Electronic Correlations within Fermionic Lattice Models

We investigate two-site electronic correlations within generalized Hubbard model, which incorporates the conventional Hubbard model (parameters: $t$ (hopping between nearest neighbours), $U$ (Coulomb repulsion (attraction)) supplemented by the intersite Coulomb interactions (parameters: $J^{(1)}$(parallel spins), $J^{(2)}$ (antiparellel spins)) and the hopping of the intrasite Cooper pairs (parameter: $V$). As a first step we find the eigenvalues $E_{\alpha}$ and eigenvectors $|E_{\alpha}>$ of the dimer and we represent each partial Hamiltonian $E_{\alpha} |E_{\alpha} > < E_{\alpha} |$ ($\alpha =1,2,..,16$) in the second quantization with the use of the Hubbard and spin operators. Each dimer energy level possesses its own Hamiltonian describing different two-site interactions which can be active only in the case when the level will be occupied by the electrons. A typical feature is the appearence of two generalized $t-J$ interactions ascribed to two different energy levels which do not vanish even for $$ and their coupling constants are equal to $\pm t$ in this case. The competition between ferromagnetism, antiferromagnetism and superconductivity (intrasite and intersite pairings) is also a typical feature of the model because it persists in the case $U=J^{(1)}=J^{(2)}=V=0$ and $t\neq 0$. The same types of the electronic, competitive interactions are scattered between different energy levels and therefore their thermodynamical activities are dependent on the occupation of these levels. It qualitatively explains the origin of the phase diagram of the model. We consider also a real lattice as a set of interacting dimers to show that the competition between magnetism and superconductivity seems to be universal for fermonic lattice models.Comment: 12 page

Hubbard Hamiltonian in the dimer representation. Large U limit

We formulate the Hubbard model for the simple cubic lattice in the representation of interacting dimers applying the exact solution of the dimer problem. By eliminating from the considerations unoccupied dimer energy levels in the large U limit (it is the only assumption) we analytically derive the Hubbard Hamiltonian for the dimer (analogous to the well-known t-J model), as well as, the Hubbard Hamiltonian for the crystal as a whole by means of the projection technique. Using this approach we can better visualize the complexity of the model, so deeply hidden in its original form. The resulting Hamiltonian is a mixture of many multiple ferromagnetic, antiferromagnetic and more exotic interactions competing one with another. The interplay between different competitive interactions has a decisive influence on the resulting thermodynamic properties of the model, depending on temperature, model parameters and assumed average number of electrons per lattice site. A simplified form of the derived Hamiltonian can be obtained using additionally Taylor expansion with respect to $x=\frac{t}{U}$ (t-hopping integral between nearest neighbours, U-Coulomb repulsion). As an example, we present the expansion including all terms proportional to t and to $\frac{t^2}U$ and we reproduce the exact form of the Hubbard Hamiltonian in the limit $U\to \infty$. The nonperturbative approach, presented in this paper, can, in principle, be applied to clusters of any size, as well as, to another types of model Hamiltonians.Comment: 26 pages, 1 figure, LaTeX; added reference

Extended Hubbard model in the dimer representation.[Cz.] 2 Dimer Hamiltonian in the large U limit

Using the exact decomposition of the sclattice into a set of interacting dimers (each dimer is described by the extended Hubbard Hamiltonian) and exact solution of the dimer problem (preceding paper) we exactly find the form of the extended Hubbard model in the case of a crystal in the large U limit. We apply a new, nonperturbative approach based on the exact projection procedure onto a dimer subspace occupied by electrons in this limit (it is the only assumption). The resulting Hamiltonian is very complicated and contains a variety of multiple magnetic and nonmagnetic interactions deeply hidden in its original form (site representation). We also present a simplified version of the model to better visualize a mixture of different interactions resulting from this approach

Extended Hubbard model in the dimer representation.[Cz.] 1 Dimer Hamiltonian in the large U limit

We consider the extended Hubbard model for the single cubic lattice and rewrite it in the form of interacting dimers, using the exact solution of the dimer problem. We analytically derive the second quantization form of the dimer Hamiltoni an eliminating from the considerations unoccupieddimer energy levels in the large U limit (it is the only assumption ). The resulting dimer Hamiltonian written with the use of the Hubbard operators and spin operators contains three terms, visualizing explicitly competing magnetic interactions (ferromagnetic, antiferromagnetic) as a generalization of the t -J model. The presented, nonperturbative method, can in principle be applied to the cluster of any size (e.g. one central atom and z its nearest neighbours). The use of the projection technique can further be applied in the case of a crystal to obtain the second quantization form of the extended Hubbard model for the sclattice in the large U limit

Histone deacetylases in RA: epigenetics and epiphenomena

Reduced synovial expression of histone deacetylases (HDACs) is proposed to contribute to pathology in rheumatoid arthritis (RA) by enhancing histone-dependent access of transcription factors to promoters of inflammatory genes. In the previous issue of Arthritis Research & Therapy, Kawabata and colleagues provided independent evidence that HDAC activity is increased in the synovium and fibroblast-like synoviocytes (FLSs) of patients with RA and is paralleled by increased HDAC1 expression and synovial tumor necrosis factor-alpha (TNFα) production. Remarkably, stimulation of RA FLSs with TNFα specifically increases HDAC activity and HDAC1 expression, suggesting that changes in synovial HDAC activity and expression may be secondary to local inflammatory status

Rak w kikucie szyjki macicy z mnogimi przerzutami do skóry krocza

Summary Metastases to the skin occur rarely in the cervical carcinoma, even in terminal stage of the disease. The frequency of metastasis is estimated from 0.01% to 2%. The presence of metastasis suggests generalized dissemination of the disease and reflects a rapidly progressive process that appear in the final stage of the disease. Case: We present a case of skin metastases in patients with squamous cell carcinoma of the cervical stump after the previous supracervical hysterectomy for benign disease of the uterus. The extensive skin changes on vulva and perineum occurred after radical trachelectomy and external radiation therapy. Patient received HDR brachytherapy for recurrent lesions, but the effect of treatment was poor and she died of progressive disease. Conclusion: As far as we know this is the first case report of squamous cell carcinoma in the cervical stump metastasizing to skin. Palliative brachytherapy has a limited role in controlling symptoms. Skin metastases indicate an aggressive and progressive process.Streszczenie Rak szyjki macicy niezwykle rzadko daje przerzuty do skóry nawet w wysokich stopniach zaawansowania klinicznego. Przedstawiono przypadek chorej z rakiem płaskonabłonkowym w kikucie szyjki macicy poddanej radykalnemu leczeniu chirurgicznemu i następowej radioterapii. Po upływie 2 miesięcy od zakończenia terapii u pacjentki stwierdzono obecność przerzutów do skóry sromu i krocza. Chorą leczono brachyterapią HDR nie uzyskując zadowalających efektów. Zgodnie z naszą wiedzą jest to pierwszy opis przerzutów raka w kikucie szyjki macicy do skóry. Zastosowanie brachyterapii ma ograniczone zastosowanie w leczeniu przerzutów do skóry. Obecność przerzutów do skóry wskazuje na agresywny i postępujący przebieg raka szyjki macicy

Desing of the algorithm, print and analysis of porous structures with modifiable parameters

The purpose of this paper was to create an algorithm able to creating a porous structure with variable properties, print and analyze them. The basic concepts related to it were introduced and the process of creating an algorithm in Rhinoceros software was described. Having a suitable test group of porous structures, it was shown that it is possible to modify their porosity. In the next step, the structures were presented for printing and its effect. The obtained physical models were examined by microtomography. The resulting cross-sections were processed in ImageJ software. Having cross-sections of the original bone and printed structures, it was possible to compare their porosity and the average diameter of the trabeculae in the structure. With this procedure, it is possible to deduce whether it is possible to print accurate structures that will serve as porous bone implants. The resulting differential porosity comparison was 2.0–7.5 %, while the thickness was about 18–35 %

SPECIES COMPOSITION AND ECOLOGICAL STRUCTURE OF CARABID’S ASSEMBLY IN A FODDER’S MIXTURE FIELD IN NORTH POLAND

It June-September of 2007 the qualitative and quantitative composition of carabids were investigated in annual fodder’s mixture field in vicinity of Bukowina village in Pomeranian province (N Poland, UTM XA83, 17°50’E and 54°25’N). It was trapping 509 specimen belonged to 23 species. The studied carabid assembly had very specific species composition and ecological structure. Was observed 7 dominant species: Calathus fuscipes, Harpalus griseus, Harpalus rufipes, Harpalus calceatus, Poecilus lepidus, Broscus cephalotes and Harpalus froelichii (more than 5% specimen). This assembly is characterized by low species richness, polydomination, high value Shannon and Pielou indexes, and not typical high seasonal activity of “autumn breeders” in first half of June. Possible reasons of such phenomena are soil condition (dry sand soil) and extreme warm winter 2006/2007