A low-temperature dynamic mode scanning force microscope operating in high magnetic fields

A scanning force microscope was implemented operating at temperatures below 4.2K and in magnetic fields up to 8T. Piezoelectric quartz tuning forks were employed for non optical tip-sample distance control in the dynamic operation mode. Fast response was achieved by using a phase-locked loop for driving the mechanical oscillator. Possible applications of this setup for various scanning probe techniques are discussed.Comment: 5 pages, 5 figures, submitted to "Review of Scientific Instruments

Operation characteristics of piezoelectric quartz tuning forks in high magnetic fields at liquid helium temperatures

Piezoelectric quartz tuning forks are investigated in view of their use as force sensors in dynamic mode scanning probe microscopy at temperatures down to 1.5 K and in magnetic fields up to 8 T. The mechanical properties of the forks are extracted from the frequency dependent admittance and simultaneous interferometric measurements. The performance of the forks in a cryogenic environment is investigated. Force-distance studies performed with these sensors at low temperatures are presented

Dynamics of quartz tuning fork force sensors used in scanning probe microscopy

We have performed an experimental characterization of the dynamics of oscillating quartz tuning forks which are being increasingly used in scanning probe microscopy as force sensors. We show that tuning forks can be described as a system of coupled oscillators. Nevertheless, this description requires the knowledge of the elastic coupling constant between the prongs of the tuning fork, which has not yet been measured. Therefore tuning forks have been usually described within the single oscillator or the weakly coupled oscillators approximation that neglects the coupling between the prongs. We propose three different procedures to measure the elastic coupling constant: an opto-mechanical method, a variation of the Cleveland method and a thermal noise based method. We find that the coupling between the quartz tuning fork prongs has a strong influence on the dynamics and the measured motion is in remarkable agreement with a simple model of coupled harmonic oscillators. The precise determination of the elastic coupling between the prongs of a tuning fork allows to obtain a quantitative relation between the resonance frequency shift and the force gradient acting at the free end of a tuning fork prong.Comment: 16 pages, 6 figures, 2 Table

Carbon fibre tips for scanning probe microscopy based on quartz tuning fork force sensors

We report the fabrication and the characterization of carbon fibre tips for their use in combined scanning tunnelling and force microscopy based on piezoelectric quartz tuning fork force sensors. We find that the use of carbon fibre tips results in a minimum impact on the dynamics of quartz tuning fork force sensors yielding a high quality factor and consequently a high force gradient sensitivity. This high force sensitivity in combination with high electrical conductivity and oxidation resistance of carbon fibre tips make them very convenient for combined and simultaneous scanning tunnelling microscopy and atomic force microscopy measurements. Interestingly, these tips are quite robust against occasionally occurring tip crashes. An electrochemical fabrication procedure to etch the tips is presented that produces a sub-100 nm apex radius in a reproducible way which can yield high resolution images.Comment: 14 pages, 10 figure

Multimodal system for recording individual-level behaviors in songbird groups

In longitudinal observations of animal groups, the goal is to identify individuals and to reliably detect their interactive behaviors including their vocalizations. However, to reliably extract individual vocalizations from their mixtures and other environmental sounds remains a serious challenge. Promising approaches are multi-modal systems that make use of animal-borne wireless sensors and that exploit the inherent signal redundancy. In this vein, we designed a modular recording system (BirdPark) that yields synchronized data streams and contains a custom software-defined radio receiver. We record pairs of songbirds with multiple cameras and microphones and record their body vibrations with custom low-power frequency-modulated (FM) radio transmitters. Our custom multi-antenna radio demodulation technique increases the signal-to-noise ratio of the received radio signals by 6 dB and reduces the signal loss rate by a factor of 87 to only 0.03% of the recording time compared to standard single-antenna demodulation techniques. Nevertheless, neither a single vibration channel nor a single sound channel is sufficient by itself to signal the complete vocal output of an individual, with each sensor modality missing on average about 3.7% of vocalizations. Our work emphasizes the need for high-quality recording systems and for multi-modal analysis of social behavior

A system for controlling vocal communication networks

Animal vocalizations serve a wide range of functions including territorial defense, courtship, social cohesion, begging, and vocal learning. Whereas many insights have been gained from observational studies and experiments using auditory stimulation, there is currently no technology available for the selective control of vocal communication in small animal groups. We developed a system for real-time control of vocal interactions among separately housed animals. The system is implemented on a field-programmable gate array (FPGA) and it allows imposing arbitrary communication networks among up to four animals. To minimize undesired transitive sound leakage, we adopted echo attenuation and sound squelching algorithms. In groups of three zebra finches, we restrict vocal communication in circular and in hierarchical networks and thereby mimic complex eavesdropping and middleman situations

Evolutionary Ecology of Prokaryotic Immune Mechanisms.

Published onlineJournal ArticleReviewBacteria have a range of distinct immune strategies that provide protection against bacteriophage (phage) infections. While much has been learned about the mechanism of action of these defense strategies, it is less clear why such diversity in defense strategies has evolved. In this review, we discuss the short- and long-term costs and benefits of the different resistance strategies and, hence, the ecological conditions that are likely to favor the different strategies alone and in combination. Finally, we discuss some of the broader consequences, beyond resistance to phage and other genetic elements, resulting from the operation of different immune strategies.S.V.H. received funding from the European Union's Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement no. 660039. We also acknowledge the NERC, the BBSRC, the Royal Society, the Leverhulme Trust, the Wellcome Trust, and the AXA research fund for funding

Safety and efficacy of Axtra® PHY 20000 TPT2 (6‐phytase) as a feed additive for poultry and porcine species

Axtra\uae PHY 20000 TPT2 is a solid preparation that contains a 6-phytase produced with a genetically modified strain of Trichoderma reesei. The production strain and its recombinant DNA were not detected in Axtra\uae PHY 20000 TPT2. From the results obtained in tolerance studies, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additive is safe for the target species at 2,000 FTU/kg feed. The studies provided to address the safety for the consumer were performed with the fermentation product that is used to formulate the additive and the results do not indicate any reason for concern for consumer safety arising from the use of the product as a feed additive. The studies provided to address the safety for the user were performed with the fermentation product that is used to formulate the additive and have been assessed in a previous opinion. Considering the results of those studies and the substances used during the formulation of Axtra\uae PHY 20000 TPT2, this formulation is not considered a dermal sensitiser. However, it should be considered a potential irritant to skin, eyes and the respiratory tract, and owing to the nature of the active substance, it should be considered a potential respiratory sensitiser. However, the exposure by inhalation is expected to be negligible. No risks to the environment are expected from the use of Axtra\uae PHY 20000 TPT2 as a feed additive. Based on the results of efficacy studies, the Panel concluded that the additive has the potential to be efficacious at 250 FTU/kg feed

Safety and efficacy of a natural mixture of dolomite plus magnesite and magnesium-phyllosilicates (Fluidol) as feed additive for all animal species

The additive, a natural mixture of dolomite plus magnesite and magnesium-phyllosilicates, is intended to be used as a technological additive (functional groups: anticaking agents) in feedingstuffs for all animal species. The additive is safe in complete feed for dairy cows, piglets and pigs for fattening at a maximum concentration of 20,000 mg/kg. No conclusions can be drawn for all the other animal species/categories. The additive is not genotoxic. As the additive is essentially not absorbed from the gut lumen, the Panel on Additives and Products or Substances used in Animal Feed considers that use of the additive in animal nutrition is safe for consumers of food products from animals fed diets containing the additive. The additive is not an irritant to the eyes and the skin, it is not a skin sensitiser and it is of low toxicity by the inhalation route. The components of the additive (dolomite, magnesite, talc and chlorite) are natural constituents of soil. Consequently, the use of the additive in animal nutrition will not pose a risk to the environment. The additive is effective as an anticaking agent at a minimum inclusion level of 5,000 mg/kg feed