Universal rates for reactive ultracold polar molecules in reduced dimensions

Analytic expressions describe universal elastic and reactive rates of quasi-two-dimensional and quasi-one-dimensional collisions of highly reactive ultracold molecules interacting by a van der Waals potential. Exact and approximate calculations for the example species of KRb show that stability and evaporative cooling can be realized for spin-polarized fermions at moderate dipole and trapping strength, whereas bosons or unlike fermions require significantly higher dipole or trapping strengths.Comment: 4 pages, 3 figure

Nontriplet feature of genetic code in Euplotes ciliates is a result of neutral evolution

The triplet nature of the genetic code is considered a universal feature of known organ-isms. However, frequent stop codons at internal mRNA positions in Euplotes ciliates ultimately specify ribosomal frameshifting by one or two nucleotides depending on the context, thus posing a nontriplet feature of the genetic code of these organisms. Here, we sequenced transcriptomes of eight Euplotes species and assessed evolution-ary patterns arising at frameshift sites. We show that frameshift sites are currently accumulating more rapidly by genetic drift than they are removed by weak selection. The time needed to reach the mutational equilibrium is several times longer than the age of Euplotes and is expected to occur after a several-fold increase in the frequency of frameshift sites. This suggests that Euplotes are at an early stage of the spread of frameshifting in expression of their genome. In addition, we find the net fitness burden of frameshift sites to be noncritical for the survival of Euplotes. Our results suggest that fundamental genome-wide changes such as a violation of the triplet char-acter of genetic code can be introduced and maintained solely by neutral evolutio

A novel-type luciferin from Siberian luminous earthworm Fridericia heliota : structure elucidation by spectral studies and total synthesis

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Wiley-VCH Verlag GmbH & Co for personal use, not for redistribution. The definitive version was published in Angewandte Chemie International Edition 53 (2014): 5566–5568, doi:10.1002/anie.201400529.We report structure elucidation and synthesis of the luciferin from the recently discovered luminous earthworm Fridericia heliota. This luciferin represents a key component of a novel ATP-dependent bioluminescence system. The UV, fluorescence, NMR and HRMS spectral studies were performed on 5 mkg of the isolated substance, and gave four isomeric structures, conforming with spectral data. These isomers were chemically synthesized and one of them was found to produce light in the reaction with a protein extract from Fridericia. The novel luciferin was found to have an unusual deeply modified peptidic nature, implying an unprecedented mechanism of action.We acknowledge support from the Program of the Government of the Russian Federation “Measures to attract leading scientists to Russian educational institutions” (grant no. 11. G34.31.0058), the programs MCB RAS, President of the Russian Federation “Leading science school” (grant 3951.2012.4) and the Russian Foundation for Basic Research (grant 14-03-01015). B.M.S. was supported by a stipend from the Program of the President of the Russian Federation.2015-04-1

Level Anticrossing of Impurity States in Semiconductor Nanocrystals

The size dependence of the quantized energies of elementary excitations is an essential feature of quantum nanostructures, underlying most of their applications in science and technology. Here we report on a fundamental property of impurity states in semiconductor nanocrystals that appears to have been overlooked—the anticrossing of energy levels exhibiting different size dependencies. We show that this property is inherent to the energy spectra of charge carriers whose spatial motion is simultaneously affected by the Coulomb potential of the impurity ion and the confining potential of the nanocrystal. The coupling of impurity states, which leads to the anticrossing, can be induced by interactions with elementary excitations residing inside the nanocrystal or an external electromagnetic field. We formulate physical conditions that allow a straightforward interpretation of level anticrossings in the nanocrystal energy spectrum and an accurate estimation of the states\u27 coupling strength

Chiral photonic super-crystals based on helical van der Waals homostructures

Chirality is probably the most mysterious among all symmetry transformations. Very readily broken in biological systems, it is practically absent in naturally occurring inorganic materials and is very challenging to create artificially. Chiral optical wavefronts are often used for the identification, control and discrimination of left- and right-handed biological and other molecules. Thus, it is crucially important to create materials capable of chiral interaction with light, which would allow one to assign arbitrary chiral properties to a light field. In this paper, we utilized van der Waals technology to assemble helical homostructures with chiral properties (e. g. circular dichroism). Because of the large range of van der Waals materials available such helical homostructures can be assigned with very flexible optical properties. We demonstrate our approach by creating helical homostructures based on multilayer As$_2$S$_3$, which offers the most pronounced chiral properties even in thin structures due to its strong biaxial optically anisotropy. Our work showcases that the chirality of an electromagnetic system may emerge at an intermediate level between the molecular and the mesoscopic one due to the tailored arrangement of non-chiral layers of van der Waals crystals and without additional patterning

Photoluminescence quenching of dye molecules near a resonant silicon nanoparticle

Luminescent molecules attached to resonant colloidal particles are an important tool to study light-matter interaction. A traditional approach to enhance the photoluminescence intensity of the luminescent molecules in such conjugates is to incorporate spacer-coated plasmonic nanoantennas, where the spacer prevents intense non-radiative decay of the luminescent molecules. Here, we explore the capabilities of an alternative platform for photoluminescence enhancement, which is based on low-loss Mie-resonant colloidal silicon particles. We demonstrate that resonant silicon particles of spherical shape are more efficient for photoluminescence enhancement than their plasmonic counterparts in spacer-free configuration. Our theoretical calculations show that significant enhancement originates from larger quantum yields supported by silicon particles and their resonant features. Our results prove the potential of high-index dielectric particles for spacer-free enhancement of photoluminescence, which potentially could be a future platform for bioimaging and nanolasers

Designing redder and brighter fluorophores by synergistic tuning of ground and excited states

We strategically modified the GFP core via chemical synthesis to make redder and brighter biomimetic fluorophores. Based on quantum calculations, solvatochromism analysis, and femtosecond Raman, we unveiled the additive effect of tuning the electronic ground and excited states, respectively, to achieve a dramatic emission redshift with a "double-donor-one-acceptor" structure

Вакцинопрофилактика пневмококковой инфекции у детей

Pneumococcal infection remains one of the leading reasons for infant mortality from vaccine-preventable infections. Today vaccination is the most effective way to prevent diseases caused by antibiotic-resistant pneumococci. In the article, authors present current approaches to vaccinal prevention of pneumococcal diseases. The plan of action for carrying out active immunoprophylaxis of pneumococcal infection is explained in detail for both healthy children and patients from risk groups for severe pneumococcal diseases development. The published work is based on key points of the guidelines of the Ministry of Health of the Russian Federation on vaccinal prevention of pneumococcal infection (developed and approved by the professional association of pediatricians «The Union of Pediatricians of Russia»).Пневмококковая инфекция остается одной из ведущих причин детской смертности от вакциноуправляемых инфекций. Вакцинация на сегодняшний день является наиболее эффективным направлением профилактики заболеваний, вызываемых устойчивыми к антибактериальным препаратам пневмококкам. В статье коллективом авторов представлены актуальные подходы к вакцинопрофилактике болезней пневмококковой этиологии. Подробно разъяснен алгоритм действий при проведении активной иммунопрофилактики пневмококковой инфекции как здоровых детей, так и пациентов из групп риска по развитию тяжелых форм пневмококковых заболеваний. Публикация основана на ключевых позициях методических рекомендаций Министерства здравоохранения РФ по вакцинопрофилактике пневмококковой инфекции (разработанных и утвержденных профессиональной ассоциацией детских врачей «Союз педиатров России»).КОНФЛИКТ ИНТЕРЕСОВАвторы статьи подтвердили отсутствие конфликта интересов, о котором необходимо сообщить