Separation of C2–C4 hydrocarbons from methane by zeolite MFI hollow fiber membranes fabricated from 2D nanosheets

Separation of higher hydrocarbons from methane is an important and energy-intensive operation in natural gas processing. We present a detailed investigation of thin and oriented MFI zeolite membranes fabricated from 2D MFI nanosheets on inexpensive α-alumina hollow fiber supports, particularly for separation of n-butane, propane, and ethane (“natural gas liquids”) from methane. These membranes display high permeances and selectivities for C₂–C₄ hydrocarbons over methane, driven primarily by stronger adsorption of C₂–C₄ hydrocarbons. We study the separation characteristics under unary, binary, ternary, and quaternary mixture conditions at 298 K and 100–900 kPa feed pressures. The membranes are highly effective in quaternary mixture separation at elevated feed pressures, for example allowing n-butane/methane separation factors of 170–280 and n-butane permeances of 710–2,700 GPU over the feed pressure range. We parametrize and apply multicomponent Maxwell–Stefan transport equations to predict the main trends in separation behavior over a range of operating conditions.     

The architecture of virtual machines

A virtual machine can support individual processes or a complete system depending on the abstraction level where virtualization occurs. Some VMs support flexible hardware usage and software isolation, while others translate from one instruction set to another. Virtualizing a system or component -such as a processor, memory, or an I/O device - at a given abstraction level maps its interface and visible resources onto the interface and resources of an underlying, possibly different, real system. Consequently, the real system appears as a different virtual system or even as multiple virtual systems. Interjecting virtualizing software between abstraction layers near the HW/SW interface forms a virtual machine that allows otherwise incompatible subsystems to work together. Further, replication by virtualization enables more flexible and efficient and efficient use of hardware resources.     

Offshore Outsourcing: A Swot Analysis of a State in India

Global trends indicate that IT spending will increasingly go to offshore solution providers. This article demonstrates the use of a SWOT analysis technique for identifying the strengths, weaknesses, threats, and opportunities associated with a potential IT outsourcing location. The factors assessed include business conditions, physical infrastructure, IT infrastructure, financial institution and government support, and various labor characteristics specific to a region: the state of Kerala in India.     

An affordable modular mobile robotic platform with fuzzy logic control and evolutionary artificial neural networks

Autonomous robotics projects encompass the rich nature of integrated systems that includes mechanical, electrical, and computational software components. The availability of smaller and cheaper hardware components has helped make possible a new dimension in operational autonomy. This paper describes a mobile robotic platform consisting of several integrated modules including a laptop computer that serves as the main control module, microcontroller‐based motion control module, a vision processing module, a sensor interface module, and a navigation module. The laptop computer module contains the main software development environment with a user interface to access and control all other modules. Programming language independence is achieved by using standard input/output computer interfaces including RS‐232 serial port, USB, networking, audio input and output, and parallel port devices. However, with the same hardware technology available to all, the distinguishing factor in most cases for intelligent systems becomes the software design. The software for autonomous robots must intelligently control the hardware so that it functions in unstructured, dynamic, and uncertain environments while maintaining an autonomous adaptability. This paper describes how we introduced fuzzy logic control to one robot platform in order to solve the 2003 Intelligent Ground Vehicle Competition (IGVC) Autonomous Challenge problem. This paper also describes the introduction of hybrid software design that utilizes Fuzzy Evolutionary Artificial Neural Network techniques. In this design, rather than using a control program that is directly coded, the robot's artificial neural net is first trained with a training data set using evolutionary optimization techniques to adjust weight values between neurons. The trained neural network with a weight average defuzzification method was able to make correct decisions to unseen vision patterns for the IGVC Autonomous Challenge. A comparison of the Lawrence Technological University robot designs and the design of the other competing schools shows that our platforms were the most affordable robot systems to use as tools for computer science and engineering education. © 2004 Wiley Periodicals, Inc.     

Cephalic tetanus: demonstration of a dual lesion

A clinical and electrophysiological study of 15 cases of cephalic tetanus is reported. This condition is a form of local tetanus which commonly follows an injury to the face or head. It is characterised by muscle paralysis which is maximal close to the site of injury, while spasm is evident at mroe distant sites. As muscle paralysis improves with time it is succeeded by spasm. It is argued that paralysis is due to high local concentrations of toxin in the brainstem while lesser concentrations cause spasm by abolishing inhibition. Electrophysiological studies indicate that paralysis is of lower motor neurone type with denervation potentials, hyperirritability, loss of motor units, and marginally increased distal latencies being the features recorded.     

PO2 in the carotid body perfused and/or superfused with cell-free media

We measured with a micro-O2 electrode the tissue PO2 (PtO2) in the cat carotid body (CB) to see whether it was adequately oxygenated when perfused or superfused with artificial, cell-free (c-f) solutions (pH = 7.4; temp = 35-38 degrees C). To obtain a relative measure of O2 consumption (VO2), we also measured the rate of disappearance of O2 following stoppage of the blood flow, and compared these disappearance curves with those during stoppage of the c-f perfusion solutions. In 14 cats normal (blood perfusion) PtO2 values ranged from 10 to 104 mmHG; chi = 72 +/- 4 (SE--as used throughout). During 3 h of c-f perfusion with air-equilibrated Locke's solution, PtO2 ranged from 62 to about 160 mmHg; chi = 133 +/- 4. When perfused with Fay's equilibrated with 98% O2-2% CO2 no PtO2 values in the CB were below 300 mmHg (4 cats). In eight additional cats the CB was cleared of blood then superfused with saline equilibrated with 50% O2 underneath and air-equilibrated saline over. Less than 5% of the PtO2 values found were below 5 mmHg. We conclude that most studies on the artificially perfused or superfused CB cannot be invalidated on the basis that the preparations were hypoxic. O2 disappearance curves taken during blood perfusion were significantly faster than during c-f perfusion indicating a marked reduction in VO2 with c-f perfusion.     

Radiotherapy in the treatment of solitary plasmacytoma

Solitary plasmacytoma of bone (SPB) and extramedullary plasmacytoma (EMP) are rare. High local control rates are reported with radiotherapy, although the optimal dose and extent of radiotherapy portals remains controversial. Between 1983 and 1993, 30 patients with solitary plasmacytoma were seen at the Regional Cancer Centre, Trivandrum, India. 23 patients had SPB and seven EMP. The mean age was 52 years and the male to female ratio 3.2:1. Diagnosis of SPB was confirmed by biopsy in 16 patients and tumour excision in seven. 20 patients received megavoltage radiotherapy to the bone lesion with limited margins, and one received chemotherapy. Two patients who underwent complete tumour excision received no further treatment. All seven patients with EMP received megavoltage radiotherapy, four following biopsy and three after tumour excision. Local control was achieved in all patients with SPB. Nine progressed to multiple myeloma and one developed a solitary plasmacytoma in another bone. Six patients with EMP achieved local control. Three later progressed to multiple myeloma and one had local relapse. Median time to relapse was 28 months in SPB and 30 months in EMP. 5-year overall survival rates were 82% and 57% for patients with SPB and EMP, respectively. The corresponding progression free survival rates were 55% and 50%, respectively. Age, sex, site of tumour, serum M protein and haemoglobin levels did not significantly influence progression free survival. The extent of surgery, radiotherapy dose or time to relapse were not significant prognostic factors. Radiotherapy appears to be an effective modality of treatment of solitary plasmacytoma. No dose-response relationship is observed, and high local control rates are achieved with limited portals. Progression to multiple myeloma is the commonest pattern of failure, although no prognostic factors for progression are identified. The role of chemotherapy in preventing disease progression needs further evaluation.