bluuebunny/crossref_metadata_2025 huggingface dataset:
Ervi, the intraspecific Barbera x Croatina crossbreed: first growing and winemaking experiences in Lombardia (northwest of Italy)
Authors: Vercesi Alberto , Garavani Alessandra , Poni Stefano , Gatti Matteo
Published: April 2019

Barbera and Croatina are the two most important grapevine varieties characterizing wines from several districts in North-West of Italy; they coexist on the hilly territories sited south of the Po river (historically known as “western-cispadana” area) where they are also blended together to obtain local wines such as Buttafuoco and Rosso Oltrepo Pavese in Lombardia, and Gutturnio in Emilia Romagna. Ervi is an intraspecific crossbreed between Barbera and Croatina performed in the ‘70s and selected over the last decades in order to improve some agronomical traits of both parents. The present study represents the first characterization of development, production and enological performance of the cv. Ervi in Lombardia and, more specifically, in the Oltrepo Pavese wine district. Long-term results related to a field-based assessment as well as the sensory profiling of wines produced at a micro scale are reported. When compared to Barbera and Croatina, Ervi shows improved productivity respect to Croatina and a better composition as compared to both its parents. Results recommend the introduction of the cv. Ervi in Lombardia for the production of high quality red wines.
Carbon partitioning between shoot organs following early leaf removal
Authors: Sabbatini Paolo , Acimovic Dana , Frioni Tommaso , Tombesi Sergio , Sivilotti Paolo , Palliotti Alberto , Poni Stefano
Published: April 2019

In grapevines, basal leaf removal at bloom often induces a reduction of fruit set. The effect is related to a reduction in carbon availability for different plant organs competing for photosynthates. To understand and quantify carbon allocation among major sink organs following the early basal leaf removal, the effect of early basal defoliation was studied in Pinot noir grapevines. The experiment was performed in Michigan, a cool climate viticultural region, and three levels of defoliation were imposed at full bloom: (1) no leaves removed (DF-0); (2) six leaves removed from six basal nodes (DF-6); and (3) ten leaves removed from ten basal nodes (DF-10). A week after the defoliation treatment,13C pulsing was executed to the defoliated shoots. Photosynthesis (Pn), carbon distribution, fruit set, vine performance and basic fruit composition were measured. LR treatments induced higher Pnwhen compared to LR-0. The highest13C allocation (%) was recorded in the shoot apex of the LR-10 treatment and LR-10 had the lowest percentage of13C transported to the cluster, with a reduced fruit set of about 60% when compared to LR-0. The severity of leaf removal reduced significantly fruit set and increased shoot apex sink strength at the expense of the cluster.
Effects of leaf removal on aromatic precursor dynamics during maturation of Ribolla Gialla grapes (Vitis viniferaL.)
Authors: Voce Sabrina , Pizzamiglio Giulia , Mosetti Davide , Bigot Giovanni , Lonardi Andrea , Comuzzo Piergiorgio , Sivilotti Paolo
Published: April 2019

Leaf removal is a viticultural practice applied in order to improve fruit-zone microclimate and berry quality. The aim of this trial was to evaluate the effect of post-flowering leaf removal on maturation and biosynthesis of terpenes and and C13-norisoprenoids in Ribolla Gialla grapes. In the seasons 2015 and 2016, basic maturation parameters were nearly unaffected by leaf removal. Contrarily, in the second season, 2016, one week before harvest, the concentration of several aroma compounds was significantly improved by leaf removal. In conclusion, the trial here showed that leaf removal improves the concentration of aroma compounds in the grapes, but the selection of the date of harvest is more crucial in order to maintain them during vinification.
Impact of delayed winter pruning on phenology and ripening kinetics of Pinot Noir grapevines
Authors: Gatti Matteo , Frioni Tommaso , Garavani Alessandra , Biagioni Arianna , Poni Stefano
Published: April 2019

Climate change impacts viticulture with even stronger effects on sparkling wines. Innovative cultural practices represent effective short-term solutions. Among these, postponement of winter pruning later than budburst delayed both vegetative and reproductive cycles as well as technological maturity of several varieties from different wine regions. This research aims to assess the impact of delayed winter pruning on grapevine performance as a function of training system.

The trial was carried out in a Pinot Noir vineyard sited at 385 m asl in Central Italy. Delayed winter pruning was performed when unpruned canes had shoots showing three unfolded leaves (BBCH 13) and compared to standard winter pruning within two separate experiments focused on: i) cane pruning, and ii) spur pruning. Grapevine phenology, vegetative growth, fruit ripening kinetics and productivity of selected vines were assessed over three years. Delayed winter pruning postponed budburst by 20 and 31 days in Guyot and spur pruned cordons, respectively; then, differences diminished over time showing a maximum delay of 17 days at bloom and 7–10 days at harvest. Despite a decrease in yield (ranging from −35 to −47% in cane and spur pruning, respectively), delayed winter pruning increased titratable acidity (40–89%) and reduced sugars (721%) as compared to control vines. Although effects of delayed pruning were stronger in spur pruned vines, delayed winter pruning was effective also on cane-pruned vines, therefore adapting to varieties marked by low basal-node fruitfulness
Effects of delayed winter pruning on vine performance and grape composition in cv. Merlot
Authors: Allegro Gianluca , Pastore Chiara , Valentini Gabriele , Filippetti Ilaria
Published: April 2019

Delaying winter pruning until after budburst is a technique that can retard vine phenological phases and reduce grape sugar concentration at harvest. Given these characteristics, many studies have recently been conducted to verify the ability of pruning after budburst to contrast the negative effects of climate change. In our trial, vines of the cv. Merlot, trained to a VSP spur pruned cordon, were pre-pruned leaving 8 nodes per shoot and hand finished when the shoots sprouted by the apical nodes were at BBCH13 (treatment LP) and BBCH18 stage (treatment VLP). Vines refinished during winter were used as control (WP). Anthocyanins and tannins of skin and seeds were analysed after both exhaustive extraction (total content) and extraction conducted with a hydroalcoholic solution (extractable portion). Vines refinished after budburst showed reduced leaf area, yield, cluster and berry weights; technological maturity of these vines was delayed as lower sugar concentration and pH were observed at harvest. Treatment VLP had a stronger effect than LP on these parameters. Considering phenolic compounds, the skin and seed tannin concentration increased only in VLP, while no effect was found on anthocyanins. In conclusion, delaying pruning until after budburst revealed interesting prospects for contrasting the negative effects of climate change.
Effect of early leaf removal on Sangiovese (Vitis vinifera L.) under thermal excess and drought conditions
Authors: Puccioni Sergio , Martini Giordano , Zombardo Alessandra , Perria Rita , Pagano Mario , Valentini Paolo , Storchi Paolo
Published: April 2019

The early defoliation of the fruiting area is a technique that offers considerable advantages both in relation to the quality of grapes and to pest control; on the other hand, when a very warm summer occurs, the risk of grape sunburn may increase. This paper reports the results of a pre-flowering defoliation trial carried out in the province of Arezzo (Italy) in 2017, an exceptionally hot and dry year. The results confirmed the validity of this technique in limiting yield while achieving a concurrent higher concentration of phenolic compounds without increasing the risk of burns and radiative damages of grapes.
Effects of treatments with ozonated water in the vineyard (cv Vermentino) on microbial population and fruit quality parameters
Authors: Modesti Margherita , Baccelloni Simone , Brizzolara Stefano , Aleandri Maria Pia , Bellincontro Andrea , Mencarelli Fabio , Tonutti Pietro
Published: April 2019

Ozone (O3) is currently employed in wineries as a sanitizing agent and is used to control microbial growth and infection. This molecule decomposes spontaneously to oxygen upon application and the use of ozonated water can represent an alternative for the control of pathogens in the vineyard. Entire canopies of Vitis vinifera (cv Vermentino) plants have been sprayed throughout the vegetative growth with water saturated with O3 to assess the effects of these treatments in reducing the microorganism population, and to evaluate if and how the oxidative stress, induced in the plant by this strong oxidizing agent, affects fruit development, the activity of the cellular antioxidant system, and the production of aromas by the grape berries at ripening. Ozonated water treatments resulted in a partial control of microorganism population, especially considering fungi. Furthermore, the treatments induced a slight delay in the technological maturity of grapes, a significant increase in antioxidant capacity and changes of aroma profile of the grapes at harvest, with an accumulation of monoterpenes. In general, ozonized water treatments showed promising results and seem to be a feasible protocol to be applied in the vineyard in order to reduce the use of chemicals.
Combined influence of bud load and bud position along the cane on vegetative and reproductive parameters of grape cv. Grillo
Authors: Di Lorenzo Rosario , Pisciotta Antonino
Published: April 2019

Cultivar Grillo vines are characterized by problems with flower biology (the fertility of basal buds) and fructification (millerandage). In this study, to manage the variability in bunch weight with winter pruning and to program others canopy management practices (i.e. early defoliation), three different treatments of bud load were set up by leaving the cane with 3, 6 or 10 buds. The effects of bud load and cane length were studies regarding bud fertility, shoot leaf area, and the number of flowers and berries, as well as the relationship between leaf area and percentage of fruit set, leaf area/flower and percentage of fruit set, and the number of hens and chicks berries. Shoots in the distal position had higher values of fertility and inflorescences with a greater number of flowers, while no ‘apical’ effect of the buds emerged. A good relationship was found between fruit set and the number of flowers, leaf area at flowering and yield, and square centimeters/flower and percentage of fruit set. Cane length was found to be a valid tool for managing bunch weight variability; the value of the leaf area/flower can be used to program early defoliation practice carried out to manage berry set.
Analysis and impact of recent climate trends on grape composition in north-east Italy
Authors: Cogato Alessia , Meggio Franco , Pirotti Francesco , Cristante Alberto , Marinello Francesco
Published: April 2019

Climate is the most relevant factor influencing the ripening of high quality grapes to produce a given wine style. This notion should be taken into account, given the increase of extreme weather events (EWE) related to climate change. Under this evolving climate scenario, North-East Italian wine regions have seen a recent expansion, potentially disregarding optimal planting choices. The use of marginal land, indeed, could lead to the establishment of vineyards in areas where it is not possible to take advantage of the best row orientation, slope and aspect. Under these conditions, the consequences of some EWE may be more severe. The objective of this study is to verify whether planting options in combination with climate conditions, may affect yield and fruit quality. An area localised in Northern Italy was analysed for row orientation and slope, taking advantage of QGIS tools. The area was also examined for climate conditions, using weather conditions and climate indices. Such variables were combined with 10-year yield and must composition of four varieties (Chardonnay, Pinot Gris, Merlot and Glera) by using linear regression. The paper reports the most significant relationships between climatic conditions and grapevine composition. The results showed high positive correlation between sugar concentration and the number of frost days during the year in three varieties. The sugar content was positively correlated with the relative humidity in June in three varieties and negatively correlated with the number of days with a temperature >25°C during the month of June in two varieties. The content of tartaric acid showed high correlations with thermal indices of May in all varieties.
Les nouvelles technologies de reproduction
Authors: Merchant Jennifer
Published: April 2019

L’objectif de cette contribution est d’analyser à l’aune d’une perspective outre-Atlantique les questions soumises à la prochaine révision française des lois dites de bioéthique, notamment dans le domaine des nouvelles technologies de reproduction (NTR). Les questions éthiques, juridiques, sociales, économiques et politiques soulevées par les NTR remettent en cause le modèle bioéthique français conçu en 1994 et, à cet effet, il est intéressant de voir comment, aux États-Unis, ces questions ont été abordées.
Bébés CRISPR
Authors: Jordan Bertrand
Published: April 2019

Analysing the data recently presented by Jiankui He and assuming that it is authentic shows that the goal of abolishing the expression of CCR5 may have been reached for one of the resulting twins, although this remains to be proven. However, the canonical delta32 mutation has not been achieved. The various preliminary experiments and controls give some confidence that major off-target modifications have not occurred; again, this is difficult to exclude. Clearly, the requirements of perfect technical mastery of the process have not been met, to say nothing of the requirements for complete transparency and full societal approval.
Régulation du métabolisme lipidique par les hormones thyroïdiennes
Authors: Hottin Catherine , Simoneau Bastien , Le Stunff Hervé
Published: April 2019

Pour la troisième année, dans le cadre du module d’enseignement « Physiopathologie de la signalisation » proposé par l’université Paris-sud, les étudiants du Master « Biologie Santé » de l’université Paris-Saclay se sont confrontés à l’écriture scientifique. Ils ont sélectionné 8 articles scientifiques récents dans le domaine de la signalisation cellulaire présentant des résultats originaux, via des approches expérimentales variées, sur des thèmes allant des relations hôte-pathogène aux innovations thérapeutiques, en passant par la signalisation hépatique et le métabolisme. Après un travail préparatoire réalisé avec l’équipe pédagogique, les étudiants, organisés en binômes, ont ensuite rédigé, guidés par des chercheurs, une Nouvelle soulignant les résultats majeurs et l’originalité de l’article étudié. Ils ont beaucoup apprécié cette initiation à l’écriture d’articles scientifiques et, comme vous pourrez le lire, se sont investis dans ce travail avec enthousiasme ! Deux de ces Nouvelles sont publiées dans ce numéro, les autres l’ont été dans les numéros précédents.
Hétéro-nucléation de cristaux de neige carbonique au débouchage d’une bouteille de champagne
Authors: Liger-Belair Gérard , Cordier Daniel
Published: April 2019

Le débouchage d’une bouteille de champagne permet de revisiter la physique des changements de phase qui accompagnent la détente adiabatique du volume de gaz sous pression dans le col de la bouteille.

On s’intéresse ici aux phénomènes de condensation qui apparaissent dans le sillage du bouchon qui saute, en fonction de la température de ladite bouteille. Pour les bouteilles stockées à 20 °C, un panache bleu azur apparait dans le col de la bouteille et dans le sillage du bouchon qui saute. Il s’évanouit au bout de quelques millisecondes.

On montre que ce panache bleu est la signature de la transformation en cristaux de neige carbonique et par nucléation hétérogène, de la vapeur de dioxyde de carbone présente dans le col de la bouteille.
Thrombose und Antikoagulation bei Tumorpatienten
Authors: Zydek Barbara , Lindhoff-Last Edelgard
Published: April 2019

Bei bis zu 20 % aller Krebspatienten treten venöse Thromboembolien im Krankheitsverlauf auf. Patienten mit aktiver Krebserkrankung, die eine venöse Thrombose erleiden, weisen ein besonders hohes Rezidivthromboserisiko auf und benötigen daher bereits nach dem ersten venösen Thromboseereignis eine langfristige Antikoagulation. Neben dem erhöhten Erst- und Rezidivthromboserisiko besteht jedoch auch gleichzeitig ein erhöhtes Blutungsrisiko unter Antikoagulation. Aktuelle Leitlinien empfehlen niedermolekulare Heparine (NMH) für 3–6 Monate nach Auftreten einer venösen Thrombose bei Patienten mit aktiver Krebserkrankung, da diese bei vergleichbarem Blutungsrisiko zu niedrigeren Rezidivthromboseraten im Vergleich zu Vitamin-K-Antagonisten führen. In 2 aktuell publizierten Studien wurde erstmals untersucht, inwiefern direkte orale Antikoagulantien (DOAK) anstelle der NMH eine Therapieoption bei Malignompatienten mit venösen Thrombosen darstellen könnten. Während Thromboserezidive unter DOAK-Therapie seltener auftraten als unter Therapie mit niedermolekularen Heparinen, kam es unter DOAK-Therapie häufiger zu schweren Blutungen, insbesondere gastrointestinalen Blutungen. DOAK stellen daher inzwischen eine neue Alternative zum bisherigen Goldstandard NMH in der Antikoagulation dar, sollten jedoch bei gastrointestinalen Tumoren mit Zurückhaltung und nur nach eingehender Aufklärung des Patienten eingesetzt werden.
Embolischer Schlaganfall unbekannter Quelle (ESUS)
Authors: Ziemann Ulf
Published: April 2019

ESUS (embolischer Schlaganfall unbekannter Quelle) wurde als pathogenetisches Konzept mit der Erwartung entwickelt, dass eine orale Antikoagulation wirksamer als eine Thrombozytenfunktionshemmung einen erneuten Schlaganfall verhindern kann. Zwei pivotale Phase-III-Studien (NAVIGATE ESUS, RE-SPECT ESUS) haben diese Erwartung nicht bestätigt. ESUS ist keine singuläre pathogenetische Entität. Zukünftige Konzepte müssen das berücksichtigen, um einer personalisierten Therapie den Weg zu ebnen.
Was gibt es Neues zum Aspirin?
Authors: Hoffmeister Hans Martin
Published: April 2019

Im Gegensatz zur Sekundärprophylaxe verschiedenster kardiovaskulärer Erkrankungen ist die Bedeutung von Aspirin in der Primärprophylaxe nicht eindeutig geklärt. Problematisch für die Klärung dieser Fragestellung ist bereits die Trennung zwischen Primär- und Sekundärprophylaxe. In den letzten Monaten sind mehrere Studien erschienen, die sich mit Aspirin in der Primärprohylaxe befasst haben: Die ARRIVE-Studie, die ASCEND-Studie und die ASPREE-Studie. Insgesamt zeigen diese Studien, dass Aspirin 100 mg/Tag bei Personen mit einem niedrigen oder niedrig-mäßigen Risiko keinen durchschlagenden positiven Effekt in der Primärprophylaxe kardiovaskulärer Erkrankungen besitzt. Dagegen manifestieren sich die mit Aspirin-assoziierten Nebenwirkungen unabhängig vom kardiovaskulären Risiko. Anders ist die Situation bei Personen mit hohem kardiovaskulären Risiko: Hier gibt es in der Regel zu Studienbeginn bereits fortgeschrittene vaskuläre und andere Veränderungen. In dieser noch nicht abschließend eindeutig zu beurteilenden Situation sollten der Patientenwunsch und das individuelle Blutungsrisiko berücksichtigt werden.
Early and Midterm Outcomes of Valve-Sparing Aortic Root Replacement—Reimplantation Technique
Authors: Cevasco Marisa , McGurk Siobhan , Yammine Maroun , Sharma Lokesh , Ejiofor Julius , Norman Anthony , Singh Michael , Shekar Prem
Published: April 2019

Background Valve-sparing aortic root replacement (VSARR) is an increasingly popular alternative to traditional aortic root replacement for aortic root aneurysm disease with a normal aortic valve. We evaluated the early and midterm outcomes of VSARR—reimplantation technique (VSARR-RT) done at a single institution over a decade.

Materials and Methods We performed a retrospective study of all patients who underwent VSARR-RT between January 2004 and July 2014.

Results A total of 85 patients underwent VSARR-RT. Median time to latest echocardiographic follow-up was 4 years (range: 15–72 months). Total observation time was 491 patient years. Mean age was 44.6 ± 14.3 years, and 13 (15%) were women. Thirty-nine (46%) patients had a connective tissue disorder and 6 (7%) had a bicuspid aortic valve. Thirty-three (39%) patients underwent concomitant procedures, including coronary artery bypass grafting (n = 9, 11%), mitral valve repair (n = 8, 9%), and aortic hemi-arch replacement (n = 7, 8%). There were no operative deaths or in-house mortality and no postoperative strokes. Kaplan-Meier analysis demonstrated survival of 99% (95% confidence interval [CI]: 97–100%) at 2 years and 98% (95% CI: 97–100%) at 8 years. Freedom from reoperation was 95.8% (95% CI: 91.2–100%) at 8 years. Freedom from endocarditis was 100% at 8 years. At the last echocardiographic follow-up, 95% of patients were free of severe aortic regurgitation (AR) and 82% free of moderate AR. Of the four patients who had severe AR, three underwent reoperations and received prosthetic valves and one is being clinically monitored.

Conclusion This study reports early and midterm outcomes after VSARR-RT at our institution, including those patients who underwent a VSARR-RT procedure combined with other procedures. Further follow-up remains necessary to determine long-term outcomes.
Syphilitic Aortic Aneurysm in the Third Millennium
Authors: Del Re Federico , Falcetta Giosuè , Pratali Stefano , Belgio Beatrice , Pucci Angela , Bortolotti Uberto
Published: April 2019

A 69-year-old man presented with precordial pain and a dilated ascending aorta with the suspicion of an intramural hematoma. At emergency operation, the aorta appeared grossly thickened with diffuse intimal scarring. Retrospectively, the patient tested positive to serologic screening for syphilis with histologic findings also compatible with a syphilitic aortitis.
Esophageal Atresia and Thenar Hypoplasia Associated with Asymmetric Crying Face
Authors: Mutlu-Albayrak Hatice , Damar Çağrı , Gürbüz Gürkan
Published: April 2019

Asymmetric crying face (ACF) is a minor congenital anomaly that is often associated with a high rate of major malformations and may be considered an indication of a syndromic clinical presentation. Here, we report a 21-month-old male presenting with left- sided ACF, thenar hypoplasia, and esophageal atresia. Ultrasonographic images of the volar surface of the left hand evidenced the absence of muscle tissue around the thenar prominence at the level of the first metacarpal bone. No pathogenic copy number variation was detected on array-comparative genomic hybridization analysis (CGH). The association of esophageal atresia, thenar hypoplasia, and ACF has not been reported before. We discuss the possibility of a distinct association or of a sequence of anomalies associated with ACF.
Effects of the introduction of a chromium oxide monolayer at the C60/Fe(001) interface
Authors: Brambilla Alberto , Picone Andrea , Achilli Simona , Fratesi Guido , Lodesani Alessandro , Calloni Alberto , Bussetti Gianlorenzo , Zani Maurizio , Finazzi Marco , Duò Lamberto , Ciccacci Franco
Published: April 2019

The introduction of a two-dimensional oxide layer at the interface between an organic semiconductor and a ferromagnetic metal (spinterface) can help in tailoring the formation of spin-polarized hybridized interface states. Here, we consider the case of a Cr4O5 monolayer at the C60/Fe(001) interface, which is already known to feature the occurrence of spin-polarized states in the fullerene molecules. In this work, we employ scanning tunneling microscopy/spectroscopy and photoemission spectroscopy to show that the C60/Cr4O5/Fe(001) spinterface is characterized by the formation of a well-ordered fullerene monolayer and of strongly hybridized interface states. These experimental results are discussed in terms of state-of-the-art ab initio calculations of the structural, electronic, and magnetic properties at the interface.
Studies of spin transport in fullerene films
Authors: Liu Haoliang , Wang Jingying , Chanana Ashish , Vardeny Z. V.
Published: April 2019

The fullerene C60, C70, and C84 molecules, that are composed of ∼99% naturally abundant 12C having spinless nuclei, are considered to have miniature hyperfine interaction and also weak intrinsic spin-orbit coupling (SOC) due to the light carbon atoms. However, it has been theoretically predicted that the curvature of the fullerene molecules may increase the SOC due to the induced hybridization of the π and σ electrons on the carbon atoms that reside on the fullerene molecule surface. In this work, we have measured the spin diffusion length in films of C60, C70, and C84 in NiFe/fullerene/Pt trilayer devices, where pure spin current is injected into the fullerene film at the NiFe/fullerene interface via spin pumping induced by microwave absorption at ferromagnet resonance conditions, and subsequently detected at the fullerene/Pt interface as electrical current via the inverse spin-Hall effect. The obtained spin diffusion lengths in the fullerene films are of the order of 10 nm and increase from C60 to C84 in which the fullerene molecule’s curvature decreases; this finding validates the existence of curvature-induced SOC in the fullerenes. Our results deepen the understanding of spin transport in fullerene films and may benefit the design of molecular spintronic devices.
Interband transitions in narrow-gap carbon nanotubes and graphene nanoribbons
Authors: Hartmann R. R. , Saroka V. A. , Portnoi M. E.
Published: April 2019

We use the robust nearest-neighbor tight-binding approximation to study the same footing interband dipole transitions in narrow-bandgap carbon nanotubes (CNTs) and graphene nanoribbons (GNRs). It is demonstrated that curvature effects in metallic single-walled CNTs and edge effects in gapless GNRs not only open up bandgaps, which typically correspond to THz frequencies, but also result in a giant enhancement of the probability of optical transitions across these gaps. Moreover, the matrix element of the velocity operator for these transitions has a universal value (equal to the Fermi velocity in graphene) when the photon energy coincides with the bandgap energy. Upon increasing the excitation energy, the transition matrix element first rapidly decreases (for photon energies remaining in the THz range but exceeding two bandgap energies, it is reduced by three orders of magnitude), and thereafter it starts to increase proportionally to the photon frequency. A similar effect occurs in an armchair CNT with a bandgap opened and controlled by a magnetic field applied along the nanotube axis. There is a direct correspondence between armchair GNRs and single-walled zigzag CNTs. The described sharp photon-energy dependence of the transition matrix element, together with the van Hove singularity at the bandgap edge of the considered quasi-one-dimensional systems, makes them promising candidates for active elements of coherent THz radiation emitters. The effect of Pauli blocking of low-energy interband transitions caused by residual doping can be suppressed by creating a population inversion using high-frequency (optical) excitation.
The design and kinetostatic modeling of 3PPR planar compliant parallel mechanism based on compliance matrix method
Authors: Yu Hongtao , Zhang Chi , Yang Bao , Chen Si-Lu , Fang Zaojun , Li Rong , Yang Guilin
Published: April 2019

Compliant Parallel Mechanisms (CPMs) are widely used in micro/nano-positioning systems. In recent years, CPMs with a large travel range (≥1 mm) have been getting increasing attention. In this paper, a 3 Prismatic-Prismatic-Revolute (3PPR) planar CPM with a motion range of 5 mm × 5 mm × 5° is designed. The mechanical structure is characterized by the application of three joints based on a compliant four-bar mechanism, which guarantees the motions along/about the specific axes to improve motion accuracy. A double blade rotary pivot is served as a revolute joint to decrease the drift of pivot and produce a large rotation range without loss of compactness. The compliance matrix method is implemented to kinetostatic modeling, and the input coupling effect, which is always neglected or modeled complicatedly in 3-Degree-of-Freedom planar CPMs, is involved with the principle of superposition. The feasibility of the mechanical design and the accuracy of the developed kinetostatic model are validated by finite element analysis and experiments, respectively. The results indicate that the modeling method based on the compliance matrix method is concise, effective, and accurate, and can be extended to other more complicated CPMs.
Direct and indirect optical transitions in bulk and atomically thin MoS2 studied by photoreflectance and photoacoustic spectroscopy
Authors: Kopaczek J. , Zelewski S. J. , Polak M. P. , Gawlik A. , Chiappe D. , Schulze A. , Caymax M. , Kudrawiec R.
Published: April 2019

Optical transitions in atomically thin MoS2 samples made by sulfidation of a metallic molybdenum layer have been studied by photoreflectance (PR) and photoacoustic (PA) spectroscopy. The obtained spectra are compared with PR and PA spectra of bulk MoS2. It is shown that the absorption edge observed in the PA spectrum shifts to blue when moving from the bulk MoS2 to the atomically thin MoS2 layers, whereas the direct optical transitions at the K point of the Brillouin zone (A and B transitions), which are observed in the PR spectrum, do not shift spectrally in a significant manner. On the other hand, the AH transition, which is related to the direct optical transition at the H point of the Brillouin zone and is typical of bulk MoS2, is not observed for atomically thin MoS2 layers. Moreover, a strong and broad PR resonance related to the band nesting (C transition) is identified in the PR spectra of studied samples. In this case, C and CH transitions are observed for bulk MoS2, while only a C transition is observed for atomically thin MoS2.
High resolution quantitative multi-species hydrocarbon gas sensing with a cw external cavity quantum cascade laser based spectrometer in the 6–11 μm range
Authors: Heinrich Robert , Popescu Alexandru , Strzoda Rainer , Hangauer Andreas , Höfling Sven
Published: April 2019

We report multi-species spectroscopy of hydrocarbons with a continuous wave external-cavity quantum cascade laser based spectrometer providing tunability from 6 to 11μm to measure direct absorption spectra of the first 7 alkanes and their mixtures. The gas spectra were acquired in the range from 1440 to 1480cm−1 at a reduced pressure of 50 mbar and at a temperature of 323 K. By linearization of the measured wavelengths with a custom-made highly temperature stable air spaced etalon, a high spectral accuracy of ±0.001cm−1 is achieved for the whole spectral range. The simultaneous high resolution of 0.001cm−1 yields spectra of unprecedented richness of detail for the heavier alkanes (C3–C5) and allows the discrimination of narrow spectral features for the lighter ones (C1–C2). Thereby, the measured spectra reveal the influences of collisional broadening effects among the measured species. Quantitative spectroscopic multi-species gas sensing relies on the comprehension of the extent of spectral broadening. Studying the spectral broadening in combination with highly accurate reference spectra is mandatory for highly sensitive and specific multi-species gas analyzers. The quantitative results that can be obtained with our approach are presented for an exemplary calibrated mixture of all 7 components and reveal an absolute accuracy below 0.5 vol. % for the determination of the mole fraction of each gas.
High-enthalpy models for boundary-layer stability and transition
Authors: Miró Miró Fernando , Beyak Ethan S. , Pinna Fabio , Reed Helen L.
Published: April 2019

The prediction of the transition dynamics of high-enthalpy boundary-layer flows requires appropriate thermodynamic and transport models. This work quantifies the influence of transport, diffusion, collision, equilibrium, and chemical-kinetics modeling on the stability characteristics and the estimated transition-onset location of canonical boundary layers. The computed behavior of second-mode instabilities is consistently highly dependent on the base-flow’s boundary-layer height. The Blottner-Eucken-Wilke transport model is seen to underpredict the boundary-layer height, hence overpredicting the growth-rate distribution and forecasting the transition onset to occur ∼38% sooner. The other low-order transport models (Brokaw and Yos) returned very close results to the most-accurate Chapman-Enskog model. The use of Gupta et al.’s collisional data instead of Wright et al.’s more accurate data is also seen to predict the transition onset to occur ∼8% closer to the leading edge. The modeling of mass diffusion and the chemical-equilibrium constant is observed to have a negligible influence on the boundary-layer height and transition-onset-location estimations (less than 5% and 2%, respectively). For the analyzed conditions, all chemical models predict the same transition-onset location (±1%); since at the streamwise positions where perturbations have reached sufficiently large amplitudes, the flow is close to equilibrium and thus independent of the reaction rates. The use of different transport models for the perturbation terms, while maintaining the same model for the basic state, leads to negligible differences in the predictions. This further reinforces the thesis that the boundary-layer height calculation is paramount to the simulation of the development of second-mode instabilities.
Comparison of directionally outcoupled photoluminescences from luminous layers on Si and Al nanocylinder arrays
Authors: Murai Shunsuke , Saito Motoharu , Kawachiya Yuki , Ishii Satoshi , Tanaka Katsuhisa
Published: April 2019

An array of nanocylinders can modulate photoluminescence (PL) of emitters via simultaneous excitation of local resonances and light diffractions. Regarding the local resonance, localized surface plasmon polaritons (LSPP) of metals has been commonly applied, while the Mie resonance of dielectrics can also be a candidate. Since these two resonances are excited in different classes of materials, experimental comparisons between their enhancement efficiencies are rarely made. In this study, we fabricated periodic arrays of Si and Al nanocylinders with the identical design and compared their PL outcoupling abilities. We deposited ultraviolet (UV)-absorbing and highly luminous dielectric films on the arrays and observed enhanced PLs from the films on the nanocylinder arrays upon a UV laser excitation. The optical transmission with varied incident angles revealed that the dispersion of the hybrid mode of diffraction with the Mie resonance in the Si nanocylinder array was sharper than that of the diffraction-LSPP hybrid in the Al nanocylinder array. The PL enhancement by the Si nanocylinder array was more selective both spectrally and spatially than that by the Al nanocylinders, which could be attributed to the difference between the mode profiles. Our findings experimentally verified the advantage of choosing Si as a constituent of the cylinder array to provide highly directional light sources.
Construction of knotted vortex tubes with the writhe-dependent helicity
Authors: Xiong Shiying , Yang Yue
Published: April 2019

We propose a feasible method for constructing knotted vortex tubes with the finite thickness and arbitrary complexity and develop an accurate algorithm to implement this method in numerical simulations. The central axis of the knotted vortex tube is determined by the parametric equation of a given smooth and non-degenerate closed curve. The helicity of the vortex tube is only proportional to the writhe of the vortex axis, a geometric measure for coiling of vortex tubes. This vortex construction can facilitate the investigation of the conversion of writhe to twist in the helicity evolution of knotted vortex tubes. As examples, we construct velocity–vorticity fields of trefoil, cinquefoil, and septafoil vortex knots. These vortex knots are used as initial conditions in the direct numerical simulation of viscous incompressible flows in a periodic box. In the evolution of vortex knots from simple flows to turbulent-like flows, all the knots are first untied. Then the vortex topology is invariant and the helicity is almost conserved for the trefoil knot, whereas the helicity decays rapidly during the breakdown and coaxial interactions of pinch-off vortex rings for cinquefoil and septafoil knots.
Origin of resistivity contrast in interfacial phase-change memory: The crucial role of Ge/Sb intermixing
Authors: Saito Yuta , Kolobov Alexander V. , Fons Paul , Mitrofanov Kirill V. , Makino Kotaro , Tominaga Junji , Robertson John
Published: April 2019

Phase-change memories based on reversible amorphous-crystal transformations in pseudobinary GeTe-Sb2Te3 alloys are one of the most promising nonvolatile memory technologies. The recently proposed superlattice-based memory, or interfacial phase-change memory (iPCM), is characterized by significantly faster switching, lower energy consumption, and better endurance. The switching mechanism in iPCM, where both the SET and RESET states are crystalline, is still contentious. Here, using the ab initio density functional theory simulations, a conceptually new switching mechanism for iPCM is derived, which is based on the change in the potential landscape of the bandgap, associated with local deviations from the pseudobinary stoichiometry across the van der Waals gaps and the associated shift of the Fermi level. The crucial role in this process belongs to Ge/Sb intermixing on the cation planes of iPCM. These findings offer a comprehensive understanding of the switching mechanisms in iPCM and are an essential step forward to the insightful development of phase-change memory technology.
Propagation behavior of microsecond pulsed positive streamer discharge in water
Authors: Wen Xiaoqiong , Xue Xiaodong , Liu Xinghui , Li Jingsen , Zhou Yibing
Published: April 2019

The propagation behavior of microsecond pulsed positive streamer discharge in low-conductivity water was investigated via photography and shadowgraph imaging. Eight successive images were acquired from a single discharge pulse, allowing for the study of the overall streamer propagation behavior; both the emission and the shadow emission-combined images of the streamer discharge were obtained. The experimental results confirmed that the streamer at the later stage of propagation is weak in illuminance and has a propagation velocity of ∼2 km/s, which is slower than that of the secondary streamer (∼30 km/s) but as fast as that of the primary one (∼2 km/s). The streamer filaments propagated stepwise in water with two different behaviors: (1) a filament head launches a shock wave, quietly moves a short distance (or short time) ahead, and then launches the next shock wave and (2) a filament head pauses for a relatively long time while the filament illuminance decays, then restarts launching shock waves and moving ahead, and the decayed filament illuminates again. These pause and reactivation behaviors randomly alternate among the filaments, resulting in different shock-wave patterns and filament illuminance. The drop of the propagation velocity from ∼30 km/s to ∼2 km/s and the many irregular spikes in the discharge current waveform can be associated with this alternation of pause and reactivation behaviors of the filament heads.
Relationship between band-offset, gate leakage current, and interface states density at SiO2/4H-SiC (000-1) interface
Authors: Indari Efi Dwi , Yamashita Yoshiyuki , Hasunuma Ryu , Nagata Takahiro , Ueda Shigenori , Yamabe Kikuo
Published: April 2019

We investigated the relationship between the band-offset, the gate leakage current, and the interface states density on SiO2/4H-SiC (000-1) structures via hard x-ray photoelectron spectroscopy and electrical measurements. From the observed band-offset, we found that conduction band offset (ΔEc) depended on the oxidation procedure, but valence band-offset (ΔEv) did not. In addition, ΔEv was larger than ΔEc, indicating that electron tunneling was more predominant than hole tunneling. SiO2 prepared by a dry oxidation procedure exhibited the highest gate leakage current onset and the highest interface states density and the largest ΔEc, whereas a wet oxidation procedure produced the lowest gate leakage current onset, the lowest interface states density, and the smallest ΔEc. Oxygen annealing after wet oxidation effectively increased gate leakage current onset, which increased the interface states density and the ΔEc. These results were related to hydrogen atoms and carbon related defects at the SiO2/4H-SiC (000-1) interface.
Noncontact photoacoustic angiography with an air-coupled ultrasonic transducer for evaluation of burn injury
Authors: Ma Haigang , Xiong Kedi , Wu Junwei , Ji Xuanrong , Yang Sihua
Published: April 2019

In vivo identification of viable and thermally coagulated blood in a burn wound can be used to profile the type, extent, and site of the burn, thus assisting the removal of necrotic tissue in preparation for skin grafts. Recently, intensive research on photoacoustic imaging (PAI) has been conducted to evaluate burn injury. However, most PAI systems usually take the approach of direct physical contact of an acoustic detector or an impedance matching medium with the vulnerable burned skin, which exposes significant limitations on the diagnosis of burn injuries. Here, we present a noncontact PAI system, based on a custom designed air-coupled ultrasonic transducer, enabling in vivo noncontact vasculature to be imaged without contrast agents. Using the natural difference in light absorption between coagulated and non-coagulated blood at the wavelength of 532 nm, this PAI system possesses an immanent advantage to discriminate viable and thermally coagulated blood in burned tissues. Phantom experiments and burned rabbit's skin imaging have been implemented to demonstrate that the noncontact PAI technique could be valuable in the adjuvant diagnosis and observation of burns.
Operation of YBCO kinetic-inductance bolometers for outer solar system missions
Authors: Chakrabarty A. , Lindeman M. A. , Bumble B. , Kleinsasser A. W. , Holmes W. A. , Cunnane D.
Published: April 2019

We developed superconducting kinetic inductance bolometers (KIBs) for hyperspectral imaging in outer solar system missions. Each bolometer is a microwave L-C resonator that will act as an individual pixel in the focal plane of an imaging Fourier transform infrared spectrometer. Our devices are fabricated from high temperature superconductor yttrium barium copper oxide (YBCO), with a superconducting transition temperature of ∼85 K. The inductors are suspended on thin Si3N4 membranes. Each resonator operates at a unique resonant frequency, and hence, many can be multiplexed on a single feed line using a large number of carrier frequencies. The resonators function as detectors because their resonant frequencies decrease with increasing temperature as the bolometers absorb incident radiation. In this paper, we discuss the thermal properties of a YBCO KIB and its response to signal power to verify that the response is near theoretical predictions.
Analyses for oxygen vacancies in (Na,K)NbO3-series piezoelectric ceramics by soft x-ray emission spectroscopy
Authors: Tanaka Kiyotaka , Takatsuka Sayaka , Nishiyama Hiroshi , Kakimoto Ken-ichi
Published: April 2019

(Na0.55K0.45)NbO3 (NKN) and acceptor-doped (Na0.55K0.45)(Nb1-xZr5x/4)O3 (NKNZ; x = 0.005 and 0.01) piezoelectric ceramics were fabricated by the conventional solid-state reaction method. Both ceramics were applied to a fatigue test for 106 cycles under an electric field at 3 kV/mm with unipolar drive. After the fatigue test, the maximum polarization of NKN and NKNZ (x = 0.005) was decreased by approximately 15 and 5%, respectively. Therefore, we found that the fatigue resistance properties of NKNZ ceramics, which substituted the Nb5+ ion with the Zr4+ ion, were improved. To study fatigue phenomena in piezoelectric ceramics, the chemical bond strength of both ceramics before and after the fatigue test was analyzed by soft X-ray emission spectroscopy (SXES), which has high energy resolution and is suitable for the evaluation of light elements in a local region with the micrometer order. We evaluated the formation of oxygen vacancies in as-sintered, poled, and fatigued ceramics by analyzing a chemical shift of the O Ka(3) peak appeared at approximately 175 eV in the SXES spectra. In NKN ceramics, the O Ka(3) peak was shifted to the higher energy side by the poling treatment and fatigue test. The peak position of fatigued NKN ceramics was close to that of the standard SrTiO3 sample. It was considered that the oxygen vacancies of the fatigued NKN ceramics had accumulated at grain boundaries instead of the oxygen moving. The improvement of the fatigue resistance for the NKNZ ceramics was attributed to the formation of a defect dipole connected with the oxygen vacancy and acceptor Zr ion.
Geometric and anisotropy effects on voltage driven magnetic switching behaviors in nanoscale multiferroic heterostructure
Authors: Song Xiao , Tian Guo , Mehmood Nasir , Hou Zhipeng , Chen Deyang , Fan Zhen , Qin Minghui , Gao Xingsen , Liu Jun-Ming
Published: April 2019

Voltage driven magnetic switching (VDMS) in multiferroic heterostructure is highly demanded for next generation energy efficient high-density memory (e.g. magnetoelectric random access memory) and spintronic devices. For practical applications in large scale integrated device, it is imperative to understand the VDMS behaviors in nanometer scale. In this work, we have investigated the effects of geometric and anisotropy parameters on 180° VDMS behaviors in a model multiferroic heterostructure system consisting of Co nano-ellipse on BiFeO3 films by using micromagnetic simulation. It was revealed that the switching behaviors can be greatly affected by geometric factors, whereby dimension shrinkage and rising aspect ratio of Co nano-ellipse can apparently increase the critical exchange coupling field (hDMcri-field) needed for triggering the VDMS, greatly reducing the watchability of VDMS. To improve the watchability, an external static perpendicular magnetoanisotropy (Kp) can be introduced to reduce the hDMcri-field, whereas too large Kp tends to reorientate the magnetization towards out-of-plane orientation. Moreover, a strategy was also proposed to assist the VDMS by applying an anisotropy pulse, which is able to reduce the hDMcri-field and expand the switching window (e.g. wider range of aspect ratio and overall dimension size) for both in-plane and out-of-plane VDMS. These results may provide some guides for further experimental modulation of VDMS for device applications.
A miniaturized biaxial tensile apparatus based on torsional loading design
Authors: Li Linan , Li Teng , Li Jun , Sun Cuiru , Wang Shibin , Li Chuanwei , Wang Zhiyong
Published: April 2019

A miniaturized biaxial tensile apparatus is presented. Based on a torsional loading design, the total dimensions and weight of the apparatus have been reduced, while the output force has been increased. Owing to the use of four independent stepping motors, the apparatus can realize arbitrary displacement ratios during the loading processes. The apparatus is designed to be applied with a laser scanning confocal microscope realizing in situ mechanical tests. Through a proof-of-principle experiment with an optimized cruciform shaped specimen, the developed biaxial tensile apparatus is proved to be suitable for in situ tests of biaxial stress analysis.
Neutron-rich magnesium undergoes unexpected transitions
Authors: Middleton Christine
Published: April 2019

The structure of an exotic isotope near the edge of stability strays from that of its lower-mass counterparts.
Atlantic water carried northward sinks farther east of previous estimates
Authors: Lopatka Alex
Published: April 2019

The first set of continuous observations in the subpolar North Atlantic challenges the long-held view that the Labrador Sea dominates ocean-circulation variability.