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Jun 232012
 

Fabian Bross and Philip Pfaller

Ludwig Maximilian-University, Munich, Germany

Journal of Unsolved Questions, 2, 2, Articles 19-24, 2012 (Received Feb 14th, accepted June 20th 2012, published online June 22nd, 2012)

The goal of this study was to test a weak form of the Sapir-Whorf Hypothesis dealing with one of the biggest unsolved questions in linguistics: Does language affect the way we think? Grammatical systems in the world’s languages differ in many aspects. Unlike English or German many languages group nouns on the basis of noun classifiers. Recently research has adressed the question if these linguistic categories built up by classifier systems influence non-linguistic thought. In this paper we studied Mandarin Chinese and Thai—two languages with classifier systems. Although both are classifier languages they categorize objects in different ways. We tested if these system differences lead to different similarity judgements of objects in a non-linguistic rating task (participants had to rate the similarity of picture pairs). In contrast to previous studies we suprisingly observed no difference in categorization. It seems that the so-called Whorf effect, i. e. that language affects the way we perceive and categorize the world, diminishes rapidly over the time speakers are exposed to a different language system such as, in this case, German.

Read more: The decreasing Whorf-effect: A study in the classifier systems of Mandarin and Thai

Feb 182012
 

Anne Jaekel and Robert B. Sim

MRC Immunochemistry Unit, Department of Biochemistry, University of Oxford, UK

Department of Pharmacology, University of Oxford, UK

Journal of Unsolved Questions, 2, 2, Articles 12-18, 2012 (Received Nov. 21st 2011, accepted Jan. 19th 2012, published online Feb. 18th, 2012)

The lung surfactant collectin proteins SP-A and SP-D have been shown to interact with phagocytic cells, such as macrophages and dendritic cells to facilitate uptake of pathogens and apoptotic cells. However, the mechanism by which the collectins interact with the phagocytes and which surface molecules on the phagocytic cells are involved is not yet clear. In the present study, we demonstrate the interaction of SP-A and SP-D with phagocytic cells including human monocyte-derived macrophages and immature dendritic cells. Results show that both proteins bind in a similar manner to both cell types. A prominent 20-22 kDa doublet band was observed on SDS- PAGE analysis as the major Ca2+ -dependent ligand for SP-A and SP-D on both macrophages and dendritic cells. However, we were unable to identify the proteins involved.

Read more: The human lung surfactant proteins A (SP-A) and D (SP-D) share similar binding mechanisms and common ligands on macrophages and dendritic cells

Dec 282011
 

Sonja Landertshamer, Clemens Schwarzinger
Johannes Kepler University Linz, Austria

Journal of Unsolved Questions, 2, 1, Articles 5-8, 2012 (Received November 8th, accepted December 3rd, published online December 27th 2011)

2,4,6-triamino-1,3,5-triazine (melamine ) was first prepared in 1834 by Liebig. It has already been used for several decades for the production of melamine-formaldehyde resins and has therefore gained industrial importance. Particularly, during the last years new possibilities for the cross-linking of melamine have been developed to replace harmful formaldehyde. The synthesis of epoxy modified melamine derivatives is one possibility for this purpose. 2-Diallylamino-4,6-bis(dimethylamino)-1,3,5-triazine was chosen as difunctional starting material, whereat solubility in organic solvents is enhanced by the use of the N-alkylated product. Epoxidations of the allyl functionalities were carried out using several common epoxidation agents. Partially, conversion took place forming mainly by-products like substituted hydroxyl amines and hydroxy triazine derivatives. Nevertheless, epoxidation of double bonds took place forming different epoxy containing structures, which may be useful starting materials for further conversions.

Read more: On the Oxidation of Allylmelamines

Dec 032011
 

Lorenz Adlung

BioQuant Insitute, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany
Zentrum fuer Molekulare Biologie der Universitaet Heidelberg, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany

Journal of Unsolved Questions, 2, 1, Articles 1-4, 2012 (Received October 17th, accepted November 30th, published December 3rd 2011)

The protein CheB is an integral component of sensory adaptation in the chemotaxis system of Escherichia coli. It catalyzes demethylation of the chemoreceptors thereby opposing the effect of ligands on kinase activity. The kinase enhances the activity of the methylesterase via phosphotransfer, thus creating a negative feedback. Although CheB phosphorylation depends on the receptor state, it is not essential for precise adaptation. Therefore, the feedback mechanism is proposed through modeling to compensate for protein fluctuations in the chemotaxis network.
Swarm plate assays revealed that chemotaxis performance in general was even more robust against deviations of single protein concentrations than predicted. However, phosphorylation deficient mutants of CheB still enabled an appropriate chemotaxis response as compared to wild type CheB. Furthermore, when simulations were recoded to include CheB phosphorylation, there was no effect on swarming. Hence both, measured and calculated swarm efficiencies indicate that CheB phosphorylation does not improve robustness of chemotaxis against perturbations in protein levels.

Dependence of E. coli Chemotaxis on CheB Phosphorylation in Silico and in Vivo

Keywords: Bacteria, Chemotaxis, Feedback, Robustness

Jul 092011
 
Francesco Calcavecchia, Francesco Pederiva, and Thomas D. Kuehne

Institute of Physical Chemistry, Johannes Gutenberg-University Mainz, Staudinger Weg 9, D-55128 Mainz, Germany
Dipartimento di Fisica, University of Trento, via Sommerive 14, I-38050 Povo, Trento, Italy
Lawrence Livermore National Laboratory Livermore, California 94550, USA
Center for Computational Sciences, Johannes Gutenberg-University Mainz, Staudinger Weg 9, D-55128 Mainz, Germany

Journal of Unsolved Questions, 1, 2, Articles 13-18, 2011 (Received June 11th, accepted June 30th, published online July 9th 2011)

We present the Fermionic Shadow Wave Function in the context of variational quantum Monte Carlo for disordered systems. Using the example of liquid 3He it is demonstrated that this allows for very accurate calculations, but due to its sign problem only for small systems. For this reason two novel methods are proposed that in principle solve the associated sign problem, but do not allow for realistic simulations yet.

Read more: On the Fermionic Shadow Wave Function and novel attempts to solve its sign problem

Keywords: Fermionic Shadow Wave Function, Variational Monte Carlo

Dec 282010
 

Leonie Anna Mueck, Johannes Gutenberg-University, Mainz, Germany

Journal of Unsolved Questions, 1, 1, Articles, 7-12, 2011 (Received December 10th, accepted December 27th, published online December 28th 2010)

The discovery of the first neutral compound with chemically bound argon HArF in 2000 was a sensation in noble gas chemistry. If HArF is interpreted as a donor- acceptor complex with H+ as an strong acceptor and F? as a donor fragment the question arises if light noble gases helium, neon and argon could also form donor- acceptor complexes with common Lewis acids and bases like AlF3 and NH3. A covalent interaction between a Lewis acid, a Lewis base and a noble gas could be achieved by spatially dividing the donor and acceptor fragment thus incorporating the donor-acceptor complex into a cage-like structure. Due to the small polarizability of the light noble gases the Lewis acidity and basicity of the employed donor and acceptor must be extremely high for the noble gas to react with the cage. Novel kinds of organic donors and acceptors were designed to fullfill these criteria. These novel donors and acceptors were included in organic cages that fix geometrical conditions to be most favourable for the formation of complexes with noble gases. Among the many considered cage-types were the particularly aesthetic egg-shaped fullerene-type cages and dragon-shaped cages. Despite their beauty and their conceptual originality, they did not meet the requirements of yielding a negative reaction energy with light noble gases but they may be useful for other purposes, e. g. as hosts for hydrogen molecules.

Read more: Egg-shaped Fullerene-Type and Dragon-Type Cages Unsuitable for Forming Donor-Acceptor Complexes with Noble Gases

Supporting information: Donor-Acceptor Complexes with Noble Gases

Keywords: Noble Gases, Donor-Acceptor Complexes, Computational Chemistry

Dec 082010
 

Toru Shiozaki, University of Stuttgart, Germany

Journal of Unsolved Questions, 1, 1, Articles, 1-6 (2011) (Received November 14th, published online December 8th 2010)

Explicitly correlated F12 theories have been developed in the past decades to rectify the slow convergence
of dynamical electron correlation models with basis size, in which additional two-electron integrals over F12 kernels
are required. This article reviews some existing algorithms for these integrals, including the author’s attempt,
and leave an open question: what will be the most efficient algorithm (and who wants to implement it into a tightly
optimized code)?

Read more: Download “Call for another Seward: Optimization of F12 integral evaluation

Keywords: theoretical chemistry, F12 methods, integral evaluation