On-chip pre-concentration and complexation of [¹⁸F]fluoride ions via regenerable anion exchange particles for radiochemical synthesis of Positron Emission Tomography tracers

Microfluidic approaches have demonstrated a relevant impact on radiochemical reactions involving Positron Emission Tomography (PET) nuclides, due to shorter reaction times and smaller precursor quantities. However, little attention has been given to the integration of the initial pre-concentration and drying of radioactive [(18)F]fluoride ions, required for the labeling of radiotracer compounds. In this work we report the design, fabrication and implementation of a glass microfluidic device filled with recyclable anion exchange particles for the repeated recovery of [(18)F] and [(19)F]fluoride ions. The device was first tested with non radioactive [(19)F]fluoride ions and it was shown to repeatedly trap and elute >95% fluoride over 40 successive experimental runs with no decrease in efficiency. The same device was then tested for the trapping and release of [(18)F]fluoride ions over 20 experiments with no measurable decrease in performance. Finally, the [(18)F]fluoride ions were eluted as a K(18)F/K2.2.2 complex, dried by repeated dissolution in acetonitrile and evaporation of residual water, and reacted with ethyl ditosylate (EtDT) leading to the desired product ([(18)F]fluoroethyltosylate) with 96 ± 3% yield (RCY). The overall time needed for conditioning, trapping, elution and regeneration was less than 6 min. This approach will be of great benefit towards an integrated platform able to perform faster and safer radiochemical synthesis on the micro-scale.     

一种不含自由参数的正电子吸收势

在准自由电子气模型的基础上得到一种不含自由参数的正电子吸收势，把它作为光学势的虚部，计算了能量在最小非弹性阀值到１００ｅＶ范围内正电子被Ｈｅ、Ｎｅ、Ａｒ原子散射的总截面和能量为２００ｅＶ和３００ｅＶ时的散射微分截面，计算结果与实验进行了比较。     

Synthesis of trifunctional somatostatin based derivatives for improved cellular and subcellular uptake

It is now well established that the biological effects of Auger-emitting radionuclides are critically dependent on their subcellular location. Therefore, for their use in molecular imaging and targeted radionuclide therapy, attempts should be made to increase the nuclear specificity of the carriers. In the present paper the synthesis of novel trifunctional somatostatin derivatives containing a nuclear localization motif is described. These derivatives of [DOTA⁰, Tyr³]-octreotide (DOTATOC, DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) were obtained in high yields using Fmoc peptide synthesis in solid and in solution phase.     

等离子体喷涂层的正电子湮没研究

本文用正电子湮没技术对等离子体喷涂铜基合金压缩形变的微观缺陷进行了测量。对等离子体喷涂合金，随着压缩量的增加，正电子寿命变短，这一现象与常规合金中观察到的情况相反。     

Generation and Detection of Infrared Single Photons and their Applications

Unbreakable secret communication has been a dream from ancient time. It is quantum physics that gives us hope to turn this wizardly dream into reality. The rapid development of quantum cryptography may put an end to the history of eavesdropping. This will be largely due to the advanced techniques related to single quanta, especially infrared single photons. In this paper, we report on our research works on single-photon control for quantum cryptography, ranging from single-photon generation to single-photon detection and their applications.     

Luminescent polymers with discrete emitter units

Optical absorption and photo-luminescence measurements were performed on a series of semiconducting polymers, based upon phenylene linkages, that have discrete emitter units. In these polymers, broken conjugation has been achieved in two ways: by introducing metalinkages between various numbers of para-connected aromatic groups or by severe steric distortion of a fully conjugated main chain. In either case, electronic states are localized on relatively small units, resulting in a large (π, π^*) band gap. The band gap decreases with increasing emitter unit conjugation, as expected. Blue light emission was observed from these materials, with the peak emission wavelength red shifted (by greater than 1 eV on average) from the peak absorption. © 1994 John Wiley & Sons, Inc.     

Positron angular correlation measurements on single-crystal aluminum at various temperatures

We have tested the trapping model by comparing the temperature dependence of the peak and the tail of the angular correlation curve from single crystal aluminum. The integral over the tail decreased as the integral over the peak increased with temperature, in such a way that the same vacancy formation energy could be deduced from both integrals. Paper B6 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973). Case Western Reserve University, Cleveland, Ohio, USA     

Triode field emitters with planar carbon-nanoparticle cathodes

We designed and fabricated three different types of triode field emitters with planar carbon-nanoparticle (CNP) cathodes such as a normal-gate structure, a double-gate structure, and a well-structure. A normal-gate structure CNP triode emitter showed good field emission properties. The field emission started at the gate-voltage of 45 V, and the anode current reached the level of 120 nA at the gate-voltage of 60 V. However, in general, normal-gate structure suffered from large gate current. Using the double-gate structure, we successfully reduced the gate current to the level less than 4% of anode currents up to the anode current of 250 nA. To simplify fabrication process while maintaining the gate current reduction effect of the double-gate structure, a triode emitter with a well-structure cathode was fabricated via reactive-ion etching of a heavily doped n-type silicon wafer. The triode emitter with a well-structure cathode and a recessed gate structure showed negligible gate current.     

基于空域非均匀傅里叶变换的傅里叶望远镜

为了在稀疏发射阵列下清晰重构目标图像,提出了一种基于空域非均匀傅里叶变换(NDFT)的傅里叶望远镜信号处理方法。依据傅里叶望远镜的发射器位置与抽取的目标空间频率关系,结合MATLAB程序特点,完成了空域非均匀傅里叶逆变换,重构了目标图像。稀疏发射阵列配置方式为:T型阵列单臂放置11个发射望远镜,连续抽取目标的8个低频信息,再抽取3个高频分量。选择不同形状和灰度分布的4个卫星作为成像目标。与补零均匀快速傅里叶变换(FFT)方法重构的图像对比发现:信噪比为100 dB时,相比补零均匀FFT方法, NDFT方法重构图像的Strehl比都有所提升,最高提升了0.159 8。     

Ionic conductivity of PVdF-co-HFP/LiClO4 in terms of free volume defects probed by positron annihilation lifetime spectroscopy

ABSTRACT

Polymers based on ionic conducting materials have important interest because of their potential applications in polymer electrolytes and membranes for fuel cell application. PVdF-co-HFP poly(viniliden-co-hexafluoropropylene) was chosen as a polymer matrix because of its high ionic conductivity and better mechanical properties. Polymer matrix composites were prepared with various amounts of LiClO₄ salt by a solution casting method. The sample-ionic conductivity measurements were recorded by AC impedance analyzer at different frequencies from 0.1?Hz to 20?MHz and at different temperatures from 273 to 373?K.

The changes of nanoscopic free volume and free volume fraction in these materials were investigated in terms of temperature from 273 to 373?K using Positron Annihilation Lifetime Spectroscopy (PALS) and Simha-Somcynsky (SS) Hole Theory. The free volume had a bump at about 3% in weight percentage of the salt and there is a slight increase after 10%. The effects of weight percentages of LiClO₄ and temperature were investigated. The mechanism of the ac ionic conductivity was presented in terms of the free volume models, however thermo-occupancy function justifies the best accurate representation of the data.