| 1. |
- Deng, Mingtang, et al.
(författare)
-
Anomalous Zero-Bias Conductance Peak in a Nb-InSb Nanowire-Nb Hybrid Device.
- 2012
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:12, s. 6414-6419
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor InSb nanowires are expected to provide an excellent material platform for the study of Majorana fermions in solid state systems. Here, we report on the realization of a Nb-InSb nanowire-Nb hybrid quantum device and the observation of a zero-bias conductance peak structure in the device. An InSb nanowire quantum dot is formed in the device between the two Nb contacts. Due to the proximity effect, the InSb nanowire segments covered by the superconductor Nb contacts turn to superconductors with a superconducting energy gap Δ(InSb) ∼ 0.25 meV. A tunable critical supercurrent is observed in the device in high back gate voltage regions in which the Fermi level in the InSb nanowire is located above the tunneling barriers of the quantum dot and the device is open to conduction. When a perpendicular magnetic field is applied to the devices, the critical supercurrent is seen to decrease as the magnetic field increases. However, at sufficiently low back gate voltages, the device shows the quasi-particle Coulomb blockade characteristics and the supercurrent is strongly suppressed even at zero magnetic field. This transport characteristic changes when a perpendicular magnetic field stronger than a critical value, at which the Zeeman energy in the InSb nanowire is E(z) ∼ Δ(InSb), is applied to the device. In this case, the transport measurements show a conductance peak at the zero bias voltage and the entire InSb nanowire in the device behaves as in a topological superconductor phase. We also show that this zero-bias conductance peak structure can persist over a large range of applied magnetic fields and could be interpreted as a transport signature of Majorana fermions in the InSb nanowire.
|
|
| 2. |
- Deng, Mingtang, et al.
(författare)
-
Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device.
- 2014
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- We explore the signatures of Majorana fermions in a nanowire based topological superconductor-quantum dot-topological superconductor hybrid device by charge transport measurements. At zero magnetic field, well-defined Coulomb diamonds and the Kondo effect are observed. Under the application of a finite, sufficiently strong magnetic field, a zero-bias conductance peak structure is observed. It is found that the zero-bias conductance peak is present in many consecutive Coulomb diamonds, irrespective of the even-odd parity of the quasi-particle occupation number in the quantum dot. In addition, we find that the zero-bias conductance peak is in most cases accompanied by two differential conductance peaks, forming a triple-peak structure, and the separation between the two side peaks in bias voltage shows oscillations closely correlated to the background Coulomb conductance oscillations of the device. The observed zero-bias conductance peak and the associated triple-peak structure are in line with Majorana fermion physics in such a hybrid topological system.
|
|
| 3. |
|
|
| 4. |
- Lee, Ho-Hsien, et al.
(författare)
-
Expression, purification and crystallization of CTB-MPR, a candidate mucosal vaccine component against HIV-1
- 2014
-
Ingår i: IUCrJ. - 2052-2525. ; 1:5, s. 305-317
-
Tidskriftsartikel (refereegranskat)abstract
- CTB-MPR is a fusion protein between the B subunit of cholera toxin (CTB) andthe membrane-proximal region of gp41 (MPR), the transmembrane envelopeprotein ofHuman immunodeficiency virus 1(HIV-1), and has previously beenshown to induce the production of anti-HIV-1 antibodies with antiviralfunctions. To further improve the design of this candidate vaccine, X-raycrystallography experiments were performed to obtain structural informationabout this fusion protein. Several variants of CTB-MPR were designed,constructed and recombinantly expressed inEscherichia coli. The first variantcontained a flexible GPGP linker between CTB and MPR, and yielded crystalsthat diffracted to a resolution of 2.3 A ̊, but only the CTB region was detectedin the electron-density map. A second variant, in which the CTB was directlyattached to MPR, was shown to destabilize pentamer formation. A thirdconstruct containing a polyalanine linker between CTB and MPR proved tostabilize the pentameric form of the protein during purification. The purificationprocedure was shown to produce a homogeneously pure and monodispersesample for crystallization. Initial crystallization experiments led to pseudo-crystals which were ordered in only two dimensions and were disordered inthe third dimension. Nanocrystals obtained using the same precipitant showedpromising X-ray diffraction to 5 A ̊resolution in femtosecond nanocrystallo-graphy experiments at the Linac Coherent Light Source at the SLAC NationalAccelerator Laboratory. The results demonstrate the utility of femtosecondX-ray crystallography to enable structural analysis based on nano/microcrystalsof a protein for which no macroscopic crystals ordered in three dimensions havebeen observed before.
|
|
| 5. |
- Xu, Guangwei, et al.
(författare)
-
Synthesis, properties, and top-gated metal-oxide-semiconductor field-effect transistors of p-type GaSb nanowires
- 2013
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 3:43, s. 19834-19839
-
Tidskriftsartikel (refereegranskat)abstract
- High-quality GaSb nanowires (NWs) have been synthesized via chemical vapor deposition. The as-synthesized NWs have a zinc-blende structure with growth direction along a < 011 > direction. Raman spectrum of the GaSb NWs consists of two peaks, corresponding to the LO and TO phonon modes, respectively. The temperature dependence of the photoluminescence spectra shows a blue-shift as the temperature decreases from 300 to 13 K. The electrical properties of the GaSb NWs are investigated over a wide range of temperatures from 25 mK to 291 K. The results show that the GaSb NWs exhibit excellent p-type transistor performance at low temperatures (<40 K). The room-temperature hole density and mobility were found to be similar to 2.2 x 10(18) cm(-3) and similar to 14.2 cm(2) V-1 s(-1), respectively. The Schottky contact characteristics were observed and the barrier height was found to be similar to 14 meV. Our results show that the GaSb NWs could be used as building blocks for emerging p-type nanoelectronic devices in extremely low temperature environments.
|
|
| 6. |
|
|
| 7. |
- Zhou, Mengtao, et al.
(författare)
-
The efficiency of continuous regional intra-arterial infusion in the treatment of infected pancreatic necrosis
- 2013
-
Ingår i: Pancreatology. - : Elsevier BV. - 1424-3903. ; 13:3, s. 212-215
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: Our aim was to investigate the efficiency of continuous regional intra-arterial infusion (CRAI) with antisecretory agents and antibiotics in the treatment of infected pancreatic necrosis. Materials and methods: CRAI was used as a new clinical technique to treat acute pancreatitis patients during a 4-year period at the First Affiliated Hospital, Wenzhou Medical College, China. In this retrospective study, thirty-four patients with proven infected pancreatic necrosis were included. Twelve patients were treated with CRAL and were matched according to age, sex, APACHE II scores, Ranson scores and remote organ dysfunction, with 22 patients with IPN treated surgically. The clinical outcome following surgery and CRAI were compared. Results: No difference was found between the two groups when comparing age, gender, APACHE II scores, Ranson scores and remote organ dysfunction (p > 0.05). The patients treated with CRAI had a lower incidence of complications (33.3% vs 72.7%), duration of hospitalization (27.1 +/- 4.7 days vs 43.0 +/- 12.0 days) and cost of hospitalization (4.09 +/- 1.64 thousand RMB vs 8.77 +/- 3.74 thousand RMB) as compared to patients treated with surgery (p < 0.05). The survival rate was significantly higher in the CRAI group as compared to the surgical group (91.7% vs 63.6%; p < 0.01). However, the two groups had similar rates of concomitant operative treatment and incidence of remote organ dysfunction (p > 0.05). Conclusions: CRAI or CRAI in combination with abscess drainage seemingly improve the clinical outcome in patients with infected pancreatic necrosis. Further confirmative prospective randomized multicenter studies are warranted prior to broad introduction of the CRAI concept. Copyright (C) 2013, IAP and EPC. Published by Elsevier India, a division of Reed Elsevier India Pvt. Ltd. All rights reserved.
|
|
