Thinning and Harvesting Regimesf or Yellow-Poplar

Grade I yellow-popular logos were recently selling for $150/mbf, three times the price for grade 2 logs in North Carolina. A computerized stand development model was used to examine the profitability of thinning and holding yellow poplar stands for increased diameter and grade. Analyses were done over wide ranges in stand age, site quality, and stocking, at 5% and 10% discount rates. At a 5% discount rate, the maximum net present stumpage value was obtained by thinning in most regimes. Lower stand age, higher initial stocking, and higher site indices favored thin-clearcut regimes over regimes with no initial thinning. At a 10% discount rate, thinning was optimal only at initial age 30 on the highest quality sites at the highest initial stocking. All other combinations of variables favored clearcutting immediately or with a 1O -year delay. Thinning options with net values within 50% of maximum were numerous at a 5% discount rate in younger stands but decrease rapidly as initial age increased. Only a few such options were available at the 10% discount rate. South. J. Appl. For. 14(3):101-103

J024 Role du complexe proteique ERM dans la transmission des effets de l’activation de l’echangeur NHE1 en reponse a l’acidification des myocytes cardiaques

Nous avons étudié le rôle du complexe protéique ezrine/radixine/ moésine (ou complexe ERM, relié au cytosquelette) dans la transmission du signal donné par l’augmentation d’activité de l’échangeur Na+/H+, NHE1, en réponse à une acidification intracellulaire. L’étude a été réalisée sur myocytes ventriculaires gauches isolés de coeurs de rats adultes (rats Wistar témoins et rats diabétiques GK). La détection des protéines ERM actives (i.e. phosphorylées) par immuno-marquage a permis de révéler que, dans les conditions basales et en dehors de toute stimulation, ces protéines sont localisées au niveau des disques intercalaires, aussi bien dans les myocytes de rats témoins que de rats GK. L’acidification entraîne une augmentation significative de la phosphorylation des protéines ERM avec remodelage intracellulaire de ces protéines; elles sont alors localisées à proximité des récepteurs de la ryanodine, vraisemblablement au niveau des tubules-T. Ces observations ont été faites aussi bien dans les cardiomyocytes ventriculaires de rats témoins que de rats diabétiques GK, avec un remodelage plus marqué chez ces derniers. Un autre résultat d’importance est l’observation d’une augmentation d’activité de Akt, parallèle à celle du complexe ERM : augmentation avec l’acidification et absence d’augmentation lorsque l’acidification a été induite en présence d’un inhibiteur de NHE1. De plus, l’exploration de deux voies cibles de Akt, la voie mTOR/p70S6K et la voie GSK-3b, a montré que seule la phosphorylation de la GSK-3b est augmentée lors d’une stimulation marquée de l’activité de la voie NHE1/ERM/ Akt. L’ensemble de ce travail, nous a permis de mettre en évidence qu’une activité élevée de l’échangeur NHE1 constitue un signal capable d’enclencher, via le complexe protéique ERM, une cascade d’événements intracellulaires pouvant notamment aboutir, comme montré précédemment1, à une réponse hypertrophique. Ceci nous semble être un résultat fondamental qui met en lumière un rôle important de NHE1, lorsque celui-ci est sollicité de façon excessive (par exemple au cours d’une ischémie chronique), à côté de son rôle reconnu de mécanisme majeur de régulation du pH interne des cellules

An Assessment of Desolvation on Rates of Acetyl Transfer: Insights into Enzyme Catalysis

Enzymes greatly enhance the rate of reactions by a variety of physical organic mechanisms. One of the more contentious of these has been desolvation. To get a quantitative assessment of this contribution, we examined acetyl transfer to oxydianions. This is a model reaction for enzymes in which a high-energy acyl phosphate is formed. The aqueous reaction of phosphate or phosphonates with p-nitrophenyl acetate (pNPA) shows a substantial negative deviation from the Brønsted correlation obtained with monoanionic nucleophiles and from the reactivity of other, larger, oxydianions (molybdate, arsenate and vanadate). This, and other data, suggests a significant contribution of desolvation to the activation energy. To further investigate this we studied the effect of various DMSO (dimethyl sulfoxide)/H_2O mixtures on the reaction of chloromethylphosphonate, and of molybdate, on the reaction with pNPA. Increasing the DMSO concentration from 1% to 90% (v/v) increases the second-order rate constant for each of these reactions by over a factor of 5000. This is over a 1000 times greater than the enhancing effect on the reaction of phenoxides and over 105 times the (inhibiting) effect on the reaction with neutral nucleophiles (imidazole). Extrapolation to pure DMSO yields a rate enhancement of ∼10^5, relative to the reaction in water, for the oxydianions. This enhancement is over 3 orders of magnitude greater than that seen with monoanionic phenoxide nucleophiles. This suggests a significant role for desolvation in the reactions in the enzyme-catalyzed nucleophilic reactions of inorganic phosphate but a modest role in reactions with less highly charged nucleophiles

TMTDyn: A Matlab package for modeling and control of hybrid rigid–continuum robots based on discretized lumped systems and reduced-order models

A reliable, accurate, and yet simple dynamic model is important to analyzing, designing, and controlling hybrid rigid–continuum robots. Such models should be fast, as simple as possible, and user-friendly to be widely accepted by the evergrowing robotics research community. In this study, we introduce two new modeling methods for continuum manipulators: a general reduced-order model (ROM) and a discretized model with absolute states and Euler–Bernoulli beam segments (EBA). In addition, a new formulation is presented for a recently introduced discretized model based on Euler–Bernoulli beam segments and relative states (EBR). We implement these models in a Matlab software package, named TMTDyn, to develop a modeling tool for hybrid rigid–continuum systems. The package features a new high-level language (HLL) text-based interface, a CAD-file import module, automatic formation of the system equation of motion (EOM) for different modeling and control tasks, implementing Matlab C-mex functionality for improved performance, and modules for static and linear modal analysis of a hybrid system. The underlying theory and software package are validated for modeling experimental results for (i) dynamics of a continuum appendage, and (ii) general deformation of a fabric sleeve worn by a rigid link pendulum. A comparison shows higher simulation accuracy (8–14% normalized error) and numerical robustness of the ROM model for a system with a small number of states, and computational efficiency of the EBA model with near real-time performances that makes it suitable for large systems. The challenges and necessary modules to further automate the design and analysis of hybrid systems with a large number of states are briefly discussed

A systematic review and network meta-analysis of randomized controlled trials evaluating the evidence base of melatonin, light exposure, exercise, and complementary and alternative medicine for patients with insomnia disorder

Insomnia is a prevalent disorder and it leads to relevant impairment in health-related quality of life. Recent clinical guidelines pointed out that Cognitive-Behavior Therapy for Insomnia (CBT-I) should be considered as first-line intervention. Nevertheless, many other interventions are commonly used by patients or have been proposed as effective for insomnia. These include melatonin, light exposure, exercise, and complementary and alternative medicine. Evaluation of comparable effectiveness of these interventions with first-line intervention for insomnia is however still lacking. We conducted a systematic review and network meta-analysis on the effects of these interventions. PubMed, PsycInfo, PsycArticles, MEDLINE, and CINAHL were systematically searched and 40 studies were included in the systematic review, while 36 were entered into the meta-analysis. Eight network meta-analyses were conducted. Findings support effectiveness of melatonin in improving sleep-onset difficulties and of meditative movement therapies for self-report sleep efficiency and severity of the insomnia disorder. Some support was observed for exercise, hypnotherapy, and transcranial magnetic resonance, but the number of studies for these interventions is still too small. None of the considered interventions received superior evidence to CBT-I, which should be more widely disseminated in primary care

On the practice of dichotomization of quantitative variables

The authors examine the practice of dichotomization of quantitative measures, wherein relationships among variables are examined after 1 or more variables have been converted to dichotomous variables by splitting the sample at some point on the scale(s) of measurement. A common form of dichotomization is the median split, where the independent variable is split at the median to form high and low groups, which are then compared with respect to their means on the dependent variable. The consequences of dichotomization for measurement and statistical analyses are illustrated and discussed. The use of dichotomization in practice is described, and justifications that are offered for such usage are examined. The authors present the case that dichotomization is rarely defensible and often will yield misleading results

Use of the extreme groups approach: A critical reexamination and new recommendations

Analysis of continuous variables sometimes proceeds by selecting individuals on the basis of extreme scores of a sample distribution and submitting only those extreme scores to further analysis. This sampling method is known as the extreme groups approach (EGA). EGA is often used to achieve greater statistical power in subsequent hypothesis tests. However, there are several largely unrecognized costs associated with EGA that must be considered. The authors illustrate the effects EGA can have on power, standardized effect size, reliability, model specification, and the interpretability of results. Finally, the authors discuss alternative procedures, as well as possible legitimate uses of EGA. The authors urge researchers, editors, reviewers, and consumers to carefully assess the extent to which EGA is an appropriate tool in their own research and in that of others.This work was funded in part by National Institute on Drug Abuse Grant DA16883, awarded to Kristopher J. Preacher

LOFAR observations of the quiet solar corona

The quiet solar corona emits meter-wave thermal bremsstrahlung. Coronal radio emission can only propagate above that radius, $R_\omega$, where the local plasma frequency eqals the observing frequency. The radio interferometer LOw Frequency ARray (LOFAR) observes in its low band (10 -- 90 MHz) solar radio emission originating from the middle and upper corona. We present the first solar aperture synthesis imaging observations in the low band of LOFAR in 12 frequencies each separated by 5 MHz. From each of these radio maps we infer $R_\omega$, and a scale height temperature, $T$. These results can be combined into coronal density and temperature profiles. We derived radial intensity profiles from the radio images. We focus on polar directions with simpler, radial magnetic field structure. Intensity profiles were modeled by ray-tracing simulations, following wave paths through the refractive solar corona, and including free-free emission and absorption. We fitted model profiles to observations with $R_\omega$ and $T$ as fitting parameters. In the low corona, $R_\omega < 1.5$ solar radii, we find high scale height temperatures up to 2.2e6 K, much more than the brightness temperatures usually found there. But if all $R_\omega$ values are combined into a density profile, this profile can be fitted by a hydrostatic model with the same temperature, thereby confirming this with two independent methods. The density profile deviates from the hydrostatic model above 1.5 solar radii, indicating the transition into the solar wind. These results demonstrate what information can be gleaned from solar low-frequency radio images. The scale height temperatures we find are not only higher than brightness temperatures, but also than temperatures derived from coronograph or EUV data. Future observations will provide continuous frequency coverage, eliminating the need for local hydrostatic density models

A review of methods for addressing components of interventions in meta-analysis

Many healthcare interventions are complex, consisting of multiple, possibly interacting, components. Several methodological articles addressing complex interventions in the metaanalytical context have been published. We hereby provide an overview of methods used to evaluate the effects of complex interventions with meta-analytical models. We summarized the methodology, highlighted new developments, and described the benefits, drawbacks, and potential challenges of each identified method. We expect meta-analytical methods focusing on components of several multicomponent interventions to become increasingly popular due to recently developed, easy-to-use, software tools that can be used to conduct the relevant analyses. The different meta-analytical methods are illustrated through two examples comparing psychotherapies for panic disorder. Copyright