| 1. |
- Ji, JZ, et al.
(författare)
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Modulation of L-type Ca(2+) channels by distinct domains within SNAP-25
- 2002
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 51:5, s. 1425-1436
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Tidskriftsartikel (refereegranskat)abstract
- Cognate soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) proteins are now known to associate the secretory vesicle with both the target plasma membrane and Ca2+ channels in order to mediate the sequence of events leading to exocytosis in neurons and neuroendocrine cells. Neuroendocrine cells, particularly insulin-secreting islet β-cells, t-SNARE proteins, 25-kDa synaptosomal-associated protein (SNAP-25), and syntaxin 1A, independently inhibit the L-type Ca2+ channel (LCa). However, when both are present, they actually exhibit stimulatory actions on the LCa. This suggests that the positive regulation of the LCa is conferred by a multi-SNARE protein complex. We hypothesized an alternate explanation, which is that each of these SNARE proteins possess distinct inhibitory and stimulatory domains that act on the LCa. These SNARE proteins were recently shown to bind the Lc753–893 domain corresponding to the II and III intracellular loop of the α1C subunit of the LCa. In this study, using patch-clamp methods on primary pancreatic β-cells and insulinoma HIT-T15 cells, we examined the functional interactions of the botulinum neurotoxin A (BoNT/A) cleavage products of SNAP-25, including NH2-terminal (1–197 amino acids) and COOH-terminal (amino acid 198–206) domains, on the LCa, particularly at the Lc753–893 domain. Intracellular application of SNAP-251–206 in primary β-cells decreased LCa currents by ∼15%. The reduction in LCa currents was counteracted by coapplication of Lc753–893. Overexpression or injection of wild-type SNAP-25 in HIT cells reduced LCa currents by ∼30%, and this inhibition was also blocked by the recombinant Lc753–893 peptide. Expression of BoNT/A surprisingly caused an even greater reduction of LCa currents (by 41%), suggesting that the BoNT/A cleavage products of SNAP-25 might possess distinct inhibitory and positive regulatory domains. Indeed, expression of SNAP-251–197 increased LCa currents (by 19% at 10 mV), and these effects were blocked by the Lc753–893 peptide. In contrast, injection of SNAP-25198–206 peptide into untransfected cells inhibited LCa currents (by 47%), and more remarkably, these inhibitory effects dominated over the stimulatory effects of SNAP-251–197 overexpression (by 34%). Therefore, the SNARE protein SNAP-25 possesses distinct inhibitory and stimulatory domains that act on the LCa. The COOH-terminal 197–206 domain of SNAP-25, whose inhibitory actions dominate over the opposing stimulatory NH2-terminal domain, likely confers the inhibitory actions of SNAP-25 on the LCa. We postulate that the eventual accelerated proteolysis of SNAP-25 brought about by BoNT/A cleavage allows the relatively intact NH2-terminal SNAP-25 domain to assert its stimulatory action on the LCa to increase Ca2+ influx, and this could in part explain the observed weak or inconsistent inhibitory effects of BoNT/A on insulin secretion. The present study suggests that distinct domains within SNAP-25 modulate LC subtype Ca2+ channel activity in both primary β-cells and insulinoma HIT-T15 cells.
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| 2. |
- Li, Z-F, et al.
(författare)
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Determination of carrier-transfer length from side-wall quantum well to quantum wire by micro-photoluminescence scanning
- 2003
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Ingår i: Journal of Electronic Materials. - : Springer Science Business Media. - 0361-5235 .- 1543-186X. ; 32:8, s. 913-916
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Tidskriftsartikel (refereegranskat)abstract
- Micro-photoluminescence (mu-PL) line scanning across a single V-groove, GaAs/AlGaAs quantum wire (QWR) has been performed at room temperature, revealing a clear spatial-dependence of the PL. After fitting each PL spectrum by multi-Gaussian line shapes, intensity profiles of each PL component from confined structures have been obtained as functions of the scanning position. The PL quenching of a side-wall quantum well (SQWL) has been recognized in a certain area in the vicinity of the QWR and is interpreted by carrier transfer into the QWR within effective transfer length. By simulating the carrier-transfer process from SQWL to QWR as a convolution of a step function for carrier distribution and a Gaussian function for exciting laser irradiance, the effective transfer length of about 1.8+/-0.3 mum has, therefore, been concluded.
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| 3. |
- Lu, W., et al.
(författare)
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Application of combinatorial material chip method on the improvement of quantum dots emission efficiency
- 2004
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Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 5277:1, s. 99-108
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Konferensbidrag (refereegranskat)abstract
- The combinatorial material chip method has been used to study the emission efficiency of InAs/GaAs quantum dots. The photoluminescence spectroscopy is performed to obtain the rule of emission efficiency on the proton implantation dose. A pronounced enhancement of room temperature emission efficiency has been obtained by the optimized quantum dots process condition. The increment of emission efficiency up to 80 itmes has been observed. This effect may be resulted from both the proton passivation and carrier capture enhancement effects. The maximum photoluminescence peak shift is about 23 meV resulted from the intermixing of quantum dots. A linear dependence behavior has been observed for both the non-radiative recombination time and carrier relaxation time on the ion-implantation dose. The maximum enhancement of the photoluminescence is observed in the proton implantation dose of 1.0 x 1014 cm-2 followed by rapid thermal annealing at 700°C. These effects will be useful for the QDs' optoelectronic devices.
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| 4. |
- Michielsen, Wim, et al.
(författare)
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Performance and cost estimations of packaged single band Voltage Controlled Oscillators
- 2004
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Ingår i: PROCEEDINGS OF THE IEEE 6TH CIRCUITS AND SYSTEMS SYMPOSIUM ON EMERGING TECHNOLOGIES: FRONTIERS OF MOBILE AND WIRELESS COMMUNICATION, VOLS 1 AND 2. - NEW YORK : IEEE. - 0780379381 ; , s. 53-56
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Konferensbidrag (refereegranskat)abstract
- This paper reports the performance and cost estimations in the early stage of a LC tank based Voltage Controlled Oscillator (VCO) design. System-on-Chip (SoC) versus System-on-package (SoP) configurations is compared for electrical performance and cost of a 1.25 GHz voltage controlled oscillator. It is found that a single chip design is not always the best solution. We obtained the best figure of merit for a SoP implementation where only the inductors were put off-chip.
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| 5. |
- Qiu, Jian-xin, et al.
(författare)
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[Study of sensitivity to impulse noise in guinea pig, rat and mouse]
- 2004
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Ingår i: Zhonghua er bi yan hou ke za zhi. - 0412-3948. ; 39:8, s. 472-475
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To study sensitivity to impulse noise in guinea pig, rat and mice. METHODS: Six groups were divided. Group I: Guinea pigs (n = 5) were exposed to 50 impulses of 160 dB SPL; Group II: Guinea pigs (n = 5) were exposed to 100 impulses of 160 dB SPL; Group III: Guinea pigs (n = 5) were exposed to 200 impulses of 160 dB SPL; Group IV: Guinea pigs (n = 6) were exposed 400 impulses of 160 dB SPL; Group V: Rats (n = 10) were exposed to 50 impulses of 160 dB SPL; Group VI: Mice (n = 10) were exposed to 50 impulses of 160 dB SPL. ABR thresholds were determined prior to, immediately, one day, one week, two weeks and four weeks after impulse noise exposure. RESULTS: The rat and mice were shown temporary threshold shift (TTS) and permanent threshold shift (PTS) after 50 times impulse noise (160), while no TTS and PTS in the guinea pigs but it was shown TTS and PTS after 400 times impulse noise (160). CONCLUSIONS: Sensitivity to impulse noise is different among guinea pig, rat and mouse. Guinea pig has less sensitivity to impulse noise while rat and mouse have higher sensitivity to impulse noise. In addition, rat has higher sensitivity to impulse noise than mouse.
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| 6. |
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| 7. |
- Shen, Meigen, et al.
(författare)
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Chip-package co-design for high performance and reliability off-chip communications
- 2004
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Ingår i: PROCEEDINGS OF THE SIXTH IEEE CPMT CONFERENCE ON HIGH DENSITY MICROSYSTEM DESIGN AND PACKAGING AND COMPONENT FAILURE ANALYSIS (HDP'04). - NEW YORK : IEEE. - 0780386205 ; , s. 31-36
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Konferensbidrag (refereegranskat)abstract
- Low interaction between chip and package has more and more limited system performance. In this paper, chip-package co-design methodology is presented. We address high performance and reliability enhancement for off-chip communications under package and interconnection constraints by using impedance control, optimal package pins assignment and transmitter equalization. From the high-speed transmitter design example, it is shown that the system-level performances such as signal integrity, bandwidth, and reliability are significantly improved through this co-design methodology.
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| 8. |
- Shen, Meigen, et al.
(författare)
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Cost and performance analysis for mixed-signal system implementation: system-on-chip or system-on-package?
- 2002
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Ingår i: IEEE transactions on electronics packaging manufacturing (Print). - 1521-334X .- 1558-0822. ; 25:4, s. 262-272
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Tidskriftsartikel (refereegranskat)abstract
- Advances, in integrated circuits and packaging technologies provided us more implementation options for mixed-signal systems. Emerging technologies are represented by system-on-chip (SoC) and system-on-package (SoP). In order to make a design decision or optimal system implementation, it is hence becoming more and more important to address the cost and performance issues for various implementation options early in a system deign phase. In this paper, we develop a modeling technique for a priori cost and performance estimations for mixed-signal system implementations. The performance model evaluates various noise isolation technologies, such as using guard rings, increasing the separation between digital and analog/RF circuitry parts, using special substrate materials (e.g., silicon-on-insulator), and partitioning the system into several chips. Besides, performance of particular analog/RF circuits such as low-noise amplifier (LNA), is also measured by their specific figure-of-merit (FoM), which considered the effects of substrate coupling, the quality factor (Q) of RF components, and packaging parasities. In cost analysis, new factors such as extra chip area and additional process steps due to mixed signal isolation, integration of intellectual property (IP) right module or "virtual components," yield and technology compatibility for merging logic, memory and analog/RF circuits on a single chip, are considered. Finally, an efficient computation algorithm, namely COMSI, was developed for cost estimation under various mixed-signal performance constraints. Case studies for SoC and Sol? integration are performed using COMSI.
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| 9. |
- Shen, Meigen, et al.
(författare)
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Robustness enhancement through chip-package co-design for high-speed electronics
- 2004
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Ingår i: ISQED 2004. - LOS ALAMITOS : IEEE COMPUTER SOC. ; , s. 184-189
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Low interaction between chip and package has more and more limited system performance. In this paper, chip-package co-design flow is presented. We address robustness enhancement under package and interconnection constraints by using impedance control, optimal package pins assignment and transmitter equalization. From the high-speed transmitter design example, co-design can reduce signal integrity problem, enhance its bandwidth, and improve high-speed electronic systems robustness.
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| 10. |
- Shen, Weiming, et al.
(författare)
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XML-Based Message Services for Internet Based Intelligent Shop Floors
- 2001
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Ingår i: Proceedings Volume 4566, Internet-based Enterprise Integration and Management. - : SPIE - International Society for Optical Engineering. ; , s. 135-144
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Konferensbidrag (refereegranskat)abstract
- Previously, we reported some preliminary results of our long-term research work on iShopFloor (Intelligent Shop Floor). This paper reports some of our recent work on the implementation of XML-based message services for Internet-based intelligent shop floors. The objective is to investigate XML for message exchange among Internet-based shop floor devices that are represented by intelligent agents. The paper discusses the advantages of using XML for message services and presents our initial implementation. From this implementation, we have seen some advantages, including: (1) simplification and standardization of message services in Internet-based intelligent shop floors; (2) facilitation of the integration of an agent-based scheduling system with other intelligent shop floor systems, including Web-based shop floor monitoring and control systems, etc.
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