A forward reconstruction, holographic method to overcome the lens effect during 3D detection of semi-transparent, non-spherical particles.

Suspensions of semi-transparent particles such as polystyrene microparticles are commonly used as model systems in the study of micro-rheology, biology, and microfluidics. Holography is a valuable tool that allows one to obtain 3-D information for particle position and orientation, but forward reconstruction techniques often struggle to infer this information accurately for semi-transparent spheroids with an O(1) aspect ratio, since the lens effect from the particle introduces complex patterns. We propose a reconstruction method that uses image moment information to generate a mask over the sharp patterns from the lens effect and gives reasonable estimation of the 3-D position and orientation of the particle. The method proposed in this work uses the average particle geometry information to determine the process parameters and identify the appropriate detection zone. The average detection error for zc is less than 25% of the average particle thickness, and the average errors in the in-plane and out-of-plane orientations ϕ and θ are 2° and 4°, respectively. Our method provides comparable accuracy in the detection of the particle center of mass (xc, yc, zc) and in-plane orientation ϕ as a recent forward reconstruction method for semi-transparent particles proposed by Byeon et al. (H. Byeon, T. Go and S. J. Lee, Appl. Opt., 2016, 54, 2106-2112; H. Byeon, T. Go and S. J. Lee, Opt. Express, 2016, 24, 598-610). This method provides a clearly defined framework for identifying the particle's out-of-plane tilt angle θ. We finally demonstrate the applicability of the method to opaque, slender (aspect ratio AR ≫ 1) particles by analyzing the 3-D motion of E. coli cells from holographic video footage.

Experimental and theoretical studies of cross-stream migration of non-spherical particles in a quadratic flow of a viscoelastic fluid.

We experimentally investigate the cross-stream migration of spherical, prolate, and oblate particles in a circular tube flow of a weakly viscoelastic fluid (De = O(10-2)) with negligible inertia (Re ≈ 0). From our previous theoretical studies, we developed mathematical models based on a second order fluid (i.e., retarded expansion for De ≪ 1) to characterize the migration trajectory of the particles in the absence of wall effects. The theory shows that the particle migration speed is proportional to the length the particle spans in the shear gradient direction (Lsg), and furthermore quantifies how particle shape alters the migration timescale. For particles with identical volume, spherical particles show the fastest migration speed among all the particles. The distinctive orientation behavior of prolate and oblate spheroids leads to a faster migration speed for an oblate particle compared to a prolate particle of the same aspect ratio. In this work, we verify our theory with microfluidic flow experiments using a model suspension of polystyrene (PS) micro-particles in a density-matched polyvinylpyrrolidone (PVP) solution (a Boger fluid). The experimental results show good qualitative and quantitative agreement with the theoretically predicted particle migration speed, indicating that the theory is able to provide reasonable predictions for real microfluidic systems.

Micronutrients and lifestyles in Taiwanese patients with stage 3 to 5 chronic kidney disease.

OBJECTIVE: Lycopene is an antioxidant that reduces oxidative stress. Analgesics are commonly used and may impair kidney function. However, the associations among plasma lycopene, analgesic use, and chronic kidney disease (CKD) are unknown. A hospital-based, case-control study was conducted to determine the association among plasma lycopene, analgesic use, and CKD. METHODS: Two hundred one patients with CKD and 313 controls were recruited, and CKD was defined as an estimated glomerular filtration rate <60 mL/min per 1.73 m(2), as calculated by the Modification of Diet in Renal Disease formula. Plasma antioxidants were measured by high-performance liquid chromatography. RESULTS: This study showed that the higher the plasma lycopene was, the lower the CKD risk. Specifically, in subjects with a plasma lycopene level >or=17.97 or 7.72-17.97 microg/dL, the adjusted odds ratio of CKD was 0.32 (95% confidence interval 0.18-0.58) or 0.49 (95% confidence interval 0.29-0.83), respectively, compared with subjects with a plasma lycopene level <7.72 microg/dL, independent of age, gender, level of education, paternal and maternal ethnicities, cigarette smoking, analgesic use, hypertension, and diabetes history. In contrast, the higher the plasma retinol level, the higher the risk of CKD. A significantly higher risk was demonstrated in analgesic users than in non-users (odds ratio 3.83, 95% confidence interval 1.75-8.40), but a significantly lower risk was shown in subjects who used analgesics on an as-needed basis than in non-users. Plasma lycopene tended to interact additively with analgesic consumption in modifying the CKD risk; however, the interactions were statistically insignificant. CONCLUSION: This is the first study showing that a low plasma lycopene level is associated with CKD risk.

Urinary arsenic species and CKD in a Taiwanese population: a case-control study.

BACKGROUND: Inorganic arsenic has been linked to decreased kidney function through oxidative damage. Arsenic methylation is believed to be a pathway for arsenic metabolism. Lycopene is an antioxidant that reduces oxidative stress; however, the association between urinary arsenic species, plasma lycopene level, and chronic kidney disease (CKD) has seldom been evaluated. STUDY DESIGN: Case-control study. SETTING & PARTICIPANTS: 125 patients with CKD and 229 controls were recruited from a hospital-based pool. PREDICTOR: Urinary arsenic species and plasma lycopene level. OUTCOMES & MEASUREMENTS: CKD was defined as estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m(2), calculated by using the Modification of Diet in Renal Disease Study equation. Plasma lycopene was measured by means of high-performance liquid chromatography. Urinary arsenic species, including arsenite, arsenate, monomethylarsonic acid, and dimethylarsinic acid, were determined by means of high-performance liquid chromatography and hydride generator-atomic absorption spectrometry. RESULTS: Lycopene level was associated positively with eGFR, and participants with a high serum lycopene level had a significant, inverse association with CKD (odds ratio, 0.41; 95% confidence interval, 0.21 to 0.81). Total arsenic level was associated significantly with CKD in a dose-response relationship, especially in participants with a total arsenic level greater than 20.74 compared with 11.78 microg/g creatinine or less (odds ratio, 4.34; 95% confidence interval, 1.94 to 9.69). Furthermore, participants with a high urinary total arsenic level or participants with a low percentage of dimethylarsinic acid had a positive association with CKD when their plasma lycopene level was low. LIMITATIONS: Because of the single spot evaluation of plasma antioxidants and urinary arsenic species and the small sample size, statistical significance should be interpreted with caution. CONCLUSIONS: This study shows that high urinary total arsenic or low plasma lycopene level is associated positively with CKD. Results suggest that the capacity for arsenic methylation may be associated with CKD in individuals who ingest low arsenic levels in drinking water and also have a low plasma lycopene level.