Showing papers in "Journal of the Indian Institute of Science in 2012"

Scattering of light in crystals

Abstract: Since its discovery1, early in 1928, the scattering of light with altered frequency has been investigated in many crystals, and much valuable information has been accumulated. The significance of the results and their relation to theories of solid state are clearly matters of great interest.

Quantum computing with trapped ions

Abstract: Quantum information encoded in single trapped ions provides a promising avenue towards a scalable quantum computer. This contribution describes most of the necessary building blocks for such a device. Particular emphasis is given to the implementation of single-qubit and multi-qubit gate operations.

Nuclear resonance in flowing liquids

Abstract: Nuclear magnetic resonance in flowing liquids has been investigated experimentally. The experiments afford a striking demonstration of the effects of finite relaxation time and afford a method of measuring relaxation times directly.

Biofertilizers for Sustainability

Abstract: Biofertilizers are gaining importance in sustainable agriculture. Various complementing combinations of microbial inoculants for management of major nutrients such as nitrogen and phosphorus are necessary for sustainability. A broad canvas of biofertilizers that enhance nitrogen and specific to legumes and non legumes along with inoculants that enhance phosphorus nutrition are discussed from several perspectives. The mode of action of these microorganisms within and the transformation of nutrients is elucidated. In the Indian scenario, use of biofertilizers faces various constraints, such as longevity, etc, need to be overcome to achieve substantial fertilizer savings. One of the key issues that still remains is the method of formulation of these biofertilizers. Some of the key difficulties associated are brought out in this review.

Sustainability of Large-Scale Algal Biofuel Production in India

Abstract: Algal biofuels are poised to become one of the sustainable sources of biofuels that could potentially replace petroleum derived fuels (PDF) in an environmentally friendly and sustainable world. In many parts of the developing world, algal biofuels as biodiesel and biomethane, like the first generation biofuels of the recent past, will compete for prime land as well as other water and nutrient resources currently used for providing food security. Within India, current analyses suggest that sustainable cultivation of various algal species for biofuels are possible at four locations: a. In paddy fields as a multi-tier crop (3.6 Mha) b. In saline brackish region of Kachch (Gujarat; 3.0 Mha), c. Urban domestic waste water (40 billion L/d), and d. On fishery deficient seashores (c.3 Mha). In order to realize a near complete substitution of the current level of fossil fuels by algal biofuels, although feasible through algal biofuels, a whole lot of decentralized algae harvesting and primary processing infrastructure needs to be set up to ensure that algal production, processing and resource recycling can occur with low losses and increased sustainability. The coupling of energy generation with wastewater treatment and consequent nutrient uptake addresses the issues of environment, low emissions, biofuel production and therefore long term sustainability. This paper brings out challenges in the areas of sustainability and sustainable development that are likely to emerge in the three tracts where large scale algal cutivation and processing is feasible.

Anaerobic digestion for bioenergy from agro-residues and other solid wastes - an overview of science, technology and sustainability.

Abstract: In the quest for a simple technology to realize the goal of ‘sustainable energy for all’, the conversion of non-lignified ‘soft’ non-woody biomass to biogas in modern anaerobic digesters is an important component. Firstly, agro-residues, agro-industrial wastes, terrestrial/aquatic weeds form a major source of sustainably raised bio-resources. Anaerobically converting them to biogas provides a sustainable energy source to a large number of users and simultaneously facilitates nutrient recycling (nutrient-rich compost) permitting nutrient-starved agricultural systems in India to become more sustainable. When processed through biogas plants, over 95% of all plant nutrients within can be recycled making India’s fragile agricultural soils more sustainable while also producing an energy source, biogas. While a lot of science and technology experience exists with regards to animal waste fed biogas plants, understanding of the underlying science, technology and sustainability of anaerobic digestion of agro-residues, weeds and leaf litter (‘non-dung’ soft biomass) for biogas/byproducts is poor. This potential has been inadequately tapped. In this paper, an attempt is made to review the microbiology of anaerobic digestion of various biomass residues, the conversion processes that are being developed/in use and finally to examine methods to make them attractive, provide multiple outputs and services than what was possible through animal dung biogas plants. The micro-organisms responsible, physico-chemical environment process and therefore the technology of digestion of biomass residues are not similar or as simple as that found for animal dung or food wastes. Therefore, novel fermentation concepts and modern digesters being developed for biomass residues are required to make this concept feasible and viable. Many more end-products, other than compost and biogas, as was done in the past, are required if the digesters have to be economically attractive to use and socially justifiable as well as sustainable in the long run. The sustainability issues that have and will shape this field are discussed. In this paper we show that simultaneous anaerobic digestion of biomass residues to biogas and multiple by-products could be an answer to the search for alternatives to achieve sustainable energy for all in this decade.

Intermediate temperature solid oxide fuel cell electrolytes

Abstract: Solid Oxide Fuel Cells (SOFCs) have suitable perspectives to replace their classical counterparts for the distributed generation of electrical energy with small and medium power sources (50 kWel). The main advantages of SOFCs rely on the high conversion efficiency and low environmental impact. Practical SOFC operating temperatures between 600 ◦C and 800 ◦C are aimed to increase life-time and reduce costs. These can be achieved only by using electrolytes with proper ionic conductivity at intermediate temperatures. This review deals with a survey of the current research on advanced materials to be used as electrolyte for intermediate or low temperature solid oxide fuel cells. Specific properties such as reaction mechanism, chemical compatibility, effects of dopants, and conductivity are discussed.

Carbonaceous anode materials for lithium-ion batteries - the road ahead

Abstract: Graphites and hard carbons are the mainstay of anode materials in practical lithium-ion batteries. With their dominance beginning to be threatened by other alternative anode materials such as silicon and intermetallics, continual research is directed at exploring known carbonaceous materials as well as at synthesizing new carbon-based anodes. After a review of lithium storage mechanisms in various carbon forms, this article explores avenues for crossovers between chemistry and materials science for tailoring carbonaceous materials that can cater to increasing power demands of emerging technologies. In particular, this review suggests opportunities and problem areas in anodes based on carbon composites as well as novel carbonaceous materials such as kish graphites, carbon nanotubes, nanofibers, curved carbon lattices and graphenes that are expected to prolong the legacy of carbon in lithium-ion batteries.

Disinction of enantiomers by NMR spectroscopy using chiral orienting media

Abstract: NMR spectroscopy is a very important analytical tool in modern organic and inorganic chemistry. Next to the identification of molecules and their structure determination, it is also used for the distinction of enantiomers and the measurement of enantiomeric purity. This article gives a brief review of the techniques being developed for enantiomeric differentiation by virtue of chiral alignment media and their induction of enantiomerically dependent anisotropic NMR parameters like residual dipolar couplings. An overview of existing chiral alignment media, a brief introduction into the basic theory and measurement of the various anisotropic parameters, and several example applications are given.

Sustainability in Human Settlements: Imminent Material and Energy Challenges for Buildings in India

Abstract: Sustainability in the living environment requires a paradigm transition to environmentally conducive habitats based on judicious energy and resource use to foster a community that is happy, harmonious, healthy and productive. Habitats, or the living environment, comprise the built- and the natural environment. The built-environment is responsible for the single largest share of resource and energy consumption and demand. This paper provides an overview of sustainability in the context of human settlements with a focus on imminent material resources and energy challenges for buildings in India. Basic arguments on sustainability and well-being in human settlements, and the role of community attitude and behaviour have been highlighted. The paper discusses imminent impacts attributed to unbridled dependence on mined material resources, emissions and pollution due to energy expenditure in buildings, and particularly draws attention to implications of unperceived modernizing rural transitions. Rural habitations, in India have thus far lived off the land with negligible demands on energy and process-intensive materials for sustenance. With a booming economy, increased affordability and exposure to urban lifestyles, the aspirations of rural habitations is now akin to middle-income urbanites. As rural habitations respond to the modernising aspirations of its inhabitants, an unrecognized but steady transition is evident from traditional local-materials based buildings to non-local high-process material based dwellings, viz., zero-energy to high-energy. The consequence is an unperceived but significant resource and energy footprint, that requires to be carefully discerned and regulated for sustainability. Key avenues for promoting sustainability in the built environment include effecting minimum alteration to (exhaustible) natural material, recycling non-organic solid waste into building products, adopting renewable construction materials and regulating energy and emissions in buildings.

Raman Spectrum of Diamond

Abstract: The new approach to the dynamics of crystal lattices made by Sir C. V. Raman leads in the case of diamond to the result that the atomic vibration spectrum of this crystal should exhibit eight distinct monochromatic frequencies. Of these, the highest frequency (1,332 cm-1 in spectroscopic units) corresponds to the triply degenerate vibration of the two Bravais lattices of the carbon atoms with respect to each other, this being active in the Raman effect. The other seven frequencies represent oscillations of the layers of carbon atoms parallel to the faces of the octahedron or the cube occurring normal or tangential to these planes with the phase reversed at each successive equivalent layer. All the seven modes of vibration of this description are inactive in the Raman effect as fundamentals. The octaves of these frequencies may however, appear as frequency shifts in the Raman spectrum, though with intensities extremely small compared with that of the Raman line of frequency shift 1,332 cm-2. Besides the octaves, various combinations of these frequencies may also appear in the Raman spectrum.

On the Burnside Algebra of a Finite Group

Abstract: In this article first we shall prove the classical theorem of Burnside which asserts that the canonical Burnside mark homomorphism of the Burnside algebra B(G) of a finite group G into the product Z-algebra of rank #CG is injective, where CG denote the set of conjugacy classes of the subgroups of G. We further prove that for any finite group G the canonical Z-algebra homomorphism ZCZG iae ZCG maps the Burnside algebra B(ZCG G ) of a finite cyclic group ZG of order #G into the Burnside algebra B(G). We deduce quite a few elementary, but important results in finite group theory by using this canonical algebra homomorphism. Finally we describe the prime spectrum SpecB(G) and maximal spectrum SpmB(G) of B(G).

Minimal Triangulations of Manifolds

Abstract: Finding vertex-minimal triangulations of closed manifolds is a very difficult problem. Except for spheres and two series of manifolds, vertex-minimal triangulations are known for only few manifolds of dimension more than 2 (see the table given at the end of Section 5). In this article, we present a brief survey on the works done in last 30 years on the following: (i) Finding the minimal number of vertices required to triangulate a given pl manifold. (ii) Given positive integers n and d, construction of n-vertex triangulations of different d-dimensional pl manifolds. (iii) Classifications of all the triangulations of a given pl manifold with same number of vertices. In Section 1, we have given all the definitions which are required for the remaining part of this article. A reader can start from Section 2 and come back to Section 1 as and when required. In Section 2, we have presented a very brief history of triangulations of manifolds. In Section 3, we have presented examples of several vertex-minimal triangulations. In Section 4, we have presented some interesting results on triangulations of manifolds. In particular, we have stated the Lower Bound Theorem and the Upper Bound Theorem. In Section 5, we have stated several results on minimal triangulations without proofs. Proofs are available in the references mentioned there. We have also presented some open problems/conjectures in Sections 3 and 5.

The Nanoaquarium: A New Paradigm in Electron Microscopy

Abstract: Since its invention, the electron microscope has facilitated numerous advances in a plethora of disciplines ranging from materials science, physics, and chemistry, to biology. Traditional electron microscopy must be carried out, however, in a high vacuum environment that does not allow for real time imaging of processes in liquid media. Consequently, traditional electron microscopy has been restricted to painstaking “postmortem” investigations on dry or frozen samples without any guarantee that an image is captured at the “right” moment. Static images also do not provide information on process dynamics, and the sample preparation may adversely impact the structure of the object to be imaged. The ability to image dynamic processes in liquid media is certain to be transformative, lead to new discoveries, and provide a better understanding ofmany important processes at the nanoscale. To overcome the limitations of traditional electron microscopy, there has been a growing interest in recent years in developing means for wet electron microscopy that will allow one to image samples in real time in their native environment and observe processes in situ as they take place. We briefly survey recent efforts pertaining to wet electron microscopy and then describe in greater detail the work of our group with a custom-made, micro-fabricated liquid cell dubbed the “nanoaquarium”. The nanoaquarium sandwiches a thin liquid layer, ranging in thickness from tens of nanometers to a few microns, between two thin, electron-transparent, silicon nitride membranes. The liquid cell is hermetically sealed from the vacuum environment of the electron microscope. The thin liquid layer scatters only a small fraction of the electrons and allows one to image objects suspended in the liquid with high resolution. We describe briefly the imaging of oriented assembly of colloidal crystals, diffusion limited aggregation of nanoparticles, and electrochemical processes.

Label—Free Integrated Optical Biosensors for Multiplexed Analysis

Abstract: The need for real time, fast and frequent monitoring in health-care, pharmaceuticals research, environmental monitoring, the food industry, and homeland security has been rising, leading to extensive research in the development of Point of Care (POC) devices for diagnostics. POC devices need to be handy, fast, robust, highly sensitive to sensing analytes, selective against other interferents, and accurate. Since, in the real world scenario, the analytes are typically complex and useful analysis depends on sensing multiple parameters, multianalyte sensing has emerged to help users arrive at concrete conclusions or inferences. Research has been conducted for exploiting a plethora of transduction phenomena, such as electrochemical, impedometric, piezoelectric, magnetic, optical, etc. Of these, optical methods of sensing have the upper hand due to their resistance to electromagnetic interference, fast response, ease of parallel analyte sensing, low Limit of Detection (LOD), and, most importantly, easy translation of well-established techniques to in silico devices. Label-free biosensing provides the advantage of simplicity and cost reduction by avoiding complex steps prior to sensing by monitoring analytes in their unmodified state i.e. detecting analytes without any alteration. Further, sensing in ultra-small quantities has been possible due to the concurrent development of MEMS technology. All this has led to the development of Lab on Chip (LOC) devices which perform various separation, and detection, operation and analysis on small chips and are cost effective due to bulk fabrication. LOC devices integrating label—free optical sensing on small chips also give rise to the possibility of multi-analyte assays using small test samples. These facilitate on-site deployment of these devices for different applications. This review will present various optical waveguide-based devices, including those based on optical absorbance, evanescent wave absorbance and surface plasmon resonance. Various configurations of such devices that aid multianalyte on-chip assays will be explored.

Advances in Cancer Nanomedicine

Abstract: Scientific advances have significantly improved the basic understanding of biology of cancer. Now it is clear that a series of genetic alterations leading to abnormal cell division, loss of growth control and the capability to develop their own blood supply resulted in this complex scenario of cancer. Due to the lack of drug availability, adverse side effects and drug resistance, the conventional therapy failed to achieve proper treatment. During the past few years, nano- medicine has showed considerable progress in improving the cancer treatment and this review highlighted some of the recent advancement in this field of research. Development of first generation nanomedcine such as cytotoxic drug loaded polymeric nanoparticles, micelles, liposomes, dendrimers, carbon nanostructures, inorganic nanoparticles, etc were discussed in detail. A detailed understanding of the mechanism of cancer leading to the evolution of second generation of nanomedicine aids more efficient targeted cancer therapy. Nanoparticle mediated magnetic hyperthermia, photothermal therapy and radiofrequency hyperthermia is also reviewed as new generation cancer nanotherapeutics.

Understanding the Structure and Properties of Phase Change Materials for Data Storage Applications

Abstract: Phase change materials possess a unique property combination which is the basis for their application potential The amorphous and crystalline phases are characterised by very different optical and electrical properties This is indicative of a significant structural rearrangement upon the phase transition Nevertheless, it is possible to rapidly and reversibly switch between the amorphous and crystalline states This property portfolio has already been successfully employed in rewritable optical data storage Phase change materials are also considered to be one of the most promising candidates for future electronic memories Hence, considerable efforts have been undertaken in the past decades to identify suitable materials, and to optimize them with respect to specific applications This article reviews the structure and the underlying bonding mechanism of phase change materials This understanding of the bonding mechanism and the resulting atomic arrangement will subsequently be utilized to explain several of the characteristic features of phase change materials Finally, the technological development both of rewritable optical storage media and future non-volatile electronic memories are reviewed

A.C. Conduction in Amorphous Semiconductors

Abstract: The recent developments in the theoretical and experimental study of frequency-dependent conductivity in amorphous semiconductors are reviewed, emphasising particularly on chalcogenide glasses. The striking similarity of a.c. conduction in quite different disordered solids is compared and discussed in terms of experimental results, modelling, and computer simulations. After giving an overview of experimental results, an existing macroscopic and a microscopic model are reviewed. More specifically, the factors such as random and non-random spatial distributions of electrically active centres responsible for the a.c. conductivity have been highlighted. Additionally, we have briefly discussed various aspects of a.c. loss behaviour on chalcogenide glasses such as effect of temperature, composition, doping, and other material properties. It is concluded that the a.c. conduction at intermediate to high temperatures is accounted for by the correlated barrier model, whereas at sufficiently low temperatures the behaviour is related to the atomic tunnelling.

Photo-Elastic Constants of Sodium Chlorate

Abstract: Sodium chlorate is the first crystal belonging to the tetrahedrite class (T) of the cubic system for which photoelastic constants have been measured. Since the crystal exhibits optical activity and no birefringence in the absence of stress, special techniques have to be adopted for measuring the birefringence introduced by stress. This has been done by the use of a petrological microscope in conjunction with the stressing apparatus and measuring the ellipticity and other characteristics of the light transmitted by the crystal. A particularly simple method is to use the “elliptic analyser”. Since the crystal does not possess four-fold axes, the relative orientation of the X- Y- and Z-axes was determined by means of X-rays. From observations on crystals compressed along [100], [110] and [111] directions,q 11–q 12,q 11–q 13 andq 44 were evaluated. All the four constants were independently obtained by combining these with polarisation measurements of light diffracted by ultrasonic waves in the crystal. The values are:q 11=1·48,q 12=3·88,q 13=2·89,q 44=−1·58×10−13 cm.2 dyne−1;p 11=0·173,p 12=0·258,p 13=0·223,p 44=−0·0187.q 12 andq 13 are different as is to be expected from Bhagavantam’s theory for crystal classes T and T h . For stress along X-axis, the values of birefringence for observation along the Y- and Z- axes differ by as much as 70%, which is the largest observed so far for a cubic crystal.

A Reassessment of Materials Issues in Microelectromechanical Systems (MEMS)

Abstract: Over the past 7 years there has been an explosion of research activity into materials for MicroElectroMechanical Systems (MEMS). This paper reviews the current issues associated with materials for MEMS. Five topical areas are addressed: the effect of lengthscale, the selection of materials and processes, the MEMS material set, microfabrication processes and material characterization. Each of these areas is examined, with particular emphasis on the potential impact of materials solutions. The paper concludes with an assessment of the progress in MEMS materials made since 2000.

Applications of carbon nanotubes in polymer electrolyte membrane fuel cells

Abstract: Carbonaceous materials play a vital role, in the performance of polymer electrolyte membrane fuel cells (PEMFC) irrespective of their use in cathode, anode and in bipolar plates. However, their use in composite electrolyte membrane has been only recognised recently especially after their functionalization to impart enhanced proton conductivity to the composite electrolyte. PEMFC development still has many material related challenges in terms of durability, degradation and more significantly cost reduction. Different methodologies have been adopted to deposit Pt electrocatalyst on CNTs and other carbonaceous materials, thus transforming them into the membrane electrode assembly. Functionalized carbon nanotubes with desired surface groups are found to be better for composite electrolytes since they increase the protonic conductivity along with increased mechanical stability. The use of CNTs doped with nitrogen indicates the possibility of total Pt removal from MEAs in the near future. Many of these recent advances in the application of carbon nanotubes and related materials in the functioning of polymer electrolyte fuel cells are discussed in this article providing an overview of their possible role and limitations.

Universal and Sustainable Access to Modern Energy Services in Rural India: An Overview of Policy-Programmatic Interventions and Implications for Sustainable Development

Abstract: India’s energy challenges are accentuated by the presence of large section of the population, especially in rural areas, lacking access to modern energy carriers. Lack of access to modern energy carrier-based services has implications for economic, social and environmental wellbeing of humanity. The implications are typically in the form of income poverty, primitive lifestyles, loss of dignity, physical hardship, health hazards, lack of employment and polluted environment. In 2007, for example in India, out of a population of about 1,125 million, 400 million were without access to electricity and 801 million were depending on solid fuels for cooking. This status indicates that the polices initiated, and the programmes implemented by the government of India as well as various state governments since the past several years have proved to be ineffective. Keeping these in mind, in this paper, an attempt has been made to provide deeper insights into the relationships between energy access status, policies and programmes and sustainable development by adopting a review methodology. In essence, the paper tries to analyse the linkage current energy access status is an outcome of policy failure, and it has given rise to negative implications for sustainable development through a synthesis of research papers and policy documents.

Nitrogen Cycle Sustainability and Sustainable Technologies for Nitrogen Fertilizer and Energy Management

Abstract: Nitrogen (N) is necessary for all forms of life and a crucial component in the increased production of food to feed the continuously increasing human and animal populations. In many ecosystems on land and sea, the supply of nitrogen controls the nature and diversity of plant life, the population dynamics of both grazing animals and their predators, and vital ecological processes such as plant productivity and the cycling of carbon and soil minerals. Since the beginning of the last century, mankind has injected increasing amounts of reactive nitrogen into the environment, intentionally as fertilizer and unintentionally as a by-product of combusting fossil fuels. As a result, nitrogen cycle is being altered causing possible grave impacts on biodiversity, global warming, water quality, human health, and even the rate of population growth in several parts of the world. The key N management technology for sustainable and profitable crop production is the synchronization of N supply with crop demand. Aiming at improving N-use efficiency in high-input cropping systems, the focus should be on higher yield with less fertilizer N. In low-input systems, additional use of N fertilizer may be required to increase yield level and yield stability. Realigning the time and rate of N application with help of modern tools, like SPAD meter, LCC, Green seeker, Simulation modeling, GIS and remote sensing as per spatial-indigenous nutrient supply capacity and temporal variability of soil enhances the synchronization between N supply and plant demand. Site specific N application with balanced fertilization and integration of locally available organic manures further improves the N use efficiencies in cropping system. Sustainable strategies for N management in energy sector are the development of technologies that either increases efficiency of fuel combustion or removes N oxides from the exhaust stream. The complete solutions, however, are closely linked to the development of non-polluting alternative energy sources. Research and development efforts needs to be strengthened to find out more effective technological solutions and try to balance them against cost and efficiency.

Sustainable Soil Nutrient Management

Abstract: Productive agriculture is dependent upon sound soil nutrient management practices. Seventeen elements are known to be essential for plants. Over years of intensive cultivation and imbalanced fertilizer use, Indian soils have become deficient in several of these nutrients and are also impoverished in organic matter. Yields of various crops have reached a plateau or are on the decline. This is of serious consequence given increasing population and diminishing per capita land availability. Several methods of nutrient management have been practiced on farms, however, the best option for the farmer is an integration of organic and inorganic approaches to nutrient management. This far a lot of emphasis has been placed on the conservation and management of N-one of the earliest reported scarce plant nutrient. However, current studies across India have shown a gradual and alarming depletion of potassium and increase in P fixation leading to sustainability concerns for these two nutrients. Among other nutrients S, Zn and B are also reaching deficient status in Indian soils. This sustainability crisis needs to be addressed holistically. This paper explains the philosophy, strategies and practices available to various users of sustainable nutrient management.

Mesoporous carbon for polymer electrolyte fuel cell electrodes

Abstract: This article features the importance of mesoporous carbon as a constituent in the gas diffusion layer for easy reactant permeation and water removal in polymer electrolyte fuel cells. The utility of mesoporous carbon as catalyst support to enhance Pt utilization is also crucial in order to reduce Pt usage to meet both cost and Pt availability constraints. We attempt to provide an overview of the strategy and benefit of using mesoporous carbon to meet the specific requirements of emerging technological applications, such as fuel cells.

Commercial Prospects for Nanomaterials in India

Abstract: The area of nanoscience and technology is growing rapidly around the world and nanomaterials based products, especially in the consumer sector, are coming into market very rapidly. India is competing, with great difficulty, with other developed countries to make its position strong in this field. In other respect, several challenges have to be overcome in terms of production of nanomaterials at commercial scale, their processing, applications and commercialization. The present article describes the present state of nanomaterials based technology development, commercialization and future prospects for this technology in our country.

Optical Resonator Based Biomolecular Sensors and Logic Devices

Abstract: Optical resonator based biosensors are emerging as one of the most sensitive microsystem biodetection technology that boasts all of the capabilities for a next-generation lab-on-chip device: label-free detection down to single molecules, operation in aqueous environment and cost- effective integration on microchips together with other photonic, electronic and fluidic components. We give a scholarly introduction to the emerging field of optical resonator based biosensing, review current applications, and explain how optical resonators are coated with biomolecules to construct logic devices.

Carbohydrate-based liquid crystals

Abstract: The carbohydrate based mesogens have gained an importance in the field of liquid crystals, primarily through the amphiphilic nature of many sugar derivatives. A constitutional requirement for the amphiphilic mesogen is that the molecule consists of distinct regions within the molecule that separately would have different responses to changes in thermal energies and/or solvations. Such molecules can be synthesized by linking one or more alkyl chains of appropriate length to both cyclic and acyclic sugars. A driving force for the mesophase formation in these molecules is the phase segregation, leading to aggregates, possessing distinct lyophilic and hydrophilic regions. In this review, we discuss the thermotropic behavior of the carbohydrate amphiphiles. We discuss the relationship between constitutions, configurations, functionalities of the sugar component and the length of the hydrophobic chains necessary to form the various types of thermotropic phases. The influence of the linking group between the hydrophilic sugar head groups and lyophilic alkyl chains on the transition temperatures and mesophase stabilities are also presented.