The development of a catalytic synthesis of münchnones: a simple four-component coupling approach to alpha-amino acid derivatives

A new palladium-catalyzed route to prepare 1,3-oxazolium-5-oxides (i.e., Münchnones) directly from imine, carbon monoxide, and acid chloride building blocks has been developed. This provides a straightforward catalytic synthesis of Münchnones and is amenable to generating a diverse range of products by simple modification of the imine or acid chloride starting materials. Münchnones are vital synthetic intermediates to a variety of heterocyclic and peptide-based molecules. As such, this methodology has been utilized to design a new catalytic synthesis of alpha-amino acid derivatives via a one-pot coupling of imines, carbon monoxide, and acid chloride followed by alcohol. The latter represents the first reported catalytic synthesis of alpha-amino acids directly from imine and carbon monoxide building blocks.     

RETRACTED: A simple spectrophotometric technique for the determination of carbaryl pesticides in various environments

This article has been retracted at the request of the Editors-in-Chief. Please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). REASON: Considerable concern was raised about the research purportedly conducted at Sri Venkateswara University, India with the alleged involvement of Prof. P. Chiranjeevi. Questions were raised as to the volume of publications, the actual capacity (equipment, orientation and chemicals) of the laboratory in which Prof. Chiranjeevi worked, the validity of certain of the research data identified in the articles, the fact that a number of papers appear to have been plagiarized from other previously published papers, and some aspects of authorship. Professor Chiranjeevi was given the opportunity to respond to these allegations. Thereafter, a committee was constituted by the University to look into these allegations. Based on the enquiry committee report, we have been informed by the head of the Department of Chemistry at Sri Venkateswara University that the university authorities have taken disciplinary action against Prof. Chiranjeevi, as the university considers that there are grounds for such action. Therefore, based on the results of this investigation, the Editor is retracting this article.     

Demonstration of plasma startup by coaxial helicity injection

The first successful results on the transfer of a coaxial helicity injection (CHI) produced discharge to inductive operation are reported. CHI-assisted plasma startup is more robust than inductive only operation. After hand off for inductive operation, the initial 90 kA of CHI-produced current drops to 40 kA, then ramps up to 170 kA, using only 30 mV s, more than 30% higher than that produced by induction alone. These significant performance enhancing results were obtained on the HIT-II spherical torus experiment (major/minor radius of 0.3/0.2 m).     

Space Efficient Suffix Trees

We give first the representation of a suffix tree that uses n lg n + O(n) bits of space and supports searching for a pattern string in the given text (from a fixed size alphabet) in O(m) time, where n is the size of the text and m is the length of the pattern. The structure is quite simple and answers a question raised by Muthukrishnan (in Proceedings of the FST and TCS Preconference Workshop on Randomization, 1997, pp. 23–27). Previous compact representations of suffix trees had either a higher lower order term in space and had some expectation assumption or required more time for searching. When the size of the alphabet k is not viewed as a constant, this structure can be modified to use the same space but take O(m lg k) time for string searching or to use an additional O(n lg k) bits but take the same O(m) time for searching. We then give several index structures for binary texts, with less space including

• a structure that uses a suffix array (lg  bits) and an additional () bits,

• an indexing structure that takes bits of space, and

• an ( lg ) bit structure which answers in () time, the decision question of whether a given pattern of length occurs in the text.

Each of these structures uses a different technique, either in the storage scheme or in the search algorithm, in reducing the space requirement. The first one uses a suffix array, a sparse suffix tree, and a table structure. Finding all the occurrences of a pattern using this structure takes O(m + s) time, where s is the number of occurrences of the pattern in the text. The second structure constructs a sparse suffix tree for all the suffixes that start with the bit that occurs more times in the given binary text. The last structure uses an iterative algorithm to search for the pattern. This structure is the first o(n lg n) bit index to support the decision version of indexing queries in time linear in the length of the pattern. But this does not support the general indexing queries where we want to find the position of the occurrence of the pattern.Our main contribution is the development of techniques to use the succinct tree representation through balanced parentheses for suffix trees.     

The diamond: Its structure and properties

A critical study of the crystal forms of diamond from various sources demonstrates that the symmetry of the structure may be either that of Class 32 or Class 31, in other words that the structure may be either centrosymmetric or non-centrosymmetric. Diamonds belonging to Class 31 may however exhibit a pseudo-octahedral symmetry of external form by reason of the interpenetration of oppositely directed structures having the lower symmetry. The existence of diamond with two differing structures provides an insight into the many remarkable properties of this material,viz., the striking differences observed in the infra-red absorption spectra, differences in transparency to ultra-violet rays, the differences in the intensity of their X-ray reflections and the variations in the intensity and colour of the luminescence exhibited by them. The modes of atomic vibration in diamond can be completely described and their frequencies evaluated by very simple procedures. The vibration frequencies can be determined experimentally by observations of the frequency shifts in the scattering of light or by infra-red spectroscopy, the results by the two methods being fully in agreement. The heat capacity of diamond may then be computed, giving results in highly satisfactory concordance with the observational data. The principal mode of atomic vibration having a frequency of 1332 cm.^?1 is triply degenerate. These vibrations can be excited in the lattice planes of diamond by the incidence of monochromatic X-rays if it belongs to crystal Class 31. The three-fold degeneracy of the vibration reveals itself as the three distinct spots in the resulting dynamic X-ray reflection by the octahedral lattice planes. The complete electronic frequency spectrum of diamond has been evaluated by a very simple procedure. The results are highly successful in explaining the known optical and spectroscopic properties of diamond.     

Synthesis and origins of the methylpropanoporphyrins from Serpiano Oil Shale

A new synthesis of the methylpropanoporphyrins from Serpiano Oil Shale using the tripyrrene-a,c-biladiene approach is reported; a plausible pathway for the geochemical genesis of these unusual petroporphyrins is presented.