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Papers by Peter McCann

Research paper thumbnail of S-Adenosylmethionine and methylation

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1996

S-Adenosylmethionine (AdoMet or SAM) plays a pivotal role as a methyl donor in a myriad of biolog... more S-Adenosylmethionine (AdoMet or SAM) plays a pivotal role as a methyl donor in a myriad of biological and biochemical events. Although it has been claimed that AdoMet itself has therapeutic benefits, it remains to be established whether it can be taken up intact by cells. S-Adenosylhomocysteine (AdoHcy), formed after donation of the methyl group of AdoMet to a methyl acceptor, is then hydrolyzed to adenosine and homocysteine by AdoHcy hydrolase. This enzyme has long been a target for inhibition as its blockade can affect methylation of phospholipids, proteins, DNA, RNA, and other small molecules. Protein carboxymethylation may be involved in repair functions of aging proteins, and heat shock proteins are methylated in response to stress. Bacterial chemotaxis involves carboxymethylation and demethylation in receptor-transducer proteins, although a similar role in mammalian cells is unclear. The precise role of phospholipid methylation remains open. DNA methylation is related to mamma...

Research paper thumbnail of Molecular beam epitaxy of PbSrSe and PbSe/PbSrSe multiple quantum well structures for use in midinfrared light emitting devices

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2000

PbSrSe layers and PbSe/PbSrSe multiple quantum well ͑MQW͒ structures have been grown on BaF 2 (11... more PbSrSe layers and PbSe/PbSrSe multiple quantum well ͑MQW͒ structures have been grown on BaF 2 (111) substrates by molecular beam epitaxy. The lattice constant of the PbSrSe alloy was determined by x-ray diffraction, and both the refractive index and absorption edge of the PbSrSe alloy with Sr composition up to 0.23 were obtained from Fourier transform infrared transmission spectra at room temperature. MQW structures exhibit strong photoluminescence ͑PL͒ in the 3-5 m wavelength range at room temperature. The PL intensity decreases monotonically with increasing temperature below 230 K.

Research paper thumbnail of Criteria for Evaluating AAA Protocols for Network Access

... requirements. We would also like to thank the members of the AAA evaluation team, Mike St. Jo... more ... requirements. We would also like to thank the members of the AAA evaluation team, Mike St. Johns, Barney Wolf, Mark Stevens, David Nelson, Dave Mitton, Basavaraj Patil and Stuart Barkley for their thorough review of this document. 7 ...

Research paper thumbnail of Molecular beam epitaxial growth of Eu-doped CaF2 and BaF2 on Si

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1996

The growth of Eu-doped CaF 2 and BaF 2 thin films on Si͑100͒, ͑110͒, and ͑111͒ substrates has bee... more The growth of Eu-doped CaF 2 and BaF 2 thin films on Si͑100͒, ͑110͒, and ͑111͒ substrates has been realized by molecular beam epitaxy using elemental Eu evaporation. Very bright blue emissions from Eu-doped CaF 2 and yellow emissions from Eu-doped BaF 2 were obtained in the wavelength range of 400-850 nm at 10 K. Depending on the Si substrate orientation, the zero-phonon line of Eu 2ϩ in the CaF 2 thin films was shifted by different amounts relative to that of bulk CaF 2 due to residual strain in these epilayers.

Research paper thumbnail of Trophic Responses of the Pancreas Differ in Aging Rats

Pancreas, 1988

We previously have shown that the response of pancreatic lipase and amylase to changes in diet co... more We previously have shown that the response of pancreatic lipase and amylase to changes in diet composition is altered in senescent rats. The present study was designed to determine if the trophic response to a defined gastrointestinal peptide stimulus differed in 3-month (young) and 27-month (aging) Fischer rats. Caerulein-secretin, administered every 8 h for 7 days, induced pancreatic hypertrophy and hyperplasia as judged by increases in pancreatic weight, protein, and DNA content in both groups. A significant increase also occurred in the content of trypsinogen, amylase, lipase and the polyamines, putrescine, spermine, and spermidine. To quantify differences in the trophic response between young and aging rats, the ratios of data in the treated animals relative to that observed in controls were determined. Pancreatic weight, protein content, and protein DNA ratio increased significantly more in young than in aging treated animals. DNA also increased more but did not reach significance. Pancreatic trypsinogen and lipase content increased significantly more in younger animals, whereas amylase responses were not different between the two groups. Stimulation of pancreatic putrescine and spermidine was also greater in young than in aged animals. We conclude that trophic responses of the pancreas are altered in senescent rats.

Research paper thumbnail of Polyamine Metabolism in Acanthamoeba : Polyamine Content and Synthesis of Ornithine, Putrescine, and Diaminopropane1

The Journal of Protozoology, 1987

Research paper thumbnail of Polyamine Depletion Following Exposure to DL-α-Difluoromethylornithine Both In Vivo and In Vitro Initiates Morphological Alterations and Mitochondrial Activation in a Monomorphic Strain ofTrypanosoma brucei brucei

The Journal of Protozoology, 1986

DLa-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase ... more DLa-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase (O m , rapidly depletes cells of intracellular putrexine. When administered to animals and humans, DFMO cures acute infections of trypanosomiasis. In order to determine if the mechanism of drug action is related to initiation of transformation and biochemical alterations subsequent to polyamine depletion, trypanosome morphology and mitochondria1 activation were studied in a monomorphic strain of Trypanosoma brucei brucei. Exposure of trypanosomes to DFMO in vivo in infected rodents or in vitro in culture resulted in a depletion of intracellular putrescine and a cessation of cell division without specific cytotoxicity. Thesc events were followed by a transformation of the long slender bloodstream form to a short stumpy form via an intermediate morphology. Putrtscine, the product of the ODC reaction, abrogates this effect. When introduced into SDM-79 medium, the intermediate form is capable of huther transformation to an "insect" procyclic Vypomastigote whereas the long slender form and short stumpy form are not. Short stumpy forms are incapable of binary fission and have lost their infectivity for the vertebrate host. In addition, the mitochondrial marker enzyme, NAD diaphorase, was found only in the short stumpy and intermediate forms. We hypothesize that the short stumpy phenotype may not be a viable stage in the natural transformation of the trypanosome from its mammalian host to the insect vector. RANSFORMATION from bloodstream to procyclic try-G l m N ET AL.-POLYAMINE DEPLETION AND TRYPANOSOMU TRANSFORMATION 7.-198 1. Stimulating effect of citrate and cis-aconitate on the transformation of T. brucei bloodstream forms to procyclic forms in vitro. Z.

Research paper thumbnail of LASERS, OPTICS, AND OPTOELECTRONICS 3673 Detection of single photons using a field-effect transistor gated by a layer of quantum dots

We demonstrate that the conductance of a field-effect transistor ͑FET͒ gated by a layer of nanome... more We demonstrate that the conductance of a field-effect transistor ͑FET͒ gated by a layer of nanometer-sized quantum dots is sensitive to the absorption of single photons. Rather than relying upon an avalanche process, as in conventional semiconductor single-photon detectors, the gain in this device derives from the fact that the conductivity of the FET channel is very sensitive to the photoexcited charge trapped in the dots. This phenomenon may allow a type of three-terminal single-photon detector to be developed based upon FET technology.

Research paper thumbnail of We Move into Distinguished Company

Spatial Economic Analysis, 2011

... The first paper in the current issue is by Daniel Heuermann and entitled 'Hu... more ... The first paper in the current issue is by Daniel Heuermann and entitled 'Human Capital Externalities in Western Germany'. ... The paper by Solène Larue, Jens Abildtrup & Bertrand Schmitt entitled 'Positive and Negative Agglomeration Externalities: Arbitration in the Pig Sector ...

Research paper thumbnail of Efficacy of combinations of difluoromethylornithine and bleomycin in a mouse model of central nervous system African trypanosomiasis

Proceedings of the National Academy of Sciences, 1983

DL-alpha-Difluoromethylornithine, a polyamine biosynthesis inhibitor, and bleomycin, a currently ... more DL-alpha-Difluoromethylornithine, a polyamine biosynthesis inhibitor, and bleomycin, a currently used antineoplastic agent, have each previously been shown to be curative for acute short-term infections of mice with Trypanosoma brucei brucei, an African trypanosome closely related to those that cause the human disease African sleeping sickness. These agents were tested singly and in combination in a previously described mouse model of sleeping sickness with demonstrable brain involvement. The original model is extended by using two additional strains of outbred mice and by demonstrating that melarsoprol, an arsenical and currently the only drug used for human African trypanosomiasis involving the brain, was also curative for these brain infections. Neither difluoromethylornithine nor bleomycin alone was curative for the brain infections; however, many combinations of the two drugs were found to be 100% curative with no evidence of immediate toxicity.

Research paper thumbnail of Simultaneous NO and CO_2 measurement in human breath with a single IV–VI mid-infrared laser

Optics Letters, 2002

A tunable diode laser absorption spectroscopy (TDLAS) system equipped with a IV-VI mid-IR laser o... more A tunable diode laser absorption spectroscopy (TDLAS) system equipped with a IV-VI mid-IR laser operating near 5.2 mm was used to measure exhaled nitric oxide (eNO) and carbon dioxide ͑CO 2 ͒ simultaneously in human breath over a single exhalation. Breath was sampled in real time, and eNO levels were measured from seven volunteers, two steroid-naive asthmatics and five nonasthmatics. Measured CO 2 levels were used as an internal standard to verify correct breath collection and calculate eNO values. Calculated eNO concentrations agreed well with reported values for asthmatic and nonasthmatic individuals.

Research paper thumbnail of Regulatory interrelations between GABA and polyamines. II. Effect of GABA on ornithine decarboxylase and putrescine levels in cell culture

Neurochemical Research, 1979

Elevation of brain GABA levels by GABA-T inhibition is accompanied by a decrease of S-adenosylmet... more Elevation of brain GABA levels by GABA-T inhibition is accompanied by a decrease of S-adenosylmethionine decarboxylase activity. This is followed by an increase of ornithine decarboxylase activity and a severalfold increase of brain putrescine levels. Spermidine and spermine levels are not significantly affected under these conditions. These unexpected findings support a regulatory interaction between GABA and polyamine metabolism.

Research paper thumbnail of The role of graphite boat design in liquid phase epitaxial growth of PbSe0.78Te0.22 on BaF2

Journal of Crystal Growth, 1994

Abstract Two different sliding substrate graphite boats were designed and fabricated for liquid p... more Abstract Two different sliding substrate graphite boats were designed and fabricated for liquid phase epitaxial (LPE) growth of PbSe0.78Te0.22 on BaF2 substrates. Layer morphologies were observed using optical and scanning electron microscopy. The first boat did not yield smooth and continuous epitaxial layers even though a number of growth variations were tried. The second boat, however, consistently produced high quality epitaxial layers of PbSe0.78Te0.22 on {100} BaF2 substrates. Differences in the way the graphite boat traps growth solution vapors over the substrate prior to growth are believed to be responsible for the dramatic differences in these LPE growth morphologies. We suspect that formation of a barium-chalcogenide reaction product on the BaF2 substrate surface prior to growth is essential for obtaining good epitaxial layers and that trapping of growth solution vapors over the substrate prior to growth allows better control of this epitaxy-enabling substrate surface reaction.

Research paper thumbnail of MBE growth of PbSe/CaF2/Si(1 1 1) heterostructures

Journal of Crystal Growth, 1997

... 1062 PJ McCann et al. /Journal of Crystal Growth 175/176 (1997) 1057-1062 References [1] H. Z... more ... 1062 PJ McCann et al. /Journal of Crystal Growth 175/176 (1997) 1057-1062 References [1] H. Zogg, S. Blunier, A. Fach, C. Maissen, P. Miller, S. Teodoropol, V. Meyer, G. Kostorz, A. Dommann and T. Richmond, Phys. Rev. B 50 (1994) 10801. ...

Research paper thumbnail of Initial growth of CaF2 and on Si(110) during molecular beam epitaxy

Journal of Crystal Growth, 1996

Reflection high-energy electron diffraction, scanning electron microscopy, atomic force microscop... more Reflection high-energy electron diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy were used to study the initial growth of CaF 2 on Si(110) and BaF 2 on CaF2/Si(ll0) by molecular beam epitaxy. Growth of CaF2/Si(110) initially proceeds two-dimensionally with a (1 x 3) surface reconstruction. The observation of core-level and Auger energy shifts for Ca and F peaks at low coverage suggests the presence of both Ca-Si and F-Si bonds at the CaF2/Si(110) interface. For higher coverages, [ll0]-oriented ridges form and growth proceeds via the stacking of (111) and (111) planes on the sidewalls of the ridges. This ridged and grooved surface morphology is believed to result from the favorable energetics of exposing low-energy {111} facets and the formation of twinned crystallographic domains. Subsequent deposition of BaF 2 on CaFJSi(110) begins with incommensurate growth and nucleation on top of the CaF 2 ridges. Growth then continues on the sidewalls, resulting in recovery of the ridged and grooved morphology at higher coverages. Intermixing between the fluorides is believed to be negligible near the BaF2/CaF2(110) interface.

Research paper thumbnail of Large mismatch heteroepitaxy of InSb on Si(1 1 1) substrates using CaF2 buffer layers

Journal of Crystal Growth, 1997

The results of initial attempts to grow large lattice-mismatched InSbSi structures using CaF2 buf... more The results of initial attempts to grow large lattice-mismatched InSbSi structures using CaF2 buffer layers are reported. Substrate temperatures in the range of 300–400°C were used and MBE growth was initiated by opening the In and Sb shutters simultaneously, producing In-terminated InSb(1 1 1)-A surfaces on Si(1 1 1) substrates. High structural quality was confirmed by reflection high-energy electron diffraction,

Research paper thumbnail of Two distinct mechanisms for ornithine decarboxylase regulation by polyamines in rat hepatoma cells

Journal of Cellular Physiology, 1979

Exogenous diamines and polyamines added to rat hepatoma (HTC) cells in culture rapidly decrease o... more Exogenous diamines and polyamines added to rat hepatoma (HTC) cells in culture rapidly decrease ornithine decarboxylase (ODC) activity. Previous evidence has suggested that these amines set either at the level of blocking new enzyme synthesis or by the induction of a non-competitive protein inhibitor, termed antizyme, which complexes with ODC to form an inactive complex. Wth the use of HMOA cells, a recently cloned rat hepatoma cell line that has a greatly stabilized ODC, it has been possible to demonstrate that 10(-5) M of exogenous putrescine blocks the increase in ODC activity, but unlike in the parent HTC cell line, without induction of the antizyme or formation of any inactive ODC-antizyme complex. However, complete blockade of ODC at 10(-2) M putrescine is effected by induction of antizyme and formation of the ODC-antizyme complex, as now evidenced by the isolation of the active enzyme and antizyme components after Sephadex column chromatography in the presence of 250 mM NaCl. These findings indicate clearly that two polyamine-regulatory mechanisms for ODC exist and are separable in this cell line.

Research paper thumbnail of Molecular beam epitaxy of InSb on Si substrates using fluoride buffer layers

Journal of Applied Physics, 1997

The molecular beam epitaxy of InSb/Si structures was accomplished using group IIa fluoride buffer... more The molecular beam epitaxy of InSb/Si structures was accomplished using group IIa fluoride buffer layers. InSb growth was initiated by opening the In and Sb shutters simultaneously at substrate temperatures between 300°C and 400°C, producing In-terminated InSb͑111͒-A surfaces on CaF 2 /Si͑111͒ substrates. Reflection high-energy electron diffraction, electron channeling, and high resolution x-ray diffraction measurements indicated that the InSb layers were of good crystalline quality. Electron mobilities at room temperature were as high as 65 000 cm 2 /V s for an 8-m-thick InSb layer grown on CaF 2 /Si͑111͒. On CaF 2 /Si͑001͒ substrates, the InSb layers grew in the ͑111͒ orientation with two domains 90°apart. These InSb layers and ones grown on BaF 2 /CaF 2 /Si͑111͒ substrates exhibited inferior electrical and structural properties compared to structures grown on CaF 2 /Si͑111͒ substrates.

Research paper thumbnail of Midinfrared photoluminescence from IV–VI semiconductors grown on silicon

Journal of Applied Physics, 2001

Research paper thumbnail of Hypertrophic cardiomyopathy, ten years’ experience

Irish Journal of Medical Science, 1987

Summary A RETROSPECTIVE study was performed of patients who were diagnosed as having hypertrophi... more Summary A RETROSPECTIVE study was performed of patients who were diagnosed as having hypertrophic cardiomyopathy by left ventricular angiography in order to assess the incidence, the clinical and haemodynamic features and prognosis of this condition. The records of the cardiac catheter laboratory were reviewed for the ten year period from May 1975 to June 1985 to obtain haemodynamic and angiographic findings at diagnosis. Clinical features were obtained from the hospital records. To assess the prognosis, the clinical status of all patients, where possible, was reviewed in June 1985. During the ten year period 64 patients were diagnosed as having hypertrophic cardiomyopathy which was approximately 1% of all cardiac catheterizations. At diagnosis 22% of patients were asymptomatic and the commonest symptoms were chest pain or dyspnoea. Only 12% of patients had a family history of hypertrophic cardiomyopathy or sudden death. A systolic murmur was the most common abnormality on physical examination. Although evidence of left ventricular hypertrophy demonstrated by ECG was very common, only 13% of patients have evidence of an intraventricular pressure gradient. Of the 52 patients (81% of total) available for follow-up in June 1985, seven (13%) had died since diagnosis, all suddenly. The patients who died were significantly younger than the survivors and evidence of left ventricular hypertrophy was also more common in those who died. Our study confirms that although hypertrophie cardiomyopathy is uncommon, it carries a definite mortality. Thus definitive diagnosis of this condition is important especially as there is now evidence to suggest that the prognosis may be improved by treatment with amiodarone.

Research paper thumbnail of S-Adenosylmethionine and methylation

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1996

S-Adenosylmethionine (AdoMet or SAM) plays a pivotal role as a methyl donor in a myriad of biolog... more S-Adenosylmethionine (AdoMet or SAM) plays a pivotal role as a methyl donor in a myriad of biological and biochemical events. Although it has been claimed that AdoMet itself has therapeutic benefits, it remains to be established whether it can be taken up intact by cells. S-Adenosylhomocysteine (AdoHcy), formed after donation of the methyl group of AdoMet to a methyl acceptor, is then hydrolyzed to adenosine and homocysteine by AdoHcy hydrolase. This enzyme has long been a target for inhibition as its blockade can affect methylation of phospholipids, proteins, DNA, RNA, and other small molecules. Protein carboxymethylation may be involved in repair functions of aging proteins, and heat shock proteins are methylated in response to stress. Bacterial chemotaxis involves carboxymethylation and demethylation in receptor-transducer proteins, although a similar role in mammalian cells is unclear. The precise role of phospholipid methylation remains open. DNA methylation is related to mamma...

Research paper thumbnail of Molecular beam epitaxy of PbSrSe and PbSe/PbSrSe multiple quantum well structures for use in midinfrared light emitting devices

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2000

PbSrSe layers and PbSe/PbSrSe multiple quantum well ͑MQW͒ structures have been grown on BaF 2 (11... more PbSrSe layers and PbSe/PbSrSe multiple quantum well ͑MQW͒ structures have been grown on BaF 2 (111) substrates by molecular beam epitaxy. The lattice constant of the PbSrSe alloy was determined by x-ray diffraction, and both the refractive index and absorption edge of the PbSrSe alloy with Sr composition up to 0.23 were obtained from Fourier transform infrared transmission spectra at room temperature. MQW structures exhibit strong photoluminescence ͑PL͒ in the 3-5 m wavelength range at room temperature. The PL intensity decreases monotonically with increasing temperature below 230 K.

Research paper thumbnail of Criteria for Evaluating AAA Protocols for Network Access

... requirements. We would also like to thank the members of the AAA evaluation team, Mike St. Jo... more ... requirements. We would also like to thank the members of the AAA evaluation team, Mike St. Johns, Barney Wolf, Mark Stevens, David Nelson, Dave Mitton, Basavaraj Patil and Stuart Barkley for their thorough review of this document. 7 ...

Research paper thumbnail of Molecular beam epitaxial growth of Eu-doped CaF2 and BaF2 on Si

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1996

The growth of Eu-doped CaF 2 and BaF 2 thin films on Si͑100͒, ͑110͒, and ͑111͒ substrates has bee... more The growth of Eu-doped CaF 2 and BaF 2 thin films on Si͑100͒, ͑110͒, and ͑111͒ substrates has been realized by molecular beam epitaxy using elemental Eu evaporation. Very bright blue emissions from Eu-doped CaF 2 and yellow emissions from Eu-doped BaF 2 were obtained in the wavelength range of 400-850 nm at 10 K. Depending on the Si substrate orientation, the zero-phonon line of Eu 2ϩ in the CaF 2 thin films was shifted by different amounts relative to that of bulk CaF 2 due to residual strain in these epilayers.

Research paper thumbnail of Trophic Responses of the Pancreas Differ in Aging Rats

Pancreas, 1988

We previously have shown that the response of pancreatic lipase and amylase to changes in diet co... more We previously have shown that the response of pancreatic lipase and amylase to changes in diet composition is altered in senescent rats. The present study was designed to determine if the trophic response to a defined gastrointestinal peptide stimulus differed in 3-month (young) and 27-month (aging) Fischer rats. Caerulein-secretin, administered every 8 h for 7 days, induced pancreatic hypertrophy and hyperplasia as judged by increases in pancreatic weight, protein, and DNA content in both groups. A significant increase also occurred in the content of trypsinogen, amylase, lipase and the polyamines, putrescine, spermine, and spermidine. To quantify differences in the trophic response between young and aging rats, the ratios of data in the treated animals relative to that observed in controls were determined. Pancreatic weight, protein content, and protein DNA ratio increased significantly more in young than in aging treated animals. DNA also increased more but did not reach significance. Pancreatic trypsinogen and lipase content increased significantly more in younger animals, whereas amylase responses were not different between the two groups. Stimulation of pancreatic putrescine and spermidine was also greater in young than in aged animals. We conclude that trophic responses of the pancreas are altered in senescent rats.

Research paper thumbnail of Polyamine Metabolism in Acanthamoeba : Polyamine Content and Synthesis of Ornithine, Putrescine, and Diaminopropane1

The Journal of Protozoology, 1987

Research paper thumbnail of Polyamine Depletion Following Exposure to DL-α-Difluoromethylornithine Both In Vivo and In Vitro Initiates Morphological Alterations and Mitochondrial Activation in a Monomorphic Strain ofTrypanosoma brucei brucei

The Journal of Protozoology, 1986

DLa-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase ... more DLa-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ornithine decarboxylase (O m , rapidly depletes cells of intracellular putrexine. When administered to animals and humans, DFMO cures acute infections of trypanosomiasis. In order to determine if the mechanism of drug action is related to initiation of transformation and biochemical alterations subsequent to polyamine depletion, trypanosome morphology and mitochondria1 activation were studied in a monomorphic strain of Trypanosoma brucei brucei. Exposure of trypanosomes to DFMO in vivo in infected rodents or in vitro in culture resulted in a depletion of intracellular putrescine and a cessation of cell division without specific cytotoxicity. Thesc events were followed by a transformation of the long slender bloodstream form to a short stumpy form via an intermediate morphology. Putrtscine, the product of the ODC reaction, abrogates this effect. When introduced into SDM-79 medium, the intermediate form is capable of huther transformation to an "insect" procyclic Vypomastigote whereas the long slender form and short stumpy form are not. Short stumpy forms are incapable of binary fission and have lost their infectivity for the vertebrate host. In addition, the mitochondrial marker enzyme, NAD diaphorase, was found only in the short stumpy and intermediate forms. We hypothesize that the short stumpy phenotype may not be a viable stage in the natural transformation of the trypanosome from its mammalian host to the insect vector. RANSFORMATION from bloodstream to procyclic try-G l m N ET AL.-POLYAMINE DEPLETION AND TRYPANOSOMU TRANSFORMATION 7.-198 1. Stimulating effect of citrate and cis-aconitate on the transformation of T. brucei bloodstream forms to procyclic forms in vitro. Z.

Research paper thumbnail of LASERS, OPTICS, AND OPTOELECTRONICS 3673 Detection of single photons using a field-effect transistor gated by a layer of quantum dots

We demonstrate that the conductance of a field-effect transistor ͑FET͒ gated by a layer of nanome... more We demonstrate that the conductance of a field-effect transistor ͑FET͒ gated by a layer of nanometer-sized quantum dots is sensitive to the absorption of single photons. Rather than relying upon an avalanche process, as in conventional semiconductor single-photon detectors, the gain in this device derives from the fact that the conductivity of the FET channel is very sensitive to the photoexcited charge trapped in the dots. This phenomenon may allow a type of three-terminal single-photon detector to be developed based upon FET technology.

Research paper thumbnail of We Move into Distinguished Company

Spatial Economic Analysis, 2011

... The first paper in the current issue is by Daniel Heuermann and entitled 'Hu... more ... The first paper in the current issue is by Daniel Heuermann and entitled 'Human Capital Externalities in Western Germany'. ... The paper by Solène Larue, Jens Abildtrup & Bertrand Schmitt entitled 'Positive and Negative Agglomeration Externalities: Arbitration in the Pig Sector ...

Research paper thumbnail of Efficacy of combinations of difluoromethylornithine and bleomycin in a mouse model of central nervous system African trypanosomiasis

Proceedings of the National Academy of Sciences, 1983

DL-alpha-Difluoromethylornithine, a polyamine biosynthesis inhibitor, and bleomycin, a currently ... more DL-alpha-Difluoromethylornithine, a polyamine biosynthesis inhibitor, and bleomycin, a currently used antineoplastic agent, have each previously been shown to be curative for acute short-term infections of mice with Trypanosoma brucei brucei, an African trypanosome closely related to those that cause the human disease African sleeping sickness. These agents were tested singly and in combination in a previously described mouse model of sleeping sickness with demonstrable brain involvement. The original model is extended by using two additional strains of outbred mice and by demonstrating that melarsoprol, an arsenical and currently the only drug used for human African trypanosomiasis involving the brain, was also curative for these brain infections. Neither difluoromethylornithine nor bleomycin alone was curative for the brain infections; however, many combinations of the two drugs were found to be 100% curative with no evidence of immediate toxicity.

Research paper thumbnail of Simultaneous NO and CO_2 measurement in human breath with a single IV–VI mid-infrared laser

Optics Letters, 2002

A tunable diode laser absorption spectroscopy (TDLAS) system equipped with a IV-VI mid-IR laser o... more A tunable diode laser absorption spectroscopy (TDLAS) system equipped with a IV-VI mid-IR laser operating near 5.2 mm was used to measure exhaled nitric oxide (eNO) and carbon dioxide ͑CO 2 ͒ simultaneously in human breath over a single exhalation. Breath was sampled in real time, and eNO levels were measured from seven volunteers, two steroid-naive asthmatics and five nonasthmatics. Measured CO 2 levels were used as an internal standard to verify correct breath collection and calculate eNO values. Calculated eNO concentrations agreed well with reported values for asthmatic and nonasthmatic individuals.

Research paper thumbnail of Regulatory interrelations between GABA and polyamines. II. Effect of GABA on ornithine decarboxylase and putrescine levels in cell culture

Neurochemical Research, 1979

Elevation of brain GABA levels by GABA-T inhibition is accompanied by a decrease of S-adenosylmet... more Elevation of brain GABA levels by GABA-T inhibition is accompanied by a decrease of S-adenosylmethionine decarboxylase activity. This is followed by an increase of ornithine decarboxylase activity and a severalfold increase of brain putrescine levels. Spermidine and spermine levels are not significantly affected under these conditions. These unexpected findings support a regulatory interaction between GABA and polyamine metabolism.

Research paper thumbnail of The role of graphite boat design in liquid phase epitaxial growth of PbSe0.78Te0.22 on BaF2

Journal of Crystal Growth, 1994

Abstract Two different sliding substrate graphite boats were designed and fabricated for liquid p... more Abstract Two different sliding substrate graphite boats were designed and fabricated for liquid phase epitaxial (LPE) growth of PbSe0.78Te0.22 on BaF2 substrates. Layer morphologies were observed using optical and scanning electron microscopy. The first boat did not yield smooth and continuous epitaxial layers even though a number of growth variations were tried. The second boat, however, consistently produced high quality epitaxial layers of PbSe0.78Te0.22 on {100} BaF2 substrates. Differences in the way the graphite boat traps growth solution vapors over the substrate prior to growth are believed to be responsible for the dramatic differences in these LPE growth morphologies. We suspect that formation of a barium-chalcogenide reaction product on the BaF2 substrate surface prior to growth is essential for obtaining good epitaxial layers and that trapping of growth solution vapors over the substrate prior to growth allows better control of this epitaxy-enabling substrate surface reaction.

Research paper thumbnail of MBE growth of PbSe/CaF2/Si(1 1 1) heterostructures

Journal of Crystal Growth, 1997

... 1062 PJ McCann et al. /Journal of Crystal Growth 175/176 (1997) 1057-1062 References [1] H. Z... more ... 1062 PJ McCann et al. /Journal of Crystal Growth 175/176 (1997) 1057-1062 References [1] H. Zogg, S. Blunier, A. Fach, C. Maissen, P. Miller, S. Teodoropol, V. Meyer, G. Kostorz, A. Dommann and T. Richmond, Phys. Rev. B 50 (1994) 10801. ...

Research paper thumbnail of Initial growth of CaF2 and on Si(110) during molecular beam epitaxy

Journal of Crystal Growth, 1996

Reflection high-energy electron diffraction, scanning electron microscopy, atomic force microscop... more Reflection high-energy electron diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy were used to study the initial growth of CaF 2 on Si(110) and BaF 2 on CaF2/Si(ll0) by molecular beam epitaxy. Growth of CaF2/Si(110) initially proceeds two-dimensionally with a (1 x 3) surface reconstruction. The observation of core-level and Auger energy shifts for Ca and F peaks at low coverage suggests the presence of both Ca-Si and F-Si bonds at the CaF2/Si(110) interface. For higher coverages, [ll0]-oriented ridges form and growth proceeds via the stacking of (111) and (111) planes on the sidewalls of the ridges. This ridged and grooved surface morphology is believed to result from the favorable energetics of exposing low-energy {111} facets and the formation of twinned crystallographic domains. Subsequent deposition of BaF 2 on CaFJSi(110) begins with incommensurate growth and nucleation on top of the CaF 2 ridges. Growth then continues on the sidewalls, resulting in recovery of the ridged and grooved morphology at higher coverages. Intermixing between the fluorides is believed to be negligible near the BaF2/CaF2(110) interface.

Research paper thumbnail of Large mismatch heteroepitaxy of InSb on Si(1 1 1) substrates using CaF2 buffer layers

Journal of Crystal Growth, 1997

The results of initial attempts to grow large lattice-mismatched InSbSi structures using CaF2 buf... more The results of initial attempts to grow large lattice-mismatched InSbSi structures using CaF2 buffer layers are reported. Substrate temperatures in the range of 300–400°C were used and MBE growth was initiated by opening the In and Sb shutters simultaneously, producing In-terminated InSb(1 1 1)-A surfaces on Si(1 1 1) substrates. High structural quality was confirmed by reflection high-energy electron diffraction,

Research paper thumbnail of Two distinct mechanisms for ornithine decarboxylase regulation by polyamines in rat hepatoma cells

Journal of Cellular Physiology, 1979

Exogenous diamines and polyamines added to rat hepatoma (HTC) cells in culture rapidly decrease o... more Exogenous diamines and polyamines added to rat hepatoma (HTC) cells in culture rapidly decrease ornithine decarboxylase (ODC) activity. Previous evidence has suggested that these amines set either at the level of blocking new enzyme synthesis or by the induction of a non-competitive protein inhibitor, termed antizyme, which complexes with ODC to form an inactive complex. Wth the use of HMOA cells, a recently cloned rat hepatoma cell line that has a greatly stabilized ODC, it has been possible to demonstrate that 10(-5) M of exogenous putrescine blocks the increase in ODC activity, but unlike in the parent HTC cell line, without induction of the antizyme or formation of any inactive ODC-antizyme complex. However, complete blockade of ODC at 10(-2) M putrescine is effected by induction of antizyme and formation of the ODC-antizyme complex, as now evidenced by the isolation of the active enzyme and antizyme components after Sephadex column chromatography in the presence of 250 mM NaCl. These findings indicate clearly that two polyamine-regulatory mechanisms for ODC exist and are separable in this cell line.

Research paper thumbnail of Molecular beam epitaxy of InSb on Si substrates using fluoride buffer layers

Journal of Applied Physics, 1997

The molecular beam epitaxy of InSb/Si structures was accomplished using group IIa fluoride buffer... more The molecular beam epitaxy of InSb/Si structures was accomplished using group IIa fluoride buffer layers. InSb growth was initiated by opening the In and Sb shutters simultaneously at substrate temperatures between 300°C and 400°C, producing In-terminated InSb͑111͒-A surfaces on CaF 2 /Si͑111͒ substrates. Reflection high-energy electron diffraction, electron channeling, and high resolution x-ray diffraction measurements indicated that the InSb layers were of good crystalline quality. Electron mobilities at room temperature were as high as 65 000 cm 2 /V s for an 8-m-thick InSb layer grown on CaF 2 /Si͑111͒. On CaF 2 /Si͑001͒ substrates, the InSb layers grew in the ͑111͒ orientation with two domains 90°apart. These InSb layers and ones grown on BaF 2 /CaF 2 /Si͑111͒ substrates exhibited inferior electrical and structural properties compared to structures grown on CaF 2 /Si͑111͒ substrates.

Research paper thumbnail of Midinfrared photoluminescence from IV–VI semiconductors grown on silicon

Journal of Applied Physics, 2001

Research paper thumbnail of Hypertrophic cardiomyopathy, ten years’ experience

Irish Journal of Medical Science, 1987

Summary A RETROSPECTIVE study was performed of patients who were diagnosed as having hypertrophi... more Summary A RETROSPECTIVE study was performed of patients who were diagnosed as having hypertrophic cardiomyopathy by left ventricular angiography in order to assess the incidence, the clinical and haemodynamic features and prognosis of this condition. The records of the cardiac catheter laboratory were reviewed for the ten year period from May 1975 to June 1985 to obtain haemodynamic and angiographic findings at diagnosis. Clinical features were obtained from the hospital records. To assess the prognosis, the clinical status of all patients, where possible, was reviewed in June 1985. During the ten year period 64 patients were diagnosed as having hypertrophic cardiomyopathy which was approximately 1% of all cardiac catheterizations. At diagnosis 22% of patients were asymptomatic and the commonest symptoms were chest pain or dyspnoea. Only 12% of patients had a family history of hypertrophic cardiomyopathy or sudden death. A systolic murmur was the most common abnormality on physical examination. Although evidence of left ventricular hypertrophy demonstrated by ECG was very common, only 13% of patients have evidence of an intraventricular pressure gradient. Of the 52 patients (81% of total) available for follow-up in June 1985, seven (13%) had died since diagnosis, all suddenly. The patients who died were significantly younger than the survivors and evidence of left ventricular hypertrophy was also more common in those who died. Our study confirms that although hypertrophie cardiomyopathy is uncommon, it carries a definite mortality. Thus definitive diagnosis of this condition is important especially as there is now evidence to suggest that the prognosis may be improved by treatment with amiodarone.