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Porous structures based on multi-metallic motifs are receiving growing interest, but their general preparation still remains a challenge. Here, we report the self-assembly and structure of a Cu

Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, a patternable oriented MOF film is designed: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH)2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylate ligand (Br2 BDC) into a copper-based MOF Cu2 L2 DABCO (DABCO = 1,4-diazabicyclo[2.2.2]octane; L = BDC/Br2 BDC). The lithographed samples act as diffraction gratings upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, the alignment of the dye in the MOF is demonstrated. By controlling the functional response to light, this MOF patterning protocol can be used for the microfabrication of optical components for photonic devices. ispartof: ADVANCED MATERIALS vol:35 issue:25 ispartof: location:Germany status: published

Using metal–organic cages (MOCs) as preformed supermolecular building-blocks (SBBs) is a powerful strategy to design functional metal–organic frameworks (MOFs) with control over the pore architecture and connectivity. However, introducing chemical complexity into the network via this route is limited as most methodologies focus on only one type of MOC as the building-block. Herein we present the pairwise linking of MOCs as a design approach to introduce defined chemical complexity into porous materials. Our methodology exploits preferential Rh-aniline coordination and stoichiometric control to rationally link Cu4L4 and Rh4L4 MOCs into chemically complex, yet extremely well-defined crystalline solids. This strategy is expected to open up significant new possibilities to design bespoke multi-functional materials with atomistic control over the location and ordering of chemical functionalities., A new strategy to design atomically precise multivariate metal–organic frameworks is presented. This is achieved by linking two preformed metal–organic cages via a precisely tuned Rh–aniline interaction.

Researchers and design engineers are increasingly interested in castellated beams because of their ability to provide greater flexural strength with lower dead loads, as well as provide services and cost-effective structures. The influence of castellation on the bending strength and stiffness of the hot-rolled steel Square Tubular Beams (STBs) and Castellated Tubular Beams (CTBs) with simply supported end conditions were investigated in this study. Totally eight bending tests were carried out on hollow tubular beams with and without castellation under three point bending. The STBs with a nominal steel tube thickness of 2.5 mm are castellated in a hexagonal pattern. The ultimate moments, moment versus mid-span deflection response curves, and failure patterns are provided as part of the test results. The bending tests show that the flexural capacities and stiffness of the hollow tubular sections significantly increased due to the castellation process. Finite element (FE) models of STBs and CTBs were established by including the material and geometric nonlinearity as well as the measured geometric imperfections. The FE models established show good agreement with the experimental test in terms of ultimate bending strength, moment vs. mid-span deflection response, and failure modes.

This paper investigates the flexural behaviour of Lean Duplex Stainless Steel (LDSS) rectangular tubular beams with rectangular web openings located centrally. The analysis procedures for the FE models were verified by validating with test results conducted by different authors for the perforated open sections as well as unperforated tubular sections. In order to study the effect of perforation on the structural response of Rectangular Hollow Sections (RHS), rectangular perforation is chosen with steel tube thicknesses ranging from 0.8 mm to 3.0 mm. It is observed that there is a linear decrease in moment capacities of the section with increase in the size of openings with local buckling being more predominant in the case of slender sections as compared to the stocky sections. The section capacities obtained were compared with the design strength calculated against the EN1993-1–4 (2006), ASCE8-02, the direct strength method (DSM) and the continuous strength method (CSM). The design strength calculated for perforated beams with respect to the CSM method gave the best predictions for strength calculation.

The biomimetic mineralization of zeolitic imidazolate framework-8 (ZIF-8) has been reported as a strategy for enzyme immobilization, enabling the heterogenization and protection of biomacromolecules. Here, we report the preparation of different Candida antarctica lipase B biocomposites (CALB@ZIF-8) formed by altering the concentrations of Zn2+ and 2-methylimidazole (2-mIM). The influence of synthetic conditions on the catalytic activity of the lipase CALB was examined by hydrolysis and transesterification assays in aqueous and organic media, respectively. We demonstrated that for both reactions, activity was retained for the biocomposites formed at low Zn2+/2-mIM ratios but notably almost entirely lost when the ligand concentration used to form the biocomposites was increased. Additionally, phosphate buffer could regenerate the activity of larger particles by degrading the crystal surfaces and releasing encapsulated CALB into solution. Transesterification reactions using CALB@ZIF-8 biocomposites were undertaken in 100% hexane, giving rise to enhanced CALB activity relative to the free enzyme. These observations highlight the fundamental importance of synthetic protocols and operating parameters for developing enzyme@MOF biocomposites with improved activity in challenging conditions.

The present research work is focused on the experimental and numerical studies on the structural behaviour of Concrete Filled Steel Tube (CFST) and Reinforced Cement Concrete (RCC) stub columns of different concrete grade. The experimental result of rectangular and square stub column of both RCC and CFST have been compared with a Finite Element (FE) study using ABAQUS platform. The concrete mix of M20, M25, M30 grade is used for the preparation of both RCC and CFST. Further in parametric study the structural dimensions of both CFST and RCC stub columns are kept same. The study has been carried out for both CFST and RCC stub columns by varying Depth/thickness (D/t) ratios in CFST stub columns (19.2, 23.5, 30.67, 45 for square sections and 23.20, 28.50, 37.33, 55.00 for circular sections), Steel percentage in RCC stub columns (8.69%, 12.62%, 16.30%, 19.75% for square sections and 7.20%, 10.50%, 13.50%, 16.40% for circular sections) and Concrete cube strengths (20, 25 and 30 MPa) for both CFST and RCC stub columns). The main aim of the study was to make a comparison on the structural behaviour of CFST and RCC stub columns. The comparison results show that the axial capacity of the CFST stub columns on an average is 50% and 55% more than the RCC stub columns with square section and circular sections respectively. Also, the effect of thickness of steel tubes, concrete cube strength and steel percentage is also studied.

The flexural behaviour of lean duplex stainless steel tubular beams with web openings is presented. A finite element study is carried out on lean duplex stainless steel sections with web openings to determine the effects of the perforations on the bending capacity, deformed shapes and local buckling characteristics. The study also aims in particular for a comparison between sections having circular or extended openings with a wide range of section slenderness. The bending capacities from the finite element results are also compared with the American specification, European specification along with direct strength method. Both ASCE and EN can give a good prediction of the design strengths, however, the direct strength method showed unconservative predictions. Modifications have been proposed to both the ASCE specification and the direct strength method for LDSS sections with web openings.

The biomimetic mineralization of zeolitic imidazolate framework-8 (ZIF-8) has been reported as a strategy for enzyme immobilization, enabling the heterogenization and protection of biomacromolecules. Here, we report the preparation of different

The incorporation of reactive functional groups onto the exterior of metal-organic cages (MOCs) opens up new opportunities to link their well-defined scaffolds into functional porous solids. Amine moieties offer access to a rich catalogue of covalent chemistry; however, they also tend to coordinate undesirably and interfere with MOC formation, particular in the case of Cu2 paddlewheel-based MOCs. We demonstrate that tuning the basicity of an aniline-functionalized ligand enables the self-assembly of a soluble, amine-functionalized Cu4L4 lantern cage (1). Importantly, we show control over the coordinative propensity of the exterior amine of the ligand, which enables us to isolate a crystalline, two-dimensional metal-organic framework composed entirely of MOC units (2). Furthermore, we show that the nucleophilicity of the exterior amine of 1 can be accessed in solution to generate a cross-linked cage polymer (3) via imine condensation.

Obtaining structural information for highly reactive metal-based species can provide valuable insight into important chemical transformations or catalytic processes. Trapping these metal-based species within the cavities of porous crystalline hosts, such as metal–organic frameworks (MOFs), can stabilise them, allowing detailed structural elucidation by single crystal X-ray diffraction. Previously, we have used a bespoke flexible MOF, [Mn3L2L′] (MnMOF-1, where L = bis-(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane and L = L′, but L′ has a vacant N,N′-chelation site), which has a chelating site capable of post-synthetically binding metal ions, to study organometallic transformations and fundamental isomerisation processes. This manuscript will report the underlying conformational flexibility of the framework, demonstrate the solvent dependency of post-synthetic metalation, and show that the structural flexibility of the linker site and framework are critical to controlling and achieving high levels of metal loading (and therefore site occupancy) during chemical transformations. From these results, a set of design principles for linker-based “matrix isolation” and structure determination in MOFs are derived.

A Cu4L4 metal–organic cage (MOC) composed of amine-protected ligands forms supramolecular coordination polymers (SCPs) upon covalent post-assembly deprotection. The amorphous SCPs form by virtue of aniline–copper coordination and possess a tunable porosity based on the rate of deprotection.

The structural processing of metal-organic frameworks (MOFs) over multiple length scales is critical for their successful use as adsorbents in a variety of emerging applications. Although significant advances in molecular-scale design have provided strategies to boost the adsorptive capacities of MOFs, relatively little attention has been directed toward understanding the influence of higher-order structuralization on the material performance. Herein, we present the main strategies that are currently available for the structural processing of MOFs and discuss the influence these processes can impart on the adsorptive properties of the materials. In all, this intriguing area of research is expected to provide significant opportunities to enhance the properties of MOFs further, which will ultimately aid in their optimization in the context of specific real-world applications.

This paper presents a Finite Element (FE) study on Lean Duplex Stainless Steel stub column with built-up sections subjected to pure axial compression with column web spacing varied at different position across the column flanges. The thicknesses of the steel sections were from 2 to 7 mm to encompass a range of section slenderness. The aim is to study and compare the strength and deformation capacities as well as the failure modes of the built-up stub columns. The FE results have been compared with the un-factored design strengths predicted through EN1993-1-4 (2006) + A1 (2015) and ASCE8-02 standards, Continuous Strength Method (CSM) and Direct Strength Method (DSM). The results showed that the design rules generally under predict the bearing capacities of the specimens. It’s been observed that the CSM method offers improved mean resistance and reduced scatter for both classes of cross-sections (i.e. slender and stocky sections) compared to the EN1993-1-4 (2006) + A1 (2015) and ASCE 8-02 design rules which are known to be conservative for stocky cross-sections.

Although metal–organic frameworks (MOFs) have been shown to catalyse a wide range of reactions, understanding the influence of nanoscale structuralisation (e.g. crystal size and morphology) on their performance is a difficult challenge. Here, we have prepared Zn(2-mIM)2 (ZIF-8; 2-mIM− = 2-methylimidazolate) crystals of varied size and morphology, and studied the catalytic properties of these samples in the context of the transesterification of vinyl acetate with hexanol. ZIF-8 has previously been shown to catalyse reactions at Lewis acidic sites at the crystal surface and at defect sites. The substrates were selected as they are significantly larger than the pore apertures, allowing the reaction to be confined to the surface of the crystals and providing the best opportunity to understand the influence of the structuralisation on the observed properties. In this case, the rate of hexyl acetate production increased as the crystal size was reduced; however, the effect of crystal morphology on the rate of reaction was not appreciable due to the instability of ZIF-8 under catalytic conditions. It was clearly observed that the surface of ZIF-8 was unstable in catalytic conditions featuring hydrophobic reagents with a polar functional groups, with scanning electron microscopy (SEM) revealing indiscriminate etching of all crystal surfaces. Atomic adsorption spectrometry (AAS) analyses confirmed the etching led to significant leaching of Zn2+, which was observed to contribute considerably to the catalytic activity of ZIF-8. Our results highlight the need for fundamental characterisation of MOF catalysts to enable their deployment under a wider variety of catalytic conditions.

In recent years, due to a relatively high price increase of nickel alloys, there is an increase in demand for lean duplex stainless steel (LDSS) with a low nickel content of ~1.5%, such as grade EN 1.4162. LDSS offers roughly twice the strength compared to austenitic stainless steels and has great potential for expanding future structural possibilities, enabling a reduction in the section sizes leading to lighter structures. This paper reports the buckling behavior of fixed-ended concrete-filled LDSS tubular (CFDSST) columns with L-, T-, and +-shape (Non-Rectangular Sections or NRSs) sections and a representative square section with varying lengths through Finite Element (FE) analysis. The purpose is to compare and assess the strength and deformation characteristics as well as the failure modes of such columns. It is seen that concrete-filled tubular columns with NRSs offered a better performance for all lengths considered, especially the T-shaped and +-shaped sections, in terms of strength. The influence of the cross-sectional shapes on the e u becomes less significant with increasing λ, but becomes increasingly significant with decreasing λ. The design standards show over conservative results for square and L-shape sections and conservative for T-shape and +-shape sections.

Convenient access to metal–organic frameworks (MOFs) with defined structural and chemical features is required to satisfy the design criteria for targeted applications. Here, we demonstrate that staggered pillaring between the layers of a binodal 2-D metal–organic framework (MOF) at only the alternating axial sites of the dimetallic copper(II) paddlewheel nodes aligns the 2-D layers and significantly increases the porosity of the resulting 3-D MOF. Two new pillared MOFs of this form were synthesized, [Cu3(bcppm)2(NO3)2(L)]·xS (where bcppm = bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane and L = DABCO and pyrazine), via a mixed ligand synthesis. Both pillared 3-D frameworks have considerably larger BET surface areas than their 2-D counterpart, due to the alignment of 2-D layers from a staggered to eclipsed arrangement in the 3-D material; this increase in pore space and surface area is realized despite both materials being 2-fold interpenetrated. The strategy outlined here demonstrates a method of designing porous 3-D MOFs from nonporous 2-D-layered materials with a minimum of layer–layer connections.

The application of metal–organic frameworks (MOFs) for gas storage, molecular separations and catalysis necessitates careful consideration of the particle size and structuralisation (e.g. pelletisation, surface-anchoring) of a material. Recently, particle size has been shown to dramatically alter the physical and structural properties of certain MOFs, but overall there is limited information on how the particle size affects the properties of flexible MOFs. Here we demonstrate that the particle size of a flexible MOF, specifically the as-synthesised form of [Cu(bcppm)H2O]·S (H2bcppm = bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane, S = solvent) (1), correlates with the rate of structural reorganisation from a “kinetically-trapped”, activated 3D form of this MOF to an “open” 2D form of the structure. We also outline two methods for synthetically reducing the particle size of 1 at room temperature, using 0.1 M NaOH (for two reaction times: 0.5 and 16 h) and with the sodium salt of the ligand Na2bcppm, producing crystals of 85 ± 15, 280 ± 14 and 402 ± 41 nm, respectively.

The preparation of porous metal–organic frameworks (MOFs) at industrial scales requires careful selection of the metal precursor to ensure the sustainability of the synthetic process, in terms of both the environmental impact and cost. The use of earth abundant minerals is attractive for this purpose, provided that they are sufficiently reactive under the conditions of MOF formation. In this work, we investigate the use of copper carbonate and its naturally occurring counterparts, malachite and azurite, as precursors for the synthesis of Cu3(BTC)2(HKUST-1; BTC3–= 1,3,5-benzenetricarboxylate). Using a water/ethanol solution of copper carbonate and H3BTC, HKUST-1 was obtained at room temperature within 3 h, as confirmed by a suite of characterization techniques. The identity of the products was determined by the reaction conditions, highlighting the importance of optimizing the synthetic parameters. When prepared under optimized conditions, HKUST-1 synthesized here showed analogous performance characteristics to materials obtained by traditional solvothermal methods; thus, our results confirm that high-quality samples of MOFs can be easily derived from mineral precursors.

Objective: To identify the genetic cause of pontocerebellar hypoplasia type III (PCH3). Methods: We studied the original reported pedigree of PCH3 and performed genetic analysis including genome-wide single nucleotide polymorphism genotyping, linkage analysis, whole-exome sequencing, and Sanger sequencing. Human fetal brain RNA sequencing data were then analyzed for the identified candidate gene. Results: The affected individuals presented with severe global developmental delay and seizures starting in the first year of life. Brain MRI of an affected individual showed diffuse atrophy of the cerebrum, cerebellum, and brainstem. Genome-wide single nucleotide polymorphism analysis confirmed the linkage to chromosome 7q we previously reported, and showed no other genomic areas of linkage. Whole-exome sequencing of 2 affected individuals identified a shared homozygous, nonsense variant in the PCLO (piccolo) gene. This variant segregated with the disease phenotype in the pedigree was rare in the population and was predicted to eliminate the PDZ and C2 domains in the C-terminus of the protein. RNA sequencing data of human fetal brain showed that PCLO was moderately expressed in the developing cerebral cortex. Conclusions: Here, we show that a homozygous, nonsense PCLO mutation underlies the autosomal recessive neurodegenerative disorder, PCH3. PCLO is a component of the presynaptic cytoskeletal matrix, and is thought to be involved in regulation of presynaptic proteins and synaptic vesicles. Our findings suggest that PCLO is crucial for the development and survival of a wide range of neuronal types in the human brain.

This paper presents a finite element (FE) study on concrete-filled lean duplex slender stainless steel tubular (CFDSST) stub columns of square and L-, T-, and +-shape (Non-Rectangular Sections or NRSs) sections under pure axial compression. The effect of cross-sectional shape and concrete compressive strength, by considering equal steel consumption (i.e. equal cross-sectional area) for all the square and NRSs sections have been reported. In CFDSST stub columns, the axial deformation (δ u ) at ultimate load (P u ) decreases with increasing concrete strengths, but increases as the sections changes from Square→L→T→+-shape. For normal concrete strength (≤40 MPa), NRSs appear to have similar or slightly enhanced P u , in comparison with the representaive square section. But in the case of a high strength concrete core (i.e. >40 MPa), NRSs are clearly at a disadvantage as far as the values of P u is concerned, however as the NRSs are lighter by 37%, they still offer an attractive option for the designers. The FE strengths over predicts the EN 1994-1-1 (2004) specification by about an average of 21, 19, 14, and 4% for the square, L, T, and +-shape sections, respectively.

This paper presents a finite element (FE) study on fixed-ended LDSS slender hollow columns with square (SHC), and non-rectangular hollow columns (NRHCs) viz., L- (LHC), T- (THC), and +- (+HC) shaped cross-sections subjected to pure axial compression using Abaqus software. SHC columns with thicknesses of 5.25 mm and 2.0 mm, which lie in Class 3 (stocky) and Class 4 (slender) sections, respectively, as per EN 1993-1-4 were considered in the study as referral sections. Variations in buckling strength with changes in the cross-sectional shapes were studied by considering NRHCs having equal material cross-sectional areas (or equal material consumption) as that of SHCs over a range of column lengths. The FE results of SHC and NRHCs were then compared with the design strengths predicted by the EN1993-1-4 and ASCE 8-02 specifications. Good agreements between the FE strengths and codal predictions have been observed, except for the ASCE 8-02 prediction of LHC where it over predicts the FE strengths. At both the slenderness regime (i.e., low and high slenderness values) of Class 3 sections and high slenderness regime of Class 4, all the sections exhibit similar structural capacities. Cross-sectional shape is found to become increasingly significant with decreasing member slenderness in Class 4 sections. In Class 3 sections, compared to SHC there is a nearly linear variation in strength (increased for +HC, similar behavior for THC and decreased for LHC) up to λ ¯ ∼2.0, then it stabilizes out. After, λ ¯ ∼2.0, Pu for +HC showed ∼30% higher; THC showed similar strength; and LHC showed∼20% lower than the corresponding value for SHC, indicating that +HC has an improved ultimate strength for all the ranges of λ ¯ . The strength enhancement as compared to that of SHC are ∼10%, 50%, and 90% higher for LHC, THC, and +HC, respectively, for Class 4 sections. Based on the reliability analyses it is recommended that both the codes can be adopted for all the design of fixed-ended LDSS columns except for LHC, wherein a suitable modification may be employed after systematic studies.

In this paper, finite element (FE) studies for LDSS (Lean Duplex Stainless Steel) hollow columns with square, L-, T-, and +-shaped cross sections (i.e., SHC, LHC, THC and +HC respectively) are presented using ABAQUS, to gain an understanding of the cross sectional shape effects. The LDSS hollow columns having equal material cross-sectional areas with thickness varying from 5 m to 20 mm were subjected to uniform axial compression. Short/Stocky columns with lengths (∼1800 mm) of about three times the outer width of square were considered for the analyses. Based on the analyses, it has been found that for all the NRHCs (i.e., LHC, THC and +HC) considered, a nearly linear variation of P u with section thicknesses has been observed, although the increase for SHC was relatively slower in thinner sections ( t P u with 300% increase in t (from 5 m to 20 mm) has been found to be ∼1273%, 1252%, 1041% and 679%, respectively, for square, L-, T-, and +-shaped sections. The gain in P u for LHC, THC and +HC sections as compared (expressed as P u / P u (sq) ) to SHC are in the range 120%–150%, 130%–170%, 140%–230%, respectively. Ductility at ultimate load has been observed to be ∼0.1–0.6% for SHC, LHC and THC (all thicknesses), and +HC ( t ≤10 mm).

We present results from a study of the dissipation in nanomechanical gold resonators. We fabricated a nanomechanical resonator consisting of a gold wire of width 300 nm, thickness 80 nm and length 7.5 μm by etching away the underlying GaAs substrate. At low temperatures the resonator had a fundamental frequency of about 7.95 MHz, in part due to tension arising from differential thermal contraction between the gold beam and the underlying semiconductor substrate. The dissipation in the resonator was measured using the magnetomotive method over the temperature range 1 K to 10 mK. We find that the Q-factor of the resonator increases by more than a factor of four between 600 mK and 10 mK. The dissipation follows a weak power law dependence on temperature, ∝T0.5, from approximately 30 mK to 600 mK.

A distinct syndrome with hand abnormalities, joint contractures, cleft palate and a Dandy-Walker malformation was reported by Aase & Smith (1968). This paper reports a second example of this syndrome in a mother and daughter.

In 1969, Robinow and colleagues described a syndrome of mesomelic shortening, hemivertebrae, genital hypoplasia, and "fetal facies". Over 100 cases have now been reported and we have reviewed the current knowledge of the clinical and genetic features of the syndrome. The gene for the autosomal recessive form was identified as the ROR2 gene on chromosome 9q22. ROR2 is a receptor tyrosine kinase with orthologues in mouse and other species. The same gene, ROR2, has been shown to cause autosomal dominant brachydactyly B, but it is not known at present whether the autosomal dominant form of Robinow syndrome is also caused by mutations in ROR2.

We report a son and a daughter of a first cousin Pakistani marriage who both have osteogenesis imperfecta and the son in addition has arthrogryposis multiplex congenita. Bruck [(1897): Dtsch Med Wochenschr 23: 152-155] first reported the case of a boy who had multiple fractures and joint ankylosis, subsequently only one sibship with three affected cases and seven sporadic cases have been reported to our knowledge. On the basis of consanguinity this suggests that the association of osteogenesis imperfecta and arthrogryposis multiplex congenita is inherited in this family as an autosomal recessive condition with variable expression.

During the past 40 years, Oman has witnessed remarkable social and economic growth, which is best reflected in the well-organised and efficient healthcare system. As a consequence, a shift in disease pattern has been observed with a significant decrease in the incidence of communicable diseases and decrease in perinatal and childhood mortality (Alwan and Modell 1997; Christianson et al. 2006, 2013). In addition with better standards of medical care for disabled children, many children with congenital disorders are now surviving longer. Accurate information on the prevalence of congenital and genetic disorders in some local populations was occasionally sparse, incomplete or out of date (Alwan and Modell 1997; Christianson et al. 2006, 2013). This current survey aimed to gain insight into expected caseload of children with congenital or genetic disorders and to assess the future demand for genetic services, and to address policies for developing genetic services in Oman.

Cobblestone lissencephaly is the characteristic brain malformation observed in Fukuyama congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), and Walker-Warburg syndrome (WWS). The diagnostic criteria for all three require the presence of congenital muscular dystrophy, and criteria for MEB and WWS require retinal abnormalities. We report three patients from two consanguineous families of Middle Eastern origin with cobblestone lissencephaly but no abnormalities of the eyes or muscle. Based on the current diagnostic criteria for the cobblestone lissencephaly syndromes, this disorder must be classified separately from the others, but it may well be allelic to MEB and WWS. Linkage studies have excluded the gene for this disorder from the region of the FCMD gene on chromosome 9q31-32.

We present measurements of the dissipation and frequency shift in nanomechanical gold resonators at temperatures down to 10 mK. The resonators were fabricated as doubly-clamped beams above a GaAs substrate and actuated magnetomotively. Measurements on beams with frequencies 7.95 MHz and 3.87 MHz revealed that from 30 mK to 500 mK the dissipation increases with temperature as $T^{0.5}$, with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behavior of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems.

We report three infants with a rare syndrome of restrictive dermopathy, in which rigidity of the skin at birth is associated with characteristic facial anomalies, generalised arthrogryposis, bony abnormalities, and lung hypoplasia. The skin has a distinctive pathology with compaction of the dermal collagen and fibrosis of the subcutaneous tissue. The inheritance is likely to be autosomal recessive and the condition appears to be fatal in the early neonatal period.

A 2H‐SiC thin film has been grown on a 6H‐SiC substrate by laser ablation using an excimer laser. The deposition of 2H‐SiC film occurred in a high vacuum system (≊10−6 Torr) with the substrate temperature near 1200 °C. Plan‐view and cross‐sectional transmission electron microscopy (TEM) were used to measure the lattice parameters and to identify the polytype. Cross‐sectional TEM images clearly show the symmetry of the film as c‐axis oriented 2H‐SiC containing columnar grains with an average diameter of 20 nm and a length of 100 nm.

A case is reported of a patient who presented with recurrent tumour at the site of a laparoscopy port where there had been no evidence of intra-abdominal tumour. Possible mechanisms of recurrence are postulated including a haematogenous spread of the primary tumour and the implantation at the port site.

The hereditary spastic paraplegias are a clinically variable and genetically heterogeneous group of disorders characterized by progressive and lower limb spasticity and weakness. Silver syndrome (SS) is a particularly disabling autosomal dominant form of the disease in which there is associated wasting of the hand muscles. In view of the fact that genes for hereditary spastic paraplegia can produce highly variable phenotypes, the eight known autosomal dominant loci were investigated for linkage to Silver syndrome. Genotyping of these loci in two large multigenerational families was incompatible with linkage to any of these regions, suggesting that an additional locus is responsible for this syndrome.

A national register of symptomatic hemoglobinopathies has been developed in Oman to facilitate the development of the National Program for the control of genetic blood disorders.The information was initially collected retrospectively through hospital records and was refined prospectively with data collected through a survey of pediatricians. The percentages of heterozygotes in different population groups and geographical locations, birth prevalence, age distribution of cases and factors determining frequencies of Hemoglobinopathies in different regions of the country were studied from the register.The register has identified 1757 cases of homozygous Sickle Cell Anemia and 243 cases of beta-thalassemia major in a population of 1.5 million in 1995. Register based national figures of heterozygote carriers approximate 10% for Sickle Cell Anemia and 4% for beta-thalassemia major.Defining regional and tribal variations can assist efficient targeting of health resources. This approach provides a simple model for other countries or regions to follow providing there is a health care system that facilitates registration.

A tremendous potential exists for the application of transrectal ultrasonography as a tool to enhance the captive management of endangered species. Reproductive study of two southern black rhinoceros (Diceros bicornis minor) females was performed daily to every other day for a approximately 60 day period to document ovarian changes, and three times weekly in early pregnancy to once monthly in late pregnancy in order to characterize changes in fetal parameters throughout gestation. All ovarian and fetal anatomical structures were measured in millimeters. The mean (+/- SD) length of the estrous cycle or interovulatory period was 26 +/- 1.4 days (n=2 cycles). Follicular growth rate of a dominant follicle was approximately 3 mm/day once the follicle reached 35 mm in diameter. Ovulation was observed to occur at a mean (+/- SD) follicular diameter of 49.5 +/- 2.6 mm (n=4) and within 48 to 72 h after observed estrus (n=2). Large ovarian structures [mean (+/- SD) diameter of 71.7 +/- 2.9 mm; n=3], considered analogous to equine anovulatory hemorrhagic follicles, were observed to form in the winter months and suggest seasonal periods of reduced fertility. Fecal progesterone assays confirmed ultrasonographic events. Although preliminary, the results of fetal sexing are presented and compared to the horse. Our data indicate that fetal eye or fetal foot diameter measurements can be used to accurately predict gestational age from about 2 months to term, providing useful information to managers of both captive and wild rhino populations. The ability to identify and quickly release animals in late term pregnancy in the wild and thereby reduce-abortions and neonatal mortalities in holding bomas is one potential practical conservation benefit of the fetal age predictive models.

The 18q-syndrome is associated with hearing impairment in 50-80 per cent of cases. The hearing loss may be sensorineural or conductive. A high proportion of cases are associated with narrow or stenosed external auditory canals. This may be a useful clinical pointer to the syndrome. Two cases with impaired hearing are presented in this paper including one case with complex external ear and middle ear malformations. The clinical and audiological features in each case are described.

Omani society has a long tradition of consanguinity, which goes back to pre-Islamic times. The aim of the present study was to determine the prevalence of consanguineous marriage and the mean coefficient of inbreeding in Oman. Consanguinity rates among 60,635 couples (20.8% of the national population of childbearing age) were determined on the basis of a questionnaire in major delivery units. In this large survey, which included all sections of the community, 24.1% of marriages were reported between first cousins and 11.8% of marriages were between second cousins. In addition, a further 20.4% of marriages were contracted within specific tribal groupings. Because of the strictly endogamous nature of the tribal groups in Oman, all marriages would be expected to be consanguineous to some degree, albeit at a level beyond that of second cousins (For = 0.0156). To obtain a more detailed picture of the patterns of consanguinity, and to assess the validity of the questionnaire-based study, 500 pedigrees were investigated in detail. The mean coefficient of inbreeding (alpha) in these pedigrees was 0.0204, compared with 0.0198 in the larger survey, suggesting that the data were broadly comparable and confirming the high degree of consanguinity in the population of Oman.