Cold Arm Research Articles

Pearls & Oy-sters: Distal subclavian artery

PEARL Thoracic outlet syndrome causing distal subclavian artery disease is a rare cause of arteryto-artery embolic stroke. Brainstem ischemic stroke is a result of compromise to the posterior circulation. This is often due to antegrade embolism from the heart or proximal vessels. Retrograde blood flow has been described in the subclavian artery, thus making the distal subclavian artery a source of possible retrograde embolism. CASE SUMMARY A 21-year-old man was admitted with a history of acute dysarthria, dysphagia, and left hemiparesis for 1 day. He also had right arm pain suggestive of claudication for 1 month. He had transiently lost consciousness a month before, but did not have any permanent neurologic deficit subsequently, and he had not sought medical advice. Neurologic examination revealed a Glasgow Coma Score of 15, pinpoint pupils, conjugate deviation of the eyes to the left, spastic left hemiparesis, and palatal palsy. He had a pulseless and cold right arm. The rest of the examination was unremarkable. Investigations revealed bilateral pontine infarctions (right more than left) on brain MRI, and a right cervical rib on cervical spine X-ray. An arch aortogram detected a stenosis of the right subclavian artery approximately 1 cm distal to the origin of the right vertebral artery (figure). There was poststenotic dilation of the artery with the distal axillary artery occluded and a number of collaterals present. Right vertebral angiography found total occlusion of the basilar artery with an embolus in situ. Retrograde blood flow was demonstrated in systole and diastole in both subclavian arteries (right greater than left) using Doppler ultrasound. Transthoracic echocardiography, thrombophilia screen, and C-reactive protein were normal. A screen for arrhythmias was negative. DISCUSSION The abrupt onset of gaze paresis associated with hemiparesis and pinpoint pupils in this patient suggested ischemic stroke involving the pons,

新型光热微驱动器的理论模型及实验研究

We present a category of novel photothermal (PT) microactuators. Each microactuator consists of two PT arms that are jointed at the free end and connected to an anchor at the fixed end. When a laser beam irradiates one of the arms (called hot arm, and the other is cold arm), light energy is absorbed and converted into heat. The asymmetric thermal expansion of the hot and cold arms results in lateral deflection. Based on conduction heat transfer theory and heat dissipation mechanism, we study the PT effects and establish the theoretical model of PT expansion for the microactuators. The temperature distribution and the linear thermal expansion can be numerically calculated. The analytical solution provides an insight into the operation of the actuators and predicts the performance of the actuators with new designs. A symmetry microactuator and a microswitch as the prototypes have been fabricated and tested. The experimental results are in good agreement with the theoretical predictions and prove the feasibility of the novel PT microactuators.

Thermal and mechanical analysis of an SU8 polymeric actuator using infrared thermography

In the current paper, report the detailed thermomechanical analysis of a polymeric thermal actuator integrated in a microelectromechanical systems microgripper, is reported. The inclusion of an actuator design which eliminates completely the parasitic resistance of the cold arm improves considerably the thermal efficiency of the system and enables large displacements at lower input voltages and operating temperatures than reported previously. Two different microgrippers built using a trilayer polymer/metal/polymer combination of SU8/gold/SU8 have been modelled, fabricated, and tested. As opposed to standard models, heat transfer by conduction to the ambient as well as between adjacent beams has been modelled. A semi-empirical approach for the calculation of conductive heat transfer coefficients has also been provided. The analysis combines simulations with electrical, deflection, and spatially resolved temperature measurements. The latter was carried out using infrared thermography, its use in polymeric actuators reported here for the first time. The good agreement between the models and the experimental data support the conclusions of the basic analytical model, i.e. thermal losses are dominated by two conduction mechanisms (into the ambient and between the hot and cold arms), and encourage its use for qualitative thermal design assessment and optimization.

Different Methods of Forming Cold Fronts in Nonmerging Clusters

Sharp edges in X-ray surface brightness with continuous gas pressure called cold fronts have been often found in relaxed galaxy clusters such as Abell 496. Models that explain cold fronts as surviving cores of head-on subcluster mergers do not work well for these clusters and competing models involving gas sloshing have been recently proposed. Here, we test some concrete predictions of these models in a combined analysis of density, temperature, metal abundances and abundance ratios in a deep Chandra exposure of Abell 496. We confirm that the chemical discontinuities found in this cluster are not consistent with a core merger remnant scenario. However, we find chemical gradients across a spiral discovered at 73 kpc north of the cluster center and coincident with the sharp edge of the main cold front in the cluster. Despite the overall SN Ia iron mass fraction dominance found within the cooling radius of this cluster, the metal enrichment along the arm, determined from silicon and iron abundances, is consistent with a lower SN Ia iron mass fraction (51% +- 14%) than that measured in the surrounding regions (85% +- 14%). The is also significantly colder than the surroundings by 0.5-1.6 keV. The arm extends from a boxy colder region surrounding the center of the cluster, where two other cold fronts are found. This cold arm is a prediction of current high resolution numerical simulations as a result of an off-center encounter with a less massive pure dark matter halo and we suggest that the cold fronts in A496 provide the first clear corroboration of such model, where the closest encounter happened ~ 0.5 Gyr ago. We also argue for a possible candidate dark matter halo responsible for the cold fronts in the outskirts of A496.

Design and testing of a polymeric microgripper for cell manipulation

This work presents the design, fabrication and testing of a thermally actuated microgripper for the manipulation of single cells and other biological particles. This microgripper has been fabricated with a particular combination of surface micromachining techniques that permit the release of stress-free polymer (SU8)/metal (Au) structures without the use of sacrificial layers. The inclusion of novel thermal actuators, which completely eliminate the parasitic resistance of the cold arm, improves considerably the efficiency of the system and therefore enables large displacements at low input voltages and operating temperatures. Two types of microgripper have been fabricated and tested producing displacements of up to 262 μm at 1.94 V input voltage and 78 mW power. Micromanipulation experiments have successfully demonstrated the gripping, holding and positioning of a micro-sized object.

Measurement of skin vasoconstrictor response in healthy subjects

Objectives Laser Doppler flowmetry enables non-invasive quantification of skin blood flow and its sympathetically mediated change. Four different maneuvers were performed in 60 healthy subjects aged 20–78 years to investigate their variability, reproducibility and to determine the influence of gender, age and height. Material and methods Skin blood flow was measured on the pulp of both index fingers using laser Doppler flowmetry. Vasoconstriction was induced by deep inspiratory gasp, arm dependency, acoustic stimulation and a modified cold pressor test. Results More than 95% of normal subjects showed a vasoconstrictor response to cold pressure test and 100% to inspiratory gasp. In all other maneuvers vasoconstrictor response was less reliable. The magnitude of vasoconstrictor responses decreased with age in all maneuvers, while latencies remained unchanged. Only during inspiratory gasp men showed more pronounced vasoconstrictor response compared with women. Body height influenced latencies if peripheral stimuli were applied like in the cold pressor and arm dependency tests. Conclusions Inspiratory gasp and the modified cold pressor test were found to be more suitable maneuvers for routine clinical testing than arm dependency and acoustic stimulation. Normal data also for side differences are provided as a base for routine clinical testing in systemic and unilateral neurological disorders.

Coupled Field Analyses in MEMS With Finite Element Analysis

This paper deals with the design and analysis of a horizontal thermal actuator common in MEMS applications using Finite Element Analysis; with the objective of exploring means to improve its sensitivity. The influence of variables like voltage and the dimensions of the cold arm of the actuator unit were examined by comprehensive, coupled thermal-stress analyses. Simulation results from this study showed that the sensitivity of the actuator increases with the applied voltage as well as the width of the cold arm of the thermal actuator. An important observation made from this study is that the size and thermal boundary conditions at the fixed end of the actuator primarily control the stroke and the operating temperature of the actuator for a given potential difference between cold and hot arms. The coupled field analyses also provided a design tool for maximizing the service voltage and dimensional variables without compromising the thermal or structural integrity of the actuator.

Design and modeling of a MEMS bidirectional vertical thermal actuator

In this paper, a new micro electro-thermal actuator with bidirectional vertical motion is introduced, analyzed and tested. In traditional vertical electro-thermal actuators, the arms of actuators are fabricated with different widths to provide high and low electrical resistance for the hot and cold arms. Applying electrical current to the arms results in different thermal expansions between the hot and cold arms, which force the tip of the device to bend. The new bidirectional vertical thermal actuator (BVTA) eliminates the parasitic electrical resistance of the cold arm through the use of a ‘U’ shape structure. This U-shape structure provides a larger deflection with improved electrical efficiency due to the use of an active return current pass. The U-shape actuator is more beneficial in applications such as variable capacitors where a larger deflection is needed to increase the tuning range. For analysis and design purposes, an effective method to transfer the continuous system to a lumped model is presented. Simulation and test results are provided to show the deflection and effects of the design parameters on the actuator performance.

Design and performance of an electrothermal MEMS microengine capable of bi-directional motion

Several microactuator technologies have been investigated for positioning individual elements in large-scale microelectromechanical systems (MEMS). Electrostatic, magnetostatic, piezoelectric and thermal expansion represent the most common modes of microactuator operation. This research focuses on the design and comparative performance evaluation of asymmetrical electrothermal actuators. The motivation is to present a unified description of the behavior of the electrothermal actuator so that it can be adapted to a variety of microsensor and microactuator applications. The MEMS polysilicon surface micromachined electrothermal actuator uses resistive (Joule) heating to generate thermal expansion and movement. In the traditional asymmetrical electrothermal actuator design, the single-hot arm is narrower than the cold arm, and thus, the electrical resistance of the hot arm is greater. When an electrical current passes through the device (both the hot and cold arms), the hot arm is heated to a higher temperature than the cold arm. This temperature differential causes the hot arm to expand along its length, thus forcing the tip of the device to rotate about the flexure. Another variant of the asymmetrical design features a double-hot arm arrangement that eliminates the parasitic electrical resistance of the cold arm. Furthermore, the second hot arm improves electromechanical efficiency by providing a return current conductor that is also mechanically active. In this design, the rotating cold arm can have a narrower flexure compared to the flexure in the traditional single-hot arm device because it no longer needs to conduct an electrical current. The narrower flexure results in an improvement in mechanical efficiency. This research compares the tip deflection performance of the asymmetrical single- and double-hot arm electrothermal actuator designs. Deflection measurements of both actuator designs as a function of arm length and applied electrical power are presented. As a practical application of the electrothermal actuator, the recent realization of a MEMS microengine is described, and evidence of its bi-directional motion is presented. The electrothermal actuator and microengine designs were accomplished with the MEMSPro® CAD software program, and they were fabricated using the MEMSCAP Integrated Microsystems Multi-User Microelectromechanical Systems (MEMS) Process® (MUMPs) foundry.

Design and performance of an electrothermal MEMS microengine capable of bi-directional motion

Several microactuator technologies have been investigated for positioning individual elements in large-scale microelectromechanical systems (MEMS). Electrostatic, magnetostatic, piezoelectric and thermal expansion represent the most common modes of microactuator operation. This research focuses on the design and comparative performance evaluation of asymmetrical electrothermal actuators. The motivation is to present a unified description of the behavior of the electrothermal actuator so that it can be adapted to a variety of microsensor and microactuator applications. The MEMS polysilicon surface micromachined electrothermal actuator uses resistive (Joule) heating to generate thermal expansion and movement. In the traditional asymmetrical electrothermal actuator design, the single-hot arm is narrower than the cold arm, and thus, the electrical resistance of the hot arm is greater. When an electrical current passes through the device (both the hot and cold arms), the hot arm is heated to a higher temperature than the cold arm. This temperature differential causes the hot arm to expand along its length, thus forcing the tip of the device to rotate about the flexure. Another variant of the asymmetrical design features a double-hot arm arrangement that eliminates the parasitic electrical resistance of the cold arm. Furthermore, the second hot arm improves electromechanical efficiency by providing a return current conductor that is also mechanically active. In this design, the rotating cold arm can have a narrower flexure compared to the flexure in the traditional single-hot arm device because it no longer needs to conduct an electrical current. The narrower flexure results in an improvement in mechanical efficiency. This research compares the tip deflection performance of the asymmetrical single- and double-hot arm electrothermal actuator designs. Deflection measurements of both actuator designs as a function of arm length and applied electrical power are presented. As a practical application of the electrothermal actuator, the recent realization of a MEMS microengine is described, and evidence of its bi-directional motion is presented. The electrothermal actuator and microengine designs were accomplished with the MEMSPro ® CAD software program, and they were fabricated using the MEMSCAP Integrated Microsystems Multi-User Microelectromechanical Systems (MEMS) Process ® (MUMPs) foundry.

Development of Electrothermal Actuator with Optimized Motion Characteristics

In this paper, we give the reasons for the phenomenon of adhesion of U-shaped electrothermal actuators onto substrates which is commonly observed for such devices. Next, we identified a significant advantage for operating these U-shaped actuators on top of a polysilicon layer with a suitable pattern design. A thorough investigation on the deflection behavior of actuators with different dimensional parameters, i.e., cold arm width, flexural beam length and hot arm length, was carried out. Finally, we discussed the effects of electrostatic force on the actuator due to these parameters. Based on these analyses, we suggested optimized dimensions for the U-shaped actuator.

A reliable single-layer out-of-plane micromachined thermal actuator

Out-of-plane electrothermal actuators have been applied to a variety of fields with the bimorph effect being the most commonly used driving method, due to simple fabrication process. However, such an actuator experiences a shear force at the interface of different materials, while actuated. Delamination therefore takes place and decreases its lifetime. In this study, a novel bi-directional out-of-plane electrothermal actuator is designed and fabricated. Unlike the bi-metal and hot–cold arm thermal actuator, this actuator can move in two directions. Since this actuator is consisted of only single-layer thin film material, it can prevent from delamination. According to the static load–deflection test, this actuator can achieve bi-directional actuation with amplitude near 6–7 μm when driven at 5 V. According to the vibration test, the dynamics of the actuator is influenced not only by the thermal characteristics but also by the vibration modes. Consequently, the thermal actuator still has a significant output when driven near 40 kHz. The actuator were experienced a fatigue test which shows that its resonant frequency remains unchanged after 109 cycles of continuous operation with driving voltage at 2.25 V.

Analysis and design of polysilicon thermal flexureactuator

An analytical model that can accurately predict the performance of a polysilicon thermal flexure actuator has been developed. This model is based on an electrothermal analysis of the actuator, incorporating conduction heat transfer. Heat radiation from the hot arm of the actuator to the cold arm is also estimated. Results indicate that heat radiation becomes significant only at high input power, and conduction heat losses to both the substrate and the anchor are mainly responsible for the operating temperature of the actuator under routine operations. Actuator deflection is computed based on elastic analysis of structures. To verify the validity of the model, polysilicon thermal flexure actuators have been fabricated and tested. Experimental results are in good agreement with theoretical predications except at high input power. An actuator with a 240 µm long, 2 µm thick, 3 µm wide hot arm and a 180 µm long, 12 µm wide cold arm deflected up to 12 µm for the actuator tip at an input voltage of 5 V while it could be expected to deflect up to 22 µm when a 210 µm long cold arm is used.

Three vascular lesions in one patient

A Z&year-old motor cyclist was transferred to our Emergency department immediately after arrival and stabilization in a regional hospital. On arrival in our hospital he was in obvious ‘shock’ with a blood pressure of 7840 mmtlg, a heart rate of 134 and a Glasgow Coma Score of 31. After fluid resuscitation with 2 1 of Ringer’s lactate, his systolic pressure was 104 and his heart rate was 110. X-Rays of his lateral cervical spine, chest and the pelvis did not reveal any fractures. There was left lung contusion and a high left hem~diaphragm. A diaphragmatic rupture could not be identified. There was marked swelling around the left shoulder and a pale and pulseless left hand. Swelling of the left hypochondral region was also noted. Ul~asono~aphy of the abdomen revealed free fluid, and a provisional diagnosis of splenic rupture was made. After further fluid resuscitation, his systolic pressure was 100 mmHg and his pulse rate was 90. A CT scan of the abdomen was then performed. This showed a laceration of the spleen. In addition a complete laceration of the left kidney with contrast extravasation of the left kidney was seen. No right kidney was seen (Figure 2). The patient was transferred immediately to the operating theatre. A laparotomy and splenectomy were performed. The aorta was then clamped above the left renal artery and the retroperitoneal space explored. All blood clots were evacuated. The left kidney was exposed, and found to have a complete rupture in its middle third, but both parts were still connected to the artery and vein. One calyceal system was disrupted and clamped. The kidney was packed in a Vicryi mesh and left in situ. The retroperitoneal space and the abdominal cavity were closed and drained. After this, the patient was sent for arte~o~aphy to assess his cold and pulseless left arm. Arteriography was performed through the right common femoral artery. An obstruction of the left subclavian artery at the level of the clavicle was observed (Figaro 2). As part of the same procedure, bleeding from the renal artery was

The cold hemiplegic arm: a community survey

The cold hemiplegic arm: a community survey

Individual differences and the effectiveness of different coping strategies for pain

The relationship between individual differences in self-statements and response to self-instruction (SI) and attention diversion (AD) coping strategies for acute pain was investigated. Previous research suggests that an individual's cognitive activity may be an important moderator variable in determining the effectiveness of different coping strategies. Sixty-eight female volunteers were given two cold pressor arm immersions. Subjects were asked to think aloud all thoughts occurring on both trials. On the basis of a median split of negative thinking emitted during the first or baseline trial, subjects were classified as either catastrophizers (CAT) or noncatastrophizers (NCAT). Subjects were randomly assigned to receive either SI or AD treatments or to a no-treatment control condition. Subjects were then given the second cold pressor trial. The results showed that NCAT subjects trained with AD improved their tolerance scores significantly more than those trained with SI. The opposite effect was found for CAT subjects. CAT subjects trained with SI showed greater improvement in tolerance scores than those trained with AD. Implications of these results as well as limitations and methodological features of this study are discussed.

Studies of the Fish of Great Slave Lake

A four-year study of the fish of Great Slave Lake was initiated one year before the lake was opened for commercial fishing. Information has been obtained about the composition, distribution and general ecology of the major species. Twenty-one species are listed and the ciscoes, probably of three species, await identification. Lake trout, common whitefish and ciscoes dominate the population and the former two species support an extensive gill-net fishery. The inconnu Stenodus, and the deepwater sculpin, Triglopsis, are of special zoogeographic interest.Sampling was mainly with standardized 300-yard gangs of gill net. In these, some 12,000 fish weighing about 20,000 pounds were taken. Some data were obtained on the selective effect of mesh size. Young and small fish were collected by seining.Great Slave Lake's area of 10,500 square miles includes a large open portion and two great arms, one to the north, the other extending eastward. Part of the north arm is shallow and its fish population is much like that of the main lake. Goldeyes, white suckers and pikeperch are found in the shallow warmer parts of these areas. None of these species are found in the deep and cold east arm, but in it grayling and round whitefish are numerous. The common whitefish is virtually absent from McLeod Bay at the extremity of the east arm.Data concerning growth in length and weight are provided for round whitefish, white sucker, longnose sucker, burbot and pikeperch. Most of these species grow a little slower in Great Slave Lake than in lakes farther south. Growth studies of five other important species have been undertaken by other workers.Analysis of the food of all the larger species shows that the main food chains are plankton→ cisco→ lake trout and plankton→ detritus→ bottom organisms→ whitefish. Pontoporeia, Mysis and cottids are important fish food in the deep water.Twenty-one species of parasites are recorded from ten species of fish.