Search

We relate two important notions in graph theory: expanders which are highly connected graphs, and modularity a parameter of a graph that is primarily used in community detection. More precisely, we show that a graph having modularity bounded below 1 is equivalent to it having a large subgraph which is an expander. We further show that a connected component H will be split in an optimal partition of the host graph G if and only if the relative size of H in G is greater than an expansion constant of H. This is a further exploration of the resolution limit known for modularity, and indeed recovers the bound that a connected component H in the host graph G will not be split if e(H) < √{2e(G)}.

Producción Científica, Gap junctions (GJs) made of connexin-43 (Cx43) are necessary for the conduction of electrical impulses in the heart. Modulation of Cx43 GJ activity may be beneficial in the treatment of cardiac arrhythmias and other dysfunctions. The search for novel GJ-modulating agents using molecular docking allows for the accurate prediction of binding affinities of ligands, which, unfortunately, often poorly correlate with their potencies. The objective of this study was to demonstrate that a Quantitative Structure-Activity Relationship (QSAR) model could be used for more precise identification of potent Cx43 GJ inhibitors. Using molecular docking, QSAR, and 3D-QSAR, we evaluated 16 known Cx43 GJ inhibitors, suggested the monocyclic monoterpene d-limonene as a putative Cx43 inhibitor, and tested it experimentally in HeLa cells expressing exogenous Cx43. The predicted concentrations required to produce 50% of the maximal effect (IC50) for each of these compounds were compared with those determined experimentally (pIC50 and eIC50, respectively). The pIC50ies of d-limonene and other Cx43 GJ inhibitors examined by our QSAR and 3D-QSAR models showed a good correlation with their eIC50ies (R = 0.88 and 0.90, respectively) in contrast to pIC50ies obtained from molecular docking (R = 0.78). However, molecular docking suggests that inhibitor potency may depend on their docking conformation on Cx43. Searching for new potent, selective, and specific inhibitors of GJ channels, we propose to perform the primary screening of new putative compounds using the QSAR model, followed by the validation of the most suitable candidates by patch-clamp techniques., Consejo de Investigación de Lituania - (grant S-MIP-23-105)

© 2014 American Physical Society. This work was supported by the DAAD (54367888), by NBRP of China (2012CB921303), by MINECO (Grants No. PRI-AIBDE-2011-0.927 and No. MAT 2010-17180), by NSFChina under Grant No. 11274364, and by PDSF-China under Grant No. 2013M540153. We acknowledge support from the German Excellence Initiative: Cluster of Excellence EXC 1056 “Center for Advancing Electronics Dresden” (cfAED). A.M.G. and E.D. contributed equally to this work., We report on spin transport along double-helical molecular systems by considering various contact configurations and asymmetries between the two helical strands in the regime of completely coherent charge transport. Our results reveal that no spin polarization appears in two-terminal molecular devices when coupled to one-dimensional electrodes. The same holds in the case of finite-width electrodes if there is a bottleneck of one single site in the system electrode-molecule-electrode. Then, additional dephasing is necessary to induce spin-filtering effects. In contrast, nonzero spin polarization is found in molecular devices with multiple terminals or with two finite-width electrodes, each of them connected to more than one site of the molecule. The magnitude of spin polarization can be enhanced by increasing the asymmetry between the two strands. We point out that the spin-filtering effects could emerge in double-helical molecular devices at low temperature without dephasing by a proper choice of the electrode number and the connection between the molecule and the electrodes., MINECO, DAAD, NBRP of China, NSF-China, PDSF-China, cfAED, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2003 The American Physical Society. P.A.O. and I.G. would like to thank Milenio ICM P99-135-F and FONDECYT for financial support under Grant No. 1020269. Work in Madrid was supported by DGIMCyT (Grant No. MAT2000-0734) and CAM (Grant No. 07N/ 0075/200). I.G. would like to thank UCN for the warm hospitality during his visit. M. L. L. d. G. was supported by Cátedra Presidencial en Ciencia F. Claro., A noninteracting quantum-dot array side coupled to a quantum wire is studied. Transport through the quantum wire is investigated by using a noninteracting Anderson tunneling Hamiltonian. The conductance at zero temperature develops an oscillating band with resonances and antiresonances due to constructive and destructive interference in the ballistic channel, respectively. Moreover, we have found an odd-even parity in the system, whose conductance vanishes for an odd number of quantum dots while it becomes 2e(2)/h for an even number. We established an explicit relation between this odd-even parity and the positions of the resonances and antiresonances of the conductivity with the spectrum of the isolated quantum-dot array., Milenio ICM, FONDECYT, DGIMCyT, Cátedra Presidencial en Ciencia, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

© 2011 American Physical Society. A. S. acknowledges discussions with I. Gruzberg and V. Kagalovsky and the hospitality of the Universidad Complutense de Madrid, where the major part of the work has been done. A. V. M. and F. D.-A. thank K. Slevin, T. Ohtsuki, and R. Römer for fruitful discus- sions. Part of the calculations were performed at the Aula Sun Cluster and the Clúster de Ca´lculo de Alta Capacidad para Técnicas Físicas, funded by the UCM and the EU under the FEDER program. Work in Madrid was supported by MICINN (Projects Mosaico and MAT2010-17180), We calculate numerically the localization length critical index within the Chalker-Coddington model of the plateau-plateau transitions in the quantum Hall effect. We report a finite-size scaling analysis using both the traditional power-law corrections to the scaling function and the inverse logarithmic ones, which provided a more stable fit resulting in the localization length critical index v = 2.616 +/- 0.014. We observe an increase of the critical exponent v with the system size, which is possibly the origin of discrepancies with early results obtained for smaller systems., UCM, EU-FEDER program, MICINN, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

DNA's charge transfer and self-assembly characteristics have made it a hallmark of molecular electronics for the past two decades. A fast and efficient charge transfer mechanism with programmable properties using DNA nanostructures is required for DNA-based nanoelectronic applications and devices. The ability to integrate DNA with inorganic substrates becomes critical in this process. Such integrations may affect the conformation of DNA, altering its charge transport properties. Thus, using molecular dynamics simulations and first-principles calculations in conjunction with Green's function approach, we explore the impact of the Au (111) substrate on the conformation of DNA and analyze its effect on the charge transport. Our results indicate that DNA sequence, leading to its molecular conformation on the Au substrate, is critical to engineer charge transport properties. We demonstrate that DNA fluctuates on a gold substrate, sampling various distinct conformations over time. The energy levels, spatial locations of molecular orbitals and the DNA/Au contact atoms can differ between these distinct conformations. Depending on the sequence, at the HOMO, the charge transmission differs up to 60 times between the top ten conformations. We demonstrate that the relative positions of the nucleobases are critical in determining the conformations and the coupling between orbitals. We anticipate that these results can be extended to other inorganic surfaces and pave the way for understanding DNA-inorganic interface interactions for future DNA-based electronic device applications., We acknowledge NSF ECCS Grant Numbers 1807391 and 1807555. We acknowledge using the Hyak supercomputer system at the University of Washington and TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources). Busra Demir further acknowledges a TUBITAK 2214-A International Doctoral Research Fellowship., NSF ECCS [1807391, 1807555]; International Doctoral Research Fellowship [TUBITAK 2214-A]

DNA's charge transfer and self-assembly characteristics have made it a hallmark of molecular electronics for the past two decades. A fast and efficient charge transfer mechanism with programmable properties using DNA nanostructures is required for DNA-based nanoelectronic applications and devices. The ability to integrate DNA with inorganic substrates becomes critical in this process. Such integrations may affect the conformation of DNA, altering its charge transport properties. Thus, using molecular dynamics simulations and first-principles calculations in conjunction with Green's function approach, we explore the impact of the Au (111) substrate on the conformation of DNA and analyze its effect on the charge transport. Our results indicate that DNA sequence, leading to its molecular conformation on the Au substrate, is critical to engineer charge transport properties. We demonstrate that DNA fluctuates on a gold substrate, sampling various distinct conformations over time. The energy levels, spatial locations of molecular orbitals and the DNA/Au contact atoms can differ between these distinct conformations. Depending on the sequence, at the HOMO, the charge transmission differs up to 60 times between the top ten conformations. We demonstrate that the relative positions of the nucleobases are critical in determining the conformations and the coupling between orbitals. We anticipate that these results can be extended to other inorganic surfaces and pave the way for understanding DNA-inorganic interface interactions for future DNA-based electronic device applications., We acknowledge NSF ECCS Grant Numbers 1807391 and 1807555. We acknowledge using the Hyak supercomputer system at the University of Washington and TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources). Busra Demir further acknowledges a TUBITAK 2214-A International Doctoral Research Fellowship., NSF ECCS [1807391, 1807555]; International Doctoral Research Fellowship [TUBITAK 2214-A]

Hybrid structures consisting of FRP(fiber reinforce polymer) composite decks connected to a steel girder superstructure are gaining more attention by combining the stiffness of steel members with good fatigue endurance and high strength to weight ratio of FRP. However, when composite material FRP is exposed to elevated temperature, delamination and strength reduction could appear due to low transition temperature of fiber and resin. As a result, predicting the temperature of the FRP bridge deck becomes a preliminary requirement for the further study of the FRP bridge deck. This research is trying to simulate the heat transfer process of the FRP bridge deck and predict the temperature changing process when it is exposed to natural environment. To reach this goal, experiment and FEM(finite element model) are used as main methods. By detecting temperature change history of the FRP bridge deck specimen during hot weathers in Delft, Netherlands, the maximum temperature and heat transfer process of the FRP bridge deck could be studied. On the basis of experimental results, an detailed FEM in Abaqus is built up to simulate the heat transfer process of the specimen used in the experiment. After validating the accuracy of FEM result with experimental data, the FEM is used to predict the temperature of FRP bridge deck that exposed to natural environment in the hottest weather of Netherlands. In conclusion, the results shows that the temperature of FRP structures could be well predicted which only has 10.5% variance predicting the maximum temperature on the top surface of the specimen and high accuracy of 6% predicting the average temperature of the FRP panels along the thickness. It also has high accuracy of 3.5% predicting the maximum web-core temperature difference. The only insufficient part is that the average temperature difference of web-core has a deviation of 21% with the experimental data. As FRP panels make up the web and flange of the bridge dec, Civil Engineering | Structural Engineering

Efforts to develop effective climate strategies necessitate a better understanding of the relationship between terrestrial water and carbon cycles. Water use efficiency (WUE) has been often used to characterize this relationship, while the role of transpiration (T) in the variation of ecosystem WUE has been less investigated. Here, we partitioned WUEET (the ratio of gross primary productivity (GPP) to evapotranspiration (ET)) into a two-component process, i.e., the ratio of gross primary productivity to plant transpiration, GPP/T, that is WUET, and the ratio of plant transpiration to evapotranspiration, T/ET. Based on two GPP datasets (i.e., GPP based on the light use efficiency model or the vegetation index- NIRv) and the GLEAM ET dataset, this study investigated the role of T in the variation of WUE in the ecosystem level and how the role is affected by drought. We found that drought can lead to the change of ET partitioning, thus affecting the variability of WUE. The variability of WUEET was dominated by WUET. In general, the proportion of T increased gradually from humid to arid areas. To adapt to drought conditions, vegetation in arid areas tend to have a high stress resistance by increasing their WUE. We further found that WUET has stronger seasonal stability than WUEET. GPP dominated WUEET variability in humid/sub humid areas, while ET and GPP jointly dominated WUEET variability in semi-arid/arid areas. GPP dataset based on light use efficiency (LUE) could better reflect the impact of drought on vegetation. This study contributes to a better understanding of the change mechanism of ecosystem WUE and emphasizes the critical role of physiological process components in water-carbon cycling., Efforts to develop effective climate strategies necessitate a better understanding of the relationship between terrestrial water and carbon cycles. Water use efficiency (WUE) has been often used to characterize this rela-tionship, while the role of transpiration (T) in the variation of ecosystem WUE has been less investigated. Here, we partitioned WUEET (the ratio of gross primary productivity (GPP) to evapotranspiration (ET)) into a two-component process, i.e., the ratio of gross primary productivity to plant transpiration, GPP/T, that is WUET, and the ratio of plant transpiration to evapotranspiration, T/ET. Based on two GPP datasets (i.e., GPP based on the light use efficiency model or the vegetation index-NIRv) and the GLEAM ET dataset, this study investigated the role of T in the variation of WUE in the ecosystem level and how the role is affected by drought. We found that drought can lead to the change of ET partitioning, thus affecting the variability of WUE. The variability of WUEET was dominated by WUET. In general, the proportion of T increased gradually from humid to arid areas. To adapt to drought conditions, vegetation in arid areas tend to have a high stress resistance by increasing their WUE. We further found that WUET has stronger seasonal stability than WUEET. GPP dominated WUEET variability in humid/sub humid areas, while ET and GPP jointly dominated WUEET variability in semi-arid/arid areas. GPP dataset based on light use efficiency (LUE) could better reflect the impact of drought on vegetation. This study contributes to a better understanding of the change mechanism of ecosystem WUE and emphasizes the critical role of physiological process components in water-carbon cycling.

To achieve the ultimate limit of device miniaturization, it is necessary to have a comprehensive understanding of the structure-property relationship in functional molecular systems used in single-molecule electronics. This study reports the synthesis and characterization of a novel series of norbornadiene derivatives capped with thioether and thioester anchor groups. Utilizing the mechanically controllable break junction technique, the impact of these capping groups on conductance across single-molecule junctions is investigated. Among the selection of anchor groups, norbornadiene capped with thioacetate and tert-butyl groups exhibits higher conductance (G ≈ 4 × 10−4 G0) compared to methyl thioether (G ≈ 2 × 10−4 G0). Electronic transmission through the considered set of single-molecule junctions has been simulated. The computational results for electron transport across these junctions align closely with the experimental findings, with the thioacetate- and tert-butyl-substituted systems outperforming the methyl thioether-capped derivative. In terms of junction stability, the methyl thioether-capped system is the most resilient, maintaining consistent conductance even after approximately 10 000 cycles. Meanwhile, the likelihood of observing molecular plateaus in both the thioacetate- and tert-butyl-substituted systems declines over time. These findings substantially advance both the design and understanding of functional molecular systems in the realm of single-molecule electronics, particularly in the context of molecular photoswitches.

Background and Aims Stomatal regulation allows plants to promptly respond to water stress. However, our understanding of the impact of above and belowground hydraulic traits on stomatal regulation remains incomplete. The objective of this study was to investigate how key plant hydraulic traits impact transpiration of maize during soil drying. We hypothesize that the stomatal response to soil drying is related to a loss in soil hydraulic conductivity at the root-soil interface, which in turn depends on plant hydraulic traits. Methods We investigate the response of 48 contrasting maize (Zea mays) genotypes to soil drying, utilizing a novel phenotyping facility. In this context, we measure the relationship between leaf water potential, soil water potential, soil water content and transpiration, as well as root, rhizosphere and aboveground plant traits. Key Results Genotypes differed in their responsiveness to soil drying. The critical soil water potential at which plants started decreasing transpiration was related to a combination of above and belowground traits: genotypes with a higher maximum transpiration and plant hydraulic conductance as well as a smaller root and rhizosphere system closed stomata at less negative soil water potentials. Conclusions Our results demonstrate the importance of belowground hydraulics for stomatal regulation and hence drought responsiveness during soil drying. Furthermore, this finding supports the hypothesis that stomata start to close when soil hydraulic conductivity drops at the root-soil interface.

We all agree with the statement “Health is wealth. It is quite true at all stages of life and for any gender. It doesn’t matter whether the person is male or female, kids or adult. Health always remained important for everyone. We cannot enjoy a single moment of our life if we don’t have good health. Good health is the strength of life and key to happiness. Here we are talking about women health. Woman who is the creator of new life on the Earth, who is the care givers of the family members and for the last few decades playing very active role in nation building. She starts her days with new challenges and try to meet her demand selflessly. How can she confront her challenges with diseased mind and body? No, it is never possible. She cannot meet her household as well as professional responsibilities with poor health. She must be healthy physically, mentally emotionally and socially only then she will perform all responsibilities successfully. Good health empowers us and makes us strong mentally as well as physically.

Одним з факторів, що впливають на електричні характеристики і параметри інтегральних мікросхем, є зовнішній тиск, який найчастіше виникає в результаті процесів розшарування в корпусі мікросхеми. Під дією тиску ширина забороненої зони напівпровідника змінюється, що призводить до зміни електричних параметрів активних і пасивних компонентів ІМС. Сучасні моделі залежності ширини забороненої зони від тиску дуже спрощені, не забезпечують точності моделювання в широкому діапазоні значень тиску, що не дозволяє розробити адекватні математичні моделі напівпровідникових компонентів для подальшого вивчення впливу тиску на електричні характеристики і параметри інтегральних схем. Для побудови більш точної математичної моделі залежності ширини забороненої зони кремнію від зовнішнього тиску було експериментально досліджено вплив тиску на електричні параметри напівпровідникового резистора і діода в інтегральній схемі. Вибір пасивних і активних компонентів для експериментальних досліджень дозволив виключити вплив особливостей технологічних процесів виготовлення і отримати більш достовірні дані для подальшої побудови апроксимаційної моделі. Дослідження проводилися в діапазоні тисків від 0 до 25 ГПа. Виміри проводилися на спеціально сконструйованому вимірювальному стенді. Стенд дозволяє проводити високоточні вимірювання опору інтегральних резисторів, ВАХ-діодів і транзисторів під дією регульованого тиску, що прикладається до поверхні пасивного або активного компонента, реалізованого на кристалі ІС. Похибка вимірювання цього стенда визначається похибкою мультиметра і становить +/- 0,001 В за напругою і +/- 0,0001 А по струму. Датчик зусилля вносить похибка в +/- 0,025 Н. Отримано вирази для визначення значення ширини забороненої зони через експериментальні значення опору резистора і струму через діод при нульовому тиску і певною величиною тиску, що дозволило побудувати емпіричну модель залежності ширини забороненої зони кремнію від тиску. Показано, що класична лінійна модель не відображ

Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

The electrical and dielectric properties of liquids can be used for sensing. Specific appli-cations, e.g., the continuous in-line monitoring of blood conductivity as a measure of the sodium concentration during dialysis treatment, require contactless measuring methods to avoid any contam-ination of the medium. The differential transformer is one promising approach for such applications, since its principle is based on a contactless, magnetically induced conductivity measurement. The objective of this work is to investigate the impact of the geometric parameters of the sample or medium under test on the sensitivity and the noise of the differential transformer to derive design rules for an optimized setup. By fundamental investigations, an equation for the field penetration depth of a differential transformer is derived. Furthermore, it is found that increasing height and radius of the medium is accompanied by an enhancement in sensitivity and precision. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

Conductance was calculated for trapezoidal nanowires with different forms and strengths of imperfection using kwant, a quantum transport software package that uses a tight-binding model. In this thesis it is found that increasing magnitudes of different imperfections such as surface charge and roughness roughen conductance steps, introduce resonances, and lower conductance overall with different character of these effects for different types of imperfections. Quantitative qualification of the effect on conductance is calculated in the form of exponential fits for Urbach tails, showing a more gradual increase in conductance as the strength of imperfections increases. These results show how different imperfections can affect transport properties in nanowires, and provide insight which can help provide a more concrete theoretical understanding of the transport-imperfection relationship as well as aid the design and characterisation of next-generation nanowire devices.

The elimination of total and fecal coliforms, from raw surface water, was carried out by electrochemical oxidation using either boron doped diamond (BDD/Ti) or graphite (GP) anodes, in a chloride-free medium. The optimal values of the operation parameters, maximizing the coliform elimination percentage, were determined using statistical experimental design. The current density ( j: 2-20 mA/cm2), the conductivity (s: 500-900 µS/cm) and the anode materials (An) were considered as variables to perform the Box-Behnken experimental design together with the response surface methodology analysis for optimization. The statistical analysis indicated that, in the evaluated range, the disinfection efficiency increased with an increase in j and decreased with an increase in s. The following optimal conditions for the elimination of total and fecal coliforms were found: j: 10 mA/cm2, s: 500 µS/cm and BDD/Ti used as anode material. The BDD/Ti electrode let to achieve complete coliform elimination after ca. 20 min of reaction while the GP one needed ca. 27 min. In water treated with both BDD/Ti and GP anode, after 7 days, any coliforms growth was observed. As a result of the oxidation process, the total organic carbon and nitrite concentration decreased while nitrate concentration increased. © IWA Publishing 2018.

The elimination of total and fecal coliforms, from raw surface water, was carried out by electrochemical oxidation using either boron doped diamond (BDD/Ti) or graphite (GP) anodes, in a chloride-free medium. The optimal values of the operation parameters, maximizing the coliform elimination percentage, were determined using statistical experimental design. The current density ( j: 2-20 mA/cm2), the conductivity (s: 500-900 µS/cm) and the anode materials (An) were considered as variables to perform the Box-Behnken experimental design together with the response surface methodology analysis for optimization. The statistical analysis indicated that, in the evaluated range, the disinfection efficiency increased with an increase in j and decreased with an increase in s. The following optimal conditions for the elimination of total and fecal coliforms were found: j: 10 mA/cm2, s: 500 µS/cm and BDD/Ti used as anode material. The BDD/Ti electrode let to achieve complete coliform elimination after ca. 20 min of reaction while the GP one needed ca. 27 min. In water treated with both BDD/Ti and GP anode, after 7 days, any coliforms growth was observed. As a result of the oxidation process, the total organic carbon and nitrite concentration decreased while nitrate concentration increased. © IWA Publishing 2018.

Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

Spin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

The electrical and dielectric properties of liquids can be used for sensing. Specific appli-cations, e.g., the continuous in-line monitoring of blood conductivity as a measure of the sodium concentration during dialysis treatment, require contactless measuring methods to avoid any contam-ination of the medium. The differential transformer is one promising approach for such applications, since its principle is based on a contactless, magnetically induced conductivity measurement. The objective of this work is to investigate the impact of the geometric parameters of the sample or medium under test on the sensitivity and the noise of the differential transformer to derive design rules for an optimized setup. By fundamental investigations, an equation for the field penetration depth of a differential transformer is derived. Furthermore, it is found that increasing height and radius of the medium is accompanied by an enhancement in sensitivity and precision. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe0.55Se0.45, a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTe0.55Se0.45, which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.

The presence of chiral modes on the edges of quantum Hall samples is essential to our understanding of the quantum Hall effect. In particular, these edge modes should support ballistic transport and therefore, in a single-particle picture, be supported in the absolutely continuous spectrum of the single-particle Hamiltonian. We show in this note that if a free fermion system on the two-dimensional lattice is gapped in the bulk and has a non-vanishing Hall conductance, then the same system put on a half-space geometry supports edge modes whose spectrum fills the entire bulk gap and is absolutely continuous.

The ever-increasing demand for green and clean energy urge the development of cheap and efficient electrode materials for supercapacitors (SCs). In this context, several naturally abundant bio-wastes have been explored to develop porous carbons for SCs due to their easy availability, high performances, and simple processing methods. Although various BDCs are utilized for SC, the relation between the bio-waste precursor and resultant carbon materials are not very well understood. Here, we highlight how the different bio-waste precursors affect the surface characteristics of the carbon nanostructures and outlined their subsequent effect on electrochemical performances. Moreover, the surface modification of carbon materials using pre-processing, carbonization and activation methods is provided. The supercapacitive properties of activated carbons (AC) with their unique surface features derived from the different feedstock are systematically summarized. Finally, the challenges and future directions for the development of AC from bio-waste are discussed. Overall, this review provides a guide to understand how best to refine and carbonize this biomass to achieve optimum supercapacitive performance. © 2021

Incorporating individual small organic molecules into electronic circuits has the potential to enable smaller and more efficient devices, while also providing an excellent experimental platform for investigating the fundamental physics and chemistry of quantum transport. Key to advancing both of these goals is the continued development of structure-function relationships that predictively connect molecular design to observed transport behavior. Despite their apparent simplicity, single-molecule systems often display complex interactions between different physical effects, and so structure-function relationships that account for these interconnections are an especially important, and relatively understudied, need for the field. A second major challenge for single-molecule transport research is that modern experimental platforms tend to produce large, stochastic, and high-dimensional datasets. Methods to robustly extract meaningful information from such datasets are thus required to fully probe the range of behaviors occurring in single-molecule circuits, and to understand how those behaviors relate back to molecular design. In this dissertation, I describe contributions to help address the need for both nuanced structure-function relationships and sophisticated data analysis strategies for single-molecule quantum transport research. The experimental platform I used to measure single-molecule charge transport is described in detail, along with the type of data it collects and the subtleties of how those data are processed. Motivated by those details, I describe my overall approach to analyzing single-molecule data and then introduce, validate, and utilize novel machine learning algorithms that I developed to address specific challenges. These include a novel segment clustering algorithm for reliably extracting molecular features and an original correlation-based framework for identifying meaningful rare events. Using some of these new tools, I then report single-molec

By using scanning tunneling microscopy (STM) we find and characterize dispersive, energy-symmetric in-gap states in the iron-based superconductor FeTe0.55Se0.45, a material that exhibits signatures of topological superconductivity, and Majorana bound states at vortex cores or at impurity locations. We use a superconducting STM tip for enhanced energy resolution, which enables us to show that impurity states can be tuned through the Fermi level with varying tip-sample distance. We find that the impurity state is of the Yu-Shiba-Rusinov (YSR) type, and argue that the energy shift is caused by the low superfluid density in FeTe0.55Se0.45, which allows the electric field of the tip to slightly penetrate the sample. We model the newly introduced tip-gating scenario within the single-impurity Anderson model and find good agreement to the experimental data.

In this thesis we theoretically study a certain class of materials, namely solids that have a crystal structure on the atomic scale, such as most metals, diamond and table salt. For such materials, quantum mechanics tells us that the electrons cannot simply do whatever they want, but can instead only be in very specific states. If there are many easily accessible states, the electrons can freely move around between the atoms that make up the material, such that the material supports electrical currents and is therefore a conductor; if this is not the case, the material is an insulator. However, materials or devices in which the electrons are strongly interacting often have much more complicated properties. The goal of this thesis is to advance our understanding of such exotic materials by studying the electric and thermal transport properties of a specific strongly interacting nanoelectronic quantum dot device. In practice, whether or not a material can have unconventional properties is often determined by measuring the electrical conductance and the heat conductance and calculating their ratio. One of the most important results of this thesis is that this common method does actually not always work: we provide an explicit example of a device with proven exotic behaviour, which does nevertheless not show any signs of such behaviour in the ratio of the electrical conductance and the heat conductance. This is an important step in the quest to properly understand strongly interacting materials, which can potentially have useful applications in future technology.

Here we report on the identification and characterization of suspended double-stranded Au atomic chains up to ∼4 atoms long, using a scanning tunneling microscope adapted for the fabrication and simultaneous recording of the conductance. These chains are one of the smallest structures with the highest stability connecting two metallic electrodes, identified from the evolution of the conductance in the process of the controlled breakage of the contact between two metals. Molecular dynamics simulations and density functional theory electron transport calculations help us to unveil the richness of the geometric structures appearing in the experiments in the form of double-stranded chains, their stability, and how these can evolve into the formation of monoatomic chains.

In the brain, the excitation-inhibition balance prevents abnormal synchronous behavior. However, known synaptic conductance intensity can be insufficient to account for the undesired synchronization. Due to this fact, we consider time delay in excitatory and inhibitory conductances and study its effect on the neuronal synchronization. In this work, we build a neuronal network composed of adaptive integrate-and-fire neurons coupled by means of delayed conductances. We observe that the time delay in the excitatory and inhibitory conductivities can alter both the state of the collective behavior (synchronous or desynchronous) and its type (spike or burst). For the weak coupling regime, we find that synchronization appears associated with neurons behaving with extremes highest and lowest mean firing frequency, in contrast to when desynchronization is present when neurons do not exhibit extreme values for the firing frequency. Synchronization can also be characterized by neurons presenting either the highest or the lowest levels in the mean synaptic current. For the strong coupling, synchronous burst activities can occur for delays in the inhibitory conductivity. For approximately equal-length delays in the excitatory and inhibitory conductances, desynchronous spikes activities are identified for both weak and strong coupling regimes. Therefore, our results show that not only the conductance intensity, but also short delays in the inhibitory conductance are relevant to avoid abnormal neuronal synchronization., Peer Reviewed

In the brain, the excitation-inhibition balance prevents abnormal synchronous behavior. However, known synaptic conductance intensity can be insufficient to account for the undesired synchronization. Due to this fact, we consider time delay in excitatory and inhibitory conductances and study its effect on the neuronal synchronization. In this work, we build a neuronal network composed of adaptive integrate-and-fire neurons coupled by means of delayed conductances. We observe that the time delay in the excitatory and inhibitory conductivities can alter both the state of the collective behavior (synchronous or desynchronous) and its type (spike or burst). For the weak coupling regime, we find that synchronization appears associated with neurons behaving with extremes highest and lowest mean firing frequency, in contrast to when desynchronization is present when neurons do not exhibit extreme values for the firing frequency. Synchronization can also be characterized by neurons presenting either the highest or the lowest levels in the mean synaptic current. For the strong coupling, synchronous burst activities can occur for delays in the inhibitory conductivity. For approximately equal-length delays in the excitatory and inhibitory conductances, desynchronous spikes activities are identified for both weak and strong coupling regimes. Therefore, our results show that not only the conductance intensity, but also short delays in the inhibitory conductance are relevant to avoid abnormal neuronal synchronization., Peer Reviewed

Here we report on the identification and characterization of suspended double-stranded Au atomic chains up to ∼4 atoms long, using a scanning tunneling microscope adapted for the fabrication and simultaneous recording of the conductance. These chains are one of the smallest structures with the highest stability connecting two metallic electrodes, identified from the evolution of the conductance in the process of the controlled breakage of the contact between two metals. Molecular dynamics simulations and density functional theory electron transport calculations help us to unveil the richness of the geometric structures appearing in the experiments in the form of double-stranded chains, their stability, and how these can evolve into the formation of monoatomic chains.

Inhomogeneous superconductors can host electronic excitations, known as Andreev bound states (ABSs), below the superconducting energy gap. With the advent of topological superconductivity, a new kind of zero-energy ABS with exotic qualities, known as a Majorana bound state (MBS), has been discovered. A special property of MBS wavefunctions is their non-locality, which, together with non-Abelian braiding, is the key to their promise in topological quantum computation. We focus on hybrid superconductor-semiconductor nanowires as a flexible and promising experimental platform to realize one-dimensional topological superconductivity and MBSs. We review the main properties of ABSs and MBSs, state-of-the-art techniques for their detection and theoretical progress beyond minimal models, including different types of robust zero modes that may emerge without a band-topological transition.Topological Majorana bound states have potential for encoding, manipulating and protecting quantum information in condensed-matter systems. This Review discusses emergence and characterization of Majorana bound states in realistic devices based on hybrid semiconducting nanowires and their connection to more conventional Andreev bound states.

Inhomogeneous superconductors can host electronic excitations, known as Andreev bound states (ABSs), below the superconducting energy gap. With the advent of topological superconductivity, a new kind of zero-energy ABS with exotic qualities, known as a Majorana bound state (MBS), has been discovered. A special property of MBS wavefunctions is their non-locality, which, together with non-Abelian braiding, is the key to their promise in topological quantum computation. We focus on hybrid superconductor-semiconductor nanowires as a flexible and promising experimental platform to realize one-dimensional topological superconductivity and MBSs. We review the main properties of ABSs and MBSs, state-of-the-art techniques for their detection and theoretical progress beyond minimal models, including different types of robust zero modes that may emerge without a band-topological transition.Topological Majorana bound states have potential for encoding, manipulating and protecting quantum information in condensed-matter systems. This Review discusses emergence and characterization of Majorana bound states in realistic devices based on hybrid semiconducting nanowires and their connection to more conventional Andreev bound states.

Micro four-point probes (M4PP) provide rapid and automated lithography-free transport properties of planar surfaces including two-dimensional materials. We perform sheet conductance wafer maps of graphene directly grown on a 100 mm diameter SiC wafer using a multiplexed seven-point probe with minor additional measurement time compared to a four-point probe. Comparing the results of three subprobes we find that compared to a single-probe result, our measurement yield increases from 72%-84% to 97%. The additional data allows for correlation analysis between adjacent subprobes, that must measure the same values in case the sample is uniform on the scale of the electrode pitch. We observe that the relative difference in measured sheet conductance between two adjacent subprobes increase in the transition between large and low conductance regions. We mapped sheet conductance of graphene as it changed over several weeks. Terahertz time-domain spectroscopy conductivity maps both before and after M4PP mapping showed no significant change due to M4PP measurement, with both methods showing the same qualitative changes over time.

Almost any interaction between two physical entities can be described through the transfer of either charge, spin, momentum, or energy. Therefore, any theory able to describe these transport phenomena can shed light on a variety of physical, chemical, and biological effects, enriching our understanding of complex, yet fundamental, natural processes, e.g., catalysis or photosynthesis. In this review, we will discuss the standard workhorses for transport in nanoscale devices, namely Boltzmann's equation and Landauer's approach. We will emphasize their strengths, but also analyze their limits, proposing theories and models useful to go beyond the state of the art in the investigation of transport in nanoscale devices.

Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate other biological processes than MET in invertebrates ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized 4 amino acids that are required for the leak conductance. The leak conductance is graded in frequency-dependent manner along the length of the cochlea and indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and-intensity. © 2019, eLife Sciences Publications Ltd. All rights reserved.

The edge states in finite quantum Hall graphene have previously been shown to be valley polarised for zigzag and armchair edges. Assuming that the valley isospin is also conserved at a smooth normal-superconducting (NS) interface, theoretical research has previously predicted that plateaus in the longitudinal conductance are expected to occur in the lowest Landau level of the incoming edge modes, which depends on the angle difference between the isospins entering and leaving the superconductor. In this thesis, this prediction is verified with a tight-binding simulation of six different NS junctions: for both zigzag and armchair edge nanoribbons, the superconductor can cover a single edge, two adjacent edges or two opposite edges. The theoretical prediction could be confirmed successfully, suggesting that the edge states are valley polarised along a smooth NS interface. Some deviations from the theory could be observed for the armchair edge ribbon with opposite edges when the width of the ribbon is not a multiple of three hexagons. Two consecutive widths show a complementary behaviour in the conductance such that their average corresponds to the predicted value with a remarkable robustness. The reason for this complementarity was briefly conjectured by using the special Andreev reflection in graphene and the coupling between sublattice and valley degree of freedom for zigzag edges. The parameter regimes allowing for the existence of conductance plateaus were established, confirming that the plateaus emerge for a system size much larger than the magnetic length and the superconducting coherence length, and that a smooth chemical potential, magnetic field strength and superconducting order parameter are necessary at the NS interface. The robustness of the NS edge states was furthermore investigated with three methods: a Fermi energy mismatch between the bulk and the superconductor, and random normally distributed variation in the onsite electrostatic potential and a ra, Applied Physics

Almost any interaction between two physical entities can be described through the transfer of either charge, spin, momentum, or energy. Therefore, any theory able to describe these transport phenomena can shed light on a variety of physical, chemical, and biological effects, enriching our understanding of complex, yet fundamental, natural processes, e.g., catalysis or photosynthesis. In this review, we will discuss the standard workhorses for transport in nanoscale devices, namely Boltzmann's equation and Landauer's approach. We will emphasize their strengths, but also analyze their limits, proposing theories and models useful to go beyond the state of the art in the investigation of transport in nanoscale devices.

Almost any interaction between two physical entities can be described through the transfer of either charge, spin, momentum, or energy. Therefore, any theory able to describe these transport phenomena can shed light on a variety of physical, chemical, and biological effects, enriching our understanding of complex, yet fundamental, natural processes, e.g., catalysis or photosynthesis. In this review, we will discuss the standard workhorses for transport in nanoscale devices, namely Boltzmann's equation and Landauer's approach. We will emphasize their strengths, but also analyze their limits, proposing theories and models useful to go beyond the state of the art in the investigation of transport in nanoscale devices.

Almost any interaction between two physical entities can be described through the transfer of either charge, spin, momentum, or energy. Therefore, any theory able to describe these transport phenomena can shed light on a variety of physical, chemical, and biological effects, enriching our understanding of complex, yet fundamental, natural processes, e.g., catalysis or photosynthesis. In this review, we will discuss the standard workhorses for transport in nanoscale devices, namely Boltzmann's equation and Landauer's approach. We will emphasize their strengths, but also analyze their limits, proposing theories and models useful to go beyond the state of the art in the investigation of transport in nanoscale devices.

Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate other biological processes than MET in invertebrates ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized 4 amino acids that are required for the leak conductance. The leak conductance is graded in frequency-dependent manner along the length of the cochlea and indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and-intensity. © 2019, eLife Sciences Publications Ltd. All rights reserved.

The edge states in finite quantum Hall graphene have previously been shown to be valley polarised for zigzag and armchair edges. Assuming that the valley isospin is also conserved at a smooth normal-superconducting (NS) interface, theoretical research has previously predicted that plateaus in the longitudinal conductance are expected to occur in the lowest Landau level of the incoming edge modes, which depends on the angle difference between the isospins entering and leaving the superconductor. In this thesis, this prediction is verified with a tight-binding simulation of six different NS junctions: for both zigzag and armchair edge nanoribbons, the superconductor can cover a single edge, two adjacent edges or two opposite edges. The theoretical prediction could be confirmed successfully, suggesting that the edge states are valley polarised along a smooth NS interface. Some deviations from the theory could be observed for the armchair edge ribbon with opposite edges when the width of the ribbon is not a multiple of three hexagons. Two consecutive widths show a complementary behaviour in the conductance such that their average corresponds to the predicted value with a remarkable robustness. The reason for this complementarity was briefly conjectured by using the special Andreev reflection in graphene and the coupling between sublattice and valley degree of freedom for zigzag edges. The parameter regimes allowing for the existence of conductance plateaus were established, confirming that the plateaus emerge for a system size much larger than the magnetic length and the superconducting coherence length, and that a smooth chemical potential, magnetic field strength and superconducting order parameter are necessary at the NS interface. The robustness of the NS edge states was furthermore investigated with three methods: a Fermi energy mismatch between the bulk and the superconductor, and random normally distributed variation in the onsite electrostatic potential and a ra, Applied Physics

Cheeger's inequality shows that any undirected graph G with minimum normalized Laplacian eigenvalue lambda_G has a cut with conductance at most O(sqrt{lambda_G}). Qualitatively, Cheeger's inequality says that if the mixing time of a graph is high, there is a cut that certifies this. However, this relationship is not tight, as some graphs (like cycles) do not have cuts with conductance o(sqrt{lambda_G}). To better approximate the mixing time of a graph, we consider a more general object. Specifically, instead of bounding the mixing time with cuts, we bound it with cuts in graphs obtained by Schur complementing out vertices from the graph G. Combinatorially, these Schur complements describe random walks in G restricted to a subset of its vertices. As a result, all Schur complement cuts have conductance at least Omega(lambda_G). We show that unlike with cuts, this inequality is tight up to a constant factor. Specifically, there is a Schur complement cut with conductance at most O(lambda_G).

Let kappa in N_+^l satisfy kappa_1 + *s + kappa_l = n, and let U_kappa denote the multislice of all strings u in [l]^n having exactly kappa_i coordinates equal to i, for all i in [l]. Consider the Markov chain on U_kappa where a step is a random transposition of two coordinates of u. We show that the log-Sobolev constant rho_kappa for the chain satisfies rho_kappa^{-1} <= n * sum_{i=1}^l 1/2 log_2(4n/kappa_i), which is sharp up to constants whenever l is constant. From this, we derive some consequences for small-set expansion and isoperimetry in the multislice, including a KKL Theorem, a Kruskal - Katona Theorem for the multislice, a Friedgut Junta Theorem, and a Nisan - Szegedy Theorem.

Background: Initially after tattooing, the skin barrier function is broken. However, the long-term impact of clinically healed tattoos on this has never been studied. The aim was to investigate the long-term effect on the skin barrier function in normal tattoos and examples of tattoos with chronic inflammatory complication. Methods: Participants were recruited from the “Tattoo clinic” of the Dermatological Department on Bispebjerg Hospital in Denmark, where patients with complicated tattoo reactions are treated. Transepidermal water loss (TEWL), conductance, capacitance, and pH were measured in tattooed skin with regional control measurements in normal non-tattooed skin. Natural moisturizing factor (NMF) was measured in collected tape strips. Results: Twenty six individuals with 28 tattoos were included, that is, 23 normal tattoos without any pathologic reaction and 5 tattoos with chronic inflammatory complications. No significant differences were found in tattooed versus non-tattooed skin with respect to TEWL (median values 6.6 vs 7.2 g/m 2 /h), conductance (76 vs 78 a.u.), pH (5.94 vs 5.79), and NMF (0.58 vs 0.59 mmol/g protein). Capacitance (64 vs 57 a.u.) was higher in tattooed skin compared to non-tattooed skin (P = 0.006). Similar results were found in tattoos with inflammatory reactions. Conclusion: Overall, skin tattoos do not affect the long-term skin barrier function markedly. The skin capacitance was, however, affected in tattooed skin areas compared to non-tattooed skin areas.

©Wiley-V C H Verlag Gmbh The authors are indebted to A. DíazFernandez and J. M. Caridad for enlightened discussions and forá critical reading of the manuscript. This research has been supported by MINECO (Grants MAT2013-46308 and MAT2016- 75955) and Junta de Castilla y Leon (Grant SA045U16)., Here, the quantization of Dirac fermions in lithographically defined grapheme nanoconstrictions is studied. Quantized conductance is observed in single nanoconstrictions fabricated on top of a thin hexamethyldisilazane layer over a Si/SiO₂ wafer. This nanofabrication method allows to obtain well defined edges in the nanoconstrictions, thus reducing the effects of edge roughness on the conductance. The occurrence of ballistic transport is proved and several size quantization plateaus are identified in the conductance at low temperature. Experimental data and numerical simulations show good agreement, demonstrating that the smoothening of the plateaus is not related to edge roughness but to quantum interference effects., Ministerio de Economía y Competitividad (MINECO), Junta de Castilla y León, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub