United Nations Conference on Desertification in Retrospect

The United Nations Conference on Desertification was the first time the nations of the world turned their concerned attention to a comprehensive plan to halt and reverse desertification. The global annual loss to desertification is in the order of 60,000 sq. km. It is man's action that degrades the land by misuse as he seeks to wrest a living from fragile ecosystems. A change to a more arid climate could be a cause, but no firm evidence is available that the climate is so changing. Conference deliberations concluded that the causes and the technical solutions to combatting desertification are known. The key to combative measures is to be found in proper land use. If desertification is to be brought to a halt by the end of the century, considerable financial resources will, however, be necessary. The paper includes a comprehensive summary of the unpublished statements of the various national governments regarding their problems, an analysis of the Conference, and a brief discussion of action taken since the Conference

Nutrition and Agricultural Development in Africa

As in other developing countries in the tropics, severe malnutrition in Africa is mainly a problem in young children and pregnant women. The various disorders are discussed. Seasonal food shortages, maldistribution, ignorance, especially with regard to weaning, and urbanization, are major contributing causes. Better nutrition should not be regarded only as a means to development, but a principal goal of development itself. Policy measures to improve nutrition are outlined

Interacting Three Fluid System and Thermodynamics of the Universe Bounded by the Event Horizon

The work deals with the thermodynamics of the universe bounded by the event horizon. The matter in the universe has three constituents namely dark energy, dark matter and radiation in nature and interaction between then is assumed. The variation of entropy of the surface of the horizon is obtained from unified first law while matter entropy variation is calculated from the Gibbss' law. Finally, validity of the generalized second law of thermodynamics is examined and conclusions are written point wise.Comment: 7 page

de Sitter thermodynamics and the braneworld

The de Sitter thermodynamics of cosmological models with a modified Friedmann equation is considered, with particular reference to high-energy Randall-Sundrum and Gauss-Bonnet braneworlds. The Friedmann equation can be regarded as the first law of thermodynamics of an effective gravitational theory in quasi de Sitter spacetime. The associated entropy provides some selection rules for the range of the parameters of the models, and is proposed for describing tunneling processes in the class of high-energy gravities under consideration.Comment: 16 pages JHEP style, no figures. v2: references added; v3: typo corrected in Eq.(3.1), supersedes published versio

Duration of low temperature changes physiological and biochemical attributes of rice seedling

Received: June 2nd, 2022 ; Accepted: August 4th, 2022 ; Published: August 18th, 2022 ; Correspondence: [email protected] low temperature (LT) is detrimental to growth of rice seedling during boro season in Bangladesh. An experiment was conducted in growth chamber during June to October, 2021 using BRRI dhan29 as planting material. The aim of this experiment was to determine the effect of variable duration of LT on growth, physiological and biochemical traits of rice seedling and to determine the age of seedling that can tolerate cold effect. In this experiment 5, 10, 15 and 20 days old seedling (DOS) were exposed to 6 °C for 1, 2, 3 and 4 days. Seedlings were also grown under room temperature (25 °C, RT) which consider as control treatment. Seedlings were grown in plastic trays filled with mixture of soil and cowdung. The experiment was conducted following completely randomized design with 3 replications. Data on shoot length and weight, root length and weight, chlorophyll (Chl), carotenoids, malondialdehyde (MDA) and proline contain were determined after 5 days of temperature sock. The results revealed that the LT was injurious to younger rice seedling when they were exposed to LT for 1 to 2 days. The shoot and root length as well as their dry weight were reduced under low temperature. Further, the Chl and carotenoid content of younger rice seedlings degraded within 2 days of LT exposure. On the contrary, the proline and MDA content of rice seedlings increased to reduce the harmful effect of under LT. It could be concluded that the rice seedlings could tolerate the detrimental effect of LT when they attain at least 15 days

Effect of deficit irrigation on raised bed wheat cultivation

The experiment was conducted during Rabi season of 2015-2016 and 2016-2017 at the Regional Agricultural Research station, BARI, Ishurdi, Pabna, Bangladesh, to determine the water requirements of wheat on raised bed and the effect of different deficit irrigation on yield, water use efficiency and applied water productivity under raised bed wheat. This study consisted of following irrigation treatments: T1 = Irrigations up to 100% field capacity (FC) at crown root initiation (CRI), botting and grain filling stages (flat bed), T2 = Irrigations up to 100% FC at CRI, botting and grain filling stages on raised bed, T3 = Irrigations up to 80% FC at CRI, botting and grain filling stages on raised bed and T4 = Irrigations up to 60% FC at CRI, botting and grain filling stages on raised bed and laid out in a randomize complete block design with three replications.The result showed that significant effect of irrigation treatments were observed on plant height, spike per m2 and grain yield. Highest grain yield (4.66 t/ha) was obtained from treatment, irrigations up to 100% FC at CRI, botting and grain filling stages on raised bed, followed by irrigation up to 100% FC at same stages on flat bed. At raised bed wheat cultivation saving 14.30% water with increasing 15.66% grain yield than flat bed. Besides, comparing deficit irrigation (20% and 40% of full irrigation) and full irrigation condition on raised bed seeding system water use could be reduced about 4.18% to 5.57%, while scarifying 18.20% to 32.33% grain yield, where reduced 14.17% to 27.54% water use efficiency. Maximum applied water productivity 1.81 kg m-3 was observed in raised bed full irrigation condition. The rate of daily evaporation started to increase as the temperature started to rise and humidity started to decrease during the crop growing period. The results will be helpful for taking policy decision regarding efficient irrigation and water management under prevailing water scarce situation

Cosmological Evolution Across Phantom Crossing and the Nature of the Horizon

In standard cosmology, with the evolution of the universe, the matter density and thermodynamic pressure gradually decreases. Also in course of evolution, the matter in the universe obeys (or violates) some restrictions or energy conditions. If the matter distribution obeys strong energy condition (SEC), the universe is in a decelerating phase while violation of SEC indicates an accelerated expansion of the universe. In the period of accelerated expansion the matter may be either of quintessence nature or of phantom nature depending on the fulfilment of the weak energy condition (WEC) or violation of it. As recent observational evidences demand that the universe is going through an accelerated expansion so mater should be either quintessence or phantom in nature. In the present work we study the evolution of the universe through the phantom barrier (i.e. the dividing line between the quintessence and phantom era) and examine how apparent and event horizon change across the barrier. Finally, we investigate the possibility of occurrence of any singularity in phantom era.Comment: 7 pages and 4 figure

Dynamics of the self-interacting chameleon cosmology

In this article we study the properties of the flat FRW chameleon cosmology in which the cosmic expansion of the Universe is affected by the chameleon field and dark energy. In particular, we perform a detailed examination of the model in the light of numerical analysis. The results illustrate that the interacting chameleon filed plays an important role in late time universe acceleration and phantom crossing.Comment: 13 pages, 8 figures, to appear in Astrophysics and Space Sc

Expanding Universe: Thermodynamical Aspects From Different Models

The pivotal point of the paper is to discuss the behavior of temperature, pressure, energy density as a function of volume along with determination of caloric EoS from following two model: $w(z)=w_{0}+w_{1}\ln(1+z)$ & $w(z)=-1+\frac{(1+z)}{3}\frac{A_{1}+2A_{2}(1+z)}{A_{0}+2A_{1}(1+z)+A_{2}(1+z)^{2}}$. The time scale of instability for this two models is discussed. In the paper we then generalize our result and arrive at general expression for energy density irrespective of the model. The thermodynamical stability for both of the model and the general case is discussed from this viewpoint. We also arrive at a condition on the limiting behavior of thermodynamic parameter to validate the third law of thermodynamics and interpret the general mathematical expression of integration constant $U_{0}$ (what we get while integrating energy conservation equation) physically relating it to number of micro states. The constraint on the allowed values of the parameters of the models is discussed which ascertains stability of universe. The validity of thermodynamical laws within apparent and event horizon is discussed.Comment: 16 pages, 3 figures(Accepted for publication in "Astrophysics and Space Science"

Effect of electromagnetic fields on the creation of scalar particles in a flat Robertson-Walker space-time

The influence of electromagnetic fields on the creation of scalar particles from vacuum in a flat Robertson-Walker space-time is studied. The Klein Gordon equation with varying electric field and constant magnetic one is solved. The Bogoliubov transformation method is applied to calculate the pair creation probability and the number density of created particles. It is shown that the electric field amplifies the creation of scalar particles while the magnetic field minimizes it.Comment: Important modifications, 20 pages, To appear in Eurpean Physical Journal C. arXiv admin note: text overlap with arXiv:1108.033