The developmental relations between conceptual and procedural knowledge: A multimethod approach.

Interactions between conceptual and procedural knowledge influence the development of mathematical competencies. However, after decades of research, these interrelations are still under debate, and empirical results are inconclusive. The authors point out a source of these problems. Different kinds of knowledge and competencies only show up intertwined in behavior, making it hard to measure them validly and independently of each other. A multimethod approach was used to investigate the extent of these problems. A total of 289 fifth and sixth graders’ conceptual and procedural knowledge about decimal fractions was measured by 4 common hypothetical measures of each kind of knowledge. Study 1 tested whether treatments affected the 2 groups of measures in consistent ways. Study 2 assessed, across 3 measurement points, whether conceptual and procedural knowledge could be modeled as latent factors underlying the measures. The results reveal substantial problems with the validities of the measures, which might have been present but gone undetected in previous studies. A solution to these problems is essential for theoretical and practical progress in the field. The potential of the multimethod approach for this enterprise is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Corrosion of platinum electrodes in phosphate buffered saline solution

A high sensitive detection method allows the direct determination of Pt²⁺/Pt⁴⁺ within a concentration range of ng/1 (ppt). The procedure was used to establish the development of soluble platinum species during constant or dynamic polarisation of platinum electrodes in phosphate buffered saline solution. Platinum showed some properties of a passive metal. In the passivated state the dissolution was influenced by a surface film. Furthermore a soluble platinum species was found to be produced during the reduction of the surface oxide. These results confirmed by direct evidence the conclusions of earlier investigations concerning the corrosion of platinum based on electrochemical measurements.     

Fecal Microbiota Transplantation Derived from Alzheimer’s Disease Mice Worsens Brain Trauma Outcomes in Wild-Type Controls

Traumatic brain injury (TBI) causes neuroinflammation and neurodegeneration, both of which increase the risk and accelerate the progression of Alzheimer’s disease (AD). The gut microbiome is an essential modulator of the immune system, impacting the brain. AD has been related with reduced diversity and alterations in the community composition of the gut microbiota. This study aimed to determine whether the gut microbiota from AD mice exacerbates neurological deficits after TBI in control mice. We prepared fecal microbiota transplants from 18 to 24 month old 3×Tg-AD (FMT-AD) and from healthy control (FMT-young) mice. FMTs were administered orally to young control C57BL/6 (wild-type, WT) mice after they underwent controlled cortical impact (CCI) injury, as a model of TBI. Then, we characterized the microbiota composition of the fecal samples by full-length 16S rRNA gene sequencing analysis. We collected the blood, brain, and gut tissues for protein and immunohistochemical analysis. Our results showed that FMT-AD administration stimulates a higher relative abundance of the genus Muribaculum and a decrease in Lactobacillus johnsonii compared to FMT-young in WT mice. Furthermore, WT mice exhibited larger lesion, increased activated microglia/macrophages, and reduced motor recovery after FMT-AD compared to FMT-young one day after TBI. In summary, we observed gut microbiota from AD mice to have a detrimental effect and aggravate the neuroinflammatory response and neurological outcomes after TBI in young WT mice.     

The effects of low frequency load cycles on crack initiation in low alloy steels

The stress corrosion behaviour of low alloy steels was investigated with low frequency cyclic loading in 2 M (NH₄)₂CO₃ at 70°C. The tests were carried out using triangular and sawtooth load cycles with a constant critical strain-rate prevailing within periods of increasing stress irrespective of frequency. Since frequency changes with stress amplitude when using equal ?-values, the effects of frequency were also determined. The experiments were concentrated on crack initiation and initial crack propagation. The results show that the threshold stress which causes stress corrosion cracking (SCC) in ammonium carbonate solution is considerably reduced for all steels tested during low-frequency load cycles. In contrast to tests with constant load, propagating stress corrosion cracks can be initiated below the lower yield strength. The effects of stress/strain amplitude and of the magnitude of deformation on crack propagation were determined.     

Zur Wissenschaftsgeschichte der aDNA-Forschung

aDNA studies are a cooperative field of research with a broad range of applications including evolutionary biology, genetics, anthropology and archaeology. Scientists are using ancient molecules as source material for historical questions. Colleagues from the humanities are observing this with both interest and concern because aDNA research is affecting academic identities and both concepts of history and historiography. aDNA research developed in a way that can be described as a Hype Cycle (Chackie Fenn). Technological triggers such as Sanger Sequencing and the Polymerase Chain Reaction kicked off a multitude of experiments with ancient DNA during the 1980s and 1990s. Geneticists, microbiologists, anthropologists and many more euphorically joined a “molecule hunt”. aDNA was promoted as a time machine. Media attention was enormous. As experiments and implementations began to fail and contamination was discovered to be a tremendous problem, media interest waned and many labs lost their interest. Some turned their disillusionment into systematic research into methodology and painstakingly established lab routines. The authenticity problem was first addressed by control oriented measures but later approached from a more cognitive theoretical perspective as the pitfalls and limits of aDNA became clearer. By the end of the 2000s the field reached its current plateau of productivity. Cross-disciplinary debates, conflicts and collaborations are increasing critical reflection among all participants. Historians should consider joining the field in a kind of critical friendship to both make the most of its possibilities and give an input from a constructivist perspective.     

Possibility of detection of crack initiation in high temperature water

The initiation of stress corrosion cracks in sensitised austenitic stainless steel under high temperature water conditions (simulated boiling water reactor environment) was detected, applying electrochemical noise measurement technique. The stress corrosion cracks were generated on pre-oxidised, unnotched standard tensile round bar specimens under constant load conditions. The elementary transients associated with stress corrosion crack initiation were found to be embedded in the basic noise pattern coming from the oxide growth reaction on the tensile specimen. Thus a simple calculation of standard deviations to identify localised corrosion phenomena under high temperature water conditions cannot be used. The changes in the track of power density spectra proved to be much more suitable to indicate stress corrosion crack initiation under high temperature water conditions.     

Stand der Erkenntnisse auf dem Gebiet der klassischen Spannungsrißkorrosion

State of knowledge in the field of classical stress corrosion cracking A summary is given of the most important results obtained using classical test methods to determine the susceptibility and resistance of unalloyed and low-alloy steels, austenitic chromium-nickel steels and certain aluminum and titanium materials to stress corrosion cracking. Particular attention is paid to the existence of the limit of critical potentials and limit of critical stresses or K_ISCC values. The results presented in this paper are intended to indicate stress corrosion properties which are common to the various metals and alloy systems. The paper concludes with a discussion of the major influential factors and the causes and requirements surrounding stress corrosion cracking and its initiation, the main issues discussed being the mechanical effects and their influence on the stress corrosion process.     

In search of the benefits of learning Latin.

The authors studied whether Latin or French as a foreign curricular language is a better preparation for learning Spanish. Fifty native German speakers who took a university Spanish course concluded their course with a translation test. English was the 1st foreign language for all students, whereas half of them had learned French and the other half had learned Latin as their 2nd foreign language at school. Participants who had learned French at school made markedly fewer grammar errors and slightly fewer vocabulary errors in the Spanish test than participants who had learned Latin. Knowledge of Latin is probably not an optimal preparation for modern language learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spannungsrißkorrosion Mo-freier und Mo-haltiger Stähle in Calciumnitrat-Lösung und Natronlauge unter zeitlich konstanter Kraft und unter CERT-Bedingungen

Stress corrosion cracking of Mo-free and Mo-bearing steels in solutions of calcium nitrate and sodium hydroxide under constant load and under CERT conditions The threshold stress a which was obtained for a low-alloy steel (0.08% C, 0.01% Mo) under free corrosion conditions and chemi- cal conditions corresponding to DIN 50915 in boiling 60% Ca(NO₃)₂ solution in constant load SCC experiments was con- firmed by electrochemically controlled experiments (potential range 0 to 0.90 V). The susceptibility to SCC is increased with the potential becoming more anodic. However, the result of the corrosion test according to DIN 50 915 is valid also at more anodic potentials, i.e. under more severe corrosion stresses. For the determination of threshold stresses by constant load SCC experiments, the criterion “life time > 1000 hrs” is reliable and should be generally preferred to the criterion “crack length 1 = 0”. In boiling 60Y0 Ca(NO₃)₂ solution, also such steels are suscep- tible to SCC under CERTconditions which, under constant load conditions (σ = const.) are resistant. The mode of mechanical loading highly influences the SCC response. Critical potential ranges of SCC were evaluated by CERT experiments. The steel composition (Mo content) has no effect on the cathodic limiting potentials (EH=0 V), but on the extension of these ranges to the anodic side. Under CERT conditions, the favourable influence of molybde- num on the resistance against SCC is not noticed in boiling 60% Ca(NO₃)₂ solution but under less severe corrosion stresses (55% Ca(NO₃)₂ solution, 75 °C). With the given stress-induced SCC system “teel/Ca(NO₃)₂ solution”, threshold stresses could not be evaluated by interrupted CERT experiments, a method which otherwise was successfully used with strain-induced SCC systems. The critical potential ranges of SCC are in the transpassive ranges of the corrosion rate vs. potential curves obtained with unloaded specimens. Critical potential ranges of susceptibility to SCC were evaluated by CERTexperiments also in boiling 35% NaOH. The potential of highest susceptibility to SCC is always found between Ea = -0.80 and -0.70 V and is not affected by influencing factors of the medium (concentration, temperature), and by the steel composi- tion (Mo content).The unfavourable effect of Mo on the resistance to SCC in NaOH is reflected by the extensionof the potential range of increased susceptibility to SCC to more anodic potentials. The critical potential ranges of SCC are in the transition range from the active to the passive state of the corrosion rate vs. potential curves. The potentials of the highest susceptibility to SCC are identical with the minima of the corrosion rate vs. potential curves which occur after passing the potential range of active corrosion. The anodic metal dissolution at the crack tip which is obviously essential for the SCC system “steel/Ca(NO₃)₂ solution” is of minor importance for the system “steeVNaOH solution”. The results of metallographic investigations of the tested SCC specimens are presented. In distinct potential ranges, the Bainite phase (calcium nitrate solution), and the Bainite or Perlite phase (sodium hydroxide solution) are preferentially dissolved. These corrosion phenomena are stress induced, and are not observed with specimens free from external stresses.