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H Hartmann

Publications and source records attributed to H Hartmann.

At least 19 recordsLinked to original sources
PubMed2006

Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism.

Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.

Journal Article↗
PubMed2006

Strategies for the anaerobic digestion of the organic fraction of municipal solid waste: an overview.

Different process strategies for anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) are reviewed weighing high-solids versus low-solids, mesophilic versus thermophilic and single-stage versus multi-stage processes. The influence of different waste characteristics such as composition of biodegradable fractions, C:N ratio and particle size is described. Generally, source sorting of OFMSW and a high content of food waste leads to higher biogas yields than the use of mechanically sorted OFMSW. Thermophilic processes are more efficient than mesophilic processes in terms of higher biogas yields at different organic loading rates (OLR). Highest biogas yields are achieved by means of wet thermophilic processes at OLRs lower than 6 kg-VS x m(-3) d(-1). High-solids processes appear to be relatively more efficient when OLRs higher than 6 kg-VS x m(-3)d(-1) are applied. Multi-stage systems show in some investigations a higher reduction of recalcitrant organic matter compared to single-stage systems, but they are seldom applied in full-scale. An extended cost-benefit calculation shows that the highest overall benefit of the process is achieved at an OLR that is lower and a hydraulic retention time (HRT) that is longer than those values of OLR and HRT, at which the highest biogas production is achieved.

Anaerobiosis↗
PubMed2006

Thermal pretreatment of the solid fraction of manure: impact on the biogas reactor performance and microbial community.

Application of thermal treatment at 100-140 degrees C as a pretreatment method prior to anaerobic digestion of a mixture of cattle and swine manure was investigated. In a batch test, biogasification of manure with thermally pretreated solid fraction proceeded faster and resulted in the increase of methane yield. The performances of two thermophilic continuously stirred tank reactors (CSTR) treating manure with solid fraction pretreated for 40 minutes at 140 degrees C and non-treated manure were compared. The digester fed with the thermally pretreated manure had a higher methane productivity and an improved removal of the volatile solids (VS). The properties of microbial communities of both reactors were analysed. The specific methanogenic activity (SMA) test showed that both biomasses had significant activity towards hydrogen and formate, while the activity with the VFA - acetate, propionate and butyrate - was low. The kinetic parameters of the VFA conversion revealed a reduced affinity of the microbial community from the CSTR fed with thermally pre-treated manure for acetate, propionate and butyrate. The bacterial and archaeal populations identified by t-RLFP analysis of 16S rRNA genes were found to be identical in both systems. However, a change in the abundance of the species present was detected.

Animals↗
PubMed2006

Status of ADSW 2005.

Abstract The status of the recent developments in anaerobic digestion of solid waste (ADSW) is outlined on the basis of a selection of papers presented at the 4th International Symposium on ADSW 2005.

Bacteria, Anaerobic↗
PubMed2004

[Platypnea-orthodeoxia of a 69-year old woman with a patent foramen ovale].

Platypnea-orthodeoxia is a rare syndrome that is often associated with interatrial shunting through a patent foramen ovale (PFO) or atrial septal defect. We describe the case of a 69-year-old woman with progressive dyspnea and hypoxia when standing, which was relieved by assuming the recumbent position. After detection of a PFO by transesophageal echocardiography the diagnosis was confirmed by transthoracic echocardiography using saline contrast injection while lying supine and standing upright. This maneuver demonstrated a large right-to-left shunt through a patent foramen ovale while the patient was in a upright position and no significant shunt while being in a recumbent position. The patient showed a rapid improvement after closure of the PFO. This case demonstrates that platypnea-orthodeoxia caused by a patent foramen ovale can be easily demonstrated by the technique of contrast transthoracic echocardiography and a simple positioning maneuver.

Aged↗
PubMed2004

Agenesis of the corpus callosum, abnormal genitalia and intractable epilepsy due to a novel familial mutation in the Aristaless-related homeobox gene.

Mutations in the Aristaless-related homeobox (ARX) gene are associated with a broad spectrum of disorders including X-linked lissencephaly with abnormal genitalia (XLAG) and absent corpus callosum. Here, we describe a family with two male infants suffering from agenesis of the corpus callosum (ACC), intractable epilepsy, and abnormal genitalia. The phenotype of both affected patients differed in severity of the cerebral malformation with one showing no obvious evidence for lissencephaly. Both infants lacked any psychomotor development and died at the age of 17 weeks and 18 months, respectively. Genetic analysis of the ARX gene revealed a novel frameshift mutation in exon 4 (nt1419_1420insAC) leading to a shortened protein lacking the aristaless domain. In summary, analysis of the ARX gene should not only be considered in male patients with typical features of XLAG but also in those presenting with early onset epilepsy, ACC, and abnormal genitalia without obvious neuroradiological features of lissencephaly.

Abnormalities, Multiple↗
PubMed2003

Subacute sclerosing panencephalitis in two brothers.

We report the occurrence of subacute sclerosing panencephalitis (SSPE) in two brothers two years after measles infection. The diagnosis was confirmed by compatible data from medical history, occurrence of autochthonic measles virus (MV) IgG production in the central nervous system (CNS), and pathognomonic EEG changes. Pathogenetically, SSPE is caused by a genome mutation of intracellularly persisting MV, causing viral nucleocapsides to accumulate in the brain cells. A specific predisposing immune defect is not known. The occurrence of two cases in one family is suggestive of a genetic predisposing factor.

Child↗
PubMed2003

Phthalic acid esters found in municipal organic waste: enhanced anaerobic degradation under hyper-thermophilic conditions.

Contamination of the organic fraction of municipal solid waste (OFMSW) with xenobiotic compounds and their fate during anaerobic digestion was investigated. The phthalic acid ester di-(2-ethylhexyl)phthalate (DEHP) was identified as the main contaminant in OFMSW in concentrations more than half of the threshold value for the use as fertilizer on agricultural soil in Denmark. Analysis of DEHP in samples before and after large-scale anaerobic digesters revealed higher concentrations of DEHP per kg dry matter in the effluent than in the influent. The concentration of DEHP and DBP (dibutylphthalate) in OFMSW was monitored in the influent and effluent of anaerobic thermophilic (55 degrees C) and hyper-thermophilic (68 degrees C) laboratory-scale reactor systems. In the thermophilic reactors with a hydraulic retention time (HRT) of 15 days 38-70% of DBP was removed, but no consistent removal of DEHP was observed. However, after treatment of the effluent from the thermophilic reactor in a hyper-thermophilic digester (HRT: 5 days) 34-53% of the DEHP content was removed and the DBP removal was increased to further 62-74%. Removal rates (k(h)) of DEHP and DBP were found to be 0.11-0.32 d(-1) and 0.41-0.79 d(-1), which is much higher than in previous investigations. It can be concluded that the higher removal rates are due to the higher temperature and higher initial concentrations per kg dry matter. These results suggest that the limiting factor for DEHP degradation is the bioavailability, which is enhanced at higher temperature and higher degradation of solid organic matter, to which the highly hydrophobic DEHP is adsorbed. The investigated reactor configuration with a thermophilic and a hyper-thermophilic treatment is, therefore, a good option for combining high rate degradation of organic matter with high biogas yields and efficient reduction of the phthalic acid ester contamination.

Agriculture↗
PubMed2002

Observation of optical Smith-Purcell radiation at an electron beam energy of 855 MeV.

Smith-Purcell radiation, generated when a beam of charged particles passes close to the surface of a diffraction grating, has been studied in the visible spectral range at wavelengths of 360 and 546 nm with the low emittance 855 MeV electron beam of the Mainz Microtron MAMI. The beam focused to a spot size of 4 microm (full width at half maximum) passed over optical diffraction gratings of echelle profiles with blaze angles of 0.8 degrees, 17.27 degrees, and 41.12 degrees and grating periods of 0.833 and 9.09 microm. Taking advantage of the specific emission characteristics of Smith-Purcell radiation a clear separation from background components, such as diffracted synchrotron radiation from upstream beam optical elements and transition radiation, was possible. The intensity scales with a modified Bessel function of the first kind as a function of the distance between electron beam and grating surface. Experimental radiation factors have been determined and compared with calculations on the basis of Van den Berg's theory [P.M. Van den Berg, J. Opt. Soc. Am. 63, 689 (1973)]. Fair agreement has been found for gratings with large blaze angles while the measurement with the shallow grating (blaze angle 0.8 degrees ) is at variance with this theory. Finally, the optimal operational parameters of a Smith-Purcell radiation source in view of already existing powerful undulator sources are discussed.

Journal Article↗
PubMed2001

The allosteric effector l-lactate induces a conformational change of 2x6-meric lobster hemocyanin in the oxy state as revealed by small angle x-ray scattering.

Hemocyanins are multisubunit respiratory proteins found in many invertebrates. They bind oxygen highly cooperatively. However, not much is known about the structural basis of this behavior. We studied the influence of the physiological allosteric effector l-lactate on the oxygenated quaternary structure of the 2x6-meric hemocyanin from the lobster Homarus americanus employing small angle x-ray scattering (SAXS). The presence of 20 mm l-lactate resulted in different scattering curves compared with those obtained in the absence of l-lactate. The distance distribution functions p(r) indicated a more compact molecule in presence of l-lactate, which is also reflected in a reduction of the radius of gyration by about 0.2 nm (3%). Thus, we show for the first time on a structural basis that a hemocyanin in the oxy state can adopt two different conformations. This is as predicted from the analysis of oxygen binding curves according to the "nesting" model. A comparison of the distance distribution functions p(r) obtained from SAXS with those deduced from electron microscopy revealed large differences. The distance between the two hexamers as deduced from electron microscopy has to be shortened by up to 1.1 nm to agree well with the small angle x-ray curves.

Allosteric Regulation↗
PubMed2001

Regulation of the components of the 150 kDa IGF binding protein complex in cocultures of rat hepatocytes and Kupffer cells by 3',5'-cyclic adenosine monophosphate.

In the circulation, most of IGFs are bound to a high molecular mass complex of 150 kDa that consists of IGF-I (or IGF-II), IGFBP-3 and the acid-labile subunit (ALS). Within rat liver, biosynthesis of these components has been localized to different cell populations with hepatocytes as source of ALS and nonparenchymal cells (endothelial and Kupffer cells (KC)) as source of IGFBP-3. In the present study, the regulatory effects of the cAMP analogs dibutyryl-cAMP (db-cAMP) and 8-bromo-cAMP (8-br-cAMP) on IGF-I, ALS, and IGFBP expression were evaluated in primary cultures of rat hepatocytes, KC as well as in cocultures of hepatocytes and KC. In cocultures, biosynthesis of IGFBP-3 and ALS was inhibited dose-dependently by db-cAMP and 8-br-cAMP while that of IGF-I, IGFBP-1, and -4 was stimulated as demonstrated by ligand and Northern blotting. IGFBP-3 expression in primary cultures of pure KC did not respond to cAMP treatment indicating the importance of a cellular interaction between KC and hepatocytes for the decreased IGFBP-3 synthesis. The inhibition of IGFBP-3 in db-cAMP-treated cocultures was due to a decrease of IGFBP-3 mRNA level accompanied by a reduced cellular degradation of IGFBP-3. We conclude that cAMP stimulate the biosynthesis of IGF-I, IGFBP-1, and -4 in cocultures of hepatocytes and KC thereby enabling the formation of binary IGF/IGFBP complexes while the formation of the 150 kDa complex is impaired through downregulation of IGFBP-3 and ALS. This complex regulation may be a prerequisite for the effects of cAMP-dependent hormones on the transfer of IGFs from circulation to peripheral tissues.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2001

Synthesis and spectral characterization of a new class of heterocyclic analogues of crystal violet dyes.

Deep purple: By the transformation of readily available N,N-disubstituted 2-aminothiophenes and 2-aminothiazoles into heterocyclic analogues of Crystal Violet, such as, tris(2-dimethylamino-5-thienyl)methinium prechlorate (cation shown), the series of dyes derived from these heterocyclic structural units as the important chromophoric component is significantly extended and a gap in the class of heteroanalogous triphenylmethane dyes has been closed.

Crystal Violet↗
PubMed2001

Small-angle neutron scattering reveals an oxygen-dependent conformational change of the immunogen keyhole limpet hemocyanin type 1 (KLH1).

The respiratory protein of the keyhole limpet, Megathura crenulata, the hemocyanin (KLH), commonly used as an immunogen, binds oxygen cooperatively, which implies the existence of different conformations. For the first time, two different conformations of KLH1 were detected upon oxygenation, a deoxy and an oxy state, using small-angle neutron scattering. Rearrangements in the quaternary structure of KLH1 were predicted from the different radii of gyration and the shifts of the minima and maxima in the scattering curves. Upon oxygenation, KLH1 becomes smaller and more compact. Model reconstruction of KLH1 indicates a hollow cylinder with two rings located close to both ends, which move slightly together upon oxygenation.

Animals↗
PubMed2001

Increase of serum estradiol in cirrhotic men treated by transjugular intrahepatic portosystemic stent shunt.

BACKGROUND/AIMS: Liver cirrhosis is frequently associated with sexual dysfunction and hormonal abnormalities. To evaluate the effect of portosystemic shunting on sex steroid serum concentrations, a prospective study was performed in cirrhotic patients treated consecutively and electively by transjugular intrahepatic portosystemic stent shunt (TIPS). METHODS: In 27 patients with liver cirrhosis we measured serum levels of testosterone (T), sexual hormone binding globulin (SHBG), luteinizing hormone, follicle-stimulating hormone, dehydroepiandrosterone sulfate, androstenedione (A), estradiol (E2), 17-OH-progesterone and the T/SHBG ratio before and 3 months after TIPS. RESULTS: In men (n = 17) 3 months after TIPS, A and E2 significantly increased, with mean serum levels rising from 4.4 +/- 2.5 to 5.6 +/- 2.9 ng/ml (P = 0.04) and from 27 +/- 9 to 40 +/- 19 pg/ml (P = 0.003), respectively. In contrast to A the increase of E2 persisted at 9 and 15 months after TIPS. Erectile dysfunction increased from 30% before TIPS to 70% after TIPS. In women (n = 10) A and E2 levels did not change significantly after TIPS. CONCLUSIONS: TIPS aggravated hormonal dysbalance of sex steroids in favor of estrogens (hyperestrogenism) in men.

Adult↗
PubMed2001

Hepatitis C virus-associated mixed cryoglobulinemia. Clinical manifestations, histopathological changes, mechanisms of cryoprecipitation and options of treatment.

Chronic hepatitis C virus (HCV) infection is frequently associated with a variety of autoimmune phenomenons. Mixed cryoglobulinemia (MC) appears in up to 50% of chronic HCV-infected patients. Cryoglobulins consist of immunoglobulin complexes precipitating in vitro when cooled below body temperature. In most cases IgM with rheumatoid factor activity is found in cryoprecipitates which could lead to vasculitis induced by the deposition of immnuocomplexes in small vessels. This vasculitis is thought to cause clinical symptoms called Meltzer's triad. This triad is represented by purpura, arthralgia and weakness. One third of patients suffering from HCV-associated mixed cryoglobulinemia are developing typical symptoms during their course of disease. The striking association between HCV infection and MC has conduced to the hypothesis that HCV is of major importance in the production of MC with followed vasculitis. Both hepatrophism and lymphotrophism have been reported for the hepatitis C virus. Infection of B-cells by HCV could probably lead to a bcl-2 translocation and immunoglobulin gene rearrangement which results in clonal lymphoproliferation and in synthesis of monoclonal IgM with rheumatoid factor activity. These IgM form immunocomplexes with IgG in the cold, which are finally responsible for the described vasculitis. Histopathological changes of the liver are dominated by chronic HCV infection. The majority of times mild activity of hepatitis or mild fibrosis could be found. Nevertheless, cirrhosis is more often found in HCV-infected patients suffering from MC compared to patients without MC. Conventional treatment of MC is aimed to reduce circulating immune complexes by immunosupression and plasmapheresis. With the emerging concept of a viral pathogenesis the therapeutic approach has changed during the last decade. Interferon treatment of MC, particularly of HCV-associated MC is well established nowadays.

Cryoglobulinemia↗
PubMed2000

Presenilin I interaction with cytoskeleton and association with actin filaments.

Presenilin I (PSI) has been shown to interact with microfilament-associated proteins of the filamin family. Here, we investigated a possible association of PSI with the cytoskeleton. Immunoblotting of detergent-insoluble fractions of rat brain homogenate revealed enrichment of neuron-specific 36 and 14 kDa proteolytic fragments of PSI, whereas 30 and 20 kDa fragments were found in the detergent-soluble fraction. Specific severing of microfilaments with gelsolin in the detergent-insoluble pellet and subsequent centrifugation led to the detection of both actin and PSI fragments in the supernatant. In addition, in vitro translated PSI cosedimented with actin filaments. Our findings provide biochemical evidence for the association of PSI fragments with actin filaments.

Actin Cytoskeleton↗