Reversible Photoalignment of Liquid Crystals: a Path toward the Creation of Rewritable Lenses.

In this work, we describe a new reversible photoalignment effect for the director in nematic liquid crystals that provides an approach for the creation of lenses whose optical power can be recorded and erased. The possibility of creating a rewritable lens has very important practical implications, for example, in the ophthalmic lens industry. A rewritable ophthalmic lens could be a convenient solution for patients whose compensation needs change over time due to age-related physiological changes, such as the onset and progression of presbyopia. Using rewritable lenses, small lens power corrections could be implemented through a rewriting procedure on the mounted lens without resurfacing or manufacturing and mounting a new lens. More generally, this new effect multiple potential applications in the creation of rewritable optical systems, such as reconfigurable optical networks, index-tunable antireflective coatings and optically rewritable phase gratings.

Numerical model of the inhomogeneous scattering by the human lens.

We present in this work a numerical model for characterizing the scattering properties of the human lens. After analyzing the scattering properties of two main scattering particles actually described in the literature through FEM (finite element method) simulations, we have modified a Monte Carlo's bulk scattering algorithm for computing ray scattering in non-sequential ray tracing. We have implemented this ray scattering algorithm in a layered model of the human lens in order to calculate the scattering properties of the whole lens. We have tested our algorithm by simulating the classic experiment carried out by Van der Berg et al for measuring "in vitro" the angular distribution of forward scattered light by the human lens. The results show the ability of our model to simulate accurately the scattering properties of the human lens.

Interleukin-28B polymorphisms and interferon gamma inducible protein-10 serum levels in seronegative occult hepatitis C virus infection.

Polymorphisms upstream interleukin (IL)-28B gene and serum levels of interferon gamma inducible protein-10 (IP-10) are associated with spontaneous and treatment-induced hepatitis C virus (HCV) clearance. Patients with seronegative occult HCV infection are anti-HCV and serum HCV-RNA negative but have viral RNA in liver and abnormal values of liver enzymes. We examined if the rs12979860 polymorphism of IL-28B and serum IP-10 levels differ between chronic and seronegative occult CV infection. IL-28B polymorphism was determined with allele specific TaqMan probes in total DNA isolated from peripheral blood mononuclear cells and IP-10 by an enzyme-linked immunosorbent assay in serum from 99 patients with seronegative occult HCV infection and 130 untreated patients with chronic hepatitis C. IL-28B genotypes were also determined in 54 healthy volunteers. Prevalence of the IL-28B CC genotype was significantly higher in seronegative occult HCV infection (52/99; 52.5%) than in chronic hepatitis C (32/130; 24.6%, P < 0.0001) or healthy controls (19/54: 32.5%, P = 0.039). Among patients with seronegative occult HCV infection, HCV-RNA load in liver was significantly lower in those with the IL-28B CC genotype than in those with CT + TT genotypes (2.8 × 10(5) ± 5.8 × 10(4) vs. 4.1 × 10(5) ± 5.9 × 10(4) copies/µg of total RNA respectively; P = 0.023). Mean serum IP-10 levels were significantly lower in patients with seronegative occult HCV infection than in patients with chronic hepatitis C (160.8 ± 17.9 vs. 288.7 ± 13.3 pg/ml respectively; P < 0.0001). These findings suggest that the host immune response plays an important role in seronegative occult HCV infection in comparison with chronic hepatitis C.

Evaluation of rotation and visual outcomes after implantation of monofocal and multifocal toric intraocular lenses.

PURPOSE: To evaluate rotational stability and its influence on postoperative visual acuity of different monofocal and multifocal toric intraocular lenses (IOLs). METHODS: A prospective interventional study was designed. Ninety-one patients with a mean age of 71.65 ± 11.82 years were implanted with toric IOLs after phacoemulsification. Three monofocal toric IOLs (the Lentis LT [Oculentis, Berlin, Germany], enVista [Bausch & Lomb, Rochester, NY], and AcrySof IQ [Alcon Laboratories, Inc., Fort Worth, TX]) and one multifocal toric IOL (AcrySof IQ ReSTOR; Alcon Laboratories, Inc.) were implanted. Preoperative and postoperative images were taken to calculate the misalignment due to the marking method. To evaluate rotation in the different follow-up visits, another photograph was taken 1 hour and 1, 7 and 30 days postoperatively. Refraction, uncorrected distance visual acuity (UDVA), and corrected distance visual acuity were measured 30 days postoperatively. RESULTS: Postoperative UDVA was 0.1 logMAR or better in 64.6% of eyes implanted with monofocal IOLs and 46.4% of eyes implanted with multifocal IOLs. The enVista toric IOL showed the best UDVA compared to the other monofocal IOLs, with 81% of eyes with 0.1 logMAR or better. The mean misalignment in the total group studied was 0.07° ± 0.60°; 69.6% of monofocal IOLs and 67.9% of multifocal IOLs showed less than 5° of rotation. A correlation was found between postoperative UDVA and rotation in the monofocal and multifocal IOLs implanted (r = 0.439 [P < .011] and = 0.787 [P = .001], respectively). CONCLUSIONS: At 1 month postoperatively, UDVA was slightly more affected by IOL rotation in multifocal than monofocal toric IOLs. The marking method was also effective.

High prevalence of occult hepatitis C virus infection in patients with chronic hepatitis B virus infection.

Hepatitis C virus (HCV) infection in the absence of detectable antibodies against HCV and of viral RNA in serum is called occult HCV infection. Its prevalence and clinical significance in chronic hepatitis B virus (HBV) infection is unknown. HCV RNA was tested for in the liver samples of 52 patients with chronic HBV infection and 21 (40 %) of them were positive for viral RNA (occult HCV infection). Liver fibrosis was found more frequently and the fibrosis score was significantly higher in patients with occult HCV than in negative ones, suggesting that occult HCV infection may have an impact on the clinical course of HBV infection.

Topographic optical profilometry by absorption in liquids.

Optical absorbance within a liquid is used as a photometric probe to measure the topography of optical surfaces relative to a reference. The liquid fills the gap between the reference surface and the measuring surface. By comparing two transmission images at different wavelengths we can profile the height distribution in a simple and reliable way. The presented method handles steep surface slopes (<90°) without difficulty. It adapts well to any field of view and height range (peak to valley). A height resolution in the order of the nanometer may be achieved and the height range can be tailored by adapting the concentration of water soluble dyes. It is especially appropriate for 3D profiling of transparent complex optical surfaces, like those found in micro-optic arrays and for Fresnel, aspheric or free-form lenses, which are very difficult to measure by other optical methods. We show some experimental results to validate its capabilities as a metrological tool and handling of steep surface slopes.

New perspectives in occult hepatitis C virus infection.

Occult hepatitis C virus (HCV) infection, defined as the presence of HCV RNA in liver and in peripheral blood mononuclear cells (PBMCs) in the absence of detectable viral RNA in serum by standard assays, can be found in anti-HCV positive patients with normal serum levels of liver enzymes and in anti-HCV negative patients with persistently elevated liver enzymes of unknown etiology. Occult HCV infection is distributed worldwide and all HCV genotypes seem to be involved in this infection. Occult hepatitis C has been found not only in anti-HCV positive subjects with normal values of liver enzymes or in chronic hepatitis of unknown origin but also in several groups at risk for HCV infection such as hemodialysis patients or family members of patients with occult HCV. This occult infection has been reported also in healthy populations without evidence of liver disease. Occult HCV infection seems to be less aggressive than chronic hepatitis C although patients affected by occult HCV may develop liver cirrhosis and even hepatocellular carcinoma. Thus, anti-HCV negative patients with occult HCV may benefit from antiviral therapy with pegylated-interferon plus ribavirin. The persistence of very low levels of HCV RNA in serum and in PBMCs, along with the maintenance of specific T-cell responses against HCV-antigens observed during a long-term follow-up of patients with occult hepatitis C, indicate that occult HCV is a persistent infection that is not spontaneously eradicated. This is an updated report on diagnosis, epidemiology and clinical implications of occult HCV with special emphasis on anti-HCV negative cases.

Role of the filter phase in phase sampling interferometry.

Any linear phase sampling algorithm can be described as a linear filter characterized by its frequency response. In traditional phase sampling interferometry the phase of the frequency response has been ignored because the impulse responses can be made real selecting the correct sample offset. However least squares methods and recursive filters can have a complex frequency response. In this paper, we derive the quadrature equations for a general phase sampling algorithm and describe the role of the filter phase.

Regularized least squares phase sampling interferometry.

In phase sampling interferometry, existing temporal analysis methods are sensitive to border effects and cannot deal with missing data. In this work we propose a quadrature filter that allows a reliable dynamic phase measurement for every sample, even in the cases involving few samples or missing data. The method is based on the use of a regularized least squares cost function that enforces the quadrature character of the filter. A comparison with existing techniques shows the effectiveness of the proposed method.

N-dimensional regularized fringe direction-estimator.

It has been demonstrated that the vectorial fringe-direction field is very important to demodulate fringe patterns without a dominant (or carrier) frequency. Unfortunately, the computation of this direction-filed is by far the most difficult task in the full interferogram phase-demodulation process. In this paper we present an algorithm to estimate this fringe-direction vector-field of a single n-dimensional fringe pattern. Despite that our theoretical results are valid at any dimension in the Euclidean space, we present some computer-simulated results in three dimensions because it is the most useful case in practical applications. As herein demonstrated, our method is based on linear matrix and vector analysis, this translates into a low computational cost.

Diagnosis of occult hepatitis C without the need for a liver biopsy.

The diagnosis of occult hepatitis C virus (HCV) infection is based on the presence of HCV-RNA in the liver. This study aimed to evaluate the use of combining non-invasive assays to diagnose occult HCV. A total of 122 patients with occult HCV (HCV-RNA in the liver without detectable anti-HCV and serum HCV-RNA) and 45 patients with cryptogenic chronic hepatitis (without HCV-RNA in the liver and negative for anti-HCV and serum HCV-RNA) were included. HCV-RNA was tested in peripheral blood mononuclear cells (PBMCs) and in 2 ml of ultracentrifuged serum. Anti-core HCV was examined by a non-commercial enzyme-linked immunosorbent assay. All controls were negative for the three HCV markers studied. Among patients with occult HCV, 36% were anti-core HCV positive, 57% had serum HCV-RNA after ultracentrifugation, and 61% had HCV-RNA in PBMCs. Combining the results of the assays, 91% of the patients were positive for at least one marker. Intrahepatic HCV-RNA load was significantly higher in patients who were positive simultaneously for the three HCV markers than in patients who were negative for all markers (P = 0.006) and than in those with one or two HCV markers (P = 0.039). Replication of HCV in liver was detected more frequently in patients with three (93%, P = 0.002), two (82%, P = 0.001), and one HCV marker (73%, P = 0.011) than in those without markers (27%). In conclusion, testing for all these markers allows diagnosis of occult HCV without the need for a liver biopsy and these assays may help to elucidate the clinical significance of occult HCV infection.

Effect of hemodialysis schedules and membranes on hepatocyte growth factor and hepatitis C virus RNA levels.

Hemodialysis induces production of the hepatocyte growth factor (HGF) and decrease of serum hepatitis C virus (HCV) RNA in patients with HCV infection, but it is not known if the hemodialysis schedule or type of membrane affect both the HGF production and HCV viremia. The effects on both parameters of alternate-day intermittent hemodialysis and short-daily hemodialysis and high and low flux membranes were investigated in 41 patients treated by hemodialysis. Sixteen (39%) patients were anti-HCV positive and 11 (69%) had HCV RNA. Twenty-six patients were on alternate-day intermittent and 15 on short-daily hemodialysis. High flux membranes were used for 29 patients and low flux membranes for 12 patients. A decrease in HCV RNA was observed at the end of hemodialysis (8.6 x 10(5) +/- 1.1 x 10(6) IU/ml vs. 4.4 x 10(5) +/- 7.3 x 10(5) IU/ml, P = 0.003). The proportion of HCV RNA decrease was similar in patients dialyzed with both schedules and with both types of membranes. The HGF levels increased from 2,605.9 +/- 1,428.7 to >8,000 pg/ml at 15 min. At the end of the session, the HGF levels decreased to 5,106.7 +/- 2,533.9 pg/ml. The HGF levels at the start of the next session were similar to those at baseline (2,680.0 +/- 1,209.3 pg/ml). The increase and dynamics of the HGF levels were similar in patient's hemodialyzed with both schedules and with both types of membranes. These results suggest that changes in HCV RNA and HGF levels during hemodialysis are not influenced by the schedule or type of membrane used.

Regularized quadratic cost function for oriented fringe-pattern filtering.

We use the regularization theory in a Bayesian framework to derive a quadratic cost function for denoising fringe patterns. As prior constraints for the regularization problem, we propose a Markov random field model that includes information about the fringe orientation. In our cost function the regularization term imposes constraints to the solution (i.e., the filtered image) to be smooth only along the fringe's tangent direction. In this way as the fringe information and noise are conveniently separated in the frequency space, our technique avoids blurring the fringes. The attractiveness of the proposed filtering method is that the minimization of the cost function can be easily implemented using iterative methods. To show the performance of the proposed technique we present some results obtained by processing simulated and real fringe patterns.

Hepatitis C virus infection in the family setting of patients with occult hepatitis C.

Family members of patients with chronic hepatitis C virus (HCV) infection are at increased risk of HCV infection but the prevalence of HCV among family members of patients with occult HCV infection is not known. Anti-HCV, serum HCV RNA and levels of liver enzymes were determined in 102 family members of 50 index patients with occult HCV infection and in 118 family members of 59 chronic hepatitis C index patients. HCV RNA and/or anti-HCV were detected in 10/102 (9.8%) relatives of patients with occult HCV infection and in 4/118 (3.4%) of patients with chronic hepatitis C. Fourteen additional family members (seven were relatives of index patients with occult HCV infection) had abnormal values of liver enzymes without serological markers of HCV infection. Two of these patients (who were relatives of two index patients with occult HCV infection) underwent a liver biopsy and were diagnosed with an occult HCV infection because HCV RNA was detected in the liver cells in the absence of serological HCV markers. In conclusion, the prevalence of HCV infection among family members of patients with occult HCV infection was similar to that found among family members of patients with chronic hepatitis C. This stresses the need to adopt strategies to prevent the transmission of HCV in the family setting of patients with occult HCV infection.

Steerable spatial phase shifting applied to single-image closed-fringe interferograms.

It is well known that spatial phase shifting interferometry (SPSI) may be used to demodulate two-dimensional (2D) spatial-carrier interferograms. In these cases the application of SPSI is straightforward because the modulating phase is a monotonic increasing function of space. However, this is not true when we apply SPSI to demodulate a single-image interferogram containing closed fringes. This is because using these algorithms, one would obtain a wrongly demodulated monotonic phase all over the 2D space. We present a technique to overcome this drawback and to allow any SPSI algorithm to be used as a single-image fringe pattern demodulator containing closed fringes. We make use of the 2D spatial orientation direction of the fringes to steer (orient) the one-dimensional SPSI algorithm in order to correctly demodulate the nonmonotonic 2D phase all over the interferogram.

Multiresolution approach based on projection matrices.

Active triangulation measurement systems with a rigid geometric configuration are inappropriate for scanning large objects with low measuring tolerances. The reason is that the ratio between the depth recovery error and the lateral extension is a constant that depends on the geometric setup. As a consequence, measuring large areas with low depth recovery error requires the use of multiresolution techniques. We propose a multiresolution technique based on a camera-projector system previously calibrated. The method consists of changing the camera or projector's parameters in order to increase the system depth sensitivity. A subpixel retroprojection error in the self-calibration process and a decrease of approximately one order of magnitude in the depth recovery error can be achieved using the proposed method.