A Knob for Changing Light Propagation from Subluminal to Superluminal

We show how the application of a coupling field connecting the two lower metastable states of a lambda-system can produce a variety of new results on the propagation of a weak electromagnetic pulse. In principle the light propagation can be changed from subluminal to superluminal. The negative group index results from the regions of anomalous dispersion and gain in susceptibility.Comment: 6 pages,5 figures, typed in RevTeX, accepted in Phys. Rev.

Quantum coherence in a degenerate two-level atomic ensemble: for a transition Fe=0↔Fg=1F_e=0\leftrightarrow F_g=1

For a transition $F_e=0\leftrightarrow F_g=1$ driven by a linearly polarized light and probed by a circularly light, quantum coherence effects are investigated. Due to the coherence between the drive Rabi frequency and Zeeman splitting, electromagnetically induced transparency, electromagnetically induced absorption, and the transition from positive to negative dispersion are obtained, as well as the populations coherently oscillating in a wide spectral region. At the zero pump-probe detuning, the subluminal and superluminal light propagation is predicted. Finally, coherent population trapping states are not highly sensitive to the refraction and absorption in such ensemble.Comment: 9 pages, 6 figure

Abundance and diversity of anammox bacteria in a mainstream municipal wastewater treatment plant

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Among the factors that obstruct the application of anammox-based technology for nitrogen removal from mainstream municipal wastewater is the water’s high organic loads. We hypothesized that some anammox species can adapt and grow in mainstream wastewater in which a minimal temperature of 13–15 °C is maintained. Using the AMX368F and AMX820R PCR-primers, anammox bacteria were detected in influent wastewater (COD/N ratio > 13) and in the anaerobic, anoxic, and aerobic chambers of a full-scale municipal wastewater treatment plant, reaching 107 copies/g VSS of the16S rRNA gene. Furthermore, anammox activity was demonstrated by 15N-isotopic tracing. The DNA sequences of clones randomly selected from a clone library were mainly clustered with Candidatus Brocadia flugida in addition to Ca. Brocadia sinica, Ca. Jettenia asiatica, and Ca. Anammoxoglobus propionicus. However, Ca. Brocadia was the only genus detected by high-throughput next-generation sequencing and denaturing gradient gel electrophoresis. The nitrite producers, ammonia-oxidizing archaea and bacteria, were both detected in the influent wastewater and the other chambers, while the nitrite consumers, Nitrospira nitrite oxidizers and the nirS-type denitrifiers, dominated all chambers. The results indicate the occurrence and potential activity of anammox bacteria in mainstream wastewater under certain conditions (proper temperature). The dominance of Brocadia flugida and Anammoxoglobus propionicus suggests a role for volatile fatty acids in selecting the anammox community in wastewater

Cranial Base Synchondrosis Lacks PTHrP-Expressing Column-Forming Chondrocytes

The cranial base contains a special type of growth plate termed the synchondrosis, which functions as the growth center of the skull. The synchondrosis is composed of bidirectional opposite-facing layers of resting, proliferating, and hypertrophic chondrocytes, and lacks the secondary ossification center. In long bones, the resting zone of the epiphyseal growth plate houses a population of parathyroid hormone-related protein (PTHrP)-expressing chondrocytes that contribute to the formation of columnar chondrocytes. Whether PTHrP+ chondrocytes in the synchondrosis possess similar functions remains undefined. Using Pthrp-mCherry knock-in mice, we found that PTHrP+ chondrocytes predominantly occupied the lateral wedge-shaped area of the synchondrosis, unlike those in the femoral growth plate that reside in the resting zone within the epiphysis. In vivo cell-lineage analyses using a tamoxifen-inducible Pthrp-creER line revealed that PTHrP+ chondrocytes failed to establish columnar chondrocytes in the synchondrosis. Therefore, PTHrP+ chondrocytes in the synchondrosis do not possess column-forming capabilities, unlike those in the resting zone of the long bone growth plate. These findings support the importance of the secondary ossification center within the long bone epiphysis in establishing the stem cell niche for PTHrP+ chondrocytes, the absence of which may explain the lack of column-forming capabilities of PTHrP+ chondrocytes in the cranial base synchondrosis

Aerobic and Anaerobic Treatments for Aquaponic Sludge Reduction and Mineralisation

Recirculating aquaculture systems, as part of aquaponic units, are effective in producing aquatic animals with a minimal water consumption through effective treatment stages. Nevertheless, the concentrated sludge produced after the solid filtration stage, comprising organic matter and valuable nutrients, is most often discarded. One of the latest developments in aquaponic technology aims to reduce this potential negative environmental impact and to increase the nutrient recycling by treating the sludge on-site. For this purpose, microbial aerobic and anaerobic treatments, dealt with either individually or in a combined approach, provide very promising opportunities to simultaneously reduce the organic waste as well as to recover valuable nutrients such as phosphorus. Anaerobic sludge treatments additionally offer the possibility of energy production since a by-product of this process is biogas, i.e. mainly methane. By applying these additional treatment steps in aquaponic units, the water and nutrient recycling efficiency is improved and the dependency on external fertiliser can be reduced, thereby enhancing the sustainability of the system in terms of resource utilisation. Overall, this can pave the way for the economic improvement of aquaponic systems because costs for waste disposal and fertiliser acquisition are decreased