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D Doughty

Publications and source records attributed to D Doughty.

At least 37 records · Page 2Linked to original sources
PubMed2002

Eta photoproduction on the proton for photon energies from 0.75 to 1.95 GeV.

Differential cross sections for gammap-->etap have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75 GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass approximately 1.8 GeV couples to the etaN channel.

Journal Article↗
PubMed2002

Q2 Dependence of quadrupole strength in the gamma*p --> Delta(+)(1232) --> p pi(0) transition.

Models of baryon structure predict a small quadrupole deformation of the nucleon due to residual tensor forces between quarks or distortions from the pion cloud. Sensitivity to quark versus pion degrees of freedom occurs through the Q2 dependence of the magnetic (M1+), electric (E1+), and scalar (S1+) multipoles in the gamma*p-->Delta(+)-->p pi(0) transition. We report new experimental values for the ratios E(1+)/M(1+) and S(1+)/M(1+) over the range Q2 = 0.4-1.8 GeV2, extracted from precision p(e,e(')p)pi(0) data using a truncated multipole expansion. Results are best described by recent unitary models in which the pion cloud plays a dominant role.

Journal Article↗
PubMed2002

First measurement of the double spin asymmetry in (-->)e(-->)p-->e(prime)pi(+)n in the resonance region.

The double spin asymmetry in the (-->)e(-->)p --> e(prime)pi(+)n reaction has been measured for the first time in the resonance region for four-momentum transfer Q2 = 0.35-1.5 GeV(2). Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid NH3 target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity-1/2 transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with Q(2) of the helicity asymmetry A1 for the F(15)(1680) resonance than expected from the analysis of the unpolarized data.

Journal Article↗
PubMed2001

Genome sequence of the plant pathogen and biotechnology agent Agrobacterium tumefaciens C58.

Agrobacterium tumefaciens is a plant pathogen capable of transferring a defined segment of DNA to a host plant, generating a gall tumor. Replacing the transferred tumor-inducing genes with exogenous DNA allows the introduction of any desired gene into the plant. Thus, A. tumefaciens has been critical for the development of modern plant genetics and agricultural biotechnology. Here we describe the genome of A. tumefaciens strain C58, which has an unusual structure consisting of one circular and one linear chromosome. We discuss genome architecture and evolution and additional genes potentially involved in virulence and metabolic parasitism of host plants.

Agrobacterium tumefaciens↗
PubMed2001

Photoproduction of the rho(0) meson on the proton at large momentum transfer.

The differential cross section, d sigma/dt, for rho(0) meson photoproduction on the proton above the resonance region was measured up to a momentum transfer -t = 5 GeV2 using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The rho(0) channel was extracted from the measured two charged-pion cross sections by fitting the pi(+)pi(-) and p pi(+) invariant masses. The low momentum transfer region shows the typical diffractive pattern expected from Reggeon exchange. The flatter behavior at large -t cannot be explained solely in terms of QCD-inspired two-gluon exchange models. The data indicate that other processes, like quark interchange, are important to fully describe rho photoproduction.

Journal Article↗
PubMed2001

The ep -->e'p eta reaction at and above the S11(1535) baryon resonance.

New cross sections for the reaction e p-->e p eta are reported for total center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q2 = 0.25--1.5 (GeV/c)(2). This large kinematic range allows extraction of important new information about response functions, photocouplings, and eta N coupling strengths of baryon resonances. Newly observed structure at W approximately 1.65 GeV is shown to come from interference between S and P waves and can be interpreted with known resonances. Improved values are derived for the photon coupling amplitude for the S11(1535) resonance.

Journal Article↗
PubMed2001

Is distortion correction necessary for digital subtraction angiography in the Gamma Knife treatment of intra-cranial arteriovenous malformations?

OBJECTIVE: The published literature maintains that distortion correction of digital subtraction angiography is essential for accurate definition of the arteriovenous malformation (AVM) nidus when performing Gamma Knife radiosurgery. However, as Gamma Knife treatments usually involve small volume targets, which are purposely positioned as close to the centre of the frame as possible, we postulated that the angiographic target images should be minimally distorted. Thus, the use of uncorrected images would not significantly compromise the accuracy of the treatment. We investigated this postulate. DESIGN: Patient and phantom images with and without distortion correction were assessed. The errors measured in the angiograms were compared to those of MR and CT images of the same subjects. Any errors less than 0.5 mm in any modality were accepted as intrinsic. RESULTS: All errors measured in the study were sub-millimetre. In the patient group, errors with distortion correction averaged 0.13 mm (range 0-0.3 mm). Without distortion correction, errors averaged 0.34 mm (range 0.1-0.6 mm). By comparison, the average error for intracranial MR imaging was 0.3 mm, with a maximum of 0.6 mm. CONCLUSION: For small, intracranial AVMs distortion correction did not significantly reduce the errors associated with the definition of the stereotactic co-ordinates. We suggest that prior to the purchase of this software, similar in-house testing should be performed.

Angiography, Digital Subtraction↗
PubMed2000

Back to the future

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Journal Article↗
PubMed2000

Integrating advanced practice and WOC nursing education.

The increased use of advanced practice nurses (APNs) in all health care settings provides new practice options for WOC nurses and new challenges for WOC nursing education. A number of WOC nurses are moving into APN roles, and APNs who are not WOC specialists are providing much of the primary care for patients with wounds, ostomies, and incontinence. New educational approaches are needed to prepare APNs for specialty practice in wound, ostomy, and/or continence care. In addition, the need exists to incorporate key WOC nursing content into the core curriculum for APNs who provide primary care for patients with or at risk for wounds or disordered elimination. This article explores potential strategies for meeting these new demands.

Curriculum↗
PubMed2000

Show me the data.

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Evidence-Based Medicine↗
PubMed1999

Stereotactically delivered cranial radiation therapy: a ten-year experience of linac-based radiosurgery in the UK.

In 1989, linear accelerator (linac)-based cranial stereotactic radiation therapy ('radiosurgery') was introduced in the UK at St Bartholomew's Hospital; a new, relocatable stereotactic frame was first used at the same time, allowing fractionated stereotactic radiotherapy. In the first decade of clinical practice using this technology, some 200 patients with blood vessel tumours/malformations have been treated, together with another 200 suffering from other conditions. The usefulness of this technique for cerebral arteriovenous malformations (AVM) has been demonstrated, and also a significant cure rate for AVM of >3 cm diameter (which is larger than for those previously reported after treatment on the gamma unit), albeit attended by a higher complication rate. The epilepsy associated with AVM is much improved by successful radiotherapy. The usefulness of radiosurgery for glomus tumours has been confirmed and new data published on the efficacy of the technique for haemangioblastoma, with new radiation therapy strategies designed for patients with von Hippel-Lindau disease. The acoustic neuroma treatment results have included improvements in hearing (a result not reported in the gamma unit literature), which are ascribed to the lower internal dose gradient within the target volume. Fractionation will, it is argued, also lead to sparing of the special sensory cochlear nerve. The risks of radiosurgery to the brainstem for chordoma of the mid-clivus are reduced by using a 'spacer' technique for the prepontine space. For meningiomas involving the cavernous sinus, conventionally fractionated radiotherapy is recommended when the meningeal base diameter exceeds 3.0 cm and radiosurgery (utilizing fractionation where appropriate) is advised for smaller lesions. Thus far, radiosurgery indications for pituitary adenomas have been restricted to recurrences after conventional radiotherapy, usually those in the cavernous sinus. In therapy for recurrent craniopharyngioma, it is argued that fractionation delivered via the relocatable frame will be important, particularly when the disease envelops the optic chiasma. For semicystic/semisolid craniopharyngiomas, the stereotactic delivery of colloidal yttrium-90 into a cystic element is useful, while stereotactic radiosurgery is delivered to the solid component. Staff at this centre consider that radiosurgery for low-grade gliomas, perhaps as boost therapy after conventional fractionation, is worthy of more research. We have been extremely selective in the use of radiosurgery for brain metastases (2% of patients, compared with about 30% in some Gamma Knife units), but future indications may become broader, probably using it as a booster technique after whole-brain conventionally-fractionated radiotherapy. Positron emission tomography scanning, co-registered with magnetic resonance imaging, allows the 'boost' concept in radiosurgery to become a sophisticated and accurate reality. Post-radiosurgical sequelae have been placed within a standard framework classification. New observations are being made with regard to subacute reactions: late-responding intrinsic and extra-axial tumours may swell in the subacute period, prior to shrinkage, and be attended by symptomatic surrounding brain oedema.

Adenoma↗
PubMed1999

Stereotactic radiosurgery, X: clinical isodosimetry of gamma knife versus linear accelerator X-knife for pituitary and acoustic tumours.

Several review articles have compared gamma unit versus linear accelerator (linac)-based radiosurgery systems, concluding that the dose gradient 'fall-off' at the margin of the target (expressed as the distance between isodoses) is very similar for both techniques as far as single isocentre treatment volumes up to 1.5 cm diameter are concerned, and that the two radiosurgical systems are, in general, comparable. 'Fine tuning' of the gamma unit can be carried out by using multiple isocentre plans, the differential use of small collimator sizes (down to 4 mm) and field weightings, and adroit use of the gamma angle, and selective beam blocking. Multiple isocentre plans, beam modification, restriction of gantry angles and arc lengths, and microcollimation can similarly improve the isodose gradients from linac units. In both instances, the dosimetric advantages occur along selected aspects of the target perimeter border. However, the more frequent use of multiple isocentred 'shots' on the gamma unit achieves greater conformity indices for more complex target volumes, but at the expense of steeper internal dose gradients. We studied two patients with tumours close to or arising from radiosensitive special sensory nerves (optic and cochlear) to compare and contrast fine tuning of the two technologies. In a previously irradiated patient with a pituitary adenoma, the dose gradient achieved at the rostral margin, adjacent to the optic chiasma, was steeper on the gamma unit (due to the concentration of small collimator shots rostrally and beam blocking), which was therefore the dosimetrically preferred technique. In contrast, the vastly smaller internal dose gradient (11% for linac/X-knife versus 100% for Gamma Knife) and the ability to fractionate on the X-knife system, gave a large dosimetric advantage to the X-knife plan in the treatment of an acoustic neuroma, where the intracanalicular component of the cochlear nerve traversed the target volume. This advantage also pertains to the cochlear ramus of the internal auditory (labyrinthine) artery and the facial nerve. Our published work on X-knife radiosurgery of acoustic neuroma has documented improvement of hearing after therapy and may be relevant in this regard. That there are advantages in physical dose distribution and fractionation, producing a reduction in the biological dose in normal tissue, argues for the use of linac technology in acoustic neuromas. Craniopharyngiomas enveloping the optic nerve/chiasma will similarly be better treated by the linac X-knife system. It is apparent that different radiosurgery systems may be indicated in particular neuro-oncological situations.

Adenoma↗
PubMed1999

Stereotactic intracavitary therapy of recurrent cystic craniopharyngioma by instillation of 90yttrium.

Six consecutively presenting patients with craniopharyngiomas, (F:M = 4.2; mean age: 35.2 years, range 17-58) histologically proven by one or more previous operations, and with recurrence of a wholly or predominantly cystic nature, were treated by 90yttrium (90Y) radioisotope instillation into the cyst. Five patients had undergone external beam radiotherapy and the remaining patient had concomitant stereotactic radiosurgery to a co-existing solid component. Seven cysts in six patients have been treated. Five cysts, previously requiring repeated aspiration at intervals of 2-20 weeks have required no further surgical intervention following 90Y treatment (FU mean 3.5 years, range 1.2-7), although two of these required a second 90Y treatment. No patient developed a visual field defect or evidence of hypothalamic dysfunction. One patient died within a month of treatment from complications related to a solid recurrence. One patient developed a large solid/cystic recurrence at 4 months and died shortly thereafter from an unrelated cause. We summarize results from other series that have demonstrated the efficacy of this technique, usually as primary therapy, but this is the first series to demonstrate its usefulness as salvage therapy. The prospect of survival with good quality of life can be offered to patients with multiply recurrent disease who have exhausted all conventional means of treatment. In our experience intracavitary 90Y is a safe and highly effective means of controlling cystic recurrence in refractory craniopharyngioma. Some patients require more than one treatment.

Adult↗
PubMed1998

Treatment of retinoblastoma vitreous base seeding.

OBJECTIVE: The purpose of the study is to describe results of a new treatment for retinoblastoma vitreous base seeding. DESIGN: The study design was a retrospective review of patients treated at an ocular oncology referral center. PARTICIPANTS: Five eyes of five patients with vitreous base seeding that occurred after previous external beam radiation therapy were treated between October 1987 and December 1994. INTERVENTION: A customized plaque made from iridium-192/platinum wire was placed to deliver 4000 cGy to the tumor apex along its entire length and systemic chemotherapy (consisting of carboplatin, vincristine, and etoposide) was given. MAIN OUTCOME MEASURES: Eye preservation and tumor control were measured. RESULTS: Vitreous base seeding was controlled completely and the eye preserved in four of the five treated eyes with an average follow-up of 26.2 months. CONCLUSIONS: The combination of a customized iridium-192 plaque and systemic chemotherapy is an effective means of treating vitreous base seeding of retinoblastoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Clinical efficacy of perceived 'CNS friendly' chemoradiotherapy for primary intracranial germ cell tumours.

The optimal treatment of intracranial germ cell tumours (IGCT) is controversial. The late sequelae of craniospinal radiotherapy and the high response rate to chemotherapy have led to new treatment strategies. The morbidity of combined modality therapy has tempered enthusiasm for aggressive chemoradiotherapy. In 1992, we described new lower morbidity chemotherapy and radiotherapy methods to be used in conjunction for IGCT treatment, employing three drugs (vincristine, carboplatin, etoposide) and a differential daily dose neuraxis radiotherapy technique (to replace a shrinking field technique). The chemoradiotherapy had the potential for a graded intensity reduction when high cure rates were maintained. Of 13 IGCT patients treated on this protocol, 8/8 germinomatous GCT and 3/5 non-germinomatous GCTs are in continuing remission. These observations have implications for other CNS tumour treatments in (young) patients, in whom late CNS toxicity (particularly neuropsychological) is a problem.

Adolescent↗