全球钨资源和未来供应

女士们、先生们,下午好: 首先我谢谢梅比先生和国际钨协邀请我今天在这里发言.在今天的发言中我侧重的是全世界的钨资源,焦点是未来钨的供应渠道. 0前言 梅比先生已经作了关于钨市场的全面报告.因此,我不准备就目前的市场形势进一步细说.然而,要对未来钨的供应渠道作一验证,有必要分析一下为什么钨市场需要新的供货渠道.图1显示了钨生产和消费的历史概况及每年和累积的库存变化.该图主要显示出过去7～8年钨的消费已经超过了生产.这意味着钨的需求量是令人可信的,原料主要是来自俄罗斯和中国的库存,而目前更多的是来自美国战略储备局.我们估计在1993～1999年期间已经消耗了超过40 000t钨含量的库存,平均每年约6 000t左右.预计钨产量滞后于消费量的状况将持续多久是很难的,因为我们不知道准确的库存量.然而,从俄罗斯售出的钨在逐渐减少,表明库存已接近枯竭,中国似乎也没有大量的库存.美国战略储备局还有相当多的库存,库存量大于需求量,不过DLA每年销售的库存量限制在2 500t. 假如事实如此的话,在未来的几年中钨市场将需要增加供应,或从现有的厂家或从新的渠道.     

Quantised vortex visualisation

No Heading If superfluid helium-4 is rotated, a triangular array of singly quantised vortices is created. The vortices have core diameters of approximately five angstroms and are pinned at the cell upper and lower boundaries. If the fluid has a free surface, the upper ends of the vortices splay out into large (0.5 mm) shallow dishes which should be visible to an optical probe under certain conditions. The vortex array is very unstable to mechanical noise but can be held stationary with the addition of helium-3 which can lie along the vortex cores or form bubbles in the surface dimples.We report investigations on free surface superfluid helium under rotation, using a cooled 77K optical CCD. We describe the difficulties encountered and how we have overcome them.PACS numbers: 67.40.Vs; 68.03.Cd; 47.37.+q.     

Low gallium-content,dysprosium III-doped,Ge–As–Ga–Se chalcogenide glasses for active mid-infrared fiber optics

A systematic investigation is presented, for the first time, of a 1000 ppmw (parts per million, by weight) Dy³⁺-doped Ge–As–Ga–Se chalcogenide glass series, with a fixed low Ga content of 1 atomic% (at. %), suitable for active mid-infrared fiber optics. Seven glasses constitute the series, which have increasing average coordination number from 2.49 to 2.61, in steps of 0.02, with the GeSe₂, As₂Se₃, and Ga₂Se₃ stoichiometries kept. Glass formation is confirmed using X-ray diffraction and differential scanning calorimetry. Fourier transform infrared spectroscopy is reported for the series. Parallel plate viscometry enables prediction of fiber-drawing temperatures and, with differential thermal analysis, determines the potential for fiber fabrication. X-ray diffraction of samples after parallel-plate viscometry shows that Ge₂₅As₉Ga₁Se₆₅ (at. %) alone, in the glass-series, devitrifies to form the single-crystalline phase: monoclinic-GeSe₂; scanning electron microscope imaging suggests that this phase is both surface and bulk grown. Overall, the recommended host glass at. % compositions for doping with rare-earth ions and drawing to active mid-infrared fiber are: Ge_17.5As₁₈Ga₁Se_63.5, Ge₁₅As₂₁Ga₁Se₆₃, and Ge_12.5As₂₄Ga₁Se_62.5.     

Adhesion between oppositely charged polyelectrolytes

The adhesion between a grafted polyelectrolyte layer (brush) and a gel of an oppositely charged polyelectrolyte has been measured as a function of applied pressure, and the interface has been traced using neutron reflectometry. The interface (in aqueous medium at pH 6) between the (polycationic) brush and the (polyanionic) gel has a limited pressure dependence, with a small amount of deformation of the interface at the brush–gel contact. Brushes with a dry thickness of up to 13 nm exhibit weak adhesion (measured using a mechanical force tester) with an adhesive failure when the gel is detached. Thicker brushes result in the gel exhibiting cohesive failure. Reversing the geometry, whereby a polycationic brush is replaced with a polyanion and the polyanionic gel is replaced with a polycation, reveals that the pH dependence of the adhesion is moderately symmetric about pH 6, but that the maximum force required to separate the polycation gel from the polyanion brush over the range of pH is greater than that for the polycation brush and polyanion gel. The polyanion used is poly(methacrylic acid) (PMAA) and polycations of poly[2-(diethylamino)ethyl methacrylate] (PDEAEMA) and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) were used.     

The cost of caring for end-stage kidney disease patients: an analysis based on hospital financial transaction records

The costs of care for end-stage renal disease patients continue to rise because of increased numbers of patients. Efforts to contain these costs have focused on the development of capitated payment schemes, in which all costs for the care of these patients are covered in a single payment. To determine the effect of a capitated reimbursement scheme on care of dialysis patients (both hemodialysis [HD] and peritoneal dialysis [PD]), complete financial records (all reimbursements for inpatient and outpatient care, as well as physician collections) of dialysis patients at a single medical center over 1 year were analyzed. For the period from July 1994 to July 1995, annualized cost per dialysis patient-year averaged $63,340, or 9.8% higher than the corrected estimate from the U.S. Renal Data Service (USRDS; $57,660). The "most expensive" 25% of patients engendered 44 to 48% of the total costs, and inpatient costs accounted for 37 to 40% of total costs. Nearly half of the inpatient costs resulted from only two categories (room charges and inpatient dialysis), whereas other categories each made up a small fraction of the inpatient costs. PD patients were far less expensive to care for than HD patients, due to reduced hospital days and lower cost of outpatient dialysis. Care for a university-based dialysis population was only slightly more expensive than estimates predicted from the USRDS. These results validate the USRDS spending data and suggest that they can be used effectively for setting capitated rates. Efforts to control costs without sacrificing quality of care must center on reducing inpatient costs, particularly room charges and the cost of inpatient dialysis.