Recent models which describe our world as a brane embedded in a higher dimensional space introduce new geometrical degrees of freedom, associated with spatial variations in the position of the brane ...and the size of the extra dimensions, that can be coherently excited by symmetry breaking in the early universe even on "mesoscopic" scales as large as 1 mm. The characteristic frequency and intensity of resulting gravitational radiation backgrounds are estimated. Extra dimensions with scale between 10(-14) and 1 mm can produce detectable backgrounds at frequencies f approximately 10(3) to 10(-4) Hz.
Review of Particle Physics
The European physical journal. C, Particles and fields,
03/1998, Letnik:
3, Številka:
1-4
Journal Article
Recenzirano
Odprti dostop
This biennial Review summarizes much of Particle Physics. Using data from previous editions, plus 1600 new measurements from 550 papers, we list, evaluate, and average measured properties of gauge ...bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http: //pdg. lbl. gov.
Our studies of mice deficient for the E2F1 and E2F2 transcription factors have revealed essential roles for these proteins in the cell cycle control of pancreatic exocrine cells and the regulation of ...pancreatic beta cell maintenance. Pancreatic exocrine cells in E2f1/E2f2 mutant mice become increasingly polyploid with age, coinciding with severe exocrine atrophy. Furthermore, mice deficient for both E2F1 and E2F2 develop nonautoimmune, insulin-dependent diabetes with high penetrance. Surprisingly, transplantation of wild-type bone marrow can prevent or rescue diabetes in E2f1-/-E2f2-/-mice. We hypothesize that exocrine degeneration results in a destructive environment for beta cells, which can be alleviated by restoration of the hematopoietic system that is also defective in E2f1-/-E2f2-/-mice. The demonstration that beta cell maintenance under conditions of stress is influenced by bone marrow-derived cells may provide important insight into the design of therapies to boost islet mass and function in diabetic patients.
The ages of the oldest stars in the Galaxy can be estimated by comparing stellar populations in globular clusters to calibrated stellar models. The best data give cluster ages of about 15.8 plus or ...minus 2.1 Gyr, which conflicts with the age of the Universe estimated from measurements of the Hubble constant and the "standard" cosmological model of a flat, matter-dominated universe.
Understanding the repopulating characteristics of human hematopoietic stem/progenitor cell fractions is crucial for predicting their performance after transplant into high-risk patients following ...high-dose therapy. We report that human umbilical cord blood cells, 78% to 100% of which express the hematopoietic progenitor cell surface marker CD34, can consistently engraft, develop, and proliferate in the hematopoietic tissues of sublethally irradiated NOD/LtSz-scid/scid mice. Engraftment and development of CD34+ cells is not dependent on human growth factor support. CD34+ cells home to the mouse bone marrow (BM) that becomes the primary site of human hematopoietic development containing myeloid, lymphoid, erythroid, and CD34+ progenitor populations. Myeloid, and in particular lymphoid cells possessing more mature cell surface markers, comprise the human component of mouse spleen and peripheral blood, indicating that development proceeds from primary hematopoietic sites to the periphery. Repopulation of secondary recipients with human cells by BM from primary recipients demonstrates the maintenance of substantial proliferation capacity of the input precursor population. These data suggest that the cells capable of initiating human cell engraftment (SCID-repopulating cells) are contained in the CD34+ cell fraction, and that this mouse model will be useful for assaying the developmental potential of other rare human hematopoietic cell fractions in vivo.
Aortic dissection (AD) is an uncommon condition that occurs mainly in the older patient population (>40 years). It is rare in younger people and is usually associated with trauma, Marfan’s syndrome, ...or pregnancy. We report a case of a young weightlifter who died from an AD, and upon autopsy, was diagnosed as having non-Marfan’s fibrillinopathy. We recommend that AD should be considered in symptomatic patients with any family history of early cardiac deaths, a history suggestive of a connective tissue disorder (that is, multiple joint surgeries) or who practise weightlifting.
Most extra-articular metacarpal fractures can be managed nonoperatively. While the conventional wisdom is that the metacarpophalangeal joint should be immobilized in a position of flexion, ...alternative methods for cast immobilization have been described. The purpose of this study was to retrospectively evaluate three methods of closed treatment; specifically, we investigated whether the position of immobilization of the metacarpophalangeal joint or the absence of a range of motion of the interphalangeal joints affected the short-term outcome or fracture alignment.
Between November 2000 and April 2004, extra-articular metacarpal fractures were immobilized for five weeks in one of three ways: with the metacarpophalangeal joints in flexion and full interphalangeal joint motion permitted (Group 1); with the metacarpophalangeal joints in extension and full interphalangeal joint motion permitted (Group 2); and with the metacarpophalangeal joints in flexion, the interphalangeal joints in extension, and no interphalangeal joint motion permitted (Group 3). Radiographs and the range of motion were evaluated at five weeks after application of the cast, and the range of motion and grip strength were assessed at nine weeks.
Two hundred and sixty-three patients met the inclusion criteria. At five weeks, there was no difference among the treatment methods with regard to the range of motion or the maintenance of fracture reduction. At nine weeks, there was no significant difference with regard to the range of motion or grip strength.
When immobilization was discontinued by five weeks, the position of the metacarpophalangeal joints and the absence or presence of interphalangeal joint motion during the immobilization had little effect on motion, grip strength, or fracture alignment. This finding contradicts the conventional teaching that the metacarpophalangeal joint must be immobilized in flexion to prevent long-term loss of joint extension. Patient comfort, ease of application, and the surgeon's familiarity with the technique should influence the choice of immobilization.
Therapeutic Level III.
To document the changes in wrist loading that occur after proximal row carpectomy in a cadaver model.
The normal radioulnar carpal pressure distributions of 7 cadaver wrists were measured using ...super-low-pressure-sensitive film. Proximal row carpectomies were performed and the loading characteristics re-evaluated.
In the lunate fossa the contact area increased 37%, the average contact pressure increased 57%, and the location of the contact moved radially 5.5 mm. With wrist motion between 40° of extension and 20° of flexion the volar/dorsal excursion of the lunate fossa contact point increased by 108%.
Significant changes in radiocarpal loading occur after proximal row carpectomy. The increased radiocarpal excursion with wrist motion may explain the low incidence of radiocapitate arthritis in patients who have had proximal row carpectomy.
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