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1.
Clin Transl Allergy ; 14(6): e12359, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38860615

ABSTRACT

OBJECTIVE: This work endeavored to examine the correlation between dietary choline intake and the odds of asthma, utilizing data from the National Health and Nutrition Examination Survey (NHANES). METHODS: Aggregated data from seven cycles (2005-2018) in the NHANES database were utilized. The independent variable was dietary choline intake, and the dependent variable was asthma. The weighted logistic regression method was used to construct a model reflecting the relationship between these two factors. This work employed stratified analysis without adjusting for confounding factors and subgroup analysis with adjusted confounding factors to mine the association between dietary choline intake and asthma. Additionally, restricted cubic spline analysis examined nonlinear associations of the two in age subgroups. RESULTS: Forty five thousand and seven hundreds ninety seven samples were included here. The model indicating the relationship between dietary choline intake and asthma was constructed (OR: 0.86, 95% CI: 0.79-0.93, p < 0.001). Stratified analysis indicated that the interaction terms of age (p < 0.001) and body mass index (BMI) (p = 0.002) with dietary choline intake significantly influenced the relationship model. In the adjusted models, accounting for demographic characteristics, poverty impact ratio, BMI, exposure to environmental tobacco smoke, and total energy intake, an increase in dietary choline intake significantly reduced the odds of asthma (OR: 0.79, 95% CI: 0.72-0.88, p < 0.001). Subgroup analyses based on age and BMI revealed a significant negative correlation between dietary choline intake and the odds of asthma in the adult population (OR: 0.76, 95% CI: 0.67-0.86, p < 0.001), as well as in individuals with a BMI between 25 and 30 kg/m2 (OR: 0.79, 95% CI: 0.63-0.99, p = 0.042), and those with a BMI >30 kg/m2 (OR: 0.73, 95% CI: 0.60-0.89, p = 0.002). CONCLUSION: Dietary choline intake was significantly inversely correlated with asthma prevalence, especially in adults and overweight/obese individuals, suggesting that increasing choline intake may reduce asthma risk. Further research is needed to explore this relationship and provide tailored dietary recommendations for different age and BMI groups to enhance asthma prevention and management.

2.
Micromachines (Basel) ; 14(2)2023 Jan 19.
Article in English | MEDLINE | ID: mdl-36837958

ABSTRACT

With its unique computer paradigm, the Ising annealing machine has become an emerging research direction. The Ising annealing system is highly effective at addressing combinatorial optimization (CO) problems that are difficult for conventional computers to tackle. However, Ising spins, which comprise the Ising system, are difficult to implement in high-performance physical circuits. We propose a novel type of Ising spin based on an electrically-controlled magnetic tunnel junction (MTJ). Electrical operation imparts true randomness, great stability, precise control, compact size, and easy integration to the MTJ-based spin. In addition, simulations demonstrate that the frequency of electrically-controlled stochastic Ising spin (E-spin) is 50 times that of the thermal disturbance MTJ-based spin (p-bit). To develop a large-scale Ising annealing system, up to 64 E-spins are implemented. Our Ising annealing system demonstrates factorization of integers up to 264 with a temporal complexity of around O(n). The proposed E-spin shows superiority in constructing large-scale Ising annealing systems and solving CO problems.

3.
Nanomaterials (Basel) ; 13(2)2023 Jan 04.
Article in English | MEDLINE | ID: mdl-36677974

ABSTRACT

This paper proposes a dual-band transparent antenna using frame-structured metal mesh conductive film (MMCF). The frame-structured metal mesh conductive film is based on the conductive-coated thin film and forms a narrow strip surrounding the edge of the antenna. The frame-structured metal mesh conductive film can resist considerable current leakage on the edge of the conductive strip to improve the antenna's efficiency by 51% at 2.1 GHz and 53% at 3.6 GHz. As a result, the transparent dual-band antenna has an operating bandwidth of 1.9-2.4 GHz and 3.2-4.1 GHz with a high transparency of 80%, which make it valuable to the applications of biomedical electronic components, wearable devices, and automobile vehicles.

4.
Nat Comput Sci ; 3(9): 748-762, 2023 Sep.
Article in English | MEDLINE | ID: mdl-38177774

ABSTRACT

Effective spatial planning of urban communities plays a critical role in the sustainable development of cities. Despite the convenience brought by geographic information systems and computer-aided design, determining the layout of land use and roads still heavily relies on human experts. Here we propose an artificial intelligence urban-planning model to generate spatial plans for urban communities. To overcome the difficulty of diverse and irregular urban geography, we construct a graph to describe the topology of cities in arbitrary forms and formulate urban planning as a sequential decision-making problem on the graph. To tackle the challenge of the vast solution space, we develop a reinforcement learning model based on graph neural networks. Experiments on both synthetic and real-world communities demonstrate that our computational model outperforms plans designed by human experts in objective metrics and that it can generate spatial plans responding to different circumstances and needs. We also propose a human-artificial intelligence collaborative workflow of urban planning, in which human designers can substantially benefit from our model to be more productive, generating more efficient spatial plans with much less time. Our method demonstrates the great potential of computational urban planning and paves the way for more explorations in leveraging computational methodologies to solve challenging real-world problems in urban science.


Subject(s)
Artificial Intelligence , City Planning , Humans , Cities , Sustainable Development
5.
Sensors (Basel) ; 22(11)2022 Jun 02.
Article in English | MEDLINE | ID: mdl-35684880

ABSTRACT

There have been several studies of hand gesture recognition for human-machine interfaces. In the early work, most solutions were vision-based and usually had privacy problems that make them unusable in some scenarios. To address the privacy issues, more and more research on non-vision-based hand gesture recognition techniques has been proposed. This paper proposes a dynamic hand gesture system based on 60 GHz FMCW radar that can be used for contactless device control. In this paper, we receive the radar signals of hand gestures and transform them into human-understandable domains such as range, velocity, and angle. With these signatures, we can customize our system to different scenarios. We proposed an end-to-end training deep learning model (neural network and long short-term memory), that extracts the transformed radar signals into features and classifies the extracted features into hand gesture labels. In our training data collecting effort, a camera is used only to support labeling hand gesture data. The accuracy of our model can reach 98%.


Subject(s)
Gestures , Recognition, Psychology , Humans , Memory, Long-Term , Ultrasonography, Doppler , Upper Extremity
6.
BMC Microbiol ; 20(1): 228, 2020 07 28.
Article in English | MEDLINE | ID: mdl-32723292

ABSTRACT

BACKGROUND: Probiotics are being considered as valuable microorganisms related to human health. Hu sheep is referred as one of the important sheep breeds in China. Goat milk produced by Hu sheep is characterized with high nutritional value and hypoallergenic in nature. Particularly, this milk contains plenty of milk prebiotic and probiotic bacteria. This study was aimed to scrutinize more bacterial strains from Hu sheep milk with potential probiotic activity. RESULTS: Based on 16S rRNA sequence analysis, pool of forty bacterial strains were identified and evaluated their antimicrobial activities against Staphylococcus aureus, enterohemorrhagic Escherichia coli (EHEC), Salmonella typhimurium, Listeria monocytogenes enterotoxigenic E. coli (ETEC) and Aeromonas caviae. Four out of these isolated strains demonstrated their efficient bacteriostatic ability and potential healthy properties. We also examined the safety aspects of these bacterial candidates including three Lactococcus lactis strains (named as HSM-1, HSM-10, and HSM-18) and one Leuconostoc lactis strain (HSM-14), and were further evaluated via in vitro tests, including antimicrobial activity, cell surface characteristics (hydrophobicity, co-aggregation, and self-aggregation), heat treatment, antibiotic susceptibility, simulated transport tolerance in the gastrointestinal tract, and acid/bile tolerance. The obtained results revealed that HSM-1, HSM-10, HSM-14, and HSM-18 showed high survival rate at different conditions for example low pH, presence of bovine bile and demonstrated high hydrophobicity. Moreover, HSM-14 had an advantage over other strains in terms of gastrointestinal tract tolerance, antimicrobial activities against pathogens, and these results were significantly better than other bacterial candidates. CONCLUSION: Hu sheep milk as a source of exploration of potential lactic acid bacteria (LAB) probiotics open the new horizon of probiotics usage from unconventional milk sources. The selected LAB strains are excellent probiotic candidates which can be used for animal husbandry in the future. Rationale of the study was to utilize Hu sheep milk as a source of potential probiotic LABs. The study has contributed to the establishment of a complete bacterial resource pool by exploring the Hu sheep milk microflora.


Subject(s)
Lactobacillales/physiology , Milk/microbiology , Probiotics , Animals , Anti-Bacterial Agents/pharmacology , Bile Acids and Salts/metabolism , Gastrointestinal Tract/microbiology , Hydrophobic and Hydrophilic Interactions , Lactobacillales/classification , Lactobacillales/genetics , Lactobacillales/isolation & purification , Microbial Viability , Phylogeny , Probiotics/classification , Probiotics/isolation & purification , Probiotics/pharmacology , RNA, Ribosomal, 16S/genetics , Sheep
7.
Nat Genet ; 52(5): 525-533, 2020 05.
Article in English | MEDLINE | ID: mdl-32313247

ABSTRACT

Polyploidy is an evolutionary innovation for many animals and all flowering plants, but its impact on selection and domestication remains elusive. Here we analyze genome evolution and diversification for all five allopolyploid cotton species, including economically important Upland and Pima cottons. Although these polyploid genomes are conserved in gene content and synteny, they have diversified by subgenomic transposon exchanges that equilibrate genome size, evolutionary rate heterogeneities and positive selection between homoeologs within and among lineages. These differential evolutionary trajectories are accompanied by gene-family diversification and homoeolog expression divergence among polyploid lineages. Selection and domestication drive parallel gene expression similarities in fibers of two cultivated cottons, involving coexpression networks and N6-methyladenosine RNA modifications. Furthermore, polyploidy induces recombination suppression, which correlates with altered epigenetic landscapes and can be overcome by wild introgression. These genomic insights will empower efforts to manipulate genetic recombination and modify epigenetic landscapes and target genes for crop improvement.


Subject(s)
Genome, Plant/genetics , Gossypium/genetics , Cotton Fiber , Domestication , Epigenomics/methods , Evolution, Molecular , Gene Expression Regulation, Plant/genetics , Genomics/methods , Phylogeny , Polyploidy
8.
Sci Rep ; 7(1): 16857, 2017 12 04.
Article in English | MEDLINE | ID: mdl-29203831

ABSTRACT

In this work, we demonstrate for the first time an ultra-low contact resistance few-layered black phosphorus (BP) transistor with metallic PGex contacts formed by rapid thermal annealing (RTA). The on-state current of the transistor can be significantly improved and the ION/IOFF ratio increases by almost 2 order. The hole mobility is enhanced by 25 times to 227 cm2V-1s-1. The contact resistance extracted by the transfer length method is 0.365 kΩ∙µm, which is the lowest value in black phosphorus transistors without degradation of ION/IOFF ratio. In addition, the I-V curve of the transistor with PGex contact is linear compared to that with Ti contact at 80 K, indicating that a metallic ohmic contact is successfully formed. Finally, X-ray photoelectron spectroscopy is used to characterize the PGex compound. A signal of P-Ge bond is first observed, further verifying the doping of Ge into BP and the formation of the PGex alloy.

9.
ACS Omega ; 2(8): 4173-4179, 2017 Aug 31.
Article in English | MEDLINE | ID: mdl-31457714

ABSTRACT

Black phosphorus (BP) is a recently rediscovered layered two-dimensional (2D) semiconductor with a direct band gap (0.35-2 eV), high hole mobility (300-5000 cm2/Vs), and transport anisotropy. In this paper, we systematically investigated the effects of metal-semiconductor interface/contacts on the performance of BP Schottky barrier transistors. First, a "clean" metal-BP contact is formed with boron nitride (BN) passivation. It is found that the contact resistance of the clean metal-BP contact is seven times less than the previously reported values. As a result, high-performance top-gate BP transistors show a record high ON-state drain current (I on) of 940 µA/µm. Second, BN tunneling barriers are formed at the source/drain contacts to help understand the abnormally high OFF-state drain current (I off) in devices with clean metal-BP contacts. This high I off is attributed to the electron tunneling current from the drain to the channel. Finally, the I on/I off of BP field-effect transistors can be significantly improved by using an asymmetric contact structure. By inserting a thin BN tunneling barrier at the drain side, I off is reduced by a factor of ∼120 with a cost of 20% reduction in I on. This case study of contacts on BP reveals the importance of understanding the metal-semiconductor contacts for 2D Schottky barrier transistors in general.

10.
Tumour Biol ; 37(6): 7989-8005, 2016 Jun.
Article in English | MEDLINE | ID: mdl-26711783

ABSTRACT

Carbonic anhydrase 8 (CA8), a member of the carbonic anhydrase family, is one of the three isozymes that do not catalyze the reversible hydration of carbon dioxide due to the lack of one important histidine. In the present study, we observed increased expression of CA8 in more aggressive types of human osteosarcoma (OS) cells and found that CA8 expression is correlated with disease stages, such that more intense expression occurs in the disease late stage. We also demonstrated that overexpression of CA8 in human OS (HOS) cells significantly increased cell proliferation both in vitro and in vivo. Downregulated CA8 sensitized cells to apoptotic stress induced by staurosporine and cisplatin, suggesting a specific role of CA8 to protect cells from stresses. In addition, downregulation of CA8 in HOS cells reduced cell invasion and colony formation ability in soft agar and further decreased matrix metalloproteinase 9 and focal adhesion kinase expression, indicating that CA8 might facilitate cancer cell invasion via the activation of FAK-MMP9 signaling. Interestingly, HOS cells with CA8 knockdown showed a significant decrease in glycolytic activity and cell death under glucose withdrawal, further indicating that CA8 may be involved in regulating aerobic glycolysis and enhancing cell viability. Knockdown of CA8 significantly decreased phosphorylated Akt expression suggesting that the oncogenic role of CA8 may be mediated by the regulation of Akt activation through p-Akt induction. Importantly, the inhibition of glycolysis by 2-deoxyglucose sensitized CA8 HOS-CA8-myc cells to cisplatin treatment under low glucose condition, highlighting a new therapeutic option for OS cancer.


Subject(s)
Biomarkers, Tumor/metabolism , Bone Neoplasms/enzymology , Carcinogenesis/metabolism , Osteosarcoma/enzymology , Animals , Apoptosis , Biomarkers, Tumor/genetics , Blotting, Western , Bone Neoplasms/drug therapy , Bone Neoplasms/pathology , Carcinogenesis/genetics , Cell Line, Tumor , Cell Movement/genetics , Cell Proliferation/genetics , Cisplatin/therapeutic use , Humans , Immunohistochemistry , Mice , Neoplasm Invasiveness/genetics , Oncogenes , Osteosarcoma/drug therapy , Osteosarcoma/pathology
11.
ACS Nano ; 6(8): 6786-92, 2012 Aug 28.
Article in English | MEDLINE | ID: mdl-22780305

ABSTRACT

A process for fabricating dense graphene nanoribbon arrays using self-assembled patterns of block copolymers on graphene grown epitaxially on SiC on the wafer scale has been developed. Etching masks comprising long and straight nanoribbon array structures with linewidths as narrow as 10 nm were fabricated, and the patterns were transferred to graphene. Our process combines both top-down and self-assembly steps to fabricate long graphene nanoribbon arrays with low defect counts. These are the narrowest nanoribbon arrays of epitaxial graphene on SiC fabricated to date.


Subject(s)
Carbon Compounds, Inorganic/chemistry , Crystallization/methods , Graphite/chemistry , Molecular Imprinting/methods , Nanostructures/chemistry , Nanostructures/ultrastructure , Photography/methods , Silicon Compounds/chemistry , Carbon Compounds, Inorganic/radiation effects , Graphite/radiation effects , Macromolecular Substances/chemistry , Macromolecular Substances/radiation effects , Materials Testing , Molecular Conformation/radiation effects , Nanostructures/radiation effects , Particle Size , Silicon Compounds/radiation effects , Surface Properties/radiation effects
12.
Nano Lett ; 12(6): 3062-7, 2012 Jun 13.
Article in English | MEDLINE | ID: mdl-22563820

ABSTRACT

High-performance graphene transistors for radio frequency applications have received much attention and significant progress has been achieved. However, devices based on large-area synthetic graphene, which have direct technological relevance, are still typically outperformed by those based on mechanically exfoliated graphene. Here, we report devices with intrinsic cutoff frequency above 300 GHz, based on both wafer-scale CVD grown graphene and epitaxial graphene on SiC, thus surpassing previous records on any graphene material. We also demonstrate devices with optimized architecture exhibiting voltage and power gains reaching 20 dB and a wafer-scale integrated graphene amplifier circuit with voltage amplification.


Subject(s)
Graphite/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/instrumentation , Transistors, Electronic , Equipment Design , Equipment Failure Analysis , Particle Size
13.
ACS Nano ; 6(3): 2610-6, 2012 Mar 27.
Article in English | MEDLINE | ID: mdl-22324780

ABSTRACT

A new mechanism for negative differential resistance (NDR) is discovered in three-terminal graphene devices based on a field-effect transistor configuration. This NDR effect is a universal phenomenon for graphene and is demonstrated in devices fabricated with different types of graphene materials and gate dielectrics. Operation of conventional NDR devices is usually based on quantum tunneling or intervalley carrier transfer, whereas the NDR behavior observed here is unique to the ambipolar behavior of zero-bandgap graphene and is associated with the competition between electron and hole conduction as the drain bias increases. These three terminal graphene NDR devices offer more operation flexibility than conventional two-terminal devices based on tunnel diodes, Gunn diodes, or molecular devices, and open up new opportunities for graphene in microwave to terahertz applications.

14.
Nano Lett ; 12(3): 1417-23, 2012 Mar 14.
Article in English | MEDLINE | ID: mdl-22316333

ABSTRACT

The superior intrinsic properties of graphene have been a key research focus for the past few years. However, external components, such as metallic contacts, serve not only as essential probing elements, but also give rise to an effective electron cavity, which can form the basis for new quantum devices. In previous studies, quantum interference effects were demonstrated in graphene heterojunctions formed by a top gate. Here phase coherent transport behavior is demonstrated in a simple two terminal graphene structure with clearly resolved Fabry-Perot oscillations in sub-100 nm devices. By aggressively scaling the channel length down to 50 nm, we study the evolution of the graphene transistor from the channel-dominated diffusive regime to the contact-dominated ballistic regime. Key issues such as the current asymmetry, the question of Fermi level pinning by the contacts, the graphene screening determining the heterojunction barrier width, the scaling of minimum conductivity, and of the on/off current ratio are investigated.


Subject(s)
Graphite/chemistry , Models, Chemical , Nanostructures/chemistry , Nanostructures/ultrastructure , Transistors, Electronic , Computer Simulation , Computer-Aided Design , Electron Transport , Equipment Design , Equipment Failure Analysis , Particle Size
15.
J Biol Chem ; 287(1): 418-428, 2012 Jan 02.
Article in English | MEDLINE | ID: mdl-22084237

ABSTRACT

Antimicrobial peptides/proteins (AMPs) are important components of the host innate defense mechanisms. Here we demonstrate that the outer membrane lipoprotein, Lpp, of Enterobacteriaceae interacts with and promotes susceptibility to the bactericidal activities of AMPs. The oligomeric Lpp was specifically recognized by several cationic α-helical AMPs, including SMAP-29, CAP-18, and LL-37; AMP-mediated bactericidal activities were blocked by anti-Lpp antibody blocking. Blebbing of the outer membrane and increase in membrane permeability occurred in association with the coordinate internalization of Lpp and AMP. Interestingly, the specific binding of AMP to Lpp was resistant to divalent cations and salts, which were able to inhibit the bactericidal activities of some AMPs. Furthermore, using His-tagged Lpp as a ligand, we retrieved several characterized AMPs, including SMAP-29 and hRNase 7, from a peptide library containing crude mammalian cell lysates. Overall, this study explores a new mechanism and target of antimicrobial activity and provides a novel method for screening of antimicrobials for use against drug-resistant bacteria.


Subject(s)
Antimicrobial Cationic Peptides/metabolism , Bacterial Outer Membrane Proteins/metabolism , Gram-Negative Bacteria/metabolism , Receptors, Cell Surface/metabolism , Amino Acid Sequence , Animals , Antimicrobial Cationic Peptides/chemistry , Antimicrobial Cationic Peptides/pharmacology , Bacterial Outer Membrane Proteins/chemistry , Drug Evaluation, Preclinical , Drug Resistance, Bacterial/drug effects , Gram-Negative Bacteria/drug effects , Molecular Sequence Data , Protein Multimerization/drug effects , Protein Structure, Quaternary/drug effects , Protein Structure, Secondary , Protein Transport/drug effects , Rabbits , Receptors, Cell Surface/chemistry , Substrate Specificity
16.
Nucleic Acid Ther ; 21(5): 323-32, 2011 Oct.
Article in English | MEDLINE | ID: mdl-21916610

ABSTRACT

Adjuvants are important components of vaccine formulations. Effective adjuvants line innate and adaptive immunity by signaling through pathogen recognition receptors. Synthetic cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) have been shown to have potentials as adjuvants for vaccines. However, the immunostimulatory effect of CpG is species-specific and depends on the sequence of CpG motifs. A CpG ODN (2135), containing 3 identical copies of GTCGTT motif, was previously reported to have the strongest effects on bovine peripheral blood mononuclear cells (PBMC). Based on the sequence of 2135, we replaced the GTCGTT motif with 11 other sequences containing CG and investigated their effects on bovine lymphocyte proliferation. Results showed that the CpG ODNs containing 3 copies of GACGTT motif had the highest lymphocyte stimulation index (7.91±1.18), which was significantly (P<0.05) higher than that of 2135 (4.25±0.56). The CpG ODNs containing 3 copies of GACGTT motif also significantly increased the mRNA expression of interferon (IFN)-α, interleukin (IL)-12, and IL-21 in bovine PBMC. When dairy cows were immunized with the keyhole limpet hemocyanin (KLH) antigen formulated with CpG ODNs containing 3 copies of GACGTT, production of KLH-specific antibodies in serum and in milk whey was significantly (P<0.05) enhanced. IFN-γ in whole blood stimulated by KLH was also significantly (P<0.05) increased in cows immunized with KLH plus CpG ODNs. Our results indicate that CpG ODNs containing 3 copies of the GACGTT motifs is a potential adjuvant for bovine vaccines.


Subject(s)
Adjuvants, Immunologic/pharmacology , Antigens/immunology , Cattle/immunology , Hemocyanins/immunology , Oligodeoxyribonucleotides/pharmacology , Animals , Base Sequence , Cell Proliferation , Cytokines/genetics , Cytokines/metabolism , Dinucleoside Phosphates/pharmacology , Female , Freund's Adjuvant/pharmacology , Gene Expression/drug effects , Immune Sera/metabolism , Immunoglobulin G/metabolism , Immunoglobulin M/metabolism , Interferon-gamma/blood , Leukocytes, Mononuclear/drug effects , Leukocytes, Mononuclear/metabolism , Lymphocytes/drug effects , Lymphocytes/physiology , Milk/metabolism , Pregnancy , Toll-Like Receptor 9/genetics , Toll-Like Receptor 9/metabolism
17.
Science ; 332(6035): 1294-7, 2011 Jun 10.
Article in English | MEDLINE | ID: mdl-21659599

ABSTRACT

A wafer-scale graphene circuit was demonstrated in which all circuit components, including graphene field-effect transistor and inductors, were monolithically integrated on a single silicon carbide wafer. The integrated circuit operates as a broadband radio-frequency mixer at frequencies up to 10 gigahertz. These graphene circuits exhibit outstanding thermal stability with little reduction in performance (less than 1 decibel) between 300 and 400 kelvin. These results open up possibilities of achieving practical graphene technology with more complex functionality and performance.

18.
Nature ; 472(7341): 74-8, 2011 Apr 07.
Article in English | MEDLINE | ID: mdl-21475197

ABSTRACT

Owing to its high carrier mobility and saturation velocity, graphene has attracted enormous attention in recent years. In particular, high-performance graphene transistors for radio-frequency (r.f.) applications are of great interest. Synthesis of large-scale graphene sheets of high quality and at low cost has been demonstrated using chemical vapour deposition (CVD) methods. However, very few studies have been performed on the scaling behaviour of transistors made from CVD graphene for r.f. applications, which hold great potential for commercialization. Here we report the systematic study of top-gated CVD-graphene r.f. transistors with gate lengths scaled down to 40 nm, the shortest gate length demonstrated on graphene r.f. devices. The CVD graphene was grown on copper film and transferred to a wafer of diamond-like carbon. Cut-off frequencies as high as 155 GHz have been obtained for the 40-nm transistors, and the cut-off frequency was found to scale as 1/(gate length). Furthermore, we studied graphene r.f. transistors at cryogenic temperatures. Unlike conventional semiconductor devices where low-temperature performance is hampered by carrier freeze-out effects, the r.f. performance of our graphene devices exhibits little temperature dependence down to 4.3 K, providing a much larger operation window than is available for conventional devices.

19.
Nat Nanotechnol ; 6(3): 179-84, 2011 Mar.
Article in English | MEDLINE | ID: mdl-21297624

ABSTRACT

A high-quality junction between graphene and metallic contacts is crucial in the creation of high-performance graphene transistors. In an ideal metal-graphene junction, the contact resistance is determined solely by the number of conduction modes in graphene. However, as yet, measurements of contact resistance have been inconsistent, and the factors that determine the contact resistance remain unclear. Here, we report that the contact resistance in a palladium-graphene junction exhibits an anomalous temperature dependence, dropping significantly as temperature decreases to a value of just 110 ± 20 Ω µm at 6 K, which is two to three times the minimum achievable resistance. Using a combination of experiment and theory we show that this behaviour results from carrier transport in graphene under the palladium contact. At low temperature, the carrier mean free path exceeds the palladium-graphene coupling length, leading to nearly ballistic transport with a transfer efficiency of ~75%. As the temperature increases, this carrier transport becomes less ballistic, resulting in a considerable reduction in efficiency.


Subject(s)
Graphite/chemistry , Nanotechnology/methods , Palladium/chemistry , Algorithms , Calibration , Electric Capacitance , Electric Impedance , Electronics/instrumentation , Electrons , Limit of Detection , Metals/chemistry , Surface Properties , Temperature , Transistors, Electronic
20.
Vaccine ; 28(50): 7956-62, 2010 Nov 23.
Article in English | MEDLINE | ID: mdl-20933041

ABSTRACT

Recombinant parvovirus VP2 (rVP2) was formulated with different types of adjuvant, including aluminum adjuvant and CpG oligodeoxynucleotides (ODNs), and the immunological responses after vaccination in ducks were examined. In comparison with the control group, production of rVP2-specific antibodies, expression of cytokines in peripheral blood mononuclear cells (PBMC) stimulated by rVP2, and percentage of CD4(+)/CD8(+) cells in PBMC were significantly increased in ducks immunized with rVP2 formulated with CpG ODNs containing 3 copies of GACGTT motif. CpG ODNs with GACGTT motifs might be used to improve the efficacy of vaccines for ducks.


Subject(s)
Capsid Proteins/immunology , Ducks/immunology , Oligodeoxyribonucleotides/immunology , Parvoviridae Infections/veterinary , Parvovirus/immunology , Poultry Diseases/prevention & control , Adjuvants, Immunologic/pharmacology , Animals , Antibodies, Viral/blood , CD4-CD8 Ratio , Cell Proliferation , Cytokines/immunology , Leukocytes, Mononuclear/immunology , Parvoviridae Infections/prevention & control , Recombinant Proteins/immunology
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