A méhen belüli növekedési visszamaradás genetikai háttere; kölcsönhatás egyéb etiológiai faktorokkal

It has been recognized that Intrauterine Growth Restriction (IUGR) is commonly due to placental dysfunction associated with both genetic and environmental factors. Nonetheless, the molecular mechanism of IUGR remains largely unexplored. IUGR is more common with maternal age around 20 years, and above 35 years. IUGR is also predicted by a subnormal gestational weight gain in the mother. Placental IGF-II and IGFBP-3 gene activities are both higher in IUGR fetuses compared to normal fetuses. This suggests a possible relationship between IUGR in the fetus and chronic diseases in the subsequent adult. Placental IGF-II gene activity is also higher in male compared to female IUGR fetuses. This may be explained by differences in gender-related development of non-specific body characteristics. Umbilical cord glucose and insulin concentrations are both significantly lower in IUGR when compared to normal fetuses. In placental samples obtained from IUGR pregnancies, the antiapoptotic Bcl-2 gene is underexpressed compared to normal pregnancies. In contrast, activity by the proapoptotic Bax gene is not significantly different in IUGR compared to normal pregnancies. Thus, the enhanced apoptotic activity found in IUGR can be explained by a decreased Bcl-2 gene activity and not through increased stimulation by the Bax gene. There is also a decreased activity of the 11-β-hydroxysteroid dehydrogenase 2 gene in IUGR compared to normal pregnancy. The decreased activity of this gene results in a dysfunctional placental barrier, leading to impaired placental defense against maternal glucocorticoids. Maternal glucocorticoids play an important role in the development of fetal programming in a fashion similar to analogous effects by IGF-II and IGFBP-3. Unopposed maternal glucocorticoid exposure can predict an increased propensity for several forms of chronic diseases in adult life. This decrease in gene activity of the 11-β-hydroxysteroid dehydrogenase 2 gene becomes detectable only after gestational week 33. The activity of this gene is also decreased in cases of fetal asphyxia associated with IUGR

Szemcsés anyagok dinamikai folyamatainak kísérleti vizsgálata = Experimental studies of dynamical processes in granular materials

A szemcsés anyagok alapvető áramlási tulajdonságait vizsgálva javaslatot tettünk a lejtőn megfigyelhető homogén áramlásokra vonatkozó ún. folyási törvény módosított alakjára, mely a kísérleti adatok jobb skálázását adja. Megmutattuk, hogy a különböző anyagokra mért folyási törvény meredeksége szisztematikusan nő a rézsűszög növelésével. Meghatároztuk a lejtőn megfigyelhető áramlás különböző módusait, és a homogén áramlás instabilitását vizsgálva megmutattuk, hogy a szemcsés anyag effektív súrlódása a nyírás növelésével először (sűrűbb áramlásnál) növekszik, majd ez a trend megfordul és (az anyag nyírás hatására történő ritkulásával párhuzamosan) csökkenni kezd. Meghatároztuk a szemcsés rétegbe bepréselt légzárvány alapvető dinamikai tulajdonságait. A lassú nyírásnak kitett szemcsés anyagban megfigyelhető nyírási lokalizáció geometriai tulajdonságait vizsgálva megmutattuk, hogy különböző súrlódási együtthatójú rétegekből álló szemcsés közegben a nyírási zóna a rétegek határán irányt változtat, mely jelenség párhuzamba állítható a fénytörés jelenségével. | The basic properties of granular flows were investigated experimentally. We have proposed a modified flow rule for granular flows on an inclined plane, which provides better scaling of the experimental data. Investigating various materials we have shown, that the slope of the flow rule increases systematically with increasing angle of repose. We have determined the various flow regimes of inclined plane flows. By carefully analyzing the instabilities of homogeneous flows we have shown that the effective friction of the granular material (for dense flows) increases with increasing shear rate, but above a certain shear rate this trend turns over and (together with decreasing density) the effective friction starts to decrease. We have determined the basic dynamical properties of air inclusions pressed into a granular layer. Geometrical properties of shear localization in slowly sheared granular materials were also studied. We have shown that in layered granular materials where the layers have different effective frictions, the shear zones are refracted at the layer boundaries, analogously to light refraction

High speed imaging of traveling waves in a granular material during silo discharge

We report experimental observations of sound waves in a granular material during resonant silo discharge called silo music. The grain motion was tracked by high speed imaging while the resonance of the silo was detected by accelerometers and acoustic methods. The grains do not oscillate in phase at neighboring vertical locations, but information propagates upward in this system in the form of sound waves. We show that the wave velocity is not constant throughout the silo, but considerably increases towards the lower end of the system, suggesting increased pressure in this region, where the flow changes from cylindrical to converging flow. In the upper part of the silo the wave velocity matches the sound velocity measured in the same material when standing (in the absence of flow). Grain oscillations show a stick-slip character only in the upper part of the silo.Comment: 5 pages, 5 figures, accepted to Phys. Rev.

Heaping, Secondary Flows and Broken Symmetry in Flows of Elongated Granular Particles

In this paper we report experiments where we shear granular rods in split-bottom geometries, and find that a significant heap of height of least 40% of the filling height can form at the particle surface. We show that heaping is caused by a significant secondary flow, absent for spherical particles. Flow reversal transiently reverses the secondary flow, leading to a quick collapse and slower regeneration of the heap. We present a symmetry argument and experimental data that show that the generation of the secondary flow is driven by a misalignment of the mean particle orientation with the streamlines of the flow. This general mechanism is expected to be important in all flows of sufficiently anisometric grains.Comment: Accepted for Soft Matte

Effects of grain shape on packing and dilatancy of sheared granular materials

Granular material exposed to shear shows a variety of unique phenomena: Reynolds dilatancy, positional order and orientational order effects may compete in the shear zone. We study granular packings consisting of macroscopic prolate, oblate and spherical grains and compare their behaviour. X-ray tomography is used to determine the particle positions and orientations in a cylindrical split bottom shear cell. Packing densities and the arrangements of individual particles in the shear zone are evaluated. For anisometric particles, we observe the competition of two opposite effects. One the one hand, the sheared granulate is dilated, but on the other hand the particles reorient and align with respect to the streamlines. Even though aligned cylinders in principle may achieve higher packing densities, this alignment compensates for the effect of dilatancy only partially. The complex rearrangements lead to a depression of the surface above the well oriented region while neigbouring parts still show the effect of dilation in the form of heaps. For grains with isotropic shapes, the surface remains rather flat. Perfect monodisperse spheres crystallize in the shear zone, whereby positional order partially overcompensates dilatancy effects. However, already slight deviations from the ideal monodisperse sphere shape inhibit crystallization.Comment: 12 pages, 13 figures, accepted in Soft Matte

Rapid granular flows on a rough incline: phase diagram, gas transition, and effects of air drag

We report experiments on the overall phase diagram of granular flows on an incline with emphasis on high inclination angles where the mean layer velocity approaches the terminal velocity of a single particle free falling in air. The granular flow was characterized by measurements of the surface velocity, the average layer height, and the mean density of the layer as functions of the hopper opening, the plane inclination angle and the downstream distance x of the flow. At high inclination angles the flow does not reach an x-invariant steady state over the length of the inclined plane. For low volume flow rates, a transition was detected between dense and very dilute (gas) flow regimes. We show using a vacuum flow channel that air did not qualitatively change the phase diagram and did not quantitatively modify mean flow velocities of the granular layer except for small changes in the very dilute gas-like phase.Comment: 10 pages, 16 figures, accepted to Phys. Rev.

Nem-egyensúlyi morfológiák dinamikája = Dynamics of non-equilibrium morphologies

Elméleti módszereket és számítógépes szimulációkat használtunk az elsőrendű fázisátalakulásokhoz kapcsolódó morfológiák képződési dinamikájának vizsgálatára. Ennek keretében sűrűség funkcionál- és fázismező modelleket dolgoztunk ki a túlhűtött egy- és többkomponensű folyadékokban, ill. oxidüvegekben történő homogén nukleáció leírására. A modellparaméterek rögzítése atomisztikus szimulációkból ill. kísérletekből származó felületi jellemzők segítségével történt. A nukleációs gát magasságára vonatkozó paraméter-mentes jóslataink jól egyeznek az atomisztikus szimulációkból ill. kísérletekből származó eredményekkel. Fázismező elméletet dolgoztunk ki az egyensúlytól távoli, binér polikristályos megszilárdulás modellezésére két- és három dimenzióban. Ennek segítségével olyan komplex, a csíraképződés és növekedés kölcsönhatásával kialakuló morfológiák képződését írtunk le elsőként, mint a rendezetlen dendrites, szferolitos, és kristálykéve alakzatoké. Alacsony dimenziós, különböző kémiai összetevőket tartalmazó rendszereket vizsgáltunk, ahol a részecskék diffúziós mozgást végeznek és közöttük kémiai reakciók jöhetnek létre (reakció-diffúzió modellek). A rendszerben lezajló nem-egyensúlyi fázisátalakulást a mintába befagyott rendezetlenség jelenlétében tanulmányoztuk renormálási csoport módszerrel és numerikus szimulációval. Megállapítottuk, hogy kellően erős rendezetlenség mellett az átalakulás egy ún. végtelenül rendezetlen fix-ponttal írható le. | We applied theoretical methods and computer simulations to investigate morphologies forming during first order transformations and their dynamics. Along these lines, density functional and phase field models have been developed for describing homogeneous crystal nucleation in undercooled one- and two component liquids, and oxide glasses. The model parameters have been fixed using interfacial properties from atomistic simulations or experiment. Our parameter free predictions for the height of the nucleation barrier are in a good agreement with results from atomistic simulations or experiment. We have worked out a phase field theory for modeling polycrystalline solidification in binary alloys far-from-equilibrium in two and three dimensions. Using this approach, we were able to describe the formation of complex morphologies appearing via interacting nucleation and growth, such as the disordered dendritic, spherulitic, and crystal sheaf structures. We have studied multi-component low dimensional systems in which the particles show diffusive motion and chemical reactions take place between them (reaction-diffusion problems). In the presence of quenched disorder we have investigated the properties of non-equilibrium phase transitions by renormalization group method and by numerical simulations. We have shown that for strong enough disorder the transition is controlled by a so called infinite disorder fixed point