A Survey on Semi-, Self- and Unsupervised Learning for Image Classification

While deep learning strategies achieve outstanding results in computer vision tasks, one issue remains: The current strategies rely heavily on a huge amount of labeled data. In many real-world problems, it is not feasible to create such an amount of labeled training data. Therefore, it is common to incorporate unlabeled data into the training process to reach equal results with fewer labels. Due to a lot of concurrent research, it is difficult to keep track of recent developments. In this survey, we provide an overview of often used ideas and methods in image classification with fewer labels. We compare 34 methods in detail based on their performance and their commonly used ideas rather than a fine-grained taxonomy. In our analysis, we identify three major trends that lead to future research opportunities. 1. State-of-the-art methods are scalable to real-world applications in theory but issues like class imbalance, robustness, or fuzzy labels are not considered. 2. The degree of supervision which is needed to achieve comparable results to the usage of all labels is decreasing and therefore methods need to be extended to settings with a variable number of classes. 3. All methods share some common ideas but we identify clusters of methods that do not share many ideas. We show that combining ideas from different clusters can lead to better performance

A new pathway for heterogenization of molecular catalysts by non-covalent interactions with carbon nanoreactors

A novel approach to heterogenisation of catalytic molecules is demonstrated using the nanoscale graphitic step-edges inside hollow graphitised carbon nanofibres (GNFs). The presence of the fullerene C60 moiety within a fullerene-salen CuII complex is essential for anchoring the catalyst within the GNF nanoreactor as demonstrated by comparison with the analogous catalyst complex without the fullerene group. The presence of the catalyst at the step-edges of the GNFs is confirmed by high resolution transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) with UV/Vis spectroscopy demonstrating only negligible (c.a. 3 %) desorption of the fullerene-salen CuII complex from the GNFs into solution under typical reaction conditions. The catalyst immobilised in GNFs shows good catalytic activity and selectivity towards styrene epoxidation, comparable to the analogous catalyst in solution. Moreover, the fullerene-salen CuII complex in GNFs demonstrates excellent stability and recyclability as it can be readily separated from the reaction mixture and employed in multiple reaction cycles with minimal loss of activity, which is highly advantageous compared to catalysts not stabilised by the graphitic step-edges that desorb rapidly from GNFs

Anti-Screening by Quarks and the Structure of the Inter-Quark Potential

The inter-quark potential is dominated by anti-screening effects which underly asymptotic freedom. We calculate the order g^6 anti-screening contribution from light fermions and demonstrate that these effects introduce a non-local divergence. These divergences are shown to make it impossible to define a coupling renormalisation scheme that renormalises this minimal, anti-screening potential. Hence the beta function cannot be divided into screening and anti-screening parts beyond lowest order. However, we then demonstrate that renormalisation can be carried out in terms of the anti-screening potential.Comment: 11 pages, some clarifications and typographical corrections, to appear in Physics Letters

Coordination chemistry of nitrile-functionalized mixed thia-aza macrocycles [9]aneN2S and [9]aneNS2 towards silver(I)

The coordination chemistry towards silver(I) of the small-ring macrocycles [9]aneN2S (1-thia-4,7-di¬aza-cyclo¬nona¬ne) and [9]aneNS2 (1,4-di¬thia-7-aza¬cyclo¬nona¬ne) incorporating nitrile-functionalized pendant arms is considered both in the presence and the absence of exogenous bridging ligands. The aim is to understand the influence of the number and length of the pendant arms on the nuclearity and dimensionality of the resulting com¬plexes. The X-ray crystal structures of the com¬plexes bis¬[4,7-bis-(cyano¬meth¬yl)-1-thia-4,7-di¬aza¬cyclo¬non¬ane-κ3N,N′,S]silver(I) tetra¬fluorido¬borate, [Ag(C10H16N4S)2]BF4 or [Ag(L1)2]BF4, [4,7-bis¬(2-cyano¬eth¬yl)-1-thia-4,7-di¬aza¬cyclo¬nonane-κ3N,N′,S](thio¬cyanato-κS)silver(I), [Ag(C12H20N4S)(NCS)] or [Ag(L2)(SCN)], and μ-thio¬cyanato-κ2S:S-bis¬{[7-(2-cyano¬eth¬yl)-1,4-di¬thia-7-aza-cyclo¬nonane-κ3N,S,S′]silver(I)} tetra¬fluor¬ido¬borate, [Ag2(C9H16N2S2)2(SCN)]BF4 or [Ag2(L3)2(μ-SCN)]BF4, are discus¬sed in relation to analogous com¬pounds in the literature

Metal-directed columnar phase formation in tetrahedral zinc(II) and manganese(II) metallomesogens

New, non-discoid M(II) complexes [MCl2(L)] {M = Mn, Zn; L = 2,6-diformyl-4- methylphenolbis[3’,4’,5’-tris(hexadecyloxy)phenylimine]} have been prepared and shown to exhibit columnar mesophases, the nature of which was found to be metal-dependent. As analysed by DSC and small-angle X-ray diffraction experiments, the complex [ZnCl2(L)] exhibits a single mesophase with rectangular symmetry (Colr) between 46 and 145 °C, whereas the Mn(II) analogue [MnCl2(L)] displays a purely hexagonal mesophase (Colh) phase between 55 and 285 °C. By combining these results with those obtained from dilatometry, a model for the molecular organisation within the columnar mesophases is proposed. The single-crystal X-ray structure of the related complex [Zn(NO3)(L’)2]NO3.3MeOH {L’ = 2,6-diformyl-4-methylphenolbis[3’,4’,5’-tris(methoxy)phenylimine]} has been determined and supports the proposed mode of binding of the ligand to the metal via only one imine and a phenol

The Structure of Screening in QED

The possibility of constructing charged particles in gauge theories has long been the subject of debate. In the context of QED we have shown how to construct operators which have a particle description. In this paper we further support this programme by showing how the screening interactions arise between these charges. Unexpectedly we see that there are two different gauge invariant contributions with opposite signs. Their difference gives the expected result.Comment: 8 pages, LaTe

The NNLO gluon fusion Higgs production cross-section with many heavy quarks

We consider extensions of the Standard Model with a number of additional heavy quarks which couple to the Higgs boson via top-like Yukawa interactions. We construct an effective theory valid for a Higgs boson mass which is lighter than twice the lightest heavy quark mass and compute the corresponding Wilson coefficient through NNLO. We present numerical results for the gluon fusion cross-section at the Tevatron for an extension of the Standard Model with a fourth generation of heavy quarks. The gluon fusion cross-section is enhanced by a factor of roughly 9 with respect to the Standard Model value. Tevatron experimental data can place stringent exclusion limits for the Higgs mass in this model.Comment: 14 pages, 1 tabl