Supramolecular structure of S-(+)-marmesin—a linear dihydrofuranocoumarin

The title compound, C₁₄H₁₄O₄, a linear dihydrofuranocoumarin, was isolated from the bark ofAegle marmelos, a plant widely used in Ayurvedic system of medicine for the treatment of various ailments. The crystal structure was determined from X-ray diffraction data using direct methods. The compound crystallizes into monoclinic space group P2₁ with unit cell parameters:a] = 5.721(1) Å, b= 13.810(1) Å, c= 7.864(2) Å, β = 100.39(1)°, Z = 2. The structure was refined by full-matrix least-squares to a finalR value of 0.0523 for 1184 observed reflections. The benzopyran moiety is perfectly planar. The dihedral angle between the pyrone and benzene rings is 0.3(1)°. The furan ring has a 2α-envelope conformation. The molecules are linked by O-H…O hydrogen bonds into chains and these chains are linked into sheets by C-H…O hydrogen bonds. Further, the π-π stacking and C-H…π (arene) interactions link all of the sheets into a supramolecular structure.     

Discrete warehouse problem

A discrete warehouse is a collection of two-dimensional unit-square objects (robot and obstacles), which are allowed to move horizontally and vertically along grid lines. In this paper, we consider motion planning problems in a discrete warehouse with movable obstacles. In such a setup one is allowed to move some of the obstacles in order to:

1. (1) navigate the robot between an initial and a final position of the warehouse, and

2. (2) construct a clearing (path) between two specified points.

The final positions of the obstacles are unimportant for our problems.

We consider two forms of obstacle manipulations:

1. (a) remote, when the obstacles are moved by a remote mechanism, and

2. (b) contact, when the obstacles are moved only by direct contact of the robot.

We present necessary and sufficient conditions for the existence of a motion in both cases, and propose efficient algorithms for constructing feasible motions.     

Anisotropic thermal expansion of stoichiometric lithium niobate crystals grown along the normal direction of facets

In this paper, a stoichiometric lithium niobate (SLN) crystal with the size up to 20 × 20 × 18 mm³ was grown along the normal direction of the (0 1 2) facet from the 16 mol% K₂O fluxed melt by the top-seeded solution growth method. The anisotropic thermal expansion of the SLN crystal and congruent lithium niobate (CLN) crystal was measured along different directions by using a Shimadzu thermomechanical analyzer. As compared with CLN, the SLN crystal exhibited slightly larger thermal expansion along the Z-axis and slightly smaller expansion along the X-axis. Both the SLN and CLN crystals showed strong anisotropy in the thermal expansion. The thermal expansion coefficient of SLN along the X-axis (16.7 × 10⁻⁶ °C⁻¹ at 300 °C) is much larger than that along the Z-axis (2.5 × 10⁻⁶ °C⁻¹ at 300 °C). Based on the experimental data and polynomial fitting results, we calculated the thermal expansion coefficients for different directions. In the case of growing the SLN crystal along the normal direction of (0 1 2) facet, we studied the radial anisotropic thermal expansion and discussed the cracking problem of the crystal according to its actual growth morphology. It is found that the cracks of SLN can be suppressed by growing the crystal along the W-axis due to its reduced radial anisotropy in the thermal expansion.     

LHAP: A lightweight network access control protocol for ad hoc networks

Most ad hoc networks do not implement any network access control, leaving these networks vulnerable to resource consumption attacks where a malicious node injects packets into the network with the goal of depleting the resources of the nodes relaying the packets. To thwart or prevent such attacks, it is necessary to employ authentication mechanisms to ensure that only authorized nodes can inject traffic into the network. We propose LHAP, a hop-by-hop authentication protocol for ad hoc networks. LHAP resides in between the network layer and the data link layer, thus providing a layer of protection that can prevent or thwart many attacks from happening, including outsider attacks and insider impersonation attacks. Our detailed performance evaluation shows that LHAP incurs small performance overhead and it also allows a tradeoff between security and performance.     

Procedural outcome and follow-up results of balloon angioplasty versus new device interventions for treatment of true bifurcation stenoses

Strategies for dilatation of bifurcation stenoses have continued to evolve over the past several years. However, there is limited experience on the efficacy of various nonballoon interventional devices and their results in comparison with balloon angioplasty. We, therefore, analysed our data in 72 patients of coronary artery disease with true bifurcation stenoses with balloon angioplasty or new device interventions (NDI). All patients underwent dilatation of both the primary vessel and side branch ostial stenosis. Balloon angioplasty using double guidewire with sequential or simultaneous (kissing balloon) balloon inflation in the two vessels was performed in 42 patients. Thirty patients underwent NDI, using directional coronary atherectomy (DCA) in 12, rotablation in 6 and elective coronary stents in 12 patients. There were no significant differences in the baseline clinical and angiographic variables between patients in the two groups. While the preprocedural luminal diameter stenosis was similar, the residual stenosis was significantly less, both in the primary vessel and side branch, after NDI compared to balloon angioplasty. The procedure was successful in 96.6 percent patients treated with NDI and 83.3 percent with balloon angioplasty (p < 0.01) with relief of obstruction in both branches without any major complications. Freedom from subsequent coronary events in the form of angina, myocardial infarction, PTCA, bypass graft surgery of death was significantly more, both at 6 months (92% versus 65.6%, p < 0.001) and 12 months (81.8% versus 53.1%, p < 0.001) in the group of patients treated with NDI compared to balloon angioplasty. It is, therefore, concluded that NDI including DCA, rotablation and elective stenting are associated with higher rate of success, lesser complications and better event-free survival in comparison to balloon angioplasty for treatment of true bifurcation stenoses.     

Melting treatment of waste asbestos using mixture of hydrogen and oxygen produced from water electrolysis

In this study, we melted four types of waste asbestos containing material such as spread asbestos, plasterboard asbestos, slate asbestos and asbestos 99 wt%, in a melting furnace at 1,450–1,550 that uses a mixture of hydrogen and oxygen (Brown’s gas) as a fuel. More volatile components (CaO, K₂O) are enriched in spread asbestos, plasterboard asbestos, and slate asbestos, while less volatile compounds (SiO₂, Fe₂O₃, MgO) remain in asbestos 99%. Through basicity of raw materials, spread asbestos, plasterboard asbestos, and slate asbestos were found to have more alkalinity, and asbestos 99% was found more acidic. SEM and EDX results revealed that all raw materials had various kinds of asbestos fiber. Spread asbestos, plasterboard asbestos, and slate asbestos were considered as tremolite asbestos, whereas asbestos 99% was considered as chrysotile asbestos. It was further confirmed by SEM and XRD studies that all waste materials contained some crystalline structures which transformed into amorphous glassy structure on melting. Also, in case of added glass cullet during the melting of spread asbestos, it transformed the raw material into a perfect vitrified product having more glassy surface and amorphous in nature     

Pharmacological actions of Pongamia pinnata seeds--a preliminary study

Direct ethanolic and sequential petroleum ether, chloroform, acetone and ethanolic extracts (50-100 mg/kg, i.p.) of P. pinnata seeds given 30-60 min before revealed anti-inflammatory, analgesic and anti-ulcerogenic activities in rats. The activities were present maximum in petroleum ether and chloroform extracts. However, the extracts also showed shortening of pentobarbitone induced 'sleep time' in rats.     

Can multiple subchannels improve the delay performance of RTS/CTS-based MAC schemes?

We analyze the delay performance of RTS/CTS-based (Request-To-Send/Clear-To-Send) multi-channel MAC (Medium Access Control) schemes for wireless networks. These schemes usually employ multiple data subchannels for data transmission and one control subchannel to send the RTS/CTS dialogue for channel reservation. Through theoretical analysis and simulations, we show that, in fully-connected networks, such multi-channel MAC schemes suffer longer delays than the corresponding single channel MAC scheme, that puts the RTS/CTS dialogue on the same channel as data packet transmissions. This conclusion holds even when data packets have different priorities and higher priority traffic is sent ahead of lower priority traffic.     

Transient heat flux measurement analysis from coaxial thermocouples at convective based step heat load

The measurement of surface heating rate is an imperative parameter in the force convection ground-based facility for short duration investigation due to the heat transfer rate is changing rapidly. The coaxial thermocouples are suitable to measure the transient heat flux in fast varying heat transfer application because of having fast response time in the range microseconds or less. In this addition, the K-type, E-type, and J-type of coaxial thermocouples are contrived as well as the thermal coefficient resistance (TCR) and sensitivity (S) has been calculated from oil-bath based technique. These handmade coaxial thermocouples are exposed in a forced convection flow facility having three different input step heat loads as well as their transient heat fluxes are estimated using one-dimensional heat conduction modeling for the semi-infinite body. The numerical simulation has also been carried out with the analogous experimental parameters using ANSYS-FLUENT v.15.0 and compared with the outcome of the experimental approach and it is found that the average value of the transient temperatures having 0.3% error and surface heat flux recovered from this temperature is 10%. This study reveals the measuring ability of these handmade coaxial thermocouples at low temperature and low velocity on short duration transient measurements.