Lignocellulose is a promising feedstock for biofuel production, while lignin poses a grand challenge on the entire process, especially enzymatic hydrolysis. In this study, different types of lignin ...inhibited enzymatic hydrolysis by different mechanisms. Organosolv lignin from Loblolly pine adsorbed enzyme nonproductively and reduced the available enzyme for cellulose, therefore decreasing hydrolysis rate and ultimate sugar yield. Kraft pine lignin precipitated on the surface of cellulose, preventing it from contacting with enzyme. The molecular weight influenced the inhibition effect of lignin. Lignin of lower molecular weight could bind enzyme nonproductively and when the molecular weight increased, the steric repulsion caused by lignin deposition on cellulose became more significant. The NMR analysis revealed that lignin structural features, e.g., functional groups, S/G ratio, determined the behaviors of lignin in enzymatic hydrolysis. High content of aliphatic hydroxyl groups, or low content of carboxylic groups led to high surface hydrophobicity, increasing the adsorption between lignin and enzyme. In addition, the substrate reactivity is also an important factor that affects enzymatic hydrolysis. Cellulose with higher crystallinity exhibited slower hydrolysis rate and lower conversion. When the crystallinity index increased from 0.43 to 0.72 and 0.81, the ultimate conversion decreased from 80 to 68% and 57%, respectively.
•The effects of different lignins on hydrolysis of different substrates were investigated.•The effect of lignin biomass resource and pretreatment method were compared.•Lignin with different molecular weight from the same source was studied.•The lignin inhibition was correlated with its structural features revealed by NMR.
The Pacific decadal oscillation (PDO), the dominant year-round pattern of monthly North Pacific sea surface temperature (SST) variability, is an important target of ongoing research within ...themeteorological and climate dynamics communities and is central to the work of many geologists, ecologists, natural resource managers, and social scientists. Research over the last 15 years has led to an emerging consensus: the PDO is not a single phenomenon, but is instead the result of a combination of different physical processes, including both remote tropical forcing and local North Pacific atmosphere–ocean interactions, which operate on different time scales to drive similar PDO-like SST anomaly patterns. How these processes combine to generate the observed PDO evolution, including apparent regime shifts, is shown using simple autoregressive models of increasing spatial complexity. Simulations of recent climate in coupled GCMs are able to capture many aspects of the PDO, but do so based on a balance of processes often more independent of the tropics than is observed. Finally, it is suggested that the assessment of PDO-related regional climate impacts, reconstruction of PDO-related variability into the past with proxy records, and diagnosis of Pacific variability within coupled GCMs should all account for the effects of these different processes, which only partly represent the direct forcing of the atmosphere by North Pacific Ocean SSTs.
The COVID-19 pandemic has disrupted established care paths worldwide. Patient awareness of the pandemic and executive limitations imposed on public life have changed the perception of when to seek ...care for acute conditions in some cases. We sought to study whether there is a delay in presentation for acute ischemic stroke patients in the first month of the pandemic in the US.
The interval between last-known-well (LKW) time and presentation of 710 consecutive patients presenting with acute ischemic strokes to 12 stroke centers across the US were extracted from a prospectively maintained quality database. We analyzed the timing and severity of the presentation in the baseline period from February to March 2019 and compared results with the timeframe of February and March 2020.
There were 320 patients in the 2-month baseline period in 2019, there was a marked decrease in patients from February to March of 2020 (227 patients in February, and 163 patients in March). There was no difference in the severity of the presentation between groups and no difference in age between the baseline and the COVID period. The mean interval from LKW to the presentation was significantly longer in the COVID period (603±1035 min) compared with the baseline period (442±435 min, P<0.02).
We present data supporting an association between public awareness and limitations imposed on public life during the COVID-19 pandemic in the US and a delay in presentation for acute ischemic stroke patients to a stroke center.
Wide-necked bifurcation aneurysms (WNBAs) make up 26-36% of all brain aneurysms. Treatments for WNBAs pose unique challenges due to the need to preserve major bifurcation vessels while achieving a ...durable occlusion of the aneurysm. Intrasaccular flow disruption is an innovative technique for the treatment of WNBAs. The Woven EndoBridge (WEB) device is the only United States Food and Drug Administration approved intrasaccular flow disruption device. In this review article we discuss various aspects of treating WNBAs with the WEB device, including indications for use, aneurysm/device selection strategies, antiplatelet therapy requirement, procedural technique, potential complications and bailouts, and management strategies for residual/recurrent aneurysms after initial WEB treatment.
There are limited data evaluating the effect of post mechanical thrombectomy (MT) blood pressure (BP) levels on early outcomes of patients with large vessel occlusions (LVO). We sought to investigate ...the association of BP course following MT with early outcomes in LVO.
Consecutive patients with LVO treated with MT during a 3-year period were evaluated. Hourly systolic BP (SBP) and diastolic BP (DBP) values were recorded for 24 hours following MT and maximum SBP and DBP levels were identified. LVO patients with complete reperfusion following MT were stratified in 3 groups based on post-MT achieved BP goals: <140/90 mm Hg (intensive), <160/90 mm Hg (moderate), and <220/110 mm Hg or <180/105 mm Hg when pretreated with IV thrombolysis (permissive hypertension). Three-month functional independence was defined as modified Rankin Scale score of 0-2.
A total of 217 acute ischemic stroke patients with LVO were prospectively evaluated. A 10 mm Hg increment in maximum SBP documented during the first 24 hours post MT was independently (
= 0.001) associated with a lower likelihood of 3-month functional independence (odds ratio OR 0.70; 95% confidence interval CI 0.56-0.87) and a higher odds of 3-month mortality (OR 1.49; 95% CI 1.18-1.88) after adjusting for potential confounders. In addition, achieving a BP goal of <160/90 mm Hg during the first 24 hours following MT was independently associated with a lower likelihood of 3-month mortality (OR 0.08; 95% CI 0.01-0.54;
= 0.010) in comparison to permissive hypertension.
High maximum SBP levels following MT are independently associated with increased likelihood of 3-month mortality and functional dependence in LVO patients. Moderate BP control is also related to lower odds of 3-month mortality in comparison to permissive hypertension.
Wide-necked bifurcation aneurysms (WNBAs) present unique technical challenges for both endovascular and surgical treatments which aim to achieve complete occlusion of the aneurysm without ...compromising the patency of the incorporated regional parent vessels. We present a meta-analysis of traditional therapies for WNBAs to provide critical benchmarks for safety and effectiveness.
Following a systematic search of the literature and the application of pre-specified appropriateness criteria, 43 (including 2794 aneurysms treated) and 65 (including 5366 patients treated) references with sufficient detail were identified to include in a meta-analysis of efficacy and safety, respectively. Effectiveness endpoints of both complete and adequate occlusion were assessed. A composite safety endpoint was based upon commonly applied metrics for major adverse events. Fleiss analyses were performed for both effectiveness and safety endpoints for the entire group, and then parsed separately by treatment modality (surgical clipping (SC) or endovascular therapy (EVT)) and location (anterior or posterior circulation).
Using the above methods, the core laboratory adjusted rate of complete occlusion was 46.3% (standard error 3.6%), 39.8% (3.7%), and 52.5% (9.6%) for all therapies, EVT, and SC, respectively. The rate of adequate occlusion was 59.4% (12.2%), 43.8% (5.3%), and 69.7% (14.3%) for all therapies, EVT, and SC, respectively. The rates of occurrence for pre-specified safety endpoints were 18.7% (2.9%), 21.1% (2.8%), and 24.3% (4.9%) for all therapies, EVT, and SC, respectively.
Conventional therapies for WNBAs are associated with relatively low rates of complete occlusion and peri-procedural complications are not uncommon. As new treatment technologies are investigated, it is important that the available data regarding predicate treatments is understood.
Following the successful completion of 5 major trials establishing the clinical efficacy of endovascular thrombectomy for ELVO in the setting of AIS, there has been a tremendous focus on identifying ...additional patient populations that may benefit from the intervention. Improved imaging modalities and subsequent trials found thrombectomy to be highly efficacious in patients presenting up to 24 hours after stroke onset, particularly with good collaterals and large penumbral regions. Iterative catheter and device development have improved the safety profile and enhanced the efficacy of the procedure with the introduction of balloon-guide catheters, larger bore navigable aspiration catheters, and smaller catheters and devices to access medium and distal vessel occlusions. While trials are ongoing to assess the utility of thrombectomy in patients presenting with large core infarcts, distal occlusions, and direct aspiration as a first-line approach, the highly effective nature of thrombectomy for ELVO is continuing to drive the field of endovascular stroke care forward.
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