Proceedings of the 6th International Wireless Communications and Mobile Computing Conference on ZZZ - IWCMC '10, 2010
We describe a general-purpose distributed system capable of traceback of malicious flow trajector... more We describe a general-purpose distributed system capable of traceback of malicious flow trajectories in the wide area despite possible source IP spoofing. Our system requires the placement of agents on a subset of the inter-autonomous system (AS) links of the Internet. Agents are instrumented with a uniform notion of attack criterion. Deployed, these agents implement a self-organizing, decentralized mechanism that is capable of reconstructing topological and temporal information about malicious flows. For example, when the attack criterion is taken to be based on excessive TCP connection establishment traffic to a destination, the system becomes a traceback service for distributed denial of service (DDoS) attacks. As another special case, when the attack criterion is taken to be based on malicious payload signature match as defined by an intrusion detection system (IDS), the agents provide a service for tracing malware propagation pathways. The main contribution of this paper, is to demonstrate that the proposed system is effective at recovering malicious flow structure even at moderate levels of deployment in large networks, including within the present Internet topology.
In this paper, we propose a non-commutative keyexchange scheme which generalizes the classical El... more In this paper, we propose a non-commutative keyexchange scheme which generalizes the classical ElGamal Cipher to polycyclic groups. We describe the criteria for groups which would provide good candidates for such cryptosystems, we also examine the complexity of the decision problems related to these key exchange.
We develop a new dynamic scheme which continuously redistributes a fixed power budget among the w... more We develop a new dynamic scheme which continuously redistributes a fixed power budget among the wireless nodes participating in a multi-hop wireless connection, with the objective of minimizing the end-to-end wireless connection bit error rate (BER). We compare the efficacy of our scheme with two static schemes: one that distributes power uniformly, and one that distributes it proportionally to the square of inter-hop distances. In our experiments we observed that the dynamic allocation scheme achieved superior performance, reducing BER by using its ability to distribute the power budget. We quantified the sensitivity of this performance improvement to various environmental parameters, including power budget size, geographic distance, and the number of hops.
We present the results of simulation experiments that compare end-to-end error management (used i... more We present the results of simulation experiments that compare end-to-end error management (used in controlled access MAC protocols) against hop-by-hop error management (used in random access MAC protocols). Our experiments are novel in that we restrict both MAC schemes to identical power budgets and power distribution strategies. By making such a normalized comparison, we observe that end-to-end schemes are more effective than hop-by-hop schemes at reducing connection BER. We are also able to quantify the sensitivity of this relative advantage to various environmental parameters, including power budget size, geographic distance, the number of hops, and power distribution scheme.
An effective protocol has been developed that allows the smooth protodecarboxylation of diversely... more An effective protocol has been developed that allows the smooth protodecarboxylation of diversely functionalized aromatic carboxylic acids within 5-15 min. In the presence of at most 5 mol % of an inexpensive catalyst generated in situ from copper(I) oxide and 1,10-phenanthroline, even nonactivated benzoates were converted in high yields and with great preparative ease.
Ingestion of corrosive substances can lead to strictures of the esophagus and stomach. Cicatrizat... more Ingestion of corrosive substances can lead to strictures of the esophagus and stomach. Cicatrization of the lower part of the esophagus can entrap vagal fibers in the process of fibrosis. The aim of the present study was to evaluate gallbladder dysfunction as a sequel to vagal damage in patients with corrosive-induced esophageal strictures. The cephalic phase of gallbladder emptying was stimulated by modified sham feeding according to the chew-and-spit method. Gallbladder volume was measured by ultrasonography using the ellipsoid method after an overnight fast and every 15 min for a period of 90 min after sham feeding in 22 patients and 10 controls. Mean fasting gallbladder volume was significantly greater in patients than in controls (22.09± 9.78 vs. 14.61± 4.42 ml; P = 0.025). After sham feeding the gallbladder ejection fraction was significantly lower in patients than in controls (32.86± 17.21 vs. 49.40± 7.86%; P = 0.007). Patients with cicatrization in the distal one-third of the esophagus had a greater basal gallbladder volume (24.57± 9.2 ml) and significantly lower ejection fraction (20.47± 8.9%) than patients with strictures at other sites (gallbladder volume, 18.50± 10.69 ml; ejection fraction, 47.48± 13.3%; P = 0.001). In conclusion, patients with corrosive-induced esophageal strictures, especially those in the distal one-third, had an increased fasting gallbladder volume and decreased cephalic phase of gallbladder emptying, pointing to impaired vagal cholinergic transmission, possibly due to vagal entrapment in the cicatrization process.
International Conference on Intelligent Systems, Modelling and Simulation, 2010
We investigate the stability properties of a novel agent-based system for the detection of networ... more We investigate the stability properties of a novel agent-based system for the detection of network bandwidth-based distributed denial of service (DDoS) attacks. The proposed system provides a description of the structure of flows which comprise the DDoS attack. In doing so, it facilitates DDoS mitigation at or near attack traffic sources. The constituent agents within the system operate at the inter autonomous system (AS) level, comprising a distributed collection of IP-layer network taps which self-organize in response to attack flows. We formalize the notion of stability for the proposed system, and show how we can use simulation to identify regions of instability within the system's parameter space. We then modify our system design to circumvent the uncovered singularities, and demonstrate the efficacy and tradeoffs implicit in our redesigned system.
Global Telecommunications Conference, . GLOBECOM . IEEE, 2006
We develop a new dynamic scheme which continuously redistributes a fixed power budget among the w... more We develop a new dynamic scheme which continuously redistributes a fixed power budget among the wireless nodes participating in a multi-hop wireless connection, with the objective of minimizing the end-to-end wireless connection bit error rate (BER). We compare the efficacy of our scheme with two static schemes: one that distributes power uniformly, and one that distributes it proportionally to the square of inter-hop distances. In our experiments we observed that the dynamic allocation scheme achieved superior performance, reducing BER by using its ability to distribute the power budget. We quantified the sensitivity of this performance improvement to various environmental parameters, including power budget size, geographic distance, and the number of hops.
International Conference on Wireless Communications and Mobile Computing, 2006
In this paper we present and evaluate a new technique to lower packet-level error rates of applic... more In this paper we present and evaluate a new technique to lower packet-level error rates of application layer connections in wireless ad-hoc networks. In our scheme, data packets submitted at a connection's source are checksummed and replicated, flowing breadth-first across an overlay network towards the destination. The destination delivers the first error-free copy of each packet, in order, to the application layer, dropping packets that are corrupt or duplicate. Specifically in this paper, we consider overlays consisting of multiple parallel multi-hop paths. We provide an algorithm which determines the optimal parameters of the overlay in terms of the number of paths, their lengths, and specific routes. We demonstrate experimentally that the proposed scheme significantly outperforms traditional routing and power allocation approaches in terms of bit error rate, even when the comparison is made under identical power consumption constraints.
The aim of this study was to determine the stability of viral load over an extended period in pat... more The aim of this study was to determine the stability of viral load over an extended period in patients with chronic hepatitis C virus (HCV). Sequential serum specimens collected from fourteen non-alcoholic adult patients with chronic HCV between 1990 and 1997 were tested retrospectively for HCV RNA levels by branched DNA assay (Quantiplex HCV RNA 2.0 [Chiron Diagnostics, Emeryville, CA]). A minimum of three serum samples was obtained at various intervals from each patient. None of the patients received antiviral therapy. Liver biopsies, available for 10 of 14 patients, showed mild or moderate hepatitis in seven and cirrhosis in three (one developed cirrhosis during follow-up). RIBA strip immunoassay showed that 7, 3, and 4 patients had viral genotypes 1, 2, and 3, respectively. The follow-up time averaged 5.3 years (range, 3.7 to 6.6 years). Eight patients (57.2%) showed increased viral levels from baseline to follow-up, the remaining six patients (42.8%) showed decreased viral levels. The three cirrhotic patients had the highest viral levels over time. The mean change was a 0.29-fold decrease (median, −5.08; range, −17.49 to +7.32). A less than twofold change in either direction was demonstrated for six patients (42.8%), and a less than threefold change was demonstrated for 10 patients (71.4%). Variation from baseline to last follow-up as calculated by log determination showed that the viremic load varied less than one log10 in all but one individual. These results show that viral load remains relatively stable over prolonged periods in most untreated patients with chronic hepatitis C.
Bile duct epithelia contain an abundance of carbonic anhydrase. Antibodies to this enzyme have be... more Bile duct epithelia contain an abundance of carbonic anhydrase. Antibodies to this enzyme have been described in autoimmune disorders. Serum from patients with immune-mediated liver diseases was studied to determine whether antibodies to carbonic anhydrase II and/or pyruvate dehydrogenase could distinguish autoimmune cholangitis as immunologically distinct from primary biliary cirrhosis. Antibody assays to carbonic anhydrase II (Western blot) and pyruvate dehydrogenase (flow cytometry) were performed on the sera of patients with autoimmune cholangitis (6), primary biliary cirrhosis (12), primary sclerosing cholangitis (12), autoimmune hepatitis (12), and control (Gilbert syndrome; 8). Reactivity to carbonic anhydrase II was detected in 5 of 6 patients with autoimmune cholangitis, 1 of 12 patients with primary biliary cirrhosis, 1 of 12 patients with autoimmune hepatitis, and no other patients. Individuals with autoimmune cholangitis were more likely than the other patients to be reactive to carbonic anhydrase II (P < 0.001). Patients with primary biliary cirrhosis were more reactive to pyruvate dehydrogenase compared with all other groups (P < 0.001). An antibody to human carbonic anhydrase II is frequently detected in the sera of patients with autoimmune cholangitis and is uncommon or not present in other cholangiopathies. These data provide evidence that autoimmune cholangitis and primary biliary cirrhosis represent distinct entities with unique patterns of immunoreactivity.
... Purchase Intention: An Empirical Study Reshma Farhat, Aligarh Muslim University, India Bilal ... more ... Purchase Intention: An Empirical Study Reshma Farhat, Aligarh Muslim University, India Bilal Mustafa Khan, Aligarh Muslim University, India ... with some people having a generally higher preferred stimulation level than others (Raju, 1980; Zuckerman, 1994). ...
Abstract In wireless sensor networks (WSN) the medium access control CSMA/CA uses binary exponen... more Abstract In wireless sensor networks (WSN) the medium access control CSMA/CA uses binary exponential backoff (BEB) algorithm to minimize collision among the contending nodes. The range of backoff exponent is limited to very small values. This causes channel access ...
Proceedings of the 6th International Wireless Communications and Mobile Computing Conference on ZZZ - IWCMC '10, 2010
We describe a general-purpose distributed system capable of traceback of malicious flow trajector... more We describe a general-purpose distributed system capable of traceback of malicious flow trajectories in the wide area despite possible source IP spoofing. Our system requires the placement of agents on a subset of the inter-autonomous system (AS) links of the Internet. Agents are instrumented with a uniform notion of attack criterion. Deployed, these agents implement a self-organizing, decentralized mechanism that is capable of reconstructing topological and temporal information about malicious flows. For example, when the attack criterion is taken to be based on excessive TCP connection establishment traffic to a destination, the system becomes a traceback service for distributed denial of service (DDoS) attacks. As another special case, when the attack criterion is taken to be based on malicious payload signature match as defined by an intrusion detection system (IDS), the agents provide a service for tracing malware propagation pathways. The main contribution of this paper, is to demonstrate that the proposed system is effective at recovering malicious flow structure even at moderate levels of deployment in large networks, including within the present Internet topology.
In this paper, we propose a non-commutative keyexchange scheme which generalizes the classical El... more In this paper, we propose a non-commutative keyexchange scheme which generalizes the classical ElGamal Cipher to polycyclic groups. We describe the criteria for groups which would provide good candidates for such cryptosystems, we also examine the complexity of the decision problems related to these key exchange.
We develop a new dynamic scheme which continuously redistributes a fixed power budget among the w... more We develop a new dynamic scheme which continuously redistributes a fixed power budget among the wireless nodes participating in a multi-hop wireless connection, with the objective of minimizing the end-to-end wireless connection bit error rate (BER). We compare the efficacy of our scheme with two static schemes: one that distributes power uniformly, and one that distributes it proportionally to the square of inter-hop distances. In our experiments we observed that the dynamic allocation scheme achieved superior performance, reducing BER by using its ability to distribute the power budget. We quantified the sensitivity of this performance improvement to various environmental parameters, including power budget size, geographic distance, and the number of hops.
We present the results of simulation experiments that compare end-to-end error management (used i... more We present the results of simulation experiments that compare end-to-end error management (used in controlled access MAC protocols) against hop-by-hop error management (used in random access MAC protocols). Our experiments are novel in that we restrict both MAC schemes to identical power budgets and power distribution strategies. By making such a normalized comparison, we observe that end-to-end schemes are more effective than hop-by-hop schemes at reducing connection BER. We are also able to quantify the sensitivity of this relative advantage to various environmental parameters, including power budget size, geographic distance, the number of hops, and power distribution scheme.
An effective protocol has been developed that allows the smooth protodecarboxylation of diversely... more An effective protocol has been developed that allows the smooth protodecarboxylation of diversely functionalized aromatic carboxylic acids within 5-15 min. In the presence of at most 5 mol % of an inexpensive catalyst generated in situ from copper(I) oxide and 1,10-phenanthroline, even nonactivated benzoates were converted in high yields and with great preparative ease.
Ingestion of corrosive substances can lead to strictures of the esophagus and stomach. Cicatrizat... more Ingestion of corrosive substances can lead to strictures of the esophagus and stomach. Cicatrization of the lower part of the esophagus can entrap vagal fibers in the process of fibrosis. The aim of the present study was to evaluate gallbladder dysfunction as a sequel to vagal damage in patients with corrosive-induced esophageal strictures. The cephalic phase of gallbladder emptying was stimulated by modified sham feeding according to the chew-and-spit method. Gallbladder volume was measured by ultrasonography using the ellipsoid method after an overnight fast and every 15 min for a period of 90 min after sham feeding in 22 patients and 10 controls. Mean fasting gallbladder volume was significantly greater in patients than in controls (22.09± 9.78 vs. 14.61± 4.42 ml; P = 0.025). After sham feeding the gallbladder ejection fraction was significantly lower in patients than in controls (32.86± 17.21 vs. 49.40± 7.86%; P = 0.007). Patients with cicatrization in the distal one-third of the esophagus had a greater basal gallbladder volume (24.57± 9.2 ml) and significantly lower ejection fraction (20.47± 8.9%) than patients with strictures at other sites (gallbladder volume, 18.50± 10.69 ml; ejection fraction, 47.48± 13.3%; P = 0.001). In conclusion, patients with corrosive-induced esophageal strictures, especially those in the distal one-third, had an increased fasting gallbladder volume and decreased cephalic phase of gallbladder emptying, pointing to impaired vagal cholinergic transmission, possibly due to vagal entrapment in the cicatrization process.
International Conference on Intelligent Systems, Modelling and Simulation, 2010
We investigate the stability properties of a novel agent-based system for the detection of networ... more We investigate the stability properties of a novel agent-based system for the detection of network bandwidth-based distributed denial of service (DDoS) attacks. The proposed system provides a description of the structure of flows which comprise the DDoS attack. In doing so, it facilitates DDoS mitigation at or near attack traffic sources. The constituent agents within the system operate at the inter autonomous system (AS) level, comprising a distributed collection of IP-layer network taps which self-organize in response to attack flows. We formalize the notion of stability for the proposed system, and show how we can use simulation to identify regions of instability within the system's parameter space. We then modify our system design to circumvent the uncovered singularities, and demonstrate the efficacy and tradeoffs implicit in our redesigned system.
Global Telecommunications Conference, . GLOBECOM . IEEE, 2006
We develop a new dynamic scheme which continuously redistributes a fixed power budget among the w... more We develop a new dynamic scheme which continuously redistributes a fixed power budget among the wireless nodes participating in a multi-hop wireless connection, with the objective of minimizing the end-to-end wireless connection bit error rate (BER). We compare the efficacy of our scheme with two static schemes: one that distributes power uniformly, and one that distributes it proportionally to the square of inter-hop distances. In our experiments we observed that the dynamic allocation scheme achieved superior performance, reducing BER by using its ability to distribute the power budget. We quantified the sensitivity of this performance improvement to various environmental parameters, including power budget size, geographic distance, and the number of hops.
International Conference on Wireless Communications and Mobile Computing, 2006
In this paper we present and evaluate a new technique to lower packet-level error rates of applic... more In this paper we present and evaluate a new technique to lower packet-level error rates of application layer connections in wireless ad-hoc networks. In our scheme, data packets submitted at a connection's source are checksummed and replicated, flowing breadth-first across an overlay network towards the destination. The destination delivers the first error-free copy of each packet, in order, to the application layer, dropping packets that are corrupt or duplicate. Specifically in this paper, we consider overlays consisting of multiple parallel multi-hop paths. We provide an algorithm which determines the optimal parameters of the overlay in terms of the number of paths, their lengths, and specific routes. We demonstrate experimentally that the proposed scheme significantly outperforms traditional routing and power allocation approaches in terms of bit error rate, even when the comparison is made under identical power consumption constraints.
The aim of this study was to determine the stability of viral load over an extended period in pat... more The aim of this study was to determine the stability of viral load over an extended period in patients with chronic hepatitis C virus (HCV). Sequential serum specimens collected from fourteen non-alcoholic adult patients with chronic HCV between 1990 and 1997 were tested retrospectively for HCV RNA levels by branched DNA assay (Quantiplex HCV RNA 2.0 [Chiron Diagnostics, Emeryville, CA]). A minimum of three serum samples was obtained at various intervals from each patient. None of the patients received antiviral therapy. Liver biopsies, available for 10 of 14 patients, showed mild or moderate hepatitis in seven and cirrhosis in three (one developed cirrhosis during follow-up). RIBA strip immunoassay showed that 7, 3, and 4 patients had viral genotypes 1, 2, and 3, respectively. The follow-up time averaged 5.3 years (range, 3.7 to 6.6 years). Eight patients (57.2%) showed increased viral levels from baseline to follow-up, the remaining six patients (42.8%) showed decreased viral levels. The three cirrhotic patients had the highest viral levels over time. The mean change was a 0.29-fold decrease (median, −5.08; range, −17.49 to +7.32). A less than twofold change in either direction was demonstrated for six patients (42.8%), and a less than threefold change was demonstrated for 10 patients (71.4%). Variation from baseline to last follow-up as calculated by log determination showed that the viremic load varied less than one log10 in all but one individual. These results show that viral load remains relatively stable over prolonged periods in most untreated patients with chronic hepatitis C.
Bile duct epithelia contain an abundance of carbonic anhydrase. Antibodies to this enzyme have be... more Bile duct epithelia contain an abundance of carbonic anhydrase. Antibodies to this enzyme have been described in autoimmune disorders. Serum from patients with immune-mediated liver diseases was studied to determine whether antibodies to carbonic anhydrase II and/or pyruvate dehydrogenase could distinguish autoimmune cholangitis as immunologically distinct from primary biliary cirrhosis. Antibody assays to carbonic anhydrase II (Western blot) and pyruvate dehydrogenase (flow cytometry) were performed on the sera of patients with autoimmune cholangitis (6), primary biliary cirrhosis (12), primary sclerosing cholangitis (12), autoimmune hepatitis (12), and control (Gilbert syndrome; 8). Reactivity to carbonic anhydrase II was detected in 5 of 6 patients with autoimmune cholangitis, 1 of 12 patients with primary biliary cirrhosis, 1 of 12 patients with autoimmune hepatitis, and no other patients. Individuals with autoimmune cholangitis were more likely than the other patients to be reactive to carbonic anhydrase II (P < 0.001). Patients with primary biliary cirrhosis were more reactive to pyruvate dehydrogenase compared with all other groups (P < 0.001). An antibody to human carbonic anhydrase II is frequently detected in the sera of patients with autoimmune cholangitis and is uncommon or not present in other cholangiopathies. These data provide evidence that autoimmune cholangitis and primary biliary cirrhosis represent distinct entities with unique patterns of immunoreactivity.
... Purchase Intention: An Empirical Study Reshma Farhat, Aligarh Muslim University, India Bilal ... more ... Purchase Intention: An Empirical Study Reshma Farhat, Aligarh Muslim University, India Bilal Mustafa Khan, Aligarh Muslim University, India ... with some people having a generally higher preferred stimulation level than others (Raju, 1980; Zuckerman, 1994). ...
Abstract In wireless sensor networks (WSN) the medium access control CSMA/CA uses binary exponen... more Abstract In wireless sensor networks (WSN) the medium access control CSMA/CA uses binary exponential backoff (BEB) algorithm to minimize collision among the contending nodes. The range of backoff exponent is limited to very small values. This causes channel access ...
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