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Biomedical subjects

B Hammer

Publications and source records attributed to B Hammer.

At least 37 records · Page 2Linked to original sources
PubMed2004

Adsorption, diffusion, and dissociation of molecular oxygen at defected TiO2(110): a density functional theory study.

The properties of reduced rutile TiO2(110) surfaces, as well as the adsorption, diffusion, and dissociation of molecular oxygen are investigated by means of density functional theory. The O2 molecule is found to bind strongly to bridging oxygen vacancies, attaining a molecular state with an expanded O-O bond of 1.44 A. The molecular oxygen also binds (with somewhat shortened bond lengths) to the fivefold coordinated Ti atoms in the troughs between the bridging oxygen rows, but only when vacancies are present somewhere in the surface. In all cases, the magnetic moment of O2 is lost upon adsorption. The expanded bond lengths reveal together with inspection of electron density and electronic density of state plots that charging of the adsorbed molecular oxygen is of key importance in forming the adsorption bond. The processes of O2 diffusion from a vacancy to a trough and O2 dissociation at a vacancy are both hindered by relative large barriers. However, we find that the presence of neighboring vacancies can strongly affect the ability of O2 to dissociate. The implications of this in connection with diffusion of the bridging oxygen vacancies are discussed.

Journal Article↗
PubMed2004

Non-surgical treatment of mandibular fractures--survey of 28 patients.

Between January 1996 and January 2001 28 patients (nine females, nineteen males) with 35 fractures were treated by observation and soft diet only. Patients with isolated high condylar neck fractures were not included. The mean age at time of trauma was 35.6 years (5/80). Only patients with normal occlusion and radiologically undisplaced fractures were included. The follow-up time was 15 weeks on average (8/33). The patients did not undergo any active treatment. They just received the instruction to reduce mouth opening and to take a soft diet for 4 weeks. During the first 2 weeks after the trauma the patients were seen twice a week. Follow-up X-rays were performed after 4 and after 8 to 12 weeks. As a preemptive therapy antibiotics (amoxicillin plus clavulanic acid 2 x 1g/day) were given for 5 days. Spontaneous healing of all fractures was observed. In two patients a tooth had to be removed out of the fracture line. One patient complained about an occlusal problem after 1 week. In his case intermaxillary fixation was installed for 2 weeks. For forensic reasons the patients have to be fully informed about possible complications before indicating this type of management. Patient selection is crucial and requires a highly experienced surgeon. Patient inconvenience due to frequent consultations must be taken into consideration. This type of treatment can be recommended only in selected cases.

Adolescent↗
PubMed2004

[Intoxication with methadone and benzodiazepines in a morbidly obese patient in the social environment of a heroin addict receiving methadone maintenance therapy].

Methadone is a well-established maintenance drug for the therapy of opioid addicts. Reduction of mortality, social stabilization and reintegration are basic goals of this therapeutic concept. In the ideal case, total opioid abstinence can be achieved. In Germany, detailed guidelines exist for methadone maintenance treatment (e. g. choice of the maintenance drug, "take home" doses) and are regularly published and updated by the National Medical Council. In the social environment of opioid addicts, misuse or accidental intoxication in non-addict family members or co-addicts may occur. We report an intoxication with methadone of the husband of a heroin-addict patient. In this morbidly obese patient, a simultaneous ingestion of benzodiazepines was suspected. This case report describes the diagnostic and therapeutical options of an opioid intoxication in a patient with severe obesity with special emphasis on the airway management strategy in an out-of-hospital situation.

Analgesics, Opioid↗
PubMed2003

[Vasopressin analogue injection as ultimate measure for counteracting severe catecholamine-refractory poisoning by several vasodilators taken with suicidal intent].

HISTORY AND CLINICAL FINDINGS: A 78-year-old woman was admitted to the intensive care unit 9 hours after ingestion of 2 g of isosorbitmononitrate, 430 mg of amlodipine, 250 mg of benazepril and 600 mg of mirtazapin in suicidal intent. INVESTIGATIONS: Clinical findings and invasive monitoring showed signs of a hyperdynamic hemodynamic cardiovascular failure caused by toxic vasodilatation. TREATMENT AND COURSE: Despite of primary detoxication, intravenous volume infusion with calcium gluconate, glucagon and naloxone and administration (norepinephrine up to 2 micro g/kg/min) no hemodynamic stabilization was achieved. Only when the vasopressin-analogue argipressin was given peripheral vasodilatation was overcome and hemodynamic stabilization resulted. 10 hours after discontinuing argipressin and norepinephrine the patient developed a mesenteric ischemia, and she finally died on the third day after admission. CONCLUSION: In circulatory shock due to toxic vasodilatation the use of vasopressin analogue argipressin can be helpful as an ultima therapeutic measure in catecholamine refractory shock caused by vasodilatation. Attention must be paid to overwhelming vasoconstrictor effects resulting in mesenteric ischemia.

Adrenergic alpha-Antagonists↗
PubMed2003

Active role of oxide support during CO oxidation at Au/MgO.

The oxidation of CO at MgO supported gold aggregates is studied by means of density functional theory calculations. In addition to serving as a structural promoter holding the gold particles, the supporting oxide also takes an active role in the bonding and activation of adsorbates bound to the gold. The oxide stabilizes a peroxolike reaction intermediate, CO.O2, and causes steric repulsion to CO. The most reactive site at Au/MgO appears where the gold shelters the MgO thereby creating a cavity where several low-coordinated Au atoms and Mg2+ cations from the substrate can interact simultaneously with an adsorbate.

Journal Article↗
PubMed2003

[Pigmented villonodular synovitis of the temporo mandibular joint. Differential diagnosis and therapy].

For the temporomandibular joint (TMJ), functional disorders are common but tumors and tumor like lesions are rare, although these are often mistaken for functional ailments. Early examination by computed tomography or, as a method of choice, magnetic resonance imaging is recommended in case of persisting TMJ problems. Pigmented villonodular synovitis (PVNS) is a rare benign but locally destructive fibrohistiocytic lesion originating in synovial tissue. Involvement of the temporomandibular joint is extremely rare, with the average age of patients being 44.6 years. This paper reports on a 13-year-old patient with diffuse PVNS involving the middle ear and middle cranial fossa. The treatment of choice involves wide local excision and reconstruction of the temporomandibular joint with long-term follow-up. Pathogenesis and differential diagnosis are discussed.

Adolescent↗
PubMed2002

[Therapy of verapamil poisoning with noradrenaline and the phosphodiesterase inhibitor enoximone].

HISTORY: A 40 year old patient was transferred to the intensive care unit five hours after the ingestion of 2.4 g of verapamil. ADMISSION FINDINGS: Clinical investigation and invasive monitoring showed signs of cardiogenic shock. THERAPY: Despite primary detoxification and administration of calcium and norepinephrine no adequate cardiovascular stabilization could be achieved. Only when the phosphodiesterase inhibitor enoximone was added, an increase in myocardial inotropy and a stable cardiovascular state was achieved which was also due to the vasoconstrictory effect of norepinephrine overcoming vasodilatation induced by enoximone. CONCLUSION: Detoxification, calcium supplementation and catecholamines are established therapeutic measures. An additional therapy with phosphodiesterase inhibitors is a promising step in conquering predominant heart failure and hypotension.

Adult↗
PubMed2002

Adsorbate-oxide interactions during the NO + CO reaction on MgO(100) supported Pd monolayer films.

The potential energy diagram for the NO+CO reaction on 1, 2, and 3 monolayer (ML) Pd films supported by MgO(100) is calculated using density functional theory. Thin Pd films are generally found to be more reactive than thick films, with a notable exception for nitrogen adsorption on 2 ML Pd/MgO(100). For this system an attractive through-the-metal adsorbate-oxide interaction of 0.5 eV is identified. Nitrogen adsorption is consequently estimated to provide a thermodynamic driving force for the reconstruction of MgO(100) supported 3 ML (or thicker) Pd clusters into thinner Pd clusters.

Journal Article↗
PubMed2002

[Endoscopically assisted Le Fort 1 osteotomy: a study in human cadaver heads].

METHODS AND RESULTS: Endoscopically assisted Le Fort 1-osteotomy was performed in a cadaver study with six human skulls. Vertical incisions were used to approach the maxilla using the endoscope. The bone cuts could be carried out with a 4-mm osteotome preserving the buccal mucosa. The downfracture of the maxilla was accomplished without damaging the descending palatal arteries, which could be verified endoscopically. Rigid fixation was performed using 1.5-mm titanium plates (Synthes, Mathys AG, Bettlach, Switzerland) and self-drilling screws. DISCUSSION: This cadaver study showed that the Le Fort 1 osteotomy could be carried out through limited approaches using endoscopic techniques and self-drilling fixation tools. Further experimental work and improvements will help to introduce this technique into clinical application.

Bone Plates↗
PubMed2002

[Individually CAD-CAM technique designed, bioresorbable 3-dimensional polycaprolactone framework for experimental reconstruction of craniofacial defects in the pig].

METHODS: Twenty orbital defects (2 x 2 cm) were created in ten adult Yorkshire pigs. Two software products (Velocity and Mimix) were evaluated with regard to image processing, three-dimensional reconstruction, and fabrication of individually shaped polycaprolactone (PCL) scaffolds to reconstruct these defects. Four different techniques were tested for the reconstruction: group 1 = no reconstruction, group 2 = polylactide sheet, group 3 = PCL scaffold, group 4 = bone marrow-coated PCL scaffold. The pigs were sacrificed at 3 months. RESULTS: In group 1 soft tissue scar formation could be found, but without any new bone. Group 2 showed a thick fibrous capsule around the PLLA sheet, whereas at the border zone of the defect signs of new bone formation could be detected. In group 3 the PCL scaffolds were filled with fibrous tissue and some areas that showed new bone formation (6.4% of the area of the defect). In group 4 the new bone formation (17.8% of the area of the defect) was significantly higher in quantity than in group 3. CONCLUSION: The PCL scaffold coated with bone marrow seems to be a material that effectively provides osteoinduction with formation of new bone. Long-term results at 12 months are still pending.

Absorbable Implants↗
PubMed2001

[Hypersensitivity syndrome during therapy with allopurinol in asymptomatic hyperuricemia with a fatal outcome].

HISTORY AND ADMISSION FINDINGS: A 86-year-old woman with chronic renal failure was treated with allopurinol for asymptomatic hyperuricemia. After one week she developed quickly progressive exanthema, bullous eruptions, epidermolysis, fever of 39.1; C and dyspnoea at rest. DIAGNOSIS, TREATMENT AND COURSE: The diagnosis of an allopurinol-induced hypersensitivity syndrome with toxic epidermal necrolysis was made from the history, the typical clinical picture and a skin biopsy. Initial therapy starts with steroids. Because of a lack of clinical improvement therapy was changed to immunoglobulins. In addition, systemic analgesia and cardiocirculatory supportive therapy were given. Because of increasing somnolence and severe pain intubation and controlled artificial ventilation were initiated. Despite intensive therapy progressive multi- organ failure developed and the patient died 3 weeks after start of symptoms. CONCLUSIONS: The life threatening hypersensitivity syndrome with fever, eosinophilia, hepatitis, renal failure and skin eruptions as severe as epidermal necrolysis is the most dangerous complication of therapy with allopurinol. The trigger seems to be oxipurinol, the main metabolite of allopurinol, which particularly accumulates in patients with renal failure and concomitant therapy with thiazides. There is no specific treatment of the disease. The use of allopurinol in patients with asymptomatic hyperuricaemia is not indicated in most cases. Dose adjustment according to the clearance of creatinine is mandatory.

Aged↗
PubMed2001

Distinct reaction mechanisms in the catalytic oxidation of carbon monoxide on Rh(110): scanning tunneling microscopy and density functional theory studies.

By means of scanning tunneling microscopy measurements and density functional theory calculations, we identify the reaction mechanism for the oxidation of carbon monoxide to carbon dioxide on the Rh(110) surface at 160 K, which appears to be completely different than the one active at room temperature. The reasons for these different behaviors are determined. Our results demonstrate that even for a very simple catalytic reaction, the microscopic mechanism can dramatically change with temperature, following pathways that differ for nucleation sites and surface propagation and involve different surface moieties.

Journal Article↗
PubMed2001

Oxygen dissociation at Pt steps.

Using scanning tunneling microscopy, thermal energy atom scattering, and density functional theory we have characterized O (2) dissociation on Pt(111) stepped surfaces at the atomic scale. The most reactive site is at the top of the Pt steps. In both the molecular precursor state (MPS) and the transition state (TS), the O (2) has its axis aligned parallel to the step edge. Controlled step decoration with Ag monatomic chains was used to locally tune the reactivity of Pt step sites. The enhanced reactivity at the Pt step sites is not caused by a decrease of the local dissociation barriers from the MPS but is related to a stabilization of both the MPS and TS.

Journal Article↗
PubMed2001

Intra-aortic counterpulsation during carotid stenting.

Postprocedural hypotension following endovascular stent placement of carotid artery disease (CAS) predicts increased in-hospital complications and long-term risk of death. Intra-aortic balloon counterpulsation (IABP) both increases mean arterial pressure and cerebral blood flow and therefore possibly reduces complications due to hemodynamic instability during and after CAS. In this study, we describe the use of IABP in a patient with severe depression of left ventricular function due to diffuse coronary artery disease undergoing CAS. Controlled studies are necessary to demonstrate a potentially protective role of IABP in high-risk CAS patients.

Aorta↗
PubMed2001

[Reconstruction of the orbits with polylactate implants: animal experimental results after 12 months and clinical prospects].

In earlier experiments healing of large orbital wall defects in sheep occurred undisturbed by osteoconductive bone growth along biodegradable membranes when there was no interference with additional bone grafts or titanium miniplate osteosynthesis. In this experiment similar bilateral defects were reconstructed with poly(L/DL 80/20) lactide implants using a microporous membrane 0.5 mm thick without further support on one side, an 0.25 mm microporous membrane supported by solid polylactide buttresses and stabilized by polylactide dowels on the opposite side. After 12 months we found a symmetrical reconstruction of the normal anatomy of the orbits in CT and X-ray examinations. In contrast, histologic investigations revealed massive foreign-body reactions around degrading buttress implants and dowels especially. Milder reactions occurred in some orbits along the membranes as well, in contrast to our earlier experiments with 4-month follow-up. None of the implants had degraded completely 12 months after surgery. In our 12-month long-term survey, polylactide microporous membranes confirmed their osteoconductive potential in orbital wall reconstruction. Nevertheless, massive polylactic implants should not be considered for clinical application in the orbit because of significant late foreign-body reactions.

Animals↗
PubMed2001

[Long-term follow-up of 37 patients with retrofixation of the temporomandibular joint disk 1987-1995].

Between January 1986 and December 1995 64 patients with anterior disc displacement were operated on, the technique being disc retrofixation. Follow-up of 37 patients was possible. Successful treatment was determined using the following criteria: one single operation, the clinical examination and the patient's opinion. The operative treatment was considered as unsuccessful if the patient had to undergo more than one operation or if, postoperatively, the clinical symptoms remained unchanged or even increased. 6 out of 37 patients were operated on twice or three times, another four patients postoperatively complained of unchanged or increased clinical symptoms. Using these criteria, disc retrofixation was ineffective in 30%. Using the correct anatomic position as an additional criterion of effective treatment, unsuccessful retrofixation would be even more than 30%. As a consequence we no longer recommend this technique.

Adolescent↗