Ibrahim Badr - Academia.edu (original) (raw)

Papers by Ibrahim Badr

With the continuous growth in the World Wide Web, the need arises for indexing and classifying We... more With the continuous growth in the World Wide Web, the need arises for indexing and classifying Web documents for fast retrieval of relevant information accessible through it. Traditionally, classification has been accomplished manually. A recent study revealed that, there exist about 29.7 billion pages on the Web in February 2007, which means that manual classification would be infeasible and reflects the need for automated techniques for accomplishing this task. Though Web documents should follow the basic definitions on Hypertext Markup Language, they are known to be unstructured or semi-structured, which imposes new challenges to Web classification especially in the area of feature selection. The objective of this paper is to investigate Web document classification approaches, and compare between recent techniques proved promising in literature within this field. Traditionally, automatic classification is performed by extracting information for representing a web document from th...

The Anatomical Record, 2015

Background: CT scanning of ancient human remains has the potential to provide insights into healt... more Background: CT scanning of ancient human remains has the potential to provide insights into health and diseases. While Egyptian mummies have undergone CT scans in prior studies, a systematic survey of the orthopedic conditions afflicting a group of these ancient individuals has never been carried out. Methods: We performed whole body CT scanning on 52 ancient Egyptian mummies using technique comparable to that of medical imaging. All of the large joints and the spine were systematically examined and osteoarthritic (OA) changes were scored 0-4 using Kellgren and Lawrence classification. Results: The cruciate ligaments and menisci could be identified frequently. There were much more frequent OA changes in the spine (25 mummies) than in the large joints (15 cases of acromioclavicular and/or glenohumeral joint OA changes, five involvement of the ankle, one in the elbow, four in the knee, and one in the hip). There were six cases of scoliosis. Individual mummies had the following conditions: juvenile aseptic necrosis of the hip (Perthes disease), stage 4 osteochondritis dissecans of the knee, vertebral compression frac-

Talanta, Jan 30, 2001

A potentiometric sensor based on the use of titanium phosphate (TP) in epoxy matrix membrane is p... more A potentiometric sensor based on the use of titanium phosphate (TP) in epoxy matrix membrane is prepared and characterized. The sensor exhibits near-Nernstian response for many anionic species over the concentration range 10(-1)-10(-5) mol l(-1). The origin of response is explained on the basis of the conversion of titanium phosphate cation exchanger into hydrated titanium oxide anion exchanger by the effect of the high pH of the epoxy matrix. The sensitivity and selectivity of the sensor for sulfite ions are optimized by conversion of sulfite into gaseous SO(x) by acidification, and diffusion of the gas through a membrane-based gas dialyzer followed by potentiometric detection of sulfite ions formed within a flowing recipient stream. No interferences are caused by many common anions and acidic gas releasing species except sulfide and nitrite ions. Determination of sulfite ion at levels as low as 10(-4) mol l(-1) or less in the presence of nitrite and sulfide ions is performed by us...

Proceedings of the 12th Conference of the European Chapter of the Association for Computational Linguistics on - EACL '09, 2009

Syntactic Reordering of the source language to better match the phrase structure of the target la... more Syntactic Reordering of the source language to better match the phrase structure of the target language has been shown to improve the performance of phrase-based Statistical Machine Translation. This paper applies syntactic reordering to English-to-Arabic translation. It introduces reordering rules, and motivates them linguistically. It also studies the effect of combining reordering with Arabic morphological segmentation, a preprocessing technique that has been shown to improve Arabic-English and English-Arabic translation. We report on results in the news text domain, the UN text domain and in the spoken travel domain.

Analytical Chemistry, 1995

The potentiometric anion selectivity of polymer membrane-based electrodes formulated with a palla... more The potentiometric anion selectivity of polymer membrane-based electrodes formulated with a palladium organophosphine complex (benzylbis(triphenylphosphine)palladium(II) chloride) as the membrane active component is examined. The electrode is shown to exhibit a non-Hofmeister selectivity pattern with a significantly enhanced response toward nitrite over the concentration range of 10 microM-10 mM (log-linear range) and a detection limit 5.0 microM. The effect of lipophilic anionic (tetraphenylborate derivatives) and cationic (tetraalkylammonium) site additives within the membrane on the anion selectivity is examined in detail. Addition of both cationic and anionic sites is shown to improve potentiometric anion selectivity, suggesting that the palladium complex may operate simultaneously as a neutral and charged carrier-type ionophore within the polymer membrane phase. Using optimal membrane formulations (with added 20-30 mol % cationic sites), the sensors prepared with the palladium complex do not exhibit proton/hydroxide response in the range of pH 3.5-12, a potential advantage over previously reported nitrite electrodes prepared with Co(III) corrins and porphyrin complexes.

Talanta, 2005

Two different polysaccharides with anticoagulant activities, heparin and chondroitin sulfate, wer... more Two different polysaccharides with anticoagulant activities, heparin and chondroitin sulfate, were used to modify the surface of sodium-selective electrodes based on asymmetric cellulose triacetate (CTA) membranes. The membranes were formulated with sodium ionophore X, anionic additive, and o-nitrophenyl octyl ether. The response behavior of the surface-modified sodium electrodes was compared with that of control CTA, as well as poly(vinyl chloride) (PVC)-based sodium-selective electrodes. It was found that the selectivity coefficients obtained with the surface modified CTA membrane electrodes were slightly higher than those of the control, but in the case of heparin-modified electrodes they still met the requirements for analysis of sodium in physiological fluids within an error of <1%; the corresponding error for chondroitin sulfate-modified electrodes was also <1% except for the case of potassium ion in which the error was 1.3%. Likewise, it was found that other response characteristics, such as detection limit, linear range, slope of the response plot, selectivity pattern, and response time were comparable in both the control and the polysaccharide-modified electrodes. Therefore, the surface modification does not significantly alter the response behavior of the sensors.

Microchimica Acta, 2004

A new sensor for anionic surfactants with a membrane consisting of 33 wt% poly(vinyl chloride) (P... more A new sensor for anionic surfactants with a membrane consisting of 33 wt% poly(vinyl chloride) (PVC), 66 wt% dioctylphthalate (DOP) plasticizer, and 1 wt% tridodecylmethylammonium chloride (TDMAC) is developed and used for flow injection analysis. The sensor displays a working response range of 5Â10 À7 -5Â10 À3 M dodecylbenzene sulfonate (DBS À ) with a Nernstian slope of 58.5 AE 0.2 mV decade À1 , a response time of 30 s and a detection limit of 1.5Â10 À7 M DBS À . Selectivity measurements with different anionic species indicate good membrane selectivity towards DBS À . The sensor is used to measure anionic surfactants (DBS À ) in different wastewater samples, commercial detergent products, and for monitoring the rate of surfactant biodegradation in sewage treatment plants. The results obtained agree fairly well with data obtained by the standard extraction-spectrophotometric method. The proposed potentiometric method offers the advantages of simplicity, accuracy, automation feasibility, and applicability to turbid and colored sample solutions.

Microchimica Acta, 2005

Membrane electrodes based on 2, 2′-dithiobis (benzothiazole), DTBBT, as a neutral carrier for sil... more Membrane electrodes based on 2, 2′-dithiobis (benzothiazole), DTBBT, as a neutral carrier for silver ions are described. Silver-selective membrane electrodes formulated with 2 wt% DTBBT ionophore and 50 mol% TFPB in an FPNPE plasticized poly (vinyl chloride) ...

Journal of Vascular Surgery, 2013

Background Atherosclerosis is thought to be a disease of modern human beings and related to conte... more Background Atherosclerosis is thought to be a disease of modern human beings and related to contemporary lifestyles. However, its prevalence before the modern era is unknown. We aimed to evaluate preindustrial populations for atherosclerosis.

Journal of the American Chemical Society, 2005

A highly selective, sensitive, and reversible fluoride optical sensing film based on aluminum(III... more A highly selective, sensitive, and reversible fluoride optical sensing film based on aluminum(III)octaethylporphyrin as a fluoride ionophore and a lipophilic pH indicator as the optical transducer is described. The fluoride optical sensing films exhibit a submicromolar detection limit and high discrimination for fluoride over several lipophilic anions such as nitrate, perchlorate, and thiocyanate.

Journal of Radioanalytical and Nuclear Chemistry Articles, 1992

The isotope exchange reaction between Na36Cl and triphenyltin chloride in dioxane-water (8020% w/... more The isotope exchange reaction between Na36Cl and triphenyltin chloride in dioxane-water (8020% w/w) and ethanol-water (9010% w/w) mixed solvents have been studied at 25°C, 35°C and 50°C. The exchange reaction was found to proceed via a bimolecular SN2, limiting mechanism with reaction rates depending on the solvent used. Inhibition of the exchange in ethanol-water is probably due to solvation of

IEEE Transactions on Audio, Speech, and Language Processing, 2000

ABSTRACT In many ways, the lexicon remains the Achilles heel of modern automatic speech recognize... more ABSTRACT In many ways, the lexicon remains the Achilles heel of modern automatic speech recognizers. Unlike stochastic acoustic and language models that learn the values of their parameters from training data, the baseform pronunciations of words in a recognizer's lexicon are typically specified manually, and do not change, unless they are edited by an expert. Our work presents a novel generative framework that uses speech data to learn stochastic lexicons, thereby taking a step towards alleviating the need for manual intervention and automatically learning high-quality pronunciations for words. We test our model on continuous speech in a weather information domain. In our experiments, we see significant improvements over a manually specified “expert-pronunciation” lexicon. We then analyze variations of the parameter settings used to achieve these gains.

Electroanalysis, 2000

Preparation, characterization, origin of response and applications of a potentiometric sensor bas... more Preparation, characterization, origin of response and applications of a potentiometric sensor based on the use of a zirconium titanium phosphate (ZTP)-epoxy membrane are described. Zirconium titanium phosphate (ZTP) cationic exchanger embedded in an epoxy matrix is converted into a hydrated zirconium oxide anion exchanger which responds to many anionic species. A sensor based on this exchanger exhibits near-Nernstian response for nitrite and other anions over the concentration range 10 71 ±10 75 M. Under optimized conditions, the gas dialyzera¯ow-injection system provides a throughput of ca. 60 samples per hour with a high selectivity for nitrite ion over most common anions and acidic gas releasing species. Determination of nitrite at levels as low as 5610 74 M or less in the presence of sul®te and sul®de ions is performed by using a modi®ed carrier buffer stream (10 72 M MES, pH 5.5 containing formaldehyde and Pb 2 ). Signi®cant advantages are offered by the ZTP-epoxy membrane based sensor including a long 1ifetime ( b 2 years), excellent stability and reproducibility (ca. 1 mV), fast response time (`30 s), wide pH working range (pH 4.5±8), low detection limit (4610 75 M) and high thermal stability(up to 80 C).

Proceedings of the 10th …, 2008

... 3. SYSTEM DEVELOPMENT WITH WAMI The WAMI toolkit supports two main threads of devel ... guage... more ... 3. SYSTEM DEVELOPMENT WITH WAMI The WAMI toolkit supports two main threads of devel ... guage model for the speech recognizer, and any application-specific processing modules for handling ... component runs on the client to capture a user's speech and stream it to the ...

Analytical Sciences, 2009

A poly(vinyl chloride) matrix membrane sensor for the selective determination of thiocyanate has ... more A poly(vinyl chloride) matrix membrane sensor for the selective determination of thiocyanate has been developed based on the use of copper(II)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex (Cu-PADAP) as a novel charged carrier, and o-nitrophenyloctyl ether (o-NPOE) as a solvent mediator. The sensor displays a significantly enhanced response towards SCN(-) ions over the concentration range 7.0 x 10(-6) to 1.0 x 10(-2) mol L(-1) with a detection limit of 5.6 x 10(-6) mol L(-1) and a calibration slope of -57.5 +/- 0.5 mV decade(-1). The sensor exhibits a long life-span, long-term stability, high reproducibility, and a fast response time. The selectivity coefficients of some anions were calculated using the separate solutions method, and found to be in the following order: SCN(-) > ClO(4)(-) > I(-) > Sal(-) > NO(2)(-) > Br(-) > NO(3)(-) = CH(3)COO(-) > Cl(-) > SO(4)(2-) = PO(4)(3-). The effects of the pH and ionic membrane additives (e.g. tridodecylmethylammonium chloride, TDMAC and potassium tetrakis[bis(3,5-trifluoromethyl)phenyl] borate, KTFPB) were examined. The sensor was used for the determination of SCN(-) ions in saliva and urine samples collected from some smoker and non-smoker donors. The developed sensor was also applied to determine the cyanide content in electroplating waste water samples after its conversion into thiocyanate. The application of the sensor to monitor the potentiometric titration of Ag(+) and Hg(2+) using SCN(-) resulted in sharp inflection breaks at the equivalent points. The data obtained using the proposed sensor correlate very well with results collected using the standard methods of thiocyanate, cyanide and metal analysis.

Analytical Chemistry, 2002

The development of an integrated analysis system for small ions based on ion-selective optodes an... more The development of an integrated analysis system for small ions based on ion-selective optodes and centrifugal microfluidics is reported. The performance of this system was evaluated through five-point calibration plots for two types of optode membranes, one being cation-selective and the other anion-selective, which were incorporated into a microfluidics platform on which fluid motion is induced via angular rotation. Additionally, the application of the microfluidic platform to ion analysis is studied via a two-point calibration protocol used to quantify an unknown sample. Calibrant solutions are delivered from reservoirs fabricated onto the platform to a measuring area that contains the optode membrane, with a change in membrane fluorescence being monitored. This work demonstrates the first instance of a microfluidic-based analysis system with detection based on ion-selective optode membranes monitored with fluorescence transduction. Furthermore, in addition to employing a standard excitation source where a fiber-optic probe is coupled to a tungsten-halogen lamp, laser diodes such as those employed in portable CD/DVD players were studied as excitation sources to enhance the observed fluorescence signals.

Analytical Chemistry, 2002

The hydrogelpoly(2-methacryloyloxyethylphosphorylcholine-co-butyl methacrylate), or poly(MPC-co-B... more The hydrogelpoly(2-methacryloyloxyethylphosphorylcholine-co-butyl methacrylate), or poly(MPC-co-BMA), was used as a coating for polyurethane- and poly(vinyl chloride)-based membranes to develop ion-selective electrodes (ISEs) with enhanced blood compatibility. Adverse interactions of poly(MPC-co-BMA) with blood were diminished due to the phosphorylcholine functionalities of the hydrogel, which mimic the phospholipid polar groups present on the surface of many cell membranes. As demonstrated by immunostaining, hydrogel-coated PVC membranes soaked in platelet-rich plasma showed less adhesion and activation of platelets than uncoated PVC membranes, indicating an improvement in biocompatibility owing to the hydrogel. Furthermore, little differences in the potentiometric response characteristics, e.g., slope, detection limit, and selectivity, of ISEs employing uncoated and coated membranes were observed.

Analytical Chemistry, 2001

A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics pl... more A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics platform and ion-selective optode membranes is described. The microfluidic architecture is composed of channels, five solution reservoirs, a measuring chamber, and a waste reservoir manufactured onto a disk-shaped substrate of poly(methyl methacrylate). Ion-selective optode membranes, composed of plasticized poly(vinyl chloride) impregnated with an ionophore, a proton chromoionophore, and a lipophilic anionic additive, were cast, with a spin-on device, onto a support layer and then immobilized on the disk. Fluid propulsion is achieved by the centrifugal force that results from spinning the disk, while a system of valves is built onto the disk to control flow. These valves operate based on fluid properties and fluid/substrate interactions and are controlled by the angular frequency of rotation. With this system, we have been able to deliver calibrant solutions, washing buffers, or "test" solutions to the measuring chamber where the optode membrane is located. An analysis system based on a potassium-selective optode has been characterized. Results indicate that optodes immobilized on the platform demonstrate theoretical responses in an absorbance mode of measurement. Samples of unknown concentration can be quantified to within 3% error by fitting the response function for a given optode membrane using an acid (for measuring the signal for a fully protonated chromoionophore), a base (for fully deprotonated chromoionophore), and two standard solutions. Further, the ability to measure ion concentrations by employing one standard solution in conjunction with acid and base and with two standards alone were studied to delineate whether the current architecture could be simplified. Finally, the efficacy of incorporating washing steps into the calibration protocol was investigated.

Analytical Chemistry, 2001

The susceptibility of segmented polyurethanes (SPUs) to in vivo oxidative cleavage and hydrolysis... more The susceptibility of segmented polyurethanes (SPUs) to in vivo oxidative cleavage and hydrolysis constitutes a drawback in the use of these materials in the fabrication of implantable devices. The introduction of poly(dimethylsiloxane) (PDMS) groups into the polymer main chain has been previously reported to enhance the stability of SPUs. Herein, we evaluated the use of BioSpan-S, a silicone-modified SPU, in the design of membranes for cation-selective electrodes. The resulting electrodes exhibited good potentiometric response with all of the tested ionophores (valinomycin, sodium ionophore X, and nonactin). The obtained selectivity coefficients meet the selectivity requirements for the determination of sodium and potassium in blood. Moreover, as reflected by SEM studies, membranes prepared with BioSpan-S showed less adhesion of platelets than membranes prepared with conventional poly(vinyl chloride) (PVC). These results lead to the conclusion that BioSpan-S would be an appropriate candidate for the fabrication of implantable ion-selective electrodes.

Analytical Chemistry, 2000

Ionophore topology has a profound effect on the behavior of ion-selective electrodes. This is dem... more Ionophore topology has a profound effect on the behavior of ion-selective electrodes. This is demonstrated with a new class of ionophores that incorporates aminochromenone moieties linked through urea spacers to different scaffolds that preorganize the ionophore binding cleft into tripodal topologies. Tris(2-aminoethylamine) and cis-1,3,5-tris(aminomethyl)cyclohexane were employed as the scaffolds. The two differ in their rigidity and in the size of ionophore cavity that they create. The electrodes based on the ionophore that incorporates the tris(2aminoethylamine) scaffold show anti-Hofmeister behavior with an improved selectivity for sulfate. In contrast, the ionophore with the cis-1,3,5-tris(aminomethyl)cyclohexane scaffold exhibits a more Hofmeister-like response.

With the continuous growth in the World Wide Web, the need arises for indexing and classifying We... more With the continuous growth in the World Wide Web, the need arises for indexing and classifying Web documents for fast retrieval of relevant information accessible through it. Traditionally, classification has been accomplished manually. A recent study revealed that, there exist about 29.7 billion pages on the Web in February 2007, which means that manual classification would be infeasible and reflects the need for automated techniques for accomplishing this task. Though Web documents should follow the basic definitions on Hypertext Markup Language, they are known to be unstructured or semi-structured, which imposes new challenges to Web classification especially in the area of feature selection. The objective of this paper is to investigate Web document classification approaches, and compare between recent techniques proved promising in literature within this field. Traditionally, automatic classification is performed by extracting information for representing a web document from th...

The Anatomical Record, 2015

Background: CT scanning of ancient human remains has the potential to provide insights into healt... more Background: CT scanning of ancient human remains has the potential to provide insights into health and diseases. While Egyptian mummies have undergone CT scans in prior studies, a systematic survey of the orthopedic conditions afflicting a group of these ancient individuals has never been carried out. Methods: We performed whole body CT scanning on 52 ancient Egyptian mummies using technique comparable to that of medical imaging. All of the large joints and the spine were systematically examined and osteoarthritic (OA) changes were scored 0-4 using Kellgren and Lawrence classification. Results: The cruciate ligaments and menisci could be identified frequently. There were much more frequent OA changes in the spine (25 mummies) than in the large joints (15 cases of acromioclavicular and/or glenohumeral joint OA changes, five involvement of the ankle, one in the elbow, four in the knee, and one in the hip). There were six cases of scoliosis. Individual mummies had the following conditions: juvenile aseptic necrosis of the hip (Perthes disease), stage 4 osteochondritis dissecans of the knee, vertebral compression frac-

Talanta, Jan 30, 2001

A potentiometric sensor based on the use of titanium phosphate (TP) in epoxy matrix membrane is p... more A potentiometric sensor based on the use of titanium phosphate (TP) in epoxy matrix membrane is prepared and characterized. The sensor exhibits near-Nernstian response for many anionic species over the concentration range 10(-1)-10(-5) mol l(-1). The origin of response is explained on the basis of the conversion of titanium phosphate cation exchanger into hydrated titanium oxide anion exchanger by the effect of the high pH of the epoxy matrix. The sensitivity and selectivity of the sensor for sulfite ions are optimized by conversion of sulfite into gaseous SO(x) by acidification, and diffusion of the gas through a membrane-based gas dialyzer followed by potentiometric detection of sulfite ions formed within a flowing recipient stream. No interferences are caused by many common anions and acidic gas releasing species except sulfide and nitrite ions. Determination of sulfite ion at levels as low as 10(-4) mol l(-1) or less in the presence of nitrite and sulfide ions is performed by us...

Proceedings of the 12th Conference of the European Chapter of the Association for Computational Linguistics on - EACL '09, 2009

Syntactic Reordering of the source language to better match the phrase structure of the target la... more Syntactic Reordering of the source language to better match the phrase structure of the target language has been shown to improve the performance of phrase-based Statistical Machine Translation. This paper applies syntactic reordering to English-to-Arabic translation. It introduces reordering rules, and motivates them linguistically. It also studies the effect of combining reordering with Arabic morphological segmentation, a preprocessing technique that has been shown to improve Arabic-English and English-Arabic translation. We report on results in the news text domain, the UN text domain and in the spoken travel domain.

Analytical Chemistry, 1995

The potentiometric anion selectivity of polymer membrane-based electrodes formulated with a palla... more The potentiometric anion selectivity of polymer membrane-based electrodes formulated with a palladium organophosphine complex (benzylbis(triphenylphosphine)palladium(II) chloride) as the membrane active component is examined. The electrode is shown to exhibit a non-Hofmeister selectivity pattern with a significantly enhanced response toward nitrite over the concentration range of 10 microM-10 mM (log-linear range) and a detection limit 5.0 microM. The effect of lipophilic anionic (tetraphenylborate derivatives) and cationic (tetraalkylammonium) site additives within the membrane on the anion selectivity is examined in detail. Addition of both cationic and anionic sites is shown to improve potentiometric anion selectivity, suggesting that the palladium complex may operate simultaneously as a neutral and charged carrier-type ionophore within the polymer membrane phase. Using optimal membrane formulations (with added 20-30 mol % cationic sites), the sensors prepared with the palladium complex do not exhibit proton/hydroxide response in the range of pH 3.5-12, a potential advantage over previously reported nitrite electrodes prepared with Co(III) corrins and porphyrin complexes.

Talanta, 2005

Two different polysaccharides with anticoagulant activities, heparin and chondroitin sulfate, wer... more Two different polysaccharides with anticoagulant activities, heparin and chondroitin sulfate, were used to modify the surface of sodium-selective electrodes based on asymmetric cellulose triacetate (CTA) membranes. The membranes were formulated with sodium ionophore X, anionic additive, and o-nitrophenyl octyl ether. The response behavior of the surface-modified sodium electrodes was compared with that of control CTA, as well as poly(vinyl chloride) (PVC)-based sodium-selective electrodes. It was found that the selectivity coefficients obtained with the surface modified CTA membrane electrodes were slightly higher than those of the control, but in the case of heparin-modified electrodes they still met the requirements for analysis of sodium in physiological fluids within an error of <1%; the corresponding error for chondroitin sulfate-modified electrodes was also <1% except for the case of potassium ion in which the error was 1.3%. Likewise, it was found that other response characteristics, such as detection limit, linear range, slope of the response plot, selectivity pattern, and response time were comparable in both the control and the polysaccharide-modified electrodes. Therefore, the surface modification does not significantly alter the response behavior of the sensors.

Microchimica Acta, 2004

A new sensor for anionic surfactants with a membrane consisting of 33 wt% poly(vinyl chloride) (P... more A new sensor for anionic surfactants with a membrane consisting of 33 wt% poly(vinyl chloride) (PVC), 66 wt% dioctylphthalate (DOP) plasticizer, and 1 wt% tridodecylmethylammonium chloride (TDMAC) is developed and used for flow injection analysis. The sensor displays a working response range of 5Â10 À7 -5Â10 À3 M dodecylbenzene sulfonate (DBS À ) with a Nernstian slope of 58.5 AE 0.2 mV decade À1 , a response time of 30 s and a detection limit of 1.5Â10 À7 M DBS À . Selectivity measurements with different anionic species indicate good membrane selectivity towards DBS À . The sensor is used to measure anionic surfactants (DBS À ) in different wastewater samples, commercial detergent products, and for monitoring the rate of surfactant biodegradation in sewage treatment plants. The results obtained agree fairly well with data obtained by the standard extraction-spectrophotometric method. The proposed potentiometric method offers the advantages of simplicity, accuracy, automation feasibility, and applicability to turbid and colored sample solutions.

Microchimica Acta, 2005

Membrane electrodes based on 2, 2′-dithiobis (benzothiazole), DTBBT, as a neutral carrier for sil... more Membrane electrodes based on 2, 2′-dithiobis (benzothiazole), DTBBT, as a neutral carrier for silver ions are described. Silver-selective membrane electrodes formulated with 2 wt% DTBBT ionophore and 50 mol% TFPB in an FPNPE plasticized poly (vinyl chloride) ...

Journal of Vascular Surgery, 2013

Background Atherosclerosis is thought to be a disease of modern human beings and related to conte... more Background Atherosclerosis is thought to be a disease of modern human beings and related to contemporary lifestyles. However, its prevalence before the modern era is unknown. We aimed to evaluate preindustrial populations for atherosclerosis.

Journal of the American Chemical Society, 2005

A highly selective, sensitive, and reversible fluoride optical sensing film based on aluminum(III... more A highly selective, sensitive, and reversible fluoride optical sensing film based on aluminum(III)octaethylporphyrin as a fluoride ionophore and a lipophilic pH indicator as the optical transducer is described. The fluoride optical sensing films exhibit a submicromolar detection limit and high discrimination for fluoride over several lipophilic anions such as nitrate, perchlorate, and thiocyanate.

Journal of Radioanalytical and Nuclear Chemistry Articles, 1992

The isotope exchange reaction between Na36Cl and triphenyltin chloride in dioxane-water (8020% w/... more The isotope exchange reaction between Na36Cl and triphenyltin chloride in dioxane-water (8020% w/w) and ethanol-water (9010% w/w) mixed solvents have been studied at 25°C, 35°C and 50°C. The exchange reaction was found to proceed via a bimolecular SN2, limiting mechanism with reaction rates depending on the solvent used. Inhibition of the exchange in ethanol-water is probably due to solvation of

IEEE Transactions on Audio, Speech, and Language Processing, 2000

ABSTRACT In many ways, the lexicon remains the Achilles heel of modern automatic speech recognize... more ABSTRACT In many ways, the lexicon remains the Achilles heel of modern automatic speech recognizers. Unlike stochastic acoustic and language models that learn the values of their parameters from training data, the baseform pronunciations of words in a recognizer's lexicon are typically specified manually, and do not change, unless they are edited by an expert. Our work presents a novel generative framework that uses speech data to learn stochastic lexicons, thereby taking a step towards alleviating the need for manual intervention and automatically learning high-quality pronunciations for words. We test our model on continuous speech in a weather information domain. In our experiments, we see significant improvements over a manually specified “expert-pronunciation” lexicon. We then analyze variations of the parameter settings used to achieve these gains.

Electroanalysis, 2000

Preparation, characterization, origin of response and applications of a potentiometric sensor bas... more Preparation, characterization, origin of response and applications of a potentiometric sensor based on the use of a zirconium titanium phosphate (ZTP)-epoxy membrane are described. Zirconium titanium phosphate (ZTP) cationic exchanger embedded in an epoxy matrix is converted into a hydrated zirconium oxide anion exchanger which responds to many anionic species. A sensor based on this exchanger exhibits near-Nernstian response for nitrite and other anions over the concentration range 10 71 ±10 75 M. Under optimized conditions, the gas dialyzera¯ow-injection system provides a throughput of ca. 60 samples per hour with a high selectivity for nitrite ion over most common anions and acidic gas releasing species. Determination of nitrite at levels as low as 5610 74 M or less in the presence of sul®te and sul®de ions is performed by using a modi®ed carrier buffer stream (10 72 M MES, pH 5.5 containing formaldehyde and Pb 2 ). Signi®cant advantages are offered by the ZTP-epoxy membrane based sensor including a long 1ifetime ( b 2 years), excellent stability and reproducibility (ca. 1 mV), fast response time (`30 s), wide pH working range (pH 4.5±8), low detection limit (4610 75 M) and high thermal stability(up to 80 C).

Proceedings of the 10th …, 2008

... 3. SYSTEM DEVELOPMENT WITH WAMI The WAMI toolkit supports two main threads of devel ... guage... more ... 3. SYSTEM DEVELOPMENT WITH WAMI The WAMI toolkit supports two main threads of devel ... guage model for the speech recognizer, and any application-specific processing modules for handling ... component runs on the client to capture a user's speech and stream it to the ...

Analytical Sciences, 2009

A poly(vinyl chloride) matrix membrane sensor for the selective determination of thiocyanate has ... more A poly(vinyl chloride) matrix membrane sensor for the selective determination of thiocyanate has been developed based on the use of copper(II)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex (Cu-PADAP) as a novel charged carrier, and o-nitrophenyloctyl ether (o-NPOE) as a solvent mediator. The sensor displays a significantly enhanced response towards SCN(-) ions over the concentration range 7.0 x 10(-6) to 1.0 x 10(-2) mol L(-1) with a detection limit of 5.6 x 10(-6) mol L(-1) and a calibration slope of -57.5 +/- 0.5 mV decade(-1). The sensor exhibits a long life-span, long-term stability, high reproducibility, and a fast response time. The selectivity coefficients of some anions were calculated using the separate solutions method, and found to be in the following order: SCN(-) > ClO(4)(-) > I(-) > Sal(-) > NO(2)(-) > Br(-) > NO(3)(-) = CH(3)COO(-) > Cl(-) > SO(4)(2-) = PO(4)(3-). The effects of the pH and ionic membrane additives (e.g. tridodecylmethylammonium chloride, TDMAC and potassium tetrakis[bis(3,5-trifluoromethyl)phenyl] borate, KTFPB) were examined. The sensor was used for the determination of SCN(-) ions in saliva and urine samples collected from some smoker and non-smoker donors. The developed sensor was also applied to determine the cyanide content in electroplating waste water samples after its conversion into thiocyanate. The application of the sensor to monitor the potentiometric titration of Ag(+) and Hg(2+) using SCN(-) resulted in sharp inflection breaks at the equivalent points. The data obtained using the proposed sensor correlate very well with results collected using the standard methods of thiocyanate, cyanide and metal analysis.

Analytical Chemistry, 2002

The development of an integrated analysis system for small ions based on ion-selective optodes an... more The development of an integrated analysis system for small ions based on ion-selective optodes and centrifugal microfluidics is reported. The performance of this system was evaluated through five-point calibration plots for two types of optode membranes, one being cation-selective and the other anion-selective, which were incorporated into a microfluidics platform on which fluid motion is induced via angular rotation. Additionally, the application of the microfluidic platform to ion analysis is studied via a two-point calibration protocol used to quantify an unknown sample. Calibrant solutions are delivered from reservoirs fabricated onto the platform to a measuring area that contains the optode membrane, with a change in membrane fluorescence being monitored. This work demonstrates the first instance of a microfluidic-based analysis system with detection based on ion-selective optode membranes monitored with fluorescence transduction. Furthermore, in addition to employing a standard excitation source where a fiber-optic probe is coupled to a tungsten-halogen lamp, laser diodes such as those employed in portable CD/DVD players were studied as excitation sources to enhance the observed fluorescence signals.

Analytical Chemistry, 2002

The hydrogelpoly(2-methacryloyloxyethylphosphorylcholine-co-butyl methacrylate), or poly(MPC-co-B... more The hydrogelpoly(2-methacryloyloxyethylphosphorylcholine-co-butyl methacrylate), or poly(MPC-co-BMA), was used as a coating for polyurethane- and poly(vinyl chloride)-based membranes to develop ion-selective electrodes (ISEs) with enhanced blood compatibility. Adverse interactions of poly(MPC-co-BMA) with blood were diminished due to the phosphorylcholine functionalities of the hydrogel, which mimic the phospholipid polar groups present on the surface of many cell membranes. As demonstrated by immunostaining, hydrogel-coated PVC membranes soaked in platelet-rich plasma showed less adhesion and activation of platelets than uncoated PVC membranes, indicating an improvement in biocompatibility owing to the hydrogel. Furthermore, little differences in the potentiometric response characteristics, e.g., slope, detection limit, and selectivity, of ISEs employing uncoated and coated membranes were observed.

Analytical Chemistry, 2001

A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics pl... more A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics platform and ion-selective optode membranes is described. The microfluidic architecture is composed of channels, five solution reservoirs, a measuring chamber, and a waste reservoir manufactured onto a disk-shaped substrate of poly(methyl methacrylate). Ion-selective optode membranes, composed of plasticized poly(vinyl chloride) impregnated with an ionophore, a proton chromoionophore, and a lipophilic anionic additive, were cast, with a spin-on device, onto a support layer and then immobilized on the disk. Fluid propulsion is achieved by the centrifugal force that results from spinning the disk, while a system of valves is built onto the disk to control flow. These valves operate based on fluid properties and fluid/substrate interactions and are controlled by the angular frequency of rotation. With this system, we have been able to deliver calibrant solutions, washing buffers, or "test" solutions to the measuring chamber where the optode membrane is located. An analysis system based on a potassium-selective optode has been characterized. Results indicate that optodes immobilized on the platform demonstrate theoretical responses in an absorbance mode of measurement. Samples of unknown concentration can be quantified to within 3% error by fitting the response function for a given optode membrane using an acid (for measuring the signal for a fully protonated chromoionophore), a base (for fully deprotonated chromoionophore), and two standard solutions. Further, the ability to measure ion concentrations by employing one standard solution in conjunction with acid and base and with two standards alone were studied to delineate whether the current architecture could be simplified. Finally, the efficacy of incorporating washing steps into the calibration protocol was investigated.

Analytical Chemistry, 2001

The susceptibility of segmented polyurethanes (SPUs) to in vivo oxidative cleavage and hydrolysis... more The susceptibility of segmented polyurethanes (SPUs) to in vivo oxidative cleavage and hydrolysis constitutes a drawback in the use of these materials in the fabrication of implantable devices. The introduction of poly(dimethylsiloxane) (PDMS) groups into the polymer main chain has been previously reported to enhance the stability of SPUs. Herein, we evaluated the use of BioSpan-S, a silicone-modified SPU, in the design of membranes for cation-selective electrodes. The resulting electrodes exhibited good potentiometric response with all of the tested ionophores (valinomycin, sodium ionophore X, and nonactin). The obtained selectivity coefficients meet the selectivity requirements for the determination of sodium and potassium in blood. Moreover, as reflected by SEM studies, membranes prepared with BioSpan-S showed less adhesion of platelets than membranes prepared with conventional poly(vinyl chloride) (PVC). These results lead to the conclusion that BioSpan-S would be an appropriate candidate for the fabrication of implantable ion-selective electrodes.

Analytical Chemistry, 2000

Ionophore topology has a profound effect on the behavior of ion-selective electrodes. This is dem... more Ionophore topology has a profound effect on the behavior of ion-selective electrodes. This is demonstrated with a new class of ionophores that incorporates aminochromenone moieties linked through urea spacers to different scaffolds that preorganize the ionophore binding cleft into tripodal topologies. Tris(2-aminoethylamine) and cis-1,3,5-tris(aminomethyl)cyclohexane were employed as the scaffolds. The two differ in their rigidity and in the size of ionophore cavity that they create. The electrodes based on the ionophore that incorporates the tris(2aminoethylamine) scaffold show anti-Hofmeister behavior with an improved selectivity for sulfate. In contrast, the ionophore with the cis-1,3,5-tris(aminomethyl)cyclohexane scaffold exhibits a more Hofmeister-like response.