| 1. |
- Jacob, A P, et al.
(författare)
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Cryogenic performance of ultrathin oxide MOS capacitors with in situ doped p(+) poly-Si1-xGex and poly-Si gate materials
- 2002
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Ingår i: Semiconductor Science and Technology. - : Iop Publishing Ltd. - 0268-1242 .- 1361-6641. ; 17:9, s. 942-946
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Tidskriftsartikel (refereegranskat)abstract
- A low-temperature electrical characterization of ultrathin oxide MOS capacitors with p(+) poly-Si1-xGex and poly-Si gate is performed. The investigated structures are suitable for future nano-scaled high speed MOSFETs. The aim of this study is to compare the low-temperature performance of poly-Si1-xGex and poly-Si gate MOS structures in the nanoscale channel length regime. Apart from the significant change in the flat band voltage, the result shows that all the poly-Si and poly-Si1-xGex gated MOS structures exhibit two centres of polarity change (zero-temperature coefficients) in capacitance. The second polarity change leads to an exclusive phenomenon in these structures. The low-temperature capacitance is found to be less than high-temperature capacitance at strong accumulation and this is in contrast to what has been observed so far in metal-gated capacitors. It is also observed that the temperature dependence of the tunnelling current is only on the oxide thickness and not on the gate material used.
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| 2. |
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| 3. |
- Ye, L L, et al.
(författare)
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Structural roughness and interface strain properties in Si/SiO2/poly-Si1-xGex tri-layer system with ultrathin oxide
- 2003
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science Business Media. - 0957-4522 .- 1573-482X. ; 14:4, s. 247-254
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Tidskriftsartikel (refereegranskat)abstract
- We have explored the microstructure and local interface strain in the poly-Si1-xGex/SiO2/Si tri-layer system with ultrathin oxides. High-resolution transmission electron microscopy (HRTEM) and high-resolution X-ray diffraction rocking curves (HR-RC) and two-dimensional reciprocal space mapping (2D-RSM) were the main characterization tools. The poly-Si1-xGex/SiO2/Si structures have x=0, 0.2, and 0.35 for ultrathin oxides (2.0-3.0 nm). The result shows that for the adopted growth process, the poly grain size depends very strongly on the Ge concentration, and it increases with increasing Ge mole fraction. In turn, this increase of the grain size in the poly-Si1-xGex/SiO2/Si reduces the strain in the film, which then affects the interface strain at the lower SiO2/Si interface. In addition, the presence of defects at the SiO2/Si interface was found to be greater for samples with no local interface strain.
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| 4. |
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| 5. |
- Surugiu, Ioana, et al.
(författare)
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Chemiluminescence imaging ELISA using an imprinted polymer as the recognition element instead of an antibody
- 2001
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 73:3, s. 487-491
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Tidskriftsartikel (refereegranskat)abstract
- An imaging assay analogous to competitive enzyme immunoassays has been developed using a molecularly imprinted polymer instead of an antibody. The antigen 2,4-dichlorophenoxyacetic acid (2,4-D) was labeled with tobacco peroxidase, and the chemiluminescence reaction of luminol was used for detection. Microtiter plates (96 or 384 wells) were coated with polymer microspheres imprinted with 2,4-D, which were fixed in place by using poly(vinyl alcohol) as glue. In a competitive mode, the analyte-peroxidase conjugate was incubated with the free analyte in the microtiter plate, after which the bound fraction of the conjugate was quantified. After addition of the chemiluminescent substrates, light emission was measured in a high-throughput imaging format with a CCD camera. Calibration curves corresponding to analyte concentrations ranging from 0.01 to 100 μg/mL were obtained.
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| 6. |
- Surugiu, Ioana, et al.
(författare)
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Development of a flow injection capillary chemiluminescent ELISA using an imprinted polymer instead of the antibody
- 2001
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 73:17, s. 4388-4392
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Tidskriftsartikel (refereegranskat)abstract
- A flow injection competitive assay analogous to enzyme immunoassays has been developed using a molecularly imprinted polymer instead of the antibody. A glass capillary was modified by covalently attaching an imprinted polymer to the inner capillary wall. The herbicide 2,4-dichlorophenoxyacetic acid was used as a model analyte. The analyte was labeled with tobacco peroxidase, and chemiluminescence was used for detection in combination with a photomultiplier tube or a CCD camera. In a competitive mode, the analyte-peroxidase conjugate was passed together with the free analyte through the polymer-coated capillary mounted in a flow system. After a washing step, the chemiluminescent substrate was injected and the bound fraction of the conjugate was quantified by measuring the intensity of the emitted light. Calibration curves corresponding to analyte concentrations ranging from 0.5 ng mL-1 to 50 μg mL-1 (2.25 nM-225 μM) were obtained. A lowered detection limit by 2 orders of magnitude was obtained when detection was done in discontinuous mode and the chemiluminescence light was conducted inside the photomultiplier tube by an optical fiber bundle, thus yielding a dynamic range of 5 pg mL-1-100 ng mL-1 (22.5 pM-450 nM).
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| 7. |
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| 8. |
- Ye, L, et al.
(författare)
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Thyroid receptor ligands. 1. Agonist ligands selective for the thyroid receptor beta1.
- 2003
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Ingår i: Journal of Medicinal Chemistry. ; 24;46:9, s. 1580-8
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Tidskriftsartikel (refereegranskat)abstract
- Endogenous thyroid receptor hormones 3,5,3',5'-tetraiodo-l-thyronine (T(4), 1) and 3,5,3'-triiodo-l-thyronine (T(3), 2) exert a significant effects on growth, development, and homeostasis in mammals. They regulate important genes in intestinal, skeletal, and cardiac muscles, the liver, and the central nervous system, influence overall metabolic rate, cholesterol and triglyceride levels, and heart rate, and affect mood and overall sense of well being. The literature suggests many or most effects of thyroid hormones on the heart, in particular on the heart rate and rhythm, are mediated through the TRalpha(1) isoform, while most actions of the hormones on the liver and other tissues are mediated more through the TRbeta(1) isoform of the receptor. Some effects of thyroid hormones may be therapeutically useful in nonthyroid disorders if adverse effects can be minimized or eliminated. These potentially useful features include weight reduction for the treatment of obesity, cholesterol lowering for treating hyperlipidemia, amelioration of depression, and stimulation of bone formation in osteoporosis. Prior attempts to utilize thyroid hormones pharmacologically to treat these disorders have been limited by manifestations of hyperthyroidism and, in particular, cardiovascular toxicity. Consequently, development of thyroid hormone receptor agonists that are selective for the beta-isoform could lead to safe therapies for these common disorders while avoiding cardiotoxicity. We describe here the synthesis and evaluation of a series of novel TR ligands, which are selective for TRbeta(1) over TRalpha(1). These ligands could potentially be useful for treatment of various disorders as outlined above. From a series of homologous R(1)-substituted carboxylic acid derivatives, increasing chain length was found to have a profound effect on affinity and selectivity in a radioreceptor binding assay for the human thyroid hormone receptors alpha(1) and beta(1) (TRalpha(1) and TRbeta(2)) as well as a reporter cell assay employing CHOK1-cells (Chinese hamster ovary cells) stably transfected with hTRalpha(1) or hTRbeta(1) and an alkaline phosphatase reporter-gene downstream thyroid response element (TRAFalpha(1) and TRAFbeta(1)). Affinity increases in the order formic, acetic, and propionic acid, while beta-selectivity is highest when the R(1) position is substituted with acetic acid. Within this series 3,5-dibromo-4-[(4-hydroxy-3-isopropylphenoxy)phenyl]acetic acid (11a) and 3,5-dichloro-4-[(4-hydroxy-3-isopropylphenoxy)phenyl]acetic acid (15) were found to reveal the most promising in vitro data based on isoform selectivity and were selected for further in vivo studies. The effect of 2, 11a, and 15 in a cholesterol-fed rat model was monitored including potencies for heart rate (ED(15)), cholesterol (ED(50)), and TSH (ED(50)). Potency for tachycardia was significantly reduced for the TRbeta selective compounds 11a and 15 compared with 2, while both 11a and 15 retained the cholesterol-lowering potency of 2. This left an approximately 10-fold therapeutic window between heart rate and cholesterol, which is consistent with the action of ligands that are approximately 10-fold more selective for TRbeta(1). We also report the X-ray crystallographic structures of the ligand binding domains of TRalpha and TRbeta in complex with 15. These structures reveal that the single amino acid difference in the ligand binding pocket (Ser277 in TRalpha or Asn331 in TRbeta) results in a slightly different hydrogen bonding pattern that may explain the increased beta-selectivity of 15.
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| 9. |
- Ye, L., et al.
(författare)
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Towards the development of molecularly imprinted artificial receptors for the screening of estrogenic chemicals
- 2001
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654. ; 126:6, s. 760-765
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers are prepared using various steroid compounds as the templates. The imprinted polymers can selectively re-bind the original print molecules, which leads to versatile potential applications. The feasibility of using these artificial receptors to replace their biological counterparts for preliminary screening of a chemical library is demonstrated. A steroid library composed of 22 closely related compounds is screened with an estrogen specific polymer. The print molecule is identified with accuracy and structural similarities of other members are correlated with normalized retention indices. Molecularly imprinted artificial receptors are envisioned as being useful for screening purposes in drug discovery or for identifying endocrine-disrupting chemicals.
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