EVALUATION OF POMEGRANATE PEEL AS A SUBSTRATE FOR CITRIC ACID PRODUCTION BY ASPERGILLUS NIGER

Objective: The present study aimed to evaluate dried pomegranate peels as a substrate for citric acid production by Aspergillus niger. Methods: The morphological study of Aspergillus niger was carried out by wet mount with lactophenol cotton blue and slide culture method. A preliminary qualitative screening of citric acid-producing ability of this fungal strain was also performed by using the Czapek-Dox agar medium containing Bromocresol green. Dried and finely powdered Pomegranate peel was used as a principal substrate for the production of citric acid by submerged fermentation. Classical method of citric acid recovery involved a precipitation technique using calcium hydroxide followed by filtration and subsequent treatment with sulphuric acid. The citric acid produced was also chemically detected and titrimetrically estimated by 0.1 N NaOH. Results: The present experiment demonstrated that pomegranate peels may serve as an inexpensive medium for the production of citric acid with a yield of 19.39 g/l by using Aspergillus niger. Conclusion: This study provided an alternative basis to recycle the fruit peel waste of pomegranate in order to achieve industrially feasible and environmentally sustainable bio-production of pharmaceutically significant citric acid

Modulation of the local density of states within the dd-density wave theory in the underdoped cuprates

The low temperature scanning tunneling microscopy spectra in the underdoped regime is analyzed from the perspective of coexisting $d$-density wave and d-wave superconducting states. The calculations are carried out in the presence of a low concentration of unitary impurities and within the framework of the fully self-consistent Bogoliubov-de Gennes theory, which allows local modulations of the magnitude of the order parameters in response to the impurities. Our theory captures the essential aspects of the experiments in the underdoped BSCCO at very low temperatures.Comment: 4 pages, 4 eps figures, RevTex4. New added material as well as reference

Preface : Fruit and Vegetable Waste Utilization and Sustainability

Fruits and vegetables are an important source of nutrition and a key element of a healthy balanced diet. Several organizations such as the World Health Organization (WHO), Food and Agriculture Organization of United Nations (FAO), and Food Health England suggest consuming more than 400 g of fruits and vegetables per day (roughly five portions per day) to improve overall health and reduce the risk of certain cardiovascular diseases and cancer; subsequently, consumption and production of fruits and vegetables are on the rise. The increased consumption/production of fruits and vegetables has resulted in huge quantities of waste (approximately 42% of the total food waste) such as pomace, seeds, stones, rind, skins, pods, and peels. This results in a huge environmental burden in relation to increased carbon footprint, greenhouse gas emissions, and global warming. Therefore, in the current situation valorization of agri-food industries wastes is important to address many economic, environmental, and social challenges associated with waste disposal. It would also help in promoting the circular economy aligned with the Sustainable Development Goals (SDGs), particularly with SDG 2 “End hunger” and SDG 12 “Sustainable Production and Consumption”

Renormalization Group Approach to the Normal State of Copper-Oxide Superconductors

We study by means of renormalization group techniques the effect that on the two-dimensional electron liquid may have the van Hove singularities observed experimentally in the copper-oxide superconductors. We find significant deviations from Fermi liquid behavior, that lead to the appearance of an unstable fixed point in the renormalization group flow of the effective coupling constant. Besides the attenuation of electron quasiparticles already known on phenomenological grounds, our approach is able to explain the reduction in the dispersion of the band as well as the pinning of the Fermi level near the singularity, as observed in the photoemission experiments.Comment: Latex manuscript, 29 pages, 4 postcript figure

Spin Liquid Phases in 2D Frustrated XY Model

In this paper we consider the $J_1-J_2-J_3$ classical and quantum 2D XY model. Spin wave calculations show that a spin liquid phase still exists in the quantum case as for Heisenberg models. We formulate a semiclassical approach of these models based on spin wave action and use a variational method to study the role played by vortices. Liquid and crystal phases of vortex could emerge in this description. These phases seem to be directly correlated with the spin liquid one and to its crystalline interpretation.Comment: 16 pages, Latex, 4 figures. To be published in Phys. Rev.

Effective Critical Exponents for Dimensional Ccrossover and Quantum Systems from an Environmentally Friendly Renormalization Group

Series for the Wilson functions of an ``environmentally friendly'' renormalization group are computed to two loops, for an $O(N)$ vector model, in terms of the ``floating coupling'', and resummed by the Pad\'e method to yield crossover exponents for finite size and quantum systems. The resulting effective exponents obey all scaling laws, including hyperscaling in terms of an effective dimensionality, {d\ef}=4-\gl, which represents the crossover in the leading irrelevant operator, and are in excellent agreement with known results.Comment: 10 pages of Plain Tex, Postscript figures available upon request from [email protected], preprint numbers THU-93/18, DIAS-STP-93-1