The Number of Group Homomorphisms from DmD_m into DnD_n

Counting homomorphisms between cyclic groups is a common exercise in a first course in abstract algebra. A similar problem, accessible at the same level, is to count the number of group homomorphisms from a dihedral group of order $2m$ into a dihedral group of order $2n$. While the solution requires only elementary group theory, the result does not appear in the literature or in the usual texts. As the solution may be of interest, particularly to those teaching undergraduate abstract algebra, it is provided in this note

Pacific decadal variability: internal variability and sensitivity to subtropics

Additional to the interannual variability, the Pacific region experiences climate fluctuations on decadal and longer time scales. It is not clear whether Tropical Pacific decadal variability is internal to Tropical Pacific, or whether the midlatitudes exhibit independent decadal variability that affects the tropics or ENSO variability. Available observational data are insufficient to determine the true causes of Tropical Pacific decadal variability. Internal and remote forcing from subtropics are investigated in this study. This is done with state of the art global circulation models (coupled and uncoupled). The leading mode of Tropical Pacific decadal variability in the ECHAM5-MPIOM model, isolated in the tropical cells (TC) index by means of SSA, has a period of about 17 years. The associated SST spatial structure is characterized by a horseshoe-like pattern with maximum explained variance in the central-western equatorial Pacific and off the equator, therefore resembling the signature of the observed decadal climate variability in the tropical Pacific. The mechanism for decadal variability in the model involves coupled oceanatmosphere processes over the western tropical South Pacific, in the region of the SPCZ. Strong positive TCs are associated with periods of increased ENSO variability and vice versa, contributing to the decadal modulation of ENSO activity. The influence of the remote subtropical forcing was studied in more detail with tailored experiments performed with the ocean-atmosphere-sea ice coupled model ECHAM5/MPI-OM. In these sensitivity experiments, the coupled model is forced with idealized sea surface temperature anomalies (SSTA) and sea surface salinity anomalies (SSSA) in the subtropics of both hemispheres. Thus, the relative impact of the subtropical North and South Pacific Oceans on the tropical climate mean state and variability can be estimated. The largest impact on tropical mean climate and variability was simulated in the SSTA experiments. Subtropical South Pacific thermal forcing had more impact on equatorial ocean sea surface temperature than the subtropical North Pacific. In response to a 2°C warming in the subtropical South Pacific, the equatorial Pacific SST increases by +0.58°C, being about 65% larger than the change in the North Pacific experiment. The results show that the subtropics affect equatorial SST mainly through the „atmospheric bridge“ for the South Pacific experiments and through the„oceanic bridge“ for the North Pacific experiments. This explains the different timescale of the response in the two experiments. Although the tropical Pacific surface response to an enhanced warming/cooling in the subtropics is to first order linear, we found that the negative thermal forcing has a stronger impact on the equatorial thermocline. Similar sensitivity experiments conducted with the AGCM ECHAM5 showed that both air-sea interactions and ocean dynamics are crucial for the generation of simulated tropical climate response to the subtropical surface warming/cooling. We found that the statistics of ENSO exhibit significant changes in amplitude and frequency in response to a warming/cooling in the subtropical South Pacific: a 2°C subtropical South Pacific SST warming can reduce the mean ENSO standard deviation by 28%, while a 2°C subtropical South Pacific SST cooling can increase the mean ENSO standard deviation by 21%. The simulated changes in the equatorial zonal SST contrast between the eastern equatorial Pacific and the warm pool region are the main contributor to the modulation of ENSO variability in our South Pacific sensitivity experiments. The simulated intensification/weakening of the annual cycle in response to an enhanced warming/cooling in subtropical South Pacific may also lead to a weaker/stronger ENSO. The subtropical North Pacific thermal forcing did not change the statistical properties of ENSO. The main results of this study suggest that subtropical South Pacific climate variations play a dominant role in tropical Pacific decadal variability and in the decadal modulation of ENSO activity

Characteristic varieties of graph manifolds and quasi-projectivity of fundamental groups of algebraic links

The present paper studies the structure of characteristic varieties of fundamental groups of graph manifolds. As a consequence, a simple proof of Papadima's question is provided on the characterization of algebraic links that have quasi-projective fundamental groups. The type of quasi-projective obstructions used here are in the spirit of Papadima's original work.Comment: 22 pages, 6 figures, to appear in European Journal of Mathematic

Window-based Streaming Graph Partitioning Algorithm

In the recent years, the scale of graph datasets has increased to such a degree that a single machine is not capable of efficiently processing large graphs. Thereby, efficient graph partitioning is necessary for those large graph applications. Traditional graph partitioning generally loads the whole graph data into the memory before performing partitioning; this is not only a time consuming task but it also creates memory bottlenecks. These issues of memory limitation and enormous time complexity can be resolved using stream-based graph partitioning. A streaming graph partitioning algorithm reads vertices once and assigns that vertex to a partition accordingly. This is also called an one-pass algorithm. This paper proposes an efficient window-based streaming graph partitioning algorithm called WStream. The WStream algorithm is an edge-cut partitioning algorithm, which distributes a vertex among the partitions. Our results suggest that the WStream algorithm is able to partition large graph data efficiently while keeping the load balanced across different partitions, and communication to a minimum. Evaluation results with real workloads also prove the effectiveness of our proposed algorithm, and it achieves a significant reduction in load imbalance and edge-cut with different ranges of dataset

Surfing through the GFC : systemic risk in Australia

We provide empirical evidence on the degree of systemic risk in Australia before, during and after the Global Financial Crisis. We calculate a daily index of systemic risk from 2004 to 2013 in order to understand how real economy firms influence the outcomes for the rest of the economy. This is done via a mapping of the interconnectedness of the financial and non-financial sectors. The financial sector is in general the home to the most consistently systemically risky firms in the economy. The mining sector becomes occasionally as systemically risky as the financial sector, reflecting the importance of understanding the interrelationships between the financial sector and the real economy in monitoring systemic risks

Chronic bacterial prostatitis: efficacy of short-lasting antibiotic therapy with prulifloxacin (Unidrox®) in association with saw palmetto extract, lactobacillus sporogens and arbutin (Lactorepens®)

Bacterial prostatitis (BP) is a common condition accounting responsible for about 5-10% of all prostatitis cases; chronic bacterial prostatitis (CBP) classified as type II, are less common but is a condition that significantly hampers the quality of life, (QoL) because not only is it a physical condition but also a psychological distress. Commonly patients are treated with antibiotics alone, and in particular fluoroquinolones are suggested by the European Urology guidelines. This approach, although recommended, may not be enough. Thus, a multimodal approach to the prolonged antibiotic therapy may be helpful.210 patients affected by chronic bacterial prostatitis were enrolled in the study. All patients were positive to Meares-Stamey test and symptoms duration was > 3 months. The purpose of the study was to evaluate the efficacy of a long lasting therapy with a fluoroquinolone in association with a nutraceutical supplement (prulifloxacin 600 mg for 21 days and an association of Serenoa repens 320 mg, Lactobacillus Sporogens 200 mg, Arbutin 100 mg for 30 days). Patients were randomized in two groups (A and B) receiving respectively antibiotic alone and an association of antibiotic plus supplement.Biological recurrence at 2 months in Group A was observed in 21 patients (27.6%) and in Group B in 6 patients (7.8%). Uropathogens found at the first follow-up were for the majority Gram - (E. coli and Enterobacter spp.). A statistically significant difference was found at the time of the follow-up between Group A and B in the NIH-CPSI questionnaire score, symptoms evidence and serum PSA.Broad band, short-lasting antibiotic therapy in association with a nutritional supplement (serenoa repens, lactobacillus sporogens and arbutin) show better control and recurrence rate on patients affected by chronic bacterial prostatitits in comparison with antibiotic treatment alone.NCT02130713Date of trial Registration: 30/04/2014

Reconciling different methods of high‐latitude blocking detection

Blocking is associated with outbreaks of easterlies induced by a continuum of features including anticyclones, cyclones or both. Blocking identification methods disagree on the levels of high-latitude blocking (HLB) activity. We investigate the cause of the disagreement in HLB activity over the Northern Hemisphere obtained by two 2D methods: the PV– (Formula presented.) index and the Absolute Geopotential Height (AGH) reversal method. Although both classify as absolute field methods, the former yields nearly twice the winter HLB activity of the latter method. We show that this discrepancy is caused by the addition of a poleward criterion in the AGH method that requires strong poleward westerlies. The additional criterion in the AGH method shifts the focus on the detection of blocking ridges and thus other blocking circulation patterns are under-represented. Both methods agree on the climatology of midlatitude blocking because the poleward criterion has been tuned to capture the strong midlatitude blocking, but the discrepancy grows in high latitudes. HLBs are different because they occur on the northern flank of the westerlies and are associated with the equatorward displacement of the midlatitude jet. HLB anticyclones are weaker and do not induce strong poleward westerlies compared to their midlatitude counterparts. The implementation of a strict poleward criterion designed to identify midlatitude blocks rejects many HLBs. The use of the less strict cut-off threshold (CT) of 0 m (°lat)−1 in the poleward criterion for latitudes higher than 60°N results in the convergence of climatology, interannual variability and trends of HLB between the two methods, especially during winter. The additional HLBs identified by the modified AGH algorithm develop from cyclonic wave breaking that is typical for oceanic blocking. The modified AGH method can be useful in detecting more robust HLB trends in climate model projections. © 2020 The Authors

AUTOMATED DRIP IRRIGATION SYSTEM POWERED BY PHOTOVOLTAIC PANELS USED FOR AGRICULTURAL CROPS

Climate change, water scarcity and higher energy requirements and electric tariff compromises the continuity of the irrigated agriculture. Precision agriculture (PA) or renewable energy sources which are based on communication and information technologies and a large amount of data are key to ensuring this economic activity and guaranteeing food security at the global level. Several works which are based on the use of PA and renewable energy sources have been developed in order to optimize different variables of irrigated agriculture such as irrigation scheduling. In general, 70% of global water consumption goes to agriculture, for crop irrigation. Irrigated agriculture represents 20% of the total cultivated land (global average), but brings 40% of food

Linear and nonlinear parameters of heart rate variability in ischemic stroke patients

Introduction Cardiovascular system presents cortical modulation. Post-stroke outcome can be highly influenced by autonomic nervous system disruption. Heart rate variability (HRV) analysis is a simple non-invasive method to assess sympatho-vagal balance. Objectives The purpose of this study was to investigate cardiac autonomic activity in ischemic stroke patients and to asses HRV nonlinear parameters beside linear ones. Methods We analyzed HRV parameters in 15 right and 15 left middle cerebral artery ischemic stroke patients, in rest condition and during challenge (standing and deep breathing). Data were compared with 15 age- and sex-matched healthy controls. Results There was an asymmetric response after autonomic stimulation tests depending on the cortical lateralization in ischemic stroke patients. In resting state, left hemisphere stroke patients presented enhanced parasympathetic control of the heart rate (higher values for RMSSD, pNN50 and HF in normalized units). Right hemisphere ischemic stroke patients displayed a reduced cardiac parasympathetic modulation during deep breathing test. Beside time and frequency domain, using short-term ECG monitoring, cardiac parasympathetic modulation can also be assessed by nonlinear parameter SD1, that presented strong positive correlation with time and frequency domain parameters RMSSD, pNN50, HFnu, while DFA α1 index presented negative correlation with the same indices and positive correlation with the LFnu and LF/HF ratio, indicating a positive association with the sympatho-vagal balance. Conclusions Cardiac monitoring in clinical routine using HRV analysis in order to identify autonomic imbalance may highlight cardiac dysfunctions, thus helping preventing potential cardiovascular complications, especially in right hemisphere ischemic stroke patients with sympathetic hyperactivation