Arch growth after staged repair of interrupted aortic arch using carotid artery interposition

BACKGROUND: Between 1980 and 1990, our practice was to perform carotid artery interposition as part of a staged repair of interrupted aortic arch with various associated cardiac defects. METHODS: This procedure was used in 16 patients with IAA type B. The median age at operation was 4.5 days and the median weight, 3.2 kg. Ten of the patients had an associated ventricular septal defect. Six more had complex anatomy. There were two death at carotid interposition, two interim deaths, and two deaths after intracardiac repair. Preoperative echocardiographic and angiographic studies were compared with postoperative studies in 11 survivors of arch repair to assess sequential growth of the interposed carotid artery. Measurements of the carotid artery were normalized to the descending aorta. RESULTS: Preoperatively, the left carotid artery had a median diameter of 3.7 mm and was 42.9% of the descending aortic diameter. Postoperative studies performed at a median age of 5.7 months disclosed that the interposed carotid artery had grown to a median diameter of 7.0 mm and was 69.6% of the diameter of the descending aorta (normal > or = 81%). On follow-up at a median time of 4 years, 6 of 9 patients have no gradient by blood pressure measurements or echocardiographic Doppler studies, and 3 have modest gradients. No patient has required revision of the arch repair. CONCLUSIONS: Survival is good after carotid artery interposition for interrupted aortic arch and growth of the carotid artery approaches that of a normal arch. Carotid artery interposition is a viable alternative for repair of this lesion should primary definitive repair not be feasible.     

The effect of nickel content on the fracture behaviour of Cu-Al-Niβ-phase alloys

The fracture behaviour of Cu-14 wt% Al alloys has been studied as a function of nickel content varying from 0 to 10 wt%. It was found that the presence of a brittle phase ₂ at the grain boundaries is responsible for intergranular fracture in low nickel alloys. Severe intergranular embrittlement exhibited by high nickel alloys in not associated with any precipitate at the grain boundaries. In fact when high nickel alloys are cooled slowly, a ductile phase () forms along the grain boundaries that resists the propagation of crack through grain boundaries and the fracture is transgranular.     

Dithiocarbamates as capping ligands for water-soluble quantum dots

We investigated the suitability of dithiocarbamate (DTC) species as capping ligands for colloidal CdSe-ZnS quantum dots (QDs). DTC ligands are generated by reacting carbon disulfide (CS(2)) with primary or secondary amines on appropriate precursor molecules. A biphasic exchange procedure efficiently replaces the existing hydrophobic capping ligands on the QD surface with the newly formed DTCs. The reaction conversion is conveniently monitored by UV-vis absorption spectroscopy. Due to their inherent water solubility and variety of side chain functional groups, we used several amino acids as precursors in this reaction/exchange procedure. The performance of DTC-ligands, as evaluated by the preservation of luminescence and colloidal stability, varied widely among amino precursors. For the best DTC-ligand and QD combinations, the quantum yield of the water-soluble QDs rivaled that of the original hydrophobic-capped QDs dispersed in organic solvents. The mean density of DTC-ligands per nanocrystal was estimated through a mass balance calculation which suggested nearly complete coverage of the available nanocrystal surface. The accessibility of the QD surface was evaluated by self-assembly of His-tagged dye-labeled proteins and peptides using fluorescence resonance energy transfer. DTC-capped QDs were also exposed to cell cultures to evaluate their stability and potential use for biological applications. In general, DTC-capped CdSe-ZnS QDs have many advantages over other water-soluble QD formulations and provide a flexible chemistry for controlling the QD surface functionalization. Despite previous literature reports of DTC-stabilized nanocrystals, this study is the first formal investigation of a biphasic exchange method for generating biocompatible core-shell QDs.     

Finite-element modeling and control of flexible fabric parts

Software based on nonlinear shell theory can simulate 3D motions related to real fabric-manufacturing processes. This simulation capability advances the technologies necessary for automating the textile and apparel industries     

Evaluation of the potential carcinogenicity and genetic toxicity to humans of the herbicide acetochlor

Comprehensive toxicological studies of the herbicide acetochlor are presented and discussed. Although it gave a negative profile of responses in the many toxicity tests conducted there were some findings that prompted further investigation. First, although non-mutagenic in the Salmonella assay, acetochlor was clastogenic to mammalian cells treated in vitro. This clastogenic potential was not expressed in vivo in four rodent cytogenetic assays (bone marrow and germ cells). Second, although acetochlor gave a negative response in rat liver UDS assays when tested at the acute MTD, gavage administration of a single, supra-MTD dose (2000 mg/kg) gave a weak positive assay response. This dose-level (2000 mg/kg) was necrotic to the liver, depressed hepatic glutathione levels by up to approximately 80%, altered the metabolism of acetochlor, and was associated with up to 33% lethality. In contrast, reference liver genotoxins such as DMN, DMH and 2AAF were shown to elicit UDS in the absence of such effects, and at approximately 400 x lower dose-levels. Finally, microscopic nasal polypoid adenomas were induced in the rat when acetochlor was administered for two years at the maximum tolerated dose (MTD). The tumours were not life-threatening, they did not metastasize, and no DNA damage was induced in the nasal cells of rats maintained on a diet containing the MTD of acetochlor for either 1 or 18 weeks (comet assay). In order to probe the mechanism of action of these high dose toxicities a series of chemical and genetic toxicity studies was conducted on acetochlor and a range of structural analogues. These revealed the chloroacetyl substructure to be the clastogenic species in vitro. Although relatively inert, this substituent is preferentially reactive to sulphydryl groupings, most evidently, to glutathione (GSH). Similar chemical reactivity and clastogenicity in vitro was observed for two related chemicals bearing a chloroacetyl group, both of which have been defined as non-carcinogens in studies reported by the US.NTP. These collective observations indicate that the source of the clastogenicity of acetochlor in vitro is also the source of its rapid detoxification in the rat in vivo, via reaction with GSH. Metabolic studies of acetochlor are described which reveal the formation of a series of GSH-associated biliary metabolites in the rat that were not produced in the mouse. The metabolism of acetochlor in the rat changes with increasing dose-levels, probably because of depletion of hepatic GSH. It is most likely that a rat-specific metabolite is responsible for the rat nasal tumours observed uniquely at elevated dose-levels. The absence of genetic toxicity to the nasal epithelium of rats exposed acutely or subchronically to acetochlor favours a non-genotoxic mechanism for the induction of these adenomas. The observation of a time- and dose-related increase in S-phase cells in the nasal epithelium is consistent with this conclusion. Despite some confusion caused by the early use of perilethal gavage administrations of acetochlor to rodents, and supra-MTD dietary concentrations in some of the chronic studies, the available MTD data are consistent with acetochlor not posing a genetic or carcinogenic hazard to humans.     

Usefulness of the carbon-13 tracer technique for characterizing terrestrial carbon pools

Application of the carbon-13 (¹³C) tracer technique to soil organic carbon emission is relatively new to many researchers and only a few results have been reported to date. This mini-review paper cites some well-documented research in organic carbon pool studies using the ¹³C tracer technique. The ¹³C abundance in soil usually remains at a stable level under a set of natural conditions. Variations in ¹³C reflect different sources and types of organic components from natural environments. An important feature of ¹³C discrimination in the soil C pool has permitted researchers to assess the dynamic nature of the pool. This discrimination may reflect a selective preference at early stage of residue decomposition by soil microbes. Crop rotation and residue input to humic substances can change the ¹³C abundance, which is a possible way to estimate soil C emission. However, the dynamic relationship between ¹³C abundance in the soil C pool and C emission is still in an early stage of development. Restrictions due to requirement of long-term experiments and duration of vegetation changes may affect its wide-spread adoptions in C emission studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Correlation between modes of drinking and modes of driving as reported by students at two American universities

This paper examines the correlates and predictors of driving under the influence behaviors (DUIBs) during the past month by college students. Measures of heavy episodic drinking, monthly drinking frequency, monthly drinking variance, monthly drinks per occasion and reported marijuana use are compared as predictors net of other predictive factors. A cross-sectional telephone survey was conducted with college students by a university social science research laboratory. Respondents attended two large public universities located in the southwestern part of the US. Participants included 803 randomly selected college students. The interview schedule included items from the Core Alcohol and Drug Survey and the College Alcohol Risk Assessment Guide. Several additional last-drinking-event items were also developed for the interview. Bivariate analyses indicate that marijuana use (past year), heavy episodic drinking, reports of DUIBs (driving under the influence or riding with a driver who is under the influence) in the past year, monthly frequency of drinking, the average number of drinks consumed when drinking and age are correlates of DUIBs during the past month. Multivariate analyses indicate past year DUIBs, monthly frequency of drinking and monthly marijuana use predicted recent DUIB.     

A PWR hybrid computer model for assessing the safety implications of control systems

As part of the ORNL study of safety-related aspects of control systems, a hybrid computer model was developed to trace the dynamic impact of single and multiple component failures on the control system and remainder of the plant. Since the thrust of this program is to investigate control system behavior, the controls are modeled in detail to accurately reproduce characteristic response under normal and off-normal transients. The balance of the model, including neutronics, thermohydraulics and component submodels, is developed in sufficient detail to provide a suitable support for the control system.The model is being used primarily to address mild to moderate transients that can occur at least partially under action of the non-safety control system. Attention initially focused on overfill events that assumed single or multiple failures of feed valves or the generator low and high level setpoints and trips that regulate the valves. In general, these calculations showed that for single-generator overfeed, water inventory in the affected generator increased to a sufficiently high level to saturate the generator fluid, quench superheat, and inject water into the steam line. Overcooling of the primary side was modest.Other events studied with the model include: insufficient main feedwater cooling induced by a steam generator high level setpoint failing low, potentially drying out the generator; secondary side depressurization induced by turbine bypass valves failing open in loop A or in combination with loop B, at low and high power levels; and steam generator tube ruptures in combination with overcooling incidents.     

Ideology and social work practice in substance abuse settings

The profession of social work has a unique role in preventing and treating alcohol and other drug problems. In human services settings shared beliefs or ideologies of care are expected to have substantial influence over the way in which problems are perceived and the types of service technologies used. Thus, it is important that social work professionals be cognizant of what beliefs they hold and how their beliefs about substance abuse treatment and prevention may affect practice. This article discusses current ideologies of care in the substance abuse arena, including the disease/abstinence, psychosocial, ecological, and harm-reduction approaches. In addition, this article examines managers' beliefs about substance abuse programs to determine if there are differences between those who have a social work background (that is, hold at least one social work degree) and those who do not. Suggestions for social work practice and future research also are provided.