Radiation Chemistry Research Articles

Development of hydrothermal corrosion model and BWR metal coating for CVD SiC in light water reactors

SiC/SiC fiber composites with CVD SiC overcoats are potential candidates for light water reactor advanced accident tolerant cladding materials. Understanding its corrosion kinetics in Light Water Reactor (LWR) conditions is essential to evaluate the concept's viability. Existing models only account for the temperature and oxygen concentration effect on the hydrothermal corrosion behavior applicable to LWR operating conditions. However, the development of a general corrosion rate for CVD SiC that accounts for the impact of irradiated microstructure, flow rate, electrical resistivity, pH, and surface roughness is critical for the practical realization of SiC/SiC-based cladding concepts. After a rigorous experimental campaign, this work updates the existing hydrothermal corrosion model to predict hydrothermal corrosion in LWRs. Numerical radiation and coolant chemistry analysis for LWRs conducted based on the updated corrosion kinetic models suggests that CVD SiC is likely a viable environmental barrier coating for Pressurized Water Reactors while questionable for Boiling Water Reactors (BWR) when the effect of irradiation damage on SiC corrosion is considered. An effective mitigation strategy for the double-layer metal coating is proposed for BWR applications. The double-layer metal coating comprising a FeCrAl overcoat with an intermediate Cr bond coating was observed to provide a stable protective barrier against SiC dissolution in BWR conditions. The proposed metal coating was also fully adherent following quench and burst tests.

Initial yield of hydrated electron production from water radiolysis based on first-principles calculation.

Many scientific insights into water radiolysis have been applied for developing life science, including radiation-induced phenomena, such as DNA damage and mutation induction or carcinogenesis. However, the generation mechanism of free radicals due to radiolysis remains to be fully understood. Consequently, we have encountered a crucial problem in that the initial yields connecting radiation physics to chemistry must be parameterized. We have been challenged in the development of a simulation tool that can unravel the initial free radical yields, from physical interaction by radiation. The presented code enables the first-principles calculation of low energy secondary electrons resulting from the ionization, in which the secondary electron dynamics are simulated while considering dominant collision and polarization effects in water. In this study, using this code, we predicted the yield ratio between ionization and electronic excitation from a delocalization distribution of secondary electrons. The simulation result presented a theoretical initial yield of hydrated electrons. In radiation physics, the initial yield predicted from parameter analysis of radiolysis experiments in radiation chemistry was successfully reproduced. Our simulation code helps realize a reasonable spatiotemporal connection from radiation physics to chemistry, which would contribute to providing new scientific insights for precise understanding of underlying mechanisms of DNA damage induction.

Effect of water vapor pressure on positive and negative tone electron-beam patterning of poly(methyl methacrylate)

Variable-pressure electron-beam lithography (VP-EBL) employs an ambient gas at subatmospheric pressures to reduce charging during electron-beam lithography. VP-EBL has been previously shown to eliminate pattern distortion and provide improved resolution when patterning poly(methyl methacrylate) (PMMA) on insulating substrates. However, it remains unknown how water vapor affects the contrast and clearing dose nor has the effect of water vapor on the negative-tone behavior of PMMA been studied. In addition, water vapor has recently been shown to alter the radiation chemistry of the VP-EBL process for Teflon AF. Such changes in radiation chemistry have not been explored for PMMA. In this work, VP-EBL was conducted on conductive substrates to study the effect of water vapor on PMMA patterning separately from the effects of charge dissipation. In addition, both positive and negative-tone processes were studied to determine the effect of water vapor on both chain scission and cross-linking. The contrast of PMMA was found to improve significantly with increasing water vapor pressure for both positive and negative-tone patterning. The clearing dose for positive-tone patterning increases moderately with vapor pressure as would be expected for electron scattering in a gas. However, the onset set dose for negative-tone patterning increased dramatically with pressure revealing a more significant change in the exposure mechanism. X-ray photoelectron spectra and infrared transmission spectra indicate that water vapor only slightly alters the composition of exposed PMMA. Also, electron scattering in water vapor yielded a much larger clear region around negative-tone patterns. This effect could be useful for increasing the range of the developed region around cross-linked PMMA beyond the backscattered electron range. Thus, VP-EBL for PMMA introduces a new means of tuning clearing/onset dose and contrast, while allowing additional control over the size of the cleared region around negative-tone patterns.

Radiolytic evaluation of select sulfur chlorides (S2Cl2 and SOCl2) for advanced low temperature chlorination of zirconium-based used nuclear fuel cladding

New sulfur chloride compounds—sulfur monochloride (S2Cl2) and thionyl chloride (SOCl2)—have been proposed as alternative chlorinating agents for the chemical decladding of zirconium-based used nuclear fuel cladding materials. However, the radiation stability of these compounds has not been thoroughly evaluated, despite envisioned process conditions involving intense, multi-component radiation fields. Knowledge of the radiation chemistry of these sulfur chlorides is essential for the development and optimization of alternative chlorination technologies. To this end, we present preliminary findings on the gamma radiolysis of neat S2Cl2 and SOCl2 at ambient temperature up to ∼ 34 MGy. In this study, Raman spectroscopy and density functional theory calculations were used to identify the Raman-active degradation products from S2Cl2 and SOCl2 radiolysis. Both sulfur chloride compounds exhibited significant radiation resistance, with respect to changes in the Raman signatures of the parent compounds and the ingrowth of Raman-active degradation products. For S2Cl2, molecular chlorine (Cl2) was directly identified as the predominant degradation product, which was completely consumed at higher absorbed doses (> 9 MGy). Similarly, the main degradation product from SOCl2 radiolysis was also Cl2, although in this system it continued to grow in with dose over the entire dose range. An “SO” containing degradation product(s) was also identified as a compliment to Cl2. Overall, the perceived radiation resistance of these sulfur chloride compounds makes them suitable for inclusion in a used nuclear fuel chemical decladding process, especially as radiolytically formed Cl2 can be used to reform the parent compounds, thereby increasing the longevity of the solvents used.

Electron and Photon Interactions with Bio (Related) Molecules

Part of the energy deposited in biological tissue by high-energy radiation is converted to secondary electrons. The knowledge at the molecular level on radiation interaction with biological species has increased due to the contributions of many different scientists working on radiation physics and radiation chemistry. The intention of this Special Issue on electron and photon interactions with (bio) molecules is to bring together different areas of knowledge that focus on radiation interactions with matter.

Radiation-induced reactions in comet analogues

AbstractComets are a source of prebiotic molecules that likely enriched the early Earth during the Late Heavy Bombardment period. Laboratory experiments that replicate cometary conditions may facilitate understanding of the chemical reactions and supplement observational studies of these icy bodies. Prebiotic compounds, such as formic acid and formaldehyde, have been observed in comets. Furthermore, these compounds can easily be formed in experimental models using a variety of gas combinations and energy sources. We conducted experimental cometary simulations using radiation chemistry tools to obtain insight into the possible fate of formic acid and formaldehyde. The main results suggest a redundant system, signifying that the irradiation of formic acid forms formaldehyde molecules and vice versa. This phenomenon ensures the permanence of prebiotic molecules in high-radiation environments. Additionally, the potential role of forsterite and graphite was explored in cometary simulations. Our experimental results show the differential formation of aldehydes and other carbonyl-containing compounds dependent on the mineral phase present.

MRI of radiation chemistry: First images and investigation of potential mechanisms.

Paramagnetic species such as O2 and free radicals can enhance T1 and T2 relaxation times. If the change in relaxation time is sufficiently large, the contrast will be generated in magnetic resonance images. Since radiation is known to be capable of altering the concentration of O2 and free radicals during water radiolysis, it may be possible for radiation to induce MR signal change. We present the first reported instance of x-ray-induced MR signal changes in water phantoms and investigate potential paramagnetic relaxation enhancement mechanisms associated with radiation chemistry changes in oxygen and free radical concentrations. Images of water and 10 mM coumarin phantoms were acquired on a 0.35 T MR-linac before, during, and after a dose delivery of 80Gy using an inversion-recovery dual-echo sequence with water nullified. Radiation chemistry simulations of these conditions were performed to calculate changes in oxygen and free radical concentrations. Published relaxivity values were then applied to calculate the resulting T1 change, and analytical MR signal equations were used to calculate the associated signal change. Compared to pre-irradiation reference images, water phantom images taken during and after irradiation showed little to no change, while coumarin phantom images showed a small signal loss in the irradiated region with a contrast-to-noise ratio (CNR) of 1.0-2.5. Radiation chemistry simulations found oxygen depletion of -11µM in water and -31µM in coumarin, resulting in a T1 lengthening of 24ms and 68ms respectively, and a simulated CNR of 1.0 and 2.8 respectively. This change was consistent with observations in both direction and magnitude. Steady-state superoxide, hydroxyl, hydroperoxyl, and hydrogen radical concentrations were found to contribute less than 1ms of T1 change. Observed radiation-induced MR signal changes were dominated by an oxygen depletion mechanism. Free radicals were concluded to play a minor secondary role under steady-state conditions. Future applications may include in vivo FLASH treatment verification but would require an MR sequence with a better signal-to-noise ratio and higher temporal resolution than the one used in this study.

Pulse Radiolysis and Transient Absorption of Aqueous Cr(VI) Solutions up to 325 °C.

Pulse radiolysis with a custom multichannel detection system has been used to measure the kinetics of the radiation chemistry reactions of aqueous solutions of chromium(VI) to 325 °C for the first time. Kinetic traces were measured simultaneously over a range of wavelengths and fit to obtain the associated high-temperature rate coefficients and Arrhenius parameters for the reactions of Cr(VI) + e aq -, Cr(VI) + H•, and Cr(V) + •OH. These kinetic parameters can be used to predict the behavior of toxic Cr(VI) in models of aqueous systems for applications in nuclear technology, industrial wastewater treatment, and chemical dosimetry.

In Memoriam - BrJAC mourns the death of Prof. Dr. Carol Hollingworth Collins and recognizes her great contribution to the Analytical Chemistry in Brazil

Professor Carol Collins graduated in Chemistry from Bates College (1952) and obtained her PhD in Organic Physical Chemistry from Iowa State University of Science and Technology (1958), when she was introduced to the recently developed gas–liquid chromatography. She conducted postdoctoral research at the University of Wisconsin and later worked on radiochemistry and nuclear medicine at the Brookhaven National Laboratory and the Western New York Nuclear Research Center in Louvain (Belgium) and Southwest Asia. Professor Collins came to the State University of Campinas (Unicamp) with her husband, Kenneth Collins, in July 1974, during the university’s first decade, and played a leading role in consolidation of the Institute of Chemistry at Unicamp and in the growth of chemistry and analytical chemistry in Brazil. Her first line of research in Brazil was radioanalytical chemistry, later focusing on chromatographic techniques, initially applied to the products of radiochemical reactions and radiation chemistry. Subsequently, her attention was directed to the preparation of stationary phases for liquid chromatography. She gained remarkable achievement in the area of chromatography that allowed her to publish two books that are very popular in Brazil: "Introduction to Chromatographic Methods" (1987) and "Fundamentals of Chromatography" (2006). Her scientific and technological contributions have been recognized through several awards, including the “Marie Curie Award” from the American Association of University Women and the “Simão Mathias Medal” from the Brazilian Chemical Society (SBQ). She also received honors in recognition of the contributions of Unicamp's 40th anniversary, SBQ's 30th anniversary, a tribute from the Journal of the Brazilian Chemical Society, the National Meeting of Analytical Chemistry, the School of Separations and the Brazilian Symposium on Chromatography and Related Techniques (SIMCRO) Medal. For her outstanding performance and leadership in the creation and consolidation of the Analytical Chemistry Division of the Brazilian Chemical Society, her name was recognized in the Carol Collins Medal given to each National Meeting of Analytical Chemistry since the 2018 edition. Professor Collins was also a full member of the Brazilian Academy of Sciences and the Academy of Sciences of São Paulo, and received the title of Professor Emerita of Unicamp on 14 May 2012, in addition to being Emeritus Researcher at the National Council for Scientific and Technological Development (CNPq). Apart from her scientific competence, some characteristics shaped her personality and made her very popular among her colleagues and students: her vast gourmet knowledge, keen taste for caipirinha and coffee, infallible memory, great love for her work and for Brazil, dedication to science, analytical chemistry/chromatography, kindness as a person and her incessant search for justice. She was always receptive to clarifying the doubts of students, teachers and interested parties, which she did with great pleasure, characteristic of those who like to teach and transmit knowledge. The contributions of Professor Collins to the training of human resources, the consolidation and development of the Institute of Chemistry at Unicamp and the analytical chemistry/chromatography sector in Brazil and abroad are immeasurable. Her brilliant trajectory will leave a huge legacy that is difficult to measure and she will remain forever in the memory of those who were fortunate enough to live with her.

The effect of linear energy transfer on the early, transient radiolytic oxygen depletion in the radiolysis of water by high-dose-rate irradiating protons

Monte Carlo multi-track chemistry simulations were carried out to study, from a radiation chemistry perspective, the effect of “linear energy transfer” (LET) on the transient yields and concentrations of radiolytic oxygen consumption in the high-dose-rate (∼107 Gy/s) radiolysis of both pure air-saturated (0.25 mmol/L O2) and oxygenated (30 µmol/L O2) cell water, in the interval ∼1 ps–10 µs. Our simulation model consisted of randomly irradiating water with single pulses of 5 MeV (LET ∼ 8 keV/µm), 1.5 MeV (LET ∼ 19.5 keV/µm), and 0.7 MeV (LET ∼ 33 keV/µm) protons at 25 °C. Similar to what is observed with low-LET irradiation (∼300 MeV protons, LET ∼ 0.3 keV/µm), our calculations showed that, in pure, aerated water, the concentration of depleted oxygen, [−O2], exhibits a pronounced maximum around ∼0.1–0.2 µs for all three high-LET irradiating protons studied. This maximum increased markedly with increasing LET. As expected, the effect of adding competing scavengers of both hydrated electrons and•OH radicals on the radiolytic O2depletion in oxygenated cell water (a more bio-mimetic model of cells) irradiated by 5 MeV protons delivered at the same dose rate led to a marked decrease in the maximum of [−O2] around 1 µs. However, contrary to what is observed for low-LET irradiation, we found that the transient O2consumption is quite substantial under high-LET irradiation conditions. This is explained by the fact that, even though their underlying mechanism of action differs, high-LET particles affect radiolysis yields in a similar way to high dose rates.

Radiolysis of Electrolytes in Batteries: A Quick and Efficient Screening Process for the Selection of Electrolyte-Additive Formulations.

Understanding aging phenomena in batteries is crucial to the design of efficient, safe, and reliable energy storage devices as a part of the current green energy transition. Among the different aspects of a battery, the behavior of the electrolyte is a key parameter. Therefore, screening the aging characteristics of different electrolytes is of major interest. However, few screening studies exist because these are time-consuming and require the monitoring of numerous charge and discharge cycles. It has been demonstrated here that radiation chemistry, i.e., the interaction between ionizing radiation and matter, is a valuable tool to screen the behavior of various electrolytes within a few hours. Indeed, the rapid radiolysis of electrolytes leads to the production of the same gases as produced by electrochemical cycling (i.e., H2 , CO2 ), and the ranking of electrolytes by their H2 production yields similar performance ratings to those reported in the literature. Therefore, this direct comparison of electrolytes alone, lasting a few hours without any manufacturing operations such as the fabrication of electrochemical cells, demonstrates that controlled irradiation makes it possible to predict battery cycling behavior. Additionally, mechanisms involved in the degradation processes of different electrolytes are proposed.

Multiscale Strategy for Predicting Radiation Chemistry in Polymers.

A primary mode for radiation damage in polymers arises from ballistic electrons that induce electronic excitations, yet subsequent chemical mechanisms are poorly understood. We develop a multiscale strategy to predict this chemistry starting from subatomic scattering calculations. Nonadiabatic molecular dynamics simulations sample initial bond-breaking events following the most likely excitations, which feed into semiempirical simulations that approach chemical equilibrium. Application to polyethylene reveals a mechanism explaining the low propensity to cross-link in crystalline samples.

(Dielectric Science & Technology Thomas Callinan Award) Materials and Processes As Enablers for Moore Moore and Beyond Moore Technologies

In this presentation, an overview will be presented of historic and recent developments achieved w.r.t. materials and processes that enabled continued performance scaling of CMOS and beyond CMOS applications. Starting from early high-k work. For decades, thermal oxidation of crystalline Silicon into SiO2 has been the gate oxide material in CMOS technology. Miniaturization for performance improvement, required the gate dielectric to decrease in thickness to support the required increase in capacitance (per unit area) and drive current (per device width). Early 2000, the thickness scaled below 1.5 nm, causing drastically increased leakage currents, high power consumption and reduced device reliability. Replacing the SiO2 gate dielectric with a high-κ (dielectric constant) material allows increased gate capacitance without the associated leakage effects. Activities involved the unit process step development of dielectric and metal deposition processes, advanced interface preparation, electrical and physical characterization and wet and dry etch process development. In a second section, emphasis will be on emerging nanomaterials. Nanotechnology is defined as the manipulation of matter with at least one dimension sized from below 100nm, thus all CMOS activities are functional nanotechnology. The latter concentrated initially on Graphene, but extended further towards Transition Metal Dicalchogenide Materials. Emphasis of the work will be on growth, functionalization, dielectric passivation and doping of these materials. Lastly, expanding on the nanomaterial know-how also progress with regard to low-k dielectrics, area selective deposition processes (for bottom-up lithography) and application of nanochemistry research for photoresist material screening, where chemical interactions at the nanoscale, related to the EUV lithography (radiation chemistry) are hampering the pattern scaling.Throughout the presentation, recognition will be given to people (PhD students) that contributed to this work and the presentation is also in honor of Prof Dolf Landheer and Professor Samares Kar with whom I organized my first ECS symposium.

Radiolysis-Driven Evolution of Gold Nanostructures - Model Verification by Scale Bridging In Situ Liquid-Phase Transmission Electron Microscopy and X-Ray Diffraction.

Utilizing ionizing radiation for in situ studies in liquid media enables unique insights into nanostructure formation dynamics. As radiolysis interferes with observations, kinetic simulations are employed to understand and exploit beam‐liquid interactions. By introducing an intuitive tool to simulate arbitrary kinetic models for radiation chemistry, it is demonstrated that these models provide a holistic understanding of reaction mechanisms. This is shown for irradiated HAuCl4 solutions allowing for quantitative prediction and tailoring of redox processes in liquid‐phase transmission electron microscopy (LP‐TEM). Moreover, it is demonstrated that kinetic modeling of radiation chemistry is applicable to investigations utilizing X‐rays such as X‐ray diffraction (XRD). This emphasizes that beam‐sample interactions must be considered during XRD in liquid media and shows that reaction kinetics do not provide a threshold dose rate for gold nucleation relevant to LP‐TEM and XRD. Furthermore, it is unveiled that oxidative etching of gold nanoparticles depends on both, precursor concentration, and dose rate. This dependency is exploited to probe the electron beam‐induced shift in Gibbs free energy landscape by analyzing critical radii of gold nanoparticles.

Transient Radiation-Induced Berkelium(III) and Californium(III) Redox Chemistry in Aqueous Solution.

Despite the significant impact of radiation-induced redox reactions on the accessibility and lifetimes of actinide oxidation states, fundamental knowledge of aqueous actinide metal ion radiation chemistry is limited, especially for the late actinides. A quantitative understanding of these intrinsic radiation-induced processes is essential for investigating the fundamental properties of these actinides. We present here a picosecond electron pulse reaction kinetics study into the radiation-induced redox chemistry of trivalent berkelium (Bk(III)) and californium (Cf(III)) ions in acidic aqueous solutions at ambient temperature. New and first-of-a-kind, second-order rate coefficients are reported for the transient radical-induced reduction of Bk(III) and Cf(III) by the hydrated electron (eaq-) and hydrogen atom (H•), demonstrating a significant reactivity (up to 1011 M-1 s-1) indicative of a preference of these metals to adopt divalent states. Additionally, we report the first-ever second-order rate coefficients for the transient radical-induced oxidation of these elements by a reaction with hydroxyl (•OH) and nitrate (NO3•) radicals, which also exhibited fast reactivity (ca. 108 M-1 s-1). Transient Cf(II), Cf(IV), and Bk(IV) absorption spectra are also reported. Overall, the presented data highlight the existence of rich, complex, intrinsic late actinide radiation-induced redox chemistry that has the potential to influence the findings of other areas of actinide science.

Fluorescence Spectroscopy Study on the Reaction of Hydroxyl Radicals and Hydrated Electrons in MXene Suspension

The reactive species including hydroxyl radicals (•OH) and hydrated electrons (eaq–) produced by radiolysis of liquid water play a central role in radiation chemistry. However, most quantification studies of the reaction of these species have been established in a homogeneous phase rather than in heterogeneous systems, which greatly limited the in-depth understanding of the knowledge of heterogeneous systems such as nanoparticle suspension. MXenes as active antioxidants and catalysts have been widely studied. Herein, the yields of radiation-induced •OH and eaq– in Ti3C2Tx (TC) MXene suspension were investigated by a simple fluorescence spectroscopy using the optimized coumarin method. The results indicate that the yield of •OH in TC suspension decreased by increasing the TC concentration with a reaction rate constant of 1.58 × 108 L g –1 s–1 between •OH and TC, which implies that TC acts as an •OH scavenger and a radioprotectant. Also, the oxidation state of Ti in TC nanosheets increased after reacting with •OH. In addition, a higher yield of eaq– was achieved in N2O-saturated TC suspension than in liquid water. The generated eaq– per gram of TC nanosheets decreased and H2 produced by TC suspension after irradiation increased by increasing the TC concentration, which indicates the competing recombination reaction of eaq– to form H2 in high-concentration TC suspension. The work provides a facile method to study the reaction of •OH and eaq– with nanoparticles dispersed in water.

Formation of Bulk Nanobubbles Induced by Accelerated Electrons Irradiation: Dependences on Dose Rates and Doses of Irradiation.

Radiation on aqueous solutions can induce water radiolysis with products of radicals, H2, H2O2, and so on, and their consequent biological effects have long been interested in radiation chemistry. Unlike the decomposition of water by electric current that produces a significant number of bubbles, the gas products from the radiolysis of water are normally invisible by bare eyes, little is known on whether nanosized bubbles can be produced and what their dynamics are upon irradiation. Here, we first presented the formation of nanoscale bulk bubbles by irradiating pure water with accelerated electrons and their concentration and size distribution changes with the dose and rate of irradiation. The nanoparticle tracking analysis showed that irradiation can actually produce a certain amount of bulk nanobubbles in pure water. They exhibited a dependence on the irradiation dose rates and irradiation doses. The results indicated that the concentration of formed bulk nanobubbles increased as the irradiation dose rates increased, but it will increase and then decrease with the increased irradiation doses. The formed bulk nanobubbles could maintain stability for several hours. Our findings will provide a new angle of view for the radiation chemistry of water, and the formed nanobubbles may help elucidate the biological effects of irradiated solutions.

In-vivo effects of Green laser radiation on hematological parameters of albino rats using direct exposure methods.

Laser beam has a thermal effect on the exposed body through oscillation of molecules. Rate of the vibrations depend on the time of exposure, intensity of the laser beam, the quantity of the absorbed dose, and the laser wavelength. Impacts of green laser beam on the hematological parameters of Albino Rats investigated in an in-vivo irradiation process. Green laser (200mW, 532nm) was used as a source of non-ionizing radiation to irradiate albino rats, the exposure carried out to heart position (in-vivo) of the rats directly. Fifteen female rats participated. Main blood components: white blood cells (WBC), red blood cells (RBC), and platelet (PLT) counts were evaluated using a direct exposure method for low and high radiation doses. High doses of laser beam affected the WBCs and PLTs significantly (P-value < 0.05), and the low doses were not significant (P-value > 0.05). Laser beam radiation affected on the main blood components at a limited time of exposure. Optimum radiation doses that had high effectiveness on blood component density depended on the type of blood components. As well as, high impacts (high significant) were on the density of PLT not RBCs. References FARHAD H M, JAAFAR M S, ISMAIL A H.( 2011). Control Light Delivery in PDT by Taking Account the Optical Properties of Hair Density on the Skin Surface. Journal of Modern Applied Science. 2 p.325-331. HUDA K.M., (2017). The effects of laser radiation on viscosity (PCV) of blood. Pak.J.Biotechnol . Vol.14, No.3 , pp.477-479. ISMAIL A. H., AND ABDULLA K. N., (2021). Biochemical and hematological study of the effects of annual exposure radiation doses on the operators of X-ray and CT-scan in some Erbil hospitals. Radiation Physics and Chemistry, Vol.184, 109466 KUTSCH, V. K. (1993). Laser in Dentistry. Jour. Amer. Dent. Asso. 124: 49-54. MARKOLF, H. N. (1996). Laser Tissue Interaction. Heidelberg, Germany. MUSTAFA S. AL MUSAWI, M. S. JAAFAR, B. AL-GAILANI, NASER M. AHMED, FATANAH M. SUHAIMI & NURSAKINAH SUARDI ,Lasers in Medical Science volume 32, pages405–411(2017). MUSTAFA S.A., JAFAAR M.S., NASER M. A., AL-GAILANY B.T., FATANAH M. S., 2016. Effects of low power violet laser irradiation on red blood cells volume and erythrocyte sedimentation rate in human blood, Journal of physics; conference series, Vol.1875, 020005-1-020005-7. RAAD SH. ALNAYLI A., ZAHRAA S. S., FAID SH. H., HADEEL H. S. (2017).The Effect of LASER on Blood Viscosity and Its Influential Relation on the Rapidity of Red Blood Cells Precipitation . American International Journal of Research in Science, Technology, Engineering & Mathematics, 19(1) pp.69- 74. SITI SAKINA M. F., SUARDI N., MUSTAFA I. S., (2018). In vitro UV-visible spectroscopy study of yellow laser irradiation on human blood. Journal of physics; conference series, Vol.995, 012053. THAIHAMMER.S, LAHR. A, CLEMENT, SENGEWALD. A, HESKL. W. M, BURGEMEISTER. R, AND SCHUTZE (2003) “Laser Micro tool in Cell Biology Medicine” laser physics ,13,5. VANENKO, M. & HERING, P. (1998). Hard Tissue Ablation with Mechanically Q – Switched CO2 Laser. SPIE Proc. 3565:110 – 115. XU Q, MING Z, DART AM, DU XJVAN PELT LF. (2007). Optimizing dosage of ketamine and xylazine in murine echocardiography. Clin Exp Pharmacol Physiol. 4(5-6):499-507. ZAHRA AL- TIMIMI (2014). Investigating the Effects of Green Laser Irradiation on Red Blood Cells: Green Laser Blood Therapy. Int.Jou. of Applied Research and Studies.Vol.3, Issue 10,pp.1-5.

The Radiation Chemistry of NH3···CO Complex in Cryogenic Media as Studied by Matrix Isolation.

The NH3···CO complex can be considered an important building block for cold synthetic astrochemistry leading to the formation of complex organic molecules, including key prebiotic species. In this work, we have studied the radiation-induced transformations of this complex in Ar, Kr, and Xe matrices using FTIR spectroscopy. On the basis of comparison with the quantum chemical calculations at the CCSD(T)/L2a_3 level of theory, it was found that the initial complex had the configuration with hydrogen bonding through the carbon atom of CO. Irradiation of the matrix isolated complex with X-rays at 6 K leads to the formation of a number of synthetic products, namely, HNCO (in all matrices), formamide NH2CHO, NH2CO, and HNCO-H2 (in argon and krypton). The matrix effect on the product distribution was explained by the involvement of different excited states of the complex in their formation. It was suggested that formamide results from the singlet excited states while other species mainly originate from triplet excited states. The latter states are efficiently populated through ion-electron recombination (in all matrices) and through intersystem crossing (particularly, in xenon). High yield of the recombination triplet states is a feature of the processes induced by high-energy radiation (in contrast to direct photolysis). NCO, CN, and NO were found as minor secondary products at high adsorbed doses. The astrochemical implications of the obtained results are discussed.

Proton Irradiations at Ultra-High Dose Rate vs. Conventional Dose Rate: Strong Impact on Hydrogen Peroxide Yield.

During ultra-high dose rate (UHDR) external radiation therapy, healthy tissues appear to be spared while tumor control remains the same compared to conventional dose rate. However, the understanding of radiochemical and biological mechanisms involved are still to be discussed. This study shows how the hydrogen peroxide (H2O2) production, one of the reactive oxygen species (ROS), could be controlled by early heterogenous radiolysis processes in water during UHDR proton-beam irradiations. Pure water was irradiated in the plateau region (track-segment) with 68 MeV protons under conventional (0.2 Gy/s) and several UHDR conditions (40 Gy/s to 60 kGy/s) at the ARRONAX cyclotron. Production of H2O2 was then monitored using the Ghormley triiodide method. New values of GTS(H2O2) were added in conventional dose rate. A substantial decrease in H2O2 production was observed from 0.2 to 1.5 kGy/s with a more dramatic decrease below 100 Gy/ s. At higher dose rate, up to 60 kGy/s, the H2O2 production stayed stable with a mean decrease of 38% ± 4%. This finding, associated to the decrease in the production of hydroxyl radical (•OH) already observed in other studies in similar conditions can be explained by the well-known spur theory in radiation chemistry. Thus, a two-step FLASH-RT mechanism can be envisioned: an early step at the microsecond scale mainly controlled by heterogenous radiolysis, and a second, slower, dominated by O2 depletion and biochemical processes. To validate this hypothesis, more measurements of radiolytic species will soon be performed, including radicals and associated lifetimes.