We summarize briefly some of our past studies, and report of preliminary recent new results conce... more We summarize briefly some of our past studies, and report of preliminary recent new results concerning the optical properties of Cr4+-doped crystals that are important for utilization as passive Q-switching devices in Nd:YAG laser systems. The host crystals involved are YAG, YSGG, GGG, LuAG and forsterite. Excited-state lifetimes of 4.0, 1.0 and 1.7 μs were measured by the Cr4+ fluorescence
EGU General Assembly Conference Abstracts, Apr 1, 2012
ABSTRACT Monitoring geomorphic changes on other planets is always a puzzle while on Earth measuri... more ABSTRACT Monitoring geomorphic changes on other planets is always a puzzle while on Earth measuring geomorphological dynamics can involve field work, i.e., ground truth. Dunes, wind streaks and other aeolian morphologies have been identified on Earth, Mars, Venus and Titan. These morphologies can be subjected to rapid and continuous changes when the surface is not stabilized by vegetation or crust and the wind is sufficiently strong. Thus, these sand bodies can change rapidly responding to the wind regime, rainfall, and sand particle availability. Identifying these changes by remote sensing (or even on the ground) is not straightforward because the entire surface may change concurrently. In this paper we demonstrate how synthetic aperture radar interferometry (InSAR) can be used to identify changes in dunes using the coherence which is normally a measure of phase noise prohibiting interferometric studies. We demonstrate this for dunes along the Negev and Sinai border region. This paper will show how ERS data were used to map the stability, and loss of it, over time ranges spanning from 1 day intervals to 2 years when eventually the entire surface changed including the, so called, stable areas. This methodology has advantages as it does not show potential mobility but rather the true mobility or stability. This methodology is applicable to planetary landscapes where there is no other indication of stability. Moreover, the methodology can be used also to measure the stability of surfaces susceptible to other mechanisms of landscape changes.
Solar pumped lasers are candidates for wireless power transmission in space, free space optical c... more Solar pumped lasers are candidates for wireless power transmission in space, free space optical communication and photochemistry. The present paper describes the progress on a joint project to develop solar pumped lasers, focusing on the temporal and spectral shaping of the laser beam, which comply with those applications. The program emphasizes the design, fabrication and testing of laser rods, passive
ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (P... more ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (PSC) selection process. This study implements a new algorithm for detection of PSC in open fields and natural areas based on high resolution TerraSAR-X images. The main challenge in PSC detection in natural areas is the lack of strong reflected targets in these areas. This cause high number of diverted targets, or low number of true PS targets (depend on the thresholds). Conventional methods for PS detection are highly depending on the fine calibration, and on the scaling of the target within the resolution cell. Our method is more robust since it less depends on fine calibration, and not depends on the target gain. The method consists of two main steps. The first step is definition of a PSC target character i.e. its amplitude time signature (ATS). The second step is detection of pixels with the same (close enough) temporal signature cone, this way strong and weak reflectors get the same chance to be a mark as a target.
Abstract. Compressive sensing theory was proposed to deal with the high quantity of measurements ... more Abstract. Compressive sensing theory was proposed to deal with the high quantity of measurements demanded by traditional hyperspectral systems. Recently, a compressive spectral imaging technique dubbed compressive sensing miniature ultraspectral imaging (CS-MUSI) was presented. This system uses a voltage controlled liquid crystal device to create multiplexed hyperspectral cubes. We evaluate the utility of the data captured using the CS-MUSI system for the task of target detection. Specifically, we compare the performance of the matched filter target detection algorithm in traditional hyperspectral systems and in CS-MUSI multiplexed hyperspectral cubes. We found that the target detection algorithm performs similarly in both cases, despite the fact that the CS-MUSI data is up to an order of magnitude less than that in conventional hyperspectral cubes. Moreover, the target detection is approximately an order of magnitude faster in CS-MUSI data.
ABSTRACT 1. ABSTRACT The PSI (Persistent scatterers Interferometry) method re-lies on identifying... more ABSTRACT 1. ABSTRACT The PSI (Persistent scatterers Interferometry) method re-lies on identifying a small group of scatterers that main-tain high phase reliability over a relatively long period of time. This study demonstrates a new algorithm to iden-tify natural PSC (persistent scatterer candidates) targets in non-inhabited areas. The application of our PSC se-lection process is conducted for a natural arid scene as opposed to the more common use of the PS technique, which is done mostly for urban areas with strong reflec-tion structures (manmade objects). We present a novel, robust, method to identify PSC in open fields and in places of low backscattering (natural areas). Our method is based on the amplitude times history signature of each point. The main difference between urban areas and open field areas is the low reflectance and less deterministic behaviour of the scatter; hence it is a challenge to de-tect these low reflection and stable points. Conventional methods for PSC detection require a preprocessing of fine calibration and are mainly suitable to use in urban areas, but may fail when used in the open fields. One of the advantages of our method is the use of a simple process of calibration which is based only on the flight geometry and gain factors without any auxiliary data or assump-tions. Consider a vector consisting of the measurement of a PS point as a function of time. We can express this sig-nal as an amplitude times a phase. The amplitude differs between PS points; however potential PS points should correlate spatially and temporally in terms of the phase, independent of their amplitude. Our method improves the ability to locates several candidate points with a narrow phase distribution and thus, enables the location of PSCs in open areas.
International Journal of Remote Sensing, Nov 3, 2011
... R. Rotman b , Dan G. Blumberg c & Anthony J. Weiss a pages 1164-1189. ... (200410. Kimura... more ... R. Rotman b , Dan G. Blumberg c & Anthony J. Weiss a pages 1164-1189. ... (200410. Kimura, H., Mizuno, T., Papathanassiou, KP and Hajnsek, I. 2004. Improvement of polarimetric SAR calibration based on the Quegan algorithm. In IEEE Proceedings of IGARSS 184187. ...
An anomaly detection algorithm for SAR (synthetic aperture radar) images, making use of multi-pol... more An anomaly detection algorithm for SAR (synthetic aperture radar) images, making use of multi-polarized data, is developed. The processing contains several stages including: calibration of the images, information parameters extraction and speckle filtering, suspect pixels detection and morphology operator application. The developed algorithm is independent of the anomaly radar cross section; it depends only on the physical structure. The proposed
Obtaining directional information is required in many applications such as nuclear homeland secur... more Obtaining directional information is required in many applications such as nuclear homeland security, contamination mapping after a nuclear incident and radiological events, or during the decontamination work. However, many directional radiation detectors are based on directional shielding, made of lead or tungsten collimators, introducing two main drawbacks. The first is the size and weight, making those detectors too heavy and irrelevant for utilization in handheld devices, drone mapping, or space applications. The second drawback is the limited field of view (FOV), which requires multiple detectors to cover the whole required FOV or machinery to rotate the detector’s narrow FOV detector. We propose a novel <inline-formula> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> directional detector based on a segmented hollow cubic detector, which uses the Compton effect interactions with no heavy collimators. The symmetrical cubical design provides both higher efficiency and <inline-formula> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> detection ability. Instead of the traditional two types of detectors (scatterer and absorber) structure, we use the same type of detector, based on Gd<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub> (GAGG) (Ce) scintillator coupled to silicon photomultiplier. An additional advantage of the proposed detector is obtained by locating the photon sensors inside the detector, behind the scintillators, which improves the radiation hardness required for space applications. Furthermore, such an arrangement flattens the temperature variation across the detector, providing better gain stability. The main advantage of the proposed detector is an efficient <inline-formula> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> radiation detection for high-energy gamma rays without the use of heavy collimators.
Silicon Photomultipliers (SiPMs) have many advantages when used in radiation detectors. Low bias ... more Silicon Photomultipliers (SiPMs) have many advantages when used in radiation detectors. Low bias voltage, compactness and immunity to electromagnetic interference are among their prominent benefits. However, due to their small size, usually an array of SiPM components is required in order to cover the coupling surface area of a scintillator. Since the SiPM is a semiconductor, biased in a reversed voltage, gain variation and strong temperature dependence are introduced. As a result, SiPM-based detectors, particularly an array of SiPMs, undergo spectral signal to noise ratio reduction. This work studies the effect of the SiPM breakdown voltage variation on the obtained energy spectrum and proposes an electronic approach to overcome this technological drawback. This developed technology provides an adequate temperature-dependent, commonly distributed high bias voltage and an individual offset-voltage fine tuning that enables adjustment of all the SiPM components to their optimum operat...
It is generally held that subtle changes in sandy environments are very difficult to detect in im... more It is generally held that subtle changes in sandy environments are very difficult to detect in imagery. Nonetheless, this study demonstrates how synthetic aperture radar (SAR) interferometric decorrelation can be used to identify changes in individual sand dunes. The use of coherence maps over time facilitates the analysis of dune dynamics, both temporally and spatially. The Ashdod‐Nizzanim coastal dunes, along the southern coastal plain of Israel, were chosen as an illustrative example of the analysis of dune dynamics. High‐resolution TerraSAR‐X (TSX) radar images covering the entire research area were acquired for the period February to July 2012, together with meteorology data (wind and rain) for the area. The coherence results enabled the stability of individual dunes to be described as a function of time. It was found that the dune crests were more stable than the windward slopes and that the degree of stability was dependent on the distance of the dune from the sea. The result...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
Among the different types of marine pollution, oil spill is a major threat to the sea ecosystems.... more Among the different types of marine pollution, oil spill is a major threat to the sea ecosystems. Remote sensing is used in oil spill response. Synthetic Aperture Radar (SAR) is an active microwave sensor that operates under all weather conditions and provides information about the surface roughness and covers large areas at a high spatial resolution. SAR is widely used to identify and track pollutants in the sea, which may be due to a secondary effect of a large natural disaster or by a man-made one . The detection of oil spill in SAR imagery relies on the decrease of the backscattering from the sea surface, due to the increased viscosity, resulting in a dark formation that contrasts with the brightness of the surrounding area. <br><br> Most of the use of SAR images for oil spill detection is done by visual interpretation. Trained interpreters scan the image, and mark areas of low backscatter and where shape is a-symmetrical. It is very difficult to apply this method fo...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
Satellite images are used widely in the risk cycle to understand the exposure, refine hazard maps... more Satellite images are used widely in the risk cycle to understand the exposure, refine hazard maps and quickly provide an assessment after a natural or man-made disaster. Though there are different types of satellite images (e.g. optical, radar) these have not been combined for risk assessments. The characteristics of different remote sensing data type may be extremely valuable for monitoring and evaluating the impacts of disaster events, to extract additional information thus making it available for emergency situations. To base this approach, two different change detection methods, for two different sensor's data were used: Coherence Change Detection (CCD) for SAR data and Covariance Equalization (CE) for multispectral imagery. The CCD provides an identification of the stability of an area, and shows where changes have occurred. CCD shows subtle changes with an accuracy of several millimetres to centimetres. The CE method overcomes the atmospheric effects differences between tw...
2013 IEEE International Conference on Microwaves, Communications, Antennas and Electronic Systems (COMCAS 2013), 2013
ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (P... more ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (PSC) selection process. This study implements a new algorithm for detection of PSC in open fields and natural areas based on high resolution TerraSAR-X images. The main challenge in PSC detection in natural areas is the lack of strong reflected targets in these areas. This cause high number of diverted targets, or low number of true PS targets (depend on the thresholds). Conventional methods for PS detection are highly depending on the fine calibration, and on the scaling of the target within the resolution cell. Our method is more robust since it less depends on fine calibration, and not depends on the target gain. The method consists of two main steps. The first step is definition of a PSC target character i.e. its amplitude time signature (ATS). The second step is detection of pixels with the same (close enough) temporal signature cone, this way strong and weak reflectors get the same chance to be a mark as a target.
We summarize briefly some of our past studies, and report of preliminary recent new results conce... more We summarize briefly some of our past studies, and report of preliminary recent new results concerning the optical properties of Cr4+-doped crystals that are important for utilization as passive Q-switching devices in Nd:YAG laser systems. The host crystals involved are YAG, YSGG, GGG, LuAG and forsterite. Excited-state lifetimes of 4.0, 1.0 and 1.7 μs were measured by the Cr4+ fluorescence
EGU General Assembly Conference Abstracts, Apr 1, 2012
ABSTRACT Monitoring geomorphic changes on other planets is always a puzzle while on Earth measuri... more ABSTRACT Monitoring geomorphic changes on other planets is always a puzzle while on Earth measuring geomorphological dynamics can involve field work, i.e., ground truth. Dunes, wind streaks and other aeolian morphologies have been identified on Earth, Mars, Venus and Titan. These morphologies can be subjected to rapid and continuous changes when the surface is not stabilized by vegetation or crust and the wind is sufficiently strong. Thus, these sand bodies can change rapidly responding to the wind regime, rainfall, and sand particle availability. Identifying these changes by remote sensing (or even on the ground) is not straightforward because the entire surface may change concurrently. In this paper we demonstrate how synthetic aperture radar interferometry (InSAR) can be used to identify changes in dunes using the coherence which is normally a measure of phase noise prohibiting interferometric studies. We demonstrate this for dunes along the Negev and Sinai border region. This paper will show how ERS data were used to map the stability, and loss of it, over time ranges spanning from 1 day intervals to 2 years when eventually the entire surface changed including the, so called, stable areas. This methodology has advantages as it does not show potential mobility but rather the true mobility or stability. This methodology is applicable to planetary landscapes where there is no other indication of stability. Moreover, the methodology can be used also to measure the stability of surfaces susceptible to other mechanisms of landscape changes.
Solar pumped lasers are candidates for wireless power transmission in space, free space optical c... more Solar pumped lasers are candidates for wireless power transmission in space, free space optical communication and photochemistry. The present paper describes the progress on a joint project to develop solar pumped lasers, focusing on the temporal and spectral shaping of the laser beam, which comply with those applications. The program emphasizes the design, fabrication and testing of laser rods, passive
ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (P... more ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (PSC) selection process. This study implements a new algorithm for detection of PSC in open fields and natural areas based on high resolution TerraSAR-X images. The main challenge in PSC detection in natural areas is the lack of strong reflected targets in these areas. This cause high number of diverted targets, or low number of true PS targets (depend on the thresholds). Conventional methods for PS detection are highly depending on the fine calibration, and on the scaling of the target within the resolution cell. Our method is more robust since it less depends on fine calibration, and not depends on the target gain. The method consists of two main steps. The first step is definition of a PSC target character i.e. its amplitude time signature (ATS). The second step is detection of pixels with the same (close enough) temporal signature cone, this way strong and weak reflectors get the same chance to be a mark as a target.
Abstract. Compressive sensing theory was proposed to deal with the high quantity of measurements ... more Abstract. Compressive sensing theory was proposed to deal with the high quantity of measurements demanded by traditional hyperspectral systems. Recently, a compressive spectral imaging technique dubbed compressive sensing miniature ultraspectral imaging (CS-MUSI) was presented. This system uses a voltage controlled liquid crystal device to create multiplexed hyperspectral cubes. We evaluate the utility of the data captured using the CS-MUSI system for the task of target detection. Specifically, we compare the performance of the matched filter target detection algorithm in traditional hyperspectral systems and in CS-MUSI multiplexed hyperspectral cubes. We found that the target detection algorithm performs similarly in both cases, despite the fact that the CS-MUSI data is up to an order of magnitude less than that in conventional hyperspectral cubes. Moreover, the target detection is approximately an order of magnitude faster in CS-MUSI data.
ABSTRACT 1. ABSTRACT The PSI (Persistent scatterers Interferometry) method re-lies on identifying... more ABSTRACT 1. ABSTRACT The PSI (Persistent scatterers Interferometry) method re-lies on identifying a small group of scatterers that main-tain high phase reliability over a relatively long period of time. This study demonstrates a new algorithm to iden-tify natural PSC (persistent scatterer candidates) targets in non-inhabited areas. The application of our PSC se-lection process is conducted for a natural arid scene as opposed to the more common use of the PS technique, which is done mostly for urban areas with strong reflec-tion structures (manmade objects). We present a novel, robust, method to identify PSC in open fields and in places of low backscattering (natural areas). Our method is based on the amplitude times history signature of each point. The main difference between urban areas and open field areas is the low reflectance and less deterministic behaviour of the scatter; hence it is a challenge to de-tect these low reflection and stable points. Conventional methods for PSC detection require a preprocessing of fine calibration and are mainly suitable to use in urban areas, but may fail when used in the open fields. One of the advantages of our method is the use of a simple process of calibration which is based only on the flight geometry and gain factors without any auxiliary data or assump-tions. Consider a vector consisting of the measurement of a PS point as a function of time. We can express this sig-nal as an amplitude times a phase. The amplitude differs between PS points; however potential PS points should correlate spatially and temporally in terms of the phase, independent of their amplitude. Our method improves the ability to locates several candidate points with a narrow phase distribution and thus, enables the location of PSCs in open areas.
International Journal of Remote Sensing, Nov 3, 2011
... R. Rotman b , Dan G. Blumberg c & Anthony J. Weiss a pages 1164-1189. ... (200410. Kimura... more ... R. Rotman b , Dan G. Blumberg c & Anthony J. Weiss a pages 1164-1189. ... (200410. Kimura, H., Mizuno, T., Papathanassiou, KP and Hajnsek, I. 2004. Improvement of polarimetric SAR calibration based on the Quegan algorithm. In IEEE Proceedings of IGARSS 184187. ...
An anomaly detection algorithm for SAR (synthetic aperture radar) images, making use of multi-pol... more An anomaly detection algorithm for SAR (synthetic aperture radar) images, making use of multi-polarized data, is developed. The processing contains several stages including: calibration of the images, information parameters extraction and speckle filtering, suspect pixels detection and morphology operator application. The developed algorithm is independent of the anomaly radar cross section; it depends only on the physical structure. The proposed
Obtaining directional information is required in many applications such as nuclear homeland secur... more Obtaining directional information is required in many applications such as nuclear homeland security, contamination mapping after a nuclear incident and radiological events, or during the decontamination work. However, many directional radiation detectors are based on directional shielding, made of lead or tungsten collimators, introducing two main drawbacks. The first is the size and weight, making those detectors too heavy and irrelevant for utilization in handheld devices, drone mapping, or space applications. The second drawback is the limited field of view (FOV), which requires multiple detectors to cover the whole required FOV or machinery to rotate the detector’s narrow FOV detector. We propose a novel <inline-formula> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> directional detector based on a segmented hollow cubic detector, which uses the Compton effect interactions with no heavy collimators. The symmetrical cubical design provides both higher efficiency and <inline-formula> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> detection ability. Instead of the traditional two types of detectors (scatterer and absorber) structure, we use the same type of detector, based on Gd<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub> (GAGG) (Ce) scintillator coupled to silicon photomultiplier. An additional advantage of the proposed detector is obtained by locating the photon sensors inside the detector, behind the scintillators, which improves the radiation hardness required for space applications. Furthermore, such an arrangement flattens the temperature variation across the detector, providing better gain stability. The main advantage of the proposed detector is an efficient <inline-formula> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> radiation detection for high-energy gamma rays without the use of heavy collimators.
Silicon Photomultipliers (SiPMs) have many advantages when used in radiation detectors. Low bias ... more Silicon Photomultipliers (SiPMs) have many advantages when used in radiation detectors. Low bias voltage, compactness and immunity to electromagnetic interference are among their prominent benefits. However, due to their small size, usually an array of SiPM components is required in order to cover the coupling surface area of a scintillator. Since the SiPM is a semiconductor, biased in a reversed voltage, gain variation and strong temperature dependence are introduced. As a result, SiPM-based detectors, particularly an array of SiPMs, undergo spectral signal to noise ratio reduction. This work studies the effect of the SiPM breakdown voltage variation on the obtained energy spectrum and proposes an electronic approach to overcome this technological drawback. This developed technology provides an adequate temperature-dependent, commonly distributed high bias voltage and an individual offset-voltage fine tuning that enables adjustment of all the SiPM components to their optimum operat...
It is generally held that subtle changes in sandy environments are very difficult to detect in im... more It is generally held that subtle changes in sandy environments are very difficult to detect in imagery. Nonetheless, this study demonstrates how synthetic aperture radar (SAR) interferometric decorrelation can be used to identify changes in individual sand dunes. The use of coherence maps over time facilitates the analysis of dune dynamics, both temporally and spatially. The Ashdod‐Nizzanim coastal dunes, along the southern coastal plain of Israel, were chosen as an illustrative example of the analysis of dune dynamics. High‐resolution TerraSAR‐X (TSX) radar images covering the entire research area were acquired for the period February to July 2012, together with meteorology data (wind and rain) for the area. The coherence results enabled the stability of individual dunes to be described as a function of time. It was found that the dune crests were more stable than the windward slopes and that the degree of stability was dependent on the distance of the dune from the sea. The result...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
Among the different types of marine pollution, oil spill is a major threat to the sea ecosystems.... more Among the different types of marine pollution, oil spill is a major threat to the sea ecosystems. Remote sensing is used in oil spill response. Synthetic Aperture Radar (SAR) is an active microwave sensor that operates under all weather conditions and provides information about the surface roughness and covers large areas at a high spatial resolution. SAR is widely used to identify and track pollutants in the sea, which may be due to a secondary effect of a large natural disaster or by a man-made one . The detection of oil spill in SAR imagery relies on the decrease of the backscattering from the sea surface, due to the increased viscosity, resulting in a dark formation that contrasts with the brightness of the surrounding area. <br><br> Most of the use of SAR images for oil spill detection is done by visual interpretation. Trained interpreters scan the image, and mark areas of low backscatter and where shape is a-symmetrical. It is very difficult to apply this method fo...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
Satellite images are used widely in the risk cycle to understand the exposure, refine hazard maps... more Satellite images are used widely in the risk cycle to understand the exposure, refine hazard maps and quickly provide an assessment after a natural or man-made disaster. Though there are different types of satellite images (e.g. optical, radar) these have not been combined for risk assessments. The characteristics of different remote sensing data type may be extremely valuable for monitoring and evaluating the impacts of disaster events, to extract additional information thus making it available for emergency situations. To base this approach, two different change detection methods, for two different sensor's data were used: Coherence Change Detection (CCD) for SAR data and Covariance Equalization (CE) for multispectral imagery. The CCD provides an identification of the stability of an area, and shows where changes have occurred. CCD shows subtle changes with an accuracy of several millimetres to centimetres. The CE method overcomes the atmospheric effects differences between tw...
2013 IEEE International Conference on Microwaves, Communications, Antennas and Electronic Systems (COMCAS 2013), 2013
ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (P... more ABSTRACT The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (PSC) selection process. This study implements a new algorithm for detection of PSC in open fields and natural areas based on high resolution TerraSAR-X images. The main challenge in PSC detection in natural areas is the lack of strong reflected targets in these areas. This cause high number of diverted targets, or low number of true PS targets (depend on the thresholds). Conventional methods for PS detection are highly depending on the fine calibration, and on the scaling of the target within the resolution cell. Our method is more robust since it less depends on fine calibration, and not depends on the target gain. The method consists of two main steps. The first step is definition of a PSC target character i.e. its amplitude time signature (ATS). The second step is detection of pixels with the same (close enough) temporal signature cone, this way strong and weak reflectors get the same chance to be a mark as a target.
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Papers by Stanley Rotman