The subfamily Ballinae is revised. To test its monophyly, 41 morphological characters, including the first phylogenetic use of scale morphology in Salticidae, were scored for 16 taxa (1 outgroup and 15 ingroup). Parsimony analysis of these data supports monophyly based on five unambiguous synapomorphies. The paper provides new diagnoses, descriptions of new genera, species, and a key to the genera. At present, Ballinae comprises 13 nominal genera, three of them new: Afromarengo, Ballus, Colaxes, Cynapes, Indomarengo, Leikung, Marengo, Philates and Sadies. Copocrossa, Mantisatta, Pachyballus and Padilla are tentatively included in the subfamily. Nine new species are described and illustrated: Colaxes horton, C. wanlessi, Philates szutsi, P. thaleri, P. zschokkei, Indomarengo chandra, L sarawakensis, Leikung kinabaluensis and Marengo deelemanae. Colaxes nitidiventris and Ballus segmentatus are redescribed. The Seychelles species Baviola spatulata is considered a junior synonym of B. braueri. The phylogenetic analysis suggests two independent origins of tentative Batesian mimicry of ants within Ballinae. (C) 2004 The Linnean Society of London.

A new species of the genus Nestacella is described from both sexes. It is characterised by the presence of a beak-shaped paracymbium. It has long legs and weak pigmentation but lacks eyes.

Magnons, i.e. the quanta of spin waves, are considered to be promising information carriers. Unlike electric currents, magnon-based spin currents could be used to transport information coherently over long distance without generating any Joule heat. Magnons in antiferromagnetic materials exhibit resonance frequencies extending up to the THz frequency range, which promises rapid response of magnon-based devices. However, it becomes difficult to control such rapid oscillations of magnetization using circuit-based electronic control. Instead, optical techniques have been investigated for the generation and control of AF magnons – however most techniques have been based upon ultrafast near-IR pump-probe techniques.

In this thesis, I investigate the feasibility of designing electromagnetic metastructures with subwavelength effective cavity volumes to realize strong light-matter coupling between suitable antiferromagnetic materials operating at over 1 THz. In these systems, light and material excitations are strongly coupled and mixed into superposition states with hybrid dispersion relation, which are termed as polaritons. Such magnon-polariton systems are of interest as they enable coherent information transferring between distinct physical platforms. While polaritons have been demonstrated between GHz-frequency photons and ferromagnetic magnons, only limited reports have been found on antiferromagnetic magnon-polaritons.

Moreover, as a potential application, the feasibility of THz magnon-polariton lasers is studied. In this thesis, I propose an idea which combines metal-metal waveguide with LC circuit- based microcavity, and introduce a design of metastructure with strong evanescent magnetic field, enabling the generation of magnon-polaritons even in a 200 nm thin antiferromagnetic film. Quantum cascade active region with intersubband transitions falling into THz frequency range can be applied into the metastructure, enabling direct amplification of magnon-polaritons. Magnon-polariton lasing becomes possible when this hybrid active metastructure/ antiferromganet is paired with an output coupler, building up a quantum cascaded vertical external cavity surface emitting laser (QC-VECSEL). The opportunity of magnon-polariton quantum cascade laser is also discussed when a thick antiferromagnetic slab is inserted in a standard VECSEL cavity.

Quantum-cascade vertical-external-cavity surface-emitting-laser (QC-VECSEL) is a recently developed compact and coherent source of THz radiation which has demonstrated excellent beam quality and scalable high-power. The key component of the QC-VECSEL is an amplifying reflectarray metasurface made up of an array of sub-wavelength metal-metal waveguides loaded with quantum-cascade (GaAs/AlGaAs) laser gain material. To further the usefulness of this technology for many applications, including spectroscopy, heterodyne detection, and multispectral imaging, broadband and tunable THz QCLs are required. In this work, I investigate the feasibility of two techniques for tuning THz metasurface-based QCLs. First, A Littrow metasurface external cavity laser (ECL) is modeled and studied. We also propose and evaluate a novel method to implement Littrow ECL based upon blazed metasurface gratings. Electromagnetic simulations show that these metasurfaces can provide up to 15% fractional tunability around the center frequency of the laser at 3.3 THz. Preliminary results on several active resonant-phonon quantum-cascade materials are also obtained. Current progress on actual fabrication and device testing is reported.

Semiconductor saturable absorber mirrors (SESAMs) are passive elements that have beenused in tandem with lasers in the visible and infrared wavelengths to generate mode-locked pulses for applications in communication and spectroscopy. In this thesis, the simulation and characterization of terahertz saturable absorber metasurfaces and mid-IR samples embedded with quantum-cascade (QC) absorbing material are discussed. The reflectance of each design is simulated to determine expected saturation parameters and compared with analytic estimates. The characterization of the saturable absorber involves focusing a QC-vertical external cavity surface emitting laser (VECSEL) onto a saturable absorber in a reflectionmode spectroscopy configuration to measure the reflected power. Using a gold mirror as a reference, the reflectance is measured for frequencies near 3.4 THz at room temperature. Improvements to this experiment and a preliminary design for an external cavity incorporating a saturable absorber metasurface are proposed.

Juvenile myelomonocytic leukemia (JMML) is a rare childhood myeloproliferative neoplasm/myelodysplastic syndrome associated with mutations in the Ras/mitogen activated protein kinase (MAPK) signaling pathway. PTPN11 is the most commonly mutated gene in JMML, accounting for 35% of cases, followed by gain-of-function mutations in KRAS and NRAS and loss-of-function mutations in NF1. The protein tyrosine phosphatase (PTP) SHP-2 encoded by the gene PTPN11 is known to play a critical role in hematopoiesis and development, and studies in Drosophila and C. elegans have identified the SHP-2 homologs corkscrew and ptp-2 as crucial mediators of Ras and growth factor receptor signaling. SHP-2 is an SH2-domain containing non-receptor PTP whose activity is basally auto-inhibited by the occlusion of its catalytic cleft by its N-SH2 domain. The most frequently identified PTPN11 mutation results in an E76K substitution that is predicted to interfere with the N-SH2/PTP domain interface, thereby disrupting the auto-inhibited conformation. SHP-2 is unusual for a PTP in that it positively regulates growth factor signaling, and the mutations identified in JMML are gain-of-function mutations resulting in a basal increase in catalytic activity. A hallmark feature of JMML is hypersensitivity of hematopoietic progenitors to granulocyte-macrophage colony-stimulating factor (GM-CSF) in an in vitro colony-forming assay (CFU-GM). It has been demonstrated that the catalytic activity of SHP-2 is required for its transforming ability, as substitution of critical catalytic residues abolishes E76K-mediated CFU-GM hypersensitivity. Utilizing PTP substrate-trapping technology, we have used tandem affinity purification and mass spectrometry to identify several putative substrates of SHP-2 E76K, including the protein parafibromin. Examination of changes in global phosphotyrosine mediated by SHP-2 E76K revealed a role for Src family kinases (SFK) in SHP-2 signaling downstream of the GM-CSF receptor, although CFU-GM transformation assays using hematopoietic progenitors from SFK-null murine models suggested that this relationship was not essential for leukemogenesis. Instead, high overexpression of SHP-2 in the human TF-1 leukemia cell line demonstrated a potential role for SHP-2 in promoting megakaryocytic differentiation via inhibition of the SFK Lyn. Lastly, the identification of mutations in C-CBL in a number of hematologic malignancies led us to discover and characterize the role of similar mutations in JMML.

Terahertz (THz) quantum-cascade lasers (QCLs) are an emerging semiconductor source of compact, high-power THz radiation. Though first realized more than 15 years ago, THz QCLs continue to suffer from poor beam quality and outcoupling efficiency due to the subwavelength nature of the semiconductor ridge-waveguides typically used. In this thesis, a new technique is discussed for obtaining high power and good beam quality from THz QCLs, the THz quantum-cascade external cavity surface emitting laser (QC-VECSEL). The concept of the QC-VECSEL is to use THz QC-gain material to design a millimeter-scale reflective amplifying surface, or metasurface, for free space THz waves and incorporate it into a free-space THz resonant cavity to provide feedback to the amplification and form a laser. In this manner, the beam shape is determined by the external cavity, which supports fundamental Gaussian solutions. Further, the metasurface itself is composed of a subwavelength array (to prevent diffraction) of surface-coupled QC-elements whose properties, such as phase and polarization response, can be engineered on a unit cell basis allowing for a variety of unique experiments.

The power output power of the QC-VECSEL can be scaled by either increasing the size of the metasurface, or increasing the density (or fill factor) of QC-elements across the surface. In this work, large area metasurfaces with high fill-factor have been studied and demonstrated up to 1.35 W of peak output power for a QC-VECSEL operating at 3.4 THz at a heat sink temperature of 4 K. A peak wall-plug efficiency of ~2% is demonstrated, but observation of self lasing from the metasurface at high bias (when no external cavity is provided) in combination with a simultaneous roll-off in VECSEL output power suggests even higher efficiency can be achieved with improved suppression of self-lasing modes. The output beam is well fit to a Gaussian distribution with a 4 degree full-width half-maximum divergence angle.

In addition to power and beam quality, the QC-VECSEL opens the door to many interesting and unique studies via engineering of the metasurface properties and external cavity. Much of this thesis describes frequency tuning of QC-VECSELs based on broadband metasurfaces by varying the length of the external cavity. By making the external cavity extremely short (comparable to the operating wavelength), we are able to push all other external cavity modes outside of the gain bandwidth of the metasurface and demonstrate more than 20% fractional single-mode tuning around a center operating frequency of 3.5 THz. Because there are almost no diffraction losses at such a short cavity, the size of the metasurface could be reduced, allowing for continuous wave lasing with up to 20 milliwatts of output power at a heatsink temperature of 77 K, though the output power is highly variable as the reflectance of the output coupler has a strong frequency dependence. At the time of writing this, these are record performances in both frequency tuning and high-temperature continuous wave operation for lasers based on THz QC-gain material. The amount of tuning that be achieved with this approach is limited by the phase response of the metasurface, which squeezes the external cavity modes closer together in the spectral domain. Development of metasurfaces with lower electrical power consumption and higher conversion efficiency for the purpose of improving continuous wave performance. A sparse, patch-based metasurface with reduced power consumption is demonstrated, though the design was not optimal and only showed a 20% reduction in current draw compared to the previously demonstrated metasurfaces. Routes towards improving the performance are discussed.

The last subject discussed is the design of a mid-infrared (IR) QC-VECSEL. Due to the large metal losses at mid-IR frequencies compared to THz, the technique used to develop THz QC-VECSELs cannot be directly extended to the mid-IR. We propose a scheme based on a diffraction grating to provide surface coupling of the QC-gain material. Progress on experimental realization is discussed, but lasing has not yet been observed.

The THz quantum-cascade vertical-external-cavity surface-emitting-laser (QC-VECSEL) is a recently developed approach for designing high-power, electrically pumped THz lasers with excellent beam quality and broadband tunability. The key component of the QC-VECSEL is an amplifying reflectarray metasurface, based on a subwavelength array of surface radiating metal-metal waveguide antenna elements loaded with QC-laser gain material. Despite its importance, the gain properties of the QC-metasurface are designed by simulation and have only been verified indirectly through observation of the QC-VECSEL lasing characteristics, or by passive FTIR reflectance measurements at room-temperature. THz time-domain spectroscopy (TDS) has been widely used to investigate gain spectra and laser dynamics of THz QC-lasers based on various ridge waveguide geometries. In this thesis, I describe my construction of a THz TDS system and present the first direct spectral measurement using reflection-mode THz TDS of an amplifying QC-metasurface resonant at 2.6 THz under different conditions. The large surface-radiating aperture of the metasurface (1.5�1.5 mm2 in this case) eases free-space TDS measurements compared to ridge waveguide QC-devices with sub-wavelength sized facets.