Utilizing a university testing program to estimate relative effectiveness of monovalent COVID-19 mRNA booster vaccine versus two-dose primary series against symptomatic SARS-CoV-2 infection

Vaccine effectiveness (VE) studies utilizing the test-negative design are typically conducted in clinical settings, rather than community populations, leading to bias in VE estimates against mild disease and limited information on VE in healthy young adults. In a community-based university population, we utilized data from a large SARS-CoV-2 testing program to estimate relative VE of COVID-19 mRNA vaccine primary series and monovalent booster dose versus primary series only against symptomatic SARS-CoV-2 infection from September 2021 to July 2022. We used the test-negative design and logistic regression implemented via generalized estimating equations adjusted for age, calendar time, prior SARS-CoV-2 infection, and testing frequency (proxy for test-seeking behavior) to estimate relative VE. Analyses included 2,218 test-positive cases (59 % received monovalent booster dose) and 9,615 test-negative controls (62 %) from 9,066 individuals, with median age of 21 years, mostly students (71 %), White (56 %) or Asian (28 %), and with few comorbidities (3 %). More cases (23 %) than controls (6 %) had COVID-19-like illness. Estimated adjusted relative VE of primary series and monovalent booster dose versus primary series only against symptomatic SARS-CoV-2 infection was 40 % (95 % CI: 33-47 %) during the overall analysis period and 46 % (39-52 %) during the period of Omicron circulation. Relative VE was greater for those without versus those with prior SARS-CoV-2 infection (41 %, 34-48 % versus 33 %, 9 %-52 %, P < 0.001). Relative VE was also greater in the six months after receiving a booster dose (41 %, 33-47 %) compared to more than six months (27 %, 8-42 %), but this difference was not statistically significant (P = 0.06). In this relatively young and healthy adult population, an mRNA monovalent booster dose provided increased protection against symptomatic SARS-CoV-2 infection, overall and with the Omicron variant. University testing programs may be utilized for estimating VE in healthy young adults, a population that is not well-represented by routine VE studies.

1916. Evaluation of nasal swab collection methods on a university campus during the SARS-CoV-2 pandemic

Background

Characterizing SARS-CoV-2 outbreaks on university campuses is critical for informed public health measures and understanding transmission dynamics. Figure 1.Dropbox and Kiosk Samples Collected September 10, 2021 to April 23, 2022.

Methods

Faculty, staff, and students at a major public university in Seattle, WA, USA were enrolled in a COVID-19 testing study. Individuals could test using observed self-swabs at on-campus kiosks or unobserved self-swabs using a kit and returning it to a dropbox on campus. Sample collection volume for observed self-swabs was limited by staffing and space. All samples were returned to the laboratory and tested for SARS-CoV-2 by qRT-PCR.

Results

From September 10, 2021 to April 23, 2022, 38,400 individuals were enrolled in the study. Of these individuals, 5,089 used dropboxes only, 14,421 used kiosks only, and 5,820 used both. A total of 21,653 dropbox swabs and 75,493 observed self-swabs were collected. Median age was similar between individuals using dropboxes and observed self-swabs (20 vs. 22 years). A greater proportion of dropbox users were students compared to faculty and staff (students made up 83% of dropbox only population, 75% of kiosk only, and 86% of both, χ² p-value&lt; 0.0001). Symptom data was reported for 65,349 swabs. Dropbox users were less likely to have symptoms compared to observed self-swab users (24% of swabs vs. 54%, χ² p-value&lt; 0.0001). SARS-CoV-2 positivity was slightly lower for dropboxes compared to kiosks (4% vs. 5%; p=0.001). Dropboxes were highly utilized during periods of increased testing demand, including after academic breaks and variant emergence (Figure 1). Of the total tests distributed for use, a greater proportion of dropbox kits were unable to be resulted (6%) compared to observed self-swab kits (0.02%).

Conclusion

Dropboxes provided a flexible, high-volume collection method at times of increased testing demand. Individuals who used dropboxes were less likely to report symptoms and slightly less likely to test positive, suggesting a role for dropbox utilization in high-risk asymptomatic individuals during periods of high community transmission on a university campus.

Disclosures

Geoffrey S. Gottlieb, MD, PhD, Abbott Molecular Diagnostics: Grant/Research Support|Alere Technologies: Grant/Research Support|BMGF: Grant/Research Support|BMS: Grant/Research Support|Cerus Corp.: Grant/Research Support|Gilead Sciences: Grant/Research Support|Janssen Pharmaceutica: Grant/Research Support|Merck & Co: Grant/Research Support|Roche Molecular Systems: Grant/Research Support|THERA Technologies/TaiMed Biologics: Grant/Research Support|ViiV Healthcare: Grant/Research Support Helen Y. Chu, MD, MPH, Cepheid: Reagents|Ellume: Advisor/Consultant|Gates Ventures: Grant/Research Support|Merck: Advisor/Consultant|Pfizer: Advisor/Consultant.

OP0074 DISTINCT CIRCULATING LYMPHOCYTE SUBSETS DISTINGUISH FLARE FROM DRUG-FREE REMISSION IN RHEUMATOID ARTHRITIS

Background

Rheumatoid arthritis (RA) is characterised by relapsing joint and systemic inflammation, yet the immunopathological basis of these disease flares and their clinical prediction remain uncertain.

Objectives

Using mass cytometry and single cell RNA sequencing, we aimed to identify circulating lymphocyte subsets associated with RA flare, and identify potential cellular biomarkers to predict flare versus drug-free remission (DFR).

Methods

We analysed peripheral blood mononuclear cells (PBMCs) from patients recruited to the BioRRA study (Figure 1), a prospective clinical trial of conventional synthetic disease-modifying anti-rheumatic drug (csDMARD) cessation.[1] Patients with RA in clinical (DAS28-CRP < 2.4) and ultrasound (absence of power Doppler signal in 7 joints) remission stopped csDMARDs, with flare defined as DAS28-CRP ≥ 2.4 during 6 month follow-up. A 44-marker mass cytometry panel was used to profile PBMCs from 36 patients (20 flare, 16 DFR) at two time points each (baseline, and flare onset / month 6 DFR). In a subset of patients (n = 12: 8 flare, 4 DFR), fluorescence-activated cell sorting of T and B cells was followed by single cell sequencing (n = 81,923 cells) incorporating 320 immune genes, 34 oligo-tagged surface protein antibodies, and TCR/BCR CDR3 sequence. Clones were defined as ≥2 cells with identical CDR3 nucleotide sequence, and clonal expansion as a significant increase in proportion from baseline to final study visit. Statistical significance was assessed after Benjamini-Hochberg multiple test correction (adj p < 0.05).

Figure 1.

Results

Mass cytometry revealed 31 distinct cell clusters: notably, greater proportions of memory (CD45RO+/PD1hi) CD4+ and CD8+ T cells, and memory (CD27+/CD21-) B cells, were observed at onset of flare versus baseline (Table 1).

Table 1.Mass cytometry (n = 20 flare + 16 DFR)ContrastClusterMedian %Adj. p (GLMM)Flare onset vs baseline: Flare patientsCD4+/CD45RO+/PD1+ memory T cells2.14 vs 0.24<0.001CD8+/CD45RO+/PD1+ memory T cells6.64 vs 0.07<0.001CD19+/CD27+/CD21- memory B cells2.39 vs 0.03<0.001Single cell RNAseq (n = 8 flare + 4 DFR)ContrastClusterMedian %Adj. p (Wilcoxon)Flare onset vs baseline: Flare patientsIgA+ plasma cells0.37 vs 0.210.020Flare vs DFR patients: BaselineCD4+/CD25+/Foxp3+ Treg cells0.55 vs 1.270.022

To better characterise these flare-associated subsets, single cell sequencing of CD45RO+/PD1hi CD4+ and CD8+ T cells, and CD19+ B cells, was performed and identified 21 distinct clusters. CDR3 sequencing revealed significant clonal expansion (Fisher exact, adj. p < 0.05) at flare onset within five unique CD8+ clones (4 patients), one CD4+ clone (1 patent), and no B clones. Overall, there was a significantly greater proportion of IgA+ plasma cells at flare onset versus baseline. In contrast, a significantly lower proportion of CD25+/FoxP3+ regulatory T cells were present at csDMARD cessation (baseline) in subsequent flare versus DFR patients (Table 1), suggesting biomarker potential.

To further assess the predictive performance of CD4+ Tregs as a biomarker for flare versus DFR, we analysed PBMCs from an independent cohort of 50 patients (25 flare, 25 DFR) stopping csDMARDs in the ongoing BIO-FLARE study.[2] By flow cytometry, we confirmed a lower proportion of CD4+/CD25hi Tregs at baseline in flare vs DFR (median 4.74 versus 6.37%, Wilcoxon p = 0.037; AUC: 0.67). In this cohort, stopping csDMARDs only in patients with elevated (> 6.11% total CD4) baseline Tregs would have prevented drug cessation in 18/25 (72%) of flare patients; 9/25 (36%) of DFR patients would have continued csDMARDs unnecessarily.

Conclusion

We present a detailed longitudinal characterisation of circulating lymphocyte surface phenotype, gene expression, and clonal expansion in RA flare vs DFR. Furthermore our data, across two independent cohorts, suggests a role for CD4+ Tregs in promoting drug-free remission meriting further investigation, with potential for future clinical biomarker development.

References

[1]Baker et al; J Autoimmunity; 105:102298

[2]Rayner et al; BMC Rheumatology; 5:22

Acknowledgements

This work was funded by research grants from Wellcome Trust [102595/Z/13/A to KFB], Newcastle NIHR Biomedical Research Centre [BH136167/PD0045 to KFB], British Society for Rheumatology [KFB], Academy of Medical Sciences [SGL022\1074 to KFB], Newcastle University Wellcome Trust Translational Partnership [KFB], Newcastle Hospitals Charity [8033 to KFB], and a National Institute for Health Research Clinical Lectureship [CL-2017-01-004 to KFB]. Our work is supported by the Research into Inflammatory Arthritis Centre Versus Arthritis (RACE) (grant number 20298), and Rheuma Tolerance for Cure (European Union Innovative Medicines Initiative 2, grant number 777357). AGP and JDI are named as inventors on a patent application by Newcastle University (“Prediction of Drug-Free Remission in Rheumatoid Arthritis”; International Patent Application Number PCT/GB2019/050902). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health and Social Care.

Disclosure of Interests

Kenneth F Baker Consultant of: Modern Biosciences Ltd, Grant/research support from: Pfizer, Genentech, Fiona Rayner: None declared, Henrique Lemos: None declared, David McDonald: None declared, Gillian Hulme: None declared, Rafiqul Hussain: None declared, Jonathan Coxhead Speakers bureau: Tesaro, Arthur Pratt Grant/research support from: Pfizer, Gilead, Amy E. Anderson: None declared, Andrew Filby Grant/research support from: Becton Dickinson, John Isaacs Speakers bureau: Abbvie, Gilead, Roche, UCB, Grant/research support from: GSK, Janssen, Pfizer.

Oral immune dysfunction is associated with the expansion of FOXP3+PD-1+Amphiregulin+ T cells during HIV infection

Residual systemic inflammation and mucosal immune dysfunction persist in people living with HIV, despite treatment with combined anti-retroviral therapy, but the underlying immune mechanisms are poorly understood. Here we report that the altered immune landscape of the oral mucosa of HIV-positive patients on therapy involves increased TLR and inflammasome signaling, localized CD4+ T cell hyperactivation, and, counterintuitively, enrichment of FOXP3+ T cells. HIV infection of oral tonsil cultures in vitro causes an increase in FOXP3+ T cells expressing PD-1, IFN-γ, Amphiregulin and IL-10. These cells persist even in the presence of anti-retroviral drugs, and further expand when stimulated by TLR2 ligands and IL-1β. Mechanistically, IL-1β upregulates PD-1 expression via AKT signaling, and PD-1 stabilizes FOXP3 and Amphiregulin through a mechanism involving asparaginyl endopeptidase, resulting in FOXP3+ cells that are incapable of suppressing CD4+ T cells in vitro. The FOXP3+ T cells that are abundant in HIV-positive patients are phenotypically similar to the in vitro cultured, HIV-responsive FOXP3+ T cells, and their presence strongly correlates with CD4+ T cell hyper-activation. This suggests that FOXP3+ T cell dysregulation might play a role in the mucosal immune dysfunction of HIV patients on therapy.

iChain: Peer-To-Peer Machine Learning Powered by Blockchain Technology

iChain is an application which was created to help meet the growing demand of machine learning. It allows users to pay those with powerful machines to run machine learning tasks for them, bypassing the need for a significant investment in a powerful computer to run it themselves. This is similar to services like a render farm. Our application functions using the Ethereum blockchain which ensures security and decentralization, as well as providing a platform for payment transactions. This article will discuss the background on machine learning and blockchain, the application, how it works, how the data moves through it, and how to use it. We hope our application will enable many without the funds to build or buy a powerful computer to experiment with and utilize complex machine learning tasks.

National survey of occupational advice for lower limb arthroplasty patients

BACKGROUND

Little is known what advice or support patients are given about return to work (RTW) after hip or knee replacement surgery.

AIMS

This study aims to understand the delivery, timing and content of 'RTW' advice currently delivered by surgical teams offering hip and knee replacements across the UK.

METHODS

National online survey exploring five specific areas relating to 'RTW' advice: (i) timings of interactions between hospital orthopaedic teams and patients prior to surgery, (ii) routine delivery of 'RTW' advice, (iii) methods used to deliver 'RTW' advice, (iv) confidence delivering advice and (v) need for an occupational 'RTW' advice intervention.

RESULTS

A total of 152 participants including surgeons, physiotherapists, occupational therapists and nurses from 59 different public and private health providers responded. Only 20% (n = 30) of respondents reported that working patients were identified as a specific subgroup in need of additional support. Overall, 62% (n = 92) stated that they did not routinely offer 'RTW' advice. When given, 'RTW' advice was almost always verbal, generic advice using blanket timescales and based on the respondent's anecdotal experience rather than the patients individualized needs. Overall, 116 (78%) felt an occupational advice intervention was needed.

CONCLUSIONS

This national survey demonstrated wide variation in the timing, content and delivery of information and advice for patients in work and intending to RTW after hip and knee replacement surgery. Current RTW advice provided to hip and knee replacement patients is inadequate.

Erratum: Observation of D^{0} Meson Nuclear Modifications in Au+Au Collisions at sqrt[s_{NN}]=200 GeV [Phys. Rev. Lett. 113, 142301 (2014)]

This corrects the article DOI: 10.1103/PhysRevLett.113.142301.

Relative Serum Antiplasmin Levels in Normal and Hemophilic Dogs Treated with Choline

Peroral administration of choline in relatively high dosage (300 or 600 mg choline dihydrogen citrate per 17-20 lb body weight, 4 times daily) caused no significant change in serum antiplasmin activity of either normal or factor VIII-deficient beagle dogs. Also, no alteration in antiplasmin level was found to be associated with the hemophilic state.

Canine serum antiplasmins are stable at low temperatures. Like human antiplasmins, they appear to have two major components which differ conspicuously in stability at 60° C.

Other data presented in this paper show that crude plasmin readily obtained from human serum euglobulins provides an enzyme preparation suitable for screening antiplasmin levels of sera by the caseinolytic method.

Soft Tissue Metastasis from Carcinoma. A Case Report

The authors report a case of a man who developed soft tissue metastasis to the thigh from pulmonary carcinoma. In the preoperative staging, computerized tomograms and magnetic resonance imaging allowed to identify and characterize the features of soft tissue masses; these studies, however, must be always completed with needle (tru-cut) or incisional biopsy.

Serum Lactate Dehydrogenase (LDH) as a Tumor Marker in Ewing's Sarcoma

The pretreatment serum lactic acid dehydrogenase (LDH) level of 246 patients with Ewing's sarcoma of bone (47 metastatic and 199 localized at presentation) was examined to evaluate the use of LDH as a tumor marker. The percentage of patients with increased serum LDH levels was significantly higher in the metastatic group than in the group of patients with localized disease (83 % vs 41 %; p < 0.01). In the latter group the relapse rate after treatment with combined therapy was significantly higher in patients with an elevated serum LDH at admission than in those with normal serum levels (68.2 % vs 39.3 %; p < 0.01). After local treatment, in 73 out of 82 patients with an elevated serum LDH at admission the enzyme level normalized whereas in 9 it fell but never reached a normal value. The rate of relapse in these two groups was respectively 64 % and 100 %. The value of serum LDH at the time of recurrence, determined in 62 patients, was elevated in 50 (80.7 %). These data demonstrate that in Ewing's sarcoma of bone pretreatment serum LDH levels have a definitive value in establishing the prognosis and could also be used in evaluating the response to therapy. A persistent elevated value of serum LDH, or an increasing value after a transient normalization, is usually followed by relapse.

Neoadjuvant Chemotherapy for Localized Ewing's Sarcoma of the Extremities: Preliminary Results of a Protocol Which uses Surgery (Alone or Followed by Radiotherapy) for Local Control

From June 1983 to December 1985, thirty-eight paients with localized Ewing's sarcoma of the extremities were treated with a protocol that consisted of an initial nine week period of polychemotherapy (vincristine, adriamycin and cyclophosphamide) followed by local therapy and additional chemotherapy (vincristine, adriamycin, cyclophosphamide and dactino-mycln) for one year. As local treatment all patients were offered surgery; thirty-two accepted and six refused. These six patients were locally treated with radiotherapy alone (50 Gy). In the remaining patients an amputation was performed in one case and a resection in thirty-one. In resected patients when a wide margin was achieved (24 cases) no further local treatment was performed; when it was marginal (5 cases) or intralesional (2 cases) radiotherapy at lower doses (40 Gy) followed. At mean follow-up of thirty-seven months the percentage of continuously disease-free patients was 50 % for those treated with radiotherapy, 76 % with surgery, and 85 % with surgery and radiotherapy. Eight patients developed metastatic disease and two patients had local recurrence and metastases. The local recurrences were seen in one patient locally treated with surgery and in one locally treated with radiotherapy. Nine major local complications were observed: three in patients treated with radiotherapy, five in patients treated with surgery, and one in a patient treated with surgery and radiotherapy. These results indicate that after induction chemotherapy conservative surgery is possible in almost all cases of Ewing's sarcoma of the extremities and that such treatment is better than radiotherapy alone as local therapy.

Dijet imbalance measurements in Au+Au and pp collisions at sqrt[s_{NN}]=200 GeV at STAR

We report the first dijet transverse momentum asymmetry measurements from Au+Au and pp collisions at RHIC. The two highest-energy back-to-back jets reconstructed from fragments with transverse momenta above 2  GeV/c display a significantly higher momentum imbalance in heavy-ion collisions than in the pp reference. When reexamined with correlated soft particles included, we observe that these dijets then exhibit a unique new feature-momentum balance is restored to that observed in pp for a jet resolution parameter of R=0.4, while rebalancing is not attained with a smaller value of R=0.2.

Traumatic pulmonary pseudocyst: An underreported entity

BACKGROUND

Traumatic pulmonary pseudocysts (TPP) are underreported cavitary lesions of the pulmonary parenchyma that can develop following blunt chest trauma. Although the occurrence of traumatic pulmonary pseudocyst is rare, this condition should be considered in the differential diagnosis of any cavitary lesion. Awareness of this injury and its clinical significance is important for successful management in order to avoid medical errors in the course of treatment.

METHODS

A literature search was conducted through Medline using the key phrases "traumatic pulmonary pseudocyst" and "traumatic pneumatocele." Relevant articles, especially those with focus on diagnosis and management of traumatic pneumatocele in adults, were selected. Due to the scarcity of literature and lack of Level I evidence on this subject, studies published in any year were considered.

RESULTS

A search of "traumatic pulmonary pseudocyst" and "traumatic pneumatocele" yielded 114 studies. Most of these were excluded based on inclusion and exclusion criteria. Thirty-five articles were reviewed. The majority of these were individual case studies; only eight articles were considered large case studies (greater than eight patients).

CONCLUSION

Traumatic pulmonary pseudocysts are lesions that occur secondary to blunt chest trauma. Diagnosis is based on a history of trauma and appearance of a cystic lesion on CT. Accurate diagnosis of traumatic pulmonary pseudocyst is imperative to achieve successful outcomes. Failure to do so may lead to unnecessary procedures and complications.

Charge-Dependent Directed Flow in Cu+Au Collisions at sqrt[s_{NN}]=200 GeV

We present the first measurement of charge-dependent directed flow in Cu+Au collisions at sqrt[s_{NN}]=200  GeV. The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1  fm/c.

An invariance principle for semi-Markov processes

Let (I(t))∞t = () be a semi-Markov process with state space II and recurrent probability transition kernel P. Subject to certain mixing conditions, where Δis an invariant probability measure for P and μb is the expected sojourn time in state b ϵΠ. We show that this limit is robust; that is, for each state b ϵ Πthe sojourn-time distribution may change for each transition, but, as long as the expected sojourn time in b is µb on the average, the above limit still holds. The kernel P may also vary for each transition as long as Δis invariant.

Measurement of the Transverse Single-Spin Asymmetry in p^{↑}+p→W^{±}/Z^{0} at RHIC

We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at sqrt[s]=500  GeV by the STAR experiment at RHIC. The measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.

Beam Energy Dependence of the Third Harmonic of Azimuthal Correlations in Au+Au Collisions at RHIC

We present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au+Au collisions for energies ranging from sqrt[s_{NN}]=7.7 to 200 GeV. The third harmonic v_{3}^{2}{2}=⟨cos3(ϕ_{1}-ϕ_{2})⟩, where ϕ_{1}-ϕ_{2} is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs Δη=η_{1}-η_{2}. Nonzero v_{3}^{2}{2} is directly related to the previously observed large-Δη narrow-Δϕ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity quark gluon plasma phase. For sufficiently central collisions, v_{3}^{2}{2} persist down to an energy of 7.7 GeV, suggesting that quark gluon plasma may be created even in these low energy collisions. In peripheral collisions at these low energies, however, v_{3}^{2}{2} is consistent with zero. When scaled by the pseudorapidity density of charged-particle multiplicity per participating nucleon pair, v_{3}^{2}{2} for central collisions shows a minimum near sqrt[s_{NN}]=20  GeV.

Centrality and Transverse Momentum Dependence of Elliptic Flow of Multistrange Hadrons and ϕ Meson in Au+Au Collisions at √[sNN]=200 GeV

We present high precision measurements of elliptic flow near midrapidity (|y|<1.0) for multistrange hadrons and ϕ meson as a function of centrality and transverse momentum in Au+Au collisions at center of mass energy √[sNN]=200  GeV. We observe that the transverse momentum dependence of ϕ and Ω v2 is similar to that of π and p, respectively, which may indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. Number of constituent quark scaling is found to hold within statistical uncertainty for both 0%-30% and 30%-80% collision centrality. There is an indication of the breakdown of previously observed mass ordering between ϕ and proton v2 at low transverse momentum in the 0%-30% centrality range, possibly indicating late hadronic interactions affecting the proton v2.

Observation of Transverse Spin-Dependent Azimuthal Correlations of Charged Pion Pairs in p^{↑}+p at sqrt[s]=200 GeV

We report the observation of transverse polarization-dependent azimuthal correlations in charged pion pair production with the STAR experiment in p^{↑}+p collisions at RHIC. These correlations directly probe quark transversity distributions. We measure signals in excess of 5 standard deviations at high transverse momenta, at high pseudorapidities η>0.5, and for pair masses around the mass of the ρ meson. This is the first direct transversity measurement in p+p collisions.

Azimuthal Anisotropy in U+U and Au+Au Collisions at RHIC

Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, v_{2}{2} and v_{2}{4}, for charged hadrons from U+U collisions at sqrt[s_{NN}]=193  GeV and Au+Au collisions at sqrt[s_{NN}]=200  GeV. Nearly fully overlapping collisions are selected based on the energy deposited by spectators in zero degree calorimeters (ZDCs). Within this sample, the observed dependence of v_{2}{2} on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. We also show that v_{2} vs multiplicity can be better described by models, such as gluon saturation or quark participant models, that eliminate the dependence of the multiplicity on the number of binary nucleon-nucleon collisions.

Precision Measurement of the Longitudinal Double-Spin Asymmetry for Inclusive Jet Production in Polarized Proton Collisions at sqrt[s]=200 GeV

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A_{LL}, in polarized pp collisions at center-of-mass energy sqrt[s]=200  GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x>0.05.

Osteopathology in the Equine Distal Phalanx Associated With the Development and Progression of Laminitis

Although the equine distal phalanx and hoof lamellae are biomechanically and physiologically integrated, bony changes in the distal phalanx are poorly described in laminitis. The aims of this study were (1) to establish a laminitis grading scheme that can be applied to the wide spectrum of lesions seen in naturally occurring cases and (2) to measure and describe changes in the distal phalanx associated with laminitis using micro-computed tomography (micro-CT) and histology. Thirty-six laminitic and normal feet from 15 performance and nonperformance horses were evaluated. A laminitis grading scheme based on radiographic, gross, histopathologic, and temporal parameters was developed. Laminitis severity grades generated by this scheme correlated well with clinical severity and coincided with decreased distal phalanx bone volume and density as measured by micro-CT. Laminitic hoof wall changes included progressive ventral rotation and distal displacement of the distal phalanx with increased thickness of the stratum internum-corium tissues with lamellar wedge formation. Histologically, there was epidermal lamellar necrosis with basement membrane separation and dysplastic regeneration, including acanthosis and hyperkeratosis, corresponding to the lamellar wedge. The changes detected by micro-CT corresponded to microscopic findings in the bone, including osteoclastic osteolysis of trabecular and osteonal bone with medullary inflammation and fibrosis. Bone changes were identified in horses with mild/early stages of laminitis as well as severe/chronic stages. The authors conclude that distal phalangeal pathology is a quantifiable and significant component of laminitis pathology and may have important implications for early detection or therapeutic intervention of equine laminitis.

ΛΛ Correlation function in Au+Au collisions at √[S(NN)]=200 GeV

We present ΛΛ correlation measurements in heavy-ion collisions for Au+Au collisions at sqrt[s_{NN}]=200  GeV using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednický-Lyuboshitz analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the ΛΛ correlation function and interaction parameters for dihyperon searches are discussed.

Observation of D0 meson nuclear modifications in Au+Au collisions at sqrt[s(NN)] = 200 GeV

We report the first measurement of charmed-hadron (D(0)) production via the hadronic decay channel (D(0) → K(-) + π(+)) in Au+Au collisions at sqrt[s(NN)] = 200 GeV with the STAR experiment. The charm production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, N(bin), from p+p to central Au+Au collisions. The D(0) meson yields in central Au + Au collisions are strongly suppressed compared to those in p+p scaled by N(bin), for transverse momenta p(T) > 3 GeV/c, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate p(T) is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.

Beam energy dependence of moments of the net-charge multiplicity distributions in Au+Au collisions at RHIC

We report the first measurements of the moments--mean (M), variance (σ(2)), skewness (S), and kurtosis (κ)--of the net-charge multiplicity distributions at midrapidity in Au+Au collisions at seven energies, ranging from sqrt[sNN]=7.7 to 200 GeV, as a part of the Beam Energy Scan program at RHIC. The moments are related to the thermodynamic susceptibilities of net charge, and are sensitive to the location of the QCD critical point. We compare the products of the moments, σ(2)/M, Sσ, and κσ(2), with the expectations from Poisson and negative binomial distributions (NBDs). The Sσ values deviate from the Poisson baseline and are close to the NBD baseline, while the κσ(2) values tend to lie between the two. Within the present uncertainties, our data do not show nonmonotonic behavior as a function of collision energy. These measurements provide a valuable tool to extract the freeze-out parameters in heavy-ion collisions by comparing with theoretical models.

Measurement of longitudinal spin asymmetries for weak boson production in polarized proton-proton collisions at RHIC

We report measurements of single- and double-spin asymmetries for W^{±} and Z/γ^{*} boson production in longitudinally polarized p+p collisions at sqrt[s]=510  GeV by the STAR experiment at RHIC. The asymmetries for W^{±} were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton's polarized quark distributions at the scale of the W mass. The results are compared to theoretical predictions, constrained by polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range 0.05<x<0.2.

Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC

Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy and tends to vanish by 7.7 GeV. This implies the dominance of hadronic interactions over partonic ones at lower collision energies.

Dielectron mass spectra from Au+Au collisions at √[s(NN)]=200 GeV

We report the STAR measurements of dielectron (e(+)e(-)) production at midrapidity (|y(ee)|<1) in Au+Au collisions at √[s(NN)]=200  GeV. The measurements are evaluated in different invariant mass regions with a focus on 0.30-0.76 (ρ-like), 0.76-0.80 (ω-like), and 0.98-1.05 (ϕ-like)   GeV/c(2). The spectrum in the ω-like and ϕ-like regions can be well described by the hadronic cocktail simulation. In the ρ-like region, however, the vacuum ρ spectral function cannot describe the shape of the dielectron excess. In this range, an enhancement of 1.77±0.11(stat)±0.24(syst)±0.33(cocktail) is determined with respect to the hadronic cocktail simulation that excludes the ρ meson. The excess yield in the ρ-like region increases with the number of collision participants faster than the ω and ϕ yields. Theoretical models with broadened ρ contributions through interactions with constituents in the hot QCD medium provide a consistent description of the dilepton mass spectra for the measurement presented here and the earlier data at the Super Proton Synchrotron energies.

Beam-energy dependence of the directed flow of protons, antiprotons, and pions in Au+Au collisions

Rapidity-odd directed flow (v1) measurements for charged pions, protons, and antiprotons near midrapidity (y=0) are reported in sNN=7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV Au+Au collisions as recorded by the STAR detector at the Relativistic Heavy Ion Collider. At intermediate impact parameters, the proton and net-proton slope parameter dv1/dy|y=0 shows a minimum between 11.5 and 19.6 GeV. In addition, the net-proton dv1/dy|y=0 changes sign twice between 7.7 and 39 GeV. The proton and net-proton results qualitatively resemble predictions of a hydrodynamic model with a first-order phase transition from hadronic matter to deconfined matter, and differ from hadronic transport calculations.