Control of spontaneous emission in a five-level system

We study the control of spontaneous emission in a five-level atomic system driven by four fields. We show that with the variation of dynamical variables, namely, Rabi frequencies and carrier phases of driven fields, a wide variety of the spectral behavior can be obtained, including extreme spectral narrowing. Our system can be found easily in real atoms.     

FT-Raman spectroscopic study of calcium-rich and magnesium-rich carbonate minerals

Calcium and magnesium carbonates are important minerals found in sedimentary environments. Although sandstones are the most common rock colonized by endolith organisms, the production of calcium and magnesium carbonates is important in survival strategies of organisms and as a source for the removal of oxalate ions. Extremophile organisms in some situations may convert or destroy carbonates of calcium and magnesium, which gives important information about the conditions under which these organisms can survive. The identification on the surface of Mars of 'White Rock' formations, in Juventae Chasma or Sabaea Terra, as possibly carbonate rocks makes the study of these minerals a prerequisite of remote Martian exploration. Here, we show the protocol for the identification by Raman spectroscopy of different calcium and magnesium carbonates and we present a database of relevance in the search for life, extinct or extant, on Mars; this will be useful for the assessment of data obtained from remote, miniaturized Raman spectrometers now proposed for Mars exploration.     

Life in the sabkha: Raman spectroscopy of halotrophic extremophiles of relevance to planetary exploration

The Raman spectroscopic biosignatures of halotrophic cyanobacterial extremophiles from sabkha evaporitic saltpans are reported for the first time and ideas about the possible survival strategies in operation have been forthcoming. The biochemicals produced by the cyanobacteria which colonise the interfaces between large plates of clear selenitic gypsum, halite, and dolomitized calcium carbonates in the centre of the salt pans are identifiably different from those which are produced by benthic cyanobacterial mats colonising the surface of the salt pan edges in the intertidal zone. The prediction that similar geological formations would have been present on early Mars and which could now be underlying the highly peroxidised regolith on the surface of the planet has been confirmed by recent satellite observations from Mars orbit and by localised traverses by robotic surface rovers. The successful adoption of miniaturised Raman spectroscopic instrumentation as part of a scientific package for detection of extant life or biomolecular traces of extinct life on proposed future Mars missions will depend critically on interpretation of data from terrestrial Mars analogues such as sabkhas, of which the current study is an example.     

Two New Spirostanol Glycosides from Cestrum parqui

Two new steroidal glycosides, parquisoside A ( 1 ) and B ( 2 ) were isolated from the aerial parts of Cestrum parqui (family Solanaceae). Their common aglycone is a new steroid of the spirostane series, which we name parquigenin. It has the structure (3β,24S,25S)‐spirost‐5‐ene‐3,24‐diol, i.e. a (24S,25S)‐24‐hydroxydiosgenin. The structures of parquisosides A and B were elucidated as (3β,24S,25S)‐spirost‐5‐ene‐3,24‐diol 3‐O‐{[α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl‐(1→4)‐α‐L ‐rhamnopyranosyl‐(1→4)}‐β‐D ‐glucopyranoside ( 1 ) and (3β,24S,25S)‐spirost‐5‐ene‐3,24‐diol 3‐O‐{[α‐L ‐rhamnopyranosyl)‐(1→4)‐α‐L ‐rhamnopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl‐(1→4)‐α‐L ‐rhamnopyranosyl‐(1→4)}‐β‐D ‐glucopyranoside ( 2 ), respectively, on the basis of detailed spectroscopic studies and chemical analysis. The crude extract of Cestrum parqui showed inhibition of carrageenin‐induced edema.     

Sheath-assisted focusing of microparticles on lab-on-a-chip platforms

Lab-on-a-chip (LOC) technologies can take advantage of sheath flows for particle/cell focusing before sensing or sorting. The integration of focusing with other microscale manipulation techniques (e.g., sorting) creates a trade-off between the throughput of the device and its performance. Therefore, exploring the effective parameters for cells/particles focusing enables us to improve the desired output of LOC devices. A common configuration for sheath-assisted focusing is Y junctions, which are parametrically studied in this paper. First, a computational model was developed and validated by comparing it with our experimental results. Using COMSOL Multiphysics modeling, the effects of multiple parameters were studied. These parameters include the sheath flow ratio (sheath flow over total flow), width ratio (width of the sheath inlet over the total width), junction angles, and particle size on the focusing width and the distribution of the particles within the focusing region. Then, the numerical data were used to develop two generalized linear models to predict the focusing width of the particles and the standard deviation of the position of the particles. The results showed that the focusing width is greatly impacted by the sheath flow rate ratio. Further, the standard deviation of the position of the particles, which represents the concentration of the particles, is mostly dependent on the flow rate ratio, width ratio, and particle size. Our results provide a better understanding of how the device geometrical and operational factors affect the position of the particles in the development of high-performance on-chip sensing and sorting of both cells and particles.     

Measurement of photon statistics via electromagnetically induced transparency

We propose a method to measure the photon statistics of a quantized radiation field in an electromagnetically induced transparency setup. The proposed method provides a direct way of measuring the photon statistics. This method is insensitive to the detector efficiency.     

A Comprehensive Computational Investigation into the Conserved Virulent Proteins of Shigella species Unveils Potential Small-Interfering RNA Candidates as a New Therapeutic Strategy against Shigellosis

Shigella species account for the second-leading cause of deaths due to diarrheal diseases among children of less than 5 years of age. The emergence of multi-drug-resistant Shigella isolates and the lack of availability of Shigella vaccines have led to the pertinence in the efforts made for the development of new therapeutic strategies against shigellosis. Consequently, designing small-interfering RNA (siRNA) candidates against such infectious agents represents a novel approach to propose new therapeutic candidates to curb the rampant rise of anti-microbial resistance in such pathogens. In this study, we analyzed 264 conserved sequences from 15 different conserved virulence genes of Shigella sp., through extensive rational validation using a plethora of first-generation and second-generation computational algorithms for siRNA designing. Fifty-eight siRNA candidates were obtained by using the first-generation algorithms, out of which only 38 siRNA candidates complied with the second-generation rules of siRNA designing. Further computational validation showed that 16 siRNA candidates were found to have a substantial functional efficiency, out of which 11 siRNA candidates were found to be non-immunogenic. Finally, three siRNA candidates exhibited a sterically feasible three-dimensional structure as exhibited by parameters of nucleic acid geometry such as: the probability of wrong sugar puckers, bad backbone confirmations, bad bonds, and bad angles being within the accepted threshold for stable tertiary structure. Although the findings of our study require further wet-lab validation and optimization for therapeutic use in the treatment of shigellosis, the computationally validated siRNA candidates are expected to suppress the expression of the virulence genes, namely: IpgD (siRNA 9) and OspB (siRNA 15 and siRNA 17) and thus act as a prospective tool in the RNA interference (RNAi) pathway. However, the findings of our study require further wet-lab validation and optimization for regular therapeutic use for treatment of shigellosis.     

Comparison of near infrared laser excitation wavelengths and its influence on the interrogation of seized drugs‐of‐abuse by Raman spectroscopy

The laser excitation wavelength is an important parameter in obtaining Raman spectra from drugs‐of‐abuse. This article compares the effect of near infrared wavelengths, 785 nm, using both benchtop and portable instrumentation and benchtop 1064 nm on the Raman spectra of seized drugs‐of‐abuse, including cocaine hydrochloride, cocaine freebase (crack), methylenedioxymethamphetamine (‘ecstasy’), amphetamine, diamorphine (heroin) and cannabis. The significant benefit of using 1064 nm for the interrogation of this type of sample is highlighted. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Al2O3 nanoparticles on ionic conductivity of PVdF-HFP/PMMA blend-based Na+-ion conducting nanocomposite gel polymer electrolyte

Journal of Solid State Electrochemistry - In the present work, the effect of dispersion of Al2O3 nanoparticles on ionic conductivity of non-aqueous PVdF-HFP/PMMA blend-based nanocomposite gel...     

Analysis of seized drugs using portable Raman spectroscopy in an airport environment—a proof of principle study

The rapid identification for drugs‐of‐abuse in airports is of critical importance. In this study we demonstrate the viability of Raman spectroscopy for the rapid identification of illicit substances in their containers in an airport environment. Raman spectra of drugs‐of‐abuse in situ were collected using portable Raman spectrometers; this technique offers distinct advantages to government agencies, first responders and forensic scientists working in the security field. We have demonstrated that the spectrometers are able to collect the spectra of suspect powders, including cocaine HCl and d‐amphetamine sulphate with unknown constituents rapidly and with a high degree of discrimination. Copyright © 2008 John Wiley & Sons, Ltd.