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A study of spring plankton blooms in shallow, coastal waters in temperate latitude suggests that annual variability in the timing of blossoming occurs due to yearly differences in incident radiation. Spring phytoplankton blooms in offshore and open ocean waters that are sensitive to annual weather variations and essential to the carbon cycle. Temperate marine planktons also depend on greenhouse warming and other factors which influence the climate system.

• Lesion detectability was not lost using proposed low-dose PET-CT protocol. • Low-dose PET-CT protocol reduces radiation exposure to 43% of standard protocol. • Machine-learning increased lesion contrast and reduced false positives. • Machine-learning enables radiation exposure reduction to 34% of standard protocol. To conduct a simplified lesion-detection task of a low-dose (LD) PET-CT protocol for frequent lung screening using 30% of the effective PETCT dose and to investigate the feasibility of increasing clinical value of low-statistics scans using machine learning. We acquired 33 SD PET images, of which 13 had actual LD (ALD) PET, and simulated LD (SLD) PET images at seven different count levels from the SD PET scans. We employed image quality transfer (IQT), a machine learning algorithm that performs patch-regression to map parameters from low-quality to high-quality images. At each count level, patches extracted from 23 pairs of SD/SLD PET images were used to train three IQT models – global linear, single tree, and random forest regressions with cubic patch sizes of 3 and 5 voxels. The models were then used to estimate SD images from LD images at each count level for 10 unseen subjects. Lesion-detection task was carried out on matched lesion-present and lesion-absent images. LD PET-CT protocol yielded lesion detectability with sensitivity of 0.98 and specificity of 1. Random forest algorithm with cubic patch size of 5 allowed further 11.7% reduction in the effective PETCT dose without compromising lesion detectability, but underestimated SUV by 30%. LD PET-CT protocol was validated for lesion detection using ALD PET scans. Substantial image quality improvement or additional dose reduction while preserving clinical values can be achieved using machine learning methods though SUV quantification may be biased and adjustment of our research protocol is required for clinical use. [ABSTRACT FROM AUTHOR]

Background: Following an acute coronary syndrome, combined CT and PET with 18F-NaF can identify coronary atherosclerotic plaques that have ruptured or eroded. However, the processes behind 18F-NaF uptake in vulnerable plaques remain unclear.Methods and Results: Ten patients with STEMI were scanned after 18F-NaF injection, for 75 minutes in a Siemens PET/MR scanner using delayed enhancement (LGE). They were then scanned in a Siemens PET/CT scanner for 10 minutes. Tissue-to-background ratio (TBR) was compared between the culprit lesion in the IRA and remote non-culprit lesions in an effort to independently validate prior studies. Additionally, we performed a proof-of-principle study comparing TBR in scar tissue and remote myocardium using LGE images and PET/MR or PET/CT data. From the 33 coronary lesions detected on PET/CT, TBRs for culprit lesions were higher than for non-culprit lesions (TBR = 2.11 ± 0.45 vs 1.46 ± 0.48; P < 0.001). Interestingly, the TBR measured on the PET/CT was higher for infarcted myocardium than for remote myocardium (TBR = 0.81 ± 0.10 vs 0.71 ± 0.05; P = 0.003). These results were confirmed using the PET/MR data (TBR = 0.81 ± 0.10 for scar, TBR = 0.71 ± 0.06 for healthy myocardium, P = 0.03).Conclusions: We confirmed the potential of 18F-NaF PET/CT imaging to detect vulnerable coronary lesions. Moreover, we demonstrated proof-of-principle that 18F-NaF concurrently detects myocardial scar tissue. [ABSTRACT FROM AUTHOR]

Amyloid deposits of wild-type apolipoprotein A-I (apoA-I), the main protein component of high-density lipoprotein, accumulate in atherosclerotic plaques where they may contribute to coronary artery disease by increasing plaque burden and instability. Using CD analysis, solid-state NMR spectroscopy, and transmission EM, we report here a surprising cooperative effect of heparin and the green tea polyphenol (-)- epigallocatechin-3-gallate (EGCG), a known inhibitor and modulator of amyloid formation, on apoA-I fibrils. We found that heparin, a proxy for glycosaminoglycan (GAG) polysaccharides that co-localize ubiquitously with amyloid in vivo, accelerates the rate of apoA-I formation from monomeric protein and associates with insoluble fibrils. Mature, insoluble apoA-I fibrils bound EGCG (KD = 30 ± 3 μM; Bmax = 40 ± 3 μM), but EGCG did not alter the kinetics of apoA-I amyloid assembly from monomer in the presence or absence of heparin. EGCG selectively increased the mobility of specific backbone and side-chain sites of apoA-I fibrils formed in the absence of heparin, but the fibrils largely retained their original morphology and remained insoluble. By contrast, fibrils formed in the presence of heparin were mobilized extensively by the addition of equimolar EGCG, and the fibrils were remodeled into soluble 20-nm-diameter oligomers with a largely α-helical structure that were nontoxic to human umbilical artery endothelial cells. These results argue for a protective effect of EGCG on apoA-I amyloid associated with atherosclerosis and suggest that EGCG-induced remodeling of amyloid may be tightly regulated by GAGs and other amyloid co-factors in vivo, depending on EGCG bioavailability. [ABSTRACT FROM AUTHOR]

Background: Capsinoids are reported to increase energy expenditure (EE) via brown adipose tissue (BAT) stimulation. However, imaging of BAT activation by capsinoids remains limited. Because BAT activation is a potential therapeutic strategy for obesity and related metabolic disorders, we sought to prove that capsinoid-induced BAT activation can be visualized by 18-fluorine fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). Objective: We compared capsinoids and cold exposure on BAT activation and whole-body EE. Design: Twenty healthy participants (8 men, 12 women) with a mean age of 26 y (range: 21-35 y) and a body mass index (kg/m2) of 21.7 (range: 18.5-26.0) underwent 18F-FDG PET and whole-body calorimetry after ingestion of 12 mg capsinoids or =2 h of cold exposure (~14.5°C) in a crossover design. Mean standardized uptake values (SUVs) of the region of interest and BAT volumes were calculated. Blood metabolites were measured before and 2 h after each treatment. Results: All of the participants showed negligible 18F-FDG uptake post-capsinoid ingestion. Upon cold exposure, 12 participants showed avid 18F-FDG uptake into supraclavicular and lateral neck adipose tissues (BAT-positive group), whereas the remaining 8 participants (BAT-negative group) showed undetectable uptake. Capsinoids and cold exposure increased EE, although cold induced a 2-fold increase in whole-body EE and higher fat oxidation, insulin sensitivity, and HDL cholesterol compared with capsinoids. Conclusions: Capsinoids only increased EE in BAT-positive participants, which suggests that BAT mediates EE evoked by capsinoids. This implies that capsinoids stimulate BAT to a lesser degree than cold exposure as evidenced by 18F-FDG uptake below the presently accepted SUV thresholds defining BAT activation. This trial was registered at www.clinicaltrials.gov as NCT02964442. [ABSTRACT FROM AUTHOR]

• The Gulf of Maine has warmed and continues to warm, to a large extent as the result of changes in advective heat fluxes driven by way of lateral exchanges with water masses in neighboring shelf and slope regions; • Water properties of the source waters themselves are shown to have been changing over time; moreover, cross shelf volume fluxes of those water masses to the Gulf have changed over time, and have become more highly variable in recent years. • Late summer episodes of abrupt influxes to the interior Gulf of warm and salty waters carrying reduced nitrate concentrations, reveal a mix that includes warm, salty, low nutrient Gulf Stream Water, which in some years arrives as an abrupt, bore-like, high salinity wave that precedes a continuing inflow of warm and salty waters over a period of several months. • A new baseline in the Gulf of Maine, of warmer temperatures and higher salinities, became established after 2010. • It was on top of that new baseline that a greater surface heat flux in the winter to summer period of 2011–2012 made possible the '2012 heat wave' in the Gulf of Maine, which was followed by two similar events in 2016 and 2021. • We suggest that these 'heat waves' are the result of 4–7 year oscillations between periods of warm and salty waters in the Gulf, and colder and fresher waters. Moreover, we suggest that this oscillation it is linked to an already-established multi-year variability, with frequency of 4–5 years, in the path of the Gulf Stream east of 60⁰W. • We present evidence that the winter-spring inflow of Scotian Shelf Water creates a barotropic pressure gradient in the Gulf that persists into the summer, thereby impeding the inflow of warm and salty Slope, and/or Gulf Stream Water, until that Scotian Shelf Water mass has become sufficiently dispersed in late summer, thereby effectively opening a valve that allows warm and salty deep waters from outside the Gulf to penetrate. We present an analysis of a 19-year time series of mooring data (T, S,) collected since 2003 in Jordan Basin in the eastern Gulf of Maine and beginning in 2016, in situ nitrate; we also include hydrographic station data collected by NOAA's ECOMON Program. Analyses support, in part, conclusions drawn by others that the Gulf of Maine has warmed and continues to warm as a result of long-term and shorter term air-sea heat fluxes. We show that warming is to a large extent a result of changes in advective heat fluxes via lateral exchanges with water masses in neighboring shelf and slope regions (Warm Slope Water and Scotian Shelf Water). Water properties of the source waters and their inflows to the Gulf have been shown to have been changing over time, and now reveal a mix that includes warm, salty, low nutrient Gulf Stream Water. The result is a new baseline in the Gulf of Maine, of warmer temperatures and higher salinities, which appears to have become established after 2010. Annual cycles of spring-to summer water column warming and fall-to-winter cooling and convective mixing are presented and discussed, showing that the maximum depth of convective mixing in the eastern interior Gulf of Maine does not usually exceed 150 m, a depth constrained by the presence a strong vertical density gradient created by layer of high salinity bottom waters. Approximately-six months after the annual late-summer influx to the Gulf of warm and salty water masses at depth and along the bottom, a mass of cold, low salinity Scotian Shelf Water arrives in the upper water layers in winter – these two major water mass fluxes are a half year out of phase with one another, every year. We suggest that these two water mass intrusion events are linked – that the winter-spring inflow of Scotian Shelf Water creates a barotropic pressure gradient in the Gulf that persists into the summer, thereby impeding the inflow of warm and salty Slope, and/or Gulf Stream Water, until that Scotian Shelf Water mass has become sufficiently dispersed in late summer, thereby effectively opening a valve that allows warm and salty deep waters from outside the Gulf to penetrate. [ABSTRACT FROM AUTHOR]

Abstract: We analyzed the distribution, abundance, and succession patterns of major phytoplankton taxa on Georges Bank in relation to hydrography, nutrients, and size-fractionated chlorophyll concentrations (>20μm; <20μm) on three oceanographic cruises from late spring through summer 2008 (28 April–5 May, 27 May–4 June, and 27 June–3 July). The April–May phytoplankton community was dominated numerically by the diatoms Skeletonema spp., Thalassiosira spp., Coscinodiscus spp., and Chaetoceros spp., with highest total diatom cell densities exceeding 200,000cellsl−1 on the Northeast Peak. In May–June, low nitrate and silicate concentrations over the Bank, along with patches of slightly elevated ammonium, were apparently supporting a predominantly dinoflagellate population; the toxic dinoflagellate Alexandrium spp. reached 13,000cellsl−1. Diatom cell densities on the second cruise in May–June were less than 60,000cellsl−1 and their spatial distributions did not overlap with the highest cell densities of Alexandrium spp. or other dinoflagellates. On the third and last cruise, in June–July, reduced nitrate and silicate concentrations were accompanied by a shift in the phytoplankton community: Alexandrium spp. cell densities were lower and heterotrophic and mixotrophic dinoflagellates, notably Polykrikos spp., Gyrodinium spp., Gymnodinium spp., and Prorocentrum spp., had become more abundant. Patches of regenerated silicate during the June–July period appeared to support a post-spring-bloom diatom community on the central crest of the Bank (total diatom cell densities >180,000cellsl−1) of Leptocylindrus spp., Dactyliosolen spp., and Guinardia flaccida. Multivariate statistical analyses of phytoplankton taxa and station locations revealed distinct assemblages of diatom and dinoflagellate taxa on the Bank throughout the late spring and summer. Results are interpreted in the ecological context of earlier-reported laboratory culture experiments on the competitive interactions between Alexandrium fundyense and diatoms. [Copyright &y& Elsevier]

Purpose: To determine whether the time course of 18-fluorine fluorodeoxyglucose (18F-FDG) activity in multiple consecutively obtained 18F-FDG positron emission tomography (PET)/computed tomography (CT) scans predictably identifies metastatic cervical adenopathy in patients with oral/head and neck cancer. It is hypothesized that the activity will increase significantly over time only in those lymph nodes harboring metastatic cancer. Patients and Methods: A prospective cohort study was performed whereby patients with oral/head and neck cancer underwent consecutive imaging at 9 time points with PET/CT from 60 to 115 minutes after injection with 18F-FDG. The primary predictor variable was the status of the lymph nodes based on dynamic PET/CT imaging. Metastatic lymph nodes were defined as those that showed an increase greater than or equal to 10% over the baseline standard uptake values. The primary outcome variable was the pathologic status of the lymph node. Results: A total of 2,237 lymph nodes were evaluated histopathologically in the 83 neck dissections that were performed in 74 patients. A total of 119 lymph nodes were noted to have hypermetabolic activity on the 90-minute (static) portion of the study and were able to be assessed by time points. When we compared the PET/CT time point (dynamic) data with the histopathologic analysis of the lymph nodes, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 60.3%, 70.5%, 66.0%, 65.2%, and 65.5%, respectively. Conclusions: The use of dynamic PET/CT imaging does not permit the ablative surgeon to depend only on the results of the PET/CT study to determine which patients will benefit from neck dissection. As such, we maintain that surgeons should continue to rely on clinical judgment and maintain a low threshold for executing neck dissection in patients with oral/head and neck cancer, including those patients with N0 neck designations. [ABSTRACT FROM AUTHOR]

Abstract: Recent oceanographic observations and a retrospective analysis of nutrients and hydrography over the past five decades have revealed that the principal source of nutrients to the Gulf of Maine, the deep, nutrient-rich continental slope waters that enter at depth through the Northeast Channel, may have become less important to the Gulf''s nutrient load. Since the 1970s, the deeper waters in the interior Gulf of Maine (>100m) have become fresher and cooler, with lower nitrate (NO3) but higher silicate (Si(OH)4) concentrations. Prior to this decade, nitrate concentrations in the Gulf normally exceeded silicate by 4–5μM, but now silicate and nitrate are nearly equal. These changes only partially correspond with that expected from deep slope water fluxes correlated with the North Atlantic Oscillation, and are opposite to patterns in freshwater discharges from the major rivers in the region. We suggest that accelerated melting in the Arctic and concomitant freshening of the Labrador Sea in recent decades have likely increased the equatorward baroclinic transport of the inner limb of the Labrador Current that flows over the broad continental shelf from the Grand Banks of Newfoundland to the Gulf of Maine. That current system now brings a greater fraction of colder and fresher deep shelf waters into the Gulf than warmer and saltier offshore slope waters which were previously thought to dominate the flux of nutrients. Those deep shelf waters reflect nitrate losses from sediment denitrification and silicate accumulations from rivers and in situ regeneration, which together are altering the nutrient regime and potentially the structure of the planktonic ecosystem. [Copyright &y& Elsevier]

Early in the history of nuclear medicine imaging it was realized that the nature of physiological mechanisms associated with the use of radiotracers prevented the identification of anatomic structures with a high degree of accuracy. This limitation often created difficulties in accurate interpretations of acquired images and caused investigators to seek methods of obtaining accurate anatomic correlations. Initial work centered on the use of software tools to combine anatomic and physiological data. Limitations in the use of these techniques, coupled with the development and refinements of anatomic imaging technologies (computed tomography [CT] and magnetic resonance imaging [MRI]), resulted in the development of hybrid imaging systems that combined CT with single-photon emission computed tomography (SPECT) and positron emission tomography (PET). With these hybrid systems, the images can be viewed separately or combined in a fused presentation for direct image correlation of anatomy and physiology. Presently, SPECT systems are available either with nondiagnostic CT capability for attenuation correction and image correlation, or with fully diagnostic CT capability, providing complementary diagnostic information. Equivalently, PET systems with diagnostic CT capability that provide high-resolution physiological and anatomic images are also now commercially available. These systems continue to evolve with the development of new detector materials and data acquisition and image processing technology. The widespread use of SPECT in cardiac imaging has resulted in the development of several new approaches to data acquisition and these new systems currently have either CT capability or the addition of this technology is planned in the future. The development and commercial availability of hybrid imaging systems has provided physicians with important new tools that significantly improve the diagnostic, staging, and treatment planning processes that are now available for their use. [Copyright &y& Elsevier]

The pure shear responses of Ti6Al4V alloy and Ti3Al2.5V alloy, conceived for unique applications in jet engine components, are compared using Digital Image Correlation technique from quasi-static (10−3/s), medium strain rate (101/s) and high strain rates (103/s). A series of bespoke torsion tests have been performed on a screw driven mechanical system, a fast hydraulic Instron machine and a Campbell split Hopkinson torsion bar, equipped with high speed photographic equipment. Observations have provided the strain rate dependence and the relation of pure shear failure at quasi-static and high strain rates. The quasi-static shear constitutive relationships including shear modulus, yield stress and failure strain of both alloys are compared at the location of failure initiation, using a bespoke four camera system. The Ti3Al2.5V alloy presents lower shear flow stress and strain rate sensitivity with higher ductility, as opposed to the Ti6Al4V alloy with limited plastic deformation capacity. Associated with modest estimated overall temperature rise until final collapse of the specimen, both ductile Ti3Al2.5V alloy and brittle Ti6Al4V alloy fail by adiabatic shear banding at high strain rates. This is different from the void growth induced failure at medium strain rate with mild temperature rise and at quasi-isothermal condition. The present results show a general description of brittle and ductile alloys in engineering design. Likewise, this study will guide the characterization of pure shear flow and failure for current and future developed impact resistant alloys. • The pure shear stress-strain relationships of ductile and relatively brittle alloys can be measured and compared using the bespoke techniques. • Dynamic torsional stress-strain relationship is similar to that under simple shear, and would be different from that under shear compression • Adiabatic shear band can occur in alloys with high ductility and low ductility with almost no plastic deformation and ignorable overall thermal softening effect. • The material failure is a void growth induced process at medium strain rate and at quasi-isothermal condition. [ABSTRACT FROM AUTHOR]

This paper studies the uniaxial and multiaxial dynamic compressive behaviour and failure of PA66-GF30 (30 wt % glass fibre reinforced polyamide 66), a typical light weight and high strength composite increasingly used in automobiles including the electric cars in applications from ambient temperature to elevated temperatures up to 90 °C. Likewise, the constitutive relation of PA66-GF30 is characterized from quasi-static to high strain rates. Constant high strain rate loading is achieved by pulse shaping technique on a bespoke split Hopkinson bar. The stress-strain relations are pressure, strain rate and temperature dependent. Effects of strain rate and temperature are found to be decoupled on the pressure sensitivity of PA66-GF30. Beyond maximum stress, micro crack has already formed in dynamically deformed PA66-GF30, which corresponds to macro strain localization monitored by high speed photography and digital image correlation techniques. The PA66-GF30 with confinement shows adiabatic shear failure, with fibres coated by severe shear matrix facets and evenly distributed filaments. This is different from the unconfined PA66-GF30 which shows fibres pull out in the fractured matrix. A modified Drucker-Prager model is proposed to describe the pressure dependent compressive strength of PA66-GF30 over various strain rates and temperatures. [ABSTRACT FROM AUTHOR]

The 1990s witnessed the development of the first dual-modality imaging devices for clinical applications. A combined PET-CT prototype underwent clinical evaluation from mid-1998 onward. The results from the three-year evaluation program stimulated the demand for commercial designs and in 2001 the first commercial PET-CT scanner was installed in the clinic. The availability of designs from all the major vendors of medical imaging equipment was followed by a rapid adoption of the technology and today, over 2500 PET-CT scanners are in clinical operation world-wide. This article briefly summarizes the short history of PET-CT, and reviews the current status of the technology. [Copyright &y& Elsevier]

Accurate anatomical localization of functional abnormalities obtained with the use of positron emission tomography (PET) is known to be problematic. Although tracers such as 18F-fluorodeoxyglucose (18F-FDG) visualize certain normal anatomical structures, the spatial resolution is generally inadequate for accurate anatomic localization of pathology. Combining PET with a high-resolution anatomical imaging modality such as computed tomography (CT) can resolve the localization issue as long as the images from the two modalities are accurately coregistered. However, software-based registration techniques have difficulty accounting for differences in patient positioning and involuntary movement of internal organs, often necessitating labor-intensive nonlinear mapping that may not converge to a satisfactory result. Acquiring both CT and PET images in the same scanner obviates the need for software registration and routinely provides accurately aligned images of anatomy and function in a single scan. A CT scanner positioned in line with a PET scanner and with a common patient couch and operating console has provided a practical solution to anatomical and functional image registration. Axial translation of the couch between the 2 modalities enables both CT and PET data to be acquired during a single imaging session. In addition, the CT images can be used to generate essentially noiseless attenuation correction factors for the PET emission data. By minimizing patient movement between the CT and PET scans and accounting for the axial separation of the two modalities, accurately registered anatomical and functional images can be obtained. Since the introduction of the first PET/CT prototype more than 6 years ago, numerous patients with cancer have been scanned on commercial PET/CT devices worldwide. The commercial designs feature multidetector spiral CT and high-performance PET components. Experience has demonstrated an increased level of accuracy and confidence in the interpretation of the combined study as compared with studies acquired separately, particularly in distinguishing pathology from normal, physiologic tracer uptake and precisely localizing abnormal foci. Combined PET/CT scanners represent an important evolution in technology that has helped to bring molecular imaging to the forefront in cancer diagnosis, staging and therapy monitoring. [Copyright &y& Elsevier]

Purpose: To investigate the role of 18-fluorine-fluorodeoxyglucose positron emission tomography/computerized tomography (18F-FDG PET/CT) in the preoperative prediction of the presence and extent of neck disease in patients with oral/head and neck cancer. Patients and Methods: Seventy patients were enrolled in the study, 47 of whom had a clinically negative neck (N0), 19 of whom had a clinically positive unilateral neck (N+), and 4 of whom were negative on 1 side of the neck and positive on the other. Each patient underwent a PET/CT study before undergoing selective neck dissection for N0 disease or modified radical neck dissection for N+ disease. Tissues were submitted for histopathologic examination and were oriented for the pathologist as to the oncologic levels so as to permit correlation between histopathologic findings and the imaging results. Results: The sensitivity and specificity of the PET/CT procedure were 79% and 82% for the N0 neck, and 95% and 25% for the N+ neck. One hundred ninety-two (11.4%) of the 1,678 nodes identified at histopathology were positive for metastases. The overall nodal sensitivity and specificity were 48% and 99%, respectively. Conclusion: In patients with clinically negative necks, a negative test would not help the surgeon in the management strategy of the patient because of the rate of false-negative results, but a positive test can diagnose metastatic deposits with a high positive predictive value. In patients with clinically positive necks, a positive test will confirm the presence of disease, although false-negative lymph nodes were additionally identified in these clinically positive necks. With respect to nodes, the sensitivity of the imaging procedure is such that the results could not help the surgeon in deciding which level to dissect and which to spare. In the final analysis, the head and neck oncologic surgeon should not depend on the results of the PET/CT scan to determine which patients will benefit from neck dissection. Rather, time-honored principles of neck surgery should be followed, particularly with regard to the liberal execution of prophylactic neck dissections in patients with clinically N0 necks. [Copyright &y& Elsevier]

Abstract: Blooms of the toxic dinoflagellate, Alexandrium fundyense, are a common feature during the summer months in the Gulf of Maine, potentially resulting in paralytic shellfish poisoning when human beings consume shellfish that have ingested these dinoflagellates. Factors that control the dynamics of offshore blooms, including their timing, distributions and cell densities were investigated on three research cruises in the Gulf of Maine: 25 April to 3 May and 5–14 June, 2000, and 19–28 July, 2001; additional samples were collected by our colleagues on separate cruises in May and June, 2001. Measurements included hydrographic data, concentrations of phytoplankton chlorophyll, inorganic nutrients, cell densities of Alexandrium at standard depths, and near-surface densities of major phytoplankton taxa. The Alexandrium bloom in 2000 began sometime between the April–May cruise, when we observed low Alexandium cell densities (<200 cells L−1), and June, when broad patches of >1000 cells L−1 were observed. In July of 2001 we observed high cell densities of Alexandrium (>10,000 cells L−1), which were most abundant at subsurface depths. Vertical pump samples collected at 1-m resolution in July 2001 revealed high densities of Alexandrium cells in thin layers at depths corresponding to the pycnocline and nutricline. We present evidence that the distributions, abundances and timing of onset of the seasonal Alexandrium bloom may be related to oceanographic processes that control differences in the relative concentrations of dissolved inorganic nitrogen (DIN) and silicate. While by no means conclusive, results are suggestive of an allelopathic interference by diatoms on Alexandrium growth, which might impede the development of high densities of Alexandrium cells. [Copyright &y& Elsevier]

Abstract: Two 24-h experiments, designed to test whether the toxic dinoflagellate Alexandrium fundyense exhibited significant changes in vertical distribution, were performed in offshore waters of the Gulf of Maine in June 2000. Standard hydrocasts with a CTD/carousel water sampler package were made hourly on-station while following a drogue set at 25m depth. Continuous measurements of T, S, and chlorophyll fluorescence were made on each down cast, and discrete water samples were collected at 5-m intervals from 55m depth to the surface on the up cast, for analyses of extracted phytoplankton chlorophyll, inorganic nutrients and cell densities of Alexandrium In the first experiment we observed a bimodal vertical distribution of cells, with relatively high cell densities near the surface (<15m depth) and a second peak of relatively high cell densities at depths between 25 and 40m, coincident with the depth of the pycnocline and nitricline. Internal waves of 10–15m amplitude appeared to exert control over the depth distribution of the deep population. Approximately 12h into the first experiment, a relatively warm surface water mass with low Alexandrium cell densities intruded over the drogue station, leaving only the deep population. In the second experiment overall cell densities of Alexandrium were much lower, but again we observed initially a bimodal depth distribution of cells. As in the first experiment, the surface population effectively disappeared after a few hours, leaving only the deep population; in this case, however, there was some evidence of an initial downward movement of the surface population prior to its complete disappearance. Evidence for intrusion of a surface-water layer was not as clear in the second experiment as in the first. In addition to higher-frequency internal waves, as was observed in the first experiment, we also observed a low-frequency internal tidal wave of greater than 20m amplitude that controlled the vertical distribution of the deep population of cells. We were unable to discern evidence of diel vertical migratory by the Alexandrium population in either of the two experiments. [Copyright &y& Elsevier]

Abstract: The life cycle of dinoflagellates of the genus Alexandrium includes sexual reproduction followed by the formation of a dormant hypnozygote cyst, which serves as a resting stage. Negatively buoyant cysts purportedly fall to the benthos where they undergo a mandatory period of quiescence. Previous reports of cysts in the surficial sediments of the Gulf of Maine, where Alexandrium blooms are well documented, show a broad distribution of cysts, with highest concentrations generally in sediments below 100m depth. We report here an exploration of cysts suspended in the water column, where they would be better positioned to inoculate springtime Alexandrium populations. During cruises in February, April, and June of 2000, water samples were collected at depths just off the bottom (within 5m), at the top of the bottom nepheloid layer, and near the surface (1m) and examined for cyst concentrations. Suspended cysts were found throughout the Gulf of Maine and westernmost Bay of Fundy. Planktonic cyst densities were generally greater in near-bottom and top of the bottom nepheloid layer samples than in near-surface water samples; densities were of the order of 102 cystsm−3 in surface waters, and 102–103 cystsm−3 at near-bottom depths. Temporally, they were most abundant in February and least abundant in April. Reports by earlier workers of cysts in the underlying sediments were on the order of 103 cystscm−3. We present calculations that demonstrate the likelihood of cyst resuspension from bottom sediments forced by swell and tidal currents, and propose that such resuspended cysts are important in inoculating the seasonal bloom. We estimate that suspended cysts may contribute significantly to the annual vegetative cell population in the Gulf of Maine. [Copyright &y& Elsevier]

The first 4 years of SeaWiFS ocean color data (September 1997–August 2001) provide the first synoptic quantification of seasonal and interannual phytoplankton chlorophyll variability in the Gulf of Maine. Climatological monthly means show spatial patterns associated with the annual cycle. Concentrations are elevated throughout the year in coastal regions and over shallow banks (Georges Bank, Nantucket Shoals and Browns Bank) with a spring and fall bloom superimposed. Over deeper basins and the Scotia Shelf, a canonical North Atlantic seasonal cycle is present with low (< 1 mg m−3) winter (December–February) concentrations, an annual maximum in March–April (>2 mg m−3), reduced concentrations in summer and a fall bloom beginning as early as September in Jordan Basin but in October–November over other regions. Strong interannual variability over the 4-year time series shows the climatological seasonal features are often a biased picture of both timing and magnitude. The clearest interannual signal is of reduced chlorophyll concentrations throughout 1998, including weak spring and fall blooms. A connection between low concentrations in 1998 and local wind forcing is not evident. However, the low concentrations are coincident with negative anomalies in satellite surface temperature fields and follow the intrusion of relatively cold, low salinity slope water into the Northeast Channel which previous authors have argued is linked to changes in Labrador slope water transport induced by the North Atlantic Oscillation. Reduced concentrations in 1998 are consistent with both lower nitrate/nitrite concentrations in the intruding water as well as reduced subsurface stratification which would delay or reduce the onset of the spring bloom. [Copyright &y& Elsevier]

Presents information on a study which measured phytoplankton chlorophyll and inorganic nutrients during the winter-spring transition in 1997 on Georges Bank. Materials and methods used in the study; Results and discussion.

Syntactic foam is being increasingly conceived for aero engine applications to enhance overall structural reliability under impact loading. Systematic compressive tests without and with lateral confinement are carried out to investigate the deformation and failure of an epoxy syntactic foam (ESF) at quasi-static 0.01/s, medium rate 10–100/s and high strain rates 500–1100/s at gradually increasing temperatures from room temperature 25 °C to 150 °C. The stress–strain response and the corresponding deformation process, complemented by Digital Image Correlation (DIC) technique, were monitored to reveal the dynamic deformation and strain localization of the foam. The elastic-brittle behavior without confinement at high strain rates can be suppressed by the lateral confinement and by elevated temperatures above 100 °C. The lateral confinement slightly increases yield stress and significantly improves the energy absorption of ESF. Both confined yield stress and energy absorption evolve nonlinearly with strain rate and temperature. The strain hardening in the elastic–plastic behavior of ESF under confinement is strain rate independent, compared to its modest temperature dependency. A nonlinear phenomenological model is found to be able to describe the unconfined and confined responses of ESF and its temperature-strain rate equivalence, and reveal the competition between strain hardening and strain softening which is influenced by temperature. [ABSTRACT FROM AUTHOR]

• The compressive behaviour of PMMA over a wide range of strain rate is studied. • The PMMA already presents brittle behavior at intermediate strain rates of about 270 s−1. • Brittle to ductile transition with adiabatic shear failure mode appears with the introduction of medium confinement to PMMA at intermediate strain rates. • The higher temperature, the lower confinement for the brittle to ductile transition. • Decoupled temperature and strain rate dependent DP model is proposed to describe the response of PMMA. Polymethylmethacrylate (PMMA) has been widely used as transparency in aerospace and automobile engineering to enhance structural reliability under impact loading such as bird strike events. This study investigates the confined compressive behaviour of PMMA at quasi-static 0.01 s−1, medium rate 1-100 s−1 and intermediate strain rates 100-1000 s−1 from room temperature to elevated temperatures. Constant intermediate strain rate loading is achieved by using pulse shaping technique on a bespoke in-house developed split Hopkinson compression bar equipped with a high-speed camera and an environmental chamber. The material presents significant strain rate, temperature and pressure sensitivities. The failure mode at intermediate strain rate changes from brittle fragmentation without confinement to adiabatic shear banding with medium lateral confinement (65.3 MPa), which can be seen from the post-peak slope in the constitutive behavior, melting flow PMMA filaments observed in high speed photography and microstructural analysis. A series of intermediate strain rate experiments at elevated temperatures indicate that the higher temperature results in ductile failure for corresponding pressures. The temperature and strain rate dependent Drucker-Prager (DP) model is found to describe the response of PMMA. The brittle-ductile transition and pressure dependent model provide a better understanding of PMMA at intermediate strain rates, which is appropriate for engineering applications. [ABSTRACT FROM AUTHOR]

Discusses the role of frontal currents in larval fish transport on Georges Bank. Description of general clockwise transport of larvae from spawning areas on the northern and northeastern parts of the Bank; Transport of larval gadids on the Bank; Examination of physical and biological mechanisms that might control the drift patterns of larvae.

It has been historically documented that deep, nutrient-rich, offshore slope waters that enter the Gulf of Maine through the Northeast Channel are the principal source of nutrients to the region. Silicate (Si(OH) 4) and nitrate (NO 3) in particular are potentially limiting nutrients for phytoplankton production. We examine here the extent to which nutrient variability in the region may be caused by internal recycling of organic material (i.e., chemical breakdown and dissolution of diatoms) versus variability in water mass sources, which can be identified by temperature and salinity properties. We present here the results from a gulf-wide survey conducted in October 2016. Nutrient samples were collected at 44 stations and compared to temperature, salinity, and beam attenuation profiles. Additionally, suspended particulate material in near-bottom waters was collected on filters at all stations and analyzed for biogenic silica. The results show that after being supplied via a slope water source, nitrate is likely to become depleted and silicate is likely to become enriched at any location in the gulf. We suspect that most of the nutrient variability is due to internal recycling, but there is evidence for an input of Scotian Shelf Water to the Jordan Basin region contributing nutrients at mid-depths and mixing with the deeper slope waters. • Nutrient distributions in the Gulf of Maine are affected by multiple internal biogeochemical processes. • Silicate accumulates in bottom waters while nitrate becomes depleted. • Evidence for shelf sources delivering silicate at mid-depths. [ABSTRACT FROM AUTHOR]

The Northeast US Continental Shelf (NES) is a highly productive marine ecosystem that has experienced wide swings in phytoplankton chlorophyll concentration (CHL). To better understand this variability, we examined changes in CHL over the period 1998–2022, while also considering three indicators of the potential supply of nutrient source waters including cross-shelf advection via deep channels, transport from beyond the shelf edge via Gulf Stream warm core rings (WCR), and input from river and estuarine discharge. Traditionally, deep channel advection of water across the NES was assumed to be derived from Labrador Slope Water (LSW) and Warm Slope Water (WSW). These designations do not fully capture the range of water types contributing to cross-shelf advection. The contribution of LSW and WSW was reciprocal over time, with the presence of WSW at an increased level in recent years. There has been an increase in the number of WCRs off the NES represented by indices of ring occupancy. Precipitation increased over the study period as well, generally over the NES region and in particular in the Mid-Atlantic Bight drainage. We see evidence of the effect of increased precipitation on the NES proper through a change in the area of the ocean surface having 555 nm reflectance with sr−1 > 0.004. Using a canonical analysis, CHL correlated positively with the proportion of LSW and negatively with WSW. These correlations suggest there are aspects of the nutrient content associated with these water masses that are key to phytoplankton growth. WCR frequency negatively correlated with CHL, which was expected since the nutrient loadings of WCRs tends to be low. Finally, CHL negatively correlated with precipitation rate, which suggests terrestrial origin nutrient inputs to the NES are minor. We suggest that in order to understand future CHL dynamics in the NES, careful consideration of advective sources of nutrients in the Northwest Atlantic is necessary. • Northeast US Continental Shelf (NES) chlorophyll concentration (CHL) was examined. • CHL correlated with the type of deep source water entering the NES via channels. • Water sources associated with the Labrador Current seems to favor CHL production. • Fishery production potential appears related to the contribution of source waters. [ABSTRACT FROM AUTHOR]

Abstract: To develop a small molecule-based tracer for in vivo apoptosis imaging, dansylhydrazone (DFNSH) was synthesized in 93% yield in less than 30min. The biological evaluation showed that DFNSH selectively binds to paclitaxel-induced apoptotic cancer cells. The high magnification fluorescent images demonstrate that DFNSH is localized within the cytoplasm of cells that bound Alexa® 488 labeled annexin V on the plasma membrane. [18F]-DFNSH ([18F]-3) was synthesized and isolated in 50–60% radiochemical yields, based on [K/K222]18F, with a synthesis time of 50min (EOB). The straightforward preparation of fluorine-18 labeled 3 makes it a promising tracer for PET imaging of apoptosis. [Copyright &y& Elsevier]

Ductile polymers have been increasingly applied in engineering applications to enhance the structural reliability under impact loading. Due to the limitation of experimental setup to achieve large tensile deformation and the difficulty to achieve dynamic force equilibrium, the localization and post-necking stages up to fracture of ductile polymers at high strain rates have less been investigated. In the present work, the dynamic strain localization of ductile polymeric rods under large tensile deformation up to fracture is studied on the bespoke Hopkinson tension bar synchronized with a high-speed camera. Transparent polycarbonate (PC) is used as a model material in the present study. Likewise, the constitutive response and fracture behaviour of polycarbonate are also characterized with the assistance of Digital Image Correction (DIC) from low to high strain rates under various temperature conditions. The results quantitatively show that the dynamic local strain rate initially increases dramatically to 200 % of the nominal strain rate due to strain localization. This is followed by a rapid drop with necking propagation, and finally tends to stay at strain rate of approximately 20 % of the nominal strain rate until fracture. The elevated temperatures would result in higher local strain rates. Two constitutive models with and without the consideration of constant strain rate condition are constructed for PC and incorporated in finite element simulations. The trend of dynamic local strain rate history with respect to nominal strain rate is successfully reproduced in simulations. The constitutive models particularly the simple dynamic amplification model, are able to reflect the phenomenological key features of the experimentally observed macroscopic and local responses of polycarbonate, and would find their potential applications in impact resistant transparency design. [Display omitted] • The dynamic strain location and fracture of ductile polymeric rods under large tensile deformation are monitored successfully. • The dynamic local strain rate increases to twice nominal strain rate during necking, and drops to five times lower than the nominal strain rate until fracture. • Dynamic fracture strain of polycarbonate rod is not apparently strain rate dependent • The higher temperature results in a higher local strain rate under corresponding nominal strain rate loading conditions [ABSTRACT FROM AUTHOR]