Effective water treatment for rural communities in Suriname : a comparison of point-of-use ceramic filters and centralized treatment with sand filters

For countless communities around the world, acquiring access to safe drinking water is a daily challenge which many organizations endeavor to meet. The villages in the interior of Suriname have been the focus of many improved drinking water projects as most communities are without year-round access. Unfortunately, as many as 75% of the systems in Suriname fail within several years of implementation. These communities, scattered along the rivers and throughout the jungle, lack many of the resources required to sustain a centralized water treatment system. However, the centralized system in the village of Bendekonde on the Upper Suriname River has been operational for over 10 years and is often touted by other communities. The Bendekonde system is praised even though the technology does not differ significantly from other failed systems. Many of the water systems that fail in the interior fail due to a lack of resources available to the community to maintain the system. Typically, the more complex a system becomes, so does the demand for additional resources. Alternatives to centralized systems include technologies such as point-of-use water filters, which can greatly reduce the necessity for outside resources. In particular, ceramic point-of-use water filters offer a technology that can be reasonably managed in a low resource setting such as that in the interior of Suriname. This report investigates the appropriateness and effectiveness of ceramic filters constructed with local Suriname clay and compares the treatment effectiveness to that of the Bendekonde system. Results of this study showed that functional filters could be produced from Surinamese clay and that they were more effective, in a controlled laboratory setting, than the field performance of the Bendekonde system for removing total coliform. However, the Bendekonde system was more successful at removing E. coli. In a life-cycle assessment, ceramic water filters manufactured in Suriname and used in homes for a lifespan of 2 years were shown to have lower cumulative energy demand, as well as lower global warming potential than a centralized system similar to that used in Bendekonde.

Review of free-space optical communications with diverging beam

The report reviews the technology of Free-space Optical Communication (FSO) and simulation methods for testing the performance of diverged beam in the technology. In addition to the introduction, the theory of turbulence and its effect over laser is also reviewed. In the simulation revision chapter, on-off keying (OOK) and diverged beam is assumed in the transmitter, and in the receiver, avalanche photodiode (APD) is utilized to convert the photon stream into electron stream. Phase screens are adopted to simulate the effect of turbulence over the phase of the optical beam. Apart from this, the method of data processing is introduced and retrospected. In the summary chapter, there is a general explanation of different beam divergence and their performance.

Calibration of a surgical microscope with automated zoom lenses using an active optical tracker

BACKGROUND: In this paper, we present a new method for the calibration of a microscope and its registration using an active optical tracker. METHODS: Practically, both operations are done simultaneously by moving an active optical marker within the field of view of the two devices. The IR LEDs composing the marker are first segmented from the microscope images. By knowing their corresponding three-dimensional (3D) position in the optical tracker reference system, it is possible to find the transformation matrix between the referential of the two devices. Registration and calibration parameters can be extracted directly from that transformation. In addition, since the zoom and focus can be modified by the surgeon during the operation, we propose a spline based method to update the camera model to the new setup. RESULTS: The proposed technique is currently being used in an augmented reality system for image-guided surgery in the fields of ear, nose and throat (ENT) and craniomaxillofacial surgeries. CONCLUSIONS: The results have proved to be accurate and the technique is a fast, dynamic and reliable way to calibrate and register the two devices in an OR environment.

Optical hysteresis of ridge waveguide magnetic garnet films and cavities in two-dimensional magneto-photonic crystal slabs

Magnetic iron garnets as well as magnetic photonic crystals are of great interests in magneto-optic applications such as isolators, current captors, circulators, TE-TM mode conversion, wavelength accordable filters, optical sensors and switches, all of which provide a promising platform for future integrated optical circuits. In the present work, two topics are studied based on magnetic iron garnet films. In the first part, the characteristics of the magnetization are investigated for ridge waveguides fabricated on (100) oriented iron garnet thin films. The magnetic response in magneto-optic waveguides patterned on epitaxial magnetic garnet films depends on the crystallographic orientation of the waveguides and the magnetic anisotropy of the material. These can be studied by polarization rotation hysteresis loops, which are related to the component of magnetization parallel to the light propagation direction and the linear birefringence. Polarization rotation hysteresis loops for low birefringence waveguides with different orientations are experimentally investigated. Asymmetric stepped curves are obtained from waveguides along, due to the large magnetocrystalline anisotropy in the plane. A model based on the free energy density is developed to demonstrate the motion of the magnetization and can be used in the design of magneto-optic devices. The second part of this thesis focuses on the design and fabrication of high-Q cavities in two-dimensional magneto-photonic crystal slabs. The device consists of a layer of silicon and a layer of iron garnet thin film. Triangular lattice elliptical air holes are patterned in the slab. The fundamental TM band gap overlaps with the first-order TE band gap from 0374~0.431(a/λ) showing that both TE and TM polarization light can be confined in the photonic crystals. A nanocavity is designed to obtain both TE and TM defect modes in the band gaps. Additional work is needed to overlap the TE and TM defect modes and obtain a high-Q cavity so as to develop miniaturized Faraday rotators.

Quantification of dental erosions in patients with GERD using optical coherence tomography before and after double-blind, randomized treatment with esomeprazole or placebo

OBJECTIVES: Dental erosion, the chemical dissolution of enamel without bacterial involvement, is a rarely reported manifestation of gastroesophageal reflux disease (GERD), as well as of recurrent vomiting and dietary habits. It leads to loss of tooth substance, hypersensitivity, functional impairment, and even tooth fracture. To date, dental erosions have been assessed using only very basic visual methods, and no evidence-based guidelines or studies exist regarding the prevention or treatment of GERD-related dental erosions. METHODS: In this randomized, double-blind study, we used optical coherence tomography (OCT) to quantify dental tissue demineralization and enamel loss before and after 3 weeks of acid-suppressive treatment with esomeprazole 20 mg b.i.d. or placebo in 30 patients presenting to the Berne University Dental Clinic with advanced dental erosions and abnormal acid exposure by 24-h esophageal pH manometry (defined as >4% of the 24-h period with pH<4). Enamel thickness, reflectivity, and absorbance as measures of demineralization were quantified by OCT before and after therapy at identical localizations on teeth with most severe visible erosions as well as several other predefined changes in teeth. RESULTS: The mean+/-s.e.m. decrease of enamel thickness of all teeth before and after treatment at the site of maximum exposure was 7.2+/-0.16 black trianglem with esomeprazole and 15.25+/-0.17black trianglem with placebo (P=0.013), representing a loss of 0.3% and 0.8% of the total enamel thickness, respectively. The change in optical reflectivity to a depth of 25 black trianglem after treatment was-1.122 +/-0.769 dB with esomeprazole and +2.059+/-0.534 dB with placebo (P 0.012), with increased reflectivity signifying demineralization. CONCLUSIONS: OCT non-invasively detected and quantified significantly diminished progression of dental tissue demineralization and enamel loss after only 3 weeks of treatment with esomeprazole 20 mg b.i.d. vs. placebo. This suggests that esomeprazole may be useful in counteracting progression of GERD-related dental erosions. Further validation of preventative treatment regimens using this sensitive detection method is required, including longer follow-up and correlation with quantitative reflux measures.

Characterization of microfluidic systems with Doppler optical coherence tomography

Doppler Optical Coherence Tomography (DOCT) is a biomedical imaging technique that allows simultaneous structural imaging and flow monitoring inside biological tissues and materials with spatial resolution in the micrometer scale. It has recently been applied to the characterization of microfluidic systems. Structural and flow imaging of novel microfluidics platforms for cytotoxicologic applications were obtained with a real-time, Near Infrared Spectral Domain DOCT system. Characteristics such as flow homogeneity in the chamber, which is one of the most important parameters for cell culture, are investigated. OCT and DOCT images were used to monitor flow inside a specific platform that is based on microchannel division for a better flow homogeneity. In particular, the evolution of flow profile at the transition between the microchannel structure and the chamber is studied.

Coronary evaginations are associated with positive vessel remodelling and are nearly absent following implantation of newer-generation drug-eluting stents: an optical coherence tomography and intravascular ultrasound study

OBJECTIVES The purpose of this study was to assess the occurrence, predictors, and mechanisms of optical coherence tomography (OCT)-detected coronary evaginations following drug-eluting stent (DES) implantation. BACKGROUND Angiographic ectasias and aneurysms in stented segments have been associated with a risk of late stent thrombosis. Using OCT, some stented segments show coronary evaginations reminiscent of ectasias. METHODS Evaginations were defined as outward bulges in the luminal contour between struts. They were considered major evaginations (MEs) when extending ≥3 mm along the vessel length, with a depth ≥10% of the stent diameter. A total of 228 patients who had sirolimus (SES)-, paclitaxel-, biolimus-, everolimus (EES)-, or zotarolimus (ZES)-eluting stents implanted in 254 lesions, were analysed after 1, 2, or 5 years; and serial assessment using OCT and intravascular ultrasound (IVUS) was performed post-intervention and after 1 year in 42 patients. RESULTS Major evaginations occurred frequently at all time points in SES (∼26%) and were rarely seen in EES (3%) and ZES (2%, P = 0.003). Sirolimus-eluting stent implantation was the strongest independent predictor of ME [adjusted OR (95% CI) 9.1 (1.1-77.4), P = 0.008]. Malapposed and uncovered struts were more common in lesions with vs. without ME (77 vs. 25%, P < 0.001 and 95 vs. 20%, P < 0.001, respectively) as was thrombus [49 vs. 14%, OR 7.3 (95% CI: 1.7-31.2), P = 0.007]. Post-intervention intra-stent dissection and protrusion of the vessel wall into the lumen were associated with an increased risk of evagination at follow-up [OR (95% CI): 2.9 (1.8-4.9), P < 0.001 and 3.3 (1.6-6.9), P = 0.001, respectively]. In paired IVUS analyses, lesions with ME showed a larger increase in the external elastic membrane area (20% area change) compared with lesions without ME (5% area change, P < 0.001). CONCLUSION Optical coherence tomography-detected MEs are a specific morphological footprint of early-generation SES and are nearly absent in newer-generation ZES and EES. Evaginations appear to be related to vessel injury at baseline; are associated with positive vessel remodelling; and correlate with uncoverage, malapposition, and thrombus at follow-up.

One-year head to head comparison of the neointimal response between sirolimus eluting stent with reservoir technology and everolimus eluting stent: an optical coherence tomography study

OBJECTIVE to compare the vascular healing process between the sirolimus-eluting NEVO and the everolimus-eluting Xience stent by optical coherence tomography (OCT) at 1-year follow-up. BACKGROUND Presence of durable polymer on a drug-eluting metallic stent may be the basis of an inflammatory reaction with abnormal healing response. The NEVO stent, having a bioresorbable polymer eluted by reservoir technology, may overcome this problem. METHODS All consecutive patients, who received NEVO or Xience stent implantation between September 2010 and October 2010 in our institution, were included. Vascular healing was assessed at 1-year as percentage of uncovered struts, neointimal thickness (NIT), in-stent/stent area obstruction and pattern of neointima. RESULTS A total 47 patients (2:1 randomization, n = 32 NEVO, n = 15 Xience) were included. Eighteen patients underwent angiographic follow-up (eight patients with nine lesions for NEVO vs. 10 patients with 11 lesions for Xience). The angiographic late loss was numerically higher but not statistically different in NEVO compared with Xience treated lesions (0.38 ± 0.47 mm vs. 0.18 ± 0.27 mm; P = 0.171). OCT analysis of 4,912 struts demonstrated similar rates of uncovered struts (0.5 vs. 0.7%, P = 0.462), higher mean NIT (177.76 ± 87.76 µm vs. 132.22 ± 30.91 µm; P = 0.170) and in stent/stent area obstruction (23.02 ± 14.74% vs. 14.17 ± 5.94%, P = 0.120) in the NEVO as compared with Xience. CONCLUSION The NEVO stent with a reservoir technology seems to exhibit more neointimal proliferation as compared to Xience stent. The findings of our study, which currently represent the unique data existing on this reservoir technology, would need to be confirmed in a large population.

Tissue coverage and neointimal hyperplasia in overlap versus nonoverlap segments of drug-eluting stents 9 to 13 months after implantation: in vivo assessment with optical coherence tomography

BACKGROUND Histologic experimental studies have reported incomplete neointimal healing in overlapping with respect to nonoverlapping segments in drug-eluting stents (DESs), but these observations have not been confirmed in human coronary arteries hitherto. On the contrary, angiographic and optical coherence tomography studies suggest that DES overlap elicits rather an exaggerated than an incomplete neointimal reaction. METHODS Optical coherence tomography studies from 2 randomized trials including sirolimus-eluting, biolimus-eluting, everolimus-eluting, and zotarolimus-eluting stents were analyzed at 9- to 13-month follow-up. Coverage in overlapping segments was compared versus the corresponding nonoverlapping segments of the same stents, using statistical pooled analysis. RESULTS Forty-two overlaps were found in 31 patients: 11 in sirolimus-eluting stents, 3 in biolimus-eluting stents, 17 in everolimus-eluting stents, and 11 in zotarolimus-eluting stents. The risk ratio of incomplete coverage was 2.35 (95% CI 1.86-2.98) in overlapping versus nonoverlapping segments. Thickness of coverage in overlaps was only 85% (95% CI 81%-90%) of the thickness in nonoverlaps. Significant heterogeneity of the effect was observed, especially pronounced in the comparison of thickness of coverage (I(2) = 90.31). CONCLUSIONS The effect of overlapping DES on neointimal inhibition is markedly heterogeneous: on average, DES overlap is associated with more incomplete and thinner coverage, but in some cases, the overlap elicits an exaggerated neointimal reaction, thicker than in the corresponding nonoverlapping segments. These results might help to understand why overlapping DES is associated with worse clinical outcomes, both in terms of thrombotic phenomena and in terms of restenosis and revascularization.

Differential healing response attributed to culprit lesions of patients with acute coronary syndromes and stable coronary artery after implantation of drug-eluting stents: An optical coherence tomography study

BACKGROUND Pathology studies have shown delayed arterial healing in culprit lesions of patients with acute coronary syndrome (ACS) compared with stable coronary artery disease (CAD) after placement of drug-eluting stents (DES). It is unknown whether similar differences exist in-vivo during long-term follow-up. Using optical coherence tomography (OCT), we assessed differences in arterial healing between patients with ACS and stable CAD five years after DES implantation. METHODS AND RESULTS A total of 88 patients comprised of 53 ACS lesions with 7864 struts and 35 stable lesions with 5298 struts were suitable for final OCT analysis five years after DES implantation. The analytical approach was based on a hierarchical Bayesian random-effects model. OCT endpoints were strut coverage, malapposition, protrusion, evaginations and cluster formation. Uncovered (1.7% vs. 0.7%, adjusted p=0.041) or protruding struts (0.50% vs. 0.13%, adjusted p=0.038) were more frequent among ACS compared with stable CAD lesions. A similar trend was observed for malapposed struts (1.33% vs. 0.45%, adj. p=0.072). Clusters of uncovered or malapposed/protruding struts were present in 34.0% of ACS and 14.1% of stable patients (adj. p=0.041). Coronary evaginations were more frequent in patients with ST-elevation myocardial infarction compared with stable CAD patients (0.16 vs. 0.13 per cross section, p=0.027). CONCLUSION Uncovered, malapposed, and protruding stent struts as well as clusters of delayed healing may be more frequent in culprit lesions of ACS compared with stable CAD patients late after DES implantation. Our observational findings suggest a differential healing response attributable to lesion characteristics of patients with ACS compared with stable CAD in-vivo.

Osteo-odonto-keratoprosthesis (OOKP) and the testing of three different adhesives for bonding bovine teeth with optical poly-(methyl methacrylate) (PMMA) cylinder.

AIM Preparation of the lamina during osteo-odonto-keratoprosthesis (OOKP) design is complex, and its longevity and watertightness important. To date, only acrylic bone cements have been used for bonding the optical cylinder to the tooth dentine. Our aim was to evaluate different dental adhesives for OOKP preparation. METHODS Specimens of bovine teeth were produced by preparing 1.5-mm thick dentine slices with holes having a diameter of 3.5 mm. Each group (n=10 per group) was luted with either classic poly-(methyl methacrylate) (PMMA) bone cement, universal resin cement or glass ionomer cement. All specimens underwent force measurement using a uniaxial traction machine. RESULTS The highest mean force required to break the bond was measured for PMMA bone cement (128.2 N) followed by universal resin cement (127.9 N), with no statistically significant difference. Glass ionomer cement showed significantly lower force resistance (78.1 N). CONCLUSIONS Excellent bonding strength combined with easy application was found for universal resin cement, and thus, it is a potential alternative to acrylic bone cement in OOKP preparation.

Incidence and Imaging Outcomes of Acute Scaffold Disruption and Late Structural Discontinuity After Implantation of the Absorb Everolimus-Eluting Fully Bioresorbable Vascular Scaffold: Optical Coherence Tomography Assessment in the ABSORB Cohort B Trial (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions).

OBJECTIVES This study sought to describe the frequency and clinical impact of acute scaffold disruption and late strut discontinuity of the second-generation Absorb bioresorbable polymeric vascular scaffolds (Absorb BVS, Abbott Vascular, Santa Clara, California) in the ABSORB (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With De Novo Native Coronary Artery Lesions) cohort B study by optical coherence tomography (OCT) post-procedure and at 6, 12, 24, and 36 months. BACKGROUND Fully bioresorbable scaffolds are a novel approach to treatment for coronary narrowing that provides transient vessel support with drug delivery capability without the long-term limitations of metallic drug-eluting stents. However, a potential drawback of the bioresorbable scaffold is the potential for disruption of the strut network when overexpanded. Conversely, the structural discontinuity of the polymeric struts at a late stage is a biologically programmed fate of the scaffold during the course of bioresorption. METHODS The ABSORB cohort B trial is a multicenter single-arm trial assessing the safety and performance of the Absorb BVS in the treatment of 101 patients with de novo native coronary artery lesions. The current analysis included 51 patients with 143 OCT pullbacks who underwent OCT at baseline and follow-up. The presence of acute disruption or late discontinuities was diagnosed by the presence on OCT of stacked, overhung struts or isolated intraluminal struts disconnected from the expected circularity of the device. RESULTS Of 51 patients with OCT imaging post-procedure, acute scaffold disruption was observed in 2 patients (3.9%), which could be related to overexpansion of the scaffold at the time of implantation. One patient had a target lesion revascularization that was presumably related to the disruption. Of 49 patients without acute disruption, late discontinuities were observed in 21 patients. There were no major adverse cardiac events associated with this finding except for 1 patient who had a non-ischemia-driven target lesion revascularization. CONCLUSIONS Acute scaffold disruption is a rare iatrogenic phenomenon that has been anecdotally associated with anginal symptoms, whereas late strut discontinuity is observed in approximately 40% of patients and could be viewed as a serendipitous OCT finding of a normal bioresorption process without clinical implications. (ABSORB Clinical Investigation, Cohort B [ABSORB B]; NCT00856856).