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Prabhakar G, Gregg P, Rishoj L, Kristensen P, Ramachandran S. Octave-wide supercontinuum generation of light-carrying orbital angular momentum. Opt Express 2019; 27:11547-11556. [PMID: 31052998 DOI: 10.1364/oe.27.011547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/04/2019] [Indexed: 06/09/2023]
Abstract
Nonlinear frequency generation of light-carrying orbital angular momentum (OAM), which facilitates realization of on-demand, frequency-diverse optical vortices, would have utility in fields such as super-resolution microscopy, space-division multiplexing and quantum hyper-entanglement. In bulk media, OAM beams primarily differ in spatial phase, so the nonlinear overlap integral for self-phase matched χ(3) processes remains the same across the 4-fold degenerate subspace of beams (formed by different combinations of spin and orbital angular momentum) carrying the same OAM magnitude. This indistinguishable nature of nonlinear coupling implies that supercontinuum generation, which substantially relies on self/cross-phase modulation, and Raman soliton shifting of ultrashort pulses typically results in multimode outputs that do not conserve OAM. Here, using specially designed optical fibers that support OAM modes whose group velocity can be tailored, we demonstrate Raman solitons in OAM modes as well as the first supercontinuum spanning more than an octave (630 nm to 1430 nm), with the entire spectrum in the same polarization as well as OAM state. This is fundamentally possible because spin-orbit interactions in suitably designed fibers lead to large effective index and group velocity splitting of modes, and this helps tailoring nonlinear mode selectivity such that all nonlinearly generated frequencies reside in modes with high spatial mode purity.
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Pidishety S, Pachava S, Gregg P, Ramachandran S, Brambilla G, Srinivasan B. Orbital angular momentum beam excitation using an all-fiber weakly fused mode selective coupler. Opt Lett 2017; 42:4347-4350. [PMID: 29088160 DOI: 10.1364/ol.42.004347] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 09/01/2017] [Indexed: 06/07/2023]
Abstract
Orbital angular momentum beam excitation through direct phase-matched coupling is experimentally demonstrated using an all-fiber weakly fused mode selective coupler consisting of a single-mode fiber and a ring-core fiber. Experimental results showing the excited OAM mode purity of up to 75% measured through the standard ring technique not only demonstrate the proof of concept but also provide a baseline for further improvement.
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Palan J, Smith MC, Gregg P, Mellon S, Kulkarni A, Tucker K, Blom AW, Murray DW, Pandit H. The influence of cemented femoral stem choice on the incidence of revision for periprosthetic fracture after primary total hip arthroplasty. Bone Joint J 2016; 98-B:1347-1354. [DOI: 10.1302/0301-620x.98b10.36534] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 05/09/2016] [Indexed: 11/05/2022]
Abstract
Aims Periprosthetic fracture (PF) after primary total hip arthroplasty (THA) is an uncommon but potentially devastating complication. This study aims to investigate the influence of cemented stem designs on the risk of needing a revision for a PF. Patients and Methods We analysed data on 257 202 primary THAs with cemented stems and 390 linked first revisions for PF recorded in the National Joint Registry (NJR) of England, Wales and Northern Ireland to determine if a cemented femoral stem brand was associated with the risk of having revision for a PF after primary THA. All cemented femoral stem brands with more than 10 000 primary operations recorded in the NJR were identified. The four most commonly used cemented femoral stems were the Exeter V40 (n = 146 409), CPT (n = 24 300), C-Stem (n = 15 113) and Charnley (n = 20 182). We compared the revision risk ratios due to PF amongst the stems using a Poisson regression model adjusting for patient factors. Compared with the Exeter V40, the age, gender and ASA grade adjusted revision rate ratio was 3.89 for the cemented CPT stem (95% confidence interval (CI) 3.07 to 4.93), 0.89 for the C-Stem (95% CI 0.57 to 1.41) and 0.41 for the Charnley stem (95% CI 0.24 to 0.70). Conclusions The limitations of the study include incomplete data capture, analysis of only PF requiring revision and that observation does not imply causality. Nevertheless, this study demonstrates that the choice of a cemented stem may influence the risk of revision for PF. Cite this article: Bone Joint J 2016;98-B:1347–54.
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Affiliation(s)
- J. Palan
- National Joint Registry England, Leicester
General Hospital, Gwendolen Road, Leicester, LE5
4PW, UK
| | - M. C. Smith
- University of Bristol, Learning & Research Building (Level 1), Southmead Hospital, Bristol, BS10 5NB, UK
| | - P. Gregg
- James Cook University Hospital, Marton
Road, Middlesbrough TS4 3BW, UK
| | - S. Mellon
- Nuffield Dept. of Orthopaedics, Rheumatology & Musculoskeletal Sciences, University of Oxford, Botnar Research Centre, Windmill Road, Oxford, OX3 7LD, UK
| | - A. Kulkarni
- Leicester General Hospital, Gwendolen
Road, Leicester LE5 4PW, UK
| | | | - A. W. Blom
- University of Bristol, Learning & Research Building (Level 1), Southmead Hospital, Bristol, BS10 5NB, UK
| | - D. W. Murray
- The Botnar Research Centre, University
of Oxford, Windmill Road, Oxford, OX3
7LD, UK
| | - H. Pandit
- The Botnar Research Centre, University
of Oxford, Windmill Road, Oxford, OX3
7LD, UK
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Gregg P, Mirhosseini M, Rubano A, Marrucci L, Karimi E, Boyd RW, Ramachandran S. Q-plates as higher order polarization controllers for orbital angular momentum modes of fiber. Opt Lett 2015; 40:1729-1732. [PMID: 25872059 DOI: 10.1364/ol.40.001729] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate that a |q|=1/2 plate, in conjunction with appropriate polarization optics, can selectively and switchably excite all linear combinations of the first radial mode order |l|=1 orbital angular momentum (OAM) fiber modes. This enables full mapping of free-space polarization states onto fiber vector modes, including the radially (TM) and azimuthally polarized (TE) modes. The setup requires few optical components and can yield mode purities as high as ∼30 dB. Additionally, just as a conventional fiber polarization controller creates arbitrary elliptical polarization states to counteract fiber birefringence and yield desired polarizations at the output of a single-mode fiber, q-plates disentangle degenerate state mixing effects between fiber OAM states to yield pure states, even after long-length fiber propagation. We thus demonstrate the ability to switch dynamically, potentially at ∼GHz rates, between OAM modes, or create desired linear combinations of them. We envision applications in fiber-based lasers employing vector or OAM mode outputs, as well as communications networking schemes exploiting spatial modes for higher dimensional encoding.
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Ramachandran S, Gregg P, Kristensen P, Golowich SE. On the scalability of ring fiber designs for OAM multiplexing. Opt Express 2015; 23:3721-3730. [PMID: 25836225 DOI: 10.1364/oe.23.003721] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The promise of the infinite-dimensionality of orbital angular momentum (OAM) and its application to free-space and fiber communications has attracted immense attention in recent years. In order to facilitate OAM-guidance, novel fibers have been proposed and developed, including a class of so-called ring-fibers. In these fibers, the wave-guiding region is a high-index annulus instead of a conventional circular core, which for reasons related to polarization-dependent differential phase shifts for light at waveguide boundaries, leads to enhanced stability for OAM modes. We review the theory and implementation of this nascent class of waveguides, and discuss the opportunities and limitations they present for OAM scalability.
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Baker PN, Rushton S, Jameson SS, Reed M, Gregg P, Deehan DJ. Patient satisfaction with total knee replacement cannot be predicted from pre-operative variables alone: A cohort study from the National Joint Registry for England and Wales. Bone Joint J 2013; 95-B:1359-65. [PMID: 24078532 DOI: 10.1302/0301-620x.95b10.32281] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Pre-operative variables are increasingly being used to determine eligibility for total knee replacement (TKR). This study was undertaken to evaluate the relationships, interactions and predictive capacity of variables available pre- and post-operatively on patient satisfaction following TKR. Using nationally collected patient reported outcome measures and data from the National Joint Registry for England and Wales, we identified 22 798 patients who underwent TKR for osteoarthritis between August 2008 and September 2010. The ability of specific covariates to predict satisfaction was assessed using ordinal logistic regression and structural equational modelling. Only 4959 (22%) of 22 278 patients rated the results of their TKR as 'excellent', despite the majority (71%, n = 15 882) perceiving their knee symptoms to be much improved. The strongest predictors of satisfaction were post-operative variables. Satisfaction was significantly and positively related to the perception of symptom improvement (operative success) and the post-operative EuroQol-5D score. While also significant within the models pre-operative variables were less important and had a minimal influence upon post-operative satisfaction. The most robust predictions of satisfaction occurred only when both pre- and post-operative variables were considered together. These findings question the appropriateness of restricting access to care based on arbitrary pre-operative thresholds as these factors have little bearing on post-operative satisfaction.
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Affiliation(s)
- P N Baker
- Newcastle University, Institute of Cellular Medicine, Newcastle upon Tyne NE1 7RU, UK
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Fitzpatrick R, Morris R, Hajat S, Reeves B, Murray DW, Hannen D, Rigge M, Williams O, Gregg P. The value of short and simple measures to assess outcomes for patients of total hip replacement surgery. Qual Health Care 2000; 9:146-50. [PMID: 10980074 PMCID: PMC1743526 DOI: 10.1136/qhc.9.3.146] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES To evaluate the performance of a patient assessed outcome measure, the Oxford Hip Score, in a national study of primary hip replacement surgery. DESIGN A survey of patients' health status before undergoing primary hip replacement surgery and three months and one year after surgery. SETTING 143 hospitals in three NHS English regions. PATIENTS 7151 patients admitted for primary total hip replacement surgery over a period of 13 months from September 1996. MAIN MEASURES For patients, Oxford Hip Score and satisfaction with hip replacement and, for surgeons, American Anesthesiologists' Society (ASA) classification of physical status. RESULTS The response rates to the postal questionnaire at three and 12 months follow up were 85.2% and 80.7%, respectively. Including all three administrations of the questionnaire, all except two items of the Oxford Hip Score were completed by 97% or more respondents and only one item at one administration appeared marginally to reduce the reliability of the score. The effect sizes for changes in the score from baseline to three months was 2.50 and to 12 months was 3.05. Patients rated by surgeons as being healthy preoperatively by the ASA classification were somewhat more likely to return a completed questionnaire at three months (79.4% versus 75.3%) and 12 months (72.4% versus 70.3%) than those rated as having poorer health. CONCLUSIONS Overall there was little evidence of difficulties for patients in completing the Oxford Hip Score or of unreliable data, except in relation to one questionnaire item. The instrument was very responsive to change over time and score changes for the Oxford Hip Score related well to patients' satisfaction with their surgery. The instrument is an appropriate measure in terms of validity, responsiveness, and feasibility for evaluating total hip replacement from the
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Affiliation(s)
- R Fitzpatrick
- Institute of Health Sciences, University of Oxford, Headington, UK.
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Gregg P. National total hip replacement audit project. Ann R Coll Surg Engl 1996; 78:232-3. [PMID: 8944494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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Stafford HJ, Roberts MT, Oni OO, Hay J, Gregg P. Localisation of bone-forming cells during fracture healing by osteocalcin immunocytochemistry: an experimental study of the rabbit tibia. J Orthop Res 1994; 12:29-39. [PMID: 8113940 DOI: 10.1002/jor.1100120105] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
An immunocytochemical method was used to localise osteocalcin-producing cells during fracture healing in a rabbit model. In preliminary studies, tibial growth plates from young rabbits were used as a source of new bone formation, in order to determine the optimal tissue preparatory techniques. In the present study, a tibial shaft fracture was created in adult rabbits to study closed fracture healing. An indirect peroxidase method was used to stain paraffin-embedded tissue sections for osteocalcin. Osteocalcin-producing cells were positively identified at the periosteal and endosteal surfaces near the fracture site. Osteocalcin staining was not demonstrated in the surrounding soft tissues. At the interface between newly formed bone trabeculae and the cartilage layer within the callus, chondrocytic cells consistently showed localisation of osteocalcin. Within cartilaginous areas of the callus, some chondrocytes showed positive staining for osteocalcin. These cells were often seen in the proximity of blood vessels. The findings suggest that during fracture healing, under certain conditions, chondrocytes are capable of producing osteocalcin and thus could be considered capable of possible transformation into osteoblasts.
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Affiliation(s)
- H J Stafford
- Department of Orthopaedic Surgery, Glenfield General Hospital, Leicester, England
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Windon RG, Dineen JK, Gregg P, Griffiths DA, Donald AD. The role of thresholds in the response of lambs to vaccination with irradiated Trichostrongylus colubriformis larvae. Int J Parasitol 1984; 14:423-8. [PMID: 6469454 DOI: 10.1016/0020-7519(84)90099-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Campbell N, Gregg P, Kelly J, Dineen J. Failure to induce homologous immunity to Fasciola hepatica in sheep vaccinated with irradiated metacercariae. Vet Parasitol 1978. [DOI: 10.1016/0304-4017(78)90005-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Gregg P, Dineen J, Rothwell T, Kelly J. The effect of age on the response of sheep to vaccination with irradiated trichostrongylus colubriformis larvae. Vet Parasitol 1978. [DOI: 10.1016/0304-4017(78)90034-1] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Gregg P, Dineen J. The response of sheep vaccinated with irradiated Trichostrongylus colubriformis larvae to impulse and sequential challenge with normal larvae. Vet Parasitol 1978. [DOI: 10.1016/0304-4017(78)90035-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Dineen JK, Gregg P, Lascelles AK. The response of lambs to vaccination at weaning with irradiated Trichostrongylus colubriformis larvae: segregation into 'responders' and 'non-responders'. Int J Parasitol 1978; 8:59-63. [PMID: 631981 DOI: 10.1016/0020-7519(78)90052-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Dineen JK, Gregg P, Windon RG, Donald AD, Kelly JD. The role of immunologically specific and non-specific components of resistance in cross-protection to intestinal nematodes. Int J Parasitol 1977; 7:211-5. [PMID: 881284 DOI: 10.1016/0020-7519(77)90049-2] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Gregg P. Death Following Vaccination. Northwest Med Surg J 1848; 1:109-110. [PMID: 37319480 PMCID: PMC9904593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
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