Development and results from a survey on students views of experiments in lab classes and research

The Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) was developed as a broadly applicable assessment tool for undergraduate physics lab courses. At the beginning and end of the semester, the E-CLASS assesses students views about their strategies, habits of mind, and attitudes when doing experiments in lab classes. Students also reflect on how those same strategies, habits-of-mind, and attitudes are practiced by professional researchers. Finally, at the end of the semester, students reflect on how their own course valued those practices in terms of earning a good grade. In response to frequent calls to transform laboratory curricula to more closely align it with the skills and abilities needed for professional research, the E-CLASS is a tool to assess students' perceptions of the gap between classroom laboratory instruction and professional research. The E-CLASS has been validated and administered in all levels of undergraduate physics classes. To aid in its use as a formative assessment tool, E-CLASS provides all participating instructors with a detailed feedback report. Example figures and analysis from the report are presented to demonstrate the capabilities of the E-CLASS. The E-CLASS is actively administered through an online interface and all interested instructors are invited to administer the E-CLASS their own classes and will be provided with a summary of results at the end of the semester

An epistemology and expectations survey about experimental physics: Development and initial results

In response to national calls to better align physics laboratory courses with the way physicists engage in research, we have developed an epistemology and expectations survey to assess how students perceive the nature of physics experiments in the contexts of laboratory courses and the professional research laboratory. The Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS) evaluates students' epistemology at the beginning and end of a semester. Students respond to paired questions about how they personally perceive doing experiments in laboratory courses and how they perceive an experimental physicist might respond regarding their research. Also, at the end of the semester, the E-CLASS assesses a third dimension of laboratory instruction, students' reflections on their course's expectations for earning a good grade. By basing survey statements on widely embraced learning goals and common critiques of teaching labs, the E-CLASS serves as an assessment tool for lab courses across the undergraduate curriculum and as a tool for physics education research. We present the development, evidence of validation, and initial formative assessment results from a sample that includes 45 classes at 20 institutions. We also discuss feedback from instructors and reflect on the challenges of large-scale online administration and distribution of results.Comment: 31 pages, 9 figures, 3 tables, submitted to Phys. Rev. - PE

Wavelength-Selective Photonic Switches for Energy Efficient Reconfigurable Data Center Networks

Wavelength-selective switches have been proposed for datacenter use to enhance datacenter scalability and to aid in meeting ever-increasing traffic demands and the resulting energy consumption. In silicon photonics, photonic integrated circuit (PIC) designers can take advantage of the high contrast between silicon and silicon dioxide---the latter of which acts as the cladding for the silicon nanowire waveguides---to design compact microring resonators with large free spectral ranges (FSRs). Furthermore, as commercial silicon photonics foundry offerings become more widely available, the ability to produce larger and more complicated PICs has become easier, as well as providing a clearer path towards large-scale manufacturability and adoption of such technologies. Thus, ring-based wavelength-selective switches are a particularly well-suited application for silicon photonics. Another major design consideration for PICs is low energy consumption. A discussion of simulation results from a model for next generation energy efficient photonic links for data centers motivates and the two wavelength-selective switch designs that are presented in this thesis. The first design is an NxN crossbar switch with L ring pairs to route up to L wavelengths at each cross-point. The second design is an NxN ring-assisted Mach-Zehnder interferometer (RAMZI) switch with L ring pairs per switch element. In both designs, multiple ring pairs of differently sized rings were utilized to partition the FSR such that any one ring pair does not have to move far in the spectrum to complete the switching, thus saving in the power consumption

Data Acquisition in a High Harmonic Generation Lab and at LCLS

In this paper, we examine data acquisition in a high harmonic generation (HHG) lab and preliminary data analysis with the Cyclohexadiene Collaboration at the Linac Coherent Lightsource (LCLS) at SLAC National Accelerator Laboratory. HHG experiments have a large number of parameters that need to be monitored constantly. In particular, the pressure of the target is critical to HHG yield. However, this pressure can fluctuate wildly and without a tool to monitor it, it is difficult to analyze the correlation between HHG yield and the pressure. I used the Arduino microcontroller board and created a complementary MATLAB graphical user interface (GUI), thereby enhancing the ease with which users can acquire time-stamped parameter data. Using the Arduino, it is much easier to match the pressure to the corresponding HHG yield. Collecting data by using the Arduino and the GUI is flexible, user-friendly, and cost-effective. In the future, we hope to be able to control and monitor parts of the lab with the Arduino alone. While more parameter information is needed in the HHG lab, we needed to reduce the amount of data during the cyclohexadiene collaboration. This was achieved by sorting the data into bins and filtering out unnecessary details. This method was highly effective in that it minimized the amount of data without losing any valuable information. This effective preliminary data analysis technique will continue to be used to decrease the size of the collected data

Wavelength-Selective Photonic Switches for Energy Efficient Reconfigurable Data Center Networks

Wavelength-selective switches have been proposed for datacenter use to enhance datacenter scalability and to aid in meeting ever-increasing traffic demands and the resulting energy consumption. In silicon photonics, photonic integrated circuit (PIC) designers can take advantage of the high contrast between silicon and silicon dioxide---the latter of which acts as the cladding for the silicon nanowire waveguides---to design compact microring resonators with large free spectral ranges (FSRs). Furthermore, as commercial silicon photonics foundry offerings become more widely available, the ability to produce larger and more complicated PICs has become easier, as well as providing a clearer path towards large-scale manufacturability and adoption of such technologies. Thus, ring-based wavelength-selective switches are a particularly well-suited application for silicon photonics. Another major design consideration for PICs is low energy consumption. A discussion of simulation results from a model for next generation energy efficient photonic links for data centers motivates and the two wavelength-selective switch designs that are presented in this thesis. The first design is an NxN crossbar switch with L ring pairs to route up to L wavelengths at each cross-point. The second design is an NxN ring-assisted Mach-Zehnder interferometer (RAMZI) switch with L ring pairs per switch element. In both designs, multiple ring pairs of differently sized rings were utilized to partition the FSR such that any one ring pair does not have to move far in the spectrum to complete the switching, thus saving in the power consumption

A gene therapy model for retrovirus-induced disease with a viral env gene: expression-dependent resistance in immunosuppressed hosts

At the initial stage of retroviral infection, virion envelope glycoprotein (env product) binds to cell surface receptors. Cells infected with retrovirus or into which the env gene was introduced, become resistant to superinfection by other retroviruses with the same receptor specificity, a phenomenon known as receptor interference. We have demonstrated previously that the introduction of an env gene from a truncated endogenous ecotropic murine leukemia virus (MuLV), the Fv-4 resistance (Fv-4r) gene, into the bone marrow hematopoietic cells of Fv-4 sensitive (Fv-4s) mice protected mice from ecotropic retrovirus-induced disease. Using the gene transfer system under the control of the retroviral vector and bone marrow transplantation (BMT), here we could show that expression of an introduced Fv-4r gene in hematopoietic cells continued for more than 1 year after BMT. To determine the inhibitory mechanism of Fv-4r env gene expression against FLV-infection in this model system, peripheral blood mononuclear cells (PBMCs), or spleen cells from chimeras with various degrees of env-expression, were mixed with green fluorescence protein (GFP)-conjugated Friend MuLV env glycoprotein (GFP-Fr-ENV). The amount of GFP-Fr-ENV bound to these cells inversely correlated with the expression intensity of the transduced env gene indicating the receptor interference effect. Next, to see whether transduction of the Fv-4r gene would protect an immunosuppressed host from FLV-induced leukemogenesis, we generated immunocompromised chimeras by transplanting env-transduced bone marrow cells into a thymectomized host. These chimeras also resisted FLV-induced leukemogenesis, indicationg that receptor interference-based gene therapy could become a therapeutic basis for immunodeficiency virus-induced diseases in vivo

In vivo distribution of receptor for ecotropic murine leukemia virus and binding of envelope protein of Friend Murine leukemia virus

Ecotropic infection by Murine leukemia virus (MuLV) infection is initiated by the interaction between the receptor-binding domain of the viral surface glycoprotein (SU) and the cell-surface receptor, mCAT-1. To study the in vivo localization of viral binding site in mice, green fluorescence protein (GFP)-tagged Friend SU (F-SU/GFP) was incubated with tissue sections. Lymphohematopoietic organs and a part of the glandular tissues of C3H as well as C57BL/6 mice revealed positive signals for F-SU/GFP binding on the cell surface. In contrast, C4W mice, which is a partial congenic mouse strain carrying the Fr-4r gene on a BALB/c genetic background, exhibited negative signals in most of the organs except for a very weak binding in the pancreas. The expression of mCAT-1 mRNA determined by reverse transcriptase (RT)-polymerase chain reaction (PCR) revealed a similar distribution in C3H, C57BL/6 and C4W mice. Most of the organs including lymphohematopoietic organs and glandular organs revealed significant expression of mRNA for mCAT-1 gene, while the liver, heart and muscle did not. The results from binding assay were consistent with the fact that Friend MuLV-induced pathogenesis was usually associated with lymphohematopoietic systems, although mRNA expression for mCAT-1 was rather ubiquitous. The discrepancy between F-SU/GFP binding and mRNA expression for mCAT-1 in lymphohematopoietic organs of C4W mice would support the receptor interference effect by the Fr-4r gene causing the resistance of C4W mouse to Friend MuLV infection