PubMed Health⌕ Search

Biomedical subjects

B Lundberg

Publications and source records attributed to B Lundberg.

At least 19 recordsLinked to original sources
PubMed2002

Dalitz plot analysis of the decay D(+)-->K(-)pi(+)pi(+) and indication of a low-mass scalar Kpi resonance.

We study the Dalitz plot of the decay D(+)-->K(-)pi(+)pi(+) with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known Kpi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K(*)(0)(1430) to float, we obtain values consistent with those from PDG but the chi(2) per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797+/-19+/-43 MeV/c(2) and width 410+/-43+/-87 MeV/c(2). The mass and width of the K(*)(0)(1430) become 1459+/-7+/-5 MeV/c(2) and 175+/-12+/-12 MeV/c(2), respectively. Our results provide new information on the scalar sector in hadron spectroscopy.

Journal Article↗
PubMed2001

Direct measurement of the pion valence-quark momentum distribution, the pion light-cone wave function squared.

We present the first direct measurements of the pion valence-quark momentum distribution which is related to the square of the pion light-cone wave function. The measurements were carried out using data on diffractive dissociation of 500 GeV/c pi(-) into dijets from a platinum target at Fermilab experiment E791. The results show that the /q&q> light-cone asymptotic wave function describes the data well for Q2 approximately 10 (GeV/c)(2) or more. We also measured the transverse momentum distribution of the diffractive dijets.

Journal Article↗
PubMed2001

Observation of color-transparency in diffractive dissociation of pions.

We have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t(min)-->0), we find that when the per-nucleus cross section for this process is parametrized as sigma = sigma0Aalpha, alpha has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.

Journal Article↗
PubMed2001

Search for rare and forbidden Charm Meson decays D0 --> Vl+l- and hhll.

We report results of a search for flavor-changing neutral current (FCNC), lepton flavor, and lepton-number violating decays of the D0 (and its antiparticle) into three and four bodies. Using data from Fermilab charm hadroproduction experiment E791, we examine modes with two leptons (muons or electrons) and a rho(0), K( *0), or straight phi vector meson or a nonresonant pi(pi), Kpi, or KK pair of pseudoscalar mesons. No evidence for any of these decays is found. Therefore, we present branching-fraction upper limits at 90% confidence level for the 27 decay modes examined (18 new).

Journal Article↗
PubMed2001

Study of the D(+)(s)-->pi(-)pi(+)pi(+) decay and measurement of f(0) masses and widths.

From a sample of 848+/-44 D(+)(s)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)(s)-->pi(-)pi(+)pi(+))/gamma(D(+)(s)-->straight phipi(+)) = 0.245+/-0.028(+0.019)(-0.012). Using a Dalitz plot analysis of this three body decay, we find significant contributions from the channels rho(0)(770)pi(+), rho(0)(1450)pi(+), f(0)(980)pi(+), f(2)(1270)pi(+), and f(0)(1370)pi(+). We also present the values obtained for masses and widths of the resonances f(0)(980) and f(0)(1370).

Journal Article↗
PubMed2001

Experimental evidence for a light and broad scalar resonance in D(+) --> pi(-)pi(+)pi(+) decay.

From a sample of 1172 +/- 61 D(+)-->pi(-)pi(+)pi(+) decays, we find gamma(D(+)-->pi(-)pi(+)pi(+))/gamma(D(+)-->K-pi(+)pi(+)) = 0.0311 +/- 0.0018(+0.0016)(-0.0026). Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478(+24)(-23) +/- 17 MeV/c(2) and width 324(+42)(-40) +/- 21 MeV/c(2) accounts for approximately half of all decays.

Journal Article↗
PubMed1997

Influence of pole length and stiffness on the energy conversion in pole-vaulting.

An impact process similar to pole-vaulting is studied, viz., the impact in a vertical plane between the bottom end of a slightly curved elastic bar (pole), with a point mass (vaulter) at the top end, and a rigid support (pole box). Before impact, the velocity of the pole and the vaulter forms a certain angle (take-off) with the horizontal ground. Finite element calculation of the trajectories of the vaulter are carried out, and a performance figure, defined as the ratio between the maximum potential energy of the vaulter and the initial kinetic energy of the vaulter and the pole, is determined as a function of dimensionless parameters. As the vaulter remains passive during the vault, in contrast to a real vaulter, this performance figure is also the efficiency of conversion of the initial kinetic energy to the achieved potential energy in the vault. It is shown that, under normal pole-vault conditions, there exists a maximum performance figure with respect to pole length and stiffness. For an initial velocity and a body mass which are representative of an elite pole-vaulter, the maximum performance figure 0.87 is obtained for a pole with length 5.5 m.

Acceleration↗
PubMed1996

Complicated course of local mycobacterial infection in an immunocompetent girl.

A complicated course of cervical Mycobacterium avium adenitis in a healthy 3-year-old girl is described. A retropharyngeal and a parotic abscess developed resulting in a salivary fistula. Surgery was not judged possible but chemotherapy was given for 6 months during which the infection healed. It is not clear whether the regression was spontaneous or caused by the therapy.

Abscess↗
PubMed1995

Simulation of 'smart' pole vaulting.

The process of pole vaulting is simulated using a finite element two-dimensional model of the pole and the vaulter. The pole is modelled with 20 beam elements and the vaulter with seven such elements linked together by pin joints. 'Smart' behaviour is achieved through control of limited muscle torques at the joints according to a given strategy. This control strategy is such that the vaulter strives to carry through a prescribed sequence of motions, corresponding to a given style, during a vault. The optimum pole length is determined for a vaulter with given initial velocity, strength and style. When a pole of optimum length is used, the maximum increase of the potential energy of the vaulter is 1.27 times the initial kinetic energy of the vaulter and the pole. This shows that the contribution from muscle work to the increase in potential energy during a vault may be significant. The simulation method should be a useful tool for optimization of pole design. It might also be useful for optimization of vaulting style or for judging the importance of vaulter strength.

Algorithms↗
PubMed1994

Preparation of drug-carrier emulsions stabilized with phosphatidylcholine-surfactant mixtures.

A method has been developed to produce lipid emulsion particles for parenteral use as drug carriers. The technique uses a mixture of a triacylglycerol oil and purified egg yolk phosphatidylcholine (EPC) as the basic system and sonication under mild conditions to produce the emulsion. A large number of mild "biological" surfactants were tested for their ability to improve the dispersing and stability properties of the basic system. The results showed a preference for polysorbate 80, and a suitable combination of oil and emulsifiers was found to be castor oil:EPC:polysorbate 80 (1:0.4:0.12, weight ratios). Repeated preparation of this emulsion system in phosphate-buffered saline (PBS) gave particles with a mean diameter near 50 nm, in a reproducible way and with a low polydispersity. The stability of the emulsion was very good (> 3 months), both in PBS and in 2.5% glycerol. The method was also tested with two lipophilic anticancer drugs, which were solubilized in castor oil, with satisfactory results. The lipid emulsion particles described in this study also have a potential use as targetable carriers for site-specific drug delivery.

Drug Carriers↗
PubMed1994

Cytotoxic activity of two new lipophilic steroid nitrogen carbamates incorporated into low-density lipoprotein.

Low-density lipoprotein (LDL) is a potential drug carrier in cancer chemotherapy. Two novel cytotoxic lipophilic steroid derivatives with two nitrogen carbamate groups on a C-17 side chain were successfully incorporated into LDL using a reassembly technique. The antineoplastic activity of the new agents against T-47D breast cancer cells in culture was approximately twice that of a previously characterized compound with only one such group.

Antineoplastic Agents↗
PubMed1993

Conjugation of apolipoprotein B with liposomes and targeting to cells in culture.

Mixed phospholipid/cholesterol (2:1 molar ratio) liposomes were conjugated with native and acetylated apolipoprotein B (apoB), the protein part of low density lipoprotein (LDL). The objective was to increase the specificity of the cellular uptake of liposomes by utilization of the LDL and scavenger receptor pathways. The method of choice for the conjugation of liposomes with apoB proved to be the detergent solubilization and removal procedure. Two detergents were tested;sodium cholate (NaC) and octyl glucoside (OG). The integrity of the resulting complexes was demonstrated by Sepharose CL-4B gel chromatography and Metrizamide gradient centrifugation. The conjugates showed a good physical stability and the leakiness was only marginally larger than for unconjugated liposomes. The interaction of apoB- and acetyl apoB-liposome conjugates with CV-1 and J774 cells, respectively, was monitored by an encapsulated pH-sensitive fluorophore, pyranine (8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS)). This dye provides means of detecting binding and endocytosis of conjugates in living cells. The internalization was a fast process and about 10-times faster for the OG-conjugates than for the corresponding unconjugated liposomes. The conjugates showed a clear concentration-dependent association of dye with cells, while this was less prominent with liposomes. The uptake was nearly an order of magnitude faster with CV-1 cells than with J774 cells. Acidification of intracellular conjugates proceeded fast during the first 30 min of incubation and reached a minimum value of approx. pH 6 after 3 h. The specificity of binding of apoB-liposome conjugates to CV-1 cells was demonstrated by displacement experiments with native LDL. The results indicate that apoB-liposome conjugates may be used as a delivery vehicle for bioactive subtsances to cells.

Animals↗
PubMed1992

Assembly of prednimustine low-density-lipoprotein complexes and their cytotoxic activity in tissue culture.

The lipophilic anticancer drug prednimustine was incorporated into model low-density-lipoprotein (m-LDL) using a novel modified method. The major steps of this procedure involve the preparation of a microemulsion containing the drug and the complexing of this emulsion with apolipoprotein B (apo B) that has been delipidated by heptane extraction. The resulting particles contained on average 338 mol prednimustine/mol apoB and exhibited a diameter that was ca. 2.5 times that of native LDL. The cellular binding, uptake, and metabolism of the complexes were found to be similar to those of native LDL. The cytotoxic activity of the complexes was monitored in vitro against T-47D breast cancer cells and normal 3T3 fibroblasts. The activity of prednimustine in m-LDL against T-47D cells after 24 h treatment was nearly 50% higher than that of the free drug, whereas in 3T3 cells the difference was relatively small. The results indicate that it is possible to target drug/m-LDL complexes to cancer cells exhibiting high LDL-receptor activity.

3T3 Cells↗
PubMed1992

Glucose polymers in diarrhoea--risk of hypernatraemia.

An infant girl with congenital heart disease was fed glucose polymers as dietary supplements. During an attack of gastroenteritis with severe diarrhoea she developed hypernatraemic dehydration, probably due to the high osmotic load of the glucose polymers. This case illustrates the importance of giving adequate amounts of free water to a child on glucose polymers, especially during excessive fluid loss.

Dehydration↗