Design and implementation of an omni-directional underwater acoustic micro-modem based on a low-power micro-controller unit.

For decades, underwater acoustic communication has been restricted to the point-to-point long distance applications such as deep sea probes and offshore oil fields. For this reason, previous acoustic modems were typically characterized by high data rates and long working ranges at the expense of large size and high power consumption. Recently, as the need for underwater wireless sensor networks (UWSNs) has increased, the research and development of compact and low-power consuming communication devices has become the focus. From the consideration that the requisites of acoustic modems for UWSNs are low power consumption, omni-directional beam pattern, low cost and so on, in this paper, we design and implement an omni-directional underwater acoustic micro-modem satisfying these requirements. In order to execute fast digital domain signal processing and support flexible interfaces with other peripherals, an ARM Cortex-M3 is embedded in the micro-modem. Also, for the realization of small and omni-directional properties, a spherical transducer having a resonant frequency of 70 kHz and a diameter of 34 mm is utilized for the implementation. Physical layer frame format and symbol structure for efficient packet-based underwater communication systems are also investigated. The developed acoustic micro-modem is verified analytically and experimentally in indoor and outdoor environments in terms of functionality and performance. Since the modem satisfies the requirements for use in UWSNs, it could be deployed in a wide range of applications requiring underwater acoustic communication.

The threat of adhesive embolization: BioGlue leaks through needle holes in aortic tissue and prosthetic grafts.

BACKGROUND: BioGlue Surgical Adhesive (CryoLife, Inc, Kennesaw, GA) is used to reinforce anastomoses during cardiovascular operations. Previous reports have raised concerns that adhesives may leak through suture-line needle holes and that resulting intraluminal glue may embolize. The purpose of this study was to determine if BioGlue leaks through anastomotic needle holes in aortic tissue and two common prosthetic graft materials. METHODS: Polypropylene suture was used to create end-to-end anastomoses in gelatin-sealed woven polyester grafts (n = 45), expanded polytetrafluoroethylene (ePTFE) grafts (n = 45), and fresh porcine aortas (n = 45). An additional 45 anastomoses were created in ePTFE grafts using ePTFE sutures. The outer surface of each anastomosis was covered with BioGlue. Anastomoses underwent inspection with direct magnification or histology. RESULTS: BioGlue leaked through needle holes and into the lumen in 10% of anastomoses (18 of 180). Leaks were significantly more common in fresh aorta (10 of 45, 22%) than in prosthetic grafts (8 of 135, 6%; p = 0.003). Suture size did not significantly affect the incidence of leak. The use of ePTFE sutures did not eliminate BioGlue leakage. Prosthetic graft leaks created discreet round adhesive particles. In contrast, aortic tissue leaks resulted in thin, friable flakes of glue extending along the intimal surface. Aortic histology confirmed that BioGlue reached the vessel lumen via the suture channels. CONCLUSIONS: BioGlue leaked through the needle holes in fresh aortic tissue and prosthetic grafts. Intraluminal adhesive particles were easily dislodged, supporting concerns regarding embolization. The potential for adhesive embolization should be a factor when considering the relative risks and benefits of using BioGlue.

Matrix metalloproteinases in ascending aortic aneurysms: bicuspid versus trileaflet aortic valves.

BACKGROUND: Abnormal matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) expression contributes to the development of abdominal aortic aneurysms. Recent data suggest that MMP-2 and MMP-9 may also play a role in thoracic aortic disease. We sought to determine (1) whether ascending aortic aneurysms are associated with increased MMP expression and (2) whether aortic inflammation and MMP expression differ between patients with congenital bicuspid aortic valves (BAVs) and those with trileaflet aortic valves (TAVs). MATERIALS AND METHODS: Samples of ascending aortic aneurysms were obtained from 29 patients; 14 patients had BAVs and 15 had TAVs. Control ascending aorta was obtained from 14 organ donors or heart transplant recipients. Aortic histology and immunohistochemistry were performed to evaluate elastin degradation, inflammatory changes, and MMP-2 and MMP-9 expression. Aortic levels of MMP-2, MMP-9, TIMP-1, and TIMP-2 were measured using ELISA. RESULTS: Aneurysms in the TAV patients exhibited marked inflammation, high CD68 expression, diminished elastin content, increased MMP-9 expression, and normal MMP-2 levels. In contrast, BAV aneurysms were characterized by a relative lack of inflammation, preservation of elastin content, normal MMP-9 levels, and elevated MMP-2 expression. TIMP-1 and TIMP-2 levels were not significantly different among the three groups. CONCLUSIONS: Ascending aortic aneurysms exhibited increased MMP expression. The pattern of MMP expression and the degree of inflammation, however, differed between aneurysms associated with BAVs and those with TAVs. Variations in the molecular mechanisms underlying different types of thoracic aortic aneurysms warrant further investigation.

A case of pyothorax-associated lymphoma simulating empyema necessitatis.

We describe a case of a diabetic man with a 40-year history of chronic tuberculous empyema presented with fever, chest pain and bulging soft tissue of the right chest wall. CT scan revealed a huge chest wall mass showing extensive necrosis with air-bubbles and destruction of the ribs. Decortication and extirpation of the chest wall mass were performed, and histopathologic examination confirmed diffused large cell type non-Hodgkin's lymphoma.

Early result of arteriovenous graft with deep forearm veins as an outflow in hemodialysis patients.

The purpose of this study was to evaluate the result of arteriovenous (A-V) grafting with the deep forearm veins as an outflow system in hemodialysis patients. Between June 1999 and July 2001, 27 A-V grafts consisting of ePTFE and deep forearm veins were constructed in 26 patients. All patients followed up for assessment of all relevant values, and the median follow-up period was 17.3 months. Seven grafts (26%) failed during the follow-up. The patency rates were 93% and 80% at 3 months and 12 months, respectively. No difference in patency rate was found between males and females, or between diabetics and nondiabetics. Graft-related complications, excluding graft thrombosis, occurred in five patients. These included operative wound dehiscence in two cases, a graft infection, a seroma, and a mild hypoperfusion in the hand. We conclude that the early patency rate of A-V graft using the forearm deep veins as an outflow system is very good and that this technique may be a recommended surgical modality for vascular access in patients with exhausted superficial veins.