The asymmetry of antimatter in the proton.

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.

Measurements of Nonsinglet Moments of the Nucleon Structure Functions and Comparison to Predictions from Lattice QCD for Q

We present extractions of the nucleon nonsinglet moments utilizing new precision data on the deuteron F_{2} structure function at large Bjorken-x determined via the Rosenbluth separation technique at Jefferson Lab Experimental Hall C. These new data are combined with a complementary set of data on the proton previously measured in Hall C at similar kinematics and world datasets on the proton and deuteron at lower x measured at SLAC and CERN. The new Jefferson Lab data provide coverage of the upper third of the x range, crucial for precision determination of the higher moments. In contrast to previous extractions, these moments have been corrected for nuclear effects in the deuteron using a new global fit to the deuteron and proton data. The obtained experimental moments represent an order of magnitude improvement in precision over previous extractions using high x data. Moreover, recent exciting developments in lattice QCD calculations provide a first ever comparison of these new experimental results with calculations of moments carried out at the physical pion mass, as well as a new approach that first calculates the quark distributions directly before determining moments.

Longitudinal-transverse separations of deep-inelastic structure functions at low Q2 for hydrogen and deuterium.

We report on a study of the longitudinal to transverse cross section ratio, R=sigmaL/sigmaT, at low values of x and Q2, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range 0.06

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly polarized photons.

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

Precision Rosenbluth measurement of the proton elastic form factors.

We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques.

Cross-section measurement of charged-pion photoproduction from hydrogen and deuterium.

We have measured the differential cross section for the gamman-->pi(-)p and gammap-->pi(+)n reactions at theta(c.m.)=90 degrees in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E(gamma) greater, similar 3.3 GeV exhibit a global scaling behavior for both pi(-) and pi(+) photoproduction, consistent with the constituent counting rule and the existing pi(+) photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi(-) to pi(+) photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.

Measurement of the tensor analyzing powers T20 and T21 in elastic electron-deuteron scattering.

The tensor analyzing power components T20 and T21 have been measured in elastic electron-deuteron scattering at the 2 GeV electron storage ring VEPP-3, Novosibirsk, in a four-momentum transfer range from 8.4 to 21.6 fm(-2). A new polarized internal gas target with an intense cryogenic atomic beam source was used. The new data determine the deuteron form factors G(C) and G(Q) in an important range of momentum transfer where the first node of the deuteron monopole charge form factor is located. The new results are compared with previous data and with some theoretical predictions.

Endovascular repair of thoracic aortic aneurysms: a paradigm shift in standard of care.

The standard open surgical treatment of thoracic aortic aneurysms is associated with significant morbidity and mortality. Endovascular repair is less invasive and potentially less morbid for patients with multiple risk factors. The authors report their results in 9 consecutive high-risk patients treated with endovascular grafts from January 1998 through June 2000. There were 7 men and 2 women patients with an average age of 75 years. Mean aneurysm diameter was 7.1 cm. All aneurysms were repaired with Gianturco Z-stent polytetrafluoroethylene prostheses. There were no perioperative deaths. Mean length of stay was 6.3 days. Technical success was achieved in all 9 patients. Two patients had neurologic complications following repair (1 patient with transient lower extremity numbness related to spinal arthritis and 1 patient with bowel and bladder incontinence). Both patients were independent with ambulation. Mean follow-up was 15.8 months. There was no evidence of endoleak or stent migration during the follow-up period. These findings support endovascular treatment of high-risk patients with thoracic aneurysm.

Longitudinal electroproduction of charged pions from (1)H, (2)H, and (3)He.

Separated longitudinal and transverse cross sections for charged pion electroproduction from (1)H, (2)H, and (3)He were measured at Q(2) = 0.4 (GeV/c)(2) for two values of the invariant mass, W = 1.15 GeV and W = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in (3)He at W = 1.60 GeV. The W = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production.

Measurement of the high energy two-body deuteron photodisintegration differential cross section.

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

Remote superficial femoral artery endarterectomy: Multicenter medium-term results.

OBJECTIVE: The results of percutaneous transluminal angioplasty, atherectomy, and laser angioplasty for the treatment of long-segment (>10 cm) superficial femoral artery (SFA) occlusive disease have proved disappointing. Remote superficial femoral artery endarterectomy (RSFAE) is a minimally invasive procedure, performed through a single limited groin incision that may offer patency rates comparable with those of above-knee femoropopliteal (AKFP) bypass graft. In this retrospective multicenter study the medium-term results of RSFAE are examined. METHODS: Sixty patients were included in this study. Indications for the procedure were claudication in 52 patients and limb salvage in eight patients. RSFAE was performed with the MollRing Cutter device through a femoral arteriotomy. The distal "flap" of atheroma was anchored by balloon/stent angioplasty through the femoral arteriotomy. All patients underwent a follow-up examination with serial color flow ultrasound scanning. RESULTS: Ten patients with heavily calcified SFAs failed as "intentions to treat"; these patients underwent AKFP bypass grafting. The mean length of the endarterectomized SFAs was 22.3 cm (range, 8-37 cm). The primary cumulative patency rate by means of life-table analysis was 61.4% +/- 9% (SE), (mean, 12.9 months; range, 3-36 months). During follow-up, percutaneous transluminal angioplasty was necessary in 14 patients, for a primary-assisted patency rate of 82.6% +/- 8%. The locations of the restenoses after RSFAE were evenly distributed along the endarterectomized SFAs. There were no deaths and one wound complication (hematoma), and the mean hospital length of stay was 1.4 days +/- 0.8 days. CONCLUSIONS: RSFAE is a safe and moderately durable procedure. If long-term patency rates are similar to those of AKFP bypass graft, RSFAE may prove to be a minimally invasive adjunct for the treatment of SFA occlusive disease that will lower operative morbidity, reduce hospital LOS, and shorten recuperation.

Polarization measurements in high-energy deuteron photodisintegration.

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Evidence for a three-nucleon-force effect in proton-deuteron elastic scattering.

Developments in spin-polarized internal targets for storage rings have permitted measurements of 197 MeV polarized protons scattering from vector polarized deuterons. This work presents measurements of the polarization observables A(y), iT11, and C(y,y) in proton-deuteron elastic scattering. When compared to calculations with and without three-nucleon forces, the measurements provide further evidence that three-nucleon forces make a contribution to the observables. This work indicates that three-body forces derived from static nuclear properties appear to be crucial to the description of dynamical properties.

Chronic Illness and health insurance-related job lock.

Job duration patterns are examined for evidence of health insurance-related job lock among chronically ill workers or workers whose family member is chronically ill. Using Cox proportional hazard models to indicate the effect of health insurance and health status on workers' job duration we allow for more general insurance effects than that shown in the existing literature. Data for workers in Indiana predating the Health Insurance Portability and Accountability Act (HIPAA) are used to examine the potential effect of HIPAA on job mobility. Among the workers in this sample who relied on their employer for coverage, chronic illness reduced job mobility by about 40 percent as compared with otherwise similar workers who did not rely on their employer for coverage. Results reported here identify previously under-appreciated job lock among chronically ill workers and workers whose family member is chronically ill, clarify how one best researches job lock, and indicate the potential effect of policies aimed at alleviating job lock and promoting inter-employer worker mobility.

Does chronic illness affect the adequacy of health insurance coverage?

Although chronically ill individuals need protection against high medical expenses, they often have difficulty obtaining adequate insurance coverage due to medical underwriting practices used to classify and price risks and to define and limit coverage for individuals and groups. Using data from healthy and chronically ill individuals in Indiana, we found that chronic illness decreased the probability of having adequate coverage by about 10 percentage points among all individuals and by about 25 percentage points among single individuals. Preexisting condition exclusions were a major source of inadequate insurance, though not the only cause. Our results emphasize the impact of enforcing the Health Insurance Portability and Accountability Act (HIPAA) of 1997, which limits preexisting condition exclusions.

Repair of mycotic paravisceral aneurysm with a fenestrated stent-graft.

PURPOSE: To report the successful endovascular repair of a mycotic paravisceral aneurysm using a fenestrated stent-graft. METHODS AND RESULTS: A 55-year-old white female with a history of rheumatoid arthritis presented with an 8-cm paravisceral aneurysm secondary to pneumonia complicated by empyema. Intravascular ultrasound identified a defect in the aortic wall at the level of the celiac axis. Repair was accomplished with a fenestrated stent-graft that excluded the aneurysm and maintained flow to the celiac axis and superior mesenteric artery. Recovery was uneventful and the patient was discharged in 2 days. Six-month follow-up computed tomographic scanning confirmed aneurysm exclusion and flow to the celiac and superior mesenteric arteries. There was no evidence of graft infection. The patient died from a clinically diagnosed myocardial infarction 10 months after the stent-graft repair. CONCLUSIONS: Fenestrated stent-graft repair may evolve into a useful technique for the treatment of mycotic paravisceral aneurysms.