A benchmark for Monte Carlo simulations in gamma-ray spectrometry Part II: True coincidence summing correction factors.

The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage.

High-energy quasi-monoenergetic neutron fields: existing facilities and future needs.

The argument that well-characterised quasi-monoenergetic neutron (QMN) sources reaching into the energy domain >20 MeV are needed is presented. A brief overview of the existing facilities is given, and a list of key factors that an ideal QMN source for dosimetry and spectrometry should offer is presented. The authors conclude that all of the six QMN facilities currently in existence worldwide operate in sub-optimal conditions for dosimetry. The only currently available QMN facility in Europe capable of operating at energies >40 MeV, TSL in Uppsala, Sweden, is threatened with shutdown in the immediate future. One facility, NFS at GANIL, France, is currently under construction. NFS could deliver QMN beams up to about 30 MeV. It is, however, so far not clear if and when NFS will be able to offer QMN beams or operate with only so-called white neutron beams. It is likely that by 2016, QMN beams with energies >40 MeV will be available only in South Africa and Japan, with none in Europe.

A comparison of the response of PADC neutron dosemeters in high-energy neutron fields.

Within the framework of the EURADOS Working Group 11, a comparison of passive neutron dosemeters in high-energy neutron fields was organised in 2011. The aim of the exercise was to evaluate the response of poly-allyl-glycol-carbonate neutron dosemeters from various European dosimetry laboratories to high-energy neutron fields. Irradiations were performed at the iThemba LABS facility in South Africa with neutrons having energies up to 66 and 100 MeV.

Automation in surgery: a systematic approach.

This chapter proposes a classification of surgical assistance systems with respect to their type and level of automation. This classification is based on previous work in the field of human factors and takes two aspects into consideration, the type of information-processing function of the surgeon that is supported by the system, as well as the type of function allocation between surgeon and systems. With respect to the former, three basic functions are distinguished, referred to as information acquisition and analysis, decision making and planning, and execution of surgical action. With respect to the type of function allocation, the status of being either "passive" or "active" comes into consideration for both objects of reference (i.e. the surgeon and the machine), depending on whether a given function is mainly performed by the surgeon, by the system, or collaboratively by both. Hence, a classification results for intraoperative assistance systems in six categories, each of these representing a different degree of automation. The classification scheme is explained and illustrated on the basis of examples of surgical assistance systems from various fields.

Investigation of the neutron contribution in the 6 MeV to 7 MeV high energy photon reference field.

In order to provide reference fields for the ionising radiation, PTB operates the ion accelerator facility. Referring to high energy photons, reference fields according to International Organization for Standardization 4037 series are produced. The neutron component of the 6-7 MeV photon field (R-F), which is produced by bombarding a CaF(2) target with protons with an energy of E(p) = 2.7 MeV, is investigated in detail for the first time. Two discriminative methods are used to determine the yield for neutrons produced in the CaF(2) target.

[Comparison of two navigation systems for CT-guided interventions under special consideration of the ergonomic properties of the used systems]. / Vergleich zweier Navigationshilfen für CT-gesteuerte Interventionen unter besonderer Berücksichtigung der Nutzungseigenschaften der verwendeten Systeme.

PURPOSE: Investigation of the influence of CT-based navigation systems on the success of an intervention, assessment of the advantages and disadvantages of the utilized systems, and evaluation of the ergonomic system properties. MATERIALS AND METHOD: A simple guiding system PatPos Invent and the computer-based navigation system PinPoint were employed on two CT systems. In order to investigate the influence of the navigation aids on the success of the interventions, 96 prospective, randomized, and standardized punctures were performed on a specifically developed, rigid phantom. 16 examiners punctured 6 targets with 3 degrees of difficulty with the navigation aids. RESULTS: Irrespective of the experience of the examiner, both navigation systems guided the target with an equal degree of certainty. PinPoint significantly reduced the length of the examination time (12 - 25 min) as compared to PatPos Invent (20 - 40 min). The expectation conformity and comprehensibility of PatPos Invent were assessed significantly more positively than PinPoint with regard to the general handling of the system. In contrast, the assessment of the usability during preoperative setup favored PinPoint. The type of navigation system has no influence on the precision of the implementation of a puncture procedure. CONCLUSION: In the overall assessment of the handling of the systems, PatPos Invent was determined to be easier to comprehend and to provide greater conformity with expectations. With regard to the self-descriptive capacity and usability, PinPoint was assessed more positively. Both systems enable safe puncturing at all degrees of difficulty. The weak point of both systems is the failure to take patient movement into account.

Characterisation of three high-energy photon and fast neutron reference radiation fields.

Three reference radiation fields for the purpose of radiation protection were characterised: (1) radiation field R-F, consisting of photons in the energy range of about 6 and 7 MeV and a small neutron contamination; (2) radiation field R-C, consisting of photons with energies of about 4.4 MeV and neutrons with energies up to 2.65 MeV; (3) radiation field R-CF, consisting of photons in the energy range of about 1 and 7 MeV and neutrons with energies about 1.5 MeV. The radiation fields R-F and R-C have previously been defined in the ISO standard 4037. Their neutron components, however, have never been described accurately in the past. The new radiation field R-CF is proposed for the first time. This radiation field can, e.g., be used to calibrate tissue-equivalent proportional counters instruments for measurements at flight altitudes.

The neutron component of two high-energy photon reference fields.

The 4.4 MeV photon reference field described in ISO 4037 is produced by the (12)C(p,p')(12)C (E(x) = 4.4389 MeV) reaction using a thick elemental carbon target and a proton beam with an energy of 5.7 MeV. The relative abundance of the isotope (13)C in elemental carbon is 1.10%. Therefore, the 4.4 MeV photon field is contaminated by neutrons produced by the (13)C(p,n) (13)N reaction (Q = -3.003 MeV). The ambient dose equivalent H*(10) produced by these neutrons is of the same order of magnitude as the ambient dose equivalent produced by the 4.4 MeV photons. For the calibration of dosemeters, especially those also sensitive to neutrons, the spectral fluence distribution of these neutrons has to be known in detail. On the other hand, a mixed photon/neutron field is very useful for the calibration of tissue-equivalent proportional counters (TEPC), if this field combines a high-linear energy transfer (LET) component produced by low-energy neutrons and a low-LET component resulting from photons with about the same ambient dose equivalent and energies up to 7 MeV. Such a mixed field was produced at the PTB accelerator facility using a thin CaF(2) + (nat)C target and a 5.7 MeV proton beam.

Selective tuning of cortical sound-feature processing by language experience.

In 'quantity-languages', such as Japanese or Finnish, sound duration is linguistically relevant. We showed that quantity-language speakers were superior to speakers of a non-quantity language in discriminating the duration of even non-speech sounds. In contrast, there was no group difference in the discrimination of sound frequency. This result, obtained both by behavioural and neural indices at attentive and automatic levels of processing, indicates precise feature-specific tuning of the auditory-cortex functions by the mother tongue.

[Clinical efficiency and the influence of human factors on ear, nose, and throat navigation systems]. / Ist der Vorteil eines Navigationssystems in der HNO-Chirurgie messbar? Ein Konzept zur Evaluation ergonomischer und chirurgischer Erfolgsparameter.

BACKGROUND: The aim of this study was to evaluate the Navibase navigation system for ear, nose, and throat (ENT) surgery. A new methodology for evaluating surgical and human factors is developed. PATIENTS AND METHODS: The evaluation is based on 102 ENT surgical applications, including 89 cases of functional endoscopic sinus surgery (FESS). The evaluation of surgical and human factors was performed by seven ENT surgeons. To evaluate surgical performance, level of quality (LOQ) in the 89 cases of FESS was determined, comparing the surgeon's own impressions with those of the navigation system on a scale from 0 to 100 and further comparing them with clinical results. Intraoperative changes in surgical strategy were documented. The human factors of total confidence (trust), situation awareness, skill set requirement and workload shift were recorded as level of reliance (LOR). RESULTS: The maximum deviation amounted to 1.93 mm. Averaging the quality of information resulted in an LOQ of 63.59. Every second application of the navigation system (47.9%) led to a change in surgical strategy. Total confidence showed a positive evaluation of 3.35 points in LOR. CONCLUSION: Application-relevant information relevant to the application beyond only technical details permits comparison with other assisting systems.

Comparative mapping of CDY and DAZ in higher primates.

The human male specific expressed gene families CDY and DAZ are known to be repetitively clustered in the Y-specific region of the human Y chromosome. Comparative FISH-mapping of DNA clones specific for CDY and DAZ resulted in a Y-specific but diverse signal pattern within the non-recombining region of the Y-chromosomes of human and great apes. It can be concluded that the non-recombining part of the Y-chromosomes including CDY and DAZ, was exposed to species-specific amplifications, diversifications and rearrangements. Evolutionary fast fixation of any of these variations was possible as long as they did not interfere with male fertility.

Loss of the Y chromosomal PAR2-region in four familial cases of satellited Y chromosomes (Yqs).

Applying fluorescence in-situ hybridization (FISH) of various Y chromosomal DNA probes to four familial cases of human Yqs, it was possible to demonstrate that the formation of Yqs must have arisen from a reciprocal translocation involving the short arm of an acrocentric autosome and the heterochromatin of the long arm of the Y chromosome (Yqh). Breakpoints map within Yqh and the proximal short arm of an acrocentric autosome resulting in the gain of a nucleolus organizer region (NOR) including the telomere repeat (TTAGGG)n combined with the loss of the pseudoautosomal region 2 (PAR2) at the long arm of the recipient Y chromosome. In no case could the reciprocal product of an acrocentric autosome with loss of the NOR and gain of PAR2 be detected. Using the 15p-specific classical satellite-III probe D15Z1 in two of the four Yqs probands presented here, it could be shown that the satellited material originated from the short arm of chromosome 15. In contrast to the loss of PAR2 in Yqs chromosomes, another Y chromosomal variant (Yqh-) showing deletion of long-arm heterochromatin in Yq12 has retained PAR2 referring to an interstitial deletion of Yq heterochromatin in such deleted Y chromosomes.

Measurement of radon and radon progenies at the German radon reference chamber.

The activity concentration of radon in the environment can vary over five orders of magnitude. Radon and its progenies thus concern all people involved in radiation protection as well as in low-level experiments. In the German radon reference chamber at the PTB, radon and its progenies are measured with different systems for alpha- and gamma-spectrometry with the full set of environmental parameters, e.g. temperature, humidity and aerosol concentration being controlled. Control of air pressure is also possible by use of an extention chamber. The sampling and measuring technique for radon and its short-lived progenies at the German radon reference chamber are the basis for fundamental studies with regard to the understanding of the equilibrium factor and the unattached fraction of progenies. The facility also serves for the calibration of radon progeny detectors.

An SRY-negative 47,XXY mother and daughter.

Females with XY gonadal dysgenesis are sterile, due to degeneration of the initially present ovaries into nonfunctional streak gonads. Some of these sex-reversal cases can be attributed to mutation or deletion of the SRY gene. We now describe an SRY-deleted 47,XXY female who has one son and two daughters, and one of her daughters has the same 47,XXY karyotype. PCR and FISH analysis revealed that the mother carries a structurally altered Y chromosome that most likely resulted from an aberrant X-Y interchange between the closely related genomic regions surrounding the gene pair PRKX and PRKY on Xp22.3 and Yp11.2, respectively. As a consequence, Yp material, including SRY, has been replaced by terminal Xp sequences up to the PRKX gene. The fertility of the XXY mother can be attributed to the presence of the additional X chromosome that is missing in XY gonadal dysgenesis females. To our knowledge, this is the first human XXY female described who is fertile.

Familial mosaicism of del(Y) and inv del(Y).

Molecular cytogenetic investigation of a male proband showing oligozoospermia (OAT I-II degrees ) has led to the detection of a Y-chromosome mosaicism. This mosaicism consists of a deleted Y chromosome with deletion of most of the long-arm heterochromatin, including the PAR2, del(Y), and a Y chromosome, which, in addition to that deletion, shows a paracentric long-arm inversion, inv del(Y), with breakpoints in the DAZ gene cluster in deletion interval 6 and within the remainder of the long-arm heterochromatin of the Y. The Y mosaicism is not confined to the sterile proband but is also detected in both his father and his fertile brother. Interestingly, the percentage of inv del(Y) is highest (80%) in the proband showing oligozoospermia.

Actin-based motility of vaccinia virus mimics receptor tyrosine kinase signalling.

Studies of the actin-based motility of the intracellular pathogens Listeria monocytogenes and Shigella flexneri have provided important insight into the events occurring at the leading edges of motile cells. Like the bacteria Listeria and Shigella, vaccinia virus, a relative of the causative agent of smallpox, uses actin-based motility to spread between cells. In contrast to Listeria or Shigella, the actin-based motility of vaccinia is dependent on an unknown phosphotyrosine protein, but the underlying mechanism remains obscure. Here we show that phosphorylation of tyrosine 112 in the viral protein A36R by Src-family kinases is essential for the actin-based motility of vaccinia. Tyrosine phosphorylation of A36R results in a direct interaction with the adaptor protein Nck and the recruitment of the Ena/VASP family member N-WASP to the site of actin assembly. We also show that Nck and N-WASP are essential for the actin-based motility of vaccinia virus. We suggest that vaccinia virus spreads by mimicking the signalling pathways that are normally involved in actin polymerization at the plasma membrane.

Interactions between vaccinia virus IEV membrane proteins and their roles in IEV assembly and actin tail formation.

The intracellular enveloped form of vaccinia virus (IEV) induces the formation of actin tails that are strikingly similar to those seen in Listeria and Shigella infections. In contrast to the case for Listeria and Shigella, the vaccinia virus protein(s) responsible for directly initiating actin tail formation remains obscure. However, previous studies with recombinant vaccinia virus strains have suggested that the IEV-specific proteins A33R, A34R, A36R, B5R, and F13L play an undefined role in actin tail formation. In this study we have sought to understand how these proteins, all of which are predicted to have small cytoplasmic domains, are involved in IEV assembly and actin tail formation. Our data reveal that while deletion of A34R, B5R, or F13L resulted in a severe reduction in IEV particle assembly, IEVs formed by the DeltaB5R and DeltaF13L deletion strains, but not DeltaA34R, were still able to induce actin tails. The DeltaA36R deletion strain produced normal amounts of IEV particles, although these were unable to induce actin tails. Using several different approaches, we demonstrated that A36R is a type Ib membrane protein with a large, 195-amino-acid cytoplasmic domain exposed on the surface of IEV particles. Finally, coimmunoprecipitation experiments demonstrated that A36R interacts with A33R and A34R but not with B5R and that B5R forms a complex with A34R but not with A33R or A36R. Using extracts from DeltaA34R- and DeltaA36R-infected cells, we found that the interaction of A36R with A33R and that of A34R with B5R are independent of A34R and A36R, respectively. We conclude from our observations that multiple interactions between IEV membrane proteins exist which have important implications for IEV assembly and actin tail formation. Furthermore, these data suggest that while A34R is involved in IEV assembly and organization, A36R is critical for actin tail formation.

Tyrosine phosphorylation is required for actin-based motility of vaccinia but not Listeria or Shigella.

Studies of the actin-based motility of pathogens have provided important insights into the events occurring at the leading edge of motile cells [1] [2] [3]. To date, several actin-cytoskeleton-associated proteins have been implicated in the motility of Listeria or Shigella: vasodilator-stimulated phosphoprotein (VASP), vinculin and the actin-related protein complex of Arp2 and Arp3 [4] [5] [6] [7]. To further investigate the underlying mechanism of actin-tail assembly, we examined the localization of components of the actin cytoskeleton including Arp3, VASP, vinculin and zyxin during vaccinia, Listeria and Shigella infections. The most striking difference between the systems was that a phosphotyrosine signal was observed only at the site of vaccinia actin-tail assembly. Micro-injection experiments demonstrated that a phosphotyrosine protein plays an important role in vaccinia actin-tail formation. In addition, we observed a phosphotyrosine signal on clathrin-coated vesicles that have associated actin-tail-like structures and on endogenous vesicles in Xenopus egg extracts which are able to nucleate actin tails [8] [9]. Our observations indicate that a host phosphotyrosine protein is required for the nucleation of actin filaments by vaccinia and suggest that this phosphoprotein might be associated with cellular membranes that can nucleate actin.

Recycling of golgi-resident glycosyltransferases through the ER reveals a novel pathway and provides an explanation for nocodazole-induced Golgi scattering.

During microtubule depolymerization, the central, juxtanuclear Golgi apparatus scatters to multiple peripheral sites. We have tested here whether such scattering is due to a fragmentation process and subsequent outward tracking of Golgi units or if peripheral Golgi elements reform through a novel recycling pathway. To mark the Golgi in HeLa cells, we stably expressed the Golgi stack enzyme N-acetylgalactosaminyltransferase-2 (GalNAc-T2) fused to the green fluorescent protein (GFP) or to an 11-amino acid epitope, VSV-G (VSV), and the trans/TGN enzyme beta1,4-galactosyltransferase (GalT) fused to GFP. After nocodazole addition, time-lapse microscopy of GalNAc-T2-GFP and GalT-GFP revealed that scattered Golgi elements appeared abruptly and that no Golgi fragments tracked outward from the compact, juxtanuclear Golgi complex. Once formed, the scattered structures were relatively stable in fluorescence intensity for tens of minutes. During the entire process of dispersal, immunogold labeling for GalNAc-T2-VSV and GalT showed that these were continuously concentrated over stacked Golgi cisternae and tubulovesicular Golgi structures similar to untreated cells, suggesting that polarized Golgi stacks reform rapidly at scattered sites. In fluorescence recovery after photobleaching over a narrow (FRAP) or wide area (FRAP-W) experiments, peripheral Golgi stacks continuously exchanged resident proteins with each other through what appeared to be an ER intermediate. That Golgi enzymes cycle through the ER was confirmed by microinjecting the dominant-negative mutant of Sar1 (Sar1pdn) blocking ER export. Sar1pdn was either microinjected into untreated or nocodazole-treated cells in the presence of protein synthesis inhibitors. In both cases, this caused a gradual accumulation of GalNAc-T2-VSV in the ER. Few to no peripheral Golgi elements were seen in the nocodazole-treated cells microinjected with Sar1pdn. In conclusion, we have shown that Golgi-resident glycosylation enzymes recycle through the ER and that this novel pathway is the likely explanation for the nocodazole-induced Golgi scattering observed in interphase cells.

The NMDA receptor subunit NR2B of neonatal rat brain: complex formation and enrichment in axonal growth cones.

The N-methyl-D-aspartate (NMDA) subtype of ionotropic glutamate receptors comprises a family of highly homologous subunits which assemble into oligomeric protein complexes. Alterations in subunit composition are developmentally regulated, leading to functionally distinct receptor populations. Here, the contribution of the subunit NR2B to NMDA receptor complex formation was analysed in neonatal rat brain, employing polyclonal antibodies raised against NR2B-specific synthetic peptides. By hydrodynamic size fractionation of the solubilized receptor protein and chemical cross-linking, NR2B antigen was found to be associated with several protein species of up to 690 kDa molecular weight. These observations show NR2B to be part of a multimeric receptor complex. Fractionation of cortex homogenates from E18 rat embryos on sucrose density gradients revealed NR2B polypeptide to be highly enriched in axonal growth cones. A similar distribution was found by fluorescence microscopy of immature hippocampal neurons, showing a preferential accumulation of NR2B antigen in axonal growth cones and varicosities. In mature cells, NR2B antigen displayed a punctated distribution pattern with redistribution to somato-dendritic spheres. The association of NR2B with axonal growth cones and processes of immature neurons suggests a role of NMDA receptors in the regulation of neurite outgrowth and migration.