Jump at the onset of saltation

We reveal a discontinuous transition in the saturated flux for aeolian saltation by simulating explicitly particle motion in turbulent flow. The discontinuity is followed by a coexistence interval with two metastable solutions. The modification of the wind profile due to momentum exchange exhibits a second maximum at high shear strength. The saturated flux depends on the strength of the wind as $q_s=q_0+A(u_*-u_t)(u_*^2+u_t^2)$

Гнійно-септична патологія заочеревинного простору: досвід діагностики та лікування

The aim of the work: to analyze the results of treatment of patients with abscesses of the retroperitoneal area, optimization of diagnosing algorithm and adequate surgical treatment. Materials and Methods. It was analyzed the results of treatment of 67 patients (40 males and 27 females, aged from 26 to 77 years old) with retroperitoneal abscesses, who were hospitalized in the clinic of General Surgery of Ternopil State Medical University in a period of 1985–2017 years. Results and Discussion. Primary purulent process in 10 patients was in perirenal fat, in 33 patients – in fat tissues around the colon, and in 24 patients – in retroperitoneal fat. It was found that diagnostic mistakes were fixed in 29 patients (43.2 %). That is why it was concluded, that the obligatory procedure for the topical diagnosis of retroperitoneal space’s abscesses should be the early computed tomography with intravenous contrast media. All patients had surgery. During the surgical treatment of retroperitoneal abscesses, it was tested and introduced into a clinical practice differential approach to choose the surgical access and drainage determined by its topography-anatomical location and the spread of purulent-septic process. Because of approved treatment, 58 patients recovered. 9 patients (13.4 %) passed away.Проанализированы результаты лечения 67 пациентов с гнойными поражениями забрюшинного пространства. Первичный гнойный процесс у 10 больных локализовался околопочечной клетчатке, в 33 – в околоободочном клетчатом пространстве, и у 24 пациентов – в собственно забрюшинной клетчатке. У 29 пациентов (43,2 %) имели место диагностические ошибки. Сделан вывод что, обязательным методом топической диагностики гнойников забрюшинного пространства должна быть ранняя компьютерная томография с внутривенным контрастированием. Все больные прооперированы. При хирургическом лечении гнойников забрюшинного пространства разработан дифференцированный подход к выбору доступа и дренирования в зависимости от их топографо-анатомической локализации и распространения процесса. В результате проведенного лечения выздоровели 58 больных. Умерли 9 (13,4 %) пациентов.У статті проаналізовано результати лікування 67 пацієнтів із гнійними ураженнями заочеревинного простору. Первинний гнійний процес у 10 хворих локалізувався в принирковій клітковині, у 33 – в навколоободовому клітковинному просторі, і у 24 пацієнтів – у власне заочеревинній клітковині. У 29 пацієнтів (43,2 %) мали місце діагностичні помилки. Зроблено висновок, що обов’язковим методом топічної діагностики гнійників заочеревинного простору має бути рання комп’ютерна томографія із внутрішньовенним контрастуванням. Усім хворим виконано операційні втручання. При хірургічному лікуванні гнійників заочеревинного простору розроблено диференційований підхід до вибору доступу та дренування залежно від їх топографо-анатомічної локалізації та поширення процесу. В результаті проведеного лікування видужали 58 хворих, померли 9 (13,4 %) пацієнтів

Numerical simulation of turbulent sediment transport, from bed load to saltation

Sediment transport is studied as a function of the grain to fluid density ratio using two phase numerical sim- ulations based on a discrete element method (DEM) for particles coupled to a continuum Reynolds averaged description of hydrodynamics. At a density ratio close to unity (typically under water), vertical velocities are so small that sediment transport occurs in a thin layer at the surface of the static bed, and is called bed load. Steady, or 'saturated' transport is reached when the fluid borne shear stress at the interface between the mobile grains and the static grains is reduced to its threshold value. The number of grains transported per unit surface is therefore limited by the flux of horizontal momentum towards the surface. However, the fluid velocity in the transport layer remains almost undisturbed so that the mean grain velocity scales with the shear velocity u\ast. At large density ratio (typically in air), the vertical velocities are large enough to make the transport layer wide and dilute. Sediment transport is then called saltation. In this case, particles are able to eject others when they collide with the granular bed, a process called splash. The number of grains transported per unit surface is selected by the balance between erosion and deposition and saturation is reached when one grain is statistically replaced by exactly one grain after a collision, which has the consequence that the mean grain velocity remains independent of u\ast. The influence of the density ratio is systematically studied to reveal the transition between these two transport regimes. Based on the mechanisms identified in the steady case, we discuss the transient of saturation of sediment transport and in particular the saturation time and length. Finally, we investigate the exchange of particles between the mobile and static phases and we determine the exchange time of particles.Comment: 17 pages, 14 figures, submitted to Physics of Fluid

Germination of seeds and emergence of seedlings of Agropyron repens (L.) Beauv.

RESP-644

A SURVEY OF WILD OATS (AVENA FATUA AND A. LUDOVICIANA) IN ENGLAND AND WALES IN 1951

RESP-340