Trust and Reputation in Internet Auctions

Exchange between anonymous actors in Internet auctions corresponds to a one-shot prisoner's dilemma-like situation. Therefore, in any given auction the risk is high that seller and buyer will cheat and, as a consequence, that the market will collapse. However, mutual cooperation can be attained by the simple and very efficient institution of a public rating system. By this system, sellers have incentives to invest in reputation in order to enhance future chances of business. Using data from about 200 auctions of mobile phones we empirically explore the effects of the reputation system. In general, the analysis of nonobtrusive data from auctions may help to gain a deeper understanding of basic social processes of exchange, reputation, trust, and cooperation, and of the impact of institutions on the efficiency of markets. In this study we report empirical estimates of effects of reputation on characteristics of transactions such as the probability of a successful deal, the mode of payment, and the selling price (highest bid). In particular, we try to answer the question whether sellers receive a "premium" for reputation. Our results show that buyers are willing to pay higher prices for reputation in order to diminish the risk of exploitation. On the other hand, sellers protect themselves from cheating buyers by the choice of an appropriate payment mode. Therefore, despite the risk of mutual opportunistic behavior, simple institutional settings lead to cooperation, relatively rare events of fraud, and efficient markets.

Reference photographs for nasolabial appearance rating in unilateral cleft lip and palate

A popular method for nasolabial rating in unilateral cleft lip and palate (UCLP) is the Asher-McDade system consisting of a 5-point ordinal scale assessing nasal form, nasal symmetry, nasal profile, and vermilion border. The aim of the current study was to identify reference photographs illustrating this scale to facilitate its use.Four observers assessed nasolabial appearance on frontal and profile photographs of the nasolabial area of 42 children of Caucasian origin with a repaired UCLP at age 9 years. Cronbachs alpha, based on the individual scores of the 4 observers, ranged from 0.73 to 0.82 for the 4 nasolabial ratings, indicating a good reliability. The reliability of the overall score (mean of the 4 component scores) was also high (Cronbachs alpha, 0.83). Both for the nasolabial component ratings and for the overall score, duplicate measurement errors were small. The reliability for the mean of the 4 observers' scores was good, Spearman rank correlation coefficients ranging from 0.56 to 0.96.Subsequently, photographs were selected that showed the highest agreement among observers. For each of the 4 components (eg, nasal form, nasal deviation, nasal profile, and shape of the vermilion border), 5 photographs were selected to illustrate the whole range of the scale (score, 1-5), resulting in the selection of 20 pictures.It was concluded that nasolabial appearance rating can be performed reliably using a panel of judges and averaging the scores of all observers. Reference photographs, as developed from this study, may facilitate the rating task.

Gait analysis in normal and spinal contused mice using the TreadScan system

Advances in spinal cord injury (SCI) research are dependent on quality animal models, which in turn rely on sensitive outcome measures able to detect functional differences in animals following injury. To date, most measurements of dysfunction following SCI rely either on the subjective rating of observers or the slow throughput of manual gait assessment. The present study compares the gait of normal and contusion-injured mice using the TreadScan system. TreadScan utilizes a transparent treadmill belt and a high-speed camera to capture the footprints of animals and automatically analyze gait characteristics. Adult female C57Bl/6 mice were introduced to the treadmill prior to receiving either a standardized mild, moderate, or sham contusion spinal cord injury. TreadScan gait analyses were performed weekly for 10 weeks and compared with scores on the Basso Mouse Scale (BMS). Results indicate that this software successfully differentiates sham animals from injured animals on a number of gait characteristics, including hindlimb swing time, stride length, toe spread, and track width. Differences were found between mild and moderate contusion injuries, indicating a high degree of sensitivity within the system. Rear track width, a measure of the animal's hindlimb base of support, correlated strongly both with spared white matter percentage and with terminal BMS. TreadScan allows for an objective and rapid behavioral assessment of locomotor function following mild-moderate contusive SCI, where the majority of mice still exhibit hindlimb weight support and plantar paw placement during stepping.

Assessment of the wind-up phenomenon in the equine nociceptive trigeminal system.

Repeated sub-threshold nociceptive electrical stimulation resulting in temporal summation of the limb nociceptive withdrawal reflex is a well-established non-invasive model to investigate the wind-up phenomenon in horses. Due to structural similarities of the trigeminal sensory nucleus to the dorsal horn of the spinal cord, temporal summation should be evoked by repeated transcutaneous electrical stimulation of trigeminal afferents. To evaluate this hypothesis repeated transcutaneous electrical stimulation was applied to the supraorbital and infraorbital nerves of 10 horses. Stimulation intensities varied between 0.5 and 1.3 times the trigemino-cervical reflex threshold defined for single stimulation. Evoked electromyographic activity of the orbicularis oculi, splenius and cleidomastoideus muscles was recorded and the signals analysed in the previously established epochs typical to the early and late component of the blink reflex and to the trigemino-cervical reflex. Behavioural reactions were evaluated with the aid of numerical rating scale. The nociceptive late component and the trigemino-cervical reflex were not elicited by sub-threshold intensity repeated transcutaneous electrical stimulation. Furthermore, the median reflex amplitude for the 10 horses showed a tendency to decline over the stimulation train so temporal summation of afferent trigeminal inputs could not be observed. Therefore, the modulation of trigeminal nociceptive processing attributable to repeated Aδ fibre stimulations seems to differ from spinal processing of similar inputs as it seems to have an inhibitory rather than facilitatory effect. Further evaluation is necessary to highlight the underlying mechanism.

Outcome study of real-time MR-guided cervical periradicular injection therapy in an open 1.0 Tesla MRI system

PURPOSE To evaluate the accuracy, safety, and efficacy of cervical nerve root injection therapy using magnetic resonance guidance in an open 1.0 T MRI system. METHODS Between September 2009 and April 2012, a total of 21 patients (9 men, 12 women; mean age 47.1 ± 11.1 years) underwent MR-guided cervical periradicular injection for cervical radicular pain in an open 1.0 T system. An interactive proton density-weighted turbo spin echo (PDw TSE) sequence was used for real-time guidance of the MR-compatible 20-gauge injection needle. Clinical outcome was evaluated on a verbal numeric rating scale (VNRS) before injection therapy (baseline) and at 1 week and 1, 3, and 6 months during follow-up. RESULTS All procedures were technically successful and there were no major complications. The mean preinterventional VNRS score was 7.42 and exhibited a statistically significant decrease (P < 0.001) at all follow-up time points: 3.86 ± 1.53 at 1 week, 3.21 ± 2.19 at 1 month, 2.58 ± 2.54 at 3 months, and 2.76 ± 2.63 at 6 months. At 6 months, 14.3 % of the patients reported complete resolution of radicular pain and 38.1 % each had either significant (4-8 VNRS score points) or mild (1-3 VNRS score points) relief of pain; 9.5 % experienced no pain relief. CONCLUSION Magnetic resonance fluoroscopy-guided periradicular cervical spine injection is an accurate, safe, and efficacious treatment option for patients with cervical radicular pain. The technique may be a promising alternative to fluoroscopy- or CT-guided injections of the cervical spine, especially in young patients and in patients requiring repeat injections.

EEG marker of inhibitory brain activity correlates with resting-state cerebral blood flow in the reward system in major depression

Frontal alpha band asymmetry (FAA) is a marker of altered reward processing in major depressive disorder (MDD), associated with reduced approach behavior and withdrawal. However, its association with brain metabolism remains unclear. The aim of this study is to investigate FAA and its correlation with resting – state cerebral blood flow (rCBF). We hypothesized an association of FAA with regional rCBF in brain regions relevant for reward processing and motivated behavior, such as the striatum. We enrolled 20 patients and 19 healthy subjects. FAA scores and rCBF were quantified with the use of EEG and arterial spin labeling. Correlations of the two were evaluated, as well as the association with FAA and psychometric assessments of motivated behavior and anhedonia. Patients showed a left – lateralized pattern of frontal alpha activity and a correlation of FAA lateralization with subscores of Hamilton Depression Rating Scale linked to motivated behavior. An association of rCBF and FAA scores was found in clusters in the dorsolateral prefrontal cortex bilaterally (patients) and in the left medial frontal gyrus, in the right caudate head and in the right inferior parietal lobule (whole group). No correlations were found in healthy controls. Higher inhibitory right – lateralized alpha power was associated with lower rCBF values in prefrontal and striatal regions, predominantly in the right hemisphere, which are involved in the processing of motivated behavior and reward. Inhibitory brain activity in the reward system may contribute to some of the motivational problems observed in MDD.