NobleBlocks
Belarusian State University logo

Belarusian State University

UniversityMinsk, Belarus

Research output, citation impact, and the most-cited recent papers from Belarusian State University (Belarus). Aggregated across the NobleBlocks index of 300M+ scholarly works.

Total works
19.6K
Citations
473.9K
h-index
213
i10-index
9.2K
Also known as
Belarusian State UniversityБеларускі дзяржаўны ўніверсітэтБелорусский государственный университет

Top-cited papers from Belarusian State University

The CMS experiment at the CERN LHC
S. Chatrchyan, G. Hmayakyan, V. Khachatryan, A. M. Sirunyan +4 more
2008· Journal of Instrumentation5.4Kdoi:10.1088/1748-0221/3/08/s08004

The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 1034 cm−2 s−1 (1027 cm−2 s−1). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (|η| ≤ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

FCC-ee: The Lepton Collider
Asmâa Abada, M. Abbrescia, Shehu AbdusSalam, I. M. Abdyukhanov +4 more
2019· The European Physical Journal Special Topics904doi:10.1140/epjst/e2019-900045-4

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today's technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.

Stress-induced electrolyte leakage: the role of K+-permeable channels and involvement in programmed cell death and metabolic adjustment
Vadim Demidchik, Darya Straltsova, Sergey S. Medvedev, Grigoriy A. Pozhvanov +2 more
2014· Journal of Experimental Botany772doi:10.1093/jxb/eru004

Electrolyte leakage accompanies plant response to stresses, such as salinity, pathogen attack, drought, heavy metals, hyperthermia, and hypothermia; however, the mechanism and physiological role of this phenomenon have only recently been clarified. Accumulating evidence shows that electrolyte leakage is mainly related to K(+) efflux from plant cells, which is mediated by plasma membrane cation conductances. Recent studies have demonstrated that these conductances include components with different kinetics of activation and cation selectivity. Most probably they are encoded by GORK, SKOR, and annexin genes. Hypothetically, cyclic nucleotide-gated channels and ionotropic glutamate receptors can also be involved. The stress-induced electrolyte leakage is usually accompanied by accumulation of reactive oxygen species (ROS) and often results in programmed cell death (PCD). Recent data strongly suggest that these reactions are linked to each other. ROS have been shown to activate GORK, SKOR, and annexins. ROS-activated K(+) efflux through GORK channels results in dramatic K(+) loss from plant cells, which stimulates proteases and endonucleases, and promotes PCD. This mechanism is likely to trigger plant PCD under severe stress. However, in moderate stress conditions, K(+) efflux could play an essential role as a 'metabolic switch' in anabolic reactions, stimulating catabolic processes and saving 'metabolic' energy for adaptation and repair needs.

Performance of the ATLAS trigger system in 2015
M. Aaboud, G. Aad, B. Abbott, J. Abdallah +4 more
2017· The European Physical Journal C737doi:10.1140/epjc/s10052-017-4852-3

During 2015 the ATLAS experiment recorded [Formula: see text] of proton-proton collision data at a centre-of-mass energy of [Formula: see text]. The ATLAS trigger system is a crucial component of the experiment, responsible for selecting events of interest at a recording rate of approximately 1 kHz from up to 40 MHz of collisions. This paper presents a short overview of the changes to the trigger and data acquisition systems during the first long shutdown of the LHC and shows the performance of the trigger system and its components based on the 2015 proton-proton collision data.

FCC Physics Opportunities
A. Abada, M. Abbrescia, Shehu AbdusSalam, I. M. Abdyukhanov +4 more
2019· The European Physical Journal C664doi:10.1140/epjc/s10052-019-6904-3

Abstract: We review the physics opportunities of the Future Circular Collider, covering its e+e-, pp, ep and heavy ion programmes. We describe the measurement capabilities of each FCC component, addressing the study of electroweak, Higgs and strong interactions, the top quark and flavour, as well as phenomena beyond the Standard Model. We highlight the synergy and complementarity of the different colliders, which will contribute to a uniquely coherent and ambitious research programme, providing an unmatchable combination of precision and sensitivity to new physics.

FCC-hh: The Hadron Collider
A. Abada, M. Abbrescia, Shehu AbdusSalam, I. M. Abdyukhanov +4 more
2019· The European Physical Journal Special Topics632doi:10.1140/epjst/e2019-900087-0

Abstract: In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.

Experimental Vapor Pressures of 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imides and a Correlation Scheme for Estimation of Vaporization Enthalpies of Ionic Liquids
Dzmitry H. Zaitsau, Gennady J. Kabo, Aliaksei A. Strechan, Yauheni U. Paulechka +3 more
2006· The Journal of Physical Chemistry A561doi:10.1021/jp060896f

Vapor pressures for a series of 1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (alkyl = ethyl, butyl, hexyl, and octyl) ionic liquids (ILs) were measured by the integral effusion Knudsen method. Thermodynamic parameters of vaporization for ILs were calculated from these data. The absence of decomposition of ILs during the vaporization process was proved by IR spectroscopy. Enthalpies of vaporization of ILs were correlated with molar volumes and surface tensions of the compounds.

Generalized mittag-leffler function and generalized fractional calculus operators
Anatoly A. Kilbas, Megumi Saigo, R. K. Saxena
2003· Integral Transforms and Special Functions553doi:10.1080/10652460310001600717

The paper is devoted to the study of the function E γ ρ,μ(z) defined for complex ρ, μ, γ (Re(ρ) > 0) by which is a generalization of the classical Mittag-Leffler function E ρ,μ(z) and the Kummer confluent hypergeometric function Φ(γ, μ; z). The properties of E γ ρ,μ(z) including usual differentiation and integration, and fractional ones are proved. Further the integral operator with such a function kernel is studied in the space L(a, b). Compositions of the Riemann–Liouville fractional integration and differentiation operators with E γ ρ,μ,ω;a+ are established. An analogy of the semigroup property for the composition of two such operators with different indices is proved, and the results obtained are applied to construct the left inversion operator to the operator E γ ρ,μ,ω;a+. Since, for γ = 0, E 0 ρ,μ,ω;a+ coincides with the Riemann–Liouville fractional integral of order μ, the above operator and its inversion can be considered as generalized fractional calculus operators involving the generalized Mittag-Leffler function E γ ρ,μ(z) in the kernels. Similar assertions are presented for the integral operators containing the Mittag-Leffler and Kummer functions, E ρ,μ(z) and Φ(γ, μ; z), in the kernels, and applications are given to obtain solutions in closed form of the integral equations of the first kind.

The Chemistry of Cyclopropanols
Oleg G. Kulinkovich
2003· Chemical Reviews518doi:10.1021/cr010012i

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Chemistry of CyclopropanolsOleg G. KulinkovichView Author Information Chemical Department, Belarussian State University, Skaryny Av. 4, 220050 Minsk, Belarus Cite this: Chem. Rev. 2003, 103, 7, 2597–2632Publication Date (Web):June 10, 2003Publication History Received14 October 2002Published online10 June 2003Published inissue 1 July 2003https://pubs.acs.org/doi/10.1021/cr010012ihttps://doi.org/10.1021/cr010012iresearch-articleACS PublicationsCopyright © 2003 American Chemical SocietyRequest reuse permissionsArticle Views8603Altmetric-Citations452LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Anions,Hydrocarbons,Ketones,Organic compounds,Reaction products Get e-Alerts

Multiplicity and transverse momentum dependence of two- and four-particle correlations in pPb and PbPb collisions
S. Chatrchyan, V. Khachatryan, A. M. Sirunyan, A. Tumasyan +4 more
2013· Physics Letters B487doi:10.1016/j.physletb.2013.06.028

Measurements of two-and four-particle angular correlations for charged particles emitted in pPb collisions are presented over a wide range in pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 31 nb -1 , were collected during the 2013 LHC pPb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. The results are compared to 2.76 TeV semi-peripheral PbPb collision data, collected during the 2011 PbPb run, covering a similar range of particle multiplicities. The observed correlations are characterized by the near-side (| | 0) associated pair yields and the azimuthal anisotropy Fourier harmonics (v n ). The second-order (v 2 ) and third-order (v 3 ) anisotropy harmonics are extracted using the two-particle azimuthal correlation technique. A four-particle correlation method is also applied to obtain the value of v 2 and further explore the multi-particle nature of the correlations. Both associated pair yields and anisotropy harmonics are studied as a function of particle multiplicity and transverse momentum. The associated pair yields, the four-particle v 2 , and the v 3 become apparent at about the same multiplicity. A remarkable similarity in the v 3 signal as a function of multiplicity is observed between the pPb and PbPb systems. Predictions based on the color glass condensate and hydrodynamic models are compared to the experimental results.

<i>Arabidopsis</i> root K+-efflux conductance activated by hydroxyl radicals: single-channel properties, genetic basis and involvement in stress-induced cell death
Vadim Demidchik, Tracey Ann Cuin, Dimitri A. Svistunenko, Susan J. Smith +4 more
2010· Journal of Cell Science479doi:10.1242/jcs.064352

Reactive oxygen species (ROS) are central to plant stress response, signalling, development and a multitude of other processes. In this study, the plasma-membrane hydroxyl radical (HR)-activated K(+) channel responsible for K(+) efflux from root cells during stress accompanied by ROS generation is characterised. The channel showed 16-pS unitary conductance and was sensitive to Ca(2+), tetraethylammonium, Ba(2+), Cs(+) and free-radical scavengers. The channel was not found in the gork1-1 mutant, which lacks a major plasma-membrane outwardly rectifying K(+) channel. In intact Arabidopsis roots, both HRs and stress induced a dramatic K(+) efflux that was much smaller in gork1-1 plants. Tests with electron paramagnetic resonance spectroscopy showed that NaCl can stimulate HR generation in roots and this might lead to K(+)-channel activation. In animals, activation of K(+)-efflux channels by HRs can trigger programmed cell death (PCD). PCD symptoms in Arabidopsis roots developed much more slowly in gork1-1 and wild-type plants treated with K(+)-channel blockers or HR scavengers. Therefore, similar to animal counterparts, plant HR-activated K(+) channels are also involved in PCD. Overall, this study provides new insight into the regulation of plant cation transport by ROS and demonstrates possible physiological properties of plant HR-activated K(+) channels.

Combined measurements of Higgs boson production and decay using up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>80</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi>fb</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math> of proton-proton collision data at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>13</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:math> collected with the ATLAS experiment
G. Aad, B. Abbott, D. C. Abbott, O. Abdinov +4 more
2020· Physical review. D/Physical review. D.476doi:10.1103/physrevd.101.012002

Combined measurements of Higgs boson production and decay using up to 80

Calcium transport across plant membranes: mechanisms and functions
Vadim Demidchik, Sergey Shabala, Stanislav V. Isayenkov, Tracey Ann Cuin +1 more
2018· New Phytologist450doi:10.1111/nph.15266

Contents Summary 49 I. Introduction 49 II. Physiological and structural characteristics of plant Ca 2+ ‐permeable ion channels 50 III. Ca 2+ extrusion systems 61 IV. Concluding remarks 64 Acknowledgements 64 References 64 Summary Calcium is an essential structural, metabolic and signalling element. The physiological functions of Ca 2+ are enabled by its orchestrated transport across cell membranes, mediated by Ca 2+ ‐permeable ion channels, Ca 2+ ‐ ATP ases and Ca 2+ /H + exchangers. Bioinformatics analysis has not determined any Ca 2+ ‐selective filters in plant ion channels, but electrophysiological tests do reveal Ca 2+ conductances in plant membranes. The biophysical characteristics of plant Ca 2+ conductances have been studied in detail and were recently complemented by molecular genetic approaches. Plant Ca 2+ conductances are mediated by several families of ion channels, including cyclic nucleotide‐gated channels ( CNGC s), ionotropic glutamate receptors, two‐pore channel 1 ( TPC 1), annexins and several types of mechanosensitive channels. Key Ca 2+ ‐mediated reactions (e.g. sensing of temperature, gravity, touch and hormones, and cell elongation and guard cell closure) have now been associated with the activities of specific subunits from these families. Structural studies have demonstrated a unique selectivity filter in TPC 1, which is passable for hydrated divalent cations. The hypothesis of a ROS ‐Ca 2+ hub is discussed, linking Ca 2+ transport to ROS generation. CNGC inactivation by cytosolic Ca 2+ , leading to the termination of Ca 2+ signals, is now mechanistically explained. The structure–function relationships of Ca 2+ ‐ ATP ases and Ca 2+ /H + exchangers, and their regulation and physiological roles are analysed.

Synthesis and characterization of thiol‐stabilized CdTe nanocrystals
Andrey L. Rogach, Lynne Katsikas, Andreas Kornowski, Dangsheng Su +2 more
1996· Berichte der Bunsengesellschaft für physikalische Chemie427doi:10.1002/bbpc.19961001104

Abstract In order to expand the range of high‐quality nanosized semiconductor materials that can be obtained as quantum dots through a wet chemical route a series of oxidize‐stable CdTe nanoclusters with narrow size distributions and extremely small particle sizes ranging from 1.3 to 2.4 nm has been prepared in aqueous solution using 2‐mercaptoethanol and 1‐thioglycerol as stabilizers. It has been investigated by means of UV‐vis absorption and photoluminescence spectroscopy, X‐ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive x‐ray analysis (EDX).

1,<i>n</i>-Dicarbanionic Titanium Intermediates from Monocarbanionic Organometallics and Their Application in Organic Synthesis
Oleg G. Kulinkovich, Armin de Meijere
2000· Chemical Reviews425doi:10.1021/cr980046z

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT1,n-Dicarbanionic Titanium Intermediates from Monocarbanionic Organometallics and Their Application in Organic SynthesisOleg G. Kulinkovich and Armin de MeijereView Author Information Chemical Department of Belarussian State University, Skaryny Av. 4, 220050 Minsk, Belarus, and Institut für Organische Chemie der Georg-August-Universität Göttingen, Tammannstrasse 2, D-37077 Göttingen, Germany Cite this: Chem. Rev. 2000, 100, 8, 2789–2834Publication Date (Web):July 21, 2000Publication History Received21 March 2000Published online21 July 2000Published inissue 1 August 2000https://doi.org/10.1021/cr980046zCopyright © 2000 American Chemical SocietyRequest reuse permissionsArticle Views6237Altmetric-Citations367LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (2 MB) Get e-AlertscloseSUBJECTS:Hydrocarbons,Organic compounds,Reaction products,Reagents,Titanium Get e-Alerts

Electrodynamics of carbon nanotubes: Dynamic conductivity, impedance boundary conditions, and surface wave propagation
G. Ya. Slepyan, С. А. Максименко, Akhlesh Lakhtakia, Oleg M. Yevtushenko +1 more
1999· Physical review. B, Condensed matter425doi:10.1103/physrevb.60.17136

Effective boundary conditions, in the form of two-sided impedance boundary conditions, are formulated for the linear electrodynamics of single- and multishell carbon nanotubes (CN's). The impedance is derived using the dynamic conductivity of CN's, which is obtained for different CN's (zigzag, armchair, and chiral) in the frame of the semiclassical as well as quantum-mechanical treatments. Propagation of surface waves in CN's is considered. The phase velocities and the slow-wave coefficients of surface waves are explored for a wide frequency range, from the microwave to the ultraviolet regimes. Relaxation is shown to qualitatively change the dispersion characteristics in the low-frequency limit, thereby rendering the existence of weakly retarded plasmons impossible. A dispersionless propagation regime is shown possible for the surface waves in the infrared regime. Attenuation and retardation in metallic and semiconductor CN's are compared.

Study of the material of the ATLAS inner detector for Run 2 of the LHC
M. Aaboud, G. Aad, B. Abbott, J. Abdallah +4 more
2017· Journal of Instrumentation409doi:10.1088/1748-0221/12/12/p12009

The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable $B$-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity $\sqrt{s}=13$ TeV $pp$ collision sample corresponding to around $2.0\,\mathrm{nb}^{-1}$ collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation.

Extraction and validation of a new set of CMS pythia8 tunes from underlying-event measurements
A. M. Sirunyan, A. Tumasyan, W. Adam, F. Ambrogi +4 more
2020· The European Physical Journal C409doi:10.1140/epjc/s10052-019-7499-4

New sets of CMS underlying-event parameters ("tunes") are presented for the pythia8 event generator. These tunes use the NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Measurements of charged-particle multiplicity and transverse momentum densities at various hadron collision energies are fit simultaneously to determine the parameters of the tunes. Comparisons of the predictions of the new tunes are provided for observables sensitive to the event shapes at LEP, global underlying event, soft multiparton interactions, and double-parton scattering contributions. In addition, comparisons are made for observables measured in various specific processes, such as multijet, Drell-Yan, and top quark-antiquark pair production including jet substructure observables. The simulation of the underlying event provided by the new tunes is interfaced to a higher-order matrix-element calculation. For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.

“Raisin Bun”-Type Composite Spheres of Silica and Semiconductor Nanocrystals
Andrey L. Rogach, Dattatri Nagesha, John W. Ostrander, Michael Giersig +1 more
2000· Chemistry of Materials395doi:10.1021/cm000244i

CdTe nanocrystals capped with 1-mercapto-2,3-propandiol, CdSe nanocrystals capped with sodium citrate, and core−shell CdSe/CdS nanocrystals capped with sodium citrate were synthesized in aqueous solutions, and their surface was modified by 3-mercaptopropyltrimethoxysilane (MPS) in water−ethanol mixtures. By addition of sodium silicate, “raisin bun”-type composite particles were formed, with either CdTe, CdSe, or CdSe/CdS nanocrystals being homogeneously incorporated as multiple cores into silica spheres of 40−80 nm size, accompanied by some alteration of optical properties of the nanoparticles and, in particular, the reduction of the luminescence quantum yield. Further, growth of larger silica spheres (100−700 nm) can be performed by the Stöber technique using either MPS-modified semiconductor nanocrystals or “raisin bun”-type composite particles as seeds, which gives semiconductor-doped silica globules of desirable sizes in the submicrometer range. The composite spheres can be used as building blocks for 3D colloidal crystals, prepared in this study for CdS/CdSe-doped 250 nm silica colloid. The shift of the photonic band gap to the red was observed in photonic crystals made of nanoparticles-doped silica due to the high refractive index of the semiconductors.

Thermal decomposition of aliphatic nylons
Sergei V. Levchik, Edward D. Weil, Menachem Lewin
1999· Polymer International391doi:10.1002/(sici)1097-0126(199907)48:7<532::aid-pi214>3.0.co;2-r

An overview of the literature together with selected authors' data on thermal and thermo-oxidative decomposition of commercial aliphatic nylons (nylon 6, nylon 7, nylon 11, nylon 12, nylon 6.6, nylon 6.10, nylon 6.12) is presented. Despite the high level of research activity and the large number of publications in the field, there is no generally accepted mechanism for the thermal decomposition of aliphatic nylons. Polylactams (nylon 6, nylon 11 and nylon 12) tend to re-equilibrate to monomeric or oligomeric cyclic products. Diacid–diamine type nylons (nylon 6.6, nylon 6.10 and nylon 6.12) produce mostly linear or cyclic oligomeric fragments and monomeric units. Because of the tendency of adipic acid to fragment with elimination of CO and H2O and to undergo cyclization, significant amounts of secondary products from nylon 6.6 are reported in some papers. Many authors have shown that the primary polyamide chain scission occurs either at the peptide C(O)NH or at adjacent bonds, most probably at the alkyl–amide NHCH2 bond which is relatively the weakest in the aliphatic chain. Hydrolysis, homolytic scission, intramolecular CH transfer and cis-elimination (a particular case of CH transfer) are all suggested as possible primary chain-scission mechanisms. There are no convincing results reported which tend to generally support one of these mechanisms relative to the others; rather, it seems that the contribution of each mechanism depends on experimental conditions. This conclusion is also supported by the wide spread of kinetic parameters measured under the different experimental conditions. More uniform results are observed in the literature regarding the mechanism of thermo-oxidative decomposition of aliphatic nylons. Most authors agree that oxygen first attacks the N-vicinal methylene group, which is followed by the scission of alkyl–amide NC or vicinal CC bond. Alternatively, it is suggested that any methylene group which is β-positioned to the amide group methylene can be initially oxidized. There are few mechanisms in the literature which explain discoloration (yellowing) of nylons. UV/visible active chromophores are attributed either to pyrrole type structures, to conjugated acylamides or to conjugated azomethines. Some secondary reactions occurring during the thermal or thermo-oxidative decomposition lead to crosslinking of nylons. Nylon 6.6 crosslinks relatively easily, especially in the presence of air, whereas nylon 11 and nylon 12 crosslink very little. Strong mineral acids, strong bases, and some oxides or salts of transition metals catalyse the thermal decomposition of nylons, but minimize crosslinking. In contrast, many fire retardant additives promote secondary reactions, crosslinking and charring of aliphatic nylons. © 1999 Society of Chemical Industry