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Search Results: 1 - 10 of 470504 matches for " Jonathan A. Hodges "
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Magnetometry of random AC magnetic fields using a single Nitrogen-Vacancy center
Abdelghani Laraoui,Jonathan S. Hodges,Carlos A. Meriles
Physics , 2010, DOI: 10.1063/1.3497004
Abstract: We report on the use of a single NV center to probe fluctuating AC magnetic fields. Using engineered currents to induce random changes in the field amplitude and phase, we show that stochastic fluctuations reduce the NV center sensitivity and, in general, make the NV response field-dependent. We also introduce two modalities to determine the field spectral composition, unknown a priori in a practical application. One strategy capitalizes on the generation of AC-field-induced coherence 'revivals', while the other approach uses the time-tagged fluorescence intensity record from successive NV observations to reconstruct the AC field spectral density. These studies are relevant for magnetic sensing in scenarios where the field of interest has a non-trivial, stochastic behavior, such as sensing unpolarized nuclear spin ensembles at low static magnetic fields.
The diamond Nitrogen-Vacancy center as a probe of random fluctuations in a nuclear spin ensemble
Abdelghani Laraoui,Jonathan S. Hodges,Colm Ryan,Carlos A. Meriles
Physics , 2011, DOI: 10.1103/PhysRevB.84.104301
Abstract: New schemes that exploit the unique properties of Nitrogen-Vacancy (NV) centers in diamond are presently being explored as a platform for high-resolution magnetic sensing. Here we focus on the ability of a NV center to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, we conduct comparative experiments where the NV spin evolves under the influence of surrounding 13C nuclei or, alternatively, in the presence of asynchronous AC fields engineered to emulate bath fluctuations. Our study reveals substantial differences that underscore the limitations of the semi-classical picture when interpreting and predicting the outcome of experiments designed to probe small nuclear spin ensembles. In particular, our study elucidates the NV center response to bath fluctuations under common pulse sequences, and explores a detection protocol designed to probe time correlations of the nuclear spin bath dynamics. Further, we show that the presence of macroscopic nuclear spin order is key to the emergence of semi-classical spin magnetometry.
Fidelity enhancement by logical qubit encoding
Michael K. Henry,Chandrasekhar Ramanathan,Jonathan S. Hodges,Colm A. Ryan,Michael J. Ditty,Raymond Laflamme,David G. Cory
Physics , 2007, DOI: 10.1103/PhysRevLett.99.220501
Abstract: We demonstrate coherent control of two logical qubits encoded in a decoherence free subspace (DFS) of four dipolar-coupled protons in an NMR quantum information processor. A pseudo-pure fiducial state is created in the DFS, and a unitary logical qubit entangling operator evolves the system to a logical Bell state. The four-spin molecule is partially aligned by a liquid crystal solvent, which introduces strong dipolar couplings among the spins. Although the system Hamiltonian is never fully specified, we demonstrate high fidelity control over the logical degrees of freedom. In fact, the DFS encoding leads to higher fidelity control than is available in the full four-spin Hilbert space.
Time-keeping with electron spin states in diamond
Jonathan S. Hodges,Dirk Englund
Physics , 2011,
Abstract: Frequency standards based on atomic states, such as Rb or Cs vapors, or single trapped ions, are the most precise measures of time. Here we introduce a complementary device based on spins in a solid-state system - the nitrogen-vacancy defect in single crystal diamond. We show that this system has comparable stability to portable atomic standards and is readily incorporable as a chip-scale device. Using a pulsed spin-echo technique, we anticipate an Allan deviation of {\sigma}_y =1E-12 ({\tau})^(-1/2) with current photoluminescence detection methods and posit exceeding 1E-14 with improved diamond material processing and nanophotonic engineering.
Staphylococcus aureus Activates the NLRP3 Inflammasome in Human and Rat Conjunctival Goblet Cells
Victoria E. McGilligan, Meredith S. Gregory-Ksander, Dayu Li, Jonathan E. Moore, Robin R. Hodges, Michael S. Gilmore, Tara C. B. Moore, Darlene A. Dartt
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0074010
Abstract: The conjunctiva is a moist mucosal membrane that is constantly exposed to an array of potential pathogens and triggers of inflammation. The NACHT, leucine rich repeat (LRR), and pyrin domain-containing protein 3 (NLRP3) is a Nod-like receptor that can sense pathogens or other triggers, and is highly expressed in wet mucosal membranes. NLRP3 is a member of the multi-protein complex termed the NLRP3 inflammasome that activates the caspase 1 pathway, inducing the secretion of biologically active IL-1β, a major initiator and promoter of inflammation. The purpose of this study was to: (1) determine whether NLRP3 is expressed in the conjunctiva and (2) determine whether goblet cells specifically contribute to innate mediated inflammation via secretion of IL-1β. We report that the receptors known to be involved in the priming and activation of the NLRP3 inflammasome, the purinergic receptors P2X4 and P2X7 and the bacterial Toll-like receptor 2 are present and functional in conjunctival goblet cells. Toxin-containing Staphylococcus aureus (S. aureus), which activates the NLRP3 inflammasome, increased the expression of the inflammasome proteins NLRP3, ASC and pro- and mature caspase 1 in conjunctival goblet cells. The biologically active form of IL-1β was detected in goblet cell culture supernatants in response to S. aureus, which was reduced when the cells were treated with the caspase 1 inhibitor Z-YVAD. We conclude that the NLRP3 inflammasome components are present in conjunctival goblet cells. The NRLP3 inflammasome appears to be activated in conjunctival goblet cells by toxin-containing S. aureus via the caspase 1 pathway to secrete mature IL1-β. Thus goblet cells contribute to the innate immune response in the conjunctiva by activation of the NLRP3 inflammasome.
Single Color Centers Implanted in Diamond Nanostructures
Birgit J. M. Hausmann,Thomas M. Babinec,Jennifer T. Choy,Jonathan S. Hodges,Sungkun Hong,Irfan Bulu,A. Yacoby,M. D. Lukin,Marko Lon?ar
Physics , 2010, DOI: 10.1088/1367-2630/13/4/045004
Abstract: The development of materials processing techniques for optical diamond nanostructures containing a single color center is an important problem in quantum science and technology. In this work, we present the combination of ion implantation and top-down diamond nanofabrication in two scenarios: diamond nanopillars and diamond nanowires. The first device consists of a 'shallow' implant (~20nm) to generate Nitrogen-vacancy (NV) color centers near the top surface of the diamond crystal. Individual NV centers are then isolated mechanically by dry etching a regular array of nanopillars in the diamond surface. Photon anti-bunching measurements indicate that a high yield (>10%) of the devices contain a single NV center. The second device demonstrates 'deep' (~1\mu m) implantation of individual NV centers into pre-fabricated diamond nanowire. The high single photon flux of the nanowire geometry, combined with the low background fluorescence of the ultrapure diamond, allows us to sustain strong photon anti-bunching even at high pump powers.
Improved Bone Morphogenetic Protein-2 Retention in an Injectable Collagen Matrix Using Bifunctional Peptides
Paul T. Hamilton, Michelle S. Jansen, Sathya Ganesan, R. Edward Benson, Robin Hyde-DeRuyscher, Wayne F. Beyer, Joseph C. Gile, Shrikumar A. Nair, Jonathan A. Hodges, Hanne Gr?n
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070715
Abstract: To promote healing of many orthopedic injuries, tissue engineering approaches are being developed that combine growth factors such as Bone Morphogenetic Proteins (BMP) with biomaterial carriers. Although these technologies have shown great promise, they still face limitations. We describe a generalized approach to create target-specific modular peptides that bind growth factors to implantable biomaterials. These bifunctional peptide coatings provide a novel way to modulate biology on the surface of an implant. Using phage display techniques, we have identified peptides that bind with high affinity to BMP-2. The peptides that bind to BMP-2 fall into two different sequence clusters. The first cluster of peptide sequences contains the motif W-X-X-F-X-X-L (where X can be any amino acid) and the second cluster contains the motif F-P-L-K-G. We have synthesized bifunctional peptide linkers that contain BMP-2 and collagen-binding domains. Using a rat ectopic bone formation model, we have injected rhBMP-2 into a collagen matrix with or without a bifunctional BMP-2: collagen peptide (BC-1). The presence of BC-1 significantly increased osteogenic cellular activity, the area of bone formed, and bone maturity at the site of injection. Our results suggest that bifunctional peptides that can simultaneously bind to a growth factor and an implantable biomaterial can be used to control the delivery and release of growth factors at the site of implantation.
Generation of bovine transgenics using somatic cell nuclear transfer
Craig A Hodges, Steven L Stice
Reproductive Biology and Endocrinology , 2003, DOI: 10.1186/1477-7827-1-81
Abstract: The bovine species has long been a focus of research due to its importance in agriculture. Advancements in bovine reproductive technologies such as artificial insemination, multiple ovulation and embryo transfer, as well as oocyte and embryo culture have improved the ability to increase superior genotypes in the dairy and beef industries [1]. In combination with these reproductive technologies, the ability to insert DNA into livestock [2,3] has provided limitless possibilities for agriculture (e.g., inserting genes affecting milk and beef production) as well as biomedicine (e.g., producing important proteins in milk). Although there have been major advances in the field of bovine transgenics since its inception, the full potential of transgenic cattle has not been realized in part due to the limitations of commonly used transgenic technologies. More recently, the success of somatic cell nuclear transfer has provided a new and faster way to produce transgenic cattle while circumventing many of the limitations of other transgenic techniques. This review will focus on summarizing the recent past and present state of bovine transgenics and how somatic cell nuclear transfer will affect the future potential of producing transgenic cattle.There are multiple ways to produce a transgenic animal. Briefly discussed below are the strengths and weaknesses of the most common ways currently available to make transgenic animals. The success, or lack thereof, of each method in creating transgenic cattle is also summarized. Although there has been limited success using retroviral vectors [4] and sperm mediated transgenesis [5,6] in cattle, these techniques will not be discussed in this review due to space limitations.One of the first techniques created to generate a transgenic animal was pronuclear microinjection or the insertion of DNA into the pronucleus of a fertilized oocyte. This technology was first used in the mouse [7] and then transferred to other animals including livestock
Informed consent for epidural analgesia in labour
R.A Dyer, O Hodges
Southern African Journal of Anaesthesia and Analgesia , 2007,
Abstract: Consent for epidural analgesia for labour is unique. The issues of patient autonomy and competence are controversial because of the limited antenatal education that most South African patients receive, and the absence of a culture of structured birth planning. Frequently, such patients are first encountered by the anaesthetist when in advanced labour and limited time is available for explanation. Overall, this represents the most extreme example of obtaining consent in compromised circumstances.
Effect of Cooking and Reconstitution Methods on the Loss of Bioactive Compounds in Pigmented and Unpigmented Potatoes  [PDF]
Mohammed Z. Alam, Gefu Wang-Pruski, Mark Hodges, Garry R. Hawkins, Martin Dino Kubik, Sherry A. E. Fillmore
Food and Nutrition Sciences (FNS) , 2017, DOI: 10.4236/fns.2017.81003
Abstract: Total phenolics, anthocyanins and antioxidant capacity of five coloured/pigmented (AR2009-10, Adirondack Red, Adirondack Blue, Congo, and POROIPG22-1) and two unpigmented potato genotypes (“Anuschka” and “Russet Burbank”) were assessed in fresh (with and without skin) and commercially processed/cooked/reconstituted products. Ascorbate profiles of the seven genotypes also were investigated using fresh tuber/tissue only. The results showed that genotypes greatly varied in their contents of bioactive compounds. Ascorbate profiles of the genotypes were not associated to any particular flesh colour/pigment. However, the pigmented potatoes had 1.5 to 2.5 times more the phenolics, 2 to 3 times more antioxidant capacity and higher levels of anthocyanins (13.98 to 38.57 mg C3GE-100g FW) compared to unpigmented genotypes. No anthocyanins were detected in the unpigmented potatoes. Significant losses of total phenolics, anthocyanins and total antioxidant capacity were found during peeling (18% - 23%), blanching process (40% - 60%) and further cooking/ reconstitution (7% - 12%) with no prominent genotype differences. Together, 65 to 90% of these bioactive compounds were lost during processing. The results suggested that pigmented potatoes contained higher amounts of total phenolics and anthocyanins and blanching step took away the most of the original bioactive compounds.
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