Biomedical subjects

N Davidson

Publications and source records attributed to N Davidson.

At least 19 recordsLinked to original sources

PubMed2007

The surgical management of patients who achieve a complete pathological response after primary chemotherapy for locally advanced breast cancer.

AIMS: Our aim was to investigate the role of minimal surgery in patients with locally advanced breast cancer (LABC) who achieve a complete pathological (pCR) response to primary chemotherapy (PC) and evaluate subsequent local recurrence (LRR), disease free survival (DFS) and overall survival (OS). METHODS: Between January 2000 and April 2005, 101 patients with operable LABC (T2, T3, N0 or N1, M0) who were not suitable for conservation surgery were treated with PC. Patients were treated with doxorubicin and cyclophosphamide for four cycles (100 patients) then four cycles with paclitaxel (91 patients). Post-PC surgery consisted of multiple core biopsies and axillary clearance for patients with a complete clinical and radiological response. If a pCR was confirmed no further breast surgery was performed. The remaining patients were treated with breast conserving surgery or mastectomy and axillary clearance as appropriate. Adjuvant radiotherapy was given to all patients. RESULTS: Breast conservation was possible in 60% of patients. Overall, 20 patients achieved a pCR of which 16 were confirmed on core biopsies alone. All patients were followed-up for a mean of 33.5 months (95% CI, 30.3-36.7). There were 10 local recurrences, four following mastectomy, four after wide excision and two after core biopsies. There was no difference in DFS (chi square=0.18; p=0.67) or OS (chi square=0.67; p=0.41) between patients achieving a pCR and the remainder. CONCLUSIONS: The local recurrence rate of these poor prognosis patients is similar to other reported series but higher than in our previously reported series of patients managed according to the same protocol. Our current management therefore now includes pre-treatment marking and subsequent surgical excision.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2006

Decay of quantum correlations in atom optics billiards with chaotic and mixed dynamics.

We perform echo spectroscopy on ultracold atoms in atom-optics billiards to study their quantum dynamics. The detuning of the trapping laser is used to change the "perturbation", which causes a decay in the echo coherence. Two different regimes are observed: first, a perturbative regime in which the decay of echo coherence is nonmonotonic and partial revivals of coherence are observed in contrast with the predictions of random matrix theory. These revivals are more pronounced in traps with mixed dynamics as compared to traps where the dynamics is fully chaotic. Next, for stronger perturbations, the decay becomes monotonic and independent of the strength of the perturbation. In this regime no clear distinction can be made between chaotic traps and traps with mixed dynamics.

Journal Article↗

PubMed2006

Intracavity coherent addition of 16 laser distributions.

The efficient intracavity coherent addition of 16 separate laser Gaussian mode distributions is presented. The coherent addition is achieved in a multichannel pulsed Nd:YAG laser resonator by use of four intracavity interferometric beam combiners. The results reveal 88% combining efficiency with a combined output beam of nearly pure Gaussian distribution.

Journal Article↗

PubMed2005

Collisional decay of a strongly driven Bose-Einstein condensate.

We study the collisional decay of a strongly driven Bose-Einstein condensate oscillating between two momentum modes. The resulting products of the decay are found to strongly deviate from the usual s-wave halo. Using a stochastically seeded classical field method we simulate the collisional manifold. These results are also explained by a model of colliding Bloch states.

Journal Article↗

PubMed2005

Determinants of false positive recall in an Australian mammographic screening program.

We conducted a case-control study (n=30128) to assess the importance of clinical (e.g., family history, age, hormone replacement therapy (HRT) use and duration) and service-related characteristics (e.g., time since introduction of Kodak MINR2000 film, year of screen) for false positive (FP) recall at BreastScreen Victoria, Australia. There was an age-adjusted upward trend in FP recall rates with year of screen at first (odds ratio (OR) 1.11, 95% confidence interval (95% CI) 1.08-1.13) and subsequent rounds (OR 1.04, 95% CI 1.01-1.06). In the multivariate analysis, the upward trend only remained for first round and age and family history also remained statistically significant at first round. At subsequent rounds the time since introduction of MINR2000, age, strong family history of breast cancer, use of HRT, recall at previous screen and previous screen at more than 27 months were all important predictors of FP recall. The rise in FP rates with year of screen at first round screening is of concern and may require further training of radiologists to improve confidence when viewing films when there a no films for comparison.

Age Factors↗

PubMed2005

Intracavity coherent addition of single high-order modes.

We report on efficient intracavity coherent addition of several single high-order mode distributions in a multichannel laser resonator. The phase locking and coherent addition is achieved by using an intracavity interferometric beam combiner. The principle, configuration, and experimental results with pulsed Nd:YAG Laguerre-Gaussian TEM01 and TEM02 laser beam distributions are presented. The results reveal more than 95% combining efficiency with a nearly pure high-order mode output beam distribution in both free-running and Q-switched operation.

Journal Article↗

PubMed2005

Zoledronic acid significantly improves pain scores and quality of life in breast cancer patients with bone metastases: a randomised, crossover study of community vs hospital bisphosphonate administration.

Patients with bone metastases from breast cancer often experience substantial skeletal complications -- including debilitating bone pain -- which negatively affect quality of life. Zoledronic acid (4 mg) has been demonstrated to reduce significantly the risk of skeletal complications in these patients and is administered via a short, 15-min infusion every 3 weeks, allowing the possibility for home administration. This study compared the efficacy and safety of zoledronic acid administered in the community setting vs the hospital setting in breast cancer patients with > or =1 bone metastasis receiving hormonal therapy. After a lead-in phase of three infusions of 4 mg zoledronic acid in the hospital setting, 101 patients were randomized to receive three open-label infusions in the community or hospital setting, followed by three infusions in the opposite venue (a total of nine infusions). The Brief Pain Inventory (BPI) and the European Organisation for Research and Treatment of Cancer Quality of Life Core Questionnaire 30 (EORTC QLQ-C30) were used to assess potential benefits of zoledronic acid therapy. At study end, analysis of the BPI showed significant reductions in worst pain (P=0.008) and average pain in the last 7 days (P=0.039), and interference with general activity (P=0.012). In each case, there were significantly greater improvements in pain scores after treatment in the community setting compared with the hospital crossover setting for worst pain (P=0.021), average pain (P=0.003), and interference with general activity (P=0.001). Overall global health status showed a significant median improvement of 8.3% (P=0.013) at study end. Physical, emotional, and social functioning also showed significant overall improvement (P=0.013, 0.005, and 0.043, respectively). Furthermore, physical, role, and social functioning showed significantly greater improvements after treatment in the community setting compared with the hospital crossover setting (P=0.018, 0.001, and 0.026, respectively). There was no difference between hospital and community administration in renal or other toxicity, with zoledronic acid being well tolerated in both treatment settings. These data confirm the safety and quality-of-life benefits of zoledronic acid in breast cancer patients with bone metastases, particularly when administered in the community setting.

Activities of Daily Living↗

PubMed2005

Optically induced polarons in bose-einstein condensates: monitoring composite quasiparticle decay.

Nonresonant light scattering off atomic Bose-Einstein condensates is predicted to give rise to hitherto unexplored composite quasiparticles: unstable polarons, i.e., local "impurities" dressed by virtual phonons. Optical monitoring of their spontaneous decay can display either Zeno or anti-Zeno deviations from the golden rule, and thereby probe the temporal correlations of elementary excitations in the condensates.

Journal Article↗

PubMed2004

High sensitivity phonon spectroscopy of Bose-Einstein condensates using matter-wave interference.

We study low-momentum excitations of a Bose-Einstein condensate using a novel matter-wave interference technique. In time-of-flight expansion images we observe strong matter-wave fringe patterns. The fringe visibility is a sensitive spectroscopic probe of in-trap phonons and is explained by use of a Bogoliubov excitation projection method applied to the rescaled order parameter of the expanding condensate. Gross-Pitaevskii simulations agree with the experimental data and confirm the validity of the theoretical interpretation. We show that the high sensitivity of this detection scheme gives access to the quantized quasiparticle regime.

Journal Article↗

PubMed2004

Phase III trial of liposomal doxorubicin and cyclophosphamide compared with epirubicin and cyclophosphamide as first-line therapy for metastatic breast cancer.

OBJECTIVE: To ascertain the efficacy and tolerability of non-pegylated liposomal doxorubicin (Myocet) and epirubicin combined with cyclophosphamide in the first-line treatment of patients with metastatic breast cancer. METHODS: One hundred and sixty anthracycline-naïve metastatic breast cancer patients were randomised to receive Myocet (M; 75 mg/m(2)) or epirubicin (E; 75 mg/m(2)) in combination with cyclophosphamide (C; 600 mg/m(2)), every 3 weeks for up to eight cycles. OUTCOME MEASURES: Response (overall response = complete + partial response rates), time to disease progression, overall survival and cardiac function (left ventricular ejection fraction). RESULTS: Overall response rates were 46% and 39% for MC and EC treatment, respectively (P=0.42). MC was superior to EC with respect to median time to treatment failure (5.7 versus 4.4 months; P=0.01) and median time to disease progression (7.7 versus 5.6 months; P=0.02). Median survival times were 18.3 and 16.0 months for MC and EC, respectively (P=0.504). Unsurprisingly, given an equimolar comparison, neutropenia and stomatitis/mucositis were significantly more common in patients who received MC. However, there was less injection site toxicity with MC. Both treatments showed a low incidence of cardiotoxicity. CONCLUSION: Myocet appears to be an acceptable alternative to epirubicin as a first-line treatment for patients with metastatic breast cancer because it combines the dose-effect reliability of doxorubicin with the level of safety provided by epirubicin.

Adult↗

PubMed2003

Three-wave mixing of bogoliubov quasiparticles in a bose-einstein condensate.

A dressed basis is used to calculate the dynamics of three-wave mixing between Bogoliubov quasiparticles in a Bose condensate. Because of the observed oscillations between different momentum modes, an energy splitting, analogous to the optical Mollow triplet, appears in the Beliaev damping spectrum of the excitations from the oscillating modes.

Journal Article↗

PubMed2003

Conversion of a high-order mode beam into a nearly Gaussian beam by use of a single interferometric element.

We present a new, compact, and practical optical mode converter that efficiently transforms a high-order Hermite-Gaussian (HG) laser beam into a nearly Gaussian beam. The mode converter is based on coherently adding different transverse parts of the high-order mode beam by use of a single planar interferometric element. The method, configuration, and experimental results obtained with a pulsed Nd:YAG HG TEM10 laser beam are presented. The results reveal that the efficiency of conversion of a HG beam to a nearly Gaussian beam can be as high as 90%.

Journal Article↗

PubMed2003

Bragg spectroscopy of the multibranch Bogoliubov spectrum of elongated Bose-Einstein condensates.

We measure the response of an elongated Bose-Einstein condensate to a two-photon Bragg pulse. If the duration of the pulse is long, the total momentum transferred to the condensate exhibits a nontrivial behavior which reflects the structure of the underlying Bogoliubov spectrum. It is thus possible to perform a spectroscopic analysis in which axial phonons with a different number of radial nodes are resolved. The local density approximation is shown to fail in this regime, while the observed data agree well with the results of simulations based on the numerical solution of the Gross-Pitaevskii equation.

Journal Article↗

PubMed2003

Echo spectroscopy and quantum stability of trapped atoms.

We investigate the dephasing of ultra cold 85Rb atoms trapped in an optical dipole trap and prepared in a coherent superposition of their two hyperfine ground states by interaction with a microwave pulse. We demonstrate that the dephasing, measured as the Ramsey fringe contrast, can be reversed by stimulating a coherence echo with a pi pulse between the two pi / 2 pulses, in analogy to the photon echo. We also demonstrate that "echo spectroscopy" can be used to study the quantum dynamics in the trap even when more than 10(6) states are thermally populated and to study the crossover from quantum to classical dynamics.

Journal Article↗

PubMed2003

An open randomised trial of second-line endocrine therapy in advanced breast cancer. comparison of the aromatase inhibitors letrozole and anastrozole.

It was previously shown that letrozole (Femara) was significantly more potent than anastrozole (Arimidex) in inhibiting aromatase activity in vitro and in inhibiting total body aromatisation in patients with breast cancer. The objective of this study was to compare letrozole (2.5 mg per day) and anastrozole (1 mg per day) as endocrine therapy in postmenopausal women with advanced breast cancer previously treated with an anti-oestrogen. This randomised, multicentre and multinational open-label phase IIIb/IV study enrolled 713 patients. Treatment was for advanced breast cancer that had progressed either during anti-oestrogen therapy or within 12 months of completing that therapy. Patients had tumours that were either positive for oestrogen and/or progesterone receptors (48%) or of unknown receptor status (52%). The primary efficacy endpoint was time to progression (TTP). Secondary endpoints included objective response, duration of response, rate and duration of overall clinical benefit (responses and long-term stable disease), time to treatment failure, and overall survival, as well as general safety. There was no difference between the treatment arms in TTP; median times were the same for both treatments. Letrozole was significantly superior to anastrozole in the overall response rate (ORR) (19.1% versus 12.3%, P=0.013), including in predefined subgroups (receptor status-unknown, and soft-tissue- and viscera-dominant site of disease). There were no significant differences between the treatment arms in the rate of clinical benefit, median duration of response, duration of clinical benefit, time to treatment failure or overall survival. Both agents were well tolerated and there were no significant differences in safety. These results support previous data documenting the greater aromatase-inhibiting activity of letrozole and indicate that advanced breast cancer is more responsive to letrozole than to anastrozole as second-line endocrine therapy.

Adult↗

PubMed2002

Beliaev damping of quasiparticles in a Bose-Einstein condensate.

We report a measurement of the suppression of collisions of quasiparticles with ground state atoms within a Bose-Einstein condensate at low momentum. These collisions correspond to Beliaev damping of the excitations, in the previously unexplored regime of the continuous quasiparticle energy spectrum. We use a hydrodynamic simulation of the expansion dynamics, with the Beliaev damping cross section, in order to confirm the assumptions of our analysis.

Journal Article↗

PubMed2002

Excitation spectrum of a Bose-Einstein condensate.

We report a measurement of the excitation spectrum omega(k) and the static structure factor S(k) of a Bose-Einstein condensate. The excitation spectrum displays a linear phonon regime, as well as a parabolic single-particle regime. The linear regime provides an upper limit for the superfluid critical velocity, by the Landau criterion. The excitation spectrum agrees well with the Bogoliubov spectrum in the local density approximation, even close to the long-wavelength limit of the region of applicability. Feynman's relation between omega(k) and S(k) is verified, within an overall constant.

Journal Article↗

PubMed2001

Observation of islands of stability in soft wall atom-optics billiards.

We report on numerical and experimental observations of islands of stability induced in a Bunimovich stadium atom-optics billiard by a soft wall repulsive potential. A deviation from exponential decay of the survival probability of atoms in an open billiard is observed, and explained by the presence of these stable islands and a sticky region surrounding them. We also investigate islands in dispersing billiards with soft walls, and predict a new mechanism for their formation.

Journal Article↗