Learning to ignore the mask in texture segmentation tasks.

Although traditionally texture segmentation has been regarded as an automatic, preattentive process, participants confronted with texture segmentation in experimental settings (i.e., with brief presentation time and subsequent masking) are initially unable to perform the task. According to perceptual learning concepts, participants must learn to fine-tune their sensory channels before perception improves under restricted viewing conditions. The present article proposes an alternative perspective that emphasizes the role of the mask. Four experiments showed that the amount of observed learning depends on the structural and temporal homogeneity or heterogeneity of the mask. The authors suggest that learning consists of separating the task-relevant signal stemming from the texture from the task-irrelevant signal of the mask and of ignoring the mask. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The benefits of incorporating utility dependencies in finite mixture probit models

OR Spectrum - We propose an application of a new finite mixture multinomial conditional probit (FM-MNCP) model that accommodates preference heterogeneity and explicitly accounts for utility...     

Rapid Determination of the Amino Acid Configuration of Xenotetrapeptide

An E. coli strain with deletions in five transaminases (ΔaspC ΔilvE ΔtyrB ΔavtA ΔybfQ) was constructed to be unable to degrade several amino acids. This strain was used as an expression host for the analysis of the amino acid configuration of nonribosomally synthesized peptides, including the novel peptide “xenotetrapeptide” from Xenorhabdus nematophila, by using a combination of labeling experiments and mass spectrometry. Additionally, the number of D ‐amino acids in the produced peptide was assigned following simple cultivation of the expression strain in D₂O.     

Volumetric hemodynamic parameters to guide fluid removal on hemodialysis in the intensive care unit

Estimation of removable excess body fluid is difficult in critically ill patients with renal failure. Volumetric hemodynamic parameters are increasingly being used to guide fluid therapy in the intensive care unit, but their suitability to monitor fluid removal with hemodialysis in critically ill patients is not known. Changes in the extravascular lung water index (EVLWI) and intrathoracic blood volume index (ITBVI) measured with transpulmonary thermodilution immediately before and after hemodialysis were analyzed from 39 hemodialysis sessions of 9 patients consecutively treated in the medical intensive care unit of a German University Hospital. Additional hemodynamic, ventilation, and oxygenation-related parameters were recorded at the same time. Online relative blood volume (RBV) monitoring was performed in 29 sessions. Comparisons of pre and postdialysis values showed a significant reduction of the EVLWI with fluid removal (p=0.009), with only a slight nonsignificant decrease in the ITBVI. The cardiac index (CI) also decreased significantly (p=0.010), whereas blood pressure remained stable. Oxygenation improved significantly (p=0.005), and the hematocrit increased significantly with dialysis (p=0.039). There was no correlation between hematocrit changes and RBV measurements. Significant correlations existed between ITBVI and CI changes (p<0.001), but not to EVLWI reduction. The removal of excess body fluid on hemodialysis is reflected by the EVLWI reduction, whereas the preservation of cardiac preload is shown by ITBVI stability. Volumetric hemodynamic parameters could be useful to guide fluid removal with hemodialysis in the intensive care unit.     

Neutral loss fragmentation pattern based screening for arginine-rich natural products in xenorhabdus and photorhabdus

Although sharing a certain degree of structural uniformity, natural product classes exhibit variable functionalities such as different amino acid or acyl residues. During collision induced dissociation, some natural products exhibit a conserved fragmentation pattern close to the precursor ion. The observed fragments result from a shared set of neutral losses, creating a unique fragmentation pattern, which can be used as a fingerprint for members of these natural product classes. The culture supernatants of 69 strains of the entomopathogenic bacteria Photorhabdus and Xenorhabdus were analyzed by MALDI-MS(2), and a database comprising MS(2) data from each strain was established. This database was scanned for concordant fragmentation patterns of different compounds using a customized software, focusing on relative mass differences of the fragment ions to their precursor ion. A novel group of related natural products comprising 25 different arginine-rich peptides from 16 different strains was identified due to its characteristic neutral loss fragmentation pattern, and the structures of eight compounds were elucidated. Two biosynthesis gene clusters encoding nonribosomal peptide synthetases were identified, emphasizing the possibility to identify a group of structurally and biosynthetically related natural products based on their neutral loss fragmentation pattern.     

Recycling soil nutrients by using channel deposits as fertilizers?

Topsoil constituents are eroded from agricultural sites and leached towards drainage channels. This transfer can affect aquatic ecosystems and deteriorate the efficiency of drainage systems and fertilisers. As long as erosion cannot be completely avoided, the recycling of sediments and associated nutrients may offer a sustainable solution to these problems. The aim of our case study at the island Sant Erasmo, lagoon of Venice (Italy) was to assess the ecological problems and potentials of sediment recycling. With our assessment we concentrated on (1) the origin of channel sediments, (2) the benefit of sediment application for increasing the nutrient stocks of the soils, and (3) the risk of heavy metal (HM) contamination of arable soils by sediment application. Samples from soils of horticultural sites, sediments, and waters from adjacent drainage channels and lagoon sediments were analyzed for the concentrations of nutrients (P and K) and HM (Cu, Pb, and Zn). Potentially available channel sediment masses and element stocks were calculated for the soil fertility classes of Sant Erasmo based on local measurements of sediment depths and analyses of aerial photographs by a geographic information system. In a column experiment, leaching of both nutrients and Cu from recently dredged sediments was analyzed. Heavy metal concentrations of soils and channel sediments were much higher than of lagoon sediments. The similarity of the chemical properties of the channel sediments and of top soil samples implies that topsoil material is eroded into the channels. The amount of sediments accumulated in the channels corresponded to soil erosion rates between 2 and 23?t?ha^?1?a^?1. Channel sediments contained higher concentrations of nutrients and organic carbon but slightly lower concentrations of HM than the soils of adjacent horticultural sites. Sediment P and K yields would be sufficient to replace fertiliser application at the horticultural sites for up to 51 and 35?years, respectively. The column experiment indicated that Cu mobilization induced by oxidation processes is restricted to the first years after sediments are applied to the soils. Our study emphasizes that for a comprehensive assessment of sediment recycling in agricultural systems the available sediment stocks as well as the contents of nutrients and pollutants of the sediment in relation to soils have to be considered.     

Rhabdopeptides as Insect‐Specific Virulence Factors from Entomopathogenic Bacteria

Six novel linear peptides, named “rhabdopeptides”, have been identified in the entomopathogenic bacterium Xenorhabdus nematophila after the discovery of the corresponding rdp gene cluster by using a promoter trap strategy for the detection of insect‐inducible genes. The structures of these rhabdopeptides were deduced from labeling experiments combined with detailed MS analysis. Detailed analysis of an rdp mutant revealed that these compounds participate in virulence towards insects and are produced upon bacterial infection of a suitable insect host. Furthermore, two additional rhabdopeptide derivatives produced by Xenorhabdus cabanillasii were isolated, these showed activity against insect hemocytes thereby confirming the virulence of this novel class of compounds.     

Effects of masked stimuli on motor activation: Behavioral and electrophysiological evidence.

Three experiments investigated the influence of unperceived events on response activation. Masked primes were presented before a target. On compatible trials, primes and targets were identical; on incompatible trials, opposite responses were assigned to them. Forced-choice performance indicated that prime identification was prevented by the masking procedure, but overt performance and motor activation as mirrored by the lateralized readiness potential (LRP) were systematically influenced by the prime. The direction of these effects was unexpected: Performance costs for compatible and performance benefits for incompatible trials were obtained relative to a neutral trial condition. The LRP revealed a sequential pattern of motor activation. A partial activation of the response corresponding to the prime was followed by a reverse activation pattern. It is argued that these effects primarily reflect an inhibition of the response initially triggered by the prime. (PsycINFO Database Record (c) 2010 APA, all rights reserved)