Full Modeling of Field-Assisted Ion Exchange for Graded Index Buried Channel Optical Waveguides

The numerical modeling of field-assisted ion exchange in glass through a finite aperture is carried out. The effects of unequal ion mobilities and thermal diffusion are included we believe for the first time in the 2-D case. This allows for the modeling of optical channel waveguides with graded index profiles. It is demonstrated that annealing of backdiffused channel guides is far superior to backdiffusion alone in improving their circular symmetry for better coupling to optical fibers

Polarization-resolved sensing with tilted fiber Bragg gratings: theory and limits of detection

Polarization based sensing with tilted fiber Bragg grating (TFBG) sensors is analysed theoretically by two alternative approaches. The first method is based on tracking the grating transmission for two orthogonal states of linear polarized light that are extracted from the measured Jones matrix or Stokes vectors of the TFBG transmission spectra. The second method is based on the measurements along the system principle axes and polarization dependent loss (PDL) parameter, also calculated from measured data. It is shown that the frequent crossing of the Jones matrix eigenvalues as a function of wavelength leads to a non-physical interchange of the calculated principal axes; a method to remove this unwanted mathematical artefact and to restore the order of the system eigenvalues and the corresponding principal axes is provided. A comparison of the two approaches reveals that the PDL method provides a smaller standard deviation and therefore lower limit of detection in refractometric sensing. Furthermore, the polarization analysis of the measured spectra allows for the identification of the principal states of polarization of the sensor system and consequentially for the calculation of the transmission spectrum for any incident polarization state. The stability of the orientation of the system principal axes is also investigated as a function of wavelength

Who is credit constrained among denied or discouraged borrowers?".

Since the seminal work of Jappelli (1990), it has become standard to identify as liquidity-constrained, borrowers who were either turned down for credit or did not apply because they might be turned down. In this paper, we show that the so-called “denied or discouraged†proxy does not capture accurately consumers’ credit access when consumers seek credit to finance expenditure on durable goods. Our sample is drawn from the Panel Study of Income Dynamics. We document systematic misclassification of unconstrained households as constrained. We argue that: for durables, this proxy captures best the intensity put forth by the borrower when shopping for a loan.Borrowing constraints; Mortgage loans; Consumer search

Hypergraph formalism for urban form specification

peer reviewe

Risk factors for deterioration of renal function after coronary artery bypass grafting

Abstract Objective: Various definitions of impairment of renal function after coronary artery bypass grafting (CABG) are used in the literature. Depending on the definition, several risk factors are identified. We analysed our data to determine the risk factors for postoperative deterioration of the creatinine clearance of 10% or more. Methods: All patients undergoing isolated coronary surgery in a single centre between January 1998 and December 2007 are included. Clinical data, including demographics and renal risk factors, were prospectively collected in our database. The most recent preoperative serum creatinine level and the maximum serum creatinine level within the first week postoperatively were used to calculate the creatinine clearance. A deterioration of 10% or more was considered to be an endpoint for this study. Results: In 10 098 out of a total of 10 626 patients, the preoperative as well as the postoperative creatinine clearance could be calculated. In 1053 patients, the deterioration of the creatinine clearance was 10% or more. We could identify the following risk factors: advanced age, diabetes, chronic obstructive pulmonary disease, peripheral vascular disease, emergency operation, previous cardiac surgery, low preoperative haemoglobin level, high preoperative C-reactive protein level, perioperative myocardial infarction, re-exploration and the number of blood transfusions. Conclusions: Risk factors for the deterioration of renal function after revascularisation have been confirmed in this study. In addition, we found peripheral vascular disease, previous cardiac surgery, low preoperative haemoglobin, increased preoperative C-reactive protein level, perioperative myocardial infarction and the number of blood transfusions to be risk factors that have not been described earlier

Transfusion of red blood cells: the impact on short-term and long-term survival after coronary artery bypass grafting, a ten-year follow-up.

Transfusion of red blood cells (RBC) and other blood products in patients undergoing coronary artery bypass grafting (CABG) is associated with increased mortality and morbidity. We retrospectively analyzed data of patients who underwent an isolated coronary bypass graft operation between January 1998 and December 2007. Mean follow-up was 1696±1026 days, with exclusion of 122 patients lost to follow-up and 80 patients who received 10 units of RBC. Of the remaining patients, 8001 (76.7%) received no RBC, 1621 (15.2%) received 1–2 units of RBC, 593 (5.7%) received 3–5 units and 220 (2.1%) received 6–10 units. The number of transfused RBC was a predictor for early but not for late mortality. When compared to expected survival, survival of patients not receiving any blood product was better, while survival of patients receiving >3 units of RBC was worse. Transfusion of RBC is an independent, dose-dependent risk factor for early mortality after revascularization. Compared to expected survival, receiving no RBC improves patient long-term survival, whereas receiving three or more units of RBC significantly decreases patient survival

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