Biomedical subjects

J Schulz

Publications and source records attributed to J Schulz.

At least 19 recordsLinked to original sources

PubMed2005

Emission of thermally activated electrons from rare gas clusters irradiated with intense VUV light pulses from a free electron laser.

The ionization dynamics of Ar and Xe clusters irradiated with intense vacuum ultraviolet light from a free-electron laser is investigated using photoelectron spectroscopy. Clusters comprising between 70 and 900 atoms were irradiated with femtosecond pulses at 95 nm wavelength (approximately 13 eV photon energy) and a peak intensity of approximately 4 x 10(12) W/cm2. A broad thermal distribution of emitted electrons from clusters with a maximum kinetic energy up to 30-40 eV is observed. The observation of relatively low-energy photoelectrons is in good agreement with calculations using a time-dependent Thomas-Fermi model and gives experimental evidence of an outer ionization process of the clusters, due to delayed thermoelectronic emission.

Journal Article↗

PubMed2005

The electronic structure of free water clusters probed by Auger electron spectroscopy.

(H2O)(N) clusters generated in a supersonic expansion source with N approximately 1000 were core ionized by synchrotron radiation, giving rise to core-level photoelectron and Auger electron spectra (AES), free from charging effects. The AES is interpreted as being intermediate between the molecular and solid water spectra showing broadened bands as well as a significant shoulder at high kinetic energy. Qualitative considerations as well as ab initio calculations explain this shoulder to be due to delocalized final states in which the two valence holes are mostly located at different water molecules. The ab initio calculations show that valence hole configurations with both valence holes at the core-ionized water molecule are admixed to these final states and give rise to their intensity in the AES. Density-functional investigations of model systems for the doubly ionized final states--the water dimer and a 20-molecule water cluster--were performed to analyze the localization of the two valence holes in the electronic ground states. Whereas these holes are preferentially located at the same water molecule in the dimer, they are delocalized in the cluster showing a preference of the holes for surface molecules. The calculated double-ionization potential of the cluster (22.1 eV) is in reasonable agreement with the low-energy limit of the delocalized hole shoulder in the AES.

Journal Article↗

PubMed2005

Multiple ionization of rare gas atoms irradiated with intense VUV radiation.

The interaction of intense vacuum-ultraviolet radiation from a free-electron laser with rare gas atoms is investigated. The ionization products of xenon and argon atomic beams are analyzed with time-of-flight mass spectroscopy. At 98 nm wavelength and approximately 10(13) W/cm(2) multiple charged ions up to Xe6+ (Ar4+) are detected. From the intensity dependence of multiple charged ion yields the mechanisms of multiphoton processes were derived. In the range of approximately 10(12)-10(13) W/cm(2) the ionization is attributed to sequential multiphoton processes. The production of multiple charged ions saturates at 5-30 times lower power densities than at 193 and 564 nm wavelength, respectively.

Journal Article↗

PubMed2005

Posttraumatic syringomyelia--a serious complication in tetra- and paraplegic patients.

Post-traumatic syringomyelia (PTS) is relatively rare, but its complications can be serious. In the beginning of the operative treatment (1900-1930), scarring could be reduced to a certain degree. In modern treatment (1980 1990) a shunt implantation showed also little effect in long-term follow-up studies. Influenced by the work of B. Williams, 58 PTS patients underwent surgery to create a pseudomeningomyelocele, an artificial CSF reservoir, performed to normalize the CSF flow. In a 10-year-postoperative follow-up study (minimum observation two years), good results were obtained in more than 70%.

Cerebrospinal Fluid Shunts↗

PubMed2005

[Detection of Coxiella burnetii in the air of a sheep barn during shearing].

Local epidemics of Q fever occur sporadically in Germany, mainly in rural residential communities. There is increasing evidence that these outbreaks, which are caused by Coxiella burnetii, are related particularly to the lambing season and shearing periods of nearby sheep holdings. It is assumed that this zoonotic agent is massively emitted from the placenta of infected ewes at birth and during shearing of wool contaminated with infected faeces of ticks. However, little is known about the airborne transmission and travel distance of this infectious agent, and only few attempts have been made to isolate it directly from the air. This paper describes for the first time the isolation and detection of C. burnetii in the air of an enclosed sheep barn during shearing of a herd which had tested positive for C. burnetii serologically and by PCR. Samples of inhalable dust samples were taken using I.O.M. samplers with glass fibre and polycarbonate filters at a flow rate of 2.5 l/min. The sampling time was nearly 4.5 h. Two sampling positions were set up on both sides of the shearing place at a distance of 3 m and 1.5 m above the ground. A third position with the same sampling equipment was not activated and served as a sampling and transport control. In the laboratory, the glass fibre filters were used to determine the dust concentration. The polycarbonate filters were treated in a specific breakdown procedure which inactivates PCR inhibitors, followed by amplification and sequencing of a specific DNA section of C. burnetii, which was found in the dust from both active sampling positions. The investigation clearly shows that the sampling and detection methods used in this small field study are suitable for the detection of C. burnetii in the air of sheep barns. The results confirm experimentally the high risk of airborne transmission of C. burnetii from sero-positive sheep herds during shearing. However, little is known about the effective travel distance of infective airborne C. burnetii particles. There is an urgent need for more detailed investigations on the emission and airborne dispersion of infectious C. burnetii particles in order to improve our understanding of the health risks caused by this zoonotic agent originating from sheep herds.

Air Microbiology↗

PubMed2004

Femtosecond interatomic Coulombic decay in free neon clusters: large lifetime differences between surface and bulk.

A quantitative determination of 2s vacancy lifetimes in surface and bulk atoms of free Ne clusters has been made. While for free atoms the 2s inner-valence hole has a ps lifetime, it reduces to 6+/-1 fs for cluster bulk atoms. For surface atoms, the lifetime is on average longer than 30 fs. The lifetime estimate was obtained from fits of high-resolution photoelectron spectra of Ne clusters. The shortening of the lifetime is attributed to the coordination dependent interatomic Coulombic decay, which is extremely sensitive to internuclear distances.

Journal Article↗

PubMed2004

Interaction of argon clusters with intense VUV-laser radiation: the role of electronic structure in the energy-deposition process.

The response of Ar clusters to intense vacuum-ultraviolet pulses is investigated with photoion spec-troscopy. By varying the laser wavelength, the initial excitation was either tuned to absorption bands of surface or bulk atoms of clusters. Multiple ionization is observed, which leads to Coulomb explosion. The efficiency of resonant 2-photon ionization for initial bulk and surface excitation is compared with that of the nonresonant process at different laser intensities. The specific electronic structure of clusters plays almost no role in the explosion dynamics at a peak intensity larger than 1.8 x 10(12) W/cm(2). The inner ionization of atoms for resonant and nonresonant excitation is then saturated and the energy deposition is mainly controlled by the plasma heating rate. Molecular dynamics simulations indicate that standard collisional heating cannot fully account for the strong energy absorption.

Journal Article↗

PubMed2004

The size of neutral free clusters as manifested in the relative bulk-to-surface intensity in core level photoelectron spectroscopy.

A new approach for obtaining an estimate of the effective size of the free neutral clusters is proposed. The approach relies on an experimental measure of the surface and interior or "bulk" cluster atoms provided by the x-ray photoelectron spectroscopy and on a model for the attenuation of photoelectrons ejected from the bulk of the cluster as the result of the ionizing irradiation. The experimental part gives the ratio of the electron signal from the bulk cluster atoms to that from the cluster surface atoms for a wide range of cluster sizes and electron kinetic energies. The attenuated response of the bulk atoms is modeled using an exponential law with the cluster size and kinetic-energy-dependent electron escape depth as parameters. For the experimental size range, model-based calculations for Ar, Kr, and Xe clusters are presented. The cluster size estimates obtained from comparison of the model calculations and experimental results agree well with those determined from the parameters of the cluster creation process. The combination of experiment and modeling also makes it possible to estimate the effective escape depth for electron propagation in free clusters. For Ar, Kr, and Xe clusters of varying mean size, absolute determination of the surface and bulk electron binding energies of the core levels used in the experiments has also been made.

Journal Article↗

PubMed2004

ZD9331 as second- or third-line therapy in patients with advanced colorectal cancer: a phase II multicenter trial.

This study investigated the efficacy and tolerability of ZD9331 as second- or third-line treatment for patients with advanced colorectal cancer (aCRC). One hundred patients were recruited to the study: 45 in group 1 (failed first-line 5-FU-based regimen) and 55 in group 2 (failed first-line 5-FU-based regimen and second-line irinotecan). Patients received ZD9331 as a 30-minute intravenous infusion on days 1 and 8 of a 3-week cycle, and treatment continued until disease progression (PD) or withdrawal. After a median of 4 cycles of treatment, there were no objective responses in group 1 (N = 37), 25 (67.6%) patients had a best overall response of stable disease (SD), and 12 (32.4%) had PD. After a median of 3 cycles of treatment, there were 2 (4.5%) partial responses in group 2 (N = 44), 21 (47.7%) patients had a best overall response of SD, 20 (45.4%) had PD, and 1 (2.3%) had clinical progression. At data cut-off, 59.5% and 77.3% of patients in groups 1 and 2, respectively, had PD. The main adverse events were neutropenia (69%), fatigue (53%), nausea (46%), and diarrhea (40%), and most (72.3%) were grade I/II. ZD9331 demonstrated minimal antitumor activity, and manageable toxicity, in the second- or third-line treatment of aCRC.

Adult↗

PubMed2004

[HDMX amplification and high levels of HDMX-S splice variant are correlated with a poor prognosis in soft tissue sarcomas].

The aim of this study was to determine the amplification status of the HDMX gene and the expression of the HDMX mRNA particularly that of the HDMX-S splice variant in soft tissue sarcomas (STS). We show that the HDMX gene is amplified in 27% of STSs, which was associated with a worse prognosis (RR = 2.8, p = 0.03). We have also found that the transcript of the HDMX-S variant was predominant in a subset of (14%) of tumor samples, which was correlated with a significantly decreased overall survival time (15 vs. 53 months, p < 0.0001, log-Rank-test) and with a 9-fold-increased risk of tumor-related death (p < 0.0001). There was no correlation between the HMDX gene amplification and the HDMX-S splice variant overexpression. In summary, our data indicate that both the overexpression of the HDMX-S transcript, as well as, the HDMX gene amplification are important prognostic markers for STS.

Alternative Splicing↗

PubMed2003

A randomized controlled trial of the NEAT expandable tip continence device.

Urethral devices are one conservative management option for stress and mixed urinary incontinence, but there is little published data about their use. The aims of this study were to assess the safety and efficacy of a new urethral device (NEAT) and compare it with the Reliance Insert. The ease of use of both devices was then evaluated. Twenty-four women with mixed or stress urinary incontinence, patients at our tertiary care urogynecology unit and who met the inclusion and exclusion criteria, were enrolled in the study. Study subjects were blinded and randomly assigned to a device group. Device efficacy was assessed by pad weighing at 0 and 4 months. Success was defined as a 50% or greater reduction in urine loss using the formula 100[(pad weight without device -pad weight with device)/pad weight with device]. Safety was evaluated using urinalysis and urine cultures. Ease of use assessment scales were also completed. Eleven patients were randomized to the Reliance Insert and 13 to the NEAT device. There were no significant differences between the two groups in age, height, weight, duration of incontinence, pad weight, leakage score, parity or quality of life score. Based on the pad weight success formula, there was no significant difference in device success between the two groups at 4 months. Women who were postmenopausal had a trend towards a higher level of success in reduction of their pad weight. Previous treatment, diagnosis and hormone replacement therapy all had no relationship to device success. Leakage score data showed that subjects had a significant decrease in urine leakage when using either device. There was no statistically significant difference in ease of use between the two devices. Adverse symptoms most commonly noted were awareness of the device (62.5%), urgency (29.2%), and urethral discomfort or pain (20.8%). One urinary tract infection (UTI) was observed. The most common finding on urinalysis was trace hematuria (15.8%). Our conclusions are that the NEAT device appears to be at least as effective and safe as the Reliance Insert. Both devices are effective at decreasing urine leakage in patients with stress or mixed urinary incontinence. The risk of UTI is low, but these devices may cause trace hematuria.

Equipment Design↗

PubMed2003

Femtosecond laser-induced two-photon polymerization of inorganic-organic hybrid materials for applications in photonics.

Investigations of two-photon polymerization of inorganic-organic hybrid materials initiated by femtosecond Ti:sapphire laser pulses are performed. First applications of this technique for the fabrication of three-dimensional microstructures and photonic crystals in inorganic-organic hybrid polymers with a structure size down to 200 nm and a periodicity of 450 nm are discussed.

Journal Article↗

PubMed2002

Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser.

Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength, a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion.

Journal Article↗

PubMed2002

Distribution of sunscreens on skin.

The effectiveness of sunscreens was originally achieved by incorporation of soluble organic UV absorbers such as cinnamates and others into cosmetic formulations. Determinations of the sun protection factor (SPF) of emulsions containing different organic UV absorbers clearly indicate that the efficacy depends on the absorption characteristics of each single UV filter substance. Nowadays, micronised pigments such as titanium dioxide or zinc oxide have also been found to be protective against harmful UV rays. Our investigations using optical and electron microscopy proved that neither surface characteristics, particle size nor shape of the micronised pigments result in any dermal absorption of this substance. Micronised titanium dioxide is solely deposited on the outermost surface of the stratum corneum and cannot be detected in deeper stratum corneum layers, the human epidermis and dermis.

Administration, Topical↗

PubMed2002

A double-blind placebo-controlled, randomised study comparing gemcitabine and marimastat with gemcitabine and placebo as first line therapy in patients with advanced pancreatic cancer.

Pancreatic cancer is the fifth most common cause of cancer death in the western world and the prognosis for unresectable disease remains poor. Recent advances in conventional chemotherapy and the development of novel 'molecular' treatment strategies with different toxicity profiles warrant investigation as combination treatment strategies. This randomised study in pancreatic cancer compares marimastat (orally administered matrix metalloproteinase inhibitor) in combination with gemcitabine to gemcitabine alone. Two hundred and thirty-nine patients with unresectable pancreatic cancer were randomised to receive gemcitabine (1000 mg m(-2)) in combination with either marimastat or placebo. The primary end-point was survival. Objective tumour response and duration of response, time to treatment failure and disease progression, quality of life and safety were also assessed. There was no significant difference in survival between gemcitabine and marimastat and gemcitabine and placebo (P=0.95 log-rank test). Median survival times were 165.5 and 164 days and 1-year survival was 18% and 17% respectively. There were no significant differences in overall response rates (11 and 16% respectively), progression-free survival (P=0.68 log-rank test) or time to treatment failure (P=0.70 log-rank test) between the treatment arms. The gemcitabine and marimastat combination was well tolerated with only 2.5% of patients withdrawn due to presumed marimastat toxicity. Grade 3 or 4 musculoskeletal toxicities were reported in only 4% of the marimastat treated patients, although 59% of marimastat treated patients reported some musculoskeletal events. The results of this study provide no evidence to support a combination of marimastat with gemcitabine in patients with advanced pancreatic cancer. The combination of marimastat with gemcitabine was well tolerated. Further studies of marimastat as a maintenance treatment following a response or stable disease on gemcitabine may be justified.

Adenocarcinoma↗

PubMed2002

Efficacy, tolerability and management of raltitrexed (Tomudex) monotherapy in patients with advanced colorectal cancer. a review of phase II/III trials.

Raltitrexed (Tomudex), a thymidylate synthase inhibitor, is an alternative to 5-fluorouracil (5-FU)/leucovorin (LV) for the first-line treatment of advanced colorectal cancer. Following the completion of four phase III studies with raltitrexed at the recommended dose of 3.0 mg/m(2), it is opportune to review the efficacy and tolerability data of raltitrexed and suggest guidelines for appropriate patient management. Data are analysed from four phase III and five phase II studies including over 1300 patients with advanced colorectal cancer, some of whom were elderly or received higher doses of raltitrexed. Median survival with raltitrexed was comparable to that of bolus or infusional 5-FU/LV in three of the four randomised studies and objective response rates in the four trials were similar for the two agents. Response rates were at least comparable in elderly patients in phase II studies. For the majority of patients, treatment with raltitrexed was well tolerated even at doses higher than that recommended or in the elderly. As with other cytotoxic agents, serious and potentially life-threatening side-effects can occur; nevertheless, adherence to simple patient guidelines should minimise the incidence of serious side-effects with raltitrexed; these include the assessment of renal function before each and every treatment, dosage adjustment in the presence of renal impairment and close monitoring with prompt treatment of toxicities, particularly diarrhoea and neutropenia.

Adult↗

PubMed2002

Do children with autism who pass false belief tasks understand the mind as active interpreter?

Interpretive diversity is the term used by Carpendale and Chandler (1996) to refer to the fact that two individuals exposed to precisely the same stimulus may interpret it in quite different, but equally plausible, ways. An appreciation of interpretive diversity is said by Carpendale and Chandler to represent a development in understanding that is qualitatively different from that necessary to succeed on false belief tasks. A study is reported in which children with autism and children with general delay were given a battery of tasks consisting of false belief tasks and tasks designed to test for an understanding of interpretive diversity. Findings from the present study offer limited support for Carpendale and Chandler's claim that tasks which test for an understanding of interpretive diversity may be more difficult than false belief tasks. Between-group differences in the consistency and quality of responses given by participants suggest that autistic and delayed children may have differed somewhat in their approach to the tasks given.

Autistic Disorder↗

PubMed2001

Role of bradykinin B2 receptors in the formation of vasogenic brain edema in rats.

Bradykinin is a mediator of brain edema acting through B2 receptors. However, it is not known if bradykinin mediates the formation of cytotoxic or vasogenic brain swelling. To investigate this question we subjected rats to a cryogenic brain lesion over the left parietal cortex, a model well known to produce predominantly vasogenic brain edema. We inhibited bradykinin B2 receptors with the recently characterized nonpeptide B2 receptor antagonist, LF 16-0687. The animals were assigned to three groups (n = 10, each) receiving 10, or 100 microg/kg/min LF 16-0687 or vehicle (0.9% NaCl). Treatment started 15 min before trauma and was continued for 24 h. Another three groups of animals (n = 10, each) received 10 microg/kg/min LF 16-0687 starting 30 or 60 min after trauma or vehicle (0.9% NaCl) for 24 h. Animals were then sacrificed and swelling and water content of the brain were determined. In the vehicle treated group the traumatized hemisphere swelled by 9.3 +/- 1.1% as compared to the untraumatized contralateral side. Pretreatment with 10 microg/kg/min LF 16-0687 decreased brain swelling significantly to 6.4 +/- 1.3% (p < 0.05). Pre-treatment with 100 microg/kg/min was found to be less effective and did not result in a significant reduction of brain swelling (7.4 + 1.3%). Treatment with LF 16-0687 for 24 h (10 microg/kg/min) started 30 or 60 min after trauma did not reduce brain water content or hemispheric swelling. These results demonstrate that brain injury-mediated bradykinin production induces vasogenic brain edema by B2 receptor stimulation. Our findings further clarify the role of bradykinin in the pathophysiology of brain edema formation and confirm the therapeutic potency of bradykinin B2 receptor inhibition.

Algorithms↗