Ratio Of D0 Research Articles

Heavy-flavor transport and hadronization in pp collisions

Recent experimental results on the Λc+/D0 ratio in proton-proton (pp) collisions have revealed a significant enhancement compared to expectations based on universal fragmentation fractions/functions across different colliding systems, from e+e− to pp. This unexpected enhancement has sparked speculation about the potential effects of a deconfined medium impacting hadronization, previously considered exclusive to heavy-ion collisions. In this study, we propose a novel approach that assumes the formation of a small, deconfined, and expanding fireball even in pp collisions, where charm quarks can undergo rescattering and hadronization. We make use of the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves local color-neutralization through recombination of charm quarks with nearby opposite color charges from the background fireball. Our model incorporates the presence of diquark excitations in the hot medium, which promotes the formation of charmed baryons. Moreover, the recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. We show that this framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, pT-spectra and elliptic-flow coefficients. Our results provide new, complementary supporting evidence that the collective phenomena observed in small systems naturally have the same origin as those observed in heavy-ion collisions. Published by the American Physical Society 2024

Constraining hadronization mechanisms with [formula omitted] production ratios in Pb–Pb collisions at [formula omitted] TeV

The production of prompt Λc+ baryons at midrapidity (|y|<0.5) was measured in central (0–10%) and mid-central (30–50%) Pb–Pb collisions at the center-of-mass energy per nucleon–nucleon pair sNN=5.02 TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum (pT=1 GeV/c) with respect to previous measurements performed by the ALICE, STAR, and CMS Collaborations in nucleus–nucleus collisions, allowing for an extrapolation down to pT=0. The pT-differential Λc+/D0 ratio is enhanced with respect to the pp measurement for 4<pT<8 GeV/c by 3.7 standard deviations (σ), while the pT-integrated ratios are compatible within 1σ. The observed trend is similar to that observed in the strange sector for the Λ/KS0 ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data.

Observation of a multiplicity dependence in the pT-differential charm baryon-to-meson ratios in proton–proton collisions at [formula omitted] TeV

The production of prompt D0, Ds+, and Λc+ hadrons, and their ratios, Ds+/D0 and Λc+/D0, are measured in proton–proton collisions at s=13 TeV at midrapidity (|y|<0.5) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum (pT) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange Ds+/D0 ratio indicates no significant multiplicity dependence, the baryon-to-meson pT-differential Λc+/D0 ratio shows a multiplicity-dependent enhancement, with a significance of 5.3σ for 1<pT<12 GeV/c, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The Λc+/D0 ratios as a function of pT present a similar shape and magnitude as the Λ/KS0 ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The pT-integrated ratios, extrapolated down to pT=0, do not show a significant dependence on multiplicity within the uncertainties.

Measurement of prompt [formula omitted]-meson production and azimuthal anisotropy in Pb–Pb collisions at [formula omitted

The production yield and angular anisotropy of prompt Ds+ mesons were measured as a function of transverse momentum (pT) in Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV collected with the ALICE detector at the LHC. Ds+ mesons and their charge conjugates were reconstructed at midrapidity (|y|<0.5) from their hadronic decay channel Ds+→ϕπ+, with ϕ→K−K+, in the pT intervals 2<pT<50GeV/c and 2<pT<36GeV/c for the 0–10% and 30–50% centrality intervals. For pT>10GeV/c, the measured Ds+-meson nuclear modification factor RAA is consistent with the one of non-strange D mesons within uncertainties, while at lower pT a hint for a Ds+-meson RAA larger than that of non-strange D mesons is seen. The enhanced production of Ds+ relative to non-strange D mesons is also studied by comparing the pT-dependent Ds+/D0 production yield ratios in Pb–Pb and in pp collisions. The ratio measured in Pb–Pb collisions is found to be on average higher than that in pp collisions in the interval 2<pT<8GeV/c with a significance of 2.3σ and 2.4σ for the 0–10% and 30–50% centrality intervals. The azimuthal anisotropy coefficient v2 of prompt Ds+ mesons was measured in Pb–Pb collisions in the 30–50% centrality interval and is found to be compatible with that of non-strange D mesons. The main features of the measured RAA, Ds+/D0 ratio, and v2 as a function of pT are described by theoretical calculations of charm-quark transport in a hydrodynamically expanding quark–gluon plasma including hadronisation via charm-quark recombination with light quarks from the medium. The pT-integrated production yield of Ds+ mesons is compatible with the prediction of the statistical hadronisation model.

Charm hadronisation measurements with the ALICE experiment

Charm quarks are produced in hard scatterings at the early stages of the hadronic collisions due to the heavy mass of the quark. The production cross section of charm can be described by pQCD calculations based on the factorisation approach. This description traditionally assumes universal fragmentation functions of charm into hadrons among different collision systems. The ALICE experiment measured charmed-baryon production in pp collisions for different baryon species, observing a significant enhancement of the charm baryon-to-meson yield ratios, for pT &lt; 10–12 GeV/c, with respect to measurements performed at e+e− and ep colliders. Measurements of charmed baryon production in pp collisions also provide a fundamental reference for heavy-ion collisions, in which an enhancement of the baryon-to-meson ratio could be due to an additional hadronisation mechanism via coalescence of charm quarks with lighter quarks in a deconfined medium. This contribution discusses the latest measurements of charm production performed by the ALICE Collaboration in pp collisions at the LHC via D mesons, Λc+, Σc0,+,++, Ξc0,+, and Ωc0 baryons at midrapidity at √s = 5.02 and 13 TeV. The most recent measurements of the Λc+/D0 ratio in Pb–Pb collisions at √sNN = 5.02 are also presented, together with the first measurement of the charm fragmentation fraction into hadrons in pp and p–Pb collisions at the same energy.

Studies of Strange and Non-Strange Beauty Productions in PbPb Collisions with the CMS Detector

Beauty quarks are considered as one of the best probes of the strongly interacting medium created in relativistic heavy-ion collisions because they are predominantly produced via initial hard scatterings. Our measurements of B mesons productions provide information on the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. In these studies, clarifying the hadronization mechanism is crucial for understanding the transport properties of beauty quarks. We propose to show our experimental results on three sets of particles: nonprompt J/ψ and D0, B0s and B+, and prompt D+s and D0. Our measurements of B0s production can shed light on the mechanisms of beauty recombination in the medium. In addition, the measurements of mesons productions containing both strange and beauty quarks can provide more information about strangeness enhancement in the quark-gluon plasma. The ratio of B0s over B+ nuclear modification factors at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using fully reconstructed B mesons with the CMS detector, are presented. We will also show the nonprompt J/ψ and D0 from the partial B mesons decay chains as well as our precise measurement the prompt D+s to D0 ratio in pp and PbPb collisions.

The effects of dietary linolenic acid to linoleic acid ratio on growth performance, tissues fatty acid profile and sex steroid hormone synthesis of yellow catfish Pelteobagrus fulvidraco

The effects of different linolenic acid (LNA)/linoleic acid (LA) on tissues fatty acid composition and steroid hormone secretion of the female yellow catfish Pelteobagrus fulvidraco were evaluated after an 8-week feeding trial. Four isonitrogenous and isolipidic formulated diets were designed to contain different LNA/LA ratios of D0.27, D0.82, D1.71 and D2.63, respectively. The result showed that there were no significant effects on the weight gain (WG), gonadosomatic index (GSI), condition factor (CF) of yellow catfish among different diet treatments (P > 0.05). The relative fecundity was greatest in the D2.63 group (P < 0.05). The muscle and hepatic fatty acids profiles reflected corresponding dietary fatty acid profiles treatments, but not ovary. Eicosapentaenoic acid (EPA), arachidonic acid (ARA) and n–3 polyunsaturated fatty acid (PUFA) concentrations were significantly increased with increasing dietary LNA/LA ratios, in both muscle and liver (P < 0.05). ARA and highly unsaturated fatty acid (HUFA) concentrations in the egg were higher than that in liver and muscle, ARA was preferentially accumulated in yellow catfish gonad, which was not influenced by the dietary LNA/LA ratios. The levels of serum testosterone (T) decreased with increasing diet ratios of LNA to LA (P < 0.05), and the mRNA levels of steroidogenesis-related genes (CYP17a1, CYP19a and erβ) were significantly down-regulated with increasing dietary LNA/LA ratios in ovary of female (P < 0.05). In parallel with the changes of plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the mRNA levels of 20 β-hydroxysteroid dehydrogenase (20β-HSD) upregulated with increasing LNA/LA ratios (P < 0.05). In conclusion, the present results suggest that dietary LNA/LA ratios regulated steroid hormone synthesis during ovarian development of yellow catfish. Higher-level dietary LNA/LA ratios are beneficial for HUFA -rich gonadal development and steroid synthesis of yellow catfish.

Effect of immune regulatory pathways after immunization with GMZ2 malaria vaccine candidate in healthy lifelong malaria-exposed adults

BackgroundDespite appreciable immunogenicity in malaria-naive populations, many candidate malaria vaccines are considerably less immunogenic in malaria-exposed populations. This could reflect induction of immune regulatory mechanisms involving Human Leukocyte Antigen G (HLA-G), regulatory T (Treg), and regulatory B (Breg) cells. Here, we addressed the question whether there is correlation between these immune regulatory pathways and both plasmablast frequencies and vaccine-specific IgG concentrations. MethodsFifty Gabonese adults with lifelong exposure to Plasmodium spp were randomized to receive three doses of either 30 µg or 100 µg GMZ2-CAF01, or 100 µg GMZ2-alum, or control vaccine (rabies vaccine) at 4-week intervals. Only plasma and peripheral blood mononuclear cells isolated from blood samples collected before (D0) and 28 days after the third vaccination (D84) of 35 participants were used to measure sHLA-G levels and anti-GMZ2 IgG concentrations, and to quantify Treg, Breg and plasmablast cells. Vaccine efficacy was assessed using controlled human malaria infection (CHMI) by direct venous inoculation of Plasmodium falciparum sporozoites (PfSPZ Challenge). ResultsThe sHLA-G concentration increased from D0 to D84 in all GMZ2 vaccinated participants and in the control group, whereas Treg frequencies increased only in those receiving 30 µg or 100 µg GMZ2-CAF01. The sHLA-G level on D84 was associated with a decrease of the anti-GMZ2 IgG concentration, whereas Treg frequencies on D0 or on D84, and Breg frequency on D84 were associated with lower plasmablast frequencies. Importantly, having a D84:D0 ratio of sHLA-G above the median was associated with an increased risk of P. falciparum infection after sporozoites injection. ConclusionRegulatory immune responses are induced following immunization. Stronger sHLA-G and Treg immune responses may suppress vaccine induced immune responses, and the magnitude of the sHLA-G response increased the risk of Plasmodium falciparum infection after CHMI. These findings could have implications for the design and testing of malaria vaccine candidates in semi-immune individuals.

Formula omitted] production in Pb–Pb collisions at [formula omitted] TeV

A measurement of the production of prompt Λc+ baryons in Pb–Pb collisions at sNN=5.02 TeV with the ALICE detector at the LHC is reported. The Λc+ and Λ‾c− were reconstructed at midrapidity (|y|<0.5) via the hadronic decay channel Λc+→pKS0 (and charge conjugate) in the transverse momentum and centrality intervals 6<pT<12 GeV/c and 0–80%. The Λc+/D0 ratio, which is sensitive to the charm quark hadronisation mechanisms in the medium, is measured and found to be larger than the ratio measured in minimum-bias pp collisions at s=7 TeV and in p–Pb collisions at sNN=5.02 TeV. In particular, the values in p–Pb and Pb–Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties in the common pT interval covered by the measurements in the two collision systems. The Λc+/D0 ratio is also compared with model calculations including different implementations of charm quark hadronisation. The measured ratio is reproduced by models implementing a pure coalescence scenario, while adding a fragmentation contribution leads to an underestimation. The Λc+ nuclear modification factor, RAA, is also presented. The measured values of the RAA of Λc+, Ds+ and non-strange D mesons are compatible within the combined statistical and systematic uncertainties. They show, however, a hint of a hierarchy (RAAD0<RAADs+<RAAΛc+), conceivable with a contribution from coalescence mechanisms to charm hadron formation in the medium.

Volume effects in radiosurgical spinal cord dose tolerance: how small is too small?

Spinal cord dose constraints are a critical feature for stereotactic body radiation therapy (SBRT). Spinal cord maximum point dose (Dmax) by Monte Carlo (MC) calculations is used as a critical cord tolerance limit for SBRT, but information is lacking about its reproducibility. This study examines uncertainty of MC dose calculations for small volumes in spine SBRT. Seven consecutive spine radiosurgery cases were randomly selected to measure precision of the Dmax calculation in comparison to other volumes. Each plan was calculated five times using MC with a 2% uncertainty objective, and variabilities in dose-volume histogram (DVH) parameters across recalculations were evaluated with coefficient of variation (standard deviation divided by mean). The average ratio of D0.03 cc/Dmax was calculated across a larger series of 130 cases. The variability of Dmax was twice as high for D0.03 cc and five times as high for D1 cc across recalculations for the seven cases. For larger volumes, the variability was lower. The standard deviation of Dmax was 0.1959 Gy, compared to 0.0931 Gy, 0.0569 Gy, and 0.0364 Gy for D0.03 cc, D0.1 cc, and D1 cc, respectively. The average D0.03 cc/Dmax among 130 cases was 0.93. Dmax has greater variability compared to D0.03 cc, D0.1 cc, and D1 cc, potentially creating risks when used for guidance for spinal cord. D0.03 cc may be an attractive alternative with higher reliability while its limits could be obtained by scaling the reported Dmax limit by a factor of 0.93. This may help guide treatment planning and aid in discovering true dose constraints for spine SBRT.

Non-strange and strange D-meson and charm-baryon production in heavy-ion collisions measured with ALICE at the LHC

We present recent results on strange and non-strange D-meson production measured with ALICE in Pb–Pb collisions at the LHC. In addition, the measurements of the Λc+-baryon production and of the Λc+/D0 ratio in pp, p–Pb, and, for the first time ever, Pb–Pb collisions are reported.

Measurements of open charm production in Au+Au collisions at [formula omitted] with the STAR experiment at RHIC

We report in these proceedings on the measurements of collision centrality and transverse momentum (pT) dependences of the Λc± production in Au+Au collisions at sNN=200GeV, using the STAR Heavy Flavor Tracker (HFT). The Λc± signal significance is greatly improved with the addition of the high-statistics data set collected in 2016 and the use of a supervised machine learning method for topological reconstruction of the decay vertices. The measured Λc±/D0 ratio shows a significant enhancement compared to the PYTHIA prediction for p+p collisions, across the measured pT range. We also report on the updated measurements of D0 nuclear modification factors RAA and RCP using the 2014 data with the HFT. The measured D0RAA in central collisions is lower than unity across the pT interval of the measurement. The D0 yields show strong suppression at high pT (> 6 GeV/c) in central collisions, consistent with that of light flavor hadrons. The cc‾ production cross section per binary nucleon collision at midrapidity in Au+Au collisions at 200 GeV is extracted based on the various charm hadron measurements by STAR. It is observed that while the charm hadrochemistry is significantly modified in Au+Au collisions compared to p+p collisions, the cc‾ production cross section at midrapidity remains consistent between Au+Au and p+p collisions.

Production of single-charm hadrons by the quark-combination mechanism in p -Pb collisions at sNN=5.02 TeV

If QGP-like medium is created in $p$-Pb collisions at extremely high collision energies, charm quarks that move in the medium can hadronize by capturing the co-moving light quark(s) or anti-quark(s) to form the charm hadrons. Using light quark $p_{T}$ spectra extracted from the experimental data of light-flavor hadrons and a charm quark $p_{T}$ spectrum that is consistent with perturbative QCD calculations, the central-rapidity data of $p_{T}$ spectra and the spectrum ratios for $D$ mesons in the low $p_{T}$ range ($p_{T}\lesssim7$ GeV/$c$) in minimum-bias $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are well described by quark combination mechanism in equal-velocity combination approximation. The $\Lambda_{c}^{+}/D^{0}$ ratio in quark combination mechanism exhibits the typical increase-peak-decrease behavior as the function of $p_{T}$, and the shape of the ratio for $p_{T}\gtrsim3$ GeV/$c$ is in agreement with the data of ALICE collaboration in central rapidity region $-0.96<y<0.04$ and the preliminary data of LHCb collaboration in forward rapidity region $1.5<y<4.0$. The global production of single-charm baryons is quantified using the data and the possible enhancement (relative to light flavor baryons) is discussed. The $p_{T}$ spectra of $\Xi_{c}^{0}$, $\Omega_{c}^{0}$ in minimum-bias events and those of single-charm hadrons in high-multiplicity event classes are predicted, which serves as the further test of the possible change of the hadronization characteristic for low $p_{T}$ charm quarks in the small system created in $p$-Pb collisions at LHC energies.

\u039bc+ production in pp collisions at sqrt{s}=7 TeV and in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV

The pT-differential production cross section of prompt Λc+ charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at sqrt{s}=7 TeV and in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV at midrapidity. The Λc+ and {overline{varLambda}}_{overline{mathrm{c}}} were reconstructed in the hadronic decay modes Λc+ → pK−π+, Λc+ → pKS0 and in the semileptonic channel Λc+ → e+νeΛ (and charge conjugates). The measured values of the Λc+/D0 ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in different colliding systems, centre-of-mass energies, rapidity and pT intervals, where the Λc+ production process may differ. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy-flavour baryons is not well understood. The first measurement at the LHC of the Λc+ nuclear modification factor, RpPb, is also presented. The RpPb is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter effects and a calculation that includes charm quark interactions with a deconfined medium.

Strange and heavy hadrons production from coalescence plus fragmentation in AA collisions at RHIC and LHC

In a coalescence plus fragmentation approach we study the pT spectra of charmed hadrons D0, Ds up to about 10 GeV and the Λ+c /D0 ratio from RHIC to LHC energies. In this study we have included the contribution from decays of heavy hadron resonances and also that due to fragmentation of heavy quarks that are left in the system after coalescence. The pT dependence of the heavy baryon/meson ratios is found to be sensitive to the heavy quark mass. In particular we found that the Λc/D0 is much flatter than the one for light baryon/meson ratio like p/π and Λ/K.

Measurements of [formula omitted] and [formula omitted] productions in Au+Au collisions at [formula omitted] from STAR

We report the first measurement of Λc+ baryon production and significantly improved measurement of Ds+ meson production, within the rapidity range of |y|<1 in Au+Au collisions at sNN=200GeV from the STAR experiment. The transverse momentum spectra of Λc+ and Ds+ as well as their yield ratios to that of D0 meson are also presented and compared to theoretical calculations. Both the Λc+/D0 and Ds+/D0 ratios are found to be significantly enhanced in Au+Au collisions with respect to those in p+p collisions predicted by PYTHIA. A model calculation including coalescence hadronization and thermalized charm quarks is consistent with the measured Λc+/D0 ratio. On the other hand, the TAMU model seems to underestimate the Ds+/D0 ratio measured in Au+Au collisions in the applicable kinematic region.

Looking for new physics via semi-leptonic and leptonic rare decays of D and Ds**Supported by National Natural Science Foundation of China (11675082, 11375128, 11405046) and Special Grant of the Xuzhou University of Technology (XKY2016211)

It is well recognized that looking for new physics at lower energy colliders is a path which is complementary to high energy machines such as the LHC. Using the large volume of data collected by BESIII, we may have a unique opportunity to tackle this. In this paper we calculate the branching ratios of the semi-leptonic processes and , and the leptonic processes D0→e−e+ and D0→e−μ+, in the frameworks of the U(1)′ model, 2HDM and unparticle model. It is found that both the U(1)′ model and 2HDM may influence the semi-leptonic decay rates, but only the U(1)′ model offers substantial contributions to the pure leptonic decays, and the resultant branching ratio of D0→e−μ+ can be as large as 10−7∼10−8. This might be observed at the future super τ-charm factory.

Abstract 5855: Radiosensitization of cervical cancer cells by HDAC inhibitors

Abstract Introduction: While histone deacetylase (HDAC) inhibitors have demonstrated in vitro and in vivo radiosensitization in several human cancer cell lines, the efficacy and mechanism of action of HDAC inhibitors in HPV-positive cancers are poorly understood. We hypothesize that HDAC inhibitors can be used to treat HPV-positive squamous cell carcinomas by enhancing radiation sensitivity. Methods: The cellular cytotoxicity of ten HDAC inhibitors was examined in HPV-positive (CaSki, SiHa, HeLa) and HPV-negative (C33a) cervical cancer cell lines by the WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt] assay, and the drug with the highest cytotoxicity (pan-HDAC inhibitor SP-1-161) was selected for further analysis. SAHA was used as a control. Evaluation of the cell cycle phase distribution was performed by flow cytometry using FACS analysis following treatment with drugs at 24, 48, and 72 hours as well as in combination with radiation in CaSki cells (HPV-16 positive). The extent of radiation sensitization was confirmed by cellular clonogenic assays in CaSki cells. Results: Of all drugs tested, cytotoxicity was demonstrated in a dose-dependent manner. The values of IC50s were at 1.071, 1.567, 1.71, and 0.929 μM (SAHA) and 0.054, 0.3554, 0.0994, and 0.095 μM (SP-1-161) for CaSki, SiHa, HeLa, and C33a cell lines, respectively. SP-1-161 conferred significant cytotoxicity (0.054 μM) in CaSki cells. Cellular radiation sensitivity is tightly associated with cell cycle phases and varies as a function of the position in the cell cycle. To assess the effects of HDAC inhibitors on the cell cycle, CaSki cells were treated with IC50 dosage (SP-1-161 at 0.054 μM, SAHA at 1 μM) for 24 hours, 48 hours, and 72 hours and then treated with radiation. The drugs alone arrested cells primarily in the G1 phase of cell cycle (77.3% for SP-1-161, 84% for SAHA), a relatively radiation sensitive phase. Pre-treatment of SP-1-161 for 24 hours prior to radiation (5 Gy) increased cell cycle arrest in the G1 phase as well. To determine the radiosensitization property of SP-1-161, the radiation clonogenic survival assay was performed following pre-treatment of SP-1-161 for 24 hours. Cells were exposed to graded doses of γ-radiation, and the data were fitted using the single-hit multitarget and the linear-quadratic models. Comparisons of survival curves revealed smaller D0 (D0 ratio 1.43) for cells irradiated in the presence of SP-1-161 (D0 = 1.4) than for controls (D0 = 2.0). Interestingly, treatment with SAHA did not impact radiosensitization (D0 = 1.9, D0 ratio 1.05). Conclusion: SP-1-161 conferred significant toxicity in CaSki cells and primarily arrested cells in the G1 phase of cell cycle. Furthermore, treatment with SP-1-161 enhanced radiosensitization, while SAHA showed little change despite cell cycle arrest primarily in the G1 phase. Together, our results support SP-1-161 as a new therapeutic agent with potential for cervical cancer. Citation Format: Ima Paydar, Alfredo Velena, Scott Grindrod, Mira Jung. Radiosensitization of cervical cancer cells by HDAC inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5855. doi:10.1158/1538-7445.AM2017-5855

Accurate Determination of Amino Acids in Serum Samples by Liquid Chromatography-Tandem Mass Spectrometry Using a Stable Isotope Labeling Strategy.

An accurate and sensitive liquid chromatography-tandem mass spectrometry method was developed for the analysis of amino acids (isoleucine, leucine, valine, tyrosine, phenylalanine and tryptophan) in serum samples using a stable isotope labeling strategy. Amino acid samples and standards were, respectively, derivatized by 10-methyl-acridone-2-sulfonyl chloride (d0-MASC) and its deuterated counterpart d3-MASC to form isotopic pairs which co-eluted and were detected by an MS detector at the same time. Accurate internal standard-based quantification was thereby achieved without the use of any internal standard analogy. The labeling reaction of MASC with amino acids is fast, simple and robust. Besides, derivatization increased the molecular weight of amino acids, and therefore they were shifted out of the background noise which was often observed in low mass region. The instrument LODs were in the range of 1.0-2.5 nmol/L. Linearities calculated by comparing theoretical peak area ratios of d0-/d3-MASC derivatives with the experimental peak area ratios were excellent with correlation coefficients of >0.995. The proposed method was successfully applied to the analysis of amino acids in serum samples with high sensitivity and accuracy.

Measurement ofD0–D¯0Mixing Parameters and Search forCPViolation UsingD0→K+π−Decays

Measurements of charm mixing parameters from the decay-time-dependent ratio of D0->K+pi- to D0->K-pi+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 fb^{-1} of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP) symmetry, the mixing parameters are determined to be x'^2=(5.5 +- 4.9)x10^{-5}, y'= (4.8 +- 1.0)x10^{-3}, and R_D=(3.568 +- 0.066)x10^{-3}. Allowing for CP violation, the mixing parameters are determined separately for D0 and D0bar mesons yielding A_D = (-0.7 +- 1.9)%, for the direct CP-violating asymmetry, and 0.75 < |q/p|< 1.24 at the 68.3% confidence level, where q and p are parameters that describe the mass eigenstates of the neutral charm mesons in terms of the flavor eigenstates. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.