard in this country. Various reports indicate that gastric cancer is highly prevalent; it is the second most common cancer in men, and fourth in the general population. The purpose of this study was to determine the 5-year survival rate of gastric cancer patients who had undergone surgical treatment at one of the most important cancer treatment centers, the Iran Cancer Institute, and to assess its associated factors. METHODS: Three hundred and thirty patients with gastric cancer who had been admitted to and operated on at the Iran Cancer Institute, Iran between January 1996 and April 2000 were enrolled in this study. The patients' life expectancy after surgery was determined, and its relationship with variables of age at the time of surgery, gender, and factors related to the disease such as the cancer site, pathologic type, stage, presence of metastasis, and sites of metastases were assessed. RESULTS: The 5-year survival rate in the studied patients was 23.6%, and the median life expectancy was 19.9 months. Univariate analysis showed that gender, cancer site, and pathologic type did not affect life expectancy significantly. However, the 5-year survival rate significantly decreases with age. As expected, those involved with metastasis had a significantly lower 5-year survival rate, and the disease stage significantly affected the patients' life expectancy (p<0.001). The Cox proportional hazards model was used to assess the effect of different variables simultaneously, and it showed that age, lymph node metastasis, and disease stage influenced the rate of survival. CONCLUSIONS: Gastric cancer patients in Iran have a low 5-year survival rate. One of the most important reasons seems to be delayed consultation and diagnosis. Most patients are seen first with the disease in the late stages. At this point, most have lymph node and liver metastasis, which makes treatment even more complex. Thus, it is necessary to employ mass media for extensive public education about the early warning signs of the disease and performing periodic examinations.