Ammonia has long been known to be toxic for many photosynthetic organisms; however, the target for its toxicity remains elusive. Here, we show that in the cyanobacterium Synechocystis sp. strain PCC 6803, ammonia triggers a rapid photodamage of photosystem II (PSII). Whereas wild-type cells can cope with this damage by turning on the FtsH2-dependent PSII repair cycle, the FtsH2-deficient mutant...

Profiles of N(2) fixation, O(2) production (gross photosynthesis), O(2) concentration, chlorophyll a concentration, and photon fluence rates were measured with 50-mum resolution in colonies of the heterocyst-forming cyanobacterium Nostoc parmelioides. Microelectrode measurements were made after 20 h of incubation under N(2) gas. Colonies were frozen, and 50-mum sections were prepared by using a...

Acceleration of high-energy hadrons in GRB blast waves will be established if highenergy neutrinos are detected from GRBs. Recent calculations of photomeson neutrino production are reviewed, and new calculations of high-energy neutrinos and the accompanying hadronic cascade radiation are presented. If hadrons are injected in GRB blast waves with an energy corresponding to the measured hard X-ra...

We simulate the dynamics of the interaction between relativistically expanding spherically symmetric shells using a 1-dimensional hydrodynamic code and calculate spectra and light-curves arising from such collisions by integrating the synchrotron and inverse Compton emission of the shocked gas. The numerical results reflect the most important features observed in Gamma-Ray Bursts: the spectrum ...

The recent demonstration of saturable absorption and negative optical conductivity in the Terahertz range in graphene has opened up new opportunities for optoelectronic applications based on this and other low dimensional materials. Recently, population inversion across the Dirac point has been observed directly by time- and angle-resolved photoemission spectroscopy (tr-ARPES), revealing a rela...

Laser-induced thermal desorption of Na dimers from rough sodium surfaces adsorbed on quartz substrates has been studied. For this purpose, laser pulses with 2=532 and 1064 nm and 7 ns duration were used. The kinetic energy distribution and the integral desorption signal of the dimers were determined as a function of the laser fluence. Measurements were also performed after reducing the surface ...

Abstract The X /Co 3 nm/ Y (where , = Au, Pt) trilayers with as deposited in-plane magnetization alignment were irradiated 30 keV Ga + ions in the wide range of ion fluence. samples investigated by means complementary techniques: magneto-optical magnetometry and spectroscopy (in photon energy from 1.2 eV to 4.5 eV), magnetic force microscopy, positron annihilation spectroscopy, x-ray diffractio...

We report on the ablation and fabrication of optical waveguide using allyl-diglycol CR39 polymer. Pulse nanosecond (ns) laser (248 nm KrF) and continuous wave (CW) (244 nm argon-ion) irradiation are performed to observe surface modification on the polymer and potentially utilize it for channel waveguide. The pulsed UV laser creates craters with different depth as fluence increases to quantify t...

BACKGROUND To develop a new procedure for laser prostatectomy through a biopsy needle, we evaluated the efficacy of interstitial laser irradiation with a pulsed Ho:YAG laser (lambda: 2.1 microns) in the normal canine prostate. METHODS Pathological studies were performed up to 6 months after interstitial laser irradiation in 26 mongrel dogs (15.4 +/- 2.6 kg). Two dogs underwent the identical p...

Strong quantum confinement and low dielectric screening impart single-walled carbon nanotubes with exciton-binding energies substantially exceeding kBT at room temperature. Despite these large binding energies, reported photoluminescence quantum yields are typically low and some studies suggest that photoexcitation of carbon nanotube excitonic transitions can produce free charge carriers. Here ...