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This systematic review aims to evaluate which effects nature exposure has on stress in women and get a more objective viewpoint using measurements of physiological markers of stress to complement the many studies using subjective questionnaires. A search was done on Scopus, Medline EBSCO, and Web of Science for peer-reviewed, published, and original research. Five studies met the inclusion criteria and were included in this review. The outcome measurements included were activity in the autonomic nervous system (ANS) measured with heart-rate variability (HRV) and cerebral activity measured by near-infrared spectroscopy (NIRS). With the definition of Shinrin-Yoku in mind, nature exposure was walking in or watching the natural environment, compared to walking in or watching an urban environment. In this systematic review, four of five studies found significant results that nature exposure alleviated stress in women compared to an urban environment. These findings contribute to a growing body of evidence suggesting that nature is valuable in reducing stress-related illnesses in women. On the individual level, these findings show that nature exposure can be used as an evidence-based intervention to reduce stress in women. Furthermore, these findings clarify the benefits of including elements from nature in urban environments on a societal level.

Hyperspectral imaging is an emerging technology in the field of biomedical engineering which may be used as a non-invasive modality to characterize tumors. In this thesis, a hyperspectral imaging system was used to characterize canine mammary tumors of unknown histopathology (pre-surgery) and correlate the results with the post-surgical histopathology results. The system consisted of a charge coupled device (CCD) camera, a liquid crystal tunable filter in the near infrared range (650-1100 nm), and a controller. Spectral signatures of malignant and benign canine mammary tumors were extracted and analyzed. The reflectance intensities of malignant tumor spectra were generally lower than benign tumor spectra over the wavelength range 650-1100nm. Previous studies have shown that cancerous tissues have a higher hemoglobin and water content, and lower lipid concentration with respect to benign tissues. The decreased reflectance intensity observed for malignant tumors is likely due to the increased microvasculature and, therefore, higher blood content of malignant tissue relative to benign tissue. Second derivative method was applied to the reflectance spectra. Peaks at 700, 840, 900 and 970 nm were observed in the second derivative reflectance spectra. These peaks were attributed to deoxy-hemoglobin, oxy-hemoglobin, lipid and water respectively. A Tissue Optical Index (TOI) was developed that enhances contrast between malignant and benign canine tumors. This index is based on the ratio of the reflectance intensity values corresponding to the wavelengths associated with the four chromophores. Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were also applied on the canine spectral dataset and the method was cross-validated. Preliminary results from 22 canine mammary tumors showed that the sensitivity and specificity of the PCA-LDA is method is 86% and 86% respectively. The sensitivity and specificity of the TOI model is 86% and 95% respectively. These results show promise in the non-invasive optical diagnosis of canine mammary cancer. / Electrical and Computer Engineering

Articular cartilage helps in the motion of the diarthroidal joints by providing a near frictionless load bearing surface. Identification of changes in articular cartilage chemical and structural properties that arise from degeneration and suboptimal tissue repair have been the target of many studies. Current methods that evaluate these changes frequently involve destructive specimen preparation. Thus there is a need to develop a method to accurately evaluate changes in cartilage during disease or repair processes. Fourier transform infrared (FTIR) spectroscopy in the mid-infrared (MIR) spectral range is based on molecular vibrations and has been used to study the chemical and structural properties of biological tissues, including cartilage. However, this technique generally requires extensive sample preparation and modification of the intact tissue. An alternative approach is to use near-infrared spectroscopy (NIRS) which does not require sample preparation due to higher depth of penetration. This doctoral dissertation focuses on identification of NIR spectral features to evaluate the major components of cartilage. These NIR spectral features are then used to evaluate compositional changes in engineered and degraded cartilage, and the results validated with histological, biochemical, mechanical and MIR analysis of the same tissue. Together, these studies lay the groundwork for clinical and in situ applications of NIRS. / Bioengineering

The objective of this study was to evaluate the relationship between tissue oxygen saturation (StO2) and oxygen delivery index (DO2I). Oxygen delivery index is product of two factors arterial oxygen content (CaO2) and cardiac index (CI). In this study the relationship between DO2I and StO2 was evaluated by manipulating both of these factors independently. In phase one of the study, CaO2 was altered by manipulating the fractional inspired oxygen (FiO2) concentration. Anesthetized dogs were evaluated at both high (0.40 and 0.95) and low (0.15 and 0.10) FiO2 sequences. In phase two of the study, CI was altered by manipulating the volemic state. Anesthetized dogs were evaluated at hypovolemic, normovolemic and hypervolemic states. In each phase dogs were instrumented for thermodilution cardiac index (CI) and sartorius muscle StO2. Data collected included hemoglobin concentration, heart rate (HR), MAP, CI, StO2. Arterial oxygen content and DO2I were calculated at each time point. Data analysis included Pearson's correlation and mixed model ANOVA (p < 0.05). In both phases one (r = 0.97; p = 0.0013) and two (r = 0.97; p = 0.005) there was a strong correlation between StO2 and DO2I. Under the conditions of this study, there was a strong correlation between StO2 and DO2I, suggesting that StO2 may be used to estimate the adequacy of oxygen delivery in dogs. / Master of Science

The neurovisceral integration model (NVM) proposes that an organisms ability to flexibly adapt to their environment is related to biological flexibility within the central autonomic network. One important aspect of this flexibility is behavioral inhibition (Thayer and Friedman, 2002). During a behavioral inhibition task, the central autonomic network (CAN), which is comprised of a series of feedback loops, must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The functioning of the CAN is shown to be associated with respiratory sinus arrhythmia (RSA), as the vagus nerve is part of this feedback system. While the NVM has been examined through neural imaging and RSA, only a few studies have examined these measures simultaneously during the neuroimaging procedure. Furthermore, these studies were done at rest or used tasks that were not targeted at processes associated with the NVM, such as behavior inhibition and cognitive flexibility. For this reason, the present study assessed RSA and neural activation in the prefrontal cortex simultaneously while subjects completed a behavior inhibition task. Using a series of go/no-go tasks, RSA and functional near-infrared spectroscopy (fNIRS) were collected to investigate the relationship between prefrontal activation and vagal activity at rest and during behavioral inhibition. There are three primary aims of this study. First, examine prefrontal activation during various inhibition tasks through fNIRS. Second, evaluate the NVM during a cognitive task using simultaneous fNIRS and RSA analysis. Third, relate task performance, imaging, and RSA measures during behavioral inhibition to deficits in flexible everyday responding, as indicated by self-report measures of behavior. Doing so will elucidate the connection with prefrontal activation and RSA as proposed by the NVM model and determine whether neural and RSA metrics can be related to broader symptoms of inflexibility. / PHD / The neurovisceral integration model (NVM) proposes that the ability to adapt to the environment is related to biological flexibility within the brain. One important aspect of the ability to adapt to the environment is behavior inhibition (e.g., the ability to stop from engaging in a habitual response, Thayer & Friedman, 2002). During a behavior inhibition task, the brain must be able to integrate information and react to these inputs flexibly to facilitate optimal performance. The brain’s ability to do this is related to a measure of heart activity known as respiratory sinus arrhythmia (RSA). The present study assessed RSA and brain activity while subjects completed a behavior inhibition task. Neural activation was measured through functional near-infrared spectroscopy (fNIRS). fNIRS measures the amount of oxygenated blood in different areas of the brain. Greater concentrations of oxygenated blood indicated greater brain activity in an area. Through simultaneous fNIRS and RSA measurement the present study examined their relationship during various inhibition tasks. Doing so clarified the connection between brain activation and RSA as proposed by the NVM model.

Sustainability is inherently a complex problem that requires new ways of thinking. To solve grand challenges such as climate change, environmental degradation, and poverty, engineers cannot rely on the same models of thinking that were used to create these problems. Engineering education is therefore critical to advance sustainable engineering solutions. Improving education relies on understanding of cognition of thinking and designing for sustainability. In this thesis, a nascent neuroimaging technology called functional near-infrared spectroscopy (fNIRS) was used to measure cognition among engineering students thinking about sustainability. fNIRS provides an opportunity to investigate how sustainability in design influences cognition, and how different concept generation techniques help students consider many aspects related to sustainability. The first manuscript provides evidence that engineering students perceive sustainability in design as a constraint, limiting the number of solutions for design and decreasing the cognitive efficiency to generate solutions. Senior engineering students generated fewer solutions than freshmen, however, seniors were better able to cognitively manage the sustainability parameter with higher cognitive efficiency. The second manuscript investigates the cognitive difference when generating concepts using concept listing or concept mapping. The results indicate that concept mapping (i.e. intentionally drawing relationships between concepts) leads to more concepts generated. An increase in concepts during concept mapping was also observed to shift cognitive load in the brain from regions associated with process sequencing to regions associated with cognitive flexibility. This research demonstrates the feasibility of fNIRS applied in engineering research and provides more understanding of the cognitive requirements for sustainability thinking. / M. S. / Sustainability brings new challenges to engineering design. To advance the practice of sustainable engineering, engineers are expected to be able to efficiently tackle socio-technical problems using a systems perspective. Engineering education is expected to help engineering students to achieve this goal. Improving education relies on understanding of mental process of thinking and designing for sustainability. In this research, a nascent neuroimaging technology-functional near-infrared spectroscopy (fNIRS) has been used to measure the cognition of engineering students thinking for sustainability. fNIRS enables us to investigate how sustainability requirements in design influence the cognition of design process, and how different concept generation ways help students understand sustainability. The first manuscript provides evidence that sustainability in design constraint, limiting the number of solutions for design and decreasing the cognitive efficiency to generate solutions. Senior engineering students generated fewer solutions than freshmen, however, seniors showed advantage to handle sustainability requirements with higher cognitive efficiency. The second manuscript investigates the cognitive difference of two concept generation ways using concept listing or mapping. The results indicate that concept mapping leads to more concepts related to sustainability and enables the cognitive load shift from regions associated with sequencing processing to regions associated with cognitive flexibility. This research demonstrates the feasibility of fNIRS applied in engineering research for sustainability and provides more understanding of the cognitive requirements for sustainability thinking.