Casimir Effect for Fermion Condensate in Conical Rings

The fermion condensate (FC) is investigated for a (2+1)-dimensional massive fermionic field confined on a truncated cone with an arbitrary planar angle deficit and threaded by a magnetic flux. Different combinations of the boundary conditions are imposed on the edges of the cone. They include the bag boundary condition as a special case. By using the generalized Abel-Plana-type summation formula for the series over the eigenvalues of the radial quantum number, the edge-induced contributions in the FC are explicitly extracted. The FC is an even periodic function of the magnetic flux with the period equal to the flux quantum. Depending on the boundary conditions, the condensate can be either positive or negative. For a massless field the FC in the boundary-free conical geometry vanishes and the nonzero contributions are purely edge-induced effects. This provides a mechanism for time-reversal symmetry breaking in the absence of magnetic fields. Combining the results for the fields corresponding to two inequivalent irreducible representations of the Clifford algebra, the FC is investigated in the parity and time-reversal symmetric fermionic models and applications are discussed for graphitic cones.

Geometrical remodeling of the mitral and tricuspid annuli in response to exercise training: a 3D echocardiographic study in elite athletes

Intense exercise exposes the heart to significant hemodynamic demands, resulting in adaptive changes in cardiac morphology and function. Nevertheless, the athletic adaptation of the atrioventricular valves remains to be elucidated. Our study aimed to characterize the geometry of mitral (MA) and tricuspid (TA) annuli in elite athletes using 3D echocardiography. Thirty-four athletes presented with functional mitral regurgitation (FMR) were retrospectively identified and compared to 34 athletes without MR, and 34 healthy, sedentary volunteers. 3DE datasets were used to quantify MA and TA geometry and leaflet tenting by dedicated softwares. MA and TA areas, as well as tenting volumes, were higher in athletes compared to controls. MA area was significantly higher in athletes with MR compared to those without (8.2±1.0 vs. 7.2±1.0cm2/m2, p<0.05). Interestingly, athletes with MR also presented with a significantly higher TA area (7.2±1.1 vs. 6.5±1.1cm2/m2, p<0.05). Non-planar angle describing the MA's saddle shape was less obtuse in athletes without MR, whereas the values of athletes with MR were comparable to controls. The exercise-induced relative increases in left ventricular (35±25%) and left atrial (40±29%) volumes were similar; however, the increment in the MA area was disproportionately higher (63±23%, overall p<0.001). The relative increase in TA area (40±23%) was also higher compared to the increment in right ventricular volume (34±25%, p<0.05). Atrioventricular annuli undergo a disproportionate remodeling in response to regular exercise. Athletic adaptation is characterized by both annular enlargement and increased leaflet tenting of both valves. There are differences in MA geometry in athletes presented with versus without FMR.

Transient Flow of a Horizontal Well with Multiple Fracture Wings in Coalbed Methane Reservoirs

Horizontal wells with multi-stage fractures have been widely used to improve coalbed methane (CBM) production from coalbed methane reservoirs. The main focus of this work is to establish a new semi-analytical method in the Laplace domain and investigate the transient pressure behavior in coalbed methane reservoirs. With the new semi-analytical method, flow regimes of a multi-fractured horizontal well in coalbed methane reservoirs were identified. In addition, the sensitivities of fracture conductivity, diffusion model, storability ratio, inter-porosity flow coefficient, adsorption index, fracture spacing, fracture asymmetry, non-planar angle, and wellbore storage were studied. Results indicate that six characteristic flow regimes can be identified for multi-fractured horizontal wells in coalbed methane reservoirs, which are bilinear flow, first linear flow, desorption-diffusion flow, first pseudo-radial flow, second linear flow, and second pseudo-radial flow. Furthermore, the sensitivity analysis shows that the early flow is mainly determined by the fracture conductivity, the asymmetry factor, the non-planar angle, and the wellbore storage; while the desorption-diffusion flow regime is mainly influenced by the diffusion model, the storability ratio, the inter-porosity flow coefficient, the adsorption index, and the fracture spacing. Our work can provide a deep insight into the fluid flow mechanism of multi-fractured horizontal wells in coalbed methane reservoirs.

Electromagnetic Vacuum Densities Induced by a Cosmic String

We investigate the influence of a generalized cosmic string in (D+1)-dimensional spacetime on the local characteristics of the electromagnetic vacuum. Two special cases are considered with flat and locally de Sitter background geometries. The topological contributions in the vacuum expectation values (VEVs) of the squared electric and magnetic fields are explicitly separated. Depending on the number of spatial dimensions and on the planar angle deficit induced by the cosmic string, these contributions can be either negative or positive. In the case of the flat bulk, the VEV of the energy–momentum tensor is evaluated as well. For the locally de Sitter bulk, the influence of the background gravitational field essentially changes the behavior of the vacuum densities at distances from the string larger than the curvature radius of the spacetime.

Crystal structures of (E)-N′-(2-hydroxy-5-methylbenzylidene)isonicotinohydrazide and (E)-N′-(5-fluoro-2-hydroxybenzylidene)isonicotinohydrazide

Two derivatives of the well-known iron chelator, (E)-N′-(2-hydroxybenzylidene)isonicotinohydrazide (SIH), substituted in the 5-position of the 2-hydroxybenzene ring by a methyl and a fluorine groupviz.(E)-N′-(2-hydroxy-5-methylbenzylidene)isonicotinohydrazide, C14H13N3O2, (I), and (E)-N′-(5-fluoro-2-hydroxybenzylidene)isonicotinohydrazide, C13H10FN3O2, (II), have been prepared and characterized by single-crystal X-ray diffraction,1H NMR and mass spectrometry. The molecules of both compounds deviate slightly from planarity [r.m.s. deviations are 0.145 and 0.110 Å for (I) and (II), respectively] and adopt anEconformation with respect to the double bond of the hydrazone bridge. In each molecule, there is an intramolecular O—H...N hydrogen bond forming anS(6) ring motif. The dihedral angles between the mean planes of the isonicotinoyl ring and the cresol ring in (I) or the fluorophenol ring in (II) are 10.49 (6) and 9.43 (6)°, respectively. In the crystals of both compounds, zigzag chains are formedviaN—H...N hydrogen bonds, in the [10-1] direction for (I) and [010] for (II). In (I), the chains are linked by weak C—H...π and π–π stacking interactions [centroid-to-centroid distances = 3.6783 (8) Å; inter-planar angle = 10.94 (5)°], leading to the formation of a three-dimensional supramolecular architecture. In (II), adjacent chains are connected through C—H...O hydrogen bonds to form sheets parallel to (100), which encloseR44(30) ring motifs. The sheets are linked by weak C—H...π and π–π [centroid-to-centroid distance = 3.7147 (8) Å; inter-planar angle = 10.94 (5)°] interactions, forming a three-dimensional supramolecular architecture.

Crystal structure of (E)-2-amino-4-methylsulfanyl-6-oxo-1-{[(thiophen-2-yl)methylidene]amino}-1,6-dihydropyrimidine-5-carbonitrile

The title compound, C11H9N5OS2, a 1-thiophen-2-ylmethyleneaminopyrimidine derivative, displays an essentially planar C—NH2group. The conformation across the N=C bond linking the pyrimidine and thienyl groups isE. The pyrimidine and thienyl ring systems subtend an inter-planar angle of 42.72 (5)°. In the crystal, molecules are linked by N–H...Nnitrileand N–H...O=C hydrogen bonds, forming chains parallel to thebaxis.

Preparation and Crystal Structure of Silver(I) Anthranilate

Silver(I) anthranilate, [Ag2(C7H6NO2)2]n, was isolated as the major constituent in the attempted preparation of the adduct of anthranilic acid (2-aminobenzoic acid) with silver(I) p-toluenesulfonate and its structure has been determined by using single-crystal X-ray diffraction. Crystals of the complex are monoclinic, space group P 21/n, with two dimers in a cell of dimensions a 5·3516(8), b 4·9746(2), c 25·386(5) Å, β 91· 547(8)°. The complex repeating unit comprises a distorted centrosymmetric biscarboxylato(-O,O′)-bridged dimer [Ag−O, 2·223, 2·409(4) Å; Ag---Ag 2·9128(9) Å] but has, in addition, a third bond to an adjacent amine nitrogen [Ag−N, 2·301(5) Å], which extends the structure into a zigzag chain polymer. The stereochemistry about each Ag centre is distorted trigonal planar [angle range, 89·9−142·9(2)°]. Relatively short inter-dimer Ag---Ag separations [2·989(1) Å] are also present.