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  • Open Access
    Authors: 
    Caroline Lamarche; Jonathan S. Maltzman;
    Publisher: Elsevier BV
  • Open Access
    Authors: 
    Pallavi Surana; Devika Kapuria; Carly Broadwell; Elizabeth C. Wright; Varun Takyar; David E. Kleiner; Marc G. Ghany; Gil Ben-Yakov; Theo Heller; T. Jake Liang; +1 more

    Abstract Background Fibrosis regression has been associated with nucleoside analogue (NA) treatment in chronic hepatitis B (CHB) patients. Although non-invasive fibrosis markers have been evaluated in CHB, their utility for monitoring on-treatment histologic regression has not been evaluated. Aims To characterize improvements in disease severity and the utility of non-invasive biomarkers in CHB NA treated patients. Methods Histology, labs, AST-to-platelet ratio index, and Fibrosis-4 (Fib-4) from treatment-naive CHB patients were evaluated at baseline and longitudinally. Relative change from baseline to various time points during treatment were evaluated. Correlative analysis of APRI and Fib-4 with histology was performed longitudinally. Results 80 CHB patients (84% male, median age 45 (IQR 32, 54)) with histology up to 17 years (median 6(IQR 3.9, 8.0)) years were studied. Median baseline Ishak fibrosis was 3 (IQR 2, 4), histologic activity index (HAI) inflammation was 9 (IQR 7, 11), and AUROC of fibrosis markers for detecting cirrhosis (Ishak ≥ 5) was >0.64. HAI improved at a rate of 54% during year 1 and 37% in year 2, both greater than in the remaining follow-up periods. Within the first year, fibrosis improved by 35%, greater than all other time periods. Non-invasive biomarkers began to correlate with histology beyond 4 years (APRI: 4–6 years: r = 0.33, p = 0.03; ≥6 years: r = 0.41, p = 0.009; Fib-4: ≥6 years: r = 0.35, p = 0.03). Conclusion Early dynamic changes in histology occur in CHB patients on NA followed by linear improvements. Non-invasive fibrosis biomarkers do not capture these dynamic changes and may demonstrate clinical utility beyond 4 years of treatment.

  • Open Access English
    Authors: 
    Josephine Ho; Constadina Panagiotopoulos; Brian W. McCrindle; Silviu Grisaru; Tamara Pringsheim;
    Publisher: Pulsus Group Inc

    Second-generation antipsychotics are commonly associated with metabolic complications. These medications are being used more frequently for the treatment of mental health disorders in children, which has stimulated the need for creating formal guidelines on monitoring their safety and effectiveness. Previous guidelines have been developed for monitoring metabolic and neurological complications. To assist practitioners who perform these monitoring procedures, a complementary set of treatment recommendations have been created for situations in which abnormal measurements or results are encountered.To create evidence-based recommendations to assist in managing metabolic complications in children being treated with second-generation antipsychotics.A systematic review of the literature on metabolic complications of second-generation antipsychotic medications in children was conducted. Members of the consensus group evaluated the information gathered from the systematic review of the literature and used a nominal group process to reach a consensus on treatment recommendations. Wherever possible, references were made to existing guidelines on the evaluation and treatment of metabolic abnormalities in children.Evidence-based recommendations are presented to assist in managing metabolic complications including weight gain; increased waist circumference; elevation in prolactin, cholesterol, triglyceride and glucose levels; abnormal liver function tests; and abnormal thyroid studies.The use of second-generation antipsychotics requires proper monitoring procedures. The present treatment guideline provides guidance to clinicians on the clinical management of metabolic complications if they occur.

  • Open Access English
    Authors: 
    Robin T. Petroze; Allison N. Martin; Edmond Ntaganda; Patrick Kyamanywa; Etienne St-Louis; Sara K. Rasmussen; James Forrest Calland; Jean Claude Byiringiro;
    Publisher: John Wiley & Sons, Ltd
    Project: NIH | Fogarty International Cli... (5R24TW007988-04), NIH | Surgical Infectious Dises... (5T32AI078875-02)

    Background Child survival initiatives historically prioritized efforts to reduce child morbidity and mortality from infectious diseases and maternal conditions. Little attention has been devoted to paediatric injuries in resource‐limited settings. This study aimed to evaluate the demographics and outcomes of paediatric injury in a sub‐Saharan African country in an effort to improve prevention and treatment. Methods A prospective trauma registry was established at the two university teaching campuses of the University of Rwanda to record systematically patient demographics, prehospital care, initial physiology and patient outcomes from May 2011 to July 2015. Univariable analysis was performed for demographic characteristics, injury mechanisms, geographical location and outcomes. Multivariable analysis was performed for mortality estimates. Results Of 11 036 patients in the registry, 3010 (27·3 per cent) were under 18 years of age. Paediatric patients were predominantly boys (69·9 per cent) and the median age was 8 years. The mortality rate was 4·8 per cent. Falls were the most common injury (45·3 per cent), followed by road traffic accidents (30·9 per cent), burns (10·7 per cent) and blunt force/assault (7·5 per cent). Patients treated in the capital city, Kigali, had a higher incidence of head injury (7·6 per cent versus 2·0 per cent in a rural town, P < 0·001; odds ratio (OR) 4·08, 95 per cent c.i. 2·61 to 6·38) and a higher overall injury‐related mortality rate (adjusted OR 3·00, 1·50 to 6·01; P = 0·019). Pedestrians had higher overall injury‐related mortality compared with other road users (adjusted OR 3·26, 1·37 to 7·73; P = 0·007). Conclusion Paediatric injury is a significant contributor to morbidity and mortality. Delineating trauma demographics is important when planning resource utilization and capacity‐building efforts to address paediatric injury in low‐resource settings and identify vulnerable populations. This study evaluated the demographics and outcomes of paediatric injury in Rwanda through a prospective trauma registry to inform capacity‐building for prevention and treatment. Patients treated in the capital city had a higher incidence of head injury and a higher overall injury‐related mortality than those in a rural town. Pedestrians had higher overall injury‐related mortality compared with other road‐users. Falls and road traffic accidents significant contributors to pediatric injury in Rwanda

  • Publication . Thesis . 1975
    Open Access
    Authors: 
    Pankratz, Nathan James;
    Country: Canada

    This in a study of a Rammohun Roy's participation in the development of Hindu religious thought. It is an attempt to understand Hindu religious thought through the writings of Rammohun Roy by examining why so much of what he said, wrote, and did was contentious. It has been customary, in studies of Rammohun Roy's religious thought, to concentrate on his opposition to the use of images in worship. This emphasis has made it appear that Rammohun Roy's most substantial contribution to the development of Hindu religious thought has been to draw attention to polytheism and image worship, and to make it clear that these do not represent the best expressions of Hindu theology and worship. That issue forms part of this study, but this study is considerably broader. It discusses Rammohun Roy's theological position both in terms of the polytheism which he opposed and the monotheism which he supported. But it includes more than his theological position. It analyzes the authority upon which he based his theology. That discussion has two dimensions: firstly there is Rammohun Roy's criticism of what he perceived to be the accepted basis of authority, and secondly there his suggestion for a more adequate basis of authority. This study also analyzes the debates which Rammohun Roy had with some of his contemporaries about the qualifications which were expected of those involved in theological discussion. This study indicates that Rammohun Roy's religious thought was contentious in many areas, and that the theological issues were not necessarily the most contentious. In fact, it is misleading to study the debates between Rammohun Roy and his contemporaries in purely theological terms, since that fails to account for the vehemence of some of the opposition which he encountered. The most contentious issues between Rammohun Roy and some of his contemporaries were not definitions of God, but questions about people's capacity to benefit from theological discussions and questions about the qualifications expected of those who engaged in such discussions. The study suggests that in this situation theological debate was contentious as much because of the context in which it occurred as because of the actual theological positions enunciated in the debate. It suggests that the distinctions between the insider and outsider, initiate and uninitiate, and qualified and unqualified are distinctions of great importance in religious discussion, and that if the implicit boundaries these categories are disregarded, serious disagreement will result. The study concludes that Rammohun Roy challenged the traditional boundaries between these categories, and that this challenge was the most important reason for the opposition to him. Doctor of Philosophy (PhD)

  • Open Access
    Authors: 
    Aminur Rab Ratul; Maryam Tavakol Elahi; Kun Yuan; Won-Sook Lee;
    Publisher: IEEE

    In the last century, we have passed two severe pandemics; the 1957 influenza (Asian flu) pandemic and the 1918 influenza (Spanish flu) pandemic with a high fatality rate. In the last few months, we have been again facing a new epidemic (COVID-19), which is a frighteningly high-risk disease and is globally threatening human lives. Among all attempts and presented solutions to tackle the COVID-19, a publicly available dataset of radiological imaging using chest radiography, also called chest X-ray (CXR) images, could efficiently accelerate the detection process of patients infected with COVID-19 through presented abnormalities in their chest radiography images. In this study, we have proposed a deep neural network (DNN), namely RAM-Net, a new combination of MobileNet with Dilated Depthwise Separable Convolution (DDSC), Residual blocks, and Attention augmented convolution. The network has been learned and validated using the COVIDx dataset, one of the most popular public datasets comprising the chest X-ray (CXR) images. Using this model, we could accurately identify the positive cases of COVID-19 viral infection while a new suspicious chest X-ray image is shown to the network. Our network’s overall accuracy on the COVIDx test dataset was 95.33%, with a sensitivity and precision of 92% and 99% for COVID-19 cases, respectively, which are the highest results on the COVIDx dataset to date, to the best of our knowledge. Finally, we performed an audit on RAM-Net based on the Grad-CAM’s interpretation to demonstrate that our proposed architecture detects SARS-CoV-2 (COVID-19) viral infection by focusing on vital factors rather than relying on irrelevant information.

  • Open Access
    Authors: 
    Simon M. Danner; Natalia A. Shevtsova; Alain Frigon; Ilya A. Rybak;
    Publisher: eLife Sciences Publications, Ltd
  • Open Access
    Authors: 
    William L. Miller; Mary Ann Moran;
    Publisher: Wiley

    The interaction between photochemical and biological processes in the degradation of marine dissolved organic matter (DOM) was investigated with seawater from a coastal southeastern U.S. salt marsh. Seawater supplemented with humic substances was exposed to alternating cycles of sunlight (equivalent to 8 h of midday sun) and dark incubations with natural bacterial populations (l-2 weeks in length). Photochemical degradation of the DOM was monitored during sunlight exposure by direct measurements of dissolved inorganic carbon (DIC) and carbon monoxide (CO) formation in 0.2-Frn filtered seawater. Bacterial degradation was monitored during dark incubations by tritiated leucine uptake and changes in bacterial numbers in bacterivore-free incubations and by direct measurements of DOM loss. The alternating cycles of sunlight and microbial activity resulted in more complete degradation of bulk DOM and marine humic substances than was found for nonirradiated controls (i.e. with microbial activity alone) by a factor of up to 3-fold. Increased decomposition was due both to direct losses of carbon gas photoproducts (DIC and CO in a 15 : 1 ratio) and to enhanced microbial degradation of photodegraded DOM, with approximately equal contributions from each pathway. Mass balance calculations indicated that low-molecular-weight carbon photoproducts, currently considered to be the compounds responsible for stimulating bacterial activity following photodegradation of DOM, were insufficient to account for the enhanced bacterial production observed. Thus, higher molecular weight, chemically uncharacterized fractions of DOM may also be modified to more biologically available forms during exposure to natural sunlight. Photochemical processes play a number of important roles in the biogeochemical cycling of dissolved organic matter (DOM) in natural waters. Water optical properties, biological processes, and trace element distributions have all been demonstrated to be affected, either directly or indirectly, by

  • Open Access
    Authors: 
    Jinluo Cheng; Julien Rioux; John E. Sipe;
    Publisher: American Physical Society (APS)
    Project: NSERC

    Using an empirical pseudopotential description of electron states and an adiabatic bond charge model for phonon states in bulk silicon, we theoretically investigate two-photon indirect optical injection of carriers and spins and two-color coherent control of the motion of the injected carriers and spins. For two-photon indirect carrier and spin injection, we identify the selection rules of band edge transitions, the injection in each conduction band valley, and the injection from each phonon branch at 4 K and 300 K. At 4 K, the TA phonon-assisted transitions dominate the injection at low photon energies, and the TO phonon-assisted at high photon energies. At 300 K, the former dominates at all photon energies of interest. The carrier injection shows anisotropy and linear-circular dichroism with respect to light propagation direction. For light propagating along the $<001>$ direction, the carrier injection exhibits valley anisotropy, and the injection into the $Z$ conduction band valley is larger than that into the $X/Y$ valleys. For $��^-$ light propagating along the $<001>$ ($<111>$) direction, the degree of spin polarization gives a maximum value about 20% (6%) at 4 K and -10% (20%) at 300 K, and at both temperature shows abundant structure near the injection edges due to contributions from different phonon branches. Forthe two-color coherent current injection with an incident optical field composed of a fundamental frequency and its second harmonic, the response tensors of the electron (hole) charge and spin currents are calculated at 4 K and 300 K. We show the current control for three different polarization scenarios. The spectral dependence of the maximum swarm velocity shows that the direction of charge current reverses under increase in photon energy. 15 pages and 14 figures

  • Publication . Article . Preprint . 2009
    Open Access
    Authors: 
    Viktoria Hnatkovska; Vadim Marmer; Yao Tang;

    This Paper Contains Supplemental Material to Hnatkovska, Marmer, and Tang (2009) 'Comparison of Misspecified Calibrated Models: The Minimum Distance Approach'.

Include:
1,195,501 Research products, page 1 of 119,551
  • Open Access
    Authors: 
    Caroline Lamarche; Jonathan S. Maltzman;
    Publisher: Elsevier BV
  • Open Access
    Authors: 
    Pallavi Surana; Devika Kapuria; Carly Broadwell; Elizabeth C. Wright; Varun Takyar; David E. Kleiner; Marc G. Ghany; Gil Ben-Yakov; Theo Heller; T. Jake Liang; +1 more

    Abstract Background Fibrosis regression has been associated with nucleoside analogue (NA) treatment in chronic hepatitis B (CHB) patients. Although non-invasive fibrosis markers have been evaluated in CHB, their utility for monitoring on-treatment histologic regression has not been evaluated. Aims To characterize improvements in disease severity and the utility of non-invasive biomarkers in CHB NA treated patients. Methods Histology, labs, AST-to-platelet ratio index, and Fibrosis-4 (Fib-4) from treatment-naive CHB patients were evaluated at baseline and longitudinally. Relative change from baseline to various time points during treatment were evaluated. Correlative analysis of APRI and Fib-4 with histology was performed longitudinally. Results 80 CHB patients (84% male, median age 45 (IQR 32, 54)) with histology up to 17 years (median 6(IQR 3.9, 8.0)) years were studied. Median baseline Ishak fibrosis was 3 (IQR 2, 4), histologic activity index (HAI) inflammation was 9 (IQR 7, 11), and AUROC of fibrosis markers for detecting cirrhosis (Ishak ≥ 5) was >0.64. HAI improved at a rate of 54% during year 1 and 37% in year 2, both greater than in the remaining follow-up periods. Within the first year, fibrosis improved by 35%, greater than all other time periods. Non-invasive biomarkers began to correlate with histology beyond 4 years (APRI: 4–6 years: r = 0.33, p = 0.03; ≥6 years: r = 0.41, p = 0.009; Fib-4: ≥6 years: r = 0.35, p = 0.03). Conclusion Early dynamic changes in histology occur in CHB patients on NA followed by linear improvements. Non-invasive fibrosis biomarkers do not capture these dynamic changes and may demonstrate clinical utility beyond 4 years of treatment.

  • Open Access English
    Authors: 
    Josephine Ho; Constadina Panagiotopoulos; Brian W. McCrindle; Silviu Grisaru; Tamara Pringsheim;
    Publisher: Pulsus Group Inc

    Second-generation antipsychotics are commonly associated with metabolic complications. These medications are being used more frequently for the treatment of mental health disorders in children, which has stimulated the need for creating formal guidelines on monitoring their safety and effectiveness. Previous guidelines have been developed for monitoring metabolic and neurological complications. To assist practitioners who perform these monitoring procedures, a complementary set of treatment recommendations have been created for situations in which abnormal measurements or results are encountered.To create evidence-based recommendations to assist in managing metabolic complications in children being treated with second-generation antipsychotics.A systematic review of the literature on metabolic complications of second-generation antipsychotic medications in children was conducted. Members of the consensus group evaluated the information gathered from the systematic review of the literature and used a nominal group process to reach a consensus on treatment recommendations. Wherever possible, references were made to existing guidelines on the evaluation and treatment of metabolic abnormalities in children.Evidence-based recommendations are presented to assist in managing metabolic complications including weight gain; increased waist circumference; elevation in prolactin, cholesterol, triglyceride and glucose levels; abnormal liver function tests; and abnormal thyroid studies.The use of second-generation antipsychotics requires proper monitoring procedures. The present treatment guideline provides guidance to clinicians on the clinical management of metabolic complications if they occur.

  • Open Access English
    Authors: 
    Robin T. Petroze; Allison N. Martin; Edmond Ntaganda; Patrick Kyamanywa; Etienne St-Louis; Sara K. Rasmussen; James Forrest Calland; Jean Claude Byiringiro;
    Publisher: John Wiley & Sons, Ltd
    Project: NIH | Fogarty International Cli... (5R24TW007988-04), NIH | Surgical Infectious Dises... (5T32AI078875-02)

    Background Child survival initiatives historically prioritized efforts to reduce child morbidity and mortality from infectious diseases and maternal conditions. Little attention has been devoted to paediatric injuries in resource‐limited settings. This study aimed to evaluate the demographics and outcomes of paediatric injury in a sub‐Saharan African country in an effort to improve prevention and treatment. Methods A prospective trauma registry was established at the two university teaching campuses of the University of Rwanda to record systematically patient demographics, prehospital care, initial physiology and patient outcomes from May 2011 to July 2015. Univariable analysis was performed for demographic characteristics, injury mechanisms, geographical location and outcomes. Multivariable analysis was performed for mortality estimates. Results Of 11 036 patients in the registry, 3010 (27·3 per cent) were under 18 years of age. Paediatric patients were predominantly boys (69·9 per cent) and the median age was 8 years. The mortality rate was 4·8 per cent. Falls were the most common injury (45·3 per cent), followed by road traffic accidents (30·9 per cent), burns (10·7 per cent) and blunt force/assault (7·5 per cent). Patients treated in the capital city, Kigali, had a higher incidence of head injury (7·6 per cent versus 2·0 per cent in a rural town, P < 0·001; odds ratio (OR) 4·08, 95 per cent c.i. 2·61 to 6·38) and a higher overall injury‐related mortality rate (adjusted OR 3·00, 1·50 to 6·01; P = 0·019). Pedestrians had higher overall injury‐related mortality compared with other road users (adjusted OR 3·26, 1·37 to 7·73; P = 0·007). Conclusion Paediatric injury is a significant contributor to morbidity and mortality. Delineating trauma demographics is important when planning resource utilization and capacity‐building efforts to address paediatric injury in low‐resource settings and identify vulnerable populations. This study evaluated the demographics and outcomes of paediatric injury in Rwanda through a prospective trauma registry to inform capacity‐building for prevention and treatment. Patients treated in the capital city had a higher incidence of head injury and a higher overall injury‐related mortality than those in a rural town. Pedestrians had higher overall injury‐related mortality compared with other road‐users. Falls and road traffic accidents significant contributors to pediatric injury in Rwanda

  • Publication . Thesis . 1975
    Open Access
    Authors: 
    Pankratz, Nathan James;
    Country: Canada

    This in a study of a Rammohun Roy's participation in the development of Hindu religious thought. It is an attempt to understand Hindu religious thought through the writings of Rammohun Roy by examining why so much of what he said, wrote, and did was contentious. It has been customary, in studies of Rammohun Roy's religious thought, to concentrate on his opposition to the use of images in worship. This emphasis has made it appear that Rammohun Roy's most substantial contribution to the development of Hindu religious thought has been to draw attention to polytheism and image worship, and to make it clear that these do not represent the best expressions of Hindu theology and worship. That issue forms part of this study, but this study is considerably broader. It discusses Rammohun Roy's theological position both in terms of the polytheism which he opposed and the monotheism which he supported. But it includes more than his theological position. It analyzes the authority upon which he based his theology. That discussion has two dimensions: firstly there is Rammohun Roy's criticism of what he perceived to be the accepted basis of authority, and secondly there his suggestion for a more adequate basis of authority. This study also analyzes the debates which Rammohun Roy had with some of his contemporaries about the qualifications which were expected of those involved in theological discussion. This study indicates that Rammohun Roy's religious thought was contentious in many areas, and that the theological issues were not necessarily the most contentious. In fact, it is misleading to study the debates between Rammohun Roy and his contemporaries in purely theological terms, since that fails to account for the vehemence of some of the opposition which he encountered. The most contentious issues between Rammohun Roy and some of his contemporaries were not definitions of God, but questions about people's capacity to benefit from theological discussions and questions about the qualifications expected of those who engaged in such discussions. The study suggests that in this situation theological debate was contentious as much because of the context in which it occurred as because of the actual theological positions enunciated in the debate. It suggests that the distinctions between the insider and outsider, initiate and uninitiate, and qualified and unqualified are distinctions of great importance in religious discussion, and that if the implicit boundaries these categories are disregarded, serious disagreement will result. The study concludes that Rammohun Roy challenged the traditional boundaries between these categories, and that this challenge was the most important reason for the opposition to him. Doctor of Philosophy (PhD)

  • Open Access
    Authors: 
    Aminur Rab Ratul; Maryam Tavakol Elahi; Kun Yuan; Won-Sook Lee;
    Publisher: IEEE

    In the last century, we have passed two severe pandemics; the 1957 influenza (Asian flu) pandemic and the 1918 influenza (Spanish flu) pandemic with a high fatality rate. In the last few months, we have been again facing a new epidemic (COVID-19), which is a frighteningly high-risk disease and is globally threatening human lives. Among all attempts and presented solutions to tackle the COVID-19, a publicly available dataset of radiological imaging using chest radiography, also called chest X-ray (CXR) images, could efficiently accelerate the detection process of patients infected with COVID-19 through presented abnormalities in their chest radiography images. In this study, we have proposed a deep neural network (DNN), namely RAM-Net, a new combination of MobileNet with Dilated Depthwise Separable Convolution (DDSC), Residual blocks, and Attention augmented convolution. The network has been learned and validated using the COVIDx dataset, one of the most popular public datasets comprising the chest X-ray (CXR) images. Using this model, we could accurately identify the positive cases of COVID-19 viral infection while a new suspicious chest X-ray image is shown to the network. Our network’s overall accuracy on the COVIDx test dataset was 95.33%, with a sensitivity and precision of 92% and 99% for COVID-19 cases, respectively, which are the highest results on the COVIDx dataset to date, to the best of our knowledge. Finally, we performed an audit on RAM-Net based on the Grad-CAM’s interpretation to demonstrate that our proposed architecture detects SARS-CoV-2 (COVID-19) viral infection by focusing on vital factors rather than relying on irrelevant information.

  • Open Access
    Authors: 
    Simon M. Danner; Natalia A. Shevtsova; Alain Frigon; Ilya A. Rybak;
    Publisher: eLife Sciences Publications, Ltd
  • Open Access
    Authors: 
    William L. Miller; Mary Ann Moran;
    Publisher: Wiley

    The interaction between photochemical and biological processes in the degradation of marine dissolved organic matter (DOM) was investigated with seawater from a coastal southeastern U.S. salt marsh. Seawater supplemented with humic substances was exposed to alternating cycles of sunlight (equivalent to 8 h of midday sun) and dark incubations with natural bacterial populations (l-2 weeks in length). Photochemical degradation of the DOM was monitored during sunlight exposure by direct measurements of dissolved inorganic carbon (DIC) and carbon monoxide (CO) formation in 0.2-Frn filtered seawater. Bacterial degradation was monitored during dark incubations by tritiated leucine uptake and changes in bacterial numbers in bacterivore-free incubations and by direct measurements of DOM loss. The alternating cycles of sunlight and microbial activity resulted in more complete degradation of bulk DOM and marine humic substances than was found for nonirradiated controls (i.e. with microbial activity alone) by a factor of up to 3-fold. Increased decomposition was due both to direct losses of carbon gas photoproducts (DIC and CO in a 15 : 1 ratio) and to enhanced microbial degradation of photodegraded DOM, with approximately equal contributions from each pathway. Mass balance calculations indicated that low-molecular-weight carbon photoproducts, currently considered to be the compounds responsible for stimulating bacterial activity following photodegradation of DOM, were insufficient to account for the enhanced bacterial production observed. Thus, higher molecular weight, chemically uncharacterized fractions of DOM may also be modified to more biologically available forms during exposure to natural sunlight. Photochemical processes play a number of important roles in the biogeochemical cycling of dissolved organic matter (DOM) in natural waters. Water optical properties, biological processes, and trace element distributions have all been demonstrated to be affected, either directly or indirectly, by

  • Open Access
    Authors: 
    Jinluo Cheng; Julien Rioux; John E. Sipe;
    Publisher: American Physical Society (APS)
    Project: NSERC

    Using an empirical pseudopotential description of electron states and an adiabatic bond charge model for phonon states in bulk silicon, we theoretically investigate two-photon indirect optical injection of carriers and spins and two-color coherent control of the motion of the injected carriers and spins. For two-photon indirect carrier and spin injection, we identify the selection rules of band edge transitions, the injection in each conduction band valley, and the injection from each phonon branch at 4 K and 300 K. At 4 K, the TA phonon-assisted transitions dominate the injection at low photon energies, and the TO phonon-assisted at high photon energies. At 300 K, the former dominates at all photon energies of interest. The carrier injection shows anisotropy and linear-circular dichroism with respect to light propagation direction. For light propagating along the $<001>$ direction, the carrier injection exhibits valley anisotropy, and the injection into the $Z$ conduction band valley is larger than that into the $X/Y$ valleys. For $��^-$ light propagating along the $<001>$ ($<111>$) direction, the degree of spin polarization gives a maximum value about 20% (6%) at 4 K and -10% (20%) at 300 K, and at both temperature shows abundant structure near the injection edges due to contributions from different phonon branches. Forthe two-color coherent current injection with an incident optical field composed of a fundamental frequency and its second harmonic, the response tensors of the electron (hole) charge and spin currents are calculated at 4 K and 300 K. We show the current control for three different polarization scenarios. The spectral dependence of the maximum swarm velocity shows that the direction of charge current reverses under increase in photon energy. 15 pages and 14 figures

  • Publication . Article . Preprint . 2009
    Open Access
    Authors: 
    Viktoria Hnatkovska; Vadim Marmer; Yao Tang;

    This Paper Contains Supplemental Material to Hnatkovska, Marmer, and Tang (2009) 'Comparison of Misspecified Calibrated Models: The Minimum Distance Approach'.