Aluminum foam sandwich (AFS) is an innovative material for lightweight structures due to its various advantages (e.g. low specific mass). Today, many material properties (e.g. strength) are still not well researched, which is why AFS is not yet considered in current material selection processes. Therefore, AFS has rarely been used in the past and its application potential remains unused. This paper presents an approach toward an appropriate method for considering AFS in material selection processes to assist designers in evaluating whether the use of AFS in an application is profitable.

OBJECTIVES/GOALS: The primary goals of this study are 1) expand our understanding of the neural circuitry influenced by the neuropeptide Neuromedin U (NMU) via its receptor Neuromedin U Receptor 2 (NMUR2), and 2) provide alternative top-down mechanisms for how NMU regulates high fat food intake and cocaine taking. METHODS/STUDY POPULATION: Immunohistochemistry (IHC) for NMUR2 and cell markers was performed on rat brain tissue containing the medial prefrontal cortex (mPFC). To identify the source of the presynaptic NMUR2, anterograde tracing from the paraventricular nucleus or dorsal raphe nucleus to the mPFC utilizing an AAV2- dsRed-synaptobrevin fusion protein were performed (n=3) and will be followed by IHC. Using in vivo calcium imaging technology (InScopix nVista), neuronal activity (calcium transients) was recorded from the mPFC of two awake, freely behaving rats. Each animal underwent a single session of 30 minutes baseline activity, intraperitoneal NMU administration, and 30 minutes of post-treatment activity. Activity was then processed and recorded as distinct events using the InScopix data acquisition software. RESULTS/ANTICIPATED RESULTS: Medial prefrontal cortex staining for NMUR2 revealed a characteristic “beads on a string” motif, consistent with presynaptic receptor expression. Furthermore, we expect the anterograde tracing experiment will show colocalization of the dsRed-synaptobrevin fusion protein with NMUR2 on synaptic inputs into the medial prefrontal cortex. Following quantification of pre- and post- treatment events using the InScopix data acquisition software, total events during the pre- and post-treatment time periods were calculated. In these studies, both animals demonstrated a clear increase in calcium transient activity between pre- and post- treatment evaluations, suggesting that NMU administration increases the neuronal activity of neurons in the prefrontal cortex. DISCUSSION/SIGNIFICANCE: This research provides a new site of action for the known therapeutic effects of NMU. We demonstrate the presence of presynaptic NMUR2 in the mPFC and show that systemic administration of NMU increases mPFC neuronal activity. This illustrates NMU may act as a top-down mediator for substance use disorders and binge eating behaviors.

OBJECTIVES/GOALS: We aimed to explore the students’ assessments of workload distribution by comparing personal reflective commentaries and team documents defining division of labor in a team science setting. METHODS/STUDY POPULATION: The Interprofessional Research Design course models the team science experience by bringing together MD and PhD students to write a research grant. Four teams of 13 students were tasked with both individual and team-based assignments: 1) Each week, each student reported their perception of their own and their team members’ effort over the week (totalling 100%). 2) Iterative work contracts for each team were submitted at four time-points; assigned work toward project completion totalled 100%. 3) Lastly, each student submitted a short commentary reflecting on the prior week’s team dynamics and teamwork. We retrospectively performed a mixed-methods analysis of the workload data. RESULTS/ANTICIPATED RESULTS: Group-reporting in the team contracts remained static throughout the course, often stating equal distribution of workload, whereas individual reporting was more dynamic. Of 13 students, 8 rated more than 50% of the weeks as balanced. Among some students, there was a discordance of workload distribution when comparing the group document to the individual perceptions of work performed by their teammates. Reflective writing mapped more closely to individual quantitative reports. The data also revealed within team variations, where one student may report a higher proportion of their contributions, while the rest of the team attributed that student a lower percentage of the total work. DISCUSSION/SIGNIFICANCE OF IMPACT: An important aspect of team function is workload distribution. Group-based workload discussions may be a useful framework, but does not provide insight into team dynamics, whereas individually reported workload distributions and short reflections seem to more accurately inform us on team function.

Aluminum foam sandwich (AFS) is an innovative sandwich material for designing lighter products and has many advantages such as high stiffness and high mechanical-energy absorption capacity. Although AFS is ready for series production, the number of use cases is low. A survey was carried out in order to identify the obstacles in the application of aluminum foam sandwich. This paper presents the results of the survey, derives the demand for a support method for designing with aluminum foam sandwich and shows various support options to simplify the application of the material.

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007

In this study the results of polychromatic X-ray microbeam analysis (PXM) of the structural changes caused by FIB in nitride heterostructures are presented and discussed in connection with micro-photoluminescence (μ-PL), fluorescent analysis, scanning electron (SEM) and transmission electron microscopy (TEM) data. It is shown that FIB processing distorts the lattice in the InGaN/GaN layer not only in the immediate vicinity of the processed area but also in the surroundings. A narrow amorphidized top layer is formed in the direct ion beam impact area.

The spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) substrates by maskless cantilever epitaxy was studied by white-beam Laue x-ray microdiffraction, scanning electron microscopy, and orientation imaging microscopy. Tilt boundaries formed at the column/wing interface with the misorientation strongly depending on the growth conditions. A depth-dependent deviatoric strain gradient is found in the GaN. Types and density of misfit dislocations as well as their arrangement within different dislocation arrays was quantified. The results are discussed with respect to the miscut of the Si(111) surface and misfit dislocations formed at the interface.

Intrinsic stresses due to lattice mismatch and high densities of threading dislocations and extrinsic stresses resulting from the mismatch in the coefficients of thermal expansion are present in almost all III-Nitride heterostructures. Stress relaxation in the GaN layers occurs in conventional and in pendeo-epitaxial films via the formation of additional misfit dislocations, domain boundaries, elastic strain and wing tilt. Polychromatic X-ray microdiffraction, high resolution monochromatic X-ray diffraction and finite element simulations have been used to determine the distribution of strain, dislocations, sub-boundaries and crystallographic wing tilt in uncoalesced and coalesced GaN layers grown by maskless pendeo-epitaxy. An important parameter was the width-to-height ratio of the etched columns of GaN from which the lateral growth of the wings occurred. The strain and tilt across the stripes increased with the width-to-height ratio. Tilt boundaries formed in the uncoalesced GaN layers at the column/wing interfaces for samples with a large ratio. Sharper tilt boundaries were observed at the interfaces formed by the coalescence of two laterally growing wings. The wings tilted upward during cooling to room temperature for both the uncoalesced and the coalesced GaN layers. It was determined that finite element simulations that account for extrinsic stress relaxation can explain the experimental results for uncoalesced GaN layers. Relaxation of both extrinsic and intrinsic stress components in the coalesced GaN layers contribute to the observed wing tilt and the formation of sub-boundaries.

The synchrotron radiation technique of x-ray standing waves (XSW), which allows to directly obtain structural and element-specific data, was successfully used for the investigation of the dopant site distribution in Si doped GaN films grown on (0001) sapphire substrates for the first time. The Si dopant concentration was chosen to 5×1018 cm-3 and 5×1019 cm-3. The measurements were performed on 300 nm thin doped films deposited on high-quality thick undoped GaN films. With this sample structure, influences of the Si dopant induced decrease of the crystalline quality on the XSW signal are suppressed. The XSW data are compared to those obtained from thick homogeneously doped GaN films. All XSW measurements were performed in (002) backscattering geometry. Independent of the dopant concentration, the results indicate that Si atoms are solely incorporated on substitutional Ga sites.

The effect of high temperature, high pressure annealing on morphology, optical and structural properties of free-standing GaN films grown by hydride vapor phase epitaxy is studied. The annealing is found to change the intensities of the photoluminescence peaks as a result of a redistribution of the impurities and native defects in the thick GaN films. A positron annihilation study shows a decrease of the Ga vacancy-related defects below the detection limit after the annealing. The defect redistribution is correlated with a flattening of the stress distribution across the thickness, as revealed by micro Raman study, and with a decrease of the curvature of the annealed free-standing films.

We present micro-photoluminescence measurements on unstructured InGaN/GaN quantum well samples. Single sharp emission lines were observed and their optical properties were studied as a function of temperature and excitation density. The experimental findings such as the independence of their spectral position on the excitation density and the observation of binding and antibinding multiexcitonic states give clear evidence for the existence of strong localization centers in the InGaN quantum well, which exhibit the same characteristics as they are known for quantum dot structures.

The effect of a highly Mg doped subcontact layer on top of GaN grown by metal organic vapor phase epitaxy and its interface to a Pd/Au contact layer was investigated by means of transmission electron microscopy and electrical characterization techniques. Use was made of prior investigations of the Mg doping characteristics, which showed the existence of a segregation related defect free layer even for doping levels as high as 5×10−19cm−3, which thickness depends on the Mg to Ga molar precursor flow ratio. For a given subcontact layer thickness of 15 nm a critical precursor molar flow ratio of 0.035 resulted in a smooth surface showing an interfacial layer indicating a Pd/Ga alloying. This layer resulted in a contact resistivity as low as 2×10−5 Ωcm2. For a flow ratio of 0.070 the surface was found to be rough due to defect formation resulting in a contact resistivity as high as 10−3 Ωcm2 similar to the value obtained without subcontact layer. Moreover, the metallization layer showed in all cases a texture of the {111} lattice planes with respect to the {0002} planes of the GaN.

In order to optimize the quantum efficiency of InGaN quantum wells, different MOVPE growth sequences are compared using photo- and electroluminescence. In one study, the surface was pretreated with trimethylindium (TMIn) prior to the well deposition. In another study, growth interruptions were performed after the quantum well deposition to desorb segregated indium. In both cases, the room-temperature photoluminescence (PL) intensity is strongly enhanced. For the samples grown with TMIn preflow the wavelength distribution in low-temperature cathodoluminescence (CL) wavelength mappings is narrowed, which can be attributed to more homogeneous quantum wells. Furthermore, the decay times of the radiative recombination increase both at RT and 2K. A reason for this could be an improved indium profile along the growth direction or a more homogeneous In wetting layer due to the pre-wetted surface.

In this paper, we are investigating the growth of a ZnSe based vertical cavity surface emitting laser (VCSEL). Undoped and p-type doped distributed Bragg reflectors (DBRs) with reflectivities exceeding 99% have been grown by molecular beam epitaxy (MBE) using Zn(S)Se layers for the high refractive index material and ZnSe/MgS superlattices (SLs) for the low index material. An undoped monolithic VCSEL structure containing a ZnCdSSe quantum well (QW) emitting in the blue-green reaches a quality factor (Q-factor) of 100, which is the best value reported so far. Temperature dependent photoluminescence (PL) measurements show that the emission of the QW is effectively guided by the cavity resonance.

The microstructural evolution of AlxGa1-xN films grown by metalorganic vapor phase epitaxy on 6H-SiC (0001) was studied by means of X-ray diffraction, atomic force microscopy and transmission electron microscopy in conjunction with energy dispersive X-ray spectroscopy. A significant spatial variation of composition was found in 100 nm thick layers the nature of which could be traced back to the initial stage of film formation. Upon nucleation two phases are formed: a wetting layer and isolated islands of high and low aluminum content, respectively. The observed results are discussed in terms of strain and growth rates.

We present results of Raman-scattering experiments on GaN doped with Si, C, and Mg, respectively, grown by molecular beam epitaxy (MBE). The influence of the different dopants on strain and free-carrier concentration was investigated. Furthermore, we report on several local vibrational modes (LVM) around 2200 cm−1 in Raman spectra of highly Mg-doped GaN. A possible explanation of these high-energy modes in terms of hydrogen-related vibrations is given. We also found a variety of new structures in the range of the GaN host lattice phonons. Secondary ion mass spectroscopy (SIMS) was applied to determine the concentration of magnesium and unintentionally incorporated hydrogen.

GaN layers were grown by molecular beam epitaxy and doped with carbon of nominal concentrations ranging from 1016 cm−3 to 1020 cm−3. The incorporation of carbon leads to a reduction of the background electron concentration by one order of magnitude but the material remains n-type. For high carbon concentrations a re-increase of the carrier concentration is observed which is related to selfcompensation. Investigations of the donor-acceptor-pair luminescence show that doping with carbon is accompanied by the generation of a new donor exhibiting a thermal activation energy of about 55 meV. Layers grown by atomic layer epitaxy are marked by an increased intensity of the donor-acceptor-pair band luminescence which is attributed to the enforced incorporation of carbon onto the nitrogen sublattice. The yellow luminescence is found to be a typical feature of all carbon doped layers in contrast to nominally undoped samples.