Properties of silicon dioxide layers with embedded metal nanocrystals produced by oxidation of Si:Me mixture

A two-dimensional layers of metal (Me) nanocrystals embedded in SiO2 were produced by pulsed laser deposition of uniformly mixed Si:Me film followed by its furnace oxidation and rapid thermal annealing. The kinetics of the film oxidation and the structural properties of the prepared samples were investigated by Rutherford backscattering spectrometry, and transmission electron microscopy, respectively. The electrical properties of the selected SiO2:Me nanocomposite films were evaluated by measuring C-V and I-V characteristics on a metal-oxide-semiconductor stack. It is found that Me segregation induced by Si:Me mixture oxidation results in the formation of a high density of Me and silicide nanocrystals in thin film SiO2 matrix. Strong evidence of oxidation temperature as well as impurity type effect on the charge storage in crystalline Me-nanodot layer is demonstrated by the hysteresis behavior of the high-frequency C-V curves

Migraine and neck pain: Mechanisms of comorbidity

Neck pain and migraine are common diseases. Neck pain seldom occurs in a patient with migraine. However, the relationship between migraine and neck pain has been inadequately investigated.Objective: to analyze neck pain in patients with migraine to determine possible comorbidity mechanisms of these diseases.Patients and methods. The investigation enrolled 63 patients with chronic migraine (CM) and 40 with episodic migraine (EM) diagnosed in accordance with the International Classification of Headache Disorders, 3rd edition (ICHD-3). Winking reflex (WR) and nociceptive flexion reflex (NFR) were examined to evaluate the function of antinociceptive systems.Results. In the patients with CM, neck pain was more common than in those with EM (53.03% versus 14.02%); and panful tenderness, sensitivity, and tension of neck muscles were more marked. There was also a significant reduction in WR and NFR thresholds. Neck pain was noted to be an integral component of the pathogenesis of CM in a large number of patients with this condition. The authors proposed several pathophysiological mechanisms of a relationship between migraine and neck pain. Neck muscles and craniovertebral junction areas serve as a source for the arrival of nociceptive pain pulses in the central nervous system (peripheral sensitization), promoting pain chronization. Muscle dysfunction in this area may be, in turn, a reflection of central sensitization and impaired descending pain control

Identification of unknown compound extracted from the hair of exhumed human remains using mass spectrometric and gas chromatographic data

Подробно рассмотрен пример хромато-масс-спектрометричес­кой идентификации неизвестного компонента экстракта образца человеческих волос, изъятых у эксгумированных останков. Этот ком­по­нент (молекулярная масса 238 Да) не удалось идентифицировать ни в результате биб­лиотечного поиска по стандартному масс-спектру (ионизация электронами), ни по значению газохро­ма­то­­графического индекса удерживания (~1540) на стандартных неполярных поли­ди­ме­тил­силоксановых неподвижных фазах с 5% фенильных групп. Однако его иден­ти­фи­­кация оказалась возможной с использованием оригинального ал­го­ритма, осно­ванного на выявлении струк­ту­р­ных аналогов неизвестных аналитов, прежде всего – их гомологов, различаю­щих­ся по молекулярным массам на ± 14 Да, а по составу – на гомологическую раз­ность СН2. Этот прием позволил выявить такие ана­ло­ги неизвестного соединения как флавесон (2,2,4,4-тетраметил-2-изо­бу­тирил­цик­ло­гекса-1,3,5-трион), лептоспермон (2,2,4,4-тетраметил-2-изопентаноил­циклогекса-1,3,5-трион) и ряд других, относящихся к такому достаточно «экзотичес­ко­му» клас­су природных соединений как циклические b-трикетоны. На основании полученных данных установлена наиболее вероятная структура “неиз­ве­с­т­­ного” ком­понента – 2,2,4,4-тетраметил-2-пропионилциклогекса-1,3,5-трион. Отличительной особенностью циклических b-трикетонов является существование в ви­де нес­ко­льких таутомерных форм. В рассматриваемом случае это структура 5-гид­рокси-2,2,6,6-тетраметил-4-пропионилциклогекс-4-ен-1,3-диона (CAS № 87552-01-0). Об­суждаемое соединение является компонентов эфирного масла Leptosper­mum scopa­rium и некоторых других растений и входит в группу структурных аналогов флавесона. Наиболее изве­с­т­ное фар­ма­цевтическое применение эфирных масел, содержащих соединения этой груп­пы, – компоненты кондиционеров для волос и кожи головы. Таким образом, уста­нов­ле­но, что рассматриваемый компонент не относится к сильнодейст­ву­ю­щим или ток­си­чным соединениям, что исключает криминальное происхождение останков.The real example of GC-MS identification of unknown constituent of human hair extract belonging to the exhumed remains is considered. The identification of this constituent (molecular weight 238 Da) was unsuccessful using both its standard mass spectrum (electron ionization) in combination with lib­ra­ry search, and its GC retention index value (~1540 on semi-standard non-polar polydimethyl siloxane stationary phases with 5% phenyl groups). However, its identification appea­red to be possible using the original algorithm of data processing. This approach implies revealing the structural analogues of unknown analytes, primarily their homologues which differ by molecular masses on ± 14 Da and by composition on CH2 homolo­go­us difference. This approach allowed revealing such analogues of unknown analyte as Flavesone (2,2,4,4-tetramethyl-2-isobutyrylcyclohexa-1,3,5-trione), Leptospermone (2,2,4,4-tetramethyl-2-isopentanoylcyclohexa-1,3,5-trione), and some others. All these compounds belong to a rather “exotic” class of natural compounds knows as cyclic b-triketones. Based on the obtained data, the possible structure of the constitu­ent under the consideration was proposed as 2,2,4,4-tetramethyl-2-propionylcyclohexa-1,3,5-trione. The principal fea­ture of cyclic b-triketones is their existence in a few tautomeric forms. Another tautomer of triketone under discussion is 5-hydroxy-2,2,6,6-tetramethyl-4-propionyl-4-en-1,3-dio­ne (CAS № 87552-01-0). This compound is found to be the constituent of Leptosper­mum scoparium essential oil and some other plants, and it belongs to the group of structural analogues of Flave­sone. The most known pharmaceutical application of essential oils containing these compounds are the components of conditioners for hair and skin. The results confirm this formerly un­known component does not belong to the group of toxic substances. This excludes the criminal origin of the remains

Electron transfer in porphyrin multimolecular self-organized nanostructures

On the base of of covalent and non-covalent bonds nanoscale self-assembling multiporphyrin arrays with well-defined geometry, the controllable number of interacting components and their spectral and photophysical properties were formed. The deactivation of excited singlet and triplet states was studied using steady-state, time-resolved picosecond fluorescence (∆½≈30 ps) and femtosecond pump-probe (∆½≈280 fs) spectroscopy in solvents of various polarity at 77-300 K. It has been found that the competition between the non-radiative energy transfer (within ≤10 ps) and charge transfer (within 300 fs - 700 ps) processes in the systems depends on the structure, spectral and redox properties of interacting subunits and may be driven by the distance, temperature and solvent polarity. The possible pathways and mechanisms of the electron transfer in the systems of various types are discussed (Marcus theory for the “normal” region and the non-adiabatic case, the “superexchange” mechanism)