鼻腔鼻窦内翻性乳头状瘤的CT诊断

目的:探讨鼻腔鼻窦内翻性乳头状瘤(SNIP)的CT特点及诊断价值。方法:回顾性分析48例经手术病理诊断为SNIP的临床手术病理及CT资料,结合文献讨论。结果:48例SNIP中,男性居多(62.5%),鼻塞、流涕为主要临床症状(100%),50%的患者涕中带血,31.25%的患者嗅觉减退,18.75%的患者嗅觉丧失,12.5%的患者6年内复发。SNIP主要为单侧发病(93.75%),病变最易累及同侧上颌窦(55.56%)。CT平扫SNIP均呈鼻腔鼻窦内软组织密度肿块,CT值(45.61±1.02)HU。受累窦腔内肿块完全充填者21例(43.75%),未完全充满窦腔者22例(45.83%),受累窦腔呈轻度膨胀性改变21例(43.75%),窦壁及鼻甲骨质吸收或破坏42例(87.5%),受累窦腔较健侧缩小7例(14.58%),局限于鼻腔呈息肉样改变2例(4.17%)。结论:SNIP具有一定的CT特点,术前CT检查对SNIP累及的部位、范围等可准确确定,可为手术治疗提供重要的参考依据。      

肺硬化性血管瘤的CT征象分析

目的:探讨肺硬化性血管瘤的CT表现特征,以提高其CT诊断准确性及鉴别诊断的能力.方法:回顾性分析18例经手术和病理证实的肺硬化性血管瘤的CT表现,其中11例行CT增强扫描.结果:术前诊断有一定的难度.中年女性为主要发病群体.女性17例(17/18,占94.44％),43～70岁之间共15例(15/18,占83.33％).发病部位集中于左下肺(9/18,占50.00％).18例肺内类圆形肿块边界清楚,6例见斑点状钙化(6/18,33.33％),3例见浅分叶,1例有纵隔淋巴结肿大,所有病例均无空洞,无胸膜凹陷和受侵,无血管切迹征.CT值为26～40 Hu.11例增强CT中10例(10/11,占90.91％)病灶呈明显强化,有一定的延迟强化,CT值增加46～60 Hu以上.结论:CT对于肺硬化性血管瘤的准确诊断具有一定的价值,增强CT是必要的补充手段.     

肺硬化性血管瘤的CT征象分析

目的:探讨肺硬化性血管瘤的CT表现特征,以提高其CT诊断准确性及鉴别诊断的能力。方法:回顾性分析18例经手术和病理证实的肺硬化性血管瘤的CT表现,其中11例行CT增强扫描。结果:术前诊断有一定的难度。中年女性为主要发病群体。女性17例(17/18,占94.44%),43～70岁之间共15例(15/18,占83.33%)。发病部位集中于左下肺(9/18,占50.00%)。18例肺内类圆形肿块边界清楚,6例见斑点状钙化(6/18,33.33%),3例见浅分叶,1例有纵隔淋巴结肿大,所有病例均无空洞,无胸膜凹陷和受侵,无血管切迹征。CT值为26～40Hu。11例增强CT中10例(10/11,占90.91%)病灶呈明显强化,有一定的延迟强化,CT值增加46～60Hu以上。结论:CT对于肺硬化性血管瘤的准确诊断具有一定的价值,增强CT是必要的补充手段。     

X线钡餐联合CT扫描在食道癌诊断中的应用

目的:分析X线钡餐与CT扫描在食道癌诊断中的影像学表现特点,以及两者的优势和不足,探讨两者的联合使用对食道癌的诊断价值,提高影像学技术对该病的诊断水平.方法:回顾分析56例经手术或病理证实的食道癌患者的影像学资料,所有病例均进行了X线钡餐及CT检查,影像学资料完整.结果:①分布部位:56例中,食管颈段8例,胸上段10例,胸中段23例,胸下段15例.②X线钡餐征象:早期表现为粘膜增粗、紊乱,蠕动减弱,以及小的允盈缺损和小龛影(13例);中晚期为粘膜破坏、管腔狭窄,管壁僵硬,以及较大的充盈缺损和恶性龛影(43例).③CT征象:直接征象为管壁不规则增厚(56例),腔内肿块(36例),管腔狭窄(51例)或闭塞(3例),狭窄以上扩张(43例);间接征象为肿瘤对临近结构的侵犯和转移,以及并发症征象.表现为食管周围脂肪线侵犯(43例),气管支气管侵犯(16例),主动脉侵犯(22例,其中3例可疑),心包侵犯(7例),淋巴结转移(8例),并发肺脓肿(1例).④与手术病理确诊对照:X线钡餐正确诊断率为83.8%,CT正确诊断率为95.3%,两者联合诊断正确率达100%.⑤CT分期:Ⅱ期13例,Ⅲ期36例,Ⅳ期7例.结论:X线钡餐与CT扫描各具其优劣.X线钡餐能观察食管的功能性改变,对病变部位长度及粘膜病变显示精准,CT扫描对肿块位置、大小、范围及周围组织器官受侵和淋巴结转移情况具优势,两者联合使用有利于全面观察食道癌的病变范围和程度,提高了对该病的影像学诊断准确率,对指导临床分期、制定治疗及手术方案、判定预后有积极作用.     

成人三房心的CT增强表现及手术病理对照

目的:探讨成人三房心的CT增强表现及其手术病理,提高对其诊断水平.方法:回顾性分析经手术病理证实的3例三房心的临床资料及CT表现.结果:三房心影像学表现典型,分常见的左侧三房心和右侧三房心(右心房憩室).左侧完全型三房心表现为左心房内纤维隔膜将其一分为二,中间有孔相通.右侧三房心示与右心房相连的囊性结构,强化同心房,可见憩室口.结论:螺旋CT增强扫描及后处理技术对三房心诊断明显,可以指导临床手术.     

胃肠道间质瘤的CT诊断与临床病理分析

目的:探讨胃肠道间质瘤(GIST)的CT表现,以提高对GIST的诊断水平.方法:搜集经手术和病理证实的胃肠道间质瘤32例,回顾性分析其CT和病理表现.所有病例均行CT平扫及增强扫描.结果:32例肿瘤均为单发,位于胃部17例,空肠和回肠7例,结肠及直肠3例,食管1例,十二指肠和肠系膜各2例.良性9例,恶性23例.CT表现为粘膜下富血供性肿块,肿瘤倾向于腔外生长,可有囊变、坏死及钙化.双期增强扫描见静脉期较动脉期强化显著.结论:CT是GIST的主要影像学检查方法,CT表现有一定的特征性,对胃肠道间质瘤的定位和定性判断,以及鉴别诊断有重要价值,但定性诊断需依赖免疫组化和电镜检查.     

HRCT及螺旋CT增强扫描在周围型小肺癌诊断中的价值

目的:探讨HRCT及螺旋CT增强扫描在周围型小肺癌诊断中的价值。方法:搜集经手术或穿刺病理证实的周围型小肺癌(直径≤3cm)46例,全部行HRCT扫描,分析其各种CT征象。25例行螺旋CT增强扫描,对病灶强化前后CT值增幅特点进行分析。结果:HRCT表现:①分叶征(91.3%);②毛刺征(87%);③胸膜凹陷征(78.3%);④血管集束征(54.3%);⑤空气支气管征及空泡征(34.8%);⑥棘状突起(32.6%);⑦磨玻璃样密度(10.9%);⑧钙化(8.7%)。强化前后CT值增幅20~30HU占16%,30~65HU占76%,>65HU占8%。结论 :HRCT及螺旋CT增强扫描是周围型小肺癌诊断中重要的检查手段。同时具备3个及其以上CT征象,尤其是前5个征象中2个以上即可确诊,其正确率为91.3%。强化前后CT值增幅在20~65HU之间,对于肺癌诊断更加可靠,正确率达92%。     

周围型肺错构瘤的多层螺旋CT表现

目的:探讨肺错构瘤的多层螺旋CT(MSCT)表现,以提高CT诊断水平.方法:回顾性分析经手术病理证实的32例肺错构瘤的MSCT平扫及22例MSCT动态增强扫描的特点.结果:MSCT上所有结节边缘光滑.结节内含有脂肪密度(无钙化)的12例,占37.5%,既有脂肪又有钙化的8例,占25.0%,只有钙化的2例,占6.3%.增强扫描(22例)强化值<20HU的20例,占90.9%,强化形态呈间隔状强化16例,占72.7%.结论:肺错构瘤的MSCT表现有一定的特征性,边缘光滑、结节内含有脂肪和钙化有助于诊断,动态MSCT增强扫描有助于与周围型肺癌的鉴别诊断.     

肋骨原发性软骨肉瘤的影像表现

目的:探讨肋骨原发性软骨肉瘤的影像学特点。方法:收集经手术病理证实的12例肋骨原发性软骨肉瘤,回顾性分析其X线、CT及MRI表现。结果:12例肋骨原发性软骨肉瘤(男性6例,女性6例)。12例肋骨原发性软骨肉瘤位于肋骨前缘肋软骨连接处7例,位于肋骨头近胸椎处4例,肋骨腋段1例。X线检查均表现为境界清楚/密度均匀的胸部肿块(左侧7例,右侧5例),邻近肋骨骨质结构变模糊。CT平扫病变处均呈溶骨性、膨胀性骨质破坏,局部软组织肿块边缘清晰伴有条状、结节状及环状钙化。CT增强扫描病变(11例)强化不明显,邻近椎体和附件表现为骨质侵蚀破坏。10例肋骨原发性软骨肉瘤接受了MRI检查,病变均表现为边界清楚的长T1、长T2混杂信号肿块,增强后不均匀环状强化。结论:钙化为肋骨原发性软骨肉瘤的特征性表现,边界清楚的软组织肿块为重要征象,环状强化为其增强CT/MRI表现特点,完善影像学检查,能明显提高诊断的准确性,指导临床手术。      

额、筛窦粘液囊肿的X线和CT诊断

目的是研究额、筛窦粘液囊肿Ｘ线和ＣＴ表现,并探讨其在诊断鼻窦粘液囊肿方面的价值。方法粘液囊肿患者１２例,共１５个粘液囊肿,所有患者都行Ｘ线平片检查和ＣＴ检查,结合手术对照分析额、筛窦粘液囊肿的Ｘ线和ＣＴ表现。结果 ９个粘液囊肿发生于筛窦, ６个粘液囊肿发生于额窦。 Ｘ线表现： １５ 个粘液囊肿都表现为窦腔透亮度的减低,不同程度的窦腔扩大,骨质变薄及窦壁骨质的吸收、破坏。ＣＴ表现：１１个粘液囊肿表现为低密度,３个表现为等密度,１个表现为高密度（同面部肌肉密度相比）。４例行ＣＴ增强扫描,３例显示囊肿周边粘膜环行强化而中央无强化。１５个粘液囊肿均表现为不同程度的窦腔膨大、骨质变薄,囊肿轮廓光滑完整,其中９个粘液囊肿可清晰显示骨质的吸收、破坏,囊肿突入到邻近结构。结论是ＣＴ检查能准确、全面显示鼻窦粘液囊肿的骨质改变,又能显示其特征性影像表现,对于粘液囊肿的诊断和鉴别有重要意义。     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Earthquake Engineering and Engineering Vibration Aims And Scope

正This journal is established by the Institute of Engineering Mechanics(IEM),China Earthquake Administration,to promote scientific exchange between Chinese and foreign scientists and engineers so as to improve the theory and practice of earthquake hazards mitigation,preparedness,and recovery.To accomplish this purpose,the journal aims to attract a balanced number of papers between Chinese and     

Solute concentrations in the lower niger river and the source rock contribution

Water quality analyses for the Niger River for the 1980/81 hydrological year are presented. The samples were collected from the main river at Lokoja, and from two main tributaries, the Kaduna and the Benue Rivers. Different water types were distinguished by the concentrations of major ions. The type Ca > Na > Mg > K - HCO₃ > SO₄ > Cl was represented at all stations during at least part of the year. Chloride was found to dominate the sulphate ion in the Kaduna and Niger, while the Benue maintained a higher concentration of sulphate relative to chloride all year round. Distinct patterns of seasonal variation in the ion concentrations were observed, particularly for the samples collected at Lokoja. Low ion concentrations were prominent during periods of high discharge, while low flow periods coincided with high dissolved ion concentrations. The contribution of rainwater to the total dissolved solids in the river waters was assessed indirectly using rainwater chemistry data from the Gulf of Guinea. The estimated rainwater contribution to the Lower Niger amounts to 5.15 mg 1^?1. Geochemical weathering calculations involving reactions of the four major minerals of granitic rocks - anorthite, biotite, albite, and K-feldspar - with carbon dioxide and water, can account for the average water composition of the Lower Niger. The proportion of the ionic components was also related to the occurrence of the respective element in the minerals.     

Scenario predictions for potential near-field and far-field earthquakes affecting Hong Kong

Historical earthquakes noted in the written records of the South China region, including Hong Kong, are not well delineated along identified prominent fault sources. Despite the lack of any definitive, localised trend in the spatial distribution of seismic activity in the region, there does appear to be some major disparity in the seismic activity rates (especially for large magnitude earthquakes) between the near-field and the far-field regions of Hong Kong. Despite this observation, previous studies of the regional seismic activity and seismic ground motion hazard (the latter using a probabilistic seismic hazard assessment, PSHA) have considered very broad source zone regions, in which uniform levels of seismic activity have been assumed. The present paper further scrutinises this broad source zone (BSZ) approach by adopting a novel expanding circular disc (ECD) method to determine the rates of earthquake recurrence. Such a method is intended to counter-check previously developed models by determining earthquake scenario events in terms of magnitude–distance (M–R) pairs or combinations, having defined values of average return period. Unlike the BSZ approach, the ECD method specifically accounts for the supposed variations in the seismic activity rates between events in the near-field and the far-field of Hong Kong.The form of the developed method is particularly suited to the determination of design-level earthquake ground motions for bedrock sites, since it assumes a directionally-independent attenuation model as described in the companion paper. It is found that, whilst the BSZ approach may indicate the overall average levels of hazard that are representative of the South China region as a whole, it does not capture the large disparity in seismic activity rates between near-field and far-field events. This important feature is expected to have a significant impact upon engineering assessments of the seismic safety of structures in Hong Kong and elsewhere in the South China region. For example, it is found that for events with M≥6, the seismic activity rate (normalised by time and area) in the very far-field is around 3.5 times larger than in the near-field and medium-field of Hong Kong. The resulting design M-R combinations, covering a range of return periods from 70 to 2500 years, are limited, for very long return periods and for distant events, by the maximum credible earthquake (MCE) magnitude. Intensive research to determine this seismic hazard parameter is recommended, in order to refine further the results of the ECD analysis, which presently conservatively assumes the MCE to range between M=6 in the near-field of Hong Kong to M=8 in the very far-field, at distances greater than 280 km from Hong Kong.     

Depositional ages and characteristics of Middle–Upper Jurassic and Lower Cretaceous lacustrine deposits in southeastern Mongolia

Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Middle Jurassic. The present study aims at establishing depositional ages and characteristics of the Jurassic and Cretaceous lacustrine deposits in Mongolia. The Lower Cretaceous Shinekhudag Formation is about 250 m thick and composed of alternating beds of shale and dolomite. The Middle Jurassic Eedemt Formation is about 150 m thick and composed of alternating beds of shale, dolomitic marl, and siltstone. The alternations of shale and dolomite in both formations were formed by lake level changes, reflecting precipitation changes. Shales were deposited in the center of a deep lake during highstand, while dolomites were formed by primary precipitation during lowstand. Based on the radiometric age dating, the Shinekhudag Formation was deposited between 123.8 ±2.0 Ma and 118.5 ±0.9 Ma of the early Aptian. The Eedemt Formation was deposited at around 165–158 Ma of Callovian–Oxfordian. The calculated sedimentation rate of the Shinekhudag Formation is between 4.7 ±2.6 cm/ky and 10.0 ±7.6 cm/ky. Shales in the Shinekhudag Formation show micrometer‐scale lamination, consisting of algal organic matter and detrital clay mineral couplets. Given the average thickness of micro‐laminae and calculated sedimentation rate, the micro‐lamination is most likely of varve origin. Both Middle–Upper Jurassic and Lower Cretaceous lacustrine oil shales were deposited in intracontinental basins in the paleo‐Asian continent. Tectonic processes and basin evolution basically controlled the deposition of these oil shales. In addition, enhanced precipitation under humid climate during the early Aptian and the Callovian–Oxfordian was another key factor inducing the widespread oil shale deposition in Mongolia.     

THEORETICAL APPROACH TO THE SOLUTION OF THE INFILTRATION PROBLEM

ABSTRACT

The one-dimensional transient downward entry of water in unsaturated soils is investigated theoretically. The mathematical equation describing the infiltration process is derived by combining Darcy's dynamic equation of motion with the continuity and thermodynamic state equations adjusted for the unsaturated flow conditions. The resulting equation together with the corresponding initial and boundary conditions constitues a mathematical initial boundary value problem requiring the solution of a nonlinear partial differential equation of the parabolic type. The volumetric water content is taken as the dependent variable and the time and the position along the vertical direction are taken as the independent variables. The governing equation is of such nature that a solution exists for t > 0 and is uniquely determined if two relationships are defined, together with the specified state of the system, at the initial time t = 0 and at the two boundaries. The two required relations are those of pressure versus permeability and pressure versus volumetric water content.

Since the partial differential equation has strong non-linear terms, a discrete solution is obtained by approximating the derivatives with finite-differences at discrete mesh points in the solution domain and integrated for the corresponding initial and boundary conditions. The use of an implicit difference scheme is employed in order to generate a system of simultaneous non-linear equations that has to be solved for each time increment. For n mesh points the two boundary conditions provide two equations and the repetition of the recurrence formula provides n—2 equations, the total being n equations for each time increment. The solution of the system is obtained by matrix inversion and particularly with a back-substitution technique. The FORTRAN statements used for obtaining the solution with an electronic digital computer (IBM 704) are presented together with the input data.

Analysis of the errors involved in the numerical solution is made and the stability and convergence of the solution of the approximate difference equation to that of the differential equation is investigated. The method applied is that of making a Fourier series expansion of a whole line of errors and then following the progress of the general term of the series expansion and also the behavior of each constituent harmonic. The errors (forming a continuous function of points in an abstract Banach space) are represented by vectors with the Fourier coefficients constituting a second Banach space. The amplification factor of the difference equation is shown to be always less than unity which guarantees the stability of the employed implicit recurrence scheme.

Experiments conducted on a vertical column packed uniformly with very fine sand, show a satisfactory agreement between the theoretically and experimentally obtained values. Many experimental results are shown in an attempt to explain the infiltration phenomenon with emphasis on the shape and movement of the wet front, and the effects of the degree of compaction, initial water content and deaired water on the infiltration rate.     

Late Permian post‐ophiolitic trondhjemites from Central Iran: a mark of subduction role in growth of Paleozoic continental crust

Late Permian trondhjemites in the Anarak area occur as stocks and dykes, which cross cut the Anarak ophiolite and its overlying metasedimentary rocks, and are exposed along the northern Anarak east–west main faults. These leucocratic intrusive bodies have enclaves of all ophiolitic units and metamorphic rocks. They are composed of amphibole, plagioclase (oligoclase), quartz, zircon and muscovite. Secondary minerals are chlorite (pycnochlorite), epidote, albite, magnetite and calcite. Whole‐rock major‐ and trace‐element analyses reveal that they are characterized by high SiO ₂ (67.8–71.0 wt%), Al ₂ O ₃ (14.9–17.1 wt%) and Na ₂ O (5.3–8.6 wt%), low K ₂ O (0.1–1.5 wt%; average: 0.8 wt%), low Rb/Sr ratio (0.01–0.40; average: 0.09), low Y (3–6 ppm), negative Ti, Nb and Ta anomalies, slightly negative or positive Eu anomaly, LREE enrichment and fractionated HREE. These rocks present 2 to 40 times enrichment in inclined chondrite‐normalized REE patterns. Geochemical characteristics of the Anarak trondhjemites all reflect melting of a mafic protolith at more than 10 kbar. The field evidence and whole‐rock chemistry reveal that these rocks have been crystallized from magmas derived from melting of subducted Anarak oceanic crust. This study reveals that melting of garnet amphibolite was an important element of continent formation in the study area.