Comparison of biological-based and dose volume-based intensity-modulated radiotherapy plans generated using the same treatment planning system

Purpose

Nowadays, most of the radiotherapy (RT) treatment planning systems (TPSs) uses dose or dose-volume (DV)-based cost functions for Intensity modulated radiation therapy (IMRT) fluence optimization. Recently, some of the TPSs incorporated biological-based cost function for IMRT optimization. Most of the previous studies compared IMRT plans optimized using biological-based and DV-based cost functions in two different TPSs. Hence, the purpose of the study is to compare equivalent uniform dose (EUD)-based and DV-based IMRT plans generated using the same TPS.

Materials and Methods

Twenty patients with prostate cancer were retrospectively selected for this study. For each patient, two IMRT plans were generated using EUD-based cost function (EUD_TP) and DV-based cost (DV_Treatment Plan (TP)), respectively. The generated IMRT plans were evaluated using both physical and biological dose evaluation indices.

Results

Biological-based plans ended up with a highly inhomogeneous target dose when compared to DV-based plans. For serial organs, D_near-max or D_2%(Gy) of EUD-based plans showed significant difference with DV-based plans (P = 0.003). For both rectum and bladder, there was a significant difference in mean dose and D_30%(Gy) dose between EUD-based plans and DV-based plans.

Conclusion

In this study, we decoupled the influence of optimization parameters from the potential use of EUD-based cost functions on plan quality by generating both plans in the same TPS.

Theoretical Investigation on the Mechanism and Kinetics of Atmospheric Reaction of Methyldichloroacetate with Hydroxyl Radical

The atmospheric reaction of methyldichloroacetate (MDCA) with OH radical is studied using electronic structure calculations. Five different pathways were considered for the initial reactions, which results in the formation of alkyl radical of MDCA along with H₂O, HOCl, and CH₃O^•. Among the five pathways studied, the α-carbon atom (-CHCl₂ site) H atom abstraction reaction, which leads to the formation of the alkyl radical intermediate ^•CCl₂C(O)OCH₃ (I1) is found to be more favorable with an energy barrier of 7.3 kcal/mol, and Cl-atom abstraction reaction is having high energy barrier of 21.3 kcal/mol at M06-2X/6-311++G(2df,2p) level. The calculated thermochemical parameters show that except Cl-atom abstraction channel the other initial reaction channels are highly exothermic. The rate constant is calculated for the initial H atom abstraction reactions using canonical variational transition state theory over the temperature range of 278 to 350 K. The Arrhenius plot shows positive temperature dependence for both the reactions. The results from the calculated thermochemical parameters and rate constants show that the formation of the alkyl radical intermediate (I1) is more favorable with the rate constant of 2.07 × 10^-13 cm³ molecule^-1 s^-1 at 298 K. The calculated atmospheric lifetime of MDCA is 28 days at normal atmospheric OH concentration. The results obtained from secondary reactions show that the major product formed from the oxidation chemistry of MDCA is methyl-2-chloro-2-oxoacetate (or) methyl oxalyl chloride.

Molecular epidemiology of goat pox viruses

Goat pox disease outbreaks were observed in different places affecting Black Bengal Goats in West Bengal (WB) and Tellicherry, Vembur and non-descriptive breeds in Tamil Nadu (TN) causing severe lesions and mortality up to 30%. Clinical specimens from all the outbreaks were screened by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) and confirmed the diseases as Goat Pox. Virus isolation in Vero cell line was done with randomly selected ten samples, cytopathic effects (CPE) characterized by syncytia and intracytoplasmic inclusion bodies were observed after several blind passages. Nucleotide sequence of complete p32 gene using randomly selected two isolates and three clinical specimens revealed presence of Goat pox virus (GTPV)-specific signature residues in all the sequences. Phylogenetic analysis using the present five sequences along with GenBank data of GTPV complete p32 gene sequences showed all the GTPV sequences cluster together except Pellor strain (NC004003) and FZ Chinese strain (KC951854). The five sequences either from WB or TN cluster more closely with GTPV isolates of Maharashtra state that were responsible for cross species outbreak of pox disease in both sheep (KF468759) and goats (KF468762) in India during the year 2010. All the Indian goat pox viruses, including the Mukteswar strain, isolated in 1946 and sequence reported in 2004 clustered together with the GTPVs causing the recent outbreaks. It was observed that GTPVs caused similar clinical manifestation irrespective of their geographical locations and breed characteristics, no variation observed among the Indian isolates based on p32 gene over the period of seventy years and disease outbreaks could not be observed or reported in vaccinated goats.

Theoretical Investigations on the Mechanism and Kinetics of OH Radical Initiated Reactions of Monochloroacetic Acid

The oxidation mechanism of monochloroacetic acid (CH₂ClCOOH) by OH radical has been systematically investigated employing quantum mechanical methods coupled with kinetic calculation using canonical variational transition state theory. Three distinct transition states were identified for the titled reaction, two corresponding to the hydrogen atom abstraction and one corresponding to the chlorine atom abstraction. The rate constants of the titled reactions are computed over the temperature range 278-350 K, and the branching ratios calculated for the hydrogen atom abstraction from the -C(O)OH site and the -CH₂Cl site are 25 and 75%, respectively, at 298 K. The computed branching ratio indicates that the kinetically favorable reaction is the hydrogen atom abstraction from the -CH₂Cl site resulting in the formation of CHClC(O)OH radical, which further undergoes secondary reaction with O₂ and other atmospheric species. The calculated overall rate constant for the hydrogen atom abstraction reactions is in consistent with the reported experimental rate constant. The atmospheric lifetime of CH₂ClCOOH is found to be around 18 days.

Social grooming among Indian short-nosed fruit bats

Social grooming is conspicuous in group-living mammals. Bats are gregarious and may groom each other, but the motivation for such social behaviour remains unclear. Here, we describe patterns and infer function of social grooming in tent-making Indian short-nosed fruit bats. Combining field and captivity observations, we found that males and their harem of females mutually groom and apply bodily secretions to one another in tight clusters. Mutual grooming is more commonly initiated by females, before emergence flight at dusk, and during the non-mating season. The within-harem association pattern suggests males may recognize female reproductive status via social grooming. Chemical analysis of the secretions applied during grooming revealed volatile organic compounds that may be involved in chemosensory-mediated communication and/or mate choice. These fruit bat harems were previously seen as simple aggregations, with limited interactions among individuals. Our findings suggest social grooming is multi-functional, with potential implications for the bats’ social lives.

The atmospheric oxidation mechanism and kinetics of 1,3,5-trimethylbenzene initiated by OH radicals – a theoretical study

The atmospheric fate of 1,3,5-trimethylbenzene is determined by OH-radical addition, and subsequent bicyclic peroxy radical ring closure and ring breaking pathways.

A study on the tolerance level of farmers toward human-wildlife conflict in the forest buffer zones of Tamil Nadu

Aim:

The aim of this work was to study the tolerance level of farmers toward different human-wildlife conflict (HWC) situations.

Materials and Methods:

This study was conducted in 24 villages of nine blocks from Kancheepuram, Coimbatore, Erode, and Krishnagiri districts of Tamil Nadu by personally interviewing 240 farmers affected with four different HWC situations such as human-elephant conflict (HEC), human-wild pig conflict (HPC), human-gaur conflict (HGC), and human-monkey conflict (HMC). A scale developed for this purpose was used to find out the tolerance level of the farmers.

Results:

In general, the majority (61.70%) of the farmers had medium level of tolerance toward HWC, whereas 25.40% and 12.90% belonged to a high and low category, respectively. The mean tolerance level of the farmer’s encountering HMC is low (8.77) among the other three wild animal conflicts. In tackling HWC, the majority (55.00%) of the HEC farmers drove the elephant once it entered into their farmland. In the HPC, more than three-fourths of the respondents drove away the wild pig once they were found in farmlands. With regard to the HMC, a less number of them (1.70%) drove the monkey away if monkeys were spotted in their village. With regard to HGC, 95.00% of the respondents frightened the gaurs if their family members were threatened by gaurs.

Conclusion:

The present study suggests that that majority of the farmers had medium level of tolerance toward HWC. The tolerance level of the HMC farmers was lower than other three HWC affected farmers. This study emphasizes the need for necessary training to tackle the problem in an effective manner for wild animal conservation.

Estimation of the effects of normal tissue sparing using equivalent uniform dose-based optimization

In this study, we intend to estimate the effects of normal tissue sparing between intensity modulated radiotherapy (IMRT) treatment plans generated with and without a dose volume (DV)-based physical cost function using equivalent uniform dose (EUD). Twenty prostate cancer patients were retrospectively selected for this study. For each patient, two IMRT plans were generated (i) EUD-based optimization with a DV-based physical cost function to control inhomogeneity (EUD_{With DV}) and (ii) EUD-based optimization without a DV-based physical cost function to allow inhomogeneity (EUD_{Without DV}). The generated plans were prescribed a dose of 72 Gy in 36 fractions to planning target volume (PTV). Mean dose, D_30%, and D_5% were evaluated for all organ at risk (OAR). Normal tissue complication probability was also calculated for all OARs using BioSuite software. The average volume of PTV for all patients was 103.02 ± 27 cm³. The PTV mean dose for EUD_{With DV} plans was 73.67 ± 1.7 Gy, whereas for EUD_{Without DV} plans was 80.42 ± 2.7 Gy. It was found that PTV volume receiving dose more than 115% of prescription dose was negligible in EUD_{With DV} plans, whereas it was 28% in EUD_{Without DV} plans. In almost all dosimetric parameters evaluated, dose to OARs in EUD_{With DV} plans was higher than in EUD_{Without DV} plans. Allowing inhomogeneous dose (EUD_{Without DV}) inside the target would achieve better normal tissue sparing compared to homogenous dose distribution (EUD_{With DV}). Hence, this inhomogeneous dose could be intentionally dumped on the high-risk volume to achieve high local control. Therefore, it was concluded that EUD optimized plans offer added advantage of less OAR dose as well as selectively boosting dose to gross tumor volume.

Atmospheric oxidation mechanism of OH-initiated reactions of diethyl ether – the fate of the 1-ethoxy ethoxy radical

The 1-ethoxy ethoxy radical resulting from the secondary peroxy chemistry in the oxidation of diethyl ether (DEE) by hydroxyl radical leads to the formation of ethyl formate in major quantities and ethyl acetate in minor quantities.

Forth-back oscillated charge carrier motion in dynamically disordered hexathienocoronene molecules: a theoretical study

Electronic structure calculations were performed to investigate the charge transport properties of hexathienocoronene (HTC) based molecules. The effective displacement of the charge carrier along the π-orbital of nearby molecules is calculated by monitoring the forth and back oscillations of the charge carrier through kinetic Monte Carlo simulation. The charge transport parameters such as charge transfer rate, mobility, hopping conductivity, localized charge density, time average effective mass and degeneracy pressure are calculated and used to study the charge transport mechanism in the studied molecules. The existence of degeneracy levels facilitates the charge transfer and is analyzed through degeneracy pressure. Theoretical results show that the site energy difference in the dynamically disordered system controls the forth-back oscillation of charge carrier and facilitates the unidirectional charge transport mechanism along the sequential localized sites. The ethyl substituted HTC has good hole and electron hopping conductivity of 415 and 894 S cm(-1), respectively, whereas unsubstituted HTC has the small hole mobility of 0.06 cm(2) V(-1) s(-1) which is due to large average effective mass of 1.42 × 10(-28) kg.

Effect of dynamic disorder on charge carrier dynamics in Ph4DP and Ph4DTP molecules

Electronic structure calculations were used to study the charge transport and optical properties of 2,2′,6,6′-tetraphenyldipyranylidene (Ph4DP) and its sulfur analogue 2,2′,6,6′-tetraphenyldithiopyranylidene (Ph4DTP) based molecules.

Triazolyl-donor-acceptor chromophore-decorated unnatural amino acids and peptides: FRET events in a β-turn conformation

The β-turn conformation and FRET process were established in the designed tripeptide containing fluorescent triazolyl donor and acceptor-decorated unnatural amino acids separated by a natural alanine.

Oxidation and nitration of tyrosine by ozone and nitrogen dioxide: reaction mechanisms and biological and atmospheric implications

The nitration of tyrosine by atmospheric oxidants, O3 and NO2, is an important cause for the spread of allergenic diseases. In the present study, the mechanism and pathways for the reaction of tyrosine with the atmospheric oxidants O3 and NO2 are studied using DFT-M06-2X, B3LYP, and B3LYP-D methods with the 6-311+G(d,p) basis set. The energy barrier for the initial oxidation reactions is also calculated at the CCSD(T)/6-31+G(d,p) level of theory. The reaction is studied in gas, aqueous, and lipid media. The initial oxidation of tyrosine by O3 proceeds by H atom abstraction and addition reactions and leads to the formation of six different intermediates. The subsequent nitration reaction is studied for all the intermediates, and the results show that the nitration affects both the side chain and the aromatic ring of tyrosine. The rate constant of the favorable oxidation and nitration reaction is calculated using variational transition state theory over the temperature range of 278-350 K. The spectral properties of the oxidation and nitration products are calculated at the TD-M06-2X/6-311+G(d,p) level of theory. The fate of the tyrosine radical intermediate is studied by its reaction with glutathione antioxidant. This study provides an enhanced understanding of the oxidation and nitration of tyrosine by O3 and NO2 in the context of improving the air quality and reducing the allergic diseases.