Chained structure of directed graphs with applications to social and transportation networks

The need to determine the structure of a graph arises in many applications. This paper studies directed graphs and defines the notions of l-chained and {l, k}-chained directed graphs. These notions reveal structural properties of directed graphs that shed light on how the nodes of the graph are connected. Applications include city planning, information transmission, and disease propagation. We also discuss the notion of in-center and out-center vertices of a directed graph, which are vertices at the center of the graph. Computed examples provide illustrations, among which is the investigation of a bus network for a city

Hochwasserschutz an der Emscher – physikalische und virtuelle Umsetzung

Aufsatz veröffentlicht in: "Wasserbau-Symposium 2021: Wasserbau in Zeiten von Energiewende, Gewässerschutz und Klimawandel, Zurich, Switzerland, September 15-17, 2021, Band 1" veröffentlicht unter: https://doi.org/10.3929/ethz-b-00049975

Acute flaccid paralysis with anterior myelitis - California, June 2012-June 2014.

In August 2012, the California Department of Public Health (CDPH) was contacted by a San Francisco Bay area clinician who requested poliovirus testing for an unvaccinated man aged 29 years with acute flaccid paralysis (AFP) associated with anterior myelitis (i.e., evidence of inflammation of the spinal cord involving the grey matter including anterior horn cell bodies) and no history of international travel during the month before symptom onset. Within 2 weeks, CDPH had received reports of two additional cases of AFP with anterior myelitis of unknown etiology. Testing at CDPH's Viral and Rickettsial Disease Laboratory for stool, nasopharyngeal swab, and cerebrospinal fluid (CSF) did not detect the presence of an enterovirus (EV), the genus of the family Picornaviridae that includes poliovirus. Additional laboratory testing for infectious diseases conducted at the CDPH Viral and Rickettsial Disease Laboratory did not identify a causative agent to explain the observed clinical syndrome reported among the patients. To identify other cases of AFP with anterior myelitis and elucidate possible common etiologies, CDPH posted alerts in official communications for California local health departments during December 2012, July 2013, and February 2014. Reports of cases of neurologic illness received by CDPH were investigated throughout this period, and clinicians were encouraged to submit clinical samples for testing. A total of 23 cases of AFP with anterior myelitis of unknown etiology were identified. Epidemiologic and laboratory investigation did not identify poliovirus infection as a possible cause for the observed cases. No common etiology was identified to explain the reported cases, although EV-D68 was identified in upper respiratory tract specimens of two patients. EV infection, including poliovirus infection, should be considered in the differential diagnosis in cases of AFP with anterior myelitis and testing performed per CDC guidelines

A dajkanyelv temporális jellemzői 4 és 8 hónapos csecsemőkhöz szóló beszédben = The temporal characteristics of motherese directed to 4 and 8 month old children

According to Lindblom’s H&H theory, speech production is speaker-oriented, i.e., in adverse listening conditions, speakers enhance intelligibility by the exaggeration of contrasts to produce „hyperspeech”. As infants are at an early stage of language acquisition, it is often hypothesized that infant directed speech (IDS) is also a type of hyperspeech (as opposed to adult directed speech, ADS, that is more on the hypospeech end of the continuum). Therefore, in IDS exaggeration of (linguistic) contrasts, e.g., phonemic contrasts, is suggested. With respect to the phonological vowel length contrast, there is only a limited amount of data available for IDS. Moreover, these data are also quite inconclusive (showing the expected contrast exaggeration in some cases, but revealing the lack of it in others), leaving us to the possible conclusion that contrast exaggeration is not necessary and/or economical for IDS speech to employ. In the present study we aim to contribute to this field of knowledge through the analysis of Hungarian IDS. Hungarian is quite unique (as opposed to e.g., English or Japanese), as it uses both spectral and durational cues combined to express phonological length contrast: while low vowels are distinguished both by spectral and durational cues, high vowels are claimed to be differentiated mostly by durational cues. We addressed the questions, i) if we find contrast exaggeration in IDS vs. ADS in Hungarian, ii) if durational or spectral cues exaggerate the contrast, and iii) if the patterns of long-short vowel contrasts show an interrelation with the infant’s age between the age of 0 and 8 months. We analysed /u/–/u:/ and /A/–/a:/ in 22 first-time mothers’ speech. Speakers read target vowels in one-syllable nonsense CVC words introduced as pixie names in a children’s story book to the experimenter (ADS), and then to their child (IDS), in pre-written sentences that contained the names in pitch-accented positions. We recorded IDS and ADS 3 times with each participant, i) the day after the baby was born (0m), ii) at the age of 4 months (4m), and iii) at the age of 8 months (8m) of the baby. We measured V durations, F1, and F2 values, and analysed absolute V durations, durational differences, and durational ratios of V pairs, and spatial differences of the Vs in the F1×F2 plane. Results showed that although in general mothers did lengthen V durations especially in long vowels, durational contrast was only exaggerated in IDS, if operationalized by durational differences (and not by duration ratios). Further, we found no enhancement in the spectral domain in any of the analysed pairs; and lastly, we found no effect of the baby’s age. We concluded that these results (especially the duration ratio data) provided further evidence to the claim that phonological vowel length contrast is not exaggerated in IDS, and pointed to the questions, if durational cues of length are sufficient in IDS to support distributional learning, or word segmentation skills developing around the age of 1 are needed for the babies to acquire phonological vowel length contrast

A magánhangzós hosszúsági fonológiai kontraszt a dajkanyelvben a csecsemő életkorának függvényében

According to Lindblom’s H&H theory, speech production is speaker-oriented, i.e., in adverse listening conditions, speakers enhance intelligibility by the exaggeration of contrasts to produce „hyperspeech”. As infants are at an early stage of language acquisition, it is often hypothesized that infant directed speech (IDS) is also a type of hyperspeech (as opposed to adult directed speech, ADS, that is more on the hypospeech end of the continuum). Therefore, in IDS exaggeration of (linguistic) contrasts, e.g., phonemic contrasts, is suggested. With respect to the phonological vowel length contrast, there is only a limited amount of data available for IDS. Moreover, these data are also quite inconclusive (showing the expected contrast exaggeration in some cases, but revealing the lack of it in others), leaving us to the possible conclusion that contrast exaggeration is not necessary and/or economical for IDS speech to employ. In the present study we aim to contribute to this field of knowledge through the analysis of Hungarian IDS. Hungarian is quite unique (as opposed to e.g., English or Japanese), as it uses both spectral and durational cues combined to express phonological length contrast: while low vowels are distinguished both by spectral and durational cues, high vowels are claimed to be differentiated mostly by durational cues. We addressed the questions, i) if we find contrast exaggeration in IDS vs. ADS in Hungarian, ii) if durational or spectral cues exaggerate the contrast, and iii) if the patterns of long-short vowel contrasts show an interrelation with the infant’s age between the age of 0 and 8 months. We analysed /u/–/u:/ and /A/–/a:/ in 22 first-time mothers’ speech. Speakers read target vowels in one-syllable nonsense CVC words introduced as pixie names in a children’s story book to the experimenter (ADS), and then to their child (IDS), in pre-written sentences that contained the names in pitch-accented positions. We recorded IDS and ADS 3 times with each participant, i) the day after the baby was born (0m), ii) at the age of 4 months (4m), and iii) at the age of 8 months (8m) of the baby. We measured V durations, F1, and F2 values, and analysed absolute V durations, durational differences, and durational ratios of V pairs, and spatial differences of the Vs in the F1×F2 plane. Results showed that although in general mothers did lengthen V durations especially in long vowels, durational contrast was only exaggerated in IDS, if operationalized by durational differences (and not by duration ratios). Further, we found no enhancement in the spectral domain in any of the analysed pairs; and lastly, we found no effect of the baby’s age. We concluded that these results (especially the duration ratio data) provided further evidence to the claim that phonological vowel length contrast is not exaggerated in IDS, and pointed to the questions, if durational cues of length are sufficient in IDS to support distributional learning, or word segmentation skills developing around the age of 1 are needed for the babies to acquire phonological vowel length contrast

Changing nutrient stoichiometry affects phytoplankton production, DOP accumulation and dinitrogen fixation – a mesocosm experiment in the eastern tropical North Atlantic

Ocean deoxygenation due to climate change may alter redox-sensitive nutrient cycles in the marine environment. The productive eastern tropical North Atlantic (ETNA) upwelling region may be particularly affected when the relatively moderate oxygen minimum zone (OMZ) deoxygenates further and microbially driven nitrogen (N) loss processes are promoted. Consequently, water masses with a low nitrogen to phosphorus (N : P) ratio could reach the euphotic layer, possibly influencing primary production in those waters. Previous mesocosm studies in the oligotrophic Atlantic Ocean identified nitrate availability as a control of primary production, while a possible co-limitation of nitrate and phosphate could not be ruled out. To better understand the impact of changing N : P ratios on primary production and N2 fixation in the ETNA surface ocean, we conducted land-based mesocosm experiments with natural plankton communities and applied a broad range of N : P ratios (2.67–48). Silicic acid was supplied at 15 µmol L−1 in all mesocosms. We monitored nutrient drawdown, biomass accumulation and nitrogen fixation in response to variable nutrient stoichiometry. Our results confirmed nitrate to be the key factor determining primary production. We found that excess phosphate was channeled through particulate organic matter (POP) into the dissolved organic matter (DOP) pool. In mesocosms with low inorganic phosphate availability, DOP was utilized while N2 fixation increased, suggesting a link between those two processes. Interestingly this observation was most pronounced in mesocosms where nitrate was still available, indicating that bioavailable N does not necessarily suppress N2 fixation. We observed a shift from a mixed cyanobacteria–proteobacteria dominated active diazotrophic community towards a diatom-diazotrophic association of the Richelia-Rhizosolenia symbiosis. We hypothesize that a potential change in nutrient stoichiometry in the ETNA might lead to a general shift within the diazotrophic community, potentially influencing primary productivity and carbon export