Growth Rate Behavior Research Articles

Anti-Inflammatory, Anti-Arthritic and Anti-Nociceptive Activities of Nigella sativa Oil in a Rat Model of Arthritis.

This study investigated the preventive efficacy of the crude oil extracted from Nigella sativa seeds in a rat model of arthritis induced by using complete Freund’s adjuvant (CFA). Nigella sativa oil at 1.82 mL/kg or 0.91 mL/kg (corresponding to 1596 and 798 mg/kg, respectively) was orally administered for 25 days from the day of immunization. One immunized group was treated orally with indomethacin (3 mg/kg) as a reference drug. Body weight growth rate, paw swelling, arthritis score, mechanical allodynia, locomotor activity and anxiety-like behavior were observed, and the levels of Interleukin 6 (IL-6), C-reactive protein, albumin and total cholesterol in plasma were measured on days 15 and 25. Nigella sativa oil showed anti-inflammatory, anti-arthritic and anti-nociceptive activities that were significant as compared to untreated arthritic rats but less than indomethacin. These results indicated that Nigella sativa oil significantly attenuated adjuvant-arthritis in rats and the higher dose (1.82 mL/kg) prevented the development of arthritis with an inhibition of 56%.

In situ scanning electron microscopy analysis of effect of temperature on small fatigue crack growth behavior of nickel-based single-crystal superalloy

In situ observation and measurement of the high-temperature deformation of advanced hot-section materials using scanning electron microscopy (SEM) is beneficial for understanding their microscopic failure mechanisms. Through in-situ measurement and subsequent analysis, crack nucleation site, growth rate and propagation behavior can be determined as well as the interaction between crack and microstructure, such as inclusion, pore or grain boundary. However, these measurements are challenging above 700 °C as the SEM images are severely degraded by the thermal electron emission. In this work, an in situ mechanical testing system for extremely high temperatures (up to 1000 °C) inside an SEM was developed and used to investigate the small fatigue crack growth behavior of a nickel-based single-crystal superalloy from room temperature to 980 °C. The fatigue crack propagation modes and growth rates were investigated at different temperatures. The mechanism of the propagation mode transition was discussed in detail. Conventional Paris law was found no longer capable of characterizing the growth behavior of small crack. Subsequently, with the help of the digital image correlation technique, plastic zone size of the crack tip was obtained, and it was found that it could characterize the growth behavior of the small crack.

Abstract 52: PDX-derived 3D InSightTM tumor microtissues as ex-vivo human experimental models for evaluating therapeutic responses

Abstract Background The selection of appropriate preclinical models comes always with the major question on how accurately and robustly they can represent the complexity of human disease. Patient-derived xenograft (PDX) models faithfully preserve the biological features and the genetic expression profile of human tumor specimens. However, one limiting aspect of patient-derived models is the replacement of the human host microenvironment by murine stroma within the tumor. Lack of cross-species compatibility compromises the induction of a broad range of signaling pathways that cannot be entirely recapitulated. With our in vitro 3D InSightTMTumor Microtissues derived from PDX lines, we provide a relevant physiological environment and a strategy to assess candidate drugs for novel therapeutic approaches. Aim Development of in vitro 3D InSightTM Tumor Microtissues from PDX lines aimed to retain the cellular heterogeneity found in the original human tumor tissue. Material & Methods and Results PDX cell suspensions of lung, breast and melanoma origin were successfully used to assess 3D aggregation in 96-well format and characterized over 10 days in culture. After careful removal of mouse cell contaminants in each PDX sample, 3D PDX cell cultures were supplied with exogenous normal human dermal fibroblasts (nHDF). Furthermore, to provide a more physiological cancer niche, PDX cells were also co-cultured with tumor-matched cancer-associated fibroblasts (CAFs). 3D in vitro tumors were analyzed histologically and cancer phenotypic alterations were evaluated through the analysis of epithelial-to-mesenchymal transition (EMT) markers. The morphology, viability and growth rate of PDX-derived microtumors were assessed by size analysis (cell scanner) and ATP assay. To assess the distribution of various cell populations within the tumor, 3D PDX samples were screened for standard stromal vs. epithelial-tumor cells markers (e.g. FAP, pan-CK, E-Cadherin), and diagnostic cancer type-specific biomarkers. 3D PDX samples were also employed to investigate the efficacy of specific targeted therapies based on distinct molecular signatures of PDX tumor models. Immunohistochemistry assessment of 3D microtumors validated the resemblance with their respective PDX tumor models. 3D tumor growth rate and cell behavior observations reflected the diversity of disease progression in vivo. Conclusion Further efforts will focus on employing this platform to establish more complex co-cultures with integration of additional relevant stromal and immune cells, to enable a reliable preclinical translational research of tumor/immune cell interactions. We suggest that in vitro 3D PDX models offer a more suitable and robust approach to expedite faithful efficacy assessment of immunomodulators and approval of optimal drug candidates. Citation Format: Francesca Chiovaro, Irina Agarkova, Nicole Buschmann, Chloe' Pichon, Teresa Langova, Armin Maier, Julia Schueler, Patrick Guye. PDX-derived 3D InSightTM tumor microtissues as ex-vivo human experimental models for evaluating therapeutic responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 52.

A viscous magnetohydrodynamic Kelvin–Helmholtz instability in the interface of two fluid layers: Part I. Basic mechanism

This study investigates the combined effect of density, velocity and magnetic field gradients on the Kelvin–Helmholtz instability of two viscous fluid layers. For the linear phase of instability that refers to the early stage of development of Kelvin–Helmholtz instability, the linear growth rate and frequency are presented. With respect to our selected variables and the Atwood number, the behaviour of growth rate and frequency are analysed. It is found that, the behaviour of frequency is not affected by the magnetic field and viscous term. The velocity gradient with the small Atwood numbers tends to stabilize KHI flows, while the velocity gradient with the large Atwood numbers has destabilizing effect on KHI. The growth rate reduces with the constant magnetic field and viscous term, while it enhances with magnetic field gradient.

Durability study of adhesive joints used in high-speed crafts manufactured with composite materials subjected to impact fatigue

Marine high-speed crafts manufactured with composite materials are exposed to constant impacts due to the cyclic contact of the vessel with the water surface. These low-energy impacts can affect the structural integrity of the hull and could be an example of impact fatigue. Certain fast boats manufactured with composite materials are designed in such a way that the hull and deck are assembled with adhesive joints. However, in most of these cases, the adhesive thickness is not measured or controlled. The purpose of this research is to evaluate the effects of the adhesive thickness on the durability and crack growth rate behaviour of adhesive joints used in certain types of high-speed crafts under constant amplitude fatigue and impact fatigue regimes. This study was performed by using experimental procedures with double cantilever beams and single lap joints specimens. The results showed that the durability at impact fatigue conditions is two orders of magnitude lower than constant amplitude fatigue at comparable force levels. In addition, the crack growth rate in impact fatigue conditions showed improvement of fatigue properties when a lower thickness of adhesive was used. On the other hand, the crack growth rate was lower in the constant amplitude fatigue regime in comparison to impact fatigue.

Fatigue Crack Growth Rate Behaviour of HSLA Steel at Varying Load Amplitudes

Steels for ship building applications has to possess adequate resistance to propagation of fatigue cracks, as majority of the failures in service are due to metal fatigue. In this work, the fatigue crack growth rate (FCGR) behaviour within the Paris regime of two high strength low alloy (HSLA) steels were studied. In particular the experiments were directed to reveal the effect of load ratio(R) (Tension-Tension) on the Paris law constants for the two grades of HSLA steels. Results indicated that there is an increase in Paris slope ‘m’ and decrease in Y intercept ‘C’ with increase in load ratio for both the steels. Fractography study was carried out using SEM at locations corresponding to various values of stress intensity factor in order to reveal possible reasons for acceleration of crack growth with change in R ratio from 0.1 to 0.5. It was found that secondary cracks are predominant in Steel A at a load ratio of R=0.1 as compared to R=0.5. However for Steel B, secondary cracks were found at both the load ratios. From the plot of crack growth ‘a’ vs no. of cycles ‘N’, it became evident, the number of cycles for the same range of crack length is lesser for R=0.1 than that for R=0.5 for both Steel A and Steel B. Limiting values of ‘∆K’ and ‘K’ max has been obtained for various crack growth rates ‘da/dN’ at different load ratio for steel A and steel B.

Influence of retrogression and re-ageing heat treatment on the fatigue crack growth behavior of 7010 aluminum alloy

Aluminum alloys are widely used in aircraft structural components where light weight, high strength and good corrosion resistance are the primary requirements. These alloys are generally used in peak-aged (T6) condition in which they are susceptible for stress corrosion cracking. In the recent years, retrogression and re-ageing (RRA) treatment on aluminum alloy is carried out to enhance their corrosion resistance maintaining the ultimate tensile strength. The aim of this work was to study the influence of RRA treatment on the fatigue crack growth rate (FCGR) behavior. The 7010 aluminum alloy was heat treated to two different conditions i.e., T6 and RRA. The microstructures of these alloys were characterized by using TEM. Standard compact tension (CT) specimens were prepared and FCGR tests were carried out by using a 100 kN servo-hydraulic test machine as per ASTM E647-15e1. The constant amplitude FCGR tests were carried out at a stress ratio, R = 0.5 using sine wave loading pattern at 10 Hz. Crack length was monitored by following compliance technique. Microstructural studies show that RRA treated alloy contain fine and densely populated precipitates in the matrix along with coarse and discontinuous precipitates in the grain boundary. The fatigue crack growth rate was observed to reduce along with an increase in the threshold stress intensity factor range (ΔKth) for RRA treated alloy compared to the T6 alloy. The mechanisms for reduction in fatigue crack growth rate of RRA treated alloy is attributed to the microstructural modifications. The increased resistance is expected to enhance the damage tolerance capability of the alloy.

Influence of Initiation Site and Lamellar Divergency on the Overall Kinetics of Cellular Growth and Coarsening in Aged U-Nb Alloys

Overall kinetics of lamellar overaging reactions in U-5.5Nb and U-7.5Nb were analyzed by Avrami-Arrhenius analyses of volume fractions measured from an extensive temperature-time (T-t) matrix of specimens. The cellular initiation site (grain boundaries, inclusions) and regimes of lamellar divergency-cum-slowing growth rate were explicitly accounted for. Avrami exponents n from T-t regimes of constant-growth rate were consistent with theory (1<n<3); those from divergent T-t regimes were smaller, n~0.7, which is not surprising given their different growth rate behavior. The apparent activation energies Q were similar for grain-boundary and inclusion-nucleated discontinuous precipitation, indicating that their nucleation site does not alter their overall kinetics. Avrami Analysis of Isothermal Aging Kinetics

No apparent negative tagging effects after 13 years at liberty for lemon shark, Negaprion brevirostris implanted with acoustic transmitter.

An intact and uncompromised internal acoustic transmitter was non-lethally recovered from a lemon shark Negaprion brevirostris, after 13 years at liberty. The shark, first tagged at an estimated age of 2 years old near South Bimini, Bahamas in 2004, was recaptured in 2017 with a total length of 264 cm. The tagged shark displayed typical growth rate, pregnancy, natal homing and pupping behaviour of other individuals in this population. This observation provides important evidence regarding the effects from long-term retention of implanted acoustic transmitters in a carcharhinid shark.

Complexity growth rate during phase transitions

We present evidences for the connection between the potential of different fields and complexity growth rates both in conformal and confining cases. By studying different models, we also establish a strong connection between phase transitions and the discontinuities in the complexity growth rates. In the first example, for the dyonic black holes which are dual to van der Waals fluids, we find a similar first order phase transition in the behavior of complexity growth rate. We then compare the Schwinger effect and also the behavior of complexity in the AdS and AdS soliton backgrounds and comment on the connection between them. Finally, in a general Gubser model of QCD, we present the connections between the potentials, entropies, speed of sounds and complexity growth rates during crossover, first and second order phase transitions and also the behavior of quasinormal modes.

Molecular Evidence for the Fitness of Cotton Aphid, Aphis gossypii in Response to Elevated CO2 From the Perspective of Feeding Behavior Analysis.

Rising atmospheric carbon dioxide (CO2) concentration is likely to influence insect–plant interactions. Aphid, as a typical phloem-feeding herbivorous insect, has shown consistently more positive responses in fitness to elevated CO2 concentrations than those seen in leaf-chewing insects. But, little is known about the mechanism of this performance. In this study, the foliar soluble constituents of cotton and the life history of the cotton aphid Aphis gossypii and its mean relative growth rate (MRGR) and feeding behavior were measured, as well as the relative transcript levels of target genes related appetite, salivary proteins, molting hormone (MH), and juvenile hormone, to investigate the fitness of A. gossypii in response to elevated CO2 (800 ppm vs. 400 ppm). The results indicated that elevated CO2 significantly stimulated the increase in concentrations of soluble proteins in the leaf and sucrose in seedlings. Significant increases in adult longevity, lifespan, fecundity, and MRGR of A. gossypii were found under elevated CO2 in contrast to ambient CO2. Furthermore, the feeding behavior of A. gossypii was significantly affected by elevated CO2, including significant shortening of the time of stylet penetration to phloem position and significant decrease in the mean frequency of xylem phase. It is presumed that the fitness of A. gossypii can be enhanced, resulting from the increases in nutrient sources and potential increase in the duration of phloem ingestion under elevated CO2 in contrast to ambient CO2. In addition, the qPCR results also demonstrated that the genes related to appetite and salivary proteins were significantly upregulated, whereas, the genes related to MH were significantly downregulated under elevated CO2 in contrast to ambient CO2, this is in accordance with the performance of A. gossypii in response to elevated CO2. In conclusion, rise in atmospheric CO2 concentration can enhance the fitness of A. gossypii by increasing their ingestion of higher quantity and higher quality of host plant tissues and by simultaneously upregulating the transcript expression of the genes related to appetite and salivary proteins, and then this may increase the control risk of A. gossypii under conditions of climate change in the future.

Fatigue and Corrosion Fatigue Properties of Additive-Manufactured Nickel Alloy 625 and Ti-6Al-4V

Abstract Specimen blanks of additive-manufactured nickel Alloy 625 and Ti-6Al-4V were produced by the laser powder-bed-fusion process (L-PBF) with the principal test axis in both the Z direction (parallel to the build direction) and the X-Y direction (perpendicular to the build direction). The high cycle fatigue and corrosion fatigue properties of these metals were measured using R. R. Moore rotating cantilever fatigue tests, both in air and with a salt water drip on the test sections. Testing was conducted in order to determine the fatigue and corrosion fatigue limits of these materials at 108 cycles. The fatigue limit for L-PBF Alloy 625 material at 108 cycles in air was roughly 48 ksi (331 MPa), independent of build orientation. This is similar to the air fatigue limit of wrought material. The corrosion fatigue limit for L-PBF Alloy 625 material at 108 cycles in salt water was roughly 39 ksi (269 MPa), which was also independent of build orientation and slightly below the values for wrought material and values obtained by other investigators. The fatigue limit for hot isostatic pressed L-PBF Ti-6Al-4V material at 108 cycles in air was roughly 90 ksi (620 MPa), independent of build orientation. This is significantly better than the air fatigue limit of wrought material. The corrosion fatigue limit for L-PBF Ti-6Al-4V material at 108 cycles in salt water was roughly 78 ksi (540 MPa), which was also independent of build orientation, better than values for wrought material, and comparable to values obtained by other investigators. The fatigue crack growth rate behavior in air was characterized and compared with information available in the literature.

Measuring the growth force of invasive plant cells using Flexure integrated Lab-on-a-Chip (FiLoC)

The pollen tube is a tip growing cell that is able to invade plant tissues in order to accomplish its function — the delivery of sperm cells to the ovule. The pistillar tissues through which the tube has to elongate represent a formidable mechanical obstacle, but it is unknown how much force the growing tube is able to exert, or how mechanical impedance affects its growth behavior. We quantified the invasive force of individual pollen tubes using a microfluidic lab-on-a-chip device featuring a microscopic cantilever. Using finite element method the maximum invasive growth force of the growing pollen tube was determined to be in the microNewton range. Real time monitoring revealed that contact with the mechanical obstacle caused a shift in the peak frequency characterizing the oscillatory behavior of the pollen tube growth rate. This suggests the presence of a feedback-based control mechanism with a mechanical regulatory component.

Abstract LB-034: Development and characterization of PDX-derived 3D tumor microtissues as platform for screening targeted molecular therapeutics

Abstract Background A major issue for improving the overall success rate in drug development is the lack of accurate experimental human in-vitro models. While there is a significant and increasing need for such better ex-vivo cell-based models, the question on how closely these systems resemble and recapitulate the original tumors is of great importance. Patient-derived xenograft (PDX) models act as vehicle systems to propagate human tumor specimens, faithfully preserving the biological features and the genetic expression profile. The retainment of such criteria in in vitro 3D InSightTM Tumor Microtissues derived from PDX lines is crucial to provide a relevant physiological environment and strategy to assess candidate drugs for novel therapeutic approaches. Aim Development and characterization of in vitro 3D InSightTM Tumor Microtissues from patient-derived xenograft models. Material & Methods and Results PDX cell suspensions of Lung, Breast and Melanoma origin were successfully used to assess 3D aggregation in 96 well format and characterized over 10 days in culture. After careful removal of mouse cell contaminants in each in vitro 3D PDX sample, PDX cell cultures were supplied with exogenous normal human dermal fibroblasts (nHDF). The morphology, biomarker phenotype (IHC) as well as cell proliferation were assessed by histological analysis. In addition to screening for standard diagnostic marker such as proliferating vs. dead cells (e.g. Ki67, ClCasp3) and stromal vs. epithelial-tumor cells (e.g. FAP, pan-CK, E-Cadherin), we also assessed the expression of cancer type-specific biomarkers. Moreover, to monitor the dynamics of cancer phenotypic alterations, epithelial-to-mesenchymal transition (EMT) marker were evaluated and scored. Immunohistochemistry assessment of 3D microtumors validated the resemblance with their respective PDX tumor models. The viability and growth rate of PDX-derived microtumors were assessed by size analysis (cell scanner) and ATP assay. 3D tumor growth rate and cell behavior observations reflected the diversity of disease progression in vivo. Further efforts will focus on employing this platform to investigate the efficacy of specific targeted therapies based on the distinct molecular signatures of PDX tumor models. Conclusion Development and characterization of In vitro 3D InSightTM Tumor Microtissues from patient-derived xenograft (PDX) lines demonstrated that the morphological and molecular features of the parental tumors are well retained. We suggest that in vitro 3D PDX models offer a more suitable and robust approach to expedite faithful efficacy assessment and approval of optimal drug candidates. Citation Format: Francesca Chiovaro, Irina Agarkova, Armin Maier, Simon Messner, Julia Schueler, Patrick Guye. Development and characterization of PDX-derived 3D tumor microtissues as platform for screening targeted molecular therapeutics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-034.

Growth and Toxin Production of Gambierdiscus spp. Can Be Regulated by Quorum-Sensing Bacteria.

Gambierdiscus spp. are the major culprit responsible for global ciguatera fish poisoning (CFP). At present, the effects of microbiological factors on algal proliferation and toxin production are poorly understood. To evaluate the regulatory roles of quorum-sensing (QS) bacteria in the physiology of Gambierdiscus, co-culture experiments with screened QS strains were conducted in this study. Except for the growth-inhibiting effect from the strain Marinobacter hydrocarbonoclasticus, the algal host generally displayed much higher growth potential and toxin production ability with the existence of QS strains. In addition, Bacillus anthracis particularly exhibited a broad-spectrum growth enhancement effect on various Gambierdiscus types, as well as a remarkable influence on algal toxicity. The variations of algal physiological status, including growth rate, chlorophyll content, and responsive behaviors, are potential reasons for the observed positive or negative affection. This study suggests that QS bacteria regulate the algal growth and toxin production. Based on the evidence, we further speculate that QS bacteria may contribute to the site-specific distribution of CFP risk through regulating the algal host biomass and toxicity.

Crack Size and Shape Considerations Related to Near-Threshold Fatigue Crack Growth Rate Behavior

Abstract It is well recognized that crack size or load history or both have an important influence on near-threshold fatigue crack rate behavior at a low stress ratio. This investigation will compare the behavior of a radial crack, such as a surface flaw or a corner crack, to that of a linear crack to see if crack shape plays a role in physically small crack to long crack behavior. Recent research has unveiled a methodology to experimentally partition plasticity from roughness- and oxide-induced crack closure, showing that nonplasticity-induced closure mechanisms have a greater influence at low Kmax by orders of magnitude. Knowledge of this is key to understanding differences between long crack and physically small crack behavior in the near-threshold regime. In this study, the well behaved 2024-T351 aluminum alloy was used to generate threshold data using numerous specimen geometries, flaw geometries, crack sizes, and test procedures to highlight not only the significance of crack size but also the role of crack shape. It will be shown both experimentally and analytically that a radial crack (surface flaw, corner crack) has significantly less remote closure and, therefore, a lower threshold than a through crack (compact tension, middle crack tension), even if the crack size is the same.

Impact of recharge water temperature on bioclogging during managed aquifer recharge: a laboratory study

To investigate the effect of recharge water temperature on bioclogging processes and mechanisms during seasonal managed aquifer recharge (MAR), two groups of laboratory percolation experiments were conducted: a winter test and a summer test. The temperatures were controlled at ~5±2 and ~15±3 °C, and the tests involved bacterial inoculums acquired from well water during March 2014 and August 2015, for the winter and summer tests, respectively. The results indicated that the sand columns clogged ~10 times faster in the summer test due to a 10-fold larger bacterial growth rate. The maximum concentrations of total extracellular polymeric substances (EPS) in the winter test were approximately twice those in the summer test, primarily caused by a ~200 μg/g sand increase of both loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS). In the first half of the experimental period, the accumulation of bacteria cells and EPS production induced rapid bioclogging in both the winter and summer tests. Afterward, increasing bacterial growth dominated the bioclogging in the summer test, while the accumulation of LB-EPS led to further bioclogging in the winter test. The biological analysis determined that the dominant bacteria in experiments for both seasons were different and the bacterial community diversity was ~50% higher in the winter test than that for summer. The seasonal inoculums could lead to differences in the bacterial community structure and diversity, while recharge water temperature was considered to be a major factor influencing the bacterial growth rate and metabolism behavior during the seasonal bioclogging process.

Fire Performance of Sandwich Panels in a Modified ISO 13784-1 Small Room Test: The Influence of Increased Fire Load for Different Insulation Materials

Four sandwich panel rooms were constructed as prescribed in the ISO 13784-1 test. However, the construction followed normal industry practice, and the panels were also subjected to the kinds of damage typically found in commercial premises, although such damage may not typically be concentrated in such a small room. The fire load was increased to simulate fires actually occurring in commercial premises by stepping up the propane burner output from the usual maximum of 300–600 kW, and by placing a substantial wooden crib in two of the rooms. The results showed significant differences in fire growth rate and burning behaviour between those panels filled with polyisocyanurate (PIR) and those filled with stone wool in both the experiments without and with the wooden crib. Most significantly, the PIR pyrolysis products caused earlier ignition (by radiation from above) of the wooden crib 11 min into the experiment (1 min after the burner was stepped up to 300 kW), whereas the crib ignited 22 min into the test (2 min after the burner had been stepped up to 600 kW, which is beyond the test standard both in time and heat input) for the stone wool panels. This interaction between building and contents is most often ignored in fire safety assessments. After a few minutes, the PIR pyrolysis products that escaped outside the room, from between the panels, ignited. The extra thermal exposure from the PIR-fuelled flames distorted the panels, which in turn exposed more PIR, resulting in large flames on both the inside and outside of the enclosure. From a fire safety perspective this is most important as it shows that with the large fire loads that are commonly found in commercial premises, steel-faced PIR filled panels are not capable of acting as fire barriers, and may support flame spread through compartment walls and ceilings. In addition, the PIR panelled rooms produced very large quantities of dense smoke and toxic effluents, whereas the stone wool panelled rooms produced small amounts of light smoke of lower toxicity. Furthermore, the experiments showed that modifications to the standard test can lead to extremely different outcomes for some of the products. As the modifications simulated real-life situations, it seems important to discuss whether the standard is robust enough for property safety scenarios encountered in industrial premises.

Natural history and management of splanchnic artery aneurysms in a single tertiary referral center

ObjectiveSplanchnic artery aneurysms (SAAs) are rare, and little is known about their natural history and management. We reviewed our single-center experience in managing this population of patients. MethodsA retrospective review of the Yale radiologic database from January 1999 to December 2016 was performed. Only patients with an SAA and a computed tomography scan of the abdomen were selected for review. Demographics of the patients, aneurysm characteristics, management, postoperative complications, and follow-up data were collected. Our primary outcomes included aneurysm growth rate and risk of rupture in those patients managed nonoperatively and morbidity and mortality of those SAA patients who underwent operative intervention. ResultsThere were 122 patients with 138 SAAs identified; 77 were male (62%), with a mean age of 66 years (range, 25-94 years). On computed tomography, 56 (45%) had previously diagnosed or concomitant aneurysms elsewhere. Of the patients managed nonoperatively, 101 patients (79%) had 108 SAAs; in the operative intervention group, 25 (21%) patients had 30 SAAs. The mean overall vessel diameter was 1.76 ± 0.83 cm. The diameter of observed and operatively repaired SAAs was 1.58 ± 0.56 cm and 2.41 ± 1.23 cm, respectively (P = .00001). Mean follow-up was 50 ± 42 months for nonoperative management without any adverse events related to SAA, including 10 patients with SAA >2.0 cm. The mean observed growth rate for SAA was 0.064 ± 0.18 cm/y. All symptomatic patients who presented with severe abdominal pain (n = 11 [44%]) underwent operative intervention. Five patients presented with a ruptured SAA (3.6%; range, 2.3-5.0 cm); all of them except one underwent operative intervention. Other indications for repair included large size in seven, rapid growth in two, other open abdominal surgical procedures in two, multiple aneurysms in one, and desire to pursue fertility treatment in one. Operative repair included 14 (56%) endovascular embolizations and 11 (44%) open abdominal operations. After endovascular embolization, two patients underwent abdominal operation for hemorrhage and splenectomy. Open repairs included bypasses in six, splenectomy in two, resection in two, and plication in one. Two patients had postoperative acute kidney injury that resolved and one died of multisystem organ failure. One bypass occluded without sequelae. On multivariable regression analysis, female sex (P = .02) was associated with faster growth rate, and a history of smoking (P = .04) was associated with slower growth rate. ConclusionsIt seems reasonable to observe asymptomatic patients with an SAA <2.0 cm because of the slow growth rate (0.064 ± 0.18 cm/y) and benign behavior. When intervention is needed, both open and endovascular options should be considered.

Probing mechanisms for microbial extracellular electron transfer (EET) using electrochemical and microscopic characterisations

Microbial fuel cell (MFC) is a bioreactor and a power generator that directly converts chemical energy (i.e. organic-inorganic matters in wastewater) to electrical energy through the metabolic activity of the microorganisms. This not only helps cutting the energy costs but also accomplishes wastewater treatment simultaneously. A MFC system has a high efficiency in wastewater treatment; still, an amount of power generated is extremely low and insufficient to power even a pumping unit in the system. One of the key factors to the power generation is the electrochemically active microorganisms that are effective in electron transfer to a solid anode. However, the exact mechanisms by which electrons are transferred between the electrode surface and the microbial metabolism still remain unclear. This work, therefore, aimed to experimentally define the possible mechanism(s) of microbial extracellular electron transfer (EET) that governs the anodic reaction efficiency through the simultaneous investigations of cell voltage, power generation and %COD removal at different inoculation/immobilisation time (t). Ex situ microbial inoculation was initially performed to investigate the microbial growth rate and growth behaviour under simulated MFC conditions using mixed microbial cultures, obtained from an up-flow anaerobic sludge blanket at Cho-heng rice vermicelli industry, Thailand. This preliminary study directed towards the optimal conditions for in situ microbial inoculation/immobilisation in a mediator- and membrane-less MFC reactor built-in house. The effect of each EET mechanism on the production of electric current was assessed at different growth states by electrochemical characterisations (including cyclic voltammetry and electrochemical impedance spectroscopy (EIS)). The cyclic voltammograms of the microbe suspension with or without the presence of soluble electron shuttle confirmed that the microbes themselves were relatively inactive to respire solid electron acceptors through the direct electron transfer (DET) via the OM cytochromes but required exogenous/endogenous mediators to carry electrons from the microbes by diffusive transport to the electrode surface. That was an explanation why the microbe-free medium exhibited superior electrochemical activity in comparison with other microbial components (including medium-free inoculum and inoculated SS mesh electrode) for the first 80 h of inoculation. The peak current was increased with the presence of extracellular biofilm matrix on the electrode surface at longer t (i.e. t = 7 and 14 days) when the extent of biofilm formation on electrode surface was found to increase in the microscopic level as visualised by environmental scanning electron microscopy (ESEM). The EIS results also suggested that the charge transfer resistance between the electrode surface and microbial metabolisms decreased greatly with the extent of biofilm coverage. Hence, the corresponding MFC performance including maximum power density and %COD removal was maximised to 465 mW cm−3 and 100% respectively at t = 7 days once the EET mechanism was mainly driven by DET via the extracellular biofilm matrix corresponding with the highest current response of inoculated SS electrode in the LSCV measurement. However, the depletion of fresh nutrient under a closed-loop and continuous MFC operation resulted in the reduction of power output dramatically to 186 mW cm−3 at the end of experimental period (t = 12 days). The MFC performance could be maintained at its maximum values under realistic MFC operation with an opened-loop and continuous feeding mode which would be contributed to the development of an economical and commercially viable MFC in the future.