bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrahepatic cytokine profiles associated with posttransplantation hepatitis C virus-related liver injury
Authors: Zekry Amany , Bishop Alex G. , Bowen David G. , Gleeson Margaret M. , Guney Seven , Painter Dorothy M. , McCaughan Geoffrey W.
Published: August 2002

Recurrent chronic hepatitis, cholestatic hepatitis, and acute rejection in conjunction with hepatitis C virus (HCV) recurrence are well-recognized clinical sequelae of reinfection of the hepatic allograft with HCV. The aim of this study is to characterize intrahepatic cytokine responses associated with reinfection of the allograft with HCV in these settings. Intrahepatic messenger RNA expression of T helper cell subtype 1 (TH1) cytokines interleukin-2 (IL-2), interferon-γ, and tumor necrosis factor-α and TH2 cytokines IL-4 and IL-10 was measured by real-time polymerase chain reaction system using TaqMan probes in 53 liver specimens from six groups of patients. These were: (1) recurrent chronic hepatitis C (CH-I; n = 15), (2) cholestatic hepatitis (n = 6), (3) acute rejection associated with HCV recurrence (AR-HCV; n = 12), (4) acute rejection in non-HCV-infected allografts (AR non-HCV; n = 5), (5) patients with chronic hepatitis C who did not undergo transplantation (CH-C; n = 10), and (6) nondiseased liver tissue (n = 6). Intrahepatic viral loads were measured using an Amplicor monitor assay (Roche Diagnostic Systems, Branchburg, NJ). The CH-I and CH-C groups had similar TH1 intrahepatic cytokine profiles. Compared with the CH-I group, the cholestatic group expressed increased levels of the TH2 cytokines IL-10 (P = .024) and IL-4 (P = .0024). The AR-HCV group also expressed more TH2 cytokines IL-10 (P = .014) and IL-4 (P = .034) compared with the CH-I group. Both the AR-HCV and AR non-HCV groups showed similar intrahepatic cytokine profiles. Intrahepatic viral loads were highest in the cholestatic group compared with the AR-HCV, CH-I, and CH-C groups (P = .0007). In conclusion, a novel observation is that the cholestatic group showed upregulation of the TH2 cytokines IL-10 and IL-4, in addition to high viral loads. In this setting, the TH2 immune response may favor viral replication and graft damage.
Fatigue and physical function after orthotopic liver transplantation
Authors: Aadahl Mette , Hansen Bent Adel , Kirkegaard Preben , Groenvold Mogens
Published: August 2002

Over the last two decades, orthotopic liver transplantation (OLT) has become an established treatment for acute and chronic liver failure. OLT impacts not only on survival, but also on health-related quality of life. This study was undertaken to describe the self-rated health of Danish liver transplant recipients, compare their self-rated health against that of the general population, and to investigate associations between sex, age, diagnosis, time after OLT, and postoperative physical function and fatigue. All adult surviving liver transplant recipients who underwent OLT in Copenhagen, Denmark, from 1990 to 1998 (n = 154) were contacted by mail and asked to complete a self-administered questionnaire. The questionnaire contained the 36-Item Short Form Health Survey, the Multidimensional Fatigue Inventory, the Hospital Anxiety and Depression Scale, and questions on marital status, education, and work. The response rate was 84.4% (n = 130). Liver transplant recipients reported poorer self-rated health than the general population in physical, but not in mental, health areas. One health aspect, fatigue, was investigated in great detail. This study found that liver transplant recipients experienced physical, rather than mental, fatigue. Diagnosis was found to be a predictor of postoperative physical function and fatigue because patients with an alcoholic or cryptogenic cirrhosis background had significantly poorer physical function and experienced more physical fatigue than liver transplant recipients with other diagnoses. Work status and survival time after OLT had significant effects on postoperative physical function and fatigue. Working and having undergone transplantation 4 to 5 years previously were associated with significantly better physical function and less physical fatigue than not working and having undergone transplantation 1 to 3 years previously. This study suggests that liver transplant recipients experience physical, rather than mental, impairment and fatigue and that diagnosis, work status, and survival time after OLT are associated with physical function and fatigue.
Current practice regarding the use of fatty livers: A Trans-Atlantic survey
Authors: Imber Charles J. , St. Peter Shawn D. , Lopez Inigo , Guiver Lynden , Friend Peter J.
Published: August 2002

A strong association exists between the presence of steatosis in a donor liver for transplantation and the development of primary nonfunction in the recipient. Despite this, appraisal of the donor remains one of the least scientific aspects of the transplantation process, and many centers base their practice on subjective opinion, rather than objective data. We conducted this survey to illuminate controversial issues and highlight the variation of opinion and practice policies both between and within the United Kingdom and the United States. A simple, anonymous, one-page, 10-question survey with tick-box answers was sent to every practicing liver transplant surgeon in the United Kingdom. The same form was sent by E-mail to liver transplant surgeons in the United States with a current E-mail address listed in the American Society of Transplant Surgeons registry. In the United Kingdom, 16 of 19 surgeons polled responded (84.2%) and thus were considered representative. From the United States, there were 78 respondents from 52 centers, representing all 11 United Network for Organ Sharing regions. We found that current practice policies differ not only between nations, but also among centers in each country. US surgeons generally follow a more conservative approach, with greater emphasis on histological assessment. Dichotomous opinions exist on the significance of microvesicular steatosis in both countries. Most evident from this survey is that more research in the field is required to help answer these questions and allow for the safe use of all viable livers.
Hepatic steatosis and its relationship to transplantation
Authors: Imber Charles J. , St. Peter Shawn D. , Handa Ashok , Friend Peter J.
Published: August 2002

Fatty infiltration of the liver is common in the brain-dead donor population and has a strong correlation with primary nonfunction after cold preservation, a condition that is catastrophic to liver transplant recipients. This literature review examines factors associated with the development, diagnosis, quantification, and clinical management of this difficult condition.
Routine endoscopic retrograde cholangiography in the detection of early biliary complications after liver transplantation
Authors: Shah Sudeep R. , Dooley James , Agarwal Raj , Patch David , Burroughs Andrew K. , Rolles Keith , Davidson Brian R.
Published: August 2002

The value of routinely performing endoscopic retrograde cholangiography (ERC) to detect biliary complications in patients undergoing orthotopic liver transplantation (OLT) with duct-to-duct anastomosis without a T-tube is not known. Eighty-nine of 171 liver transplant recipients (61 men; mean age, 49.9 years) underwent ERC 14.5 ± 4.5 (SD) days after surgery between January 1997 and August 1999. Findings of ERC and need for intervention for biliary complications were noted. ERC was successful in 71of 89 patients (80%). Nineteen patients (21%) required intervention for biliary complications (stricture, 13 patients; bile leak, 6 patients). Protocol ERC detected eight of these complications (42%). In 4 patients, ERC failed, and 7 patients with a normal ERC result subsequently required intervention (2 patients in the same admission, and 5 patients after discharge). Sensitivity, specificity, and positive and negative predictive values for successful ERC in detecting early biliary complications were 80%, 98%, 89%, and 97%, whereas those for predicting the overall rate of biliary complications were 53%, 98%, 89%, and 89%, respectively. Although highly specific and moderately sensitive in detecting early biliary complications, ERC performed routinely has low sensitivity in predicting the overall risk for biliary complications in patients undergoing OLT with unsplinted duct-to-duct anastomosis.
Metabolic changes in the liver graft monitored continuously with microdialysis during liver transplantation in a pig model
Authors: Nowak Grzegorz , Ungerstedt Johan , Wernerman Jan , Ungerstedt Urban , Ericzon Bo-Göran
Published: August 2002

Microdialysis provides the opportunity to continuously monitor metabolic changes in tissue. The aim of the study is to monitor metabolic changes in the liver graft over time during transplantation in a pig model. Fourteen littermate female pigs with a body weight of 30 to 34 kg were used for seven orthotopic liver transplantations. Intrahepatic implantation of a microdialysis catheter into the liver graft was performed in the donor. Microdialysis samples were collected at 20-minute intervals during the donor operation, cold preservation, and for 7 hours after reperfusion in the recipient. Glucose, lactate, pyruvate, and glycerol concentrations were measured. After cold perfusion, glucose, lactate, and glycerol levels increased, whereas pyruvate levels decreased rapidly. During cold storage, glucose and glycerol levels increased, whereas lactate levels remained stable and pyruvate levels were undetectable. During implantation of the liver graft, glucose, lactate, and glycerol levels showed an accelerated increase. After portal reperfusion, glucose, lactate, and glycerol levels continued to increase for another 40 to 60 minutes, after which they decreased and finally settled at normal levels. At this time, pyruvate levels increased, with a peak within 2 hours after reperfusion, and then decreased to normal levels. Calculated lactate-pyruvate ratio increased after cold perfusion and remained stable during cold storage. During rewarming, it showed an accelerated increase, but after reperfusion, it decreased rapidly. Rewarming and reperfusion are most harmful to the liver, reflected by an accelerated increase in glucose and glycerol levels and lactate-pyruvate ratio. High intrahepatic glucose levels during ischemia appear to be a liver-specific event, which may represent glycogen degradation in injured hepatocytes.
Recurrent portal hypertension after composite liver/small bowel transplantation
Authors: Fishbein Thomas M. , Florman Sander , Gondolesi Gabriel , LeLeiko Neal S. , Mitty Harold A. , Tschernia Allan , Kaufman Stuart S.
Published: August 2002

Late technical complications of composite liver/small bowel transplantation procedures are often complex and have not been well defined. Here we describe the unusual presentation and management of two cases of recurrent thrombocytopenia due to hypersplenism resulting from portacaval shunt stenosis. Both patients presented with portal hypertension late after composite liver/small bowel transplantation. One patient presented with recurrent bouts of upper gastrointestinal hemorrhage and was ultimately found to have a stenosis of her native portacaval shunt. After unsuccessful balloon dilatation of the anastomosis, a successful side-to-side distal splenorenal shunt was performed. The second patient presented with severe thrombocytopenia, the etiology of which was determined to be a short segment occlusion of the inferior vena cava between the native portacaval shunt and the piggyback outflow anastomosis of the liver graft. Total caval occlusion prevented balloon dilatation; the patient was relisted for transplantation but died of chronic rejection four months later. Recurrent portal hypertension is challenging in patients who have had combined liver/small bowel transplantation. Surgeons performing intestinal transplantation need to be increasingly aware of these possible late complications.
Preliminary results: Outcome of liver transplantation for hepatitis B virus varies by hepatitis B virus genotype
Authors: Devarbhavi Harshad C. , Cohen Ari J. , Patel Robin , Wiesner Russell H. , Dickson Rolland C. , Ishitani Michael B.
Published: August 2002

Hepatitis B virus (HBV) is a leading cause of liver failure throughout the world. HBV has seven different genotypes based on variations within the viral nucleotide sequence. Initially, patients who underwent liver transplantation for HBV had high recurrence rates and poor survival. Recently, improved outcomes have been reported when patients are administered hepatitis B immunoglobulin (HBIg) infusions to maintain high serum hepatitis B surface antibody titers after transplantation. Unfortunately, recurrence rates are still high in patients with active pretransplant HBV replication. The aims of this study are to evaluate the impact of HBV genotype on pretransplantation HBV replication and posttransplantation HBV recurrence rate, morbidity, and mortality. Sera from 22 patients who underwent transplantation for HBV at our center were tested for HBV genotype by an enzyme-linked immunosorbent assay technique using monoclonal antibodies to the pre-S2 region. All patients were administered HBIg after transplantation; 5 patients were administered both lamivudine and HBIg. HBV genotypes were distributed as follows: genotype A (10 patients), genotype C (6 patients), genotype D (5 patients), and genotype E (1 patient). Pretransplantation HBV replication was most common with genotype A (80%), whereas less so with genotypes C (33%) and D (40%). Nine patients (41%) developed recurrent HBV infection: genotype A (2 patients; 20%), genotype C (3 patients; 50%), and genotype D (4 patients; 80%). Mortality was greatest with genotype D (40%). Our data suggest that patients with genotype A have the lowest risk for HBV recurrence despite having the highest rate of pretransplantation HBV viral replication. Patients with genotype D appear to have the highest risk for HBV recurrence and mortality. Additional larger multicenter studies are needed to confirm these findings.
Auxiliary liver transplantation for fulminant hepatitis B: Results from a series of six patients with special emphasis on regeneration and recurrence of hepatitis B
Authors: Durand François , Belghiti Jacques , Handra-Luca Adriana , Francoz Claire , Sauvanet Alain , Marcellin Patrick , Farges Olivier , Bernuau Jacques , Valla Dominique
Published: August 2002

Emergency liver transplantation is the treatment of choice for the most severe forms of fulminant hepatitis B. Auxiliary liver transplantation is an attractive alternative, offering the possibility of regeneration and discontinuation of immunosuppression. However, the use of auxiliary transplantation for fulminant hepatitis B is controversial because the remnant part of the native liver could be the source of recurrence of HBV infection. We report the results of auxiliary liver transplantation in six patients with fulminant hepatitis B. Postoperatively, all patients received gancyclovir and anti-hepatitis B surface immune globulins. Graft function has been satisfactory in all cases and all patients had rapid neurologic improvement. One patient died with a functional graft because of disseminated aspergillosis on postoperative day 17. The remaining 5 patients are currently alive. The 4 patients with more than 1-year follow-up had complete regeneration of the native liver and are free of immunosuppression. None of these patients had recurrence of hepatitis B. These results suggest that the use of an auxiliary graft is a safe alternative in selected patients with fulminant hepatitis B. Regeneration of the native liver, even if slow, seems to occur in most cases, allowing discontinuation of immunosuppression, which is a major advantage over conventional transplantation. Finally, the remnant part of the native liver does not compromise immunization against HBV.
Recurrence of primary sclerosing cholangitis after liver transplantation
Authors: Graziadei Ivo W.
Published: August 2002

Orthotopic liver transplantation (OLT) has become the only effective therapeutic option for patients with end-stage liver disease caused by primary sclerosing cholangitis (PSC). Excellent long-term outcome has been reported, with 5-year patient survival rates of approximately 80%. In the last few years, increasing evidence has emerged that PSC recurs after OLT. The diagnosis of PSC is based on well-defined cholangiographic features combined with biochemical and histological findings. However, none of these features is specific for PSC, particularly after OLT, because biliary strictures in the liver allograft can occur from a variety of causes other than recurrence. Therefore, PSC recurrence remains a controversial issue, especially because of a lack of a gold standard for diagnosis and well-established diagnostic criteria. Some reports provided cholangiographic evidence that post-OLT biliary strictures occurred more frequently in patients with PSC than in those who underwent OLT for other liver diseases (including patients with a Roux-en-Y biliary reconstruction). Because no other possible cause of biliary strictures could be invoked to explain the greater prevalence of these strictures, recurrent disease has been implicated. There also is histological evidence suggesting that PSC recurs after OLT. Histological findings suggestive of PSC were found more often in PSC allografts compared with a control group. Furthermore, histological features typical for PSC (fibro-obliterative lesions) were seen exclusively in liver biopsy specimens from patients with PSC. Recurrence of PSC was defined in a recent study from the Mayo Clinic by means of strict cholangiographic and histological criteria in a large cohort of patients with PSC in whom other causes of biliary strictures were excluded. PSC recurrence was found in 20% of patients. No risk factor for PSC recurrence could be found, and recurrent disease did not influence patient or graft survival after a mean follow-up of 4.5 years. In conclusion, several studies provided convincing evidence that PSC recurs after OLT, with an incidence of 5% to 20% and an interval to diagnosis of at least 1 year after OLT. To date, patient and graft survival do not appear to be negatively affected by disease recurrence in the intermediate term of follow-up. (Liver Transpl 2002;8:575-581.)
Glomerular filtration rate assessment in individuals after orthotopic liver transplantation based on serum cystatin C levels
Authors: Schück Otto , Gottfriedova Halima , Maly Jan , Jabor Antonin , Stollova Milena , Bruzkova Iva , Skibova Jelena , Ryska Miroslav , Spicak Julius , Trunecka Pavel , Novakova Jana
Published: August 2002

Individuals after orthotopic liver transplantation (OLT) often show renal dysfunction, which may substantially affect the post-OLT course. Renal function after OLT is commonly assessed by means of serum creatinine (Scr) concentration or renal creatinine clearance (Ccr). A glomerular filtration rate (GFR) estimate based on Scr level is not accurate enough because even a more marked decrease in GFR need not be associated with an increase in Scr level, especially in jaundiced patients. The study intends to try to estimate GFR in individuals after OLT by means of determining serum cystatin C (Scyst) concentrations. In 58 individuals (mean age, 49 ± 7 years; 31 men, 27 women) at various intervals from OLT (mean, 14 ± 10 months), GFR was estimated by using simultaneous determinations of Scyst, Scr, Ccr, and renal inulin clearance (Cin). In most subjects (91.3%), Cin was decreased to less than the lower limit of normal (80 mL/min/1.73 m2). A significant correlation (r = 0.70; P < .001) was found between 1/Scyst and Cin. Receiver operating characteristic analysis was performed on Scyst and Scr using a Cin cutoff value of 80 mL/min/1.73 m2. The area under the curve for Scyst was 0.912 ± 0.044, and that for Scr, 0.899 ± 0.049. There was no statistically significant difference between these values. The sensitivity for a Scyst level of 1.20 mg/L (upper limit of normal value) to detect a decrease in GFR (measured as Cin) below the lower limit of normal (80 mL/min/1.73 m2) was 96.1%. The sensitivity of Scyst level was significantly greater (P < .01) than the sensitivity of Scr level for men and at borderline significance for women (P = .05). Findings support the assumption that a Scyst level less than 1.2 mg/L indicates with a high degree of probability (P < .001) that GFR is not decreased to less than the normal limit. Scyst assessment in individuals after OLT could be proposed as a confirmatory test of a decrease in GFR in individuals with normal Scr levels. (Liver Transpl 2002;8:594-599.)
Cigarette smoking is associated with an increased incidence of vascular complications after liver transplantation
Authors: Pungpapong Surakit , Manzarbeitia Cosme , Ortiz Jorge , Reich David J. , Araya Victor , Rothstein Kenneth D. , Muñoz Santiago J.
Published: August 2002

Hepatic artery thrombosis (HAT) and other vascular complications are significant causes of morbidity after liver transplantation. Although cigarette smoking increases the risk of vascular complications after renal transplantation, its impact after liver transplantation remains unknown. Between May 1995 and April 2001, 288 liver transplantations were performed in 263 patients. Vascular complications developed in 39 patients (13.5%) (arterial complications, 28 patients [9.7%]; venous complications, 11 patients [3.8%]). Patient demographics, comorbid illnesses, and risk factors were analyzed using the Mann-Whitney U test, Chi-squared test, and Fisher’s exact test. In patients with a history of cigarette smoking, incidence of vascular complications was higher than in those without history of cigarette smoking (17.8% v 8%, P = .02). Having quit cigarette smoking 2 years before liver transplantation reduced the incidence of vascular complications by 58.6% (24.4% v 11.8%, P = .04). The incidence of arterial complications was also higher in patients with a history of cigarette smoking compared with those without such history (13.5% v 4.8%, P = .015). Cigarette smoking cessation for 2 years also reduced the risk of arterial complications by 77.6% (21.8% v 5.9%, P =.005). However, the incidence of venous complications was not associated with cigarette smoking. Furthermore, there was no significant association between development of vascular complications and all other characteristics studied. Cigarette smoking is associated with a higher risk for developing vascular complications, especially arterial complications after liver transplantation. Cigarette smoking cessation at least 2 years before liver transplantation can significantly reduce the risk for vascular complications. Cigarette smoking cessation should be an essential requirement for liver transplantation candidates to decrease the morbidity arising from vascular complication after liver transplantation.
Reduced use of intensive care after liver transplantation: Patient attributes that determine early transfer to surgical wards
Authors: Mandell Susan M. , Lezotte Dennis , Kam Igal , Zamudio Stacy
Published: August 2002

Part 1 of our report, presented in the same issue of the Journal, shows that immediate postoperative extubation and direct transfer to the surgical ward is safe and reduces reliance on the intensive care unit in most liver transplant recipients. However, there is no method to preoperatively predict which patients will need ventilatory support after surgery. To address this issue, we examined the relationship between perioperative patient attributes and extubation outcome in patients entered into our immediate postoperative extubation study from 1996 to 1998. Variables chosen stemmed from considerations in the literature. We examined the influence of 13 preoperative and 6 intraoperative factors on extubation outcome. Preoperative attributes included sex, race, diagnosis, United Network for Organ Sharing status, Child-Pugh score, presence of a portosystemic shunt, ascites, encephalopathy, coagulation, age, body mass index (BMI), creatinine level, and year of surgery. Intraoperative factors were type of surgery, surgeon, anesthesiologist, number of red blood cells administered, length of surgery, and surgical start time. Female sex (P = .02), BMI of 32 or greater (P = .015), portosystemic shunt (P = .022), and encephalopathy (P = .041) were associated with no attempt by the physician to extubate, whereas encephalopathy (P = .01) and BMI of 34 or greater (P = .002) were associated with failure to meet criteria for postoperative extubation (described in part 1 of this study). We conclude there are limited factors that predict an increased risk for postoperative respiratory failure in liver transplant recipients. Our results indicate that physicians are conservative in their approach to extubation immediately after surgery, and sole reliance on physician judgment to determine suitability for postoperative extubation leads to unnecessary use of postoperative cardiopulmonary support.
All the King's Horses and All the King's Men: Pain Management From Hospital to Home
Authors: Hellsten Melody Brown
Published: August 2002

Pain management in children with cancer continues to be less than adequate in most settings. Children in pain often have multiple caregivers, each imposing a significant risk to adequate pain management if they are uninformed about the principles of pain management and the child's specific pain management regimen. This article reviews current pain management guidelines for children, obstacles to adequate pain management, and the challenges of managing pain across care settings (hospital to home). Using the hospice model of care, case studies are presented that illustrate both threats to adequate pain control and the coordination of care necessary to ensure consistent pain management between the hospital and home. Implications for improvement in pain manage ment between settings and future directions for advancing skills and knowledge related to pain management in children with cancer are provided.
Ischemic Bandage Injuries: A Case Series and Review of the Literature
Authors: Anderson Davina M. , White Richard A.S.
Published: August 2002

Objective—To determine the prognosis and distribution of ischemic injuries caused by inappropriate bandaging of the lower limb in dogs and cats.

Study Design—Retrospective clinical study.

Animal Population—Eleven client‐owned animals, including 9 dogs and 2 cats with a history of injuries consistent with incorrect application of a bandage.

Methods—Medical records for dogs and cats referred to the Queen's Veterinary School Hospital with limb wounds between 1995 and 1999 were reviewed for clinical history and referring veterinary surgeons' reports, indicating that the injury was directly related to the application of a bandage to the limb.

Results—The indications for bandage application included 2 postoperative cruciate ligament ruptures, 2 lacerations, 3 internal fixations, an onychectomy, a shoulder dislocation, a dog bite, and a tendon strain. None of the patients had other body systems involved or underlying or concurrent diseases. Five different types of bandage were described (support, Robert Jones, pressure, splint, and Velpeau), and no particular age or breed was overrepresented. Of the 11 animals, 5 required full‐thickness skin grafts, 3 had to have digits amputated, and 2 required limb amputations. Nine animals survived, but only 4 became fully functional on the affected limb.

Conclusions—Bandage‐related injuries are potentially serious sequelae to a routine procedure. A guarded prognosis should be given when there is loss of deeper structures.

Clinical Relevance—A review of bandaging principles is presented. Method of application, choice of materials, and close monitoring of the bandage are important factors in preventing iatrogenic injury.
Modelling desert dune fields based on discrete dynamics
Authors: Bishop Steven R. , Momiji Hiroshi , Carretero-González Ricardo , Warren Andrew
Published: August 2002

A mathematical formulation is developed to model the dynamics of sand dunes. The physical processes display strong non‐linearity that has been taken into account in the model. When assessing the success of such a model in capturing physical features we monitor morphology, dune growth, dune migration and spatial patterns within a dune field. Following recent advances, the proposed model is based on a discrete lattice dynamics approach with new features taken into account which reflect physically observed mechanisms.
Preparation and Properties of High Molecular Weight Polyamic Ester Having a Cyclobutane Moiety in the Main Chain
Authors: Hasegawa Masaki , Miura Hirohiko , Haga Naoki , Hayakawa Akira , Saito Kiyoshi
Published: August 2002

Preparation and properties of the polyimide derived from cyclobutanetetracarboxylic dianhydride (CBDA) with diamines are investigated, focusing on the interfacial polycondensation of cyclobutanetetracarboxylic acid dimethylester dichloride (2a) with diamines.

Dimethylester was conveniently prepared from CBDA by refluxing in methanol solution. Dimethylester consists of two regio isomers; one is α-type (1a) with centrosymmetry, the other is β-type (1b) with plane symmetry. Separation of the mixture into each of pure 1a and 1b was successfully performed by fractional crystallization. The structure of the first fraction is 1a, which was determined by x-ray crystal analysis. The second fraction was necessarily assigned to 1b. 1a was converted into 2a by the reaction of thionyl chloride. The interfacial polycondensation of 2a with diamines afforded a high molecular weight polyamic ester. Polyimide was obtained only by heating the polyamic ester to about 230–280 °C. The cyclobutane polyimide thus obtained was thermally stable up to 400 °C, and less stable under hydrolysis than polypyromellitic imide.
Synthesis and Characterization of Modified Phenylethynyl Imides
Authors: Jensen B J , Chang A C
Published: August 2002

As an ongoing effort to develop structural adhesives for high-performance aerospace applications, recent work has focused on phenylethynyl terminated imide (PETI) oligomers. The work reported herein involves the synthesis and characterization of a series of phenylethynyl containing oligomers designated LARC™ MPEI (modified phenylethynyl imide). These oligomers presumably contain mixtures of linear, branched and star-shaped molecules. The fully imidized polymers exhibited minimum melt viscosities as low as 600 poise at 335 °C, significantly lower than equivalent molecular weight linear materials. Ti/Ti lap shear specimens processed at 288 °C under 15 psi showed tensile shear strengths as high as ∼6000 psi and ∼5200 psi at ambient temperature and 177 °C respectively. The chemistry and properties of these new MPEIs are presented and compared with an optimized linear PETI, LARC™ PETI-5.
IM7/LARC™ MPEI-1 Polyimide Composites
Authors: Hou T H , Cano R J , Jensen B J
Published: August 2002

LARC™ MPEI-1 (Langley Research Center™ modified phenylethynyl imide-1) phenylethynyl containing aromatic polyimide, is based on the reaction of biphenyl dianhydride (BPDA), 3,4′-oxydianiline (3,4′-ODA), 1,3-bis(3-aminophenoxy)benzene (APB), 2,4,6-triaminopyrimidine (TAP) and 4-phenylethynyl phthalic anhydride (PEPA), presumably resulting in a mixture of linear, branched and star shaped phenylethynyl containing imides which was evaluated as a matrix for high-performance composites. The poly(amid acid) solution of MPEI-1 in N-methypyrrolidinone was synthesized at 35% and 42% solids. Unidirectional prepreg was fabricated from these solutions and Hercules IM7 carbon fibre utilizing NASA-Langley’s multipurpose prepreg machine. The temperature-dependent volatile depletion rates, thermal crystallization behaviour and resin rheology were characterized. Based on this information, a composite moulding cycle was developed which yielded well consolidated, voidfree laminates. Composite mechanical properties such as short beam shear strength, longitudinal and transverse flexural strength and flexural modulus, longitudinal tensile strength and notched and unnotched compression strengths were measured at room temperature (RT) and elevated temperatures. These mechanical properties are compared with those of IM7/LARC™ PETI-5 composites.
Synthesis of Poly(Dinaphthylene Ether) by Oxidative Coupling Polymerization of Di(1-Naphthoxy)Pentane Using Cobalt (III) Acetylacetonate
Authors: Okada Takashi , Amou Satoru , Haba Osamu , Ueda Mitsuru
Published: August 2002

Poly(dinaphthylene ether) was prepared by oxidative coupling polymerization of 1,5-di(naphthoxy)pentane. Polymerizations were conducted in 1,2-dichloroethane in the presence of cobalt (III) acetylacetonate and methanesulfonic acid at room temperature and produced poly(dinaphthylene ether)s with number-average molecular weights up to 10 000. The polymer structure was characterized by 1H and 13C-NMR spectroscopies, and selective coupling was found to occur at the C-4 position of the 1-substituted naphthalene ring. The model reactions were studied to demonstrate the feasibility of polymer formation.
The Mesogenic Index: An Empirical Method for Predicting Polymeric Liquid Crystallinity
Authors: Dolden J G , Alder P T
Published: August 2002

An empirical method for predicting the chemical compositions of random or partially ordered copolymers that exhibit mesophases was devised by the authors in 1989, while working on liquid crystal copolymer synthesis for BP Chemicals. A brief description of the method and its application to the chemical synthesis of amorphous thermotropic polyamides was given by the authors in a previous paper. Thermotropic polyimides were also synthesized by the authors as a result of the use of the predictive method. Subsequently, the method has been updated and applied to polycarbonates and polyimides.

The new approach has been termed ‘the mesogenic index’ (MI) and has successfully been applied to 23 copolymer systems in which the critical compositions for mesophase formation have been established by means of varying constituent monomer concentrations. It is also consistent in predicting liquid crystalline behaviour in several hundred main-chain polymer systems containing amide, ester, carbonate, ether and urethane groups.

It is inherent in the MI system that the mesogenic length is defined in terms of the number of monomer units for a given polymer class. From published work in the literature, it was first established that ester and amide groups need at least two and three aromatic rings in the mesogen respectively. Using these values to define mesogen length in polyester and polyamide copolymers, the condition MI > 10 has been determined for mesophase formation. This rule has been applied to other linking groups, such as carbonate or imide, with the surprising result that the corresponding mesogen lengths for these condensation polymers are simple numbers. Moreover, the rule has been applied successfully to mixed systems, by simply averaging the contributions of the different groups to the mesogen length in strictly molar proportions.

The mesogenic index is based upon summing functional group contributions towards rigidity and/or resonance stabilization of the mesogen. To the best of our knowledge, this is the first simple method to be published that successfully correlates chemical composition with mesophase formation.
Preparation and Properties of Porous Polyimide Films
Authors: Takeichi Tsutomu , Zuo Min , Ito Akihiro
Published: August 2002

Porous polyimide films were prepared in two steps. The first step was the preparation of poly(urethane-imide) films by a reaction between a phenol-terminated polyurethane prepolymer and poly(amide acid) obtained from pyromellitic dianhydride (PMDA) and oxydianiline (ODA) followed by thermal treatment at 200 °C. The second step was the pyrolysis of the poly(urethaneimide) films. Upon thermal treatment of the poly(urethane-imide) films at 300 to 400 °C, the thermally less stable urethane domains decomposed, leaving porous polyimide films. The presence of pores was confirmed from the scanning electron microscope (SEM) picture of the surface and the cross section of the films. The size distribution of the pores was narrow. With increasing urethane content, the apparent density decreased but the size of the pore did not increase so much. Instead, the number of pores increased. Tensile measurements revealed that, with increasing urethane component the tensile modulus did not vary very much, but the elongation and thus the tensile strength decreased. Viscoelastic analyses showed that all the porous polyimide films had a high glass transition temperature, above 400 °C, and storage moduli were maintained up to 400 °C.
Luminescence Studies of Polymer Matrices: 2. on the Phosphorescence Characteristics of 2-Benzoylnaphthalene Dispersed in Various Acrylic Polymers
Authors: Ebdon John R , Soutar Ian , Brown Paul , Lane Anthony R , McCabe Alasdair J , Swanson Linda
Published: August 2002

The phosphorescence characteristics of 2-benzoylnaphthalene (2BN) dispersed within thin films of poly(methyl methacrylate), poly(methyl acrylate), polystyrene and poly(acrylic acid) (PAA) respectively, are described. The excited state decay kinetics of the probe are complex in each of the macromolecular hosts studied: such behaviour is considered to result from differing degrees of phosphor–host matrix interaction but may also reflect, particularly in the case of PAA, heterogeneities within the bulk polymer phase. The thermal dependence of the intensity and average lifetime of phosphorescence of the various phosphor/polymer combinations were also investigated with a view to identifying a host matrix for a high-performance coding ink. Preliminary data indicate that the longest-lived, most intense triplet emission results from the 2BN doped PAA system.
Photocurable Monomers and Oligomers for Space Applications
Authors: Crivello James V
Published: August 2002

The rationale and prospects for using photocurable monomers for a variety of space applications are discussed. In particular, the fabrication of lightweight composite structures for use in earth orbit as well as for planetary exploration using ambient solar irradiation appears to be attractive. Such structures could be transported either into space or to the surface of the moon or planetary bodies in a collapsed condition. Therefore, they could be deployed by inflation with a gas and then allowed to become rigid as a result of polymerizations induced by light. The key to this technology is the development of photosensitive initiators and specially tailored monomers and reactive oligomers.
Reduced Temperature Curing of Acetylenic Polyimides
Authors: Hawthorne D G , Hodgkin J H , Morton T C
Published: August 2002

The onset temperature for the curing reactions of phenylethynyl-terminated oligomers can be lowered by the addition of disulfides which dissociate to form thiyl radicals on heating. Studies using model compounds have shown that the products obtained from these reactions are structurally different from those obtained in the absence of the additives. The low-temperature cure reactions of oligomers containing aromatic disulfides as backbone moieties initially yield high molecular weight thermoplastic polymers containing benzothiophene linkages. On further heating these polymers can be converted to lightly crosslinked, tough, thermally stable materials with general properties similar to those of the NASA PETI series, and suitable for matrix resins in high-temperature composites, but differing significantly in processing characteristics.
Increasing the Electrical Discharge Endurance of Acid Anhydride Cured DGEBA Epoxy Resin by Dispersion of Nanoparticle Silica
Authors: Henk P O , Kortsen T W , Kvarts T
Published: August 2002

A fluid DGEBA/methyl nadicanhydride epoxy system has been filled with inorganic particles, cast as bubble-free plates and cured. The ability of both the pure network polymer and the polymer/particle composites to withstand partial electrical discharges has been investigated. Three types of particle combinations were used: (a) fumed nanoparticle silicon dioxide referred to as Aerosil, (b) equal volumes of Aerosil and nanoparticle anatase, and (c) Aerosil plus anatase in combination with coarse-particle filler grade calcium–magnesium carbonate dolomite. A test for endurance using the CIGRE method II electrode arrangement was applied, the test comprising the establishment of partial discharges running perpendicularly onto one face of a plate specimen for a period measured until breakdown

Our results show that the endurance of the pure polymer is low. Increased loading with Aerosil increases the endurance by a factor of up to 20 as the Aerosil content goes from zero to 5.4 vol.%. Aerosil mixed with anatase has a similar effect. The high level of endurance is maintained with an additional high-volume (35 vol.%) filling of coarse-particle dolomite to an epoxy system already containing Aerosil and anatase. The results are discussed in the light of estimated interparticle spacings and interface areas.
Molecular Design of Rigid-Chain Polyheteroarylenes and the Effect of Substituents at the Central Heterocyclic Fragment on the Polyheteroarylene Equilibrium Rigidity
Authors: Ronova Inga A , Ponomarev Igor I , Kovalevsky Andrey Yu , Shishkin Oleg V
Published: August 2002

Quantum-chemical calculations and calculations by the Monte Carlo method were used for conformational analysis of heterocyclic polymers. The steric effect of various substituents on the equilibrium geometry and conformational dynamics of 1, 4, 5, 8-naphthalenetetracarboxydiimide was studied using the AM1 semiempirical quantum-chemical method. It was shown that addition of bulky groups to the naphthalene moiety of 1, 4, 5, 8-naphthalenetetracarboxydiimide increases conformational rigidity of the imide rings. Using the example of rigid-chain polymers containing the naphthoileneimide ring, it was demonstrated that the introduction of four bulky substituents into the structure of 1, 4, 5, 8-naphthalenetetracarboxydiimide results in a considerable increase in the equilibrium rigidity of the polymer.
Thermal and Radiation Curing of Phenylethynyl Terminated Macromers
Authors: Preston Christopher M L , Hill David J T , Pomery Peter J , Whittaker Andrew K , Jensenk Brian J
Published: August 2002

The thermal and gamma-irradiation induced curing of two phenylethynyl terminated composite resin systems, DFB/BPF and PETI5A, was investigated. Thermal curing of these matrix resin samples was performed at a temperature of 360 °C, gamma irradiation of the samples was conducted at 300 °C at a dose rate of 2.2 kGy h−1. The reaction and subsequent loss of ethynyl groups in the resins for both cure methods was demonstrated by observing the decrease of the 2215 cm−1 peak in the Raman spectra of the resins. Fully cured resin samples were found to have glass transition temperatures of 244–246 °C and 278–280 °C for DFB/BPF and PETI5A respectively. Similar relationships between Tg and fractional conversion were observed in both resins. The apparent polymerization rate, Rp, for thermal cure at 360 °C, was found to be 4 :79 × 10−22%s−1 in PETI5A and 3.22 × 10−2%s−1 in DFB/BPF. Catastrophic degradation under nitrogen was observed to commence near 450 °C and 530 °C, with 5% weight losses occurring at 455 °C and 540 °C for DFB/BPF and PETI5A respectively. Gamma radiation induced cure at 300 °C was shown to be feasible, with full cure being reached with doses of 40 kGy for DFB/BPF and 100 kGy for PETI5A.
New Parabanate Products by 1, 3-Dipolar Cycloaddition Reaction (‘Criss-Cross’ Cycloaddition)
Authors: Caraculacu Adrian A , Scorţanu Elena , Caraculacu Georgeta
Published: August 2002

New parabanate products containing 1, 3, 5, 7-tetraazabicyclo[3, 3, 0]octane-2, 6-dione are described. The synthesis of αω-diisocyanato-telechelics starting from two diisocyanates having a preformed parabanic unit using a [3+2] dipolar cycloaddition reaction was studied. The obtained products were characterized by IR spectroscopy, elemental and thermogravimetric analyses and solubility tests. The proposed structure was confirmed by analytical data.
Shuttle and MIR Special Environmental Effects and Hardware Cleanliness
Authors: Harvey Gale A , Humes Donald H , Kinard William H
Published: August 2002

The Evaluation of Space Environment and Effects on Materials (ESEM) experiments were developed, flown in-space on the STS-85 mission (August 1997), returned to Earth and analysed as one element of a collaboration between the National Space Development Agency (NASDA) of Japan and the National Aeronautics and Space Agency (NASA) of the United States. The primary objectives of the ESEM experiments were to investigate atomic oxygen effects on materials, cosmic dust and man-made debris, and Shuttle-induced contamination. In particular, the change in scattering of light from the 1/4 mil aluminized Kapton film due to atomic oxygen erosion and Shuttle-induced molecular contamination are discussed. The MIR environmental effects payload (MEEP) was attached to the docking module of the MIR space station for 18 months during calendar years 1996 and 1997 (March 1996, STS 76 to October 1997, STS 86). A solar panel array with more than 10 years space exposure was removed from the MIR core module in November 1997 and returned to Earth in January 1998, STS 89. MEEP and the returned solar array are part of the International Space Station (ISS) Risk Mitigation Program. This space flight hardware has been inspected and studied by teams of space environmental effects (SEE) investigators for micrometeoroid and space debris effects, space exposure effects on materials and electrical performance. This paper reports changes in cleanliness of parts of MEEP and the solar array due to the space exposures. Special attention is given to the extensive water soluble residues deposited on some of the flight hardware surfaces. Directionality of deposition and chemistry of these residues are discussed.
Functional Copolymers of N-(4-Formyl-Phenoxy-4′-Carbonylphenyl) Maleimide with Styrene
Authors: Hulubei Camelia , Morariu Simona
Published: August 2002

A new reactive N-substituted maleimide monomer containing an aldehyde function, N-(4-formyl-phenoxy-4′-carbonylphenyl) maleimide (MI-CHO), was synthesized. The radical copolymerization of MI-CHO with styrene was performed at 60 °C in the presence of 2,2′-azoisobutyronitrile as an initiator in dimethylsulfoxide. The copolymerization of MI-CHO with styrene yielded the ‘nearly equimolar’ alternating copolymers for the mole fractions of MI-CHO in the feed ranging from 0.2 to 0.7. The monomer reactivity ratios ( r1, r2) in the polymerization of MI-CHO ( M1) with styrene ( M2) and the Alfrey–Price Q1 and e1 parameters were determined. The thermal properties of the copolymers were investigated by using thermogravimetric analysis and differential scanning calorimetry.
Thermo-Processable Polyimides with High Thermo-Oxidative Stability as Derived from Oxydiphthalic Anhydride and Bisphenol a Type Dianhydride
Authors: Shi Zemin , Hasegawa Masatoshi , Shindo Yoichi , Yokata Rikio , He Feifeng , Yamaguchi Hiroaki , Ozawa Hideo
Published: August 2002

Two series of homopolyimides based on oxydiphthalic anhydride and bisphenol A bisether-4-diphthalic anhydride were synthesized with 12 kinds of aromatic diamines. Several thermo-processable homopolyimides were the focus of further investigation. The structure–property relationships of these homopolyimides were examined as functions of the glass transition temperature ( Tg), melting point ( Tm), thermal decomposition temperature ( Td), and melt-flowability. The effects of the chemical and higher-order structures on these properties were discussed in this work to obtain an indication for the molecular design of high-performance thermoprocessable polyimides. A series of thermoplastic copolyimides were prepared to achieve higher Tg and Td without sacrificing thermo-processability. The copolyimides investigated exhibited a comparable or lower melt viscosity, higher Tg and Td, and higher long-term thermo-oxidative stability than those of ULTEM type polyimides. One of them exhibited a low melt viscosity (4700 poise at 400 °C), a high Tg (224 °C), and excellent thermo-oxidative stability.