Effect of tryptophan position and lysine/arginine substitution in antimicrobial peptides on antifungal action

Every year, the overprescription, misuse, and improper disposal of antibiotics have led to the rampant development of drug-resistant pathogens and, in turn, a significant increase in the number of patients who die of drug-resistant fungal infections. Recently, researchers have begun investigating the use of antimicrobial peptides (AMPs) as next-generation antifungal agents to inhibit the growth of drug-resistant fungi. The antifungal activity of alpha-helical peptides designed using the cationic amino acids containing lysine and arginine and the hydrophobic amino acids containing isoleucine and tryptophan were evaluated using 10 yeast and mold fungi. Among these peptides, WIK-14, which is composed of a 14-mer with tryptophan sequences at the amino terminus, showed the best antifungal activity via transient pore formation and ROS generation. In addition, the in vivo antifungal effects of WIK-14 were investigated in a mouse model infected with drug-resistant Candida albicans. The results demonstrate the potential of AMPs as antifungal agents.

Development of postbiotics by whey bioconversion with Enterococcus faecalis M157 KACC81148BP and Lactococcus lactis CAU2013 KACC81152BP for treating periodontal disease and improving gut health

This study developed postbiotics with whey bioconversion product produced by Enterococcus faecalis M157 KACC 81148BP, and mixed whey bioconversion products produced by E. faecalis M157 KACC 81148BP and Lactococcus lactis ssp. lactis CAU2013 KACC 81152BP to alleviate periodontitis (PD) and to improve gut health. The powdered whey bioconversion product (EF) produced by E. faecalis M157 KACC 81148BP, mixed whey bioconversion products (EF+LL) from E. faecalis M157 KACC 81148BP and L. lactis CAU2013 KACC 81152BP, and phosphate-buffered saline (PBS; control) were administered orally to PD-induced rats for 8 wk. Infiltration of inflammatory cells and epithelial proliferation in periodontal tissue were found in control, but the lesions were reduced in PD+EF group (administration of EF to PD-induced rats), and no lesions were observed in PD+EF+LL group (administration of EF+LL to PD-induced rats). The bone loss volumes in PD+EF and PD+EF+LL groups were lower than in control. Cytokine production levels related to inflammation were lower and antioxidative stress markers were higher in PD+EF and PD+EF+LL groups than in control for both periodontal tissue and gut. The ratios of Lactobacillus spp. in gut microbiome of PD+EF and PD+EF+LL groups were higher than in control. These results indicate that the whey bioconversion product produced by E. faecalis M157 KACC 81148BP, and mixed whey bioconversion products produced by E. faecalis M157 KACC 81148BP and L. lactis CAU2013 KACC 81152BP are effective on relieving periodontitis and improving the gut health.

Fermented milk with Lactobacillus curvatus SMFM2016-NK alleviates periodontal and gut inflammation, and alters oral and gut microbiota

This study aimed to analyze the effect of milk fermented with Lactobacillus curvatus SMFM2016-NK on periodontal diseases and gut health in a rat model. To improve the effect of Lb. curvatus SMFM2016-NK-fermented milk administration for relieving periodontitis, the periodontitis rat models were treated with the following for 4 wk: 10% skim milk (normal), periodontitis + 10% skim milk (negative control), periodontitis + Lactobacillus rhamnosus GG-fermented milk (positive control), and periodontitis + Lb. curvatus SMFM2016-NK-fermented milk (PD+LCFM). Transcriptional analysis of inflammatory cytokines [tumor necrosis factor α (TNF-α), IL-1β, IL-6, and IL-10] was performed via quantitative reverse-transcription PCR. The changes in the oral and gut microbiomes after administering Lb. curvatus SMFM2016-NK-fermented milk were analyzed with metagenomics sequencing using DNA extracted from the oral gingival tissues and feces from the cecum of the rat models. After treatment with Lb. curvatus SMFM2016-NK-fermented milk, the relative gene expression levels of TNFA and IL1B in the gingiva decreased in the PD+LCFM group compared with those in the negative control group. In the oral microbiome, the proportion of the phylum Proteobacteria in the PD+LCFM group was lower than that in the negative control after treatment with Lb. curvatus SMFM2016-NK-fermented milk. For the effect in the gut, the relative gene expression levels of inflammatory cytokines in the colon between the normal and negative control groups were not different; however, the expression levels of TNFA and IL1B in the PD+LCFM and positive control groups, respectively, were lower than those in the negative control group. The composition and diversity of the gut microbiome differed among normal, periodontitis, and Lb. curvatus SMFM2016-NK-fermented milk treatment groups. These results indicate that Lb. curvatus SMFM2016-NK-fermented milk could alleviate periodontal and gut inflammation and change oral and gut microbiota.

Abstract P6-17-09: Event-free survival by ADCC status from a follow-up study comparing SB3 (trastuzumab biosimilar) with reference trastuzumab for HER2 positive breast cancer in neoadjuvant setting

Background: SB3 has been approved by the European Commission as a biosimilar of reference trastuzumab (TRZ). Equivalent breast pathologic complete response (bpCR) rate and comparable event-free survival (EFS) and overall survival between SB3 and TRZ have been reported.1-3 Upon monitoring quality attributes of TRZ for the development of SB3, a marked downward shift in antibody-dependent cell-mediated cytotoxicity activities (ADCC) was observed in TRZ lots with expiry dates from Aug 2018 to Dec 2019.4 Some of these lots were used in this study. The objective of this report is to evaluate event-free survival by ADCC status from an additional one-year follow-up study.

Methods: Patients with HER2 positive early or locally advanced breast cancer were randomly assigned to receive SB3 or TRZ in neoadjuvant setting concurrently with chemotherapy. Patients then underwent surgery followed by adjuvant SB3 or TRZ. After completion of therapy, patients from selected countries participated in a long-term follow-up study. In TRZ, patients exposed to at least one shifted ADCC lot and those not exposed to shifted ADCC lot during neoadjuvant period were considered as “Exposed” and “Unexposed,” respectively. EFS was defined as the time from the date of randomization to the date when the first event occurred. An event was defined as disease recurrence or progression (local, regional, distant or contralateral) or death due to any cause. EFS after additional one-year follow-up was analyzed by ADCC status in the long-term follow-up set (LFS).

Results: A total of 367 patients (SB3, N=186; TRZ, N=181) were included in the LFS. Within TRZ, 55 patients were Unexposed and 126 patients were Exposed. At a median follow-up duration of 30.1 months in SB3 and 30.2 months in TRZ from initiation of study treatment, 4.8% patients in SB3, 3.6% in Unexposed and 10.3% in Exposed experienced events. 4.3% patients in SB3, 1.8% in Unexposed and 9.5% in Exposed experienced recurrence after surgery (Table). Two-year EFS rate was 96.7% in SB3, 98.2% in Unexposed and 92.5% in Exposed.

Conclusion: A significantly higher proportion of patients experienced events in Exposed compared to Unexposed (HR 0.07, 95% CI 0.01-0.58, p-value=0.0137). No significant difference in EFS was found between SB3 and Unexposed. Although this study has a relatively short follow-up and has not been powered to evaluate the impact of ADCC on survival, these results suggest a possible correlation between ADCC and clinical efficacy. Further long-term results will follow.

Summary of Event-free Survival (LFS)  TRZEFS Hazard ratio (95% CI), p-value SB3 N=186All N=181Unexposed N=55Exposed N=126SB3 vs TRZ AllSB3 vs TRZ UnexposedTRZ Unexposed vs TRZ ExposedPatients with event, n (%)9 (4.8%)15 (8.3%)2 (3.6%)13 (10.3%)0.49 (0.21, 1.14) p=0.09751.19 (0.23, 6.18) p=0.83760.07 (0.01, 0.58) p=0.0137Recurrence after surgery8 (4.3%)13 (7.2%)1 (1.8%)12 (9.5%)   Progression before surgery1 (0.5%)1 (0.6%)1 (1.8%)0 (0.0%)   Death0 (0.0%)1 (0.6%)0 (0.0%)1 (0.8%)   

Reference:

1. Pivot X et al. J Clin Oncol. 2018; 36:968-74

2. Pivot X et al. Eur J Cancer. 2018; 93:19-27

3. Pivot X et al. J Clin Oncol. 2018; 36 (suppl; abstr e12631)

4. Kim S et al. MAbs. 2017; 9:704-14

Citation Format: Pegram MD, Pivot X, Cortes J, Curigliano G, Yoon Y, Lim J, Song S, Hong E. Event-free survival by ADCC status from a follow-up study comparing SB3 (trastuzumab biosimilar) with reference trastuzumab for HER2 positive breast cancer in neoadjuvant setting [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-09.

A luminous blue kilonova and an off-axis jet from a compact binary merger at z = 0.1341

The recent discovery of a gamma-ray burst (GRB) coincident with the gravitational-wave (GW) event GW170817 revealed the existence of a population of low-luminosity short duration gamma-ray transients produced by neutron star mergers in the nearby Universe. These events could be routinely detected by existing gamma-ray monitors, yet previous observations failed to identify them without the aid of GW triggers. Here we show that GRB150101B is an analogue of GRB170817A located at a cosmological distance. GRB150101B is a faint short burst characterized by a bright optical counterpart and a long-lived X-ray afterglow. These properties are unusual for standard short GRBs and are instead consistent with an explosion viewed off-axis: the optical light is produced by a luminous kilonova, while the observed X-rays trace the GRB afterglow viewed at an angle of ~13°. Our findings suggest that these properties could be common among future electromagnetic counterparts of GW sources.

A faint gamma-ray burst (GRB 170817A) has been recently detected in coincidence with the gravitational wave (GW) event GW 170817. Here, the authors report that another faint short GRB at a cosmological distance (GRB150101B) and its late time emission are analogous to the neutron star merger event GRB 170817A.

Prediction of radiographic abnormalities by the use of bag-of-features and convolutional neural networks

This study evaluated the feasibility of bag-of-features (BOF) and convolutional neural networks (CNN) for computer-aided detection in distinguishing normal from abnormal radiographic findings. Computed thoracic radiographs of dogs were collected. For the purposes of this study, radiographic findings were used to distinguish between normal and abnormal in the following areas: (1) normal cardiac silhouette vs. cardiomegaly, (2) normal lung vs. abnormal lung patterns, (3) normal mediastinal position vs. mediastinal shift, (4) normal pleural space vs. pleural effusion, and (5) normal pleural space vs. pneumothorax. Images for training and testing the models consisted of ventrodorsal and lateral projection images of the same scale. The number of images used for each finding are as follow: 3142 for cardiomegaly (1571 normal and 1571 abnormal from 1143 dogs), 2086 for lung pattern (1043 normal and 1043 abnormal from 1247 dogs), 892 for mediastinal shift (446 normal and 446 abnormal from 387 dogs), 940 for pleural effusion (470 normal and 470 abnormal from 284 dogs), and 78 for pneumothorax (39 normal and 39 abnormal from 61 dogs). All data samples were divided so that 60% would be used for training the algorithms and 40% for testing the two models. The performance of the classifiers was evaluated by calculating the accuracy, sensitivity and specificity. The accuracy of both models ranged from 79.6% to 96.9% in the testing set. CNN showed higher accuracy (CNN; 92.9-96.9% and BOF; 79.6-96.9%) and sensitivity (CNN; 92.1-100% and BOF; 74.1-94.8%) than BOF. In conclusion, both BOF and CNN have potential to be useful for improving work efficiency by double reading.

Evaluation of Salmonella Growth at Low Concentrations of NaNO2 and NaCl in Processed Meat Products Using Probabilistic Model

This study developed probabilistic models to predict Salmonella growth in processed meat products formulated with varying concentrations of NaCl and NaNO2. A five-strain mixture of Salmonella was inoculated in nutrient broth supplemented with NaCl (0%, 0.25%, 0.5%, 0.75%, 0.5%, 1.0%, 1.25%, and 1.75%) and NaNO2 (0, 15, 30, 45, 60, 75, 90, 105, and 120 ppm). The inoculated samples were then incubated under aerobic and anaerobic conditions at 4°C, 7°C, 10°C, 12°C, and 15°C for up to 60 days. Growth (assigned the value of 1) or no growth (assigned the value of 0) for each combination was evaluated by turbidity. These growth response data were analyzed with a logistic regression to evaluate the effect of NaCl and NaNO2 on Salmonella growth. The results from the developed model were compared to the observed data obtained from the frankfurters to evaluate the performance of the model. Results from the developed model showed that a single application of NaNO2 at low concentrations did not inhibit Salmonella growth, whereas NaCl significantly (p<0.05) inhibited Salmonella growth at 10°C, 12°C, and 15°C, regardless of the presence of oxygen. At 4°C and 7°C, Salmonella growth was not observed in either aerobic or anaerobic conditions. When NaNO2 was combined with NaCl, the probability of Salmonella growth decreased. The validation value confirmed that the performance of the developed model was appropriate. This study indicates that the developed probabilistic models should be useful for describing the combinational effect of NaNO2 and NaCl on inhibiting Salmonella growth in processed meat products.

Quantitative analysis of a spinal surgeon’s learning curve for scoliosis surgery

Aims

The aim of this study was a quantitative analysis of a surgeon’s learning curve for scoliosis surgery and the relationship between the surgeon’s experience and post-operative outcomes, which has not been previously well described.

Patients and Methods

We have investigated the operating time as a function of the number of patients to determine a specific pattern; we analysed factors affecting the operating time and compared intra- and post-operative outcomes. We analysed 47 consecutive patients undergoing scoliosis surgery performed by a single, non-trained scoliosis surgeon. Operating time was recorded for each of the four parts of the procedures: dissection, placement of pedicle screws, reduction of the deformity and wound closure.

Results

The median operating time was 310 minutes (interquartile range 277.5 to 432.5). The pattern showed a continuous decreasing trend in operating time until the patient number reached 23 to 25, after which it stabilised with fewer patient-dependent changes. The operating time was more affected by the patient number (r =- 0.75) than the number of levels fused (r = 0.59). Blood loss (p = 0.016) and length of stay in hospital (p = 0.012) were significantly less after the operating time stabilised. Post-operative functional outcome scores and the rate of complications showed no significant differences. Take home message: We describe a detailed learning curve for scoliosis surgery based on a single surgeon’s practise, providing useful information for novice scoliosis surgeons and for those responsible for training in spinal surgery. Cite this article: Bone Joint J 2016;98-B:679–85.

Investigations on flame dynamics of premixed H2–air mixtures in microscale tubes

The flame propagation is affected by flame shape angle and wall heat transfer coeff. A minimum flame propagation speed is observed for planar flames with nearly zero flame shape angle for 580 h⁻² K⁻¹ wall heat transfer coeff. range.

Kinetic Behavior of Escherichia coli on Various Cheeses under Constant and Dynamic Temperature

In this study, we developed kinetic models to predict the growth of pathogenic Escherichia coli on cheeses during storage at constant and changing temperatures. A five-strain mixture of pathogenic E. coli was inoculated onto natural cheeses (Brie and Camembert) and processed cheeses (sliced Mozzarella and sliced Cheddar) at 3 to 4 log CFU/g. The inoculated cheeses were stored at 4, 10, 15, 25, and 30°C for 1 to 320 h, with a different storage time being used for each temperature. Total bacteria and E. coli cells were enumerated on tryptic soy agar and MacConkey sorbitol agar, respectively. E. coli growth data were fitted to the Baranyi model to calculate the maximum specific growth rate (μ max; log CFU/g/h), lag phase duration (LPD; h), lower asymptote (log CFU/g), and upper asymptote (log CFU/g). The kinetic parameters were then analyzed as a function of storage temperature, using the square root model, polynomial equation, and linear equation. A dynamic model was also developed for varying temperature. The model performance was evaluated against observed data, and the root mean square error (RMSE) was calculated. At 4°C, E. coli cell growth was not observed on any cheese. However, E. coli growth was observed at 10°C to 30°C with a μ max of 0.01 to 1.03 log CFU/g/h, depending on the cheese. The μ max values increased as temperature increased, while LPD values decreased, and μ max and LPD values were different among the four types of cheese. The developed models showed adequate performance (RMSE = 0.176-0.337), indicating that these models should be useful for describing the growth kinetics of E. coli on various cheeses.

Tuning the Fano resonance with an intruder continuum

Through a combination of experiment and theory we establish the possibility of achieving strong tuning of Fano resonances (FRs), by allowing their usual two-path geometry to interfere with an additional, "intruder", continuum. As the coupling strength to this intruder is varied, we predict strong modulations of the resonance line shape that, in principle at least, may exceed the amplitude of the original FR itself. For a proof-of-concept demonstration of this phenomenon, we construct a nanoscale interferometer from nonlocally coupled quantum point contacts and utilize the unique features of their density of states to realize the intruder. External control of the intruder coupling is enabled by means of an applied magnetic field, in the presence of which we demonstrate the predicted distortions of the FR. This general scheme for resonant control should be broadly applicable to a variety of wave-based systems, opening up the possibility of new applications in areas such as chemical and biological sensing and secure communications.

Stroke recurrence patterns are predicted by the subtypes and mechanisms of the past, non-cardiogenic stroke

BACKGROUND AND PURPOSE

The association between past stroke subtypes and recurrent stroke subtypes in non-cardiogenic stroke remains unknown.

METHODS

Patients with ischaemic stroke who had a past history of large-artery disease (LAD) or small-artery disease (SAD) subtypes were assessed. LAD was subdivided into intracranial atherosclerosis (ICAS) and extracranial atherosclerosis (ECAS). LAD stroke mechanisms were categorized as artery-to-artery embolism, in situ thrombotic occlusion and local branch occlusion, while SAD was subdivided into lacunar infarction (LI) and branch atheromatous disease (BAD) on the basis of magnetic resonance imaging findings. The relationship between past and current strokes was analyzed.

RESULTS

Among the 202 patients enrolled, the LAD group (n = 111) had 64 and 47 patients with ICAS and ECAS, and the SAD group (n = 91) had 63 and 28 patients with LI and BAD, respectively, at the time of past stroke. Patients with LAD developed LAD-associated strokes most often (n = 99, 89.2%), and patients with SAD developed SAD most often (n = 69, 75.8%; P < 0.001). Patients with ICAS were more likely to develop ICAS later (n = 46, 79.3%), whereas those with ECAS developed ECAS more often (n = 31, 75.6%; P < 0.001). Patients with ICAS presenting with artery-to-artery embolism more often developed artery-to-artery embolism later (n = 26, 72.2%), whereas those with local branch occlusion developed recurrent local branch occlusion most often (n = 10, 66.7%, P = 0.005). In the SAD group, patients with BAD developed LAD more frequently than the LI group (n = 11, 39.3% vs. n = 9, 14.3%, P = 0.022).

CONCLUSIONS

The subtypes and mechanisms of recurrent stroke are significantly influenced by those of the past stroke.

Test of the Jarzynski and Crooks fluctuation relations in an electronic system

Recent progress on micro- and nanometer-scale manipulation has opened the possibility to probe systems small enough that thermal fluctuations of energy and coordinate variables can be significant compared with their mean behavior. We present an experimental study of nonequilibrium thermodynamics in a classical two-state system, namely, a metallic single-electron box. We have measured with high statistical accuracy the distribution of dissipated energy as single electrons are transferred between the box electrodes. The obtained distributions obey Jarzynski and Crooks fluctuation relations. A comprehensive microscopic theory exists for the system, enabling the experimental distributions to be reproduced without fitting parameters.

First Report of Rice stripe virus of Proso Millet in Korea

Rice stripe virus (RSV; genus Tenuivirus) is a serious threat to rice production in Korea (2). In 1965, a disease outbreak was observed on rice in South Korea, with plants showing yellow stripe symptoms (2). Reoccurrence of RSV in rice was observed again in 1980 in Gyeonggi and Chungcheong. In 2001, RSV was estimated to be infecting approximately 4,663 ha of rice in the provinces of Gyeonggi and Gangwha and approximately 5,000 ha of riceland in the provinces of Buan and, Seocheon (3). Proso millet (Panicum miliaceum L.) is grown as a cereal grain crop and used mainly for human food in South Korea (1). In June 2009, proso millet plants that displayed yellow stripe symptoms were collected at Sinjeon-Myeon, Gangjin-Gun, and Jeollanam-do provinces, where an outbreak of RSV in rice was reported. Diseased plants tested positive to RSV with an ELISA Kit (KisanBio, Seoul, Korea). Total RNA was extracted from leaf tissue with an RNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). RSV coat protein specific-primers were produced (5' TGTGGAACATAGTCCCACAGTAAGT 3'(upstream), 5' CTAAGCCGCAACCATTCCTCCAGT 3'(downstream). Reverse transcription-PCR confirmed the presence of a 494-bp product as predicted for the presence of RSV. The coat protein of RSV isolates collected from proso millet, rice, and foxtail millet in the same area was also sequenced. Results confirmed that phylogenetic relationships were of high homology: 98.9% between RSV isolates from rice and foxtail millet, 99.2% between isolates from rice (GenBank Accession No. JN245626) and proso millet (GenBank Accession No. JN245627); 99.6% between rice and foxtail millet (GenBank Accession No. JN245628); and 99.6% between foxtail millet and proso millet. In addition, sequence comparisons showed 96 to 99% identity with known RSV sequences available in GenBank (Accession No. X53563) (4). To our knowledge, this is the first report of RSV of proso millet in South Korea. The finding of this disease confirms further spread of the virus within the northern part of South Korea and the need for research to develop more effective management options to reduce the impact of RSV in proso millet. References: (1) Y. Y. Choi et al. Biosci. Biotechnol. Biochem. 69:31, 2005. (2) B. C. Lee et al. Res. Plant Dis. 10:30, 2004. (3) B. C. Lee et al. Res. Plant Dis. 14:210, 2008. (4) Y. Zhu. J. Gen. Virol. 72:763, 1991.

Curcumin suppresses Streptococcus mutans adherence to human tooth surfaces and extracellular matrix proteins

Streptococcus mutans is the key causative agent of caries and infective endocarditis. The first step in biofilm development and the consequent initiation of further disease is bacterial adherence to host cell surfaces. Therefore, the aim of this study was to evaluate the inhibitory effect of curcumin on S. mutans adherence to extracellular matrices and tooth surfaces. The effect of curcumin on the ability of S. mutans to adhere to glass surfaces coated with collagen and fibronectin was tested in order to determine whether the decrease of the bacterial adhesion by curcumin is achieved by hindering the bacteria in adhering to collagen and/or fibronectin. Also, human teeth inoculated with S. mutans were treated with curcumin in vitro in order to assess the relevance of the anti-adhesive effect to oral conditions in vivo. The minimum inhibitory concentration (MIC) at which curcumin completely inhibited bacterial growth was 128 μg/mL. The addition of curcumin below the MIC diminished bacterial adherence onto both collagen- and fibronectin-coated glass surfaces and human tooth surfaces. It appears that the anti-adhesive effect of curcumin against S. mutans is mediated through collagen and fibronectin. These results support the widespread use of curcumin as a food-based antimicrobial agent.

Interlayer tunneling in counterflow experiments on the excitonic condensate in quantum Hall bilayers

The effect of tunneling on the transport properties of quantum Hall double layers in the regime of the excitonic condensate at a total filling factor one is studied in counterflow experiments. If the tunnel current I is smaller than a critical I{C}, tunneling is large and is effectively shorting the two layers. For I>I{C} tunneling becomes negligible. Surprisingly, the transition between the two tunneling regimes has only a minor impact on the features of the filling-factor one state as observed in magnetotransport, but at currents exceeding I{C} the resistance along the layers increases rapidly.

Asarone inhibits adipogenesis and stimulates lipolysis in 3T3-L1 adipocytes

Asarone is a molecule found in certain plants such as Acorus calamus, the root of which is used in traditional medicine to treat diabetes. We determined the molecular mechanism underlying the anti-diabetic activity of asarone. Treatment of asarone significantly inhibited the differentiation of 3T3-L1 preadipocytes through suppression of expression of the transcription factors, CCAAT/enhancer binding protein-alpha and peroxisome proliferator activated receptor-gamma, which activate adipogenesis. Intracellular triglyceride levels were reduced by asarone in a dose-dependent manner and asarone treatment stimulated the phosphorylation of hormone-sensitive lipase. Together, the present findings indicate that asarone inhibits adipogenesis by down-regulation of PPARgamma and C/EBPalpha and reduces lipid accumulation by stimulation of lipolysis through an increase in hormone-sensitive lipase activity.

Carbon nanotube reservoirs for self-healing materials

A novel nanoreservoir made of carbon nanotubes (CNTs) is proposed for realizing tougher and automated self-healing materials. The advantages of the approach are that CNTs have the potential to play the role of reinforcing elements prior to and after sealing a crack and that the number of voids is reduced after the material and the CNTs themselves are healed. The focus of this paper is on investigating the feasibility of using CNTs as a nanoreservoir by analyzing the dynamics of a fluid flowing out of a ruptured single-walled CNT (SWNT), where the fluid resembles an organic healing agent. With this in mind the escaping mechanism of organic molecules stored inside a cracked SWNT was investigated through a molecular dynamics study. The study shows that, when a SWNT wall suffers the formation of a crack, a certain amount of organic molecules, stored inside the SWNT, escape into space in a few picoseconds. This phenomenon is found to depend on the temperature and on the size of the cracks. The results of this study indicate that CNTs have the potential to be successfully used to realize the next generation of stronger, lighter and self-healing materials.

Characterization of fish sauce aroma-impact compounds using GC-MS, SPME-Osme-GCO, and Stevens' power law exponents

The objectives of this study were to characterize volatile compounds and to determine the characteristic aromas associated with impact compounds in 4 fish sauces using solid-phase micro-extraction, gas chromatography-mass spectrometry, Osme, and gas chromatography olfactometry (SPME-Osme-GCO) coupled with Stevens' Power Law. Compounds were separated using GCMS and GCO and were identified with the mass spectral database, aroma perceived at the sniffing port, retention indices, and verification of compounds by authentic standards in the GCMS and GCO. Aromas that were isolated and present in all 4 fish sauce samples at all concentrations included fishy (trimethylamine), pungent and dirty socks (combination of butanoic, pentanoic, hexanoic, and heptanoic acids), cooked rice and buttery popcorn (2,6-dimethyl pyrazine), and sweet and cotton candy (benzaldehyde). All fish sauces contained the same aromas as determined by GCO and GCMS (verified using authentic standard compounds), but the odor intensity associated with each compound or group of compounds was variable for different fish sauce samples. Stevens' Power Law exponents were also determined using this analytical technique, but exponents were not consistent for the same compounds that were found in all fish sauces. Stevens' Power Law exponents ranged from 0.14 to 0.37, 0.24 to 0.34, 0.09 to 0.21, and 0.10 to 0.35 for dirty socks, fishy, buttery popcorn, and sweet aromas, respectively. This demonstrates that there is variability in Stevens' Power Law exponents for odorants within fish sauce samples.

Autoinducer-2 activity of gram-negative foodborne pathogenic bacteria and its influence on biofilm formation

This study evaluated whether autoinducer-2 (AI-2) activity would be associated with biofilm formation by Salmonella and Escherichia coli O157:H7 strains on food contact surfaces. In study I, a Salmonella Typhimurium DT104 strain and an E. coli O157:H7 strain, both AI-2 positive, were individually inoculated into 50 mL of Luria-Bertani (LB) or LB + 0.5% glucose (LBG) broth, without or with stainless steel or polypropylene (Salmonella) coupons. At 0, 14 (Salmonella), 24, 48, and 72 h of storage (25 degrees C), cells in suspension and detached cells from the coupons, obtained by vortexing, were enumerated on tryptic soy agar. In study II, a Salmonella Thompson AI-2-positive strain and an AI-2-negative strain, and an E. coli O157:H7 AI-2-positive strain and an AI-2-negative strain were inoculated into LB broth with stainless steel coupons. Cells were enumerated as in study I. In both studies, AI-2 activity was determined in cell-free supernatants. Cell numbers of S. Typhimurium DT104 on biofilms were higher (P < 0.05) in LB than those in LBG, while the E. coli O157:H7 strain showed no difference (P>or= 0.05) in biofilm cell counts between LB and LBG after storage for 72 h. Both S. Typhimurium DT104 and E. coli O157:H7 strains produced higher (P < 0.05) AI-2 activity in LBG than LB cell suspensions. Cell counts of AI-2-positive and-negative S. Thompson and E. coli O157:H7 strains were not different (P>or= 0.05) within suspensions or coupons (study II). The results indicated that, under the conditions of this study, AI-2 activity of the pathogen strains tested may not have a major influence on biofilm formation on food contact surfaces, which was similar between AI-2-positive and -negative strains.