Ice sheet and precession controlled subarctic Pacific productivity and upwelling over the last 550,000 years.

The polar oceans play a vital role in regulating atmospheric CO2 concentrations (pCO2) during the Pleistocene glacial cycles. However, despite being the largest modern reservoir of respired carbon, the impact of the subarctic Pacific remains poorly understood due to limited records. Here, we present high-resolution, 230Th-normalized export productivity records from the subarctic northwestern Pacific covering the last five glacial cycles. Our records display pronounced, glacial-interglacial cyclicity superimposed with precessional-driven variability, with warm interglacial climate and high boreal summer insolation providing favorable conditions to sustain upwelling of nutrient-rich subsurface waters and hence increased export productivity. Our transient model simulations consistently show that ice sheets and to a lesser degree, precession are the main drivers that control the strength and latitudinal position of the westerlies. Enhanced upwelling of nutrient/carbon-rich water caused by the intensification and poleward migration of the northern westerlies during warmer climate intervals would have led to the release of previously sequestered CO2 from the subarctic Pacific to the atmosphere. Our results also highlight the significant role of the subarctic Pacific in modulating pCO2 changes during the Pleistocene climate cycles, especially on precession timescale ( ~ 20 kyr).

The protection of acute spinal cord injury by subarachnoid space injection of Danshen in animal models.

CONTEXT/OBJECTIVE: Following acute spinal cord injury (ASCI) in rabbits, subarachnoid space injection of Danshen was performed to protect the neurological damage. In this study, we established rabbit models of spinal cord injury using a modified Allen's method. DESIGN: After the operation introducing the injuries, the rabbits were randomized into two different groups, control group (normal saline, NS) and Danshen, a component extracted from Chinese herb, treatment group. Each rabbit was supplied with either the drug or placebo at 0.3 ml/kg each day through subarachnoid cavity. SETTING: Rabbit model of acute spinal cord injury were used for the response to Danshen treatment. PARTICIPANTS: Total 48 Chinese rabbits aged four∼ five months old provided by Experimental Animal Center of Hubei Province were used for this study. INTERVENTIONS: Danshen drug or placebo was administered via a silicon tube embedded under the spinal dura mater to administer the drugs into subarachnoid cavity. OUTCOME MEASURES: After the treatment, damage indicators including cell apoptosis, morphological changes and oxidative damages were assessed. RESULTS: We found out that cell apoptosis was decreased after Danshen injection as determined by downregulation of apoptosis index (AI) by TUNEL analysis as well as propidium iodide (PI) percentage by FACS analysis. In the meanwhile, we observed cells after the treatment have increased numbers of BCL-2 positive cells, this indicated the antiapoptotic gene expression is increased after Danshen treatment. When we check the oxidative damage indicators, we found superoxide dismutase (SOD) was increased and malondiadehyde (MDA) levels were decreased after the treatment. CONCLUSION: Danshen can protect ASCI through inhibition of oxidative damage in the injured cells and thus reduce the subsequent cell apoptosis in the spinal.

Continuous wave and Q-switched laser output of laser-diode-end-pumped disordered Nd:LGS laser.

Laser-diode (LD)-pumped high-power cw and passively Q-switched laser performance has been demonstrated with a disordered Nd-doped La(3)Ga(5)SiO(14) (Nd:LGS) crystal for the first time to our knowledge. A cw output power of 2.25 W was obtained under an absorbed pump power of 7.84 W with a slope efficiency of 30.2%. Using a Cr:YAG as a saturable absorber, the passively Q-switched laser was achieved. The maximum pulse energy, shortest pulse width, and highest peak power were measured to be 117.5 muJ, 23.4 ns, and 5.02 kW, respectively.

Passive mode-locking performance with a mixed Nd:Lu(0.5)Gd(0.5)VO(4) crystal.

Continuous-wave (cw) mode-locking of a diode-pumped Nd:Lu(0.5)Gd(0.5)VO(4) mixed crystal laser is reported for the first time to our knowledge with a simply compact three-mirror cavity. Stable pulses as short as 5.5 ps were generated at a repetition rate of 147 MHz. At the absorbed pump power of 16 W, a mode-locked laser with average output power of 5.31 W was obtained, giving an optical conversion efficiency of 33.2%, and a slope efficiency of 46.7%.

High-power dual-wavelength laser with disordered Nd:CNGG crystals.

We demonstrate the high-power dual-wavelength laser output with disordered Nd:CNGG laser crystals. Continuous-wave output power of 4.03 W was obtained under the incident pump power of 15.62 W. In the passively Q-switched operation, the shortest pulse width, largest pulse energy, and highest peak power were achieved to be 12.9 ns, 173.16 microJ, and 12.3 kW, respectively, with Cr(4+):YAG crystals as the saturable absorbers. By spectral analysis, the output lasers were found to have dual wavelengths. We believed that the passively Q-switched dual-wavelength laser should be possible to be used as a source for the generation of terahertz radiation.

Continuous-wave and passively Q-switched laser performance with a disordered Nd:CLNGG crystal.

We demonstrated efficient high-power continuous-wave (cw) and passively Q-switched disordered Nd:CLNGG laser performance. In cw operations, the output power was obtained to be 3.81 W with a slope efficiency of 30.3%. To our knowledge, they are the highest cw power and efficiency with Nd:CLNGG as the gain medium and a laser-diode (LD) as the pump source. Recorded with a spectrum analyzer, no splitting was found in the Nd:CLNGG laser, which is different with that of its isomorph Nd:CNGG. The LD pumped passively Q-switched Nd:CLNGG laser was obtained for the first time to our knowledge. The shortest pulse width, largest pulse energy and highest peak power were achieved to be 12.3 ns, 199.1 microJ and 16 kW, respectively, with Cr(4+):YAG crystals as the saturable absorbers.

Thermal properties measurement and laser operation of a new Yb: Gd0.68Lu0.32VO4 crystal.

A new series mixed vanadate crystals, Yb:Gd(x)Lu(1-x)VO(4) (x=0.2, 0.35, 0.53, 0.68 and 0.84), were grown by the Czochralski method. The thermal conductivities of these crystals were measured from room temperature to 280?C, and the thermal conductivities of Yb:Gd(0.68)Lu(0.32)VO(4) at room temperature are 6.4 and 6.9 W m(-1)K(-1) along a- and c-axis, respectively. The material constants of Yb:Gd(x)Lu(1-x)VO(4) series crystals were estimated. The properties of Yb:Gd(x)Lu(1-x)VO(4) series crystals were compared with those of Yb:LuVO(4) and Yb:GdVO(4) crystals. Laser output power of 1.25 W at 1031 nm was obtained with a slope efficiency of 26% by use of diode pumping for Yb:Gd(0.68)Lu(0.32)VO(4) crystal.

Growth and passively self-Q-switched laser output of new Nd3+,Cr5+:GdVO4 crystal.

A new passively self-Q-switched Nd, Cr:GdVO(4) laser crystal was grown by Czochralski method for the first time to our knowledge. Polarized absorption spectra were measured at room temperature. The absorption bands display polarization character and an absorption band of Cr(5+) ions at 1110 nm enables the crystal to be a self-Q-switched laser material at 1.06 mum. In the passive self-Q-switching operation, the maximum output power, shortest pulse width, and largest pulse energy were obtained to be 265 mW, 230 ns, and 1.12 microJ, respectively.

Passively mode-locked Nd:LuVO(4) laser with a GaAs wafer.

We report on the passive mode locking of a diode-pumped Nd:LuVO(4) laser with a GaAs wafer as output coupler. Using the interference modulation effect of the GaAs wafer, high-power continuous-wave mode locking with a pulse width of about 7.1 ps and an average output power of 3.11 W was achieved. Our result shows that Nd:LuVO(4) could be an excellent gain medium for diode-pumped high-power mode-locked lasers.

Enhancement of passive Q-switching performance with mixed Nd:LuxGd1-xVO4 laser crystals.

Passive Q-switching operation has been demonstrated with a class of mixed Nd:Lu(x)Gd(1-x)VO(4) laser crystals. With respect to that obtained with Nd:GdVO(4), the passive Q-switching performance, including threshold, pulse energy, and peak power, was found to be greatly enhanced with the mixed vanadate crystals. The shortest pulse width of 6.2 ns, largest pulse energy of 192.5 microJ, and highest peak power of 31.1 kW were obtained at the incident pump power of 13.75 W with the mixed crystal for x=0.5.

Cr(5+):GdVO(4) as a saturable absorber for a diode-pumped Nd:Lu(0.5)Gd(0.5)VO(4) laser.

A new Q-switched crystal Cr(5+):GdVO(4) was grown by the Czochralski method for the first time, to our knowledge. Polarized absorption spectra of Cr(5+)+:GdVO(4) were measured at room temperature. The results showed that the crystal has polarized absorption properties, and the absorption band of pi-polarized spectra located at 900 to 1300 nm should be suitable as a passive saturable absorber Q-switched laser at about 1 mum. With Cr(5+):GdVO(4) as a saturable absorber, the pulsed laser performance of Nd:Lu(0.5)Gd(0.5)VO(4) at 1.06 mum was demonstrated. The maximum average output power of 122 mW was obtained under a pump power of 3.79 W. The shortest pulse width and largest pulse energy obtained were 361 ns and 0.77 muJ, respectively. To our knowledge, it is the first time the absorption spectra of Cr(5+):GdVO(4) and a pulsed laser with the crystal as the saturable absorber have been obtained.