The intriguing notion of a Zero-Knowledge Proof System has been introduced by Goldwasser, Micali ... more The intriguing notion of a Zero-Knowledge Proof System has been introduced by Goldwasser, Micali and Rackoff [GMR] and its wide applicability has been demonstrated by Goldreich, Micali and Wigderson [GMW1]-[GMW2]. Based on complexity theoretic assumptions, Zero-Knowledge Proof Systems exist, provided that (i) The prover and the verifier are allowed to talk back and forth. (ii) The verifier is allowed to
We present 850 and 450 μ m continuum images of 9 infrared dark clouds (IRDCs; Egan et al. 1998, A... more We present 850 and 450 μ m continuum images of 9 infrared dark clouds (IRDCs; Egan et al. 1998, ApJ, 494, L199) taken with the Submillimeter Common-User Bolometer Array (SCUBA) on the JCMT. The IRDCs appear to be very large (1-10 pc diameter) molecular cores with gas densities > 106 cm-3 and temperatures around 10 K. Approximately 5000 IRDCs have been identified in a survey of the inner Galactic Plane with the distribution of IRDCs peaking at the longitudes of spiral arm tangent points and the molecular ring. All nine clouds were detected as strong submillimeter sources with peak flux densities of 1 Jy/beam at 850 μ m. In general, the submillimeter emission follows the mid-infrared extinction and H2CO rotational line emission morphologies (Carey et al. 1998, ApJ, 508, 721). The submillimeter data reveals substructure in the IRDCs including bright 850 μ m knots. The observed H2CO line profiles are non-Gaussian suggesting the presence of molecular outflows in some of the IRDCs. It is likely that the 850 μ m emission peaks are either Class 0 protostars or pre-protostellar objects. Estimates of the dust mass and temperature will be compared to previous estimates of gas mass and temperature for IRDCs.
We have observed molecular species of high, intermediate and low volatility towards the mid-infra... more We have observed molecular species of high, intermediate and low volatility towards the mid-infrared extinction maxima of three infrared-dark clouds (IRDCs) using the NRAO/UASO 12m telescope and the JCMT. IRDCs are large molecular cores with significant (1-3) magnitudes of extinction from 8-25 microns. They are characterized by large columns of dense (N(H2) ˜106 cm-3), cold (T ˜7-20 K) molecular gas. Significant depletions of H2CO in IRDCs have been previously reported in Carey et al. (1998). Isotopomers of CO, HCO+, CS, SO, N2H+, HCO2+, SO2, NH2D and HCN are being used to measure molecular depletion and grain desorption rates in the interiors of IRDCs. Preliminary results indicate that molecules of lower volatility are more depleted than the higher volatility species. Sulphur bearing molecules with the exception of CS are significantly depleted.
Laboratory work has established that PO is likely to be the most abundant molecule containing pho... more Laboratory work has established that PO is likely to be the most abundant molecule containing phosphorus in dense interstellar clouds. Using recently measured microwave frequencies, the authors have searched for the J = 5/2→3/2 transition of PO at 109 GHz in four galactic sources. The limit in DR 21(OH), in particular, suggests that phosphorus may be severely depleted in dense molecular clouds.
The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the ... more The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the diffuse 8micron Galactic background, and in emission from cold dust at 850micron. Detailed comparison of the dust properties at these two wavelengths reveals that standard models for the diffuse interstellar dust in the Galaxy are not consistent with the observations. The ratio of absorption coefficients within the cloud is kappa_8/kappa_850 <= 1010, which is well below that expected for the diffuse ISM where kappa_8/kappa_850 ~ 1700. This may be due to the formation of ice mantles on the dust and grain coagulation, both of which are expected within dense regions of molecular clouds. The 850micron emission probes the underlying radial structure of the filament. The profile is well represented by a marginally resolved central region and a steeply falling envelope, with Sigma(r) proportional to r^(-a), where a <= 3, indicating that G11.11-0.12 is the first observed filament with a profile similar to that of a non-magnetic isothermal cylinder.
Proceedings of the twentieth annual ACM symposium on Theory of computing - STOC '88, 1988
Abstract: We exhibit randomized Byzantine agreement (BA) algo-rithms achieving optimal running ti... more Abstract: We exhibit randomized Byzantine agreement (BA) algo-rithms achieving optimal running time and fault tolerance against all types of adversaries ever considered in the lit terature. Our BA algorithms do not require trusted par-ties, preprocessing, or non-consnuctive ...
Proceedings of The International Astronomical Union, 2005
SiO emission is a good chemical tracer of shocked gas in the ISM because the molecular abundance ... more SiO emission is a good chemical tracer of shocked gas in the ISM because the molecular abundance of SiO is enhanced behind strong shocks. Our observations of SiO (6-5) with the JCMT identified strongly shocked gas in dense clumps within MSX Infrared-Dark Clouds. We interpreted the presence of shocked gas as evidence for bipolar outflows from low-mass YSOs embedded in
Linearly distributed methanol masers are associated with young massive stars and have been genera... more Linearly distributed methanol masers are associated with young massive stars and have been generally hypothesized to trace edge-on circumstellar disks around them. Several of these sources have been recently imaged in near-infrared H2 emission (an outflow indicator) and it was discovered that the methanol masers were often aligned with the position angle of H2 emission on the fields. It was therefore argued that this is evidence that the methanol masers are instead associated with outflows from these young massive stars. However, because H2 can be excited by means other than outflow, we have undertaken a series of observations in an independent outflow indicator, namely SiO. We performed single-dish observations with the JCMT to detect SiO (6-5) in 7 out of 9 fields from the H2 survey. Wide wings were found in the SiO lines, supporting the outflow hypothesis. Interferometric follow-up observations of SiO (2-1) with the ATCA at high-spatial resolution have now been analyzed for 4 of ...
Odin has successfully observed the molecular coreOph A in the 572.5 GHz rotational ground state l... more Odin has successfully observed the molecular coreOph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 ! 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 × 10−9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 × 10−10.
Proceedings of the twentieth annual ACM symposium on Theory of computing - STOC '88, 1988
... Actually, as recently pointed out by Ben-Or, Gol-dreich, Goldwasser, Hastad, Micali and Rogaw... more ... Actually, as recently pointed out by Ben-Or, Gol-dreich, Goldwasser, Hastad, Micali and Rogaway [BGGHMR], the same is true for all languages in IP; also, as pointed out by Blum [B2], any theorem at all admits a proof that conveys zero-knowledge other than betraying its own ...
The intriguing notion of a Zero-Knowledge Proof System has been introduced by Goldwasser, Micali ... more The intriguing notion of a Zero-Knowledge Proof System has been introduced by Goldwasser, Micali and Rackoff [GMR] and its wide applicability has been demonstrated by Goldreich, Micali and Wigderson [GMW1]-[GMW2]. Based on complexity theoretic assumptions, Zero-Knowledge Proof Systems exist, provided that (i) The prover and the verifier are allowed to talk back and forth. (ii) The verifier is allowed to
We present 850 and 450 μ m continuum images of 9 infrared dark clouds (IRDCs; Egan et al. 1998, A... more We present 850 and 450 μ m continuum images of 9 infrared dark clouds (IRDCs; Egan et al. 1998, ApJ, 494, L199) taken with the Submillimeter Common-User Bolometer Array (SCUBA) on the JCMT. The IRDCs appear to be very large (1-10 pc diameter) molecular cores with gas densities > 106 cm-3 and temperatures around 10 K. Approximately 5000 IRDCs have been identified in a survey of the inner Galactic Plane with the distribution of IRDCs peaking at the longitudes of spiral arm tangent points and the molecular ring. All nine clouds were detected as strong submillimeter sources with peak flux densities of 1 Jy/beam at 850 μ m. In general, the submillimeter emission follows the mid-infrared extinction and H2CO rotational line emission morphologies (Carey et al. 1998, ApJ, 508, 721). The submillimeter data reveals substructure in the IRDCs including bright 850 μ m knots. The observed H2CO line profiles are non-Gaussian suggesting the presence of molecular outflows in some of the IRDCs. It is likely that the 850 μ m emission peaks are either Class 0 protostars or pre-protostellar objects. Estimates of the dust mass and temperature will be compared to previous estimates of gas mass and temperature for IRDCs.
We have observed molecular species of high, intermediate and low volatility towards the mid-infra... more We have observed molecular species of high, intermediate and low volatility towards the mid-infrared extinction maxima of three infrared-dark clouds (IRDCs) using the NRAO/UASO 12m telescope and the JCMT. IRDCs are large molecular cores with significant (1-3) magnitudes of extinction from 8-25 microns. They are characterized by large columns of dense (N(H2) ˜106 cm-3), cold (T ˜7-20 K) molecular gas. Significant depletions of H2CO in IRDCs have been previously reported in Carey et al. (1998). Isotopomers of CO, HCO+, CS, SO, N2H+, HCO2+, SO2, NH2D and HCN are being used to measure molecular depletion and grain desorption rates in the interiors of IRDCs. Preliminary results indicate that molecules of lower volatility are more depleted than the higher volatility species. Sulphur bearing molecules with the exception of CS are significantly depleted.
Laboratory work has established that PO is likely to be the most abundant molecule containing pho... more Laboratory work has established that PO is likely to be the most abundant molecule containing phosphorus in dense interstellar clouds. Using recently measured microwave frequencies, the authors have searched for the J = 5/2→3/2 transition of PO at 109 GHz in four galactic sources. The limit in DR 21(OH), in particular, suggests that phosphorus may be severely depleted in dense molecular clouds.
The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the ... more The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in absorption against the diffuse 8micron Galactic background, and in emission from cold dust at 850micron. Detailed comparison of the dust properties at these two wavelengths reveals that standard models for the diffuse interstellar dust in the Galaxy are not consistent with the observations. The ratio of absorption coefficients within the cloud is kappa_8/kappa_850 <= 1010, which is well below that expected for the diffuse ISM where kappa_8/kappa_850 ~ 1700. This may be due to the formation of ice mantles on the dust and grain coagulation, both of which are expected within dense regions of molecular clouds. The 850micron emission probes the underlying radial structure of the filament. The profile is well represented by a marginally resolved central region and a steeply falling envelope, with Sigma(r) proportional to r^(-a), where a <= 3, indicating that G11.11-0.12 is the first observed filament with a profile similar to that of a non-magnetic isothermal cylinder.
Proceedings of the twentieth annual ACM symposium on Theory of computing - STOC '88, 1988
Abstract: We exhibit randomized Byzantine agreement (BA) algo-rithms achieving optimal running ti... more Abstract: We exhibit randomized Byzantine agreement (BA) algo-rithms achieving optimal running time and fault tolerance against all types of adversaries ever considered in the lit terature. Our BA algorithms do not require trusted par-ties, preprocessing, or non-consnuctive ...
Proceedings of The International Astronomical Union, 2005
SiO emission is a good chemical tracer of shocked gas in the ISM because the molecular abundance ... more SiO emission is a good chemical tracer of shocked gas in the ISM because the molecular abundance of SiO is enhanced behind strong shocks. Our observations of SiO (6-5) with the JCMT identified strongly shocked gas in dense clumps within MSX Infrared-Dark Clouds. We interpreted the presence of shocked gas as evidence for bipolar outflows from low-mass YSOs embedded in
Linearly distributed methanol masers are associated with young massive stars and have been genera... more Linearly distributed methanol masers are associated with young massive stars and have been generally hypothesized to trace edge-on circumstellar disks around them. Several of these sources have been recently imaged in near-infrared H2 emission (an outflow indicator) and it was discovered that the methanol masers were often aligned with the position angle of H2 emission on the fields. It was therefore argued that this is evidence that the methanol masers are instead associated with outflows from these young massive stars. However, because H2 can be excited by means other than outflow, we have undertaken a series of observations in an independent outflow indicator, namely SiO. We performed single-dish observations with the JCMT to detect SiO (6-5) in 7 out of 9 fields from the H2 survey. Wide wings were found in the SiO lines, supporting the outflow hypothesis. Interferometric follow-up observations of SiO (2-1) with the ATCA at high-spatial resolution have now been analyzed for 4 of ...
Odin has successfully observed the molecular coreOph A in the 572.5 GHz rotational ground state l... more Odin has successfully observed the molecular coreOph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 ! 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 × 10−9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 × 10−10.
Proceedings of the twentieth annual ACM symposium on Theory of computing - STOC '88, 1988
... Actually, as recently pointed out by Ben-Or, Gol-dreich, Goldwasser, Hastad, Micali and Rogaw... more ... Actually, as recently pointed out by Ben-Or, Gol-dreich, Goldwasser, Hastad, Micali and Rogaway [BGGHMR], the same is true for all languages in IP; also, as pointed out by Blum [B2], any theorem at all admits a proof that conveys zero-knowledge other than betraying its own ...
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