Accuracy assessment of the MODIS 16-day albedo product for snow: comparisons with Greenland in situ measurements

The accuracy of the Moderate Resolution Imaging Spectroradiometer (MODIS) 16-day albedo product (MOD43) is assessed using ground-based albedo observations from automatic weather stations (AWS) over spatially homogeneous snow and semihomogeneous ice-covered surfaces on the Greenland ice sheet. Data from 16 AWS locations, spanning the years 2000-2003, were used for this assessment. In situ reflected shortwave data were corrected for a systematic positive spectral sensitivity bias of between 0.01 and 0.09 on a site-by-site basis using precise optical black radiometer data. Results indicate that the MOD43 albedo product retrieves snow albedo with an average root mean square error (RMSE) of ±0.07 as compared to the station measurements, which have ±0.035 RMSE uncertainty. If we eliminate all satellite retrievals that rely on the backup algorithm and consider only the highest quality results from the primary bidirectional reflectance distribution function (BRDF) algorithm, the MODIS albedo RMSE is ±0.04, slightly larger than the in situ measurement uncertainty. There is general agreement between MODIS and in situ observations for albedo <0.7, while near the upper limit, a −0.05 MODIS albedo bias is evident from the scatter of the 16-site composite.     

Prospective predictors of posttraumatic stress disorder symptoms: Direct and mediated relations.

This study assessed the relations between pretrauma risk (neuroticism, negative affect, prior distress) and protective (self-esteem, optimism) factors and posttraumatic stress disorder (PTSD) symptoms and potential mediators (subjective event-related distress, unsupportive social interactions, perceived control) of those relations. Students (N = 1,528) at four U.S. universities completed online surveys assessing pretrauma risk and protective factors at Time 1 (T1); 84% (N = 1,281) completed a survey 2 months later (T2). PTSD symptoms and the three potential mediators were assessed among those who experienced potentially traumatic events between T1 and T2 (n = 264). PTSD symptoms related to prior traumas were controlled in all analyses. In structural equation modeling (SEM) analyses, the relation between risk factors and PTSD symptoms was mediated by unsupportive social interactions. Protective factors did not independently predict PTSD symptoms when risk factors also were included in the SEM models. Implications for research and practice are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Assimilation of traumatic experiences and physical-health outcomes: Cautions for the Pennebaker paradigm.

This study reports an application of the assimilation model, a theory of psychotherapeutic change, to an analogue study in which 43 students were asked to write for 20 minutes a day for 4 days ("Pennebaker paradigm") about a traumatic experience. Contrary to expectations based on previous research, participants who showed the greatest change in assimilation level and achieved the highest levels of assimilation during the study subsequently had more health-center visits than participants whose assimilation was less. Qualitative exploratory work suggested that there may be negative consequences of exposing traumatic experiences in the absence of supportive therapy to contain and fully integrate the experiences. A more measured approach to the benefits of brief exposition of traumatic experiences may be warranted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

LiTaO3的声学声子测量

一、引言自六十年代后期以来,不少人对LiTaO_3和LiNbO_3的相变问题进行了广泛的研究,采用的手段各异,有红外光谱、喇曼光谱、热中子散射等。有人认为是位移型相变,有人认为属于有序-无序型,还有人认为是二者之结合,但至今尚无一个肯定性的意见。我们希望通过热中子非弹性散射实验,对LiTaO_3相变机制进行研究。作为第一步,先在两个主要对称方向上测量了色散曲线的声学支,并根据小q值处色散曲线的斜率算出了在晶体内的声速,与其它的结果进行了比较。     

Measuring scenic quality at the urban fringe

The emerging discipline of Landscape Ecology is described, and its historical development studied. Differences between European and North American practice are revealed and the discipline is seen to emerge as much from ecological studies as from geography, forestry and landscape architecture. An extensive list of references is given.     

Oxidation of vanillin by peroxomonosulphate-thermodynamic and kinetic investigation

The oxidation of vanillin by peroxomonosulphate (PMS) in acetic acid–sodium acetate buffered medium was carried out at 308 K. The rate was first order with respect to [vanillin] and [PMS]. The rate increased with increase in pH and the rate was too fast to be measured at pH 5.2. The rate increased with increase in [acetate] and the plot of k_obs versus [acetate] was a straight line with positive intercept. Variation of ionic strength had no effect on the rate of the reaction. Effects of polarity were studied with five different solvents and in all the cases, log k_obs versus 1/? were linear with negative slope. The reaction had been carried out at four different temperatures and the activation and thermodynamic parameters were calculated. The product of oxidation was confirmed as vanillic acid by IR, ¹H NMR and GC-MS spectral analysis. Based on the results obtained a reaction scheme had been proposed and the rate law was derived.     

Making sense of the meaning literature: An integrative review of meaning making and its effects on adjustment to stressful life events.

Interest in meaning and meaning making in the context of stressful life events continues to grow, but research is hampered by conceptual and methodological limitations. Drawing on current theories, the author first presents an integrated model of meaning making. This model distinguishes between the constructs of global and situational meaning and between “meaning-making efforts” and “meaning made,” and it elaborates subconstructs within these constructs. Using this model, the author reviews the empirical research regarding meaning in the context of adjustment to stressful events, outlining what has been established to date and evaluating the strengths and weaknesses of current empirical work. Results suggest that theory on meaning and meaning making has developed apace, but empirical research has failed to keep up with these developments, creating a significant gap between the rich but abstract theories and empirical tests of them. Given current empirical findings, some aspects of the meaning-making model appear to be well supported but others are not, and the quality of meaning-making efforts and meanings made may be at least as important as their quantity. This article concludes with specific suggestions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)