Equal Pressure Research Articles

What happens to myocardial work after transcatheter aortic valve replacement?

Abstract Background Novel echocardiographic speckle-tracking techniques such as global longitudinal strain (GLS) and myocardial work (MW) have been used in many cardiac conditions for myocardial functional assessment. In severe aortic stenosis (SAS) this evaluation is more challenging since left ventricular (LV) systolic pressure (SP) does not equal non-invasive systolic pressure (NISP) owing to the fixed obstruction of a stenotic valve. Few studies have evaluated the immediate impact of transcatheter aortic valve replacement (TAVR) in patients with SAS on GLS and MW parameters. Aim To assess differences in GLS and MW parameters values, pre- and post-TAVR, in patients with SAS. Methods One-single center retrospective analysis of consecutive patients with SAS submitted to TAVR, between January 2018 and December 2021, who performed transthoracic echocardiography (TTE) bfore and after the procedure (within the same hospital admission). NISP was determined at TTE performance. For pre-TAVR assessment, corrected SP by adding the mean aortic gradient was introduced in the software for MW parameters calculations, namely global work index (GWI), global constructive work (GCW), global wasted work (GWW) and global work efficiency (GWE). Continuous variables were assessed for normality using Shapiro-Wilk test. Normal variables were represented as mean and standard deviation (SD) and compared using a paired-sample t-test. Non-normal variables were represented as median and interquartile range (IQR) and compared using a Wilcoxon-Signed rank test. Statistical significance was defined as two-sided p value < 0.05. All statistical analysis were done with JASP (version 0.16.0.0). Results 50 patients entered the primary analysis. Mean age was 82 years and 56% were female sex. Before TAVR, mean aortic gradient was 49 ± 15 mmHg, mean aortic valve area was 0.76 ± 0.22 cm2 and LV ejection fraction was 52 ± 11%. Table 1 represents the mean GLS and MW parameters values pre- and post-TAVR from our study population. Patients had significant lower values of GWI (1764.4 ± 704.9 vs. 1197 ± 372.6, p < 0.001) and GCW (2309.5 ± 810.9 vs. 1627.8 ± 488.5, p < 0.001) post-TAVR when compared with the pre-TAVR values. There were no significant differences in GLS (p=0.837), GWW (p=0.055) and GWE (P=0.438) values pre- and post-TAVR. Conclusion In our study population, GLS was impaired in patients with SAS and it remained identical after TAVR, suggesting un underlying myopathy that does not reverse immediately after the procedure. Furthermore, MW as assessed by GWI was significantly reduced after TAVR, which may reflect the reduced workload needed after the procedure due to acute afterload reduction. Further studies with longer follow-up are needed to acess the long term impact of TAVR in MW. TAVR MW

Effects of Different Blood Flow Restriction Training Modes on Body Composition and Maximal Strength of Untrained Individuals.

The objective of this study was to examine the impacts of absolute cuff pressure blood flow restriction (A-BFR) training and incremental cuff pressure blood flow restriction (I-BFR) training, under equal cuff pressures, on body composition and maximal strength among untrained adults. Additionally, we aimed to compare these effects with those observed in high-load resistance training (HL-RT). Thirty-three adults without prior professional sports or resistance training experience were recruited and randomly assigned to three groups (n = 11 per group) for an 8-week training program, held three times weekly. The A-BFR group trained with a 20% 1RM load and a cuff occlusion pressure set at 190 mmHg. The I-BFR group initiated training with an occlusion pressure of 160 mmHg, which incrementally increased by 20 mmHg every two weeks, with other conditions mirroring those of the A-BFR group. The HL-RT group trained with a 70% 1RM load. All three groups demonstrated a statistically significant improvement in lower-body maximal strength (p < 0.01), with no significant differences observed among the groups (p > 0.05). A notable increase in left-leg muscle mass was seen across all groups (p < 0.05). However, total muscle mass, right-leg muscle mass, fat-free mass, BMI, bone mineral density, and bone mineral content remained relatively unchanged (p > 0.05), with no significant differences among the groups (p > 0.05). Only the HL-RT group exhibited a significant increase in left-leg thigh circumference (p < 0.05), while right-leg thigh circumference remained stable (p > 0.05), with no significant intergroup differences (p > 0.05). While A-BFR and I-BFR did not yield statistically significant differences in overall training outcomes, A-BFR demonstrated a slightly stronger potential. A-BFR and I-BFR achieved comparable gains in muscle strength and improvements in body composition to those seen with HL-RT. However, HL-RT demonstrated more significant improvements in leg circumference.

Smooth Muscle Mechanosensitivity Generates and Maintains Pressure Gradients Across the Intestine.

The gut, the ureter, or the Fallopian tube all transport biological fluids by generating trains of propagating smooth muscle constrictions collectively known as peristalsis. These tubes connect body compartments at different pressures. We extend here Poiseuille's experiments on liquid flow in inert tubes to an active, mechanosensitive tube: the intestine. We use as a miniature myogenic peristaltic pump model, the fetal chicken gut, and measured the flow and contractile wave propagation as a function of the initially applied pressures and pressure gradients. We dissect the molecular pathways of smooth muscle mechanosensitivity by measuring the force generated by gut rings in different pharmacological conditions. We demonstrate that smooth muscle contractions in response to stretch or pressure is mediated by L-type Ca2+ channels and IP3 receptors. We show that this positive-feedback mechanosensitive behavior can spontaneously generate pressure gradients across gut segments initially subject to equal pressure; this same mechanism tends to stabilize initially applied pressure gradients; it can act jointly or compete with the pressure gradient induced by directional peristaltic waves. We demonstrate that high pressure differentials can reverse the physiological propagation direction of contractile waves imparted by interstitial cell of Cajal pacemaker activity. We find that flow rate increases with tube length, but that the maximum pressure differential generated depends solely on smooth muscle contractile force and on the initial resting pressure applied inside the organ. We provide fundamental mechanical and hydrodynamic insight into the myogenic mechanisms of transport in the gastrointestinal tract. We scale up our results to other human peristaltic organs and discuss their implications for pathophysiology of intestinal obstruction, vesicoureteral reflux and endometriosis.

Modulating the Biliverdin Reductase (BVR)/ERK1/2 Axis to Attenuate Oxidative Stress in Rat Arterial Rings

Background: Biliverdin reductase (BVR) plays a central role in bile pigment metabolism by reducing biliverdin (BV) to bilirubin (BR), a potent antioxidant that scavenges reactive oxygen species (ROS) under normal and pathological conditions. Elevated oxidative stress activates extracellular signal-regulated protein kinases 1/2 (ERK1/2) signaling, which strongly interacts with BVR’s C and D motifs, forming the BVR/ERK1/2 axis. In pathological states, increased ERK1/2 activity inhibits BVR’s ability to convert BV to BR, exacerbating oxidative damage and contributing to cardiovascular disease. Therefore, the interaction between BVR and ERK1/2 is critical in modulating oxidative stress. Objectives: This study aimed to evaluate the effects of BR and the ERK1/2 inhibitor PD-98059, both individually and in combination, on ROS levels, ERK1/2 activity, and vascular responses under normoxic and hypoxia-reoxygenation (H-R) injury conditions. Methods: Aortic rings from rats were subjected to equal distending pressure after oxidative stress induction using 22'-Azobis (2-amidinopropane) dihydrochloride (ABAP) in an organ bath. Different doses of BR were administered in combination with the ERK1/2 inhibitor PD-98059 to assess their impact on ROS depletion, vascular relaxation, and maximal effect (Emax). Results: The combination of BR and PD-98059 significantly enhanced aortic relaxation and Emax under both normoxic and H/R conditions compared to either treatment alone. Inhibiting ERK1/2 with PD-98059 appeared to upregulate BVR activity, increasing BR synthesis and reducing oxidative damage in aortic rings. Conclusions: Biliverdin reductase plays a vital role in defending against oxidative stress and endothelial dysfunction through its dual-specificity kinase activity and interaction with ERK1/2. ERK1/2 inhibition further enhances BR’s ROS-scavenging ability and vascular protective effects. Targeting the interaction between BVR and ERK1/2 holds potential as an effective therapeutic strategy for conditions characterized by excessive ROS levels, such as cardiovascular diseases.

Multi focus acoustic field generation using Dammann gratings for phased array transducers

Phased array transducers can shape acoustic fields for versatile manipulation; however, generating multiple focal points typically involves complex optimization. This study demonstrates that Dammann gratings – binary phase gratings originally used in optics to generate equal-intensity spot arrays – can be adapted for acoustics to create multiple equal-strength focal points with a phased array transducer. The transducer elements were assigned phases of 0 or π, based on a Dammann grating defined by its transition points. Simulations show that simple gratings with two transition points can generate fields with up to 12 focal points of nearly equal acoustic pressures. Compared to conventional multi-focus phase optimization techniques, the Dammann grating approach offers computational efficiency and facile reconfiguration of the focal pattern by adjusting the grating hologram. We tested this approach in numerical simulations with a hypothetical high-resolution array, achieving up to 12 focal points, and validated the efficacy of the Dammann grating in a conventional 16x16 transducer array through both simulations and experiments. This comparison highlights that while Dammann gratings effectively generate multi-focus fields, the recreation ability of these gratings in a conventional array shows a lower resolution than the hypothetical array. This study underlines the potential of adapting binary phase functions from photonics to enhance ultrasound-based acoustic manipulation for tasks requiring parallel actuation at multiple points.

A Multichamber Pulsating-Flow Device With Optimized Spatial Shear Stress and Pressure for Endothelial Cell Testing.

Design and analysis are presented for a new device to test the response of endothelial cells to the simultaneous action of cyclic shear stresses and pressure fluctuations. The design consists of four pulsatile-flow chambers connected in series, where shear stress is identical in all four chambers and pressure amplitude decreases in successive chambers. Each flow chamber is bounded above and below by two parallel plates separated by a small gap. The design of the chamber planform must ensure that cells within the testing region experience spatially uniform time-periodic shear stress. For conditions typically encountered in applications, the viscous unsteady flow exhibits order-unity values of the associated Womersley number. The corresponding solution to the unsteady lubrication problem, with general nonsinusoidal flowrate, is formulated in terms of a stream function satisfying Laplace's equation, which can be integrated numerically to determine the spatial distribution of shear stresses for chambers of general planform. The results are used to optimize the design of a device with a hexagonal planform. Accompanying experiments using particle tracking velocimetry (PTV) in a fabricated chamber were conducted to validate theoretical predictions. Pressure readings indicate that intrachamber pressure variations associated with viscous pressure losses and acoustic fluctuations are relatively small, so that all cells in a given testing region experience nearly equal pressure forces.

Hydrogen and Natural Gas in Pipeline Networks: A Comparative Energy Analysis

Abstract In this study, a Simscape model for the transmission and distribution pipeline network of natural gas, hydrogen blended into natural gas and pure hydrogen, is developed. The transmission consists of a 250 km pipelines with a diameter of 48 in and two gas compression stations. The distribution network serves six end users. Two simulations are conducted for each gas: the first maintaining equal operational pressure in the transmission pipeline, while the second ensuring equal energy content at the final users by modifying the operational pressure. A comparative energy analysis is carried out to assess the gas mass flow rate, the thermal power delivered, the mechanical power required by compressors and the pressure losses along the pipeline.

Constrictive physiology is not present in all dogs with idiopathic chylothorax.

To determine whether subtotal pericardectomy affects recurrence and long-term outcomes in dogs with idiopathic chylothorax (IC). 12 client-owned dogs diagnosed with IC between July 26, 2016, and March 23, 2023. The diagnosis of constrictive physiology (CP) was established with cardiac catheterization and defined as elevated and equal diastolic pressures in all 4 cardiac chambers. Dogs were then entered into the constrictive physiology (CP) group or non-CP (NCP) group. All dogs received at least a thoracic duct ligation (TDL). The dogs in the CP group had a subtotal pericardectomy performed in addition to TDL. Repeated surgical interventions, recurrence, long-term outcomes, and survival times were recorded. 8 dogs were entered into the CP group and underwent TDL and subtotal pericardectomy. Four dogs were entered in the NCP group and underwent only a TDL. Four dogs in the CP group and 1 in the NCP group required multiple surgeries for recurrent chylothorax. The 1-, 2-, and 3-year disease-free rates were, respectively, 100%, 100%, and 50% for the NCP group and 87.5%, 72.9%, and 72.9% for the CP group (P = .935). The 1-, 2-, and 3-year survival rates were, respectively, 100%, 100%, and 100% for the NCP group and 87.5%, 72.9%, and 72.9% for the CP group (P = .317). Constrictive physiology should be evaluated by cardiac catheterization before surgical treatment of IC in dogs. If CP is not diagnosed, subtotal pericardectomy may not be required.

Effects of different masks on diaphragm motion in OSAS patients undergoing CPAP: results from an ultrasound-based proof of concept study.

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway narrowing or collapse during sleep. Continuous positive airway pressure (CPAP) remains the preferred treatment in selected patients and masks' choice plays an important role for subsequent respiratory events' reduction. It is known that oronasal masks are not as effective at opening the upper airway compared to nasal ones. Thus, the objective of this study was to investigate differences in US-assessed diaphragmatic excursion (DE) using oronasal vs. nasal CPAP masks. This observational study included 50 OSA patients presenting a moderate to severe apnea-hypopneaindex and requiring CPAP treatment. All participants received US evaluations on diaphragm motion during their oronasal and nasal CPAP trial at equal positive end-expiratory pressure level. The difference of DE switching mask during CPAP was assessed by using the non-parametric Wilcoxon signed-rank test. A statistically significant increase in US- assessed DE was found when shifting from oronasal to nasal mask (p-value < 0.01). Linear regression models revealed that increased neck circumference and more severe AHI were associated with decreased DE when shifting to an oronasal mask. This study evaluated the acute impact on US-assessed DE after changing CPAP route from oronasal to nasal mask. Our results suggest that the nasal type should be the more suitable option for most patients with OSA, especially those with higher nasal circumference. Diaphragmatic motion throughout US may become a practical tool to help in the choice of the fittest mask in patients undergoing CPAP.

Understanding Mass Transport at High Current Densities in an Industrial Scale PEM Electrolysis Test Cell - a Segmented Along-the-Channel Approach

Industrial PEM water electrolysis stack designs can suffer from an unevenly distributed water amount over the cell area. This can lead to performance differences and thermal hot spots due to the lack of reactant supply and poor thermal management. Undersupplied spots could also degrade more quickly [1,2]. Especially in the water flow direction, gradients are expected due to the water consumption and gas evolution and accumulation along the supply channels.To face these issues, we built up a segmented along the channel (AtC) PEM electrolysis test cell in industrial scale for locally-resolved investigations. The cell has a length of 30 cm at 2 cm cell width with a straight parallel flow field. To minimize transverse currents the cell is divided into 10 equal segments along the channels. The main focus of our investigation is locally-resolved electrochemical impedance spectroscopy (EIS). With a shunt resistor approach, it is feasible to measure the impedance of each segment and the mean cell in parallel. Additionally, it is possible to measure the current density and temperature distribution of the anodic bipolar plate highly resolved using 120 sensors over the cell length.With this test cell we want to understand mass transport processes along the channel in industrial scale. Diffusion and mass transport overpotentials are usually dominant at high current densities. To be able to face extreme conditions and investigate possible future operation points the cell was designed up to 10 A∙cm-2 (600 A absolute) and successfully tested. Furthermore, an operation of 10 bar differential and equal pressure is possible.Figure 1 shows the cell design (a), the mean cell polarization curve of the AtC cell (60 cm²) in comparison with measurements of the same setup in our 4 cm² test cell (b) and locally-resolved high frequency resistance (HFR) free EIS at 7 A∙cm-2 (c). It is noticeable, that the here used commercially available materials do not show high mass transport limitations, neither in the 4 cm² ISE-reference cell nor in the 60 cm² AtC cell. An increase of the slope of the polarization curve towards higher current densities remains out, see Figure 1 (b). Instead of this the slope of the polarization curve is constantly decreasing. This can not only be explained by the temperature increase of the catalyst-coated membrane (CCM) due to higher heat dissipation. Using EIS, we here can detect an additional electrochemical process at low frequencies of inductive type which is increasing with increasing current density. In the locally-resolved EIS in Figure 1 (c) the inductive process (positive imaginary values) is detectable as the so called “inductive loop”. This phenomenon has a negative resistance magnitude and therefore a beneficial impact on the cell performance. Inductive Loops are discussed in several electrochemical applications, like batteries and fuel cells [3,4]. Despite this, in PEM electrolysis this process has not been discussed yet. We could show that this phenomenon is reproducible and has an important impact on the cell performance and impedance-based performance analyses when operating at current densities > 1 A∙cm-2 [5].For diffusion analyses, the inductive loop is essential to be considered since both processes happen at similar frequencies. In Figure 1 (c) an increasing of the number of time constants at frequencies < 100 Hz is detectable towards the cell outlet (e.g. segment 9 and 10). These slow processes are most likely diffusion related.Our upcoming investigations will face locally-resolved measurements with varying structural parameters of porous transport layers (PTL) and CCMs with different anodic catalyst loadings to gain a better understanding of mass transport processes for future PEM electrolysis cells along the channel.Reference List:[1] IMMERZ, C., et al. Experimental characterization of inhomogeneity in current density and temperature distribution along a single-channel PEM water electrolysis cell. Electrochimica acta, 2018, 260. Jg., S. 582-588.[2] VERDIN, B., et al. Operando current mapping on PEM water electrolysis cells. Influence of mechanical stress. International Journal of Hydrogen Energy, 2017, 42. Jg., Nr. 41, S. 25848-25859.[3] KLOTZ, Dino. Negative capacitance or inductive loop?–A general assessment of a common low frequency impedance feature. Electrochemistry Communications, 2019, 98. Jg., S. 58-62.[4] GERLING, Christophe, et al. Experimental and Numerical Investigation of the Low-Frequency Inductive Features in Differential PEMFCs: Ionomer Humidification and Platinum Oxide Effects. Journal of The Electrochemical Society, 2023, 170. Jg., Nr. 1, S. 014504.[5] HENSLE, Niklas, et al. On the role of inductive loops at low frequencies in PEM electrolysis. Electrochemistry Communications, 2023, 155. Jg., S. 107585. Figure 1

(Invited) Stack Test Facility for PEM Water Electrolysis up to 400 Kilowatt and Lessons Learned at Stack Scale-up

A new type of energy system based on renewable energy sources and hydrogen technologies is put into operation at Forschungszentrum Jülich, Germany. The aim of the "Living Lab Energy Campus (LLEC)" project is testing and optimizing the systems interactions. Central components are wind power and PV systems, PEM electrolysis system, conditioning and subsequent gas transport in H2 and O2 pipelines, H2 storage in LOHC reactors and hydrogen use in combined heat and power plants.The PEM electrolysis system in Fig. 1, left, is an R&D test platform which was jointly configured by Forschungszentrum Jülich (IEK-14) and Greenlight Innovation Corp. and built by Greenlight. It offers a range of different operating modes and system configurations that will be studied embedded into the LLEC: Equal pressure or differential pressure anode/cathode up to 50 bar(g).Water circulation on anode and/or cathode side.Stack cabin with flexible connections for fluid inlets and outlets as well as electrical current. This makes it easy to connect and operate different stacks (also from other manufacturers).Automated system operation, simulation of load profiles (e.g. wind/PV). The system is CE-certified and can run continuously under automatic control. Critical system conditions, such as exceeding the H2 concentration limit (currently set at 30 % LEL) in the O2 gas flow, immediately initiate an emergency shutdown program. In the emergency shutdown program, the power supply unit is first switched off and the pressure on the anode and cathode side is reduced to ambient pressure. The reason for the fault leading to the shutdown is stored in the system control unit and can be called up. In addition, all measured values and states of the installed sensors and actuators are recorded by the system control unit and stored with an adjustable time resolution. The measured values can be used to monitor the system behavior and detect problems at an early stage, but also to characterize and balance the overall system, system components and the stack.For generating large amounts of hydrogen within the LLEC project, IEK-14 initiated the development of a PEM electrolysis stack. The electric design data was taken from the performance data of a laboratory cell (1.75 V at 3 A cm-2, 20 cm² active area) and scaled up. The stack consists of 60 cells with an active cell area of 1056 cm².The bipolar plate was completely redeveloped. The main features are: Use of porous layer structures with different degrees of fineness as a flowfield structure.Welding of all components of the bipolar plate to form a material-locking unit. Preliminary tests in short stacks with bipolar plates on a smaller scale (100 cm² active cell area) showed promising results. The design and manufacturing process for the bipolar plates have now been patented (EP4128399) and published (Janßen H et al., A facile and economical approach to fabricate a single-piece bipolar plate for PEM electrolyzers, Int. J. of Hydrogen Energy, 2023).An interesting aspect that will be discussed further in the presentation is the scale-up of both the active cell area and the number of cells. Ultimately, the aim is to understand which parameters (and their fluctuations) are mainly influencing the stack performance during scale-up. A data analysis of component properties and a comparison with operating data should provide initial indications. Fig. 1, right, shows a 60-cell PEM stack with an active cell area of 1056 cm², of which short stacks with 4 cells were also constructed. Figure 1

A combined endovascular and open repair of innominate artery bifurcation pseudoaneurysm: a case report

BackgroundInnominate artery aneurysms (IAAs) are rare and may result in rupture, distal arterial embolization, or local compression without timely treatment. Rupture is the most dangerous of these complications. This article reports a case of innominate artery bifurcation pseudoaneurysm.Case presentationThe patient was a 45-year-old man who was admitted to the emergency department due to chest discomfort. The computed tomographic angiography (CTA) imaging indicated the presence of a 3.6*2.4 cm saccular aneurysm in the bifurcation of the innominate artery, involving both the right proximal subclavian and common carotid arteries. The patient’s vital signs were normal, there was equal blood pressure in the upper arms and no neurological dysfunction was observed. Gadolinium-enhanced magnetic resonance angiography indicated that the circle of Willis was intact. The treatment involved open surgery combined with endovascular therapy. The external carotid artery was first transposed to the right subclavian artery (RSA) and an 8-mm woven Dacron graft was inserted in the middle. The covered stent graft was then placed in the proximal part of the innominate artery to close the entrance of the aneurysm. Lastly, an occluder was implanted at the origin of the RSA. There were no perioperative or postoperative complications. At 1-year follow-up, no aneurysm was observed on CTA and the right vertebral artery was patent.ConclusionsThis study indicated that the combined use of endovascular therapy and open repair surgery is an effective strategy to treat innominate artery bifurcation pseudoaneurysm.

Radial artery pulse wave age-related assessment for diabetic patients based on multiple linear regression time domain analysis method

The global incidence of diabetes increases yearly. About 10 % of adults are affected. This study established a multiple linear regression (MLR) time domain analysis model of radial artery pulse wave characteristic parameters in CUN, GUAN and CHI based on traditional Chinese medicine (TCM) to assess diabetes. Pulse signals of diabetic subjects were collected by a pulse instrument. The locations of CUN, GUAN and CHI were determined by a TCM practitioner, and all pulse signals were normalized. Measurement data from 100 male and 100 female patients were used to establish a new time domain analysis method for extracting pulse wave characteristic parameters called equal pressure pulse transit time (EP-PTT). For these mentioned samples, the EP-PTT is different for male and female diabetic subjects, it was smaller for male diabetic subjects than those of female diabetic subjects. EP-PTT1 and EP-PTT6 are relevant to predicting age based on CUN, GUAN and CHI signals, which showed a linear negative correlation (P < 0.05). The EP-PTTi (i = 2, 3, 4) of female diabetic subjects are linearly correlated with age, and all of these are positively correlated (P < 0.05). These observations were clearly different from observations in healthy controls. The pulse waveform of CUN, GUAN and CHI of diabetic subjects can explore the relationship between the age of diabetic subjects and EP-PTT. The preliminary findings will provide foundational data for type 2 diabetes assessment based on CUN, GUAN and CHI pulse signals of radial artery, and the proposed new analysis method can be used for assessing type 2 diabetes.

Compaction and Segregation of DNA in Escherichia coli.

Theoretical and experimental approaches have been applied to study the polymer physics underlying the compaction of DNA in the bacterial nucleoid. Knowledge of the compaction mechanism is necessary to obtain a mechanistic understanding of the segregation process of replicating chromosome arms (replichores) during the cell cycle. The first part of this review discusses light microscope observations demonstrating that the nucleoid has a lower refractive index and thus, a lower density than the cytoplasm. A polymer physics explanation for this phenomenon was given by a theory discussed at length in this review. By assuming a phase separation between the nucleoid and the cytoplasm and by imposing equal osmotic pressure and chemical potential between the two phases, a minimal energy situation is obtained, in which soluble proteins are depleted from the nucleoid, thus explaining its lower density. This theory is compared to recent views on DNA compaction that are based on the exclusion of polyribosomes from the nucleoid or on the transcriptional activity of the cell. These new views prompt the question of whether they can still explain the lower refractive index or density of the nucleoid. In the second part of this review, we discuss the question of how DNA segregation occurs in Escherichia coli in the absence of the so-called active ParABS system, which is present in the majority of bacteria. How is the entanglement of nascent chromosome arms generated at the origin in the parental DNA network of the E. coli nucleoid prevented? Microscopic observations of the position of fluorescently-labeled genetic loci have indicated that the four nascent chromosome arms synthesized in the initial replication bubble segregate to opposite halves of the sister nucleoids. This implies that extensive intermingling of daughter strands does not occur. Based on the hypothesis that leading and lagging replichores synthesized in the replication bubble fold into microdomains that do not intermingle, a passive four-excluding-arms model for segregation is proposed. This model suggests that the key for segregation already exists in the structure of the replication bubble at the very start of DNA replication; it explains the different patterns of chromosome arms as well as the segregation distances between replicated loci, as experimentally observed.

Effects of pressure ratio allocation on the flow characteristics in a five-stage ionic liquid compressor

Ionic liquid compressors are a new type of hydrogen compressor technology with significant advantages when applied to high-pressure hydrogen refueling stations, where multi-stage compression is an ideal solution. The utilization of a liquid piston introduces complex two-phase flow phenomena within the cylinders, and understanding the characteristics of two-phase flow is crucial for the thermodynamic performance of the compressor. For the multi-stage compressors, pressure ratio allocation has a significant influence on the structural design and energy conversion efficiency of the compressor, however, there is a lack of relevant research in the existing studies. In this paper, the compression cylinder structures of a five-stage ionic liquid compressor under three pressure ratio allocation strategies are designed, and then the two-phase flow characteristics inside the cylinder are numerically investigated. Based on the analysis of the two-phase flow pattern in the cylinder, the minimum initial liquid heights in each stage that ensure the solid piston is not exposed are determined, and the escape characteristics of ionic liquid and the energy efficiency of the ionic liquid compressor were then analyzed. Under the same total pressure ratio and flow rate, when the consumption cost of ionic liquid was considered as a secondary factor, the strategy of equal pressure ratio allocated for five stages was recommended as the compressor efficiency was higher with better heat transfer performance.

Branching Exponents of Synthetic Vascular Trees Under Different Optimality Principles.

The branching behavior of vascular trees is often characterized using Murray's law. We investigate its validity using synthetic vascular trees generated under global optimization criteria. Our synthetic tree model does not incorporate Murray's law explicitly. Instead, we show that its validity depends on properties of the optimization model and investigate the effects of different physical constraints and optimization goals on the branching exponent that is now allowed to vary locally. In particular, we include variable blood viscosity due to the Fåhræus-Lindqvist effect and enforce an equal pressure drop between inflow and the micro-circulation. Using our global optimization framework, we generate vascular trees with over one million terminal vessels and compare them against a detailed corrosion cast of the portal venous tree of a human liver. Murray's law is fulfilled when no additional constraints are enforced, indicating its validity in this setting. Variable blood viscosity or equal pressure drop lead to different optima but with the branching exponent inside the experimentally predicted range between 2.0 and 3.0. The validation against the corrosion cast shows good agreement from the portal vein down to the venules. Not enforcing Murray's law increases the predictive capabilities of synthetic vascular trees, and in addition reduces the computational cost. The ability to study optimal branching exponents across different scales can improve the functional assessment of organs.

Modeling and development of a narrowband gas-combustion infrasound source

An invaluable tool in characterization of any receiver, propagation path, or detection system, is a source with known and repeatable signal characteristics. This talk will discuss development of a well-controlled narrowband infrasound source with frequency capabilities over the 0.1 to 10.0 Hz band. Design of a transportable sound source within this band is a difficult engineering challenge. The simple source equation, which will govern any portable infrasound source due to the long wavelengths, shows this fundamental difficulty. As frequency decreases, volume displacement must increase by the squared inverse factor of frequency in order to maintain an equal pressure at equal range. To combat this, the authors have developed a source system that uses gas combustion to displace large volumes in the open atmosphere using the gaseous and highly heated combustion constituents of propane and atmospheric oxygen. Measurements have verified the capability of generating narrowband signals with reasonable signal-to-noise ratio (SNR) over the full band at close range. Signals at 1 Hz have been measured with reasonable SNR to ranges greater than 2 km. Development of the infrasound source prototype, experimental measurements, and modeling of the acoustic pressure output will be discussed.

Continuous Positive Airway Pressure versus Nasal Intermittent Positive Pressure Ventilation in Preterm Neonates: What if Mean Airway Pressures Were Equivalent?

Respiratory support for preterm neonates in modern neonatal intensive care units is predominantly with the use of noninvasive interfaces. Continuous positive airway pressure (CPAP) and nasal intermittent positive pressure ventilation (NIPPV) are the prototypical and most commonly utilized forms of noninvasive respiratory support, and each has unique gas flow characteristics. In meta-analyses of clinical trials till date, NIPPV has been shown to likely reduce respiratory failure and need for intubation compared to CPAP. However, a significant limitation of the included studies has been the higher mean airway pressures used during NIPPV. Thus, it is unclear to what extent any benefits seen with NIPPV are due to the cyclic pressure application versus the higher mean airway pressures. In this review, we elaborate on these limitations and summarize the available evidence comparing NIPPV and CPAP at equivalent mean airway pressures. Finally, we call for further studies comparing noninvasive respiratory support modes at equal mean airway pressures. KEY POINTS: · Most current literature on CPAP vs. NIPPV in preterm neonates is confounded by use of higher mean airway pressures during NIPPV.. · In this review, we summarize existing evidence on CPAP vs. NIPPV at equivalent mean airway pressures.. · We call for future research on noninvasive support modes to account for mean airway pressures..

Experimental study on dynamic characteristics of tailings under different consolidation conditions

The dynamic stability of tailing ponds depend largely on the dynamic characteristics of tailings sand. To explore the dynamic characteristics of tailings sand under different consolidation conditions, consolidated undrained triaxial tests under different dry densities, consolidation ratios and containing pressures, the dynamic shear stress, liquefaction stress ratio, dynamic strength index, dynamic pore water pressure, dynamic modulus, and damping ratio of tailings sand under different consolidation conditions were analyzed. The dynamic shear stress linearly changed with the number of failure vibrations. The liquefaction stress ratio increases with an increase in consolidation ratio, conforming to the quadratic polynomial of the origin. With an increase in failure vibration times, the dynamic internal friction angle decreases gradually. Under different failure vibration times, the dynamic internal friction angle increases with an increase in consolidation ratio and dry density. An exponential function model of dynamic pore pressure growth suitable for equal pressure and bias consolidation conditions is proposed, and the fitting effect is favorable. The dynamic shear modulus ratio decreases with an increase in dynamic shear strain; the damping ratio increases with an increase in dynamic shear strain. The research results can provide a theoretical reference for seismic liquefaction of tailings dams in high-intensity seismic areas.

Влияния кинематических параметров на процесс кавитационной обработки промывочных жидкостей и тампонажных растворов

The paper presents a numerical study of the original design of the rotary pulsating apparatus (RPA). In comparison with the traditional geometry, the simulation of a combined channel consisting of a narrowing section of the rotor and a diverging stator was performed for the first time. The results of numerical simulation of the RPA operation without additional inlet pressure in a wide range of rotor speeds are presented. Distributions of static pstat and total ptot pressure are obtained. The points of extremes and patterns of their changes are revealed. The length of the cavitation cavity in the RPA channel is determined, the equations of dependence. The cavitation characteristics of the RPA were evaluated. The distribution of the volume fraction of the vapor phase and the mathematical dependenceof the maximum value of the vapor phase on the frequency with equal pressures at the inlet and outlet are obtained.