Optimal villi density for maximal oxygen uptake in the human placenta

We present a stream-tube model of oxygen exchange inside a human placenta functional unit (a placentone). The effect of villi density on oxygen transfer efficiency is assessed by numerically solving the diffusion-convection equation in a 2D+1D geometry for a wide range of villi densities. For each set of physiological parameters, we observe the existence of an optimal villi density providing a maximal oxygen uptake as a trade-off between the incoming oxygen flow and the absorbing villus surface. The predicted optimal villi density $0.47\pm0.06$ is compatible to previous experimental measurements. Several other ways to experimentally validate the model are also proposed. The proposed stream-tube model can serve as a basis for analyzing the efficiency of human placentas, detecting possible pathologies and diagnosing placental health risks for newborns by using routine histology sections collected after birth

Inverse medium problem for a singular contrast

We consider an inverse medium problem in two- and three-dimensional cases. Namely, we investigate the problem of reconstruction of unknown compactly supported refractive index (contrast) from L-2 with a fixed positive wave number. The proof is based on the new estimates for the Green-Faddeev function in L-infinity space. The main goal of this work is to prove a uniqueness result in the two- and three-dimensional cases and to discuss some possible constructive methods for solving the problem. Finally, we present some numerical examples to demonstrate the results in two dimensions. Published under license by AIP Publishing.Peer reviewe

Peter the Great’s Second Voyage to Europe in the Letters of Baron P. P. Shafirov to Prince A. D. Menshikov (1716–1717)

The article was submitted on 16.03.2017.Предлагаемая корреспонденция барона П. П. Шафирова светлейшему князю А. Д. Меншикову относится к осени 1716 – лету 1717 г. и освещает подробности пребывания Петра I в Копенгагене, различных германских городах и в Нидерландах во время второго европейского путешествия. Будучи одним из руководителей российского внешнеполитического ведомства и входя в круг ближайших соратников царя, П. П. Шафиров оказался в центре многих политических и домашних событий, произошедших в этой поездке. Как большинство лиц, окружавших государя, барон неофициально извещал А. Д. Меншикова, остававшегося во время отъезда монарха во главе государственного управления, обо всех заслуживающих внимания делах. Публикуемые впервые, письма П. П. Шафирова дошли до наших дней в виде копий, сделанных в канцелярии князя в феврале 1723 г., и ныне хранятся в фонде 198 (А. Д. Меншиков) РГАДА. Информация, отразившаяся в письмах, имеет многоплановый характер. Ее основу составляют донесения важного политического и военного значения: будучи достаточно известными, исторические сюжеты дополняются благодаря донесениям П. П. Шафирова многими интересными деталями. Второй пласт информации связан с известиями о перемещении Петра I и его жены царицы Екатерины Алексеевны по Европе. Особенный интерес представляют уникальные известия барона о тяжелом заболевании царя в Амстердаме зимой 1716–1717 гг. Третий, косвенный пласт информации позволяет реконструировать характер взаимоотношений между П. П. Шафировым и А. Д. Меншиковым и их семьями, уточняет датировки и маршрут царского поезда, дает богатый материал по истории климата в странах пребывания в описываемый период и о деталях состояния транспортных коммуникаций, способах передвижения, почтовой и курьерской службе, скорости доставки правительственной корреспонденции. Все это делает письма П. П. Шафирова ценным историческим источником, чье значение полностью раскрывается при их контекстном источниковедческом анализе в корпусе аналогичной документации, связанной со вторым европейским турне Петра Великого и в целом с событиями Великой Северной войны.This article examines correspondence between Baron P. P. Shafirov and Prince A. D. Menshikov from the spring of 1716 to the summer of 1717. These letters reveal the details of Peter I’s stay in Copenhagen, different German cities, and the Netherlands during his second European voyage. As one of the leaders of the Russian foreign ministry and a close companion of the tsar, Shafirov was at the centre of many of the political and domestic events that occurred during this tour. Like the majority of those surrounding the tsar, the baron unofficially informed A. D. Menshikov of all business requiring attention, since Menshikov was in charge of managing the Russian state during Peter’s absence. Published here for the first time, Shafirov’s letters come down to us in the form of copies made in Menshikov’s chancellery in February 1723: these are kept in fond 198 (A. D. Menshikov) of RGADA (Russian State Archive of Ancient Acts). The information in these letters is multisided. Firstly, one finds important military and political reports. While these historical narratives are rather well-known, Shafirov provides additional interesting details. Secondly, these letters are of interest because they provide news about the movement of Peter I and his wife, Tsarina Yekaterina Alekseevna, around Europe. Of particular note are the baron’s reports about the tsar’s serious illness in Amsterdam during the winter of 1716-17. The epistles also clarify the dates and routes that the tsar took, allow us to look at the climate in the countries where he stayed, and provide details about transport and communication links. Thirdly, and rather indirectly, the correspondence helps us to reconstruct the nature of the relationship between Shafirov and Menshikov and their families. All of these reasons make Shafirov’s letters a valuable historical source. Their significance is fully revealed when analysed alongside analogous documentation connected with Peter the Great’s second tour of Europe and the Great Northern War in general.Исследование подготовлено в рамках реализации гранта Правительства РФ по привлечению ведущих ученых в российские образовательные учреждения высшего профессионального образования и научные учреждения государственных академий наук и государственные научные центры Российской Федерации (лаборатория эдиционной археографии, Уральский федеральный университет). Договор № 14.А12.31.0004 от 26.06.2013 г

Wave packet evolution approach to ionization of hydrogen molecular ion by fast electrons

The multiply differential cross section of the ionization of hydrogen molecular ion by fast electron impact is calculated by a direct approach, which involves the reduction of the initial 6D Schr\"{o}dinger equation to a 3D evolution problem followed by the modeling of the wave packet dynamics. This approach avoids the use of stationary Coulomb two-centre functions of the continuous spectrum of the ejected electron which demands cumbersome calculations. The results obtained, after verification of the procedure in the case atomic hydrogen, reveal interesting mechanisms in the case of small scattering angles.Comment: 7 pages, 8 Postscript figure

“In the Evening the Mayor Arrived from the Russian Camp”: The First 34 Years of the Life of Wilhelm Henning

The article was submitted on 12.12.2018.Статья являет собой первый опыт специального обозрения событий начального этапа биографии Вилима Геннина, признанного организатора металлургической промышленности России XVIII в., основателя Екатеринбурга. Рассмотрены вопросы о месте и времени рождения В. Геннина, о его родственном круге. Подтверждено мнение об идентичности В. Геннина с Георгом Вильгельмом Генниным (Georg Wilhelm Henning), рожденным в октябре 1676 г. в г. Зигене. На основе анализа выявленных сведений о юности В. Геннина мотивировано предположение об отсутствии у него не только высшего, но и законченного среднего образования. На основании архивных документов, впервые введенных в научный оборот, уточнены обстоятельства вступления Вилима Геннина в российскую службу, опровергнута устоявшаяся точка зрения о его личном знакомстве с Петром I в 1698 г. Высказано мнение, что мотивом перехода В. Геннина на службу русскому царю явилось очевидное отсутствие у него карьерных перспектив в Западной Европе. Выявлен факт искажения Вилимом Генниным в личной записке 1743 г. событий начала службы в России. Документально установлено, что на протяжении первых трех лет пребывания в Москве В. Геннин являлся мастером Оружейной палаты. Обоснованы предположения о том, что, перейдя в ведомство Приказа артиллерии, Вилим Геннин не участвовал ни в одной из кампаний Великой Северной войны 1702–1709 гг., а также о покровительстве ему со стороны братьев генералов Я. В. и Р. В. Брюсов. Показано, что непосредственное участие в боевых действиях В. Геннин принял лишь в 1710 г., отличившись в качестве артиллерийского офицера в ходе осад Выборга и Кексгольма. Мотивировано предположение о том, что перелом в карьере В. Геннина в России произошел в 1710 г. Этот перелом был связан с его первой личной встречей с Петром I, которая состоялась в связи с командированием В. Геннина к царю с сообщением о взятии Кексгольма. Сумев произвести на главу государства благоприятное впечатление, Вилим Геннин обеспечил себе дальнейший карьерный рост (первоначально в Санкт-Петербурге) в качестве военного инженера и организатора литейного производства.This article is the first attempt to make a special review of the events in the early life of Wilhelm Henning, a founding father of the metallurgical industry of 18th-century Russia and of Yekaterinburg. The article concerns some issues connected with Henning’s place and time of birth and his family. The author substantiates the fact that the person known as Vilim de Gennin was originally known as Georg Wilhelm Henning, born in October 1676 in Siegen. Referring to archival sources which have not been previously studied, the author clarifies the circumstances underlying the entry of Wilhelm Henning into Russian service, refuting the long-established opinion about his personal acquaintance with Peter I in 1698. He argues that the motive behind Henning’s transition to the service of the Russian tsar was obviously a lack of career prospects in Western Europe. Additionally, the article demonstrates that Wilhelm Henning distorted the events of his early life in Russia in his personal note (1743). It is documented that during the first three years of his stay in Moscow, Henning worked as a master in the State Armoury; this helps prove the assumption that, by transferring to the Artillery Prikaz, Henning did not participate in campaigns of the Great Northern War during 1702–1709 and received the patronage of the Bruce brothers, Jacob and Robert. It is shown that Henning took part in military actions only in 1710, having distinguished himself as an artillery officer during the sieges of Vyborg and Kexholm. The author thus argues that the turning point of Henning’s career in Russia was 1710. This was when he had his first personal meeting with Peter I, when Henning was sent to the tsar to notify him of the siege of Kexholm. Having managed to produce a favourable impression on the tsar, Henning secured further career growth (at first in St Petersburg) as a military engineer and organiser of the metallurgical industry

Gas chromatography of indium in macroscopic and carrier-free amounts using quartz and gold as stationary phases

The chemical investigation of E113 is likely to become soon feasible. The determination of chemical properties of carrier-free amounts of the lighter homologues of element 113, especially indium and thallium, allows designing experimental set-ups and selecting experimental conditions suitable for performing these studies. Here, we present investigations of the interaction of indium species with quartz and gold surfaces. Deposition temperatures as well as enthalpies of adsorption were determined for indium Tdep=739±20°C (−ΔHads(In)=227±10kJ mol−1) and for indium hydroxide Tdep=250±20°C (−ΔHads(InOH)= 124±10kJ mol−1) respectively, on quartz. In case of adsorption of indium on a gold surface only a lower limit of the deposition temperature was established Tdep>980°C (−ΔHads(In)≥315±10kJ mol−1). Investigations of macroscopic amounts of indium in thermosublimation experiments at similar experimental conditions were instrumental to establish a tentative speciation of the observed indium specie

The thermal release of scandium from titanium metal - a simple way to produce pure 44Sc for PET application

The radionuclide-generator based access to radiopharmaceutical isotopes represents a valuable alternative to directly produced isotopes at particle accelerators or nuclear reactors. The 44Ti based generator is of increasing interest for the delivery of PET-radiopharmaceutical isotopes used for imaging. The product of this generator 44Sc represents with its 3.97h half-life and 94.3% positron branching[1] a very promising candidate for labeling PET radiopharmaceuticals. The long half-life of 58.9±0.3y[2] of the 44Ti assures a constant and long lasting production of the daughter nuclide. Here we present a gas phase separation method of scandium from titanium via thermal release in vacuum. Titanium foils were irradiated with 40Ar to produce scandium in multi-nucleon transfer reactions. Another production reaction used was the irradiation of titanium by neutrons from the SINQ neutron source at the Paul Scherrer Institute (PSI). The titanium metal foils containing 44mSc and 46Sc were heated up for time periods of 15 and 60min to temperatures between 900°C and 1500°C in vacuum. Thus, release properties of scandium from titanium under these conditions were studied. The released scandium was collected on tantalum foils and could be rinsed of with concentrated nitric acid resulting in carrier free scandium nitrate solutions. From the experimental results optimum release conditions are suggeste

Adsorption interaction of carrier-free thallium species with gold and quartz surfaces

The adsorption interactions of thallium and its compounds with gold and quartz surfaces were investigated. Carrier-free amounts of thallium were produced in nuclear fusion reactions of alpha particles with thick gold targets. The method chosen for the studies was gas thermochromatography and varying the redox potential of the carrier gases. It was observed that thallium is extremely sensitive to trace amounts of oxygen and water, and can even be oxidized by the hydroxyl groups located on the quartz surface. The experiments on aquartz surface with O2, He, H2 gas in addition with water revealed the formation and deposition of only one thallium species - TlOH. The adsorption enthalpy was determined to be Δ HSiO2ads(TlOH) = −134±5kJ mol−1. Aseries of experiments using gold as stationary surface and different carrier gases resulted in the detection of two thallium species - metallic Tl (H2 as carrier gas) and TlOH (O2, O2+H2O and H2+H2O as pure carrier gas or carrier gas mixture) with Δ HAuads(Tl) = −270±10kJ mol− and Δ HAuads(TlOH) = −146±3kJ mol−1. These data demonstrate a weak interaction of TlOH with both quartz and gold surfaces. The data represent important information for the design of future experiments with the heavier homologue of Tl in group 13 of the periodic table - element 113 (E113