Design, fabrication and performance evaluation of a 22-channel direct reading atomic emission spectrometer using inductively coupled plasma as a source of excitation

The indigenous design, fabrication and performance evaluation of a polychromator, using inductively coupled plasma (ICP) as a source of excitation, are described. A concave holographic grating is used as the dispersing element and a Paschen-Runge mount is chosen to focus the spectra over a wide range along the Rowland circle. Twenty-two exit slits, mounted along the circle, precisely correspond to the wavelengths used for determination of up to twenty elements present in the plasma. Radiations emerging from the exit slits are detected by photomultiplier tubes placed behind them. The photomultiplier signal is recorded by an electronic system consisting of an integrator and a PC-based data acquisition system. The performance of the spectrometer has been evaluated with an ICP excitation source. Synthetic standards in deionized water containing a mixture of twenty impurities have been analysed. Typical determination limits observed for elements range from sub-ppm to ppm levels. All the elements present as impurities can be detected simultaneously. It is also observed that each element has a different emitting region in the ICP flame for which the maximum signal to the background is obtained. The determination limits obtained corresponding to these zones are the lowest. A study of the sensitive emitting zones for several elements has been carried out and the results are demonstrated by photographs of the ICP flame. The study will help in achieving the minimum value of determination limit for an impurity element

Metformin and the gastrointestinal tract

Metformin is an effective agent with a good safety profile that is widely used as a first-line treatment for type 2 diabetes, yet its mechanisms of action and variability in terms of efficacy and side effects remain poorly understood. Although the liver is recognised as a major site of metformin pharmacodynamics, recent evidence also implicates the gut as an important site of action. Metformin has a number of actions within the gut. It increases intestinal glucose uptake and lactate production, increases GLP-1 concentrations and the bile acid pool within the intestine, and alters the microbiome. A novel delayed-release preparation of metformin has recently been shown to improve glycaemic control to a similar extent to immediate-release metformin, but with less systemic exposure. We believe that metformin response and tolerance is intrinsically linked with the gut. This review examines the passage of metformin through the gut, and how this can affect the efficacy of metformin treatment in the individual, and contribute to the side effects associated with metformin intolerance

Projects not initiated by investigators: A retrospective analysis of the queries raised by the institutional ethics committees of a teaching hospital

Background: Some investigators on receiving queries from Institutional Ethics Committee (IEC), either leave the queries unanswered or withdraw their studies. The present study was conducted to assess the queries raised by two IECs after reviewing studies that were not initiated and to identify reasons for the same. Clinical Trials Registry-India (CTRI) website was checked to review approval status of these studies at other sites. Materials and Methods: A retrospective analysis of studies (submitted between January 2006 and December 2011) not initiated by investigators on receiving queries from IECs were identified. The nature of of these studies: whether sponsored (pharmaceutical industry (pharma)/government/investigator initiated), single-centre/multi-centric, and queries raised were analyzed. Status of multi-centric trials; not initiated at our site was checked at CTRI. Data was analyzed using descriptive statistics. Results: A total of 219/2075 (11%) studies were not initiated. The proportions in pharma sponsored, investigator initiated, and government sponsored were 33%. 7.4%, and 8%, respectively. Out of a total of 1676 queries, the maximum queries were related to ethics (42%) and the least were administrative (7%). The largest proportion of queries in the pharma studies was ethical (47%), whereas majority were scientific queries (45.5%) for the investigator initiated studies. Twenty-one of the 94 multi-centric studies not initiated at our site were found registered at the CTRI and were ongoing or completed at 2-55 sites. Conclusion: Inability of investigators to defend studies due to lack of good clinical research practice (GCP) and research methodology training or unwillingness of sponsors to comply with local IEC requirements could be potential reasons for studies remaining uninitiated. Continued GCP training of investigators and IEC members and development of uniform ethical review standards across IECs are strongly recommended

Valence states of sm in smrusn3

To obtain a better insight into the nature of valence states of Sm ions in SmRuSn3 and to verify the differing conclusions reached by T. Fukuhara, I. Sakamoto, and H. Sato [J. Phys. Condens. Matter 3, 8917 (1991)] and C. Godart et al. [Phys. Rev. B 48, 16 402 (1993)], we have systematically analyzed the magnetic-susceptibility data by considering the effects of crystalline electric field, exchange interaction, and valence fluctuation. In this compound, Sm ions occupy two different sites, 6d and 2a, in the ratio of 3:1. Our analysis shows that Sm ions at the 6d site are in a trivalent state and those at the 2a sites are in a valence fluctuating state. This supports the claim made by C. Godart et al. [Phys. Rev. B 48, 16 402 (1993)]

SUPERCONDUCTING AND MAGNETIC-PROPERTIES OF TLSR2CA(1-X)R(X)CU(2)O(7) [R=PR,TB]

The magnetic and superconducting properties of the TISr<SUB>2</SUB>Ca<SUB>1&#8722;x</SUB>R<SUB>x</SUB>Cu<SUB>2</SUB>O<SUB>7</SUB> [R=Pr (x=0.2-1.0); Tb (x=0.6 and 1.0)] system are reported. The observation of superconductivity in TISr<SUB>2</SUB>Ca<SUB>0.4</SUB>Pr<SUB>0.6</SUB>Cu<SUB>2</SUB>O<SUB>7 </SUB>(T<SUB>c</SUB>=74 K) suggests that the Pr ions are in the trivalent state. The value of the effective magnetic moment, &#181;<SUB>eff</SUB>=3.15&#181;<SUB>B</SUB>, for the TISr<SUB>2</SUB>Ca<SUB>0.4</SUB>Pr<SUB>0.6</SUB>Cu<SUB>2</SUB>O<SUB>7</SUB> compound, lies between the free-ion values expected for Pr<SUP>3+</SUP> (3.58 &#181;<SUB>B</SUB>) and Pr<SUP>4+</SUP> (2.54&#181;<SUB>B</SUB>). The reduced value of &#181;<SUB>eff</SUB> for the Pr<SUP>3+</SUP> ion is explained in terms of crystal-field effects. For TISr<SUB>2</SUB>TbCu<SUB>2</SUB>O<SUB>7</SUB>, the Tb magnetic moments order antiferromagnetically at 7.0 K, which is the highest magnetic ordering temperature among the known Tb-containing high-T<SUB>c</SUB> related compounds. Superconductivity (T<SUB>c</SUB>=74 and 62 K) and antiferromagnetic ordering (T<SUB>N</SUB>=5 and 6.2 K) coexist in TISr<SUB>2</SUB>Ca<SUB>0.4</SUB>R<SUB>0.6</SUB>Cu<SUB>2</SUB>O<SUB>7</SUB> with R=Pr and Tb, respectively

Fundamental limitations on efficiently forecasting certain epidemic measures in network models

The ongoing COVID-19 pandemic underscores the importance of developing reliable forecasts that would allow decision makers to devise appropriate response strategies. Despite much recent research on the topic, epidemic forecasting remains poorly understood. Researchers have attributed the difficulty of forecasting contagion dynamics to a multitude of factors, including complex behavioral responses, uncertainty in data, the stochastic nature of the underlying process, and the high sensitivity of the disease parameters to changes in the environment. We offer a rigorous explanation of the difficulty of short-term forecasting on networked populations using ideas from computational complexity. Specifically, we show that several forecasting problems (e.g., the probability that at least a given number of people will get infected at a given time and the probability that the number of infections will reach a peak at a given time) are computationally intractable. For instance, efficient solvability of such problems would imply that the number of satisfying assignments of an arbitrary Boolean formula in conjunctive normal form can be computed efficiently, violating a widely believed hypothesis in computational complexity. This intractability result holds even under the ideal situation, where all the disease parameters are known and are assumed to be insensitive to changes in the environment. From a computational complexity viewpoint, our results, which show that contagion dynamics become unpredictable for both macroscopic and individual properties, bring out some fundamental difficulties of predicting disease parameters. On the positive side, we develop efficient algorithms or approximation algorithms for restricted versions of forecasting problems