Predicting laser-induced bulk damage and conditioning for deuterated potassium dihydrogen phosphate crystals using an absorption distribution model.

We present an empirical model that describes the experimentally observed laser-induced bulk damage and conditioning behavior in deuterated potassium dihydrogen phosphate (DKDP) crystals. The model expands on an existing nanoabsorber precursor model and the multistep absorption mechanism to include two populations of absorbing defects, one with linear absorption and another with nonlinear absorption. We show that this model connects previously uncorrelated small-beam damage initiation probability data to large-beam damage density measurements over a range of nanosecond pulse widths. In addition, this work predicts the damage behavior of laser-conditioned DKDP.

Drugs for mental illnesses in ancient greek medicine.

Drugs with psychedelic, hypnotic, narcotic, analgesic, suppressive, euphoric and stimulating effects were used in various ways during the ancient times. We can classify drug use in ancient times into two main categories. On the one hand, ancient physicians prescribed drugs based on their pharmaceutical-therapeutic actions. On the other hand, people not pertaining to medicine and not relating to its accurate implementation often abused drugs to achieve an euphoric state of mind, either for personal gratification or as an indispensable element of religion and mythology. Ancient Greek medical literature contains ample prescriptions and recipes indicating that plants were the essential components of drugs. Pedanius Dioscorides dedicated his lifetime's work to the synthesis of ancient drugs. One can find a plethora of information concerning the production methods and the plants used in drugs for the treatment of psychiatric diseases. These were herbs like black and white hellebore, mandrake, hyoscyamus (henbane), Papaver somniferum (also known as opium poppy), Strychnos, Frankincense-tree and dorycnium. The preparation of narcotics included the addition of other elements, mainly wine, to the opus of plants or to their extracts. Drugs were produced via methods of dehumidification/desiccation, grinding, squeezing or boiling of the plants' roots with a formation of a juice, oil or mush extract. In addition, drugs could also be inhaled if burnt. Many physicians of antiquity, such as Hippocrates, Galen, Ctesias and Aretaeus of Cappadocia, all refer to many of these aforementioned drugs analyzing the different symptoms which they could address, and the risks accompanying their use. Physicians of antiquity used drugs for the treatment of somatic, as well as psychiatric disorders. Most of these drugs affected the central nervous system. Taking advantage of their analgesic properties, physicians used them for the management of severe and chronic painful conditions. The hypnotic effects of some drugs were desirable in order to be used as anesthetics for surgical operations and cauterization. Drug use was also established in the initial treatment of epilepsy and seizures, regardless of their cause. Public rituals and mythology were the two main contexts in which drug use flourished, outside the realms of medicine. The psychotropic and especially the hallucinatory effects of drugs caused the person under their influence to lose control, rendering him incapable of governing his actions and thoughts. These consciousness-altering medications were frequently the central focus of mythology. In this case, one would dictate and give orders to another person, which under any other circumstances would not be carried out. This led to the formation of the concept of the magic potion. Theophrastus frequently referred to magic potions.

When perforation is not the culprit : case report and systematic review of mechanical small-bowel obstruction complicating colonoscopy.

Colonoscopy is generally safe, although expansion of colorectal cancer prevention programs is likely to increase the number of post-colonoscopy complications. We report the case of a 42-year old woman with a prior history of 2 cesarean section deliveries who developed abdominal pain after an otherwise uneventful screening colonoscopy. Urgent exploration revealed closed-loop obstruction involving the terminal ileum, caused by an adhesive band close to the site of her previous Pfannenstiel incision. A systematic review of the literature revealed 11 reports (1985-2008) describing a total of 13 cases of mechanical small bowel obstruction (MSBO) after colonoscopy, 9 of which were confirmed by laparotomy. Colonoscopy-induced MSBO is practically impossible to anticipate, and only a prior history of abdominal/pelvic surgery may be deemed as a predisposing factor. However, it is related to significant morbidity, as it often leads to an ischemic bowel with need for surgical resection. Thus, endoscopists should be aware and maintain a low operative threshold to this rare, but hazardous, complication of colonoscopy.

Demonstration of high-energy 2 omega (526.5 nm) operation on the National Ignition Facility Laser System.

A single beamline of the National Ignition Facility (NIF) has been operated at a wavelength of 526.5 nm (2 omega) by frequency converting the fundamental 1053 nm (1 omega) wavelength with an 18.2 mm thick type-I potassium dihydrogen phosphate (KDP) second-harmonic generator (SHG) crystal. Second-harmonic energies of up to 17.9 kJ were measured at the final optics focal plane with a conversion efficiency of 82%. For a similarly configured 192-beam NIF, this scales to a total 2 omega energy of 3.4 MJ full NIF equivalent (FNE).

National Ignition Facility laser performance status.

The National Ignition Facility (NIF) is the world's largest laser system. It contains a 192 beam neodymium glass laser that is designed to deliver 1.8 MJ at 500 TW at 351 nm in order to achieve energy gain (ignition) in a deuterium-tritium nuclear fusion target. To meet this goal, laser design criteria include the ability to generate pulses of up to 1.8 MJ total energy, with peak power of 500 TW and temporal pulse shapes spanning 2 orders of magnitude at the third harmonic (351 nm or 3omega) of the laser wavelength. The focal-spot fluence distribution of these pulses is carefully controlled, through a combination of special optics in the 1omega (1053 nm) portion of the laser (continuous phase plates), smoothing by spectral dispersion, and the overlapping of multiple beams with orthogonal polarization (polarization smoothing). We report performance qualification tests of the first eight beams of the NIF laser. Measurements are reported at both 1omega and 3omega, both with and without focal-spot conditioning. When scaled to full 192 beam operation, these results demonstrate, to the best of our knowledge for the first time, that the NIF will meet its laser performance design criteria, and that the NIF can simultaneously meet the temporal pulse shaping, focal-spot conditioning, and peak power requirements for two candidate indirect drive ignition designs.

Radiation-driven hydrodynamics of high- hohlraums on the national ignition facility.

The first hohlraum experiments on the National Ignition Facility (NIF) using the initial four laser beams tested radiation temperature limits imposed by plasma filling. For a variety of hohlraum sizes and pulse lengths, the measured x-ray flux shows signatures of filling that coincide with hard x-ray emission from plasma streaming out of the hohlraum. These observations agree with hydrodynamic simulations and with an analytical model that includes hydrodynamic and coronal radiative losses. The modeling predicts radiation temperature limits with full NIF (1.8 MJ), greater, and of longer duration than required for ignition hohlraums.

Hot images from obscurations.

Certain damage observed on the optics in NOVA is consistent with a phenomenon akin to holographic imaging. (NOVA is the Lawrence Livermore National Laboratory's 10-beam Nd:glass laser used for inertial confinement fusion research.) The minimization of similar damage in next-generation laser systems is sought by first identifying the sources for these holographic images, specifying glass parameters appropriately, and staging the amplifier chain to circumvent the problem. The insight gained has lead to an explanation for a 20-year-old puzzle.

Kinoform phase plates for focal plane irradiance profile control.

A versatile, rapidly convergent, iterative algorithm is presented for the construction of kinoform phase plates for tailoring the far-field intensity distribution of laser beams. The method consists of repeated Fourier transforming between the near-field and the far-field planes with constraints imposed in each plane. For application to inertial confinement fusion, the converged far-field pattern contains more than 95% of the incident energy inside a desired region and is relatively insensitive to beam aberrations.

Spatial filter pinhole for high-energy pulsed lasers.

Spatial filters are essential components for maintaining high beam quality in high-energy pulsed laser systems. The long-duration (21 ns) high-energy pulses envisioned for future inertial-confinement fusion drive systems, such as the U.S. National Ignition Facility (NIF), are likely to lead to increased plasma generation and closure effects within the pinholes in the spatial filters. The design goal for the pinhole spatial filter for the NIF design is to remove small-angle scatter in the beam to as little as a ?100-murad divergence. It is uncertain whether this design requirement can be met with a conventional pinhole design. We propose a new pinhole architecture that addresses these issues by incorporating features intended to reduce the rate of plasma generation. Initial experiments with this design have verified its performance improvement relative to a conventional pinhole design.