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2.
Nature ; 590(7847): 561-565, 2021 02.
Article in English | MEDLINE | ID: mdl-33627814

ABSTRACT

The fundamental building blocks of the proton-quarks and gluons-have been known for decades. However, we still have an incomplete theoretical and experimental understanding of how these particles and their dynamics give rise to the quantum bound state of the proton and its physical properties, such as its spin1. The two up quarks and the single down quark that comprise the proton in the simplest picture account only for a few per cent of the proton mass, the bulk of which is in the form of quark kinetic and potential energy and gluon energy from the strong force2. An essential feature of this force, as described by quantum chromodynamics, is its ability to create matter-antimatter quark pairs inside the proton that exist only for a very short time. Their fleeting existence makes the antimatter quarks within protons difficult to study, but their existence is discernible in reactions in which a matter-antimatter quark pair annihilates. In this picture of quark-antiquark creation by the strong force, the probability distributions as a function of momentum for the presence of up and down antimatter quarks should be nearly identical, given that their masses are very similar and small compared to the mass of the proton3. Here we provide evidence from muon pair production measurements that these distributions are considerably different, with more abundant down antimatter quarks than up antimatter quarks over a wide range of momenta. These results are expected to revive interest in several proposed mechanisms for the origin of this antimatter asymmetry in the proton that had been disfavoured by previous results4, and point to future measurements that can distinguish between these mechanisms.

3.
Phys Rev Lett ; 102(18): 182001, 2009 May 08.
Article in English | MEDLINE | ID: mdl-19518860

ABSTRACT

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a hydrogen target. The polar and azimuthal angular distribution parameters have been extracted over the kinematic range 4.5

4.
Phys Rev Lett ; 100(6): 062301, 2008 Feb 15.
Article in English | MEDLINE | ID: mdl-18352463

ABSTRACT

We report a high statistics measurement of Upsilon production with an 800 GeV/c proton beam on hydrogen and deuterium targets. The dominance of the gluon-gluon fusion process for Upsilon production at this energy implies that the cross section ratio, sigma(p+d-->Upsilon)/2sigma(p+p-->Upsilon), is sensitive to the gluon content in the neutron relative to that in the proton. Over the kinematic region 0

5.
Phys Rev Lett ; 99(8): 082301, 2007 Aug 24.
Article in English | MEDLINE | ID: mdl-17930942

ABSTRACT

We report a measurement of the angular distributions of Drell-Yan dimuons produced using an 800 GeV/c proton beam on a deuterium target. The muon angular distributions in the dilepton rest frame have been measured over the kinematic range 4.5

Subject(s)
Mesons , Protons , Deuterium , Elementary Particle Interactions , Models, Theoretical , Motion , Nuclear Physics
6.
Phys Rev Lett ; 86(12): 2529-32, 2001 Mar 19.
Article in English | MEDLINE | ID: mdl-11289972

ABSTRACT

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.

12.
Bone Miner ; 7(1): 13-22, 1989 Aug.
Article in English | MEDLINE | ID: mdl-2765712

ABSTRACT

The ionized plasma calcium concentration in foetal lambs during the last third of gestation is greater than that in the ewe. Since foetal plasma immunoreactive parathyroid hormone is less than that in the ewe the role of the foetal parathyroid glands is not clear. The effects of foetal parathyroidectomy (PTX) on the foetal:maternal gradient and on skeletal development are examined. The histomorphometry and ash content of six PTX lambs was compared with that of 11 intact animals. A reversal of the plasma ionized calcium gradient took place within 3 days without significant change in the foetal plasma inorganic phosphate or 1,25-dihydroxycholecalciferol content. Skeletal changes consistent with rickets were observed and increased in severity with the time after PTX. It is concluded that the foetal parathyroid glands play an important role in placental calcium transfer and skeletal calcification. However, the agent may be a hypercalcaemic substance other than parathyroid hormone.


Subject(s)
Embryonic and Fetal Development , Lumbar Vertebrae/embryology , Osteogenesis , Parathyroid Glands/physiology , Animals , Female , Lumbar Vertebrae/cytology , Lumbar Vertebrae/drug effects , Osteogenesis/drug effects , Pregnancy , Reference Values , Sheep , Thyroidectomy , Thyroxine/pharmacology
13.
Clin Orthop Relat Res ; (243): 294-305, 1989 Jun.
Article in English | MEDLINE | ID: mdl-2721071

ABSTRACT

Previous studies of microanatomic changes in normal bone with age have suggested that underlying differences in bone remodeling between male subjects and female subjects give rise to different patterns of bone loss. The relationship between microanatomic and histologic levels of organization are herein examined in two groups of osteoporotic subjects, one with idiopathic and the other with corticosteroid-induced osteoporosis. Using tissue from the iliac crest, total trabecular surface and trabecular width and number were measured, together with bone volume and static and dynamic indices of formation (osteoid surface, seam width, mean wall thickness, lamellar thickness, calcification fronts, and mineralization rate) and resorption (total resorption cavities and osteoclast incidence). The results suggest that while a similar loss of trabecular bone volume is common to both groups, there is a marked distinction in the distribution of the remaining bony tissue and indices of remodeling. A decline in trabecular number accompanied by a relative increase in resorption characterized both sexes with primary osteoporosis, whereas a decline in trabecular width associated with depressed formation was the predominant feature in the secondary disease. Thus trabecular attenuation is principally the manifestation of depressed formation, while trabecular discontinuity is primarily the manifestation of bone resorption.


Subject(s)
Osteoporosis/pathology , Adrenal Cortex Hormones/adverse effects , Adult , Aged , Aged, 80 and over , Aging/physiology , Female , Humans , Ilium/pathology , Male , Middle Aged , Osteoporosis/chemically induced , Sex Factors
14.
Clin Orthop Relat Res ; (215): 260-71, 1987 Feb.
Article in English | MEDLINE | ID: mdl-3802645

ABSTRACT

Histomorphometric changes in normal bone were investigated using tissue from the ilium of 86 women and 98 men, aged 20-90 years. While loss of trabecular volume was common to both sexes, the histologic basis for the loss differed. Decreased formation (expressed primarily as static indices) seemed to be the principal factor in bone loss in men; in women these features remained unchanged, suggesting that increased resorption was the principal factor. Bone loss in women was principally attributable to the total removal of individual trabeculae; conversely in men, there was generalized attenuation of trabecular bone. Similar findings in bone tissues of vertebral bodies suggest that differences in bone remodelling between the sexes produce different patterns of bone loss as a sequence of aging.


Subject(s)
Aging/pathology , Osteoporosis/pathology , Adult , Aged , Aged, 80 and over , Cadaver , Female , Humans , Ilium/pathology , Male , Middle Aged , Reference Values , Sex Characteristics , Spine/pathology
15.
J Histochem Cytochem ; 32(12): 1251-61, 1984 Dec.
Article in English | MEDLINE | ID: mdl-6209330

ABSTRACT

Histological studies on bone from the human iliac crest have suggested that if the customary techniques of labeling in vivo with certain fluorochromes such as tetracycline are replaced or augmented by simple whole tissue staining in vitro using the same reagents, differences in the pattern of extracellular fluorescence between normal and pathological states are retained. In particular, the association of the fluorescence with the calcification front in stained examples is closely comparable to similar examples that have been labeled (r = 0.988, p less than 0.001) and to other tinctorial methods (r = 0.891, p less than 0.001). While the stain alone lacks the time lapse of multiple labels, when administered some days after a single label at the time of biopsy, it provides an effective second marker and a measure of mineralization rate that does not differ significantly from that using double labels. Moreover, since the problems of toxicity are avoided by staining, a range of contrasting fluorochromes previously restricted to animal studies may now be used in man. In particular, the enhanced color differentiation brought about by the combination of tetracycline label followed by xylenol orange stain improves image resolution and greatly aids interpretation.


Subject(s)
Bone Diseases/pathology , Bone and Bones/pathology , Calcification, Physiologic , Bone and Bones/cytology , Fluorescent Dyes , Humans , Ilium/pathology , Staining and Labeling
16.
Scott Med J ; 29(3): 171-5, 1984 Jul.
Article in English | MEDLINE | ID: mdl-6533788

ABSTRACT

Trabecular bone volume, forming surface and percent surface resorption have been determined in iliac crest samples obtained post mortem from 43 young men and 49 elderly men and in biopsies obtained from 22 males with spinal osteoporosis. The mean bone volume was significantly lower in the old than in the young controls and significantly lower again in the osteoporotic cases. Forming surfaces were significantly lower in the old than the young controls but were not different as between old controls and cases of osteoporosis. Percent surface resorption was the same in young and old controls but significantly increased in the osteoporotics. Multiple regression analysis showed that trabecular bone volume was a significant positive function of forming surface and a significant inverse function of fractional surface resorption. Age-related (simple) osteoporosis in men appears to be due to reduced bone formation whereas pathological (accelerated) osteoporosis is due to increased bone resorption.


Subject(s)
Bone Development , Bone Resorption , Ilium/physiology , Osteoporosis/physiopathology , Adult , Aged , Humans , Ilium/physiopathology , Male , Middle Aged , Regression Analysis
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