Estimating Basic Characteristics of Arrival Processes in Telecommunication Networks by Empirical Data

Considering the realistic teletraffic analysis in advanced telecommunication networks, the estimation of basic characteristics of arrival processes by empirical data is an important subject of current research. Using independent observations of the interarrival times between events and the mean numbers of events in intervals of fixed length, we propose methods to estimate the intensity of a nonhomogeneous arrival stream, particularly a Poisson process, and the renewal function of a renewal process. We formulate the estimation task as stochastically ill-posed problem and apply procedures for the stabilization of the estimates.     

Breast cancer among women exposed to polybrominated biphenyls

We conducted a nested case-control study with 1,925 women enrolled in a polybrominated biphenyl (PBB) registry to examine the association between breast cancer and serum PBBs. Twenty women who developed breast cancer were matched to 290 control subjects on sex, race, and age. Women with serum PBB levels of 2.0-3.0 parts per billion (ppb) [odds ratio (OR) = 3.5; 95% confidence interval (CI) = 0.9-13] or 4.0 ppb or greater (OR = 3.1; 95% CI = 0.8-12) had a higher estimated risk for breast cancer than women with less than 2.0 ppb. The odds ratios were unchanged when available breast cancer risk factors were included in the analysis.     

Statisches und dynamisches Werkzeugverhalten beim Innenrundschleifen mit axial vorgespannten Werkzeugen

Zusammenfassung Die in diesem Beitrag vorgestellten theoretischen Betrachtungen zum statischen und dynamischen Werkzeugverhalten beim Innenrundschleifen langer Bohrungen nach dem ILB-Verfahren haben wichtige Hinweise für das Proze?verhalten ergeben. Durch geeignete Modellbildung kann hiermit der Einflu? unterschiedlicher Werkzeugspezifikationen sowohl auf die statische Nachgiebigkeit der Werkzeuge und damit letztendlich auf den L?ngsformfehler am Bauteil als auch auf das dynamische Verhalten, insbesondere das Auftreten kritischer Resonanzfrequenzen, vorherbestimmt werden. Die analytischen Berechnungen konnten durch praktische Untersuchungen verfiziert werden. Durchgeführte Schleifversuche haben die Eignung des ILB-Verfahrens als Alternative zur konventionellen Innenrundbearbeitung langer Bohrungen in keramischen Bauteilen best?tigt. Zukünftige Untersuchungen am IFW werden sich auch mit dem Innenrundschleifen langer Bohrungen in Bauteilen aus Hartmetall und geh?rtetem Stahl befassen. Dipl.-Ing.W. Buchholz und Dipl.-Ing.U. Wasmann, wissenschafliche Mitarbeiter des IFW.     

Kontinuierliche Reaktionsführung mit löslichen Enzymen

Continuous processes with soluble enzymes. This paper surveys the use of continuously operating enzyme-membrane reactors with enforced flow where the retention of soluble enzymes in the reaction vessel is achieved by means of an ultrafiltration membrane. This technique has been commercialized in the acylase process for the synthesis of L -amino acids on a 200 ton/year level. It is especially useful for the application of multi-enzyme systems with cofactor regeneration. The synthesis of L -tert-leucine from the corresponding α-keto acid has been achieved on a kilogram scale. Coenzymes coupled to water soluble polymers are retained in the membrane-reactor together with the enzymes. Use of suitable conditions prevents loss of enzyme and coenzyme by passage through the membrane or by deactivation. Therefore the costs of enzymes and coenzymes are no longer limitations for economic processes. In the continuously operating enzyme-membrane reactor regeneration of the coenzyme up to 600 000 times was achieved. In continuous peptide synthesis space-time yields of 25 kg/(l d) were obtained. To suppress side reactions very high catalyst concentrations are possible, yielding residence times below 4 min.     

Mechanical, rheological, and thermal behavior assessments in HDPE/PA-6/EVOH ternary blends with variable morphology

Visco-elastic and dielectric spectra of multiwalled carbon-nanotube reinforced silicon elastomer nanocomposites were used to study relaxation behavior. SEM photomicrographs shows well dispersion of MWCNT in elastomer matrix. In visco-elastic analysis primary relaxation was studied as a function of temperature (?100 to 100 °C) at frequency 1Hz and strain 1 %. The effect of MWCNT loadings on storage modulus, loss modulus, and loss tangent has been studied. The non-linearity in loss tangent, storage modulus and loss modulus was explained on the basis of MWCNT-elastomer interaction and the inter-aggregate attraction of MWCNT. The secondary β relaxation was studied using dielectric relaxation spectra in the frequency range of 0.1 Hz to 10⁶ Hz. The effect of MWCNT loadings on the complex and real parts of impedance was distinctly visible which has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium and relaxation dynamics of polymer chains in the vicinity of fillers. The dielectric formalism has been utilized to further investigate the conductivity and relaxation phenomenon. The ‘percolation limit’ of the MWCNT in the silicon elastomer was found to be in the range of 4 phr loading.     

The G-Protein-Coupled Estrogen Receptor (GPER/GPR30) in Ovarian Granulosa Cell Tumors

Ovarian granulosa cell tumors (GCTs) are thought to arise from cells of the ovarian follicle and comprise a rare entity of ovarian masses. We recently identified the G-protein-coupled estrogen receptor (GPER/GPR30) to be present in granulosa cells, to be regulated by gonadotropins in epithelial ovarian cancer and to be differentially expressed throughout folliculogenesis. Thus, supposing a possible role of GPER in GCTs, this study aimed to analyze GPER in GCTs. GPER immunoreactivity in GCTs (n = 26; n (primary diagnosis) = 15, n (recurrence) = 11) was studied and correlated with the main clinicopathological variables. Positive GPER staining was identified in 53.8% (14/26) of GCTs and there was no significant relation of GPER with tumor size or lymph node status. Those cases presenting with strong GPER intensity at primary diagnosis showed a significant reduced overall survival (p = 0.002). Due to the fact that GPER is regulated by estrogens, as well as gonadotropins, GPER may also be affected by endocrine therapies applied to GCT patients. Moreover, with our data supposing GPER to be associated with GCT prognosis, GPER might be considered as a possible confounder when assessing the efficacy of hormone-based therapeutic approaches in GCTs.