240 research outputs found
Nondissipative optimum charge regulator advanced study Semiannual report
Improved reliability of multiphase nondissipative optimum charge regulato
Order induced by dipolar interactions in a geometrically frustrated antiferromagnet
We study the classical Heisenberg model for spins on a pyrochlore lattice
interacting via long range dipole-dipole forces and nearest neighbor exchange.
Antiferromagnetic exchange alone is known not to induce ordering in this
system. We analyze low temperature order resulting from the combined
interactions, both by using a mean-field approach and by examining the energy
cost of fluctuations about an ordered state. We discuss behavior as a function
of the ratio of the dipolar and exchange interaction strengths and find two
types of ordered phase. We relate our results to the recent experimental work
and reproduce and extend the theoretical calculations on the pyrochlore
compound, GdTiO, by Raju \textit{et al.}, Phys. Rev. B {\bf 59},
14489 (1999).Comment: 5 pages, 5 figures, AMSLaTe
Medically inoperable peripheral lung cancer treated with stereotactic body radiation therapy
BACKGROUND: Lung cancer is the most frequent cause of cancer-related death in North America. There is wide variation between patients who are medically inoperable and those managed surgically. The use of stereotactic body radiotherapy (SBRT) has narrowed the gap in survival rates between operative and non-operative management for those with early stage disease. This retrospective study reports outcomes for the treatment of peripheral non-small cell lung carcinoma (NSCLC) with SBRT from a single community practice. METHODS: Sixty-seven consecutive patients (pts) with inoperable, untreated peripheral lung tumors were treated from 2010 through 2012 and included in this study. Stereotactic targeting was facilitated by either spine or lung-based image guidance, either with or without fiducial marker tracking with a frameless robotic radiosurgery system. Peripheral tumors received a median biological effective dose (BED) of 105.6 Gy10 or in terms of a median physical dose, 48 Gy delivered over 4 daily fractions. Survival was measured using the Kaplan-Meier method to determine rates of local control, progression of disease and overall survival. The Cox proportional hazards regression model was used to study the effects of tumor size, stage, histology, patient age, tumor location (lobe), tracking method, and BED on the survival distributions. RESULTS: The median follow-up for this cohort was 24.5 months (range: 2.4-50.3) with an overall (OS) 3-year survival of 62.4 % (95 % CI: 74.3-47.3). The median progression-free survival was 28.5 months (95 % CI: 15.8 months to not reached). Local control (LC), defined as a lack of FDG uptake on PET/CT or the absence of tumor growth was achieved in 60 patients (90.9 %) at the time of first follow-up (median 3 months, range: 1-6). Local control at one year for the entire cohort was 81.8 % (95 % CI, 67.3-90.3). The one-year OS probability among those who achieved local control at first follow-up was 86.2 % (95 % CI, 74.3-92.9) but no patients who did not achieve LC at first follow-up survived one year. Of the 60 pts that achieved initial LC, 16 have died. The rates of local control, progression-free survival and overall survival were not statistically different for patients treated using a fiducial target tracking system versus non-invasive guidance. (p = 0.44, p = 0.97 and p = 0.66, respectively). No National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE-4) grade 3 or greater toxicity was observed. CONCLUSION: SBRT is an effective treatment for medically inoperable NSCLC patients with peripherally located tumors. This therapy appears to be well tolerated with low toxicity, and patient outcomes when using non-invasive tumor tracking systems are not inferior to traditional fiducial-based techniques
Play and metaphor in clinical supervision: keeping creativity alive
This article explores the use of play and metaphor in clinical supervision. The intention is not to attempt to cover the whole area of play, or the use of metaphor in clinical supervision, but rather to highlight particular aspects of their respective roles in the service of learning about therapeutic work. The relevance of the arts - especially the visual arts - in relation to this is also discussed. A number of brief clinical vignettes are included by way of illustration. All names, and some identifying details, have been changed to preserve confidentiality. (C) 2010 Elsevier Inc. All rights reserved
Stuffed Rare Earth Pyrochlore Solid Solutions
Synthesis and crystal structures are described for the compounds
Ln2(Ti2-xLnx)O7-x/2, where Ln = Tb, Dy, Ho, Er, Tm, Yb, Lu, and x ranges from 0
to 0.67. Rietveld refinements on X-ray powder diffraction data indicate that in
Tb and Dy titanate pyrochlores, extra Ln3+ cations mix mainly on the Ti4+ site
with little disorder on the original Ln3+ site. For the smaller rare earths
(Ho-Lu), stuffing additional lanthanide ions results in a pyrochlore to defect
fluorite transition, where the Ln3+ and Ti4+ ions become completely randomized
at the maximum (x=0.67). In all of these Ln-Ti-O pyrochlores, the addition of
magnetic Ln3+ in place of nonmagnetic Ti4+ adds edge sharing tetrahedral spin
interactions to a normally corner sharing tetrahedral network of spins. The
increase in spin connectivity in this family of solid solutions represents a
new avenue for investigating geometrical magnetic frustration in the rare earth
titanate pyrochlores.Comment: 25 pages, 7 figures, submitted to J. Solid State Che
The order parameter-entropy relation in some universal classes: experimental evidence
The asymptotic behaviour near phase transitions can be suitably characterized
by the scaling of with , where is
the excess entropy and is the order parameter. As is obtained by
integration of the experimental excess specific heat of the transition , it displays little experimental noise so that the curve versus is better constrained than, say,
versus . The behaviour of for different
universality classes is presented and compared. In all cases, it clearly
deviates from being a constant. The determination of this function can then be
an effective method to distinguish asymptotic critical behaviour. For
comparison, experimental data for three very different systems, Rb2CoF4,
Rb2ZnCl4 and SrTiO3, are analysed under this approach. In SrTiO3, the function
does not deviate within experimental resolution from a straight
line so that, although Q can be fitted with a non mean-field exponent, the data
can be explained by a classical Landau mean-field behaviour. In contrast, the
behaviour of for the antiferromagnetic transition in Rb2CoF4 and
the normal-incommensurate phase transition in Rb2ZCl4 is fully consistent with
the asymptotic critical behaviour of the universality class corresponding to
each case. This analysis supports, therefore, the claim that incommensurate
phase transitions in general, and the ABX compounds in particular, in
contrast with most structural phase transitions, have critical regions large
enough to be observable.Comment: 13 pp. 9 ff. 2 tab. RevTeX. Submitted to J. Phys.: Cond. Matte
Magnetic susceptibility of diluted pyrochlore and SCGO antiferromagnets
We investigate the magnetic susceptibility of the classical Heisenberg
antiferromagnet with nearest-neighbour interactions on the geometrically
frustrated pyrochlore lattice, for a pure system and in the presence of
dilution with nonmagnetic ions. Using the fact that the correlation length in
this system for small dilution is always short, we obtain an approximate but
accurate expression for the magnetic susceptibility at all temperatures. We
extend this theory to the compound SrCr_{9-9x}Ga_{3+9x}O_{19} (SCGO) and
provide an explanation of the phenomenological model recently proposed by
Schiffer and Daruka [Phys. Rev. B56, 13712 (1997)].Comment: 4 pages, Latex, 4 postscript figures automatically include
- …