bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of dead reckoning‐based location service for mobile ad hoc networks
Authors: Kumar Vijay , Das Samir R. 
Published: March 2004

AbstractA predictive model‐based mobility tracking method, called dead reckoning, is developed for mobile ad hoc networks. It disseminates both location and movement models of mobile nodes in the network so that every node is able to predict or track the movement of every other node with a very low overhead. The basic technique is optimized to use ‘distance effect’, where distant nodes maintain less accurate tracking information to save overheads. The dead reckoning‐based location service mechanism is evaluated against three known location dissemination service protocols: simple, distance routing effect algorithm for mobility (DREAM) and geographic region summary service (GRSS). The evaluation is done with geographic routing as an application. It is observed that dead reckoning significantly outperforms the other protocols in terms of packet delivery fraction. It also maintains low‐control overhead. Its packet delivery performance is only marginally impacted by increasing speed or noise in the mobility model, that affects its predictive ability. Copyright © 2004 John Wiley & Sons, Ltd.
An adaptive hierarchical mobile IPv6 using mobility profile
Authors: Hwang Seung‐Hee , Lee Bo‐Kyung , Han Youn‐Hee , Hwang Chong‐Sun 
Published: March 2004

AbstractThe Hierarchical Mobile IPv6 (HMIPv6), which is based on the Mobile IPv6 (MIPv6), has been proposed by IETF to reduce registration control signaling. It separates micro‐mobility from macro‐mobility with the help of an intermediate mobility agent, called the mobility anchor point (MAP), and exploits a Mobile Node's (MN's) spatial locality. However, all packets from a Correspondent Node (CN) to an MN are delivered through the MAP. That causes delay in packets delivery and the congestion of packets in the MAP so that it results in deterioration of network capability. To alleviate these problems, we propose a Hierarchical Mobile IPv6 protocol using not only spatial locality but also temporal locality. We introduce a profile for management of these locality information. According to the information in the profile, some packets are directly delivered to an MN, if MN seems to reside for a long time in the current subnet. Also, we introduce a handover scheme with the help of an L2 trigger, so that the proposed scheme takes nearly the same handover delay time as HMIPv6. The other contribution of this paper is to suggest a mathematical modeling and analysis of network traffic costs, MAP processing costs and handover latency for both HMIPv6 and the proposed scheme. Copyright © 2004 John Wiley & Sons, Ltd.
Performance evaluation of TCP under dynamic allocation scheme for down‐link transmission rate in W‐CDMA systems
Authors: Fukuda Yutaka , Koga Hiroyuki , Ikenaga Takeshi , Oie Yuji 
Published: March 2004

AbstractIMT‐2000 has attracted much attention as the Next Generation Mobile Communication System. IMT‐2000 can provide high‐bit‐rate data communication service, so that a great number of packets conveyed by TCP (transmission control protocol) can be transmitted over a wireless link. W‐CDMA, standardized in 3GPP (which standardizes IMT‐2000), allows dynamically allocating transmission rates to flow over a wireless link in response to a changing FER for each flow, which is thought to be essential for a next generation mobile communication system. Therefore, in this paper, we study the characteristics of the dynamic allocation scheme when TCP flows share a wireless link, and, in particular, we focus on the throughput performance of these TCP flows. First, we use simulations to examine the effectiveness of the dynamically allocating down‐link transmission rate for TCP flows in response to changing the frame error rate (FER). Through the simulation results, we will show how it can improve the total throughput performance of TCP flows. Furthermore, we can obtain an effective way to allocate transmission rates to flows with different FERs in order to achieve high total throughput. Finally, we will deal with a case of multiple flows from a fixed host to a mobile host. In actual networks, this often happens. In this case, we will show that the total throughput of TCP flows degrades less than in the single‐flow case, even when the FER is high. Copyright © 2004 John Wiley & Sons, Ltd.
Size/geometry optimization of trusses by the force method and genetic algorithm
Authors: Kaveh A. , Kalatjari V. 
Published: March 2004

AbstractIn this article size/geometry optimization of trusses is performed using the force method and genetic algorithm. A large number of design variables consisting of cross‐sectional areas and nodal coordinates are involved in such an optimization, and due to a large number of constraints, the dimensions of the design space are often numerous and in the case of discrete values for cross sections usually discontinuous. In order to avoid local optima, modified genetic algorithms are developed. Furthermore, the force method is employed to improve the speed of the optimization. In the first phase of the described method, the initial geometry of the truss is fixed and near optimum ranges for the cross‐section areas are obtained using the relationships from the force method. In the second phase, the geometry of the structure is altered with the aim of designing lower‐weight structures. Within the Genetic Algorithm a new dynamic penalty function is defined and a modified process of reproduction is presented. A contraction process is also employed for the design space using shorter substrings for the design variables.
Popliteal Aneurysm: Diagnostic Workup and Results of Surgical Treatment
Authors: Harder Yves , Notter Hanspeter , Nussbaumer Peter , Leiser Alfred , Canova Corina , Furrer Markus 
Published: March 2004

AbstractUntreated popliteal aneurysm (PA) may cause serious complications. Early detection and surgery are beneficial. What are the circumstances under which the diagnosis of PA is made? What risks are associated with the treatment? A total of 36 consecutive PAs in 22 men and 2 women were treated in a single‐center series. Altogether, 26 surgical reconstructions (group 1) were performed using a medial approach, and two PAs were resected through a dorsal approach. Eight patients with eight PAs did not undergo surgery (group 2): Two were awaiting surgery, and six had refused it. At the time of diagnosis, 25 PAs were symptomatic: local pain, swelling, or ”pulsation” in the popliteal groove (29%); claudication of the foot/calf (39%); critical ischemia (21%). Eleven asymptomatic cases were discovered during screening duplex sonography of known aortic aneurysms Among the 28 PAs that underwent surgery, 6 produced acute symptoms. The following complications were observed: five postoperative hematomas, one infected polytetrafluoroethylene (PTFE) graft, two early graft occlusions, and two significant stenoses of the distal anastomosis. After a mean follow‐up of 15 months (range 2‐43 months), group 1 had a limb salvage rate of 100% and a secondary patency rate of 96%. Two patients are still awaiting surgery. Critical ischemia represents an absolute indication for surgical repair, but the observed zero mortality and relatively low morbidity associated with the intervention combined with a favorable patency rate justify the liberal use of surgery even for asymptomatic PAs. The extensible medial approach is preferred. Sequential reconstruction is advised for bilateral PAs.
Pathogenesis of Pain in Chronic Pancreatitis: Ongoing Enigma
Authors: Bornman Philippus C. , Marks Israel N. , Girdwood Andrew W. , Berberat Pascal O. , Gulbinas Antanas , Büchler Markus W. 
Published: March 2004

AbstractThe pathogenesis of pain in chronic pancreatitis remains an enigma. The cause of pain is almost certainly multifactorial and may vary at different stages of the disease process. These factors may include the release of excessive oxygen‐derived free radicals, tissue hypoxia and acidosis, inflammatory infiltration with influx of pain transmittent substances into damaged nerve ends, and the development of pancreatic ductal and tissue fluid hypertension due to morphological changes of the pancreas. Investigations into the causes of pain have been limited by changes in the dynamics with the progression of the disease process, limitations in studying functional and morphological changes of the pancreas in the clinical setting, and the psychosomatic profile of patients. Many of these patients are addicted to alcohol, and suffer from personality disorders. The difficulty in quantifying pain, which is at best subjective, further compounds the issue, especially when assessing the efficacy of treatment.
Endoscopic Retrograde Cholangiopancreatography in Chronic Pancreatitis
Authors: Bolan Peter J. , Fink Aaron S. 
Published: March 2004

AbstractEndoscopic retrograde cholangiopancreatography (ERCP) plays an important diagnostic and therapeutic role in the management of chronic pancreatitis. New techniques are being developed which should further improve outcomes of endoscopic intervention. The ultimate role of these therapeutic interventions for chronic pancreatitis awaits prospective randomized data demonstrating their efficacy and safety in comparison to surgery. Until such time, these often difficult techniques should be performed by experienced endoscopists with significant experience in pancreatic disease, ideally within the context of controlled clinical trials.
Pancreatoduodenectomy in the Treatment of Chronic Pancreatitis
Authors: Russell R. Christopher G. , Theis Belinda A. 
Published: March 2004

AbstractThe value of surgical resection for patients with chronic pancreatitis has been debated on account of persistent symptoms and the morbidity of the operative procedure, both immediate and delayed. This paper explores the consequence of pancreatoduodenectomy in 175 patients with chronic pancreatitis who were operated on between 1976 and 1997. All patients were carefully selected after varying periods of conservative management. The operation was a classical Kausch‐Whipple resection in 98 patients and a pylorus‐preserving procedure in 67. There were four postoperative deaths (days 7, 10, 35, and 70), and only two reoperations were performed. The median number of postoperative events was one, with delayed gastric emptying being the most common (31 patients). The median length of in‐hospital stay was 20 days (range: 8–215 days), but no patient was discharged until medical and social disabilities were resolved. There were seven late deaths, most of them linked to cigarette smoking and alcohol consumption; 75% of patients had a good clinical outcome, but 18 patients required further pancreatic surgery at a mean of 12 months, either a pancreatojejunostomy or a completion pancreatectomy. Diabetes occurred in 40% of patients by 5 years, and most, at some stage of their postoperative period, required pancreatic enzyme supplementation. It is suggested that resection of the pancreas provides a reasonable life‐style in 75% of patients, but the outcome depends in large part on the predisposing disease.
Pylorus‐preserving Pancreaticoduodenectomy in the Treatment of Chronic Pancreatitis
Authors: Jimenez Ramon E. , Fernandez‐del Castillo Carlos , Rattner David W. , Warshaw Andrew L. 
Published: March 2004

AbstractThe pylorus‐preserving pancreaticoduodenectomy (PPPD) is an alternative to the standard Whipple resection in the treatment of chronic pancreatitis. The operation is safe and can be performed with a low mortality rate. The most common early complication is delayed gastric emptying, which occurs in 25% to 30% of patients, and generally results in longer hospital stays than the standard Whipple procedure. Follow‐up studies show that both operations are equally effective in relieving pain in approximately 75% of selected patients. In the long term, the PPPD successfully preserves physiologic gastric emptying, but at the cost of a higher marginal ulceration rate. The purported nutritional advantages of the PPPD over the classic Whipple resection have not been clearly established. At present, the PPPD is the procedure of choice for patients with chronic pancreatitis requiring panceraticoduodenectomy. Based on available information, this recommendation appears to arise form the fact that the PPPD is less radical than the regular Whipple procedure, and some surgeons find it technically easier. Our experience fails to show a distinct superiority of the PPPD over the Whipple operation.
Comparison of Local Resection of the Head of the Pancreas Combined with Longitudinal Pancreaticojejunostomy (Frey Procedure) and Duodenum‐Preserving Resection of the Pancreatic Head (Beger Procedure)
Authors: Frey Charles F. , Mayer Kathrin L. 
Published: March 2004

AbstractThe etiology of pain in chronic pancreatitis may be ductal hypertension, increased parenchymal pressure, or neural damage. It is difficult to assess the severity of pain in this patient population, a problem made more challenging by the frequency of narcotic dependency. Therapeutic interventions developed to relieve the pain of chronic pancreatitis include denervation of the pancreas, decompression of the main duct of the pancreas, resection of part or all of the diseased pancreas, and reduction of pancreatic secretion. Operative intervention for patients with chronic pain is indicated when severe pain, complications of pain, or potential malignancy are present. The operations that consistently provide long‐lasting pain relief all have in common resection of all or a portion of the head of the pancreas. Adverse effects on exocrine and endocrine function, nutrition, and quality of life are related to the amount of pancreas resected. The ideal procedure should be easy to perform, have a low morbidity and mortality rate, provide long‐lasting pain relief, and not augment endocrine and exocrine insufficiency. No single operation fulfills this ideal. The local resection of the head of the pancreas combined with longitudinal pancreaticojejunostomy (LR‐LPJ) proposed by Frey and the duodenum‐preserving resection of the head of the pancreas (DPHR) proposed by Beger are discussed. The conceptualization, development, and technique of LR‐LPJ are discussed, and comparisons of patient outcomes are made with the outcomes of other procedures for chronic pancreatitis.
Subtotal Pancreatectomy for Chronic Pancreatitis
Authors: Eckhauser Frederic , Cowles Robert , Colletti Lisa 
Published: March 2004

AbstractChronic pancreatitis results when pancreatic structure or function is irreversibly damaged by repeated or ongoing inflammation, regardless of the underlying etiology. Most patients present with medically intractable pain and radiological evidence of diffuse gland involvement. Surgical therapy is directed mainly toward palliation of symptoms, and cure is unusual except when the inflammatory process is limited to a specific segment of the pancreas. Surgical strategy should be individualized on the basis of alterations in pancreatic morphology and duct anatomy. In properly selected patients, duct drainage procedures effectively relieve pain and preserve pancreatic function with low perioperative morbidity and mortality. Extensive distal pancreatectomy is effective in relieving pain, but it can be technically challenging and in general should be limited to patients with small‐duct disease because of severe metabolic consequences. Intraportal islet cell autotransplantation or segmental pancreatic autotransplantation may ameliorate the long‐term effects of insulin‐dependent diabetes, but it will have limited applicability until methods for optimizing and purifying islets are developed and the optimal route and site of islet cell implantation have been identified.
Pancreatic Autotransplantation in Chronic Pancreatitis
Authors: Watkins J. Guillermo , Krebs Alfred , Rossi Ricardo L. 
Published: March 2004

AbstractThe apancreatic state secondary to resective surgery for chronic pancreatitis is associated with a high rate of late morbidity and mortality that is due, in part, to endocrine insufficiency. Resective procedures should, therefore, be used very selectively. Over the last 2 decades we have seen a shift from extensive distal resections to limited proximal resections. This is because of the lowering of the operative mortality of pancreatic head resection and its better results in pain relief, while preserving in situ the body and tail of the gland with its metabolic functions. Islet autotransplantation and segmental pancreatic autotransplantation were introduced in 1977 and 1978, respectively. Over 150 and 25 cases of these operations have been reported, respectively. Both techniques are evolving with a goal to improve results. Procedures placing the graft in the iliac fossa and anastomosing the pancreatic duct to the jejunum are now favored over groin placement and duct occlusion. Islet autotransplants achieve a higher yield of islet cells and decrease the exocrine impurity of the preparation. Both methods can prevent or delay the onset of diabetes mellitus, and when diabetes mellitus does occur, it is frequently easier to manage. The long‐term function of the grafts appears to be dependent on the β‐cell mass available in the diseased pancreas, the loss of cells related to the transplant procedure, and the characteristics of gradual loss of function from the type of transplant used. Although extensive pancreatic resections are occasionally required, the possibility of autotransplantation should be considered in those patients.
Splenic Vein Thrombosis and Gastrointestinal Bleeding in Chronic Pancreatitis
Authors: Weber Sharon M. , Rikkers Layton F. 
Published: March 2004

AbstractThe most common cause of isolated thrombosis of the splenic vein is chronic pancreatitis caused by perivenous inflammation. Although splenic vein thrombosis (SVT) has been reported in up to 45% of patients with chronic pancreatitis, most patients with SVT remain asymptomatic. In those patients with gastrointestinal bleeding secondary to esophageal or gastric varices, the diagnostic test of choice to assess for the presence of SVT is late‐phase celiac angiography. Splenectomy effectively eliminates the collateral outflow and is the treatment of choice. Other underlying pathology, such as pseudocysts, can be treated at the same time.
Selection of donors and recipients for living donor liver transplantation
Authors: Trotter James F. 
Published: March 2004

Key Points
1. Living donor liver transplantation (LDLT) is increasingly used for adults with end-stage liver disease.
2. Standards for acceptable rates of donor morbidity, and even mortality, must be evaluated in the context of recipient risk of dying while on the waiting list and outcome after transplantation.
3. Use of our current criteria in Colorado for selection of donors and recipients indicated that 15% of recipients could undergo LDLT.
Treatment options for other hepatic malignancies
Authors: O’Grady John G. 
Published: March 2004

Key Points
1. Resection rates for cholangiocarcinoma (unrelated to primary sclerosing cholangitis) have increased to 54% to 79%, and the subsequent 5-year survival rates are 24% to 31%.
2. Multimodality approaches involving various combinations of chemotherapy, irradiation, and surgery increasingly are being used to treat cholangiocarcinoma.
3. The role of liver transplantation in the management of cholangiocarcinoma is limited by the perception that it is inappropriate to use scarce organs when 5-year survival rates are 25%.
4. Liver transplantation is an important intervention in patients with tumors that remain unresectable after chemotherapy. The role of liver transplantation in patients with extrahepatic disease that responds to chemotherapy is controversial. Careful timing of surgery is required to avoid secondary drug resistance.
5. Liver transplantation has been successfully applied to a range of rare hepatic malignancies, but small numbers preclude strong recommendations on the appropriateness of this practice.
Retransplantation for hepatitis C: Implications of different policies
Authors: Rosen Hugo R. 
Published: March 2004

Key Points
1. Approximately 20% of hepatitis C virus (HCV)-positive liver transplant recipients develop evidence of allograft cirrhosis by year 5.
2. The prevalence of HCV infection in patients undergoing retransplantation has significantly increased since 1990.
3. Retransplantation for recurrent HCV is associated with poor long-term survival.
4. Preoperative hyperbilirubinemia (billirubin ≥5 mg/dL) and renal failure predict poor outcome after retransplantation.
5. Retransplantation is the only viable option for patients in whom allografts fail because of recurrent HCV disease.
Living donor liver transplantation in adults: Outcome in Japan
Authors: Todo Satoru , Furukawa Hiroyuki , Jin Maeng Bon , Shimamura Tsuyoshi 
Published: March 2004

Key Points
1. Twenty centers in Japan performed 308 living donor liver transplants (LDLT) in adults.
2. Right lobe grafts were used in the minority of cases (27.1%); most had left lobe grafts (72.9%). Survival was not influenced by the type of graft.
3. There were no donor deaths (0%); 9.3% of donors experienced mild to moderate complications. Biliary complications were the most frequent.
4. Overall recipient survival was 72.4%.
Ethical issues surrounding adult-to-adult living donor liver transplantation
Authors: Shapiro Robyn S. , Adams Mark 
Published: March 2004

Key Points
1. The ethical principle of utility is enhanced by living donor liver transplantation (LDLT). LDLT carries the potential to optimize efficient use of organs, minimize pretransplant morbidity and mortality, and increase availability of cadaveric organs.
2. The most serious ethical concerns in LDLT focus on the risks to the donor and relate to the principle of nonmaleficence—“do no harm”. Although exact risk remains uncertain, there is potential for significant donor morbidity and even mortality.
3. Careful consideration must be given to development of the best approach to obtaining truly informed consent.
4. Specific criteria for LDLT should be developed for transplant centers, donors, and recipients. Informed consent should be standardized.
5. A national registry for donors and recipients of LDLT is needed.
Living donor liver transplantation in adults: Outcome in Europe
Authors: Broelsch Christoph E. , Malagó Massimo , Testa Giuliano , Gamazo Camino Valentin 
Published: March 2004

Key Points
1. Eleven European centers have performed 228 living donor liver transplants (LDLT): 105 in children and 123 in adults.
2. Right lobe donation was used in 111 of 123 adult cases (90%).
3. There was 1 donor death (˜0.8%), and 17.8% of donors experienced significant complications.
4. Eighty-six percent of recipients and 83% of grafts survived. Biliary complications occurred in 14.6%.