Highly Ordered Monolayers of µm-Sized Polystyrene Spheres Studied by Grazing-Incidence Small-Angle X-ray Scattering, Simulations, and Geometrical Calculations.

Unraveling the two-dimensional (2D) structural ordering of colloidal particles assembled at a flat surface is essential for understanding and optimizing their physical properties. So far, grazing-incidence small-angle X-ray scattering (GISAXS) has been widely used to determine crystallographic information on 2D self-assembled structures of nanosize objects. However, solving the structure of 2D lattices consisting of micrometer (µm)-sized objects still remains a challenge using scattering methods. Here, a model 2D SCALMS (supported catalytically active liquid metal solution) template is fabricated from µm-sized polystyrene (PS) spheres that form a monolayer on top of the flat solid support. GISAXS patterns of the sample were collected for rotation angles around its surface normal in steps of 3°. For every rotation angle, different Bragg-type interference maxima along the out-of-plane (qz) direction were observed. On the basis of simulations of GISXAS patterns of single domains of ordered particle arrangements using the distorted wave Born approximation (DWBA) and validation against a simple geometrical scattering model, the interference maxima could nicely be interpreted to originate from a monolayer of the µm-sized spherical particles which are arranged in domains of hexagonal 2D paracrystalline order. This novel GISAXS evaluation technique serves as a proof of principle for determining the µm-size periodicity of 2D crystalline domains and demonstrates its potential to spatially resolve the relative orientations of such domains with respect to a reference direction.

Screening of osmotic stress-tolerant bacteria for plant growth promotion in wheat (Triticum aestivum L.) and brinjal (Solanum melongena L.) under drought conditions.

Drought stress adversely affects plant growth and productivity. Therefore, the application of plant growth-promoting bacteria is a viable option for combating drought resistance in crops. In this study, 144 bacteria were isolated from the Kutch desert soil in Gujarat. Based on osmotic stress tolerance and PGP properties, two strains, Bacillus tequilensis (KS5B) and Pseudomonas stutzeri (KS5C) were tested for their effect on wheat (Triticum aestivum L.) and brinjal (Solanum melongena L.) under drought stress conditions. Inoculation with osmotic stress-tolerant bacteria showed 15·15-29·27% enhancement in root length of wheat and 15·27-32·59% in brinjal plants. Similarly, the enhancement of shoot length ranged from 14·72 to 37·70% for wheat and 59·39-95·94% for brinjal plants. Furthermore, the inoculated plants showed significant improvement in chlorophyll content and antioxidant properties such as proline, peroxidase and polyphenol oxidase activity compared to the control. Therefore, the bacterial strains identified in this study can be used to mitigate drought stress and enhance plant biomass.

Effect of macro-calcification on the failure mechanics of intracranial aneurysmal wall tissue.

BACKGROUND: Calcification was recently found to be present in the majority of cerebral aneurysms, though how calcification and the presence or absence of co-localized lipid pools affect failure properties is still unknown. OBJECTIVE: The primary objective is to quantify the biomechanical effect of a macro-calcification with surrounding Near-Calcification Region (NCR) of varying mechanical properties on tissue failure behavior. METHODS: We utilized a structurally informed finite element model to simulate pre-failure and failure behavior of a human cerebral tissue specimen modeled as a composite containing a macro-calcification and surrounding NCR, embedded in a fiber matrix composite. Data from multiple imaging modalities was combined to quantify the collagen organization and calcification geometry. An idealized parametric model utilizing the calibrated model was used to explore the impact of NCR properties on tissue failure. RESULTS: Compared to tissue without calcification, peak stress was reduced by 82% and 49% for low modulus (representing lipid pool) and high modulus (simulating increase in calcification size) of the NCR, respectively. Failure process strongly depended on NCR properties with lipid pools blunting the onset of complete failure. When the NCR was calcified, the sample was able to sustain larger overall stress, however the failure process was abrupt with nearly simultaneous failure of the loaded fibers. CONCLUSIONS: Failure of calcified vascular tissue is strongly influenced by the ultrastructure in the vicinity of the calcification. Computational modeling of failure in fibrous soft tissues can be used to understand how pathological changes impact the tissue failure process, with potentially important clinical implications.

Chiral Spin Mode on the Surface of a Topological Insulator.

Using polarization-resolved resonant Raman spectroscopy, we explore collective spin excitations of the chiral surface states in a three dimensional topological insulator, Bi_{2}Se_{3}. We observe a sharp peak at 150 meV in the pseudovector A_{2} symmetry channel of the Raman spectra. By comparing the data with calculations, we identify this peak as the transverse collective spin mode of surface Dirac fermions. This mode, unlike a Dirac plasmon or a surface plasmon in the charge sector of excitations, is analogous to a spin wave in a partially polarized Fermi liquid, with spin-orbit coupling playing the role of an effective magnetic field.

High T_{c} via Spin Fluctuations from Incipient Bands: Application to Monolayers and Intercalates of FeSe.

We investigate superconductivity in a two-band system with an electronlike and a holelike band, where one of the bands is away from the Fermi level (or "incipient"). We argue that the incipient band contributes significantly to spin-fluctuation pairing in the strong coupling limit where the system is close to a magnetic instability and can lead to a large T_{c}. In this case, T_{c} is limited by a competition between the frequency range of the coupling (set by an isolated paramagnon) and the coupling strength itself, such that a domelike T_{c} dependence on the incipient band position is obtained. The coupling of electrons to phonons is found to further enhance T_{c}. The results are discussed in the context of experiments on monolayers and intercalates of FeSe.

Probing the Pairing Interaction and Multiple Bardasis-Schrieffer Modes Using Raman Spectroscopy.

In unconventional superconductors, understanding the form of the pairing interaction is the primary goal. In this regard, Raman spectroscopy is a very useful tool, as it identifies the ground state and also the subleading pairing channels by probing collective modes. Here, we propose a general theory for a multiband Raman response and identify new features in the spectrum that can provide a robust test for a pairing theory. We identify multiple Bardasis-Schrieffer type collective modes and connect the weights of these modes to the subleading gap structures within a microscopic pairing theory. While our conclusions are completely general, we apply our approach to interpret the specific case of B_{1g} Raman scattering in hole-doped BaFe_{2}As_{2}.

Discovery of a superconducting high-entropy alloy.

High-entropy alloys (HEAs) are multicomponent mixtures of elements in similar concentrations, where the high entropy of mixing can stabilize disordered solid-solution phases with simple structures like a body-centered cubic or a face-centered cubic, in competition with ordered crystalline intermetallic phases. We have synthesized an HEA with the composition Ta34Nb33Hf8Zr14Ti11 (in at. %), which possesses an average body-centered cubic structure of lattice parameter a=3.36 Å. The measurements of the electrical resistivity, the magnetization and magnetic susceptibility, and the specific heat revealed that the Ta34Nb33Hf8Zr14Ti11 HEA is a type II superconductor with a transition temperature Tc≈7.3 K, an upper critical field µ0H_c2≈8.2 T, a lower critical field µ0Hc1≈32 mT, and an energy gap in the electronic density of states (DOS) at the Fermi level of 2Δ≈2.2 meV. The investigated HEA is close to a BCS-type phonon-mediated superconductor in the weak electron-phonon coupling limit, classifying it as a "dirty" superconductor. We show that the lattice degrees of freedom obey Vegard's rule of mixtures, indicating completely random mixing of the elements on the HEA lattice, whereas the electronic degrees of freedom do not obey this rule even approximately so that the electronic properties of a HEA are not a "cocktail" of properties of the constituent elements. The formation of a superconducting gap contributes to the electronic stabilization of the HEA state at low temperatures, where the entropic stabilization is ineffective, but the electronic energy gain due to the superconducting transition is too small for the global stabilization of the disordered state, which remains metastable.

The hyperactive Sleeping Beauty transposase SB100X improves the genetic modification of T cells to express a chimeric antigen receptor.

Sleeping Beauty (SB3) transposon and transposase constitute a DNA plasmid system used for therapeutic human cell genetic engineering. Here we report a comparison of SB100X, a newly developed hyperactive SB transposase, to a previous generation SB11 transposase to achieve stable expression of a CD19-specific chimeric antigen receptor (CAR3) in primary human T cells. The electro-transfer of SB100X expressed from a DNA plasmid or as an introduced mRNA species had superior transposase activity in T cells based on the measurement of excision circles released after transposition and emergence of CAR expression on T cells selectively propagated upon CD19+ artificial antigen-presenting cells. Given that T cells modified with SB100X and SB11 integrate on average one copy of the CAR transposon in each T-cell genome, the improved transposition mediated by SB100X apparently leads to an augmented founder effect of electroporated T cells with durable integration of CAR. In aggregate, SB100X improves SB transposition in primary human T cells and can be titrated with an SB transposon plasmid to improve the generation of CD19-specific CAR+ T cells.

Evolution of the superconducting state of Fe-based compounds with doping.

We introduce an effective low-energy pairing model for Fe-based superconductors with s- and d-wave interaction components and a small number of input parameters and use it to study the doping evolution of the symmetry and the structure of the superconducting gap. We argue that the model describes the entire variety of pairing states found so far in the Fe-based superconductors and allows one to understand the mechanism of the attraction in s(±) and d(x(2)-y(2)) channels, the competition between s- and d-wave solutions, and the origin of superconductivity in heavily doped systems, when only electron or only hole pockets are present.

Effect of Fermi surface nesting on resonant spin excitations in Ba(1-x)K(x)Fe2As2.

We report inelastic neutron scattering measurements of the resonant spin excitations in Ba(1-x)K(x)Fe(2)As(2) over a broad range of electron band filling. The fall in the superconducting transition temperature with hole doping coincides with the magnetic excitations splitting into two incommensurate peaks because of the growing mismatch in the hole and electron Fermi surface volumes, as confirmed by a tight-binding model with s(±)-symmetry pairing. The reduction in Fermi surface nesting is accompanied by a collapse of the resonance binding energy and its spectral weight, caused by the weakening of electron-electron correlations.

Spatio-temporal evolution of magnetohydrodynamic blood flow and heat dynamics through a porous medium in a wavy-walled artery.

BACKGROUND AND OBJECTIVE: In a healthy body, the elastic wall of the arteries forms wave-like structures resulting from the continuous pumping of the heart. The systolic and diastolic phases generate a contraction and expansion pattern, which is mimicked in this study by considering a wavy-walled arterial structure. A numerical investigation of the spatio-temporal flow of blood and heat transfer through a porous medium under the action of magnetic field strength is conducted. METHOD: The governing equations of the blood flow in the Darcy model are simulated by applying a vorticity-stream function formulation approach. The transformed dimensionless equations are further discretized using the finite difference method by developing the Peaceman-Rachford alternating direction implicit (P-R ADI) scheme. RESULTS: The computational results for the axial velocity, temperature distribution, flow visualization using the streamlines and vorticity contours, isotherms, wall shear stress and the average Nusselt number are presented graphically for different values of the physical parameters. CONCLUSIONS: The study shows that the axial velocity increases with an increase in the Darcy number, and a similar phenomenon is observed because of an amplitude variation in the wavy wall. Both temperature and wall shear stress decreases with an increase in the Darcy number. The average Nusselt number increases with the magnetic field strength, while it has a reducing tendency due to the permeability of the porous medium.

Training programme in gasless laparoscopy for rural surgeons of India (TARGET study) - Observational feasibility study.

BACKGROUND: Benefits of laparoscopic surgery are well recognised but uptake in rural settings of low- and middle-income countries is limited due to implementation barriers. Gasless laparoscopy has been proposed as an alternative but requires a trained rural surgical workforce to upscale. This study evaluates a feasibility of implementing a structured laparoscopic training programme for rural surgeons of North-East India. METHODS: A 3-day training programme was held at Kolkata Medical College in March 2019. Laparoscopic knowledge and Fundamentals of Laparoscopic Skills (FLS) were assessed pre and post simulation training using multiple choice questions and the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS), respectively. Competency with an abdominal lift device was assessed using the Objective Structured Assessment of Technical Skills (OSATS) and live operating performance via the Global Operative Assessment of Laparoscopic Skills (GOALS) scores during live surgery. Costs of the training programme and qualitative feedback were evaluated. RESULTS: Seven rural surgeons participated. There was an improvement in knowledge acquisition (mean difference in MCQ score 5.57 (SD = 4.47)). The overall normalised mean MISTELS score for the FLS tasks improved from 386.02 (SD 110.52) pre-to 524.40 (SD 94.98) post-training (p = 0.09). Mean OSATS score was 22.4 out of 35 (SD 3.31) indicating competency with the abdominal lift device whilst a mean GOALS score of 16.42 out of 25 (SD 2.07) indicates proficiency in performing diagnostic laparoscopy using the gasless technique during live operating. Costs of the course were estimated at 354 USD for trainees and 461 USD for trainers. CONCLUSION: Structured training programme in gasless laparoscopy improves overall knowledge and skills acquisition in laparoscopic surgery for rural surgeons of North-East India. It is feasible to deliver a training programme in gasless laparoscopy for rural surgeons. Larger studies are needed to assess the benefits for wider adoption in a similar context.

Measurement of the attachment and assembly of small amyloid-ß oligomers on live cell membranes at physiological concentrations using single-molecule tools.

It is thought that the pathological cascade in Alzheimer's disease is initiated by the formation of amyloid-ß (Aß) peptide complexes on cell membranes. However, there is considerable debate about the nature of these complexes and the type of solution-phase Aß aggregates that may contribute to their formation. Also, it is yet to be shown that Aß attaches strongly to living cell membranes, and that this can happen at low, physiologically relevant Aß concentrations. Here, we simultaneously measure the aggregate size and fluorescence lifetime of fluorescently labeled Aß(1-40) on and above the membrane of cultured PC12 cells at near-physiological concentrations. We find that at 350 nM Aß concentration, large (>>10 nm average hydrodynamic radius) assemblies of codiffusing, membrane-attached Aß molecules appear on the cell membrane together with a near-monomeric species. When the extracellular concentration is 150 nM, the membrane contains only the smaller species, but with a similar degree of attachment. At both concentrations, the extracellular solution contains only small (∼2.3 nm average hydrodynamic radius) Aß oligomers or monomers. We conclude that at near-physiological concentrations only the small oligomeric Aß species are relevant, they are capable of attaching to the cell membrane, and they assemble in situ to form much larger complexes.

Flexible cold cathode with ultralow threshold field designed through wet chemical route.

A flexible cold cathode based on a uniform array of ZnO nanowires over carbon fabrics was designed via a simple wet chemical route. The structural parameters of the nanowires (i.e. length, diameter) as well as their arrangement over the carbon fibers were tailored by adjusting nutrient solution composition and growth duration. The optimized arrays of ZnO nanowires exhibit excellent electron emission performance with ultralow turn-on as well as threshold fields of 0.27 and 0.56 V µm(-1). This threshold field value is the lowest compared to any of the previous zinc-oxide-based cold cathodes realized through either chemical or vapor phase processes. In addition, the current density can reach an exceptionally high value of ∼ 11 mA cm(-2) at an applied electric field of only 0.8 V µm(-1). Flexible electronic devices based on a field emitter cold cathode may thus be realized through chemical processing at low budget but having high efficiency.

Mesenchymal stem cell tailored bioengineered scaffolds derived from bubaline diaphragm and aortic matrices for reconstruction of abdominal wall defects.

Bioengineered scaffolds derived from the decellularized extracellular matrix (ECM) obtained from discarded animal organs and tissues are attractive candidates for regenerative medicine applications. Tailoring these scaffolds with stem cells enhances their regeneration potential making them a suitable platform for regenerating damaged tissues. Thus, the study was designed to investigate the potential of mesenchymal stem cells tailored acellular bubaline diaphragm and aortic ECM for the repair of full-thickness abdominal wall defects in a rabbit model. Tissues obtained from bubaline diaphragm and aorta were decellularized and bioengineered by seeding with rabbit bone marrow derived mesenchymal stem cells (r-BMSC). Full-thickness abdominal wall defects of 3 cm × 4 cm size were created in a rabbit model and repaired using five different prostheses, namely, polypropylene sheet, nonseeded diaphragm ECM, nonseeded aorta ECM, r-BMSC bioengineered diaphragm ECM, and r-BMSC bioengineered aorta ECM. Results from the study revealed that biological scaffolds are superior in comparison to synthetic polymer mesh for regeneration in terms of collagen deposition, maturation, neovascularization, and lack of any significant (P > 0.05) adhesions with the abdominal viscera. Seeding with r-BMSC significantly increased (P < 0.05) the collagen deposition and biomechanical strength of the scaffolds. The bioengineered r-BMSC seeded acellular bubaline diaphragm showed even superior biomechanical strength as compared to synthetic polymer mesh. Tailoring of the scaffolds with the r-BMSC also resulted in significant reduction (P < 0.01) in antibody and cell mediated immune reactions to the xenogeneic scaffolds in rabbit model.

Measuring serotonin distribution in live cells with three-photon excitation.

Tryptophan and serotonin were imaged with infrared illumination by three-photon excitation (3PE) of their native ultraviolet (UV) fluorescence. This technique, established by 3PE cross section measurements of tryptophan and the monoamines serotonin and dopamine, circumvents the limitations imposed by photodamage, scattering, and indiscriminate background encountered in other UV microscopies. Three-dimensionally resolved images are presented along with measurements of the serotonin concentration ( approximately 50 mM) and content (up to approximately 5 x 10(8) molecules) of individual secretory granules.

Spatial pH jump measures chemical kinetics in a steady-state system.

We measure chemical kinetics in a steady-state solution where we create a microscopic open region with conditions different from the bulk. Individual reactant molecules spontaneously diffuse through this "reaction volume". We measure the changes which take place within their short residence time in the volume. The advantage of this approach is that the time resolution is limited only by the residence time tau(D) of the molecules in the reaction volume (which can easily be <50 mus), while the time taken to average the data can be arbitrarily long. In addition, if the chemical changes are reversible, the system is always in a steady state, and no replenishment of the reactants is necessary. Also, the total specimen volume required can be very small (<20 muL). We demonstrate the scheme by measuring the protonation induced changes of the fluorescence properties of fluorescein. We first show that a pH jump of >1 unit can be achieved by multiphoton excitation of ortho-nitro benzaldehyde (o-NBA). We then perform fluorescence correlation spectroscopy (FCS) to show that the residence time tau(D) of fluorescein in this low-pH region is approximately 30 mus. Subsequently, we use time correlated single photon counting (a widely used probing technique with an inherently long averaging time), and show that the data can be averaged for an arbitrarily long time, yet it captures the fluorescence lifetime of the low-pH species which exists only for the short time tau(D). Finally, we show that the time resolution can be tuned by over 3 orders of magnitude, by changing the focal volume and by changing the viscosity of the solution. The latter experiment also shows that small chemically induced changes in the fluorescence lifetime can be resolved by our technique.

Dynamic trajectories of volatile and non-volatile specialised metabolites in 'overnight' fragrant flowers of Murraya paniculata.

Ephemeral flowers, especially nocturnal ones, usually emit characteristic scent profiles within their post-anthesis lifespans of a few hours. Whether these flowers exhibit temporal variability in the composition and profile of volatile and non-volatile specialised metabolites has received little attention. Flowers of Murraya paniculata bloom in the evenings during the summer and monsoon, and their sweet, intense fragrance enhances the plant's value as an ornamental. We aimed to investigate profiles of both volatile and non-volatile endogenous specialised metabolites (ESM) in nocturnal ephemeral flowers of M. paniculata to examine whether any biochemically diverse groups of ESM follow distinct patterns of accumulation while maintaining synchrony with defensive physiological functions. Targeted ESM contents of M. paniculata flowers were profiled at ten time points at 2-h intervals, starting from late bud stage (afternoon) up to the start of petal senescence (mid-morning). Emitted volatiles were monitored continuously within the whole 20-h period using headspace sampling. The ESM contents were mapped by time point to obtain a highly dynamic and biochemically diverse profile. Relative temporal patterns of ESM accumulation indicated that the active fragrance-emitting period might be divided into 'early bloom', 'mid-bloom' and 'late bloom' phases. Early and late bloom phases were characterised by high free radical generation, with immediate enhancement of antioxidant enzymes and phenolic compounds. The mid-bloom phase was relatively stable and dedicated to maximum fragrance emission, with provision for strong terpenoid-mediated defence against herbivores. The late bloom phase merged into senescence with the start of daylight; however, even the senescent petals continued to emit fragrance to attract diurnal pollinators. Our study suggests that dynamic relations between the different ESM groups regulate the short-term requirements of floral advertisement and phytochemical defence in this ephemeral flower. This study also provided fundamental information on the temporal occurrence of emitted volatiles and internal pools of specialised metabolites in M. paniculata flowers, which could serve as an important model for pollination biology of Rutaceae, which includes many important fruit crops.

Intermolecular association provides specific optical and NMR signatures for serotonin at intravesicular concentrations.

Neurotransmitter vesicles contain biomolecules at extraordinarily high concentrations (hundreds of millimoles/liter). Such concentrations can drive intermolecular associations, which may affect vesicular osmolarity and neuronal signaling. Here we investigate whether aqueous serotonin (a monoamine neurotransmitter) forms oligomers at intravesicular concentrations and whether these oligomers have specific spectroscopic signatures that can potentially be used for monitoring neuronal storage and release. We report that, as serotonin concentration is increased from 60 microM to 600 mM, the normalized fluorescence spectrum of serotonin displays a growing long-wavelength tail, with an isoemissive point at 376 nm. The fluorescence decay is monoexponential with a lifetime of 4 ns at low concentrations but is multiexponential with an average lifetime of 0.41 ns at 600 mM. A 600 mM serotonin solution has 30% less osmolarity than expected for monomeric serotonin, indicating oligomer formation. The proton NMR chemical shifts move upfield by as much as 0.3 ppm at 600 mM compared to those at 10 mM, indicating a stacking of the serotonin indole moieties. However, no intermolecular crosspeak is evident in the two-dimensional NMR rotating frame Overhauser effect spectroscopy spectrum even at 600 mM, suggesting that oligomeric structures are possibly weakly coupled. The appearance of a single peak for each proton suggests that the rate of interconversion between the monomeric and the oligomeric structures is faster than 240 Hz. A stopped-flow kinetic experiment also confirms that the rate of dissociation is faster than 100 ms. We conclude that serotonin forms oligomers at intravesicular concentrations but becomes monomeric quickly on dilution. NMR signatures of the oligomers provide potential contrast agents for monitoring the activity of serotonergic neurons in vivo.

Three-photon microscopy shows that somatic release can be a quantitatively significant component of serotonergic neurotransmission in the mammalian brain.

Recent experiments on monoaminergic neurons have shown that neurotransmission can originate from somatic release. However, little is known about the quantity of monoamine available to be released through this extrasynaptic pathway or about the intracellular dynamics that mediate such release. Using three-photon microscopy, we directly imaged serotonin autofluorescence and investigated the total serotonin content, release competence, and release kinetics of somatic serotonergic vesicles in the dorsal raphe neurons of the rat. We found that the somata of primary cultured neurons contain a large number of serotonin-filled vesicles arranged in a perinuclear fashion. A similar distribution is also observed in fresh tissue slice preparations obtained from the rat dorsal raphe. We estimate that the soma of a cultured neuron on an average contains about 9 fmoles of serotonin in about 450 vesicles (or vesicle clusters) of < or =370 nm average diameter. A substantial fraction (>30%) of this serotonin is released with a time scale of several minutes by K(+)-induced depolarization or by para-chloroamphetamine treatment. The amount of releasable serotonin stored in the somatic vesicles is comparable to the total serotonin content of all the synaptic vesicles in a raphe neuron, indicating that somatic release can potentially play a major role in serotonergic neurotransmission in the mammalian brain.