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At least 955 records · Page 53Linked to original sources
PubMed2004

A space radiation transport method development.

Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary design concepts to the final design. In particular, we will discuss the progress towards a full three-dimensional and computationally efficient deterministic code for which the current HZETRN evaluates the lowest-order asymptotic term. HZETRN is the first deterministic solution to the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard finite element method (FEM) geometry common to engineering design practice enabling development of integrated multidisciplinary design optimization methods. A single ray trace in ISS FEM geometry requires 14 ms and severely limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given in terms of re-configurable computing and could be utilized in the final design as verification of the deterministic method optimized design.

Cosmids↗
PubMed2002

Desmoplastic small round cell tumour of the pleura: a case report with unusual follow-up.

In 1994 a 19-year-old woman presented with a few weeks history of back ache. Routine chest X-ray and CT examination revealed a lesion originating from the parietal pleura and destroying the ribs. The tumour was resected during thoracotomy. The histological examination raised the possibility of atypical carcinoid tumour. One year later the tumour recurred. After its re-resection, the patient received radiotherapy. Three years after the initial presentation multiple pulmonary metastases developed. The patient was treated with chemotherapy, receiving vincristine, epi-adriamycin and cyclophosphamide in 8 cycles, which resulted in complete remission. Between 1998 and 1999 progressions and partial remissions were observed, while the patient received further cycles of chemotherapy. Histological revision was performed in 1999 and a final diagnosis of desmoplastic small round cell tumour of the pleura was made. Immunohistochemically co-expression of cytokeratin, vimentin, desmin, and NSE was observed. The patient died in June 2000. The whole follow-up period was 76 months. We thought this case to be worth for presentation because this unusual long survival, which was probably due to the aggressive complex anticancer treatment.

Adult↗
PubMedDate not supplied

Assessment of distal tip position of long-term central venous feeding catheters using transesophageal echocardiology.

BACKGROUND: Central vein catheter position is a vital element in promoting longevity and minimizing adverse events associated with long-term parenteral nutrition. Traditionally, position has been verified using a chest radiograph. However, this mode of assessment has limitations as the catheter is placed in a dynamic system subject to forces from changes in posture and diaphragmatic movement. METHODS: We compared the reported position using a chest x-ray compared with assessment using transesophageal echocardiology (TOE) in 9 patients receiving home parenteral nutrition. The x-ray was reported by a radiologist unaware of the study. RESULTS: There were discordant results in 7 of the 9 cases with catheter tip placed in the right atrium or impinging in the tricuspid valve which was not evident from the chest x-ray. TOE offered greater information of catheter tip position and relationship to adjacent anatomy. CONCLUSIONS: Further work is required but this observational study suggests guidelines suggesting the use of a chest radiograph to confirm catheter position may need to be re-assessed.

Catheterization, Central Venous↗
PubMed2005

Relationship between tunnel widening and different rehabilitation procedures after anterior cruciate ligament reconstruction with quadrupled hamstring tendons.

BACKGROUND: It has been demonstrated that bone tunnel widening could appear after knee anterior cruciate ligament (ACL) reconstruction, especially for those patients whose ruptured ACL were reconstructed with semitendinosus and gracilis tendons. Many factors can influence the extent of tunnel widening. Few studies have investigated the relationship between bone tunnel widening and rehabilitation procedures. This research was carried out to find the rehabilitation procedures' influence on the tibial bone tunnel widening after ACL reconstruction. METHODS: Sixty-five cases, whose ACL reconstructions were done using quadrupled semitendinosus and gracilis tendons, were divided into two groups. Group A had 33 cases, 19 men, 14 women, averaged (31.2 +/- 12.4) years old, only ACL reconstruction was done using Paessler's technique, and aggressive rehabilitation procedure was used for function recovery post operation. Group B had 32 cases, 20 men, 12 women, averaged (30.3 +/- 10.3) years old. Except for ACL reconstruction, every patient in group B accepted meniscus repair using re-fixation methods or cartilage repair using microfracture technique, conservative rehabilitation procedure was used post operation. Six months post operation, standard posterior-anterior radiographic plates were taken for each case, CorelDRAW 8.0 software was used to digitize all X-ray plates and measure the upper, middle and lower parts of the tibial tunnel. Magnification effect of X-ray plates was taken out after measurement. RESULTS: Six months after ACL reconstruction the tibial tunnel widening of the upper, middle and lower parts on both the posterior-anterior and lateral X-ray plates in Group A with aggressive rehabilitation procedure was much more serious than in Group B with conservative rehabilitation. KT-1000 knee stability measurement and clinical manifestation showed no difference between the two groups. CONCLUSIONS: Rehabilitation procedure after ACL reconstruction is one of the reasons for tunnel widening. It not only can directly influence the function recovery of ACL reconstructed knee, but also perhaps indirectly influence the function recovery and long-term clinical result of the operated knee by influencing the tunnel widening.

Adult↗
PubMed1998

X-ray structure of a blue-copper nitrite reductase in two crystal forms. The nature of the copper sites, mode of substrate binding and recognition by redox partner.

Denitrification is one of the main steps of the global nitrogen cycle that is sustained by prokaryotic organisms. Denitrifying bacteria use two entirely different enzymes in this process, one based on haem cd1 prosthetic groups and the other on type 1-type 2 Cu centres. Copper-containing nitrite reductases (NiRs) are sub-divided into blue and green NiRs, which are respectively thought to be redox partners of azurins and pseudo-azurins. Crystallographic structures of the blue nitrite reductase from Alcaligenes xylosoxidans (AxNiR) are presented in the oxidised hexagonal form and the substrate-bound orthorhombic form to 2.1 A and 2.8 A resolution, respectively. The complete amino acid sequence of AxNiR has been determined by conventional chemical analysis. A 3 A structure of AxNiR has been published where the modelling was based on the sequence of another blue NiR. The higher resolution of the hexagonal form together with the correct sequence allows a detailed comparison with the crystallographic structures of the green NiRs. There is a striking difference in the overall surface charge distribution between the two sub-groups, providing a neat structural explanation for their different reactivities to pseudoazurin or azurin and supporting the view that electron transfer proceeds via complex formation. A detailed examination of the type-1 Cu site, the site responsible for the colour, reveals several subtle differences, including a lateral displacement of 0.7 A for Smet. The structure of the type-2 Cu site, and changes that occur upon substrate binding are discussed in terms of the catalytic mechanism. The similarity of the type 2 Cu site to the catalytic Zn site in carbonic anhydrase and the catalytic Cu site of superoxide dismutase is re-examined in view of the high-resolution (2.1 A) structure.

Alcaligenes↗
PubMed2005

Induction of DNA-double-strand breaks by auger electrons from 99mTc complexes with DNA-binding ligands.

The potential of certain Auger electron emitting nuclides for systemic radiotherapeutic applications has recently gained much attention. In particular, the ability of several nuclides, including 111In, 125I, and 123I, to induce DNA double-strand breaks (dsb), a good indicator of cytotoxicity, has been extensively studied. However, this ability has never previously been shown experimentally for 99mTc, which, besides the well-known gamma radiation that is used for diagnostic applications, also emits an average of 1.1 conversion electrons and 4 Auger or Coster-Kronig electrons per decay. Owing to the short range of Auger electrons, the radionuclide needs to be located very close to the DNA for dsb to occur. We synthesized two cationic 99mTcI-tricarbonyl complexes with pendant DNA binders, pyrene and anthraquinone. The X-ray crystal structures of the two complexes could be elucidated. Linear dichroism and UV/Vis spectroscopy revealed that the complex with pyrene intercalates DNA with a stability constant, K, of 1.1 x 10(6) M(-1), while the analogous complex with anthraquinone interacts with DNA in a groove-binding mode and has an affinity value of K=8.9 x 10(4) M(-1). We showed with phiX174 double-stranded DNA that the corresponding 99mTc complexes induce a significant amount of dsb, whereas non-DNA-binding [TcO4]- and nonradioactive Re compounds did not. These results indicate that the Auger electron emitter 99mTc can induce dsb in DNA when decaying in its direct vicinity and this implies potential for systemic radiotherapy with 99mTc complexes.

DNA↗
PubMed1992

Molecular modelling of the three-dimensional structure and conformational flexibility of bacterial lipopolysaccharide.

Molecular modelling techniques have been applied to calculate the three-dimensional architecture and the conformational flexibility of a complete bacterial S-form lipopolysaccharide (LPS) consisting of a hexaacyl lipid A identical to Escherichia coli lipid A, a complete Salmonella typhimurium core oligosaccharide portion, and four repeating units of the Salmonella serogroup B O-specific chain. X-ray powder diffraction experiments on dried samples of LPS were carried out to obtain information on the dimensions of the various LPS partial structures. Up to the Ra-LPS structure, the calculated model dimensions were in good agreement with experimental data and were 2.4 nm for lipid A, 2.8 nm for Re-LPS, 3.5 nm for Rd-LPS, and 4.4 nm for Ra-LPS. The maximum length of a stretched S-form LPS model bearing four repeating units was evaluated to be 9.6 nm; however, energetically favored LPS conformations showed the O-specific chain bent with respect to the Ra-LPS portion and significantly smaller dimensions (about 5.0 to 5.5 nm). According to the calculations, the Ra-LPS moiety has an approximately cylindrical shape and is conformationally well defined, in contrast to the O-specific chain, which was found to be the most flexible portion within the molecule.

Carbohydrate Conformation↗
PubMed2001

Kinetics and mechanisms of catalytic oxygen atom transfer with oxorhenium(V) oxazoline complexes.

The rhenium(V) monooxo complexes (hoz)2Re(O)Cl (1) and [(hoz)2Re(O)(OH2)][OTf] (2) have been synthesized and fully characterized (hoz = 2-(2'-hydroxyphenyl)-2-oxazoline). A single-crystal X-ray structure of 2 has been solved: space group = P1, a = 13.61(2) A, b = 14.76(2) A, c = 11.871(14) A, alpha = 93.69(4) degrees, beta = 99.43(4) degrees, gamma = 108.44(4) degrees, Z = 4; the structure was refined to final residuals R = 0.0455 and Rw = 0.1055. 1 and 2 catalyze oxygen atom transfer from aryl sulfoxides to alkyl sulfides and oxygen-scrambling between sulfoxides to yield sulfone and sulfide. Superior catalytic activity has been observed for 2 due to the availability of a coordination site on the rhenium. The active form of the catalyst is a dioxo rhenium(VII) intermediate, [Re(O)2(hoz)2]+ (3). In the presence of sulfide, 3 is rapidly reduced to [Re(O)(hoz)2]+ with sulfoxide as the sole organic product. The transition state is very sensitive to electronic influences. A Hammett correlation plot with para-substituted thioanisole derivatives gave a reaction constant rho of -4.6 +/- 0.4, in agreement with an electrophilic oxygen transfer from rhenium. The catalytic reaction features inhibition by sulfides at high concentrations. The equilibrium constants for sulfide binding to complex 2 (cause of inhibition), K2 (L x mol(-1)), were determined for a few sulfides: Me2S (22 +/- 3), Et2S (14 +/- 2), and tBu2S (8 +/- 2). Thermodynamic data, obtained from equilibrium measurements in solution, show that the S=O bond in alkyl sulfoxides is stronger than in aryl sulfoxides. The Re=O bond strength in 3 was estimated to be about 20 kcal x mol(-1). The high activity and oxygen electrophilicity of complex 3 are discussed and related to analogous molybdenum systems.

Catalysis↗
PubMed1989

Computerized axial tomo-epidurographic and radiographic documentation of unilateral epidural analgesia.

A 23-year-old primigravid patient who received epidural analgesia for pain of labour presented with persistent, apparently irremediable, unilateral analgesia. Computerized axial tomo-epidurography demonstrated absence of circumferential spread due to lateral placement of the catheter. Transforaminal escape of contrast medium into the paravertebral area had occurred and anterior and posterior midline partitioning of the epidural space was obvious. All the usual measures to promote contralateral analgesia, except re-insertion of the catheter, had been tried without success.

Adult↗
PubMed2005

Transport and deposition of sediment-associated Escherichia coli in natural streams.

The association of microorganisms with sediment particles is one of the primary complicating factors in assessing microbial fate in aquatic systems. The literature indicates that the majority of enteric bacteria in aquatic systems are associated with sediments and that these associations influence their survival and transport characteristics. Yet, the nature of these associations has not been fully characterized. In this study, a combination of field experiments and mathematical modeling were used to better understand the processes which control the fate and transport of enteric bacteria in alluvial streams. An experimental procedure, involving the use of a tracer-bacteria, was developed to simulate the transport and deposition of bacteria-laden bed sediments in a small alluvial stream during steady flow conditions. The experimental data and mathematical model were used to determine dispersion coefficients, deposition rates, and partitioning coefficients for sediment-associated bacteria in two natural streams. The results provided evidence that bacterial adsorption can be modeled as an irreversible process in freshwater environments. Net settling velocities of fine sediments and associated bacteria were typically two orders of magnitude lower than those predicted from Stokes equation, due to re-entrainment of settled particles. The information presented in this study will further the development of representative microbial water quality models.

Biodegradation, Environmental↗
PubMed1999

Radioresponsiveness at low doses: hyper-radiosensitivity and increased radioresistance in mammalian cells.

The rationale for and importance of research on effects after radiation at "low doses" are outlined. Such basic radiobiological studies on induction of repair enzymes, protective mechanisms, priming, and hypersensitivity are certainly all relevant to treatment of cancer (see Section 1, Studies at low doses - relevance to cancer treatment). Included are examples from many groups, using various endpoints to address the possibility of an induced resistance, which has been compared to the adaptive response [M.C. Joiner, P. Lambin, E.P. Malaise, T. Robson, J.E. Arrand, K.A. Skov, B. Marples, Hypersensitivity to very low single radiation doses: its relationship to the adaptive response and induced radioresistance, Mutat. Res. 358 (1996) 171-183.]. This is not intended to be an exhaustive review--rather a re-introduction of concepts such as priming and a short survey of molecular approaches to understanding induced resistance. New data on the response of HT29 cells after treatment (priming) with co-cultured activated neutrophils are included, with protection against X-rays (S1). Analysis of previously published results in various cells lines in terms of increased radioresistance (IRR)/intrinsic sensitivity are presented which complement a study on human tumour lines [P. Lambin, E.P. Malaise, M.C. Joiner, Might intrinsic radioresistance of human tumour cells be induced by radiation?, Int. Radiat. Biol. 69 (1996) 279-290].It is not feasible to extrapolate to low doses from studies at high doses. The biological responses probably vary with dose, LET, and have variable time frames. The above approaches may lead to new types of treatment, or additional means to assess radioresponsiveness of tumours. Studies in many areas of biology would benefit from considerations of different dose regions, as the biological responses vary with dose. There may also be some implications in the fields of radiation protection and carcinogenesis, and the extensions of concepts of hyper-radiosensitivity (HRS)/IRR extended to radiation exposure are considered in Section 2, Possible relevance of IRR concepts to radiation exposure (space). More knowledge on inducible responses could open new approaches for protection and means to assess genetic predisposition. Many endpoints are used currently--clonogenic survival, mutagenesis, chromosome aberrations and more direct--proteins/genes/functions/repair/signals, as well as different biological systems. Because of scant knowledge of the relevant aspects at low doses, such as inducible/protective mechanisms, threshold, priming, dose-rate effects, LET within one system, it is still too early to draw conclusions in the area of radiation exposure. Technological advances may permit much needed studies at low doses in the areas of both treatment and protection.

Animals↗
PubMed2000

Incoherent imaging with the soft X-ray microscope

The imaging characteristics for X-ray wavelengths in the "water window" under incoherent imaging conditions (large detector aperture) are examined for the King's College London scanning transmission X-ray microscope with zone-plate objective installed at the Daresbury (UK) synchrotron. The principal consideration was to express image theory, incorporating wave aberrations and apodised zone plates, and to apply the theory to experimental data. Comparisons are made, showing reasonable agreement, for a range of defocus values and two wavelengths. Due to problems in fabrication it was necessary to determine the effective, or operational, zone-plate parameters (radius of outermost active zone rN, width of outermost active zone drN); this was accomplished by through-focus series. Calculated point spread functions were used to deblurr images, in through-focus series of two-dimensional scanned X-ray images of specimen holes and test grating patterns. Significant contrast enhancement is achieved after deconvolution with a best point-to-point resolution of about 35 nm.

Journal Article↗
PubMed2004

Evaluation of lyophilised, gamma-irradiated amnion as a biological dressing.

Burns, non-healing wounds and pressure sores cause extensive damage to the skin leading to infection and loss of precious body fluids. Despite advances in burn management the mortality rate continues to be high and the search for an economical and easily available dressing to control burn wound infection continues. Autologous skin has limited availability and is associated with additional scarring. Conventional dressings require frequent changes which can be painful and may even require anaesthesia. Amnion is an excellent biological dressing and its use in the treatment of burns has special appeal in India as there are religious barriers to the acceptance of bovine and porcine skin.Lyophilised, irradiated amnion provided for the first time in the country by the Tata Memorial Hospital Tissue Bank was evaluated as a temporary biological dressing. It was used to treat 35 patients with burns, 21 patients with bedsores and non-healing ulcers and the skin graft donor sites of 11 patients. The amnion was easy to handle and stuck well to the raw wound bed. An open dressing was used in most of the second degree burns which healed with hyperemia and early pigmentation. In patients with third degree burns, ulcers or skin graft donor sites, closed dressings were used. The exudate and induration were reduced and patients were more comfortable and experienced less pain. There was healthy granulation with good re-epithelialisation. Amnion was not used in patients with infected third degree burns.

Adult↗
PubMed2004

Pyridylthiocarbazide complexes of rhenium with potential radiopharmaceutical applications.

Attachment of a thioamide tethering group provides a modification of the well-known pyridylhydrazine based route to radiolabelling of biomolecules (the HYNIC system) and gives a proligand which gives stable, well-defined chelated derivatives with both Re(v) oxo and Re(III) diazenide cores. Both display previously unknown bonding modes for the pyridylthiocarbazide ligands.

Crystallography, X-Ray↗
PubMed1982

Congenital neurosyphilis: a re-appraisal.

An investigation was undertaken to determine the presence and incidence of neurosyphilis in cases of congenital syphilis. Twenty infants, diagnosed as having congenital syphilis on the basis of a positive serum fluorescent-treponemal-antibody-absorbed immunoglobulin M (FTA-IgM) test, were studied. Eleven had clinical disease, while 3 had non-specific illnesses, but x-rays very suggestive of syphilis. Six were asymptomatic newborns, born of mothers known to have positive VDRL tests. There was no clinical evidence of neurosyphilis. The cerebrospinal fluid (CSF) was definitely abnormal in 2 babies, most likely abnormal in a third, and very doubtfully positive in 2 premature babies. The incidence of neurosyphilis in this series is much lower than that reported in the past. The problems of diagnosing neurosyphilis, and reasons for the low incidence here are discussed.

Diagnosis, Differential↗