Thermal, solution and reductive decomposition of Cu-Al layered double hydroxides into oxide products

Cu-Al layered double hydroxides (LDHs) with Cu/Al ratio 2 adopt a structure with monoclinic symmetry while that with the ratio 0.25 adopt a structure with orthorhombic symmetry. The poor thermodynamic stability of the Cu-Al LDHs is due in part to the low enthalpies of formation of Cu(OH)2 and CuCO3 and in part to the higher solubility of the LDH. Consequently, the Cu-Al LDH can be decomposed thermally (150 °C), hydrothermally (150 °C) and reductively (ascorbic acid, ambient temperature) to yield a variety of oxide products. Thermal decomposition at low (400 °C) temperature yields an X-ray amorphous residue, which reconstructs back to the LDH on soaking in water or standing in the ambient. Solution decomposition under hydrothermal conditions yields tenorite at 150 °C itself. Reductive decomposition yields a composite of Cu2O and Al(OH)3, which on alkali-leaching of the latter, leads to the formation of fine particles of Cu2O (<1 μm). © 2009 Elsevier Inc. All rights reserved

Near-Infrared and Optical Studies of the fast nova V4643 Sgr (Nova Sagittarii 2001)

V4643 Sagittarii or Nova Sagittarii 2001 was discovered in outburst at 7.7 mag. on 2001 February 24. Here, we present near-infrared results of this fast classical nova obtained in the early decline phase in 2001 March followed by optical observations about one month later. Subsequently we also present near-infrared spectra taken later in the nova's evolution, about four months after the outburst, when V4643 Sgr had entered the coronal phase. The spectra in the early decline phase are dominated by emission lines of the HI Brackett series and also the Paschen beta and gamma lines. We study the cause of the excitation of the the OI line at 1.128 micron and discuss the variation in its strength with time after outburst. We discuss the role of optical depth effects on the observed strengths of the hydrogen Brackett and Paschen lines and discuss possible reasons for the puzzling behavior of the Br gamma line strength and whether it is correlated with the OI 1.128 micron line behavior. An optical spectrum is presented which shows that HeII lines are the most prominent features - after HI - to be seen in early 2001 April. We present and also discuss spectra taken in 2001 June and August which prominently show coronal lines of [Si VI] and [Si VII] at 1.9641 micron and 2.4807 micron respectively.Comment: Accepted in MNRA

Effects of noise suppression and envelope dynamic range compression on the intelligibility of vocoded sentences for a tonal language

Vocoder simulation studies have suggested that the carrier signal type employed affects the intelligibility of vocoded speech. The present work further assessed how carrier signal type interacts with additional signal processing, namely, single-channel noise suppression and envelope dynamic range compression, in determining the intelligibility of vocoder simulations. In Experiment 1, Mandarin sentences that had been corrupted by speech spectrum-shaped noise (SSN) or two-talker babble (2TB) were processed by one of four single-channel noise-suppression algorithms before undergoing tone-vocoded (TV) or noise-vocoded (NV) processing. In Experiment 2, dynamic ranges of multiband envelope waveforms were compressed by scaling of the mean-removed envelope waveforms with a compression factor before undergoing TV or NV processing. TV Mandarin sentences yielded higher intelligibility scores with normal-hearing (NH) listeners than did noise-vocoded sentences. The intelligibility advantage of noise-suppressed vocoded speech depended on the masker type (SSN vs 2TB). NV speech was more negatively influenced by envelope dynamic range compression than was TV speech. These findings suggest that an interactional effect exists between the carrier signal type employed in the vocoding process and envelope distortion caused by signal processing

The lead discrepancy in intrinsically s-process enriched post-AGB stars in the Magellanic Clouds

Context: Our understanding of the s-process nucleosynthesis in asymptotic giant branch (AGB) stars is incomplete. AGB models predict, for example, large overabundances of lead (Pb) compared to other s-process elements in metal-poor low-mass AGB stars. This is indeed observed in some extrinsically enhanced metal-poor stars, but not in all. An extensive study of intrinsically s-process enriched objects is essential for improving our knowledge of the AGB third dredge-up and associated s-process nucleosynthesis. Aims: We compare the spectral abundance analysis of the SMC post-AGB star J004441.04-732136.4 with state-of-the-art AGB model predictions with a main focus on Pb. The low S/N in the Pb line region made the result of our previous study inconclusive. We acquired additional data covering the region of the strongest Pb line. Methods: By carefully complementing re-reduced previous data, with newly acquired UVES optical spectra, we improve the S/N of the spectrum around the strongest Pb line. Therefore, an upper limit for the Pb abundance is estimated from a merged weighted mean spectrum using synthetic spectral modeling. We then compare the abundance results from the combined spectra to predictions of tailored AGB evolutionary models from two independent evolution codes. In addition, we determine upper limits for Pb abundances for three previously studied LMC post-AGB objects. Results: Although theoretical predictions for J004441.04-732136.4 match the s-process distribution up to tungsten (W), the predicted very high Pb abundance is clearly not detected. The three additional LMC post-AGB stars show a similar lack of a very high Pb abundance. Conclusion: From our study, we conclude that none of these low-mass, low-metallicity post-AGB stars of the LMC and SMC are strong Pb producers. This conflicts with current theoretical predictions.Comment: 4 pages, 3 figure

Relative humidity-​induced reversible hydration of sulfate-​intercalated layered double hydroxides

Layered double hydroxides (LDH) are extremely important materials for industrial processes. In the environment, LDH physicochem. behavior depends in large part on their hydration state, but characterization of these hydration effect on their properties is incomplete. This work examd. interpoly-​type transitions induced by variations in ambient humidity among LDH. The cooperative behavior of intercalated water mols. resulted in a sudden, single-​step, reversible dehydration of the [Zn-​Cr-​SO4] LDH. The [Zn-​Al-​SO4] LDH provided an interesting contrast with: the coexistence of hydration cycle end-​members at a 40-​20​% relative humidity range during the dehydration cycle; and a random inter-​stratified intermediate in the hydration cycle. These observations showed the [Zn-​Al-​SO4] LDH offered sites with a range of hydration enthalpies, where at crit. hydration levels (20-​40​%)​, non-​uniform swelling of the structure resulted in an inter-​stratified phase. Domain size variation during reversible hydration was also responsible for differences obsd. in hydration vs. the dehydration pathways. This behavior was attributed to distortion in the OH-​ array which departs from hexagonal symmetry due to cation ordering as shown in structure refinement by the Rietveld method. This distortion was much less in [Zn-​Cr-​SO4] LDH, where the nearly hexagonal OH-​ array offered sites of uniform hydration enthalpy for intercalated water mols. On this case, all water mols. experienced the same force of attraction and dehydrated reversibly in a single step. Changes in basal spacing were also accompanied by interpoly-​type transitions involving rigid translations of metal hydroxide layers relative to one another

Synthesis and reversible hydration behavior of the thiosulfate intercalated layered double hydroxide of Zn and Al

The thiosulfate-intercalated layered double hydroxide of Zn and Al undergoes reversible hydration with a variation in the relative humidity of the ambient. The hydrated and dehydrated phases, which represent the end members of the hydration cycle, both adopt the structure of the 3R1 polytype. In the intermediate range of relative humidity values (40-60), the hydrated and dehydrated phases coexist. The end members of the hydration cycle adopt the structure of the same polytype, and vary only in their basal spacings. This points to the possibility that all the intermediate phases have a kinetic origin. © 2013 Elsevier Inc

Explicit MBR All-Symbol Locality Codes

Node failures are inevitable in distributed storage systems (DSS). To enable efficient repair when faced with such failures, two main techniques are known: Regenerating codes, i.e., codes that minimize the total repair bandwidth; and codes with locality, which minimize the number of nodes participating in the repair process. This paper focuses on regenerating codes with locality, using pre-coding based on Gabidulin codes, and presents constructions that utilize minimum bandwidth regenerating (MBR) local codes. The constructions achieve maximum resilience (i.e., optimal minimum distance) and have maximum capacity (i.e., maximum rate). Finally, the same pre-coding mechanism can be combined with a subclass of fractional-repetition codes to enable maximum resilience and repair-by-transfer simultaneously

Comparison of Partial Recording Protocols in Disease Assessment among Periodontitis Patients in a Central Indian Population

Objectives: Partial recording protocols may be used for the purpose of assessing periodontal disease extent and severity in epidemiological studies. As there is very little data at present regarding the reliability of any partial examination methods among Indian populations, as an initial study, an attempt was made to determine the reliability of 9 different protocols in estimating the extent and severity of periodontal disease among periodontitis patients in a central Indian population. Study Design: Probing depths (PD) and clinical attachment levels (CAL) were recorded in 85 periodontitis patients on 6 sites on all the teeth excluding the third molars. Nine partial recording protocols (PRP) were compared with the full-mouth examination. Intra-class correlation coefficients (ICC) were calculated for mean PD, mean CAL, and percentage of sites with various thresholds of PD and CAL to determine the agreement between the PRP and the full-mouth examination. The sensitivity of different PRP for defining prevalence of sites with PD ≥6 and ≥7 mm and CAL ≥7 and ≥8 mm was also determined. Results: For all the tested PRP, the ICCs were consistently >0.9. The methods involving examination of 4 sites/ tooth slightly over-estimated the disease extent and severity in comparison with the full-mouth examination as well as PRP involving examination of 6 sites/tooth. Conclusions: The findings of the present study suggest that the tested PRP are in good agreement with the fullmouth examination. However, further studies need to be conducted with an improved methodology in a larger sample of subjects from the general population

Mandibular Fractures and Associated Factors at a Tertiary Care Hospital

Objectives: The aim of this study was to evaluate the distribution, etiology and type of mandibular fractures in subjects referred to our institution. Methods: A retrospective study of 689 subjects, during the period from May 2010 to September 2013 with mandibular fractures was conducted. Information on age, gender, mechanism of injury and sites of trauma was obtained from the trauma registry. Data were tabulated and analyzed statistically. Results: A total of 653 subjects had mandibular fractures, out of which 574 were males. The mean age of the participants was 31.54 ± 13.07. The majority of the subjects were between 21-40 years of age, in both males (61.7%) and females (54.4%). The major cause of fractures was road traffic accidents (87.4%) followed by fall (6.9%) and assault (4%), with the least frequent being gunshot injuries (0.3%). Almost half of the patients had parasymphysis fractures (50.2%), followed by angle (24.3%), condyle (20.4%), ramus (2.3%) and coronoid (2%). A total of 115 patients had bilateral fractures out of which 29 had parasymphysis, 12 had body fractures and 74 had bilateral condylar fractures. Double mandibular fractures were reported in 193 subjects; out of which 151 subjects had double contralateral and 42 had double unilateral fractures. Triple unilateral fracture was reported in only one subject. A total of 338 subjects had multiple fractures among the study population. Conclusions: Mandibular fractures can be complicated and demanding, and have a compelling impact on patients’ quality of life. Our study reported that parasymphysis was the most common region involved in mandible fractures

Design and Development of Network Monitoring and Controlling Tool for Department of Computer Studies CSIBER

In most of the organizations it is highly desirable to perform different tasks on different machines based on their configuration and permissions assigned to the machines for execution of different tasks. This can be achieved by performing a user-machine mapping by stating clearing the list of tasks that can be performed by a particular user on a particular machine. This kind of discipline further enables traffic control, prevents internal DOS (Denial Of Service) attacks for legitimate users and helps in fair resource sharing. The intent of this research is to enable the end user performing only the tasks permissible to him/her. In this paper we have developed a network monitor and control tool for monitoring the tasks on a medium sized local area network. To facilitate this, task permissions are assigned to different machines which is stored in XML configuration file which is then parsed using JDOM (Java Document Object Model) Parser. The configuration file contains the details such as machine name, and the list of tasks not permitted on that machine. The list of machines and the list of tasks denied on that machine is configurable by an end user. A background thread will continuously monitor the execution of illegal task on a machine and will abort and report the same in a database. This also facilitates the control of network traffic thereby improving the network performance by aborting illegal tasks. Network monitoring tool is tested for local area network of department of computer studies at SIBER by setting up specific monitors to check status and to carry out specific operations. The tool developed by us requires a small amount of system resources, and it is an open source tool. Presently, the tool generates a report comprising of a list of illegal tasks in a specified time period, which enables network administrator to take corrective measures for the smooth operation of the network. DOI: 10.17762/ijritcc2321-8169.15037