\bar u - \bar d asymmetry - a few remarks

We make a few remarks on possible sources of uncertainties of the $\bar d - \bar u$ asymmetry obtained by different methods and comment on its possible verification in the future. In addition we comment on its present understanding.Comment: 3 pages, a talk at the 7th International Workshop on Deep Inelastic Scattering and QCD (DIS99), Zeuthen, April 199

Ureteroscopic treatment of larger renal calculi (\u3e2 cm).

OBJECTIVES: To evaluate the current status of ureteroscopic lithotripsy (UL) for treating renal calculi of \u3e2 cm, as advances in flexible ureteroscope design, accessory instrumentation and lithotrites have revolutionised the treatment of urinary calculi. While previously reserved for ureteric and small renal calculi, UL has gained an increasing role in the selective management of larger renal stone burdens. METHODS: We searched the available databases, including PubMed, Google Scholar, and Scopus, for relevant reports in English, and the article bibliographies to identify additional relevant articles. Keywords included ureteroscopy, lithotripsy, renal calculi, and calculi \u3e2 cm. Retrieved articles were reviewed to consider the number of patients, mean stone size, success rates, indications and complications. RESULTS: In all, nine studies (417 patients) were eligible for inclusion. After one, two or three procedures the mean (range) success rates were 68.2 (23-84)%, 87.1 (79-91)% and 94.4 (90.1-96.7)%, respectively. Overall, the success rate was \u3e90% with a mean of 1.2-2.3 procedures per patient. The overall complication rate was 10.3%, including six (1.4%) intraoperative and 37 (8.9%) postoperative complications, most of which were minor. The most common indications for UL were a failed previous treatment (46%), comorbidities (18.2%), and technical and anatomical factors (12.3%). CONCLUSIONS: UL is safe and effective for treating large renal calculi. While several procedures might be required for total stone clearance, UL should be considered a standard approach in the urologist\u27s options treating renal calculi of \u3e2 cm

Extraction of the gluon density of the proton at x

The gluon momentum density xg(x, Q2) of the proton was extracted at Q2 = 20 GeV2 for small values of x between 4 × 10-4 and 10-2 from the scaling violations of the proton structure function F2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F2 at low x constrained by measurementsfrom NMC at larger x; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x. © 1995

Measurement of Elastic Φ Photoproduction at HERA

The production of φ mesons in the reaction e+p → e+φp (φ → K+K-) at a median Q2 of 10-4 GeV2 has been studied with the ZEUS detector at HERA. The differential φ photoproduction cross section dσ/dt has an exponential shape and has been determined in the kinematic range 0.1 \u3c |t| \u3c 0.5 GeV2 and 60 \u3c W \u3c 80 GeV. An integrated cross section of σγp→φp = 0.96 ± 0.19+0.21-.18 μb has been obtained by extrapolating to t = 0. When compared to lower energy data, the results show a weak energy dependence of both σγp→φp and the slope of the t distribution. The φ decay angular distributions are consistent with s-channel helicity conservation. From lower energies to HERA energies, the features of φ photoproduction are compatible with those of a soft diffractive process

Novel Six-Quark Hidden-Color Dibaryon States in QCD

The recent observation of a hadronic resonance $d^*$ in the proton-neutron system with isospin $I = 0$ and spin-parity $J^P = 3^+$ raises the possibility of producing other novel six-quark dibaryon configurations allowed by QCD. A dramatic example of an exotic six-quark color-singlet system is the charge $Q=+4$, isospin I=3, $I^z=+3$ $|uuuuuu>$ state which couples strongly to $\Delta^{++}$ + $\Delta^{++} .$ The width and decay properties of such six-quark resonances could be regarded as manifestations of "hidden-color" six-quark configurations, a first-principle prediction of QCD -- SU(3)-color gauge theory for the deuteron distribution amplitude. Other implications and possible future experiments are discussed

Study of certain regularities of polymeric dielectric film’s destruction under the influence of electric field at partial discharges limitation

Робота присвячена дослідженню процеса електричного старіння і руйнування полімерних діелектричних плівок. Показано, що пробій твердих полімерних діелектриків під дією електричного поля не є критичною подією, а є процесом, що розвивається у часі та проявляється у накопиченні дефектів в матеріалі. Розділяються умови навантаження електричним полем, в яких протікає старіння полімерів, показано, що старіння під дією електричного поля навіть в умовах обмеження часткових розрядів є неминучим явищем. Для мінімізації впливу часткових розрядів та задля запобігання електричної ерозії полімеру запропоновано просту методику їх обмеження, яка передбачає зменшення області полімерної плівки, що підпадає під дію електричного поля та занурення зразків у діелектричну рідину з метою виключення можливості виникнення поверхневих розрядів. Розглядаються результати експерименту з перевірки гіпотези про оборотність змін, що відбуваються в полімерних плівках під впливом електричного поля в умовах обмеження часткових розрядів. Виявлено, що можливий такий вплив електричного поля протилежної полярності на полімерний діелектрик, що дозволяє частково відновити його погіршені ізоляційні властивості. Висунуто гіпотези щодо механізму явища регенерації за рахунок компенсації процесів накопичення об’ємних зарядів в полімері. Обговорюються можливі шляхи підвищення працездатності електротехнічних пристроїв, що мають в конструкції діелектрика полімерні плівки шляхом додаткової дії на діелектрик електричних полів протилежної полярності. Намічено шляхи подальших теоретичних та практичних досліджень електричного старіння та пробою твердих полімерних діелектриків.The paper is devoted to the electrical aging, destruction and breakdown of polymer dielectric films. The necessity of partial discharges’ limitation is explained because they are the main reason of film aging from electroerossion. It is shown that the necessary condition for the breakdown of a polymer film of micron thickness under the electric field influence is the formation of a cavity with a reduced density in a homogeneous polymer material, thus a pre-breakdown phenomena develops in this cavity. Possible ways of such a cavities’ formation under the influence of strong electric field are discussed. A technically simple and reliable method for partial discharges limiting is described. It implies diminution of polymeric volume, subjected to electric field influence, and limitation of surface discharges due to film samples’ immersion in dielectric liquid. The aim of study – is the hypothesis of destructive events in film polymer dielectric reversibility’s verification. The results of an experiment, testing the hypothesis of the reversibility of changes, occurring in polymer films under the influence of an electric field under the conditions of partial discharges limitation, are considered. It is established that the action of a constant electric field on film samples, at conditions when the influence of partial discharges have been minimized, reduces the longevity of polymer in the case of the subsequent action of the field with the same polarity, but their longevity increases by the electric field’s of opposite polarity action. Possible mechanisms of conditions’ formation for the polymeric dielectrics breakdown under the action of an electric field (at conditions of partial discharges suppression) are discussed. Certain ways of increasing the efficiency and reliability of electrical devices that have polymer films as a dielectric are proposed. The further researches area is outlined

Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2