Absence Of Deposits Research Articles

Ramucirumab in second‑line advanced colorectal cancer therapy: A study on therapeutic outcomes and hepatic sinusoidal platelet aggregation.

The present study investigated the role of ramucirumab (RAM) in treating liver metastases (LMs) as a second-line or salvage treatment in patients with advanced CRC. Of the 36 patients, 21 (58%) received RAM plus folinic acid, fluorouracil and irinotecan (FOLFIRI) as second-line treatment, whereas 15 (42%) received it in a salvage setting. The median overall survival time was 23 months [95% confidence interval (CI), 12-34 months] for those in the second-line treatment group and 8 months (95% CI, 5-19 months) for those in the salvage treatment group. Of the 36 patients, 14 (39%) underwent surgical resection of LMs during chemotherapy. A total of 6 patients underwent surgical resection for LMs for the first time during second-line RAM plus FOLFIRI (RAM-LM); of the remaining 8 patients, 6 underwent resection of LMs during first-line bevacizumab (BEV)-based chemotherapy (BEV-LM). Immunohistochemical analysis of CD42b showed that the platelet aggregation score (CD42b score), which ranges from 0 (absence of deposition) to 3 (presence of linear deposition), tended to decrease with the increasing duration of treatment with both RAM and BEV. Although there was no significant difference in the mean duration of anti-VEGF antibody treatment between the BEV-LM and RAM-LM groups, the median CD42b score was higher in the RAM-LM group (median CD42b score, 3; range, 0-3) compared with that in the BEV-LM group (median CD42b score, 1; range, 0-3; P=0.01), suggesting that RAM induces a different degree of platelet aggregation in liver sinusoids compared to BEV.

Evaporation of process water from recycled containerboard mills

The reduction of the specific effluent discharge volumes of paper mills leads to concentrated process waters that are difficult to treat. Evaporation is an effective water reclamation technology; however, its feasibility largely depends on the fouling behavior of the calcium rich process water. A pilot plant study was conducted to investigate fouling of an evaporator processing the production water from a recycled containerboard mill. The evaporator was operated continuously for five weeks at an evaporation temperature of 55°C and a differential temperature of 5°C, and with a recovery rate of approximately 90%. The calcium ion concentration of the circulating liquor exceeded 7,000 mg/L with a pH of 6. Despite the high fouling potential of the circulating liquor, the heat transfer coefficient did not decline over the investigated trial. The absence of deposits on large areas of the heating surfaces demonstrate that the process water does not generally form deposits under the conditions that were investigated. Calcium sulfate deposits were only found in areas where there was inadequate coverage of liquid over the heating surfaces. The findings show that evaporators can be used to effectively close the water system of recycled containerboard mills without fouling impacting the energy efficiency.

Longitudinal effect of myocardial fat deposition on left ventricular diastolic function: a retrospective cohort study.

There is a known correlation between myocardial steatosis and heart function, but it is unclear how left ventricular diastolic function worsens over time in the myocardial steatosis setting. We sought to investigate whether intramyocardial fat deposition affects diastolic function over time. This was a retrospective analysis of patients who had undergone 1-3 echocardiography assessments between April 2011 and April 2017. Patients were divided into two groups: those with the presence of myocardial fat deposition in the left ventricular myocardium (assessed by having tissue within any 10-mm2 region with computed tomography values between - 190 and - 30 Hounsfield units; + MF), and those with absence of deposition not meeting the threshold (- MF). The rates of change of the standard early diastolic mitral annulus velocity (e') and the transmitral early peak velocity (E)/e' ratio at the second and third echocardiograph assessments were calculated relative to baseline. In total, 125 patients were eligible (+ MF, n = 39; - MF, n = 86) for inclusion. Compared with the - MF group, e' was significantly lower and E/e' was significantly higher in the + MF group at each scan timepoint, even when adjusted for body mass index and sex. A significant average decrease in e' and increase in E/e' was also observed in the + MF group across all scans compared with the - MF group. Myocardial steatosis was associated with an acceleration of decreased left ventricular diastolic function over time.

Middle Palaeolithic, Transitional or Upper Palaeolithic: Geoarchaeological revision of the southern part of the loess site Dzierżysław 1, SW Poland

Sites identified as the Early Upper Palaeolithic (EUP or transitional industries) in Central Europe (CE) have become subject to extensive discussion on the possible interactions between anatomically modern humans and indigenous human species which inhabited the area in the Marine Isotopic Stage 3 (MIS 3, 50–35 ka BP). An open-air site Dzierżysław 1 (SW Poland), known for nearly a hundred years, played a crucial role in envisaging scenarios associated with the development and adaptation of the EUP society. In the late 20th c., due to the excavations in the southern part of the site, it was given status of a multicultural site, with artefacts assigned to the Micoquian, Bohunician and Szeletian culture.This paper presents the findings of the multi-faceted revision of this site. We present the results of field work and chronometric analyses based on a new set of samples and archaeological study of archive records. The use of optically stimulated luminescence (OSL) showed that all the sediments of the site should be assigned to the Plenivistulian (MIS 4/3 and MIS 2). The new chronometric assessment indicates the absence of deposits corresponding to the transitional industries' time window. The sedimentological data integrating with spatial distribution of finds and raw material variation as well as state of preservation and typo-technological features of lithic artefacts indicate that the inventory represents a compilation of the late Middle Palaeolithic (MP, Micoquian) and classical Upper Palaeolithic industries (Aurignacian or Gravettian) with very few pieces corresponding with indeterminate EUP industry.The revision throws a light on the situation in the Moravian Gate and areas north of the Carpathians and Sudetes. The results suggest that sites from the late MP are more numerous than those from the EUP. It seems that the over-representation may result from a long time of accumulation during the MP period. It cannot be excluded that the small number of EUP sites reflects a marginal role of the area north of the Sudetes and Carpathians in the human occupation system of that time.

Custom made polymeric artificial eye: Appearance and characteristics of wear and care

A prosthetic eye may enhance the appearance of individuals who have lost sight due to injury or illness. Implanting a polymeric ocular prosthesis (POP) after an eye is surgically removed following an enucleation, evisceration, or orbital exenteration is always advised. This implant supports proper eyelid functioning as well as increasing patient confidence by restoring natural appearance. From February 2013 to January 2019, an experimental study was done on five hundred cases. The included patients experienced enucleation or evisceration procedure and had ocular prosthesis fitting. Data were entered, coded, cleaned, and analyzed using IBM SPSS statistics. A total of 500 cases completed the questionnaire. Of these, 55.8% were male, and 44.2% were female, with 50.2% of the patients lost their eyes because of injuries. In terms of operation variety, evisceration was done in 61.4% of the patients, enucleation in 37.6%, and others are in only five congenital cases (1%). According to this study, 28.8% of patients suffered from deposits formed on the prosthetic eye, while the absence of deposits was 71.2%. Significant psychological, as well as social consequences can result from the disfigurement associated with eye loss. Despite using the available materials and techniques to treat such patients, one needs to be a little creative and very inventive. Ocular prostheses act as a tool for restoring patients’ self-confidence and facilitating changes in their social convenience. Precise attention is essential to preserve the prosthesis and reminiscent of tissue health.

Investigation of organic precursors and plasma mixtures allowing control of carbon passivation when etching HgCdTe in hydrocarbon-based inductively coupled plasmas

Our interest in introducing oxygen and/or nitrogen atoms in CH4/H2/Ar plasma mixtures by means of organic precursors in the place of CH4 or by partly substituting O2 or N2O for H2 and thereby controlling carbon deposition and surface passivation when etching HgCdTe under low substrate bias conditions is investigated in this study. Using in situ ellipsometry, in situ x-ray photoelectron spectroscopy, atomic force microscopy, and secondary electron microscopy (SEM), we show that nitromethane as a precursor and N2O substitution are attractive alternatives for the following: the absence of deposition although no bias is applied, equivalent postetch surface composition, and comparable performances in terms of etch rate and surface roughness for the latter. Such an approach could provide the soft dry etching conditions needed to reduce the pixel pitch of HgCdTe infrared photovoltaic detectors. The mechanisms that allow suppressing carbon deposition upon O2 or N2O substitution in CH4/H2/Ar plasmas are studied by combining plasma diagnostics (optical emission spectroscopy, actinometry, and ion flux measurements) and surface characterizations. First, using Si as a reference substrate, it is shown that deposition is suppressed whenever the O2 and N2O flow rate is half and twice that of CH4, respectively. Moreover, the study reveals that oxygen is the true etch reactant controlling the competition between film growth and etching in both substituted processes, whereas incorporation of nitrogen in the film upon N2O substitution favors its etching kinetics simultaneously. Second, on HgCdTe, deposition of a hydrocarbonitride film is observed at a low N2O/CH4 ratio (∼0.6). SEM and SEM-energy dispersive x-ray spectroscopy imaging suggest that the film nucleates and grows preferentially on regions where the Cd removal mechanisms happen to be less efficient. At a high N2O/CH4 ratio (∼4), oxidation of the HgCdTe surface is observed.

Nanocatalytic chemohydrodynamic instability: Deposition effects.

Due to the high surface area to volume ratio of nanoparticles, nanocatalytic reactive flows are widely utilized in various applications, such as water purification, fuel cell, energy storage, and biodiesel production. The implementation of nanocatalysts in porous media flow, such as oil recovery and contaminant transport in soil, can trigger or modify the interfacial instabilities called viscous fingering. These instabilities grow at the interface of the fluids when a less viscous fluid displaces a high viscous one in porous media. Here the flow dynamics and the total amount of chemical product are investigated when two reactive miscible fluids meet in a porous medium while undergoing A+B+n → C+n reaction. Nanocatalysts (n) are dispersed in the displacing fluid and deposited gradually with time. Four generic regimes are observed over time as a result of the particle deposition: (1) the initial diffusive regime, where the flow is stable with decreasing production rate, (2) the mixing-dominant fingering regime, where the flow is unstable and the production rate generally increases, (3) the transition regime, where the production rate generally decreases regardless of whether the system is stable or unstable, and (4) the final zero-production regime, where the product diffuses and fades away in the channel. Although the general trend shows a decreasing reaction rate with nanocatalysts deposition, there is a period in which the production rate increases due to the moderate deposition rates. Such an increase of production, however, is not observed in two groups: first, those systems in which the nanocatalysts do not change the viscosity of the base fluid and, second, a subgroup of the systems that are stable before and after the reaction in the absence of deposition.

Differential diagnostic OCT-criteria of acute and chronic central serous chorioretinopathy

to define differential diagnostic criteria for acute and chronic CSC basing on the chorioretinal complex analysis by EDI-optical coherence tomography (OCT). A retrospective analysis was performed that included data of 112 patients with CSC, who were assigned to either the 'acute' (52 patients) or 'chronic' (60 patients) group depending on symptoms duration (3 months) and fluorescein angiography findings. With the enhanced depth imaging (EDI) module mounted on OCT (Spectralis, Heidelberg, Germany), the structure of the chorioretinal complex was studied. In acute CSC, the height of the neuroepithelium detachment (310.73±113.63 μm) was greater than that in chronic CSC (205.68±90.80 μm), p=0.03. The frequency of subretinal deposits also differed (17.3% and 100% of cases, respectively), p<0.01. The subfoveal choroidal thicknesses were similar (462.7±110.7 and 494.7±132.1 μm, respectively, p=0.6), however, in acute CSC, diffuse thickening of the choroid was noted (39 patients, 75% of cases), while chronic CSC was marked by local dilatation of the Haller's layer (39 eyes, 65% of cases). The diameter of hyporeflective pockets in the Haller's layer in the 'acute' (324±98.1 μm) and 'chronic' (352.0±84.3 μm) groups correlated with choroidal thicknesses (r=0.68, r=0.75). Hyperreflective intrachoriodal dots were more common in the 'chronic' group (acute - 1.9%, chronic - 68.3%), so did hyperreflective vascular walls -13.5% and 68.3%, respectively, p<0.01. Dome-shaped RPE detachments were observed equally often in both groups (acute - 67.3%, chronic - 68.3%, p=0.9), while the 'double-layer sign' was only characteristic of chronic CSC (86.7%). OCT criteria of acute CSC include a dome-shaped detachment of neuroepithelium and diffuse thickening of the choroid in the absence of deposits; of chronic CSC - subretinal deposits, local dilatation of the Haller's layer vessels, hyperreflective vascular walls, intrachoroidal dots, and the 'double-layer sign'.

Hydrodynamic Perspective on Asphaltene Agglomeration and Deposition

In this work, we propose a detailed numerical model for asphaltene agglomeration and deposition, as induced by a resolved turbulent liquid carrier phase flow, in which transport, breakup, and re-entrainment are also taken into account. Asphaltene phase separation is represented by the appearance of adhesive primary particles, which bond upon collision and act as a precursor to agglomerate formation. Deposition is considered using a novel approach in the context of agglomerate structure resolving simulations: the attractive particle–wall interaction is modeled by a damped harmonic oscillator, whereas the deceleration of depositing particles occurs with a characteristic relaxation time. In the absence of deposition, agglomeration and breakup give rise to a statistical steady state. Universal scaling relations, valid for a large range of Reynolds numbers, accurately predict the mean agglomerate mass in this steady state. We show that the shape of the agglomerates is insensitive to the breakup mechanism considered and that the fractal dimension is similar to experimental values reported in the literature for asphaltenes. It is found that the properties of the agglomerates change when two-way coupling is considered instead of one-way coupling, but not when large-eddy simulations are conducted instead of direct numerical simulations. When particle–wall interactions are included, deposition predominantly occurs close to the region where asphaltene phase separation takes place. The morphology of the deposit layer is shown to depend upon the local concentration and the mobility of the deposited particles; we also present how these features depend upon the parameters of the deposition model.

Development of a Long-Term Superficial Device for Partial Circulatory Support

The Symphony is a new circulatory support device that can be implanted with a superficial operation and provides synchronous, partial circulatory support. Potential advantages are:1) less invasive operation,2) promotes heart recovery,3) improved hemodynamics to allow up-titration of meds, and 4)avoids sternotomy. We present pre-clinical implant data in support of the first-in-man clinical trial. The Symphony system has 3 components:1) 30 ml pumping chamber that is sewn via a short graft to the subclavian artery, 2) a wearable (<2.3 kg) pneumatic driver and, 3) subcutaneous (subQ) EKG leads. The device is placed through an infraclavicular incision as for pacemaker placement. Hemocompatibility is achieved with tangential inflow that creates continuous washing and no objects (valves, impellers) in blood path. The device removes blood from arterial circulation during systole to provide afterload reduction and returns blood during diastole to augment coronary and systemic flow. In a bovine model, the device was sewn to the carotid artery with superficial placement in the neck to assess the subQ leads (n=4,7 days, n=2, 14 days) and final device design (n=5, 14 days, n=6, 30 days-2 complete,4 ongoing). All animals were maintained on support with no episodes of device malfunction. At explant, all pumps and grafts had excellent hemocompatibility with absence of deposits on all blood contacting surfaces. There was no significant hemolysis. Necropsies had no evidence of thromboembolism. SubQ EKG leads were easily placed through the original incision. R wave detection with subQ leads was equal to epicardial leads at rest (beats analyzed 133,627, PPV(positive predicted value) =95.6%,sensitivity=95.1%) and with exercise (beats analyzed 37,154, PPV=92.7%, sensitivity=90.0%). We have demonstrated excellent hemocompatibilty and device function. This is the first long-term circulatory support device that can be placed with a minor operation. This operartive approach combined with synchronized suppport may increase the incidence of myocardial recovery and improve tolerance of HF meds. Device and implant costs will be less than current devices. Final preparations for a FIM clinical trial are underway. The Symphony is a new circulatory support device that can be implanted with a superficial operation and provides synchronous, partial circulatory support. Potential advantages are:1) less invasive operation,2) promotes heart recovery,3) improved hemodynamics to allow up-titration of meds, and 4)avoids sternotomy. We present pre-clinical implant data in support of the first-in-man clinical trial. The Symphony system has 3 components:1) 30 ml pumping chamber that is sewn via a short graft to the subclavian artery, 2) a wearable (<2.3 kg) pneumatic driver and, 3) subcutaneous (subQ) EKG leads. The device is placed through an infraclavicular incision as for pacemaker placement. Hemocompatibility is achieved with tangential inflow that creates continuous washing and no objects (valves, impellers) in blood path. The device removes blood from arterial circulation during systole to provide afterload reduction and returns blood during diastole to augment coronary and systemic flow. In a bovine model, the device was sewn to the carotid artery with superficial placement in the neck to assess the subQ leads (n=4,7 days, n=2, 14 days) and final device design (n=5, 14 days, n=6, 30 days-2 complete,4 ongoing). All animals were maintained on support with no episodes of device malfunction. At explant, all pumps and grafts had excellent hemocompatibility with absence of deposits on all blood contacting surfaces. There was no significant hemolysis. Necropsies had no evidence of thromboembolism. SubQ EKG leads were easily placed through the original incision. R wave detection with subQ leads was equal to epicardial leads at rest (beats analyzed 133,627, PPV(positive predicted value) =95.6%,sensitivity=95.1%) and with exercise (beats analyzed 37,154, PPV=92.7%, sensitivity=90.0%). We have demonstrated excellent hemocompatibilty and device function. This is the first long-term circulatory support device that can be placed with a minor operation. This operartive approach combined with synchronized suppport may increase the incidence of myocardial recovery and improve tolerance of HF meds. Device and implant costs will be less than current devices. Final preparations for a FIM clinical trial are underway.

Two-fluid pressure-driven channel flow with wall deposition and ageing effects

Two-fluid, stratified pressure-driven channel flow is studied in the limit of small viscosity ratios. Cases are considered in which the core fluid undergoes phase separation that results in the ‘precipitation’ of a distinct phase and the formation of a wall layer; these situations are common in the oil industry where ‘fouling’ deposits are formed during the flow. The thickness of this layer increases as a result of continual deposition through Stefan-like fluxes, which are related to the phase behaviour of the core fluid through a chemical equilibria model that treats the fluid as a bi-component mixture. The deposit also undergoes an ‘ageing’ process whereby its viscosity increases due to the build-up of internal structure; the latter is modelled here via a Coussot-type relation. Lubrication theory is used in the wall layer and an integral balance in the core fluid wherein inertial effects are important. By choosing appropriate semi-parabolic velocity and temperatures closures for the laminar flow in the channel core, and a closure relation for the wall layer rheology, evolution equations are derived that describe the flow dynamics. In the presence of ageing but absence of deposition, it is demonstrated how the time-varying deposit rheology alters the wave dynamics; for certain parameter ranges, these effects can give rise to the formation of steep waves and what appears to be finite-time ‘blow-up’. With both ageing and deposition, the spatio-temporal evolution of the deposit is shown together with the increase in the deposition rate with increasing temperature difference between the wall and the inlet.

Late Pleistocene stratigraphy, sedimentology and paleoenvironmental evolution of the Tarija-Padcaya basin (Bolivian Andes)

We illustrate the results of geomorphological, stratigraphical and sedimentological analysis of the Tarija-Padcaya basin, a wide depression in the eastern side of the Bolivian Cordillera. The basin is well known for the rich mammal fauna discovered since the beginning of the 19th century. The sedimentary infilling belongs to the Tolomosa Formation, corresponding to a major synthem subdivided into three main sub-synthems, mostly made of fluvial and alluvial fan sediments locally weathered by paleoalfisols (Ancon Grande sub-synthem), glacial and fluvio-glacial sediments (Puente Phayo sub-synthem) and finally alluvial fan and alluvial plain sediments (San Jacinto sub-synthem). Radiocarbon dating provides a chronology for the last sub-synthem and testifies that the sequence encompasses the Last Interglacial–Glacial cycle and constitutes a good proxy record for Late Pleistocene climatic changes. The occurrence of glacial deposits in the deeper part of the sedimentary filling suggests a major ice advance during MIS 4 and, together with glacial geomorphological evidence, points to further glacial erosion during the Last Glacial Maximum (LGM). The importance of glacial deposition and erosion opens the question of correlation with the events reported in the nearby Altiplano, where glacial deposits have been recognized only along the slopes of the higher volcanoes. In the Altiplano the LGM has been claimed to be characterized by an absence of deposition or deep erosion, due to extreme dryness, but the Tarija record suggests an erosional event of a scale that would imply the occurrence of a large ice cap.

Pebble abrasion during fluvial transport: Experimental results and implications for the evolution of the sediment load along rivers

In actively eroding landscapes, fluvial abrasion modifies the characteristics of the sediment carried by rivers and consequently has a direct impact on the ability of mountain rivers to erode their bedrock and on the characteristics and volume of the sediment exported from upland catchments. In this experimental study, we use a novel flume replicating hydrodynamic conditions prevailing in mountain rivers to investigate the role played by different controlling variables on pebble abrasion during fluvial transport. Lithology controls abrasion rates and processes, with differences in abrasion rates exceeding two orders of magnitude. Attrition as well as breaking and splitting are efficient processes in reducing particle size. Mass loss by attrition increases with particle velocity but is weakly dependent on particle size. Fragment production is enhanced by the use of large particles, high impact velocities and the presence of joints. Based on our experimental results, we extrapolate a preliminary generic relationship between pebble attrition rate and transport stage (τ*/τ*c), where τ* = fluvial Shields stress and τ*c = critical Shields stress for incipient pebble motion. This relationship predicts that attrition rates are independent of transport stage for (τ*/τ*c) ≤ 3 and increase linearly with transport stage beyond this value. We evaluate the extent to which abrasion rates control downstream fining in several different natural settings. A simplified model predicts that the most resistant lithologies control bed load flux and fining ratio and that the concavity of transport‐limited river profiles should rarely exceed 0.25 in the absence of deposition and sorting.

Quantitative Identification of Metallogenic Epochs and Provinces: Application to Phanerozoic Porphyry Copper Deposits

The terms “metallogenic epoch” and “metallogenic province” have been widely used for many years, but are so poorly defined that most of Earth’s surface and geologic history has been designated a metallogenic feature of some sort. We propose defining metallogenic epoch and metallogenic province as those time intervals of Earth history and regions of Earth, respectively, which contain a significantly greater number of deposits or larger tonnage of a specific deposit type than would have resulted from average rates of mineralization that have occurred over Phanerozoic time. Here, we evaluate the application of this definition to porphyry copper deposits. Metallogenic epochs for porphyry copper deposits can be identified by comparison between a real-Earth age-frequency distribution based on ages of known deposits and a model age-frequency distribution that simulates the formation of porphyry copper deposits and their subsequent vertical uplift and/or subsidence (relative to the Earth’s surface) after they form. The latter represents the age-frequency distribution that would be expected if rates of mineralization did not deviate from the Phanerozoic average, and is determined by least-squared minimization of differences between model and real-Earth age-frequency values. Metallogenic epochs are defined as (duration-normalized) time periods in which real-Earth numbers or sizes of deposits differ significantly from the model value of average numbers or sizes of deposits that have formed over the past ~545 m.y. of Earth history. Eight of the 80 Phanerozoic stages, constituting 5.5 percent of this time interval, meet this definition; these include the upper Eocene, Paleocene (all 3 stages), lower Triassic, middle Pennsylvanian, upper Silurian, and upper Ordovician. Metallogenically impoverished stages occurred during the Upper Cretaceous and the upper Oligocene. Time intervals of deposit enrichment (and scarcity) exhibit little correlation with records of widely known global geologic features or processes. At a more regional scale, however, mineralization along South and Central America slightly postdated times of enhanced production of East Pacific sea floor, and many Paleocene deposits underwent enhanced preservation beneath younger rocks. Metallogenic provinces appear to be recognizable through use of the power-law relationship between the duration-normalized spatial density of real-Earth deposits and the size of areas that host the deposits. Comparison of real-Earth spatial densities to a best-fit line to data for all areas containing deposits allows recognition of areas that have greater spatial densities. Our analysis suggests that variation in the distribution of porphyry copper deposits in both time and space are largely unpredictable at even epoch and regional scales of consideration, respectively, and indicate that the presence or absence of deposits in one time interval or region does not effectively predict the abundance of other deposits in other time intervals or geographic localities. This conclusion, however, does not preclude the importance of geologic controls on either deposits or metallogenic features. Rather, it strongly affirms the widely accepted fact that the distribution of ore deposits and metallogenic features is due to a large number of geologic factors and processes that vary from place to place and time to time. More rigorous definition of metallogenic epochs and provinces and more detailed geologic study at the local scale will lead to a better understanding of those processes that account for statistically anomalous concentrations of mineralization in both time and space.

Influence of heat transfer on the application of solid lubricant on hot dies

This paper proposes a mechanism for the build-up of solid lubricant sprayed as a water suspension on a hot surface such as a casting or forging die. During this process, lubricant build-up depends on heat transfer in the die. The proposed mechanism also explains experimental observations of the absence of deposition at high die temperatures, and runoff of lubricant at low temperatures. The model is compared with experiments, and a critical “sticking temperature” is determined for the experimental conditions.

The fate of the (reactive) primary ion: Sputtering and desorption

Accurate modeling of the enhancement of the ionization probabilities of secondary ions (positive and negative) by the presence of reactive species requires a precise determination of their concentration at the outermost surface and thus a fundamental understanding of their incorporation and release processes. In the present paper we discuss these processes for oxygen, cesium and cluster ion bombardment with a special emphasis on their importance at (very) low bombardment energies. At these energies the sputtering processes becomes very small and deposition instead of erosion is predicted while for some species such as oxygen and cesium, an additional process, i.e. desorption, becomes more important thereby enabling a stationary state without deposition. The desorption process is a property of the primary ion and element specific and can be predicted based on the sputter yields and heat of sublimation. For those species/conditions where desorption is not operational (such as for C 60-beams), depth profiling at very low energies and with low sputter yields (<1) will not be possible and accumulation of the primary ion (thin film growth) is observed. The absence of deposition under oxygen, cesium and (SF 5) n -bombardment and the positive impact of oxygen flooding on C 60 bombardment can all be explained when the desorption mechanism is included in the balance equation.

UNCERTAINTIES IN AEROSOL DEPOSITION WITHIN THE RESPIRATORY TRACT USING THE ICRP 66 MODEL: A STUDY IN WORKERS

This study estimates uncertainties in aerosol deposition within the main regions of the human respiratory tract calculated using the ICRP 66 model. Uniform, triangular, normal, or lognormal distributions were assigned to the model parameters, which involve physical properties of aerosols, their inhalability, their thermo- and aerodynamic deposition efficiencies, and the anatomy, physiology, and exertion level of the individuals. Calculations were performed over a range of aerosol sizes from 0.01 to 50 mum. Monodispersed aerosols were characterized by their aerodynamic diameter (dae). Polydispersed aerosols were characterized by their activity median aerodynamic diameters (AMADs) and the geometric standard deviation (GSD) in diameter. Lognormal distributions of particle deposition were generally observed with low GSD (< 2). The highest uncertainties were observed within the deep lung for the smallest and the largest aerosol sizes, which were mainly due either to particle density or to aerodynamic deposition efficiencies and anatomical and physiological variability, respectively. In the case of diameters larger than 5 mum, uncertainties in the deep lung deposition were much more important for monodispersed than for polydispersed aerosols. This was explained both by the size distribution of the deposited aerosol, the median of which corresponded to a maximal dae value of about 7 and 5 in bronchioles and alveoli, respectively, and by the absence of deposition, which occurs for dae equal to or larger than 50 mum, depending on the exertion level. Thus, in the range of AMADs considered, for the four default workers proposed by ICRP 66, uncertainties in aerosol deposition remain low, with GSD smaller than 3.

Dislocation-driven surface dynamics on solids.

Dislocations are line defects that bound plastically deformed regions in crystalline solids. Dislocations terminating on the surface of materials can strongly influence nanostructural and interfacial stability, mechanical properties, chemical reactions, transport phenomena, and other surface processes. While most theoretical and experimental studies have focused on dislocation motion in bulk solids under applied stress and step formation due to dislocations at surfaces during crystal growth, very little is known about the effects of dislocations on surface dynamics and morphological evolution. Here we investigate the near-equilibrium dynamics of surface-terminated dislocations using low-energy electron microscopy. We observe, in real time, the thermally driven nucleation and shape-preserving growth of spiral steps rotating at constant temperature-dependent angular velocities around cores of dislocations terminating on the (111) surface of TiN in the absence of applied external stress or net mass change. We attribute this phenomenon to point-defect migration from the bulk to the surface along dislocation lines. Our results demonstrate that dislocation-mediated surface roughening can occur even in the absence of deposition or evaporation, and provide fundamental insights into mechanisms controlling nanostructural stability.

Complement factor B and the alternative pathway of complement activation in bovine milk.

The contribution of the alternative pathway of complement activation to the capacity of normal milk to deposit C3 fragments on bacteria was tested by attempting to block C3 deposition with antibodies to the alternative pathway component factor B (fB). Factor B was purified and antibodies of the IgY class, which does not activate mammalian complement, were obtained from the egg yolk of immunized laying hens. These antibodies specifically inhibited the deposition of C3. This inhibition and the absence of deposition of C4 demonstrated that C3 deposition in normal milk resulted from the activation of the alternative pathway. Antibodies raised in rabbit were used to develop an ELISA for measuring fB concentrations in milk. The mean concentration of fB was 2.06 microg/ml (+/- 0.18, SEM), 0.57% of the mean value found in serum (360 microg/ml). This proportion was comparable to that of serum albumin (0.63% of serum value) but less than the proportion of C3 in milk (2.71%). Nevertheless, fB was apparently not a limiting factor for the functioning of the alternative pathway, since addition of purified fB to normal milk did not improve C3 deposition. In serum, mild heat-treatment (56 degrees C for 3 min or 50 degrees C for 45 min) blocked the alternative pathway and destroyed fB, as shown by loss of antigenicity in ELISA. In milk, mild heat-treatment did not abrogate C3 deposition, and fB was protected, retaining its functionality and antigenicity. Heating at 56 degrees C for at least 45 min was necessary to completely inhibit C3 deposition in normal milk.

An objective method for mapping hazardous flow deposits from the stratigraphic record of stratovolcanoes: a case example from Montagne Pelée

A method is described that enables a variety of maps, which indicate the probabilities of deposition, to be constructed in a reproducible manner from the stratigraphie information typically available at well-studied stratovoicanoes. These maps can then be used as a basis for hazard assessment. The sampling of the deposits of previous eruptions is subject to uncertainties due to erosion, sectoral deposition and non-exposure. A model-based, iterative algorithm is used to compensate for the incomplete sampling. For each site, the available evidence from the other sites is used to estimate the probability of deposition for missing deposits. A geographical information system (GIS)-based method that uses Thiessen polygons to represent the presence or absence of deposits, together with simple cartographic rules based on depositional processes, then defines the extent of deposition. The combined operation of these two techniques is presented for Montagne Pelee in Martinique, using the amended stratigraphic record of Smith and Roobol (1990) for the past 6000 years. Three types of maps are created: maps for individual depositional events (the 1902 block-and-ash flow and surge deposits are used to verify the technique); maps for different deposit types aggregated over 6000 years of activity; and scenario maps which, in Montagne Pelee’s case, recognise that during the next Peleean or Plinian eruption a variety of hazards will have to be confronted.