Design and optimization of a high-energy optical parametric amplifier for broadband, spectrally incoherent pulses.

Spectrally incoherent laser pulses with sufficiently large fractional bandwidth are in demand for the mitigation of laser-plasma instabilities occurring in high-energy laser-target interactions. Here, we modeled, implemented, and optimized a dual-stage high-energy optical parametric amplifier for broadband, spectrally incoherent pulses in the near-infrared. The amplifier delivers close to 400 mJ of signal energy through noncollinear parametric interaction of 100-nJ-scale broadband, spectrally incoherent seed pulses near 1053 nm with a narrowband high-energy pump operating at 526.5 nm. Mitigation strategies for high-frequency spatial modulations in the amplified signal caused by index inhomogeneities in the Nd:YLF rods of the pump laser are explored and discussed in detail.

Characterizing the multi-dimensional reaction dynamics of dihalomethanes using XUV-induced Coulomb explosion imaging.

Site-selective probing of iodine 4d orbitals at 13.1 nm was used to characterize the photolysis of CH2I2 and CH2BrI initiated at 202.5 nm. Time-dependent fragment ion momenta were recorded using Coulomb explosion imaging mass spectrometry and used to determine the structural dynamics of the dissociating molecules. Correlations between these fragment momenta, as well as the onset times of electron transfer reactions between them, indicate that each molecule can undergo neutral three-body photolysis. For CH2I2, the structural evolution of the neutral molecule was simultaneously characterized along the C-I and I-C-I coordinates, demonstrating the sensitivity of these measurements to nuclear motion along multiple degrees of freedom.

Electron shell ionization of atoms with classical, relativistic scattering.

We investigate forward scattering of ionization from neon, argon, and xenon in ultrahigh intensities of 2 × 10(19) W/cm(2). Comparisons between the gases reveal the energy of the outgoing photoelectron determines its momentum, which can be scattered as far forward as 45° from the laser wave vector k(laser) for energies greater than 1 MeV. The shell structure in the atom manifests itself as modulations in the photoelectron yield and the width of the angular distributions. We arrive at an agreement with theory by using an independent electron model for the atom, a dipole approximation for the bound state interaction, and a relativistic, three-dimensional, classical radiation field including the laser magnetic field. The studies provide the atomic physics within plasmas, radiation, and particle acceleration in ultrastrong fields.

On the Exact Performance Analysis of Molecular Communication via Diffusion for Internet of Bio-Nano Things.

Internet of Bio-Nano Things, (IoBNT), is an ecosystem, where integration of micro and nano scale devices designed via synthetic biology communicates information. One of the communication concepts adopted in IoBNT is molecular communications via diffusion (MCvD). Inter-symbol interference (ISI) is a major cause of the performance degradation in MCvD systems. The accurate determination of the bit error probability (BEP) when ISI is present is therefore important. Most of the past literature has used the normal approximation to a binomial distribution to evaluate the approximate BEP in MCvD systems. In this paper, we derive a new expression to evaluate the exact BEP without using a normal or any other approximation when the ISI caused by a bit extends over an arbitrary number of future bit intervals. Our BEP expression applies to any receiver, full or partial absorbing, as long as its hitting probability distribution is known. In order to prove the applicability of the new expression, we present the numerical results for the BEP computed using our expression for a full absorption spherical receiver and compare them with the results obtained by particle-based simulations. Our results agree closely with the simulation results.

Needs and demands for dental care in patients attending the University Dental Hospital in Sri Lanka.

AIMS: To determine the needs and demands for dental care in patients visiting a university dental hospital. DESIGN: A cross-sectional study of first visit patients. SETTING: The University Dental Hospital in Peradeniya, Sri Lanka. PARTICIPANTS: A total of 849 first visit patients. METHODS: The main complaint of each patient was recorded and was considered as a measure of demand for dental care. Tooth based and orthodontic treatment needs were assessed using the WHO basic methods. Periodontal treatment need was assessed by the periodontal treatment needs system. Need for prosthetic care was also assessed. RESULTS: Thirty per cent and 23% of patients demanded treatment for decayed teeth and toothache respectively. Nearly 34%, 27% and 17% of patients needed surgical, restorative and periodontal care respectively for the main complaint. Of those seeking care, 94% needed treatment other than what was required for the main complaint. The predominant normative treatment need was for periodontal care (77%) whilst 47% needed restorations or extractions. CONCLUSION: Normative needs of patients demanding treatment were high and many had demanded treatment before acute symptoms had developed. However, delays in seeking care were evident. Further studies are needed to identify factors for delay in obtaining care.