Recommendations for modeling upper plenum injection system for a pressurized water reactor

The present work examines the unique heat transfer modeling problems associated with analysis of performance of an upper plenum emergency core cooling injection system during a postulated Loss-of-Coolant Accident (LOCA) in a pressurized water reactor. The particular system under study consists of four 4-inch pipes conveying emergency core cooling water from outside the pressure vessel through four spare control and rod mechanism housings and internal pipings, discharging the water directly over the top of the reactor core. Previously, it has been assumed that the water injected into the upper plenum passes through the reactor core to the lower plenum without any heat interaction with the fuel rods during a LOCA. This simplified model neglects the many beneficial and adverse effects that accompany the upper plenum injection. This study is undertaken to examine the following items · heat transfer to the emergency core coolant before reaching the core · flow and heat transfer through the reactor core · reflood heat transfer. The phenomena occurring will be delineated and recommendations made for calculating both conservative and best estimate values. The method of solving these problems will be illustrated in a series of examples given in the appendices.Final report for research project sponsored by Northeast Utilities Service Co

Decompression of cavernous sinus meningioma for preservation and improvement of cranial nerve function

Journal ArticleMeningiomas are the most common tumors affecting the cavernous sinus (CS). Despite advances in microsurgery and radiosurgery, treatment of CS meningiomas remains difficult and controversial. As in cases of other meningiomas, the goal of treatment for CS meningioma is long-term growth control and preservation of neural function. Gross-total resection, the ideal treatment for meningioma, is not always possible to obtain in patients with CS meningiomas with an acceptable level of morbidity. Therefore, microsurgery and radiosurgery have recently been advocated as a combined therapy to achieve good control of tumor growth and favorable functional outcome. The authors describe a technique in which tumor volume can be reduced to a minimal residual amount, while preserving cranial nerve function. This enables the smallest field to be treated radiosurgically. The optic nerve is decompressed, and the tumor mass is reduced to provide at least a 5-mm interpositional distance between the optic nerve and the residual lesion. Direct decompression of the CS, with opening of the lateral and superior sinus walls, and piecemeal removal of the tumor in "safe" locations are performed to facilitate an improvement in cranial nerve function. The authors describe the use of this technique in a series of patients and demonstrate improvement of cranial nerve function in a subset of these patients

Posterior fossa brain tumors and arterial hypertension

ManuscriptHypertension caused by arterial compression of the rostral ventrolateral medulla is well described. Much less information is available on the association between neurogenic hypertension and posterior fossa brain tumors. To date, multiple reports have supported the impression that a small subpopulation of patients with posterior fossa tumors can present with arterial hypertension, and many of those patients achieved significant improvement of their hypertension after tumor resection and medullary decompression. To review the relationship between posterior fossa brain tumors and hypertension, we detail the history, basic science, and clinical reports along with an illustrative case regarding this topic

Resolution of an anterior-inferior cerebellar artery feeding aneurysm with the treatment of a transverse-sigmoid dural arteriovenous fistula

ManuscriptThe authors describe a 27-year old man who developed an unruptured anterior-inferior cerebellar artery feeding aneurysm from a transverse-sigmoid dAVF and its subsequent resolution with the treatment of the dAVF. The patient, with a known history of left transverse and sigmoid sinus thrombosis, presented with pulse-synchronous tinnitus. Angiography revealed an extensive dAVF, with feeders from both the extracranial and intracranial circulations, involving the right transverse sinus, the torcula, and the left transverse/sigmoid sinuses. Multimodal endovascular and open surgical therapy was employed. Prior to a planned second-stage treatment for the left sigmoid sinus component, the dAVF improved significantly, but a small flow-related aneurysm developed on the left AICA feeding the petrous dural region in the interval. Resection of the involved sigmoid sinus resulted in resolution of the aneurysm. This is the first reported case of an unruptured feeding-artery aneurysm in an intracranial dAVF that resolved spontaneously with the treatment of the dAVF. Until more is known about its natural history, the decision on when and whether to treat an unruptured dAVF feedingartery aneurysm must be made on an individual basis

Simple closure following transsphenoidal surgery

Journal ArticleThe most common nonendocrine complication after transsphenoidal surgery is cerebrospinal fluid (CSF) leak. Many neurosurgeons have advocated the routine reconstruction of the floor of the sella turcica using autologous fat, muscle, fascia, and either cartilage or bone after transsphenoidal surgery to prevent postoperative CSF fistulas. However, the use of autologous grafting requires a second incision, prolongs operative time, and adds to the patient's postoperative discomfort. In addition, the presence of sellar packing may interfere with the interpretation of postoperative images. To avoid these disadvantages, the authors suggest that routine sellar reconstruction or closure after transsphenoidal surgery is unnecessary unless an intraoperative CSF leak is encountered. The incidence of postoperative CSF leakage in the patients reported on in this series is no higher than that reported by others, and no other complications such as pneumatocele have been encountered in approximately 2700 patients in whom no intraoperative CSF leak was encountered. The authors conclude that routine closure of the floor of the sella turcica or sphenoid is unnecessary in the absence of intraoperative CSF leak

Radiographic features of tumefactive giant cavernous angiomas

ManuscriptGiant cavernous angiomas (GCAs) are very rare, and imaging features of GCAs can be very different from those of typical cavernous angiomas (CAs), making them a diagnostic challenge. The purpose of the study was to evaluate the radiographic features of GCAs, with an emphasis on the differentiating features from neoplastic lesions. Methods. The neuroradiological findings of 18 patients who harbored a histologically verified GCA (CA of 4 cm or larger) were reviewed retrospectively. The magnetic resonance imaging (MRI) appearance, enhancement pattern, presence of edema or mass effect, size, and location of each lesion was recorded. When available, pertinent clinical information, including age, sex, and mode of presentation, was obtained. Findings. Seizures, neurologic deficits, hemorrhage, and hydrocephalus were the most common presenting symptoms. The lesions were hyperdense and nonenhancing on computed tomography with frequent calcifications. On MRI, the lesions most commonly had a multicystic appearance, representing blood of various ages, and multiple complete hemosiderin rings. GCAs can present in any location with associating edema and mass effect, giving them a tumefactive appearance. No developmental venous anomaly was observed with any lesion. Conclusions. Most GCAs in our series presented as multicystic lesions with complete hemosiderin rings on MRI, giving a "bubbles of blood" appearance. Although this characteristic feature is helpful in the diagnosis of many cases of GCAs, the correct diagnosis in the remaining cases may not be apparent until histopathological evaluation of the specimen is made

Minimally invasive thoracoscopic resection of paraspinal neurogenic tumors: technical case report

Journal ArticleOBJECTIVE: The posterior mediastinum is a common location for benign neurogenic tumors. They are frequently asymptomatic but can present with local compressive or neurological symptoms. METHODS: Thoracoscopy is used increasingly over posterolateral thoracotomy for the removal of these lesions. RESULTS: Complete resection of these tumors through a thoracoscopic approach is possible in most cases, but dumbbell tumors present as special challenges, which require a combined thoracoscopic and open posterior approach. CONCLUSION: In this article, we outline the technique of thoracoscopic resection of paraspinal neurogenic tumors through an operative video and a review of the literature to summarize the surgical outcomes of patients with these lesions

Giant fusiform aneurysm in an adolescent with PHACES syndrome treated with a high-flow external carotid artery-M3 bypass

Journal ArticleThe acronym PHACES describes a rare neurocutaneous syndrome that comprises posterior fossa malformations, facial hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, eye abnormalities, and sternal defects. Facial hemangiomas constitute the hallmark of this disorder. Giant intracranial aneurysms have not been previously reported in the literature as manifestations of PHACES syndrome and can present difficult therapeutic challenges. The authors describe a unique case of a 13-year-old adolescent boy with an incomplete phenotypic expression of PHACES syndrome who harbored diffuse cerebral angiodysplasia and a giant fusiform internal carotid artery (ICA) aneurysm extending from the distal cavernous segment to the supraclinoid segment. The aneurysm was successfully treated with a high-flow saphenous vein graft bypass from the external carotid artery to the distal middle cerebral artery followed by proximal ICA occlusion. This case represents a unique vascular manifestation of PHACES syndrome that required a complex management strategy. The authors review the literature on this rare disorder and emphasize the importance of considering the diagnosis of PHACES syndrome in child with a facial hemangioma

Delay test for diagnosis of power switches

Power switches are used as part of power-gating technique to reduce leakage power of a design. To the best of our knowledge, this is the first work in open-literature to show a systematic diagnosis method for accurately diagnosingpower switches. The proposed diagnosis method utilizes recently proposed DFT solution for efficient testing of power switches in the presence of PVT variation. It divides power switches into segments such that any faulty power switch is detectable thereby achieving high diagnosis accuracy. The proposed diagnosis method has been validated through SPICE simulation using a number of ISCAS benchmarks synthesized with a 90-nm gate library. Simulation results show that when considering the influence of process variation, the worst case loss of accuracy is less than 4.5%; and the worst case loss of accuracy is less than 12% when considering VT (Voltage and Temperature) variations

Carotid artery-sparing repair of a cavernous carotid artery pseudoaneurysm

Journal ArticleCarotid artery (CA) injury after transsphenoidal and endoscopic sinus surgery is a well-recognized but fortunately rare complication.1 It is associated with significant morbidity and mortality rates5 and is more common in cases of repeated surgery, cavernous sinus invasion, prior radiotherapy, and anatomical anomalies of the sphenoid and cavernous sinuses.4 It usually results in CA stenosis, occlusion, or pseudoaneurysm formation followed by serious complications, such as stroke and caroticocavernous fistulas.5 Direct surgical repair is difficult, and treatment may require parent vessel sacrifice and possibly vascular bypass.5 We describe the successful treatment of a cavernous? CA pseudoaneurysm with a novel CA-sparing approach. This 62-year-old woman with recurrent esthesioneuroblastoma underwent endoscopic tumor resection. A CA injury occurred intraoperatively. Hemostasis was rapidly achieved by packing the bleeding site with cottonoid and packing strip gauze within the sphenoid sinus. Postoperative angiography performed immediately after surgery revealed a 2-mm pseudoaneurysm at the anterior genu of the left cavernous internal CA (ICA) with minimal stenosis (Fig. 1 left). Eight days after the initial arterial injury, repeat angiography demonstrated persistence of the aneurysm. To repair the arterial defect and preserve the CA, an endovascular stent was placed across the puncture site to restore its normal caliber and to provide a buttressing surface for surgical repair by graft apposition (Fig. 1 right). Subsequently, with the aid of the operating microscope, a small piece of autologous fascia lata graft was placed directly over the arterial puncture site via a transnasal?transsphenoidal approach and bound using BioGlue (CryoLife, Inc., Kennesaw, GA), a two-component (bovine serum albumin and glutaraldehyde) surgical adhesive that is used as an adjunct to open surgical repair of large vessels, such as the aorta, femoral artery, and CA.2 The fascia lata graft was placed over the puncture site to patch the hole in the arterial wall directly because the pseudoaneurysm remained and was unchanged after stent placement alone, presumably because of the interstices of the stent