Direct molecular-level characterization of different heterogeneous freezing modes on mica – Part 1

The mechanisms behind heterogeneous ice nucleation are of fundamental importance to the prediction of the occurrence and properties of many cloud types, which influence climate and precipitation. Aerosol particles act as cloud condensation and freezing nuclei. The surface–water interaction of an ice nucleation particle plays a major, not well explored, role in its ice nucleation ability. This paper presents a real-time molecular-level comparison of different freezing modes on the surface of an atmospherically relevant mineral surface (mica) under varying supersaturation conditions using second-harmonic generation spectroscopy. Two sub-deposition nucleation modes were identified (one- and two-stage freezing). The nonlinear signal at the water–mica interface was found to drop following the formation of a thin film on the surface regardless of (1) the formed phase (liquid or ice) and (2) the freezing path (one or two step), indicating similar molecular structuring. The results also revealed a transient phase of ice at water–mica interfaces during freezing, which has a lifetime of around 1 min. Such information will have a significant impact on climate change, weather modification, and the tracing of water in hydrosphere studies

NEWZKIOSK.COM

As we are a part of a world full of news, every second there is something happening in the world. IT major players companies did a lot of effort helping the users to find news and follow them by making new technologies like Really Simple Syndication (RSS), online news portals, and SMS subscriptions. Each of those has many problems. For example, RSS could send more than 12,000 emails in less than 8 hours. SMS could help the user to follow only one source of news and the user has to pay for it. NEWZKIOSK IS offering the main headlines from the most famous news sources (CNN, BBC, NYT, Reuters). RSS and WordPress platform will allow Newzkiosk to offer the users the most compatible news portal over the web, less advertisements for more users' satisfaction and convenience

Water Vapor Adsorption and Soil Wetting

Soil water management and irrigation practices largely depend on a timely and accurate characterization of temporal and spatial soil moisture dynamics in the root zone. Consequently, measurements and detailed information about soil water sorption, water content, behavior, and potential are required. In that concern, water vapor adsorption is an important phenomenon in arid and semi-arid regions, as well as in dry periods of tropical soils. Therefore, quantifying adsorption is important for agricultural water management, surface energy balance studies, ecological studies, and remote sensing investigations (changes in surface soil moisture content will affect land surface properties such as albedo, emissivity, and thermal inertia). The vapor pressure and isothermal adsorption of water vapor can be used to predict soil moisture adsorption capacity (Wa), specific surface area, and hydro-physical properties of arid soils such as in Egypt and in the tropical soils in Ecuador. Theory of adsorption of water vapor on soil particles is developed among the mono-molecular and poly-molecular adsorption with respect to Brunauer, Emmett, and Teller (BET) theory. Data of soil-water adsorption (W%) at different relative vapor pressures (P/Po) can be obtained for the soils, where the W% values are increased with increasing P/Po in general. The highest values of water adsorption capacity (Wa), specific surface area (S), and other hygro-physical properties such as adsorbed layers and maximum hygroscopic water are observed in the clay depths of soil profiles, while the lowest values can be found in coarse textured soils (sandy and sandy loam soils profiles). Two equations were assumed: (1) to predict P/Po at water adsorption capacity (Wa) and (2) to apply Wa in prediction of soil moisture retention, i.e., ψ (W) function at pF < 4.5

Nonlinear optical spectroscopy at the Liquid- / Solid- interface

Sorption-desorption of fatty organic compounds on clay minerals influence the migration process of these compounds in their soil environment, particularly in aquatic medium. In order to understand part of the interaction between such organic compounds and clay minerals, a simple system was considered. Crystalline sapphire was taken as a model for natural clay minerals, and methanol, ethanol, 1-Propanol, 1-butanol, chloroform and propionic acid were chosen as simple but representative model molecules for the more complex organic compounds found in soil. Linear and nonlinear techniques were combined to study the mechanisms of interaction. Sum Frequency Generation (SFG) as a nonlinear interface selective technique was used to probe the adsorption-desorption mechanism at the interfaces for the different systems under study by tracking changes in their average orientation and density at and in vicinity of the surface. Reflectivity in total internal reflection geometry (TIR) was conducted to determine the optical constants of the interface with such high precision that the analysis of the SFG data became feasible, in particular with respect to the determination of molecular orientations. Contact angle and XPS technique were used as inspection tools for the cleanness of the crystal surface. Particular accuracy was required in this work to allow tracking of even subtle changes in the interactions. To achieve such high accuracy, the commercial SFG system applied was further developed and improved to a level of high stability and data reproducibility. The study was carried out by observing the molecules under study through their nonlinear optical vibrational fingerprints in the spectral range from 2500 to 4000 cm-1, which covers the CH and OH vibrations of the selected media. It was found that the results are highly dependent on the nature of the sapphire surface. In the literature, it has been speculated that a strongly bound water layer exists on the sapphire surface prepared and cleaned with a given procedure. All the reactions found and observed in the present study could be explained in terms of hydrogen bonding competition. Meanwhile and marginal off the presented study, two novel spectroscopic techniques were developed. It is assumed that these techniques will be useful in future work on the adsorption kinetics of organic molecules and compounds of different kind. The first technique was the development of a real time spatially and temporally resolved sum frequency generation system based on a broadband femtosecond laser source. The second technique was a combination of in-situ Second Harmonic Generation (SHG) and Ellipsometry to probe surface coverage and thickness of adsorbed layers of the Self-assembled organic Monolayers (SAMs) simultaneously and in real time

Unusual etiology for a common problem

Introduction: Diagnosing the etiology of iron deficiency anemia can be very challenging.Hypothesis: Etiology of iron deficiency anemia is not always straightforwardStudy design: Case ReportResults: 2-year-old female presented with fever, cough, pallor for 4 days. CXR showed diffuse pulmonary opacities. CRP 3.45, ESR 21, WBC 6, platelet of 361, Hgb of 4 gm/dl, MCV 54, developed hemoptysis and was transferred to the PICU with respiratory failure. Bronchiolar lavage and lung biopsy showed extensive hemosiderin-laden macrophages. Iron deficiency anemia, progressive cough, dyspnea, and infiltrates on CXR was consistent with idiopathic pulmonary hemosiderosis. Pneumocystis, HIV, histoplasma, SLE, vasculitides were negative. Patient responded to a burst of steroid with normalization of breathing and Hgb level during follow up.16 y/o female marathon runner with iron deficiency anemia refractory to iron supplementation, Hgb 7.4gm/dl over 6 month period despite taking iron supplements. MVC was 68, ferritin of 2, transferrin/TIBC levels were elevated. Hemoccult stool negative. Combination of intense physical exercise, refractory iron deficiency anemia, and lack of GI blood loss led to consideration of march hemoglobinuria. Urinalysis positive for blood, confirming the diagnosis. With IV iron and reduction of intensity of running, Hgb was up to 14.1.Conclusion: These two cases of uncommon causes of blood loss highlight the importance of considering rare causes for iron deficiency anemia especially when it is not responding to iron supplement. Without treatment of underlying cause, anemia would persist

Effect of dexamethasone on reducing pain and gastrointestinal symptoms associated with cesarean section: a systematic review and meta-analysis

Background: Dexamethasone has analgesic and antiemetic actions that have been documented in the literature. Therefore, we performed a systematic review and meta-analysis to investigate its overall effectiveness in reducing a variety of negative outcomes after cesarean section. Objectives: To investigate the efficacy and safety of dexamethasone for reducing pain associated with cesarean section, nausea, vomiting, pruritus, postoperative need for analgesia, postoperative antiemetic requests and headache. Methods: We searched PubMed, Cochrane CENTRAL, SCOPUS, and Web of Science for relevant clinical trials. We then performed a systematic review and meta-analysis, including only randomized, placebo-controlled clinical trials. Our main population target was women undergoing elective cesarean delivery. The intervention under consideration was dexamethasone administered both by intravenous (IV) or subcutaneous (SC) over a variety of doses. The comparator was a placebo. Our main outcomes included: (1) perceptions as indicated by pain scores, (2) occurrence of nausea and (3) occurrence of vomiting. Secondary outcomes included: (4) occurrence of pruritus, (5) need for postoperative analgesia, (6) need for postoperative antiemetic drugs and (7) occurrence of headache. We assessed the quality of included studies using the risk of bias tool described in Cochrane\u27s handbook for systematic reviews of interventions. Results: We found that dexamethasone seemed to significantly reduce scores for pain at rest (p<0.001), as well as occurrence of nausea (p<0.001) and vomiting (p<0.001). The drug also showed significant reduction of negative symptoms in other secondary outcomes, including need for postoperative analgesia (p<0.001) and postoperative antiemetic drugs (p<0.001). However, the drug showed no significant effect in reducing headache and pruritus or in improving pain at movement scores. Conclusion: Dexamethasone appears to decrease perception of pain at rest and protects against nausea and vomiting. However, it does not seem effective against headaches or pruritus

PHIPS-HALO : the airborne Particle Habit Imaging and Polar Scattering probe - Part 2 : Characterization and first results

The novel aircraft optical cloud probe PHIPS-HALO has been developed to establish clarity regarding the fundamental link between the microphysical properties of single atmospheric ice particles and their appropriated angular light scattering function. After final improvements have been implemented to the polar nephelometer part and the acquisition software of PHIPS-HALO, the instrument was comprehensively characterized in the laboratory and was deployed in two aircraft missions targeting cirrus and Arctic mixed-phase clouds. This work demonstrates the proper function of the instrument under aircraft conditions and highlights the uniqueness, quality, and limitations of the data that can be expected from PHIPS-HALO in cloud-related aircraft missions

Charging Behavior of Clays and Clay Minerals in Aqueous Electrolyte Solutions — Experimental Methods for Measuring the Charge and Interpreting the Results

We discuss the charging behavior of clays and clay minerals in aqueous electrolyte solutions. Clay platelets exhibit different charging mechanisms on the various surfaces they expose to the solution. Thus, the basal planes have a permanent charge that is typically considered to be independent of pH, whereas the edge surfaces exhibit the amphoteric behavior and pH-dependent charge that is typical of oxide minerals. Background electrolyte concentration and composition may affect these two different mechanisms of charging in different ways. To guide and to make use of these unique properties in technical application, it is necessary to understand the effects of the various master variables (i.e. pH and background salt composition and concentration). However, how to disentangle the various contributions to the charge that is macroscopically measurable via conventional approaches (i.e. electrokinetics, potentiometric titrations, etc.) remains a challenge. The problem is depicted by discussing in detail the literature data on kaolinite obtained with crystal face specificity. Some results from similar experiments on related substrates are also discussed. As an illustration of the complexity, we have carried out extensive potentiometric mass and electrolyte titrations on artificial clay samples (Na-, Ca-, and Mg-montmorillonite). A wide variety of salts was used, and it was found that the different electrolytes had different effects on the end point of mass titrations. In the case of a purified sample (i.e. no acid-base impurities), the end point of a mass titration (the plateau of pH achieved for the highest concentrations of solid), in principle, corresponds to the point of zero net proton and hydroxide consumption, at which in ideal systems, such as oxide minerals, the net proton surface charge density is zero. To such concentrated (dense) suspensions of clay particles, aliquots of salts can be added and the resulting pH indicates the specificity of a given salt for a given clay particle system. In the experimental data, some ambiguity remains, which calls for further detailed and comprehensive studies involving the application of all the available techniques to one system. Although, right now, the overall picture appears to be clear from a generic point of view (i.e. concerning the trends), clearly, in a quantitative sense, huge differences occur for nominally identical systems and only such a comprehensive study will allow to proof the current phenomenological picture and allow the next step to be taken to understand the fine details of the complex clay-electrolyte solution interfaces

Parametric Excitation of Coupled Nonlinear Microelectromechanical Systems

The commencement of the semi-conductor industry in the second half of the last century gave a surprising new outlook for engineered dynamical mechanical systems. It enabled, thanks to the continuously evolving microfabrication methods, the implementation of Micro Electromechanical systems (MEMS) followed by their nano-counterpart or NEMS. Nowadays M/NEMS constitute a massive portion of the small-scaled sensors industry, in addition to electrical, optical and telecommunication components. Since these tiny dynamical electromechanical systems involve sometimes couplings between degrees of freedom as well as nonlinearities, the theory of stability in dynamical systems plays a significant role in their design and implementation. From a practical point of view, the approach to stability problems often takes two different perspectives. The first one, most commonly in linear systems, aims to avoid any instability which could cause destructive consequences for mechanical structures or for electrical and electronic components. On the contrary in nonlinear systems, the second perspective aims to drive the system into regions of instability for the trivial solution, while searching for stable nontrivial steady-state solutions of the underlying differential equations. With the advent of micro and nanosystems, the second perspective could acquire increased importance. This is attributed to their capability to exhibit typical nonlinear behavior and higher amplitudes at normal operation conditions, when compared to macroscale systems. Higher amplitudes, in this sense, allows for a better amplification of an input excitation, and thereby higher sensitivity for miniature sensors and measurement devices. In addition, if the system parameters were time-periodic, the trivial solution could turn to be unstable at the so called parametric resonances. Known as parametric pumping in micro and nanosystems, the system’s response is usually amplified at these resonance frequencies for higher sensitivity and accuracy. For these reasons, this work is mainly focused on parametrically excited nonlinear systems. Nevertheless, a systematic approach is followed in this thesis, where the origins of destabilization are surveyed in time-invariant systems before proceeding to carry out a theoretical study on time-periodic systems in general, and time-periodic nonlinear systems in particular. Through this theoretical study, a novel idea for the M/NEMS industry is presented, namely the broadband parametric amplification using a bimodal excitation method. This idea is then implemented in microsystems, by investigating a particular example, that is the microgyorscope. Given the low-cost of this device in comparison with other inertial sensors, it is being currently enhanced to reach a relatively higher sensitivity and accuracy. To this end, the theoretical findings, including the mentioned idea, are implemented in this device and prove to contribute effectively to its performance. Moreover, an experimental investigation is carried out on an analogous microsystem. Through the experimental study, an electronic system is introduced to apply the proposed bimodal parametric excitation method on the microsystem. By comparing the stability charts in theory and experiment, the theoretical model could be validated. In conclusion, a theoretical study is carried out through this work on parametrically excited nonlinear systems, then implemented on microgyroscopes, and finally experimentally validated. Thereby, this work puts a first milestone for the utilization of the proposed excitation method in the M/NEMS industry