A prediction framework with time-frequency localization feature for detecting the onset of seismic events.

Onset detection of P-wave in seismic signals is of vital importance to seismologists because it is not only crucial to the development of early warning systems but it also aids in estimating the seismic source parameters. All the existing P-wave onset detection methods are based on a combination of statistical signal processing and time-series modeling ideas. However, these methods do not adequately accommodate some advanced ideas that exist in fault detection literature, especially those based on predictive analytics. When combined with a time-frequency (t-f) / temporal-spectral localization method, the effectiveness of such methods is enhanced significantly. This work proposes a novel real-time automatic P-wave detector and picker in the prediction framework with a time-frequency localization feature. The proposed approach brings a diverse set of capabilities in accurately detecting the P-wave onset, especially in low signal-to-noise ratio (SNR) conditions that all the existing methods fail to attain. The core idea is to monitor the difference in squared magnitudes of one-step-ahead predictions and measurements in the time-frequency bands with a statistically determined threshold. The proposed framework essentially accommodates any suitable prediction methodology and time-frequency transformation. We demonstrate the proposed framework by deploying auto-regressive integrated moving average (ARIMA) models for predictions and the well-known maximal overlap discrete wavelet packet transform (MODWPT) for the t-f projection of measurements. The ability and efficacy of the proposed method, especially in detecting P-waves embedded in low SNR measurements, is illustrated on a synthetic data set and 200 real-time data sets spanning four different geographical regions. A comparison with three prominently used detectors, namely, STA/LTA, AIC, and DWT-AIC, shows improved detection rate for low SNR events, better accuracy of detection and picking, decreased false alarm rate, and robustness to outliers in data. Specifically, the proposed method yields a detection rate of 89% and a false alarm rate of 11.11%, which are significantly better than those of existing methods.

Visible Light Mediated Bidirectional Control over Carbonic Anhydrase Activity in Cells and in Vivo Using Azobenzenesulfonamides.

Two azobenzenesulfonamide molecules with thermally stable cis configurations resulting from fluorination of positions ortho to the azo group are reported that can differentially regulate the activity of carbonic anhydrase in the trans and cis configurations. These fluorinated probes each use two distinct visible wavelengths (520 and 410 or 460 nm) for isomerization with high photoconversion efficiency. Correspondingly, the cis isomer of these systems is highly stable and persistent (as evidenced by structural studies in solid and solution state), permitting regulation of metalloenzyme activity without continuous irradiation. Herein, we use these probes to demonstrate the visible light mediated bidirectional control over the activity of zinc-dependent carbonic anhydrase in solution as an isolated protein, in intact live cells and in vivo in zebrafish during embryo development.

Reversible Solid-State Isomerism of Azobenzene-Loaded Large-Pore Isoreticular Mg-CUK-1.

A large-pore version of Mg-CUK-1, a water-stable metal-organic framework (MOF) with 1-D channels, was synthesized in basic water. Mg-CUK-1L has a BET surface area of 2896 m2 g-1 and shows stark selectivity for CO2 sorption over N2, O2, H2, and CH4. It displays reversible, multistep gated sorption of CO2 below 0.33 atm. The dehydrated single-crystal structure of Mg-CUK-1L confirms retention of the open-channel structure. The MOF can be loaded with organic molecules by immersion in hot melts, providing single crystals suitable for X-ray diffraction. trans-Azobenzene fills the channels in a 2 × 2 arrangement. Solid-state UV-vis spectroscopy reveals that azobenzene molecules undergo reversible trans-cis isomerization, despite being close-packed; this surprising result is confirmed by DFT-simulated UV-vis spectra.

Pull-Down of Metalloproteins in Their Native States by Using Desthiobiotin-Based Probes.

One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+ -containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated.

In Situ Photoregulation of Carbonic Anhydrase Activity Using Azobenzenesulfonamides.

We report two small molecule azobenzenesulfonamide probes, CAP1 and CAP2, capable of photomodulating the activity of carbonic anhydrase (CA) on demand. In the trans form, CAP azobenzene probes adopt a linear shape, making them suitable for occupying the CA active site and interacting with Zn2+, thereby inhibiting enzyme activity. Following irradiation with either 365 or 410 nm light, the CAP probes isomerize to their cis form. Because of the change in steric profile, the probe exits the active site, and the activity of the enzyme is restored. The cis isomer can revert back to the trans isomer through thermal relaxation or via photoirradiation with 460 nm light and thereby inhibit protein activity again. This process can be repeated multiple times without any photodegradation and thus can be used to inhibit or activate the protein reversibly. Importantly, we demonstrate our ability to apply CAP azobenzene probes to regulate CA activity both in an isolated protein solution and in live cells, where the two isomers of CAP1 differentially regulate the intracellular cytosolic pH.