Quantum dot photolithography

This dissertation presents a simple method for the photolithographic patterning of silica hydrogel monoliths and planar substrates with quantum dots and inorganic semiconductor nanoparticles. We developed a method for surface patterning and bulk (3D) patterning of silica hydrogel monoliths and surface patterning of planar substrates with CdS, CdSe, PbS and PbSe quantum dots using infrared light, ultraviolet light, X-rays, and multi-photon ionization radiation. Precursor combinations were prepared which can readily dissociate with IR, UV, X-rays, and multi-photon ionization radiation. Different capping agents were used for improving quantum dot size distribution. The luminescence quantum yield of the composites can be increased to up to 30% with photoactivation. A masking technique was developed with which we can photolithograph sophisticated patterns with CdSe quantum dots on the surface of silica hydrogels that are highly luminescent without any further photoactivation. These are bottom-up methods, water-based, use readily available reagents and need only a few simple processing steps. These are attractive features for applications, and we anticipate that the technique may be employed for large-scale production of quantum dots in the near future --Abstract, page iv

COMPARATIVE STUDIES ON THE IN VITRO ANTIOXIDANT PROPERTIES OF METHANOLIC LEAFY EXTRACTS FROM SIX EDIBLE LEAFY VEGETABLES OF INDIA

Objective: Antioxidants are vital substances which possess the ability to protect the body from damage caused by free radical induced oxidative stress. Epidemiological studies specify that intake of fruits and vegetables have the ability to inhibit the damaging behavior of free radicals in the human body. In this study, we assessed antioxidative properties of the methanolic extracts of Mentha arvensis, Moringa oleifera, Spinacia oleracea, Trigonella foenum-graecum, Tamarindus indica, and Amaranthus viridis. Methods: The methanolic extracts were studied for phytochemical screening and antioxidant properties by different in-vitro experiments including DPPH radical assay, ABTS radical assay, Total antioxidant assay, Reducing activity assay for ascorbic acid equivalents, Total Phenolic content for gallic acid equivalents and Total flavonoid content for quercetin equivalent. Results: The present study revealed that Mentha arvensis extract exhibited the highest DPPH radical scavenging activity (IC50 value of 28 µg/ml), Reducing activity (1.731±0.072), Total antioxidant activity (208 µg/ml expressed as ascorbic acid equivalents), Total phenolic content (75 µg/ml expressed as gallic acid equivalents) and Total flavonoid contents (674 µg/ml expressed as quercetin equivalents) and Tamarindus indica extract showed highest ABTS radical scavenging activity (IC50 value of 35 µg/ml), The results obtained in the present study indicate that the leaves of Mentha arvensis showed potential antioxidant and free radical scavenging activity. Conclusion: The results obtained in the present study indicate that leaves of Mentha arvensis, Moringa oleifera plant materials have potent, Trigonella foenum-graecum, Tamarindus indica have moderate and Amaranthus viridis, Spinacia oleracea have mild antioxidant activity and/or free radical scavenging activity. Key words: Leafy vegetables, Methanolic extracts, In-vitro antioxidant activit

Adjuvant drugs in management of osteoarthritis: spotlight on type II collagen

Osteoarthritis (OA) is a common musculoskeletal disorder that affects large and small joints and is seen in all ages due to diverse aetiologies. Pain, joint stiffness and limitation of daily activities affects the quality of life of individuals with OA. Conventional analgesics like non-steroidal anti-inflammatory drugs affect pain and inflammatory component but do not target the disease pathogenesis. Damage to the joint cartilage is central to the pathogenesis of OA. Better understanding of the pathogenesis has led to evolution of various adjuvant drugs in management of OA. Among them, undenatured type II collagen induces immune tolerance and thereby provide benefits by reducing the joint damage. Studies assessing efficacy and safety of undenatured type II collagen in OA have shown to reduce clinical symptoms like pain, joint stiffness and improvement in physical activities, and thus improving the quality of life. It is well tolerated and safe for use in OA. This article discusses the pathophysiology of OA with inflammation and beyond, and overviews the various drugs that are used as adjuvants in the management of OA with special focus on the use of type 2 collagen

X-Ray Lithography of Metal and Semiconductor Nanoparticles

In the last few years, a considerable amount of research has focused on the three-dimensional fabrication of contacts and electronic devices. Most techniques, however, are essentially based on photoreduction, and are limited to noble- and semi-noble metals. We present here a general method that allows patterning of porous matrices in 3D with metal, but also with semiconductor nanoparticles which is of potential relevance for microfabrication applications. In our method, the pore-filling solvent of a sol-gel material is exchanged with a solution of precursors. The precursors are photodissociated and nanoparticles are formed when the monoliths are irradiated. In a series of previous publications we showed that noble metals but also semiconductor quantum dots can be produced with our technique. Here we focus on the Xray variation of our technique and show that monoliths can be patterned with metals and also with semiconductor nanoparticles. The patterns have the same resolution than the masks, i.e., around 10 μm, and extend into the bulk of the monoliths for up to a depth of 12 mm. Our method possesses several attractive features. Sample preparation is very simple; the technique has a bottom-up character; it allows access to a wide number of materials, such as noble metals and II-VI semiconductor materials; and it has a 3D character. With additional developments, our technique could be possibly used to complement more established techniques such as LIGA and multiphoton fabrication techniques which are currently used for 3D microfabrication

Laser Writing of Semiconductor Nanoparticles and Quantum Dots

Silica aerogels were patterned with CdS using a photolithographic technique based on local heating with infrared (IR) light. The solvent of silica hydrogels was exchanged with an aqueous solution of the precursors CdNO3 and NH4 OH, all precooled to a temperature of 5°C. Half of the bathing solution was then replaced by a thiourea solution. After thiourea diffused into the hydrogels, the samples were exposed to a focused IR beam from a continuous wave, Nd-YAG laser. The precursors reacted in the spots heated by the IR beam to form CdS nanoparticles. We lithographed features with a diameter of about 40 µm, which extended inside the monoliths for up to 4 mm. Samples were characterized with transmission electron microscopy and optical absorption, photoluminescence, and Raman spectroscopies. Spots illuminated by the IR beam were made up by CdS nanoparticles dispersed in a silica matrix. The CdS nanoparticles had a diameter in the 4-6 nm range in samples exposed for 4 min to the IR beam, and of up to 100 nm in samples exposed for 10 min

Driver Mutations in Leukemia Promote Disease Pathogenesis through a Combination of Cell-Autonomous and Niche Modulation

Studies of patients with acute myeloid leukemia (AML) have led to the identification of mutations that affect different cellular pathways. Some of these have been classified as preleukemic, and a stepwise evolution program whereby cells acquire additional mutations has been proposed in the development of AML. How the timing of acquisition of these mutations and their impact on transformation and the bone marrow (BM) microenvironment occurs has only recently begun to be investigated. We show that constitutive and early loss of the epigenetic regulator, TET2, when combined with constitutive activation of FLT3, results in transformation of chronic myelomonocytic leukemia-like or myeloproliferative neoplasm-like phenotype to AML, which is more pronounced in double-mutant mice relative to mice carrying mutations in single genes. Furthermore, we show that in preleukemic and leukemic mice there are alterations in the BM niche and secreted cytokines, which creates a permissive environment for the growth of mutation-bearing cells relative to normal cells

Trochleoplasty and medial patellofemoral ligament reconstruction for recurrent patellar dislocation

We report a case of recurrent patellar dislocation with high-grade trochlear dysplasia which persisted despite two previous operations. We did a Dejour's sulcus deepening trochleoplasty, medial patellofemoral ligament reconstruction, and lateral retinacular release. Trochleoplasty and medial patellofemoral ligament reconstruction is required in patients with high grade trochlear dysplasia

Intra-abdominal pressure: A simple, yet reliable indicator for the diagnosis and prognosis of appendicitis

Introduction: Appendicitis is one of the more common surgical emergencies and it is one of the most common causes of an acute abdomen. Left untreated, appendicitis has the potential for severe complications. Despite initial optimism, it has become apparent that in most units the normal appendix rate remains 15-30%. In view of this scenario, this study was undertaken to assess the role of intra-abdominal pressure (IAP) in the diagnosis and prognosis of acute appendicitis. Materials and Methods: A total of 200 patients with initial diagnosis of appendicitis were evaluated. Patients were grouped according to the final diagnoses as appendicitis (acute and acute on chronic), perforated appendicitis and negative exploration for appendicitis. A simple fluid column manometry system through the Foley′s catheter is used to measure the IAP. Results: Out of a total of 200 cases 104 were female and 96 were male in the age range of 7-74 years. A normal appendix was found in 18 patients and 124 patients had appendicitis. A total of 58 cases were of appendicular perforation. The mean pre-operative values of IAP for cases of normal appendix, appendicitis and appendicular perforation were 3 ± 0.4, 8.2 ± 0.4 and 9.6 ± 0.3 respectively (P < 0.001). Post-operative 1 st day and 2 nd day values of the IAP for appendicitis, perforated appendicitis and normal appendix groups were 3 ± 0.2 and 1.0 ± 0.1, 4.2 ± 0.1 and 1.5 ± 0.1, 0.8 ± 0.6 and 0.5 ± 0.6 cm H 2 O respectively. Conclusion: IAP increases among patients with appendicitis and a further increase is encountered among patients with perforated appendicitis. Therefore, addition of this parameter to support the clinical diagnosis of acute appendicitis and perforative appendicitis is advocated specially in a rural setting. However, randomized controlled trials are required to support our findings

Antioxidant and Anticancer Activity of Rhynchosia rufescens (Willd.) DC.

857-867The present study deals with the chemical composition, antioxidant, antimicrobial and anticancer efficacy of Rhynchosia rufescens (RR) leaf methanol (RRME), ethyl acetate (RREAE) and petroleum ether (RRPE) extracts. Preliminary phytochemical results revealed that alkaloids, coumarins, flavonoids, volatile oils, fatty acids, and phenols were present in the test extracts. Gas chromatographic analysis of RRPE revealed the identification of 25 volatile compounds. The oil contains monoterpenes (9.6%) and fatty acids (6.12%). The major components of the oil are beta- copaene (32.06%), cyclofenchene (16.53%), beta- pinene (5.69%), 3-carene (3.48%) and sabinene (3.22%). Quantitative estimation of total phenols (TPC) and flavonoids (TFC) indicated that TPC ranged from 8.99 ±1.00 to 60.00±1.15 mg GAE/g dry weight and TFC was between 4.98±0.08 to 20.4±0.50 mg QE/ g dry weight respectively. Methanol extract showed the highest phosphomolybdenum dependent antioxidant capacity, while ethyl acetate extracts strongly inhibited DPPH and hydroxyl radicals. Anticancer study results revealed that ethyl acetate extract enhanced caspase-3 mediated DNA fragmentation in HCT – 116 cell lines than standard cisplatin. In conclusion, R. rufescens extracts showed potent antioxidant, antibacterial activity and potential anticancer activity in HCT-116 cell lines. The observations of this study indicated that R. rufescens extracts are a rich source of natural antioxidants and anticancer components