Recently, we reported the isothermal crystallization behaviors of poly(L-lactic acid) (PLLA) from the melt and glassy states, respectively [J. ]. Surprisingly, the quite different infrared (IR) spectral evolutions occur in the two crystallization processes at different temperatures in which the same crystal modification is expected to be formed. To clarify this unusual phenomenon, the crystal modifications and thermal behavior of PLLA samples prepared under different crystallization temperatures are investigated in detail by TEM, WAXD, and FTIR techniques. On the basis of the WAXD and IR data, a new crystal modification named the Ŕ form is proposed for the crystal structure of PLLA samples annealed at temperature below 120°C. Such crystal modification with loose 103 helical chain packing is less thermally stable than the standard R form of PLLA. This assignment can explain all the experiment observations well. Other possible mechanisms for the IR spectral difference of bulk PLLA samples annealed at different temperatures are also discussed.

It has been found that, dependent on the crystallization temperature (T c ), the disorder (R′) and order (R) phases of poly(L-lactide) (PLLA) are formed at low (T c < 100°C) and high (T c g 120°C) temperatures, respectively. In the DSC curves, the sample with R′ phase demonstrates a peculiar small exothermal peak around 160°C just prior to the melting point, while the sample crystallized at temperatures around 120°C (between 110 and 130°C) shows a double melting behavior. These distinct thermal behaviors of various PLLA samples were investigated in detail by simultaneous measurements of WAXD and DSC. It is confirmed that the small exothermal peak corresponds to the disorder-to-order (R′-to-R) phase transition, in which the chain packing of the crystal lattice becomes more compacted. In the process of the R′-to-R phase transition, the isosbestic points were found in the temperature-dependent WAXD profiles. So far, the R′-to-R transition was considered to occur apparently continuously as long as the main 200/110 peak was measured, but detailed investigation of higher 2θ peaks has revealed for the first time that the R′ phase transforms discretely to the R phase in the first-order transition mode. On the basis of the X-ray diffraction and DSC data, a kind of phase diagram concerning the R′ and R forms has been constructed reasonably.

Abstract. We propose a multi-expert restoration scheme to address the model drift problem in online tracking. In the proposed scheme, a tracker and its historical snapshots constitute an expert ensemble, where the best expert is selected to restore the current tracker when needed based on a minimum entropy criterion, so as to correct undesirable model updates. The base tracker in our formulation exploits an online SVM on a budget algorithm and an explicit feature mapping method for efficient model update and inference. In experiments, our tracking method achieves substantially better overall performance than 32 trackers on a benchmark dataset of 50 video sequences under various evaluation settings. In addition, in experiments with a newly collected dataset of challenging sequences, we show that the proposed multi-expert restoration scheme significantly improves the robustness of our base tracker, especially in scenarios with frequent occlusions and repetitive appearance variations.

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We aim to model the top-down attention of a Convolutional Neural Network (CNN) classifier for generating task-specific attention maps. Inspired by a top-down human visual attention model, we propose a new backpropagation scheme, called Excitation Backprop, to pass along top-down signals downwards in the network hierarchy via a probabilistic Winner-Take-All process. Furthermore, we introduce the concept of contrastive attention to make the top-down attention maps more discriminative. In experiments, we demonstrate the accuracy and generalizability of our method in weakly supervised localization tasks on the MS COCO, PASCAL VOC07 and ImageNet datasets. The usefulness of our method is further validated in the text-to-region association task. On the Flickr30k Entities dataset, we achieve promising performance in phrase localization by leveraging the top-down attention of a CNN model that has been trained on weakly labeled web images.

SUMMARY Small cell lung cancer (SCLC) is an aggressive disease with high mortality. The identification of effective pharmacological strategies to target SCLC biology represents an urgent need. Using a high-throughput cellular screen of a diverse chemical library we observe that SCLC is sensitive to transcription-targeting drugs, and in particular to THZ1, a recent identified covalent inhibitor of cyclin-dependent kinase 7 (CDK7). We find that expression of super-enhancer associated transcription factor genes including MYC family proto-oncogenes and neuroendocrine lineage-specific factors are highly vulnerability to THZ1 treatment. We propose that downregulation of these transcription factors contributes, in part, to SCLC sensitivity to transcriptional inhibitors and that THZ1 represents a prototype drug for tailored SCLC therapy.

The nature of the "peculiarly strong" interaction between the poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains was investigated by real time infrared spectroscopy during the isothermal melt crystallization process of the PLLA/PDLA stereocomplex. A very small low-frequency shift (about 1 cm -1 ) of νas(CH3) and a larger low-frequency shift (about 5 cm -1 ) of ν(CdO) were observed. The typical butterfly pattern in the two-dimensional (2D) asynchronous correlation spectrum and the second-derivative spectra reveal that there is a "peak shift" for ν(CdO). The red shifts of the stretching vibration modes of the methyl and carbonyl groups suggest that the interaction between the PLLA/PDLA stereocomplex is ascribed to CH3‚‚‚OdC hydrogen bonding. Another interesting result is that the peak shift of the ν(CdO) band already occurs in the induction period, which indicates that the CH3‚‚‚OdC interaction is the driving force for forming the racemic nucleation of the PLLA/PDLA stereocomplex. Moreover, the 2D correlation analysis indicates that the structural adjustment of the CH3 group occurs prior to that of the C-O-C backbone during the stereocomplexation process of PLLA/PDLA. The CH3‚‚‚OdC interaction may be the reason for this sequence of structural changes.

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