Bistable states of quantum dot array junctions for high-density memory

We demonstrate that two-dimensional (2D) arrays of coupled quantum dots (QDs) with six-fold degenerate p orbitals can display bistable states, suitable for application in high-density memory device with low power consumption. Due to the inter-dot coupling of $p_x$ and $p_y$ orbitals in these QD arrays, two dimensional conduction bands can be formed in the x-y plane, while the $p_z$ orbitals remain localized in the x-y plane such that the inter-dot coupling between them can be neglected. We model such systems by taking into account the on-site repulsive interactions between electrons in $p_z$ orbitals and the coupling of the localized $p_z$ orbitals with the 2D conduction bands formed by $p_x$ and $p_y$ orbitals. The Green's function method within an extended Anderson model is used to calculate the tunneling current through the QDs. We find that bistable tunneling current can exist for such systems due to the interplay of the on-site Coulomb interactions (U) between the $p_z$ orbitals and the delocalized nature of conduction band states derived from the hybridization of $p_x$ / $p_y$ orbitals. This bistable current is not sensitive to the detailed band structure of the two dimensional band, but depends critically on the strength of $U$ and the ratio of the left and right tunneling rates. The behavior of the electrical bistability can be sustained when the 2D QD array reduces to a one-dimensional QD array, indicating the feasibility for high-density packing of these bistable nanoscale structures

Lessons of Defeat and Success: Taiwan’s 2012 Elections in Comparative Perspective

In early 2011, the Kuomintang (KMT, Guomindang) government appeared to be in danger of losing power in the upcoming presidential elections. The DPP had recovered sufficiently from its disastrous electoral performance in 2008 to pose a real challenge to Ma Ying-jeou (Ma Yingjiu) and had matched the KMT’s vote share in mid-term local elections. Ma also faced the challenge of an independent presidential candidate, James Soong (Song Chuyu), who had come a close second in 2000 and now threatened to divide the pro KMT vote. Nevertheless, the KMT was able to win reduced majorities in both the presidential and legislative elections in January 2012. This article seeks to explain how the KMT was able to hold on to power by comparing the campaign with earlier national-level elections. We are interested in identifying the degree to which the Democratic Progressive Party (DPP, Minjindang) learnt from its electoral setbacks in 2008 and whether the KMT employed a similar campaign strategy to the one that had been so effective in returning it to power in 2008. Our analysis relies of an examination of campaign propaganda and campaign strategies as well as participant observation and survey data from 2012 and earlier contests

Effects of varying acupuncture manipulations at ST36 (Zusanli) on gastric electrical frequency and amplitude in bradygastria rabbits

Objective. To observe the effects of different manual acupuncture (MA) manipulation on gastric electrical amplitude and frequency for noradrenaline-induced bradygastria in rabbits. Methods. A total of 60 rabbits were randomly allocated into six groups: four MA manipulation groups; reinforcing by twisting the manipulation group (FTG), reducing by twisting the manipulation group (RTG), reinforcing by lifting and thrusting the manipulation group (FLG), and reducing by lifting and thrusting the manipulation group (RLG), a control group (CG), and a model group (MG). The total treatment time length was 45 minutes. The bradygastria was induced via administration of noradrenaline via the marginal ear vein of the rabbits at 5 minutes from baseline, and the bradygastria model was established at 12 minutes from baseline. The rabbits in the four MA manipulation groups received different stimulation parameters at ST36 (Zusanli) for a duration of 3 minutes in accordance with their respective group allocation. The needles were then retained without further manipulation for a further 25 minutes. Gastric electrical amplitude and frequency were recorded using a data acquisition system (Biopac System MP150) at five different time points: baseline (for a duration of 5 minutes), after the bradygastria model was established at 12 minutes from baseline (for a duration of 5 minutes), during MA manipulation commencing at 17 minutes from baseline (for a duration of 3 minutes), 5 minutes after MA manipulation at 25 minutes from baseline (for a duration of 5 minutes), and at 20 minutes following MA manipulation at 40 minutes from baseline (for a duration of 5 minutes). Results. After noradrenaline induction, gastric electrical frequency levels in MA and MG groups were significantly decreased compared to the CG group (P 0.05). During MA manipulation, gastric electrical frequency levels in RTG, FLG, and RLG groups were higher than in the MG group (P < 0.05). At 5 minutes after MA manipulation, gastric electrical frequency levels in RTG and FLG groups were higher than in the MG group (P < 0.05), and gastric electrical frequency level in the RTG group was higher than in the CG group (P < 0.05). At 20 minutes after MA manipulation, gastric electrical frequency levels in FTG, RTG, and FLG groups were higher than in the MG group (P < 0.05). Conclusion. All four variations of MA manipulations have a recovery effect on the gastric electrical frequency of rabbits with bradygastria. In particular, results indicated that FTG, RTG, and FLG at ST36 may have a regular and significant recovery trend through the whole process of the acupuncture intervention

Morphology and tectonics of the Mid-Atlantic Ridge, 7°–12°S

We present swath bathymetric, gravity, and magnetic data from the Mid-Atlantic Ridge between the Ascension and the Bode Verde fracture zones, where significant ridge–hot spot interaction has been inferred. The ridge axis in this region may be divided into four segments. The central two segments exhibit rifted axial highs, while the northernmost and southernmost segments have deep rift valleys typical of slow-spreading mid-ocean ridges. Bathymetric and magnetic data indicate that both central segments have experienced ridge jumps since ~1 Ma. Mantle Bouguer anomalies (MBAs) derived from shipboard free air gravity and swath bathymetric data show deep subcircular lows centered on the new ridge axes, suggesting that mantle flow has been established beneath the new spreading centers for at least ~1 Myr. Inversion of gravity data indicates that crustal thicknesses vary by ~4 km along axis, with the thickest crust occurring beneath a large axial volcanic edifice. Once the effects of lithospheric aging have been removed, a model in which gravity variations are attributed entirely to crustal thickness variations is more consistent with data from an axis-parallel seismic line than a model that includes additional along-axis variations in mantle temperature. Both geophysical and geochemical data from the region may be explained by the melting of small (&lt;200 km) mantle chemical heterogeneities rather than elevated temperatures. Therefore, there may be no Ascension/Circe plume

Bistability in the Tunnelling Current through a Ring of NN Coupled Quantum Dots

We study bistability in the electron transport through a ring of N coupled quantum dots with two orbitals in each dot. One orbital is localized (called b orbital) and coupling of the b orbitals in any two dots is negligible; the other is delocalized in the plane of the ring (called d orbital), due to coupling of the d orbitals in the neighboring dots, as described by a tight-binding model. The d orbitals thereby form a band with finite width. The b and d orbitals are connected to the source and drain electrodes with a voltage bias V, allowing the electron tunnelling. Tunnelling current is calculated by using a nonequilibrium Green function method recently developed to treat nanostructures with multiple energy levels. We find a bistable effect in the tunnelling current as a function of bias V, when the size N>50; this effect scales with the size N and becomes sizable at N~100. The temperature effect on bistability is also discussed. In comparison, mean-field treatment tends to overestimate the bistable effect.Comment: Published in JPSJ; minor typos correcte

Molecular layer-by-layer re-stacking of MoS2–In2Se3 by electrostatic means: assembly of a new layered photocatalyst

2D-layered transition metal chalcogenides are useful semiconductors for a wide range of opto-electronic applications. Their similarity as layered structures offers exciting possibility to modify their electronic properties by creating new heterojunction assemblies from layer-by-layer restacking of individual monolayer sheets, however, the lack of specific interaction between these layers could induce phase segregation. Here, we employed a chemical method using n-BuLi to exfoliate MoS2 and In2Se3 into their monolayer-containing colloids in solution. The bulky Se atoms can be selectively leached from In2Se3 during Li treatment which gives positively charged surface monolayers in neutral pH whereas the strong polarization of Mo–S with moderate S leaching gives a negatively charged surface. Specific interlayer electrostatic attraction during their selective assembly gives a controllable atomic AB-type of layer stacking as supported by EXAFS, STEM with super-EDX mapping, TAS/TRPL and DFT calculations. Using this simple but inexpensive bottom-up solution method, a new photocatalyst assembled from layers for photo water splitting can be tailor-made with high activity

Molecular layer-by-layer re-stacking of MoS2–In2Se3 by electrostatic means: assembly of a new layered photocatalyst

2D-layered transition metal chalcogenides are useful semiconductors for a wide range of opto-electronic applications. Their similarity as layered structures offers exciting possibility to modify their electronic properties by creating new heterojunction assemblies from layer-by-layer restacking of individual monolayer sheets, however, the lack of specific interaction between these layers could induce phase segregation. Here, we employed a chemical method using n-BuLi to exfoliate MoS2 and In2Se3 into their monolayer-containing colloids in solution. The bulky Se atoms can be selectively leached from In2Se3 during Li treatment which gives positively charged surface monolayers in neutral pH whereas the strong polarization of Mo–S with moderate S leaching gives a negatively charged surface. Specific interlayer electrostatic attraction during their selective assembly gives a controllable atomic AB-type of layer stacking as supported by EXAFS, STEM with super-EDX mapping, TAS/TRPL and DFT calculations. Using this simple but inexpensive bottom-up solution method, a new photocatalyst assembled from layers for photo water splitting can be tailor-made with high activity

Composition-Tuned Pt-Skinned PtNi Bimetallic Clusters as Highly Efficient Methanol Dehydrogenation Catalysts

Platinum is the most active anode and cathode catalyst in next-generation fuel cells using methanol as liquid source of hydrogen. Its catalytic activity can be significantly improved by alloying with 3d metals, although a precise tuning of its surface architecture is still required. Herein, we report the design of a highly active low-temperature (below 0 °C) methanol dehydrogenation anode catalyst with reduced CO poisoning based on ultralow amount of precisely defined PtxNi1–x (x = 0 to 1) bimetallic clusters (BCs) deposited on inert flat oxides by cluster beam deposition. These BCs feature clear composition-dependent atomic arrangements and electronic structures stemming from their nucleation mechanism, which are responsible for a volcano-type activity trend peaking at the Pt0.7Ni0.3 composition. Our calculations reveal that at this composition, a cluster skin of Pt atoms with d-band centers downshifted by subsurface Ni atoms weakens the CO interaction that in turn triggers a significant increase in the methanol dehydrogenation activity

Association between the risk of heart failure hospitalization and end-stage renal disease with digoxin usage in patients with cardiorenal syndrome: A population-based study

BackgroundThe management of the coexistence of heart disease and kidney disease is increasingly challenging for clinicians. Chronic kidney disease (CKD) is not only a prevalent comorbidity of patients with heart failure but has also been identified as a noteworthy risk factor for all-cause mortality and poor clinical outcomes. Digoxin is one of the commonest treatments for heart disease. There are few trials investigating the role of digoxin in patients with cardiorenal syndrome (CRS). This study aims to examine the association between digoxin usage and clinical outcomes in patients with CRS in a nationwide cohort.MethodWe conducted a population-based study that included 705 digoxin users with CRS; each patient was age, sex, comorbidities, and medications matched with three non-users who were randomly selected from the CRS population. Cox proportional hazards regression analysis was conducted to estimate the effects of digoxin on the incidence of all-cause mortality, congestive heart failure (CHF) hospitalization, coronary artery disease (CAD) hospitalization, and end-stage renal disease (ESRD).ResultsThe all-cause mortality rate was significantly higher in digoxin users than in non-users (adjusted hazard ratio [aHR] = 1.26; 95% confidence interval [CI] = 1.09–1.46, p = 0.002). In a subgroup analysis, there was significantly high mortality in the 0.26–0.75 defined daily dose (DDD) subgroup of digoxin users (aHR = 1.49; 95% CI = 1.23–1.82, p&lt;0.001). Thus, the p for trend was 0.013. With digoxin prescription, the CHF hospitalization was significantly higher [subdistribution HR (sHR) = 1.17; 95% CI = 1.05–1.30, p = 0.004], especially in the &gt;0.75 DDD subgroup (sHR = 1.19; 95% CI = 1.01–1.41, p = 0.046; p for trend = 0.006). The digoxin usage lowered the coronary artery disease (CAD) hospitalization in the &gt; 0.75 DDD subgroup (sHR = 0.79; 95% CI = 0.63–0.99, p = 0.048). In renal function progression, more patients with CRS entered ESRD with digoxin usage (sHR = 1.34; 95% CI = 1.16–1.54, p&lt;0.001). There was a significantly greater incidence of ESRD in the &lt; 0.26 DDD and 0.26–0.75 DDD subgroups of digoxin users (sHR = 1.32; 95% CI = 1.06–1.66, p = 0.015; sHR = 1.44; 95% CI = 1.18–1.75; p for trend&lt;0.001).ConclusionDigoxin should be prescribed with caution to patients with CRS

Allosteric mechanism of Ca2+ activation and H+-inhibited gating of the MthK K+ channel

MthK is a Ca2+-gated K+ channel whose activity is inhibited by cytoplasmic H+. To determine possible mechanisms underlying the channel’s proton sensitivity and the relation between H+ inhibition and Ca2+-dependent gating, we recorded current through MthK channels incorporated into planar lipid bilayers. Each bilayer recording was obtained at up to six different [Ca2+] (ranging from nominally 0 to 30 mM) at a given [H+], in which the solutions bathing the cytoplasmic side of the channels were changed via a perfusion system to ensure complete solution exchanges. We observed a steep relation between [Ca2+] and open probability (Po), with a mean Hill coefficient (nH) of 9.9 ± 0.9. Neither the maximal Po (0.93 ± 0.005) nor nH changed significantly as a function of [H+] over pH ranging from 6.5 to 9.0. In addition, MthK channel activation in the nominal absence of Ca2+ was not H+ sensitive over pH ranging from 7.3 to 9.0. However, increasing [H+] raised the EC50 for Ca2+ activation by ∼4.7-fold per tenfold increase in [H+], displaying a linear relation between log(EC50) and log([H+]) (i.e., pH) over pH ranging from 6.5 to 9.0. Collectively, these results suggest that H+ binding does not directly modulate either the channel’s closed–open equilibrium or the allosteric coupling between Ca2+ binding and channel opening. We can account for the Ca2+ activation and proton sensitivity of MthK gating quantitatively by assuming that Ca2+ allosterically activates MthK, whereas H+ opposes activation by destabilizing the binding of Ca2+