Mean residence time of gas in mechanically agitated gas–liquid contactors

In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature.     

Experimental estimate of self-irradiation of building bricks due to incorporated radionuclides

A method is described for experimentally determining the dose rate created in building bricks by incorporated natural radionuclides. It was established using the thermoluminescence dosimetry method that the measured dose rate depends on the detector thickness, the mass of the ceramic product investigated, and the irradiation geometry. The contributions to the measured dose of weakly penetrating α and β radiation and hard ψ radiation are separated, the ratio between them depending on the experimental conditions. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 62–66, July, 1996.     

The structure and management of service level agreements innetworks

The paper proposes a structure for quality-of-service (QoS)-centered service level agreements (SLA), and a framework for their real-time management in multiservice packet networks. The SLA is structured to be fair to both parties, the service provider and their customer. The SLA considered here are for QoS assured delivery of aggregate bandwidth from ingress to egress nodes; however, the control and signaling is for the more granular flows or calls. A SLA monitoring scheme is presented in which revenue is generated by the admission of flows into the network, and penalty incurred when flows are lost in periods when the service provider is not SLA compliant. In the SLA management scheme proposed, the results of a prior off-line design are used, in conjunction with measurements taken locally at ingress nodes, to classify the loading status of routes. The routing and resource management are based on virtual partitioning and its supporting mechanism of bandwidth protection. The effectiveness of SLA management is measured by the robustness in performance in the presence of substantial diversity in actual traffic conditions. A simulation testbed called D'ARTAGNAN has been built from which we report numerical results for a case study. The results show that the SLA management scheme is robust, fair and efficient over a broad range of traffic conditions     

Prevalence of adrenal carcinoma among incidentally discovered adrenal masses. A retrospective study from 1989 to 1994. Gruppo Piemontese Incidentalomi Surrenalici

BACKGROUND: The incidental discovery of an adrenal mass poses the problem of distinguishing between the frequent benign masses and the infrequent malignant ones that require surgery. Univocal guidelines to approach this problem are unavailable. OBJECTIVE: To perform a survey of the clinical management of incidentally discovered adrenal masses (ie, adrenal incidentalomas). DESIGN: A multicentric retrospective analysis of hospital medical records of adrenal incidentalomas diagnosed during a 5-year period; the medical records were scrutinized for demographic data and clinical details by means of a specifically tailored questionnaire. SETTING: The major surgical and medical centers of Piedmont, a northern Italian region with approximately 4 million inhabitants. The recruitment pattern of these centers was unselected. PATIENTS: The definition of adrenal incidentaloma was limited to patients with a physical examination and a clinical history unindicative of adrenal disease. Exclusion criteria also included hypertension of suspected endocrine origin and a history of neoplasms known to metastasize frequently in the adrenal glands. Two hundred twenty-four medical records were collected, and 210 were analyzed (14 excluded a posteriori). RESULTS: Most patients were in their 50s and 60s, and women were predominantly affected. The frequency of adrenocortical cancer was 13% among patients operated on. The tumor diameter was highly correlated with the risk of cancer; a cutoff at 5 cm had a sensitivity of 93% with a specificity of 64% in discriminating between benign and malignant cortical lesions. CONCLUSIONS: The occurrence of adrenocortical carcinoma among adrenal incidentalomas is not rare. The evaluation of the mass size is a simple and effective method for selecting patients at risk for cancer. The indication for surgery of masses larger than 5 cm, or of masses of any diameter that have suspicious imaging characteristics, limits unnecessary operations and costs.     

Asymmetric dilation of multiwavelength cross-connect switches forlow-crosstalk WDM optical networks

We predict that, for wavelength division multiplexing optical-network applications, an asymmetrically dilated configuration of a 2×2 cross-connect is significantly better in terms of overall crosstalk when the levels of the bar-port crosstalk and the cross-port crosstalk are significantly different from each other, as is the case with optical-frequency filters which utilize grating-assisted coupling. As a verification, we present a simulation study with 2×2 polarization-diversified acousto-optic tunable filters. We present a recursive method to extend the principle of asymmetric dilation to larger-size cross-connect switches, and make a recommendation for an asymmetrically dilated 4×4 cross-connect configuration