Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 20
Filter
Add more filters










Publication year range
1.
Acad Radiol ; 2024 Jul 01.
Article in English | MEDLINE | ID: mdl-38955593

ABSTRACT

RATIONALE AND OBJECTIVES: To evaluate glymphatic function changes and their relationships with clinical features in patients with metabolic dysfunction-associated fatty liver disease (MAFLD), thereby facilitating early intervention before this disease progresses to cirrhosis. MATERIALS AND METHODS: A cross-sectional cohort of 46 pre-cirrhotic MAFLD patients and 30 age-, sex-, and education-matched controls was enrolled, with diffusion-tensor imaging (DTI) data, laboratory and neurocognitive scores collected. The DTI analysis along the perivascular space (DTI-ALPS) index was computed for qualifying glymphatic function. Generalized linear model and partial correlation analyses were applied to evaluate relationships between the ALPS index and clinical variables. RESULTS: MAFLD group exhibited a decreased ALPS index and increased diffusivity along the y-axis in the projection fiber compared to the controls. The altered ALPS index was associated with clock drawing test (CDT) score (3.931 [0.914, 6.947], P = 0.011) and was correlated with diastolic pressure level (r = -0.315, P = 0.033) in MAFLD group. The relationships of ALPS index with CDT score (6.263 [2.069, 10.458], P = 0.003) and diastolic pressure level (r = -0.518, P = 0.014) remained in the MAFLD with metabolic syndrome (MetS) group. Furthermore, the ALPS index was even associated with Auditory Verbal Learning Test-Immediate recall score (-23.853 [-45.417, -2.289], P = 0.030) in MAFLD with MetS group. CONCLUSION: MAFLD patients may have a glymphatic dysfunction prior to cirrhosis, and this alteration may be related to cognition and diastolic pressure. Glymphatic dysfunction has a more severe impact on cognition when MAFLD patient is accompanied by MetS.

2.
J Neuroradiol ; 51(5): 101209, 2024 May 29.
Article in English | MEDLINE | ID: mdl-38821316

ABSTRACT

BACKGROUND: It remains unclear whether alterations in brain function occur in the early stage of pediatric type 1 diabetes mellitus(T1DM). We aimed to examine changes in spontaneous brain activity and functional connectivity (FC) in children with T1DM using resting-state functional magnetic resonance imaging (rs-fMRI), and to pinpoint potential links between neural changes and cognitive performance. METHODS: In this study, 22 T1DM children and 21 age-, sex-matched healthy controls underwent rs-fMRI. The amplitude of low frequency fluctuations (ALFF) and seed-based FC analysis were performed to examine changes in intrinsic brain activity and functional networks in T1DM children. Partial correlation analyses were utilized to explore the correlations between ALFF values and clinical parameters. RESULTS: The ALFF values were significantly lower in the lingual gyrus (LG) and higher in the left medial superior frontal gyrus (MSFG) in T1DM children compared to controls. Subsequent FC analysis indicated that the LG had decreased FC with bilateral inferior occipital gyrus, and the left MSFG had decreased FC with right precentral gyrus, right inferior parietal gyrus and right postcentral gyrus in children with T1DM. The ALFF values of LG were positively correlated with full-scale intelligence quotient and age at disease onset in T1DM children, while the ALFF values of left MSFG were positively correlated with working memory scores. CONCLUSION: Our findings revealed abnormal spontaneous activity and FC in brain regions related to visual, memory, default mode network, and sensorimotor network in the early stage of T1DM children, which may aid in further understanding the mechanisms underlying T1DM-associated cognitive dysfunction.

3.
Int J Ophthalmol ; 16(12): 1911-1918, 2023.
Article in English | MEDLINE | ID: mdl-38111923

ABSTRACT

AIM: To investigate the relationship between dynamic tear meniscus parameters and dry eye using an automated tear meniscus segmentation method. METHODS: The analysis of tear meniscus videos captured within 5s after a complete blink includes data from 38 participates. By processing video data, several key parameters including the average height of the tear meniscus at different lengths, the curvature of the tear meniscus's upper boundary, and the total area of the tear meniscus in each frame were calculated. The effective values of these dynamic parameters were then linearly fitted to explore the relationship between their changing trends and dry eye disease. RESULTS: In 94.74% of the samples, the average height of central tear meniscus increased over time. Moreover, 97.37% of the samples exhibited an increase in the overall tear meniscus height (TMH) and area from the nasal to temporal side. Notably, the central TMH increased at a faster rate compared to the nasal side with the temporal side showing the slowest ascent. Statistical analysis indicates that the upper boundary curvature of the whole tear meniscus as well as the tear meniscus of the nasal side (2, 3, and 4 mm) aid in identifying the presence of dry eye and assessing its severity. CONCLUSION: This study contributes to the understanding of tear meniscus dynamics as potential markers for dry eye, utilizing an automated and non-invasive approach that has implications for clinical assessment.

4.
Appl Opt ; 62(14): 3581-3588, 2023 May 10.
Article in English | MEDLINE | ID: mdl-37706973

ABSTRACT

A novel approach that employs active plasmonic metamaterials to create a digital coding Fano resonator is proposed, to the best of our knowledge. The meta-device consists of three concentric spoof localized surface plasmon (LSP) resonators and three positive-intrinsic-negative (PIN) diodes positioned at three slits located in the middle and inner LSP resonators. Four Fano resonant modes can be independently switched by controlling the biased voltage applied to the three diodes. This provides a means for encoded modulation of multiple Fano resonances in metamaterials, which could have broad applications in fields such as multiway sensing, plasmonic circuits, and switching. We experimentally demonstrate the effectiveness of the proposed approach, which offers promising potential for practical implementation.

5.
Ying Yong Sheng Tai Xue Bao ; 31(1): 165-172, 2020 Jan.
Article in Chinese | MEDLINE | ID: mdl-31957393

ABSTRACT

The unreasonable resource allocation and lower resource use efficiency for rice-wheat double cropping system in Jianghuai region resulted from climate change severely limit the coordinated development of annually high yield and high efficiency crops. Optimizing seasonal resource allocation through sowing date adjustment is an important way to tap the annual high-yield potential and improve resource use efficiency. To quantify the effects of sowing date of rice and wheat on annual yield and resource allocation and utilization efficiency, field experiments were conducted in 2013-2015. Results showed that compared with the conventional rice-wheat cropping system (T2), the two seasons appropriate late-cast cropping system (T3) could coordinate resource allocation in the two seasons through the sowing date adjustment, and transfer the redundant radiation and heat resources in the wheat season to the rice. The distribution rate of accumulated temperature, radiation and rainfall resources for T3 were: rice season accounted for 60.5%, 46.5% and 56.7%, wheat season accounted for 36.3%, 50.0% and 40.9%, and the ratio between two seasons was 1.67, 0.94 and 1.39, respectively. Rice yield and its proportion of annual production were significantly increased. The wheat yield was significantly decreased, with the variation range being smaller than that of rice. The total annual yield was increased by 336.3 kg·hm-2 as compared with T2. The temperature, radiation and rainfall production efficiency for rice in T3 were increased by 9.8%, 5.6% and 8.3% in compared to T2, respectively. There was no significant difference in the climate resource utilization efficiency of wheat season. The annual resource production efficiency of T3 was increased by 4.8%, 3.1% and 6.0% over the T2, respectively. Earlier (T1) or latest sowing (T4) of two seasons cropping system was not appropriate for annual yield formation and resource utilization. In summary, improving resource utilization efficiency in rice season is the key way to increase annual grain yield potential in Jianghuai region. The results provided theoretical and practical bases for the excavation of yield potential of the regional annual cropping system and the adjustment of planting structure.


Subject(s)
Oryza , Triticum , Agriculture , Crops, Agricultural , Edible Grain , Seasons
6.
Appl Opt ; 58(36): 9797-9802, 2019 Dec 20.
Article in English | MEDLINE | ID: mdl-31873622

ABSTRACT

Here, selective amplification of spoof localized surface plasmons (LSPs) has been demonstrated, where two coupling stubs gathering energies from the spoof LSPs resonator are designed on the back of the corrugated metal-insulator-metal ring resonator. The quadrupole mode is selected and amplified through the coupling stubs and the incorporated amplifier chip, and the measured transmission intensity has been increased from $ - {6.46}\;{\rm dB}$-6.46dB to 10.74 dB by adjusting the bias voltage. The amplification mechanism is fully investigated by using the circuit simulation and the full-wave simulation. The numerical simulations and experimental measurement agree well with each other. The active amplified resonator can be widely used in chemical and biological sensing in microwave frequency.

7.
Opt Express ; 26(19): 25460-25470, 2018 Sep 17.
Article in English | MEDLINE | ID: mdl-30469647

ABSTRACT

By directly incorporating a sub-wavelength amplifier chip into the spoof plasmonic resonator, the quality (Q) factor of the original passive resonator has been significantly increased by several orders of magnitude. The spoof plasmonic resonator is composed of a corrugated ring with a slit whose optimized offset angle φ is 45°, aiming to achieve a better Q-factor. By tuning the bias voltage applied to the amplifier chip that is placed across the slit, the Q factor has been increased from 9.8 to 21000 for the quadrupole mode when a plastic pipe filled with polar liquids is placed upon the resonator. Experiments at the microwave frequencies verify that the amplifier chip could greatly compensate the loss introduced by the polar liquids under investigation, resulting in an ultra-high-Q sensor for the detection of polar liquids.

8.
Appl Opt ; 57(28): 8472-8477, 2018 Oct 01.
Article in English | MEDLINE | ID: mdl-30461805

ABSTRACT

In this paper, we propose a microfluidic chemical sensor based on quarter-mode spoof plasmonic resonators with more compact overall size and higher sensitivity. First, a microfluidic channel engraved on polydimethylsiloxane is aligned to the upper part of the spoof plasmonic metal-insulator-metal (MIM) ring resonator where the strongest electric fields are observed at resonance. Although a resonant frequency shift of 270 MHz has been observed when the microfluidic channel is filled with pure ethanol, there is no resonant frequency shift when the ethanol concentration is changed from 40% to 60%. Then the spoof localized surface plasmons modes on the quarter corrugated MIM ring are analyzed, and a microfluidic sensor based on the quarter-mode spoof plasmonic resonator has been proposed. The proposed microfluidic sensor requires a very small amount (3.9 µL) of liquid for testing. After infilling the microfluidic channel with pure ethanol, the resonant frequency shift of 940 MHz has been observed on account of the dielectric changes. It is observed that the resonant frequency of the proposed sensor shifts from 5.07 to 6.62 GHz when the ethanol concentration is varied from 10% to 90%. It has been demonstrated that such quarter-mode spoof plasmonic resonator is well suited to a highly sensitive and compact microfluidic chemical sensor.

9.
Sci Rep ; 7(1): 14237, 2017 10 27.
Article in English | MEDLINE | ID: mdl-29079760

ABSTRACT

ABSTARCT: We demonstrate a novel route to control the filtering of spoof localized surface plasmons (LSPs) on the corrugated metal-insulator-metal (MIM) ring resonator. The spoof LSPs resonance modes can be effectively tuned to achieve broad passband (covering the quadrupole mode and the hexapole mode) by selecting proper lengths in the input and output coupling area. The mutual coupling between the input and output lines produces the flat-top transmission response and sharp out-of-band rejection. Compared with the wideband bandpass filters based on spoof plasmonic waveguides, the proposed filter is ultra-compact and only 0.35λ*0.35λ. In order to further improve the property of the bandpass plasmonic filter, all the out-of-band frequencies (the dipole mode and the octopole mode) have been rejected by introducing a shunt stepped-impedance resonator and double C-shaped rings on the back of the substrate of the filter. Simulated results are confirmed via experiment, showing good rejection and wideband filtering performance with low insertion loss, flat-top transmission response and sharp out-of-band suppression. The proposed filter can find more applications in the highly integrated plasmonic circuits and systems in both terahertz and microwave regimes.

10.
Spine J ; 17(2): 230-235, 2017 02.
Article in English | MEDLINE | ID: mdl-27664342

ABSTRACT

BACKGROUND CONTEXT: Accurately evaluating the extent of trunk imbalance in the coronal plane is significant for patients before and after treatment. We preliminarily practiced a new method, axis-line-angle technique (ALAT), for evaluating coronal trunk imbalance with excellent intra-observer and interobserver reliability. Radiologists and surgeons were encouraged to use this method in clinical practice. However, the optimal cutoff value of the ALAT for determination of the extent of coronal trunk imbalance has not been calculated up to now. PURPOSE: The purpose of this study was to identify the cutoff value of the ALAT that best predicts a positive measurement point to assess coronal balance or imbalance. STUDY DESIGN/SETTING: A retrospective study at a university affiliated hospital was carried out. PATIENT SAMPLE: A total of 130 patients with C7-central sacral vertical line (CSVL) >0 mm and aged 10-18 years were recruited in this study from September 2013 to December 2014. OUTCOME MEASURES: Data were analyzed to determine the optimal cutoff value of the ALAT measurement. METHODS: The C7-CSVL and ALAT measurements were conducted respectively twice on plain film within a 2-week interval by two radiologists. The optimal cutoff value of the ALAT was analyzed via receiver operating characteristic (ROC) curve. Comparison variables were performed with chi-square test between the C7-CSVL and ALAT measurements for evaluating trunk imbalance. Kappa agreement coefficient method was used to test the intra-observer and interobserver agreement of C7-CSVL and ALAT. RESULTS: The ROC curve area for the ALAT was 0.82 (95% confidence interval: 0.753-0.894, p<.001). The maximum Youden index was 0.51, and the corresponding cutoff point was 2.59°. No statistical difference was found between the C7-CSVL and ALAT measurements for evaluating trunk imbalance (p>.05). Intra-observer agreement values for the C7-CSVL measurements by observers 1 and 2 were 0.79 and 0.91 (p<.001), respectively, whereas intra-observer agreement values for the ALAT measurements were both 0.89 by observers 1 and 2 (p<.001). The interobserver agreement values for the first and second measurements with the C7-CSVL were 0.78 and 0.85 (p<.001), respectively, whereas the interobserver agreement values for the first and second measurements with the ALAT were 0.91 and 0.88 (p<.001), respectively. CONCLUSIONS: The newly developed ALAT provided an acceptable optimal cutoff value for evaluating trunk imbalance in the coronal plane with a high level of intra-observer and interobserver agreement, which suggests that the ALAT is suitable for clinical use.


Subject(s)
Radiography, Thoracic/methods , Scoliosis/diagnostic imaging , Torso/diagnostic imaging , Adolescent , Child , Female , Humans , Male , Observer Variation , ROC Curve , Reproducibility of Results , Retrospective Studies
11.
Zhongguo Zhong Yao Za Zhi ; 40(13): 2486-91, 2015 Jul.
Article in English | MEDLINE | ID: mdl-26697667

ABSTRACT

Synthetic biology research methods which design and build a new artificial biological systems (medicinal plants or microorganisms system) with specific physiological functions through clarifying and simulating the basic law of the biosynthesis of active components of traditional Chinese medicine, is considered to be a potential method to produce an abundant resources of bioactive components. Tanshinones is a kind of diterpene quinone compounds with important pharmacological activities from traditional Chinese medicine Salvia miltiorrhiza. This article systematically introduced the research progress of the synthetic biology of S. miltiorrhiza, in order to provide references for studies on other terpenoid bioactive components of traditional Chinese medicines, and give new research strategies for the sustainable development of traditional Chinese medicine resources.


Subject(s)
Abietanes/biosynthesis , Medicine, Chinese Traditional , Salvia miltiorrhiza/metabolism , Synthetic Biology
12.
Sci Rep ; 5: 14819, 2015 Sep 30.
Article in English | MEDLINE | ID: mdl-26420668

ABSTRACT

We numerically demonstrate that spoof localized surface plasmons (LSPs) resonant modes can be enhanced based on ultrathin corrugated metal-insulator-metal (MIM) ring resonator. Further enhancement of the LSPs modes has been achieved by incorporating an efficient and ease-of-integration exciting method. Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line. Experimental results validate the high-efficiency excitation and resonance enhancements of spoof LSPs modes on the MIM ring resonator in the microwave frequencies. We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test. The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform.

13.
Plant Cell Rep ; 34(12): 2179-88, 2015 Dec.
Article in English | MEDLINE | ID: mdl-26449416

ABSTRACT

KEY MESSAGE: We found triptolide synthesis is correlated with the expressions of TwGGPPS1 and TwGGPPS4 . This lays the foundation for future studies of biosynthetic pathways for triptolide and other diterpenoids in T. wilfordii. Tripterygium wilfordii is a traditional Chinese medical plant commonly used to treat rheumatoid arthritis. One of its main bioactive compounds is triptolide, which is identified as an abietane-type diterpenoid natural product. Geranylgeranyl diphosphate synthase (GGPPS) catalyses the synthesis of GGPP (geranylgeranyl diphosphate), the common precursor of diterpenes, and is therefore a crucial enzyme in diterpene biosynthesis. A previous study showed that GGPP could be catalyzed by copalyl diphosphate synthase and kaurene synthase like of Salvia miltiorrhiza (SmCPS, SmKSL) to miltiradiene, a key intermediate in tanshinone biosynthesis. In this paper, five new full-length cDNAs (TwGGPPS) encoding GGPP synthases were cloned from T. wilfordii. Sequence comparisons revealed that all six TwGGPPSs (including TwGGPPS2 cloned previously) exhibit similarities to GGPPSs of other plants. Subsequent functional complement assays demonstrated that TwGGPPS1, TwGGPPS4 and TwGGPPS5 can participate in miltiradiene biosynthesis in the recombinant E. coli. Correlation analysis of gene expressions and secondary metabolite accumulation indicated that TwGGPPS1 and TwGGPPS4 are likely involved in the biosynthesis of triptolide. These findings lay the foundation for future studies of the biosynthetic pathways for triptolide and other diterpenoids in T. wilfordii.


Subject(s)
Diterpenes/metabolism , Farnesyltranstransferase/genetics , Phenanthrenes/metabolism , Tripterygium/enzymology , Acetates/metabolism , Amino Acid Sequence , Biosynthetic Pathways , Cloning, Molecular , Cyclopentanes/metabolism , Diterpenes/chemistry , Epoxy Compounds/chemistry , Epoxy Compounds/metabolism , Escherichia coli/genetics , Escherichia coli/metabolism , Farnesyltranstransferase/metabolism , Molecular Sequence Data , Oxylipins/metabolism , Phenanthrenes/chemistry , Phylogeny , Plant Growth Regulators/metabolism , Plant Proteins/genetics , Plant Proteins/metabolism , Polyisoprenyl Phosphates/chemistry , Polyisoprenyl Phosphates/metabolism , Sequence Alignment , Tripterygium/genetics
14.
Opt Express ; 23(16): 21434-42, 2015 Aug 10.
Article in English | MEDLINE | ID: mdl-26367991

ABSTRACT

We have investigated the fundamental and high-order spoof localized surface plasmons (LSPs) modes in the proposed corrugated ring resonator printed on a thin dielectric substrate with or without ground plane. An efficient and ease-of-integration method to excite spoof LSPs in the textured ring resonator has been adopted to suppress unwanted high-order modes and enhance fundamental modes. A multi-band-pass filter has been proposed and numerically demonstrated. Experimental results at the microwave frequencies verify the high performances of the corrugated ring resonator and the filter, showing great agreements with the simulation results. We have also shown that the fabricated device is sensitive to the variation of the refraction index of materials under test, even when the material is as thin as paper.

15.
Appl Opt ; 54(14): 4529-33, 2015 May 10.
Article in English | MEDLINE | ID: mdl-25967512

ABSTRACT

Although subwavelength planar terahertz (THz) plasmonic devices can be implemented based on planar spoof surface plasmons (SPs), they still suffer from a little high propagation loss. Here the dispersion and propagation characteristics of the spoof plasmonic waveguide composed of double metal strips corrugated with dumbbell shaped grooves have been investigated. It has been found that much lower propagation loss and longer propagation length can be achieved based on the waveguide compared with the conventional spoof plasmonic waveguide with rectangular grooves. Moreover, the waveguide can implement a decrease in size of about 22%. An ultra-wideband THz plasmonic filter for planar circuits has been demonstrated based on the proposed waveguide. The experimental verification at the microwave frequency has been conducted by scaling up the geometry size of the filter.

16.
Opt Express ; 22(18): 21589-99, 2014 Sep 08.
Article in English | MEDLINE | ID: mdl-25321538

ABSTRACT

We propose a broadband slow wave system based on the thin metal-insulator-metal (MIM) graded grating structure composed of two corrugated metal strips with periodic array of grooves on a thin dielectric substrate. The guided spoof surface plasmon polaritons (SSPPs) at different frequencies can be localized at different positions along the ultrathin MIM grating. By introducing specially designed non-corrugated MIM branches with specific lengths at the locations where the EM waves are trapped, the trapped EM waves can be released and propagate along these branches. A 4-way wavelength demultiplexer based on such plasmonic broadband slow wave system is then demonstrated and fabricated. To improve the isolations between different branches at lower frequencies, band-reject filters are inserted at the front of some MIM branches. The measurements and the simulation results have shown very good agreements, which validate the feasibility of the 4-way wavelength demultiplexer.

17.
Yao Xue Xue Bao ; 49(1): 37-43, 2014 Jan.
Article in Chinese | MEDLINE | ID: mdl-24783503

ABSTRACT

Bioactive natural products are the material bases of Chinese materia medica resources. With successful applications of synthetic biology strategies to the researches and productions of taxol, artemisinin and tanshinone, etc, the potential ability of synthetic biology in the sustainable utilization of Chinese materia medica resources has been attracted by many researchers. This paper reviews the development of synthetic biology, the opportunities of sustainable utilization of Chinese materia medica resources, and the progress of synthetic biology applied to the researches of bioactive natural products. Furthermore, this paper also analyzes how to apply synthetic biology to sustainable utilization of Chinese materia medica resources and what the crucial factors are. Production of bioactive natural products with synthetic biology strategies will become a significant approach for the sustainable utilization of Chinese materia medica resources.


Subject(s)
Biosynthetic Pathways , Drugs, Chinese Herbal/metabolism , Metabolic Engineering/methods , Salvia miltiorrhiza/genetics , Salvia miltiorrhiza/metabolism , Synthetic Biology , Abietanes/genetics , Abietanes/metabolism , Artemisinins/metabolism , Biotechnology , Escherichia coli/metabolism , Ginsenosides/genetics , Ginsenosides/metabolism , Paclitaxel/metabolism , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolism
18.
Yao Xue Xue Bao ; 48(10): 1618-23, 2013 Oct.
Article in Chinese | MEDLINE | ID: mdl-24417091

ABSTRACT

Tanshinones are the bioactive components of the Chinese medicinal herb Salvia miltiorrhiza, while its biosynthetic pathway remains to be characterized. Rapid identification and characterization of the genes correlated to tanshinones biosynthesis is very important. As one of the intermediates of tanshinones biosynthesis, the ferruginol content is relative low in both root and engineered bacteria. It is urgent to construct an efficient system for conversion of miltiradiene to ferruginol to obtain large amount of ferruginol as the substrates for further identifying other downstream genes involved in tanshinones biosynthesis. In this study, we constructed the whole-cell yeast biocatalysts co-expressing miltiradiene oxidase CYP76AH1 and cytochrome P450 reductases (SmCPR1) from Salvia miltiorrhiza, and then characterized it with RT-PCR. After permeabilization, the yeast whole-cell could catalyze turnover of miltiradiene to ferruginol efficiently through single-step biotransformation with a conversion efficiency up to 69.9%. The yeast whole-cell biocatalyst described here not only provide an efficient platform for producing ferruginol in recombinant yeast but also an alternative strategy for identifying other CYP genes involved in tanshinones biosynthesis.


Subject(s)
Abietanes/biosynthesis , Diterpenes/metabolism , Saccharomyces cerevisiae , Salvia miltiorrhiza/chemistry , Abietanes/chemistry , Biosynthetic Pathways , Biotransformation , Cytochrome P-450 Enzyme System/genetics , Cytochrome P-450 Enzyme System/metabolism , Electrophoresis, Agar Gel , Gene Amplification , NADPH-Ferrihemoprotein Reductase/genetics , NADPH-Ferrihemoprotein Reductase/metabolism , Open Reading Frames , Plasmids , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolism
19.
Opt Express ; 19(6): 5260-7, 2011 Mar 14.
Article in English | MEDLINE | ID: mdl-21445162

ABSTRACT

Bidirectional surface wave splitters excited by a cylindrical wire in the microwave frequency have been proposed and fabricated. Compared to the bidirectional subwavelength-slit splitter, the novelty of the proposed structure is the coupling mechanism from the cylindrical wire to the surface gratings. By designing the grating structures with different depths and the feeding wire, electromagnetic waves at the designed frequencies will be confined and guided in the predetermined opposite directions. The finite integral time-domain method is used to model the splitters. Experimental results are presented in the microwave frequencies to verify the new structure, which have very good agreements to the simulated results. Based on the same coupling mechanism, a bidirectional surface wave splitter excited by a cylindrical wire in the terahertz (THz) frequencies is further been proposed and modeled. The simulation results demonstrate the validity of the THz splitter.

20.
Appl Microbiol Biotechnol ; 83(2): 305-13, 2009 May.
Article in English | MEDLINE | ID: mdl-19214500

ABSTRACT

Streptolydigin, a secondary metabolite produced by Streptomyces lydicus, is a potent inhibitor of bacterial RNA polymerases. It has been suggested that streptolydigin biosynthesis is associated with polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS). Thus, there is great interest in understanding the role of fatty acid biosynthesis in the biosynthesis of streptolydigin. In this paper, we cloned a type II fatty acid synthase (FAS II) gene cluster of fabDHCF from the genome of S. lydicus and constructed the SlyfabCF-disrupted mutant. Sequence analysis showed that SlyfabDHCF is 3.7 kb in length and encodes four separated proteins with conserved motifs and active residues, as shown in the FAS II of other bacteria. The SlyfabCF disruption inhibited streptolydigin biosynthesis and retarded mycelial growth, which were likely caused by the inhibition of fatty acid synthesis. Streptolydigin was not detected in the culture of the mutant strain by liquid chromatography-mass spectrometry. Meanwhile, the streptolol moiety of streptolydigin accumulated in cultures. As encoded by fabCF, acyl carrier protein (ACP) and beta-ketoacyl-ACP synthase II are required for streptolydigin biosynthesis and likely involved in the step between PKS and NRPS. Our results provide the first genetic and metabolic evidence that SlyfabCF is shared by fatty acid synthesis and antibiotic streptolydigin synthesis.


Subject(s)
Aminoglycosides/biosynthesis , Bacterial Proteins/metabolism , Fatty Acid Synthase, Type II/metabolism , Streptomyces/metabolism , Aminoglycosides/chemistry , Bacterial Proteins/genetics , Fatty Acid Synthase, Type II/genetics , Molecular Sequence Data , Operon , Streptomyces/enzymology , Streptomyces/genetics
SELECTION OF CITATIONS
SEARCH DETAIL
...