bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarisation‐insensitive dual‐band transmissive rasorber designed on a single layer substrate
Authors: Zargar Mehran Manzoor , Rajput Archana , Saurav Kushmanda , Koul Shiban Kishen
Published: June 2020

In this study, a frequency selective surface (FSS)‐based rasorber has been proposed by combining the designs of split‐ring absorber and dual bandpass FSS, which are printed on the front and backside of 0.8‐mm thick FR‐4 substrate, respectively. The proposed FSS‐based rasorber is a thin single layer structure and also exhibits the polarisation‐insensitive behaviour due to its four‐fold symmetry. The split‐ring structure at the front contributes to the resonant absorption at 6.2 GHz, while the bandpass FSS structure at the backside provides two transmission windows at 3.1 and 8.4 GHz, respectively. The parameters of the design are optimised such that at the absorption frequency, the bandpass FSS acts as a complete metallic ground. The operating principle of the proposed rasorber is analysed using an equivalent circuit model. The effects of design parameters on the performance of the rasorber are studied, and accordingly an optimum range of lower and upper transmission bands with respect to the absorption band are determined. A array of the proposed rasorber unit cell is fabricated, and the results are experimentally verified.
Time‐based multi‐component irregular FM micro‐Doppler signals decomposition via STVMD
Authors: Li Yi , Xia Weijie , Dong Shiqi
Published: June 2020

The decomposition of multi‐component micro‐Doppler signals overlapping in the time‐frequency (T‐F) domain is critical and challenging, especially in the case of irregular instantaneous Doppler frequency. The authors propose a novel time‐based decomposition method called the short‐time variational mode decomposition (STVMD) to analyse the irregular (FM) micro‐Doppler signals, and present an optimal model combined with T‐F transformation. Then, considering the STVMD may fail to extract the instantaneous frequency (IF) of overlapped components, an improved STVMD algorithm is put forward. Since the dependence of the STVMD algorithm on the initial value, they adopt the Kalman filtering to implement IF tracking and regrouping under the global constraint, further accelerating the convergence of the algorithm. Furthermore, due to the mode aliasing at the intersection point, they adopt a degenerate STVMD model to decompose the signals with known centre frequencies, which can be viewed as a Wiener filter. With the two steps, the improved STVMD algorithm can effectively solve the decomposition of T‐F overlapping irregular FM micro‐Doppler signals. Compared with the peak ridge technique and the ridge path regrouping and intrinsic chirp component decomposition (RPRG + ICCD), the proposed method shows the effectiveness and adaptability even for irregular FM signals with large T‐F spectrum amplitude fluctuation in the low signal‐to‐noise ratio environment.
Evaluation method for impact of jamming on radar based on expert knowledge and data mining
Authors: Li Tingpeng , Wang Zelong , Liu Jiying
Published: June 2020

The effects of complex electromagnetic environment on a radar system involve many factors and their interrelationships are also complicated, so it is difficult to quantitatively describe the impact of jamming on the radar. In this study, the authors start from the signal models of several jamming types and the basic signal processing flow of pulse‐Doppler radar and propose a unified evaluation framework based on expert knowledge and data mining. On the one hand, the evaluation index from expert knowledge is calculated by the two‐dimensional image entropy of the time–frequency distributions of echoes. On the other hand, the evaluation index from data mining is constructed from the principle patterns extracted from samples by robust principal component analysis. In addition, the fused evaluation index is achieved by taking a weighted average of the indices from expert knowledge and data mining, where the weights are designed from the samples. Finally, the proposed evaluation approach is validated by analysing its feasibility, consistency and robustness in experiments and the results show that it can stably and quantitatively measure the impact of jamming on the radar.
Revisiting dual AGN candidates with spatially resolved LBT spectroscopy
Authors: Husemann B. , Heidt J. , De Rosa A. , Vignali C. , Bianchi S. , Bogdanović T. , Komossa S. , Paragi Z.
Published: June 2020

Context.The merging of supermassive black holes (SMBHs) is a direct consequence of our hierarchical picture of galaxy evolution. It is difficult to track the merging process of SMBHs during mergers of galaxies as SMBHs are naturally difficult to observe.

Aims.We want to characterise and confirm the presence of two independent active galactic nuclei (AGN) separated by a few kiloparsec in seven strongly interacting galaxies previously selected from the Sloan Digital Sky Survey (SDSS) as Seyfert-Seyfert pairs based on emission-line ratio diagnostics.

Methods.Optical slit spectra taken with MODS at the Large Binocular Telescope are presented to infer the detailed spatial distribution of optical emission lines, and their line ratios and AGN signatures with respect to the host galaxies, thereby quantifying the impact of beam smearing and large fibre apertures on the spectra captured by the SDSS.

Results.We find that at most two of the seven targets actually retain a Seyfert-Seyfert dual AGN, whereas the others may be more likely powered by post-AGB stars in retired galaxies or through shocks in the ISM based on spatially resolved optical line diagnostics. The major cause of this discrepancy is a bias caused by the spillover of flux from the primary source in the secondary SDSS fibre which can be more than an order of magnitude at < 3″ separations. Previously reported extremely low X-ray–to–[O III] luminosity ratios may be explained by this misclassification, as can heavily obscured AGN for the primaries. We also find that the nuclei with younger stellar ages host the primary AGN.

Conclusions.Studies of close dual AGN selected solely from fibre-based spectroscopy can create severe biases in the sample selection and interpretation of the results. Spatially resolved spectroscopy should ideally be used in the future to characterise such compact systems together with multi-wavelength follow-up observations.
Die Analyse von Schnarchen bei Patienten mit obstruktiver Schlafapnoe (OSA) anhand von Polysomnografie und LEOSound
Authors: Moaeri S. , Hildebrandt O. , Cassel W. , Viniol C. , Schäfer A. , Kesper K. , Sohrabi K. , Gross V. , Koehler U.
Published: June 2020

Einleitung In dieser Studie wird bei Patienten mit OSA parallel zur Erfassung des Biosignals Schnarchen aus der Polysomnografie auch eine akustische Aufzeichnung mit dem LEOSound (akustische Langzeitregistrierung der Atem- und Atemnebengeräusche) durchgeführt. Es stellt sich die Frage, wie viele der obstruktiven Apnoen bei apnoeterminierender Wiederaufnahme der Atmung mit Schnarchen einhergehen.

Methode Parallel zur polysomnografischen Messung wurde bei 40 Patienten mit OSA (AHI > 15/h) eine Atem- und Atemnebengeräuschaufzeichnung mit dem LEOSound-Rekorder durchgeführt. Das durchschnittliche Alter der Patienten lag bei 57 ± 11 Jahren. Das durchschnittliche Körpergewicht betrug 100 ± 19 kg bei einem mittleren Body-Mass-Index (BMI) von 33 ± 7 kg/m2. 12 der 40 Aufzeichnungen mussten aufgrund qualitativ unzureichender Messqualität von der Bewertung ausgeschlossen werden. Die visuell detektierten Schnarchereignisse in der Polysomnografie wurden mit den audiovisuell erfassten im LEOSound verglichen.

Ergebnisse Insgesamt konnten 3778 obstruktive Apnoephasen registriert werden. In der Polysomnografie gingen 2229 (58,8 %) Apnoen mit Schnarchen einher, in der akustischen Messung 1921 (51,0 %). Bei einem der Patienten war eine ausgeprägtere Abweichung der Frequenz der Schnarchereignisse von PSG und LEOSound nachweisbar.

Diskussion Schnarchen wird in beiden Verfahren bei etwa 60 % der obstruktiven Apnoephasen gefunden. Eine audiovisuelle Beurteilung von Schnarchen ist mittels Geräuschaufzeichnung sehr zuverlässig durchführbar. Es bedarf der weiteren Klärung, warum nur 60 % der apnoeterminierenden Hyperpnoen mit Schnarchen einhergehen. Pathophysiologisch wäre zu erwarten, dass das Öffnen des obstruierten Atemwegs in einem sehr viel höheren Prozentsatz mit einer turbulenten Strömung, Weichteilschwingung und damit auch Schnarchen kombiniert ist.
Paraneoplastisches Cushing-Syndrom als Ursache von therapierefraktärer Hypokaliämie
Authors: Gerhardt Louisa M. S. , Sabath Lisa , Müller Beat , Capraro Joel , Borm Katrin
Published: June 2020

Anamnese und klinischer Befund Ein 58-jähriger Mann stellte sich mit therapierefraktärer Hypokaliämie und rascher Gewichtszunahme vor. Klinisch bestanden hypertensive Blutdruckwerte, eine stammbetonte Adipositas und ausgeprägte Beinödeme.

Untersuchungen und Diagnose Die Laboruntersuchungen ergaben eine hypokaliämische metabolische Alkalose bei ACTH-abhängigem Hyperkortisolismus. Die Thorax-Abdomen-CT zeigte eine pulmonale Raumforderung und eine Raumforderung der rechten Nebenniere. Bioptisch wurde die Diagnose eines ACTH-produzierenden kleinzelligen Lungenkarzinoms gestellt.

Therapie und Verlauf Unter Therapie mit Ketoconazol und Chemotherapie war der Tumor größenregredient, der Hyperkortisolismus konnte kontrolliert werden. Die Raumforderung der rechten Nebenniere war im Verlauf größenkonstant, sodass wir von einem inzidentellen Nebennierenadenom ausgingen.

Folgerung Die Diagnose des paraneoplastischen Cushing-Syndroms kann eine Herausforderung sein, da klassische Cushing-Stigmata aufgrund des raschen Auftretens fehlen können. Bei neu aufgetretener, therapierefraktärer Hypokaliämie, metabolischer Alkalose und arterieller Hypertonie sollte man daher nicht zuletzt an Hyperkortisolismus denken.
Hemodynamic and Pressor Responses to Combination of Yoga and Blood
Flow Restriction
Authors: Wooten Savannah V. , Stray-Gundersen Sten , Tanaka Hirofumi
Published: June 2020

A combination of yoga and blood flow restriction, each of which elicits marked
pressor responses, may further increase blood pressure and myocardial oxygen
demand. To determine the impact of a combination of yoga and blood flow
restriction on hemodynamic responses, twenty young healthy participants
performed 20 yoga poses with/without blood flow restriction bands placed
on both legs. At baseline, there were no significant differences in any of the
variables between the blood flow restriction and non-blood flow restriction
conditions. Blood pressure and heart rate increased in response to the various
yoga poses (p<0.01) but were not different between the blood flow
restriction and non-blood flow restriction conditions. Rate-pressure products,
an index of myocardial oxygen demand, increased significantly during yoga
exercises with no significant differences between the two conditions. Rating of
perceived exertion was not different between the conditions. Blood lactate
concentration was significantly greater after performing yoga with blood flow
restriction bands (p=0.007). Cardio-ankle vascular index, an index of
arterial stiffness, decreased similarly after yoga exercise in both conditions
while flow-mediated dilation remained unchanged. In conclusion, the use of lower
body blood flow restriction bands in combination with yoga did not result in
additive or synergistic hemodynamic and pressor responses.
Wart Treated with Constitutional Homoeopathic Remedy Natrum muriaticum: A Case Study
Authors: Garg Arvindra Kumar , Agarwal Neha
Published: June 2020

Wart is a common problem in younger and elder persons. Most of the warts are seen on neck, face and armpit. Practically there is no complaint due to wart, but it causes cosmetic problem so there is need for treatment. The best way to treat them is by homoeopathic medicines. Other methods like burning and cutting can cause more harm than help. Here I am presenting a case of warts that is treated very beautifully with Natrum muriaticum.
Linking Emotional Intelligence to Successful Health Care Leadership: The Big Five Model of Personality
Authors: Cavaness Keith , Picchioni Anthony , Fleshman James W.
Published: June 2020

Research has identified emotional intelligence as the ability to understand and manage emotions. This is especially important for surgical leaders who must interact constructively with teams, administrators, patients, colleagues, and the community. Conventional intelligence emphasizes the rational and analytical brain. When one becomes aware of emotional intelligence, it adds to the repertoire of the surgical leader. It gives them insight into the dynamics of interpersonal relationships. This will allow the surgeon to control the emotional side of communication. Specifically, emotional intelligence focuses on self-awareness, self-management, social skills, and resiliency. With these skills, they are able to modulate their leadership style, allowing for increased conflict management and persuasiveness, more effective change management, and consensus-building. Emotional intelligence is not innate; these are learned skills. With practice and attention, it is possible to acquire the skills to enhance relationships.
Surgical Leadership
Authors: Peters Walter , Picchioni Anthony , Fleshman James W.
Published: June 2020

There are few topics of more importance in health care today than surgical leadership. The surgical leader will need to organize and maintain a collective effort if the organization is going to be effective. Health care teams work in a volatile, uncertain, complex, and ambiguous ecosystem. Therefore, surgeons must develop skills beyond the operating room. The facilitative leader will lead from the middle, not the top. They will empower coworkers to participate in creating a vision by building consensus, developing teams, clarifying roles, and earning the loyalty and trust of their colleagues. Surgical leaders will use communication as the vehicle for their success, including intentional listening, asking open-ended questions, and creating dialog instead of argumentative exchanges. The future of health care belongs to the physicians who are investing the time and effort today to become leaders.
The structural information filtered features (SIFF) potential: Maximizing information stored in machine-learning descriptors for materials prediction
Authors: Zeledon Jorge Arturo Hernandez , Romero Aldo H. , Ren Pengju , Wen Xiaodong , Li Yongwang , Lewis James P.
Published: June 2020

Machine learning inspired potentials continue to improve the ability for predicting structures of materials. However, many challenges still exist, particularly when calculating structures of disordered systems. These challenges are primarily due to the rapidly increasing dimensionality of the feature-vector space which in most machine-learning algorithms is dependent on the size of the structure. In this article, we present a feature-engineered approach that establishes a set of principles for representing potentials of physical structures (crystals, molecules, and clusters) in a feature space rather than a physically motivated space. Our goal in this work is to define guiding principles that optimize information storage of the physical parameters within the feature representations. In this manner, we focus on keeping the dimensionality of the feature space independent of the number of atoms in the structure. Our Structural Information Filtered Features (SIFF) potential represents structures by utilizing a feature vector of low-correlated descriptors, which correspondingly maximizes information within the descriptor. We present results of our SIFF potential on datasets composed of disordered (carbon and carbon–oxygen) clusters, molecules with C7O2H2 stoichiometry in the GDB9-14B dataset, and crystal structures of the form (AlxGayInz)2O3 as proposed in the NOMAD Kaggle competition. Our potential's performance is at least comparable, sometimes significantly more accurate, and often more efficient than other well-known machine-learning potentials for structure prediction. However, primarily, we offer a different perspective on how researchers should consider opportunities in maximizing information storage for features.
Fano-ADC(2,2) method for electronic decay rates
Authors: Kolorenč P. , Averbukh V.
Published: June 2020

Fano-ADC is a family of ab initio methods for the prediction of electronic decay widths in excited, singly and doubly ionized systems. It has been particularly successful in elucidating the geometry dependence of the inter-atomic decay widths in clusters and facilitated the prediction of new electronic decay phenomena. However, the available Fano-ADC schemes are limited to the second-order treatment of the initial state and the first-order treatment of the final states of the decay. This confines the applicability of the Fano-ADC approach to first-order decay processes, e.g., normal but not double Auger decay (DAD), and compromises the numerical accuracy of the schemes through the unbalanced treatment of electronic correlation. Here, we introduce the ADC(2,2) approximation for singly ionized states, which describes both initial and final states of the decay up to second order. We use the new scheme to construct the Fano-ADC(2,2) approximation for the decay widths and show that it provides superior accuracy for the decay widths of a series of processes. Moreover, the Fano-ADC(2,2) method provides access to second-order decay processes, such as DAD, which are qualitatively beyond the reach of the previously available Fano-ADC implementations.
Silicon carbide zipper photonic crystal optomechanical cavities
Authors: Lu Xiyuan , Lee Jonathan Y. , Lin Qiang
Published: June 2020

We demonstrate a silicon carbide (SiC) zipper photonic crystal optomechanical cavity. The device is on a 3C–SiC-on-silicon platform and has a compact footprint of ∼30 × 1 μm. The device shows an optical quality of 2800 at telecom and a mechanical quality of 9700 at 12 MHz with an effective mass of ∼3.76 pg. The optical mode and mechanical mode exhibit strong nonlinear interaction, namely, the quadratic spring effect, with a nonlinear spring constant of 3.3 × 104 MHz2/nm. The SiC zipper cavity is potentially useful in sensing and metrology in harsh environments.
Classically entangled Ince–Gaussian modes
Authors: Yao-Li  , Hu Xiao-Bo , Perez-Garcia Benjamin , Bo-Zhao  , Gao Wei , Zhu Zhi-Han , Rosales-Guzmán Carmelo
Published: June 2020

Complex vector light modes, classically entangled in their spatial and polarization degrees of freedom (DoF), have become ubiquitous in a vast diversity of research fields. Crucially, while polarization is limited to a bi-dimensional space, the spatial mode is unbounded, and it can be specified by any of the sets of solutions the wave equation can support in different coordinate systems. Here, we report on a class of vector beams with elliptical symmetry where the spatial DoF is encoded in the Ince–Gaussian modes of the cylindrical elliptical coordinates. We outline their geometric representation on the higher-order Poincaré sphere, demonstrate their experimental generation, and analyze the quality of the generated modes via Stokes polarimetry. We anticipate that such vector modes will be of great relevance in applications, such as optical manipulations, laser material processing, and optical communications among others.
Rational design of a conformation-specific antibody for the quantification of Aβ oligomers
Authors: Aprile Francesco A. , Sormanni Pietro , Podpolny Marina , Chhangur Shianne , Needham Lisa-Maria , Ruggeri Francesco S. , Perni Michele , Limbocker Ryan , Heller Gabriella T. , Sneideris Tomas , Scheidt Tom , Mannini Benedetta , Habchi Johnny , Lee Steven F. , Salinas Patricia C. , Knowles Tuomas P. J. , Dobson Christopher M. , Vendruscolo Michele
Published: June 2020

Significance

The accurate quantification of the amounts of small oligomeric assemblies formed by the amyloid β (Aβ) peptide represents a major challenge in the Alzheimer’s field. There is therefore great interest in the development of methods to specifically detect these oligomers by distinguishing them from larger aggregates. The availability of these methods will enable the development of effective diagnostic and therapeutic interventions for this and other diseases related to protein misfolding and aggregation. We describe here a single-domain antibody able to selectively quantify oligomers of the Aβ peptide in isolation and in complex protein mixtures from animal models of disease.
Breeding and genetics.
Authors: Wehner Todd C. , Naegele Rachel P. , Myers James R. , Dhillon Narinder P. S. , Crosby Kevin
Published: June 2020

This chapter provides information on breeding and genetics of cucurbits. Manual pollination, tissue culture, interspecific hybridization, cytology, genes, genomics, and historical and novel breeding techniques are discussed.
Fruit and seed production.
Authors: Wehner Todd C. , Naegele Rachel P. , Myers James R. , Dhillon Narinder P. S. , Crosby Kevin
Published: June 2020

This chapter deals with some aspects of fruit and seed production of cucurbit crops, such as cucumber, melon, squash and watermelon. The control of sex expression, pollination, harvesting, postharvest handling and storage (fruits and seeds) are discussed.
Abiotic stresses.
Authors: Wehner Todd C. , Naegele Rachel P. , Myers James R. , Dhillon Narinder P. S. , Crosby Kevin
Published: June 2020

Numerous abiotic stresses impact yield, quality and adaptation of cucurbit crops under the diverse cultivation systems across the globe. Irrigation systems, elevation, soil type, solar radiation, wind, pathogens, fertility and genotype all interact to determine the degree to which abiotic stress may impact the crop. This chapters describes some abiotic stresses affecting cucurbit cultivation, such as cold, heat, drought, flooding, nutrient deficiencies and excesses, and salinity. Tolerance or resistance to abiotic stress factors has been documented in the germplasm of multiple cucurbit crops. Utilizing wild accessions, landraces and known resistance sources, genes for abiotic stress resistance are being identified and introgressed into cultivars with desirable fruit quality. With the new gene editing technology, it may be possible to modify these endogenous stress resistance genes to enhance their effects in the near future.
Neuroblastoma‐secreted exosomes carrying miR‐375 promote osteogenic differentiation of bone‐marrow mesenchymal stromal cells
Authors: Colletti Marta , Tomao Luigi , Galardi Angela , Paolini Alessandro , Di Paolo Virginia , De Stefanis Cristiano , Mascio Paolo , Nazio Francesca , Petrini Stefania , Castellano Aurora , Russo Ida , Caruso Roberta , Piga Simone , De Vito Rita , Pascucci Luisa , Peinado Hector , Masotti Andrea , Locatelli Franco , Di Giannatale Angela
Published: June 2020

Bone marrow (BM) is the major target organ for neuroblastoma (NB) metastasis and its involvement is associated with poor outcome. Yet, the mechanism by which NB cells invade BM is largely unknown. Tumour microenvironment represents a key element in tumour progression and mesenchymal stromal cells (MSCs) have been recognized as a fundamental part of the associated tumour stroma. Here, we show that BM‐MSCs isolated from NB patients with BM involvement exhibit a greater osteogenic potential than MSCs from non‐infiltrated BM. We show that BM metastasis‐derived NB‐cell lines secrete higher levels of exosomal miR‐375, which promotes osteogenic differentiation in MSCs. Of note, clinical data demonstrate that high level of miR‐375 correlates with BM metastasis in NB patients. Our findings suggest, indeed, a potential role for exosomal miR‐375 in determining a favourable microenvironment in BM to promote metastatic progression. MiR‐375 may, thus, represent a novel biomarker and a potential target for NB patients with BM involvement.
ERdj8 governs the size of autophagosomes during the formation process
Authors: Yamamoto Yo-hei , Kasai Ayano , Omori Hiroko , Takino Tomoe , Sugihara Munechika , Umemoto Tetsuo , Hamasaki Maho , Hatta Tomohisa , Natsume Tohru , Morimoto Richard I. , Arai Ritsuko , Waguri Satoshi , Sato Miyuki , Sato Ken , Bar-Nun Shoshana , Yoshimori Tamotsu , Noda Takeshi , Nagata Kazuhiro
Published: June 2020

In macroautophagy, membrane structures called autophagosomes engulf substrates and deliver them for lysosomal degradation. Autophagosomes enwrap a variety of targets with diverse sizes, from portions of cytosol to larger organelles. However, the mechanism by which autophagosome size is controlled remains elusive. We characterized a novel ER membrane protein, ERdj8, in mammalian cells. ERdj8 localizes to a meshwork-like ER subdomain along with phosphatidylinositol synthase (PIS) and autophagy-related (Atg) proteins. ERdj8 overexpression extended the size of the autophagosome through its DnaJ and TRX domains. ERdj8 ablation resulted in a defect in engulfing larger targets. C. elegans, in which the ERdj8 orthologue dnj-8 was knocked down, could perform autophagy on smaller mitochondria derived from the paternal lineage but not the somatic mitochondria. Thus, ERdj8 may play a critical role in autophagosome formation by providing the capacity to target substrates of diverse sizes for degradation.
Averting cumulative lifetime attributable risk (LAR) of cancer by decontamination of residential areas affected by a large-scale nuclear power plant fallout: time aspects of radiological benefits for newborns and adults
Authors: Rääf C , Finck R , Martinsson J , Hinrichsen Y , Isaksson M
Published: June 2020

The averted cumulative lifetime attributable risk (LAR), the residual dose and highest ground deposition of 137Cs complying with a reference dose level of 20 mSv yr−1 to an individual returning after one year to an area contaminated by unfiltered releases of fission products from a nuclear power plant (NPP) were evaluated by applying an existing exposure model designed to compute age- and gender-dependent time-integrated LAR. The model was applied to four types of nuclear fallout scenarios, partly based on data from the Chernobyl and Fukushima releases and from theoretical source terms from Swedish NPPs. For rapid decontamination measures that achieve a 50% relative reduction in external dose rate within 1 year, compliance with the reference level 20 mSv yr−1 can be attained for an initial 137Cs ground deposition of up to 2 MBq m−2 with relaxed food restrictions. This compliance can be attained at even higher ground deposition (up to 4.5 MBq m−2) if using the strict food restrictions employed in Japan after 2011. Considering longer than 1 year return times it was also found that the benefit of implementing decontamination decreases rapidly with time (2–3 years half-time), especially if the fallout has a high initial 134Cs to 137Cs activity ratio and if the ecological half-time of the external dose rate is short (<5 years). Depending on fallout scenario the averted cumulative LAR for newborn girls by decontamination that is achieved after 5 years is only between 6% and 11% of that obtained by evacuation alone during the same time, indicating a rather limited radiological benefit of decontamination if delayed more than a few years. We conclude that decision makers and emergency response planners need to consider that protracted decontamination measures may have limited radiological benefit compared with evacuation in terms of averted future cancer cases, albeit it may have other societal benefits.
Wettability and aging of polylactide films as a function of AC-discharge plasma treatment conditions
Authors: Demina T S , Piskarev M S , Shpichka A I , Gilman A B , Timashev P S
Published: June 2020

Plasma treatment is among the most versatile and promising tools for modifying the properties of polymeric surfaces. It is mainly used to control the hydrophilic-hydrophobic balance of a surface and to optimize its adhesion properties, including material/cell interactions. From this point of view, a wide set of variable plasma processing conditions and their effect on surface wettability, as well as the tendency of plasma-treated surfaces to restore their initial characteristics after storage, require preliminary optimization of the treatment conditions. This work is aiming to study the effect of AC-discharge plasma treatment conditions (duration, power, frequency) on the wettability contact angle of poly(L, L-lactide) film and to evaluate the aging of this effect in time as a function of the plasma treatment parameters.
Diagnostics of process plasma used for the production of memristive devices
Authors: Cipo J , Schlichting F , Zahari F , Gauter S , Kohlstedt H , Kersten H
Published: June 2020

Memristive devices have been the object of intensive studies for non-volatile memories, neuromorphic engineering and image processing algorithms. The intrinsic properties of these devices are determined by its I-V characteristics influenced by different process parameters. The double-barrier memristive devices investigated in this work are based on the motion of charged species, i.e. oxygen vacancies or ions, within a NbOx layer. Since the layers are deposited by magnetron sputtering, it is important to understand the physics of the discharge and its effect on the film properties.

For plasma diagnostics we used a calorimetric probe, which can be operated simultaneously as a passive thermal probe for energy flux measurement and as a planar Langmuir probe for measuring the ion current, the floating and plasma potentials and the electron temperature. In particular, we investigated the reactive sputter deposition of the NbOx layer by a floating and a biased probe. The parameters were determined in dependence on the radial position of the probe across the substrate region. The results allowed us to find correlations between the plasma parameters and the electrical properties of the memristive devices produced on one 100-mm wafer. Furthermore, we could point out the dominating factors affecting strongly the properties of these thin films.
Particle-in-cell simulations of an inverted sheath
Authors: Gomez I , Valič A , Gyergyek T , Costea S , Kovačič J
Published: June 2020

An inverted sheath is simulated by particle-in-cell simulations using the XPDP1 code. It is shown that a stable monotonically decreasing potential structure can be formed in a bounded plasma system, where positive ions and source electrons are injected from the right-hand side (source) electrode and emitted electrons are injected from the left-hand side (collector) electrode. Such inverted sheath structure is created in the absence of collisions or ionization, provided that the ratio of injection fluxes of both electron groups is large enough. In this work preliminary results are reported and some effects of different ion injection are illustrated.
Theoretical determination of the gas temperature in a nanosecond pulsed longitudinal discharge exciting high-power strontium atom lasers
Authors: Temelkov K A , Slaveeva S I , Kostadinov I K , Fedchenko Yu I
Published: June 2020

Assuming that the gas temperature varies only in the radial direction, an analytical solution of the steady-state heat conduction equation is found for a uniform power input in various gas mixtures and for different discharge tube designs. For this purpose, the heat conductivities of several 2- and 3-component gas mixtures are obtained under gas-discharge conditions optimal for the strontium atom laser.
Plasimo modeling of hollow-cathode geometry: laser tube configuration for sputtering metal-vapor lasers
Authors: Yordanova D , Temelkov K , Mihailova D , Van Dijk J
Published: June 2020

We report results of the studies of a new version of a hollow-cathode discharge, namely, a multiple hollow-cathode discharge. The geometry comprises a main cylindrical cathode, which defines the active laser volume, and a number of short cylindrical side cathodes arranged radially to the main cathode along its length. PLASIMO’s Drift-Diffusion module is used to describe numerically the new laser tube configuration and to demonstrate its advantages.
Heat distribution simulation in electron-beam surface modification of 316L stainless steel samples
Authors: Koleva E , Tsonevska T , Koleva L , Vutova K , Mladenov G , Naplatanova M , Trushnikov D , Varushkin S
Published: June 2020

A time-dependent heat model is implemented for the simulation of the heat distribution in 316L stainless steel samples during electron-beam irradiation. The influence is studied of the electro-beam power and processing time on the temperature field produced in the samples. The simulation results are compared with real experimental data of electron-beam surface modification of 0.5-mm-thick 316L stainless steel samples using the ELIT-60 installation in the Institute of Electronics BAS. The simulation and the experimental results show good agreement.
Influence of the processes of additional phosphate post-treatment of ceria conversion coatings deposited on Al 1050 on their corrosion protective behavior
Authors: Andreeva R , Stoyanova E , Tsanev A , Stoychev D
Published: June 2020

Systematic studies were carried out with respect to the elucidation of the role of additional “post-treatment” immersion phosphate processing on conversion corrosion protective ceria coatings CCOC deposited on aluminium Al 1050. Thereupon, the influence of various compositions of the CCOC as well as the conditions of such treatment were studied, based on solutions of Na3PO4 or NH4H2PO4. The results obtained with respect to the corrosion behavior, respectively the corresponding changes in the chemical composition of the studied corrosion-protective systems, give us the reason to suppose that the phosphate layers formed on the CCOC play the role of not only protective barrier coating, but they also change the kinetics of the conjugated electrochemical reactions characterizing the corrosion of aluminium. Key words: aluminum, pre-treatment, cerium-containing conversion films, corrosion
Nanoindentation study of the mechanical properties and deformation behavior of nanoporous alumina films
Authors: Bankova A , Videkov V , Tzaneva B , Mitov M , Potiron S , Molinari M
Published: June 2020

Over the past decade, anodic aluminium oxide (AAO) has become one of the most widely used materials as a platform for developing new types of devices in micro- and nanotechnology. Due to the potential use of highly ordered honeycomb porous AAO membranes in many engineering applications, considerable attention is being paid to the mechanical characterization of such thin films. In this study, the mechanical properties and deformation behavior of a nanoporous alumina film were investigated by nanoindentation. AAO films with an average pore diameter of 40 nm were fabricated electrochemically. The morphology and the mechanical properties of AAO were studied using scanning electron microscopy and nanoindentation, respectively. The force-displacement dependences obtained revealed that in the case of a freestanding AAO membrane the sample demonstrates extremely high elasticity. The indentation modulus and the hardness were found to decrease nonlinearly with an increase in the applied force.
Initial conditions for preparation of thin AlN films by atomic layer deposition
Authors: Beshkova M , Blagoev B S , Mehandzhiev V , Yakimova R , Georgieva B , Avramova I , Terziyska P , Kovacheva D , Strijkova V
Published: June 2020

Thin AlN films were grown on Si substrates in a Beneq TFS-200 ALD reactor. The atomic layer deposition (ALD) process consisted of two half cycles – aluminum adsorption and nitridization separated by a purging step. TMA (trimethylaluminum) and NH3 were used as precursors, and nitrogen (N2), as a carrier gas. The pulse duration, purging time, deposition temperature and other deposition conditions were varied to obtain AlN films with desired properties. The X-ray diffraction (XRD) data showed that the AlN films had an amorphous character. The films’ chemical composition and bonding states were investigated by X-ray photoelectron spectroscopy. The high resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 74.1 eV and 397.7 eV, respectively, for all layers.
Corrosion resistance of sol-gel ZrO2 coatings deposited on stainless steel
Authors: Stambolova I , Dimitrov O , Shipochka M , Yordanov S , Blaskov V , Vassilev S , Jivov B , Simeonova S , Balashev K , Grozev N , Lakov L
Published: June 2020

Corrosion-resistant ZrO2 coatings were deposited on stainless steel plates using organic (A) and inorganic (B) Zr precursors containing polyethylene glycol as structure directing agent. The dipping-drying cycles were repeated five times; the coatings were then treated at 500 °C. The samples were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and by automated contact-angle goniometry. The corrosion resistance of the ZrO2 coatings were examined in NaCl and artificial sea water. The XRD analyses revealed a crystallized monoclinic ZrO2 phase. The AFM observation proved that after the corrosion attack the surface had no signs of corrosion (scratches or cracks). The A and B coatings had corrosion rates of 4×10−5 and 2×10−4 g/m2 h, respectively. The A coatings possessed a fine grained structure and a lower wettability (contact angle of 107°) and a lower oxygen content than the B coatings, which determined their better corrosion properties in both corrosive media.
Development of ALD ZnO:Al as transparent conductive films
Authors: Napoleonov B , Marinova V , Petrova D , Blagoev B , Avramova I , Dimitrov D
Published: June 2020

We report the deposition of ultrathin Al-doped ZnO (AZO) films by using atomic layer deposition (ALD) and results from X-ray photoelectron spectroscopy (XPS) and photoelectrical measurements. The AZO films were deposited on glass, silicon and polyethylene terephthalate (PET) substrates and their structural and photoelectrical properties were measured and discussed. Based on the results, selected AZO films deposited on PAT were implemented as transparent electrodes in a polymer dispersed liquid crystal display device (PDLC). The electro-optical modulation characteristics of these devices are comparable to those of devices using commercial ITO electrodes.
Deposition and study of N-In co-doped sol-gel ZnO films
Authors: Ivanova T , Harizanova A , Koutzarova T , Vetruyen B
Published: June 2020

Single and doped ZnO films are successfully deposited by a sol-gel method. ZnO:N, ZnO:In and co-doped (N, In) ZnO films are thermally treated at 300 °C and 600 °C. Their structural, vibrational and optical properties are studied. The ZnO:In:N films crystallize in a wurtzite phase, revealing a preferential orientation in the 002 plane. FTIR analysis shows that the two dopants affect greatly the shapes and positions of the absorption features. The ZnO:N:In films are highly transparent above 90% in the visible spectral range. The ZnO:In and ZnO:N:In films annealed at 400-600°C show a tendency of narrowing the optical band gap compared to ZnO.
Electrochromic and optical study of sol-gel TiO2-MnO films
Authors: Ivanova T , Harizanova A , Koutzarova T , Vetruyen B
Published: June 2020

We present a study on the structural, optical and electrochromic properties of sol-gel films of TiO2 and TiO2-MnO. The XRD analyses show that the incorporation of Mn in the TiO2 host matrix inhibits the crystallization process, as compared to single TiO2 films, which are well crystallized in anatase phase. This conclusion is supported by FTIR analysis. Adding Mn to the TiO2 films leads to a significant narrowing of the optical band gap. The electrochromic characteristics of TiO2-MnO films are better than those of the single titanium dioxide films after annealing at 300 °C.
Modification of thin carbon films by UVC light
Authors: Milenov T , Avramova I , Dikovska A , Avdeev G , Mladenoff J , Kolev S , Valcheva E
Published: June 2020

We modified by UVC light single to few-layered nano-sized graphene films deposited by pulsed laser deposition (PLD) on ~300-nm SiO2/Si substrates. The samples were irradiated by UVC lamps (wavelength of 254 nm) for 15, 30, 60 and 90 minutes in air. The influence of the modification was evaluated by following the changes in the X-ray photoelectron and Raman spectra of the samples after UVC irradiation.
Deposition of vertical carbon nanosheets by MPECVD at atmospheric pressure
Authors: Marinov S , Vachkov V , Kiss’ovski Zh
Published: June 2020

The deposition process is studied of vertical carbon nanosheets by microwave (MW) plasma-enhanced chemical vapor deposition (PECVD) at atmospheric pressure. A coaxial MW plasma source with a surface-wave discharge at 2.45 GHz produces plasma in a gas mixture (Ar/H2/CH4) in the processing chamber. The emissive spectra of the plasma column in pulsed regime of the source are registered by an iHR550 spectrometer. The light from the plasma column is collected by a lens system connected to the spectrometer by an optical fiber. The dependence of the gas temperature in the plasma column on the absorbed MW power is obtained from the recorded OH-band and CN-band spectra by using the LIFBASE program. The plasma density is estimated from the Stark broadening of the Hβ-line, while the electron temperature is estimated by the line-ratio method using argon lines. The composition of the outlet gases from the chamber is measured and analyzed by an Agilent Micro gas chromatograph. The results obtained demonstrate the high efficiency of the methane decomposition process in the hot region of the plasma column (T
g ~ 3000 K). The deposition of vertical carbon nanosheets is carried out at fixed plasma parameters and controlled substrate temperature. Cu plate and Ni-foam are used as substrates. The carbon nanostructures formed on the metallic substrates are studied by SEM; the dependence is thus obtained of their morphology on the plasma parameters, gas temperature and substrate temperature. The structures are confirmed as graphene sheets via Raman spectroscopy. The results demonstrate the viability of our system for deposition of vertical carbon sheets at atmospheric pressure.
Very thin carbon-based films for transmissive photocathodes
Authors: Balalykin Nikolay I , Huran Jozef , Nozdrin Mikhail A , Sasinková Vlasta , Kováčová Eva , Kobzev Alexander P , Shirkov Grigory D
Published: June 2020

Very thin carbon-based nitrogen-doped films of different thicknesses were deposited on double-side polished sapphire substrates by RF reactive magnetron sputtering. RBS and ERD were used to determine the elemental concentration in the films, and Raman spectroscopy, to determine their chemical structure. The RBS and ERD analyses indicated that the films contained carbon, nitrogen and small amounts of hydrogen and oxygen. The Gaussian-fitted and identified Raman spectra of the films showed the D and G bands in the range 1000-1800 cm−1, and the 2 D and D+G bands, in the range 2500-3100 cm−1. The photo-induced (pulsed laser, 266 nm) electron emission properties of the films were determined by measuring the cathodes’ bunch charge and calculating their quantum efficiency. The paper discusses the structural properties of the very thin nitrogen-doped carbon-based films deposited on a sapphire substrate with different thicknesses in view of their use as backside-illuminated transmissive vacuum photocathodes.
Ellipsometric characterization of CrTiAlN coating deposited at low temperatures by unbalanced magnetron sputtering
Authors: Chitanov V , Kolaklieva L , Cholakova T , Sharif R , Hesser G , Hinterreiter A , Kakanakov R , Hingerl K
Published: June 2020

Ellipsometric characterization is presented of a CrTiAlN hard coating deposited by unbalanced magnetron sputtering at low temperatures. Such coatings find applications where the tool material cannot withstand temperatures exceeding 200 °C. The Cr/CrN/CrTiAlN coatings deposited using the UDP-850 equipment is characterized by UV-VIS and IR ellipsometry. A FIB cross-section is made and the thickness of the coating is measured using SEM. The roughness of the coating surface is determined by AFM. The ellipsometric measurements yielded data on the phase difference Δ, amplitude ratio ψ, the frequency dependent real (ε1(ω)) and imaginary (ε2(ω)) part of the dielectric function and the corresponding refractive and extinction indexes n(ω) and k(ω). The optical parameters are modelled by regression analysis implemented using the WVASE© software. A very good fit is achieved between the measured optical data and the corresponding models. The results show that the ellipsometric characterization data can be used to determine the surface structure, chemical composition and optical reflection characteristics of CrTiAlN hard coatings.
Composition, structure and adhesion of cathodic-arc and glow-discharge deposited TiN/TiO2 coatings: a case study
Authors: Nikolova M P , Valkov S , Yankov E , Petrov P
Published: June 2020

Titanium-based vacuum coatings, such as TiN and TiO2, are being widely used for functionalization of the surfaces and for forming protective surface layers for a number of applications. In this study, TiN/TiO2 coatings were deposited by two physical vacuum deposition (PVD) methods: cathodic-arc (for TiN) and glow-discharge (for TiO2) deposition. We studied the bilayer film composition, structure and properties by means of X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and scratch test analysis. The XRD spectrum indicated the presence of both anatase and rutile TiO2 phases, together with TiN reflections. The Ti 2p, O 1s and N 1s core level of XPS spectra in the depth of the oxide up to the oxide-nitride interface indicated intimate heterojunction between the layers. This results in a lower coefficient of friction and improved adhesion strength of the TiN/TiO2 film compared with pristine TiN coating.
Comparative analysis of platelets adhesion to the surface of Ta-based ceramic coatings deposited by magnetron sputtering
Authors: Zykova A , Safonov V , Yakovin S , Dudin S , Melnikova G , Petrovskaya A , Tolstaya T , Kuznetsova T , Chizhik S A , Donkov N
Published: June 2020

The adhesion of platelets to the surface of implants and stents depends on the material’s properties, such as surface roughness, topography and wettability. The present study analyzes the composition and surface properties of nanostructured Ta, Ta2O5 and TaON coatings and their correlation with the adhesion of platelets. The surface morphology and topography were observed by atomic force microscopy and electron scanning microscopy; while the elemental distribution and chemical composition were analyzed by energy dispersive X-ray spectroscopy. The coated surfaces’ advancing contact angles were evaluated by tensiometric measurements. The surface free energy (SFE) was calculated by the Owens, Wendt, Rabel and Kaeble method. The results of in vitro tests demonstrated that the deposition of Ta-based coatings leads to a decrease in the platelets adhesion and agglomeration ability.
Effect of copper and silver doping on the antibacterial properties of magnetron-sputtered aluminium oxide coatings
Authors: Donkov N , Zykova A , Safonov V , Dudin S , Yakovin S , Kussovski V , Avramov L
Published: June 2020

Ag- and Cu- doped aluminium oxide coatings were deposited by magnetron sputtering and their structure and composition were analyzed by means of scanning electron microscopy (SEM) and photoelectron spectroscopy (XPS). The coatings’ antimicrobial properties and efficiency against representative bacterial strains of Gram-positive, Gramnegative bacteria and fungi were analyzed by in vitro tests. The results of the study suggest that Ag and Cu doped aluminium oxide coatings possess a combined bactericidal effect and demonstrate a promising potential for various medical applications.