Femtosecond dynamics of electron localization at interfaces

The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes.     

Mobilization of Cu and Pb from multi-metal contaminated soils by dissolved humic substances extracted from leonardite and factors affecting the process

Journal of Soils and Sediments - The aim of the research was to determine the potential of dissolved humic substances extracted from leonardite to mobilize Cu and Pb from multi-metal contaminated...     

Analysis of bovine trigeminal ganglia following infection with bovine herpesvirus 1

Following primary infection of the eye, oral cavity, and/or nasal cavity, bovine herpesvirus 1 (BHV-1) establishes latency in trigeminal ganglionic (TG) neurons. Virus reactivation and spread to other susceptible animals occur after natural or corticosteroid-induced stress. Infection of calves with BHV-1 leads to infiltration of lymphocytes in TG and expression of IFN-gamma (interferon-gamma), even in latently infected calves. During latency, virus antigen and nucleic acid positive non-neural cells were occasionally detected in TG suggesting there is a low level of spontaneous reactivation. Since we could not detect virus in ocular or nasal swabs, these rare cells do not support high levels of productive infection and virus release or they do not support virus production at all. Dexamethasone (DEX) was used to initiate reactivation in latently infected calves. Foci of mononuclear or satellite cells undergoing apoptosis were detected 6h after DEX treatment, as judged by the appearance of TUNEL+ cells (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling). BHV-1 antigen expression was initially detected in lymphocytes and other non-neural cells in latently infected calves following DEX treatment. At 24h after DEX treatment, viral antigen expression and nucleic acid were readily detected in neurons. Our data suggest that persistent lymphocyte infiltration and cytokine expression occur during latency because a low number of cells in TG express BHV-1 proteins. Induction of apoptosis and changes in cytokine expression following DEX treatment correlates with reactivation from latency. We hypothesize that inflammatory infiltration of lymphoid cells in TG plays a role in regulating latency.     

A study of experimental autoimmune encephalomyelitis in dogs as a disease model for canine necrotizing encephalitis

In the present study, the use of dogs with experimental autoimmune encephalomyelitis (EAE) as a disease model for necrotizing encephalitis (NE) was assessed. Twelve healthy dogs were included in this study. Canine forebrain tissues (8 g), including white and grey matter, were homogenized with 4 mL of phosphate-buffered saline for 5 min in an ice bath. The suspension was emulsified with the same volume of Freund''s complete adjuvant containing 1 mg/mL of killed Mycobacterium tuberculosis H37Ra. Under sedation, each dog was injected subcutaneously with canine brain homogenate at four sites: two in the inguinal and two in the axillary regions. A second injection (booster) was administered to all the dogs using the same procedure 7 days after the first injection. Clinical assessment, magnetic resonance imaging, cerebrospinal fluid analyses, necropsies, and histopathological and immunohistochemical examinations were performed for the dogs with EAE. Out of the 12 animals, seven (58%) developed clinically manifest EAE at various times after immunization. Characteristics of canine EAE models were very similar to canine NE, suggesting that canine EAE can be a disease model for NE in dogs.     

Foot-and-mouth disease eradication efforts in the Republic of Korea

On March 20, 2000, a suspected vesicular disease in cattle was reported to the National Veterinary Research and Quarantine Service (NVRQS) of the Republic of Korea. This represented the index case of a foot-and-mouth disease (FMD) outbreak, which spread through several provinces. The Republic of Korea had been free of FMD for 66 years prior to the reintroduction of the virus and had recently suspended imports of pork and pork products from neighboring Japan owing to a reported FMD outbreak in that country. The Korean outbreak was ultimately controlled through the combination of preemptive slaughter, animal movement restrictions, and a strategy of ring vaccination. The purpose of this paper is to review the current FMD situation in Korea in the aftermath of its 2000 epizootic and how it may affect future efforts to eradicate or reduce risk of reintroduction of the disease into Korea.     

V1 neurons signal acquisition of an internal representation of stimulus location

A fundamental aspect of visuomotor behavior is deciding where to look or move next. Under certain conditions, the brain constructs an internal representation of stimulus location on the basis of previous knowledge and uses it to move the eyes or to make other movements. Neuronal responses in primary visual cortex were modulated when such an internal representation was acquired: Responses to a stimulus were affected progressively by sequential presentation of the stimulus at one location but not when the location was varied randomly. Responses of individual neurons were spatially tuned for gaze direction and tracked the Bayesian probability of stimulus appearance. We propose that the representation arises in a distributed cortical network and is associated with systematic changes in response selectivity and dynamics at the earliest stages of cortical visual processing.