Bounds on heavy sterile neutrinos revisited

We revise the bounds on heavy sterile neutrinos, especially in the case of their mixing with muon neutrinos in the charged current. We summarize the present experimental limits, and we reanalyze the existing data from the accelerator neutrino experiments and from Super-Kamiokande to set new bounds on a heavy sterile neutrino in the range of masses from 8 MeV to 390 MeV. We also discuss how the future accelerator neutrino experiments can improve the present limits.Comment: 14 pages, 6 figures; a detailed and expanded versio

Reactor Neutrino Experiments with a Large Liquid Scintillator Detector

We discuss several new ideas for reactor neutrino oscillation experiments with a Large Liquid Scintillator Detector. We consider two different scenarios for a measurement of the small mixing angle $\theta_{13}$ with a mobile $\bar{\nu}_e$ source: a nuclear-powered ship, such as a submarine or an icebreaker, and a land-based scenario with a mobile reactor. The former setup can achieve a sensitivity to $\sin^2 2\theta_{13} \lesssim 0.003$ at the 90% confidence level, while the latter performs only slightly better than Double Chooz. Furthermore, we study the precision that can be achieved for the solar parameters, $\sin^2 2\theta_{12}$ and $\Delta m_{21}^2$, with a mobile reactor and with a conventional power station. With the mobile reactor, a precision slightly better than from current global fit data is possible, while with a power reactor, the accuracy can be reduced to less than 1%. Such a precision is crucial for testing theoretical models, e.g. quark-lepton complementarity.Comment: 18 pages, 3 figures, 2 tables, revised version, to appear in JHEP, Fig. 1 extended, Formula added, minor changes, results unchange

Activity in perirhinal and entorhinal cortex predicts perceived visual similarities among category exemplars with highest precision

Vision neuroscience has made great strides in understanding the hierarchical organization of object representations along the ventral visual stream (VVS). How VVS representations capture fine-grained visual similarities between objects that observers subjectively perceive has received limited examination so far. In the current study, we addressed this question by focusing on perceived visual similarities among subordinate exemplars of real world-categories. We hypothesized that these perceived similarities are reflected with highest fidelity in neural activity patterns downstream from inferotemporal regions, namely in perirhinal and anterolateral entorhinal cortex in the medial temporal-lobe. To address this issue with fMRI, we administered a modified 1-Back task that required discrimination between category exemplars as well as categorization. Further, we obtained observer-specific ratings of perceived visual similarities, which predicted behavioural performance during scanning. As anticipated, we found that activity patterns in perirhinal and anterolateral entorhinal cortex predicted the structure of perceived visual similarity relationships among category exemplars, including its observer-specific component, with higher precision than any other VVS region. Our findings provide new evidence that subjective aspects of object perception that rely on fine-grained visual differentiation are reflected with highest fidelity in the medial temporal lobe

Natural Antibiotic Production

As bacteria continue to evolve, several species have adopted increasingly advanced antibiotic-resistant qualities. These multi-drug resistant (MDR) bacteria pose a threat to the medical field where the invention of new antibiotics is constantly underway in efforts to plateau the effects of potentially dangerous bacteria.  Our Major Qualifying Project focuses on the production of antibiotics from isolated bacteria retrieved from select microenvironments found in soil. This research was conducted using samples collected from our group in 2019 and continued through the duration of our senior year. We determined the effects of our isolate’s antibiotic production capabilities using ESKAPE safe relatives and other safe relatives, noting inhibition against Mycobacterium smegmatis. We then attempted to identify the genus of our isolate using PCR to amplify the 16S rRNA gene. To confirm the genus of our isolate, we moved forward to a full genomic extraction. Subsequently, we attempted to isolate the proposed antibiotic-producing agent through organic extraction, followed by HPLC. We found clear separations through our organic solvents, and our HPLC runs produced multiple fractions that were used to test the success of our isolation. Ultimately, no clear signs of inhibition were recorded by these means, and we were unsuccessful in confirming the antibiotic capabilities of our isolate