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

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

Measurement of charged and neutral current e-p deep inelastic scattering cross sections at high Q2

Deep inelastic e-p scattering has been studied in both the charged current (CC) and neutral current (NC) reactions at momentum transfers squared Q2 above 400 GeV2 using the ZEUS detector at the HERA ep collider. The CC and NC total cross sections, the NC to CC cross section ratio, and the differential cross sections d/dQ2 are presented. From the Q2 dependence of the CC cross section, the mass term in the CC propagator is determined to be MW=76 16 13 GeV. © 1995 The American Physical Society

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

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

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of x and Q2 using the ZEUS detector. The evolution of the scaled momentum, xp, with Q2, in the range 10 to 1280 GeV2, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of Q2. © 1997 Elsevier Science B.V

Measurement of the t Distribution in Diffractive Photoproduction at HERA

Photon diffractive dissociation, γp → Xp, has been studied at HERA with the ZEUS detector using ep interactions where the virtuality Q2 of the exchanged photon is smaller than 0.02 GeV2. The squared four-momentum t exchanged at the proton vertex was determined in the range 0.073 \u3c \t\ \u3c 0.40 GeV2 by measuring the scattered proton in the ZEUS Leading Proton Spectrometer. In the photonproton centre-of-mass energy interval 176 \u3c W \u3c 225 GeV and for masses of the dissociated photon system 4 \u3c Mx \u3c 32 GeV, the t distribution has an exponential shape, dN/d\t\ ∝ exp (-b\t\), with a slope parameter b = 6.8 ± 0.9 (stat.) +1.2-1.1 (syst.) GeV-2

Inclusive transverse momentum distributions of charged particles in diffractive and non-diffractive photoproduction at HERA

Inclusive transverse momentum spectra of charged particles in photoproduction events in the laboratory pseudorapidity range -1.2\u3cη\u3c1.4 have been measured up to pT=8 GeV usign the ZEUS detector. Diffractive and non-diffractive reactions have been selected with an average γp centre of mass (c.m.) energy of 〈W〉=180 GeV. For diffractive reactions, the pT spectra of the photon dissociation events have been measured in two intervals of the dissociated photon mass with mean values 〈MX〉=5 GeV and 10 GeV. The inclusive transverse momentum spectra fall exponentially in the low pT region. The non-diffractive data show a pronounced high pT tail departing from the exponential shape. The pT distributions are compared to lower energy photoproduction data and to hadron-hadron collisions at a similar c.m. energy. The data are also compared to the results of a next-to-leading order QCD calculation. © 1995 Springer-Verlag

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