Empirical research in on-line trust: a review and critical assessment

Lack of trust is one of the most frequently cited reasons for consumers not purchasing from Internet vendors. During the last four years a number of empirical studies have investigated the role of trust in the specific context of e-commerce, focusing on different aspects of this multi-dimensional construct. However, empirical research in this area is beset by conflicting conceptualizations of the trust construct, inadequate understanding of the relationships between trust, its antecedents and consequents, and the frequent use of trust scales that are neither theoretically derived nor rigorously validated. The major objective of this paper is to provide an integrative review of the empirical literature on trust in e-commerce in order to allow cumulative analysis of results. The interpretation and comparison of different empirical studies on on-line trust first requires conceptual clarification. A set of trust constructs is proposed that reflects both institutional phenomena (system trust) and personal and interpersonal forms of trust (dispositional trust, trusting beliefs, trusting intentions and trust-related behaviours), thus facilitating a multi-level and multi-dimensional analysis of research problems related to trust in e-commerce.     

The chemical oxygen iodine laser in the presence of a magneticfield. II. Frequency tuning behavior

For pt.I, see ibid., vol.29, no.3, p.933-43 (1993). Results are presented from an experimental/theoretical investigation of the frequency shifting and tuning behavior of a chemical oxygen-iodine laser in the presence of an applied magnetic field. Frequency shifting measurements are presented for both P and S polarization over a range of magnetic field strength from 0 to 3000 G, in a pressure regime (3 torr) where the line shape is Doppler broadened. Theoretical predictions of the location and magnitude of the frequency shifts are shown to be in good agreement with both the present measurements and a previous investigation in the pressure broadened regime     

Unitary events in multiple single-neuron spiking activity: I. Detection and significance.

It has been proposed that cortical neurons organize dynamically into functional groups (cell assemblies) by the temporal structure of their joint spiking activity. Here, we describe a novel method to detect conspicuous patterns of coincident joint spike activity among simultaneously recorded single neurons. The statistical significance of these unitary events of coincident joint spike activity is evaluated by the joint-surprise. The method is tested and calibrated on the basis of simulated, stationary spike trains of independently firing neurons, into which coincident joint spike events were inserted under controlled conditions. The sensitivity and specificity of the method are investigated for their dependence on physiological parameters (firing rate, coincidence precision, coincidence pattern complexity) and temporal resolution of the analysis. In the companion article in this issue, we describe an extension of the method, designed to deal with nonstationary firing rates.     

Phosphatidylinositol 4,5-bisphosphate phospholipase C activity in particulate preparations from rat brain

We describe the hydrolysis of phosphatidylinositol 4,5-bisphosphate by a particulate rat brain preparation in the presence of the cationic detergent, cetrimide. The optimum cetrimide concentration was in the range 0.2–0.4 mg/ml; at higher or lower concentrations, the reaction rate diminished abruptly, suggesting that the electrical charge density of the micelle is critical for enzymatic attack. In other respects, such as its partial requirement for Ca⁺⁺ and its pH optimum of about 7.0, the particulate enzyme seems similar to soluble preparations which have been reported previously. Interestingly, the particulate preparation could be stimulated about fourfold by a soluble brain extract in the presence of 1 mM guanosine triphosphate, confirming that the enzyme is the catalytic subunit in a membrane-bound signal-transduction system.     

Bowker's test for symmetry and modifications within the algebraic framework

Categorical data occur in a wide range of statistical applications. If the data are observed in matched pairs, it is often of interest to examine the differences between the responses. The focus is on tests of axial symmetry in two-way tables. A commonly used procedure is the Bowker test which is a generalization of the McNemar test. The test decision is based on a chi-squared approximation which might not be adequate, for example if the table is sparse. Therefore, modifications of the test statistic have been discussed. A test of symmetry based on Bowker's test and Markov Chain Monte Carlo methods is proposed. A simulation study is carried out to determine and compare the performances of the simulation test, the Bowker test and two modifications.     

On what we cannot learn from proximity data.

Different issues raised in the commentaries are elaborated in this reply. The focus was on the following five topics: (a) the nature of storage deficits in the patient groups and the different meanings that can be attached to it, (b) the possible explanations for the disordered responses of the patients, (c) suggestions for the use of other techniques to study semantic deficits, (d) the Warrington and Shallice criteria to distinguish between access and storage problems, and (e) some technical (statistical) issues raised in the commentaries. The reply concludes by highlighting the key findings reported in the target article that seem to be accepted by the large majority of the commentators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective ablation of GABA neurons in the ventral tegmental area increases spontaneous locomotor activity.

γ-aminobutyric acid (GABA) neurons in the ventral tegmental area (VTA) provide innervation to cortical and subcortical regions of the brain. To solidify the importance of these VTA GABA neurons in behavioral function, we employed the neurotoxin dermorphin-saporin (DS) to selectively lesion VTA GABA neurons prior to assessing spontaneous motor activity. Rats were bilaterally microinfused with DS (1.0 or 2.0 pmol/200 nl/side) or blank-saporin control (BS, 200 nl/side) into the VTA. Seven days later, DS-treated rats exhibited significantly elevated motility in comparison with BS-treated rats; this elevated motility normalized by Day 14 following pretreatment with 1.0 pmol of DS but was sustained on Day 14 after pretreatment with 2.0 pmol of DS. A selective loss of VTA GABA neurons on Day 14 was demonstrated through reduced expression of mRNA for glutamic acid decarboxylase-67 and μ-opioid receptor, but not tyrosine hydroxylase (a dopamine neuron marker), in the VTA. Thus, a dose- and time-related selective loss of VTA GABA neurons was accomplished using this novel neurotoxin. This loss of GABA VTA neurons was associated with hypermotility, further supporting their important regulatory role in the generation of behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bestimmung natürlich vorkommender steroidaler Sexualhormone (Androgene und Gestagene) in Rindfleisch

The content of 10 naturally occurring steroidal sex hormones (androgens and progestogens), their biosynthetic precursors and metabolites was determined in 62 samples of beef (bulls, steers, heifers). After enzymatic hydrolysis of their conjugates, the steroids were extracted from the tissue by liquid-liquid extraction and purified by solid phase extraction. The identification and quantification was carried out by GC-MS of the trimethylsilyl ethers. The progestogens progesterone and pregnenolone were quantitatively dominant (43,7 and 6,5 μg/kg respectively). The highest steroid concentrations were determined in female cattle.