Time-, wavelength-, and code-domain optical reflection monitoring for next-generation access-metro networks

Distributed optical reflectors are proposed to implement essential fault management operations such as fault detection, localization, and notification, in next generation all-optical access-metro networks in the optical layer. Fixed time-slots, wavelengths, or optical codes are assigned to selected key network locations along the path of a monitoring signal where corresponding mirrors are placed. The reflection received at a transmitting node enables online all-optical monitoring of the selected locations. After detailing the network architecture, we explore fundamental system design issues such as real-time fault localization algorithms, fault notification delay upperbounds, and delay line calculation algorithms for synchronous operation. Our simulation results showcase standard and long-reach passive optical networks, and demonstrate that our algorithms achieve fault notification at light speed using off-the-shelf components.     

Reducing False Flood Warnings of TRMM Rain Rates Thresholds over Riyadh City,Saudi Arabia by Utilizing AMSR-E Soil Moisture Information

Rainfall rates and soil moisture content have been recognized as the most critical parameters in flood forecasts; the former known as forcing and the latter as the state variable. The main objective of this article is the incorporation of antecedent soil moisture information to reduce false flood warnings over Riyadh City, Saudi Arabia. The forcing variable was obtained from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) Real Time (RT) data (3B42RT). Soil moisture (SM) information was obtained from Advanced Microwave Scanning Radiometer (AMSR-E) as the state variable. Long time series SM information (2002–2011) provided Cumulative Distribution Function (CDF) of SM. CDF with 90% was taken as the SM threshold value. Flooding is indicated for rainy dates exceeding the rain thresholds with the previous satellite overpass SM being greater than 90% CDF of the respective month. The methodology removed the false flood warnings substantially when compared to the flood warnings where SM information was absent. The method is robust and simple, and it can be applied on TRMM and AMSR-E follow on missions; like Global Precipitation Measurement (GPM) and Soil Moisture Active Passive (SMAP).     

Optical Coding for Enhanced Real-Time Dynamic Bandwidth Allocation in Passive Optical Networks

In this paper, optical pulse encoding and decoding technology is proposed to enable real-time signaling in a passive optical network (PON) setting. Unique optical codes are assigned to selected optical network units (ONUs) equipped with the corresponding encoders. An out-of-band pulse train is broadcast from the optical line terminal (OLT) and is modulated by ONU-based switches. The encoded reflections of pulses are thus used to update the status of the OC-enabled queues at the OLT in real time. We explore the enhanced PON architecture and define its major design parameters. Through extensive simulations, we investigate the design principles and limits of our system parameters. Through a performance comparison of native interleaved polling with adaptive cycle time with its OC-enhanced counterpart, we show that our OC enhancement breaks the fundamental delay lower bound associated to the polling cycle. We propose and investigate new dynamic bandwidth allocation (DBA) algorithms that exploit real-time queue updates enabled through OC-enhanced polling. We also explore the pay-as-you-grow implementation of OC-enhanced polling to realize quality-of-service (QoS) differentiation, elaborate on possible migration paths from conventional PONs, and investigate absolute QoS performance guarantee improvements achieved through OC-enabled real-time DBA algorithms.     

Studies on spironolactone polymorphic forms

The phenomenon of polymorphism of spironolactone was studied using melting point and aqueous solubility determinations, infrared spectroscopy, differential thermal analysis, X-ray powder diffraction and powder dissolution. The results showed that spironolactone crystals obtained from ethyl acetate had the lowest melting range, while those obtained from acetonitrile had the highest range. The aqueous solubility data indicated the presence of different forms of spironolactone, each with a specific solubility, although practically all of these forms could be considered to be water-insoluble. The infrared spectra were not useful in clearly distinguishing between the different forms. Differential thermal analysis curves indicated that some of the forms obtained by treating spironolactone with different solvents were somewhat similar, others were variable, but all of them were different from the original form of the drug. Moreover, the thermal study proved the absence of any solvates. X-ray patterns were different in spacing (d) values and intensities of radiation absorption, confirming the presence of four different forms of spironolactone. The form obtained from ethyl acetate had the highest dissolution rate, while that obtained from acetonitrile had the lowest rate.

Spironolactone is known to crystallize out from different solvents in different polymorphic forms and to undergo structural rearrangements on heating.^{1, 2} The study was mainly concerned with the infrared identification of steroids, and the results showed that sample preparation techniques have a profound effect on the spectra of these steroids.

Florence and Salole³ undertook a brief investigation into the effects of grinding on the crystalline properties of spironolactone. The results showed no major changes in infrared spectrum after grinding, apart from a decrease in resolution of the absorption peaks. The premelting behavior of the drug was altered, which would indicate that grinding significantly affected the spironolactone crystallinity.

El-dalsh et al.⁴ showed that spironolactone co-precipitate with povidone using different solvents such as absolute ethyl alcohol, acetonitrile and chloroform had a different X-ray diffraction pattern which may be explained on the basis of various polymorphic forms.

The purpose of the present work is to carry out studies to specify the number of polymorphs of spironolactone under the crystallization conditions.     

OCDMA and Optical Coding: Principles, Applications, and Challenges [Topics in Optical Communications]

We survey the current trends in OCDMA and optical coding through their applications. Although a prerequisite for OCDMA, optical coding distinguishes itself from OCDMA through major applications where codes are not applied to data and carry network-level information other than user identity. After introducing the principles of coding, we discuss OCDMA and its applications, particularly OCDMA PON. Optical coding and its applications are then reviewed.     

Addition of arylureas to aroyl isothiocyanates and the synthesis of 1-aroyl-5-aryl-2-thiobiurets and 2-aryl-5-aroylamino-2,3-dihydro-1,2,4-thiadiazol-3-ones

The hitherto unknown 1-aroyl-5-aryl-2-thiobiurets ( 5a – h ) were synthesized by addition of mono arylureas ( 4 ) to aroyl isothiocyanates ( 3 ). Treatment of 1-aroyl-5-aryl-2-thiobiurets ( 5a – h ) with alkali gave 5-aryl-2-thiobiurets ( 6a – e ). Oxidation of 1-aroyl-5-aryl-2-thiobiurets ( 5d , f , h ) with hydrogen peroxide in the presence of hydrochloric acid or bromine in chloroform gave 2-aryl-5-aroylamino-2,3-dihydro-1,2,4-thiadiazol-3-ones ( 7a – c ).