Decomposition of excited electronic state s-tetrazine and its energetic derivatives, such as 3-amino-6-chloro-1,2,4,5-tetrazine-2,4-dioxide (ACTO), and 3,3(')-azobis (6-amino-1,2,4,5-tetrazine)-mixed ...N-oxides (DAATO(3.5)), is investigated through laser excitation and resonance enhanced multi photon ionization techniques. The N(2) molecule is detected as an initial product of the s-tetrazine decomposition reaction, through its two photon, resonance absorption transitions a(") (1)Σ(g)(+) (v(') = 0) ← X (1)Σ(g)(+) (v(") = 0). The suggested mechanism for this reaction is a concerted triple dissociation yielding rotationally cold (∼20 K) ground electronic state N(2) and 2 HCN molecules. The comparable decomposition of excited electronic state ACTO and DAATO(3.5) yields an NO product with a cold rotational (∼20 K) but a hot vibrational (∼1200 K) distribution. Thus, tetrazine and its substituted energetic materials ACTO and DAATO(3.5) evidence different decomposition mechanisms upon electronic excitation. N(2)O is excluded as a potential intermediate precursor of the NO product observed from these two s-tetrazine derivatives through direct determination of its decomposition behavior. Calculations at the CASMP2∕CASSCF level of theory predict a concerted triple dissociation mechanism for generation of the N(2) product from s-tetrazine, and a ring contraction mechanism for the generation of the NO product from the energetic s-tetrazine derivatives. Relaxation from S(n) evolves through a series of conical intersections to S(0), upon which surface the dissociation occurs in both mechanisms. This work demonstrates that the substituents on the tetrazine ring change the characteristics of the potential energy surfaces of the derivatives, and lead to a completely different decomposition pathway from s-tetrazine itself. Moreover, the N(2) molecule can be excluded as an initial product from decomposition of these excited electronic state energetic materials.
The radical cationic reactivity of the peptide analogue molecule CH(3)CO-Gly-NH(2) is addressed both experimentally and theoretically. The radical cation intermediate of CH(3)CO-Gly-NH(2) is created ...by single-photon ionization of this molecule at 118.22 nm (~10.5 eV). The two most stable conformers (C(7) and C(5)) of this molecule exhibit different folds along the backbone: the C(7) conformer has a γ-turn structure, and the C(5) conformer has a β-strand structure. The experimental results show that the radical cation intermediate of CH(3)CO-Gly-NH(2) dissociates and generates a fragment-ion signal at 73 amu that is observed through TOFMS. Theoretical results show how the fragment-ion signal at 73 amu is generated by only one conformer of CH(3)CO-Gly-NH(2) (C(7)) and how local charge and specific hydrogen bonding in the molecule influence fragmentation of the radical cation intermediate of CH(3)CO-Gly-NH(2). The specific fold of the molecule controls fragmentation of this reactive radical cation intermediate. Whereas the radical cation of the C(7) conformer dissociates through a hydrogen-transfer mechanism followed by HNCO elimination, the radical cation of the C(5) conformer does not dissociate at all. CASSCF calculations show that positive charge in the radical cationic C(7) conformer is localized at the NH(2)CO moiety of the molecular ion. This site-specific localization of the positive charge enhances the acidity of the terminal NH(2) group, facilitating hydrogen transfer from the NH(2) to the COCH(3) end of the molecular ion. Positive charge in the C(5) conformer of the CH(3)CO-Gly-NH(2) radical cation is, however, localized at the COCH(3) end of the molecular ion, and this conformer does not have enough energy to surmount the energy barrier to dissociation on the ion potential energy surface. CASSCF results show that conformation-specific localization of charge in the CH(3)CO-Gly-NH(2) molecular ion occurs as a result of the different hydrogen-bonding interactions involved in the different molecular conformers.
Early thyroid cancers have excellent long-term outcomes, yet the word "cancer" draws unnecessary apprehension. This study aimed to define when the recommendations for observation and surveillance may ...be extended to early thyroid cancers at the population level.
Non-metastasized thyroid cancers ≤40 mm diameter were identified from the 1975-2016 Surveillance, Epidemiology and End Results (SEER) database. Causes of death were compared across demographic data. Disease-specific outcomes were compared to the age-adjusted healthy United States (US) population. Survival estimates were computed using Kaplan-Meier and compared using the Cox proportional hazard model. Dynamic benchmarks impacting disease-specific overall survival were determined by decision tree modeling and tested by the Cox model.
Of the 28,728 thyroid cancers included in this study, 98.4% underwent some form of thyroid-specific treatment and were followed for a maximum of 10.9 years. This group had a 4.3% mortality rate at the end of follow-up (10.9 years maximum), with 13 times more deaths attributed to competing risks rather than thyroid cancer (stage T1a versus stage T1b, P=1.000; T1 versus T2, P<0.001). Among the untreated T1a or T1b tumors, the risk of disease-specific death was 21 times lower than death due to other causes. There was no significant difference between T1a and T1b tumors nor across sex. The age-adjusted risk of death for the healthy US population was higher than for the population with thyroid cancer. Dynamic categorization demonstrated worsening outcomes up to 73 years, uninfluenced by sex or tumor size. For patients over 73 years of age, only tumors >26 mm impacted outcomes.
Based on the current data, T1a and T1b nodules have similar survival outcomes and are not significantly impacted even when left untreated. Multi-institutional prospective studies are needed to confirm these findings so that current observation and surveillance recommendations can be extended to certain T1 thyroid nodules.
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•Protonated DMNA ion and its hydrated complex have been produced in the gas phase by electrospray ionization.•They have been investigated by low energy collision induced dissociation ...and ab initio MP2 level of theory.•Protonated DMNA has been observed to only eliminate OH.•The fragmentation of the hydrated DMNA complex shows the competition between passive dissociation and NO elimination.
Positive ions of dimethylnitramine (DMNA), a model system for nitramine energetic molecules, have been produced in the gas phase by electrospray ionization. Protonated dimethylnitramine ion DMNA+H+ and its hydrated complex 2DMNA+H2O+2H2+ have been investigated by both low energy collision induced dissociation (CID) and ab initio MP2 level of theory. Ion structure has been calculated. Fragments have been experimentally determined and dissociation mechanisms have been elucidated. Interestingly, the favored fragmentation pathways depend on the local environment of the ion: the hydrated complex primarily loses NO via nitro nitrite isomerization, while only OH elimination is observed in the case of protonated DMNA.
Blogs have developed in two major ways: as a personal diary online and as a technologically enhanced multimedia diary that can be manipulated to suit the user’s needs. This paper investigates one ...such blogging programme in India vis-à-vis its effect on autonomy. As a part of their curriculum, the students were asked to create their own blogs. The majority of students being unaware of blogging, a qualitative analysis of the reflective reports showed that it helped the students to be more aware of developing interaction within the virtual space. It also made the students more autonomous since they had to create and edit their own blogs to make them attractive enough for others to visit. The assigned topics also ensured that within the strict assessment necessities of the Indian university evaluation system, the students did not feel that they were doing something ‘extra’ that was outside their regular curriculum.
Landslides constitute one of the major natural hazards that could cause significant loss of life and various human settlements. Mansa Devi hill near Haridwar city has encountered with such potential ...hazard for several years due to the instability of the slopes. Therefore, preparedness both on regional and site-specific basis at spatial level in the form of surface movements is extremely important to diminish the damage of human life and settlements. Though the surface movement measurement through field-based technique is always very accurate, this technique is time-consuming and unfeasible over a widely affected region. Therefore, areal and satellite remote sensing is gaining importance in landslide investigation due to its wide coverage. In recent years, synthetic aperture radar has already proven its potential for mapping ground deformation due to earthquake, landslide, volcano, etc. Therefore, in this study, an attempt has been made to identify the potential landslide-affected region in Mansa Devi area using one multi-temporal SAR technique and intensity tracking technique. Intensity tracking technique has identified significant mass movement in the landslide-affected region where the other conventional multi-temporal technique, SBAS, fails. An error analysis has been carried out in order to demonstrate the applicability of intensity tracking technique. This study demonstrated that intensity tracking can be considered as an alternative to conventional interferometry for the estimation of land surface displacement when latter is limited by loss of coherence due to rapid and incoherent surface movement and/or large acquisition time intervals between the two SAR images.
Although hyperspectral images contain a wealth of information due to its fine spectral resolution, the information is often redundant. It is therefore expedient to reduce the dimensionality of the ...data without losing significant information content. The aim of this paper is to show that proposed fractal based dimensionality reduction applied on high dimensional hyperspectral data can be proved to be a better alternative compared to some other popular conventional methods when similar classification accuracy is desired at a reduced computational complexity. Amongst a number of methods of computing fractal dimension, three have been applied here. The experiments have been performed on two hyperspectral data sets acquired from AVIRIS sensor.
•Dimensionality reduction applied on spectral domain of hyperspectral data.•Fractal dimension has been used as a feature in the reduced dimensional set for the first time.•Enhanced the location information along an SRC by introducing multiple fractal dimensions along a single SRC.•Nature of spectral response unaltered in the reduced domain, thus keeping the physical meaning of the curve unaltered.•While compared with conventional methods, statistically equivalent classification accuracy has been achieved at a much reduced computational burden.
Land surface displacement is a phenomenon of ground movement, which may occur due to various reasons including unplanned mining. The quantification of land surface displacement through conventional ...field surveys is based on sparingly distributed point data, which may be insufficient for many applications. A detailed spatial and temporal monitoring of land surface displacements through remote sensing-based synthetic aperture radar (SAR) interferometry may be valuable. Over the last two decades, differential SAR interferometry (DInSAR) has been effectively used globally for the estimation of spatial land surface displacements caused due to natural and man-made hazards. However, it has not gained momentum in India, where occurrences of natural and man-made hazards are a common phenomenon. In this article, preliminary results from DInSAR to measure land surface displacement in Jharia coal fields have been presented. DInSAR results effectively identified the land surface displacement due to several mining activities in the region during a one-month period.
Earthquake is one of the most destructive natural hazards which pose a real threat to India with nearly 59% of its geographical area vulnerable to seismic disturbance of varying intensities including ...the capital city of the country. India has experienced several major earthquakes mainly in Himalayan region and is also considered as one of the most earthquake prone regions in the world. Therefore, during past few decades, the Himalayan region has been studied extensively in terms of present ongoing displacements. It can be believed that a better estimate of the current Himalayan convergence rate and possible rupture can improve seismic hazard evaluations. Moreover, an improved convergence rate is also necessary to estimate if any slip deficit is available to drive future earthquakes in this region. In recent years, SAR interferometry has been successfully used for generating large scale surface displacement maps in radar look direction on a dense grid and with a centimeter to millimeter accuracy. In this context, the usefulness of SAR interferometry technique and its variations for estimation of displacements has been studied and presented in this paper. To study the displacement both conventional and multi-temporal Differential SAR interferometry has been used. In order to get the 3-D surface displacement, interferogram from both ascending and descending track can be used. However, due to the unavailability of ascending track data, a well-known mathematical model also has been used. Overall average displacement rates in the present study are found to be relatively lower as compared to the reported convergence rates. From geophysical point of view, the results presented in this paper for a small area are quite promising. Several explanations have also been presented in this paper to support the results. The reported low convergence rate may be due to the occurrence of silent/quite earthquakes, aseismic slip, differential movement of Delhi Hardwar ridge, etc. Therefore, in view of the contemporary seismicity and conspicuous displacements, a study of long-term observations of this surface movement has been recommended in future.
•Objective of this research was to estimate the current Himalayan convergence rate using SAR interferometry to improve seismic hazard evaluations.•Overall average displacement rate in this study was found as relatively lower as compared to the reported convergence rates.•The overall average convergence rate was also found to be consistent with DInSAR technique by using a mathematical model.•From geophysical point of view several explanations were also presented in this paper to support the results.•Significant conclusion was drawn as the building up of slow strain across the locked portion of the Himalayan thrust system.
The reactivity of radical cation carboxylic acids is investigated on the basis of mass spectrometry, infrared-vacuum ultraviolet (IR-VUV) photoionization spectroscopy, and high level correlated ab ...initio calculations. Their reactivity is found to be highly conformation specific and is governed by their initial charge distribution following ionization. In the present work, the radical cations of lactic acid, pyruvic acid, glycine, and valine are studied to probe their stability and conformation specific reactivity following single photon, vertical ionization at 10.5 eV. For lactic acid, glycine, and valine, the localization site of the hole following sudden removal of an electron depends on their specific intramolecular hydrogen bonding network. Lactic acid, glycine, and valine undergo complete fragmentation following vertical ionization at 10.5 eV; however, pyruvic acid does not completely dissociate following vertical ionization. Only 45% of the pyruvic acid parent ions undergo C(alpha)-C(carboxylic) bond dissociation. If the hole is localized on the COOH moiety of glycine, valine, and lactic acid, a hydrogen transfer is favored from the COOH to the alpha-substituent. If the hole is localized on the alpha-hydroxy or -amine substituent and the singly occupied molecular orbital (SOMO, where the hole resides) is parallel to the C(alpha)-C(carboxylic) bond, C(alpha)-C(carboxylic) bond dissociation occurs through charge transfer from the alpha-substituent to the C(alpha)-C(carboxylic) bond. The present study reveals that the specific conformations of alpha-substituted carboxylic acids govern their radical cationic reactivity. The radical cation of pyruvic acid exhibits a special stability due to enolization of the alpha-keto form on the cationic surface.
