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.