HISTORY, DISTRIBUTION AND ECOLOGICAL CHARACTERIZATION OF OLD GROWTH FORESTS IN SARDINIA

ABSTRACT - Thesis of Sergio Fantini: HISTORY, DISTRIBUTION AND ECOLOGICAL CHARACTERIZATION OF OLD GROWTH FORESTS IN SARDINIA. Old forests globally play a very important role. The most widely used definition of primary forest is: “Naturally regenerated forest of native species, where there are no clearly visible indications of human activities and the ecological processes are not significantly disturbed” (FAO). Their biodiversity, their ability to mitigate CO2 emissions, and to globally and locally modify the water cycle and climate, make these fundamental ecosystems very important to be studied and preserved. Globally, it is well known that currently primary forests are in decline. Also in Sardinia, only a small percentage of the original forest heritage was saved from the deforestation that began in the early nineteenth century and continued until after the half of the twentieth century. Despite the great importance, there was not a complete knowledge of the consistency, structure, distribution, threats and types of ancient forests. This research tried to fill, at least in part, these gaps and produced a first characterisation of the ancient residual forests of Sardinia. The first phase of the study consisted in the research, identification and field mapping of the oldgrowth stands. The feedback provided by local experts from public forestry agencies and research institutes universities through the compilation of a questionnaire was essential. A total of 68 plots were surveyed throughout the island. The identification of old-growth features was based on: amount of large-size and old trees, tree species composition, canopy heterogeneity, occurrence and amount of deadwood. The main goal of this work was to determine the degree of old-growthness of each single plot and, for this reason, several structural variables were surveyed. Because no one single proxy indicator can be a measure of old-growthness alone, a structural index (Structural Heterogeneity Index, SHI) was elaborated in order to summarisethe above-mentioned variables in one single value. Finally, how the SHI varied among environmental or human-related factors was statistically evaluated. In the second part of the work, the relationship between the presence of great longhorn beetles (saproxylic beetles that play an important role as an ecosystem engineer) and the structure of old-growth holm oak, the most widespread and representative forest type present in Sardinia, was analysed. Finally, the degree of protection of the old-growth stands from the legislative point of view and from wildfire hazard, was studied. These analyses, performed in GIS environment, allowed to identify which surfaces of the old-growth stands were included in the regional protection network and, through the visibility analysis of the fire lookouts network, the risk ofold-growth forest fires was assessed. To do this, the application of a parametric method allowed an assessment and the creation of a vulnerability map through the integration of visibility, old-growthness and wildfire hazard parameters of each oldgrowth stand

Higher order perturbation theory for the diffusion equation in heterogeneous media: application to layered and slab geometries

n/

General perturbative approach to the diffusion equation in the presence of absorbing defects: frequency-domain and time-domain results

n/

Method for Measuring Absolute Optical Properties of Turbid Samples in a Standard Cuvette

Many applications seek to measure a sample's absorption coefficient spectrum to retrieve the chemical makeup. Many real world samples are optically turbid, causing scattering confounds which many commercial spectrometers cannot address. Using diffusion theory and considering absorption and reduced scattering coefficients on the order of 0.01 per mm and 1 per mm, respectively, we develop a method which utilizes frequency-domain to measure absolute optical properties of turbid samples in a standard cuvette (45 mm by 10 mm by 10 mm). Inspired by the self calibrating method, which removes instrumental confounds, the method uses measurements of the diffuse complex transmittance at two sets of two different source-detector distances. We find: this works best for highly scattering samples (reduced scattering coefficient above 1 per mm); higher relative error in the absorption coefficient compared to the reduced scattering coefficient; accuracy is tied to knowledge of the samples index of refraction. Noise simulations with 0.1 percent amplitude and 0.1 deg (1.7 mrad) phase uncertainty find errors in absorption and reduced scattering coefficients of 4 percent and 1 percent, respectively. We expect that higher error in the absorption coefficient can be alleviated with highly scattering samples and that boundary condition confounds may be suppressed by designing a cuvette with high index of refraction. Further work will investigate implementation and reproducibility

Principi della spettroscopia nel vicino infrarosso e applicazioni per studi diagnostici e funzionali

2007-10-22Sardegna Ricerche, Edificio 2, Località Piscinamanna 09010 Pula (CA) - ItaliaDispositivi medicali non invasivi per la Cardiologia e la Ematologia: sviluppi e applicazion

Spectral and Spatial Dependence of Diffuse Optical Signals in Response to Peripheral Nerve Stimulation

Using non-invasive, near-infrared spectroscopy we have previously reported optical signals measured at or around peripheral nerves in response to their stimulation. Such optical signals featured amplitudes on the order of 0.1% and peaked about 100 ms after peripheral nerve stimulation in human subjects. Here, we report a study of the spatial and spectral dependence of the optical signals induced by stimulation of the human median and sural nerves, and observe that these optical signals are: (1) unlikely due to either dilation or constriction of blood vessels, (2) not associated with capillary bed hemoglobin, (3) likely due to blood vessel(s) displacement, and (4) unlikely due to fiber-skin optical coupling effects. We conclude that the most probable origin of the optical response to peripheral nerve stimulation is from displacement of blood vessels within the optically probed volume, as a result of muscle twitch in adjacent areas.National Institutes of Health (R01-NS059933); U.S. Army Medical Acquisition Activity (W81XWH-07-2-0011

Domain Adaptation for Robust Workload Level Alignment Between Sessions and Subjects using fNIRS

Significance: We demonstrated the potential of using domain adaptation on functional Near-Infrared Spectroscopy (fNIRS) data to classify different levels of n-back tasks that involve working memory. Aim: Domain shift in fNIRS data is a challenge in the workload level alignment across different experiment sessions and subjects. In order to address this problem, two domain adaptation approaches -- Gromov-Wasserstein (G-W) and Fused Gromov-Wasserstein (FG-W) were used. Approach: Specifically, we used labeled data from one session or one subject to classify trials in another session (within the same subject) or another subject. We applied G-W for session-by-session alignment and FG-W for subject-by-subject alignment to fNIRS data acquired during different n-back task levels. We compared these approaches with three supervised methods: multi-class Support Vector Machine (SVM), Convolutional Neural Network (CNN), and Recurrent Neural Network (RNN). Results: In a sample of six subjects, G-W resulted in an alignment accuracy of 68 $\pm$ 4 % (weighted mean $\pm$ standard error) for session-by-session alignment, FG-W resulted in an alignment accuracy of 55 $\pm$ 2 % for subject-by-subject alignment. In each of these cases, 25 % accuracy represents chance. Alignment accuracy results from both G-W and FG-W are significantly greater than those from SVM, CNN and RNN. We also showed that removal of motion artifacts from the fNIRS data plays an important role in improving alignment performance. Conclusions: Domain adaptation has potential for session-by-session and subject-by-subject alignment of mental workload by using fNIRS data

Spatial distribution of vastus lateralis blood flow and oxyhemoglobin saturation measured at the end of isometric quadriceps contraction by multichannel near-infrared spectroscopy.

Muscle blood flow (MBF) and muscle oxygen saturation (SmO(2)) were measured at eight locations (four proximal, four distal) over a 4 x 8 cm(2) area of the vastus lateralis at rest and immediately after isometric, maximal quadriceps contraction using multichannel, frequency-domain, near-infrared spectroscopy. A venous occlusion was applied 20 s before the end of the exercise, so that the venous-occlusion-induced increase in total hemoglobin was recorded without any delay after the end of the exercise. Therefore, we were able to investigate the relationship between the exercise-induced changes in vastus lateralis MBF and SmO(2). After exercise, MBF increased significantly at each measured location. Comparing the MBF values measured at the end of exercise in the proximal and distal regions, we observed that only one proximal region had a significantly higher MBF than the corresponding distal one. The maximum desaturation measured during exercise was positively correlated with the postexercise to pre-exercise MBF ratio in both the proximal (P=0.016) and distal (P=0.0065) regions. These data confirm that frequency-domain tissue oximeters are noninvasive, powerful tools to investigate the spatial and temporal features of muscle blood flow and oxygenation, with potential applications in areas of pathophysiology