Searching for relativistic axions in the sky

Relativistic axions produced in decays of ${\mathcal O}(10^{-7}-10^{-2}$ $\text{eV})$ dark matter (DM) partially convert to photons after traversing the galactic magnetic field, giving rise to a signal observable by the Square Kilometer Array (SKA) radio telescope. We show that for axions lighter than a few $\times$ $10^{-13}$ eV a 100\,h SKA observation of the local dwarf galaxy Seg I would probe parameter space not constrained by stellar cooling and cosmological observations, with sensitivity several orders of magnitude better than the planned dedicated axion dark matter search experiments. We quantify the uncertainties in the SKA sensitivity projections due to two effects that enhance the photon flux: the presence of turbulent magnetic fields inside the galaxy, and the Bose enhancement of the DM decays to axions, where the latter, in particular, warrants further study.Comment: 24 pages, 12 figure

Current concepts of diagnosis and management of pericardial cysts

Pericardial cysts are rare with an incidence of about 1 in every 100,000 persons and one in 10 pericardial cysts may actually be a pericardial diverticulum. Pericardial cysts and diverticula share similar developmental origin and may appear as an incidental finding in chest roentgenogram in an asymptomatic patient. CT scan is considered as best modality for diagnosis and delineation of the surrounding anatomy. Cardiac MRI is recommended in the evaluation of the compressive effects caused by the pericardial cysts. The authors recommend echocardiography for serial follow up and image guided aspiration of the pericardial cyst in presence of compressive effects leading to cardiovascular and airway symptoms. A systematic approach is desirable for management of pericardial cysts depending on size, shape and compression effects, symptoms and easy access to serial Echocardiographic follow up. However, pericardial diverticulum may not be differentiated from cysts by the above testing, and only identified at surgery

OFFLINE CHARACTER RECOGNITION USING MONTE CARLO METHOD AND NEURAL NETWORK

ABSTRAC

Pyrene-based fluorescent supramolecular hydrogel: scaffold for energy transfer

The self-assembled gelation of an amino-acid-based low molecular weight gelator having a pyrene moiety at the N terminus and a bis-ethyleneoxy unit linked with succinic acid at the C terminus is reported. This amphiphile is capable of gelating binary mixtures (1/3 v/v) of CH3CN/water, DMSO/water, and DMF/water, and the minimum gelation concentration (MGC) varied from 0.2 to 0.3 % w/v. The sodium salt of the amphiphile efficiently gelates water with an MGC of 1.5 % w/v. The participation of different noncovalent interactions in supramolecular gelation by formation of fibrillar networks was investigated by spectroscopic and microscopic methods. High mechanical strength of the supramolecular gels is indicated by storage moduli on the order of 103 Pa. The hydrogel was utilized for energy transfer, whereby inclusion of only 0.00075 % w/v of acridine orange resulted in about 50 % quenching of the fluorescence intensity of the gel through fluorescence resonance energy transfer

Pyrene-based fluorescent ambidextrous gelators: scaffolds for mechanically robust SWNT-gel nanocomposites

With the rapid progress in the development of supramolecular soft materials, examples of low-molecular-weight gelators (LMWGs) with the ability to immobilise both water and organic solvents by the same structural scaffold are very limited. In this paper, we report the development of pyrene-containing peptide-based ambidextrous gelators (AGs) with the ability to efficiently gelate both organic and aqueous solvents. The organo- and hydrogelation efficiencies of these gelators are in the range 0.7–1.1 % w/v in various organic solvents and 0.5–5 % w/v in water at certain acidic pH values (pH 2.0–4.0). Moreover, for the first time, AGs have been utilised to prepare single-walled carbon-nanotube (SWNT)-included soft nanocomposites in both hydro- and organogel matrices. The influence of different non-covalent interactions such as hydrogen bonding, hydrophobic, π–π and van der Waals interactions in self-assembled gelation has been studied in detail by circular dichroism, FTIR, variable-temperature NMR, 2D NOESY and luminescence spectroscopy. Interestingly, the presence of the pyrene moiety in the structure rendered these AGs intrinsically fluorescent, which was quenched upon successful integration of the SWNTs within the gel. The prepared hydro- and organogels along with their SWNT-integrated nanocomposites are thermoreversible in nature. The supramolecular morphologies of the dried gels and SWNT–gel nanocomposites have been studied by transmission electron microscopy, fluorescence microscopy and polarising optical microscopy, which confirmed the presence of three-dimensional self-assembled fibrillar networks (SAFINs) as well as the integrated SWNTs. Importantly, rheological studies revealed that the inclusion of SWNTs within the ambidextrous gels improved the mechanical rigidity of the resulting soft nanocomposites up to 3.8-fold relative to the native gels

pH-Triggered conversion of soft nanocomposites: in situ synthesized AuNP-hydrogel to AuNP-organogel

Amino acid based amphiphilic gelators (carboxylate salts) were employed for the in situ synthesis of gold nanoparticles (GNPs) in hydrogel networks at room temperature without using any external reducing or capping agents for the development of AuNP-hydrogel soft composite. Synthesized AuNP-hydrogel composites were then successfully converted to AuNP-organogel composites simply by lowering the pH of the aqueous medium, as the hydrogelating amphiphilic carboxylates were transformed to corresponding carboxylic acids that are efficient organogelators. These water insoluble carboxylic acids spontaneously moved from the aqueous phase to the nonpolar organic media (toluene) along with the synthesized GNPs to form the AuNP-organogel composite. The phase transfer of the GNPs from a hydrogel network to an organogel network was investigated by UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) studies. Supramolecular networks of both the gels played a crucial role in stabilization of the GNPs. Fluorescence spectroscopy was used to investigate the mechanistic detail of the in situ GNP synthesis. The characterizations indicated the formation of spherical and uniform sized GNPs and even phase transfer of the nanoparticles did not result in change of shape or size of the nanoparticles. Rational designing of the gelator/nongelator molecules helped us to recognize the key structural components required for the efficient synthesis and stabilization of the GNPs in both the phases. Rheological study suggested that the hydrogel-GNP composites possess improved viscoelastic property than the native hydrogel

Variability of Presentation and Surgical Approach in Patients with Congenital Cystic Adenomatoid Malformation: Report of Two Cases

International audienceCongenital cystic adenomatoid malformation (CCAM) is a rare hypoplastic, dysplastic or hamartomatous disorder of lung. Two such cases were referred to our institute and managed surgically. The first case, a 4 month old male baby diagnosed antenatally with cystic lesions in the lung and suffered from respiratory tract infection postnatally. A computerised tomography scan (CT scan) was done to assess area of involvement in the lung. As apical and anterior basal segment (Segment 6 and 7) was found to be involved, segmentectomy was performed. The second patient, a 2 month old female baby, presented with features of pneumothorax with a normal perinatal history. CT scan revealed multiple cystic lesions of different sizes involving whole left lobe. Left lower lobectomy was performed. The authors emphasize on postnatal confirmation of CCAM by CT scan and lobectomy or segmentectomy as early as possible after 1 month of age guided by CT scan and thoracotomy finding even in asymptomatic patient

Gel-nanocomposites: materials with promising applications

The race to develop newer materials with superior properties/applications in diversified fields is gathering momentum in modern day science. In this context, an exciting avenue of research deals with the development of hybrid materials resulting from the combination of gels with nanoparticles of different origins. These varying kinds of nanoparticles (inorganic nanoparticles, Au/Ag based nanoparticles and carbonaceous nanostructures like carbon nanotube and graphene) are being used in conjunction with diverse self-assemblies to develop gel-nanocomposites with the scope of generating advanced applications. The present review will track the noteworthy progress of gel-nanocomposites and also will highlight the recent advances in their synthesis, improved properties/features and applications for developing mechanically robust materials to antimicrobial hydrogels

Pristine carbon-nanotube-included supramolecular hydrogels with tunable viscoelastic properties

Research investigations involving pristine carbon nanotubes (CNTs) and their applications in diversified fields have been gathering enormous impetus in recent times. One such emerging domain deals with the hybridization of CNTs within hydrogels to form soft nanocomposites with superior properties. However, till now, reports on the inclusion of pristine CNTs within low-molecular-weight hydrogels are very scarce due to their intrinsic feature of remaining in the bundled state and strong repulsive behavior to the aqueous milieu. Herein, the synthesis of a series of amino acid/dipeptide-based amphiphilic hydrogelators having a quaternary ammonium/imidazolium moiety at the polar head and a C16 hydrocarbon chain as the hydrophobic segment is reported. The synthesized amphiphiles exhibited excellent hydrogelation (minimum gelation concentration (MGC) ≈0.7–5 % w/v) as well as single-walled carbon nanotube (SWNT) dispersion ability in aqueous medium. Interestingly, the dispersed SWNTs were incorporated into the supramolecular hydrogel formed by amphiphiles with an imidazolium moiety at the polar end through complementary cation–π and π–π interactions. More importantly, the newly synthesized hydrogelators were able to accommodate a significantly high amount of pristine SWNTs (2–3.5 % w/v) at their MGCs without affecting the gelating properties. This is the first time that such a huge amount of SWNTs has been successfully incorporated within hydrogels. The efficient inclusion of SWNTs to develop soft nanocomposites was thoroughly investigated by spectroscopic and microscopic methods. Remarkably, the developed nanocomposites showed manifold enhancement (≈85-fold) in their mechanical strength compared with native hydrogel without SWNTs. The viscoelastic properties of these nanocomposites were readily tuned by varying the amount of incorporated CNTs

Organogel-hydrogel transformation by simple removal or inclusion of N-boc-protection

Development of organo- and hydrogelators is on the rise because of their extensive applications, from advanced materials to biomedicine. However, designing both types of gelator from a common structural scaffold is challenging, and becomes more significant if transformation between them can be achieved by a simple method. The present work reports the design and synthesis of both organo- and hydrogelators from amino acid/peptide-based amphiphilic precursors with a naphthyl group at the N terminus and a primary amine-containing hydrophilic ethyleneoxy unit at the C terminus. In alkaline medium, tert-butyloxycarbonyl (Boc) protection at the primary amine of the amphiphiles resulted in efficient organogelators (minimum-gelation concentration (MGC)=0.075–1.5 % w/v). Interestingly, removal of the Boc protection from the ethyleneoxy unit, under acidic conditions, yielded amphiphiles capable of gelating water (MGC=0.9–3.0 % w/v). Simple protection and deprotection chemistry was used to achieve transformation between the organogel and hydrogel by alteration of the pH. Combinations of different aliphatic and aromatic amino acids were investigated to discover their cumulative effect on the gelation properties. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to investigate the supramolecular morphology of the thermoreversible gels. Spectroscopic investigations (FTIR, photoluminescence, XRD) revealed that noncovalent interactions, such as hydrogen bonding, π–π stacking, and van der Waals interactions play a decisive role in self-assembled gelation