Pressure Instability Research Articles

Mach reflection of detonation waves over a porous concave wedge

An experimental study of the differences in the Mach reflection process over smooth and porous concave wedges was systematically performed based on soot track measurement. Meanwhile, the interaction mechanism among the incident detonation, the Mach stem, and the porous wall was analyzed in detail. The results show that introducing multiple pores on the concave surface induces an additional attenuation region. In contrast, the triple-point over porous wedges starts traveling later and ends up colliding with the concave surface earlier. Moreover, the Mach stem height is shorter at the same wall position. For the transition angle of Mach-to-regular reflection over porous wedges, it is found to be negatively correlated with the length-scale ratio R/λ of the radius of curvature (R) to the cell size (λ), gas instability, and porosity. Although the experimental transition angle disagrees with the Chester–Chisnell–Whitham (CCW) and the reactive CCW theories, it is in agreement with the trend over smooth wedges that the experimental transition angle approaches to reactive CCW theory as R/λ increases. For the triple-point trajectory, it is almost a straight line when wall angle θ≤30° at R = 522 mm. It is also found that the triple-point trajectory is similar at the beginning for different mixture compositions at an equivalent initial pressure. The height of the Mach stem is shorter over a porous wedge with higher porosity, but it reaches a maximum value at a wall angle of 30° for wedges. Moreover, the Mach stem height decreases with increasing initial pressure or gas instability.

Magnetically dominated discs in tidal disruption events and quasi-periodic eruptions

ABSTRACT The classical radiation pressure instability has been a persistent theoretical feature of thin, radiatively efficient accretion discs with accretion rates $\sim $ 1 per cent–100 per cent of the Eddington rate. But there is only limited evidence of its occurrence in nature: rapid heartbeat oscillations of a few X-ray binaries and now, perhaps, the new class of hourly X-ray transients called quasi-periodic eruptions (QPEs). The accretion discs formed in tidal disruption events (TDEs) have been observed to peacefully trespass through the range of unstable accretion rates without exhibiting any clear sign of the instability. We try to explain the occurrence or otherwise of this instability in these systems, by constructing steady state 1D models of thin magnetic accretion discs. The local magnetic pressure in the disc is assumed to be dominated by toroidal fields arising from a dynamo sourced by magneto-rotational instability (MRI). We choose a physically motivated criterion of MRI saturation, validated by recent magnetohydrodynamic simulations, to determine the disc magnetic pressure. The resulting magnetic pressure support efficiently shrinks: (1) the parameter space of unstable mass accretion rates, explaining the absence of instability in TDEs and (2) the range of unstable radii in the inner accretion disc, which can shorten the quasi-periods of instability limit-cycles by more than three orders of magnitude, explaining the short periods of QPEs. In addition to examining stability of strongly magnetized discs, we predict other observational signatures such as spectral hardening and jet luminosities to test the compatibility of our disc models with observations of TDE discs.

DETERMINANTS OF OFFICE BLOOD PRESSURE VARIABILITY AND INSTABILITY IN CHILDREN, ADOLESCENTS AND YOUNG ADULTS

Objective: To evaluate the determinants of office blood pressure (BP) variability and instability within a single visit in young individuals. Design and method: Apparently healthy individuals aged 6-25 years referred for elevated blood pressure (BP) were subjected to triplicate office BP measurements in a single visit and 24h ambulatory BP monitoring. BP variability and instability were assessed separately for systolic and diastolic BP using: (i) standard deviation (SD) (ii) coefficient of variation (CV) (iii) average real variability (ARV) (iv) maximum office BP (Max) (v) maximum-minimum office BP difference (MMD) (vi) ratio of difference between 1st-3rd measurement to the average office BP (Relative change). White-coat effect was defined as the difference between office and daytime ambulatory BP. Results: 320 individuals were analyzed (mean age 13.6±3.6 years, 66.8% males, BMI z-score 1.12±0.96, average office BP 122.6±16.6/72.6±10.7 mmHg, 24h ambulatory BP 119.3±11.5/67.8±6.8). Based on office and 24h ambulatory BP, 21.3% of the participants had white-coat hypertension, 8.1% masked and 16.6% sustained hypertension. Age was associated with SD (r = 0.23, p<0.001), CV (r = 0.11, p<0.05), Max (r = 0.54, p<0.001) and MMD (r = 0.23, p<0.001) of office systolic BP, and Max (r = 0.29, p<0.001) and ARV (r = 0.12, p<0.05) of diastolic. In multivariable log-linear regression models [(independent variables: age, sex, BMI z-score, heart rate, office BP, white-coat effect (> = 5/6 mmHg systolic/diastolic, 75th centile)], office BP was an independent determinant for indices of systolic BP variability and instability [SD (↓ = 0.01, p<0.001), ARV (↓ = 0.01, p<0.001), Max (↓ = 0.01, p<0.001), MMD (↓ = 0.01, p<0.001) and Relative change (↓ = 0.001, p<0.05)], and for CV (↓ = -0.06, p<0.001) and Max (↓ = 0.01, p<0.001) of diastolic. White-coat effect was a significant determinant for CV of office systolic BP (↓ = 0.15, p<0.05) and Relative change of office diastolic BP (↓ = 0.03, p<0.05). Conclusions: These results suggest that in healthy children, adolescents, and young adults the indices of office BP variability and instability within the first visit seem to be determined by the level of office BP and the magnitude of the white-coat effect.

OFFICE BLOOD PRESSURE VARIABILITY AND INSTABILITY IN CHILDREN, ADOLESCENTS AND YOUNG ADULTS: ASSOCIATION WITH PRECLINICAL ORGAN DAMAGE

Objective: To evaluate the association of systolic blood pressure (SBP) variability and instability within a single office visit with preclinical target organ damage in young individuals. Design and method: Apparently healthy individuals aged 6-25 years referred for elevated blood pressure (BP) were subjected to triplicate office BP measurements in a single visit and 24h ambulatory BP monitoring. SBP variability and instability were quantified using (i) standard deviation (SD) (ii) coefficient of variation (CV) (iii) average real variability (ARV) (iv) maximum office SBP (v) maximum-minimum office SBP difference (MMD) (vi) ratio of difference between 1st-3rd measurement to the average office SBP (Relative change). Preclinical organ damage was evaluated by (i) carotid intima-media thickness (cIMT), (ii) carotid-femoral pulse wave velocity (PWV; Complior device), and (iii) echocardiographic left ventricular mass index (LVMI). Results: 301 individuals were analyzed (mean age 13.8±3.7 years, 66.8% males, BMI z-score 1.12±0.95, average office BP 122.6±16.9/72.5±10.7 mmHg, 24h ambulatory BP 119.1±11.4/67.8±6.8 mmHg). LVMI measurements were available in 258 participants, IMT in 208 and PWV in 60. LVMI, IMT and PWV were associated with office SBP (r = 0.30/0.23/0.42, respectively, p< = 0.001), 24h ambulatory SBP (r = 0.35/0.33/0.48, p< = 0.001) and maximum office SBP (r = 0.31/0.30/0.41, p< = 0.001). LVMI and IMT were associated with SD (r = 0.14/0.15, p<0.05) and MMD (r = 0.13/0.15, p<0.05), while IMT and PWV with age (r = 0.31/0.38, p<0.001). Other indices of variability were not associated with indices of organ damage. In stepwise multivariable linear regression models (independent variables: age, sex, BMI z-score, office SBP, 24h ambulatory SBP, maximum office SBP, SD, MMD), LVMI was determined by BMI z-score and 24h ambulatory SBP, IMT by age, male sex and 24h ambulatory SBP, and PWV by 24h ambulatory SBP. Conclusions: These results suggest that in young individuals the variability and instability of office SBP within a single visit are not associated with preclinical organ damage.

Reverse flow in a pressure suppression system due to condensation instabilities

The Vacuum Vessel Pressure Suppression System (VVPSS) is designed to protect the ITER reactor (Vacuum Vessel, VV) from an overpressurization accident. The VVPSS is mainly composed of four Vapour Suppression Tanks (VSTs) partially filled with water inside which venting pipes (spargers) are immersed to direct the steam in the subcooled pool to condense it. Since the maximum pressure allowed inside the VV is only 0.15 MPa, a sub-atmospheric pressure must be maintained inside the VSTs. During a series of experimental campaigns funded by ITER Organization to study and validate the correct operability of the VVPSS and conducted in a large-scale plant built at the B. Guerrini laboratory of the University of Pisa, pressure instability and reverse flow through the sparger holes have been observed. The analysis of acceleration signals recorded during this pressure inversion, showed large amplitude oscillations at low frequency due to the Condensation Induced Water Hammer (CIWH).

Acceptance rate, hesitancy and comorbidities in pregnant women

We analyzed the electronic data (e-data) of n=5231 vaccinated candidates including n=3671 males and n=1560 females. We studied the COVID-19 vaccine brands such as Sino pharm, CanSino, SinoVac, Moderna and Pfizer. We noted adverse effects in post-vaccinated candidates were Instability in blood pressure 29.5%, Swelling 3.5%, Redness 14.2%, Itching 7.13%, and Rashes 2.4%. Comorbidities in the vaccinated candidates such as Hypertension 33%, Diabetes mellitus 17%, Kidney disease 42%, and Chronic respiratory disease 9%. COVID-19 vaccine hesitancy 1153, 22% and Non-Hesitant 4078, 77%. We analyzed the e-data of COVID-19 vaccinated candidates, the acknowledgement of COVID-19 immunization in pregnant women. Worrying about vaccine safety was the significant justification for hesitancy. Recognizing mentalities among study groups will be valuable for coming up with vaccine strategies that increment the ongoing pandemic.

Analysis of the global economic situation in light of the recession crisis and the war on Ukraine.

The Covid 19 pandemic led to a global recession in 2020, and despite the rapid recovery of the global economy from it, the latter collided with the Russian invasion of Ukraine, which led to a slowdown in growth again; and the emergence of new crises such as the energy crisis and food insecurity. This research aims to highlight the policies for dealing with economic recession crises, and analyze the current conditions and the reasons that contributed to the decline in global economic indices. The study concluded that the spillovers from Russia’s invasion of Ukraine has accelerated the global economic slowdown, leading to high commodity prices, adding to supply disruptions, increasing food insecurity and poverty, exacerbating inflation .This contributed to increasing pressure and financial instability in various economies

Clinical trial of home blood pressure monitoring following midodrine administration in hypotensive individuals with spinal cord injury

Background Individuals with spinal cord injury (SCI) above thoracic level-6 (T6) experience impaired descending cortical control of the autonomic nervous system which predisposes them to blood pressure (BP) instability, including includes hypotension, orthostatic hypotension (OH), and autonomic dysreflexia (AD). However, many individuals do not report symptoms of these BP disorders, and because there are few treatment options that have been proven safe and effective for use in the SCI population, most individuals remain untreated. Objective The primary aim of this investigation was to determine the effects of midodrine (10 mg) prescribed TID or BID in the home environment, compared to placebo, on 30-day BP, study withdrawals, and symptom reporting associated with OH and AD in hypotensive individuals with SCI. Design/Methods Participants were randomly assigned to received midodrine/placebo or placebo/midodrine, with a 2-weeks washout period in between, and both the participants and investigators were blinded to randomization order. Study medication was taken 2 or 3 times/day, depending on their sleep/wake schedule, BP, and any related symptoms were recorded before and 1 h after each dosage and periodically throughout the day. Results Nineteen individuals with SCI were recruited; however, 9 withdrew prior to completion of the full protocol. A total of 1892 BP recordings (75 ± 48 recordings/participant/30-day period) were collected in the 19 participants over the two 30-day monitoring periods. Average 30-day systolic BP was significantly increased with midodrine compared to placebo (114 ± 14 vs. 96 ± 11 mmHg, respectively; P = 0.004), and midodrine significantly reduced the number of hypotensive BP recordings compared to placebo (38.7 ± 41.9 vs. 73.3 ± 40.6, respectively; P = 0.01). However, compared to placebo, midodrine increased fluctuations in BP, did not improve symptoms of OH, but did significantly worsen the intensity of symptoms associated with AD (P = 0.03). Conclusion Midodrine (10 mg) administered in the home environment effectively increases BP and reduces the incidence of hypotension; however these beneficial effects come at the expense of worsened BP instability and AD symptom intensity.

Modified models of radiation pressure instability applied to 10, 105, and 107 M⊙ accreting black holes

Context. Some accreting black holes exhibit much stronger variability patterns than the usual stochastic variations. Radiation pressure instability is one of the proposed mechanisms that might account for this effect. Aims. We model luminosity changes for objects with a black hole mass of 10, 105, and 107 solar masses, using the time-dependent evolution of an accretion disk that is unstable as a result of the dominant radiation pressure. We concentrate on the outburst timescales. We explore the influence of the hot coronal flow above the cold disk, the inner purely hot flow, and the effect of the magnetic field on the time evolution of the disk-corona system. For intermediate-mass black holes and active galactic nuclei, we also explore the role of the disk outer radius because a disk that is fed by tidal disruption events (TDE) can be quite small. Methods. We used a 1D vertically integrated time-dependent numerical scheme that models the simultaneous evolution of the disk and corona, which is coupled by the vertical mass exchange. We parameterized the strength of the large-scale toroidal magnetic fields according to a local accretion rate. We also discuss a possible inner optically thin flow, the advection-dominated accretion flow (ADAF). This flow would require modification of the inner boundary condition of the cold disk flow. For the set of the global parameters, we calculated the variability timescales and outburst amplitudes of the disk and the corona. Results. We found that the role of the inner ADAF and the accreting corona are relatively unimportant, but the outburst character strongly depends on the magnetic field and on the outer radius of the disk if this radius is smaller (due to the TDE phenomenon) than the size of the instability zone in a stationary disk with infinite radius. For microquasars, the dependence on the magnetic field is monotonic, and the period decreases with the field strength. For higher black hole masses, the dependence is nonmonotonic, and an initial rise of the period is later replaced with a relatively rapid decrease as the magnetic field continues to rise. A still stronger magnetic field stabilizes the disk. When we assumed a smaller disk outer radiusfor 105 and 107 M⊙, the outbursts were shorter and led to complex multiscale outbursts for some parameters, thus approaching the behavior of deterministic chaos. Conclusions. Our computations confirm that the radiation pressure instability model can account for heartbeat states in microquasars. The rapid variability detected in intermediate-mass black holes in the form of quasi-periodic eruptions can be consistent with the model, but only when it is combined with the TDE phenomenon. The yearly repeating variability in changing-look active galactic nuclei in our model also requires a small outer radius either due to the recent TDE or due to the gap in the disk that is related to a secondary black hole.

Can Offshore Meteoric Groundwater Generate Mechanical Instabilities in Passive Continental Margins?

AbstractOffshore meteoric groundwater (OMG) has long been hypothesized to be a driver of seafloor geomorphic processes in continental margins worldwide. Testing this hypothesis has been challenging because of our limited understanding of the distribution and rate of OMG flow and seepage, and their efficacy as erosive/destabilizing agents. Here we carry out numerical simulations of groundwater flow and slope stability using conceptual models and evolving stratigraphy—for passive siliciclastic and carbonate margin cases—to assess whether OMG and its evolution during a late Quaternary glacial cycle can generate the pore pressures required to trigger mechanical instabilities on the seafloor. Conceptual model results show that mechanical instabilities using OMG flow are most likely to occur in the outer shelf to upper slope, at or shortly before the Last Glacial Maximum sea‐level lowstand. Models with evolving stratigraphy show that OMG flow is a key driver of pore pressure development and instability in the carbonate margin case. In the siliciclastic margin case, OMG flow plays a secondary role in preconditioning the slope to failure. The higher degree of spatial/stratigraphic heterogeneity of carbonate margins, lower shear strengths of their sediments, and limited generation of overpressures by sediment loading may explain the higher susceptibility of carbonate margins, in comparison to siliciclastic margins, to mechanical instability by OMG flow. OMG likely played a more significant role in carbonate margin geomorphology (e.g., Bahamas, Maldives) than currently thought.

Diffuse interface model for a single-component liquid-vapor system.

We elucidate the theoretical relationships among fundamental physical concepts that are involved in the diffuse interface modeling for an isothermal single-component liquid-vapor system, which cover both the equationof state (EOS) and the surface tension force. As an example, a flat surface at equilibrium is discussed both theoretically and numerically by using two different approaches. Particularly, the force structure in the transition region is clearly presented, which demonstrates that the capillary contributions due to the density gradients can suppress the mechanical instability of the thermodynamic pressure and lead to constant hydrodynamic pressure (and chemical potential). Then, by comparing with the van der Waals (vdW) EOS for a flat interface at equilibrium, it is shown that applying the double-well approximation can give qualitative predictions for relatively high density ratio (ρ_{l}/ρ_{g}=7.784) and satisfactory results for relatively low density ratio (ρ_{l}/ρ_{g}=1.774). The main cause for this observation is attributed to the nonlinear variation of the generalized coefficient function in the double-well formulation at different density ratios. In addition, for the latter case, we simulate a droplet impact on a hydrophilic wall by using a recently proposed well-balanced discrete unified gas kinetic scheme (WB-DUGKS), which justifies the applicability of the double-well approximation to complex interfacial dynamics in the low-density-ratio limit. Furthermore, the reason for the inconsistency between the coefficients of the mean-field force expressions in the existing literature is explained.

Boiling Heat Transfer Characteristics of Porous Microchannel with Pore-Forming Agent

Traditional microchannel needs to face the flow-reversal difficulty in high heat fluxes due to limited space. It results in large pressure and temperature fluctuation. Porous microchannels arouse more interest to provide a new solution to this problem. Flow boiling experiments in porous microchannels with PFA were investigated. Porous microchannels were sintered by 10 μm (or 30 μm) spherical copper particles with pore-forming agent (Na2CO3, 60–90 μm). Porous microchannels were composed of 23 parallel porous microchannels with 600 μm in width and 1200 μm in depth.The addition of PFA (pore-forming agent) could increase the sample porosity. For Q10 series, sample porosities increase from 20.4% to 52.9% with the PFA percentage change from 0% to 40%, while for the Q30 series they increase from 26.6% to 47.5%. Experimental results showed the boiling heat transfer coefficient (HTC) reached the maximum at the moderate porosity for both Q10 and Q30 series. Too large or too small porosity would degrade boiling heat transfer performance. It demonstrated that there existed an optimal range of PFA content for sintered microchannels. PFA content has a minor effect on the average pressure drop and would not cause the rapid increase in flow resistance. Visual observation disclosed that the sample porosity would affect the pressure instability significantly. The sample with moderate porosity showed periodic pressure fluctuation and could establish rhythmical boiling. Particle size also exerted a certain influence on the boiling heat transfer performance. Q30 series could achieve higher HTC and CHF (Critical heat flux) than Q10 series. This is attributed to the larger ratio of layer-thickness-to-particle-size (δ/d) for Q10-series samples.

Observation of low-frequency oscillation in argon helicon discharge

We present here a kind of low-frequency oscillation in argon helicon discharge with a half helical antenna. This time-dependent instability shows a global quasi-periodic oscillation of plasma density and electron temperature, with a typical frequency of a few tens of Hz which increases with external magnetic field as well as radiofrequency (RF) power. The relative oscillation amplitude decreases with magnetic field and RF power, but the rising time and pulse width do not change significantly under different discharge conditions. The oscillation can only be observed in some specific conditions of low magnetic fields and low RF power when the gas flows in from one end of the discharge area and out from another end. This global instability is suggested to be attributed to the pressure instability of neutral depletion, which is the result of compound action of gas depletion by heating expansion and gas replenishment from upstream. There are two kinds of oscillations, large and small amplitude oscillations, occurring in different discharge modes. This study could be a good verification of and complement to earlier experiments. This kind of spontaneous pulse phenomenon is also helpful in realizing a pulsing plasma source without a pulsed power supply.

Implementing intact cord resuscitation in very preterm infants: feasibility and pitfalls.

The purpose of this study is to evaluate the feasibility of intact cord resuscitation (ICR) in very preterm infants using a custom-equipped mobile resuscitation trolley (LifeStart®). We collected maternal and neonatal data of all inborn infants < 32weeks eligible for ICR per our protocol over 9months from ICR implementation. We compared rates of ICR between the beginning and the end of the study period. We reviewed maternal and neonatal adverse events related to the procedure and direct outcomes. In order to assess potential quality improvements related to the procedure, we collected the same data in the infants born in the 9-month period preceding ICR implementation. Out of 44 infants born < 32weeks during the period, 27 were eligible for ICR. Failure to initiate ICR occurred in 9/27, exclusively in the first 5.5months of the study. In one infant, ICR was interrupted prior to 2min due to placental abruption. No ICR procedure had to be interrupted due to insufficient cord length. Among the 18 infants who completed ICR, cord clamping timing increased significantly over the study period, from 3.0 [2.5-3.5] to 4.2min [3.1-8.3] (p = 0.02). No significant maternal blood loss or wound complications were noted. No infant deaths were attributable to failure or direct consequence of ICR, and no infant experienced hypoxic respiratory failure (intubation, FiO2 ≥ 0.4), asphyxia (pH < 7.2), or blood pressure instability (< 2 SD) following stabilization. Hemoglobin level after cord clamping was higher in the ICR cohort than in the pre-implementation group. Seven out of 18 infants exposed to ICR had a temperature < 36.5°C on admission. Conclusion: ICR is feasible in very preterm infants. Temperature management requires special attention. Multidisciplinary simulation training before implementation and systematic post-implementation quality improvement meetings may significantly increase ICR program success. What is Known: • Because infants born < 32weeks often require cardiorespiratory resuscitation at birth, they are not offered delayed cord clamping in the majority of neonatal intensive care units. • Recently, fully equipped mobile trolleys have been developed in order to allow bedside resuscitation with an intact cord. What is New: • Variable timing of cord clamping based on the infant's transition and respiratory stability, i.e., "physiology-based cord clamping," is safely achievable in very preterm infants. • Intact cord resuscitation requires specific equipment, operational protocols, and a high level of preparation from both obstetrical and neonatal teams, with a learning curve that can be streamlined by multidisciplinary simulation training.

Rayleigh-Taylor instability of radiation pressure driven foils: 2D effects

Rayleigh–Taylor instability of radiation pressure accelerated ultra-thin foils of different thickness profiles and initial curvature is investigated in two dimensions using numerical simulations. The convex curvature of the foil (when viewed from the rear side of the foil) provides radially inward motion to the off-axis ions countering the radial divergence due to the Gaussian intensity distribution of the laser. Nonuniform foils, having maximum thickness on laser axis have similar effect. When a small ripple is superimposed on the foil on the scale of laser wavelength, the radiation pressure acts nonuniformly on the microscopic scale and the perturbation grows as the foil moves. After a certain distance of travel, the foil crests turn into cusps and the phase of quasi mono-energy ion acceleration terminates. The planar foil with uniform laser has a strong growth of Rayleigh–Taylor instability (RTI). The foils with curvature and nonuniform thickness have marginally lower growth rate. However, under all circumstances, RTI is found to induce additional energy spread, in radiation pressure acceleration (RPA) of thin foils.

Effect of welding stability on process porosity in laser arc hybrid welding of dissimilar steel

Welding porosity is an important factor affecting the mechanical properties of welded joints. This study investigated the effect of welding stability on weld porosity to solve the problem of welding porosities in laser-arc hybrid welding of dissimilar steels. The type and formation mechanism of welding porosity were analyzed. The study results showed that the porosities generated during the welding process were process welding porosities. The generation of bubbles was closely related to the instability of the steam pressure inside laser keyhole. The droplet transfer form was an essential factor affecting the stability of the laser keyhole. When the droplet was in the projected transfer mode, the weld porosity could be effectively reduced. Penetration weld was also greatly helpful in reducing weld porosity.

Increased Prevalence of Blood Pressure Instability Over Twenty-Four Hours in Chronic Spinal Cord Injury.

Spinal cord injury (SCI) leads to cardiovascular dysregulation, including persistent low blood pressure (BP), orthostatic hypotension, and autonomic dysreflexia, leading to daily BP instability that may not be adequately recognized. We compared mean systolic BP, diastolic BP, and heart rate from awake and asleep measurements over a 24-h period among persons with chronic SCI (n = 33; 30 cervical injuries and three upper thoracic injuries), ambulatory/non-injured (Ambulatory-NI; n = 13), and non-injured (NI) in a wheelchair (n = 9). Stability of awake BP was evaluated by deviation of systolic BP from 115 mmHg and percent of systolic BP measurement within and outside of 90-140 mmHg. Variability over 24 h was compared using coefficient of variation and average real variability. Awake hyper- and hypotensive events (change in systolic BP ±20 mmHg from the median) were compared to symptoms reported by the participants corresponding to BP events. Participants with SCI had a lower percentage of awake systolic BP measurements within 90-140 mmHg than Ambulatory-NI and a greater deviation below 115 mmHg. Coefficient of variation and successive differences of awake systolic and diastolic BP were greater in SCI than Ambulatory-NI. Finally, all SCI participants had hyper- and/or hypotensive events and 88% experienced the BP events asymptomatically. In conclusion, participants with SCI had significantly greater BP instability compared with NI, with many hyper- and hypotensive events occurring without symptoms. Clinical management of BP instability, regardless of symptoms, should be a priority after SCI to reduce the risk of cardiovascular disease and improve quality of life.

The new mechanism of cognitive decline induced by hypertension: High homocysteine-mediated aberrant DNA methylation.

The prevalence and severity of hypertension-induced cognitive impairment increase with the prolonging of hypertension. The mechanisms of cognitive impairment induced by hypertension primarily include cerebral blood flow perfusion imbalance, white and gray matter injury with blood-brain barrier disruption, neuroinflammation and amyloid-beta deposition, genetic polymorphisms and variants, and instability of blood pressure. High homocysteine (HHcy) is an independent risk factor for hypertension that also increases the risk of developing early cognitive impairment. Homocysteine (Hcy) levels increase in patients with cognitive impairment induced by hypertension. This review summarizes a new mechanism whereby HHcy-mediated aberrant DNA methylation and exacerbate hypertension. It involves changes in Hcy-dependent DNA methylation products, such as methionine adenosyltransferase, DNA methyltransferases, S-adenosylmethionine, S-adenosylhomocysteine, and methylenetetrahydrofolate reductase (MTHFR). The mechanism also involves DNA methylation changes in the genes of hypertension patients, such as brain-derived neurotrophic factor, apolipoprotein E4, and estrogen receptor alpha, which contribute to learning, memory, and attention deficits. Studies have shown that methionine (Met) induces hypertension in mice. Moreover, DNA hypermethylation leads to cognitive behavioral changes alongside oligodendroglial and/or myelin deficits in Met-induced mice. Taken together, these studies demonstrate that DNA methylation regulates cognitive dysfunction in patients with hypertension. A better understanding of the function and mechanism underlying the effect of Hcy-dependent DNA methylation on hypertension-induced cognitive impairment will be valuable for early diagnosis, interventions, and prevention of further cognitive defects induced by hypertension.

Devastating delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

BackgroundWe investigated the proportion of patients in an initial good clinical condition who developed devastating DCI, and aimed to characterize these patients by aneurysm location, blood pressure instability prior to DCI, and the extent of cerebral ischemia.MethodsWe included aSAH patients admitted between 2010 and 2021 with a Glasgow Coma Scale of 11 or higher 24 h after aneurysm treatment, who developed devastating DCI, defined as DCI leading to coma for at least 48 h with cerebral infarction on the subsequent scan. Blood pressure instability was defined as nimodipine-induced blood pressure drops, dosage adjustments, or the use of blood pressure drugs before onset of DCI. Descriptive statistics were used to summarize the data.ResultsOut of 1,211 consecutive aSAH patients, 617 patients had a good clinical condition after aneurysm treatment of whom 16 (3%) patients [14 (88%) women] were included in this study. Thirteen (81%) patients had an aneurysm in the anterior circulation. Thirteen patients (81%) had blood pressure instability: twelve (75%) had nimodipine-induced blood pressure drops, eleven (69%) received antihypertensive drugs, and 7 (44%) received hypertension induction before onset of DCI. Thirteen (81%) patients had bilateral ischemia, mainly in the anterior circulation (56%).ConclusionsThe proportion of aSAH patients with a good clinical condition after aneurysm treatment who develop devastating DCI is small. The vast majority of these patients had blood pressure instability. Future studies are needed to investigate if a reduction in the number and extent of blood pressure fluctuations decreases the incidence of devastating DCI.

Left and right ventricular function alterations in obstructive sleep apnea patients assessed by 2D speckle tracking echocardiography

Abstract Introduction Obstructive sleep apnea (OSA) is related to increased left ventricular (LV) transmural pressure, blood pressure instability and increased pulmonary artery pressure (PAP) leading to left and right ventricular (RV) dysfunction and heart failure. 2D speckle tracking echocardiography (STE) is useful method for subclinical biventricular dysfunction diagnosis, thus might help to earlier treatment for OSA patients. Purpose The aim of the study was to evaluate changes of biventricular function and mechanics in patients with OSA. Methods We obtained 2D STE from 47 obese patients. 13 patients either did not have OSA, or it was mild (apnea/hypopnea index (AHI) 5–14/hour). OSA group (N=34) consisted of subjects with moderate or severe OSA (AHI ≥15/hour). New indexing for LV myocardial mass and LA volume by height was applied according new guidelines for obese patients. Statistical analyses were performed using the SPSS 27.0 software. The value of p&amp;lt;0.05 was considered as statistically significant. Results BMI did not differ between groups (p=0.108). Control group patients were younger, had higher female ratio, meanwhile arterial hypertension was more prevalent in OSA group (26 (76.5%) vs. 5 (38.5%), p=0.014). New indexing by height for left ventricular myocardial mass revealed higher LV MMi in OSA patients (p=0.007), and higher prevalence of LV diastolic dysfunction (p=0.023) was found in this group of patients. Moreover, LA reservoir function was significantly lower in OSA group compared to controls p&amp;lt;0.001. LV ejection fraction and conventional RV function parameters (s', fractional area change (FAC)) did not differ between groups, however LV and RV global longitudinal strain was reduced in OSA patients (p=0.035 and p=0.026, respectively). OSA patients had significantly higher RA diameter, and mean PAP (p=0.043 and p=0.037, respectively) (Table 1). Conclusions Moderate or severe obstructive sleep apnea is related to reduced biventricular longitudinal strain, more prevalent LV diastolic dysfunction and lower LA reservoir function. New indexing for LV myocardial mass by height helps to identify myocardial structural changes in obese patients with OSA. Funding Acknowledgement Type of funding sources: None.