Esophageal tolerance to high-dose stereotactic ablative radiotherapy.

Dose-volume parameters are needed to guide the safe administration of stereotactic ablative radiotherapy (SABR). We report on esophageal tolerance to high-dose hypofractionated radiation in patients treated with SABR. Thirty-one patients with spine or lung tumors received single- or multiple-fraction SABR to targets less than 1 cm from the esophagus. End points evaluated include D(5cc) (minimum dose in Gy to 5 cm(3) of the esophagus receiving the highest dose), D(2cc) , D(1cc) , and D(max) (maximum dose to 0.01 cm(3) ). Multiple-fraction treatments were correlated using the linear quadratic and linear quadratic-linear/universal survival models. Three esophageal toxicity events occurred, including esophagitis (grade 2), tracheoesophageal fistula (grade 4-5), and esophageal perforation (grade 4-5). Chemotherapy was a cofactor in the high-grade events. The median time to development of esophageal toxicity was 4.1 months (range 0.6-6.1 months). Two of the three events occurred below a published D(5cc) threshold, all three were below a D(2cc) threshold, and one was below a D(max) threshold. We report a dosimetric analysis of incidental dose to the esophagus from SABR. High-dose hypofractionated radiotherapy led to a number of high-grade esophageal adverse events, suggesting that conservative parameters to protect the esophagus are necessary when SABR is used, especially in the setting of chemotherapy or prior radiotherapy.

Effects of mechanical harvest plus chipping and prescribed fire on Sierran runoff water quality.

Fire suppression in Sierran ecosystems creates a substantial wildfire hazard and may exacerbate nutrient inputs into Lake Tahoe by allowing the buildup of O horizon material, which serves as a source for high N and P concentrations in runoff water. The purpose of this study was to evaluate the effects of biomass reduction using cut-to-length mechanical harvest followed by chipping and controlled burning on surface runoff volume and water quality. Based on previous findings regarding N and P leaching flux and soil solution concentrations, we hypothesized that controlled burning and/or mechanical harvest with residue chipping does not increase inorganic N, P, and S concentrations in overland flow. Runoff, snowmelt, and rainfall were collected, volume measurements were taken, and samples were analyzed for NO(3)-N, NH(4)-N, PO(4)-P, and SO(4). Runoff volume, season, and year were identified as important parameters influencing overland flow nutrient concentrations and loads. Higher nutrient concentrations were commonly associated with summer rather than winter runoff, but the opposite was true for nutrient loads due to the higher runoff volumes. Treatment (unharvested, harvested, unburned, burned) effect was a strong predictor for discharge loads of NO(3)-N and SO(4) but was a weak predictor for PO(4)-P. Discharge loads of NO(3)-N and SO(4) were greater for the unburned harvested and the burned unharvested treatments than for the unburned, unharvested control sites or the burned and harvested combined treatment. Although mechanical harvest and/or controlled burning had a small initial impact on increased nutrient loading, the effects were minimal compared with background levels. Hence, these management practices may have the potential to improve forest health without the danger of large-magnitude nutrient mobilization and degradation of runoff water quality found with wildfire.

High efficiency photomodulators for millimeter wave and THz radiation.

Photomodulators for mm-wave and THz radiation are an essential component for many imaging and signal processing applications. While a myriad of schemes have been devised to enhance photomodulation by enhancing the light-matter interaction, there has been less focus on the photoconductive materials themselves, which are often the limiting factor. Here, we present an approach to increase the photomodulation efficiency of silicon by orders of magnitude, using post treatment of off-the-shelf silicon wafers. The increase in efficiency removes the need for bulky and costly amplified laser sources, and creates the potential for compact and cost-effective modulators for real-world applications. By passivating the surfaces of long bulk-lifetime silicon wafers with Al2O3, the recombination of the photoexcited carriers at the surfaces is mostly eliminated. This results in vastly longer excess carrier lifetimes (up to ~50 ms), with corresponding increases in photoconductivity. The resulting modulators are highly efficient, with the transmission through them being reduced from ~90% to <10% over a narrow frequency band with a continuous wave excitation intensity of just 10 Wm-2, whilst modulation factors of greater than 80% can be achieved over a broad band with similar intensities. We also discuss the limitations of such long-lifetime modulators for applications where the switching speed or spatial resolution of a modulator may be critical.

A technical, economic, and environmental analysis of energy production from newspaper in Ireland.

The production of newspaper corresponds to 37 kg per person per annum in Ireland. Newspaper becomes a waste product in a short period of time; only 13% of domestic waste paper is recycled (data on newspaper is not available). Four scenarios, which generate energy from newspaper, are analysed. These scenarios may be summarised as follows: lignocellulosic biomass conversion to ethanol (transport fuel); co-digestion with the organic fraction of municipal solid waste and production of CH4-enriched biogas (transport fuel); co-firing with the residue of municipal solid waste in an incinerator; and gasification of newspaper as a sole fuel. Two of the scenarios involve transport fuel production; two involve the production of electricity and heat. Two of the scenarios involve newspaper as the sole ingredient; two involve co- utilisation of newspaper with another waste stream. Assuming no economic market for heat, then only the transport scenarios have the potential to be economic; indeed the biogas scenario is shown to be extremely competitive generating a potential profit of euro 227/t newspaper. A greenhouse-gas analysis indicates that the biogas scenario generated the best net greenhouse-gas savings. However when a market for heat is available, gasification was shown to be most advantageous.

Factors controlling headspace pressure in a manual manometric BMP method can be used to produce a methane output comparable to AMPTS.

The manual manometric biochemical methane potential (mBMP) test uses the increase in pressure to calculate the gas produced. This gas production may be affected by the headspace volume in the incubation bottle and by the overhead pressure measurement and release (OHPMR) frequency. The biogas and methane yields of cellulose, barley, silage and slurry were compared with three incubation bottle headspace volumes (50, 90 and 180ml; constant 70ml total medium) and four OHPMR frequencies (daily, each third day, weekly and solely at the end of experiment). The methane yields of barley, silage and slurry were compared with those from an automated volumetric method (AMPTS). Headspace volume and OHPMR frequency effects on biogas yield were mediated mainly through headspace pressure, with the latter having a negative effect on the biogas yield measured and relatively little effect on methane yield. Two mBMP treatments produced methane yields equivalent to AMPTS.

Wildfire effects on soil nutrients and leaching in a tahoe basin watershed.

A wildfire burned through a previously sampled research site, allowing pre- and post-burn measurements of the forest floor, soils, and soil leaching near Lake Tahoe, Nevada. Fire and post-fire erosion caused large and statistically significant (P < or = 0.05) losses of C, N, P, S, Ca, and Mg from the forest floor. There were no statistically significant effects on mineral soils aside from a decrease in total N in the surface (A11) horizon, an increase in pH in the A11 horizon, and increases in water-extractable SO4(2-) in the A11 and A12 horizons. Burning caused consistent but nonsignificant increases in exchangeable Ca2+ in most horizons, but no consistent or statistically significant effects on exchangeable K+ or Mg2+, or on Bray-, bicarbonate-, or water-extractable P concentrations. Before the burn, there were no significant differences in leaching, but during the first winter after the fire, soil solution concentrations of NH4+, NO3-, ortho-P, and (especially) SO4(2-) were elevated in the burned area, and resin lysimeters showed significant increases in the leaching of NH4+ and mineral N. The leaching losses of mineral N were much smaller than the losses from the forest floor and A11 horizons, however. We conclude that the major short-term effects of wildfire were on leaching whereas the major long-term effect was the loss of N from the forest floor and soil during the fire.

Modelling a demand driven biogas system for production of electricity at peak demand and for production of biomethane at other times.

Four feedstocks were assessed for use in a demand driven biogas system. Biomethane potential (BMP) assays were conducted for grass silage, food waste, Laminaria digitata and dairy cow slurry. Semi-continuous trials were undertaken for all feedstocks, assessing biogas and biomethane production. Three kinetic models of the semi-continuous trials were compared. A first order model most accurately correlated with gas production in the pulse fed semi-continuous system. This model was developed for production of electricity on demand, and biomethane upgrading. The model examined a theoretical grass silage digester that would produce 435kWe in a continuous fed system. Adaptation to demand driven biogas required 187min to produce sufficient methane to run a 2MWe combined heat and power (CHP) unit for 60min. The upgrading system was dispatched 71min following CHP shutdown. Of the biogas produced 21% was used in the CHP and 79% was used in the upgrading system.

Increased loading rates and specific methane yields facilitated by digesting grass silage at thermophilic rather than mesophilic temperatures.

This study was conducted to advance the understanding of thermophilic grass digestion. Late harvested grass silage was fermented at thermophilic conditions at increasing organic loading rates (OLR). Stable digestion took place at an OLR between 3 and 4gVSL(-1)d(-1). This enabled specific methane yields (SMY) as high as 405LCH4kgVS(-1). An accumulation of volatile fatty acids (VFA), accompanied by a gradual deterioration of pH, FOS/TAC (ratio of VFA to alkalinity) arose at an OLR between 5 and 7gVSL(-1)d(-1), yet inhibition did not occur. SMY decreased with reduced retention time ranging between 336 and 358LCH4kgVS(-1) at OLR 7 and 5gVSL(-1)d(-1) respectively. The biomethane efficiencies remained high (92-103%) at corresponding retention times. Comparative results indicated a superior performance with respect to higher loading and SMY as compared with mesophilic conditions.

Assessment of increasing loading rate on two-stage digestion of food waste.

A two-stage food waste digestion system involved a first stage hydrolysis reactor followed by a second stage methanogenic reactor. Organic loading rates (OLR) were increased from 6 to 15 g VS L(-1) d(-1) in the hydrolysis reactor and from 2 to 5 g VS L(-1) d(-1) in the methanogenic reactor. The retention time was fixed at 4 days (hydrolysis reactor) and 12 days (methane reactor). A single-stage digester was subjected to similar loading rates as the methanogenic reactor at 16 days retention. Increased OLR resulted in higher quantities of liquid fermentation products from the first stage hydrolysis reactor. Solubilisation of chemical oxygen demand peaked at 47% at the maximum loading. However, enhanced hydrolysis yields had no significant impact on the specific methane yields. The two-stage system increased methane yields up to 23% and enriched methane content by an average of 14% to levels of 71%.

Influence of temperature and reaction time on the conversion of polystyrene waste to pyrolysis liquid oil.

This paper aims to investigate the effect of temperature and reaction time on the yield and quality of liquid oil produced from a pyrolysis process. Polystyrene (PS) type plastic waste was used as a feedstock in a small pilot scale batch pyrolysis reactor. At 400°C with a reaction time of 75min, the gas yield was 8% by mass, the char yield was 16% by mass, while the liquid oil yield was 76% by mass. Raising the temperature to 450°C increased the gas production to 13% by mass, reduced the char production to 6.2% and increased the liquid oil yield to 80.8% by mass. The optimum temperature and reaction time was found to be 450°C and 75min. The liquid oil at optimum conditions had a dynamic viscosity of 1.77mPas, kinematic viscosity of 1.92cSt, a density of 0.92g/cm3, a pour point of -60°C, a freezing point of -64°C, a flash point of 30.2°C and a high heating value (HHV) of 41.6MJ/kg this is similar to conventional diesel. The gas chromatography with mass spectrophotometry (GC-MS) analysis showed that liquid oil contains mainly styrene (48%), toluene (26%) and ethyl-benzene (21%) compounds.

Prospective detection by Doppler color flow imaging of additional defects in infants with a large ventricular septal defect.

The use of Doppler color flow imaging and axial contrast angiography in the preoperative detection of additional ventricular septal defects (in the setting of a known large defect) were compared in a prospective fashion. One hundred seventy-nine infants with two ventricles (each of at least normal size) and a large, nonrestrictive ventricular septal defect underwent reparative surgery before 2 years of age. The reference standard for the presence of additional defects was intraoperative verification or (in cases in which the surgeon did not visualize any additional defect) subsequent identification at postoperative angiography, postoperative color Doppler examination or reoperation. Only six patients (3%) had additional ventricular septal defects confirmed at the time of repair; an additional five (3%) had defects found only postoperatively. The negative predictive value of Doppler color flow imaging and angiography was 0.95 (168 of 176) and 0.97 (168 of 174), respectively. The sensitivity was 0.27 (3 of 11) and 0.45 (5 of 11), respectively. For certain malformations with a very low prevalence of additional muscular defects (such as perimembranous ventricular septal defect with normally aligned great arteries), a clinical trial of reparative surgery without prior invasive study appears reasonable.

Two-dimensional and Doppler echocardiographic assessment of neonatal arterial repair for transposition of the great arteries.

The arterial switch procedure has become an accepted reparative technique for transposition of the great arteries with or without ventricular septal defect. In this study the accuracy of prospective noninvasive imaging in detecting arterial tract obstruction and the prevalence and severity of arterial valvular regurgitation (as assessed by Doppler ultrasound) were evaluated in survivors of arterial repair. All 53 study patients underwent two-dimensional echocardiographic examination 2 days to 20 months (median 7 months) postoperatively; 43 patients also had pulsed and continuous wave Doppler studies. The accuracy of the noninvasive evaluation of arterial tract obstruction was determined by comparison of Doppler maximal instantaneous gradients with peak to peak gradients at nonsimultaneous catheterization in 26 patients. Twenty-one (81%) of the 26 patients underwent catheterization and successful pulsed and continuous wave Doppler examination of the right heart; 17 (81%) of these 21 had a maximal pressure gradient within 20 mm Hg of the peak to peak gradient obtained at catheterization. Echocardiographic identification of the stenotic site was correct in all eight of the patients in this group requiring reoperation. Twenty-three (88%) of the 26 patients who underwent catheterization had successful Doppler interrogation of the aortic tract; 22 (96%) of these 23 had a maximal instantaneous gradient within 20 mm Hg of the peak to peak catheterization gradient. Fourteen (32%) of 43 patients had mild or moderate pulmonary regurgitation by Doppler study. Three (7%) of the 43 had mild aortic regurgitation.

Accuracy of prospective two-dimensional/Doppler echocardiography in the assessment of reparative surgery.

Between January 1987 and January 1989, all 129 patients (aged 11 days to 25 years, median 39 months) undergoing both an echocardiographic examination and cardiac catheterization after reparative surgery were prospectively included in a study to assess the accuracy of combined two-dimensional and Doppler color flow imaging. The patient diagnoses were transposition of the great arteries (n = 20), tetralogy of Fallot (n = 38), coarctation of the aorta (n = 24), complete atrioventricular (AV) canal (n = 15), atrial septal defect (n = 8), ventricular septal defects (n = 3), pulmonary stenosis (n = 4), aortic stenosis (n = 8) and subaortic stenosis (n = 9). In arterial tract stenosis, there was high correlation between Doppler estimates and catheterization-derived measurements of residual right ventricular outflow tract obstruction in patients after the arterial switch operation for transposition of the great arteries (r = 0.95) as well as in patients after corrective repair of tetralogy of Fallot (r = 0.84). In semilunar/AV valve regurgitation, graded as none, mild, moderate or severe, echocardiographic estimates correlated exactly with angiographic grading in 84% and differed by one angiographic grade in the other 16%. In residual left to right shunting, no hemodynamically significant shunt was missed by echocardiography. For residual shunts at the ventricular level (n = 32), addition of Doppler color flow imaging improved the sensitivity (from 63% to 94%) and the negative predictive value (from 88% to 98%). In elevated right ventricular pressure, Doppler-derived right ventricular-right atrial pressure estimates in 24 patients correlated well with catheterization measurements (r = 0.93). Combined two-dimensional and Doppler color flow echocardiography was highly accurate in the prospective evaluation of these four types of postoperative residual.

Hypoplastic left heart syndrome: hemodynamic and angiographic assessment after initial reconstructive surgery and relevance to modified Fontan procedure.

After undergoing initial reconstructive surgery for hypoplastic left heart syndrome performed between August 1985 and March 1989, 59 patients (age range 3 to 27 months, mean 13.8 +/- 4.5) underwent elective cardiac catheterization in anticipation of a modified Fontan procedure. Five important hemodynamic and anatomic features considered to be components of successful reconstructive surgery were specifically addressed. 1) Interatrial communication: Only two patients had a measured pressure difference of greater than 4 mm Hg across the atrial septum. 2) Tricuspid valve function: Angiography demonstrated significant tricuspid valve regurgitation in only five patients (moderate in two and severe in three). 3) Aortic arch: Pressure tracings from the right ventricle to the descending aorta revealed a gradient greater than 25 mm Hg in only two patients. 4) Pulmonary vasculature: Ten patients had a calculated pulmonary vascular resistance greater than 4 U.m2; 51 (86%) of the 59 patients had no evidence of distortion (stenosis or hypoplasia) of either the left or the right pulmonary artery. 5) Right ventricular function: Five patients had an end-diastolic pressure in the right ventricle greater than 12 mm Hg and two patients had qualitative assessment of decreased ventricular function. Comparison of catheterization data between survivors and nonsurvivors of the subsequent modified Fontan procedure showed that only significant tricuspid regurgitation is a possible predictor of poor outcome. After first stage reconstructive surgery for hypoplastic left heart syndrome, most survivors have favorable anatomy and hemodynamics at follow-up cardiac catheterization for a subsequent Fontan procedure.

Investigation of effect of particle size and rumen fluid addition on specific methane yields of high lignocellulose grass silage.

This work examines the digestion of advanced growth stage grass silage. Two variables were investigated: particle size (greater than 3 cm and less than 1cm) and rumen fluid addition. Batch studies indicated particle size and rumen fluid addition had little effect on specific methane yields (SMYs). In continuous digestion of 3 cm silage the SMY was 342 and 343 L CH4 kg(-1)VS, respectively, with and without rumen fluid addition. However, digester operation was significantly affected through silage floating on the liquor surface and its entanglement in the mixing system. Digestion of 1cm silage with no rumen fluid addition struggled; volatile fatty acid concentrations rose and SMYs dropped. The best case was 1cm silage with rumen fluid addition, offering higher SMYs of 371 L CH4 kg(-1)VS and stable operation throughout. Thus, physical and biological treatments benefited continuous digestion of high fibre grass silage.

Nocturnal enuresis secondary to heart block: report of cure by cardiac pacemaker implantation.

This report describes an unusual case of secondary nocturnal enuresis presumptively secondary to progressive bradycardia from complete heart block. Congenital complete heart block occurs in approximately 1 of 22,000 livebirths and is typically associated with structural congenital heart disease or maternal collagen vascular diseases. It can be entirely asymptomatic during infancy and childhood, depending in part on the escape rate and rhythm and other hemodynamic variables. The case described above was not diagnosed until the patient coincidentally underwent cardiac monitoring. The picture was confusing initially, as a tricyclic antidepressant medication had been ingested. Heart block is one of the known cardiovascular effects of tricyclic antidepressant overdose. However, the conduction disturbance should have resolved as the drug was excreted from the body. As children with congenital complete heart block get older, the ventricular escape rate typically decreases. In addition, as activity increases with age, more demand is placed for cardiac output. The resting end-diastolic volume is increased to elevate stroke volume in compensation for lower heart rate. As the escape rate decreases and the metabolic demand increases, patients with congenital complete heart block then may begin to develop symptoms. Typical symptoms in children include dizziness, Stokes-Adams syncopal attacks, fatigue, daytime somnolence, and other somatic complaints. Bedwetting has not been reported as an initial symptom, but in this case is likely secondary to the excessive somnolence and difficulty with arousal.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacokinetics of injectable allopurinol in newborns with the hypoplastic left heart syndrome.

OBJECTIVE: The purpose of this investigation was to determine the pharmacokinetic disposition of intravenous allopurinol and its metabolite oxypurinol in neonates with the hypoplastic left heart syndrome (HLHS) and to evaluate the subsequent degree of xanthine oxidase inhibition using serum uric acid as a marker. METHODS: Pharmacokinetic data were evaluated in 12 stable preoperative neonates with HLHS after a single intravenous allopurinol administration of 5 mg/kg or 10 mg/kg. Pharmacokinetic parameters were determined for elimination half-life, clearance, volume of distribution, and mean residence time. Xanthine oxidase inhibition, measured by serum uric acid reduction, was also measured. RESULTS: Pharmacokinetic parameters revealed no statistically significant differences between a 5-mg/kg and 10-mg/kg dose of intravenous allopurinol on elimination half-life, clearance, volume of distribution, and mean residence time. Mean serum uric acid levels were significantly reduced from baseline by 39.99 and 42.94%, respectively, in the 5- and 10-mg/kg treatment groups. DISCUSSION: The enzyme xanthine oxidase plays a key biochemical role in the generation of toxic oxygen-derived free radicals during ischemia-reperfusion conditions. Allopurinol and its active metabolite oxypurinol inhibit xanthine oxidase, and significantly reduce the conversion of hypoxanthine to xanthine and xanthine to uric acid. Cell injury may be caused by toxic oxygen free radicals produced by ischemia-reperfusion injury such as could occur during the repair of HLHS under hypothermic total circulatory arrest. We hypothesize that allopurinol may provide protection from cellular injury in this clinical context.

Intraoperative balloon angioplasty of aortic coarctation in infants with hypoplastic left heart syndrome.

During a 1-year period, 9 children, aged 3 to 18 months, underwent intraoperative transluminal balloon angioplasty of coarctation of the aorta. Each patient had previously undergone palliative surgery for hypoplastic left heart syndrome. In 1 patient the angioplasty catheter was introduced into the ascending aorta during surgery to correct intracardiac defects. In the other 8 infants the catheters were inserted directly into the descending thoracic aorta via thoracotomy because the catheter size precluded percutaneous insertion into the femoral artery. In each case, after measuring the systolic pressure gradient across the coarctation, the angioplasty catheters were advanced over the guidewire across the coarctation site. The balloons were then inflated 2 to 3 times with an internal pressure of 3 to 6 atm. After the dilation sequence the angioplasty catheters were removed and the pressures were again measured above and below the coarctation. Preoperative gradients across the coarctation site ranged from 26 to 85 mm Hg (mean 45). Immediately after the procedure the gradient decreased in each case, ranging from 0 to 12 mm Hg (mean 4.3). There were no signs of disruption of the aortic wall. Relief of the pressure gradient persisted in the 7 patients who underwent follow-up cardiac catheterization after the procedure. The patients have been followed for as long as 18 months after the procedure and none has shown physical or echocardiographic evidence of recurrent aortic obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Postmortem echocardiography and tomographic anatomy of hypoplastic left heart syndrome after palliative surgery.

A study was undertaken to improve the understanding of the 3-dimensional (3-D) topology of a complex surgical reconstruction. The pathologic anatomy was investigated by first fixing postmortem heart specimens in such a way as to preserve the 3-D relations. Next, a technique for postmortem 2-D echocardiography was developed to aid in selection of tomographic planes for sectioning the specimens. Subsequent adjustment of planes of section was made to better show particular facets of the anatomy. The material for this investigation was drawn from cases of hypoplastic left heart syndrome after surgical palliation by the Norwood procedure. Three potential hemodynamic sequelae--restrictive inter atrial communication, aortic obstruction at any level and distortion of the pulmonary artery confluence--served as the anatomic focus for this study. Careful preservation of 3-D topology and postmortem 2-D echocardiographic imaging coupled with tomographic sectioning of specimens led to development of new, clinically relevant echocardiographic views for imaging specific atrial septal and aortic arch anomalies. These techniques offer insight into the spectrum of anatomic sequelae of this type of surgery and may be applied to echocardiographic imaging of patients and refinement of surgical technique for other forms of complex congenital heart disease.

Transposition of the great arteries with posterior aorta. Anatomic repair.

An uncommon but historically important form of transposition of the great arteries (S,D,D) was originally recognized in 1971. The unusual features of an aorta that is posterior and to the right of the pulmonary artery, a hypoplastic subaortic conus, and a well-developed subpulmonary conus influenced the evolution of the contemporary classification of conotruncal abnormalities and concepts of their development. Presented in this report is the case of a patient with transposition of the great arteries (S,D,D) and posterior aorta treated by an arterial switch operation. The unusual orientation of the great arteries did not preclude coronary transplantation or a satisfactory pulmonary arterial anastomosis. Moreover, the ventricular septal defect, which is characteristic of this atypical form of transposition of the great arteries, was most accessible for closure through the native aortic valve.