Competition effects in an afrotemperate forest

Background Information about competition responses is mainly available for monospecific stands or mixed stands with a small number of species. Studies on complex multi-species and highly structured forest ecosystems are scarce. Accordingly, the objective of this study was to quantify competition effects and analyse competition responses in a species-diverse afrotemperate forest in South Africa, based on an observational study with mapped tree positions and long-term diameter increment records. Methods The sensitivity to competition was analysed for individual species and involved the calculation of the slope of the linear relation between the value of a competition index (CI) and diameter growth as a measure of sensitivity. In a next step different competition indices were combined and tree diameters were grouped in three classes as surrogates for canopy status and ontogenetic stage. Results Five competition indices were found to be effective in showing sensitivity to competition for a number of canopy and sub-canopy species. Significant linear regressions were fitted for 18 of a total of 25 species. Species reactions varied significantly in their sensitivity to the different CIs. The indices were classified as belonging to two groups, those that responded more to local crowding and those that are more sensitive to overtopping, which revealed species-specific sensitivities to both factors. The analysis based on diameter classes revealed that species clearly changed their sensitivity to crowding or overtopping depending on diameter. Canopy and sub-canopy species showed distinct differences in their reactions. Conclusions The application of multiple CIs brought novel insights relating to the dynamics of afrotemperate forests. The response patterns to different competition indices that focus on crowding and overtopping are varied and tree diameter dependent, indicating that oversimplified assumptions are not warranted in the interpretation of CI- growth relations

Co dimers on hexagonal carbon rings proposed as subnanometer magnetic storage bits

It is demonstrated by means of density functional and ab-initio quantum chemical calculations, that transition metal - carbon systems have the potential to enhance the presently achievable area density of magnetic recording by three orders of magnitude. As a model system, Co_2-benzene with a diameter of 0.5 nm is investigated. It shows a magnetic anisotropy in the order of 0.1 eV per molecule, large enough to store permanently one bit of information at temperatures considerably larger than 4 K. A similar performance can be expected, if cobalt dimers are deposited on graphene or on graphite. It is suggested that the subnanometer bits can be written by simultaneous application of a moderate magnetic and a strong electric field.Comment: 13 pages, 4 figure

Nanoscale morphology of polyanhydride copolymers

The microphase separation in polyanhydride random copolymers composed of 1,6-bis(p-carboxyphenoxy)hexane and sebacic acid is described. Though the copolymers are random, the monomers are sufficiently long and the segment-segment interaction parameter is sufficiently high to promote microphase separation when the copolymer is rich in one component. Solid-state NMR spin diffusion experiments and synchrotron small-angle X-ray scattering are used to discern the length scales of the microphase separation. Both techniques reveal a nanostructure with domain sizes less than 25 Ã…. This nanostructure is compared to approximate calculations of chain dimensions based on a random coil model and discussed in the context of the rational design of these materials for drug delivery applications

Tumour assessment in advanced melanoma: value of FDG-PET/CT in patients with elevated serum S-100B

Purpose: To evaluate the usefulness of PET/CT in melanoma patients with an elevated serum S-100B tumour marker level. Methods: Out of 165 consecutive high-risk melanoma patients referred for PET/CT imaging, 47 had elevated (>0.2μg/l) S-100B serum levels and a contemporaneous 18F-FDG PET/CT scan. PET/CT scans were evaluated for the presence of metastases. To produce a composite reference standard, we used cytological, histological, MRI and PET/CT follow-up findings as well as clinical and S-100B follow-up. Results: Among the 47 patients with increased S-100B levels, PET/CT correctly identified metastases in 38 (30 distant metastases and eight lymph node metastases). In one patient with cervical lymph node metastases, PET/CT was negative. Eight patients had no metastases and PET/CT correctly excluded metastases in all of them. Overall sensitivity for metastases was 97% (38/39), specificity 100% (8/8) and accuracy 98% (46/47). S-100B was significantly higher in patients with distant metastases (mean 1.93μg/l, range 0.3-14.3μg/l) than in patients with lymph node metastases (mean 0.49μg/l, range 0.3-1.6μg/l, p = 0.003) or patients without metastases (mean 0.625μg/l, range 0.3-2.6μg/l, p = 0.007). However, 6 of 14 patients with a tumour marker level of 0.3μg/l had no metastases. Conclusion: In melanoma patients with elevated S-100B tumour marker levels, FDG-PET/CT accurately identifies lymph node or distant metastases and reliably excludes metastases. Because of the significant number of false positive S-100B tumour marker determinations (17%), we recommend repetition of tumour marker measurements if elevated S-100B levels occur before extensive imaging is use

Clinical impact of 18F-choline PET/CT in patients with recurrent prostate cancer

Purpose: To investigate the clinical value of 18F-fluorocholine PET/CT (CH-PET/CT) in treatment decisions in patients with recurrent prostate cancer (rPCA). Methods: The study was a retrospective evaluation of 156 patients with rPCA and CH-PET/CT for restaging. Questionnaires for each examination were sent to the referring physicians 14-64months after examination. Questions included information regarding initial extent of disease, curative first-line treatment, and the treatment plan before and after CH-PET/CT. Additionally, PSA values at diagnosis, after initial treatment, before CH-PET/CT and at the end of follow-up were also obtained from the questionnaires. Results: Mean follow-up was 42months. The mean Gleason score was 6.9 at initial diagnosis. Initial treatment was: radical prostatectomy in 110 patients, radiotherapy in 39, and combined prostatectomy and radiotherapy in 7. Median PSA values before CH-PET/CT and at the end of follow-up were 3.40ng/ml and 0.91ng/ml. PSA levels remained stable, decreased or were below measurable levels in 108 patients. PSA levels increased in 48 patients. In 75 of the 156 patients (48%) the treatment plan was changed due to the CH-PET/CT findings. In 33 patients the therapeutic plan was changed from palliative treatment to treatment with curative intent. In 15 patients treatment was changed from curative to palliative. In 8 patients treatment was changed from curative to another strategy and in 2 patients from one palliative strategy to another. In 17 patients the treatment plan was adapted. Conclusion: CH-PET/CT has an important impact on the therapeutic strategy in patients with rPCA and can help to determine an appropriate treatmen

Combined PET/CT-perfusion in patients with head and neck cancers

Objectives: Computed tomography perfusion (CTP) can provide information about angiogenesis and blood-flow characteristics in tumours. [18F]Fluoro-2-deoxy-d-glucose-positron emission tomography/computed tomography (FDG-PET/CT) is one of the major oncological imaging techniques which provides information about viability of the tumour cell and partly also about its aggressiveness. The aim of the study was to investigate the relationship between FDG and CTP data in patients with head and neck cancers. Materials and methods: Forty-one patients with a clinically suspected head and neck cancer were prospectively included. All patients underwent a combined PET/CT with an integrated CTP examination in the area of the head and neck tumour. CTP data (BF, BV and MTT) and PET data (SUVmax, SUVmean, TLG, PETvol) were compared between tumours and (1) healthy contralateral tissue, (2) inflammatory lesions, (3) metastatic lymph nodes, and CTP data and PET data were correlated in tumours. Results: Thirty-five patients had a head and neck cancer. All CTP data were statistically different between tumours, inflammatory lesions, healthy tissue and metastatic lymph nodes; PET/CT data were in part significantly different. CTP and PET parameters were not significantly correlated. Conclusion: CTP and PET parameters were not significantly correlated; thus, the additional CTP values provide additional insights into tumour behaviour and their glycolytic status. Key Points : • Computed tomography perfusion (CTP) can be performed in combined positron emission tomography (PET)/CT. • CTP in addition to PET provides additional insights into tumour behaviour. • CTP can possibly differentiate between head and neck tumours and inflammatory lesions. • PET/CT with integrated CTP is possible without additional contrast medi

Improved detection of blood stream pathogens by real-time PCR in severe sepsis

Objective: Evaluation of the technical and diagnostic feasibility of commercial multiplex real-time polymerase chain reaction (PCR) for detection of blood stream infections in a cohort of intensive care unit (ICU) patients with severe sepsis, performed in addition to conventional blood cultures. Design: Dual-center cohort study. Setting: Surgical ICU of two university hospitals. Patients and participants: One hundred eight critically ill patients fulfilling the American College of Chest Physicians/Society of Critical Care Medicine (ACCP/SCCM) severe sepsis criteria were included. Interventions: None. Measurements and results: PCR results obtained in 453 blood samples from 108 patients were compared with corresponding blood culture results. PCR resulted in a twofold higher positivity rate when compared with conventional blood culture (BC) testing (114 versus 58 positive samples). In 40 out of 58 PCR positive assays the results of the corresponding blood cultures were identical to microorganisms detected by PCR. In 18 samples PCR and BC yielded discrepant results. Compared with conventional blood culture the sensitivity and specificity of PCR was 0.69 and 0.81, respectively. Further evaluation of PCR results against a constructed gold standard including conventional microbiological test results from other significant patient specimen (such as bronchio-alveolar lavage fluid, urine, swabs) and additionally generated clinical and laboratory information yielded sensitivity of 0.83 and specificity of 0.93. Conclusions: Our cohort study demonstrates improved pathogen detection using PCR findings in addition to conventional blood culture testing. PCR testing provides increased sensitivity of blood stream infection. Studies addressing utility including therapeutic decision-making, outcome, and cost-benefit following diagnostic application of PCR tests are needed to further assess its value in the clinical settin