Numerical analysis of the influence of vortex acoustic flows on the efficiency of agglomeration

It is known and experimentally proven many times that ultrasonic vibrations in the gas phase contribute to the appearance of stationary acoustic flows. Since the flows are caused by energy losses during absorption of oscillations, and they do work against the frictional forces that cause this absorption, then these flows have a vortex character. According to numerous studies and developments in the field of inertial dust separation, at a centripetal acceleration of 10 m/s2 or more, local compaction of particles is observed near the periphery of the vortex flow. Due to this, particles are captured in existing devices based on the inertial dust separation principle. In this regard, the article presents the results of theoretical studies of the potential for the use of acoustic flows for a local increase in the concentration of particles and, consequently, an increase in the efficiency of agglomeration. A model of the influence of vortex acoustic flows on the efficiency of agglomeration is proposed. As a result of the numerical analysis of the model, the fundamental possibility of a significant (more than 4 times) increase in the efficiency of ultrasonic agglomeration of submicron particles due to the formation of vortex acoustic flows in the resonant intervals was revealed.

Chromatin Fiber Folding Represses Transcription and Loop Extrusion in Quiescent Cells

Determining the conformation of chromatin in cells at the nucleosome level and its relationship to cellular processes has been a central challenge in biology. We show that in quiescent yeast, widespread transcriptional repression coincides with the local compaction of chromatin fibers into structures that are less condensed and more heteromorphic than canonical 30-nanometer forms. Acetylation or substitution of H4 tail residues decompacts fibers and leads to global transcriptional de-repression. Fiber decompaction also increases the rate of loop extrusion by condensin. These findings establish a role for H4 tail-dependent local chromatin fiber folding in regulating transcription and loop extrusion in cells. They also demonstrate the physiological relevance of canonical chromatin fiber folding mechanisms even in the absence of regular 30-nanometer structures.

Hemodynamic differences by increasing low profile visualized intraluminal support (LVIS) stent local compaction across intracranial aneurysm orifice

Background The Low-profile Visualized Intraluminal Support device (LVIS) has been successfully used to treat cerebral aneurysm, and the push-pull technique has been used clinically to compact the stent across aneurysm orifice. Our aim was to exhibit the hemodynamic effect of the compacted LVIS stent. Methods Two patient-specific aneurysm models were constructed from three-dimensional angiographic images. The uniform LVIS stent, compacted LVIS and Pipeline Embolization Device (PED) with or without coil embolization were virtually deployed into aneurysm models to perform hemodynamic analysis. Intra-aneurysmal flow parameters were calculated to assess hemodynamic differences among different models. Results The compacted LVIS had the highest metal coverage across the aneurysm orifice (case 1, 46.37%; case 2, 67.01%). However, the PED achieved the highest pore density (case 1, 19.56 pores/mm2; case 2, 18.07 pores/mm2). The compacted LVIS produced a much higher intra-aneurysmal flow reduction than the uniform LVIS. The PED showed a higher intra-aneurysmal flow reduction than the compacted LVIS in case 1, but the results were comparable in case 2. After stent placement, the intra-aneurysmal flow was further reduced as subsequent coil embolization. The compacted LVIS stent with coils produced a similar reduction in intra-aneurysmal flow to that of the PED. Conclusions The combined characteristics of stent metal coverage and pore density should be considered when assessing the flow diversion effects of stents. More intra-aneurysmal flow reductions could be introduced by compacted LVIS stent than the uniform one. Compared with PED, compacted LVIS stent may exhibit a flow-diverting effect comparable to that of the PED.

High-density micro- and nanogranular ceramics. Transition of open pores to closed ones. Part 1. Preparation of powder, molding material, molding

An explanation of the processes that occur when producing high-density micro- and nanogranular ceramics without the use of external pressure is proposed on the basis of data accumulated in the literature. It is known that pore growth begins after the beginning of the transition of open pores to closed ones, which begins at about 30 % open porosity. It is necessary to maintain open pores to the maximum possible total density of sintered ceramics. This can be achieved by slowing down the formation of areas of local compaction (unequal density of samples) by various methods. Preservation of open pores is facilitated by such a decrease in the rate of shrinkage at which a self-consistent compaction of the local seals and the less dense zones surrounding them is realized. Such a regime can be implemented in different ways: by reducing the activity of powder particles (preliminary heat treatment of the powder, preliminary low-temperature sintering ― presintering), the use of additives that slow down shrinkage (obtaining transparent ceramics without external pressure), at the stages of preparing the molding material, molding blanks, removing the binder by adjusting the heating rate of the sample (sintering with an adjustable rate of shrinkage), prolonged sintering at a relatively low temperature in 2-stage sintering. This is part 1 of a series of 3 articles. Ref. 61.

The State of the Art and Challenges in Geomechanical Modeling of Injector Wells: A Review Paper

Fluid injection is a common practice in the oil and gas industry found in many applications such as waterflooding and disposal of produced fluids. Maintaining high injection rates is crucial to guarantee the economic success of these projects; however, there are geomechanical risks and difficulties involved in this process that may threat the viability of fluid injection projects. Near wellbore reduction of permeability due to pore plugging, formation failure, out of zone injection, sand production, and local compaction are challenging the effectiveness of the injection process. Due to these complications, modeling and simulation has been used as an effective tool to assess injectors' performance; however, different problems have yet to be addressed. In this paper, we review some of these challenges and the solutions that have been proposed as a primary step to understand mechanisms affecting well performance.

Nuclear constriction segregates mobile nuclear proteins away from chromatin

As a cell squeezes its nucleus through adjacent tissue, penetrates a basement membrane, or enters a small blood capillary, chromatin density and nuclear factors could in principle be physically perturbed. Here, in cancer cell migration through rigid micropores and in passive pulling into micropipettes, local compaction of chromatin is observed coincident with depletion of mobile factors. Heterochromatin/euchromatin was previously estimated from molecular mobility measurements to occupy a volume fraction f of roughly two-thirds of the nuclear volume, but based on the relative intensity of DNA and histones in several cancer cell lines drawn into narrow constrictions, f can easily increase locally to nearly 100%. By contrast, mobile proteins in the nucleus, including a dozen that function as DNA repair proteins (e.g., BRCA1, 53BP1) or nucleases (e.g., Cas9, FokI), are depleted within the constriction, approaching 0%. Such losses—compounded by the occasional rupture of the nuclear envelope—can have important functional consequences. Studies of a nuclease that targets a locus in chromosome-1 indeed show that constricted migration delays DNA damage.

The State of the Art and Challenges in Geomechanical Modeling of Injector Wells: A Review Paper

Fluid injection is a common practice in the Oil and Gas industry found in many applications such as waterflooding and disposal of produced fluids. Maintaining high injection rates is crucial to guarantee the economic success of these projects; however, there are geomechanical risks and difficulties involved in this process that may threat the viability of fluid injection projects. Near wellbore reduction of permeability due to pore plugging, formation failure, out of zone injection, sand production, and local compaction are challenging the effectiveness of the injection process. Due to these complications, modeling and simulation has been used as an effective tool to assess injectors’ performance, however, different problems have yet be addressed. In this paper, we review some of these challenges and the solutions that have been proposed as a primary step to understand mechanisms affecting well performance.

Axial contraction and short-range compaction of chromatin synergistically promote mitotic chromosome condensation

The segregation of eukaryotic chromosomes during mitosis requires their extensive folding into units of manageable size for the mitotic spindle. Here, we report on how phosphorylation at serine 10 of histone H3 (H3 S10) contributes to this process. Using a fluorescence-based assay to study local compaction of the chromatin fiber in living yeast cells, we show that chromosome condensation entails two temporally and mechanistically distinct processes. Initially, nucleosome-nucleosome interaction triggered by H3 S10 phosphorylation and deacetylation of histone H4 promote short-range compaction of chromatin during early anaphase. Independently, condensin mediates the axial contraction of chromosome arms, a process peaking later in anaphase. Whereas defects in chromatin compaction have no observable effect on axial contraction and condensin inactivation does not affect short-range chromatin compaction, inactivation of both pathways causes synergistic defects in chromosome segregation and cell viability. Furthermore, both pathways rely at least partially on the deacetylase Hst2, suggesting that this protein helps coordinating chromatin compaction and axial contraction to properly shape mitotic chromosomes.