CKM Favored Semileptonic Decays of Heavy Hadrons at Zero Recoil

We study the properties of Cabibbo-Kobayashi-Maskawa (CKM) favored semileptonic decays of mesons and baryons containing a heavy quark at the point of no recoil. We first use a diagrammatic analysis to rederive the result observed by earlier authors that at this kinematic point the $B$ meson decays via $b\to c$ transitions can only produce a $D$ or $D^*$ meson. The result is generalized to include photon emissions which violate heavy quark flavor symmetry. We show that photons emitted by the heavy quarks and the charged lepton are the only light particles that can decorate the decays $\bar{B}\to D(D^*) + \ell\nu$ at zero recoil, and the similar processes of heavy baryons. Implications for the determinations of the CKM parameter $V_{cb}$ are discussed. Also studied in this paper is the connection between our diagrammatic analysis of suppression of particle emission and the formal observation based on weak currents at zero recoil being generators of heavy quark symmetry. We show that the two approaches can be unified by considering the Isgur-Wise function in the presence of an external source.Comment: 27 pages, including 11 figures using macros FEYNMAN.te

Perturbative QCD Analysis of BB Meson Decays

Resummation of large QCD radiative corrections, including leading and next-to-leading logarithms, in pion electromagnetic form factor is reviewed. Similar formalism is applied to exclusive processes involving heavy mesons, and leads to Sudakov suppression for the semi-leptonic decay $B\to\pi l\nu$. It is found that, with the inclusion of Sudakov effects, perturbative QCD analysis of this decay is possible for the energy fraction of the pion above 0.3. By combining predictions from the soft pion theorems, we estimate that the upper limit of the KM matrix element $|V_{ub}|$ is roughly 0.003.Comment: 26 pages in latex, figures are available for reques

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C

The global retinoblastoma outcome study : a prospective, cluster-based analysis of 4064 patients from 149 countries

DATA SHARING : The study data will become available online once all analyses are complete.BACKGROUND : Retinoblastoma is the most common intraocular cancer worldwide. There is some evidence to suggest that major differences exist in treatment outcomes for children with retinoblastoma from different regions, but these differences have not been assessed on a global scale. We aimed to report 3-year outcomes for children with retinoblastoma globally and to investigate factors associated with survival. METHODS : We did a prospective cluster-based analysis of treatment-naive patients with retinoblastoma who were diagnosed between Jan 1, 2017, and Dec 31, 2017, then treated and followed up for 3 years. Patients were recruited from 260 specialised treatment centres worldwide. Data were obtained from participating centres on primary and additional treatments, duration of follow-up, metastasis, eye globe salvage, and survival outcome. We analysed time to death and time to enucleation with Cox regression models. FINDINGS : The cohort included 4064 children from 149 countries. The median age at diagnosis was 23·2 months (IQR 11·0–36·5). Extraocular tumour spread (cT4 of the cTNMH classification) at diagnosis was reported in five (0·8%) of 636 children from high-income countries, 55 (5·4%) of 1027 children from upper-middle-income countries, 342 (19·7%) of 1738 children from lower-middle-income countries, and 196 (42·9%) of 457 children from low-income countries. Enucleation surgery was available for all children and intravenous chemotherapy was available for 4014 (98·8%) of 4064 children. The 3-year survival rate was 99·5% (95% CI 98·8–100·0) for children from high-income countries, 91·2% (89·5–93·0) for children from upper-middle-income countries, 80·3% (78·3–82·3) for children from lower-middle-income countries, and 57·3% (52·1-63·0) for children from low-income countries. On analysis, independent factors for worse survival were residence in low-income countries compared to high-income countries (hazard ratio 16·67; 95% CI 4·76–50·00), cT4 advanced tumour compared to cT1 (8·98; 4·44–18·18), and older age at diagnosis in children up to 3 years (1·38 per year; 1·23–1·56). For children aged 3–7 years, the mortality risk decreased slightly (p=0·0104 for the change in slope). INTERPRETATION : This study, estimated to include approximately half of all new retinoblastoma cases worldwide in 2017, shows profound inequity in survival of children depending on the national income level of their country of residence. In high-income countries, death from retinoblastoma is rare, whereas in low-income countries estimated 3-year survival is just over 50%. Although essential treatments are available in nearly all countries, early diagnosis and treatment in low-income countries are key to improving survival outcomes.The Queen Elizabeth Diamond Jubilee Trust and the Wellcome Trust.https://www.thelancet.com/journals/langlo/homeam2023Paediatrics and Child Healt

Composition of the seed oil of Hibiscus abelmoschus L. (Malvaceae) growing in Vietnam

The essential oils of ambrette (Hibiscus abelmoschus 1., syn. Abelmoschus moschatus) were produced from seeds collected in the different provinces of Vietnam. Five samples were investigated and 35 components were identified by a combination of high resolution GC, GC/MS and 13C-NMR spectrometry. The major constituents were found to be (E)-2,3-dihydrofarnesyl acetate (32.9-67.3%), (E,E)farnesyl acetate 04.9-35.5%), the macrocyclic lactone ambrettolide (3.0-5.5%) and (Z,E)-farnesyl acetate (0.9-5.1%). The oils consisted for more than 90% of acetates and aldehydes

Seroprevalence of Scrub Typhus, Typhus, and Spotted Fever Among Rural and Urban Populations of Northern Vietnam

AbstractRickettsial infections are recognized as important causes of fever throughout southeast Asia. Herein, we determined the seroprevalence to rickettsioses within rural and urban populations of northern Vietnam. Prevalence of individuals with evidence of prior rickettsial infections (IgG positive) was surprisingly low, with 9.14% (83/908) testing positive to the three major rickettsial serogroups thought to circulate in the region. Prevalence of typhus group rickettsiae (TG)-specific antibodies (6.5%, 58/908) was significantly greater than scrub typhus group orientiae (STG)- or spotted fever group rickettsiae (SFG)-specific antibodies (P < 0.05). The majority of TG seropositives were observed among urban rather than rural residents (P < 0.05). In contrast, overall antibody prevalence to STG and SFG were both very low (1.1%, 10/908 for STG; 1.7%, 15/908 for SFG), with no significant differences between rural and urban residents. These results provide data on baseline population characteristics that may help inform development of Rickettsia serological testing criteria in future clinical studies

Complexity Bounds for Batch Active Learning in Classification

International audienceActive learning is a branch of Machine Learning in which the learning algorithm, instead of being directly provided with pairs of problem instances and their solutions (their labels), is allowed to choose, from a set of unlabeled data, which instances to query. It is suited to settings where labeling instances is costly. This paper analyzes the speed-up of batch (parallel) active learning compared to sequential active learning (where instances are chosen 1 by 1): how faster can an algorithm become if it can query instances at once? There are two main contributions: proving lower and upper bounds on the possible gain, and illustrating them by experimenting on usual active learning algorithms. Roughly speaking, the speed-up is asymptotically logarithmic in the batch size (i.e. when ! 1). However, for some classes of functions with finite VC-dimension V , a linear speed-up can be achieved until a batch size of V . Practically speaking, this means that parallelizing computations on an expensive-to-label problem which is suited to active learning is very beneficial until V simultaneous queries, and less interesting (yet still bringing improvement) afterwards