phase transfer
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2022 ◽  
Vol 13 (1) ◽  
Cecilia Clivati ◽  
Alice Meda ◽  
Simone Donadello ◽  
Salvatore Virzì ◽  
Marco Genovese ◽  

AbstractQuantum mechanics allows distribution of intrinsically secure encryption keys by optical means. Twin-field quantum key distribution is one of the most promising techniques for its implementation on long-distance fiber networks, but requires stabilizing the optical length of the communication channels between parties. In proof-of-principle experiments based on spooled fibers, this was achieved by interleaving the quantum communication with periodical stabilization frames. In this approach, longer duty cycles for the key streaming come at the cost of a looser control of channel length, and a successful key-transfer using this technique in real world remains a significant challenge. Using interferometry techniques derived from frequency metrology, we develop a solution for the simultaneous key streaming and channel length control, and demonstrate it on a 206 km field-deployed fiber with 65 dB loss. Our technique reduces the quantum-bit-error-rate contributed by channel length variations to <1%, representing an effective solution for real-world quantum communications.

2022 ◽  
Vol 12 (1) ◽  
Marcin Konopka ◽  
Artur R. Stefankiewicz

AbstractWe describe here an unorthodox approach to dynamic covalent chemistry in which the initially-unexpected in-situ hydrolysis of a bis-imide is employed to control the composition of a library of structurally diverse macrocycles. A single building block is used to generate a library of numerous disulfide-based architectures in a one-pot single-step process. The dual-stimuli method is based on simultaneous changes in pH and DMSO concentration to expand the structural diversity of the macrocyclic products. Mechanistic details of this complex process are investigated by the kinetics analysis. We delivered a facile strategy for the synthesis of water-soluble, multicomponent and dynamic macrocycles equipped with number of different functional groups, thus giving a prospect of their application in guest-driven phase transfer.

2022 ◽  
Vol 15 ◽  
Jiakai Lian ◽  
Yuxi Luo ◽  
Minglong Zheng ◽  
Jiaxi Zhang ◽  
Jiuxing Liang ◽  

Depression is a prevalent mental illness with high morbidity and is considered the main cause of disability worldwide. Brain activity while sleeping is reported to be affected by such mental illness. To explore the change of cortical information flow during sleep in depressed patients, a delay symbolic phase transfer entropy of scalp electroencephalography signals was used to measure effective connectivity between cortical regions in various frequency bands and sleep stages. The patient group and the control group shared similar patterns of information flow between channels during sleep. Obvious information flows to the left hemisphere and to the anterior cortex were found. Moreover, the occiput tended to be the information driver, whereas the frontal regions played the role of the receiver, and the right hemispheric regions showed a stronger information drive than the left ones. Compared with healthy controls, such directional tendencies in information flow and the definiteness of role division in cortical regions were both weakened in patients in most frequency bands and sleep stages, but the beta band during the N1 stage was an exception. The computable sleep-dependent cortical interaction may provide clues to characterize cortical abnormalities in depressed patients and should be helpful for the diagnosis of depression.

2022 ◽  
Ankita Rai ◽  
Prashant Shukla ◽  
Manorama Singh ◽  
Vijai K. Rai

We report herein unprecedented conjugate addition of enolizable ketones and unprotected mercaptoacetic acid to electron poor alkenes using graphene oxide as phase transfer catalyst. The envisaged protocol is versatile and...

2021 ◽  
Vol 12 (1) ◽  
pp. 321
Raisa N. Krasikova ◽  
Viktoriya V. Orlovskaya

Incorporation of [18F]fluorine into PET radiotracer structure has traditionally been accomplished via nucleophilic pathways. The [18F]fluoride is generated in an aqueous solution via proton irradiation of oxygen-18 enriched water and must to be introduced into water-free organic solutions in order to generate reactive species. Thus nucleophilic 18F-fluorination traditionally included steps for [18F]fluoride concentration on the anion exchange resin, followed by removal of residual water via azeotropic distillation with MeCN, a time-consuming process associated with radioactivity losses and difficult automation. To circumvent this, several adsorption/elution protocols were developed based on the minimization of water content in traditional kryptofix-based [18F]fluoride eluents. The use of pre-dried KOH/kryptofix solutions, tertiary alcohols, and strong organic bases was found to be effective. Advances in transition metal-mediated SNAr approaches for radiolabeling of non-activated aromatic substrates have prompted development of alternative techniques for reactive [18F]fluoride species generation, such as organic solutions of non-basic alkyl ammonium and pyridinium sulfonates, etc. For radiofluorinations of iodonium salts precursors, a “minimalist” approach was introduced, avoiding the majority of pitfalls common to more complex methods. These innovations allowed the development of new time-efficient and convenient work-up procedures that are easily implementable in modern automated synthesizers. They will be the subject of this review.

Sambit Dash ◽  
Pragna Rao ◽  
Ullas Kamath ◽  
Aparna R Pai ◽  
Prasanna Kumar Reddy Gayam ◽  

Gold nanoparticles have found a wide range of application in biomedical sciences. Unique properties of these metal nanoparticles include surface plasmon resonance and size dependent colour change. Various molecules have been functionalized on the gold nanoparticles surface but carbohydrates have garnered attention due to their properties and their role in living systems. However certain challenges make carbohydrate-gold nanoparticles association difficult to obtain and stabilize. This study was carried out to chemically remodel gold nanoparticles by adding a monosaccharide mannose to its surface. A modified phase transfer method was used to synthesize gold nanoparticles. The surface of the nanoparticles was fixed with cyanuric chloride to serve as a linker. Mannose was then linked to the linker molecule. All three stages of the process, gold nanoparticles, and gold nanoparticles with linker and gold nanoparticles with the carbohydrate were analyzed for size and stability. Zeta potential and UV-vis data exhibited stable gold nanoparticles dispersion, successful binding of linker molecule as well as the carbohydrate. This study shows a simple, cost-effective and robust method of glycomodification of gold nanoparticles surface which can further find use in wide ranging applications.

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1545
Assunta D’Amato ◽  
Giorgio Della Sala

Vinylogous enolate and enolate-type carbanions, generated by deprotonation of α,β-unsaturated compounds and characterized by delocalization of the negative charge over two or more carbon atoms, are extensively used in organic synthesis, enabling functionalization and C–C bond formation at remote positions. Similarly, reactions with electrophiles at benzylic and heterobenzylic position are performed through generation of arylogous and heteroarylogous enolate-type nucleophiles. Although widely exploited in metal-catalysis and organocatalysis, it is only in recent years that the vinylogy and arylogy principles have been translated fruitfully in phase-transfer catalyzed processes. This review provides an overview of the methods developed to date, involving vinylogous and (hetero)arylogous carbon nucleophiles under phase-transfer catalytic conditions, highlighting main mechanistic aspects.

2021 ◽  
Majda Mekic ◽  
Thomas Schaefer ◽  
Hartmut Herrmann

&lt;p&gt;Anthropogenic and biogenic sources produce numerous primary emitted gases, organic compounds, and aerosols in the atmosphere. An important group of such compounds are &amp;#945;, &amp;#946;-unsaturated carbonyl molecules, which can be formed in the atmosphere due to their secondary origin, including oxidation of their precursors such as hydrocarbons with common atmospheric oxidants such as hydroxyl radicals (&amp;#8231;OH). Since those compounds contain at least one double bond and one carbonyl group, they are characterized as water-soluble molecules, which can diffuse on the cloud droplets&amp;#8217; surface and undergo a phase transfer from the gas phase to the atmospheric aqueous phase. In the latter, the oxidized organic compounds can contribute to aerosol mass production through in-cloud processes, yielding aqueous phase secondary organic aerosols (aqSOA). Due to their strong photochemical behavior, the development of a new analytical approach for evaluating the OH radical kinetics in the aqueous phase under dark conditions was essential. One of the most studied non-photolytic reactions is Fenton chemistry (Fe(II)/H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;), which serves as an OH radical source in the dark in the atmospheric aqueous phase after catalytic decomposition of H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; in the presence of Fe(II) at acidic pH values. In a typical experiment, temperature-dependent second-order rate constants of OH radicals with unsaturated dialdehydes, such as (1) crotonaldehyde, and (2) 1,4-butenedial, were determined in a bulk reactor by using the competition kinetics method. In the newly developed method, the role of radical scavenger was performed by isotopically labeled 2-propanol (d8), while the OH-initiated oxidation produces deuterated acetone (d6), being analyzed with GC-MS after derivatization. The findings from our research will be incorporated in the CAPRAM model to explain discrepancies between experimentally observed and predicted aqSOA properties.&lt;/p&gt;

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