Adaptive behavior in optimal sequential search

Sequential decision making-making a decision where available options are encountered successively-is a hallmark of everyday life. Such decisions require deciding to accept or reject an alternative without knowing potential future options. Prior work focused on understanding choice behavior by developing decision models that capture human choices in such tasks. We investigated people's adaptive behavior in changing environments in light of their cognitive strategies. We present two studies in which we modified (a) outcome variance and (b) the time horizon and provide empirical evidence that people adapt to both context manipulations. Furthermore, we apply a recently developed threshold model of optimal stopping to our data to disentangle different cognitive processes involved in optimal stopping behavior. The results from Study 1 show that participants adaptively scaled the values of the sampling distribution to its variance, suggesting that the value of an option is perceived in relative rather than absolute terms. The results from Study 2 suggest that increasing the time horizon decreases the initial acceptance level, but less strongly than would be optimal. Furthermore, for longer sequences, participants more weakly adjusted this acceptance threshold over time than for shorter sequences. Further correlations between individual estimates in each condition indicate that individual differences between the participants' thresholds remain fairly stable between the conditions, pointing toward an additive effect of our manipulations

Self-assembly of the chiral donor-acceptor molecule DCzDCN on Cu(100)

Donor-acceptor (D-A) structured molecules are essential components in organic electronics. The respective molecular structure of these molecules and their synthesis are primarily determined by the intended area of application. Typically, D-A molecules promote charge separation and transport in organic photovoltaics (OPV) or organic field-effect transistors (OFET). D-A molecules showing a larger twist angle between D and A units are, e.g., extremely important for the development of high internal quantum efficiency in organic light-emitting diodes (OLEDs). A prototypical molecule of this D-A type is DCzDCN (5-(4,6-diphenyl-1,3,5-triazin-2-yl)benzene-1,3-dinitrile). In most cases, these molecules are only investigated regarding their electronic and structural interaction in bulk aggregates but not in ultra-thin films supported by a metallic substrate. Here, we present growth and electronic structure studies of DCzDCN on a Cu(100) surface. In a complementary approach, through the use of Scanning Tunneling Microscopy and Spectroscopy (STM and STS), we were able to view both the adsorption geometry and the local electronic states of the adsorbed molecules in direct comparison with the integral electronic structure of the DCzDCN/CU(100) interface using Ultraviolet and Inverse Photoemission Spectroscopy (UPS and IPS). The orientation of the molecules with the donor part towards the substrate results in a chiral resolution at the interface due to the molecular as well as the substrate symmetry and additional strong molecular electrostatic forces. Thus, the formation of various bulk-unlike homochiral structures and the appearance of hybrid interface states (HIS) modifies the molecular electronic properties of the DCzDCN/Cu(100) system significantly compared to that of a single DCzDCN molecule. This may be not only useful for optoelectronic applications but also in organic spintronics.Comment: 28 +5 pages, 9 + 5 figures (paper + supplement

Glucose Transporter 9 (GLUT9) Plays an Important Role in the Placental Uric Acid Transport System.

BACKGROUND Hyperuricemia is a common laboratory finding in pregnant women compromised by preeclampsia. A growing body of evidence suggests that uric acid is involved in the pathogenesis of preeclampsia. Glucose transporter 9 (GLUT9) is a high-capacity uric acid transporter. The aim of this study was to investigate the placental uric acid transport system, and to identify the (sub-) cellular localization of GLUT9. METHODS Specific antibodies against GLUT9a and GLUT9b isoforms were raised, and human villous (placental) tissue was immunohistochemically stained. A systemic GLUT9 knockout (G9KO) mouse model was used to assess the placental uric acid transport capacity by measurements of uric acid serum levels in the fetal and maternal circulation. RESULTS GLUT9a and GLUT9b co-localized with the villous (apical) membrane, but not with the basal membrane, of the syncytiotrophoblast. Fetal and maternal uric acid serum levels were closely correlated. G9KO fetuses showed substantially higher uric acid serum concentrations than their mothers. CONCLUSIONS These findings demonstrate that the placenta efficiently maintains uric acid homeostasis, and that GLUT9 plays a key role in the placental uric acid transport system, at least in this murine model. Further studies investigating the role of the placental uric acid transport system in preeclampsia are eagerly needed

Anatomical Reconstruction and Functional Imaging Reveal an Ordered Array of Skylight Polarization Detectors in Drosophila

Many insects exploit skylight polarization as a compass cue for orientation and navigation. In the fruit fly, Drosophila melanogaster, photoreceptors R7 and R8 in the dorsal rim area (DRA) of the compound eye are specialized to detect the electric vector (e-vector) of linearly polarized light. These photoreceptors are arranged in stacked pairs with identical fields of view and spectral sensitivities, but mutually orthogonal microvillar orientations. As in larger flies, we found that the microvillar orientation of the distal photoreceptor R7 changes in a fan-like fashion along the DRA. This anatomical arrangement suggests that the DRA constitutes a detector for skylight polarization, in which different e-vectors maximally excite different positions in the array. To test our hypothesis, we measured responses to polarized light of varying e-vector angles in the terminals of R7/8 cells using genetically encoded calcium indicators. Our data confirm a progression of preferred e-vector angles from anterior to posterior in the DRA, and a strict orthogonality between the e-vector preferences of paired R7/8 cells. We observed decreased activity in photoreceptors in response to flashes of light polarized orthogonally to their preferred e-vector angle, suggesting reciprocal inhibition between photoreceptors in the same medullar column, which may serve to increase polarization contrast. Together, our results indicate that the polarization-vision system relies on a spatial map of preferred e-vector angles at the earliest stage of sensory processing

A linear threshold model for optimal stopping behavior

In many real-life decisions, options are distributed in space and time, making it necessary to search sequentially through them, often without a chance to return to a rejected option. The optimal strategy in these tasks is to choose the first option that is above a threshold that depends on the current position in the sequence. The implicit decision-making strategies by humans vary but largely diverge from this optimal strategy. The reasons for this divergence remain unknown. We present a model of human stopping decisions in sequential decision-making tasks based on a linear threshold heuristic. The first two studies demonstrate that the linear threshold model accounts better for sequential decision making than existing models. Moreover, we show that the model accurately predicts participants’ search behavior in different environments. In the third study, we confirm that the model generalizes to a real-world problem, thus providing an important step toward understanding human sequential decision making

Behavioral Health Risk Factors and Motivation to Change among Cardiovascular General Hospital Patients Aged 50 to 79 Years

Little is known about the (co-)occurrence of smoking, alcohol at-risk drinking, physical inactivity and overweight, and the motivation to change these behavioral health risk factors (HRFs) in older general hospital patients with cardiovascular disease. Between October and December 2016, all consecutively admitted patients aged 50 to 79 years were proactively recruited on 3 cardiology wards and asked to participate in a survey on HRFs and behavior change motivation. Of the eligible patients, 80.4% participated in the survey (n = 328). The mean age was 66.5 years (standard deviation 9.0), and 65.5% were male. At least 1 HRF was present in 91.8% (n = 280), at least 2 HRFs in 54.4% (n = 166), and 3 or 4 HRFs in 12.1% (n = 37) of participants. The proportion of older adults who contemplated or were changing or planning to change their behavior to meet health behavior recommendations ranged between 66.0% (smoking) and 93.2% (alcohol consumption). The results indicate a notable co-occurrence of behavioral HRFs in older patients with cardiovascular disease. The majority of older adults were at least considering changing the respective behavior. To prevent and treat diseases efficiently, hospitalization may be a suitable moment for systematic multiple HRF screening and intervention.Peer Reviewe

Placental expression of the angiogenic placental growth factor is stimulated by both aldosterone and simulated starvation

Aldosterone is an important factor supporting placental growth and fetal development. Recently, expression of placental growth factor (PlGF) has been observed in response to aldosterone exposure in different models of atherosclerosis. Thus, we hypothesized that aldosterone up-regulates growth-adaptive angiogenesis in pregnancy, via increased placental PlGF expression. We followed normotensive pregnant women (n = 24) throughout pregnancy and confirmed these results in a second independent first trimester cohort (n = 36). Urinary tetrahydroaldosterone was measured by gas chromatography-mass spectrometry and corrected for creatinine. Circulating PlGF concentrations were determined by ELISA. Additionally, cultured cell lines, adrenocortical H295R and choriocarcinoma BeWo cells, as well as primary human third trimester trophoblasts were tested in vitro. PlGF serum concentrations positively correlated with urinary tetrahydroaldosterone corrected for creatinine in these two independent cohorts. This observation was not due to PlGF, which did not induce aldosterone production in cultured H295R cells. On the other hand, PlGF expression was specifically enhanced by aldosterone in the presence of forskolin (p < 0.01) in trophoblasts. A pronounced stimulation of PlGF expression was observed with reduced glucose concentrations simulating starvation (p < 0.001). In conclusion, aldosterone stimulates placental PlGF production, enhancing its availability during human pregnancy, a response amplified by reduced glucose supply. Given the crucial role of PlGF in maintaining a healthy pregnancy, these data support a key role of aldosterone for a healthy pregnancy outcome

An open label randomized multicentre phase IIIb trial comparing parenteral substitution versus best supportive nutritional care in subjects with pancreatic adenocarcinoma receiving 5-FU plus oxaliplatin as 2nd or higher line chemotherapy regarding clinical benefit - PANUSCO

<p>Abstract</p> <p>Background</p> <p>Pancreatic cancer is an extremely aggressive malignancy. Subjects are afflicted with a variety of disconcerting symptoms, including profound cachexia. Recent data indicate that the outcome of oncological patients suffering from cancer cachexia could be improved by parenteral nutrition and that parenteral nutrition results in an improvement of quality of life and in prolonged survival.</p> <p>Currently, there is no recommendation of routine use of parenteral nutrition. Furthermore, there is no clear recommendation for 2^ndline therapy (or higher) for pancreatic adenocarcinoma but often asked for.</p> <p>Methods/Design</p> <p>PANUSCO is an open label, controlled, prospective, randomized, multicentre phase IIIb trial with two parallel arms. All patients will be treated with 5-fluorouracil, folinic acid and oxaliplatin on an outpatient basis at the study sites. Additionally, all patients will receive best supportive nutritional care (BSNC). In the experimental group BSNC will be expanded with parenteral nutrition (PN). In contrast, patients in the control group obtain solely BSNC. Parenteral nutrition will be applied overnight and at home by experienced medical staff.</p> <p>A total of 120 patients are planned to be enrolled. Primary endpoint is the comparison of the treatment groups with respect to event-free survival (EFS), defined as the time from randomization till time to development of an event defined as either an impairment (change from baseline of at least ten points in EORTC QLQ-C30, functional domain total score) or withdrawal due to fulfilling the special defined stopping criteria for chemotherapy as well as for nutritional intervention (NI) or death from any cause (whichever occurs first).</p> <p>Discussion</p> <p>The aim of this clinical trial is to evaluate whether parenteral nutrition in combination with defined 2^ndline or higher chemotherapy has an impact on quality of life for patients suffering from pancreatic adenocarcinoma.</p> <p>Trial registration</p> <p>Current Controlled Trials ISRCTN60516908.</p