Unpolarized laser method for infrared spectrum calculation of amide I CO bonds in proteins using molecular dynamics simulation.

The investigation of the strong infrared (IR)-active amide I modes of peptides and proteins has received considerable attention because a wealth of detailed information on hydrogen bonding, dipole-dipole interactions, and the conformations of the peptide backbone can be derived from the amide I bands. The interpretation of experimental spectra typically requires substantial theoretical support, such as direct ab-initio molecular dynamics simulation or mixed quantum-classical description. However, considering the difficulties associated with these theoretical methods and their applications are limited in small peptides, it is highly desirable to develop a simple yet efficient approach for simulating the amide I modes of any large proteins in solution. In this work, we proposed a comprehensive computational method that extends the well-established molecular dynamics (MD) simulation method to include an unpolarized IR laser for exciting the CO bonds of proteins. We showed the amide I frequency corresponding to the frequency of the laser pulse which resonated with the CO bond vibration. At this frequency, the protein energy and the CO bond length fluctuation were maximized. Overall, the amide I bands of various single proteins and amyloids agreed well with experimental data. The method has been implemented into the AMBER simulation package, making it widely available to the scientific community. Additionally, the application of the method to simulate the transient amide I bands of amyloid fibrils during the IR laser-induced disassembly process was discussed in details.

Evaluación de los puntos "A" como parámetro dosimétrico en braquiterapia ginecológica guiados por imágenes tridimensionales

Objetivos: se evaluó si la técnica de prescripción de dosis puntual, punto "A", es adecuada para la estimación de dosis en el volumen de tratamiento clínico por alta tasa de dosis (CTV-HR), usando la braquiterapia ginecológica 3D. Métodos: se recopiló planes de tratamiento para 35 pacientes con cáncer cervicouterino estadio IB2-IVA (140 fracciones o planes de tratamiento) tratados entre los años 2019 al 2021, cuya dosis prescrita fue de 28 Gy en 4 fracciones. Se reconstruyeron los puntos "A", se normalizó la dosis prescrita a la isodosis del 100% para comparar con las dosis en CTV-HR (D90%). Resultados: el promedio de la dosis absorbida al CTV- HR (D90%) fue de 88,82 ± 2,53 Gy y al normalizar la isodosis del 100% al punto "A", se obtuvo dosis promedio en CTV-HR (D90%) de 99,3±5,85Gy. Esta variación de dosis promedio al CTV-HR (D90%) representó un incremento del 18%, dando como resultado que un 80% de los tratamientos correspondiente a 28 pacientes queden fuera de la variación aceptable del protocolo EMBRACE II y solo un 20% de los tratamientos correspondientes a 7 pacientes se encuentren dentro del rango de la variación aceptable del protocolo en mención. Conclusiones: la técnica de prescripción de dosis al punto "A", se traduce clínicamente en una sobredosis del tejido tumoral y sano (recto, sigmoide, vejiga e intestino).

Objective: to assess whether the punctual dose prescription technique, point A, is adequate for dose estimation in CTV-HR using 3D gynecological brachytherapy. Methods: treatment plans were collected for 35 patients with stage IB2-IVA (140 fractions or treatment plans) cervical cancer treated between 2019 and 2021, whose prescribed dose was 28Gy in 4 fractions. Points A were reconstructed, the prescribed dose was normalized to 100% isodose to compare with the doses in CTV- HR(D90%). Results: the average dose absorbed at CTV-HR(D90%) was 88.82 ±2.53 Gy and when normalizing the isodose of 100% at point A, average dose at CTV-HR(D90%) was obtained. of 99.3±5.85Gy. This average dose variation to the CTV-HR(D90%) represented an increase of 18%, resulting in 80% of the treatments corresponding to 28 patients falling outside the acceptable variation of the EMBRACE II protocol and only 20% of the treatments corresponding to 7 patients are within the range of the acceptable variation of the protocol in question. Conclusions: the dose prescription technique at point A clinically translates into an overdose of tumor and healthy tissue (rectum, sigmoid, bladder and intestine).

Recent Development of Heat and Mass Transport in the Presence of Hall, Ion Slip and Thermo Diffusion in Radiative Second Grade Material: Application of Micromachines.

This article describes the incompressible two-dimensional heat and mass transfer of an electrically conducting second-grade fluid flow in a porous medium with Hall and ion slip effects, diffusion thermal effects, and radiation absorption effects. It is assumed that the fluid is a gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. It is assumed that the liquid is opaque and absorbs and emits radiation in a manner that does not result in scattering. It is considered an unsteady laminar MHD convective rotating flow of heat-producing or absorbing second-grade fluid across a semi-infinite vertical moving permeable surface. The profiles of velocity components, temperature distribution, and concentration are studied to apply the regular perturbation technique. These profiles are shown as graphs for various fluid and geometric parameters such as Hall and ion slip parameters, radiation absorption, diffusion thermo, Prandtl number, Schmidt number, and chemical reaction rate. On the other hand, the skin friction coefficient and the Nusselt number are determined by numerical evaluation and provided in tables. These tables are then analysed and debated for various values of the flow parameters that regulate it. It may be deduced that an increase in the parameters of radiation absorption, Hall, and ion slip over the fluid region increases the velocity produced. The resulting momentum continually grows to a very high level, with contributions from the thermal and solutal buoyancy forces. The temperature distribution may be more concentrated by raising both the heat source parameter and the quantity of radiation. When one of the parameters for the chemical reaction is increased, the whole fluid area will experience a fall in concentration. Skin friction may be decreased by manipulating the rotation parameter, but the Hall effect and ion slip effect can worsen it. When the parameter for the chemical reaction increases, there is a concomitant rise in the mass transfer rate.

Towards the Configuration of a Photoelectrocatalytic Reactor: Part 1-Determination of Photoelectrode Geometry and Optical Thickness by a Numerical Approach.

Photoelectrocatalysis has been highlighted as a tertiary wastewater treatment in the textile industry due to its high dye mineralisation capacity. However, design improvements are necessary to overcome photo-reactors limitations. The present work proposes a preliminary configuration of a photoelectrocatalytic reactor to degrade Reactive Red 239 (RR239) textile dye, using computational fluid dynamics (CFD) to analyse the mass transfer rate, radiation intensity loss (RIL), and its effect on kinetics degradation, over a photoelectrode based on a TiO2 nanotube. A study to increase the space-time yield (STY) was carried out through mass transfer rate and kinetic analysis, varying the optical thickness (δ) between the radiation entrance and the photocatalytic surface, photoelectrode geometry, inlet flow rate, and the surface radiation intensity. The RIL was determined using a 1D Beer-Lambert-based model, and an extinction coefficient experimentally determined by UV-Vis spectroscopy. The results show that in RR239 solutions below concentrations of 6 mg/L, a woven mesh photoelectrode and an optimal optical thickness δ of 1 cm is enough to keep the RIL below 15% and maximise the mass transfer and the STY in around 110 g/m3-day.

Eco-Geopolymers: Physico-Mechanical Features, Radiation Absorption Properties, and Mathematical Model.

Waste ashes and radiation are hazardous environmental and health factors; thus, a lot of attention is paid to their reduction. We present eco-geopolymer building materials (GPBMs) based on the class F fly ashes (FFAs) from thermal power plants (TPPs) and their implementation as a barrier against radioactive radiation. Different methods of production, ratios of FFA to alkali activator, and temperatures of curing were tested. Small spherical particles and higher content of SiO2 resulted in developed surface area and higher reactivity of Isken TPP FFA than Catalagzi TPP FFA. Lower activator concentration (10% vs. 20%) and curing temperature (70 vs. 100 °C) caused an increase in GPBM compressive strength; the highest value was measured as 93.3 MPa. The highest RA was measured for GPBMs, provided alkali activator ratio (Na2SiO3/NaOH) was >2 and its concentration was 20%. The mathematical model developed in this study proved FFA quantity, and thus GPBM mechanical properties, as key factors influencing RA. In the light of these results, the lightweight GPBMs can be excellent materials for the construction sector dedicated to immobilization, storage, and disposal for radionuclides or barriers against radiation; however, multiple steps of their production require careful optimization.

Dosimetry.

The dosimeters used to measure radiation dose produce a value which has to be calibrated to be in keeping with the values in an approved laboratory, which will be one of an international network of such laboratories at the center of which is the Bureau International des Poids et Mesures in France (BIPM). Dosimeters work by producing a quantitatively proportional change in status to the intensity of the radiation being measure. Amongst the techniques in use are thermoluminescent devices, radiographic film, radiochromic film, semiconductors, ionization chambers, silicon diodes and gel dosimeters. The Gamma Knife radiation has been difficult to measure directly because the beams have been to fine for accurate measurement by commonly available dosimeters. For more modern dosimeters this is less of a problem. During the treatment of a patient, a variety of indices are recorded to assist in the standardization and accuracy of treatment. Having determined the dose in the beams, it is necessary to calculate how much energy is lost during the passage of radiation from the source to the target. There has been a steady evolution of these calculations to make them more accurate.

Exceptional Radiation Absorption in a Pentagon-Based Si Allotrope.

Excellent photovoltaic performance is predicted in a pentagonal covalent network of Si in a hollow structure exhibiting both thermal and dynamical stability. Consisting of a combination of sp2 and sp3 hybridized Si atomic orbitals, the GW0 computed band structure shows an indirect band gap near the zone edge and also a manifold of directly absorbing transitions at frequencies in the window of visible light, in distinction with conventional Si. Hydrogenation of a single sp2 site is predicted to lead to a robust local magnetic moment. We find a low formation energy at low pressure that is compatible with other experimentally known phases, suggesting that a stable phase might be obtained.

Design and performance evaluation of a photocatalytic reactor for indoor air disinfection.

Since COVID-19 pandemic, indoor air quality control has become a priority, and the development of air purification devices effective for disinfecting airborne viruses and bacteria is of outmost relevance. In this work, a photocatalytic device for the removal of airborne microorganisms is presented. It is an annular reactor filled with TiO2-coated glass rings and irradiated internally and externally by UV-A lamps. B. subtilis spores and vegetative cells have been employed as model biological pollutants. Three types of assays with aerosolized bacterial suspensions were performed to evaluate distinct purification processes: filtration, photocatalytic inactivation in the air phase, and photocatalytic inactivation over the TiO2-coated rings. The radiation distribution inside the reactor was analysed by performing Monte Carlo simulations of photon absorption in the photocatalytic bed. Complete removal of a high load of microorganisms in the air stream could be achieved in 1 h. Nevertheless, inactivation of retained bacteria in the reactor bed required longer irradiation periods: after 8 h under internal and external irradiation, the initial concentration of retained spores and vegetative cells was reduced by 68% and 99%, respectively. Efficiency parameters were also calculated to evaluate the influence of the irradiation conditions on the photocatalytic inactivation of bacteria attached at the coated rings.

Inter-relationship between intercepted radiation and rice yield influenced by transplanting time, method, and variety.

Photosynthetically active radiation (PAR) is one of the most important environmental factors that determine the productivity and grain quality of the crops. Continuous rainy days or cloudy weather throughout crop growth especially at critical stages often resulted in great loss of grain quality and yield in rice. Low light stress has rigorously constrained the rice production in various rice-growing regions, especially in Southeast Asia. Method and time of planting are the major management factors contributing to the higher yield potential of rice by influencing light harvesting and use efficiency. Present study was executed consecutively for 5 years (kharif seasons of 2012-2016) to determine whether planting time improves the radiation absorption and use efficiency in different duration rice cultivars. We evaluated the difference in plant growth and development leading to yield formation under different planting time which related to radiation incidence and interception. The results of the study revealed that PAR interception depends on morphological characters of cultivars and also with agronomic management such as transplanting time and method. Long duration cultivar intercepted more PAR but interception decreased due to late planting (3rd week of July), whereas short duration cultivars (Naveen) when planted earlier (1st week of June) could not effectively utilize intercepted PAR constraining the biomass accumulation and yield formation. Effect of planting density and crop architecture on PAR absorption was apparent among establishment methods as light interception at crop canopy was highest in the system of rice intensification and lowest in that of wet direct seeding. In general, Pooja as a long duration cultivar intercepted more PAR per day but when compared on same date of planting, the comparative absorption of radiation was 30.6% higher in Naveen. The lower yields in the wet season are attributed mostly to reduction in grain number per panicle or per unit land area, which is a consequence of high spikelet sterility. Grain yield of rice planted in July third week was reduced by 3.8, 12.3, and 6.9% over June first and third week and July first week, respectively, mainly due to spikelet sterility (26%) and lower grains per panicle (18%). Our results indicated that agronomic management like optimum time of sowing, cultivar duration, and establishment methods should be followed for yield improvement in tropical lowlands where light intensity is limiting due to prevailing weather situations.

The effect of iodine uptake on radiation dose absorbed by patient tissues in contrast enhanced CT imaging: Implications for CT dosimetry.

OBJECTIVES: To investigate the effect of iodine uptake on tissue/organ absorbed doses from CT exposure and its implications in CT dosimetry. METHODS: The contrast-induced CT number increase of several radiosensitive tissues was retrospectively determined in 120 CT examinations involving both non-enhanced and contrast-enhanced CT imaging. CT images of a phantom containing aqueous solutions of varying iodine concentration were obtained. Plots of the CT number increase against iodine concentration were produced. The clinically occurring iodine tissue uptake was quantified by attributing recorded CT number increase to a certain concentration of aqueous iodine solution. Clinically occurring iodine uptake was represented in mathematical anthropomorphic phantoms. Standard 120 kV CT exposures were simulated using Monte Carlo methods and resulting organ doses were derived for non-enhanced and iodine contrast-enhanced CT imaging. RESULTS: The mean iodine uptake range during contrast-enhanced CT imaging was found to be 0.02-0.46% w/w for the investigated tissues, while the maximum value recorded was 0.82% w/w. For the same CT exposure, iodinated tissues were found to receive higher radiation dose than non-iodinated tissues, with dose increase exceeding 100% for tissues with high iodine uptake. CONCLUSIONS: Administration of iodinated contrast medium considerably increases radiation dose to tissues from CT exposure. KEY-POINTS: • Radiation absorption ability of organs/tissues is considerably affected by iodine uptake • Iodinated organ/tissues may absorb up to 100 % higher radiation dose • Compared to non-enhanced, contrast-enhanced CT may deliver higher dose to patient tissues • CT dosimetry of contrast-enhanced CT imaging should encounter tissue iodine uptake.

Disinfection of urban wastewater by solar driven and UV lamp - TiO2 photocatalysis: effect on a multi drug resistant Escherichia coli strain.

The effect of TiO2 photocatalysis on the inactivation of an antibiotic resistant Escherichia coli strain selected from an urban wastewater treatment plant (UWWTP) effluent was investigated. Different light sources including a 250 W wide spectrum lamp, a 125 W UV-A lamp and solar radiation, as well as, photocatalysts loadings (TiO2 Degussa P25) in the range from 0.05 to 2.00 g TiO2 L(-1) were evaluated. The higher efficiency (total bacterial inactivation after 10 min of irradiation) was observed in the absence of TiO2 when the wastewater was irradiated using the 250 W lamp. In the presence of TiO2 a decreasing inactivation trend was observed (99.76% and 72.22% inactivation after 10 min irradiation at 0.10 and 2.00 g TiO2 L(-1) respectively). Under solar simulated conditions the highest inactivation efficiency (93.17%) after 10 min of irradiation was achieved at the lower photocatalyst loading (0.05 g TiO2 L(-1)). The concept of "reactor optical thickness" was introduced to explain the rates of disinfection observed. The optimum photocatalyst loading estimated by radiation absorption-scattering modeling was found to be 0.1 g TiO2 L(-1) for all lamps. The difference between experimental tests and modeling may be due to TiO2 particles aggregation. Comparative kinetic tests between solar and solar simulated photocatalytic (SSP) processes using 0.05 g TiO2 L(-1) in suspension showed a quite similar inactivation behavior up to 30 min of irradiation, but only the SSP process resulted in a total inactivation of bacteria after 60 min of exposure. Antibiotic resistant test (Kirby-Bauer) on survived colonies showed that the SSP and SP processes affected in different ways the resistance of E. coli strain to the target antibiotics.