Showing papers by "Michael Hughes published in 2009"

Quantitative deep sequencing reveals dynamic HIV-1 escape and large population shifts during CCR5 antagonist therapy in vivo.

Abstract: High-throughput sequencing platforms provide an approach for detecting rare HIV-1 variants and documenting more fully quasispecies diversity. We applied this technology to the V3 loop-coding region of env in samples collected from 4 chronically HIV-infected subjects in whom CCR5 antagonist (vicriviroc [VVC]) therapy failed. Between 25,000–140,000 amplified sequences were obtained per sample. Profound baseline V3 loop sequence heterogeneity existed; predicted CXCR4-using populations were identified in a largely CCR5-using population. The V3 loop forms associated with subsequent virologic failure, either through CXCR4 use or the emergence of high-level VVC resistance, were present as minor variants at 0.8–2.8% of baseline samples. Extreme, rapid shifts in population frequencies toward these forms occurred, and deep sequencing provided a detailed view of the rapid evolutionary impact of VVC selection. Greater V3 diversity was observed post-selection. This previously unreported degree of V3 loop sequence diversity has implications for viral pathogenesis, vaccine design, and the optimal use of HIV-1 CCR5 antagonists.

Can a high sense of control and john henryism be bad for mental health

Abstract: Social stratification profoundly affects mental health. Specifically, substantial empirical evidence finds that higher status promotes mental health via a higher sense of control and a propensity to cope actively with problems. An unresolved issue, though, is whether the effects of sense of control and active coping on mental health are uniformly beneficial across levels of socioeconomic status. Perceived control and John Henryism, an active coping style, may undermine mental health, especially for lower-status persons, who lack resources. Using data from the National Comorbidity Survey for African Americans, Hispanics, and whites, we find that both sense of control and John Henryism tend to be monotonically related to positive mental health regardless of socioeconomic status and race/ethnicity.

Safety and efficacy of nevirapine- and efavirenz-based antiretroviral treatment in adults treated for TB-HIV co-infection in Botswana.

Abstract: APPROXIMATELY 60% of adults with active tuberculosis (TB) in Botswana are also infected by human immunodeficiency virus type 1 (HIV-1).1 The Botswana National Antiretroviral Treatment Programme (or Masa Programme, meaning `new dawn' in Setswana) provides highly active antiretroviral treatment (ART) to all adults with the presence of an acquired immune-deficiency syndrome (AIDS) defining illness (including suspected or confirmed extra-pulmonary TB) and/or a CD4+ cell count of <200 cells/mm3.2 For HIV and TB co-infected adults with advanced immune suppression (CD4+ cell count <100 cells/mm3) who are most at risk for potentially life-threatening opportunistic infections, ART is begun as early as 2 weeks following the initiation of TB treatment. Co-infected adults with a recent CD4+ cell count of 100-200 cells/mm3 are offered ART once they have completed the first 2-month intensive phase of TB treatment.2 Standard TB treatment in Botswana consists of 2 months of daily isoniazid (INH), rifampicin (RMP), pyrazinamide, and ethambutol, followed by 4 months of daily INH and RMP (2HRZE/4HR). The concentrations of both widely used non-nucleoside reverse transcriptase inhibitors (NNRTIs), nevirapine (NVP) and efavirenz (EFV), are lowered with concurrent RMP use.3-5 Data from Asia and Africa suggest that immunologic and virologic responses are preserved despite concurrent use of EFV and RMP-based TB treatment.6-9 However, few reports have been published on the safety and efficacy of NVP with concurrent TB treatment.10-13 RMP, INH, NVP and EFV are associated with hepatotoxicity, and little is known about the relative rates of hepatotoxicity with either NVP or EFV in the setting of TB treatment. In this study, we retrospectively analyzed the Masa Programme Database of ART-treated adults receiving longitudinal care at the Infectious Disease Care Clinic (IDCC), Princess Marina Hospital, in the capital city of Gaborone, Botswana, between 2001 and 2004. We identified patients concurrently treated for both HIV and TB while comparing their outcomes with those of adults treated for HIV but not TB. Our aim was to assess whether virologic outcomes, immunologic outcomes and rates of hepatotoxicity were affected by concurrent use of either NVP- or EFV-based ART with TB treatment.

Response to Vicriviroc in Treatment-Experienced Subjects, as Determined by an Enhanced-Sensitivity Coreceptor Tropism Assay: Reanalysis of AIDS Clinical Trials Group A5211

Abstract: The enhanced-sensitivity Trofile assay (Monogram Biosciences) was used to retest coreceptor use at both study screening and study entry for 118 treatment-experienced subjects in AIDS Clinical Trials Group A5211 who had CCR5-tropic (R5) virus detected by the original Trofile assay at study screening. Among 90 recipients of vicriviroc, a significantly (P< .001) greater mean reduction in HIV-1 RNA was observed in 72 subjects with R5 virus versus 15 subjects reclassified as having dual/mixed-tropic viruses at screening: -1.11 versus -0.09 log(10) copies/mL at day 14 and -1.91 versus -0.57 log(10) copies/mL at week 24, respectively. Results suggest that the enhanced-sensitivity assay is a better screening tool for determining patient eligibility for CCR5 antagonist therapy.

Early Initiation of Lopinavir/Ritonavir in Infants Less Than 6 Weeks of Age: Pharmacokinetics and 24 Week Safety and Efficacy

Abstract: It is estimated that between 350,000 – 540,000 children became infected with HIV in 2007, nearly 90% of them living in sub-Saharan Africa.1 In resource-limited settings it is estimated that 35% of HIV-infected infants die by one year of age and 53% by age two.2 In a natural history cohort study of HIV-infected infants from resource-limited settings, disease progression was rapid, with 85% of infants meeting WHO criteria for ART initiation within 6 months of age.3 In addition, a randomized strategy trial showed that among infants aged 6 to 12 weeks with CD4% ≥25, early ART reduced mortality by 76% over a median follow up period of 32 weeks.4 Nevirapine (NVP) for prevention of mother to child transmission has been the first line agent used in most resource-limited settings; however, limited data in HIV-infected infants who have failed single dose NVP suggest that there may be a higher rate of virologic failure when NVP is used for treatment within the first year of life.5 It is therefore important to study highly active agents other than NVP that could be used to treat very young infants. Lopinavir/ritonavir (LPV/r) is safe and effective in infants and children older than 6 weeks of age, but its pharmacokinetic profile in younger infants has not been studied. Because infants in the first months of life generally have immature drug elimination processes and altered absorption, extrapolating doses from older children risks different drug exposure in young infants and incomplete virologic suppression and/or potential toxicity. The current study was initiated to evaluate the dose requirements as well as the safety, tolerability, and efficacy of LPV/r in infants <6 months of age; the 24 week results from the older cohort (≥ 6 weeks to < 6 months) have been reported elsewhere6 and this report includes 24 week results for the cohort of infants ages ≥14 days and <6 weeks.

A case-crossover analysis of predictors of condom use by female bar and hotel workers in Moshi, Tanzania

Abstract: Background Factors related to specific sexual encounters can influence condom use during these encounters. These situation-specific factors have not been adequately studied in resource-poor countries where HIV infection has in some areas reached epidemic levels. This study was undertaken to identify situation-specific factors associated with condom use among 465 female bar and hotel workers in Moshi, Tanzania. Methods We conducted a case-crossover study in which women provided information about their most recent unprotected and protected sexual encounters. Conditional logistic regression was used to estimate paired odds ratios and 95% confidence intervals for the association between situation-specific factors and condom use. Results A subject-based or mutual decision about condom use (compared with partner based), casual partner type, a first-time sexual encounter and receiving gifts in exchange for sex were independently associated with increased odds of condom use, while sex at home and sex with a partner more than 10 years older was associated with reduced odds of use. There was also effect modification between partner type and decision-making: subject-based or mutual decisions were more protective with casual than regular partners; also, when the partner made the decisions about condom use, the type of partner had no effect. Conclusions Decision-making about condom use is a potentially modifiable predictor of unprotected sex, but its effect varies by partner type. Behavioural interventions are needed that encourage discussion about condom use and increase women's self-efficacy, but other types of interventions as well as female-controlled HIV prevention methods are needed for women in regular partnerships.

Treatment Responses in Antiretroviral Treatment-Naive Premenopausal and Postmenopausal HIV-1-Infected Women: An Analysis from AIDS Clinical Trials Group Studies

Abstract: Menopause may affect antiretroviral treatment (ART) response. Immunologic and virologic responses to ART were compared in 220 premenopausal and 47 postmenopausal women enrolled in 2 studies involving ART-naive persons. Changes in CD4 counts or human immunodeficiency virus type 1 RNA levels were similar at 24, 48, and 96 weeks after treatment initiation. ART-naive women should respond to ART regardless of menopausal status.

Simplified dynamic focus method for time domain OCT

Abstract: A new optical arrangement for performing dynamic focus in time domain optical coherence tomography (OCT) is demonstrated. Unlike previously reported schemes which require mechanical coupling of the object and reference arms, this method is confined to the object arm only and therefore does not impose design constraints on the OCT system layout. The scheme is tested on a high lateral resolution OCT system (NA = 0.13) and it is shown that the effective depth of focus is extended from 200 mum to better than 2 mm. The optimum correction is for media with a mean refractive index of 1.4.

Lymphoma Diagnosis and Plasma Epstein-Barr Virus Load during Vicriviroc Therapy: Results of the AIDS Clinical Trials Group A5211

Abstract: Ninety percent to 95% of the adult human population carries Epstein-Barr virus (EBV) as a chronic latent infection; the vast majority of these patients experience no serious sequelae. Healthy adults experience episodes of transient EBV viremia, with EBV DNA levels in whole blood usually <2000 copies/mL [1]. In HIV-infected patients, EBV has been associated with the development of AIDS-related diffuse large cell Hodgkin and Burkitt lymphomas [2]. The CCR5 antagonist maraviroc is approved for treatment-experienced patients with HIV infection [3, 4], and several other agents are in various stages of clinical development [5, 6]. Functional inactivation of CCR5 because of a homozygous 32 amino acid deletion of this protein (CCR5Δ32/CCR5Δ32) is generally well tolerated. However, studies of CCR5 knockout mice and epidemiological data from human CCR5Δ32 homozygotes suggest that this deletion may increase the susceptibility to and severity of certain infections, including tickborne encephalitis and West Nile virus [7–13]. The AIDS Clinical Trials Group (ACTG) protocol A5211 was a randomized, placebo-controlled phase IIb study that assessed the safety and efficacy of the investigational CCR5 antagonist vicriviroc (VCV) in 118 treatment-experienced patients [14]. Among the 118 enrolled participants, 4 of 90 VCV recipients and none of 28 control subjects developed lymphomas within the first 13 months of VCV treatment. In light of the known link between EBV and lymphomas, we explored whether VCV treatment affected the level of EBV viremia over time.

Marginal Adaptation of Ceramic Veneers Investigated with en-face Optical Coherence Tomography

Abstract: The aim of this study was to analyze the quality of marginal adaptation and gap width of Empress veneers using en-face optical coherence tomography. The results prove the necessity of investigating the marginal adaptation after each veneer bonding process.

Early detection of tooth wear by en-face optical coherence tomography

Abstract: Excessive dental wear (pathological attrition and/or abfractions) is a frequent complication in bruxing patients. The parafunction causes heavy occlusal loads. The aim of this study is the early detection and monitoring of occlusal overload in bruxing patients. En-face optical coherence tomography was used for investigating and imaging of several extracted tooth, with a normal morphology, derived from patients with active bruxism and from subjects without parafunction. We found a characteristic pattern of enamel cracks in patients with first degree bruxism and with a normal tooth morphology. We conclude that the en-face optical coherence tomography is a promising non-invasive alternative technique for the early detection of occlusal overload, before it becomes clinically evident as tooth wear.

Optical coherence tomography and confocal microscopy investigations of dental structures and restoration materials

Abstract: Nowadays, optical tomographic techniques are of particular importance in the medical imaging field, because these techniques can provide non-invasive diagnostic images. The present study evaluates the potential of en-face optical coherence tomography (OCT) as a possible non-invasive high resolution imaging method in supplying the necessary information on the quality of dental hard tissues and defects of dental restorative materials. Teeth after several treatment methods are imaged in order to asses the material defects and micro-leakage of tooth-filling interface as well as to evaluate the quality of dental hard tissue. C-scan and B-scan OCT images as well as confocal images are acquired from a large range of samples. Cracks and voids in the dental structures as well as gaps between the dental interfaces and material defects are clearly exposed. The advantages of the OCT method consist in non-invasiveness and high resolution.

Left vocal cord paralysis in systemic lupus erythematosus

Abstract: Left vocal cord palsy is a well-recognised rare complication of SLE. We encountered a gentleman who during an acute flare developed left vocal fold palsy (VCP). Immunosuppression was increased, but this only produced partial improvement. VCP is commonly but not exclusively caused by recurrent laryngeal nerve palsy. Other causes may affect phonation, including mucosal ulceration, vasculitis and pulmonary hypertension. There is limited literature on the diagnosis of and treatment options for VCP in SLE.

Occlusal Overload Investigations by Non Invasive Technology: Fluorescence Microscopy and En — Face Optical Coherence Tomography

Abstract: The aim of this study is the early detection and monitoring of occlusal overload in bruxing patients. En-Face Optical coherence tomography (eF-OCT) and fluorescence microscopy (FM) were used for the imaging of several anterior teeth extracted from patients with light active bruxism. We found a characteristic pattern of enamel cracks, that reached the tooth surface. We concluded that the combination of the en-Face OCT and FM is a promising non-invasive alternative technique for reliable monitoring of occlusal overload.

Assessing Human Immunodeficiency Virus Type 1 Tropism: Comparison of Assays Using Replication-Competent Virus versus Plasma-Derived Pseudotyped Virions

Abstract: Detection of CXCR4-using human immunodeficiency virus by the Trofile assay was compared to that by assays using virus isolates or replication-competent recombinants. Concordance with the Trofile assay was good, but assays using replicating viruses did not increase substantially the ability to detect the presence of CXCR4-using virus.

Control of visibility profile in spectral low-coherence interferometry

Abstract: It is demonstrated that, by obstructing half of one of the two beams from a low coherence interferometer before it is incident on the diffraction grating in a spectral interferometry setup, an asymmetric profile can be generated for the visibility of the channelled spectrum (V) with optical path difference (OPD). Together with a lateral shift of the beam, as inspired by Talbot bands studies, this can be used to optimise V(OPD). The model for the visibility of Talbot bands is improved by considering the spectrometer resolution and an improved Talbot band experiment is demonstrated. It is also shown that it is possible to obtain regions of no interference around zero OPD.

Randomized controlled trial of feeding a concentrated formula to infants born to women infected by human immunodeficiency virus.

Abstract: OBJECTIVE We tested the hypothesis that concentrated formula (CF) begun within the first 2 weeks of life increases growth in infants born to human immunodeficiency virus (HIV)-infected mothers. MATERIALS AND METHODS HIV-exposed infants from the United States, the Bahamas, and Brazil were randomized in a double-blind, controlled trial to receive either a CF (87 kcal/100 mL [26 kcal/oz]) or a standard formula (SF; 67 kcal/100 mL [20 kcal/oz]) for 8 weeks. This article presents results for infants who were not determined to be HIV infected based on testing at 4 weeks. Primary outcomes were safety, tolerability, and growth in weight and length. RESULTS Two thousand ninety-seven infants were enrolled, of whom 1998 were uninfected and had study formula dispensed. At weeks 4 and 8, uninfected infants receiving CF showed higher energy intake than those who were receiving SF (P < 0.001). By week 8, uninfected infants assigned to CF weighed more than infants receiving SF. There were no consistent differences in measures of tolerability, and rates of discontinuation or perceived formula intolerance were similar between treatment groups. CONCLUSIONS A CF is well tolerated and results in increased weight gain compared with SF. Until the HIV status of an infant is reliably determined, early introduction of a CF in HIV-exposed children may have beneficial effects on growth. The role of early nutritional intervention remains to be determined for individuals living in countries with endemic malnutrition for whom formula feeding is a viable option.

Optical coherence tomography combined with confocal microscopy for investigation of interfaces in class V cavities

Abstract: Standardized class V cavities, prepared in human extracted teeth, were filled with Premise (Kerr) composite. The specimens were thermo cycled. The interfaces were examined using a system employing two simultaneous imaging channels, an en-face Optical Coherence Tomography channel and a confocal microscopy channel.

En Face Optical Coherence Tomography Investigation of Interface Fiber Posts/Adhesive Cement/Root Canal Wall

Abstract: This study analyzes the adaptation and gap width between fiber posts, adhesive luting cement and root canal wall using optical coherence tomography. The results prove the importance of assessing the quality of the interface after each process of fiber post luting.

"I don"t want to go up the hill": Symbolic Boundary Work Among Residents of an Assisted Living Community

Abstract: In this study I explore boundary work processes that older adults do which influences friendships among residents of a progressive care retirement community. Accounts of boundary work as mechanisms for including some and excluding other residents as potential friends were collected by using a combination of quantitative surveys and qualitative interviews from residents (age 65+) of a progressive care retirement community in the United States. First, a survey explored symbolic boundaries related to cultural capital, defined as music and leisure interest and participation, as well as structural and social aspects of friendships among residents (N=66). Second, in-depth interviews of a sub-sample of residents of an assisted living facility within the community (N=15), were conducted to examine older adults‟ narratives of how they use cultural capital as a mechanism of symbolic boundary work that influences their friendships with others in the retirement community. The administrator of the assisted living facility (N=1) was also interviewed. Findings from this study suggested that cultural capital was associated with sociability which offers some support for the relational “tool kit” model of the theory. However, findings from in-depth interviews suggested that while music and leisure interests and participation may be important, valuations of bodies were more likely to influence “othering” of residents, although the two are related. This study enriches our understanding of how symbolic boundary use varies by group and context, as well as makes theoretical contributions to the literature on symbolic boundaries by exploring the ways in which aging may alter the use of boundaries.

Investigation of osteoconductive bone substitute by particles analysis, numerical simulation and optical coherence tomography

Abstract: The amount of available alveolar ridge is an important factor in planning to replace a tooth with an implant. Inadequate bone height and width may compromise the implant placement. Therefore, augmenting ridge defects is essential in the proper installation of the implant. In case an implant is placed in a defective ridge, additional augmentation will be required in order to improve the aesthetic appearance. An osteoconductive bone substitute promotes bone growth in periodontal and maxillofacial osseous defects. It provides the body with a matrix for bone cell migration and is integrated into the natural physiologic remodelling process. In order to investigate the osteoconductive bone substitute, particle analysis was used. Numerical simulation and optical coherence tomography were employed in order to analyze the results of the remodelling process. A particle analyzer can offer two complementary measurement techniques. Its concept integrates laser and video measurements to provide complete sample information on both particle size distribution and particle shape distribution. The analyzer used can measure particle sizes in a range of 100 Nanometer up to 3600 Micron. Numerical simulation provides information concerning the biomechanical behaviour of the augmentation materials in the whole bone volume. For the Optical Coherence Tomography Investigation, a combined OCT/confocal system operating at 1300 nm/970 nm was used. This has a high numerical aperture (NA) interface optics which gives a small field of view of 1 mm by 1 mm with a transverse resolution of better than 4 mu m. Results of bone remodelling process are presented using different osteoconductive bone substitutes which have been proven through years of clinical experience.

Marginal adaptation analysis performed with en face optical coherence tomography in fixed partial dentures

Abstract: Frameworks for fixed partial denture made out of dental alloys thought classic techniques currently involve many errors like marginal and internal gaps. The aim of this study is to present alternative technologies in making frameworks from dental alloys using selective laser sintering/ selective laser melting (SLS/ SLM) and to investigate the marginal adaptation of the fixed dental prostheses using the en face optical coherence tomography. These procedures imply the use of a scanning device PROBIS, SMART OPTICS with the help of 3D Dental Scanner software. For digitizing the 3D model we used the Dental Wings Kunde Software. The files obtained were sent to a SLS/ SLM machine, Hint-Els rapidPro, where the CoCr powder was sintered/melt by selectively consolidating successive layers of powder material on top of each other, using thermal energy supplied by a focused and computer controlled laser beam. Through this technique can be produced up to 80 pieces in only one step. A parallel between the classic casting technique and this new technology reveal the least has several advantages: fast finishing time, excellent marginal and internal fit, biocompatibility and superior chemical properties. SLS/ SLM proved to be a promising technology that may overcome the classic ones, because of the superior marginal fit of the fixed dental prostheses to the teeth.

En-Face Optical Coherence Tomography and Fluorescence in Evaluation of Orthodontic Interfaces

Abstract: Bonding has become a routine procedure in several dental specialties – from prosthodontics to conservative dentistry and even orthodontics. In many of these fields it is important to be able to investigate the bonded interfaces to assess their quality. All currently employed investigative methods are invasive, meaning that samples are destroyed in the testing procedure and cannot be used again. We have investigated the interface between human enamel and bonded ceramic brackets non-invasively, introducing a combination of new investigative methods – optical coherence tomography (OCT), fluorescence OCT and confocal microscopy (CM). Brackets were conventionally bonded on conditioned buccal surfaces of teeth. The bonding was assessed using these methods. Three dimensional reconstructions of the detected material defects were developed using manual and semi-automatic segmentation. The results clearly prove that OCT, fluorescence OCT and CM are useful in orthodontic bonding investigations. Keywords—Optical coherence tomography, Confocal Microscopy, Orthodontic Bonding.

A qualitative approach on marginal adaptation of conditioned dental infrastructures using optical coherence tomography

Abstract: Ceramic prosthesis performed through additive and subtractive technologies, lead to superior esthetic results towards metal-ceramic prosthesis. Ceramic veneers can be bonded to dental preparations with different types of cement. 100 ceramic veneers were performed on a preparation at the central maxilar incisor. The veneers were treated with different methods for obtaining a superior adhesion to dental structures. The veneers were devided into five groups and treated by (1) sandblasting, (2) sandblasting and then conditioned with HFA 9, 6% (hidrofluoric acid), (3)sandblasting with HFA (hidrofluoric acid) 5, 5%, (4) HFA 9, 6% (hidrofluoric acid), (5) HFA 5, 5% (hidrofluoric acid). After conditioning, the surfaces were investigated by Scanning Electronic Microscopy technology (SEM). The aim of this study was to analyze the quality of marginal adaptation and gap width of Empress veneers using en-face optical coherence tomography. The results prove the importance of investigation the marginal adaptation after every veneer bonding.

Effect of masticatory load on crack deflection/penetration investigated with en-face optical coherence tomography in ceramic fixed partial dentures

Abstract: Optical Coherence Tomography (OCT) allows a better characterization of dental prostheses. The detection of substance defects within the ceramic layers for metal-ceramic prostheses was demonstrated. The detected defects have a large volume and therefore there is a high likelihood for fracture lines to be generated in the proximal areas of the ceramic fixed partial dentures. If the detection of such defects is feasible before inserting the prosthesis into the oral cavity, then timely corrective measures are possible in order to avoid the fracture of the ceramic component later on. After noninvasive localization of cracks in ceramic fixed partial dentures, the effect of the biaxial loading on crack deflection/penetration at the ceramic interface was investigated. A biaxial loaded geometry was numerically investigated using Finite Element Analysis in order to determine the energy release rate. The obtained results could be used in conjunction with criteria at interface for estimating the path of the crack after the interface was reached.

Time domain and spectral optical coherence tomography investigations of integral ceramic fixed partial dentures

Abstract: The common investigations methods of fixed partial dentures imply sectioning and metallographic microscopic analysis. These methods could lead to damage of the small dimension material defects. Also these methods are limited to the dimensions of the cutting devices. The method used in this paper is the optical coherent tomography, a non-invasive method, which permits the determinations of materials defects in the ceramic layers depth. Both time domain and spectral methods were used in order to investigate the possibility of materials defects detection. For this study 237 integral ceramic fixed partial dentures were used. For each investigate area 500 slices were obtain and a 3D reconstruction was perform from each stuck. As a conclusion the optical coherent tomography, as a non-invasive method, can be used as a control technique in metalceramic technology. Combining the optical coherence tomography with the confocal microscopy allow to investigate in details the dental structure with a high resolution.

Investigation of Er:YAG laser root canal irradiation using en-face OCT

Abstract: This pilot study was designed to investigate the quality of endodontic treatment performed with/without Er:YAG laser using en-face Optical Coherence Tomography (OCT) prototype which evinced the presence of voids and microleakage within the root canal.

Correlation study between contamination and signal degradation in single-mode APC connectors

Abstract: This paper summarizes the correlation study between contamination and scratches on singlemode APC connectors and signal degradation; leading to an Acceptance Criteria Matrix. The study is a continuation of International Electronics Manufacturing Initiative (iNEMI) research on development of cleanliness specification for singlemode angled physical contact (SM-APC) connectors. Twenty-five APC SC connectors on one-meter patch cords were used for this study. The Design of the Experiment (DoE) was a multi-step process that involved: (1) inspecting, cleaning and inspecting connectors being tested (devices under test, or DUTs) and launch connectors; (2) making multiple matings and dematings of each DUT, in a pristine state, with a reference connector, and recording Return Loss (RL) data after each cycle; (3) manually applying dust to the cleaned end-faces of the DUTs; then (4) mating contaminated DUTs with clean reference connectors at least five times, taking RL measurements after each mating and saving fiber end-face images for both connectors. It was shown that connectors with the contamination at the core (9um diameter) demonstrated a dramatic decrease in average RL of 14.2 dB. In comparison, the samples with contamination on the cladding and clear core demonstrated a negligible change in RL of 0.15 dB. For highly contaminated samples in the cladding layer, we found the changes of RL to be about 5-6 dB. Further investigation established that particle migration during successive matings also occurs on the ferrule within the contact zone (approximately <250 μm in diameter). Polishing scratches had no impact on RL of APC connectors. Based on the experimental data described in this paper, an inspection criteria matrix is proposed for SM-APC connectors including the zone definitions and number of allowable defects (contamination and scratches) for each zone. The recommendations on pass/fail criteria have been provided to the IEC (International Electrotechnical Committee). It is expected IEC-61300-3-25, which contains these criteria, will publish in 2009.

From Talbot bands to no mirror terms in Fourier domain OCT: a quest on the fundamental origin of the sensitivity decay with depth

Abstract: We show that the decay of sensitivity with depth in Fourier Domain (FD)-OCT can be explained based on the superposition of wavetrain lengths after dispersion (diffraction). The more coherent the dispersed waves are, the slower the decay of sensitivity. An asymmetry in the decay curve with the optical path difference (OPD) can be introduced via an "intrinsic" delay which has the effect of shifting axially the two wavetrains relative to each other, originating from the object and reference beam of an interferometer. In this way, an equivalent Talbot Bands set-up is implemented, characterized by no mirror terms for the "extrinsic" delay introduced in the interferometer. Such configurations require that the two interfering beams use different parts of the diffraction grating in the interrogating spectrometer. Theory of Talbot Bands is presented and then how this knowledge can be transferred to the field of FD-OCT to achieve A-scans mirror terms free in one step. A theoretical rigorous model and a heuristic model are presented to quantify the Talbot bands.

Investigation of Er:YAG laser root canal irradiation using en face OCT

Abstract: This pilot study was designed to investigate the quality of endodontic treatment performed with/without Er:YAG laser using en-face Optical Coherence Tomography (OCT) prototype which evinced the presence of voids and microleakage within the root canal.