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2. On stochastic optimization methods for Monte Carlo least-squares problems

Author

Pfeiffer, Gustavo T. and Sato, Yoichi

Subjects
Mathematics - Optimization and Control
Abstract

This work presents stochastic optimization methods targeted at least-squares problems involving Monte Carlo integration. While the most common approach to solving these problems is to apply stochastic gradient descent (SGD) or similar methods such as AdaGrad and Adam, which involve estimating a stochastic gradient from a small number of Monte Carlo samples computed at each iteration, we show that for this category of problems it is possible to achieve faster asymptotic convergence rates using an increasing number of samples per iteration instead, a strategy we call increasing precision (IP). We then improve pre-asymptotic convergence by introducing a hybrid approach that combines the qualities of increasing precision and otherwise "constant" precision, resulting in methods such as the IP-SGD hybrid and IP-AdaGrad hybrid, essentially by modifying their gradient estimators to have an equivalent effect to increasing precision. Finally, we observe that, in some problems, incorporating a Gauss-Newton preconditioner to the IP-SGD hybrid method can provide much better convergence than employing a Quasi-Newton approach or covariance-preconditioning as in AdaGrad or Adam.

Published
2018

3. Phosphorylation patterns in the AT1R C-terminal tail specify distinct downstream signaling pathways.

Author

Gareri, Clarice, Pfeiffer, Conrad T., Jiang, Xue, Paulo, Joao A., Gygi, Steven P., Pham, Uyen, Chundi, Anand, Wingler, Laura M., Staus, Dean P., Stepniewski, Tomasz Maciej, Selent, Jana, Lucero, Emilio Y., Grogan, Alyssa, Rajagopal, Sudarshan, and Rockman, Howard A.

Subjects
G proteins, ANGIOTENSIN II, MOLECULAR dynamics, LIGANDS (Biochemistry), G protein coupled receptors, PHOSPHORYLATION
Abstract

Different ligands stabilize specific conformations of the angiotensin II type 1 receptor (AT1R) that direct distinct signaling cascades mediated by heterotrimeric G proteins or β-arrestin. These different active conformations are thought to engage distinct intracellular transducers because of differential phosphorylation patterns in the receptor C-terminal tail (the "barcode" hypothesis). Here, we identified the AT1R barcodes for the endogenous agonist AngII, which stimulates both G protein activation and β-arrestin recruitment, and for a synthetic biased agonist that only stimulates β-arrestin recruitment. The endogenous and β-arrestin–biased agonists induced two different ensembles of phosphorylation sites along the C-terminal tail. The phosphorylation of eight serine and threonine residues in the proximal and middle portions of the tail was required for full β-arrestin functionality, whereas phosphorylation of the serine and threonine residues in the distal portion of the tail had little influence on β-arrestin function. Similarly, molecular dynamics simulations showed that the proximal and middle clusters of phosphorylated residues were critical for stable β-arrestin–receptor interactions. These findings demonstrate that ligands that stabilize different receptor conformations induce different phosphorylation clusters in the C-terminal tail as barcodes to evoke distinct receptor-transducer engagement, receptor trafficking, and signaling. Editor's summary: The specific patterns of phosphorylation in the intracellular tail of a G protein–coupled receptor (GPCR) are thought to act as a barcode that determines whether G proteins are stimulated or β-arrestins are recruited. Gareri et al. investigated the role of phosphorylation barcodes in signaling by the angiotensin II type 1 receptor (AT1R). AT1R elicits both G protein activation and β-arrestin recruitment in response to the endogenous agonist AngII but stimulates only β-arrestin recruitment in response to a synthetic biased agonist. The authors identified patterns of serine and threonine phosphorylation that stabilized specific conformations of β-arrestin and were necessary for β-arrestin function. These findings demonstrate the importance of phosphorylation barcodes in determining the consequences of AT1R activation. —Annalisa M. VanHook [ABSTRACT FROM AUTHOR]

Published
2024
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5. Preventing Health Disparities during COVID through Perinatal Home Screening as Black Authoritative Knowledge

Author

Chapman, Rachel R., primary, Mohamed, Sumaya B., additional, Rage, Hodan, additional, Abdulahi, Ayan, additional, Jimenez, Jan, additional, Gavin, Amelia R., additional, Zetell, Jasmine, additional, Chatterjee, Kavya N., additional, Valderrábano, Susie, additional, Sundar, Savita, additional, Madey, Halima, additional, and Pfeiffer, James T., additional

Published
2023
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9. The SPARC Toroidal Field Model Coil Program

Author

Hartwig, Zachary S., Vieira, Rui F., Dunn, Darby, Golfinopoulos, Theodore, LaBombard, Brian, Lammi, Christopher J., Michael, Philip C., Agabian, Susan, Arsenault, David, Barnett, Raheem, Barry, Mike, Bartoszek, Larry, Beck, William K., Bellofatto, David, Brunner, Daniel, Burke, William, Burrows, Jason, Byford, William, Cauley, Charles, Chamberlain, Sarah, Chavarria, David, Cheng, JL, Chicarello, James, Diep, Van, Dombrowski, Eric, Doody, Jeffrey, Doos, Raouf, Eberlin, Brian, Estrada, Jose, Fry, Vincent, Fulton, Matthew, Garberg, Sarah, Granetz, Robert, Greenberg, Aliya, Greenwald, Martin, Heller, Samuel, Hubbard, Amanda E., Ihloff, Ernest, Irby, James H., Iverson, Mark, Jardin, Peter, Korsun, Daniel, Kuznetsov, Sergey, Lane-Walsh, Stephen, Landry, Richard, Lations, Richard, Leccacorvi, Rick, Levine, Matthew, Mackay, George, Metcalfe, Kristen, Moazeni, Kevin, Mota, John, Mouratidis, Theodore, Mumgaard, Robert, Muncks, JP, Murray, Richard A., Nash, Daniel, Nottingham, Ben, O'Shea, Colin, Pfeiffer, Andrew T., Pierson, Samuel Z., Purdy, Clayton, Radovinsky, Alexi, Ravikumar, Dhananjay K., Reyes, Veronica, Riva, Nicolo, Rosati, Ron, Rowell, Michael, Salazar, Erica E., Santoro, Fernando, Sattarov, Akhdiyor, Saunders, Wayne, Schweiger, Patrick, Schweiger, Shane, Shepard, Maise, Shiraiwa, Syun'ichi, Silveira, Maria, Snowman, FT, Sorbom, Brandon N., Stahle, Peter, Stevens, Ken, Stillerman, Joshua, Tammana, Deepthi, Toland, Thomas L., Tracey, David, Turcotte, Ronnie, Uppalapati, Kiran, Vernacchia, Matthew, Vidal, Christopher, Voirin, Erik, Warner, Alex, Watterson, Amy, Whyte, Dennis G., Wilcox, Sidney, Wolf, Michael, Wood, Bruce, Zhou, Lihua, and Zhukovsky, Alex

Abstract

The SPARC Toroidal Field Model Coil (TFMC) Program was a three-year effort between 2018 and 2021 that developed novel rare earth barium copper oxide (REBCO) superconductor technologies and then successfully utilized these technologies to design, build, and test a first-in-class, high-field (∼20 T), representative-scale (∼3 m) superconducting toroidal field (TF) coil. The program was executed jointly by the MIT Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems (CFS) as a technology enabler of the superconducting high-field pathway to fusion energy, and, in particular, as a risk retirement program for the no insulation (NI) TF magnet in the SPARC net-energy fusion tokamak. The TFMC achieved its programmatic goal of experimentally demonstrating a large-scale high-field REBCO magnet, achieving 20.1 T peak field-on-conductor with 40.5 kA of terminal current, 815 kN/m of Lorentz loading on the REBCO stacks, and almost 1 GPa of mechanical stress accommodated by the structural case. Fifteen internal demountable pancake-to-pancake joints operated in the 0.5 to 2.0 nΩ range at 20 K and in magnetic fields up to 12 T. The dc and ac electromagnetic performance of the magnet predicted by new advances in high-fidelity computational models was confirmed in two test campaigns while the parallel, single-pass, pressure-vessel style coolant scheme capable of large heat removal was validated. In the test facility, a feeder system composed of REBCO current leads and cables was experimentally qualified up to 50 kA, and a liquid-free cryocooler-based helium cryogenic system provided 600 W of cooling power at 20 K with mass flow rates up to 70 g/s at a maximum design pressure of 2 MPa for the test campaigns. Finally, the feasibility of using passive, self-protection against a quench in a fusion-scale NI TF coil was experimentally assessed. While the TFMC was intentionally not optimized for quench resiliency—and suffered localized thermal damage in response to an intentional open-circuit quench at 31.5 kA terminal current—the extensive data and validated models that it produced represent a critical step towards this important objective.

Published
2024
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10. Development of the first non-planar REBCO stellarator coil using VIPER cable.

Author

Riva, N, Granetz, R S, Vieira, R, Hubbard, A, Pfeiffer, A T, Harris, P, Chamberlain, C, Hartwig, Z S, Watterson, A, Anderson, D, and Volberg, R

Subjects
STELLARATORS, HIGH temperature superconductors, SUPERCONDUCTING magnets, VIPERIDAE, CRITICAL currents, COPPER oxide, MAGNETIC fields
Abstract

The benefits of operating fusion devices, such as tokamaks and stellarators, at high fields make high-temperature superconducting magnets necessary to realize a compact fusion power system. Superconducting stellarators, such as W7-X, have used standard low-temperature superconductor technology niobium-titanium. ARPA-E has recently funded a two-year project led by the startup Type One Energy and involving the Fusion Technology Institute at the University of Wisconsin-Madison, the Plasma Science to design and fabricate the first non-planar high-temperature superconductor (HTS) rare-earth barium copper oxide (REBCO) coil for a high-field stellarator based on the SPARC tokamak's VIPER cable concept. The design consists of a 1.5-turn non-planar REBCO coil supported by a pair of 3D printed stainless steel radial plates. The ultimate goals of the project are to determine if commercial REBCO tapes and additive manufacturing can be used to fabricate high field ( ⩾ 10 T ) non-planar coils with tight bending radii ( ≃ 100 m m ) and with a degradation of the critical current smaller than 20% with respect to the expected performance. In this work we present numerical analysis for non-planar coils (critical current, magnetic field map, Lorentz forces and quench aspects) at the operating conditions of 77 K and 20 K and the fabrication and testing in liquid nitrogen (77 K) of the first two non-planar demonstrators for stellarators based on a VIPER cable. The first demonstrator is a short NO n-planar V IP E R cab L e (cable demonstrator at which we will refer to as NOVEL) equipped with 100 HTS REBCO tapes and with a critical current of 5700 A at 77 K (self-field); the second is a M ult I ple turns (1.5-turns) NO n-pl AN ar coil (coil demonstrator at which we will refer to as MINOAN) equipped with 30 HTS tapes and with a critical current of 2100 A at 77 K (self-field). Both demonstrators were tested at 77 K (liquid nitrogen bath) and the results showed that—even after being bent into non-planar shapes with bend radii ≃ 100 m m —the degradation of the critical current I c was within 15%, meeting the expected goals of the project. [ABSTRACT FROM AUTHOR]

Published
2023
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11. The SPARC Toroidal Field Model Coil Program

Author

Hartwig, Zachary S., primary, Vieira, Rui F., additional, Dunn, Darby, additional, Golfinopoulos, Theodore, additional, LaBombard, Brian, additional, Lammi, Christopher J., additional, Michael, Philip C., additional, Agabian, Susan, additional, Arsenault, David, additional, Barnett, Raheem, additional, Barry, Mike, additional, Bartoszek, Larry, additional, Beck, William K., additional, Bellofatto, David, additional, Brunner, Daniel, additional, Burke, William, additional, Burrows, Jason, additional, Byford, William, additional, Cauley, Charles, additional, Chamberlain, Sarah, additional, Chavarria, David, additional, Cheng, JL, additional, Chicarello, James, additional, Diep, Van, additional, Dombrowski, Eric, additional, Doody, Jeffrey, additional, Doos, Raouf, additional, Eberlin, Brian, additional, Estrada, Jose, additional, Fry, Vincent, additional, Fulton, Matthew, additional, Garberg, Sarah, additional, Granetz, Robert, additional, Greenberg, Aliya, additional, Greenwald, Martin, additional, Heller, Samuel, additional, Hubbard, Amanda E., additional, Ihloff, Ernest, additional, Irby, James H., additional, Iverson, Mark, additional, Jardin, Peter, additional, Korsun, Daniel, additional, Kuznetsov, Sergey, additional, Lane-Walsh, Stephen, additional, Landry, Richard, additional, Lations, Richard, additional, Leccacorvi, Rick, additional, Levine, Matthew, additional, Mackay, George, additional, Metcalfe, Kristen, additional, Moazeni, Kevin, additional, Mota, John, additional, Mouratidis, Theodore, additional, Mumgaard, Robert, additional, Muncks, JP, additional, Murray, Richard A., additional, Nash, Daniel, additional, Nottingham, Ben, additional, O'Shea, Colin, additional, Pfeiffer, Andrew T., additional, Pierson, Samuel Z., additional, Purdy, Clayton, additional, Radovinsky, Alexi, additional, Ravikumar, Dhananjay K., additional, Reyes, Veronica, additional, Riva, Nicolo, additional, Rosati, Ron, additional, Rowell, Michael, additional, Salazar, Erica E., additional, Santoro, Fernando, additional, Sattarov, Akhdiyor, additional, Saunders, Wayne, additional, Schweiger, Patrick, additional, Schweiger, Shane, additional, Shepard, Maise, additional, Shiraiwa, Syun'ichi, additional, Silveira, Maria, additional, Snowman, FT, additional, Sorbom, Brandon N., additional, Stahle, Peter, additional, Stevens, Ken, additional, Stillerman, Joshua, additional, Tammana, Deepthi, additional, Toland, Thomas L., additional, Tracey, David, additional, Turcotte, Ronnie, additional, Uppalapati, Kiran, additional, Vernacchia, Matthew, additional, Vidal, Christopher, additional, Voirin, Erik, additional, Warner, Alex, additional, Watterson, Amy, additional, Whyte, Dennis G., additional, Wilcox, Sidney, additional, Wolf, Michael, additional, Wood, Bruce, additional, Zhou, Lihua, additional, and Zhukovsky, Alex, additional

Published
2023
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15. School Picture Day and Self-Concept: A Smile Is Worth the Trouble

Author

Pfeiffer, Margaret A. and Pfeiffer, Karl T.

Abstract

School picture day--it's an almost universal experience of waiting in line with a new comb, perching nervously on a stool, smiling under the bright lights, and then moving quickly out into the hall. For the past 8 years the authors have been increasingly aware of a picture day bias in the pictures taken of their oldest son. It appears to them that bias contributes to the process of seeing a child with disabilities in a particularly unflattering light. This stigma may be perpetuated with school photographs. These photographs become permanent records of the student and class identities. This image is how other people see their child, at least people who haven't gotten to know him. Disability as stigma, explains the looks of disgust or pity they get at the store, the first unveiled looks of shock at a family reunion, the glances of discomfort and fear at church. These looks from strangers are based on a prejudice that only getting to know the person can disarm. Teachers may facilitate school photographs in ways that maintain the stigma or mitigate it. A smile is worth the trouble.

Published
2011

16. Community Services, Issues, and Service Gaps for Individuals with Developmental Disabilities Who Exhibit Inappropriate Sexual Behaviors.

Author

Ward, Karen M., Pfeiffer, Karl T., and Trigler, Jordan S.

Abstract

A national survey of 243 community agencies evaluated services provided for individuals with developmental disabilities who exhibit high-risk sexual behaviors and identified issues and service gaps. Common offenses were sexual behavior in public situations, inappropriate involvement of others, and involvement of minors. Major issues and problems were systemic, specifically staff issues and service gaps, followed by funding. (Contains references.) (DB)

Published
2001

22. VIPER: an industrially scalable high-current high-temperature superconductor cable

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hartwig, Zachary Seth, Vieira, Rui F, Sorbom, Brandon N, Badcock, Rodney A, Bajko, Marta, Beck, William K., Castaldo, Bernardo, Craighill, Christopher L, Davies, Michael, Estrada, Jose, Fry, Vincent, Golfinopoulos, Theodore, Hubbard, Amanda E, Irby, James Henderson, Kuznetsov, Sergey, Lammi, Christopher J, Michael, Philip C, Mouratidis, Theodore, Murray, Richard A., Pfeiffer, Andrew T., Pierson, Samuel Z, Radovinsky, Alexey, Rowell, Michael D, Salazar, Erica E, Segal, Michael, Stahle, Peter W, Takayasu, Makoto, Toland, Thomas L, Zhou, Lihua, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Hartwig, Zachary Seth, Vieira, Rui F, Sorbom, Brandon N, Badcock, Rodney A, Bajko, Marta, Beck, William K., Castaldo, Bernardo, Craighill, Christopher L, Davies, Michael, Estrada, Jose, Fry, Vincent, Golfinopoulos, Theodore, Hubbard, Amanda E, Irby, James Henderson, Kuznetsov, Sergey, Lammi, Christopher J, Michael, Philip C, Mouratidis, Theodore, Murray, Richard A., Pfeiffer, Andrew T., Pierson, Samuel Z, Radovinsky, Alexey, Rowell, Michael D, Salazar, Erica E, Segal, Michael, Stahle, Peter W, Takayasu, Makoto, Toland, Thomas L, and Zhou, Lihua

Abstract

High-temperature superconductors (HTS) promise to revolutionize high-power applications like wind generators, DC power cables, particle accelerators, and fusion energy devices. A practical HTS cable must not degrade under severe mechanical, electrical, and thermal conditions; have simple, low-resistance, and manufacturable electrical joints; high thermal stability; and rapid detection of thermal runaway quench events. We have designed and experimentally qualified a vacuum pressure impregnated, insulated, partially transposed, extruded, and roll-formed (VIPER) cable that simultaneously satisfies all of these requirements for the first time. VIPER cable critical currents are stable over thousands of mechanical cycles at extreme electromechanical force levels, multiple cryogenic thermal cycles, and dozens of quench-like transient events. Electrical joints between VIPER cables are simple, robust, and demountable. Two independent, integrated fiber-optic quench detectors outperform standard quench detection approaches. VIPER cable represents a key milestone in next-step energy generation and transmission technologies and in the maturity of HTS as a technology.

Published
2021

25. VIPER: an industrially scalable high-current high-temperature superconductor cable

Author

Hartwig, Zachary S, primary, Vieira, Rui F, additional, Sorbom, Brandon N, additional, Badcock, Rodney A, additional, Bajko, Marta, additional, Beck, William K, additional, Castaldo, Bernardo, additional, Craighill, Christopher L, additional, Davies, Michael, additional, Estrada, Jose, additional, Fry, Vincent, additional, Golfinopoulos, Theodore, additional, Hubbard, Amanda E, additional, Irby, James H, additional, Kuznetsov, Sergey, additional, Lammi, Christopher J, additional, Michael, Philip C, additional, Mouratidis, Theodore, additional, Murray, Richard A, additional, Pfeiffer, Andrew T, additional, Pierson, Samuel Z, additional, Radovinsky, Alexi, additional, Rowell, Michael D, additional, Salazar, Erica E, additional, Segal, Michael, additional, Stahle, Peter W, additional, Takayasu, Makoto, additional, Toland, Thomas L, additional, and Zhou, Lihua, additional

Published
2020
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27. HIV-exposed infant follow-up in Mozambique: Formative research findings for the design of a cluster randomized controlled trial to improve testing and ART initiation

Author

Vieira, Lúcia C, primary, Mahumane, Arlete Miloque, additional, Napua, Manuel, additional, Chale, Falume Azamo, additional, Manuel, João Luís, additional, Cowan, Jessica Greenberg, additional, Sherr, Kenneth, additional, Chapman, Rachel R, additional, and Pfeiffer, James T, additional

Published
2020
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30. ICRF antenna matching systems with ferrite tuners for the Alcator C-Mod tokamak

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lin, Yijun, Binus, Alan, Wukitch, Stephen James, Koert, Peter, Murray, Richard A, Pfeiffer, Andrew T, Massachusetts Institute of Technology. Plasma Science and Fusion Center, Lin, Yijun, Binus, Alan, Wukitch, Stephen James, Koert, Peter, Murray, Richard A, and Pfeiffer, Andrew T

Abstract

Real-time fast ferrite tuning (FFT) has been successfully implemented on the ICRF antennas on Alcator C-Mod. The former prototypical FFT system on the E-port 2-strap antenna has been upgraded using new ferrite tuners. A new FFT system with two ferrite tuners and one fixed-length stub has been installed on the transmission line of the D-port 2-strap antenna. These two systems are able to achieve and maintain the reflected power to the transmitters to less than 1% in real time under almost all plasma conditions and help ensure reliable high power operation of the antennas. The loading insensitivity feature vs. plasma conditions of the innovative field-aligned (FA) 4-strap antenna on the J-port allows us to significantly improve the matching by installing a carefully designed stub on each of the two transmission lines. The reduction of the RF voltages in the transmission lines has enabled the J-port FA antenna to deliver 3.7 MW RF power to plasmas out of 4 MW source power. The matching on the J-port antenna can be further improved by adding a single ferrite tuner under real-time control on each transmission line and this scheme will be implemented in the near future., United States. Department of Energy (Agreement DE-FC02-99ER54512)

Published
2018

34. Option B+ in Mozambique: Formative Research Findings for the Design of a Facility-Level Clustered Randomized Controlled Trial to Improve ART Retention in Antenatal Care

Author

Napúa, Manuel, primary, Pfeiffer, James T., additional, Chale, Falume, additional, Hoek, Roxanne, additional, Manuel, Joao, additional, Michel, Cathy, additional, Cowan, Jessica G., additional, Cowan, James F., additional, Gimbel, Sarah, additional, Sherr, Kenneth, additional, Gloyd, Stephen, additional, and Chapman, Rachel R., additional

Published
2016
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39. Early ART initiation among HIV-positive pregnant women in central Mozambique: a stepped wedge randomized controlled trial of an optimized Option B+ approach

Author

Cowan, James F, primary, Micek, Mark, additional, Cowan, Jessica F Greenberg, additional, Napúa, Manuel, additional, Hoek, Roxanne, additional, Gimbel, Sarah, additional, Gloyd, Stephen, additional, Sherr, Kenneth, additional, Pfeiffer, James T, additional, and Chapman, Rachel R, additional

Published
2015
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41. [Early detection of depressive illnesses]

Author

Ulrich Hegerl and Pfeiffer-Gerschel T

Subjects
Patient Care Team, Suicide Prevention, Depressive Disorder, Suicide, Early Diagnosis, Humans, Mass Screening, Suicide, Attempted, Family Practice, Prognosis, Survival Analysis
Abstract

At the primary care level, depressive states are common, often severe, and possibly even life-threatening, illnesses. Early identification is important if we are to reduce unnecessary suffering, progression and chronification. The detection rate can be improved by screening and active investigation. The Competency Network on Depression and Suicidality is an email-based consulting service (www.psychiatriekonsil.de) available to physicians, psychotherapists and pharmacists, which provides advice, free of charge and anonymously, to all those seeking support on depressive or other psychiatric illnesses.

Published
2007

42. [Modern discussion forum 'depression, suicidality']

Author

Pfeiffer-Gerschel T, Niedermeier N, and Ulrich Hegerl

Subjects
Suicide Prevention, Depressive Disorder, Internet, Self-Help Groups, Suicide, Patient Education as Topic, Quality Assurance, Health Care, Germany, Humans, Social Support, Health Education
Abstract

Five years ago, with the appearance on the internet of the competence network "Depression, Suicidality", a conducted discussion forum was established to serve as a platform for an internet-based self-help group. Today, the forum has more than 3,000 registered visitors, and is the largest virtual group concerned with depression in the German-speaking area. In comparison with a "real" self-help group, this virtual form offers specific possibilities to those concerned, such as, for example, 24-hour access to other sufferers. Admittedly, specific limitations must nevertheless be noted, which, among other things, have to do with the particular features of internet-based communication and the heterogeneity of the participants. Overall, this virtual self-help group represents a rational and useful addition to the existing possibilities for self help.

Published
2006

43. [Elements for the effective treatment of patients with depressive disorders at the primary care level]

Author

Ulrich Hegerl, Pfeiffer-Gerschel T, and Althaus D

Subjects
Diagnosis, Differential, Patient Care Team, Psychotherapy, Depressive Disorder, Surveys and Questionnaires, Humans, Mass Screening, Family Practice, Somatoform Disorders, Referral and Consultation, Antidepressive Agents, Physicians' Offices
Abstract

Patients with a depressive disorder usually consult their family doctor, in particular when physical symptoms are to the fore. With the aid of a screening questionnaire that the patient completes in the waiting room, it can be determined whether depression might be present. In the next step, the diagnosis is clarified by specific questioning about the core symptoms. At the start of treatment, the patient should be informed about the nature of his illness. The more convincingly an appropriate treatment concept can be explained to the patient, the better will his cooperation be. Mild or moderate depression is treated by the general physician. If the patient fails to respond to treatment within two to three weeks, or if complications occur, a specialist should be consulted.

Published
2004

48. An intermediate power amplifier upgrade for 40 to 80 Mhz for the alcator C-mod ICRF transmitters

Author

Massachusetts Institute of Technology. Plasma Science and Fusion Center, Binus, Alan, Pfeiffer, Andrew T., Murray, Richard A., Lin, Yijun, Wukitch, Stephen James, Gwinn, D., Massachusetts Institute of Technology. Plasma Science and Fusion Center, Binus, Alan, Pfeiffer, Andrew T., Murray, Richard A., Lin, Yijun, Wukitch, Stephen James, and Gwinn, D.

Abstract

ICRF operations with Alcator C-Mod consists of 4 transmitters, of which two are tunable within the 40 MHz to 80 MHz band. These transmitters were comprised of 3 stages all of which employed vacuum tube amplifiers. As a part of the general plan to upgrade the two tunable transmitters, a project was implemented to replace the first stage, the intermediate power amplifier, with a 10 kilowatt solid state broadband amplifier. There were two primary benefits from the upgrade. The tuning of the transmitters was considerably simplified and better performance was obtained under a variety of operational conditions by having a conservative power margin. The improvements obtained are an important first step toward advancing the overall radio frequency performance of the transmitters and minimizing the time intensive task of changing the frequency of operation., United States. Dept. of Energy (Cooperative Grant No. DE-FC02-99ER54512-C-Mod)

Published
2010

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