507 research outputs found
Complete sets of cyclic mutually unbiased bases in even prime power dimensions
We present a construction method for complete sets of cyclic mutually
unbiased bases (MUBs) in Hilbert spaces of even prime power dimensions. In
comparison to usual complete sets of MUBs, complete cyclic sets possess the
additional property of being generated by a single unitary operator. The
construction method is based on the idea of obtaining a partition of
multi-qubit Pauli operators into maximal commuting sets of orthogonal operators
with the help of a suitable element of the Clifford group. As a consequence, we
explicitly obtain complete sets of cyclic MUBs generated by a single element of
the Clifford group in dimensions for .Comment: 10 page
Randomized Dynamical Decoupling Strategies and Improved One-Way Key Rates for Quantum Cryptography
The present thesis deals with various methods of quantum error correction. It
is divided into two parts. In the first part, dynamical decoupling methods are
considered which have the task of suppressing the influence of residual
imperfections in a quantum memory. The suppression is achieved by altering the
dynamics of an imperfect quantum memory with the help of a sequence of local
unitary operations applied to the qudits. Whereas up to now the operations of
such decoupling sequences have been constructed in a deterministic fashion,
strategies are developed in this thesis which construct the operations by
random selection from a suitable set. Furthermore, it is investigated if and
how the discussed decoupling strategies can be employed to protect a quantum
computation running on the quantum memory.
The second part of the thesis deals with quantum error-correcting codes and
protocols for quantum key distribution. The focus is on the BB84 and the
6-state protocol making use of only one-way communication during the error
correction and privacy amplification steps. It is shown that by adding
additional errors to the preliminary key (a process called noisy preprocessing)
followed by the use of a structured block code, higher secure key rates may be
obtained. For the BB84 protocol it is shown that iterating the combined
preprocessing leads to an even higher gain.Comment: PhD thesis, 223 pages, TU Darmstadt;
http://tuprints.ulb.tu-darmstadt.de/1389
Some perspectives on the design and discovery of new multi-component reactions
This thesis is divided into three parts. Part one presents an overview of multi-component reactions, contrasting isocyanide based and non-isocyanide based multi-component reactions, and gives examples of the most important examples of these types of reactions. In addition, a brief discussion of 1,3-dipolar cycloadditions is given to serve as a framework for the discussion in part two of the results obtained. Part two is divided into three sections and discusses two conceptually different approaches to the development of new multi-component reactions. The first discusses the use of combinatorial methods for the generation and screening of reaction libraries and the limitations encountered in this approach. The second section deals with the use of isocyanides in a 1,4-cycloaddition followed by a 1,3-dipolar cycloaddition affording isoxazolines. A series of isocyanides were successfully employed both in an intra- and intermolecular fashion. Furthermore, the results gained from attempts using electron rich dipolarophiles as trapping agents in the latter 1,3-dipolar cycloaddition, suggest an alternative mechanism proceeding g through an intermediate nitronate, rather than the nitrile oxide as previously assumed. The initial low yields were improved upon by the use of lithium perchlorate as a promoter of the cycloaddition reaction. The third section details the attempts made at utilising silylated nucleophiles to generate silyinitronates from nitroalkenes and their subsequent use in inter- and intramolecular 1,3-dipolar cycloadditions. Part three describes the experimental procedures employed and results obtained
Improved one-way rates for BB84 and 6-state protocols
We study the advantages to be gained in quantum key distribution (QKD)
protocols by combining the techniques of local randomization, or noisy
preprocessing, and structured (nonrandom) block codes. Extending the results of
[Smith, Renes, and Smolin, quant-ph/0607018] pertaining to BB84, we improve the
best-known lower bound on the error rate for the 6-state protocol from 14.11%
for local randomization alone to at least 14.59%. Additionally, we also study
the effects of iterating the combined preprocessing scheme and find further
improvements to the BB84 protocol already at small block lengths.Comment: 17 pages, to appear in Quantum Information & Computation. Replaced by
accepted versio
Modelling and Implementing a Knowledge Base for Checking Medical Invoices with DLV
Checking medical invoices, done by every health insurance company,
is a labor-intensive task. Both speed and quality of executing
this task may be increased by the knowledge-based
decision support system ACMI which we present
in this paper.
As the relevant regulations also contain various default rules,
ACMI`s knowledge core is modelled
using the answer set programming paradigm. It turned out
that all relevant rules could be expressed directly in this framework,
providing for a declarative and easily extendable and
modifiable knowledge base.
ACMI is implemented using the DLV system
Chironomid-inferred summer temperature development during the late Rissian glacial, Eemian interglacial and earliest WĂĽrmian glacial at FĂĽramoos, southern Germany
Eemian pollen records from central Europe describe a transition from thermophilous tree taxa in the early Eemian to boreal tree taxa in the late Eemian with forest opening in the subsequent stadial. Available summer-temperature reconstructions for the mid- to late Eemian transition show decreasing values during that time. We present a new chironomid record from southern Germany that covers the mid-Eemian to the end of the first Würmian stadial ( c . 125-105 ka) and also parts of the late Rissian glaciation and early Brörup interstadial of the early Würmian glaciation. Based on this record we describe lake development in the former Füramoos palaeolake and quantitatively reconstruct July air temperature during the examined interval. Late Rissian sediments are dominated by two chironomid taxa, Sergentia coracina -type and Micropsectra radialis -type, indicating very cold conditions. Following an uncertain interval, probably including a hiatus at the late Rissian/Eemian transition, mid-Eemian sediments contain Tanytarsus glabrescens -type and Tanytarsus mendax -type suggesting relatively high July air temperatures. During the late Eemian, typically thermophilic taxa such as Tanytarsus glabrescens -type disappear, suggesting decreasing temperatures. Stadial A is associated with increases in Microtendipes pedellus -type suggesting more oligotrophic conditions. Early Brörup sediments contain Tanytarsus glabrescens -type, suggesting a slight increase in July air temperature. Reconstructed July air temperatures show temperatures of 7-8 °C during the late Rissian and a decline from ~15.5-12 °C during the mid- to late Eemian associated with decreasing Northern Hemisphere July insolation. July air temperature values vary between 12 and 14 °C in the late Eemian, while reconstructed temperatures remain within 12-13.5 °C during Stadial A. Our new chironomid-based temperature reconstruction provides valuable corroboration and new quantification of temperature development from the mid-Eemian to the early Brörup interstadial as well as for sections of the late Rissian from the alpine foreland of southern Germany
Physiological function and catalytic versatility of bacterial multihaem cytochromescinvolved in nitrogen and sulfur cycling
Bacterial MCCs (multihaem cytochromes c) represent widespread respiratory electron-transfer proteins. In addition, some of them convert substrates such as nitrite, hydroxylamine, nitric oxide, hydrazine, sulfite, thiosulfate or hydrogen peroxide. In many cases, only a single function is assigned to a specific MCC in database entries despite the fact that an MCC may accept various substrates, thus making it a multifunctional catalyst that can play diverse physiological roles in bacterial respiration, detoxification and stress defence mechanisms. The present article briefly reviews the structure, function and biogenesis of selected MCCs that catalyse key reactions in the biogeochemical nitrogen and sulfur cycles
Origins of Relative Age Effects in Youth Football - A Nationwide Analysis
Introduction: Relative age effects (RAEs) refer to the overrepresentation of players born earlier in the selection year compared to late-born players within the same age category. To date, the origins and mechanisms of RAEs are still unclear. To evaluate the development of RAEs in terms of age group and selection level, we analyzed data of all registered child and adolescent football players in Switzerland.
Methods: Age category, selection level, and birthdate from all licensed 101,991 Swiss child and youth football players assigned to a specific team [9,149 girls (9.0%) and 92,842 boys (91.0%); age range: 4.6–19.6 years] were analyzed. Additionally, out of 1,128 clubs, 54 clubs provided their documented waiting lists (1,224 players). Birthdate distributions were split by age category, sex, and birth quarter (Q1 = January to March, Q4 = October to December). RAEs were calculated using odds ratios (Q1 vs. Q4) with 95% confidence intervals (95% CI).
Results: We found small RAEs among U8 players (OR 1.44 [95% CI 1.31, 1.59]) and U10 (OR 1.24 [95% CI 1.16, 1.32]). The RAE was negligible in all other age categories, independent of gender. In children's football, 5,584 (71.3%) teams performed selections. In teams without selection, there were no obvious RAEs. However, teams with selections for the same age category showed small RAEs with an overrepresentation of Q1 athletes in the first team (OR = 1.29 [95% CI 1.24, 1.35]) and inverse RAEs with an underrepresentation of Q1 athletes in the last team (OR = 0.85 [95% CI 0.82, 0.89]). Only small RAEs were observed on the waiting lists for the U8 (OR = 1.48 [1.13, 1.95]).
Discussion and Conclusion: RAEs have a small, but consistent effect on participation in Swiss children's football at the grassroots level. Contrary to expectations, no inverse RAEs were found on the waiting lists. Nonetheless, first time coach selections seem to be the origin of RAEs. To protect young athletes from discrimination, RAE biases should be analyzed and eliminated at all stages of sport participation, selection, and dropout situations. Modifications to the organizational structure of sport and athlete development systems are recommended to prevent RAE-related discrimination in youth sports
Design, synthesis, and biological evaluation of an allosteric inhibitor of HSET that targets cancer cells with supernumerary centrosomes
Centrosomes associate with spindle poles; thus, the presence of two centrosomes promotes bipolar spindle assembly in normal cells. Cancer cells often contain supernumerary centrosomes, and to avoid multipolar mitosis and cell death, these are clustered into two poles by the microtubule motor protein HSET. We report the discovery of an allosteric inhibitor of HSET, CW069, which we designed using a methodology on an interface of chemistry and biology. Using this approach, we explored millions of compounds in silico and utilized convergent syntheses. Only compound CW069 showed marked activity against HSET in vitro. The inhibitor induced multipolar mitoses only in cells containing supernumerary centrosomes. CW069 therefore constitutes a valuable tool for probing HSET function and, by reducing the growth of cells containing supernumerary centrosomes, paves the way for new cancer therapeutics
Expression of a novel versican variant in dorsal root ganglia from spared nerve injury rats
The size and modular structure of versican and its gene suggest the existence of multiple splice variants. We have identified, cloned, and sequenced a previously unknown exon located within the noncoding gene sequence downstream of exon 8. This exon, which we have named exon 8β, specifies two stop-codons. mRNAs of the versican gene with exon 8β are predicted to be constitutively degraded by nonsense-mediated RNA decay. Here, we tested the hypothesis that these transcripts become expressed in a model of neuropathic pain
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