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Any optimization algorithm programming interface can be seen as a black-box function with additional free parameters. In this spirit, simulated annealing (SA) can be implemented in pseudo-code within the dimensions of a single slide with free parameters relating to the annealing schedule. Such an implementation, however, necessarily neglects much of the structure necessary to take advantage of advances in computing resources and algorithmic breakthroughs. Simulated annealing is often introduced in myriad disciplines, from discrete examples like the Traveling Salesman Problem (TSP) to molecular cluster potential energy exploration or even explorations of a protein’s configurational space. Theoretical guarantees also demand a stricter structure in terms of statistical quantities, which cannot simply be left to the user. We will introduce several standard paradigms and demonstrate how these can be “lifted” into a unified framework using object-oriented programming in Python. We demonstrate how clean, interoperable, reproducible programming libraries can be used to access and rapidly iterate on variants of Simulated Annealing in a manner which can be extended to serve as a best practices blueprint or design pattern for a data-driven optimization library.

Graphic abstract The popularity of traditional fermented food products is based on their healthiness. The addition of a starter brings consistent, desirable, and predictable food changes with improved nutritive, functional, and sensory qualities. The addition of a mixture of plant residues as a starter or source of microbes is an age-old practice to prepare traditional fermented food and beverages, and most of the reported data on traditional foods were based on the analysis of the final product. The contribution of an individual starter component (plant residue) is not experimentally substantiated for any traditional fermented food, but this data are very essential for the formulation of an effective starter. In this study, Asparagus racemosus, which used as a common ingredient of starter for preparation of rice fermented food in the Indian sub-continent, was used as a starter for the preparation of rice fermented food under laboratory scale, and its microbial and nutrient profile was evaluated. The fermented product was a good source of lactic acid bacteria, Bifidobacterium sp., yeast, etc. The food product was acidic and enriched with lactic acid and acetic acid with titratable acidity of 0.65%. The content of protein, fat, minerals, and vitamins (water-soluble) was considerably improved. Most notably, oligosaccharide (G3-matotriose), unsaturated fatty acids (ω3, ω6, ω7, and ω9), and a pool of essential and non-essential amino acids were enriched in the newly formulated food. Thus, the herbal starter-based rice fermented food would provide important macro- and micronutrients. They could also deliver large numbers of active microorganisms for the sustainability of health. Therefore, the selected plant part conferred its suitability as an effective starter for the preparation of healthier rice-based food products.

Hypercalcaemia is defined as a serum calcium level of more than 10.50 mg/dl. Although there are several causative factors for hypercalcaemia, primary hyperparathyroidism and malignancy are the two most common causes encountered in clinical practice. Other causes include vitamin D intoxication, granulomatous diseases like sarcoidosis, tuberculosis and some fungal infections, thyrotoxicosis, Addison’s disease, milk-alkali syndrome, vitamin A intoxication, therapy with thiazide diuretics and lithium, familial hypocalciuric hypercalcaemia and prolonged immobilization. All these account for fewer than 10 % of all causes of hypercalcaemia. These rare causes of hypercalcaemia are important to consider in certain clinical situations when the underlying cause of hypercalcaemia cannot be attributed to primary hyperparathyroidism or overt malignancy.[1]

The structure and solvation behaviour of binary liquid mixtures of Methanol (MeOH) and N, N-Dimethylformamide (DMF) are explored by ascertaining their intermolecular interactions with either Rhodamine-B (RhB) or Rhodamine101 (Rh101) dye through steady-state absorption, emission, and two-photon induced fluorescence. Specifically, in the present investigation, we examine the strong synergistic solvation observed for the combinations of hydrogen bond donating (MeOH) and accepting (DMF) solvent pairs. Solvatochromism causes the solvatochromic probe molecules to sense increased polarity compared to their bulk counterparts. The origin of synergism was explained in terms of solute-solvent and solvent-solvent interactions in binary solvent mixtures interactions, as evidenced by probe dependence. The solvation behaviour of the Methanol and DMF binary solvent mixture shows strong probe dependence, with Rh101 showing synergism while RhB does not.

BACKGROUND Anaemia is a very frequently occurring disorder associated with hypothyroidism especially in the elderly age group. Both conditions have similar presentations and are often confused with the nonspecific symptoms of old age. Although there is abundant data regarding relationships between hypothyroidism and anaemia in the general population, studies on the association between anaemia in hypothyroidism in the elderly population and the types of anaemia associated with elderly hypothyroidism are limited. In view of these considerations the current study, conducted at Gauhati Medical College, Guwahati, Assam, aims to seek the morphological types of anaemia associated with elderly hypothyroid patients. METHODS In the study, a total of 125 hypothyroid patients aged 60 years and above attending the outpatient and inpatient ward of the Department of Medicine, GMCH were examined clinically and through necessary investigations and the morphological types of anaemia associated with hypothyroidism were determined. RESULTS It was found that out of 125 elderly hypothyroid patients, the most common morphological type of anaemia was found to be normocytic normochromic type (59.4%) followed by macrocytic anaemia (21.6%) and microcytic hypochromic anaemia (19%). CONCLUSIONS Normocytic normochromic anaemia is the most common morphological type of anaemia associated in elderly hypothyroid patients, followed by macrocytic anaemia and microcytic anaemia.

The present study has been aimed at evaluating the antiobesity, antihyperglycemic, and antidepressive potentials of Asparagus racemosus starter-based rice fermented foods. High-throughput NGS technology has revealed a number of bacterial genera in the prepared fermented rice, such as Lactobacillus (29.44%), Brevundimonas (16.21%), Stenotrophomonas (6.18%), Pseudomonas (3.11%), Bacillus (2.88%), and others (Lactobacillus, and Bifidobacterium, as well as the suppressed growth rate of γ- and δ-Proteobacteria and Firmicutes in the gut after fermented food intake. In the intestine, the latter group of microorganisms possibly modulate short-chain fatty acid (SCFA) levels such as acetate, butyrate, and propionate more than twofold. The impairment of memory-learning and anxiety-like obesity-associated cognitive phenotypes is mitigated significantly (p < 0.01) by fermented food as well. Thus, the formulated fermented food could be used as a natural therapeutic to alleviate obesity and its associated psychological and pathophysiological ailments.

We use time-resolved thermal lens (TL) experiments to examine the convective heat transfer at microscale in the first eight members of the homologous series of primary alcohols. TL measurements enable a direct study of these primary alcohols without adding any chromophore as a function of varying heat loads created via femtosecond laser pulses at 1560 nm. Convective heat transfer leads to the asymmetrical and reduced thermal gradient, which substantially weakens the TL signal. The inflection in the time profile of the TL signal of methanol at higher powers is attributed to the greater molecular convection in methanol compared to other samples. This inflection dies out with a decrease in laser power. Our results demonstrate that the convection is more prominent at higher laser powers in all samples, and it modifies the trend in the steady-state TL signal of different alcohols with pump laser power. Methanol also has the highest steady-state TL among the primary alcohol series at low laser powers. The maxima in the TL signal are shifted systematically from methanol to ethanol and then to propanol as the laser power increases. Semiempirical analysis of time-resolved TL signal by using the latest theoretical TL model enabled us to extract the coefficient of convective heat transfer in methanol at different laser powers. In addition to that, analysis of other members of alcohol series at the highest (7.3 mW) laser power shows that convection is more facile in short-chain alcohols compared to the long-chain alcohols.

On Tuesday, 02 October 2018, Arthur Ashkin of the United States, who pioneered a way of using light to manipulate physical objects, shared the first half of the 2018 Nobel Prize in Physics. The second half was divided equally between Gerard Mourou of France and Donna Strickland of Canada for their method of generating high-intensity, ultra-short optical pulses. With this announcement, Donna Strickland, who was awarded the Nobel for herwork as a PhD student with GerardMourou, became the third woman to have ever won the Physics Nobel Prize, and the 96-year-old Arthur Ashkin who was awarded for his work on optical tweezers and their application to biological systems, became the oldest Nobel Prize winner. According to Nobel.org, the practical applications leading to the Prize in 2018 are tools made of light that have revolutionised laser physics–a discipline which in turn is represented by generations of advancements and not just a single example of brilliant work.

A facile synthesis and detailed photophysical investigation of E/Z-isomerization of fluorescent diphenylamine tethered stilbene derivatives (DPASs) under white light exposure have been carried out to understand the effect on fluorescence, electrochemical properties, and photostability under various activation/deactivation pathways. In solution state, in the dark, the E-isomer of DPASs (6a–d) exhibited high fluorescence quantum yields (Φfl ≈ 53% to 60% in DMSO). However, on white light exposure, 1H NMR and HPLC studies revealed that pure E-isomer of the DPAS 6a (∼9.5 mM) started converting into its Z-form by photoisomerization until it reaches to nearly equilibrium. At low concentrations (∼10 μM), the absorption band of the pure E-isomer in the range of 350–450 nm gradually decreased to adopt Z-conformation 6a′ until a photostationary state was reached. The structure of the E-isomer 6a was unequivocally confirmed by X-ray diffraction analysis. The synthesized DPAS compounds 6a–d possessed positive solvatoc...

Non-contact localized laser heating-based thermal lensing has emerged as a technique for probing the heat transport in liquids. A mode-mismatched dual-beam pump–probe spectroscopic technique was employed to investigate the photothermal response and modes of heat dissipation in methanol and binary mixtures of methanol with polar (water, methanol (MeOH)) and nonpolar (CCl4) solvents. We recorded the time-resolved thermal lens (TL) signal of a probe beam at 780 nm after heat deposition by a 1560 nm pump beam. For pure solvents, the TL signal was found to be approximately one order of magnitude larger for methanol than for water, DMSO, or CCl4, implying that the energy deposition is larger for methanol than for any of the other solvents. Subsequently, binary mixtures were studied where the TL signal increased with an increase in the volume fraction of methanol. All TL signals are shown to have a physical interpretation in terms of heat conduction and convection. In the case of methanol–water, the observed trend can be rationalized in terms of a strong intermolecular interaction. Convective heat transfer is shown to dominate the overall heat transfer in pure methanol and in binary mixtures for all volume fractions where MeOH is in excess of 50%. No convection is observed for very dilute mixtures with a small amount of methanol; in this case, heat conduction is sufficient to reach equilibration. Interestingly, for binary mixtures of methanol with DMSO or water, a decreasing trend is observed in the concentration range between 90% and 100% volume fraction of methanol. We observe also that the TL signal is modified in case of intermolecular interactions forming large clusters of methanol with the cosolvent. In such cases, heat diffusion is affected. Thus, TL can be seen as a sensitive probe for intermolecular interactions as well.

The Harmonized Diagnostic Assessment of Dementia for Longitudinal Aging Study in India (LASI-DAD) is a population-representative, prospective cohort study of late-life cognition and dementia. It is part of an ongoing international research collaboration that aims to measure and understand cognitive impairment and dementia risk by collecting a set of cognitive and neuropsychological assessments and informant reports, referred to as the Harmonized Cognitive Assessment Protocol (HCAP). LASI-DAD provides nationally representative data drawn from a subsample of the ongoing Longitudinal Aging Study in India (LASI). One of LASI-DAD's distinctive features is its rich geriatric assessment, including the collection of venous blood samples and brain imaging data for a subsample of respondents. In this paper, we discuss the methodological considerations of developing and implementing the HCAP protocol in India. The lessons we learned from translating and applying the HCAP protocol in an environment where illiteracy and innumeracy are high will provide important insights to researchers interested in measuring and collecting data on late-life cognition and dementia in developing countries. We further developed an innovative blood management system that enables us to follow the collection, transportation, assay, and storage of samples. Such innovation can benefit other population surveys collecting biomarker data.

Typical single-beam optical tweezers use continuous wave (CW) lasers, which can be explained through force balancing the light pressure from a tightly focused laser beam used for trapping microscopic particles. Recent years have also seen a surge in single-beam optical trapping research with high-repetition-rate femtosecond lasers that has shown certain differences from the CW tweezers, one of which is its sensitive detection capability of the ultrashort pulse induced background free two-photon fluorescence signals. The high peak power of each laser pulse is enough to provide instantaneous trapping potential, while the high repetition rate ensures sustained stable trapping from the successive pulses. Though the capability and usefulness of the optical-tweezers are well established, for both CW and pulsed lasers, simulating real-time scenarios to predict optical trapping behaviour remains a challenging problem. This is especially true for femtosecond laser tweezers since high peak powers are involved when the laser is tightly focused for achieving the tweezing action. The nonlinear optical effect and thermal nonlinearity become much more significant for femtosecond optical trapping. We demonstrate the importance of including these nonlinear interactions for femtosecond pulsed laser mediated optical trapping via their effect in scattering and gradient forces in the Rayleigh regime. Our optical-tweezers model includes thermal and optical nonlinear interactions, making it easier to predict the optical-trap stability in real optical trapping scenarios for both CW and pulsed lasers. Our model provides predictive metrics for choosing solvents, probes, and several optical parameters, which can be validated from our experiments.

INTRODUCTION Hepatic encephalopathy is the term used to describe the complex, sometimes irreversible, and variable changes in neuropsychiatric status that can complicate both acute and chronic liver disease. A spectrum of neuropsychiatric abnormalities exists ranging from clinically indiscernible changes in cognition to clinically obvious changes in intellect behaviour, motor function, and consciousness. METHODS We conducted a hospital-based observational descriptive study comprising of 80 patients of chronic liver disease from June 2014-May 2015 who had been diagnosed on the basis of a thorough history, physical examination, including mini-mental status examination, Glasgow Coma Score, biochemical tests including arterial ammonia, radiological findings, EEG and CFF (critical flicker frequency) Tests after excluding other causes of neurological impairment. The patients were admitted in Gauhati Medical College and Hospital, Guwahati, Assam (India) and fulfilled the inclusion and exclusion criteria of the study. Statistical analysis was performed using one way ANOVA method of analysis. RESULTS In our study, 61 patients were male and 19 patients were female. 30% patients were in the third decade of life followed by 26.25% in the fourth decade and 18.75% in the fifth decade. Most of the patients were in Child-Pugh Class C (72.5%) followed by Class A (16.25%) and Class B (11.25%). The patients were assigned grades of hepatic encephalopathy according to the West-Haven classification. Majority of patients were in grade I hepatic encephalopathy (30%) followed by grade III (28.75%) and grade IV (21.25%). The lowest mean arterial ammonia level was found in grade 0 and grade I hepatic encephalopathy - 39.2±7.4 mg/dL and 58.7±9.8 mg/dL (mean±standard deviation) respectively and the highest values were found in the highest grades of hepatic encephalopathy - grade III and IV (98.4±10.7 mg/dL and 145.0±17.0 mg/dL respectively). CONCLUSION The arterial ammonia correlates with the grades of hepatic encephalopathy and interventions aimed at reducing the ammonia level improves the outcome and prognosis.

BACKGROUND An alarming incidence and severity of jaundice in Malaria, especially in the Plasmodium falciparum variety, has been reported from various parts of the world and at times it causes diagnostic dilemma in both endemic and non-endemic areas, even sometimes affecting the outcome adversely. There are reports depicting association of severe jaundice with falciparum malaria masquerading as fulminant hepatic failure. This study is done to clinically evaluate the cases of malaria with hepatitis in terms of its presentations, extent of hepatic involvement and biochemical parameters. MATERIAL AND METHOD This study was done on 100 confirmed cases of malaria with jaundice, who were admitted in Gauhati Medical College and Hospital during a period of 12 months (1 st July 2012 to 30 th June 2013). Patients were admitted due to complications of malaria like jaundice, nausea and vomiting, pain abdomen, respiratory difficulty, oliguria, altered sensorium, etc. Detailed history, clinical examination, biochemical parameters for liver function test and other blood tests were done in all patients. RESULTS Age of the patients ranged from 13-55 years. Among all patients, 96% cases were P. falciparum and 4% cases were P. vivax. Fever and jaundice were present in 100% of cases. Among the cases, 14% had only splenomegaly, 30% had only hepatomegaly whereas 56% had enlargement of both the organs. The mean serum bilirubin level was 8.9 ± 8 mg/dL with predominantly conjugated hyperbilirubinaemia. Majority of the cases had elevated transaminases and alkaline phosphatase levels. Lowering of serum albumin level and derangement of prothrombin time was also noted in more than half of the patients while serum ammonia was elevated in small number of cases. Acute renal failure and cerebral malaria were the other complications noted frequently in cases of Malaria presenting with jaundice. CONCLUSION The evidence of predominant conjugated hyperbilirubinaemia, increased levels of liver enzymes along with relative changes in other important parameters are strong evidence of gross hepatocytic dysfunction in patients of malaria. Awareness about these possible alterations are pertinent towards proper diagnosis and treatment of cases of Malaria with jaundice.

We illustrate control of a polarized laser optical trapping potential landscape through the nonideal mixing of binary liquids. The inherent trapping potential asymmetry (ITPA) present in the trapping region results from the asymmetric intensity distribution in focal volume due to the high numerical aperture objective lens. Experimentally, we show that this ITPA effect can be modified and/or removed by the use of binary liquid mixtures. From our femtosecond optical tweezers experiments, we determine the topograph of the trapping potential base on the fluctuation-dissipation theorem. Additionally, the Brownian motion of the trapped bead is sensitive to the frictional force (FF) of the surroundings that is exerted by clusters of water and alcohol binary mixture through extended hydrogen bonding. Thus, using these two effects, ITPA and FF of the medium, we have shown that one can indeed modify the effective trapping potential landscape. Water-alcohol binary mixtures display a nonlinear dependence on the microrheological properties of the solvent composition as a result of rigid cluster formation. Volumetrically, at about 30% methanol in water binary mixture, the trapping asymmetry is minimal. In this particular binary mixture composition, the hydrophobic part of the methanol molecule is surrounded by ‘cages’ of water molecules. Enhanced H-bonding network of water molecules results in higher viscosity, which contributes to the higher frictional force. Increased viscosity decreases the degree of anisotropy due to hindered dipolar rotation. However, at higher methanol concentrations, the methanol molecules are no longer contained within the water cages and are free to move, which decrease their overall bulk viscosity. Thus, for pure solvents, experimentally measured anisotropy matches quite well with the theoretical prediction, but this fails in case of the binary mixtures due to the increased frictional force exerted by binary mixtures that result from the formation of cage-like structures.

Spectrally resolved photon echo spectroscopy in the off-resonance condition is reported for the first time to study the coherence and population dynamics of CdSe quantum dots. In this case, the information related to the system dynamics can be inferred indirectly. This is especially useful when such dynamical information might be hidden under the absorption maxima of the sample. We observe that a substantial intensity of the photon echo signal was obtained in two different CdSe quantum dot samples (CdSe 610 and CdSe 640), which have absorption maxima at 620 nm and 590 nm, respectively. Due to the difference in sizes of these two quantum dots, a small change is observed in the molecular dynamics of these two quantum-dot samples. Specifically, the spectral diffusion of CdSe 640 occurs within the first 50 fs, whereas that for CdSe 610 occurs at about 100 fs timescale. The integrated plots of the photon echo signal, as a function of population time, result in two decay constants. The faster among the two decay components is pulse width limited and is in between 30 and 40 fs at different fixed coherence times for both samples. The slower decay component for the CdSe 610 sample is found to be in the range of 75–85 fs, while that for CdSe 640, it is between 82 and 92 fs at different fixed coherence times. SYNOPSIS Excitonic dynamics of CdSe quantum-dots is presented using time-dependent spectrally-resolved photon-echo spectroscopy at 810 nm, which is ~160 nm red-shifted from their absorption maxima. Information related to system dynamics is inferred indirectly from such ‘far-from-resonance’ photon-echo experiments, which would be especially useful when the information is hidden within the sample’s absorption maxima.

A novel on-the-fly calibration method of optical tweezers is presented, which enables in situ control and measure of absolute temperature and viscosity at nanoscale dimensions. Such noncontact measurement and control at the nanoscale are challenging as the present techniques only provide off-line measurements that do not provide absolute values. Additionally, some of the present methods have a low spatial resolution. We simultaneously apply the high temporal sensitivity of position autocorrelation and equipartition theorem to precisely measure and control in situ temperature and the corresponding microrheological property around the focal volume of the trap at high spatial resolution. The femtosecond optical tweezers (FOTs) use a single-beam high repetition rate laser for optical trapping to result in finer temperature gradients in comparison to the continuous-wave laser tweezers. Such finer temperature gradients are due to the additional nonlinear optical (NLO) phenomena occurring only at the nanoscale focal plane of the FOTs. Because NLO processes are laser peak power-dependent, they promote an effective study of physical properties occurring only at the focal plane. Using FOTs at optically benign near-infrared wavelengths, we demonstrate microrheological control and measurement in water by adding a highly absorbing yet low fluorescent dye (IR780).

The nonlinear optical absorption properties of three meso-substituted aromatic, neutral tetrathia[22]porphyrin(2.1.2.1) compounds were investigated using an open aperture Z-scan technique at 527 nm with a pulse width of 100 ns in dichloromethane. The responses obtained were accounted for by invoking reverse saturable absorption arising due to strong excited state absorption. Both ground and excited state absorption cross-sections are reported, which follow the same trend as the respective structural parameters.

BACKGROUND Japanese Encephalitis is one of the most common causes of Acute Encephalitic Syndrome in Asia. During the period of June to August in 2014 an epidemic occurred in Assam, a northestern state of India. METHODS Patients admitted in the Medicine Department in Gauhati Medical College and Hospital (GMCH), Guwahati, Assam, India, with clinical features of Acute Encephalitic Syndrome (AES) i.e. acute onset fever and a change in mental status (including symptoms such as confusion, disorientation, coma, or inability to talk) and/or new onset seizures (excluding simple febrile seizures) from June to August 2014 underwent ELISA for Japanese Encephalitis Immunoglobulin M in cerebrospinal fluid (CSF) at the time of admission. Clinical features, demographic profile and laboratory investigations were recorded in positive patients. RESULTS 226 AES patients were admitted in 6 different units of Medicine ward in GMCH, out of which 76 patients were diagnosed to be JE positive with CSF IgM ESLIA, coming from 17 districts of Assam. Out of 76 patients, 69 patients were from rural area, only 7 patients were from urban area. 59 (77.63%) patients were farmers or daily labourers by occupation and 23 (30.26%) patients were illiterate. Mean age of patients was 47.7 years and male to female ratio was 1.7:1. Mean duration of fever was 6.5 days, convulsion was found in 13.15% patients, out of which most common was generalised seizure (9.2%). 55.2% patients had meningeal signs, 23.68% patients had focal neurological deficits in the form of hemiparesis and monoparesis and mean GCS score was 9.28. Extra pyramidal features present in patients were rigidity (23.68%), abnormal posturing (15.78%) and abnormal movements (23.68%). 23.68% patients had Leukocytosis and Thrombocytopenia was found in 21 (27.6%) patients. Mean CSF cell count was 34.34 cells/mm3 with mean 29.67% polymorphs, mean CSF protein and sugar was 56.15 mg/dl and 66.92 mg/dl respectively. Serum bilirubin level was normal however elevated liver enzymes were present in 63.15% of patients. CT scan brain was done in 52 JE positive patients, cerebral oedema was found in 19 (36.52%) patients and hypodensities in thalamus, midbrain and basal ganglia was found in 16 (30.65%) patients. CONCLUSION One of the important findings of the present study is Thrombocytopenia and elevation of liver enzymes in JE patients which were not reported in previous studies except one study in Thailand and another in India in Paediatrics patients. Though the study was small it needs further stu

Kunal Dhoke, Martin Zanni, Upendra Harbola, Ravi Kumar Venkatraman, Elangannan Arunan, King-Chuen Lin, Artur Nenov, Jonathan Skelton, R J Dwayne Miller, Jonathan D. Hirst, Vincenzo Aquilanti, John R. Helliwell, Srihari Keshavamurthy, Sai Ramesh, Mike Ashfold, Anuradha Pallipurath, Priyadarshi Roy Chowdhury, Sanghamitra Mukhopadhyay, Jemmis E D, Himani Medhi, Debabrata Goswami, Prasenjit Halder, Wolfgang Junge, Mahesh Hariharan, Santosh Kumar Singh, Siva Umapathy, Adithya Lakshmannam, Martin Meedom Nielsen, Sankarampadi Aravamudhan, Volker Deckert, Kenneth Ghiggino, Keisuke Tominaga and Alison Edwards

Martin Zanni, E. D. Jemmis, Sankarampadi Aravamudhan, Elangannan Arunan, Neil Hunt, Sanghamitra Mukhopadhyay, Helena J. Shepherd, Srihari Keshavamurthy, Arend G. Dijkstra, Mike Ashfold, Himangshu Prabal Goswami, Artur Nenov, Himani Medhi, Kenneth Ghiggino, Kiran Moirangthem, R. J. Dwayne Miller, Debabrata Goswami, Siva Umapathy, John R. Helliwell, Jonathan D. Hirst, Stephen Meech, Shaul Mukamel, Biman Bagchi and Marylise Buron-Le Cointe

We have shown experimentally the successful engineering of femtosecond pulse shaping at a 76 MHz repetition rate input pulse with an acousto-optic modulator (AOM). High repetition rate (HRR) femtosecond laser pulse shaping using an AOM in the Fourier plane was incomprehensible because of its intrinsic 100 kHz acoustic update limit. We demonstrate an effective way of pulse selection and a calibration routine (Fourier shift theorem), which enables generation of ∼10 MHz shaped output pulses from the HRR input pulse train. We have generated a temporally shifted rectangular shaped pulse profile by applying modulation on both the phase and amplitude of the ‘sinc’ RF modulation function.

We present a novel method of microrheology based on femtosecond optical tweezers, which in turn enables us to directly measure and control in situ temperature at microscale volumes at the solid–liquid interface. A noninvasive pulsed 780 nm trapped bead spontaneously responds to changes in its environment induced by a co-propagating 1560 nm pulsed laser due to mutual energy transfer between the solvent molecules and the trapped bead. Strong absorption of the hydroxyl group by the 1560 nm laser creates local heating in individual and binary mixtures of water and alcohols. “Hot Brownian motion” of the trapped polystyrene bead is reflected in the corner frequency deduced from the power spectrum. Changes in corner frequency values enable us to calculate the viscosity as well as temperature at the solid–liquid interface. We show that these experimental results can also be theoretically ratified.

Non-resonant molecular fragmentation of n-propyl benzene with femtosecond laser pulses is dependent on the phase and polarization characteristics of the laser. We find that the effect of the chirp and polarization of the femtosecond pulse when applied simultaneously is mutually independent of each other, which makes chirp and polarization as useful ‘logic’ implementing knobs.

Dependence of ultrafast dynamics on the excited state evolution and ground state recovery of a cyanine dye (IR125) in dichloromethane (DCM) solvent interfaced with neat water is presented. We use degenerate pump-probe transient absorption spectroscopy to show that the excited-state dynamics of the dye molecule is strongly dependent on the position of the measurements from bulk DCM solution to the solution near the water layer. The decay component of the transient corresponding to the excited state lifetime increases from bulk DCM solution to its interface with water. Such results show that the effect of the presence of water layer over the dye solution in DCM extends several micrometers, indicating the surfactant nature of the IR125 molecules, and provides us a measure of the penetration of water into the DCM layer. The initial ultrafast decay component (coherent spike) directly correlates to the pulse-width of our near-transform limited pulses used in these experiments. This approach of measuring the excited state decay of a dye across an immiscible liquid interface can provide important characteristics of microtransport across such interfaces.

For a series of rhodamine dyes, two-photon absorption (TPA) and two-photon fluorescence (TPF) have been performed in different solvents. Solvent-dependent TPA spectra of these dyes were measured with open aperture z-scan method and compared to their respective single-photon spectra at equivalent energies. In the TPA spectra, relative peak intensities and positions are highly solvent dependent, which could be a result of vibronic couplings that depend on solvent environment. Measured TPA cross-sections of rhodamine dyes are consistently higher in nonpolar solvents. Certain complementary and similarity between TPA and TPF are also elucidated. Finally, a two-photon figure-of-merit is presented for these dyes in different solvents as a function of wavelength.

Spectrally resolved femtosecond three-pulse photon echo signal from some metal–octaethyl porphyrins (OEPs) like Zn(II)–OEP, Ni(II)–OEP, Co(II)–OEP is reported. Excited state dynamics is studied by time evolving photon echo spectra for different values of coherence and population relaxation times. Dependence on the spectrally resolved photon echo spectra on varying metal center is analyzed. For all these metallo-porphyrins, the electronic relaxation timescale is found to be limited by our laser pulsewidth of 50 fs whereas the timescale for intramolecular vibrational relaxation, occurring within the Q00 band was found to be over a picosecond for Co(II)–OEP and Ni(II)–OEP and within a picosecond for Zn(II)–OEP., Graphical abstract Spectrally resolved femtosecond three-pulse photon echo signal from some metal–octaethyl porphyrins (M–OEPs) like Zn(II)–OEP, Ni(II)–OEP, Co(II)–OEP is reported.

We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

Graphical abstract A molecular structure-property relationship is established from the variation of third-order nonlinear susceptibility and thermal-diffusivity for a primary alcohol series., We apply ultrafast single beam Z-scan technique to measure saturation absorption coefficients and nonlinear-refraction coefficients of primary alcohols at 1560 nm. The nonlinear effects result from vibronic transitions and cubic nonlinear-refraction. To measure the pure total third-order nonlinear susceptibility, we removed thermal effects with a frequency optimized optical-chopper. Our measurements of thermal-relaxation dynamics of alcohols, from 1560 nm thermal lens pump and 780 nm probe experiments revealed faster and slower thermal-relaxation timescales, respectively, from conduction and convection. The faster timescale accurately predicts thermal-diffusivity, which decreases linearly with alcohol chain-lengths since thermal-relaxation is slower in heavier molecules. The relation between thermal-diffusivity and alcohol chain-length confirms structure-property relationship.

We demonstrate coded self-assembly in nanostructures using the code seeded at the component level through computer simulations. Defects or cavities occur in all natural assembly processes including crystallization and our simulations capture this essential aspect under surface minimization constraints for self-assembly. Our bottom-up approach to nanostructures would provide a new dimension towards nanofabrication and better understanding of defects and crystallization process.

Two chromophores with diaza-18-crown-6 as receptor have been synthesized in high yields. The electronic structure, one-photon absorption (OPA) spectra, and two-photon absorption (TPA) properties have been studied in detail. When no metal ion is added as input, both show negligible TPA cross-section (σ2). However, in the presence of Zn(II)/Cd(II)/Mg(II)/Ca(II) ion, each exhibits large TPA cross-section value. Binding of metal ion in the receptor increases the symmetric charge transfer leading to large σ2 values. Theoretical calculations at the B3LYP functional with 6-31G∗ and LanL2DZ mixed basis set under DFT formalism support experimental results.