Autoresonant-spectrometric determination of the residual gas composition in the ALPHA experiment apparatus

Knowledge of the residual gas composition in the ALPHA experiment apparatus is important in our studies of antihydrogen and nonneutral plasmas. A technique based on autoresonant ion extraction from an electrostatic potential well has been developed that enables the study of the vacuum in our trap. Computer simulations allow an interpretation of our measurements and provide the residual gas composition under operating conditions typical of those used in experiments to produce, trap, and study antihydrogen. The methods developed may also be applicable in a range of atomic and molecular trap experiments where Penning-Malmberg traps are used and where access is limited.

Description and first application of a new technique to measure the gravitational mass of antihydrogen

Physicists have long wondered whether the gravitational interactions between matter and antimatter might be different from those between matter and itself. Although there are many indirect indications that no such differences exist and that the weak equivalence principle holds, there have been no direct, free-fall style, experimental tests of gravity on antimatter. Here we describe a novel direct test methodology; we search for a propensity for antihydrogen atoms to fall downward when released from the ALPHA antihydrogen trap. In the absence of systematic errors, we can reject ratios of the gravitational to inertial mass of antihydrogen >75 at a statistical significance level of 5%; worst-case systematic errors increase the minimum rejection ratio to 110. A similar search places somewhat tighter bounds on a negative gravitational mass, that is, on antigravity. This methodology, coupled with ongoing experimental improvements, should allow us to bound the ratio within the more interesting near equivalence regime.

The effect of triclosan on microbial community structure in three soils

The application of sewage sludge to land can expose soils to a range of associated chemical toxicants. In this paper we explore the effects of the broad spectrum anti-microbial compound triclosan on the phenotypic composition of the microbial communities of three soils of contrasting texture (loamy sand, sandy loam and clay) using phospholipid fatty-acid (PLFA) analysis. Each soil type was dosed and subsequently re-dosed 6 weeks later with triclosan at five nominal concentrations in microcosms (10, 100, 500, 1000 mg kg(-1) and a zero-dose control). PLFA profiles were analysed using multivariate statistics focussing on changes in the soil phenotypic community structure. Additionally, ratios of fungal:bacterial PLFA indicators and cyclo:mono-unsaturated PLFAs (a common stress indicator) were calculated. It was hypothesised that triclosan addition would alter the community structure in each soil with a particular effect on the fungal:bacterial ratio, since bacteria are likely to be more susceptible to triclosan than fungi. It was also hypothesised that the PLFA response to re-dosing would be suppressed due to acclimation. Although the microbial community structure changed over the course of the experiment, the response was complex. Soil type and time emerged as the most important explanatory factors. Principal component analysis was used to detect phenotypic responses to different doses of triclosan in each soil. As expected, there was a significant increase in the fungal:bacterial ratio with triclosan dose especially in treatments with the highest nominal concentrations. Furthermore, the PLFA response to re-dosing was negligible in all soils confirming the acclimation hypothesis.

Fate of triclosan in field soils receiving sewage sludge

The anti-microbial substance triclosan can partition to sewage sludge during wastewater treatment and subsequently transfer to soil when applied to land. Here, we describe the fate of triclosan in a one-year plot experiment on three different soils receiving sludge. Triclosan and methyl-triclosan concentrations were measured in soil samples collected monthly from three depths. A large fraction of triclosan loss appeared to be explained by transformation to methyl-triclosan. After 12 months less than 20% of the initial triclosan was recovered from each soil. However, the majority was recovered as methyl-triclosan. Most of the chemical recovered at the end of the experiment (both triclosan and methyl-triclosan) was still in the top 10 cm layer, although there was translocation to lower soil horizons in all three soils. Between 16.5 and 50.6% of the applied triclosan was unaccounted for after 12 months either as a consequence of degradation or the formation of non-extractable residues.

Resonant quantum transitions in trapped antihydrogen atoms

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

Centrifugal separation and equilibration dynamics in an electron-antiproton plasma

Charges in cold, multiple-species, non-neutral plasmas separate radially by mass, forming centrifugally separated states. Here, we report the first detailed measurements of such states in an electron-antiproton plasma, and the first observations of the separation dynamics in any centrifugally separated system. While the observed equilibrium states are expected and in agreement with theory, the equilibration time is approximately constant over a wide range of parameters, a surprising and as yet unexplained result. Electron-antiproton plasmas play a crucial role in antihydrogen trapping experiments.

Autoresonant excitation of antiproton plasmas

We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.

Evaporative cooling of antiprotons to cryogenic temperatures

We report the application of evaporative cooling to clouds of trapped antiprotons, resulting in plasmas with measured temperature as low as 9 K. We have modeled the evaporation process for charged particles using appropriate rate equations. Good agreement between experiment and theory is observed, permitting prediction of cooling efficiency in future experiments. The technique opens up new possibilities for cooling of trapped ions and is of particular interest in antiproton physics, where a precise CPT test on trapped antihydrogen is a long-standing goal.

The Triple Threat of Recurrence after Breast Conserving Therapy: Race, Receptor Status and Age

PurposeThe purpose of this study is to evaluate the impact of race, receptor status, and age on recurrence in patients undergoing breast conserving therapy (BCT).MethodsThe study population consisted of 510 primary invasive female breast cancer patients (excluding Stage IV), who resided in Fulton-Dekalb counties, in Atlanta, GA. These patients were diagnosed in 2003-2004 and treated within the Emory University Affiliated Hospitals. Data was obtained from the SEER cancer registry and augmented with medical record abstraction. Median follow-up was 3.5 and 4.4 years for recurrence and survival, respectively. Breast tumors were categorized as either triple negative (TN), which were estrogen, progesterone, and Her2-neu receptor negative tumors, versus (vs) non-TN, all other possible iterations. Women were evaluated for recurrence and death by TN status, race (African American (AA) vs Caucasian (C)), age, grade, tumor size, nodal status, socioeconomic status (SES), and receipt of chemotherapy. Both recurrence and survival were evaluated using chi-square, fisher exact, and cox regression analyses, p ≤ 0.05 significance.ResultsOf the 510 women, 193 received BCT. Of the 193, 92% completed radiation therapy and 45% received chemotherapy. Of the 184 women with known recurrence status, 11 recurred locally, 11 distantly, and none regionally. Compared to patients with non-TN tumors, TN patients had significantly higher local (13% vs 5%) and distant (16% vs 4%) recurrence rates. AA women had non-significant higher local recurrence than C women (7% vs 4%) and a higher distant recurrence rate (8% vs 3%). Finally, compared to women ≥50 years old, women age <50 had a significantly higher local and distant recurrence rates, (13% vs 4%) and (9% vs 5%) respectively.Unadjusted hazard ratios (HR) and 95% confidence intervals (CI) for any recurrence were calculated: TN status (HR=2.8, 95%CI 1.2-6.5), AA race (HR=2.3, 95% CI 0.9-5.8), age <50 years (HR= 2.3, 95%CI 1.0-5.1), grade 2/3 vs 1 (HR=2.3, 95%CI 1.0-5.1), and chemotherapy receipt (HR=3.0, 95%CI 1.2-7.4). Factors that were highly non-statistically significant included stage, tumor size, nodal status, and SES.In a multivariate model including receptor status, race, and age results were similar (HR = 2.5, 2.1, and 2.1 respectively). When tumor size, nodal status, grade, SES, and chemotherapy status were included in the previous model, only AA race independently predicted recurrence (HR=3.4, 95%CI 1.1-11.1), while TN status demonstrated a trend (HR=1.9, 95%CI 0.8-5.7).In survival analyses, neither TN status, AA race, nor age <50 years predicted outcome in any of the models described above. However, TN status did show a trend for significance (HR=2.6, 95%CI 0.8-9.0).ConclusionWe observed that there was a significant increase in local and distant metastatic recurrence rates after BCT among patients diagnosed with TN breast cancers, AA women, and women <50 years old. In contrast, we did not observe differences in survival, with the exception of TN breast cancers. This study suggests that among women who receive BCT, current standard radiation and systemic therapies may not be adequate in preventing recurrence among women with TN breast cancers, of AA race, or younger age.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6045.

Antiproton, positron, and electron imaging with a microchannel plate/phosphor detector

A microchannel plate (MCP)/phosphor screen assembly has been used to destructively measure the radial profile of cold, confined antiprotons, electrons, and positrons in the ALPHA experiment, with the goal of using these trapped particles for antihydrogen creation and confinement. The response of the MCP to low energy (10-200 eV, <1 eV spread) antiproton extractions is compared to that of electrons and positrons.

Compression of antiproton clouds for antihydrogen trapping

Control of the radial profile of trapped antiproton clouds is critical to trapping antihydrogen. We report the first detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial profile and its relation to that of the electron plasma.