Biomedical subjects

A Bean

Publications and source records attributed to A Bean.

At least 73 records · Page 4Linked to original sources

PubMed2001

Inclusive jet production in pp(macro) collisions.

We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.

Journal Article↗

PubMed2001

Search for large extra dimensions in dielectron and diphoton production.

We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.

Journal Article↗

PubMed2001

First observation of the sigma(+)(c) baryon and a new measurement of the sigma(+)(c) mass.

Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the Sigma(*+)(c) charmed baryon, and an updated measurement of the mass of the Sigma(+)(c) baryon. We find M(Sigma(*+)(c))-M(Lambda(+)(c)) = (231.0+/-1.1+/-2.0) MeV, and M(Sigma(+)(c))-M(Lambda(+)(c)) = (166.4+/-0.2+/-0.3) MeV, where the errors are statistical and systematic, respectively.

Journal Article↗

PubMed2001

Study of B Decays to Charmonium States: B-->eta(c)K and B --> chi(c0)K.

In a sample of 9.66x10(6)B&Bmacr; pairs collected with the CLEO detector we make the first observation of B decays to an eta(c) and a kaon. We measure branching fractions B(B+-->eta(c)K+) = (0.69(+0.26)(-0.21)+/-0.08+/-0.20)x10(-3) and B(B degrees -->eta(c)K degrees ) = (1.09(+0.55)(-0.42)+/-0.12+/-0.31)x10(-3), where the first error is statistical, the second is systematic, and the third is from the eta(c) branching fraction uncertainty. From these we extract the eta(c) decay constant in the factorization approximation, f(eta(c)) = 335+/-75 MeV. We also search for B decays to a chi(c0) and a kaon. No evidence for a signal is found and we set 90% C.L. upper limits: B(B+-->chi(c0)K+)<4.8x10(-4) and B(B degrees -->chi(c0)K degrees )<5.0x10(-4).

Journal Article↗

PubMed2001

Healing practices of the people of Belize.

Few countries in the world offer health care enthusiasts the chance to explore holistic models more than the tiny country of Belize in Central America. Situated in the lush rain forests of the tropics, Belize provides the context for practitioners who are trying to blend treatment modalities as old as the Mayan Empire with the unrelenting influx of intensive care technologies from the West. Herein are the stories of a cadre of healers in Belize who model an integration of the traditional and the professional and how they have accomplished it.

Belize↗

PubMed2000

Measurements of the mass, total width, and two-photon partial width of the eta(c) meson.

Using 13.4 fb(-1) of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudoscalar charmonium in the decay eta(c)-->K(0)(S)K-/+pi(+/-). We have measured the eta(c) mass to be [2980.4+/-2.3 (stat)+/-0.6 (syst)] MeV and its full width as [27.0+/-5.8 (stat)+/-1.4 (syst)] MeV. We have determined the two-photon partial width of the eta(c) meson to be [7.6+/-0.8 (stat)+/-0.4 (syst)+/-2.3 (br)] keV, with the last uncertainty associated with the decay branching fraction.

Journal Article↗

PubMed2000

Probing Balitsky-Fadin-Kuraev-Lipatov dynamics in the dijet cross section at large rapidity intervals in pp collisions at sqrt[s]=1800 and 630 GeV.

Inclusive dijet production at large pseudorapidity intervals (Deltaeta) between the two jets has been suggested as a regime for observing Balitsky-Fadin-Kuraev-Lipatov (BFKL) dynamics. We have measured the dijet cross section for large Deltaeta in pp collisions at sqrt[s]=1800 and 630 GeV using the D0 detector. The partonic cross section increases strongly with the size of Deltaeta. The observed growth is even stronger than expected on the basis of BFKL resummation in the leading logarithmic approximation. The growth of the partonic cross section can be accommodated with an effective BFKL intercept of alphaBFKL(20 GeV)=1.65+/-0.07.

Journal Article↗

PubMed2000

Search for the decay &Bmacr;(0)-->D(*0)gamma

We report results of a search for the rare radiative decay &Bmacr;(0)-->D(*0)gamma. Using 9.66x10(6) B&Bmacr; meson pairs collected with the CLEO detector at the Cornell Electron Storage Ring, we set an upper limit on the branching ratio for this decay of 5.0x10(-5) at 90% C.L. This provides evidence that the anomalous enhancement is absent in W-exchange processes and that weak radiative B decays are dominated by the short-distance b-->sgamma mechanism in the standard model.

Journal Article↗

PubMed1999

ChT1, an Ig superfamily molecule required for T cell differentiation.

The thymus is colonized by circulating progenitor cells that differentiate into mature T cells under the influence of the thymic microenvironment. We report here the cloning and function of the avian thymocyte Ag ChT1, a member of the Ig superfamily with one V-like and one C2-like domain. ChT1-positive embryonic bone marrow cells coexpressing c-kit give rise to mature T cells upon intrathymic cell transfer. ChT1-specific Ab inhibits T cell differentiation in embryonic thymic organ cultures and in thymocyte precursor cocultures on stromal cells. Thus, we provide clear evidence that ChT1 is a novel Ag on early T cell progenitors that plays an important role in the early stages of T cell development.

Amino Acid Sequence↗

PubMed1998

CD38+ CD45RB(low) CD4+ T cells: a population of T cells with immune regulatory activities in vitro.

An antibody reactive with CD38 revealed both phenotypic and functional heterogeneity amongst CD45RB(low) cells. Functional analysis of the CD38+ and CD38- fractions showed that the latter contained T cells which responded to recall antigens and produced high levels of cytokine in response to polyclonal stimulation. In contrast, the CD38+ population failed to proliferate or to produce detectable levels of cytokines. Despite appearing unresponsive, the CD38+ population significantly inhibited anti-CD3-induced proliferation and cytokine secretion by the reciprocal CD38- population. Immune suppression required stimulation through the TCR and was dependent on a physical interaction between regulatory and responding CD4+ populations. It did not involve killing of the responding T cells or secretion of IL-10 or TGF-beta. Despite some similarities there is no direct correlation between the in vitro suppression characteristic of the CD38+ CD45RB(low) subset and in vivo suppression which has been shown to be mediated by unseparated CD45RB(low) CD4+ T cells. However, these results demonstrate that two functionally distinct subsets of T cells reside within the antigen-exposed or CD45RB(low) CD4+ T cell population and are thus generated in vivo: (1) conventional memory T cells which proliferate and secrete cytokines in response to activation and (2) a population of regulatory T cells which inhibit T cell activation in vitro. Antibodies reactive with CD38 may provide a useful tool with which to study the role of these T cell subsets in the induction and regulation of the immune response.

ADP-ribosyl Cyclase↗

PubMed1998

Manipulation for cervical spinal dislocation under general anaesthesia: serial review for 4 years.

Manipulation under anaesthesia is an important method to reduce cervical spinal dislocations in the acute stage. Causes of failure have not been clearly identified and neurological complications can be the major concern. All cervical dislocations have been traditionally treated by manipulation under anaesthesia in the Christchurch Spinal Injuries Unit as the primary treatment. We reviewed all 31 patients treated from 1991-1995, with detailed documentation of neurological progression and final outcome. Three patterns were identified: bilateral dislocation, unifacet dislocation and fracture dislocation. Most of the dislocations (74%) were successfully reduced by manipulation alone with minimum complications. The remaining 26% patients required open reduction. The predominant causes of failure of reduction by manipulation were co-existing fractures. The success rate of reduction by manipulation was 90% for pure bifacet and unifacet dislocations, but was only 22% for the fracture dislocations. The study concluded that manipulation under anaesthesia is a safe and effective procedure for pure cervical spinal dislocations. Fractures related to the dislocation should be identified early and open reduction be considered.

Adolescent↗

PubMed1997

A retention signal necessary and sufficient for Golgi localization maps to the cytoplasmic tail of a Bunyaviridae (Uukuniemi virus) membrane glycoprotein.

Members of the Bunyaviridae family mature by a budding process in the Golgi complex. The site of maturation is thought to be largely determined by the accumulation of the two spike glycoproteins, G1 and G2, in this organelle. Here we show that the signal for localizing the Uukuniemi virus (a phlebovirus) spike protein complex to the Golgi complex resides in the cytoplasmic tail of G1. We constructed chimeric proteins in which the ectodomain, transmembrane domain (TMD), and cytoplasmic tail (CT) of Uukuniemi virus G1 were exchanged with the corresponding domains of either vesicular stomatitis virus G protein (VSV G), chicken lysozyme, or CD4, all proteins readily transported to the plasma membrane. The chimeras were expressed in HeLa or BHK-21 cells by using either the T7 RNA polymerase-driven vaccinia virus system or the Semliki Forest virus system. The fate of the chimeric proteins was monitored by indirect immunofluorescence, and their localizations were compared by double labeling with markers specific for the Golgi complex. The results showed that the ectodomain and TMD (including the 10 flanking residues on either side of the membrane) of G1 played no apparent role in targeting chimeric proteins to the Golgi complex. Instead, all chimeras containing the CT of G1 were efficiently targeted to the Golgi complex and colocalized with mannosidase II, a Golgi-specific enzyme. Conversely, replacing the CT of G1 with that from VSV G resulted in the efficient transport of the chimeric protein to the cell surface. Progressive deletions of the G1 tail suggested that the Golgi retention signal maps to a region encompassing approximately residues 10 to 50, counting from the proposed border between the TMD and the tail. Both G1 and G2 were found to be acylated, as shown by incorporation of [3H]palmitate into the viral proteins. By mutational analyses of CD4-G1 chimeras, the sites for palmitylation were mapped to two closely spaced cysteine residues in the G1 tail. Changing either or both of these cysteines to alanine had no effect on the targeting of the chimeric protein to the Golgi complex.

Amino Acid Sequence↗

PubMed1996