Oxygen and nitrogen concentrations in the Ti-6Al-4V alloy manufactured by direct metal laser sintering (DMLS) process

Published ArticleTwo machines from two scientific centers (Russia and South Africa) were used for the manufacturing of the Ti6Al4V alloys by the direct metal laser sintering. The chemical composition of powders complies with the ASTM F-136 (grade 5), ASTM B348 (grade 23) standard for medical applications. Analysis of the oxygen and nitrogen contamination in DMLS alloys was done with Van de Graaff accelerator with two Mega Volts. It is found that structures of the samples manufactured with two different machines used the same regimes are close to each other. TEM studies found the metastable martensitic structure and silicon nitride Si3N4. It was found that the oxygen and nitrogen contents in both samples are within the normal range for medical grade titanium alloys

Environmental literacy – as a way of dealing with greenwashing

Статья посвящена проблеме повышения экологической грамотности поселения России. Представлена информация о наиболее авторитетных экологических знаках, описана возможность оценить экологическую маркировку продукции с помощью мобильного приложения «Ecolabel Guide».The article is devoted to the problem of increasing ecological literacy of the Russian settlement. Presents information on the most reputable environmental marks, described the ability to assess the environmental labeling of products using a mobile app «Ecolabel Guide»

Indicators of Pasture Digression in Steppe Ecosystems of Mongolia

The research shows that widely used key measures of vegetation structure (species diversity, projected cover and above-ground phytomass) are not always suitable as indicators of pasture degradation. Based on an analysis above-ground phytomass composition, new quantitative indices are offered that give a more realistic picture of rangeland condition in Mongolia

New insights into electron spin dynamics in the presence of correlated noise

The changes of the spin depolarization length in zinc-blende semiconductors when an external component of correlated noise is added to a static driving electric field are analyzed for different values of field strength, noise amplitude and correlation time. Electron dynamics is simulated by a Monte Carlo procedure which keeps into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin depolarization is studied by examinating the decay of the initial spin polarization of the conduction electrons through the D'yakonov-Perel process, the only relevant relaxation mechanism in III-V crystals. Our results show that, for electric field amplitude lower than the Gunn field, the dephasing length shortens with the increasing of the noise intensity. Moreover, a nonmonotonic behavior of spin depolarization length with the noise correlation time is found, characterized by a maximum variation for values of noise correlation time comparable with the dephasing time. Instead, in high field conditions, we find that, critically depending on the noise correlation time, external fluctuations can positively affect the relaxation length. The influence of the inclusion of the electron-electron scattering mechanism is also shown and discussed.Comment: Published on "Journal of Physics: Condensed Matter" as "Fast Track Communications", 11 pages, 9 figure

Two-magnon bound state causes ultrafast thermally induced magnetisation switching.

There has been much interest recently in the discovery of thermally induced magnetisation switching using femtosecond laser excitation, where a ferrimagnetic system can be switched deterministically without an applied magnetic field. Experimental results suggest that the reversal occurs due to intrinsic material properties, but so far the microscopic mechanism responsible for reversal has not been identified. Using computational and analytic methods we show that the switching is caused by the excitation of two-magnon bound states, the properties of which are dependent on material factors. This discovery allows us to accurately predict the onset of switching and the identification of this mechanism will allow new classes of materials to be identified or designed for memory devices in the THz regime

Precision of the PET activity range during irradiation with ¹⁰C, ¹¹C, and ¹²C beams

Objective. Beams of stable ions have been a well-established tool for radiotherapy for many decades. In the case of ion beam therapy with stable 12C ions, the positron emitters 10,11C are produced via projectile and target fragmentation, and their decays enable visualization of the beam via positron emission tomography (PET). However, the PET activity peak matches the Bragg peak only roughly and PET counting statistics is low. These issues can be mitigated by using a short-lived positron emitter as a therapeutic beam. Approach. An experiment studying the precision of the measurement of ranges of positron-emitting carbon isotopes by means of PET has been performed at the FRS fragment-separator facility of GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany. The PET scanner used in the experiment is a dual-panel version of a Siemens Biograph mCT PET scanner. Main results. High-quality in-beam PET images and activity distributions have been measured from the in-flight produced positron emitting isotopes 11C and 10C implanted into homogeneous PMMA phantoms. Taking advantage of the high statistics obtained in this experiment, we investigated the time evolution of the uncertainty of the range determined by means of PET during the course of irradiation, and show that the uncertainty improves with the inverse square root of the number of PET counts. The uncertainty is thus fully determined by the PET counting statistics. During the delivery of 1.6 × 107 ions in 4 spills for a total duration of 19.2 s, the PET activity range uncertainty for 10C, 11C and 12C is 0.04 mm, 0.7 mm and 1.3 mm, respectively. The gain in precision related to the PET counting statistics is thus much larger when going from 11C to 10C than when going from 12C to 11C. The much better precision for 10C is due to its much shorter half-life, which, contrary to the case of 11C, also enables to include the in-spill data in the image formation. Significance. Our results can be used to estimate the contribution from PET counting statistics to the precision of range determination in a particular carbon therapy situation, taking into account the irradiation scenario, the required dose and the PET scanner characteristics.</p

Magnetisation switching of FePt nanoparticle recording medium by femtosecond laser pulses

Manipulation of magnetisation with ultrashort laser pulses is promising for information storage device applications. The dynamics of the magnetisation response depends on the energy transfer from the photons to the spins during the initial laser excitation. A material of special interest for magnetic storage are FePt nanoparticles, for which switching of the magnetisation with optical angular momentum was demonstrated recently. The mechanism remained unclear. Here we investigate experimentally and theoretically the all-optical switching of FePt nanoparticles. We show that the magnetisation switching is a stochastic process. We develop a complete multiscale model which allows us to optimize the number of laser shots needed to switch the magnetisation of high anisotropy FePt nanoparticles in our experiments. We conclude that only angular momentum induced optically by the inverse Faraday effect will provide switching with one single femtosecond laser pulse.EC under Contract No. 281043, FemtoSpin. The work at Greifswald University was supported by the German research foundation (DFG), projects MU MU 1780/8-1, MU 1780/10-1. Research at Göttingen University was supported via SFB 1073, Projects A2 and B1. Research at Uppsala University was supported by the Swedish Research Council (VR), the Röntgen-Ångström Cluster, the Knut and Alice Wallenberg Foundation (Contract No. 2015.0060), and Swedish National Infrastructure for Computing (SNIC). Research at Kiel University was supported by the DFG, projects MC 9/9-2, MC 9/10-2. P.N. acknowledges support from EU Horizon 2020 Framework Programme for Research and Innovation (2014-2020) under Grant Agreement No. 686056, NOVAMAG. The work in Konstanz was supported via the Center for Applied Photonics

Precision of the PET activity range during irradiation with ¹⁰C, ¹¹C, and ¹²C beams

Objective. Beams of stable ions have been a well-established tool for radiotherapy for many decades. In the case of ion beam therapy with stable ¹²C ions, the positron emitters ¹⁰,¹¹C are produced via projectile and target fragmentation, and their decays enable visualization of the beam via positron emission tomography (PET). However, the PET activity peak matches the Bragg peak only roughly and PET counting statistics is low. These issues can be mitigated by using a short-lived positron emitter as a therapeutic beam. Approach. An experiment studying the precision of the measurement of ranges of positron-emitting carbon isotopes by means of PET has been performed at the FRS fragment-separator facility of GSI Helmholtzzentrum für Schwerionenforschung GmbH, Germany. The PET scanner used in the experiment is a dual-panel version of a Siemens Biograph mCT PET scanner. Main results. High-quality in-beam PET images and activity distributions have been measured from the in-flight produced positron emitting isotopes ¹¹C and ¹⁰C implanted into homogeneous PMMA phantoms. Taking advantage of the high statistics obtained in this experiment, we investigated the time evolution of the uncertainty of the range determined by means of PET during the course of irradiation, and show that the uncertainty improves with the inverse square root of the number of PET counts. The uncertainty is thus fully determined by the PET counting statistics. During the delivery of 1.6 × 10⁷ ions in 4 spills for a total duration of 19.2 s, the PET activity range uncertainty for ¹⁰C, ¹¹C and ¹²C is 0.04 mm, 0.7 mm and 1.3 mm, respectively. The gain in precision related to the PET counting statistics is thus much larger when going from ¹¹C to ¹⁰C than when going from ¹²C to ¹¹C. The much better precision for ¹⁰C is due to its much shorter half-life, which, contrary to the case of ¹¹C, also enables to include the in-spill data in the image formation. Significance. Our results can be used to estimate the contribution from PET counting statistics to the precision of range determination in a particular carbon therapy situation, taking into account the irradiation scenario, the required dose and the PET scanner characteristics

Оценка межэкспертной согласованности врачей-рентгенологов в диагностике ишемического инсульта в бассейне средней мозговой артерии с помощью компьютерной томографии

Background. To evaluate the diagnostic accuracy of radiologists with a wide range of experience and training in emergency neuroradiology and other specialty hospitals, as well as the level of inter-experts’ agreement regarding CT signs of ischemic stroke.Material and methods. Our study included a retrospective cohort of 100 patients who underwent NCCT, CT angiography (mCTA) and CT perfusion in St. Petersburg clinical hospital. Fifty patients had confirmed middle cerebral artery ischemic stroke. The study also randomly included fifty patients in whom this diagnosis was excluded, including on the basis of dynamic follow-up as part of further clinical evaluation and follow-up CT scan of the brain. All 100 CT were reviewed by 21 radiologists who independently assessed each study for CT evidence of ischemic stroke. Statistical analysis included the Kappa-Fleiss coefficient ( ) calculation of agreement for each sign of ischemic stroke, specificity, sensitivity, and accuracy of detection of these changes.Results. The staff radiologist’s mean experience in emergency neuroradiology affects both diagnostic performance and consistency for detection of most CT features of ischemic stroke. At the same time, experience does not affect the diagnostic efficiency of radiologists with no experience in stroke assessment. The most highly specific and reproducible sign of ischemic stroke was the hyperdense middle cerebral artery sign, and the most ambiguous diagnostic sign was the gyral effacement. At the same time, all radiologists, regardless of length of service record and experience in emergency neuroradiology, are prone to over-diagnosis.Conclusion. Further search for tools and solutions is needed to level out interexpert variability regarding assessment of ischemic CT signs, since this problem has high clinical importance.Цель исследования: определение показателей диагностической эффективности врачей с различным стажем в ургентной нейрорадиологии, а также уровня их согласия в отношении КТ-признаков ишемического инсульта.Материал и методы. За 2021 г. из базы городской клинической больницы Санкт-Петербурга были ретроспективно отобраны 100 пациентов, которым были проведены бесконтрастная КТ, КТ-ангиография брахиоцефальных артерий и артерий головного мозга, а также КТ-перфузия. У 50 пациентов был подтвержден ишемический инсульт в бассейне средней мозговой артерии. Также в исследование рандомно включены 50 пациентов, у которых данный диагноз был исключен, в том числе на основе динамического наблюдения в рамках дальнейшей клинической оценки и контрольного КТ-исследования головного мозга. Все 100 исследований были проанализированы 21 рентгенологом, которые независимо друг от друга оценивали каждое исследование на наличие КТ-признаков ишемического инсульта. Статистический анализ включал определение коэффициента каппа Флейсса (κ) относительно согласия по каждому признаку ишемического инсульта, специфичности, чувствительности и точности выявления данных изменений.Результаты. Стаж работы врачей экстренной нейрорадиологии в Региональном сосудистом центре влияет как на диагностическую эффективность, так и на согласованность в отношении большинства КТ-признаков ишемического инсульта. В то же время стаж не влияет на диагностическую эффективность врачей, не имеющих опыта в оценке инсульта. Как наиболее высокоспецифичный и воспроизводимый признак ишемического инсульта был выявлен симптом гиперденсной средней мозговой артерии, а самым неоднозначным диагностическим признаком оказался симптом сглаженности корковых борозд. При этом все врачи независимо от стажа и опыта работы в ургентной нейрорадиологии склонны к гипердиагностике.Заключение. Необходим дальнейший поиск инструментов и решений, способных нивелировать межэкспертную вариативность в отношении оценки КТ-признаков ишемического инсульта, поскольку данная проблема имеет высокую значимость в клинической практике