Showing papers by "Kyungpook National University published in 2011"

Determination of jet energy calibration and transverse momentum resolution in CMS

Abstract: Measurements of the jet energy calibration and transverse momentum resolution in CMS are presented, performed with a data sample collected in proton-proton collisions at a centre-of-mass energy of 7TeV, corresponding to an integrated luminosity of 36pb−1. The transverse momentum balance in dijet and γ/Z+jets events is used to measure the jet energy response in the CMS detector, as well as the transverse momentum resolution. The results are presented for three different methods to reconstruct jets: a calorimeter-based approach, the ``Jet-Plus-Track'' approach, which improves the measurement of calorimeter jets by exploiting the associated tracks, and the ``Particle Flow'' approach, which attempts to reconstruct individually each particle in the event, prior to the jet clustering, based on information from all relevant subdetectors

Observation and studies of jet quenching in PbPb collisions at √sNN=2.76 TeV

Abstract: Jet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied with the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity of 6.7 inverse microbarns. Jets are reconstructed using the energy deposited in the CMS calorimeters and studied as a function of collision centrality. With increasing collision centrality, a striking imbalance in dijet transverse momentum is observed, consistent with jet quenching. The observed effect extends from the lower cut-off used in this study (jet transverse momentum = 120 GeV/c) up to the statistical limit of the available data sample (jet transverse momentum approximately 210 GeV/c). Correlations of charged particle tracks with jets indicate that the momentum imbalance is accompanied by a softening of the fragmentation pattern of the second most energetic, away-side jet. The dijet momentum balance is recovered when integrating low transverse momentum particles distributed over a wide angular range relative to the direction of the away-side jet.

Tumor regression in vivo by photothermal therapy based on gold-nanorod-loaded, functional nanocarriers.

Abstract: We developed a very effective hyperthermia system for successful photothermal cancer therapy. Instead of applying individual gold nanorods (GNRs) that can absorb NIR light, GNRs were loaded into functional nanocarriers that could provide stable storage of GNRs and selective delivery to a target tumor site. The functional nanocarriers (chitosan-conjugated, Pluronic-based nanocarriers) were prepared by chemically cross-linking Pluronic F 68 with chitosan conjugation to form a flexible, soft, and excellent reservoir for biomacromolecules as well as tumor targeting. In vivo characteristics of the nanocarriers including a long circulation time, a good tumor accumulation, and low liver uptake were previously characterized by us. When GNRs were delivered by using these nanocarriers, much enhanced in vitro cellular uptake and a photothermal effect were observed for a cancer cell line. More importantly, an intravenous injection of this system followed by NIR laser irradiation to the tumor site resulted in a very e...

Low Dose Organochlorine Pesticides and Polychlorinated Biphenyls Predict Obesity, Dyslipidemia, and Insulin Resistance among People Free of Diabetes

Abstract: Background There is emerging evidence that background exposure to persistent organic pollutants (POPs) are important in the development of conditions predisposing to diabetes as well as of type 2 diabetes itself. We recently reported that low dose POPs predicted incident type 2 diabetes in a nested case-control study. The current study examined if low dose POPs predicted future adiposity, dyslipidemia, and insulin resistance among controls without diabetes in that study.

Smart nanocarrier based on PEGylated hyaluronic acid for cancer therapy.

Abstract: Tumor targetability and site-specific drug release of therapeutic nanoparticles are key factors for effective cancer therapy. In this study, poly(ethylene glycol) (PEG)-conjugated hyaluronic acid nanoparticles (P-HA-NPs) were investigated as carriers for anticancer drugs including doxorubicin and camptothecin (CPT). P-HA-NPs were internalized into cancer cells (SCC7 and MDA-MB-231) via receptor-mediated endocytosis, but were rarely taken up by normal fibroblasts (NIH-3T3). During in vitro drug release tests, P-HA-NPs rapidly released drugs when incubated with cancer cells, extracts of tumor tissues, or the enzyme Hyal-1, which is abundant in the intracellular compartments of cancer cells. CPT-loaded P-HA-NPs (CPT-P-HA-NPs) showed dose-dependent cytotoxicity to cancer cells (MDA-MB-231, SCC7, and HCT 116) and significantly lower cytotoxicity against normal fibroblasts (NIH-3T3) than free CPT. Unexpectedly, high concentrations of CPT-P-HA-NPs demonstrated greater cytotoxicity to cancer cells than free CPT. ...

Three-dimensional display technologies of recent interest: principles, status, and issues [Invited]

Abstract: Recent trends in three-dimensional (3D) display technologies are very interesting in that both old-fashioned and up-to-date technologies are being actively investigated together. The release of the first commercially successful 3D display product raised new research topics in stereoscopic display. Autostereoscopic display renders a ray field of a 3D image, whereas holography replicates a wave field of it. Many investigations have been conducted on the next candidates for commercial products to resolve existing limitations. Up-to-date see-through 3D display is a concept close to the ultimate goal of presenting seamless virtual images. Although it is still far from practical use, many efforts have been made to resolve issues such as occlusion problems.

Search for supersymmetry at the LHC in events with jets and missing transverse energy

Abstract: A search for events with jets and missing transverse energy is performed in a data sample of pp collisions collected at sqrt(s) = 7 TeV by the CMS experiment at the LHC. The analyzed data sample corresponds to an integrated luminosity of 1.14 inverse femtobarns. In this search, a kinematic variable, alphaT, is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. No excess of events over the standard model expectation is found. Exclusion limits in the parameter space of the constrained minimal supersymmetric extension of the standard model are set. In this model, squark masses below 1.1 TeV are excluded at 95% CL. Gluino masses below 1.1 TeV are also ruled out at 95% CL for values of the universal scalar mass parameter below 500 GeV.

The Pilot Study in Qualitative Inquiry: Identifying Issues and Learning Lessons for Culturally Competent Research

Abstract: This article discusses the importance of a pilot study in undertaking phenomenological qualitative inquiry for culturally competent research. The pilot work was conducted in preparation for a dissertation on Korean-American family dementia caregiving. The definition and useful functions of pilot studies in qualitative inquiry are particularly identified. To highlight the benefits of pilot work, it describes the specific practical and methodological issues emerging in the pilot exercise as well as the modifications made for the main study as a result of the pilot work. The implementation of the pilot exercise proved to be essential in four ways. These comprise (1) finding issues and barriers related to recruiting potential participants, (2) engaging the use of oneself as a researcher in a culturally appropriate way and from a phenomenological perspective, (3) reflecting the importance of the epoche process and its difficulty in conducting phenomenological inquiry, and (4) modifying interview questions. Fin...

Light-harvesting multi-walled carbon nanotubes and CdS hybrids: Application to photocatalytic hydrogen production from water

Abstract: This study reports the synthesis and surface characterization of multi-walled carbon nanotubes (CNT), CdS, and metal catalyst (M) hybrids (CdS/CNT/M), and their novel application to photocatalytic hydrogen production under visible light (λ > 400 nm) in the presence of electron donor (Na2S and Na2SO3). In the binary hybrids between CNT and CdS (CdS/CNT) the CNT annealed at 500 °C (h-CNT) has the larger amount of hydrogen production than crude (c-CNT) or acid-treated CNT (a-CNT) due to highly improved purity and suitable work function. When hybridized with CdS and M, however, a-CNT has the largest amount of hydrogen production (a-CNT > h-CNT > c-CNT) even though all the CNTs have similar functional groups for binding metal catalyst on their surfaces. Photocurrent measurements also indicated that CdS/a-CNT/Pt ternary generates a higher photocurrent than that of CdS/a-CNT binary (ternary > binary > CdS alone). In such ternary hybrids, Pt, Ni, and Ru are found to be effective in catalyzing proton/water but other metals (Pd, Au, Ag, Cu) showed very low activities with the following order: Pt > Ni > Ru > Pd > Au > Ag > Cu. The enhanced hydrogen production in the binary and ternary hybrids is ascribed partially to suitably positioned work functions among the hybrid components and thereby vectorial charge transfer through the work function energy gradient. Detailed surface studies were also described using Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

microRNAs in the Regulation of Adipogenesis and Obesity

Abstract: Worldwide obesity is a growing health problem, associated with increased risk of chronic disease. Understanding the molecular basis of adipogenesis and fat cell development in obesity is essential to identify new biomarkers and therapeutic targets for the development of anti-obesity drugs. microRNAs (miRNAs) appear to play regulatory roles in many biological processes associated with obesity, including adipocyte differentiation, insulin action and fat metabolism. Recent studies show miRNAs are dysregulated in obese adipose tissue. During adipogenesis miRNAs can accelerate or inhibit adipocyte differentiation and hence regulate fat cell development. In addition miRNAs may regulate adipogenic lineage commitment in multipotent stem cells and hence govern fat cell numbers. Recent findings suggest miR-519d may be associated with human obesity, but larger case-control studies are needed. Few miRNA targets have been experimentally validated in adipocytes but interestingly both miR-27 and miR-519d target PPAR family members, which are well established regulators of fat cell development. In this review recent advances in our understanding of the role of miRNAs in fat cell development and obesity are discussed. The potential of miRNA based therapeutics targeting obesity is highlighted as well as recommendations for future research which could lead to a breakthrough in the treatment of obesity.

Chemical and thermal stability of isotypic metal-organic frameworks: effect of metal ions.

Abstract: Chemical and thermal stabilities of isotypic metal-organic frameworks (MOFs) like Al-BDC (Al-benzenedicarboxylate called MIL-53-Al), Cr-BDC (MIL-53-Cr) and V-BDC (MIL-47-V), after purification to remove uncoordinated organic linkers, have been compared to understand the effect of the central metal ions on the stabilities of the porous MOF-type materials. Chemical stability to acids, bases, and water decreases in the order of Cr-BDC>Al-BDC>V-BDC, suggesting stability increases with increasing inertness of the central metal ions. However, thermal stability decreases in the order of Al-BDC>Cr-BDC> V-BDC, and this tendency may be explained by the strength of the metal-oxygen bond in common oxides like Al(2)O(3), Cr(2)O(3), and V(2)O(5). In order to evaluate precisely the stability of a MOF, it is necessary to remove uncoordinated organic linkers that are located in the pores of the MOF, because a filled MOF may be more stable than the same MOF after purification.

Upsilon production cross section in pp collisions at √s=7 TeV

Abstract: The Upsilon production cross section in proton-proton collisions at sqrt(s) = 7 TeV is measured using a data sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 3.1 +/- 0.3 inverse picobarns. Integrated over the rapidity range |y|<2, we find the product of the Upsilon(1S) production cross section and branching fraction to dimuons to be sigma(pp to Upsilon(1S) X) B(Upsilon(1S) to mu+ mu-) = 7.37 +/- 0.13^{+0.61}_{-0.42}\pm 0.81 nb, where the first uncertainty is statistical, the second is systematic, and the third is associated with the estimation of the integrated luminosity of the data sample. This cross section is obtained assuming unpolarized Upsilon(1S) production. If the Upsilon(1S) production polarization is fully transverse or fully longitudinal the cross section changes by about 20%. We also report the measurement of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections as a function of transverse momentum and rapidity.

New mechanisms and the anti-inflammatory role of curcumin in obesity and obesity-related metabolic diseases

Abstract: Purpose A metabolic abnormality such as obesity is a major obstacle in the maintenance of the human health system and causes various chronic diseases including type 2 diabetes, hypertension, cardiovascular diseases, as well as various cancers. This study was designed to summarize the recent scientific knowledge regarding the anti-obesity role of curcumin (diferuloylmethane), which is isolated from the herb curcuma longa, known to possess anti-inflammatory activities. However, little is known about its exact underlying molecular mechanisms in the treatment of obesity and metabolic diseases. Furthermore, cell cultures, animal models of obesity, and few human clinical and epidemiological studies have added the promise for future therapeutic interventions of this dietary compound.

Measurement of the inclusive W and Z production cross sections in pp collisions at √s = 7 TeV with the CMS experiment

Abstract: A measurement of inclusive W and Z production cross sections in pp collisions at sqrt(s)=7 TeV is presented. The electron and muon decay channels are analyzed in a data sample collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 36 inverse picobarns. The measured inclusive cross sections are sigma(pp-> WX) B(W-> l nu) = 10.30 +/- 0.02 (stat.) +/- 0.10 (syst.) +/- 0.10 (th.) +/- 0.41 (lumi.) nb and sigma(pp -> ZX) B(Z-> l^+l^-) = 0.974 +/- 0.007 (stat.) +/- 0.007 (syst.) +/- 0.018 (th.) +/- 0.039 (lumi.) nb, limited to the dilepton invariant mass range 60 to 120 GeV. The luminosity-independent cross section ratios are [sigma(pp->WX) B(W-> l nu)]/[sigma(pp-> ZX) B(Z->l^+l^-)] = 10.54 +/- 0.07 (stat.) +/- 0.08 (syst.) +/- 0.16 (th.) and [sigma(pp->W^+X) B(W^+ -> l^+nu)] / [sigma(pp->W^- X) B(W^- -> l^- nu)] = 1.421 +/- 0.006 (stat.) +/- 0.014 (syst.) +/- 0.029 (th.). The measured values agree with next-to-next-to-leading order QCD cross section calculations based on recent parton distribution functions.

Measurements of inclusive W and Z cross sections in pp collisions at \sqrt {s} = 7 TeV

Abstract: Measurements of inclusive W and Z boson production cross sections in pp collisions at sqrt(s)=7 TeV are presented, based on 2.9 inverse picobarns of data recorded by the CMS detector at the LHC. The measurements, performed in the electron and muon decay channels, are combined to give sigma(pp to WX) times B(W to muon or electron + neutrino) = 9.95 \pm 0.07(stat.) \pm 0.28(syst.) \pm 1.09(lumi.) nb and sigma(pp to ZX) times B(Z to oppositely charged muon or electron pairs) = 0.931 \pm 0.026(stat.) \pm 0.023(syst.) \pm 0.102(lumi.) nb. Theoretical predictions, calculated at the next-to-next-to-leading order in QCD using recent parton distribution functions, are in agreement with the measured cross sections. Ratios of cross sections, which incur an experimental systematic uncertainty of less than 4%, are also reported.

Prevalence of Eye Diseases in South Korea: Data from the Korea National Health and Nutrition Examination Survey 2008-2009

Abstract: Epidemiological studies provide information on the prevention, treatment, and minimization of the impact of diseases on society. In the past two decades, a wide range of epidemiologic studies in ophthalmology have provided important information on the pattern of visual impairment and the major eye diseases that cause such vision loss [1]. Although several epidemiological studies of several age-related eye diseases (e.g., glaucoma, age-related macular degeneration, and cataract) have been conducted in Korea [2-4], these studies were hospital-based or were conducted primarily in urban areas. Data on the prevalence of diseases based on the number of hospital visits or surveys conducted in limited areas are easy to obtain; however, substantial differences may exist between such data and that obtained in large-scale population studies, which are more accurate and can represent entire populations. Large-scale population-based studies conducted over the past two decades in many countries, including the United States [5-14], Western Europe [15-17], Australia [18-21], Japan [22-26], Singapore [27-30], and China [31-35], have been used to guide public health policy and plan preventive strategies. However, these studies were conducted mostly with regard to major age-related eye diseases, such as cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy, which are major causes of vision loss. Nation-wide epidemiological studies of all age groups for the prevalence of common eye diseases have not been performed. The Korea Center for Disease Control and Prevention (CDC) conducted a series of Korea National Health and Nutrition Examination Surveys (KNHANES) in 1998, 2001, 2005 and 2007-2009 for examination of the general health and nutrition status of Koreans. As of the fourth KNHANES (2007-2009), an annual total of 4,600 households were selected, and the participating household members were interviewed regarding health and nutrition and underwent a basic health examination that included blood pressure measurements, blood and urine collection, a pulmonary function test, and a dental examination. Since the Korean Ophthalmologic Society has participated in this survey since 2008, ophthalmologic interviews and examinations were also conducted with the same participants. The purpose of this study is to investigate the national prevalence of common eye diseases in South Korea based on the survey data obtained from the KNHANES and to analyze the prevalence of diseases according to age and gender. Data obtained from KNHANES may offer further insight into the etiology, ethnic differences, and public health impact of the most common eye diseases affecting Korean people living in Asia.

Vestibular Rehabilitation Therapy: Review of Indications, Mechanisms, and Key Exercises

Abstract: Vestibular rehabilitation therapy (VRT) is an exercise-based treatment program designed to promote vestibular adaptation and substitution. The goals of VRT are 1) to enhance gaze stability, 2) to enhance postural stability, 3) to improve vertigo, and 4) to improve activities of daily living. VRT facilitates vestibular recovery mechanisms: vestibular adaptation, substitution by the other eye-movement systems, substitution by vision, somatosensory cues, other postural strategies, and habituation. The key exercises for VRT are head-eye movements with various body postures and activities, and maintaining balance with a reduced support base with various orientations of the head and trunk, while performing various upper-extremity tasks, repeating the movements provoking vertigo, and exposing patients gradually to various sensory and motor environments. VRT is indicated for any stable but poorly compensated vestibular lesion, regardless of the patient's age, the cause, and symptom duration and intensity. Vestibular suppressants, visual and somatosensory deprivation, immobilization, old age, concurrent central lesions, and long recovery from symptoms, but there is no difference in the final outcome. As long as exercises are performed several times every day, even brief periods of exercise are sufficient to facilitate vestibular recovery. Here the authors review the mechanisms and the key exercises for each of the VRT goals.

Acinetobacter baumannii secretes cytotoxic outer membrane protein A via outer membrane vesicles.

Abstract: Acinetobacter baumannii is an important nosocomial pathogen that causes a high morbidity and mortality rate in infected patients, but pathogenic mechanisms of this microorganism regarding the secretion and delivery of virulence factors to host cells have not been characterized. Gram-negative bacteria naturally secrete outer membrane vesicles (OMVs) that play a role in the delivery of virulence factors to host cells. A. baumannii has been shown to secrete OMVs when cultured in vitro, but the role of OMVs in A. baumannii pathogenesis is not well elucidated. In the present study, we evaluated the secretion and delivery of virulence factors of A. baumannii to host cells via the OMVs and assessed the cytotoxic activity of outer membrane protein A (AbOmpA) packaged in the OMVs. A. baumannii ATCC 19606T secreted OMVs during in vivo infection as well as in vitro cultures. Potential virulence factors, including AbOmpA and tissue-degrading enzymes, were associated with A. baumannii OMVs. A. baumannii OMVs interacted with lipid rafts in the plasma membranes and then delivered virulence factors to host cells. The OMVs from A. baumannii ATCC 19606T induced apoptosis of host cells, whereas this effect was not detected in the OMVs from the ΔompA mutant, thereby reflecting AbOmpA-dependent host cell death. The N-terminal region of AbOmpA22-170 was responsible for host cell death. In conclusion, the OMV-mediated delivery of virulence factors to host cells may well contribute to pathogenesis during A. baumannii infection.

Long-term curcumin administration protects against atherosclerosis via hepatic regulation of lipoprotein cholesterol metabolism.

Abstract: Scope: Atherosclerosis is a major cause of cardiovascular disease caused by high cholesterol Stains are widely prescribed to lower cholesterol levels, but natural dietary compounds may also be effective Therefore, we studied the effect of the natural dietary compound curcumin on atherosclerosis and its underlying mechanisms based on plasma and hepatic lipid metabolism Methods and results: LDLR−/− mice were fed a high-cholesterol diet and treated with curcumin, lovastatin or control (n=10 per group) for 18 wk Aortic arch sections revealed curcumin ameliorated early atherosclerotic lesions, lipid infiltration, ICAM-1 and VCAM-1 localization, similar to lovastatin treatment Furthermore, curcumin lowered plasma cholesterol, triglycerides, LDL cholesterol and Apo B levels as well as CETP activity, while curcumin increased plasma HDL cholesterol and liver Apo A-I expression, similar to lovastatin treatment Curcumin caused transcriptional inhibition of HMG-CoA reductase, independent of ACAT1 and ACAT2 expression Hepatic PPARα and LXRα expression was upregulated by curcumin treatment Hepatic complement factor D (Cfd) and systemic CRP levels, markers of immune complement pathway activation, were significantly reduced by curcumin treatment Conclusion: Long-term curcumin treatment lowers plasma and hepatic cholesterol and suppresses early atherosclerotic lesions comparable to the protective effects of lovastatin The anti-atherogenic effect of curcumin is mediated via multiple mechanisms including altered lipid, cholesterol and immune gene expression

Polychlorinated biphenyls and organochlorine pesticides in plasma predict development of type 2 diabetes in the elderly: the prospective investigation of the vasculature in Uppsala Seniors (PIVUS) study

Abstract: OBJECTIVE Persistent organic pollutants (POPs), lipophilic chemicals that accumulate mainly in adipose tissue, have recently been linked to type 2 diabetes. However, evidence from prospective studies is sparse. This study was performed to evaluate prospective associations of type 2 diabetes with selected POPs among the elderly. RESEARCH DESIGN AND METHODS Nineteen POPs (14 polychlorinated biphenyl [PCB] congeners, 3 organochlorine pesticides, 1 brominated diphenyl ether, and 1 dioxin) were measured in plasma collected at baseline in 725 participants, aged 70 years, of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). RESULTS After adjusting for known type 2 diabetes risk factors, including obesity, odds ratios (ORs) (95% CIs) for type 2 diabetes at age 75 years ( n = 36) according to the quintiles of a summary measure of concentrations of PCBs (vs. the lowest quintile) were 4.5, 5.1, 8.8 (1.8–42.7), and 7.5 (1.4–38.8) ( P trend trans -nonachlor showed that P trend = 0.03. Adjusted ORs (95% CIs) across quintiles of the sum of three organochlorine pesticides were 1.1, 1.6, 1.5, and 3.4 (1.0–11.7) ( P trend = 0.03). Neither brominated diphenyl ether 47 nor dioxin was significantly associated with incident diabetes. The sum of PCBs improved reclassification significantly when added to traditional risk factors for diabetes. CONCLUSIONS Despite the small number of incident cases, this study found that environmental exposure to some POPs substantially increased risk of future type 2 diabetes in an elderly population.

Proteomic analysis of urinary exosomes from patients of early IgA nephropathy and thin basement membrane nephropathy

Abstract: To identify biomarker candidates associated with early IgA nephropathy (IgAN) and thin basement membrane nephropathy (TBMN), the most common causes presenting isolated hematuria in childhood, a proteomic approach of urinary exosomes from early IgAN and TBMN patients was introduced. The proteomic results from the patients were compared with a normal group to understand the pathophysiological processes associated with these diseases at the protein level. The urinary exosomes, which reflect pathophysiological processes, collected from three groups of young adults (early IgAN, TBMN, and normal) were trypsin-digested using a gel-assisted protocol, and quantified by label-free LC-MS/MS, using an MS(E) mode. A total of 1877 urinary exosome proteins, including cytoplasmic, membrane, and vesicle trafficking proteins, were identified. Among the differentially expressed proteins, four proteins (aminopeptidase N, vasorin precursor, α-1-antitrypsin, and ceruloplasmin) were selected as biomarker candidates to differentiate early IgAN from TBMN. We confirmed the protein levels of the four biomarker candidates by semi-quantitative immunoblot analysis in urinary exosomes independently prepared from other patients, including older adult groups. Further clinical studies are needed to investigate the diagnostic and prognostic value of these urinary markers for early IgAN and TBMN. Taken together, this study showed the possibility of identifying biomarker candidates for human urinary diseases using urinary exosomes and might help to understand the pathophysiology of early IgAN and TBMN at the protein level.

Indications of suppression of excited? States in Pb-Pb collisions at sNN2.76 TeV

Abstract: A comparison of the relative yields of Upsilon resonances in the mu(+) mu(-) decay channel in PbPb and pp collisions at a centre-of-mass energy per nucleon pair of 2.76 TeV, is performed with data collected with the CMS detector at the LHC. Using muons of transverse momentum above 4 GeV/c and pseudorapidity below 2.4, the double ratio of the Upsilon(2S) and Upsilon(3S) excited states to the Upsilon(1S) ground state in PbPb and pp collisions,(Upsilon(2S+3S)/Upsilon(1S)[PbPb])/(Upsilon(2S+3S)/Upsilon(1S)[pp]), is found to be 0.31 - 0.15 + 0.19 (stat.) +/- 0.03 (syst.). The probability to obtain the measured value, or lower, if the true double ratio is unity, has been calculated to be less than 1%.

Anisotropic Dirac fermions in a Bi square net of SrMnBi2

Abstract: We report the observation of highly anisotropic Dirac fermions in a Bi square net of ${\mathrm{SrMnBi}}_{2}$, based on a first-principles calculation, angle-resolved photoemission spectroscopy, and quantum oscillations for high-quality single crystals. We found that the Dirac dispersion is generally induced in the $(\mathrm{SrBi}{)}^{+}$ layer containing a double-sized Bi square net. In contrast to the commonly observed isotropic Dirac cone, the Dirac cone in ${\mathrm{SrMnBi}}_{2}$ is highly anisotropic with a large momentum-dependent disparity of Fermi velocities of $\ensuremath{\sim}8$. These findings demonstrate that a Bi square net, a common building block of various layered pnictides, provides a new platform that hosts highly anisotropic Dirac fermions.