Evaporation of Inclined Drops: Formation of Asymmetric Ring Patterns.

Evaporation of colloidal drops on horizontal surfaces deposits the contained particles at the drop-edge producing radially symmetric ring-like stains. The symmetry in the particle deposition is broken when the drop is placed on a tilted surface due to the influence of gravity on the suspended particles and the drop itself. Using extremely small drops generated by electrospray, we explore cases where different mechanisms of particle transport dominate. We show that the asymmetric residues are formed as the gravity-induced effects compete with the capillary flow. Our results give a broad insight into the pattern formation of evaporating inclined drops.

Theoretical Investigation of a Vital Step in the Gas-Phase Formation of Interstellar Ammonia NH2+ + H2 → NH3+ + H.

A crucial step in the gas-phase formation of ammonia in the interstellar medium (ISM) is the reaction of NH2+ with molecular hydrogen. Understanding the electronic structure of the participating species in this reaction and the evaluation of the rate coefficients at interstellar temperatures are, therefore, critical to gain new insights into the mechanisms of formation of interstellar ammonia. We present here the first theoretical results of the rate coefficients of this reaction as a function of temperatures relevant to the ISM, computed using transition-state theory. The results are in reasonable agreement with recent experimental data. This exothermic reaction features a tiny barrier which is primarily a consequence of zero-point energy corrections. The results demonstrate that quantum mechanical tunneling and core-electron correlations play significant roles in determining the rate of the reaction. The noteworthy failure of popular density functionals to describe this reaction is also highlighted.

Vibrational Predissociation Spectroscopy of Cold Protonated Tryptophan with Different Messenger Tags.

Vibrational spectra of protonated tryptophan were recorded by predissociation of H2 messenger tags using cryogenic ion traps. We explore the issue of messenger induced spectral changes by solvating TrpH+(H2) n with n = 1-5 to obtain single photon vibrational spectra of TrpH+ and of its partly deuterated isotopomer in the spectral region of 800-4400 cm-1. Depending on the number of messenger molecules, the spectra of several conformational isomers associated with multiple H2 binding locations along with two natural conformations of TrpH+ were found using the two photon MS3IR2 conformational hole burning method. Most probable messenger positions were established by comparison with predictions from DFT calculations on various candidate structures. Mechanical anharmonicity effects associated with the charged amino group were modeled by Born-Oppenheimer ab initio molecular dynamics. The spectra of TrpH+(H2O) m=1,2, recorded by infrared multiphoton dissociation (IRMPD), reveal broad features in the NH stretching region of the NH3+ group, indicating strong hydrogen bonding in acceptor-donor configuration with the benzene ring for the first water molecule, while the second water appears to attach to a less strongly perturbing site, yielding unique transitions associated with the free OH stretching fundamentals. We discuss the structural deformations induced by the water molecules and compare our results to recent experiments on similar hydrated cationic systems.

A versatile 16-pole ion trap setup for investigating photophysics of biomolecular ions.

A linear 16-pole ion trap-based experimental setup has been designed, implemented, and characterized to investigate the photophysics of biomolecules in the gas phase. Electrospray ionization is employed to generate the ions in the gas phase at atmospheric pressure. The voltage configuration on the ion funnel, the ion optic device in the first vacuum interface, is used to control the energy of the ions. A home-built quadrupole mass-filter is utilized for the mass-selection of the ions of interest. A 16-pole ion trap designed and built in-house is implemented for ion trapping. The instrument's versatility and capability are showcased by demonstrating the fragmentation patterns of protonated and deprotonated tryptophan, as well as describing the photodetachment decay of deprotonated indole.

Laser-Induced Fluorescence (LIF) Spectroscopy of Trapped Molecular Ions in the Gas Phase.

This review focuses on the laser-induced fluorescence (LIF) spectroscopy of trapped gas-phase molecular ions, a developing field of research. Following a brief description of the theory and experimental approaches employed in general for fluorescence spectroscopy, the review summarizes the current state-of-the-art intrinsic fluorescence measurement techniques employed for gas-phase ions. Whereas the LIF spectroscopy of condensed matter systems is a well-developed area of research, the instrumentation used for such studies is not directly applicable to gas-phase ions. However, some measurement schemes employed in condensed-phase experiments could be highly beneficial for gas-phase investigations. We have included a brief discussion on some of these techniques as well. Quadrupole ion traps are commonly used for spatial confinement of ions in the ion-trap-based LIF. One of the main challenges involved in such experiments is the poor signal-to-noise ratio (SNR) arising due to weak gas-phase fluorescence emission, high background noise, and small solid angle for the fluorescence collection optics. The experimental approaches based on the integrated high-finesse optical cavities employed for the condensed-phase measurements provide a better (typically an order of magnitude more) SNR in the detected fluorescence than the single-pass detection schemes. Another key to improving the SNR is to exploit the maximum solid angle of light collection by choosing high numerical aperture (NA) collection optics. A combination of these two approaches integrated with ion traps could transmogrify this field, allowing one to study even weak fluorescence emission from gas-phase molecular ions. The review concludes by discussing the scope of the advances in the LIF instrumentation for detailed spectral characterization of fluorophores of weak gas-phase fluorescence emission, considering fluorescein as one example.

UV photodissociation dynamics of deprotonated 2'-deoxyadenosine 5'-monophosphate [5'-dAMP-H]-.

The UV photodissociation dynamics of deprotonated 2'-deoxyadenosine 5'-monophosphate ([5'-dAMP-H](-)) has been studied using a unique technique based on the coincident detection of the ion and the neutral fragments. The observed fragment ions are m/z 79 (PO(3)(-)), 97 (H(2)PO(4)(-)), 134 ([A-H](-)), 177 ([dAMP-H-A-H(2)O](-)), and 195 ([dAMP-H-A](-)), where "A" refers to a neutral adenine molecule. The relative abundances are comparable to that found in previous studies on [5'-dAMP-H](-) employing different excitation processes, i.e., collisions and UV photons. The fragmentation times of the major channels have been measured, and are all found to be on the microsecond time scale. The fragmentation mechanisms for all channels have been characterized using velocity correlation plots of the ion and neutral fragment(s). The findings show that none of the dissociation channels of [5'-dAMP-H](-) is UV specific and all proceed via statistical fragmentation on the ground state after internal conversion, a result similar to fragmentations induced by collisions.

Comparative evaluation of enamel microhardness after using two different remineralizing agents on artificially demineralized human enamel: An in vitro study.

AIM: The purpose of this study was to compare the remineralization outcomes of two agents using the Vickers microhardness test (VMHT) on artificially induced enamel subsurface lesions. MATERIALS AND METHODS: Forty sound extracted premolars were selected as samples for the current study and divided into four groups of 10 teeth each: Clinpro (group 1), Remin Pro (group 2), untreated positive control (group 3), and a demineralized negative control (group 4). All the sample groups were assessed first at baseline then after demineralization and remineralization using DIAGNOdent. After the remineralization process, VMHT was performed on all sample groups to assess surface microhardness (SMH). The results obtained were then compared using a one-way analysis of variance (ANOVA) for the difference in SMH. RESULTS: Vickers microhardness number values were analyzed using one-way ANOVA and samples in the experimental groups 1 and 2 showed a statistically significant difference compared to the control groups (P < 0.05). Remineralization was higher in the Remin Pro group, followed by Clinpro group. CONCLUSIONS: The results of this in vitro study show that both Remin Pro and Clinpro are equally effective as remineralizing agents. Although Remin Pro tended to yield a higher microhardness, no significant differences were observed between the two agents. RELEVANCE FOR PATIENTS: Enamel mineral loss leads to the degradation of the surface and subsurface structures of teeth. Natural remineralization that occurs physiologically is not sufficient to overcome the hurdles of mineral loss a tooth undergoes due to changes in food habits and lifestyle. A thought on remineralization and management such as prescribing remineralizing agents and regular professional topical fluoride applications would definitely render satisfactory results by a strong healthy enamel.

A polyherbal ayurvedic drug--Indukantha Ghritha as an adjuvant to cancer chemotherapy via immunomodulation.

Indukantha Ghritha (IG) is a polyherbal preparation consisting of 17 plant components widely prescribed by ayurvedic physicians for various ailments. Though it is a known ayurvedic drug, no attempt has been made to scientifically validate its mechanism of action. Preliminary studies in our laboratory showed IG to possess considerable immunomodulatory effects with a Th1 type of immune response. In this regard, we attempted to elucidate its role as an adjuvant to cancer chemotherapy. BALB/c mice were administered IG, for a period of 14 days and parameters such as Hb, total and differential WBC count, bone marrow cellularity, lymphocyte proliferation and function, macrophage phagocytosis and tumor remission were studied. Administration of IG could inhibit tumor development in mice challenged with Dalton's lymphoma ascites. IG-induced leukopoiesis and enhanced median survival time as well as life span in tumor bearing animals. Macrophage phagocytic capacity was also elevated. Flow cytometric analysis of lymphocyte subsets and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium salt] assay for lymphocyte proliferation, yielded promising results which reinforces its use as an adjuvant to cancer chemotherapy. The polyherbal drug could reverse cyclophosphamide-induced myelosuppression in control tumor bearing animals significantly to values near or above normal levels. These results demonstrate the potential of IG, especially in several immunosuppressed conditions and patients suffering from leukopenia as a consequence of cancer chemotherapy.

Psychiatric comorbidities in acute coronary syndromes: Six-month follow-up study.

INTRODUCTION: Acute coronary syndrome (ACS) caused by coronary atherosclerosis include ST-segment elevation myocardial infarction (STEMI), non-STEMI, and unstable angina. The relation between psychiatric disorders and coronary artery disease is a complex one which includes the effect of the psychosocial factors on heart and vice versa. Point prevalence studies have been reported, but there is paucity of follow-up studies from India. MATERIALS AND METHODS: The study is a follow-up evaluation at discharge of 248 consecutive patients presented with ACS at JSS Hospital, Mysuru, Karnataka, over a period of 6 months to assess the psychiatric comorbidities. The patients were assessed on a structured and validated pro forma before discharge, at 3 months, and at 6 months. Screening of psychiatric disorders was done using Mini International Neuropsychiatric Interview PLUS 5.0.0 and assessment of depression was done using Hamilton Depression Rating Scale. ANOVA, Student's t-test, and SPSS 21 were used for statistical analysis. RESULTS: The most common psychiatric comorbidities include major depressive disorder (44%), it persisted at the end of 3 (P < 0.001) and 6 (P < 0.001) months. A spectrum of anxiety disorders including panic disorder (12.10%), dysthymia (3.60%), agoraphobia (2.40%), social phobia (2%), obsessive-compulsive disorder (1.6%), specific phobia (1.2%), and posttraumatic stress disorder (0.8%) in descending order at the end of 6 months were found. Significant reduction in substance use of nicotine (66.1%) and alcohol (56.0%) was reported on follow-up. CONCLUSION: Depression, anxiety, and substance use occur in patients with ACS which persist on follow-up. Early recognition at discharge and appropriate counseling on follow-up improve the clinical outcomes.

UV Photofragmentation Dynamics of Protonated Cystine: Disulfide Bond Rupture.

Disulfide bonds (S-S) play a central role in stabilizing the native structure of proteins against denaturation. Experimentally, identification of these linkages in peptide and protein structure characterization remains challenging. UV photodissociation (UVPD) can be a valuable tool in identifying disulfide linkages. Here, the S-S bond acts as a UV chromophore and absorption of one UV photon corresponds to a σ-σ* transition. We have investigated the photodissociation dynamics of protonated cystine, which is a dimer of two cysteines linked by a disulfide bridge, at 263 nm (4.7 eV) using a multicoincidence technique in which fragments coming from the same fragmentation event are detected. Two types of bond cleavages are observed corresponding to the disulfide (S-S) and adjacent C-S bond ruptures. We show that the S-S cleavage leads to three different fragment ions via three different fragmentation mechanisms. The UVPD results are compared to collision-induced dissociation (CID) and electron-induced dissociation (EID) studies.