Green synthesis of biocompatible carbon dots using aqueous extract of Trapa bispinosa peel

We are reporting highly economical plant based method for the production of luminescent water soluble carbon dots (C-dot) using Indian water plant Trapa bispinosa peel extract without adding any external oxidizing agent at 90 °C. C-dots ranging from 5 to 10 nm were found in the solution with a prominent green fluorescence under UV-light (λ_ex = 365 nm). UV–vis spectra recorded at different time intervals (30–120 min) displayed signature absorption of C-dots between 400 and 600 nm. Fluorescence spectra of the dispersion after 120 min of synthesis exhibited characteristic emission peaks of C-dots when excited at 350, 400, 450 and 500 nm. C-dots were further analyzed using X-ray diffraction (XRD), Raman Spectroscopy and Thermo-Gravimetric Analysis (TGA). Structure of the C-dots was found to be turbostratic when studied using XRD. C-dots synthesized by our method were found to be exceptionally biocompatible against MDCK cells.     

Energy and economic analysis of traditional versus introduced crops cultivation in the mountains of the Indian Himalayas: A case study

This study analyzed the energy and economics associated with cultivation of traditional and introduced crops in the mountains of the Central Himalaya, India. The production cost in terms of energy for introduced crops such as tomato (Lycopersicon esculentum) and bell pepper (Capsicum annuum) cultivation was 90,358–320,516 MJ ha⁻¹ as compared to between 19,814 and 42,380 MJ ha⁻¹ for traditional crops within Himalayan agroecosystems. For the introduced crops, high energy and monetary input was associated with human labor, forest resources, chemical fertilizer and pesticides. However, energy threshold/projection for farmyard manure in traditional crop cultivation was 80–90% of the total energy cost, thus traditional crop cultivation was more efficient in energy and economics. During the study, the farm productivity of introduced crops cultivation declined with increasing years of cultivation. Consequently, the energy output from the system has been declining at the rate of −y20,598 to y20,748 MJ ha⁻¹ yr⁻¹ for tomato and y12,072 to y15,056 MJ ha⁻¹ yr⁻¹ for bell pepper under irrigated and rain-fed land use in the mountains, respectively. The comparative analysis on this paradigm shift indicates that more research is needed to support sustainable crop cultivation in the fragile Himalayan environment.     

Fault Table Computation on GPUs

In this paper, we explore the implementation of fault table generation on a Graphics Processing Unit (GPU). A fault table is essential for fault diagnosis and fault detection in VLSI testing and debug. Generating a fault table requires extensive fault simulation, with no fault dropping, and is extremely expensive from a computational standpoint. Fault simulation is inherently parallelizable, and the large number of threads that a GPU can operate on in parallel can be employed to accelerate fault simulation, and thereby accelerate fault table generation. Our approach, called GFTABLE, employs a pattern parallel approach which utilizes both bit-parallelism and thread-level parallelism. Our implementation is a significantly modified version of FSIM, which is pattern parallel fault simulation approach for single core processors. Like FSIM, GFTABLE utilizes critical path tracing and the dominator concept to reduce runtime. Further modifications to FSIM allow us to maximally harness the GPU’s huge memory bandwidth and high computational power. Our approach does not store the circuit (or any part of the circuit) on the GPU. Efficient parallel reduction operations are implemented in our implementation of GFTABLE. We compare our performance to FSIM*, which is FSIM modified to generate a fault table on a single core processor. Our experiments indicate that GFTABLE, implemented on a single NVIDIA Quadro FX 5800 GPU card, can generate a fault table for 0.5 million test patterns on average 15.68× faster when compared with FSIM*. With the NVIDIA Tesla server, our approach would be potentially 89.57× faster.     

Flow and heat transfer in serpentine channels

Serpentine channels are often used in microchannel reactors and heat exchangers. These channels offer better mixing, higher heat and mass‐transfer coefficients than straight channels. In the present work, flow and heat transfer experiments were carried out with a serpentine channel plate comprising of 10 units (single unit dimensions: 1 × 1.5 mm² in cross section, length 46.28 mm, D_h 1.2 mm) in series. Pressure drop and heat‐transfer coefficients were experimentally measured. Flow and heat transfer in the experimental set‐up were simulated using computational fluid dynamics (CFD) models to understand the mechanisms responsible for performance enhancement. The CFD methodology, thus, developed was applied to understand the effect of various geometrical parameters on heat transfer enhancement. A criterion was defined for evaluation of heat transfer performance (heat transfer per unit pumping power), thus, ensuring due considerations to required pumping power. The effect of geometrical parameters and the corresponding mechanisms contributing for enhancement are discussed briefly. Based on the results, a design map comprising different serpentine channels showing heat transfer enhancement with pumping power was developed for Reynolds number of 200 which will be useful for further work on flow and heat transfer in serpentine channels. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1814–1827, 2013     

Spin Polarization and Quantum Spins in Au Nanoparticles

The present study focuses on investigating the magnetic properties and the critical particle size for developing sizable spontaneous magnetic moment of bare Au nanoparticles. Seven sets of bare Au nanoparticle assemblies, with diameters from 3.5 to 17.5 nm, were fabricated with the gas condensation method. Line profiles of the X-ray diffraction peaks were used to determine the mean particle diameters and size distributions of the nanoparticle assemblies. The magnetization curves M(H_a) reveal Langevin field profiles. Magnetic hysteresis was clearly revealed in the low field regime even at 300 K. Contributions to the magnetization from different size particles in the nanoparticle assemblies were considered when analyzing the M(H_a) curves. The results show that the maximum particle moment will appear in 2.4 nm Au particles. A similar result of the maximum saturation magnetization appearing in 2.3 nm Au particles is also concluded through analysis of the dependency of the saturation magnetization M_P on particle size. The M_P(d) curve departs significantly from the 1/d dependence, but can be described by a log-normal function. Magnetization can be barely detected for Au particles larger than 27 nm. Magnetic field induced Zeeman magnetization from the quantum confined Kubo gap opening appears in Au nanoparticles smaller than 9.5 nm in diameter.     

Three-dimensional reduced-symmetry of colloidal plasmonic nanoparticles

Owing to their novel optical properties, three-dimensional plasmonic nanostructures with reduced symmetry such as a nanocrescent and a nanocup have attracted considerable current interest in biophotonic imaging and sensing. However, their practical applications have been still limited since the colloidal synthesis of such structures that allows, in principle, for in vivo application and large-scale production has not been explored yet. To date, these structures have been fabricated only on two-dimensional substrates using micro/nanofabrication techniques. Here we demonstrate an innovative way of breaking symmetry of colloidal plasmonic nanoparticles. Our strategy exploits the direct overgrowth of Au on a hybrid colloidal dimer consisting of Au and polystyrene (PS) nanoparticles without the self-nucleation of Au in an aqueous solution. Upon the overgrowth reaction, the steric crowding of PS leads to morphological evolution of the Au part in the dimer ranging from half-shell, nanocrescent to nanoshell associated with the appearance of the second plasmon absorption band in near IR. Surface-enhanced Raman scattering signal is obtained directly from the symmetry-broken nanoparticles solution as an example showing the viability of the present approach. We believe our concept represents an important step toward a wide range of biophotonic applications for optical nanoplasmonics such as targeting, sensing/imaging, gene delivery, and optical gene regulations.     

Hydrothermal synthesis of ZnO nanorods in the presence of a surfactant

Controlling the dimensions, positioning, and shapes of semiconductor nanowires, nanorods, and nanobelts lies in the synthesis and understanding of their growth mechanism. Controlled growth and synthesis is required in the fabrication of nanodevices and nanosensors. Among methods utilized for one-dimensional nanostructure synthesis, the hydrothermal process--a simple and cost-effective technique involving a low process temperature--has emerged as a powerful tool for the fabrication of anisotropic nanomaterials. Under hydrothermal conditions, many starting materials can undergo quite unexpected reactions, which are often accompanied by the formation of nanoscopic morphologies that are not accessible by classical routes. Synthesized ZnO nanostructures from aqueous solutions are usually poor in terms of morphology and size control. To improve the growth conditions and the controllability of the process, the use of surfactants or organic solvents has been attempted. In the present work, ZnO nanorods were grown on templates with a pre-sputtered ZnO seed layer over oxidized Si (100) substrates, and polyvinyl pyrrolidone (PVP) was used as a surfactant. By varying the PVP concentration in the growth solution, we can control the diameter and density of ZnO nanorods. The optical property of ZnO nanorods is highly improved by PVP addition.     

Rheological,thermal and structural behavior of poly(ε-caprolactone) and nanoclay blended films

Poly(ε-caprolactone)/nanoclay composite (PCLNC) films were prepared by solvent casting method using a wide range of layered silicate (2.5–10%) and were characterized by different techniques. Nanofiller dispersions in PCL matrix were studied by wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM), and results indicated the formation of some intercalated nanostructure of PCLNC. Rheological and thermal properties of PCLNC were measured by parallel-plate oscillatory rheometry and differential scanning calorimetry (DSC), respectively. Rheological study indicated that the predominating liquid-like properties (viscous modulus, G″ > elastic modulus, G′) of neat PCL gradually transformed to solid-like (G′ > G″) behavior after incorporation of clay in the temperature range of 90–120 °C. A plot of G′ vs. G″ provide information on intercalation and microstructure of nanocomposite. Applicability of time–temperature superposition (TTS) principle and van Gurp–Palmen plot (phase angle vs. absolute complex modulus) on rheological data of clay incorporated PCL were employed and found that the results failed to follow the rules. Incorporation of the nanoclay into PCL matrix increased the crystallization temperature (T_c) and melting temperature (T_m) of neat PCL from 28.7 to 32.3 °C and 56.3 to 59.2 °C, respectively due to the nucleating effect, but the glass transition temperature (T_g) (≈−65 °C) was remained unaffected. The decrease in crystallinity with increase in clay concentration was confirmed by both XRD and DSC data.     

LDPE/EVA/PCR/MWNT nanocomposites: Radiation crosslinking and physicomechanical characteristics

Nanocomposites of low‐density polyethylene (LDPE)/ethyl vinyl acetate (EVA)/poly(chloroprene) rubber (PCR) blends and multiple walled carbon nanotubes (MWNT) were prepared in different compositions by melt mixing. The nanocomposites were subjected to different radiation doses and efficacy of radiation crosslinking and physic‐mechanical characteristics were analyzed in detail. Gel content and crosslinking density increased with dose and with the MWNT fraction in the nanocomposites. The elastic modulus of the nanocomposite increased, while elongation at break exhibited downward trend with radiation dose. Micromechanical modeling of elastic modulus indicated presence of agglomeration in the matrix. Bulk density of the nanocomposites increased with the addition of MWNT while the melt flow index of the nanocomposites decreased sharply. DSC, XRD and TGA investigations revealed the peculiarity of the MWNT led nucleation in LDPE/EVA/PCR/MWNT nanocomposites. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers