Biomedical subjects

E Zaremba

Publications and source records attributed to E Zaremba.

At least 19 recordsLinked to original sources

PubMed2003

Nonlinear screening in two-dimensional electron gases.

We have performed self-consistent calculations of the nonlinear screening of a point charge Z in a two-dimensional electron gas using a density functional theory method. We find that the screened potential for a Z=1 charge supports a bound state even in the high-density limit where one might expect perturbation theory to apply. To explain this behavior, we prove a theorem to show that the results of linear response theory are in fact correct even though bound states exist.

Journal Article↗

PubMed2002

Accidental suppression of landau damping of the transverse breathing mode in elongated bose-einstein condensates.

We study transverse radial oscillations of an elongated Bose-Einstein condensate using finite-temperature simulations, in the context of a recent experiment at ENS [F. Chevy, Phys. Rev. Lett. 88, 250402 (2002)]]. The mode observed experimentally corresponds to an in-phase collective oscillation of both the condensate and the thermal cloud. Our simulations are in excellent agreement with experiment, accounting for the very small damping rates observed. In contrast to other condensate modes, interatomic collisions are found to be the dominant damping mechanism in this case.

Journal Article↗

PubMed2002

Quadrupole collective modes in trapped finite-temperature Bose-Einstein condensates.

Finite-temperature simulations are used to study quadrupole excitations of a trapped Bose-Einstein condensate. We focus specifically on the m = 0 mode, where a long-standing theoretical problem is to account for an anomalous variation of the mode frequency with temperature. We explain this behavior in terms of the excitation of two separate modes, corresponding to the coupled motion of the condensate and the thermal cloud. The relative amplitude of the modes depends sensitively on the temperature and on the frequency of the harmonic drive used to excite them. Good agreement with experiment is found for appropriate drive frequencies.

Journal Article↗

PubMed2002

Dynamical instability of a condensate induced by a rotating thermal gas.

We study surface modes of the condensate in the presence of a rotating thermal cloud in an axisymmetric trap. By considering collisions that transfer atoms between the condensate and the noncondensate, we find that m>0 modes, which rotate in the same sense as the thermal cloud, damp less strongly than m<0 modes, where m is the polarity of the excitation. We show that above a critical angular rotation frequency, equivalent to the Landau stability criterion, m>0 modes become dynamically unstable, leading to the possibility of vortex nucleation. We also generalize our stability analysis to treat the case where the stationary state of the condensate already possesses a single vortex.

Journal Article↗

PubMed2001

Finite-temperature simulations of the scissors mode in Bose-Einstein condensed gases.

The dynamics of a trapped Bose-condensed gas at finite temperatures is described by a generalized Gross-Pitaevskii equation for the condensate order parameter and a semiclassical kinetic equation for the thermal cloud, solved using N-body simulations. The two components are coupled by mean fields as well as collisional processes that transfer atoms between the two. We use this scheme to investigate scissors modes in anisotropic traps as a function of temperature. Frequency shifts and damping rates of the condensate mode are extracted, and are found to be in good agreement with recent experiments.

Journal Article↗

PubMed1997

Evaluation of CA 15-3 serum levels in breast cancer patients.

The usefulness of post operative serum CA 15-3 determination was evaluated in a group of 57 breast cancer patients. CA 15-3 was assayed at baseline and every 3 months for a median follow-up of 34 months. Recurrence-free survival probability for patients with elevated serum CA 15-3 levels before surgery was 53.5% versus 88% for patients with normal serum CA 15-3 levels (p < 0.201). In 12 of the 15 patients with increased trend for CA 15-3 during follow-up, elevated CA 15-3 levels preceded (10 patients) coincided (2 patients) with the clinical detection of tumour recurrence, providing a predictive value of an increased trend of 80%. In the group of 10 patients who showed elevated serum CA 15-3 levels prior to the detection of recurrence, the median load-time was 5 months/(range 3-11 months). We concluded that CA 15-3 had prognostic value in breast cancer. Serial determinations of CA 15-3 was consistent with the treatment results.

Adult↗

PubMed1997

Activity of cancer procoagulant (CP) in serum of patients with cancer of lung, breast, oesophagus and colorectum.

Activity of cancer procoagulant (CP) was studied in blood serum of 90 patients with cancer of lung, breast, oesophagus and colorectum, and of 15 healthy people. The activity of CP was determined by the coagulation method. Sera of patients with cancer showed higher mean activity of CP than sera of healthy control. Of the 90 cancer patients 78 were identified correctly by this test as having cancer (sensitivity 85%). In the case of lung and colorectal cancers the higher CP activity was observed the more advanced was the clinical stage of cancer, and the test was positive in 100%. After radical removal of malignant tumor of lung, decreased CP activity was found.

Biomarkers, Tumor↗

PubMed1997

Cancer procoagulant (CP) in lung cancer.

Lung cancers (squamous cell carcinoma, microcellular carcinoma, macrocellular carcinoma and adenocarcinoma) show procoagulant activity. It mainly depends on the presence of cancer procoagulant (CP) in lung cancer cells.

Biomarkers, Tumor↗

PubMed1996