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Transition metal dichalcogenides (TMDs) are key players in the two-dimensional materials nanoarena due to their exquisite optoelectronic properties under a standard environment (room temperature and atmospheric pressure). Nevertheless, as reported in the literature, they may also portray interesting physical properties under different environments. Here, we show two distinct and significant electromechanical modulations in TMD nanosheets which are tuned by the environmental conditions (applied pressure and adsorbents). Using scanning probe microscopy techniques, we modify the environmental conditions and observe steplike rises in the electrical response of all studied TMDs (MoS2, WS2, MoSe2, and WSe2—monolayers and few layers). Ab initio calculations enable full understanding of specific mechanisms behind these electromechanical modulations, which may find important applications in the design of TMD-based environmental sensors.

Despite several theoretically proposed two-dimensional (2D) diamond structures, experimental efforts to obtain such structures are in initial stage. Recent high-pressure experiments provided significant advancements in the field, however, expected properties of a 2D-like diamond such as sp3 content, transparency and hardness, have not been observed together in a compressed graphene system. Here, we compress few-layer graphene samples on SiO2/Si substrate in water and provide experimental evidence for the formation of a quenchable hard, transparent, sp3-containing 2D phase. Our Raman spectroscopy data indicates phase transition and a surprisingly similar critical pressure for two-, five-layer graphene and graphite in the 4–6 GPa range, as evidenced by changes in several Raman features, combined with a lack of evidence of significant pressure gradients or local non-hydrostatic stress components of the pressure medium up to ≈ 8 GPa. The new phase is transparent and hard, as evidenced from indentation marks on the SiO2 substrate, a material considerably harder than graphene systems. Furthermore, we report the lowest critical pressure ( ≈ 4 GPa) in graphite, which we attribute to the role of water in facilitating the phase transition. Theoretical calculations and experimental data indicate a novel, surface-to-bulk phase transition mechanism that gives hint of diamondene formation.

In this work we apply first principles calculations to investigate the flat band phenomenology in twisted antimonene bilayer. We show that the relatively strong interlayer interactions which characterize this compound have profound effects in the emergence and properties of the flat bands. Specifically, when the moiré length becomes large enough to create well defined stacking patterns along the structure, out-of-plane displacements take place and are stabilized in the regions dominated by the AB stacking, leading to the emergence of flat bands. The interplay between structural and electronic properties allows for detection of flat bands in higher twist angles comparable to other two-dimensional materials. We also show that their energy position may be modulated by noncovalent functionalization with electron acceptor molecules.

Low-dimensionality materials are highly susceptible to interfaces. Indeed, intercalation of different chemical species in between epitaxial graphene and silicon carbide (SiC), for instance, may decouple the graphene with respect to the substrate due to the conversion of the buffer layer into a graphene layer. O-intercalation is known to release the strain of such 2D material and to lead to the formation of high structural quality AB-stacked bilayer graphene. Nonetheless, this interface transformation concomitantly degrades graphene electronic transport properties. In this work we employed different techniques in order to better understand the structure of the graphene/SiC interface generated by O-intercalation and to elucidate the origin of the poor electronic properties of graphene. Experimental results revealed the formation of a SiO2 rich layer with a defective transition layer in between it and the SiC, which is characterized by the existence of silicon oxycarbide structures. Scanning tunneling spectroscopy measurements revealed an extensive presence of electronic states just around the Fermi level all over the sample surface, which may suppress the charge carriers mobility around this region. According to theoretical calculations, such states are mainly due to the formation of silicon oxicarbides within the interfacial layer.

Transition metal dichalcogenides (TMDs) possess spin-valley locking and spin-split K/K′ valleys, which have led to many fascinating physical phenomena. However, the electronic structure of TMDs also exhibits other conduction band minima with similar properties, the Q/Q′ valleys. The intervalley K–Q scattering enables interesting physical phenomena, including multivalley superconductivity, but those effects are typically hindered in monolayer TMDs due to the large K–Q energy difference (ΔEKQ). To unlock elusive multivalley phenomena in monolayer TMDs, it is desirable to reduce ΔEKQ, while being able to sensitively probe the valley shifts and the multivalley scattering processes. Here, we use high pressure to tune the electronic properties of monolayer MoS2 and WSe2 and probe K–Q crossing and multivalley scattering via double-resonance Raman (DRR) scattering. In both systems, we observed a pressure-induced enhancement of the double-resonance LA and 2LA Raman bands, which can be attributed to a band gap opening and ΔEKQ decrease. First-principles calculations and photoluminescence measurements corroborate this scenario. In our analysis, we also addressed the multivalley nature of the DRR bands for WSe2. Our work establishes the DRR 2LA and LA bands as sensitive probes of strain-induced modifications to the electronic structure of TMDs. Conversely, their intensity could potentially be used to monitor the presence of compressive or tensile strain in TMDs. Furthermore, the ability to probe K–K′ and K–Q scattering as a function of strain shall advance our understanding of different multivalley phenomena in TMDs such as superconductivity, valley coherence, and valley transport.

Abstract A 39–year–old man came to our attention after being identified as a carrier of the mutation lle68Leu in the transthyretin (TTR) gene, following his father’s diagnosis of cardiac amyloidosis. From then on, the patient underwent periodical follow–up for early detection of target organs involvement, with normal echocardiographic results of blood test and echocardiography. At the age of 41, he was hospitalized after a transient loss of consciousness (TLS) episode while riding a bicycle. The echocardiogram showed normal systolic function with an akinetic basal septum. A coronary angiogram excluded the presence of coronary artery disease. One year later, ECG abnormalities developed, with a new–onset right bundle branch block and posterior fascicular block. The echocardiogram showed a dilated cardiomyopathy with severe left systolic function impairment (ejection fraction 30%). SPECT with bisphosphonate ruled out cardiac amyloidosis. Cardiac MRI was significant for patchy areas of late gadolinium enhancement in the left ventricle. Before the following cardiological evaluation for a possible ICD implantation the patient was again hospitalized after a resuscitated cardiac arrest.Thoracic CT, performed in the emergency department, was significant for hilar lymphadenopathies and pulmonary nodules highly suggestive for sarcoidosis. FDG–PET showed multiorgan phlogistic–infiltrative involvement, including the myocardium. A subsequent hepatic CT–guided biopsy eventually confirmed the diagnosis of sarcoidosis. In secondary prevention, the patient underwent ICD implantation but continued to experience arrhythmic events.

Two-dimensional (2D) materials and their moiré superlattices represent a new frontier for quantum matter research due to the emergent properties associated with their reduced dimensionality and extreme tunability. The properties of these atomically thin van der Waals (vdW) materials have been extensively studied by tuning a number of external parameters such as temperature, electrostatic doping, magnetic field, and strain. However, so far pressure has been an under-explored tuning parameter in studies of these systems. The relative scarcity of high-pressure studies of atomically thin materials reflects the challenging nature of these experiments, but, concurrently, presents exciting opportunities for discovering a plethora of unexplored new phenomena. Here, we review ongoing efforts to study atomically thin vdW materials and heterostructures using a variety of high-pressure techniques, including diamond anvil cells, piston cylinder cells, and local scanning probes. We further address issues unique to 2D materials such as the influence of the substrate and the pressure medium and overview efforts to theoretically model the application of pressure in atomically thin materials.

The fine structure in the spectral lines of the visible fluorescence of Tb

We apply first-principles calculations to address the problem of the formation and characterization of covalently linked porphyrin-like structures. We show that upon pressure a rehybridization process takes place which leads to one-dimensional compounds resembling nanothreads, in which carbon atoms are all 4-fold coordinated. We also show that the resulting nanostructures have metallic character and possess remarkable mechanical properties. Moreover, in the case of porphyrin-metal complexes, we find that the covalently linked structures may be a platform for the stabilization of straight metallic wires.

Scanning probe microscopy and ab initio calculations reveal modifications on the electronic and structural properties of graphene/h-BN heterostructures induced by compression. Using AFM and EFM techniques, with charge injection being made in the heterostructures at different pressures, the charge injection efficiency monotonically decreases with increasing pressure for monolayer-graphene (MLG)+BN heterostructures, indicative of a conductor-insulator electronic transition. Bilayer-graphene (BLG)+BN and trilayer-graphene (TLG)+BN heterostructures show a non-monotonic behavior of charge injection versus pressure, indicative of competing electronic structure modifications. First-principle calculations of these systems indicate a pressure-induced van der Waals-to-covalent interlayer transition, where such interlayer covalent binding, in the presence of water molecules, results in a disordered insulating structure for the MLG + BN case, while it leads to an ordered conducting structure for both BLG + BN and TLG + BN heterostructures. These opposing effects may have a strong influence on graphene/h-BN-based electronic devices and their physics under pressurized environments.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

This study determined the prevalence of fibrinous pericarditis and its correlation with other pluck lesions in 658 batches of pigs from 236 intensive farms located in Northern Italy over a 12-month period. All pigs were slaughtered at 170 kg, and a total 57,943 plucks (approximately 90 pigs/batch) were individually assessed for the presence of fibrinous pericarditis, pneumonia, pleuritis, and liver milk spots. There was no seasonal variation in the prevalence of plucks with fibrinous pericarditis and annual mean prevalence was 5.6% (range, 0-26.3% at batch level; median, 4.71%). Farm of origin, evaluated as a random effect, accounted for 17.7% batch variation. Batches with a high prevalence of fibrinous pericarditis (≥7.7%) had higher prevalences of pleural, pulmonary, and liver lesions than those with low-middle prevalence of pericarditis; high prevalence of pericarditis was predictive of pluck lesions (P0.001). There was a highly significant association between fibrinous pericarditis and severe pleuritis, and 55% of plucks with the highest score for pleuritis also had ongoing fibrinous pericarditis, with a positive correlation at batch level (r

Danbred gilts at about 120 kg were group housed for estrous detection. At detection of estrus, gilts either remained in pens (P) or were re-housed into individual gestation stalls (S) and were inseminated (DS), or not (SC), with a dose of frozen/thawed dead semen. Groups were P-DS (n = 81), P-SC (n = 70), S-DS (n = 98) and S-SC (n = 90). All gilts were inseminated with semen containing viable sperm at the second detected estrus and 24 h later. Pregnant gilts that were stall housed were moved to pens 35 d after insemination. There were no effects of insemination or housing management on farrowing rates or litter sizes.

The association of organic molecules with two-dimensional (2D) materials, creating hybrid systems with mutual influences, constitutes an important testbed for both basic science self-assembly studies and perspective applications. Following this concept, in this work, we show a rich phenomenology that is involved in the interaction of thionine with graphene, leading to a hybrid material formed by well-organized self-assembled structures atop graphene. This composite system is investigated by atomic force microscopy, electric transport measurements, Raman spectroscopy, and first principles calculations, which show (1) an interesting time evolution of thionine self-assembled structures atop graphene; (2) a highly oriented final molecular assembly (in accordance with the underlying graphene surface symmetry); and (3) a strong n-type doping effect introduced in graphene by thionine. The nature of the thionine-substrate interaction is further analyzed in experiments using mica as a polar substrate. The present results may help pave the way to achieve tailored 2D material hybrid devices via properly chosen molecular self-assembly processes.

The goal of this work is to study transformations that occur upon heating Bi2Se3 to temperatures up to 623 K. X-ray diffraction (XRD) and scanning tunneling microscopy (STM) and spectroscopy (STS) techniques were used in our investigation. XRD was measured following the 00L and 01L truncation rods. These measurements revealed that upon heating there is a coexistence of a major Bi2Se3 phase and other ones that present structures of quintuple-layers intercalated with Bismuth bilayers. STM measurements of the surface of this material showed the presence of large hexagonal BixSey domains embedded in a Bi2Se3 matrix. STS experiments were employed to map the local electronic density of states and characterize the modifications imposed by the presence of the additional phases. Finally, density functional theory (DFT) calculations were performed to support these findings.

In swine production, the economic gain in the farrowing room corresponds to the number of weaned piglets/sow per year. Pre-weaning mortality is at least 11–13% of total losses within one herd, considering a previous 7–8% of the stillbirths. Piglet crushing by the sow contributes significantly to the overall piglet mortality. It is caused by multiple factors related to the sow, the piglet and due to modern swine husbandry along the last 50 years. This study aimed to compare three different designs of farrowing crates during the first three days of life in relation to piglet-crushing mortality in intensive herd. One hundred fifty-eight sows with spontaneous deliveries were housed in the following farrowing crates groups: group A (n = 51) farrowing within conventional crates, group B (n = 47) farrowing within the slide cage and group C (n = 60) in the up and down designed, for a total of 2487 live born piglets. In the first three days of life, group C reported the lower crushing mortality rate (0.54%), while groups B and A reported 2.37% and 5.46%, respectively. The comparison between the group C value compared with group A values (p

There are no reports of saccharolytic enzymes being used in the preparation of formulations for animal semen extenders. In the present study, the use of an innovative semen extender (Formula12®) in the long-term liquid storage of boar semen at 17 °C was evaluated. The formulation included use of a disaccharide (sucrose) as the energy source precursor coupled to an enzymatic agent (invertase). The innovative extender was evaluated and compared in vitro to a commercial extender (Vitasem LD®) for the following variables: Total Motility (TM), Forward Progressive Motility (FPM), sperm morphology, membrane integrity, acrosome integrity, and chromatin instability. Boar sperm diluted in Formula12® and stored for 12 days at 17 °C maintained a commercially acceptable FPM (>70%). Using the results from the in vitro study, an AI field trial was performed. A total of 170 females were inseminated (135 with Formula12® and 35 with Vitasem LD®). The pregnancy rates were 97.8% compared with 91.4%, and the farrowing rates were 96.3% compared with 88.6% when Formula12® and Vitasem LD® were used, respectively. The mean number of piglets born/sow were 14.92 ± 0.46 compared with 13.83 ± 0.70, and the number of piglets born alive/sow were 14.07 ± 0.46 compared with 12.12 ± 0.70 (P

The control of geometric structure is a key aspect in the interplay between theoretical predictions and experimental realization in the science and applications of nanomaterials. This is particularly important in one-dimensional structures such as nanoribbons, in which the edge morphology dictates most of the electronic behavior in low energy scale. In the present work we demonstrate by means of first principles calculations that the oxidation of few-layer antimonene may lead to an atomic restructuring with formation of ordered multilayer zig-zag nanoribbons. The widths are uniquely determined by the number of layers of the initial structure, allowing the synthesis of ultranarrow ribbons and chains. We also show that the process may be extended to other compounds based on group V elements, such as arsenene. The characterization of the electronic structure of the resulting ribbons shows an important effect of stacking on band gaps and on modulation of electronic behavior.

Background Poorly differentiated and undifferentiated sarcomas are the most common primary tumors of the pulmonary arteries. They usually affect large caliber vessels and present with predominantly intraluminal growth. Dyspnea, cough, chest pain, and hemoptysis are the most common presenting symptoms; patients may have signs of chronic pulmonary hypertension. Clinical and imaging manifestations can mimic pulmonary embolism. The overall prognosis is poor combined therapy with surgical resection and chemo-radiotherapy offers the best survival rates. Case presentation A 31-year-old male was referred to our department because of recent onset dyspnea, a pre-syncopal episode and a new heart murmur. He had normal spirometry results but a significant desaturation during the 6MWT. A thoracic CT scan showed an incremented diameter of the pulmonary artery.The echocardiogram showed the presence of a mass with irregular borders attached to the pulmonary trunk almost obliterating its lumen. The mass determined a flow acceleration with maximal velocity of 3.8 m/sec, and a peak gradient of 60mmHg; Doppler findings on the pulmonary valve and right heart function were within normal values. Compression ultrasonography ruled out the presence of deep vein thrombosis. The lesion showed a dishomogeneous impregnation in the contrastographic phase at cardiac MRI and had an intense glucidic metabolism at a PET-CT scan. These findings were highly suggestive of an angiosarcoma of the pulmonary artery. Biopsy specimens were taken through bronchoscopy. The patient then decided to continue treatment in another hospital, where the histologic samples were sent; the cytologic results showed atypical cellular elements. The patient died a few months later. Discussion The presence of a unique mass in the main pulmonary artery or proximal branches and rapidly progressive dyspnea in a patient at low risk of pulmonary embolism should raise the suspicion of primary sarcoma of the pulmonary artery, which is a rare but aggressive tumor with a very poor prognosis. Abstract P233 Figure.

Background Primary cardiac lymphoma (PLC) is a rare neoplasm, defined as a lymphoma with the main bulk localized in the heart; diffuse B-cell lymphoma (DLBCL) is the most common type. It usually involves the pericardium and the right heart, especially the right atrium, and have a poor prognosis with a median survival of less than one year. Case summary A 62-year-old female presented to the emergency department on February 2018 for palpitations and recent-onset dyspnea on exertion. Her previous medical history was unremarkable except for a hospital admission in october 2017 for dyspnea, when she underwent pleuroscopy of a left pleural effusion with histologic findings negative for a neoplastic process. The echocardiogram showed a round-shaped mass (23x13mm) in the left atrium, attached to its lateral wall, a mild circumferential pericardial effusion and an hyperechogenic mass at the level of the atrio-ventricular junction of suspected pericardial origin. A subsequent thoracic CT scan demonstrated the presence of a bulky mediastinal mass with colliquative aspects developing around the cardiac structures, strictly attached to the left heart and infiltrating its posterior wall, the left pulmonary veins and the inferior lobar bronchus. Another mass of similar characteristics surrounded the antero-superior portion of the right heart. Colliquative lymphadenopathies and a left basal pleural effusion were also present. After performing a total-body CT scan which excluded the presence of lesions in other districts, the patient underwent CT-guided biopsy and the diagnosis of double-expressor DLBCL was made. Given the potential risk of heart rupture during chemotherapy, the first cycle of R-CHOP was performed in a in-hospital setting with initial reduction of the mediastinal mass and of the lymphadenopathies. The patient was discharged home and referred to the hematology department. After completing 6 cycles of R-CHOP, imaging studies showed rapid progression of the disease; the patient was then started on the salvation protocol R-DHAOX but died of septic shock in december 2018. Discussion PCL is rare and accounts for less than 2% of primary cardiac tumors; double-expressor DLBCL carries a poor prognosis. As in most cases, diagnosis was made after the onset of nonspecific symptoms (dyspnea) but -despite the strong predilection for right heart involvement reported in literature- our patient had a predominant left atrial infiltration. Abstract P848 Figure.

Oesophago-gastric ulcers (OGU) are a production and welfare problem in pigs. Stomach condition was scored for 22 551 pigs in 228 batches over a 7-month period at an abattoir in Italy processing heavy pigs for ham production. Mild or severe ulceration was observed in 20.7% of pigs, of which 13% had scar tissue. Variation between batches was high (0% to 36% prevalence of severe ulcers) and showed a significant effect of farm of origin (P

Low symmetry 2D materials offer an alternative for the fabrication of optoelectronic devices which are sensitive to light polarization. The investigation of electron–phonon interactions in these materials is essential since they affect the electrical conductivity. Raman scattering probes light–matter and electron–phonon interactions, and their anisotropies are described by the Raman tensor. The tensor elements can have complex values, but the origin of this behavior in 2D materials is not yet well established. In this work, we studied a single-layer triclinic ReSe2 by angle-dependent polarized Raman spectroscopy. The obtained values of the Raman tensor elements for each mode can be understood by considering a new coordinate system, which determines the physical origin of the complex nature of the Raman tensor elements. Our results are explained in terms of anisotropy of the electron–phonon coupling relevant to the engineering of new optoelectronic devices based on low-symmetry 2D materials.

Background: Germline variants in the melanocortin 1 receptor gene (MC1R) might increase the risk of childhood and adolescent melanoma, but a clear conclusion is challenging because of the low number of studies and cases. We assessed the association of MC1R variants with childhood and adolescent melanoma in a large study comparing the prevalence of MC1R variants in child or adolescent patients with melanoma to that in adult patients with melanoma and in healthy adult controls. Methods: In this retrospective pooled analysis, we used the M-SKIP Project, the Italian Melanoma Intergroup, and other European groups (with participants from Australia, Canada, France, Greece, Italy, the Netherlands, Serbia, Spain, Sweden, Turkey, and the USA) to assemble an international multicentre cohort. We gathered phenotypic and genetic data from children or adolescents diagnosed with sporadic single-primary cutaneous melanoma at age 20 years or younger, adult patients with sporadic single-primary cutaneous melanoma diagnosed at age 35 years or older, and healthy adult individuals as controls. We calculated odds ratios (ORs) for childhood and adolescent melanoma associated with MC1R variants by multivariable logistic regression. Subgroup analysis was done for children aged 18 or younger and 14 years or younger. Findings: We analysed data from 233 young patients, 932 adult patients, and 932 healthy adult controls. Children and adolescents had higher odds of carrying MC1R r variants than did adult patients (OR 1·54, 95% CI 1·02–2·33), including when analysis was restricted to patients aged 18 years or younger (1·80, 1·06–3·07). All investigated variants, except Arg160Trp, tended, to varying degrees, to have higher frequencies in young patients than in adult patients, with significantly higher frequencies found for Val60Leu (OR 1·60, 95% CI 1·05–2·44; p=0·04) and Asp294His (2·15, 1·05–4·40; p=0·04). Compared with those of healthy controls, young patients with melanoma had significantly higher frequencies of any MC1R variants. Interpretation: Our pooled analysis of MC1R genetic data of young patients with melanoma showed that MC1R r variants were more prevalent in childhood and adolescent melanoma than in adult melanoma, especially in patients aged 18 years or younger. Our findings support the role of MC1R in childhood and adolescent melanoma susceptibility, with a potential clinical relevance for developing early melanoma detection and preventive strategies. Funding: SPD-Pilot/Project-Award-2015; AIRC-MFAG-11831. © 2019 Elsevier Ltd

The ability to create materials with improved properties upon transformation processes applied to conventional materials is the keystone of materials science. Here, hexagonal boron nitride (h-BN), a large-band-gap insulator, is transformed into a conductive two-dimensional (2D) material- bonitrol-that is stable at ambient conditions. The process, which requires compression of at least two h-BN layers and hydroxyl ions, is characterized via scanning probe microscopy experiments and ab initio calculations. This material and its creation mechanism represent an additional strategy for the transformation of known 2D materials into artificial advanced materials with exceptional properties.

In this work we have used atomically-resolved scanning tunneling microscopy and spectroscopy to study the interplay between the atomic and electronic structure of graphene formed on copper via chemical vapor deposition. Scanning tunneling microscopy directly revealed the epitaxial match between a single layer of graphene and the underlying copper substrate in different crystallographic orientations. Using scanning tunneling spectroscopy we have directly measured the electronic density of states of graphene layers near the Fermi level, observing the appearance of a series of peaks in specific cases. These features were analyzed in terms of substrate-induced perturbations in the structural and electronic properties of graphene by means of atomistic models supported by density functional theory calculations.

The goal of this work is to study transformations that occur upon heating Bi

Os avancos tecnologicos e o aumento da complexidade nas plantas industriais e dos equipamentos empregados nos processos de manufatura tem exigido cada vez mais a proposicao de novas tecnicas de modelagem dos processos produtivos. As ferramentas derivadas da rede de Petri se mostram eficientes nas etapas de modelagem do objeto de controle e no projeto de sistemas de controle para sistemas produtivos. O objetivo deste trabalho e apresentar uma proposta de sistematica para geracao de modelos de controle para Sistemas Flexiveis de Manufatura utilizando a metodologia PFS/E-MFG considerando a modelagem da estrutura de dados presente nas marcas individuais da rede E-MFG utilizando o diagrama de objetos do UML.

The charge transfer between neighboring single-walled carbon nanotubes (SWNTs) on a silicon oxide surface was investigated as a function of both the SWNT nature (metallic or semiconducting) and the anode/cathode distance using scanning probe techniques. Two main mechanisms were observed: a direct electron tunneling described by the typical Fowler-Nordheim model, and indirect electron transfer (hopping) mediated by functional groups on the supporting surface. Both mechanisms depend on the SWNT nature and on the anode/cathode separation: direct electron tunneling dominates the charge transfer process for metallic SWNTs, especially for large distances, while both mechanisms compete with each other for semiconducting SWNTs, prevailing one over the other depending on the anode/cathode separation. These mechanisms may significantly influence the design and operation of SWNT-based electronic devices.

In this paper we present a method to determine the occupation of Mn ions in epitaxial (In,Mn)As nanostructures by resonant x-ray diffraction near the Mn $K$-absorption edge, exploiting the dependency of the intensity of both (200) superstructure and the (400) fundamental reflections. The concentrations of Mn atoms on substitutional In sites, as well as on In- and As-interstitial sites, were unambiguously determined. A threshold concentration for the interstitial sites, which are occupied first for low nominal Mn deposition content, was found. Calculations using density-functional theory indicate that a higher occupancy of such sites can be favorable with respect to the occupation of substitutional sites, depending on surface potentials and growth kinetic effects.

First-principles calculations based on the density functional theory showed that the building blocks of the oxygen e-high-pressure solid phase spontaneously form when oxygen molecules are enclosed within fullerenes and small-diameter nanotubes. The building blocks consist of O8 clusters, which are able to self-assemble into periodic arrays inside nanotubes. Such chains are semiconductors when isolated or when encapsulated in boron nitride nanotubes and become doped when confined in carbon materials. Molecular dynamics simulations confirmed the formation and stability of the clusters and chains in ambient conditions.

 Premise of the study: The term colleter is applied to trichomes or emergences positioned close to developing vegetative and fl oral meristems that secrete a sticky, mucilaginous, and/or lipophilic exudate. Several ecological functions are attributed to these glands, but none are exclusive to colleters. Patterns of morphology and distribution of colleters may be valuable for systematics and phylogeny, especially concerning problematic and large groups such as the subtribe Pleurothallidinae, and are also essential to understand the evolution of these glands in Orchidaceae as a whole.  Methods: We used scanning electron and light microscopy to examine the structure and occurrence of trichomes on bracts and sepals and in the invaginations of the external ovary wall (IEOW) in flin several developmental stages from species in seven genera.  Key results: The exudate was composed of polysaccharides, lipophilic, and phenolic compounds. Colleters were secretory only during the development of florgans, except for the glands in the IEOW that were also active in flat anthesis. After the secretory phase, fungal hyphae were found penetrating senescent trichomes.  Conclusions: Trichome-like colleters seem to be a widespread character in Epidendroideae, and digitiform colleters are possibly the common type in this subfamily. Mucilage from IEOW colleters may aid in the establishment of symbiotic fungi necessary for seed germination. The presence of colleters in the IEOW may be a case of homeoheterotopy, in which extrafl oral nectaries that produce simple sugar-based secretions (as in other orchid species) have changed to glands that produce secretions with complex polysaccharides, as in Pleurothallidinae.

To counteract the effects of perinatal hypoxia in piglets, the oral administration of caffeine to sows with induced parturition was evaluated. On day 113 of gestation 9 sows received 27 mg/kg body weight (BW) of caffeine mixed with 200 g of standard diet. The same amount of feed without the addition of caffeine was administered to 9 control sows. Additionally, on day 113 of gestation, all sows were treated by two injections in the perianal area of 1 mg of alfaprostol (at 8:00 am and 14:00 pm), and on the morning of farrowing by 14 IU of oxytocin in the perianal area. Caffeine did not affect BW of piglets and size of litters; however piglets from treated sows showed a higher capacity to adapt to extra-uterine life. Particularly, they showed a greater thermoregulatory ability (P 80 nmol/L) in piglets born from treated sows (P=0.001). In conclusion, the caffeine orally administered to sows with induced parturition showed a protective effect on the consequences of neonatal hypoxia in tissue ischemia–reperfusion injury in piglets.

Topological insulators such as Bi2Se3 and Bi2Te3 have extremely promising transport properties, due to their unique electronic behavior: they are insulators in the bulk and conducting at the surface. Recently, the coexistence of two types of surface conducting channels has been observed for Bi2Se3, one being Dirac electrons from the topological state and the other electrons from a conventional two-dimensional gas. As an explanation for this effect, a possible structural modification of the surface of these materials has been hypothesized. Using scanning tunneling microscopy we have directly observed the coexistence of a conducting bilayer and the bare surface of bulk-terminated Bi2Te3. X-ray crystal truncation rod scattering was used to directly show the stabilization of this epitaxial bilayer which is primarily composed of bismuth. Using this information, we have performed density functional theory calculations to determine the electronic properties of the possible surface terminations. They can be used to understand recent angular resolved photoemission data which have revealed this dual surface electronic behavior.

We probe electron and hole mobilities in bilayer graphene under exposure to molecular oxygen. We find that the adsorbed oxygen reduces electron mobilities and increases hole mobilities in a reversible and activated process. Our experimental results indicate that hole mobilities increase due to the screening of long-range scatterers by oxygen molecules trapped between the graphene and the substrate. First principle calculations show that oxygen molecules induce resonant states close to the charge neutrality point. Electron coupling with such resonant states reduces the electron mobilities, causing a strong asymmetry between electron and hole transport. Our work demonstrates the importance of short-range scattering due to adsorbed species in the electronic transport in bilayer graphene on SiO2 substrates.

We apply first-principles calculations to investigate the existence and properties of edge states in TiO2 nanoribbons. We show that edge states may be found either in the gap region or defining the bottom of the conduction band. In both cases, the addition of electrons to the ribbons, which is facilitated by the large work function of TiO2 materials, may drive the systems to a half-metallic state, with conduction taking place along the edges and with only one spin component. We also show that a U-negativity phenomenology may show up in some configurations, resulting in the stabilization of the charged edges.

The synthesis and characterization of two-dimensional (2D) molecular crystals composed of long and linear phosphonic acids atop graphene is reported. Using scanning probe microscopy in combination with first-principles calculations, we show that these true 2D crystals are oriented along the graphene armchair direction only, thereby enabling an easy determination of graphene flake orientation. We have also compared the doping level of graphene flakes via Raman spectroscopy. The presence of the molecular crystal atop graphene induces a well-defined shift in the Fermi level, corresponding to hole doping, which is in agreement with our ab initio calculations.

We study single wall carbon nanotubes (SWNTs) deposited on quartz. Their Raman spectrum depends on the tube-substrate morphology, and in some cases, it shows that the same SWNT-on-quartz system exhibits a mixture of semiconductor and metal behavior, depending on the orientation between the tube and the substrate. We also address the problem using electric force microscopy and ab initio calculations, both showing that the electronic properties along a single SWNT are being modulated via tube-substrate interaction.

In this work, we apply first-principles calculations combined with model potential dynamics simulations to investigate structural and electronic aspects of toxins. The dynamics were carried out for ω-conotoxins MVIIA and MVIIC as well as for mutated structures in which tyrosine at position 13, a key residue for the toxin function, was replaced by alanine. An analysis of the electronic structure of specific snapshots shows that structural changes may be mapped in the local electronic behavior of carbonyl groups.

We apply first-principles calculations to predict the stability of porous nanotubes and fullerenes based on covalent organic frameworks (COF’s). Two-dimensional COF’s are extended sheets of covalently linked organic units forming porous materials composed only of light elements. We show that such sheets may be rolled up to form stable nanotubes, and, based on energetic aspects, even a fullerene-based COF might be observed. The electronic and elastic properties of COF nanotubes are also discussed. These materials might have interesting applications as molecular filters or carriers, in gas storage, or as building blocks for three-dimensional structures.