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Peroxiredoxins (PRDX) are a family of thiol-dependent peroxidases. Among the six mammalian members of this family, PRDX6 is the only protein that additionally exhibits phospholipase A2 (PLA2) activity. The physiologic role of this interesting PRDX6 feature is largely unknown at present. In this study, we show that PRDX6 increases the metastatic potential of lung cancer cells. Functional analyses of the enzymatic activities of PRDX6, using specific pharmacologic inhibitors and mutagenesis studies, reveal that both peroxidase and PLA2 activities are required for metastasis. Specifically, peroxidase activity facilitates the growth of cancer cells, and PLA2 activity promotes invasiveness. Further investigation of the latter event discloses that PLA2 activity promotes accumulation of arachidonic acid, which, in turn, induces the invasive pathway involving p38 kinase, phosphoinositide 3-kinase, Akt, and urokinase-type plasminogen activator. This study is the first to define the functions of the enzymatic activities of PRDX6 in metastasis and to show the involvement of arachidonic acid in PRDX6 action in intact cells. These novel findings provide a significant step toward elucidating the role of PRDX6 in cancer and the mechanism of its action. Mol Cancer Ther; 9(4); 825–32. ©2010 AACR.

Supplementary Data from Phospholipase A2 Activity of Peroxiredoxin 6 Promotes Invasion and Metastasis of Lung Cancer Cells

Purpose We aimed to develop a novel method for orthotopic colon cancer model, using tissue adhesive in place of conventional surgical method.Materials and Methods RFP HCT 116 cell line were used to establish the colon cancer model. Fresh tumor tissue harvested from a subcutaneous injection was grafted into twenty nude mice, divided into group A (suture method) and group B (tissue adhesive method). For the group A, we fixed the tissue on the serosa layer of proximal colon by 8-0 surgical suture. For the group B, tissue adhesive (10 μL) was used to fix the tumor. The mortality, tumor implantation success, tumor metastasis, primary tumor size, and operation time were compared between the two groups. Dissected tumor tissue was analyzed for the histology and immunohistochemistry. Also, we performed tumor marker analysis.Results We observed 30% increase in graft success and 20% decrease in mortality, by using tissue adhesive method, respectively. The median colon tumor size was significantly increased by 4 mm and operation time was shortened by 6.5 minutes. The H&E showed similar tumor structure between the two groups. The immunohistochemistry staining for cancer antigen 19-9, carcinoembryonic antigen, cytokeratin 20, and Ki-67 showed comparable intensities in both groups. Real-time quantitative reverse transcription analysis showed eight out of nine tumor markers are unchanged in the tissue adhesive group. Western blot indicated the tissue adhesive group expressed less p-JNK (apototic marker) and more p-MEK/p-p38 (proliferation marker) levels.Conclusion We concluded the tissue adhesive method is a quick and safe way to generate orthotopic, colon cancer model.

Downward propagating flames ignited at the open end of an open-closed tube exhibit thermo-acoustic instability due to interaction of combustion generated acoustic fluctuations with the flame front. At sufficiently high laminar burning velocity (SL) two regimes of thermo-acoustic instability are observed, namely, primary instability (where initial cellular flame transitions to a vibrating flat flame) and a secondary instability (where vibrating flat flame transitions to vibrating turbulent flame due to parametric instability of flame front). On further increasing SL to a particular value, “complete instability” of flat flames is observed meaning flat flame cannot be stabilized and initial cellular flame transitions directly to parametric instability. This particular SL introduced in this work is termed “critical SL”. In past experimental works, stability of flat flames in the acoustic field had only been studied in terms of acoustic velocity amplitude and a critical acoustic velocity amplitude had been measured at the onset of parametric instability. The novelty of this work is that boundary of unconditional instability of flat flame (flat flame is unstable irrespective of acoustic velocity amplitude) is determined in terms of mixture conditions, e.g., SL. Particularly for propagating flames, this critical SL can be measured more easily and accurately than the critical acoustic velocity. This work presents the effect of Le (Lewis number) on critical SL. Three different fuels, CH4, C2H4 and C3H8 are tested with two different dilution gases (N2 and CO2) for equivalence ratio of 0.8 (lean) and 1.2 (rich). Twelve different Le ranging from 0.7 to 1.9 are generated through these mixture combinations. Generally, larger Le mixtures show higher critical SL than lower Le mixtures for any fuel. Theoretical calculations are performed to predict critical SL by studying instability of planar flame fronts in presence of acoustic forcing. Theoretical calculations successfully captured the effect of Le as predicted stability region of planar flame is narrower for lower Le than that for higher Le. However, accurate quantitative predictions of critical SL couldn't be obtained from existing theory, particularly for non-unity Le. Hence, a correction (a function of Zeldovich number, β and Le) to width of stability region is proposed to obtain better quantitative agreement for critical SL between experiments and theory and performs significantly well. The correction factor acts to compensate for the inaccuracies in Markstein number obtained from an analytical relationship during calculation of stability region width.

Water-soluble rubber-asphalt-based waterproof coating materials are mainly used for the purpose of preventing leakage from the inside of a structure to the outside or to the lower floor. In this study, water-soluble rubber-asphalt-based waterproof coating materials were prepared based on different mixture ratios to develop a new method to improve the physical properties of the materials. In order to improve the overall physical properties, additives were added to the coating material and analyzed for the change in performance, and the analyzed additives were used in combination to improve the physical properties of waterproofing materials. In particular, in the quality standards, ‘Attachment performance and fatigue resistance performance are the performance required for the outside of the structure’, but in the rubber asphalt category, the value of the adhesion performance quality standard was excluded, so it was limited to external use as a waterproofing material. The degree of improvement was compared and analyzed according to the quality standards of the Korean Industrial Standard KS F 3211-‘15’ Paint Waterproofing Materials for Construction. Therefore, in this study, a total of 27 complex additive tests were conducted, and among them, basic property evaluation was performed on 14 items, excluding 13 items that had defects in the drying process. As a result, in the test conducted with complex additives, about 98% to 104% of the quality standard was obtained, and it was judged that stable waterproofing performance would appear if additional quality improvements were made based on this combination in the future.

SummaryLipid A, the membrane-anchored portion of lipopolysaccharide, is an essential component of the outer membrane (OM) of nearly all Gram-negative bacteria. Here, we identify regulatory and structural factors that together permit Caulobacter crescentus to eliminate lipid A from its OM. Mutations in the ferric uptake regulator fur allow Caulobacter to survive in the absence of either LpxC, which catalyzes an early step of lipid A synthesis, or CtpA, a tyrosine phosphatase homolog which we find is needed for wild-type lipid A structure and abundance. Alterations in Fur-regulated processes, rather than iron status per se, underlie the ability to eliminate lipid A. Fitness of lipid A-deficient Caulobacter requires a previously uncharacterized anionic sphingolipid, ceramide phosphoglycerate (CPG), which also mediates sensitivity to the antibiotic colistin. Our results demonstrate that, in an altered regulatory landscape, anionic sphingolipids can support the integrity of a lipid A-deficient OM.

The heteroatom doping of carbon materials can significantly improve the electrochemical performance of sodium-ion batteries. However, conventional doping techniques involve more than two steps, making them unsuitable for scale-up. In this study, an S and P co-doped carbon material is synthesized using a simple, one-step plasma-in-liquid process. The synthesized material consists of abundant macropores, which can improve the electrochemical properties of sodium-ion batteries. When the synthesized anode material is applied to a sodium-ion half-cell, the cell exhibits a remarkable cycling life of 3000 cycles at a high current density of 10 A g−1, with a high reversible capacity over 125 mAh g−1. These results indicate that S and P co-doped carbon materials are promising candidates as anodes for sodium-ion batteries, and the plasma-in-liquid process is an effective strategy for heteroatom co-doping.

Backgrounds: Secondary lymphedema is a common complication of parasitization and breast or gynecologic cancer therapy; however, options for the treatment of lymphedema are ineffective and limited. A mouse tail model is one of the most successful animal models for a lymphatic study. Lymphedema of the mouse tail is characterized by increases in the volume of the extremity caused by accumulation of tissue fluid, proliferation of fibroblasts and adipocytes, and excessive production of collagen. However, the study of lymphedema using mouse has been plagued with difficulty in directly assessing physiologic changes owing to limitations in the measurement of the mouse tail volume. Furthermore, the mouse tail volume cannot be obtained using the general in vivo measurement method such as volumetric water displacement. Methods and Results: Lymphatic researchers have used the truncated cone formula to approximate the volume as used in the numerical approximation of a cylindrical figure. Although this formula is simple and easy to use, it has difficulties of repeatability and accuracy because the measurement procedure is highly subjective and the accuracy depends on the number of divided segments on the tail. In this article, two novel volumetric measurement methods for the mouse tail model were introduced. The methods were evaluated and compared using three mice with surgically created lymphedema on the tails. Conclusions: The two continuous measuring methods showed a possibility to improve the conventional method by continuous measurement using visual and physical detecting methods. The proposed methods facilitate the extraction of longitudinal section-specific information, which can be an important clue in a lymphatic study.

Background: Robotic-assisted TKA was introduced to enhance the precision of bone preparation and component alignment with the goal of improving the clinical results and survivorship of TKA. Although numerous reports suggest that bone preparation and knee component alignment may be improved using robotic assistance, no long-term randomized trials of robotic-assisted TKA have shown whether this results in improved clinical function or survivorship of the TKA. Questions/purposes: In this randomized trial, we compared robotic-assisted TKA to manual-alignment techniques at long-term follow-up in terms of (1) functional results based on Knee Society, WOMAC, and UCLA Activity scores; (2) numerous radiographic parameters, including component and limb alignment; (3) Kaplan-Meier survivorship; and (4) complications specific to robotic-assistance, including pin-tract infection, peroneal nerve palsy, pin-site fracture, or patellar complications. Methods: This study was a registered prospective, randomized, controlled trial. From January 2002 to February 2008, one surgeon performed 975 robotic-assisted TKAs in 850 patients and 990 conventional TKAs in 849 patients. Among these patients 1406 patients were eligible for participation in this study based on prespecified inclusion criteria. Of those, 100% (1406) patients agreed to participate and were randomized, with 700 patients (750 knees) receiving robotic-assisted TKA and 706 patients (766 knees) receiving conventional TKA. Of those, 96% (674 patients) in the robotic-assisted TKA group and 95% (674 patients) in the conventional TKA group were available for follow-up at a mean of 13 (± 5) years. In both groups, no patient older than 65 years was randomized because we anticipated long-term follow-up. We evaluated 674 patients (724 knees) in each group for clinical and radiographic outcomes, and we examined Kaplan-Meier survivorship for the endpoint of aseptic loosening or revision. Clinical evaluation was performed using the original Knee Society knee score, the WOMAC score, and the UCLA activity score preoperatively and at latest follow-up visit. We also assessed loosening (defined as change in the position of the components) using plain radiographs, osteolysis using CT scans at the latest follow-up visit, and component, and limb alignment on mechanical axis radiographs.To minimize the chance of type-2 error and increase the power of our study, we assumed the difference in the Knee Society score to be 5 points to match the MCID of the Knee Society with power of 0.99, which revealed that a total of 628 patients would be needed in each group. Results: Clinical parameters at the latest follow-up including the Knee Society knee scores (93 ± 5 points in the robotic-assisted TKA group versus 92 ± 6 points in the conventional TKA group [95% confidence interval 90 to 98]; p = 0.321) and Knee Society knee function scores (83 ± 7 points in the robotic-assisted TKA group versus 85 ± 6 points in the conventional TKA group [95% CI 75 to 88]; p = 0.992), WOMAC scores (18 ± 14 points in the robotic-assisted TKA group versus 19 ± 15 points in the conventional TKA group [95% CI 16 to 22]; p = 0.981), range of knee motion (125 ± 6° in the robotic-assisted TKA group versus 128 ± 7° in the conventional TKA group [95% CI 121 to 135]; p = 0.321), and UCLA patient activity scores (7 points versus 7 points in each group [95% CI 5 to 10]; p = 1.000) were not different between the two groups at a mean of 13 years' follow-up. Radiographic parameters such as the femorotibial angle (mean 2° ± 2° valgus in the robotic-assisted TKA group versus 3° ± 3° valgus in the conventional TKA group [95% CI 1 to 5]; p = 0.897), femoral component position (coronal plane: mean 98° in the robotic-assisted TKA group versus 97° in the conventional TKA group [95% CI 96 to 99]; p = 0.953; sagittal plane: mean 3° in the robotic-assisted TKA group versus 2° in the conventional TKA group [95% CI 1 to 4]; p = 0.612) and tibial component position (coronal plane: mean 90° in the robotic-assisted TKA group versus 89° in the conventional TKA group [95% CI 87 to 92]; p = 0.721; sagittal plane: 87° in the robotic-assisted TKA group versus 86° in the conventional TKA group [95% CI 84 to 89]; p = 0.792), joint line (16 mm in the robotic-assisted TKA group versus 16 mm in the conventional TKA group [95% CI 14 to 18]; p = 0.512), and posterior femoral condylar offset (24 mm in the robotic-assisted TKA group versus 24 mm in the conventional TKA group [95% CI 21 to 27 ]; p = 0.817) also were not different between the two groups (p > 0.05). The aseptic loosening rate was 2% in each group, and this was not different between the two groups. With the endpoint of revision or aseptic loosening of the components, Kaplan-Meier survivorship of the TKA components was 98% in both groups (95% CI 94 to 100) at 15 years (p = 0.972). There were no between-group differences in terms of the frequency with which complications occurred. In each group, 2% of knees (15) had a superficial infection treated with intravenous antibiotics for 2 weeks. No deep infection occurred in these knees. In the conventional TKA group, 0.8% of knees (six) had a motion limitation (< 60°). Conclusions: At a minimum follow-up of 10 years, we found no differences between robotic-assisted TKA and conventional TKA in terms of functional outcome scores, aseptic loosening, overall survivorship, and complications. Considering the additional time and expense associated with robotic-assisted TKA, we cannot recommend its widespread use. Level of evidence: Level I, therapeutic study.

Robotic-assisted TKA was introduced to enhance the precision of bone preparation and component alignment with the goal of improving the clinical results and survivorship of TKA. Although numerous reports suggest that bone preparation and knee component alignment may be improved using robotic assistance, no long-term randomized trials of robotic-assisted TKA have shown whether this results in improved clinical function or survivorship of the TKA.In this randomized trial, we compared robotic-assisted TKA to manual-alignment techniques at long-term follow-up in terms of (1) functional results based on Knee Society, WOMAC, and UCLA Activity scores; (2) numerous radiographic parameters, including component and limb alignment; (3) Kaplan-Meier survivorship; and (4) complications specific to robotic-assistance, including pin-tract infection, peroneal nerve palsy, pin-site fracture, or patellar complications.This study was a registered prospective, randomized, controlled trial. From January 2002 to February 2008, one surgeon performed 975 robotic-assisted TKAs in 850 patients and 990 conventional TKAs in 849 patients. Among these patients 1406 patients were eligible for participation in this study based on prespecified inclusion criteria. Of those, 100% (1406) patients agreed to participate and were randomized, with 700 patients (750 knees) receiving robotic-assisted TKA and 706 patients (766 knees) receiving conventional TKA. Of those, 96% (674 patients) in the robotic-assisted TKA group and 95% (674 patients) in the conventional TKA group were available for follow-up at a mean of 13 (± 5) years. In both groups, no patient older than 65 years was randomized because we anticipated long-term follow-up. We evaluated 674 patients (724 knees) in each group for clinical and radiographic outcomes, and we examined Kaplan-Meier survivorship for the endpoint of aseptic loosening or revision. Clinical evaluation was performed using the original Knee Society knee score, the WOMAC score, and the UCLA activity score preoperatively and at latest follow-up visit. We also assessed loosening (defined as change in the position of the components) using plain radiographs, osteolysis using CT scans at the latest follow-up visit, and component, and limb alignment on mechanical axis radiographs. To minimize the chance of type-2 error and increase the power of our study, we assumed the difference in the Knee Society score to be 25 points to match the MCID of the Knee Society score with a SD of 5; to be able to detect a difference of this size, we calculated that a total of 628 patients would be needed in each group in order to achieve 80% power at the α = 0.05 level.Clinical parameters at the latest follow-up including the Knee Society knee scores (93 ± 5 points in the robotic-assisted TKA group versus 92 ± 6 points in the conventional TKA group [95% confidence interval 90 to 98]; p = 0.321) and Knee Society knee function scores (83 ± 7 points in the robotic-assisted TKA group versus 85 ± 6 points in the conventional TKA group [95% CI 75 to 88]; p = 0.992), WOMAC scores (18 ± 14 points in the robotic-assisted TKA group versus 19 ± 15 points in the conventional TKA group [95% CI 16 to 22]; p = 0.981), range of knee motion (125 ± 6° in the robotic-assisted TKA group versus 128 ± 7° in the conventional TKA group [95% CI 121 to 135]; p = 0.321), and UCLA patient activity scores (7 points versus 7 points in each group [95% CI 5 to 10]; p = 1.000) were not different between the two groups at a mean of 13 years' follow-up. Radiographic parameters such as the femorotibial angle (mean 2° ± 2° valgus in the robotic-assisted TKA group versus 3° ± 3° valgus in the conventional TKA group [95% CI 1 to 5]; p = 0.897), femoral component position (coronal plane: mean 98° in the robotic-assisted TKA group versus 97° in the conventional TKA group [95% CI 96 to 99]; p = 0.953; sagittal plane: mean 3° in the robotic-assisted TKA group versus 2° in the conventional TKA group [95% CI 1 to 4]; p = 0.612) and tibial component position (coronal plane: mean 90° in the robotic-assisted TKA group versus 89° in the conventional TKA group [95% CI 87 to 92]; p = 0.721; sagittal plane: 87° in the robotic-assisted TKA group versus 86° in the conventional TKA group [95% CI 84 to 89]; p = 0.792), joint line (16 mm in the robotic-assisted TKA group versus 16 mm in the conventional TKA group [95% CI 14 to 18]; p = 0.512), and posterior femoral condylar offset (24 mm in the robotic-assisted TKA group versus 24 mm in the conventional TKA group [95% CI 21 to 27 ]; p = 0.817) also were not different between the two groups (p0.05). The aseptic loosening rate was 2% in each group, and this was not different between the two groups. With the endpoint of revision or aseptic loosening of the components, Kaplan-Meier survivorship of the TKA components was 98% in both groups (95% CI 94 to 100) at 15 years (p = 0.972). There were no between-group differences in terms of the frequency with which complications occurred. In all, 0.6% of knees (four) in each group had a superficial infection, and they were treated with intravenous antibiotics for 2 weeks [corrected]. No deep infection occurred in these knees. In the conventional TKA group, 0.6% of knees (four) had motion limitation (60°) [corrected].At a minimum follow-up of 10 years, we found no differences between robotic-assisted TKA and conventional TKA in terms of functional outcome scores, aseptic loosening, overall survivorship, and complications. Considering the additional time and expense associated with robotic-assisted TKA, we cannot recommend its widespread use.Level I, therapeutic study.

Inflammatory response plays an essential role in the resolution of infections. However, inflammation can be detrimental to an organism and cause irreparable damage. For example, during sepsis, a cytokine storm can lead to multiple organ failures and often results in death. One of the strongest triggers of the inflammatory response is bacterial lipopolysaccharides (LPS), acting mostly through Toll-like receptor 4 (TLR4). Paradoxically, while exposure to LPS triggers a robust inflammatory response, repeated or prolonged exposure to LPS can induce a state of endotoxin tolerance, a phenomenon where macrophages and monocytes do not respond to new endotoxin challenges, and it is often associated with secondary infections and negative outcomes. The cellular mechanisms regulating this phenomenon remain elusive. We used metabolic measurements to confirm differences in the cellular metabolism of na&iuml, ve macrophages and that of macrophages responding to LPS stimulation or those in the LPS-tolerant state. In parallel, we performed an unbiased secretome survey using quantitative mass spectrometry during the induction of LPS tolerance, creating the first comprehensive secretome profile of endotoxin-tolerant cells. The secretome changes confirmed that LPS-tolerant macrophages have significantly decreased cellular metabolism and that the proteins secreted by LPS-tolerant macrophages have a strong association with cell survival, protein metabolism, and the metabolism of reactive oxygen species.

International audience; The Consortium for Top-Down Proteomics (www.topdownproteomics.org) launched the present study to assess the current state of top-down mass spectrometry (TD MS) and middle-down mass spectrometry (MD MS) for characterizing monoclonal antibody (mAb) primary structures, including their modifications. To meet the needs of the rapidly growing therapeutic antibody market, it is important to develop analytical strategies to characterize the heterogeneity of a therapeutic product's primary structure accurately and reproducibly. The major objective of the present study is to determine whether current TD/MD MS technologies and protocols can add value to the more commonly employed bottom-up (BU) approaches with regard to confirming protein integrity, sequencing variable domains, avoiding artifacts, and revealing modifications and their locations. We also aim to gather information on the common TD/MD MS methods and practices in the field. A panel of three mAbs was selected and centrally provided to 20 laboratories worldwide for the analysis: Sigma mAb standard (SiLuLite), NIST mAb standard, and the therapeutic mAb Herceptin (trastuzumab). Various MS instrument platforms and ion dissociation techniques were employed. The present study confirms that TD/MD MS tools are available in laboratories worldwide and provide complementary information to the BU approach that can be crucial for comprehensive mAb characterization. The current limitations, as well as possible solutions to overcome them, are also outlined. A primary limitation revealed by the results of the present study is that the expert knowledge in both experiment and data analysis is indispensable to practice TD/MD MS.

To evaluate the technical feasibility, safety, and efficacy of a novel full sense device (FSD) for the treatment of obesity in a porcine model. The novel FSD comprised a self-expanding metallic esophageal stent connected to a star-shaped nitinol disk. Three types of FSD were used: fully covered (type A), fully covered with barbs (type B), and uncovered with barbs (type C). Nine juvenile pigs were divided into two groups: FSD (n = 6) and control (n = 3). FSD type A was placed in the FSD group. In case of migration, either FSD type B or type C was then randomly placed. Food intake was monitored daily. Weight changes and ghrelin hormone levels were monitored weekly for 12 weeks. FSD placement was technically successful in all pigs. All FSDs except one migrated to the stomach within 1 week after placement. The pig in which the FSD was retained showed decreased food intake in the first week after FSD placement, and there was a difference in the final weight between the FSD pig and control pigs. The percentage of weight gain was 116.6% in the control group and 105.3% in the FSD pig. FSD placement under fluoroscopic and endoscopic guidance is technically feasible and safe in a porcine model. The uncovered FSD appears to decrease food intake and reduce the rate of weight gain. However, the high FSD migration rate is not encouraging.

Recent investigations suggested that the primary influence of an electric field on a flame is flow modification caused by ionic wind, and that negative ions produced by the electron impact attachment should play a key role in the bi-directional ionic wind. In order to prove this hypothesis in electric fields parallel to the propagating flames, we designed a coflow experiment with laminar lifted flames in vertical electric fields produced by a nozzle and ground electrode installed over the flame. We found that applying DC and AC increased the flame displacement speed, and decreased the unburned velocity even to negative velocity. Velocity measurements revealed the influence of the electric body force on the flow volume, indicating the importance of the electron impact attachment when the nozzle was charged with positive voltage. The flame propagation speeds were estimated by subtracting the unburned velocity from the displacement speed, and were well correlated with those of stationary lifted flames without an applied electric field as a function of flame curvature. This supported our hypothesis that the effect of the electric field is reflected in the flow modification, and that the flame is affected by the modified flow. It also suggested that the propagation direction of premixed or nonpremixed edge flames can be manipulated by coupling the appropriate electric fields.

A vortical structure occurring at the fuel stream in laminar nonpremixed jet flames was recently found and shown to have both a fluid-dynamic impact on the flow field and a possible influence on the flame stability and soot formation. We designed a systematic experiment and numerical simulation to investigate the physical mechanisms of this recirculation phenomenon in a coflow system. We hypothesized that a negative buoyancy, caused by the fuel jet being heavier than the ambient air, may play a significant role in the recirculation. Therefore, we experimentally varied the density of the fuel jet using a binary mixture of methane and n-butane, and tested the density of the coflow oxidizer by replacing nitrogen with carbon dioxide. Several fuel jet velocities, flame temperatures, and nozzle diameters were also studied to thoroughly investigate all parameters that might possibly affect the recirculation. As a result, we found that our modified Richardson number, which is based on the cold density difference between the fuel and the coflow, the flame length, and the jet momentum flux, explained the physical mechanism of the recirculation well, with Ri ∼60 being the critical value for formation of the recirculation. The negative buoyancy was the primary driving force behind the recirculation, while the jet momentum mitigated its formation.

The oscillating lifted flame in a laminar nonpremixed nitrogen-diluted fuel jet is known to be a result of buoyancy, though the detailed physical mechanism of the initiation has not yet been properly addressed. We designed a systematic experiment to test the hypothesis that the oscillation is driven by competition between the positive buoyancy of flame and the negative buoyancy of a fuel stream heavier than the ambient air. The positive buoyancy was examined with various flame temperatures by changing fuel mole fraction, and the negative buoyancy was investigated with various fuel densities. The density of the coflow was also varied within a certain range by adding either helium or carbon dioxide to air, to study how it affected the positive and negative buoyancies at the same time. As a result, we found that the range of oscillation was well-correlated with the positive and the negative buoyancies; the former stabilized the oscillation while the latter triggered instability and became a source of the oscillation. Further measurements of the flow fields and OH radicals evidenced the important role of the negative buoyancy on the oscillation, detailing a periodic variation in the unburned flow velocity that affected the displacement of the flame.

Lipid A, the membrane-anchored portion of lipopolysaccharide (LPS), is an essential component of the outer membrane (OM) of nearly all Gram-negative bacteria. Here we identify regulatory and structural factors that together render lipid A nonessential in Caulobacter crescentus. Mutations in the ferric uptake regulator fur allow Caulobacter to survive in the absence of either LpxC, which catalyzes an early step of lipid A synthesis, or CtpA, a tyrosine phosphatase homolog we find is needed for wild-type lipid A structure and abundance. Alterations in Fur-regulated processes, rather than iron status per se, underlie the ability to survive when lipid A synthesis is blocked. Fitness of lipid A-deficient Caulobacter requires an anionic sphingolipid, ceramide phosphoglycerate (CPG), which also mediates sensitivity to the antibiotic colistin. Our results demonstrate that, in an altered regulatory landscape, anionic sphingolipids can support the integrity of a lipid A-deficient OM.

We report on the characterization of three different Surface Acoustic Wave Nebulization (SAWN) chip designs for use in mass spectrometric (MS) analysis of the bacterial glycolipid known as lipid A. We used three different statistical methods to objectively calculate MS noise level and, subsequently, signal-to-noise ratio for the purpose of choosing the optimum SAWN chip between three different designs. The best performing standing wave SAWN chip enabled MS detection of 125 fmol of the commercial standard monophosphoryl lipid A. All three chips allowed detection of lipid A extracted from 9 × 10 4 CFU of Francisella novicida. Finally, we show that SAWN-MS could be used to distinguish between different Gram-negative bacterial species based on their lipid A MS profiles, which has implications in the field of bacterial phenotyping.

According to previous theory, pulsating propagation in a premixed flame only appears when the reduced Lewis number, β ( Le -1), is larger than a critical value (Sivashinsky criterion: 4(1 + 3 ) ≈ 11), where β represents the Zel'dovich number (for general premixed flames, β ≈ 10), which requires Lewis number Le > 2.1. However, few experimental observation have been reported because the critical reduced Lewis number for the onset of pulsating instability is beyond what can be reached in experiments. Furthermore, the coupling with the unavoidable hydrodynamic instability limits the observation of pure pulsating instabilities in flames. Here, we describe a novel method to observe the pulsating instability. We utilize a thermoacoustic field caused by interaction between heat release and acoustic pressure fluctuations of the downward-propagating premixed flames in a tube to enhance conductive heat loss at the tube wall and radiative heat loss at the open end of the tube due to extended flame residence time by diminished flame surface area, i.e., flat flame. The thermoacoustic field allowed pure observation of the pulsating motion since the primary acoustic force suppressed the intrinsic hydrodynamic instability resulting from thermal expansion. By employing this method, we have provided new experimental observations of the pulsating instability for premixed flames. The Lewis number (i.e., Le ≈ 1.86) was less than the critical value suggested previously.