钛宝石激光器中用优化Gires-Tournois镜产生15fs脉冲

根据飞秒脉冲锁模钛宝石激光器脉冲压缩的要求，介绍了负色散镜补偿色散的基本原理及其特点。详细阐述了优化Gires-Tournois(OG-T)镜的设计过程，并通过计算机优化得到理想设计膜系。采用离子束溅射的方法镀制了优化Gires—Tournois镜。测量了优化Gires-Tournois镜(编号为OGT#1)的透射率和群延迟色散，并与设计值进行了比较，分析了实测值产生偏差的原因，从而对镀膜参量进行了相应的调整，制造了第二批优化Gires—Tournois镜(编号为OGT#2)。将优化Gires—Tourn

细胞色素b6f蛋白复合体中叶绿素 a的性质和功能研究

细胞色素b6f蛋白复合体（Cytochrome b6f complex, Cyt b6f）是光合膜上参与光合作用原初反应过程的主要膜蛋白超分子复合体之一。莱茵衣藻和嗜热蓝细菌的Cyt b6f三维晶体结构均显示，每Cyt b6f单体分子含有1分子Chlorophyll a (Chl a )，充分肯定了Chl a 是Cyt b6f天然成分的观点(Kurisu et al，2003;Stroebel et al，2003)。研究表明不同来源的Cyt b6f中Chla单线激发态寿命(或荧光寿命)并不一样，多数的研究结果认为Cyt b6f中Chla单线激发态寿命只有200ps左右，但是也有Cyt b6f中Chla单线激发态寿命为～600ps的报道;而甲醇中游离Chl a 的单线激发态寿命为4ns左右。针对Cyt b6f中Chla单线激发态寿命快速淬灭的现象，Dashdorj 等(2005)根据晶体结构推测Cyt b6f中Chla单线激发态和邻近的Cyt b6亚基上Tyr105残基发生电子交换传递，从而快速淬灭Chla单线激发态，减少了三线态Chl a和单线态氧的产生，并且认为这是Cyt b6f保护自身不受单线态氧破坏的一种机制，但是这一推测缺乏有力的证据。另外，Cyt b6f中Chla的功能仍然未知。本文以菠菜Cyt b6f为对象，结合多种实验手段，测定了菠菜Cyt b6f中Chl a单线激发态寿命，并对复合体中Chl a 单线激发态淬灭的机理进行了深入研究。此外，我们还对复合体中Chl a 可能的功能进行了初步地探讨。获得了如下的结果： 1．针对不同来源的Cyt b6f中Chla单线激发态寿命（或荧光寿命）测定结果不同的报道，仔细分析了其中的原因，发现除了样品来源的差异外，使用不同的去垢剂可能是一个不可忽视的因素。在实验中，不同的研究者分别采用了十二烷基麦芽糖苷（n-Dodecyl β-D-maltoside，DDM，）和八烷基葡萄糖苷（n-Octyl β-D-glucopyranoside，β－OG)作为溶解样品的去垢剂。因此，本文借助稳态吸收和稳态荧光光谱、瞬态光散射技术，CD光谱和亚皮秒时间分辨吸收光谱等技术，分别研究了这两种去垢剂对Cyt b6f结构和功能的不同影响。结果表明，DDM去垢剂能使Cyt b6f处于较好的分散体系中，其中血红素和Chl a分子处于特定的蛋白环境中，不会导致Cyt b6f变性;而β－OG去垢剂会使Cyt b6f产生聚合现象，其中的血红素和Chl a与蛋白环境的相互作用减弱，和DDM相比其电子传递活性显著降低，Chl a单线激发态寿命延长，Chl a更容易被光破坏。通过这一工作，我们优化和确定了Cyt b6f的溶解条件，为下面的研究工作打下了良好的基础。 2．利用Tyr的特异性修饰剂p-Nitrobenzenesulfonyl Fluoride（NBSF）对Cyt b6f样品进行特性修饰，经原子吸收谱、荧光谱、CD谱、质谱等方法对修饰后的样品进行鉴定，并结合时间分辨飞秒吸收光谱技术，测得修饰后的样品在660nm激发下Chl a 单线激发态寿命延长，从而在实验上提供了Tyr与淬灭Chla单线激发态有关的证据。但是对Cyt b6f 中Chl a瞬态吸收图谱仔细研究表明，菠菜Cyt b6f 中Chl a单线激发态快速淬灭过程中并没有发现Tyr与Chl a 之间发生电子传递时所形成的Chla•¯。以上结果表明，Cyt b6f 中Chl a单线激发态快速的淬灭确实和邻近的Tyr105有关，但是与Dashdorj 等提出的Chla单线激发态和Tyr105残基发生了电子交换传递从而淬灭Chla单线激发态这一想法不符，关于这一问题值得进一步深入研究。 3．红光和绿光对Cyt b6f 照射，Cyt f可以被还原，并且红光比绿光更容易使Cyt f 还原，暗示Cyt f 的还原与Chl a 的关系密切，有可能是Chl a 被激发后，其被激发的电子传给Cyt f。对这一现象的进一步研究表明，Cyt b6f在光照条件下，Cyt f 的还原与体系内C10－PQ库的氧化还原状况相关，氧化型的C10－PQ可能介导电子从Chla传向Cyt f。由于在体内质体醌库的氧化还原状态往往决定Cyt b6f 的氧化还原状态，而通过对Cyt b6f不同氧化和还原状态的吸收谱和荧光谱的研究表明，氧化态和还原态的Cyt b6f 中，Chl a 与蛋白的结合状态是有差异的。这些差异可能暗示着Chl a 分子在行使其功能时与复合体的氧化还原状态是有关系的。通过以上的结果，对Cyt b6f中Chl a 可能的功能进行了假设。 4．此外，我们还发现Cyt b6f具有明显的过氧化物酶活性。在0.1 mmol/L乙酸钠缓冲液，pH3.6，25℃，[H2O2] <40mmol/L的条件下，其催化反应的速度常数为kobs＝26±1.2M•s-1;对H2O2的Km 值为50mmol/L，对guaiacol的Km 值为2mmol/L;反应的最适pH为3.6，最适离子强度为0.1，最适温度为35℃。推测Cyt b6f的这种过氧化物酶活性可能是在胁迫环境下使Cyt b6f中的血红素和Chl a 分子免受H2O2的破坏。

Unveiling the morphology of buried In(Ga)As nanostructures by selective wet chemical etching: From quantum dots to quantum rings

The three-dimensional morphology of In(Ga)As nanostructures embedded in a GaAs matrix is investigated by combining atomic force microscopy and removal of the GaAs cap layer by selective wet etching. This method is used to investigate how the morphology of In(Ga)As quantum dots changes upon GaAs capping and subsequent in situ etching with AsBr3. A wave function calculation based on the experimentally determined morphologies suggests that quantum dots transform into quantum rings during in situ etching. (c) 2007 American Institute of Physics.

Tuning the Exciton Binding Energies in Single Self-Assembled InGaAs/GaAs Quantum Dots by Piezoelectric-Induced Biaxial Stress

We study the effect of an external biaxial stress on the light emission of single InGaAs/GaAs(001) quantum dots placed onto piezoelectric actuators. With increasing compression, the emission blueshifts and the binding energies of the positive trion (X+) and biexciton (XX) relative to the neutral exciton (X) show a monotonic increase. This phenomenon is mainly ascribed to changes in electron and hole localization and it provides a robust method to achieve color coincidence in the emission of X and XX, which is a prerequisite for the possible generation of entangled photon pairs via the recently proposed "time reordering'' scheme.

Gate controlled Aharonov-Bohm-type oscillations from single neutral excitons in quantum rings

We report on a magnetophotoluminescence study of single self-assembled semiconductor nanorings which are fabricated by molecular-beam epitaxy combined with AsBr3 in situ etching. Oscillations in the neutral exciton radiative recombination energy and in the emission intensity are observed under an applied magnetic field. Further, we control the period of the oscillations with a gate potential that modifies the exciton confinement. We infer from the experimental results, combined with calculations, that the exciton Aharonov-Bohm effect may account for the observed effects.

Stretchable Graphene: A Close Look at Fundamental Parameters through Biaxial Straining

Tunable biaxial stresses, both tensile and compressive, are applied to a single layer graphene by utilizing piezoelectric actuators. The Gruneisen parameters for the phonons responsible for the D, G, 2D and 2D' peaks are studied. The results show that the D peak is composed of two peaks, unambiguously revealing that the 2D peak frequency (omega(2D)) is not exactly twice that of the D peak (omega(D)). This finding is confirmed by varying the biaxial strain of the graphene, from which we observe that the shift of omega(2D)/2 and omega(D) are different. The employed technique allows a detailed study of the interplay between the graphene geometrical structures and its electronic properties.

the ebb-tidal delta of the venice lagoon,Italy

Very high-resolution seismic lines were collected offshore the Venice Lagoon in the framework of the Co.Ri.La'New very high resolution seismic methods to study the Venice Lagoon subsoil' project. The 140 km boomer profiles led to the identification of a convex-upward,lens-shaped body just outside the Lido inlet,one of the three lagoon inlets,which has been interpreted as an ebb-tidal delta.The comparison between the scismostratigraphic setting og this deposit, as revealed by the seismic lines,and the analyses of historicalbathymetric maps highlighted the key role of human interventions in the formation and evolution of the Lido inlet cbb-tidal delta.To preserve the lagoon environment but also to ensure a navigable way, human interventions at the Lidoinlet,performed since the fourteenth centtury, caused profound variations in the inlet dynamics,ldading to a progressive increase in the sediment dispersion from the lagoon interior towards the sea. The ebb-tidal delta of the Lido nilet is thus a very recent feature compared with the formation of the Venice lagoon and formed mainly as a consequence of the construction of the two jetties that have bound the inlet form AD 1886 to the present day.

Bluish-white emission from radical carbonyl impurities in amorphous Al2O3 prepared via the Pechini-type sol-gel process

Many efforts have been devoted to exploring novel luminescent materials that do not contain expensive or toxic elements, or do not need mercury vapor plasma as the excitation source. In this paper, amorphous Al2O3 powder samples were prepared via the Pechini-type sol-gel process. The resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), photoluminescence (PL) excitation and emission spectra, kinetic decay, and electron paramagnetic resonance (EPR).

A NOVEL SHELL COLOR VARIANT OF THE PACIFIC ABALONE HALIOTIS DISCUS HANNAI INO SUBJECT TO GENETIC CONTROL AND DIETARY INFLUENCE

Molluscan shells may display a variety of colors, which formation, inheritance, and evolutionary significance are not Well understood. Here we report a new variant of the Pacific abalone Haliotis discus hannai that displays a novel orange shell coloration (O-type) that is clearly distinguishable from the Wild green-shelled abalone (G-type). Controlled mating experiments between O- and G-type abalones demonstrated apparent Mendelian segregations (1:1 or 3:1) in shell colors in F-2 families, which support the notion that the O- and G-types are under strict genetic control at a single locus With a recessive o (for orange shell) allele and a dominant G (for green shell) allele. Feeding with different diets caused modifications of shell color within each genotype, ranging from orange to yellow for O-type and green to dark-brown for the G-type, without affecting the distinction between genotypes. A previously described bluish-purple (B-type) shell color was found in one of the putative oo X oG crosses, suggesting that the B-type may be it recessive allele belonging to the same locus. The new O-type variant had no effect on the growth of Pacific abalone on the early seed-stage. This Study demonstrates that shell color in Pacific abalone is subject to genetic control as well as dietary modification, and the latter probably offers selective advantages in camouflage and predator avoidance.

Isolation of the main light-harvesting chlorophyll a/b-protein complex from thylakoid membranes of marine alga, Bryopsis corticulans by a direct method

The main chlorophyll a/b light-harvesting complex (LHC 11) has been isolated directly from thylakoid membranes of marine green alga (Bryopsis corticulans Setch.) by two consecutive runs of anion exchange and gel-filtration chromatography. LHC 11 proteins in the membrane extracts treated with 3% n-Octyl-b-D-glucopyranoside (OG) obtained specific binding ability on Q Sepharose column, and thus were isolated from the thylakoid membranes in a highly selective fraction. The monomeric, trimeric and oligomeric subcomplexes of LHC 11 have been obtained by fractionation of the LHC 11 mixes with sucrose density gradient ultracentrifugation. The SDS-PAGE analysis of peptide composition and absorption spectrum showed that LHC 11 monomers, trimers and oligomers prepared through this work were intact and in high purity. Our report is the first to show that it is possible to purify LHC If directly from thylakoid membranes without extensively biochemical purification.