An Abundance of Heterotic Vacua

We explicitly construct the largest dataset to date of heterotic vacua arising from stable vector bundles on Calabi-Yau threefolds. Focusing on elliptically fibered Calabi-Yau manifolds with spectral cover bundles, we show that the number of heterotic models with non-zero number of generations is finite. We classify these models according to the complex base of their Calabi-Yau threefold and to the unification gauge group that they preserve in four dimensions. This database of the order of $10^7$ models, which includes potential Standard Model candidates, is subjected to some preliminary statistical analyses. The additional constraint that there should be three net generations of particles gives a dramatic reduction of the number of vacua.Comment: 27 pages, 12 figures, added reference

POLYMORPHISM OF FOUR ENANTIOTROPIC CRYSTALLINE SYSTEMS CONTAINING Ni(II), H\u3csub\u3e2\u3c/sub\u3eO, 15-Crown-5 AND NO\u3csub\u3e3\u3c/sub\u3e\u3csup\u3e-\u3c/sup\u3e

The series of compounds [M(H2O)2(15-crown-5)](NO3)2, M = Mg, Mn, Co, Cu and Zn, has been extended to include two new phases for M = Fe and two new phases for M = Ni. The system [M(H2O)2(15-crown-5)](NO3)2 is remarkable for having many high-Z’ phases (Z’ \u3e 1) with similar packing and for having solid-solid phase transitions through which there is no significant loss of crystallinity. The synthesis of the analogous Ni complex was carried out. Single-crystal X-ray diffraction showed that the coordination of the Ni2+ ion is different from that of the other six M2+ ions in the system [M(H2O)2(15-crown- 5)](NO3)2. High temperature phases with high Z’ (8) were isolated for M = Mg, Fe and Zn. The refinements of such phases are challenging because of the lack of information in the diffraction patterns. Full details of the refinements for these three phases are discussed. Six other Ni(II) complexes consisting of Ni2+, NO3-, 15-crown-5 and different solvents were found when efforts were made to synthesize the compound [Ni(H2O)2(15-crown- 5)](NO3)2. In these chemically different environments, the Ni2+ ions are not coordinated by the 15-crown-5 molecules; rather, one-dimensional H-bonded chains are formed from uncomplexed 15-crown-5 molecules and the Ni(II) complexes. Among these six Ni(II) complexes, the compounds [Ni(H2O)6](NO3)2·(15-crown-5)·H2O, [Ni(H2O)6](NO3)2·(15-crown-5)·2H2O and [Ni(H2O)2(MeCN)(NO3)2]·(15-crown- 5)·MeCN were found to have reversible solid-solid phase transitions between structurally related phases. In all of these transitions, no significant crystal damage was detectable. The two latter systems are unusual because their phase sequences include three transitions and four phases between 90 and 295 K and because of the existence of high-Z’ phases. These high-Z’ phases are best depicted as being intermediate to low- and hightemperature phases. A method based on thermal analyses and X-ray diffraction has been developed for studying such sets of phase transitions

Linear scanning ATR-FTIR for chemical mapping and high-throughput studies of Pseudomonas sp. biofilms in microfluidic channels

A fully automated linear scanning attenuated total reflection (ATR) accessory is presented for Fourier transform infrared (FTIR) spectroscopy. The approach is based on the accurate displacement of a multi-bounce ATR crystal relative to a stationary infrared beam. To ensure accurate positioning and to provide a second sample characterization mode, a custom-built microscope was integrated into the system and the computerized work flow. Custom software includes automated control and measurement routines with a straightforward user interface for selecting parameters and monitoring experimental progress. This cost-effective modular system can be implemented on any research-grade spectrometer with a standard sample compartment for new bioanalytical chemistry studies. The system was validated and optimized for use with microfluidic flow cells containing growing Pseudomonas sp. bacterial biofilms. The complementarity among the scan positioning accuracy, measurement spatial resolution and the microchannel dimensions paves the way for parallel biological assays with real-time control over environmental parameters and minimal manual labor. By rotating the channel orientation relative to the beam path, the system could also be used for acquisition of linear biochemical maps and stitched microscope images along the channel length.Comment: 9 pages, 6 figure

Pilot Flying vs. Pilot Monitoring during the approach phase: an eye–tracking study

The adequate monitoring of the flight parameters in the cockpit is a critical issue for flight safety. However, little is known about how the crew supervises the flight deck. In this paper, the preliminary results of a project dedicated to analyze pilot flying and pilot monitoring eyes movements collected in full flight simulator during approach phases are presented. First analyses were conducted over 32 approach phases (8 different crews performing 4 approaches each). The results revealed that the pilot flying and the pilot monitoring exhibited similar ocular behavior during the approach. Moreover, the findings suggested that the pilot monitoring’s attentional allocation may not be optimal especially during the short final with low percentage of dwell time on the speed indicator and high percentage of dwell time out of the window

Large Language Models, scientific knowledge and factuality: A systematic analysis in antibiotic discovery

Inferring over and extracting information from Large Language Models (LLMs) trained on a large corpus of scientific literature can potentially drive a new era in biomedical research, reducing the barriers for accessing existing medical evidence. This work examines the potential of LLMs for dialoguing with biomedical background knowledge, using the context of antibiotic discovery as an exemplar motivational scenario. The context of biomedical discovery from natural products entails understanding the relational evidence between an organism, an associated chemical and its associated antibiotic properties. We provide a systematic assessment on the ability of LLMs to encode and express these relations, verifying for fluency, prompt-alignment, semantic coherence, factual knowledge and specificity of generated responses. The systematic analysis is applied to nine state-of-the-art models (including ChatGPT and GPT-4) in two prompting-based tasks: chemical compound definition generation and chemical compound-fungus relation determination. Results show that while recent models have improved in fluency, factual accuracy is still low and models are biased towards over-represented entities. The ability of LLMs to serve as biomedical knowledge bases is questioned, and the need for additional systematic evaluation frameworks is highlighted. The best performing GPT-4 produced a factual definition for 70% of chemical compounds and 43.6% factual relations to fungi, whereas the best open source model BioGPT-large 30% of the compounds and 30% of the relations for the best-performing prompt. The results show that while LLMs are currently not fit for purpose to be used as biomedical factual knowledge bases, there is a promising emerging property in the direction of factuality as the models become domain specialised, scale-up in size and level of human feedback.Comment: 23 pages, 3 figure