Spatiotemporal solitons in multidimensional optical media with a quadratic nonlinearity

We consider solutions to the second-harmonic generation equations in two-and three-dimensional dispersive media in the form of solitons localized in space and time. As is known, collapse does not take place in these models, which is why the solitons may be stable. The general solution is obtained in an approximate analytical form by means of a variational approach, which also allows the stability of the solutions to be predicted. Then, we directly simulate the two-dimensional case, taking the initial configuration as suggested by the variational approximation. We thus demonstrate that spatiotemporal solitons indeed exist and are stable. Furthermore, they are not, in the general case, equivalent to the previously known cylindrical spatial solitons. Direct simulations generate solitons with some internal oscillations. However, these oscillations neither grow nor do they exhibit any significant radiative damping. Numerical solutions of the stationary version of the equations produce the same solitons in their unperturbed form, i.e., without internal oscillations. Strictly stable solitons exist only if the system has anomalous dispersion at both the fundamental harmonic and second harmonic (SH), including the case of zero dispersion at SH. Quasistationary solitons, decaying extremely slowly into radiation, are found in the presence of weak normal dispersion at the second-harmonic frequency.

Topological charge and angular momentum of light beams carrying optical vortices

We analyze the properties of light beams carrying phase singularities, or optical vortices. The transformations of topological charge during free-space propagation of a light wave, which is a combination of a Gaussian beam and a multiple charged optical vortex within a Gaussian envelope, are studied both in theory and experiment. We revise the existing knowledge about topological charge conservation, and demonstrate possible scenarios where additional vortices appear or annihilate during free propagation of such a combined beam. Coaxial interference of optical vortices is also analyzed, and the general rule for angular-momentum density distribution in a combined beam is established. We show that, in spite of any variation in the number of vortices in a combined beam, the total angular momentum is constant during the propagation. [S1050-2947(97)09910-1].

Assessment of flow in perforating arteries during intracranial aneurysm surgery using intraoperative near-infrared indocyanine green videoangiography

OBJECTIVE: Perforating arteries are commonly involved during the surgical dissection and clipping of intracranial aneurysms. Occlusion of perforating arteries is responsible for ischemic infarction and poor outcome. The goal of this study is to describe the usefulness of near-infrared indocyanine green videoangiography (ICGA) for the intraoperative assessment of blood flow in perforating arteries that are visible in the surgical field during clipping of intracranial aneurysms. In addition, we analyzed the incidence of perforating vessels involved during the aneurysm surgery and the incidence of ischemic infarct caused by compromised small arteries. METHODS: Sixty patients with 64 aneurysms were surgically treated and prospectively included in this study. Intraoperative ICGA was performed using a surgical microscope (Carl Zeiss Co., Oberkochen, Germany) with integrated ICGA technology. The presence and involvement of perforating arteries were analyzed in the microsurgical field during surgical dissection and clip application. Assessment of vascular patency after clipping was also investigated. Only those small arteries that were not visible on preoperative digital subtraction angiography were considered for analysis. RESULTS: The ICGA was able to visualize flow in all patients in whom perforating vessels were found in the microscope field. Among 36 patients whose perforating vessels were visible on ICGA, 11 (30%) presented a close relation between the aneurysm and perforating arteries. In one (9%) of these 11 patients, ICGA showed occlusion of a P1 perforating artery after clip application, which led to immediate correction of the clip confirmed by immediate reestablishment of flow visible with ICGA without clinical consequences. Four patients (6.7%) presented with postoperative perforating artery infarct, three of whom had perforating arteries that were not visible or distant from the aneurysm. CONCLUSION: The involvement of perforating arteries during clip application for aneurysm occlusion is a usual finding. Intraoperative ICGA may provide visual information with regard to the patency of these small vessels.

Evaluation of retinal nerve fiber layer thickness measurements using optical coherence tomography in patients with tobacco-alcohol-induced toxic optic neuropathy

Three patients with progressive visual loss, chronic alcoholism and tabagism were submitted to a complete neuro-ophthalmic examination and to retinal nerve fiber layer (RNFL) measurements using optical coherence tomography (OCT) scanning. Two patients showed marked RNFL loss in the temporal sector of the optic disc. However, a third patient presented RNFL measurements within or above normal limits, based on the Stratus-OCT normative database. Such findings may be due to possible RNFL edema similar to the one that may occur in the acute phase of toxic optic neuropathies. Stratus-OCT was able to detect RNFL loss in the papillomacular bundle of patients with tobacco-alcohol-induced toxic optic neuropathy. However, interpretation must be careful when OCT does not show abnormality in order to prevent diagnostic confusion, since overestimation of RNFL thickness measurements is possible in such cases.

Comparison of Fourier-Domain and Time-Domain Optical Coherence Tomography in the Detection of Band Atrophy of the Optic Nerve

PURPOSE: To compare the ability of Fourier-domain (FD) optical coherence tomography (3D OCT-1000; Top, con, Tokyo, Japan) and time domain (TD) OCT (Stratus; Carl Zeiss Meditec Inc, Dublin, California, USA) to detect axonal loss in eyes with band atrophy (BA) of the optic nerve. DESIGN: Cross-sectional study. METHODS: Thirty-six eyes from 36 patients with BA and temporal visual field (VF) defect from chiasmal compression and 36 normal eyes were studied. Subjects were submitted to standard automated perimetry and macular and retinal nerve fiber layer (RNFL) measurements were taken using 3D OCT-1000 and Stratus OCT. Receiver operating characteristic (ROC) curves were calculated for each parameter. Spearman correlation coefficients were obtained to evaluate the relationship between RNFL and macular thickness parameters and severity of VF loss. Measurements from the two devices were compared. RESULTS: Regardless of OCT device, all RNFL and macular thickness parameters were significantly lower in eyes with BA compared with normal eyes, but no statistically significant difference was found with regard to the area under the ROC curve. Structure-function relationships were also similar for the two devices. In both groups, RNFL and macular thickness measurements were generally and in some cases significantly smaller with 3D OCT-1000 than with Stratus OCT. CONCLUSIONS: The introduction of FD technology did not lead to better discrimination ability for detecting BA of the optic nerve compared with TD technology when using the software currently provided by the manufacturer. 3D OCT-1000 FD OCT RNFL and macular measurements were generally smaller than TD Stratus OCT measurements. Investigators should be aware of this fact when comparing measurements obtained with these two devices. (Am J Oplathalmol 2009;147: 56-63. (c) 2009 by Elsevier Inc. All rights reserved.)

Comparison of the GDx VCC scanning laser polarimeter and the stratus optical coherence tomograph in the detection of band atrophy of the optic nerve

Aim To compare the ability of scanning laser polarimeter (SLP) with variable corneal compensation (GDx VCC) and optical coherence tomograph (Stratus OCT) to discriminate between eyes with band atrophy (BA) of the optic nerve and healthy eyes. Methods The study included 37 eyes with BA and temporal visual field (VF) defects from chiasmal compression, and 29 normal eyes. Subjects underwent standard automated perimetry (SAP) and retinal nerve fibre layer (RNFL) scans using GDx VCC and Stratus OCT. The severity of the VF defects was evaluated by the temporal mean defect (TMD), calculated as the average of 22 values of the temporal total deviation plot on SAP. Receiver operating characteristic (ROC) curves were calculated. Pearson`s correlation coefficients were used to evaluate the relationship between RNFL thickness parameters and the TMD. Results No significant difference was found between the ROC curves areas (AUCs) for the GDx VCC and Stratus OCT with regard to average RNFL thickness (0.98 and 0.99, respectively) and the superior (0.94; 0.95), inferior (0.96; 0.97), and nasal (0.92; 0.96) quadrants. However, the AUC in the temporal quadrant (0.77) was significantly smaller (P < 0.001) with GDx VCC than with Stratus OCT (0.98). Lower TMD values were associated with smaller RNFL thickness in most parameters from both equipments. Conclusion Adding VCC resulted in improved performance in SLP when evaluating eyes with BA, and both technologies are sensitive in detecting average, superior, inferior, and nasal quadrant RNFL loss. However, GDx VCC still poorly discriminates RNFL loss in the temporal quadrant when compared with Stratus OCT.

Ductus venosus Doppler and postnatal outcomes in fetuses with absent or reversed end-diastolic flow in the umbilical arteries

Objective: To evaluate the relationship between ductus venosus Doppler findings on the day of delivery and postnatal outcomes in pregnancies with absent or reversed end-diastolic (ARED) flow in the umbilical arteries. Study design: Postnatal outcomes of 103 newborns of pregnancies with a diagnosis of ARED flow on Doppler velocimetry of the umbilical arteries were analyzed retrospectively between January 1997 and December 2004. Single pregnancies and fetuses without malformations were included. The cases were divided into two groups according to the flow during atrial contraction (a-wave) in the ductus venosus on the day of delivery: group A, 20 cases with absent or reversed flow in the ductus venosus and group B, 83 cases with positive flow. The results were analyzed statistically using the chi-square test, Fisher`s exact test and the Mann-Whitney U test with the level of significance set at 5%. Results: All newborns were delivered by cesarean section. Gestational age was similar in the two groups (group A: 30 weeks and group B: 30.9 weeks, P = 0.23). Absent or reversed ductus venosus flow was associated with the following adverse postnatal outcomes: lower birthweight (P < 0.001), lower Apgar scores in the first (P = 0.001) and fifth minute (P = 0.001), a higher frequency of orotracheal intubation (P = 0.001) and pH at birth less than 7.20 (P < 0.001), pulmonary hemorrhage (P = 0.03), thrombocytopenia (P = 0.02), hypoglycemia (P = 0.01), intracranial hemorrhage (P = 0.02), and postnatal death (P = 0.007). Conclusion: The study of ductus venosus flow may provide additional information regarding the best time for interruption of pregnancies with ARED flow in the umbilical arteries characterized by extreme prematurity. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

Effect of sildenafil on clitoral blood flow and sexual response in postmenopausal women with orgasmic dysfunction

Objective: To analyze the effects of sildenafil citrate on clitoral blood flow and sexual response in postmenopausal women with orgasmic dysfunction. Method: In this randomized, double-blind, placebo-controlled trial 22 women received a 50-mg dose of sildenafil (n=11) or placebo (n=11) daily for 15 days. The Golombok Rust Inventory of Sexual Satisfaction (GRISS) was used for subjective evaluation of the sexual-response cycle. Clitoral blood flow was measured by color and pulse Doppler at baseline, after 1 hour of taking the first dose, and after 15 days of treatment. Results: Blood flow was significantly more improved in the sildenafit than in the placebo group (P<0.05), and a positive correlation between Doppler values and GRISS scores was noted in the sildenafil group after only 15 days of treatment. Conclusion: Sildenafil may improve clitoral blood flow and increase the GRISS scores in postmenopausal women with orgasmic dysfunction. (C) 2008 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

Effects of estradiol and norethisterone on lipids, insulin resistance and carotid flow

Objectives: To evaluate the lipid profile, insulin resistance and vasomotricity, and the interaction between these factors, in postmenopausal women receiving hormone therapy. Methods: A prospective, randomized, double-blind study was carried out in which 77 postmenopausal women received one of the three treatment regimens: (A) 2 mg oral micronized estradiol (E(2)) (n = 25); (B) 2 mg oral E(2) + 1 mg oral norethisterone acetate (NETA) (n = 28); or Q placebo (n = 24), daily for 6 months. Evaluations were carried out at baseline and at the end of treatment on lipid and lipoprotein profiles, homeostasis model assessment of insulin resistance (HOMA-IR) and pulsatility index (PI) of the internal carotid artery by Doppler ultrasonography. Results: Mean increases of 15.6% and 2.4% and a reduction of 6.4% in high-density lipoprotein (HDL) levels were found for the E(2), E(2) + NETA and placebo groups, respectively. Reductions of 9.5% and 3.7% and an increase of 12.1% in low-density lipoprotein (LDL), and reductions of 20.0% and 3.8% and an increase of 28.8% in the LDL:HDL ratio were found for the E(2), E(2) + NETA and placebo groups, respectively (p < 0.001 in all cases). Insulin levels and HOMA-IR decreased 12.8% and 12.3% in the E2 group and increased 12.9% and 16.0% in the E(2) + NETA group (p < 0.05), respectively. Carotid PI following treatment was 1.18 +/- 0.23, 1.38 +/- 0.20 and 1.41 +/- 0.21 for the E(2), E(2) + NETA and placebo groups, respectively (p = 0.0006). Conclusions: Oral estrogen therapy led to an improvement in lipid profile, insulin resistance and carotid blood flow, which was cancelled when NETA was associated. (c) 2008 Elsevier Ireland Ltd. All rights reserved.

Pulmonary morphofunctional effects of mechanical ventilation with high inspiratory air flow

Objective: Uncertainties about the numerous degrees of freedom in ventilator settings leave many unanswered questions about the biophysical determinants of lung injury. We investigated whether mechanical ventilation with high air flow could yield lung mechanical stress even in normal animals. Design. Prospective, randomized, controlled experimental study. Setting: University research laboratory. Subjects. Thirty normal male Wistar rats (180-230 g). Interventions: Rats were ventilated for 2 hrs with tidal volume of 10 mL/kg and either with normal inspiratory air flow (V`) of 10 mL/s (F10) or high V` of 30 mL/s (F30). In the control group, animals did not undergo mechanical ventilation. Because high flow led to elevated respiratory rate (200 breaths/min) and airway peak inspiratory pressure (PIP,aw = 17 cm H2O), two additional groups were established to rule out the potential contribution of these variables: a) normal respiratory rate = 100 breaths/min and V` = 30 mL/sec; and b) PIP,aw = 17 cm H2O and V` 10 mL/sec. Measurements and Main Results: Lung mechanics and histology (light and electron microscopy), arterial blood gas analysis, and type III procollagen messenger RNA expression in lung tissue were analyzed. Ultrastructural microscopy was similar in control and F10 groups. High air flow led to increased lung plateau and peak pressures, hypoxemia, alveolar hyperinflation and collapse, pulmonary neutrophilic infiltration, and augmented type III procollagen messenger RNA expression compared with control rats. The reduction of respiratory rate did not modify the morphofunctional behavior observed in the presence of increased air flow. Even though the increase in peak pressure yielded mechanical and histologic changes, type III procollagen messenger RNA expression remained unaltered. Conclusions: Ventilation with high inspiratory air flow may lead to high tensile and shear stresses resulting in lung functional and morphologic compromise and elevation of type III procollagen messenger RNA expression.

Effect of Disease Severity and Optic Disc Size on Diagnostic Accuracy of RTVue Spectral Domain Optical Coherence Tomograph in Glaucoma

PURPOSE. To evaluate the effect of disease severity and optic disc size on the diagnostic accuracies of optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular parameters with RTVue (Optovue, Fremont, CA) spectral domain optical coherence tomography (SDOCT) in glaucoma. METHODS. 110 eyes of 62 normal subjects and 193 eyes of 136 glaucoma patients from the Diagnostic Innovations in Glaucoma Study underwent ONH, RNFL, and macular imaging with RTVue. Severity of glaucoma was based on visual field index (VFI) values from standard automated perimetry. Optic disc size was based on disc area measurement using the Heidelberg Retina Tomograph II (Heidelberg Engineering, Dossenheim, Germany). Influence of disease severity and disc size on the diagnostic accuracy of RTVue was evaluated by receiver operating characteristic (ROC) and logistic regression models. RESULTS. Areas under ROC curve (AUC) of all scanning areas increased (P < 0.05) as disease severity increased. For a VFI value of 99%, indicating early damage, AUCs for rim area, average RNLI thickness, and ganglion cell complex-root mean square were 0.693, 0.799, and 0.779, respectively. For a VFI of 70%, indicating severe damage, corresponding AUCs were 0.828, 0.985, and 0.992, respectively. Optic disc size did not influence the AUCs of any of the SDOCT scanning protocols of RTVue (P > 0.05). Sensitivity of the rim area increased and specificity decreased in large optic discs. CONCLUSIONS. Diagnostic accuracies of RTVue scanning protocols for glaucoma were significantly influenced by disease severity. Sensitivity of the rim area increased in large optic discs at the expense of specificity. (Invest Ophthalmol Vis Sci. 2011;92:1290-1296) DOI:10.1167/iovs.10-5516

Direct measurement of instantaneous source speed for a HDR brachytherapy unit using an optical fiber based detector

Purpose: Several attempts to determine the transit time of a high dose rate (HDR) brachytherapy unit have been reported in the literature with controversial results. The determination of the source speed is necessary to accurately calculate the transient dose in brachytherapy treatments. In these studies, only the average speed of the source was measured as a parameter for transit dose calculation, which does not account for the realistic movement of the source, and is therefore inaccurate for numerical simulations. The purpose of this work is to report the implementation and technical design of an optical fiber based detector to directly measure the instantaneous speed profile of a (192)Ir source in a Nucletron HDR brachytherapy unit. Methods: To accomplish this task, we have developed a setup that uses the Cerenkov light induced in optical fibers as a detection signal for the radiation source moving inside the HDR catheter. As the (192)Ir source travels between two optical fibers with known distance, the threshold of the induced signals are used to extract the transit time and thus the velocity. The high resolution of the detector enables the measurement of the transit time at short separation distance of the fibers, providing the instantaneous speed. Results: Accurate and high resolution speed profiles of the 192Ir radiation source traveling from the safe to the end of the catheter and between dwell positions are presented. The maximum and minimum velocities of the source were found to be 52.0 +/- 1.0 and 17.3 +/- 1:2 cm/s. The authors demonstrate that the radiation source follows a uniformly accelerated linear motion with acceleration of vertical bar a vertical bar = 113 cm/s(2). In addition, the authors compare the average speed measured using the optical fiber detector to those obtained in the literature, showing deviation up to 265%. Conclusions: To the best of the authors` knowledge, the authors directly measured for the first time the instantaneous speed profile of a radiation source in a HDR brachytherapy unit traveling from the unit safe to the end of the catheter and between interdwell distances. The method is feasible and accurate to implement on quality assurance tests and provides a unique database for efficient computational simulations of the transient dose. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3483780]

Flow-through peritoneal dialysis in neonatal enema-induced hyperphosphatemia

Fleet enemas are hypertonic solutions with an osmotic action and a high concentration of phosphate. When retained in the human body they have a great toxic potential, causing severe hydro-electrolyte disorders in children, especially in newborns. We report the case of a previously healthy 8-day-old newborn who needed neonatal intensive care treatment after the inadvertent administration of an osmotically active hypertonic phosphate enema. Taking into account that phosphate removal by peritoneal dialysis (PD) strongly depends on total dialysate turnover, we chose continuous flow PD (CFPD) as the treatment option, with a successful outcome. Clinical experience with this dialytic modality is limited to a few case reports in pediatric and adult patients. To the best of our knowledge, we report here the first description of CFPD in the setting of acute phosphate nephropathy in the neonatal period. The modality of PD described here has potential as an alternative management option as it is a highly efficient, methodologically simple, and low-cost method without any need for sophisticated equipment. Physicians and parents should be aware of the adverse effects of a hypertonic phosphate enema and should never use these medications in infants and newborns.

Comparison of Different Spectral Domain Optical Coherence Tomography Scanning Areas for Glaucoma Diagnosis

Purpose: To evaluate retinal nerve fiber layer (RNFL), optic nerve head (ONH), and macular thickness measurements for glaucoma detection using the RTVue spectral domain optical coherence tomograph. Design: Diagnostic, case-control study. Participants: One hundred forty eyes of 106 glaucoma patients and 74 eyes of 40 healthy subjects from the Diagnostic Innovations in Glaucoma Study (DIGS). Methods: All patients underwent ocular imaging with the commercially available RTVue. Optic nerve head, RNFL thickness, and macular thickness scans were obtained during the same visit. Receiver operating characteristic (ROC) curves and sensitivities at fixed specificities (80% and 95%) were calculated for each parameter. Main Outcome Measures: Areas under the ROC curves (AUC) and sensitivities at fixed specificities of 80% and 95%. Results: The AUC for the RNFL parameter with best performance, inferior quadrant thickness, was significantly higher than that of the best-performing ONH parameter, inferior rim area (0.884 vs 0.812, respectively; P = 0.04). There was no difference between ROC curve areas of the best RNFL thickness parameters and the best inner macular thickness measurement, ganglion cell complex root mean square (ROC curve area = 0.870). Conclusions: The RTVue RNFL and inner retinal macular thickness measurements had good ability to detect eyes with glaucomatous visual field loss and performed significantly better than ONH parameters.

Introduction to Discounted Cash Flow Analysis and Financial Functions in Excel

The financial and economic analysis of investment projects is typically carried out using the technique of discounted cash flow (DCF) analysis. This module introduces concepts of discounting and DCF analysis for the derivation of project performance criteria such as net present value (NPV), internal rate of return (IRR) and benefit to cost (B/C) ratios. These concepts and criteria are introduced with respect to a simple example, for which calculations using MicroSoft Excel are demonstrated.