The distribution of stars around the Milky Way's black hole III: Comparison with simulations

The distribution of stars around a massive black hole (MBH) has been addressed in stellar dynamics for the last four decades by a number of authors. Because of its proximity, the centre of the Milky Way is the only observational test case where the stellar distribution can be accurately tested. Past observational work indicated that the brightest giants in the Galactic Centre (GC) may show a density deficit around the central black hole, not a cusp-like distribution, while we theoretically expect the presence of a stellar cusp. We here present a solution to this long-standing problem. We performed direct-summation $N-$body simulations of star clusters around massive black holes and compared the results of our simulations with new observational data of the GC's nuclear cluster. We find that after a Hubble time, the distribution of bright stars as well as the diffuse light follow power-law distributions in projection with slopes of $\Gamma \approx 0.3$ in our simulations. This is in excellent agreement with what is seen in star counts and in the distribution of the diffuse stellar light extracted from adaptive-optics (AO) assisted near-infrared observations of the GC. Our simulations also confirm that there exists a missing giant star population within a projected radius of a few arcsec around Sgr A*. Such a depletion of giant stars in the innermost 0.1 pc could be explained by a previously present gaseous disc and collisions, which means that a stellar cusp would also be present at the innermost radii, but in the form of degenerate compact cores.Comment: Accepted for publication, few typos fixe

Interactions in crystals, 88 [1 - 3]. Donor/acceptor complexes of alkylbenzenes, pyrene or perylene and tetrahalogen-p-benzoquinones: structures and properties

The following mixed-stack donor/acceptor complexes {D · · · A }∞ have been crystallized and their structures determined: { 1 ,2,4,5-tetramethylbenzene · · · tetrabromo-p -benzoquinone}∞ , {hexamethylbenzene · · · tetrabromo-p-benzoquinone}∞ , { ( 1 ,2 ,4,5-tetramethyl-benzene)2 · · · tetrachloro -p -benzoquinone}∞ , {pyrene · · · tetrafluoro-p-benzoquinone}∞ , {pyrene · · · tetrabromo-p-benzoquinone}∞ and {perylene · · · tetrabromo-p-benzoquinone}∞ . They exhibit an interesting lattice packing, especially the 2:1 tripeldecker sandwich of tetrachloro-p-benzoquinone, which crystallizes in a herringbone pattern. Their interplanar distances are around 340 pm, i. e. two van der Waals π radii. None of them , however, exhibits in neither the donor nor the acceptor components significant structural changes due to complex formation. Their colours range from orange-red to black in the crystal and to green in H2CCl2 solution. Their long-wavelengths charge transfer absorption maxim a correspond to a lowering in excitation energy of up to 2 eV relative to that of the components. The different charge transfer in the ground and excited states of the donor/acceptor complexes investigated is further discussed referring to data such as cyclovoltammetric reduction potentials as w ell as to results from semiempirical calculations based on the crystal structure data determined and including configuration interaction

Interactions in Crystals, 89 [ 1 - 3]. Donor/Acceptor Complexes of Alkyl and Aminobenzenes, Anthracene or Pyrene and 1,3,5-Cyano/nitro-benzenes: Crystallisation, Structures and Electronic Spectra

The following mixed-stack donor/acceptor complexes {D···A}∞ have been crystallized and their structures determined: {hexamethylbenzene···3,5-dicyano-1-nitrobenzene hexamethylbenzene···3,5-dinitro-1-cyanobenzene}∞, {pyrene···3,5-dinitro-1-cyanobenzene}∞, {anthracene···(3,5-dinitro-1-cyanobenzene)2}∞, {N,N-dimethylanilin···3,5-dinitro- 1-cyanobenzene}∞ and { 1-3-phenylenediamine···3,5-dinitro-1-cyanobenzene}∞. Their lattice packing consists of parallel layers, which contain either donors and acceptors as for hexamethylbenzene and pyrene or composite ones as in the 1:2 complex of anthracene with each one of the acceptors above and below its peripheral rings. The isostructural hexamethylbenzene complexes exhibit almost identical packing coefficients as well as a hexagonal coplanar arrangement of the C6(CH3)6 donors. Weak intermolecular van der Waals interactions are also observed between antiparallel cyano substituents. The interplanar n distances range between 334 and 353 pm, i. e. around 340 pm of two van der Waals n radii. In none of the complexes, however, significant structural changes in either the donor or the acceptor components due to the complex formation are observed. In both the crystals as well as in solution, the donor/acceptor complexes exhibit colours between yellow and red; their long-wavelength charge transfer absorption maxima, therefore, correspond to a lowering in excitation energy of only up to 1 eV relative to that of the components. The different charge transfer in the ground and the CT excited states is also discussed referring to other data such as vertical first ionization energies or interplanar distances {D···A}, as well as to results from semiempirical calculations based on the crystal structure data determined and including approximate configuration interaction

Brain Metastases in Elderly Patients—The Role of Surgery in the Context of Systemic Treatment

In patients with brain metastases (BM), advanced age is considered a negative prognostic factor. To address the potential reasons for that, we assessed 807 patients who had undergone BM resection; 315 patients aged at least 65 years (group A) were compared with 492 younger patients (group B). We analyzed the impact of the pre- and postoperative Karnofsky performance status (KPS), postoperative treatment structure and post-treatment survival. BM resection significantly improved KPS scores in both groups (p = 0.0001). Median survival after BM resection differed significantly between the groups (A: 5.81 vs. B: 8.12 months; p = 0.0015). In both groups, patients who received postoperative systemic treatment showed significantly longer overall survival (p = 0.00001). However, elderly patients less frequently received systemic treatment (p = 0.0001) and the subgroup of elderly patients receiving such therapies had a significantly higher postsurgical KPS score (p = 0.0007). In all patients receiving systemic treatment, age was no longer a negative prognostic factor. Resection of BM improves the functional status of elderly patients, thus enhancing the likeliness to receive systemic treatment, which, in turn, leads to longer overall survival. In the context of such a treatment structure, age alone is no longer a prognostic factor for survival

Hypoxia, Hypoxia-inducible Transcription Factors, and Renal Cancer

CONTEXT Renal cancer is a common urologic malignancy, and therapeutic options for metastatic disease are limited. Most clear cell renal cell carcinomas (ccRCC) are associated with loss of von Hippel-Lindau tumor suppressor (pVHL) function and deregulation of hypoxia pathways. OBJECTIVE This review summarizes recent evidence from genetic and biological studies showing that hypoxia and hypoxia-related pathways play critical roles in the development and progress of renal cancer. EVIDENCE ACQUISITION We used a systematic search for articles using the keywords hypoxia, HIF, renal cancer, and VHL. EVIDENCE SYNTHESIS Identification of the tumor suppressor pVHL has allowed the characterization of important ccRCC-associated pathways. pVHL targets α-subunits of hypoxia-inducible transcription factors (HIF) for proteasomal degradation. The two main HIF-α isoforms have opposing effects on RCC biology, possibly through distinct interactions with additional oncogenes. Furthermore, HIF-1α activity is commonly diminished by chromosomal deletion in ccRCCs, and increased HIF-1 activity reduces tumor burden in xenograft tumor models. Conversely, polymorphisms at the HIF-2α gene locus predispose to the development of ccRCCs, and HIF-2α promotes tumor growth. Genetic studies have revealed a prominent role for chromatin-modifying enzyme genes in ccRCC, and these may further modulate specific aspects of the HIF response. This suggests that, rather than global activation of HIF, specific components of the response are important in promoting kidney cancer. Some of these processes are already targets for current therapeutic strategies, and further dissection of this pathway might yield novel methods of treating RCC. CONCLUSIONS In contrast to many tumor types, HIF-1α and HIF-2α have opposing effects in ccRCC biology, with HIF-1α acting as a tumor suppressor and HIF-2α acting as an oncogene. The overall effect of VHL inactivation will depend on fine-tuning of the HIF response. PATIENT SUMMARY High levels of hypoxia-inducible transcription factors (HIF) are particularly important in the clear cell type of kidney cancer, in which they are no longer properly regulated by the von Hippel-Lindau protein. The two HIF-α proteins have opposing effects on tumor evolution