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"Ma, Michael"
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China's long-range bomber flights : drivers and implications
\"This report examines the key drivers behind China's strategic bomber flights throughout the Asia-Pacific region, assessing Chinese commentary on flights and leveraging a number of sources, including interviews in Taipei and Tokyo, to better understand and gauge regional reactions. The report recommends specific responses for consideration by the U.S. Air Force and U.S. policymakers, as well as allies and partners, offering an in-depth analysis of the key issues driving top Chinese leaders to move in the direction of conducting these overwater bomber flights. Since March 2015, the Chinese People's Liberation Army Air Force (PLAAF) has sent its strategic bomber on long-range overwater flights on at least 38 separate occasions to important areas throughout the Asia-Pacific region. Chinese leaders seek to achieve at least four key objectives with PLAAF bomber flights throughout the region: First, bombers enable Beijing to send a deterrence message or to signal resolve in the conventional military domain to defend its maritime territorial claims. Second, overwater flights significantly enhance realistic training for PLAAF operators. Third, successful bomber flights offer Chinese leaders the opportunity to play up their achievements for domestic consumption, highlighting progress toward the building of 'world-class' military forces. And fourth, the increased operational tempo of PLAAF bomber flights around Taiwan appear to be designed, at least in part, to ratchet up pressure against Taiwanese president Tsai Ing-wen, as she has refused to acknowledge the 1992 Consensus, also known as the One China Consensus, since taking office in May 2016\"--Rand website.
Book
Decay of ultralight axion condensates
A
bstract
Axion particles can form macroscopic condensates, whose size can be galactic in scale for models with very small axion masses
m
∼ 10
−22
eV, and which are sometimes referred to under the name of Fuzzy Dark Matter. Many analyses of these condensates are done in the non-interacting limit, due to the weakness of the self-interaction coupling of axions. We investigate here how certain results change upon inclusion of these interactions, finding a decreased maximum mass and a modified mass-radius relationship. Further, these condensates are, in general, unstable to decay through number-changing interactions. We analyze the stability of galaxy-sized condensates of axion-like particles, and sketch the parameter space of stable configurations as a function of a binding energy parameter. We find a strong lower bound on the size of Fuzzy Dark Matter condensates which are stable to decay, with lifetimes longer than the age of the universe.
Journal Article
Functionally coupled ion channels begin co-assembling at the start of their synthesis
Calcium binding to BK channels lowers BK activation threshold, substantiating functional coupling with calcium-permeable channels. This coupling requires close proximity between different channel types, and the formation of BK-Ca V 1.3 hetero-clusters at nanometer distances exemplifies this unique organization. To investigate the structural basis of this interaction, we tested the hypothesis that BK and Ca V 1.3 channels assemble before their insertion into the plasma membrane. Our approach incorporated four strategies: (1) detecting interactions between BK and Ca V 1.3 proteins inside the cell, (2) identifying membrane compartments where intracellular hetero-clusters reside, (3) measuring the proximity of their mRNAs, and (4) assessing protein interactions at the plasma membrane during early translation. These analyses revealed that a subset of BK and Ca V 1.3 transcripts are spatially close in micro-translational complexes, and their newly synthesized proteins associate within the endoplasmic reticulum (ER) and Golgi. Comparisons with other proteins, transcripts, and randomized localization models support the conclusion that BK and Ca V 1.3 hetero-clusters form before their insertion at the plasma membrane.
Journal Article
Congenital Heart Surgical Admissions in Patients with Trisomy 13 and 18: Frequency, Morbidity, and Mortality
Congenital heart defects are common among patients with trisomy 13 and 18; surgical repair has been controversial and rarely studied. We aimed to assess the frequency of cardiac surgery among admissions with trisomy 13 and 18, and evaluate their associations with resource use, complications, and mortality compared to admissions without these diagnoses. We evaluated congenital heart surgery admissions of ages < 18 years in the 1997, 2000, 2003, 2006, and 2009 Kids’ Inpatient Database. Bivariate and multivariate analyses examined the adjusted association of trisomy 13 and 18 on resource use, complications, and inpatient death following congenital heart surgery. Among the 73,107 congenital heart surgery admissions, trisomy 13 represented 0.03% (
n
= 22) and trisomy 18 represented 0.08% (
n
= 58). Trisomy 13 and 18 admissions were longer; trisomy 13: 27 days vs. 8 days,
p
= 0.003; trisomy 18: 16 days vs. 8 days,
p
= 0.001. Hospital charges were higher for trisomy 13 and 18 admissions; trisomy 13: $160,890 vs. $87,007,
p
= 0.010; trisomy 18: $160,616 vs. $86,999,
p
< 0.001. Trisomy 18 had a higher complication rate: 52% vs. 34%,
p
< 0.006. For all cardiac surgery admissions, mortality was 4.5%; trisomy 13: 14% and trisomy 18: 12%. In multivariate analysis, trisomy 18 was an independent predictor of death: OR 4.16, 95% CI 1.35–12.82,
p
= 0.013. Patients with trisomy 13 and 18 represent 0.11% of pediatric congenital heart surgery admissions. These patients have a 2- to 3.4-fold longer hospital stay and double hospital charges. Patients with trisomy 18 have more complications and four times greater adjusted odds for inpatient death.
Journal Article
Benign biliary strictures: prevalence, impact, and management strategies
Benign biliary strictures (BBSs) may form from chronic inflammatory pancreaticobiliary pathologies, postoperative bile-duct injury, or at biliary anastomoses following liver transplantation. Treatment aims to relieve symptoms of biliary obstruction, maintain long-term drainage, and preserve liver function. Endoscopic therapy, including stricture dilatation and stenting, is effective in most cases and the first-line treatment of BBS. Radiological and surgical therapies are reserved for patients whose strictures are refractory to endoscopic interventions. Response to treatment is dependent upon the technique and accessories used, as well as stricture etiology. In this review, we discuss the various BBS etiologies and their management strategies.
Journal Article
Ex Vivo Modeling of Atrioventricular Valve Mechanics in Single Ventricle Physiology
Single ventricle physiology (SVP) is used to describe any congenital heart lesion that is unable to support independent pulmonary and systemic circulations. Current treatment strategies rely on a series of palliation surgeries that culminate in the Fontan physiology, which relies on the single functioning ventricle to provide systemic circulation while passively routing venous return through the pulmonary circulation. Despite significant reductions in early mortality, the presence of atrioventricular valve (AVV) regurgitation is a key predictor of heart failure in these patients. We sought to evaluate the biomechanical changes associated with the AVV in SVP physiologies. Left and right ventricles were sutured onto patient-derived 3D-printed mounts and mounted into an ex vivo systemic heart simulator capable of reproducing Norwood, Glenn, Fontan and Late Fontan physiologies. We found that the tricuspid anterior leaflet experienced elevated maximum force, average force, and maximum yank compared to the posterior and septal leaflets. Between physiologies, maximum yank was greatest in the Norwood physiology relative to the Glenn, Fontan, and Late Fontan physiologies. These contrasting trends suggest that long- and short-term mechanics of AVV failure in single ventricle differ and that AVV interventions should account for asymmetries in force profiles between leaflets and physiologies.
Journal Article
Comparison of long and short axis quantification of left ventricular volume parameters by cardiovascular magnetic resonance, with ex-vivo validation
Background
The purpose of the study was to compare the accuracy and evaluation time of quantifying left ventricular (LV), left atrial (LA) volume and LV mass using short axis (SAX) and long axis (LAX) methods when using cardiovascular magnetic resonance (CMR).
Materials and methods
We studied 12 explanted canine hearts and 46 patients referred for CMR (29 male, age 47 ± 18 years) in a clinical 1.5 T CMR system, using standard cine sequences. In standard short axis stacks of various slice thickness values in dogs and 8 mm slice thickness (gap 2 mm) in patients, we measured LV volumes using reference slices in a perpendicular, long axis orientation using certified software. Volumes and mass were also measured in six radial long axis (LAX) views.
LV parameters were also assessed for intra- and inter-observer variability. In 24 patients, we also analyzed reproducibility and evaluation time of two very experienced (> 10 years of CMR reading) readers for SAX and LAX.
Results
In the explanted dog hearts, there was excellent agreement between ex vivo data and LV mass and volume data as measured by all methods for both, LAX (r
2
= 0.98) and SAX (r
2
= 0.88 to 0.98). LA volumes, however, were underestimated by 13% using the LAX views. In patients, there was a good correlation between all three assessed methods (r
2
≥ 0.95 for all). In experienced clinical readers, left-ventricular volumes and ejection fraction as measured in LAX views showed a better inter-observer reproducibility and a 27% shorter evaluation time.
Conclusion
When compared to an ex vivo standard, both, short axis and long axis techniques are highly accurate for the quantification of left ventricular volumes and mass. In clinical settings, however, the long axis approach may be more reproducible and more time-efficient. Therefore, the rotational long axis approach is a viable alternative for the clinical assessment of cardiac volumes, function and mass.
Journal Article
Histologic changes in systemically loaded right ventricles at time of transplantation
In a subset of complex congenital heart disease patients, the right ventricle (RV) is connected to the higher-resistance systemic circulation, often leading to RV dysfunction. This study characterizes the systemic RV histology at time of heart transplantation in two groups - patients with hypoplastic left heart syndrome with Fontan palliation (HLHS-F) and those with dextro-transposition of the great arteries post atrial switch operation (d-TGA-AS). We sought to better understand histological differences between the systemic RV in the single ventricle vs. biventricular circulations.
We procured RV tissue samples at the mid-cavity free walls from nine explanted recipient hearts: six HLHS-F and three d-TGA-AS. RV and LV muscle samples from two organ donors whose hearts were unused for non-cardiac reasons served as controls. Tissue sections were stained with Masson's Trichrome and Hematoxylin and Eosin. Given the small cohort size and heterogeneity, analyses were descriptive. Continuous variables are reported as median (range).
The d-TGA-AS population was older than the HLHS-F population (median: 42 years; range: 38-44 vs. median: 24 years; range: 12-32, respectively). RV fibrosis in the d-TGA-AS population was greater at 28% (7-35) vs. the HLHS-F population which was 4% (2-24) and donor controls (median: 2% range: 0-4). In contrast, RV wall thickness was greater in HLHS-F (median: 12,303 µm; range: 9,976-15,745) than in d-TGA-AS (median: 9,063 µm; range: 8,316-10,322) and donors (median 7,984 µm; range: 2,582-13,386). Donor LV thickness (median: 17,056 µm; range: 16,688-17,423) exceeded all RV groups.
The primary histologic finding for the d-TGA-AS group was fibrosis, while the HLHS-F group showed predominantly hypertrophy. The temporal presentation of the patients was different, with the HLHS-F patients presenting earlier for transplant than the d-TGA-AS. These observations suggest that different histologic changes may occur in response to longstanding systemic pressures in these two anatomic subgroups of patients with systemic RV.
Journal Article
Preexisting right ventricular systolic dysfunction in high-risk patients undergoing non.emergent open abdominal surgery: A retrospective cohort study
Background: The prognostic value of right ventricular systolic dysfunction in high-risk patients undergoing non-emergent open abdominal surgery is unknown. Here, we aim to evaluate whether presence of preexisting right ventricular systolic dysfunction in this surgical cohort is independently associated with higher incidence of postoperative major adverse cardiac events and all-cause in-hospital mortality.
Methods: This is a single-centered retrospective study. Patients identified as American Society Anesthesiology Classification III and IV who had a preoperative echocardiogram within 1 year of undergoing non-emergent open abdominal surgery between January 2010 and May 2017 were included in the study. Incidence of postoperative major cardiac adverse events and all-cause in-hospital mortality were collected. Multivariable logistic regression was performed in a step-wise manner to identify independent association between preexisting right ventricular systolic dysfunction with outcomes of interest.
Results: Preexisting right ventricular systolic dysfunction was not associated with postoperative major adverse cardiac events (P = 0.26). However, there was a strong association between preexisting right ventricular systolic dysfunction and all-cause in-hospital mortality (P = 0.00094). After multivariate analysis, preexisting right ventricular systolic dysfunction continued to be an independent risk factor for all-cause in-hospital mortality with an odds ratio of 18.9 (95' CI: 1.8-201.7; P = 0.015).
Conclusion: In this retrospective study of high-risk patients undergoing non-emergent open abdominal surgery, preexisting right ventricular systolic dysfunction was found to have a strong association with all-cause in-hospital mortality.
Journal Article
Recent outcomes of the extracardiac Fontan procedure in patients with hypoplastic left heart syndrome
Objective: To investigate patient-related factors, echocardiographic, and anatomic variables associated with immediate and long-term clinical outcomes after extracardiac Fontan procedure at our institution.
Materials and Methods: Retrospective review of preoperative cardiac catheterizations and echocardiograms as well as medical records of all children with hypoplastic left heart syndrome (HLHS) who underwent Fontan between June 2002 and December 2018.
Results: Seventy-seven patients with HLHS were included (age 4 years [1.5-11.7]). Seventy patients (91%) received a nonfenestrated Fontan and 57 patients (74%) underwent Fontan without cardiopulmonary bypass (CPB). Presence of a Fontan fenestration (P = 0.69) and use of CPB (P = 0.79) did not differ between those with <2 weeks compared to those with =2 weeks of chest tube drainage. There were no differences in either pre- or intra-operative hemodynamics between patients who weighed <15 kg compared to those who weighed ≥15 kg at time of surgery; incidence of death, transplant, and transplant listing were similar between weight groups. Inferior vena cava (IVC) diameter z-score did not differ among patients with and without chylous chest tube drainage (P = 0.78), with and without development of protein losing enteropathy (P = 0.23), or death/heart transplant/transplant listing compared to survivors without transplant (P = 0.26)
Conclusion: In HLHS patients undergoing Fontan, preoperative weight and IVC diameter appeared to have no influence on immediate postoperative outcomes. Performing the Fontan off CPB and with a fenestration also conferred no added clinical benefit. These observations should be considered when deciding optimal timing for Fontan completion.
Journal Article