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X R Qi

Publications and source records attributed to X R Qi.

At least 19 recordsLinked to original sources
PubMed2006

Measurement of the K0 charge radius and a CP-violating asymmetry and a search for CP-violating E1 direct photon emission in the rare decay KL--> pi+ pi- e+ e-.

Using the complete KTeV data set of 5,241 candidate K(L)--> pi(+) pi(-) e(+) e(-) decays (including an estimated background of 204 +/- 14 events), we have measured the coupling g(CR)= 0.163 +/- 0.0149(stat) +/- 0.023(syst) of the CP conserving charge radius process and from it determined a K(0) charge radius of = [-0.077 +/- 0.007(stat) +/- 0.011(syst)]fm(2). We have determined a first experimental upper limit of 0.04 (90% C.L.) /g(e1)/ / /g(M1)/ of the couplings for the E1 and M1 direct photon emission processes. We also report the measurement of /g(M1)/ including a vector form factor /g(M1)/(1 + (a(1)/a(2))/((M(2)(p)-(M(2)(k))= 2M(K)E(gamma*)), where vector /g(M1)/= 1.11+/- 0.12(stat) +/- 0.08(syst) and a(1)/a(2) = [-0.744 +/- 0.027(stat) +/- 0.032(syst)] GeV(2)/c(2). Finally, a CP-violating asymmetry of [13.6 +/- 1.4(stat) +/- 1.5(syst)]% in the CP and T odd angle phi between the decay planes of the e(+) e(-) and pi(+) pi(-) pairs in the K(L) center of mass is reported.

Journal Article↗
PubMed2005

Observation of the decay xi0 --> sigma+ mu- nu(mu).

The xi0 muon semileptonic decay has been observed for the first time with nine identified events using the KTeV beam line and detector at Fermilab. The decay is normalized to the xi0 beta decay mode and yields a value for the ratio of decay rates gamma(xi0 --> sigma+ mu- nu(mu))/gamma(xi0 --> sigma+ e- nu(e)) of [1.8(-0.5)(+0.7)(stat) +/- 0.2(syst)] x 10(-2). This is in agreement with the SU(3) flavor symmetric quark model.

Journal Article↗
PubMed2004

A determination of the Cabibbo-Kobayashi-Maskawa parameter |V us| using KL decays.

We present a determination of the Cabibbo-Kobayashi-Maskawa parameter |V(us)| based on new measurements of the six largest K(L) branching fractions and semileptonic form factors by the KTeV (E832) experiment at Fermilab. We find |V(us)|=0.2252+/-0.0008(KTeV)+/-0.0021(ext), where the errors are from KTeV measurements and from external sources. We also use the measured branching fractions to determine the CP violation parameter |eta(+-)|=(2.228+/-0.005(KTeV)+/-0.009(ext))x10(-3).

Journal Article↗
PubMed2004

Search for the rare decay K(L)-->pi(0)e(+)e(-).

The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay K(L)-->pi(0)e(+)e(-). This mode is expected to have a significant CP violating component. The measurement of its branching ratio could support the standard model or could indicate the existence of new physics. This Letter reports new results from the 1999-2000 data set. One event is observed with an expected background at 0.99+/-0.35 events. We set a limit on the branching ratio of 3.5x10(-10) at the 90% confidence level. Combining with the previous result based on the data set taken in 1997 yields the final KTeV result: BR(K(L)-->pi(0)e(+)e(-))<2.8x10(-10) at 90% C.L.

Journal Article↗
PubMed2003

Measurements of the Decay KL-->e+ e- mu+ mu-.

The KTeV experiment at Fermilab has isolated a total of 132 events from the rare decay K(L)-->e+ e- mu+ mu-, with an estimated background of 0.8 events. The branching ratio of this mode is determined to be [2.69+/-0.24(stat)+/-0.12(syst)]x10(-9), with a radiative cutoff of M(2)(ee mu mu)/M(2)(K)>0.95. The first measurement using this mode of the parameter alpha from the D'Ambrosio-Isidori-Portolès (DIP) model of the K(L)gamma*gamma* vertex yields a result of -1.59+/-0.37, consistent with values obtained from other decay modes. Because of the limited statistics, no sensitivity is found to the DIP parameter beta. We use this decay mode to set limits on CP and lepton violation.

Journal Article↗
PubMed2002

Search for the KL-->pi 0 pi 0 e+e- decay in the KTeV experiment.

The recent discovery of a large CP violating asymmetry in KL-->pi+pi-e+e- mode has prompted us to seach for the associated KL-->pi 0 pi 0 e+e- decay mode in the KTeV-E799 experiment at Fermilab. In 2.7 x 10(11) K(L) decays, one candidate event has been observed with an expected background of 0.3 event, resulting in an upper limit for the KL-->pi 0 pi 0 e+e- branching ratio of 6.6 x 10(-9) at the 90% C.L.

Journal Article↗
PubMed2002

Radiative decay width measurements of neutral kaon excitations using the primakoff effect.

We use K(L)'s in the 100-200 GeV energy range to produce 147 candidate events of the axial vector pair K1(1270)-K1(1400) in the nuclear Coulomb field of a Pb target and determine the radiative widths Gamma(K1(1400)-->K0+gamma)=280.8+/-23.2(stat)+/-40.4(syst) keV and Gamma(K1(1270)-->K0+gamma)=73.2+/-6.1(stat)+/-28.3(syst) keV. These first measurements appear to be lower than the quark-model predictions. We also place upper limits on the radiative widths for K(*)(1410) and K(*)(2)(1430) and find that the latter is vanishingly small in accord with SU(3) invariance in the naive quark model.

Journal Article↗
PubMed2002

Measurement of the K(L) charge asymmetry.

We present a measurement of the charge asymmetry delta(L) in the mode K(L)-->pi(+/-)e(-/+)nu based on 298 x 10(6) analyzed decays. We measure a value of delta(L) = [3322+/-58(stat)+/-47(syst)]x10(-6), in good agreement with previous measurements and 2.4 times more precise than the current best published result. The result is used to place more stringent limits on CPT and DeltaS = DeltaQ violation in the neutral kaon system.

Journal Article↗
PubMed2001

First measurement of form factors of the decay Xi(0) --> Sigma(+)e(-)nu macro(e).

We present the first measurement of the form factor ratios g(1)/f(1) (direct axial vector to vector), g(2)/f(1) (second class current), and f(2)/f(1) (weak magnetism) for the decay Xi(0)-->Sigma(+)e(-)nu macro(e) using the KTeV (E799) beam line and detector at Fermilab. From the Sigma(+) polarization measured with the decay Sigma(+)-->p pi(0) and the e(-)-nu; correlation, we measure g(1)/f(1) to be 1.32+/-(0.21)(0.17)(stat)+/-0.05(syst), assuming the SU(3)(f) (flavor) values for g(2)/f(1) and f(2)/f(1). Our results are all consistent with exact SU(3)(f) symmetry.

Journal Article↗
PubMed2001

Branching ratio measurement of the decay K(L) --> e(+)e(-)mu(+)mu(-).

We have collected a 43 event sample of the decay K(L)-->e(+)e(-)mu(+)mu(-) with negligible backgrounds and measured its branching ratio to be (2.62+/-0.40+/-0.17)x10(-9). We see no evidence for CP violation in this decay. In addition, we set the 90% confidence upper limit on the combined branching ratios for the lepton flavor violating decays K(L)-->e(+/-)e(+/-)mu(-/+)mu(-/+) at B(K(L)-->e(+/-)e(+/-)mu(-/+)mu(-/+))< or =1.23x10(-10), assuming a uniform phase space distribution.

Journal Article↗
PubMed2001

[Structure characteristics of insulin liposomes].

AIM: To study the molecular location and state of insulin within insulin-lipids. METHODS: Particle size and distribution of insulin-lipids was determined by using laser light scattering instrument, and transmission electron microscopy (TEM) was used to examine the morphology of insulin-lipids. HPLC, fluorescence scanning, digestion with trypsin and polyacrylamide gel electrophoresis was used to determine the molecular localization and state of insulin in the lipids. RESULTS: The mean particle size, polydispersity and sample quality were 218.3 nm, 0.073 and 7.2 respectively. The results of HPLC determination showed insulin exist in the insulin-lipids. There was no insulin emission spectrum in the insulin-lipids fluorescence spectrum; nearly no insulin digested in the test of insulin digestion by trypsin, and no insulin band in the insulin-lipids in figure of polyacrylamide gel electrophoresis. CONCLUSION: Insulin was encapsulated within lipids.

Chromatography, High Pressure Liquid↗
PubMed2000

[Interactions of insulin with dipalmitoylphosphatidylcholine liposomes].

AIM: To study the interactions of insulin with dipalmitoylphosphatidylcholine liposomes. METHODS: The liposomes were prepared by reverse-phase evaporation vesicle method. The entrapped efficiency, size and distribution of the liposomes were determined, and the influences of insulin on entrapped efficiency, size and distribution of the liposomes were investigated. The influences of liposomes on the fluorescence emission spectra of insulin and the calcein leakage from the liposomes entrapped calcein induced by insulin were measured. RESULTS: Insulin has little influence on the size and distribution of the liposomes while the sizes of the liposomes were about 170-190 nm. The insertion of tyrosine of insulin into dipalmitoylphosphatidylcholine liposomes membrane was not deep. The insulin disturbed the liposomes membrane, induced the calcein leakage from the calcein-loaded liposomes. CONCLUSION: Amphiphilic, example insulin, may disturb the intact membrane of liposome through the interaction either hydrophobic or hydrophilic. The attention should be paid to the entrapment process of peptides into liposomes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1999

Remote loading of diclofenac, insulin and fluorescein isothiocyanate labeled insulin into liposomes by pH and acetate gradient methods.

Remote loading of the model drugs diclofenac, insulin and fluorescein isothiocyanate labeled insulin (FITC-insulin) into liposomes by formation of transmembrane gradients were examined. A trapping efficiency of almost 100% was obtained for liposomal diclofenac, by the calcium acetate gradient method, whereas liposomes prepared by the conventional reverse-phase evaporation vesicle method had 1-8% trapping efficiencies. Soybean-derived sterol was a better stabilizer of the dipalmitoylphosphatidylcholine bilayer membrane than cholesterol, as shown from trapping efficiencies and drug release. The pH gradient method resulted in a 5-50% of FITC-insulin liposomal trapping efficiency, while insulin could not be loaded by this method. Liposomes released calcein in response to insulin, showing insulin interacts with the liposomal membrane in the presence of a transmembrane gradient. The present work has demonstrated a remote loading method for weak acids such as diclofenac into liposomes by the acetate gradient method. From the result of remote loading of FITC-insulin into liposomes by the pH gradient method, this method may be available for the preparation of liposomal peptides.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1998

Targeting of soybean-derived sterylglucoside liposomes to liver tumors in rat and mouse models.

The blood clearance, tissue uptake and antitumor efficacy against liver metastasis of M5076 reticulosarcoma in mice and against primary liver cancer in rats of doxorubicin (DOX) encapsulated in two types of liposomes, with and without a soYbean-derived sterylglucoside mixture (SG), were examined. Liposomes entrapping DOX were composed of dipalmitoylphosphatidylcholine (DPPC), SG and cholesterol (Ch) at a molar ratio of 6:1:3, (SG-liposomes) and 6:0:4 (non-SG-liposomes). Pharmacokinetic analysis of drug disposition was based on the area under the curve (AUC) for liposomes up to 24 h following i.v. injection. SG-liposomes showed lower DOX concentrations in blood and higher concentrations in liver compared with non-SG-liposomes. The highest AUC of SG-liposomes in tissue was in liver, 2.4 times higher than that of the free drug. The antitumor efficacy of SG-liposomes was compared with that of free DOX and non-SG-liposomes at a dose of 5 mg DOX/kg. SG-liposomes displayed stronger antitumor activity than the free drug and non-SG-liposomes in murine reticulosarcoma M5076 tumor models and primary liver cancer models reflecting accumulation in hepatocytes. The antitumor activity of SG-liposomes in rats with primary liver cancer was significantly higher compared with free DOX and non-SG-liposomes (ILS: 92.7%).

Animals↗
PubMed1995

Rates of systemic degradation and reticuloendothelial system uptake of calcein in the dipalmitoylphosphatidylcholine liposomes with soybean-derived sterols in mice.

The systemic degradation and the reticuloendothelial system (RES) uptake of calcein entrapped in dipalmitoylphosphatidylcholine (DPPC) liposomes with soybean-derived sterols (SS) were examined after intravenous administration to mice by measuring the free and liposomal calcein levels in the blood. The results indicate that the rates of systemic degradation and the RES uptake of liposomes decrease with the addition of SS in DPPC liposomes since the SS has the ability to stabilize the liposomes. The rate of uptake by RES is larger than the rate of systemic degradation. The rate of leakage of calcein from liposomes by incubation in plasma in vitro is almost the same as that of systemic degradation in vivo.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Effects of orally administered liposomes with soybean-derived sterols and their glucosides on rat body weight.

The effects on Wistar rat body weight were examined after a single subcutaneous (s.c.) or oral (p.o.) administration of dipalmitoylphosphatidylcholine (DPPC) liposomes composed of soybean-derived sterols (SS) and their glucosides (SG) with or without entrapping recombinant human erythropoietin (Epo) for 1 week. Body weight increased significantly after both types of administration compared with the control groups irrespective of the existence of Epo. The neutral lipid concentration in plasma increased with the increase in body weight whereas the total contents of cholesterol and high density lipoprotein cholesterol in the plasma did not change significantly. The SS and SG suspensions following p.o. administration, however, did not alter the body weight. These findings suggest that liposomal SS and SG may be absorbed through the intestinal membrane and induce a change in the uptake of lipid, in contrast to the suspension state. SS in liposomes significantly increased body weight more than SG after p.o. administration.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Evaluation of liposomal erythropoietin prepared with reverse-phase evaporation vesicle method by subcutaneous administration in rats.

We encapsulated erythropoietin (Epo) in dipalmitoylphosphatidylcholine (DPPC) liposomes with soybean-derived sterols (SS-liposomes) and its glucoside (SG-liposomes) by reverse-phase evaporation vesicle method, and evaluated them by subcutaneous administration in rats. With 4 min of sonication, the damage to Epo activity was observed mainly in the non-encapsulated Epo in the liposomes. This study indicated that the bilayer of liposomes had the ability to protect the Epo activity, by reducing the aggregation that was caused by interaction between Epo molecules. The SG-liposomes had a higher retention of the Epo activity the SS-liposomes. 25.3% or 33.6% of activity was retained by SS-liposomes under the conditions of 4 min or 1 min of sonication, while 53.3% or 58.3% of the activity was retained by SG-liposomes under the same conditions. Shorter sonication was available to minimize the loss of the Epo activity. Epo in SG-liposomes appeared to increase the activity.

1,2-Dipalmitoylphosphatidylcholine↗