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Biomedical subjects

F Wilhelm

Publications and source records attributed to F Wilhelm.

At least 19 recordsLinked to original sources
PubMed2006

Enhanced orbital magnetism in Fe(50)Pt(50) nanoparticles.

X-ray absorption and magnetic circular dichroism spectra at both the Fe and Pt L(3,2) edges were measured on wet-chemically synthesized monodisperse Fe(50)Pt(50) particles with a mean diameter of 6.3 nm before and after complete removal of the organic ligands and the oxide shell covering the particles by soft hydrogen plasma resulting in a pure metallic state. After thermal treatment of the metallic particles, the coercive field increased by a factor of 6, the orbital magnetic moment at the Fe site increased by 330% and is reduced at the Pt site by 30%, while the effective spin moments did not change. A decrease of the frequency of oscillations in the extended x-ray absorption fine structure at the Pt L(3,2) edges provides evidence for crystallographic changes towards the L1(0) phase.

Journal Article↗
PubMed2005

Urinary steroid measurements in some endocrine and psychiatric diseases.

In 1990, the worldwide accepted Shackleton method, which provides a possibility of determining the steroid metabolites from urine, was adopted in our laboratory. The procedure is very useful in the diagnosis of different endocrine diseases and in the recognition of dysfunction or absence of enzymes with an important role in steroid metabolism, and it gives possibility to control the treatment in patients with these diseases. Besides the proximate clinical application, the method gives a convenient tool to study the steroid background of these disorders, helping us understand the mechanism of their development. In the last few years, we have examined the steroid profile of patients with hair (androgen alopecia /AA/, effluvium /E/), psychiatric problems (major depression /MD/, eating disorders /EDS/, especially anorexia nervosa and bulimia) and osteoporosis (OP). In all of the examined hair loss diseases, the levels of main androgen metabolites were increased, and elevated 5alpha-reductase activity were found. We could observe the alteration of the activity of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzyme and marked gender differences in the changes of the steroid metabolism in patients with major depression (MD). In women with OP, the significantly decreased level of certain metabolites points to the role of testosterone, androstenedione and DHEA in postmenopausal bone loss in women. Our experiences contribute to the knowledge of the nature and steroid background of some endocrine and psychiatric diseases.

Adult↗
PubMed2004

Advanced detection systems for X-ray fluorescence excitation spectroscopy.

This paper accounts for selected detector developments carried out over the past 15 years within the ESRF X-ray Absorption Spectroscopy group. This includes various types of photodiodes used as integrated current detectors. Special emphasis is put on the long-standing development of a Si drift-diode array suitable for energy-dispersive detection of X-ray fluorescence. This detector, which is now operational, was used to record high-quality XMCD/XAFS spectra on [Fe70Pt30] nanoparticles highly dispersed on a Si wafer. Using numerically deconvoluted spectra, energy resolution was decreased to 82 eV for the Si Kalphabeta line, 126 eV for the Fe Kalpha line and 176 eV for the Pt Lalpha line. A high-vacuum-compatible high-energy-resolution crystal analyzer was also installed on ID12, making it possible to record X-ray fluorescence excitation spectra in the photon-in/photon-out mode over a wide spectral range. Prospects of adapting these methods in order to investigate biological samples are briefly discussed.

Equipment Design↗
PubMed2004

[HIV seroprevalence in ophthalmologic patients of Cameroon].

BACKGROUND: It is difficult to estimate the exact HIV infection rates in countries such as Cameroon because of diagnostic and statistical problems. The majority of people seek help from traditional healers outside the health system. PATIENTS AND METHODS: A screening for human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) was performed on 2452 patients of the western province of Cameroon. All data were evaluated regarding HIV seroprevalence and ophthalmological findings in HIV-seropositive patients. The test covered all patients who came for cataract surgery (group 1), all outpatients with suspicious ophthalmological findings (group 2), and all remarkable patients of the collaborating department of general medicine (group 3) between 20 September 2000 and 20 September 2001. RESULTS: Of the 2452 screened patients, 467 (19.0%) were HIV seropositive. A positive test result was obtained in 29 (5.5%) of the 525 patients in group 1, 154 (35.6%) of the 433 patients in group 2, and 284 (19.0%) of the 1494 patients in group 3. The main ocular manifestations of the 154 HIV-seropositive patients in group 2 were uveitis (17.6%), squamous cell carcinoma of the conjunctiva (14.9%), zoster ophthalmicus (14.9%), and corneal ulcers (11.0%). CONCLUSIONS: This study shows that the seroprevalence of the screened population of Cameroon lies between 5.5% (results of group 1) and 19.0% (results of group 3).

AIDS-Related Opportunistic Infections↗
PubMed2004

[Contact lens fitting as a possibility for visual rehabilitation in patients after open globe injuries].

INTRODUCTION: Visual rehabilitation after open globe injury may be a challenging process because of ametropia following aphakia, corneal scarring with high or irregular corneal astigmatism or loss of contrast sensitivity due to traumatic aniridia. We report on contact lens fitting for visual rehabilitation in patients after open globe injury. PATIENTS: From 2000 to 2003, contact lenses were fitted unilaterally for the visual rehabilitation in 13 patients after open globe injury. In three patients we found unilateral aphakia, in 8 patients a high or irregular astigmatism after penetrating or autorotation keratoplasty and in two patients a traumatic aniridia, in one case combined with aphakia. RESULTS: 11 rigid contact lenses were fitted with different designs of the front and back surface as well as two iris-print lenses. In 11 patients (86 %) a good visual rehabilitation was achieved with an increase of visual acuity up to 9 lines while obtaining a good contact lens tolerance. One patient wearing an iris-print contact lens was unable to tolerate the contact lens due to its thickness and its weight. In another patient fitting of a contact lens was not possible because of the complicated corneal condition. We did not observed severe contact lens complications at any time. CONCLUSIONS: In addition to operative procedures for visual rehabilitation after open globe injuries, the use of contact lenses is another possible procedure for refractive correction. Different problems such as ametropia following aphakia, irregular or high astigmatism or aniridia can be solved with good visual results, good tolerance and less complications.

Adolescent↗
PubMed2002

X-ray magnetochiral dichroism: a new spectroscopic probe of parity nonconserving magnetic solids.

We report the first experimental detection of x-ray magnetochiral dichroism in magnetoelectric Cr2O3. This dichroism, which does not require any polarized x-ray beam, is related to the time-reversal odd part of the optical activity tensor dominated by electric dipole-electric quadrupole E1E2 interference terms. The experiments were carried out using either a single crystal or a powdered pellet required to grow a single antiferromagnetic domain by magnetoelectric annealing. This new element (edge) specific spectroscopy offers unique access to the atomic orbital anapole moment Omega-z.

Journal Article↗
PubMed2002

[Phacoemulsification of human lens nucleus with a water jet].

BACKGROUND: Today, phacoemulsification with ultrasound represents the gold standard in cataract surgery. Nevertheless, new technologies for this operation are being developed to reduce the loss of endothelial cells, the heating of the tissue, and the size of the accesses. In addition to bimanual phacoemulsification, laser phacoemulsification, and mechanic phacolysis, the waterjet is discussed as an alternative. MATERIALS AND METHODS: Human soft and hard nuclei of the lens obtained by extracapsular cataract extraction (ECCE) were divided in the water bath with the waterjet, whereby the parameter pressure was varied and the time needed for fragmentation was recorded. RESULTS: In spite of different consistencies, all nuclei could be divided under the direct force of the waterjet. For the emulsification of hard nuclei of the lens, a pressure of no less than 10 bar was necessary. This value was obviously higher than a lens capsule can tolerate. For the fragmentation of soft nuclei of the lens with lower acceptable pressures of 5 bar, comparatively long operating times (in some cases over 5 min) were measured. This means that also in these cases a pressure of 10 bar was required. CONCLUSION: Intraocular use of the waterjet with direct effect of the stream with these pressures is not justifiable. Instruments for waterjet phacoemulsification should be developed which pose no danger to the corneal endothelium and lens capsule.

Culture Techniques↗
PubMed2001

Systematics of the induced magnetic moments in 5d layers and the violation of the third Hund's rule.

X-ray magnetic circular dichroism measurements are reported at the beginning (W) and at the end (Ir, Pt) of the 5d series of the periodic table. Considerable induced magnetic moments of about 0.2 mu(B)/atom were probed for the nonmagnetic W and Ir and compared to previous data for the Pt induced moments in multilayers. W was found to couple antiferromagnetically and Ir ferromagnetically to the 3d layers. Finally, the W spin and orbital magnetic moment couple in parallel, contrary to what is expected from the third Hund's rule. This remarkable finding shows that the induced magnetic behavior of 5d layers may be radically different than that of impurities and alloys.

Journal Article↗
PubMed2001

Element-specific magnetization curves and crossover in Co/Cu/Ni/Cu(001) trilayers studied by XMCD.

We present temperature-dependent measurements via the element-specific XMCD technique for Co/Cu/Ni trilayers for cases where the ordering temperature of Co is lower than the one of Ni. Our work focuses mainly on the influence of the interlayer coupling on the shape of the temperature-dependent magnetization curves of Ni. By electing 1.3 ML of Co and 4 ML of Ni we get a lower T(C)(Co) approximately 90 K and a higher T(C)(Ni) approximately 180 K. The crossing of the M(T) curves leads to a rotation of the remanent magnetization of Ni. A case where the sublayer magnetizations change gradually their angle as a function of the temperature is recorded and attributed to a competition between coupling and anisotropy mechanisms.

Journal Article↗
PubMed2001

Magnetic EXAFS at Gd L-edges: the spin-pair-distribution function of Gd neighbors.

The purpose of the experiment is to study the normal and the Magnetic EXAFS (MEXAFS) since EXAFS is the method of choice to investigate the local pair- and spin-pair-distribution function. We present MEXAFS and EXAFS measurements at the L-edges of a Gd single crystal in the temperature range of 10 K to 250 K. Therefore we are able to investigate the MEXAFS in a wide range of the reduced temperature t=T/Tc of 0.04 < or = t < or = 0.85 with Tc=293 K. We find a strong decrease of the nearest neighbor EXAFS which retains only about 35% of its 10 K value already at 250 K. This highlights the importance of lattice vibrations. To analyze the individual scattering contributions to the MEXAFS and the EXAFS, ab initio calculations (FEFF code) have been carried out. The comparison of the temperature-dependent damping of the normal EXAFS with the spin-dependent MEXAFS allows us to separate the influence of lattice vibrations (Debye temperature 160 K) from the magnetic ordering (Curie temperature) on the MEXAFS.

Journal Article↗
PubMed2001

[Olanzapine and pregnancy].

The appearance of psychosis during pregnancy means a challenge for clinicians, either untreated psychiatric disorders or pharmacological treatment of pregnant psychotic females increase risk of complications. Controlled clinical trials can't be evaluated because of ethical considerations, so case reports have higher scientific values than in other clinical issues. The authors inform about a delivery of a young psychotic female, who was treated with olanzapine (atypical antipsychotic) after the 25th weeks of her pregnancy. A healthy newborn was born in the observed case, the Apgar score was 7 at the first minute and 9 at fifth minute.

Adult↗
PubMed2001

[Incidence of potential transmitters of Creutzfeldt-Jakob disease. A study of a collective of potential cornea donors].

BACKGROUND: The prevalence of Creutzfeldt-Jakob disease (CJD) is 1.5 cases per million persons. In addition to familial and sporadic forms, fewer than 5% of cases are due to iatrogenic transmission. Corneal transplantation has clearly been implicated as the origin of CJD in four cases. MATERIALS AND METHODS: We examined possible risks factors for corneal transplantation in material from 2545 deceased patients at the University Hospital of Halle. RESULTS: Two patients had died of CJD or slow virus disease. Also in the 109 identified as being at higher risk of CJD no organs or tissues were harvested. CONCLUSION: We strongly recommend that patients at higher risk group of CJD, patients dying of CNS diseases of unknown origin and cause, and patients dying in psychiatric clinics be excluded from donating organ and tissue.

Adult↗
PubMed2001

[Antimicrobial decontamination of corneal donor material: infection prevention and quality assurance].

BACKGROUND: Microbiological examinations in eye banks have found an increased contamination rate in preservation media. We studied the effect of prolonged submersion time for decontaminating donor globes. MATERIALS AND METHODS: We retrospectively analyzed the primary contamination of conjunctival smears in 76 cornea donors. The submersion time of donor eyes in PVP iodine solution before preparation was prolonged from 1 min to 5 min, and the contamination rate of storage vessels was compared. RESULTS: In 13 of the 76 conjunctival smears we found no contamination. Before prolonging submersion time, the preservation medium was contaminated in 15 cases, but after 5 min no contamination was observed. CONCLUSION: Prolonging the submersion time of donor globes from 1 to 5 min was effective. The model presented here provides guidelines for existing eye banks as well as for those yet to be established.

Antisepsis↗