Integrated Calendar

After some introduction to the notion of jets in particle physics I will move to describe the status of jets at the Tevatron and LHC experiments, where jets are copiously produced.
However, due to soft collinear divergencies (a notion that I will try to explain), narrow jets tend to be of low mass.
Of particular interest are those uncommon and unique events where a jet of very large mass is obtained.
The large mass yield a new perturbative scale which provides us with a glimpse into the mechanism of showering in a new kinematical regime. Maybe more importantly, narrow jets of electroweak masses (or above) are the focus of various beyond the standard model (SM) searches related to new form of strong dynamics & extra dimension, supersymmetry and even the celebrated, yet elusive, Higgs boson.
Thus, we discuss some of the theory of massive boosted jets, recent experimental effort at the CDF experiment and a new technique to distinguish between non-SM signals and QCD backgrounds.

Parkinson’s disease (PD) is a characterized, in addition to loss of dopaminergic neurons in the substantia nigra, by loss of cholinergic neurons in the basal nucleus (Zarow et al., 2003) and pathology of alpha-synuclein, a protein implicated in familial PD, in this region concurrently with pathology of alpha-synuclein pathology in the substantia nigra (Braak et al., 2003), as well as decrease in the activity of choline acetyltransferase, the rate limiting enzyme in the synthesis of acetylcholine (Ziabreva et al., 2006). Mild cognitive deficits are also observed in the early stages of PD (Elgh et al., 2009; Mamikonyan et al., 2009). Mice over-expressing the human wild-type alpha-synuclein under the Thy1 promoter (Thy1-aSyn) present progressive sensorimotor and non-motor behavioral abnormalities reminiscent of the pre-manifest early stages of PD (Magen and Chesselet, ’10) and subsequently exhibit a loss of striatal DA (Lam et al. ’11). We now examined whether these mice also exhibit cognitive deficits in tests sensitive to cholinergic function, and whether they present cholinergic deficits.
Thy1-aSyn mice on a mixed C57BL/6-DBA/2 background presented spatial working memory deficits in the Y-maze which showed progression from 3-4 to 5-6 months and to 7-9 months. Thy1-aSyn mice also showed spatial memory deficits in the novel place recognition test and recognition memory deficits in the novel object recognition test at 4-5 months of age. In a reversal learning task at 4-5 months, Thy1-aSyn mice learned the initial contingency rule as equally well as WT littermates, but were impaired in learning a reversal of this rule, mirroring the cognitive inflexibility displayed by early PD patients in similar tasks. Expression of both proteinase-K resistant and non-resistant alpha-synuclein in the medial septum and the basal nucleus, two major regions of cholinergic input into the forebrain, was increased in Thy1-aSyn mice at 5 months of age, and cholinergic neurons in both regions expressed both human and mouse alpha-synuclein in Thy1-aSyn mice, while endogenous (murine) alpha-synuclein expression was either lower or absent in cholinergic neurons in WT mice. However, morphological features of the cholinergic neurons such as cell body diameter did not change in either the basal nucleus or the septum. Acetylcholine levels decreased by 30% in the cortex of Thy1-aSyn mice at 6 months, further suggesting a link between acetylcholine pathology and the cognitive deficits.
Our data indicate that Thy1-aSyn mice display cognitive dysfunction at an early age, which is associated with decreased acetylcholine levels. As the cognitive tests used are sensitive to cholinergic function (Barker et al., 2008; Yang et al., 2009; Botton et al., 2010), future pharmacological studies will attempt to reverse these deficits using cholinergic agonists and/or acetylcholinesterase inhibitors. A study with an acute nicotine treatment is to be performed soon, to determine whether nicotine can reverse the cognitive deficits, which might point to a causal relation between the cognitive deficits and the compromised cholinergic system. In addition, the cognitive phenotype faithfully reproduces the early cognitive deficits in PD, whereas the lack of any neuropathology in cholinergic neurons suggests that the Thy1-aSyn models mild cognitive deficits rather than dementia, which is mostly associated with a gross neuropathology. Thus, it can serve as a basis for the testing of cognitive enhancers other than cholinergic agents.

Slow waves and sleep spindles are the two fundamental brain oscillations of NREM sleep, yet they have been mostly studied in vitro, under anesthesia, within few brain regions or with scalp EEG recordings. We examined intracranial depth EEG and single-unit activity recorded simultaneously in up to 12 brain regions in neurosurgical patients to better characterize regional diversity in these sleep oscillations. First, we found changes in spindle occurrence, frequency, and timing between regions and across sleep, reflecting anatomical projections and thalamocortical hyperpolarization levels that change with sleep depth. We further show that both slow waves (and the underlying active and silent neuronal states) and sleep spindles occur mostly locally, thereby showing that constrained intracerebral communication is an important feature of sleep. Next, we confirmed that in freely behaving rats, slow waves and silent periods in sleep likewise occur predominantly locally. Moreover, after a long period of being awake, while both EEG and behavior indicate wakefulness, local populations of neurons go offline, exhibiting "local sleep". We are now exploring whether such local sleep may lead to cognitive consequences, such as lapses of attention, in awake people who are sleep deprived
Another line of research focuses on disconnection from the external environment - conditions in which sensory stimuli fail to be incorporated into our perceptual stream. To this end, we are examining neuronal responses to sounds in rats across spontaneous vigilance states with an emphasis on comparing wakefulness with REM sleep. Responses of individual neurons in primary auditory cortex are comparable in wake and sleep, calling into question the proposal that the thalamus does not relay peripheral signals effectively to the cortex in sleep. Important differences between waking and sleep may lie in how signals propagate across cortical regions and layers.

Every chemist and every scientist in the neighbouring fields is familiar with those little curved arrows in Lewis structures of reactants of pericyclic reactions - they represent the net electron transfers or fluxes of valence electrons during the reactions in the electronic ground state, and they allow to predict which chemical bonds are broken, which are formed, etc. But in spite of many empirical successes and also many theoretical investigations e.g. concerning the Woodward-Hoffmann rules for pericyclic reactions, those electron fluxes have never been observed or evaluated, during 84 years after the discovery of the Schrödinger equation. On the experimental side, the first real-time observation of valence electron motion in atoms is a break-through which should pave the way to monitoring electron motions during reactions [1]. On the theoretical side, the fundamental obstacle has been the Born Oppenheimer approximation: On one hand it is the doorway to all successful quantum chemistry calculations of molecular properties. But on the other hand it is a disaster because it predicts zero (0 !) electron flux densities. We overcome this problem by means of the continuity equation and Gauss' theorem. The result is - for the first time! - the quantum quantification of those little arrows in Lewis structures, i.e. we are able to answer question such as: in which directions do the electrons really flow during the pericyclic reaction? How many electrons are really transferred? Do they flow synchronously? On which time scale? The electron fluxes are visualized by movies for simple model systems.

The results have been achieved in wonderful cooperation with PhD students Timm Bredtmann, Falko Marquardt, Axel Schild, with post-docs and visiting scientists Dirk Andrae, Ingo Barth, Anatole Kenfack and Gennadii K. Paramonov, with my colleagues, Hans-Christian Hege and Beate Paulus, and with invaluable advice from several colleagues from organic and theoretical chemistry. Our work is supported, by Deutsche Forschungsgemeinschaft, and by Fonds der Chemischen Industrie.

[1] E. Goulielmakis et al.: Real-time observation of valence electron motion, Nature, 466, 739-744 (2010)