Search for R-parity violating supersymmetry in two-muon and four-jet topologies

We present results of a search for R-parity-violating decay of the neutralino chi;01, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling lambda(')(2jk) (j=1,2; k=1,2,3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5+/-3.9 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron in pp collisions at sqrt[s]=1.8 TeV, and with an expected background of 0.18+/-0.03+/-0.02 events, we set limits on squark and gluino masses within the framework of the minimal low-energy supergravity-supersymmetry model.

Search for leptoquark pairs decaying into nunu+jets in pp collisions at square root[s] = 1.8 TeV

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.

Direct search for charged higgs bosons in decays of top quarks

We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp collisions at sqrt[s] = 1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M(H+/-),tan(beta)) parameter space where the decay t--> H(+)b has a branching fraction >0.36 and B(H+/--->tau(nu)(tau)) is large.

Ratio of isolated photon cross sections in pp macro collisions at square root of s = 630 and 1800 GeV

The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.

Search for new physics using QUAERO: a general interface to D0 event data

We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.

Validity of birth certificate data for the outcome of the previous pregnancy, Georgia, 1980-1995

The author evaluated the validity of four historically based variables collected on Georgia birth certificates: outcome of preceding pregnancy, history of delivery of a low- (<2,500 g) or high- (>4,000 g) birth-weight infant, and death of the baby resulting from the preceding pregnancy. Data were derived from birth and fetal death certificates that were linked for the first and second deliveries of 231,075 women in Georgia from 1980 through 1995. Deaths that occurred during the infant's first year of life were also linked to the birth certificate. For all but the survival variable, the outcome of the first birth as reported on the certificate for the second birth was compared with the outcome recorded on the certificate for the first birth, which was assumed to be correct. Except for ascertainment of death of the firstborn infant, sensitivities for the history of poor outcomes were low. Furthermore, sensitivities were higher when an extremely adverse outcome occurred in the first pregnancy or an adverse outcome recurred. The only high sensitivity was for past infant death (85.4%). These results suggest caution when using these variables to identify high-risk subsets for further research or control for confounding.

Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family

Phylogenetic relationships within the family Otariidae were investigated using two regions of the mitochondrial genome. A 360-bp region of the cytochrome b gene was employed for the primary phylogenetic analysis, while a 356-bp segment of the control region was used to enhance resolution of the terminal nodes. Traditional classification of the family into the subfamilies Arctocephalinae (fur seals) and Otariinae (sea lions) is not supported, with the fur seal Callorhinus ursinus having a basal relationship relative to the rest of the family. This is consistent with the fossil record which suggests that this genus diverged from the line leading to the remaining fur seals and sea lions about 6 million years ago (mya). There is also little evidence to support or refute the monophyly of sea lions. Four sea lion clades and five fur seal clades were observed, but relationships among these clades are unclear. Similar genetic divergences between the sea lion clades (D(a) = 0.054-0.078), as well as between the major Arctocephalus fur seal clades (D(a) = 0.040-0.069) suggest that these groups underwent periods of rapid radiation at about the time they diverged from each other. Rapid radiations of this type make the resolution of relationships between the resulting species difficult and indicate the requirement for additional molecular data from both nuclear and mitochondrial genes. The phylogenetic relationships within the family and the genetic distances among some taxa highlight inconsistencies in the current taxonomic classification of the family.

Adenocarcinoma arising in a transplanted pancreas

Tumor transmission or de novo tumor development in the transplanted organ is a rare event. Appreciation of the organ-specific risk factors for tumor development and careful inspection of the organ at procurement may reduce but not eliminate this complication. We report the first known combined kidney-pancreas recipient who developed adenocarcinoma in the transplanted pancreas. Molecular typing of the tumor by DNA sequencing supports donor derivation of the tumor. Despite cessation of immunosuppression and reconstitution of the recipient's immune response, the patient died from metastatic pancreatic adenocarcinoma. Comparison is made to the reported outcomes after diagnosis of renal cell carcinoma that appeared early after transplantation

Search for heavy particles decaying into electron-positron pairs in pp collisions

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.

AlphaIIb's cytoplasmic domain is not required for ligand-induced clustering of integrin alphaIIbbeta3

The platelet integrin alphaIIbbeta3 exhibits bidirectional signaling, in that intracellular messengers enable adhesive macromolecules to bind to its ectodomain, while ligation promotes the association of cytoskeletal proteins with its cytoplasmic domains. In order to understand the linkage between these distant regions, we investigated the effects of receptor occupancy on the solution structure of both full-length recombinant alphaIIbbeta3 and alphaIIbDelta991beta3, an integrin truncation mutant which lacks one cytoplasmic domain. Lysates of (35)S-labeled human A549 cells expressing either full-length alphaIIbbeta3 or alphaIIbDelta991beta3 were examined by sucrose density gradient sedimentation followed by immunoprecipitation to determine the distributions of integrin protomers and oligomers. Recombinant alphaIIbbeta3 exhibited a weight-average sedimentation coefficient, S(w)=11.3+/-1.4 S with 73% sedimenting as protomers/dimers (9.1+/-1.0 S) and 27% as oligomers (15.4+/-0.4 S). Truncation mutant alphaIIbDelta991beta3 exhibited a similar pattern with 65% sedimenting as protomers/dimers. Upon ligation with eptifibatide, both full-length alphaIIbbeta3 and alphaIIbDelta991beta3 sedimented mainly at >14 S, indicating 2-3-fold increased oligomerization. Thus we have demonstrated that alphaIIb's cytoplasmic region is not required for integrin clustering, a key event in outside-in signaling.

Cholecystitis in the octogenarian: is laparoscopic cholecystectomy the best approach?

Management of biliary disease in the octogenarian has evolved over the last decade. Laparoscopic cholecystectomy is now more commonly performed in this patient population. Octogenarians with biliary pathology frequently present with complications of acute disease such as biliary pancreatitis, choledocholithiasis, and acute cholecystitis. As a result, laparoscopic management in this patient population can frequently be more challenging than in younger patients. We retrospectively reviewed 70 patients who were 80 years of age and older who underwent cholecystectomy at our institution for biliary tract disease. Seventeen patients presented to the Day Surgery unit for elective management of chronic biliary disease. Sixteen (94%) of these patients were attempted laparoscopically and one (6%) underwent open cholecystectomy. Two patients attempted laparoscopically were converted to open surgery (conversion rate 12.5%). Average length of hospital stay was 3.7 days for those treated laparoscopically and 11 days for patients treated with open cholecystectomy. There were three complications (19%) in this group and no deaths. The remaining 53 patients presented via the emergency room with acute complications of cholelithiasis. Laparoscopic cholecystectomy was attempted in 28 (52%) and open cholecystectomy was performed in 25 (48%) patients. Ten (37%) of the patients attempted laparoscopically were converted to an open procedure. Average length of stay in this group was 11.7 days for those treated laparoscopically and 15.7 days for patients managed with open technique. There were ten (56%) complications in the laparoscopic group and five (14%) complications in the open group. There were four deaths (22%) among those treated laparoscopically and three deaths (8.6%) in the open cholecystectomy group. Comorbid conditions were common in the patients with acute biliary pathology and those presenting for elective cholecystectomy. Laparoscopic cholecystectomy is the procedure of choice in the elective management of biliary tract disease in the octogenarian. Laparoscopic cholecystectomy has no benefit with respect to morbidity and mortality over open cholecystectomy in the management of acute biliary tract disease in this elderly population. When possible, chronic cholecystitis in the elderly should be managed with elective laparoscopic cholecystectomy rather than waiting for complications to develop.

The forensic application of allozyme electrophoresis to the identification of blowfly larvae (Diptera: Calliphoridae) in southern Australia

Most known carrion-breeding species of blowflies in southern Australia are of the genus Calliphora. The morphological similarity of the immatures of these species means that correctly identifying them poses a challenge for forensic entomologists. This study investigates the potential of allozyme analysis to assist with this task. Molecular profiles of third-instar larvae and adults representing four of these carrion-breeding species, Calliphora stygia, C. dubia, C. hilli hilli, and C. vicina, were compared at 42 allozyme loci. The two life stages were found to display almost identical allozyme profiles in each species (93% of loci were expressed in both life history stages), enabling the reliable identification of larvae in these four species. Integration of these results with data from a previous study indicates that allozyme analysis would also be suitable for rapid, species-level identification of the larvae of six other carrion-breeding Calliphora species occurring in southern Australia. This is the first report of the application of allozyme data to the identification of forensically important blowflies.

Quasi-model-independent search for new high p(T) physics at D0

We apply a quasi-model-independent strategy ("Sleuth") to search for new high p(T) physics in approximately 100 pb(-1) of pp collisions at square root of (s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p(T) physics is observed.

Simian virus 40 detection in human mesothelioma: reliability and significance of the available molecular evidence

Simian virus 40 was discovered as a contaminant of early poliovirus vaccines that were inadvertently administered to millions of people in Europe and the United States between 1955 and 1963. Although SV40 was proven to be oncogenic in rodents and capable of transforming human and animal cells in vitro, its role in human cancer could not be proven epidemiologically. The matter was forgotten until 1993 when SV40 was accidentally found to cause mesotheliomas in hamsters injected intra-cardially. Subsequently, DNA sequences associated with its powerful oncogenic principal, the large T antigen, were found with high frequency in human pleural mesothelioma using the polymerase chain reaction (PCR). Since then many laboratories have confirmed the human findings. However, a few laboratories have failed to reproduce these data and the authors of the studies have claimed that the detection of SV40 DNA may simply represent PCR contamination artefacts. The controversy raised by this viewpoint is reviewed in this article together with a critical appraisal of the reliability of the molecular techniques used to detect SV40 DNA, in order to evaluate the potential aetiopathogenic role of SV40 in human mesothelioma.