Record fifth-harmonic-generation efficiency producing 211 nm, joule-level pulses using cesium lithium borate.

The fifth harmonic of a pulsed Nd:YLF laser has been realized in a cascade of nonlinear crystals with a record efficiency of 30%. Cesium lithium borate is used in a Type-I configuration for sum-frequency mixing of 1053 and 266 nm, producing 211 nm pulses. Flat-topped beam profiles and pulse shapes optimize efficiency. The energies of the fifth harmonic up to 335 mJ in 2.4 ns pulses were demonstrated.

Antiferromagnetic Resonance and Terahertz Continuum in α-RuCl_{3}.

We report measurements of optical absorption in the zigzag antiferromagnet α-RuCl_{3} as a function of temperature T, magnetic field B, and photon energy ℏω in the range ∼0.3-8.3 meV, using time-domain terahertz spectroscopy. Polarized measurements show that threefold rotational symmetry is broken in the honeycomb plane from 2 to 300 K. We find a sharp absorption peak at 2.56 meV upon cooling below the Néel temperature of 7 K at B=0 that we identify as the magnetic-dipole excitation of a zero-wave-vector magnon, or antiferromagnetic resonance (AFMR). With the application of B, the AFMR broadens and shifts to a lower frequency as long-range magnetic order is lost in a manner consistent with transitioning to a spin-disordered phase. From a direct, internally calibrated measurement of the AFMR spectral weight, we place an upper bound on the contribution to the dc susceptibility from a magnetic excitation continuum.

Two-photon absorption measurements of deep UV transmissible materials at 213 nm.

We report on two-photon absorption measurements at 213 nm of deep UV transmissible media, including LiF, MgF2, CaF2, BaF2, sapphire (Al2O3), and high-purity grades of fused-silica (SiO2). A high-stability 24 ps Nd:YAG laser operating at the 5th harmonic (213 nm) was used to generate a high-intensity, long-Rayleigh-length Gaussian focus inside the samples. The measurements of the fluoride crystals and sapphire indicate two-photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two-photon absorption; however, there are differences in linear losses associated with purity. A low two-photon absorption cross section is measured for MgF2, making it an ideal material for the propagation of high-intensity deep UV lasers.

Absolute calibration of optical streak cameras on picosecond time scales using supercontinuum generation.

We report a new method using high-stability, laser-driven supercontinuum generation in a liquid cell to calibrate the absolute photon response of fast optical streak cameras as a function of wavelength when operating at fastest sweep speeds. A stable, pulsed white light source based around the use of self-phase modulation in a salt solution was developed to provide the required brightness on picosecond time scales, enabling streak camera calibration in fully dynamic operation. The measured spectral brightness allowed for absolute photon response calibration over a broad spectral range (425-650 nm). Calibrations performed with two Axis Photonique streak cameras using the Photonis P820PSU streak tube demonstrated responses that qualitatively follow the photocathode response. Peak sensitivities were one photon/count above background. The absolute dynamic sensitivity is less than the static by up to an order of magnitude. We attribute this to the dynamic response of the phosphor being lower.

Counterpropagating Radiative Shock Experiments on the Orion Laser.

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

Ultrafast probing of magnetic field growth inside a laser-driven solenoid.

We report on the detection of the time-dependent B-field amplitude and topology in a laser-driven solenoid. The B-field inferred from both proton deflectometry and Faraday rotation ramps up linearly in time reaching 210 ± 35 T at the end of a 0.75-ns laser drive with 1 TW at 351 nm. A lumped-element circuit model agrees well with the linear rise and suggests that the blow-off plasma screens the field between the plates leading to an increased plate capacitance that converts the laser-generated hot-electron current into a voltage source that drives current through the solenoid. ALE3D modeling shows that target disassembly and current diffusion may limit the B-field increase for longer laser drive. Scaling of these experimental results to a National Ignition Facility (NIF) hohlraum target size (∼0.2cm^{3}) indicates that it is possible to achieve several tens of Tesla.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System.

We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85%-87% extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

Risk-based approach for systematic development of gastroretentive drug delivery system.

The research envisioned was the development of diltiazem hydrochloride effervescent floating matrix tablet using a risk-based approach. Preliminarily, the in vitro drug release profile was derived which theoretically simulated the in vivo condition after oral administration. Considering this as a rationale, the formulation development was initiated with defining the quality target product profile (QTPP) and critical quality attributes (CQAs). The preliminary studies were conducted to screen material attributes and process parameters followed by their risk assessment studies to select the plausible factors affecting the drug product CQAs, i.e., floating lag time and drug release profile. A 3(2) full factorial design was used to estimate the effect of the amount of swelling polymer (X 1) and gas-generating agent (X 2) on percent drug release (Q t1h and Q t8h) and floating lag time. Response and interaction plots were generated to examine the variables. Selection of an optimized formulation was done using desirability function and further validated. The model diagnostic plots represent the absence of outliers. The optimized formula obtained by the software was further validated, and the result of drug release and floating lag time was close to the predicted values. In a clear and concise way, the current investigations report the successful development of an effervescent floating matrix tablet for twice daily administration of diltiazem hydrochloride.

Laboratory analogue of a supersonic accretion column in a binary star system.

Astrophysical flows exhibit rich behaviour resulting from the interplay of different forms of energy-gravitational, thermal, magnetic and radiative. For magnetic cataclysmic variable stars, material from a late, main sequence star is pulled onto a highly magnetized (B>10 MG) white dwarf. The magnetic field is sufficiently large to direct the flow as an accretion column onto the poles of the white dwarf, a star subclass known as AM Herculis. A stationary radiative shock is expected to form 100-1,000 km above the surface of the white dwarf, far too small to be resolved with current telescopes. Here we report the results of a laboratory experiment showing the evolution of a reverse shock when both ionization and radiative losses are important. We find that the stand-off position of the shock agrees with radiation hydrodynamic simulations and is consistent, when scaled to AM Herculis star systems, with theoretical predictions.

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets.

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 µm spatial resolution. Optical trapping of 10 ± 4 µm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 µm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10(17) W cm(-2)) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

Multiwavelength interferometry system for the Orion laser facility.

We report on the design and testing of a multiwavelength interferometry system for the Orion laser facility based upon the use of self-path matching Wollaston prisms. The use of UV corrected achromatic optics allows for both easy alignment with an eye-safe light source and small (∼ millimeter) offsets to the focal lengths between different operational wavelengths. Interferograms are demonstrated at wavelengths corresponding to first, second, and fourth harmonics of a 1054 nm Nd:glass probe beam. Example data confirms the broadband achromatic capability of the imaging system with operation from the UV (263 nm) to visible (527 nm) and demonstrates that features as small as 5 µm can be resolved for object sizes of 15 by 10 mm. Results are also shown for an off-harmonic wavelength that will underpin a future capability. The primary optics package is accommodated inside the footprint of a ten-inch manipulator to allow the system to be deployed from a multitude of viewing angles inside the 4 m diameter Orion target chamber.

Monochromatic radiography of high energy density physics experiments on the MAGPIE generator.

A monochromatic X-ray backlighter based on Bragg reflection from a spherically bent quartz crystal has been developed for the MAGPIE pulsed power generator at Imperial College (1.4 MA, 240 ns) [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (2005)]. This instrument has been used to diagnose high energy density physics experiments with 1.865 keV radiation (Silicon He-α) from a laser plasma source driven by a ∼7 J, 1 ns pulse from the Cerberus laser. The design of the diagnostic, its characterisation and performance, and initial results in which the instrument was used to radiograph a shock physics experiment on MAGPIE are discussed.

Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry (invited).

A suite of laser based diagnostics is used to study interactions of magnetised, supersonic, radiatively cooled plasma flows produced using the Magpie pulse power generator (1.4 MA, 240 ns rise time). Collective optical Thomson scattering measures the time-resolved local flow velocity and temperature across 7-14 spatial positions. The scattering spectrum is recorded from multiple directions, allowing more accurate reconstruction of the flow velocity vectors. The areal electron density is measured using 2D interferometry; optimisation and analysis are discussed. The Faraday rotation diagnostic, operating at 1053 nm, measures the magnetic field distribution in the plasma. Measurements obtained simultaneously by these diagnostics are used to constrain analysis, increasing the accuracy of interpretation.

Interpenetration, deflection, and stagnation of cylindrically convergent magnetized supersonic tungsten plasma flows.

The interpenetration and interaction of supersonic, magnetized tungsten plasma flows has been directly observed via spatially and temporally resolved measurements of the Thomson scattering ion feature. A novel scattering geometry allows independent measurements of the axial and radial velocity components of the ions. The plasma flows are produced via the pulsed power driven ablation of fine tungsten wires in a cylindrical wire array z pinch. Fits of the data reveal the variations in radial velocity, axial velocity, and temperature of the ion streams as they interpenetrate and interact. A previously unobserved increase in axial velocity is measured near the array axis. This may be the result of v[over →]×B[over →] bending of the ion streams by a toroidal magnetic field, advected to and accumulated about the axis by the streams.

The argon beam coagulator: a more effective and expeditious way to address presacral bleeding.

Presacral bleeding is a dreaded complication of pelvic surgery. Rapid and effective control of such bleeding is important to avoid potentially life-threatening outcomes. Various methods for controlling presacral bleeding, all with only limited success, have been described in the literature. We report the alternative technique of using the argon beam coagulator (ABC) to control presacral bleeding. We demonstrate its efficacious use in both open surgery and a laparoscopic case. Our approach involved applying an argon beam at bone setting directly to the bleeders and using a "point and shoot" technique. We found that ABC is a simpler, equally effective and expeditious way of addressing presacral bleeding. To the best of our knowledge, there has been only one previously reported case in the literature of the use of ABC to control presacral bleeding.

Optical Thomson scattering measurements of plasma parameters in the ablation stage of wire array Z pinches.

A Thomson scattering diagnostic has been used to measure the parameters of cylindrical wire array Z pinch plasmas during the ablation phase. The scattering operates in the collective regime (α>1) allowing spatially localized measurements of the ion or electron plasma temperatures and of the plasma bulk velocity. The ablation flow is found to accelerate towards the axis reaching peak velocities of 1.2-1.3×10(7) cm/s in aluminium and ∼1×10(7) cm/s in tungsten arrays. Precursor ion temperature measurements made shortly after formation are found to correspond to the kinetic energy of the converging ablation flow.

Direct compression high functionality excipient using coprocessing technique: a brief review.

Tablets are still the most commonly used dosage form because of the ease of manufacturing, convenience in administration, accurate dosing and excellent stability. Direct compression is the preferred method for the preparation of tablets. However, it has been estimated that less than 20 percent of the active pharmaceutical ingredients (API) can be processed into tablets via direct compression since the majority of API lack the flow, cohesion or lubricating properties required for direct compression. Increasing trends toward direct compression suggests the need for development of high functional excipients. High functionality of excipients can be obtained by development of new excipients or by particle engineering of existing excipients. Particle engineering using coprocessing provides a way to obtain an excipient with high functionality. Coprocessed excipients are the mixture of two or more excipients interacting at sub-particle level; that can provide an excipient with improved functionality as well as masking undesirable properties. Coprocessing is very cost effective method of providing high functional excipient. The present review discusses the advantages of coprocessed excipients, role of material science in coprocessing, methods of coprocessing of excipients and properties of various coprocessed excipients available in the market.

Arthemeter-loaded lipid nanoparticles produced by modified thin-film hydration: Pharmacokinetics, toxicological and in vivo anti-malarial activity.

Artemether-loaded lipid nanoparticles (ARM-LNP) composed of 5% (w/v) lipid mass were produced by a modified thin-film hydration method using glyceryl trimyristate (solid lipid) and soybean oil (as liquid lipid in a concentration ranging from 0 to 45% (w/v) with respect to the total lipid mass). The particles were loaded with 10% of the anti-malarial ARM and surface-tailored with a combination of non-ionic, cationic or anionic surfactants. ARM-LNP were further characterized for their mean particle size, zeta potential and encapsulation efficiency, reporting optimized values below 120nm (PI<0.250), -38mV and 97% (w/w), respectively. ARM-LNP composed of 45% soybean oil depicted a spherical-like shape by transmission electron microscopy and a biphasic release profile in phosphate buffer. Haemolytic activity was within the acceptable range (7%) revealing low toxicity risk of LNP for parenteral delivery of ARM. Biocompatibility was confirmed by hepato- and nephrotoxicity analyses. Histopathological analysis showed no significant histological changes in liver and kidney tissues in adult Swiss Albino mice treated with the selected formulations. In vivo anti-malarial activity of ARM was enhanced when formulated as LNP, in comparison to a conventional plain drug solution and to a marketed formulation which are currently in use to treat malaria patients.

FNAC of salivary gland lesions with histopathological correlation.

HYPOTHESIS: Analysis of salivary gland lesions by FNAC and correlation with histopathology. To evaluate utility of FNAC in salivary gland lesions.Back ground: Salivary gland lesions form about 2-6.5% of all head and neck neoplasms in adults. They are easily accessible for FNAC (Fine Needle Aspiration Cytology) and risks of fistula formation or tumour implantation are low compared surgical biopsy. Also, cytology can provide a distinction between asalivary and non salivary lesion, benign and malignant lesions so also specific and non specific inflammation. METHODS: Seventy patients were studied prospectively over two years. FNAC was done using 10 cc syringes and 20-22 no. needle. Histomorphology was assessed on routine H & E (haemotxylin and eosin) stained paraffin sections. SPAS (periodic acid Schiff) and mucicarmine satins were also done. RESULTS: 80% of the lesions were neoplastic (61% benign, 31% malignant) and 20% were neoplastic. Pleomorphic adenoma was the most frequent benign neoplasm while mucoepidermoid carcinoma was the most frequent malignant lesion. Among the non neoplastic lesions, the maximum number of cases were of chronic sialadentis. In the present study, FNAC has a sensitivity of 94.54% and specificity of 80.95% for neoplastic lesions. CONCLUSIONS: FNAC was found to be a useful diagnostic tool in the evaluation of salivary gland lesions because of its simplicity, excellent patient compliance and rapid diagnosis. This cost effective tool is invaluable in planning the surgical management of the patient.

Classification of HIV protease inhibitors on the basis of their antiviral potency using radial basis function neural networks.

HIV protease inhibitors are being used as frontline therapy in the treatment of HIV patients. Multi-drug-resistant HIV mutant strains are emerging with the initial aggressive multi-drug treatment of HIV patients. This necessitates continued search for novel inhibitors of viral replication. These protease inhibitors may further be useful as pharmacological agents for inhibition of other viral replication. Classification models of HIV Protease inhibitors are developed using a data set of 123 compounds containing several heterocycles. Their inhibitory concentrations expressed as log (IC50) ranged from -1.52 to 2.12 log units. The dataset was divided into active and inactive classes on the basis of their antiviral potency. Initially a two-class problem (active, inactive) is explored using k-nearest neighbor approach. In order to introduce non-linearity in the classifier different approaches were investigated. This led to the goal of a fast, simple, minimum user input, radial basis function neural network (RBFNN) classifier development. Then the same two-class problem was resolved using the (RBFNN) classifier. A genetic algorithm with RBFNN fitness evaluator was used to search for the optimum descriptor subsets. The application of majority rules was also tested for the RBFNN classification. The best six descriptor model found by the new cost function showed predictive ability in the high 80% range for an external prediction set.