Vortex Waves and Channel Capacity: Hopes and Reality

Several recent contributions have envisioned the possibility of increasing currently exploitable maximum channel capacity of a free space link, both at optical and radio frequencies, by using vortex waves, i.e. carrying Orbital Angular Momentum (OAM). Our objective is to disprove these claims by showing that they are in contradiction with very fundamental properties of Maxwellian fields. We demonstrate that the Degrees of Freedom (DoF) of the field cannot be increased by the helical phase structure of electromagnetic vortex waves beyond what can be done without invoking this property. We also show that the often-advocated over-quadratic power decay of OAM beams with distance does not play any fundamental role in the determination of the channel DoF.Comment: 8 pages, 7 figure

Plasma glial fibrillary acidic protein detects Alzheimer pathology and predicts future conversion to Alzheimer dementia in patients with mild cognitive impairment.

INTRODUCTION: Plasma glial fibrillary acidic protein (GFAP) is a marker of astroglial activation and astrocytosis. We assessed the ability of plasma GFAP to detect Alzheimer's disease (AD) pathology in the form of AD-related amyloid-β (Aβ) pathology and conversion to AD dementia in a mild cognitive impairment (MCI) cohort. METHOD: One hundred sixty MCI patients were followed for 4.7 years (average). AD pathology was defined using cerebrospinal fluid (CSF) Aβ42/40 and Aβ42/total tau (T-tau). Plasma GFAP was measured at baseline and follow-up using Simoa technology. RESULTS: Baseline plasma GFAP could detect abnormal CSF Aβ42/40 and CSF Aβ42/T-tau with an AUC of 0.79 (95% CI 0.72-0.86) and 0.80 (95% CI 0.72-0.86), respectively. When also including APOE ε4 status as a predictor, the accuracy of the model to detect abnormal CSF Aβ42/40 status improved (AUC = 0.86, p = 0.02). Plasma GFAP predicted subsequent conversion to AD dementia with an AUC of 0.84 (95% CI 0.77-0.91), which was not significantly improved when adding APOE ε4 or age as predictors to the model. Longitudinal GFAP slopes for Aβ-positive and MCI who progressed to dementia (AD or other) were significantly steeper than those for Aβ-negative (p = 0.007) and stable MCI (p < 0.0001), respectively. CONCLUSION: Plasma GFAP can detect AD pathology in patients with MCI and predict conversion to AD dementia

Blood and cerebrospinal fluid neurofilament light differentially detect neurodegeneration in early Alzheimer's disease

Cerebrospinal fluid (CSF) neurofilament light (NfL) concentration has reproducibly been shown to reflect neurodegeneration in brain disorders, including Alzheimer’s disease (AD). NfL concentration in blood correlates with the corresponding CSF levels, but few studies have directly compared the reliability of these 2 markers in sporadic AD. Herein, we measured plasma and CSF concentrations of NfL in 478 cognitively unimpaired (CU) subjects, 227 patients with mild cognitive impairment, and 113 patients with AD dementia. We found that the concentration of NfL in CSF, but not in plasma, was increased in response to Ab pathology in CU subjects. Both CSF and plasma NfL concentrations were increased in patients with mild cognitive impairment and AD dementia. Furthermore, only NfL in CSF was associated with reduced white matter microstructure in CU subjects. Finally, in a transgenic mouse model of AD, CSF NfL increased before serum NfL in response to the development of Ab pathology. In conclusion, NfL in CSF may be a more reliable biomarker of neurodegeneration than NfL in blood in preclinical sporadic AD

Characterizing Van Kampen Squares via Descent Data

Categories in which cocones satisfy certain exactness conditions w.r.t. pullbacks are subject to current research activities in theoretical computer science. Usually, exactness is expressed in terms of properties of the pullback functor associated with the cocone. Even in the case of non-exactness, researchers in model semantics and rewriting theory inquire an elementary characterization of the image of this functor. In this paper we will investigate this question in the special case where the cocone is a cospan, i.e. part of a Van Kampen square. The use of Descent Data as the dominant categorical tool yields two main results: A simple condition which characterizes the reachable part of the above mentioned functor in terms of liftings of involved equivalence relations and (as a consequence) a necessary and sufficient condition for a pushout to be a Van Kampen square formulated in a purely algebraic manner.Comment: In Proceedings ACCAT 2012, arXiv:1208.430

Prediction of future Alzheimer's disease dementia using plasma phospho-tau combined with other accessible measures

A combination of plasma phospho-tau (P-tau) and other accessible biomarkers might provide accurate prediction about the risk of developing Alzheimer’s disease (AD) dementia. We examined this in participants with subjective cognitive decline and mild cognitive impairment from the BioFINDER (n = 340) and Alzheimer’s Disease Neuroimaging Initiative (ADNI) (n = 543) studies. Plasma P-tau, plasma Aβ42/Aβ40, plasma neurofilament light, APOE genotype, brief cognitive tests and an AD-specific magnetic resonance imaging measure were examined using progression to AD as outcome. Within 4 years, plasma P-tau217 predicted AD accurately (area under the curve (AUC) = 0.83) in BioFINDER. Combining plasma P-tau217, memory, executive function and APOE produced higher accuracy (AUC = 0.91, P < 0.001). In ADNI, this model had similar AUC (0.90) using plasma P-tau181 instead of P-tau217. The model was implemented online for prediction of the individual probability of progressing to AD. Within 2 and 6 years, similar models had AUCs of 0.90–0.91 in both cohorts. Using cerebrospinal fluid P-tau, Aβ42/Aβ40 and neurofilament light instead of plasma biomarkers did not improve the accuracy significantly. The clinical predictions by memory clinic physicians had significantly lower accuracy (4-year AUC = 0.71). In summary, plasma P-tau, in combination with brief cognitive tests and APOE genotyping, might greatly improve the diagnostic prediction of AD and facilitate recruitment for AD trials

Plasma GFAP is an early marker of amyloid-β but not tau pathology in Alzheimer's disease

Although recent clinical trials targeting amyloid-β (Aβ) in Alzheimer's disease (AD) have shown promising results, there is increasing evidence suggesting that understanding alternative disease pathways that interact with Aβ metabolism and amyloid pathology might be important to halt the clinical deterioration. In particular, there is evidence supporting a critical role of astroglial activation and astrocytosis in AD. However, to this date, no studies have assessed whether astrocytosis is independently related to either Aβ or tau pathology, respectively, in vivo. To address this question, we determined the levels of the astrocytic marker glial fibrillary acidic protein (GFAP) in plasma and cerebrospinal fluid (CSF) of 217 Aβ-negative cognitively unimpaired individuals, 71 Aβ-positive cognitively unimpaired individuals, 78 Aβ-positive cognitively impaired individuals, 63 Aβ-negative cognitively impaired individuals and 75 patients with a non-AD neurodegenerative disorder from the Swedish BioFINDER-2 study. Subjects underwent longitudinal Aβ (18F-flutemetamol) and tau (18F-RO948) positron emission tomography (PET) as well as cognitive testing. We found that plasma GFAP concentration was significantly increased in all Aβ-positive groups compared with subjects without Aβ pathology (p < 0.01). In addition, there were significant associations between plasma GFAP with higher Aβ-PET signal in all Aβ-positive groups, but also in cognitively normal individuals with normal Aβ values (p < 0.001), which remained significant after controlling for tau-PET signal. Furthermore, plasma GFAP could predict Aβ-PET positivity with an area under the curve of 0.76, which was greater than the performance achieved by CSF GFAP (0.69) and other glial markers (CSF YKL-40: 0.64, sTREM2: 0.71). Although correlations were also observed between tau-PET and plasma GFAP, these were no longer significant after controlling for Aβ-PET. In contrast to plasma GFAP, CSF GFAP concentration was significantly increased in non-AD patients compared to other groups (p < 0.05) and correlated with Aβ-PET only in Aβ-positive cognitively impaired individuals (p = 0.005). Finally, plasma GFAP was associated with both longitudinal Aβ-PET and cognitive decline, and mediated the effect of Aβ-PET on tau-PET burden, suggesting that astrocytosis secondary to Aβ aggregation might promote tau accumulation. Altogether, these findings indicate that plasma GFAP is an early marker associated with brain Aβ pathology but not tau aggregation, even in cognitively normal individuals with a normal Aβ status. This suggests that plasma GFAP should be incorporated in current hypothetical models of AD pathogenesis and be used as a non-invasive and accessible tool to detect early astrocytosis secondary to Aβ pathology

Cerebrospinal fluid concentrations of inflammatory markers in Parkinson's disease and atypical parkinsonian disorders

Inflammation has been implicated in the pathogenesis of Parkinson’s disease (PD). We here investigate levels of inflammatory biomarkers in cerebrospinal fluid (CSF) in PD and atypical parkinsonian disorders (APD) compared with neurologically healthy controls. We included 131 patients with PD and 27 PD with dementia (PDD), 24 with multiple system atrophy (MSA), 14 with progressive supranuclear palsy (PSP) and 50 controls, all part of the Swedish BioFINDER study. CSF was analyzed for CRP, SAA, IL-6, IL-8, YKL-40 and MCP-1 (CCL2) as well as α-synuclein (α-syn), tau, tau phosphorylated at Thr181 (P-tau), Aβ42 and NfL. In this exploratory study, we found higher levels of the inflammatory biomarker SAA in PDD and MSA compared with controls and PD and higher levels of CRP in PDD and MSA compared with PD. YKL-40 was lower in PD compared with controls. There were multiple positive correlations between the inflammatory markers, α-syn and markers of neuroaxonal injury (NfL and tau). In PD, higher levels of inflammatory biomarkers correlated with worse motor function and cognitive impairment. Thus, inflammatory biomarkers were increased in PDD and MSA. Furthermore, inflammatory biomarkers correlated with more severe disease regarding motor symptoms and cognitive impairment in PD, indicating an association between inflammation and more aggressive disease course. However, the results need confirmation in follow-up studies

Product costing and activity-based costing/management in Bacalhôa Vinhos de Portugal

The present Work Project introduces a case study addressing the adoption of an ABC/M system in a winemaking company. The system was implemented in only one area of the company, and its adoption allows the company to perform ABM analysis resorting to the ABC information. A mixed approach is used to cost the products: both traditional and ABC systems are used although in different areas of the company. ABC/M implementation was perceived as ‘successful’ despite not following recommendations prescribed in literature