Nonperturbative Instability of AdS_5 x S^5/Z_k

We study the AdS/CFT correspondence with boundary conditions AdS_5 x S^5/Z_k, where the Z_k acts freely but breaks all supersymmetry. While there are closed string tachyons at small 't Hooft coupling, there are no tachyons at large coupling. Nevertheless, we show that there is a nonperturbative instability directly analogous to the decay of the Kaluza-Klein vacuum. We discuss the implications of this instability for the strongly coupled dual field theory, and compare with earlier studies of this theory at weak coupling.Comment: 20 pages, 1 figure, v2: minor changes and references adde

Constructing wilderness: the nexus of preservation and ocean-space in the United States

The ocean has long played a minor role in human geography; imagining it as natural space rather than an extractive space even less significant. This dissertation explores the most revered kind of American nature preservation: wilderness. Despite the millions of acres set aside as wilderness in the United States, no such designation exists for ocean-space as a discrete entity. Through the analysis of congressional hearings, bills, resolutions, public laws, and maps, this dissertation uncovers the complex constructs of the production of legal wilderness. Furthermore, it uncovers a novel vein of inquiry, that of the ocean as a preserved natural space. Looking to the Wilderness Act of 1964 and the Marine Protection, Research, and Sanctuaries Act of 1972, this research establishes how the former fails to construct ocean wilderness and how the latter does much the same. Despite the ocean’s prominent place as the largest earth covering, the largest wilderness, and one of the most economically viable spaces on the planet, we systematically fall short in its preservation. With the limited exception of the 2006 advent of the Marine National Monument, most spaces are protected in varying degrees of conservation (resource extractive) rather than preservation (protection for inherent value). Furthermore, human geography has largely and paradoxically overlooked the spatial qualities of ocean-space; often looking only to its fringes (the littoral) and its surface-space as viable social domains. This dissertation proposes an additional layer of spatial construction, where volume and water column are as integral to the concept of the ocean as littoral and surface spaces; and, where the ocean is its own standalone, singular feature, rather than an appendage to adjoining lands

Percutaneous Treatment of Malignant Jaundice Due to Extrahepatic Cholangiocarcinoma: Covered Viabil Stent Versus Uncovered Wallstents

To compare clinical effectiveness of Viabil-covered stents versus uncovered metallic Wallstents, for palliation of malignant jaundice due to extrahepatic cholangiocarcinoma, 60 patients were enrolled in a prospective and randomized study. In half of the patients a bare Wallstent was used, and in the other half a Viabil biliary stent. Patients were followed up until death. Primary patency, survival, complication rates, and mean cost were calculated in both groups. Stent dysfunction occurred in 9 (30%) patients in the bare stent group after a mean period of 133.1 days and in 4 (13.3%) patients in the covered stent group after a mean of 179.5 days. The incidence of stent dysfunction was significantly lower in the covered stent group (P = 0.046). Tumor ingrowth occurred exclusively in the bare stent group (P = 0.007). Median survival was 180.5 days for the Wallstent and 243.5 days for the Viabil group (P = 0.039). Complications and mean cost were similar in the two groups. Viabil stent-grafts proved to be significantly superior to Wallstents for the palliation of malignant jaundice due to extrahepatic cholangiocarcinoma, with comparable cost and complication rates. Appropriate patient selection should be performed prior to stent placement

Endovascular management of massive post-partum haemorrhage in abnormal placental implantation deliveries

Objectives: To retrospectively evaluate safety and efficacy of pelvic artery embolisation (PAE) in post-partum haemorrhage (PPH) in abnormal placental implantation (API) deliveries. Methods: From January 2009 to November 2013, 12 patients with API and intractable intraoperative PPH underwent PAE after caesarean delivery to control a haemorrhage (in four of these cases after hysterectomy). Arterial access was obtained prior to the delivery; PAE was performed in the obstetrics operating room by an interventional radiologist that was present with an interventional radiology (IR) team during the delivery. Results: PAE was successful in preventing bleeding and avoid hysterectomy in four cases (group A). Uterine atony and disseminated intravascular coagulation caused failure of PAE requiring hysterectomy in four patients (group B). PAE prevented bleeding post-hysterectomy in the remaining four cases (group C). Technical success (cessation of contrast extravasation on angiography or occlusion of the selected artery) was 100 %. Maternal and foetal mortality and morbidity were 0 %. Conclusions: PAE is a minimal invasive technique that may help to prevent hysterectomy and control PPH in API pregnancies without complications. Embolisation should be performed on an emergency basis. For such cases, an IR team on standby in the obstetrics theatre may be useful to prevent hysterectomy, blood loss and limit morbidity. Key Points: • Endovascular treatment is a validated technique in post-partum haemorrhage. • Abnormal placental implantation is a risk factor for post-partum haemorrhage. • We propose an interventional radiologist standby in the delivery room. © 2015, European Society of Radiology

Management of malignant biliary obstruction: Technical and clinical results using an expanded polytetrafluoroethylene fluorinated ethylene propylene (ePTFE/FEP)-covered metallic stent after 6-year experience

To evaluate the efficacy and safety of an expanded polytetrafluoroethylene- fluorinated ethylene-propylene (ePTFE/FEP)-covered metallic stent in the management of malignant biliary obstruction. Eighty consecutive patients with malignant common bile duct strictures were treated by placement of 83 covered metallic stents. The stent-graft consists of an inner ePTFE/FEP lining and an outer supporting structure of nitinol wire. Clinical evaluation, assessment of serum bilirubin and liver enzyme levels were analyzed before biliary drainage, before stent-graft placement and during the follow-up period at 1, 3, 6, 9 and 12 months. Technical success was obtained in all cases. After a mean follow-up of 6.9±4.63 months, the 30-day mortality rate was 14.2%. Survival rates were 40% and 20.2% at 6 and 12 months, respectively. Stent-graft patency rates were 95.5%, 92.6% and 85.7% at 3, 6 and 12 months, respectively. Complications occurred in five patients (6.4%); among these, acute cholecystitis was observed in three patients (3.8%). A stent-graft occlusion rate of 9% was observed. The percentage of patients undergoing lifetime palliation (91%) and the midterm patency rate suggest that placement of this ePTFE/FEP-covered stent-graft is safe and highly effective in achieving biliary drainage in patients with malignant strictures of the common bile duct. © 2008 European Society of Radiology

Inflammatory markers as prognostic factors of survival in patients affected by hepatocellular carcinoma undergoing transarterial chemoembolization

Transarterial chemoembolization (TACE) is a good choice for hepatocellular carcinoma (HCC) treatment when surgery and liver transplantation are not feasible. Few studies reported the value of prognostic factors influencing survival after chemoembolization. In this study, we evaluated whether preoperative inflammatory factors such as neutrophil to lymphocyte ratio and platelet to lymphocyte ratio affected our patient survival when affected by hepatocellular carcinoma. Methods. We retrospectively evaluated a total of 72 patients with hepatocellular carcinoma that underwent TACE. We enrolled patients with different etiopathogeneses of hepatitis and histologically proven HCC not suitable for surgery. The overall study population was dichotomized in two groups according to the median NLR value and was analyzed also according to other prognostic factors. Results. The global median overall survival (OS) was 28 months. The OS in patients with high NLR was statistically significantly shorter than that in patients with low NLR. The following pretreatment variables were significantly associated with the OS in univariate analyses: age, Child-Pugh score, BCLC stage, INR, and NLR. Pretreated high NLR was an independently unfavorable factor for OS. Conclusion. NLR could be considered a good prognostic factor of survival useful to stratify patients that could benefit from TACE treatment

Euclidean Wormholes in String Theory

We show that toroidal compactification of type II string theory to six dimensions admits axionic euclidean wormhole solutions. These wormholes can be inserted into $AdS_3 \times S^3 \times T^4$ backgrounds, which have a well-defined CFT dual. AdS/CFT duality then suggests that the wormhole solutions cannot be interpreted using $\alpha$ parameters as originally suggested by Coleman.Comment: 18 pages. ver. 2: typos corrected, references adde

Techniques and future perspectives for the prevention and treatment of endoleaks after endovascular repair of abdominal aortic aneurysms.

The presence of endoleaks remains one of the main drawbacks of endovascular repair of abdominal aortic aneurysms leading to the increase of the size of the aneurysmal sac and in most of the cases to repeated interventions. A variety of devices and percutaneous techniques have been developed so far to prevent and treat this phenomenon, including sealing of the aneurysmal sac, endovascular embolisation, and direct sac puncture. The aim of this review is to analyse the indications, the effectiveness, and the future perspectives for the prevention and treatment of endoleaks after endovascular repair of abdominal aortic aneurysms

Endovascular management of giant visceral artery aneurysms

Endovascular management of small visceral artery aneurysms is an established treatment with satisfactory outcomes. However, when size exceeds 5 cm visceral aneurysms are considered as “giant” (giant visceral artery aneurysms or GVAAs) and management is significantly more complex. Between August 2007 and June 2019 eleven cases of GVAAs that were endovascularly treated were retrospectively reviewed and included in this single center study. Mean size was 80 mm (± 26.3 mm) x 46 mm (+ -11.8 mm). Nine of the lesions were true aneurysms, and two were pseudoaneurysms. In 8 patients, the lesion was causing compression symptoms in the surrounding organs, one patient developed a contained rupture while 2 patients were completely asymptomatic. However, all patients were hemodynamically stable at the time of treatment. Technical success was defined as immediate complete exclusion of the aneurysmal sac, and clinical success as complete relief from clinical symptoms. Follow-up was performed with CT angiography, ultrasound and clinical examination. Mean follow-up was 45 months (range 6–84). Technical and clinical success were both 91%. Complications were one lack of control of contained rupture that was subsequently operated, one case of self-limiting non-target spleen embolization and one case of splenic abscess. Three patients died, one due to the contained rupture 15 days after procedure, the other two for other causes and occurred during the long-term follow-up. This series suggests that endovascular treatment of giant visceral artery aneurysms and pseudoaneuryms is a valid minimally invasive solution with very satisfactory immediate and long-term outcomes unless the aneurysm is already ruptured. A variety of endovascular tools may be required for successful treatment