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Sheaths ahead of interplanetary coronal mass ejections (ICMEs) are turbulent heliospheric structures. Knowledge of their structure and fluctuations is important for understanding their geoeffectiveness, their role in accelerating particles, and the interaction of ICMEs with the solar wind. We studied observations from the Parker Solar Probe of a sheath observed at 0.5 au in March 2019, ahead of a slow streamer blowout CME. To examine the MHD-scale turbulent properties, we calculated fluctuation amplitudes, magnetic compressibility, partial variance of increments (PVI), cross helicity ($\sigma_c$), residual energy ($\sigma_r$), and the Jensen-Shannon permutation entropy and complexity. The sheath consisted of slow and fast flows separated by a 15-min change in magnetic sector that coincided with current sheet crossings and a velocity shear zone. Fluctuation amplitudes and PVI were greater through the sheath than upstream. Fluctuations had mostly negative $\sigma_r$ and positive $\sigma_c$ in the sheath, the latter indicating an anti-sunward sense of propagation. The velocity shear region marked an increase in temperature and specific entropy, and the faster flow behind had local patches of positive $\sigma_r$ as well as higher fluctuation amplitudes and PVI. Fluctuations in the preceding wind and sheath were stochastic, with the sheath fluctuations showing lower entropy and higher complexity than upstream. The two-part sheath structure likely resulted from a warp in the heliospheric current sheet (HCS) being swept up and compressed. The ejecta accelerated and heated the wind at the sheath rear, which then interacted with the slower wind ahead of the HCS warp. This caused differences in fluctuation properties across the sheath. Sheaths of slow ICMEs can thus have complex structure where fluctuation properties are not just downstream shock properties, but are generated within the sheath., Comment: 11 pages, 10 figures, accepted for publication in Astronomy & Astrophysics

Magnetic clouds are large-scale transient structures in the solar wind with low plasma $\beta$, low-amplitude magnetic field fluctuations, and twisted field lines with both ends often connected to the Sun. Their inertial-range turbulent properties have not been examined in detail. In this Letter, we analyze the normalized cross helicity, $\sigma_c$, and residual energy, $\sigma_r$, of plasma fluctuations in the November 2018 magnetic cloud observed at 0.25 au by the Parker Solar Probe. A low value of $|\sigma_c|$ was present in the cloud core, indicating that wave power parallel and anti-parallel to the mean field was approximately balanced, while the cloud's outer layers displayed larger amplitude Alfv\'enic fluctuations with high $|\sigma_c|$ values and $\sigma_r\sim0$. These properties are discussed in terms of the cloud's solar connectivity and local interaction with the solar wind. We suggest that low $|\sigma_c|$ is likely a common feature of magnetic clouds given their typically closed field structure. Anti-sunward fluctuations propagating immediately upstream of the cloud had strongly negative $\sigma_r$ values., Comment: 9 pages, 4 figures; accepted for publication in the Astrophysical Journal Letters 2020 August 17

International audience; We present a statistical study of interplanetary conditions and geospace response to 89 coronal mass ejection‐driven sheaths observed during Solar Cycles 23 and 24. We investigate in particular the dependencies on the driver properties and variations across the sheath. We find that the ejecta speed principally controls the sheath geoeffectiveness and shows the highest correlations with sheath parameters, in particular in the region closest to the shock. Sheaths of fast ejecta have on average high solar wind speeds, magnetic (B) field magnitudes, and fluctuations, and they generate efficiently strong out‐of‐ecliptic fields. Slow‐ejecta sheaths are considerably slower and have weaker fields and field fluctuations, and therefore they cause primarily moderate geospace activity. Sheaths of weak and strong B field ejecta have distinct properties, but differences in their geoeffectiveness are less drastic. Sheaths of fast and strong ejecta push the subsolar magnetopause significantly earthward, often even beyond geostationary orbit. Slow‐ejecta sheaths also compress the magnetopause significantly due to their large densities that are likely a result of their relatively long propagation times and source near the streamer belt. We find the regions near the shock and ejecta leading edge to be the most geoeffective parts of the sheath. These regions are also associated with the largest B field magnitudes, out‐of‐ecliptic fields, and field fluctuations as well as largest speeds and densities. The variations, however, depend on driver properties. Forecasting sheath properties is challenging due to their variable nature, but the dependence on ejecta properties determined in this work could help to estimate sheath geoeffectiveness through remote‐sensing coronal mass ejection observations.

Background/objectives: Previous studies have shown that the temperament traits are related to risk factors for chronic diseases, which could be partly explained by lifestyle habits. However, little is known whether temperament traits associate with diet. The aim of this study was to examine the cross-sectional associations between temperament traits and the whole diet. Subjects/methods: We studied 1668 men and women, aged 56−70, from the Helsinki Birth Cohort Study. Temperament was measured using the Tridimensional Personality Questionnaire. Information on diet was collected by a validated 128-item food frequency questionnaire. The associations of temperament traits; novelty seeking (NS), harm avoidance (HA), reward dependence (RD), and persistence (P), with diet were tested by linear regression analysis. Results: After adjustment for potential confounders, greater HA was related to poorer diet quality, including lower consumption of vegetables, fruits, fish and several vitamins. RD was associated with healthier diet quality, including higher consumption of vegetables and intake of vitamin E and lower intake of alcohol. NS was significantly related to higher intake of fish, fat and alcohol and lower consumption of cereals, milk products and carbohydrates. No significant associations between P and intake of foods and nutrients were observed. Conclusions: Our results suggest that there is an association between temperament traits and diet. Especially greater HA seems to associate with poorer diet quality and greater RD with healthier diet quality.

Background: previous studies have shown that maternal grand multiparity may predict an increased risk of mental disorders in young adult offspring, but whether such effects persist throughout adulthood remains unknown. The current study examined if maternal grand multiparity predicts the risks of severe mental disorders, suicides, suicide attempts and dementias throughout adult life.Methods: our study sample comprised 13243 Helsinki Birth Cohort Study 1934–1944 participants (6905 men and 6338 women). According to hospital birth records, 341 offspring were born to grand multiparous mothers. From Finnish national hospital discharge and causes of death registers, we identified 1682 participants diagnosed with mental disorders during 1969–2010.Results: maternal grand multiparity predicted significantly increased risks of mood disorders (Hazard Ratio = 1.64, p = 0.03), non-psychotic mood disorders (Hazard Ratio = 2.02, p = 0.002), and suicide attempts (Hazard Ratio = 3.94, p = 0.01) in adult offspring. Furthermore, women born to grand multiparous mothers had significantly increased risks of any severe mental disorder (Hazard Ratio = 1.79, p = 0.01), non-psychotic substance use disorders (Hazard Ratio = 2.77, p = 0.02) schizophrenia, schizotypal and delusional disorders (Hazard Ratio = 2.40, p = 0.02), mood disorders (Hazard Ratio = 2.40, p = 0.002), non-psychotic mood disorders (Hazard Ratio = 2.91, pConclusions: women born to grand multiparous mothers are at an increased risk of severe mental disorders and suicide attempts across adulthood. Our findings may inform the development of preventive interventions for mental disorders

The chemisorption of tellurium on atomically clean Cu(111) surface has been studied under ultra-high vacuum conditions. At room temperature, the initial stage of growth was an ordered 23×23R30° phase (0.08 ML). An ordered 3×3R30° phase is formed at 0.33 ML coverage of Te. The adsorption sites of the Te atoms on the Cu(111) surface at 0.08 ML and 0.33 ML coverages are explored by quantitative low energy electron diffraction (LEED) and density functional theory (DFT). Our results indicate that substitutional surface alloy formation starts at very low coverages.

Replication errors (RER) are frequently seen in both sporadic and hereditary forms of colorectal cancer. In hereditary nonpolyposis colorectal cancer (HNPCC), RER is associated with defects in DNA mismatch repair genes. Two of these genes, MSH2 and MLH1, account for a major share of this cancer syndrome. In order to assess the role of these genes in sporadic RER+ colorectal carcinoma, we have carried out a mutation analysis of MSH2 and MLH1 by two-dimensional (2-D) DNA electrophoresis, including heteroduplexing and separation in a denaturing gradient. All exons were amplified using multiplex PCR and were separated on the basis of both size and base pair composition under a single set of experimental conditions. Exons showing a spot position different from normal were sequenced. In screening 33 unselected, sporadic RER+ colorectal tumors, a germline mutation accompanied by loss of heterozygosity in tumor tissue was found in two patients. They were among the 4 patients out of the 33 screened that were diagnosed before the age of 50 years. In 8 of the remaining 31 tumors (26%), presence of somatic mutations (9 in total) could be demonstrated. While suggesting involvement of other genes in a substantial part of sporadic RER+ colorectal carcinomas, our results also demonstrate a clear role of MSH2 and MLH1 in these sporadic tumors and show that young sporadic RER+ colorectal carcinoma patients have a high probability of germline mutations. This has important implications for genetic testing and management of young colorectal cancer patients and their families. (C) 1997 Wiley-Liss, Inc.

As smart phones, tablets, and wireless devices in general grow more and more popular, the demand for wireless connectivity keeps rising. At the same time, applications and services require more data to be transmitted for single users, which puts even more stress on service providers to increase capacity. One option is to build new base stations and provide different ways to connect — especially in the areas of dense usage. However, this is expensive and requires end-user devices to be able to use different wireless techniques and to switch between them according to position and data usage. On the other hand, the variance of wireless technologies and specific spectrum allocation has caused another phenomenon: in certain areas, the spectrum allocated to one user group is heavily utilized but the spectrum usage might otherwise be minimal. To answer these rising problems on capacity and spectrum utilization, developing and researching of new solutions is required. A prominent area of research that can make a difference is cognitive technology: it provides ways to use spectrum and existing technology more efficiently than in their current state. Meanwhile it can also optimize the use of radio and operator resources when building new equipment and systems. The goal of this master’s thesis work is to implement an interface between a cognitive trial environment and a separately functioning cognitive radio network. The cognitive trial environment is built around a cognitive engine, which is an entity that manages network resources according to the information it receives from the environment. The outside network consists of cognitive radio devices called Wireless Open-access Research Platforms and a cognitive engine of its own. They are able to provide information and management capabilities that are beneficial for the environment. The interface will be a solution for the environment’s cognitive engine to gain knowledge of the outside network and manage the resources of the cognitive radio devices residing in it. This thesis work will also discuss the meaning and the development of cognitive radio and network techniques. The discussion takes a look at the underlying reasons to develop cognitive solutions and how the cognition could be implemented in the future. Älypuhelinten, tablettien ja muiden langattomien laitteiden suosion kasvaessa myös langattomien yhteyksien kysyntä nousee yhä suuremmaksi. Uudet sovellukset ja palvelut vaativat yhtä suurempien tietomäärien siirtämistä, mikä entisestään vaatii kapasiteetin lisäämistä ja lisää painetta palveluntarjoajien suuntaan. Erityisesti alueilla, joilla käyttöä on paljon, tarvetta voidaan helpottaa rakentamalla uusia tukiasemia ja tarjoamalla muita liitäntätapoja. Tämä on kuitenkin kallista ja vaatii käyttäjien laitteilta kykyä käyttää eri tekniikoita ja kykyä vaihdella niiden välillä sijainnin ja tiedonsiirtomäärien mukaan. Langattomien teknologioiden laaja kirjo ja tarkat spektrimääritykset ovat toisaalta aiheuttaneet toisen ilmiön: joillain alueilla yhdelle taholle määritetty spektri voi olla hyvin raskaalla käytöllä vaikka spektri muuten olisikin lähes tyhjä. Näihin ongelmiin vastaaminen vaatii kehittämistä ja tutkimustyötä uusien ratkaisujen parissa. Kognitiivinen teknologia on yksi tällainen lupaava tutkimusalue, joka saattaa tuoda ratkaisun: sen avulla spektriä ja nykyistä teknologiaa voidaan käyttää entistä tehokkaammin, samalla kun uutta laitteistoa voidaan rakentaa entistä optimoidummin palveluntarjoajien resursseja ajatellen. Tämän diplomityön tavoitteena on luoda käyttöliittymä kognitiivisen testiympäristön ja erillisen kognitiiviradioverkon välille. Kognitiivinen testiympäristö rakentuu verkkoresursseja ympäristöltä saadun tiedon mukaan muokkaavan kognitiivikoneen ympärille. Ulkopuolinen verkko, jolla on oma kognitiivikoneensa, taas koostuu WARP:ksi (Wireless Open-access Research Platform) kutsutuista kognitiiviradioista, jotka kykenevät antamaan tietoa itsestään ja ympäristöstään sekä samalla muuntamaan omia toimintojaan tarpeen ja vaatimusten mukaan. Käyttöliittymä tulee olemaan ratkaisu, jolla kognitiivinen ympäristö saa tietoa ulkoisesta verkota ja jonka avulla se voi vaikuttaa ulkopuolisen verkon kognitiiviradioresursseihin. Tämä diplomityö käsittelee myös kognitiiviradion ja -verkon tarkoitusta, hyötyä ja vaatimuksia. Samalla se tutustuu myös syihin, joiden takia kognitiivisia ratkaisuja tarvitaan ja miten niitä voitaisiin tulevaisuudessa hyödyntää.

The DNA mismatch repair genes MSH2 and MLH1 have been shown to account for a major share of hereditary non-polyposis colorectal cancer (HNPCC). We searched for germline mutations in these genes in 35 HNPCC kindreds fulfilling the Amsterdam diagnostic criteria and in a further 20 kindreds with an average of four affected members per family but not meeting the formal criteria. We first screened for truncations by reverse transcriptase (RT)-PCR. If no mutation was found, we screened genomic DNA by a novel application of two-dimensional (2-D) DNA electrophoresis that allows the simultaneous study of all exons of each gene. All abnormalities were followed up by sequencing. Eight different pathogenic germline mutations were found, two in MSH2 and six in MLH1. We report three major conclusions. First, these mutations together accounted for 86% (30/35) of the kindreds meeting the Amsterdam criteria, but only 30% (6/20) of the remaining kindreds, suggesting differences in etiology. Second, MLH1 was involved in >90% (34/36) of kindreds with a known predisposing mutation, suggesting that mutations in the MLH1 gene are responsible for most HNPCC kindreds in Finland. Third, our results indicate that the successive application of RT-PCR and 2-D DNA electrophoresis is a sensitive and efficient method for mutation screening in typical HNPCC.

A susceptibility to hereditary nonpolyposis colorectal cancer (HNPCC) was recently shown to be due to mutations in the MSH2 gene on chromosome 2p. A second susceptibility locus has been mapped to chromosome 3p in two families. The present report describes the results of a genetic study of Finnish HNPCC kindreds. Of 18 apparently unrelated families living in different parts of the country, 11 could be genealogically traced to a common ancestry dating at least 13 generations back in a small geographic area. Linkage studies were possible in 9 families, revealing conclusive or probable linkage to markers on 3p in 8. Five of these were among those having shared ancestry. The location of the gene was refined by a linkage study comprising 12 marker loci. By analysis of recombinations in such families, the HNPCC locus could be assigned to the 1-centimorgan interval between marker loci D3S1561 and D3S1298. A haplotype encompassing 10 centimorgans around the HNPCC locus was conserved in five of the pedigrees with shared ancestry and present in 2 further families in which linkage analysis was not possible. Our results suggest the presence of a widespread single ancestral founding mutation. Moreover, the map position of the 3p gene for HNPCC susceptibility was greatly refined.

The design of a slot coupled microstrip patch antenna with four parasitic elements for the 77 GHz frequency range is presented. Full wave electromagnetic simulations were used for antenna modeling and optimization. The antenna was fabricated using Ferro A6-M Low Temperature Co-fired Ceramic technology. The "on wafer" measurements showed a central operating frequency of 78 GHz with reflection losses of -19 dB. The frequency bandwidth (defined for reflection losses lower than -10 dB) was from 76.4 GHz to 79.3 GHz. Using electromagnetic simulations based parametric study it is demonstrated that the central frequency shift is mainly due to the fabrication tolerances that affect the active patch dimensions. (11 refs.)

Session Orale : 1B.

International audience

A considerable fraction of families with HNPCC shows no germline mismatch repair (MMR) gene mutations. We previously detected 'hidden' MMR gene defects in 42% of such families, leaving the remaining 58% 'truly' mutation negative. Here, we characterized 50 colorectal carcinomas and five adenomas arising in HNPCC families; 24 truly MMR gene mutation negative and 31 MMR gene mutation positive. Among 31 tumors from MMR gene mutation positive families, 25 (81%) had active Wnt signaling as indicated by aberrant beta-catenin localization with or without CTNNB1 mutations, compared to only 7/18 tumors from MMR gene mutation negative families (39%; P=0.005). CGH studies revealed stable profiles in 9/16 (56%) of MMR gene mutation negative tumors, which was significantly associated with membranous beta-catenin (P=0.005). Tumors with membranous beta-catenin from the MMR gene mutation negative group also showed low frequency of TP53 mutations compared to those with nuclear beta-catenin. Thus, a majority of the MMR gene mutation negative cases exhibited a novel molecular pattern characterized by the paucity of changes in common pathways to colorectal carcinogenesis. This feature distinguishes the MMR gene mutation negative families from both HNPCC families linked to MMR defects and sporadic cases, suggesting the involvement of novel predisposition genes and pathways in such families.

This paper provides the project engineer with guidelines or a checklist on tasks that must be considered, defined and documented before the project can successfully implement a document management system in geographically distributed project environment. Topics ranging from configuration management, approval process, document types, user administration and document naming are covered. The underlying cases of the paper are that of CERN (European Laboratory for Particle Physics) and its latest accelerator project, together with the Nordisk Industrifond -funded Connecting Distributed Competencies (NI#: 98082) project, with a focus on distributed shipbuilding processes. Keywords: distributed project management, product data management, networking, document management, virtual workspaces

I rapporten redovisas och diskuteras resultat från tre separata mätinsatser. Den första gäller upprepade VOC-mätningar vid Åkersjön i Krokoms kommun i samband med 'Skoterns julafton', januari 1996. Syftet var dels att följa upp resultaten från föregående år och dels att testa personburen provtagning för bestämning av VOC-exponering. Den andra är en förundersökning kring VOC-exponering vid spårdragning med skoter. Syftet var att försöka uppskatta vilken effekt ett PFI (peroxid fuel injection) system har för emissionerna av VOC. Den tredje utgörs av mer omfattande mätning kring skillnader i VOC-exponering vid färd med skoter, med och utan PFI-system. Målsättningen var också att klarlägga hur exponeringen påverkas vid färd med flera skotrar i kolonn. Resultaten tyder på att: * emissionen av VOC från skotrar minskas om dessa utrustas med PFI-system * reduceringen av enkla aromater, vid kolonnkörningen, var mellan 7 och 21% · skoterförare, som kör ensamma eller först i en kolonn, exponeras för VOC-halter som är mångfaldigt högre än vad man uppmäter som 'urban bakgrund' i svenska tätorter. * åskådare till skotertävlingar kan exponeras för väsentligt högre halter än en ensam skoterförare, vilket också gäller passagerare på släde efter skotern * vid kolonnkörningen med 10 skotrar exponerades föraren av skoter nr 8 för ca 20 ggr högre halt än föraren av skoter nr 1 I rapporten redovisas och diskuteras resultat från tre separata mätinsatser. Den första gäller upprepade VOC-mätningar vid Åkersjön i Krokoms kommun i samband med 'Skoterns julafton', januari 1996. Syftet var dels att följa upp resultaten från föregående år och dels att testa personburen provtagning för bestämning av VOC-exponering. Den andra är en förundersökning kring VOC-exponering vid spårdragning med skoter. Syftet var att försöka uppskatta vilken effekt ett PFI (peroxid fuel injection) system har för emissionerna av VOC. Den tredje utgörs av mer omfattande mätning kring skillnader i VOC-exponering vid färd med skoter, med och utan PFI-system. Målsättningen var också att klarlägga hur exponeringen påverkas vid färd med flera skotrar i kolonn. Resultaten tyder på att: * emissionen av VOC från skotrar minskas om dessa utrustas med PFI-system * reduceringen av enkla aromater, vid kolonnkörningen, var mellan 7 och 21% · skoterförare, som kör ensamma eller först i en kolonn, exponeras för VOC-halter som är mångfaldigt högre än vad man uppmäter som 'urban bakgrund' i svenska tätorter. * åskådare till skotertävlingar kan exponeras för väsentligt högre halter än en ensam skoterförare, vilket också gäller passagerare på släde efter skotern * vid kolonnkörningen med 10 skotrar exponerades föraren av skoter nr 8 för ca 20 ggr högre halt än föraren av skoter nr 1

Two susceptibility loci for hereditary nonpolyposis colo-rectal cancer (HNPCC) have been identified, and each contains a mismatch repair gene: MSH2 on chromosome 2p and MLH1 on chromosome 3p. We studied the involvement of these loci in 13 large HNPCC kindreds originating from three different continents. Six families showed close linkage to the 2p locus, and a heritable mutation of the MSH2 gene was subsequently found in four. The 2p-linked kindreds included a family characterized by the lack of extracolonic manifestations (Lynch I syndrome), as well as two families with cutaneous manifestations typical of the Muir-Torre syndrome. Four families showed evidence for linkage to the 3p locus, and a heritable mutation of the MLH1 gene was later detected in three. One 3p-linked kindred was of Amerindian origin. Of the remaining three families studied for linkage, one showed lod scores compatible with exclusion of both MSH2 and MLH1, while lod scores obtained in the other two families suggested exclusion of one HNPCC locus (MSH2 or MLH1) but were uninformative for markers flanking the other locus. Our results suggest that mismatch repair genes on 2p and 3p account for a major share of HNPCC in kindreds that can be evaluated by linkage analysis.

Recent reports have suggested that one or more genes may cause replication errors (RER) during colorectal tumorigenesis. Additional alleles are seen in the tumors when analyzing random microsatellite loci. We have studied seven dinucleotide repeat loci, located on seven different chromosomes, by use of polymerase chain reaction amplification and denaturing polyacrylamide gel electrophoresis. We found that 16.5% (40 of 243) colorectal cancers showed RER at one or several loci (RER+). This includes 31% (4 of 13) among cases with a strong positive family history according to previously published criteria and 17% (35 of 207) among cases with no history of familial cancer. Interestingly, no significant association was found between RER+ tumors and a general familial clustering of cancer. Microsatellite instability was significantly associated with DNA diploid status of the tumor (P0.001), with the location of the tumor in the proximal colon (P0.001), and with poorly differentiated tumor phenotype (P0.001). Patients with RER+ ator = 2 loci tumors had an increased survival (P = 0.05). We further analyzed 84 breast cancers and 86 male germ cell cancers using the same seven markers. None of the tumors were RER+, indicating that this phenomenon may be specific to certain types of tumors.

The chemisorption of tellurium on atomically clean Cu(111) surface has been studied under ultra-high vacuum conditions. At room temperature, the initial stage of growth was an ordered 23×23R30° phase (0.08ML). An ordered 3×3R30° phase is formed at 0.33ML coverage of Te. The adsorption sites of the Te atoms on the Cu(111) surface at 0.08ML and 0.33ML coverages are explored by quantitative low energy electron diffraction (LEED) and density functional theory (DFT). Our results indicate that substitutional surface alloy formation starts at very low coverages.

International audience; We report a statistical analysis of magnetic field fluctuations in 79 coronal mass ejection- (CME-) driven sheath regions that were observed in the near-Earth solar wind. Wind high-resolution magnetic field data were used to investigate 2 h regions adjacent to the shock and ejecta leading edge (Near-Shock and Near-LE regions, respectively), and the results were compared with a 2 h region upstream of the shock. The inertial-range spectral indices in the sheaths are found to be mostly steeper than the Kolmogorov −5/3 index and steeper than in the solar wind ahead. We did not find indications of an f − 1 spectrum, implying that magnetic fluctuation properties in CME sheaths differ significantly from planetary magnetosheaths and that CME-driven shocks do not reset the solar wind turbulence, as appears to happen downstream of planetary bow shocks. However, our study suggests that new compressible fluctuations are generated in the sheath for a wide variety of shock/upstream conditions. Fluctuation properties particularly differed between the Near-Shock region and the solar wind ahead. A strong positive correlation in the mean magnetic compressibility was found between the upstream and downstream regions, but the compressibility values in the sheaths were similar to those in the slow solar wind (

The mechanism by which germline mutations of DNA mismatch repair genes cause susceptibility to tumour formation is not yet understood. Studies in vitro indicate that heterozygosity for these mutations, unlike homozygosity, does not affect mismatch repair. Surprisingly, no loss of heterozygosity at the predisposing loci has so far been described in hereditary nonpolyposis colorectal cancers. Here, we show that loss of heterozygosity (LOH) of markers within or adjacent to the MLH1 gene on chromosome 3p occurs nonrandomly in tumours from members of families in which the disease phenotype cosegregates with MLH1. In every informative case, the loss affects the wild type allele. These results suggest that DNA mismatch repair genes resemble tumour suppressor genes in that two hits are required to cause a phenotypic effect.