What We Don’t Know About Time

String theory has transformed our understanding of geometry, topology and space-time. Thus, for this special issue of Foundations of Physics commemorating “Forty Years of String Theory”, it seems appropriate to step back and ask what we do not understand. As I will discuss, time remains the least understood concept in physical theory. While we have made significant progress in understanding space, our understanding of time has not progressed much beyond the level of a century ago when Einstein introduced the idea of space-time as a combined entity. Thus, I will raise a series of open questions about time, and will review some of the progress that has been made as a roadmap for the future.     

Identification and quantitation of pathogenic bacteria via in-situ formation of silver nanoparticles on cell walls,and their detection via SERS

Microchimica Acta - The authors present a fast and sensitive surface-enhanced Raman spectroscopy (SERS) method for the determination of Mycobacterium smegmatis. It is based on the formation of...     

Thermal behavior of carbon fiber precursor polymers with different stereoregularities

The effect of stereoregularity, in terms of isotactic triad content on the thermal behavior of carbon fiber precursor polymers synthesized through different polymerization routes such as solid state and radical solution polymerization techniques, was investigated by the thermogravimetric analysis and differential scanning calorimetric measurements. The isotactic contents of I-PAN and A-PAN were estimated with ¹³C NMR. The thermal cyclization reactions of atactic polyacrylonitrile (A-PAN) with low isotactic content (26.4–29.7 %) occurred at a lower temperature than that of isotactic polyacrylonitrile (I-PAN) with higher content (48.7–51.6 %). The percentage of mass loss observed in I-PAN was less as compared to A-PAN. The molecular mass characteristics of PAN obtained through solid state and radical solution polymerization were [M _n (10.2–14.3 × 10⁴), M _v (2.44–3.26 × 10⁵)] and [M _n (10.2–14.3 × 10⁴), M _v (2.29–2.74 × 10⁵)] Daltons (Da).     

Reaction of Dichlorocarbene with Substituted Cyclopentadienones Under Phase Transfer Conditions

The cycloaddition reactions involving dichlorocarbene generated under phase transfer conditions have been studied extensively in the past few years due to the simplicity of the procedure involved.¹ The facile formation of dichlorocyclopropanes provides an easy entry to functionalised aromatics and expanded carbocyclic compounds.² The dichlorocarbene generated under phase transfer conditions is capable of adding even to electron deficient olefins. We describe here the cyclo-addition reaction of dichlorocarbene to tetrasubstituted cyclopentadienones.     

Synthesis of Novel Fluorinated 11H‐Azaindolo[3,2‐c]isoquinolines

A series of novel fluorinated 11H‐azaindolo[3,2‐c]isoquinolines ( 7 ) have been synthesized starting from 2(1H)pyridones ( 1 ) via azaindoles ( 5 ). Initially, compound 1 was treated with POCl₃/DMF, and the resulting compound 2 was reacted with benzylamine to obtain compounds 3 that were subjected to cyclization after protecting the secondary amine to get azaindoles ( 5 ). Further, compounds 5 were subjected to cyclization as per Pictet–Spengler reaction condition. However, it was not successful. Subsequently, the azaindoles ( 5 ) were acetylated and then cyclized to give title compounds 7 . These compounds are new and well characterized by spectral data.     

Synthesis of on resin poly(propylene imine) dendrimer and its use as organocatalyst

Solid phase synthesis of poly(propylene imine) dendrimer is described. An iterative synthesis including double Michael addition of acrylonitrile to the primary amino groups on crosslinked polystyrene support followed by reduction of nitrile groups to amino groups give poly(propylene imine) dendrimers up to third generation attached to the polystyrene support. The supported dendrimer is used as an organocatalyst to Knoevenagel condensations. The supported catalyst showed good selectivity and the product was obtained in excellent yield under green reaction conditions. Densely packed amino groups enhance catalysis by a co-operative effect. The catalyst is recoverable and reusable.     

Development of fish gelatin-based artificial fish baits incorporating bioattractants from seafood processing waste

The study dealt with evolving an artificial fish bait by incorporating bioattractant concentrates derived from seafood processing wastes by enzymatic hydrolysis namely fish waste concentrate (FWC), squid waste concentrate (SWC), and shrimp processing concentrate (SPWC). They were characterized based on amino acid content and presence of different functional groups using FTIR. Among them, SWC was found to have the highest amino acid content of 60.85mg/100 mg followed by FWC (42.21mg/100 mg) and SPWC (24.82mg/100 mg). The developed artificial fish baits were subjected to protein leaching, solubility in seawater besides testing for acceptability by the red snapper. The study revealed that the bait incorporated with SWC at 3% level was found be the most ideal, with the protein leaching rate of 24.82 mg/g/h, solubility rate of 36.6 mg/g/h and the attractability score of 29/30. The amino acid leaching rate was 3.11 mg/h/100 mg and it was found to contain five amino acids such as glycine, proline, glutamic acid, alanine and serine. The study revealed that the hydrolyzed squid waste concentrate can be incorporated at 3% (w/w) with fish gelatin based biomatrix during gelation to prepare artificial bait.     

An overview of heterogeneous photocatalysis for the degradation of organic compounds: A special emphasis on photocorrosion and reusability

Heterogeneous photocatalysis has been extensively investigated for the degradation of organic pollutants from wastewater. The remarkable advantages of the heterogeneous photocatalysis process depend upon its ability to produce reactive oxygen species under visible/UV/solar light irradiation. However, the long-term stability and reuse potential of these catalysts are of great concern these days, yet understudied. This review aims to systematically present a state of the art understanding of such catalysts' reuse potential. Various important surface characteristics of the photocatalysts for improving the photostability and activity of the catalyst are discussed. Besides, the synergistic effect of different surface modified materials, composite materials and their surface characteristics for their enhanced activity are also covered. Finally, a discussion on various regeneration processes used for such catalysts is also presented, identifying some vital research needs in this field.     

Investigating the effect of π-configurations and methoxy substitution on donor and π- spacers based dyes for dye-sensitized solar cell applications–computational approach

Research on Chemical Intermediates - Triphenylamine and methoxy substituted triphenylamine-based dyes are examined by density-functional theory and time-dependent density-functional theory. The...