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Radiation Field (radiation + field)
Selected AbstractsMalignant fibrous histiocytoma of the sinonasal tractHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 1 2009Cheng-Ping Wang MD Abstract Background Sinonasal malignant fibrous histiocytoma (MFH) is rare. Methods Twenty-five patients were registered with a diagnosis of sinonasal MFH at our hospital in the past 30 years. Clinical data were retrospectively reviewed. Results Eight tumors were primary MFH and 17 tumors were post-irradiated MFH, located within the radiation field for previous nasopharyngeal carcinoma. Twenty-one tumors originated from the maxillary sinus, 3 from the nasopharynx, and 1 from the nasal cavity. Twenty-three patients underwent surgery but only 12 tumors were removed completely. The 5-year overall and disease-free survival rates were 25.1% and 21.5%, respectively. Multivariate analyses showed that previous radiation was the only adverse prognostic factor for disease-free survival (p = .045). The 5-year disease-free survival rates of primary MFH and post-irradiated MFH were 72.9% and 0%. Conclusion In this series, post-irradiated MFH was more common than primary MFH. The prognosis of post-irradiated MFH is poor, whereas primary MFH is fair. © 2008 Wiley Periodicals, Inc. Head Neck, 2009 [source] Monte Carlo model of UV-radiation interaction with TiO2 -coated spheresAICHE JOURNAL, Issue 10 2007Gustavo E. Imoberdorf Abstract Photocatalysis is one of the advanced oxidation techniques that are being studied for the treatment of polluted air and water from different sources. From a kinetic point of view, photocatalytic reaction rates are strongly dependent not only on the reactant and product concentrations, but also on the rate of photon absorption. Unfortunately, the local rate of photon absorption is usually difficult to evaluate because of (i) the inherent complexity of the system and (ii) the lack of data concerning the photocatalyst optical properties. The final objective of this project is focused on the development of a complete model of the radiation field; the bed structure, and the flow pattern to describe the operation of a fixed bed photocatalytic reactor. In this article, the interaction between radiative energy and TiO2 -coated fused-silica sphere beds was studied. The proposed model was built applying the Monte Carlo method, taking into account the complex reflection/refraction/absorption interactions between radiation and the packed bed. To obtain experimental measurements, an ad hoc device was designed and built. This device allows us to validate the proposed radiation model, and to obtain the optical parameters of the composite photocatalyst, i.e., the refractive index and the surface rough index of the fused-silica spheres, as well as the refractive index and the optical thickness of the TiO2 films. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Calculation of antenna array far field impulse response using the finite-difference time-domain methodMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2006Chen Wu Abstract The waveform in the radiation field of a radar antenna can be obtained by using the convolution of the transmitted signal and the antenna far-field impulse response (AFFIR). In this paper, the finite-difference time-domain (FDTD) method is applied to calculate the AFFIR of an X-band 54-element waveguide slot array at different radiation angles using the excitation of a wideband Gaussian pulse. To demonstrate the usage of the far-field impulse response, the waveforms in the radiation field of a narrowband Gaussian pulse are calculated at three different radiation angles by the convolution of the pulse and the waveguide slot-array AFFIR. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 424,430, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21370 [source] Modification of the gamma-ray spectra by internal absorption in optically violently variable blazars: the example cases of 3C 273 and 3C 279MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008J. Sitarek ABSTRACT Recent observations with the low-threshold Cherenkov telescopes proved that sub-TeV ,-rays are able to arrive from active galaxies at relatively large distances in spite of the expected severe absorption in the extragalactic background light (EBL). We calculate the ,-ray spectra at TeV energies from two example optically violently variable quasars, 3C 273 and 3C 279, assuming that ,-rays are injected in the inner parts of the jets launched by the accretion discs. It is assumed that ,-rays in the broad energy range (from MeV up to TeV) are produced in these blazars with a power-law spectrum with the spectral index as observed from these objects by the EGRET telescope at GeV energies. We take into account the internal absorption of these ,-rays by considering a number of models for the radiation field surrounding the jet. The classical picture of a relativistic blob in a jet for the injection of primary ,-rays is considered, with the injection rate of ,-rays as observed by the EGRET telescope in the GeV energy range. The results of calculations are compared with positive detection and the upper limits on the sub-TeV ,-ray fluxes from these two sources. It is concluded that, even with the Stecker EBL model, the level of ,-ray emission from 3C 279 is close to the recent measurements in the sub-TeV ,-ray energies, provided that the injected ,-ray spectrum extends from the GeV energies over the next two decades with this same spectral index. We also suggest that a flare with a time-scale of a few days from 3C 273 could be detected by the MAGIC II stereo telescopes. [source] Non-local thermodynamic equilibrium dust nucleation in subsaturated vapoursMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Davide Lazzati ABSTRACT We use the kinetic theory of nucleation to explore the properties of dust nucleation in subsaturated vapours. Due to radiation losses, the subcritical clusters have a smaller temperature compared to their vapour. This alters the dynamical balance between the attachment and detachment of monomers, allowing for stable nucleation of grains in vapours that are subsaturated for their temperature. We find this effect particularly important at low densities and in the absence of a strong background radiation field. We find new conditions for stable nucleation in the n,T phase diagram. The nucleation in the non-local thermodynamic equilibrium (non-LTE) regions is likely to be at much slower rate than in the supersaturated vapours. We evaluate the nucleation rate, warning the reader that it does depend on poorly substantiated properties of the macro-molecules assumed in the computation. On the other hand, the conditions for nucleation depend only on the properties of the large stable grains and are more robust. We finally point out that this mechanism may be relevant in the early Universe as an initial dust pollution mechanism, since once the interstellar medium is polluted with dust, mantle growth is likely to be dominant over non-LTE nucleation in the diffuse medium. [source] Deep spectroscopy of the FUV,optical emission lines from a sample of radio galaxies at z, 2.5: metallicity and ionization,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008A. Humphrey ABSTRACT We present long-slit near-infrared (NIR) spectra, obtained using the Infrared Spectrometer And Array Camera (ISAAC) instrument at the Very Large Telescope, which sample the rest-frame optical emission lines from nine radio galaxies at z, 2.5. One-dimensional spectra have been extracted and, using broad-band photometry, have been cross-calibrated with spectra from the literature to produce line spectra spanning a rest wavelength of ,1200,7000 Å. The resulting line spectra have a spectral coverage that is unprecedented for radio galaxies at any redshift. We have also produced a composite of the rest-frame ultraviolet (UV),optical line fluxes of powerful, z, 2.5 radio galaxies. We have investigated the relative strengths of Ly,, H,, H,, He ii,1640 and He ii,4687, and we find that Av can vary significantly from object to object. In addition, we have identified new line ratios to calculate electron temperature: [Ne v],1575/[Ne v],3426, [Ne iv],1602/[Ne iv],2423, O iii],1663/[O iii],5008 and [O ii],2471/[O ii],3728. We calculate an average O iii temperature of 14100+1000,600 K. We have modelled the rich emission line spectra, and we conclude that they are best explained by active galactic nucleus (AGN) photoionization with the ionization parameter U varying between objects. For shock models (with or without the precursor) to provide a satisfactory explanation for the data, an additional source of ionizing photons is required , presumably the ionizing radiation field of the AGN. Single slab photoionization models are unable to reproduce the high- and the low-ionization lines simultaneously: the higher ionization lines imply higher U than do the lower ionization lines. This problem may be alleviated either by combining two or more single slab photoionization models with different U, or by using mixed-medium models such as those of Binette, Wilson & Storchi-Bergmann. In either case, U must vary from object to object. On the basis of N v/N iv] and N iv]/C iv we argue that, while photoionization is the dominant ionization mechanism in the extended emission line regions (EELR), shocks make a fractional contribution (,10 per cent) to its ionization. The N v/N iv] and N iv]/C iv ratios in the broad-line region (BLR) of some quasars suggest that shock ionization may be important in the BLR also. We find that in the EELR of z, 2 radio galaxies the N/H abundance ratio is close to its solar value. We conclude that N/H and metallicity do not vary by more than a factor of 2 in our sample. These results are consistent with the idea that the massive ellipticals which become the hosts to powerful AGN are assembled very early in the history of the universe, and then evolve relatively passively up to the present day. [source] The dust temperatures of the pre-stellar cores in the , Oph main cloud and in other star-forming regions: consequences for the core mass functionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007Dimitris Stamatellos ABSTRACT We estimate the dust temperatures of the clumps in the , Oph main cloud taking into account the 3D geometry of the region, and external heating from the interstellar radiation field and from HD 147879, a nearby luminous B2V star, which is believed to dominate the radiation field in the region. We find that the regions where pre-stellar cores are observed (i.e. at optical visual extinctions >7 mag) are colder than ,10 ,11 K. These dust temperatures are smaller than those which previous studies of the same region have assumed. We use the new dust temperatures to estimate the masses of the pre-stellar cores in the , Oph main cloud from millimetre observations, and we find core masses that are larger than previous estimates by a factor of ,2 ,3. This affects the core mass function (CMF) of the region; we find that the mass at which the core mass spectrum steepens from a slope ,, 1.5 to a slope ,, 2.5 has moved from ,0.5 to ,1 M,. In contrast with the CMF in other star-forming regions (e.g. Orion), there is no indication for a turnover down to the completeness limit (,0.2 M,), but the CMF may flatten at around ,0.4 M,. We generalize our results to the pre-stellar cores in Taurus and in Orion. In Taurus, the ambient radiation field heating the pre-stellar cores is believed to be weaker than that in , Oph. Hence, the dust temperatures of the cores in Taurus are expected to be below ,10 ,11 K. In Orion, the radiation field is believed to be 103 times stronger than the standard interstellar radiation field. Based on this assumption, we estimate that the dust temperatures of the pre-stellar cores in Orion are around ,20 ,30 K. [source] Radiative torques: analytical model and basic propertiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007A. Lazarian ABSTRACT We attempt to get a physical insight into grain alignment processes by studying basic properties of radiative torques (RATs). For this purpose we consider a simple toy model of a helical grain that reproduces well the basic features of RATs. The model grain consists of a spheroidal body with a mirror attached at an angle to it. Being very simple, the model allows analytical description of RATs that act upon it. We show a good correspondence of RATs obtained for this model and those of irregular grains calculated by ddscat. Our analysis of the role of different torque components for grain alignment reveals that one of the three RAT components does not affect the alignment, but induces only for grain precession. The other two components provide a generic alignment with grain long axes perpendicular to the radiation direction, if the radiation dominates the grain precession, and perpendicular to magnetic field, otherwise. The latter coincides with the famous predictions of the Davis,Greenstein process, but our model does not invoke paramagnetic relaxation. In fact, we identify a narrow range of angles between the radiation beam and the magnetic field, for which the alignment is opposite to the Davis,Greenstein predictions. This range is likely to vanish, however, in the presence of thermal wobbling of grains. In addition, we find that a substantial part of grains subjected to RATs gets aligned with low angular momentum, which testifies that most of the grains in diffuse interstellar medium do not rotate fast, that is, rotate with thermal or even subthermal velocities. This tendency of RATs to decrease grain angular velocity as a result of the RAT alignment decreases the degree of polarization, by decreasing the degree of internal alignment, that is, the alignment of angular momentum with the grain axes. For the radiation-dominated environments, we find that the alignment can take place on the time-scale much shorter than the time of gaseous damping of grain rotation. This effect makes grains a more reliable tracer of magnetic fields. In addition, we study a self-similar scaling of RATs as a function of ,/aeff. We show that the self-similarity is useful for studying grain alignment by a broad spectrum of radiation, that is, interstellar radiation field. [source] Fate of clumps in damped Ly, systemsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Ilian T. Iliev ABSTRACT Recent observations have revealed that damped Ly, clouds (DLAs) host star formation activity. In order to examine if such star formation activity can be triggered by ionization fronts, we perform high-resolution hydrodynamics and radiative transfer simulations of the effect of radiative feedback from propagating ionization fronts on high-density clumps. We examine two sources of ultraviolet (UV) radiation field to which high-redshift (z, 3) galaxies could be exposed: one corresponding to the UV radiation originating from stars within the DLA, itself, and the other corresponding to the UV background radiation. We find that, for larger clouds, the propagating I-fronts created by local stellar sources can trigger cooling instability and collapse of significant part, up to 85 per cent, of the cloud, creating conditions for star formation in a time-scale of a few Myr. The passage of the I-front also triggers collapse of smaller clumps (with radii below ,4 pc), but in these cases the resulting cold and dense gas does not reach conditions conducive to star formation. Assuming that 85 per cent of the gas initially in the clump is converted into stars, we obtain a star formation rate of ,0.25 M, yr,1 kpc,2. This is somewhat higher than the value derived from recent observations. On the other hand, the background UV radiation which has harder spectrum fails to trigger cooling and collapse. Instead, the hard photons which have long mean free-path heat the dense clumps, which as a result expand and essentially dissolve in the ambient medium. Therefore, the star formation activity in DLAs is strongly regulated by the radiative feedback, both from the external UV background and internal stellar sources and we predict quiescent evolution of DLAs (not starburst-like evolution). [source] ISO observations of 3,200 ,m emission by three dust populations in an isolated local translucent cloudMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2005M. G. Rawlings ABSTRACT We present isophot spectrophotometry of three positions within the isolated high-latitude cirrus cloud G 300.2,16.8, spanning from the near- to far-infrared (NIR to FIR). The positions exhibit contrasting emission spectrum contributions from the unidentified infrared bands (UIBs), very small grains (VSGs) and large classical grains, and both semi-empirical and numerical models are presented. At all three positions, the UIB spectrum shapes are found to be similar and the large grain emission may be fitted by an equilibrium temperature of ,17.5 K. The energy requirements of both the observed emission spectrum and optical scattered light are shown to be satisfied by the incident local interstellar radiation field (ISRF). The FIR emissivity of dust in G 300.2,16.8 is found to be lower than in globules or dense clouds and is even lower than model predictions for dust in the diffuse interstellar medium (ISM). The results suggest physical differences in the ISM mixtures between positions within the cloud, possibly arising from grain coagulation processes. [source] Constraints on the ultraviolet metagalactic emissivity using the Ly, forestMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2003Avery Meiksin ABSTRACT Numerical hydrodynamical simulations have proven a successful means of reproducing many of the statistical properties of the Ly, forest as measured in high redshift quasar spectra. The source of ionization of the intergalactic medium (IGM), however, remains unknown. We investigate how the Ly, forest may be used to probe the nature of the sources. We show that the attenuation of Lyman continuum photons by the IGM depends sensitively on the emissivity of the sources, permitting a strong constraint to be set on the required emissivity to match the measured values of the mean IGM Ly, optical depth. We find that, within the observational errors, quasi-stellar object (QSO) sources alone are able to account for the required ultraviolet (UV) background at z, 4. By contrast, the emissivity of Lyman-break galaxies (LBGs) must decline sharply with redshift, compared with the estimated emissivity at z, 3, so as not to overproduce the UV background and drive the mean Ly, optical depth to values that are too low. We also investigate the effect of fluctuations in the UV background, as would arise if QSOs dominated. To this end, we derive the distribution function of the background radiation field produced by discrete sources in an infinite universe, including the effects of attenuation by an intervening absorbing medium. We show that, for z, 5, the fluctuations significantly boost the mean Ly, optical depth, and so increase the estimate for the mean ionization rate required to match the measured mean Ly, optical depths. The fluctuations will also result in large spatial correlations in the ionization level of the IGM. We show that the large mean Ly, optical depth measured at z, 6 suggests such large correlations will be present if QSOs dominate the UV background. A secondary, smaller effect of the UV background fluctuations is a distortion of the pixel flux distribution. While the effect on the distribution may be too small to detect with existing telescopes, it may be measurable with the extremely large telescopes planned for the future. We also show that if QSOs dominate the UV background at z, 6, then they will be sufficient in number to rejuvenate the ionization of a previously ionized IGM if it has not yet fully recombined. [source] What can we learn on the thermal history of the Universe from future cosmic microwave background spectrum measurements at long wavelengths?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003C. Burigana ABSTRACT We analyse the implications of future observations of the cosmic microwave background (CMB) absolute temperature at centimetre and decimetre wavelengths, where both ground, balloon and space experiments are currently under way to complement the accurate COBE/FIRAS data available at ,, 1 cm. Our analysis shows that forthcoming ground and balloon measurements will allow a better understanding of free,free distortions but will not be able to significantly improve the constraints already provided by the FIRAS data on the possible energy exchanges in the primeval plasma. The same holds even for observations with sensitivities up to ,10 times better than those of forthcoming experiments. Thus, we have studied the impact of very high-quality data, such as those, in principle, achievable with a space experiment such as the Diffuse Microwave Emission Survey (DIMES) planned to measure the CMB absolute temperature at 0.5 ,,, 15 cm with a sensitivity of ,0.1 mK, close to that of FIRAS. We have demonstrated that such high-quality data would improve by a factor of ,50 the FIRAS results on the fractional energy exchanges, ,,/,i, associated with dissipation processes possibly occurred in a wide range of cosmic epochs, at intermediate and high redshifts (yh, 1), and that the energy dissipation epoch could also be significantly constrained. By jointly considering two dissipation processes occurring at different epochs, we demonstrated that the sensitivity and frequency coverage of a DIMES -like experiment would allow one to accurately recover the epoch and the amount of energy possibly injected into the radiation field at early and intermediate epochs even in the presence of a possible late distortion, while the constraints on the energy possibly dissipated at late epochs can be improved by a factor of ,2. In addition, such measurements can provide an independent and very accurate cross-check of FIRAS calibration. Finally, a DIMES -like experiment will be able to provide indicative independent estimates of the baryon density: the product ,bH20 can be recovered within a factor of ,2,5 even in the case of (very small) early distortions with ,,/,i, (5,2) × 10,6. On the other hand, for ,b (H0/50)2, 0.2, an independent baryon density determination with an accuracy at , per cent level, comparable to that achievable with CMB anisotropy experiments, would require an accuracy of ,1 mK or better in the measurement of possible early distortions but up to a wavelength from , few × dm to ,7 dm, according to the baryon density value. [source] The age of the Geminids: a constraint from the spin-up time-scaleMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002Martin Beech Abstract Interpreting fireball flickering in terms of the rotational modulation of the ablation process, the time since ejection into space of three Geminid meteoroids is determined. By estimating the time required to spin-up a meteoroid through non-isotropic photon scattering interactions with the solar radiation field, we find meteoroid ages consistent with ejection times some 1000,4000 yr ago. There appears to be some indication that the stream formation process lasted for at least ,1000 yr. We also estimate the rotational bursting conditions for the three Geminid meteoroids and find tensile strengths of some 3 × 105 Pa. We interpret our results as being supportive of the argument that the parent body to the Geminid stream, (3200) Phaethon, is an aged cometary nucleus. [source] Effects of Scatter Radiation on ICD and CRT FunctionPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2008SURAJ KAPA M.D. Background: Effects of direct radiation on implantable cardiac devices have been well studied. However, the effects of scatter radiation are not as clear. Recommendations on management of patients with implantable cardiac devices undergoing radiotherapy are based on limited studies mostly involving pacemakers. We sought to elucidate the effects of scatter radiation on implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy (CRT)-ICDs. Methods: We exposed 12 ICDs and eight CRT-ICDs to 400 cGy of scatter radiation from a 6-MV photon beam. Devices were programmed with nominal parameters and interrogated prior to radiation, after each fraction, upon completion of the radiation course and again 1 week later. A retrospective review of patients undergoing radiotherapy at the Mayo Clinic,Rochester between 2002 and 2007 in whom the device was outside the radiation field was also performed. There were 13 patients with devices undergoing radiotherapy during this time period, 12 of whom were interrogated prior to and after radiation. Results: Interrogation reports were reviewed for device reset or parameter changes. There was no evidence of reset or malfunction during or after radiation. Also, no episodes of device reset, inappropriate sensing or therapy, or changes in programmed parameters were found in our review of patients undergoing radiotherapy. Conclusions: Device reset or malfunction associated with scatter radiation likely represents an unpredictable, rare occurrence. While we see no clear contraindication to radiotherapy in patients with ICDs or CRT-ICDs, precautions should be taken to avoid direct radiation exposure and to closely evaluate patient outcomes before and after the radiation course. [source] Intra-abdominal desmoid tumor after successful treatment for Hodgkin diseasePEDIATRIC BLOOD & CANCER, Issue 5 2005Philip M. Rosoff MD Abstract The risk of second malignancies after successful treatment for Hodgkin disease can be considerable. The most common malignancies are solid tumors arising in irradiated sites, such as the breast and thyroid gland after mantle field radiation. Sarcomas and other musculoskeletal tumors are also seen. We describe a young woman who developed an intra-abdominal desmoid tumor more than 4 years after completing therapy for Stage IIB Hodgkin disease, treated with combination chemotherapy (ABVD) and mantle irradiation. The tumor did not occur at either a surgical site or within a radiation field. She did not carry a mutation for familial adenomatosis polypoli. © 2005 Wiley-Liss, Inc. [source] Motility of Daphnia spinulata as Affected by Solar Radiation Throughout an Annual Cycle in Mid-latitudes of Patagonia,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Rodrigo J. Gonçalves During an annual cycle, Daphnia spinulata collected from a plankton community of Patagonia was exposed outdoors to assess the impact of recently received solar radiation on motility (i.e. swimming speed and gravitaxis). Individual values of these parameters were obtained by video recordings and image analysis at different time intervals during the day. Initial swimming speed varied throughout the year, and changes in speed during exposure were not significantly affected by any waveband used in our experimental design (i.e. PAB, 280,700 nm; PA, 320,700 nm; and P, 400,700 nm). Overall, most of the individuals swam downwards, regardless of the radiation treatment imposed to the samples. We found that multifactor interactions (i.e. not a single parameter explained more than 40% of the observed variability) explained most of our observations on motility parameters. These factors include not only solar radiation, but other physical (underwater radiation field and wind intensity) and biological parameters (food availability, presence of predators and congeners). Our findings indicate that the plankton dynamics in the study site is likely to be governed by a sum of factors which must be taken into account when considering solar radiation effects on aquatic ecosystems. [source] Malignancies of the Ear in Irradiated Patients of Nasopharyngeal CarcinomaTHE LARYNGOSCOPE, Issue 12 2008Wu-Chia Lo MD Abstract Objectives/Hypothesis: To report on the clinical profiles and treatment experiences of patients with second primary ear malignancy after treatment of nasopharyngeal carcinoma (NPC). Study Design: Retrospective case series. Methods: A retrospective review of the clinical outcomes and pathology of 11 irradiated NPC patients who subsequently had second primary malignancies of the ear at a single institution. Results: Ten tumors were squamous cell carcinoma and one tumor was chondrosarcoma occurring within the radiation field of previous treatment for NPC. The interval between previous radiotherapy and diagnosis of ear malignancy was 3 to 27 years with a median time of 17 years. Six tumors were located in the external auditory canal, two in the middle ear cavity, two in the periauricular region and one in the mastoid cavity. Four patients underwent surgery, and the other seven patients underwent surgery plus adjuvant radiotherapy. The 3-year disease-free and overall survival rates were 30.3% and 20%, respectively. Conclusions: Postirradiated malignancy of the ear is extremely rare, but is one of the causes of death for NPC long-term survivors despite curative-intended treatment with surgery plus adjuvant radiotherapy is instituted. [source] Effects of CO2 and dust on present-day solar radiation and climate on MarsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 611 2005Hannu Savijärvi Abstract A comprehensive spectrum-resolving radiative transfer model (SRM) was used to simulate the average, present-day, solar radiation field on Mars. A CO2 -only 6 hPa Martian atmosphere absorbs about 1% of zenith solar radiation, producing a modest heating rate of 4,5 K day,1 in the lowest 10 km. The trace gases have an insignificant effect but airborne dust reduces the downwelling solar flux effectively, and the reflected flux somewhat less. This produces an anti-greenhouse trend (cooling at the surface, warming within the atmosphere, reflection at the top), which increases strongly with the dust load. For instance, with dust visible optical depth of unity and sun in zenith, the surface solar irradiation is attenuated by 26% and the solar heating rate increases to about 70 K day,1 in the lowest 25 km. The numbers are however strongly dependent on the optical properties of the dust, which are not known very well. Several fast two-stream methods for dust were compared with the SRM results. Their common systematic errors were reduced by a simple, physically-based correction. The global albedo of Mars was then studied as a function of dust load, dust optics and surface albedo. The crossover from added airborne dust tending to make the whole planet look whiter or darker occurred at surface albedo of about 35%, nearly independently of the dust load. We demonstrate, however, that this value is sensitive to the optical properties of the assumed dust. Copyright © 2005 Royal Meteorological Society [source] Accounting for overlap of fractional cloud in infrared radiationTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 570 2000J. Li Abstract The cloud-matrix method for describing the mutual cloud-coverage relationship between any two levels is systematically discussed. A general method is devised for calculating the effective cloud emissivity for maximum-random overlap clouds. For several cloud configurations with extreme variation in fractional cloud amounts, the errors are generally very small (<5%). The radiative-transfer process that corresponds to the random-overlap cloud scheme is discussed. Compared with the purely random clouds scheme, the maximum-random overlap scheme always produces a smaller cooling rate in the lower layers of a cloud block and a smaller downward flux. The difference in cooling rate can be about 3 K d,1 and the difference in the downward flux near the surface can be as large as 20 W m,2. The calculations show that the scheme of effective cloud emissivity commonly used in general-circulation models could cause underestimation of cloud cooling rate. The clear-sky and the cloudy-sky radiation field can be obtained through a single calculation process but with different water-vapour profiles. The results show that for the all-sky case the separate treatment of the water-vapour profile for clear and cloudy portions makes only a very small difference in the cooling rate and upward flux at the top of the atmosphere in comparison with the results of an averaged water-vapour profile. [source] Experimental and theoretical assessment of maximum productivities for the microalgae Chlamydomonas reinhardtii in two different geometries of photobioreactorsBIOTECHNOLOGY PROGRESS, Issue 2 2010Hosni Takache Abstract The validity of a simple, reliable, and useful recently published formula enabling to calculate the maximum volumetric biomass productivities in photobioreactors (PBRs) was investigated through the cultivation of the microalga Chlamydomonas reinhardtii. Experimental maximum kinetic performances accurately obtained in two different, artificially lightened torus-plane and cylindrical reactors having the same specific illuminated area confirmed the availability, power, and robustness of such formula. The predictive kinetic parameters previously proposed and validated with cyanobacteria were then proved general and robust in case of eukaryotic microalgae, as postulated in the founding article. In this case, an additional criterion requiring rigorous control of the working illuminated fraction , = 1 ± (15%) inside the reactor is demonstrated. For this, the usefulness and reliability of a generalized two-flux model accurately describing the radiation field inside turbid culture media of C. reinhardtii were also established in this article. These important results contribute to identify the main engineering factors governing light-limited PBRs functioning and then to clarify some misinterpretations widely reported in the literature. Together with the referenced previous work, this article gives a framework toward optimal conception of PBRs on a strong physical basis. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Health status of the oldest adult survivors of cancer during childhood,,CANCER, Issue 2 2010Lisa B Kenney MD Abstract BACKGROUND: Young adult survivors of childhood cancer have an increased risk for treatment-related morbidity and mortality. In this study, the authors assessed how treatment for childhood cancer affects older-adult health and health practices. METHODS: One hundred seven adults treated for childhood cancer between 1947 and 1968, known to have survived past age 50 years, were identified from a single-institution cohort established in 1975. Updated vital status on eligible cases was obtained from public records. Survivors and a control group of their age-matched siblings and cousins completed a mailed survey to assess physical and social function, healthcare practices, and the prevalence of common adult illnesses. RESULTS: Of the 107 survivors known to be alive at age 50 years, 16 were deceased at follow-up; 7 deaths could be associated with prior treatment (second malignancy in radiation field [3], small bowel obstruction after abdominal radiation [2], and cardiac disease after chest irradiation [2]). The 55 survivors (median age, 56 years; range, 51-71 years), and 32 family controls (median age, 58 years; range, 48-70 years), reported similar health practices, health-related quality of life, and social function. However, survivors reported more frequent visits to healthcare providers (P < .05), more physical impairments (P < .05), fatigue (P = .02), hypertension (P = .001), and coronary artery disease (P = .01). An increased risk of hypertension was associated with nephrectomy during childhood (odds ratio, 18.9; 95% confidence interval, 3.0-118.8). CONCLUSIONS: The oldest adult survivors of childhood cancer continue to be at risk for treatment-related complications that potentially decrease their life expectancy and compromise their quality of life. Cancer 2010. © 2010 American Cancer Society. [source] Salvage laryngectomy and pharyngocutaneous fistulae after primary radiotherapy for head and neck cancer: A national survey from DAHANCAHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 9 2003Cai Grau MD, DMSc Objective. In 1998, the Danish Society for Head and Neck Oncology decided to conduct a nationwide survey at the five head and neck oncology centers with the aim of evaluating the surgical outcome of salvage laryngectomy after radiotherapy with special emphasis on identifying factors that could contribute to the development of pharyngocutaneous fistulae. Patients. A total of 472 consecutive patients undergoing postirradiation salvage laryngectomy in the period July 1, 1987,June 30, 1997 were recorded at the five head and neck oncology centers in Denmark. Age ranged from 36 to 84 years, median 63 years, 405 men and 67 women. Primary tumor site was glottic larynx (n = 242), supraglottic larynx (n = 149), other larynx (n = 45), pharynx (n = 27), and other (n = 9). All patients had received prior radiotherapy. Results. Median time between radiotherapy and laryngectomy was 10 months (range, 1,348 months). A total of 89 fistulae lasting at least 2 weeks were observed, corresponding to an overall average fistulae risk of 19%. The number of performed laryngectomies per year decreased linearly (from 58 to 37), whereas the annual number of fistulae increased slightly (from 7 to 11), which meant that the corresponding estimated fistulae risk increased significantly from 12% in 1987 to 30% in 1997. Other significant risk factors for fistulae in univariate analysis included younger patient age, primary advanced T and N stage, nonglottic primary site, resection of hyoid bone, high total radiation dose, and large radiation fields. Multiple logistic regression analysis of these parameters suggested that nonglottic tumor site, late laryngectomy period (1987,1992 vs 1993,1997), and advanced initial T stage were independent prognostic factors for fistulae risk. Surgical parameters like resection of thyroid/tongue base/trachea or radiotherapy parameters like overall treatment time or fractions per week did not influence fistulae risk. Conclusions. The risk of fistulae is especially high in patients initially treated with radiotherapy for nonglottic advanced stage tumors. A significant decrease in the number of performed salvage laryngectomies over the 10 years was seen. Over the same time period, the annual number of fistulae remained almost constant. The resulting more than doubling of fistulae rate could thus in part be explained by less surgical routine. © 2003 Wiley Periodicals, Inc. Head Neck 25: 711,716, 2003 [source] Elastoplastic dynamic analysis with hybrid stress elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2002J. A. Teixeira de Freitas Abstract The stress model of the hybrid finite element formulation is applied to the solution of dynamic elastoplastic structural problems. The stress field is approximated in the domain of the elements and the displacements on its boundary. The displacement, velocity and acceleration approximations in the domain of the element are implicit, in the sense that they result from a combination of the stress estimate with the time integration procedure that ensures that the equilibrium condition is locally satisfied. The finite elements are subdivided in plastic cells where a gradient dependent model is implemented using a hybrid formulation based on the approximation of the plastic parameter and the plastic radiation fields in the domain and on the boundary of the plastic cells, respectively. Generalized variables associated with orthogonal and naturally hierarchical bases are used. The resulting solving systems are symmetric, sparse, p -adaptive and well suited to parallel processing. The performance of the element is assessed using a representative set of testing problems. Copyright © 2001 John Wiley & Sons, Ltd. [source] Formation of hard very high energy gamma-ray spectra of blazars due to internal photon,photon absorptionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008Felix A. Aharonian ABSTRACT The energy spectra of TeV gamma-rays from blazars, after being corrected for intergalatic absorption in the extragalactic background light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle acceleration in TeV blazars and/or to the EBL models. In this paper, we show that the internal absorption of gamma-rays caused by interactions with dense narrow-band radiation fields in the vicinity of compact gamma-ray production regions can lead to the formation of gamma-ray spectra of an almost arbitrary hardness. This allows significant relaxation of the current tight constraints on particle acceleration and radiation models, although at the expense of enhanced requirements to the available non-thermal energy budget. The latter, however, is not a critical issue, as long as it can be largely compensated by the Doppler boosting, assuming large (>10) Doppler factors of the relativistically moving gamma-ray production regions. The suggested scenario of formation of hard gamma-ray spectra predicts detectable synchrotron radiation of secondary electron,positron pairs which might require a revision of the current ,standard paradigm' of spectral energy distributions of gamma-ray blazars. If the primary gamma-rays are of hadronic origin related to pp or p, interactions, the ,internal gamma-ray absorption' model predicts neutrino fluxes close to the detection threshold of the next generation high-energy neutrino detectors. [source] Infrared properties of cirrus clouds in climate modelsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 623 2007Ruben Rodriguez De Leon Abstract The representation in global climate models of the infrared radiative properties of cirrus clouds is assessed by comparing their radiative forcing calculated using airborne in-situ -measured size distributions and retrievals from combined lidar and Doppler-radar data. The latter are fitted to a bimodal function, allowing the inclusion of the size distribution's shape, normally omitted in the characterization of cirrus. The impact of the particle size distribution's shape on the atmosphere's radiation fields is evaluated using a two-stream radiative code. The comparisons show that the effect of the shape of the size distributions used to calculate the radiative forcing of a cirrus layer composed of hexagonal cylinders is not negligible, evidencing the ambiguity linked to the commonly used two-parameter (effective radius and ice water content) characterization of cirrus, and showing that the inclusion of a simple measure of the relative concentration of small particles improves its radiative parameterization. Copyright © 2007 Royal Meteorological Society [source] | ||||||||||||||||