Autocorrelation and relaxation time measurements on metal oxide core: dielectric shell beads in an optical trap

Optical Tweezers are capable of trapping individual particles of sizes that range from micrometers to sub micrometers. One can compute the trap strength experienced by a particle by analyzing the fluctuations in the position of the trapped particle with time. It is reported that the trap strength of a dielectric bead increases linearly with increase in the power of the trapping laser. The situation with metallic particles, however, is strongly dependent on the particle size. Available literature shows that metallic Rayleigh particles experience enhanced trap strengths when compared to dielectric particles of similar sizes due to a larger polarizability. On the contrary, micrometer sized metallic particles are poor candidates for trapping due to high reflectivity. We report here that commercially available micrometer sized metal oxide core - dielectric shell (core – shell) beads are trapped in a single beam optical tweezer in a manner similar to dielectric beads. However as the laser power is increased these core – shell beads are trapped with a reduced corner frequency, which represents a lowered trap strength, in contrast to the situation with ordinary dielectric beads. We attribute this anomaly to an increase in the temperature of the medium in the vicinity of the core – shell bead due to an enhanced dissipation of the laser power as heat. We have computed autocorrelation functions for both types of beads at various trapping laser powers and observe that the variation in the relaxation times with laser power for core - shell beads is opposite in trend to that of ordinary dielectric beads. This supports our claim of an enhanced medium temperature about the trapped core – shell bead. Since an increase in temperature should lead to a change in the local viscosity of the medium, we have estimated the ratio of viscosity to temperature for core – shell and dielectric beads of the same size. We observe that while for ordinary dielectric beads this ratio remains a constant with increasing laser power, there is a decrease for core – shell beads. We plan to extend this work towards studying the hydrodynamic correlations between a pair of trapped beads where one of the beads acts as a heat source. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Probing the interaction between two microspheres in a single Gaussian beam optical trap

Interactions between trapped microspheres have been studied in two geometries so far: (i) using line optical tweezers and (ii) in traps using two counter propagating laser beams. In both trap geometries, the stable inter bead separations have been attributed to optical binding. One could also trap two such beads in a single beam Gaussian laser trap. While there are reports that address this configuration through theoretical or simulation based treatments, there has so far been no detailed experimental work that measures the interactions. In this work, we have recorded simultaneously the fluctuation spectra of two beads trapped along the laser propagation direction in a single Gaussian beam trap by measuring the back scattered signal from the trapping and a tracking laser beam that are counter propagating . The backscattering from the trapping laser monitors the bead encountered earlier in the propagation path. The counter propagating tracking laser, on the other hand, is used to monitor the fluctuations of the second bead. Detection is by using quadrant photo detectors placed at either end. The autocorrelation functions of both beads reveal marked departures from that obtained when there is only one bead in the trap. Moreover, the fall-off profiles of the autocorrelation indicates the presence of more than one relaxation time. This indicates a method of detecting the presence of a second bead in a trap without directly carrying out measurements on it. Further, a careful analysis of the relaxation times could also reveal the nature of interactions between the beads. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Estimation of Membrane Bending Modulus of Stiffness Tuned Human Red Blood Cells from Micropore Filtration Studies

Human red blood cells (RBCs) need to deform in order to pass through capillaries in human vasculature with diameter smaller than that of the RBC. An altered RBC cell membrane stiffness (CMS), thereby, is likely to have consequences on their flow rate. RBC CMS is known to be affected by several commonly encountered disease conditions. This study was carried out to investigate whether an increase in RBC CMS, to the extent seen in such commonly encountered medical conditions, affects the RBC flow rate through channels with diameters comparable to that of the RBC. To do this, we use RBCs extracted from a healthy individual with no known medical conditions and treated with various concentrations of Bovine Serum Albumin (BSA). We study their flow through polycarbonate membranes with pores of diameter 5μm and 8μm which are smaller than and comparable to the RBC diameter respectively. The studies are carried out at constant hematocrit and volumetric flow rate. We find that when the diameter of the capillary is smaller than that of the RBC, the flow rate of the RBCs is lowered as the concentration of BSA is increased while the reverse is true when the diameter is comparable to that of the RBC. We confirm that this is a consequence of altered CMS of the RBCs from their reorientation dynamics in an Optical Tweezer. We find that a treatment with 0.50mg/ml BSA mimics the situation for RBCs extracted from a healthy individual while concentrations higher than 0.50mg/ml elevate the RBC CMS across a range expected for individuals with a condition of hyperglycemia. Using a simple theoretical model of the RBC deformation process at the entry of a narrow channel, we extract the RBC membrane bending modulus from their flow rate. FT PubMed

Correction: Estimation of membrane bending modulus of stiffness tuned human red blood cells from micropore filtration studies.

[This corrects the article DOI: 10.1371/journal.pone.0226640.]

Concomitant intraperitoneal onlay mesh repair with endoscopic component separation and sleeve gastrectomy

Bariatric surgery can be safely combined with laparoscopic intraperitoneal onlay mesh (IPOM) repair. In case of large ventral hernias, laparoendoscopic component separation can also be combined to achieve tension-free closure of the defect. Concomitant bariatric surgery and hernia repair also offer the additional benefit of reduction in recurrence of hernias as obesity, one of the risk factors, is treated in the process. We present a case of 60-year-old man with a body mass index of 45.3 kg/m2 with a large recurrent ventral hernia. We performed a lap sleeve gastrectomy with laparoendoscopic anterior component separation with IPOM. The operative steps included hernia contents reduction, conventional sleeve gastrectomy, anterior component separation on either side, intra-corporeal closure of hernia defect and placement of a composite mesh. Patient recovery was uneventful. Concomitant bariatric surgery with laparoendoscopic component separation with IPOM may be safe, but more studies are required

Effectiveness of school dental screening on stimulating dental attendance rates in Vikarabad town: A randomized controlled trial

Background: The school dental screening program has been in existence from the beginning of 20 th century. Its value in encouraging attendance among school children is not fully established. Aim: The aim was to determine the effectiveness of school dental screening on stimulating dental attendance rates among school children in Vikarabad town. Objectives: (a) To compare the dental attendance rates between 6-9 and 10-13 years old age groups, among male and female school children in Vikarabad town. (b) To identify the type of dental treatment received by the school children. Materials and Methods: A randomized controlled trial was conducted among school children aged 6-13 years old from 16 schools that were randomly selected and divided into two groups. Eight schools had a dental screening program (study group = 300 children) and had blanket referral cards and 8 schools that did not have the intervention (control group = 300). The dental attendance rates were determined after 3 months of follow-up period by evaluating the blanket referral cards for the study group and by an oral questionnaire for the control group. Results: The dental attendance rate was 27% for the study group and 18% for the control group which is statistically significant. The attendance rate was higher among 10-13 years of children both in test group and control groups. Among the children who visited the dentist, 53% in the control group and 69% from the test group got simple amalgam and glass ionomer cement restorations. Conclusion: The dental attendance rates were improved following school dental screening

Thoraco-laparoscopic Ivor-Lewis esophagectomy: the most extensive Indian experience

Aim: The overall incidence of adenocarcinoma is on the rise, mainly in the western population. Minimally invasive thoracolaparoscopic esophagectomy for adenocarcinoma of gastroesophageal junction tumors is being adopted worldwide, albeit with a slower pace. This study is to share our experience and technical modifications over two decades.Methods: This a retrospective data from 2009-2018 at a single center, including all the 143 cases of thora-colaparoscopic Ivor Lewis esophagectomies performed. There were no exclusions. The study objectives were to evaluate postoperative recovery, complications, and pathological completeness.Results: In 11 years, we have performed 532 cases of minimally invasive esophagectomies for both malignant and benign etiologies. Out of which 143 cases were of Ivor Lewis esophagectomy. The mean age of patients was 64.4 ± 10.86 years, and male to female ratio is 3:1. Out of these cases, 139 (97.20%) were performed for malignancy and 4 (2.79%) for benign cases, which include peptic stricture, sigmoid esophagus. The mean operative time is 457.97 ± 79.35 min. The mean blood loss was 138.08 ± 29.3mL. Out of these cases, the hand-sewn anastomosis was performed in 72 (50.34%), circular stapler anastomosis in 46 (32.16%) and, linear stapled anastomosis in 25 (17.48%). The mean lymph node retrieval rate was 22.68 ± 9.49 nodes. The average ICU stay in the postoperative period was 4.68 ± 3.95 days, and overall hospital stay was 13.48 ± 7.43 days. Among malignant cases (139), adenocarcinoma in 121 (87.05%), squamous cell carcinoma in 18 (12.94%). Among these cases T2, lesions in 56 (40.28%), T3 lesions in 77 (55.39%), T4 lesions in 6 (4.31%) The overall complication rate was 12.58% (pneumonia- 8.39%, RLN injury in 1.39%, anastomotic leak in 2.09%, chyle leak in 0.69%, anastomotic stricture in 12.58%). 3 (2.09%) cases had re-intervention in the form of combined endoscopic procedures (stenting) and re-thoracoscopic lavage in 3. Overall 30-day mortality in 1 case (0.69%).Conclusion: Thoracolaparoscopic esophagectomy with intrathoracic Ivor Lewis anastomosis is an excellent option for selected patients, in experienced hands

Development of Cellulose-Reinforced Polyurethane Coatings: A Novel Eco-Friendly Approach for Wind Turbine Blade Protection

Wind energy is considered a clean energy source and is predicted to be one of the primary sources of electricity. However, leading-edge erosion of wind turbine blades due to impacts from rain drops, solid particles, hailstones, bird fouling, ice, etc., is a major concern for the wind energy sector that reduces annual energy production. Therefore, leading-edge protection of turbine blades has been an important topic of research and development in the last 20 years. Further, there are critical issues related to the amount of waste produced, including glass fiber, carbon fiber, and various harmful volatile organic compounds in turbine fabrication and their end-of-life phases. Hence, it is vital to use eco-friendly, solvent-free materials and to extend blade life to make wind energy a perfect clean energy source. In this study, cellulose microparticles (CMP) and cellulose microfibers (CMF) have been used as fillers to reinforce water-based polyurethane (PU) coatings developed on glass fiber reinforced polymer (GFRP) substrates by a simple spray method for the first time. Field emission scanning electron microscopy images show the agglomerated particles of CMP and fiber-like morphology of CMF. Fourier transform infrared spectra of CMP, CMF, and related coatings exhibit associated C–H, C=O, and N–H absorption bands of cellulose and polyurethane. Thermal gravimetric analysis shows that CMP is stable up to 285 °C, whereas CMF degradation is observed at 243 °C. X-ray photoelectron spectroscopy of C 1s and O 1s core levels of CMP, CMF and related coatings show C–C/C–H, C–O, C–OH, and O–C=O bonds associated with cellulose structure. The solid particle erosion resistance properties of the coatings have been evaluated with different concentrations of CMP and CMF at impact angles of 30° and 90°, and all of the coatings are observed to outperform the PU and bare GFRP substrates. Three-dimensional (3D) profiles of erosion scans confirm the shape of erosion scars, and 2D profiles have been used to calculate volume loss due to erosion. CMP-reinforced PU coating with 5 wt.% filler concentration and CMF-reinforced PU coating with 2 wt.% concentration are found to be the best-performing coatings against solid particle erosion. Nanoindentation studies have been performed to establish a relation between H3/E2 and the average erosion rate of the coatings