Rate Acceleration Research Articles

Transmission and Growth Characteristics of Severe PM2.5 Pollution Events from 2013 to 2021 in Xingtai, Hebei

The correlation between the growth rate of PM2.5 with transport source, atmospheric circulation, and wind field were analyzed, focusing on the severe and above pollution process (SAAP) in Xingtai, Hebei Province from 2013 to 2021. The results showed that from 2013 to 2021, a total of 164 pollution processes and 103 SAAP occurred in Xingtai. In the ground circulation, although the probability occurrence of the inverted trough was low, the probability of pollution was the highest (61.1%), followed by the high-pressure control type (>50.0%). In the 500 hPa, the control of the straight westerly wind belt had the highest probability of severe and above pollution (20.7%), followed by the post-trough type (16.1%), with the highest occurrence frequency. In SAAP, the distribution of the PM2.5 hourly growth rate (ΔPM2.5) was mainly concentrated between ±150 μg·(m3·h)-1, and the PM2.5 hourly growth rate was positive (+ΔPM2.5), contributing 61.7%. Among them, the average proportion of explosive growth was 13.9% (from 2013 to 2021), and the overall trend was decreasing annually. In the full wind speed, in terms of occurrence frequency and pollution probability, north-east (NE) was the wind direction most closely related to air pollution, especially severe and above pollution. The mean value of ΔPM2.5 in SAAP was lower than that of quiet wind in most wind directions. However, in some of the east-north (EN) and south-west (SW) wind direction intervals, the mean ΔPM2.5 in moderate wind speed was significantly higher than that of quiet wind (related to pollution transmission). The impact of larger wind speed on ΔPM2.5 was more complicated. The backward trajectories showed that the backward trajectories of slow, rapid, and explosive growth in SAAP could be divided into three main paths:west-north, east-north, and south. With the acceleration of the growth rate, the proportion of the west-north air mass gradually increased. The humidity (RH) of the slow-growth air mass was relatively large (more than 80% RH>50%), the relative humidity of the rapidly growing air mass was relatively concentrated (mainly distributed in 35%-55%), and the proportion of low-humidity (<50%) air masses increased significantly (by approximately 63%) in the explosive growth. The simulation analysis showed that the types of SAAP pollution could be divided into five categories:local accumulation, east-northern transmission, north-west transmission, mixed transmission, and south transmission. Among them, the proportion of mixed transmission was the highest, followed by that of the north-west transmission. The high and low-altitude configurations with the highest occurrence probability among the southerly transmission, the local accumulation type, and the north-easterly transport type were all high-altitude trough rear type combined with ground equalization field type. Among the north-westerly type, the high-pressure on the ground with the behind trough on high-altitude had the highest probability of occurrence. In mixed transmission, the probabilities of various circulation ratios were relatively balanced.

Insight into the mechanism of CO2 to initiate and regulate ethanol-driven chain elongation by microbial community and metabolic analysis

The present study investigated the impact of CO2 on ethanol-driven chain elongation and its related mechanism. The findings showed that CO2 acts as the initiator of chain elongation. Specifically, the effect of different CO2 dosages (0.5, 1.0, and 2.0 LCO2·L-1·d-1) on chain elongation was examined, revealing that the lower dosage of CO2 (0.5 LCO2·L-1·d-1) favored caproate biosynthesis, as evidenced by higher caproate yield and selectivity compared to the higher dosages (1.0 and 2.0 LCO2·L-1·d-1). A higher dosage of CO2 resulted in the acceleration of ethanol oxidation rate and excessive oxidation of ethanol. The isotopic experiment using 13CO2 indicated that CO2-C is incorporated into microbial biomass and extracellular products, providing direct evidence of CO2 fixation in bacteria involved in the chain elongation process. Furthermore, analysis of 16 S rRNA genes revealed that CO2 dosages have effects on microbial community structure. The relative abundance of chain elongators, such as Clostridium kluyveri and Oscillibacter valericigenes, was significantly increased after the addition of CO2 at 0.5 LCO2·L-1·d-1. Metagenomic analysis showed that the relative abundance of key functional genes related to reverse β-oxidization pathway and fatty acid biosynthesis pathway was upgraded more than 30% under the addition of 0.5 LCO2·L-1·d-1. Overall, this research provides a systematic investigation of the effect of CO2 on chain elongation and offers a research basis for optimizing the chain elongation system.

Using life expectancy as a risk assessment metric: The case of respirable crystalline silica

The change in age-related mortality patterns is an important characteristic of the population that can be used as a metric of risk by comparing exposed and non-exposed populations.In this paper, the mortality parameters were predicted for populations exposed to crystalline silica, a proven lung carcinogen.Seven hazard functions were tested for a dose–response relationship between lung cancer and characteristics of exposure. Life tables were calculated, along with parameters of the Gompertz-Makeham model for the force of mortality.It was demonstrated, in particular, that exposure to crystalline silica in the range from 0.03 to 0.3 mg/m3 for 40 years starting at age 20 causes a predicted drop in average life expectancy in the range of from 0.15 to 1.38 years.It was demonstrated that the lost life expectancy linearly correlates with relative risk (R = 0.995, R2 = 0.989, p< 0.00001). The probability of the life expectancy increasing while relative risk decreases was as low as 0.01.It was found that exponential parameter α of the Gompertz-Makeham equation increases with crystalline silica exposure, while the two linear parameters A and R (which are negatively correlated between each other) increase or decrease with exposure depending on the duration and onset age. Modal age of death in the cohort decreases with cumulative exposure with R = -0.977, R2 = 0.954, p < 0.0001.Based on several different approaches, it was suggested that the threshold of cumulative crystalline silica exposure concentration causing statistically significant change in the cohort life tables can be found in the range from 1.81 to 2.50 mg/m3-years. The change of average age of death in exposed male population does not exceed 1% below cumulative exposure of 3.5 mg/m3-years, and does not exceed 5% at cumulative exposure less than 9.8 mg/m3-years. It shows that no significant acceleration of death rate with age is happening even at the high levels of exposure to crystalline silica.The study demonstrated the value and advantages of the use of life expectancy and other lifetable characteristics as a tool for quantitative risk assessment.

Observations of the synthesis of straight single wall carbon nanotubes directed by electric fields in an Environmental Transmission Electron Microscope

We report here observations in real time of the aligning effect of electric fields during the synthesis of carbon nanotubes in an environmental transmission electron microscope (ETEM). Growths took place using C2H2 as precursor gas at ∼10−4 mbar, a temperature of ∼700°C and within a micro-capacitor incorporated in a specifically-designed heating micro-chip. Individual nanotubes are easily resolved as they appear as extremely straight lines growing parallel to the electric field. These nanotubes are predominantly Single Wall Carbon Nanotubes (SWNTs). Owing to the very good alignment of nanotubes in the object plane of the microscope we can obtain unprecedented excellent determination of the nanotubes’ growth rates and follow them dynamically. Constant growth rates are observed in most cases but other behaviours are observed such as growth rate acceleration. For low applied voltages the growing nanotubes can cross the gap and connect to the opposite electrode although some are destroyed by mechanical failure or during the contact. For high applied fields and positive biasing allowing Field Emission (FE), the growth is limited within the gap as FE can occur during growth leading to new saturation or destruction processes. These different mechanisms are presented as well as the observed balance between electrostatic and adhesion forces.

Influence of microbial biomass content on biodegradation and mechanical properties of poly(3-hydroxybutyrate) composites

Biodegradation rates and mechanical properties of poly(3-hydroxybutyrate) (PHB) composites with green algae and cyanobacteria were investigated for the first time. To the authors knowledge, the addition of microbial biomass led to the biggest observed effect on biodegradation so far. The composites with microbial biomass showed an acceleration of the biodegradation rate and a higher cumulative biodegradation within 132 days compared to PHB or the biomass alone. In order to determine the causes for the faster biodegradation, the molecular weight, the crystallinity, the water uptake, the microbial biomass composition and scanning electron microscope images were assessed. The molecular weight of the PHB in the composites was lower than that of pure PHB while the crystallinity and microbial biomass composition were the same for all samples. A direct correlation of water uptake and crystallinity with biodegradation rate could not be observed. While the degradation of molecular weight of PHB during sample preparation contributed to the improvement of biodegradation, the main reason was attributed to biostimulation by the added biomass. The resulting enhancement of the biodegradation rate appears to be unique in the field of polymer biodegradation. The tensile strength was lowered, elongation at break remained constant and Young’s modulus was increased compared to pure PHB.

Study of the influence of universal gearing of steering system on vehicle handling stability.

The handling stability of a vehicle is a crucial performance aspect. In this study, the focus is on investigating the impact of the universal gearing of the steering shaft on the handling stability of the vehicle. The research involves a theoretical analysis of how the structural parameters of universal gearing affect the handling stability of the vehicle, which is then validated through a series of simulation experiments including swept-sine steering input simulation, constant radius cornering simulation, and cornering with steer release. Evaluation is based on objective indices such as the steering wheel angle, yaw rate, and lateral acceleration. Moreover, the trends of these indices with respect to the phase angle and initial angle of universal gearing are determined. The findings reveal that the steering ratio of the vehicle varies significantly for varying phase angle and initial angle, resulting in different handling performance. The relationship between the phase angle and fluctuation magnitude of steering ratio is particularly noteworthy, while the impact of initial angle is primarily on the phase of steering ratio. Furthermore, within a certain range, changing the structural parameters of the universal gearing has the potential to enhance the handling performance of the vehicle.

Role of automated detection of respiratory related heart rate changes in the diagnosis of sleep disordered breathing

Study objectivesThe objective of this study was to determine whether electrocardiogram (ECG) and heart rate accelerations that occur in the vicinity of respiratory events could predict the severity of sleep-disordered breathing (SDB).MethodsDe-identified polysomnogram (NPSG) recordings from 2091 eligible participants in the Sleep Heart Health Study (SHHS) were evaluated after developing and validating an automated algorithm using an initial set of recordings from 1,438 participants to detect RR interval (RRI) dips in ECG and heart rate accelerations from pulse rate signal. Within-subject comparisons were made between the apnea-hypopnea index (AHI) and both the total RRI dip index (total RRDI) and total heart rate acceleration index (total HRAI).ResultsThe estimated AHIs using respiratory-related HRAI correlated with NPSG AHI both in the unadjusted and adjusted model (B: 0.83 and 0.81, respectively P &amp;lt; 0.05). Respiratory-related HRAI had a strong agreement with NPSG AHI (intraclass correlation coefficient-ICC: 0.64, whereas respiratory-related RRDI displayed weaker agreement and ICC: 0.38). Further assessment of respiratory-related HRAI (≥5 events/h) showed a strong diagnostic ability (78, 87, 81, and 56% agreement for traditional AHI cutoffs 5, 10, 15, and 30 events/h, respectively). At the AHI cutoff of 5 events/h the receiver operating curves (ROC) revealed an area under the curve (AUCs) of 0.90 and 0.96 for RE RRDI and RE HRAI respectively.ConclusionThe automated respiratory-related heart rate measurements derived from pulse rate provide an accurate method to detect the presence of SDB. Therefore, the ability of mathematical models to accurately detect respiratory-related heart rate changes from pulse rate may enable an additional method to diagnose SDB.

Salt-Mediated Coarsening in Conversion-Reaction-Synthesized Nanoporous Metals and Nanocomposites Resolved through In Situ Synchrotron Diffraction Studies

High-energy synchrotron X-rays were used to probe the structural and microstructural evolution in Fe, Co, and Cu nanoporous metals (NPMs) and metal/salt nanocomposites (NCs) produced by recently developed conversion reaction synthesis (CRS) methods. Microstructure analysis of as-synthesized samples via whole pattern fitting showed that the NPMs exhibit domain sizes that increase as Co < Fe < Cu, with both Fe and Co having crystallite sizes below 3.0 nm. The as-synthesized metal/salt NCs had similar metal sizes, and additionally, the salt in the composite had unusually large lattice microstrain whose origin is attributed to chemical substitution of metal ions into the salt (e.g., Li1–3xFexCl for Fe3+). When thermal annealing is used to modify crystallite size, pore collapse often occurs in NPMs but NCs can be effectively tuned without this problem. While the NC coarsening occurs slowly at low temperatures, it was found that there is a drastic acceleration of the reaction rate at a specific onset temperature that results in the crystallite size increasing by an order of magnitude in about a minute. Curiously, there was no evidence in the diffraction data for salt melting at this onset temperature. However, there was a sharp reduction in the salt chemical lattice strain at the onset temperature, indicating that rapid metal coarsening is facilitated by the salt. This behavior indicates an unexpectedly coupled reaction mechanism by which the metal ions needed for grain growth are supplied by the salt in a rate-limiting fashion.

Absolute Stimulated Raman Cross Sections of Molecules

Stimulated Raman scattering (SRS) is a fundamental optical process that was discovered more than 60 years ago. While the early SRS spectroscopy studies have provided valuable insights into materials systems, the advent of SRS microscopy has launched a rapidly growing field in biological imaging. However, a fundamental understanding of the molecular response under SRS is still lacking. Herein we present a new framework to introduce molecule-intrinsic stimulated Raman scattering cross sections, σSRS, in the unit of Göppert-Mayer (GM). The absolute SRS cross sections determined for real molecular systems challenge the conventional wisdom that Raman spectroscopy is always a weak process. The enormous rate acceleration of SRS, captured by an apparent SRS cross section, stems from a synergistic effect between the field and the molecule. Our new framework goes beyond the conventional optics-centric view and presents a molecule-inclusive perspective, thus offering a comprehensive foundation for the future growth of SRS spectroscopy and microscopy.

Spin state and deep interior structure of Mars from InSight radio tracking.

Knowledge of the interior structure and atmosphere of Mars is essential to understanding how the planet has formed and evolved. A major obstacle to investigations of planetary interiors, however, is that they are not directly accessible. Most of the geophysical data provide global information that cannot beseparated into contributions from the core, the mantle and the crust. The NASA InSight mission changed this situation by providing high-quality seismic and lander radio science data1,2. Here we use the InSight's radio science data to determine fundamental properties of the core, mantle and atmosphere of Mars. By precisely measuring the rotation of the planet, we detected a resonance with a normal mode that allowed us to characterize the core and mantle separately. For an entirely solid mantle, we found that the liquid core has a radius of 1,835 ± 55 km and a mean density of 5,955-6,290 kg m-3, and that the increase in density at the core-mantle boundary is 1,690-2,110 kg m-3. Our analysis of InSight's radio tracking data argues against the existence of a solid inner core and reveals the shape of the core, indicating that there are internal mass anomalies deep within the mantle. We also find evidence of a slow acceleration in the Martian rotation rate, which could be the resultof a long-term trend either inthe internal dynamics of Mars or in its atmosphere and ice caps.

Cooperative Covalent Polymerization of N-carboxyanhydrides: from Kinetic Studies to Efficient Synthesis of Polypeptide Materials

ConspectusPolypeptides, as the synthetic analogues of natural proteins, are an important class of biopolymers that are widely studied and used in various biomedical applications. However, the preparation of polypeptide materials from the polymerization of N-carboxyanhydride (NCA) is limited by various side reactions and stringent polymerization conditions. Recently, we report the cooperative covalent polymerization (CCP) of NCA in solvents with low polarity and weak hydrogen-bonding ability (e.g., dichloromethane or chloroform). The polymerization exhibits characteristic two-stage kinetics, which is significantly accelerated compared with conventional polymerization under identical conditions. In this Account, we review our recent studies on the CCP, with the focus on the acceleration mechanism, the kinetic modeling, and the use of fast kinetics for the efficient preparation of polypeptide materials.By studying CCP with several initiating systems, we found that the polymerization rate was dependent on the secondary structure as well as the macromolecular architecture of the propagating polypeptides. The molecular interactions between the α-helical, propagating polypeptide and the monomer played an important role in the acceleration, which catalyzed the ring-opening reaction of NCA in an enzyme-mimetic, Michaelis–Menten manner. Additionally, the proximity between initiating sites further accelerated the polymerization, presumably due to the cooperative interactions of macrodipoles between neighboring helices and/or enhanced binding of monomers. A two-stage kinetic model with a reversible monomer adsorption process in the second stage was developed to describe the CCP kinetics, which highlighted the importance of cooperativity, critical chain length, binding constant, [M]0, and [M]0/[I]0. The kinetic model successfully predicted the polymerization behavior of the CCP and the molecular-weight distribution of resulting polypeptides.The remarkable rate acceleration of the CCP offers a promising strategy for the efficient synthesis of polypeptide materials, since the fast kinetics outpaces various side reactions during the polymerization process. Chain termination and chain transfer were thus minimized, which facilitated the synthesis of high-molecular-weight polypeptide materials and multiblock copolypeptides. In addition, the accelerated polymerization enabled the synthesis of polypeptides in the presence of an aqueous phase, which was otherwise challenging due to the water-induced degradation of monomers. Taking advantage of the incorporation of the aqueous phase, we reported the preparation of well-defined polypeptides from nonpurified NCAs. We believe the studies of CCP not only improve our understanding of biological catalysis, but also benefit the downstream studies in the polypeptide field by providing versatile polypeptide materials.

Accelerating SN2 nucleophilic fluorination of primary alkyl bromide using an 18-crown-6 and fluorinated bulky alcohol phase transfer system

A new phase transfer system for nucleophilic fluorination of alkyl halides with potassium fluoride, based on the combination of 18-crown-6 and the bulky fluorinated alcohol 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, was found to be very effective. A primary alkyl bromide was fluorinated in 24 h of reaction time with a mild temperature of 82 °C using acetonitrile solvent, obtaining 80% yield and only a trace of elimination product. The rational choice of this alcohol was based on a free energy profile of a reaction model including the solubilization of the KF salt and on the theoretical calculations of the stability of the KF(18-crown-6)(alcohol) complexes. The fluorinated bulky alcohol leads to a substantial increase in the concentration of KF complexed with 18-crown-6, which compensates for the decreased reactivity of the solubilized complex. The present study shows the importance of the modulation of the hydrogen bonding strength to obtain the rate acceleration effect.

Interleukin 4 Reduces Brain Hyperexcitability after Traumatic Injury by Downregulating TNF-α, Upregulating IL-10/TGF-β, and Potential Directing Macrophage/Microglia to the M2 Anti-inflammatory Phenotype.

Macrophage/microglia are activated after Traumatic brain injury (TBI), transform to inflammatory phenotype (M1) and trigger neuroinflammation, which provokes epileptogenesis. Interleukin-4 (IL-4) is a well-known driveof macrophage/microglia to the anti-inflammatory phenotype (M2). We tested effect of IL-4 on speed of epileptogenesis, brain expression of inflammatory and anti-inflammatory cytokines, and lesion size in TBI-injured male rats. Rats underwent TBI by Controlled Cortical Impact. Then 100 ng IL-4 was injected into cerebral ventricles. One day after TBI, pentylenetetrazole (PTZ) kindling started and development of generalized seizures was recorded. The lesion size, cell survival rate, TNF-α, TGF-β, IL-10, and Arginase1 (Arg1) was measured in the brain 6 h, 12 h, 24 h, 48 h, and 5 days after TBI. Astrocytes and macrophage/microglia activation/polarization was assessed by GFAP/Arg1 and Iba1/Arg1 immunostaining. TBI-injured rats were kindled by 50% less PTZ injections than control and sham-operated rats. IL-4 did not change kindling rate in sham-operated rats but inhibited acceleration of kindling rate in the TBI-injured rats. IL-4 decreased damage volume and number of destroyed neurons. IL-4 stopped TNF-α whereas upregulated TGF-β, IL-10, and Arg1 expressions. Iba1/Arg1 positive macrophage/microglia was notably increased 48 h after IL-4 administration. IL-4 suppresses TBI-induced acceleration of epileptogenesis in rats by directing TBI neuroinflammation toward an anti-inflammatory tone and inhibition of cell death.

Energetics of the Glycosyl Transfer Reactions of Sucrose Phosphorylase.

From its structure and mechanism, sucrose phosphorylase is a specialized glycoside hydrolase that uses phosphate ions instead of water as the nucleophile of the reaction. Unlike the hydrolysis reaction, the phosphate reaction is readily reversible and, here, this has enabled the study of temperature effects on kinetic parameters to map the energetic profile of the complete catalytic process via a covalent glycosyl enzyme intermediate. Enzyme glycosylation from sucrose and α-glucose 1-phosphate (Glc1P) is rate-limiting in the forward (kcat = 84 s-1) and reverse direction (kcat = 22 s-1) of reaction at 30 °C. Enzyme-substrate association is driven by entropy (TΔSb ≥ +23 kJ/mol), likely arising from enzyme desolvation at the binding site for the leaving group. Approach from the ES complex to the transition state involves uptake of heat (ΔH⧧ = 72 ± 5.2 kJ/mol) with little further change in entropy. The free energy barrier for the enzyme-catalyzed glycoside bond cleavage in the substrate is much lower than that for the non-enzymatic reaction (knon), ΔΔG⧧ = ΔGnon⧧ - ΔGenzyme⧧ = +72 kJ/mol; sucrose. This ΔΔG⧧, which also describes the virtual binding affinity of the enzyme for the activated substrate in the transition state (∼1014 M-1), is almost entirely enthalpic in origin. The enzymatic rate acceleration (kcat/knon) is ∼1012-fold and similar for reactions of sucrose and Glc1P. The 103-fold lower reactivity (kcat/Km) of glycerol than fructose in enzyme deglycosylation reflects major losses in the activation entropy, suggesting a role of nucleophile/leaving group recognition by the enzyme in inducing the active-site preorganization required for optimum transition state stabilization by enthalpic forces.

Rationalizing and Adapting Water-Accelerated Reactions for Sustainable Flow Organic Processes.

Water-accelerated reactions, wherein at least one organic reactant is not soluble in water, are an important class of organic reactions, with a potentially pivotal impact on sustainability of chemical manufacturing processes. However, mechanistic understanding of the factors controlling the acceleration effect has been limited, due to the complex and varied physical and chemical nature of these processes. In this study, a theoretical framework has been established to calculate the rate acceleration of known water-accelerated reactions, giving computational estimations of the change to ΔG‡ which correlate with experimental data. In-depth study of a Henry reaction between N-methylisatin and nitromethane using our framework led to rationalization of the reaction kinetics, its lack of dependence on mixing, kinetic isotope effect, and different salt effects with NaCl and Na2SO4. Based on these findings, a multiphase flow process which includes continuous phase separation and recycling of the aqueous phase was developed, and its superior green metrics (PMI-reaction = 4 and STY = 0.64 kg L-1 h-1) were demonstrated. These findings form the essential basis for further in silico discovery and development of water-accelerated reactions for sustainable manufacturing.

Acceleration of the Deamination of Cytosine through Photo-Crosslinking.

Herein, we report the major factor for deamination reaction rate acceleration, i.e., hydrophilicity, by using various 5-substituted target cytosines and by carrying out deamination at high temperatures. Through substitution of the groups at the 5'-position of the cytosine, the effect of hydrophilicity was understood. It was then used to compare the various modifications of the photo-cross-linkable moiety as well as the effect of the counter base of the cytosine to edit both DNA and RNA. Furthermore, we were able to achieve cytosine deamination at 37 °C with a half-life in the order of a few hours.

Artificial esterase for cooperative catalysis of ester hydrolysis at pH 7

Ester is one of the most prevalent functional groups in natural and man-made products. Natural esterases hydrolyze nonactivated alkyl esters readily but artificial esterases generally use highly activated p-nitrophenyl esters as substrates. We report synthetic esterases constructed through molecular imprinting in cross-linked micelles. The water-soluble nanoparticle catalysts contain a thiouronium cation to mimic the oxyanion hole and a nearby base to assist the hydrolysis. Whereas this catalytic motif readily affords large rate acceleration for the hydrolysis of p-nitrophenyl hexanoate, nonactivated cyclopentyl hexanoate demands catalytic groups that can generate a strong nucleophile (hydroxide) in the active site. The hydroxide is stabilized by the protonated base when the external solution is at pH 7, enabling the hydrolysis of activated and nonactivated esters under neutral conditions.

Enzymatic Bioconjugation: A Perspective from the Pharmaceutical Industry.

Enzymes have firmly established themselves as bespoke catalysts for small molecule transformations in the pharmaceutical industry, from early research and development stages to large-scale production. In principle, their exquisite selectivity and rate acceleration can also be leveraged for modifying macromolecules to form bioconjugates. However, available catalysts face stiff competition from other bioorthogonal chemistries. In this Perspective, we seek to illuminate applications of enzymatic bioconjugation in the face of an expanding palette of new drug modalities. With these applications, we wish to highlight some examples of current successes and pitfalls of using enzymes for bioconjugation along the pipeline and try to illustrate opportunities for further development.

PO-05-056 FAILURE OF INTRINSIC ANTI-TACHYCARDIA PACING TO TERMINATE VENTRICULAR TACHYCARDIA AND POTENTIAL PROARRHYTHMIC EFFECTS

Intrinsic anti-tachycardia pacing (iATP™) is a novel, automated ATP algorithm that provides individualized therapy to terminate ventricular tachycardia (VT). If the first ATP attempt is unsuccessful, the algorithm analyzes the tachycardia cycle length and the post-pacing interval (PPI) and adjusts the subsequent sequence to successfully terminate VT. This algorithm was effective in a single clinical study without a comparator arm and case reports have corroborated this success in clinical practice. Despite the previously presented data, iATP™ failure has not been well documented in the literature. We present the first case series of iATP™ failure in routine clinical practice with detailed episode analysis and the apprise the electrophysiology community of the potential proarrhythmic effect of the algorithm. We retrospectively evaluated 262 patients with Medtronic Cobalt XT defibrillators followed at Mayo Clinic campuses in Minnesota, Florida, and Arizona. 119 patients had devices with the iATP™ feature turned on. 4 out of 119 patients (3.36%) had an acceleration of their ventricular arrhythmias within our cohort. Illustrative Case: A 74-year-old male with a history of idiopathic, non-ischemic cardiomyopathy (LVEF) 21%) status post-cardiac resynchronization therapy (CRT)-defibrillator for primary prevention, subsequent VT, and atrial fibrillation presented to our heart rhythm clinic for evaluation of syncope. The patient was riding an all-terrain vehicle when he felt a sudden onset of dyspnea and pre-syncope. His device interrogation revealed a presenting rhythm of VT at 200 beats per minute (bpm). The patient underwent four unsuccessful rounds of ATP. The 4th round of ATP resulted in acceleration (figure 1A) and degeneration into ventricular fibrillation (VF), followed by a successful 39.5 J shock (figure 1B). Figure 1C shows the dot plot for the entire episode with the blue box highlighting the acceleration in ventricular rate after the 4th ATP sequence. Given concern for a proarrhythmic effect, iATP™ was turned off. The patient was treated with amiodarone and mexiletine and underwent endocardial ablation with substrate modification in the inferolateral LV. He is currently doing well without a subsequent need for VT therapies. While the novel adaptive algorithm and its underlying concepts are intriguing, clinicians should be aware of the potential for acceleration and degeneration of VT by iATP™ and prepared to turn off the feature when this occurs.

Accelerated glacier mass loss in the southeastern Tibetan Plateau since the 1970s

The southeastern Tibetan Plateau (SETP) is a region in High Mountain Asia with the most serious glacier mass loss. However, long-term and large regional-scale studies that estimate glacier mass balance in this area remain limited. In this study, we generated a KH-9 Digital Elevation Model (DEM) (covering 87.6% of the glacier area) for the 1970s from KH-9 Hexagon imagery and quantified geodetic glacier mass over the SETP from the 1970s to 2020 using KH-9 DEM, NASADEM and ICESat-2 ATL06 data. The results show that the SETP was in a state of serious mass loss (at a rate of −0.35 ± 0.03 m w.e. per year) from the 1970s to 2020, and the rate of mass loss accelerated from −0.15 ± 0.05 to −0.56 ± 0.10 m w.e. per year between the 1970s–2000 and 2000–2020. Within the SETP, the glacier mass balance revealed a remarkable spatial heterogeneity. The maximum mean glacier mass loss rate was observed in the Hengduan Shan. Nyainqentanglha exhibited the highest acceleration in the mass loss rate since the 1970s. The warming of air temperature and decreasing snowfall can partly explain the accelerated glacier mass loss in the SETP. The study provides a new long-term glacier mass balance estimation covering almost the entire SETP that suggests the acceleration in glacier mass loss observed in the SETP since the 1970s is a regional tendency, which is crucial for understanding the relationship between glaciers and climate changes.