Inverse freezing in α-cyclodextrin solutions probed by quasi elastic neutron scattering

Solutions of α-cyclodextrin, 4-methylpyridine and water undergo a reversible liquid–solid phase transition on heating (“inverse freezing”). In this paper quasi elastic neutron scattering (QENS) measurements are reported, from which the diffusive dynamics of different components in the liquid and solid phases is determined. Results imply that, in solution, α-cyclodextrin is contained in a solvation shell of 4-methylpyridine molecules, while in the crystal phase, the majority of the cell contents are immobilized on the nanosecond timescale. This information will be important in evaluating the entropy of the system in its different phases and in understanding the unusual phase transition.     

Preparation of Super Soft Granules from Nanosized Ceramic Powders by Spray Freezing

Owing to their extremely high specific surfaces and their high surface-to-volume ratios nanosized ceramic powders show a strong tendency to agglomeration and poor flowability. For improved properties of these powders during storage, transport and shaping a granulation step is necessary. However, the granules must be completely destroyed during dry pressing or redispersion; otherwise, the advantages of nanoparticles in comparison to conventional powders will not be realized. Spray freezing is a new granulation technique which combines the advantages of a conventional granulation by spray drying and a sublimation drying process. Different suspensions of nanosized oxide powders were rapidly frozen by spray freezing and subsequently dried by freeze drying. Thus, capillary forces can be excluded by this process. The achieved granulates show spheric granules with very low strength, improved flowability and increased bulk density. They were redispersible and can be destroyed under very low pressures.     

利用大失谐腔场中的两个原子实现量子相位门

本文讨论同时囚禁于单模、大失谐腔场中两个不同原子构成的系统,结论指出:只要仔细选择两不同原子的跃迁频率差、原子与腔场相互作用时间,可实现一个快速的量子相位门。这一方案不需要辅助的原子能级。     

Solid‐phase extraction of explosive nitramines on macroreticular polymers modified by freezing with water or acetone

A novel approach is proposed to modify the porous structure and surface properties of the polymers used in solid‐phase extraction. The approach involves soaking in water or acetone, followed by freezing in liquid nitrogen (77.4 K) and was employed for two polymeric materials: Amberlite XAD‐7 and Amberlite XAD‐16. Variations in the surface properties of the adsorbents were justified by the action of acetone and water as solvents affecting the textural and other characteristic of the materials. The initial and treated adsorbents were used in extraction of explosive nitramines from aqueous samples. The performed modifications of the polymer texture allow us to increase the recovery rate as compared with the initial adsorbents. The results were justified by the swelling of fragments of the polymers and by the additional process of sorption of nitramines. The results indicate that polymeric adsorbents can be easily modified by the soaking/freezing process and the materials can be achieved that prove usefulness for the effective separation of explosive nitramines from aqueous samples.     

基于FPGA与DDS的磁共振成像射频脉冲发生器

设计了一种基于现场可编程门阵列(FPGA)与直接数字频率合成(DDS)的磁共振成像(MRI)射频脉冲发生器,采用FPGA实现DDS,并内置软脉冲波形双端口随机存取存储器(RAM)、乘法器以及相关的控制逻辑.实现了较高的技术指标,其中频率、相位与幅度分辨率分别为32 bits、16 bits与16 bits,软脉冲波形的时间精度可达0.1?s.FPGA提供了一个可编程的接口,便于序列控制器对其进行控制,以输出射频脉冲.MRI实验结果证明了该设计的可行性.     

Synthesis and photophysical behavior of thia-aza macrocycles with 9-anthracenylmethyl moiety as fluorescent appendage

1,3-Bis(bromomethyl)-2-methoxy-5-methylbenzene, 1,3-bis(bromomethyl)-2,4,6-trimethylbenzene, 1,3- and 1,4-bis(bromomethyl)benzene undergo nucleophilic substitution with methyl mercaptoacetate to provide respective diesters 6–9. These diesters (6–9) on stirring with bis(3-aminopropyl)amine and diethylenetriamine in methanol–toluene (1:1) mixture undergo intermolecular cyclization to give respective thia-aza macrocycles 10–15. The alkylation of macrocycles 10–13 with 9-anthracenylmethyl chloride gave amine N-(anthracenylmethyl) substituted macrocycles 16–19. The extraction profile of macrocycles 10–15 towards alkali (Li⁺, Na⁺, K⁺), alkaline earth (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), Ag⁺, Tl⁺ and Pb²⁺ picrates shows preferential extraction of Ag⁺ with these macrocycles. The macrocycles 16–19 show fluorescence spectrum typical of anthracene moiety and depending on their structures exhibit 0–80 times increase in fluorescence on addition of transition metal ions. Fluorescent receptors 16, 17, and 19 are capable of functioning as a very efficient multi input OR logic gate.

---

Graphical abstract 1,3- and 1,4-Bis(bromomethyl)benzene and its substituted derivatives undergo nucleophilic substitution with methyl mercaptoacetate to provide respective diesters 6–8. These diesters (6–8) on stirring with bis(3-aminopropyl)amine in methanol–toluene (1:1) mixture undergo intermolecular cyclization to give respective thia-aza macrocycles 10–12. The alkylation of macrocycles 10–12 with 9-anthracenylmethyl chloride gave amine N-(anthracenylmethyl) substituted macrocycles 16–18. The macrocycles 16–18 exhibit 0–80 times increase in fluorescence on addition of transition metal ions.

     

Simultaneous determination of simvastatin and simvastatin acid in human plasma by LC-MS/MS without polarity switch: application to a bioequivalence study

A simple, specific and sensitive LC-MS/MS assay for simultaneous determination of simvastatin (SV) and its active beta-hydroxy acid metabolite, simvastatin acid (SVA) in human plasma was developed using a statin analog as internal standard (IS). The method was validated over a dynamic linear range of 0.20-100.00 ng/mL for SV and 0.10-50.00 ng/mL for SVA with correlation coefficient r > or = 0.9987 and 0.9989, respectively. The analytes and IS were extracted from 500 microL aliquots of human plasma via liquid-liquid extraction using methyl tert-butyl ether and separated through an Aquasil C18 column (100 mm x 2.1 mm, 5 microm). Detection of analytes and IS was done by MS/MS with a turbo ion spray interface operating in positive ion and selective reaction monitoring acquisition mode. The total chromatographic run time was 3.0 min. Flash freezing of the aqueous phase was an added advantage during liquid-liquid extraction, which considerably reduced time and labour. The method was extensively validated for its accuracy, precision, recovery, stability studies and matrix effect. The method was successfully used for bioequivalence study of 40 mg SV tablet formulation in 12 human subjects under fasting condition.     

Programmable quantum processor implemented with superconducting circuit

A quantum processor might execute certain computational tasks exponentially faster than a classical processor. Here, using superconducting quantum circuits we design a powerful universal quantum processor with the structure of symmetric all-to-all capacitive connection. We present the Hamiltonian and use it to demonstrate a full set of qubit operations needed in the programmable universal quantum computations. With the device the unwanted crosstalk and ZZ-type couplings between qubits can be effectively suppressed by tuning gate voltages, and the design allows efficient and high-quality couplings of qubits. Within available technology,the scheme may enable a practical programmable universal quantum computer.     

Synthesis of some three-qubit gates and their implementation in a three spins system coupled with Ising interaction

The synthesis of the Toffoli gate, Fredkin gate, three-qubit Inversion-on-equality gate and D(α) gate, as well as their implementation in a three spins system coupled with Ising interaction are investigated. The sequences of the control pulse and the drift process to implement these gates are given. It is revealed that the implementation of some three-qubit gates in a circular spin chain is much better than in a linear spin chain, and every two measurements of the quantum computation complexity are not always consistent. It is significant to directly study the implementation of the multi-qubit gates and even more complicated components of quantum information processing without resorting to their synthesis.