| 1. |
- Acx, A. G., et al.
(författare)
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Radio Resource Management
- 2000
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Ingår i: Third generation mobile communication systems. - Boston, Mass : Artech House. - 1580530826 ; , s. 386-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Aspholm-Hurtig, Marina, et al.
(författare)
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Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin.
- 2004
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 305:5683, s. 519-22
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Tidskriftsartikel (refereegranskat)abstract
- Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations.
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| 3. |
- Berg, Anna, 1975-, et al.
(författare)
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Nitric oxide-an endogenous inhibitor of gastric acid secretion in isolated human gastric glands
- 2004
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Ingår i: BMC Gastroenterology. - 1471-230X. ; 4:16
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundEndothelial nitric oxide synthase (eNOS) has previously been detected in the glandular part of the human gastric mucosa. Furthermore, nitric oxide (NO) has been shown to influence gastric secretion in various animal models. The present study was conducted to investigate the influence of exogenously and endogenously derived NO on histamine- and cAMP-stimulated gastric acid secretion in isolated human oxyntic glands.MethodsOxyntic glands were isolated from human gastric biopsies and were subsequently pre-treated with NO donors and nitric oxide synthase inhibitors and then exposed to histamine or dibutyryl-cAMP (db-cAMP). The secretory response of the glands was determined as accumulation of [14C]aminopyrine.ResultsThe histamine- or db-cAMP-induced acid secretion was attenuated by L-arginine, a known source of endogenous NO, and also by the NO-donors sodium nitroprusside (SNP) and S-nitroso-N-acetyl-penicillamine (SNAP). Pre-treatment with either of the NOS inhibitors NG-nitro-L-arginine methyl ester (L-NAME) or NG-nitro-L-arginine (L-NNA) enhanced the secretory response.ConclusionOur results show that NO inhibits gastric acid secretion in isolated human gastric glands, and that there is endogenous formation of NO within the glandular epithelium in the vicinity of the parietal cells.
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| 4. |
- Berg, Jonas, 1973, et al.
(författare)
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A study on integration of molecular devices into CMOS compatible technology
- 2004
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Ingår i: Physica Scripta. - 1402-4896 .- 0031-8949. ; T114, s. 175-180
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Tidskriftsartikel (refereegranskat)abstract
- One main obstacle for measuring matter at the level of single molecule is the technology to make a bridge between molecules and microscopic structures (electrodes). A method of fabricating vertical silicon based nanogaps for contacting nanoscale elements has been developed and exploited to confront this problem. The developed technique is compatible to existing CMOS fabrication technology, reproducible and the gap size is easy to measure by simple capacitance measurements. Chemical treatment to attach any kind of nanoscale elements into the nanogap is an important issue. In this paper, we address problems related to surface leakage induced from different chemical processes. We have studied the effects of solvents on the surface leakage as well as surface leakage induced by nano components themselves. Surface leakage is a diffusion current process, and a set of parameters describing it has been used to compare the influence from different chemical processes. The study on solvents confirmed no predominant surface leakage induced by the presence of solvents like toluene and chloroform.
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| 5. |
- Berg, Jonas, 1973, et al.
(författare)
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Analysis of the use of molecular resonant tunneling diodes for local refresh of dynamic random access memory cells
- 2001
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Ingår i: MRS Spring Meeting. ; 679E, s. B1.6-
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Konferensbidrag (refereegranskat)abstract
- Simulations have been made to analyze the use of molecular resonant tunneling diodes for local refresh of DRAM (Dynamic Random Access Memory) cells. Local refresh can be provided by a latch consisting of a pair of resonant tunneling diodes connected to the storage capacitor of the cell. Such a solution would significantly reduce the standby power consumption of the DRAM cell. We have compared the requirements on the resonant tunneling diodes for proper refresh operation with the electrical properties of published molecules with resonant IV-curves. The simulations show that no molecules with resonant electrical properties published so far in the literature have properties making them useful for this particular application. This is true also for low temperature operation. The issues of maximum tolerable series resistance and of maximum tolerable fluctuations in the number of attached molecules have also been addressed. Our results show that the focus for development of molecules with resonant electrical properties should be to find molecules with resonance for lower applied voltages and lower current levels than the molecules published so far. If the synthesis of new molecules with attractive properties is successful the merging of silicon technology and molecular electronics, for instance for new generations of DRAM cells, is a realistic future path of microelectronics.
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| 6. |
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| 7. |
- Berg, Jonas, 1973, et al.
(författare)
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Can molecular resonant tunneling diodes be used for local refresh of DRAM memory cells?
- 2001
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Ingår i: 7th MELARI/NID workshop.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of molecular resonant tunneling diodes (RTDs) for use as local refresh of low-power DRAM cells has been studied. A pair of RTDs connected to the cell forms a latch that provides local refresh. This reduces the standby power of the cell, as the refresh operation is very power consuming. In this work, we compare the demands of future DRAM generations with the electrical properties of published molecules showing negative differential resistance. Simulations show that no one of the so far published molecular RTDs, other low-current RTDs made in SiGe, or III-V-materials fulfill these requirements.The simulations show that the focus of molecule development should be to find molecules with resonance for lower applied voltages and with lower current levels in general. The issues of maximum tolerable series resistance in the connection between the molecules and the silicon, and the maximum tolerable fluctuations in the number of attached molecules are also addressed.
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| 8. |
- Berg, Jonas, 1973, et al.
(författare)
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Simulation of SOI MOSFETs at GHz frequencies
- 2000
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Ingår i: GHz 2000. ; , s. 399-402
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Silicon-on-Insulator (SOI) technology shows advantages over bulk silicon technology at high frequencies. In this work, the performance of SOI MOSFETs has been simulated at GHz frequencies for SOI materials of different substrate resistivities using the device simulator Atlas. The transistors with an effective channel length of 0.24 µm were assumed to be made in a fully depleted SOI material consisting of a 30 nm silicon film on top of 100 nm buried silicon dioxide on top of a silicon substrate. The substrate resistivity was varied from 0.01 Ohmcm to 10 kOhmcm. The simulated transistors had a maximum oscillation frequency (fmax) of approximately 62 GHz. It was found that the high frequency properties of intrinsic transistors were independent of the substrate resistivity, but a system consisting of both active and passive components showed reduced fmax and fT for low substrate resistivity.
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| 9. |
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| 10. |
- Berg, Stefan, et al.
(författare)
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Sequence properties of the 1,2-diacylglycerol 3-glucosyltransferase from Acholeplasma laidlawii membranes : Recognition of a large group of lipid glycosyltransferases in eubacteria and archaea
- 2001
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:25, s. 22056-22063
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of the nonbilayer-prone α-monoglucosyldiacylglycerol (MGlcDAG) is crucial for bilayer packing properties and the lipid surface charge density in the membrane ofAcholeplasma laidlawii. The gene for the responsible, membrane-bound glucosyltransferase (alMGS) (EC 2.4.1.157) was sequenced and functionally cloned in Escherichia coli, yielding MGlcDAG in the recombinants. Similar amino acid sequences were encoded in the genomes of several Gram-positive bacteria (especially pathogens), thermophiles, archaea, and a few eukaryotes. All of these contained the typical EX7E catalytic motif of the CAZy family 4 of α-glycosyltransferases. The synthesis of MGlcDAG by a close sequence analog from Streptococcus pneumoniae (spMGS) was verified by polymerase chain reaction cloning, corroborating a connection between sequence and functional similarity for these proteins. However, alMGS and spMGS varied in dependence on anionic phospholipid activators phosphatidylglycerol and cardiolipin, suggesting certain regulatory differences. Fold predictions strongly indicated a similarity for alMGS (and spMGS) with the two-domain structure of the E. coli MurG cell envelope glycosyltransferase and several amphipathic membrane-binding segments in various proteins. On the basis of this structure, the alMGS sequence charge distribution, and anionic phospholipid dependence, a model for the bilayer surface binding and activity is proposed for this regulatory enzyme.
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