Plateau Stage Research Articles

Serial splintage: Preoperative treatment of upper limb contracture

IntroductionThe present study aimed to study the efficacy of preoperative splints in treatment of upper limb contractures and to evaluate the response of contracture to splints depending on the etiology and the joint involved. MethodsNinety joints of 42 patients were studied. Patients age, gender, etiology, duration of contracture, contracture site and joint and type of contracture was noted. The range of motion of the involved joint was recorded. Serial static splints made of thermoplastic material were applied after customizing them for each patient. The range of motion and percentage movement was recorded at weekly interval and the splints were modified as per need. Time taken to reach a plateau stage was noted. To compare the statistical significance between two groups and more than two groups of continuous variable unpaired t-test and one way ANOVA respectively was applied. We considered differences to be statistically significant when the p value was below 0.05. The strength of relationship between the two continuous variables was analyzed by Pearson correlation analysis. ResultsEtiological factors were thermal burns (36.7%), electrical burns (13.3%), post traumatic (35.6%) and post cellulitis (14.4%). Age ranged from 2 to 70 years with a mean of 28.9±13.4 years. Sixty-two patients treated were males (68.9%) and 28 were female (31.1%). The mean range of motion present across all joints before starting the therapy was 54.7±23.6 degrees. The mean improvement in contracture angle obtained by serial splintage was 37.4±28.1 degrees. The mean time taken to achieve plateau was 23.6±3.2 days. Maximum improvement was seen in thermal burn contractures (41.2±30.3 degrees). Least improvement was seen in contractures due to cellulitis (6.5±16.2 degrees). This finding was statistically significant [F(3,86)=4.25, p=0.005]. Significant difference was seen in response to therapy based on the joint involved [F(3,86)=3.36, p=0.02]. Highest improvement in the range of motion was seen in the metacarpophalangeal joint (49.61±31.3 degrees). ConclusionsThe preoperative use of splints may lead to lesser surgical intervention and in selective cases obviate surgery. Thermal burns which are the most common cause of contractures of the upper limb, show the maximum response to preoperative serial splintage. Patient with minor contracture and supple tissues are fully corrected with splints without surgical intervention. In patients undergoing surgical correction, skin graft decreases due to decreased contracture angle.

Enhanced mechanical properties and degradability of poly(butylene succinate) and poly(lactic acid) blends

To improve the tensile properties and degradability of poly(butylene succinate) (PBS) for biomedical usage, biodegradable polymer blends have been developed. A series of PBS and poly(lactic acid) (PLA) blends were prepared, and their degradation behaviors in simulated body fluid for 16 months were investigated based on morphology, tensile test, weight analysis, and molecular weight. The results showed that the incorporation of PLA into PBS increased the initial tensile strength to some extent, and the blends lost their tensile properties earlier than their parent polymers with the proceeding of hydrolysis. Both blends and parent polymers went through a plateau and subsequent rise stage in mass loss and water absorption, but the blends hydrolyzed faster than the parent polymers. The molecular weight variations also demonstrated faster hydrolysis of the blends. Moreover, both blends and their parent polymers underwent a slow-to-fast transition in their hydrolysis rates. When the Mn of PBS and PLA reached 4.0 × 104 and 9.0 × 104, the hydrolysis of parent polymers and blends began to accelerate, which is the start of auto-acceleration. The blends hydrolyzed faster in both stages. The interface between the components initiated accelerating hydrolysis in the first stage, and the reciprocal auto-acceleration effect resulted in faster hydrolysis of the blends in the second stage.

A Class of Numerical Algorithm for Impact Degree Assessment of Emergency Systems

A standard procedure for the evaluation of emergency impact is developed, concentrating on variation of the impact degree. A numerical method is presented in this paper. The concepts of impact depth and impact width are introduced to assess the impact degree, and both of which determine the evolution path of impact. Based on the variation pattern of impact depth, the evolution path could be divided into rising stage, plateau stage, and recession stage, and path of each stage could be expressed in terms of specified functions. The major goal of this procedure is to measure the emergency impact and make predictions for the consequences. In the case study, we applied this procedure to the analysis of the impact caused by 3.11 earthquake in Japan and demonstrated the algorithm's effectiveness and feasibility. Although this methodology shows improvement in quantitative analysis of the emergency impact, the accuracy of the impact path and the derivative effect of secondary derivative events are issues that yet to be further studied.

Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection

Background:The purpose of this study was to elucidate the mechanism of natural uptake of nonfunctionalized quantum dots in comparison with microinjected quantum dots by focusing on their time-dependent accumulation and intracellular localization in different cell lines.Methods:The accumulation dynamics of nontargeted CdSe/ZnS carboxyl-coated quantum dots (emission peak 625 nm) was analyzed in NIH3T3, MCF-7, and HepG2 cells by applying the methods of confocal and steady-state fluorescence spectroscopy. Intracellular colocalization of the quantum dots was investigated by staining with Lysotracker®.Results:The uptake of quantum dots into cells was dramatically reduced at a low temperature (4°C), indicating that the process is energy-dependent. The uptake kinetics and imaging of intracellular localization of quantum dots revealed three accumulation stages of carboxyl-coated quantum dots at 37°C, ie, a plateau stage, growth stage, and a saturation stage, which comprised four morphological phases: adherence to the cell membrane; formation of granulated clusters spread throughout the cytoplasm; localization of granulated clusters in the perinuclear region; and formation of multivesicular body-like structures and their redistribution in the cytoplasm. Diverse quantum dots containing intracellular vesicles in the range of approximately 0.5–8 μm in diameter were observed in the cytoplasm, but none were found in the nucleus. Vesicles containing quantum dots formed multivesicular body-like structures in NIH3T3 cells after 24 hours of incubation, which were Lysotracker-negative in serum-free medium and Lysotracker-positive in complete medium. The microinjected quantum dots remained uniformly distributed in the cytosol for at least 24 hours.Conclusion:Natural uptake of quantum dots in cells occurs through three accumulation stages via a mechanism requiring energy. The sharp contrast of the intracellular distribution after microinjection of quantum dots in comparison with incubation as well as the limited transfer of quantum dots from vesicles into the cytosol and vice versa support the endocytotic origin of the natural uptake of quantum dots. Quantum dots with proteins adsorbed from the culture medium had a different fate in the final stage of accumulation from that of the protein-free quantum dots, implying different internalization pathways.

Antimicrobial Activity and Molecular Mechanism of the CRES Protein

Cystatin-related epididymal spermatogenic (CRES) protein, a member of the cystatin superfamily of cysteine protease inhibitors (also known as CST8), exhibits highly specific, age-dependent expression in mouse testis and epididymis. The CRES protein possesses four highly conserved cysteine residues which govern the overall conformation of the cystatins through the formation of two disulfide bonds. Previous studies have revealed that other cystatin family members, such as cystatin 3 and cystatin 11, show antibacterial activity in vitro. This prompted us to investigate the potential antimicrobial activity of the CRES protein. Colony forming assays and spectrophotometry were used to investigate the effects of recombinant CRES protein on Escherichia coli (E. coli) and Ureaplasma urealyticum (Uu), respectively, in vitro. After incubation of E. coli with CRES recombinant protein fused with glutathione-S-transferase (GST), a substantial decrease in colony forming units was observed, and the effect was dose and time dependent. Furthermore, it took longer for Uu to grow to plateau stage when incubated with GST-CRES recombinant protein compared with the control GST. The antibacterial and Anti-Uu activities were not impaired when the cysteine residues of CRES protein were mutated, indicating that the antimicrobial effect was not dependent on its disulfide bonds. Functional analysis of three CRES polypeptides showed that the N-terminal 30 residues (N30) had no antimicrobial activity while N60 showed similar activity as full-length CRES protein. These results suggest that the active center of CRES protein resides between amino acid residues 31 and 60 of its N-terminus. Mechanistically, E. coli membrane permeabilization was increased in a dose-dependent manner, and macromolecular synthesis was inhibited on treatment with GST-CRES. Together, our data on the antimicrobial activities of CRES protein suggest that it is a novel and innate antimicrobial protein which protecting the male reproductive tract against invading pathogens.

Restructuring on a vertiginous plateau: The evolutionary trajectories of British Columbia’s forest industries 1980–2010

The volatility of British Columbia’s (BC’s) forest industries over the last three decades has not only reflected the immediate impacts of demand fluctuations arising from the broader vicissitudes of capitalist economies but the evolutionary implications of industrial and resource dynamics. The 1980s recession in particular marked a turning point in the evolutionary trajectory of BC’s forest industries, associated with global paradigmatic changes driven by flexibility imperatives, the maturation of the forestry resource cycle to the plateau or fall-down stage, and conflicts caused by environmental, social and trade protectionist opposition to vested industry interests. This paper focuses on the broad contours of the restructuring of BC’s forest industries since 1980. Conceptually, the paper elaborates a resource industry life-cycle model (RILCM) that integrates industry and resource cycle dynamics and the implications of economic crisis. Empirically, the analysis uses longitudinal output and employment data, summaries of the policy re-regulation of the BC forest economy since 1980, and comparative static plant-level data, 1980–2008. The analysis reveals the 1980s recession as a turning point in the transformation of BC’s forest industries, characterized by high levels of volatility and long-term decline in the main commodities. Industrial restructuring has also witnessed a fragmentation of production, the emergence of small firm dominated value-added activities, and broad changes to the coreperiphery structure of the forest industries within BC. It is argued that evolutionary approaches to economic geography need to incorporate resource peripheries and crisis and acknowledge the role of crisis and non-economic factors in shaping regional transformation.

Spectroscopic observations of the transient OT J213806.6+261957 in Pegasus

We report about the spectroscopic follow-up of the transient OT J213806.6+261957 in Pegasus. The object, a SU UMa system, underwent a superoutburst in 2010. We observed the transient in 2010 and 2011, from the decay after the initial plateau stage to the long fading tail. Our observations showed Balmer and He I lines in emission at all stages, suggesting that the accretion disk was progressively becoming optically thin and that the emission lines were caused by collisional excitation. We show that the evolution of OT J213806.6+261957 is similar to that of GW Lib during the 2007 superoutburst, as reported by Hiroi (2009). We also show that the Pegasus transient, with its small period and its close distance, is a candidate gravitational wave source of potential interest for the space interferometer LISA.

Characterisation of the intracranial pressure waveform during infusion studies by means of central tendency measure

In the present study an attempt was made to quantify and characterise the changes in the intracranial pressure (ICP) waveform over the wide pressure range covered during infusion studies by means of the central tendency measure (CTM). CTM is a non-linear approach using continuous chaotic modelling that summarises the degree of variability in a signal. CTM of the ICP wave in the lumbar subarachnoid space was analysed in 77 infusion studies performed in patients with idiopathic and secondary forms of normal pressure hydrocephalus (median age 74years, range 22-88). Four artefact-free epochs were selected during the baseline, infusion, plateau and relaxation stages of every infusion study. The average pressure, pulse amplitude and CTM were determined for each epoch. Correlations among these parameters were explored. CTM of the ICP waveform decreases, i.e. variability increases, as infusion studies progress from baseline pressure to the plateau stage. Significant correlations were found during all phases of infusion testing, except at baseline, between CTM and pressure, CTM and amplitude and pressure and amplitude. Partial correlations emphasised the relationship between CTM and amplitude. When pulse amplitude is held constant, CTM and the pressure range do not correlate. Volume loading leads to increased variability of the ICP signal measured by means of CTM. This finding summarises numerically the long-established phenomenon of increasing amplitude and rounding of ICP pulses associated with ICP elevation during infusion studies. CTM could be a suitable approach to quantify and characterise the pulsatile nature of the ICP wave.

Effects of specimen aspect ratio on the compressive properties of Mg alloy foam

Closed-cell AZ31Mg alloy foams were successfully prepared by melt-foaming method. The effects of specimen aspect ratio (the thickness/width ratio, AR) on the compressive properties of closed-cell Mg alloy foams were investigated systematically. The results showed that the length of stress–strain plateau stage extended and ideality energy absorption efficiency improved with the specimen AR increasing and the yield strength decreased. Specimens with the AR=1.00 possess good combination of yield strength, plateau stage length and compressive stability when compressed under the experiment conditions.

Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic

AbstractA peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (∼2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss‐dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water‐saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. δ15N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in δ13C values appear to reflect mainly changes in plant assemblages. Positive shifts in both δ15N and δ13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N‐enrichment. Copyright © 2012 John Wiley & Sons, Ltd.

Comment on Dörr and Zulauf: Elevator tectonics and orogenic collapse of a Tibetan-style plateau in the European Variscides: the role of the Bohemian shear zone. Int J Earth Sci (Geol Rundsch) (2010) 99: 299–325

The present comment disproves the tectonic model of a late Devonian/early Carboniferous Tibetan-style collisional plateau in the Tepla-Barrandean (TB) part of the Bohemian Massif, which later collapsed by thermal weakening of the underlying crust. Contrary to this model, the TB neither reveals major crustal thickening nor uplift and erosion, and eastern continuations of the TB were, during the relevant time-span, areas of open marine sedimentation. Late Devonian/early Carboniferous marine sediments widespread also in the Armorican and Central Massifs of France testify to low topography in central parts of the Variscan orogen. Notional traces of a Permo-Carboniferous ice cap on the French Massif Central do not support the plateau model, because they are questionable and much younger than the inferred plateau stage of the TB. The relative uplift of high-grade metamorphic rocks to the NW and the SE of the TB is not due to sinking of an elevated TB, but, instead, to the hydraulic and buoyant expulsion of HP material from the Saxo-Thuringian and Moldanubian subduction channels. The rise of lower-grade HT rocks along the southwestern margin of the Bohemian Massif was effected by late Carboniferous transpression. The high temperature and the resulting low viscosity of the rising materials were probably not caused by Variscan mantle delamination, but relate to lithospheric thinning and heating at the tip of the westward propagating Tethys Rift.

Multi-axial strength criterion of lightweight aggregate (LWA) concrete under the Unified Twin-shear strength theory

The strength theory of concrete is significant to structure design and nonlinear finite element analysis of concrete structures because concrete utilized in engineering is usually subject to the action of multi-axial stress. Experimental results have revealed that lightweight aggregate (LWA) concrete exhibits plastic flow plateau under high compressive stress and most of the lightweight aggregates are crushed at this stage. For the purpose of safety, therefore, in the practical application the strength of LWA concrete at the plastic flow plateau stage should be regarded as the ultimate strength under multi-axial compressive stress state. With consideration of the strength criterion, the ultimate strength surface of LWA concrete under multi-axial stress intersects with the hydrostatic stress axis at two different points, which is completely different from that of the normal weight concrete as that the ultimate strength surface is open-ended. As a result, the strength criteria aimed at normal weight concrete do not fit LWA concrete. In the present paper, a multi-axial strength criterion for LWA concrete is proposed based on the Unified Twin-Shear Strength (UTSS) theory developed by Prof Yu (Yu et al. 1992), which takes into account the above strength characteristics of LWA under high compressive stress level. In this strength criterion model, the tensile and compressive meridians as well as the ultimate strength envelopes in deviatoric plane under different hydrostatic stress are established just in terms of a few characteristic stress states, i.e., the uniaxial tensile strength <TEX>$f_t$</TEX>, the uniaxial compressive strength <TEX>$f_c$</TEX>, and the equibiaxial compressive <TEX>$f_{bc}$</TEX>. The developed model was confirmed to agree well with experimental data under different stress ratios of LWA concrete.

A simple method for solving the voltage overshoots of LiFePO4-based lithium-ion batteries with different capacity classes

To simulate the energy storage process of an energy harvesting device, a step-charging current protocol for LiFePO4-based lithium-ion batteries is considered, in which lower current rates are applied in both the earlier and latter steps of the voltage profile, while the maximum current (0.2 C-rate) is applied in the middle voltage region. The protocol is applied to three stages of voltage profile, i.e., initial step (stage 1), middle plateau (stage 2), and final step (stage 3) regions. In spite of their capacity-classes, lithium-ion batteries containing sub-μm-sized LiFePO4 have shown voltage overshoots in the step regions of the voltage profile, thus involving anomalous degradation of active materials and diminishing the stability and safety of the batteries. In order to overcome this overshoot problem, a simple method of blending a small amount of μm-sized LiCoO2 with the LiFePO4 is proposed. The results show that adding the LiCoO2 eliminates voltage overshoots. The small quantity of μm-sized LiCoO2 extends the operating voltage region as the short appearance of the LiCoO2 plateau serves to block the emergence of an overvoltage. In addition, battery performance is further improved by an increase in the electrode density brought about by the close packing of different-sized particles.

Effect of 100&amp;deg;C Heating on Further Ductility Improvement of Friction Stir Processed AZ31 Magnesium Alloy

Friction stir processed (FSPed) AZ31 Mg alloy with fine grains was deformed in tension at room temperature (RT) and 100°C to be compared with the same alloy in the extruded condition with coarse grains. Results indicate that texture affects the deformation behavior of AZ31 alloy more than grain refinement does. The work hardening rate of the FSPed alloy shows a prolonged ascending stage at RTand a plateau stage at 100°C, while that of the extruded alloy keeps dropping rapidly. The above discrepancy between the tensile properties of the two test materials arises since basal slip and f10� 12g tension twin of low critical resolved shear stress are favored by the FSPed texture but not by the extruded texture. 100°C heating allows basal slip and f10�g tension twin to contribute significant improvement to tensile ductility in the FSPed alloy, but hastens the instability in plastic strain of the extruded alloy. The work hardening characteristics and deformation properties of the FSPed specimen in tension at RT and 100°C will be compared further in this paper to examine the different tensile behaviors at these two temperatures. [doi:10.2320/matertrans.M2012081]

The Cenomanian/Turonian Boundary event (CTBE) at Tarfaya, Morocco: Palaeoecological aspects as reflected by marine palynology

Two sections from the Cenomanian–Turonian boundary event (CTBE) at Tarfaya, northwest Africa, were analysed fully quantitatively by marine palynology. The results are compared and integrated with published data from micropalaeontology, total organic carbon content (TOC), isotope geochemistry and, for selected intervals, the distribution of chlorobactanes. A rise in eustatic sea level, composed of several third-order transgression pulses, is reflected by various palynologic proxies. A combination of productivity and preservation is proposed as the main control on TOC accumulation preceding and across the CTBE. Strong episodic upwelling events, reflected by significant increases of the peridinioid/gonyaulacoid (p/g) ratio of dinocysts, are documented at the onset of eustatic transgression and closely preceding the onset as well as within the plateau stage of the positive δ 13C anomaly. These events are considered as initial and sustaining causes respectively for TOC accumulation. The peak abundance of both green algal groups, Botryococcus and prasinophytes, is coincident with pelagic sedimentation and is strongly related to the increase of both oxygen deficiency in the water column and total organic carbon content. An episodic halocline stratification of the water column is suggested, possibly related to both a globally intensified hydrologic cycle and a current induced input of high- to middle-latitude surface waters into the Tarfaya Basin. This is corroborated by the prominent episodic appearance of Bosedinia, a peridinioid dinocyst with probable freshwater/reduced salinity affinity, as well as several euryhaline taxa common within late Mesozoic high to mid-latitude waters. A slight correlation with contents of chlorobactanes is documented at least for the prasinophyte distribution, which may reflect a moderate availability of reduced nitrogen within photic zone waters. However, maxima of chlorobactanes are related to palynologically barren or depleted intervals, possibly reflecting the sulfidic stage of redox conditions within photic zone waters. The almost coeval appearance of the suggested high-latitude taxon ? Ginginodinium sp. close to the onset of the δ 13C anomaly both at Tarfaya and at Wunstorf, northwest Germany, corroborates a connection of surface water circulation between high and low latitude sites during the eustatic sea-level high.

Spectroscopy and photometry of the symbiotic nova PU Vul during its nebular phase and minimum of 2007

We present the results of our analysis of the spectrophotometric and photometric data for the symbiotic nova PU Vul acquired in 2001–2008. The continuum in the optical observed in 2006–2008 cannot be reconciled with a standard model including light from the cool component, hot component, and nebula. The hot component’s temperature increased to 194 000 K by 2008, while its luminosity decreased by a factor of ten compared to the plateau of 1979–1991. The evolution of the hot component as reflected by the Hertzsprung-Russell diagram does not agree with a theoretical model describing the evolution of a thermonuclear outburst in a white-dwarf envelope. We estimate the mass of the hot component to be 0.5M ⊙ based on the luminosity of the hot component during the plateau stage. Our spectroscopy reveals periodic continuum-flux variations due to brightness variability of the cool component, with an amplitude of at least 2 m at 7000 A. The spectral type of the cool component in 2008 was M6.3.

Changes of saccadic eye movements in thyroid-associated ophthalmopathy

To establish whether or not the dynamics of saccadic eye movements are significantly changed in patients with different stages of thyroid-associated ophthalmopathy (TAO) and, subsequently, if analysis of saccades could serve as an additional diagnostic tool for early detection of inflammatory activity in TAO. Thirty-seven patients with TAO and 10 age- and gender-matched control subjects were investigated. The patients were divided into four groups according to the stage of the disease: (i) early mild disease (n = 10), (ii) early severe disease (n = 11), (iii) long-standing restrictive disease (n = 10) and (iv) proven auto-immune hyperthyroidism without any signs of TAO (n = 6). Horizontal and vertical saccades with amplitudes of 10°, 20°, 30° and 40° were recorded binocularly using the induction scleral search coil technique. The two main sequence constants V(max) and C were calculated for each eye. Repeated measurement analysis of variance was carried out to test for differences between different gaze directions, eyes and groups. In horizontal saccades, significant differences were found between groups but not between abduction and adduction. In vertical saccades, differences between groups and the interaction between groups and up- and down-gaze saccades were significant. Compared with the control group, analysis of the main sequence curves revealed larger differences in patients of group 3 and 4 than in those of group 1 and 2. Whereas in the control group down-gaze saccades were faster than up-gaze saccades, the opposite behaviour was found in all patient groups. The largest differences were detected among those patients who had no signs of TAO (group 4). In this study, significant saccade differences were detected in all patients with TAO. In contrast to our earlier studies where evaluation of multiple individual saccade parameters did not reveal significant differences, analysis of the main sequence constants and mathematical reconstruction of the main sequence curves turned out to be a sensitive technique for reliable detection of subtle ocular motility changes. Significant differences were detected even in patients with auto-immune thyroiditis where no clinical signs of TAO were apparent.

FE Analysis of Nitinol Leaf Springs Used in a Compression Anastomosis Device

Reconstruction of the digestive system lumen patency (anastomosis creation) after its partial surgical removal is a common and crucial procedure. The conventional anastomosis methods use devices for mechanical suturing which are associated with high failure risk and can lead to major complications. The compression anastomosis as a sutureless method seems to be a promising alternative. However, attempts during the last two centuries have not been completely successful due to the complex character of the tissue-healing process. The specific mechanical behavior of Nitinol alloys was applied to the force element of the compression devices. These devices are becoming more widely adopted in surgery practice. The compression anastomosis device enables the anastomosis of colonic and intestinal tissue based on compression forces exerted by Nitinol leaf springs. By means of changing the strain distribution in the stressed leaves with varying moments of inertia, one can gain full control of the different stages in the force-deflection profile (i.e., linear elastic stage and the force plateau stage). The target of this study is the comparison of different Nitinol leaf geometries and evaluation of the finite elements analysis as a tool for preliminary design of such geometries. The results of this analysis allow us to establish regulation of the spring’s mechanical behavior, thus controlling the anastomosis creation in the compression anastomosis device.

Energy absorption properties of multi-layered corrugated paperboard in various ambient humidities

This paper develops a mathematical model to depict the energy absorption properties of multi-layered corrugated paperboard (MLCP) in various ambient humidities. It is a piecewise function to model the energy absorptions corresponding to three deformation stages of MLCP (elastic stage, plateau stage and densification stage) separately. Simple formulas are derived for each stage which relating the energy absorption capacity of MLCP to the thickness-to-flute pitch ratio ( t c / λ ) of corrugated-core cell, the mechanical properties of corrugated medium tested under a controlled atmosphere [23 °C and 50% relative humidity (RH)], and the RH. The theoretical energy absorption curves are then compared with experimental ones and good agreements are achieved for MLCP with wide range ratios of t c / λ in various ambient humidities. Results of this research can be applied in the optimum design and material selection of cushioning packaging with multi-layered corrugated paperboard.

Characterization of Ti–6Al–4V alloy foams synthesized by space holder technique

Ti–6Al–4V foams, biomedical candidate materials, were synthesized by powder metallurgical space holder technique as a result of evaporation of magnesium to achieve desired porosity content. Final products contained porosities in the range ∼43–64% with an average macropore size between 485 and 572 μm and a lamellar type Widmanstätten microstructure composed of α-platelets and β-laths. Unlike the case of bulk Ti–6Al–4V alloy tested under compression loading, compression stress–strain curves of manufactured Ti–6Al–4V foams were similar to those of elastic–plastic foams, which contain a linear elastic region; a plateau stage; and a densification stage. In the plateau region deformation bands perpendicular to the compression axis were developed and cell collapsing took place together with the buckling and fracture of some of the cell walls and edges in a ductile manner. Calculated elastic modulus and yield strength were in the range 1.42–14.7 GPa and 28.2–150 MPa, respectively, and the foam mechanical properties were found to be dependent on micro porous cell wall properties, which in turn depends on neck size between powder particles. Around 330 MPa yield strength value was calculated for porous cell walls by the use of Ti–6Al–4V alloy powder samples sintered in loose and compacted conditions, which were utilized to simulate the cell wall structure of foams. In addition, overall mechanical properties of foams were investigated considering macro porosity fraction, p macro, and the yield strength of foams exhibited a power law dependence, similar to commonly used minimum solid area models, in the form of A * (1 − p macro) n , where the proportionality constant “ A” was found to be the yield strength of micro porous cell walls.