Circular intensity differential scattering of light for biophotonics applications

This thesis demonstrate the application of a label-free, non-invasive biophysical method based on angle-resolved light scattering calculations to characterize different biological samples; virus particles, chromatin fiber, and hierarchical chiral polymers. Chapter 1 provides an introduction on the foundation of electromagnetic theory, light scattering phenomenon, Mueller scattering matrix and its applications to characterize various samples based on numerical simulations and experimental measurements. A numerical method to calculate light scattering quantities, discrete dipole approximation (DDA) method is discussed. In this thesis we have performed the electromagnetic scattering calculations using the DDA method implemented as ADDA code. Chapter 2 demonstrates the angle-resolved circularly polarized light scattering calculations to characterize virus model particles. A coronavirus particle is modeled as having a spherical shaped envelope with cylindrical spikes projected from the envelope surface, and the single-stranded RNA genome polymer has been mimicked with a toroidal helix. The influence of genome polymer packaged as a standard helix in the virion core is also demonstrated. We investigated four different electromagnetic models: (i) a nucleated sphere with spikes that is a coronavirus particle, (ii) a nucleated sphere with no spikes, (iii) a homogeneous sphere, and (iv) a respiratory fluid containing a virus particle. The angular pattern of scattered circularly polarized light, the circular intensity differential scattering of light (CIDS), served as a particle's signature. This scattering signature is found sensitive to the chiral parameters that reveal information about the particles. The effect of changes in the RNA polymer, changes in its packaging, number of turns, handedness, and size are demonstrated on the scattering calculations. Additionally, the extinction efficiency, the depolarization ratio, the total scattered intensity, and the effect of changes in the wavelength of incident light on these scattering quantities are investigated. This biophysical method can offer a label-free identification of virus particles and can help understand their interaction with light. Chapter 3 focus on the the characterization of chromatin organization. Understanding the structural organization of chromatin is essential to comprehend the gene functions. The chromatin organization changes in the cell cycle, and it conforms to various compaction levels. We investigated a chromatin solenoid model with nucleosomes shaped as cylindrical units arranged in a helical array. The solenoid with spherical-shaped nucleosomes was also modeled. The changes in chiral structural parameters of solenoid induced different compaction levels of chromatin fiber. We calculated the angle-resolved scattering of circularly polarized light to probe the changes in the organization of chromatin fiber in response to the changes in its chiral parameters. The electromagnetic scattering calculations were performed using discrete dipole approximation (DDA). In the chromatin structure, nucleosomes have internal interactions that affect chromatin compaction. The merit of performing computations with DDA is that it takes into account the internal interactions. We demonstrated sensitivity of the scattering signal's angular behavior to the changes in these chiral parameters: pitch, radius, the handedness of solenoid, number of solenoid turns, the orientation of solenoid, the orientation of nucleosomes, number of nucleosomes, and shape of nucleosomes. These scattering calculations can potentially benefit applying a label-free polarized-light-based approach to characterize chromatin DNA and chiral polymers at the nanoscale level. Chapter 4 demonstrates the differential scattering of circularly polarized light to characterize the macromolecular structures consisting of hierarchical chirality. We modeled the B-DNA structure composed of a double-helix and a base-pairs helical structure. The angle-resolved scattering of circularly polarized light calculated for the B-DNA shows the additive behavior of the scattering signal contributed from the two individual chirality levels of B-DNA structure, a double-helix and a base-pairs helix. This additive behavior of angle-resolved scattering signal has also been demonstrated for other macromolecular structures comprising different chirality levels; a biological cell is also mimicked as a nucleated sphere, a sphere with a helical nucleus in its core. The individual chiral features of a structure add up to the angle-resolved scattering signal of circularly polarized light produced by the parent structure. These electromagnetic wave scattering calculations can offer a label-free approach to characterize chiral macromolecular structures with hierarchical chirality

Micro Electromechanical Systems (MEMS) Based Microfluidic Devices for Biomedical Applications

Micro Electromechanical Systems (MEMS) based microfluidic devices have gained popularity in biomedicine field over the last few years. In this paper, a comprehensive overview of microfluidic devices such as micropumps and microneedles has been presented for biomedical applications. The aim of this paper is to present the major features and issues related to micropumps and microneedles, e.g., working principles, actuation methods, fabrication techniques, construction, performance parameters, failure analysis, testing, safety issues, applications, commercialization issues and future prospects. Based on the actuation mechanisms, the micropumps are classified into two main types, i.e., mechanical and non-mechanical micropumps. Microneedles can be categorized according to their structure, fabrication process, material, overall shape, tip shape, size, array density and application. The presented literature review on micropumps and microneedles will provide comprehensive information for researchers working on design and development of microfluidic devices for biomedical applications

Jaundice: a basic review

Jaundice is a complex disease. Jaundice is actually the high bilirubin level in the body. Yellowing of skin, mucous membranes and skin are common presentations of jaundice. Jaundice has various variants including pre-hepatic jaundice (due to hemolysis of red blood cells), hepatic jaundice (due to defect in capture, conjugation and excretion of bilirubin by liver) and post hepatic jaundice (due to the obstruction of extra hepatobiliary system). The causes of various variants of Jaundice is either acquired or congenital. High plasma bilirubin level can cause various manifestations involving satiety, gastrointestinal bleeding, diarrhea, anemia, edema, weight-loss and can be fatal because it can cause psychosis, lethargy, seizures, coma or even death. High bilirubin level can help in the diagnosis of Jaundice. Differential diagnosis of various variants of Jaundice can be carried out on the basis of bilirubin level (conjugated and unconjugated), ultrasonography and other radiological techniques. The proper management of Jaundice is high water intake and low fat diet. The primary effective treatment for pre-hepatic jaundice and neonatal physiological jaundice is phototherapy. Infusion of immunoglobulins is also used for treatment of pre-hepatic jaundice. Proper nutrition, steroids and immunosuppressant are used for treatment of hepatic jaundice. The treatment for post hepatic jaundice is decompression and surgery

Papillary Thyroid Microcarcinoma Presenting as Horner’s Syndrome: A Novel Clinical Presentation

Background: There is considerable worldwide rising incidence of slow growing Papillary Thyroid Microcarcinoma (PTMC) due to increasing availability of modern imaging tools. Cervical lymph node metastasis still remains the most frequent site of its metastasis. Here we present a rare case of PMC resulting in Horner’s syndrome, which to our knowledge is the first case in the history of known medical literature.Case Report: A 32 years old male presented with right posterior triangle cervical lymphadenopathy, drooping of right eyelid and anhydrosis for last 3 years. Biopsy of the swelling revealed metastatic papillary thyroid carcinoma. US neck and computerized tomography showed a mass in the right suprclavicular region closely adherent to the common carotid and the stellate ganglion area without any significant pathology within thyroid and the lung. The patient underwent total thyroidectomy with type II block neck dissection. The specimen revealed microscopic foci of papillary thyroid carcinoma involving right lobe, largest focus measuring 0.2cm. Cervical lymph nodes of level II were negative for cancer metastasis however level III, IV and V were positive for metastasis. Patient underwent I131 radio-ablation postoperatively and is disease free since operation.Conclusion: Here we demonstrate a novel presentation of the PTMC inform of Horner’s syndrome and give brief review of literature regarding presentation of PTMC

Diabetes insipidus: the basic and clinical review

Diabetes insipidus (DI) is a complex disease. DI is inability of the body to conserve water. Polydipsia and polyuria are the major manifestations of DI. DI has various variants including central diabetes insipidus (due to defect in ADH secretion), nephrogenic diabetes insipidus (due to defect in ADH receptors or urea receptors), gestational diabetes insipidus (due to catabolism of ADH by placental vasopressinase) and primary polydipsia (due to massive fluid intake). The cause of various variants of DI is either acquired or congenital. High plasma osmolality due to hypotonic urine excretion can be fatal because it can cause psychosis, lethargy, seizures, coma or even death. Polyuria and polydipsia help in the diagnosis of DI. Differential diagnosis of various variants of DI can be carried out on the basis of water deprivation test, MRI and other radiological techniques. The proper management of DI is the replenishment of water loss and correction of clinical presentations produced as a result of DI, major is hypernatremia. The best management for primary polydipsia is fluid restriction while fluid intake is used for adipsic diabetes insipidus. ADH replacement therapy is widely used to treat DI. DDAVP or desmopressin is mostly preferred ADH analogue because it has less side effects and resistant to placental vasoprssinase

Enhancing EDM Machining Precision through Deep Cryogenically Treated Electrodes and ANN Modelling Approach

The critical applications of difficult-to-machine Inconel 617 (IN617) compel the process to be accurate enough that the requirement of tight tolerances can be met. Electric discharge machining (EDM) is commonly engaged in its machining. However, the intrinsic issue of over/undercut in EDM complicates the achievement of accurately machined profiles. Therefore, the proficiency of deep cryogenically treated (DCT) copper (Cu) and brass electrodes under modified dielectrics has been thoroughly investigated to address the issue. A complete factorial design was implemented to machine a 300 μm deep impression on IN617. The machining ability of DCT electrodes averagely gave better dimensional accuracy as compared to non-DCT electrodes by 13.5% in various modified dielectric mediums. The performance of DCT brass is 29.7% better overall compared to the average value of overcut (OC) given by DCT electrodes. Among the non-treated (NT) electrodes, the performance of Cu stands out when employing a Kerosene-Span-20 modified dielectric. In comparison to Kerosene-Tween-80, the value of OC is 33.3% less if Kerosene-Span-20 is used as a dielectric against the aforementioned NT electrode. Finally, OC’s nonlinear and complex phenomena are effectively modeled by an artificial neural network (ANN) with good prediction accuracy, thereby eliminating the need for experiments

Simulation, synthesis, and analysis of strontium-doped ZnO nanostructures for optoelectronics and energy-harvesting devices

The demand for clean and sustainable alternative energy resources is linearly increasing day by day due to the prevailing electricity crisis. Small-scale energy harvesting is considered a sustainable way to generate clean energy. Advanced energy solar cells, mainly dye-sensitized solar cells use solar energy and convert it into electrical energy. Similarly, MEMS-based piezoelectric materials are used to convert mechanical energy into electrical energy. For these applications, zinc oxide is considered one of the most suitable materials with high conductive, tunable band gap, and piezoelectric properties. However, altering these properties can be carried out by the addition of metal and other materials. Various research work has been carried out to study the addition of conductive metal as a dopant to alter the properties of zinc oxide. In this study, Strontium has been doped in ZnO to form a nanostructure for application in DSSC and microelectromechanical systems (MEMS) energy harvesters. Analysis has been conducted using the simulation and fabrication method. The results show that the doping and the pore size of the substrate (Anodic Aluminum oxide membrane) largely affect the output voltage and current. The difference between the simulated and experimental results was less than 1%, which shows the accuracy of the simulation. Tuning of the band gap can be observed by the addition of Sr in the ZnO nanostructure. For microelectromechanical systems energy harvesters, Sr-doped ZnO nanostructures deposited on anodic aluminum oxide show 7.10 mV of voltage and 1.11 uA of current output. The addition of Sr doping in ZnO shows the improvement in the generated current and voltage for the energy harvester and the improvement in overall power conversion efficiency for dye-sensitized solar cells. MEMS-based energy harvesting devices and low-cost advanced solar cells are promising to improve the efficiency of energy generation at a small scale

Xanthogranulomatous Cholecystitis Mimicking as Gallbladder Carcinoma：A Caution for Hepatobiliary Surgeon

Background: Xanthogranulomatous Cholecystitis (XGC) is a destructive inflammatory process of the gall bladder which can rarely extend into neighboring structures mimicking advanced carcinoma of the gall bladder. To the best of our knowledge six such cases have been reported in medical literature in which Xanthogranulomatous cholecystitis had lead to involvement of surrounding structures. Preoperative diagnosis of such a lesion remains difficult and most of such cases are diagnosed postoperatively following resectional surgery. Case Presentation: A 40 years old lady was admitted with the clinical picture of cholecystitis and gastric outlet obstruction. Ultrasonography showed gall stones with pericholecystic collection communicating with GB lumen. CT scan showed a mass arising from gallbladder with pericholecystic fluid with gross distension of the stomach. LFTs, CEA and CA 19-9 levels were within normal limits. Endoscopy of the stomach showed an apparently non-epithelial rounded mass projecting into gastric lumen causing partial obstruction of the gastric outlet. On exploration, a firm mass involving gallbladder and stomach was identified for which en-bloc extended cholecystectomy and Billroth-II gastrectomy was performed. Histopathology of the specimen revealed XGC with secondary involvement of pylorus of the stomach.Conclusion: Given the rarer preoperative diagnosis of XGC, which morphologically and radiologically mimics carcinoma, such cases should be managed aggressively. A brief literature review has also been discussed

Modeling and piezoelectric analysis of nano energy harvesters

The expedient way for the development of microelectromechanical systems (MEMS) based devices are based on two key steps. First, perform the simulation for the optimization of various parameters by using different simulation tools that lead to cost reduction. Second, develop the devices with accurate fabrication steps using optimized parameters. Here, authors have performed a piezoelectric analysis of an array of zinc oxide (ZnO) nanostructures that have been created on both sides of aluminum sheets. Various quantities like swerve, stress, strain, electric flux, energy distribution, and electric potential have been studied during the piezo analysis. Then actual controlled growth of ZnO nanorods (NRs) arrays was done on both sides of the etched aluminum rod at low-temperature using the chemical bath deposition (CBD) method for the development of a MEMS energy harvester. Micro creaks on the substrate acted as an alternative to the seed layer. The testing was performed by applying ambient range force on the nanostructure. It was found that the voltage range on topside was 0.59 to 0.62 mV, and the bottom side was 0.52 to 0.55 mV. These kinds of devices are useful in low power micro-devices, nanoelectromechanical systems, and smart wearable systems.Open Access funding was provided by the Qatar National Library. This work is supported by Qatar University Internal Grant No. QUCG-CAM-2020\21-1