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183 results on '"Dhanjal S"'

1. Nanosecond dynamics of a gallium mirror's light-induced reflectivity change

Author

Albanis, V., Dhanjal, S., Emelyanov, V. I., Fedotov, V. A., MacDonald, K. F., Petropoulos, P., Richardson, D. J., and Zheludev, N. I.

Subjects
Physics - Optics, Physics - General Physics
Abstract

Transient pump-probe optical reflectivity measurements of the nano/microsecond dynamics of a fully reversible, light-induced, surface-assisted metallization of gallium interfaced with silica are reported. The metallization leads to a considerable increase in the interface's reflectivity when solid a-gallium is on the verge of melting. The reflectivity change was found to be a cumulative effect that grows with light intensity and pulse duration. The reflectivity relaxes back to that of alpha-gallium when the excitation is withdrawn in a time that increases critically at gallium's melting point. The effect is attributed to a non-thermal light-induced structural phase transition., Comment: HTML text with 4 figures

Published
2000
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12. Evaluation of PCR-based preimplantation genetic diagnosis applied to monogenic diseases: A collaborative ESHRE PGD consortium study

Author

Dreesen, J. Destouni, A. Kourlaba, G. Degn, B. Mette, W.C. Carvalho, F. Moutou, C. Sengupta, S. Dhanjal, S. Renwick, P. Davies, S. Kanavakis, E. Harton, G. Traeger-Synodinos, J.

Subjects
lipids (amino acids, peptides, and proteins), respiratory system
Abstract

Preimplantation genetic diagnosis (PGD) for monogenic disorders currently involves polymerase chain reaction (PCR)-based methods, which must be robust, sensitive and highly accurate, precluding misdiagnosis. Twelve adverse misdiagnoses reported to the ESHRE PGD-Consortium are likely an underestimate. This retrospective study, involving six PGD centres, assessed the validity of PCR-based PGD through reanalysis of untransferred embryos from monogenic-PGD cycles. Data were collected on the genotype concordance at PGD and follow-up from 940 untransferred embryos, including details on the parameters of PGD cycles: category of monogenic disease, embryo morphology, embryo biopsy and genotype assay strategy. To determine the validity of PCR-based PGD, the sensitivity (Se), specificity (Sp) and diagnostic accuracy were calculated. Stratified analyses were also conducted to assess the influence of the parameters above on the validity of PCR-based PGD. The analysis of overall data showed that 93.7% of embryos had been correctly classified at the time of PGD, with Se of 99.2% and Sp of 80.9%. The stratified analyses found that diagnostic accuracy is statistically significantly higher when PGD is performed on two cells versus one cell (P=0.001). Se was significantly higher when multiplex protocols versus singleplex protocols were applied (P=0.005), as well as for PGD applied on cells from good compared with poor morphology embryos (P=0.032). Morphology, however, did not affect diagnostic accuracy. Multiplex PCR-based methods on one cell, are as robust as those on two cells regarding false negative rate, which is the most important criteria for clinical PGD applications. Overall, this study demonstrates the validity, robustness and high diagnostic value of PCR-based PGD. © 2014 Macmillan Publishers Limited All rights reserved.

Published
2014

14. The dynamically light-induced low-reflectivity state in gallium

Author

Bratfalean, R. T., Dhanjal, S., Zheludev, N., Periklis Petropoulos, Richardson, D. J., and Emelyanov, V. I.

Subjects
Materials science, business.industry, chemistry.chemical_element, Nonlinear optics, State (functional analysis), Reflectivity, Nonlinear optical, Optics, chemistry, Light induced, Melting point, Optoelectronics, Specular reflection, Gallium, business
Abstract

Summary form only given. Confined elemental gallium has recently attracted much attention because of its unique nonlinear optical properties on the verge of a structural phase transition. We report, for the first time, a light-induced state of the gallium-silica interface with specular reflectivity as low as 6%. The low-reflectivity state can be induced at light power levels starting around one milliwatt, and only within a narrow, less than one degree Celsius, temperature interval, below the bulk melting point of gallium.

Published
2000

15. Passively mode-locked diode-pumped surface-emitting diode laser

Author

Häring, R., Paschotta, R., Morier-Genoud, F., Keller, U., Roberts, J.S., Hoogland, S., Dhanjal, S., and Tropper, A.C.

Subjects
Physics::Optics
Abstract

We demonstrate to our knowledge the first passively mode-locked surface-emitting semiconductor laser. We used a 3-W high-brightness diode laser as pump source and a semiconductor saturable absorber mirror (SESAM [1,2]) as modelocker. The laser generates two stably mode-locked output beams with 11 mW average power each, 26ps pulse duration, and a repetition rate of 4.4 GHz. In contrast to edge-emitting semiconductor optically pumped semiconductor vertical external cavity surface emitting lasers [OPS-VECSELs) allow one to scale up the mode area in order to generate a high average power and high pulse energies, while the external cavity enforces a diffraction-limited output. A diffraction-limited output with >0.5 W in cw operation has been demonstrated for a similar kind of device [3]. Thus our concept promises to be scalable to much higher average and peak powers than can be obtained from electrically pumped surface-emitting mode-locked diode lasers or from edge emitting diode lasers. Only synchronously pumped surface emitting semiconductor lasers have generated pulses with high average power and pulse energy, but these require a powerful pulsed pump source [4]. Compared to mode-locked laser based on ion-doped crystals or glasses. mode-locked semiconductor lasers can generate high repetition rate (multi-GHz) pulse trains without Q-switching instabilities [5]. Their broad amplification bandwidth is sufficient for pulse durations in the femtosecond regime.

Published
2000

16. Real time mineral analysis using COSMA.

Author

Dhanjal S., Process control applications in mining and metallurgical plants 23-Aug-0926-Aug-09, Dhanjal S., and Process control applications in mining and metallurgical plants 23-Aug-0926-Aug-09

Abstract

Continuous on-stream mineral analysis (COSMA) technology, a system that provides direct and continuous online mineral analysis using X-ray diffraction, has taken XRD out of the laboratory and into the field. COSMA provides rapid measurement, analysis and feedback of data in real time in the field and can measure about 0.5 tons of material per day compared with conventional XRD techniques which measure a few grams at a time, requires longer periods of time from sampling to analysis and plant operators often do not acquire the data in time to control a process or respond to a problem. COSMA has been designed to communicate directly with plant control systems, so that mineral analysis can be used for process control. An example of a typical use of COSMA is in cement production; cement standards allow for the addition of limestone as a filler at the end of the process. However, there is an upper limit that must not be exceeded and so plants typically remain well below the upper limit so as not to overshoot and produce off-specification product. COSMA determines the limestone content continuously and so plants can approach the limit without the risk of overshooting. This allows for optimum operation of the plant, reducing costs and increasing quality., Continuous on-stream mineral analysis (COSMA) technology, a system that provides direct and continuous online mineral analysis using X-ray diffraction, has taken XRD out of the laboratory and into the field. COSMA provides rapid measurement, analysis and feedback of data in real time in the field and can measure about 0.5 tons of material per day compared with conventional XRD techniques which measure a few grams at a time, requires longer periods of time from sampling to analysis and plant operators often do not acquire the data in time to control a process or respond to a problem. COSMA has been designed to communicate directly with plant control systems, so that mineral analysis can be used for process control. An example of a typical use of COSMA is in cement production; cement standards allow for the addition of limestone as a filler at the end of the process. However, there is an upper limit that must not be exceeded and so plants typically remain well below the upper limit so as not to overshoot and produce off-specification product. COSMA determines the limestone content continuously and so plants can approach the limit without the risk of overshooting. This allows for optimum operation of the plant, reducing costs and increasing quality.

Published
2009

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